JP2000293029A - Image forming device - Google Patents

Abstract

(57) [Summary] [Problem] As a result of accurately and accurately detecting the toner concentration in a two-component developer, a high image density can be maintained and a high-quality image free of fog can be stably obtained. Providing a good image forming apparatus even in a rotary developing system. A rotatable developer carrier for developing an electrostatic latent image with a two-component developer having a non-magnetic toner and a magnetic carrier, and a developing device having a magnetic field generator fixedly disposed inside the developer carrier In an image forming apparatus having a control means for controlling a toner concentration by detecting a change in magnetic permeability of a developer by using a coil inductance to determine a mixing ratio between a non-magnetic toner and a magnetic carrier, the two-component developer has a weight average particle size. Diameter 1
An image forming apparatus comprising a spherical magnetic coated carrier of 5 to 60 μm and a spherical non-magnetic toner, and detecting a change in the magnetic permeability of the developer with the developer on the developer carrier.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus used for developing an electric latent image or a magnetic latent image in an electrophotographic method or an electrostatic printing method.
The present invention relates to an image forming apparatus capable of significantly improving the life of a developer used in the image forming apparatus and forming a high-quality image with a stable image density.

[0002]

2. Description of the Related Art Conventionally, a dry developer as a developer is carried on the surface of a developer carrier, and this developer is transported and supplied to the vicinity of the surface of a photosensitive drum carrying an electrostatic latent image. , And alternate between photoreceptor drum and developing sleeve
A method of developing an electrostatic latent image while applying an electric field to visualize the image is well known. In general, a developing sleeve is often used as the developing sleeve. In the following description, the developing sleeve is also referred to as a “developing sleeve”. In general, a photosensitive drum is used as a latent image carrier. Also called "drum".

As a method of developing the electrostatic latent image, conventionally, for example, a developer (two-component developer) having a two-component composition (carrier particles and toner particles) is used, and a magnet is arranged inside. A magnetic brush is formed on the surface of the developing sleeve, and the magnetic brush is rubbed or brought close to the photosensitive drum opposed to the photosensitive drum while maintaining a minute developing gap, and is continuously connected between the developing sleeve and the photosensitive drum (between SD). A so-called magnetic brush development method is known, in which the development is performed by repeatedly applying and alternately applying an alternating electric field to repeatedly transfer and reverse the transfer of toner particles from the developing sleeve to the photosensitive drum. JP-A-55-3260, JP-A-59-16
No. 5082).

The developing device for developing a two-component magnetic brush has a structure as shown in FIG. As shown in FIG. 1, the image forming apparatus includes a photosensitive drum 1 as an electrostatic latent image carrier, and further includes a developing device 4 facing the photosensitive drum 1.
Is arranged. Hereinafter, the developing device 4 will be described. First, the inside of the developing container 16 of the developing device 4 is
7, a developing chamber (first chamber) R ₁ and a stirring chamber (second chamber) R ₂
Is partitioned into bets, above the stirring chamber R ₂ is the toner storage chamber R ₃ is formed by partition walls. Developing chamber R _l and stirring chamber R
Within ₂ are accommodated developer 19 comprising a toner and a carrier, the replenishing toner (non-magnetic toner) 18 is stored in the toner storage chamber R _3. The toner storage chamber R ₃ is provided with supply port 20 via the supply port 20, the amount of the replenishment toner 18 commensurate to the consumed toner is supplied from falling into the stirring chamber R ₂ It is configured as follows. In the image forming apparatus of the present invention, a two-component developer composed of a mixture of non-magnetic toner 19a and magnetic carrier 19b is used as developer 19.

[0005] The developing chamber R ₁ is provided with conveying screw 13, by the rotation of the conveying screw 13, the developer 19 in the developing chamber R _1, the developing sleeve 11
Is configured to be conveyed in the longitudinal direction.
Similarly, a conveyance screw 14 is provided in the storage chamber R ₂ , and the toner that has fallen into the stirring chamber R ₂ from the supply port 20 by the rotation of the conveyance screw 14 extends along the longitudinal direction of the developing sleeve 11. It is configured to be conveyed.

As shown in FIG. 1, an opening is provided in a portion of the developing container 16 which is opposed to and close to the photosensitive drum 1.
A part of the developing sleeve 11 projects outside from the opening,
At a position where the developing sleeve 11 and the photosensitive drum 1 face each other, a certain gap is provided between them. A bias applying unit (not shown) for applying a bias is arranged on the developing sleeve 11 formed of a non-magnetic material.

Further, a magnet roller as a fixed magnetic field generating means, that is, a magnet 12 is provided in the developing sleeve 11. The magnet 12 has a developing magnetic pole N, a magnetic pole S located downstream thereof, and magnetic poles N, S, and S for transporting the developer 19. Further, the developing sleeve 11
Are arranged such that the developing magnetic pole N faces the photosensitive drum 1. With the above configuration, the developing magnetic pole N forms a magnetic field near the developing section between the developing sleeve 11 and the photosensitive drum 1, and the magnetic field forms a magnetic brush.

Reference numeral 15 in the figure denotes a regulating blade which is disposed below the developing sleeve 11 and regulates the layer thickness of the developer 19 on the developing sleeve 11.
It is made of a non-magnetic material such as US316 or a magnetic material that is iron or an alloy thereof. This regulation blade 1
5 is preferably 200 to 1000 μm, more preferably 300 to 900 μm.
It is kept at μm. That is, if the distance is less than 200 μm, the magnetic carrier is likely to be clogged in the gap, causing unevenness in the developer layer. However, there is a tendency that only a developed image having a small density and a lot of unevenness can be obtained. Further, in order to prevent non-uniform coating (so-called blade clogging) due to unnecessary particles mixed in the developer, the distance is preferably set to 300 μm or more. On the other hand, if it is larger than 1000 μm, the developing sleeve 11
Since the amount of the developer applied on the photosensitive drum 1 increases, the thickness of the developer layer cannot be regulated, the adhesion of the magnetic carrier particles to the photosensitive drum 1 increases. There is a tendency that the regulation of the layer thickness of the developer is weakened, the tribo of the toner is insufficient, and the image tends to be fogged.

The magnetic carrier particle layer (developer layer) having toner particles formed on the surface of the developing sleeve 11 has a binding force based on magnetic force and gravity even when the developing sleeve 11 is driven to rotate in the direction of the arrow. The movement becomes slower as the distance from the sleeve surface increases due to the balance between the transfer force of the developing sleeve 11 in the moving direction. Of course, some fall under the influence of gravity. Therefore, by appropriately selecting the arrangement positions of the magnetic poles N and S of the magnet in the developing sleeve 11 and the fluidity and magnetic characteristics of the magnetic carrier particles, the magnetic carrier particle layer becomes closer to the developing sleeve 11 with the magnetic pole N To form a moving layer. Due to the movement of the magnetic carrier particles, the developer is conveyed to the developing area with the rotation of the developing sleeve 11 and is used for development.

A non-magnetic toner 19a is contained in the developing container 16.
-Component developer 1 in which a magnetic carrier 19b is mixed
9, the mixing ratio of the toner particles to the magnetic carrier (hereinafter referred to as the T / C ratio) is such that the replenishment toner 18 is stored in an amount corresponding to the toner consumed by the development. by being appropriately fall replenished from the toner storage chamber R _3, it is kept constant. The developing container 16 at this time
The detection method of the mixing ratio between the toner particles and the magnetic carrier in the
Conventionally, various types have been proposed. For example,
Detecting means is provided around the photosensitive drum 1, and the developing sleeve 1
A method in which light is applied to the toner displaced from the photosensitive drum 1 side to the photosensitive drum 1 side, and the T / C ratio is detected from the transmitted light and the reflected light at this time; 11 that detects the T / C ratio from the reflected light when light is applied to the developer applied on the developer 11;
6, a sensor that detects the change in the apparent magnetic permeability (μ) of the carrier contained in the developer in a certain volume near the sensor using the inductance of the coil, and detects the T / C ratio. Has been proposed and put into practical use.

However, the method of detecting the T / C ratio from the amount of the developed toner on the photosensitive drum 1 has a problem that a space for installing the detecting means cannot be secured due to the downsizing of the copying machine or the image forming apparatus. Further, the method of detecting the T / C ratio from the reflected light when light is applied to the developer applied on the developing sleeve 11 is used when the detecting means is dirty due to toner scattering or the like. Or
When a toner containing carbon black is used as the non-magnetic toner 18, there is a problem that a sufficient amount of reflected light cannot be obtained and the T / C ratio cannot be accurately detected. On the other hand, a method of detecting the T / C ratio by detecting a change in the apparent magnetic permeability (μ) of the carrier contained in the developer 19 in a certain volume near the sensor by using the inductance of the coil (hereinafter, referred to as “T / C ratio”) , Which is referred to as a toner density detection sensor), the cost of the sensor alone is inexpensive, and it is not affected by the above-mentioned space problem and the problem of dirt due to toner scattering. It can be said that this is a means for detecting an optimum T / C ratio in an image forming apparatus.

A toner density detection sensor utilizing a change in the magnetic permeability (μ) of the developer detects the T / C ratio as described below, and the value of the T / C ratio becomes constant according to the detection result. Is controlled as follows. For example, when the magnetic permeability (μ) increases, the T /
Since the C ratio has decreased, in other words, the toner amount in the developer has decreased, toner replenishment is started. Conversely, when the magnetic permeability decreases, the development within a certain volume is performed. This means that the T / C ratio in the developer has increased, in other words, the amount of toner in the developer has increased.
/ C ratio is controlled.

[0013]

However, in the various types of toner concentration detecting sensors for detecting the change in the apparent magnetic permeability (μ) of the carrier contained in the developer in a certain volume as described above, for some reason, If the bulk density of the developer itself changes, the apparent magnetic permeability of the developer changes with the change in the bulk density, and the sensor output also changes in accordance with the change in magnetic permeability. There is. That is, if the T / C ratio in the developing container is constant but the bulk density changes in the developing container, the amount of developer (carrier) in a certain volume near the toner concentration detection sensor changes, Changes in the magnetic permeability appear in the sensor output. As a result, a sensor output indicating that the toner has been reduced is output without actually consuming the toner, and the toner is replenished, or even though the toner amount is actually reduced, However, there is a problem in that the sensor outputs such that the amount of toner is not reduced, and toner supply is not performed.

As a result, in the former case, excessive toner replenishment occurs, resulting in a problem that the image density becomes high, a problem that the developer amount increases with an increase in the toner amount, and the developer overflows from the developing container. Alternatively, a problem such as toner scattering due to a decrease in toner charge amount due to an increase in the toner ratio in the developer is caused. In the latter case, problems such as image deterioration due to a decrease in the amount of toner in the developer, low image density, and low image density due to an increase in toner charge amount are caused. These problems are particularly likely to occur in a so-called rotary developing system in which a developing container is attached to and detached from a photosensitive drum while rotating in a full-color developing machine. That is, in the rotary developing system, the developer in the container is disturbed by the rotation of the developing container, and the bulk density becomes unstable, so that the above-mentioned problem occurs remarkably.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art and to accurately and accurately detect toner density by a very simple method when forming an image using a two-component developer. An object of the present invention is to provide an image forming apparatus which can stably maintain a high image density of an obtained image by performing the image formation and stably obtain a high-quality image without fog. Furthermore, the object of the invention is, inter alia,
An object of the present invention is to provide an image forming apparatus that can obtain the above-described excellent effects even in a rotary developing system.

[0016]

The above objects are achieved by the present invention described below. That is, the present invention provides a latent image carrier for carrying an electrostatic latent image; a latent image forming means for forming an electrostatic latent image on the initially charged latent image carrier; Carrying a two-component developer having a non-magnetic toner and a magnetic carrier disposed opposite to and transporting to a developing position,
Developing means having a rotatable developer carrier for developing the electrostatic latent image into a visible image, a plurality of magnetic field generators fixedly provided inside the developer carrier, and Developing device having toner concentration control means for detecting the change in the magnetic permeability of the developer using the inductance of the coil to determine the mixing ratio of the non-magnetic toner and the magnetic carrier of the component developer and controlling the toner concentration in the developer based on the change The two-component developer comprises a spherical magnetic coated carrier having a weight average particle size of 15 to 60 μm and a spherical non-magnetic toner, and develops a change in the magnetic permeability of the developer. An image forming apparatus configured to detect with a developer on a developer carrier.

The effect provided by the image forming apparatus of the present invention having the above-described structure is that the developing means is constituted by a plurality of developing devices configured to move while rotating or sliding to the developing position of the photosensitive drum. Is remarkable. This is particularly effective when the developing device is configured to move while rotating. Further, in addition to the above-described configuration, a configuration in which the magnetic permeability of the developer is detected when the developing device is not at the developing position, or the developing unit includes a plurality of developing devices, and the plurality of developing devices If the configuration is such that the detection of the change in the magnetic permeability of the developer is performed by one sensor, more excellent effects can be obtained. The effect provided by the image forming apparatus of the present invention is particularly remarkable when the toner used for development is a non-magnetic toner containing at least carbon black.

In the image forming apparatus of the present invention having the above structure, a two-component developer comprising a spherical magnetic coat carrier having a small particle diameter having a specific average particle diameter and a spherical toner is used. The change in the bulk density of the developer, which was particularly remarkable when the ferrite carrier to be used is reduced in particle size, has been achieved, thereby improving the stability of toner density control. Furthermore, if a spherical magnetic powder-dispersed coated carrier is used in addition to the above configuration, and further, a spherical magnetic powder-dispersed coated carrier manufactured by a polymerization method is used, the fluidity of the carrier changes over a long period of time. As a result, the change in the bulk density of the developer can be reduced, and the stability of the toner density control can be further improved.

Further, in the image forming apparatus of the present invention,
In particular, in addition to the above configuration, a carrier having a configuration having at least a binder resin containing a phenolic resin and a magnetic metal oxide and a nonmagnetic metal oxide is used.
When a carrier having such a structure manufactured by a polymerization method is used, it is easier to achieve more uniform transportability of the developer.

Further, in the image forming apparatus of the present invention, in addition to the above configuration, the developing sleeve rotates in the opposite direction with respect to the photosensitive drum, and the developer regulating blade is disposed below the developing sleeve. It is preferable to adopt the configuration described above. That is, if the developer regulating blade is located above, uniform conveyance of the developer cannot be achieved unless the developer is compressed to overcome the gravity of the developer. As a result, the developer on the developing sleeve becomes different from the developer in the developing container, and the amount of carrier on the sleeve fluctuates. On the other hand, if the developer regulating blade is arranged below the developing sleeve, it is not necessary to compress to overcome the gravity, and even if the amount of the developer accumulated near the blade is reduced, the uniformity of the developer can be maintained. As a result, it is possible to suppress the deterioration due to the compression of the developer, and to reduce the change in the amount of the carrier on the developing sleeve.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail by way of preferred embodiments of the present invention. The present inventors have conducted intensive studies on the above-mentioned problems of the prior art,
It has a toner concentration control means for detecting the change in the magnetic permeability of the developer using the inductance of the coil to determine the mixture ratio of the non-magnetic toner and the magnetic carrier of the two-component developer and controlling the toner concentration in the developer based on the change. In an image forming apparatus provided with a developing device, the two-component developer
If a developer composed of a spherical magnetic coated carrier having a particle diameter of 0 μm and a spherical non-magnetic toner is used, and a change in the magnetic permeability of the developer is detected by the developer on the developing sleeve, the development used The present invention was found to improve the life of the agent and to stably obtain a high-quality image with stable image density and no fog.

The toner used in the image forming apparatus of the present invention will be described. First, as a preferable embodiment of the toner used in the present invention, in particular, a suspension polymerization method toner has a sharp particle size distribution, easily increases the bulk density of the toner, and as a result, can reduce the change in the bulk density of the developer. It is preferred. Further, a toner obtained by a seed polymerization method in which a monomer is further adsorbed on the obtained polymer particles and then polymerized using a polymerization initiator can also be suitably used in the present invention.

In the case where the toner used in the image forming apparatus of the present invention is obtained by a direct polymerization method, specifically,
The toner can be manufactured by the following manufacturing method. First, a releasing agent composed of a low-softening substance, a colorant, a charge control agent, a polymerization initiator, and other additives were added to the polymerizable monomer, and the mixture was uniformly dissolved or dispersed by a homogenizer, an ultrasonic disperser, or the like. The monomer system is dispersed in an aqueous phase containing a dispersion stabilizer using a conventional stirrer, homomixer, homogenizer, or the like. At this time, it is preferable to perform granulation by adjusting the stirring speed and time so that the monomer-based droplet has a desired size of the toner particles. Thereafter, stirring may be performed to such an extent that the particle state is maintained by the action of the dispersion stabilizer and the sedimentation of the particles is prevented.
The polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C.

In the present invention, the effect of the present invention can be further enhanced by using a toner in which part or all of the toner is formed by a polymerization method. In particular, for a toner in which such a portion of the toner surface is formed by a polymerization method, a pre-toner (monomer composition) particle is made to exist in a dispersion medium, and then a necessary portion is generated by a polymerization reaction. , It is possible to obtain a considerably smoothed one.

Furthermore, a toner suitable for use in the image forming apparatus of the present invention can be easily produced by using a toner having a core / shell structure and a shell portion formed by polymerization. . Therefore, in this sense, a toner having a core / shell structure is preferably used in the present invention. The advantage of using a toner having a core / shell structure in the image forming apparatus of the present invention is, of course, a blocking resistance that can be imparted without impairing the excellent fixability of the toner. When only the shell portion is polymerized, the residual monomer can be easily removed in the post-treatment step after the polymerization step, as compared with the polymerized toner as above.

The main component of the core used at this time is preferably a low softening point substance.
It is preferable to use a compound having a main maximal peak value measured according to D3418-8 of from 40 to 90 ° C. That is, if the maximum peak is less than 40 ° C., the self-cohesive force of the low softening point substance is weakened, and as a result, the high-temperature offset resistance of the toner is undesirably weakened. on the other hand,
If the maximum peak exceeds 90 ° C., the fixing temperature of the toner is undesirably high. Further, when toner is obtained by a direct polymerization method, since granulation and polymerization are performed in an aqueous system, when the temperature of the maximum peak value is high, a substance having a low softening point mainly precipitates during granulation, and a suspension system is used. This is not preferred because it may cause the inhibition of

The temperature of the maximum peak value of the low softening point substance can be measured by a known method. In the present invention, the temperature was measured using DSC-7 manufactured by Perkin Elemer Co., Ltd. in the following method. At this time, the melting point of indium and zinc was used for the temperature correction of the device detecting unit, and the indium heat of fusion was used for the correction of the calorific value. The measurement sample was set in an aluminum pan, a similar empty pan was set as a control, and the temperature was raised at a rate of 10 ° C./min. Was measured.

Specific examples of the low softening point substance include paraffin wax, microcrystalline wax, polyolefin wax, Fischer-Tropsch wax, carnauba wax, amide wax, alcohol, higher fatty acid, acid amide wax, and ester wax. , Ketones, hydrogenated castor oil, plant-based, animal-based, mineral-based, petrolactam, etc., and derivatives or graft / block compounds thereof. The low softening point substance is preferably added to the toner in an amount of 5 to 30% by weight. If the addition is less than 5% by weight, it takes a burden to remove the residual monomers described above. If the addition exceeds 30% by weight, coalescence of the toner particles tends to occur during granulation even in the production by the polymerization method. Those having a wide distribution are easy to generate and are not suitable for the present invention.

In the case of producing the toner used in the image forming method of the present invention, particularly, when the particle size distribution is relatively easy, the weight average particle diameter is 1 to 9 μm, and higher image quality is intended. Is particularly preferably produced by a suspension polymerization method under normal pressure or under pressure, which can obtain a fine particle toner having a particle size of 3 to 8 μm. As a specific method of encapsulating the low softening point substance, the polarity of the material in the aqueous medium is set to be lower for the low softening point substance than for the main monomer, and a small amount of a large polar resin or a single monomer is used. By adding a body, a toner having a so-called core / shell structure in which a low softening point substance is coated with an outer shell resin can be obtained. To control the particle size distribution and particle size of the toner, the method of changing the type and amount of the dispersant that acts as a poorly water-soluble inorganic salt or protective colloid, and mechanical device conditions, such as rotor peripheral speed, number of passes, and stirring Stirring conditions such as blade shape, container shape,
Alternatively, the desired toner used in the present invention can be easily obtained by controlling the solid concentration in the aqueous solution.

As described above, the toner used in the present invention is preferably a toner having a core / shell structure obtained by the above method. The following method can be used as a specific method for measuring the toner tomographic plane for confirming that the toner has a core / shell structure. First, a toner is added to a room temperature curable epoxy resin and dispersed sufficiently, and then cured in an atmosphere at a temperature of 40 ° C. for 2 days. After staining with osmium, a flaky sample is cut out using a microtome with diamond teeth to prepare a measurement sample. Then, for the sample obtained above, the tomographic morphology of the toner is measured using a transmission electron microscope (TEM). In the above, it is preferable to use a ruthenium tetroxide dyeing method in order to provide a contrast between materials by using a slight difference in crystallinity between the low softening point substance used and the resin constituting the outer shell.

When the toner used in the image forming apparatus of the present invention is a toner having a core / shell structure, the shell resin constituting the toner may be, for example, a commonly used styrene- (meth) resin. Acrylic copolymer, polyester resin, polycarbonate resin, epoxy resin,
Styrene-butadiene copolymer can be utilized. When a toner is directly obtained by a polymerization method, the following polymerizable monomers capable of forming the above-mentioned resins are preferably used. Specifically, styrene, o- (m-, p-)-methylstyrene, m- (p
-)-Styrene monomers such as ethylstyrene; (meth)
Methyl acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate,
Octyl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, biphenyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, (meth) acryl (Meth) acrylate monomers such as diethylaminoethyl acrylate; ene monomers such as butadiene, isoprene, cyclohexene, (meth) acrylonitrile, and acrylamide are preferably used. These are used alone, generally in the published Polymer Handbook, 2nd edition, III-P 139-192 (John Wiley).
& Sons Corporation) theoretical glass transition temperature (Tg)
Can be used by appropriately mixing the above-mentioned polymerizable monomers so that the temperature is 40 to 75 ° C. That is,
When the theoretical glass transition temperature is lower than 40 ° C., there is a possibility that a problem may occur in terms of storage stability of the toner and durability stability of the developer. On the other hand, when the temperature exceeds 75 ° C., the fixing point increases, and especially in the case of a full-color toner,
The color mixture of each color toner is insufficient and the color reproducibility is poor, and furthermore, the transparency of the OHP image is remarkably reduced, which is not preferable from the viewpoint of high image quality.

The molecular weight of the outer shell resin was measured by GPC (gel permeation chromatography) according to the following method. As a specific GPC measurement method, the toner is extracted in advance with a toluene solvent using a Soxhlet extractor for 20 hours, and then the toluene is distilled off using a rotary evaporator. After sufficiently washing with an organic solvent that cannot be dissolved, for example, chloroform, the solution dissolved in THF (tetrahydrofuran) is filtered through a solvent-resistant membrane filter having a pore diameter of 0.3 μm and measured. Prepare a sample for use. The measurement was performed using 150C manufactured by Waters Co., Ltd., and A-801, 802, 80 manufactured by Showa Denko
3, 804, 805, 806, and 807 were connected, and the molecular weight distribution was measured using a standard polystyrene resin calibration curve.

In the present invention, the number average molecular weight (Mn) of the resin component obtained as described above is from 5,000 to 5,000.
1,000,000, and a weight average molecular weight (M
w) and the number average molecular weight (Mn) ratio (Mw / Mn) is
It is preferable to use a toner having a core / shell structure obtained by using an outer shell resin having 2 to 100.

In the present invention, when a toner having a core / shell structure is produced, in particular, a polar resin is further added to the above-mentioned outer shell resin for encapsulating a low softening point substance in the outer shell resin. It is preferable to add them. As the polar resin used at this time, for example, a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer,
Saturated polyester resins, epoxy resins and the like are preferably used. It is particularly preferable to use a polar resin which does not contain an unsaturated group capable of reacting with the outer shell resin and / or its polymerizable monomer in the molecule. If a polar resin having an unsaturated group is added, a cross-linking reaction occurs between the polymer and a polymerizable monomer for forming the outer shell resin layer, resulting in an extremely high molecular weight. As a toner, it is disadvantageous when four color toners are mixed, which is not preferable.

Further, a core / preferably used in the image forming apparatus of the present invention
The toner having the shell structure may be one in which an outermost shell resin layer is further provided on the toner surface. The glass transition temperature of the resin forming the outermost shell resin layer is designed to be equal to or higher than the glass transition temperature of the outer shell resin layer in order to further improve the blocking resistance. It is preferably crosslinked. Further, it is preferable that the outermost resin layer contains a polar resin and a charge control agent for improving the chargeability.

The method for providing the outermost shell layer is not particularly limited, and examples thereof include the following method. (1) In the second half or after the end of the polymerization reaction, if necessary, a monomer in which a polar resin, a charge control agent, a cross-linking agent, etc. are dissolved and dispersed is added to the reaction system, the mixture is adsorbed on the polymer particles, and the polymerization initiator is added. A method in which an outermost shell layer is formed by adding and performing polymerization. (2) If necessary, emulsion polymerization particles or soap-free polymerization particles composed of a monomer containing a polar resin, a charge control agent, a cross-linking agent, etc., are added to the reaction system, and are aggregated on the surface of the polymerization particles. A method of fixing the polymer particles to the surface of the polymer particles by heat or the like according to the conditions. (3) A method in which emulsion polymerized particles or soap-free polymerized particles made of a monomer containing a polar resin, a charge control agent, a cross-linking agent, and the like, if necessary, are dry-mechanically fixed to the toner particle surfaces.

As the charge control agent used above, known ones can be used. In the case of a color toner, in particular, the toner is colorless, the charging speed of the toner is fast, and a constant charge amount can be stably maintained. It is particularly preferred to use a charge control agent. Further, in the present invention, when a direct polymerization method is used, it is particularly preferable to use a charge control agent having no polymerization inhibition and having no solubilized substance in an aqueous system. Specific examples of the negative compound include metal compounds of salicylic acid, naphthoic acid, and dicarboxylic acid; polymer compounds having sulfonic acid and carboxylic acid in the side chain; boron compounds, urea compounds, silicon compounds, calixarenes, and the like. Can be used. As the positive compound, a quaternary ammonium salt; a polymer compound having the quaternary ammonium salt in the side chain; a guanidine compound, an imidazole compound and the like are preferably used.

The above-mentioned charge control agent is preferably used in the form of fine particles. In this case, the number average particle size is 2 μm.
It is particularly preferable to use a charge control agent in the form of fine particles of m or less, more preferably 1 μm or less. The charge control agent is a binder resin 1
It is preferably used in the range of 0.05 to 5 parts by weight with respect to 00 parts by weight. However, the addition of a charge control agent is not essential, and a sufficient amount of charge can be imparted to the toner simply by utilizing frictional charge with the carrier.
It is not necessary to include a charge control agent.

When a direct polymerization method is used for producing the toner used in the image forming method of the present invention, for example, 2,2′-azobis- (2,4
-Dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis (cyclohexane-1-carbonitrile), 2,2, -azobis-4-methoxy-2,4-dimethylvalero Azo polymerization initiators such as nitrile and azobisisobutyronitrile; peroxide polymerization initiators such as benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, 2,4-dichlorobenzoyl peroxide and lauroyl peroxide; Can be used. The amount of the polymerization initiator to be added varies depending on the desired degree of polymerization, but is generally used in the range of 0.5 to 20% by weight based on the polymerizable monomer.
The type of the initiator slightly varies depending on the polymerization method, but may be used alone or in combination with reference to the 10-hour half-life temperature. In order to control the degree of polymerization, a known crosslinking agent, chain transfer agent, polymerization inhibitor or the like may be further added and used.

When the toner used in the image forming method of the present invention is produced by suspension polymerization, the following inorganic and organic dispersants can be used. For example, inorganic dispersants include tricalcium phosphate, hydroxyapatite, magnesium phosphate, aluminum phosphate, zinc phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, and metasilicate. Calcium, calcium sulfate, barium sulfate, bentonite, silica, alumina,
A magnetic material, ferrite, or the like can be used. Examples of the organic dispersant include polyvinyl alcohol, gelatin, methylcellulose, methylhydroxypropylcellulose, ethylcellulose, sodium salts of carboxymethylcellulose, starch and the like, and these can be used by dispersing them in an aqueous phase. it can.
These dispersants are preferably used in the range of 0.2 to 10.0 parts by weight based on 100 parts by weight of the polymerizable monomer.

Further, as these dispersants, commercially available ones may be used as they are, but in order to obtain finely dispersed particles having a uniform particle size, the inorganic compound is produced under high-speed stirring in a dispersion medium. It can also be used. For example, in the case of tricalcium phosphate, a dispersant suitable for a suspension polymerization method can be obtained by mixing an aqueous solution of sodium phosphate and an aqueous solution of calcium chloride under high-speed stirring.
Further, for making these dispersants finer, 0.001 to 0.1
About 10 parts by weight of a surfactant may be used in combination. As the surfactant used at this time, commercially available nonionic, anionic and cationic surfactants can be used, for example, sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate,
Sodium oleate, sodium laurate, potassium stearate, calcium oleate and the like are preferably used.

When a direct polymerization method is used for the production of a toner, the toner can be specifically produced by the following production method. First, in the polymerizable monomer, a low-softening substance, a release agent, a colorant, a charge control agent, a polymerization initiator, and other additives are added, and the mixture is uniformly dissolved by a homogenizer, an ultrasonic disperser, or the like. Alternatively, the dispersed monomer composition is dispersed in an aqueous phase containing a dispersion stabilizer using a conventional stirrer, homomixer, homogenizer, or the like. Next, preferably, the granulation is performed by adjusting the stirring speed and time so that the droplets composed of the monomer composition have a desired size of the toner particles. Thereafter, the dispersion stabilizer may be stirred to such an extent that the particle state is maintained and the particles are prevented from settling. The polymerization is performed at a polymerization temperature of 40 ° C. or higher, generally 50 to 90 ° C. In addition, the temperature may be raised in the latter half of the polymerization reaction. Further, in order to remove unreacted polymerizable monomers and by-products for the purpose of improving durability properties, the temperature may be increased in the latter half of the reaction or after the completion of the reaction. The partial aqueous medium may be distilled off. After the completion of the reaction, the generated toner particles are recovered by washing and filtration, and dried. In the above suspension polymerization method, usually, 300 to 3,000 water is added to 100 parts by weight of the monomer system.
It is preferable to use 0 parts by weight as a dispersion medium.

Examples of the binder resin for constituting the toner used in the present invention include the following.
For example, homopolymers of styrene such as polystyrene, poly-p-chlorostyrene, and polyvinyltoluene and substituted products thereof; styrene-p-chlorostyrene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer , Styrene-acrylate copolymer,
Styrene-methacrylate copolymer, styrene-
α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer Styrene-based copolymers such as styrene-isoprene copolymer, styrene-acrylonitrile-indene copolymer; polyvinyl chloride, phenolic resin, naturally modified phenolic resin, natural resin modified maleic acid resin, acrylic resin, methacrylic resin, polystyrene Vinyl acetate, silicone resin, polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin and the like can be used. Further, a crosslinked styrene resin is also a preferable binder resin.

When a styrene copolymer is used as the binder resin, comonomer for the styrene monomer includes:
For example, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, dodecyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methacrylic acid, methyl methacrylate,
Ethyl methacrylate, butyl methacrylate, octyl methacrylate, acrylonitrile, methacrylonitrile,
Monocarboxylic acid having a double bond such as acrylamide or the like; a dicarboxylic acid having a double bond such as maleic acid, butyl maleate, methyl maleate, dimethyl maleate, and the like; For example, vinyl esters such as vinyl chloride, vinyl acetate, vinyl benzoate and the like, for example, ethylene-based olefins such as ethylene, propylene and butylene;
For example, use of vinyl ketones such as vinyl methyl ketone and vinyl hexyl ketone; vinyl monomers such as vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl inbutyl ether alone or in combination Can be.

When a crosslinked styrene resin or the like is used, a compound having two or more polymerizable double bonds is mainly used as a crosslinking agent. For example, aromatic divinyl compounds such as divinylbenzene and divinylnaphthalene; double bonds such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, and 1,3-butanediol dimethacrylate
Carboxylic acid esters; divinyl compounds such as divinylaniline, divinyl ether, divinyl sulfide and divinyl sulfone; and compounds having three or more vinyl groups can be used alone or as a mixture.
In particular, it is preferable to add a polar resin such as a copolymer of styrene and (meth) acrylic acid, a maleic acid copolymer, and a saturated polyester resin.

When a pressure fixing system is used for fixing a toner image, the binder resin for the toner may be a low molecular weight polyethylene, a low molecular weight polypropylene, an ethylene-vinyl acetate copolymer, -Acrylate copolymer, higher fatty acid, polyamide resin,
It is preferable to use a polyester resin. These are preferably used alone or as a mixture. In particular, when the toner used in the present invention is used by a direct polymerization method, it is preferable to use a toner having no polymerization inhibition and having no solubilized substance in an aqueous system.

The following colorants are used for forming the toner used in the image forming apparatus of the present invention. First, as a black colorant, carbon black, which is toned to black using a yellow / magenta / cyan colorant shown below, is used. As described above, the image forming apparatus of the present invention employs a plurality of developing devices each including a toner of each color. In particular, the excellent effects of the present invention can be obtained.

As the yellow colorant, for example, compounds represented by condensed azo compounds, isoindolinone compounds, anthraquinone compounds, azo metal complexes, methine compounds and allylamide compounds are used. Specifically, C.I.
I. Pigment Yellow 12, 13, 14, 15, 1
7, 62, 74, 83, 93, 94, 95, 97, 10
9, 110, 111, 120, 127, 128, 12
9, 147, 168, 174, 176, 180, 18
1, 191 and the like are preferably used.

Examples of the magenta colorant include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinone compounds, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds and perylene compounds. In particular,
C. I. Pigment Red 2, 3, 5, 6, 7, 23,
48: 2, 48: 3, 48: 4, 57: 1, 81: 1,
144, 146, 166, 169, 177, 184, 1
85, 202, 206, 220, 221, 254 are particularly preferred.

As the cyan coloring agent, copper phthalocyanine compounds and derivatives thereof, anthraquinone compounds, basic dye lake compounds and the like can be used. Specifically, C.I. I.
Pigment Blue 1, 7, 15, 15: 1, 15: 2,
15: 3, 15: 4, 60, 62, 66, etc. can be particularly preferably used.

These colorants may be used alone or in combination.
Further, it can be used in a solid solution state. These colorants may be appropriately selected in terms of hue angle, saturation, brightness, weather resistance, OHP transparency, and dispersibility in toner. The colorant is generally used in an amount of 1 to 20 parts by weight based on 100 parts by weight of the binder resin.

The toner that can be used in the image forming apparatus of the present invention may be one in which inorganic fine powder is added as an external additive to the surface of toner particles. As the inorganic fine powder that can be used at this time, for example, alumina, titanium oxide,
In addition to inorganic oxides such as silica, zirconium oxide and magnesium oxide, inorganic fine particles such as silicon carbide, silicon nitride, boron nitride, aluminum nitride, magnesium carbonate, organosilicon compounds and the like can be mentioned. Among them, alumina, titanium oxide, zirconium oxide, magnesium oxide or a silica-treated fine particle thereof, silicon nitride, an organosilicon compound, etc., can be used for toner having a stable charging characteristic without being affected by temperature and humidity. Is preferred because Further, it is preferable to use alumina or titanium oxide fine particles, or silica surface-treated fine particles thereof, since the fluidity of the toner can be improved. Although there is no particular limitation on the production method, a method of oxidizing a halide or an alkoxide in a gas phase, or a method of producing while hydrolyzing in the presence of water can be used. Low-temperature baking that does not cause coagulation of the particles is preferred.

In the present invention, in particular, spherical particles made of amorphous or anatase type titanium oxide fired at a low temperature and amorphous or γ type alumina are added because they are spherical and easily dispersed in primary particles. Preferably. The term “spherical particles” as used herein means particles having a ratio of a major axis diameter to a minor axis diameter of 1.5 or less, more preferably 1.3 or less, in a dispersed state on the toner surface. In order for the spherical particles to move moderately on the toner surface,
SF-1 is 130 or less, preferably 125 or less.

Further, the inorganic fine powder to be externally added to the surface of the toner particles is preferably subjected to a hydrophobizing treatment in order to reduce the dependence of the charge amount applied to the toner on the environment such as temperature and humidity, and It is preferable to prevent separation from the toner surface. As the hydrophobizing agent at this time, for example,
Coupling agents such as silane coupling agents, titanium coupling agents, and aluminum coupling agents; and oils such as silicone oils, fluorine-based oils, and various modified oils. Among the hydrophobizing agents listed above,
In particular, the coupling agent easily reacts with the residual groups on the fine powder or the adsorbed water to easily achieve uniform treatment, and is preferable in terms of stabilizing the charge of the toner and imparting fluidity. Particularly preferably, alumina or titanium oxide fine particles subjected to surface treatment while hydrolyzing a silane coupling agent are extremely effective in terms of stabilizing charging and imparting fluidity.

Further, the degree of hydrophobicity of the inorganic fine powder used as an external additive and subjected to the hydrophobic treatment by the above method is preferably 20 to 80%, more preferably 40 to 80%.
%% That is, the degree of hydrophobicity of the inorganic fine powder is 2
If it is less than 0%, the charge amount is greatly reduced due to long-term storage under high humidity, so that a charging promotion mechanism on the hardware side is required, which complicates the apparatus. On the other hand, the degree of hydrophobicity is 80%
If the ratio exceeds the above, it is difficult to control the charging of the inorganic fine powder itself, and as a result, the toner is likely to be charged up under low humidity.

The inorganic fine powder subjected to the hydrophobic treatment is 0.01 to 0.4 μm, preferably 0.015 to 0.4 μm.
It is preferable that the particles have an average dispersed particle diameter of 0.2 μm in terms of imparting fluidity of the toner and preventing separation from the toner surface during durability. That is, when the toner having an average dispersed particle size of less than 0.01 μm is used, it is too small to be easily embedded in the surface of the toner particles, and the toner changes. Conversely, the stability tends to decrease. On the other hand, when the thickness exceeds 0.4 μm, it is difficult to obtain sufficient fluidity of the toner, and the toner tends to be non-uniformly charged. As a result, toner scattering and fogging of an image are likely to occur.

It is preferable that the hydrophobic inorganic fine powder used as an external additive of the above-mentioned toner has a light transmittance of 40% or more at a light length of 400 nm.
That is, the inorganic fine powder used above, even if the primary particle diameter is small, when actually contained in the toner, is not necessarily dispersed in the state of primary particles, secondary particles May be present. Therefore,
No matter how small the primary particle diameter is, the effect of the present invention described above may be reduced if the effective diameter acting as a secondary particle is large. However, the higher the light transmittance at 400 nm, which is the lower limit wavelength in the visible region, the smaller the secondary particle size, the better the results in terms of the fluidity-imparting ability and the sharpness of the OHP projected image in the case of color toner. it can. The reason for selecting 400 nm is a boundary region between ultraviolet and visible light, and since it is said that particles having a particle diameter of 以下 or less of the light wavelength are transmitted, the transmittance at wavelengths longer than that naturally increases, It doesn't make much sense.

As a method for producing the above-mentioned hydrophobic inorganic fine powder, the inorganic fine particles are mechanically dispersed in the presence of water so as to have a primary particle size, and the surface treatment is carried out while hydrolyzing the coupling agent. Is preferred. According to such a production method, coalescence of the particles hardly occurs, and a charge repulsion action between the particles by the treatment works, so that the fine particles are surface-treated in a substantially primary particle state, which is preferable. In addition, in this method, when surface treatment is performed while hydrolyzing the coupling agent in the presence of water, a mechanical force for dispersing the fine particles into the primary particles is applied, so that chlorosilanes and silazanes are used. It is not necessary to use a coupling agent that generates a gas, and it is also possible to use a high-viscosity coupling agent that cannot be used because the particles are united or a silicone oil can be used in combination. The effect of the conversion is enormous.

The coupling agent may be any one of a silane coupling agent, a titanium coupling agent and the like, and particularly preferably used is a silane coupling agent represented by the following general formula. Can be.

Embedded image (Where R is an alkoxy group, m is an integer of 1 to 3,
Y: a hydrocarbon group including an alkyl group, a vinyl group, a glycidoxy group, and a methacryl group, and n is an integer of 1 to 3. )

Examples of such a material include vinyltrimethoxysilane, vinyltriethoxysilane, γ-
Methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, methyltrimethoxysilane, methyltriethoxysilane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane , N
-Hexadecyltrimethoxysilane, 1-octadecyltrimethoxysilane, and the like. More preferably, a compound represented by the following formula may be used.

[0061]

Embedded image

Here, when a in the above general formula is smaller than 4, the treatment becomes easy, but sufficient hydrophobicity cannot be achieved. When a is larger than 12, hydrophobicity is sufficient,
There is a tendency that coalescence between particles increases and the ability to impart fluidity is reduced. On the other hand, if b in the above general formula is greater than 3, the reactivity will decrease, and the hydrophobicity will not be sufficiently achieved. Therefore, a in the above general formula
Is preferably 4 to 12, preferably 4 to 8, and b is 1 to 3, preferably 1 or 2. The processing amount is 1 to 50 parts by weight based on 100 parts by weight of the inorganic fine powder.
In order to enable uniform treatment without unifying the parts by weight and particles, the content is more preferably 3 to 40 parts by weight, and the degree of hydrophobicity is 20 to 98%, preferably 30 to 90%. More preferably, it may be adjusted so as to be 40 to 80%.

Further, the toner used in the image forming apparatus of the present invention may be further used together with the above-mentioned spherical fine powder.
It is effective to use a non-spherical inorganic fine powder in combination. For improving charge stability, developability, fluidity and storage stability, for example,
It is preferably one selected from silica, alumina, titania, and double oxides thereof. In particular, silica is preferred in that coalescence of primary particles can be controlled to some extent arbitrarily by oxidizing conditions such as a starting material and temperature. For example, as the silica used in this case,
A so-called dry method produced by vapor phase oxidation of silicon halide or alkoxide, or a so-called wet silica produced from dry silica and alkoxide called fumed silica, water glass, etc. can be used, surface,
And there are few silanol groups inside the silica fine powder,
Further, dry silica having less production residues such as Na ₂ O and SO ₃ ^2- is more preferable. In the case of fumed silica, it is also possible to obtain a composite fine powder of silica and another metal oxide by using another metal halide such as aluminum chloride and titanium chloride together with a silicon halide in the manufacturing process. And also includes them.

Further, as the shape of the non-spherical inorganic fine powder, a shape having a bent portion instead of a simple non-spherical shape such as a rod shape or a column shape is the other external additive described above. It is more preferable that the spherical inorganic fine particles can be prevented from being embedded in the surface of the toner, and that the developer can be prevented from being closely packed, so that the change in the bulk density of the developer can be reduced.

The term "non-spherical particles" as used herein means that the major axis diameter of the toner is 2.0 times or more the minor axis diameter, preferably 3.0 times or more, and more than the other spherical fine particles. Is more desirable. Further, contrary to the above-mentioned spherical particles, it is preferable that the non-spherical particles do not move much on the toner in order to maintain the spacer function.
May be greater than 130, preferably greater than 150.

The amount of the spherical particles is 0.1 to 2 parts by weight, preferably 0.2 to 2 parts by weight in terms of imparting fluidity, to 100 parts by weight of the toner in order to stabilize the charge amount of the toner.
~ 2 parts by weight, more preferably 0.2 ~
It is preferable to use 1.5 parts by weight. On the other hand, in order to stabilize the bulk density of the developer, the non-spherical particles contain 0.3 to 3 parts by weight,
Preferably, it is 0.5 to 3 parts by weight in terms of prevention of embedding of spherical particles, more preferably 0.5 to 2 parts by weight for storage stability under high humidity, and 0 to 3 parts by weight for OHP permeability. .
It is desirably 5 to 1.5 parts by weight.

The toner usable in the present invention has a primary particle size of 50 to improve transferability and / or cleaning performance.
It is also a preferable embodiment to further add inorganic or organic particles having a spherical shape or more having a specific surface area of at least nm (preferably less than 50 m ² / g). For example, spherical silica particles, spherical polymethylsilsesquioxane particles, spherical resin particles and the like are preferably used.

In the toner used in the image forming apparatus of the present invention, other additives such as Teflon (registered trademark) powder, zinc stearate powder, polyvinylidene fluoride, etc. are used as long as they do not substantially adversely affect the toner. Lubricant powders such as powders; abrasives such as cerium oxide powders, silicon carbide powders, strontium titanate powders;
An anti-caking agent such as aluminum oxide powder, or
For example, a conductivity-imparting agent such as carbon black powder, zinc oxide powder, tin oxide powder, or the like, or a small amount of reverse polarity organic-like particles and inorganic fine particles can be used as a developability improver.

In order to achieve the formation of a high quality image with the image forming apparatus of the present invention, it is necessary to use yellow,
The weight average diameters of the magenta, cyan, and black toners are 1 to 9 μm, respectively.
The thickness is preferably 8 μm, and 3 to 8 μm to prevent fog and scattering. That is, when a toner having toner particles having a weight average diameter of less than 1 μm is used for image formation, a large amount of untransferred toner is present on the photoreceptor due to a decrease in transfer efficiency.
Further, the toner tends to cause non-uniform unevenness of an image due to fogging and transfer failure, and is not preferable as the toner used in the present invention. On the other hand, if the weight average diameter of the toner particles exceeds 9 μm, characters and line images are likely to scatter.

The average particle size and the particle size distribution of the toner can be measured by using a Coulter Counter TA-II or a Coulter Multisizer (manufactured by Coulter) or the like, and an interface (manufactured by Nikkaki) for outputting the number distribution and volume distribution, and PC98.
01 personal computer (NEC) was connected for measurement. As the electrolyte solution used at this time, a 1% NaCl aqueous solution prepared using primary sodium chloride can be used. As such, for example, ISOT
ON R-II (manufactured by Coulter Scientific Japan).

As a specific measuring method, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersion in 100 to 150 ml of the above aqueous electrolyte solution, and the sample to be measured is further added. 2 to 20
Add mg. Then, the electrolyte solution in which the sample was suspended was subjected to dispersion treatment for about 1 to 3 minutes using an ultrasonic disperser, and then 100 μm was used as an aperture by the Coulter counter.
Using an m aperture, the volume of toner of 2 μm or more,
The number is measured to calculate the volume distribution and the number distribution. Then, a volume-based weight average particle size (D ₄ ) obtained from the volume distribution and a number-based length average particle size (D ₁ ) obtained from the number distribution were obtained.

Next, the carrier constituting the two-component developer used in the image forming apparatus of the present invention will be described in detail. In the present invention, a spherical magnetic coated carrier having a weight average particle diameter (50% average particle diameter) of 15 to 60 μm is used as the carrier. More preferably, the weight-average particle diameter is 20 to 45 μm, and carrier particles smaller than 22 μm are 20% or less, preferably 0.05 to 15%
More preferably, it is 0.1 to 12%, and carrier particles smaller than 16 μm are 3% or less, preferably 2% or less,
More preferably, a spherical magnetic coated carrier having a sharp particle size distribution of 1% or less is used. Further, the amount of coarse powder of the carrier having a size of 62 μm or more closely correlates with the sharpness of an image. However, it is preferable to use a carrier in which the amount of such coarse powder is controlled to about 0.2 to 10%. If the particle size distribution is out of the range, the change in bulk density is large, and it is difficult to achieve a suitable degree of compression. Furthermore, when the amount of fine powder is large, carrier adhesion is likely to occur. Conversely, when the amount of coarse powder is large, problems such as fog and image density reduction may occur.

The carrier used in the present invention is a spherical magnetic coated carrier, and the material of the carrier core material is a magnetic metal powder or a magnetic powder obtained by dispersing a magnetic metal powder or a magnetic powder in a binder resin in iron powder or ferrite. Resin particles and the like. In particular,
It is preferable to use polymerized resin particles containing magnetite produced by a polymerization method, since a change in bulk density is less likely to occur when used as a developer. Furthermore,
From the viewpoint that the magnetic properties can be arbitrarily controlled, magnetite-containing polymerized resin particles containing a nonmagnetic metal oxide are particularly preferable. The non-magnetic metal oxide used at this time is, for example, Fe ₂ O ₃ , Al ₂ O ₃ , Si
It is preferable to use O ₂ , CaO, SrO, MnO, or a mixture thereof.

In this case, the amount of magnetite is
It is preferably 0.2 to 0.98 parts based on all metal oxides. Further, it is preferable to use magnetite that has been subjected to a lipophilic treatment, if necessary. At that time, in order to improve the hydrophobicity, lipophilic treatment may be performed after surface treatment with silica, alumina, titania or the like.
Similarly, it is preferable to use a non-magnetic oxide that has been subjected to lipophilic treatment.

As the resin for coating the surface of the magnetic carrier core material particles as described above, a specific crosslinkable silicone resin, a fluorine atom-containing resin, a copolymer of a fluorine atom-containing resin and an acrylic resin, or A mixture of these can be preferably used. Further, as a method of forming a resin coating layer on the magnetic carrier core material particle surface,
The resin composition as described above is dissolved in an appropriate solvent, and the magnetic carrier core material particles made of the materials mentioned above are immersed in the obtained solution, and thereafter, the solvent is removed, dried, and high-temperature baked. A method of suspending magnetic carrier core particles in a fluidizing system, spraying and applying a solution in which the resin composition is dissolved, drying and baking at a high temperature; Any method such as mixing with a powder or an aqueous emulsion can be used.

As a particularly preferred coating method, water is used in an amount of 0.1 to 5 parts by weight, preferably 100 parts by weight of a solvent containing 5% by weight or more, preferably 20% by weight or more of a polar solvent such as ketones and alcohols. There is a method using a mixed solvent containing 0.3 to 3 parts by weight. According to this method, the reactive silicone resin can be firmly adhered to the magnetic carrier core particles. In the above method, if the amount of water is less than 0.1 part by weight, the hydrolysis reaction of the reactive silicone resin is not sufficiently performed, and a thin and uniform coating on the surface of the magnetic carrier core material particles becomes difficult. If the amount exceeds the above range, it becomes difficult to control the reaction, and conversely, the coating strength decreases.

According to the present invention, a two-component developer is prepared by mixing a carrier and a toner. 12% by weight, more preferably 5 to 10% by weight
In general, good results are obtained. If the toner concentration is less than 1% by weight, the image density tends to be low.

The image forming apparatus according to the present invention comprises: a latent image carrier for carrying an electrostatic latent image; a latent image forming means for forming an electrostatic latent image on the initially charged latent image carrier; A rotatable developing device for carrying a two-component developer having a non-magnetic toner and a magnetic carrier disposed opposite to the latent image carrier, transporting the developer to a developing position, and developing the electrostatic latent image into a visible image Developer means having a plurality of magnetic field generators fixedly provided inside the developer carrier, and a coil ratio of the non-magnetic toner and the magnetic carrier of the two-component developer. A developing device having a toner concentration control means for detecting a change in the magnetic permeability of the developer using the above, and controlling the toner concentration in the developer based on the change;
The latent image carrier (photosensitive drum) among them will be described below. As the photosensitive drum, any of conventionally known structures can be used. In a preferred embodiment, a conductive substrate, a charge generation layer on the substrate, and a charge transport layer on the charge generation layer are preferable. Those laminated sequentially are mentioned.

Examples of the conductive substrate include metals such as aluminum and stainless steel, aluminum alloys and indium oxide-tin oxide alloys, plastics having a coating layer of these metals and alloys, paper impregnated with conductive particles, and the like. Plastic, cylindrical cylinders such as plastics with conductive polymers, and films are used. On these conductive substrates, it is possible to improve the adhesion of the photosensitive layer provided thereon, improve the coating properties, protect the substrate, cover defects on the substrate, improve the charge injection property from the substrate, and protect the photosensitive layer from electrical destruction. An undercoat layer may be provided for protection or the like. The undercoat layer is made of polyvinyl alcohol, poly-N-vinylimidazole,
It is formed of materials such as polyethylene oxide, ethyl cellulose, methyl cellulose, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, casein, polyamide, copolymerized nylon, glue, gelatin, polyurethane, and aluminum oxide. The film thickness is usually about 0.1 to 10 μm, preferably about 0.1 to 3 μm.

The charge generation layer is made of an azo pigment, a phthalocyanine pigment, an indigo pigment, a perylene pigment, a polycyclic quinone pigment, a squarylium pigment, a pyrylium salt,
By applying a coating liquid in which a charge generating substance such as a thiopyrium salt, a triphenylmethane dye, and an inorganic substance such as selenium or amorphous silicon is dispersed in an appropriate binder resin,
Alternatively, it is formed by vapor deposition or the like. The binder resin used at this time can be selected from a wide range of binder resins, for example, polycarbonate resin, polyester resin, polyvinyl butyral resin, polystyrene resin, acrylic resin, methacryl resin, phenol resin, silicone resin, epoxy resin, And vinyl acetate resin. Further, the amount of the binder resin contained in the charge generation layer,
It is in the range of 80% by weight, preferably 0 to 40% by weight.
The thickness of the charge generation layer is 5 μm or less,
２2 μm is preferred.

The charge transport layer provided on the charge generation layer has a function of receiving charge carriers from the charge generation layer in the presence of electrolysis and transporting the carriers. Such a charge transporting layer is formed by dissolving a charge transporting substance in a solvent together with a binder resin if necessary, and coating the charge transporting material. As the charge transport substance, biphenylene, anthracene,
Polycyclic aromatic compounds having a structure such as pyrene or phenanthrene; indole, carbazole, oxadiazole,
Nitrogen-containing cyclic compounds such as pyrazoline; hydrazine compounds;
Styryl compound; inorganic compounds such as selenium, selenium-tellurium, amorphous silicon, and cadmium sulfide; and these can be used as appropriate.

Examples of the binder resin for dispersing these charge transporting substances include resins such as polycarbonate resin, polyester resin, polymethacrylate, polystyrene resin, acrylic resin and polyamide resin, poly-N-vinylcarbazole and polyvinyl resin. Organic photoconductive polymers such as anthracene are exemplified.

Further, it is preferable that lubricant particles are contained in the surface layer of the photosensitive drum. The reason is that if lubricant particles are included, the friction between the photosensitive member and the charging member during charging is reduced, so that the charging nip can be expanded and the charging characteristics can be improved. As the lubricant particles, it is particularly preferable to use a fluorine-based resin, a silicone resin, or a polyolefin having a low critical surface tension. More preferably, ethylene tetrafluoride resin (PTFE) is preferred. In this case, the addition amount of the lubricant particles is 2 to 50% by weight, preferably 5 to 40% by weight in terms of the binder resin.
If it is less than 2% by weight, the amount of lubricant particles is not sufficient,
If it exceeds 0% by weight, the resolution of the image and the sensitivity of the photoconductor may be greatly reduced.

Particularly suitable lubricant particles include fluorine atom-containing resin fine particles. As the fluorine atom-containing resin used at this time, for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, tetrafluoroethylene-hexa There are fluoropropylene copolymers, tetrafluoroethylene-ethylene copolymers, and tetrafluoroethylene-hexafluoropropylene-perfluoroalkylvinyl ether copolymers, and one or more selected from these are used. be able to. Incidentally, commercially available fine particles of fluorine-containing resin can be used as they are. In particular,
Resins having a molecular weight of 3,000 to 5,000,000 can be used, and 0.01 to 10 μm, preferably 0.05 to 2.0 μm.
Fine particles having a diameter of μm are preferred.

When the photosensitive drum is formed, for example, the above-mentioned fine particles of the fluorine atom-containing resin, the charge generating material and the charge transporting material are dispersed and contained in a binder resin having a film forming property. It is preferable to form a protective solution and a photosensitive layer by forming a working solution and sequentially forming a film on the conductive substrate using the working solution.

Next, an image forming process by the image forming apparatus of the present invention will be described. In the image forming apparatus of the present invention, the two-component developer having the nonmagnetic toner and the magnetic carrier is circulated and conveyed on the developer carrier (developing sleeve), and the latent image carrier (photoconductor drum) and the developing sleeve are moved. In the facing development area, the latent image held on the photosensitive drum is developed with a two-component developer on the development sleeve,
A toner image is formed and visualized.

Here, the magnetic characteristics of the carrier are affected by a plurality of magnetic field generators fixedly provided inside the developing sleeve, for example, a magnet roller built in the developing sleeve, and the developing characteristics of the developer and the transport are Has a significant effect on sex. In the image forming apparatus of the present invention, the two-component developer is circulated and conveyed on the developing sleeve by fixedly disposing the magnet roller incorporated in the developing sleeve, and rotating the developing sleeve by itself. The electrostatic latent image held on the surface of the photosensitive drum is developed with a developer. In the image forming apparatus of the present invention, (1)
The magnet roller has a pole configuration having repulsive poles,
(2) The magnetic flux density in the development area is 500 to 1200 Gauss, and (3) σ _{1000 of the} carrier is 20 to 50 Am
^When it is ² / kg, the uniformity of the image and the gradation reproducibility are excellent, which is preferable.

In the image forming apparatus of the present invention, it is preferable to apply a developing bias in the developing area to develop the electrostatic latent image with the toner constituting the two-component developer. Hereinafter, particularly preferred developing bias will be described in detail. In the image forming apparatus of the present invention, in order to form a developing electric field in a developing region where the photosensitive drum and the developing sleeve face each other,
A developing voltage having a discontinuous AC component as shown in FIG. 2 is applied to the developer carrier, whereby the latent image held on the photosensitive drum is held on the developing sleeve. It is preferable to develop with a toner of an agent.
The developing voltage applied at this time is, specifically, a first voltage that directs the toner from the photosensitive drum to the photosensitive drum in the developing area, and a second voltage that directs the toner from the developing sleeve to the photosensitive drum. Applying a second voltage and a third voltage between the first voltage and the second voltage to the developing sleeve;
A developing electric field is formed between the photosensitive drum and the developing sleeve.

Further, the total time for applying the above-described first voltage for directing the toner from the photosensitive drum to the developing sleeve and the second voltage for directing the toner from the developing sleeve to the photosensitive drum, that is, AC The time during which the third voltage between the first voltage and the second voltage is applied to the developing sleeve, that is, the time during which the component is acting (T ₁ ),
It is preferable to lengthen the time during which the AC component is at rest (T ₂ ). With this configuration, as described below, the toner can be rearranged on the photosensitive drum, so that the latent image can be reproduced more faithfully.

Specifically, between the photosensitive drum and the developing sleeve in the developing area, an electric field in which the toner travels from the photosensitive drum to the developing sleeve and an electric field in which the toner travels from the developing sleeve to the photosensitive drum are formed at least once. After that, in the image portion of the photosensitive drum, the toner moves from the developing sleeve to the photosensitive drum, while in the non-image portion of the photosensitive drum, the toner forms an electric field from the photosensitive drum to the developing sleeve for a predetermined time. In this method, the latent image held on the photosensitive drum is developed with the toner of the two-component developer carried on the developing sleeve. The electric field from the photosensitive drum to the developing sleeve and the developing sleeve from than the total time of the time for forming the electric field in which the toner is directed (T ₁₎ to the photosensitive drum, the toner is developed scan in the image portion of the photosensitive drum Directed from over blanking the photosensitive drum, it is preferable to increase towards the time to form an electric field in which the toner is directed to the developing sleeve from the photosensitive drum (T ₂₎ in the non-image portion of the photosensitive drum.

In the developing method in which the above-described specific developing electric field, that is, an alternating electric field is formed and developed, when the developing is performed using the developing electric field in which the alternation is periodically turned off, carrier adhesion is more likely to occur. I found it difficult. The reason for this is not yet clear, but is considered as follows. That is, in the conventional continuous sine wave or rectangular wave, when the electric field strength is increased in order to achieve a high image density, the toner and the carrier integrally reciprocate between the photosensitive drum and the developing sleeve. As a result, the carrier is strongly rubbed against the photosensitive drum, and carrier adhesion occurs. This tendency was more remarkable as the amount of the fine powder carrier contained in the carrier was larger.

However, when a specific AC electric field as described above is applied, the toner or carrier reciprocates between the developing sleeve and the photosensitive drum in one pulse so that the reciprocating motion cannot be completed. When the potential difference V _cont between the surface potential of the photosensitive drum and the DC component of the developing bias is V _cont <0, V _cont acts to cause the carrier to fly from the developing sleeve, but the magnetic characteristics of the carrier and the magnetic roller By controlling the magnetic flux density in the development area, carrier adhesion can be prevented and V _cont
If> 0, the magnetic field force and V _cont work to attract the carrier to the developing sleeve side, and no carrier adhesion occurs.

The magnetic characteristics of the carrier are affected by the magnet roller incorporated in the developing sleeve, and greatly affect the developing characteristics and transportability of the developer. In the present invention, on a developing sleeve having a built-in magnet roller, the magnet roller is fixed and the developing sleeve is rotated alone, and a two-component developer composed of a carrier composed of magnetic particles and an insulating color toner is placed on the developing sleeve. When developing the electrostatic latent image held on the surface of the electrostatic latent image holding body with the two-component developer, the magnet roller has a polar configuration having a repulsive pole; ) The magnetic flux density in the development area is set to 500 to 1,200 gauss, and (3) σ _{1000 of the} carrier is set to ²⁰ to 50 Am ² / kg.
In this case, the color copying is excellent in image uniformity and gradation reproducibility, and is suitable.

If σ ₁₀₀₀ exceeds 50 Am ² / kg (for an applied magnetic field of 1,000 Oersteds),
At the time of development, the brush-like spikes formed by the carrier and the toner on the developing sleeve facing the electrostatic latent image on the photoreceptor are firmly tightened, and the gradation and the reproduction of halftone are deteriorated. On the other hand, if it is less than 20 Am ² / kg, it becomes difficult to hold the toner and the carrier on the developing sleeve, and the problem that the adhesion of the carrier and the scattering of the toner are deteriorated easily occurs.

FIG. 3 is a schematic view showing an example of the image forming apparatus of the present invention. In this example, a first image forming unit 34, a second image forming unit 35,
Third image forming unit 36 and fourth image forming unit 3
7 are provided side by side, and images of different colors are formed on the transfer material through the processes of latent image formation, development of the latent image, and transfer.

The configuration of each image forming unit provided in the above image forming apparatus will be described by taking the image forming unit 36 as an example. The image forming unit 36 is adjacent to an electrophotographic photosensitive drum 33 of 80φ serving as a latent image carrier, and the photosensitive drum 33 is configured to rotate in the direction of the arrow in FIG. . In this example, a carrier brush charger that is in contact with the photosensitive drum 33 and that is carried on a 16φ sleeve is used as the primary charger 46 as a charging unit. Reference numeral 31 denotes an exposure device as a latent image forming means for forming an electrostatic latent image on the photosensitive drum 33 whose surface is uniformly charged by the primary charger 46. Reference numeral 36 denotes a developing device as developing means for developing a latent image formed on the photosensitive drum 33 to form a color toner image, and holds a color toner. A transfer unit 44 transfers the color toner image formed on the surface of the photosensitive drum 33 to the surface of the transfer material conveyed by the transfer material carrier 46. The transfer unit 44 includes a transfer material carrier. The transfer corona can be applied to the back surface of the transfer member 40.

As shown in FIG. 3, the image forming apparatus according to the present invention has the same configuration as the above-described image forming unit 36, and forms images of different colors of the color toner held in the developing device. The unit 34, the image forming unit 35, the image forming unit 36, and the image forming unit 37 are provided together with four image forming units. For example, yellow toner is used for the first image forming unit 34, magenta toner is used for the second image forming unit 35, cyan toner is used for the third image forming unit 36, and black toner is used for the fourth image forming unit 37. In the transfer sections of these image forming units, the transfer of each color toner image to a transfer material is sequentially performed. In this step, each color toner image is superimposed by one transfer of the transfer material on the same transfer material while adjusting the registration.
When the transfer is completed, the transfer material carrier 40 is
The transfer material is separated from the top and sent to the fixing device 32 by a conveyance means such as a conveyance belt, and a final full-color image is obtained by a single fixing.

The fixing device 32 comprises a pair of 40-φ fixing rollers and a 30-φ pressing roller, and has a heating means inside the fixing roller. The web for removing dirt on the fixing roller may not be provided. The unfixed color toner image transferred onto the transfer material passes through a pressure contact portion between the fixing roller and the pressure roller of the fixing device 32, and is fixed on the transfer material by the action of heat and pressure.

As the transfer means, instead of a transfer corona provided opposite to the back side of the transfer material carrier, a transfer roller in the form of a blade or a roller abuts on the back side of the transfer material carrier. It is possible to use a contact transfer unit capable of directly applying the transfer device.

Reference numeral 56 in FIG. 3 denotes a toner concentration detection sensor which detects the change in the magnetic permeability of the developer by using the inductance of the coil to determine the mixing ratio between the non-magnetic toner and the magnetic carrier of the two-component developer. This is a toner concentration control unit for controlling the toner concentration in the developer by a change, and has a coil (not shown) therein.

Hereinafter, methods for measuring various values used in the present invention will be described. (1) Measurement of Magnetic Properties of Carrier A BHU-60 type magnetization measurement apparatus (manufactured by RIKEN) is used. About 1.0 g of a sample to be measured is weighed, packed into a cell having an inner diameter of 7 mm and a height of 10 mm, and set in the above-mentioned apparatus. In the measurement, an applied magnetic field is gradually applied to change the maximum to 1,000 Oe. Next, the applied magnetic field is reduced, and finally a hysteresis curve of the sample is obtained on the recording paper. From this, σ ₁₀₀₀ , residual magnetization, and coercive force are obtained.

(2) Measurement of Apparent Density Using a powder tester, a sieve having an opening of 75 μm was vibrated at an amplitude of 1 nm and passed through the sieve to measure the apparent density.

(3) Measurement of the degree of compression Using a powder tester, the tap density P after 180 reciprocations up and down was measured and calculated by the following equation.

(Equation 1)

(4) Method of Measuring SF-1 of Toner Particles, External Additive of Toner and Carrier Particles A sample to be measured is, for example, FE-SEM manufactured by Hitachi, Ltd.
5,000 times for toner particles, 50,000 times for toner external additives, 3,000 times for carrier particles, and randomly sample 100 toner or carrier particles each. The image information was introduced into, for example, an image analyzer (Luzex III) manufactured by Nireco via an interface and analyzed. Then, in the present invention, the value obtained from the following equation is used as the shape factor SF−
1 and the value of the shape factor SF-1 is 100 ≦ SF−1 ≦ 1
A case of 30 was defined as a spherical particle, and a case of 130 <SF-1 was defined as a non-spherical particle.

[0105]

(Equation 2)

[0106]

EXAMPLES Examples of the present invention will be shown below, but the present invention is not limited to these examples. “Parts” indicates “parts by weight”.

(Production Example 1 of Developing Carrier) After mixing and dispersing phenol / 37 wt% formaldehyde monomer (50:75) in an aqueous medium, magnetite particles surface-treated with alumina were mixed with isopropoxy based on the weight of the monomer. 700 parts of magnetic powder hydrophobized with triisostearoyl titanate and 300 parts of nonmagnetic hematite particles hydrophobized with isopropoxytriisostearoyl titanate were uniformly dispersed. The monomer was polymerized while appropriately adding ammonia thereto to obtain a spherical magnetic resin carrier core material containing magnetic particles. The surface of the carrier core material was modified using 0.3 parts of an aminosilane coupling agent represented by the following formula (b).

[0108]

Embedded image

On the other hand, toluene 20 parts, butanol 20
Parts, 20 parts of water and 40 parts of ice in a four-necked flask, and while stirring, 15 mol of CH ₃ SiCl ₃ and (CH ₃ ) ₂ SiC
l ₂ is a mixture composed at a ratio of 10 moles added and 40 parts of the catalyst, the mixture was stirred an additional 30 minutes for 1 hour condensation at 60 ° C.. Thereafter, the siloxane was sufficiently washed with water and dissolved in a mixed solvent of toluene, methyl ethyl ketone and butanol to prepare a silicone varnish having a solid content of 10%.

The silicone varnish was prepared by adding 2.0 parts of ion-exchanged water to 100 parts of siloxane solids, and
2.0 parts of a curing agent (a) represented by the following formula and 2.0 parts of an aminosilane coupling agent (b) represented by the following formula
Was added at the same time to prepare a carrier coating solution I.

[0111]

Embedded image

While continuously applying a shearing stress to the carrier coating solution I, the toluene is volatilized and applied to 100 parts of the above-mentioned carrier core material so that the resin coating amount becomes 1 part. The coated carrier I was obtained. The resistance of the obtained carrier was 4 × 10 ¹³ Ω · cm. or,
SF-1 was 108, σ ₁₀₀₀ was 41 Am ² / kg, holding power was 60 Oersted, and weight average particle size was 33 μm.

(Production Example 2 of carrier for development) 30 parts of styrene-methyl methacrylate (70:30) copolymer 100 parts of magnetite (EPT-1000: manufactured by Toda Kogyo Co., Ltd.) 100 parts of the above components with a pressure kneader The mixture was melted and kneaded, and then pulverized and classified using a turbo mill and a classifier to obtain non-spherical developing carrier particles II having a weight average particle size of 37 μm. The resistance of this carrier is 4 × 10 ⁹ Ω · cm,
SF-1 was 158, σ ₁₀₀₀ was 57 Am ² / kg, holding power was 85 Oersted, and weight average particle size was 37 μm.

(Production Examples 3 and 4 of Developing Carrier) In Production Example 1 of the developing carrier, the resistance was 2 × 10 ¹³ Ω ·
cm, SF-1 is 118, σ ₁₀₀₀ is 42 Am ² / kg,
65 Oersted holding power and 13μ weight average particle size
m, a spherical coated carrier III for development and a resistance of 5 × 1
^{0 13 Ω · cm, SF-} 1 is 111, sigma ₁₀₀₀ is 42Am ²
/ Kg, a holding force of 62 Oe and a weight average particle diameter of 65 μm.

(Production Example 5 of Developing Carrier) In the same manner as in Production Example 1 of the developing carrier, except that a ferrite core material having an Mg—Mn—Sr—Fe composition was used, the resistance was 2 × 10 ¹⁰ Ω · cm, SF-1 is 109, σ ₁₀₀₀ 58
A carrier V having an Am ² / kg, a holding power of 5 Oersted, and a weight average particle size of 37 μm was obtained.

(Production Example 1 of Cyan Toner) 450 g of 0.1 M Na ₃ PO ₄ aqueous solution was charged into 710 g of ion-exchanged water, heated to 60 ° C., and then subjected to TK homomixer (manufactured by Tokushu Kika Kogyo). And stirred at 12,000 rpm. 68 g of a 1.0 M CaCl ₂ aqueous solution was gradually added thereto to obtain an aqueous medium containing fine calcium phosphate.

(Monomer) Styrene 165 g n-butyl acrylate 35 g (Colorant) C.I. I. Pigment Blue 15: 3 12 g On the other hand, after finely dispersing the above composition by a ball mill, (charge control agent) aluminum salicylate compound 2 g (polar resin) saturated polyether resin 10 g (release agent) ester wax (melting point 70 ° C.) 25 g was added. Using a TK homomixer heated to 60 ° C., the mixture was uniformly dissolved and dispersed at 12,000 rpm. Into this, 10 g of a polymerization initiator 2,2'-azobis (2,4-dimethylvaleronitrile) was dissolved to prepare a polymerizable monomer composition.

After adjusting the pH to 6 by adding dilute hydrochloric acid to the aqueous medium prepared above, the polymerizable monomer composition was charged, and the mixture was treated at 60 ° C. under a N ₂ atmosphere with a Clare mixer (M Technique). The mixture was stirred at 10,000 rpm for 10 minutes to granulate the polymerizable monomer composition. Thereafter, while stirring with a paddle stirring blade, the temperature was raised to 80 ° C., and the reaction was performed for 10 hours. After the completion of the polymerization reaction, the remaining monomer was distilled off under reduced pressure. After cooling, hydrochloric acid was added to dissolve the calcium phosphate, followed by filtration, washing with water, and drying to give a weight average particle size of 6.5.
Colored suspension particles having a sharp particle size distribution of μm were obtained.

100 parts of the obtained particles were treated with 10 parts of isobutyltrimethoxysilane in an aqueous medium to obtain a rutile-type hydrophobic titanium oxide having an average particle size of 0.03 μm and a BET of 150 m ² / g. Part, and an average particle size of 0.06 μm treated with 10 parts of hexamethyldisilazane, B
ET specific surface area is 35 m ² / g, SF-1 is 180
0.7 part of the non-spherical silica fine powder was externally added to obtain a suspension polymerization toner 1. SF-1 of the obtained toner was 109.

(Production Example 2 of Cyan Toner) Polyester resin obtained by condensing propoxylated bisphenol with fumaric acid and trimellitic acid 100 parts Phthalocyanine pigment 4 parts Aluminum compound of di-tert-butylsalicylic acid 4 Parts-Low molecular weight polypropylene 4 parts

The above composition was preliminarily mixed by a Henschel mixer, and melt-kneaded by a twin-screw extruder.
After cooling, the mixture was roughly pulverized to about 1 to 2 mm using a hammer mill, then pulverized by a pulverizer using an air jet method, and then classified to obtain a blue powder having a weight average particle diameter of 6.3 μm. Then, in the same manner as in Production Example 1 for cyan toner,
Titanium oxide and non-spherical silica having an SF-1 of 180 were externally added to obtain a cyan toner 2. Obtained cyan toner 2
SF-1 was 150.

(Production Example 3 of Cyan Toner) In Production Example 1 of cyan toner, SF-
Cyan Toner 3 was obtained in the same manner except that spherical silica fine powder of No. 1 was used. SF-1 of the obtained cyan toner 3 was 109.

(Production Example 4 of Cyan Toner) A cyan toner 4 was obtained in the same manner as in Production Example 1 of cyan toner except that silica fine powder was not externally added. SF-1 of the obtained cyan toner 2 was 110.

(Production Example of Yellow, Magenta, and Black Toner) In Production Example 1 of the cyan toner, P.I. Y. 93, a yellow toner 5, a magenta toner 6, and a black toner 7 were prepared in the same manner except that a quinacridone pigment was used as a magenta colorant and carbon black was used as a black colorant. The yellow toner 5 had an SF-1 value of 108 and a weight average particle size of 6.7 μm. The magenta toner 6 is SF
-1 was 111 and the weight average particle size was 7.0 μm. Further, the black toner 7 has an SF-1 value of 106
And the weight average particle size was 7.3 μm.

(Example 1) First, the above-prepared cyan toner 1 and developing carrier I were mixed at a toner concentration of 8% to form a two-component cyan developer (compression degree 11%, apparent density 1. 45) was produced. Table 1 shows the compositions of the developers used in Examples and Comparative Examples.

Next, the developing container of a commercially available copying machine CLC500 (manufactured by Canon) was modified as shown in FIG. 1 so that the developing sleeve rotated in the opposite direction to the photosensitive drum, and Using an image forming apparatus having a configuration in which a regulating blade is disposed, an image was formed using the developer prepared above. The conditions at that time were a development contrast of 200 V and an inversion contrast with fog of -150.
V, 23 ° C. using the cyan developer (containing cyan toner 1) prepared above using the AC electric field of FIG.
An image was formed under the condition of / 65%. In the present embodiment, FIG.
As described above, the inductance detection sensor 56 is provided near the developing sleeve of the developing device so that the magnetic permeability of the developer on the developing sleeve can be detected when the developing device is not at the developing position.

As described above, the two types of originals having the image area ratios of 30% and 4% are alternately used every 2,000 pages, and the toner density is measured every 5,000 pages while 30,000 pages are measured. Was continuously copied. About the obtained image,
The toner density, image density, and fog at each stage were measured by the methods described below, and the results are shown in Tables 2-1 to 2-3. As fixing device, both upper and lower rollers are 1.2μ
m of PFA (perfluoroalkoxy fluororesin) coated on the surface layer, and no fixing oil was used. As is clear from Tables 2-1 to 2-3, in the image forming apparatus according to the present embodiment, the toner density control is performed stably regardless of the original document, the image quality is good, and the image by continuous copying is obtained. It was found that the change was small and toner scattering was very good without any problem.

The above image density and fog were measured by the following methods. (1) Image density The image density was measured by Macbeth densitometer RD918 type (Macb
eth Densitometer RD918 ma
nufactured by Macbeth C
o. ) Was measured as the relative density of the image formed on plain paper.

(2) Fog The average reflectance Dr (%) of plain paper before image formation was measured using a reflectometer (“REFECTOM” manufactured by Tokyo Denshoku Co., Ltd.).
ETER ODEL TC-6DS "). On the other hand, a solid white image was formed on plain paper, and the reflectance Ds (%) of the solid white image was measured. Fog (%)
Was calculated from the following equation and evaluated according to the following criteria.

(Equation 3) （(Excellent): less than 0.4 (%) ○ (good): 0.4 or more and less than 0.8 (%) Δ (acceptable): 0.8 or more and less than 1.2 (%) × (bad): 1 .2 (%) or more

Comparative Example 1 An image was formed in the same manner as in Example 1 except that a non-spherical uncoated developing carrier II was used. , The image density and the toner density are both low,
Further, the state of occurrence of fog was also deteriorated. Therefore, the measurement was performed up to 15K, but the evaluation was stopped thereafter. This is because the carrier constituting the developer used in this comparative example is non-spherical, so that the bulk density of the developer is reduced and the actual amount of the carrier carried on the developing sleeve is reduced. In spite of the above, it is probable that the toner concentration was erroneously recognized in the detection by the inductance detection sensor 56 and the toner was not replenished. That is,
As a result of continuous image formation with insufficient toner amount,
It is presumed that the toner deterioration accelerated, the image density decreased, and the fog state appearing in the image also deteriorated.

Comparative Example 2 An image was formed in the same manner as in Example 1 except that the developing carrier III having a fine particle diameter of 13 μm was used. As a result, both the image density and the toner density decreased with the endurance, and cleaning failure occurred at 10K. Therefore, the evaluation was stopped. This is because the carrier particle constituting the two-component developer has a too small particle diameter, so that the transportability onto the developing sleeve is reduced. It is presumed that the toner concentration decreased and the carrier adhered to the photoreceptor.

Comparative Example 3 An image was formed in the same manner as in Example 1 except that the developing carrier IV having a large average particle diameter of 65 μm was used. As a result, fog became worse at 20K, and the evaluation was stopped thereafter. This is presumed to be due to the fact that the carrier diameter of the toner was reduced because the carrier diameter was too large, and the uniform mixing state of the two-component developer composed of the carrier and the toner was not maintained with the endurance. You.

Comparative Example 4 An image was formed in the same manner as in Example 1 except that the toner 2 having a non-spherical shape was used. The density and toner density were not stable, and both changed greatly, and the fog also worsened. This is presumed to be because the toner has a non-spherical shape, and the bulk density of the developer greatly changes. As a result, the detection by the inductance detection sensor 56 becomes inaccurate, and the toner concentration in the developer fluctuates. You.

(Example 2) In Example 1, the toner 1
The image was formed in the same manner as in Example 1 except that spherical toner 3 was used instead of the toner. As a result, the change in toner density and the change in image density were slightly larger than those in Example 1; Good results without problems were obtained. The difference between the toner density change and the image density change was slightly larger than that of the first embodiment. Unlike in the first embodiment, the toner density change and the image density change were caused by using spherical silica fine powder as an external additive of toner. It is presumed that the change in the bulk density of the agent was slightly larger than that in Example 1.

(Example 3) Image formation was performed in the same manner as in Example 1 except that spherical toner 4 to which silica was not externally added was used. It was at a level with no practical problems. The reason for the increase in fog is presumed to be that the mixing property between the toner and the carrier deteriorated because silica fine powder was not externally added to the toner.

(Example 4) In Example 1, Mg-M
An image was formed in the same manner as in Example 1 except that the carrier V using a ferrite core material having an n-Sr-Fe composition was used. As a result, the image density was slightly low, and fog was slightly conspicuous. There was no problem. This is because the ferrite carrier used in this example is heavier than the carrier 1 used in Example 1, and the weight of the ferrite carrier increases the damage to the toner mixed with the carrier. It is presumed that it became slightly inferior.

(Example 5) The cyan toner 1, yellow toner 5, magenta toner 6, and black toner 7 prepared above and the developing carrier I were each provided with a toner concentration of 8%.
Were mixed so that each color developer was prepared. The resulting developer was mounted on each of the four developing devices shown in FIG. 3, and 10,000 images were output. As a result, a good full-color image was stably obtained.

[0138]

Table 1 Main components of two-component developers used in Examples and Comparative Examples

[0139]

Table 2-1: Evaluation results (toner density)

[0140]

Table 2-2: Evaluation results (image density)

[0141]

[Table 4] Table 2-3: Evaluation results (fog)

[0142]

As described above, according to the present invention,
An image forming apparatus capable of accurately and accurately detecting toner concentration in a two-component developer by a very simple method and stably maintaining an optimum toner concentration even in long-term durability is provided. As a result, even in the case of continuous copying, a high-quality image free from fog and having a maintained image density can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus provided with a two-component magnetic brush developing device.

FIG. 2 shows a configuration of a developing voltage applied to form a developing electric field.

FIG. 3 is a schematic configuration diagram of an example of an image forming apparatus of the present invention.

[Explanation of symbols]

1: photosensitive drum 11: developing sleeve 12: magnet 13, 14: transport screw 16: developing container 17: partition wall 18: toner for replenishment 19: developer 19a: toner 19b: carrier 20: replenishing port R ₁ : developing chamber R ₂ : Stirring chamber R ₃ : toner storage chamber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shinya Taniuchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Shigeru Matsuzaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in the company (reference) 2H005 AA06 BA03 BA06 BA11 BA15 CA15 CB07 CB18 EA02 EA05 2H031 AA01 AC01 AC08 AC14 AC19 AC20 AC30 AD03 BA04 BA09 BC03 CA07 CA10 DA01 FA01 2H077 AA11 AB02 AB06 AC02 AD02 AD06 AD13 AD36 BA10 DA10 GA13

Claims (13)

[Claims] A latent image carrier for carrying an electrostatic latent image;
Latent image forming means for forming an electrostatic latent image on the latent image carrier having been initially charged; a two-component developer having a non-magnetic toner and a magnetic carrier disposed opposite to the latent image carrier; A rotatable developer carrier for carrying and transporting to the developing position and developing the electrostatic latent image into a visible image, and a plurality of magnetic field generators fixedly provided inside the developer carrier. Developing means having a mixture ratio of the non-magnetic toner and the magnetic carrier of the two-component developer, detecting a change in the magnetic permeability of the developer using the inductance of the coil, and controlling the toner concentration in the developer based on the change. The two-component developer comprises a spherical magnetic coated carrier having a weight average particle diameter of 15 to 60 μm and a spherical non-magnetic toner;
And an image forming apparatus configured to detect a change in the magnetic permeability of the developer with the developer on the developer carrier. 2. The image forming apparatus according to claim 1, wherein the developing unit is a plurality of developing devices configured to move while rotating or sliding to a developing position of the latent image carrier. 3. The image forming apparatus according to claim 1, wherein the developing device is configured to move while rotating. 4. The image forming apparatus according to claim 1, wherein the magnetic permeability of the developer is detected when the developing device is not at the developing position. 5. The image forming apparatus according to claim 1, comprising a plurality of developing devices, wherein a change in the magnetic permeability of the developer of the plurality of developing devices is detected by a single sensor. apparatus. 6. The non-magnetic toner according to claim 1, comprising a plurality of developing devices, wherein the non-magnetic toner used in at least one of the plurality of developing devices contains at least carbon black. The image forming apparatus according to claim 1. 7. The image forming apparatus according to claim 1, wherein the spherical coated carrier is configured by dispersing at least a magnetic powder in a binder resin. 8. The image forming apparatus according to claim 1, wherein the spherical coated carrier is configured to contain at least a phenol resin as a binder resin. 9. The image forming apparatus according to claim 1, wherein the spherical coated carrier is configured to contain at least a phenol resin, a magnetic powder, and a nonmagnetic compound. 10. The image forming apparatus according to claim 1, wherein the weight average particle diameter of the spherical coated carrier is 20 to 45 μm. 11. The image forming apparatus according to claim 1, wherein the spherical coated carrier is manufactured by a polymerization method. 12. The image forming apparatus according to claim 1, wherein the spherical coated carrier contains at least a binder resin, a magnetic powder, and a nonmagnetic metal oxide. 13. The developer carrier according to claim 1, wherein the developer carrier rotates in a direction opposite to the latent image carrier, and a developer regulating blade is disposed below the developer carrier. The image forming apparatus according to claim 1.