JPH09190016A - Electrophotographic carrier - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To provide a two-component developer capable of maintaining a sharp image free from image density reduction and fog even after continuous copying of a color original having a large image area until the endurance. To provide a carrier for electrophotography. In an electrophotographic carrier containing at least magnetic particles and a resin, the magnetic particles contain Al ₂ O ₃ in an Al ₂ O ₃ / Fe ₂ O ₃ weight ratio of 1 to 50% on an oxide basis. The carrier for electrophotography has a weight average particle diameter of 15 to 60 μm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier constituting a two-component developer used for developing an electric latent image or a magnetic latent image in an electrophotographic method, an electrostatic printing method, etc. The present invention relates to a carrier for electrophotography which has markedly improved properties, image quality and environmental characteristics.

[0002]

2. Description of the Related Art Carriers constituting a two-component developer are
The conductive carrier is roughly classified into an insulating carrier, and an oxidized or unoxidized iron powder is usually used as the conductive carrier. In the two-component type developer containing the iron powder carrier as a component, the triboelectrification property with respect to the toner is unstable, so that there is a problem in that a visible image is easily fogged. That is, since the toner particles adhere to and accumulate on the surface of the iron powder carrier particles (spent toner) with the use of the two-component developer, the electric resistance of the iron powder carrier particles increases and the bias current decreases. In addition, the triboelectrification becomes unstable, and as a result, the image density of the visible image formed is reduced and fog increases. Therefore, if a two-component developer containing an iron powder carrier is continuously used for copying with an electronic copying machine, the two-component developer will deteriorate with a small number of copies. It will need to be replaced, which will result in high costs.

A typical example of the insulating carrier is a carrier obtained by uniformly coating the surface of a carrier core material made of a ferromagnetic material such as iron, nickel and ferrite with an insulating resin. In the two-component type developer using the insulating carrier, the toner particles are not significantly fused to the carrier surface as compared with the case of the conductive carrier, and at the same time, the triboelectric charging property between the toner and the carrier can be controlled. It is easy, has excellent durability, and has a long service life, which is an advantage that it is particularly suitable for high-speed electrophotographic copying machines.

There are various characteristics required for the insulating carrier, but as particularly important characteristics, proper chargeability, impact resistance, abrasion resistance, good adhesion between the core and the coating material, charge distribution Uniformity and the like can be mentioned.

In view of the above required characteristics, the conventionally used insulating carrier still has a problem to be improved, and a perfect one is not known so far.
For example, the use of an acrylic resin as a carrier coating material is disclosed in, for example, JP-A-47-13954 and JP-A-60-208765. Especially as for the molecular weight,
For example, it is disclosed in JP-A-60-208767, and it is known in this publication that the chargeability of a coated carrier is stabilized by controlling the molecular weight to a constant level. However, in order to attach the coating resin to the carrier core material, it is easily affected by the conditions of the apparatus and the environment for coating, particularly humidity, and even if they are strictly controlled, the resin is stably attached to the core material, At present, there is nothing satisfactory in order to have sufficient chargeability and durability.

On the other hand, it has been proposed to improve the durability by using a resin having a small surface energy as a coating layer in order to prevent the spent of the carrier such as toner fusion, and for example, a silicone resin is a resin having a small surface energy. Can be mentioned.

The silicone resin has the advantage of high water repellency in addition to low surface energy and surface tension. On the other hand, since the silicone resin has low adhesiveness, it has a problem that it is easily peeled off when used in the coating layer.

In order to solve this problem, for example, a method using a resin-modified silicone resin (Japanese Patent Laid-Open No. 55-1275).
69), a method of reacting with another resin containing vinylsilane (JP-A-56-32149), a method of using a mixture of trialkoxysilane and ethyl cellulose (USP 3,840,464), and an organosilicone terpolymer. A method (USP 3,849,127) of using a mixture of a resin and a polyphenylene resin has been proposed. However, a high temperature of 300 ° C. or higher is required to form the coating film, or the compatibility between the silicone resin and another resin is low and the coating film becomes nonuniform, so that expected characteristics cannot be obtained. There was a problem to say.

Further, it has been proposed to form a coating film at a relatively low curing temperature (Japanese Patent Laid-Open No. 55-127569), but the adhesiveness is insufficient and the toughness of the coating film is low. Insufficient wear due to insufficient, for example, when the carrier particles collide with the inner wall of the developing unit or the surface of the photoconductor by strong stirring for a long time in the developing unit such as a high-speed copying machine, or when the particles collide with each other, The silicone resin coating layer peels off due to wear or damage over time, and the triboelectric charge changes from the charge between the toner and the silicone resin to the charge of the toner and the carrier core material, so the charge amount of the toner cannot be kept constant. However, the image quality is deteriorated.

Further, in recent years, demands for high definition and high image quality of copying machines have been increasing in the market, and in this technical field, an attempt has been made to achieve high image quality color by reducing the particle size of toner. However, as the particle size becomes finer, the surface area per unit weight increases, and the amount of electrification of the toner tends to increase, and there is a concern about deterioration in durability such as low image density, fog, and toner scattering.

Further, in color copying using chromatic color toner, continuous gradation is an important factor affecting the image quality, and an edge effect in which only the peripheral portion of the image is emphasized does not occur after copying a large number of sheets. The gradation of the image is greatly impaired. Copying reproducibility including color reproducibility in color copying is reduced by forming a pseudo contour by the edge effect in the vicinity of the actual contour.

Further, the image area used in the conventional black-and-white copy is 10% or less, and the image is almost a line image portion as in letters, documents, and reports, whereas it is a color copy image. The image area is at least 20
%, And solid images having gradation such as photographs, catalogs, maps, and paintings occupy a considerable frequency or area.

When continuous copying is performed using such an original having a large image area, a copy having a high image density is usually obtained in the initial stage, but the toner supply to the two-component developer cannot be completed in time. When the density decreases or the charging is insufficient, the replenishment toner and the carrier are mixed with each other, which may cause fog, and the partial toner density (showing the mixing ratio of the toner and the carrier) on the developing sleeve. There is a tendency that an increase or decrease occurs and image blurring and image density uniformity cannot be obtained. This tendency is more remarkable when the toner diameter is reduced.

This is because the amount of toner included in the two-component developer (that is, the toner concentration) is too low, or the rapid rise of triboelectric charging between the replenishment toner and the carrier in the two-component developer is poor. It is considered that these insufficient development and fog occur due to the fact that the toner having an insufficiently controllable charge amount is involved in the development.

As a color developer, the ability to always output a high quality image by continuously copying an original having a large image area is essential. Conventionally, in order to cope with an original having a large image area and a very large amount of toner consumption, improvement of the developing device rather than improvement of the developer itself has been dealt with more. That is, in order to increase the chance of contact of the developing sleeve with the electrostatic latent image, the peripheral speed of the developing sleeve is increased, and the size of the developing sleeve is increased.

Although these measures improve the developing ability, contamination of the inside of the machine due to toner scattering from the developing device,
Due to an overload on the driving of the developing device, the life of the device may be significantly limited. Furthermore, in order to make up for the lack of developing ability of the developer, it may be possible to deal with it by introducing a large amount of developer into the developing device, but these also increase the weight of the entire device and increase the cost by increasing the size of the device. However, as in the case described above, it may result in an overload on the driving of the developing device, which is not preferable.

On the other hand, as an indication of the average particle size and particle size distribution of the carrier, JP-A-51-3238, JP-A-58-144839 and JP-A-61-20464 have been proposed.
No. 6 publication. JP-A-51-3238 refers to a rough particle size distribution. However, it does not specifically disclose the magnetic properties closely related to the developability of the developer and the transportability in the developing device. Further, regarding the particle size of the carrier, all the carriers in the examples are 250.
There is about 80% by weight or more of mesh and the average particle size is 6
0 μm or more.

Japanese Unexamined Patent Publication (Kokai) No. 58-144839 discloses only the average particle size of the carrier, and the amount of fine powder that affects the carrier adhesion to the photoreceptor and the coarse powder that affects the sharpness of the image. The amount is not mentioned, and the distribution is not described in detail in consideration of the characteristics of color reproduction.

Japanese Unexamined Patent Publication (Kokai) No. 61-204646 discloses a combination of a copying machine and a suitable developer as the main point of the invention, and does not specifically describe the particle size distribution or magnetic characteristics of the carrier. Furthermore, it does not even disclose why the developer is effective in the copying machine.

Japanese Unexamined Patent Publication (Kokai) No. 49-70630 discloses a magnetic force of a carrier, but this is for iron powder having a larger specific gravity than ferrite as a carrier material and a high saturation magnetism. is there. Iron powder carriers have been widely used in the past, but due to their large specific gravity, the weight of the copying machine and the overload of the driving torque are apt to occur, and the environmental dependence is large.

The ferrite carrier described in Japanese Patent Application Laid-Open No. 58-23032 is for a porous material having many pores, and such a carrier is liable to have an edge effect and poor in durability. Therefore, it has been found to be unsuitable as a color carrier.

Up to now, there is a demand for a developer which can continuously copy an image having a large image area with a small amount of developer and which can satisfy the characteristic peculiar to color copying without causing an edge effect even after endurance. ing. Although developers and carriers have been studied, most of them have been proposed in consideration of black-and-white copying, and very few have been proposed as applicable to full-color copying. Furthermore, a carrier having the ability to continue copying an image having an image area of 20% or more, which is almost similar to a solid image, the reduction of edge effect, and the ability to maintain the uniformity of image density in one copy are Long-awaited.

[0023]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carrier for electrophotography, which solves the above problems, and a carrier for the same.

That is, it is an object of the present invention to provide an electrophotographic carrier which does not cause image density reduction and blurring even when a color original having a large image area is continuously copied.

A further object of the present invention is to provide a carrier for electrophotography which has clear image characteristics free from fog and has excellent durability stability.

Another object of the present invention is to provide an electrophotographic carrier in which the image density has little environmental dependence.

[0027]

Means and operation for the present invention, there is provided at least in the electrophotographic carrier comprising magnetic particles and a resin, Al ₂ O ₃ / F magnetic particles on an oxide basis of Al ₂ O ₃
The carrier for electrophotography is characterized in that the weight ratio of e ₂ O ₃ is in the range of 1 to 50%, and the weight average particle diameter of the carrier is 15 to 60 μm.

The inventors of the present invention have conducted various studies and studies to improve the above-mentioned conventional problems, and as a result, a carrier using a resin of a specific composition as a carrier core material of a specific composition is effective in improving various characteristics. After finding out that there is something, the present invention has been completed.

That is, the inventors of the present invention have made earnest studies on the image density, highlight reproducibility and fine line reproducibility of the two-component developer, and as a result, when using a carrier having specific carrier magnetic characteristics and fluidity, They have found that excellent image quality can be achieved with high image density, highlight reproduction, and fine line reproduction.

Up to now, in order to form a high-quality image, the saturation magnetization value of the carrier is set to 50 emu / g (Am ² / kg) or less as disclosed in JP-A-59-104663. Although it has been proposed that an image can be obtained, the reproducibility of fine lines is improved by using a carrier with a smaller saturation magnetization value, while the carrier becomes an electrostatic image carrier, a so-called photosensitive The phenomenon that particles adhere to the drum (adhering to the carrier) becomes more noticeable, which is not always satisfactory, and the central particle size is also coarse. For continuous copying of original documents with high image ratio, Further improvements are desired.

The carrier used in the present invention has a saturation magnetization of 2
It has a small particle size of 0 to 50 Am ² / kg and a small particle size, but because of the use of a specific composition and a specific resin, the carrier itself has a very high fluidity and is extremely resistant to the action of magnetic fields and electric fields. It was found to be faithful and carrier adhesion did not occur.

Japanese Unexamined Patent Publication (Kokai) No. 2-33159 also discloses coating with a silicone resin and Al ₂ as an example of an additive.
Although O ₃ is described, the present invention is characterized by containing Al ₂ O ₃ as an essential component in a specific weight ratio with respect to Fe ₂ O _{3 so} as to interact with, and more preferably react with, a silicone resin. As a result, a coated carrier with improved strength can be obtained, which is different from the above invention.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION As a carrier core material usable in the present invention, Al ₂ O ₃ in the carrier core material is A based on oxide.
l ₂ O ₃ / Fe ₂ O ₃ weight ratio of 1 to 50%, preferably 2 to
It is characterized by containing 40%. If the above value is less than 1%, effective magnetic properties cannot be obtained, and as a result, the toner is likely to deteriorate and the durability is impaired. On the other hand, when the value is larger than the above value, the surface property of the carrier core material becomes non-uniform, the stability of the coating resin is deteriorated, and the durability such as fog is deteriorated due to the deterioration of the charging property.

That is, the Al ₂ O ₃ / Fe ₂ O ₃ ratio is 1 to 5
Saturation magnetization of 20 to 50 Am ² /
Even if a carrier having a particle size distribution of fine particle size as described above is used in kg, carrier adhesion or the like did not occur, and a long-life carrier without drum scratches or image deterioration could be achieved.

The coating resin preferably used in the present invention is a reactive silicone resin and / or a fluorine-containing resin. Particularly preferred is a reactive silicone resin containing at least a curing agent represented by the following general formula (I).

[0036]

Embedded image

That is, in the interaction on the surface of the carrier core material of the present invention, SiOH remaining in the silicone resin is
The oxime type silane coupling agent is very excellent in terms of appropriate control of the group, storage stability and cost.

Examples of the curing agent in the present invention include those shown in the following (1) to (4).

[0039]

Embedded image

The amount of the curing agent added is 0.1 to 10 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the siloxane solid content. If it is less than 0.1 part by weight, a sufficient crosslinking effect cannot be obtained, and if it exceeds 10 parts by weight,
The residue cannot be removed sufficiently or a compound that has not reacted sufficiently remains, resulting in deterioration of charging characteristics and strength.

In order to make the present invention more effective, the coating amount of the crosslinked silicone resin is a with respect to 100 g of the carrier.
(G), the carrier specific surface area S (c
(a / s) × 10 ⁴ with respect to m ² / g) is 2 to 30, preferably 5 to 20, where a is 0.01 to 2.0,
It is preferably 0.02 to 1.5.

In the present invention, the general formula (II) is further used.
You may add the aminosilane coupling agent shown by.

R _m —Si—Y _n Formula (II) (wherein R is an alkoxy group, Y is a hydrocarbon group containing an amino group, m is an integer of 1 to 3, and n is an integer of 3 to 1). Show.)

Examples of this aminosilane coupling agent include those shown in the following (5) to (13).

[0045]

Embedded image

The amount of the coupling agent added is 0.1 to 8 parts by weight, preferably 0.3 to 5 parts by weight, based on 100 parts by weight of the siloxane solid content. If it is less than 0.1 part by weight, a sufficient addition effect cannot be obtained, and the charging property is apt to be deteriorated and the coating strength is apt to be deteriorated. If it exceeds 8 parts by weight, sufficient reaction is not carried out, and conversely the coating strength is lowered. Will end up.

In the present invention, the coupling agent further includes the following general formula (III) R _4-a -Si-Xa formula (III) (wherein R _4-a is a vinyl group, a methacryl group or an epoxy group). Group, an amino group, a mercapto group, and a substituent selected from the group consisting of derivatives thereof, and X represents a halogen or an alkoxy group.) May be used in combination.

Examples of such a coupling agent include those shown in the following (14) to (17), and those containing an epoxy group are particularly preferable, including the chargeability under high humidity.

[0049]

Embedded image

In the present invention, as means for containing a specific amount of Al ₂ O ₃ , Fe ₂ O ₃ , MgO, MnO, Li _{2
O, CaO, SrO, SiO 2} , Bi 2 O 3, K 2 O, Na
₂ O or the like may be present in the ferrite-forming raw material,
The starting material may be added as Al ₂ O ₃ or an aluminate at the time of granulation, and may also function as a dispersion stabilizer at the time of granulation prevention or granulation.

In the present invention, the carrier Al ₂ O ₃ / F
With respect to the carrier core material, the e ₂ O ₃ ratio was determined by quantifying Fe and Al by the ZAF method of scanning electron microscope-X-ray analysis (SEM-XMA) in the carrier core material as it was, and was converted to an oxide standard. In the case of a coated carrier, after solidifying the carrier with epoxy resin or the like, cutting with a laser cutter or the like, removing the coating material, exposing the carrier core material, and calculating by quantifying the portion as described above. You can

Regarding the particle size distribution of the carrier, the weight average particle size of the carrier is 15 to 60 μm, preferably 20 to 5
Carrier particles having a diameter of 0 μm and smaller than 22 μm are 1 to
20% by weight, preferably 2 to 15% by weight, more preferably 4 to 12% by weight, and 3% by weight or less of carrier particles smaller than 16 μm, preferably 2% by weight or less, more preferably 1% by weight or less. It should be contained.

When the content of the fine powder exceeds the upper limit of the above range, it becomes difficult to uniformly coat the resin on the carrier core material, adhesion of the carrier occurs, smooth charging with the toner is hindered, and fogging and the like occur. Image deterioration will occur. If the carrier particles smaller than 22 μm are less than 1% by weight, the magnetic brush will be in a sparse state, resulting in image deterioration such as deterioration of solid homogeneity and fine line reproducibility.

Carrier particles of 62 μm or more closely correlate with the sharpness of the image, and the content of this coarse powder is preferably 2 to 20% by weight. When the content of the coarse powder exceeds 20% by weight, the toner carrying ability of the carrier is lowered, the scattering of the toner to the non-image area is increased, the resolution of the image is lowered, and the highlight reproducibility is lowered. If it is less than 2% by weight, even if it is a thin layer coated carrier, the fluidity of the carrier is lowered, that is, the fluidity of the developer is lowered, and the charge imparting ability to the toner is lowered, so that the carrier is stable. It becomes difficult to obtain an image.

For coating the carrier core material with a resin, a method of dissolving the resin composition in a suitable solvent, immersing the core material particles in the resulting solution, and then removing the solvent, drying and baking at high temperature , Or floating the core material particles in the fluidization system,
Spraying and applying the dissolved solution of the resin composition, drying,
A method of baking at high temperature, a method of simply mixing core material particles with a powder of a resin composition or an aqueous emulsion, and the like can be used.

The method preferably used in the present invention is to add 0.1 to 5 parts by weight, preferably 0.3 to 3 parts by weight of water in 100 parts by weight of a solvent containing a polar solvent such as ketones and alcohols. The method of using the mixed solvent is preferable in order to firmly attach the reactive silicone resin to the core material particles. If the amount of water is less than 0.1 parts by weight, the hydrolysis reaction of the reactive silicone resin does not sufficiently occur,
It becomes difficult to coat the surface of the magnetic carrier core material particles in a thin layer and uniformly, and when it exceeds 5 parts by weight, the reaction control becomes difficult, and conversely the coating strength decreases.

The carrier of the present invention thus obtained is mixed with a toner and used as a magnetic brush developer for developing an electrostatic latent image.

As the toner, any toner in which a colorant is dispersed in a binder resin and which is generally used in the electrophotographic method can be used and is not particularly limited.

When a two-component developer is prepared by mixing the carrier and the toner according to the present invention, the mixing ratio is 1 to 12 parts by weight as the toner concentration in the two-component developer,
Good results are usually obtained when the amount is preferably 2 to 9% by weight. If the toner concentration is less than 1% by weight, the image density is too low to be practical, and if it exceeds 12% by weight, fog and scattering in the machine are increased and the useful life of the two-component developer is shortened.

As the colorant contained in the toner, known dyes and pigments such as phthalocyanine blue, induslen blue, peacock blue, permanent red, lake red, rhodamine lake, Hansa yellow, permanent yellow and benzidine yellow can be used. You can The content thereof is preferably 12 parts by weight or less, more preferably 0.1 part by weight or less with respect to 100 parts by weight of the binder resin so as to sensitively reflect the transparency of the OHP film.
5 to 9 parts by weight is preferable.

If necessary, the toner may be mixed with an additive within a range that does not impair the characteristics of the toner. Examples of such an additive include a lubricant such as Teflon, zinc stearate, and polyvinylidene fluoride. Alternatively, fixing aids (eg, low molecular weight polyethylene, low molecular weight polypropylene, etc.) can be used.

In the production of the toner, a method in which the constituent materials are well kneaded by a heat kneader such as a heat roll, a kneader or an extruder and then mechanically pulverized and classified, or a binder resin solution containing a colorant is used. The toner is obtained by dispersing the toner raw material and then spray-drying it, or by mixing a predetermined material with a polymerizable monomer that can form the binder resin and then polymerizing the emulsion suspension. A method for producing a polymerized toner can be applied.

Various resins are used as the binder resin used in the toner.

For example, styrene-based copolymers such as polystyrene, styrene-butadiene copolymer and styrene-acrylic copolymer, ethylene-based polymers such as polyethylene, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer. Examples thereof include copolymers, phenolic resins, epoxy resins, acrylic phthalate resins, polyamide resins, polyester resins and maleic acid resins. The production method of any resin is not particularly limited.

Among these resins, the effect of the present invention is remarkable when a polyester resin having a high negative chargeability is used. That is, while the polyester-based resin has excellent fixability and is suitable for color toners, it has a strong negative charging ability and tends to be excessively charged, but as a binder resin for the toner combined with the above-mentioned carrier of the present invention, a polyester resin is used. When the above is used, the harmful effect is improved and an excellent toner is obtained.

In particular, the following formula

[0067]

Embedded image (In the formula, R represents an ethylene or propylene group, x,
Each y is an integer of 1 or more, and the average value of x + y is 2 to 10. ) Is a diol component, and a divalent or higher carboxylic acid, an acid anhydride thereof or a lower alkyl ester thereof is a carboxylic acid component (for example, fumaric acid, maleic acid, maleic anhydride, phthalic acid, A terephthalic acid, a trimellitic acid, a pyromellitic acid), and a polyester resin obtained by copolycondensation of the diol component and the carboxylic acid component are more preferable because they have sharp melting characteristics.

Further, the present invention provides an external additive for toner,
It is preferable to contain at least alumina fine particles and titanium oxide fine particles in order to further stabilize charging. Particularly preferably, alumina fine particles and titanium oxide fine particles that have been surface-treated while hydrolyzing the coupling agent in the presence of water are extremely effective from the viewpoints of stabilizing charging and imparting fluidity.

Further, the fine particles have an average particle diameter of 0.00.
It is preferable that the light transmittance is 1 to 0.2 μm, the hydrophobicity is 20 to 95%, and the light transmittance at 400 μm is 40% or more.

The measuring method in the present invention will be described below.

Fog density measuring method REFLECTOME manufactured by Tokyo Denshoku Co., Ltd. was used for evaluation of fog.
TE MODEL TC-6DS was used for the measurement, and an cyan filter was used for the cyan toner image. The smaller the value, the less fog.

Fog (reflectance) (%) = reflectance of standard paper (%)-reflectance of non-image part of sample (%)

Measurement of Specific Surface Area The specific surface area is measured by the following procedure using a Shimadzu powder specific surface area measuring device (SS-100 type). 1) To fill the sample iron powder, turn on the power of the autoslider of the powder tester and adjust it to 100V. 2) Adjust the timer to 1 minute by tapping the changeover switch on the passender tester (50 times ± 1 time / 1 minute). 3) Put a sieve plate in a plastic sample tube, lay a piece of filter paper on it, and put the sample on it up to 1/3 of the sample tube. 4) Set the sample tube on the tap stand of the powder tester and insert the start button (tap for 1 minute). 5) The sample cylinder is tapped further and the sample is ⅔ of the sample cylinder.
Insert up to 6) Perform the same work as in 4 above. 7) Insert a supplemental cylinder (plastic) on top of the sample cylinder and place the sample on top of it. 8) Perform the same work as the above 4 and 6. 9) Take out the tapped sample tube from the tap mount, remove the supplementary tube, and cut the extra sample with a spatula. 10) Fill the water up to the S scale of the specific surface area measuring tube. 11) Connect the sample tube to the measuring tube (after filling the sample, apply grease to the mating surface). 12) Open the cock at the lower outlet and let the water level of the measuring tube be zero.
Start the stopwatch as it passes the scale (lower runoff received in beaker). 13) Measure the time for the water surface to drop to the 20 scale (unit: cc). 14) Remove the sample tube and measure the weight of the sample. 15) Calculation of specific surface area

The specific surface area is calculated by the following formula.

[0075]

[Equation 1]

SW: specific surface area of powder cm ² / g e: porosity of sample-packed layer ρ: density of powder g / cm ² η: viscosity coefficient of fluid g / cm · sec L: thickness of sample layer cm Q: sample layer permeation fluid amount cc ΔP: pressure difference between both ends of sample layer g / cm ² A: cross sectional area of sample layer cm ² t: time required for Qcc fluid (air) to permeate sample layer sec W : Sample weight g

[0077]

[0078]

EXAMPLES Examples of the present invention will be shown below, and "part" means "part by weight".

(Production Example 1 of carrier core material) Al ₂ O ₃ 2
After 0 part and 80 parts of Fe ₂ O ₃ were each atomized, water was added and mixed and granulated, followed by firing at 1400 ° C. and particle size adjustment, and then carrier core material A (Al ₂ O ₃ / Fe ₂ O ₃ ratio = 3
3%).

(Production Example 2 of carrier core material) Al_TwoO_Three 1
5 parts, MgO 15 parts, CaO 5 parts, Fe_TwoO_Three 60
Example 1 with the exception that parts are used and baked at 1100 ° C.
Similarly, carrier core material B (Al _TwoO_Three/ Fe_TwoO_ThreeRatio = 2
3%).

(Production Example 3 of carrier core material) Al ₂ O ₃ 5
When 0 part and 50 parts of Fe ₂ O ₃ were used and the same procedure as in Production Example 1 was carried out, firing could not be successfully performed and a carrier core material could not be formed (Al ₂ O ₃ / Fe ₂ O ₃ ratio = 100%).

(Production Example 4 of Carrier Core Material) MgO 20
Parts, 20 parts of MnO, and 40 parts of Fe ₂ O ₃ were mixed in an aqueous solution of sodium aluminate and then granulated.
Similarly to carrier core material C (Al ₂ O ₃ / Fe ₂ O ₃ ratio = 4
%).

(Production Example 5 of carrier core material) 98 parts of 0.8 μm magnetite particles and 2 parts of 0.8 μm α-alumina fine particles are mixed and dispersed in a phenol / formaldehyde monomer and then polymerized to obtain a carrier core material. D (Al ₂
O ₃ / Fe ₂ O ₃ ratio = 3%) was obtained.

(Production Example 6 of carrier core material) Fe ₂ O ₃ 1
Carrier core material E (Al ₂ O ₃ / Fe ₂ O ₃ ratio = 2) is the same as in Production Example 4 except that 100 parts is used and firing is performed at 1400 ° C.
%).

Production Example 7 of Carrier Core Material A carrier core material F was prepared in the same manner as in Production Example 1 except that Al ₂ O ₃ was not used.
(Al ₂ O ₃ / Fe ₂ O ₃ ratio = 0) was obtained.

<Production Examples 1 to 6 of Carrier> Toluene 20
Part, butanol 20 parts, water 20 parts, and ice 40 parts are placed in a four-necked flask, and while stirring, 40 parts of a mixture of 15 mol of CH ₃ SiCl _{3 and} 10 mol of (CH ₃ ) ₂ SiCl ₂ is added, and further for 30 minutes. After stirring, the condensation reaction was performed at 60 ° C. for 1 hour. Then, the siloxane was thoroughly washed with water and dissolved in a toluene-methylethylketone-butanol-water mixed solvent to prepare a silicone varnish having a solid content of 10%.

2.0 parts of the following curing agent was added to 100 parts of siloxane solid content in this silicone varnish.

[0088]

[Chemical 6] And 3.0 parts of the following aminosilane coupling agent

[0089]

Embedded image Was simultaneously added to prepare a carrier coating solution I.

This coating solution I was coated with a coating machine (made by Okada Seiko:
The above-mentioned carrier core material particles 100
Parts A to F were coated such that the resin coating amount was 0.45 parts, to obtain coating carriers 1 to 6, respectively. Table 1
Shows the physical properties of each carrier.

[Toner Production Example 1] Polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 4 parts Di-tert-butylsalicylic acid aluminum complex 4 parts were sufficiently premixed with a Henschel mixer. Then, the mixture was melt-kneaded by a twin-screw extrusion type kneader, cooled, coarsely pulverized to about 1 to 2 mm using a hammer mill, and then finely pulverized by an air jet type fine pulverizer. Further, the obtained finely pulverized product was classified to obtain a cyan powder having a negative triboelectrification property and a weight average particle diameter of 5.8 μm.

100 parts of the above colored powder and 15 parts of nC ₄
Cyan toner a was obtained by mixing with Henschel mixer 1.5 parts of anatase type titanium oxide fine powder obtained by treating H ₉ —Si— (OCH ₃ ) ₃ in the presence of water.

Example 1 The above cyan toner and carrier 1 were mixed at a toner concentration of 7% to prepare a developer, and a color copying machine CLC700 (manufactured by Canon Inc.) was used. % Original document, 23 ℃ / 65% RH, 30 ℃ / 80%
Table 2 shows the results of image formation on 10,000 sheets under RH and 20 ° C / 10% RH. From Table 2, the above-mentioned developers show little variation in the printing durability test, and there is no problem in scattering after 10,000 sheets,
It turns out to be very good. Table 2 shows the evaluation results.

Examples 2, 3, 4, 5 and Comparative Example 1 Instead of the carrier 1 used in Example 1, the carriers 2, 3, 4, 5 and 6 shown in Table 1 were used, respectively. A developer was prepared in the same manner as in Example 1 and evaluated in the same manner. Table 2 shows the results.

<Production Example 7 of carrier> Carrier 7 was obtained in the same manner as in carrier 2 except that a mixed solvent of toluene-methyl ethyl ketone was used.

Example 6 Carrier 2 used in Example 2
Instead of using the carrier 7 shown in Table 1, a developer was prepared in the same manner as in Example 2 and evaluated in the same manner. The results are shown in Table 2, but the durability was slightly lower than that of Example 1. It is considered that this is because water was not present at the time of resin coating.

<Production Example 8 of Carrier> A styrene-methylmethacrylate copolymer / polytetrafluoroethylene-polyvinylidene fluoride copolymer (50:50) was dissolved in a toluene-methylethylketone mixed solvent to obtain a coating solution II. A carrier 8 was obtained in the same manner as in Production Example 2 except that coating was performed using the coating solution II.

Example 7 Carrier 2 used in Example 2
Instead of using the carrier 8 shown in Table 1, a developer was prepared in the same manner as in Example 2 and evaluated in the same manner, and good results were obtained.

[Comparative Example 2] Carrier 2 used in Example 2
Instead of using the carrier core material B, a developer was prepared in the same manner as in Example 2 and evaluated in the same manner. As a result, the image deteriorated.

[Toner Production Example 2] In the toner production example 1, instead of the anatase type titanium oxide fine powder,

[0101]

Embedded image A cyan toner b was obtained in the same manner as in Toner Production Example 1 except that 20 parts of amorphous alumina fine powder (primary particle size: 10 nm) was used.

[Toner Production Example 3] In the toner production example 1, instead of the anatase type titanium oxide fine powder, in the presence of water vapor in the gas phase,

[0103]

Embedded image Cyan toner c was obtained in the same manner except that amorphous titanium oxide fine particles (primary particle size 20 nm) treated with 15 parts were used.

[Examples 8 and 9] Developers were prepared and evaluated in the same manner as in Example 2 except that the toners b and c were used in place of the toner a used in Example 2. Then, good results were obtained.

[0105]

[Table 1]

[0106]

[Table 2]

[0107]

The electrophotographic carrier of the present invention has at least the surface of the carrier core material containing a specific amount of Al ₂ O ₃ ,
In particular, by coating with a silicone resin containing a coupling agent having a specific structure, the toughness of the coating is increased and the durability is excellent in environmental characteristics.

Claims (9)

[Claims] 1. A carrier for electrophotography comprising at least magnetic particles and a resin, the magnetic particles are Al ₂ O ₃ in the range _{Al 2 O 3 / Fe 2 O} 3 weight ratio on an oxide basis is 1% to 50% An electrophotographic carrier containing the carrier, wherein the carrier has a weight average particle diameter of 15 to 60 μm. 2. The carrier for electrophotography according to claim 1, wherein the carrier has a magnetic particle core material surface coated with a resin. 3. The carrier comprises a magnetic particle core material surface,
The electrophotographic carrier according to claim 1, which is coated with a reactive silicone resin and / or a fluorine-containing resin. 4. The carrier comprises a magnetic particle core material surface,
The electrophotographic carrier according to claim 1, which is coated with a reactive silicone resin in the presence of water. 5. The electrophotographic carrier according to claim 1, wherein the carrier has magnetic particles dispersed in a binder resin. 6. The electrophotographic carrier according to claim 5, wherein the carrier is a magnetic carrier core material in which magnetic particles are dispersed in a binder resin, the resin being coated on the core material. 7. The carrier for electrophotography according to claim 6, wherein the coating resin is a reactive silicone resin and / or a fluorine-containing resin. 8. The carrier for electrophotography according to claim 6, wherein the coating resin is coated with a reactive silicone resin in the presence of water. 9. The saturation magnetization of the carrier with respect to an applied magnetic field of 3000 Oersted is 20 to 50 Am ² / kg.
9. The electrophotographic carrier according to claim 1, wherein the carrier is an electrophotographic carrier.