JPH08262805A - Production of developer and carrier used for same and image forming method - Google Patents

Abstract

PURPOSE: To obtain a carrier for a negative charge type developer having small dependency of the quantity of electric charges on the environment and maintaining it over a long period of time, to obtain a developer using the carrier and to provide an image forming method. CONSTITUTION: In this developer consisting of colored particles contg. at least a bonding resin and a colorant and a carrier, the carrier is a negative charge type carrier obtd. by coating magnetic particles with resin layers each consisting of monomers including at least alicyclic methacrylic ester and chain methacrylic ester or a copolymer and inorg. fine particles. An image is formed using this developer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a developer and a carrier used therein, and an image forming method.

[0002]

2. Description of the Related Art Conventionally, the development of an electrostatic latent image formed by an electrophotographic method has been mainly performed by a dry development method, and the dry development method uses a one-component developer containing a magnetic toner as a main component. And a two-component developer including a non-magnetic toner and a magnetic carrier.

The two-component developer has a more stable charging performance than the one-component developer containing only toner in that the toner and the carrier are mechanically agitated to impart a desired charge to the toner, and is preferably used. . The magnetic carrier is required to have appropriate triboelectrification properties, fluidity, developability, and high durability to withstand long-term use, and it is also required that the surface of the image forming body is not damaged during development and cleaning. .

Therefore, for example, in Japanese Patent Laid-Open No. 59-104664,
Alicyclic methacrylic acid ester polymer resin, JP-A-63-373
No. 60 proposes a carrier coated with a chain-type methacrylic acid ester polymer resin, which describes that it is excellent in triboelectrification property, fluidity and toner spent resistance, and prevents water absorption of the carrier.

However, in recent years, with the decrease in the particle diameter of toner, various external additives have been added in large amounts from the viewpoint of further improving the fluidity or the developability. As the external additive for toner, a hydrophobic one is used in order to prevent the migration of the charging sequence due to the adsorption of water under high humidity and reduce the environmental difference in the charge amount. The toner absorbs water and causes an environmental difference in charge amount. Under such circumstances, promoting the hydrophobicity of the carrier results in further increasing the environmental difference in the charge amount.

There are roughly two types of carrier coating methods. A coating solution prepared by dissolving a coating resin in a solvent is spray-coated on the surface of magnetic particles using a fluidized bed and dried to obtain a fluidized-bed spray coated carrier or a coating resin as a solvent. In the coating solution prepared by dissolution, the magnetic particles are applied by coating, and the coating solution prepared by dissolving the immersion coated carrier obtained by drying and the coating resin in a solvent, Solvent coating carrier such as a sintered type coated carrier obtained by coating the surface of magnetic particles and sintering a resin, and a machine without using a solvent like JP-A-2-8860 and 3-143579. It is a dry type coating carrier that applies a dynamic impact to adhere and fix the resin in a dry type.

In order to realize the two-component non-contact development which is widely used in recent full-color image forming apparatuses and the like, it is necessary to make the developer layer thickness as thin as possible. It is said that it is necessary to keep the distance to 1 mm or less. In order to carry out non-contact development under these conditions, a developer layer having a uniform thickness must be stably formed. Among the current technologies, the thin layer forming method using a rigid rod-shaped magnetic material proposed in Japanese Patent Laid-Open No. 2-50184 is effective in forming a stable layer thickness. However, although the thin layer forming method using the rod-shaped magnetic material has an advantage of forming a stable layer, it also has the following two drawbacks when the conventional developer is used.

(1) The stress that the developer receives is large,
In particular, the situation becomes more severe as the device becomes smaller. The increase in stress causes breakage and peeling of the carrier coat layer, which has a great adverse effect on the durability of the developer.

(2) When the charge amount of the developer fluctuates due to the environment, the filling interval between the developer particles changes, and the amount of withdrawal and the amount of conveyance of the developer also change. This change causes a variation in the thickness of the developer layer formed on the developer carrying member, and since the developer layer is a thin layer, the variation ratio is high and the development performance is affected to a large extent. Regarding the destruction of the coating layer, in the thin layer forming method, since the stress received by the developer is very large as described above, peeling at the interface between the coating layer itself of the carrier or the coating layer and the magnetic particles to be the core, Scraping of the coating layer may be a major factor. To improve it, hydrophobic silica is added to the coating layer as seen in, for example, JP-A-59-232362, but hydrophobic silica has some effect. However, it is hard to say that it is still fully effective.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a carrier for a negatively chargeable developer which has a small environmental difference in charge amount and maintains it for a long period of time, and a developer using the same. Furthermore, it is to develop an image forming method.

[0011]

The present invention is achieved by using a carrier coating resin for preventing toner spent and adding inorganic fine particles.

That is, in a developer comprising colored particles containing at least a binder resin and a colorant, and a carrier, the carrier has magnetic particles on which alicyclic methacrylic acid ester containing at least inorganic fine particles is contained. The object of the present invention is achieved by a developer characterized by being a negatively-charged carrier coated with a resin layer of a polymer composed of a chain-type methacrylic acid ester.

The magnetic particles are coated with a polymer composed of an alicyclic methacrylic acid ester containing at least inorganic fine particles and a chain methacrylic acid ester by a dry coating for applying and fixing by mechanical shock. This is achieved by the method for producing a carrier for a negatively chargeable developer as described above.

Further, a developer consisting of colored particles containing at least a binder resin and a colorant and a carrier is thinned to a developer layer thickness of 20 to 500 μm by a developer regulator to form an image. In the image forming method of non-contact development of an electrostatic latent image on a body, the carrier comprises a polymer composed of an alicyclic methacrylic acid ester containing at least inorganic fine particles on a magnetic particle and a chain methacrylic acid ester. It is achieved by an image forming method which is a negatively chargeable carrier coated with a resin layer.

The alicyclic methacrylic acid ester polymer and the chain methacrylic acid ester polymer each exist as a single polymer, and a blend of these polymers also exists as a copolymer. Anything is fine. Further, each may be a copolymer with a monomer such as styrene which is not related to the present invention. One of the reasons why the resin of the present invention is good is that the film peeling occurs even in long-term use, which is excellent in the adhesiveness between the alicyclic methacrylic acid ester component which does not deteriorate even in long-term use and the magnetic particles. It is presumed that this is because a chain type methacrylic acid ester component having no It is thought that this makes the abrasion-resistant property of the polymer containing an alicyclic methacrylate ester and the property of the chain-methacrylic acid ester polymer difficult to be worn out balanced by copolymerization or blending. Be done. Therefore, when the carriers are rubbed with each other, the fresh carrier surface is always exposed by scraping off the toner which is not worn more than necessary and is spent by moderate wear, so that the carrier refreshing effect may be exhibited.

Further, the effect of adding the inorganic fine particles is estimated as follows. The cause of the decrease in the amount of charge under high humidity is that an external additive added as a fluidity improver to the toner absorbs water and the charge sequence moves. Conventionally, in order to prevent water absorption of the external additive under high humidity, the external additive added to the toner has been made as hydrophobic as possible. But,
Even though it was hydrophobized, it was still insufficient, so it was not effective enough. Therefore, in the present invention, the inorganic fine particles are also added to the carrier, and water absorption of the inorganic fine particles under high humidity also moves the chargeability of the carrier by an amount corresponding to the movement of the chargeability of the toner. Therefore, it is possible to suppress the generation of the weakly charged toner even under high humidity, and it is possible to reduce the environmental difference in charging property.

Further, among the inorganic fine particles, hydrophilic silica having a hydrophobicity of 20 or less is particularly excellent in water absorption and also has an effect as a dispersibility-imparting material for the carrier coating material. It also acts to disperse.

Further, among the inorganic fine particles, the magnesium compound is excellent in positive charging property, so that the carrier containing the magnesium compound is immediately positively charged, and as a result, the charging effect of the negative toner is remarkably improved. There is. Further, since the single crystal magnesium compound has a small particle size, the use thereof improves the dispersibility in the carrier shell.

That is, although the film strength is slightly weakened by the addition of the inorganic fine particles, the film strength is improved by using a polymer composed of an alicyclic methacrylic acid ester and a chain methacrylic acid ester, which has high adhesiveness to the core. You can be strong.

However, conversely, the alicyclic methacrylic acid ester and the chain methacrylic acid ester polymer have high hydrophobicity and have an effect of preventing water absorption of the carrier, so that in a system in which a fluidity-imparting agent is added to the toner, high temperature and high humidity are used. This results in a large difference in the amount of charge below.

Therefore, by adding inorganic fine particles to absorb moisture in the carrier, the environmental difference in the charge amount can be reduced.

That is, by using the alicyclic methacrylic acid ester, the chain methacrylic acid ester polymer, and the inorganic fine particles in combination, the disadvantages can be compensated for while maintaining the effects of both.

[0023]

The raw materials and techniques used in the present invention will be further described.

<Carrier><< Magnetic Particles >> Iron, ferrite, magnetite and other metals such as iron, nickel, cobalt, copper, zinc, and alloys or compounds containing these metals are mentioned. When the magnetic particles of 3 to 7 are used,
It is preferable because stress applied to the developer during mixing and stirring in the developing device is reduced.

Further, it is preferable that the saturation magnetization is 15 to 80 emu / g and the volume average particle diameter is 15 to 100 μm. Microtrac SRA MK-II (manufactured by Nikkiso Co., Ltd.) was used for measuring the volume average particle diameter.

<< Resin >> An alicyclic methacrylic acid ester monomer and a chain methacrylic acid ester monomer are used in a ratio of 1: 9 to 9:
1, preferably a polymer copolymerized in a molar ratio of 3: 7 to 7: 3 or a blend of polymers polymerized separately, is used as a resin containing 50% by weight or more. The copolymer is styrene together with an alicyclic methacrylic acid ester monomer and a chain methacrylic acid ester monomer.
It may be a copolymer of a styrene-based monomer such as α-styrene and parachlorostyrene, in which case a styrene-based monomer or the like is added to the chain or alicyclic methacrylic acid ester monomer. The body is less than 50 mol%.

The alicyclic methacrylic acid ester monomer is assumed to have a cycloalkyl ring having 3 to 7 carbon atoms, for example, cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate. , Cycloheptyl methacrylate and the like. However, cyclohexyl methacrylate having a cycloalkyl ring having 6 carbon atoms is particularly preferable for exhibiting the refreshing effect on the surface of the carrier.

The chain methacrylic acid ester monomer copolymerized with the alicyclic methacrylic acid ester monomer includes methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate and hexyl methacrylate. , Octyl methacrylate, 2-ethylhexyl methacrylate and the like. However, from the viewpoint of the refreshing effect, those having a hexyl group from a methyl group having 1 to 6 carbon atoms are preferable.

When a polymer obtained by polymerizing the alicyclic methacrylic acid ester monomer alone and a polymer obtained by polymerizing the chain methacrylic acid ester monomer alone are blended and used, Converted to each monomer 1: 9 ~
A resin containing a mixture of 9: 1, preferably 3: 7 to 7: 3 in a molar ratio of 50% by weight or more based on the total amount of the coated carrier resin.

Furthermore, as described above, in the resin forming the coating layer of the resin-coated carrier of the present invention, other than the specific resin, other resin may be mixed in an amount of less than 50% by weight, For example, styrene resin, acrylic resin, styrene-acrylic resin, vinyl resin, ethylene resin,
Rosin-modified resin, polyamide resin, polyester resin,
A resin such as a silicone resin can be used. Also, these resins may be used in combination. The coating amount of these resins is 0.5 to 5.5% by weight, and particularly preferably 1.0 to 4.0% by weight, based on the magnetic particles. When the resin layer is 0.5% by weight or less, the surface of the magnetic particles is exposed because the coating layer is too thin, and when it exceeds 5.5% by weight, the coating layer is too thick and the magnetic particles are As a result, the adhesion is weakened and the film peels off from the interface.

<< Inorganic Fine Particles >> Although not particularly limited, examples thereof include silica, titania, alumina, magnesium and the like, and the smaller the degree of hydrophobicity is, the more preferable. The degree of hydrophobicity is based on the methanol wettability shown below.

Method for measuring methanol wettability 1. Silica powder 0.2 in a beaker with a capacity of 150 ml
Weigh g.

2. Add 50 ml of distilled water colored with methylene blue. You may use demineralized water.

3. With a magnetic stirrer, slowly add methanol intermittently while stirring the solution. The burette set on the edge of the beaker should be immersed in the liquid for about 1 cm.

4. Continue to add methanol until the silica is completely wet, that is, no longer floating on the water surface.

5. Methanol volume% at the end of titration is defined as methanol wettability.

Among them, hydrophilic silica having a hydrophobicity of 20 or less is preferable because it is excellent in water absorption and also has the effect of a dispersibility improving agent for the coating material. Further, magnesium oxide, magnesium carbonate, magnesium hydroxide, or a magnesium compound obtained by subjecting the surface of magnesium to a hydroxylation treatment is preferable because it also has the effect of improving the charge rising performance.

Further, these inorganic fine particles preferably have an average particle diameter of 1 to 200 nm and a BET specific surface area of 500 to 10 m ² / g. Particularly, the average particle size is 5 to 100 nm and the BET specific surface area is 20.
Particles of 0 to ²⁰ m ² / g are more preferable from the viewpoint of dispersibility. Particles of less than 1 nm and more than 500 m ² / g are likely to be embedded in the carrier. Further, particles having a particle size of more than 200 nm and 10 m ² / g or less are difficult to disperse in the coating layer, and the amount of free components increases, and the chargeability with the toner is likely to be impaired.

The average particle size is the transmission electron microscope LPA-3000 / 3.
The number average primary particle size measured by 100 (manufactured by Otsuka Electronics) is shown. BET specific surface area is measured by Flow So
The value measured by the one-point method measured by rb2300 (manufactured by Shimadzu Corporation) is shown.

Further, the resistance is preferably 10 ⁶ to 10 ¹⁰ Ωcm. The resistance measurement method shows a value measured in a powder state under the condition that a constant pressure is applied. This measurement shows the volume resistivity measured at 20 ° C. and 50% RH environment.

The addition amount of the inorganic fine particles in the coating layer is preferably 0.5 to 70% by weight, more preferably 1 to 60% by weight. If the addition amount is less than 0.5% by weight, the effect is insufficient, and if it exceeds 70% by weight, it becomes difficult to form the coating layer, and the durability such as film peeling is deteriorated. These inorganic fine particles may be used alone or in combination of two or more.

<Production Method of Carrier> Although a sufficient effect can be obtained by a dip coating method, a spray coating method, a fluidized bed coating method, etc., the inorganic fine particles are uniformly dispersed in the resin, and the coating layer is magnetic particles. It has excellent adhesiveness, and it is a dry mechanical impact method from the viewpoint of excellent durability because it is formed by driving resin particles into magnetic particles by mechanical impact force to fix them by the dry method. Is particularly preferable.

In this method, in the first step, magnetic particles, inorganic fine particles, and resin particles are mixed and stirred by an ordinary stirring device or the like, and the magnetic particles are physically or electrostatically adhered to their surfaces. Apply evenly. The first step may be performed without heating or may be performed under heating to such an extent that the resin particles are slightly softened. The first step is completed as described above.

As the apparatus for carrying out the first step, various mixing and stirring apparatuses can be used, but from the viewpoint of production efficiency and the like, an apparatus capable of continuously carrying out the subsequent second step is preferable.

When the first step is completed as described above,
Subsequently, the second step is performed. In the second step, the mixture obtained in the first step is stirred with a strong stirring force without heating or under heating and the impact force is repeatedly applied to the mixture to coat the surface of the particles with a coating agent ( Resin fine particles and inorganic fine particles) are fixed.

Even when the second step is carried out without heating, the temperature of the mixture usually rises to 30 to 60 ° C. due to the natural heat generation due to friction of the mixture, and the heat causes the carrier obtained in the first step to rise. The surface of is softened and the coating agent can be fixed easily. When heating, 60-120 degreeC is especially preferable. If the heating temperature is excessively high, magnetic particles tend to aggregate with each other.

<Toner> Although a general toner can be used, a toner externally added with inorganic fine particles, which can improve the developing property and the cleaning property by improving the fluidity, is preferable.

As the inorganic fine particles, silica fine particles and titania fine particles whose surfaces are hydrophobized with a silane coupling agent, a titanium coupling agent or the like are preferably used because of their negative charge imparting ability and fluidity improving effect. The inorganic fine particles preferably have a number average primary particle diameter of 5 to 100 nm.

As the binder resin, a polyester resin is preferably used because it has a high capability of imparting negative chargeability. Moreover, in order to further improve the charge rising characteristics,
It is more preferable to add a negatively chargeable charge control agent such as a chromium-containing metal complex.

As the colorant used in the toner,
For example, carbon black, nigrosine dye or the like is used as the black toner, and C.I. is used as the pigment for the yellow, magenta and cyan toners. I. Pigment Blue 15: 3, C.I. I. Pigment Blue 15, C.I. I.
Pigment Blue 15: 6, C.I. I. Pigment Blue 68, C.I. I. Pigment Red 48-3, C.I. I. Pigment Red 122, C.I. I. Pigment Red 21
2, C.I. I. Pigment Red 57-1, C.I. I. Pigment Yellow 17, C.I. I. Pigment Yellow-8
1, C.I. I. Pigment Yellow-154 and the like can be preferably used.

<Photoreceptor> Although not particularly limited, any of the commonly used selenium photoreceptor, amorphous silicon photoreceptor, organic photoreceptor and the like can be used.

<Thin Layer Forming Method><< Developer Layer Thickness >> 20 to 500 μm is appropriate, and especially 50 to 400
μm is preferred. To reliably produce such a developer layer thickness on the developer carrying member, a rod-shaped regulating member having the following physical properties is used and pressed against the developer carrying member.

<< Rigidity of developer regulating body >> Rigidity rate 10 ⁴ kg /
(1.0 to 10) × 10 ⁴ k containing various magnetic metals such as iron and its alloys having a cm ² or more and magnetic powder
Hard resin having a rigidity of about g / cm ² , iron plated with chromium or the like, and iron alloy are also used.

<< Pressing force on the developer >> (1 to 20) gf / mm is appropriate, and (2 to 10) gf / mm is particularly preferable.

<Image Forming Method> FIG. 1 is a schematic sectional view of a typical image forming apparatus using the developer according to the present invention.

In FIG. 1, reference numeral 10 is a photosensitive drum which is an image bearing member, and an organic photosensitive layer is coated on the drum, grounded, and driven and rotated clockwise. Reference numeral 12 denotes a scorotron charger, which applies uniform charging to the peripheral surface of the photosensitive drum 10 by corona discharge. Prior to the charging by the charging device 12, the peripheral surface of the photoconductor may be erased by performing exposure by 11 using a light emitting diode or the like in order to eliminate the history of the photoconductor in the previous image formation.

After uniformly charging the photosensitive member, the image exposing means 13 performs image exposure based on the image signal. The image exposure means 13 in this figure bends the optical path by a reflection mirror 132 via a polygon mirror 131, an f.theta. Lens, etc., which rotate using a laser diode (not shown) as a light source, and scans the photosensitive drum to form an electrostatic latent image. To be done.

The electrostatic latent image is then developed by the developing device 14. At the periphery of the photosensitive drum 10, there are provided developing devices 14 each containing a developer composed of toner such as yellow (Y), magenta (M), cyan (C), and black (K), and a carrier. The development of the first color is carried out by the developing sleeve 141 which contains a magnet and holds the developer and rotates. The developer is a carrier in which ferrite is used as a core and an insulating resin is coated around the core, a polyester is used as a main material, a pigment corresponding to a color, a charge control agent, silica,
It is composed of toner added with titanium oxide, etc., and the developer is 100-600 μm on the developing sleeve 141 by the layer forming means.
The layer thickness is regulated by the layer thickness and the sheet is conveyed to the developing area and development is performed. At this time, normally, a DC or AC bias potential is applied between the photosensitive drum 10 and the developing sleeve 141 to perform development.

In the color image formation, after the visualization of the first color is completed, the process for forming the second color image is started, and the scorotron charger 12 performs uniform charging again to form the latent image of the second color image. It is formed by the exposure means 13. An image forming process similar to that for the second color is performed for the third and fourth colors, and a visible image of four colors is formed on the peripheral surface of the photosensitive drum 10.

On the other hand, in the monochrome electrophotographic apparatus, the developing device 14
Is composed of one kind of black toner, and an image can be formed by one development.

After the image formation, the recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 17 when the transfer timing is adjusted.

In the transfer area, the transfer roller 18 is pressed against the peripheral surface of the photosensitive drum 10 in synchronization with the transfer timing.
The supplied recording paper P is sandwiched and the multicolor image is transferred at once.

Next, the recording paper P is discharged at almost the same time by the separating brush 19 which is brought into a pressure contact state, separated by the peripheral surface of the photosensitive drum 10 and conveyed to the fixing device 20, and the heat roller 201.
The toner is fused by heating and pressurizing the pressure roller 202, and then the toner is ejected to the outside of the apparatus through the paper ejection roller 21. The transfer roller 18 and the separation brush 19 are withdrawn from the peripheral surface of the photosensitive drum 10 after the recording paper P has passed and are ready for the next toner image formation.

On the other hand, the photosensitive drum after the recording paper P is separated
Residual toner is removed / cleaned by the pressure contact of the blade 221 of the cleaning device 22, and the charge removing unit 11 again receives the charge removal from the charge removing unit 11 and the charging unit 12 to start the next image forming process. When superimposing a color image on the photoconductor, the blade 221 moves immediately after cleaning the photoconductor surface and retracts from the peripheral surface of the photoconductor drum 10.

Reference numeral 30 is a removable cartridge in which the image holding member, the charging means, the developing means and the cleaning means are integrated.

An electrophotographic apparatus is constructed by integrally combining a plurality of constituent elements such as the above-mentioned photosensitive member, developing means, cleaning means and the like as an apparatus unit, and this unit can be detachably attached to the apparatus main body. It may be configured to.
For example, a unit is formed by integrally supporting at least one of a charging unit, a developing unit, and a cleaning unit together with a photoconductor to form a unit, which is detachably attached to the apparatus body, and is attached and detached by using a guide unit such as a rail of the apparatus body. It may be configured freely. At this time, the above device unit may be provided with a charging unit and / or a developing unit.

When the electrophotographic apparatus is used as a copying machine or a printer, the image exposure means irradiates the photoconductor with reflected light or transmitted light from the original document, or a sensor reads the original document and converts it into a signal. According to the method, the laser beam is scanned, the LED array is driven, or the liquid crystal shutter array is driven to irradiate the photoconductor with light.

When used as a printer for a facsimile, the image exposure means 13 provides exposure for printing received data.

[0069]

EXAMPLES The present invention will be described below, but the present invention is not limited to these examples. In addition, "part" represents a weight part below.

[Toner] The materials shown in "Table 1" below were used and kneaded, kneaded, crushed and classified to obtain a powder having a volume average particle diameter of 8 µm. Further, 100 parts of this powder and 2.0 parts of hydrophobic silica fine particles (number average primary particle diameter 16 nm) were mixed with a Henschel mixer to obtain toners A, B, C and D.

[0071]

[Table 1]

[Production of Carrier] On the surface of Cu—Zn ferrite particles having a specific gravity of 5.0, a volume average particle size of 50 μm and a saturation magnetization of 25 emu / g when an external magnetic field of 1000 oersted is applied, the average film thickness of the coating layer is The thickness was set to 2.0 μm, and the layer was manufactured as shown in “Table 2” below.

[0073]

[Table 2]

[Preparation of Developer] Toners A (black), B (yellow), C (magenta), D (cyan), and carriers C-1 to C-9 and HC-1 to HC-3 are used as toners. Using a V-type mixer so that the concentration becomes 7% under test environment (3
After mixing for 20 minutes at 0 ° C .; 80% RH, the following developer D is used.
-1 to D-9 and HD-1 to HD-3 were produced.

[0075]

[Table 3]

[Evaluation] << 1 >> Evaluation of Charge Amount in Each Environment Measurement was carried out in a low temperature and low humidity environment (10 ° C., 10% RH) and a high temperature and high humidity environment (33 ° C., 90% RH).

1 g of the toner and 19 g of the carrier are weighed, put in a 20 cc sample bottle so that the carrier is on the lower side and the toner is on the upper side, and left under predetermined conditions for 3 hours or more.

Using a shaker (Yayoi type New-YS), the mixture was mixed for 10 minutes at a swing angle of 30 ° and a shaking rate of 200 strokes / min, and the charge amount was measured with a blow-off type charge amount measuring device.

[0079]

[Table 4]

With the carrier of the present invention, a large amount of charge can be obtained with a substantially constant value in both low temperature and low humidity environment and high temperature and high humidity environment, and the difference in the charge amount is small.

<< 2 >> Evaluation of Actual Machine The test was carried out using high-temperature and high-humidity (33 ° C .; 90% RH) and low-temperature and low-humidity (10 ° C .; 10% RH) using the image forming methods -1 and -2. ), The actual shooting test was performed, and the difference in the initial developability and transferability depending on the environment and the actual shooting 1
The state of toner scattering after the completion of 10,000 sheets was evaluated.

Further, with respect to the image forming method-2 in which the stress applied to the developer is large, the spent resistance / abrasion resistance was evaluated at the end of 10,000 sheets.

{Image forming method-1} Konica Copier K
An onica U-BIX3035 modified machine was used.

[Main Modifications of Device] (1) Charging Part The discharge polarity was changed from negative to positive so that the photoconductor potential in the image area was 750V and the photoconductor potential in the non-image area was 50V.

(2) Transfer Part The discharge polarity was changed from positive to negative.

(3) Developing part The developing bias is -150V.
Changed to.

[Image Forming Method-2] A color copying machine Konica 9028 manufactured by Konica Corporation was used.

The Konica 9028 is a non-contact reversal development type multicolor image forming apparatus. In this developing method, the developer adhering to the developing sleeve is thinned by a magnetic stainless steel pressure regulating rod (SUS416 type) and conveyed to the developing area in a state where it is not in contact with the organic photoreceptor, This is a method of developing an electrostatic latent image on an organic photoconductor under an oscillating electric field obtained by applying a sleeve AC bias voltage.

(Development conditions) Photoconductor surface potential: -700 v DC bias: -500 v AC bias: (peak to peak value) 2.2 kv Developing sleeve rotation speed: 400 rpm Developer layer thickness: 300 μm Developer regulator pressing force: 5 gf / mm Developer regulated body diameter: 6 mm [Evaluation items] (1) Developability Original density 1.3 Area 10 cm ²
Of the developed toner, the amount of developed toner per 1 cm ² (m
g) was calculated.

However, although the image forming method-1 is an evaluation of one color of the black developer, the image forming method-2 prints an image with a pixel ratio of 5% for each of yellow, magenta, cyan and black. The developability was evaluated with this full-color image.

(2) Transferability In the same manner as the developing property measurement,
The evaluation was made by the ratio of the toner on the transfer member to the total amount of developing toner.

(3) Toner Scattering A particle counter was installed in the machine to determine the number of toner scatters at the end of 10,000 actual images.

[0093]

[Table 5]

[0094]

[Table 6]

As is apparent from Tables 5 and 6, the developability,
In terms of both transferability and toner scattering, the properties of the present invention are much better than the comparative examples of the invention.

(4) Spent Resistance / Abrasion Resistance (Coverage) Only for Image Forming Method-2, the developer at the end of 10,000 sheets was washed with water to separate the toner, and the carrier was dried. To get The coating layer of the obtained carrier was dissolved with methyl ethyl ketone, the weight of the magnetic particles was measured, and the coating rate was calculated by the following formula.

The results are shown in Table 7 together with the number of broken coat layers.

Carrier coverage (% by weight) = {(AB)
/ B} × 100 A: Weight of carrier obtained after drying coating layer B: Weight of magnetic particles after dissolution of coating layer

[0099]

[Table 7]

It can be seen that the amount of change in the carrier coverage is extremely small in the present invention as compared with the comparative examples not in the invention.

[0101]

According to the present invention, there is provided a carrier for a negatively chargeable developer which has a small difference in the amount of charge in the environment and maintains it for a long period of time, and a developer using the same and an image forming method. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus according to the present invention.

[Explanation of symbols]

 10 Photoreceptor Drum 12 Scorotron Charger 13 Image Exposure Means 14 Developer

Claims (3)

[Claims] 1. A developer comprising colored particles containing at least a binder resin and a colorant, and a carrier, wherein the carrier has magnetic particles on which at least inorganic fine particles are contained. A developer which is a negatively-charged carrier coated with a resin layer of a polymer composed of a chain-type methacrylic acid ester. 2. A magnetic particle is coated with a polymer composed of an alicyclic methacrylic acid ester containing at least inorganic fine particles and a chain methacrylic acid ester by a dry coating for applying and fixing by mechanical impact. A method for producing a carrier for a negatively chargeable developer, which comprises: 3. A developer comprising a colored particle containing at least a binder resin and a colorant and a carrier is thinned by a developer regulator to a developer layer thickness of 20 to 500 μm, thereby forming an image forming body. In the image forming method of developing the above electrostatic latent image in a non-contact manner, the carrier is a resin comprising a polymer composed of an alicyclic methacrylic acid ester containing at least inorganic fine particles on a magnetic particle and a chain methacrylic acid ester. An image forming method, which is a negatively chargeable carrier having a layer coated thereon.