JP7404981B2 - Electrophotographic photoreceptor, electrophotographic image forming apparatus, and electrophotographic image forming method - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor, an electrophotographic image forming apparatus, and an electrophotographic image forming method. More specifically, the present invention relates to an electrophotographic photoreceptor, an electrophotographic image forming apparatus, and an electrophotographic image forming method that have good cleaning properties, scratch resistance, and can suppress point defects over a long period of time.

In recent years, image formation using electrophotographic copying machines and printers has been desired to have even higher durability and higher image quality. Image formation that requires output is also increasing.
Therefore, electrophotographic photoreceptors are also required to have higher durability, higher image quality, higher printing rate, and support for image output with higher image density.

In particular, demands for high durability are increasing in order to contribute to the realization of a sustainable society, and mechanical strength such as abrasion resistance and scratch resistance is the most important factor determining the durable life of photoconductors. is particularly important.

On the other hand, with regard to high image quality, it is necessary to be able to maintain high image quality over a long period of time, and it is also important to maintain good cleaning performance, which affects image quality.

Therefore, it is known to incorporate organic resin particles into the surface layer of a hardened type in order to improve the abrasion resistance and scratch resistance that lead to a longer life of the photoreceptor, as well as to improve the cleanability of the photoreceptor. .

For example, Patent Document 1 proposes that organic resin particles (hereinafter also referred to as melamine resin particles) made of a resin containing structural units derived from melamine be contained in a hardening type surface layer using a monomer having two or more functionalities. .

However, as shown in the examples, when a trifunctional monomer is used alone, compared to when it is used in combination with a bifunctional monomer, brittle parts may be formed in the resin part, and unreacted polymerizable groups tend to remain. Therefore, there is room for improvement in terms of scratch resistance, cleanability, and point defects, especially when the printing rate is high and the image density is high.

Additionally, if a bifunctional monomer is used alone, the crosslinking density will be insufficient and it will be difficult to obtain sufficient film strength, so there is room for improvement from the perspective of ensuring scratch resistance during long-term use. In addition, it becomes difficult to maintain cleanability, especially when the printing rate is high and the image density is high.

In addition, a proposal has been made to contain organic resin particles in the surface layer using a combination of a trifunctional monomer and a compound having a monovalent hydrocarbon group with 7 or more carbon atoms and a polymerizable functional group in the same molecule (monofunctional monomer). (Patent Document 2).

However, when a monofunctional monomer and a trifunctional monomer are used together, the crosslinking density becomes insufficient and it becomes difficult to obtain sufficient film strength.

As a result, problems arise in maintaining good scratch resistance during long-term use. In addition, particularly when the printing rate is high and the image density is high, it becomes difficult to maintain good cleaning performance.

Japanese Patent Application Publication No. 2015-114453 JP2019-45862A

The present invention has been made in view of the above-mentioned problems and circumstances, and an object to be solved is to provide an electrophotographic photoreceptor and an electrophotographic image that can achieve good cleaning performance, scratch resistance, and suppression of point defects over a long period of time. An object of the present invention is to provide a forming apparatus and an electrophotographic image forming method.

In order to solve the above problem, in the process of examining the causes of the above problem, the present inventor discovered that the outermost layer should be made of a polymerizable monomer with trifunctionality or more, a bifunctional monomer with a specific structure, and a monomer within a specific range. By forming a composition containing organic resin particles having a particle size of This discovery led to the present invention.
That is, the above-mentioned problems related to the present invention are solved by the following means.

1. An electrophotographic photoreceptor having a curable outermost layer at least on the photosensitive layer,
a first polymerizable monomer in which the outermost layer has at least three or more polymerizable groups in one monomer molecule;
a second polymerizable monomer having two polymerizable groups in one monomer molecule;
A cured product formed from a composition containing organic resin particles,
The content of the second polymerizable monomer is within the range of 30 to 70% by mass based on the total polymerizable monomers,
The organic resin particles contain at least a compound having a melamine structure, and
The particle size of the organic resin particles is 0. 20-2 . An electrophotographic photoreceptor characterized in that the particle diameter is within a range of 50 μm.

2. The electron according to item 1, wherein the two polymerizable groups of the second polymerizable monomer have a structure in which they are bonded via a linking group containing three or more atoms having an atomic weight of 12 or more. Photographic photoreceptor.

3. 3. The electrophotographic photoreceptor according to item 1 or 2, wherein the two polymerizable groups of the second polymerizable monomer have at least a linking group having an alkylene structure having 2 or more carbon atoms.

4 . 3. The electrophotographic photoreceptor according to any one of Items 1 to 3 , wherein the first polymerizable monomer has three polymerizable groups in one monomer molecule.

5 . A bifunctional polymerizable monomer is contained as a third polymerizable monomer other than the first polymerizable monomer or the second polymerizable monomer, and the second polymerizable monomer and the third polymerizable monomer The electrophotograph according to any one of Items 1 to 4 , wherein the total amount of Photoreceptor.

6 . An electrophotographic image forming apparatus comprising the electrophotographic photoreceptor according to any one of items 1 to 5 .

7 . At least a charging step for charging the surface of the electrophotographic photoreceptor, an exposure step for forming an electrostatic latent image by exposing the surface of the electrophotographic photoreceptor, and a step for making the electrostatic latent image visible with toner. An electrophotographic image forming method comprising a developing step of forming a toner image and a transfer step of transferring the toner image to a transfer medium, the method comprising: an electrophotographic image forming method according to any one of items 1 to 5 ; An electrophotographic image forming method characterized by using a photographic photoreceptor.

By means of the above means of the present invention, it is possible to provide an electrophotographic photoreceptor, an electrophotographic image forming apparatus, and an electrophotographic image forming method that can achieve good cleaning properties, scratch resistance, and suppression of point defects over a long period of time.

Although the mechanism of expression or action of the effects of the present invention is not clear, it is speculated as follows.

In the cured surface layer containing organic resin particles, by using the first monomer (trifunctional or higher polyfunctional) and the second monomer (bifunctional) together, in addition to improving the cleanability of the organic resin particles, It is possible to form a film with fewer reactive polymerizable groups, and it is also possible to reduce the stress on the resin part due to the large-diameter organic resin particles, achieving both good cleaning performance and scratch resistance, and long-term point defect suppression. I can do it.

By using the second monomer (bifunctional monomer) together with the first monomer (polyfunctional monomer), the reaction rate can be increased without impairing the film strength.
In order to increase the reaction rate, it is effective to use monomers with fewer functional groups, but the crosslinking density tends to decrease.

Therefore, when a polyfunctional monomer and a monofunctional monomer are used in combination, or when a difunctional monomer is used alone, the crosslinking density becomes insufficient and the scratch resistance deteriorates.

On the other hand, when polyfunctionality of trifunctionality or higher is used alone or in combination with polyfunctionality, the number of unreacted polymerizable groups increases and local resistance decreases, resulting in image defects such as dots printed on non-printed areas. is more likely to occur.

On the other hand, since large-diameter organic resin particles can lower the surface energy and friction coefficient of the photoreceptor, the adhesion force between the photoreceptor and toner is reduced, and cleaning performance is improved.
In particular, when melamine is used as the organic resin particles, from the viewpoint of compatibility with the resin, it is possible to suppress the particles from falling off during durability, making it possible to maintain cleanability over a long period of time.

However, if large-diameter fine particles are simply contained in the hardening type surface layer, the organic resin particles apply stress to the resin portion, making the film brittle and easily deteriorating the scratch resistance.

Therefore, when a bifunctional monomer is used as the second monomer, the crosslinking density is appropriately reduced and stress is less likely to be applied to the resin part.
In particular, when the second monomer has a structure in which two (meth)acryloyloxy groups, which are polymerizable groups, are separated, the resin part has a flexible structure, so the stress applied to the resin part is smaller, and the film More effective in improving strength.

A sectional view showing an example of the structure of the electrophotographic photoreceptor of the present invention A schematic diagram showing an example of the overall configuration of a tandem-type electrophotographic image forming apparatus including an electrophotographic photoreceptor of the present invention. A schematic diagram showing an example of the configuration of a fine particle manufacturing apparatus used for manufacturing composite particles used in Examples of the present invention Example of FT-IR spectrum Schematic diagram for explaining the photoreceptor evaluation method (test image consisting of a vertical striped solid image with 10% coverage) Schematic diagram for explaining the photoreceptor evaluation method (test image consisting of a horizontal striped solid image with 40% coverage) Schematic diagram for explaining the photoreceptor evaluation method (test image consisting of a horizontal striped solid image with 25% coverage)

The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a curable outermost layer on at least a photosensitive layer, wherein the outermost layer has at least three or more polymerizable groups in one monomer molecule. It is a cured product formed from a composition containing a first polymerizable monomer, a second polymerizable monomer having two polymerizable groups in one monomer molecule, and organic resin particles. The content of the polymerizable monomer is within the range of 30 to 70% by mass based on the total polymerizable monomers, and the organic resin particles contain at least a compound having a melamine structure, and Particle size is 0. 20-2 . It is characterized by being within a range of 50 μm.
This feature is a technical feature common to or corresponding to each of the embodiments described below.

As an embodiment of the present invention, it is preferable that the two polymerizable groups of the second polymerizable monomer have a structure in which they are bonded via a linking group containing three or more atoms having an atomic weight of 12 or more.
By having such a linking group, it becomes possible to provide a flexible portion to the resin part, and therefore it becomes possible to enhance the effect of reducing stress on the resin due to the organic resin particles.

Further, it is preferable that the two polymerizable groups of the second polymerizable monomer have at least an alkylene structure in which the connecting group has two or more carbon atoms.
When two polymerizable groups are connected via a linking group having fewer than 18 atoms having an atomic weight of 12 or more, the reduction in crosslink density can be reduced and damage resistance can be prevented from deteriorating.

Further, the organic resin particles are organic resin particles containing at least a compound having a melamine structure, and have excellent compatibility with the resin.

Further, it is preferable that the first polymerizable monomer has three polymerizable groups in one molecule of the monomer from the viewpoint of improving the reaction rate.

Moreover, a bifunctional polymerizable monomer is contained as a third polymerizable monomer other than the first polymerizable monomer or the second polymerizable monomer, and the second polymerizable monomer and the third polymerizable monomer are It is preferable that the total amount with the monomer is within the range of 45 to 70% by mass based on the total content of the polymerizable monomers from the viewpoint of achieving effects.

When the third polymerizable monomer is a bifunctional polymerizable monomer, the total amount of the second polymerizable monomer and the third polymerizable monomer is based on the total content of polymerizable monomers: 4 The amount is within the range of 5 to 70 % by mass , which improves the effect of suppressing reduction in reaction rate and reduction in crosslinking density.

The electrophotographic photoreceptor of the present invention is suitably used in an electrophotographic image forming apparatus.

Further, the electrophotographic photoreceptor of the present invention is suitably used in an electrophotographic image forming method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention, its constituent elements, and forms and aspects for carrying out the present invention will be described below. In this application, "~" is used to include the numerical values described before and after it as a lower limit value and an upper limit value.

<Electrophotographic photoreceptor>
The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a curable outermost layer on at least a photosensitive layer, wherein the outermost layer has at least three or more polymerizable groups in one monomer molecule. It is a cured product formed from a composition containing a first polymerizable monomer, a second polymerizable monomer having two polymerizable groups in one monomer molecule, and organic resin particles. The content of the polymerizable monomer is within the range of 30 to 70% by mass based on the total polymerizable monomers, and the organic resin particles contain at least a compound having a melamine structure, and Particle size is 0. 20-2 . It is characterized by being within a range of 50 μm.

[Basic configuration of electrophotographic photoreceptor]
FIG. 1 is a sectional view showing an example of the structure of an electrophotographic photoreceptor of the present invention.
FIG. 1(a) is a cross-sectional view showing an electrophotographic photoreceptor 101A having a first configuration, in which an intermediate layer 103 is formed on a conductive support 102, a photosensitive layer 104 is provided thereon, and the The outermost layer 105 according to the present invention is formed on the surface thereof, and the outermost layer 105 includes a first polymerizable monomer having at least three or more polymerizable groups in one molecule of the monomer; This is a cured product formed from a composition containing a second polymerizable monomer having two monomers in one monomer molecule and organic resin particles.

Further, FIG. 1(b) is a cross-sectional view showing an electrophotographic photoreceptor 101B having a second configuration, in which an intermediate layer 103 is formed on a conductive support 102, and a charge generation layer 106 and a charge generation layer 106 are formed on the intermediate layer 103. A photosensitive layer 104 composed of a charge transport layer 107 is formed, and an outermost layer 105 according to the present invention is formed on the outermost surface. A cured product formed from a composition containing a first polymerizable monomer having three or more polymerizable groups, a second polymerizable monomer having two polymerizable groups in one monomer molecule, and organic resin particles. .

Further, the outermost layer of the electrophotographic photoreceptor of the present invention may contain a polymerizable monomer (third polymerizable monomer) other than the first polymerizable monomer and the second polymerizable monomer.
Below, details of the main components of the electrophotographic photoreceptor of the present invention will be explained.

1. Outermost Layer The outermost layer according to the present invention comprises a first polymerizable monomer having at least three or more polymerizable groups in one monomer molecule, and a second polymerizable monomer having two polymerizable groups in one monomer molecule. monomer and a particle size of 0. 20-2 . This is a cured product formed from a composition containing organic resin particles having a particle size within the range of 50 μm.

Hereinafter, details of each component of the outermost layer according to the present invention will be explained.

(1.1) Polymerizable monomer The polymerizable monomer according to the present invention has a polymerizable group, and can be polymerized ( It is a compound that, when cured, becomes a resin that is generally used as a binder resin for photoreceptors.

The polymerizable monomer is preferably a radically polymerizable monomer that is cured through a radical polymerization reaction.

Examples of the polymerizable monomer include styrene monomers, acrylic monomers, methacrylic monomers, vinyltoluene monomers, vinyl acetate monomers, and N-vinylpyrrolidone monomers.

Examples of the binder resin include polystyrene, polyacrylate, and the like.

The polymerizable group of the polymerizable monomer preferably has a carbon-carbon double bond and is a polymerizable group.

The polymerizable group is preferably an acryloyloxy group (CH ₂ =CHCOO-) or a methacryloyloxy group (CH ₂ =C(CH ₃ )COO-) because it can be cured with a small amount of light or in a short time. Particularly preferred.

The polymerizable monomer includes a first polymerizable monomer and a second polymerizable monomer, and contains a polymerizable monomer (third polymerizable monomer) other than the first polymerizable monomer and the second polymerizable monomer. You may.
The polymerizable monomer can be synthesized by a known method, and can also be obtained as a commercially available product.

(1.1.1) First polymerizable monomer The first polymerizable monomer is a polyfunctional monomer (hereinafter also referred to as a trifunctional or higher polyfunctional monomer) having three or more polymerizable groups in one monomer molecule. be.

By using the second polymerizable monomer (bifunctional monomer) in combination with the first polymerizable monomer (polyfunctional monomer), the reaction rate can be increased without impairing the film strength.
In order to increase the reaction rate, it is effective to use monomers with fewer functional groups, but the crosslinking density tends to decrease.
Therefore, when a polyfunctional monomer and a monofunctional monomer are used in combination, or when a difunctional monomer is used alone, the crosslinking density becomes insufficient and the scratch resistance deteriorates.

On the other hand, the crosslinking density can also be lowered by introducing a flexible moiety into a trifunctional or higher polyfunctional monomer.

However, when a flexible moiety is introduced into a trifunctional or higher polyfunctional monomer, since there are many polymerizable groups, the reaction rate decreases and the number of unreacted polymerizable groups increases, resulting in worsening of point defects.
Furthermore, the reduction in crosslinking density causes a reduction in membrane strength, which is an advantage of polyfunctional monomers.

The ratio of the first polymerizable monomer to the second polymerizable monomer can be adjusted as appropriate within a range that allows the electrophotographic photoreceptor to achieve the effects of the present invention.
In addition, from the viewpoint of improving the reaction rate, the first polymerizable monomer is preferably a compound having three polymerizable groups in one molecule of the monomer.
Specific examples of the first polymerizable monomer include, but are not limited to, the following compounds M1 to M12.
In the following formulas, R represents an acryloyloxy group, and R' represents a methacryloyloxy group.

The first polymerizable monomer is preferably a monomer having three polymerizable groups from the viewpoint of improving the reaction rate.

(1.1.2) Second polymerizable monomer The second polymerizable monomer is a bifunctional monomer having two polymerizable groups in one monomer molecule.

The content of the second polymerizable monomer is within the range of 30 to 70% by mass, and 35 to 65% by mass based on the total polymerizable monomers, from the viewpoint of exhibiting the effect of the second polymerizable monomer. It is preferably within the range of %.

When the amount of the second polymerizable monomer is greater than 30 % by mass, the contribution to improving the reaction rate becomes large, and the effect of suppressing point defects is more likely to be exhibited.

On the other hand, when the second polymerizable monomer is reduced to less than 70 % by mass, it is possible to suppress the decrease in crosslinking density, and there is a tendency to ensure sufficient film strength, so it exhibits an effect on scratch resistance. It can be made easier.
By using the first polymerizable monomer and the second polymerizable monomer, which is a bifunctional polymerizable monomer, the reaction rate of the polymerization reaction can be increased, and the polymerization that causes local resistance reduction can be increased. It becomes possible to reduce the number of unreacted sites.
In the present invention, the effect is achieved by improving the reaction rate using a bifunctional polymerizable monomer and by reducing the stress exerted on the resin by the organic fine particles described later by reducing the crosslinking density appropriately.
Although it is possible to increase the polymerization reaction rate when a monofunctional monomer is used in unreacted sites, the crosslinking density is greatly reduced, making it difficult to ensure sufficient film strength.
From the viewpoint of reducing the stress on the resin due to the organic resin particles, it is preferable that the two polymerizable groups of the second polymerizable monomer are separated from each other.

Specifically, it is preferable that the two polymerizable groups have atoms having an atomic weight of 12 or more bonded to each other via three or more linking groups.

By having such a linking group, it becomes possible to provide a flexible portion to the resin part, and therefore it becomes possible to enhance the effect of reducing stress on the resin due to the organic resin particles.

Examples of the linking group having three or more atoms having an atomic weight of 12 or more include an alkylene group, an ether bond, an ester bond, a cyclic structure, and the like, and may have a branched structure.

More preferably, the two polymerizable groups have atoms having an atomic weight of 12 or more bonded via 3 to 18 linking groups.

The two polymerizable groups have atoms with an atomic weight of 12 or more bonded through 3 to 18 linking groups, which increases the effect of reducing the stress on the resin due to the organic resin particles and reduces the crosslink density. It is possible to suppress deterioration of scratch resistance.

A more preferable structure of the second polymerizable monomer is that at least the connecting group of the two polymerizable groups has an alkylene structure having 2 or more carbon atoms, and it is further preferable that the connecting group does not have a cyclic structure. More preferably, the linking group is an alkylene group having 3 or more carbon atoms.

When the linking group has an alkylene structure having 2 or more carbon atoms, a more flexible portion can be provided to the resin portion.

Further, since a ring-shaped structure results in a rigid portion, a structure that does not have a ring-shaped structure can prevent the portion from becoming brittle.

Since alkylene groups have a linear structure, when the linking group is an alkylene group with 3 or more carbon atoms, the distance between two polymerizable groups can be increased more efficiently, making it easier to impart flexibility. , it becomes possible to more effectively reduce the stress on the resin part due to the organic resin particles.

As a result, even when the printing rate and image density are particularly high, good cleaning performance can be maintained, and furthermore, scratch resistance can be improved.

Here, when the bifunctional polymerizable monomer accounts for 30 % by mass or more of the total polymerizable monomers, the amount of the polyfunctional polymerizable monomer decreases, and a decrease in the reaction rate can be suppressed.
As a result, it is advantageous for suppressing point defects.
In addition, when the content is less than 70 % by mass, a decrease in crosslinking density can be suppressed, and the effect on scratch resistance becomes greater.
From the viewpoint of producing effects, it is preferable that both the bifunctional polymerizable monomer and the trifunctional or higher functional polymerizable polyfunctional monomer be 30 to 70 % by mass of the monomers as a whole.

Examples of the second polymerizable monomer include bifunctional alkyl (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene (meth)acrylate, tricyclodecanol (meth)acrylate, and alkoxylated bisphenol A (meth)acrylate. Can be mentioned.

Specific examples of commercially available second polymerizable monomers include the following compounds, including alkyl (meth)acrylates: A-HD-N, A-NOD-N, A-NPG, BD, HD- N, DOD-N (manufactured by Shin-Nakamura Chemical Co., Ltd.), SR206, SR213 (manufactured by Sartomer), FA-129AS (manufactured by Hitachi Chemical Co., Ltd.), etc., polyethylene glycol (meth)acrylate: A-1000 , 4G, 9G (manufactured by Shin-Nakamura Chemical Co., Ltd.), SR272, SR344, SR209 (manufactured by Sartomer), FA-222A, FA-204M (manufactured by Hitachi Chemical Co., Ltd.), etc. ) Acrylates: APG-200, 3PG, 9PG (manufactured by Shin-Nakamura Chemical Co., Ltd.), SR508, SR644 (manufactured by Sartomer), FA-P207A (manufactured by Hitachi Chemical Co., Ltd.), etc., tricyclodecanol (manufactured by Hitachi Chemical Co., Ltd.), etc. ) Acrylates: DCP (manufactured by Shin Nakamura Chemical Co., Ltd.), SR833S (manufactured by Sartomer), etc., Alkoxylated bisphenol A (meth)acrylates: BPE-80N, ABE-200 (manufactured by Shin Nakamura Chemical Co., Ltd.), Examples include KAYARAD R-551 (manufactured by Nippon Kayaku Co., Ltd.), SR480, SR602 (all manufactured by Sartomer), and FA-302M (manufactured by Hitachi Chemical Co., Ltd.).

The ratio of the first polymerizable monomer to the second polymerizable monomer can be adjusted as appropriate within a range that allows the electrophotographic photoreceptor to achieve the effects of this embodiment.

(1.1.3) Third polymerizable monomer The monomer according to the present invention is a polymerizable monomer other than the first polymerizable monomer and the second polymerizable monomer (hereinafter also referred to as third polymerizable monomer). May contain. Moreover, in order to exhibit the effects of the present invention, it is preferable that the third polymerizable monomer accounts for less than 20% by mass of the total polymerizable monomers.

When a monofunctional polymerizable monomer is contained as the third polymerizable monomer, from the viewpoint of film strength, the monofunctional polymerizable monomer is preferably less than 10% by mass of the total polymerizable monomers.

When a bifunctional polymerizable monomer is contained as the third polymerizable monomer, the total amount of the second polymerizable monomer and the third polymerizable monomer is 45 to 70 % by mass based on the total polymerizable monomer. It is preferable that it is within the range of .

When the bifunctional polymerizable monomer accounts for 30 % by mass or more of the total polymerizable monomers, the amount of the polyfunctional polymerizable monomer decreases, making it difficult for the reaction rate to decrease.
As a result, there is a tendency to be advantageous in suppressing point defects.
On the other hand, if it is less than 70 % by mass, the decrease in crosslinking density will be small and the effect on scratch resistance will be large.

(1.2) Organic resin particles Examples of organic resin particles used in the present invention include melamine resin particles, fluororesin particles, silicone resin particles, acrylic resin particles, polystyrene resin particles, benzoguanamine resin particles, olefin resin particles, and other polymers. Examples include particles.

Melamine resin particles are resin particles containing at least a structural unit derived from melamine, and specific examples thereof include polycondensates of melamine and formaldehyde, copolycondensates of melamine, benzoguanamine, and formaldehyde, etc. It will be done.

Examples of the fluororesin particles include polytetrafluoroethylene (PTFE), polytrifluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyfluoroalkyl vinyl ether, polychlorotrifluoroethylene, polyhexafluoropropylene, polydifluorodichloroethylene, or the like. Examples include copolymers.

Examples of the silicone resin particles include organopolysiloxanes such as methylhydrogenpolysiloxane, dimethylpolysiloxane, methoxypolysiloxane, methylphenylpolysiloxane, and cyclohexylpolysiloxane.

Examples of the acrylic resin particles include polymers of acrylic esters or methacrylic esters, copolymers of acrylic esters or methacrylic esters and styrene, and may have a crosslinked structure.

Examples of the polystyrene resin particles include styrene polymers, which may have a crosslinked structure.

Examples of benzoguanamine resin particles include polycondensates of benzoguanamine and formaldehyde.

Examples of the olefin resin include polyethylene, polypropylene, polybutene, polyhexene, and the like.

Specific examples of commercially available organic resin particles include the following compounds.

Melamine resin particles: Eposter S, Eposter S6, Eposter S12, Eposter M30 (all manufactured by Nippon Shokubai Co., Ltd.), Optobeads 2000M, Optobeads 3500M (all manufactured by Nissan Chemical Co., Ltd.), etc.

Fluororesin particles: KTL-1N (manufactured by Kitamura Co., Ltd.), Polymist F5A (manufactured by Solvay Specialty Polymers Japan Co., Ltd.), etc.

Silicone resin particles: Tospearl XC99-A8808, Tospearl 120 (manufactured by Momentive Performance Materials Japan LLC), KMP-605 (manufactured by Shin-Etsu Chemical Co., Ltd.), etc.

Acrylic resin particles: Eposter MA1002, Eposter MA1004, Eposter MA2003 (all manufactured by Nippon Shokubai Co., Ltd.), FS102, FS201 (all manufactured by Nippon Paint Industrial Coatings Co., Ltd.), etc.

Polystyrene resin particles: SX-130H, KSR-3A (manufactured by Soken Chemical Co., Ltd.), etc.

Benzoguanamine resin particles: Epostor MS (manufactured by Nippon Shokubai Co., Ltd.), etc.
can be mentioned.

(1.2.1) Melamine resin particles Examples of the organic resin particles used in the present invention include melamine resin particles.
By using melamine resin particles, drop-off of the particles during durability can be suppressed from the viewpoint of compatibility with the resin, so it is possible to maintain good cleaning performance over a long period of time.

(1.2.2) Number average primary particle size of organic resin particles The number average primary particle size of the organic resin particles used in the present invention is 0. 20-2 . It is within the range of 50 μm, more preferably within the range of 0.30 to 1.50 μm.

When the number average primary particle size of the organic resin particles is 0.20 μm or more, good cleaning performance can be obtained, and when it is 0.30 μm or more, even better cleaning performance can be obtained.

On the other hand, when the number average primary particle size of the organic resin particles is 2.50 μm or less, curing inhibition is further suppressed when forming the outermost layer, and when it is 1.50 μm or less, curing inhibition is further suppressed. Good scratch resistance can be obtained.
The number average primary particle size of organic resin particles is defined as the number average primary particle size measured by the following method.

First, an enlarged photograph of a sample (organic resin particles, etc.) taken at a magnification of 30,000 times using a scanning electron microscope (manufactured by JEOL Ltd.) is taken into a scanner.

Next, from the obtained photographic images, 300 organic resin particle images excluding aggregated organic resin particles were randomly processed using the automatic image processing analysis system Luzex AP Software Ver. 1.32 (manufactured by Nireco Co., Ltd.) to perform binarization processing to calculate the Feret diameter in the horizontal direction of each of the organic resin particle images.

Then, the average value of the Feret diameter in the horizontal direction of each of the organic resin particle images is calculated and set as the number average primary particle diameter.

Here, the horizontal direction Feret diameter refers to the length of the side parallel to the x-axis of the circumscribed rectangle when the organic resin particle image is binarized.

(1.2.3) Surface modifier for organic resin particles The organic resin particles of the present invention may be surface-modified with a surface modifier. The surface modification treatment is made possible by subjecting untreated organic resin particles, which are raw materials, to surface modification treatment using a surface modifier.

The organic resin particles surface-modified with the surface modifier are considered to become surface-coated resin particles containing the chemical species (coating layer) derived from the surface modifier and the organic resin particles. Note that it is sufficient that the surface-modified organic resin particles have a chemical species (coating layer) derived from the surface modifier on at least a portion of the surface thereof.

In the present invention, there are no particular limitations on the surface modifier applied to the surface modification treatment of organic resin particles, and conventionally known ones can be used. Specific examples of the surface modifier include silane coupling agents, titanium coupling agents, fluorine-based surface modifiers, and surface modifiers having silicone chains.

The surface modifiers can be used alone or in combination of two or more. Further, the surface modifier may be a synthetic product or a commercially available product.

(1.2.4) Shape of organic resin particles The shape of the organic resin particles is not particularly limited, and examples thereof include spherical, elliptical in cross section, needle, disc, and irregular shape. From the viewpoint of improving cleaning performance, a spherical shape is preferable.

(1.2.5) Content ratio of organic resin particles The organic resin particles are preferably contained in a ratio of 3 to 50 parts by mass, more preferably 3 to 30 parts by mass, per 100 parts by mass of the cured resin. be. When the content of the organic resin particles is within the above range, good cleaning performance can be ensured.

(1.3) Inorganic filler The outermost layer of the present invention may contain an inorganic filler. When containing an inorganic filler, there are no particular limitations on the inorganic filler that can be used, but examples include magnesium oxide, lead oxide, aluminum oxide, zinc oxide, tin oxide, silicon dioxide, tantalum oxide, indium oxide, bismuth oxide, Yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, titanium dioxide, niobium oxide, molybdenum oxide, vanadium oxide, copper-aluminum composite oxide, tin oxide doped with antimony, etc. can be mentioned. Among them, aluminum oxide (Al ₂ O ₃ ), tin oxide (SnO ₂ ), titanium dioxide (TiO ₂ ), and copper-aluminum composite oxide (CuAlO ₂ ) are preferable.

The above-mentioned inorganic filler may be used alone or in combination of two or more types. Further, the inorganic filler may be a synthetic product or a commercially available product.

Further, the inorganic filler according to the present invention may be a composite fine particle formed by adhering a conductive metal oxide to the surface of a core material made of an insulating material.

That is, the inorganic filler may be a composite fine particle having a core-shell structure, in which the inorganic filler has a shell made of the inorganic filler as described above on the surface of a core made of an insulating material.

(1.3.1) Composite Particles with Core-Shell Structure Examples of the core material constituting the composite particles with the above-mentioned core-shell structure include barium sulfate, aluminum oxide, and silica.

Preferred examples of composite fine particles with a core-shell structure include composite particles having a core material made of barium sulfate and an outer shell made of tin oxide. Note that the ratio between the number average primary particle diameter of the core material and the thickness of the outer shell may be appropriately set depending on the types of the core material and outer shell used, and the combination thereof.

(1.3.2) Number average primary particle size of inorganic filler The number average primary particle size of the inorganic filler is preferably within the range of 10 to 200 nm. If the number average primary particle size of the inorganic filler is 10 nm or more, sufficient scratch resistance can be obtained.

On the other hand, if the number average primary particle size of the inorganic filler is 200 nm or less, when the inorganic filler is dispersed in a solvent during the formation of the outermost layer, the inorganic filler does not settle in the dispersion liquid, and the photoreceptor can be stably formed. can be manufactured.

Further, since the cleaning property improving effect of the organic resin particles is exhibited when the organic resin particles and the toner come into contact, it is preferable that the number average primary particle size of the inorganic filler is smaller than that of the organic resin particles.

When the inorganic filler aggregates, it is preferable that the secondary particle size is smaller than the organic resin particles. When an inorganic filler aggregates, it is thought that 2 to 3 primary particles will aggregate, so the secondary particle size may be about 2.5 times the number average primary particle size at most.

For example, in the case of an inorganic filler having a number average primary particle size of 20 nm, the maximum secondary particle size may be about 50 nm.
The number average primary particle size of the inorganic filler is defined as the number average primary particle size measured by the following method.

First, a 30,000 times enlarged photograph of a sample (inorganic filler, etc.) is taken using a scanning electron microscope (manufactured by JEOL Ltd.).

Specifically, an enlarged photograph of a sample (inorganic filler, etc.) taken at a magnification of 30,000 times using a scanning electron microscope (manufactured by JEOL Ltd.) is taken into a scanner.

Next, from the obtained photographic images, 300 inorganic filler images excluding aggregated inorganic fillers were randomly processed using the automatic image processing analysis system Luzex AP software Ver. 1.32 (manufactured by Nireco Co., Ltd.) to perform binarization processing to calculate the Feret diameter in the horizontal direction of each of the inorganic filler images.

Then, the average value of the Feret diameter in the horizontal direction of each of the inorganic filler images is calculated and set as the number average primary particle diameter.

Here, the horizontal direction Feret diameter refers to the length of the side parallel to the x-axis of the circumscribed rectangle when the inorganic filler image is binarized.

Furthermore, the measurement of the number average primary particle diameter of the inorganic filler is performed on an inorganic filler that does not contain a chemical species (coating layer) derived from a surface modifier.

Even if the inorganic filler is subjected to the surface modification treatment described below, it is thought that the thickness will be within the error range compared to the inorganic filler (roughly, the thickness is about 1/10000 of the inorganic filler diameter), and for this reason, the surface It is assumed that the average primary particle diameter does not change due to the modification treatment.

(1.3.3) Surface modifier for inorganic filler In addition, the inorganic filler may be surface modified with a surface modifier. The surface modification treatment is made possible by subjecting the raw material, untreated inorganic filler, to surface modification treatment using a surface modifier.

The inorganic filler surface-modified with the surface modifier is considered to become a surface-coated filler containing the chemical species (coating layer) derived from the surface modifier and the inorganic filler. Note that the surface-modified inorganic filler only needs to have a chemical species (coating layer) derived from the surface modifier on at least a portion of its surface.

When the surface of an inorganic filler is modified with a surface modifier, the inorganic filler is effectively made hydrophobic.

When a composition is prepared using the surface-modified inorganic filler and two types of polymerizable monomers, and the polymerized and cured product forms the outermost layer of the photoreceptor, the surface-modified inorganic filler Since the compatibility with the polymerizable monomer is improved, it is advantageous for dispersibility. Moreover, it is one of the preferred forms that the inorganic filler has a polymerizable group.

In the present invention, there are no particular limitations on the surface modifier applied to the surface modification treatment of the inorganic filler, and conventionally known ones can be used. Specific examples of the surface modifier include silane coupling agents, titanium coupling agents, fluorine-based surface modifiers, and surface modifiers having silicone chains.

The surface modifiers can be used alone or in combination of two or more. Further, the surface modifier may be a synthetic product or a commercially available product. Specific examples of commercially available surface modifiers include the following compounds.

In the present invention, the polymerizable group has a carbon-carbon double bond and is a polymerizable group. The polymerizable groups that the inorganic filler may have may be one or more, and may be the same or different from each other, and the polymerizable groups that the polymerizable monomer forming the polymerizable cured product has may be the same or different.

The inorganic filler having a polymerizable group can be obtained, for example, by subjecting the inorganic filler to surface modification treatment using a surface modifier made of a compound having a polymerizable group.

When an inorganic filler having a polymerizable group is used, the inorganic filler and the polymerizable monomer polymerize, making it easier to obtain mechanical strength and making it difficult for the inorganic filler to fall off, making it easier to exhibit effects over a long period of time.

(1.3.4) Shape of Inorganic Filler The shape of the above-mentioned inorganic filler is not particularly limited, and examples thereof include spherical shape, elliptical cross-sectional shape, needle shape, disk shape, and irregular shape. From the viewpoint of dispersibility, etc., a spherical shape or an elliptical cross-sectional shape is preferable.

(1.4) Other components The outermost layer may further contain components other than the above components. Examples of other components include, but are not limited to, charge transport substances, silicone oil, lubricants, antioxidants, and the like.

For example, the charge transport material is not particularly limited, and any known material can be used. Examples include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone Examples include derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, and the like. Among these, triarylamine derivatives are preferred.

Next, other constituent elements of the electrophotographic photoreceptor of the present invention will be explained.

2. Conductive Support The conductive support constituting the photoreceptor of the present invention is not particularly limited as long as it has conductivity. Those formed into sheets, those made by laminating metal foil such as aluminum or copper on plastic film, those made by vapor-depositing aluminum, indium oxide, tin oxide, etc. on plastic film, and those made by coating conductive substances alone or together with binder resin. Examples include metals provided with conductive layers, plastic films, and paper.

3. Intermediate Layer In the photoreceptor of the present invention, an intermediate layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. Considering various failure prevention and the like, it is preferable to provide an intermediate layer.

Such an intermediate layer contains, for example, a binder resin (hereinafter also referred to as "intermediate layer binder resin") and, if necessary, conductive particles or metal oxide particles.

The binder resin for the intermediate layer is not particularly limited, and examples thereof include casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide resin, polyurethane resin, and gelatin. Among these, alcohol-soluble polyamide resins are preferred. These intermediate layer binder resins may be used alone or in combination of two or more.

The intermediate layer can contain various conductive particles and metal oxide particles for the purpose of adjusting resistance. For example, various metal oxide particles such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, and bismuth oxide can be used. Further, conductive particles (ultrafine particles) such as tin-doped indium oxide, antimony-doped tin oxide, and zirconium oxide can be used.

The number average primary particle size of such conductive particles or metal oxide particles is preferably 0.3 μm or less, more preferably 0.1 μm or less.

These conductive particles or metal oxide particles may be used alone or in combination of two or more. When two or more types are mixed, they may be in the form of a solid solution or fusion.

The content of the conductive particles or metal oxide particles is preferably in the range of 20 to 400 parts by weight, more preferably in the range of 50 to 350 parts by weight, based on 100 parts by weight of the binder resin.

The thickness of the intermediate layer is preferably within the range of 0.1 to 15 μm, more preferably within the range of 0.3 to 10 μm.

4. Photosensitive Layer The photoreceptor of the present invention has a photosensitive layer between the intermediate layer and the outermost layer. The photosensitive layer is a layer for forming an electrostatic latent image of a desired image on the surface of the photoreceptor by an exposure means to be described later. The photosensitive layer may have a single layer structure in which a charge generation function and a charge transport function are imparted to one layer, or the functions of the photosensitive layer may be separated into a charge generation layer having a charge generation function and a charge transport layer having a charge transport function. A laminated structure may also be used.

Having a functionally separated layer structure, such as a laminated structure of a charge transport layer and a charge generation layer, not only makes it possible to control the increase in residual potential due to repeated use, but also controls various electrophotographic properties to suit the purpose. It has the advantage of being easy to do.
Negatively charging photoreceptors have a charge generation layer on the intermediate layer and a charge transport layer thereon, while positively charging photoreceptors have a charge transport layer on the intermediate layer and a charge generation layer on top of that. Take composition.
A preferable layer structure of the photosensitive layer is a negatively charging photoreceptor having the above-mentioned functionally separated structure.

Below, as a preferred example of the photosensitive layer, a photosensitive layer of a functionally separated type negatively charging photoreceptor, that is, a photosensitive layer in which a charge generation layer and a charge transport layer are laminated will be described.

(4.1) Charge generation layer The charge generation layer in the photosensitive layer constituting the photoreceptor contains a charge generation substance and a binder resin (hereinafter also referred to as "binder resin for charge generation layer"). .

Examples of the charge generating substance include azo raw materials such as Sudan red and Diane blue, quinone pigments such as pyrenequinone and anthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and polypropylene such as pyranthrone and diphthaloylpyrene. Examples include, but are not limited to, ring quinone pigments and phthalocyanine pigments. Among these, polycyclic quinone pigments and titanyl phthalocyanine pigments are preferred. These charge generating substances may be used alone or in combination of two or more.

As the binder resin for the charge generation layer, known resins can be used, such as polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, Polyurethane resins, phenolic resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (e.g., vinyl chloride-vinyl acetate copolymer resins, chlorinated Examples include, but are not limited to, vinyl-vinyl acetate-maleic anhydride copolymer resin), poly-vinyl carbazole resin, and the like. Among these, polyvinyl butyral resin is preferred. These binder resins for the charge generation layer may be used alone or in combination of two or more.

The content of the charge generating substance in the charge generating layer is preferably within the range of 1 to 600 parts by weight, more preferably within the range of 50 to 500 parts by weight, based on 100 parts by weight of the binder resin for the charge generating layer. It is.

The thickness of the charge generation layer varies depending on the characteristics of the charge generation substance, the characteristics of the binder resin for the charge generation layer, the content ratio, etc., but is preferably within the range of approximately 0.01 to 5 μm, more preferably 0.01 to 5 μm. It is within the range of 0.05 to 3 μm.

(4.2) Charge transport layer The charge transport layer in the photosensitive layer constituting the photoreceptor contains a charge transport substance and a binder resin (hereinafter also referred to as "binder resin for charge transport layer"). .

Examples of the charge transporting substance in the charge transporting layer that transport charges (holes) include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, and butadiene compounds.

The charge transport layer formed at the bottom of the outermost layer preferably contains a charge transport substance with high mobility and a large molecular weight, and known compounds can be used in combination as such charge transport substances. For example, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene, etc. can be mentioned. These compounds can be used alone or in combination of two or more.

Known resins can be used as the binder resin for the charge transport layer, such as polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylate ester resin, styrene-methacrylate ester. Examples include copolymer resins, but polycarbonate resins are preferred. Furthermore, BPA (bisphenol A) type, BPZ (bisphenol Z) type, dimethyl BPA type, BPA-dimethyl BPA copolymer type polycarbonate resins, etc. are preferable in terms of crack resistance, abrasion resistance, and charging characteristics. These binder resins for the charge transport layer may be used alone or in combination of two or more.

The content ratio of the charge transport substance in the charge transport layer is preferably within the range of 10 to 500 parts by mass, more preferably within the range of 20 to 250 parts by mass, based on 100 parts by mass of the binder resin for the charge transport layer. It is.

The thickness of the charge transport layer varies depending on the characteristics of the charge transport material, the characteristics and content ratio of the binder resin for the charge transport layer, but is preferably within the range of 5 to 40 μm, more preferably within the range of 10 to 30 μm. It is within.

Antioxidants, electronic conductive agents, stabilizers, silicone oil, etc. may be added to the charge transport layer. Preferably, the antioxidant is disclosed in JP-A-2000-305291, and the electronic conductive agent is disclosed in JP-A-50-137543, JP-A-58-76483, and the like.

[Method for manufacturing electrophotographic photoreceptor]
The method for producing the photoreceptor of the present invention includes the steps of forming an uncured film containing a polymerizable compound on a photosensitive layer on a conductive support, and irradiating the uncured film with light to form a cured resin. Although not particularly limited, it is preferably manufactured by a manufacturing method having the following steps, although not particularly limited.

Step (1): a step of forming an intermediate layer by applying a coating liquid for forming an intermediate layer on the outer peripheral surface of the conductive support and drying it;
Step (2): Apply a coating liquid for forming a charge generation layer to the outer peripheral surface of the conductive support or to the outer peripheral surface of the intermediate layer formed on the conductive support in step (1), and dry. forming a charge generation layer by,
Step (3): Applying a coating solution for forming a charge transport layer to the outer peripheral surface of the conductive support or the outer peripheral surface of the charge generation layer formed on the intermediate layer, and forming a charge transport layer by drying. process,
Step (4): A step of forming an outermost layer by applying a coating liquid for forming an outermost layer on the outer peripheral surface of the charge transport layer formed on the charge generation layer, polymerizing and curing the coating liquid.

The concentration of each component in the coating liquid for forming each layer is appropriately selected according to the layer thickness and production rate of each layer.

In the coating liquid for forming each layer, an ultrasonic dispersion machine, a ball mill, a sand mill, a homo mixer, etc. can be used as a means for dispersing particles such as conductive particles and metal oxide particles and charge generating substances. However, it is not limited to these.

The method of applying the coating liquid to form each layer is not particularly limited, but examples include dip coating method, spray coating method, spinner coating method, bead coating method, blade coating method, beam coating method, slide hopper method, circular Known methods such as the slide hopper method may be used.

The method for drying the coating film can be appropriately selected depending on the type of solvent and layer thickness, but thermal drying or natural drying is preferable.

The details of the formation process of each layer will be explained below.

<Step (1): Formation of intermediate layer>
For the intermediate layer, prepare a coating solution for forming the intermediate layer by dissolving the binder resin for the intermediate layer in a solvent, and add other components such as conductive particles, metal oxide particles, dispersant, and leveling agent as necessary. After dispersing or dissolving the coating liquid, the coating liquid can be applied to a conductive support to a certain thickness to form a coating film, and the coating film can be dried.

The intermediate layer forming coating liquid is preferably applied using a dip coating method.

The solvent used in the step of forming the intermediate layer is preferably one that can disperse the conductive particles and metal oxide particles well and dissolve the binder resin for the intermediate layer, particularly the polyamide resin. Specifically, alcohols having 1 to 4 carbon atoms such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, and sec-butanol (2-butanol) improve the solubility of polyamide resin. It has excellent coating performance and is preferred. Further, in order to improve storage stability and particle dispersibility, co-solvents that can be used in combination with the above-mentioned solvents to obtain favorable effects include benzyl alcohol, toluene, dichloromethane, cyclohexanone, and tetrahydrofuran.

<Step (2): Formation of charge generation layer>
The charge generation layer is prepared by dispersing a charge generation substance in a solution in which a binder resin for the charge generation layer is dissolved in a solvent to prepare a coating solution for forming a charge generation layer, and applying the coating solution uniformly over the intermediate layer. It can be formed by coating to a layer thickness of , forming a coating film, and drying the coating film.

The charge generation layer forming coating liquid is preferably applied using a dip coating method.

Examples of the solvent used to form the charge generation layer include toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexane, ethyl acetate, tert-butyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, tert-butanol, sec-butanol (2-butanol), methyl cellosolve, 4-methoxy-4-methyl-2-pentanone, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, diethylamine Examples include, but are not limited to, the following.

<Step (3): Formation of charge transport layer>
For the charge transport layer, a charge transport layer forming coating solution is prepared by dissolving a charge transport layer binder resin and a charge transport substance in a solvent, and the coating solution is applied to a constant layer thickness on the charge generation layer. It can be formed by forming a coating film and drying the coating film.

The coating liquid for forming the charge transport layer is preferably applied using a dip coating method.

Examples of the solvent used to form the charge transport layer include toluene, xylene, dichloromethane, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n- Examples include, but are not limited to, butanol, tert-butanol, sec-butanol (2-butanol), tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine, and the like.

<Step (4): Formation of outermost layer>
The outermost layer includes the first polymerizable monomer, the second polymerizable monomer, organic resin particles, an inorganic filler treated with a surface modifier, and optionally a polymerization initiator and a specific radical scavenger. A coating solution for forming the outermost layer is prepared by adding other components such as a lubricant, a lubricant, and a charge transport substance to a known solvent, and this coating solution for forming the outermost layer is used to transfer the charge transport material formed in step (3). It is applied to the outer peripheral surface of a layer to form a coating film, dried, and irradiated with actinic rays such as ultraviolet rays or electron beams to polymerize and cure the polymerizable compound components in the coating film. The outermost layer can be formed by

The coating liquid for forming the outermost layer is preferably applied by a slide hopper method using a circular slide hopper coating device, and can be applied, for example, by a method disclosed in JP-A No. 2015-114454.

As the solvent used to form the outermost layer, any solvent can be used as long as it can dissolve or disperse the polymerizable compound, metal oxide particles, etc. For example, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-propyl alcohol, etc. -Butanol, tert-butanol, sec-butanol (2-butanol), benzyl alcohol, toluene, xylene, dichloromethane, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3 - Examples include, but are not limited to, dioxolane, pyridine, diethylamine, and the like.

The method of reacting the polymerizable compound is not particularly limited, but examples include a method of reacting by electron beam cleavage, a method of adding a radical polymerization initiator and reacting with light or heat, and the like.

The cured resin component is produced by irradiating the coating film with actinic rays as a curing treatment, generating radicals to polymerize, and forming crosslinking bonds through a crosslinking reaction between and within the molecules, thereby curing the coating. As the active radiation, ultraviolet rays and electron beams are more preferable, and ultraviolet rays are particularly preferable because they are easy to use.

As the ultraviolet light source, any light source that generates ultraviolet light can be used without restriction. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, etc. can be used.

Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is preferably within the range of 5 to 500 mJ/cm ² , more preferably within the range of 5 to 100 mJ/cm ² .

The power of the lamp is preferably in the range of 0.1 to 5 kW, more preferably in the range of 0.5 to 4 kW, even more preferably in the range of 0.5 to 3 kW.

The irradiation time to obtain the required dose of active radiation is preferably 0.1 seconds to 10 minutes, and more preferably 0.1 seconds to 5 minutes from the viewpoint of work efficiency.

In the step of forming the outermost layer, drying can be performed before or after irradiation with active radiation, or during irradiation with active radiation, and the timing of drying can be appropriately selected by combining these.

(Curing equipment and conditions for outermost layer)
In the present invention, the surface hardness in the long axis direction of the photoreceptor can be adjusted by adjusting the light irradiation conditions after coating the outermost layer.

The reason why the surface hardness of the photoconductor can be changed by the light irradiation device is that the surface hardness is correlated with the cumulative amount of light irradiated onto the photoconductor, and the cumulative amount of irradiation is calculated as follows: (cumulative amount of irradiation) = (photoconductor drum) Since it is determined by (amount of irradiation light per unit area of the surface) x (irradiation time per unit area), the surface hardness of the photoreceptor can be changed by changing (i) the amount of irradiation light or (ii) the irradiation time. .

For example, when using the light irradiation device described in JP-A-2013-57787, when pulling up the photoreceptor workpiece from below to above, (i) changing the light irradiation intensity at any position; (ii) By changing the lifting speed of the workpiece, that is, by changing the irradiation time, the cumulative amount of irradiation light on the photoreceptor drum surface can be changed in the long axis direction of the photoreceptor, and the surface hardness of the photoreceptor can be changed. . In particular, the method (ii) of changing the workpiece lifting speed is preferable from the viewpoint of controllability.

<Electrophotographic image forming method>
The electrophotographic image forming method according to the present invention includes at least the following:
1) A charging step of charging the surface of the electrophotographic photoreceptor;
2) an exposure step of forming an electrostatic latent image by exposing the surface of the electrophotographic photoreceptor;
3) a developing step of visualizing the electrostatic latent image with toner to form a toner image;
4) a transfer step of transferring the toner image to a transfer medium;
The electrophotographic photoreceptor used in steps 1) to 4) is preferably the electrophotographic photoreceptor of the present invention.

In addition, if necessary, 5) a cleaning step to remove residual toner;
6) Static elimination process to remove residual charges,
may have.

The electrophotographic photoreceptor (hereinafter also simply referred to as photoreceptor) of the present invention can be used in various known electrophotographic image forming methods. For example, it can be used in a monochrome image forming method or a full color image forming method. Full-color image forming methods include a 4-cycle image forming method consisting of four types of color developing devices for each of yellow, magenta, cyan, and black and one photoreceptor, and a color developing method for each color. Any image forming method can be used, such as a tandem image forming method in which image forming units each having a device and a photoreceptor are mounted for each color.

Specifically, the electrophotographic image forming method according to the present invention includes using the photoconductor of the present invention, charging the photoconductor with a charging device (charging step), and performing imagewise exposure (exposure step). The electrostatic latent image formed is developed using a developing device (developing step) to be visualized and a toner image is obtained. This toner image is transferred onto a transfer medium such as copy paper or a transfer belt (transfer step), and then a static elimination step is performed and the next image forming cycle is performed. The toner image transferred onto a transfer medium such as a transfer belt is transferred onto copy paper, and the toner image transferred onto the copy paper is fixed onto the copy paper by a fixing process such as a contact heating method (fixing process). Obtain a visible image. After the transfer process, the toner remaining on the photoreceptor (transfer residual toner) is removed using a rubber blade or the like (cleaning process). This cleaning process may be performed before or after the static elimination process, but if the static elimination process is performed by light irradiation, it is better to perform the cleaning process after the cleaning process so that the toner remaining on the photoreceptor absorbs the static elimination light. This is preferable because static electricity can be effectively eliminated without any interference.

In the static neutralization process, either AC static neutralization (AC static neutralization) or optical static neutralization may be used, but AC static neutralization requires the installation of an AC power source, which poses problems such as space issues and the large scale of the equipment. Static elimination is preferable.

<Electrophotographic image forming apparatus>
Next, a specific electrophotographic image forming method will be explained using an electrophotographic image forming apparatus.

In the present invention, an electrophotographic image forming apparatus uses the photoconductor of the present invention, includes a charging means for charging the photoconductor with a charging device, and an exposure device for forming an electrostatic latent image by imagewise exposure. A developing means for developing a toner image by developing it using a developing device, a transfer means for transferring this toner image onto a transfer medium such as paper or a transfer belt, and a static elimination means. . The toner image directly transferred onto the copy paper and the toner image transferred onto the paper via a transfer medium such as a transfer belt are used to obtain a visible image by a fixing means that fixes them to the copy paper through a fixing process such as a contact heating method. After the transfer, the toner remaining on the photoreceptor (transfer residual toner) is removed by a cleaning means such as a cleaning blade.

FIG. 2 is a schematic cross-sectional view showing the structure of a tandem-type electrophotographic image forming apparatus including the electrophotographic photoreceptor of the present invention.

The image forming apparatus 100 shown in FIG. 2 is called a tandem color image forming apparatus, and includes four sets of image forming sections (image forming units) 10Y, 10M, 10C, and 10Bk, an intermediate transfer body unit 7, and a supply unit 7. It consists of a paper means 21 and a fixing means 24. A document image reading device SC is arranged at the top of the main body A of the electrophotographic image forming apparatus.

The four image forming units 10Y, 10M, 10C, and 10Bk rotate around the photoreceptors 1Y, 1M, 1C, and 1Bk, along with charging means 2Y, 2M, 2C, and 2Bk, and exposure means 3Y, 3M, 3C, and 3Bk. From developing means 4Y, 4M, 4C, 4Bk for cleaning, primary transfer rollers 5Y, 5M, 5C, 5Bk as primary transfer means, and cleaning means 6Y, 6M, 6C, 6Bk for cleaning photoreceptors 1Y, 1M, 1C, 1Bk. It is configured.

The electrophotographic image forming apparatus of the present invention uses the photoconductors of the present invention described above as the photoconductors 1Y, 1M, 1C, and 1Bk, respectively.

The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the toner colors provided are different, such as yellow (Y), magenta (M), cyan (C), and black (Bk). It is. Therefore, the image forming unit 10Y will be described in detail below as an example.

The image forming unit 10Y includes a charging means 2Y, an exposing means 3Y, a developing means 4Y, and a cleaning means 6Y around the photoreceptor 1Y, which is an image forming member, and forms a yellow (Y) toner image on the photoreceptor 1Y. It is something that forms.

The charging means 2Y is a means for uniformly charging the surface of the photoreceptor 1Y to negative polarity. As the charging means 2Y, for example, a corona discharge type charger is used.

The exposure means 3Y is a means for exposing the photoreceptor 1Y, which has been given a uniform potential by the charging means 2Y, based on an image signal (yellow) to form an electrostatic latent image corresponding to a yellow image. be. As the exposure means 3Y, one composed of an LED having light emitting elements arranged in an array in the axial direction of the photoreceptor 1Y and an imaging element, a laser optical system, etc. is used.

The developing means 4Y includes, for example, a developing sleeve (not shown) that has a built-in magnet and rotates while holding the developer, a photoreceptor, and a voltage application device that applies a DC and/or AC bias voltage between the developing sleeve and the developing sleeve. It is more than that.

The developing means 4Y includes, for example, a developing sleeve that has a built-in magnet and rotates while holding the developer, and a voltage application device that applies a DC and/or AC bias voltage between the developing sleeve and the photoreceptor. .

The fixing means 24 is, for example, a heat roller fixing device that includes a heating roller equipped with a heat source inside and a pressure roller that is provided in pressure contact with the heating roller so as to form a fixing nip. Examples include methods.

The cleaning means 6Y is composed of a cleaning blade. Note that a brush roller may be provided upstream of the cleaning blade.
Further, a lubricant supply means (not shown) may be provided to supply (apply) a lubricant to the surface of the photoreceptor 1Y. The lubricant supply means can be provided, for example, downstream of the primary transfer roller 5Y and upstream of the cleaning means 6Y. However, it may be on the downstream side of the cleaning means 6Y.

The image forming apparatus 100 is configured by integrally combining components such as a photoreceptor, a developing means, and a cleaning means as a process cartridge (image forming unit), and this image forming unit is detachably attached to the main body of the apparatus. may be configured. Further, at least one of a charging means, an exposure means, a developing means, a transfer means, and a cleaning means are integrally supported together with a photoreceptor to form a process cartridge (image forming unit), and a single image forming unit that can be attached and detached from the main body of the apparatus is formed. It may be constructed as a unit and configured to be detachable using guide means such as rails on the main body of the device.

The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier in the form of a semiconductive endless belt, which is wound around a plurality of rollers and rotatably supported.

Images of each color formed by the image forming units 10Y, 10M, 10C and 10Bk are sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C and 5Bk as primary transfer means. to form a composite color image. The transfer material (image support that carries the fixed final image: for example, plain paper, transparent sheet, etc.) stored in the paper feeding cassette 20 is fed by the paper feeding means 21, and is fed by a plurality of intermediate rollers 22A, 22B, 22C, 22D, and the registration roller 23, it is conveyed to a secondary transfer roller 5b as a secondary transfer means, and is secondarily transferred onto the transfer material P, so that the color image is transferred all at once. The transfer material P on which the color image has been transferred is subjected to a fixing process by the fixing means 24, and is held between paper ejection rollers 25 and placed on a paper ejection tray 26 outside the machine. Here, a transfer support for a toner image formed on a photoreceptor, such as an intermediate transfer member or a transfer material, is collectively referred to as a transfer medium.

On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b serving as the secondary transfer means, the residual toner is removed from the endless belt-shaped intermediate transfer body 70, which is obtained by separating the transfer material P by curvature, by the cleaning means 6b. Ru.

During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C contact the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

The secondary transfer roller 5b comes into contact with the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through it and secondary transfer is performed.

Further, the casing 8 can be pulled out from the apparatus main body A via support rails 82L and 82R.

The housing 8 includes image forming sections 10Y, 10M, 10C, and 10Bk, and an endless belt-shaped intermediate transfer body unit 7.

The image forming units 10Y, 10M, 10C, and 10Bk are arranged in columns in the vertical direction. An endless belt-shaped intermediate transfer unit 7 is arranged on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, and 74, primary transfer rollers 5Y, 5M, 5C, and 5Bk, and cleaning means 6b. Consisting of

<Toner and developer>
In the present invention, "toner base particles" constitute a matrix of "toner particles." The "toner base particles" contain at least a binder resin and a colorant, and may contain other components such as a release agent (wax) and a charge control agent, if necessary. The "toner base particles" are called "toner particles" by adding external additives. The term "toner" refers to an aggregate of "toner particles."

In the present invention, the toner to be applied to the image forming apparatus is not particularly limited, and various known toners can be used.

Although either a pulverized toner or a polymerized toner can be used as the toner, it is preferable to use a polymerized toner from the viewpoint of obtaining a high quality image.

The average particle size of the toner is not particularly limited, but it is preferably within the range of 2 to 8 μm on a volume basis. By setting it as this range, resolution can be made higher.

In addition, appropriate amounts of inorganic particles such as silica and titania with an average particle size of about 10 to 300 nm, abrasives of about 0.2 to 3 μm, etc. are added to the toner base particles as external additives. be able to.

When the toner is used as a two-component developer, conventionally known materials such as ferromagnetic metals such as iron, alloys of ferromagnetic metals and ferromagnetic metals such as aluminum and lead, and compounds of ferromagnetic metals such as ferrite and magnetite can be used as carriers. Magnetic particles consisting of can be used. Among these, ferrite is particularly preferred.

As the carrier, it is preferable to use a carrier further coated with a resin or a so-called resin-dispersed carrier in which magnetic particles are dispersed in the resin. The coating resin composition is not particularly limited, but it is preferable to use, for example, a cyclohexyl methacrylate-methyl methacrylate copolymer.

The volume-based median diameter of the carrier is preferably within the range of 15 to 100 μm, more preferably within the range of 25 to 60 μm.

The concentration of toner contained in the two-component developer is preferably within the range of 4.0 to 8.0% by mass.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto. In addition, in the following examples, unless otherwise specified, operations were performed at room temperature (25° C.). Further, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[Preparation of organic resin particles 1 to 8 and 10 and organic resin particles 9]

The details of organic resin particles 1 to 10 listed by abbreviations in Table I are as follows.
<Organic resin particles 1> S6: Epostor S6 (melamine resin particles, manufactured by Nippon Shokubai Co., Ltd.)
<Organic resin particles 2> FS201: Fine Sphere FS201
(Acrylic resin particles, manufactured by Nippon Paint Industrial Coatings)
<Organic resin particles 3> X99-A8808: Tospearl X99-A8808
(Silicone resin particles, manufactured by Momentive Performance Materials Japan LLC)
<Organic resin particles 4> SS: Epostor SS (melamine resin particles, manufactured by Nippon Shokubai Co., Ltd.)
<Organic resin particles 5> S: Epostor S (melamine resin particles, manufactured by Nippon Shokubai Co., Ltd.)
<Organic resin particles 6> M30: Epostor M30 (melamine resin particles, manufactured by Nippon Shokubai Co., Ltd.)
<Organic resin particles 7> 2000M: Opto beads 2000M
(Melamine resin particles, manufactured by Nissan Chemical Co., Ltd.)
<Organic resin particles 8> S12: Epostor S12 (melamine resin particles, manufactured by Nippon Shokubai Co., Ltd.)
<Organic resin particles 9> RP-1: Produced by the following production method.
<Organic resin particles 10> 3500M: Opto beads 3500M
(Melamine resin particles, manufactured by Nissan Chemical Co., Ltd.)

[Preparation of organic resin particles 9 (RP-1)]
A 2 L reaction flask equipped with a stirrer, a reflux condenser, and a thermometer was charged with 45 g of melamine, 100 g of 37% formalin, 27 g of colloidal silica (manufactured by Nissan Chemical Industries, Ltd., trade name: Snowtex S), and 720 g of water. The pH was adjusted to 8.5 with % ammonia water.
Thereafter, the temperature of the above mixture was raised while stirring, and the temperature was maintained at 70°C, and the reaction was carried out for 30 minutes.
Next, while maintaining the temperature at 70° C., a 10% by mass aqueous solution of dodecylbenzenesulfonic acid was added to adjust the pH to 7.0.
After the inside of the reaction system became cloudy and cured melamine resin particles were precipitated, the temperature was raised to 90° C. and the curing reaction was continued for 3 hours.
After cooling, the resulting reaction solution was filtered and dried to produce organic resin particles 9 (RP-1) with a particle size of 0.05 μm.

<Preparation of organic resin particle dispersions PD-1 to PD-10>
[Preparation of organic resin particle dispersion PD-1]
The following constituent components were dispersed for 120 minutes using an ultrasonic homogenizer (US-150AT, manufactured by Nippon Seiki Seisakusho Co., Ltd.) at an amplitude of 30 μm.

Organic resin particles 1: Epostor S6 150 parts by mass 2-butanol 850 parts by mass

[Preparation of organic resin particle dispersions PD-2 to PD-10]
Organic resin particle dispersions PD-2 to PD-10 were prepared in the same manner as in the preparation of organic resin fine particle dispersion PD-1 except that the organic resin particles used were changed as shown in Table I.

[Preparation of inorganic fillers F-1 to F-3]
[Preparation of inorganic filler F-1]
20 g of tin oxide (number average primary particle size: 20 nm) as a matrix was added to 40 mL of methanol, and dispersed for 120 minutes using an ultrasonic homogenizer.
Next, 1 g of 3-methacryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name: KBM503) and 40 mL of toluene were added as a surface modifier containing a reactive organic group having a polymerizable group, and the mixture was stirred at room temperature for 2 hours. did.
Next, after removing the solvent with an evaporator, the inorganic filler F-1 having a polymerizable group was subjected to surface modification treatment with a reactive organic group-containing surface modifier (KBM503) by heating at 120° C. for 1 hour. was created.

[Preparation of inorganic filler F-2]
Inorganic filler F-2 was produced in the same manner as inorganic filler F-1 except that the inorganic filler matrix was changed to titanium oxide (number average primary particle size: 100 nm).

[Preparation of inorganic filler F-3]
First, using the microparticle manufacturing apparatus shown in FIG. 3, composite particles were prepared by forming a tin oxide shell on the surface of barium sulfate as a core particle.

Specifically, 3500 mL of pure water was poured into the mother liquor tank 11 shown in FIG. 3, and then 900 g of spherical barium sulfate core material having a number average primary particle size of 100 nm was poured, and the mixture was circulated for 5 cycles. .

The flow rate of the slurry flowing out from the mother liquor tank 11 was 2280 mL/min. Further, the stirring speed of the strong dispersion device 13 was set to 16,000 rpm.

After the circulation was completed, the slurry was diluted to a total volume of 9000 mL with pure water, and 1600 g of sodium stannate and 2.3 mL of aqueous sodium hydroxide solution (concentration 25 N) were added thereto and circulated for 5 cycles to prepare a mother liquor. .

Next, while circulating this mother liquor so that the flow rate S1 flowing out from the mother liquor tank 11 is 200 mL/min, 20% by mass of sulfuric acid is added to a "homogenizer magic LAB" (manufactured by IKA Japan Co., Ltd.) serving as a strong dispersion device 13. was supplied.

The supply rate S3 was set to 9.2 mL/min. The volume of the homogenizer was 20 cm ³ and the stirring speed was 16000 rpm. Circulation was carried out for 15 minutes, during which time sulfuric acid was continuously fed into the homogenizer.

In this way, core-shell type particles were obtained in which a tin oxide coating layer (shell layer) was formed on the surface of the barium sulfate core material.

The obtained slurry containing particles was repulped and washed until its conductivity became 600 μS/cm or less, and then subjected to Nutsche filtration to obtain a cake.

This cake was dried in air at 150°C for 10 hours. The obtained dry cake was pulverized, and the pulverized powder was reduced and calcined at 450° C. for 45 minutes in a 1% by volume H ₂ /N ₂ atmosphere.

As a result, composite particles having a number average primary particle size of 100 nm were produced, in which an outer shell (shell layer) of tin oxide was formed on the surface of the barium sulfate core material.

Here, in the particle manufacturing apparatus shown in FIG. 3, reference numerals 12 and 14 are circulation piping for forming a circulation path between the mother liquor tank 11 and the strong dispersion device 13, and numerals 15 and 16 are circulation piping. Pumps provided in the paths 12 and 14, 11a is a stirring blade, 13a is a stirring section, 11b and 13b are shafts, and 11c and 13c are motors.
Next, inorganic filler F-3 was produced in the same manner as inorganic filler F-1 except that the inorganic filler matrix was changed to the composite particles produced above.

<Preparation of inorganic filler dispersions FD-1 to FD-3>
[Preparation of inorganic filler dispersion liquid FD-1]
The following constituent components were dispersed for 120 minutes using an ultrasonic homogenizer (US-150AT, manufactured by Nippon Seiki Seisakusho Co., Ltd.) at an amplitude of 30 μm.

Inorganic filler F-1 200 parts by mass 2-butanol 800 parts by mass

[Preparation of inorganic filler dispersions FD-2 and FD-3]
Inorganic filler dispersions FD-2 and FD-3 were prepared in the same manner as in the preparation of inorganic filler dispersion FD-1 except that the inorganic fillers used were changed to F-2 and F-3.

<Production of photoreceptors 1 to 24>
[Preparation of photoreceptor 1]
(1) Preparation of conductive support The surface of a cylindrical aluminum support was cut to prepare a conductive support.

(2) Preparation of Intermediate Layer The following components were mixed and dispersed batchwise for 10 hours using a sand mill as a disperser to prepare a coating solution for forming an intermediate layer. The prepared intermediate layer forming coating solution was applied to the surface of the conductive support prepared above by dip coating, and dried at 110°C for 20 minutes to form an intermediate layer with a thickness of 2 μm on the conductive support. did.

Polyamide resin: X1010 manufactured by Daicel-Evonik 100 parts by mass Titanium oxide particles: SMT500SAS manufactured by Teika 110 parts by mass Titanium oxide particles: SMT150MK manufactured by Teika 160 parts by mass Ethanol 2000 parts by mass

(3) Formation of charge generation layer The following components were mixed, and using a circulating ultrasonic homogenizer (RUS-600TCVP; manufactured by Nippon Seiki Seisakusho Co., Ltd.), the circulating flow rate was 40 L/hour at 19.5 kHz and 600 W. A coating solution for forming a charge generation layer was prepared by dispersing for .5 hours.

The charge generation layer forming coating solution prepared above was applied to the surface of the intermediate layer by dip coating and dried to form a charge generation layer having a thickness of 0.3 μm.

The charge generating substances described below are titanyl phthalocyanine and ( A mixed crystal of a 1:1 adduct of 2R,3R)-2,3-butanediol and unadducted titanyl phthalocyanine was used.

Charge generating substance 24 parts by mass Polyvinyl butyral resin: S-LEC (registered trademark) BL-1 manufactured by Sekisui Chemical Co., Ltd.)
12 parts by mass Mixed solvent: 3-methyl-2-butanone/cyclohexanone = 4/1 (volume ratio)
1000 parts by mass

(4) Formation of charge transport layer A coating solution for forming a charge transport layer containing the following components is applied onto the surface of the charge generation layer by dip coating, and dried at 120°C for 70 minutes to form a film with a thickness of 24 μm. A charge transport layer was formed.

Charge transport substance 1 (see below) 180 parts by mass Polycarbonate resin: Iupilon Z300 (manufactured by Mitsubishi Gas Chemical Co., Ltd., bisphenol Z type polycarbonate) 300 parts by mass Antioxidant: IRGANOX1010 (manufactured by BASF Corporation) 4 parts by mass Mixed solvent: THF/toluene =4/1 (volume ratio) 2000 parts by mass Silicone oil "KF-96" (manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass

(5) Formation of outermost layer After mixing and stirring the first polymerizable monomer, second polymerizable monomer, organic resin particle dispersion, and inorganic filler dispersion described below, the following polymerization initiator was stirred under light shielding. to prepare a coating solution for forming the outermost layer.

This coating liquid for forming the outermost layer was applied onto the surface of the charge transport layer using a circular slide hopper coating machine.

Next, the applied outermost layer coating film was irradiated with ultraviolet rays (main wavelength: 365 nm) for 1 minute using a metal halide lamp (ultraviolet illuminance: 16 mW/cm ² , cumulative light amount: 960 mJ/cm ² ) to remove the outermost layer coating film. By curing the photoreceptor 1, an outermost layer having a thickness of 5.0 μm was formed on the charge transport layer, thereby producing a photoreceptor 1.

First polymerizable monomer: Exemplary compound M2 50 parts by mass Second polymerizable monomer: HD-N shown below 50 parts by mass Organic resin particle dispersion: PD-1 100 parts by mass Inorganic filler dispersion: FD-1 650 Parts by mass Polymerization initiator: IRGACURE819 (manufactured by BASF) 10 parts by mass

[Preparation of photoreceptors 2 to 22]
In the production of the photoreceptor 1, the types of organic resin particle dispersion, the type of inorganic filler dispersion, and the types/amounts of the first/second polymerizable monomers used for forming the outermost layer were set to the combinations listed in Table II. Photoreceptors 2 to 22 were produced in the same manner except for the following changes.

Details of the monomers listed by abbreviations in Table II are as follows.

[Preparation of photoreceptor 23]
Photoreceptor 23 was produced in the same manner as in the production of photoreceptor 1 except that the first polymerizable monomer used to form the outermost layer was 100 parts by mass and the second polymerizable monomer was not added.

[Preparation of photoreceptor 24]
In the production of the photoreceptor 1, the first polymerizable monomer used to form the outermost layer was changed to exemplary compound M1, and the monofunctional monomer MM-1 was used as the third polymerizable monomer instead of the second polymerizable monomer. A photoreceptor 24 was produced in the same manner except that .

[Preparation of photoreceptor 25]
In the production of photoreceptor 1, the same process was carried out except that the first polymerizable monomer used to form the outermost layer was changed to 42 parts by mass, and 8 parts by mass of the monofunctional monomer MM-1 was added as the third polymerizable monomer. A photoreceptor 25 was manufactured in the following manner.

[Preparation of photoreceptor 26]
The photoreceptor 1 was produced in the same manner except that the first polymerizable monomer used to form the outermost layer was changed to 35 parts by mass, and 15 parts by mass of the bifunctional monomer SR206 was added as the third polymerizable monomer. , a photoreceptor 26 was produced. In addition, in the photoreceptor 26, the total of the second polymerizable monomer and the third polymerizable monomer, which are bifunctional monomers, is 65% of the total monomer mass.

[Preparation of photoreceptor 27]
The photoreceptor 26 was manufactured in the same manner except that the first polymerizable monomer used for forming the outermost layer was changed to 65 parts by mass, and the second polymerizable monomer was changed to 20 parts by mass. was created. In addition, in the photoreceptor 27, the total amount of the second polymerizable monomer and the third polymerizable monomer, which are bifunctional monomers, is 35% based on the total monomer mass.

[Preparation of photoreceptor 28]
A photoreceptor 28 was prepared in the same manner as the photoreceptor 1 except that 25 parts by mass of charge transport substance 2 described below was added.

(Measurement of reaction rate)
Using the coating liquid for forming the outermost layer used for photoreceptors 1 to 28, the reaction rate was measured by the method shown below. Table II shows the measured values.

<Method of measuring reaction rate>
Two PET sheets are prepared by applying the coating liquid for the outermost layer using a wire bar. One sheet is shielded from light to prevent the polymerization reaction from occurring (pre-reaction sample). The other sheet is cured by irradiating it with ultraviolet light (post-reaction sample). FT-IR spectra of the sample before and after the reaction were measured, and the reaction rate was calculated from the change in the spectrum.
Each condition in the above is as follows.

≪Curing conditions≫
Under a nitrogen atmosphere, the PET sheet coated with the surface layer was irradiated with ultraviolet rays (main wavelength: 365 nm) using a metal halide lamp for 1 minute (ultraviolet illuminance: 16 mW/cm ² , cumulative light amount: 960 mJ/cm ² ), and cured. I let it happen.

≪Measurement conditions≫
It can be determined from the peak intensity ratio of a spectrum obtained by total reflection method (ATR method) using a Fourier transform infrared spectrometer (FT-IR; NICOLET380, manufactured by Thermo Fisher Scientific).
An example of the peak at that time is shown in FIG.
The ATR measurement was performed using a diamond prism under the conditions of a resolution of 4 cm ⁻¹ and a number of integrations of 32 times.

≪Analysis conditions≫
The intensity of the peak around 2955 cm ^-1 , which is derived from CH (aliphatic) whose structure does not change before and after the reaction, and the peak around 1405 cm ^-1 , which is derived from CH (alkene), whose number decreases due to the reaction, is The reaction rate [%] was calculated from the following formula.

Formula: 100 - ({After curing Abs (1405 cm ^-1 ) / Abs (2955 cm ^-1 )} / {Before curing Abs (1405 cm ^-1 ) / Abs (2955 cm ^-1 )}) x 100

The peak height of 1405 cm ^-1 (Abs (1405 cm ^-1 )) is 1400 cm ^-1 when the minimum values from 1390 cm ^-1 to 1400 cm -1 and the minimum values between 1410 cm ^-1 and 1430 cm ^-1 are used as base points ^. It is defined as the maximum value of 1410 cm ⁻¹ from

The peak height of 2955 cm ^-1 (Abs (2955 cm ^-1 )) is 2945 cm -1 when the minimum value of 2560 cm ^-1 to 2590 cm ^-1 and the minimum value of 3135 cm ^-1 and 3165 cm ^-1 are used as base points ^. It is defined as the maximum value of 2965 cm ⁻¹ from

<Evaluation of photoreceptor>
(point defect)
[Preparation of image forming device]
Using an image forming apparatus in which a full color printing machine (bizhub PRESS C1070, manufactured by Konica Minolta) was modified to a linear speed of 200 mm/sec, each of the photoreceptors prepared above was placed at the black (K) position of the image forming unit. An image forming apparatus for evaluation was manufactured.

Further, according to the method described below, point defects were evaluated for images formed at the initial stage of printing and after the durability test.
FIG. 2 is a schematic diagram showing an example of the overall configuration of a tandem type electrophotographic image forming apparatus including the electrophotographic photoreceptor of the present invention.

(1) Preparation of printed matter for evaluating point defects in the initial stage of printing Evaluation of point defects in the initial stage of printing was carried out using transfer material: "POD gloss coat (A3 size, 100 g/m ² )" in an environment of 30°C and 85% RH. (manufactured by Oji Paper Co., Ltd.) under conditions of a grid voltage of -800 V and a developing bias of -700 V to form a plain image (white solid image) to produce a printed matter for evaluation of point defects at the initial stage of printing.

(2) Preparation of printed matter for point defect evaluation after durability test The durability test was carried out in an environment of 23°C and 50% RH by horizontally feeding a test image consisting of a vertical striped solid image with 10% coverage as shown in Figure 5 on A4 paper. 500,000 sheets were printed continuously.

Next, in the same manner as the initial printing evaluation method described above, a grid was applied on the transfer material: "POD Gloss Coat (A3 size, 100 g/m ² )" (manufactured by Oji Paper Co., Ltd.) in an environment of 30° C. and 85% RH. A plain image (solid white image) was formed under the conditions of a voltage of -800V and a developing bias of -700V, and a printed matter for evaluation of point defects after the durability test was produced.

(3) Evaluation method for point defects For each evaluation printed matter created as described above, count the number of black spots with a diameter of 0.1 mm or more in an area of 10 cm x 10 cm on the transfer material, and rank them according to the following evaluation criteria. went. Here, as an evaluation rank, ranks A to C were considered to be passed, and ranks D to E were judged to be failed.

(4) Evaluation criteria for point defects A: No black spots with a diameter of 0.1 mm or more are observed in an area of 10 cm x 10 cm. (Passed)
B: 1 to 3 black spots with a diameter of 0.1 mm or more in an area of 10 cm x 10 cm. (Passed)
C: 4 to 9 black spots with a diameter of 0.1 mm or more in an area of 10 cm x 10 cm. (Passed)
D: 10 to 49 black spots with a diameter of 0.1 mm or more in an area of 10 cm x 10 cm. (failure)
E: 50 or more black spots with a diameter of 0.1 mm or more in an area of 10 cm x 10 cm. (failure)

(Evaluation of cleaning performance)
[Preparation of image forming device]
Using an image forming apparatus that had been modified from a full-color printing press (bizhub PRESS C1070, manufactured by Konica Minolta) so that the linear speed was 500 mm/sec and the lubricant pressing force was halved, each of the photoreceptors prepared above was transferred to an image forming unit. An image forming apparatus for evaluation was manufactured by arranging the image forming apparatus at the cyan (C) position.

In addition, cleaning properties were evaluated at the initial stage of printing and after the durability test according to the following method.
(1) Method for preparing and checking printed matter for evaluating cleaning performance at the initial stage of printing The cleaning performance at the initial stage of printing was evaluated using a horizontal striped solid image with 40% coverage as shown in Figure 6 in an environment of 10°C and 20% RH. 20,000 test images were continuously printed on A4 paper with horizontal feed.

Note that the coverage of the top and bottom printed areas (bands) of this image is 100% in the direction perpendicular to the rotation axis direction of the photoconductor (circumferential direction), and the coverage of the two printed areas (bands) in the center is 100%. Part) has a coverage of 50% in the direction (circumferential direction) perpendicular to the rotational axis direction of the photoreceptor. Thereafter, the photoreceptor was removed from the unit, and the lubricant application brush was visually checked for contamination.

(2) Preparation and confirmation method of printed matter for cleaning performance evaluation after durability test The durability test was conducted by printing a test image consisting of a vertical striped solid image with 10% coverage as shown in Figure 5 in an environment of 23°C and 50% RH. Continuously printed 500,000 sheets in A4 horizontal feed.

Next, in the same manner as the initial printing evaluation method described above, 20,000 sheets of A4 paper were printed with a test image consisting of a horizontal striped solid image with a coverage of 40% as shown in FIG. 6 in an environment of 10° C. and 20% RH. , the photoreceptor was removed from the unit, and the lubricant application brush was visually checked for contamination.

(3) Method for evaluating cleaning performance The lubricant coated brushes after the above evaluation were ranked according to the following evaluation criteria. Here, as an evaluation rank, ranks A to C were considered to be passed, and ranks D to E were judged to be failed.

(4) Evaluation criteria for cleaning performance A: Good quality with no contamination of lubricant application brush. (Passed)
B: White staining is observed on the lubricant application brush only in the area corresponding to the image corresponding to 100% coverage in the circumferential direction, but there is no problem in practical use. (Passed)
C: In addition to the area corresponding to the image with 100% coverage in the circumferential direction, white contamination is observed on the lubricant application brush in the area with 50% coverage, but there is no practical problem. (Passed)
D: Contamination with toner is observed on the lubricant application brush only in the area corresponding to the image corresponding to 100% coverage in the circumferential direction, which poses a practical problem. (failure)
E: In addition to the area corresponding to the image with 100% coverage in the circumferential direction, contamination with toner was observed on the lubricant application brush in the area with 50% coverage, which is a practical problem. (failure)

(Evaluation of scratch resistance)
[Preparation of image forming device]
Using an image forming apparatus in which a full color printing machine (bizhub PRESS C1070, manufactured by Konica Minolta) was modified to a linear speed of 500 mm/sec, each photoreceptor produced above was placed at the black (K) position of the image forming unit. An image forming apparatus for evaluation was manufactured.

(1) Preparation and confirmation method of printed matter for evaluation of scratch resistance after durability test As a durability test, a test image consisting of a vertical striped solid image with 10% coverage as shown in Fig. 5 was produced in an environment of 23°C and 50% RH. Continuously printed 500,000 sheets in A4 horizontal feed.

Next, in an environment of 23° C. and 50% RH, 200,000 sheets of a test image consisting of a horizontal band-shaped solid image with a coverage of 25% as shown in FIG. 7 were continuously printed in A4 horizontal feed. Note that the coverage of the printed portion of this image is 100% in the direction (circumferential direction) perpendicular to the direction of the rotation axis of the photoreceptor.

Next, under an environment of 23° C. and 50% RH, the surface condition of the photoreceptor was visually observed, and the photoreceptor after the durability test was used as an A3 size transfer material: “POD Gloss Coat (100 g/m ² )”. (manufactured by Oji Paper Co., Ltd.) A halftone image (relative reflection density 0.4 using a Macbeth densitometer) was printed on the entire surface.
The presence or absence of image defects after the durability test was visually confirmed.

(2) Evaluation method of scratch resistance The photoreceptor surface after the above evaluation was ranked according to the following criteria. Here, as evaluation ranks, ranks A to C were considered to be passed, and rank D was judged to be failed.

(3) Evaluation criteria for scratch resistance A: There are no visible scratches on the surface of the photoconductor, and no image defects corresponding to scratches on the photoconductor were observed in the output halftone image, indicating good quality. It is.
B: One to three minor scratches are visually observed on the surface of the photoreceptor, but no image defects corresponding to the photoreceptor scratches were found in the output halftone image, and there is no problem in practical use.
C: Although 4 to 6 minor scratches are visually observed on the surface of the photoreceptor, no image defects corresponding to the photoreceptor scratches were found in the output halftone image, and there is no problem in practical use.
D: Visually obvious scratches were observed on the surface of the photoconductor, and image defects corresponding to the scratches on the photoconductor were also observed in the output halftone image, which is a practical problem.

As shown in Table III, the present invention can maintain good cleaning performance and suppress point defects over a long period of time, and also has good scratch resistance.

1Y, 1M, 1C, 1Bk Photoreceptor 2Y, 2M, 2C, 2Bk Charging means 3Y, 3M, 3C, 3Bk Exposure means 4Y, 4M, 4C, 4Bk Developing means 5Y, 5M, 5C, 5Bk Primary transfer roller 5b Secondary transfer Rollers 6Y, 6M, 6C, 6Bk, 6b Cleaning means 7 Intermediate transfer unit 8 Housing 10Y, 10M, 10C, 10Bk Image forming unit 20 Paper feed cassette 21 Paper feed means 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper discharge roller 26 Paper discharge tray 70 Intermediate transfer body 71, 72, 73, 74 Roller 77 Intermediate transfer body 82L, 82R Support rail 100 Image forming device A Main body SC Original image reading device P Transfer material 101A, 101B Electronic Photographic photoreceptor 102 Conductive support 103 Intermediate layer 104 Photosensitive layer 105 Outermost layer 106 Charge generation layer 107 Charge transport layer 10 Conductive particle manufacturing device 11 Mother liquor tank 11a Stirring blade 11b First shaft 11c First motor 12 First piping 13 Strong dispersion device 13a Stirring section 13b Second shaft 13c Second motor 14 Second piping 15 First pump 16 Second pump

Claims (7)

An electrophotographic photoreceptor having a curable outermost layer at least on the photosensitive layer,
a first polymerizable monomer in which the outermost layer has at least three or more polymerizable groups in one monomer molecule;
a second polymerizable monomer having two polymerizable groups in one monomer molecule;
A cured product formed from a composition containing organic resin particles,
The content of the second polymerizable monomer is within the range of 30 to 70% by mass based on the total polymerizable monomers,
The organic resin particles contain at least a compound having a melamine structure, and
The particle size of the organic resin particles is 0. 20-2 . An electrophotographic photoreceptor characterized in that the particle diameter is within a range of 50 μm. The electron according to claim 1, characterized in that the two polymerizable groups of the second polymerizable monomer have a structure in which they are bonded via a linking group containing three or more atoms having an atomic weight of 12 or more. Photographic photoreceptor. 3. The electrophotographic photoreceptor according to claim 1, wherein the two polymerizable groups of the second polymerizable monomer have an alkylene structure in which at least a linking group has two or more carbon atoms. 4. The electrophotographic photoreceptor according to claim 1 , wherein the first polymerizable monomer has three polymerizable groups in one monomer molecule. A bifunctional polymerizable monomer is contained as a third polymerizable monomer other than the first polymerizable monomer or the second polymerizable monomer, and the second polymerizable monomer and the third polymerizable monomer The electrophotograph according to any one of claims 1 to 4 , characterized in that the total amount of the electrophotography is within the range of 45 to 70% by mass based on the total content of polymerizable monomers. Photoreceptor. An electrophotographic image forming apparatus comprising the electrophotographic photoreceptor according to any one of claims 1 to 5 . At least a charging step for charging the surface of the electrophotographic photoreceptor, an exposure step for forming an electrostatic latent image by exposing the surface of the electrophotographic photoreceptor, and a step for making the electrostatic latent image visible with toner. An electrophotographic image forming method comprising a developing step of forming a toner image and a transfer step of transferring the toner image to a transfer medium, the electrophotographic image forming method according to any one of claims 1 to 5 . An electrophotographic image forming method characterized by using a photographic photoreceptor.