JP2002268257A - Electrophotographic photoreceptor and manufacturing method thereof, electrophotographic method, electrophotographic apparatus and process cartridge for electrophotographic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoreceptor having high durability and capable of suppressing image deterioration due to the increase of residual potential or the generation of image blur and stably obtaining high quality image against the repeating use for a long period. SOLUTION: In the electrophotographic photoreceptor provided with a photosensitive layer containing at least a charge generating material and a charge transfer material on a conductive supporting body, a protective layer containing at least filler and a dispersing agent is formed on the photosensitive layer and the concentration of the dispersing agent contained in the protective layer is changed to be lowest in the outermost surface region of the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention has high durability,
The present invention also relates to an electrophotographic photoreceptor realizing high image quality and a method for manufacturing the same. The present invention also relates to an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge using the photoconductor.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable development of information processing system equipment using an electrophotographic system. Particularly, laser printers and digital copiers that convert information into digital signals and record information by light have remarkably improved in print quality and reliability. Further, they have been applied to laser printers or digital copying machines capable of full-color printing by fusing with high-speed technology. From such a background, high image quality has become a particularly important issue as one of the required functions of the photoconductor.

As the photoreceptors used in these electrophotographic laser printers and digital copiers, those using organic photosensitive materials are generally widely used due to cost, productivity, and pollution-free properties. Applied. Organic electrophotographic photoreceptors include polyvinyl carbazole (PV).
Photoconductive resin photoreceptor represented by K), PVK-TNF
A charge transfer complex type photoreceptor represented by (2,4,7-trinitrofluorenone) and a pigment dispersion type photoreceptor represented by a phthalocyanine-binder are known. At present, a charge generating substance and a charge transporting substance are known. A function-separated type photoreceptor using a combination of the above is widely applied.

The mechanism of the formation of an electrostatic latent image in a function-separated type photoreceptor is that, when the photoreceptor is charged and irradiated with light, the light passes through the charge transport layer, is absorbed by the charge generating substance in the charge generation layer, and is charged. Generate The charges generated thereby are injected into the charge transport layer at the interface between the charge generation layer and the charge transport layer, and further move in the charge transport layer by an electric field. After that, the photosensitive member moves to the surface of the photoreceptor and neutralizes the surface charge of the photoreceptor to form an electrostatic latent image.

However, organic photoreceptors are liable to suffer from film abrasion due to repeated use, and as the film abrasion of the photosensitive layer progresses, the charge potential of the photoreceptor decreases, the photosensitivity deteriorates, and the surface of the photoreceptor is scratched. There is a strong tendency for background contamination, image density reduction or image quality deterioration to be accelerated, and the abrasion resistance of the photoreceptor has been conventionally cited as a major problem. Further, in recent years, with the increase in the speed of the electrophotographic apparatus or the reduction in the diameter of the photoconductor accompanying the miniaturization of the apparatus, it has become an even more important issue to increase the durability of the photoconductor. Therefore, in the case of organic electrophotographic photoreceptors, it is cited as the most important issue to achieve both high image quality and high durability.

In order to realize high durability of the photosensitive member, it is necessary to improve the wear resistance of the photosensitive member. As the thickness of the photosensitive layer of the photoreceptor becomes thinner, the electric field intensity becomes higher, and image defects such as background contamination become more likely to occur. on the other hand,
When the film thickness of the photosensitive layer is increased more than necessary, there is a tendency that the resolution is greatly reduced and the image quality is deteriorated. In addition, if the amount of decrease in film thickness during repeated use is large, the image quality tends to fluctuate, and the photoconductor must be replaced in a short cycle. Therefore, it is important to reduce the variation in the thickness of the photoconductor not only for high durability but also for high image quality.

As a means for improving the abrasion resistance of the photoreceptor, there is widely known a method in which a protective layer is provided on the outermost surface of the photoreceptor, and the protective layer is provided with lubricity, is cured, or contains a filler. Have been. In particular, the method of adding a filler to the protective layer is one of the effective and useful methods for increasing the durability of the photoreceptor since the effect can be obtained stably over a relatively long period.

However, the increase in charge trapping sites caused by the inclusion of the filler causes a significant increase in the residual potential. The increase in the residual potential leads to a high bright portion potential in the electrophotographic apparatus, which causes a remarkable decrease in image density and gradation, and causes deterioration in image quality. To compensate for this, it is necessary to increase the dark area potential, but increasing the dark area potential increases the electric field strength,
Not only is it easy to cause image defects such as background contamination, but also the life of the photoconductor is significantly reduced. The problem of increasing the residual potential presents a more serious problem when used repeatedly. When the photoreceptor is used repeatedly for a long period of time, the charge transporting substance is decomposed or deteriorated by the influence of the generated ozone, and at the same time, the number of charge trap sites further increases, causing a significant increase in the residual potential. This results in a reduction in image density and gradation, and eventually leads to a significant reduction in the life of the photoconductor.

The effect of the filler on the residual potential is as follows.
Due to the resistance of the filler, the effect of the increase in the residual potential increases when a filler having a high electrical insulating property is used. On the other hand, when the conductive filler is contained, the effect of the increase in the residual potential is relatively small, but the outline of the image is blurred, that is, the so-called image blur is apt to occur, and the effect on the image quality appears strongly. This is considered to be due to the movement of electric charges in the lateral direction of the photoreceptor, and is particularly noticeable under high temperature and high humidity. From these facts, if the insulation of the filler is increased, the influence of the image blur is reduced and the residual potential is easily increased, and if the insulation of the filler is reduced, the influence of the increase of the residual potential is reduced. Charge transfer to the surface of the substrate, and image blurring is likely to occur. Therefore, it is necessary to prevent image blurring and to maintain a minimum residual potential.

Further, it is known that the image blur is not caused only by the kind of the filler, but also greatly affected by the contamination of the photoreceptor surface due to repeated use. NOx and ozone gas generated when the photoreceptor is charged in the external use atmosphere decompose or degrade the charge transport material and the binder resin, and the resulting substance adheres to the photoreceptor surface. The body surface has low resistance, and image blurring is likely to occur. On the contrary, the conventional photoreceptor has low durability and has a large amount of abrasion of the photoreceptor due to repeated use. In addition, image blur was hard to occur.
However, in order to realize high durability of the photoconductor, it is necessary to minimize the amount of abrasion of the photoconductor, and a new problem that image blur is likely to occur occurs.

In the prior art, a filler having a low insulating property, which is relatively little affected by a rise in residual potential, is used, and a means for mounting a drum heater for heating a photosensitive member is mainly used for image blur caused by the filler. Used. Certainly, although the occurrence of image blur can be suppressed by heating the photoconductor, the diameter of the photoconductor must be large in order to mount a drum heater. It cannot be applied to a small-diameter photoconductor, which is becoming increasingly difficult, and it has been difficult to increase the durability of the small-diameter photoconductor. Furthermore, the installation of the drum heater necessitates a large-sized device, which significantly increases power consumption and takes a lot of time when starting up the device. What was left was the actual situation.

As described above, in order to achieve both high durability and high image quality of the photoconductor, it is necessary to not only improve the wear resistance of the photoconductor but also simultaneously suppress the rise in residual potential and the occurrence of image blur. Is essential.

In the prior art, as a method of suppressing the rise in residual potential, the protective layer becomes substantially transparent by setting the average particle size of the metal or metal oxide contained as a filler to 0.3 μm or less. A method for suppressing the accumulation of residual potential (Japanese Patent Application Laid-Open No. 57-30846) is disclosed. This method is inadequate as an effect of suppressing an increase in the residual potential, and has not yet solved the problem. This is because the increase in the residual potential caused by the inclusion of the filler is more likely to be caused by the charge trapping due to the presence of the filler and the dispersibility of the filler than the charge generation efficiency. Even if the average particle size of the filler is 0.3 μm or more, transparency can be obtained by increasing the dispersibility, and the average particle size is 0.1 μm.
Even if it is 3 μm or less, the transparency of the film will be reduced if the filler is considerably aggregated.

In addition, by including a charge transporting substance together with a filler in the protective layer, the protective layer has mechanical strength,
Method for suppressing increase in residual potential (JP-A-4-28146)
No. 1) is disclosed. This means is effective for improving the mobility of electric charges and is an effective method for reducing the residual potential. However, the remarkable increase in the residual potential caused by the inclusion of the filler is attributed to the increase in charge trapping sites due to the presence of the filler. There is a limit. Therefore, in reality, this method alone did not satisfy the required durability.

As another means for suppressing the rise in residual potential, a method of adding a Lewis acid or the like to the protective layer (Japanese Patent Laid-Open No.
-133444), a method of adding an organic protonic acid to the protective layer (JP-A-55-157748), a method of containing an electron-accepting substance (JP-A-2-4275), and an acid value of 5 (mgKOH / g). ) The following method (Japanese Unexamined Patent Publication No. 2000-66434) containing a wax is disclosed. These methods improve the charge injectability at the interface between the protective layer and the charge transport layer, and form a low-resistance portion in the protective layer, so that the charge can easily reach the surface. Is believed to be Although these methods have the effect of reducing the residual potential, they tend to cause image blurring, and have the side effect of notably affecting the image. In addition, when an organic acid is added, the dispersibility of the filler is liable to be reduced, so that the effect is not sufficient, and in reality, the problem has not been solved.

As one means for realizing high image quality in an electrophotographic photoreceptor containing a filler for high durability, the present inventors have studied the above-mentioned rise in residual potential and image blur. At the same time, it has been found that it is important to allow the charge to reach the surface of the photoreceptor linearly without being obstructed by the filler. To that end, the dispersibility of the filler in the protective layer greatly affects.
In the state where the filler is aggregated, when the injected charge moves to the surface, the movement is easily blocked or trapped by the filler, and as a result, the dots formed by the toner are scattered and the resolution is increased. Greatly decreases. Further, when a protective layer containing a filler is provided on the surface, when the writing light is scattered by the filler and the light transmittance is reduced, similarly, the resolution is greatly adversely affected. The effect is also closely related to the dispersibility of the filler. In addition, the dispersibility of the filler greatly affects the abrasion resistance.The filler causes strong agglomeration. This has a great adverse effect on high durability and high image quality. Therefore, in an electrophotographic photoreceptor having a protective layer containing a filler for high durability, it is important to enhance the dispersibility of the filler in the protective layer in order to simultaneously achieve high image quality. .

In order to improve the dispersibility of the filler in the protective layer, it is important to improve the dispersibility of the filler in the coating dispersion. If the dispersibility of the coating dispersion is poor, it is difficult to improve the filler dispersibility in the protective layer using any coating means, and by promoting the sedimentation of the filler, The quality stability of the photoreceptor is reduced, and the life of the dispersion is also significantly reduced.

In addition, in order to achieve both high durability and high image quality of the photoconductor, it is important to suppress contamination of the photoconductor surface by NOx and ozone gas as described above. N
The influence of Ox or ozone gas not only causes image blurring but also lowers charging, lowers sensitivity and lowers abrasion resistance, and is a major obstacle to high durability. As described above, it is considered that these influences are mainly caused by the fact that the charge transporting substance, the binder resin, and the like are decomposed and deteriorated by NOx or ozone gas, thereby contaminating the photoconductor surface.

As a suppression method in these prior arts, a method of polishing the surface of a photoreceptor (JP-A-2-52373)
And JP-A-3-92822, and a method for incorporating an antioxidant into the photosensitive layer (JP-A-2-64549, JP-A-2-64549).
JP-A-64550, JP-A-6-332216, etc., and a method of incorporating a fluorine-based resin powder on a photosensitive layer (JP-A-Hei.
67566, JP-A-2-189550, JP-A-2-
No. 189551), a method of incorporating a lubricant powder into the photoreceptor surface layer (JP-A-1-284857, JP-A-1-285).
949, JP-A-4-21855), and a method of heating the photoreceptor (JP-A-1-191883, JP-A-1-206)
No. 386, JP-A-1-233474) and the like. However, these methods cause an increase in residual potential or a decrease in sensitivity, or a decrease in durability or image blur, or a decrease in film quality. It is hard to say that this method is satisfactory for the task.

On the other hand, a method has been disclosed in which a charge transport layer is formed into multiple layers and the content of the charge transport material is set low in the charge transport layer close to the surface (JP-A-11-288128). This method aims at improving the corona resistance. However, when the concentration of the charge transporting substance in the outermost surface layer is reduced, the effect of the rise in the residual potential is remarkably exhibited unless the layer is as thin as several μm. Has not been solved. Also, a method in which a plurality of charge transport layers are provided on the conductive support side from the protective layer, and a large amount of charge transport material is contained near the interface between the protective layer and the charge transport layer (JP-A-3-318)
No. 46) is disclosed. In this method, the protective layer is a vacuum thin film, and also deals with the deterioration of the charge transport layer when an active gas such as ozone passes through the protective layer. In the present invention, the influence of the decomposition or alteration of the constituent material by the active gas is intended to be dealt with by the protective layer on the outermost surface since the outermost surface layer region is the strongest, and the configuration and its effect are greatly different. It is. Therefore, in the prior art, the effect is often insufficient or the effect of side effects is large in most cases, and a method satisfying both high durability and high image quality has not been found. Met.

In order to increase the durability of the photoreceptor, it is indispensable to improve the abrasion resistance. At the same time, it is necessary to realize a high image quality. It is important to suppress blurring and to improve the dispersibility of the filler in the protective layer. Furthermore, even when the battery is repeatedly used, the rise in residual potential is small, and minimizing the influence on NOx and ozone gas is indispensable for high durability. However, no effective means has been found to solve them at the same time, and in fact, there remains a major problem in achieving both high durability and high image quality. In order to reduce those effects, a means for finally mounting a drum heater is used, which has been a great obstacle to downsizing the apparatus and reducing power consumption. Furthermore, in the case of a small-diameter photoreceptor that requires the most durability, high-durability has not been realized due to the difficulty in applying such means, and the development of a photoreceptor that achieves both high durability and high image quality has been eagerly desired. Was.

[0022]

DISCLOSURE OF THE INVENTION The present invention has high durability, suppresses image deterioration due to a rise in residual potential or occurrence of image blur, and can provide a high-quality image even when used repeatedly for a long time. It is an object of the present invention to provide a photoconductor that can be obtained stably. In addition, the present invention realizes high-speed printing or downsizing of the apparatus due to reduction of the diameter of the photoconductor by using those photoconductors, which eliminates the need for replacement of the photoconductor. Another object of the present invention is to provide an electrophotographic method, an electrophotographic apparatus, and a process cartridge for electrophotography, which can stably obtain the toner.

[0023]

It is known that it is effective to form a layer containing a filler on the outermost surface of a photoconductor in order to realize high durability of an electrophotographic photoconductor. This has the side effect of deteriorating image quality, such as an increase in residual potential and occurrence of image blur. It is considered that this is mainly caused by an increase in charge trap sites due to the filler contained, susceptibility to the influence of external water, and obstruction of charge transfer or light transmission. Therefore, in order to reduce these effects, it is necessary to improve not only the physical properties of the filler but also the dispersibility of the filler.

When the photosensitive member is repeatedly used for a long period of time, the resolution is greatly reduced by exposing the photosensitive member to the atmosphere of the outside or NOx or ozone gas generated during charging.
In order to obtain a photosensitive member that achieves both high durability and high image quality, it is important to reduce these effects. The effects of these active gases are strongest on the surface of the photoreceptor, and the effects of the active gas on the image are particularly the decomposition and alteration of the charge transport material, binder resin, dispersant, etc. present on the surface of the photoreceptor. Is considered as one of the causes. Therefore, if the content of these materials can be reduced without affecting other characteristics, it is possible to reduce the influence of the active gas on the image.

Therefore, in the present invention, by satisfying the following constitutional requirements, it is possible to achieve both high durability and high image quality, and to obtain an electrophotographic photosensitive member capable of stably obtaining a high quality image even when repeatedly used. It has been made possible to provide an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge capable of stably obtaining a high-quality image even in repeated use. (1) In an electrophotographic photosensitive member having a photosensitive layer containing at least a charge generating substance and a charge transporting substance on a conductive support, a protective layer containing at least a filler and a dispersant is formed on the photosensitive layer. And an electrophotographic photoreceptor characterized in that the concentration of the dispersant contained in the protective layer has a concentration change which is lowest in the outermost surface region of the protective layer. (2) The dispersant contained in the protective layer has a concentration gradient in which the concentration of the dispersant decreases continuously from the interface between the protective layer and the photosensitive layer toward the outermost surface of the protective layer. The electrophotographic photosensitive member according to the above (1). (3) The electrophotographic photoreceptor according to the above (1) or (2), wherein the photosensitive layer has a single-layer structure containing at least a charge generating substance and a charge transporting substance. (4) The electron according to (1) or (2), wherein the photosensitive layer has a laminated structure of at least a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance. Photoreceptor. (5) The method according to any one of (1) to (4) above, wherein the dispersant contained in the protective layer is an organic compound containing at least one carboxyl group in a structure. Electrophotographic photoreceptor. (6) The electrophotographic photoreceptor according to the above (5), wherein the dispersant contained in the protective layer is a polycarboxylic acid derivative. (7) The dispersant contained in the protective layer is 10 to 400.
The electrophotographic photoreceptor according to any one of the above (1) to (6), which is an organic compound having an acid value of (mgKOH / g). (8) The above-mentioned (1) to (7), wherein the amount of the dispersant added to the protective layer satisfies the following relational expression.
The electrophotographic photosensitive member according to any one of the above. 0.1 ≦ (addition amount of dispersant × acid value of dispersant) / (content of filler) ≦ 20 (9) The filler contained in the protective layer is at least one kind of inorganic pigment. (1) to above
The electrophotographic photosensitive member according to any one of (8) and (7). (10) The filler according to (9), wherein the filler contained in the protective layer is at least one kind of metal oxide.
The electrophotographic photosensitive member according to the above. (11) The electrophotographic photoreceptor according to the above (9) or (10), wherein the pH of at least one kind of inorganic pigment or metal oxide contained in the protective layer is 5 or more. (12) The electrophotograph according to any one of the above (9) to (11), wherein the dielectric constant of at least one inorganic pigment or metal oxide contained in the protective layer is 5 or more. Photoconductor. (13) The above (9) to (12), wherein at least one kind of inorganic pigment or metal oxide contained in the protective layer has been subjected to a surface treatment with at least one kind of surface treatment agent. The electrophotographic photosensitive member according to any one of the above. (14) In the surface treated inorganic pigment or metal oxide contained in the protective layer, the surface treatment agent is at least a titanate coupling agent, a higher fatty acid or a metal salt of a higher fatty acid. The above (1
3) The electrophotographic photosensitive member according to the above. (15) In the inorganic pigment or metal oxide subjected to surface treatment contained in the protective layer, the surface treatment amount is 2 to 2.
The electrophotographic photoreceptor according to the above (13) or (14), wherein the content is 30 wt%. (16) The electrophotographic photoreceptor according to any of (1) to (15), wherein the average primary particle diameter of the filler contained in the protective layer is 0.01 to 0.5 μm. . (17) The electrophotographic photoreceptor according to any one of the above (1) to (16), wherein the protective layer contains at least one kind of charge transport material. (18) The electron according to (17), wherein the following relationship is established between the ionization potential Ip of the charge transport material contained in the protective layer and that of the charge transport material contained in the photosensitive layer. Photoreceptor. Ip of the charge transport material contained in the protective layer ≦ Ip of the charge transport material contained in the charge transport layer (19) In the charge transport material contained in the protective layer, the concentration of the charge transport material contained in the protective layer Has the lowest concentration change in the outermost surface region of the protective layer. (20) The charge transporting substance contained in the protective layer has a concentration gradient in which the concentration of the charge transporting substance decreases continuously from the interface between the protective layer and the photosensitive layer toward the outermost surface. The electrophotographic photosensitive member according to the above (19), wherein (21) As the charge transport material contained in the protective layer,
The electrophotographic photoreceptor according to any one of the above (17) to (20), wherein the charge transport polymer material is entirely or partially contained. (22) The binder resin according to (1), wherein the binder resin contained in the protective layer contains any one of a polycarbonate resin, a polyarylate resin, and a polyester resin, or a mixture of two or more of them. The electrophotographic photosensitive member according to any one of (1) to (21). (23) The electrophotographic photoreceptor according to the above (22), wherein the binder resin contained in the protective layer is a polymer alloy, and at least it is a polymer alloy with polyethylene terephthalate. (24) The binder resin contained in the protective layer has an acid value of 1
The electrophotographic photoreceptor according to any one of the above (1) to (23), which contains 0 to 400 (mgKOH / g) of a resin. (25) A method for producing an electrophotographic photosensitive member according to any one of the above (1) to (24), wherein a spray coating method is used as a method for forming a protective layer. Production method. (26) The method for producing an electrophotographic photoreceptor according to the above (25), wherein the protective layer is sequentially laminated by using dispersions having different concentrations of the contained materials to give a change in concentration to the protective layer. (27) The method according to the above (25), wherein a plurality of dispersion liquids having different concentrations of the contained materials are simultaneously applied using a plurality of spray guns while providing a time difference to give a concentration change to the protective layer. A method for manufacturing an electrophotographic photoreceptor. (28) An electrophotograph, wherein the electrophotographic photoconductor according to any one of the above (1) to (24) is used, and at least charging, image exposure, development, and transfer are repeatedly performed on the electrophotographic photoconductor. Method. (29) Using the electrophotographic photosensitive member according to any one of the above (1) to (24), the electrophotographic photosensitive member is repeatedly subjected to at least charging, image exposure, development, and transfer, and A digital electrophotographic method comprising writing an electrostatic latent image on a photoreceptor by using an LD or an LED. (30) The electrophotographic photosensitive member according to any one of (1) to (24), and at least a charging unit, an image exposing unit, a developing unit, a transferring unit, and an electrophotographic photosensitive member. Electrophotographic equipment. (31) An electrophotographic photosensitive member according to any one of the above (1) to (24), and at least a charging unit, an image exposing unit, a developing unit, a transfer unit and an electrophotographic photosensitive member,
A digital electrophotographic apparatus, wherein an electrostatic latent image is written on a photoreceptor by using an LD or an LED as an image exposure unit. (32) A process cartridge for an electrophotographic apparatus, comprising at least the electrophotographic photosensitive member according to any one of the above (1) to (24).

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. Highly durable electrophotographic photoreceptors in which a filler is contained in a protective layer formed on the surface of the electrophotographic photoreceptor have an adverse effect on image quality, such as increased residual potential, reduced resolution, and image blurring. However, it has been difficult to achieve both high durability and high image quality. This makes it difficult to solve the problem that there is a trade-off relationship between image blur and residual potential.

As a result of intensive studies, the present inventors have found that a filler contained in the protective layer is made of an inorganic filler effective for abrasion resistance, and among them, a filler having a high insulating property is used. Suppress the occurrence of image blur,
The suppression of the increase in the residual potential caused thereby can be achieved by improving the dispersibility of the filler by adding a dispersant and reducing the charge trap sites of the filler.

When the filler contained in the protective layer is deagglomerated and the dispersibility is good, the charge injected into the protective layer can easily reach the surface, so that the increase in the residual potential can be suppressed. Therefore, the reproducibility of the dots formed by the toner becomes more faithful, and a high-resolution image can be obtained. On the other hand, when the filler is in an extremely agglomerated state, the movement of the charge is hindered by the filler, and not only the resolution is lowered due to the decrease in the straightness of the charge transfer, but also the charge is easily trapped. In addition, the occurrence of image blur and the residual potential are increased.

Aggregation of fillers is more likely to occur with inorganic (hydrophilic) fillers having low affinity for organic solvents, binder resins, and the like. In that case, in order to improve the filler dispersibility, in addition to the method of surface treating the filler, by adding an organic compound having a carboxyl group in the structure found in the present invention as a dispersant, the inorganic filler and It is possible to increase the affinity with an organic solvent, a binder resin or the like, and as a result, it has the effect of increasing the filler dispersibility. Further, the dispersant itself has the effect of increasing the dispersibility, and thus has the effect of reducing the charge trapping sites. In addition, the dispersant itself has an appropriate acid value, thereby synergistically reducing the residual potential. The effect can be obtained.

The effect of improving the filler dispersibility of the entire protective layer by this method is not limited to merely suppressing the increase in the residual potential, but also reduces the scattering of dots formed by the toner and enables more faithful dot reproduction. In addition to
By preventing the occurrence of image density unevenness by making the transmittance of the writing light uniform, higher image quality can be realized. In addition, it has become possible to obtain a high-quality image for a long period of time by improving wear resistance and suppressing uneven wear during repeated use. In addition, by improving the dispersibility of the filler, it is possible to suppress the occurrence of abnormal images and prevent the occurrence of coating film defects, and achieve a long life and high stability of the dispersion liquid. It also has.

By the above-mentioned method, internal factors of the photoreceptor which affect image quality deterioration are improved, and high image quality is realized while maintaining abrasion resistance. Not suppressing the effects of NOx or ozone gas generated during charging and lowering the resolution and lowering the charging does not mean that both high durability and high image quality are achieved. The effect of NOx and ozone gas on the image is due to the decomposition or alteration of the charge transport material, binder resin, dispersant, etc. contained in the protective layer located on the outermost surface of the photoreceptor, or contamination of the photoreceptor surface caused by this Is considered as one of the causes of the occurrence, and the influence thereof is the strongest on the outermost surface side of the photoreceptor, and the influence tends to diffuse into the inside of the layer.

Therefore, if the protective layer does not contain a charge transporting substance, a dispersant, or the like having a large influence on the above, or if the content thereof is small, it is possible to suppress the deterioration of the image quality. However, when the content of the charge transporting substance or the dispersant in the entire protective layer is reduced, the effect of the increase in the residual potential appears remarkably, and the deterioration of the image quality is promoted. Therefore, in the present invention, in the outermost surface region closer to the outside, the content of the dispersant and the charge transporting substance contained in the protective layer is made smaller than in other regions, so that the dispersant and the charge It was configured to give a change in the concentration of the transport substance.

Conventionally, when the durability of an electrophotographic photosensitive member is increased, side effects that cause deterioration in image quality such as an increase in residual potential and image blur occur, and it is extremely difficult to achieve both high durability and high image quality. Have been. According to the present invention, it is possible to simultaneously suppress an internal factor and an external factor of the photoconductor that affect the image quality deterioration, and realize high durability and high image quality. By these methods, it has become possible to obtain an electrophotographic photosensitive member that achieves both high durability and high image quality, and an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge using the same.

Hereinafter, the electrophotographic photosensitive member used in the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating an example of the electrophotographic photoreceptor of the present invention. Further, a protective layer 39 containing a filler and a dispersant is formed thereon, and the protective layer 3
9 has a configuration in which the concentration of a dispersant or the like changes.

FIG. 2 shows an example in which a charge generating layer 35 mainly composed of a charge generating substance and a charge transporting layer 37 mainly composed of a charge transporting substance are laminated on a conductive support 31. I am taking. Further, a protective layer 39 containing a filler and a dispersant is formed thereon, and the protective layer 39 has a configuration in which the concentration of the dispersant and the like changes.

FIG. 3 shows an example in which a charge transport layer 37 mainly composed of a charge transport substance and a charge generation layer 35 mainly composed of a charge generation substance are laminated on a conductive support 31. ing. A protective layer 39 containing a filler and a dispersant is formed thereon, and the protective layer 39 has a configuration in which the concentration of the dispersant and the like changes.

The conductive support 31 has a volume resistance of 10
Those exhibiting a conductivity of ¹⁰ Ωcm or less, for example, aluminum, nickel, chromium, nichrome, copper, gold, silver, metals such as platinum, tin oxide, metal oxides such as indium oxide, by evaporation or sputtering, Film or cylindrical plastic or paper coated, or plates of aluminum, aluminum alloy, nickel, stainless steel, etc., and extruded, drawn, etc., turned into a tube, then cut, super-finished, polished, etc. And the like can be used. Also, Japanese Patent Application Laid-Open No. 52-36
The endless nickel belt and the endless stainless belt disclosed in No. 016 can also be used as the conductive support 31.

In addition, those obtained by dispersing a conductive powder in a suitable binder resin on the above-mentioned support and applying the same can also be used as the conductive support 31 of the present invention. This conductive powder includes carbon black, acetylene black, aluminum, nickel, iron, nichrome,
Metal powder of copper, zinc, silver, etc., or conductive tin oxide, I
Metal oxide powder such as TO can be used. The binder resins used simultaneously include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, and vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene,
Thermoplastic, thermosetting or photocurable resins such as poly-N-vinylcarbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenolic resin, and alkyd resin. Such a conductive layer can be provided by dispersing the conductive powder and the binder resin in an appropriate solvent, for example, tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene, or the like, and applying the dispersion.

Further, heat shrinkage of a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) or the like containing the conductive powder on a suitable cylindrical substrate. A conductive layer provided with a tube can also be favorably used as the conductive support 31 of the present invention.

Next, the photosensitive layer will be described. The photosensitive layer may be a single layer or a laminated layer. First, the case where the photosensitive layer is composed of the charge generation layer 35 and the charge transport layer 37 will be described.

The charge generation layer 35 is a layer containing a charge generation substance as a main component, and disperses or dissolves the charge generation substance, a binder resin, and the like in an appropriate solvent, and disperses or dissolves the charge generation substance on a conductive support or an undercoat layer. It can be formed by coating and drying on the top.

For the charge generation layer 35, all known charge generation substances can be used.
It is possible to use all known charge generating substances,
Representative examples thereof include phthalocyanine pigments such as titanyl phthalocyanine, vanadyl phthalocyanine, copper phthalocyanine, hydroxygallium phthalocyanine, and metal-free phthalocyanine, monoazo pigments, disazo pigments, asymmetric disazo pigments, azo pigments such as trisazo pigments, perylene pigments, and perinone pigments. Known materials such as, indigo pigments, pyrrolopyrrole pigments, anthraquinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squarium pigments, etc., are useful. These charge generating substances can be used alone or in combination of two or more.

The charge generation layer 35 is formed by dispersing a charge generation material together with a binder resin in an appropriate solvent using a ball mill, an attritor, a sand mill, ultrasonic waves, or the like, if necessary, and dispersing this on a conductive support. It is formed by coating and drying.

If necessary, the binder resin used for the charge generation layer 35 may be polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, Poly-N-vinyl carbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulose resin, casein, polyvinyl alcohol, polyvinyl And pyrrolidone.
The amount of the binder resin is 0 to 100 parts by weight of the charge generating substance.
500 parts by weight, preferably 10 to 300 parts by weight, is suitable. The binder resin may be added before or after dispersion.

The solvents used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane,
Toluene, xylene, ligroin and the like can be mentioned. Particularly, ketone solvents, ester solvents and ether solvents are preferably used. These may be used alone or as a mixture of two or more.

The charge generation layer 35 contains a charge generation substance, a solvent, and a binder resin as main components, and contains any additives such as a sensitizer, a dispersant, a surfactant, and a silicone oil. It may be.

As a method for applying the coating solution, a dip coating method, a spray coat, a beat coat, a nozzle coat, a spinner coat, a ring coat and the like can be used.
The thickness of the charge generation layer 35 is suitably about 0.01 to 5 μm, and preferably 0.1 to 2 μm.

The charge transport layer 37 can be formed by dissolving or dispersing a charge transport material and a binder resin in an appropriate solvent, applying the solution on the charge generation layer, and drying. In addition, if necessary, it is possible to add one or more plasticizers, leveling agents, antioxidants, lubricants, etc.
Useful.

The charge transport materials are classified into hole transport materials and electron transport materials. Examples of the electron transport material include chloranil, bromanil, tetracyanoethylene,
Tetracyanoquinodimethane, 2,4,7-trinitro-
9-fluorenone, 2,4,5,7-tetranitro-9
Fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,
Electron accepting substances such as 6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, benzoquinone derivatives and the like. Can be

Examples of the hole transport material include poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethylglutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, polysilane, Oxazole derivatives, oxadiazole derivatives, imidazole derivatives,
Monoarylamine derivatives, diarylamine derivatives,
Triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives,
Other known materials such as a butadiene derivative, a pyrene derivative, a bisstilbene derivative, an enamine derivative, and the like are included. These charge transport materials are used alone or in combination of two or more.

Examples of the binder resin include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, and polystyrene. Vinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, Urethane resin,
Thermoplastic or thermosetting resins such as phenolic resins and alkyd resins are exemplified.

The amount of the charge transporting substance is 20 to 300 parts by weight, preferably 40 to 150 parts by weight, per 100 parts by weight of the binder resin.
Parts by weight are appropriate. The thickness of the charge transport layer is preferably 25 μm or less from the viewpoint of resolution and response. The lower limit depends on the system used (especially the charging potential, etc.), but is preferably 5 μm or more.

The solvents used here are tetrahydrofuran, dioxane, toluene, dichloromethane,
Monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. These may be used alone or in combination of two or more.

Next, the case where the photosensitive layer has a single-layer structure (33) will be described. The photosensitive layer is formed by dispersing the above-described charge generating substance, charge transporting substance, binder resin, and the like in a suitable solvent, applying the dispersion on a conductive support, and drying.
The photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance, and a binder resin in an appropriate solvent, and applying and drying the resulting solution. If necessary, various additives such as a plasticizer, a leveling agent, an antioxidant, a lubricant and the like can be added. The charge generating material and the charge transport material are
The materials listed for the charge generation layer 35 and the charge transport layer 37 can be used. Further, as the binder resin, in addition to the binder resin described above for the charge transport layer 37, the binder resin described for the charge generation layer 35 may be mixed and used. Of course, the above-mentioned polymer charge transport materials can also be used favorably. The amount of the charge generating substance is preferably 5 to 40 parts by weight, and the amount of the charge transporting substance is 0 to 1 part by weight based on 100 parts by weight of the binder resin.
90 parts by weight are preferred, and more preferably 50 to 150 parts by weight.
Parts by weight. The photosensitive layer includes a charge generating substance, a binder resin, and a charge transporting substance together with tetrahydrofuran, dioxane,
It can be formed by applying a coating liquid dispersed using a solvent such as dichloroethane or cyclohexane using a dip coating method, a spray coating method, a bead coating method, a ring coating method, or the like, followed by drying. The thickness of the photosensitive layer is 5 to 25 μm.
About m is appropriate.

On the photosensitive layer, a filler, a dispersant, a binder resin, and a charge transporting substance are dispersed or dissolved in a suitable solvent for the purpose of improving durability, and coating and drying are performed. Layer 39 is formed.

A filler material is added to the protective layer for the purpose of improving abrasion resistance. Fillers are classified into organic fillers and inorganic fillers.Examples of the organic filler material include fine particles of a fluororesin such as polytetrafluoroethylene, fine particles of a silicone resin, and a-carbon powder.As the inorganic filler material, copper, Metal powders such as tin, aluminum and indium, silica, tin oxide, zinc oxide, titanium oxide, alumina, zirconium oxide, indium oxide, antimony oxide, bismuth oxide,
Metal oxides such as calcium oxide, antimony-doped tin oxide, tin-doped indium oxide, tin fluoride,
Examples include metal fluorides such as calcium fluoride and aluminum fluoride, and inorganic materials such as potassium titanate and boron nitride. Among these fillers, it is advantageous to use an inorganic material from the viewpoint of the hardness of the filler for improving wear resistance.

As the filler which does not easily cause image blur, a filler having high electric insulation is preferable, and a filler having a pH of 5 or more and a filler having a dielectric constant of 5 or more are particularly effective. , Alumina, zinc oxide, zirconium oxide and the like can be particularly effectively used.
In addition, a filler having a pH of 5 or more or a filler having a dielectric constant of 5 or more can be used alone.
It is also possible to use a mixture of two or more fillers having a pH of 5 or more and a filler having a dielectric constant of 5 or more, or two or more fillers having a dielectric constant of 5 or more and a dielectric constant of 5 or more. is there. Among these fillers, α-type alumina, which has high insulation properties, high thermal stability, and high wear resistance, is particularly useful in terms of suppressing image blur and improving wear resistance. It is.

The average primary particle size of the filler is from 0.01 to
The thickness is preferably 0.5 μm from the viewpoint of the light transmittance and abrasion resistance of the protective layer. The average primary particle size of the filler is 0.01
When it is less than μm, abrasion resistance is reduced due to agglomeration and dispersibility, and when it is more than 0.5 μm, sedimentation of the filler is promoted or obtained by a photoreceptor manufactured using the filler. There is a possibility that an abnormal image may occur in the image to be obtained.

These fillers can be surface-treated with at least one surface treating agent, and it is preferable to do so from the viewpoint of dispersibility of the filler. A decrease in the dispersibility of the filler causes not only an increase in the residual potential, but also a decrease in the transparency of the coating film and the occurrence of coating film defects, and also causes a decrease in wear resistance and an increase in uneven wear. There is a possibility that it will develop into a big problem that hinders high image quality. As the surface treatment agent, any conventionally used surface treatment agent can be used, but a surface treatment agent capable of maintaining the insulating property of the filler is preferable. For example, titanate-based coupling agents, aluminum-based coupling agents,
Zircoaluminate-based coupling agents, higher fatty acids or metal salts such as aluminum stearate, or a mixture thereof, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , silicone, aluminum stearate, or a mixture thereof Is more preferable from the viewpoint of filler dispersibility and image blur. The single treatment with the silane coupling agent has a strong effect of image blur especially at high temperature and high humidity, but the effect may be suppressed by performing the mixing treatment of the above surface treatment agent and the silane coupling agent. . The amount of surface treatment varies depending on the average primary particle size of the filler used, but is preferably 2 to 30% by weight, and 3 to 20% by weight.
wt% is more preferred. If the surface treatment amount is less than this, the effect of dispersing the filler cannot be obtained, and if it is too large, the residual potential increases. Further, even when the filler has a low insulating property and the image is easily blurred, the surface treatment can enhance the insulating property and reduce the influence of the image blur.

By containing these fillers, it is possible to realize high durability and to suppress image blurring at high temperature and high humidity, but the effect of a rise in residual potential increases. In order to suppress the increase in the residual potential, by adding an organic compound having a carboxyl group in the structure as a dispersant, it becomes possible to improve the dispersibility of the filler and reduce the charge trap sites. In order to reduce the residual potential, the dispersant is used in an amount of 10 to 40.
Having an acid value of 0 (mgKOH / g) also plays an important role, and among these, polycarboxylic acid derivatives can be used particularly effectively. The acid value is defined as the number of milligrams of potassium hydroxide required to neutralize free fatty acids contained in 1 g. Further, the dispersant and the material having an acid value can be made to function by different materials, respectively. For example, the acid value of the dispersant is 10 to 400 (mg
KOH / g), the acid value is 10 to 400.
(MgKOH / g) can be sufficiently functioned by mixing a resin, an additive, and the like. As an example, a generally known organic fatty acid, a high acid value resin, and the like can be mixed. is there.

As the dispersant in the present invention, a known dispersant can be used. In particular, an organic compound having a structure containing at least one carboxyl group in a polymer or copolymer is preferable. Thus, a polycarboxylic acid derivative is more preferable. The carboxylic acid moiety in the dispersant gives an acid value and plays an important role in enhancing dispersibility. As described above, the hydrophilic inorganic filler has low affinity with the organic solvent and the binder resin, and is not well dispersed as it is by using any dispersing means. However, the dispersant in the present invention has a high affinity for the inorganic filler at the carboxylic acid site and a high affinity for the binder resin and the organic solvent at the other polymer sites. It is possible to increase the affinity with an organic solvent, a binder resin, or the like. This makes it possible to significantly increase the dispersibility of the filler. Further, even if the dispersant has one carboxyl group, the effect is recognized, but a polycarboxylic acid derivative having more carboxyl groups is more effective in improving filler dispersibility and reducing residual potential. It is effective in. In that case, not only the affinity between the dispersant and the filler is further enhanced, but also the affinity between the dispersants can be improved, thereby improving the dispersibility of the filler,
This effect can be maintained, and the effect of suppressing the sedimentation of the filler can be obtained.

The acid value of these dispersants is 1
0 to 400 mgKOH / g is preferable, and 30 to 200 mgKOH / g is more preferable. If the acid value is higher than necessary, the effect of image blurring may appear. If the acid value is too low, it is necessary to increase the amount of addition, and the effect of reducing the residual potential becomes insufficient. It is necessary to determine the acid value of the dispersant based on the balance with the amount added. The acid value of the dispersant does not directly affect the residual potential reducing effect, but is affected by the structure and molecular weight of the dispersant used, or the type and dispersibility of the filler. In some cases, by mixing these materials with organic fatty acids,
The effect of reducing the residual potential may increase. Further, since the vicinity of the interface between the protective layer and the charge transport layer has a large effect on the residual potential, a material having an acid value higher near the interface between the protective layer and the photosensitive layer than on the surface side should be used in the protective layer in the present invention. It can be contained, and is useful in suppressing a rise in residual potential.

The addition amount of the above dispersant preferably satisfies the following relational expression depending on the acid value of the dispersant used, but is more preferably set to the necessary minimum amount. If the added amount is increased more than necessary, the effect of image blur may appear.If the added amount is too small, the effect of improving the dispersibility and reducing the residual potential will not be sufficiently exhibited, causing the occurrence of abnormal images. Become. 0.1 ≦ (addition amount of dispersant × acid value of dispersant) / (addition amount of filler) ≦ 20

In the present invention, by changing the concentration of the dispersant contained in the protective layer by making it the lowest in the outermost surface region of the protective layer, the concentration is changed, so that the residual potential is hardly affected and NOx and NOx are not affected. It is possible to reduce the influence of the decrease in resolution or charge due to ozone. In particular, it is preferable to give a concentration gradient such that the concentration of the dispersant continuously decreases as going from the interface between the protective layer and the photosensitive layer toward the outermost surface, and the influence on the residual potential rise is further reduced. Since the dispersant of the present invention has an acid value, it has a high effect of reducing the residual potential.
There is a possibility that the effect of resolution reduction due to Ox or ozone gas may be increased. However, if the concentration of the dispersant is reduced in the entire protective layer in order to avoid this, the residual potential rises remarkably and the image quality deteriorates. In the present invention, the region that is strongly affected by NOx or ozone gas is limited to the surface region of the photoreceptor, and in particular, the concentration of the dispersant is reduced at least 1 μm or 2 μm from the surface of the protective layer. Let N
It has become possible to suppress the influence of image quality deterioration due to Ox and ozone. In addition, it was confirmed that the area where the concentration of the dispersant was the lowest was the outermost surface area of the photoreceptor, and if the area was as thin as 2 μm or less, the effect on the residual potential was very small. Accordingly, in the present invention, a constitution in which the concentration of the dispersant gives the lowest concentration in the outermost surface region of the protective layer, preferably from the interface of the protective layer / photosensitive layer to the outermost surface, the concentration of the dispersant is continuously increased. By adopting a configuration in which a decreasing concentration gradient is provided, it is possible to suppress the influence of image quality deterioration due to NOx and ozone without significantly affecting the residual potential.

As the binder resin contained in the protective layer, all the binder resins used in the charge transport layer 37 described above can be used, but the filler dispersibility is also affected by the binder resin. Therefore, it is important not to adversely affect the dispersibility of the filler. The resin having an acid value is
It is also useful in reducing the residual potential, and can be used as a binder resin in all or mixed with another binder resin and partially added. Examples of usable resins include polyester, polycarbonate, acrylic resin, polyethylene terephthalate, polybutylene terephthalate, various copolymers using acrylic acid and methacrylic acid, styrene acrylic copolymer, polyarylate, polyacrylate, polystyrene, Epoxy resin,
ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, aryl resin, phenol resin, polyacetal, polyamide, polyamide imide, polyallyl sulfone, polybutylene, polyether sulfone, polyethylene, polyimide, polymethylbenten, Resins or copolymers such as polypropylene, polyphenylene oxide, polysulfone, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, and polyvinylidene chloride are exemplified. These materials can be used as a mixture of two or more kinds.

Further, the binder resin has a great effect on image blur, and the use of a binder resin having high NOx resistance or ozone resistance not only suppresses image blur but also reduces abrasion resistance. Is also improved. As such a binder resin, a polymer alloy can also be used effectively, and at least a polymer alloy with polyethylene terephthalate has a high image blur suppressing effect and is useful.

The protective layer in the present invention preferably contains at least one kind of charge transporting substance in order to reduce the residual potential. As the charge transporting substance contained in the protective layer, all the charge transporting substances contained in the charge transporting layer 37 formed on the charge generating layer described above can be used. The transport material and the charge transport material contained in the charge transport layer may be different from each other. In that case, the charge injecting property at the charge transport layer / protective layer interface is improved by giving the charge transport material contained in the protective layer a lower ionization potential than the charge transport material contained in the charge transport layer. This is very effective in reducing the residual potential. The ionization potential can be measured by various methods such as a method of spectroscopically determining and a method of electrochemically determining.

Further, the protective layer in the present invention has a large influence on the residual potential by changing the concentration of the charge transporting substance contained in the protective layer so as to be the lowest in the outermost surface region of the protective layer. It is possible to reduce the effect of image quality deterioration due to NOx and ozone gas.
In particular, it is more preferable to provide a concentration gradient in which the concentration of the charge transporting substance decreases continuously from the interface between the protective layer and the photosensitive layer toward the outermost surface side of the protective layer, in order to suppress a rise in residual potential. One of the causes of these deteriorations in image quality is considered to be the decomposition and alteration of the charge transport material.It is necessary to reduce the effect by reducing the concentration of the charge transport material contained in the protective layer. Is possible. However, it causes a rise in the residual potential. On the other hand, the influence of NOx and ozone is strongest near the surface of the photoreceptor, and the effect tends to diffuse inside the photoreceptor. Therefore, in the present invention, by giving a concentration change such that the concentration of the charge transporting substance becomes lower in the outermost surface region of the protective layer, it is possible to reduce the influence of NOx and ozone gas without greatly affecting the residual potential. It became. In particular, from the viewpoint of reducing the residual potential, it is more preferable to have a structure in which the concentration gradient is provided so that the concentration of the charge transporting substance continuously decreases from the protective layer / photosensitive layer interface to the outermost surface.

For the protective layer, a polymer charge transporting material having both a function as a charge transporting material and a function as a binder resin is preferably used. The charge transport layer composed of these polymeric charge transport materials has excellent abrasion resistance. As the polymer charge transport material, known materials can be used. In particular, a triarylamine structure having a main chain and / or
Alternatively, a polycarbonate contained in a side chain is preferably used.
Among them, polymer charge transport materials represented by the formulas (I) to (X) are preferably used. These are illustrated below and specific examples are shown.

Embedded imageWhere R₁, R_Two, R_ThreeAre each independently substituted or
Unsubstituted alkyl group or halogen atom, R_FourIs a hydrogen atom
Or a substituted or unsubstituted alkyl group, R_Five, R ₆Is replaced
Or an unsubstituted aryl group, o, p and q are each independently
And an integer from 0 to 4, k and j represent compositions, and 0.1 ≦ k
≦ 1, 0 ≦ j ≦ 0.9, n represents the number of repeating units, and
It is an integer of 5000. X is an aliphatic divalent group, a cyclic fat
A divalent group of a group or a divalent group represented by the following general formula.

Embedded image In the formula, R ₁₀₁ and R ₁₀₂ each independently represent a substituted or unsubstituted alkyl group, aryl group or halogen atom.
l and m are integers from 0 to 4, Y is a single bond, and has 1 to 1 carbon atoms.
2 linear, branched or cyclic alkylene group, -O
-, - S -, - SO -, - SO 2 -, - CO -, - CO
—O—Z—O—CO— (wherein, Z represents an aliphatic divalent group) or

Embedded image (In the formula, a represents an integer of 1 to 20, b represents an integer of 1 to 2000, and R ₁₀₃ and R ₁₀₄ represent a substituted or unsubstituted alkyl group or aryl group.) Where R ₁₀₁ and R ₁₀₂ , R
₁₀₃ and R ₁₀₄ may be the same or different.

Embedded image In the formula, R ₇ and R ₈ represent a substituted or unsubstituted aryl group;
r ₁ , Ar ₂ and Ar ₃ represent the same or different arylene groups. X, k, j and n are the same as in the case of the formula (I).

Embedded image In the formula, R ₉ and R ₁₀ are a substituted or unsubstituted aryl group,
Ar ₄ , Ar ₅ and Ar ₆ represent the same or different arylene groups. X, k, j and n are the same as in the case of the formula (I).

Embedded image In the formula, R ₁₁ and R ₁₂ are a substituted or unsubstituted aryl group,
Ar ₇ , Ar ₈ and Ar ₉ are the same or different arylene groups, and p represents an integer of 1 to 5. X, k, j and n are
This is the same as in the case of the formula (I).

Embedded imageWhere R₁₃, R₁₄Is a substituted or unsubstituted aryl group,
Ar_Ten, Ar₁₁, Ar ₁₂Are the same or different allylenes
Group, X₁, X_TwoIs a substituted or unsubstituted ethylene group, or
Represents a substituted or unsubstituted vinylene group. X, k, j and
And n are the same as in the case of the formula (I).

Embedded image In the formula, R ₁₅ , R ₁₆ , R ₁₇ , and R ₁₈ are substituted or unsubstituted aryl groups, Ar ₁₃ , Ar ₁₄ , Ar ₁₅ , and Ar ₁₆ are the same or different arylene groups, and Y ₁ , Y ₂ , and Y ₃ are A single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom, and a vinylene group may be the same or different. X, k, j and n are
This is the same as in the case of the formula (I).

Embedded imageWhere R₁₉, R₂₀Is a hydrogen atom, substituted or unsubstituted
Represents an aryl group; ₁₉And R₂₀May form a ring
No. Ar₁₇, Ar₁₈, Ar₁₉Are the same or different ants
Represents a len group. X, k, j and n are the same as in the case of the formula (I).
Is the same.

Embedded image In the formula, R ₂₁ is a substituted or unsubstituted aryl group, A
r ₂₀ , Ar ₂₁ , Ar ₂₂ and Ar ₂₃ represent the same or different arylene groups. X, k, j and n are the same as in the case of the formula (I).

Embedded image In the formula, R ₂₂ , R ₂₃ , R ₂₄ , and R ₂₅ are a substituted or unsubstituted aryl group, Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ , Ar ₂₈
Represents the same or different arylene groups. X, k,
j and n are the same as in the case of the formula (I).

Embedded image In the formula, R ₂₆ and R ₂₇ represent a substituted or unsubstituted aryl group, and Ar ₂₉ , Ar ₃₀ , and Ar ₃₁ represent the same or different arylene groups. X, k, j and n are the same as in the case of the formula (I).

The filler material can be dispersed together with at least an organic solvent and a dispersant by a conventional method such as a ball mill, an attritor, a sand mill, and ultrasonic waves. Among them, a ball mill which can increase the contact efficiency between the filler and the dispersant and has a small amount of impurities mixed from the outside is more preferable from the viewpoint of dispersibility. Regarding the material of the media used, all media such as zirconia, alumina, and agate which are conventionally used can be used.However, it is more preferable to use alumina from the viewpoint of the dispersibility of the filler and the effect of reducing the residual potential. Preferably, α-type alumina having excellent wear resistance is particularly preferred. Zirconia has a large amount of abrasion of the medium at the time of dispersion. Not only does the residual potential increase significantly due to the incorporation of the zirconia, but also the dispersibility decreases due to the incorporation of the abrasion powder, and the sedimentation of the filler significantly decreases. On the other hand, when alumina is used for the medium, the amount of abrasion of the medium at the time of dispersion is suppressed to a low level, and the influence of the mixed abrasion powder on the residual potential is very small. Further, even if the abrasion powder is mixed, the influence on the dispersibility is small as compared with other media. Therefore, it is more preferable to use alumina for the medium used for dispersion. Further, the dispersant is preferably added together with the filler or the organic solvent before dispersion since the dispersant suppresses agglomeration of the filler in the coating liquid and further suppresses the sedimentation of the filler and significantly improves the dispersibility of the filler. On the other hand, the binder resin and the charge transporting substance can be added before dispersion, but in this case, the dispersibility may be slightly reduced. Therefore, it is preferable that the binder resin and the charge transporting substance are added after being dispersed in a state of being dissolved in the organic solvent.

The coating method of the dispersion obtained as described above includes dip coating, spray coating, beat coating, nozzle coating, spinner coating, ring coating and the like.
Conventional coating methods can be used, but spray coating is most suitable for forming a relatively thin film uniformly and a film having good filler dispersibility. Any method can be used to give the protective layer a change in the concentration of the dispersant or the charge transporting substance, and specific examples include the following methods.

A method in which a relatively thin film is applied using a single spray gun, and the application is repeated while changing to dispersions having different concentrations of the materials, and the layers are laminated. A method in which a protective layer is formed by simultaneously applying a plurality of spray guns and a plurality of dispersion liquids having different material concentrations while providing a time difference.

The thickness of the entire protective layer is 1 to 10 μm.
m, preferably 2 to 6 μm. If the film thickness is extremely thin, the uniformity of the film may be reduced, or sufficient abrasion resistance may not be obtained. Or a decrease in light transmittance may cause a decrease in resolution or dot reproducibility.

In the photoreceptor of the present invention, an undercoat layer can be provided between the conductive support 31 and the photosensitive layer.
The undercoat layer generally contains a resin as a main component. However, considering that these resins are coated on the photosensitive layer with a solvent,
It is desirable that the resin has high solvent resistance to general organic solvents. Examples of such a resin include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, copolymer-soluble nylons, alcohol-soluble resins such as methoxymethylated nylon, polyurethane, melamine resins, phenol resins, alkyd-melamine resins, and epoxy resins. Curable resins that form a three-dimensional network structure, such as resins, are exemplified. Further, a fine powder pigment of a metal oxide exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the undercoat layer in order to prevent moiré and reduce residual potential. These undercoat layers can be formed using an appropriate solvent and a coating method as in the above-described photosensitive layer. Further, as an undercoat layer of the present invention, a silane coupling agent, a titanium coupling agent,
A chromium coupling agent can also be used. Further, various dispersants can be added. In addition,
The undercoat layer according to the present invention may be a layer provided with Al ₂ O ₃ by anodic oxidation, an organic substance such as polyparaxylylene (parylene), or an inorganic substance such as SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO _2. Can be satisfactorily used by a vacuum thin film forming method. In addition, known materials can be used. The thickness of the undercoat layer is suitably from 0 to 5 μm.

In the photosensitive member of the present invention, an intermediate layer may be provided between the photosensitive layer and the protective layer. The intermediate layer generally uses a binder resin as a main component. Examples of these resins include polyamide, alcohol-soluble nylon, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol. As a method for forming the intermediate layer, a coating method generally used as described above is employed. The thickness of the intermediate layer is suitably about 0.05 to 2 μm.

In the present invention, the charge generation layer, the charge transport layer, the undercoat layer, the protective layer, the intermediate layer, etc. are used for the purpose of improving the environmental resistance, especially for the purpose of preventing the sensitivity from lowering and the increase in the residual potential. Conventionally known antioxidants, plasticizers, lubricants,
UV absorbers, low molecular charge transport materials and leveling agents can be added.

Next, the electrophotographic method and the electrophotographic apparatus of the present invention will be described in detail with reference to the drawings. FIG. 4 is a schematic diagram for explaining the electrophotographic process and the electrophotographic apparatus of the present invention, and the following examples also belong to the category of the present invention. In FIG. 4, the photoconductor 1 is provided with at least a photosensitive layer, and the outermost protective layer contains a filler. The photoconductor 1 has a drum shape, but may have a sheet shape or an endless belt shape. Charger 3, pre-transfer charger 7, transfer charger 1
0, separation charger 11, charger 1 before cleaning
For 3, a corotron, a scorotron, a solid state charger (solid state charger), a charging roller, and the like are used, and all known means can be used. These chargers may be in contact with the photoreceptor or not.
It is also possible to superimpose an AC component on a DC component in the charger. As the transfer means, generally, the above-mentioned charger can be used, but as shown in the figure, a combination of a transfer charger and a separation charger is effective.

Light sources such as the image exposure section 5 and the neutralizing lamp 2 include a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, and a light emitting diode (LE).
D), semiconductor lasers (LD), electroluminescence (EL), and other general light-emitting materials can be used. Then, in order to irradiate only light in a desired wavelength range, various filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used. The light source irradiates the photoreceptor with light by providing a transfer step, a charge removal step, a cleaning step, or a pre-exposure step using light irradiation in addition to the steps shown in the figure.

The toner developed on the photoreceptor 1 by the developing unit 6 is transferred to the transfer paper 9, but not all of the toner is transferred, and some toner remains on the photoreceptor 1. Such toner is supplied to the cleaning brush 1
4 and the blade 15 remove the photoconductor. Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

When a positive (negative) charge is applied to the electrophotographic photosensitive member and image exposure is performed, a positive (negative) electrostatic latent image is formed on the surface of the photosensitive member. If this is developed with toner of negative (positive) polarity (electrostatic detection fine particles), a positive image can be obtained, and if it is developed with toner of positive (negative) polarity, a negative image can be obtained. A known method is applied to such a developing unit.
In addition, a known method is used for the charge removing means.

FIG. 5 shows another example of the electrophotographic process according to the present invention. The photoconductor 21 has at least a photosensitive layer, and further contains a filler in a protective layer on the outermost surface,
The charger 23 is driven by the drive rollers 22a and 22b.
, Image exposure by light source 24, development (not shown), transfer using charger 25, pre-cleaning exposure by light source 26, cleaning by brush 27, light source 2
8 is repeatedly performed. In FIG. 5, the photoconductor 21 (of course, the support is translucent in this case) is irradiated with light for pre-cleaning exposure from the support side.

The above-described electrophotographic process is an example of the embodiment of the present invention, and other embodiments are of course possible. For example, in the above example, the pre-cleaning exposure is performed from the support side. However, this may be performed from the photosensitive layer side, or the image exposure and the irradiation of the static elimination light may be performed from the support side. On the other hand, the light irradiating step includes image exposure, pre-cleaning exposure, and static elimination exposure. Irradiation can also be performed.

The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, or may be incorporated in the apparatus in the form of a process cartridge. The process cartridge includes a photoreceptor, and further includes a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit.
Devices (parts). Although there are many shapes and the like of the process cartridge, a general example is shown in FIG. The photoreceptor 16 is provided on a conductive support,
It has at least a photosensitive layer and contains a filler in the outermost protective layer.

[0084]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited by the examples. All parts shown below are parts by weight. Also,
The ionization potential Ip of the charge transporting substance was measured with a surface analyzer (manufactured by Riken Keiki, AC-1).

Example 1 An undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following compositions were sequentially applied on an aluminum cylinder by dip coating, and dried to about 3.5 μm. , A charge generation layer of about 0.2 μm, and a charge transport layer of about 22 μm.

◎ Coating liquid for undercoat layer ・ Titanium dioxide powder: 400 parts ・ Melamine resin: 65 parts ・ Alkyd resin: 120 parts ・ 2-butanone: 400 parts

Coating solution for charge generation layer Bisazo pigment of the following structural formula (1): 12 parts

Embedded image ・ Polyvinyl butyral: 3 parts ・ 2-butanone: 200 parts ・ Cyclohexanone: 400 parts

◎ Coating solution for charge transport layer ・ Polycarbonate (Z Polyka, manufactured by Teijin Chemicals): 12 parts ・ Charge transport material of the following structural formula (2) (Ip: 5.4e)
V): 8 copies

Embedded image

The above-mentioned charge transporting layer was further coated by spray coating using protective layer coating solutions 1 to 3 having the following composition in order to form a protective layer having a total thickness of about 5 μm. Photoconductor 1 was prepared.

Protective layer coating liquid 1 Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical): 2.5 parts Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, manufactured by BYK Chemie): 0.08 partsPolycarbonate (Z-Polyka, manufactured by Teijin Chemicals): 10 partsTetrahydrofuran: 230 partsCyclohexanone: 70 parts

◎ Coating solution for protective layer 2 ・ Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.): 2.5 parts ・ Unsaturated polycarboxylic acid polymer (acid value: 180 mg KO)
H / g, manufactured by BYK Chemie): 0.05 partsPolycarbonate (Z Polyka, manufactured by Teijin Chemicals): 10 partsTetrahydrofuran: 230 partsCyclohexanone: 70 parts

Protective layer coating liquid 3 Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.): 2.5 parts Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, manufactured by BYK Chemie): 0.01 partPolycarbonate (Z Polyka, manufactured by Teijin Chemicals): 10 partsTetrahydrofuran: 230 partsCyclohexanone: 70 parts

Example 2 An electrophotographic photosensitive member 2 was prepared in the same manner as in Example 1, except that the coating liquids for protective layer 1 to 3 were changed to the following compositions.

Coating solution for protective layer 1 Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.): 2.5 parts Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.08 part ・ Charge transporting substance represented by the above structural formula (2): 4 parts ・ Polycarbonate (Z Polyka, manufactured by Teijin Chemicals): 6 parts ・ Tetrahydrofuran: 230 parts ・ Cyclohexanone : 70 parts

◎ Coating solution for protective layer 2 ・ Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical): 2.5 parts ・ Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.05 part ・ Charge transporting material represented by the above structural formula (2): 4 parts ・ Polycarbonate (Z Polyka, manufactured by Teijin Chemicals): 6 parts ・ Tetrahydrofuran: 230 parts ・ Cyclohexanone : 70 parts

Coating solution for protective layer 3 Alumina (average primary particle size: 0.3 μm, manufactured by Sumitomo Chemical Co., Ltd.): 2.5 parts Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.01 part ・ Charge transporting substance represented by the above structural formula (2): 4 parts ・ Polycarbonate (Z Polyka, manufactured by Teijin Chemicals): 6 parts ・ Tetrahydrofuran: 230 parts ・ Cyclohexanone : 70 parts

Example 3 In Example 2, the protective layer coating liquid 1 was applied immediately after the protective layer coating liquid 1 was applied using three spray coating machines. , And immediately after that, an electrophotographic photoreceptor 3 was prepared in the same manner as in Example 2 except that the protective layer coating solution 3 was applied to form a protective layer of about 6 μm. .

Comparative Example 1 An electrophotographic photosensitive member 4 was prepared in the same manner as in Example 2 except that alumina as a filler was not added to the protective layer coating liquids 1 to 3.

Comparative Example 2 The procedure of Example 2 was repeated except that the unsaturated polycarboxylic acid polymer as a dispersant was not added to the protective layer coating liquids 1 to 3.
An electrophotographic photosensitive member 5 was produced in the same manner as in Example 2.

Comparative Example 3 An electrophotographic photoreceptor was prepared in the same manner as in Example 2 except that the coating was repeated three times by spraying using only the protective layer coating liquid 1 to form a protective layer. No. 6 was produced.

Comparative Example 4 An electrophotographic photoreceptor was prepared in the same manner as in Example 2 except that the coating was repeated three times by spraying using only the protective layer coating liquid 2 to form a protective layer. 7 was produced.

Comparative Example 5 An electrophotographic photoreceptor was prepared in the same manner as in Example 2 except that the coating was repeated three times by spraying using only the protective layer coating liquid 3 to form a protective layer. No. 8 was produced.

Example 4 An electrophotographic photosensitive member was prepared in the same manner as in Example 2 except that the amount of the dispersant contained in the coating liquids for protective layer 1 to 3 was changed as follows. Body 9 was produced. Coating liquid 1: unsaturated polycarboxylic acid polymer (acid value 180
mgKOH / g, manufactured by BYK Chemie): 0.06 parts Coating liquid 2: unsaturated polycarboxylic acid polymer (acid value: 180)
mgKOH / g, manufactured by BYK Chemie): 0.02 parts Coating liquid 3: unsaturated polycarboxylic acid polymer (acid value 180)
mgKOH / g, manufactured by BYK Chemie): 0.02 parts

Example 5 An electrophotographic apparatus was prepared in the same manner as in Example 2 except that the dispersants contained in the protective layer coating liquids 1 to 3 and the amounts of the dispersants were changed as described below. Photoconductor 10 was prepared. Coating liquid 1: unsaturated polycarboxylic acid polymer (acid value 365)
mgKOH / g, manufactured by BYK Chemie): 0.03 parts Coating liquid 2: unsaturated polycarboxylic acid polymer (acid value 365)
mgKOH / g, manufactured by BYK Chemie): 0.02 part Coating liquid 3: unsaturated polycarboxylic acid polymer (acid value 365)
mgKOH / g, manufactured by BYK Chemie): 0.01 part

Example 6 An electrophotography was performed in the same manner as in Example 2 except that the dispersants contained in the coating liquids for protective layers 1 to 3 and the amounts of the dispersants were changed as described below. Photoconductor 11 was produced. Coating liquid 1: acrylic acid / hydroxyethyl methacrylate copolymer (acid value 130 mg KOH / g): 0.10 parts Coating liquid 2: acrylic acid / hydroxyethyl methacrylate copolymer (acid value 130 mg KOH / g): 0.1. 05 parts Coating liquid 3: acrylic acid / hydroxyethyl methacrylate copolymer (acid value 130 mgKOH / g): 0.02 part

Example 7 An electrophotographic photosensitive member 12 was prepared in the same manner as in Example 2 except that the fillers contained in the protective layer coating liquids 1 to 3 were changed as follows. did. Titanium oxide (average primary particle size 0.3 μm, manufactured by Ishihara Sangyo):
2.5 parts

Example 8 An electrophotographic photosensitive member 13 was prepared in the same manner as in Example 2 except that the fillers contained in the protective layer coating liquids 1 to 3 were changed as follows. did. Alumina (average particle size 0.015 μm, manufactured by Aerosil):
2.0 copies

Example 9 An electrophotographic photosensitive member 14 was prepared in the same manner as in Example 1 except that the fillers contained in the protective layer coating liquids 1 to 3 were changed as follows. did. Alumina treated with titanate coupling (processing amount 3%):
3.0 parts

Example 10 The procedure of Example 2 was repeated except that the amounts of the charge transport material and the binder resin contained in the protective layer coating liquids 1 to 3 were changed as follows. Thus, an electrophotographic photoreceptor 15 was produced. Charge transport material of the above structural formula (2): 6.0 parts, polycarbonate: 4.0 parts Charge transport material of the above structural formula (2): 4.0 parts, polycarbonate: 6.0 parts The above structural formula (2) Charge transport material: 1.0 part, polycarbonate: 9.0 parts

Example 11 In Example 10, the charge transport material contained in the protective layer coating liquids 1 to 3 was changed to the charge transport material (I) of the following structural formula (3).
p: 5.3 eV).
In the same manner as in the above, an electrophotographic photosensitive member 16 was produced.

Embedded image

Example 12 In Example 10, the charge transport material contained in the protective layer coating liquids 1 to 3 was changed to the charge transport material (I) of the following structural formula (4).
p: 5.5 eV) except that Example 10 was used.
In the same manner as in the above, an electrophotographic photosensitive member 17 was produced.

Embedded image

Example 13 The procedure of Example 2 was repeated, except that the charge transport material and the binder resin contained in the protective layer coating liquids 1 to 3 were changed to the following materials. Photoconductor 18
Was prepared. -A polymer charge transport material of the following structural formula (5) (Ip:
4 eV): 15 parts

Embedded image

Example 14 An electrophotographic photosensitive member 19 was prepared in the same manner as in Example 2 except that the binder resin contained in the coating liquids for protective layers 1 to 3 was changed as follows. Was prepared.・ Polyarylate resin (U polymer / PET, manufactured by Unitika): 6 parts

Example 15 An electrophotographic photosensitive member 20 was prepared in the same manner as in Example 2 except that the binder resin contained in the protective layer coating liquids 1 to 3 was changed as follows. Was prepared.・ Polycarbonate (C polycarbonate, manufactured by Teijin Chemicals): 6 parts

Example 16 An electrophotographic method was performed in the same manner as in Example 2 except that the coating solution for the charge generation layer, the coating solution for the charge transport layer, and the coating solution for the protective layer were changed to the following. Photoconductor 21 was produced.

Coating solution for charge generation layer Polyvinyl butyral: 5 parts 2-butanone: 400 parts Titanyl phthalocyanine having an XD spectrum shown in FIG. 7: 8 parts

◎ Coating solution for charge transport layer ・ Polycarbonate (Z-Polyka, manufactured by Teijin Chemicals): 12 parts ・ Charge transport material of the above structural formula (3): 8 parts ・ Tetrahydrofuran: 100 parts

Coating solution 1 for protective layer: Zinc oxide (average primary particle size: 0.04 μm, manufactured by Sakai Chemical):
2.5 parts ・ Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.06 partsPolycarbonate (Z Polyka, Teijin Chemicals): 5.8
Parts-Acrylic resin (acid value 80 mg KOH / g): 0.2 parts-Charge transport material of the above structural formula (3): 4.0 parts-Tetrahydrofuran: 250 parts-Cyclohexanone: 50 parts

Coating solution 2 for protective layer: Zinc oxide (average primary particle size 0.04 μm, manufactured by Sakai Chemical):
2.5 parts ・ Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.04 parts ・ Polycarbonate (Z-Polyka, Teijin Chemicals): 5.9
Part: acrylic resin (acid value: 80 mg KOH / g): 0.1 part charge transport material of the above structural formula (3): 4.0 parts tetrahydrofuran: 250 parts cyclohexanone: 50 parts

Coating solution 3 for protective layer: Zinc oxide (average primary particle size 0.04 μm, manufactured by Sakai Chemical):
2.5 parts ・ Unsaturated polycarboxylic acid polymer (acid value 180 mg KO)
H / g, BYK Chemie): 0.02 partsPolycarbonate (Z-Polyka, manufactured by Teijin Chemicals): 8.0
Parts: charge transporting material of the above structural formula (3): 2.0 parts tetrahydrofuran: 250 parts cyclohexanone: 50 parts

The electrophotographic photosensitive members 1 to 5 produced as described above
25 is mounted on an electrophotographic process cartridge (however, there is no pre-cleaning exposure), and the image exposure light source is set to 6
Ricoh imagi using 55nm semiconductor laser
o Using a MF2200 remodeling machine, the measurement of the bright portion potential and the image evaluation were performed, and then the bright portion potential and the image evaluation after continuously printing 20,000 sheets in total were performed. Furthermore, the wear amount was evaluated from the difference in film thickness between the initial stage and after printing 20,000 sheets. The results are shown in Table 1.

[0122]

[Table 1]

From the evaluation results in Table 1, it can be seen that the protective layer formed on the outermost surface of the photoreceptor contains a filler,
Although the amount of abrasion can be reduced, the light area potential increased significantly. However, by adding a dispersant having a carboxyl group in the structure together with the filler to the coating liquid to improve the dispersibility, it was possible to drastically reduce both the light portion potential and the abrasion amount. In particular, when the concentration of the dispersing agent is reduced, the light-area potential increases significantly. Without giving, it became possible to reduce the concentration of the dispersant in the protective layer. Furthermore, even after printing 20,000 sheets, the rise in the bright portion potential was small, and it was confirmed that a high-quality image could be stably obtained over a long period of time. At the same time, by changing the concentration of the charge transporting material so that the concentration is lower in the outermost surface region, the concentration of the charge transporting material in the outermost surface region can be reduced without significantly affecting the bright portion potential. It became possible, and it was confirmed that the amount of wear was further reduced.

Examples 17 to 26 and Comparative Examples 7 and 8 The electrophotographic photosensitive members 1, 2, 6, and 6 produced as described above.
For 7, 9, 10, 14, 15, 16, 19, 20, and 21, an accelerated deterioration test (10 ppm,
(20 hours and 70 hours), and after the completion of the exposure, dark adaptation was performed under the temperature and humidity conditions in the laboratory, and then image evaluation was performed. These electrophotographic photoreceptors were mounted on an electrophotographic process cartridge, and image evaluation was performed using a Ricoh imagegio MF2200 modified machine using a semiconductor laser having an image exposure light source of 655 nm. The results are shown in Table 2. The image quality was classified into four levels by the following symbols from the image samples on which the image evaluation was performed using each photoconductor. ◎: level at which high image quality can be determined, ：: level at which image quality slightly decreased but no problem occurred, Δ: level at which image quality was clearly reduced, ×: level at which image discrimination was difficult

[0125]

[Table 2]

As can be seen from the evaluation results in Table 2, even when the dispersant was added to reduce the light potential and the abrasion loss, the accelerated deterioration test by exposure to ozone showed a decrease in resolution. When the photoreceptor is repeatedly used, the influence of ozone is unavoidable, and unless the influence of ozone exposure is not avoided, high durability and high image quality cannot be said to be compatible. In the present invention, as a result of adopting a configuration in which the concentration of the dispersant contained in the protective layer is reduced in the outermost surface region, the bright portion potential is not significantly affected. Also, the effect of suppressing image quality deterioration was confirmed. Further, the resolution of the charge transporting material is reduced by giving a concentration change to lower the concentration in the outermost surface region, performing a surface treatment on the filler, and using a polymer alloy of polyarylate / polyethylene terephthalate for the binder resin. This makes it possible to enhance the effect of suppressing the image quality, thereby realizing both high durability and high image quality.

[0127]

According to the present invention, a filler is contained in a protective layer of a photoreceptor to enhance the durability of the photoreceptor, thereby improving the dispersibility of the filler, thereby suppressing an increase in residual potential and
Suppress image quality deterioration such as occurrence of image unevenness and deterioration of gradation,
Further, uneven wear and abnormal wear can be suppressed. However, countermeasures against the problem that the resolution is reduced by NOx and ozone which are affected by repeated use of the photoreceptor have been insufficient. However, according to the present invention, by giving a concentration change or a concentration gradient such that the concentration of the dispersant contained in the protective layer becomes lower in the outermost surface region, the residual potential is not greatly affected, and
It became possible to reduce the influence of Ox and ozone. Furthermore, it is known that it is effective to include a charge transport material in the protective layer in order to reduce the residual potential. However, since the charge transport material is easily affected by NOx and ozone, the protective layer is protected. By making the surface of the protective layer lower in the concentration of the charge transporting substance contained in the layer, the influence of NOx and ozone can be reduced without significantly affecting the residual potential. It became possible to control. As described above, various effects on image quality and durability, such as increase in residual potential, occurrence of abnormal images, uneven wear and abnormal wear, and decrease in resolution due to NOx and ozone, etc., in an electrophotographic photosensitive member having a protective layer containing a filler. According to the present invention, these problems have been solved simultaneously, and it has become possible to provide an electrophotographic photoreceptor that achieves both high durability and high image quality.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an electrophotographic photosensitive member according to the present invention.

FIG. 2 is a cross-sectional view illustrating another example of the electrophotographic photosensitive member according to the present invention.

FIG. 3 is a cross-sectional view illustrating still another example of the electrophotographic photosensitive member according to the present invention.

FIG. 4 is a schematic diagram illustrating an electrophotographic process and an electrophotographic apparatus according to the present invention.

FIG. 5 is a schematic view for explaining another example of the electrophotographic process according to the present invention.

FIG. 6 is a schematic diagram for explaining a configuration example of a process cartridge according to the present invention.

FIG. 7 is a view showing an XD spectrum of titanyl phthalocyanine used in Example 16.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor 2 static elimination lamp 3 charging charger 4 eraser 5 image exposure unit 6 developing unit 7 pre-transfer charger 8 registration roller 9 transfer paper 10 transfer charger 11 separation charger 12 separation claw 13 pre-cleaning charger 14 cleaning brush 15 blade 16 photoconductor 17 Charging charger 18 Cleaning brush 19 Image exposure unit 20 Developing roller 21 Photoconductor 22a, 22b Driving roller 23 Charging charger 24 Image exposure source 25 Transfer charger 26 Pre-cleaning exposure 27 Cleaning brass 28 Static elimination light source

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Kurimoto 1-3-6 Nakamagome, Ota-ku, Tokyo Stock inside Ricoh Company (72) Inventor Eritoshi Paper 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh F term (reference) 2H068 AA03 AA04 AA09 AA20 AA21 AA31 AA32 BA12 BA13 BA57 BB05 BB23 BB25 BB27 BB41 BB49 CA33 EA17 FA27 FB07 FB08

Claims (32)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive support and a photosensitive layer containing at least a charge generating substance and a charge transporting substance, wherein a protective layer containing at least a filler and a dispersant is provided on the photosensitive layer. An electrophotographic photoreceptor characterized in that the concentration of a dispersant formed and contained in a protective layer has a concentration change that is lowest in the outermost surface region of the protective layer. 2. The dispersant contained in the protective layer has a concentration gradient in which the concentration of the dispersant decreases continuously from the interface between the protective layer and the photosensitive layer toward the outermost surface of the protective layer. The electrophotographic photosensitive member according to claim 1, wherein: 3. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer has a single-layer structure containing at least a charge generating substance and a charge transporting substance. 4. The electrophotography according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generating layer containing at least a charge generating substance and a charge transporting layer containing a charge transporting substance. Photoconductor. 5. The electron according to claim 1, wherein the dispersant contained in the protective layer is an organic compound containing at least one carboxyl group in the structure. Photoreceptor. 6. The electrophotographic photoreceptor according to claim 5, wherein the dispersant contained in the protective layer is a polycarboxylic acid derivative. 7. The dispersant contained in the protective layer is preferably 10
The electrophotographic photoreceptor according to any one of claims 1 to 6, wherein the electrophotographic photoreceptor is an organic compound having an acid value of from 400 to 400 (mgKOH / g). 8. The method according to claim 1, wherein the amount of the dispersant contained in the protective layer satisfies the following relational expression.
8. The electrophotographic photosensitive member according to any one of 7. 0.1 ≦ (addition amount of dispersant × acid value of dispersant) / (content of filler) ≦ 20 9. The electrophotographic photosensitive member according to claim 1, wherein the filler contained in the protective layer is at least one kind of inorganic pigment. 10. The filler contained in the protective layer,
The electrophotographic photoconductor according to claim 9, wherein the electrophotographic photoconductor is at least one kind of metal oxide. 11. The at least one of the protective layers
The electrophotographic photoreceptor according to claim 9 or 10, wherein the pH of the inorganic pigment or the metal oxide is 5 or more. 12. At least one component contained in the protective layer
The electrophotographic photoreceptor according to any one of claims 9 to 11, wherein the kind of inorganic pigment or metal oxide has a dielectric constant of 5 or more. 13. At least one component contained in the protective layer
The electrophotographic photoreceptor according to any one of claims 9 to 12, wherein at least one kind of inorganic pigment or metal oxide has been subjected to surface treatment with at least one kind of surface treatment agent. 14. The surface-treated inorganic pigment or metal oxide contained in the protective layer, wherein the surface treatment agent is at least a titanate coupling agent, a higher fatty acid or a metal salt of a higher fatty acid. The electrophotographic photosensitive member according to claim 13, wherein 15. The surface treatment amount of the surface-treated inorganic pigment or metal oxide contained in the protective layer is 2 to 30% by weight.
Or the electrophotographic photosensitive member according to 14. 16. The electrophotographic photoreceptor according to claim 1, wherein the average primary particle diameter of the filler contained in the protective layer is 0.01 to 0.5 μm. 17. The electrophotographic photoreceptor according to claim 1, wherein the protective layer contains at least one kind of charge transport material. 18. The method according to claim 17, wherein the following relationship is established between the ionization potential Ip of the charge transport material contained in the protective layer and that of the charge transport material contained in the photosensitive layer. Electrophotographic photoreceptor. Ip of charge transport material contained in protective layer ≦ Ip of charge transport material contained in charge transport layer 19. The charge transport material contained in the protective layer has a concentration change in which the concentration of the charge transport material contained in the protective layer is lowest in the outermost surface region of the protective layer. 19. The electrophotographic photosensitive member according to 17 or 18. 20. A charge transporting substance contained in the protective layer, wherein the charge transporting substance has a concentration gradient that decreases continuously from the interface between the protective layer and the photosensitive layer toward the outermost surface. The electrophotographic photosensitive member according to claim 19, wherein: 21. The electrophotograph according to claim 17, wherein the charge transport material contained in the protective layer contains a polymer charge transport material in whole or in part. Photoconductor. 22. A binder resin contained in the protective layer,
The electrophotographic photoreceptor according to any one of claims 1 to 21, wherein the electrophotographic photoreceptor comprises one of a polycarbonate resin, a polyarylate resin, and a polyester resin, or a mixture of two or more thereof. 23. The electrophotographic photoreceptor according to claim 22, wherein the binder resin contained in the protective layer is a polymer alloy, and at least it is a polymer alloy with polyethylene terephthalate. 24. A binder resin contained in the protective layer,
The electrophotographic photoreceptor according to any one of claims 1 to 23, further comprising a resin having an acid value of 10 to 400 (mgKOH / g). 25. A method for producing an electrophotographic photosensitive member according to claim 1, wherein a spray coating method is used for forming a protective layer. Method. 26. The method for producing an electrophotographic photosensitive member according to claim 25, wherein the protective layer is sequentially laminated by using dispersion liquids having different concentrations of the contained materials to give a change in the concentration to the protective layer. 27. The method according to claim 25, wherein a plurality of dispersion liquids having different concentrations of the contained materials are simultaneously applied using a plurality of spray guns while providing a time lag to change the concentration of the protective layer. A method for producing an electrophotographic photoreceptor. 28. An electrophotographic method using the electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member is repeatedly subjected to at least charging, image exposure, development, and transfer. . 29. The electrophotographic photosensitive member according to claim 1, wherein at least charging, image exposure, development, and transfer are repeatedly performed on the electrophotographic photosensitive member. A digital electrophotographic method, wherein an electrostatic latent image is written on a photoreceptor by using an LD or an LED. 30. An electrophotographic photosensitive member according to claim 1, wherein at least a charging unit, an image exposing unit,
An electrophotographic apparatus comprising a developing unit, a transfer unit, and an electrophotographic photosensitive member. 31. An electrophotographic photosensitive member according to claim 1, wherein at least a charging unit, an image exposing unit,
A digital system comprising a developing unit, a transferring unit and an electrophotographic photosensitive member, wherein an electrostatic latent image is written on the photosensitive member by using an LD or an LED as an image exposing unit. Electrophotographic equipment. 32. A process cartridge for an electrophotographic apparatus, comprising at least the electrophotographic photosensitive member according to any one of claims 1 to 24.