JP2002351115A - Electrophotographic photoreceptor and electrophotographic method, electrophotographic device and process cartridge for electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high durability in which stable high-quality images can be obtained for repeated use. SOLUTION: The electrophotographic photoreceptor has an organic photosensitive layer and a surface layer containing a filler formed on a conductive supporting body. The filler has >=10<10> Ω.cm resistivity. The filler is distributed in the surface layer with such density gradient that the strength of the filler continuously increases from the photoreceptor side to the surface side, or the surface layer is formed into a plurality of layers with the filler density successively increasing from the photosensitive layer side to the surface side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member having high sensitivity, high resolution and high durability. Further, the present invention relates to an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge using a photoconductor provided with a surface layer having a specific configuration.

[0002]

2. Description of the Related Art As an electrophotographic method, a Carlson process and various deformation processes thereof are known, and are widely used in copiers and printers. Among the photoreceptors used in such an electrophotographic method, those using an organic photosensitive material have recently begun to be used because of their advantages such as low cost, mass productivity, and no pollution. Organic electrophotographic photoreceptors include polyvinyl carbazole (PV
K), a photoconductive resin represented by PVK-TNF (2,
(4,7-trinitrofluorenone), a pigment-dispersion type represented by a phthalocyanine-binder, and a function-separated type photoreceptor using a combination of a charge generating material and a charge transporting material. In particular, a function-separated type photoconductor has attracted attention.

[0003] 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 a transparent charge transport layer and is charged by a charge generating substance in the charge generation layer. The absorbed charge-generating substance, which has absorbed light, generates charge carriers, which are injected into the charge-transporting layer, move in the charge-transporting layer in accordance with the electric field generated by the charging, and charge the photoreceptor surface. The latent image is formed by neutralization. In a function-separated type photoreceptor, it is known and useful to use a charge transport material having absorption mainly in the ultraviolet region and a charge generation material having absorption mainly in the visible region.

In recent years, there has been a demand for a photoreceptor having a smaller diameter and a machine and a photoreceptor having higher durability (longer life). As described above, the development of vigorous materials for organic photoreceptors has ensured high sensitivity and high electrostatic durability. However, it is the present ability that the mechanical durability, particularly the wear resistance, is not always sufficient. In view of this point, photoconductors having a function of improving mechanical durability on the surface of an organic photoconductor have been proposed. Most of these studies have examined the type of binder resin used for the outermost layer of the photoreceptor, but have not always been satisfactory.

Another idea is to use a protective layer on the outermost surface of the photoreceptor. The examination of the protective layer as the surface layer of the photoconductor starts with an inorganic photoconductor, and is described in, for example, Japanese Patent Publication No. 2-3171 and Japanese Patent Publication No. 2-7.
No. 058 and Japanese Patent Publication No. 3-43618. When the protective layer was provided on the surface of the inorganic photoreceptor, a filler having a relatively low resistance was favorably used for the protective layer. Therefore, when the photoreceptor is charged, the surface of the photoreceptor is often charged rather than charged on the surface of the protective layer or on the interface between the protective layer and the inorganic photosensitive layer. Indeed, when the latent image is formed not on the surface of the photoconductor but inside the protective layer (including the interface with the inorganic photoconductive layer), there is an advantage that the effect of the shape (scratch etc.) of the surface of the photoconductor is reduced. Was. However, when the surface layer is to have a function as a protective layer, it is necessary to add a large amount of a conductive metal oxide as a filler to be added to the surface layer. In this case, even if the transparency of the surface layer is ensured by the selection of the material, the bulk or the surface resistance of the surface layer is reduced, so that there is a case where a defect such as image blurring appears upon repeated use. In order to solve such a drawback, Japanese Patent Publication No. 2-7057 and Japanese Patent No. 2675035 disclose a method of changing the concentration of a conductive metal oxide in a surface layer in a depth direction from a coating film surface. ing. As a result, image blur and flow are eliminated.

As a method for eliminating image blurring by processing during the process, means for mounting a drum heater for heating a photoreceptor is used. Although the occurrence of image blur can be suppressed by heating the photoconductor,
To mount a drum heater, the diameter of the photoreceptor must be large. It has been difficult. Furthermore, the installation of the drum heater necessitates an increase in the size of the device, which significantly increases power consumption and requires a lot of time to start up the device. Was. On the other hand, a surface layer (protective layer) using a low-resistance filler is laminated on a photoconductor (generally referred to as an OPC) using an organic charge generation material and a charge transport material by applying the above-described technology. When a test of repeated use was performed, image deletion occurred due to poor matching with OPC. In addition, almost the same results were obtained when the method of imparting a concentration distribution to the surface layer of the conductive metal oxide, which was effective for inorganic photoconductors, was used.

Although the details of the above-mentioned causes are unknown, the method disclosed in Japanese Patent No. 2675035 discloses a method in which the direction of the distribution of the filler concentration in the surface layer is opposite to that of the present invention, and the concentration is low toward the surface side. Has become. For this reason, the abrasion resistance of the photoreceptor surface is not so high, and the surface is susceptible to scratches and the like.In repeated use, low-resistance substances generated by the reactive gas generated from the charger and the like are likely to accumulate. It is presumed that it is. Also,
In the case of the method disclosed in Japanese Patent Publication No. 2-7057, although the filler concentration distribution in the surface layer is in the same direction as that of the present invention, the specific resistance of the filler used is small and the filler shows conductivity. It is. Further, the filler concentration on the surface is 40% by weight or more. For this reason, the surface resistance or the bulk resistance in the surface layer is extremely small, and it is presumed that image deletion has occurred in repeated use. In recent electrophotography processes using organic photoreceptors, digital signals have been written as dots on the photoreceptor, and this type of usage has occurred since inorganic photoreceptors were the mainstream of photoreceptors. Is very different. It can be seen that the level of resolution required from the machine side has changed significantly, and this phenomenon (defect) has become significant.

Under such circumstances, it is essential to use a filler having high resistance instead of conductivity for the surface layer of the organic photoreceptor. However, when a filler having a high resistance is used, a problem that the residual potential increases may occur. An increase in the residual potential, which is often seen, leads to a high light-part potential in an electrophotographic apparatus, which causes a decrease in image density and gradation. In order to compensate for this, it is necessary to increase the dark area potential. Connect.

In the prior art, as a method of suppressing a rise in residual potential, a method of using a photoconductive layer as a protective layer (JP-B-44-834, JP-B-43-16198,
JP-B-49-10258) is disclosed. However, since the amount of light reaching the photosensitive layer is reduced due to the absorption of light by the protective layer, there is a problem that the sensitivity of the photosensitive member is reduced, and the effect is small.

On the other hand, by setting the average particle size of the metal or metal oxide contained as a filler to 0.3 μm or less, the protective layer becomes substantially transparent, and a method of suppressing the accumulation of residual potential (Japanese Patent Laid-Open Publication No. No. 57-30846). Although this method has an effect of suppressing the increase in the residual potential, the effect is insufficient, and in fact, it 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 diameter of the filler is 0.3 μm or more, it is possible to obtain transparency by increasing the dispersibility, and even if the average particle diameter is 0.3 μm or less, the filler is considerably aggregated. If this is the case, the transparency of the film will decrease.

In addition, by including a charge transporting material together with a filler in the protective layer, the protective layer has a mechanical strength,
Method for suppressing increase in residual potential (Japanese Patent Laid-Open No. 4-28146)
No. 1) is disclosed. The addition of the charge transport material to the protective layer is effective in improving the charge mobility 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 the resistance due to the presence of the filler or the increase in the charge trapping site. There is a limit to control. Therefore, in reality, the thickness of the protective layer and the content of the filler must be reduced, and the required durability has not been satisfied.

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.
JP-A-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 ( (JP-A-2000-66434) 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 this method has an effect of reducing the residual potential, it tends to cause image blurring, and has a side effect in which the effect on the image is noticeable. 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.

Further, in order to realize high image quality in an electrophotographic photosensitive member containing a filler for high durability, not only the occurrence of the above-described image blur and the increase in residual potential but also the charge It is also important that the charge linearly reaches the surface of the photoreceptor without being hindered by the filler in the protective layer. To that end, the dispersibility of the filler in the protective layer film has a great effect. In the state where the filler is aggregated, when the charge injected from the charge transport layer to the protective layer moves to the surface, the progress is easily hindered by the filler, and as a result, the dots formed by the toner are scattered. The resolution is greatly reduced. Also, in the case where the protective layer is provided, when the writing light is scattered by the filler and the light transmittance is reduced, similarly, the resolution is greatly affected, but the influence on the light transmittance is also affected by the filler. It is closely related to dispersibility. Furthermore,
Filler dispersibility also has a significant effect on abrasion resistance,
The filler undergoes strong agglomeration, and in a state of poor dispersibility, abrasion resistance is greatly reduced. Therefore, in the electrophotographic photoreceptor formed with a protective layer containing a filler for high durability, in order to simultaneously achieve high image quality, in addition to suppressing the occurrence of image blur and rise in residual potential, It is important to enhance the dispersibility of the filler in the protective layer film.

However, no effective means has been found to solve them at the same time, and when a filler is contained in the outermost surface layer of the photoreceptor for high durability, the effects of image blur and increase in the residual potential may be caused. In reality, the problem of high image quality still remains. Furthermore, since it is necessary to mount a drum heater to reduce these effects, high durability of the small-diameter photoreceptor, which requires the most durability, has not been realized. In fact, it is also a major obstacle to reducing power consumption.

An organic photoreceptor has come to surpass an inorganic photoreceptor in light sensitivity, spectral sensitivity range, pollution-free properties, electrostatic durability, and the like. Improving mechanical durability is urgently needed, and its development has been eagerly sought in the design of highly durable machines and processes.

As a full-color image forming apparatus using an electrophotographic system, two systems are generally known. One is a single type or a single drum type, in which one electrophotographic photosensitive member is mounted in an apparatus and four color developing members are mounted. In this method, four colors (cyan, magenta, yellow, and black) are applied to a photosensitive member or a transferred member (directly transferred to output paper or temporarily transferred to an intermediate transfer member, and then transferred to paper). A toner image is formed. In this case, the charging member, the exposure member, the transfer member, the cleaning member, and the fixing member disposed around the photoreceptor can be shared, and the design is smaller and lower cost than the tandem type described later. Is possible.

On the other hand, there is another system called a tandem system or a tandem drum system. In this case, at least a plurality of electrophotographic photosensitive members are mounted in the apparatus. Generally, for one drum,
Each member of charging, exposure, development, and cleaning is arranged one by one to form one electrophotographic element, and a plurality (generally four) of these are mounted. In this method, a single color toner image is formed by one electrophotographic element, and the toner image is sequentially transferred to a transfer target to form a full color image. The first advantage of this method is that high-speed image formation is possible. This is because, as described above, toner images of each color can be produced by parallel processing. For this reason, the image forming processing time is about one-fourth the time required in the single system, and it is possible to cope with four times the high-speed printing. A second advantage is that the durability of each member provided in the electrophotographic element including the photoreceptor can be substantially increased. This is because, in the single system, each of the charging, exposure, and development processes is performed four times with one photosensitive member to form one full-color image, whereas in the tandem system, the above operation is performed once by one unit. This is because it is only performed. However, it also has disadvantages in that the entire apparatus becomes large and the cost becomes high. Regarding the increase in the size of the entire apparatus, measures have been taken by reducing the diameter of the photoreceptor, miniaturizing the members provided around the photoreceptor, and reducing the size of one electrophotographic element. As a result, not only the miniaturization of the apparatus but also the effect of reducing the material cost have been brought about, and the cost reduction of the entire apparatus has progressed somewhat. However, with the downsizing and miniaturization of the apparatus, a new problem has arisen that the durability of each member including the photoreceptor mounted on the electrophotographic element must be increased.

Further, in tandem type image formation, since a plurality of image forming elements must simultaneously form an image, the plurality of image forming elements have almost the same characteristics both initially and after aging (repeated use). It also has a problem that it must have. The most influential in this regard is the electrostatic properties of the photoreceptor in the imaging element. If the characteristics of photoreceptors used for a plurality of image forming elements vary widely, the color balance of the output image changes, and the color reproducibility differs from the original input image, which is fatal to a full-color image forming apparatus. Problems occur.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoreceptor capable of forming a high-quality image which is durable and stable for repeated use. Specifically, to provide a photoreceptor that has high durability, suppresses image deterioration due to a rise in residual potential or occurrence of image blur, and can stably obtain a high-quality image even when used repeatedly for a long time. It is in. Another object of the present invention is to provide a photoreceptor having good color reproducibility even after repeated use in a tandem type image forming apparatus. Another object of the present invention is to eliminate the need for replacement of the photoreceptor by using those photoreceptors, and realize high-speed printing or downsizing of the apparatus due to reduction in the diameter of the photoreceptor. An object of the present invention is to provide an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge capable of stably obtaining a high-quality image.

[0020]

Means for Solving the Problems As described above, the present inventors have conducted further studies based on the results obtained in the past, and as a result, the following has been found. That is, when a surface layer such as a protective layer is provided on the organic photosensitive layer, it is necessary to add a filler for the purpose of imparting abrasion resistance. When a small material (conductive material) is used, an abnormal image such as blurred image or image deletion occurs at the initial or repeated use. Therefore, it is necessary to use a filler having a large specific resistance. However, when a filler having a large specific resistance is used, an abnormal image such as image blur can be avoided, but a new problem occurs in that the residual potential (potential after exposure) increases.

The inorganic photoconductors used in the past include:
It has been used positively with or without a protective layer. On the other hand, charge transport materials used in organic photoreceptors have been developed for both hole transport type and electron transport type.
What has actually reached the practical level is the hole transport type. For this reason, in the function-separated type photoreceptor designed to make the most of the characteristics of the OPC, negative charging occupies most of it. Some single-layer photosensitive layers and reverse-layer photosensitive layers have been developed, but are not the mainstream.

As described above, it is considered that one of the reasons why the protective layer technology developed for the inorganic photoreceptor cannot be spread horizontally to the organic photoreceptor is due to the charging polarity. That is, the charging potential of the inorganic photoconductor and that of the organic photoconductor are almost the same. At this time, in consideration of the discharging efficiency of the charger, the charging efficiency is generally higher in positive charging than in positive charging. It is also known that, when comparing the amount of generated reactive gas and the like during positive charging and negative charging, the amount of negative charging is overwhelmingly larger. It is understood that the phenomenon of image blur is caused at least by a decrease in the surface resistance of the photoconductor, and this reduction in the surface resistance causes the low-resistance substance generated by the reactive gas to adhere to the surface of the photoconductor. It is also known to be the main cause.

In order to improve such a point, a contact-type charging system has been proposed. However, although positive data such as a decrease in the ozone concentration near the charging member is disclosed, the present invention has been disclosed. According to the results measured by the inventors, it has become clear that the amount of the low-resistance substance adhered to the surface of the photoreceptor is almost the same as when a non-contact type charging member is used. This is because although the contact type charging member is used, the voltage applied to the charging member can be reduced, but the distance between the photosensitive member and the discharger is reduced, and the airflow does not flow well, or the contact is low resistance material. This is considered to be caused by directly pressing the photoconductor against the surface of the photoconductor.

In view of the above, when a surface layer is provided to impart abrasion resistance to a negatively charged type photosensitive member, it is essential to use a filler having a large specific resistance, which has been disclosed in the past. It has been found that it is necessary to change the concept of the protective layer used on the inorganic photosensitive member.

As described above, based on the results obtained in the past, further studies have resulted in the following. When the filler concentration in the surface layer (protective layer) is constant, the residual potential depends on the surface layer thickness and is proportional to the square of the film thickness. When the surface layer thickness is constant, the residual potential depends on the filler concentration, and the residual potential increases as the filler concentration increases. When the surface layer thickness is kept constant, the wear resistance depends on the filler concentration, and the wear resistance improves with an increase in the filler concentration. If the wear resistance is too large, image blur is likely to occur.

Therefore, the two points of improving wear resistance and reducing residual potential, and improving wear resistance and suppressing image blur tend to be in a trade-off relationship. Therefore, the present inventors have repeatedly studied in the direction of improving the layer configuration of the surface layer. As a result, (i) a configuration in which the surface layer has a filler concentration gradient (a configuration in which the surface layer is gradually increased from the support side to the surface side). Or (i
i) It has been found that the above two problems can be solved at the same time by making the surface layer a multi-layer structure of two or more layers having different filler concentrations and sequentially increasing in height from the support side to the surface side. An electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge capable of designing a photoreceptor capable of forming a stable high-quality image for use and capable of forming a stable high-quality image at high speed even in repeated use. Thus, the present invention was completed. Further, by using the photoconductor of the above configuration, even in a tandem-type full-color image forming apparatus using a plurality of image forming elements, the change in the electrostatic characteristics of the photoconductor between the plurality of image forming elements and the amount of abrasion can be reduced. It has been found that a tandem-type full-color image forming apparatus with reduced variation and good color reproducibility even after repeated use can be designed.

According to the present invention, the following (1) to (16) are provided. (1) In an electrophotographic photosensitive member having a photosensitive layer containing at least an organic charge generating substance and an organic charge transporting substance and a surface layer on a conductive support, the surface layer has a specific resistance of 10%.
An electrophotographic photoreceptor comprising a filler of ¹⁰ Ω · cm or more and having a concentration gradient in which the concentration of the filler continuously increases from the support side to the surface side.

(2) In an electrophotographic photosensitive member having a photosensitive layer containing at least an organic charge-generating substance and an organic charge-transporting substance on a conductive support and a surface layer, the surface layer is composed of two or more layers. An electrophotographic photoreceptor characterized in that each surface layer contains a filler having a specific resistance of 10 ¹⁰ Ω · cm or more, and the concentration of the filler increases from the support side to the surface side, and gradually increases. .

(3) The filler concentration at the outermost surface of the surface layer is 5 to 40 with respect to all the materials constituting the surface layer.
The electrophotographic photoreceptor according to the above (1) or (2), which is in terms of% by weight.

(4) The electrophotographic photosensitive member according to any one of (1) to (3), wherein the filler contained in the surface layer is an inorganic pigment having a specific resistance of 10 ¹⁰ Ω · cm or more. body.

(5) The inorganic pigment has a specific resistance of 10 ¹⁰ Ω ·
The electrophotographic photoreceptor according to the above (4), wherein the electrophotographic photoreceptor is a metal oxide having a diameter of not less than 1 cm.

(6) The metal oxide is selected from silica, alumina and titanium oxide and has a specific resistance of 10
^The electrophotographic photosensitive member according to the above (5), which has a resistivity of ¹⁰ Ω · cm or more.

(7) The electrophotographic photoreceptor according to any one of the above (1) to (6), wherein the surface layer contains a charge transport material.

(8) In the method for producing a surface layer of a photoreceptor according to any one of the above (1), (3) to (7), two or more kinds of coating liquids having different filler concentrations are used, A method for producing an electrophotographic photoreceptor, characterized by applying the following coating liquid and laminating it before the previously applied coating film is dry to the touch, by applying the liquid in order from the lowest liquid to the next. Method.

(9) In the method for producing a surface layer of a photoreceptor according to any one of the above (2) to (7), two or more kinds of coating liquids having different filler concentrations are used, and a liquid having a low filler concentration is used. A method for producing an electrophotographic photoreceptor, which comprises applying a coating solution in order by spraying, and then applying and laminating the next coating solution after the previously applied coating film has been dried to the touch.

(10) In an electrophotographic method in which at least charging, image exposure, development and transfer are repeatedly performed on the electrophotographic photosensitive member, the electrophotographic photosensitive member may be any one of the above-mentioned (1) to (7). An electrophotographic method characterized by being a photographic photoreceptor.

(11) An electrophotographic apparatus comprising at least a charging means, an image exposing means, a developing means, a transferring means and an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is as described in (1) to (7) above. An electrophotographic apparatus comprising the electrophotographic photosensitive member according to any one of the above.

(12) The electrophotographic apparatus according to the above (11), wherein the charging means has a charging member in contact with or close to the photosensitive member.

(13) The electrophotographic apparatus according to the above (12), wherein the gap between the charging member and the photosensitive member is 200 μm or less.

(14) The charging device as described in any one of (11) to (13) above, wherein the charging means superimposes a DC component on a charging member to impart a charge to the photosensitive member. Electrophotographic equipment.

(15) A full-color electrophotographic apparatus in which a plurality of image forming elements each including at least an electrophotographic photosensitive member, a charging unit, an image exposing unit, a developing unit, and a transfer unit are arranged. A full-color electrophotographic apparatus, which is the electrophotographic photosensitive member according to any one of the above (1) to (7).

(16) A process cartridge for an electrophotographic apparatus comprising at least an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is any one of the above (1) to (7). A process cartridge for an electrophotographic apparatus.

More preferred embodiments of the above-described electrophotographic photosensitive member, electrophotographic method, and electrophotographic apparatus are as follows.

(A) The photosensitive layer of the electrophotographic photosensitive member has a laminated structure of at least a charge generation layer containing an organic charge generation substance and a charge transport layer containing an organic charge transport substance. Further, the organic charge generating substance is an azo pigment or a phthalocyanine pigment. (B) The inorganic pigment or metal oxide contained in the surface layer of the electrophotographic photoreceptor has a pH or more and / or a dielectric constant of 5 or more.
That is all. (C) The inorganic pigment or metal oxide has been subjected to a surface treatment with at least one surface treatment agent. This surface treatment agent is a titanate coupling agent, an aluminum coupling agent, a higher fatty acid, Al ₂ O ₃ , TiO _2
2 , one selected from ZrO _{2 and the} like, or a mixture thereof, or a mixture thereof with a silane coupling agent. In addition, in the surface-treated inorganic pigment or metal oxide, the surface treatment amount is 3 to
30 wt%. (D) The average primary particle diameter of the filler contained in the outermost surface layer of the electrophotographic photosensitive member is 0.01 μm to 0.5 μm. (E) The charge transport material contained in the surface layer of the electrophotographic photoreceptor is a polymer charge transport material. The polymer charge transport material is a polycarbonate containing at least a triarylamine structure in a main chain and / or a side chain. The charge transport material contained in the surface layer is the same as the charge transport material contained in the photosensitive layer or the charge transport layer formed as a lower layer of the surface layer. (F) The binder resin contained in the surface layer of the electrophotographic photosensitive member contains at least one of a polycarbonate resin and a polyarylate resin. (G) In the method for producing an electrophotographic photoreceptor, the number of coating liquids to be used is continuously applied by using a spray head. (H) In the electrophotographic method, a so-called digital electrophotographic method in which an electrostatic latent image is written on a photoreceptor by an LD or an LED at the time of image exposure is employed. (I) In the electrophotographic apparatus, a so-called digital electrophotographic apparatus in which an electrostatic latent image is written on a photoreceptor by using an LD, an LED, or the like as an image exposure unit is employed.

[0045]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an electrophotographic photosensitive member used in the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view illustrating a configuration example of the electrophotographic photoreceptor of the present invention, in which a single-layer photosensitive layer 33 having a charge generation material and a charge transport material as main components is provided on a conductive support 31, Further, a surface layer 39 is provided on the surface of the photosensitive layer. In this case, the surface layer 39 contains a filler, and has a configuration in which the filler concentration is continuously increased (has a concentration gradient) from the support side toward the surface side. The filler used here has a specific resistance of 10 ¹⁰
Ω · cm or more.

FIG. 2 is a cross-sectional view showing another example of the configuration of the electrophotographic photosensitive member of the present invention, in which a charge generating layer 35 mainly composed of a charge generating material and a charge transporting material are provided on a conductive support 31. And a charge transport layer 37 whose main component is a layer, and a surface layer 39 is further provided on the charge transport layer. In this case, the surface layer 39 contains a filler, and has a configuration in which the filler concentration is continuously increased (has a concentration gradient) from the support side toward the surface side. The filler used here has a specific resistance of 10 ¹⁰ Ω · cm or more.

FIG. 3 is a cross-sectional view showing another example of the structure of the electrophotographic photosensitive member of the present invention. A single-layer photosensitive layer mainly composed of a charge generating material and a charge transport material is provided on a conductive support 31. 33
And a plurality of surface layers 39 having different filler concentrations (for example, 39-1, 39-2, 39-) on the surface of the photosensitive layer.
3). In this case, the plurality of surface layers 39 contain a filler having a specific resistance of 10 ¹⁰ Ω · cm or more, and the filler concentration is gradually increased from the support side toward the surface side.

FIG. 4 is a cross-sectional view showing still another example of the structure of the electrophotographic photosensitive member of the present invention, in which a charge generation layer 35 mainly composed of a charge generation material and a charge transport layer are provided on a conductive support 31. It has a configuration in which a charge transport layer 37 mainly composed of a material is laminated, and a plurality of surface layers 39 having different filler concentrations (for example, 39-1 and 39-) are formed on the charge transport layer.
2, a surface layer composed of 39-3). In this case, the plurality of surface layers 39 contain a filler having a specific resistance of 10 ¹⁰ Ω · cm or more, and the filler concentration is gradually increased from the support side toward the surface side.

In the structure shown in FIGS. 1 to 4, two or more fillers may be used as a mixture. In such a case, they may be made of the same material (material) or different materials. When it is not desired to largely change the characteristics as the protective layer bulk, by using the same material, stable characteristics can be obtained. On the other hand, when it is desired to adjust the resistance of the bulk of the protective layer or to control the transmittance in the bulk direction, two or more fillers having different specific resistances may be mixed, or the particle size distribution (average particle size) Two different
You may mix and use more than one kind of filler. In such a case, if a component having a small resistance is contained on the surface side, a side effect may occur in which image blur is likely to occur. For this reason, it is effective to use a high-resistance filler on the surface side and a low-resistance filler on the support (photosensitive layer) side. When a filler having a small particle size is used on the surface side, side effects such as a decrease in wear resistance may occur. Therefore, it is effective to use a filler having a large particle diameter on the surface side and a filler having a small particle diameter on the photosensitive layer side. As described above, adding the gradient of the specific resistance and the gradient of the particle size at the same time as forming the gradient of the filler concentration distribution makes the effect of the present invention more remarkable.

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 made of aluminum, aluminum alloy, nickel, stainless steel, etc., and extruded, drawn, etc., made into a tube, then cut, super finished, polished, etc. And the like can be used. Further, an endless nickel belt and an endless stainless belt disclosed in JP-A-52-36016 can also be used as the conductive support 31.

Of these, a cylindrical support made of aluminum, which can be easily subjected to the anodic oxide film treatment, can be most preferably used. The aluminum referred to here includes both pure aluminum and aluminum alloy. Specifically, JIS1000 series,
Aluminum or aluminum alloys in the 3000s and 6000s are most suitable. The anodized film is obtained by anodizing various metals and various alloys in an electrolyte solution. Among them, a film called alumite obtained by anodizing aluminum or an aluminum alloy in an electrolyte solution is a photoconductor used in the present invention. Is most suitable for In particular, they are excellent in preventing point defects (black spots, background stains) generated when used in reversal development (negative / positive development).

The anodic oxidation treatment includes chromic acid, sulfuric acid, oxalic acid,
The reaction is performed in an acidic bath such as phosphoric acid, boric acid, and sulfamic acid. Of these, treatment with a sulfuric acid bath is most suitable. For example, sulfuric acid concentration: 10 to 20%, bath temperature:
5 to 25 ° C., current density: 1 to 4 A / dm ² , electrolytic voltage:
The processing is performed within a range of 5 to 30 V and a processing time of about 5 to 60 minutes, but is not limited thereto.

Since the anodic oxide film thus produced is porous and has high insulation properties, the surface is very unstable. For this reason, there is a change with time after production,
The physical property value of the anodic oxide film is easily changed. In order to avoid this, it is desirable to further seal the anodic oxide film.

For the sealing treatment, a method of immersing the anodic oxide film in an aqueous solution containing nickel fluoride or nickel acetate,
There are a method of immersing the anodic oxide film in boiling water and a method of treating the film with pressurized steam. Among them, a method of immersing in an aqueous solution containing nickel acetate is most preferable.

After the sealing treatment, a cleaning treatment of the anodic oxide film is performed. The main purpose of this is to remove excess metal salts and the like attached by the sealing treatment. If this remains on the surface of the support (anodic oxide film) excessively,
Not only does this adversely affect the quality of the coating film formed thereon, but also generally causes a low resistance component to remain, which in turn causes the occurrence of background fouling.

The washing may be carried out once with pure water, but usually at another stage. At this time, it is preferable that the final cleaning liquid is as clean (deionized) as possible. In addition, it is desirable to perform physical rubbing cleaning with a contact member in one of the other cleaning steps.

The thickness of the anodic oxide film formed as described above is desirably about 5 to 15 μm. If the thickness is too thin, the barrier effect as an anodic oxide film is not sufficient.If the thickness is too thick, the time constant of the electrode becomes too large, and the generation of residual potential and the response of the photoreceptor decrease. May be.

In addition to the above, a support obtained by dispersing a conductive powder in a suitable binder resin on the above support and applying the same can also be used as the conductive support 31 of the present invention. As the conductive powder, carbon black, acetylene black, aluminum, nickel, iron, nichrome, copper, zinc,
Metal powder such as silver, or metal oxide powder such as conductive tin oxide and ITO can be used. Further, the binder resin used simultaneously, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer,
Styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral Thermoplastic, thermosetting or photo-curable resins such as polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin and alkyd resin. Can be 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, a conductive material is formed on a suitable cylindrical substrate by means of a heat-shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber or fluororesin. Those provided with a conductive layer 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 stacked layer, but for convenience of explanation, the case where the photosensitive layer is composed of the charge generation layer 35 and the charge transport layer 37 will be described first.

The charge generation layer 35 is a layer containing a charge generation substance as a main component. For the charge generation layer 35, known charge generation substances can be used. Representative examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, and quinone condensed polycyclic pigments. Compounds, squaric acid-based dyes, other phthalocyanine-based pigments, naphthalocyanine-based pigments, azurenium salt-based dyes, and the like can be used. These charge generating substances may be used alone or in combination of two or more.

Among them, azo pigments and / or phthalocyanine pigments are effectively used. In particular, an azo pigment represented by the following structural formula (I) and a diffraction peak (± 0.2 °) of titanyl phthalocyanine, particularly CuKα, with a characteristic X-ray (wavelength 1.542 °) at a Bragg angle 2θ of at least 27.2. Titanyl phthalocyanine having the maximum diffraction peak at ゜ can be effectively used.

[0063]

Embedded image In the formula, Cp ₁ and Cp ₂ represent coupler residues, which may be the same or different. R ₂₀₁ and R ₂₀₂ each represent any one of a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, and a cyano group, and may be the same or different. Further, Cp ₁ and Cp ₂ are represented by the following formula (II),

Embedded image In the formula, R ₂₀₃ represents a hydrogen atom, an alkyl group such as a methyl group or an ethyl group, or an aryl group such as a phenyl group. R
₂₀₄ , R ₂₀₅ , R ₂₀₆ , R ₂₀₇ , and R ₂₀₈ each represent a hydrogen atom, a nitro group, a cyano group, a halogen atom such as fluorine, chlorine, bromine, or iodine, or an alkyl group such as a trifluoromethyl group, a methyl group, or an ethyl group. Represents an alkoxy group such as a methoxy group or an ethoxy group, a dialkylamino group, or a hydroxyl group, and Z represents a group of atoms necessary to form a substituted or unsubstituted aromatic carbocyclic ring or a substituted or unsubstituted aromatic heterocyclic ring. Represents

In particular, the asymmetric azo pigment having a structure in which Cp1 and Cp2 are different from each other often has better photosensitivity than a target azo pigment in which Cp1 and Cp2 have the same structure. It can cope with high-speed processes and is used effectively.

The diffraction peak at the Bragg angle 2θ (±
Among titanyl phthalocyanines having a maximum diffraction peak at 27.2 ° as 0.2 °), titanyl phthalocyanines having a peak at 7.3 ° as the lowest angle (JP-A-200
Described in Japanese Patent Application Laid-Open No. 1-18771) is highly sensitive, has a small decrease in chargeability upon repeated use, and can be used particularly effectively.

The charge generation layer 35 is dispersed in a suitable solvent together with a binder resin if necessary by using a ball mill, an attritor, a sand mill, ultrasonic waves, or the like, and the dispersion is applied on a conductive support and dried. It is formed by doing.

The binder resin used for the charge generation layer 35 as necessary includes polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, and the like. 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 solvents used herein 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. As a method of applying the coating liquid, a method such as a dip coating method, a spray coat, a beat coat, a nozzle coat, a spinner coat, and a ring coat 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 transporting layer 37 can be formed by dissolving or dispersing the charge transporting substance and the binder resin in a suitable solvent, applying this on the charge generating layer, and drying. Also,
If necessary, a plasticizer, a leveling agent, an antioxidant and the like can be added.

The charge transport material includes a hole transport material and an electron transport material. Examples of the charge 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, 2,6,8-
Examples thereof include electron accepting substances such as trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, and benzoquinone derivatives.

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 derivative, benzidine derivative, diarylmethane derivative, triarylmethane derivative, 9
And other known materials such as styryl anthracene derivative, pyrazoline derivative, divinylbenzene derivative, hydrazone derivative, indene derivative, butadiene derivative, pyrene derivative, bisstilbene derivative, enamine derivative and the like. 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, polyalate, 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 Thermoplastic or thermosetting resins such as resin, phenolic resin, and alkyd resin 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. Further, the thickness of the charge transport layer is preferably 25 μm or less from the viewpoint of resolution and response. Although the lower limit varies depending on the system used (especially the charged potential, etc.), the lower limit 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 can be mentioned.

In the photoreceptor of the present invention, a plasticizer or a leveling agent may be added to the charge transport layer 37. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount of the plasticizer is 0 to 30 with respect to the binder resin.
A suitable amount is about weight%. Examples of the leveling agent include silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in a side chain. 1% by weight is suitable.

Next, the case where the photosensitive layer has a single-layer structure 33 will be described. A photoconductor in which the above-described charge generating substance is dispersed in a binder resin can be used. The single-layer photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance, and a binder resin in a suitable solvent, and applying and drying the same. Further, this photosensitive layer may be of a function-separated type in which the above-described charge transporting material is added, and can be used favorably. If necessary, a plasticizer, a leveling agent, an antioxidant and the like can be added.

As the binder resin, in addition to using the binder resin described above for the charge transport layer 37 as it is, the charge generation layer 3
The binder resins described in 5 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.
It is preferably 90 parts by weight, more preferably 50 to 150 parts by weight.

The single-layer photosensitive layer comprises a charge-generating substance and a binder resin together with a charge-transporting substance if necessary,
It can be formed by applying a coating liquid dispersed by a disperser or the like using a solvent such as dioxane, dichloroethane, or cyclohexane by a dip coating method, a spray coat, a bead coat, or the like. The thickness of the single-layer photosensitive layer is suitably about 5 to 25 μm.

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, but 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 by using an appropriate solvent and a coating method as in the above-mentioned photosensitive layer. Further, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the undercoat layer of the present invention. In addition, the undercoat layer of the present invention includes Al ₂
O ₃ provided by anodization, organic substances such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , Ti
Those provided with an inorganic substance such as O ₂ , ITO and CeO ₂ by a vacuum thin film forming method can also be used favorably. In addition, known materials can be used. The thickness of the undercoat layer is 0 to 5 μm
Is appropriate.

In the photoreceptor of the present invention, a surface layer 39 is provided on the photosensitive layer for the purpose of protecting the photosensitive layer. The surface layer 39 has a filler concentration from the support side toward the surface side,
It is configured to increase continuously (FIGS. 1 and 2). Alternatively, the surface layer 39 is composed of a plurality of layers having different filler concentrations (FIGS. 3 and 4), and in this case, the filler concentration is sequentially increased from the support side to the surface side. Thereby, it is possible to achieve both improvement of the wear resistance of the surface and reduction of the residual potential.

The filler concentration in the surface layer varies depending on the type of filler used and the electrophotographic process conditions using the photoreceptor. In the outermost layer or the outermost layer, the ratio of the filler to the total solid content is The content is preferably 40% by weight or less, preferably 30% by weight or less, 5% by weight or more, and preferably about 10% by weight or more. In the layer on the side of the most photosensitive layer, the content is preferably 30% by weight or less, preferably about 10% by weight or less. Filler concentration of the outermost surface of the surface layer is 5
If it is less than 10% by weight, abrasion resistance cannot be obtained, and variation in film thickness due to abrasion due to repeated use increases.
On the other hand, when the content is 40% by weight or more, a rise in residual potential due to repeated use becomes large, surface properties become rough, and scattering of writing light becomes large.

The material used for the surface layer 39 is AB
S resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide,
Polyacrylate, polyallyl sulfone, polybutylene, polybutylene terephthalate, polycarbonate,
Polyarylate, polyether sulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS
Resin, butadiene-styrene copolymer, polyurethane,
Resins such as polyvinyl chloride, polyvinylidene chloride, and epoxy resin are exemplified. Among them, polycarbonate or polyarylate can be most preferably used.

Further, a filler material is added to the surface layer of the photoreceptor for the purpose of improving abrasion resistance. Examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, and the like.As the inorganic filler material,
Metal powders such as copper, tin, aluminum, indium,
Inorganic materials such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide, and other metal oxides, and potassium titanate can be used. Particularly, from the viewpoint of the hardness of the filler, it is advantageous to use an inorganic material among them. In particular, silica, titanium oxide, and alumina can be used effectively.

Further, as a filler which is less likely to cause image blur, a filler having a high electric insulating property (a specific resistance of 10 ¹⁰ Ω) is used.
Cm or more), and those having a filler pH of 5 or more and those having a filler dielectric constant of 5 or more 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 may be used alone. It is also possible to use a mixture of two or more kinds of fillers having a dielectric constant of 5 or less and fillers having a dielectric constant of 5 or more. Among these fillers, α-alumina, which has high insulation properties, high thermal stability, and high wear resistance, has a hexagonal close-packed structure, from the viewpoint of suppressing image blur and improving wear resistance Particularly useful.

The specific resistance of the filler used in the present invention is defined as follows. Powders such as fillers
Since the specific resistance value differs depending on the filling rate, it is necessary to measure under a certain condition. In the present invention, the method disclosed in
The specific resistance value of the filler was measured using an apparatus having the same configuration as that of the measuring apparatus disclosed in Japanese Patent No. 94049 (FIG. 1) and Japanese Patent Application Laid-Open No. 5-113688 (FIG. 1), and this value was used. In the measuring device, the electrode area is 4.0 cm ² . Before measurement, apply a load of 4 kg to one electrode for one minute,
The amount of the sample is adjusted so that the distance between the electrodes becomes 4 mm. At the time of the measurement, the measurement is performed under the load state of the weight (1 kg) of the upper electrode, and the applied voltage is measured at 100V. 10 ⁶ Ω
cm or more is HIGH RESISTANCE
METER (Yokogawa Hewlett-Packard), digital multimeter (Fluke)
Was measured by The specific resistance value thus obtained is defined as the specific resistance value according to the present invention.

The pH of the filler, which is one of the constituent elements of the present invention, greatly affects the resolution and the dispersibility of the filler. As one of the reasons, it is considered that hydrochloric acid or the like remains in the filler, particularly the metal oxide during the production. If the remaining amount is large, the occurrence of image blur is inevitable,
It may also affect the dispersibility of the filler, depending on the amount remaining. Another reason is that there is a difference in chargeability on the surface of the filler, especially the metal oxide. Normally, particles dispersed in a liquid are positively or negatively charged, and ions with the opposite charge gather to keep it electrically neutral, where an electric double layer is formed. The dispersion state of the particles is stabilized. As the distance from the particle increases, its potential (zeta potential) gradually decreases, and the potential of a region sufficiently far from the particle and electrically neutral becomes zero. Therefore, the stability is increased by increasing the absolute value of the zeta potential to increase the repulsive force of the particles, and the particles tend to aggregate and become unstable as the value approaches zero. On the other hand, the zeta potential fluctuates greatly depending on the pH value of the system, and at a certain pH value, the potential becomes zero, and has an isoelectric point. Therefore, the dispersion system is stabilized by increasing the absolute value of the zeta potential as far as possible from the isoelectric point of the system.

In the constitution of the present invention, as the filler, those having a pH at the above isoelectric point of at least 5 or more are preferable from the viewpoint of suppressing image blur, and the more basic the filler, the higher the effect. It was confirmed that there was a tendency. The filler having a high pH at the isoelectric point and exhibiting a basic property has a higher zeta potential when the system is acidic, so that the dispersibility and the stability thereof are improved. Here, the pH of the filler in the present invention
Indicates the pH value at the isoelectric point from the zeta potential.
At this time, the zeta potential was measured with a laser zeta potentiometer manufactured by Otsuka Electronics Co., Ltd. The dielectric constant of the filler was measured as follows. After applying a load using the same cell as the measurement of the specific resistance as described above, the capacitance was measured, and the dielectric constant was obtained from the capacitance. The capacitance was measured using a dielectric loss measuring device (manufactured by Ando Electric Co., Ltd.).

Further, these fillers can be surface-treated with at least one kind of surface treatment agent, and it is preferable to do so from the viewpoint of dispersibility of the filler. A decrease in the dispersibility of the filler not only increases the residual potential, but also causes a decrease in the transparency of the coating film, the occurrence of coating film defects, and a decrease in abrasion resistance, which hinders high durability or high image quality. It can evolve into a big problem. As the surface treatment agent, all the surface treatment agents conventionally used can be used, but a surface treatment agent capable of maintaining the insulating property of the filler is preferable. For example, a titanate-based coupling agent, an aluminum-based coupling agent, a zircoaluminate-based coupling agent, a higher fatty acid, or the like, or a mixing treatment of these with a silane coupling agent, Al ₂ O ₃ , Ti
O ₂ , ZrO ₂ , silicone, aluminum stearate, or the like, or a mixture thereof is more preferable from the viewpoint of filler dispersibility and image blur. The treatment with the silane coupling agent has a strong effect on image blur, but the effect of mixing the surface treatment agent and the silane coupling agent may be suppressed in some cases.

The amount of surface treatment varies depending on the average primary particle size of the filler used, but 3 to 30% by weight is suitable, and 5 to 20% by weight is more preferable. If the amount of the surface treatment is smaller than this, the effect of dispersing the filler cannot be obtained, and if the amount is too large, the residual potential is significantly increased. These filler materials are used alone or in combination of two or more. The surface treatment amount of the filler is defined by the weight ratio of the used surface treatment agent to the filler amount as described above.

These filler materials can be dispersed by using an appropriate disperser. The average particle size of the filler is preferably 1 μm or less, more preferably 0.5 μm or less, from the viewpoint of the transmittance of the surface layer. The average particle size of the filler in the present invention is a volume average particle size unless otherwise specified, and is an ultracentrifugal automatic particle size distribution analyzer: CAP
A-700 (manufactured by Horiba, Ltd.).
At this time, the particle size (Medi) corresponding to 50% of the cumulative distribution
an). It is important that the standard deviation of each particle measured at the same time is 1 μm or less. If the value of the standard deviation is larger than this, the particle size distribution may be too wide and the effect of the present invention may not be obtained remarkably.

The thickness of the surface layer is 0.1 mm in total of the plurality of layers.
About 1 to 10 μm is appropriate.

As the method for forming the surface layer of the present invention, a usual coating method is employed. Among them, the spray method is an effective means. A method in which a plurality of surface layer coating liquids having different filler concentrations are sequentially laminated by a spray method before the lower layer is dry to the touch, or a method in which the lower layer is sequentially laminated by the spray method after the dry to the touch. But is most suitable. In this case, it is desirable to prepare spray heads by the number of coating liquids and perform coating continuously.

Further, the surface layer 39 may contain a charge transport material for reducing the residual potential and improving the response. As the charge transport substance, the materials described in the description of the charge transport layer can be used. When a low molecular charge transport material is used as the charge transport material, the concentration in a plurality of surface layers may be changed. It is an effective means to reduce the concentration on the surface side in order to improve abrasion resistance. The concentration referred to here indicates the ratio of the weight of the low-molecular charge transporting substance to the total weight of all the materials constituting the surface layer, and the concentration gradient is such that the concentration decreases on the surface side at the above weight ratio. Indicates that

The charge transport material used for the surface layer is
The charge transport material used in the photosensitive layer or the charge transport layer formed as the lower layer of the surface layer may be the same as the charge transport material used in the low molecular charge transport material or the polymer charge transport material described below. Is preferred. This is because when a photocarrier formed in the photosensitive layer is transported to the surface of the photoreceptor, charges are transferred from the photosensitive layer (charge transport layer) to the surface layer. This is because the smooth transfer of the electric charge is performed without forming the electric field.

For the surface 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 surface layer composed of these polymer charge transport materials has excellent abrasion resistance. As the polymer charge transporting substance, known materials can be used, and particularly, a polycarbonate containing a triarylamine structure in a main chain and / or a side chain is preferably used. Among them,
Polymer charge transport materials represented by the formulas (III) to (XII) are favorably used. These are exemplified below, and specific examples are shown below.

Formula (III)

Embedded image In the formula, R ₁ , R ₂ and R ₃ are each independently a substituted or unsubstituted alkyl group or a halogen atom, R 4 is a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₅ and R 6 are a substituted or unsubstituted An aryl group, o, p, and q are each independently an integer of 0 to 4, k and j each represent a composition, and 0.1 ≦
k ≦ 1, 0 ≦ j ≦ 0.9, and n represents the number of repeating units.
It is an integer of ５5000. X represents an aliphatic divalent group, a cycloaliphatic divalent 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.

Formula (IV)

Embedded image In the formula, R ₇ and R ₈ represent a substituted or unsubstituted aryl group, A
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 (III).

Equation (V)

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 (III).

Formula (VI)

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, p
Represents an integer of 1 to 5. X, k, j and n are (II
I) Same as equation.

Formula (VII)

Embedded imageWhere R₁₃, R₁₄Is a substituted or unsubstituted aryl group,
Ar_Ten, Ar₁₁, Ar ₁₂Are the same or different arylene groups,
X₁, X_TwoIs a substituted or unsubstituted ethylene group, or
Alternatively, it represents an unsubstituted vinylene group. X, k, j and
n is the same as in the case of the formula (III).

Formula (VIII)

Embedded image In the formula, R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are a substituted or unsubstituted aryl group, 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
The same as in the case of the formula (III).

Formula (IX)

Embedded image In the formula, R ₁₉ and R _{20 each} represent a hydrogen atom or a substituted or unsubstituted aryl group, and R ₁₉ and R ₂₀ may form a ring. Ar ₁₇ , Ar ₁₈ and Ar ₁₉ represent the same or different arylene groups. X, k, j and n are the same as in the case of the formula (III).

Formula (X)

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 (III).

Formula (XI)

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 ₂₅ , 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 (III).

Formula (XII)

Embedded imageWhere R₂₆, R₂₇Is a substituted or unsubstituted aryl group,
Ar₂₉, Ar₃₀, Ar ₃₁Represents the same or different arylene groups
Represent. X, k, j and n are the same as in the case of the formula (III)
It is.

The polymer charge transporting material used for the protective layer may be a polymer or an oligomer having an electron donating group when the protective layer is formed. A polymer having a two-dimensional or three-dimensional crosslinked structure is finally included by a curing reaction or a crosslinking reaction performed later.

The protective layer composed of the polymer having an electron donating group or the polymer having a crosslinked structure has excellent abrasion resistance. Normally, in the electrophotographic process, the charged potential (the unexposed portion potential) is constant, so if the surface layer of the photoreceptor is worn by repeated use,
The electric field intensity applied to the photoconductor increases accordingly. As the electric field strength increases, the frequency of occurrence of background contamination increases. Therefore, the high wear resistance of the photoconductor is advantageous for background contamination. The protective layer composed of the polymer having an electron donating group is excellent in film-forming properties because it is a polymer compound itself, and has a higher density of charge transport sites than the protective layer composed of a low molecular weight dispersed polymer. And has an excellent charge transporting ability. Therefore, a high-speed response can be expected for a photoreceptor having a protective layer using a polymer charge transport material.

Examples of other polymers having an electron donating group include copolymers of known monomers, block polymers, graft polymers, star polymers and, for example,
-109406, JP-A-2000-206723
It is also possible to use a crosslinked polymer having an electron donating group as disclosed in JP-A-2001-34001 and JP-A-2001-34001.

In the photoreceptor of the present invention, an intermediate layer can be provided between the photosensitive layer and the protective layer.
Generally, a binder resin is used as a main component. These resins include polyamide, alcohol-soluble nylon,
Water-soluble polyvinyl butyral, polyvinyl butyral,
Polyvinyl alcohol and the like. As a method for forming the intermediate layer, a normal coating method is employed as described above.
The thickness of the intermediate layer is suitably about 0.05 to 2 μm.

In the present invention, antioxidants, plasticizers, lubricants, ultraviolet absorbers, low molecular weight compounds are added to each layer for the purpose of improving environmental resistance, especially for preventing a decrease in sensitivity and an increase in residual potential. Charge transport materials and leveling agents can be added. Representative materials of these compounds are described below.

Examples of the antioxidant that can be added to each layer include, but are not limited to, the following.

(A) Phenol compound 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n- Octadecyl-3- (4'-hydroxy-3 ', 5'-di-t-butylphenol),
2,2'-methylene-bis- (4-methyl-6-t-butylphenol), 2,2'-methylene-bis- (4-
Ethyl-6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-t-butylphenol),
4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3-tris- (2-methyl-4-hydroxy-5-tert-butylphenyl) butane,
1,3,5-trimethyl-2,4,6-tris (3,5
-Di-t-butyl-4-hydroxybenzyl) benzene, tetrakis- [methylene-3- (3 ', 5'-di-
t-butyl-4'-hydroxyphenyl) propione-
G] methane, bis [3,3'-bis (4'-hydroxy-3'-t-butylphenyl) butyric acid] cricol ester, tocopherols and the like.

(B) Paraphenylenediamines N-phenyl-N'-isopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl- p-
Phenylenediamine, N, N'-di-isopropyl-p
-Phenylenediamine, N, N'-dimethyl-N, N '
-Di-t-butyl-p-phenylenediamine and the like.

(C) Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t
-Octyl-5-methylhydroquinone, 2- (2-octadecenyl) -5-methylhydroquinone and the like.

(D) Organic sulfur compounds Dilauryl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, ditetradecyl-3,3'-thiodipropionate and the like.

(E) Organic phosphorus compounds Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

Examples of the plasticizer that can be added to each layer include, but are not limited to, the following.

(A) Phosphate ester plasticizers Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichloroethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, tri-2 phosphate -Ethylhexyl, triphenyl phosphate and the like.

(B) Phthalate ester plasticizers Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-phthalate Octyl, dinonyl phthalate, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, methyl oleyl phthalate, octyl decyl phthalate, dibutyl fumarate, Dioctyl fumarate and the like.

(C) Aromatic carboxylic acid ester-based plasticizers Trioctyl trimellitate, Tri-n-trimellitic acid
-Octyl, octyl oxybenzoate and the like.

(D) Aliphatic dibasic ester plasticizer dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-adipate
Octyl, n-octyl-n-octyl-n-decyl adipate, diisodecyl adipate, dicapryl adipate, di-2-ethylhexyl azelate, dimethyl sebacate,
Diethyl sebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexyl sebacate, di-2-ethoxyethyl sebacate, dioctyl succinate, diisodecyl succinate, dioctyl tetrahydrophthalate, dihydrotetrahydrophthalate -N-octyl and the like.

(E) Fatty acid ester derivatives butyl oleate, glycerin monooleate, methyl acetyl ricinoleate, pentaerythritol ester, dipentaerythritol hexaester,
Triacetin, tributyrin and the like.

(F) Oxyacid ester plasticizers Methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, acetyl tributyl citrate and the like.

(G) Epoxy plasticizer Epoxidized soybean oil, epoxidized linseed oil, butyl epoxy stearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxy stearate, dioctyl epoxy hexahydrophthalate, epoxy hexahydro Didecyl phthalate and the like.

(H) Dihydric alcohol ester plasticizers Diethylene glycol dibenzoate, triethylene glycol di-2-ethyl butyrate and the like.

(I) Chlorinated plasticizers Chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxy chlorinated fatty acid methyl and the like.

(J) Polyester plasticizer Polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester and the like.

(K) Sulfonic acid derivatives p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfonethylamide, o-toluenesulfonethylamide, toluenesulfone-N-ethylamide, p-toluenesulfon-N-cyclohexyl Amides and the like.

(L) Citric acid derivatives Triethyl citrate, triethyl acetyl citrate, tributyl citrate, tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, n-octyldecyl acetyl citrate and the like.

(M) Others terphenyl, partially hydrogenated terphenyl, camphor, 2
-Nitrodiphenyl, dinonylnaphthalene, methyl abietic acid and the like.

Examples of the lubricant that can be added to each layer include the following, but are not limited thereto.

(A) Hydrocarbon compounds Liquid paraffin, paraffin wax, microwax, low-polymerized polyethylene and the like.

(B) Fatty Acid Compounds Lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and the like.

(C) Fatty acid amide compound Stearyl amide, palmityl amide, olein amide, methylene bis-stearamide, ethylene bis-stearamide and the like.

(D) Ester compounds Lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, polyglycol esters of fatty acids and the like.

(E) Alcohol compounds Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethylene glycol, polyglycerol and the like.

(F) Metal soaps Lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate and the like.

(G) Natural waxes Carnauba wax, candelilla wax, beeswax, whale wax, Ibota wax, montan wax and the like.

(H) Others Silicone compounds, fluorine compounds and the like.

Examples of the ultraviolet absorber which can be added to each layer include the following, but are not limited thereto.

(A) Benzophenone 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ', 4-trihydroxybenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 2,2'- Dihydroxy 4-methoxybenzophenone and the like.

(B) Salicylates Phenyl salicylate, 2,4-di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate and the like.

(C) Benzotriazole type (2′-hydroxyphenyl) benzotriazole,
(2′-hydroxy 5′-methylphenyl) benzotriazole, (2′-hydroxy 5′-methylphenyl)
Benzotriazole, (2′-hydroxy 3′-tert-butyl 5′-methylphenyl) 5-chlorobenzotriazole

(D) Cyanoacrylates Ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate and the like.

(E) Quencher (metal complex salt) Nickel (2,2'thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyl dithiocarbamate, nickel dibutyl dithiocarbamate, cobalt dicyclohexyl dithiophosphate, and the like.

(F) HALS (hindered amine) bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1 -[2- [3-
(3,5-di-t-butyl-4-hydroxyphenyl)
Propionyloxy] ethyl] -4- [3- (3,5-
Di-tert-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpyridine,
8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy-2,
2,6,6-tetramethylpiperidine and the like.

Next, the electrophotographic method and the electrophotographic apparatus of the present invention will be described in detail with reference to the drawings. FIG. 5 is a schematic diagram for explaining the electrophotographic process and the electrophotographic apparatus of the present invention, and the following modified examples also belong to the category of the present invention. In FIG. 5, the photoreceptor 1 is provided with at least a photosensitive layer and a surface layer having a filler concentration gradient or a surface layer composed of a plurality of layers having different filler concentrations on a conductive support. The photoconductor 1 has a drum shape, but may have a sheet shape or an endless belt shape. Known means such as a corotron, a scorotron, a solid state charger (solid state charger), and a charging roller are used for the charging member 3, the pre-transfer charger 7, the transfer charger 10, the separation charger 11, and the pre-cleaning charger 13. Can be The charging member 3 is preferably used in contact with or close to the photoconductor 1.

The contact-type charging member mentioned here is of a type in which the surface of the charging member comes into contact with the surface of the photoreceptor, and includes a charging roller, a charging blade, and a charging brush. Among them, a charging roller and a charging brush are preferably used. In addition, a charging member disposed in close proximity refers to a gap of 200 μm or less between the photosensitive member surface and the charging member surface.
In a non-contact state so as to have close proximity. It is distinguished from known chargers represented by corotron and scorotron based on the distance of the gap. The charging member disposed in the vicinity used in the present invention may have any shape as long as it has a mechanism capable of appropriately controlling the gap with the surface of the photoreceptor. For example, the rotation axis of the photoreceptor and the rotation axis of the charging member may be mechanically fixed so as to have an appropriate gap. Among them, using a charging member in the shape of a charging roller, disposing a gap forming member at both ends of the non-image forming portion of the charging member, bringing only this portion into contact with the photoconductor surface, and disposing the image forming region in a non-contact manner, Alternatively, a photoconductor non-image forming portion both end gap forming member is arranged, and only this portion is brought into contact with the charging member surface,
A method in which the image forming area is arranged in a non-contact manner is a method capable of stably maintaining the gap by a simple method. In particular, Japanese Patent Application Nos. Hei 13-212448 and Hei 13-226432.
The method described in the item can be used successfully. FIG. 9 shows an example of a proximity charging mechanism in which a gap forming member is arranged on the charging member side.
Shown in

When the photosensitive member is charged by the charging member, the photosensitive member is charged by an electric field in which a DC component is superimposed on an AC component on the charging member, so that charging unevenness can be reduced and effective. is there.

As the transfer means, the above-mentioned charger can be generally used, but as shown in FIG.
A combination of the above and the separation charger 11 is effective.

The 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.
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. Such a light source or the like 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 step shown in FIG.

The toner developed on the photoreceptor 1 by the developing unit 6 is transferred to the transfer paper 9, but not all is transferred, and some toner remains on the photoreceptor 1. Such toner is removed from the photoconductor by the fur brush 14 and the blade 15. 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. 6 shows another example of the electrophotographic process according to the present invention. The photoreceptor 21 is provided with at least a photosensitive layer and a surface layer having a filler concentration gradient or a surface layer composed of a plurality of layers having different filler concentrations on a conductive support. Driven by the drive rollers 22a and 22b, charging by the charger 23, image exposure by the light source 24, development (not shown), transfer using the charger 25, pre-cleaning exposure by the light source 26, cleaning by the brush 27, cleaning by the light source 28 Static elimination is performed repeatedly. In FIG. 6, the photoreceptor 21 (of course, in this case, the support is translucent) is irradiated with light for pre-cleaning exposure from the support.

The above illustrated electrophotographic process is an example of the embodiment of the present invention, and other embodiments are of course possible. For example, in FIG. 6, the pre-cleaning exposure is performed from the support side, but this may be performed from the surface 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 irradiation step
Although the image exposure, the pre-cleaning exposure, and the charge removal exposure are illustrated, the photosensitive member may be irradiated with light by providing other pre-transfer exposure, image exposure pre-exposure, and other known light irradiation steps.

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 photoconductor, and further includes a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit.
Devices (parts). There are many shapes and the like of the process cartridge. As a general example, there is a process cartridge shown in FIG. The photoconductor 23 is provided on a conductive support,
At least a photosensitive layer and a surface layer having a filler concentration gradient or a surface layer composed of a plurality of layers having different filler concentrations are provided.

FIG. 10 is a schematic diagram for explaining a tandem-type full-color electrophotographic apparatus of the present invention, and the following modified examples also belong to the category of the present invention.
In FIG. 10, reference numerals 1C, 1M, 1Y, and 1K denote drum-shaped photoconductors.
Rotates in the direction of the arrow in the drawing, and the charging members 2C, 2M, 2Y, 2K, the developing member 4C,
4M, 4Y, 4K, cleaning members 5C, 5M, 5
Y and 5K are arranged. Charging member 2C, 2M, 2
Y and 2K are charging members that constitute a charging device for uniformly charging the surface of the photoconductor. This charging member 2C, 2
M, 2Y, 2K and the developing member 4C, 4M, 4Y, 4K, laser light 3
C, 3M, 3Y, and 3K are irradiated, and the photoconductors 1C, 1M,
An electrostatic latent image is formed on each of 1Y and 1K.
Then, the four image forming elements 6C, 6M, 6Y, and 6K centered on the photosensitive members 1C, 1M, 1Y, and 1K.
Are arranged side by side along a transfer conveyance belt 10 as a transfer material conveyance unit. The transfer conveyance belt 10 includes developing members 4C, 4M, 4
Y, 4K and the cleaning members 5C, 5M, 5Y, 5K are in contact with the photoconductors 1C, 1M, 1Y, and 1K, and the surface (rear surface) that contacts the back side of the transfer conveyance belt 10 on the photoconductor side.
, A transfer brush 11C for applying a transfer bias,
11M, 11Y, and 11K are arranged. Each of the image forming elements 6C, 6M, 6Y, and 6K has a different color of the toner inside the developing device, and applies only the DC component to the black toner image forming charging member 2K according to the present invention. An alternating electric field in which an AC component is superimposed on a DC component is applied to the charging members 2C, 2M, and 2Y, and all other components have the same configuration.

In the color electrophotographic apparatus having the structure shown in FIG. 10, the image forming operation is performed as follows. First, in each of the image forming elements 6C, 6M, 6Y, and 6K,
The charging members 2C, 2M, 2Y, and 2R in which the photoconductors 1C, 1M, 1Y, and 1K rotate in the direction of the arrow (the direction along with the photoconductor).
Charged by K, and then the laser beam 3C, 3
M, 3Y, and 3K form an electrostatic latent image corresponding to the image of each color to be created. Next, the developing members 4C, 4M, 4
The toner image is formed by developing the latent image using Y and 4K.
Developing members 4C, 4M, 4Y, and 4K are developing members that perform development with C (cyan), M (magenta), Y (yellow), and K (black) toners, respectively.
The toner images of the respective colors formed on C, 1M, 1Y, and 1K are superimposed on the transfer paper. The transfer paper 7 is sent out of a tray by a paper feed roller 8, temporarily stopped by a pair of registration rollers 9, and sent to a transfer conveyance belt 10 at the same time as the image formation on the photoconductor. Transfer conveyor belt 10
The transfer paper 7 held above is conveyed, and each photoconductor 1C,
The transfer of the toner image of each color is performed at a contact position (transfer portion) with 1M, 1Y, and 1K. The toner image on the photoconductor is transferred onto the transfer paper 7 by an electric field formed by a transfer bias applied to the transfer brushes 11C, 11M, 11Y, and 11K and a potential difference between the photoconductors 1C, 1M, 1Y, and 1K. You. Then, the recording paper 7 on which the toner images of four colors are superimposed through the four transfer units is conveyed to the fixing device 12, where the toner is fixed, and is discharged to a discharge unit (not shown). In addition, the residual toner remaining on each of the photoconductors 1C, 1M, 1Y, and 1K without being transferred by the transfer unit is removed by cleaning devices 5C, 5M, 5Y, and 5K.
Collected by K.

In the example shown in FIG. 10, the image forming elements are C (cyan) from the upstream side to the downstream side in the transfer paper transport direction.
The colors are arranged in the order of M (magenta), Y (yellow), and K (black), but are not limited to this order, and the color order can be set arbitrarily. When a black-only document is created, image forming elements other than black (6C,
6M, 6Y) can be particularly effectively used in the present invention. Further, although the charging member is in contact with the photoreceptor in FIG. 10, by providing an appropriate gap (about 10 to 200 μm) between the two, the amount of wear of both can be reduced and the charging member Less toner filming and good use.

The image forming means as described above may be fixedly incorporated in a copying machine, a facsimile or a printer, but each electrophotographic element is incorporated in the apparatus in the form of a process cartridge. Is also good. The process cartridge is one device (part) that includes a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a charge removing unit, and the like.

[0162]

The present invention will be described below with reference to examples.
The present invention is not limited by the embodiments. All parts are parts by weight.

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 and dried on an aluminum cylinder, and a 3.5 μm undercoat was applied. An electrophotographic photoreceptor comprising a layer, a 0.2 μm charge generation layer, a 20 μm charge transport layer, and a 5 μm surface layer was formed. In addition, the undercoat layer, the charge generation layer, and the charge transport layer were applied by a dip coating method, and the surface layer was applied by a spray method.

Undercoat layer coating liquid: 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 having the following structure: 12 parts

Embedded image Polyvinyl butyral 2 parts 2-butanone 200 parts Cyclohexanone 400 parts

Coating solution for charge transport layer: A type polycarbonate 10 parts Charge transport material of the following structural formula 8 parts

Embedded image 200 parts of tetrahydrofuran

Surface layer coating liquid 1: C-type polycarbonate 10 parts Charge-transporting substance of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 2: C-type polycarbonate 10 parts Charge transporting material of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 4 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: C-type polycarbonate 10 parts Charge-transporting substance of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle diameter: 0.3 μm) 7 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

The above surface layer coating liquid is the surface layer coating liquid 1,
Using three spray heads in the order of 2, 3, coating was continuously performed by a spray method. In this case, continuous means that the next coating liquid is laminated by a spraying method after the lower layer is coated and before touch drying. In addition, the surface layer coating liquids 1 and 2 were coated by 2 μm each, and the surface layer coating liquid 3 was coated by 1 μm to form a total of 5 μm surface layers.

Example 2 A photoconductor was prepared in the same manner as in Example 1, except that the surface layer coating liquids 1, 2, and 3 in Example 1 were changed to the following compositions.

Surface layer coating liquid 1: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 1 part 400 parts tetrahydrofuran 200 parts 200 parts cyclohexanone

Surface layer coating liquid 2: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 3 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that only the surface layer coating solution 1 was used as the surface layer and a surface layer corresponding to 5 μm was formed.

(Comparative Example 2) A photoconductor was prepared in the same manner as in Example 1, except that only the surface layer coating liquid 3 was used as the surface layer and a surface layer corresponding to 5 μm was formed.

(Comparative Example 3) Filler (alumina fine particles) contained in surface layer coating liquids 1, 2, and 3 in Example 1
A photoconductor was prepared in the same manner as in Example 1, except that was changed to the following. Filler: conductive tin oxide (specific resistance: 5 × 10 ⁵ Ω · c
m, average primary particle size: 0.3 μm)

Comparative Example 4 A photoconductor was prepared in the same manner as in Example 2 except that the surface layer in Example 2 was formed using only the surface layer coating solution 1 and a surface layer corresponding to 5 μm was formed.

Comparative Example 5 A photoconductor was prepared in the same manner as in Example 2 except that the surface layer in Example 2 was formed using only the surface layer coating solution 1 and a surface layer corresponding to 5 μm was formed.

The photosensitive members of Examples 1 and 2 and Comparative Examples 1 to 5 produced as described above were mounted on an electrophotographic process shown in FIG. 5 (however, there was no exposure before cleaning, and the charging member was a scorotron charger). Using a 655 nm semiconductor laser (image writing by a polygon mirror) as an image exposure light source, printing 20,000 sheets continuously,
The images at that time were evaluated at the initial stage and after 20,000 sheets. Further, the abrasion amount of the photoreceptor surface after 20,000 sheets was also measured. The above results are also shown in Table 1.

[0181]

[Table 1]

Example 3 The charging member of the electrophotographic process shown in FIG. 5 used in Example 1 was changed from a scorotron charger to a charging roller, and the charging roller was arranged so as to contact the photosensitive member. The photosensitive member produced in Example 1 was mounted on this apparatus, and the same evaluation as in Example 1 was performed under the following charging conditions. Charging conditions: DC bias: -930 V As a result, the initial image and the image on the 20,000th sheet were both good, but the image after the 20,000th image was very slight based on the contamination of the charging roller (toner filming). An abnormal image (dirt) was observed. However, the ozone odor during continuous printing was much less than in the case of Example 1.

Example 4 An insulating tape having a thickness of 50 μm and a width of 5 mm was attached to both ends of the charging roller used in Example 3, and a spatial gap (50 μm) was formed between the surface of the charging roller and the surface of the photoreceptor. It was arranged so that it might have. The other conditions were evaluated exactly as in Example 3. As a result, the charging roller stains observed in Example 3 were not recognized at all, and both the initial and 20,000th images were good. However, when the halftone image was output after 20,000 sheets, although very slight, image unevenness due to charging unevenness was observed.

(Example 5) Evaluation was made in the same manner as in Example 4 except that the charging conditions were changed as follows. Charging conditions: DC bias: -900 V AC bias: 2.0 kV (peak to pee)
ak), frequency 2 kHz Images at the initial stage and after 20,000 sheets were good. The charging roller stains observed in Example 3 and the halftone image unevenness observed in Example 4 were not observed at all.

Example 6 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 and dried on a nickel belt.
0.3 μm charge generation layer, 22 μm charge transport layer, 3 μm
An electrophotographic photoreceptor having a surface layer of m was formed. In addition,
The undercoat layer, the charge generation layer, and the charge transport layer were applied by a dip coating method, and the surface layer was applied by a spray method.

Undercoat layer coating liquid: titanium dioxide powder 100 parts alcohol-soluble nylon 100 parts methanol 500 parts butanol 300 parts

Coating solution for charge generation layer: 10 parts of bisazo pigment having the following structure

Embedded image Polyvinyl butyral 2 parts 2-butanone 200 parts Cyclohexanone 400 parts

Coating solution for charge transport layer: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 7 parts

Embedded image 200 parts of tetrahydrofuran

Surface layer coating liquid 1: Z-type polycarbonate 10 parts Charge transporting material having the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.3 μm) 1.5 parts Toluene 600 parts

Surface layer coating liquid 2: Z-type polycarbonate 10 parts Charge transporting material of the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.3 μm) 4 parts Toluene 600 parts

Surface layer coating liquid 3: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.3 μm) 7 parts Toluene 600 parts

The surface layer coating solution was prepared as surface layer coating solution 1,
Using three spray heads in the order of 2, 3, coating was continuously performed by a spray method. In this case, “continuous” means that the next coating liquid is laminated by a spraying method after the lower layer is coated and before touch drying. In addition, the surface layer coating liquid 1,
Coatings 2 and 3 were applied in an amount of 1 μm each to form a surface layer having a total thickness of 3 μm.

Example 7 A photoconductor was prepared by the same way as that of Example 6 except that the surface layer coating liquids 1, 2, and 3 in Example 6 were changed to the following compositions. Surface layer coating liquid 1: 7 parts of a polymer charge transport material having the following structural formula (Mw = 135000)

Embedded image Silica fine particles (resistivity: 4 × 10 ¹³ Ω · cm, average primary particle diameter: 0.3 μm) 1 part 400 parts tetrahydrofuran 200 parts cyclohexanone

Surface layer coating liquid 2: 7 parts of a polymer charge transport material having the following structural formula (Mw = 135000)

Embedded image Silica fine particles (specific resistance: 4 × 10 ¹³ Ω · cm, average primary particle diameter: 0.5 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: 7 parts of polymer charge transporting material having the following structural formula (Mw = 135000)

Embedded image Silica fine particles (specific resistance: 4 × 10 ¹³ Ω · cm, average primary particle diameter: 0.3 μm) 3 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Comparative Example 6 A photoconductor was prepared in the same manner as in Example 6, except that only the surface layer coating liquid 1 was used as the surface layer and a surface layer corresponding to 3 μm was formed.

(Comparative Example 7) A photoconductor was prepared in the same manner as in Example 6, except that the surface layer of Example 6 was formed by using only the surface layer coating liquid 3 and forming a surface layer equivalent to 3 µm.

Comparative Example 8 Example 6 was repeated except that the surface layer was not laminated and the charge transport layer was 25 μm.
A photoreceptor was prepared in the same manner as described above.

Comparative Example 9 A photoconductor was prepared in the same manner as in Example 6, except that the filler (titanium oxide fine particles) contained in the surface layer coating liquids 1, 2, and 3 in Example 6 was changed to the following. Was prepared. Filler: conductive titanium oxide (resistivity: 7.1 × 10 ⁷
Ω ・ cm)

Comparative Example 10 A photoconductor was prepared in the same manner as in Example 7, except that the surface layer of Example 7 was formed using only the surface layer coating liquid 1 and a surface layer corresponding to 3 μm was formed.

(Comparative Example 11) A photoconductor was prepared in the same manner as in Example 7 except that the surface layer of Example 7 was formed using only the surface layer coating liquid 1 and a surface layer corresponding to 3 μm was formed.

The photoreceptors of Examples 6 and 7 and Comparative Examples 6 to 10 produced as described above were mounted in the electrophotographic process shown in FIG. 6 (however, there was no exposure before cleaning), and the light source for image exposure was 655 nm. As the LED, 30,000 sheets were continuously printed, and the images at that time were evaluated at the initial stage and after 30,000 sheets. Further, the amount of abrasion on the photoreceptor surface on 30,000 sheets was also measured. The above results are also shown in Table 2.

[0203]

[Table 2]

(Examples 8 and 9) The filler (titanium oxide fine particles) used in Example 6 was subjected to a surface treatment with a titanate coupling agent and Al ₂ O ₃ so that the treatment amount became 20 wt%. Using this filler, Example 6
, Surface layer coating liquids 1, 2, and 3 were prepared. About these, the average particle size in a coating liquid (manufactured by Horiba, Ltd .: CAP
A700) and the sedimentation of the coating solution (the degree of sedimentation of the coating solution particles left in a test tube was visually confirmed). Table 3 shows the results. The values shown in Table 3 are
It is a measurement result of each surface layer coating liquid 3.

[0205]

[Table 3]

(Examples 10 and 11) Using the dispersions prepared in Examples 8 and 9, photoconductors were prepared in the same manner as in Example 6. In addition, only a surface layer was formed on a polyester film as a transmittance measurement sample. Table 4 shows the appearance results, the surface roughness Rz, and the transmittance at 655 nm of the photoreceptor.

[0207]

[Table 4]

(Examples 12 and 13) The photosensitive members produced in Examples 10 and 11 were mounted on the same apparatus as used in the evaluation of Example 6 described above, and image evaluation was performed. As a result, the photoconductors using the dispersions of Examples 8 and 9 had higher resolution than the photoconductors using the dispersion of Example 6.

Example 14 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 and dried on an aluminum cylinder to a thickness of 3.5 μm.
An electrophotographic photoreceptor comprising an undercoat layer, a 0.2 μm charge generation layer, a 21 μm charge transport layer and a 4 μm surface layer was formed.

Undercoat layer coating liquid: titanium dioxide powder 400 parts melamine resin 65 parts alkyd resin 120 parts 2-butanone 400 parts

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

Coating solution for charge transport layer: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 7 parts

Embedded image 80 parts of methylene chloride

Surface layer coating solution 1: 10 parts of polyarylate 8 parts of a charge transport material having the following structural formula

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 2: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 8 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 4 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 8 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 8 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

The surface layer coating solution was prepared as surface layer coating solution 1,
Using three spray heads in the order of 2, 3, coating was continuously performed by a spray method. In this case, “continuous” means that the next coating liquid is laminated by a spraying method after the lower layer is coated and before touch drying. The surface layer coating liquids 1, 2
Is applied by 1.5 μm each, and the surface layer coating liquid 3 is 1 μm
A considerable amount of coating was applied to form a surface layer having a total thickness of 4 μm.

(Comparative Example 12) A photoconductor was prepared in the same manner as in Example 14, except that the surface layer of Example 14 was formed using only the surface layer coating liquid 1 and a surface layer corresponding to 4 µm was formed.

(Comparative Example 13) A photoconductor was prepared in the same manner as in Example 14, except that the surface layer of Example 14 was formed using only the surface layer coating liquid 3 and a surface layer corresponding to 4 µm was formed.

Comparative Example 14 A photoconductor was prepared by the same way as that of Example 14 except that the surface layer was not laminated and the charge transport layer was changed to 25 μm.

The photosensitive members of Example 14 and Comparative Examples 12 to 14 produced as described above were mounted on an electrophotographic process cartridge shown in FIG. 5, and an image exposure light source was set to 780 nm.
As a semiconductor laser (image writing by a polygon mirror), 20,000 sheets were continuously printed, and the images at that time were evaluated at the initial stage and after 20,000 pages. Further, the abrasion amount of the photoreceptor surface on 20,000 sheets was also measured. The above results
Also shown in Table 5.

[0221]

[Table 5]

Example 15 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 and dried on an aluminum cylinder to a thickness of 3.5 μm.
An electrophotographic photoreceptor comprising an undercoat layer, a 0.2 μm charge generation layer, a 20 μm charge transport layer, and a 5 μm surface layer was formed. In addition, the undercoat layer, the charge generation layer, and the charge transport layer were applied by a dip coating method, and the surface layer was applied by a spray method.

Undercoat layer coating liquid: titanium dioxide powder 400 parts melamine resin 65 parts alkyd resin 120 parts 2-butanone 400 parts

Coating solution for charge generation layer: 10 parts of bisazo pigment having the following structure

Embedded image Polyvinyl butyral 2 parts 2-butanone 200 parts Cyclohexanone 400 parts

Coating solution for charge transport layer: A type polycarbonate 10 parts Charge transport material of the following structural formula 8 parts

Embedded image 200 parts of tetrahydrofuran

Surface Layer Coating Solution 1: A-Type Polycarbonate 10 parts Charge transport material of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 2: A type polycarbonate 10 parts Charge transporting material of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 4 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: A-type polycarbonate 10 parts Charge transporting material of the following structural formula 7 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle diameter: 0.3 μm) 7 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

The above surface layer coating liquid was prepared as surface layer coating liquid 1,
Using three spray heads in the order of 2, 3, coating was performed sequentially by the spray method. In this case, the sequential coating means that after the lower layer is coated, when the touch drying is completed, the next coating liquid is laminated by a spray method. The surface layer coating liquids 1 and 2 are 2
The surface layer coating liquid 3 was applied in an amount equivalent to 1 μm to form a surface layer having a total thickness of 5 μm.

Example 16 A photoconductor was prepared by the same way as that of Example 15 except that the surface layer coating liquids 1, 2, and 3 in Example 15 were changed to the following compositions.

Surface Layer Coating Solution 1: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 1 part 400 parts tetrahydrofuran 200 parts 200 parts cyclohexanone

Surface layer coating liquid 2: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: 7 parts of a polymer charge transporting material having the following structural formula (Mw = 130,000)

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.3 μm) 3 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Comparative Example 15 A photoconductor was prepared in the same manner as in Example 15 except that the surface layer in Example 15 was formed using only the surface layer coating solution 1 and a surface layer corresponding to 5 μm was formed.

Comparative Example 16 A photoconductor was prepared in the same manner as in Example 15 except that the surface layer of Example 15 was formed using only the surface layer coating liquid 3 and a surface layer corresponding to 5 μm was formed.

Comparative Example 17 A photoconductor was prepared in the same manner as in Example 15 except that the fillers (alumina fine particles) contained in the surface layer coating liquids 1, 2, and 3 in Example 15 were changed to the following. Produced. Filler: conductive tin oxide (specific resistance: 5 × 10 ⁵ Ω · c
m, average primary particle size: 0.3 μm)

(Comparative Example 18) A photoconductor was prepared in the same manner as in Example 16 except that the surface layer in Example 16 was formed using only the surface layer coating solution 1 and a surface layer corresponding to 5 µm was formed.

(Comparative Example 19) A photoconductor was prepared in the same manner as in Example 16 except that the surface layer of Example 16 was used and only a surface layer coating liquid 1 was used to form a surface layer equivalent to 5 µm.

The photosensitive members of Examples 15 and 16 and Comparative Examples 15 to 19 manufactured as described above were mounted on an electrophotographic process shown in FIG. 5 (however, there was no exposure before cleaning, and the charging member was a scorotron charger). Using a 655 nm semiconductor laser (image writing by a polygon mirror) as an image exposure light source, 20,000 sheets were continuously printed, and the images at that time were evaluated at the initial stage and after 20,000 pages. Further, the abrasion amount of the photoreceptor surface after 20,000 sheets was also measured. The above results are also shown in Table 6.

[0240]

[Table 6]

Example 17 FIG. 5 used in Example 15
The charging member for the electrophotographic process shown in (1) was changed from a scorotron charger to a charging roller, and the charging roller was arranged so as to contact the photosensitive member. Example 1
The same evaluation as in Example 15 was carried out under the following charging conditions with the photoconductor prepared in No. 5 mounted. Charging conditions: DC bias: -930 V As a result, both the initial and 20,000 sheets of images were good, but the images after 20,000 sheets were very slight due to charging roller contamination (toner filming). An abnormal image (dirt) was observed. However, the ozone odor during continuous printing was significantly less than that in Example 15.

(Example 18) An insulating tape having a thickness of 50 µm and a width of 5 mm was attached to both ends of the charging roller used in Example 17, and a spatial gap (50 µm) was formed between the surface of the charging roller and the surface of the photoreceptor. It was arranged so that it might have. The other conditions were evaluated exactly as in Example 17. As a result, the charging roller stains observed in Example 17 were not observed at all, and both the initial and 20,000th images were good. However, when the halftone image was output after 20,000 sheets, although very slight, image unevenness due to charging unevenness was observed.

(Embodiment 19) In the evaluation of Embodiment 18, except that the charging conditions were changed as follows.
The same evaluation was performed. Charging conditions: DC bias: -900 V AC bias: 2.0 kV (peak to peak)
k), the images at the initial frequency of 2 kHz and after 20,000 sheets were good. The charging roller stains observed in Example 17 and the halftone image unevenness observed in Example 18 were not observed at all.

Example 20 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 and dried on a nickel belt.
0.3 μm charge generation layer, 22 μm charge transport layer, 3 μm
An electrophotographic photoreceptor having a surface layer of m was formed. In addition,
The undercoat layer, the charge generation layer, and the charge transport layer were applied by a dip coating method, and the surface layer was applied by a spray method.

Undercoat layer coating liquid: titanium dioxide powder 100 parts alcohol-soluble nylon 100 parts methanol 500 parts butanol 300 parts

Coating solution for charge generating layer: 10 parts of bisazo pigment having the following structure

Embedded image Polyvinyl butyral 2 parts 2-butanone 200 parts Cyclohexanone 400 parts

Coating solution for charge transport layer: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 7 parts

Embedded image 200 parts of tetrahydrofuran

Surface layer coating liquid 1: Z-type polycarbonate 10 parts Charge transporting material of the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.4 μm) 1.5 parts Toluene 600 parts

Surface layer coating liquid 2: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.4 μm) 4 parts Toluene 600 parts

Surface layer coating liquid 3: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 6 parts

Embedded image Titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.4 μm) 7 parts Toluene 600 parts

The above-mentioned surface layer coating liquid was prepared as surface layer coating liquid 1,
Using three spray heads in the order of 2, 3, coating was performed sequentially by the spray method. In this case, the sequential coating means that, after the lower layer is coated, when the touch drying is completed, the next coating liquid is laminated by a spray method. The surface layer coating liquids 1, 2,
No. 3 was applied by 1 μm each to form a surface layer having a total thickness of 3 μm.

Example 21 A photoconductor was prepared by the same way as that of Example 20 except that the surface layer coating liquids 1, 2, and 3 in Example 20 were changed to the following compositions. Surface layer coating liquid 1: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Silica fine particles (specific resistance: 4 × 10 ¹³ Ω · cm, average primary particle size: 0.3 μm) 1 part 400 parts tetrahydrofuran 200 parts 200 parts cyclohexanone

Surface layer coating liquid 2: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Silica fine particles (specific resistance: 4 × 10 ¹³ Ω · cm, average primary particle diameter: 0.4 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface layer coating liquid 3: 7 parts of a polymer charge transport material having the following structural formula (Mw = 130,000)

Embedded image Silica fine particles (specific resistance: 4 × 10 ¹³ Ω · cm, average primary particle size: 0.4 μm) 3 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Comparative Example 20 A photoconductor was prepared in the same manner as in Example 20, except that the surface layer in Example 20 was formed using only the surface layer coating solution 1 and a surface layer corresponding to 3 μm was formed.

(Comparative Example 21) A photoconductor was prepared in the same manner as in Example 20, except that the surface layer of Example 20 was formed using a surface layer coating liquid 3 alone and a surface layer corresponding to 3 μm was formed.

Comparative Example 22 A photoconductor was prepared by the same way as that of Example 20 except that the surface layer was not laminated and the charge transport layer was changed to 25 μm.

Comparative Example 23 A photoconductor was prepared in the same manner as in Example 20, except that the filler (titanium oxide fine particles) contained in the surface layer coating liquids 1, 2, and 3 in Example 20 was changed to the following. Was prepared. Filler: conductive titanium oxide (resistivity: 7.1 × 10 ⁷
Ω ・ cm)

Comparative Example 24 A photoconductor was prepared in the same manner as in Example 21 except that the surface layer in Example 21 was formed using a surface layer coating liquid 1 alone and a surface layer corresponding to 3 μm was formed.

(Comparative Example 25) A photoconductor was prepared in the same manner as in Example 21 except that the surface layer in Example 21 was formed using a surface layer coating liquid 1 alone and a surface layer corresponding to 3 μm was formed.

The photosensitive members of Examples 20 and 21 and Comparative Examples 20 to 25 produced as described above were mounted in the electrophotographic process shown in FIG. 6 (however, there was no exposure before cleaning), and the image exposure light source was 655 nm. As the LED, 30,000 sheets were continuously printed, and the images at that time were evaluated at the initial stage and after 30,000 sheets. Further, the amount of abrasion on the photoreceptor surface on 30,000 sheets was also measured. The above results are also shown in Table 7.

[0262]

[Table 7]

(Examples 22 and 23) The filler used in Example 20 was subjected to a surface treatment with a titanate coupling agent and Al ₂ O ₃ so that the treatment amount became 20 wt%. Using this filler, surface layer coating liquids 1, 2, and 3 in Example 20 were prepared. These were evaluated for the average particle size in the coating solution (measured by CAPA700 manufactured by HORIBA, Ltd.) and the sedimentation of the coating solution (the degree of sedimentation of the coating solution particles left in a test tube was visually confirmed). . Table 8 shows the results. The values shown in Table 8 are the measurement results of the respective surface layer coating liquids 3.

[0264]

[Table 8]

(Examples 24 and 25) Using the dispersions prepared in Examples 22 and 23, photoconductors were prepared in the same manner as in Example 20. In addition, only a surface layer was formed on a polyester film as a transmittance measurement sample. Table 9 shows the results of the appearance of the photoconductor, and the surface roughness Rz and the transmittance at 655 nm.
Shown in

[0266]

[Table 9]

(Examples 26 and 27) The photosensitive members manufactured in Examples 24 and 25 were mounted on the same apparatus as used in the evaluation of Example 20 described above, and image evaluation was performed. As a result, the photoconductors using the dispersion of Example 20 were more excellent than those of Examples 24 and 25.
The resolution of the photoreceptor using the dispersion was superior.

Example 28 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 and dried on an aluminum cylinder to a thickness of 3.5 μm.
An electrophotographic photoreceptor comprising an undercoat layer, a 0.2 μm charge generation layer, a 21 μm charge transport layer and a 4 μm surface layer was formed.

Undercoat layer coating liquid: titanium dioxide powder 400 parts melamine resin 65 parts alkyd resin 120 parts 2-butanone 400 parts

Coating solution for charge generation layer: 8 parts of titanyl phthalocyanine having an XD spectrum shown in FIG. 8 8 parts of polyvinyl butyral 400 parts of 2-butanone

Coating solution for charge transport layer: Z-type polycarbonate 10 parts Charge transport material of the following structural formula 7 parts

Embedded image 80 parts of methylene chloride

Surface layer coating liquid 1: 10 parts of polyarylate 8 parts of a charge transport material having the following structural formula

Embedded image Alumina fine particles (resistivity: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm) 2 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface Layer Coating Solution 2: Polyarylate 10 parts Charge transporting material of the following structural formula 8 parts

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm) 4 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

Surface Layer Coating Solution 3: 10 parts of polyarylate 8 parts of a charge transport material having the following structural formula

Embedded image Alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm) 8 parts Tetrahydrofuran 400 parts Cyclohexanone 200 parts

The above-mentioned surface layer coating liquid was prepared as surface layer coating liquid 1,
Using three spray heads in the order of 2, 3, coating was performed sequentially by the spray method. In this case, the sequential coating means that, after the lower layer is coated, when the touch drying is completed, the next coating liquid is laminated by a spray method. In addition, the surface layer coating liquids 1 and 2 were coated by 1.5 μm each, and the surface layer coating liquid 3 was coated by 1 μm to form a total of 4 μm surface layers.

(Comparative Example 26) A photoconductor was prepared in the same manner as in Example 28 except that the surface layer in Example 28 was formed using only the surface layer coating liquid 1 and a surface layer corresponding to 4 μm was formed.

Comparative Example 27 A photoconductor was prepared in the same manner as in Example 28 except that the surface layer in Example 28 was formed using only the surface layer coating solution 3 and a surface layer corresponding to 4 μm was formed.

Comparative Example 28 A photoconductor was prepared by the same way as that of Example 28 except that the surface transport layer was not laminated and the charge transport layer was changed to 25 μm.

The photosensitive members of Example 28 and Comparative Examples 26 to 28 produced as described above were mounted on the cartridge for an electrophotographic process shown in FIG. 5, and an image exposure light source was a 780 nm semiconductor laser (image writing using a polygon mirror). ), 20,000 sheets were continuously printed, and the images at that time were evaluated at the initial stage and after 20,000 sheets. Further, the abrasion amount of the photoreceptor surface on 20,000 sheets was also measured. The above results
The results are shown in Table 10.

[0280]

[Table 10]

(Example 29) In Example 28, the conductive support (JIS 1050) was subjected to the following anodic oxide film treatment, and then the charge generation layer and the charge were formed in the same manner as in Example 28 without providing an undercoat layer. A transport layer and a protective layer were provided to prepare a photoreceptor. [Anodized film treatment] The support surface is mirror-polished, degreased and washed with water, and the liquid temperature is 20 ° C and sulfuric acid is 1%.
It was immersed in a 5 vol% electrolytic bath and subjected to an anodic oxide film treatment at an electrolytic voltage of 15 V for 30 minutes. Further, after water washing, sealing treatment was performed with a 7% nickel acetate aqueous solution (50 ° C.). Thereafter, the substrate was washed with pure water to obtain a support on which an anodized film of 6 μm was formed.

The photoreceptors prepared in Examples 28 and 29 were mounted on the cartridge for the electrophotographic process shown in FIG. 7, and the image exposure light source was continuously set as a 780 nm semiconductor laser (image writing by a polygon mirror). 2
After printing 10,000 sheets, the images at that time were evaluated at the initial stage and after 20,000 sheets. Comparing the two images after 20,000 sheets, there is no problem in actual use, but dirt on the background (black spots)
However, the image of Example 28 was slightly more than the image of Example 29.

(Example 30) The photoreceptor produced in Example 1 was mounted on the electrophotographic apparatus shown in FIG. 10, and all four image forming elements were evaluated for 20,000 full-color images under the following process conditions. Was done. Table 11 shows the results. Charging conditions DC bias: -800 V AC bias: 2.0 kV (peak to peak)
k), frequency 2 kHz-Exposure condition 655 nm semiconductor laser (image writing by polygon mirror)

(Comparative Example 29) An image evaluation test was carried out in the same manner as in Example 30, except that the photoreceptor prepared in Comparative Example 1 was used instead of the photoreceptor used in Example 30. Table 11 shows the results.

(Comparative Example 30) An image evaluation test was performed in the same manner as in Example 30 except that the photoconductor produced in Comparative Example 2 was used instead of the photoconductor used in Example 30. Table 11 shows the results.

[0286]

[Table 11]

[0287]

According to the present invention, side effects (abrasion resistance and residual potential generation, improvement in abrasion resistance and image quality) in a photoconductor in which a filler is added to a surface layer for enhancing the durability of an organic photoconductor. Trade-off relationship such as blurring)
The concentration of the filler in the surface layer is continuously increased from the photosensitive layer side to the surface side by giving a concentration gradient, or the surface layer is composed of a plurality of layers, and the filler concentration is adjusted by the photosensitive layer. By adopting a configuration in which the height is gradually increased from the side toward the surface side, it is possible to achieve both. This provides a photosensitive member that can form a high-quality image that is highly durable and stable for repeated use. Further, an electrophotographic method, an electrophotographic apparatus, and an electrophotographic process cartridge capable of forming a stable high-quality image at high speed even in repeated use are provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a layer configuration of an electrophotographic photosensitive member of the present invention.

FIG. 2 is a diagram illustrating a layer configuration of another electrophotographic photosensitive member of the present invention.

FIG. 3 is a diagram illustrating a layer configuration of another electrophotographic photosensitive member of the present invention.

FIG. 4 is a diagram illustrating a layer configuration of still another electrophotographic photosensitive member of the present invention.

FIG. 5 is a view for explaining the electrophotographic apparatus of the present invention.

FIG. 6 is a view for explaining another electrophotographic apparatus of the present invention.

FIG. 7 is a view for explaining a process cartridge of the present invention.

FIG. 8 is a view showing an X-ray diffraction spectrum of titanyl phthalocyanine used in Examples 14 and 28.

FIG. 9 is a view for explaining an example of a proximity charging mechanism in which a gap forming member is arranged on the charging member side.

FIG. 10 is a diagram illustrating a full-color electrophotographic apparatus according to the present invention.

[Explanation of symbols]

 (In FIGS. 1 to 4) 31 conductive support 33 single-layer photosensitive layer 35 charge generation layer 37 charge transport layer 39 surface layer (in FIG. 9) 29 photosensitive member 30 charging roller 31 gap forming member 32 metal shaft 33 image formation Area 34 Non-image forming area (in FIG. 10) 1 Drum-shaped photoreceptor 2 Charging member 3 Laser beam 4 Developing member 5 Cleaning member 6 Image forming element 7 Transfer paper 8 Feed roller 9 Registration roller 10 Transfer transport belt 11 Transfer brush 12 Fixing device

Continued on the front page (72) Inventor Nozomu Tamoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Satoshi Kurimoto 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Company (72) Inventor Paper Eri 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Company (reference) 2H068 AA04 AA05 AA09 AA10 BA13 CA06 CA29 CA33 EA17 FA27 FB13 FC01 2H200 GA12 GA13 GA14 GA16 GA23 GA24 GA33 GA47 GB02 GB25 HA02 HA12 HA13 HA28 HB03 HB07 HB12 HB14 HB22 HB48 JA02 JB06 JB10 KA07 NA06

Claims (16)

[Claims] 1. An electrophotographic photosensitive member comprising a photosensitive layer containing at least an organic charge generating substance and an organic charge transporting substance and a surface layer on a conductive support, wherein the surface layer has a specific resistance of 10 ¹⁰ Ω · cm. An electrophotographic photoreceptor comprising the above filler and having a concentration gradient in which the concentration of the filler continuously increases from the support side to the surface side. 2. An electrophotographic photoreceptor comprising a photosensitive layer containing at least an organic charge-generating substance and an organic charge-transporting substance and a surface layer on a conductive support.
Composed of a plurality of layers, each having a specific resistance of 1
An electrophotographic photoreceptor comprising a filler of at least 0 ¹⁰ Ω · cm, wherein the concentration of the filler is gradually increased from the support side toward the surface side. 3. The electrophotographic photoreceptor according to claim 1, wherein a filler concentration at an outermost surface of the surface layer is 5 to 40% by weight based on all materials constituting the surface layer. . 4. The electrophotographic photoconductor according to claim 1, wherein the filler contained in the surface layer is an inorganic pigment having a specific resistance of 10 ¹⁰ Ω · cm or more. 5. The method according to claim 1, wherein the inorganic pigment has a specific resistance of 10 ¹⁰ Ω · cm.
The electrophotographic photoreceptor according to claim 4, wherein the electrophotographic photoreceptor is a metal oxide as described above. 6. The method according to claim 1, wherein the metal oxide is silica, alumina,
Selected from titanium oxide and its specific resistance is 10 ¹⁰ Ω
The electrophotographic photoreceptor according to claim 5, characterized in that: cm. 7. The electrophotographic photoreceptor according to claim 1, wherein the surface layer contains a charge transport material. 8. The method for producing a surface layer of a photoreceptor according to claim 1, wherein two or more types of coating liquids having different filler concentrations are used, and the liquids having lower filler concentrations are sprayed in order. A method for producing an electrophotographic photoreceptor, characterized in that the following coating liquid is applied and laminated before the previously applied coating film is dried to the touch. 9. The method for producing a surface layer of a photoreceptor according to claim 2, wherein the filler has different filler concentrations.
Using more than one kind of coating liquid, apply by spraying method from the liquid with the lowest filler concentration. At this time, apply the next coating liquid after the previous coating has finished drying to the touch. A method for producing an electrophotographic photosensitive member, comprising laminating. 10. An electrophotographic photosensitive member comprising:
An electrophotographic method in which image exposure, development, and transfer are repeated, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 7. 11. At least charging means, image exposure means,
An electrophotographic apparatus comprising a developing unit, a transfer unit, and an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is provided.
An electrophotographic apparatus comprising the electrophotographic photosensitive member according to any one of claims 1 to 7. 12. An electrophotographic apparatus according to claim 11, wherein said charging means has a charging member in contact with or close to a photosensitive member. 13. A gap between the charging member and the photoreceptor is 20.
13. The electrophotographic apparatus according to claim 12, wherein the thickness is 0 μm or less. 14. An electrophotographic apparatus according to claim 11, wherein said charging means superimposes a direct current component and an alternating current component on a charging member to charge the photosensitive member. . 15. A full-color electrophotographic apparatus in which a plurality of image forming elements each including at least an electrophotographic photosensitive member, a charging unit, an image exposing unit, a developing unit, and a transfer unit are arranged. Item 8. A full-color electrophotographic apparatus, which is the electrophotographic photosensitive member according to any one of Items 1 to 7. 16. A process cartridge for an electrophotographic apparatus comprising at least an electrophotographic photosensitive member, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to claim 1. A process cartridge for an electrophotographic apparatus.