JPS61169851A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain a durable photosensitive layer which does not break away in long-period repetitive use by positioning end parts of coating layers except the uppermost and lower most layers which are laminated on a conductive base inside of end parts of those uppermost and lowermost layers. CONSTITUTION:A photosensitive body is formed by laminating plural coating layers 2-5 on the conductive base 1 and end parts 3e and 4e of the coating layers 3 and 4 excluding the uppermost layer 5 and lower most layer 2 are positioned inside of end parts 5e and 2e of the uppermost layer 5 and lowermost layer 2. Consequently, the end parts 3e and 4e of the coating layers 3 and 4 sandwiched between the uppermost layer 5 and lowermost layer 2 are covered with the uppermost layer 5, so even when a cleaning blade, etc., come into direct contact in a developing cleaning process, etc., troubles such as a breakaway and a damage are hardly caused. Consequently, the photosensitive body is used stably for a long period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor used in electronic copying machines and the like, and more specifically, to an electrophotographic photoreceptor that is improved so that a photosensitive layer provided on a substrate is difficult to peel off. Regarding photographic photoreceptors.

[Prior art]

Electrophotographic photoreceptors (hereinafter simply referred to as photoreceptors) are typically constructed by disposing thin layers of various photoconductive materials on an electrically conductive substrate. Inorganic materials such as selenium, cadmium sulfide, and amorphous silicon are used as photoconductive materials, but in recent years so-called OPC photoreceptors made of organic materials having photoconductivity have been put into practical use.

Some OPC photoreceptors use a single organic leading material, but a laminated type in which the charge generation function and charge transport function of the photoconductor are divided into separate materials has particularly excellent performance. Because of this, it is widely used in practice.

These types of photoreceptors typically consist of a conductive substrate and a plurality of coating layers overlaid thereon.

The coating layers include a subbing layer that helps the substrate and the photosensitive layer adhere to each other, a charge generation layer that contributes to photosensitization, a charge transport layer, etc., and a protective layer that protects the surface of the photoreceptor, etc., if necessary. Sometimes it happens. The conductive substrate usually has a cylindrical shape, and the plurality of coating layers are coated on the outer periphery of the substrate to form a photoreceptor.

Image formation by electrophotography consists of processes such as charging the entire surface of the photoreceptor, image exposure, toner development using a magnetic brush, etc., transferring the toner image to a transfer material such as paper, and cleaning the photoreceptor surface using a cleaning blade or the like. This is the most common method, and in practical use, these processes are sometimes repeated on the same photoreceptor.

During these processes, especially during the development and cleaning process, the developer rollers, cleaning blades, etc. come into direct contact with the surface of the photoreceptor and cause friction, so if the photoreceptor is used for a long time, the photosensitive layer may peel off from the edges and be damaged. There is.

The peeling of the photosensitive layer is of course related to the adhesion between the overlaid layers, but also has a great influence on the relative position of the edge of the coating layer. For example, JP-A-59-18435
In No. 9, a subbing layer, a charge generation layer, and a charge transport layer are coated on a conductive substrate such that the end of each layer is located on the inner side of the upper layer. A PC photoreceptor is described.

[Problem that the invention seeks to solve]

However, especially in laminated photoreceptors using organic photoconductors, the charge generation layer is generally fragile and easily peels off, and even with the preventive measures described above, it is not possible to completely prevent peeling over a long period of use. It was difficult. The charge generation layer is composed of a pigment and Pi/Da, which are charge generating substances, but because of its performance, the amount of Pi/Da must be reduced, so the formed layer is brittle and easily peeled off.

An object of the present invention is to provide an electrophotographic photoreceptor having a strong photosensitive layer that does not peel off even when used repeatedly over a long period of time.

[Means for solving problems]

As a result of various studies, the present inventors have found that in an electrophotographic photoreceptor having a plurality of coating layers stacked on a conductive substrate, coatings other than the top and bottom layers of the coating layers of the electrophotographic photoreceptor The inventors have discovered that the problem of layer peeling can be solved by locating the ends of the layers inside the ends of the top and bottom layers, leading to the present invention. In this way, the ends of the coating layer or layers sandwiched between the top layer and the bottom layer are covered by the top layer, so it is possible to prevent the layers from peeling off or being damaged from this area. can.

There is also no particular limitation on the relationship between the positions of the ends of the uppermost layer and the lowermost layer, but it is more preferable that the end of the uppermost layer is located inside the photoreceptor than the end of the lowermost layer. When there are a plurality of coating layers between the top layer and the bottom layer, the relative positions thereof are not particularly limited.

FIG. 1 is a sectional view schematically showing the structure of the end portion of the coating layer on the substantially closed side of the photoreceptor of the present invention.

Figures 1A and 1B are examples of photoreceptors with three coated layers;
A first layer 2 as the bottom layer, a second layer 3, and a third layer 4 as the top layer are layered on top.

In Figure 1, the end of the coating layer on the closed end side of the substrate is arranged from the center of the photoreceptor (lower in the figure) to the second layer 3, the third layer 4, and the first layer 2.
The end portion 3e of the second layer 3, which is a coating layer other than the top layer and the bottom layer, is located closest to the center of the conductive substrate. In Fig. 1B, the end 4e of the third layer (top layer) is the first
This is an example in which the end 2e of the layer (lowest layer) is closer to the side edge of the base body, but the end 3e of the second layer is the same as the example in Figure 1 in that the end 3e is closest to the center of the base body 1. .

FIG. 1C shows a fourth coating layer 5 in addition to the three coating layers mentioned above.
In this case, the fourth layer 5 is the uppermost layer, and the second layer 3 and the fourth layer 40 portion 3a are coating layers other than the uppermost layer 5 and the lowermost layer 2.

4e is located closer to the center of the conductive substrate 1 than the end 5e of the top layer and the end 2e of the bottom layer. Although the present invention has been described above in terms of the positional relationship of the ends of the coating layer on the cylindrical conductive substrate in which one side end is substantially closed and the other side end is open, the present invention Needless to say, the present invention is not limited to the present invention, and can also be applied to the positional relationship of the end portions of the coating layer of an endless belt photoreceptor. In other words, in the case of an endless belt photoreceptor, the supporting member and the coating layer must be flexible, so peeling of the coating layer from the edges and cracking become a bigger problem, but this problem has been solved by the present invention. can do.

Further, the structure of the other side end of the conductive substrate, that is, the end of the coating layer on the opening side, is not particularly limited as long as it does not easily cause layer peeling, but preferred examples include the above-mentioned BAIC of the present invention. Examples of the structure of the end portion of the coating layer on the closed side of the substrate include those shown in FIGS. 2A to 2C, or the structure in which the end of the coating layer is located inside the opening of the substrate as shown in FIG. With the structure shown in Figure 2, the edge of the coated layer is not exposed on the outer periphery of the substrate and does not come into contact with the rollers of the transfer material developer, cleaning blade, etc., which may induce peeling of the layer from the edge. There isn't.

The number of coating layers on the photoreceptor of the present invention is not limited to the above example, nor are the compositions, functions, etc. thereof particularly limited, and can be freely set according to the design intention of the photoreceptor. However, as a preferred embodiment, the first layer, the second layer, and the third layer are respectively a subbing layer, a charge generation layer, and a charge transport layer; Each of the four layers is a subbing layer, a charge generation layer, a charge transport layer, a protective layer, or a subbing layer,
Examples include charge transport layers, charge generation layers, and protective layers. In this case, the subbing layer is acrylic, methacrylic acid,
Vinyl chloride, vinyl acetate, epoxy, polyurethane, phenol, polyester, alkyd,
Polycarbonate-based, silicone-based, melamine-based, vinyl chloride/vinyl acetate copolymer, vinyl chloride/vinyl acetate,
It can be formed from various resins such as maleic anhydride copolymers, and the charge generation layer can be formed from azo dyes such as monoazo dyes, disazo dyes, and trisazo dyes, and perylene dyes such as perylenic anhydride and perylenic acid imide. , indigo pigments such as indigo and thioindigo, polycyclic quinos/classes such as anthraquinone, pyrenequinone and flavanmelones, quinacridine pigments, bisbenzimidazole pigments, induthrone pigments, squarelylium pigments, metal phthalocyanines, Various known charge-generating substances, such as phthalocyanine pigments such as metal phthalocyanine, biryllium salt dyes, and eutectic complexes formed from thiapyrylium salt dyes and polycarbonate, are dissolved or dispersed in a solvent together with an appropriate binder, and applied. It can be formed by

In addition, the charge transport layer may be made of electron-accepting substances that easily transport electrons, such as trinitrofluorenone or tetranitrofluorononone, as well as heavy metals having a heterocyclic compound in the side chain, such as BoIJ-N-vinylcarbazole. combination, triazole derivatives, oxadiazole derivatives,
imidazole derivatives, pyrazoline derivatives, polyarylalkali/derivatives, phenine/diamine derivatives, hydrazone derivatives, amino-substituted chalcone derivatives, triarylamine derivatives, carbazole derivatives, stilbene derivatives,
It can be formed by dissolving various known charge transporting substances that easily transport holes, such as phenothiazine derivatives, in a solvent together with a suitable binder, coating, and drying.

Examples of the above-mentioned binders include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, and styrene copolymer resin (for example, styrene-
Butageno copolymer, styrene methyl methacrylate copolymer, acrylonitrile copolymer resin (e.g. vinylidene chloride-acrylonitrile copolymer, etc.), vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer Polymers, silicone resins, silicone-alkyd resins, phenolic resins (e.g. fair -/l/-
Formaldehyde resin, m-cresol-formaldehyde resin, etc.), styrene-alkybuto resin, poly-N-
Film-forming polymers such as vinyl carbazole, polyvinyl butyral, and polyvinyl 7-olmar are preferred.

The shape, material, etc. of the conductive base are not particularly limited, but a cylindrical base made of aluminum or the like is preferably used.

In addition, the protective layer contains polyurethane, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin as the charge transporting substance and a binder.
It can be formed from epoxy resins, phenolic resins, polyester resins, phenolic resins, polyester resins, polycarbonate resins, silicone resins, medimil resins, etc., and copolymer resins containing two or more repeating units of these resins. .

The conductive substrate used in the photoreceptor of the present invention is preferably made of a conductive metal such as aluminum, and the surface thereof is coated with a conductive coating such as metal powder such as aluminum powder, carbon powder, oxidized It may be provided with a coating containing tin powder, titanium oxide powder, or the like. Also preferably used are films, papers, etc., on which metals such as aluminum are vapor-deposited or laminated.

A dipping method is preferably used to apply the plurality of coating layers as described above to the conductive substrate. FIG. 2 is a cross-sectional view showing the coating process by dipping.

A cylindrical substrate n whose upper end is closed and whose lower end is open is submerged in the coating liquid 21 (Fig. 2 A-+B) and gradually pulled up (Fig. 2 C) to coat the outer peripheral surface of the conductive substrate with the coating liquid. Paint layer 21
' is formed and dried. B is a container for the coating liquid, and S is a substrate holder at the tip of the robot arm that holds and moves the substrate. In order to stack a plurality of coating layers, the above-described operation may be repeated by changing the composition of the coating liquid each time.

The upper end of the coating layer obtained by this method is determined by the position a of the liquid level when the substrate is immersed in the deepest position, and can be adjusted by changing the amount of coating liquid 21 in the container n or the immersion position of the substrate B. be.

Therefore, when coating multiple layers, the position of the substrate at the time of coating or the liquid level position a can be adjusted for each layer by changing the liquid volume. Photoreceptors can be easily produced.

In addition, as shown in FIG. 4, a gear pump 42
The coating liquid 43 is fed into the coating liquid tank 44 through the coating liquid tank 44, the conductive substrate 1 fixed in advance in the coating liquid 21 is immersed, and then the liquid level is raised from the coating liquid tank material at a predetermined speed by the gear pump 42. Coating can also be performed by returning the 5&C coating liquid to the coating liquid reservoir 41 as it decreases.

In this case, the position of the end of the coating layer can be adjusted by adjusting the amount of coating liquid fed.

As shown in the figure, the coating liquid slightly penetrates into the lower end of the base due to hydraulic pressure, so that a continuous coating layer is formed from the outer periphery to the inner surface of the inner cylinder. According to the present invention, the end part K as shown in FIG. 2A is formed by wiping the outer periphery of the substrate with a constant width immediately after each coating to remove the coated layer, and the width to be removed is adjusted so that each layer is at a predetermined relative position. You can set it to 5. If no removal is performed, the end portion of the coating layer will be in the state shown in the second diagram, and in either case, a photoreceptor suitable for practical use can be obtained.

The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto.

〔Example〕

A coating solution having the following composition was prepared.

(1) Undercoat layer coating liquid (2) Charge generation layer coating liquid (3) Charge transport layer coating liquid (4) Protective layer coating liquid C Acridic A-851 (manufactured by Inu Nippon Ink Chemical Co., Ltd.) Oy Outer diameter 100 An aluminum substrate with a length of 3,501 m was prepared, and a subbing layer, a charge generation layer, and a charge transport layer were coated in this order from the substrate side using a dipping method to form photoreceptors 1 to 1/I.
64 or four layers of photoreceptor scraps 5 and 6 each having a protective layer layered thereon were prepared. However, the immersion position at the time of coating was adjusted for each sample, and the condition of the end of the coating layer on the closed side of the substrate was determined as shown in Figure 1A for sample layer 1, Figure 1B for sample layer 2, and Figure 1B for sample layer 5. I made it look like Figure C.

Samples /I63, /I64, and No. 6 were prepared as control samples as shown in FIGS. 5A, B, and C in which the conditions of the end portions were not compatible with the present invention. In this example, 1 in the figure is a conductive substrate, 2
3 is a subbing layer, 3 is a charge generation layer, 4 is a charge transport layer, and 5 is a protective layer. The deviation between the edges of each layer is approximately 2
It was set as m.

In each sample, the end of the coating layer on the substrate opening side was also wiped after each coating to give the same structure as the end on the substrate closing side.

In order to evaluate the peeling resistance of the photosensitive layer of each sample, a test was conducted in which cellophane tape was pasted with a cutter in a grid pattern at 1f1 intervals near the edge of the photosensitive layer and then peeled off, and the following results were obtained.

Samples 41, 42, 5: No peeling of the photosensitive layer was observed.

Sample 3, Scrap 6: The surface layer of the charge generation layer was partially peeled off.

Sample 44: There was peeling from the charge generation layer and charge transport layer in the areas where there was no subbing layer, and some peeling also occurred on the inner side.

These results revealed that the photoreceptor according to the present invention was extremely excellent in terms of peeling resistance.

〔Effect of the invention〕

As is clear from the above examples, the electrophotographic photoreceptor according to the present invention has strong resistance to peeling of the photosensitive layer that occurs from the edges of the photosensitive layer, and failures due to peeling of the photosensitive layer do not occur. Therefore, it can be used stably for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electrophotographic photoreceptor according to the present invention. FIG. 2 is a sectional view showing a preferable state of the coating layer on the opening side of the substrate. Figures 3 and 4 are schematic diagrams of dip coating. FIG. 5 is a cross-sectional view of the end of the photosensitive layer of the comparative photoreceptor prepared in Example. 1... Conductive substrate 2... First layer 3... Second layer 4... Third layer 5... Fourth layer Patent applicant Roku Konishi Photo Industry Co., Ltd. Figure 1 8 8 Figure 2 O

Claims (1)

[Claims] In an electrophotographic photoreceptor having a plurality of coating layers stacked on a conductive substrate, the ends of the coating layers other than the uppermost layer and the lowermost layer of the electrophotographic photoreceptor are the uppermost layer. and an electrophotographic photoreceptor, characterized in that it is located inside the end of the bottom layer.