JPS62299857A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To coat a conductive substrate with a coating material and to enhance surface property without treating the surface of the conductive substrate by incorporating a fine silicone resin powder in an undercoat layer. CONSTITUTION:The undercoat layer 3 mixed with the fine silicone resin powder is formed on the conductive substrate 6, and on this layer 3 a photosensitive layer composed of an electric charge generating layer 4 and a charge transfer layer 5 is laminated. The conductive substrate 6 has a laminate structure obtained by laminating an electrically conductive layer 2 on a conductive or nonconductive support 1. As the resin to be used for the undercoat layer 3, polyvinyl alcohol, a phenol resin, and a phenol resin containing a butyral resin are suitable. The layer 3 is obtained by mixing the fine silicone resin powder, preferably, in an amount of 10-20wt% into the resin to be used for the layer 3, and sufficiently dispersed with a sand mill or the like.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor having at least an undercoat layer and a photosensitive layer on a conductive support.

The present invention also relates to an electrophotographic photoreceptor that uses coherent light as incident light during image formation.

[Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium sulfide, and zinc chloride as photoreceptor components have been known.

On the other hand, many organic photoconductors have been developed since it was discovered that certain organic compounds reduce photoconductivity. For example, organic photoconductive P1 polymers such as poly-N-vinylcarbasol and polyvinylanthracene; low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxazoles, hydrazones, and polyarylalkane; and phthalocyanine pigments; Azo pigment, cyanide dye,
Polycyclic quinone pigments, perylene pigments, indigo dyes 1,
Organic pigments and dyes such as thioindigo dyes and squaric butymethine dyes are known.

In particular, organic pigments and dyes 1 that have photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. 1 Organic pigments and dyes have been proposed for conductivity. For example, US Pat. No. 4,123,270, US Pat. No. 4,247,614, US Pat.
315+ Specification, Specification No. 4251614, No. 42
As disclosed in 56821, 4260672, 4268596, 14278747, and 4293628, a charge generation layer and a charge transport layer are separated in function. Electrophotographic photoreceptors using a photoconductive disazo pigment as a charge-generating substance in a photosensitive layer are known.

In addition, photoreceptors for electrophotographic printers that use coherent light, such as a laser, as a light source include selenium, selenium-based alloys, cadmium sulfide resin dispersions, and charge-transfer complexes of polyvinyl carbazole and trinitrofluorenone. I've been exposed to it.

In addition, lasers include helium-cadmium, argon,
Gas lasers such as helium-neon have been used, but recently semiconductor lasers, which are small, low cost, and capable of direct modulation, have come into use.

However, semiconductor lasers have an oscillation wavelength of 750 nm or more.
The photoreceptor shown in -J- had low photosensitivity in that wavelength range and was difficult to use.

Therefore, a laminated type photoreceptor including a charge generation layer and a charge transport layer, which allows a relatively freely selected photosensitive wavelength region, is attracting attention as a photoreceptor for semiconductor laser printers.

The charge generation layer of the laminated photoreceptor has the role of absorbing light and generating free charges, and its thickness is as thin as 0.5 to 5 mm in order to shorten the range of the generated photo carriers. It is customary.

This means that most of the incident light is absorbed by the charge generation layer, generating many photocarriers, and that the generated photocarriers are injected into the charge transport layer without being deactivated by recombination or capture. This is due to the need to do so.

The charge transport layer has the role of receiving static charges and transporting free charges, and is made of a material that hardly absorbs image forming light, and its thickness is usually 5 to 30 mm. It is.

When using such a laminated photoreceptor and producing an image by scanning a line of laser light with a laser printer, there is no problem with line images such as single characters, but with solid images, density unevenness like interference fringes occurs. appeared. The reason for this is that the charge generation layer is formed as a thin layer as mentioned above, which limits the amount of light absorbed by this layer, which causes the light that passes through the charge generation layer to reach the surface of the conductive support. This is thought to be due to interference between the reflected light and the reflected light on the surface of the photosensitive layer.

As shown in FIG. 2, which shows a cross-sectional view of a conventional electrophotographic photoreceptor, the laminated electrophotographic photoreceptor has a charge generation layer 4 and a charge transport layer 5 laminated on a conductive support 6. It is configured.

As shown in FIG. 3, which explains the optical path of light incident on a conventional electrophotographic photoreceptor, a laser beam 7 (oscillation wavelength is approximately 780 nm for a semiconductor laser and approximately 630 nm for a helium-neon laser) is applied to a laminated photoreceptor. When incident light 8 enters the charge transport layer 5 into the photoreceptor, this incident light 8 is reflected by the surface of the conductive support 6, and the conductive light 8 comes out from the surface of the charge transport layer 5. Interference with the reflected light 9 on the support surface occurs.

If the refractive index of the laminated layer of the charge generation layer and the charge transport layer is n, the thickness is d, and the wavelength of the laser beam is λ, then when nd is an integral multiple of /2, the intensity of the reflected light is maximum, i.e. , the intensity of the light entering the charge transport layer is minimal (according to the law of conservation of energy), and when nd is an odd multiple of input/4, the reflected light is minimal, that is, the light entering the layer is maximal. Become.

By the way, thickness unevenness of 0.2 colors or more in d is unavoidable due to manufacturing reasons.

On the other hand, since the laser f-light has good chromaticity and is coherent, the above-mentioned interference conditions change in response to the thickness unevenness of d, causing unevenness in the amount of laser light absorbed in the charge generation layer. It is thought that this appears as interference fringe-like unevenness in shading in the evening image.

Note that in a normal copying machine, since the light source is not monochromatic, the width of the interference fringe-like density unevenness changes depending on the wavelength, and is averaged out and becomes invisible.

Conventionally, in the electrophotographic method using a laser, for example, the reflective surface of the conductive support, the undercoat layer, and the laminated interface of the photosensitive layer are roughened and roughened to create a phase difference in the reflected light. , the occurrence of density unevenness in the form of interference fringes was prevented.

However, in the case of a laminated photoreceptor, such a surface roughening method does not result in a uniform photosensitive layer formed on the uneven surface.
Therefore, image defects and electrophotographic properties are significantly deteriorated.

In order to improve the above-mentioned problems, it has been attempted to coat the conductive support with a paint to improve its surface properties without surface treatment.

- The paint described in (1) has low electrical resistance and does not accumulate residual charge due to its characteristics, (2) has no adverse effect on electrophotographic properties, and (3) has good adhesion to the conductive support. and (4) sufficient solvent resistance for the paint applied thereon.

Conventionally, materials for forming the undercoat layer include polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, ethyl cellulose, methyl cellulose, ethylene acrylic acid copolymer, casein, gelatin,
Polyamide etc. are known.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoreceptor that overcomes the drawbacks of the prior art described above.

That is, an object of the present invention is to provide an electrophotographic photoreceptor in which the surface properties of a conductive support are improved by coating the conductive support with a paint without subjecting the conductive support to surface treatment.

Furthermore, by removing the interference of the image forming light using a simple method,
An object of the present invention is to provide an electrophotographic photoreceptor for a laser printer that prevents the occurrence of uneven density caused by interference.

[Means and effects for solving the problems] The present invention provides an electrophotographic photoreceptor having at least an undercoat layer and a photosensitive layer on a conductive support, wherein the undercoat layer contains fine silicone resin powder. It consists of an electrophotographic photoreceptor.

As shown in FIG. 1, the electrophotographic photoreceptor of the present invention is provided with an undercoat layer 3 containing fine silicone resin powder on a conductive support 6, and a charge generation layer 4 and a charge transport layer on top of the undercoat layer 3. A photosensitive layer consisting of 5 is laminated.

The conductive support 6 has a laminated structure having a conductive layer 2 on the 4-layer of the support 1, and it does not matter whether the support 1 is conductive or non-conductive.If the support 1 is conductive, it is conductive. R2 may not be laminated.

As the conductive support l, for example, an aluminum cylinder,
Examples of the aluminum sheet or non-conductive support 1 include polymer films, polymer cylinders, paper plastics, composite materials such as metals, and the like.

The resin in which the conductive pigment powder and, if necessary, the particles for forming surface irregularities are dispersed must (1) have strong adhesion to the conductive support 6, and (2) have good dispersibility of the powder. (3) It can be used as long as it has sufficient solvent resistance, but in particular, curable rubber, polyurethane, epoxy resin, alkyd resin, polyester, silicone resin, acrylic-melamine resin, etc. Thermosetting resins are preferred. The volume resistivity of the resin in which the conductive powder is dispersed is 1 (H3Ωcm or less, preferably l
9120cm or less is suitable.

Therefore, in the coating film, the conductive powder contains 10 to 6
It is preferable that the content is 0% by weight. For dispersion, conventional methods such as roll mill 1, vibrating ball mill, attritor, sand mill, colloid mill, etc. are used. When the conductive support 6 is in the form of a sheet, coating may be performed by wire barcode coating, blade coating, knife coating, roll coating, or
Screen coating is suitable, and when the conductive support 6 is cylindrical, dip coating is suitable.

Examples of the resin used for the undercoat layer 3 include polyvinyl alcohol, polyvinyl methyl ether, and poly-N-
Examples include vinyl imidazole, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, polyamide, phenolic resin, butyral resin, polyurethane, polyacrylonitrile, etc., especially polyamide, phenolic resin, and phenolic resin with butyral resin added. is suitable.

In the electrophotographic photoreceptor of the present invention, fine silicone resin powder is mixed in the undercoat layer.

The characteristics of silicone resin fine powder are (1) excellent water repellency, (2) excellent lubricity, (3) lower specific gravity than inorganic fine powder, and (4) heat resistance than organic fine powder. and (5) insolubility in organic solvents.

The undercoat layer 3 preferably contains 10 to 20% by weight of the silicone resin fine powder.

As for its compounding method, fine silicone resin powder is mixed into the resin used for the above-mentioned undercoat layer and sufficiently dispersed using, for example, a propeller stirrer or a sand mill.

By mixing and dispersing silicone resin fine powder in the undercoat layer, the laser beam 9 reflected on the surface of the conductive support 6 is
is diffused in the undercoat layer 3 and does not interfere with the incident laser light 7, so that density unevenness due to interference fringes is no longer seen on the image.

The particle size (average particle size) of the silicone resin fine powder used in the present invention is suitably 5#L or less, particularly in the range of 0.1 to 2L. If more than 5 pieces are used, the surface of the undercoat layer will become rough,
A charge generation layer, which will be described later, is provided on the undercoat layer, but the surface of the charge generation layer becomes rough, causing image defects. If it is less than O.ip, the diffusion hardening of the laser light in the undercoat layer will be degraded, so that it may not be possible to prevent density unevenness due to interference fringes.

The thickness of the undercoat layer is suitably in the range of 0.1 to 10 μL, preferably 0.3 to 6 pL.

If it is less than 0.1, the undercoat layer mixed with the silicone resin powder tends to become uneven, and since the charge generation layer provided on the undercoat layer is also thin, it is easy to pick up the unevenness, resulting in image defects. There is no particular problem if the amount is 10 pL or more, which is likely to cause
If it is not added in an amount of more than % by weight, no effect will be obtained, and the cost of the resin used in the undercoat layer and the cost of the silicone resin fine powder will be high, which is not very preferable.

Therefore, in the present invention, the desirable conditions for the undercoat layer 3 are that the film thickness is within the range of 0.1 to 6 JL, the particle size (average particle size) of the mixed silicone resin fine powder is 0.1 to 2 JL, I
When the embossed stitching is 10 to 20% by weight, it is possible to deal with uneven density due to interference fringes and other image defects without roughening the surface of the conductive support as an electrophotographic photoreceptor that uses a laser as a light source for image exposure. became possible.

The charge generation layer 4 provided on the undercoat layer 3 is made of azo pigments such as Sudan Red, Guianpoule, and Jenas Green B, quinone pigments such as Algol Yellow, Pyrene Quinone, Indanthrene Brilliant Violet) RRP, and quinocyanine pigments. , indigo pigments such as perylene pigments, indigo, thioindigo, bisbenzimidazole pigments such as India Fast Orange toner, phthalocyanine pigments such as copper phthalocyanine, aluminum chloride-phthalocyanine, charge generating substances such as quinacridone pigments, polyester, polystyrene, polyvinyl butyral. , polyvinylpyrrolidone, methylcellulose, polyacrylic esters, cellulose esters, or the like is applied and dried. The film thickness is about 0.01 to 1 μl, preferably 0.05 to 0.5 Ji.

The charge transport layer 5 contains a polycyclic aromatic compound such as anthracene, pyrene, phenanthrene, and coronene, or indole, carbazole, oxazole, inoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, and thiadiazole in the main chain or side chain. ,
It is formed by applying a coating liquid in which a compound having a nitrogen-containing ring compound such as a triazole, or a charge transporting substance such as a hydrazone compound is dissolved or dispersed in a resin with film-forming properties, and then drying it. The film thickness is about 5 to 2 degrees.

[Example] Example 1 Conductive titanium oxide powder (manufactured by Titan Kogyo ■) 100 parts (parts by weight, the same applies hereinafter), titanium oxide powder (manufactured by Sakai Kogyo ■) 10
0 parts, 125 parts of phenol resin (trade name: Bleiofen, manufactured by Ingi ■) were mixed with a solvent of 50 parts of methanol and 50 parts of methyl cellosolve, and then mixed in a ball mill with 6
distributed over time. This dispersion liquid is 60φX 260
It was applied by dip coating onto a 20 mm aluminum cylinder and heat cured at 150° C. for 30 minutes to form a conductive layer with a thickness of 20 μm.

Next, copolymerized nylon (trade name Amilan CM-8000)
, manufactured by Azuma Shimari) was dissolved in a mixed solution of 60 parts of methanol and 40 parts of butanol. In the solution in which this copolymerized nylon is dissolved, the average particle size of the copolymerized nylon is 0.
．． 15% by weight of silicone resin fine powder pulverized to 3 pL (product used: XC99-501 average particle size 2k, Toshiba Silicone ■V) was mixed in and dispersed for 2 hours using a propeller stirrer. This solution was applied on the conductive layer for 50 minutes.
A 3-thick undercoat layer was formed by drying with hot air for 3 minutes with Cl2O.

Next, 100 parts of ε-type copper phthalocyanine (manufactured by Ink ■), 50 parts of butyral resin (manufactured by Tsukiki Kagaku ■) and 1350 parts of cyclohexane were dispersed for 200 hours in a sand mill apparatus using 1φ glass beads. Add 2,700 parts of methyl ethyl ketone to this dispersion, dip coat it onto the undercoat layer, heat dry at 50°C for 110 minutes, and give 0.15 g/m
A charge generation layer of coating material No. 2 was provided.

Then, p-diethylaminobenzaldehyde-N-β
- 10 parts of naphthyl-N-phenylhydrazone and styrene-methyl methacrylate copolymer (trade name MS2)
00, manufactured by Seitetsu Kagaku ■) was dissolved in 80 parts of toluene. This solution was applied onto the charge generation layer at 100°C for 1 hour.
A charge transport layer having a thickness of 16 tiles was formed by drying with hot air for an hour.

The laminated photoreceptor thus created was used as a gallium-aluminum arsenide semiconductor laser (oscillation wavelength: 780 nm, output: 5 mW).
), a corona charger (charging is negative polarity), a developer,
Images were produced using an experimental laser printer equipped with a transfer charger and cleaner. As a result, an image with uniform image density in the solid image area and sharp line images was obtained.

Example 2 A conductive layer was applied in the same manner as in Example 1, and 20 parts of phenol resin (trade name Pryophen J-325, manufactured by Dainichi Ink ■) and butyral resin (trade name Kosuretsuk B, BH) were applied on top of the conductive layer. -3, manufactured by Building Block Chemical ■) 5 parts methanol 6
0 parts and 30 parts of butanol. In this liquid, for the phenol resin and butyral resin mixture, silicone resin fine powder that has been crushed in advance to an average particle size of 1 (products used and 1. 12% by weight was mixed in with 12% by weight of 100% of the product (manufactured by the company) and milled in a ball mill for 2 hours. This solution was applied on the conductive layer and dried with hot air at 150° for 0.30 minutes.
A square thick undercoat layer was formed.

Hereinafter, the charge generation layer and charge transport layer were formed using the same materials as in Example 1.

Images were formed on this electrophotographic photoreceptor in the same manner as in Example 1, and as a result, the image density in the solid image area was uniform. Although the line image was slightly lower than that of Example 1, a sharp image was obtained.

Comparative Example 1 Except for removing the silicone resin fine powder in the undercoat layer,
A conductive layer, an undercoat layer, a charge generation layer, and a charge transport layer were coated in exactly the same manner as in Example 1 to prepare a comparative photoreceptor.

When this comparative photoreceptor was attached to the same laser printer experimental machine as described above and an image was produced, there was no problem with the line image, but uneven density occurred in the solid image area due to interference.

Comparative Example 2 In the undercoat layer, zinc oxide powder (average particle size 2 l) was added to the resin used in Example 1 instead of fine silicone resin powder.
After coating and drying with hot air at 50° C. for 20 minutes, a 51 L thick undercoat layer was formed on the same conductive layer as in Example 1. Further, a charge generation layer and a charge transport layer were provided on this undercoat layer in the same manner as in Example 1 to prepare a comparative photoreceptor.

As a result of performing image printing using this comparative photoreceptor in the same manner as in Example 1, no density unevenness due to interference was observed in the solid image area.
When this was done with 0 sheets in a row, black spots due to pinholes appeared.

[Effects of the Invention] According to the electrophotographic photoreceptor of the present invention, no density unevenness in the form of interference fringes occurs after image exposure Φ development, and clear electrophotographs can be obtained. Such an effect is particularly remarkable when coherent light, especially a laser, is used as a light source for image exposure, and it can be extremely advantageously applied as an electrophotographic photoreceptor for a laser printer. Moreover, since the surface condition is smooth without using methods such as roughening the conductive support of the photoreceptor or the laminated interface of the photosensitive layer, there are extremely few defects, resulting in improved image quality and image density after durability. No deterioration or pinholes occur.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the electrophotographic photoreceptor of the present invention and an explanatory diagram showing the optical path of incident light. FIG. 2 is a cross-sectional view of a conventional electrophotographic photoreceptor. FIG. FIG. 3 is an explanatory diagram showing an optical path of light incident on a photoreceptor. In each of the above drawings, reference numeral 1 indicates a support, 2 indicates a conductive layer, 3 indicates a subbing layer containing silicone resin fine powder, 3° indicates an undercoating layer, 4 indicates a charge generation layer, 5 indicates a charge transport layer, and 6 indicates a conductive layer. Support (If the support 1 is conductive, the conductive layer 2 may not be laminated), 7 is the incident laser beam, 8 is the incident light inside the photoreceptor, 9 is the surface of the conductive support The reflected light 10 indicates the laser light diffused by the undercoat layer 3.

Claims (3)

[Claims] (1) An electrophotographic photoreceptor having at least an undercoat layer and a photosensitive layer on a conductive support, wherein the undercoat layer contains fine silicone resin powder. (2) The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer has a thickness in the range of 0.1 to 10 μm. (3) The electrophotographic photoreceptor according to claim 1, which is applied to electrophotography using a laser as an image exposure light source.