JPH0549219B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic photoreceptor.

The present invention also relates to an electrophotographic photoreceptor that can be applied to electrophotography using laser light as an image exposure light source during image formation.

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

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. For example, organic photoconductive polymers such as polyN-vinylcarbazole and polyvinylanthracene; low-molecular organic photoconductors such as carbazole, anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkane; and phthalocyanine pigments; Organic pigments and dyes such as azo pigments, cyanine pigments, polycyclic quinone pigments, perylene pigments, indigo dyes, thioindigo dyes, and methine squaric acid dyes are known.

In particular, organic pigments and dyes with photoconductivity are easier to synthesize than inorganic materials, and the variety of compounds that exhibit photoconductivity in an appropriate wavelength range has been expanded. Photoconductive organic pigments and dyes have been proposed.

For example, U.S. Pat. No. 4,123,270;
Specification No. 4247614, Specification No. 4251613, Specification No.
Specification No. 4251614, Specification No. 4256821, Specification No.
Specification No. 4260672, Specification No. 4268596, Specification No.
An electrophotographic photoreceptor using a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer as disclosed in Specification No. 4278747, Specification No. 4293628, etc. etc. are known.

Conventionally, gas lasers such as helium-cadmium, argon, helium-neon, etc. have been used as lasers for photoreceptors in electrophotographic printers that use coherent light as a light source, but recently, smaller, lower cost lasers have been used. Semiconductor lasers that can be directly modulated have come into use. However, the emission wavelength of semiconductor lasers is 750nm.
In many cases, the above-mentioned photoreceptors have low photosensitivity in that wavelength range and are difficult to use.

For this reason, a laminated type photoreceptor including a charge generation layer and a charge transport layer, which allows the photosensitive wavelength region to be selected relatively freely, 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 set to 0.1 to 0.1 to shorten the range of the generated photo carriers.
It is usually as thin as 5μ. 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 accepting 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 microns.

When using such a photoreceptor and producing an image by scanning a line of laser light with a laser printer, there was no problem with line images such as letters, but in the case of solid images, density unevenness like interference fringes appeared. . The reason for this is that, as the charge generation layer is formed as a thin layer as mentioned above, the amount of light absorbed by this layer is limited, and as a result, the light that has passed through the charge generation layer is reflected on the substrate surface, and this reflected light is This is thought to be due to interference between the light and the reflected light on the surface of the photoconductive layer.

The laminated electrophotographic photoreceptor is made of a conductive support 1, as shown in FIG. It has a structure in which a charge generation layer 2' and a charge transport layer 3 are laminated.

When a laser beam 7 (oscillation wavelength is approximately 780 nm for a semiconductor laser and approximately 630 nm for a helium-neon laser) is incident on this laminated photoreceptor, the laser beam 8 incident on the inside of the photoreceptor is transmitted to the surface of the conductive support 1. Interference occurs with the reflected light 9 coming out from the surface of the charge transport layer 3.

If the refractive index of the laminated layer of the charge generation layer 2' and the charge transport layer 3 is n, the thickness is d, and the wavelength of the laser beam is λ, then when nd is an integral multiple of λ/2, the intensity of the reflected light is When nd is an odd multiple of λ/4, the reflected light is minimum, that is, the intensity of light entering the charge transport layer is maximum (according to the law of conservation of energy). Become.

By the way, thickness unevenness of 0.2μ or more cannot be avoided in d due to manufacturing reasons.

On the other hand, since laser light has good monochromaticity and is coherent, the above-mentioned interference conditions change corresponding to the uneven thickness of d, causing unevenness in the amount of laser light absorbed in the charge generation layer, which causes solid images. It is thought that this appears as interference fringe-like unevenness in the concentration of .

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

Conventionally, in electrophotography using laser light, interference fringes are created by roughening the surface condition of the reflective surface of the substrate, the laminated interface of the base layer, and the photosensitive layer, and creating irregularities to create a phase difference in the reflected light. The occurrence of density unevenness was prevented.

However, in the case of a laminated type photoreceptor, such a surface roughening method does not result in a uniform photosensitive layer formed on the uneven surface, resulting in image defects and a significant deterioration of photographic properties.

[Problems to be Solved by the Invention] An object of the present invention is to provide an electrophotographic photoreceptor that eliminates the drawbacks of the prior art described above, and in particular, to diffuse laser light without roughening the substrate and the laminated interface, thereby eliminating interference fringes. An object of the present invention is to provide an electrophotographic photoreceptor for a laser printer that prevents the occurrence of uneven density.

[Means and effects for solving the problems] The present invention provides an electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive support,
Consisting of an electrophotographic photoreceptor characterized by containing fine silicone resin powder in the charge generation layer,
In particular, the embodiment includes an electrophotographic photoreceptor suitable for application to electrophotography using a laser beam as a light source for image exposure.

The present invention will be specifically explained with reference to the drawings.

FIG. 1 shows an example of the structure of an electrophotographic photoreceptor of the present invention and the path of laser light inside the photoreceptor when laser light is incident thereon. FIG. 2 shows a conventional electrophotographic photoreceptor and the path of laser light inside the photoreceptor when laser light is incident thereon.

1 is a conductive support, 2 is a charge generation layer containing fine silicone resin powder, 2' is a charge generation layer, 3 is a charge transport layer, 4 is a support, 5 is a conductive layer, 6 is a fine silicone resin powder, 7 8 indicates incident laser light, 8 indicates incident laser light into the photoreceptor, 9 indicates reflected light on the surface of the conductive support, and 10 indicates laser light diffused by the charge generation layer containing fine silicone resin powder.

In the electrophotographic photoreceptor of the present invention, as shown in FIG. 1, a photosensitive layer consisting of a charge generation layer 2 and a charge transport layer 3 is laminated on an electrically conductive support 1, containing fine silicone resin powder.

The conductive support 1 has a laminated structure having a conductive layer 5 on a support 4.

The support 4 may be electrically conductive or non-conductive.

For example, the conductive support may be an aluminum cylinder or an aluminum sheet, and the non-conductive support may be a polymer film or cylinder, or a composite material such as paper, plastic or metal.

Regarding the conductive layer 5, the resin in which the conductive pigment powder and, if necessary, the particles for forming surface irregularities are dispersed, must have strong adhesion to the substrate, good dispersibility of the powder, and solvent resistance. Any material can be used as long as it satisfies the conditions such as having sufficient properties, but thermosetting resins such as curable rubber, polyurethane, epoxy resin, alkyd resin, polyester, silicone resin, and acrylic-melamine resin are particularly suitable. .

The volume resistivity of the resin in which conductive powder is dispersed is
A value of 10 ¹³ Ωcm or less, preferably 10 ¹² Ωcm or less is suitable.

Therefore, in the coating film, the conductive powder
The content is preferably 60% by weight.

Dispersion is carried out by a conventional method such as a roll mill, vibratory ball mill, attritor, sand mill, or colloid mill.

If the substrate is in sheet form, coating can be done by wire bar coating, blade coating, knife coating,
Roll coating, screen coating, etc. are suitable, and when the substrate is cylindrical, dip coating is suitable.

The charge generation layer 2 containing fine silicone resin powder is composed of sudanredo,
Azo pigments such as Diane Blue and Jenas Green B, quinone pigments such as Algol Yellow, Pyrenequinone, and Indanthrene Brilliant Violet RRP, indigo pigments such as quinocyanine pigments, perylene pigments, indigo and thioindigo, and India First Orange Toner. Charge generating substances such as bisbenzimidazole pigments, phthalocyanine pigments such as copper phthalocyanine and aluminum chloride phthalocyanine, and quinacridone pigments are combined with binding resins such as polyester, polystyrene, polyvinyl butyral, polyvinyl pyrrolidone, methylcellulose, polyacrylic acid esters, and cellulose esters. It is dispersed and formed.

The present invention is characterized in that the charge generation layer contains silicone resin fine powder 6.

The characteristics of silicone resin fine powder include () lower specific gravity than inorganic fine powder, () superior heat resistance than organic fine powder, () insolubility in organic solvents, and () water repellency. is excellent,
() Excellent lubricity.

In the present invention, the particle size (average particle size) of the silicone resin fine powder is preferably 4 microns or less, particularly 0.2 to 2.0 microns.

If it exceeds 2μ, the charge generation layer becomes rougher,
Although density unevenness in the form of interference fringes is eliminated, resolution is reduced and causes image defects.

There is no particular problem if it is less than 2μ.

A particle size of 0.2 to 4 μm has excellent light scattering properties and is particularly effective in preventing interference of coherent light, making it desirable for electrophotographic photoreceptors for laser printers.

Further, the amount to be mixed is 2 to 20% by weight based on the binding resin used in the charge generation layer.

If it is less than 2% by weight, the laser diffusion effect in the charge generation layer or at its interface with the conductive layer or the charge transport layer will be reduced, making it impossible to prevent interference fringes.
If the particle size exceeds 2μ, the same symptoms will occur if the particle size exceeds 2μ.

The mixing method is to sufficiently mix and disperse using a propeller stirrer or a sand mill.

The charge generation layer 2 contains silicone resin fine powder dispersed therein, so that the laser light 8 incident on the photosensitive layer and the laser light 9 reflected on the surface of the conductive support are transferred to the charge generation layer and the charge. Since the laser light is diffused at the interface of the transport layer and in the charge generation layer (laser light 10 diffused by the charge generation layer containing fine silicone resin powder), there is no interference, and no density unevenness due to interference fringes is seen on the image.

The charge transport layer 3 has a main chain or side chain containing a polycyclic aromatic compound such as anthracene, pyrene, phenanthrene, coronene, or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, It is formed by applying and drying a coating liquid in which a compound having a nitrogen-containing cyclic compound such as triazole or a charge transporting substance such as a hydrazone compound is dissolved or dispersed in a resin with film-forming properties.

The thickness of the charge transport layer is preferably 5 to 20 microns.

In the present invention, a subbing layer having a barrier function and an adhesion function is provided between the conductive layer and the photosensitive layer, if necessary.

The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. Can be formed. The appropriate thickness of the subbing layer is 0.1 to 5 microns, preferably 0.5 to 3 microns.

[Example] Example 1 Conductive titanium oxide powder (manufactured by Titanium Co., Ltd.) 100 parts (parts by weight, the same applies hereinafter), titanium oxide powder (manufactured by Sakai Kogyo Co., Ltd.)
(manufactured by Dainippon Ink Co., Ltd.), 125 parts of phenolic resin (trade name: Plyophene, manufactured by Dainippon Ink Co., Ltd.) and methanol.
The mixture was mixed with 50 parts of methyl cellosolve and 50 parts of methyl cellosolve, and then dispersed in a ball mill for 6 hours.

This dispersion was applied by dipping onto an aluminum cylinder of 60 φ x 260 mm and thermally cured at 150° C. for 30 minutes to form a conductive layer with a thickness of 20 μm. The surface roughness on this conductive layer was 1.5μ.

Next, copolymerized nylon (product name Amilan)
10 parts of CM8000 (manufactured by Toray Industries, Inc.) was dissolved in a mixed solution of 60 parts of methanol and 40 parts of butanol, and the solution was dip coated onto the above conductive layer to provide a 1 μ thick polyamide layer (undercoat layer).

Next, ε-type copper phthalocyanine (manufactured by Toyo Ink Co., Ltd.)
100 parts, butyral resin (manufactured by Sekisui Chemical Co., Ltd.) 50 parts,
Adding 1350 parts of cyclohexane and 10 parts of silicone resin fine powder (trade name XC99-501, manufactured by Toshiba Silicone Corporation) with an average particle size of 2μ to the butyral resin,
The mixture was dispersed for 20 hours using a sand mill using 1.0 mmφ glass beads. Add methyl ethyl ketone to this dispersion.
2,700 parts of the mixture was added, dip-coated onto the polyamide layer, and dried by heating at 80° C. for 30 minutes to form a charge generation layer with a thickness of 5 μm.

Next, 10 parts of a hydrazone compound with the following structure, and 15 parts of styrene-methyl methacrylate copolymer (trade name: MS200, manufactured by Steel Chemical Co., Ltd.) in toluene.
Dissolved in 80 parts. This liquid was applied onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer with a thickness of 16 μm.

The created laminated photosensitive drum was heated using a gallium-aluminum arsenide semiconductor laser (emission wavelength 780 nm, output
5mW), corona charger (charging is negative polarity),
Images were produced by attaching it to an experimental laser printer equipped with a developer, transfer charger, and cleaner. As a result, the image density in the solid image area is uniform,
A sharp line image was also obtained.

Example 2 A conductive layer and a subbing layer were coated in the same manner as in Example 1, and a fine silicone resin powder (trade name: XC99-) was added to the same charge generation layer composition as in Example 1.
301 (manufactured by Toshiba Silicone Co., Ltd.) with an average particle size of 4 μm was crushed using a ball mill, etc., and 5 parts of the average particle size of 0.5 μm was added, and the dispersed liquid was applied in the same manner as in Example 1. The mixture was dried at 80° C. for 30 minutes to form a charge generation layer with a thickness of 4 μm, and on top of this, the same charge transport layer as in Example 1 was provided to prepare an electrophotographic photoreceptor.

Images were formed using this photoreceptor in the same manner as in Example 1. As a result, the image density in the solid image area was uniform, and the line image was slightly better than in Example 1.

Comparative Example 1 In the charge generation layer, a conductive layer, an undercoat layer,
A comparative photosensitive drum was prepared by laminating a charge generation layer and a charge transport layer in this order.

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 The conductive layer, undercoat layer, charge generation layer, A comparative photosensitive drum was prepared by laminating the charge transport layer in this order.

As a result of producing an image using this photoreceptor in the same manner as in Example 1, no density unevenness due to interference was observed in the solid image area, but the charge generation layer was mixed with zinc oxide. Perhaps because it became more difficult to inject into the charge transport layer than the charge generation layer, the sensitivity decreased and the image became thinner.

[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 and development, and clear electrophotographs can be obtained.

This effect is particularly remarkable when coherent light, especially laser light, is used as a light source for image exposure, and it can be extremely advantageously applied as an electrophotographic photoreceptor for laser printers.

Moreover, since the surface condition is smooth regardless of methods such as roughening the substrate of the photoreceptor or the laminated interface of the photoreceptor layers, there are extremely few defects.

Therefore, image quality is improved, and image density decrease after repeated durability, toner fusion to the photosensitive drum, and pinholes do not occur.

[Brief explanation of drawings]

FIG. 1 shows an example of the structure of an electrophotographic photoreceptor of the present invention and the path of laser light inside the photoreceptor when laser light is incident thereon. FIG. 2 shows a conventional electrophotographic photoreceptor and the path of laser light inside the photoreceptor when laser light is incident thereon. 1 is a conductive support, 2 is a charge generation layer containing fine silicone resin powder, 2' is a charge generation layer, 3 is a charge transport layer, 4 is a support, 5 is a conductive layer, 6 is a fine silicone resin powder, 7 8 indicates incident laser light, 8 indicates incident laser light into the photoreceptor, 9 indicates reflected light on the surface of the conductive support, and 10 indicates laser light diffused by the charge generation layer containing fine silicone resin powder.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer laminated on a conductive support, characterized in that the charge generation layer contains silicone resin fine powder. Photoreceptor. 2. The electrophotographic photoreceptor according to claim 1, which is applied to electrophotography using laser light as a light source for image exposure.