JPS60256153A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent uneven density like interference fringes by controlling the surface roughness of the electrically conductive layer of a photosensitive body to half the wavelength of imagewise exposing light or more. CONSTITUTION:The photosensitive body consists of an electrostatic charge generating layer 2 and the charge transfer layer 3 which are provided respectively on a conductive substrate 1 and the conductive susbstrate 1 consists of a support 5 and the conductive layer 4. The surface roughness of the layer 4 is controlled to half the wavelength of imagewise exposing light or more by dispersing inorg. or org. pigment particles or the like into the layer 4. Since the lighr incident on the layer 4 is reflected and diffused, and interference fringes between the incident light and the reflected light hardly occur, uneven density like interference fringes can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic photoreceptor for radar printers.

[Prior art]

Conventionally, selenium and selenium-based alloys have been used as photoreceptors for electrophotographic printers that use lasers as light sources.

A cadmium sulfide resin dispersion system, a charge transfer m-form of polyvinylcarbazole and trinitrofluorenone, etc. have been used. Also, as a laser, helium-cadmium,
Gas lasers such as argon and helium-neon have been used, but recently semiconductor lasers, which are small, low cost, and capable of direct modulation, have come into use. However, many semiconductor lasers have an emission wavelength of 750 nm or more, and such photoreceptors have low photosensitivity in that wavelength range, making them difficult to use. For this reason, a laminated type photoreceptor including a charge generation layer and a charge transport layer, which can relatively freely select the photosensitive wavelength range, has been attracting attention as a photoreceptor for semiconductor laser printers.

The charge generation layer of a laminated photoreceptor has the role of absorbing light and generating free charges, and its thickness is as thin as 0.1 to 5 μm in order to shorten the range of the generated photocarriers. 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 necessity of doing 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 μm.

When using such a laminated photoreceptor and outputting an image by scanning a line of laser light with a laser printer, there is no problem with line images such as characters, but with peta images, density unevenness like interference fringes occurs. 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 reflection This is thought to be due to interference between light and reflected light on the surface of the photoconductive layer. The laminated electrophotographic photoreceptor has a structure in which a charge generation layer 2 and a charge transport layer 3 are laminated on a metal conductive support 1, as shown in FIG. Laser light 6 (oscillation wavelength is approximately 780 nm for semiconductor radar) is applied to this laminated photoreceptor.
*When a helium-neon laser (approximately 630 nm) is incident, the intruding light 7 enters the charge transport layer 3, and this intruding light 7 is reflected by the surface of the metal conductive support 1 and is emitted from the surface of the charge transport layer 30. Interference with the emerging reflected light 8 occurs. The refractive index of the stacked layer of charge generation layer 2 and charge transport layer 3 is n
, the thickness is d, and the wavelength of the radar light is λ, then nd is λ
When nd is an integer multiple of λ/2, the intensity of the reflected light is maximum; that is, the intensity of the light entering the charge transport layer is minimum (according to the law of conservation of energy).When nd is an odd multiple of λ/4, the intensity of the reflected light is maximum. is minimal, meaning the light entering the interior is maximal.

By the way, thickness unevenness of 0.2 μm or more cannot be avoided in d due to manufacturing reasons. On the other hand, since the radar light is monochromatic and coherent, the above-mentioned interference conditions change depending on the thickness variation of d, causing unevenness in the amount of absorption of the radar light in the charge generation layer. It is thought that this appears as interference fringe-like bugs in the density of the solid 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 (5) it is averaged out and becomes invisible.

[Purpose of the invention]

An object of the present invention is to provide an electrophotographic photoreceptor that eliminates the drawbacks of the prior art described above.

Another object of the present invention is to provide an electrophotographic photoreceptor for a laser printer that prevents the occurrence of density unevenness in the form of interference fringes.

The above object is to provide an electrophotographic photoreceptor having a conductive support formed by laminating a conductive layer on the support and a photosensitive layer, in which the surface roughness of the surface of the conductive layer is in the half-wavelength direction of a light source for image exposure ( Hereinafter, one wavelength of the light source for image exposure may be referred to as λ). Further, the electrophotographic photoreceptor of the present invention can be used in electrophotography, which includes a step of charging the photosensitive layer using a radar as a light source for imagewise exposure, and a step of performing imagewise exposure by irradiating laser light. , suitably applied.

That is, in order to eliminate interference with coherent light such as laser light, (6) unevenness is provided on the reflective surface of the laser light, that is, on the surface of the conductive layer, so as to produce a phase difference in the reflected light. By using an electrophotographic photoreceptor provided with a conductive support and a photosensitive layer, interference-like density unevenness is prevented from occurring, and all of the above-mentioned drawbacks of the prior art are eliminated. Regarding the degree of unevenness on the surface of the conductive layer, a retardation of 1/2λ or more is a necessary and sufficient condition (in the case of a single-layer photoconductor) due to interference conditions. For reasons such as reflection, it is practically sufficient to have a phase difference of 2 or more. The phase difference mentioned here is caused by the unevenness of the surface of the conductive layer, so if it is converted to the surface roughness of the conductive layer (the depth from the convex points to the four points), it is 1/
Requires different surface roughness of 2λ or more.

Various types of laser light can be used in the present invention, such as semiconductor laser helium neon lasers, etc., as a light source for image exposure.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the electrophotographic photoreceptor of the present invention. As shown in FIG. 1, the electrophotographic photoreceptor of the present invention has a photosensitive layer comprising a charge generation layer 2 and a charge generation layer 3 laminated on a conductive support 1.

In some cases, a subbing layer may be provided between the conductive support and the charge generation layer.

The conductive support 1 has a laminated structure having a conductive layer 4 on a support 5, and the conductive layer 4 has a surface roughness of λ/2 or more. The support 5 may be electrically conductive or non-conductive. For example, the conductive support 5 may be an aluminum cylinder or an aluminum sheet, and the non-conductive support 5 may be a polymer film or cylinder, or a composite material such as paper, plastic metal, or the like.

As the conductive layer 4, in order to make the surface roughness of the surface S λ/2 or more, conductive powder is dispersed in a resin, or an inorganic pigment is used to further adjust the Kfi surface roughness.・It is formed as a coating layer containing dispersed surface-corrugated phase particles such as organic pigments.

As the conductive powder, specialized materials such as Al, SnrAg, etc.
Monometallic powder, conductive carbon powder, or metal oxides such as titanium oxide, barium oxide, zinc oxide, tin oxide, etc. are used. The surface roughness may be adjusted by incorporating powder with a particle size of λ/2 or more into this conductive powder, or when adjusting the surface roughness with particles other than these conductive powders,
Alternatively, when forming surface irregularities in combination with these, various irregularity-forming particles are added. Inorganic pigment particles for forming unevenness include metal oxides such as alumina oxide and silicon oxide, or metal oxides such as calcium carbonate and strontium carbide; organic particles for forming unevenness include vinylidene chloride, polytetrafluoroethylene, etc. It is a powder that actively adjusts the surface roughness by adding one or more types of various particles such as halogen-containing polymer powder or olefin polymer powder such as Hiropolyethylene and polynolopyrene. .

The resin in which the conductive pigment powder and, if necessary, the particles for forming surface irregularities are dispersed must have (2) good adhesion to the substrate, (2) good dispersibility of the powder, and (9) (3) It can be used as long as it has sufficient solvent resistance, but in particular, curable rubber, polyurethane resin, epoxy resin, alkyd resin, polyester resin, silicone resin, acrylic-melamine A thermosetting resin such as a resin is suitable.The volume resistivity of the resin in which conductive powder and, if necessary, particles for forming surface irregularities are dispersed is suitable to be 1 o 130 or less, preferably 10 Ωα or less. In the film, it is preferable that the conductive powder is contained in a proportion of 10 to 60% by weight in the coating film.Dispersion is performed by a conventional method such as a roll mill, vibrating ball mill, attritor, sand mill, or colloid mill.

When the substrate is in the form of a sheet, wire barcode, blade coating, knife coating, roll coating, screen coating, etc. are suitable for coating, and when the substrate is in the form of a cylinder, the dip coating method is suitable. Are suitable.

The charge generating layer 2 in the present invention includes aso pigments such as Sudan Red, Guianpoule, and Jenas Green B, quinone pigments such as alcohol yellow, pyrene quinone, (lO) indanthrene brilliant violet RRP, quinocyanine pigments, and yrylene pigments. Pigments, indigo pigments such as indigo and thioindigo, bisbenzimidazole pigments such as India First Orange Toner, phthalocyanine pigments such as copper phthalocyanine aluminum chlor-phthalocyanine, and charge generating substances such as quinacridine pigments, polyester, polystyrene, polyvinyl butyral, polyvinyl It is formed by dispersing it in a binder resin such as pyrrolidone, methylcellulose, I-lyacrylic acid esters, and cellulose ester. Its thickness is 0.01~I
n, preferably about 0.05 to 0.5μ.

The charge transport layer 3 may contain polycyclic aromatic compounds such as anthracene, pyrene, phenanthre/coronene, etc., or indole, carnozole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, etc. in the main chain or side chain. pyrazoline, cyanoazole,
Compounds having nitrogen-containing cyclic compounds such as triazole,
It is formed by dissolving a hole-transporting substance such as a hydrazone compound in a film-forming resin. This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. Such resins include polycargonate,
Examples include polymethacrylates, polyarylates, polystyrene, polyesters, polysulfones, styrene-acrylonitrile copolymers, styrene/methyl methacrylate copolymers, and the like. The thickness of the charge transport layer 3 is 5
~20μ.

A subbing layer with barrier and adhesive functions is provided between the conductive layer and the photosensitive layer. The subbing layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 6.6,
It can be formed from nylon 6110, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc.

The thickness of the undercoat layer is suitably 0.1 to 5 microns, preferably 0.5 to 3 microns.

In the above-mentioned conductive support, the surface roughness of the conductive layer surface is λ
/2 or less, when an electrophotographic photoreceptor with a photosensitive layer provided thereon is scanned and exposed to radar light, a developed image will have shading of an interference fringe pattern. According to the photoreceptor, such an interference fringe pattern does not occur.

The invention will be explained below according to examples.

Example-1 Conductive titanium oxide powder (manufactured by Titanium Industries) 100 parts by weight,
Titanium oxide powder (manufactured by Sakai Kogyo Co., Ltd.) 100 parts Phenol resin (manufactured by Dainippon Ink Co., Ltd., !Lio-7en) 125 parts by weight, silicone surfactant (Toshi Silicone) 0.0
2 parts by weight and 10 parts by weight of polyvinylidene fluoride powder (Kynar) were mixed in a solvent of 50 parts by weight of methanol and 1 part by weight of methyl alsolp, and then dispersed in a ball mill over a period of time. This dispersion 'i60φ×2
60.0 applied by dipping method onto an aluminum cylinder,
It was thermally cured at 150° C. for 30 minutes to form a conductive layer (13) with a thickness of 20 μm. The surface roughness on this conductive layer was 1.5 μm.

Next, copolymerized nylon resin (product name: Amilan CM80
00, made by Toshi) (parts by weight, hereinafter referred to as O1) was dissolved in a mixed solution of 60 parts of methanol and 40 parts of butanol, and applied by dip coating onto the above intermediate layer to form a 1〃thick polyamide resin layer. Ta.

Next, 100 parts by weight of ε-type copper phthalocyanine (Toyo Ink!E), 50 parts by weight of butyral resin (1 water chemical system), and 1350 parts by weight of cyclohexane were dispersed for 20 hours in a sand mill device using 1φ glass beads.This dispersion was dispersed for 20 hours. 2,700 parts by weight of methyl ethyl ketone was added to the above polyamide resin layer, and the mixture was dip coated onto the polyamide resin layer and dried by heating at 50° C. for 10 minutes to form a charge generating layer with a coating weight of 0.15 El/m 2 .

Next, 10 parts (14) of a hydrazone compound having the following structural formula and 15 parts of a styrene-methyl methacrylate copolymer resin (product name: MS200, manufactured by Tetsutsu Kagaku Co., Ltd.) were mixed with 80 parts of toluene.
It was dissolved in 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.

This laminated photosensitive drum was attached to an experimental laser printer (charged with negative polarity) equipped with a gallium-aluminum arsenide semiconductor laser (emission wavelength: 780 nm, output: 5 my) to produce an image. As a result, an image with uniform image density in the solid image area and sharp line images was obtained.

Comparative Example-1 A conductive layer was formed on an aluminum cylinder except for the polyvinylidene fluoride powder in the conductive layer of Example-1. The surface roughness of this conductive layer was 0.5 μm. Furthermore, a comparative photosensitive drum was prepared in exactly the same manner as in Example-1.

When this comparative photosensitive drum 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.

Example-2 Conductive Kagen paint (Dotai l- manufactured by Fujiogi Kasei) 100
Heavy inspector melamine stratum (Dainippon Ink Castle Sue e-Belagan) 50 weight-I 1 part, alumina oxide powder (average particle size 5
5 parts by weight of the product were mixed in a solvent containing 100 parts of toluene, and then dispersed in a rubber mill for 9 hours. This dispersion was applied onto an aluminum cylinder using a dipping method.
It was thermally cured at 150° C. for 30 minutes to form a conductive layer with a thickness of 20 μm. The surface roughness of this conductive layer was 1 μm.

Next, the polyamide resin layer, charge generation layer, and charge transport layer used in Example-1? After forming an electrophotographic photoreceptor by sequentially forming I1, an image was formed in the same manner as in Example 1, and a solid image with uniform density and a line image with a laser-like appearance were obtained.

Comparative Example-2 A conductive layer was formed except for the aluminum oxide powder in the conductive layer of Example-2. The surface roughness of this 2F+Electric J- was 0.3 μm. Further, a photosensitive drum was prepared in the same manner as in Example-2. An image was formed on this drum for comparison in the same manner as in Example 1. Although the line image was not a problem, the solid image area was shaded due to interference.

Example 3 The conductive layer of Example 1 was formed with a film thickness of 20 μm on a 60φ×260m+ FRP cylinder molded from glass fiber-containing polyester resin (manufactured by Toyobo Co., Ltd.).The surface roughness of the conductive layer was 1.5 μm. Ta. Furthermore, after sequentially forming the polyamide resin layer, charge generation layer, and transport layer used in Example-1, image formation was performed in the same manner as in Example-1, and the density of the solid image was uniform and the line image was sharp. A great image was obtained.

〔Effect of the invention〕

According to the electrophotographic photoreceptor of the present invention, clear electrophotographs can be obtained without causing density unevenness in the form of interference fringes after image exposure and development. Such an effect is particularly remarkable when coherent light, especially a laser, is used as a light source for image exposure, and it is extremely advantageously applied as an electrophotographic photoreceptor for laser printers (17).

[Brief explanation of drawings]

FIG. 1 is a sectional view of the electrophotographic photoreceptor of the present invention. FIG. 2 is an explanatory diagram showing the optical path of light incident on the electrophotographic photoreceptor. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Charge generation layer, 3... Charge transport layer, 4... Conductive layer, 5... Support, 6...
Incident laser light, 7... Incident light into the inside of the photoreceptor, 8.
...Reflected light on the surface of a conductive substrate. (18)

Claims (8)

[Claims] (1) In an electrophotographic photoreceptor having a conductive support formed by laminating a conductive layer on the support and a photosensitive layer, the surface roughness of the conductive layer is equal to or higher than the half wavelength of the imagewise exposure light source. An electrophotographic photoreceptor characterized by: (2) The electrophotographic photoreceptor according to claim (1), wherein the surface roughness of the conductive layer is one wavelength or more of a light source for image exposure. (3) Claim (1) applied to an electrophotographic method comprising the steps of charging a photosensitive layer using a laser as a light source for imagewise exposure, and performing imagewise exposure by irradiating laser light. The electrophotographic photoreceptor described above. (4) The electrophotographic photoreceptor according to claim (1), wherein the surface irregularities on the surface of the conductive layer are imparted at the time of forming the conductive layer. (5) The conductive layer is made of a conductive powder and a binder), and the conductive powder particles include particles having a particle size equal to or more than half the wavelength of the light source for image exposure. The electrophotographic photoreceptor described in . (6) The conductive layer is composed of a conductive powder, particles for forming surface irregularities, and a binder, and the particles for forming surface irregularities include particles having a particle size of a half wavelength or more of the light source for image exposure. %￥!
f: The electrophotographic photoreceptor according to item (1) f: j4. (7) The particles for forming surface irregularities are one or more types of halodane-containing polymer particles, olefin polymer particles, and inorganic, lj-based rice grain particles. Photographic photoreceptor. (8) The electrophotographic photoreceptor according to claim (1), wherein the photosensitive layer includes a subbing layer, a charge generation layer, and a charge transport layer.