JPS58205157A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To reduce light memory effect, and to enhance sensitivity, by using a styrene-contg. polymer as the film forming resin of the charge transfer layer, and thickening the charge transfer layer to a specified times as thick as the charge generating layer or more. CONSTITUTION:A charge generating material, such as bisazo pigment, quinone pigment, or phthalocyanine pigment, is dispersed into a binder resin, such as polyvinyl butyral resin, a conductive substrate, such as aluminum cylinder, is coated with this dispersion to form a charge generating layer. Then, a charge transfer material, such as tetracyanoethylene or N-ethylcarbazole, is dispersed into a styrene-contg. polymer, such as polystyrene or acrylonitrile-styrene copolymer, and the charge generating layer is coated with this dispersion by the spray method or the like, and dried to form a charge transfer layer in a thickness >=150 times as thick as that of the charge generating layer. As a result, the objective electrophotographic receptor is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor that completely reduces changes in the front surface of the photosensitive layer due to light and can provide clear images even under high temperature and high humidity conditions. It is something.

An electrophotographic photoreceptor has S e %5e- on a conductive substrate.
Te, 5e-Te-Ass Zn0X Cd5qCdS
A photosensitive layer containing a photoconductive substance such as amorphous S r SP VK-, phthalocyanine, or pyrazoline is formed.

Organic photoconductive materials are less polluting than inorganic photoconductive materials.
Although it has advantages such as high performance, its low sensitivity has made it difficult to put it into practical use. For this reason, several sensitization methods have been proposed, but it is known that an effective method is to use a functionally separated photoreceptor in which a charge generation layer and a charge transport layer are laminated.

The charge generation layer is made of azo pigments such as Sudan Red, Diane Blue, and Jenas Green B, Algol Yellow,
Charges include quinone pigments such as pyrenequinone and indanthrene brilliant violet RRP, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, bisbenzimidazole pigments such as India First Orange toner, phthalocyanine pigments such as steel phthalocyanine, and quinacridone pigments. It is formed by dispersing the shipping material in a binder resin such as polyester, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic, polyvinylpyrrolidone, methylcellulose, hydroxyglobil methylcellulose, polyvinyl butyral, etc. and coating it on a substrate.

The charge transport layer on the charge generation layer contains polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, coronene, or indole, carbazole, oxusuzole, isoxazole, thiazole, imidazole, etc. in the main chain or side chain. It is formed by dissolving a charge-transporting substance such as a compound having a nitrogen-containing cyclic compound such as pyrazole, oxadiazole, pyrazoline, thiadiazole, or triazole, or a hydrazone compound in a resin that has film-forming properties. This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. Examples of such resins include polyester, polysulfone, polycarbonate, polymethacrylic acid esters, polystyrene, styrene-acrylonitrile copolymer, and the like.
.

The basic property of a photosensitive layer consisting of a charge generation layer and a charge transport layer is that its electrical resistance changes depending on the intensity of light exposure, and this is utilized to change the charging potential of the photosensitive layer. The desirable characteristics are that the charging potential reaches a predetermined potential during charging, and then, by image exposure, the white part of the image (
The potential decreases corresponding to the bright area potential) and the black area (dark area 1). This characteristic must be constant regardless of the condition of the photoreceptor.

However, depending on the nature of the material of the photosensitive layer, there are some whose potential characteristics are susceptible to change due to the prior beating of the photoreceptor.

In other words, if a photoreceptor is left under bright external lighting conditions before it is used, that is, before it is installed in a copying machine, when the potential is measured using that photoreceptor, the potential will be extremely low. There are cases where it is low. This is a characteristic sometimes called the optical memory effect, and is an inconvenient characteristic when using a photoreceptor.

The reason for this is that under bright lighting conditions, many charge transport carriers (carriers) are generated inside the photosensitive layer, and they do not disappear immediately even when it gets dark, reducing the limiting factor for carrier movement (tramp). In addition, chemical changes in the photosensitive layer due to light are considered to be another cause.

Such a photomemory effect occurs not only in the previous state before the photoreceptor is installed in the copying machine, but also due to light irradiation during image exposure during the copying process. In other words, the part of the photosensitive layer exposed to the white part of the image will be charged the next time.
The potential is lower than the black part of the image.For this reason, normal copying machines irradiate the photosensitive layer with light stronger than the image exposure light before charging, called pre-exposure, to reduce the image exposure light. Efforts are made to cancel out the difference in strength, but if the optical memory effect is large, the charged potential may drop or the image may remain unerased forever.

An object of the present invention is to obtain a functionally separated electrophotographic photoreceptor having a charge generation layer and a charge transport layer, in which the photomemory effect as described above is reduced.

The inventors' experiments have confirmed that the original memory effect is largely caused by the thickness of the charge generation layer and the charge transport layer. It was also confirmed that the degree of the photomemory effect varies depending on the type of film-forming resin of the charge transport layer, and that the photomemory effect is reduced when the resin contains styrene.

Based on these experimental results, in order to reduce the original memory effect, the present invention uses a styrene-containing polymer as the film-forming resin of the charge transport layer, and the film thickness (dry film thickness) is t - charge generation. It is characterized by being 150 times or more the film thickness (dry film thickness) of the layer. In case 1, where the film thickness is less than 150 times, the influence of the free carrier IJr of the charge generation layer extends deep into the charge transport layer, so it is thought that the optical memory effect becomes large. ○ To explain the film thickness in more detail: As the thickness of the charge generation layer increases, the sensitivity improves, but on the other hand, there are disadvantages such as an increase in the optical memory effect, an increase in changes in characteristics due to environmental changes (particularly humidity changes), and a decrease in durability. The film thickness of the charge transport layer contributes to the acceptance potential, sensitivity, etc., and is usually in an appropriate range of approximately FiIO to 20μ. Therefore, since the thickness of the charge generation layer is 1/150 or less of that thickness, an appropriate range is 0.13 to 0.065 μm or less. It is sufficient if the thickness is 1/150 or less, but if it is less than 0.03μ, the sensitivity may become very poor, so a too thin film thickness is not preferable.

The styrene-containing polymer used in the charge transport layer is preferably polystyrene, acrylonitrile-styrene copolymer, styrene-methyl methacrylate copolymer, or styrene-butadiene copolymer, and a mixture of these may also be used. It is valid. In the case of a steele-methyl methacrylate copolymer, methyl methacrylate preferably contains 10 to 40 M parts and is lower than 100 parts by weight of styrene. The physical properties of this charge transport layer, such as film formation performance, strong film strength, environmental stability, and durability, depend on the 4 molecular weight of the styrene-containing polymer, but usually 2,000 to 100, Styrene-containing polymers having a molecular weight of around 0.000 are preferred.

Charge transporting substances that can be contained in the charge transporting layer include electron transporting substances and hole transporting substances, and examples of electron transporting substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2. 4.7-) dinitro-9-fluorenone, 2.4.5.7-tetranitro-9-fluorenone, 2,4.7-dolinitro-9-
Zine anomethylene fluorenone, 2,4,5,7-titranitroxa 7 tons, λ4,8-trinitrothioxa 7
There are magneton-attracting substances such as tungsten, polymers of these electron-attracting substances, and the like.

Examples of hole-transporting substances include pyrene, N-ethylcarbazole, N-ingrovir-rubazole, and N-methol-N.
-Phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylan-10-ethylphenol 1shi11,'tothiacin, N, N-7 phenylhydrazino 3-methylidene-10-ethylphenoxadi/, P-diethylaminobenzaldehyde N, N-diphenylhydrazone,
P-diethylaminohenzaldehyde N-α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-N, N-diphenylhydrazone, 1.3.
3-trimethylindolenine-ω-aldehyde-N,
Hydrazones such as N-diphenylhydrazone, P-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxacyazole, 1- Phenyl-3-(P-diethylaminostyryl)-5-CP
-diethylaminophenyl)pyrazoline, 1-[quinolyl(2))-3-(P-diethylaminostyryl)-5
-(P-diethylaminophenyl) pyrazoline, 1-
[Pyridyl(odor)-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl) hirazoline,
1-(6-medoxybilidyl(2))-3-(P-diethylaminostyryl+-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl+3))-3-(
P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[Levidyl (2))
-3-(P-diethylaminophenyl-5-CP-diethylaminophenyl)pyrazoline, 1-[pyridyl(
]-3-(P-diethylaminostyryl)-4-methyl-5-(P-diethylaminophenyl)pyrazoline,
■-[Pyridyl (2))-3-(d-methyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)hilazoline, 1-phenyl-3-(P-diethylaminostyryl]-4-methyl-5 -(P-diethylaminophenyl)pyrazoline, 1-phenyl-3-(α-
benzyl-P-diethylaminostyryl)-5-(P-
pyrazolines such as diethylaminophenyl) pyrazoline and spiropyrazoline, 2-(P-diethylaminostyryl)-6-dietheraminopenzoxazole, 2-
(P-diethylaminophenyl)-4-(P-'/methylaminophenyl)-5-(2-#rollophenyl)
Oxazole compounds such as oxazole, 2- (P-
thiazole compounds such as diethylaminosteryl)-6-dinithylaminobenzothiazole, triaryl♂thane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1.1-bis(4-N ,
N-diethylamine-2-methylphenyl)hebutane,
Polyarylalkanes such as 1,1,2.2-tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane, triphenylamine, vinylcarbazole, polyvinylpyrene, polyvinylanthracene, Polyvinyl acridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin, etc. In addition to the above-mentioned styrene-containing polymer, the charge transport layer used in the present invention may also contain other resins, For example, polyester, polyarylate, polycarbonate, polysulfone, Borych:Nylpetyral, acrylonitrile-butadiene copolymer, polyacrylamide, polyamide, chlorinated rubber, etc. can also be contained to the extent that they do not impede the effects of the present invention.

The charge transport layer is electrically connected to the charge generation layer and has the function of receiving and receiving charge carriers injected from the charge generation layer in the presence of an electric field and transporting these charge carriers to the surface. have. At this time, this charge transport layer may be laminated on or under the charge generation layer. However, it is desirable that the charge transport layer is laminated on the charge generation layer.

The organic solvent used when forming such a charge transport layer is
It depends on the type of binder used, and it is preferable to select one that does not dissolve the charge generation layer or underlying subbing layer. Specific organic solvents include methanol,
Alcohols such as ethanol and isoglopanol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N,N-dimethylformamide and N,N-dimethylacetamide.

Sulfoxides such as dimethyl sulfoxide, tetrahydrofuran, dioxane, ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, chloroform, methylene chloride, dichloroethylene, carbon tetrachloride, carbonized aliphatic halides such as trichlorethylene Hydrogens or benzene, tolu,
Aromatics such as T-7,9'/L/n, refloin, monochlorobenzene, and dichlorobenzene can be used.

Coating methods include dip coating method, spray coating method, spinner coating method, bead coating method,
Coating methods such as Meyer par coating method, blade coating method, roller coating method, curtain coating method? It can be done using A preferred method is to dry to the touch using a drying lamp at room temperature, followed by heating and drying. Heat drying can be carried out with wet hair at 30° C. to 200° C. for a period of time ranging from 5 minutes to 2 hours, either stationary or with air blowing.

The charge transport layer of the present invention can contain various additives. Such additives include diphenyl, diphenyl chloride, 0-1-phenyl, P-terphenyl, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, methylnaphthalene triphenylphosphate, benzophenone, chlorinated paraffin, dilauryl thioglobionate. , 3,5-dinitrosalicylic acid, and various fluorocarbons.

The charge generation layer used in the present invention includes azo pigments such as Sudan Red, Diane Blue, and Jenas Green B, quinone pigments such as Algol Yellow, Pyrene Quinone, and Indanthrene Brilliant Violet RRP, quinocyanine pigments, perylene pigments, indigo, thioindigo, etc. indigo pigments, bisbenzimidazole pigments such as India First Orange Toner, copper phthalocyanine, etc.
A charge generating substance such as a talocyanine pigment or a quinacridone pigment is dispersed in a binder resin such as polyester, polystyrene, polyvinyl chloride, polyvinyl acetate, acrylic, polyvinylpyrrolidone, methylcellulose, hydroxyglobil methylcellulose, or polyvinyl butyral, and then applied to a substrate. It can be formed by applying it to In addition, an amorphous silicon layer, a selenium-tellurium vapor deposited layer, a perylene pigment vapor deposited layer, etc. can be used as the charge generation layer.

A photosensitive layer having such a laminated structure of a charge generation layer and a charge transport layer is provided on a substrate having a conductive layer. Examples of substrates having a conductive layer include those in which the substrate itself is conductive;
For example, aluminum, aluminum alloy, copper, zinc, stainless steel, ha, molybdenum, chromium, titanium, nickel, indium, gold, platinum, etc. can be used.In addition, aluminum, aluminum alloy, indium oxide, indium tin oxide, etc. can be used. - Plastics such as tin oxide alloys with a layer formed by gold vacuum vaporization method (e.g. polyethylene, polypropylene, vol.
vinyl chloride, polyethylene terephthalate, acrylic resin, polyfluorinated ethylene, etc.), conductive particles (e.g. carbon black, silver particles, etc.) coated on plastic with a suitable binder, and conductive particles impregnated into plastic or paper. A conductive substrate, a plastic having a conductive polymer, etc. can be used.

A subbing layer with barrier and adhesive functions may be provided between the conductive layer and the photosensitive layer. One subbing 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. The thickness of the undercoat layer is from 0.1 micron to 5 micron, preferably 0.1 micron to 5 micron. Appropriate values are 5"S ri-n to 3 miku.

Although the electrophotographic photoreceptor according to the present invention has little optical memory effect and is easy to use as a photoreceptor,
The details will be explained with reference to examples.

Example 1 80$X30011! The aluminum cylinder of II was used as the base. A 50% methanol solution of polyamide resin (trade name: Amilan CM8000, manufactured by Toshi) was applied to this by dipping to form an undercoat layer with a thickness of 1 μm.

Next, 10 parts of bisazo pigment with the following structural formula (heavy electric part, the same applies hereinafter), polyvinyl butyral resin (trade name: Eslec BXL)
8 parts (manufactured by Sekisui Chemical's Taru) and 60 parts of cyclohexanone were dispersed for 20 hours in a sand mill apparatus using 1 glass beads. Add methyl ethyl ketone 70 to 12 to this dispersion.
0 parts (as appropriate) were added and coated onto the undercoat layer. The coating was applied so that the film thickness was 0.03°, 0.06 micron, and 0.12 micron, and three films were prepared for each film.

Next, a solution prepared by dissolving 7 parts of a hydrazone compound having the structural formula and to parts of polystyrene resin (trade name: Dialex HF-55; Mitsubishi Monsanto Kasei II) in 50 parts of monochlorobenzene was applied onto the charge generation layer. It was coated under different coating conditions and dried. At this time, the coatings were applied so that the film thickness after drying was 12.degree. and 16.20 microns, respectively. Photoreceptors prepared with respective film thicknesses were designated with symbols A-I as shown below.

This electrophotographic photoreceptor A-I was subjected to % -5,6 kV corona charging, image exposure, dry toner development, toner transfer to plain paper, and urethane rubber bond (hard 1f70o).

Pressure 10 gw/cm, angle 200 to photoreceptor)
The electrophotographic characteristics were evaluated by attaching it to an electrophotographic copying machine that has a cleaning process etc. V,.) and sensitivity measurements. The sensitivity is -120V when iJ1 dark decays for 2 seconds after corona charging at -5,6kV.
Table 1 shows the results of Nine et al.

However, the ratio of the thickness of the t-charge transport layer to the thickness of the charge generation layer was defined as the thickness magnification.

Table 1 In the case of photoreceptors A, D, and G, the thickness of the charge generation layer is as thin as 0.03μ, so the sensitivity is inferior compared to the others, but
There was very little optical memory, and there was almost no change in image JI IK.

Photoreceptors B, E, and H had appropriate sensitivity and optical memory effect, and were preferred photoreceptors. In particular, photoreceptor E has a good balance of potential, sensitivity, and optical memory effect.
It was the best.

In the case of photoreceptors C, F, and I, the optical memory effect was severe, and the potential decreased significantly when used repeatedly. When copy images were taken, a decrease in image density was observed, and as the number of copies was taken, the images gradually became lighter.

Example 2 An aluminum cylinder coated with an undercoat layer was prepared in the same manner as in Example 1.

Next, a dispersion liquid for charge generation 1-coating was prepared in the same manner as in Example 1, and coated on three cylinders each so that the film thickness after drying was 0.06 microns.

Furthermore, 7 parts of the same hydrazone compound as in Example 1 and styrene-methyl methacrylate (monocomolar ratio 8:2) copolymer resin were added with @product name: MS-200;
! ) A solution prepared by dissolving 10 parts of monochlorobenzene in 50 parts of monochlorobenzene was applied onto the charge generating layer so that the film thickness after drying was 12 parts.
, 16.20 microns. Let these three types be photoreceptors J and L. When the characteristics were measured, the results were as shown in Table 2.

In the case of photoreceptors J and K in Table 2, the film thickness magnification is 150 times or more,
It has been found that the optical memory effect is very small, and the photoreceptor has good sensitivity.

The photoreceptor had a large optical memory, and changes in image density were observed.

Comparative example Exposure 1 by changing the resin of the charge transport layer as follows. Get your body for $1! Debt Maru.

M: Polymethyl methacrylate (Product name: Dial B
R, 88, made by Mitsubishi Rayon) N: Vinyl chloride vinegar picopolymer (product name: VYHH1UCC Co., Ltd.): Polyester resin (product name: Vylon 290, made by Toyobo Co., Ltd.) However, the film thickness of the charge generation layer is 0.06μ, The thickness of the charge transport layer was 16 μm.The results are summarized in Table 3.

In all cases in Table 3, the potential was low, and therefore the sensitivity was relatively good, but the image in Figure 1 had a very low density.

Examples 3 to 5 Even when the following resin was used as the film-forming resin for the charge transport layer, it was possible to penetrate the photoreceptor with high sensitivity and little optical memo IJ effect.

Example 3: Styrene-acrylonitrile copolymer resin (trade name;
Sevian NL2687 Daicel Chemical = #) 4; Styrene methyl methacrylate copolymer resin (Product name: Estyley MS3QO0 Steel Chemical JJl 5; Polystyrene resin (@Product name: Daicel Chemical)
-2500, Inu Nippon Ink Chemical Co., Ltd.) Patent grantor: Canon Co., Ltd. Agent Patent attorney: Gi Marushima -

Claims (1)

[Claims] An electrophotographic photoreceptor having a charge generation layer and a charge transport layer, wherein the charge transport layer contains a styrene-containing polymer and has a thickness that is 150 times or more the thickness of the charge generation layer. Photoreceptor.