JPH0321903B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor that has a charge generation layer and a charge transport layer, and has low dark decay and little optical fatigue. Conventionally, inorganic photoconductive substances such as selenium, zinc oxide, titanium oxide, and cadmium sulfide have been mainly used in electrophotographic materials that utilize photoconductive substances as photosensitive materials. However, many of these are highly toxic,
There are also problems with the method of disposal. On the other hand, photosensitive materials using organic photoconductive compounds are generally less toxic than those using inorganic photoconductive substances, and are also transparent, flexible, lightweight, and
Recently, it has been widely studied due to its advantages in terms of surface smoothness, cost, etc. Composite photoreceptors, which separate the functions of charge generation and transport, have been rapidly gaining popularity in recent years because they can significantly improve sensitivity, which was a major drawback of conventional photoreceptors using organic photoconductive compounds. progress is being made. However, when these composite photoreceptors are applied to, for example, an electrophotographic device using the Carlson method, the initial potential decreases with repeated use and dark decay increases, causing fogging in the resulting copied images. Image contrast is often significantly impaired. Furthermore, when applied to an electrophotographic device that obtains multiple copies of images by repeating development and transfer without damaging the electrostatic latent image formed by a single exposure, the dark attenuation is large and the density of the copied images is low. gradually decreases. Although the composite type photoreceptor has high sensitivity as described above, it has the disadvantage that dark decay is large, and when exposed for a long time, a photofatigue phenomenon occurs in which the initial potential decreases and the dark decay increases. Particularly when the charge generation layer is thick, the characteristics deteriorate significantly due to optical fatigue. The present invention solves these problems, and has the following features: (1) dark decay is small; (2) even if charging exposure is repeated, the charge potential decreases small, and dark decay does not increase (i.e., (3) Furthermore, the present invention provides a composite electrophotographic photoreceptor that exhibits high sensitivity. That is, the present invention provides an electrophotographic photoreceptor having a conductive layer, a charge generation layer containing an organic pigment that generates a charge, and a charge transport layer containing a charge transporting substance and having a charge retention and transport function. The present invention relates to an electrophotographic photoreceptor in which a charge generation layer contains a silane coupling agent. The materials used in the electrophotographic photoreceptor of the present invention will be described in detail below. First, the charge-generating organic pigments contained in the charge generation layer include azoxybenzene-based, disazo-based, trisazo-based, benzimidazole-based, polycyclic quinone-based, indigoid-based, quinacridone-based, phthalocyanine-based, perylene-based, and methine-based pigments. Pigments known to generate electric charges, such as those based on pigments, can be used. These pigments are described, for example, in Japanese Patent Application Laid-Open No. 47-37453.
Publication No. 1987-37544, Japanese Patent Application Laid-Open No. 1987-37544
Publication No. 18543, Japanese Patent Application Publication No. 1854-1854, Publication No. 18544
-43942 Publication, JP-A-48-70538, JP-A-Sho
It is disclosed in JP-A-49-1231, JP-A-49-105536, JP-A-50-75214, JP-A-50-92738, etc. In addition to these, any organic pigment that generates charge carriers upon irradiation with light can be used. Charge transporting substances contained in the charge transport layer include polymer compounds such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylindoquinoxaline, polyvinylbenzothiophene, and polyvinylanthracene. , polyvinylacridine, polyvinylpyrazoline, etc., and low molecular weight compounds such as fluorene, fluorenone, 2,7-dinitro-9-fluorenone, 2,4,7-trinitro-
9-fluorenone, 4H-indeno(1,2,6)
Thiophen-4-one, 3,7-dinitro-dibenzothiophene-5-oxide, 1-bromopyrene, 2-phenylpyrene, carbazole, 3-
Phenylcarbazole, 2-phenylindole, 2-phenylnaphthalene, oxadiazole, triazole, 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl)pyrazoline, 2-phenyl- 4-
Examples include (4-diethylaminophenyl)-5-phenyloxazole, triphenylamine, imidazole, chrysene, tetraphene, acridene, and derivatives thereof. Further, additives such as a binder, a plasticizer, a fluidity imparting agent, and a pinhole suppressing agent, which are commonly used in electrophotographic photoreceptors, can be used in the charge generation layer and the charge transport layer. As a binder, silicone resin, polyamide, polyurethane, polyester,
epoxy resin, polyketone, polycarbonate,
Examples include polystyrene, polymethyl methacrylate, polyacrylamide, etc., and silicone resins, styrene resins, etc. are particularly suitable as binders used in the charge transport layer. Furthermore, thermosetting and photocuring resins that are crosslinked by heat and/or light can also be used. In any case, there are no particular limitations as long as the resin is insulative and has a film-forming ability in a normal state, or a resin that can be cured by heat and/or light to form a film. Examples of the plasticizer include halogenated paraffin, dimethylnaphthalene, and dibutyl phthalate. Examples of fluidity imparting agents include Modaflow (manufactured by Monsanto Chemical Co.) and Acronal 4F (manufactured by Basf Corporation), and examples of pinhole inhibitors include benzoin and dimethyl terephthalate. These may be selected and used as appropriate, and the amount thereof may be determined as appropriate. Silane coupling agents used in the present invention include vinylsilanes such as vinyltrichlorosilane, vinyltriethoxysilane, vinyltris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyl Epoxysilane such as trimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)
Examples include aminosilanes such as -γ-aminopropyltrimethoxysilane, hydrochlorides thereof, and mercaptosilanes such as γ-mercaptopropyltrimethoxysilane. In particular, aminosilane is highly effective in improving dark decay and optical fatigue. When the charge generation layer contains the above-mentioned silane coupling agent, it is contained in the charge generation layer in an amount of 0.5 to 40% by weight;
Preferably it is contained in an amount of 1 to 20% by weight. 0.5% by weight
If it is less than 40% by weight, it will not be effective in reducing dark decay and light fatigue, and if it exceeds 40% by weight, the effect of improving the initial potential, dark decay, and light fatigue will be good, but the sensitivity will decrease. In addition to the above-mentioned organic pigment and silane coupling agent, the charge generation layer contains a cyanine dye base represented by the following general formula () and/or the following general formula (), which has an effect of improving dark decay and light fatigue.
A styryl dye base represented by can also be added. (However, in the general formula (), R ₁ , R ₂ , R ₃ , R ₄ ,
R ₅ and R ₆ are a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an acyl group, a hydroxyl group, a phenyl group or a substituted phenyl group,
R ₁ to R ₆ may be the same or different. ) (However, in general formula (), R ₇ , R ₈ , R ₉ and
R ₁₀ is a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, an acyl group, a hydroxyl group, a phenyl group, or a substituted phenyl group, and R ₁ to _{R 4} may be the same or different. R ₁₁ and R ₁₂ are hydrogen atoms or alkyl groups, R ₁₁ and R ₁₂
may be the same or different. ) Examples of the cyanine dye base represented by the general formula () include: Examples of the styryl dye base represented by the general formula () include: etc. When the above cyanine dye base and/or styryl dye base is used in combination with the above silane coupling agent, the total content of the silane coupling agent and the cyanine dye base and/or styryl dye base in the charge generation layer It is necessary to adjust the content of each so that it is 40% by weight or less. If it exceeds 40% by weight, the sensitivity of the electrophotographic photoreceptor will decrease. Components in the charge generation layer other than the organic pigment, silane coupling agent, and optionally used cyanine dye base and/or styryl dye base include the binders, plasticizers, additives, and the like.
The binder is used in an amount of 300% by weight or less based on the organic pigment. If it exceeds 300% by weight, electrophotographic properties will deteriorate. The plasticizer is 5% for the above organic pigment.
It is preferable to use less than % by weight. Other additives may be used in an amount of 3% by weight or less. In the present invention, the conductive layer is a conductive material such as paper or plastic film treated for conductivity, a plastic film laminated with metal foil such as aluminum, or a metal plate. The electrophotographic photoreceptor of the present invention preferably has a charge generation layer formed on a conductive layer and a charge transport layer formed thereon in terms of electrophotographic properties, but the lamination order of the charge generation layer and charge transport layer is It may be the other way around.
The thickness of the charge generation layer is 0.1 to 10 μm, preferably
A thickness of 0.2 to 5 μm is desirable. If it is less than 0.1 μm, it will be difficult to uniformly form a charge generation layer, and if it exceeds 10 μm, the electrophotographic properties will deteriorate. In addition, the thickness of the charge transport layer is 5 to 50 μm, preferably 8 to 20 μm.
It is. Below 5μm, the initial potential decreases;
Sensitivity decreases when the value is exceeded. To form the charge generation layer and charge transport layer,
The components of each layer are uniformly dissolved or dispersed in a ketone solvent such as acetone or methyl ethyl ketone, an ether solvent such as tetrahydrofuran, or an aromatic solvent such as toluene or xylene, and then coated on the conductive layer and dried. be able to. The electrophotographic photoreceptor of the present invention may further have a thin adhesive layer or barrier layer immediately above the conductive layer. Further, a protective layer such as silicon can be provided on the surface. In the copying method using the electrophotographic photoreceptor of the present invention, as in the conventional method, the surface is charged and exposed, then developed, and the image is transferred and fixed onto plain paper. The electrophotographic photoreceptor of the present invention has excellent advantages such as high sensitivity, low dark decay, and little optical fatigue. Regarding the mechanism of action in which the electrophotographic photoreceptor of the present invention exhibits the above-mentioned excellent effects, the electrophotographic photoreceptor of the present invention is a composite type in which charge generation and transport are separated into two different layers. Therefore, the probability of recombination of charges is extremely low in the first place, and the silane coupling agent involved in this has little negative effect (less decrease in sensitivity).In addition, the silane coupling agent added to the charge generation layer Improving charging properties (increasing initial potential and decreasing dark decay) by existing near the interface where the charge generation layer and charge transport layer contact, and suppressing charge traps caused by non-uniformity of the layer near the interface. It is presumed that in order to achieve this (less optical fatigue), the initial potential is increased while suppressing a decrease in sensitivity, dark decay is reduced, optical fatigue is reduced, and electrophotographic characteristics are greatly improved. Comparative examples and examples are shown below. Each material used in the examples below is listed below.
The numbers in parentheses indicate abbreviations. (1) Organic pigments that generate electric charge Γ disazo type: Symular Fast Blue 4135 (SFB) [Dainippon Ink & Chemicals Co., Ltd. trade name] Γ phthalocyanine type: Fastogen Blue FGF
(FGF) [Product name of Dainippon Ink and Chemicals Co., Ltd.] Γ Monoazo system: Resino Red BX (BX) [Product name of Konishiroku Photo Co., Ltd.] (2) Charge transporting substance Γ 2-(p-diethylamino ) phenyl-4
-(p-dimethylamino)phenyl-6-(o
-chloro)phenyl-1,3-oxazole
(OXZ) Γ 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline (PYZ) (3) Silane coupling agent in the present invention Γ N-β-(aminoethyl )-γ-Aminopropyltrimethoxysilane: [KBM 603, Shin-Etsu Chemical Co., Ltd. trade name] γ-Mercaptopropyltrimethoxysilane as Γ mercaptosilane: [KBM803, Shin-Etsu Chemical Co., Ltd. trade name] (4) Binder Γ polystyrene: Hammer ST [Mitsui Toatsu Chemical Co., Ltd. trade name] Γ silicone varnish: KP-255 (non-volatile content 50%) [Shin-Etsu Chemical Co., Ltd. trade name] Γ polyester: Byron 200 [Toyobo Co., Ltd. )Product name〕 (5) Pigment base Γ cyanine pigment base [NK-2321, Japan Photosensitive Color Research Institute product name] Gamma styryl dye base [NK-2020, Japan Photosensitive Color Research Institute product name] Comparative Examples 1 to 3 A predetermined amount of the organic pigment and binder shown in Table 1 were blended,
Methyl ethyl ketone was added to this so that the solid content was 3% by weight, and 80 g of this mixed solution was kneaded for 8 hours using a ball mill (3-inch pot mill manufactured by Nihon Kagaku Togyo Co., Ltd.). The obtained pigment dispersion was applied onto a sodium plate (conductive layer) using an applicator, and
It was dried at ℃ for 15 minutes to form a charge generation layer with a thickness of 1 μm. Next, predetermined amounts of the charge-transporting substance and binder shown in Table 1 are blended, and methyl ethyl ketone is added to the solid content.
It was added to 30% by weight and completely dissolved. This solution was applied onto the charge generation layer using an applicator and dried at 90°C for 20 minutes to form a thickness of 15 μm.
A charge transport layer was formed. The electrophotographic properties of the obtained photoreceptor were measured using an electrostatic recording paper tester (SP-428 manufactured by Kawaguchi Denki), and the results are shown in Table 1. In addition, the initial potential (V ₀ ) in the table indicates the charged potential when the corona is instantly discharged with a negative 5KV, and the dark decay (Vk) indicates the potential decay when the corona is left for 10 seconds after that, and is halved. Exposure (E ₅₀ ) is 10x
It shows the light amount value until the potential is halved when white light is irradiated. In addition, in order to examine the effects of photofatigue, the photoreceptor was
Table 1 also shows the electrophotographic characteristics immediately after exposure to x white light for 10 minutes and the ratio of initial potentials before and after exposure (V ₀ '/V ₀ ), which is a measure of photofatigue. Examples 1 to 3 A predetermined amount of the silane coupling agent shown in Table 1 was added to a pigment dispersion prepared by blending predetermined amounts of the organic pigment and binder shown in Table 1 and kneaded according to Comparative Examples 1 to 3, and dissolved therein. This coating liquid was applied onto an aluminum plate using an applicator, dried at 90℃ for 15 minutes, and the thickness
A charge generation layer of 1 μm was formed. The charge transport layer was formed according to Comparative Examples 1 to 3 using the formulation shown in Table 1. Table 1 shows the electrophotographic properties of the obtained photoreceptor. Examples 4 to 6 A predetermined amount of the organic pigment and binder shown in Table 1 were blended and kneaded according to Comparative Examples 1 to 3. A predetermined amount of the silane coupling agent shown in Table 1 was added and dissolved. This coating liquid was applied onto an aluminum plate using an applicator and dried at 90° C. for 15 minutes to form a charge generation layer with a thickness of 1 μm. Next, a charge transport material, a binder, and a silane coupling agent shown in Table 1 were blended to form a charge transport layer according to Comparative Examples 1 to 3. Table 1 shows the electrophotographic properties of the obtained photoreceptor. Comparative Examples 4 to 6 Comparative Examples 1 to 3 were followed except that the charge generation layer was made thicker. The formulation, film thickness, and electrophotographic properties of each material are shown in Table 2. Examples 7 to 9 Examples 1 to 3 and 4 to 6 were conducted except that the charge generation layer was made thicker. The formulation, film thickness, and electrophotographic properties of each material are shown in Table 2. Example 10 SFB1.08g, aminosilane [KBM 603] 0.24
g and 20 g of tetrahydrofuran were placed in a ball mill (3-inch pot mill manufactured by Nihon Kagaku Tou Co., Ltd.) and kneaded for 1 hour. Next, silicone varnish [KR-255] 1.2g,
Add 28g of tetrahydrofuran to the ball mill,
The mixture was kneaded for 3 hours. After that, KR-255 0.96g again,
Mix 29g of tetrahydrofuran in a ball mill,
The mixture was kneaded for 4 hours. The obtained pigment dispersion was applied onto an aluminum plate using an applicator and heated at 90°C.
It was dried for 15 minutes to form a charge generation layer with a thickness of 1 μm. Charge transporting substances and binders shown in Table 3 were blended in predetermined amounts to form charge transporting layers according to Comparative Examples 1 to 3. Table 3 shows the electrophotographic characteristics of the obtained photoreceptor. Example 11 SFB0.96g, mercaptosilane [KBM803]
0.48g, polyester [Byron 200] 0.36g,
20 g of methyl ethyl ketone was placed in a ball mill (3-inch pot mill manufactured by Nihon Kagaku Togyo Co., Ltd.) and kneaded for 2 hours. Next, add 0.3 g of polyester [Byron 200] and 35 g of methyl ethyl ketone to the ball mill,
Kneaded for hours. Thereafter, 0.3 g of polyester [Byron 200] and 22 g of methyl ethyl ketone were mixed in the ball mill again and kneaded for 3 hours. The obtained pigment dispersion was applied onto an aluminum plate using an applicator and dried at 90° C. for 15 minutes to form a charge generation layer with a thickness of 1 μm. Charge transporting substances, binders, and silane coupling agents shown in Table 3 were blended in predetermined amounts to form charge transport layers according to Comparative Examples 1 to 3. Table 3 shows the electrophotographic properties of the obtained photoreceptor. Examples 12 to 19 Predetermined amounts of the organic pigments and binders shown in Table 4 were blended and kneaded according to Comparative Examples 1 to 3, and a pigment dispersion was mixed with the silane coupling agent shown in Table 4 and optionally (Example 12, 13 and 16-19) A predetermined amount of cyanine dye base and/or styryl dye base was added and dissolved. This coating liquid was applied onto an aluminum plate using an applicator and dried at 90° C. for 15 minutes to form a charge generation layer with a thickness of 1 μm. Next, charge transporting substances, binders and silane coupling agents shown in Table 4, optionally (Examples 14 to 3)
19) A predetermined amount of a cyanine dye base and/or a styryl dye base was blended to form a charge transport layer with a thickness of 15 μm according to Comparative Examples 1 to 3. Table 4 shows the electrophotographic properties of the obtained photoreceptor.

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[Table] As shown in Table 1, Comparative Examples 1 to 3 have low dark decay (Vk) of about 40%, high optical fatigue, and (V ₀ ′)
has decreased to about 20% of (V ₀ ). However, it can be seen that in Examples 1 to 6 in which a silane coupling agent was added to at least one of the charge generation layer and the charge transport layer, both dark decay and light fatigue were significantly improved. In particular, Examples 4-
6, when a silane coupling agent is added to both the charge generation layer and the charge transport layer, 1250
The dark attenuation before and after exposure to white light of x is improved by about 50 to 60%, and the optical fatigue is improved by about 60 to 70%. Incidentally, even when a silane coupling agent is added, there is almost no decrease in the half-life exposure amount _E50 . The degree of photofatigue is also influenced by the type of binder in the charge transport layer and the thickness of the charge generation layer. As shown in Comparative Example 4 in Table 2, when polystyrene is used as the binder for the charge transport layer, when the thickness of the charge generation layer is 1 μm, the light is less The decrease in (V ₀ ′) due to fatigue is relatively small. However, when the thickness of the charge generation layer increases, even if polystyrene is used as a binder in the charge transport layer, optical fatigue (V ₀ ′)
The decrease in the amount of water becomes significantly worse (Comparative Examples 5 and 6). However, even if the thickness of the charge generation layer increases in this way, by adding the silane coupling agent of the present invention, the decrease in (V ₀ ') due to optical fatigue is extremely small and the dark decay is also good ( Examples 7-9). The method for producing the pigment dispersion, which is the coating liquid for the charge generation layer, is as shown in Examples 1 to 9. , Examples 10 and 11
As shown in Figure 2, the method involves sequential dispersion in several steps, but the latter method is better in dispersing the pigment. The electrophotographic properties of the obtained photoreceptor are also shown in Table 3.
Samples 13 and 14 are slightly better than Examples 2 and 6. On the other hand, as shown in Table 4, even in systems in which a silane coupling agent and a cyanine dye base and/or a styryl dye base are used in the charge generation layer and/or charge transport layer, electrophotographic properties and optical fatigue are good. It shows the value. As described above, the electrophotographic photoreceptor according to the present invention is a composite electrophotographic photoreceptor having good electrophotographic properties with significantly improved dark decay and optical fatigue.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor having a conductive layer, a charge generation layer containing an organic pigment that generates a charge, and a charge transport layer containing a charge transporting substance and having a function of holding and transporting charges. , an electrophotographic photoreceptor comprising a silane coupling agent contained in the charge generation layer. 2 Add 0.5% of the silane coupling agent into the charge generation layer.
The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor contains up to 40% by weight. 3. Claim 1 or 2, wherein the silane coupling agent is an aminosilane coupling agent.
The electrophotographic photoreceptor described in . 4. The electrophotographic photoreceptor according to claim 1, wherein the charge generation layer and/or the charge transport layer contain a cyanine dye base and/or a styryl dye base. 5 Add a silane coupling agent to the charge generation layer.
5. The electrophotographic photoreceptor according to claim 4, which contains a total of 0.5% by weight or more and 40% by weight or less of a silane coupling agent, a cyanine dye base, and/or a styryl dye base.