JP2998306B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member. Specifically, it has excellent ozone resistance, stability,
The present invention relates to an electrophotographic photosensitive member having excellent durability.

[0002]

2. Description of the Related Art Conventionally, inorganic photoconductive materials such as selenium, selenium-tellurium alloy, arsenic selenide, and cadmium sulfide have been widely used in electrophotographic photoreceptors. In recent years, research on the use of organic photoconductive materials for the photosensitive layer has become active, and since it is suitable for mass production and has the potential to be highly safe, charge carriers are generated particularly by absorbing light. A stacked photoreceptor having a charge generation layer and a charge transport layer, which separates the function of transferring a generated charge carrier from the function of transferring the generated charge carriers, has been devised and has become the mainstream of research. Highly sensitive photoreceptors have been obtained by combining organic compounds having a highly efficient charge generating action and a charge transport action with each other, and the laminated photoreceptor has been put to practical use. Such a laminated electrophotographic photoreceptor has a charge transport layer laminated on a charge generation layer, and since the charge transport layer usually has only a hole transport function, sensitivity is increased only when negatively charged. Have
Used under negative charge.

On the other hand, in the electrophotographic method, the photosensitive member is usually charged by corona discharge. However, it is more difficult for negative corona discharge to cause uniform discharge in the wire direction than for positive corona discharge. The selenium-based photoreceptor, which was the core of the conventional technology, was positively charged, and we want to use the conventional technology for the developer and other peripheral processes used in this system. Also, an organic photoreceptor that can be used for positive charging has been studied. For example, a so-called inverted two-layer type photoconductor in which a charge transport layer and a charge generation layer are laminated in this order on a support, and a dispersion type photoconductor in which particles of a charge generation material are dispersed in a charge transport medium have been proposed and studied. ing. In the case of a reverse two-layer, dispersion type photoreceptor, incident light is absorbed on the surface, and the region where carriers are generated becomes near the surface and is used with positive charge.

As described above, photoconductors having several configurations have been proposed and studied, and photoconductors having excellent chargeability and sensitivity have been developed. However, the electrophotographic photoreceptor is used repeatedly in the system, and in it, constant and stable electrophotographic characteristics are required. Regarding such stability and durability, in any configuration, At present it is not enough yet. That is, as the device is used repeatedly, a decrease in potential, a rise in residual potential, a change in sensitivity, and the like occur. Not all of the causes of these deteriorations are known, but there are several possible causes. In particular, it has been found that oxidizing gases such as ozone and nitrogen oxides emitted from a corona discharge charger significantly damage the photosensitive layer. These oxidizing gases chemically change the material in the photosensitive layer and cause various changes in characteristics. For example, a decrease in charging potential, an increase in residual potential, a decrease in resolution due to a decrease in surface resistance, and the like are observed. As a result, image quality is significantly reduced, and the life of the photoconductor is shortened. In response to this, there have been proposals to efficiently exhaust and replace the gas around the corona charger to avoid the effect on the photoconductor, and to add antioxidants and stabilizers to the photosensitive layer to prevent deterioration. Have been. For example, addition of an antioxidant having a triazine ring and a hindered phenol skeleton in a molecule disclosed in JP-A-62-105151,
No. 18355 describes the addition of specific hindered amines. Also, JP-A-63-4238,
JP-A-63-216055 describes the addition of trialkylamines and aromatic amines.

[0005]

However, even with these conventional techniques, a sufficient ozone resistance effect has not yet been obtained, or electrophotographic properties such as sensitivity and residual potential have been reduced by the addition of such an antioxidant. At present, only sufficient effects for practical use, such as worsening, were obtained.

[0006]

Means for Solving the Problems The present inventors have made intensive studies on the improvement of the ozone resistance of an organic photoreceptor having a charge generating substance and a charge transporting substance, and as a result, added a specific amine compound to the photosensitive layer. As a result, the present inventors have found that a photoreceptor having significantly improved ozone resistance and excellent electrical properties can be obtained, thereby completing the present invention.

That is, the gist of the present invention is that a conductive support is
An electrophotographic photoreceptor comprising a photosensitive layer containing at least a charge generating substance, a charge transporting substance and an amine compound represented by the following general formula (I).

[0008]

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(However, n represents an integer of 0 to 6. R ₁ and R ₂ each represent a hydrogen atom, an alkyl group or an aralkyl group, and the alkyl group and the aralkyl group each represent a substituent. A ₁ and A ₂ each represent an aryl group, a heteroaryl group, or a cycloalkyl group, provided that R ₁ and R ₂ each represent a hydrogen atom; The present invention will be described in detail below.

The photosensitive layer of the present invention contains at least a charge generating substance and a charge transporting substance. More specifically, a laminated photoconductor in which a charge generation layer mainly containing a charge generation substance, a charge transport layer mainly containing a charge transport substance and a binder resin is laminated on a conductive support in this order. ● An inverted two-layer photoreceptor in which a charge transport layer mainly composed of a charge transport substance and a binder resin and a charge generation layer mainly composed of a charge generation substance are laminated in this order on a conductive support. ● A dispersion type photoreceptor in which a charge generation substance is dispersed in a layer containing a charge transport substance and a binder resin on a conductive support. Such a configuration is given as an example of a basic form.

These photosensitive layers are formed on a conductive support by a known method such as roll coating, bar coating, dip coating, spray coating and the like. If necessary, a barrier layer such as polyamide, polyurethane or aluminum oxide may be provided between the conductive substrate and the photosensitive layer. Further, a protective layer made of polyamide, thermosetting silicone resin, crosslinked acrylic resin, or the like may be provided on the surface of the photosensitive layer as needed.

Various known conductive supports can be used. For example, a metal drum of aluminum, copper, nickel, stainless steel, etc .; a metal foil laminated, a metal, a conductive oxide deposited or sputtered, or a metal powder, carbon black, copper iodide, tin oxide, etc. Plastic films, plastic drums, glass drums, paper, etc., which have been subjected to a conductive treatment such as applying a conductive material together with a binder resin as required, may be mentioned.

As the charge generating substance used in the present invention, various inorganic and organic charge generating substances can be used. For example, as the inorganic charge generating substance, various alloy materials containing selenium as a main component such as amorphous selenium, selenium-tellurium alloy, trigonal selenium, arsenic triselenide; II to VI such as cadmium sulfide and cadmium selenide; A known material such as amorphous silicon and silicon hydride is used in the form of fine particles. Further, phthalocyanine pigments, perylene pigments, polycyclic quinones, quinacridone pigments, indigo pigments, squarylium salts, azo pigments, and the like can be used as organic charge generation substances.

Among them, phthalocyanine pigments and azo pigments can be used as more preferable materials. Examples of the phthalocyanine pigment include those represented by the following general formula.

[0015]

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The above M is Cu, Fe, Mg, Si, G
e, Sn, Pb, InCl, GaCl, AlCl, Ti
Examples include phthalocyanine containing a metal atom such as O, and metal-free phthalocyanine to which two hydrogen atoms have been added. X includes a hydrogen atom, a lower alkyl group, a lower alkoxy group, a nitro group, a cyano group, a halogen atom and the like, and m represents an integer of 0 to 4.

As the azo pigments, various ones can be mentioned. More preferred materials are monoazo pigments having at least one coupler component represented by the following general formula:
Examples include bisazo pigments, trisazo pigments and other polyazo pigments.

[0018]

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Wherein A is a divalent group of an aromatic hydrocarbon,
Or a heterocyclic divalent group containing a nitrogen atom in the ring. In the case of a laminated structure, the charge generating substance is used as a main component of the charge generating layer, and may be used as a uniform layer formed by a method such as evaporation or sputtering, or may be used as a binder in the form of fine particles. It may be used in a form dispersed in a resin. In this case, as the binder resin, polyvinyl acetate, polyacrylate, methacrylate resin,
Various binder resins such as polyester resins, polycarbonate resins, polyvinyl acetal resins such as polyvinyl butyral and polyvinyl formal, phenoxy resins, cellulose esters, cellulose ethers, urethane resins and epoxy resins can be used. The composition ratio of the charge generating substance to the binder resin is usually preferably in the range of 100: 10 to 5: 100 by weight, and a charge transporting substance may be mixed in this layer. It is preferable that the charge generation layer is usually used in a thickness of 0.1 to 10 μm. In the case of the dispersion type photosensitive layer configuration as described above, the charge generating substance is dispersed in the form of fine particles in a matrix having a charge transporting substance and a binder resin.

As the charge transporting material used in the present invention, various known materials used for an electrophotographic photosensitive member can be mentioned. Compounds having a heterocyclic ring such as carbazole, indole, imidazole, thiazole, oxadiazole, pyrazole and pyrazoline; aniline derivatives such as phenylamine, diphenylamine and triphenylamine; hydrazone derivatives; stilbene derivatives; An electron donating substance such as a polymer having a main chain or a side chain may be used.

Particularly preferred substances include hydrazone derivatives, allinine derivatives and stilbene derivatives.
Various known resins can be used as the binder resin used together with the charge transport material. Thermoplastic resins and curable resins such as polycarbonate resin, polyester resin, polyarylate resin, acrylic resin, methacrylate resin, styrene resin, and silicone resin can be used.
Polycarbonate resin with less wear and scratches,
Polyacrylate resins and polyester resins are preferred.
As the bisphenol component of the polycarbonate resin, bisphenol A, bisphenol C, bisphenol Z
And various known components can be used.

The compounding ratio of the charge transporting material to the binder resin is, for example, 20 to 200 parts by weight, preferably 40 to 150 parts by weight, per 100 parts by weight of the resin. In the case of a laminated photoreceptor, the charge transporting layer is formed mainly of the above-mentioned components, and the thickness of the charge transporting layer is usually 5 to 50 μm, preferably 10 to 40 μm.

In the case of a dispersion type photoreceptor, the charge generating substance is dispersed as fine particles in a matrix mainly composed of the charge transporting substance and the binder resin in the above-described mixing ratio, but the particle diameter must be sufficiently small. Required, preferably 1
It is used at most μm, more preferably at most 0.5 μm. If the amount of the charge generating substance dispersed in the photosensitive layer is too small, sufficient sensitivity cannot be obtained, and if the amount is too large, the chargeability decreases,
There are adverse effects such as a decrease in sensitivity.
It is used in the range of 5 to 50% by weight, more preferably in the range of 1 to 20% by weight. The thickness of the photosensitive layer is usually 5 to 50 μm.
m, more preferably 10 to 40 μm.

The amine compound used in the present invention is a compound represented by the general formula (I) as described above. Formula (I)
In the formula, n represents any one of integers from 0 to 6.
R ₁ and R ₂ are selected from a hydrogen atom, an alkyl group and an aralkyl group, and the alkyl group and the aralkyl group may have a substituent such as a hydroxyl group, an alkoxy group and an alkyl group.
R ₁ and R ₂ may be the same or different.
It is preferred that at least one of them has 3 or more carbon atoms, except that both ₁ and R ₂ are hydrogen atoms. Decyl group,
Particularly preferred is a sterically bulky alkyl group such as a tertiary butyl group, or an aralkyl group such as a benzyl group.

A ₁ and A ₂ are selected from an aryl group such as a phenyl group and a naphthyl group; a heteroaryl group such as a pyridyl group; a cycloalkyl group such as a cyclohexyl group, and these are substituted with a substituent such as an alkoxy group or an alkyl group. May have. A ₁ and A ₂ may be the same or different, but are particularly preferably a phenyl group. Specific examples of the compound represented by such a general formula are shown in Table 1 below.

In the examples of Table 1, n, A ₁ , A ₂ , R ₁ and R ₂ in the general formula (I) are represented by chemical formulas or names. In the following examples, a naphthyl group,
The positions where the pyridyl group and the anthryl group are bonded are indicated by numerical values in the following figure.

[0027]

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Table 1 Exemplary Compounds Compound No. Compound (1) n; 1 A ₁ and A ₂ ; -C ₆ H ₅ R ₁ ; -HR ₂ ; -CH ₂ OCH ₃ (2) n; 1 A ₁ and _{A 2; -C 6 H 4 CH} 3 ( attached at the para _{position) R 1; -CH 2 CH (} C 6 H 4 CH 3) ( attached in the _{para-position) 2 R 2; -H (3} ) n; 1 A ₁ and _{A 2; -C 6 H 5 R} 1; -CH 2 CH (C 6 H 5) 2 R 2; -CH 2 (CH 2) 8 CH 3 (4) n; 1 A 1 and A _{2; -C 6 H 4 C (CH 3} ) 3 ( attached at the para position) R ₁ and _{R 2; -CH 2 OH (5} ) n; 2 A 1 and _{A 2; -C 6 H 5 R} 1; -CH 2 _{CH 2 CH (C 6 H 5} ) 2 R 2; -H (6) n; 2 A 1 and _{A 2; -C 6 H 5 R} 1 and _{R 2; -CH 2 CH 2 CH} (C 6 H 5) _{2 (7) n; 2 A} 1 and _{A 2; -C 6 H 5 R} 1 and R _2; -CH _{2 6 H 5 (8) n;} 2 A 1 and _{A 2; -C 6 H 5 R} 1; -CH 2 CH 2 CH (C 6 H 5) 2 R 2; -CH 2 C 6 H 5 (9) n ; 2 A ₁ and _{A 2; -C 6 H 5 R} 1; -H R 2; -C (CH 3) 3 (10) n; 2 A 1 and _{A 2; -C 6 H 5 R} 1 and R _{2 ; -CH 2 (CH 2) 8} CH 3 (11) n; 5 a 1 and a _2; (attached at 2) naphthyl groups R ₁ and _{R 2; -CH 2 C 6 H} 5 (12) n; 2 A ₁ and A ₂ ; pyridyl group (attached at position 4) R ₁ and R ₂ ; —CH ₂ C ₆ H ₅ (13) n; 3 A ₁ and A ₂ ; cyclohexyl group R ₁ and R ₂ ; CH ₃ (14) n; 2 A ₁ ; naphthyl group (bonded at position 2) A ₂ ; cyclohexyl group R ₁ ; —CH ₃ R ₂ ; —CH ₂ C ₆ H ₄ C (CH ₃ ) ₃ (para position in binding) (15) n; 2 A 1 and A _2; - _{6 H 5 R 1; -CH 2} CH 2 CH (C 6 H 5) 2 R 2; -CH 2 C 6 H 4 CH 2 N [CH 2 CH 2 CH (C 6 H 5) 2] 2 ( para (16) n; 6 A ₁ ; anthryl group (bonded at position 1) A ₂ ; —C ₆ H ₄ OCH ₃ (bonded at para position) R ₁ ; —CH ₂ C ₆ H ₄ OCH ₃ ( R ₂ ; -H

These amine compounds are added to all or part of the photosensitive layer. Since the deterioration proceeds from the surface, it is preferable that it is added to at least the surface layer. When a protective layer or a blocking layer is provided, it is added to these layers as needed. The amount of the amine compound to be added is usually 0.1 to 20% by weight, more preferably 1 to 16% by weight in the layer.

Further, in the photosensitive layer of the present invention, a known plasticizer for improving film formability, flexibility, mechanical strength, etc., an additive for suppressing accumulation of residual potential, and a dispersion improving dispersion stability. And a leveling agent for improving applicability, for example, silicone oil, and other additives may be added.

[0031]

The electrophotographic photoreceptor of the present invention has excellent electrophotographic characteristics, is not easily affected by ozone and nitrogen oxides generated from the system, and has stable characteristics and image quality even when used repeatedly. It has the advantage of being a photoreceptor with extremely high durability. The photoreceptor of the present invention can be used in a wide range of electrophotographic applications, such as electrophotographic copying machines and various printers.

[0032]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In the examples, “parts” means “parts by weight”. Example 1 180 parts of cyclohexanone was added to 5 parts of a bisazo compound having the following structure, and preliminarily dispersed by a sand grinding mill.

[0033]

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On the other hand, 50 parts of a polycarbonate resin (viscosity average molecular weight: about 22,000) having 380 parts of cyclohexanone having the following repeating structural unit,

[0035]

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A hydrazone compound 50 having the following structure:
And 1.5 parts of the amine compound represented by (6) in Table 1 above were dissolved, and the above preliminary dispersion was further added, followed by main dispersion treatment using a homogenizer to obtain a coating liquid.

[0037]

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This coating solution was applied onto a polyester film on which aluminum had been vapor-deposited, and then applied to a thickness of 20 μm after drying to obtain Sample 1A. When the electrophotographic characteristics of this sample 1A were measured, the initial charged voltage was +539.
V, the exposure amount E1 / 2 required to attenuate the surface potential from 500 V to 250 V was 1.0 luxsec, and the residual potential +7 V after 10 seconds of exposure.

Next, to examine the ozone resistance of the photoreceptor, the sample was left in a corona discharge atmosphere. A corona charger was placed in the box, a voltage of -7 kV was applied, and air was circulated by a fan provided in the box to create a uniform atmosphere. The ozone concentration at this time was 25 ppm. After being exposed to this atmosphere for 5 hours, it was stored in the atmosphere for 19 hours, and further, after being exposed to this ozone atmosphere for 5 hours, the characteristics of these photoreceptors were examined. Did not.

Next, the amine compounds (7) and (8)
Samples 1B to 1C were prepared in the same manner as Sample 1A, except that was added. These samples were evaluated for electrophotographic properties and ozone resistance in the same manner as in Example 1. Table 2 shows the results. Comparative Example 1 A comparative sample 1D was prepared in the same manner as in Example 1 except that the amine compound was omitted for comparison. Next, Comparative Samples 1E to 1H were prepared in the same manner except that the following amine compounds (i) to (vi), which are known to be added to an organic electrophotographic photosensitive member as an amine compound, were added. .

[0041]

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Next, a well-known antioxidant, di-t-butylhydroxytoluene (hereinafter abbreviated as BHT), which is also added to the photosensitive layer instead of the amine compound, was added except that an equal amount was added. Is the same as Comparative Sample 1
I was created. These samples were evaluated for electrophotographic properties and ozone resistance in the same manner as in Example 1. The results are shown in Table 2 below. As can be seen from the graph, the photosensitive layers of Examples have excellent sensitivity and excellent ozone resistance. However, when the amine compound of the present invention was not added, a marked decrease in charged voltage was observed due to ozone exposure. As described above, the addition of the known amine compound improves the change in potential due to exposure to ozone, but significantly lowers the initial sensitivity. It can also be seen that the effect of a known antioxidant, a phenolic antioxidant, is insufficient (Comparative Sample 1I).

[0043]

[Table 1] ^* ) Potential holding ratio (%) = (charge potential after O ₃ exposure) ÷ (initial charge potential) × 100

Example 2 1 part of the same bisazo compound as used in Example 1 was added to 20 parts of dimethoxyethane and dispersed by a sand grinder. Then, a polyvinyl acetal resin (trade name: Denka Kagaku Kogyo KK) Butyral # 6000C)
5 parts were dissolved in 10 parts of dimethoxyethane to obtain a dispersion. 75 μm of this liquid with aluminum deposited
0.4 g / m ² after drying on polyester film of thickness
To form a charge generation layer.

90 parts of N-methylcarbazole diphenylhydrazone and 100 parts of a polycarbonate resin (NOVAREX 7030A, manufactured by Mitsubishi Kasei Co., Ltd.) are formed on the charge generation layer.
, A solution prepared by dissolving 3 parts of the exemplified compound (6) in Table 1 and 4 parts of the following electron-withdrawing compound in 700 parts of dioxane was applied so that the film thickness after drying was 20 μm to form a charge transfer layer. Sample 2A was made.

Next, Samples 2B and 2C were prepared in the same manner as Sample 2A except that the exemplified compounds (7) and (8) were added as amine compounds.

[0047]

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Comparative Example 2 For comparison, a comparative sample 2D was prepared in the same manner as in Example 2 except that no amine compound was added. A comparative sample 2E was prepared in exactly the same manner except that the known amine compound (vi) used in Comparative Example 1 was added instead of the exemplary compound (6).

Next, instead of the sensitivity E1 / 2, the surface potential 5
Exposure E1 required to attenuate 00V to 100V
The electrophotographic characteristics and ozone resistance of these samples were evaluated in the same manner as in Example 1 except that / 5 was obtained. The results are shown in Table 3 below. From this, the addition of the known amine compound has the disadvantage that the characteristics are drastically reduced, such as a decrease in sensitivity and a high level of residual potential, whereas the samples 2A to 2C of the present invention have excellent sensitivity and residual potential. It shows that it shows characteristics and also has excellent ozone resistance.

[0050]

[Table 2]

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 5/00 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. An electrophotograph comprising: (1) a photosensitive layer containing at least a charge generating substance, a charge transporting substance and an amine compound represented by the following general formula (I) on a conductive support. Photoconductor. Embedded image (However, n represents any integer of 0 to 6.
R ₁ and R ₂ each represent a hydrogen atom, an alkyl group, or an aralkyl group, and the alkyl group and the aralkyl group may have a substituent. However, this excludes those in which both R ₁ and R ₂ are hydrogen atoms. A ₁ and A ₂ each represent an aryl group, a heteroaryl group or a cycloalkyl group, and these may have a substituent. )