JPH08160647A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE: To provide a photoreceptor having a good undercoating layer having a good electric characteristic and no carrier injection by containing a polyvinyl acetal resin having specific component units in the undercoating layer. CONSTITUTION: This electrophotographic photoreceptor is provided with an undercoating layer and a photosensitive layer on a conducting base, and the undercoating layer contains a polyvinyl acetal resin having the component units expressed by the formulas I and II, where R1 indicates hydrogen, methyl group, or ethyl group, and R2 indicates the saturated or unsaturated aliphatic hydrocarbon group having the carbon number of 3-7. An insulating base of a polyester film, paper, or glass provided with a conductive layer of aluminum, copper, palladium, tin oxide, or indium oxide on the surface of a metal material such as aluminum, stainless steel, copper, or nickel is used for the conducting base, for example. The photoreceptor using such a binder as the undercoating layer has a good blocking property for the carrier injection from an electrode, and it has an electrification characteristic excellent in uniformity.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor. More specifically, it relates to an electrophotographic photoreceptor using a specific undercoat layer.

[0002]

2. Description of the Related Art Electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers in recent years because of its ability to obtain images of instant quality and high quality. Photoreceptors, which are the core of electrophotographic technology, have recently been formed as pollution-free inorganic photoconductors such as selenium, arsenic-selenium alloy, cadmium sulfide, and zinc oxide. A photoreceptor using an organic photoconductive material, which has advantages such as easy and easy manufacture, has been developed.

Among organic photoconductors, a so-called laminated type photoconductor in which a charge generation layer and a charge transfer layer are laminated has been devised and is the mainstream of research. The multi-layered photoconductor is such that a highly sensitive photoconductor can be obtained by combining a highly efficient charge generation substance and a charge transfer substance, and a photoconductor having a wide selection range of materials and high safety can be obtained. Further, since the coating productivity is high and the cost is comparatively advantageous, the possibility of becoming the mainstream of the photoreceptor is high and the coating has been earnestly developed. In general, an electrophotographic photosensitive member is formed by providing such a photosensitive layer on a conductive substrate such as aluminum, but the substrate surface has a great influence when used in an actual electrophotographic process. For example, stains, foreign matter, scratches, etc. existing on the surface of the substrate more or less affect the electrical characteristics and eventually appear as image defects. In order to remove such defects on the surface of the substrate as much as possible, it is necessary to perform secondary processing such as cutting and mirror polishing, which leads to an increase in the cost of the photosensitive member, and precise cleaning. On the other hand, it is known as a known technique to provide an undercoat layer between the substrate and the photosensitive layer as a means for obtaining a uniform and clean substrate surface without going through such steps.

Examples of the undercoat layer include an anodized aluminum film, an inorganic layer such as aluminum oxide and aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, melamine. Organic layers such as resins, phenolic resins and polyamides, or those in which metal oxides or fine metal powders are dispersed using these resins as binders are known.

[0005]

The characteristics required for the undercoat layer are, first of all, the electrical characteristics. That is, it is necessary not to affect the electrophotographic characteristics such as sensitivity, chargeability and dark decay. For this purpose, it is necessary that the electric resistance is low and that the electric resistance does not change extremely with respect to changes in the external environment. It is also necessary that there is no carrier injection property to the photosensitive layer. The use of an undercoat layer having a carrier injecting property with respect to the photosensitive layer reduces the charging potential, resulting in a reduction in image contrast and fog. Furthermore, various defects on the surface of the substrate are coated within a range that does not impair the electrical characteristics of the photoconductor, so that it is also necessary to make the film thickness as thick as possible. Under the present circumstances, for example, the undercoating layer known so far is not always satisfied with such required characteristics.

[0006]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made earnest studies on an undercoating material that can satisfy the required properties of the above-mentioned undercoating layer. As a result, an undercoating layer using a specific binder resin is very effective. The present invention has been accomplished by finding that the undercoat layer can be provided with good productivity. That is, the gist of the present invention is an electrophotographic photosensitive member comprising an electroconductive substrate on which at least an undercoat layer and a photosensitive layer are provided, wherein the undercoat layer contains structural units of the following general formulas (c) and (d). An electrophotographic photosensitive member characterized by containing a polyvinyl acetal resin.

[0007]

Embedded image

In (c) and (d), R ₁ represents hydrogen, a methyl group or an ethyl group, and R ₂ has 3 to 10 carbon atoms.
7 represents a saturated or unsaturated aliphatic hydrocarbon group. )

The present invention will be described in detail below. The photoconductor of the present invention is provided on a conductive substrate. As the conductive substrate, for example, metal materials such as aluminum, stainless steel, copper, nickel, aluminum, copper, palladium on the surface,
An insulating substrate such as a polyester film provided with a conductive layer of tin oxide, indium oxide or the like, paper, glass or the like is used. Among them, an endless pipe made of metal such as aluminum is a preferable substrate.

The undercoat layer of the present invention is provided between the conductive substrate and the photosensitive layer. For the undercoat layer in the present invention, a polyvinyl acetal resin containing the above general formulas (c) and (d) as a constituent unit is used as a binder resin. Specifically, a polyvinyl acetal resin having the following general formulas (a) to (d) as a constitutional unit is used.

[0011]

Embedded image

In the general formulas (a) to (d), (a),
The existing molar ratios of (b), (c) and (d) are respectively m,
0.1 mol% ≦ m ≦ 20mo when n, p, and q
1%, 10 mol% ≦ n ≦ 40 mol% 40 mol% ≦ p + q ≦ 85 mol%, p:
Although q is preferably in the range of 1:99 to 99: 1, 0.1 mol% ≦ m ≦ 10 mol% and 10 mo
1% ≦ n ≦ 30 mol%, 40 mol% ≦ p + q ≦ 70
Within the range of mol%, p: q is 30:70 to 70:30.
Is more preferably in the range. R ₁ represents hydrogen, a methyl group or an ethyl group, and R ₂ represents a saturated or unsaturated aliphatic group having 3 to 7 carbon atoms. Among them, R ₁ is preferably a methyl group or an ethyl group, and R ₂ is preferably a saturated or unsaturated aliphatic hydrocarbon group having 4 to 6 carbon atoms.

The solution viscosity of this polyvinyl acetal resin is 10 in a 5% solution of ethanol: toluene = 1: 1.
~ 300 cps, preferably 20-200 cps is suitable for coating. In the undercoat layer in the present invention, the binder resin may be used alone, but in combination with other binder resins, or in order to further stabilize the electrical characteristics, a known metal or metal oxide fine powder, It is more preferable to add and use an organic pigment or an inorganic pigment.

As the other binder resin, for example, polyvinyl alcohol, sodium caseinate, polyvinylpyrrolidone, polyacrylic acid, methyl cellulose, nitrocellulose, polyvinyl acetal, gelatin, starch, phenoxy, epoxy, polyurethane, polyimide, polyamide resin or the like is used alone or cured. Can be used in a cured form with the agent.

Among them, alcohol-soluble copolymerized poiamide, modified polyamide, phenoxy, epoxy resin and the like are preferable because they show good dispersibility and coatability. When another resin is mixed and used, it is preferably used in the range of 20 to 200 parts by weight with respect to 100 parts by weight of the binder resin according to the present invention. Known metal or metal oxide fine powders that may be added include, for example, aluminum, copper, tin, zinc, titanium, titanium oxide, zinc oxide, copper oxide, iron oxide, aluminum oxide, silicon oxide, tin oxide, and oxide. Indium or the like can be used. Among them, it is preferable to use aluminum oxide, silicon oxide, titanium oxide, tin oxide and the like. More preferably, when aluminum oxide particles are used by being dispersed in the binder resin of the present invention, it is possible to obtain a good image free from initial fog and fine black spots, especially in the reversal development process. As the inorganic pigment, calcium carbonate, barium sulfate, calcium sulfate, magnesium carbonate and the like, as the organic pigment, a phthalocyanine pigment,
Azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, benzimidazole pigments and the like can be used. Out of these, for example, better results can be obtained when a phthalocyanine pigment, an azo pigment, a perylene pigment, etc. are used in combination.

More specifically, for example, Japanese Patent Laid-Open No. 63-195.
No. 657, Japanese Patent Publication No. 61-30265, and Japanese Patent Laid-Open No. 62-6.
The pigments described in JP-A No. 7094 and JP-A No. 62-119547 can be used. When these particles are added to the binder resin according to the present invention and used, the amount is 20 parts by weight to 300 parts by weight based on 100 parts by weight of the binder resin.
It is preferable to use in the range of parts by weight, and further 40
More preferably, it is from 200 to 200 parts by weight.

The thickness of the undercoat layer is from 0.05 μm to 20 μm.
Most preferably, it is used in the range of m, preferably 0.05 μm to 10 μm, more preferably 0.05 μm to 5 μm. Next, a photosensitive layer is formed on such an undercoat layer, and as the photosensitive layer, a dispersion type or laminated type photoreceptor is formed.

In the case of a laminated type photoreceptor, examples of the charge generating material used in the charge generating layer include selenium and its alloys, cadmium sulfide, and other inorganic photoconductive materials.
Various photoconductive materials such as organic pigments such as phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, and benzimidazole pigments can be used, particularly organic pigments, and further phthalocyanine pigments, azo pigments Is preferred. For example, polyester particles, polyvinyl acetate,
Polyacrylic acid ester, polymethacrylic acid ester,
It is used in the form of being bound with various binder resins such as polyester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester and cellulose ether. The usage ratio in this case is 30 with respect to 100 parts by weight of the binder resin.
To 500 parts by weight, and the film thickness is usually 0.1 μm to 1 μm, preferably 0.15 μm to 0.6 μm.

Examples of the charge transfer material of the charge transfer layer include electron-withdrawing substances such as 2,4,7-trinitrofluorenone and tetracyanoquinodimethane, carbazole, indole, imidazole, oxazole and pyrazole.
Heterocyclic compounds such as oxadiazole, pyrazoline, thiadiazole, aniline derivatives, hydrazone compounds,
Examples thereof include an electron-donating substance such as an aromatic amine derivative, a stilbene derivative, or a polymer having a group composed of these compounds in its main chain or side chain. A low molecular weight compound that is not a polymer is particularly preferable. A binder resin is blended with these charge transfer materials as needed. Examples of preferred binder resins include vinyl polymers such as polymethylmethacrylate, polystyrene, polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, phenoxy, epoxy, silicone resin, and the like. These partially crosslinked cured products can also be used.
Further, the charge transfer layer may contain various additives such as an antioxidant and a sensitizer, if necessary. The thickness of the charge transfer layer is 10 to 50 μm, preferably 10 to 40 μm.

In the case of the dispersion type, the above-mentioned charge generation material and charge transfer material are used in the form of being bound by a binder resin such as polyester resin, polyvinyl acetate, polyacrylic acid ester, polymethacrylic acid ester, polyester, polycarbonate or the like. It In this case, it is preferable to use the charge generating material in an amount of 1 to 50 parts by weight and the charge transfer material in an amount of 30 to 150 parts by weight with respect to 100 parts by weight of the binder resin. The film thickness is usually 5 to 50 μm,
It is preferably 10 to 30 μm. If necessary, various additives such as antioxidants and sensitizers may be included.

[0021]

The photoconductor using the binder of the present invention as the undercoat layer exhibits a good blocking property against the injection of carriers from the electrodes, and therefore exhibits excellent characteristics of uniform charging. Therefore, the occurrence of image defects such as minute black spots and initial fog, which are often problems especially in the reversal phenomenon process, are hardly seen even in a wide environment from low temperature low humidity to high temperature high humidity, and a stable image can always be obtained. . Therefore, the photoconductor according to the present invention can be widely used not only in copying machines but also in laser printers, digital copiers, digital color copiers, and the like. Further, when various powders such as metal oxides are used by being dispersed in the present binder, the dispersion stability is excellent, the dispersion liquid can be easily managed, and the dispersion liquid can be applied to the substrate with excellent productivity. Furthermore,
In addition, since the electric resistance of the undercoat layer has little humidity dependency, it shows stable electric characteristics with little residual potential accumulation even when it is repeatedly used in low humidity.

[0022]

The present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the invention is not limited thereto. Production Example-1 Polyvinyl alcohol (AH manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)
-22) 15 g was dispersed in 1,4-dioxane 300 mL, and n-butyraldehyde 2.3 g and acetaldehyde 5.6 g were added. Next, after adding 0.5 g of 35% hydrochloric acid, the temperature was raised to 80 ° C. and the reaction was carried out at the same temperature for 4 hours. Then, after cooling to room temperature, 200 mL of 1,4-
Dioxane was added to dilute, and unreacted polyvinyl alcohol was separated and removed by filtration under reduced pressure. Next, the polymer solution obtained here was dropped into 4 L of demineralized water over 2 hours to precipitate a polymer. Subsequently, it was separated by vacuum filtration, washed thoroughly with demineralized water, and then dried under reduced pressure at 60 ° C. for 24 hours to obtain 14 g of a polyvinyl acetal resin. This polymer is P
VB / A-1.

The PVB / A-1 obtained as described above was dissolved in a mixed solution of toluene / ethanol = 50/50 wt% to prepare a 5% solution. The solution viscosity of this polymer solution was measured with a rotational viscometer (EMD type manufactured by Tokyo Keiki Co., Ltd.) and found to be 92 centipoise. Next, the H ¹ -NMR of PBV / A-1 was measured. As a result, the molar ratio of butyral to acetal was 1/1.
(Q: p). Next, the composition ratio of the hydroxyl group and the acetyl group was measured by the titration method to find that each was 22 mol%
(N) was 3 mol% (m).

Example 1 8% PVB / A-1 mixed alcohol (methanol / n
-Propanol = 70/30) A mixed alcohol dispersion liquid (solid content: 8 wt) of aluminum oxide (manufactured by Nippon Aerosil Co., Ltd., aluminum oxide-C, average particle diameter of primary particles: 20 nm) previously dispersed by ultrasonic waves in 10 parts by weight of the solution.
%) 5 parts by weight and further subjected to dispersion treatment by ultrasonic waves to prepare an undercoat layer coating solution.

Next, this undercoat layer coating solution was applied onto a polyester film having aluminum vapor-deposited on it by a wire bar so that the film thickness after drying would be 0.2 μm. Next, oxytitanium phthalocyanine (10 parts by weight) and polyvinyl butyral (Sekisui Chemical Co., Ltd. Eslec BH-3) (5 parts by weight) were added with 1,2-dimethoxyethane (500 parts by weight), and the mixture was pulverized and dispersed by a sand grind mill. It was This dispersion was applied onto the undercoat layer with a wire bar so that the film thickness after drying was 0.4 μm.

[0026]

[Chemical 4]

And 100 parts by weight of a polycarbonate resin (Novarex 7030A manufactured by Mitsubishi Kasei Co., Ltd.).
700 parts by weight of 4-dioxane and tetrahydrofuran 3
A liquid dissolved in 00 parts by weight of a mixed solvent was applied, and a charge transfer layer was provided so that the film thickness after drying was 17 μm. A belt-shaped photosensitive member A was prepared by fusing the end portions of the sheet-shaped photosensitive member thus obtained.

Example-2 A belt-shaped photosensitive member B was prepared in the same manner as in Example-1, except that the thickness of the undercoat layer was changed to 0.5 μm in Example-1. Comparative Example-1 A belt-shaped comparative photoreceptor C was prepared in the same manner as in Example-1, except that the undercoat layer was not provided in Example-1.

Each of the photoconductors prepared as described above was mounted on a commercially available reversal development type color printer, and was subjected to normal temperature and normal humidity (25 ° C., 60%) and high temperature and high humidity (35 ° C., 85%).
%) Was used for image evaluation. For image evaluation, the degree of initial fog and minute black spots in a white background image were compared. The results are shown in Table 1. In the photoreceptor of the present invention, initial fog and fine black spots were at a good level without any problems under any conditions.

[0030]

[Table 1]

Example 4 8% PVB / A-1 mixed alcohol (methanol / n
-Propanol = 70/30) A mixed alcohol dispersion liquid (solid content: 8 wt) of aluminum oxide (manufactured by Nippon Aerosil Co., Ltd., aluminum oxide-C, average particle diameter of primary particles: 20 nm) previously dispersed by ultrasonic waves in 10 parts by weight of the solution.
%) 10 parts by weight and further subjected to dispersion treatment by ultrasonic waves to prepare an undercoat layer coating solution.

The coating liquid for undercoat layer thus prepared had an outer diameter of 30 mm, a wall thickness of 0.75 mm and a length of 254 mm.
The aluminum cylinder of No. 2 was dipped and an undercoat layer was provided so that the film thickness after drying was 0.2 μm. Next, a charge generation layer and a charge transfer layer similar to those in Example-1 were formed on this undercoat layer to prepare a drum-shaped photoreceptor D. At the same time, a drum-shaped photoreceptor E having the same composition and a charge transfer layer having a thickness of 13 μm is used.
Also created.

Example 5 PVB / A-1 8% mixed alcohol (methanol / n
-Propanol = 70/30) A mixed alcohol dispersion liquid (solid content: 8 wt) of aluminum oxide (manufactured by Nippon Aerosil Co., Ltd., aluminum oxide-C, average particle diameter of primary particles: 20 nm) previously dispersed by ultrasonic waves in 10 parts by weight of the solution.
%) 15 parts by weight and further subjected to dispersion treatment by ultrasonic waves to prepare an undercoat layer coating solution.

The coating liquid for the undercoat layer thus prepared had an outer diameter of 30 mm, a wall thickness of 0.75 mm and a length of 254 mm.
The aluminum cylinder of No. 2 was dipped and an undercoat layer was provided so that the film thickness after drying was 0.2 μm. Next, a charge generation layer and a charge transfer layer similar to those in Example-1 were formed on this undercoat layer to prepare a drum-shaped photoreceptor F. At the same time, a drum-shaped photoreceptor G having the same composition and a charge transfer layer thickness of 13 μm
Also created.

Comparative Example-2 The procedure of Example-4 was repeated except that the undercoat layer was not provided.
A drum-shaped comparative photoconductor H having a thickness of μm and a comparative photoconductor I having a thickness of 13 μm were prepared. These photoconductors D to I were mounted on a commercially available laser printer, and image fog was evaluated in each environment shown in Table 2. As a result, the comparative photoconductor H having no undercoat layer could not obtain a good image in all environments, and the comparative photoconductor I could not obtain a good image under the normal temperature and normal humidity condition. On the other hand, with the photoreceptors of the present invention, good images free from fog were obtained in all environments.

[0036]

[Table 2]

Example 6 150 parts by weight of 10 parts by weight of an azo compound having the following structure
4-methoxy-4-methylpentanone-2,
It was crushed and dispersed by a sand grind mill. this
The thus-obtained pigment dispersion is mixed with polyvinyl butyral.
Acetal resin (presence ratio of general formulas (a) to (d))
m, n, p, and q are m = 2 mol%, n = 38 mol%,
p = 30 mol%, q = 30 mol%, R₁= H, R₂
= C₃H ₇) 5% dimethoxyethane solution 100 parts by weight
And phenoxy resin (made by Union Carbide, trade name
PKHH) of 5% dimethoxyethane solution of 100 parts by weight
In addition to the mixed solution, finally apply an undercoat layer with a solid content of 4%
A liquid was created. The surface of the undercoat layer coating solution is mirror finished.
80 mm outer diameter, 348 mm long, 1 mm thick
Film after aluminum cylinder dip coating and drying
An undercoat layer was provided so as to have a thickness of 0.6 μm.

[0038]

Embedded image

Next, an azo compound 1 having the structure of the following formula 1
0 parts by weight was added to 150 parts by weight of 4-methoxy-4-methylpentanone-2, and the mixture was pulverized and dispersed by a sand grind mill. 100% by weight of a 5% dimethoxyethane solution of polyvinyl butyral acetal resin (manufactured by Denki Kagaku Kogyo KK, trade name # 6000C) and a phenoxy resin (trade name, manufactured by Union Carbide Co., Ltd.) PKHH) was added to a mixed solution of 100 parts by weight of a 5% dimethoxyethane solution to finally prepare a charge generation layer coating solution having a solid content concentration of 4%.

An aluminum cylinder provided with the above-mentioned subbing layer was dip-coated with this charge generation layer coating liquid, and the charge generation layer was provided so that the film thickness after drying was 0.4 μm. On this charge generation layer, 110 parts by weight of a hydrazone compound represented by the following formula 2, 0.5 part of a cyano compound having the structure of the following formula 3, and a polycarbonate resin having two repeating structures represented by the following formulas 4 and 5 (ratio: Is 1: 1) 10
A liquid in which 0 part by weight was dissolved in a mixed solvent of 1,4-dioxane and tetrahydrofuran was applied by dip coating to form a charge transfer layer so that the film thickness after drying was 35 μm. The photoconductor thus created is referred to as a photoconductor J.

[0041]

[Chemical 6]

Example-7 A photosensitive member K was prepared in the same manner as in Example-6 except that the thickness of the undercoat layer was changed to 0.72 μm in Example-6. Comparative Example-3 The surface has a mirror-finished outer diameter of 80 mm and a length of 348 m.
m, a 1 mm thick aluminum cylinder, a copolyamide resin ε-caprolactam / adipic acid / 1,
6% mixed alcohol solution of 6-hexamethylenediamine / lauryllactam (composition ratio 46/24/24/30 mol%) (methanol / n-propanol = 70/3)
0% by weight) is applied by dip coating, and the film thickness after drying is 0.1μ
An undercoat layer was provided so as to have m. A charge generation layer and a charge transport layer were formed on this undercoat layer in the same manner as in Example-6. This photoconductor is referred to as comparative photoconductor L. At the same time, a photosensitive layer was formed in the same manner except that the thickness of the undercoat layer was 0.3 μm, and a comparative photoconductor M was also prepared.

The characteristics of the photoreceptor prepared as described above are
Evaluation was carried out as follows using a commercially available copying machine under the conditions of 25 ° C., 60% RH and 5 ° C., 15% RH. First, under the environmental conditions of 25 ° C. and 60% RH, adjust the output of the charger so that the surface potential of the photoreceptor at the developing position becomes −700 V, and then measure the half-exposure sensitivity and residual potential of each photoreceptor. did. Then, the surface potential, the half-exposure sensitivity, and the residual potential under the conditions of 5 ° C. and 15% RH were measured without changing the settings. These results are summarized in Table 3, and the photoconductor using the undercoat layer according to the present invention does not extremely increase the residual potential as compared with the comparative example even under the conditions of 5 ° C. and 15% RH, and is good. It can be seen that it exhibits various characteristics.

[0044]

[Table 3]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hajime Kojima 1060 Narita, Odawara-shi, Kanagawa Mitsubishi Chemical Corporation Odawara Works

Claims (4)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive substrate and at least an undercoat layer and a photosensitive layer provided on the conductive substrate, wherein the undercoat layer contains a constitutional unit represented by the following general formulas (c) and (d). An electrophotographic photoreceptor comprising a resin. Embedded image (In the general formulas (c) and (d), R ₁ represents hydrogen, a methyl group or an ethyl group, and R ₂ represents a saturated or unsaturated aliphatic hydrocarbon having 3 to 7 carbon atoms.) 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a laminated type photosensitive member including a charge generation layer and a charge transfer layer. 3. The electrophotographic photosensitive member according to claim 1, wherein the undercoat layer contains aluminum oxide particles. 4. The electrophotographic photosensitive member according to claim 1, wherein the undercoat layer contains organic pigment particles.