JPH1152601A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably obtain high image quality without electrostatic charge and residual potential being influenced by environmental change by containing a metal complex or metal salt of aromatic carboxylic acid in an under-coating layer. SOLUTION: A monolayer type electrophotographic photoreceptor is composed of a conductive base body 1, an under-coating layer 2, a charge generating layer 3, a charge transport layer 4 and a photosensitive layer 6. Metal such as aluminium, nickel or stainless steel is used as the conductive base body 1. The under-coating layer 2 contains a metal complex or metal salt of aromatic carboxylic acid, and binder resin. An alkyl group, an aryl group, an aryloxyl group or the like is used as aromatic carboxylic acid. Metal forming the metal complex or metal salt of aromatic carboxylic acid is not particularly limited, but Al, Ni, Sn or the like can be used. Polyvinyl butyral, polyvinyl alcohol, polyvinyl acetate or the like is used as the binder resin used for the under- coating layer 2.

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 having an improved undercoat layer, and more particularly to an electrophotographic photosensitive member having an undercoat layer which is not affected by environmental humidity.

[0002]

2. Description of the Related Art An electrophotographic photoreceptor basically has a structure in which a photosensitive layer is provided on a conductive base body. To cover surface defects of the conductive substrate, prevent charge injection from the conductive substrate to the photosensitive layer, and the like, provide an undercoat layer in which a resin or an inorganic filler is dispersed in a resin between the conductive substrate and the photosensitive layer. That is being done.

The undercoat layer is required to have the above-mentioned performance and at the same time, to have a low electric resistance so as not to adversely affect the electrophotographic characteristics.
Alternatively, it is necessary that the charging potential, the residual potential, and the sensitivity characteristics are stable against changes in the environment in which the device is used.
When dispersing an inorganic filler to prevent interference of laser light or to adjust the electric resistance of the undercoat layer, unevenness defects due to aggregation of the inorganic filler and pinholes at the time of forming a coating film, etc. No smooth surface is required.

On the other hand, in an electrophotographic process, when applying a so-called contact charging method in which a charging member to which a voltage is applied is brought into direct contact with the surface of a photoreceptor to uniformly charge the surface of the photoreceptor, the undercoat layer is charged with a charging voltage. It is necessary that the photosensitive layer has an appropriate withstand voltage and does not cause image defects due to electrical destruction of the photosensitive layer. As a resin used for the undercoat layer, for example, a resin such as a cellulose resin, a polyamide resin, a polyvinyl alcohol resin, or a polyester resin is known. In particular, when used in a low-temperature and low-humidity environment, the electric resistance of the undercoat layer becomes extremely high, which causes a decrease in image density and background contamination. When the thickness of the undercoat layer is increased in order to sufficiently cover defects on the surface of the conductive substrate or to adjust the withstand voltage, the same decrease in sensitivity and increase in residual potential occur. Can not be used with

As a method for preventing these problems and adjusting the electric resistance of the undercoat layer, the undercoat layer contains, for example, a metal powder such as Al or Ni or a conductive metal oxide such as indium oxide, tin oxide or zinc oxide. A method, a method of containing an electron conductive polymer such as polypyrrole and polyaniline, and a method of containing an ion conductive polymer represented by polyamide have been proposed.

[0006]

However, when dispersing metal powder or conductive metal oxide, it is technically difficult to uniformly disperse the filler. When the above-mentioned electronic conductive polymers are used, problems remain in their solubility, pot life of the coating solution, and the like. When a solvent-soluble polyamide is used as the ionic conductive polymer, the initial electric characteristics can be adjusted appropriately because the electric resistance is relatively low as compared with other resins, but the environment to be used because the polyamide has a very high hygroscopicity is used. It is susceptible to changes, especially atmospheric humidity, and environmental stability becomes a problem. On the other hand, in a layer configuration in which a photosensitive layer is provided on a conductive substrate via an undercoat layer, the photosensitive layer is often formed by a dip coating method or a spray coating method. Depending on the type, the undercoat layer may be dissolved or deteriorated, causing potential unevenness or image unevenness due to coating film unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to form an undercoat layer having a high ionic conductivity and an ionic conductivity which is not affected by changes in environmental humidity. An object of the present invention is to provide a photoconductor for electrophotography in which a contact charging type electrophotographic process can be applied by increasing the film thickness and the electric characteristics are stable.

[0008]

According to the present invention, there is provided an electrophotographic photosensitive member comprising a conductive substrate and an undercoat layer and a photosensitive layer sequentially provided on the conductive substrate, wherein the undercoat layer comprises an aromatic carboxylic acid. This is achieved by including a metal complex or a metal salt and a binder resin. In the above invention, it is effective that the binder resin is a thermosetting resin or that the undercoat layer contains titanium oxide surface-treated with a silane coupling agent.

The metal complex or metal salt of the aromatic carboxylic acid dissolves in the binder resin and dissociates to generate ions, and the undercoat layer becomes ionic conductive. This ionic conductivity is unaffected by environmental humidity changes. The conductive mechanism of a conventional undercoat layer using only a resin is ionic conductivity due to moisture absorption of the resin, which is different from that in a low humidity environment in which conductivity is greatly reduced and sensitivity is reduced. When the conductivity is adjusted with a conductive filler, coating film defects due to aggregation of the filler are likely to occur, but the undercoat layer of the present invention is a solution in which a metal complex or metal salt of an aromatic carboxylic acid is dissolved in a binder resin. The type does not cause such a problem.

When the binder resin of the undercoat layer is a thermosetting resin, the undercoat layer does not dissolve when the photosensitive layer is applied on the undercoat layer. Titanium oxide surface-treated with a silane coupling agent has good dispersibility.

[0011]

FIG. 1 is a sectional view showing a negatively-charged function-separated type electrophotographic photosensitive member according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a positively-charged function-separated type electrophotographic photoconductor according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view showing a mainly positively charged single-layer type electrophotographic photosensitive member according to an embodiment of the present invention. 1 is a conductive substrate, 2 is an undercoat layer, 3 is a charge generation layer,
4 is a charge transport layer, 5 is a surface protective layer, and 6 is a photosensitive layer.
Aluminum, nickel, chromium,
Applying or impregnating a metal such as stainless steel, a plastic film provided with a thin film such as aluminum, titanium, nickel, chromium, stainless steel, gold, vanadium, tin oxide, indium oxide, ITO, or a conductivity imparting agent Paper, plastic, etc. are used. These conductive substrates are used in the shape of a drum, sheet, plate, or the like, but are not limited thereto. Further, if necessary, the surface of the conductive substrate is subjected to an oxidizing treatment, a chemical treatment, a coloring treatment, or an irregular reflection treatment such as sandblasting.

The undercoat layer provided on the conductive substrate is used for (1) blocking charge injection from the conductive substrate, (2) not causing a change in electric resistance due to an environmental change, and (3) repeated use. In such a case, electrical characteristics such as not causing accumulation of electric charge, (4) having an appropriate withstand voltage with respect to a charging voltage and not causing dielectric breakdown, are required, and (5) scattering of reflected light. (6)
It is necessary to cover the surface defects of the conductive substrate.

The binder resin used in the undercoat layer of the present invention includes polyvinyl butyral, polyvinyl alcohol, polyvinyl acetate, polyacrylate,
Thermoplastic resins such as polymethacrylic acid ester, polyester, polyamide, polystyrene, and polycarbonate, and thermosetting resins such as polyurethane resin, phenolic resin, epoxy resin, and melamine resin can be used alone or in combination. . In particular, when the photosensitive layer is applied by an immersion method after the formation of the undercoat layer, the undercoat layer may be dissolved or deteriorated depending on the type of the solvent used for the photosensitive layer. It is preferable to use it or to make it insoluble or hardly soluble in a solvent.

For the undercoat layer, a metal complex or metal salt of an aromatic carboxylic acid is used. Examples of the aromatic carboxylic acid include alkyl, aryl, aryloxyl, arylcarboxyl, aryloxycarboxyl, carboxyl, alkylcarbonyl, alkoxycarbonyl, hydroxyl, nitro, cyano, and halogen atoms. Substituted or unsubstituted benzene,
Examples thereof include aromatic carbocyclic carboxylic acids such as naphthalene and anthracene, and aromatic heterocyclic carboxylic acids such as the above-mentioned substituted or unsubstituted carbazole.
The metal forming the metal complex or metal salt of the aromatic carboxylic acid is not particularly limited.
i, Sn, Zn, Cr, Co, Fe and the like. An example of a metal salt of an aromatic carboxylic acid is bis (3,3,3), which is synthesized from sodium tert-butylsalicylate and zinc chloride.
Zinc 5-di-tert-butylsalicylate is shown in chemical formula (1).

[0016]

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The undercoat layer of the present invention has a thickness of, for example, 5
Even when the thickness is from 10 μm to 10 μm, the sensitivity does not decrease and the residual potential does not increase, so that the film can be made thicker than before, and the surface defects of the support can be sufficiently covered, and at the same time, the pressure resistance becomes high. Therefore, even in an electrophotographic apparatus to which the contact charging method is applied, dielectric breakdown can be prevented. The amount of the metal complex or metal salt added to the binder resin is 0.1
The content is from 30 to 30% by weight, preferably from 1 to 10% by weight, but is appropriately determined depending on the electric resistance required for the undercoat layer and the compatibility with the binder resin.

When such an undercoat layer is used in an electrophotographic apparatus using laser light as a light source, it is necessary to prevent printing defects caused by interference between incident light and reflected light. It is desirable to include an inorganic filler such as a substance, and among them, a titanium oxide pigment is effective in terms of hiding properties and a refractive index. In addition, depending on the binder resin and solvent used, minute image defects due to aggregation of the filler may occur. Therefore, it is preferable to improve the dispersibility by treating the surface of the filler with a silane coupling agent. Examples of the silane coupling agent include vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltrisilane. Ethoxysilane,
γ-mercaptopropyltrimethoxysilane, β-3,
4-epoxycyclohexyltrimethoxysilane and the like, and the treatment amount for the filler is 0.5 to
5% by weight is suitable.

The average particle size of the filler is 0.4 μm.
m is preferable, and when it exceeds 0.4 μm, the filler causes aggregation and causes image defects such as minute black spots. In order to cause scattering of laser light, a particle diameter of about half of the light wavelength (0.4 to 0.8 μm) is preferable,
It is desirable to use particles of about 0.2 to 0.4 μm.
The amount of the filler is 50 to 3 with respect to the binder resin.
00% by weight is good. If it is less than 50%, the light scattering effect is insufficient, and if it exceeds 300%, image failure due to charge reduction occurs, and filler coagulation and sedimentation in the coating liquid tend to occur, shortening the pot life.

The charge generation layer uses organic pigments such as azo pigments, phthalocyanine pigments, disazo pigments, indigo pigments, perylene pigments and the like, and inorganic pigments such as selenium powder, amorphous silicon powder and zinc oxide powder. These pigments can be formed by dispersing these pigments in a binder resin solution such as polyester, polycarbonate, polyvinyl butyral, etc., applying this on an undercoat layer, and drying. The thickness of the charge generation layer is suitably about 0.1 to 2 μm.

The charge transporting layer is formed by dissolving a charge transporting substance such as a hydrazone compound, a styryl compound or an amine compound in a suitable solvent together with a resin compatible with these substances, for example, polyester, polycarbonate, polystyrene, styrene acrylate, etc. This is deposited on the charge generation layer with a thickness of 5
It is obtained by coating and drying to about 40 μm.

[0022]

Next, an embodiment of the present invention will be described with reference to the drawings. Example 1 60 parts by weight of blocked isocyanate (manufactured by Sumitomo Bayer, Dismodur CT Stable) and 40 of acrylic polyol (manufactured by Sumitomo Bayer, Dismodur A165)
Parts by weight dissolved in 300 parts by weight of tetrahydrofuran, and a titanium oxide treated with γ-aminopropyltrimethoxysilane (TA-20 manufactured by Fuji Titanium Industry Co., Ltd.)
0) 100 parts by weight and 3 parts by weight of a zinc salt of an aromatic carboxylic acid represented by the chemical formula (1) were put into a ball mill pot, and ball-milled with alumina balls of 10 mmφ for 48 hours to prepare an undercoat layer coating solution. .

[0023]

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This coating solution was dipped and applied to the surface of an aluminum cylindrical conductive substrate having an outer diameter of 30 mmφ.
After drying at 0 ° for 30 minutes, an undercoat layer having a thickness of 5 μm was formed. Next, 1 part by weight of a polyvinyl butyral resin (ESREC BL-S manufactured by Sekisui Chemical Co., Ltd.) was added to tetrahydrofuran 98
The resulting solution was added with 1 part by weight of an X-type metal-free phthalocyanine, and dispersed in a ball mill for 48 hours. The obtained coating solution is dipped on the undercoat layer and dried at 100 ° C. for 10 minutes to form a film having a thickness of about 0.2 μm.
m of the charge generation layer was formed.

Further, a hydrazone compound (manufactured by Anan Kofu, C
TC191) 10 parts by weight and 10 parts by weight of a polycarbonate resin (L-1225 manufactured by Teijin Chemicals)
The solution was uniformly dissolved in parts by weight, coated on the charge generation layer in the same manner as described above, and dried at 100 ° C. for 30 minutes to form a charge transfer layer having a thickness of 25 μm. Example 2 A photoconductor was prepared in the same manner as in Example 1, except that the metal salt used in Example 1 was replaced with an aluminum complex of an aromatic carboxylic acid represented by the chemical formula (2).

[0026]

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Example 3 A photoconductor was prepared in the same manner as in Example 1, except that a chromium salt of an aromatic carboxylic acid represented by the chemical formula (3) was used instead of the metal salt used in Example 1.

[0028]

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Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that no metal complex or metal salt was added. The photoconductor characteristics of each photoconductor produced in this manner were evaluated. FIG. 4 is a schematic view showing a photoreceptor process tester used for evaluating the photoreceptor characteristics. Photoreceptor 11 was mounted on a tester, and the peripheral speed was 60 mm / s.
, And charged to about -600 V by the corotron 14, and the dark portion potential (charge potential) is given by the potential when no light is irradiated.
And Subsequently, light having a wavelength of 780 nm and an irradiance of ² μw / cm ² was irradiated using the exposure unit 12 and the probe 13,
The potential after 2 seconds was defined as a bright portion potential (residual potential), and the charge on the photoreceptor was removed using a filter 15 and a light elimination light source 16. The cycle of charging and exposure was repeated 100,000 times, and the fluctuation amount of the dark part potential and the light part potential was measured. Table 1 shows the measurement results.

[0030]

[Table 1]

As is clear from the results in Table 1, Examples 1 to 3
It can be seen that the photoreceptor of the present invention does not increase the residual potential even after 100,000 cycles, and has very excellent performance.

[0032]

According to the present invention, since the undercoat layer contains a metal complex or metal salt of an aromatic carboxylic acid and a binder resin, the charge, residual potential and sensitivity are not affected by changes in the environment in which they are used. High image quality can be obtained stably. In addition, since the binder resin is a thermosetting resin, it has sufficient solvent resistance to the solvent of the photosensitive layer coating liquid applied on the undercoat layer, and also has strong adhesion between the conductive substrate and the photosensitive layer. can do.

Further, since the undercoat layer contains titanium oxide having a good dispersibility and surface-treated with a silane coupling agent, image defects due to light interference can be prevented even in an electrophotographic apparatus using laser light as a light source. effective. Even if the thickness of the undercoat layer is set to be large, the residual potential is low and no charge is accumulated even when the undercoat layer is used repeatedly. Therefore, the surface defect of the conductive substrate is sufficiently covered by the thickness of the undercoat layer. Thus, the cost of processing and cleaning the surface of the conductive substrate can be significantly reduced. In addition, since it has a high withstand voltage with respect to a charging potential, an image defect caused by dielectric breakdown can be prevented particularly when a contact charging method is used.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a negatively-charged function-separated type electrophotographic photoconductor according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view showing a positively-charged function-separated type electrophotographic photoconductor according to an embodiment of the present invention;

FIG. 3 is a sectional view showing a positively charged single-layer type electrophotographic photoreceptor according to an embodiment of the present invention;

FIG. 4 is a schematic diagram showing a photoconductor process tester used for evaluating photoconductor characteristics.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 charge generation layer 4 charge transport layer 5 surface protection layer 6 photosensitive layer 11 photosensitive member 12 exposure unit 13 probe 14 corotron 15 filter 16 light-eliminating light source

Claims (3)

[Claims] 1. An electrophotographic photoreceptor comprising an undercoat layer and a photosensitive layer sequentially provided on a conductive substrate, wherein the undercoat layer contains a metal complex or metal salt of an aromatic carboxylic acid and a binder resin. A photoconductor for electrophotography, comprising: 2. The electrophotographic photoconductor according to claim 1, wherein the binder resin is a thermosetting resin. 3. The electrophotographic photosensitive member according to claim 1, wherein the undercoat layer contains titanium oxide surface-treated with a silane coupling agent.