JP2864578B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a transparent substrate, and particularly suitable for exposure from the back side. Things.

[Prior Art] At present, as a conductive substrate for an electrophotographic photosensitive member, a metal substrate such as an aluminum cylinder is mainly used. In recent years, as copiers and printers have become smaller, lighter, and more colorized,
A seamless belt photoreceptor is required.
With the proposal of a process for exposing from the back side of a photoreceptor as disclosed in 61-285470 and JP-A-61-260281, a seamless belt-like photoreceptor having a transparent substrate is required. As a conductive layer used in such a photoreceptor, a layer in which a metal thin film or a metal oxide thin film is provided on the surface of an insulating film by vapor deposition or sputtering is well known.

[Problems to be Solved by the Invention] However, it is difficult to form such a conductive layer on a seamless belt, and when a metal thin film is used, the light transmittance is low, the adhesiveness is insufficient, and the cost is high. The light transmittance is high when a metal oxide thin film is used,
Good adhesion, but more expensive. As the conductive layer, there is a method in which a metal or metal oxide powder is dispersed in a resin and used. JP-A-56-143443 discloses an average particle size of 0.5 μm.
It is stated that a good conductive layer can be obtained by dispersing the conductive metal oxide fine particles of m or less in a resin. However, in this method, the conductivity is insufficient, and when the added amount of the fine particles is increased to increase the conductivity, the light transmittance and the mechanical strength decrease, and further, in the organic photoreceptor in which the charge generation layer and the charge transfer layer are combined, The charge transfer between the charge generation layer and the conductive layer is not performed well, the residual potential in the repetition characteristics increases, and the charge is easily injected from the conductive layer to the charge generation layer in the dark, and the charge potential decreases. Printing defects occur,
In addition, delamination occurs due to poor adhesion between the conductive layer and the photosensitive layer. Further, in the case where an intermediate layer is provided to prevent charge injection into the photosensitive layer, delamination occurs due to poor adhesion between the conductive layer and the intermediate layer.

SUMMARY OF THE INVENTION An object of the present invention is to solve the conventional drawbacks and to provide an electrophotographic photosensitive member having sufficient conductivity, high light transmittance, suitable for backside exposure, high mechanical strength, and stable characteristics.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

That is, the present invention relates to an electrophotographic photoreceptor comprising a transparent support, a transparent conductive layer comprising a conductive powder and a binder resin, an intermediate layer and a photosensitive layer laminated on a transparent support. It is composed of a conductive metal oxide having a diameter of 0.6 to 1.0 μm, and a conductive powder / binder resin has a deposition ratio of 20/80 to 40/60, and the intermediate layer is a resin for forming a core intermediate layer. And 1 to 20% by weight of an organic titanate.

In the present invention, the transparent conductive layer formed on the transparent support is made of a conductive powder and a binder resin, and has a wavelength of 400.
It is preferable that the light transmittance in the entire wavelength range of 900900 nm or a specific wavelength between 400 and 900 nm is 70% or more.

Examples of the conductive powder include ZnO, T having an average particle diameter of 0.6 to 1.0 μm.
A metal oxide such as iO ₂ , SnO ₂ , In ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , Sb ₂ O ₃ or a composite metal oxide thereof is used. If the particle size of the conductive powder is smaller than 0.6 μm, sufficient conductivity cannot be obtained, the charge transfer between the photosensitive layer and the conductive layer is not performed well, and the residual potential increases. In addition, it becomes difficult to obtain surface irregularities described later while maintaining the mechanical strength and the coating properties of the intermediate layer and the photosensitive layer, and the adhesiveness between the conductive layer and the intermediate layer and between the intermediate layer and the photosensitive layer is reduced. Also, when the particle size of the conductive powder is larger than 1.0 μm, the surface irregularities of the conductive layer become large, and coating layer defects of the intermediate layer and the photosensitive layer formed thereon occur, and further, a sufficient light transmittance is obtained. Can not be.

The resistance of the conductive layer and the transfer of electric charge between the photosensitive layer and the conductive layer are determined by the particle size of the transfer powder and the deposition ratio between the conductive powder and the binder resin.

The ratio of conductive powder / binder resin is 20/80 to 40/60 by volume.
So that In this range, the surface of the conductive layer has sea-island-like irregularities of 0.05 to 0.3 μm formed by the conductive powder and the binder resin, and sufficient adhesiveness to the intermediate layer or the photosensitive layer is obtained, and the conductive powder and The contact area between the intermediate layer and the photosensitive layer is large, and the charge transfer between the photosensitive layer and the conductive layer is performed well. If the ratio of the binder resin is larger than this, the conductivity decreases and the conductive powder on the surface of the conductive layer is covered with the binder resin, so that the contact area between the conductive powder and the intermediate layer or the photosensitive layer is reduced, and the photosensitive area is reduced. The charge transfer between the layer and the conductive layer is not performed well, and the residual potential increases.
In addition, when the ratio of the binder resin is small, the irregularities on the surface of the conductive layer become large, and the conductive layer becomes sandy, so that coating layer defects of the intermediate layer and the photosensitive layer are generated, and the mechanical strength is reduced.

As the binder resin, generally known resins can be used.However, epoxy resin, urethane resin, acrylic resin,
Curable resins such as alkyd resins, phenol resins, and melamine resins, polyvinyl alcohol resins, ethyl cellulose resins, polyacrylamide resins, and the like are preferable.

The thickness of the conductive layer is preferably 1 to 10 μm. If the thickness is smaller than this, sufficient conductivity cannot be obtained. On the other hand, when the thickness is large, sufficient light transmittance cannot be obtained, and the mechanical strength is also reduced. The conductive layer thus formed has a surface resistance of 10 ⁵ Ω /
□ The following can be achieved.

The conductive powder and the binder resin are dispersed together with a solvent by an ordinary dispersion method, and the coating liquid is applied on a transparent support, and then dried and, if necessary, cured by heat, ultraviolet light, or an electron beam to conduct the conductive treatment. Form a layer.

Examples of the solvent include those composed of one or more mixed liquids of alcohols, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, halogenated hydrocarbons, esters, and the like, but are not particularly limited. It is not something to be done.

As a dispersing method, a dispersing machine such as a ball mill, a sand mill, a paint shaker, a homogenizer, and an attritor is used.

As the transparent support, any of transparent synthetic resins such as polyester resin, polycarbonate resin, polyketone resin, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polystyrene resin, polyamide polyimide resin, and cellulose resin can be used.

The intermediate layer formed between the photosensitive layer and the transparent conductive layer is for preventing charge injection into the photosensitive layer and stabilizing the characteristics.

An organic titanate is added to the intermediate layer. Thereby, the adhesion between the conductive layer and the photosensitive layer is improved, and the mechanical strength is increased.

As organic titanates, tetraisopropyl titanate, tetra-n-butyl titanate, titanium tetraacetylacetonate, diisopropoxytitanium bisacetylacetonate, tetrakis (2-ethylhexyloxy) titanium, dihydroxybis (lactato) titanium,
Isopropyl triisostearoyl titanate and isopropyl tri (N-aminoethyl-aminoethyl) titanate;

As the addition amount of the organic titanate, the organic titanate is blended in the range of 1 to 20% by weight with respect to the resin used for the intermediate layer. Preferably it is 3 to 10% by weight.

Examples of the resin used for the intermediate layer include polyamide resins, polyvinyl alcohol resins, polyvinyl butyral resins, polyvinyl formal resins, polyurethane resins, casein and cellulose, which are insoluble or difficult to dissolve in aromatic organic solvents used in preparing a coating solution for the photosensitive layer. The one that is soluble is selected.

When the amount of the organic titanate is less than 1% by weight, the adhesiveness is not improved. When the amount is more than 20% by weight, the characteristics become unstable, and particularly the residual potential increases.

The thickness of the intermediate layer is preferably from 0.1 to 1 μm. When the thickness is less than 0.1 μm, charge injection from the conductive layer to the photosensitive layer easily occurs, the characteristics become unstable, and the charging potential is particularly lowered. If the thickness is more than 1 μm, the residual potential increases.

As the photosensitive layer, a laminated organic photoconductor composed of a charge generation layer and a charge transport layer is preferable, and the charge generation layer is a charge generation material such as a disazo pigment, a trisazo pigment, a quinone pigment, an indigo pigment, a perylene pigment, and a phthalocyanine pigment. To
A binder resin such as a polyester resin, a polyester polycarbonate resin and a polyvinyl butyral resin and a dispersion solvent such as dichloroethane, chlorobenzene, cyclohexanone, dioxane, and butanol are dispersed to form an intermediate layer. The thickness is preferably from 0.1 to 1.0 μm.

The charge transport layer is composed of a charge transport material such as a hydrazone compound, a carbazole compound, an oxadiazole compound, an indole compound, and a pyrazoline compound. In the solvent and is formed on the charge generation layer. The film thickness is preferably from 10 to 30 μm.

In the present invention, the average particle size was measured by a particle size distribution analyzer (CAPA-500, manufactured by Horiba, Ltd.). As the measurement conditions, the rotation speed was 2000 rpm, the specific gravity of the coating solution was 0.8 to 1.0,
The specific gravity of the conductive fine powder is 5.0 to 7.0 and the coating liquid viscosity is 2.0 to
The viscosity of the coating solution was measured using a B-type viscometer (BL, manufactured by Tokyo Keiki) using 3.0 cp.

The light transmittance was measured by a self-recording spectrophotometer (UV-260, manufactured by Shimadzu Corporation).

The surface resistance was measured by a surface high resistance meter (“Hiresta”, manufactured by Mitsubishi Yuka).

[Examples] Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

Example 1 100 parts by weight of conductive fine powder of tin oxide containing 12% of antimony oxide (average particle diameter 0.74 μm), 75 parts by weight of acrylic polyol (“Nipporan” 174, manufactured by Nippon Polyurethane Industry), 80 parts by weight of toluene, xylene 80 Parts by weight, ethyl acetate
65 parts by weight were dispersed in a paint shaker for 3 hours, and 6 parts by weight of isocyanate ("Coronate" EH, manufactured by Nippon Polyurethane Industry) was added to the dispersion to obtain a coating liquid. 80μ of this coating liquid
Apply to a m-thick polyethylene terephthalate (PET) seamless belt and heat dry at 120 ° C for 10 minutes to obtain a film thickness of 3.0μ
m, a surface resistance of 4 × 10 ⁴ Ω / □ and a light transmittance of 80.7% were obtained. The volume ratio of this conductive powder / binder resin is 30/70
And the surface unevenness was about 0.1 μm. 4 parts by weight of a polyamide resin (“Amilan” CM8000, manufactured by Toray) and 0.2 parts by weight of diisopropoxytitanium bisacetylacetonate (TC-100, manufactured by Matsumoto Pharmaceutical) (5% by weight based on the polyamide resin) A coating solution dissolved in 100 parts by weight of butanol was applied and dried by heating at 120 ° C. for 10 minutes to provide a 0.3 μm intermediate layer.

Next, 10 parts by weight of a τ-type metal-free phthalocyanine pigment (manufactured by Toyo Ink), 10 parts by weight of polyvinyl butyral resin (“Eslec” BL-1, manufactured by Sekisui Chemical Co., Ltd.) and 150 parts by weight of cyclohexanone are dispersed in a paint shaker for 6 hours. This was applied on the intermediate layer and dried to obtain a 0.3 μm charge generation layer.

Next, 10 parts by weight of 1-phenyl-1,2,3,4-tetrahydroquinoline-6-carbaldehyde-1 ', 1'-diphenylhydrazone and 10 parts by weight of a polyarylate resin (U-100, manufactured by Unitika) were added to dichloroethane. Dissolve in 80 parts by weight,
This was applied on the charge generation layer, and then heated and dried at 80 ° C. for 30 minutes to provide a 20 μm charge transport layer, thereby obtaining an electrophotographic photosensitive member.

Table 1 shows the evaluation results. As is clear from Table 1, the photoreceptor of the present invention has stable electrophotographic characteristics,
There was no increase in residual potential, and the mechanical strength was good, with no delamination between the conductive layer and the intermediate layer and between the intermediate layer and the charge generation layer.

Comparative Example 1 In Example 1, diisopropoxytitanium bisacetylacetonate was not added to the intermediate layer, and the drying conditions were 80 ° C.
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the time was changed to 10 minutes.

The evaluation results are shown in Table 1. The characteristics of this photoreceptor were as good as in Example 1, but the delamination was inferior to Example 1.

Comparative Example 2 Antimony oxide 1 having an average particle size of 0.4 μm in Example 1
A conductive layer was obtained using a conductive powder of tin oxide containing 2%, and diisopropoxytitanium bisacetylacetonate was not added to the intermediate layer.
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the time was changed to 10 minutes. Table 1 shows the evaluation results. The surface resistance of the conductive layer of Comparative Example 1 was 2.0 × 10 ⁶ Ω / □, the light transmittance was 81.5%, and the surface unevenness was 0.05 μm or less. In this photoreceptor, delamination occurred between the conductive layer and the intermediate layer with a slight increase in the residual potential.

Comparative Example 3 Antimony oxide 1 having an average particle size of 1.2 μm in Example 1
A conductive layer is obtained using conductive fine powder of tin oxide containing 2%,
Diisopropoxy titanium bisacetylacetonate was not added to the intermediate layer, and the drying conditions when forming the intermediate layer were 80 ° C.
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that -10 minutes was used. Table 1 shows the evaluation results.

The surface resistance of the conductive layer of Comparative Example 2 was 1.0 × 10 ⁴ Ω / □, the light transmittance was 61.5%, and the surface unevenness was 0.5 μm. When the intermediate layer and the charge generation layer were formed on the conductive layer, the coating liquid of the intermediate layer and the charge generation layer penetrated into the conductive layer, and a coating film defect occurred. In the electrophotographic characteristics, the charging potential was significantly reduced, and delamination occurred between the PET film and the conductive layer.

[Effects of the Present Invention] According to the present invention, a belt-shaped or sheet-shaped electrophotographic photoreceptor having excellent electrophotographic properties and mechanical peel strength and having a transparent substrate suitable for a process of performing exposure from the back surface can be obtained.

Continuation of the front page (56) References JP-A-63-48562 (JP, A) JP-A-1-249436 (JP, A) JP-A-59-214858 (JP, A) JP-A-60-144755 (JP, A) JP-A-62-284362 (JP, A) JP-A-61-129654 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 5/00-5/16

Claims (2)

(57) [Claims] An electrophotographic photosensitive member comprising a transparent support, a transparent conductive layer comprising a conductive powder and a binder resin, an intermediate layer, and a photosensitive layer, wherein the conductive powder in the transparent conductive layer has an average particle size. It is made of a conductive metal oxide of 0.6 to 1.0 μm, and the conductive powder / binder resin has a volume ratio of 20/80 to 40/60, and the intermediate layer is formed with respect to the resin forming the core intermediate layer. An electrophotographic photoreceptor comprising 1 to 20% by weight of an organic titanate. 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a laminated organic photoconductor.