JPH07109520B2 - Electrophotographic photoconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to improvement of an electrophotographic photoreceptor having a charge injection preventing intermediate layer.

[Prior art]

Conventionally, a general electrophotographic photosensitive member provided with a photosensitive layer on a conductive substrate, particularly a laminated type electrophotographic photosensitive member in which the photosensitive layer is composed of a charge generation layer and a charge transfer layer has high chargeability, high sensitivity and Various attempts have been made to impart low residual potential. As one of them, it has been proposed to provide an intermediate layer for preventing injection of a charge having a polarity opposite to that of the charged charge from the side of the conductive substrate during charging into the high-sensitivity charge generation layer. For example, JP-A-47-6341, JP-A-48-3544 and JP-A-48-12034, a cellulose nitrate resin intermediate layer, JP-A-48-47344,
52-25638, 58-30757, 58-63945, 58-953
Nos. 51, 58-98739, 60-66258 and 61-110153 have a polyamide resin intermediate layer, and JP-A-48-26141 has a vinyl acetate resin intermediate layer. -69332 and 52-1
No. 0138 discloses a maleic acid resin intermediate layer, and JP-A-58-58
No. 105155 discloses polyvinyl alcohol-based intermediate layers.

However, in the case of a conventionally known photoreceptor provided with an intermediate layer, when repeatedly used, the charging potential rises slowly and the charging characteristics are deteriorated, so that the image density is lowered, and especially in the case of reversal development, There was a drawback that it caused stains.

〔Purpose〕

An object of the present invention is to provide an electrophotographic photosensitive member which maintains a high sensitivity even after repeated use, does not deteriorate the charging property, and therefore gives a good image without lowering the image density or causing scumming. .

〔Constitution〕

According to the present invention, in an electrophotographic photoreceptor in which an intermediate layer and a photosensitive layer are sequentially provided on a conductive substrate, the intermediate layer has an oxyethylene group and an oxypropylene group as constitutional units, and the terminal of the molecule is There is provided an electrophotographic photoreceptor containing a random copolymer or a block copolymer having a hydroxyl group.

The electrophotographic photoreceptor of the present invention, as the main component of the intermediate layer,
Having at least an oxyethylene group and an oxypropylene group as a constitutional unit, and since the terminal of the molecule contained a random copolymer or a block copolymer, even if it was repeatedly used, As described above, since the charging characteristics are not deteriorated, a clear copy image without deterioration of image density and background stain is provided.

Hereinafter, the present invention will be described in detail.

The basic constitution of the photoreceptor of the present invention is as shown in FIG. 2 in which a charge injection preventing intermediate layer 2 and a single layer type photosensitive layer 3 are provided on a conductive substrate 1 as shown in FIG. In addition, a laminate type photosensitive layer 3'comprising a charge injection preventing intermediate layer 2, a charge generating layer 4 and a charge transfer layer 5 is provided on a conductive substrate 1.

Next, each constituent material used in the present invention will be described.

The conductive substrate is intended to supply a charge having a polarity opposite to the charged charge to the substrate side and has an electric resistance of 10 ⁸
It is possible to use a material having an Ωcm or less and capable of withstanding the film forming conditions of the intermediate layer, the charge generation layer and the charge transfer layer. Examples of these include electrically conductive metals and alloys such as Al, Ni, Cr, Zn, and stainless steel, and inorganic insulating substances such as glass and ceramics and organic insulating properties such as polyester, polyimide, phenol resin, nylon resin, and paper. The surface of the material is Al, Ni, Cr, Zn, stainless steel, carbon, SnO ₂ , I by vacuum evaporation, sputtering, spray coating, etc.
Examples thereof include those that have been subjected to a conductive treatment by coating an electrically conductive substance such as n ₂ O ₃ .

The charge injection preventive intermediate layer prevents charge injection from the conductive substrate to the photosensitive layer during charging of the photoconductor to maintain chargeability, and at the time of exposing the photoconductor to one of the charges generated in the photosensitive layer, that is, the conductive substrate side. It has the effect of moving charges of the opposite polarity to the blocked charges to the side of the conductive substrate. In particular, when the photosensitive layer has high sensitivity, it is necessary because the chargeability of the photosensitive layer deteriorates. In the present invention, a random copolymer or block copolymer having an oxyethylene group and an oxypropylene group in the intermediate layer and having a hydroxyl group at the end of the molecule is used.

Such a copolymer is a conventionally known one, and various commercially available products can be used in the present invention, but a molecular weight of 500 to 100,000, preferably 200 to 5,000.
0, the average number of added oxyethylene groups is 1 to 100
It is preferable to use one having an average molar number of addition of oxypropylene groups of 1 to 2000, preferably 1 to 600, and 1 to 2000, preferably 1 to 1000. Specific examples of such random copolymers or block copolymers include Newpole manufactured by Sanyo Kasei Co., Ltd .; PE-61, PE-62, PE-64, PE-68, PE-71, PE-74. , P
E-75, PE-78, PE-85, PE-88, PE-108, PE-2700; Newpol 75H-90000; Pluronic L manufactured by Asahi Denka Co., Ltd.
Series, P series, F series: Epang series manufactured by Daiichi Kogyo Seiyaku Co., Ltd .: Pronon 102, 104, 105, 201, 204, 208 manufactured by NOF CORPORATION.

The intermediate layer of the present invention contains the above-mentioned random copolymer or block copolymer as a main component, but a resin commonly used in this type of intermediate layer can be used in combination if necessary. Examples of such a resin include polyester,
Examples include thermoplastic resins such as polycarbonate, polyvinyl butyral, polyamide, polystyrene, polyurethane, polypropylene, polyacrylate and polyvinyl chloride, as well as thermosetting resins such as phenol resins, melamine resins and epoxy resins, or photocurable resins. It In the intermediate layer, conductive powder such as SnO ₂ , Sb ₂ O ₃ and / or
White pigments such as ZnO, ZnS, and TiO ₂ can also be included. The intermediate layer is formed on the conductive substrate by a roll coating method,
Film is formed by dip coating method, spray coating method, blade coating method, etc. and dried or cured at 50 to 200 ° C to obtain a film thickness of 0.05.
The film has a thickness of -10 μm, preferably 0.2-2 μm.

The photosensitive layer in the present invention may be either a single layer type as shown in FIG. 1 or a laminated type as shown in FIG.

The single-layer type photosensitive layer has both functions of charge generation and charge transfer in one layer, and is a layer intended to form a charge latent image by imagewise exposure.

This type of photosensitive layer is a dye-sensitized photoconductive powder of zinc oxide, titanium oxide, zinc sulfide, etc., amorphous silicon powder,
A crystalline selenium powder, a phthalocyanine pigment, an azo pigment, and a binder resin are formed on the intermediate layer together with a charge transfer substance described later, if necessary. As the binder resin, the same one as that of the laminated type photosensitive layer described later is used. A single layer type photosensitive layer in which a charge transfer substance is added to a eutectic complex formed of a pyrylium type dye and bisphenol A type polycarbonate can also be used. A suitable thickness is 5 to 30 μm.

The charge generation layer in the laminated photosensitive layer is a layer intended to generate and separate charges by imagewise exposure. In the present invention, the charge generation layer is an organic dye or pigment,
Crystalline selenium or arsenic selenide is used as a charge generating substance, and as an organic pigment, a phthalocyanine pigment,
Examples include disazo pigments, trisazo pigments, perylene pigments, squalic salt dyes, azulenium salt dyes, and quinone condensed polycyclic compounds. Specific examples of the disazo pigment and the trisazo pigment are shown below.

These organic dyes and pigments are ball mills, sand mills, three rolls, with or without a resin added with an organic solvent.
It is used by dispersing it with an attritor or ultrasonic method. Examples of the resin (binder) that disperses these organic dyes and pigments include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polycarbonate and polyether, and polystyrene, polyacrylate, polymethacrylate, poly-N-vinylcarbazole and polyvinyl. Examples thereof include polymers and copolymers such as butyral, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, etc., which are required to have insulation and adhesiveness. Dispersion is performed by the same dispersing means as above, and a film is formed on the intermediate layer and dried in the same manner as the intermediate layer to form a charge generation layer having a thickness of 0.05 μm to several μm. The content of the organic dye / pigment is preferably 60% by weight to 100% by weight.

When crystalline selenium or arsenic selenide alloy powder is used, it is used in combination with a charge transfer binder and / or a charge transfer organic compound. Examples of such a charge transfer substance include polyvinylcarbazole and its derivatives (for example, those having a halogen such as chlorine and bromine in the carbazole skeleton, and a substituent such as a methyl group and an amino group), polyvinylpyrene, oxadiazole, pyrazoline, There are nitrogen-containing compounds such as hydrazone, diarylmethane, α-phenylstilbene and triphenylamine compounds, and diarylmethane compounds, and polyvinylcarbazole and its derivatives are particularly preferable. Further, these substances may be mixed and used. Even when they are used as a mixture, it is preferable to add another charge transfer organic compound to polyvinylcarbazole and its derivative. If desired, a binder resin used in combination with an organic pigment may be used for the purpose of improving adhesiveness, flexibility and the like. The content of this type of charge generating substance is preferably 30 to 90% by weight based on the entire layer. Further, when the charge generating substance is used, the thickness of the charge generating layer is suitably 0.2 to 5 μm.

The charge transfer layer provided on the charge generation layer has the purpose of retaining the charged charge on the surface thereof and also transferring the charge generated and separated in the charge generation layer by exposure to combine with the retained charge. And the layer. High electrical resistance is required to achieve the purpose of retaining the electrostatic charge,
Further, in order to achieve the purpose of obtaining a high surface potential with the retained charged charges, it is required that the permittivity is small and the charge mobility is good. In order to satisfy these requirements, an organic charge transfer layer containing an organic charge transfer substance as an active ingredient is used. As the organic charge transfer substance, for example,
Poly-N-vinylcarbazole compound, pyrazoline compound, α-phenylstyreneben compound, hydrazone compound, diarylmethane compound, triphenylamine compound, divinylbenzene compound, fluorein compound, anthracene compound, Conventionally known compounds such as oxadiazole compounds and diaminocarbazole compounds can be used. These organic charge transfer substances other than polymers such as polyvinyl carbazole are compounded and used in the same resins as those described above as the binder for the charge generation layer. However, the resin used in the charge generation layer and the resin used in the charge transfer layer need not be the same. In addition, a plasticizer is added to these if necessary. Examples of such a plasticizer include halogenated paraffin, dimethylnaphthalene, dibutyl phthalate, dioctyl phthalate, tricresyl phosphate, and the like, and polymers and copolymers of polyester and the like. The charge transfer substance, the binder resin, and silicone oil (as a leveling agent during film formation) are dissolved in an organic solvent, and the film is formed and dried in the same manner as the intermediate layer and the charge generation layer to form a film. A charge transfer layer having a thickness of 5 μm to 100 μm is formed on the charge generation layer. The ratio of charge transfer material to resin binder is
The weight ratio is 2/8 to 8/2, and the amount of silicone oil to the resin binder is 0.001% to 1% by weight.

〔effect〕

The electrophotographic photoreceptor of the present invention, as the main component of the intermediate layer,
Having an oxyethylene group and an oxypropylene group as a constitutional unit, and since a random copolymer or a block copolymer in which the terminal of the molecule is a hydroxyl group is used, the charging characteristics do not deteriorate even after repeated use, It gives a clear copy image without deterioration of image density and background stain.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 [Coating solution for intermediate layer] HOC ₂ H ₄ O ₈₀ C ₃ H ₆ O ₈₀ C ₂ H ₄ O ₈₀ H (Newyole PE68 manufactured by Sanyo Kasei Co., Ltd.) 4 parts by weight Nylon resin (Toray ( CM-8000) 4 〃 methanol 60 〃 butanol 32 〃 The above mixture was mixed to prepare an intermediate layer coating solution.

[Coating liquid for charge generation layer]

Into a φ15 cm glass pot, ½ of the volume of a stainless ball of φ1 cm, 400 g of cyclohexanone and 25 g of the azo pigment No. 1 were charged and mixed for 48 hours. After further adding 400 g of cyclohexanone and mixing for another 24 hours, 800 g of methyl ethyl ketone was added dropwise while stirring 800 g of the taken-out dispersion solution to prepare a charge generation layer coating liquid.

[Coating liquid for charge transfer layer]

α-Phenylstilbene type charge transfer material 10 parts by weight (the following compounds) Polycarbonate (trade name, Panlite C 1400: Teijin Ltd.) 10 parts by weight Silicone oil (trade name, KF 50: Shin-Etsu Silicone Co., Ltd.) 0.
0002 parts by weight Tetrahydrofuran 80 parts by weight Next, the surface of an Al vapor-deposited 100 μm thick PET film (Lumirror manufactured by Toray Industries, Inc.) was coated with the coating solution for the intermediate layer with a doctor blade and heated at 120 ° C. for 10 minutes. It was dried to provide an intermediate layer having a film thickness of 1 μm. Next, the charge generation layer coating liquid was applied onto the intermediate layer with a blade,
It is heated and dried at 0 ° C. for 10 minutes to form a charge generation layer having a film thickness of 0.1 μm, and the charge transfer layer coating solution is further coated on it with a blade, and dried by heating at 120 ° C. for 20 minutes, Film thickness 20μm
To form a charge transfer layer, and the electrophotographic photoreceptor of Example 1 was prepared.

Comparative Example 1 An electrophotographic photoconductor of Comparative Example 1 was prepared in the same manner as in Example 1 except that Neupol PE68 was omitted from the coating liquid for intermediate layer of Example 1.

Example 2 An electrophotographic photoreceptor of Example 2 was prepared in the same manner as in Example 1 except that the coating liquid for the intermediate layer was changed to the following liquid.

[Coating liquid for intermediate layer]

HOC ₂ H ₄ O ₈₀ C ₃ H ₆ O ₉₀ C ₂ H ₄ O ₈₀ H (Sanyo Chemical Co., Ltd., Newpol PE68) 4 parts by weight Polyvinyl alcohol (Denki Kagaku Co., Ltd., Poval B-24) 4 parts by weight Methanol 41 〃 Water 41 〃 Comparative Example 2 An electrophotographic photoconductor of Comparative Example 2 was prepared in the same manner as in Example 2 except that Neupol PE68 was omitted from the coating liquid for the intermediate layer of Example 2. .

Example 3 An electrophotographic photosensitive member of Example 3 was prepared in the same manner as in Example 1 except that the coating liquid for intermediate layer was changed to the following liquid.

[Coating liquid for intermediate layer]

HOC ₂ H ₄ O ₃₀₀ C ₃ H ₆ O ₉₀₀ C ₂ H ₄ O ₉₀₀ H (Sanyo Kasei Co., Ltd., New Pole 75H-90000) 0.5 parts by weight Nylon resin (Toray Co., CM-8000) 7.5 〃Methanol 60 〃Butanol 32 〃 Example 4 For electrophotography of Example 4 in the same manner as in Example 1 except that Pigment No47 was used in place of Pigment No1 used in the charge generation layer coating solution of Example 1. A photoconductor was created.

Comparative Example 3 An electrophotographic photoconductor of Comparative Example 3 was prepared in the same manner as in Example 4 except that Neupol PE68 was omitted from the intermediate layer coating solution of Example 4.

Example 5 In Example 4, the charge transfer material was An electrophotographic photosensitive member of Example 5 was prepared in the same manner as in Example 4 except that

Comparative Example 4 An electrophotographic photosensitive member of Comparative Example 4 was prepared in the same manner as in Example 5 except that Neupol PE68 was omitted from the intermediate layer coating solution of Example 5.

Example 6 Newpol PE instead of Newpole PE68 of Example 4
77 (manufactured by Sanyo Kasei Co., Ltd., HO (C ₂ H ₄ O ₅₅ C ₃ H ₆ O ₃₅ C ₂
An electrophotographic photoconductor of Example 6 was prepared in the same manner as in Example 4 except that H ₄ O ₅₅ H was used.

Example 7 HOC ₂ H ₄ O ₈₀ C ₃ H ₆ O ₃₀ C ₂ H ₄ O ₈₀ H (manufactured by Sanyo Kasei Co., Ltd., New Pole PE68) 5 parts by weight nylon resin (manufactured by Toray Co., CM-8000) 5〃 Fine powder of tin oxide 5 parts by weight Titanium oxide powder 3 parts by weight Disperse a liquid consisting of 40 parts of methanol in a ball mill for 72 hours, then dilute with a mixed solvent of methanol / butanol (20/30 parts by weight) and again in the ball mill. Treated for 48 hours.

An electrophotographic photosensitive member of Example 7 was prepared in the same manner as in Example 1 except that this liquid was used as the intermediate layer coating liquid.

Example 8 HOC ₂ H ₄ O ₈₀ C ₃ H ₆ O ₃₀ C ₂ H ₄ O ₈₀ H (manufactured by Sanyo Kasei Co., Ltd., Newpol PE68) 45 parts by weight Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., BL-1) ) 48〃 Fine powder of tin oxide 48〃 Tolylene diisocyanate 14.5〃 Cyclohexanone 552〃 Methyl ethyl ketone 130〃 is used as the intermediate layer coating solution.
An electrophotographic photosensitive member of Example 8 was prepared in the same manner as in Example 1 except that the heat treatment was carried out at 1 ° C. for 1 hour.

The electrophotographic photoreceptor thus prepared was evaluated for electrophotographic characteristics in the following manner by using an electrostatic copying paper tester (SP428 type manufactured by Kawaguchi Denki Seisakusho). First, -6KV corona charging was performed for 20 seconds, then left in the dark and the surface potential became -800V, then irradiated with 4.5lux of tungsten light, the surface 2 seconds after the start of charging at this time. The potential V ₂ and the exposure amount S (lu
x sec) was measured. In addition, after this, the color temperature of the photoreceptor is 285
The tungsten light at 6 ° K was irradiated for 100,000 lux sec, and the charging potential V ₂ ′ and the exposure amount S ′ were determined again in the same manner as above.

Example 9 An Al drum having a thickness of 3 mm and 80φ × 340 mm was dip-coated with the same coating solution for an intermediate layer as in Example 1 and dried by heating at 130 ° C. for 20 minutes to form an intermediate layer having a thickness of 1 μm. Was formed. Further, the same charge generation layer coating solution as in Example 1 was applied on the above by dip coating, and heated and dried at 130 ° C. for 20 minutes to form a 0.1 μm charge generation layer. Further, a charge transfer layer coating solution was applied onto the layer by dip coating, and dried by heating at 130 ° C. for 30 minutes to obtain a charge transfer layer having a film thickness of 20 μm.

FT4060 with the photoconductor drum created in this way improved in charging, transfer charger and developing bias to negative polarity
When it was mounted on a (Ricoh Copier) to output an image, a clear image was obtained. At this time, the surface potential of the photoconductor was measured immediately after passing through the charging charger.
It was 0V. After this, further charge and expose this photoconductor
After repeating 10,000 times, the same operation was performed, but there was no decrease in image density and the surface potential was -770V.

Comparative Example 5 A photoreceptor similar to that in Example 9 was prepared using the same coating liquid for each layer as in Comparative Example 1, and the measurement was performed. The initial surface potential was −800 V, but after repeating 10,000 times The surface potential of the sample was remarkably lowered to -520V, and the image density was also lowered.

[Brief description of drawings]

1 and 2 are schematic cross-sectional views of the electrophotographic photosensitive member according to the present invention. 1: conductive substrate, 2: charge injection preventing intermediate layer 3: single layer type photosensitive layer, 3 ': laminated type photosensitive layer 4: charge generation layer, 5: charge transfer layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Taniguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Co., Ltd. (72) Minor Umeda 1-3-6 Nakamagome, Ota-ku, Tokyo Stock Company Ricoh

Claims (1)

[Claims] 1. An electrophotographic photosensitive member comprising an electroconductive substrate, on which an intermediate layer and a photosensitive layer are sequentially provided, wherein the intermediate layer has an oxyethylene group and an oxypropylene group as constituent units, and the terminal of the molecule is a hydroxyl group. An electrophotographic photoreceptor containing the random copolymer or block copolymer of