JPH07109518B2 - 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 contains a mono- or diester of polyethylene glycol. Provided.

The electrophotographic photoreceptor of the present invention, as the main component of the intermediate layer,
Since at least the mono- or diester of polyethylene glycol is contained, even if it is repeatedly used, the charging characteristics are not deteriorated unlike the conventional ones, and a clear copy image free from reduction in image density and scumming 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, by vacuum evaporation, sputtering, spray coating, etc., Al, Ni, Cr, Zn, stainless steel, carbon, SnO ₂ ,
Examples thereof include those which are coated with an electrically conductive substance such as In ₂ O _{3 and} subjected to a conductive treatment.

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 mono- or diester of polyethylene glycol represented by the following general formulas (I) and (II) is used for the intermediate layer.

(In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 10 to 20 carbon atoms, n represents an average number of moles added, and 1 or more, preferably a real number of 1 to 30. This polyethylene glycol mono- or diester is
Conventionally known compounds and various commercially available compounds are used in the present invention, but those having a molecular weight of 100 to 10,000, preferably 100 to 2000 are suitably used.

The intermediate layer of the present invention contains a mono- or diester of polyethylene glycol as a main component, but if necessary, a resin commonly used for this type of intermediate layer can be used together. Examples of such a resin include polyester, polycarbonate, polyvinyl butyral, polyamide, polystyrene, polyurethane, polypropylene,
In addition to thermoplastic resins such as polyacrylate and polyvinyl chloride, thermosetting resins such as phenol resins, melamine resins and epoxy resins, or photocurable resins are exemplified. Further, the intermediate layer may contain a conductive powder such as SnO ₂ or Sb ₂ O ₃ and / or a white pigment such as ZnO, ZnS or TiO ₂ . The formation of the intermediate layer on the conductive substrate is 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 dispersed and used by a method such as an attritor or an 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 organic dyes and pigments is 60% to 10%
0% by weight is preferred.

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,
Since the mono- or diester of polyethylene glycol is used, the charging characteristics are not deteriorated even when it is repeatedly used, so that a clear copy image which does not cause a decrease in image density or scumming is provided.

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

Example 1 [Coating liquid for intermediate layer] Polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS400; n = 9) 4 parts by weight Nylon resin (manufactured by Toray Co., CM-8000) 4 〃 Methanol 60 〃 Butanol 32 〃 The above mixture was mixed to obtain a coating liquid for intermediate layer.

[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 additionally adding 400 g of cyclohexane and mixing for another 24 hours,
While stirring 800 g of the taken-out dispersion solution, 800 g of methyl ethyl ketone was added dropwise to obtain a charge generation layer coating liquid.

[Coating liquid for charge transfer layer]

α-Phenylstilbene type charge transfer material (the following compounds) 10 parts by weight Polycarbonate (trade name, Panlite C 1400: Teijin Ltd.) 10 parts by weight Silicone oil (trade name, KF50: Shin-Etsu Silicone Co., Ltd. 0.0002 parts by weight Tetrahydrofuran 80 parts by weight) Next, 100 μm thick PET film deposited with Al ( The coating liquid for the intermediate layer was applied to the surface of Lumirror manufactured by Toray Industries, Inc. with a doctor blade and dried by heating at 120 ° C. for 10 minutes to form an intermediate layer having a film thickness of 1 μm. The charge generation layer coating solution is coated on the above with a blade, 12
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
The charge transfer layer of 1 was formed to prepare the electrophotographic photoreceptor of Example 1.

Comparative Example 1 An electrophotographic photoreceptor of Comparative Example 1 was prepared in the same manner as in Example 1 except that polyethylene glycol monostearate was removed 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]

Polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS400: n = 9) 4 parts by weight Polyvinyl alcohol (manufactured by Denki Kagaku Kogyo Co., Ltd., Poval B-24) 4 〃 Methanol 41 〃 Water 41 〃 Comparative Example 2 An electrophotographic photoreceptor of Comparative Example 2 was prepared in the same manner as in Example 2 except that polyethylene glycol monostearate was removed from the coating liquid for 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]

Polyethylene glycol distearate (manufactured by Sanyo Kasei Co., Ltd., Ionette DS400: n = 9) 4 parts by weight Nylon resin (manufactured by Toray Industries, Inc., CM-8000) 4 〃 methanol 60 〃 butanol 32 〃 Example 4 Example 1 An electrophotographic photosensitive member of Example 4 was prepared in the same manner as in Example 1 except that Pigment No. 47 was used in place of Pigment No. 1 used in the charge generation layer coating solution of No. 2.

Comparative Example 3 An electrophotographic photoconductor of Comparative Example 3 was prepared in the same manner as in Example 4 except that polyethylene glycol distearate was removed from the intermediate layer coating liquid 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 photoreceptor of Comparative Example 4 was prepared in the same manner as in Example 5 except that polyethylene glycol monostearate was removed from the intermediate layer coating solution of Example 5.

Example 6 Instead of the polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS400: n = 9) of Example 4, polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS 1000: n = 23) was used. The electrophotographic photosensitive member of Example 6 was prepared in the same manner as in Example 4 except that

Example 7 Polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS400: n = 9) 5 parts by weight Nylon resin (manufactured by Toray Industries, Inc., CM-8000) 5 〃 tin oxide fine powder 5 〃 titanium oxide powder 3 A solution consisting of 40 parts by weight of methanol was dispersed in a ball mill for 72 hours, then diluted with a mixed solvent of methanol / butanol (20/30 parts by weight) and treated again in the ball mill 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 Polyethylene glycol monostearate (manufactured by Sanyo Kasei Co., Ltd., Ionet MS400: n = 9) 48 parts by weight Polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., BL-1) 48 〃 Tin oxide fine powder 48 〃 Tolylene diisocyanate 14.5 〃 Cyclohexanone 552 parts by weight Methyl ethyl ketone 130 〃 was used as the coating solution for the intermediate layer.
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 photosensitive member produced as described above was evaluated for electrophotographic characteristics in the following manner by using an electrostatic copying paper test apparatus (Kawaguchi Denki Seisakusho SP428 type). First, -6KV corona charging was performed for 20 seconds, then left in the dark and the surface potential became -800V, and 4.5lux tungsten light was irradiated, and the surface was charged for 2 seconds after the start of charging. The potential V ₂ and the exposure amount S required to bring the surface potential to −400 V during light irradiation
(Lux sec) was measured. After that, the photosensitive member is irradiated with tungsten light having a color temperature of 2856 ° K for 100000 lux sec,
Again, the charging potential V ₂ ′ and the exposure amount S ′ were determined 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 dried by heating at 130 ° C. for 20 minutes to form a charge generation layer of 0.1 μm. 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 the image density did not decrease and the surface potential was -740V.

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 Toshio Fukagai 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Satoshi Taniguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Stock company Ricoh

Claims (1)

[Claims] 1. An electrophotographic photoconductor in which an intermediate layer and a photosensitive layer are sequentially provided on a conductive substrate, wherein the intermediate layer contains a mono- or diester of polyethylene glycol.