JP2001305757A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high sensitivity and capable of forming a high quality image by using a coating solution for an electric charge generating layer which incurs little disturbance due to the dissolution of the electric charge generating layer in the formation of an electric charge transferring layer by coating and which has sensitivity maintained in its own way because an electric charge transferring material enters into the electric charge generating layer in a degree and has good dispersibility. SOLUTION: In the laminate type electrophotographic photoreceptor with at least an electrically conductive substrate, an electric charge generating layer and an electric charge transferring layer, a resin slightly soluble in a coating solution for the electric charge transferring layer and a resin soluble in the coating solution are used as the resin medium of the electric charge generating layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoreceptor for electrophotography, and more particularly, to a high-sensitivity photoreceptor for electrophotography capable of forming a charge generating layer having a good film quality and providing a high quality image.

[0002]

2. Description of the Related Art In general, an electrophotographic photoreceptor has various problems due to repeated use, such as a decrease in chargeability, an increase in residual potential, and a deterioration in image characteristics. In particular, in the case of the reversal development method, there is a problem that abnormal images such as black spots and black spots often appear on the image. Although there are various factors, the resin of the charge generation layer between the undercoat layer and the charge transport layer dissolves at the time of coating the charge transport layer, and the charge transport material is transferred to the undercoat layer or the surface of the electrode (that is, the conductive support). It is thought that one of the factors is that the vicinity of the charge generation layer is disturbed due to, for example, dissolution.

[0003] From the above phenomenon, the charge transporting material impregnated in the undercoat layer has a hole transporting property, causing hole injection from below, or a charge generating layer (hereinafter, CGL).
The charge generating material (hereinafter referred to as C)
GM) may be aggregated to partially reduce the chargeability and cause black spots. Therefore, it is preferable to use a resin that does not dissolve or swell when the charge transport layer is coated.

However, since the dispersibility of the pigment is greatly affected by the type of the resin, there is a limitation in terms of the stability of the coating solution, and at present, a satisfactory charge generating layer coating solution has not yet been obtained. . Also, depending on the pigment, sensitivity may be generated by the contact between the charge generating substance and the charge transporting substance, and it is assumed that some dissolution of the charge generating layer resin and the intrusion of the charge transporting substance due to the dissolution may be required. You.

In the photoreceptor proposed in JP-A-3-37669, an undercoat layer (hereinafter sometimes referred to as UL) is formed of an alcohol-insoluble resin, and a charge generation layer (hereinafter referred to as UL) is formed of an alcohol-soluble resin. CGL). The purpose of this is to prevent the undercoat layer from being disturbed during the application of the charge generation layer. However, in the case of this publication, a polyamide resin or a butyral resin is used alone as an alcohol-soluble resin, but our investigation results show that a polyamide resin alone has a very poor dispersibility of a charge generating substance,
It was found that the sensitivity was low and the chargeability was poor. on the other hand,
Butyral resin is widely known as a resin for a charge generation layer and has some characteristics. However, unlike polyamide, it is soluble in ether-based and halogen-based solvents, so that a charge transport layer (hereinafter sometimes referred to as CTL) is coated. Thereafter, the vicinity of the charge generation layer is disturbed, and the rate of occurrence of abnormal images such as black spots is high.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce disturbance due to dissolution of CGL during CTL coating,
In addition, the charge transport material slightly enters the CGL, the sensitivity thereof is maintained, and an electrophotograph having high sensitivity and capable of forming a high-quality image using a charge generation layer coating solution having good dispersibility. To provide a photoreceptor for use.

[0007]

According to the present invention, first, in a laminated electrophotographic photosensitive member having at least a conductive support, a charge generation layer and a charge transport layer, a resin medium of the charge generation layer is used. An electrophotographic photoreceptor characterized in that a resin that is substantially insoluble in a coating solution for the charge transport layer and a resin that is soluble in the coating solution are provided.

[0008] Secondly, the electron of the first aspect, wherein the resin of the charge generation layer is a resin substantially insoluble in a cyclic ether-based or halogen-based solvent and a resin soluble therein. A photoreceptor is provided.

Thirdly, there is provided the electrophotographic photosensitive member according to the first or second aspect, wherein the resin in the charge generation layer is a polyamide resin and a butyral resin.

[0010] Fourthly, there is provided the electrophotographic photosensitive member according to the first, second or third aspect, wherein the charge generating material is titanyl phthalocyanine.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a representative electrophotographic photoreceptor of the present invention, in which an undercoat layer 2 is provided on a conductive support (electrode) 1.
And a charge generation layer 3 and a charge transport layer 4 are laminated. Of course, other intermediate layers and protective layers can be provided as needed. It is also basically effective when there is no undercoat layer or when the conductive support (electrode) is anodized.

On the other hand, an electrophotographic photosensitive member in which a resin soluble in a charge transport layer coating solution is used as a conventional resin medium for the charge generation layer (the layer structure is the same as that shown in FIG. 1) 2), the resin of the charge generation layer dissolves at the time of coating the charge transport layer, and the charge transport substance dissolves into the undercoat layer, and in some cases, the surface of the conductive support. Of the photosensitive member, resulting in deterioration of the photosensitive member characteristics.

As described above, the electrophotographic photoreceptor of the present invention has a laminated structure having at least a conductive support, a charge generation layer, and a charge transport layer. The charge generating material and the charge transporting material are not limited at all, and may be appropriately selected from conventionally known materials and used. These materials will be briefly described below.

The conductive support 1 has a volume resistance of 10 ¹⁰
What shows conductivity of Ωcm or less, for example, aluminum, nickel, chromium, nichrome, copper, gold, silver, metals such as platinum, tin oxide, metal oxides such as indium oxide, by evaporation or sputtering, by film Or cylindrical plastic or paper coated, or plates of aluminum, aluminum alloy, nickel, stainless steel, etc. and extruded, drawn, etc., turned into a tube, then cut, super-finished, polished, etc. A treated tube or the like can be used. Also, Japanese Patent Application Laid-Open
An endless nickel belt and an endless stainless belt disclosed in JP-B-36016 can also be used as the conductive support 1.

In addition, a conductive powder dispersed on a suitable binder resin and coated on the above support can be used as the conductive support 1 of the present invention. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc, and silver, and metal oxide powder such as conductive tin oxide and ITO. Can be The binder resins used simultaneously include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, and vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-
Vinyl carbazole, acrylic resin, silicone resin,
Examples include thermoplastic resins such as epoxy resins, melamine resins, urethane resins, phenol resins, and alkyd resins, thermosetting resins, and photocurable resins. Such a conductive layer can be provided by dispersing the conductive powder and the binder resin in an appropriate solvent, for example, tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene, or the like, and applying the dispersion.

Further, heat shrinkage of a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, Teflon (registered trademark) or the like containing the conductive powder on a suitable cylindrical substrate. Also those that have a conductive layer provided by a tube,
It can be used favorably as the conductive support 1 of the present invention.

The charge generation layer 3 is prepared by dispersing a pigment together with a binder resin in an appropriate solvent using a ball mill, an attritor, a sand mill, ultrasonic waves, or the like, coating the dispersion on a conductive support, and drying. It is formed.

The charge generating material used in the charge generating layer 3, that is, the pigment includes monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, squaric acid Dyes, phthalocyanine pigments, naphthalocyanine pigments, azulhenium salt dyes, and the like. However, the present invention is particularly effective when a phthalocyanine-based pigment in which black spots are easily generated due to aggregation of the charge generation layer is used.

The charge transporting layer 4 can be formed by dissolving or dispersing a charge transporting substance and a binder resin in a suitable solvent, applying this on the charge generating layer, and drying. If necessary, a plasticizer, a leveling agent, an antioxidant and the like can be added.

The charge transport material includes a hole transport material and an electron transport material. Examples of the electron transporting substance include chloranil, bromanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone,
2,4,8-trinitrothioxanthone, 2,6,8-
Examples thereof include electron accepting substances such as trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, and benzoquinone derivatives.

Examples of the hole transport material include poly-N-vinylcarbazole and its derivatives, poly-γ-galvazolylethylglutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, polysilane, Oxazole derivatives, oxadiazole derivatives, imidazole derivatives,
Monoarylamine derivatives, diarylamine derivatives,
Triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazoline derivatives, divinylbenzene derivatives, hydrazine derivatives, indene derivatives,
Other known materials such as butadiene derivatives, pyrene derivatives, bisstilbene derivatives, and enamine derivatives are exemplified.
These charge transport materials are used alone or in combination of two or more.

As described above, the electrophotographic photosensitive member of the present invention can be provided with the undercoat layer 2 between the conductive support 1 and the charge generation layer 3. The undercoat layer generally contains a resin as a main component, but it is preferable to add a metal oxide in order to prevent moiré and reduce residual potential. In this case, the undercoat layer is formed by applying and drying a metal oxide together with various resins, for example, a thermoplastic resin or a thermosetting resin. As a method for forming the undercoat layer, an ordinary coating method, a dip coating method, a spray method, or the like is employed.

The metal oxide in this case includes titanium oxide, tin oxide, aluminum oxide, indium oxide, zirconium oxide, iron oxide, silicon oxide, zinc oxide and the like. As the binder resin, a binder resin having good adhesion such as polyamide resin, alcohol-soluble polyamide resin, water-soluble polyvinyl butyral, polyvinyl butyral, and polyvinyl alcohol, or a thermosetting resin such as alkyd resin and melamine resin is used.

The present invention relates to a laminated electrophotographic photoreceptor having at least a conductive support, a charge generation layer, and a charge transport layer, which is substantially difficult to use as a resin medium for the charge generation layer in a coating solution for the charge transport layer. A photosensitive member characterized in that a soluble resin and a substantially soluble resin are present in a coating solution for the charge transport layer. As long as it is within this range, there is no limitation on the solvent type for each layer coating.

In general, as a solvent for coating the charge generation layer, for example, isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate,
Dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like are used, and as a solvent for coating the charge transport layer,
Tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used.

Here, a case where a halogen-based solvent such as dichloromethane or a cyclic ether-based solvent such as tetrahydrofuran, which has been widely used, is used for coating the charge transport layer will be described. In that case, as the resin that does not substantially dissolve in the charge transport layer coating solution, a polyamide resin,
There are cellulose resins, polyvinyl alcohol resins, polyethylene resins, and thermosetting resins. Typically, it is a polyamide resin.

On the other hand, resins soluble in halogen-based or cyclic ether-based solvents include acetal resins, polyvinyl acetate resins, polycarbonate resins, polyvinyl formal, polystyrene, polymethyl methacrylate, and polyester. Typically, it is an acetal resin.

As the binder resin for the charge transporting layer, polycarbonate, polyarylate, polystyrene, polyester resin, acrylic resin or the like which is dissolved in a usual cyclic ether-based or halogen-based solvent is used.

In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer 4. As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in a side chain are used.

In the electrophotographic photosensitive member of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. Materials used for the protective layer include ABS resin and A
CS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallyl sulfone, polybutylene, polybutylene terephthalate, polycarbonate, polyether sulfone, polyethylene, Polyethylene terephthalate, polyimide, acrylic resin, polymethylpentene,
Resins such as polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, polyvinyl chloride, polyvinylidene chloride, and epoxy resin.

[0031]

The present invention will be described below with reference to examples.
The present invention is not limited by these embodiments. All parts are parts by weight.

(Example 1) Into a 15 cm hard glass pot, 1/2 cm of a volume of 1 cm alumina sintered ball and fine powder of titanium oxide (trade name: CR-EL, manufactured by Ishihara Sangyo Co., Ltd.)
00 gr, 150 gr of an oil-free alkyd resin (Beccolite M6401-50, manufactured by Dainippon Ink and Chemicals, Inc.) having a solid content of 50% by weight, and butyl melamine resin (Super Beckamine G821-6) having a solid content of 60% by weight.
80, manufactured by Dainippon Ink and Chemicals, Inc.) was diluted with 300 gr of methyl ethyl ketone and milled at 80 RPM for 100 hours. Further, 300 gr of methyl ethyl ketone was added and milling was performed for 3 hours. 130 ℃
And drying on an aluminum plate with a subbing layer (film thickness of about 3.5
μm).

<Coating Solution for Charge Generating Layer> To a 50 cc glass sample bottle, 2 milliliter zirconia balls were added, and titanyl phthalocyanine (2θ = 27.2 ° in X-ray diffraction spectrum) was added.
0.2 part, 4 parts of a solution containing 5% by weight of a polyamide resin (manufactured by Toray Co., Ltd., CM8000) (solvent: methanol / butanol = 5/5), and 5.1 parts of methanol Was shaken with a vibration milling machine for 2 hours, further 12 parts of methanol was added, and the mixture was further shaken for 30 minutes to prepare a dispersion liquid (A).

To the solution (A), 5 parts of a methyl ethyl ketone solution containing 2% by weight of butyral resin (trade name: BM-S, manufactured by Sekisui Chemical Co., Ltd.) was added, and vibration was added for 1 hour. Thus, a dispersion having a weight ratio of titanyl phthalocyanine / polyamide resin / butyral resin = 2/2/1 was prepared. Using this solution, a charge generation layer was formed on the undercoat layer (film thickness: about 0.5 μm).

<Coating solution for charge transport layer> A coating solution having the following composition was applied on the charge generation layer and dried to form a charge transport layer. Polycarbonate (Polycarbonate Z) 10 parts Charge transport material of the following structural formula 7 parts

Embedded image Methylene chloride 80 parts Thickness of the charge transport layer is about 26 μm.

Examples 2 to 4 Photoconductors were prepared in the same manner as in Example 1 except that the composition of the charge generation layer and the solvent composition of the coating solution were as shown in Table 1.

(Comparative Examples 1 and 2) Photoconductors were prepared in the same manner as in Example 1 except that the composition of the charge generation layer and the solvent composition of the coating solution were as shown in Table 1.

[0038]

[Table 1]

Next, the thus obtained laminate type electrophotographic
To determine the sensitivity of the photoconductor at 780 nm,
In a dark place using a Ricoh electrostatic property evaluation machine.
A corona discharge of 5.2 kV is performed for 20 seconds to charge the battery.
Vm (V) was measured and left for 20 seconds in a dark place
After that, the surface potential Vo (V) was measured. Then 780
Irradiation with monochromatic light of nm, the potential from -800 volts is 1 /
Exposure E to 5 _1/5(ΜJ / cm^Two)
Was. Furthermore, the residual potential 30 seconds after the light irradiation was measured. Ma
5.6 μA at a potential of −800 V (sample surface
Product 30cm^TwoWith the flowing setting, take 15 minutes or fatigue
Was. Table 2 shows the results.

[0040]

[Table 2]

When the photoreceptor of Example 1 was formed on an aluminum drum and an image was formed by a reversal developing type copying machine (Imagio MF200 manufactured by Ricoh Company), a good image was obtained. When the conventional charge generation layer is made of butyral resin alone (Comparative Example 2), CGL swells and CGM partially coagulates at the time of application of the charge transport layer, thereby generating minute black spots and reducing the charge transport material. By entering the layer side,
A black spot pattern may occur. Further, when the polyamide resin was used alone (Comparative Example 1), the dispersibility was quite poor.

[0042]

As described above, in the laminated electrophotographic photoreceptor, as the resin medium of the charge generation layer, a resin that is hardly soluble in the coating liquid for the charge transport layer and a resin that is soluble in the appropriate ratio are used. By mixing, the film quality and sensitivity of the charge generation layer of the photoreceptor are improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an electrophotographic photoconductor of the present invention.

FIG. 2 is a view for explaining a state of a photoconductor when a resin soluble in a charge transport layer coating liquid is used as a resin medium of a charge generation layer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductive support (electrode) 2 Undercoat layer 3 Charge generation layer 4 Charge transport layer

Claims (4)

[Claims] 1. A laminate type electrophotographic photoreceptor having at least a conductive support, a charge generation layer and a charge transport layer, wherein the resin medium of the charge generation layer is substantially insoluble in a coating solution of the charge transport layer. A photosensitive member for electrophotography, characterized in that the photosensitive resin and a soluble resin are present. 2. The electrophotographic photosensitive member according to claim 1, wherein the resin of the charge generation layer is a resin substantially insoluble in a cyclic ether-based or halogen-based solvent and a resin soluble therein. body. 3. The electrophotographic photoconductor according to claim 1, wherein the resin in the charge generation layer is a polyamide resin and a butyral resin. 4. The photoconductor for electrophotography according to claim 1, wherein the charge generating material is titanyl phthalocyanine.