JP2002351101A - Electrophotographic photoreceptor used for wet developing type image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which shows little degradation in the electric characteristics for a long time even when the photoreceptor is used for an image forming device using a wet developing method by properly increasing the wear amount of the photosensitive layer. SOLUTION: The electrophotographic photoreceptor is provided with a photosensitive layer consisting of a binder resin containing at least a charge generating agent and a charge transfer agent on a conductive substrate. The wear amount of the binder resin is larger than the wear amount of a bisphenol Z type polycarbonate resin having 25,000 viscosity average molecular weight and smaller than the wear amount of a bisphenol Z type polycarbonate resin having 5,000 viscosity average molecular weight. The photoreceptor is used for an image forming device by a wet developing method which uses a developing solution having toner particles dispersed in the liquid. Therefore, when the photoreceptor is used for the image forming device by the wet developing method, the photoreceptor shows little degradation in the electric characteristics for a long time since the deteriorated surface of the photosensitive layer is properly ground.

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 used in a wet development type image forming apparatus such as an electrophotographic copying machine, a facsimile, and a laser beam printer. More specifically, the present invention relates to an organic photoreceptor that can be used in an image forming apparatus of a wet development type using a developing solution in which toner particles are dispersed in a liquid.

[0002]

2. Description of the Related Art Electrophotographic developing systems utilizing the Carlson process are broadly classified into dry developing systems and wet developing systems. 2. Description of the Related Art An image forming apparatus using a dry developing method is widely and generally used at present, such as a copying machine and a printer. On the other hand, an image forming apparatus using a wet developing method has been developed and commercialized for a long time, but at present, an image forming apparatus using a dry developing method occupies most of the market.

However, in an image forming apparatus using a wet developing method, generally, a toner is dispersed in a liquid, and a toner particle size can be reduced to 1 μm or less. High image quality. For this reason, with the expansion of the market for full-color printers that require high image quality in recent years, they have been spotlighted again and are being developed.

An image forming apparatus using a wet developing method is
As described above, in order to use a developing solution in which toner particles are dispersed in a liquid, all or a part of the photosensitive drum is immersed in the developing solution. As a liquid used for the developing solution, for example, an aliphatic hydrocarbon solvent called Isopar is mainly used. In general, an inorganic photoreceptor such as selenium or amorphous silicon, in which a photosensitive layer component is not eluted in the isoper, is used.

On the other hand, the organic photoreceptor is easier to manufacture and lower in cost than the conventional inorganic photoreceptor, and has a wide variety of photoreceptor materials such as a charge transporting agent, a charge generating agent and a binder resin. In recent years, they have been used more widely than the inorganic photoreceptors because of their advantages of high degree of freedom in functional design and no toxicity.

[0006] The organic photoreceptor includes a single-layer type photoreceptor in which a charge transporting agent (a hole transporting agent or an electron transporting agent) is dispersed in the same photosensitive layer together with a charge generating agent, and a charge generating agent containing a charge generating agent. There is a laminated photoconductor in which a layer and a charge transport layer containing a charge transport agent are laminated.

[0007] In particular, the single-layer type photoreceptor has been spotlighted because it has a simple structure and is easy to manufacture, it can suppress film defects when forming layers, has few interfaces between layers, and can improve optical characteristics. Is taking a bath.

The above-mentioned laminated photoreceptor and single-layer type photoreceptor can be used for both positive and negative charging types. However, in general, due to the order of the layer constitution and the characteristics of the material constituting the photoreceptor, The mainstream is to use a negative charge for the laminated type and a positive charge for the single layer type.

For this reason, inorganic photoreceptors such as selenium and amorphous silicon which are generally used in an image forming apparatus using the above-mentioned wet developing method are usually used in a positive charge type, and thus have been conventionally used. It is advantageous to replace the inorganic photoreceptor with an organic photoreceptor since the single-layer type organic photoreceptor is the same positively charged type.

[0010]

SUMMARY OF THE INVENTION A general organic photoreceptor is
When used in an image forming apparatus using a wet development method,
As described above, since all or a part of the photoconductor drum is immersed in the isopar, a change in appearance such as a crack occurs on the surface of the photoconductor and a low level of a charge transport agent (a hole transport agent or an electron transport agent) or the like. The molecular weight substance elutes into the isopar, causing a phenomenon such as a decrease in charge and a decrease in sensitivity.
It becomes difficult to obtain a good image.

Therefore, by using an organic photoreceptor in which the surface of the organic photoreceptor is further overcoated (surface protective layer) with a thermosetting resin such as a melamine resin or an epoxy resin, the durability against the above-mentioned isoper is improved. It has been proposed and put to practical use that it manifests and prevents elution of the charge transport agent. In recent years, a general organic photoconductor using a dry development method has been used by using a solvent almost inactive for an organic photoconductive layer, such as silicone oil or fluorine oil, as a liquid (toner dispersion solvent). Can be used and development is underway.

In particular, in the method using a silicone oil as a toner dispersion solvent, a general organic photoreceptor can be used as described above, and the silicone oil is completely odorless unlike Isopar. It is characterized by the following.

On the other hand, an image forming apparatus using a wet developing method also generally has a blade cleaning device for collecting untransferred toner. However, the toner dispersion solvent is composed of a photosensitive layer surface-toner particle surface-blade. Therefore, the friction coefficient between the surface of the organic photosensitive layer and the blade is reduced as compared with the blade cleaning of the image forming apparatus using the dry developing method, so that the wear amount of the photosensitive layer is reduced. In particular, when the above-mentioned silicone oil is used as the toner dispersion solvent, the reduction rate of the friction coefficient is large and the abrasion amount is significantly reduced.

In an image forming apparatus using a wet developing method, as in an image forming apparatus using a dry developing method,
Active gas such as ozone or NOx is generated from the vicinity of the charging or transfer charger, and deteriorates the surface of the organic photosensitive layer. Further, it is considered that the developing solution also deteriorates the surface of the organic photosensitive layer. However, as described above, when the abrasion loss is significantly reduced due to the reduction in the coefficient of friction, the surface of the deteriorated organic photosensitive layer becomes difficult to be scraped off, and a phenomenon such as a decrease in the surface potential of the photoconductor and a decrease in sensitivity occurs, and the electrical characteristics deteriorate. I do.

Accordingly, an object of the present invention is to provide an organic photosensitive material which has a small deterioration in electric characteristics for a long period of time even when used in an image forming apparatus utilizing a wet developing method by appropriately increasing the abrasion amount of the photosensitive layer. Is to provide the body.

[0016]

[Detailed description of the invention]

[0017]

The electrophotographic photoreceptor of the present invention is used in a wet image forming apparatus using a developing solution in which toner particles are dispersed in a liquid. The electrophotographic photoreceptor has at least a charge generator and a charge transporter on a conductive substrate. A photosensitive layer made of a binder resin containing an agent, wherein the wear amount of the binder resin is larger than the wear amount of a bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 25,000, and the viscosity average molecular weight is 5,000.
0 is smaller than the wear amount of the bisphenol Z-type polycarbonate resin.

The measurement of the amount of abrasion varies depending on the measuring instrument and the measuring conditions, but it goes without saying that it is a value measured under the same measuring instrument and under the same measuring conditions. For example, in the measurement of the amount of abrasion by a Taber abrasion tester, a film thickness of 100 mm produced by applying a binder resin solution onto an aluminum disk and heat drying is used.
μm binder resin molded sample, temperature 24 ± 1
Under the environment of ℃, humidity 50 ± 5% RH, load 100
g, a rotation speed of 80 rpm and a condition of 1000 rotations, and a change in weight of the binder resin molded sample before and after the test is defined as a wear amount (mg).

That is, bisphenol Z having a viscosity average molecular weight of 25,000, measured with the above measuring instrument and measuring conditions.
Assuming that the wear amount of the polycarbonate resin is X (mg) and the wear amount of the bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 5,000 is Y (mg), the wear of the binder resin used in the electrophotographic photosensitive member of the present invention is A (m
g) satisfies the relational expression of X <A <Y.

When the abrasion loss of the binder resin used in the electrophotographic photoreceptor of the present invention is not more than the abrasion loss of a bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 25,000, an active gas such as ozone or NOx, or development. The surface of the photosensitive layer that has deteriorated due to the solution is hardly scraped, and the electrical characteristics are significantly deteriorated, so that a good image cannot be obtained over a long period of time. On the other hand, if the abrasion amount of the bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 5,000 is greater than the abrasion amount, the photosensitive layer is cut off more than necessary, and the electrical characteristics are similarly significantly deteriorated.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrophotographic photoreceptor of the present invention is used in a wet image forming apparatus using a developing solution in which toner particles are dispersed in a liquid, and has at least a charge generating agent and a charge transporting agent on a conductive substrate. A photosensitive layer made of a binder resin containing an agent, wherein the wear amount of the binder resin is larger than the wear amount of a bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 25,000, and the viscosity average molecular weight is 5,0
Any photoconductor may be used as long as it is smaller than the abrasion loss of the bisphenol Z-type polycarbonate resin of No. 00, and a single-layer photoconductor containing a charge generating agent and a charge transporting agent in a single photosensitive layer. Or a laminated photoconductor in which a charge generation layer and a charge transport layer are laminated.

When the electrophotographic photoreceptor of the present invention is a single layer type, it is preferable to use a hole transporting agent and an electron transporting agent together as a charge transporting agent, but usually the mobility of the electron transporting agent is lower than that of the hole transporting agent. Since it is smaller than the mobility, it is preferable to use a positive charging type. For the same reason, in the case of the stacked type,
It is preferable to use a negative charge type in which a charge transport layer containing a hole transport agent is laminated on the charge generation layer.
Hereinafter, the materials used for the electrophotographic photoreceptor of the present invention will be described in detail.

[Binder Resin] The wear amount of the binder resin used in the electrophotographic photosensitive member of the present invention is larger than the wear amount of the bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 25,000, and the viscosity average molecular weight is 5,000.
0 is smaller than the wear amount of the bisphenol Z-type polycarbonate resin.

As the binder resin used in the electrophotographic photoreceptor of the present invention, various resins conventionally used for a photosensitive layer can be used as long as the above conditions are satisfied. For example, bisphenol Z type, bisphenol ZC type, bisphenol C type, bisphenol A type, etc., polycarbonate resin, polyester resin, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer Polymer, acrylic copolymer, styrene-acrylic acid copolymer, polyethylene, ethylene-vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, Polyamide, polyurethane, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, thermoplastic resin such as polyether resin, silicone resin, epoxy resin, phenol resin,
Resins such as urea resins, melamine resins, other cross-linkable thermosetting resins, and photo-curing resins such as epoxy acrylate and urethane-acrylate can be used.

In particular, a bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of more than 5,000 and less than 25,000, or a compound represented by the general formula [1] or [2]
A binder resin containing the structural unit of (1) is preferably used. General formula [1]:

Embedded image (In the general formula [1], R ¹⁰ and R ¹¹ are the same or different and each represent a hydrogen atom or a phenyl group which may have a substituent.)

General formula [2]:

Embedded image (In the general formula [2], R ²⁰ and R ²¹ are the same or different and each represent a hydrogen atom or a phenyl group which may have a substituent.)

The above-mentioned binder resins can be used alone or as a blend or copolymer of two or more.

[Charge Generator] Examples of the charge generator used in the electrophotographic photoreceptor of the present invention include phthalocyanine pigments such as metal-free phthalocyanine, oxotitanyl phthalocyanine and hydroxygallium phthalocyanine, perylene pigments and bisazo pigments. , Diketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azulenium pigments, cyanine pigments, pyrylium pigments, anthanthrone pigments, triphenylmethane pigments, sulene pigments, Organic photoconductors such as toluidine pigments, pyrazoline pigments, and quinacridone pigments, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide,
Conventionally known charge generating agents such as inorganic photoconductive materials such as amorphous silicon can be used.

The charge generating agents exemplified above can be used alone or in combination of two or more so as to have an absorption wavelength in a desired region.

Among the above-described charge generating agents, in particular, a digital optical image forming apparatus such as a laser beam printer or a facsimile using a light source such as a semiconductor laser includes:
Since a photoreceptor having a sensitivity in a wavelength region of 700 nm or more is required, a phthalosinine-based pigment such as a metal-free phthalocyanine, oxotitanyl phthalocyanine, or hydroxygallium phthalocyanine is preferably used. The crystal form of the phthalocyanine pigment is not particularly limited, and various types can be used.

[Charge Transport Agent] As the charge transport agent used in the electrophotographic photosensitive member of the present invention, a conventionally known electron transport agent or hole transport agent can be used. In particular, in the case of a single-layer type photoreceptor, it is preferable that an electron transporting agent and a hole transporting agent are blended and contained in the photosensitive layer.

<Hole transport agent> Examples of the hole transport agent usable in the electrophotographic photoreceptor of the present invention include N, N, and N.
N ′, N′-tetraphenylbenzidine derivatives, N,
N, N ', N'-tetraphenylphenylenediamine derivative, N, N, N', N'-tetraphenylnaphthylenediamine derivative, N, N, N ', N'-tetraphenylphenanthrylenediamine derivative, 2 Oxadiazole compounds such as 9,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole Compounds, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazolin,
Nitrogen-containing cyclic compounds such as hydrazone-based compounds, indole-based compounds, oxazole-based compounds, isoxazole-based compounds, thiazole-based compounds, thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, and triazole-based compounds, and condensed polycyclic compounds Is mentioned.

In particular, the hole transporting agent preferably contains a compound represented by the general formula [3], [4], [5] or [6].

General formula [3];

Embedded image (In the general formula [3], R ³⁰ , R ³¹ , R ³² and R ³³ are the same or different and represent an alkyl group, an alkoxy group, an aryl group, an aralkyl group, or a halogen atom;
n, p and q are the same or different and represent an integer of 0-3. R ³⁴ and R ³⁵ are the same or different and each represent a hydrogen atom or an alkyl group. Also, -X-

Embedded image Or

Embedded image Is shown. )

General formula [4];

Embedded image (In the general formula [4], R ⁴⁰ and R ⁴² represent the same or different alkyl groups which may have a substituent, and R ⁴¹ and R ^42
43 is the same or different and represents a hydrogen atom or an alkyl group which may have a substituent. )

General formula [5];

Embedded image (In the general formula [5], R ⁵⁰ , R ⁵¹ , R ⁵² , R ⁵³ and R
⁵⁴ is the same or different and is a hydrogen atom, a halogen atom,
It represents an alkyl group or an alkoxy group which may have a substituent. )

General formula [6];

Embedded image (In the general formula [6], R ⁶⁰ , R ⁶¹ , R ⁶² and R ⁶³ are the same or different and each may have a halogen atom or a substituent.
It represents an alkyl group, an alkoxy group or an aryl group.
a, b, c and d are the same or different and each represents an integer of 0 to 5; When a, b, c or d is 2 or more, each R
⁶⁰ , R ⁶¹ , R ⁶² and R ⁶³ may be different. )

In the present invention, only one kind of hole transporting agent may be used, or two or more kinds thereof may be blended and used.

<Electron Transport Agent> Examples of the electron transport agent usable in the electrophotographic photoreceptor of the present invention include diphenoquinone derivatives, benzoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3,4 5,5,7-tetranitro-9-fluorenone derivative, dinitroanthracene derivative, dinitroacridine derivative, nitroantaraquinone derivative, dinitroanthraquinone derivative, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, Various compounds having an electron-accepting property, such as dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, and dibromomaleic anhydride, may be mentioned.

General formula [7];

Embedded image (In the general formula [7], R ⁷⁰ and R ⁷¹ represent the same or different alkyl groups which may have a substituent.)

General formula [8];

Embedded image (In the general formula [8], R ⁸⁰ and R ⁸¹ represent the same or different monovalent hydrocarbon groups which may have a substituent.)

Formula [9];

Embedded image (In the general formula [9], R ⁹⁰ represents a halogen atom, an optionally substituted alkyl group or an aryl group, and R ⁹¹ represents an optionally substituted alkyl group or an aryl group, or a group: .R ^91a showing a -O-R ^91a represents an alkyl group or an aryl group which may have a substituent.)

General formula [10];

Embedded image (In the general formula [10], R ¹⁰⁰ , R ¹⁰¹ , R ¹⁰² , and R ¹⁰³ are
It represents the same or different alkyl groups which may have a substituent. )

General formula [11];

Embedded image (In the general formula [11], R ¹¹⁰ and R ¹¹¹ represent the same or different alkyl groups which may have a substituent.)

General formula [12];

Embedded image (In the general formula [12], R ^{120 to} R ¹²³ are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms,
To 12 alkoxy groups, aryl groups which may have a substituent, cycloalkyl groups, aralkyl groups which may have a substituent, and halogenated alkyl groups. The substituent represents a halogen atom, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. )

General formula [13];

Embedded image (In the general formula [13], R ¹³⁰ and R ¹³¹ are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms,
To 12 alkoxy groups, aryl groups which may have a substituent, cycloalkyl groups, aralkyl groups which may have a substituent, and halogenated alkyl groups. R ^{132 to} R ¹³⁶ are
Same or different, hydrogen atom, halogen atom, carbon number 1
Alkyl group of 12 to 12, alkoxy group having 1 to 12 carbon atoms,
It represents an aralkyl group which may have a substituent, a phenoxy group which may have a substituent, and an alkyl halide group, and two or more groups may combine to form a ring. The substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or a halogenated alkyl group. )

General formula [14];

Embedded image (In the general formula [14], R ^{140 to} R ¹⁴³ are the same or different and are each a hydrogen atom, an alkyl group having 1 to 12 carbon atoms,
To 12 alkoxy groups, aryl groups which may have a substituent, cycloalkyl groups, aralkyl groups which may have a substituent, and halogenated alkyl groups. R ¹⁴⁴ and R ¹⁴⁵ are
The same or different and represent a hydrogen atom and an alkyl group having 1 to 12 carbon atoms. R ^{146 to} R ¹⁵³ are the same or different and are a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a halogenated alkyl group; Is shown. The substituent is a halogen atom, an alkyl group having 1 to 6 carbon atoms, 1 to 6 carbon atoms.
Represents an alkoxy group, a hydroxyl group, a cyano group, an amino group, a nitro group, and a halogenated alkyl group. )

In the present invention, the electron transporting agent may be used alone or in combination of two or more.

When the photosensitive layer is a single layer, the thickness of the photosensitive layer is 5
To 100 μm, and more preferably about 10 to 50 μm.
The charge generating agent is 0.1 to 5 with respect to the total weight of the binder resin.
It is preferable to contain 0 wt%, more preferably 0.5 to 30 wt%. The electron transporting agent is preferably contained in an amount of 5 to 100% by weight, more preferably 10 to 80% by weight based on the total weight of the binder resin. The hole transport agent is 5 to 500 wt%, and more preferably 25 to 200 wt%, based on the total binder resin weight.
It is preferable to include them. When the electron transporting agent and the hole transporting agent are mixed and used, the total amount of the electron transporting agent and the hole transporting agent is 20 to 500 w
It is preferable to contain t%, more preferably 30 to 200 wt%.

When the photosensitive layer has a laminated structure, the thickness of the charge generation layer is preferably about 0.01 to 5 μm, more preferably about 0.1 to 3 μm, and the thickness of the charge transport layer is 2 to 100 μm, more preferably 5 to 100 μm. About 50 μm is preferable. The charge generation layer contains the charge generation material in an amount of 0.1 to 50 wt.
%, More preferably 0.5 to 30 wt%, and the charge transport layer contains the charge transport material in an amount of 20 to 500 wt% based on the entire binder resin.
%, More preferably 30 to 200 wt%.

In the photosensitive layer, in addition to the above-described components, various conventionally known additives such as an antioxidant, a radical scavenger, a singlet quencher, Deterioration inhibitors such as UV absorbers, softeners,
Plasticizers, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, and the like can be added. Also, in order to improve the sensitivity of the photosensitive layer, for example,
Known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.

A barrier layer may be formed between the support and the photosensitive layer or between the laminated layers as long as the characteristics of the photosensitive member are not impaired.

As the support on which the photosensitive layer is formed, various conductive materials can be used.
Iron, aluminum, copper, tin, platinum, silver, vanadium,
Molybdenum, chromium, cadmium, titanium, nickel,
Examples of the material include simple metals such as palladium, indium, stainless steel, and brass; plastic materials on which the above metals are deposited or laminated; glass coated with aluminum iodide, tin oxide, indium oxide, and the like.

The shape of the support may be sheet-like or drum-like depending on the structure of the image forming apparatus to be used, and the support itself has conductivity or the surface of the support has What is necessary is just to have electroconductivity. The support preferably has a sufficient mechanical strength when used.

When the photosensitive layer is formed by a coating method, the above-described charge generating agent, charge transporting agent, binder resin and the like are used together with a suitable solvent in a known manner, for example, a roll mill, a ball mill, an attritor, a paint coater. What is necessary is just to disperse and mix using an acre, an ultrasonic disperser or the like to prepare a dispersion, apply it by a known means, and dry it.

As the solvent for preparing the dispersion, various organic solvents can be used, for example, alcohols such as methanol, ethanol, isopropanol and butanol, and aliphatic solvents such as n-hexane, octane and cyclohexane. Aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether. Ethers, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and methyl acetate, dimethylformaldehyde, dimethylformamide, dimethyls Rufoxide and the like. These solvents are used alone or in combination of two or more.

Further, a surfactant, a leveling agent and the like may be used in order to improve the dispersibility of the charge generating agent, the charge transporting agent and the like and the smoothness of the surface of the photosensitive layer.

Next, a wet image forming apparatus using the electrophotographic photosensitive member of the present invention will be described. FIG. 1 is a schematic cross-sectional view of an essential part of the image forming apparatus using wet development as an example.

The photosensitive member 1 is rotating at a constant speed in the direction of the arrow, and the electrophotographic process is performed on the surface of the photosensitive member 1 in the following order. That is, charging by the charger 2, exposure of the print pattern by the exposure light source 3, development by forming a toner image of the print pattern by the wet developing device 4, transfer of the toner to the transfer material (paper) 6 by the transfer device 5, and cleaning blade The toner is scraped off by 7 and finally static elimination by the static elimination light source 8 is performed.

The developing solution 4a in which the toner is dispersed is carried by the developing roller 4b, and by applying a developing bias to the developing roller 4b, the toner is attracted to the surface of the photoconductor 1 and developed. The solid concentration of the developing solution 4a is preferably 5 to 25% by weight. As the liquid (toner dispersion solvent) used for the developing solution 4a, a silicone-based oil is suitably used as described above, and a silicone-based oil having a viscosity at 20 ° C of 10 to 500 cSt is particularly preferable.

The present invention will be described below with reference to examples and comparative examples. Note that the following embodiments are merely examples embodying the present invention, and do not limit the technical scope of the present invention.

Examples 1 to 4 Comparative Examples 1 and 2 X-type metal-free phthalocyanine (3.5 parts by weight) as a charge generating agent, HTM-1 (65 parts by weight) as a hole transporting agent, electron transporting agent ETM-1 (35 parts by weight), and as a binder resin, a polycarbonate resin having a viscosity average molecular weight of 21,000 (Resin-1 to -6) 100
Parts by weight were dispersed or dissolved together with 400 parts by weight of tetrahydrofuran in a ball mill for 24 hours to prepare a single-layer type photosensitive layer coating solution. Then, this coating solution was applied by dip coating on an alumite-treated aluminum tube as a support, and dried with hot air at 130 ° C. for 40 minutes to obtain a single-layer photoreceptor having a thickness of 30 μm. Produced.

[Examples 5 to 8] [Comparative Examples 3 and 4] (3, 4)
000-30,000) A single-layer photoreceptor was produced in the same manner as in Examples 1 to 5, except that a bisphenol Z-type polycarbonate resin (Resin-7 to -12) was used.

The structural formulas of various materials used in the above Examples and Comparative Examples are shown below.

[HTM-1]

Embedded image

[ETM-1]

Embedded image

[Resin-1]

Embedded image

[Resin-2]

Embedded image

[Resin-3]

Embedded image

[Resin-4]

Embedded image

[Resin-5]

Embedded image

[Resin-6]

Embedded image

[Resin-7 to -12]

Embedded image

<Printing Test and Change in Electrical Characteristics of Photoconductor>
The single-layer type photoreceptors obtained in the above Examples and Comparative Examples were
printer having a wet development process similar to that of FIG. 1 using an nm laser as an exposure light source (An made by Kyocera Mita Corporation)
(Tico70 remodeled machine), 30,000 printing tests were performed, and the surface potential and residual potential (sensitivity) were measured by the probe 9 (Fig. 1) at the initial stage (before the printing test) and after the printing test. did. The initial surface potential was set to +500 V for all single-layer photoconductors.

The rate of change in surface potential and the rate of change in sensitivity were calculated according to the following equations. If the rate of change in surface potential or the rate of change in sensitivity is greater than 20%, a decrease in image density, image fogging, and the like are likely to occur, making it difficult to obtain a high-quality image. Surface potential change rate (%) = [(initial surface potential) − (surface potential after printing test)] / (initial surface potential) × 100 Sensitivity change rate (%) = [(residual potential after printing test) − ( (Initial residual potential)] / (initial residual potential) × 100

<Measurement of Binder Resin Abrasion by Taber Abrasion Tester> The measurement of the amount of abrasion was performed by a Taber abrasion tester. Then, a binder resin molded sample having a thickness of 100 μm prepared by applying a binder resin solution on an aluminum disk and heat-drying, was subjected to a temperature of 24 ± 1 ° C. and a humidity of 50 ° C.
The test was carried out under an environment of ± 5% RH under a condition of a load of 100 g and a rotation speed of 80 rpm for 1000 rotations, and a weight change of the binder resin molded sample before and after the test was defined as a wear amount (mg).

The viscosity average molecular weight 2 measured under the above measurement conditions
The wear amount of the 5,000 bisphenol Z-type polycarbonate resin was 2.5 mg. Similarly, the abrasion loss of the bisphenol Z-type polycarbonate resin having a viscosity average molecular weight of 5,000 measured under the above measurement conditions was 10.0 mg. That is, it suffices that the wear amount A (mg) of the binder resin used for the single-layer type photoreceptor satisfies the relational expression of 2.5 <A <10.0.

Tables 1 and 2 show the evaluation results. FIG. 2 shows the relationship between the amount of wear of the binder resin used for the single-layer type photoreceptor, the surface potential change rate and the sensitivity change rate.
FIG. 3 shows the relationship between the viscosity average molecular weight and the abrasion loss of the bisphenol Z-type polycarbonate resin used for the single-layer type photoreceptor.

[0078]

[Table 1]

[0079]

[Table 2]

FIG. 2 shows that the abrasion loss of the binder resin used for the single-layer type photosensitive member was more than 2.5 mg and 10.0 mg.
When it was smaller, the surface potential change rate before and after the printing test and the sensitivity change rate were within 20%.

However, when the amount of wear of the binder resin used for the single-layer type photoreceptor is 2.5 mg or less, the photosensitive layer surface deteriorated by an active gas such as ozone or NOx or a developing solution is not scraped, and printing is not performed. It is considered that the surface potential change rate before and after the test and the sensitivity change rate showed values larger than 20%.

On the other hand, when the wear amount of the binder resin used for the single-layer type photoreceptor is 10.0 mg or more, the wear amount of the photosensitive layer by the cleaning blade becomes extremely large, and the surface potential change before and after the printing test, and 20% change in sensitivity
It is considered that the value was larger.

FIG. 3 shows that when the binder resin used for the single-layer type photoreceptor is a bisphenol Z-type polycarbonate resin, there is a good correlation between the viscosity average molecular weight and the wear amount, and the viscosity average molecular weight is high. The larger the value, the smaller the amount of wear. This is presumably because the higher the viscosity average molecular weight, the higher the entanglement density of the resin molecules and the lower the amount of wear.

[0084]

According to the present invention, a photosensitive layer comprising a binder resin containing at least a charge generating agent and a charge transporting agent is provided on a conductive substrate, and the abrasion loss of the binder resin is a bisphenol Z type having a viscosity average molecular weight of 25,000. It is larger than the abrasion loss of the polycarbonate resin and has a viscosity average molecular weight of 5,000.
When the electrophotographic photoreceptor, which is characterized by being smaller than the wear amount of the bisphenol Z-type polycarbonate resin of No. 0, was used in an image forming apparatus using a wet developing method, the change in surface potential and sensitivity was small.

[0085]

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an essential part of an image forming apparatus using wet development in which an electrophotographic photoreceptor of the present invention is used as an example.

FIG. 2 is a graph showing the relationship between the amount of wear of a binder resin used for a single-layer type photoreceptor by a Taber abrasion tester, the rate of change in surface potential, and the rate of change in sensitivity.

FIG. 3 is a graph showing the relationship between the viscosity average molecular weight of a bisphenol Z-type polycarbonate resin used for a single-layer type photoreceptor and the amount of wear by a Taber abrasion tester.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H068 AA13 AA21 AA31 BB26 BB51 BB52 FA30 FB40 2H069 BA00 DA08

Claims (5)

[Claims] 1. A bisphenol Z type photosensitive material comprising a photosensitive layer comprising a binder resin containing at least a charge generating agent and a charge transporting agent on a conductive substrate, wherein the binder resin has an abrasion loss of a viscosity average molecular weight of 25,000. It is larger than the abrasion loss of the polycarbonate resin, and has a viscosity average molecular weight of 5,000.
An electrophotographic photoreceptor characterized in that it is used in an image forming apparatus of a wet development system using a developing solution in which toner particles are dispersed in a liquid, which is smaller than an abrasion amount of a bisphenol Z-type polycarbonate resin of No. 0. 2. The electrophotographic photosensitive member according to claim 1, wherein said photosensitive layer is a single-layer type containing a charge generating agent and a charge transporting agent in the same layer. 3. The method according to claim 1, wherein the binder resin is bisphenol Z.
The electrophotographic photosensitive member according to claim 1, wherein the photosensitive member is a mold-type polycarbonate resin. 4. The electrophotographic photoreceptor according to claim 1, wherein the binder resin contains a structural unit represented by the general formula [1] or [2]. General formula [1]: (In the general formula [1], R ¹⁰ and R ¹¹ are the same or different and each represent a hydrogen atom or a phenyl group which may have a substituent.) General formula [2]: (In the general formula [2], R ²⁰ and R ²¹ are the same or different and each represent a hydrogen atom or a phenyl group which may have a substituent.) 5. The liquid used in the developing solution is at 20 ° C.
Is a silicone oil having a viscosity of 10 to 500 cSt, and a solid content concentration of the developing solution is 5
5. The electrophotographic photoreceptor according to claim 1, wherein the content of the electrophotographic photoreceptor is about 25% by weight.