JP2005062813A - Electrophotographic photoreceptor for wet development and image forming apparatus for wet development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor for wet development having an excellent solvent resistance and an image forming apparatus equipped with such electrophotographic photoreceptor for wet development. <P>SOLUTION: The electrophotographic photoreceptor for wet development is equipped with a photoreceptor layer including a binder resin, a charge generating agent, an electron transport material, and a hole transport material, in which the hole transport material is a diazo compound expressed by general formula (1) or (2). In the general formula (1) and (2), A<SP>1</SP>and A<SP>2</SP>are each an aryl group or amine structure and X<SP>1</SP>is an arylene group or polycyclic structure. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic photoreceptor for wet development and an image forming apparatus for wet development having the same, and more particularly, to an electrophotographic photoreceptor for wet development having excellent solvent resistance and an image forming apparatus for wet development having the same. About.

Conventionally, as an electrophotographic photoreceptor for wet development used in an image forming apparatus or the like, an organic material composed of an organic photoreceptor material such as a charge transport agent (a hole transport material or an electron transport material), a charge generator, and a binder resin. Photoconductors are widely used. Such an organic photoreceptor is advantageous in that it is easy to manufacture and configure as compared to a conventional inorganic photoreceptor, and it is easy to perform wet development using a liquid developer.
However, the conventional electrophotographic photosensitive member for wet development has a problem that it is easily immersed in a liquid developer called isopar when used for a long time.

  Therefore, the present applicant is an electrophotographic photosensitive member for wet development comprising a charge generator, a hole transport material, an electron transport material, and a binder resin, wherein A single layer type electrophotographic photosensitive member for wet development having excellent solvent resistance has been already proposed by using a polycarbonate resin having a repeating structural unit (for example, Reference 1).

Further, the present applicant is an electrophotographic photoreceptor for wet development comprising a charge generator, a hole transport material, an electron transport material, and a binder resin, and is specified as a hole transport material. A single-layer type electrophotographic photoreceptor for wet development having excellent solvent resistance by using the stilbene compound has already been proposed (for example, Reference 2).
JP 2002-116560 (Claims etc.) JP 2001-192359 A (Claims etc.)

However, the electrophotographic photosensitive member for wet development described in Patent Document 1 and Patent Document 2 focuses on a hole transport material using a binder resin or a stilbene compound. In some cases, the sensitivity characteristics were still insufficient.
Therefore, the present inventors have shown that the use of a hole transport material having a specific amine structure not only improves the solvent resistance of the photoreceptor over a long period of time, but also improves the sensitivity characteristics. The headline and the present invention were completed.
That is, an object of the present invention is to provide an electrophotographic photosensitive member for wet development excellent in solvent resistance and sensitivity characteristics, and an image forming apparatus provided with such an electrophotographic photosensitive member for wet development.

According to the present invention, there is provided an electrophotographic photoconductor for wet development comprising a photoconductor layer comprising a binder resin, a charge generator, an electron transport material, and a hole transport material, the hole transport material. Is a diazo compound represented by the following general formula (1) or (2), and provides an electrophotographic photoreceptor for wet development, which can solve the above-mentioned problems.
That is, by using a hole transport material having a specific diazo structure in the molecule, an electrophotographic photoreceptor for wet development having excellent solvent resistance and sensitivity characteristics can be provided.

(In the general formulas (1) and (2), A ¹ and A ² are each independently a substituted or unsubstituted aryl group or an amine structure, and X ¹ is a substituted or unsubstituted arylene group or It is a polycyclic structure.)

In constructing the electrophotographic photoreceptor for wet development of the present invention, the photoreceptor layer is preferably a single layer type.
In this way, by including a binder resin, a charge generating agent, an electron transport material, and a specific hole transport material in a single layer, it is easy to manufacture and configure, It is possible to obtain an electrophotographic photosensitive member for wet development that has a small potential change value before and after use and improved durability.

In constructing the electrophotographic photoreceptor for wet development of the present invention, the amine structure represented by A ¹ and A ² in the general formulas (1) and (2) is represented by the following general formula (3) or (4). It is preferable that it is an amine structure shown by these.
That is, by using a hole transport material having such a specific structure at the terminal, an electrophotographic photoreceptor for wet development that is excellent not only in solvent resistance and sensitivity characteristics but also in mechanical characteristics and film formability is obtained. Can be provided.

(In general formula (3), R ¹ and R ² are substituted or unsubstituted aryl groups, and Ar ¹ is a substituted or unsubstituted arylene group.)

（一般式（４）中、Ｒ³およびＲ⁴は置換または非置換のアリール基であり、Ａｒ²およびＡｒ³は置換または非置換のアリーレン基である。）

(In General Formula (4), R ³ and R ⁴ are substituted or unsubstituted aryl groups, and Ar ² and Ar ³ are substituted or unsubstituted arylene groups.)

In constructing the electrophotographic photosensitive member for wet development of the present invention, the diazo structure in the general formulas (1) and (2) is formed by condensation of a nitroso form with an amine form, reduction of the nitro form, amine form and nitro form. An azo structure obtained by condensation with an azo compound or an azo coupling reaction with a diazonium salt is preferable.
With this configuration, a diazo compound that exhibits stable optical characteristics and is relatively inexpensive can be obtained. As a result, the electrophotographic film for wet development has stable optical characteristics and low raw material costs. A photoreceptor can be provided.

In constituting the electrophotographic photosensitive member for wet development according to the present invention, it is preferable that the charge generator contains at least one compound of metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine.
By comprising in this way, the more stable optical characteristic can be exhibited.

In constituting the electrophotographic photosensitive member for wet development of the present invention, the binder resin is preferably a copolymeric polycarbonate represented by the following general formula (5).
By comprising in this way, the electrophotographic photoreceptor for wet development excellent not only in solvent resistance and sensitivity characteristics but also in mechanical characteristics and film formability can be provided.

(In the general formula (5), R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X ² is an alkylene group (hydrocarbon group). And m and n satisfy the relational expression of 0.05 <m / (m + n) <0.4.)

In constructing the electrophotographic photoreceptor for wet development according to the present invention, the photoreceptor layer is immersed in a hydrocarbon solvent used as a developer for wet development at a temperature of 25 ° C. for 2000 hours. The elution amount of the hole transport material is preferably 7 × 10 ⁻⁷ g · cm ⁻³ or less.
By comprising in this way, the solvent resistance of the electrophotographic photoreceptor for wet development can be estimated in a short time. For example, the solvent resistance in the case where 100,000 images are formed can be estimated by a 2000 hour immersion test.

In constructing the electrophotographic photoreceptor for wet development according to the present invention, the photoreceptor layer is immersed in a hydrocarbon solvent used as a developer for wet development at a temperature of 25 ° C. for 2000 hours. The sensitivity change is preferably set to a value of 13 V or less.
With this configuration, the sensitivity characteristics of the electrophotographic photoreceptor for wet development can be reliably estimated in a short time. For example, the solvent resistance in the case where 100,000 images are formed can be estimated by a 2000 hour immersion test.

Another aspect of the present invention includes any one of the electrophotographic photoconductors for wet development described above, and a charging step, an exposure step, a development step, and a transfer step around the electrophotographic photoconductor for wet development. An image forming apparatus for wet development, wherein the image is formed using a liquid developer in which toner is dispersed in a hydrocarbon solvent in the developing step.
As described above, since the electrophotographic photoreceptor for wet development excellent in solvent resistance and sensitivity characteristics is provided, stable image characteristics can be maintained over a long period of time.

  Hereinafter, embodiments of the electrophotographic photoreceptor for wet development and an image forming apparatus according to the present invention will be specifically described with reference to the drawings as appropriate.

[First embodiment]
A first embodiment is an electrophotographic photosensitive member for wet development including a photosensitive layer including a binder resin, a charge generating agent, an electron transporting material, and a hole transporting material. An electrophotographic photoreceptor for wet development, wherein the material is a specific diazo compound represented by the following general formula (1) or (2).

(In the general formulas (1) and (2), A ¹ and A ² are each independently a substituted or unsubstituted aryl group or an amine structure, and X ¹ is a substituted or unsubstituted arylene group or It is a polycyclic structure.)

Here, the electrophotographic photosensitive member for wet development includes a single layer type and a laminated type, and the electrophotographic photosensitive member for wet development of the present invention is applicable to both.
However, it can be used for both positive and negative chargeability, has a simple structure and is easy to manufacture, and suppresses film defects when forming the photoreceptor layer, so there are few interfaces between layers, improving optical characteristics For reasons such as being possible, it is more preferable to apply to a single layer type.

1. Single Layer Type Photoreceptor (1) Basic Configuration A single layer type photoconductor is obtained by providing a single photoconductor layer on a conductive substrate. This photoreceptor layer is formed by applying a coating solution containing a binder resin, a charge generating agent, an electron transporting material, a hole transporting material, and, if necessary, a solvent onto an aluminum base tube and drying it. Can be obtained. Such a single-layer type photoreceptor is advantageous in that it can be applied to both positive and negative charging types by a single configuration and has a simple layer configuration and excellent productivity.

(2) Binder Resin As the binder resin for dispersing the charge generating agent and the like, various resins conventionally used for photoreceptors can be used. For example, polycarbonate resin such as bisphenol Z type, bisphenol ZC type, bisphenol C type, bisphenol A type, polyarylate resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic copolymer Polymer, styrene-acrylic acid copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer resin, vinyl chloride-vinyl acetate copolymer, alkyd resin, Thermoplastic resins such as polyamide resin, polyurethane resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, silicone resin, epoxy resin, phenol resin, urea resin, melamine Fat, other crosslinking thermosetting resins, epoxy acrylate, urethane - is available resin such as a photocurable resin such as acrylate

Of these binder resins, it is more preferable to use a copolymerized polycarbonate represented by the following general formula (5).
This is because such a copolycarbonate is hardly soluble in a hydrocarbon solvent and has high oil repellency. As a result, the interaction between the surface of the photoreceptor layer and the above-mentioned hydrocarbon solvent is reduced, and the change in the appearance of the surface of the photoreceptor layer is reduced over a long period of time.

(In the general formula (5), R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, X ² is an alkylene group, polycyclic ring, (It is a heterocyclic ring, and m and n satisfy the relational expression 0.05 <m / (m + n) <0.4.)

(3) Charge generating agent Examples of the charge generating agent used in the electrophotographic photoreceptor of the present invention include phthalocyanine pigments such as metal-free phthalocyanine and oxotitanyl phthalocyanine, perylene pigments, bisazo pigments, diketopyrrolopyrrole pigments. , Metal-free naphthalocyanine pigment, metal naphthalocyanine pigment, squaraine pigment, trisazo pigment, indigo pigment, azulenium pigment, cyanine pigment, pyrylium pigment, ansanthrone pigment, triphenylmethane pigment, selenium pigment, toluidine pigment, pyrazoline pigment Conventionally known charge generating agents such as organic photoconductors such as pigments and quinacridone pigments and inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon can be used.

  Of these charge generators, it is more preferable to use phthalocyanine pigments (CGM-1 to CGM-4) represented by the following formulas (6) to (9).

Among the charge generating agents described above, in particular, when used in a digital optical image forming apparatus such as a laser beam printer or a facsimile provided with a light source such as a semiconductor laser, a photosensitive material having sensitivity in a wavelength region of 700 nm or more. Therefore, it is preferable that at least one of metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine is contained.
On the other hand, when used in an image forming apparatus of an analog optical system such as an electrostatic copying machine equipped with a white light source such as a halogen lamp, a photoreceptor having sensitivity in the visible region is required. Pigments and bisazo pigments are preferably used.
In the case of a single-layer type photoreceptor, the amount of charge generator added is preferably set to a value in the range of 0.1 to 50% by weight, based on the total weight of the binder resin, 0.5 to 30 More preferably, the value is within the range of% by weight.

(4) Electron Transport Material (4) -1 Types As the types of electron transport materials suitable for the electrophotographic photoreceptor of the present invention, in addition to diphenoquinone derivatives and benzoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone Derivatives, 3,4,5,7-tetranitro-9-fluorenone derivatives, dinitroanthracene derivatives, dinitroacridine derivatives, nitroantharaquinone derivatives, dinitroanthraquinone derivatives, tetracyanoethylene, 2,4,8-trinitrothioxanthone, di Various compounds having electron accepting properties such as nitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, succinic anhydride, maleic anhydride, dibromomaleic anhydride and the like can be mentioned, German one or more blended may be used.
Of these compounds, compounds having an electron mobility of 1.0 × 10 ⁻⁸ cm ² / V / sec or more at an electric field strength of 5 × 10 ⁵ v / cm are more preferable.

(4) -2 Specific Example Further, in order to further improve the isopar resistance (developer resistance) and the photosensitivity, the electron transporting material itself is also less soluble in isopar and transports electrons with a small content. It is preferable that the property is high. As such an electron transporting material, for example, compounds (ETM-1 to ETM-4) represented by the following formulas (10) to (13) are preferably used.

(4) -3 Addition amount In constituting the electrophotographic photosensitive member for wet development, the addition amount of the electron transport material is a value within the range of 5 to 100 parts by weight with respect to 100 parts by weight of the binder resin. It is preferable to do.
The reason for this is that when the added amount of the plurality of electron transport materials is less than 5 parts by weight, the sensitivity is lowered and a practical problem may occur. On the other hand, when the added amount of the plurality of electron transport materials exceeds 100 parts by weight, the electron transport material is likely to be crystallized, and an appropriate film as a photoreceptor may not be formed.
Therefore, it is more preferable to set the addition amount of the electron transport material to a value within the range of 10 to 80 parts by weight.

In addition, when determining the addition amount of an electron transport material, it is preferable to consider the addition amount of the hole transport material mentioned later. More specifically, the addition ratio (total ETM / total HTM) of the electron transport material (total ETM) is a value within the range of 0.25 to 1.3 with respect to the hole transport material (total HTM). It is preferable to do.
This is because if the ratio of all ETMs / all HTMs is outside this range, the sensitivity is lowered, which may cause practical problems.
Therefore, it is more preferable that the ratio of the total ETM / total HTM is set to a value within the range of 0.5 to 1.25.

(5) Hole transport material (5) -1 type As a type of the hole transport material, the diazo compound represented by the general formula (1) or (2) described above is used.
The reason for this is that by introducing a specific diazo structure in the molecule, the solvent resistance against Isopar can be improved, and excellent image formation can be carried out over a long period of time. Further, the diazo compound represented by the general formula (1) or (2) is excellent in sensitivity characteristics, and can exhibit further excellent image characteristics.

In the diazo compound represented by the above general formula (1) or (2), the amine structures A ¹ and A ² in the formula are independent of each other, and are represented by the general formula (3) or (4). It is preferable that it is an amine structure shown by these.
The reason is that by introducing such a specific structure at the molecular end, not only the solvent resistance and sensitivity characteristics can be further improved, but also the mechanical characteristics and film formability are improved. Therefore, it is possible to efficiently provide a single layer type electrophotographic photoreceptor for wet development that maintains excellent image characteristics over a long period of time and is easy to manufacture.

In addition, the diazo structure in the general formulas (1) and (2) can be obtained by condensation of nitroso and amine, reduction of nitro, condensation of amine and nitro, or azo coupling reaction with diazonium salt. The obtained azo structure is preferred.
The reason is that the azo structure thus obtained can provide an excellent sensitivity characteristic and a relatively inexpensive diazo compound. As a result, it is possible to efficiently provide an electrophotographic photoreceptor for wet development with stable optical characteristics and low raw material costs.
As an example, it is preferable to introduce a diazo structure according to the following reaction formula (14).

(5) -2 Specific Example Specific examples of the hole transport material include diazo compounds (HTM-1 to HTM-9) represented by the following formulas (15) to (23).

  It is also preferable to use a conventionally known hole transport material in combination with the photoreceptor layer. Examples of the hole transport material include N, N, N ′, N′-tetraphenylbenzidine derivatives, N, N, N ′, N′-tetraphenylphenylenediamine derivatives, N, N, N ′, N ′. -Tetraphenylnaphthylenediamine derivatives, N, N, N ', N'-tetraphenylphenanthrylenediamine derivatives, 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, etc. Oxadiazole compounds, styryl compounds such as 9- (4-diethylaminostyryl) anthracene, carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, pyrazolines such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline Compounds, hydrazone compounds, indole compounds, oxazole compounds, isoxazo Le compounds, thiazole compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, and nitrogen-containing cyclic compounds such as triazole compounds, and condensed polycyclic compounds.

(5) -3 Addition Amount The addition amount of the hole transport material is preferably set to a value within the range of 10 to 80 parts by weight with respect to 100 parts by weight of the binder resin.
The reason for this is that when the added amount of the hole transport material is less than 10 parts by weight, the sensitivity is lowered and a practical problem may occur. On the other hand, when the added amount of the hole transport material exceeds 80 parts by weight, the hole transport material is likely to be crystallized, and an appropriate film as a photoreceptor may not be formed.
Therefore, it is more preferable to set the addition amount of the hole transport material to a value within the range of 30 to 70 parts by weight.

(6) Additive In addition to the above-mentioned components, the photoreceptor layer has various conventionally known additives such as an antioxidant, a radical scavenger, a singlet as long as it does not adversely affect the electrophotographic characteristics. Deterioration inhibitors such as quenchers and ultraviolet absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersion stabilizers, waxes, acceptors, donors, and the like can be blended. In order to improve the sensitivity of the photoreceptor layer, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.

(7) Structure The thickness of the photoreceptor layer in the single-layer photoreceptor is usually a value in the range of 5 to 100 μm, preferably a value in the range of 10 to 50 μm.
As the conductive substrate on which such a photoreceptor layer is formed, various conductive materials can be used, for example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium. , Cadmium, titanium, nickel, palladium, indium, stainless steel, brass and the like, plastic materials on which the above metal is deposited or laminated, glass covered with aluminum iodide, tin oxide, indium oxide, etc. .

Further, the shape of the conductive substrate may be any of a sheet shape, a drum shape, or the like in accordance with the structure of the image forming apparatus to be used. The substrate itself is conductive or the surface of the substrate is conductive. As long as it has. The conductive substrate preferably has sufficient mechanical strength when used. When the photoreceptor layer is formed by a coating method, the above-described charge generator, charge transport agent, binder resin and the like together with a suitable solvent, a known method such as a roll mill, a ball mill, an attritor, a paint shaker, A dispersion liquid may be prepared by dispersing and mixing using an ultrasonic disperser or the like, and this may be applied and dried by a known means.
Furthermore, with respect to the configuration of the single-layer type photoreceptor, a barrier layer may be formed between the conductive substrate and the photoreceptor layer as long as the characteristics of the photoreceptor are not impaired. Further, a protective layer may be formed on the surface of the photoreceptor.

(8) Manufacturing method Various organic solvents can be used as a solvent for preparing the dispersion. For example, alcohols such as methanol, ethanol, isopropanol, and butanol; aliphatic systems such as n-hexane, octane, and cyclohexane Hydrocarbons: aromatic hydrocarbons such as benzene, toluene, xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether Ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformaldehyde, dimethylformamide, dimethylsulfoxide Sid etc. are mentioned. These solvents are used alone or in admixture of two or more.
Further, a surfactant, a leveling agent or the like may be used in order to improve the dispersibility of the charge transport agent or the charge generator and the smoothness of the surface of the photoreceptor layer.

2. Laminated Photoreceptor (1) Basic Structure A laminated photoconductor is formed by first forming a charge generating layer containing a charge generating agent on a conductive substrate by means of vapor deposition or coating, and then on the charge generating layer. And applying a coating liquid containing at least one diazo compound (hole transport material) represented by the general formula (1) or (2) and a binder resin, followed by drying to form a charge transport layer. It is produced by.
Conversely, a charge transport layer may be formed on a conductive substrate, and a charge generation layer may be formed thereon. However, since the charge generation layer is much thinner than the charge transport layer, it is preferable to form the charge generation layer on the conductive substrate and to form the charge transport layer on the conductive base for protection. .
The charge generating agent, hole transporting material, electron transporting material, binder and the like can be the same as those of the single-layer type photoreceptor.

In addition, a positive or negative charge type is selected depending on the formation order of the charge generation layer and the charge transport layer and the kind of the charge transport agent used in the charge transport layer. For example, when a charge generation layer is formed on a conductive substrate and a charge transport layer is formed thereon, a hole transport material such as a stilbene derivative is used as a charge transport agent in the charge transport layer. The photoreceptor is of a negative charge type. In this case, the charge generation layer may contain an electron transport material. In the case of a multilayer electrophotographic photoreceptor, the residual potential of the photoreceptor is greatly reduced, and the sensitivity can be improved.
Regarding the thickness of the photoreceptor layer in the multilayer photoreceptor, the charge generation layer is about 0.01 to 5 μm, preferably about 0.1 to 3 μm, and the charge transport layer is 2 to 100 μm, preferably 5 to 5 μm. It is about 50 μm.

[Second Embodiment]
The second embodiment includes the electrophotographic photosensitive member for wet development of the first embodiment (hereinafter sometimes simply referred to as a photosensitive member), and around the electrophotographic photosensitive member for wet development. Image formation for wet development characterized in that a charging process, an exposure process, a development process, and a transfer process are arranged, and in the development process, an image is formed using a liquid developer in which a toner is dispersed in a hydrocarbon solvent. Device. In this example of the image forming apparatus for wet development, the case where a single layer type photoreceptor is used as the electrophotographic photoreceptor will be described.

That is, as shown in FIG. 1, in such an image forming apparatus for wet development, a charger 2 for performing a charging process and an exposure light source for performing an exposure process are provided around the electrophotographic photosensitive member for wet development. 3. It is preferable that at least a wet developing device 4 for carrying out the developing step and a transfer device 5 for carrying out the transferring step are provided.
The photoconductor 1 rotates at a constant speed in the direction of the arrow, and the electrophotographic process is performed on the surface of the photoconductor 1 in the following order. More specifically, the charger 1 charges the entire surface of the photoreceptor 1, and then the print pattern is exposed by the exposure light source 3. Next, the toner is developed by the wet developing device 4 in accordance with the print pattern, and the toner is transferred onto the transfer material (paper) 6 by the transfer device 5. Finally, the excess toner remaining on the photosensitive member 1 is scraped off by the cleaning blade 7, and the charge removal of the photosensitive member 1 is performed by the charge removal light source 8.

Here, the liquid developer 4a in which the toner is dispersed is conveyed by the developing roller 4b, and the toner is attracted onto the surface of the photosensitive member 1 by applying a predetermined developing bias, and is developed on the photosensitive member 1. Will be. Further, the solid content concentration in the liquid developer 4a is preferably set to a value in the range of 5 to 25% by weight, for example. Further, as the liquid (toner dispersion solvent) used in the liquid developer 4a, a hydrocarbon solvent or a silicone oil is preferably used.
Then, in the photoreceptor 1, by using a hole transport material having a specific amine structure, a single-layer type electrophotographic photoreceptor for wet development having excellent solvent resistance and sensitivity characteristics can be obtained. In addition, excellent image characteristics can be maintained.

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

[Example 1]
(1) Preparation of electrophotographic photosensitive member for wet development In an ultrasonic disperser, 3.5 parts by weight of X-type metal-free phthalocyanine (CGM-1) represented by formula (6) as a charge generator 40 parts by weight of the diazo compound (HTM-1) represented by the formula (15) as the hole transporting material and 50 parts by weight of the naphthoquinone derivative (ETM-1) represented by the formula (10) as the electron transporting material. Parts, 100 parts by weight of polycarbonate resin represented by the following formula (24) as binder resin, and 0.1 parts by weight of KF-96-50CS (manufactured by Shin-Etsu Chemical Co., Ltd.) which is dimethyl silicone oil as a leveling agent And 750 parts by weight of tetrahydrofuran as a solvent were stored, followed by ultrasonic treatment for 3 minutes to mix and disperse to prepare a coating solution.
The obtained coating solution was applied by dip coating on a conductive base material (anodized aluminum base tube) having a diameter of 30 mm and a length of 254 mm. Thereafter, it was dried with hot air at 130 ° C. for 30 minutes to obtain an electrophotographic photoreceptor for wet development having a single-layer photoreceptor layer with a thickness of 20 μm.
For reference, FIG. 2 shows an infrared spectroscopic chart of the diazo compound (HTM-1) represented by the formula (15) as a hole transport material, and FIG. An NMR chart is shown.

(2) Evaluation (2) -1 Sensitivity Measurement The light potential in the obtained electrophotographic photoreceptor for wet development was measured. That is, using a drum sensitivity tester (produced by GENTEC), it was charged to 700 V, and then monochromatic light with a wavelength of 780 nm (half-value width: 20 nm, light amount) extracted from the light of the halogen lamp using a hand pulse filter. : 1.0 μJ / cm ² ). The potential after 330 msec after exposure was measured and used as the initial sensitivity. The entire photoreceptor was immersed in Isopar H (aliphatic hydrocarbon solvent) at a temperature of 25 ° C. for 2000 hours. Thereafter, the electrophotographic photosensitive member for wet development was taken out from the ISOPAR solution, and the sensitivity was measured in the same manner, and the difference between the initial sensitivity and the sensitivity after ISOPAR immersion was calculated.

(2) -2 Solvent Resistance Evaluation The obtained single layer type electrophotographic photoreceptor for wet development was immersed in Isopar H used as a developer for wet development under conditions of a temperature of 25 ° C. and 2000 hours. . On the other hand, the hole transport material was forcibly dissolved in Isopar H by changing the concentration of the hole transport material. In this state, the absorbance at the ultraviolet absorption peak wavelength was measured, and a concentration-absorbance calibration curve for the hole transport material was prepared in advance. Next, wet absorption electrophotographic photoreceptor immersed in Isopar H is subjected to ultraviolet absorption measurement, and the amount of elution of the hole transport material is calculated from the absorbance at the ultraviolet absorption peak wavelength of the hole transport material in light of the calibration curve. did. The obtained results are shown in Table 1.

(2) -3 Appearance Evaluation The appearance of the electrophotographic photoreceptor for wet development after the solvent resistance evaluation was visually observed, and the appearance was evaluated according to the following criteria. The obtained results are shown in Table 1.
A: No change in appearance is observed.
○: No significant change in appearance is observed.
Δ: Some change in appearance is observed.
X: A remarkable change in appearance is observed.

[Examples 2-6 and Comparative Examples 1-2]
In Examples 2 to 6, a single layer type was used as in Example 1 except that diazo compounds represented by formulas (16) to (20) were used instead of the hole transporting material of formula (15). An electrophotographic photosensitive member for wet development was prepared and evaluated.
In Comparative Examples 1 and 2, amine compounds (HTM-10 to HTM-11) represented by the following formulas (25) and (26) were used instead of the hole transport material of the formula (15). In the same manner as in Example 1, a single layer type electrophotographic photoreceptor for wet development was prepared and evaluated. The obtained results are shown in Table 1.

As described above in detail, according to the present invention, by using a hole transport material having a specific amine structure, an electrophotographic photoreceptor for wet development excellent in solvent resistance and sensitivity characteristics, and so on. An image forming apparatus having an electrophotographic photosensitive member for wet development can be obtained.
Therefore, the electrophotographic photoreceptor for wet development of the present invention is expected to contribute to cost reduction, speedup, performance enhancement, etc. in various image forming apparatuses such as electrostatic copying machines and laser beam printers.

It is a figure provided in order to demonstrate the image forming apparatus provided with the electrophotographic photoreceptor for wet development. 2 is an infrared spectroscopic chart of an example of a hole transport material used in the electrophotographic photoreceptor for wet development of the present invention. It is a proton-NMR chart of the example of a hole transport material used for the electrophotographic photoreceptor for wet development of this invention.

Explanation of symbols

1: Photoconductor 2: Charger 3: Exposure light source 4: Wet developer 4a: Liquid developer 5: Transfer device
7: Cleaning blade 8: Static elimination light source

Claims (8)

An electrophotographic photoreceptor for wet development comprising a photoreceptor layer comprising a binder resin, a charge generator, an electron transport material, and a hole transport material,
The electrophotographic photoreceptor for wet development, wherein the hole transport material is a diazo compound represented by the following general formula (1) or (2).

(In General Formulas (1) and (2), A ¹ and A ² are each independently a substituted or unsubstituted aryl group or an amine structure, and X ¹ is a substituted or unsubstituted arylene group or It is a polycyclic structure.)   2. The electrophotographic photoreceptor for wet development according to claim 1, wherein the photoreceptor layer is a single layer type. The amine structure represented by A ¹ and A ² in the general formulas (1) and (2) is an amine structure represented by the following general formula (3) or (4): Item 2. The electrophotographic photosensitive member for wet development according to Item 1.

(In general formula (3), R ¹ and R ² are substituted or unsubstituted aryl groups, and Ar ¹ is a substituted or unsubstituted arylene group.)

(In General Formula (4), R ³ and R ⁴ are substituted or unsubstituted aryl groups, and Ar ² and Ar ³ are substituted or unsubstituted arylene groups.)   The electrophotographic image for wet development according to any one of claims 1 to 3, wherein the charge generating agent includes at least one compound of metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine. Photoconductor. The electrophotographic photosensitive member for wet development according to any one of claims 1 to 4, wherein the binder resin is a copolymer polycarbonate represented by the following general formula (5).

(In the general formula (5), R ⁵ , R ⁶ , R ⁷ and R ⁸ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and X ² is a substituted or unsubstituted alkylene. A group, a polycycle, or a heterocycle, and m and n satisfy the relational expression of 0.05 <m / (m + n) <0.4.) When the photoreceptor layer is immersed in a hydrocarbon solvent used as a developing solution for wet development under conditions of a temperature of 25 ° C. and 2000 hours, an elution amount of the hole transport material is 7 × 10 ⁻⁷ g. The electrophotographic photosensitive member for wet development according to any one of claims 1 to 5, wherein the value is cm ^-3 or less.   The sensitivity change when the photosensitive layer is immersed in a hydrocarbon solvent used as a developing solution for wet development under conditions of a temperature of 25 ° C. and 2000 hours is set to a value of 13 V or less. The electrophotographic photosensitive member for wet development according to any one of 1 to 6.   The electrophotographic photosensitive member for wet development according to any one of claims 1 to 7, and a charging step, an exposure step, a developing step, and a transfer step are arranged around the electrophotographic photosensitive member for wet development. An image forming apparatus for wet development, wherein in the development step, image formation is performed using a liquid developer in which toner is dispersed in a hydrocarbon solvent.

Images