JP6287367B2 - Electrophotographic photosensitive member for liquid development and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member used for a copying machine, a printer, and the like. More particularly, the present invention relates to an electrophotographic photosensitive member for liquid development having excellent solvent resistance and good electrical characteristics, an image forming apparatus and an image forming method of a liquid development system.

  In the electrophotographic technology, the development process methods for visualizing an image are roughly classified into a dry development method and a liquid (wet) development method. Among these, the liquid development method has a long history that originated in the 1950s, but there are problems for office use, such as using a developing solvent (usually an organic solvent). Generally, dry development is exclusively used for office use. The system is currently used. However, a toner with a small diameter of 0.1 μm to 2 μm can be used, higher resolution than dry type, high image quality close to that of offset printing can be obtained, and high speed can be supported. It is increasingly used in place of offset printing for new commercial printing systems such as demand printing.

  On the other hand, an electrophotographic photoreceptor (hereinafter referred to as “photoreceptor” as appropriate) which is the core of the electrophotographic technology has advantages such as pollution-free and easy film formation, easy production and low cost. Photoconductors using organic photoconductive materials are the mainstream. Examples of the photoreceptor using the organic photoconductive material (organic photoreceptor) include, for example, a so-called dispersed photoreceptor (single-layer photoreceptor) in which photoconductive fine powder is dispersed in a binder resin, and charge generation layer. In addition, a laminate type photoreceptor (function separation type photoreceptor) in which a charge transport layer is laminated is known. Among them, the laminated type photoreceptor can obtain a highly sensitive photoreceptor by combining a charge generation material having high charge generation efficiency and a charge transport material having a high mobility and an ionization potential matched to the charge generation material. It is widely used because it offers a wide selection range and a highly safe photoconductor, and because it can easily form a photosensitive layer by coating, has high productivity, and is advantageous in terms of cost.

  In the liquid developing system, such an organic photoreceptor is in contact with a developing solvent used as a carrier for a certain period of time during the developing process. In particular, in a normal color process, a developer having four or more colors is used, and therefore, the developer is exposed to a developing solvent for a longer time. When the photosensitive member is repeatedly exposed to the developing solvent in this way, defects called cracks are generated on the surface of the photosensitive member, which appear as streak defects in the printed image, which may hinder improvement in durability.

  There are various theories about the mechanism of the occurrence of such cracks. For one thing, low molecular components of the photoreceptor are eluted by the developing solvent, creating voids, which are repeatedly subjected to mechanical loads from the surroundings. Fatigue-breaking mechanisms such as growth and cracking can be considered. In such a case, by improving the mechanical properties of the binder resin used in the surface layer of the photoreceptor, it is expected that the voids are prevented from growing and cracking, resulting in improved durability. The

Further, most of the conductive support of the photosensitive member (hereinafter referred to as “support” as appropriate) is in the form of a drum (cylinder), but the properties are flexible and the degree of freedom in design when arranging in the apparatus. A sheet or belt-shaped photoconductor is also used for reasons such as a large size. In that case, the photosensitive layer is formed by applying a coating solution containing a photoconductive substance and a binder resin on a sheet-like support by reverse coating, gravure coating, bar coating, roll coating, blade coating, or the like. The Alternatively, a sheet-like or seamless belt-like support can be wound around a drum-like support and applied by a coating method such as dip coating. In these layer forming methods, a coating solution obtained by dissolving a substance contained in a layer in a solvent is used. In many processes, a coating solution is prepared in advance and stored until it is applied. Therefore, the binder resin is also required to have excellent solubility in the solvent used in the coating process and to be stable in the coating solution after dissolution.

  Conventional photoconductors do not have sufficient solvent resistance and crack resistance for use in liquid development systems, and there are cases where cracks occur on the surface during repeated use, resulting in image defects. . In particular, when a part of the polycarbonate resin, which is highly versatile and inexpensive, is used, there is a problem that a crack is generated on the surface and an image defect is caused. As a technique for solving this problem, there is a technique using a specific polyarylate resin for a photosensitive layer (Patent Document 6).

  In addition, for commercial printing systems, it has been studied to transport the electrophotographic photosensitive member using a roller having a small diameter in order to increase the width or area of the photosensitive member and to reduce the size of the electrophotographic apparatus for higher speed. Yes. In either case, there has been a problem that a warp (curl) occurs in the photoconductor, and troubles such as the side edge of the photoconductor being lifted and touching the charger occur. As a technique for solving this problem, there is a technique for adjusting the residual solvent amount in the charge transport layer by setting the film thickness of the photosensitive layer to 21 μm or more (Patent Document 7). In the system of the example of Patent Document 7, the smaller the residual solvent, the better the electrical characteristics. However, even if the electrical characteristics are somewhat inferior, the residual solvent is set within a certain range to prevent curling.

JP 2003-295485 A JP 2006-113352 A JP 2006-113354 A JP 2006-89702 A JP 2005-115091 A JP 2010-96811 A JP 2000-267308 A

The resin described in Patent Document 6 cannot sufficiently satisfy the electric characteristics, and when the charge transport layer is a thin film advantageous in terms of cost, the electric characteristics are further deteriorated. In addition, the technique described in Patent Document 7 cannot cope with downsizing and does not have sufficient crack resistance.
The present invention has been made to solve such problems. That is, the object of the present invention is to have sufficient solvent stability and crack resistance in a liquid development system even in the case where a charge transport material or resin having low crack resistance is used, and even in a thin film, the electric characteristics are sufficiently excellent. An object of the present invention is to provide an electrophotographic photosensitive member and an image forming apparatus provided with the same.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a resin having a specific structure in the charge transport layer, and by setting the film thickness of the charge transport layer and the residual solvent amount to a specific range. The present invention has been completed by finding that the obtained photoreceptor exhibits excellent crack resistance and electrical characteristics even when a charge transport material or binder resin, which has a disadvantageous cracking performance with respect to the developing solvent, is used.

That is, the gist of the present invention resides in the following <1> to <6>.
<1> A laminate type liquid developing electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer has a repeating structure represented by the following formula (1): contains a polyester resin having, charge transport layer having a thickness of 20μm or less, the electrophotographic photosensitive liquid developer, characterized in that the residual solvent content of the charge transport layer is 5mg / cm ³ ~50mg / cm ³ body.

(In Formula (1), Ar ¹ and Ar ² each independently represent an arylene group having 30 or less carbon atoms, which may have a substituent. X ¹ represents a single bond, an oxygen atom, a sulfur atom, A divalent organic residue having a structure represented by the formula (2) or a structure represented by the formula (3) is represented.k represents an integer of 0 to 3.)

(R ¹ and R ^{2 in} formula (2) each independently represent a hydrogen atom, an alkyl group, or an aryl group, or a cycloalkylidene group formed by combining R ¹ and R ^2. )
—O—R ³ —O— Formula (3)
(R ³ in Formula (3) represents an alkylene group, an arylene group, or a group represented by Formula (4).)
—R ⁴ —Ar ³ —R ⁵ — Formula (4)
(R ⁴ and R ^{5 in} Formula (4) each independently represent an alkylene group, and Ar ³ represents an arylene group which may have a substituent.)
<2> The electrophotographic photosensitive member for liquid development according to <1>, wherein the charge transport layer contains a polycarbonate resin having a repeating structure represented by the following formula (A).

<3> The electrophotographic photosensitive member for liquid development according to <1> or <2>, wherein the charge transport layer contains a polycarbonate resin having a repeating structure represented by the following formula (B).

<4> The charge transport layer contains 30 parts by mass or more of the polyester resin with respect to 100 parts by mass of the total resin in the charge transport layer. Any one of <1> to <3> The electrophotographic photosensitive member for liquid development described in <5> is 25 with respect to 100 parts by mass of the total resin in the charge transport layer.
The electrophotographic photosensitive member for liquid development according to any one of <1> to <4>, characterized by containing at least part by mass.

<6> An image forming apparatus comprising the electrophotographic photosensitive member for liquid development according to any one of <1> to <5>.
<7> The image forming apparatus according to <6>, comprising a liquid developing toner in which hydrocarbons of C10 to C13 occupy 80% or more of the solvent.

  According to the present invention, it is possible to provide an electrophotographic photosensitive member having excellent solvent resistance stability and crack resistance and sufficiently excellent electrical characteristics even in a thin film, and an image forming apparatus including the same.

1 is a diagram schematically illustrating an example of a main configuration of an image forming apparatus of the present invention. (A), (b) is a figure which shows typically an example of the unit structure of the liquid developing device of the image forming apparatus as one Embodiment of this invention. 1 is an X-ray diffraction pattern of oxytitanium phthalocyanine used in Examples. 1 is an X-ray diffraction pattern of oxytitanium phthalocyanine used in Examples.

  Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be arbitrarily modified and implemented without departing from the gist of the present invention.

[1. Polyester resin]
The charge transport layer of the electrophotographic photoreceptor to which this exemplary embodiment is applied includes a polyester resin having a repeating structure represented by the following formula (1).

(In Formula (1), Ar ¹ and Ar ² each independently represent an arylene group having 30 or less carbon atoms, which may have a substituent. X ¹ represents a single bond, an oxygen atom, a sulfur atom, A divalent organic residue having a structure represented by the formula (2) or a structure represented by the formula (3) is represented.k represents an integer of 0 to 3.)

(R ¹ and R ^{2 in} formula (2) each independently represent a hydrogen atom, an alkyl group, or an aryl group, or a cycloalkylidene group formed by combining R ¹ and R ^2. )
—O—R ³ —O— Formula (3)
(R ³ in Formula (3) represents an alkylene group, an arylene group, or a group represented by Formula (4).)
—R ⁴ —Ar ³ —R ⁵ — Formula (4)
(R ⁴ and R ^{5 in} Formula (4) each independently represent an alkylene group, and Ar ³ represents an arylene group which may have a substituent.)
In the formula (1), Ar ¹ and Ar ² are preferably an arylene group having 6 to 20 carbon atoms, and examples thereof include a phenylene group, a naphthylene group, an anthrylene group, a phenanthrylene group, and a pyrenylene group. Among these, a phenylene group and a naphthylene group are particularly preferable from the viewpoint of production cost.

  Examples of the substituent that may be independently present in the arylene group include an alkyl group, an alkoxy group, an aryl group, a condensed polycyclic group, and a halogen group. Among these, an alkyl group, an alkoxy group, an aryl group, and a halogen group are preferable. Considering the mechanical properties as the binder resin for the photosensitive layer and the solubility in the coating solution for forming the photosensitive layer, the aryl group is preferably a phenyl group or a naphthyl group, and the halogen group is a fluorine atom, a chlorine atom, a bromine atom or an iodine atom. The alkoxy group is preferably a methoxy group, an ethoxy group, or a butoxy group, and the alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 4 carbon atoms. Examples of the alkyl group include linear alkyl groups such as a methyl group, an ethyl group, and a propyl group, branched alkyl groups such as an isopropyl group, a tertbutyl group, and an isobutyl group, a cyclic alkyl group such as a cyclohexyl group and a cyclopentyl group, Examples thereof include halogenated alkyl groups such as chloromethyl group and methyl fluoride group, and benzyl group. Among these, from the viewpoint of synthesis, a linear alkyl group is preferable, and a methyl group or an ethyl group is more preferable.

The number of substituents for Ar ¹ and Ar ² is not particularly limited, but is preferably 3 or less, more preferably 2 or less, and particularly preferably 1 or less. Further, in the formula (1), Ar ¹ and Ar ² are preferably the same arylene group having the same substituent, and particularly preferably an unsubstituted phenylene group.

In formula (1), X ¹ is a divalent organic residue having a single bond, an oxygen atom, a sulfur atom, a structure represented by formula (2), or a structure represented by formula (3). R ¹ and R ^{2 in} Formula (2) each independently represent a hydrogen atom, an alkyl group, or an aryl group, or a cycloalkylidene group formed by combining R ¹ and R ² . Examples of the alkyl group represented by R ¹ and R ² in the formula (2) include a straight chain alkyl group such as a methyl group, an ethyl group, and a propyl group, a branched alkyl group such as an isopropyl group, a tertbutyl group, and an isobutyl group, and cyclohexyl Groups, cyclic alkyl groups such as cyclopentyl group, halogenated alkyl groups such as chloromethyl group and methyl fluoride group, and benzyl group. Among these, from the viewpoint of synthesis, a linear alkyl group is preferable, and a methyl group or an ethyl group is more preferable. Examples of the aryl group include a phenylene group, a naphthylene group, an anthrylene group, a phenanthrylene group, and a pyrenylene group, and a phenylene group is preferable. In addition, examples of the cycloalkylidene group formed by combining R ¹ and R ² in the formula (2) include a cyclopentylidene group, a cyclohexylidene group, a cycloheptylidene group, and the like. preferable.

Furthermore, R ³ in Formula (3) is an alkylene group, an arylene group, or a group represented by Formula (4). R ⁴ and R ^{5 in} Formula (4) each independently represent an alkylene group, and Ar ³ represents an arylene group. Examples of the alkylene group of R ³ in the formula (3) include a methylene group, an ethylene group, and a propylene group. Examples of the arylene group of the R ³ in the formula (3) include a phenylene group and a terphenylene group. It is done. Specific examples of the group represented by the formula (4) include a group represented by the following formula (5). Among these, from the viewpoint of wear resistance, X ¹ is preferably an oxygen atom.

In the formula (1), k is an integer of 0 to 3, preferably an integer of 0 to 1, and most preferably 1 from the viewpoint of wear resistance.
In the present invention, the formula (1) is particularly preferably the following general formula (6).

In formula (6), R ¹⁷ and R ¹⁸ are each independently a hydrogen atom, an alkyl group, an aryl group, a halogen group, or an alkoxy group, and n ¹ and m ¹ are each independently an integer of 0 to 4. is there. R ¹⁷ and R ^{18 in} formula (6) are, for example, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms; an aryl group such as a phenyl group or a naphthyl group; a fluorine atom, a chlorine atom, a bromine atom, iodine Halogen groups such as atoms; alkoxy groups such as methoxy, ethoxy and butoxy groups. In view of the convenience in production of the divalent carboxylic acid compound derived from the divalent carboxylic acid residue represented by the formula (6), R ¹⁷ and R ¹⁸ are a hydrogen atom, an alkyl group having 1 carbon atom (methyl Group) is particularly preferred.

n1 and m1 are each independently an integer of 0 to 4, particularly preferably n1 = m1 = 0.
Specific examples of the divalent carboxylic acid compound derived from the divalent carboxylic acid residue represented by the formula (6) include, for example, diphenyl ether-2,2′-dicarboxylic acid, diphenyl ether-2,4′-dicarboxylic acid, and diphenyl ether. -4,4'-dicarboxylic acid and the like. Among these, diphenyl ether-4,4′-dicarboxylic acid is particularly preferable in view of manufacturing convenience.

  The repeating structure represented by the formula (1) can be used in combination with a plurality of repeating structural units as necessary. Specific examples of the divalent carboxylic acid compound that can be combined include, for example, adipic acid, suberic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, toluene-2,5-dicarboxylic acid, p-xylene-2,5. -Dicarboxylic acid, pyridine-2,3-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, pyridine-2,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-3,4-dicarboxylic acid, pyridine -3,5-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-2,3-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, biphenyl-2,2'-dicarboxylic acid, biphenyl-4,4 '-Dicarboxylic acid, diphenyl ether-2,2'-dicarboxylic acid, diphenyl ether-2,3'-dicarboxylic acid, diphenyl Ether 2,4'-dicarboxylic acid, diphenyl ether-3,3'-dicarboxylic acid, diphenyl ether-3,4'-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid. Considering the simplicity of production of the dicarboxylic acid component, isophthalic acid, terephthalic acid, and diphenyl ether-4,4′-dicarboxylic acid are particularly preferable.

In the polyester resin in the present invention, the content of the repeating structure represented by the formula (1) is generally 10 mol% or more, preferably 15 mol% or more, in all polyester resins. The upper limit is preferably 100 mol% or less. If the content is too small, the wear resistance may be insufficient, and if the content is too large, the solubility may decrease.
Moreover, it is preferable that the polyester resin in this invention contains the polyester resin which has a repeating structure represented by following formula (7).

(In Formula (7), R < ⁷ > -R < ¹⁴ > is a C1-C20 alkyl group, alkoxyl group, halogen group, or carbon number 30 which may have a hydrogen atom and a substituent each independently. X ² represents a single bond, an alkylene group, —CR ¹⁵ R ¹⁶ —, an oxygen atom or a sulfur atom, and R ¹⁵ and R ¹⁶ each independently have a hydrogen atom or a substituent. It represents either an alkyl group which may be substituted, an aryl group which may have a substituent, or a group in which R ¹⁵ and R ¹⁶ are bonded to each other to form a ring which may have a substituent. )

Specific examples of the alkyl group in R ^{7 to} R ¹⁴ include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, an isobutyl group, a cyclohexyl group, a chloromethyl group, a fluorinated alkyl group, A benzyl group etc. are mentioned. Specific examples of the alkoxy group which may have a substituent include a methoxy group, an ethoxy group, a propoxy group, a cyclohexoxy group, and the like. Specific examples of the aryl group include a phenyl group, a chlorophenyl group, and a fluorophenyl group.

As a preferable combination in R ^{7 to} R ¹⁴ , R ⁸ , R ¹⁰ , R ¹¹ , and R ¹³ are hydrogen atoms, and R ⁷ , R ⁹ , R ¹² , and R ¹⁴ are hydrogen atoms or having 1 to 3 carbon atoms. It is an alkyl group. From the viewpoint of mechanical properties, R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , R ¹³ and R ¹⁴ are particularly preferably hydrogen atoms, and R ⁷ and R ¹² are hydrogen atoms or methyl groups.
Specific examples of the alkylene group for X ² include — (CH ₂ ) ₂ —, — (CH ₂ ) ₃ — and the like. Specific examples of the alkyl group that may have a substituent in R ¹⁵ and R ¹⁶ include a methyl group, an ethyl group, a propyl group, and a cyclohexyl group. Specific examples of the aryl group that may have a substituent include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a tolyl group. Specific examples of the group that forms a ring in which R ¹⁵ and R ¹⁶ may be bonded to each other may include a cyclohexylidene group.

In Formula (7), X ² is preferably —CR ¹⁵ R ¹⁶ —. Specifically, bis- (4-hydroxyphenyl) methane, 1,1-bis- (4-hydroxyphenyl) ethane, 2,2-bis- (4-hydroxyphenyl) propane, 2,2-bis- ( 4-hydrokey 3-methylphenyl) propane, bis- (4-hydroxy-3-methylphenyl) methane, 1,1-bis- (4-hydroxyphenyl) cyclohexane, 1,1-bis- (4-hydroxy-3) -Methylphenyl) ethane, bis- (4-hydroxy-3,5-dimethylphenyl) methane, 1,1-bis- (4-hydroxy-3,5-dimethylphenyl) ethane, 2,2-bis- (4 -Hydroxy-3,5-dimethylphenyl) propane, bis- (4-hydroxy-3,6-dimethylphenyl) methane, 1,1-bis- (4-hydroxyphenyl) -1-phenyl ethane, 1,1-bis - (4-hydroxyphenyl) propane.

  Among these, bis (4-hydroxyphenyl) methane, 1,1-bis- (4-hydroxyphenyl) ethane, 1,1-bis-(( 4-hydroxy-3-methylphenyl) ethane, bis- (4-hydroxy-3-methylphenyl) methane, 2,2-bis- (4-hydroxy-3-methylphenyl) propane are particularly preferred. It is also possible to use a combination of a plurality of these dihydric phenol components.

  Specific examples of suitable structures of the binder resin are shown below. These specific examples are shown for illustration, and any known binder resin may be mixed and used as long as it does not contradict the gist of the present invention.

In addition, it is preferable that the carboxylic acid value of the polyester resin in this invention shall be 100 microequivalent / g or less, More preferably, it is 50 microequivalent / g or less. When the carboxylic acid value exceeds 100 µequivalent / g, the electrical characteristics of the photoreceptor tend to deteriorate, and further, the storage stability when the resin is dissolved in a solvent to form a coating solution tends to be lowered. .
The amount of the free divalent carboxylic acid contained in the polyester resin in the present invention is not particularly limited, but is preferably 50 ppm or less, and more preferably 10 ppm or less. When the content of the free divalent carboxylic acid exceeds 50 ppm, the electrical characteristics of the photoreceptor may be deteriorated or it may become a foreign substance appearing in image evaluation. The smaller the amount of free divalent carboxylic acid, the better from the viewpoint of the electrical properties and image characteristics of the photoreceptor, but from the viewpoint of the stability of the polyester resin, it is preferably 0.01 ppm or more, and 0.1 ppm or more. It is particularly preferred that

  Furthermore, the amount of the free dihydric phenol contained in the polyester resin in the present invention is not particularly limited, but is preferably 100 ppm or less, more preferably 50 ppm or less. If it exceeds 100 ppm, foreign matters may be produced depending on the deterioration of electrical characteristics, coloring, and the solvent used. From the viewpoint of the electrical characteristics of the photoreceptor, the less free divalent phenol is better, but from the viewpoint of ease of production, it is preferably 0.001 ppm or more, and particularly preferably 0.01 ppm or more.

[2. Electrophotographic photoreceptor for liquid development]
A specific configuration of the photoreceptor is a laminated liquid developing electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support. For example, a photosensitive layer (laminated photosensitive layer or functionally separated photosensitive layer) in which a charge generating layer mainly composed of a charge generating substance and a charge transporting layer mainly composed of a charge transporting substance and a binder resin are laminated on a support. And a layered (or function-separated) photoreceptor. Further, a protective layer may be provided on the outermost surface layer.

[3. Conductive support]
Examples of the material of the support include, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, and nickel; a resin material that includes a conductive powder such as metal, carbon, and tin oxide; In general, a resin, glass, paper, or the like on which a conductive material such as nickel or ITO (indium tin oxide alloy) is deposited or applied is used. In addition, a conductive material having an appropriate resistance value may be applied to the surface of the support such as a metal material in order to control conductivity and surface properties or to cover defects.

  As the form of the support, for example, a drum shape, a sheet shape, a belt shape or the like is used. Among these, in the photoreceptor of the present invention, it is preferable to use a sheet-like support. Among these, specifically, those in which a metal layer is formed on a film such as a biaxially stretched film are particularly preferably used. This is because the degree of freedom in design in the image forming apparatus, the ease of application of the coating solution for forming the photosensitive layer, the low cost, and the like.

  Examples of the material of the film include linear polyester resins such as polyethylene terephthalate resin, polyethylene naphthalate resin, and polybutylene terephthalate resin; polyolefin resins such as polyethylene resin and polypropylene resin; and polyvinyl chloride resin. Among these, a linear polyester resin is preferable from the viewpoint of mechanical strength and dimensional stability, and a polyethylene terephthalate resin is particularly preferable. From the viewpoint of heat resistance, polyethylene terephthalate resin and polyethylene naphthalate resin are preferable. In addition, these resin may use one type and may use two or more types together by arbitrary combinations and arbitrary ratios.

  The thickness of the film is usually 30 μm or more, preferably 50 μm or more, more preferably 70 μm or more, and usually 200 μm or less, preferably 150 μm or less, more preferably 120 μm or less. By setting the thickness within this range, it is advantageous in terms of cost, can prevent deformation (curl) after drying, and can ensure sufficient mechanical strength such as tensile strength.

  Moreover, as a metal of the metal layer which comprises a support body, although copper, nickel, zinc, aluminum, ITO (indium-tin oxide) etc. are mentioned, for example, aluminum is preferable. In addition, these metals may use 1 type and may use 2 or more types together by arbitrary combinations and arbitrary ratios. The thickness of the metal layer is usually 40 nm or more and 100 nm or less.

  When a metal layer is formed on the film, the metal vapor deposition layer is usually formed by a vapor deposition method. As the vapor deposition method, for example, a known vapor deposition method such as an electrothermal melting deposition method, an ion beam vapor deposition method, or an ion plating method of the metal is used. Moreover, as a metal layer, metal foil, such as aluminum foil and nickel foil, and the laminate film which laminated | stacked these metals can be used. In this case, the thickness of the metal foil is preferably 5 μm or less. Further, a conductive material having a more appropriate resistance value can be laminated on the metal foil.

  The surface of the support may be smooth, or may be roughened, for example, by mixing particles having a large particle diameter with a resin. By roughening the surface, it is possible to obtain effects such as suppressing the occurrence of interference fringes with respect to coherent light such as a laser and increasing the adhesion of the photosensitive layer.

[4. Undercoat layer]
An undercoat layer may be provided between the support and the photosensitive layer in order to improve adhesion and blocking properties.
As the undercoat layer, a resin, a resin in which particles such as a metal oxide are dispersed, or the like is used. Examples of metal oxide particles used for the undercoat layer include metal oxide particles containing one metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, titanium Examples thereof include metal oxide particles containing a plurality of metal elements such as strontium acid and barium titanate. Among these metal oxide particles, titanium oxide and aluminum oxide are preferable, and titanium oxide is particularly preferable. The surface of the titanium oxide particles may be treated with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide; or an organic substance such as stearic acid, polyol, or silicone. As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. One particle may contain a plurality of crystal states.

One kind of these metal oxide particles may be used, or two kinds may be used in any combination and in any ratio.
Moreover, as the particle size of the metal oxide particles, various particles can be used. Among them, from the viewpoint of characteristics and the stability of the coating liquid for forming the undercoat layer, the average primary particle size is preferably 10 nm or more and 100 nm or less, Especially preferably, they are 10 nm or more and 50 nm or less.

The undercoat layer is preferably formed with a structure in which metal oxide particles are dispersed in a binder resin. As the binder resin used for the undercoat layer, for example, phenoxy resin, epoxy resin, polyvinyl pyrrolidone resin, polyvinyl alcohol resin, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, etc. are used alone or cured. Can be used in a cured form with the agent. Among these, alcohol-soluble copolymerized polyamide, modified polyamide, and the like are preferable because they exhibit good dispersibility and coatability. In addition, these may use one type and may use two types together by arbitrary combinations and arbitrary ratios.

  The amount ratio of the metal oxide particles to the binder resin can be arbitrarily selected, but is usually 10% by mass or more, preferably 50% by mass or more, more preferably 70% by mass or more, more preferably 100% by mass or more, and usually 500% by mass. % Or less, preferably 400% by mass or less, more preferably 380% by mass or less, and particularly preferably 350% by mass or less. This is for improving the stability and coating property of the coating solution for forming the undercoat layer.

The thickness of the undercoat layer can be arbitrarily selected, but is usually 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, and usually 25 μm or less, preferably 20 μm or less, more preferably Is 15 μm or less, particularly preferably 10 μm or less. This is to improve the characteristics of the photoreceptor and the coating property of the coating solution for forming the undercoat layer.
The undercoat layer may contain an additive such as a known antioxidant.
Furthermore, it is good also as a two-layer structure of a conductive layer and a blocking layer as an undercoat layer.

[5. Charge generation layer]
The charge generation layer of the multilayer photoconductor contains a charge generation material and usually contains a binder resin and other components used as necessary. Specifically, such a charge generation layer is prepared by, for example, preparing a coating solution (coating solution for forming a charge generation layer) by dissolving or dispersing a charge generation material and a binder resin in a solvent, and forming the coating solution in a sequential lamination type. In the case of a photosensitive layer, it can be obtained by coating and drying on a support (when an undercoat layer is provided, on the undercoat layer), and in the case of a reverse lamination type photosensitive layer, it can be applied and dried on a charge transport layer. .

  Examples of charge generation materials include selenium and its alloys, cadmium sulfide, and other inorganic photoconductive materials; phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, benzimidazole pigments Various photoconductive materials such as organic pigments; In particular, organic pigments are preferable, and phthalocyanine pigments and azo pigments are particularly preferable. Note that one type of charge generation material may be used, or two or more types may be used in any combination and in any ratio.

  In particular, when a phthalocyanine compound is used as a charge generation material, specific examples thereof include metal-free phthalocyanine; metals such as copper, indium, gallium, tin, titanium, zinc, vanadium, silicone, germanium, or oxides and halides thereof. And the like coordinated phthalocyanines; Examples of the ligand to the trivalent or higher metal atom include a hydroxyl group and an alkoxy group in addition to the oxygen atom and chlorine atom shown above. Particularly preferred are X-type, τ-type metal-free phthalocyanine, titanyl phthalocyanine such as A-type, B-type, and D-type, vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, and hydroxygallium phthalocyanine. Of the crystal forms of titanyl phthalocyanine mentioned here, A type and B type are described in W.W. Heller et al. Have shown them as phase I and phase II (Zeit. Kristallogr. 159 (1982) 173), respectively, and the A type is also called the β type and is known as the stable type. D-type is a metastable type, also called Y-type, and is a crystal type characterized by a clear peak at a diffraction angle 2θ ± 0.2 ° of 27.3 ° in powder X-ray diffraction using CuKα rays. is there.

  As the phthalocyanine compound, only a single compound may be used, or several mixed states may be used. As the mixed state in the phthalocyanine compound or the crystalline state here, the respective constituent elements may be mixed and used later, or a mixed state is generated in the production and processing steps of the phthalocyanine compound such as synthesis, pigmentation, and crystallization. It can be stuffed. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known.

  These charge generation materials usually have fine particles such as polyester resin, polyvinyl acetate resin, polyacrylate resin, polymethacrylate resin, polyester resin, polycarbonate resin, polyvinyl acetoacetal resin, polyvinyl propional resin, polyvinyl butyral. It is used in a form bound with various binder resins such as resin, phenoxy resin, epoxy resin, urethane resin, cellulose ester, and cellulose ether. In this case, the polyester resin according to the present invention may be used as the binder resin. Moreover, 1 type may be used for binder resin and it may use 2 or more types together by arbitrary combinations and arbitrary ratios.

The use ratio of the charge generation material in the charge generation layer is usually 30 parts by mass or more, preferably 50 parts by mass or more, and usually 500 parts by mass or less, preferably 300 parts by mass or less with respect to 100 parts by mass of the binder resin. .
The thickness of the charge generation layer is usually 0.1 μm or more, preferably 0.15 μm or more, and usually 1 μm or less, preferably 0.6 μm or less.

  The charge generation layer may contain components other than those described above as long as the effects of the present invention are not significantly impaired. For example, the charge generation layer may contain an additive. These additives are used to improve film forming properties, flexibility, coating properties, stain resistance, gas resistance, light resistance, and the like. For example, plasticizers, antioxidants , Ultraviolet absorbers, electron withdrawing compounds, dyes, pigments, leveling agents, residual potential inhibitors, dispersion aids, visible light shading agents, sensitizers, surfactants and the like. The use of a plasticizer can improve the mechanical strength of the layer, the use of a residual potential inhibitor can suppress the residual potential, the use of a dispersion aid can improve dispersion stability, and a leveling agent can be used. If it is, the applicability | paintability of a coating liquid can be improved. Examples of the antioxidant include hindered phenol compounds and hindered amine compounds. Examples of dyes and pigments include various pigment compounds and azo compounds. Examples of surfactants include silicone oil and fluorine-based oil. In addition, an additive may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and arbitrary ratios. Further, for the purpose of reducing frictional resistance and wear on the surface of the photosensitive member, the surface layer may contain silicone oil and wax, and resin particles such as fluorine resin, polystyrene resin, and silicone resin. Moreover, you may contain the particle | grains of an inorganic compound.

[6. Charge transport layer]
The charge transport layer of the multilayer photoreceptor contains a charge transport material and usually contains a binder resin and other components used as necessary. Specifically, such a charge transport layer is prepared by, for example, preparing a coating liquid (coating liquid for forming a charge transport layer) by dissolving or dispersing a charge transport material and a binder resin in a solvent. In the case of a photosensitive layer, it can be obtained by coating and drying on a charge generation layer, and in the case of a reverse lamination type photosensitive layer, on a support (or on an undercoat layer if an undercoat layer is provided). .

The charge transport material is not particularly limited, and any material can be used. Examples of known charge transport materials include aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, electron withdrawing materials such as quinone compounds such as diphenoquinone, and carbazole derivatives. , Indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, heterocyclic compounds such as benzofuran derivatives, aniline derivatives, hydrazone derivatives, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives and multiple types of these compounds Or an electron donating substance such as a polymer having a group composed of these compounds in the main chain or side chain. Among these, carbazole derivatives, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives, and those in which a plurality of these compounds are bonded are preferable. Any one of these charge transport materials may be used alone, or two or more thereof may be used in any combination. The following specific examples are given for illustrative purposes, and any known charge transport material may be used as long as it does not contradict the spirit of the present invention.

Among these, from the viewpoint of cracks, a charge transport material represented by the following formula (W) is preferable.

  As the charge transport material and the binder resin, the above-mentioned [1. The resin detailed in [Polyester resin] is used. The content of the polyester resin is usually 10 parts by mass or more, preferably 20 parts by mass or more, more preferably 35 parts by mass or more with respect to 100 parts by mass of the total resin in the charge transport layer from the viewpoint of crack resistance. . The upper limit is usually 100 parts by mass or less, and preferably 80 parts by mass or less from the viewpoint of electrical characteristics.

  As the binder resin, in addition to the polyester resin of the present invention, any binder resin can be used in combination as long as it is usually applicable to an electrophotographic photoreceptor. Other resins used in combination include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, thermoplastic resins such as polycarbonate, polyester, polyester polycarbonate, polysulfone, phenoxy, epoxy, and silicone resin. And various thermosetting resins. Among these resins, a polycarbonate resin is preferable.

  Specific examples of suitable structures of the binder resin are shown below. These specific examples are shown for illustration, and any known binder resin may be mixed and used as long as it does not contradict the gist of the present invention.

  Among these, it is preferable to contain the polycarbonate resin which has a repeating structure represented by (A) or (B) in a charge transport layer from a viewpoint of an electrical property and crack resistance. Furthermore, a copolymer resin of (A) and (B) is preferable.

In the polycarbonate resin having a repeating structure represented by (A) or (B), (A
) Or (B), the lower limit of the content of the repeating structure represented by (B) is usually 10 mol% or more, preferably 15 mol% or more. The upper limit is usually 100 mol% or less, preferably 80 mol% or less, more preferably 50 mol% or less. (A) has insufficient electrical properties if the content is too low, (B) may have insufficient wear resistance if the content is too low, and (A) has solubility if it is too high. If the amount of (B) is too large, the electrical characteristics may be deteriorated. The mixing ratio of the polycarbonate resin having a repeating structure represented by (A) or (B) and the polyester resin having a repeating structure represented by formula (1) is crack resistant to 100 parts by mass of the polyester resin. From the viewpoint of safety, it is usually 200 parts by mass or less, preferably 150 parts by mass or less, and more preferably 100 parts by mass or less. From the viewpoint of electrical characteristics, it is usually 10 parts by mass or more, preferably 20 parts by mass or more, and more preferably 50 parts by mass or more.

The amount of solvent remaining in the charge transport layer ^is in the range of ^{5mg / cm 3 ~50mg / cm 3} , preferably from the viewpoint of the drying time is 30 mg / cm ³ or less. The residual solvent can be measured by gas chromatography by dissolving a certain range of photosensitive layer in a solvent. 5 mg ^/ cm 3 to a range of to 50 mg / cm ^3, for example when the film thickness of the charge transport layer with a sheet-shaped photosensitive member is 18Um, 2 minutes at a temperature of 125 ° C. The drying time of the charge transport layer 5 The method of making it about minutes is mentioned.

  The residual solvent is not directly involved in the electrical properties, but is considered to be due to the spatial action due to the presence of the solvent in the layer, so the type of residual solvent is not particularly limited, A solvent or a dispersion medium used for preparing the coating solution is preferable. Specific examples include alcohols such as methanol, ethanol, propanol and 2-methoxyethanol, ethers such as tetrahydrofuran, 1,4-dioxane and dimethoxyethane, esters such as methyl formate and ethyl acetate, acetone, methyl ethyl ketone and cyclohexanone. Ketones such as benzene, toluene, xylene, etc., dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, tetrachloroethane, 1,2 -Chlorinated hydrocarbons such as dichloropropane and trichloroethylene, nitrogen-containing compounds such as n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine and triethylenediamine, acetonitrile N- methylpyrrolidone, N, N- dimethylformamide, aprotic polar solvents such as dimethyl sulfoxide and the like. Moreover, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and kinds.

  The film thickness of the charge transport layer is not particularly limited, but is usually 5 μm or more, preferably 10 μm or more from the viewpoint of long life and image stability, and on the other hand, it is 20 μm or less from the viewpoint of miniaturization and coating properties and further high resolution. Preferably, it is 18 μm or less. The film thickness can be measured by a contact-type film thickness meter using eddy current or an optical non-contact film thickness meter using light interference.

[7. Other functional layers]
The photosensitive layer or each of the layers constituting the photosensitive layer is a well-known antioxidant, plasticizer, UV absorber for the purpose of improving film forming properties, flexibility, coating properties, stain resistance, gas resistance, light resistance, etc. You may contain additives, such as an agent, an electron withdrawing compound, a leveling agent, and a visible light shading agent.

[8. Application method of each layer]
There is no restriction | limiting in the formation method of a photosensitive layer, Arbitrary methods can be used. For example, a coating solution obtained by dissolving or dispersing a substance to be contained in each layer in a solvent (charge generating layer forming coating solution, charge transport layer forming coating solution, dispersion type photosensitive layer forming coating solution, etc.) sequentially. It is formed by applying and drying.

  The coating method is not particularly limited, and for example, a dip coating method, a spray coating method, a nozzle coating method, a bar coating method, a roll coating method, a blade coating method, or the like can be used. In particular, as a coating method in the case of a photoreceptor (sheet-shaped photoreceptor) provided with a sheet-like support, a coating solution is applied onto the support by a known die coating method, reverse coating method, gravure coating method, bar coating method, or the like. It is formed by coating.

The coated photoreceptor is usually subjected to a drying process until the solvent of the coating film is substantially removed by evaporation. As a drying method, a conventionally known method can be applied. For example, it is performed by at least one of a heating roller, a hot air dryer, a steam dryer, an infrared dryer, a far infrared dryer and the like. The drying temperature is usually in the range of 60 ° C to 140 ° C.
When the photoreceptor of the present invention is a sheet-like photoreceptor, for example, both end portions thereof are joined by a known method such as ultrasonic fusion, and used as an endless belt. Further, for example, the sheet-like photoconductor can be used by being wound around a drum as it is. In the case of winding around a drum, for example, a thin roll may be held inside the drum for unwinding, or a single sheet may be wound.

[9. Image forming apparatus]
Next, an embodiment of an image forming apparatus using the photoconductor of the present invention will be described with reference to the drawings for the main configuration of the apparatus. However, the embodiment of the present invention is not limited to the following description, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
FIG. 1 is a diagram schematically showing a main configuration of an image forming apparatus as an embodiment of the present invention. As shown in FIG. 1, the image forming apparatus according to the present embodiment includes a photoreceptor 1, a charging device 2 as a charging unit, an exposure device 3 as an exposure unit, and a developing device 4 as a developing unit. Further, a transfer device 5 as a transfer unit, a cleaning device 6 as a cleaning unit, and a fixing device (not shown) as a fixing unit are provided as necessary.

The shape of the photoreceptor 1 is not particularly limited as long as it is the photoreceptor of the present invention described above. In FIG. 1, as an example, the above-described photosensitive layer is formed on the surface of a sheet-like support, and ultrasonic welding is performed. An endless belt-shaped photoconductor is shown.
The charging device 2 charges the photoreceptor 1 and is a device that uniformly charges the surface of the photoreceptor 1 to a predetermined potential. In FIG. 1, a corona discharge type charging device (corotron) is shown as an example of the charging device 2. However, for example, a corona charging device such as a scorotron or a contact type charging device such as a charging roller or a charging brush is often used. Used.

  In many cases, the photoreceptor 1 and the charging device 2 are designed to be removable from the main body of the image forming apparatus as a cartridge including both of them (hereinafter referred to as “photosensitive cartridge” as appropriate). For example, when the photoreceptor 1 or the charging device 2 deteriorates, the photoreceptor cartridge can be detached from the image forming apparatus main body, and another new photoreceptor cartridge can be mounted on the image forming apparatus main body. . In addition, the developer described later is often stored in a cartridge and designed to be removable from the main body of the image forming apparatus. It can be removed from the main body of the forming apparatus and another new cartridge can be mounted. Further, a cartridge provided with all of the photosensitive member 1, the charging device 2, and the developer may be used.

  The type of the exposure device 3 is not particularly limited as long as it can expose the photosensitive member 1 to form an electrostatic latent image on the photosensitive surface of the photosensitive member 1. Specific examples include halogen lamps, fluorescent lamps, lasers such as semiconductor lasers and He—Ne lasers, LEDs, and the like. Further, the support of the photoconductor may be made light transmissive, and exposure may be performed by a photoconductor internal exposure method.

  The light used for the exposure is arbitrary. For example, the exposure may be performed using monochromatic light with a wavelength of 780 nm, monochromatic light with a wavelength slightly shorter than 600 nm to 700 nm, or monochromatic light with a short wavelength of 380 nm to 500 nm. . In particular, when light having a wavelength of 380 nm to 500 nm is used, the photoconductor can be exposed with light having a smaller spot size, and a high quality image having high resolution and high gradation can be formed. This is preferable when an image is desired.

The developing device 4 represents a liquid developing device. The developer to be used is usually a toner obtained by dispersing a charged pigment and resin in a developing solvent (usually an organic solvent) having a high insulating property. Since the toner charged in the liquid is electrophoresed in response to the development electric field, the mobility of the toner in the developing solvent with viscosity is related, but the basic electric field model is the same as dry development. It is.

  2A and 2B schematically show an example of the unit configuration of the liquid developing device 4. FIG. The liquid developing device 4 shown in FIG. 2A includes a developing roller 7 and a squeeze roller 8 that are close to or in contact with the photoconductor 1 in this order along the transfer direction of the photoconductor 1. First, a developing solution having a low density is transferred from the developing roller 7 to the photosensitive member, and development is performed. Subsequently, excess developing solvent on the photosensitive member 1 is squeezed out with the squeeze roller 8 while borrowing the power of the electric field. A thin, uniform and high density toner image can be formed on the body 1.

  On the other hand, the liquid developing device 4 shown in FIG. 2B includes a developing roller 7 that is close to the photoreceptor 1 and a squeeze roller 8 that is in contact with the developing roller 7. Then, a thin toner layer having a high density and high charge is formed in advance on the developing roller 7 by an electric field and pressure between the developing roller 7 and the squeeze roller 8 before development, and then this toner layer is developed with the photoreceptor 1. By developing with an electric field between the rollers 7, a high-density toner image can be formed. If necessary, the liquid developing device 4 may be provided with a cleaning roller 9 for removing the developer remaining on the developing roller 7 and the squeeze roller 8.

  The type of the transfer device 5 is not particularly limited. For example, an apparatus using an arbitrary system such as an electrostatic transfer method such as corona transfer, roller transfer, or belt transfer, a pressure transfer method, or an adhesive transfer method may be used. it can. Here, it is assumed that the transfer device 5 includes a transfer charger, a transfer roller, a transfer belt, and the like disposed so as to face the photoreceptor 1. The transfer device 5 applies a predetermined voltage value (transfer voltage) having a polarity opposite to the charging potential of the toner, and transfers the toner image formed on the photoreceptor 1 onto a recording paper (paper, medium, transfer material) P. Is. FIG. 1 shows a direct transfer method from the photosensitive member to the recording paper P. However, the toner image is transferred from the photosensitive member to an intermediate transfer member such as an intermediate transfer belt and an intermediate transfer roller, and then transferred to the recording paper P. An intermediate transfer method can also be used.

There is no restriction | limiting in particular about the cleaning apparatus 6, For example, arbitrary cleaning apparatuses, such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, a blade cleaner, can be used. The cleaning device 6 is for scraping off residual toner adhering to the photoreceptor 1 with a cleaning member and collecting the residual toner.
When the toner transferred onto the recording paper P normally passes through a fixing device (not shown), the toner is heated and heated to a molten state, and is cooled after passing through to fix the toner on the recording paper P. The type of the fixing device is not particularly limited. For example, a fixing device of an arbitrary method such as heat roller fixing, flash fixing, oven fixing, pressure fixing, or the like can be provided.

  In the image forming apparatus configured as described above, an image is recorded as follows by a liquid developing type image forming method using a developer. That is, as shown in FIG. 1, first, the surface (photosensitive surface) of the photoreceptor 1 is charged to a predetermined potential (for example, −600 V) by the charging device 2 (charging process). At this time, charging may be performed by a DC voltage, or charging may be performed by superimposing an AC voltage on the DC voltage.

Subsequently, the photosensitive surface of the charged photoreceptor 1 is exposed by the exposure device 3 according to the image to be recorded, and an electrostatic latent image is formed on the photosensitive surface (exposure process). Then, development of the electrostatic latent image formed on the photosensitive surface of the photoreceptor 1 is performed by the developing device 4 (developing process).
As shown in FIGS. 2A and 2B, when the charged toner carried on the developing roller 7 of the developing device 4 is in contact with or close to the surface of the photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photoreceptor. 1 is formed on the photosensitive surface. This toner image is transferred onto the recording paper P by the transfer device 5 (manual printing process). Thereafter, toner remaining on the photosensitive surface of the photoreceptor 1 without being transferred is removed by the cleaning device 6 (cleaning step). After the transfer of the toner image onto the recording paper P, the final image is obtained by passing the toner image through the fixing device and thermally fixing the toner image onto the recording paper P (fixing step).

  Note that the image forming apparatus may have a configuration capable of performing the static elimination process in addition to the above-described configuration. The neutralization step is a step of canceling excess charged charges on the photosensitive member by exposing the photosensitive member or applying an alternating voltage. As the charge removal device, for example, an exposure device such as a fluorescent lamp or LED, a wire capable of applying an alternating current, or the like is used. When exposure is used in the static elimination process, the light intensity is often light having an exposure energy that is three times or more that of exposure light.

Further, the image forming apparatus may be further modified. For example, the image forming apparatus may have a configuration capable of performing processes such as a pre-exposure process and an auxiliary charging process, or a full color system configuration using a plurality of types of toner. Further, for example, instead of the endless belt-like photoconductor, a sheet-like photoconductor may be attached on a metal drum by electrostatic force or the like.
Note that the photosensitive member 1 can be combined with one or more of a charging device 2, an exposure device 3, a developing device 4, a transfer device 5, a cleaning device 6 and a fixing device, as required. It may be configured as an (electrophotographic cartridge), and the electrophotographic cartridge may be detachable from a main body of an electrophotographic apparatus such as a copying machine or a laser beam printer. In this case, similarly to the cartridge described in the above embodiment, for example, when the photosensitive member 1 or other member deteriorates, the electrophotographic cartridge is removed from the image forming apparatus main body, and another new electrophotographic cartridge is replaced with the image forming apparatus. By attaching to the main body, maintenance and management of the image forming apparatus are facilitated.

[10. toner]
Liquid toner suspends toner particles mainly composed of a resin colored with a pigment or dye having a color such as carbon black, cyan, magenta, yellow, etc., in a solvent with high electrical resistivity, and further, as a charge control agent. What added metal soaps, such as a lecithin and a barium stearate, can be used. As the solvent having a high electrical resistivity, a hydrocarbon solvent is used, and a liquid toner in which C10 to C13 hydrocarbons occupy 80% or more of the solvent is preferable from the viewpoints of affinity with the pigment and drying property. In general, liquid toner is smaller in particle diameter than dry toner, which is advantageous in terms of high resolution image quality.

<Example 1>
Aluminum oxide particles having an average primary particle diameter of 13 nm (Aluminum Oxide C, manufactured by Nippon Aerosil Co., Ltd.) were dispersed in a mixed solvent of methanol / 1-propanol with ultrasonic waves to obtain a dispersion slurry of aluminum oxide. The dispersion slurry, a mixed solvent of methanol / 1-propanol (mass ratio 7/3), and ε-caprolactam [compound represented by the following formula (A)] / bis (4-amino-3-methylcyclohexyl) methane [Compound represented by the following formula (B)] / hexamethylenediamine [compound represented by the following formula (C)] / decamethylene dicarboxylic acid [compound represented by the following formula (D)] / octadecamethylene dicarboxylic acid [following Copolymer polyamide pellets having a composition molar ratio of the compound represented by formula (E) of 60% / 15% / 5% / 15% / 5% are stirred and mixed while heating to obtain polyamide pellets. After dissolution, ultrasonic dispersion treatment is performed to obtain a solid content concentration of 8.0% containing aluminum oxide / copolymerized polyamide at a mass ratio of 1/1. It was a gas layer for dispersion.

  The coating solution for forming the undercoat layer thus obtained was applied on a polyethylene terephthalate sheet (thickness 75 μm) vapor-deposited on the surface with a wire bar so that the film thickness after drying was 1.2 μm, and dried. Thus, an undercoat layer was provided.

As a charge generation material, 20 parts of titanium oxyphthalocyanine having a powder X-ray diffraction spectrum pattern with respect to CuKα characteristic X-ray shown in FIG. Dispersion processing was performed. Subsequently, 400 parts of a 2.5% 1,2-dimethoxyethane solution of polyvinyl butyral (trade name “Denkabutyral” # 6000C, manufactured by Denki Kagaku Kogyo Co., Ltd.) and 170 parts of 1,2-dimethoxyethane were mixed. Dispersion 1) was thus prepared. Next, the same operation was performed on titanium oxyphthalocyanine having a powder X-ray diffraction spectrum pattern with respect to the CuKα characteristic X-ray shown in FIG. 4 to prepare dispersion 2). A mixture obtained by mixing and stirring these dispersions at a ratio of 1: 1 was applied onto the undercoat layer with a bar coater to form a charge generation layer so that the film thickness after drying was 0.4 μm.

Next, on this film, the following first binder resin (1a) (viscosity average molecular weight: 3700)
0) 50 parts, the following second binder resin (AB) (viscosity average molecular weight: 30000) 50 parts, charge transport material (W) having the following structure 35 parts, antioxidant having the following structure 8 parts, and leveling A solution obtained by dissolving 0.1 part of silicone oil in 640 parts of a tetrahydrofuran / toluene (8/2) mixed solvent as an agent is applied, dried at 125 ° C. for 3 minutes, and charged so that the film thickness after drying becomes 18 μm. A transport layer was provided to prepare a photoreceptor. This photoreceptor is referred to as a photoreceptor X1. At this time, the amount of residual solvent (toluene) in the photosensitive layer was 7.2 mg / cm ³ .

<Example 2>
In Example 1, the second binder resin ( AB ) is replaced with a binder resin having the following repeating structure (
A) (Viscosity average molecular weight: 30000)) was used, and a photoconductor X2 was obtained in the same manner as in Example 1 except that dioxolane was used as a solvent.

<Comparative Example 1>
In Example 1, a photoreceptor Y1 was obtained in the same manner as in Example 1 except that the following first binder resin (1a) was not used and 100 parts of the second binder resin ( AB ) was used.
<Example 3>
In Example 1, 30 parts of first binder resin (1a), second binder resin (AB)
A photoconductor X3 was obtained in the same manner as in Example 1 except that 70 parts of was used.

<Example 4>
In Example 2, Photoreceptor X4 was obtained in the same manner as Example 2 except that 20 parts of the first binder resin (1a) and 80 parts of the second binder resin (A) were used.
<Example 5>
In Example 1, the first binder resin (1a) (viscosity average molecular weight: 37000) 10
Part and the second binder resin (A) were used in the same manner as in Example 1 except that 90 parts of the second binder resin (A) was used.

<Example 6>
In Example 1, Photoreceptor X6 was obtained in the same manner as Example 1 except that the binder resin (1b) having the following repeating structure was used instead of the first binder resin (1a).

  A crack test was performed on the manufactured photoreceptor sheets X1 to X6 and Y1. These results are summarized in Table 1.

<Crack test>
The photoconductor sheet prepared above was cut into 1 cm × 20 cm strips, and the solvent; Isopar L was thinly applied to the surface of the photoconductor and left for about 3 hours. Attach this strip to the Tensilon Universal Material Testing Machine TENSILON RTM100 (A & D Co., Ltd.), re-apply Isopar L and pull it for 2 minutes with a force of 10 Newton and 20 Newton, causing cracks on the surface of the photoconductor The presence or absence was observed. A photoconductor that is weak in cracking properties generates cracks with a force of 10 Newton, while a photoconductor that is resistant to cracks does not generate cracks even with a force of 20 Newtons.

From the results in Table 1, it can be seen that the examples are excellent in crack resistance.
<Reference Example 1>
In Comparative Example 1, a photoreceptor Y2 was obtained in the same manner as Comparative Example 1 except that the charge transport material ( Z ) having the following structure was used as the charge transport material.

<Reference Example 2>
Comparative Example 1 except that the number of parts of the charge transport material (W) was changed to 25 parts in Comparative Example 1.
In the same manner as described above, a photoreceptor Y3 was obtained.
The crack test was performed on the manufactured photoreceptor sheets Y1 to Y3. These results are summarized in Table 2.

From the results of Table 2, it was found that even if the same resin was used, there were systems (Reference Examples 1 and 2) in which cracks did not occur in the crack test, and Comparative Example 1 was a system in which cracks were likely to occur. Therefore, it can be said that the crack tests performed in Examples 1 to 6 and Comparative Example 1 are more severe conditions. Even if severe conditions are imposed, the charge transport layer contains a polyester resin having a repeating structure represented by the formula (1), the film thickness is 20 μm or less, and the residual solvent amount is 5 mg / cm ^3.
If it is -50 mg / cm < ³ >, it turns out that it is resistant to a crack.

<Comparative example 2>
In Example 1, a photoconductor Y4 was obtained in the same manner as in Example 1 except that the drying time for providing the charge transport layer was 6 minutes.
<Comparative Example 3>
In Example 1, a photoreceptor Y5 was obtained in the same manner as in Example 1 except that the drying time for providing the charge transport layer was 20 minutes.

<Comparative Example 4>
In Example 3, a photoreceptor Y6 was obtained in the same manner as in Example 3 except that the drying time for providing the charge transport layer was 20 minutes.
<Comparative Example 5>
In Comparative Example 1, a photoreceptor Y7 was obtained in the same manner as in Comparative Example 1 except that the drying time for providing the charge transport layer was 20 minutes.

<Comparative Example 6>
In Example 1, a photoconductor Y8 was obtained in the same manner as in Example 1 except that the drying time for providing the charge transport layer was 1 minute.
<Comparative Example 7>
In Example 1, a photoreceptor Y9 was obtained in the same manner as in Example 1 except that the film thickness when providing the charge transport layer was 25 μm.
Bright part potential was measured about manufactured photoreceptor sheet | seat X1-X2, Y4-Y9. These results are summarized in Table 3.

<Light area potential measurement>
The photoreceptor sheet was affixed onto an aluminum base tube (outer diameter 80 mmφ), and the bright portion potential was measured. First, the angle between the static eliminator and the exposure position is set to 150 °, the angle between the charger and the exposure position is set to 70 °, the angle between the exposure position and the bright portion potential measurement probe is set to −70 °, and the photosensitive member is rotated. The scorotron charging conditions were set such that the surface potential was -700 V when rotating at a speed of 50 revolutions / minute and not exposed. Under these conditions, the potential (bright part potential) of each photoreceptor when exposed to 0.6 μJ / cm ² of 780 nm light was measured. Further, the difference between the bright part potential after repeating the above process 3000 times and the initial bright part potential was measured as ΔVL.

From the result of Table-3, it can be seen from the comparison between Comparative Example 2 and Comparative Example 5 that the first binder resin is a resin having a high bright part potential. Was found by comparison between Example 1 and Comparative Examples 2, 3, and 4. On the other hand, it was found by comparison between Example 1 and Comparative Example 6 that the amount of residual solvent is too large, which is not preferable because the increase in ΔVL during repetition becomes large. It was also found from Comparative Example 7 that the electrical characteristics cannot be satisfied when the film thickness is large.

<Example 9>
The undercoat layer coating solution prepared in Example 1 was applied to a roll of aluminum-deposited polyethylene terephthalate film (width was 500 mm, and the surface was roughened by containing silica particles in the film (Ra = 0.1 μm). ) Rolls having an aluminum vapor deposition film having a thickness of 70 nm on the surface of a biaxially stretched polyethylene terephthalate film having a thickness of 75 μm, while using a reverse coating method, the film thickness after drying is 1. An undercoat layer was provided by applying to 2 μm.

Next, using the reverse coating method while unwinding the roll of the aluminum vapor-deposited polyethylene terephthalate film on which the undercoat layer was formed, the coating solution for charge generation layer prepared in Example 1 was dried on it. The charge generation layer was provided by coating so that the film thickness was 0.4 μm.
Next, using the die coating method, the coating solution for the charge transport layer prepared in Example 4 was unwound from the roll of the aluminum vapor-deposited polyethylene terephthalate film on which the undercoat layer and the charge generation layer were formed. It applied so that the film thickness after drying might be set to 18 micrometers, and provided the electric charge transport layer.
The roll sheet coated with the photosensitive layer thus obtained was cut into a size of 353 mm × 584 mm using a continuous cutting machine to obtain a photoreceptor sheet.

<Real machine test>
The produced photoreceptor sheet was mounted on a commercially available liquid developing type light printing machine, TurboStream manufactured by Hewlett Packard, and image evaluation was performed. In mounting, the photosensitive sheet was wound around an aluminum drum in the machine, and the photosensitive sheet was held on the drum by superimposing uncoated areas at both ends. By removing the aluminum layer on one side, it was possible to superimpose easily by static electricity.

  Using this photosensitive sheet, 100 halftone images were output continuously, but there was no change in density and a good image was obtained. Furthermore, there were no problems such as cracks in the photosensitive layer even after repeated use, and there was no problem in practical use.

Claims (7)

A laminated type electrophotographic photosensitive member for liquid development having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge transport layer has a repeating structure represented by the following formula (1) containing, electric film thickness of charge transport layer is 20μm or less, the liquid developer for electrophotographic photoreceptor, wherein the residual solvent content of the charge transport layer is ^{5mg / cm 3 ~50mg / cm 3} .

(In Formula (1), Ar ¹ and Ar ² each independently represent an arylene group having 30 or less carbon atoms, which may have a substituent. X ¹ represents a single bond, an oxygen atom, a sulfur atom, A divalent organic residue having a structure represented by the formula (2) or a structure represented by the formula (3) is represented.k represents an integer of 0 to 3.)

(R ¹ and R ^{2 in} formula (2) each independently represent a hydrogen atom, an alkyl group, or an aryl group, or a cycloalkylidene group formed by combining R ¹ and R ^2. )
—O—R ³ —O— Formula (3)
(R ³ in Formula (3) represents an alkylene group, an arylene group, or a group represented by Formula (4).)
—R ⁴ —Ar ³ —R ⁵ — Formula (4)
(R ⁴ and R ^{5 in} Formula (4) each independently represent an alkylene group, and Ar ³ represents an arylene group which may have a substituent.) 2. The electrophotographic photosensitive member for liquid development according to claim 1, wherein the charge transport layer contains a polycarbonate resin having a repeating structure represented by the following formula (A).

3. The electrophotographic photosensitive member for liquid development according to claim 1, wherein the charge transporting layer contains a polycarbonate resin having a repeating structure represented by the following formula (B).

4. The liquid development according to claim 1, wherein the charge transport layer contains 35 parts by mass or more of the polyester resin with respect to 100 parts by mass of the total resin in the charge transport layer. Electrophotographic photoreceptors The charge transport layer contains at least 25 parts by mass of a compound represented by the following formula (W) with respect to 100 parts by mass of the total resin in the charge transport layer. The electrophotographic photosensitive member for liquid development described in the item.

  An image forming apparatus comprising the electrophotographic photosensitive member for liquid development according to claim 1.   The image forming apparatus according to claim 6, further comprising a liquid developing toner in which C10 to C13 hydrocarbons occupy 80% or more of the solvent.

Images