JP4437066B2 - Electrophotographic photoreceptor and image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus provided with the same, and more particularly, an image of a simultaneous development cleaning system (or cleanerless system). The present invention relates to an image forming apparatus applicable to a forming apparatus.

  In an image forming apparatus, various photosensitive members having sensitivity in a wavelength region of a light source used in the apparatus are used. One is an inorganic photoreceptor using an inorganic material such as selenium for the photosensitive layer, and the other is an organic photoreceptor using an organic material for the photosensitive layer. Organic photoconductors are easier to manufacture than inorganic photoconductors, and have a wide range of material options such as charge generators, charge transport agents (electron transport agents / hole transport agents), binder resins, etc. Due to its high degree, it has been used in recent years. Furthermore, in recent years, it has been desired to produce a photoconductor that does not cause image defects and has excellent durability and high sensitivity.

  The following Patent Document 1 specifies as a charge transport agent (hole transport agent) in order to prevent deterioration of the surface of the photoreceptor and to obtain a photoreceptor with high sensitivity and good repetitive characteristics and changes with time. It has been proposed to use the distyryl compound.

  However, the hole transport agent described in Patent Document 1 has a problem that the solubility in a solvent and the compatibility with a binder resin are low when a photosensitive layer is produced. When the solubility and the compatibility are low as described above, there is a problem that the content of the hole transport agent in the photosensitive layer is limited and crystallization occurs on the surface of the photosensitive layer.

By the way, there is known an image forming apparatus of a simultaneous development cleaning system that does not use an elastic blade for cleaning. In this image forming apparatus, a charging unit, an exposing unit, a developing unit, and a transferring unit are sequentially arranged around the electrophotographic photosensitive member, and the toner remaining on the surface of the electrophotographic photosensitive member is collected by the developing unit. It is. Unlike the image forming apparatus having the cleaning process, the image forming apparatus of the simultaneous development cleaning method does not use an elastic blade. Therefore, the size of the apparatus is reduced, and the wear resistance of the photosensitive layer is not impaired and the life is long. An image forming apparatus can be obtained. On the other hand, paper dust generated when cutting the paper to be transferred into a predetermined size, paper dust generated due to friction with the rollers when the paper passes through various conveying rollers, etc. It adheres to the surface of the photoreceptor due to electrostatic attraction and pressure during transfer, and it becomes extremely difficult to remove paper dust from the photoreceptor. Further, as the number of copies increases, the attracted paper powder adheres firmly to the surface of the photoreceptor. If paper dust adheres to the photoreceptor in this way, there is a problem that image defects such as black streaks and black spots occur. As a cause of the adhesion of the paper dust, crystallization (particularly minute crystallization) on the surface of the photosensitive layer can be considered.
JP-A-4-225362

  It is an object of the present invention to improve the solubility of a hole transport agent in a solvent and the compatibility of a hole transport agent with a binder resin when preparing a photosensitive layer, so that crystallization on the surface of the photosensitive layer is achieved. It is an object of the present invention to provide an electrophotographic photosensitive member that does not cause image defects and has excellent durability and high sensitivity, and an image forming apparatus including the electrophotographic photosensitive member.

  As a result of intensive studies to solve the above problems, the present inventors have used a compound having a specific chemical structure shown below as a hole transport agent, so that it has solubility in a solvent and compatibility with a binder resin. Has been improved, and crystallization on the surface of the photosensitive layer can be prevented, and the present invention has been completed.

  That is, the electrophotographic photosensitive member and the image forming apparatus in the present invention have the following configurations.

(1) A single-layer electrophotographic photosensitive member in which a single photosensitive layer containing at least a hole transport agent is provided on a conductive substrate, wherein the hole transport agent is represented by the following formula (I) And a compound represented by the following formula (A), (B), (C), (D), (E) or (F) : .

［式中、ＲａおよびＲｅは、それぞれ同一または異なる基であって、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。Ｒｂ、Ｒｃ、Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ＲｆおよびＲｇは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。Ｘ１およびＸ２は、それぞれ同一または異なる基であって、下記式（ＩＩ）で表される。

[Wherein, Ra and Re are the same or different groups, and each represents an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. Rb, Rc, and Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group that may have a substituent, an alkoxy group, or a halogen atom. Rf and Rg are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. X1 and X2 are the same or different groups, and are represented by the following formula (II).

（式中、ＲｈおよびＲｉは、それぞれ同一または異なる基であって、水素原子、アルキル基または置換基を有してもよいアリール基を示す。Ｒｊは、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。Ｘ１およびＸ２に対するｎは、いずれか一方が２であり、他方が１または２である。ｏは０〜５の整数を示す。ただし、ｏが２以上のとき、各Ｒｊは同一または異なる基であってもよい。）］

(In the formula, Rh and Ri are the same or different groups and each represents a hydrogen atom, an alkyl group or an aryl group which may have a substituent. Rj may have an alkyl group or a substituent. A good aryl group, an alkoxy group or a halogen atom, one of n for X1 and X2 is 2, and the other is 1 or 2. o represents an integer of 0 to 5, provided that o is 2. In the above, each Rj may be the same or different group.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

（式中、Ｒａ〜Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ただし、ｌ〜ｏが２以上のとき、各Ｒａ〜Ｒｄは同一または異なる基であってもよい。）]

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.

  (2) The content of the compound represented by the formula (I) is 1 to 80% by weight with respect to all hole transporting agents in the photosensitive layer. Electrophotographic photoreceptor.

(3) The electrophotographic photosensitive member according to any one of (1) to (2), wherein the photosensitive layer further contains an electron transfer agent.

(4) An image forming apparatus comprising the electrophotographic photosensitive member according to any one of (1) to (3).

(5) Charging means for charging the electrophotographic photosensitive member, exposure means for forming an electrostatic latent image on the charged electrophotographic photosensitive member, developing the electrostatic latent image with toner, and the electrophotographic photosensitive member (4) characterized in that it comprises: developing means for collecting toner remaining on the surface of the body; and transfer means for transferring the toner of the electrophotographic photosensitive member developed by the developing means to a member to be transferred. ).

According to the above (1) to (3) , it is possible to improve the solubility of the hole transport agent in the solvent and the compatibility of the hole transport agent in the binder resin when producing the photosensitive layer. . Thus, by improving the solubility and compatibility, the hole transport agent can be blended in the photosensitive layer from a low concentration to a high concentration. Further, the improvement of the solubility and the compatibility can prevent crystallization on the surface of the photosensitive layer and reduce the adhesion of paper dust. As a result, it is possible to provide an electrophotographic photosensitive member that does not cause image defects and has excellent durability and high sensitivity.

According to the above (4) and (5) , since the electrophotographic photosensitive member is provided and crystallization on the surface of the photosensitive layer can be prevented and adhesion of paper dust can be reduced, image defects can occur. Therefore, it is possible to provide an image forming apparatus having excellent durability and high sensitivity (particularly, an image forming apparatus employing a simultaneous development cleaning method).

  In the electrophotographic photoreceptor of the present invention, a photosensitive layer containing a hole transport agent, an electron transport agent and a charge generator is provided on a conductive substrate. And the compound represented by the said Formula (I) is contained as a hole transport agent. In addition, although the photosensitive layer here has a single layer type photosensitive layer and a laminated type photosensitive layer, any photosensitive layer may be provided in the present invention.

<Hole transport agent>
In the present invention, the compound represented by the above formula (I) is contained as a hole transport agent. Ra and Re in the formula (I) are the same or different groups, and each represents an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. In other words, Ra and Re in the formula (I) are groups other than a hydrogen atom.

  By providing the groups of Ra and Re as described above, in the present invention, the solubility of the hole transport agent in the solvent and the compatibility of the hole transport agent in the binder resin when producing the photosensitive layer are as follows. Can be improved. That is, the concentration of the hole transport agent applicable in the photosensitive layer can be expanded from a lower concentration to a higher concentration than before. As a result, it is possible to prevent crystallization on the surface of the photosensitive layer, thereby reducing the adhesion of paper dust, suppressing the occurrence of image defects, and providing an electrophotographic photosensitive member having excellent durability and high sensitivity. be able to.

  Specific examples of the compound represented by the above formula (I) include HTM-1 and HTM-10 to 11 shown in the following formula. In addition, you may use the compound represented by the said formula (I) as a hole transport agent 1 type or in mixture of 2 or more types.

In the present invention, the hole transporting agent contains the compound represented by the formula (I) and another hole transporting agent.

  The content of the compound represented by the above formula (I) in the other hole transport agent is 1 to 80% by weight, preferably 1 to 60% by weight with respect to all the hole transport agents in the photosensitive layer. It is good to do. In addition, like the compound of Formula (I), it is preferable that the other hole transport agent has higher solubility in a solvent and higher compatibility with a binder resin.

  Examples of the other hole transporting agent include compounds represented by the following formulas (A) to (F).

［式中、Ｒａ〜Ｒｆは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ｐおよびｑは０〜４の整数を示す。ただし、ｌ〜ｑが２以上のとき、各Ｒａ〜Ｒｆは同一または異なる基であってもよい。］

[Wherein, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. p and q show the integer of 0-4. However, when 1 to q is 2 or more, Ra to Rf may be the same or different groups. ]

［式中、Ｒａ〜Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ただし、ｌ〜ｏが２以上のとき、各Ｒａ〜Ｒｄは同一または異なる基であってもよい。］

[Wherein, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. However, when 1 to o is 2 or more, each Ra to Rd may be the same or different groups. ]

［式中、Ｒａ〜Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ただし、ｌ〜ｏが２以上のとき、各Ｒａ〜Ｒｄは同一または異なる基であってもよい。］

[Wherein, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. However, when 1 to o is 2 or more, each Ra to Rd may be the same or different groups. ]

［式中、Ｒａ〜Ｒｆは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ｐおよびｑは０〜４の整数を示す。ただし、ｌ〜ｑが２以上のとき、各Ｒａ〜Ｒｆは同一または異なる基であってもよい。］

[Wherein, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. p and q show the integer of 0-4. However, when 1 to q is 2 or more, Ra to Rf may be the same or different groups. ]

［式中、Ｒａ〜Ｒｆは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ｐおよびｑは０〜４の整数を示す。ただし、ｌ〜ｑが２以上のとき、各Ｒａ〜Ｒｆは同一または異なる基であってもよい。］

[Wherein, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. p and q show the integer of 0-4. However, when 1 to q is 2 or more, Ra to Rf may be the same or different groups. ]

［式中、Ｒａ〜Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｌ、ｍ、ｎ、およびｏは、０〜５の整数を示す。ただし、ｌ〜ｏが２以上のとき、各Ｒａ〜Ｒｄは同一または異なる基であってもよい。］

[Wherein, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. l, m, n, and o represent an integer of 0 to 5. However, when 1 to o is 2 or more, each Ra to Rd may be the same or different groups. ]

  Moreover, HTM-5-9 of a following formula is mentioned as a specific example of the said other hole transport agent.

<Electron transport agent>
The electrophotographic photoreceptor of the present invention preferably contains an electron transport agent in the photosensitive layer. Examples of the electron transporting agent that can be used in the present invention include diphenoquinone derivatives, benzoquinone derivatives, naphthoquinone derivatives, anthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, thioxanthone derivatives (2,4,8-trinitrothioxanthone, etc.), fluorenone derivatives ( 3,4,5,7-tetranitro-9-fluorenone derivatives, etc.), anthracene derivatives, acridine derivatives, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride derivatives, maleic anhydride derivatives, dibromomaleic anhydride derivatives, Examples thereof include compounds having electron accepting properties. These charge transport materials may be used alone or in combination of two or more. In addition, as an electron transfer agent that can be used in the present invention, a mobility of 5.0 × 10 ⁻⁷ cm ² / V · sec or more is preferable in order to achieve high sensitivity.

  In the present invention, for example, compounds represented by the following formulas (a) to (e) can be used as the electron transport agent.

［式中、Ｒａ〜Ｒｅは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。］

[In the formula, Ra to Re are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. ]

［式中、Ｒａ〜Ｒｂは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。］

[Wherein, Ra to Rb are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. ]

［式中、Ｒａ〜Ｒｈは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。］

[Wherein, Ra to Rh are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. ]

［式中、Ｒａ〜Ｒｄは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。］

[Wherein, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. ]

［式中、Ｒａ〜Ｒｂは、それぞれ同一または異なる基であって、水素原子、アルキル基、置換基を有してもよいアリール基、アルコキシ基またはハロゲン原子を示す。ｎは０〜８の整数を示す。ただし、ｎが２以上のとき、各Ｒ ｂ は同一または異なる基であってもよい。］

[Wherein, Ra to Rb are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. n represents an integer of 0 to 8. However, when n is 2 or more, each R b may be the same or different group. ]

  Specific examples of the electron transfer agent include compounds represented by the following formulas ETM-1 to ETM-5.

<Charge generator>
Examples of the charge generating agent that can be used in the present invention include metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, Y-titanyl phthalocyanine, V-hydroxygallium phthalocyanine, and the like, and perylene Pigments, bisazo pigments, diketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azurenium pigments, cyanine pigments, pyrylium pigments, ansanthrone pigments, triphenylmethanes Organic photoconductors such as pigment, selenium pigment, toluidine pigment, pyrazoline pigment, quinacridone pigment, selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide Beam, such as an inorganic photoconductive material and the like such as amorphous silicon. Of these, α-titanyl phthalocyanine, Y-titanyl phthalocyanine, and V-hydroxygallium phthalocyanine are preferable. These charge generating agents may be used alone or in combination of two or more. In the present invention, at least one selected from phthalocyanine pigments, particularly metal-free phthalocyanine, titanyl phthalocyanine, hydroxygallium phthalocyanine, and chlorogallium phthalocyanine is used as a charge generator. It is preferable in view of the electrical characteristics of the photoreceptor when external light is used as the exposure light source.

<Binder resin>
Examples of the binder resin that can be used in the present invention include polymer compounds having a styrylamine structure. As the polymer compound having a styrylamine structure, various polymer compounds can be used, and polycarbonate resin is particularly preferable.

<Photosensitive layer>
The film thickness of the photosensitive layer is 5 to 100 μm, preferably 10 to 50 μm. The charge generating agent is 0.1 to 50% by mass, preferably 0.5 to 30% by mass, based on the total amount of the binder resin. Further, the electron transfer agent is 1 to 100% by mass, preferably 5 to 80% by mass, based on the total amount of the binder resin.

  In addition to the components described above, various additives can be blended in the photosensitive layer within a range that does not adversely affect image formation. Examples of such additives include antioxidants, radical scavengers, singlet quenchers, deterioration inhibitors such as UV absorbers, softeners, plasticizers, surface modifiers, extenders, thickeners, dispersions Stabilizers, waxes, acceptors, donors and the like can be mentioned. In order to improve sensitivity, for example, known sensitizers such as terphenyl, halonaphthoquinones, and acenaphthylene may be used in combination with the charge generator.

A barrier layer may be formed between the conductive substrate and the photosensitive layer as long as the characteristics of the photoreceptor are not impaired. A protective layer may be formed on the surface of the photosensitive layer.

<Conductive substrate>
As the conductive substrate, various conductive materials can be used. For example, iron, aluminum, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel And a simple metal such as brass, a plastic material on which the above metal is deposited or laminated, and glass coated with aluminum iodide, tin oxide, indium oxide, or the like.

  The conductive substrate is used in the form of a drum or a sheet according to the structure of the image forming apparatus to be used. The conductive substrate preferably has sufficient mechanical strength.

<Single layer type photoreceptor>
A single-layer type photoreceptor is obtained by providing a single photosensitive layer on a conductive substrate. This photosensitive layer is a roll mill containing a polymer compound having a styrylamine structure as a binder resin, a hole transporting agent, a charge generating agent, and optionally a binder resin other than the electron transporting agent and the polymer compound together with an appropriate solvent. A dispersion is prepared by mixing using a ball mill, an attritor, a paint shaker, an ultrasonic disperser or the like, and this is applied by a known means and dried.

  Examples of the solvent for preparing the dispersion include alcohols such as methanol, ethanol, isopropanol and butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, and aromatic hydrocarbons such as benzene, toluene and xylene. , Halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ketones such as acetone, methyl ethyl ketone, cyclohexanone, acetic acid Examples include esters such as ethyl and methyl acetate, dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. That. These solvents may be used alone or in combination of two or more.

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

<Multilayer photoconductor>
The electrophotographic photoreceptor of the present invention may be a laminated photoreceptor. For example, the electrophotographic photoreceptor of the present invention may be constituted by laminating a charge transport layer containing a charge transport agent and a charge generation layer containing a charge generator on a conductive substrate. Further, a photoconductive layer containing a charge transporting agent together with a charge generating agent may be combined with a charge transporting layer and a charge generating layer.

<Image forming apparatus>
Next, an image forming apparatus of the simultaneous development cleaning system according to the present invention to which the electrophotographic photoreceptor is applied will be described. A schematic diagram of this image forming apparatus is shown in FIG. An image forming apparatus 10 according to the present invention includes a charging unit 2, an exposing unit 3, a developing unit 4, a transfer unit 5, and a paper dust removing brush (cleaning unit) 6 around a rotatable image carrier (photosensitive drum 1). Each means is sequentially provided. The photosensitive drum 1 is formed with a photosensitive layer containing the above-described hole transport agent.

  The charging means 2 faces the photosensitive drum 1 and is arranged at a predetermined interval so as not to contact. For example, the charging unit 2 can corona discharge from a charging wire such as tungsten to uniformly charge the surface of the photosensitive drum 1 to a predetermined potential. The surface of the photosensitive drum 1 is preferably set so that its initial charging potential is about 800 to 900 V, for example.

  The exposure unit 3 is disposed on the downstream side of the charging unit 2 in the rotation direction of the photosensitive drum 1. The exposure unit 3 can form an electrostatic latent image based on predetermined image data on the surface of the charged photosensitive drum 1 by using, for example, high-speed scanning of a laser beam or analog exposure. By such exposure, a potential difference appears between the unexposed portion and the exposed portion. That is, the initial charging potential is maintained in the unexposed portion of the photosensitive drum 1, and is attenuated to, for example, about 100 to 300 V in the exposed portion.

  The developing means 4 is disposed further downstream of the exposure means 3. The developing means 4 is an electrostatic latent image formed on a charged electrophotographic photosensitive member (that is, an exposed portion of the uniformly charged surface exposed by the exposure means 3 and having a lowered potential). In addition, a positively charged toner is supplied inside the developing unit 4. By this supply, the developing unit 4 selectively carries the toner on the surface of the photosensitive drum 1 to form a visible image. As the developing means 4, for example, a two-component magnetic brush developing system or the like can be adopted.

  In the image forming apparatus of the present invention, a so-called simultaneous development cleaning method (cleanerless method) is adopted in which the toner remaining on the surface of the photosensitive drum 1 is collected by the developing means 4 at the next development. Specifically, a developing bias having a DC voltage is applied between the developing unit 4 and the photosensitive drum 1 by, for example, a developing bias applying power source. This development bias voltage is usually set to an intermediate potential between the potential of the exposed portion of the photosensitive drum 1 and the potential of the unexposed portion. The potential difference between the developing bias potential and the surface potential of the photosensitive drum 1 becomes toner moving energy, and the toner moves from the developing means 4 to the attenuated portion (latent image portion) of the surface of the photosensitive drum 1. At this time, among the untransferred toner that remains on the surface of the photosensitive drum 1 and adheres thinly, the toner in the unexposed area moves from the surface of the photosensitive drum 1 to the developing unit 4 and is collected. On the other hand, the toner in the exposure unit moves from the developing unit 4 to the exposure unit of the photosensitive drum 1 without moving from the surface of the photosensitive drum 1 to the developing unit 4, and the toner on the surface of the photosensitive drum 1. Form an image.

  For example, when the surface potential of the photosensitive drum 1 is +200 V at the exposed portion, +800 V at the unexposed portion, and the developing bias potential applied to the developing means 4 is +400 V, the positively charged toner includes the developing means at the exposed portion. A repulsive force due to a potential difference of +200 V works from 4 to the photosensitive drum 1. In the unexposed area, a repulsive force due to a potential difference of +400 V acts from the photosensitive drum 1 to the developing means 4. Due to the repulsive force due to these potential differences, the toner moves, and the residual toner is collected together with the development of the latent image.

  The transfer unit 5 is disposed further downstream of the developing unit 4. At the time of transfer, a visible image carried on the photosensitive drum 1 is transferred to the transfer member while the transfer target member (for example, paper) passes between the photosensitive drum 1 and the transfer unit 5. In addition, due to this transfer, the charged potential after transfer of the unexposed portion on the surface of the photosensitive drum 1 is lowered to, for example, about 500 to 600V.

  When paper is used as the transfer member, paper dust adheres to the surface of the photosensitive drum 1 when the electrophotographic photosensitive member comes into contact with the paper. The adhering paper dust may be disposed, for example, further downstream and physically entangled with the paper dust collecting brush 6 whose tip is in contact with the surface of the photosensitive drum 1. Further, in order to apply a bias voltage applied from a DC power source to the paper dust collecting brush 6, a bias voltage applying means (not shown) may be provided. Paper dust can be captured electrically by the bias voltage applied by the bias voltage applying means.

  The toner image transferred to the transfer member is then melted and fixed on the surface of the transfer member by applying heat and pressure by a fixing unit (not shown).

  In the image forming apparatus of the present invention, the paper dust removing brush 6 described above is usually provided between the transfer unit 5 and the charging unit 2. The paper dust removing brush 6 not only aims at removing paper dust but also disperses the untransferred toner remaining on the surface of the photosensitive drum 1 so as to weaken electrostatic coupling with the surface charge of the photosensitive drum 1. May function. Accordingly, even when the apparatus adopts a system that collects toner at the same time during development without going through a cleaning step using an elastic blade or the like, the toner at the time of development can be collected more efficiently.

  As described above, in the photosensitive drum 1 which is the electrophotographic photosensitive member of the present invention, minute crystallization of the surface of the photosensitive layer is suppressed. Therefore, the image forming apparatus (image forming apparatus using the simultaneous development cleaning method) can prevent adhesion of paper powder due to micro crystallization of the surface of the photosensitive layer, thereby preventing image defects such as black streaks and black spots. can do.

  Further, the present invention is applicable to an image forming apparatus in which paper dust easily adheres to a photosensitive drum such that the diameter of the photosensitive drum is 16 to 40 mm and the peripheral speed of the photosensitive drum is 50 mm / second or more. By using the photosensitive drum 1 which is an electrophotographic photosensitive member, image defects due to paper dust can be prevented.

<Color image forming apparatus>
The electrophotographic photoreceptor of the present invention can be used in a color image forming apparatus. For example, a toner image is formed on the surface of the electrophotographic photosensitive member of the present invention using toners of various colors such as black toner, cyan toner, magenta toner, and yellow toner, and a full color image is formed on the transfer paper by sequentially transferring it onto a predetermined transfer paper. Can be formed. Further, this transfer paper is introduced into a fixing device arranged on the paper discharge side of the transfer belt, and an image is formed by fixing the transfer image on the transfer paper. Of course, the electrophotographic photosensitive member of the present invention is used in a so-called tandem type full-color image forming apparatus in which a dedicated electrophotographic photosensitive member is used for each color toner, and these electrophotographic photosensitive members are arranged on a transfer belt. Also good. This tandem full-color image forming apparatus has an advantage that image formation can be performed while the transfer paper is continuously conveyed by a transfer belt.

[ Reference Examples 1 to 13 ]
<Production of single layer type electrophotographic photoreceptor>
4 parts by weight of an x-type metal-free phthalocyanine, 50 parts by weight of a hole transport agent shown in Table 1 below, 30 parts by weight of an electron transport agent shown in Table 1 below, and Z-type polycarbonate (manufactured by Teijin Chemicals, Panlite TS2020 as a binder resin) 100 parts by weight were mixed and dispersed in a ball mill for 50 hours together with 800 parts by weight of tetrahydrofuran to prepare a photoreceptor coating solution. Next, the above coating solution is applied to a conductive substrate (aluminum tube) by dip coating, and then dried with hot air at 100 ° C. for 40 minutes, and a photosensitive drum (single-layer type electrophotographic photoreceptor having a film thickness of 25 μm). ) Thereafter, the appearance of the obtained photosensitive drum was visually observed, and the presence or absence of crystallization on the surface was evaluated.

Next, a sensitivity evaluation experiment was performed using the obtained photosensitive drum. Specifically, monochromatic light having a wavelength of 780 nm extracted from the white light of a halogen lamp using a bandpass filter in a state where the surface potential is charged to +850 V using a drum sensitivity tester manufactured by GENTEC, exposure energy 1 Irradiation was performed at 0.5 μJ / cm ² , and the surface potential when 0.5 seconds elapsed from the start of exposure was defined as the bright potential. That is, the lower the bright potential, the higher the sensitivity of the photoreceptor.

  In addition, HTM-1 to 2, HTM-10 to 11 and ETM-1 to 5 described in Table 1 are the aforementioned compounds. HTM-3 and HTM-4 are shown below.

According to Table 1, in Reference Examples 1 to 9 , the appearance of the drum was also good. On the other hand, in Reference Examples 10 to 13 , crystallization was observed in the appearance evaluation of the drum.

[ Examples 1-7, Comparative Examples 1-4 ]
4 parts by weight of x-type metal-free phthalocyanine, 40 parts by weight of any of HTM1 to 4 as a hole transport agent, 40 parts by weight of any of HTM-5 to 9, 30 parts by weight of an electron transport agent and Z type as a binder resin 100 parts by weight of polycarbonate (manufactured by Teijin Chemicals Ltd., Panlite TS2020) was mixed and dispersed in a ball mill for 50 hours together with 800 parts by weight of tetrahydrofuran to prepare a photoreceptor coating solution. Next, this coating solution was applied to a conductive substrate (aluminum base tube) by dip coating, and then dried with hot air at 100 ° C. for 40 minutes to obtain a photosensitive drum (electrophotographic photosensitive member) having a film thickness of 25 μm. In addition, HTM-1 to 9 and ETM-1 to 5 described in Table 2 are the above-described compounds.

According to Table 2, in Examples 1-7 , the external appearance of the drum was also good. On the other hand, in Comparative Examples 1 to 4 , crystallization was observed on the entire surface in the appearance evaluation of the drum.

[ Examples 8 to 12 ]
A single-layer electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that 40 parts by weight of HTM1 and 40 parts by weight of any of HTM-5 to 9 were used as the hole transport agent. . The results are shown in Table 3 below together with the results of Example 1 .

Further, the mobility (cm ² / V · sec) of the hole transport agents HTM-5 to 9 is shown in Table 4 below. This mobility was measured by a normal TOF (Time of Flight) method in a normal temperature (25 ± 1 ° C.) environment. The electric field strength was 3 × 10 ⁵ V / cm. As a measurement sample, 40% by weight of the charge transfer agent to be measured is blended with the binder resin (bisphenol Z-type polycarbonate resin), and a coating solution dissolved by adding a solvent is applied onto the substrate. The film was formed by heat treatment at 80 ° C. for 30 minutes and dried to form a film (film thickness: 7 μm).

According to Table 3 and Table 4, the mobility of the other hole transport agent used together with the hole transport agent represented by the formula (I) should be 1.0 × 10 ⁻⁵ cm ² / V · sec or more. Thus, it can be seen that an electrophotographic photosensitive member having a low bright potential and high sensitivity can be obtained.

[ Examples 12 to 16 ]
Photosensitization is carried out in the same manner as in Examples 1 to 7 except that HTM-1 and HTM-5 are used in parts by weight shown in Table 5 below as hole transporting agents and ETM-1 is used as an electron transporting agent. A body drum was made.

  As shown in Table 5, when the content of HTM-1 is 1 to 80% by weight, preferably 1 to 60% by weight, based on all the hole transport agents in the photosensitive layer, It can be seen that a photosensitive drum having a good appearance and high sensitivity was obtained.

<Testing with image forming apparatus>
The photosensitive drum (single-layer type electrophotographic photosensitive member) obtained in Reference Examples 1 to 9 and Reference Examples 10 to 13 was used as a printer manufactured by Kyocera Mita (printer DP-560: photosensitive drum diameter 16 mm, photosensitive drum circumference). It was mounted at a speed of 60 mm / sec). This printer is an image forming apparatus based on a simultaneous development cleaning system as shown in FIG. Image when printing 100,000 sheets by using plain paper (A4 size) as transfer paper, setting main charging potential to + 850V and developing bias voltage to + 400V, and repeating image forming cycle by reversal development through transfer paper Evaluation was performed visually. The results are shown in Table 5. In the image evaluation items in Table 5, “◎” indicates that no black spots were observed on the image, and “◯” indicates that black spots are slightly observed on the image but are not noticeable and have no problem. “×” indicates that a black spot was observed on the image.

According to Table 6, those using the photosensitive drums of Reference Examples 1 to 9 gave good results. This is presumably because the photosensitive drums of Reference Examples 1 to 9 do not crystallize on the surface of the photosensitive member as shown in Table 1. On the other hand, in the photosensitive drums obtained in Reference Examples 10 to 13 , black spots were observed on the image. This is presumably because the photosensitive drums of Reference Examples 10 to 13 are crystallized on the surface of the photosensitive member as shown in Table 1.

1 is a schematic explanatory diagram illustrating an embodiment of an image forming apparatus of the present invention.

1 Electrophotographic photoreceptor ((single layer type) photoreceptor drum)
2 Charging means 3 Exposure means 4 Developing means 5 Transfer means 6 Cleaning means (paper dust removing brush)

Claims (5)

A single-layer electrophotographic photoreceptor in which a single photosensitive layer containing at least a hole transport agent is provided on a conductive substrate,
As the hole transport agent, a compound represented by the following formula (I) and a compound represented by the following formula (A), (B), (C), (D), (E) or (F) An electrophotographic photosensitive member comprising:

[Wherein, Ra and Re are the same or different groups, and each represents an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. Rb, Rc, and Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group that may have a substituent, an alkoxy group, or a halogen atom. Rf and Rg are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. X1 and X2 are the same or different groups, and are represented by the following formula (II).

(In the formula, Rh and Ri are the same or different groups and each represents a hydrogen atom, an alkyl group or an aryl group which may have a substituent. Rj may have an alkyl group or a substituent. A good aryl group, an alkoxy group or a halogen atom, one of n for X1 and X2 is 2, and the other is 1 or 2. o represents an integer of 0 to 5, provided that o is 2. In the above, each Rj may be the same or different group.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

(In the formula, Ra to Rf are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. p and q represent integers of 0 to 4. However, when 1 to q is 2 or more, each Ra to Rf may be the same or different groups.

(In the formula, Ra to Rd are the same or different groups, and each represents a hydrogen atom, an alkyl group, an aryl group which may have a substituent, an alkoxy group or a halogen atom. L, m, n, and o represents an integer of 0 to 5. However, when l to o are 2 or more, each Ra to Rd may be the same or different groups.   2. The electrophotographic photoreceptor according to claim 1, wherein the content of the compound represented by the formula (I) is 1 to 80 wt% with respect to all the hole transporting agents in the photosensitive layer. .   The electrophotographic photosensitive member according to claim 1, further comprising an electron transport agent in the photosensitive layer.   An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1. Charging means for charging the electrophotographic photoreceptor;
  Exposure means for forming an electrostatic latent image on the charged electrophotographic photosensitive member;
  Developing means for developing the electrostatic latent image with toner and collecting the toner remaining on the surface of the electrophotographic photosensitive member;
  The image forming apparatus according to claim 4, further comprising: a transfer unit that transfers the toner of the electrophotographic photosensitive member developed by the developing unit to a member to be transferred.

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