JP4658741B2 - Electrophotographic photoreceptor and image forming apparatus - Google Patents

Description

  The present invention includes an electrophotographic photosensitive member capable of preventing paper dust from adhering to the photosensitive member by optimizing the configuration of the photosensitive member and suppressing the generation of black spots and black streaks, and the same. The present invention relates to an image forming apparatus.

  In the image forming apparatus, a transfer medium (for example, paper) or a developer is used. Since the paper and developer contain powdery substances such as talc, silicon compound, and titanium compound, they are filmed on the photosensitive drum of the image forming apparatus. Also, when contaminants such as oil components on the surface of the photoconductor, or when the photoconductor is incorporated in the unit, various components such as the development and transfer mechanism come into contact with each other, so that bleed components from the materials constituting them adhere to it. The photosensitive layer is contaminated and cracks occur. When filming or cracks occur, image defects often occur. As a specific example of the image defect, toner is developed on the drum at a place other than a desired place (blank area), and appears as black spots / black streaks or fog on the image.

  In recent image forming apparatuses, it is required to increase the processing speed. When such a high speed is achieved, the load on the paper in the transport path increases. As a result, more paper dust is generated and paper dust adheres to the photosensitive member.

  Furthermore, in recent image forming apparatuses, considering the fact that the apparatus is made compact and that blade cleaning is impossible when using almost perfect toner, a simultaneous development cleaning system (cleanerless system) The image forming apparatus is often used. Since such a cleaner-less method cannot remove paper dust or the like, Patent Document 1 below proposes a cleaner-less image forming apparatus provided with a paper dust removing unit or the like.

As described above, as a countermeasure against image defects, an approach based on the removal of adhering matter such as paper dust in the cleaning process is generally used, but it cannot be said that it is sufficient. . For example, if a cleaning process using a fur brush (rotary brush), a roller, or the like is provided, efficient paper dust collection is possible. However, in order to achieve a compact image forming apparatus, such a cleaning process is required. It is not preferable to prepare. Therefore, in order to achieve the compactness of the apparatus, the image forming apparatus is provided with a simple cleaning process such as a fixed brush. However, there is a problem that it is difficult to completely collect the paper dust. Further, the above approach is to remove the adhering paper dust, and does not reduce the paper dust adhering itself.
JP 2000-194242 A

  The problem of the present invention is not the approach of removing deposits such as paper dust in the cleaning process, but it is possible to cope with the speedup of the image forming apparatus by suppressing the occurrence of image defects by another approach. An object of the present invention is to provide an electrophotographic photosensitive member and an image forming apparatus having the same.

  As a result of intensive studies to solve the above problems, the present inventors have found that when a hole transport agent having a large conjugated planar structure in the molecule is used, paper dust is likely to adhere, and black spots / black It was found that streaks are likely to occur. In addition, if the threshold value for the occurrence and non-occurrence of black spots is derived from the relationship between the hole mobility and the molecular weight of the hole transport agent, and further using the threshold value to optimize the photoconductor configuration, paper dust and the like Can prevent adhesion to the photoconductor, and if contaminants adhere to the photoconductor surface, the monomer component in the photoconductive layer, especially the charge transport agent, is likely to crack due to dissolution from the photoconductive layer, It has been found that by adding a plasticizer as an additive to the photosensitive layer, the occurrence of cracks can be prevented and the generation of black spots and black streaks can be suppressed, and the present invention has been completed. That is, the electrophotographic photoreceptor of the present invention has the following characteristics.

  (1) An electrophotographic photosensitive member provided with a photosensitive layer containing at least a charge generator and a hole transport agent, wherein the hole transport agent satisfies the following formulas (A) and (B): Electrophotographic photoreceptor.

  (2) In the molecule, the hole transport agent is either a biphenyl moiety represented by the following (a) or an orthobisstilbene moiety represented by the following (b) (1) The electrophotographic photosensitive member according to (1), wherein

  (3) The electrophotographic photosensitive member according to (1), wherein the hole transport agent is represented by any of the following formulas (I) to (III).

（式中、R₁〜R₄は、同一または異なる基であって、水素原子または炭素数1〜6のアルキル基を示す。R₅〜R₁₀ 、R_5aおよびR_6aは、同一または異なる基であって、水素原子、アルキル基またはアリール基を示す。Aは、アリーレン基または2つの芳香族環がそれぞれ1価基となったビフェニル残基を示す。ｐ、ｑ、ｒ、ｓ、ｘ、およびｙは、0〜2の整数を示す。ｔおよびｕは1〜4の整数を示す。）

(In the formula, R _{1 to} R ₄ are the same or different groups and represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R _{5 to} R ₁₀ , R _5a and R _6a are the same or different groups. Wherein A represents a hydrogen atom, an alkyl group or an aryl group, A represents an arylene group or a biphenyl residue in which two aromatic rings are each a monovalent group, p, q, r, s, x, And y represents an integer of 0 to 2. t and u represent an integer of 1 to 4.)

  (4) The electrophotographic layer according to any one of (1) to (3), wherein the photosensitive layer contains at least one selected from the following compounds (IV) to (VII) as an additive: Photoconductor.

（式中、R₁₂〜R₃₁およびRは、同一または異なる基であって、水素原子、置換基を有しても良いアルキル基、置換基を有しても良いアリール基、置換基を有しても良いアラルキル基、置換基を有しても良いシクロアルキル基、ハロゲン原子、アルコキシ基、ヒドロキシル基、シアノ基、ニトロ基、アミノ基、またはハロゲン化アルキル基を示す。）

(In the formula, R _{12 to} R ₃₁ and R are the same or different groups having a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, and a substituent. An aralkyl group that may be substituted, a cycloalkyl group that may have a substituent, a halogen atom, an alkoxy group, a hydroxyl group, a cyano group, a nitro group, an amino group, or a halogenated alkyl group.

  (5) The electrophotographic photosensitive member according to (4), wherein the additive is contained in an amount of 1.5 to 15.0% by weight based on the total amount of components constituting the photosensitive layer.

  (6) The electrophotographic photosensitive member as described in (4) or (5), wherein the compound (IV) has at least one selected from the structures of the following formulas (VIII) -1 to 4.

  (7) The electrophotographic photosensitive material according to any one of (4) to (6), wherein the compound (VII) has at least one selected from the structures of the following formulas (IX) -1 to 8: body.

  (8) The electrophotographic photosensitive member according to any one of (1) to (3), wherein the electrophotographic photosensitive member is a single layer type electrophotographic photosensitive member containing the charge generating agent and the hole transporting agent in the same layer.

  (9) The electrophotographic photosensitive member according to any one of (1) to (8), wherein the electrophotographic photosensitive member is applied to an image forming apparatus employing a simultaneous development cleaning method.

  (10) An image forming apparatus in which at least a charging unit, an exposure unit, a developing unit, and a transfer unit are arranged along the moving direction of the electrophotographic photosensitive member, and is described in any one of (1) to (8) An image forming apparatus employing a simultaneous development cleaning system, comprising an electrophotographic photosensitive member.

  According to the above (1) to (3) and (8) to (10), the electrophotographic photosensitive member using the hole transporting agent satisfying the formula (A) is a paper powder based on the results of many experiments. It was found that the generation of black spots was small because of the small amount of adhesion. Furthermore, since the hole transporting agent that satisfies the formula (B), that is, has a hole mobility of a certain level or more is used, it is possible to cope with an increase in the speed of the image forming apparatus. As a result, an electrophotographic photosensitive member that can reduce the occurrence of image defects by not reducing paper dust in the cleaning process, but reducing the adhesion of paper dust, and can also support high-speed image forming devices. Can be provided.

  According to the above (4) to (7), since the plasticizer is added to the photosensitive layer as an additive, the occurrence of cracks is suppressed by reducing the dissolution of the monomer component from the photosensitive layer, and the anti-contaminant material. The amount of the monomer component dissolved can be reduced.

According to (8) to (10), there is little adhesion of paper dust to the surface of the photoconductor, and even if there is adhesion of contaminants or the like, high quality images can be maintained, and the speed of the apparatus can be accommodated. It has an electrophotographic photosensitive member. As a result, miniaturization can be realized by minimizing the cleaning process, and a high-speed image forming apparatus can be obtained.

<Mechanism of sunspot generation>
The electrophotographic photosensitive member of the present invention is optimized to prevent the paper dust from adhering to the photosensitive member, and further to suppress the generation of cracks due to the adhesion of contaminants, etc. Generation of muscles can be suppressed. First, a mechanism for generating black spots will be described.

  One of the causes of black spots appearing on the image is that the toner is developed on the photoreceptor other than the desired location (blank area). As described above, the toner is developed on the photosensitive member in the blank paper portion. The toner to be carried on the developing roller by the electric field strength between the photosensitive member and the developing roller in the blank paper portion is caused from the developing roller by some force. It is thought that it has moved onto the photoreceptor.

  Many black spots are observed under high humidity. Therefore, particularly under high humidity, the adhesion between the photosensitive member and the toner increases, and the adhesion force locally exceeds the toner carrying force on the developing roller, resulting in black spots and black streaks. It is thought that.

  If the phenomenon occurring in the toner and the photoconductor under high humidity is analyzed, it is considered that the toner is less likely to take a normal movement as a result of the toner charge amount decreasing as the humidity increases.

  In the photoconductor, when filming due to paper dust has occurred, it is likely that the photosensitive member is easily affected by humidity, the charging potential is lowered, and a desired electric field strength cannot be obtained in the white paper portion. Further, when the paper dust is filmed on the photoconductor, the adhering force of the toner to the photoconductor is increased by the moisture adsorbed on the paper powder, and the toner easily adheres to the photoconductor. This phenomenon becomes prominent when the polarity of the transfer process is negative and a transfer member (for example, a transfer roller) is disposed in contact with the photoreceptor. That is, when a negative electric field is applied in the transfer process, the paper powder that tends to be negatively charged tends to adhere to the photoconductor in the transfer process. If paper dust is not collected by the cleaning means, a part of the paper powder will be fixed (filming) on the photoreceptor, and local potential reduction and water cross-linking power increase are likely to occur. In other words, in the case of the positively charged reversal development method, since the polarity of the transfer process is negative, filming is likely to occur, and black spots are likely to occur.

  Further, when the developing method is a contact type or when the distance between the developing roller and the photosensitive member is extremely short, the toner easily adheres to the photosensitive member, so that black spots are likely to occur. Furthermore, if the speed of the image forming apparatus is increased, the load on the paper increases and paper dust is more likely to be generated, so that many black spots are generated.

  In conclusion, the generation of black spots is considered to be one of the causes of paper dust adhering to the photoconductor. Here, the factors affecting the adhesion of paper dust to the photoconductor are summarized as follows. Become.

(Element 1) Paper dust that tends to be negatively charged when the transfer polarity is negative is drawn toward the photoreceptor by electrostatic force.
(Element 2) In order to promote downsizing of the image forming apparatus and to use a substantially perfect toner, an image forming apparatus of a simultaneous development cleaning (cleanerless) system is employed. If a cleaning process for collecting paper dust is installed, the downsizing of the image forming apparatus is hindered, so it is desirable to avoid the installation. Even when a cleaning process is installed, it must be downsized and it is difficult to obtain a sufficient cleaning effect.
(Element 3) When there are few rubbing members to the photosensitive member, it is difficult to remove adhering paper dust and it is easy to fix (filming). In particular, in the simultaneous development (cleanerless) type image forming apparatus, since there are few rubbing members, paper dust is likely to be fixed (filming).
(Element 4) As the speed of the image forming apparatus increases, the load on the paper in the transport path increases, and paper dust is likely to occur.

  On the other hand, another cause of black spots appearing on the image is a crack generated on the surface of the photoreceptor. This is because the toner that should be carried on the developing roller due to the electric field strength between the photoconductor and the developing bias in the blank paper portion leaks at the crack occurrence site and cannot be charged, and moves from the developing roller onto the drum. It is thought to be because.

  When a contaminant having an oil component or the like adheres to the surface of the photoreceptor, the monomer component in the photosensitive layer is easily dissolved from the photosensitive layer. It is considered that when the monomer component is dissolved, voids are formed in the binder resin of the photosensitive layer, a local force acts on the part, and a crack is generated due to the destruction of the part.

  As a result of studying the factors affecting the adhesion of the paper dust to the photoconductor and the crack generation mechanism, the present inventor has not approached the paper on the photoconductor rather than an approach by removing paper dust or contaminants in the cleaning process. We thought that an approach to reduce the adhesion of powder itself and to suppress the generation of cracks was necessary. That is, it has been found that by optimizing the configuration of the photoconductor, paper dust can be prevented from adhering to the photoconductor, and further, the generation of cracks can be suppressed. Specifically, the configuration of the photoreceptor was optimized using specific hole transporting agents and additives.

<Hole transport agent>
In order to identify the hole transport agent for optimizing the structure of the photoconductor, verification by many experiments was required. However, if the hole transport agent has a larger conjugated planar structure in the molecule, It has been found that the adhesion of black spots and black spots and black streaks are likely to occur. Then, the threshold for black spot generation was derived from the relationship between the hole mobility of the hole transport agent and the molecular weight. The result is the above formula (A).

The hole transporting agent used in the present invention satisfies the formula (A), but this is a hole transporting agent whose hole mobility does not increase beyond a certain value even when the molecular weight of the hole transporting agent increases. It means that there is. In other words, the hole transporting agent satisfying this formula can be said to be a compound having no twisted structure in the molecule without a large conjugated plane portion in the molecule.

Further, if the molecular weight of the hole transport agent becomes excessively large, the hole transport agent becomes difficult to dissolve in the solvent for preparing the photoreceptor coating solution. Therefore, it is preferable that μ / M is 0.25 × 10 ⁻⁸ or more. .

  Furthermore, the hole transport agent used in the present invention also satisfies the formula (B). That is, since a hole transport agent having a certain or higher hole mobility is used, it is possible to cope with an increase in the speed of the image forming apparatus.

  In addition, it is preferable that the positive hole transport agent used by this invention has the site | part in any one of said (a)-(b). Examples of the site (a) include a site having a biphenyl skeleton and a site having a dimethyl-biphenyl skeleton, but the bonding position is not particularly limited. The groups (a) to (b) may have a substituent such as an alkyl group or an aryl group. Examples of the substituent include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, n-butyl group, isobutyl group, s-butyl group, t-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group and other alkyl groups having 1 to 6 carbon atoms, phenyl group, tolyl group, xylyl group, etc. Can be mentioned.

Furthermore, the hole transport agent used in the present invention is preferably represented by any one of the above formulas (I) to (III). Examples of the alkyl group having 1 to 6 carbon atoms in R _{1 to} R ₄ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, Examples thereof include a pentyl group, an isopentyl group, a neopentyl group, and a hexyl group. Examples of the alkyl group in R _{5 to} R ₁₀ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, an isopentyl group, C1-C6 alkyl groups, such as a neopentyl group and a hexyl group, are mentioned. The aryl group in R ₅ to R _10, a phenyl group, a tolyl group, an aryl group having 6 to 20 carbon atoms, such as xylyl. The aryl group may have a substituent, and examples of the substituent include an alkyl group having 1 to 6 carbon atoms and an alkoxy group having 1 to 6 carbon atoms.

Further, among R ₁ to R _4, it is preferable that at least one is an alkyl group having 1 to 6 carbon atoms. By having an alkyl group having 1 to 6 carbon atoms at a specific substitution position, it is possible to effectively have a twisted structure in the molecule of the hole transport agent, and the solubility in the compound binder resin is improved. The mobility of the transport agent can be increased.

  In the formula (I), examples of the arylene group of A include an o-phenylene group, an m-phenylene group, a p-phenylene group, and a naphthylene group, and the bonding position is not particularly limited. Examples of the biphenyl residue in which two aromatic rings in A are each a monovalent group include a group having a biphenyl skeleton and a group having a dimethyl-biphenyl skeleton, and the bonding position is not particularly limited.

  Examples of the hole transport agent having the groups (a) to (b) and the hole transport agents represented by the formulas (I) to (III) include the following HTM-1 to 7. .

  In the present invention, one or more hole transporting agents satisfying the above formulas (A) and (B) may be used. Moreover, you may use the hole transport agent in this invention together with another hole transport agent as needed.

<Charge generator>
Next, the charge generating agent used for obtaining the electrophotographic photosensitive member of the present invention will be described. Examples of the charge generator include phthalocyanine pigments such as metal-free phthalocyanine, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, α-titanyl phthalocyanine, Y-titanyl phthalocyanine, and V-hydroxygallium phthalocyanine, perylene pigments, bisazo pigments, diketopyrrolo Pyrrole pigment, metal-free naphthalocyanine pigment, metal naphthalocyanine pigment, squaraine pigment, trisazo pigment, indigo pigment, azulenium pigment, cyanine pigment, pyrylium pigment, ansanthrone pigment, triphenylmethane pigment, selenium pigment, toluidine pigment, Organic photoconductors such as pyrazoline pigments and quinacridone pigments, inorganic light such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, and amorphous silicon Material and the like. These charge generating agents may be used alone or in combination of two or more.

  In the present invention, a phthalocyanine pigment, particularly a metal-free phthalocyanine (for example, X-type metal-free phthalocyanine), titanyl phthalocyanine, hydroxygallium phthalocyanine and chlorogallium phthalocyanine is used as a charge generator. In view of the electrical characteristics of the photoreceptor when red or infrared light having a wavelength of 650 nm or more is used as an exposure light source, it is preferable.

<Electron transport agent>
Examples of the electron transport agent 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), anthracene derivatives, acridine derivatives, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride derivatives, maleic anhydride derivatives, dibromomaleic anhydride derivatives, etc. Can be mentioned.

<Additives>
The additive used for obtaining the electrophotographic photoreceptor of the present invention is preferably represented by any one of the above formulas (IV) to (VII). Examples of the alkyl group in R and R _{12 to} R ₃₁ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, a pentyl group, and an isopentyl group. C1-C6 alkyl groups, such as a group, a neopentyl group, and a hexyl group. As the aryl group in R ₁₂ to R _31, a phenyl group, a tolyl group, a xylyl group, a biphenylyl group, an aryl group having 6 to 20 carbon atoms such as naphthyl group. Examples of the aralkyl group in R _{12 to} R ₃₁ include benzyl, α-methylbenzyl, phenethyl, styryl, cinnamyl, 3-phenylpropyl, 4-phenylbutyl, 5-phenylpentyl, 6-phenylhexyl and the like. Of the aralkyl group. Examples of the cycloalkyl group in R _{12 to} R ₃₁ include C 3-10 cycloalkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl and the like. Examples of the alkoxy group for R _{12 to} R ₃₁ include C 1-6 alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, t-butoxy, pentyloxy, and hexyloxy. Examples of the halogenated alkyl group for R _{12 to} R ₃₁ include monochloromethyl, monobromomethyl, monoiodomethyl, monofluoromethyl, dichloromethyl, dibromomethyl, diiodomethyl, difluoromethyl, trichloromethyl, tribromomethyl, triiodomethyl, Substituted with 1 to 3 halogen atoms, such as trifluoromethyl, monochloroethyl, monobromoethyl, monoiodoethyl, monofluoroethyl, dibromobutyl, diiodobutyl, difluorobutyl, chlorhexyl, bromohexyl, iodohexyl or fluorohexyl And an alkyl group having 1 to 6 carbon atoms.

  Furthermore, in the additive used in the present invention, the compound represented by the above formula (IV) preferably has any one or more of the structures of the above formulas (VIII) -1 to 4.

  Furthermore, in the additive used in the present invention, the compound represented by the above formula (V) preferably has any one or more of the structures of the above formulas (IX) -1 to 7.

  The additive is preferably added in an amount of 0.1 to 20 Wt% of the total amount of components constituting the photosensitive layer. More preferably, it is 1.5-15.0 Wt%. When the amount of the additive exceeds 15.0 Wt%, crystallization is likely to occur due to pressure bonding of the transfer roller of the photosensitive layer and the member resistance may be deteriorated.

<Binder resin>
As the binder resin, for example, styrene polymer, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic polymer, styrene-acrylic copolymer, polyethylene, ethylene- Vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, vinyl chloride-vinyl acetate copolymer, polyester, polyamide, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin Thermoplastic resins such as silicone resin, epoxy resin, phenol resin, urea resin, melamine resin, unsaturated polyester, alkyd resin, polyurethane, other crosslinkable thermosetting resin, and epoxy-acre relay , Urethane - like photocurable resin such as acrylate. These can be used alone or in combination of two or more.

<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 electrophotographic photoreceptor>
The electrophotographic photosensitive member of the present invention is preferably a single layer type electrophotographic photosensitive member containing the charge generating agent and the hole transporting agent in the same layer in order to effectively prevent paper dust from adhering. . Single layer type electrophotographic photosensitive member is a roll generator, ball mill, attritor, paint shaker, ultrasonic wave, charge generator, electron transport agent, binder resin, hole transport agent and other additives as appropriate, along with appropriate solvent. What is necessary is just to prepare a dispersion liquid by mixing using a disperser etc., apply | coating this dispersion liquid on an electroconductive base | substrate by a well-known means, and drying it. The thickness of the photosensitive layer after drying is 5 to 100 μm, preferably 10 to 50 μm.

  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, 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, ethyl acetate , Esters such as methyl acetate, dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide, etc.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.

  In the single-layer type electrophotographic photosensitive member, the charge generating agent is 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, and the hole transporting agent is 5 to 5 parts by weight with respect to 100 parts by weight of the binder resin. It is good to contain in the ratio of 500 weight part, especially 25-200 weight part. When the electron transfer agent is contained, it is preferably contained in an amount of 5 to 100 parts by weight, particularly 10 to 80 parts by weight, based on 100 parts by weight of the binder resin.

  In addition, the electrophotographic photosensitive member having a single-layer type photosensitive layer as the photosensitive layer has advantages that the structure is simple and easy to manufacture, the generation of film defects can be suppressed, and the optical characteristics can be improved. There is. In addition, a photoreceptor having a single-layer type photosensitive layer can be used for both positively charged and negatively charged types by using both an electron transporting agent and a hole transporting agent as charge transporting agents. The application range of the photoreceptor can be expanded.

<Laminated electrophotographic photoreceptor>
In the case of a laminated type photoreceptor, a dispersion is prepared by mixing a charge generator and a charge transport agent together with an appropriate binder resin and solvent using a roll mill, ball mill, attritor, paint shaker, ultrasonic disperser, etc. The dispersion may be applied on a conductive substrate by a known means and dried. The thickness of each layer after drying is 0.01 to 5 μm, preferably 0.1 to 3 μm for the charge generation layer, and 2 to 100 μm, preferably 5 to 50 μm for the charge transport layer.

  In the charge generation layer of the multilayer photoconductor, the charge generation agent is preferably contained in an amount of 5 to 1000 parts by weight, particularly 30 to 500 parts by weight, based on 100 parts by weight of the binder resin. In the charge transport layer, the hole transport agent may be contained in an amount of 10 to 100 parts by weight, particularly 30 to 80 parts by weight with respect to 100 parts by weight of the binder resin. Moreover, when using together a positive hole transport agent and an electron transport agent, it is good to contain the total amount in the ratio of 10-500 weight part with respect to 100 weight part of binder resin, especially 30-200 weight part.

  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.

  Between the single layer type photosensitive layer or the multilayer type photosensitive layer and the conductive substrate, or between the charge generation layer and the charge transport layer constituting the multilayer type photosensitive layer, as long as the characteristics of the photosensitive member are not hindered. A layer, a barrier layer, or the like may be formed. A protective layer may be formed on the surface of the photosensitive 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. The image forming apparatus 10 of the present invention sequentially includes a charging unit 2, an exposing unit 3, a developing unit 4, and a transfer unit 5 around a rotatable photosensitive member (photosensitive drum 1). The photosensitive drum 1 is formed with a photosensitive layer containing the above-described hole transport agent. A paper dust removing brush 6 may be provided as a simple cleaning means that does not hinder downsizing of the image forming apparatus.

  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, when the paper dust removing brush 6 is installed, it 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.

  The photosensitive drum 1 which is the electrophotographic photosensitive member of the present invention uses the hole transport agent as described above. Therefore, the image forming apparatus (image forming apparatus of the simultaneous development cleaning type) can prevent paper dust from adhering and prevent image defects such as black streaks and black spots.

  Even in an image forming apparatus in which paper dust easily adheres to the photosensitive drum, the diameter of the photosensitive drum is 25 mm or less and the peripheral speed of the photosensitive drum is 100 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.

  Hereinafter, the electrophotographic photosensitive member of the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited only to the following Examples.

[Example]
(Measurement of hole mobility)
Twenty kinds of hole transporting agents (HTM-1 to 20) were prepared as hole transporting agents, and their hole mobility was measured. The hole mobility was measured in an environment of 25 ° C. by an ordinary TOF (Time Of Flight) method. The electric field intensity was 3 ra 10 ⁵ (V / cm). For the measurement sample, a coating solution is prepared so that the content of the charge transport agent is 30% by weight with respect to the total weight of the binder resin (Panlite TS2020 manufactured by Teijin Chemicals Ltd.) and the charge transport agent. After coating on an aluminum substrate, heat treatment was performed at 80 ° C. for 30 minutes. The sample film thickness was 7 μm. Note that HTM-1 to 7 are the same as described above. HTM-8 to 20 are shown below.

[Examples 1-7 and Comparative Examples 1-13]
<Production of single layer type electrophotographic photoreceptor>
4 parts by weight of a charge generating agent (X-type metal-free phthalocyanine), 50 parts by weight of a hole transporting agent, 30 parts by weight of an electron transporting agent and 100 parts by weight of a binder resin are mixed with a solvent (tetrahydrofuran) for 800 hours in a ball mill for 50 hours. Dispersed to prepare a photoreceptor coating solution. The binder resin is polycarbonate having an average molecular weight of 30000, and the hole transport agents used in Examples 1 to 7 and Comparative Examples 1 to 13 are shown in Table 1 below. Next, the photosensitive member coating solution is applied on a conductive substrate (aluminum base tube) by dip coating, and then dried with hot air at 100 ° C. for 40 minutes to obtain a single-layer electrophotographic photosensitive member having a film thickness of 25 μm. It was. The chemical formulas of the charge generator, electron transport agent, and binder resin used here are shown below.

<Spot evaluation test>
The produced single-layer type electrophotographic photosensitive member is mounted on a printer (DP-560) manufactured by Kyocera Mita Co., Ltd. from which the static elimination process has been removed, and 5000 sheets are obtained under high temperature and high humidity conditions (room temperature 40 ° C., relative humidity 90%). Was printed. Next, after leaving the printer for 6 hours under high temperature and high humidity conditions, A4 size white paper was printed, and black spots generated on one sheet were counted. This test is a test under harsh conditions in an environment outside the product compensation range. If the evaluation shows 100 or less black spots, the image can be guaranteed.

The results of the black spot evaluation test are shown in FIG. FIG. 2 shows μ / M of the hole transport agent used (μ: hole mobility of the hole transport agent (cm ² · V ⁻¹ · second ⁻¹ ), M: molecular weight of the hole transport agent), It is a graph which shows the relationship with the black spot generation | occurrence | production number per A4 paper. In addition, the molecular weight of the hole transport agent was calculated by obtaining Mol Wt from software (Chem Draw Std. 8.0 (manufactured by CambridgeSoft)) and rounded off to the second decimal place.

<Initial sensitivity evaluation test>
The photoreceptors obtained in Examples 1 to 7 and Comparative Examples 1 to 13 were mounted on a printer (DP-560) manufactured by Kyocera Mita Co., Ltd. from which the charge removal process was removed, the charging potential was set to +800 V, and 20 ° C. The sensitivity at the development position was measured under the environment. The results are shown in Table 2.

According to FIG. 2 and Table 1, it can be seen that when μ / M is less than 1.2 × 10 ⁻⁸ , the number of black spots generated is less than 100. On the other hand, when μ / M is larger than 1.2 × 10 ⁻⁸ (Comparative Examples 1 to 7), it can be seen that the number of sunspots rapidly increases. In Comparative Examples 8 to 13, since μ / M is less than 1.2 × 10 ⁻⁸ , the number of black spots generated is less than 100, but the hole mobility is 5.0 × 10 ⁻⁶ or less. Therefore, as shown in Table 2, the sensitivity is poor and it is difficult to cope with the high speed of the image forming apparatus. Therefore, the hole transport agent of Examples 1 to 7 satisfying the condition that μ / M is less than 1.2 × 10 ⁻⁸ and the hole mobility is greater than 5.0 × 10 ⁻⁶ is preferable. I can say that. In addition, when the surface of the photoreceptor was visually confirmed after the above test was finished, those having a μ / M of less than 1.2 × 10 ⁻⁸ (Examples 1 to 7 and Comparative Examples 8 to 13) are μ / M. Compared with those having M of 1.2 × 10 ⁻⁸ or more (Comparative Examples 1 to 7), the adhesion of paper dust was small.

[Examples 8 to 33]
<Production of single layer type electrophotographic photoreceptor>
The photoreceptor here is a single layer type electron in Examples 1 to 7 and Comparative Examples 1 to 13 except that 0 to 30 parts by weight of any one of the following additives A to E is added. It was produced in the same manner as the photographic photoreceptor. The chemical formula of the additive used here is shown below.

<Crack resistance evaluation test, member resistance test and evaluation methods thereof>
(Crack resistance evaluation test)
Sebum was directly attached to the surface of the photosensitive layer and stored for 5 days in a normal environment (room temperature 20 ° C., relative humidity 60%). Thereafter, the surface of the photoconductor was observed with a microscope, and it was confirmed whether or not cracks were generated at the sebum adhesion site.
The growth rate of cracks was calculated based on the measurement results of elapsed time and crack length.
After the evaluation test, the crack resistance is evaluated as follows: crack length less than 2.00 mm, 2.00 to less than 4.00 mm, 4.00 to 5.00 mm, and 5.00 mm or more. X.
(Material resistance test)
A transfer roller was pressed against the surface of the photoreceptor and stored for 5 days under high temperature and high humidity conditions (room temperature 50 ° C., relative humidity 90%). Thereafter, the surface of the photoreceptor was observed with a microscope to confirm whether crystals or cracks were generated.
In the evaluation of the member resistance, the case where the press-contact mark of the transfer roller to the photosensitive member was not visually confirmed was evaluated as ◯, and the case where it was slightly confirmed was evaluated as △.
Table 3 shows the results of the evaluation test.

  According to Table 3, even if any of the additives A to E is used, if the amount of the additive satisfies 0.3 to 17.0 Wt% with respect to the total amount of the components constituting the photosensitive layer. (Examples 8 to 29) Crack resistance is good. When it was less than 1.5 Wt% (Examples 30 to 33), although the crack resistance was slightly lowered, the results showed no problem in practical use. When the amount of the additive satisfies 1.5 to 15.0 Wt% (Examples 8 to 12, 15 to 29), the member resistance shows a good result, and when the amount exceeds 15.0 Wt% (Example 13) 14), or less than 1.5 Wt% (Examples 30 to 33), although the member resistance was slightly lowered, practically no problem was shown.

1 is a schematic explanatory diagram illustrating an embodiment of an image forming apparatus of the present invention. It is a graph which shows the result of the black spot evaluation test in an Example.

Explanation of symbols

1 Electrophotographic photoreceptor ((single layer type) photoreceptor drum)
2 Charging means 3 Exposure means 4 Development means 5 Transfer means 6 Paper dust removing brush (cleaning means)

Claims (7)

A single-layer electrophotographic photoreceptor comprising a photosensitive layer containing at least a charge generator and a hole transport agent in the same layer ,
The hole transferring material, together satisfy the following formula (A) and (B), the electrophotographic photosensitive member, characterized by being represented by any one of the following formulas (I) ~ (III).

(In the formula, R _{1 to} R ₄ are the same or different groups and represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. R _{5 to} R ₁₀ , R _5a and R _6a are the same or different groups. Wherein A represents a hydrogen atom, an alkyl group or an aryl group, and A represents an arylene group or a biphenyl residue in which two aromatic rings are each a monovalent group, p, q, r, s, x, And y represents an integer of 0 to 2. t and u represent an integer of 1 to 4.) The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer contains at least one selected from the following compounds (IV) to (VII) as additives.

(In the formula, R _{12 to} R ₃₁ and R are the same or different groups having a hydrogen atom, an alkyl group which may have a substituent, an aryl group which may have a substituent, and a substituent. An aralkyl group that may be substituted, a cycloalkyl group that may have a substituent, a halogen atom, an alkoxy group, a hydroxyl group, a cyano group, a nitro group, an amino group, or a halogenated alkyl group. The electrophotographic photoreceptor according to claim 2 , wherein the additive is contained in an amount of 1.5 to 15.0% by weight based on the total amount of components constituting the photosensitive layer. The electrophotographic photosensitive member according to claim 2 or 3 , wherein the compound (IV) has at least one selected from the structures of the following formulas (VIII) -1 to 4.

5. The electrophotographic photosensitive member according to claim 2, wherein the compound (VII) has at least one selected from structures of the following formulas (IX) -1 to 8 :

The electrophotographic photosensitive member according to any one of claims 1 to 5, characterized in that applied to the image forming apparatus of cleaning simultaneous with developing system. An image forming apparatus in which at least a charging unit, an exposure unit, a developing unit, and a transfer unit are disposed along a moving direction of the electrophotographic photoconductor, and the electrophotographic photoconductor according to any one of claims 1 to 5. An image forming apparatus employing a simultaneous development cleaning system.

Images