JP2014130236A - Positively-charged single-layer type electrophotographic photoreceptor and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a positively-charged single-layer type electrophotographic photoreceptor that has excellent abrasion resistance and electric characteristics, and an image forming apparatus that includes the positively-charged single-layer type electrophotographic photoreceptor as an image carrier.SOLUTION: A positively-charged single-layer type electrophotographic photoreceptor has a single-layer structured photosensitive layer formed on a conductive substrate, the photosensitive layer including a charge generating material, a charge transport material, a filler, and a binder resin, and is used as an image carrier in an image forming apparatus that includes a charging unit employing a contact charging method. The photosensitive layer contains the filler including one or more types of fine particles having the volume average particle diameter within a predetermined range and selected from the group consisting of silica fine particles and resin fine particles.

Description

  The present invention relates to a positively charged single layer type electrophotographic photosensitive member and an image forming apparatus including the positively charged single layer type electrophotographic photosensitive member.

  As an electrophotographic photoreceptor provided in an electrophotographic image forming apparatus, an inorganic photoreceptor having a photosensitive layer made of an inorganic material such as selenium or amorphous silicon, and mainly a binder resin, a charge generating material, a charge transporting material, etc. And an organic photoreceptor having a photosensitive layer made of any of the above organic materials. Among these photoreceptors, organic photoreceptors are widely used because they are easier to manufacture than inorganic photoreceptors, and the material of the photosensitive layer can be selected from a wide range of materials, and the degree of freedom in design is high. Yes.

  Examples of such an organic photoreceptor include a single layer type organic photoreceptor having a photosensitive layer containing a charge generation material and a charge transport material in the same layer. The single layer type organic photoreceptor has a single layer structure as compared with a multilayer type organic photoreceptor in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated on a conductive substrate. For this reason, it is known that production is easy, and since positive charging is performed, there is little generation of oxidizing gas such as ozone during charging, and generation of film defects can be suppressed.

  On the other hand, as a charging method of the electrophotographic photosensitive member, a charging method using a charging roller or the like to charge the surface of the photosensitive member in a state where the charging unit and the photosensitive layer are in contact, and a charging unit and a photosensitive layer using a scorotron or the like. There is a non-contact charging method in which the surface of the photoconductor is charged in a state where the distance from the surface is separated, but from this point of view, the contact charging method is excellent because it hardly generates an oxidizing gas such as ozone.

  Therefore, when charging the surface of the electrophotographic photosensitive member, it does not adversely affect the life of the electrophotographic photosensitive member and the office environment. Therefore, the contact charging method and the positively charged single layer type electrophotographic photosensitive member are used in combination. It is preferable.

  Photoconductors are required to be capable of forming images with high sensitivity and few defects. To meet such demands, titanium oxide or tin oxide is the main component, and the average primary particle size is 50 nm or less. A positively charged single-layer type organic photoreceptor having a single-layer type photosensitive layer containing certain metal oxide fine particles has been proposed (see Patent Document 1).

JP 2002-221808 A

  However, the positively charged single layer type organic photoreceptor described in Patent Document 1 has a photosensitive layer formed by friction between the charging unit and the surface of the photosensitive member when used in an image forming apparatus including a contact charging type charging unit. Easy to wear. Further, the positively charged single layer type electrophotographic photosensitive member described in Patent Document 1 is difficult to be charged to a desired potential on the surface of the photosensitive member.

  The present invention has been made in view of such circumstances, and includes a positively charged single layer type electrophotographic photoreceptor excellent in wear resistance and electrical characteristics, and the positively charged single layer type electrophotographic photoreceptor. An object of the present invention is to provide an image forming apparatus provided as an image carrier.

  In the positively charged single layer type electrophotographic photosensitive member used as an image carrier in an image forming apparatus having a contact charging type charging unit, the volume average particle diameter is within a predetermined range, and the silica The inventors have found that the above problems can be solved by including a filler containing one or more fine particles selected from the group consisting of fine particles and resin fine particles in the photosensitive layer on the conductive substrate, and have completed the present invention. . Specifically, the present invention provides the following.

The first aspect of the present invention is:
A photosensitive layer having a single layer structure including a charge generation material, a charge transport material, a filler, and a binder resin is formed on a conductive substrate, and used as an image carrier in an image forming apparatus having a contact charging type charging unit. A positively charged single layer type electrophotographic photosensitive member,
The filler includes one or more fine particles selected from the group consisting of silica fine particles and resin fine particles,
The present invention relates to a positively charged single layer type electrophotographic photosensitive member in which the filler has a volume average particle diameter of 5 nm or more and 5 μm or less.

The second aspect of the present invention is:
An image carrier;
A contact charging type charging unit for charging the surface of the image carrier;
An exposure unit for exposing a surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
A transfer portion for transferring the toner image from the image carrier to a transfer target, wherein the image carrier is a positively charged single layer type electrophotographic photosensitive member according to the first aspect. An image forming apparatus.

  According to the present invention, there are provided a positively charged single layer type electrophotographic photosensitive member excellent in wear resistance and electrical characteristics, and an image forming apparatus including the positively charged single layer type electrophotographic photosensitive member as an image carrier. be able to.

1 is a schematic cross-sectional view showing the structure of a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention. 1 is a schematic diagram illustrating a configuration of an image forming apparatus including a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. . In addition, although description may be abbreviate | omitted suitably about the location where description overlaps, the summary of invention is not limited.

[First Embodiment]
In the first embodiment, a photosensitive layer having a single-layer structure including a charge generating material, a charge transporting material, a filler, and a binder resin is formed on a conductive substrate, and an image is formed with a contact charging type charging unit. The present invention relates to a positively charged single layer type electrophotographic photosensitive member (hereinafter sometimes referred to as a single layer type photosensitive member or a photosensitive member) used as an image carrier in an apparatus. The filler includes one or more fine particles selected from the group consisting of silica fine particles and resin fine particles. The volume average particle diameter of the filler is 5 nm or more and 5 μm or less.

  As shown in FIG. 1, a positively charged single layer type electrophotographic photoreceptor 10 according to the first embodiment includes a conductive substrate 12 and a charge generation material and a hole transport material formed on the conductive substrate 12. , An electron transport material, and a single photosensitive layer 14 containing a binder resin. The positively charged single layer type electrophotographic photoreceptor 10 is not particularly limited as long as it includes the conductive substrate 12 and the photosensitive layer 14. Specifically, for example, as shown in FIG. 1A, the photosensitive layer 14 may be directly provided on the conductive substrate 12, or the positively charged single layer type electrophotographic photosensitive shown in FIG. 1B. Like the body 10, an intermediate layer 16 may be provided between the conductive substrate 12 and the photosensitive layer 14. Further, as shown in FIGS. 1A and 1B, the photosensitive layer 14 may be exposed as an outermost layer, or the positively charged single layer type electrophotographic photosensitive shown in FIG. 1C. Like the body 10, a protective layer 18 may be provided on the photosensitive layer 14.

  Hereinafter, the conductive substrate and the photosensitive layer will be described in order.

[Conductive substrate]
The conductive substrate is not particularly limited as long as it can be used as a conductive substrate of a positively charged single layer type electrophotographic photosensitive member. Specifically, for example, a material having at least a surface portion made of a conductive material can be used. Specifically, for example, it may be made of a conductive material, or may be a plastic material or the like whose surface is covered with a conductive material. Examples of the conductive material include aluminum, iron, copper, tin, platinum, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass. Moreover, as a material which has electroconductivity, the material which has electroconductivity may be used by 1 type, and may be used as an alloy etc., for example, combining 2 or more types. Further, among the above, the conductive substrate is preferably made of aluminum or an aluminum alloy. By doing so, a positively charged single layer type electrophotographic photosensitive member capable of forming a more suitable image can be provided. This is considered to be due to good charge transfer from the photosensitive layer to the conductive substrate.

  The shape of the conductive substrate can be appropriately selected according to the structure of the image forming apparatus to be used. For example, a sheet-like or drum-like substrate can be suitably used. Further, the thickness of the conductive substrate can be appropriately selected according to the shape.

(Photosensitive layer)
The photosensitive layer provided in the positively charged single layer type electrophotographic photosensitive member is a photosensitive layer having a single layer structure including a charge generation material, a charge transport material, a filler, and a binder resin, and the filler includes silica fine particles and resin fine particles. There is no particular limitation as long as it contains one or more fine particles selected from the group. Hereinafter, the charge generation material, the charge transport material, the filler, the binder resin, the additive, and the method for producing the positively charged single layer type electrophotographic photoreceptor, which are the components constituting the photosensitive layer, will be described.

(Charge generation material)
The charge generation material is not particularly limited as long as it can be used as a charge generation material for a positively charged single layer type electrophotographic photosensitive member. Specifically, for example, phthalocyanine pigments, perylene pigments, bisazo pigments, dithioketopyrrolopyrrole pigments, metal-free naphthalocyanine pigments, metal naphthalocyanine pigments, squaraine pigments, trisazo pigments, indigo pigments, azulenium pigments, cyanine pigments, Powders of inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, amorphous silicon, pyrylium salts, ansanthrone pigments, triphenylmethane pigments, selenium pigments, toluidine pigments, pyrazoline pigments, Examples include quinacridone pigments.

  Further, the charge generation material may be used alone or in combination of two or more kinds so as to have an absorption wavelength in a desired region. Further, among the above-described charge generating materials, in particular, in a digital optical image forming apparatus such as a laser beam printer or a facsimile using a light source such as a semiconductor laser, a positively charged single layer having sensitivity in a wavelength region of 700 nm or more Since a type electrophotographic photoreceptor is required, for example, phthalocyanine pigments such as metal-free phthalocyanine and oxotitanyl phthalocyanine are preferably used. The crystal form of the phthalocyanine pigment is not particularly limited, and various types can be used. In addition, an image forming apparatus of an analog optical system such as an electrostatic copying machine using a white light source such as a halogen lamp needs a positively charged single layer type electrophotographic photosensitive member having sensitivity in the visible region. For example, perylene pigments and bisazo pigments are preferably used.

Specific examples of the phthalocyanine pigment include X-type metal-free phthalocyanine (x-H ₂ Pc) represented by the following formula (I) and oxotitanyl such as α-type and Y-type represented by the following formula (II). Examples include phthalocyanine.

Among these, (A) the CuKα characteristic X-ray diffraction spectrum has a main peak at a Bragg angle 2θ ± 0.2 ° = 27.2 °, and (B) in the differential scanning calorimetry, In addition to the accompanying peak, oxotitanyl phthalocyanine having one peak in the range of 50 ° C. or more and 270 ° C. or less,
In addition to the characteristics of (A), and (C) in differential scanning calorimetry, oxo titanyl phthalocyanine having no peak in the range of 50 ° C. or higher and 400 ° C. or lower, other than the peak accompanying vaporization of adsorbed water,
In addition to the characteristics of (A), and (D) in differential scanning calorimetry, there is no peak in the range of 50 ° C. or higher and 270 ° C. or lower except for the peak accompanying vaporization of adsorbed water, and 270 ° C. or higher and 400 or higher. Oxo titanyl phthalocyanine having one peak in the range of 0 ° C. or lower is preferred in terms of sensitivity.

(Charge transport material)
The charge transport material used in the present invention includes one or more materials selected from a hole transport material (HTM) and an electron transport material (ETM). Hereinafter, the hole transport material and the electron transport material will be described in order.

-Hole transport material As a hole transport material (HTM), if it can be used as a hole transport material contained in the photosensitive layer of a positively charged single layer type electrophotographic photosensitive member, it will not specifically limit. Specific examples of the hole transport material include benzidine derivatives, oxadiazole compounds such as 2,5-di (4-methylaminophenyl) -1,3,4-oxadiazole, 9- (4-diethylaminostyryl). ) Styryl compounds such as anthracene, carbazole compounds such as polyvinyl carbazole, organic polysilane compounds, pyrazoline compounds such as 1-phenyl-3- (p-dimethylaminophenyl) pyrazoline, hydrazone compounds, triphenylamine compounds, Examples thereof include nitrogen-containing cyclic compounds such as indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, triazole compounds, and condensed polycyclic compounds. Among these hole transport materials, triphenylamine compounds having one or more triphenylamine skeletons in the molecule are more preferable. These hole transport materials may be used alone or in combination of two or more.

Electron transport material The electron transport material (ETM) is not particularly limited as long as it can be used as an electron transport material contained in the photosensitive layer of the positively charged single layer type electrophotographic photosensitive member. Specifically, for example, quinone derivatives such as naphthoquinone derivatives, diphenoquinone derivatives, anthraquinone derivatives, azoquinone derivatives, nitroantharaquinone derivatives, dinitroanthraquinone derivatives, malononitrile derivatives, thiopyran derivatives, trinitrothioxanthone derivatives, 3, 4, 5, 7-tetranitro-9-fluorenone derivative, dinitroanthracene derivative, dinitroacridine derivative, tetracyanoethylene, 2,4,8-trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, succinic anhydride, maleic anhydride, dibromoanhydride And maleic acid. An electron transport material may be used independently and may be used in combination of 2 or more type.

(Filler)
The photosensitive layer included in the positively charged single layer type electrophotographic photosensitive member according to the first embodiment of the present invention includes a filler. The filler includes one or more fine particles selected from the group consisting of silica fine particles and resin fine particles. The volume average particle diameter of the filler is 5 nm or more and 5 μm or less. By including such a filler in the photosensitive layer, it is possible to obtain a positively charged single layer type electrophotographic photoreceptor excellent in wear resistance.

  The material of the resin fine particles is not particularly limited as long as the object of the present invention is not impaired. Preferable examples of the material of the resin fine particles include silicone rubber, silicone resin such as organopolysiloxane, polyphenylene sulfide resin, and fluorine-containing resin such as polytetrafluoroethylene resin. As the silicone resin, polysilsesquioxane is preferable, and polymethylsilsesquioxane is more preferable.

  The silica fine particles can be appropriately selected from known silica fine particles as long as the object of the present invention is not impaired. As the silica fine particles, those treated with a surface treatment agent such as a silane coupling agent or silicone oil can also be used.

  The volume average particle diameter of the filler is 5 nm or more and 5 μm or less, more preferably 5 nm or more and 1 μm or less, and particularly preferably 5 nm or more and 0.1 μm or less. When the volume average particle diameter of the filler is excessive, the surface of the photoreceptor tends to be hardly charged, and it is difficult to obtain a positively charged single layer type electrophotographic photoreceptor excellent in electrical characteristics.

  The filler may contain other types of fine particles other than silica fine particles and resin fine particles as long as the object of the present invention is not impaired. Other types of fine particles other than silica fine particles and resin fine particles are positively charged single layer type electrophotographic photoreceptors obtained from fine particles such as metal oxide fine particles, inorganic metal salt fine particles, and organic metal salt fine particles. It is selected in consideration of the performance. When the filler includes other types of fine particles other than silica fine particles and resin fine particles, the total content of silica fine particles and resin fine particles in the filler is 80% by mass or more based on the mass of the filler. Is preferable, 90 mass% or more is preferable, and 95 mass% or more is particularly preferable.

(Binder resin)
The binder resin is not particularly limited as long as it can be used as a binder resin contained in the photosensitive layer of the positively charged single layer type electrophotographic photosensitive member. Specific examples of the resin suitably used as the binder resin include polycarbonate resin, styrene resin, styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, styrene-acrylic acid copolymer. Polymer, acrylic copolymer, polyethylene resin, ethylene-vinyl acetate copolymer, chlorinated polyethylene resin, polyvinyl chloride resin, polypropylene resin, ionomer, vinyl chloride-vinyl acetate copolymer, alkyd resin, polyamide resin, polyurethane resin , Thermoplastic resins such as polyarylate resin, polysulfone resin, diallyl phthalate resin, ketone resin, polyvinyl butyral resin, polyether resin, polyester resin; silicone resin, epoxy resin, phenol resin, urea resin, melamine resin Thermosetting resin such other crosslinking thermosetting resins, epoxy acrylate resins, urethane - include photocurable resins such as acrylate copolymer resin. These resins may be used alone or in combination of two or more.

  Among these resins, a photosensitive layer having a good balance of processability, mechanical properties, optical properties, and abrasion resistance can be obtained. Therefore, bisphenol Z-type polycarbonate resins, bisphenol ZC-type polycarbonate resins, and bisphenol C-type polycarbonates are obtained. A resin and a polycarbonate resin such as a bisphenol A type polycarbonate resin are more preferable.

(Additive)
The photosensitive layer of the positively charged single layer type electrophotographic photosensitive member contains various additives in addition to the charge generating material, the hole transporting material, the electron transporting material, and the binder resin as long as the electrophotographic characteristics are not adversely affected. You may go out. Additives that can be incorporated into the photosensitive layer include, for example, antioxidants, radical scavengers, singlet quenchers, UV absorbers and other deterioration inhibitors, softeners, plasticizers, surface modifiers, extenders, Examples thereof include a sticking agent, a dispersion stabilizer, a wax, an acceptor, a donor, a surfactant, and a leveling agent.

(Method for producing positively charged single layer type electrophotographic photoreceptor)
The method for producing the positively charged single layer type electrophotographic photosensitive member is not particularly limited as long as the object of the present invention is not impaired. A preferred example of a method for producing a positively charged single layer type electrophotographic photosensitive member includes a method of forming a photosensitive layer by applying a coating solution for a photosensitive layer on a conductive substrate. Specifically, a charge generation material, a hole transport material, an electron transport material, a binder resin, and, if necessary, a coating solution in which various additives are dissolved or dispersed in a solvent are coated on a conductive substrate and dried. By doing so, a photosensitive layer can be produced. The application method is not particularly limited, and examples thereof include a method using a spin coater, applicator, spray coater, bar coater, dip coater, doctor blade and the like. Moreover, as a drying method of the coating film formed on the electroconductive base | substrate, the method of hot-air drying etc. on the conditions for 15 to 120 minutes at 80 to 150 degreeC are mentioned, for example.

  In the positively charged single layer type electrophotographic photosensitive member, the contents of the charge generation material, the hole transport material, the electron transport material, and the binder resin are appropriately selected and are not particularly limited. Specifically, for example, the content of the charge generation material is preferably 0.1 parts by mass or more and 50 parts by mass or less, and more preferably 0.5 parts by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin. . 5 mass parts or more and 100 mass parts or less are preferable with respect to 100 mass parts of binder resin, and, as for content of an electron transport material, 10 mass parts or more and 80 mass parts or less are more preferable. The content of the hole transport material is preferably 5 parts by mass or more and 500 parts by mass or less, and more preferably 25 parts by mass or more and 200 parts by mass or less with respect to 100 parts by mass of the binder resin. Further, the total amount of the hole transport material and the electron transport material, that is, the content of the charge transport material is preferably 20 parts by mass or more and 500 parts by mass or less with respect to 100 parts by mass of the binder resin, and 30 parts by mass. More preferably, it is 200 parts by mass or less.

  The thickness of the photosensitive layer of the positively charged single layer type electrophotographic photosensitive member is not particularly limited as long as it can sufficiently function as the photosensitive layer. Specifically, for example, it is preferably 5 μm or more and 100 μm or less, and preferably 10 μm or more and 50 μm or less.

  The solvent contained in the coating solution for the photosensitive layer is not particularly limited as long as each component constituting the photosensitive layer can be dissolved or dispersed. Specifically, 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; dichloromethane, dichloroethane and tetrachloride Halogenated hydrocarbons such as carbon and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, and diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as ethyl acetate and methyl acetate Aprotic polar organic solvents such as dimethylformaldehyde, dimethylformamide, and dimethyl sulfoxide. These solvents may be used alone or in combination of two or more.

  The positively charged single layer type electrophotographic photosensitive member is used as an image carrier of an image forming apparatus including a contact charging type charging unit described later. The positively charged single layer type electrophotographic photosensitive member according to the first embodiment is less likely to be worn even when used in an image forming apparatus having a configuration in which the photosensitive layer is likely to be worn by being provided with a contact charging type charging unit. Excellent characteristics. Therefore, an image forming apparatus capable of forming a high-quality image by using the positively charged single layer type electrophotographic photosensitive member of the first embodiment as an elephant carrier in an image forming apparatus having a contact charging type charging unit. Can be provided.

[Second Embodiment]
In the second embodiment, an image carrier, a contact charging unit that applies a voltage for charging the surface of the image carrier, and the surface of the charged image carrier are exposed to expose the image carrier. An exposure unit for forming an electrostatic latent image on the surface, a developing unit for developing the electrostatic latent image as a toner image, and a transfer unit for transferring the toner image from the image carrier to the transfer target. And an image forming apparatus using the positively charged single layer type electrophotographic photosensitive member according to the first embodiment as an image carrier.

  The image forming apparatus of the present invention can be applied to both a monochrome image forming apparatus and a tandem type color image forming apparatus using a plurality of colors of toner as described later. Here, a tandem type color image forming apparatus is used. The image forming apparatus will be described.

  Note that the tandem type color image forming apparatus including the positively charged single layer type electrophotographic photosensitive member according to the present embodiment is arranged in parallel in a predetermined direction in order to form toner images of different colors of toner on the respective surfaces. A plurality of image carriers that are provided, and arranged to face each image carrier, carry and convey toner on the surface, and supply the conveyed toner to the surface of each image carrier, respectively. A positively charged single layer type electrophotographic photosensitive member according to the first embodiment is used as each image bearing member.

  FIG. 2 is a schematic diagram showing a configuration of an image forming apparatus including a positively charged single layer type electrophotographic photosensitive member according to an embodiment of the present invention. Here, the color printer 1 will be described as an example of the image forming apparatus.

  As shown in FIG. 2, the color printer 1 has a box-shaped device main body 1a. In the apparatus main body 1a, a toner image based on image data and the like is transferred to the paper P while feeding the paper P fed from the paper feeding unit 2 and the paper P fed from the paper feeding unit 2. An image forming unit 3 and a fixing unit 4 for performing a fixing process for fixing the unfixed toner image transferred onto the paper P by the image forming unit 3 to the paper P are provided. Further, on the upper surface of the apparatus main body 1a, a paper discharge unit 5 for discharging the paper P subjected to the fixing process by the fixing unit 4 is provided.

  The paper feed unit 2 includes a paper feed cassette 121, a pickup roller 122, paper feed rollers 123, 124 and 125, and a registration roller 126. The paper feed cassette 121 is provided so as to be detachable from the apparatus main body 1a, and stores paper P of each size. The pickup roller 122 is provided at the upper left position of the paper feed cassette 121 shown in FIG. 2 and takes out the paper P stored in the paper feed cassette 121 one by one. The paper feed rollers 123, 124, and 125 send out the paper P picked up by the pickup roller 122 to the paper transport path. The registration roller 126 temporarily waits for the paper P sent to the paper transport path by the paper feed rollers 123, 124, 125, and then supplies the paper P to the image forming unit 3 at a predetermined timing.

  The paper feeding unit 2 further includes a manual feed tray (not shown) and a pickup roller 127 that are attached to the left side surface of the device main body 1a shown in FIG. The pickup roller 127 takes out the paper P placed on the manual feed tray. The paper P taken out by the pickup roller 127 is sent out to the paper transport path by the paper feed rollers 123 and 125, and is supplied to the image forming unit 3 by the registration roller 126 at a predetermined timing.

  The image forming unit 3 includes an image forming unit 7, an intermediate transfer belt 31 on which a toner image based on image data transmitted from a computer or the like to the surface (contact surface) of the image forming unit 7 is primarily transferred, A secondary transfer roller 32 is provided for secondary transfer of the toner image on the intermediate transfer belt 31 onto the paper P fed from the paper feed cassette 121.

  The image forming unit 7 includes a black unit 7K, a yellow unit 7Y, a cyan unit 7C, and a magenta unit 7M which are sequentially arranged from the upstream side (right side in FIG. 2) to the downstream side. ing. Each of the units 7K, 7Y, 7C, and 7M has a positively charged single-layer type electrophotographic photosensitive member 37 (hereinafter referred to as a photosensitive member 37) as an image carrier capable of rotating in the direction of an arrow (clockwise) at the center position. Is arranged. Around each photoconductor 37, there are a charging unit 39, an exposure unit 38, a developing unit 71, a cleaning unit (not shown), and a static elimination unit (not shown) in order from the upstream side in the rotation direction. Has been placed. As the photoreceptor 37, the positively charged single layer type electrophotographic photoreceptor according to the first embodiment is used.

  The charging unit 39 uniformly charges the peripheral surface of the photoconductor 37 rotated in the direction of the arrow. As a specific example of the charging unit 39, charging including a contact-type charging roller and a charging brush that charges the peripheral surface (surface) of the photosensitive member 37 while the charging roller and the charging brush are in contact with the photosensitive member 37. The charging unit 39 provided with a charging roller is preferably used.

  The charging unit 39 including a contact-type charging roller charges the peripheral surface (surface) of the photoconductor 37 while the charging roller is in contact with the photoconductor 37. As such a charging roller, for example, a roller that rotates depending on the rotation of the photoconductor 37 while being in contact with the photoconductor 37 can be used. Moreover, as a charging roller, the roller etc. which the surface part was comprised with resin at least are mentioned, for example. More specifically, for example, a core metal that is rotatably supported, a resin layer formed on the metal core, and a voltage application unit that applies a voltage to the metal core may be used. The charging unit 39 including such a charging roller can charge the surface of the photoreceptor 37 that is in contact with the cored bar by applying a voltage to the cored bar by the voltage applying unit.

  The voltage applied to the charging roller by the voltage application unit is not particularly limited, but it is preferable that only the DC voltage is applied rather than the application of the superimposed voltage obtained by superimposing the AC voltage on the AC voltage or DC voltage. When only a DC voltage is applied to the charging roller, the amount of wear of the photosensitive layer tends to decrease, and a suitable image can be formed. The DC voltage applied to the positively charged single layer type electrophotographic photosensitive member is preferably 1000 V to 2000 V, more preferably 1200 V to 1800 V, and particularly preferably 1400 V to 1600 V.

  In the case where the image forming apparatus includes a charging unit that applies a voltage including a charging roller and a positively charged single layer type electrophotographic photosensitive member as an image carrier, a transfer memory tends to occur. When the positively charged single layer type electrophotographic photosensitive member according to the above is used as an image carrier, the transfer memory can be suppressed and the occurrence of image defects can be suppressed.

  Further, the resin constituting the resin layer of the charging roller is not particularly limited as long as the peripheral surface of the photoreceptor 37 can be charged satisfactorily. Specific examples of the resin used for the resin layer include a silicone resin, a urethane resin, and a silicone-modified resin. Further, the resin layer may contain an inorganic filler.

  The exposure unit 38 is a so-called laser scanning unit, and irradiates the peripheral surface of the photoreceptor 37 uniformly charged by the charging unit 39 with laser light based on image data input from a personal computer (PC) as a host device. Then, an electrostatic latent image based on the image data is formed on the photoreceptor 37. The developing unit 71 supplies toner to the circumferential surface of the photoreceptor 37 on which the electrostatic latent image is formed, thereby forming a toner image based on the image data. The toner image is primarily transferred to the intermediate transfer belt 31. The cleaning unit cleans the toner remaining on the peripheral surface of the photoreceptor 37 after the primary transfer of the toner image to the intermediate transfer belt 31 is completed. The neutralization unit neutralizes the peripheral surface of the photoreceptor 37 after the primary transfer is completed. The peripheral surface of the photoconductor 37 cleaned by the cleaning unit and the charge eliminating unit is directed to the charging unit 39 for a new charging process, and a new charging process is performed.

  The intermediate transfer belt 31 is an endless belt-like rotating body, and includes a driving roller 33, a driven roller 34, a backup roller 35, and 1 so that the surface (contact surface) side is in contact with the circumferential surface of each photoconductor 37. It is stretched over a plurality of rollers such as the next transfer roller 36. The intermediate transfer belt 31 is configured to rotate endlessly by a plurality of rollers in a state where the intermediate transfer belt 31 is pressed against the photoconductor 37 by a primary transfer roller 36 disposed to face each photoconductor 37. The driving roller 33 is rotationally driven by a driving source such as a stepping motor, and provides a driving force for rotating the intermediate transfer belt 31 endlessly. The driven roller 34, the backup roller 35, and the primary transfer roller 36 are rotatably provided, and are driven to rotate with the endless rotation of the intermediate transfer belt 31 by the driving roller 33. These rollers 34, 35, 36 are driven to rotate via the intermediate transfer belt 31 according to the main rotation of the drive roller 33 and support the intermediate transfer belt 31.

  The primary transfer roller 36 applies a primary transfer bias (a polarity opposite to the toner charging polarity) to the intermediate transfer belt 31. By doing so, the toner image formed on each photoconductor 37 circulates in the direction of the arrow (counterclockwise) by driving the drive roller 33 between each photoconductor 37 and the primary transfer roller 36. The images are sequentially transferred (primary transfer) to the intermediate transfer belt 31 in an overcoated state. Thereafter, if desired, after neutralization is performed by a neutralization unit (not shown) for neutralizing the surface of each photoconductor 37 with neutralizing light, each photoconductor 37 is further rotated to move to the next process. .

  The secondary transfer roller 32 applies a secondary transfer bias having a polarity opposite to that of the toner image to the paper P. By doing so, the toner image primarily transferred onto the intermediate transfer belt 31 is transferred to the paper P between the secondary transfer roller 32 and the backup roller 35, whereby a color toner image is transferred to the paper P. Transcribed.

  The fixing unit 4 performs a fixing process on the transfer image transferred to the paper P by the image forming unit 3. The fixing unit 4 is disposed opposite to the heating roller 41 heated by the energized heating element and the heating roller 41. Is provided with a pressure roller 42 that is pressed against the peripheral surface of the heating roller 41.

  The transferred image transferred to the paper P by the secondary transfer roller 32 in the image forming unit 3 is subjected to a fixing process by heating when the paper P passes between the heating roller 41 and the pressure roller 42. To be established. The paper P subjected to the fixing process is discharged to the paper discharge unit 5. Further, in the color printer 1 of the present embodiment, the transport roller 6 is disposed at an appropriate position between the fixing unit 4 and the paper discharge unit 5.

  The paper discharge unit 5 is formed by recessing the top of the device main body 1a of the color printer 1, and a paper discharge tray 51 for receiving the discharged paper P is formed at the bottom of the concave portion. .

  The color printer 1 forms an image on the paper P by the image forming operation as described above. Since the tandem type image forming apparatus as described above is provided with the positively charged single layer type electrophotographic photosensitive member according to the first embodiment which is excellent in wear resistance and electrical characteristics as an image carrier, charging by a contact charging method is performed. Even in an image forming apparatus having a configuration in which wear of the photosensitive layer including the portion is likely to occur, a suitable image can be formed while suppressing wear of the photosensitive layer.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited at all by the Example.

  In Examples and Comparative Examples, the following charge generation materials (CGM1 to 3), hole transport materials (HTM-1 to 4), electron transport materials (ETM-1 to 4), and fillers (F1 to 12) are used. ) And a binder resin.

<Charge generating material (CGM)>
CGM1: _x-H 2 Pc
CGM2: y-TiOPc
An oxo titanyl phthalocyanine crystal having a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and no peak at 26.2 ° in a CuKα characteristic X-ray diffraction spectrum.
CGM3: k-TiOPc
In the CuKα characteristic X-ray diffraction spectrum, it has a maximum peak at a Bragg angle 2θ ± 0.2 ° = 27.2 ° and no peak at 26.2 °, and in the differential scanning calorimetry, vaporization of adsorbed water A titanyl phthalocyanine crystal having one peak from 270 ° C. to 400 ° C. other than the peak associated with.

<Hole Transport Material (HTM)>
HTM1

HTM2

HTM3

HTM4

<Electron Transport Material (ETM)>
ETM1

ETM2

ETM3

ETM4

<Filler>
F1: SiO ₂ fine particles (RX200 (manufactured by Nippon Aerosil Co., Ltd.), volume average particle size 0.012 μm)
F2: SiO ₂ fine particles (RX300 (manufactured by Nippon Aerosil Co., Ltd.), volume average particle diameter 0.007 μm)
F3: polymethylsilsesquioxane fine particles (MSP-N050 (manufactured by Nikko Rica Co., Ltd.), volume average particle diameter 0.6 μm)
F4: polymethylsilsesquioxane fine particles (MSP-3500 (manufactured by Nikko Rika Co., Ltd.), volume average particle diameter 5.0 μm)
F5: polymethylsilsesquioxane fine particles (MSP-4000 (manufactured by Nikko Rica Co., Ltd.), volume average particle size 3.0 μm)
F6: polyphenylene sulfide resin fine particles (Treapearl PPS (manufactured by Toray Industries, Inc.), volume average particle diameter 0.8 μm)
F7: Silicone resin fine particles (X52-854 (manufactured by Shin-Etsu Chemical Co., Ltd.), volume average particle diameter 0.8 μm)
F8: Silicone resin fine particles (MMP-594 (manufactured by Shin-Etsu Chemical Co., Ltd.), volume average particle size 0.8 μm)
F9: SiO ₂ fine particles (NAX50 (manufactured by Nippon Aerosil Co., Ltd.), volume average particle size 0.03 μm)
F10: polytetrafluoroethylene resin fine particles (KTL-8HM (manufactured by Kitamura Co., Ltd.), volume average particle size 4.2 μm)
F11: Titanium oxide (P25 (manufactured by Nippon Aerosil Co., Ltd.), volume average particle size 0.002 μm)
F12: Antimony / tin oxide (ATO (Mitsui Metals Mining Co., Ltd.), volume average particle size 0.002 μm)

<Binder resin>
Polycarbonate resin composed of units derived from bisphenol Z and having a viscosity average molecular weight of 40,000

[Examples 1 to 20 and Comparative Examples 1 to 3]
Charge generation materials of the types and amounts described in Tables 1-4, 50 parts by mass of hole transport materials of the types described in Tables 1 to 4, and 50 parts by mass of electron transport materials of the types described in Tables 1 to 4 The fillers of the types and amounts described in Tables 1 to 4, 100 parts by mass of binder resin, and 800 parts by mass of tetrahydrofuran were added to a ball mill, mixed and dispersed for 50 hours to prepare a coating solution for the photosensitive layer. . The obtained coating solution is applied on a conductive substrate by dip coating, treated at 100 ° C. for 40 minutes to remove tetrahydrofuran from the coating film, and a positively charged single layer electrophotographic photosensitive member having a photosensitive layer with a film thickness of 25 μm. Got the body.

≪Evaluation≫
About the positively charged single-layer electrophotographic photoreceptors of Examples and Comparative Examples, the abrasion resistance and electrical characteristics of the photoreceptors were evaluated according to the following methods.

<Abrasion resistance evaluation method>
A positively charged single-layer type electrophotographic photosensitive member is mounted on a printer (FS-5300DN, manufactured by Kyocera Mita Corporation) in which a charging unit is replaced with a charging roller. As a continuous printing test, in an environment of 30 ° C. and 80% RH, A test pattern having a printing rate of 4% was continuously printed on an A4 size recording medium (high quality PPC paper manufactured by Fuji Xerox) on 5000 sheets. The film thickness of the photosensitive layer before and after the continuous printing test was measured, and the amount of change in the film thickness of the photosensitive layer after the continuous printing test was determined. Abrasion resistance was evaluated from the amount of change in film thickness according to the following criteria.
○: Change in film thickness is less than 3 μm.
X: The film thickness change amount is 3 μm or more.

<Evaluation method of electrical characteristics>
A test pattern with a printing rate of 4% using a positively charged single-layer electrophotographic photosensitive member mounted on the same printer as that used for the evaluation of wear resistance, and using the same recording medium as used for the evaluation of wear resistance. Was continuously printed on a recording medium in an environment of 30 ° C. and 80% RH. The sensitivity of the photoreceptor after continuous printing was measured, and the amount of change in sensitivity of the photoreceptor before and after continuous printing was determined. The electrical characteristics were evaluated from the amount of change in sensitivity according to the following criteria. Monochromatic light having a wavelength of 780 nm (exposure amount: 0.5 μJ / cm) taken out from the white light of a halogen lamp using a bandpass filter while the surface of the photoreceptor is charged to +700 V using a GENTEC drum sensitivity tester. ² ) was irradiated on the surface of the photoconductor, and the surface potential at the time when 0.1 second passed from the start of exposure was measured as the sensitivity of the photoconductor.
○: Sensitivity change is less than 80V.
X: Sensitivity change amount is 80 V or more.

According to Examples 1-20, the volume average in a range particle diameter D ₅₀ of a given, silica fine particles and the photosensitive layer containing a filler comprising one or more particles selected from the group consisting of resin particles When a positively charged single-layer type electrophotographic photosensitive member provided with is used as an image carrier in an image forming apparatus having a contact charging type charging unit, it is understood that the wear of the photosensitive layer and the change in sensitivity of the photosensitive member are less likely to occur. .

  According to Comparative Example 1, when a positively charged single layer type electrophotographic photosensitive member that does not contain a filler in the photosensitive layer is used as an image carrier in an image forming apparatus having a contact charging type charging unit, It can be seen that wear occurs.

  According to Comparative Examples 2 and 3, in an image forming apparatus including a positively charged single layer type electrophotographic photosensitive member containing a filler other than silica fine particles and resin fine particles in a photosensitive layer, and a contact charging type charging unit. When used as an image carrier, it can be seen that the sensitivity of the photoreceptor changes significantly.

DESCRIPTION OF SYMBOLS 10 Positively charged single layer type electrophotographic photosensitive member 12 Conductive substrate 14 Photosensitive layer 16 Intermediate layer 18 Protective layer

Claims (3)

A photosensitive layer having a single layer structure including a charge generation material, a charge transport material, a filler, and a binder resin is formed on a conductive substrate, and used as an image carrier in an image forming apparatus having a contact charging type charging unit. A positively charged single layer type electrophotographic photosensitive member,
The filler includes one or more fine particles selected from the group consisting of silica fine particles and resin fine particles,
A positively charged single layer type electrophotographic photoreceptor, wherein the filler has a volume average particle diameter of 5 nm or more and 5 μm or less.   The positively charged single layer type electrophotographic photosensitive member according to claim 1, wherein a content of the filler is 0.5 part by mass or more and 30 parts by mass or less with respect to 100 parts by mass of the binder resin. An image carrier;
A contact charging type charging unit for charging the surface of the image carrier;
An exposure unit for exposing a surface of the charged image carrier to form an electrostatic latent image on the surface of the image carrier;
A developing unit for developing the electrostatic latent image as a toner image;
A transfer unit for transferring the toner image from the image carrier to a transfer target, wherein the image carrier is a positively charged single layer type electrophotographic photosensitive member according to claim 1 or 2. An image forming apparatus.

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