JP2012014091A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method allowing stably obtaining of images with high precision and high image quality over a long period of time without deteriorating a photoreceptor due to cracking or without deteriorating a liquid developer in electrophotographic image formation using a liquid developer.SOLUTION: In an image forming method for forming an image by developing an electrostatic latent image formed on an electrophotographic photoreceptor with a liquid developer, the electrophotographic photoreceptor comprises at least a photosensitive layer and a surface layer laminated on a conductive substrate. The photoreceptor uses a photosensitive material which substantially contains no charge transport material on its surface, while containing a reaction product of metal oxide fine particles surface treated with a reactive compound and a polymerizable compound.

Description

  The present invention relates to an image forming method, and more particularly to an image forming method using an electrophotographic photosensitive member having a surface layer and a liquid developer.

  In recent years, an image forming method using an electrophotographic system is required to have higher image quality and higher speed. In order to realize a high-definition image, the toner tends to be atomized. On the other hand, an electrophotographic image forming method has been applied to the large-format production printing field by utilizing the advantages of high image quality and high speed, and has expanded its application to the large-format production printing field. Under such circumstances, a liquid developing method capable of reproducing a high-definition image is attracting attention instead of the dry developing method which has been the mainstream. The liquid development method is expected as a high-quality image forming method because the toner can be atomized as compared with the dry development method and can cope with large format printing.

  However, the liquid developing method has an advantage that a high-quality image can be reproduced. However, since an organic solvent is used, an organic photoreceptor that is currently widely used is required to have high resistance to the solvent.

  For example, as a photoreceptor for a liquid developer, a protective layer is provided on the surface of the photoreceptor to crosslink the charge transport material and the binder resin to form a network structure, thereby preventing elution of the charge transport material and generating cracks. A technique for preventing this is disclosed (for example, see Patent Document 1).

  In addition, using a photoconductor containing inorganic fine particles and organic fine particles in the surface layer of the photoconductor, there are no white spots in solid images or character images, and a high-density, high-sharpness toner image can be obtained. Is disclosed (for example, see Patent Document 2).

  Further, as a technique for obtaining an electrophotographic photoreceptor having high resistance to a carrier liquid of a liquid developer, a technique of an organic photoreceptor that does not contain a charge transport material having a molecular weight of 1000 or less on the outermost surface is disclosed (for example, a patent). Reference 3).

  On the other hand, a technique is disclosed in which after developing with a liquid developer, the organic photoreceptor is dried to prevent the photoreceptor from being deteriorated by the developer (for example, see Patent Document 4).

Japanese Patent Laid-Open No. 10-221875 JP 2007-86131 A JP 7-84459 A Japanese Patent Laid-Open No. 4-1774

  The image forming method using the organic photoreceptor and the liquid developer needs to solve the problem of deterioration of the organic photoreceptor due to the carrier liquid used in the liquid developer or elution of the charge transport material. Therefore, various techniques for realizing an organic photoreceptor having high solvent resistance that can be applied to a liquid developer as described above have been proposed. However, there is no technology that can prevent the elution of the charge transport material under severe conditions such as in a high temperature and high humidity environment, and in order to prevent the elution of the charge transport material, a polymerizable compound and a cross-linked structure are formed in the surface layer. Even if the matrix is formed using a charge transport material that can be formed, the amount of addition that can maintain the charge transport function causes internal stress in the matrix. In fact, an organic photoreceptor that has high resistance and does not generate cracks has not yet been realized.

  In addition, there is a method of providing a mechanism for drying the photosensitive member after development, but it not only has a disadvantage that the structure of the copying machine is complicated, but it can completely prevent the deterioration of the photosensitive member. It was the actual situation that was not possible.

  When the charge transport material is eluted, the electrophotographic characteristics of the photoconductor such as the potential holding performance and sensitivity deteriorate, and this becomes manifest as an image defect. Further, when the eluted charge transporting substance is mixed in the developer, the charging performance of the toner is changed, or the toner is contaminated to cause image smearing.

  Further, even if the crack on the surface of the photoreceptor is small, it appears remarkably as an image defect. Once the crack is generated, it rapidly expands, and the image defect also rapidly expands accordingly. When it is severe, there is a problem that spider web-like image defects occur on the entire printed image.

  The present invention has been made to solve the problems of the image forming method using the liquid developer and the organic photoreceptor, and cracks are generated on the surface of the photosensitive layer even in contact with the carrier liquid constituting the liquid developer. Therefore, there is no occurrence of image defects due to cracks, and there is no elution of the charge transport material in the photosensitive layer, so that a high-quality image can be obtained and an image forming method with high durability of the developer and the organic photoreceptor The purpose is to provide.

The above-mentioned object of the present invention has heretofore been provided as a photoreceptor having a surface layer having a structure free from internal stress that is free from elution of charge transport material (CTM) that causes liquid deterioration and further causes cracking. Is achieved by the following configuration.
1. In an image forming method in which an electrostatic latent image formed on an electrophotographic photosensitive member is developed with a liquid developer to form an image, the electrophotographic photosensitive member has at least a photosensitive layer and a surface layer on a conductive support. An electrophotographic photoreceptor provided, wherein the surface layer does not substantially contain a charge transport material, and the surface layer is surface-treated with a reactive compound, and a reaction product of a metal oxide fine particle and a polymerizable compound An image forming method using a photoconductor containing a product.
2. 2. The image forming method as described in 1 above, wherein the liquid developer comprises at least a toner containing a colorant and a resin, and a carrier liquid.
3. 3. The image forming method as described in 1 or 2 above, wherein the functional group of the polymerizable compound is an acryloyloxy group or a methacryloyloxy group.
4). 4. The image forming method according to any one of 1 to 3, wherein the metal oxide fine particles are surface-treated with a reactive compound having an acryloyloxy group or a methacryloyloxy group.
5. 5. The image forming method according to any one of 1 to 4, wherein the metal oxide fine particles are at least one selected from alumina, tin oxide, titanium oxide, silica, and zinc oxide.

  By adopting the above-described configuration, the present invention improves the durability of the organic photoreceptor and the liquid developer by eliminating the generation of cracks and the elution of the charge transport material, and enables high-definition, high-quality images to be produced over a long period of time. An excellent image forming method that can be obtained stably can be obtained.

1 is a schematic cross-sectional view showing an example of a layer structure of an organic photoreceptor according to the present invention. FIG. 3 is a schematic configuration diagram illustrating an example of an image forming process in which a toner image is formed from a liquid developer using an electrostatic latent image formed on an organic photoreceptor, and the toner image is transferred to a recording medium.

  By incorporating metal oxide fine particles (hereinafter also referred to as surface-treated metal oxide fine particles) that are surface-treated with a reactive compound and a polymerizable compound into the surface layer of the photoreceptor, and cross-linking them to form a network structure, The organic solvent resistance of the layer is increased. Further, by containing a metal oxide in the surface layer, the volume resistance of the surface layer is reduced, thereby eliminating the need to contain a charge transport material in the surface layer. It is possible to provide an image forming method capable of stably obtaining a high-quality image over a long period of time without causing contamination, the sensitivity characteristics of the electrophotographic photoreceptor and the development characteristics of the liquid developer are stable. It is.

  That is, in the present invention, the metal oxide fine particles surface-treated with the reactive compound added to the surface layer and the polymerizable compound are crosslinked to form a network structure, thereby forming a dense and strong film on the surface layer. . As a result, the organic solvent used in the carrier liquid of the liquid developer is less likely to penetrate, and is not subject to stress due to repeated swelling and drying due to the penetration of the solvent, resulting in the occurrence of cracks in the surface layer called cracks. It can be prevented. Further, in the present invention, since the surface layer does not contain a charge transport material, not only does the charge transport material not elute into the carrier liquid, but also the surface layer coating becomes denser and stronger, so that the carrier liquid is contaminated. It is thought that the durability is increased.

  Hereinafter, embodiments of the present invention will be described in detail, but the embodiments of the present invention are not limited thereto.

<Organic photoconductor>
The organic photoreceptor used in the present invention is preferably one in which at least a photosensitive layer and a surface layer are sequentially laminated on a conductive support.

(Organic photoconductor layer structure)
The layer structure of the organic photoreceptor of the present invention is not particularly limited, and specific examples thereof include the following structures.

1) A structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
2) A structure in which a single layer containing a charge transport material and a charge generation material is formed as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
3) A structure in which a charge transport layer and a charge generation layer are sequentially laminated as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
The photoreceptor of the present invention may have any of the above-described structures, but among these, a photoreceptor in which a charge generation layer, a charge transport layer, and a surface layer are provided on a conductive support is preferable.

  In the present invention, an intermediate layer can be provided between the conductive support and the photosensitive layer for the purpose of improving electrical characteristics and adhesion.

  FIG. 1 is a schematic diagram showing an example of a layer structure of a photoreceptor used in the present invention.

  In FIG. 1, 1 is a conductive support, 3 is an intermediate layer, 2 is a photosensitive layer, 4 is a charge generation layer, 5 is a charge transport layer, 6 is a surface layer, and 7 is a surface-treated metal oxide fine particle.

(Create photoconductor)
The photoreceptor can be prepared by dip coating, circular amount regulation type coating, or a combination of dip coating and round amount regulation type coating, but is not limited to this. The circular amount regulation type application is described in detail in JP-A No. 58-189061.

  Next, the members constituting the conductive support, the intermediate layer, the photosensitive layer, and the surface layer and the method for forming each layer will be described.

(Conductive support)
Examples of the conductive support used in the present invention include a sheet-like or cylindrical conductive support.

  Examples of the material for the conductive support include metal drums such as aluminum and nickel, plastic materials on which aluminum, tin oxide, indium oxide, and the like are vapor-deposited, paper coated with a conductive material, plastic, and the like.

The conductive support used in the present invention means a cylindrical support necessary for forming an endless image by rotating. Here, the conductive support preferably has a specific resistance of 10 ³ Ω · cm or less, and specific examples include cylindrical aluminum whose surface has been cleaned after cutting.

(Middle layer)
The intermediate layer is formed by applying and drying an intermediate layer coating liquid composed of a binder resin and a dispersion solvent on a conductive support.

  Examples of the binder resin for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of the repeating units of these resins. Among these resins, a polyamide resin is preferable because an increase in residual potential due to repeated use can be reduced.

  As the solvent for preparing the intermediate layer coating solution, a solvent that satisfactorily dissolves the intermediate layer binder resin such as polyamide resin is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are preferable because of excellent binder resin solubility and coating performance. .

  The thickness of the intermediate layer is preferably 0.2 μm to 40 μm, and more preferably 0.3 μm to 20 μm.

(Photosensitive layer)
The photosensitive layer may have a single layer structure in which the charge generation function and the charge transport function are assigned to one layer. More preferably, the function of the photosensitive layer is separated into the charge generation layer (CGL) and the charge transport layer (CTL). It is more preferable to adopt the layer structure. By adopting a layer structure with separated functions, it is possible to control the increase in residual potential with repeated use and to easily control other electrophotographic characteristics according to the purpose. In the negatively charged photoreceptor, a charge generation layer is formed on the intermediate layer, and a charge transport layer is formed thereon. In the positively charged photoreceptor, the order of the layer configuration is opposite to that of the negatively charged photoreceptor. A preferred photosensitive layer structure is a function-separated negatively charged photoreceptor in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support.

  Each layer of the function-separated negatively charged photoreceptor will be described below.

(Charge generation layer)
The charge generation layer contains a charge generation material (CGM). Other substances may contain a binder resin and other additives as necessary.

  As the charge generation material, a known charge generation material can be used. For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, or an azulenium pigment can be used. Among these, the charge generating material that can minimize the increase in the residual potential due to repeated use has a three-dimensional structure capable of taking a stable aggregate structure among a plurality of molecules, and specifically has a specific crystal structure. Examples include phthalocyanine pigments and perylene pigments. For example, charge generation materials such as titanyl phthalocyanine having a maximum peak when the Bragg angle θ is 27.2 ° with respect to the Cu—Kα line and benzimidazole perylene having the maximum peak when 2θ is 12.4 ° are deteriorated by repeated use. Almost no residual potential can be achieved.

  When a binder resin is used as a dispersion medium in the charge generation layer, a known resin can be used as the binder resin, but the most preferable resins are formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Is mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.

(Charge transport layer)
The charge transport layer contains a charge transport material (CTM) and a binder resin. As other substances, an antioxidant, a dispersant and the like may be contained as necessary.

  A known charge transport material can be used as the charge transport material. For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are mixed with an arbitrary binder resin to form a layer.

  Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, Examples thereof include polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resin repeating units. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be given.

  The most preferred binder resin for these charge transport layers is a polycarbonate resin. The polycarbonate resin is most preferable in terms of good compatibility with the charge transport material and good electrophotographic characteristics.

(Antioxidant)
Further, by adding an antioxidant to the photoreceptor of the present invention, it is possible to effectively prevent fogging and image blur at high temperature and high humidity.

  Here, examples of the antioxidant include known compounds. A typical example is a substance that has the property of preventing or suppressing the action of oxygen under conditions of light, heat, discharge, etc., against an auto-oxidizing substance present in the electrophotographic photosensitive member or on the surface of the photosensitive member. is there. Specifically, the following compound groups can be mentioned.

(1) Radical chain inhibitor Examples of the radical chain inhibitor include phenolic antioxidants (hindered phenols), amine antioxidants (hindered amines, diallyldiamines, diallylamines), and hydroquinone antioxidants. It is done.

(2) Peroxide decomposing agent Examples of the peroxide decomposing agent include sulfur-based antioxidants (thioethers) and phosphoric acid-based antioxidants (phosphorous esters).

  Among the above antioxidants, the radical chain inhibitor (1) is good, and a hindered phenol-based or hindered amine-based antioxidant is particularly preferable. Two or more kinds may be used in combination, for example, a combination of (1) a hindered phenol antioxidant and (2) a thioether antioxidant. Further, the above-mentioned structural unit, for example, a hindered phenol structural unit and a hindered amine structural unit may be contained in the molecule.

  Among the antioxidants, hindered phenol-based and hindered amine-based antioxidants are particularly effective in preventing fogging and image blurring at high temperatures and high humidity. Examples of the antioxidant effective in the present invention include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010 (manufactured by Ciba Japan)), 3, 5-di-t-butyl-4-hydroxytoluene and the like.

  The content of the hindered phenol-based or hindered amine-based antioxidant in the resin layer is preferably 0.01 to 20 parts by mass. If it is less than 0.01 parts by mass, there is no effect on fogging and image blur at high temperature and high humidity, and if the content is more than 20 parts by mass, the charge transport ability in the resin layer is lowered, and the residual potential is likely to increase. Moreover, the film strength is reduced.

  The thickness of the charge transport layer is preferably 10 μm to 40 μm, more preferably 15 μm to 30 μm.

(Surface layer)
The surface layer contains a compound obtained by reacting a metal oxide fine particle surface-treated with the reactive compound according to the present invention and a polymerizable compound. As necessary, other substances may contain an antioxidant, a dispersant and the like.

(Surface-treated metal oxide fine particles)
Examples of the metal oxide fine particles constituting the surface-treated metal oxide fine particles include those having an effect of reducing the surface charge in place of the charge transport material, and are selected from alumina particles, titanium oxide particles, and tin oxide particles. Things can be mentioned. Among these, tin oxide particles and alumina particles are preferable. Further, these metal oxide fine particles are preferably surface-treated with a reactive compound.

  The number average primary particle size of the metal oxide fine particles is preferably 0.01 μm or more and 1.00 μm or less. Particularly preferably, it is 0.03 μm or more and 0.3 μm or less.

  Here, the number average primary particle diameter of the metal oxide fine particles is calculated from a photograph image obtained by observing and photographing the metal oxide fine particles with a transmission electron microscope. The magnification of the microscope is set to 10,000 times. Photographing is performed, and 100 metal oxide fine particles are randomly extracted and calculated from a photographic image. Specifically, the average diameter in the ferret direction of 100 metal oxide fine particles is measured by image analysis processing, and this is used as the number average primary particle diameter. Note that the image analysis processing can be automatically performed by, for example, driving a program built in the transmission electron microscope measurement apparatus. In the present invention, a transmission electron microscope JEM-2000FX (manufactured by JEOL Ltd.) was used for measuring the particle size of the metal oxide fine particles.

  The ratio of the surface-treated metal oxide fine particles in the surface layer is preferably 1.0 part by mass or more and 50 parts by mass or less of the entire surface layer. Particularly preferably, it is 5.0 parts by mass or more and 30 parts by mass or less.

  The surface-treated metal oxide fine particles of the present invention have been surface-treated with a reactive compound described below. Thus, unlike the conventional photoconductor, the surface layer does not need to contain a charge transport material and can operate stably, and the surface of the metal oxide becomes a cross-linking point, and the cross-linking of the surface layer is possible. In order to form a film, it is assumed that the structure has no internal stress that is easily released. This can be understood from the fact that when a metal oxide that has not been surface-treated with the reactive compound of the present invention is used, the effect that the particles have become crosslinking points does not occur, and cracks are likely to occur.

(Reactive compounds)
Next, a reactive compound (hereinafter also referred to as a reactive surface treating agent) used for the surface treatment of the metal oxide fine particles will be described.

  The reactive surface treating agent may be a compound having reactivity with a hydroxyl group or the like present on the surface of the metal oxide fine particles. Examples of such reactive surface treatment agents include the compounds described below.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
S-3: CH ₂ = CHSiCl _{3
S-4: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
_{S-6: CH 2 = CHCOO} (CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7: CH 2 = CHCOO} (CH 2) 3 Si (OCH 3) 3
_{S-8: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) Cl 2
_{S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
S-11: CH ₂ = CHCOO (CH ₂ ) ₃ SiCl _{3
S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19: CH 2 = C} (CH 3) COO (CH 2) 3 SiCl 3
_{S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = C} (CH 3) Si (CH 3) (OCH 3) 2
_{S-24: CH 2 = CHSi} (CH 3) Cl 2
_{S-25: CH 2 = CHCOOSi} (OCH 3) 3
_{S-26: CH 2 = CHCOOSi} (OC 2 H 5) 3
_{S-27: CH 2 = C} (CH 3) COOSi (OCH 3) 3
_{S-28: CH 2 = C} (CH 3) COOSi (OC 2 H 5) 3
_{S-29: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-30: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) 2 (OCH 3)
_{S-31: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCOCH 3) 2
_{S-32: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (ONHCH 3) 2
_{S-33: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OC 6 H 5) 2
_{S-34: CH 2 = CHCOO} (CH 2) 2 Si (C 10 H 21) (OCH 3) 2
_{S-35: CH 2 = CHCOO} (CH 2) 2 Si (CH 2 C 6 H 5) (OCH 3) 2
Moreover, as a reactive surface treating agent, you may use the silane compound which has the reactive organic group which can be radically polymerized other than said S-1 to S-35.

  As the reactive surface treating agent used in the present invention, those having an acryloyloxy group or a methacryloyloxy group are preferable.

  These reactive surface treating agents can be used alone or in admixture of two or more.

(Preparation of surface-treated metal oxide fine particles)
When performing the surface treatment, the reactive surface treating agent is treated with 0.1 to 100 parts by mass and the solvent 50 to 5000 parts by mass with respect to 100 parts by mass of the metal oxide fine particles using a wet media dispersion type apparatus. Is preferred. Moreover, it can also process by a dry type.

  Below, the method to manufacture the metal oxide microparticles | fine-particles surface-treated uniformly with the reactive compound is demonstrated.

  That is, by subjecting a slurry (solid particle suspension) containing untreated metal oxide fine particles and a reactive surface treatment agent to wet pulverization, the metal oxide fine particles are refined and the surface treatment of the fine particles proceeds at the same time. . Then, the metal oxide fine particles surface-treated with the reactive compound uniformly can be obtained by removing the solvent and pulverizing.

  The wet media dispersion type apparatus, which is a surface treatment apparatus used in the present invention, is filled with beads as a medium in a container, and further rotated at high speed a stirring disk attached perpendicularly to the rotation axis, thereby forming a metal oxide. It is an apparatus having a step of crushing and pulverizing / dispersing the aggregated particles, and the configuration is such that the metal oxide fine particles are sufficiently dispersed when the surface treatment is performed on the metal oxide fine particles and the surface treatment can be performed. For example, various types such as a vertical type, a horizontal type, a continuous type, and a batch type can be adopted without any problem. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. These dispersion-type devices are pulverized and dispersed by impact crushing, friction, shearing, shear stress, etc., using a grinding medium (media) such as balls and beads.

  As the media used in the sand mill, beads made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 to 2 mm are usually used, but in the present invention, those having a diameter of about 0.1 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon and ceramic can be used for the disk and container inner wall used in the wet media dispersion type apparatus. In the present invention, the disk and container inner wall made of ceramic such as zirconia or silicon carbide are particularly used. Is preferred.

  Metal having a reactive organic group capable of reacting with other radical polymerizable functional groups (for example, reactive acryloyloxy group, reactive methacryloyloxy group, etc.) by surface treatment with a reactive compound by the wet treatment as described above. Oxide fine particles can be obtained.

(Polymerizable compound)
The polymerizable compound used in the present invention is preferably a radical polymerizable compound, and among these radical polymerizable compounds, a polymerizable compound having an acryloyloxy group or a methacryloyloxy group is preferable.

The acryloyloxy group and methacryloyloxy group referred to in the present invention are as follows. Acryloyloxy group: CH ₂ ═CHCOO—
Methacryloyloxy group: CH ₂ ═CCH ₃ COO—
Specific examples of the polymerizable compound used in the present invention are shown below, but the polymerizable compound used in the present invention is not limited thereto.

  Further, the number of Ac groups referred to below represents the number of acryloyloxy groups or methacryloyloxy groups.

  However, in the above, R and R 'are respectively shown below.

  In the present invention, the polymerizable compound preferably has 2 or more functional groups, particularly preferably 4 or more. In the polymerizable compound, the ratio of the molecular weight M of the compound having an acryloyloxy group or methacryloyloxy group to the number Ac of the acryloyloxy group or methacryloyloxy group (Ac / M, number of acryloyloxy groups or methacryloyloxy groups / molecular weight) is 0. Compounds greater than 0.005 are preferred. When such a compound is used and Ac / M is increased by increasing the polymerization reaction rate, an electrophotographic photoreceptor having a high film density and excellent gas barrier properties can be obtained.

  Further, the range in which the polymerizable compound has a methacryloyloxy group and the Ac / M is greater than 0.005 and less than 0.012 is particularly preferable.

  By using in this relationship range, the crosslinking density is increased and the abrasion resistance of the photoreceptor is improved.

  In the present invention, two or more kinds of polymerizable compounds having different functional group densities may be mixed and used.

  In addition to these, various polymerizable oligomers can also be used. For example, an epoxy methacrylate oligomer, a urethane methacrylate oligomer, or a polyester methacrylate oligomer can be used.

  Moreover, although the specific example of a preferable oxetane compound is shown below, this invention is not limited to these.

  Examples of the epoxy compound include aromatic epoxides, alicyclic epoxides, and aliphatic epoxides.

  Furthermore, the surface layer according to the present invention can be formed by using a known resin together with the compound obtained by the reaction.

  Known resins include polyester resins, polycarbonate resins, polyurethane resins, acrylic resins, epoxy resins, silicone resins, alkyd resins, and the like.

  In addition to these, the surface layer according to the present invention may be formed by containing a polymerization initiator, a filler, lubricant particles and the like as necessary.

(Polymerization initiator)
In the present invention, it is preferable that the surface layer is formed by curing reaction between the silicone oil having a radical polymerizable functional group and the metal oxide fine particles surface-treated with the reactive compound and the polymerizable compound. The curing reaction is preferably performed by a method using a cleavage reaction or a method using a radical polymerization initiator in the presence of light or heat. When a curing reaction is performed using a radical polymerization initiator, both a thermal polymerization initiator and a photopolymerization initiator can be used as the polymerization initiator. Also, both heat and light initiators can be used in combination.

  As polymerization initiators, 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylazobisvaleronyl), 2,2'-azobis (2-methylbutyronitrile) ), Benzoyl peroxide (BPO), di-tert-butyl hydroperoxide, tert-butyl hydroperoxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide In addition to thermal polymerization initiators such as products, diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl -(2-hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1 (4-morpholinophenyl) butanone-1 (Irgacure 369: manufactured by Ciba Japan), 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-2-morpholino (4-methylthio) Acetophenone-based or ketal-based photopolymerization initiators such as phenyl) propan-1-one and 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime, benzoin, benzoin methyl ether, benzoin ethyl ether, Benzoin ether photopolymerization initiators such as benzoin isobutyl ether and benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl ether Benzophenone-based photopolymerization initiators such as acrylated benzophenone and 1,4-benzoylbenzene, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichloro Examples thereof include thioxanthone photopolymerization initiators such as thioxanthone.

  Other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine Examples thereof include oxide, bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compound, triazine compound, and imidazole compound. Moreover, what has a photopolymerization acceleration effect can also be used individually or in combination with the said photoinitiator. Examples include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, (2-dimethylamino) ethyl benzoate, 4,4′-dimethylaminobenzophenone, and the like.

  The polymerization initiator used in the present invention is preferably a photopolymerization initiator, preferably an alkylphenone compound or a phosphine oxide compound, more preferably an initiator having an α-hydroxyacetophenone structure or an acylphosphine oxide structure. preferable.

  These polymerization initiators may be used alone or in combination of two or more. Content of a polymerization initiator is 0.1-40 mass parts with respect to 100 mass parts of polymeric compounds, Preferably it is 0.5-20 mass parts.

  The surface layer of the present invention is characterized by containing substantially no charge transport material. If a charge transport material is contained, the charge transport compound may be mixed in the liquid developer, and the stability of the liquid developer may be lowered and the good image may not be obtained after long-term use. There is. The phrase “substantially free of a charge transport material” means 5% by mass or less in terms of the concentration in the protective layer. If it is 5% by mass or less, elution that causes deterioration does not occur throughout the life of a normal liquid developer.

<Liquid developer>
The liquid developer used in the present invention includes a colorant composed of a pigment or a dye and a toner mainly composed of a resin, an insulating carrier liquid, and a resin as necessary. A dispersion of 1 to 20% by mass is preferable.

The median diameter (D ₅₀ ) based on the number of toners is preferably 0.3 to 5.0 μm, more preferably 0.5 to 4.0 μm, and still more preferably 0.6 to 3 μm. By setting the median diameter (D ₅₀ ) based on the number of toners within this range, it can be stably dispersed in the carrier liquid, and a high-resolution toner image can be obtained.

The median diameter (D ₅₀ ) based on the number of toners can be measured by a centrifugal particle size distribution measuring device “SA-CP3” (manufactured by Shimadzu Corporation). The liquid developer is diluted with a carrier solution so as to meet the absorbance measurement range of the measuring machine, and the particle distribution is measured from the change in absorbance in the accelerated rotation mode of 2400 rpm / min. Calculate with median diameter.

(Carrier liquid)
The carrier liquid is generally insulating, has a boiling point of 100 ° C. or higher and 300 ° C. or lower, a volume resistivity of 10 ⁹ Ω · cm or higher, and a known solvent having a relative dielectric constant of 3 or lower. Examples thereof include aliphatic hydrocarbons, aromatic hydrocarbons, halogenated hydrocarbons and the like. From the viewpoint of volatility, safety, odor and the like, octane, nonane, decane, undecane, dodecane and isomers thereof, or a mixture thereof are preferably used.

  Specific examples of commercially available products include Isopar L, Isopar M, Isopar G (manufactured by Exxon Chemical), JWS8947 (manufactured by Esso Petroleum), Isosol 400 (manufactured by Nippon Petrochemical), NP-LC, NP-HCS, NP -SH (manufactured by Mitsui Texaco Chemical Co., Ltd.), NAS-4 (manufactured by Nippon Oil & Fats Co., Ltd.) and the like are preferable, and more preferably Isopar M, JWS 8947, Isosol 400, NP-LC, NP-HCS, NP-SH, NAS-4 Can be mentioned.

(Dispersant)
A dispersant may be used to disperse the toner in the carrier liquid. As the dispersant preferably used in the present invention, a known dispersant can be used. For example, a dispersant of a polyester polymer compound is used, and specifically, Solsperse 13940 (manufactured by Fuji Film Imaging Colorant Co., Ltd.) and the like are preferable.

(toner)
The toner is mainly composed of a colorant comprising a pigment or a dye and a resin, and a toner in which the pigment is dispersed in the resin is preferred. The ratio of the pigment in the toner is preferably 5% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less. When the ratio of the pigment is less than 5% by mass, the coloring power is insufficient, and when it exceeds 30% by mass, the fixing property is insufficient, which may cause problems with the gloss of the printed matter.

(Toner resin)
Examples of the resin for toner include an alkyd resin, a styrene resin, a phenol resin, an acrylic resin, a styrene-acrylic resin, a polyester resin, a rosin-modified phenol resin, and a rosin-modified resin. It is preferable to use a rosin-modified resin. . The rosin-modified resin preferably has an acid value of 50 or more and 250 or less, a softening point of 70 ° C. or more and 150 ° C. or less, and a ratio of gum rosin in the rosin of 20% or more. As such a rosin-modified resin, it is preferable to use a rosin-modified maleic acid resin or a rosin-modified fumaric acid resin. Specific examples include FGM-310 and FGM-312 manufactured by Arakawa Chemical Co., UNIREZ 709 manufactured by UNION CAP, 710, 8112, 8115 and the like.

(Coloring agent)
As the colorant composed of a pigment or a dye, known ones can be used. As the black color, carbon black (commercially available products such as # 30, # 40, # 50, MA-7, 11 manufactured by Mitsubishi Chemical Corporation) can be used. 100, 220, Cabot MONARCH 800, 900, MOGUL-L, BLACK PEARLS 130, REGAL 330, 400, 660R, Columbia Carbon Raven 1255, 1020, 1000, etc.), alkali blue, etc. are mixed with carbon black. It is also possible to use it.

  Examples of yellow type include C.I. I. Pigment Yellow 1, 3, 4, 5, 6, 12, 13, 14, 15, 16, 17, 18, 24, 55, 65, 73, 74, 81, 83, 87, 93, 94, 95, 97, 98 , 100, 101, 104, 108, 109, 110, 113, 116, 117, 120, 123, 128, 129, 133, 138, 139, 147, 151, 153, 154, 155, 156, 168, 169, 170 171, 172, 173, Naphthol Yellow S, Resol Fast Yellow 2G, and the like.

  Examples of red are C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 17, 18, 22, 23, 31, 37, 38, 41, 42, 48: 1, 48 : 2, 48: 3, 48: 4, 49: 1, 49: 2, 50: 1, 52: 1, 52: 2, 53: 1, 54, 57: 1, 58: 4, 60: 1, 63 : 1, 63: 2, 64: 1, 65, 66, 67, 68, 81, 83, 88, 90, 90: 1, 112, 114, 115, 122, 123, 133, 144, 146, 147, 149 , 150, 151, 166, 168, 170, 171, 172, 174, 175, 176, 177, 178, 179, 185, 187, 188, 189, 190, 193, 194, 202, 208, 209, 214, 216 , 220, 221, 224, 2 2, 243, 243: 1, 245, 246, 247, permanent red 4R, brilliant first scarlet, hansa yellow, benzidine yellow, resol red, lake red, lake red D, brilliant carmine 6B, permanent red F5R, pigment scarlet 3B, Examples include Bordeaux 10B and naphthol red.

  In addition, as a blue system, C.I. I. Pigment Blue 1, 2, 9, 14, 15, 16, 17: 1, 19, 21, 22, 24, 25, 56, 60, 61, 63, 64, phthalocyanine blue, and the like. In addition to colorants other than the above, green, purple, orange and other pigments such as phthalocyanine green, oil violet, methyl orange, and methyl violet may be mixed or singly as necessary for color adjustment. Can be used.

(Other additives)
The liquid developer used in the present invention may contain a charge control agent, a dispersion stabilizer and other additives as necessary. As the charge control agent, known ones conventionally used for liquid developers can be used, and either positive or negative can be charged by appropriately selecting the charge control agent. Specifically, for example, low molecular weight lecithin, barium petrate, sodium alkyl succinate, cobalt naphthate, aluminum stearate, cobalt octate, zirconium naphthate, quaternary ammonium salt and tertiary amine, and other polymers. Type charge control agents and the like can be used.

<Image forming method>
The image forming apparatus of the present invention includes the following charging process, exposure process, development process, and transfer process, and further includes a fixing process and a cleaning process as necessary.

(Charging process)
In the charging means, wire discharge or a roller charging device is used in order to apply a charge to the photoreceptor according to the present invention.

(Exposure process)
In the exposure means, a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 800 nm is used as a light source in order to form an electrostatic latent image on the photoreceptor.

(Development process)
In the developing means, each color developing device is used to form each color toner image from the electrostatic latent image formed on the photoreceptor using a liquid developer.

<Transfer process>
The transfer unit uses a transfer device that sequentially transfers the toner images of the respective colors formed on the photosensitive member to the intermediate transfer member, and a transfer device that collectively transfers the toner images on the intermediate transfer member to the recording medium.

(Fixing process)
The fixing unit uses a thermal fixing device to fix the toner image formed on the recording medium to the recording medium.

(Cleaning process)
The cleaning unit uses a blade cleaning device to clean the transfer residual toner on the photosensitive member or the transfer residual toner on the intermediate transfer member.

<Image formation process>
Next, an image forming process using the liquid developing system of the present invention will be described with reference to FIG. FIG. 2 is a schematic configuration diagram for explaining an example of an image forming process using the liquid developing system based on the embodiment of the present invention.

  Around the drum-shaped organic photoreceptor 110, a charging device 116, an exposure device 118, and a developing device 108 are arranged in the order of the rotation directions indicated by the arrows, and are used for transferring from the squeeze roller 111 and the organic photoreceptor 110 to the recording paper. A transfer roller 114 and a cleaning blade 104 which is a cleaning member for removing the carrier liquid remaining on the organic photoreceptor are disposed.

  The developing device 108 includes a developing tank 105 that stores a liquid developer containing toner and a carrier liquid, a developing roller 106, and a cleaning blade 107 that is a cleaning member for removing the liquid developer (carrier liquid) remaining on the developing roller. including. Here, the liquid developer mainly comprises an insulating liquid as a carrier liquid, a toner for developing an electrostatic latent image, and a dispersant for dispersing the toner.

  A certain amount of liquid developer is supplied to the developing roller 106, and an electric charge is given to the toner contained in the liquid developer on the developing roller 106 by a pre-development charger (not shown). Thereafter, the image information is exposed by the exposure device 118 to form an electrostatic latent image on the surface of the photoconductor 110. Next, the electrostatic latent image on the photoconductor 110 is developed with the liquid developer containing toner and carrier liquid by the developing device 108 as described above, and a toner image is formed on the surface of the photoconductor 110. At this time, not only the toner but also the carrier liquid adheres to the surface of the photoreceptor 110.

  The cleaning blade 107 removes the carrier liquid remaining on the developing roller 106 after development on the photoreceptor 110. In this example, the cleaning blade 107 is counter-contacted with the rotation direction of the developing roller 106 as an example of the configuration for scraping the remaining carrier liquid, but the remaining carrier liquid is scraped off. If it is the structure which can do, it will not be specifically limited to the contact direction. The same applies to other cleaning blades. Further, in this example, the configuration for removing the remaining carrier liquid using a cleaning blade is described. However, the remaining carrier liquid is removed while the web roll-shaped paper, cloth, etc. are pressed against the photosensitive member and wound up. A so-called web cleaning system for removal can also be employed.

  Next, excess liquid developer is removed from the toner image on the photoconductor 110 by the squeeze roller 111. The squeeze roller 111 is provided with a cleaning blade 112 for scraping off the removed liquid developer. In the squeeze roller 111, the carrier liquid between the toner layers is not removed.

  Then, the toner image formed on the photoconductor 110 is moved to a position (transfer position) facing the transfer roller 114 to which a predetermined voltage is applied, and is conveyed via the conveyance belt 119 at the transfer position. A toner image is formed on the recording paper. Specifically, a predetermined voltage is applied to the transfer roller 114, and an electric field is formed between the photoconductor 110 and the recording paper, and the toner image is electrostatically attracted to the recording paper by this electric field. As a result, a toner image is formed on the recording paper 300.

  The recording paper 300 onto which the toner image has been transferred is conveyed to the fixing device 109 via the conveyance belt 119.

  The fixing device 109 includes a fixing roller 71, a pressure roller 72, and a cleaning device 85 for removing the carrier liquid remaining on the fixing roller.

  In the fixing device 109, a fixing process for fixing the toner image transferred to the recording paper 300 by heat and pressure is performed by the fixing roller 71 and the pressure roller 72 each including a heater (heat source) therein, and the fixing process ends. . In this example, the case where the fixing roller 71 and the pressure roller 72 are each provided with a heater (heat source) will be described, but either one may be used.

  Here, the conveyance path of the recording paper will be described. The recording paper taken out from the paper feed cassette 51 is transported onto the transport belt 119 by the transport roller 64. The conveyor belt 119 is driven by driving rollers 113 and 115. The recording paper 300 conveyed on the conveying belt 119 is sent to a transfer device between the transfer roller 114 and the photoreceptor 110, and a toner image is transferred onto the surface of the recording paper. Then, the toner image is fixed in the fixing device 109. Then, the recording paper on which the toner image is fixed is discharged out of the apparatus by a paper discharge mechanism (not shown).

  EXAMPLES Next, although an Example demonstrates this invention concretely, the aspect of this invention is not limited to these.

<Creation of organic photoreceptor>
<Preparation of surface-treated metal oxide fine particles>
(Preparation of surface-treated metal oxide fine particles 1)
100 parts by weight of “alumina particles” having a number average primary particle size of 11 nm, 30 parts by weight of “Exemplary Compound S-15” as a surface treating agent, and 1000 parts by weight of methyl ethyl ketone are placed in a wet sand mill (alumina beads having a diameter of 0.5 mm). The mixture was mixed at 6 ° C. for 6 hours, and then methyl ethyl ketone and alumina beads were separated by filtration and dried at 60 ° C. to prepare “surface-treated metal oxide fine particles 1”.

(Preparation of surface-treated metal oxide fine particles 2)
In the preparation of the surface-treated metal oxide fine particles 1, “surface-treated metal oxide fine particles 2” were similarly prepared except that the exemplified compound S-15 was changed to 20 parts by weight of the “exemplary compound S-28”.

(Preparation of surface-treated metal oxide fine particles 3)
In the preparation of the surface-treated metal oxide fine particles 1, the “surface-treated metal oxide fine particles 3” were similarly obtained except that the alumina particles having a number average primary particle size of 11 nm were changed to “tin oxide particles” having a number average primary particle size of 6 nm. Was prepared.

(Preparation of surface-treated metal oxide fine particles 4)
In the preparation of the surface-treated metal oxide fine particles 1, the “surface-treated metal oxide fine particles 4” were similarly obtained except that the alumina particles having a number average primary particle size of 11 nm were changed to “titanium oxide particles” having a number average primary particle size of 100 nm. Was prepared.

(Preparation of surface-treated metal oxide fine particles 5)
In the preparation of the surface-treated metal oxide fine particles 1, particles that were not subjected to the surface treatment of the surface treatment agent S-15 were designated as “surface-treated metal oxide fine particles 5”.

  Photoreceptor 1 was produced as follows.

<Preparation of Photoreceptor 1>
(Preparation of conductive support)
The surface of the cylindrical aluminum support was cut to prepare a conductive support having a surface roughness Rz = 1.5 (μm).

(Formation of intermediate layer)
A dispersion having the following composition was diluted twice with the same mixed solvent, allowed to stand overnight, and then filtered (filter; using a lysh mesh 5 μm filter manufactured by Nippon Pole Co., Ltd.) to prepare an intermediate layer coating solution.

Polyamide resin CM8000 (manufactured by Toray Industries, Inc.) 1 part by mass Titanium oxide SMT500SAS (manufactured by Teica) 3 parts by mass Methanol 10 parts by mass Using a sand mill as a disperser, dispersion was carried out for 10 hours in a batch system.

  The said coating liquid was apply | coated and dried by the dip coating method so that it might become a dry film thickness of 2 micrometers on the said electroconductive support body, and the "intermediate layer" was formed.

(Formation of charge generation layer)
The following compositions were mixed and dispersed for 10 hours using a sand mill to prepare a charge generation layer coating solution.

Charge generation material: titanyl phthalocyanine pigment (titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3 ° by Cu-Kα characteristic X-ray diffraction spectrum measurement) 20 parts by mass Polyvinyl butyral resin (# 6000-C: electrochemical 10 parts by mass t-butyl acetate 700 parts by mass 4-methoxy-4-methyl-2-pentanone 300 parts by mass This charge generation layer coating solution is applied onto the intermediate layer by a dip coating method and dried. Then, a “charge generation layer” having a dry film thickness of 0.3 μm was formed.

(Formation of charge transport layer)
The following composition was mixed and dissolved to prepare a charge transport layer coating solution.

Charge transport material (CTM-1: 4,4′-dimethyl-4 ″-(β-phenylstyryl) triphenylamine) 225 parts by mass Binder: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 300 parts by mass Antioxidant ( Irganox 1010 (manufactured by Ciba Japan) 6 parts by mass THF 1600 parts by mass Toluene 400 parts by mass Silicone oil (KF-54: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part by mass Coating was performed using a regulation type coating machine and dried to form a “charge transport layer” having a dry film thickness of 20 μm, thereby preparing “Photoreceptor 1”. Further, a surface layer was provided on the “photosensitive member 1”, and the “photosensitive member 11” was prepared from the “photosensitive member 2”.

<Preparation of Photoreceptor 2>
The following surface layer was applied and formed on “Photoreceptor 1” produced as described above to provide a photocurable surface layer.

(Formation of surface layer)
The following composition was dissolved and dispersed to prepare a surface layer coating solution.

Surface treated metal oxide fine particles 1 100 parts by weight Polymerizable compound (Exemplary Compound 9) 100 parts by weight Polymerization initiator (Irgacure 369: manufactured by Ciba Japan) 7.5 parts by weight 1-propyl alcohol 100 parts by weight This surface layer The coating solution was applied onto the charge transport layer using a circular amount regulating type coating device to form a surface layer. After drying the formed surface layer, the distance from the light source to the photoreceptor surface was set to 100 mm under a nitrogen stream using a metal halide lamp, and irradiated with ultraviolet rays for 1 minute at a lamp output of 4 kW. A “surface layer” was formed to produce “Photoreceptor 2” of the present invention.

<Preparation of photoconductors 3-9>
“Photoreceptors 3 to 9” of the present invention were produced in the same manner except that the materials and curing conditions used for the surface layer of “photoreceptor 2” were changed as shown in Table 1. In addition, what was heat-cured used 7.5 mass parts of benzoyl peroxide as a polymerization initiator, and heat-cured conditions were 100 degreeC for 1 hour.

  In addition, 10 parts by mass (4.6% by mass in the surface layer) of CTM-1 is added to the surface layer of “Photoreceptor 6”, and 14 parts by mass of CTM-1 is added to the surface layer of “Photoreceptor 7” ( 6.3% by mass in the surface layer). “Photoreceptor 8” used metal oxide fine particles 10 (non-surface-treated) as a surface layer.

  The “photoreceptor 9” used methyl methacrylate as a polymerizable compound for the surface layer.

<Preparation of Photoreceptor 10>
The “photoreceptor 10” did not contain surface-treated metal oxide fine particles as described below.

Charge transport material having a hydroxy group (CTM-2) 3 parts by weight Isocyanate compound (substance of “Chemical Formula 13” below) 2 parts by weight Methyl ethyl ketone 5 parts by weight Cyclohexanone 5 parts by weight Polymerization initiator (benzoyl peroxide) 0.1 part by weight Is dissolved in a solvent consisting of the above, and is spray-coated on the charge transport layer of the “photoreceptor 1”, dried at room temperature for 10 minutes, and then heated at 130 ° C. for 60 minutes to form a surface protective layer having a thickness of 4 μm. Thus, “Photoreceptor 10” was produced.

<Preparation of Photoreceptor 11>
The “photoreceptor 11” does not contain a polymerizable compound in the surface layer, and was prepared as follows.

Surface-treated metal oxide fine particles 3 8 parts by mass Polymerizable charge transport material (CTM-3) 10 parts by mass Polymerization initiator (Irgacure 369: manufactured by Ciba Japan) 1 part by mass n-propyl alcohol 40 parts by mass The mixture was stirred and sufficiently dissolved and dispersed to prepare a surface layer coating solution. A coating film of the coating solution was formed on the charge transport layer of the previous “photosensitive member 1” using a circular amount-regulating coating machine. Thereafter, ultraviolet rays were irradiated for 5 minutes using a metal halide lamp to form a surface layer having a dry film thickness of 2.0 μm to produce “Photoreceptor 11”.

  Regarding the photoconductors produced as described above, “Photoconductors 1, 7, 8, 10, and 11” were evaluated as comparative photoconductors.

<Create toner>
<Creation of liquid developer>
(Preparation of liquid developer 1)
The following compositions were mixed and dispersed using a sand grinder to prepare “Liquid Developer 1”.

Composition Carbon black “MA-100” (manufactured by Mitsubishi Carbon Corporation) 100 parts by mass Styrene-vinyl acetate copolymer 800 parts by mass Lecithin 5 parts by mass Isopar M 3000 parts by mass (Preparation of liquid developer 2)
“Liquid developer 2” was produced in the same manner except that “Isopar M” used in the production of liquid developer 1 was changed to “JWS8947”.

<Evaluation>
The actual image evaluation was performed by replacing the developing unit of the copying machine “bizhub 421” manufactured by Konica Minolta Business Technologies with a liquid developing unit.

  The original was an A4 size character image with a pixel rate of 7%, and was copied by copying 100,000 copy images on A4 size transfer paper (recording paper) in an environment of 25 ° C. and 50% RH. A black solid image was printed after copying 500 sheets and 100,000 sheets, and the surface of the photoreceptor was visually observed for cracks. The results are shown in Table 2.

<Criteria>
(Black solid image evaluation)
○: No abnormality △: Some white spots are generated ×: White spots are generated entirely (Evaluation of cracks on the surface of the photoreceptor)
○: No abnormality △: Cracked in part (cracked in part)
×: Cracks on the entire surface of the photoconductor (cracks occur on the entire surface)

  As is apparent from the above results, in image formation using the photoreceptor of the present invention and a liquid developer, the image characteristics and the durability of the photoreceptor are excellent compared to image formation using a comparative photoreceptor. You can see that it works. Here, since the “photosensitive member 1” of Comparative Example 1 was cracked from the initial stage, the actual image evaluation of up to 500 sheets was not performed.

  That is, in the “photosensitive member 1” of Comparative Example 1, since the surface layer of the present invention was not present, white spots were generated in the entire black solid image after copying 500 sheets, and cracks were further generated on the surface of the photosensitive member. Further, the “photoreceptor 7” of Comparative Example 2 contained 5% or more of CTM in the surface layer, and white spots were generated in the black solid image. The “photoreceptor 8” of Comparative Example 3 containing metal oxide fine particles not subjected to surface treatment was similarly cracked in 500 sheets. Furthermore, in the “photoreceptor 10” of Comparative Example 4 and the “photoreceptor 11” of Comparative Example 5 which does not contain the metal oxide fine particles of the present invention and uses a polymerizable compound other than the present invention, 100, Cracks occurred after 000 sheets, which were not practical.

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Photosensitive layer 3 Intermediate | middle layer 4 Charge generation layer 5 Charge transport layer 6 Surface layer 7 Metal oxide microparticle 51 Paper feed cassette 71 Fixing roller 72 Pressure roller 73, 104, 107, 112 Cleaning blade 80 Leveling Member 81 heating roller 85 cleaning device 105 developing tank 106 developing roller 108 developing device 109 fixing device 110 photoconductor 111 squeeze roller 113, 115 driving roller 114 transfer roller 116 charging device 118 exposure device 119 conveying belt 300 recording paper

Claims (5)

  In an image forming method in which an electrostatic latent image formed on an electrophotographic photosensitive member is developed with a liquid developer to form an image, the electrophotographic photosensitive member has at least a photosensitive layer and a surface layer on a conductive support. An electrophotographic photoreceptor provided, wherein the surface layer does not substantially contain a charge transport material, and the surface layer is surface-treated with a reactive compound, and a reaction product of a metal oxide fine particle and a polymerizable compound An image forming method using a photoconductor containing a product.   2. The image forming method according to claim 1, wherein the liquid developer comprises at least a toner containing a colorant and a resin, and a carrier liquid.   The image forming method according to claim 1, wherein the functional group of the polymerizable compound is an acryloyloxy group or a methacryloyloxy group.   The image forming method according to any one of claims 1 to 3, wherein the metal oxide fine particles are surface-treated with a reactive compound having an acryloyloxy group or a methacryloyloxy group.   5. The metal oxide fine particles according to claim 1, wherein the metal oxide fine particles are at least one selected from alumina, tin oxide, titanium oxide, silica, and zinc oxide. Image forming method.

Images