JP2006064724A - Organic photoreceptor,image forming apparatus, image forming method, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic photoreceptor obtaining satisfactory electrophotographic images for a long period of time by preventing the occurrence of image defects, such as dielectric breakdown and black spots, liable to arise in the organic photoreceptor used for an an image forming apparatus of a contact electrostatic charge system, and also provide a process cartridge, an image forming apparatus, and an image forming method. <P>SOLUTION: The organic photoreceptor used for the image forming apparatus has: the organic photoreceptor; an electrostatic charging means for charging the organic photoreceptor by bringing an electrostatic charging member into contact with the surface of the organic photoreceptor; a latent image forming means for forming the electrostatic latent image on the organic photoreceptor; a developing means for developing the electrostatic latent image by toner to a sensible image and forming the toner image on the organic photoreceptor; and a transferring means for transferring the toner image on a transfer material and repetitively forms the electrophotographic images. The organic photoreceptor has an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains a binder resin and brucite type titanium oxide. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an organic photoreceptor used in the field of copying machines and printers, an image forming apparatus using the organic photoreceptor, an image forming method, and a process cartridge.

  Organic photoconductors have great advantages such as wide selection of materials, excellent environmental suitability and low production costs compared to inorganic photoconductors such as selenium photoconductors and amorphous silicon photoconductors. In recent years, electrophotographic photoreceptors have become the mainstream in place of inorganic photoreceptors.

  On the other hand, in the image forming method based on the Carlson method, a charged, electrostatic latent image is formed on an organic photoreceptor, a toner image is formed, the toner image is transferred to a transfer paper, and this is fixed and a final image is formed. Is formed.

  A corona discharger is the best known charging member that has been used as a member of the charging means. The corona discharger has an advantage that stable charging can be performed. However, since a high voltage must be applied to the corona discharger, a large amount of ionized oxygen, ozone, moisture, nitric oxide compound, etc. is generated, leading to deterioration of the organic photoreceptor (hereinafter also referred to as a photoreceptor). Or have problems such as adversely affecting the human body.

  Therefore, in recent years, use of a contact charging method that does not use a corona discharger has been studied. Specifically, a voltage is applied to a magnetic brush or a conductive roller that is a charging member to bring it into contact with a photosensitive member that is a member to be charged, and the surface of the photosensitive member is charged to a predetermined potential. If such a contact charging method is used, the voltage can be lowered and the amount of ozone generated can be reduced as compared with a non-contact charging method using a corona discharger.

In the contact charging method, a direct current voltage or a direct current superimposed on an alternating current is applied to a charging member having a resistance of about 10 ² to 10 ¹⁰ Ω · cm, and the photosensitive member is pressed and brought into contact with the photosensitive member to give an electric charge. Is the method. Since this charging method is performed by discharging from the charging member to the member to be charged in accordance with Paschen's law, charging is started by applying a voltage equal to or higher than a certain threshold value. In this contact charging method, compared with the corona charging method, the voltage applied to the charging member is lowered, and the generation amount of ozone and nitrogen oxides is reduced.

  On the other hand, digitalization has progressed in recent image forming methods, and an image forming method using laser light as an exposure light source is often used for forming an electrostatic latent image on an organic photoreceptor.

  However, in the contact charging method with a charging roller or the like, an organic photoreceptor support processed to prevent interference fringes (hereinafter also referred to as moire) due to laser light exposure, that is, the surface is roughened by cutting or the like. When an aluminum support or the like is used, there is a problem that dielectric breakdown is likely to occur when the convex portion of the cut surface is contact charged. In addition, when the surface of the organic photoreceptor is repeatedly charged, cracks and contamination, etc. generated in the organic photoreceptor occur, and as a result, charges concentrate on the cracked and contaminated portions, resulting in dielectric breakdown, black spots, etc. Image defects are likely to occur, and image blur is likely to occur. In particular, these problems are likely to occur under severe conditions such as high temperature and high humidity and low temperature and low humidity.

  An organic photoreceptor having a structure in which an intermediate layer is provided between a conductive substrate and a photosensitive layer and titanium oxide particles are dispersed in a resin is known for such problems. In addition, a technique for an intermediate layer containing titanium oxide subjected to surface treatment is also known. For example, titanium oxide surface-treated with iron oxide or tungsten oxide (Patent Document 1), titanium oxide surface-treated with an amino group-containing coupling agent (Patent Document 2), titanium oxide surface-treated with an organosilicon compound (Patent Document 2) Patent Document 3), an intermediate layer using titanium oxide surface-treated with methylhydrogenpolysiloxane (Patent Document 4), dendritic titanium oxide surface-treated with a metal oxide or an organic compound (Patent Document 5) An organophotoreceptor has been proposed.

However, even if these techniques are used, in order to prevent dielectric breakdown and black spots that are likely to occur in the contact charging method, it is necessary to configure the intermediate layer with a sufficient film thickness of, for example, 5 μm or more. When the film thickness is increased, the residual potential with repeated use increases, the image density tends to decrease, and it is difficult to achieve both the prevention of dielectric breakdown and the occurrence of black spots and sufficient image density.
Japanese Patent Laid-Open No. 4-303846 JP-A-9-96916 JP 9-258469 A JP-A-8-328283 JP-A-11-344826

  An object of the present invention is to solve the above-described problems of an organic photoreceptor used in a contact charging type image forming apparatus. More specifically, the conventional organic photoreceptor having an intermediate layer containing titanium oxide. An organic photoreceptor, an image forming apparatus, an image forming method, and an image forming apparatus capable of solving the above problems, preventing the occurrence of image defects such as dielectric breakdown and black spots, and stably obtaining a good electrophotographic image for a long period of time A process cartridge is provided.

As a result of repeated investigations on the above-mentioned problems of organic photoreceptors used in contact charging type image forming apparatuses, the intermediate layer of the organic photoreceptor has a high charge rectifying property, and has a plate shape and a conductive support. By incorporating brookite-type titanium oxide, which has a large shielding effect on the surface of the surface, it is possible to prevent the occurrence of image defects such as dielectric breakdown and black spots, and to stably obtain a good electrophotographic image for a long period of time. The headline and the present invention were completed. That is, the present invention is achieved by having the following configuration.
(Claim 1)
An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an organic photoreceptor for use in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. An organic photoreceptor having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains a binder resin and brookite-type titanium oxide.
(Claim 2)
2. The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide has a number average primary particle size of 1 to 600 nm.
(Claim 3)
The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide is a plate-like particle.
(Claim 4)
The organophotoreceptor according to claim 3, wherein the plate-like particles have a plate surface area of 1 to 10,000 nm ² and a plate thickness of 0.5 to 100 nm.
(Claim 5)
The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide is subjected to a surface treatment.
(Claim 6)
An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an organic photoreceptor for use in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. An organic photoreceptor having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains a binder resin and plate-like titanium oxide.
(Claim 7)
The organophotoreceptor according to claim 6, wherein the plate-like titanium oxide is subjected to a surface treatment.
(Claim 8)
The organic photoreceptor according to any one of claims 1 to 7, wherein the binder resin of the intermediate layer is a resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less.
(Claim 9)
The organic photosensitive resin according to claim 8, wherein the resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less is a polyamide having a repeating unit structure represented by the following general formula (1). body.

(In General Formula (1), Y ₁ is a group containing a divalent alkyl-substituted cycloalkane, Z ₁ is a methylene group, m is a natural number of 1 to 3, and n is a natural number of 3 to 20.)
(Claim 10)
An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an image forming apparatus that includes a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image, the organic photoreceptor An image forming apparatus comprising an intermediate layer and a photosensitive layer on a conductive support, wherein the intermediate layer contains a binder resin and brookite-type titanium oxide.
(Claim 11)
An image forming method comprising forming an electrophotographic image using the image forming apparatus according to claim 10.
(Claim 12)
An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In a process cartridge used in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. 10. The image forming apparatus main body, wherein the organic photoreceptor according to claim 1 and at least one of a charging unit, a latent image forming unit, a developing unit, a transfer unit, and a charge eliminating unit are integrally supported. A process cartridge which can be detachably attached to the cartridge.

  By using the organic photoreceptor of the present invention in a contact charging type image forming apparatus, it is possible to prevent dielectric breakdown and black spots, which have been problems in the past, and to form a high-density electrophotographic image. In addition, an image forming method, an image forming apparatus, and a process cartridge using the organic photoreceptor can be provided.

  Hereinafter, the present invention will be described in detail.

  The organic photoreceptor of the present invention comprises a charging means for charging by bringing a charging member into contact with the organic photoreceptor, a latent image forming means for forming an electrostatic latent image on the organic photoreceptor, and the electrostatic latent image. An organic photosensitive resin used in an image forming apparatus that repeatedly forms an electrophotographic image, having a developing unit that visualizes the toner image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material. The organic photoreceptor has an intermediate layer and a photosensitive layer on a conductive substrate, and the intermediate layer contains a binder resin and brookite-type titanium oxide.

  The organophotoreceptor of the present invention has the structure as described above, thereby preventing the occurrence of dielectric breakdown and black spots that are likely to occur in a contact charging type image forming apparatus and forming a good electrophotographic image at a high density. be able to.

  That is, brookite-type titanium oxide (also referred to as brookite-type titanium oxide) has high rectification characteristics with respect to charge carriers and can easily form pigment particles having a plate-like shape. By providing the intermediate layer between the conductive support and the photosensitive layer, free carrier injection from the conductive support can be efficiently prevented. In addition, even if the intermediate layer containing brookite-type titanium oxide is installed with a film thickness of 5 μm or more, there is almost no increase in the residual potential, and as a result, the charging characteristics of the organic photoreceptor in the contact charging method are stabilized. In addition, it is possible to produce an organic photoreceptor capable of preventing dielectric breakdown and occurrence of black spots and forming a good electrophotographic image at a high concentration.

  In addition, it is easy to obtain brookite-type titanium oxide pigments with a plate-like pigment structure. When this plate-like pigment is contained in the intermediate layer, the pigments overlap in the intermediate layer, thereby shielding the conductive support. In addition to the large free carrier blocking effect described above, the effect of preventing moire that is likely to occur due to the reflection of laser light from the conductive support is also great.

  The brookite-type titanium oxide of the present invention can be confirmed by, for example, an X-ray diffraction method. The powder X-ray diffraction pattern can be confirmed by the presence of three strong peaks having d values of about 0.350, 0.347 and 0.289 nm. Of these, the peak at 0.350 nm often overlaps the strongest line of anatase that coexists, but if the intensity ratio I (0.289 nm) / I (0.350 nm) to 0.289 nm is about 0.9, anatase Are not considered to coexist.

  The brookite-type titanium oxide of the present invention may be mixed with the anatase-type titanium oxide or rutile-type titanium oxide in the particles (pigments), but the brookite-type crystals in the mixed-crystal pigment. It is necessary to contain the most structure. The ratio of each crystal structure of the mixed crystal pigment is calculated by calculating the X-ray diffraction peak intensity from the plane index peculiar to each crystal structure and obtaining the ratio of the peak intensity corresponding to each crystal structure. The ratio of structures can be determined.

  That is, in the X-ray diffraction spectrum, in the case of brookite type titanium oxide, the half width of the peak from the (1.1.1) plane is measured, and in the case of anatase type titanium oxide, from the (1.0.1) plane. Measure the full width at half maximum of the peak, and if rutile titanium oxide is mixed, measure the full width at half maximum of the peak from the (2.1.1) plane, and obtain the peak intensity by calculation using the Debye-Scherrer equation. be able to.

  The fine particles containing the brookite-type titanium oxide of the preservation invention have a crystallite diameter in the range of 1 to 50 nm, and the crystallites are grown or are composed of a polycrystalline body in which crystallites are aggregated. The average particle diameter is in the range of 1 to 600 nm. When the crystallite diameter is less than 1 nm, the crystallinity tends to be insufficient, and it is difficult to obtain a crystallite diameter exceeding 50 nm.

The brookite-type titanium oxide of the present invention is preferably plate-like particles. A plate-like particle is defined as a generic term that is wide in the plane direction and thin in the thickness direction. The surface includes not only a smooth surface but also a slightly uneven or curved surface. The shape of the surface is not limited, and may be any shape such as a circle, an ellipse, a hexagon, or a polygon such as a quadrangle. The size of the plate-like particles, about ² plate surface area is 1 nm ² ～10000Nm, more preferably better about 5 nm ² 1000 nm ^2, the thickness is about 0.5 to 50 nm, more preferably about 1~10nm . The size of the plate-like particles can be measured by observation with an electron microscope.

  The number average primary particle diameter of brookite-type titanium oxide is a photograph obtained by magnifying and photographing with a scanning electron microscope, and 100 or more particles are measured and measured as the number average diameter of the ferret diameter. The number average diameter is preferably 1 nm to 600 nm, more preferably 5 nm to 200 nm, and most preferably 10 nm to 100 nm.

  As the binder resin of the intermediate layer of the present invention, it is preferable to use a resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less. By using the binder resin together with the brookite-type titanium oxide, the charging characteristics and sensitivity characteristics of the photoreceptor are improved in humidity resistance, no fogging occurs, and image defects such as dielectric breakdown and black spots occur. It is possible to obtain a good electrophotographic image that is prevented. That is, by using the resin having the heat of fusion and water absorption as described above as the binder resin for dispersing the brookite-type titanium oxide pigment, the characteristics of the photoreceptor as a semiconductor change even when the external environment of temperature and humidity changes. The improvement effect as described above appears remarkably. That is, when the heat of fusion is higher than 40 J / g, the solvent solubility of the binder is reduced, fine binder resin agglomerates are generated in the intermediate layer, and the dispersion of the brookite-type titanium oxide pigment is also deteriorated. The uniformity of physical properties is insufficient, resulting in the occurrence of dielectric breakdown, black spots, and increase in residual potential. In addition, the dispersion of the charge generating material applied on the intermediate layer is not sufficiently uniform, and the residual potential is increased or sensitivity is deteriorated. The heat of fusion is more preferably 0 to 30 J / g, and most preferably 0 to 20 J / g. On the other hand, when the water absorption rate exceeds 5% by mass, the water content in the intermediate layer increases, and electrophotographic characteristics such as dielectric breakdown, black spots, residual potential, and fog are reduced. The water absorption is more preferably 3% by mass or less.

  The heat of fusion of the resin is measured by DSC (Differential Scanning Calorimetry). However, if the same measurement value as the DSC measurement value is obtained, the DSC measurement method is not particular. The heat of fusion is determined from the endothermic peak area when the DSC temperature rises.

  On the other hand, the water absorption rate of the resin is determined by mass change by the water immersion method or by the Karl Fischer method.

  The binder resin for the intermediate layer of the present invention is preferably an alcohol-soluble polyamide resin. As the binder resin for the intermediate layer of the organic photoreceptor, a resin having excellent solvent solubility is required in order to form the intermediate layer with a uniform film thickness. As such an alcohol-soluble polyamide resin, a copolymerized polyamide resin or a methoxymethylated polyamide resin composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon described above is known. This resin has a high water absorption rate, and the intermediate layer using such a polyamide tends to be highly environment-dependent. As a result, for example, charging characteristics and sensitivity under high temperature and high humidity and low temperature and low humidity are likely to change. Black spots are also likely to occur.

  The alcohol-soluble polyamide resin of the present invention improves the above-mentioned drawbacks, and gives the characteristics of a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less. Thus, even if the external environment changes or the organic photoreceptor is used continuously for a long time, a good electrophotographic image can be obtained.

  Hereinafter, the alcohol-soluble polyamide resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less will be described.

  The alcohol-soluble polyamide resin is preferably a polyamide resin containing a repeating unit structure having 7 to 30 carbon atoms between amide bonds in an amount of 40 to 100 mol% of the entire repeating unit structure.

  Here, a repeating unit structure having 7 to 30 carbon atoms between amide bonds will be described. The repeating unit structure means an amide bond unit forming a polyamide resin. This is because a polyamide resin (type A) formed by condensation of a compound having a repeating unit structure having both an amino group and a carboxylic acid group, and a polyamide resin (type B) formed by condensation of a diamino compound and a dicarboxylic acid compound. ) In both examples.

  That is, the repeating unit structure of type A is represented by the general formula (2), and the carbon number contained in X is the carbon number of the amide bond unit in the repeating unit structure. On the other hand, the type B repeating unit structure is represented by the general formula (3), and the number of carbon atoms contained in Y and the number of carbon atoms contained in Z are the carbon number of the amide bond unit in the repeating unit structure.

In general formula (2), R ₁ is a hydrogen atom, a substituted or unsubstituted alkyl group, X is a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and these A mixed structure is shown, and l is a natural number.

In general formula (3), R ₂ and R ₃ are each hydrogen atom, a substituted or unsubstituted alkyl group, Y and Z are each substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, and a divalent group. And m and n are natural numbers.

  As described above, the repeating unit structure having 7 to 30 carbon atoms includes a substituted or unsubstituted alkylene group, a group containing a divalent cycloalkane, a divalent aromatic group, and a chemical structure having a mixed structure thereof. Among them, a chemical structure having a group containing a divalent cycloalkane is preferable.

  The polyamide resin of the present invention has 7 to 30 carbon atoms between amide bonds in the repeating unit structure, preferably 9 to 25, more preferably 11 to 20. The proportion of the repeating unit structure having 7 to 30 carbon atoms between amide bonds in the entire repeating unit structure is 40 to 100 mol%, preferably 60 to 100 mol%, more preferably 80 to 100 mol%.

  When the carbon number is less than 7, the hygroscopicity of the polyamide resin is large, the electrophotographic characteristics, particularly the humidity dependency of the potential during repeated use is large, and image defects such as black spots are likely to occur. If it is larger than 30, the dissolution of the polyamide resin in the coating solvent becomes worse, and it is not suitable for forming a coating film of the intermediate layer.

  Further, when the ratio of the repeating unit structure having 7 to 30 carbon atoms between amide bonds to the entire repeating unit structure is smaller than 40 mol%, the above effect is reduced.

  Preferred polyamide resins of the present invention include polyamides having a repeating unit structure represented by the following general formula (1).

In General Formula (1), Y ₁ represents a group containing a divalent alkyl-substituted cycloalkane, Z ₁ represents a methylene group, m represents 1 to 3, and n represents 3 to 20.

In the general formula (1), the group containing a divalent alkyl-substituted cycloalkane of Y ₁ preferably has the following chemical structure. That is, the polyamide resin of the present invention in which Y ₁ has the following chemical structure has a remarkable effect of improving black spots.

In the above chemical structure, A represents a single bond and an alkylene group having 1 to 4 carbon atoms, R ₄ represents a substituent, represents an alkyl group, and p represents a natural number of 1 to 5. However, the plurality of R ₄ may be the same or different.

  Specific examples of the polyamide resin of the present invention include the following examples.

  In the above specific examples, “%” in parentheses indicates the ratio (mol%) of the repeating unit structure having 7 or more carbon atoms between amide bonds in the repeating unit structure.

  Among the above specific examples, N-1 to N-4 polyamide resins having a repeating unit structure of the general formula (1) are particularly preferable.

  The molecular weight of the polyamide resin of the present invention is preferably 5,000 to 80,000 in terms of number average molecular weight, and more preferably 10,000 to 60,000. When the number average molecular weight is 5,000 or less, the uniformity of the film thickness of the intermediate layer is deteriorated, and the effects of the present invention are not sufficiently exhibited. On the other hand, if it is larger than 80,000, the solvent solubility of the resin tends to be lowered, and an aggregated resin is likely to be generated in the intermediate layer, and image defects such as black spots are likely to occur.

  A part of the polyamide resin of the present invention is already commercially available. For example, the polyamide resin is sold under the trade names such as Vestamelt X1010 and X4585 manufactured by Daicel Degussa Co., Ltd., and is prepared by a general polyamide synthesis method. An example of synthesis is given below.

Synthesis of exemplified polyamide resin (N-1) 215 parts by mass of lauryl lactam, 3-aminomethyl-3,5,5-trimethylcyclohexylamine in a polymerization kettle equipped with a stirrer, nitrogen, nitrogen introduction tube, thermometer, dehydration tube, etc. 112 parts by mass, 153 parts by mass of 1,12-dodecanedicarboxylic acid and 2 parts by mass of water were mixed and reacted for 9 hours while distilling water under heating and pressure. When the polymer was taken out and the copolymer composition was determined by C ¹³ -NMR, it coincided with the composition of N-1. The melt flow index (MFI) of the synthesized copolymer was 5 g / 10 min under the condition of (230 ° C./2.16 kg).

  Solvents for dissolving the polyamide resin of the present invention to prepare a coating solution include alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like. Preferably, it is excellent in the solubility of polyamide and the applicability of the prepared coating solution. These solvents are 30 to 100% by mass, preferably 40 to 100% by mass, and more preferably 50 to 100% by mass in the total solvent. Examples of co-solvents that can be used in combination with the above-mentioned solvent to obtain preferable effects include methanol, benzyl alcohol, toluene, methylene chloride, cyclohexanone, and tetrahydrofuran.

  When brookite-type titanium oxide is included in the intermediate layer of the present invention, moire due to laser light, which is one of image defects, is reduced, or free carriers in the intermediate layer (electrons and holes entering from a conductive support, etc.) In addition, in the present invention, by using the resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less as the binder resin of the intermediate layer, it is possible to prevent external temperature and humidity changes. An intermediate layer having stable characteristics can be obtained. As a result, the electrophotographic characteristics of the photoreceptor are stabilized, and a photoreceptor having stable characteristics against external temperature and humidity changes can be obtained.

  In addition to the above-described effects, the intermediate layer having the above structure is placed on a conductive substrate (Rz: 0.5 to 2.5 μm) whose surface is roughened. In addition to improving the film formation, there is a remarkable effect in preventing the occurrence of moire that tends to occur in image formation using image exposure light such as laser light. In order to prevent black spots that are likely to be generated by roughening the surface of the conductive substrate, the thickness of the intermediate layer of the present invention is preferably 0.7 Rz or more. Furthermore, the film thickness T of the intermediate layer is more preferably Rz or more and 10 μm or less. If the film thickness T of the intermediate layer is less than 0.7 Rz, dielectric breakdown and black spots are likely to occur, and if it is thicker than 20 μm, the residual potential tends to increase and the image density tends to decrease.

  The brookite-type titanium oxide of the present invention can be produced by a known production method, for example, the production method described in JP-A No. 2000-335919.

  The brookite-type titanium oxide of the present invention is preferably subjected to a surface treatment with a reactive organosilicon compound. The surface treatment of the brookite-type titanium oxide pigment with the reactive organosilicon compound can be performed by the following wet method. The surface treatment of the reactive organosilicon compound means that a reactive organosilicon compound is used for the treatment liquid.

  That is, the brookite-type titanium oxide pigment is added to a solution obtained by dissolving or suspending the reactive organosilicon compound in an organic solvent or water, and the mixture is dispersed in a medium for several minutes to one day. And depending on the case, after heat-processing a liquid mixture, it passes through processes, such as filtration, It dries, The brookite type titanium oxide which coat | covered the surface with the organosilicon compound is obtained. Note that the reactive organosilicon compound may be added to a suspension in which titanium oxide is dispersed in an organic solvent or water.

  The amount of the reactive organosilicon compound used for the surface treatment is 0.1 to 10 parts by mass of the reactive organosilicon compound with respect to 100 parts by mass of the brookite-type titanium oxide pigment in the charged amount during the surface treatment. More preferably, 0.1 to 5 parts by mass is used. When the surface treatment amount is less than the above range, the surface treatment effect is not sufficiently imparted, and the rectifying action and dispersibility of the titanium oxide particles in the intermediate layer are deteriorated. Further, when the surface treatment amount exceeds the above range, the electrophotographic characteristics are deteriorated, and as a result, the residual potential is increased and the charged potential is decreased.

  Examples of the reactive organosilicon compound used in the present invention include compounds represented by the following general formula (4), but any compound that undergoes a condensation reaction with a reactive group such as a hydroxyl group on the surface of titanium oxide can be used. It is not limited to.

General formula (4)
(R) _n -Si- (X) _4-n
(In the formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3.)
In the organosilicon compound represented by the general formula (4), the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl. Group, aryl group such as phenyl, tolyl, naphthyl, biphenyl, epoxy-containing group such as γ-glycidoxypropyl, β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl, γ-methacryloxypropyl (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl and 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, Amino-containing groups such as N-β (aminoethyl) -γ-aminopropyl, γ-chloropropyl, , 1,1-tri fluoroalkyl propyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.

  Moreover, the organosilicon compound represented by General formula (4) may be individual, and may be used in combination of 2 or more type.

  Moreover, in the specific compound of the organosilicon compound represented by the general formula (4), when n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by General formula (4), R and X may be the same between each compound, and may differ.

  Moreover, a polysiloxane compound is mentioned as a preferable reactive organosilicon compound. In particular, methyl hydrogen polysiloxane is preferred. The polysiloxane compound having a molecular weight of 1000 to 20000 is generally easily available, and has a good function to prevent occurrence of black spots.

  Another surface treatment of the titanium oxide of the present invention is titanium oxide particles that have been surface treated with an organosilicon compound having a fluorine atom. It is preferable to perform the surface treatment with the organosilicon compound having a fluorine atom and the wet method described above.

  In the present invention, the surface of the titanium oxide particles is coated with a reactive organosilicon compound because photoelectron spectroscopy (ESCA), Auger electron spectroscopy (Auger), secondary ion mass spectrometry (SIMS), and diffuse reflection. This is confirmed by combining surface analysis techniques such as FI-IR.

  Another example of the surface treatment of the brookite-type titanium oxide pigment is at least one surface treatment selected from alumina, silica, and zirconia.

  The alumina treatment, silica treatment, and zirconia treatment are treatments for precipitating alumina, silica, or zirconia on the surface of brookite-type titanium oxide. The alumina, silica, and zirconia deposited on these surfaces are water of alumina, silica, and zirconia. Japanese products are also included.

  The treatment of alumina and silica may be performed simultaneously, but it is particularly preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  The surface treatment of brookite-type titanium oxide with a metal oxide such as alumina, silica, and zirconia can be performed by a wet method. For example, brookite-type titanium oxide subjected to surface treatment of silica or alumina can be produced as follows.

  When using brookite-type titanium oxide, titanium oxide particles (number average primary particle size: 50 nm) are dispersed in water at a concentration of 50 to 350 g / L to form an aqueous slurry, which is water-soluble silicate or water-soluble Add aluminum compound. Thereafter, alkali or acid is added for neutralization, and silica or alumina is precipitated on the surface of the titanium oxide particles. Subsequently, filtration, washing, and drying are performed to obtain the target surface-treated titanium oxide. When sodium silicate is used as the water-soluble silicate, it can be neutralized with an acid such as sulfuric acid, nitric acid or hydrochloric acid. On the other hand, when aluminum sulfate is used as the water-soluble aluminum compound, it can be neutralized with an alkali such as sodium hydroxide or potassium hydroxide.

  In addition, the amount of the metal oxide used for the surface treatment is 0.1 to 50 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the titanium oxide particles in the amount charged in the surface treatment. These metal oxides are used. In the case of using alumina and silica as described above, for example, in the case of brookite-type titanium oxide particles, it is preferable to use 1 to 10 parts by mass with respect to 100 parts by mass of titanium oxide particles, and the amount of silica is larger than that of alumina. Is preferred.

Moreover, it is preferable that the intermediate layer of the present invention is an insulating layer substantially. Here, the insulating layer has a volume resistance of 1 × 10 ⁸ to 10 ¹⁵ Ω · cm. The volume resistance of the intermediate layer of the present invention is preferably 1 × 10 ⁹ to 10 ¹⁴ Ω · cm, more preferably 2 × 10 ⁹ to 1 × 10 ¹³ Ω · cm. The volume resistance can be measured as follows.

  Measurement conditions: According to JIS: C2318-1975.

Measuring instrument: Hiresta IP manufactured by Mitsubishi Yuka
Measurement conditions: Measurement probe HRS
Applied voltage: 500V
Measurement environment: 30 ± 2 ℃, 80 ± 5RH%
If the volume resistance is less than 1 × 10 ⁸ , the charge blocking property of the intermediate layer decreases, the occurrence of black spots increases, the potential holding property of the organic photoreceptor deteriorates, and good image quality cannot be obtained. On the other hand, if it is greater than 10 ¹⁵ Ω · cm, the residual potential tends to increase in repeated image formation, and good image quality cannot be obtained.

  The intermediate layer coating solution prepared for forming the intermediate layer of the present invention is composed of a surface-treated brookite-type titanium oxide such as the above-mentioned surface-treated titanium oxide, a binder resin, a dispersion solvent, and the like. The same solvent as the resin is used as appropriate.

  The intermediate layer of the present invention contains brookite-type titanium oxide in a proportion of 10 to 10,000 parts by mass, preferably 50 to 1,000 parts by mass with respect to 100 parts by mass of the binder resin. By using the brookite-type titanium oxide within this range, the dispersibility of the brookite-type titanium oxide can be kept good, no dielectric breakdown or black spots occur, and a good intermediate layer with little initial potential fluctuation is formed. can do.

  By dispersing and including the brookite-type titanium oxide as described above in the polyamide resin of the present invention, the electrophotographic characteristics, particularly the humidity dependency of the potential during repeated use, and the effect of improving image defects such as black spots are increased. Can be made.

  Next, the structure of the photoreceptor preferably used in the present invention other than the intermediate layer will be described.

  As the photoreceptor of the present invention, it is preferable to apply the intermediate layer of the present invention to an organic electrophotographic photoreceptor (also referred to as an organic photoreceptor) for the purpose of the present invention.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to the configuration of the electrophotographic photoconductor. All known organic electrophotographic photoreceptors such as a photoreceptor composed of the above organic charge generating substance or organic charge transporting substance, a photoreceptor composed of a polymer complex with a charge generating function and a charge transporting function are contained.

  The layer structure of the organic photoreceptor is not particularly limited, but is basically a charge generation layer, a charge transport layer, or a charge generation / charge transport layer (a layer having both charge generation and charge transport functions). Although it is comprised from a photosensitive layer, the structure which coated the surface layer on it may be sufficient. Further, since the surface layer has a protective layer function and a charge transport function, it may be used in place of the charge transport layer.

  Hereinafter, a specific configuration of the photoreceptor used in the present invention will be described.

Conductive substrate (conductive support)
As the conductive substrate used in the photoreceptor of the present invention, either a sheet or a cylindrical substrate may be used, but a cylindrical conductive substrate is preferable in order to design the image forming apparatus compactly.

  The cylindrical conductive substrate of the present invention means a cylindrical substrate necessary to be able to form an endless image by rotating, and the conductivity within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. These substrates are preferred. Exceeding the roundness and shake range makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive substrate preferably has a specific resistance of 10 ³ Ωcm or less at room temperature.

  As the conductive substrate used in the present invention, a substrate having a sealed anodized film formed on the surface thereof may be used. The alumite treatment is usually performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid, etc., but anodizing treatment in sulfuric acid gives the most preferable result. In the case of anodizing in sulfuric acid, the sulfuric acid concentration is preferably 100 to 200 g / l, the aluminum ion concentration is 1 to 10 g / l, the liquid temperature is about 20 ° C., and the applied voltage is preferably about 20 V. It is not limited. The average film thickness of the anodized film is usually 20 μm or less, particularly preferably 10 μm or less.

    The organophotoreceptor of the present invention is preferably produced so that the surface roughness of the conductive substrate is 10-point average surface roughness Rz and is 0.5 to 2.5 μm. By installing the intermediate layer having the transition brookite-type titanium oxide of the present invention on the conductive substrate processed to such a surface roughness, even when using interference light such as a laser, the generation of moire is efficiently performed. Can be prevented.

Definition and measurement method of surface roughness Rz Rz in the present invention means a value of a reference length of 0.25 mm described in JIS B0601-1982. That is, it is the difference between the average height of the top five peaks and the average height of the bottom five valleys over a distance of the reference length of 0.25 mm.

  In Examples described later, the roughness Rz was measured with a surface roughness meter (Surfcoder SE-30H manufactured by Kosaka Laboratory Ltd.). However, other measuring devices may be used as long as the measuring device produces the same result within the error range.

  The surface roughness Rz of the conductive substrate can be processed within the scope of the present invention by using a sandblasting method or the like by cutting the surface of the conductive substrate or causing fine particles to collide with the substrate surface. . Further, it can be processed within the scope of the present invention by chemical surface treatment such as anodizing.

Intermediate Layer In the present invention, an intermediate layer containing brookite-type titanium oxide is provided between the conductive support and the photosensitive layer. The thickness of the intermediate layer of the present invention is preferably 1 to 30 μm, more preferably 3 to 20 μm, and most preferably 5 to 15 μm. In the intermediate layer of the present invention, anatase titanium oxide or rutile titanium oxide may be used in combination with brookite titanium oxide. If the brookite type titanium oxide is 5% by mass or more of the total titanium oxide, the effect of the present invention is exhibited.

Photosensitive layer The photosensitive layer configuration of the photoreceptor of the present invention may be a single-layer photosensitive layer configuration in which the intermediate layer has a charge generation function and a charge transport function in one layer, but more preferably the function of the photosensitive layer. The charge generation layer (CGL) and the charge transport layer (CTL) may be separated from each other. By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

  The structure of the photosensitive 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.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments.

  As a phthalocyanine pigment, a titanyl phthalocyanine pigment having the following chemical structural formula is well known as a charge generating substance.

(In the formula, X represents a halogen atom, and n represents a number of 0 to 1). When X is a chlorine atom, n is preferably 0 to 0.5, and more preferably 0 to 0.1.

  In the present invention, among these titanyl phthalocyanine pigments, titanyl phthalocyanine (oxytitanyl phthalocyanine) having a maximum peak at 27.2 ° at the Bragg angle (2θ ± 0.2 °) of X-ray diffraction with respect to Cu-Kα X-ray, It is preferable to use a titanyl phthalocyanine pigment having significant peaks at 7.5 ° and 28.5 ° at 2θ ± 0.2. These titanyl phthalocyanine pigments change the sensitivity characteristics when environmental fluctuations in temperature and humidity occur, generate black belt-like image defects, generate black spots in high-temperature and high-humidity environments, or for a long time. Although it has a characteristic that the image density is likely to be lowered by continuous printing, when combined with the intermediate layer of the present invention, such disadvantages are eliminated and a good electrophotographic image can be obtained.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be 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 associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.1 μm to 2 μm.

Charge Transport Layer The charge transport layer contains a charge transport material (CTM) and a binder resin that forms a film by dispersing CTM. Other substances may contain additives such as antioxidants as necessary.

  A known charge transport material (CTM) can be used as the charge transport material (CTM). 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 usually dissolved in a suitable binder resin to form a layer. Among these, the CTM capable of minimizing the increase in residual potential due to repeated use has a high mobility and an ionization potential difference from the combined CGM of 0.5 (eV) or less, preferably 0 .30 (eV) or less.

  The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).

  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, and polycarbonate. Resin, silicone resin, melamine resin, and copolymer resin containing two or more of repeating unit structures of these resins. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used.

  Most preferred as a binder for these CTLs is a polycarbonate resin. The polycarbonate resin is most preferable in improving the dispersibility and electrophotographic characteristics of CTM. The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

Surface layer As a surface layer (protective layer) of the photoreceptor, a layer using siloxane polycarbonate or a crosslinking type siloxane-based resin as a binder may be provided.

  In the above, the most preferable layer structure of the photoreceptor of the present invention is exemplified, but in the present invention, a photoreceptor layer structure other than the above may be used.

  As a solvent or dispersion medium used for forming a layer such as a photosensitive layer, an intermediate layer, and a surface layer, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone , Methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane , Tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, etc. And the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  Further, the coating solution for each layer is preferably filtered with a metal filter, a membrane filter or the like in order to remove foreign matters and aggregates in the coating solution before entering the coating step. For example, it is preferable to select a pleat type (HDC), a depth type (profile), a semi-depth type (profile star), etc., manufactured by Nippon Pole Co., Ltd. according to the characteristics of the coating solution and perform filtration.

  Next, as a coating processing method for manufacturing the organic photoreceptor, a coating processing method such as dip coating, spray coating, circular amount regulation type coating, etc. is used. In order to prevent dissolution as much as possible, and in order to achieve uniform coating processing, it is preferable to use a coating processing method such as spray coating or circular amount regulation type (circular slide hopper type is a typical example). It is most preferable to use the circular amount regulation type coating method for the protective layer. The circular amount regulation type coating is described in detail in, for example, Japanese Patent Application Laid-Open No. 58-189061.

  Next, an image forming apparatus and an image forming method using the organic photoreceptor of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of an image forming apparatus 1 using a contact charging method according to the present invention. The image forming apparatus 1 includes a photosensitive cartridge 2, a developing cartridge 3, an exposure device 4 that emits a laser beam modulated based on an image signal from the outside while deflecting, a paper feeding device 5 that supplies recording paper, A transfer roller 6, a fixing device 7 and a paper discharge tray 8 are provided.

  The photoconductor cartridge 2 includes a photoconductor 21 formed by forming a thin film layer of an organic photoconductive material on the outer peripheral surface of a cylindrical body, a charging brush 22 and the like. The developing cartridge 3 includes a developing sleeve (not shown), a stirring roller, and a toner tank in which toner and a carrier are accommodated. A developing bias is applied to the developing sleeve from a developing power source (not shown). Both cartridges are closed when inserted into the image forming apparatus 1 in order to prevent problems caused by mechanical contact when the cartridge is attached to or detached from the image forming apparatus 1, and are removed from the image forming apparatus 1. A protective cover (not shown) that is sometimes opened is provided.

  Since the image forming process is well known, only a brief description will be given below. First, the surface of the photoreceptor 21 is uniformly charged with a predetermined voltage by the charging brush 22. The exposure device 4 generates a modulated laser beam (indicated by a broken arrow in the figure), deflects the laser beam by a polygon mirror (not shown), deflects and scans the surface of the photosensitive member 21, and applies it to the charged surface. The electrostatic latent images corresponding to the image information are sequentially formed.

  In the image forming apparatus of the present invention, it is preferable to form a dot latent image using a semiconductor laser or a light emitting diode as an image exposure light source when forming an electrostatic latent image on a photoreceptor. By using these image exposure light sources, the spot diameter of the image exposure (the spot diameter of the exposure beam) is reduced to 80 nm or less, preferably 60 nm or less, and 15 nm or more, and digital exposure is performed on the organic photoreceptor, A high-resolution electrophotographic image of 2400 dpi can be obtained from 400 dpi (dpi: the number of dots per 2.54 cm) or more.

The spot diameter of the exposure beam is defined as a diameter of the perfect circle area by converting an area corresponding to a light intensity at which the intensity of the exposure beam is 1 / e ² or more of the peak intensity into a perfect circle area.

  The toner in the toner tank is stirred by a stirring roller and then supplied onto the developing sleeve to form a toner image corresponding to the electrostatic latent image at a portion facing the photoreceptor 21. At the same time, residual toner existing in a portion (non-image portion) that has not been exposed on the surface of the photoconductor 21 is developed using the potential difference between the developing bias voltage applied to the developing sleeve and the surface potential of the photoconductor 21. Collected in cartridge. On the other hand, the toner image is electrostatically transferred onto the recording paper by the transfer roller 6 disposed facing the photoconductor 21. Note that the recording paper is conveyed from the paper feeding device 5 along a conveyance path indicated by a solid line arrow in the drawing. Next, the recording paper is conveyed to the fixing device 7 where the unfixed toner image is heat-fixed on the recording paper. Finally, the recording paper on which a desired image is formed is discharged from the paper discharge tray 8. By repeating the above-described series of processes, a large amount of original can be duplicated at high speed.

  The charging brush mechanically agitates the residual toner sent to the contact portion with the photoconductor by the rotation of the photoconductor and diffuses it on the surface of the photoconductor until it becomes unreadable. The charging brush electrostatically adsorbs and collects residual toner having the opposite polarity (reverse polarity) to the charging polarity of the photoconductor, and charges it to the same polarity (regular polarity) as the charging polarity of the photoconductor. Discharge onto the surface of the photoreceptor.

  The image forming apparatus 1 collects the residual toner on the photoconductor finally by a developing sleeve, and without charging the organic photoconductor after transfer of the toner image to a cleaning unit that contacts the surface of the organic photoconductor A cleaner-less method (cleaner-less process) that repeatedly circulates and repeatedly forms an electrophotographic image is used. When the organic photoreceptor of the present invention is applied to an image forming apparatus using both the contact charging method and the cleaner-less process, the effects of the present invention tend to be more noticeable.

  FIG. 2 is a schematic cross-sectional view of a photosensitive cartridge 2 that is detachable from the image forming apparatus 1. The photosensitive member cartridge 2 includes a protective member 28 with a protective cover, a photosensitive member 21 as an image carrier, a charging brush 22 disposed around the photosensitive member 21, and a power source for applying a predetermined voltage to the charging brush 22. The connecting member 23, the pre-charge film 24, the charge leveling members (sponge-like charging members) 25 and 26, and the power source connecting member 27 are accommodated.

  The photosensitive member 21 is rotated in the direction of the arrow in the drawing by a driving device (not shown). The charging brush 22 is obtained by implanting conductive yarn made of hairy fibers on a brush support. The charging brush 22 is in contact with the surface of the photosensitive member 21 and is rotated in the same direction as the rotational direction of the photosensitive member 21 in the direction of the arrow in the drawing, that is, in the contact portion with the photosensitive member 21 by a driving device (not shown). . At the time of image formation, a voltage is applied to the charging brush 22 from a charging power source (not shown), whereby the surface of the photoreceptor 21 is uniformly charged to a predetermined polarity. On the other hand, at the time of non-image formation, a voltage having a polarity opposite to that at the time of image formation is applied to the charging brush 22 from the charging power source. The charging polarity of the toner is the same as the polarity of the charging voltage at the time of image formation. Therefore, at the time of non-image formation, the toner accumulated in the charging brush 22 can be ejected onto the photoreceptor 21 by electrostatic repulsion.

  The development pre-charge film 24 and the charge leveling members 25 and 26 are disposed for the purpose of compensating uneven charging due to the charging brush 22.

  In the image forming apparatus of the present invention, it is preferable to use a polymerized toner as a developer used in the developing unit. By using a polymerized toner having a uniform shape and particle size distribution in combination with the organic photoreceptor of the present invention, an electrophotographic image with better sharpness can be obtained.

  Here, the polymerized toner means a toner obtained by forming a resin for a toner binder and forming the toner shape by polymerization of a raw material monomer of the binder resin and subsequent chemical treatment. More specifically, it means a toner obtained through a polymerization reaction such as suspension polymerization or emulsion polymerization and, if necessary, a subsequent step of fusing particles.

  Since the polymerized toner is produced by uniformly dispersing the raw material monomers in an aqueous system and then producing the toner, a toner having a uniform toner particle size distribution and shape can be obtained.

  The polymerized toner is produced by emulsion polymerization of monomers in a suspension polymerization method or in a solution to which an emulsion of necessary additives is added to produce fine polymer particles, and then an organic solvent, an aggregating agent, etc. It can manufacture by the method of adding and associating. A method of preparing by mixing with a dispersion liquid such as a release agent or a colorant necessary for the composition of the toner at the time of association, or a toner component such as a release agent or a colorant is dispersed in the monomer And a method of emulsion polymerization. Here, the association means that a plurality of resin particles and colorant particles are fused.

  That is, various constituent materials such as a colorant and, if necessary, a release agent, a charge control agent, and a polymerization initiator are added to the polymerizable monomer, and a homogenizer, a sand mill, a sand grinder, an ultrasonic disperser, etc. Various constituent materials are dissolved or dispersed in the polymerizable monomer. The polymerizable monomer in which these various constituent materials are dissolved or dispersed is dispersed in oil droplets having a desired size as a toner in an aqueous medium containing a dispersion stabilizer using a homomixer or a homogenizer. Thereafter, the stirring mechanism is transferred to a reaction apparatus which is a stirring blade described later, and the polymerization reaction is advanced by heating. After completion of the reaction, the dispersion stabilizer is removed, filtered, washed, and dried to prepare a toner.

  Further, as a method for producing the toner of the present invention, a method of preparing by associating or fusing resin particles in an aqueous medium can also be mentioned. The method is not particularly limited, and examples thereof include methods disclosed in JP-A-5-265252, JP-A-6-329947, and JP-A-9-15904. That is, a method of associating a plurality of fine particles composed of resin particles and colorants, etc., or particles composed of resin and colorant, in particular, after dispersing them in water using an emulsifier, the critical aggregation concentration The above flocculant is added for salting out, and at the same time, the formed polymer itself is heated and fused at a temperature higher than the glass transition temperature to gradually grow the particle size while forming fused particles. Then, a large amount of water is added to stop the particle size growth, and the shape is controlled by smoothing the particle surface while heating and stirring, and the particles are heated and dried in a fluidized state while containing water, whereby toner Can be formed. Here, an organic solvent that is infinitely soluble in water may be added simultaneously with the flocculant.

  Note that materials and manufacturing methods for producing a uniform toner such as a shape factor used in the present invention, a polymerization toner reaction device, and the like are described in detail in JP-A-2000-214629.

  A charging roller may be used in place of the charging brush shown in FIGS. FIG. 3 is a sectional view showing the configuration of the charging roller.

  As shown in FIG. 3, the charging roller 22R is composed of a core metal 22a and a rubber layer such as chloroprene rubber, urethane rubber, silicone rubber or the like, which is a conductive elastic member provided on the outer periphery thereof, or a sponge layer 22b thereof. Preferably, the outermost layer is configured by providing a protective layer 22c made of a releasable fluorine-based resin or silicone resin layer having a thickness of 0.01 to 1 μm.

  The charging roller is preferably brought into contact with the photoreceptor 21 with a pressure contact force of 10 to 100 g / cm. The rotation of the charging roller is preferably 1 to 8 times the peripheral speed of the photosensitive drum 21.

  Although the image forming apparatus is a contact charging type monochrome laser printer, the same effect can be obtained by using a non-contact type laser printer as a charging unit. The present invention can be similarly applied to a color laser printer and a copy. The exposure light source may also be a light source other than a laser, such as an LED light source.

  A magnetic brush charger may be used instead of the charging brush shown in FIGS. FIG. 4 is a diagram illustrating an example of a cross section of the magnetic brush charger.

In FIG. 4, 120 is a magnetic brush charger, 21 is a photosensitive drum, T charging unit, 120a is a charging sleeve, 121 is a magnet body 121, 123 is a scraper, and 124 is a stirring screw. The magnetic brush charger 120 is opposed to the rotating photosensitive drum 21 and serves as a magnetic particle carrier for charging that rotates in the same direction (counterclockwise) at a portion close to the photosensitive drum 21 (charging portion T). For example, a cylindrical charging sleeve 120a using an aluminum material or a stainless material, a magnet body 121 having N and S poles provided inside the charging sleeve 120a, and the magnet body 121 on the outer peripheral surface of the charging sleeve 120a. A magnetic brush composed of magnetic particles that are formed and charge the photosensitive drum 21, and the charging sleeve 120 a at the NN magnetic pole portion of the magnet body 121. A scraper 123 that scrapes the upper magnetic brush, and a stirring screw 124 that stirs the magnetic particles in the magnetic brush charger 120 or causes the used magnetic particles to overflow from the outlet 125 of the magnetic brush charger 120 and discharge the magnetic particles when supplying the magnetic particles. And a brushing restriction plate 126 of the magnetic brush. The charging sleeve 120 a is rotatable with respect to the magnet body 121, and is 0.1 to 1.0 times in the same direction (counterclockwise) as the movement direction of the photosensitive drum 21 at a position facing the photosensitive drum 21. It is preferably rotated at a peripheral speed. As the charging sleeve 120a, a conductive carrier capable of applying a charging bias voltage is used. In particular, the magnet body 121 having a plurality of magnetic poles inside the conductive charging sleeve 120a having a particle layer formed on the surface thereof. Those having a structure provided with are preferably used. In such a carrier, the magnetic particle layer formed on the surface of the conductive charging sleeve 120a moves up and down in a wave shape due to the relative rotation with the magnet body 121. Even if the magnetic particle layer on the surface of the charging sleeve 120a is somewhat uneven in thickness, the influence is sufficiently covered so as not to cause a problem due to the wavy undulations. The surface of the charging sleeve 120a preferably has an average surface roughness of 5.0 to 30 [mu] m for stable and uniform transfer of magnetic particles. If the surface is smooth, the surface cannot be sufficiently transported. Overcurrent flows from the part, and in any case, uneven charging tends to occur. Sand blasting is preferably used to achieve the above surface roughness. Further, the outer diameter of the charging sleeve 120a is preferably 5.0 to 20 mm. This ensures a contact area necessary for charging. If the contact area is larger than necessary, the charging current becomes excessive, and if it is small, charging unevenness is likely to occur. Further, when the diameter is small as described above, magnetic particles are likely to be scattered or adhere to the photosensitive drum 21 due to centrifugal force, so that the linear velocity of the charging sleeve 120a is almost the same as the moving velocity of the photosensitive drum 21 or more. It is also preferable that it is slow.

Further, the thickness of the magnetic particle layer formed on the charging sleeve 120a is preferably a thickness that is sufficiently scraped off by the regulating means to form a uniform layer. If there is too much magnetic particles on the surface of the charging sleeve 120a in the charging region, the magnetic particles will not vibrate sufficiently, causing photoconductor wear and charging unevenness and overcurrent easily flowing, and driving torque of the charging sleeve 120a. Has the disadvantage of becoming larger. On the other hand, if the amount of the magnetic particles on the charging sleeve 120a in the charged region is too small, an incomplete portion is formed in contact with the photosensitive drum 21 and the magnetic particles adhere to the photosensitive drum 21 and uneven charging occurs. become. Result of repeated experimentation, the preferred deposition amount of the magnetic particles in the charging area is 100 to 400 mg / cm ^2, particularly preferably has proven 200-300 mg / cm ^2. This adhesion amount is an average value in the charging region of the magnetic brush.

  The image forming method and the image forming apparatus of the present invention are generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also display, recording, and light printing using electrophotographic technology. It can also be widely applied to apparatuses such as plate making and facsimile.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means part by mass.

  A photoreceptor used for evaluation was produced as follows.

Preparation of photoreceptor 1 Intermediate layer 1
On the washed cylindrical aluminum substrate (surface roughness Rz: processed to 1.0 μm by cutting), the following intermediate layer coating solution is applied by a dip coating method to form an intermediate layer 1 having a dry film thickness of 5.0 μm. did.

  The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.

(Preparation of intermediate layer dispersion)
Binder resin: (Exemplary polyamide N-1) 1 part Brookite-type titanium oxide A1 (primary particle diameter 35 nm; surface treatment is treated with ethyltrimethoxysilane fluoride) 3.0 parts Isopropyl alcohol 10 parts Using a disperser, the mixture was dispersed in a batch system for 10 hours to prepare an intermediate layer dispersion.

Charge generation layer The following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.3 μm on the intermediate layer.

Y-form oxytitanyl phthalocyanine (X-ray diffraction spectrum by Cu-Kα characteristic X-ray, maximum peak angle is 27.3 at 2θ) 20 parts Polyvinyl butyral (# 6000-C, manufactured by Denki Kagaku Kogyo) 10 parts Acetic acid t -Butyl 700 parts 4-Methoxy-4-methyl-2-pentanone 300 parts Charge transport layer The following components were mixed and dissolved to prepare a charge transport layer coating solution. This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a dry film thickness of 24 μm.

Charge transport material (4-methoxy-4 ′-(4-methyl-α-phenylstyryl) triphenylamine) 75 parts Polycarbonate resin “Iupilon-Z300” (Mitsubishi Gas Chemical Co., Ltd.) 100 parts Antioxidant (Compound A below) ) 2 parts Tetrahydrofuran / toluene (volume ratio 7/3) 750 parts Preparation of photoconductors 2 to 14 Compositions such as surface roughness Rz of the aluminum substrate, particles of the intermediate layer, binder resin, and dry film thickness are as shown in Table 1. Photoconductors 2 to 15 were produced in the same manner as Photoconductor 1 except for the changes.

  * 1 in Table 1 is the shape of the titanium oxide particles confirmed by a scanning microscope.

In Table 1,
A1 is brookite type titanium oxide (100% brookite type, number average particle size 35 nm)
A2 is brookite-type titanium oxide (100% brookite-type, number average particle size 180 nm)
A3 is brookite type titanium oxide (52% brookite type, the rest is rutile type 32%, anatase type 16%, number average particle size 73 nm)
A4 is brookite-type titanium oxide (100% brookite-type, number average particle size 15 nm)
A5 is rutile titanium oxide (100% rutile type, number average particle size 35 nm)
In Table 1, surface treatment refers to the material used for the surface treatment applied to the surface of the titanium oxide pigment (however, silica / alumina indicates the material deposited on the surface of the anatase titanium oxide pigment).

  The heat of fusion and water absorption in Table 1 were measured as follows.

Measurement conditions of heat of fusion Measuring machine: Measured using Shimadzu Corporation “Shimadzu heat flow rate differential scanning calorimeter DSC-50”.

  Measurement conditions: The measurement sample is set in the above-mentioned measuring machine, measurement is started from room temperature (24 ° C.), the temperature is raised to 200 ° C. at 5 ° C./min, and then cooled to room temperature at 5 ° C./min. This is repeated twice, and the heat of fusion is calculated from the endothermic peak area due to melting during the second temperature increase.

Measurement condition of water absorption rate The sample to be measured is sufficiently dried at 70 to 80 ° C. for 3 to 4 hours, and its mass is accurately weighed. Next, the sample is put into ion-exchanged water maintained at 20 ° C., and after a certain period of time, the sample surface is pulled up and wiped off with a clean cloth, and the mass is measured. The above operation was repeated until the increase in mass was saturated, and the value obtained by dividing the increased mass (increase) of the resulting sample by the initial mass was taken as the water absorption rate.

  In Table 1, the ratio of the unit structure having 7 or more carbon atoms refers to the ratio (mol%) of the repeating unit structure having 7 or more carbon atoms between amide bonds in the repeating unit structure.

<< Evaluation 1 >>
The photoconductors 1 to 15 obtained as described above are basically EPSONLP-2400 having the structure shown in FIGS. 1 and 2 (Epson Co., Ltd. sales: A4 paper 16 sheets / min. Printer: contact charging with a charging brush) And a cleaner-less process), and durability tests were conducted at low temperature and low humidity (LL: 10 ° C, 20% RH) (however, dielectric breakdown was high temperature and high humidity (HH: 30 ° C, 80% RH). ) Also evaluated under conditions). Specifically, a total of 20,000 image images in which the character ratio, halftone image, solid white image, and solid black image with a pixel rate of 7% are divided into quarters are printed, and evaluated at the start and every 5000 images. did. Evaluation items and evaluation criteria are shown below. The evaluation results are shown in Table 2.

Exposure condition Exposure part potential target: Set to an exposure amount to be less than -50V.

Exposure beam: Image exposure with a dot density of 600 dpi (dpi is the number of dots per 2.54 cm) was performed. 780 nm semiconductor laser is used as the laser. Development conditions: Non-magnetic one-component developer (non-magnetic one-component developer containing a weight-average particle size of 6.3 μm, 0.3 μm hydrophobic titanium oxide and 15 nm hydrophobic silica external additive) Reversal development using component developer) Image density Measured using Macbeth RD-918. The relative reflection density was measured with the paper reflection density set to “0”. As the residual potential increases on multiple copies, the image density decreases.

A: Black solid image is higher than 1.2 (good)
○: Black solid image is 1.0 or more and 1.2 or less (no problem in practical use)
×: Black solid image is less than 1.0 (practical problem)
The fog density was measured by reflection density of a solid white image using RD-918 manufactured by Macbeth. The reflection density was evaluated by a relative density (the density of A4 paper not printed is 0.000).

A: Density is less than 0.010 (good)
○: Concentration is 0.010 or more and 0.020 or less (a level that causes no problem in practice)
X: Concentration is higher than 0.020 (a level causing a practical problem)
Black spots The periodicity coincided with the period of the photoconductor, and it was determined how many black spots and black streak-like image defects that can be seen per A4 size.

A: Frequency of image defects of 0.4 mm or more: All printed images are 5 / A4 or less (good)
○: Frequency of image defects of 0.4 mm or more: 1 or more of 6 / A4 or more and 10 / A4 or less (no problem in practical use)
X: Frequency of image defects of 0.4 mm or more: 11 or more A4 or more occurred (practical problem)
Dielectric breakdown: evaluated at low temperature and low humidity (LL: 10 ° C., 20% RH), high temperature and high humidity (30 ° C., 80% RH) ○: No dielectric breakdown of the photoreceptor due to charge leakage at LL or HH.

  X: Dielectric breakdown of the photoreceptor due to charge leakage occurred in LL or HH.

  From Table 2, the contact charging type image forming apparatus includes the photoconductor of the present invention, that is, the photoconductors 1 to 13 having the intermediate layer containing the brookite-type titanium oxide of the present invention. Alternatively, the occurrence of black spots is prevented, and the evaluation of image density and fog is good, and an electrophotographic image with good sharpness is obtained. In particular, the photoreceptors 1 to 3 and 7 to 13 in which the water content of the binder resin in the intermediate layer is 3% by mass or less have a large improvement effect. On the other hand, in the photoreceptors 14 and 15 using the rutile titanium oxide pigment outside the present invention, the image density is lowered and the image quality is deteriorated in the photoreceptor 14 having an intermediate layer thickness of 5 μm. In the photoreceptor 15 having a film thickness of 1 μm, dielectric breakdown and black spots increase, and image defects increase.

<< Evaluation 2 >>
The charging brush of the evaluation machine of Evaluation 1 was changed to a charging roller, and the photoreceptors 1 to 15 were evaluated. The evaluation results of the respective photoreceptors were almost the same as the evaluation 1.

Production of Photoreceptor 16 Photoreceptor 16 was produced in the same manner as Photoreceptor 1 except that the following charge injection layer was used on the charge transport layer in the production of Photoreceptor 1.

Charge injection layer The surface was treated with methyl hydrogen silicone oil (trade name KF99, manufactured by Shin-Etsu Silicone Co., Ltd.). Surface with 72 parts of antimony-doped tin oxide fine particles having an average particle size of 0.02 μm (trade name: T-1, manufactured by Mitsubishi Materials Corporation) and a fluorine-modified silane coupling agent (trade name: LS1090, manufactured by Shin-Etsu Silicone Co., Ltd.) Processed. 48 parts of antimony-doped tin oxide fine particles (same as above) having an average particle size of 0.02 μm, sand mill together with 43.2 parts of acrylic monomer (trade name TMP3A-3, manufactured by Osaka Organic Chemical Co., Ltd.) having the following chemical structure and 210 parts of ethanol For 90 hours.

  To this liquid, 200 parts of the following PTFE particle dispersion was mixed and dispersed in a sand mill for 2 hours. Further, 6.48 parts of 2,4-diethylthioxanthone as a photopolymerization initiator and 4,4′-bis as an initiation assistant. 2.16 parts of (diethylamino) benzophenone was added and dissolved to prepare a charge injection layer coating solution.

The charge injection layer coating solution is applied onto the charge transport layer of the photoreceptor 1 with a circular slide hopper type coater, and irradiated with ultraviolet rays at a light intensity of 1.20 × 10 ⁻⁵ W / m ² for 30 seconds with a metal halide lamp. Then, photocuring was carried out, followed by drying with hot air at 120 ° C. for 1 hour and 40 minutes to form a charge injection layer (surface layer) having a film thickness of 6 μm.

<Preparation of polytetrafluoroethylene resin particle (PTFE particle) dispersion>
Using PTFE particles (PTFE particles having an average primary particle size of 0.12 μm and PTFE particles having a crystallinity of 91.3 and heat-treated at 250 ° C. for 40 minutes to a crystallinity of 82.2), the following PTFE particles were used. A dispersion was prepared.

PTFE particles (PTFE1: average primary particle size 0.12 μm, crystallinity 82.2)
200 parts Toluene 600 parts Fluorine-based comb-type graft polymer (trade name GF300, manufactured by Toa Gosei Chemical Co., Ltd.) 15 parts is mixed, and then dispersed in a sand grinder (made by Amex Co., Ltd.) using glass beads. A particle dispersion was prepared.

<< Evaluation 3 >>
Under the evaluation conditions of Evaluation 1, the charger is changed from the charging brush to the magnetic brush shown in FIG. 4, a DC bias of −600 V is applied to the magnetic brush, and an AC bias of Vpp = 650 v and Vf = 1000 Hz is superimposed. Thus, charge was injected into the photoconductor, a surface potential of −600 V was applied to the photoconductor surface voltage, and the same evaluation as that of the photoconductor 1 was performed.

  The evaluation results of the photoreceptor 16 are shown in Table 3.

  From Table 3, the photosensitive member 16 also prevents the occurrence of dielectric breakdown or black spots, and also has good evaluation of image density and fog, and has obtained an electrophotographic image with good sharpness.

1 is a schematic cross-sectional view of an image forming apparatus using a contact charging system according to the present invention. 2 is a schematic cross-sectional view of a photosensitive cartridge that is detachable from an image forming apparatus. FIG. It is sectional drawing which showed the structure of the charging roller. It is a figure which shows an example of the cross section of a magnetic brush charger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Photoconductor cartridge 3 Developer cartridge 4 Exposure apparatus 5 Paper feeder 6 Transfer roller 7 Fixing device 8 Paper discharge tray 21 Photoconductor 22 Charging brush 23, 27 Power supply connection member 24 Pre-charge film 25, 26 Charging Element

Claims (12)

An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an organic photoreceptor for use in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. An organic photoreceptor having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains a binder resin and brookite-type titanium oxide. 2. The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide has a number average primary particle size of 1 to 600 nm. The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide is a plate-like particle. The organophotoreceptor according to claim 3, wherein the plate-like particles have a plate surface area of 1 to 10,000 nm ² and a plate thickness of 0.5 to 100 nm. The organophotoreceptor according to claim 1, wherein the brookite-type titanium oxide is subjected to a surface treatment. An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an organic photoreceptor for use in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. An organic photoreceptor having an intermediate layer and a photosensitive layer on a conductive substrate, wherein the intermediate layer contains a binder resin and plate-like titanium oxide. The organophotoreceptor according to claim 6, wherein the plate-like titanium oxide is subjected to a surface treatment. The organic photoreceptor according to any one of claims 1 to 7, wherein the binder resin of the intermediate layer is a resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less. The organic photosensitive resin according to claim 8, wherein the resin having a heat of fusion of 0 to 40 J / g and a water absorption of 5% by mass or less is a polyamide having a repeating unit structure represented by the following general formula (1). body.

(In General Formula (1), Y ₁ is a group containing a divalent alkyl-substituted cycloalkane, Z ₁ is a methylene group, m is a natural number of 1 to 3, and n is a natural number of 3 to 20.) An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In an image forming apparatus that includes a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image, the organic photoreceptor An image forming apparatus comprising an intermediate layer and a photosensitive layer on a conductive support, wherein the intermediate layer contains a binder resin and brookite-type titanium oxide. An image forming method comprising forming an electrophotographic image using the image forming apparatus according to claim 10. An organic photosensitive member, a charging means for charging by bringing a charging member into contact with the organic photosensitive member, a latent image forming means for forming an electrostatic latent image on the organic photosensitive member, and the electrostatic latent image developed with toner. In a process cartridge used in an image forming apparatus that has a developing unit that forms an image and forms a toner image on the organic photoreceptor, and a transfer unit that transfers the toner image to a transfer material, and repeatedly forms an electrophotographic image. 10. The image forming apparatus main body, wherein the organic photoreceptor according to claim 1 and at least one of a charging unit, a latent image forming unit, a developing unit, a transfer unit, and a charge eliminating unit are integrally supported. A process cartridge which can be detachably attached to the cartridge.

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