JP7424905B2 - Coating liquid for electrophotographic photoreceptor undercoat layer and its uses - Google Patents

Description

The present invention relates to a coating liquid for electrophotographic photoreceptor undercoat layer (hereinafter also referred to as "coating liquid for undercoat layer") and its uses. More specifically, the present invention relates to an undercoat layer coating liquid, an electrophotographic photoreceptor (hereinafter also referred to as "photoreceptor") having an undercoat layer formed using the same, and an image forming apparatus equipped with the same.

In digital image formation, which has become mainstream in recent years, a laser, particularly a semiconductor laser or an LED, is used as a light source for writing image information converted into a digital electric signal as an electrostatic latent image on a photoreceptor. However, forming a latent image using a laser beam is known to have a unique image problem of generation of interference fringes due to reflection on the substrate surface.
Further, in digital writing, the exposure beam diameter is small and the writing speed is slow, so a combination with reversal development is mainly used as a developing method for the exposed portion. However, in image formation using reversal development, a unique phenomenon occurs in which toner adheres to areas where images should originally be formed as white background areas, causing fog, or black spots due to local defects in the photoreceptor. Image problems are known.

In order to solve these problems, specifically, in order to ensure adhesion between the conductive support and the photosensitive layer and to improve the carrier injection properties of the photosensitive layer, an undercoat layer ("intermediate layer") is added to the photoreceptor. ) has been developed.
For example, a photoreceptor is known that has a structure in which an undercoat layer in which metal oxide particles such as titanium oxide particles are dispersed in a resin is provided between a conductive support and a photoreceptor layer. Also known is a technique that uses metal oxide particles that have been surface-treated to improve dispersibility.
Specifically, JP-A-59-093453 (Patent Document 1) discloses a technique using titanium oxide fine particles coated with alumina, etc., and JP-A-04-172362 (Patent Document 2) discloses a technique using titanium oxide fine particles coated with alumina etc. A technique using metal oxide particles surface-treated with a coupling agent has been disclosed.
Furthermore, Japanese Patent Application Laid-Open No. 03-150572 (Patent Document 3) states that when the undercoat layer contains moisture, it has the same effect as moisture adhering to the aluminum surface constituting the conductive support. It is stated that if chlorine ions are present even at a few ppm, the aluminum oxide film undergoes local destruction and pits (pitting corrosion) occur.

Japanese Unexamined Patent Publication No. 59-093453 Japanese Patent Application Publication No. 04-172362 Japanese Patent Application Publication No. 03-150572

The coating liquid for the undercoat layer is a dispersion of pigment, but the viscosity increases during dispersion, which may inhibit the progress of dispersion, or cause local fluctuations in solid content due to sedimentation or an increase in particle size due to aggregation. However, there were problems such as the thickness of the undercoat layer becoming non-uniform, resulting in uneven density and increased image defects on the coated surface and images. Such density unevenness and image defects can become fatal defects in photoreceptors when improving the image quality of printers and copying machines.
Furthermore, there is a problem that the life of the dispersion as a paint is shortened due to sedimentation and aggregation of the dispersed pigment particles, and in order to solve these problems, further stabilization of the dispersion state of the dispersion is required. Although various techniques have been proposed in the above-mentioned prior art, they have not been sufficient to solve the above-mentioned problems.

Therefore, the present invention provides an undercoat that prevents viscosity increase during dispersion, has excellent dispersibility and stability over time, has good applicability to the surface of a conductive support, and can form a uniform undercoat layer. It is an object of the present invention to provide a layer coating liquid, a photoreceptor having an undercoat layer formed using the same, and having good image characteristics with little change in electrical characteristics due to repeated use, and an image forming apparatus equipped with the same. Take it as a challenge.

As a result of extensive research to solve the above problems, the present inventors found that a mixed solvent containing a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and water and a water-soluble organic solvent, Since the metal oxide fine particles are dispersed in a mixed solvent, it has good applicability to the surface of the conductive support and can form a uniform undercoat layer, and is used to form the undercoat layer. The inventors have discovered that by doing so, it is possible to obtain a photoreceptor with good image characteristics and less change in electrical characteristics due to repeated use, and an image forming apparatus equipped with the same, and have completed the present invention.
In addition, the present inventors have found that by adding water to the undercoat layer coating solution, the coating properties and dispersion stability are improved, which surprisingly solves the problem of corrosion of aluminum substrates as described in Patent Document 3. It has been found that the photoreceptor can maintain excellent characteristics without causing any problems.

Thus, according to the present invention, a mixed solvent containing a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and water and a water-soluble organic solvent is included, and the metal oxide fine particles are contained in the mixed solvent. A coating liquid for an electrophotographic photoreceptor undercoat layer is provided, which is characterized in that the present invention is dispersed.

Further, according to the present invention, at least an undercoat layer and a photosensitive layer are sequentially laminated on a conductive support, and the undercoat layer is formed using the above-mentioned coating liquid for an electrophotographic photoreceptor undercoat layer. Provided is an electrophotographic photoreceptor characterized by a layer formed thereon.

Further, according to the present invention, the above electrophotographic photoreceptor, a charging means for charging the electrophotographic photoreceptor, and an exposure means for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image. , a developing device that develops the electrostatic latent image formed by exposure to form a toner image, a transfer device that transfers the toner image formed by development onto a recording medium, and a transfer device that transfers the toner image formed by the development onto a recording medium. A fixing means for fixing to form an image on the recording medium, a cleaning means for removing and collecting toner remaining on the electrophotographic photoreceptor, and a static eliminating means for removing surface charges remaining on the electrophotographic photoreceptor. An image forming apparatus is provided which is characterized by at least the following.

According to the present invention, an undercoat that prevents viscosity increase during dispersion, has excellent dispersibility and stability over time, has good applicability to the surface of a conductive support, and can form a uniform undercoat layer. It is an object of the present invention to provide a layer coating liquid, a photoreceptor having an undercoat layer formed using the same, and having good image characteristics with little change in electrical characteristics due to repeated use, and an image forming apparatus equipped with the same. can.

The undercoat layer coating liquid of the present invention exhibits the above-mentioned effects more effectively when any one of the following conditions (1) to (4) is satisfied.
(1) The proportion of water in the mixed solvent is 2 to 10% by mass based on the metal oxide fine particles.
(2) The blending ratio of metal oxide fine particles and binder resin is 75/25 to 90/10 in mass ratio.
(3) The binder resin is an organic solvent-soluble polyamide resin.
(4) The metal oxide fine particles are titanium oxide or zinc oxide fine particles.
(5) The water-soluble organic solvent of the mixed solvent is methanol, 1,3-dioxolane, or a mixed solvent thereof.

1 is a schematic cross-sectional view showing the configuration of essential parts of a photoreceptor (photoreceptor 1) of the present invention. 1 is a schematic cross-sectional view showing the configuration of main parts of a photoreceptor (photoreceptor 2) of the present invention. 1 is a schematic cross-sectional view showing the configuration of essential parts of a photoreceptor (photoreceptor 3) of the present invention. 1 is a schematic cross-sectional view showing the configuration of main parts of a photoreceptor (photoreceptor 4) of the present invention. FIG. 1 is a schematic side view showing the configuration of main parts of an image forming apparatus of the present invention. FIG. 3 is a diagram showing the relationship between the blending ratio of water in the undercoat layer coating solution of the present invention and the viscosity after dispersion during preparation.

(1) Coating liquid for undercoat layer The coating liquid for undercoat layer of the present invention contains a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and a mixed solvent containing water and a water-soluble organic solvent. , characterized in that the metal oxide fine particles are dispersed in the mixed solvent.
That is, the characteristics of the undercoat layer coating liquid of the present invention are that it contains metal oxide fine particles whose surface has not been treated with an organic compound, and that it contains water.

When dispersing metal oxide fine particles in an organic solvent, as the dispersion progresses, the particles are crushed and pulverized, reducing the particle size, increasing the surface area, and increasing the interaction between particles, which increases the viscosity and slows down the dispersion. Progress may be inhibited, and local solids content fluctuations and flocculation may occur due to sedimentation.
Interactions between particles are generally proportional to the Hamaker constant. The value of the Hamaker constant changes depending on the medium in which the particles are present; in the case of metal oxide fine particles such as titanium oxide or zinc oxide, it is low in water and high in organic solvents with a low dielectric constant. Therefore, when water is added to metal oxide fine particles dispersed in an organic solvent, the effect of reducing interparticle interactions is obtained compared to when using only an organic solvent, and as the dispersion progresses, the viscosity increases and the occurrence of aggregation is prevented. It is thought that this will be suppressed.
First, a coating liquid for an undercoat layer will be explained, and then a photoreceptor having an undercoat layer formed using the coating liquid and an image forming apparatus equipped with the photoreceptor will be explained.

<Metal oxide fine particles>
The metal oxide fine particles are not surface-treated with an organic compound.
"Not surface-treated with an organic compound" means, for example, that the metal oxide fine particles are not 100% coated (surface-treated) with an organic compound such as methylhydrogenpolysiloxane described in the comparative example described below, i.e. This means that the metal oxide fine particles have not been subjected to hydrophobization treatment.
On the other hand, as described later, the metal oxide fine particles may be coated with a metal oxide different from the metal oxide constituting the fine particles.

The metal oxide fine particles are preferably titanium oxide or zinc oxide fine particles, and those that are not surface-treated with an organic compound such as a higher fatty acid or silicone are used.
For inorganic particles whose surface has been treated with an organic compound, the surface treatment agent released during the dispersion treatment to prepare the coating solution for the undercoat layer and the unreacted surface treatment agent may be used repeatedly in the high temperature and high humidity conditions of the photoreceptor. may have an adverse effect on electrical characteristics.
There are three types of crystal forms of titanium oxide: anatase type, rutile type, and brookite type, and any of these types may be used, or a mixture thereof may be used.

The volume resistance value of the metal oxide fine particles is in the range of 10 ⁵ Ω・cm ^or more and 10 ^{10 Ω・cm or less, as the volume resistance value of the green compact (also referred to as "powder resistance value") at a press pressure of 100} kg/cm 2 It is desirable that the resistance be high.
If the powder resistance value of the metal oxide fine particles is less than 10 ⁵ Ω·cm, the resistance value as an undercoat layer may decrease and it may not function as a charge blocking layer. For example, when a conductive treatment such as an antimony-doped tin oxide conductive layer is applied, the powder resistance value is extremely low at 10 ⁰ to 10 ¹ Ω・cm, and an undercoat layer using this has a photoreceptor characteristic. It cannot be used because the charging properties of the battery deteriorate. On the other hand, if the powder resistance value of the inorganic particles exceeds 10 ¹⁰ Ω・cm and becomes equal to or higher than the volume resistance value of the binder resin, the resistance value as an undercoat layer will be too high and the carriers generated during light irradiation will transport may be inhibited and the residual potential may increase.

In addition, metal oxide fine particles are metal oxides whose surfaces are different from the metal oxides that make up the metal oxide fine particles, such as alumina (aluminum oxide) or silica (silicon oxide) (also called "inorganic compounds"). It is preferable that the surface be coated (surface treated) with. This surface treatment can be expected to have an effect of preventing black spots on the photoreceptor and an effect of improving the dispersibility of the coating liquid for the undercoat layer.
As a method for surface treatment of metal oxide fine particles with an inorganic compound, for example, an aqueous slurry in which inorganic particles are dispersed in water at a concentration of 50 to 350 g/L is prepared, and water-soluble silicate or water-soluble aluminum is added to the slurry. What is necessary is to add an inorganic compound such as a chemical compound, neutralize it by adding an alkali or an acid, precipitate silica or alumina on the surface of the inorganic particles, and then filter, wash, and dry the particles.
When sodium silicate is used as a water-soluble silicate, it can be neutralized with acids such as sulfuric acid, nitric acid, and hydrochloric acid, and when aluminum sulfate is used as a water-soluble aluminum compound, it can be neutralized with hydroxide. It can be neutralized with alkalis such as sodium or potassium hydroxide.

The average primary particle diameter of the metal oxide fine particles is preferably 5.0 to 100 nm, more preferably 10 to 70 nm. The average primary particle diameter is determined by enlarging metal oxide fine particles by 10,000 times using a TEM (transmission electron microscope), observing 100 particles at random as primary particles, and determining the average diameter in the Feret direction by image analysis. means.
If the average primary particle diameter is less than 5.0 nm, it will be difficult to uniformly disperse the particles in the undercoat layer, tend to form aggregated particles, and a uniform coating film of the undercoat layer may not be formed. On the other hand, if the average primary particle diameter exceeds 100 nm, large irregularities are likely to be formed on the surface of the undercoat layer, and dielectric breakdown and black spots are likely to occur through these large irregularities. Inorganic particles tend to precipitate and aggregates tend to occur, which may impede the formation of a coating film of the undercoat layer.

<Binder resin>
Examples of the binder resin include acetal resin, polyamide resin, polyurethane resin, polyester resin, acrylic resin, epoxy resin, phenol resin, melanin resin, and urethane resin. The binder resin must not dissolve or swell in the solvent used to form the photoreceptor layer on the undercoat layer, have excellent adhesion to the conductive support, and have flexibility. Among the above binder resins, organic solvent-soluble polyamide resins are preferred, and alcohol-soluble nylon resins are particularly preferred.
Alcohol-soluble nylon resins include, for example, homopolymerized or copolymerized nylons such as 6-nylon, 66-nylon, 610-nylon, 11-nylon and 12-nylon, and N-alkoxymethyl-modified nylons. Examples include physically denatured types.

The mixing ratio of the metal oxide fine particles and the binder resin is preferably 75/25 to 95/5 in terms of mass ratio.
If the blending ratio is less than 75/25 in terms of mass ratio, the sensitivity of the photoreceptor may decrease. On the other hand, if the blending ratio exceeds 95/5 in terms of mass ratio, the binder resin cannot be sufficiently adsorbed to the particles during dispersion, which increases the interaction between particles, making it easier for metal oxide fine particles to aggregate and settle, resulting in stable storage. Sexuality may worsen. The preferred blending ratio is 75/25 to 90/10, more preferably 70/30 to 90/10 in terms of mass ratio.

<Mixed solvent>
The mixed solvent contains water and an organic solvent.
Examples of the organic solvent in the mixed solvent include lower alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol, and isobutanol, and ketones such as acetone, cyclohexanone, and 2-butanone. , tetrahydrofuran, dioxane, 1,3-dioxolane, ethylene glycol, diethyl ether and other ethers, and halogenated hydrocarbons such as methylene chloride and ethylene chloride. Appropriate solvents are selected from these solvents based on the solubility of the binder resin, the surface smoothness of the undercoat layer, etc., and one type can be used alone or two or more types can be used in combination.
Among these organic solvents, methanol, 1,3-dioxolane, and mixed solvents thereof are preferred from the viewpoint of dispersibility and storage stability. Specifically, methanol/1, as used in the examples, , 3-dioxolane=3/2 (mass ratio).

The proportion of water in the mixed solvent is preferably 1 to 12% by mass based on the metal oxide fine particles.
If the blending ratio of water is less than 1% by mass based on the metal oxide fine particles, the effect of suppressing the increase in viscosity is not sufficient and aggregation occurs, which may cause problems in storage stability. On the other hand, if the blending ratio of water exceeds 12% by mass based on the metal oxide fine particles, the solubility of the binder resin decreases, which impairs the storage stability of the coating solution, and also impairs the electrical properties and repeated electrical properties of the photoreceptor. may worsen. The preferred mixing ratio of water is 1 to 10% by mass, more preferably 2 to 10% by mass, based on the metal oxide fine particles.

<Method for producing coating liquid for undercoat layer>
The coating solution for an undercoat layer of the present invention is produced by mixing a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and a mixed solvent by a known method, and dispersing the metal oxide fine particles in the mixed solvent. It can be prepared.
In order to disperse the metal oxide fine particles in the mixed solvent, known devices such as a ball mill, sand mill, attritor, vibration mill, ultrasonic disperser, and paint shaker may be used.

(2) Photoreceptor The photoreceptor of the present invention is formed by sequentially laminating at least an undercoat layer and a photosensitive layer on a conductive support, and the undercoat layer is formed using the undercoat layer coating liquid of the present invention. It is characterized by being a formed layer.
The photoreceptor of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

<Photoreceptor 1: Embodiment 1>
FIG. 1 is a schematic cross-sectional view showing the configuration of essential parts of a photoreceptor (photoreceptor 1) of the invention.
The photoreceptor 1 is provided with an undercoat layer 18 containing metal oxide fine particles 19 formed using the undercoat layer coating solution of the present invention on a conductive support 11, and a charge-generating layer 18 formed on the conductive support 11. A photosensitive layer 14 having a laminated structure is provided in which a charge generation layer 15 containing a substance 12 and a charge transport layer 16 containing a charge transport substance 13 and a binder resin 17 for binding them are laminated in this order. It is a laminated type photoreceptor.
Each configuration will be explained below.

<Conductive support 11>
The conductive support has a function as an electrode of the photoreceptor and a support member, and its constituent material is not particularly limited as long as it is a material used in the technical field.
Specifically, metal materials such as aluminum, aluminum alloy, copper, zinc, stainless steel, and titanium, as well as metal foil lamination, metal vapor deposition treatment, or conductive compounds such as conductive polymers, tin oxide, and indium oxide, are used. Examples include polymeric materials such as polyethylene terephthalate, nylon and polystyrene, hard paper, and glass on which layers have been deposited or painted. Among these, aluminum is preferred from the viewpoint of ease of processing, and aluminum alloys such as JIS 3003 series, JIS 5000 series, and JIS 6000 series are particularly preferred.
The shape of the conductive support is not limited to a cylindrical shape (drum shape) as shown in FIG. 5, but may be a sheet shape, a cylindrical shape, an endless belt shape, or the like.
In addition, if necessary, the surface of the conductive support may be anodized, treated with chemicals or hot water, or colored to prevent interference fringes caused by laser light within a range that does not affect image quality. The surface may be subjected to a treatment or a diffused reflection treatment such as roughening the surface.

<Undercoat layer (also referred to as “intermediate layer”) 18>

Generally, the undercoat layer coats and evens out the irregularities on the surface of the conductive support, improves the film-forming properties of the photosensitive layer, here the charge generation layer, and suppresses the peeling of the photosensitive layer from the conductive support. Improves adhesion between the conductive support and the photosensitive layer. Specifically, injection of charge from the conductive support into the photosensitive layer is prevented, thereby preventing deterioration in the chargeability of the photosensitive layer and preventing image fogging (so-called black spots).
In the present invention, the undercoat layer includes a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and a mixed solvent containing water and a water-soluble organic solvent, and the metal oxide fine particles are contained in the mixed solvent. Since the layer is formed using a coating liquid for an undercoat layer dispersed in the undercoat layer, a photoreceptor with good image characteristics, with little change in electrical characteristics due to repeated use, can be provided.

The undercoat layer is formed using the undercoat layer coating liquid described in (1) above.
The method for applying the coating liquid for the undercoat layer may be appropriately selected by taking into consideration the physical properties and productivity of the coating liquid, and examples thereof include spraying, bar coating, roll coating, blade coating, etc. Examples include the ring method and the dip coating method.
Among these, the dip coating method is a method in which a layer is formed on the surface of the substrate by immersing the substrate in a coating tank filled with a coating solution and then pulling it up at a constant speed or a speed that changes sequentially. Since it is simple and excellent in terms of productivity and cost, it can be suitably used for manufacturing photoreceptors. The apparatus used for the dip coating method may be provided with a coating liquid dispersion device, typified by an ultrasonic generator, in order to stabilize the dispersibility of the coating liquid.
During the manufacturing process of the undercoat layer, the viscosity of the undercoat layer coating solution may increase. In this case, water should be added to the undercoat layer coating solution so that the mixing ratio falls within the above range. It's okay.

The solvent in the coating film may be removed by natural drying, but the solvent in the coating film may be forcibly removed by heating.
The temperature in such a drying step is not particularly limited as long as the used solvent can be removed, but approximately 50 to 140°C is appropriate, and approximately 80 to 130°C is particularly preferred.
If the drying temperature is less than 50° C., the drying time may become long, and the solvent may not evaporate sufficiently and may remain in the photoreceptor layer. Further, if the drying temperature exceeds about 140° C., the electrical characteristics of the photoreceptor during repeated use may deteriorate, and the resulting images may deteriorate.
Such temperature conditions are common not only to the undercoat layer but also to layer formation such as a photosensitive layer, which will be described later, and other treatments.

The thickness of the undercoat layer is not particularly limited, but is preferably 0.5 to 30 μm, more preferably 1 to 20 μm.
If the thickness of the undercoat layer is less than 0.5 μm, the effect of preventing black spots under high temperature and high humidity may not be sufficiently achieved. On the other hand, if the thickness of the undercoat layer exceeds 30 μm, the change in sensitivity during continuous printing at low temperature and low humidity may become large, and thus the change in image density may become large.

<Charge generation layer 15>
The charge generation layer has the function of generating charges by absorbing light emitted from a semiconductor laser beam in an image forming device, etc., and contains a charge generation substance as a main component, and contains binder resin and additives as necessary. Contains.

As the charge generating substance, compounds used in the field can be used, and specifically, azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments; indigo pigments such as indigo and thioindigo; perylene imide and perylene. Perylene pigments such as acid anhydrides; polycyclic quinone pigments such as anthraquinone and pyrenequinone; phthalocyanine pigments such as metal phthalocyanines and metal-free phthalocyanines such as titanium phthalocyanine; squarylium pigments, pyrylium salts, thiopyrylium salts, triphenylmethane pigments and inorganic photoconductive materials such as selenium and amorphous silicon, and those having sensitivity in the exposure wavelength range can be appropriately selected and used. These charge generating substances can be used alone or in combination of two or more.
Among these charge generating substances, the following general formula (A):

(In the formula, X ¹ , X ² , X ^{3 and} is an integer)
It is preferable to use a titanyl phthalocyanine represented by:
Titanyl phthalocyanine is a charge-generating substance that has high charge generation efficiency and charge injection efficiency in the emission wavelength range (near infrared light) of laser light and LED light that are currently commonly used, and it has the ability to absorb light. This makes it possible to generate a large amount of charge and to efficiently inject the generated charge into the charge transport material 13 without accumulating it inside.

The titanium phthalocyanine compound represented by general formula (A) can be produced by known production methods such as those described in Phthalocyanine Compounds by Moser, Frank H. and Arthur L. Thomas, Reinhold Publishing Corp., New York, 1963. can do.
For example, in the case of unsubstituted titanium phthalocyanine in which r, s, y, and z are 0 among the titanium phthalocyanine compounds represented by the general formula (A), phthalonitrile and titanium tetrachloride are melted by heating or Dichlorotitanium phthalocyanine is synthesized by a heating reaction in a suitable solvent such as α-chloronaphthalene, and then hydrolyzed with a base or water.
Titanium phthalocyanine can also be produced by heating isoindoline and a titanium tetraalkoxide such as tetrabutoxytitanium in a suitable solvent such as N-methylpyrrolidone.

The charge generation layer can be formed by vacuum evaporating a charge generation substance onto a conductive support, or by dispersing a charge generation substance in a solvent to form a charge generation layer coating solution on a conductive support. There are various methods of coating. Among these methods, there is a method in which a charge generating substance is dispersed in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method, and a coating liquid for a charge generating layer is applied onto a conductive support. preferable. This method will be explained below.

The binder resin is not particularly limited, and any resin known in the field can be used, such as polyester resin, polystyrene resin, polyurethane resin, phenol resin, alkyd resin, melamine resin, epoxy resin, silicone resin, and acrylic resin. , methacrylic resins, polycarbonate resins, polyarylate resins, phenoxy resins, polyvinyl butyral resins, and polyvinyl formal resins, and copolymer resins containing two or more of the repeating units constituting these resins. Can be done.
Examples of the copolymer resin include insulating resins such as vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, and acrylonitrile-styrene copolymer resin. These resins can be used alone or in combination of two or more.

Examples of solvents include halogenated hydrocarbons such as dichloromethane and dichloroethane, ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran (THF) and dioxane, 1,2 - Alkyl ethers of ethylene glycol such as dimethoxyethane, aromatic hydrocarbons such as benzene, toluene and xylene, or aprotic polar solvents such as N,N-dimethylformamide and N,N-dimethylacetamide. . These solvents can be used alone or in combination of two or more.

The blending ratio of the charge generating substance and the binder resin is preferably such that the proportion of the charge generating substance is in the range of 10 to 99% by mass.
If the proportion of the charge generating substance is less than 10% by mass, sensitivity may decrease. On the other hand, if the proportion of the charge-generating substance exceeds 99% by mass, not only the film strength of the charge-generating layer decreases, but also the dispersibility of the charge-generating substance decreases and coarse particles increase, which must be erased by exposure to light. The surface charge on other parts may decrease, resulting in image defects, especially image fog called black spots, where toner adheres to the white background and forms minute black dots.

Before dispersing the charge generating material in the binder resin solution, the charge generating material may be pulverized using a pulverizer. Examples of the pulverizer used in the pulverization process include a ball mill, a sand mill, an attritor, a vibration mill, and an ultrasonic dispersion machine.
Examples of the dispersing machine used to disperse the charge generating substance into the binder resin solution include a paint shaker, a ball mill, and a sand mill. As the dispersion conditions at this time, appropriate conditions may be selected so as to prevent contamination of impurities due to wear of the containers used and the members constituting the dispersion machine.
The method for applying the coating liquid for the charge generation layer includes the same method as the method for applying the coating liquid for the undercoat layer, and a dip coating method is particularly preferred.

The thickness of the charge generation layer is not particularly limited, but is preferably 0.05 to 5 μm, more preferably 0.1 to 1 μm.
If the thickness of the charge generation layer is less than 0.05 μm, the efficiency of light absorption may decrease and the sensitivity of the photoreceptor may decrease. On the other hand, if the thickness of the charge generation layer exceeds 5 μm, charge movement within the charge generation layer becomes a rate-determining step in the process of erasing charges on the surface of the photosensitive layer, and the sensitivity of the photoreceptor may decrease.

<Charge transport layer 16>
The charge transport layer has a function of accepting charges generated by the charge generating substance and transporting them to the surface of the photoreceptor, and contains a charge transport substance, a binder resin, and, if necessary, additives.

As the charge transport material 13, compounds used in the field can be used.
Specifically, carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, Ring aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives , enamine derivatives, benzidine derivatives, polymers having groups derived from these compounds in the main chain or side chain (poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly -9-vinylanthracene, etc.), polysilane, etc. These charge transport materials can be used alone or in combination of two or more.
Among these, stilbene derivatives, butadiene derivatives, enamine derivatives, and combinations of multiple types of these compounds are preferred.

Among these various charge transport substances, particularly preferred compounds in terms of electrical properties, durability and chemical stability are illustrated below.

The charge transport layer is formed by dispersing a charge transport substance in a binder resin solution obtained by mixing a binder resin in a solvent using a conventionally known method, and applying a charge transport layer coating solution onto the charge generation layer. A coating method is preferred. This method will be explained below.

The binder resin is not particularly limited, and any resin known in the art can be used, such as vinyl polymer resins such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymer resins thereof, and polycarbonate, Resins such as polyester, polyester carbonate, polysulfone, polyphenoxy, epoxy resin, silicone resin, polyarylate, polyamide, polyether, polyurethane, polyacrylamide, phenolic resin, thermosetting resins that are partially crosslinked of these resins, etc. Can be mentioned. These binder resins can be used alone or in combination of two or more.
Among these, polystyrene, polycarbonate, polyarylate, and polyphenylene oxide are preferred because they have a volume resistivity of 10 ¹³ Ω or more, have excellent electrical insulation, and are also excellent in film formability, potential characteristics, etc., and polycarbonate is particularly preferred. .

The ratio A/B of the charge transport material (A) and the binder resin (B) is preferably 10/12 to 10/30.
If the ratio A/B is less than 10/30 and the ratio of binder resin is high, when forming a charge transport layer by dip coating, the viscosity of the coating solution will increase, resulting in a decrease in coating speed and significantly poor productivity. Become. Furthermore, if the amount of solvent in the coating solution is increased in order to suppress an increase in the viscosity of the coating solution, a brushing phenomenon may occur and the formed charge transport layer may become cloudy. On the other hand, when the ratio A/B exceeds 10/12 and the ratio of the binder resin becomes low, the printing durability becomes lower than when the ratio of the binder resin is high, and the amount of wear of the photosensitive layer may increase.

The charge transport layer may contain additives such as a plasticizer or a leveling agent, if necessary, in order to improve film formability, flexibility, and surface smoothness.
Examples of the plasticizer include dibasic acid esters such as phthalate esters, fatty acid esters, phosphate esters, chlorinated paraffins, and epoxy type plasticizers.
Examples of the leveling agent include silicone leveling agents.
Further, the charge transport layer may contain fine particles of an inorganic compound or an organic compound in order to enhance mechanical strength and improve electrical properties.

Solvents include aromatic hydrocarbons such as benzene, toluene, xylene and monochlorobenzene, halogenated hydrocarbons such as dichloromethane and dichloroethane, ethers such as THF, dioxane and dimethoxymethyl ether, and N,N-dimethylformamide. Examples include aprotic polar solvents. Further, if necessary, a solvent such as alcohol, acetonitrile or methyl ethyl ketone may be further added. Among these solvents, non-halogen organic solvents are preferably used in consideration of the global environment. These solvents can be used alone or in combination of two or more.

The charge transport layer can be formed, for example, by dissolving or dispersing the charge transport material 13 and the binder resin 17, as well as the above-mentioned additives if necessary, in a suitable solvent, as in the case of forming the charge generation layer 15 described above. A coating solution for the charge transport layer is prepared by using the method, and this coating solution is applied onto the charge generation layer 15 by a spray method, a bar coating method, a roll coating method, a blade method, a ring method, a dip coating method, or the like. Ru. Among these coating methods, the dip coating method is particularly superior in various respects as described above, and is therefore often used for forming charge transport layers.

The thickness of the charge transport layer is not particularly limited, but is preferably 5 to 50 μm, more preferably 10 to 40 μm.
If the thickness of the charge transport layer is less than 5 μm, the charge retention ability of the surface of the photoreceptor may be reduced. On the other hand, if the thickness of the charge transport layer exceeds 50 μm, the resolution of the photoreceptor may decrease.

<Photoreceptor 2: Embodiment 2>
FIG. 2 is a schematic cross-sectional view showing the configuration of essential parts of the photoreceptor (photoreceptor 2) of the invention.
The photoreceptor 2 includes an undercoat layer 18 containing metal oxide fine particles 19 on a conductive support 11, and a charge generating substance 12, a charge transporting substance 13, and a binder resin 17 binding them together. This is a single-layer photoreceptor provided with a single-layer photoreceptor layer 14 containing the following functions as a charge generation layer and a charge transport layer.

The single-layer type photosensitive layer is formed by the same method as in the case of forming the charge transport layer. For example, a charge-generating substance, a charge-transporting substance, and a binder resin are dissolved or dispersed in a suitable solvent to prepare a coating solution for a photosensitive layer, and this coating solution for a photosensitive layer is applied onto an undercoat layer by dip coating or the like. Formed by coating.
The single-layer type photosensitive layer may contain an appropriate amount of the same additives as those contained in the charge generation layer, if necessary, within a range that does not impede the effects of the present invention.

The ratio of the charge transport substance 13 to the binder resin 17 in the photosensitive layer is 10/12 to 10/12 by mass, similar to the ratio A/B of the charge transport substance 13 to the binder resin 17 in the charge transport layer 16 described above. It is 10/30.

The thickness of the single-layer type photosensitive layer is not particularly limited, but is preferably 5 to 100 μm, more preferably 10 to 50 μm.
If the thickness of the single-layer photosensitive layer is less than 5 μm, the charge retention ability of the photoreceptor surface may be reduced. On the other hand, if the thickness of the single-layer type photosensitive layer exceeds 100 μm, productivity in manufacturing the photoreceptor may decrease.
In the photoreceptor of the present invention, the photosensitive layer may be either of the above-mentioned laminated type or single layer type, but from the viewpoint of the performance of the photoreceptor, a laminated type in which charge generation and charge transport functions are separated is preferable. .

<Surface protective layer 20>
The photoreceptor of the present invention may have a surface protective layer on the photosensitive layer, as shown in FIGS. 3 and 4.
3 and 4 are schematic cross-sectional views showing the configurations of essential parts of photoreceptors 3 and 4 (embodiments 3 and 4) of the present invention, respectively, and are of the photoreceptors 1 and 2 of the present invention shown in FIGS. This photoreceptor has a surface protective layer 20 on a photosensitive layer 14 (outermost layer).
The surface protective layer has a function of improving the durability of the photoreceptor, and contains a binder resin and, if necessary, additives. Further, the surface protective layer may contain one or more of the same charge transport substances as the charge transport layer in order to stabilize electrical properties.

As the binder resin, resins having binding properties used in the field can be used, and examples thereof include resins such as polystyrene, polyacetal, polyethylene, polycarbonate, polyarylate, polysulfone, polypropylene, and polyvinyl chloride. These binder resins can be used alone or in combination of two or more.
Among these, polycarbonate and polyarylate are particularly preferred in consideration of wear characteristics and electrical characteristics.

Furthermore, a filler material may be added to the surface protective layer for the purpose of improving wear resistance.
Examples of organic filler materials include fluororesin powders such as polytetrafluoroethylene, silicone resin powders, and a-carbon powders; examples of inorganic filler materials include metal powders such as copper, tin, aluminum, and indium; Examples include metal oxides such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide, and inorganic materials such as potassium titanate. In terms of filler hardness, inorganic filler materials are particularly preferred.
The average primary particle diameter of the filler is preferably 0.01 to 0.5 μm from the viewpoint of light transmittance and abrasion resistance of the surface protective layer.

Further, the filler material may be surface-treated with an inorganic substance or an organic substance in order to improve dispersibility in a coating liquid for forming a coating. Examples include those treated with a silane coupling agent for water repellency, those treated with a fluorine-based silane coupling agent, those treated with higher fatty acids, and those treated with alumina, zirconia, tin oxide, or silica on the filler surface. It will be done.
The higher the content of the filler material in the surface protection layer, the better the wear resistance will be, but if it is too high, it may cause adverse effects such as an increase in residual potential and a decrease in the writing light transmittance of the surface protection layer. be. Therefore, the filler material is generally 50% by weight or less, preferably 30% by weight or less based on the total solids content.

The thickness of the surface protective layer is not particularly limited, but is preferably 0.1 to 10 μm, more preferably 1.0 to 8.0 μm.
Photoreceptors that are used repeatedly over a long period of time are designed to be mechanically durable and resistant to wear. However, in an actual machine, ozone and NOx gas are generated from a charging member and the like and adhere to the surface of the photoreceptor, causing image deletion. In order to prevent this image deletion, it is necessary to wear the photosensitive layer at a certain speed or higher, and when considering repeated use over a long period of time, the surface protective layer preferably has a thickness of at least 1.0 μm or more. Furthermore, if the thickness of the surface protective layer exceeds 8.0 μm, problems such as increased residual potential and decreased reproducibility of fine dots may occur.

(3) Image forming apparatus 100
The image forming apparatus of the present invention includes a photoconductor of the present invention, a charging device that charges the photoconductor, an exposure device that exposes the charged photoconductor to form an electrostatic latent image, and an electrostatic latent image formed by the exposure. A developing device that develops the electrostatic latent image to form a toner image (visualizes it), a transfer device that transfers the toner image formed by the development onto a recording medium, and a transfer device that transfers the transferred toner image onto the recording medium. The image forming apparatus is characterized in that it includes at least a fixing means for fixing the toner to form an image, a cleaning means for removing and recovering toner remaining on the photoreceptor, and a charge removing means for removing surface charges remaining on the photoreceptor.
The image forming apparatus of the present invention and its operation will be described with reference to the drawings, but the present invention is not limited to the following description.

FIG. 5 is a schematic side view showing the configuration of the image forming apparatus of the present invention.
An image forming apparatus (laser printer) 100 in FIG. 5 includes a photoreceptor 1 of the present invention, an exposure means (semiconductor laser) 31, a charging means (charger) 32, a developing means (developing device) 33, and a transfer means. The image forming apparatus includes a transfer charger (transfer charger) 34, a conveyor belt (not shown), a fixing device (fixer) 35, and a cleaning device (cleaner) 36. Reference numeral 51 indicates a recording medium (recording paper or transfer paper).

The photoreceptor 1 is rotatably supported by the main body of the image forming apparatus 100 (not shown), and is rotationally driven in the direction of an arrow 41 about a rotation axis 44 by a driving means (not shown). The driving means includes, for example, an electric motor and a reduction gear, and rotates the photoreceptor 1 at a predetermined circumferential speed by transmitting the driving force to the conductive support that constitutes the core of the photoreceptor 1. . The charging means (charger) 32, the exposure means 31, the developing means (developing device) 33, the transfer means (transfer charger) 34, and the cleaning means (cleaner) 36 are installed along the outer peripheral surface of the photoreceptor 1 in this order. , are provided from the upstream side to the downstream side in the rotational direction of the photoreceptor 1, which is indicated by an arrow 41.

The charger 32 is a charging device that uniformly charges the outer peripheral surface of the photoreceptor 1 to a predetermined potential.
The exposure unit 31 includes a semiconductor laser as a light source, and irradiates the surface of the photoreceptor 1 between the charger 32 and the developer 33 with a laser beam output from the light source, thereby exposing the charged photoreceptor 1 to the surface of the photoreceptor 1. Exposure is applied to the outer peripheral surface of the image according to the image information. The light is repeatedly scanned in the direction in which the rotational axis 44 of the photoreceptor 1 extends, which is the main scanning direction, and images are formed to sequentially form electrostatic latent images on the surface of the photoreceptor 1. That is, the amount of charge on the photoreceptor 1, which is uniformly charged by the charger 32, differs depending on whether the laser beam is irradiated or not, and an electrostatic latent image is formed.

The developing device 33 is a developing device that uses a developer (toner) to develop an electrostatic latent image formed on the surface of the photoreceptor 1 by exposure to light, and is provided facing the photoreceptor 1 and is provided on the outer peripheral surface of the photoreceptor 1. A casing 33b that supports the developing roller 33a rotatably about a rotational axis parallel to the rotational axis 44 of the photoreceptor 1 and stores a developer containing toner in its internal space. Be prepared.

The transfer charger 34 supplies a toner image, which is a visible image formed on the outer circumferential surface of the photoreceptor 1 by development, between the photoreceptor 1 and the transfer charger 34 from the direction of arrow 42 by a conveying means (not shown). This is a transfer means for transferring onto a transfer paper 51 which is a recording medium. The transfer charger 34 is, for example, a contact-type transfer device that includes a charging device and transfers the toner image onto the transfer paper 51 by applying an electric charge having a polarity opposite to that of the toner to the transfer paper 51 .

The cleaner 36 is a cleaning unit that removes and collects the toner remaining on the outer peripheral surface of the photoreceptor 1 after the transfer operation by the transfer charger 34, and includes a cleaning blade 36a that peels off the toner remaining on the outer peripheral surface of the photoreceptor 1; A collection casing 36b that accommodates the toner peeled off by the cleaning blade 36a is provided. Further, this cleaner 36 is provided together with a static elimination lamp (not shown).

Further, the image forming apparatus 100 is provided with a fixing device 35, which is a fixing means for fixing the transferred image, on the downstream side where the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34 is conveyed. It will be done. The fixing device 35 includes a heating roller 35a having a heating means (not shown), and a pressure roller 35b that is provided opposite to the heating roller 35a and is pressed by the heating roller 35a to form a contact portion.
The reference numeral 37 indicates a separating means for separating the transfer paper and the photoreceptor, and the reference numeral 38 indicates a casing that accommodates each of the above-mentioned means of the image forming apparatus.

The image forming operation by the image forming apparatus 100 is performed as follows.
First, when the photoreceptor 1 is rotationally driven in the direction of arrow 41 by the driving means, the photoreceptor 1 is is uniformly charged to a predetermined positive potential.

Next, the exposure means 32 irradiates the surface of the photoreceptor 1 with light according to the image information. Through this exposure, the surface charge of the portion of the photoreceptor 1 that is irradiated with light is removed, and a difference occurs between the surface potential of the portion that is irradiated with light and the surface potential of the portion that is not irradiated with light. A latent image is formed.
Toner is supplied to the surface of the photoreceptor 1 on which the electrostatic latent image is formed from the developing device 33 provided on the downstream side in the rotational direction of the photoreceptor 1 than the image forming point of light by the exposure means 33, and the electrostatic latent image is formed. is developed to form a toner image.

A transfer paper 51 is supplied between the photoreceptor 1 and the transfer charger 34 in synchronization with the exposure of the photoreceptor 1 . The transfer charger 34 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 51, and the toner image formed on the surface of the photoreceptor 1 is transferred onto the transfer paper 51.
The transfer paper 51 on which the toner image has been transferred is conveyed to the fixing device 35 by a conveyance means, and is heated and pressurized as it passes through the abutting portion between the heating roller 35a and the pressure roller 35b of the fixing device 35, and the toner image is transferred to the transfer paper 51. The image is fixed on the transfer paper 51 and becomes a solid image. The transfer paper 51 on which the image has been formed in this manner is discharged to the outside of the image forming apparatus 100 by a conveying means.

On the other hand, toner remaining on the surface of the photoreceptor 1 even after the toner image is transferred by the transfer charger 34 is peeled off from the surface of the photoreceptor 1 by the cleaner 36 and collected. The charge on the surface of the photoreceptor 1 from which the toner has been removed in this manner is removed by light from the static elimination lamp, and the electrostatic latent image on the surface of the photoreceptor 1 disappears. Thereafter, the photoreceptor 1 is further driven to rotate, and a series of operations starting from charging again are repeated to form images continuously.

EXAMPLES The present invention will be specifically explained below using Examples and Comparative Examples based on the drawings, but the present invention is not limited to these Examples.
In the Examples and Comparative Examples, a photoreceptor having a structure having a functionally separated photosensitive layer was used, but similar effects can be obtained by using a photoreceptor having a structure having a single layer type photosensitive layer.
Note that Examples 8 to 11 are reference examples.

(Example 1)
8.0 parts by mass of titanium oxide (surface alumina/silica treatment/average primary particle diameter 35 nm, manufactured by Teika Corporation, brand name: MT-500SA) and copolymerized nylon (manufactured by Toray Industries, Inc., product name: Amilan (registered trademark), A mixed solvent of 2.0 parts by mass of grade: CM8000), 30 parts by mass of methanol, 20 parts by mass of 1,3-dioxolane, and 0.24 parts by mass of distilled water (3% by mass based on the titanium oxide of the metal oxide fine particles). In addition, using zirconia beads with a diameter of 0.5 mm as a dispersion medium, a coating solution for an undercoat layer was prepared by performing a dispersion treatment for 5 hours in a paint shaker. The viscosity of the undercoat layer coating liquid immediately after dispersion was measured and found to be 35 mPa·s.
A coating bath was filled with the obtained coating liquid, and the conductive support was immersed in the bath, then pulled out and air-dried to form an undercoat layer 18 having a thickness of 1.0 μm.
The conductive support was made of an aluminum drum with a diameter of 30 mm and a length of 372 mm, which had been cut (processed to a ten-point surface roughness Rz = 0.80 μm as specified in JIS B-0601) and whose surface had been cleaned. A conductive substrate was used.

Titanyl phthalocyanine used as a charge generating substance was prepared in advance.
40 g of o-phthalodinitrile, 18 g of titanium tetrachloride, and 500 mL of α-chloronaphthalene were heated and stirred in a nitrogen atmosphere at a temperature of 200 to 250 °C for 3 hours to react, and after cooling to a temperature of 100 to 130 °C, filtered. The mixture was washed with 200 mL of α-chloronaphthalene heated to 100° C. to obtain a dichlorotitanium phthalocyanine crude product.
The obtained crude product was washed at room temperature with 200 mL of α-chloronaphthalene, then with 200 mL of methanol, and further washed with hot suspension in 500 mL of methanol for 1 hour. After filtration, the obtained crude product was stirred and dissolved in 100 mL of concentrated sulfuric acid, and insoluble materials were collected by filtration. The obtained sulfuric acid solution was poured into 3000 mL of water, the precipitated crystals were collected by filtration, and after repeated hot washing in 500 mL of water until the pH reached 6 to 7, the resulting wet crystals were collected by filtration. The cake was treated with dichloromethane, washed with methanol, and then dried to obtain titanyl phthalocyanine.

2 parts by mass of the obtained titanyl phthalocyanine and 1 part by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product: S-LEC BM-2) were added to 97 parts by mass of methyl ethyl ketone and dispersed in a paint shaker for 4 hours to generate a charge. A layer coating solution was prepared.
The obtained coating liquid was applied onto the undercoat layer by the same dip coating method as in the case of the undercoat layer, and air-dried to form a charge generation layer 15 having a thickness of 0.3 μm.

Next, 5.0 parts by mass of compound (1) (N,N'-diphenyl-N,N'-di(m-tolyl)benzidine, manufactured by Tokyo Kasei Kogyo Co., Ltd., product code: D2448) as a charge transport substance, A charge transport layer coating liquid was prepared by mixing 7.5 parts by mass of polycarbonate resin (manufactured by Teijin Ltd., grade name: TS2050) as binder resin 17 and using 47 parts by mass of tetrahydrofuran as a solvent.
The resulting coating solution was applied onto the charge generation layer by the same dip coating method as in the case of the undercoat layer, and dried at a temperature of 120°C for 1 hour to form a charge transport layer with a thickness of 28 μm. Photoreceptor 1 was obtained.

(Example 2)
Other than replacing 0.24 parts by mass of distilled water (3% by mass with respect to the titanium oxide in the metal oxide fine particles) with 0.40 parts by mass of distilled water (5% by mass with respect to the titanium oxide in the metal oxide fine particles) Photoreceptor 1 was produced in the same manner as in Example 1.

(Example 3)
Other than replacing 0.24 parts by mass of distilled water (3% by mass with respect to the titanium oxide in the metal oxide fine particles) with 0.64 parts by mass of distilled water (8% by mass with respect to the titanium oxide in the metal oxide fine particles) Photoreceptor 1 was produced in the same manner as in Example 1.

(Example 4)
8.0 parts by mass of titanium oxide (surface alumina/silica treatment/average primary particle diameter 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was changed to 7.0 parts by mass, and copolymerized nylon (manufactured by Toray Industries, Inc., trade name: : 2.0 parts by mass of Amilan (registered trademark), grade: CM8000) was added to 3.0 parts by mass of copolymerized nylon (manufactured by Arkema Corporation, brand name: Platamid (registered trademark) M1276), and 0.24 parts by mass of distilled water ( Same as Example 1 except that 0.35 parts by mass of distilled water (5% by mass based on the titanium oxide of the metal oxide microparticles) was replaced with 0.35 parts by mass of distilled water (3% by mass based on the titanium oxide in the metal oxide microparticles). A photoreceptor was produced.

(Example 5)
8.0 parts by mass of titanium oxide (surface alumina/silica treatment/average primary particle diameter 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was added to 7.5 parts by mass, and copolymerized nylon (manufactured by Toray Industries, Inc., trade name: : Amiran (registered trademark), grade: CM8000) 2.0 parts by mass to 2.5 parts by mass, 0.24 parts by mass of distilled water (3% by mass based on titanium oxide of metal oxide fine particles) to 0 parts by mass of distilled water A photoreceptor was produced in the same manner as in Example 1, except that the amount was changed to .375 parts by mass (5% by mass based on the titanium oxide of the metal oxide fine particles).

(Example 6)
8.0 parts by mass of titanium oxide (surface alumina/silica treatment/average primary particle size 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was changed to 9.0 parts by mass, and copolymerized nylon (manufactured by Toray Industries, Inc., trade name: : 2.0 parts by mass of Amiran (registered trademark), grade: CM8000) was added to 1.0 parts by mass of copolymerized nylon (manufactured by Arkema Corporation, brand name: Platamid (registered trademark) M1276), and 0.24 parts by mass of distilled water ( Same as Example 1 except that 0.45 parts by mass of distilled water (5% by mass based on the titanium oxide of the metal oxide microparticles) was replaced with 0.45 parts by mass of distilled water (3% by mass based on the titanium oxide in the metal oxide microparticles). A photoreceptor was produced.

(Example 7)
8.0 parts by mass of titanium oxide (surface alumina/silica treatment/average primary particle diameter 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was added to 9.5 parts by mass, and copolymerized nylon (manufactured by Toray Industries, Inc., trade name: : Amiran (registered trademark), grade: CM8000) 2.0 parts by mass to 0.5 parts by mass, 0.24 parts by mass of distilled water (3% by mass based on titanium oxide of metal oxide fine particles) to 0 parts by mass of distilled water A photoreceptor was produced in the same manner as in Example 1, except that the amount was changed to .475 parts by mass (5% by mass based on the titanium oxide of the metal oxide fine particles).

(Example 8)
Titanium oxide (surface alumina/silica treatment/average primary particle size 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was replaced with titanium oxide (surface untreated/average primary particle size 35 nm, manufactured by Teika Co., Ltd., brand: MT-500B) ) A photoreceptor was produced in the same manner as in Example 1, except that .

(Example 9)
Titanium oxide (surface alumina/silica treatment/average primary particle diameter 35 nm, manufactured by Teika Corporation, brand: MT-500SA) was mixed with zinc oxide (surface untreated/average primary particle diameter 35 nm, manufactured by Teika Corporation, brand: MZ-300) ) A photoreceptor was produced in the same manner as in Example 1, except that

(Example 10)
Other than replacing 0.24 parts by mass of distilled water (3% by mass with respect to the titanium oxide of the metal oxide fine particles) with 0.08 parts by mass of distilled water (1% by mass with respect to the titanium oxide of the metal oxide fine particles) Photoreceptor 1 was produced in the same manner as in Example 1.

(Example 11)
Except that 0.24 parts by mass of distilled water (3% by mass based on the titanium oxide in the metal oxide fine particles) was replaced with 0.96 parts by mass of distilled water (12% by mass based on the titanium oxide in the metal oxide fine particles). A coating solution for an undercoat layer was prepared in the same manner as in Example 1. Since the increase in viscosity was large, photoreceptor 1 was prepared in the same manner as in Example 1 by diluting it with a 3/2 mixed solvent of methanol and 1,3-dioxolane to lower the viscosity of the undercoat layer coating solution.

(Comparative example 1)
A coating solution for an undercoat layer was prepared in the same manner as in Example 1, except that distilled water was not added. However, since the viscosity increased significantly, it was diluted with a 3/2 mixed solvent of methanol and 1,3-dioxolane. Photoreceptor 1 was prepared in the same manner as in Example 1, except that the viscosity of the undercoat layer coating liquid was lowered.

(Comparative example 2)
A coating solution for an undercoat layer was prepared in the same manner as in Example 8, except that distilled water was not added. However, since the viscosity increased significantly, it was diluted with a 3/2 mixed solvent of methanol and 1,3-dioxolane. Photoreceptor 1 was prepared in the same manner as in Example 8, except that the viscosity of the undercoat layer coating liquid was lowered.

(Comparative example 3)
A coating solution for an undercoat layer was prepared in the same manner as in Example 9, except that distilled water was not added. However, since the viscosity increased significantly, it was diluted with a 3/2 mixed solvent of methanol and 1,3-dioxolane. Photoreceptor 1 was prepared in the same manner as in Example 9, except that the viscosity of the undercoat layer coating liquid was lowered.

(Comparative example 4)
Methyl hydrogen polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., product name: KF-99) to 10.0 parts by mass of titanium oxide (surface untreated/average primary particle diameter 35 nm, manufactured by Teika Co., Ltd., brand: MT-500B) ) and 50 parts by mass of toluene as a solvent were mixed, and the resulting suspension was heated to 100° C. and stirred for 4 hours. The solvent was removed from the treated suspension by vacuum distillation to obtain surface-coated titanium oxide. The obtained titanium oxide was further heat-treated at a temperature of 140° C. for 1 hour to obtain titanium oxide surface-treated with methyl hydrogen polysiloxane.
Example 1 except that titanium oxide (surface alumina/silica treatment/average primary particle size 35 nm, manufactured by Teika Co., Ltd., brand: MT-500SA) was replaced with titanium oxide surface-treated with methylhydrogenpolysiloxane. A coating solution for the undercoat layer was prepared in the same manner, but the viscosity increased significantly, so the viscosity of the coating solution for the undercoat layer was lowered by diluting it with a 3/2 mixed solvent of methanol and 1,3-dioxolane. Photoreceptor 1 was produced in the same manner as in Example 1.

[Evaluation of coating liquid for undercoat layer]
The viscosity of the undercoat layer coating solution prepared in Examples 1 to 11 and Comparative Examples 1 to 4 after primary dispersion was measured using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., model: RE-85). did.
In addition, the coating solution for the undercoat layer placed in a sample bottle with a capacity of 20 mL was allowed to stand for one week in a constant temperature bath at a temperature of 20°C, and the coating solution for the undercoat layer was visually observed after the pot life, and the condition of the coating solution ( (precipitation) Pot life evaluation was conducted.

The undercoat layer coating solution after the pot life was evaluated based on the following criteria.
<Evaluation criteria>
VG: No flocculation/sedimentation G: Slight flocculation but no sedimentation NB: Slight sedimentation, but no problem in actual use B: Flocculation/sedimentation

[Evaluation of photoreceptor]
The photoreceptors produced in Examples 1 to 11 and Comparative Examples 1 to 4 were mounted in the black position (black unit) of a digital copying machine (manufactured by Sharp Corporation, model: MX-5150FV) modified for testing. , the surface potential of the photoreceptor in the developing section, specifically, the surface potential VL (-V) of the photoreceptor in the black background area when exposed to light in order to check the sensitivity.
The measurement was carried out by removing the developing device from the test digital copying machine and instead providing a surface electrometer (manufactured by Trek Japan, model: MODEL 344) at the developing site.
The initial electrical characteristics are at a low temperature/low humidity (L/L) environment of 5°C/20% relative humidity, and the repeated electrical characteristics are at 35°C/85% relative humidity immediately after copying the 1st and 1000th sheet. The measurement was carried out under a high temperature/high humidity (H/H) environment of %. Furthermore, image evaluation (white solid image evaluation = black dots) was performed under an H/H environment.

[Image evaluation (white solid image evaluation = black spots)]
After copying the 1000th sheet, print three solid white (plain) images, and check that the periodicity of black spots on each hard copy (A3 size) matches the period of the photoreceptor and is visible. The number of black spots (diameter 0.4 mm or more) was measured, and the results were evaluated based on the following criteria.
<Evaluation criteria>
VG: There is no frequency of black spots in all hard copies. G: The frequency of black spots is 3 or less per sheet in all hard copies (good).
NB: Frequency of occurrence of black spots is 4 to 10 pieces/more than 1 out of 3 pieces (no problem in practice)
B: The frequency of occurrence of black spots is 11 pieces/sheet or more, which occurs on more than 1 out of 3 sheets (practical problem)

[Initial sensitivity under L/L environment]
Initial sensitivity VL (-V) under L/L environment was evaluated based on the following criteria.
<Evaluation criteria>
VG: | VL | <200
G: 200≦｜VL｜<235
NB: 235≦｜VL｜<270
B: 270≦｜VL｜

[Sensitivity change under H/H environment]
The difference Δ(V) between the initial sensitivity under H/H environment and the sensitivity after continuous use of 1000 sheets was evaluated based on the following criteria.
<Evaluation criteria>
VG: Δ≦5
G:5<Δ≦15
NB: 15<Δ≦35
B: 35<Δ

*Please check the position of the equals and inequality signs “≦” and “<”.

[Comprehensive judgment]
Based on the above evaluation results, comprehensive judgment was made using the following criteria.
VG: VG (good) in all evaluations
G: G or higher in all evaluations (no problems in actual use)
NB: NB or higher in all evaluations (may be usable in actual use)
B: There is a B in any of the evaluations (unusable)
Table 1 shows the metal oxide fine particles, binder resin, their blending ratio, and water blending ratio used in the coating solution for the undercoat layer, and Table 2 shows the above evaluation results.
Further, FIG. 6 shows the relationship between the mixing ratio of water (relative to metal oxide fine particles) in the undercoat layer coating solution and the viscosity after dispersion during preparation.

From Tables 1 and 2, the following can be seen.
(1) The water-added undercoat layer coating solution of the present invention (Examples 1 to 11) has a higher level of dispersion during dispersion than the conventional undercoat layer coating solution without water addition (Comparative Examples 1 to 3). (2) The photoconductor produced using the water-added undercoat layer coating solution (Examples 1 to 11) of the present invention is suppressed from thickening and has excellent storage stability. /H, there should be no problems in both the image characteristics, the initial sensitivity, and the repeated electrical characteristics in continuous printing. In Example 10), the increase in viscosity during dispersion was suppressed compared to conventional undercoat layer coating liquids without water addition (Comparative Examples 1 to 3), but some solid content sedimentation was observed. (4) The undercoat layer coating liquid (Example 11) containing 12% by mass of water, which exceeds 10% by mass based on the metal oxide fine particles, suppresses the increase in viscosity during dispersion, but the solubility of the resin Deterioration of the storage stability of the coating solution and repeated electrical characteristics may be observed due to drop-off or the influence of excessively added moisture.

(5) Conventional undercoat layer coating solutions without water addition (Comparative Examples 1 to 3) significantly thickened during dispersion, poor storage stability of the coating solution, and dispersion was inhibited due to sedimentation. Due to local solid content fluctuations and agglomeration, the image characteristics of the fabricated photoreceptor often show image defects such as black spots. Even when water was added to the undercoat layer coating liquid (Comparative Example 4), the effect of suppressing thickening during dispersion could not be obtained, and the storage stability of the dispersion coating liquid and the image characteristics of the photoreceptor were deteriorated. (7) The undercoat layer coating liquids (Examples 4 and 6) using various binders in the undercoat layer have suppressed viscosity increase during dispersion and have good storage stability. The produced photoreceptor has no problems in H/H image characteristics, initial sensitivity, and repeated electrical characteristics during continuous printing. (8) Undercoating with a changed mass ratio of metal oxide fine particles and binder resin In the layer coating liquids (Examples 4 to 7), if there is a large amount of binder resin, the initial sensitivity tends to deteriorate, and if there is a large amount of metal oxide fine particles, the storage stability tends to deteriorate. It is better if the mass ratio with the binder is 75/25 to 90/10.

1, 2, 3, 4 Electrophotographic photoreceptor 11 Conductive support 12 Charge generating substance 13 Charge transporting substance 14 Photosensitive layer 15 Charge generating layer 16 Charge transporting layer 17 Binder resin (binder resin)
18 Undercoat layer (middle)
19 Metal oxide fine particles 20 Surface protective layer

31 Exposure means (semiconductor laser)
32 Charging means (charger)
33 Developing means (developing device)
33a developing roller 33b casing 34 transfer means (transfer charger)
35 Fixing means (fixing device)
35a heating roller 35b pressure roller 36 cleaning means (cleaner)
36a Cleaning blade 36b Recovery casing 37 Separation means 38 Housing 41, 42 Arrow mark 44 Rotation axis 51 Recording medium (recording paper or transfer paper)
100 Image forming device (laser printer)

Claims (7)

comprising a binder resin, metal oxide fine particles whose surface has not been treated with an organic compound, and a mixed solvent containing water and a water-soluble organic solvent, the metal oxide fine particles being dispersed in the mixed solvent ,
The mixing ratio of water in the mixed solvent is 2 to 8% by mass with respect to the metal oxide fine particles,
The metal oxide fine particles have a volume resistivity of 10 ⁵ Ω·cm to 10 ¹⁰ Ω·cm and an average primary particle size of 10 to 35 nm when formed into a green compact at a press pressure of 100 kg/cm ^{2 .} 1. A coating liquid for an undercoat layer of an electrophotographic photoreceptor , which comprises fine particles of titanium oxide, and the fine particles of titanium oxide are surface-treated with alumina and silica . The coating liquid for an electrophotographic photoreceptor undercoat layer according to claim 1 , wherein the blending ratio of the metal oxide fine particles and the binder resin is from 75/25 to 90/10 in mass ratio. The coating liquid for an electrophotographic photoreceptor undercoat layer according to claim 1 or 2 , wherein the binder resin is an organic solvent-soluble polyamide resin. 4. The coating liquid for an electrophotographic photoreceptor undercoat layer according to any one of 1 to 3 , wherein the water-soluble organic solvent of the mixed solvent is methanol, 1,3-dioxolane, or a mixed solvent thereof. At least an undercoat layer and a photosensitive layer are sequentially laminated on a conductive support, and the undercoat layer is a coating liquid for an electrophotographic photoreceptor undercoat layer according to any one of claims 1 to 4 . An electrophotographic photoreceptor characterized in that the layer is formed using. The electrophotographic photoreceptor according to claim 5 , wherein the photosensitive layer is a laminated photosensitive layer in which at least a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance are laminated in this order. . The electrophotographic photoreceptor according to claim 5 or 6 , a charging means for charging the electrophotographic photoreceptor, an exposure means for exposing the charged electrophotographic photoreceptor to form an electrostatic latent image, and an exposure means for exposing the electrophotographic photoreceptor to light to form an electrostatic latent image. a developing unit that develops the electrostatic latent image formed by the developer to form a toner image; a transfer unit that transfers the toner image formed by the development onto a recording medium; and a transfer unit that transfers the toner image formed by the development onto a recording medium; The image forming apparatus includes at least a fixing means for fixing and forming an image on a medium, a cleaning means for removing and recovering toner remaining on the electrophotographic photoreceptor, and a static eliminating means for removing surface charges remaining on the electrophotographic photoreceptor. An image forming apparatus characterized by:

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