JP2023054576A - Electrophotographic photoreceptor, process cartridge equipped with the same, and image forming device - Google Patents

Abstract

To provide an electrophotographic photoreceptor having good electrical characteristics and having good durability and good light fastness, a process cartridge equipped with the same, and an image forming device.SOLUTION: Provided is an electrophotographic photoreceptor comprising at least a multilayer photosensitive layer composed of a charge generating layer containing a charge generating substance and a charge transport layer containing a charge transport substance that are laminated in the order stated, or comprising at least the multilayer photosensitive layer and a surface protective layer that is laminated thereupon. At least one or both of the charge transport layer and the surface protective layer contain a light absorbent, the outermost surface layer of the electrophotographic photoreceptor contains a silica filler, and a 50% or greater transmissivity to light in wavelength of 600 nm is had, the ratio T600/T550 of transmissivity T600 to light in wavelength of 600 nm to transmissivity T550 to light in wavelength of 550 nm being 1.10 to 2.20 inclusive.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor having good electrical properties, good durability and good light resistance, and a process cartridge and an image forming apparatus having the same.

2. Description of the Related Art Electrophotographic image forming apparatuses (electrophotographic apparatuses) that form images using electrophotographic technology are widely used in copiers, printers, facsimile machines, and the like.
An electrophotographic photoreceptor (hereinafter also referred to as a "photoreceptor") used in this electrophotographic process is composed of a photosensitive layer containing a photoconductive material laminated on a substrate, and is composed mainly of an organic photoconductive material. Photoreceptors (also referred to as “organic photoreceptors”) having a photosensitive layer of

A drawback of photoreceptors is light resistance. During normal use, the photoreceptor is not exposed to external light such as fluorescent lamps. are exposed to external light. When the photoreceptor is exposed to external light, the photoreceptor is severely damaged, which may cause image problems.
As a means to overcome this drawback, a method of adding an ultraviolet absorber to the photosensitive layer (for example, JP-A-2016-143024: Patent Document 1) or a method of adding a material that absorbs a specific wavelength to the photosensitive layer ( For example, Japanese Patent Application Laid-Open No. 10-048856: Patent Document 2) has been proposed.

JP 2016-143024 A JP-A-10-048856

The indoor fluorescent light to which the image forming apparatus is exposed has a spectral distribution, and the light resistance of the photoreceptor is improved by including in the photosensitive layer an ultraviolet absorber that has spectral absorption mainly in the wavelength range of 500 to 700 nm. can be made However, when the charge-removing light in the image forming apparatus has a maximum spectral distribution in the wavelength range of 550 to 650 nm, the transmittance of the light within this range is suppressed by the ultraviolet absorber and reaches the charge generation layer. This leads to the problem that the light for static elimination is suppressed, the efficiency of static elimination is lowered, and the residual potential is increased.

In addition, the surface of the organic photoreceptor is more likely to be worn due to the recent increase in the use of a contact charging method using roller charging and the extension of the life, miniaturization, and speeding up of electrophotographic devices such as digital copiers and printers. exposed to harsh conditions. In order to solve such problems, studies have been made to improve printing durability by adding fine particles such as silica, alumina, and polyethylene terephthalate (PTFE) as a filler to the outermost layer of the photoreceptor.
However, the addition of fillers tends to reduce the transmittance of the photosensitive layer, and adding an ultraviolet absorber to a photosensitive layer containing fillers to improve light resistance causes an increase in residual potential. It is known that it is difficult to achieve both printing durability and printing durability.

Accordingly, it is an object of the present invention to provide an electrophotographic photoreceptor having good electrical properties, good durability and good light resistance, and a process cartridge and an image forming apparatus having the same. do.

As a result of intensive studies to solve the above problems, the present inventors have found that the outermost layer of a photoreceptor contains a specific light absorbing agent and a silica filler, controls the dispersion state of the silica filler, The inventors have found that by optimizing the transmittance of the layer, both durability and prevention of deterioration due to external light can be achieved, and the above problems can be solved, leading to the completion of the present invention.

Thus, according to the present invention, at least a laminated photosensitive layer is provided on a conductive support, in which a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated in this order. or an electrophotographic photoreceptor comprising at least the laminated photosensitive layer and a surface protective layer laminated thereon,
both or one of the charge transport layer and the surface protective layer contains a light absorbing agent,
The outermost layer of the electrophotographic photosensitive member contains a silica filler, has a transmittance of 50% or more for light with a wavelength of 600 nm, and has a transmittance T ₆₀₀ for light with a wavelength of 600 nm and a light with a wavelength of 550 nm. An electrophotographic photoreceptor is provided in _{which a ratio T 600 /} T ₅₅₀ to a transmittance T 550 is 1.10 or more and 2.20 or less.

Further, according to the present invention, the above electrophotographic photoreceptor, charging means for charging the electrophotographic photoreceptor, developing means for developing an electrostatic latent image formed by exposure to form a toner image, and the electron and at least one cleaning means for removing toner remaining on the photoreceptor.

Further, according to the present invention, the above electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, and exposure means for exposing the charged electrophotographic photosensitive member to form an electrostatic latent image. developing means for developing the electrostatic latent image formed by exposure to form a toner image; transferring means for transferring the toner image formed by the development onto a recording medium; fixing means for fixing and forming an image on the recording medium; cleaning means for removing and recovering toner remaining on the electrophotographic photosensitive member; and neutralizing means for removing surface charges remaining on the electrophotographic photosensitive member. There is provided an image forming apparatus comprising at least:

According to the present invention, it is possible to provide an electrophotographic photoreceptor having good electrical properties, good durability and good light resistance, and a process cartridge and an image forming apparatus having the same.

1 is a schematic cross-sectional view showing the structure of a main part of a photoreceptor (laminated photoreceptor) 1 of the present invention; FIG. 1 is a schematic side view showing the configuration of a main part of an image forming apparatus 100 of the present invention; FIG.

(1) Photoreceptor The photoreceptor of the present invention is a laminated photosensitive layer in which a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated in this order on a conductive support. or an electrophotographic photoreceptor comprising at least the laminated photosensitive layer and a surface protective layer laminated thereon,
both or one of the charge transport layer and the surface protective layer contains a light absorbing agent,
The outermost layer of the electrophotographic photosensitive member contains a silica filler, has a transmittance of 50% or more for light with a wavelength of 600 nm, and has a transmittance T ₆₀₀ for light with a wavelength of 600 nm and a light with a wavelength of 550 nm. The ratio T ₆₀₀ /T ₅₅₀ to transmittance T 550 is characterized by being 1.10 or more _and 2.20 or less.
First, the "light absorbing agent" contained in both or one of the charge transport layer and the surface protective layer, the "silica filler" contained in the outermost layer of the photoreceptor, and the outermost surface layer, which are features of the present invention. The light transmittance of the layers will be described, and then (1) each configuration of the photoreceptor, (2) a process cartridge including the photoreceptor, and (3) an image forming apparatus will be described.

<Light absorber>
The light absorber has a function of effectively blocking the action of the light wavelength component of external light on the charge generating substance.
The reason why external light such as fluorescent lamps and LEDs damages the photoreceptor is that the external light passes through the charge transport layer, and the transmitted light acts on the charge generating substance to generate charge traps. A typical fluorescent lamp has light wavelength components around 440 nm, 490 nm, 550 nm, 580 nm and 620 nm, and a white LED has light wavelength components of 460 nm and 500 to 700 nm. Permeation through the transport layer will act on the charge generating material to generate charge traps.
In the present invention, the light absorber absorbs external light and suppresses the occurrence of charge traps.
Therefore, the light absorbing agent contained in both or one of the charge transport layer and the surface protective layer is preferably a compound having spectral absorption at a wavelength of 400 to 700 nm.
The spectral absorption of the more preferred light absorbing agent is in the wavelength range of 450-550 nm.

On the other hand, light wavelength components with a wavelength of 550 to 650 nm need to be transmitted because they are used in LEDs that expose a photoreceptor to form an electrostatic latent image, laser light, and LEDs that remove surface charges remaining on the photoreceptor. Therefore, the transmittance of the outermost layer of the photoreceptor for light with a wavelength of 600 nm and the ratio T ₆₀₀ /T _{550 between the transmittance T 600 for light with a wavelength of 600 nm and the transmittance T 550 for light} with a wavelength of 550 nm are set. The transmittance T ₆₀₀ and the ratio T ₆₀₀ /T ₅₅₀ will be described in the section <Light Transmittance of Outermost Surface Layer>.

The light absorber is not particularly limited as long as it is a compound that has the above optical properties and does not inhibit the effects of the present invention. Examples thereof include perimidine compounds, azoquinone compounds and pyrazolone compounds.
Specifically, as the light absorber, the following structural formula (A):

で表されるペリミジン化合物（ペリミジン化合物（Ａ））、下記構造式（Ｂ）：

A perimidine compound (perimidine compound (A)) represented by the following structural formula (B):

で表されるアゾキノン化合物（アゾキノン化合物（Ｂ））および下記構造式（Ｃ）：

Azoquinone compound represented by (azoquinone compound (B)) and the following structural formula (C):

で表されるピラゾロン化合物（ピラゾロン化合物（Ｃ））から選択される化合物が挙げられ、本発明においてこれらを好適に用いることができる。

and compounds selected from pyrazolone compounds (pyrazolone compounds (C)) represented by and can be preferably used in the present invention.

Examples of the perimidine compound (A) include the perimidine compound (A) used in Example 1 (C.I. Solvent Red179, manufactured by American Dyestuff, product name: Amesolve RedA), and the azoquinone compound (B) includes: Azoquinone compound (B) (manufactured by Hodogaya Chemical Industry Co., Ltd., product name: EAC-39) as used in Example 4 can be mentioned.
Also, the pyrazolone compound can be synthesized, for example, by the method described in Japanese Patent No. 4041741.

The content of the light absorbing agent in the charge transport layer is preferably 0.05 to 1.00% by mass based on the total solid content of the charge transport layer.
If the content of the light absorbing agent is less than 0.05% by mass, the effect on light resistance may not be sufficiently obtained. On the other hand, if the content of the light absorbing agent exceeds 1.00% by mass, the electrical properties of the photoreceptor may deteriorate.
The content of the light absorbing agent is more preferably 0.15 to 0.40% by mass, particularly preferably 0.20 to 0.35% by mass.

<Silica filler>
"Silica" of silica filler means silicon dioxide ( _SiO2 ).
The silica filler suitably used in the present invention is not limited to the origin of the manufacturing method, and includes fumed silica obtained by burning silicon tetrachloride, arc method silica that is made into fine particles in the gas phase by high energy such as plasma. dry process silica; precipitation process silica synthesized under alkaline conditions using an aqueous sodium silicate solution as a raw material; wet process silica such as gel process silica synthesized under acidic conditions; colloidal silica obtained by; and sol-gel method silica obtained by hydrolysis of an organic silane compound.

The silica filler may be surface treated with a surface treatment agent to improve electrical properties of the photoreceptor.
Examples of surface treatment agents include hexamethyldisilazane, N-methyl-hexamethyldisilazane, N-ethyl-hexamethyldisilazane, hexamethyl-N-propyldisilazane, dimethyldichlorosilane, and polydimethylsiloxane. .
Among these, dimethyldichlorosilane and hexamethyldisilazane have good reactivity with hydroxyl groups on the surface of silica particles, so they can reduce the amount of hydroxyl groups on the surface of silica filler. It is particularly preferable because deterioration of the electrical properties of the body can be suppressed.

In the present invention, the silica filler treated with the surface treatment agent can be used, but commercially available silica fine particles treated with the surface treatment agent can also be used. Commercially available silica granules include, for example, product names of Nippon Aerosil Co., Ltd.: R972, R972V, R974, R976, RX200, NX130, NX90G, NX90S, NAX50, RX50; product names of Cabot Japan Co., Ltd.: TS610, TG709F, TG6110G. , Admatechs Co., Ltd. under the product name: YA010C.

The silica filler preferably has an average primary particle size of 30 nm or less.
When the average primary particle size of the silica filler exceeds 30 nm, the aggregate structure formed in the photosensitive layer becomes large, which may easily cause problems such as poor cleaning. If the average primary particle size of the silica filler is too small, the silica filler has a strong cohesive force, is difficult to crush, and may deteriorate in dispersibility.
In addition, the average primary particle diameter is obtained by magnifying silica particles 30,000 to 300,000 times, for example, 10,000 times by observation with a scanning electron microscope, randomly observing 100 particles as primary particles, and using image analysis as the Feret direction average diameter. is the measured value.

The silica filler is preferably contained in an amount of 7 to 18% by weight with respect to the total solid content of the outermost surface layer of the photoreceptor.
If the content of the silica filler is less than 7% by mass based on the total solid content of the outermost surface layer of the photoreceptor, the effect on printing durability may not be sufficiently obtained. On the other hand, if the silica filler content exceeds 18% by weight, the electrical properties of the photoreceptor may deteriorate.
A more preferable silica filler content is 7 to 15% by mass, and particularly preferably 8 to 13% by mass.

It is preferable that the silica filler is uniformly dispersed and distributed in the charge transport layer and the surface protective layer without agglomeration.
To control the dispersion state of the silica filler, adjust the sharing conditions (dispersion method, dispersion time, media diameter, media amount, media material) in the preparation of the charge transport layer coating liquid and the surface protection layer coating liquid. It can be done by Specifically, it will be described in Examples.

<Light transmittance of outermost surface layer>
The outermost layer of the photoreceptor has a transmittance of 50% or more for light with a wavelength of 600 nm, and a ratio T ₆₀₀ between the transmittance T 600 for light with a wavelength of 600 nm and the transmittance T ₅₅₀ for light with a wavelength of ₅₅₀ nm. / _T550 is 1.10 or more and 2.20 or less.

If the transmittance T ₆₀₀ for light with a wavelength of 600 nm is less than 50%, the efficiency of static elimination may decrease and the residual potential may increase. Its upper limit is about 85%.
If the ratio T ₆₀₀ /T ₅₅₀ between the transmittance T ₆₀₀ for light with a wavelength of 600 nm and the transmittance T ₅₅₀ for light with a wavelength of 550 nm is less than 1.10, external light may damage the photoreceptor and cause image defects. be. On the other hand, if the ratio T ₆₀₀ /T ₅₅₀ exceeds 2.20, it may cause an increase in residual potential.
The ratio T ₆₀₀ /T ₅₅₀ is preferably 1.10 or more and 1.50 or less, more preferably 1.15 or more and 1.30 or less.

<Photoreceptor>
The photoreceptor of the present invention comprises at least a laminated photosensitive layer in which a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance are laminated in this order on a conductive support, Alternatively, it comprises at least the laminated photosensitive layer and a surface protective layer laminated thereon.
The photoreceptor of the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.
FIG. 2 is a schematic cross-sectional view showing the configuration of the main part of the photoreceptor (laminated photoreceptor) 1 of the present invention.
The photoreceptor 1 comprises a conductive support 11, a charge generation layer 15 containing an undercoat layer 18 and a charge generation substance 12, a charge transport substance 13, a binder resin 17, a silica filler 19 and a light absorber 20. It has a photosensitive layer (laminated photosensitive layer) 14 in which a charge transport layer 16 is laminated in this order.
The photoreceptor of the present invention may have a surface protective layer on the photosensitive layer 14 . The surface protective layer will be described in the <Surface protective layer> section.

<Conductive support 11>
The conductive support (also referred to as “conductive substrate” or “substrate”) 11 has a function as an electrode of a photoreceptor and a function as a support member, and its constituent material is a material used in the relevant technical field. is not particularly limited.
Specifically, metal materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, and titanium, and metal foil lamination, metal vapor deposition, or conductive compounds such as conductive polymers, tin oxide, and indium oxide on the surface. Examples include polymeric materials such as polyethylene terephthalate, nylon and polystyrene, hard paper and glass, with deposited or coated layers. Among these, aluminum is preferable from the viewpoint of ease of processing, and aluminum alloys such as JIS3003 series, JIS5000 series and JIS6000 series are particularly preferable.
The shape of the conductive support is not limited to a cylindrical shape (drum shape) as shown in FIG.
If necessary, the surface of the conductive support may be subjected to anodic oxide film treatment, surface treatment with chemicals or hot water, coloring, etc., in order to prevent interference fringes due to laser light within a range that does not affect image quality. It may be treated or subjected to irregular reflection treatment such as roughening of the surface.

<Undercoat layer 18>
The photoreceptor of the present invention preferably comprises an undercoat layer (also referred to as an “intermediate layer”) between the conductive support 11 and the laminated photosensitive layer 14 .
The undercoat layer generally covers the unevenness of the surface of the substrate and makes it uniform to improve the film-forming property of the laminated photosensitive layer, suppress the peeling of the photosensitive layer from the conductive support, and adhere the substrate and the photosensitive layer. improve sexuality. Specifically, it is possible to prevent the injection of charges from the substrate into the photosensitive layer, prevent deterioration of the chargeability of the photosensitive layer, and prevent image fogging (so-called black spots).
The undercoat layer is formed by, for example, dissolving or dispersing a binder resin in an appropriate solvent to prepare a coating solution for the undercoat layer, applying this coating solution to the surface of the substrate, and drying to remove the organic solvent. can do.

Examples of binder resins include acetal resins, polyamide resins, polyurethane resins, polyester resins, acrylic resins, epoxy resins, phenol resins, melanin resins, and urethane resins. The binder resin should not dissolve or swell in the solvent used to form the photoreceptor layer on the undercoat layer, should have excellent adhesion to the conductive support, and should have flexibility. Among the above binder resins, polyamide resins are preferred, and polyamide resins containing alcohol-soluble nylon resins and piperazine compounds are particularly preferred.
Examples of alcohol-soluble nylon resins include homopolymeric or copolymeric nylons such as 6-nylon, 66-nylon, 610-nylon, 11-nylon and 12-nylon, and N-alkoxymethyl-modified nylon. specifically denatured type.
Alternatively, a cured film may be formed by using a curing agent that crosslinks the binder resin. As the curing agent, blocked isocyanate is preferable from the viewpoint of the storage stability and electrical properties of the coating liquid.

Examples of solvents include water, lower alcohols such as methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, 2-butanol and isobutanol, ketones such as acetone, cyclohexanone and 2-butanone, tetrahydrofuran, Examples include ethers such as dioxane, ethylene glycol and diethyl ether, and halogenated hydrocarbons such as methylene chloride and ethylene chloride. An appropriate solvent is selected from these solvents based on the solubility of the binder resin, the surface smoothness of the undercoat layer, and the like, and can be used alone or in combination of two or more.
Among these solvents, for example, non-halogenated organic solvents can be preferably used in consideration of the global environment.

The undercoat layer coating liquid may contain metal oxide particles. The metal oxide particles can easily adjust the volume resistivity of the undercoat layer, can further suppress the injection of charges into the charge generation layer, and maintain the electrical properties of the photoreceptor under various environments. can do.
Materials that can be used for the metal oxide particles include, for example, titanium oxide, aluminum oxide, aluminum hydroxide and tin oxide.
The ratio (A/B) between the total mass A of the binder resin and the metal oxide particles and the mass B of the solvent in the undercoat layer coating liquid is, for example, preferably about 1/99 to 30/70, and 2/ About 98 to 40/60 is particularly preferred.
Further, the ratio (C/D) between the mass C of the binder resin and the mass D of the metal oxide particles is, for example, preferably about 90/10 to 1/99, particularly preferably about 70/30 to 5/95. .

As the coating method for the undercoat layer coating solution, an optimum method may be appropriately selected in consideration of the physical properties and productivity of the coating solution. ring method and dip coating method.
Among them, the dip coating method is a method of forming a layer on the surface of the substrate by dipping the substrate in a coating tank filled with a coating solution and then lifting the substrate at a constant speed or a speed that varies sequentially. Since it is simple and excellent in terms of productivity and cost, it can be suitably used in the production of photoreceptors. The apparatus used for the dip coating method may be provided with a coating liquid dispersion device, typically an ultrasonic generator, in order to stabilize the dispersibility of the coating liquid.

Although the solvent in the coating film may be removed by natural drying, 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 it can remove the solvent used.
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. On the other hand, if the drying temperature exceeds about 140° C., the electrical properties of the photoreceptor may deteriorate during repeated use, resulting in deterioration of the resulting image.
Such temperature conditions are common not only to the formation of the undercoat layer, but also to the formation of layers 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 0.01 to 20 μm, more preferably 0.05 to 10 μm.
If the thickness of the undercoat layer is less than 0.01 μm, the effect of blocking injection of electrons from the conductive substrate side and sufficient effect against interference fringes due to light scattering may not be obtained. On the other hand, if the thickness of the undercoat layer exceeds 20 μm, the change in sensitivity during continuous printing may become large, resulting in a large change in image density.

<Charge generating layer 15>
The charge generation layer 15 has a function of generating charges by absorbing light irradiated by a light emitting device such as a light beam such as a semiconductor laser in an electrophotographic apparatus such as an image forming apparatus. is the main component, and if necessary, it contains a binder resin and additives.

As the charge-generating substance, compounds used in the art can be used, and specific examples include azo pigments such as monoazo pigments, bisazo pigments and trisazo pigments; indigo pigments such as indigo and thioindigo; peryleneimide and perylene. perylene pigments such as acid anhydrides; polycyclic quinone pigments such as anthraquinone and pyrenequinone; phthalocyanine pigments such as metal phthalocyanines such as titanyl phthalocyanine and metal-free phthalocyanines; squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes 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 singly or in combination of two or more.
Among these charge-generating substances, the following general formula (a):

(Wherein, X ¹ , X ² , X ³ and X ⁴ are the same or different and represent a halogen atom, an alkyl group or an alkoxy group; r, s, y and z are the same or different and represent 0 to 4 integer)
It is preferable to use titanyl phthalocyanine represented by.
Titanyl phthalocyanine is a charge-generating substance that has high charge-generating efficiency and charge-injection efficiency in the emission wavelength region (near-infrared light) of laser light and LED light, which are generally used at present, and absorbs light. Therefore, it is possible to generate a large amount of charge and efficiently inject the generated charge into the charge transport material without accumulating it inside.

The titanyl phthalocyanine represented by the general formula (a) can be prepared 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 be manufactured.
For example, among the titanyl phthalocyanine compounds represented by the general formula (a), in the case of an unsubstituted titanyl phthalocyanine in which r, s, y and z are 0, phthalonitrile and titanium tetrachloride are heated and melted. Alternatively, it can be obtained by synthesizing dichlorotitanylphthalocyanine by subjecting it to heat reaction in a suitable solvent such as α-chloronaphthalene, followed by hydrolysis with a base or water.
A titanyl phthalocyanine composition can also be produced by reacting isoindoline and a titanium tetraalkoxide such as tetrabutoxytitanium by heating in a suitable solvent such as N-methylpyrrolidone.

Methods for forming the charge generation layer include a method of vacuum vapor deposition of a charge generation substance on a conductive support, and a method of applying a charge generation layer coating liquid obtained by dispersing a charge generation substance in a solvent onto a conductive support. There are other methods of coating. Among these methods, a method of dispersing a charge-generating substance in a binder resin solution obtained by mixing a binder resin in a solvent by a conventionally known method and applying the charge-generating layer coating liquid onto the conductive substrate is a method. preferable. This method will be described below.

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

Solvents include, for example, 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 singly or in combination of two or more.

As for the blending ratio of the charge-generating substance and the binder resin, the charge-generating substance ratio is preferably in the range of 10 to 99% by mass.
If the proportion of the charge-generating substance is less than 10% by mass, the sensitivity may decrease. On the other hand, when the ratio of the charge-generating substance exceeds 99% by mass, not only does the film strength of the charge-generating layer decrease, but also the dispersibility of the charge-generating substance decreases, resulting in an increase in coarse particles, which should be erased by exposure. A decrease in the surface charge in areas other than the portion may often cause image defects, particularly image fogging called black spots, in which fine black spots are formed due to toner adhering to the white background.

Prior to dispersing the charge-generating substance in the binder resin solution, the charge-generating substance may be pulverized in advance using a pulverizer. Pulverizers used for pulverization include ball mills, sand mills, attritors, vibration mills, and ultrasonic dispersers.
A paint shaker, a ball mill, a sand mill, or the like can be used as a dispersing machine for dispersing the charge-generating substance in the binder resin solution. As the dispersing conditions at this time, appropriate conditions may be selected so as not to cause contamination by impurities due to abrasion of the members constituting the container and dispersing machine used.
As a method for applying the charge generation layer coating liquid, the same method as the method for applying the undercoat layer coating liquid can be used, and dip coating 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 be lowered, and the sensitivity of the photoreceptor may be lowered. On the other hand, when the thickness of the charge generation layer exceeds 5 μm, the charge transfer inside the charge generation layer becomes the rate-limiting step in the process of erasing the charge on the surface of the laminated photosensitive layer, and the sensitivity of the photoreceptor may be lowered.

<Charge transport layer 16>
The charge transport layer 16 has a function of accepting the charge generated by the charge generating material and transporting it to the surface of the photoreceptor, and contains the charge transport material, binder resin, light absorber, silica filler, and additives as necessary. do.
In the photoreceptor of the present invention, it is essential that the photoabsorber be contained in both or one of the charge transport layer and the surface protective layer. If so, the light absorber is an essential component of the charge transport layer, while the light absorber is an optional component of the charge transport layer when the photoreceptor has a surface protective layer containing the light absorber. .
In addition, in the photoreceptor of the present invention, it is essential that the silica filler be contained in the outermost surface layer of the photoreceptor. It is an optional component of the transport layer, while the silica filler becomes an essential component of the charge transport layer when the photoreceptor does not have a surface protective layer.

As the charge-transporting substance, compounds used in this 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 , butadiene derivatives, enamine derivatives, benzidine derivatives, polymers (poly-N-vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole-formaldehyde resin, triphenylmethane polymer, poly-9-vinylanthracene, etc.), polysilane, and the like. These charge transport substances can be used singly or in combination of two or more.

Among these various charge-transporting materials, stilbene derivatives, butadiene derivatives, enamine derivatives, and combinations of a plurality of these compounds are preferred in terms of electrical properties, durability, and chemical stability. A stilbene derivative is more preferable because it absorbs light and has a wide range of absorption as a charge transport substance, and has the following general formula (I):

(wherein R ₁ , R ₂ , R ₅ and R ₆ are the same or different and are an alkyl group, an alkoxy group, an aryl group or an aralkyl group; m, n, p and q are the same or different; an integer of 0 to 3, and R ₃ and R ₄ are the same or different and are a hydrogen atom or an alkyl group.)
A stilbene compound represented by is particularly preferable in that it causes less increase in residual potential and deterioration in sensitivity, and can exhibit good electrophotographic properties.

The substituents R ₁ , R ₂ , R ₅ and R ₆ in general formula (I) are explained.
Examples of alkyl groups include alkyl groups having 1 to 6 carbon atoms such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl and n-hexyl. be done.
Examples of alkoxy groups include alkoxy groups having 1 to 6 carbon atoms such as methoxy, ethoxy, n-propoxy, isopropoxy, tert-butoxy, n-pentyloxy and n-hexyloxy.
Aryl groups include, for example, phenyl, naphthyl, anthryl, phenanthryl, fluorenyl, biphenylyl, o-terphenyl, and the like.
Aralkyl groups include, for example, benzyl, phenethyl, benzhydryl, trityl and the like.
Halogen atoms include fluorine, chlorine, bromine, and iodine.

m, n, p and q indicating indices of substituents R ₁ , R ₂ , R ₅ and R ₆ are the same or different and are integers of 0 to 3, and when this index is 2 or more, each substituent can be different from each other.
Examples of alkyl groups for substituents R ₃ and R ₄ in general formula (I) include alkyl groups having 1 to 3 carbon atoms such as methyl, ethyl, n-propyl and isopropyl.
The stilbene compound represented by general formula (I) can be synthesized, for example, by the method described in Japanese Patent No. 3272257.

Examples of the stilbene compound represented by the general formula (I) include the following compounds (1) to (3), and compound (1) is particularly preferred from the standpoint of printing durability when formed into a laminated photosensitive layer. preferable.

The charge transport layer is formed by dispersing a charge transport material in a binder resin solution obtained by mixing a binder resin in a solvent by 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 described below.

The binder resin is not particularly limited, and resins having binding properties used in the relevant technical field can be used, and those having excellent compatibility with the charge-transporting substance are preferable.
Specifically, polymethyl methacrylate, polystyrene, polyvinyl chloride and other vinyl polymer resins and copolymer resins thereof, polycarbonate, polyester, polyester carbonate, polysulfone, phenoxy resin, epoxy resin, silicone resin, polyarylate, Resins such as polyamides, polyethers, polyurethanes, polyacrylamides, phenolic resins, and polyphenylene oxides, and thermosetting resins obtained by partially cross-linking these resins can be used. These binder resins can be used singly or in combination of two or more.
Among these, polystyrene, polycarbonate, polyarylate and polyphenylene oxide are preferable because they have a volume resistivity of 10 ¹³ Ω or more and are excellent in electrical insulation, and are also excellent in film formability, potential characteristics, etc. Polycarbonate and polyarylate is more preferred, and polycarbonate is particularly preferred.

Solvents include, for example, aromatic hydrocarbons such as benzene, toluene, xylene and monochlorobenzene; halogenated hydrocarbons such as dichloromethane and dichloroethane; ethers such as tetrahydrofuran, dioxane and dimethoxymethyl ether; Examples include aprotic polar solvents such as dimethylformamide. In addition, a solvent such as alcohols, acetonitrile or methyl ethyl ketone can be further added and used as necessary. These solvents can be used singly or in combination of two or more.
Among these solvents, for example, non-halogenated organic solvents can be preferably used in consideration of the global environment.
The ratio (G/H) between the mass G of the charge transport material and the mass H of the binder resin is preferably, for example, about 10/12 to 10/30.

Although the film thickness of the charge transport layer is not particularly limited, it is preferably about 20 to 40 μm, more preferably about 25 to 40 μm.
If the film thickness of the charge transport layer is less than 20 μm, the effect on light resistance may not be sufficiently obtained. On the other hand, if the film thickness of the charge transport layer exceeds 40 μm, the electrical properties may deteriorate.

<Surface protective layer (not shown in FIG. 1)>
The photoreceptor 1 of the present invention may have a surface protective layer on the photosensitive layer 14 .
The surface protective layer has a function of improving the durability of the photoreceptor and contains a binder resin, a light absorbing agent, a silica filler and, if necessary, additives.
In the photoreceptor of the present invention, it is essential that the photoabsorber be contained in both or one of the charge transport layer and the surface protective layer. If so, the light absorber is an essential component of the surface protective layer, while the light absorber is an optional component of the surface protective layer when the photoreceptor has a charge transport layer containing a light absorber. .
In addition, in the photoreceptor of the present invention, it is essential that the silica filler be contained in the outermost surface layer of the photoreceptor, and when the photoreceptor has a surface protective layer, the silica filler is an essential component of the surface protective layer. become.
In addition, the protective layer may contain one or more of the same charge-transporting substances as the charge-transporting layer for stabilizing electrical properties.
Examples of the binder resin include the binder resins exemplified for the charge transport layer, and among these, polycarbonate and polyarylate are particularly preferable in consideration of wear characteristics and electrical characteristics.
The light absorber and silica filler are the same as those for the charge transport layer.

Although the film thickness of the protective layer is not particularly limited, it is preferably about 3 to 7 μm, more preferably about 4 to 6 μm.
If the film thickness of the protective layer is less than 3 μm, sufficient effects on durability and light resistance may not be obtained. On the other hand, if the film thickness of the protective layer exceeds 7 μm, the electrical properties may deteriorate.

(2) Process Cartridge The process cartridge of the present invention comprises the photoreceptor of the present invention, charging means for charging the photoreceptor, developing means for developing an electrostatic latent image formed by exposure to form a toner image, and the and at least one selected from cleaning means for removing toner remaining on the electrophotographic photosensitive member.

For example, the process cartridge of the present invention is constructed by integrating the photoreceptor, charging device, developing device and cleaning device of the present invention with a support member. By incorporating such a process cartridge into the image forming apparatus 100 , the image forming apparatus 100 is provided with the components of the process cartridge.
Since the process cartridge is detachable from the image forming apparatus 100, it is easy to replace it when it is exhausted.

(3) Image forming apparatus 100
The image forming apparatus of the present invention comprises the photoreceptor of the present invention, a charging means for charging the photoreceptor, an exposure means for exposing the charged photoreceptor to form an electrostatic latent image, and an electrostatic latent image formed by exposure. Developing means for developing an electrostatic latent image to form (visualize) a toner image, transferring means for transferring the toner image formed by development onto a recording medium, and transferring the transferred toner image onto the recording medium. fixing means for forming an image by fixing to the surface, cleaning means for removing and recovering toner remaining on the photoreceptor, and static elimination means for eliminating surface charges remaining on the photoreceptor.
The image forming apparatus of the present invention and its operation will be described below with reference to the drawings, but the present invention is not limited to the following description.

FIG. 2 is a schematic side view showing the configuration of the main part of the image forming apparatus 100 of the invention.
The image forming apparatus (laser printer) 100 shown in FIG. It includes means (developer) 33 , transfer means (transfer charger) 34 , transport belt (not shown), fixing means (fixer) 35 , and cleaning means (cleaner) 36 . Reference numeral 51 denotes a recording medium (recording paper or transfer paper).

Photoreceptor 1 is rotatably supported by the main body of image forming apparatus 100 and driven to rotate in the direction of arrow 41 about rotation axis 44 by driving means (not shown). The driving means includes, for example, an electric motor and a reduction gear, and transmits its driving force to the conductive support constituting the core of the photoreceptor 1, thereby rotationally driving the photoreceptor 1 at a predetermined peripheral speed. . Charging means (charger) 32, exposure means 31, developing means (developer) 33, transfer means (transfer charger) 34, and cleaning means (cleaner) 36 are arranged along the outer peripheral surface of the photoreceptor 1 in this order. , from the upstream side to the downstream side in the rotational direction of the photoreceptor 1 indicated by an arrow 41 .

The charger 32 is charging means for uniformly charging the outer peripheral surface of the photoreceptor 1 (corresponding to the photoreceptor F01 in FIG. 2) to a predetermined potential. The charging means includes, for example, a non-contact charging system such as a corona charging system using a charging charger, and a contact charging system using a charging roller or charging brush.
The exposure unit 31 has a semiconductor laser as a light source, and irradiates the surface of the photoreceptor 1 between the charging device 32 and the developing device 33 with a laser beam emitted from the light source, thereby charging the photoreceptor 1 . is exposed to light according to image information. The light is repeatedly scanned in the direction in which the rotation axis 44 of the photoreceptor 1 extends, which is the main scanning direction. That is, the charging amount of the photoreceptor 1 uniformly charged by the charger 32 differs depending on whether the laser beam is irradiated or not, thereby forming an electrostatic latent image.

The developing device 33 is developing means for developing an electrostatic latent image formed on the surface of the photoreceptor 1 by exposure with a developer (toner). and a casing 33b which supports the developing roller 33a rotatably about a rotation axis parallel to the rotation axis 44 of the photoreceptor 1 and accommodates developer containing toner in its internal space. Prepare.

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

The cleaner 36 is a cleaning means for removing and recovering toner remaining on the outer peripheral surface of the photoreceptor 1 after the transfer operation by the transfer charger 34. A cleaning blade 36a for removing the toner remaining on the outer peripheral surface of the photoreceptor 1; and a collection casing 36b for containing the toner peeled off by the cleaning blade 36a. Also, 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 as fixing means for fixing the transferred image on the downstream side to which the transfer paper 51 that has passed between the photoreceptor 1 and the transfer charger 34 is conveyed. be done. The fixing device 35 includes a heating roller 35a having a heating means (not shown), and a pressure roller 35b provided opposite to the heating roller 35a and pressed against the heating roller 35a to form a contact portion.
Reference numeral 37 denotes separating means for separating the transfer paper and the photoreceptor, and reference numeral 38 denotes a housing for housing the above-mentioned means of the image forming apparatus.

An 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 drive means, the photoreceptor 1 is rotated by the charger 32 provided on the upstream side in the rotation direction of the photoreceptor 1 with respect to the imaging point of the light by the exposure means 31 . 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. This exposure removes the surface charge of the light-irradiated portion of the photoreceptor 1, causing a difference between the surface potential of the light-irradiated portion and the non-light-irradiated portion. 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 rotation direction of the photoreceptor 1 with respect to the image forming point of the light by the exposing means 33 to form the electrostatic latent image. 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 . A transfer charger 34 applies a charge of 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 onto which the toner image has been transferred is conveyed to the fixing device 35 by the conveying means, and is heated and pressurized when passing through the abutting portion between the heating roller 35a and the pressure roller 35b of the fixing device 35. The image is fixed on the transfer paper 51 and becomes a strong image. The transfer paper 51 on which the image has been formed in this way is discharged to the outside of the image forming apparatus 100 by the conveying means.

On the other hand, the toner remaining on the surface of the photoreceptor 1 after the transfer of the toner image by the transfer charger 34 is removed 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 charge removing 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 are repeated to continuously form images.

The image forming apparatus 100 described above is a monochrome image forming apparatus (printer), but may be, for example, an intermediate transfer type color image forming apparatus capable of forming a color image. Specifically, even if a so-called tandem type full-color image forming apparatus has a configuration in which a plurality of electrophotographic photosensitive members on which toner images are respectively formed are arranged side by side in a predetermined direction (for example, the horizontal direction H or substantially the horizontal direction H). good. Also, the image forming apparatus 100 may be another color image forming apparatus, copier, multifunction machine, or facsimile machine.

EXAMPLES The present invention will be specifically described below by way of examples and comparative examples based on the drawings, but the present invention is not limited by these examples.

(Example 1)
(Formation of undercoat layer)
Titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., product name: Tybake TTO-D-1) 3 parts by mass and copolymerized polyamide (nylon) (manufactured by Toray Industries, Inc., product name: Amilan (registered trademark), grade: CM8000) 2 mass was added to 25 parts by mass of methyl alcohol and dispersed for 8 hours using a paint shaker to prepare 3 liters of a coating solution for an undercoat layer.
A coating tank is filled with the resulting undercoat layer coating liquid, and an aluminum drum-shaped support having a diameter of 30 mm and a length of 255 mm is immersed as the conductive support 11 and pulled out, and the obtained coating is allowed to dry naturally. Then, an undercoat layer 18 having a thickness of 1 μm was formed on the conductive support 11 .

(Formation of charge generation layer)
A titanyl phthalocyanine represented by the following structural formula was prepared in advance to be used as a charge-generating substance.

29.2 g of diiminoisoindoline and 200 ml of sulfolane were mixed, 17.0 g of titanium tetraisopropoxide was added, and the mixture was reacted at 140° C. for 2 hours under nitrogen atmosphere. After allowing the resulting reaction mixture to cool, the precipitate was collected by filtration, washed successively with chloroform and 2% aqueous hydrochloric acid, and further washed successively with water and methanol, and dried to give 25.5 g of bluish purple crystals. got
As a result of chemical analysis of the obtained compound, it was confirmed to be titanyl phthalocyanine represented by the above structural formula (yield 88.5%).

1 part by mass of the obtained titanyl phthalocyanine and 1 part by mass of butyral resin (manufactured by Sekisui Chemical Co., Ltd., product name: S-Lec BM-2) are added to 98 parts by mass of methyl ethyl ketone, and dispersed for 2 hours in a paint shaker to generate charge. Three liters of layer coating solution was prepared.
The charge generation layer coating liquid thus obtained was applied onto the undercoat layer 18 by the same dipping method as in the formation of the undercoat layer, and the resulting coating film was allowed to dry naturally to form a coating film having a thickness of 0.3 μm. A charge generation layer 15 was formed.

(Formation of charge transport layer)
Next, 70.0 g of silica particles (number average primary particle size 16 nm, dimethyldichlorosilane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972) are added to 390 g of tetrahydrofuran, suspended and mixed, and the diameter 2 mm glass beads (162 g, about 20% by volume of the mixed solution) were added, stirred for 15 hours in a ball mill, and then the glass beads were removed. The resulting silica filler suspension was defoamed for 10 minutes using a rotation/revolution mixer (Awatori Mixer, atmospheric pressure type, model: ARE-310, manufactured by THINKY Co., Ltd.).

Next, 250 g of stilbene compound (1) as a charge-transporting substance, 375 g of polycarbonate (manufactured by Teijin Chemicals Ltd., product name: TS2050), and perimidine compound (A) (C.I.) as a light absorber were added to the obtained silica filler suspension. I. Solvent Red 179 (manufactured by American Dyestuff, product name: Amesolve Red A) (1.75 g) and 2400 g of tetrahydrofuran were added and stirred for 30 hours in a ball mill. The resulting mixture was subjected to 6-pass dispersion treatment using a particle dispersing device (manufactured by Microfluidics, model: Microfluidizer M110P). The resulting mixed solution was allowed to stand at a temperature of 20° C. for one week to prepare 3207 g of a charge transport layer coating solution.
The resulting charge transport layer coating liquid is applied onto the charge generation layer 15 by the same dipping method as in the formation of the undercoat layer, and the resulting coating film is dried at 120° C. for 1 hour to form a film. A charge transport layer having a thickness of 30 μm was formed to obtain the photoreceptor 1 shown in FIG.
A stilbene compound (1) prepared in advance according to the method described in Japanese Patent No. 3272257 was used as the charge transport material.

(Example 2)
In the preparation of the charge transport layer coating liquid, instead of silica particles (number average primary particle diameter 16 nm, dimethyldichlorosilane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972), silica particles (number Photosensitized Example 2 in the same manner as in Example 1, except for using an average primary particle size of 16 nm, dimethyldichlorosilane surface treatment, product name: AEROSIL (registered trademark) ADMAFINE NX-130 manufactured by Nippon Aerosil Co., Ltd. Body 1 was produced.

(Example 3)
Photoreceptor 1 of Example 3 was produced in the same manner as in Example 1, except that in the formation of the charge transport layer, the coating time was adjusted so that the film thickness of the charge transport layer was changed from 30 μm to 28 μm.

(Example 4)
Except for using an azoquinone compound (B) (manufactured by Hodogaya Chemical Industry Co., Ltd., product name: EAC-39) as a light absorber in place of the perimidine compound (A) in the preparation of the charge transport layer coating solution, Photoreceptor 1 of Example 4 was produced in the same manner as in Example 1.

(Example 5)
In the preparation of the charge transport layer coating liquid, instead of silica particles (number average primary particle diameter 16 nm, dimethyldichlorosilane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) R972), silica particles (number Photoreceptor 1 of Example 5 was prepared in the same manner as in Example 1, except that an average primary particle size of 40 nm, a hexamethyldisilazane surface treatment, manufactured by Nippon Aerosil Co., Ltd., product name: AEROSIL (registered trademark) RX50) was used. made.

(Example 6)
70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 40.0 g and 220 g, respectively, in the preparation of the silica filler suspension of the coating liquid for the charge transport layer, and the perimidine compound (A ) and 2400 g of tetrahydrofuran were changed to 1.70 g and 2450 g, respectively.

(Example 7)
In the preparation of the silica filler suspension of the charge transport layer coating liquid, 70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 47.0 g and 260 g, respectively. ) and 2400 g of tetrahydrofuran were changed to 1.70 g and 2435 g, respectively.

(Example 8)
70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 138 g and 765 g, respectively, in the preparation of the silica filler suspension of the charge-transporting layer coating liquid; Photoreceptor 1 of Example 8 was prepared in the same manner as in Example 1 except that 0.75 g and 2400 g of tetrahydrofuran were changed to 1.90 g and 2295 g, respectively.

(Example 9)
70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 147 g and 815 g, respectively, in the preparation of the silica filler suspension of the coating liquid for the charge transport layer. Photoreceptor 1 of Example 9 was produced in the same manner as in Example 1 except that 0.75 g and 2400 g of tetrahydrofuran were changed to 1.90 g and 2280 g, respectively.

(Examples 10-13)
Examples 10 to 13 were prepared in the same manner as in Example 1, except that in the formation of the charge transport layer, the coating time was adjusted so that the film thickness of the charge transport layer of 30 μm was 18 μm, 20 μm, 40 μm and 42 μm. Photoreceptor 1 was produced.

(Comparative example 1)
Photoreceptor 1 of Comparative Example 1 was prepared in the same manner as in Example 1, except that the perimidine compound (A) was not used as the light absorber in the preparation of the charge transport layer coating liquid.

(Comparative example 2)
Comparative Example 2 was prepared in the same manner as in Example 1, except that 1.75 g of the perimidine compound (A) and 2,400 g of tetrahydrofuran as light absorbers were changed to 1.55 g and 2,500 g, respectively, in the preparation of the charge transport layer coating liquid. Photoreceptor 1 was produced.

(Comparative Example 3)
70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 111 g and 615 g, respectively, in the preparation of the silica filler suspension of the charge-transporting layer coating liquid; Photoreceptor 1 of Comparative Example 3 was prepared in the same manner as in Example 1 except that 0.75 g and 2400 g of tetrahydrofuran were changed to 3.70 g and 2350 g, respectively.

(Comparative Example 4)
70.0 g of silica particles and 390 g of tetrahydrofuran were changed to 157 g and 875 g, respectively, in the preparation of the silica filler suspension of the charge transport layer coating liquid; Photoreceptor 1 of Comparative Example 4 was prepared in the same manner as in Example 1 except that 0.75 g and 2400 g of tetrahydrofuran were changed to 4.35 g and 2270 g, respectively.
Table 1 shows the main constituent materials of the charge transport layer, their contents, and the film thicknesses of the photoreceptors 1 of Examples 1 to 13 and Comparative Examples 1 to 4.

[evaluation]
Photoreceptors 1 produced in Examples 1 to 13 and Comparative Examples 1 to 4 were evaluated on the following items.
In evaluations 2 and 3, each photoreceptor 1 was attached to a unit of a digital copying machine (manufactured by Sharp Corporation, model: MX-B455W) modified for testing.

[Evaluation 1: Transmittance]
Using an ultraviolet-visible spectrophotometer (manufactured by Shimadzu Corporation, model: UV-2450), in an environment of temperature 20° C. and relative humidity 50%, the wavelength of the charge transport layer, which is the outermost layer of each photoreceptor 1. Transmittances T ₅₅₀ (%) and T ₆₀₀ (%) for light of 550 nm and 600 nm were measured, and the ratio T ₆₀₀ /T ₅₅₀ was calculated.

[Evaluation 2: Electrical characteristics (sensitivity)]
Remove the developer from the digital copier, attach a surface potential meter (manufactured by Trek Japan, model: model 344) to the development site instead, and perform actual aging of paper in an environment of 25°C temperature and 50% relative humidity. 5000 sheets, and the residual potential Vr (-V) of the photoreceptor surface after static elimination immediately after aging was measured.
The obtained results were evaluated according to the following criteria.
<Evaluation Criteria>
VG: Vr<40
Can be used without problems in high-speed multifunction devices or printers that require high sensitivity G: 40≤Vr<60
Can be used without problems in mid-to-low speed MFPs or printers NB: 60≤Vr<100
If it is a low-speed and inexpensive multifunction device or printer, it can be used without problems, although the density is slightly low. B: 100 ≤ Vr
Due to poor sensitivity, the density is low, which poses a problem in actual use.

[Evaluation 3: light exposure]
The photoreceptor surface was masked with black paper except for a part, and the unmasked part was irradiated with light from a white fluorescent lamp whose illuminance was adjusted to 400 Lux for 5 minutes, then allowed to stand for 5 minutes, and a halftone image was printed on A4 paper. One sheet was output and the resulting image was visually observed.
The obtained results were evaluated according to the following criteria.
<Evaluation Criteria>
VG: No difference between irradiated and non-irradiated parts G: Slight difference between irradiated and non-irradiated parts, but no big difference NB: Slight difference between irradiated and non-irradiated parts (problem in actual use) none)
B: Large difference between irradiated and non-irradiated areas (problem in practical use)

[comprehensive evaluation]
Based on the evaluation results of evaluations 2 and 3, a comprehensive evaluation was made according to the following criteria.
In the comprehensive evaluation, in VG, G and NB, the transmittance T ₆₀₀ (%) for light with a wavelength of 600 nm in evaluation 1 is 50% or more, and the ratio of the transmittance T ₅₅₀ (%) for light with a wavelength of 550 nm It is essential that _T600 / _T550 be 1.10 or more and 2.20 or less.
VG: VG judgment in all items (very good)
G: Any item includes a G rating, but all items have a G rating or higher.
NB: NB judgment is included in any item, but NB judgment or higher in all items (can be used without problems if it is an inexpensive multifunction device or printer)
B: Any item was judged as B and practical use is not possible Table 2 shows the obtained evaluation results.

Tables 1 and 2 show the following.
(1) Photoreceptors containing both a light absorbing agent and a silica filler in the charge transport layer (Examples 1 to 13) were compared to a photoreceptor containing no light absorbing agent in the charge transport layer (Comparative Example 1), Compared to the photoreceptor (Comparative Example 2) containing no silica filler in the transport layer, the photoreceptor should have good electrical properties and excellent resistance to exposure to external light.

(2) In the charge transport layer, the transmittance for light with a wavelength of 600 nm is 50% or more, and the ratio T ₆₀₀ /T ₅₅₀ between the transmittance T ₆₀₀ for light with a wavelength of 600 nm and the transmittance T ₅₅₀ for light with a wavelength of 550 nm is Photoreceptors with a T 600 of 1.10 or more and 2.20 or less (Examples 1-13) performed better than photoreceptors with a T ₆₀₀ of less than 50% or a ratio of T ₆₀₀ /T ₅₅₀ of less than 2.20. It must have electrical properties and excellent resistance to exposure to external light.

(3) The transmittance T ₆₀₀ for light with a wavelength of 600 nm is preferably 60% or more from the results of Examples 2 and 3, and preferably 70% or more from the results of Example 1.

(4) From the results of Example 5, the average primary particle size of the silica filler contained in the outermost layer (charge transport layer) is preferably 30 nm or less. worsening

(5)) The content of the silica filler contained in the outermost surface layer (charge transport layer) is preferably 7 to 18% by mass from the results of Examples 6 to 9, and if it is less than 7% by mass, the effect on light resistance is not sufficient, and if it exceeds 18% by mass, the electrical properties will deteriorate.

(6) From the results of Examples 10 to 13, the film thickness of the outermost surface layer (charge transport layer) is preferably 20 μm to 40 μm. If the film thickness is less than 20 μm, the effect on light resistance is not sufficient, and if it exceeds 40 μm, the electrical properties deteriorate.

1 electrophotographic photoreceptor (laminated electrophotographic photoreceptor)
REFERENCE SIGNS LIST 11 conductive support 12 charge-generating substance 13 charge-transporting substance 14 photosensitive layer (laminated photosensitive layer)
REFERENCE SIGNS LIST 15 charge generation layer 16 charge transport layer 17 binder resin 18 undercoat layer 19 silica filler 20 light absorber

31 exposure means (semiconductor laser)
32 charging means (charger)
33 developing means (developer)
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 collecting casing 37 separating means 38 housing 41, 42 arrow 44 rotation axis 51 recording medium (recording paper or transfer paper)
100 image forming apparatus (laser printer)

Claims (9)

At least a laminated photosensitive layer in which a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are laminated in this order on a conductive support, or the laminated photosensitive layer and An electrophotographic photoreceptor comprising at least a surface protective layer laminated thereon,
both or one of the charge transport layer and the surface protective layer contains a light absorbing agent,
The outermost layer of the electrophotographic photosensitive member contains a silica filler, has a transmittance of 50% or more for light with a wavelength of 600 nm, and has a transmittance T ₆₀₀ for light with a wavelength of 600 nm and a light with a wavelength of 550 nm. An electrophotographic photoreceptor, wherein a ratio _T600 / _T550 to a transmittance T550 is 1.10 or more and 2.20 or _less . 2. The electrophotographic photoreceptor according to claim 1, wherein the ratio _T600 / _T550 is from 1.10 to 1.50. 3. The electrophotographic photoreceptor according to claim 1, wherein the light absorbing agent is a compound having spectral absorption at a wavelength of 400-700 nm. The light absorber has the following structural formula (A):

A perimidine compound represented by the following structural formula (B):

and an azoquinone compound represented by the following structural formula (C):

4. The electrophotographic photoreceptor according to any one of claims 1 to 3, which is selected from pyrazolone compounds represented by: 5. The electrophotographic photoreceptor according to claim 1, wherein the silica filler has an average primary particle size of 30 nm or less. 6. The electrophotographic photoreceptor according to any one of claims 1 to 5, wherein the silica filler is contained in a proportion of 7 to 18% by mass with respect to the total solid content of the outermost layer of the electrophotographic photoreceptor. 7. The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer has a thickness of 20 μm or more and 40 μm or less. 8. The electrophotographic photoreceptor according to claim 1, charging means for charging the electrophotographic photoreceptor, and developing means for developing an electrostatic latent image formed by exposure to form a toner image. and at least one cleaning means for removing toner remaining on the electrophotographic photosensitive member. The electrophotographic photoreceptor according to any one of claims 1 to 7, charging means for charging the electrophotographic photoreceptor, and exposing the charged electrophotographic photoreceptor to form an electrostatic latent image. exposure means; developing means for developing the electrostatic latent image formed by exposure to form a toner image; transfer means for transferring the toner image formed by development onto a recording medium; fixing means for fixing a toner image on the recording medium to form an image; cleaning means for removing and collecting toner remaining on the electrophotographic photosensitive member; and removing surface charges remaining on the electrophotographic photosensitive member. An image forming apparatus comprising at least a charge eliminating means.

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