JP2010286707A - Electrophotographic photoreceptor, electrophotographic cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which includes a photosensitive layer containing a charge generating material and a charge transport material in one and the same layer, excels in charge retaining ability, substantially avoids reduction of surface potential when used in repeated image formation, and is able to obtain proper images which are free of the occurrence of image memory, and to provide an electrophotographic cartridge and an image forming apparatus, each of which includes the electrophotographic photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor is such that in an electrophotographic photoreceptor which has on a conductive support a photosensitive layer, containing a charge generating material and a charge transport material in one and the same layer, a protective layer is disposed on the photosensitive layer and the volume resistivity of the protective layer is smaller than that of the photosensitive layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member. More specifically, the present invention relates to an electrophotographic photosensitive member having a single-layer type photosensitive layer containing at least a charge generating substance and a charge transporting substance, and an electrophotographic cartridge or an image forming apparatus including the electrophotographic photosensitive member. is there.

In recent years, research on using organic photoconductive materials for the photosensitive layer of electrophotographic photoreceptors has progressed, and some of them have been put into practical use. The organic photoconductive substance is lighter than the inorganic photoconductive substance, is easy to form a film, and is easy to produce a photoconductor. Depending on the type, a transparent photoconductor can be produced. It has many advantages such as non-polluting material.
In particular, since an electrophotographic photosensitive member (so-called function-separated type electrophotographic photosensitive member) in which functions such as generation and movement of charge carriers are assigned to different organic photoconductive substances is effective for high sensitivity, It has become mainstream in recent years. Several layer configurations have been devised for the photosensitive layer of such a function-separated electrophotographic photosensitive member. Among them, a charge generation layer and a charge transport layer are laminated to separate the functions of charge generation and charge transport, a so-called laminated photosensitive layer, and a so-called layer-containing photosensitive layer containing a charge generation material and a charge transport material in the same layer. A single-layer type photosensitive layer (see, for example, Patent Documents 1 to 5) is generally used.

  An example of an image recording method in an image forming apparatus using such an electrophotographic photosensitive member will be described with reference to FIG. The electrophotographic photoreceptor 1 is rotationally driven at a predetermined peripheral speed around a predetermined axis (not shown). In the rotation process of the electrophotographic photoreceptor 1, the surface (photosensitive layer) of the electrophotographic photoreceptor 1 is charged to a predetermined positive or negative potential (for example, −600 V) by the charging unit 2. Subsequently, the exposure light intensity-modulated in response to the time-series electric digital image signal of the target image information output from the image exposure means 3 is received. As a result, electrostatic latent images corresponding to target image information are sequentially formed on the surface (photosensitive layer) of the electrophotographic photoreceptor 1.

  The formed electrostatic latent image is then visualized as a transferable particle image (toner image) by regular development or reversal development with toner in the developing means 4. Specifically, the developing unit 4 thins the toner T supplied by the supply roller 43 by a regulating member (developing blade) 45 and has a predetermined polarity (here, the same polarity as the charging potential of the photoreceptor 1). And negatively charged), conveyed while being carried on the developing roller 44, and brought into contact with the surface of the electrophotographic photosensitive member 1. When the charged toner T carried on the developing roller 44 contacts the surface of the electrophotographic photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the electrophotographic photoreceptor 1.

  Thereafter, the electrophotographic photosensitive member 1 is transferred to the transfer target (recording paper) P fed from the paper feeding unit P between the electrophotographic photosensitive member 1 and the transfer means 5 in synchronization with the rotation of the electrophotographic photosensitive member 1. The toner images formed and supported on the surface of the toner are sequentially transferred by the transfer means 5. At this time, a bias voltage having a polarity opposite to the charge held in the toner is applied to the transfer means from a bias power source (not shown).

The transferred material (recording paper) P that has received the transfer of the toner image is separated from the surface of the electrophotographic photosensitive member 1 and conveyed to the fixing means 7, and undergoes a toner image fixing process to thereby form an image formed product (print, As a copy).
The surface of the electrophotographic photoreceptor 1 after the transfer of the toner image is cleaned by removing the deposits such as toner remaining after the transfer by the cleaning means 6. In recent years, a cleaner-less system has also been studied, and there are cases in which a transfer residual toner is directly collected by a developing device or the like.

JP-A-61-77054 JP-A 61-188543 JP-A-2-228670 Japanese Examined Patent Publication No. 7-97223 Japanese Examined Patent Publication No. 7-97225

Conventionally, when a single-layer type photosensitive layer containing a charge generation material or a charge transport material in the same layer is used as the electrophotographic photosensitive member, exposure light absorption and subsequent charge generation occur near the OPC surface. , Exposure light and electric charge are less scattered and diffused, resulting in higher resolution. Moreover, since it is a single layer structure, the production process can be simplified, which is preferable from an industrial viewpoint.
On the other hand, when this single-layer type photosensitive layer is used, the generation of image memory and the occurrence of fogging and black spots when repeatedly used for image formation have been problems. In particular, in order to suppress the generation of the image memory, it is important to suppress the decrease in the surface potential due to the increase in dark attenuation after repeated use. However, the prior art is not always satisfactory in terms of overcoming the above-described problems, and further improvements have been required.

  Therefore, in view of the above circumstances, the present invention has a photosensitive layer containing a charge generation material and a charge transport material in the same layer, has excellent charge holding ability, and lowers the surface potential when repeatedly used for image formation. It is an object to provide an electrophotographic photoreceptor capable of obtaining a good image free from image memory generation and free of fog and black spots, and an electrophotographic cartridge and an image forming apparatus having the electrophotographic photoreceptor. And

  The inventors of the present invention have made extensive studies on an electrophotographic photosensitive member that can satisfy the above-mentioned object. As a result, a protective layer having a predetermined volume resistivity in relation to the photosensitive layer is provided on the photosensitive layer to maintain the charge. The present inventors have found that it is possible to obtain a good image that is excellent in ability, has little decrease in surface potential when repeatedly used for image formation, and does not generate an image memory.

That is, the present inventors have found that the above problem is solved by the following <1> to <4> configurations.
<1> In an electrophotographic photosensitive member having a photosensitive layer containing a charge generating substance and a charge transporting substance in the same layer on a conductive support, a protective layer is provided on the photosensitive layer, and the volume resistance of the protective layer An electrophotographic photoreceptor, wherein the rate is smaller than the volume resistivity of the photosensitive layer.
<2> The electrophotographic photosensitive member according to <1>, wherein the protective layer has a volume resistivity of 10 ¹⁰ to 10 ¹⁵ (Ω · cm).
<3> An electrophotographic cartridge comprising the electrophotographic photosensitive member according to <1> or <2>.
<4> An image forming apparatus comprising the electrophotographic photosensitive member according to <1> or <2>.

  According to the present invention, there is provided an electrophotographic photosensitive member that is excellent in charge retention capability and has a small decrease in surface potential even when repeatedly used for image formation, and capable of forming a high-quality image, and the electrophotographic photosensitive member. An electrophotographic cartridge having a body and an image forming apparatus can be provided.

1 is a schematic diagram illustrating a configuration of a main part of an embodiment of a general image forming apparatus.

  Hereinafter, the present invention will be described in detail, but the present invention is not limited to the following description, and various modifications can be made within the scope of the gist of the present invention.

<Electrophotographic photoreceptor>
The electrophotographic photosensitive member of the present invention has a photosensitive layer containing a charge generating substance and a charge transporting substance in the same layer on a conductive support, a so-called single layer type photosensitive layer, on the photosensitive layer. It is characterized by having a protective layer having a predetermined volume resistivity.
According to the present invention, by providing a predetermined protective layer on the photosensitive layer, it is excellent in charging ability, suppresses a decrease in surface voltage when repeatedly used for image formation, and has a high definition in a desired pattern shape. An electrophotographic photosensitive member capable of image formation can be obtained.
Hereinafter, each part (conductive support, undercoat layer, photosensitive layer, protective layer) constituting the electrophotographic photoreceptor of the present invention will be described.

<Conductive support>
First, the conductive support used in the photoreceptor of the present invention will be described.
The conductive support is not particularly limited as long as it supports a photosensitive layer and a protective layer described later and exhibits conductivity. As the conductive support, for example, a metal material such as aluminum, aluminum alloy, stainless steel, copper, nickel, or a resin material imparted with conductivity by coexisting conductive powder such as metal, carbon, tin oxide, Mainly used are resin, glass, paper, etc., on which the conductive material such as aluminum, nickel, ITO (indium tin oxide alloy) is deposited or applied. As a form, a drum shape, a sheet shape, a belt shape, or the like is used. A conductive material having an appropriate resistance value may be coated on a conductive support made of a metal material for controlling conductivity, surface properties, etc., or for covering defects.

When a metal material such as an aluminum alloy is used as the conductive support, it may be used after an anodized film is applied to the metal material.
For example, an anodized film is formed on the surface of the metal material by anodizing the metal material in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, boric acid, sulfamic acid. In particular, anodization in sulfuric acid gives better results. In the case of anodization in sulfuric acid, the sulfuric acid concentration is usually 100 g / l or more and 300 g / l or less, the dissolved aluminum concentration is usually 2 g / l or more and 15 g / l or less, the liquid temperature is usually 15 ° C. or more, 30 ° C. or less, The electrolysis voltage is preferably set in the range of usually 10 V or more and 20 V or less, and the current density is usually set in the range of 0.5 A / dm ² or more and 2 A / dm ² or less, but is not limited to the above conditions.

  When an anodized film is applied to a metal material, it is preferable to perform a sealing treatment. The sealing treatment can be performed by a known method. For example, a low temperature sealing treatment in which the metal material is immersed in an aqueous solution containing nickel fluoride as a main component, or a high temperature sealing treatment in which the metal material is immersed in an aqueous solution containing nickel acetate as a main component is performed. It is preferable.

  The concentration of the aqueous nickel fluoride solution used in the case of the low-temperature sealing treatment can be selected as appropriate, but more preferable results are obtained when the aqueous solution concentration is in the range of 3 g / l or more and 6 g / l or less. Moreover, as processing temperature for advancing sealing processing smoothly, it is 25 degreeC or more, Preferably it is 30 degreeC or more. Moreover, it is 40 degrees C or less normally, Preferably it is 35 degrees C or less. Moreover, the pH of the nickel fluoride aqueous solution is usually 4.5 or more, preferably 5.5 or more, and the pH is usually 6.5 or less, preferably 6.0 or less.

As the pH adjuster, for example, oxalic acid, boric acid, formic acid, acetic acid, sodium hydroxide, sodium acetate, aqueous ammonia and the like can be used.
It is preferable that the treatment time is usually 1 minute or more and 3 minutes or less per 1 μm of film thickness. In order to further improve the physical properties of the film, cobalt fluoride, cobalt acetate, nickel sulfate, or a surfactant may be allowed to coexist in the nickel fluoride aqueous solution. Subsequently, it is washed with water and dried to finish the low temperature sealing treatment.

  Moreover, as a sealing agent in the case of the said high temperature sealing process, metal salt aqueous solution, such as nickel acetate, cobalt acetate, lead acetate, nickel acetate-cobalt, barium nitrate, can be used, but especially nickel acetate is used. It is preferable to use it. The concentration in the case of using an aqueous nickel acetate solution is usually preferably 5 g / l or more and 20 g / l or less. The treatment temperature at this time is 80 ° C. or higher, preferably 90 ° C. or higher, and 100 ° C. or lower, preferably 98 ° C. or lower. Furthermore, it is preferable that the pH of the nickel acetate aqueous solution is usually 5.0 or more and 6.0 or less.

  As a pH adjuster, ammonia water, sodium acetate, etc. can be used, for example. The treatment time is 10 minutes or longer, preferably 15 minutes or longer. In this case, in order to improve the film physical properties, for example, sodium acetate, an organic carboxylic acid, an anionic or nonionic surfactant or the like may be contained in the nickel acetate aqueous solution. Furthermore, you may process with high temperature water and high temperature steam which do not contain salt substantially. Subsequently, it is washed with water and dried to finish the high temperature sealing treatment.

  In addition, when the average film thickness of an anodic oxide film is thick, it is preferable to make it a strong sealing condition by increasing the concentration of the sealing liquid and by processing at a high temperature for a long time. However, if the sealing conditions are strong, productivity is reduced and surface defects such as spots, dirt, and dusting may occur on the coating surface. Therefore, the average film thickness of the anodized film is usually 20 μm or less, and particularly preferably 7 μm or less.

The surface of the conductive support may be smooth, or may be roughened by using a special cutting method or by performing a polishing treatment. Further, it may be roughened by mixing particles having an appropriate particle diameter with the material constituting the support.
In addition, an undercoat layer described later may be provided between the conductive support and the photosensitive layer in order to improve adhesion and blocking properties.

<Photosensitive layer>
Next, the photosensitive layer used in the electrophotographic photoreceptor of the present invention will be described in detail below.

[material]
First, materials used for the photosensitive layer will be described. The photosensitive layer used in the present invention is preferably composed of a single layer containing a charge transport material and a charge generation material, but may be a laminate of a plurality of layers having different constituent components or composition ratios. . Even in the latter case, it is called a single-layer type photosensitive layer because of the function of the material in the photosensitive layer. In this case, at least one of the layers constituting the photosensitive layer may contain the charge transport material and the charge generation material in the same layer.
Hereinafter, materials (charge generating substance, charge transporting substance, binder resin, etc.) used for the photosensitive layer will be described.

(Charge generating material)
Examples of charge generating materials used in the photosensitive layer include selenium and its alloys, cadmium sulfide, and other inorganic photoconductive materials; phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments. And various photoconductive materials such as organic pigments such as benzimidazole pigments. Among these, organic pigments are particularly preferable, and phthalocyanine pigments and azo pigments are more preferable.

  In particular, when a phthalocyanine pigment is used as a charge generation material, specifically, metal such as metal-free phthalocyanine, copper, indium, gallium, tin, titanium, zinc, vanadium, silicon, germanium, or an oxide or halide thereof. Coordinated phthalocyanines are used. Examples of the ligand to the trivalent or higher metal atom include a hydroxyl group and an alkoxy group in addition to the oxygen atom and chlorine atom shown above. Among them, particularly sensitive X-type, τ-type metal-free phthalocyanine, A-type, B-type, and D-type titanyl phthalocyanine, vanadyl phthalocyanine, chloroindium phthalocyanine, chlorogallium phthalocyanine, hydroxygallium phthalocyanine, and the like are preferable.

  Of the crystal forms of titanyl phthalocyanine mentioned here, A type and B type are described in W.W. It has been shown by Heller et al. As phase I and phase II, respectively (Zeit. Kristallogr. 159 (1982) 173), and type A is known as a stable type. The D type is a crystal type characterized by a clear peak at a diffraction angle 2θ ± 0.2 ° of 27.3 ° in powder X-ray diffraction using CuKα rays.

When an azo pigment is used, various known bisazo pigments and trisazo pigments are preferably used. Examples of preferred azo pigments are shown below. In the following formula, Cp ¹ to Cp ³ represent a coupler.

The couplers Cp ¹ to Cp ³ preferably have the following structures.

  Specific examples of the azo pigment include the following compounds.

  Among these, a compound represented by the following formula (1) is particularly preferable.

In formula (1), R ¹² represents an alkyl group having 1 to 20 carbon atoms in total. Z represents a group represented by the following formula (1A) or formula (1B). Ring X may have a substituent.

  Examples of the substituent that the ring X may have include, for example, a halogen atom such as a fluorine atom, an iodine atom, and a chlorine atom; a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, Examples thereof include alkyl groups such as n-hexyl group; alkoxy groups such as methoxy group, ethoxy group and n-propoxy group. Among these, a fluorine atom, a chlorine atom, and a methyl group are preferable. Among the compounds represented by the formula (1), a more preferable structure is a case where no substituent is present on the benzene ring represented by X, or the ring X has a methyl group as a substituent.

In Formula (1), the bonding position of the —OR ¹² group is arbitrary, but it is preferably bonded to the meta position with respect to the carbon atom to which the —CONH— group is bonded. As the alkyl group represented by R ¹² , the alkyl group moiety has 20 or less carbon atoms, more preferably 15 or less. Moreover, carbon number is 1 or more normally, Preferably it is 3 or more. The alkyl group moiety can be classified into a linear, branched, or cyclic structure depending on its structure, but it is preferable to have a branched or cyclic structure from the viewpoint of the characteristics of the electrophotographic photoreceptor, and a cycloalkyl structure in the alkyl group It is more preferable to have.

  Further, the charge generation materials may be used alone or in combination of two or more in any combination and ratio. Furthermore, when two or more kinds of charge generating materials are used in combination, the mixed state of the charge generating materials to be used together or the mixed state in the crystalline state may be used by mixing the respective constituent elements later, Alternatively, a mixed state may be generated and used in the charge generation material production / treatment process such as pigmentation or crystallization. As such treatment, acid paste treatment, grinding treatment, solvent treatment and the like are known.

In this case, it is desirable that the particle size of the charge generation material is sufficiently small. Specifically, it is usually preferably 1 μm or less, more preferably 0.5 μm or less.
Furthermore, if the amount of the charge generating material dispersed in the photosensitive layer is too small, there is a possibility that sufficient sensitivity cannot be obtained, and if it is too large, chargeability and sensitivity may be lowered. Therefore, the amount of the charge generating material in the photosensitive layer is usually preferably 0.1% by weight or more, more preferably 0.5% by weight or more, and usually preferably 50% by weight or less, more preferably 20% by weight or less. And

(Charge transport material)
In the photosensitive layer of the electrophotographic photoreceptor of the present invention, any known charge transport material can be used as a charge transport material, or two or more kinds can be used in any combination and ratio.
The charge transport material is not particularly limited, and any material can be used. Examples of known charge transport materials include electron-withdrawing materials such as aromatic nitro compounds such as 2,4,7-trinitrofluorenone, cyano compounds such as tetracyanoquinodimethane, and quinone compounds such as diphenoquinone, carbazole derivatives , Indole derivatives, imidazole derivatives, oxazole derivatives, pyrazole derivatives, thiadiazole derivatives, benzofuran derivatives and other heterocyclic compounds, aniline derivatives, hydrazone derivatives, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives and multiple types of these compounds Or an electron donating substance such as a polymer having a group consisting of these compounds in the main chain or side chain. Among these, carbazole derivatives, aromatic amine derivatives, stilbene derivatives, butadiene derivatives, enamine derivatives, hydrazone derivatives, and those in which a plurality of these compounds are bonded are preferable.

  Specific examples of suitable structures of the charge transport material are shown below. However, these specific examples are shown for illustration, and any known charge transport material may be used in the present invention as long as it does not contradict the gist of the present invention. Note that Bu represents a butyl group, and t-Bu represents a tertiary butyl group.

(Binder resin)
Next, the binder resin used for the photosensitive layer will be described. Examples of the binder resin used in the photosensitive layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride or copolymers thereof; butadiene resins; styrene resins; vinyl acetate resins; vinyl chloride resins, acrylate resins. Methacrylic acid ester resin; vinyl alcohol resin; polymers and copolymers of vinyl compounds such as ethyl vinyl ether; polyvinyl butyral resin; polyvinyl formal resin; partially modified polyvinyl acetal resin; polyarylate resin; polyamide resin; Resin; Silicone-alkyd resin; Poly-N-vinylcarbazole resin; Polycarbonate resin; Polyester resin; Polyester carbonate resin; Polysulfone resin; Carboxymethyl resins, epoxy resins, silicone resins; and partially crosslinked cured product thereof. The resin may be modified with a silicon reagent or the like. Moreover, these may be used individually by 1 type and can also use 2 or more types by arbitrary ratios and combinations.

  In particular, the binder resin preferably contains one kind or two or more kinds of polymers obtained by interfacial polymerization. Interfacial polymerization is a polymerization method that utilizes a polycondensation reaction that proceeds at the interface of two or more solvents (mostly organic solvents-water systems) that do not mix with each other. For example, a dicarboxylic acid chloride is dissolved in an organic solvent, a glycol component is dissolved in alkaline water or the like, and both liquids are mixed at room temperature to be separated into two phases, and a polycondensation reaction proceeds at the interface to produce a polymer. Examples of other two components include phosgene and an aqueous glycol solution. Further, as in the case of condensing a polycarbonate oligomer by interfacial polymerization, the two components are not divided into two phases, but the interface may be used as a polymerization field.

  As the reaction solvent in the interfacial polymerization, it is preferable to use two layers of an organic phase and an aqueous phase, the organic phase is preferably methylene chloride, and the aqueous phase is preferably an alkaline aqueous solution. Moreover, it is preferable to use a catalyst at the time of the said reaction, and the amount of the condensation catalyst used by reaction is 0.005 mol% or more normally with respect to diol, for example, when making glycol react, Preferably it is 0.03 mol% or more. . Moreover, it is 0.1 mol% or less normally, Preferably it is 0.08 mol% or less. When the above range is exceeded, a great deal of labor may be required to extract and remove the catalyst in the washing step after polycondensation.

  The reaction temperature in the interfacial polymerization is usually 80 ° C. or lower, preferably 60 ° C. or lower, more preferably 50 ° C. or lower, and the lower limit is usually 10 ° C. or higher. If the reaction temperature is too high, side reactions may not be controlled. On the other hand, when the reaction temperature is low, it is a favorable situation in terms of reaction control, but the refrigeration load increases, which may increase the cost accordingly. The reaction time depends on the reaction temperature and the type of the target composition, but is usually 0.5 minutes or longer, preferably 1 minute or longer, and usually 30 hours or less, preferably 15 hours or less.

  The concentration of the reaction component in the organic phase may be in a range in which the resulting composition is soluble, specifically 10 wt% or more, preferably 15 wt% or more. Moreover, it is 40 weight% or less normally, Preferably it is 35 weight% or less. The proportion of the organic phase is preferably a volume ratio of 0.2 or more and 1.0 or less with respect to the aqueous phase. The amount of the solvent is preferably adjusted so that the concentration of the produced resin in the organic phase obtained by polycondensation is 5% by weight or more and 30% by weight or less. Thereafter, an aqueous phase containing water and alkali metal hydroxide is newly added, and the initial polycondensation is completed according to the interfacial polycondensation method. At this time, it is preferable to contain a condensation catalyst in order to adjust the polycondensation conditions. The ratio of the organic phase to the aqueous phase during the polycondensation is preferably 0.2 or more and 1 or less in the aqueous phase when the organic phase is set to 1 by volume ratio.

  The binder resin obtained by the interfacial polymerization is preferably a polycarbonate resin or a polyester resin, and particularly preferably a polycarbonate resin or a polyarylate resin. Moreover, it is preferable that it is especially a polymer which uses an aromatic diol as a raw material, As a preferable aromatic diol compound, the compound represented by following formula (2) is mentioned.

In the above formula (2), X ^a represents a linking group represented by any one of the following formulas or a single bond.

In the above formula, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, optionally substituted aryl group, or a halogenated alkyl group. Z represents a substituted or unsubstituted carbocycle having 4 to 20 carbon atoms.

In formula (2), Y ¹ to Y ⁸ each independently represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, an optionally substituted aryl group, or a halogenated alkyl group.

Further, bisphenol having the following structural formula or a polycarbonate resin or polyarylate resin containing a biphenol component is preferable from the viewpoint of the sensitivity and residual potential of the electrophotographic photosensitive member, and among them, the polycarbonate resin is more preferable from the viewpoint of mobility.
This illustration is made for the purpose of clarifying the gist, and is not limited to the illustrated structure unless contrary to the gist of the present invention.

  In particular, in order to maximize the effects of the present invention, a polycarbonate containing a bisphenol derivative having the following structure is preferable.

  In order to improve mechanical properties, it is preferable to use polyester, particularly polyarylate. In this case, it is preferable to use a bisphenol component having the following structure.

  Moreover, it is preferable to use what has the following structure as an acid component.

  Moreover, when using terephthalic acid and isophthalic acid, the one where the molar ratio of terephthalic acid is larger is preferable, and it is preferable to use what has the following structure.

  Here, the ratio of the binder resin to the charge transport material is usually preferably 20 parts by weight or more, more preferably 30 parts by weight or more from the viewpoint of reducing the residual potential, with respect to 100 parts by weight of the binder resin. From the viewpoints of stability during repeated use and charge mobility, 40 parts by weight or more is more preferable. On the other hand, from the viewpoint of thermal stability of the photosensitive layer, it is usually preferably 200 parts by weight or less, more preferably 120 parts by weight or less from the viewpoint of compatibility between the charge transport material and the binder resin, and durability during repeated valence image formation. 110 parts by weight or less is more preferable from the viewpoint of property, and 100 parts by weight or less is particularly preferable from the viewpoint of scratch resistance of the photosensitive layer. If the amount of the charge transport material is too small, the electrical characteristics tend to be lowered, and if it is too much, the coating film becomes brittle and the wear resistance tends to be lowered.

  In addition, the above-described charge generation material, that is, the phthalocyanine compound and / or other charge generation material is further dispersed in the charge transport medium having the above-described mixing ratio. In that case, the particle size of the charge generating material is preferably sufficiently small, usually 1 μm or less, more preferably 0.5 μm or less. If the amount of the charge generating material dispersed in the photosensitive layer is too small, sufficient sensitivity cannot be obtained, and if it is too large, chargeability and sensitivity may be lowered. Therefore, the amount of the charge generating substance is generally preferably 0.1% by weight or more, more preferably 0.5% by weight, preferably 50% by weight or less, more preferably 20% by weight or less in the photosensitive layer. The amount of the charge generation material is the total amount of the phthalocyanine compound and / or other charge generation materials.

(Other substances)
In addition to the above materials, the photosensitive layer contains well-known antioxidants, plasticizers, and UV absorbers to improve film formability, flexibility, coatability, stain resistance, gas resistance, light resistance, and the like. You may contain additives, such as an agent, an electron withdrawing compound, a leveling agent, and a visible light shading agent. In addition, the photosensitive layer may contain various additives such as a leveling agent for improving the coating property, an antioxidant, a sensitizer, a dye, a pigment, and a surfactant as necessary. Examples of dyes and pigments include various dye compounds and azo compounds. Examples of surfactants include silicone oil and fluorine oil. In the present invention, these may be appropriately used alone or in combination of two or more in any ratio and combination.
Further, for the purpose of reducing frictional resistance and wear on the surface of the electrophotographic photosensitive member, the surface layer of the photosensitive layer may contain a fluorine-based resin, a silicone resin, etc., and particles of these resins or inorganic compounds such as aluminum oxide. Particles may be included.
Here, in the present invention, the following antioxidant and electron-withdrawing compound are particularly preferably contained.

<Antioxidant>
The antioxidant is a kind of stabilizer used for preventing oxidation of the electrophotographic photosensitive member of the present invention.
Antioxidants should just have a function as a radical scavenger, and specifically, a phenol derivative, an amine compound, a phosphonic acid ester, a sulfur compound, a vitamin, a vitamin derivative, etc. are mentioned.
Of these, phenol derivatives, amine compounds, vitamins and the like are preferable. Further, a hindered phenol or a trialkylamine derivative having a bulky substituent in the vicinity of the hydroxy group is more preferable.
Furthermore, an aryl compound derivative having a t-butyl group at the o-position of the hydroxy group and an aryl compound derivative having two t-butyl groups at the o-position of the hydroxy group are particularly preferable.

  Further, when the molecular weight of the antioxidant is too large, the antioxidant ability may be lowered, and a compound having a molecular weight of 1500 or less, particularly a molecular weight of 1000 or less is preferred. Moreover, a minimum is 100 or more normally, Preferably it is 150 or more, More preferably, it is 200 or more.

  Hereinafter, the antioxidant which can be used for this invention is shown. As the antioxidant that can be used in the present invention, all materials known as antioxidants for plastics, rubber, petroleum, fats and oils, ultraviolet absorbers, and light stabilizers can be used. Especially, the material chosen from the following compound group can be used preferably. In the present invention, one or two or more of such antioxidants can be used in any ratio and combination.

(1) Phenols described in JP-A-57-122444, phenol derivatives described in JP-A-60-18895, and hindered phenols described in JP-A-63-18356.

(2) Paraphenylenediamines described in JP-A-57-122444, paraphenylenediamine derivatives described in JP-A-60-188756, and paraphenylene described in JP-A-63-18356 Diamines.

(3) Hydroquinones described in JP-A-57-122444, hydroquinone derivatives described in JP-A-60-18895, and hydroquinones described in JP-A-63-18356.

(4) Sulfur compounds described in JP-A-57-188956 and organic sulfur compounds described in JP-A-63-18356.

(5) Organophosphorus compounds described in JP-A-57-122444 and organophosphorus compounds described in JP-A-63-18356.

(6) Hydroxyanisoles described in JP-A-57-122444.

(7) Piperidine derivatives and oxopiperazine derivatives having a specific skeleton structure described in JP-A-63-18355.

(8) Carotenes, amines, tocopherols, Ni (II) complexes, sulfides and the like described in JP-A-60-188956.

  Moreover, the hindered phenols shown below are particularly preferable. In addition, hindered phenol shows phenols which have a bulky substituent in the hydroxy group vicinity. Specifically, dibutylhydroxytoluene, 2,2′-methylenebis (6-tert-butyl-4-methylphenol), 4,4′-butylidenebis (6-tert-butyl-3-methylphenol), 4,4 '-Thiobis (6-t-butyl-3-methylphenol), 2,2'-butylidenebis (6-t-butyl-4-methylphenol), α-tocophenol, β-tocophenol, 2,2,4 -Trimethyl-6-hydroxy-7-t-butylchroman, pentaerythryltetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 2,2'-thiodiethylenebis [3 -(3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,6-hexanediol bis [3- (3,5-di-tert-butyl-4-l Droxyphenyl) propionate], butylhydroxyanisole, dibutylhydroxyanisole, octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate (Octadecyl-3,5-di-tert-butyl-4-hydroxycinnamate) Or 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) -benzene (1,3,5-trimethyl-2,4,6- tris- (3,5-di-tert-butyl-4-hydroxybenzoyl) -benzene) and the like.

Among the above hindered phenols, in particular, dibutylhydroxytoluene, octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate (Octadecyl-3,5-di-tert-butyl-4-hydroxyhydrocinnamate) Or 1,3,5-trimethyl-2,4,6-tris- (3,5-di-t-butyl-4-hydroxybenzyl) -benzene (1,3,5-trimethyl-2,4,6- tris- (3,5-di-tert-butyl-4-hydroxybenzoyl) -benzene) is more preferred.
These compounds are known as antioxidants for rubbers, plastics, oils and the like, and some are available as commercial products.

  The amount of the antioxidant used is not particularly limited, but is 0.1 parts by weight or more, preferably 1 part by weight or more per 100 parts by weight of the binder resin in the photosensitive layer. In order to obtain good electrical characteristics, the amount is usually 25 parts by weight or less. However, if the amount of the antioxidant is too large, not only the electrical characteristics but also the printing durability may be lowered. Below, more preferably 20 parts by weight or less.

<Electron withdrawing compound>
In addition, the electrophotographic photoreceptor of the present invention may have an electron-withdrawing compound, and is particularly preferably contained in the photosensitive layer.
Specific examples of the electron-withdrawing compound include a sulfonic acid ester compound, a carboxylic acid ester compound, an organic cyano compound, a nitro compound, an aromatic halogen derivative, and the like, preferably a sulfonic acid ester compound and an organic cyano compound. And particularly preferably a sulfonic acid ester compound. The electron-withdrawing compound may be used alone or in combination of two or more in any ratio and combination.

  Further, it is understood that the electron withdrawing ability of the electron withdrawing compound can be predicted by the LUMO value (hereinafter referred to as LUMOcal as appropriate). In the present invention, among the above, LUMOcal is based on structure optimization using semiempirical molecular orbital calculation using PM3 parameters (hereinafter, this may be simply referred to as semiempirical molecular orbital calculation). A compound having a value of −0.5 or more and −5.0 eV or less is preferably used. When the absolute value of LUMOcal is smaller than 0.5 eV, the effect of electron withdrawing cannot be expected so much, and when it exceeds 5.0 eV, there is a concern that the charge is reduced. The absolute value of LUMOcal is more preferably 1.0 eV or more, still more preferably 1.1 eV or more, and particularly preferably 1.2 eV or more. The absolute value is preferably 4.5 eV or less, more preferably 4.0 eV or less, and particularly preferably 3.5 eV or less.

  Examples of the compound in which the absolute value of the LUMOcal is within the above range include the following compounds.

  The amount of the electron-withdrawing compound used in the electrophotographic photosensitive member in the present invention is not particularly limited, but when the electron-withdrawing compound is used in the photosensitive layer, it is 0 per 100 parts by weight of the binder resin contained in the photosensitive layer. 0.01 parts by weight or more is preferable, and more preferably 0.1 parts by weight or more. In order to obtain good electrical characteristics, the amount is usually preferably 50 parts by weight or less. If the amount of the electron-withdrawing compound is too large, not only the electric characteristics but also the printing durability may be lowered. Therefore, the amount is more preferably 40 parts by weight or less, and further preferably 30 parts by weight or less.

(Method for forming photosensitive layer)
Next, a method for forming the photosensitive layer will be described. The method for forming the photosensitive layer is not particularly limited. For example, the charge generation material is dispersed in a coating solution in which a charge transport material, a binder resin, and other materials are dissolved (or dispersed) in a solvent (or dispersion medium). It can be formed by coating on a conductive support (if an intermediate layer such as an undercoat layer described later is provided, these intermediate layers).
Hereinafter, the solvent or dispersion medium used for forming the photosensitive layer and the coating method will be described.

<Solvent or dispersion medium>
Examples of the solvent or dispersion medium used for forming the photosensitive layer include alcohols such as methanol, ethanol, propanol and 2-methoxyethanol; ethers such as tetrahydrofuran, 1,4-dioxane and dimethoxyethane; methyl formate and acetic acid. Esters such as ethyl; ketones such as acetone, methyl ethyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, and xylene; dichloromethane, chloroform, 1,2-dichloroethane, 1,1,2-trichloroethane, 1,1 , 1-trichloroethane, tetrachloroethane, 1,2-dichloropropane, trichloroethylene and other chlorinated hydrocarbons; n-butylamine, isopropanolamine, diethylamine, triethanolamine, ethylenediamine, triethylene Nitrogen-containing compounds such as amines; acetonitrile, N- methylpyrrolidone, N, N- dimethylformamide, aprotic polar solvents such as dimethyl sulfoxide and the like. These may be used alone or in combination of two or more in any ratio and combination.

<Application method>
Examples of the application method of the coating solution for forming the photosensitive layer include a spray coating method, a spiral coating method, a ring coating method, and a dip coating method.

  Examples of the spray coating method include air spray, airless spray, electrostatic air spray, electrostatic airless spray, rotary atomizing electrostatic spray, hot spray, and hot airless spray. Considering the atomization degree for obtaining a uniform film thickness, adhesion efficiency, etc., it is a rotary atomizing electrostatic spray, which is a conveying method disclosed in the republication No. 1-805198, that is, a cylindrical workpiece. A method of continuously conveying the sheet without rotating in the axial direction while rotating is preferable. Thereby, a photosensitive layer excellent in film thickness uniformity can be obtained with a comprehensively high adhesion efficiency.

  Examples of the spiral coating method include a method using a liquid injection coating machine or a curtain coating machine disclosed in Japanese Patent Application Laid-Open No. 52-119651, and a minute opening disclosed in Japanese Patent Application Laid-Open No. 1-2231966. For example, a method of causing the coating material to continuously fly in a streaky manner, a method using a multi-nozzle body disclosed in JP-A-3-193161, and the like.

In the dip coating method, the total solid concentration of the coating solution or dispersion is preferably 5% by weight or more, more preferably 10% by weight or more. Further, it is preferably 50% by weight or less, more preferably 35% by weight or less.
The viscosity of the coating liquid or dispersion is preferably 50 mPa · s or more, more preferably 100 mPa · s or more. Further, it is preferably 700 mPa · s or less, more preferably 500 mPa · s or less. Thereby, it can be set as the photosensitive layer excellent in the uniformity of film thickness.

  After the coating film is formed by the above coating method, the coating film is dried, but it is preferable to adjust the drying temperature time so that necessary and sufficient drying is performed. If the drying temperature is too high, bubbles may be mixed in the photosensitive layer. If the drying temperature is too low, it takes time to dry, and the amount of residual solvent may increase and affect electrical characteristics. , Preferably it is 110 degreeC or more, More preferably, it is 120 degreeC or more. The temperature is usually 250 ° C. or lower, preferably 170 ° C. or lower, more preferably 140 ° C. or lower, and the temperature may be changed stepwise. As a drying method, a hot air dryer, a steam dryer, an infrared dryer, a far infrared dryer, or the like can be used.

  The thickness of the photosensitive layer is appropriately selected depending on the material used, but is preferably 5 μm or more, more preferably 10 μm or more, and particularly preferably 15 μm or more from the viewpoint of life. From the viewpoint of electrical characteristics, it is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less.

The volume resistivity of the photosensitive layer is not limited particularly greater than the volume resistivity of the protective layer to be described later, from the viewpoint of the image, preferably at least 10 ¹³ Ω · cm, more preferably at least 10 ¹⁴ Ω · cm, 10 ¹⁵ Ω · cm or more is particularly preferable. From the viewpoint of electrical characteristics, it is preferably 10 ¹⁹ Ω · cm or less, more preferably 10 ¹⁸ Ω · cm or less, and particularly preferably 10 ¹⁷ Ω · cm or less.
In addition, as a measuring method of volume resistivity, as described in the Example column described later, a known apparatus (for example, Hiresta UP (MCP-450) manufactured by Dia Instruments Co., Ltd.) is used, and the temperature is 25 ° C., relative It can be determined by measuring at an applied voltage of 100 V (for 1 minute) in an environment of 50% humidity.

<Protective layer>
Next, the protective layer used in the photoreceptor of the present invention will be described. The protective layer used in the present invention is formed on the above-mentioned photosensitive layer, and its volume resistivity is smaller than the volume resistivity of the photosensitive layer and is preferably 10 ¹⁰ to 10 ¹⁵ (Ω · cm).
The material used for the protective layer is not particularly limited as long as the protective layer exhibits a predetermined volume resistivity with the photosensitive layer. Among these, a protective layer containing a binder resin and metal oxide particles is preferable from the viewpoints of excellent mechanical strength, easy control of volume resistivity, and easy film formation.
Hereinafter, suitable materials (binder resin, metal oxide particles) used for the protective layer will be described.

<Binder resin>
It does not specifically limit as binder resin used for the protective layer of this invention, If it is soluble in water or an organic solvent, it is preferable.
As such a binder resin, for example, phenoxy, epoxy, polyvinyl pyrrolidone, polyvinyl alcohol, casein, polyacrylic acid, celluloses, gelatin, starch, polyurethane, polyimide, polyamide, etc. are used alone or in a cured form together with a curing agent. Among them, alcohol-soluble copolymer polyamide and modified polyamide resin are preferable.
As the polyamide resin, for example, nylon such as so-called copolymer nylon obtained by copolymerizing 6-nylon, 66-nylon, 610-nylon, 11-nylon, 12-nylon, or the like, or N-alkoxymethyl-modified nylon is used. Examples thereof include alcohol-soluble nylon resins such as chemically modified types. Specific product names include, for example, “CM4000”, “CM8000” (manufactured by Toray), “F-30K”, “MF-30”, “EF-30T” (manufactured by Nagase Chemtech).
Among these polyamide resins, a copolymerized polyamide resin containing a diamine represented by the following formula (3) as a constituent component is particularly preferably used because of its good environmental stability.

In formula (3), R ^{4 to} R ⁷ each independently represents a hydrogen atom or an organic substituent. m and n each independently represents an integer of 0 to 4, and when there are a plurality of substituents (when m and n are 2 or more), these substituents may be different from each other.
The organic substituent represented by R ^{4 to} R ⁷ is preferably a hydrocarbon group having 20 or less carbon atoms and optionally containing a hetero atom, more preferably a methyl group, an ethyl group, an n-propyl group, Alkyl groups such as isopropyl groups; alkoxy groups such as methoxy groups, ethoxy groups, n-propoxy groups, isopropoxy groups; aryl groups such as phenyl groups, naphthyl groups, anthryl groups, pyrenyl groups, and more preferably alkyl groups Or an alkoxy group. Particularly preferred are a methyl group and an ethyl group.

  Examples of the copolymerized polyamide resin containing a diamine represented by the formula (3) as a constituent component include, for example, lactams such as γ-butyrolactam, ε-caprolactam, lauryllactam; 1,4-butanedicarboxylic acid, 1, Dicarboxylic acids such as 12-dodecanedicarboxylic acid, 1,20-eicosanedicarboxylic acid; diamines such as 1,4-butanediamine, 1,6-hexamethylenediamine, 1,8-octamethylenediamine, 1,12-dodecanediamine A combination of piperazine and the like and copolymerized into binary, ternary, quaternary, and the like. Although there is no limitation in particular about this copolymerization ratio, Preferably the diamine component represented by Formula (3) is 5-40 mol% in all the structural components, More preferably, it is 5-30 mol%.

The number average molecular weight of the copolymerized polyamide is preferably 10,000 to 50,000, particularly preferably 15,000 to 35,000. Even if the number average molecular weight is too small or too large, it is difficult to maintain the uniformity of the film.
There is no particular limitation on the method for producing the copolymerized polyamide, and a normal polyamide polycondensation method is appropriately applied, and a melt polymerization method, a solution polymerization method, an interfacial polymerization method, or the like is used. In the polymerization, a monobasic acid such as acetic acid or benzoic acid, or a monoacid base such as hexylamine or aniline may be added as a molecular weight regulator.
It is also possible to add a heat stabilizer represented by sodium phosphite, sodium hypophosphite, phosphorous acid, hypophosphorous acid and hindered phenol, and other polymerization additives.

  Specific examples of the copolymerized polyamide used in the present invention are shown below. However, in specific examples, the copolymerization ratio represents the charge ratio (molar ratio) of the monomer.

<Metal oxide particles>
The protective layer of the present invention may contain metal oxide particles.
As the metal oxide particles, any metal oxide particles that can be generally used for an electrophotographic photosensitive member can be used. More specifically, as metal oxide particles, metal oxide particles containing one kind of metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, strontium titanate And metal oxide particles containing a plurality of metal elements such as barium titanate. Among these, metal oxide particles having a band gap of 2 to 4 eV are preferable. As the metal oxide particles, only one type of particles may be used, or a plurality of types of particles may be mixed and used. Among these metal oxide particles, titanium oxide, aluminum oxide, silicon oxide, and zinc oxide are preferable, titanium oxide and aluminum oxide are more preferable, and titanium oxide is particularly preferable.

  As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. In addition, those having a plurality of crystal states from those having different crystal states may be included.

  The metal oxide particles may be subjected to various surface treatments on the surface. For example, treatment with an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, a polyol, or an organosilicon compound may be performed. In particular, when titanium oxide particles are used, surface treatment with an organosilicon compound is preferable. Examples of organosilicon compounds include silicone oils such as dimethylpolysiloxane and methylhydrogenpolysiloxane, organosilanes such as methyldimethoxysilane and diphenyldidimethoxysilane, silazanes such as hexamethyldisilazane, vinyltrimethoxysilane, and γ-mercaptopropyltrimethyl. Silane coupling agents such as methoxysilane and γ-aminopropyltriethoxysilane are common, but the silane treatment agent represented by the structure of the following formula (4) has good reactivity with metal oxide particles, It is the best treatment agent.

In formula (4), R ¹ and R ² each independently represents an alkyl group, preferably a methyl group or an ethyl group. R ³ represents an alkyl group or an alkoxy group, and more preferably represents a group selected from the group consisting of a methyl group, an ethyl group, a methoxy group, and an ethoxy group. Although the outermost surface of these surface-treated particles is treated with such a treatment agent, it may be treated with a treatment agent such as aluminum oxide, silicon oxide or zirconium oxide before the treatment. I do not care. As the metal oxide particles, only one type of particles may be used, or a plurality of types of particles may be mixed and used.

  In general, the metal oxide particles used preferably have an average primary particle size of 500 nm or less, more preferably 1 nm to 100 nm, and still more preferably 5 to 50 nm. This average primary particle diameter can be obtained by an arithmetic average value of particle diameters directly observed by a transmission electron microscope (hereinafter also referred to as TEM).

Among the metal oxide particles according to the present invention, as specific trade names of titanium oxide particles, ultrafine titanium oxide “TTO-55 (N)” that has not been subjected to surface treatment, Al ₂ O ₃ coating was applied. Ultrafine titanium oxide “TTO-55 (A)”, “TTO-55 (B)”, ultrafine titanium oxide “TTO-55 (C)” surface-treated with stearic acid, Al ₂ O ₃ and organosiloxane Ultra-fine titanium oxide “TTO-55 (S)” surface-treated with high purity titanium oxide “CR-EL”, sulfuric acid method titanium oxide “R-550”, “R-580”, “R-630” , “R-670”, “R-680”, “R-780”, “A-100”, “A-220”, “W-10”, chlorinated titanium oxide “CR-50”, “CR-” 58 "," CR-60 "," CR-60-2 ", CR-67 ", conductive titanium oxide" SN-100P "," SN-100D "," ET-300W "(above, manufactured by Ishihara Sangyo Co., Ltd.)," R-60 "," A-110 "," including titanium oxide, such as a-0.99 ", was subjected to _Al 2 _{O 3} coating" SR-1 "," R-GL "," R-5N "," R-5N-2 "," R-52N " , "RK-1", _"a-SP", was subjected to SiO 2, _Al 2 _{O 3} coating "R-GX", "R-7E", was subjected _ZnO, the SiO 2, _Al 2 _{O 3} coating " “R-650”, “R-61N” coated with ZrO ₂ and Al ₂ O ₃ (manufactured by Sakai Chemical Industry Co., Ltd.), and “TR-700” surface-treated with SiO ₂ and Al ₂ O ₃ ", _ZnO, surface-treated with SiO 2, _Al 2 _{O 3"} TR-840 "," TA-500 Other, "TA-100", "TA-200", "TA-300" titanium oxide surface-untreated like, "TA-400" was subjected to a surface treatment with _Al 2 _{O 3} (or more, manufactured by Fuji Titanium Industry stock company, Ltd.), not subjected to a surface treatment "MT-150W", _"MT-500B", have been surface-treated with SiO 2, _Al 2 _{O 3} "MT-100SA", "MT-500SA", _SiO 2, Al Examples thereof include “MT-100SAS” and “MT-500SAS” (manufactured by Teika Co., Ltd.), which are surface-treated with ₂ O ₃ and organosiloxane.

Moreover, as a specific brand name of aluminum oxide particles, “Aluminium Oxide C” (manufactured by Nippon Aerosil Co., Ltd.) and the like can be mentioned.
Moreover, as a concrete brand name of a silicon oxide particle, "200CF", "R972" (made by Nippon Aerosil Co., Ltd.), "KEP-30" (made by Nippon Shokubai Co., Ltd.), etc. are mentioned.
Moreover, "SN-100P" (made by Ishihara Sangyo Co., Ltd.) etc. are mentioned as a specific brand name of a tin oxide particle.
Specific examples of the trade name of the zinc oxide particles include “MZ-305S” (manufactured by Teika Co., Ltd.), but the metal oxide particles usable in the present invention are not limited to these.

  The amount of the metal oxide particles used in the protective layer of the electrophotographic photoreceptor according to the present invention is not particularly limited, but the metal oxide particles are 0.5 parts by weight to 4 parts by weight with respect to 1 part by weight of the binder resin. It is preferable to use within the range of parts.

(Method for forming protective layer)
Next, a method for forming the protective layer will be described. The method for forming the protective layer is not particularly limited. For example, a coating solution in which a binder resin, metal oxide particles, and other substances are dissolved (or dispersed) in a solvent (or dispersion medium) is coated on the photosensitive layer. Can be formed.
Hereinafter, the solvent or dispersion medium used for forming the protective layer and the coating method will be described.

<Solvent used for coating liquid for forming protective layer>
The organic solvent used in the coating liquid for forming a protective layer of the present invention is any organic solvent that can dissolve the binder resin for the protective layer according to the present invention and does not attack the photosensitive layer. Anything can be used. Specifically, alcohols having 5 or less carbon atoms such as methanol, ethanol, isopropyl alcohol, or normal propyl alcohol; halogens such as chloroform, 1,2-dichloroethane, dichloromethane, trichrene, carbon tetrachloride, 1,2-dichloropropane, etc. Hydrocarbons; nitrogen-containing organic solvents such as dimethylformamide; aromatic hydrocarbons such as toluene and xylene. Of these, an arbitrary combination and a mixed solvent in an arbitrary ratio can be used. Moreover, even if it is an organic solvent that does not dissolve the binder resin for the protective layer according to the present invention alone, for example, if it can be dissolved by using a mixed solvent with the above organic solvent, it is used. be able to. In general, coating unevenness can be reduced by using a mixed solvent.
The amount ratio of the organic solvent used in the coating liquid for forming the protective layer of the present invention and the solid content of the binder resin, metal oxide particles and the like varies depending on the coating method of the coating liquid for forming the protective layer, and is uniform in the applied coating method. What is necessary is just to change suitably and use it so that a coating film may be formed.

<Application method>
The coating method of the coating liquid for forming the protective layer is not particularly limited, and examples thereof include a spray coating method, a spiral coating method, a ring coating method, and a dip coating method. Any coating method can be used as long as it does not damage the photosensitive layer.

  After the coating film is formed by the above coating method, the coating film is dried, but the temperature and time are not limited as long as necessary and sufficient drying is obtained.

  The thickness of the protective layer is appropriately selected depending on the material used, but is preferably 0.1 μm or more, more preferably 0.2 μm or more, and particularly preferably 0.5 μm or more from the viewpoint of life. Further, when the thickness is 0.8 μm or more, generation of image memory is further suppressed. Further, in terms of electrical characteristics, it is preferably 20 μm or less, more preferably 10 μm or less, and particularly preferably 5 μm or less.

The volume resistivity of the protective layer is not particularly limited as long as it is smaller than the volume resistivity of the photosensitive layer, but is preferably 10 ¹⁰ Ω · cm or more, more preferably 10 ¹¹ Ω · cm or more, from the viewpoint of image characteristics. ¹² Ω · cm or more is particularly preferable. Further, from the viewpoint of electrical characteristics, 10 ¹⁵ Ω · cm or less is preferable, and 10 ¹⁴ Ω · cm or less is more preferable.
In addition, the logarithmic difference of the volume low efficiency between the protective layer and the photosensitive layer (log (volume low efficiency of the photosensitive layer) −log (volume low efficiency of the protective layer)) is related to the occurrence of image memory, and fog and black spots. 1 or more are preferable and 2 or more are more preferable at the point by which generation | occurrence | production is suppressed. On the other hand, if the above difference is too large, the charge retention capacity decreases, so the upper limit is preferably 7 or less, more preferably 5 or less, and even more preferably 3 or less from the viewpoint of suppressing the occurrence of fog and black spots.
In addition, as a measuring method of volume resistivity, as described in the Example column described later, a known apparatus (for example, Hiresta UP (MCP-450) manufactured by Dia Instruments Co., Ltd.) is used, and the temperature is 25 ° C., relative It can be determined by measuring at an applied voltage of 100 V (1 minute) in an environment of 50% humidity.

<Underlayer>
The electrophotographic photosensitive member of the present invention may have an undercoat layer between the photosensitive layer and the conductive support.
As the undercoat layer, for example, a resin, a resin in which particles such as an organic pigment or a metal oxide are dispersed, or the like is used. Examples of organic pigments used in the undercoat layer include phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, and benzimidazole pigments. Among these, phthalocyanine pigments and azo pigments, specifically, phthalocyanine pigments and azo pigments when used as the above-described charge generation material are exemplified.
Examples of metal oxide particles used for the undercoat layer include metal oxide particles containing one metal element such as titanium oxide, aluminum oxide, silicon oxide, zirconium oxide, zinc oxide, iron oxide, calcium titanate, titanium Examples thereof include metal oxide particles containing a plurality of metal elements such as strontium acid and barium titanate. In the undercoat layer, only the one kind of particles may be used, or a plurality of kinds of particles may be mixed and used in an arbitrary ratio and combination.

  Among the metal oxide particles, titanium oxide and aluminum oxide are preferable, and titanium oxide is particularly preferable. The surface of the titanium oxide particles may be treated with, for example, an inorganic substance such as tin oxide, aluminum oxide, antimony oxide, zirconium oxide, or silicon oxide, or an organic substance such as stearic acid, polyol, or silicone. As the crystal form of the titanium oxide particles, any of rutile, anatase, brookite, and amorphous can be used. Moreover, the thing of a several crystal state may be contained.

  The particle size of the metal oxide particles used for the undercoat layer is not particularly limited, but is 10 nm as the average primary particle size from the standpoint of the properties of the undercoat layer and the stability of the solution for forming the undercoat layer. The thickness is preferably 100 nm or less, more preferably 50 nm or less.

  Here, the undercoat layer is preferably formed in a form in which particles are dispersed in a binder resin. Examples of the binder resin used in the undercoat layer include polyvinyl butyral resins, polyvinyl formal resins, polyvinyl acetal resins such as partially acetalized polyvinyl butyral resins in which a part of butyral is modified with formal, acetal, or the like, polyarylate Resin, polycarbonate resin, polyester resin, modified ether polyester resin, phenoxy resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polystyrene resin, acrylic resin, methacrylic resin, polyacrylamide resin, polyamide resin, polyvinyl pyridine Resin, cellulosic resin, polyurethane resin, epoxy resin, silicone resin, polyvinyl alcohol resin, polyvinylpyrrolidone resin, casein, vinyl chloride-vinyl acetate Vinyl chloride-vinyl acetate copolymers such as copolymers, hydroxy-modified vinyl chloride-vinyl acetate copolymers, carboxyl-modified vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl acetate-maleic anhydride copolymers, Styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, styrene-alkyd resin, silicone-alkyd resin, insulating resin such as phenol-formaldehyde resin, poly-N-vinylcarbazole, polyvinylanthracene, polyvinylperylene It can be selected from organic photoconductive polymers such as, but not limited to these polymers. These binder resins may be used alone or in combination of two or more, or may be used in a form cured with a curing agent. Among them, polyvinyl butyral resin, polyvinyl formal resin, partially acetalized polyvinyl butyral resin partially modified with formal, acetal, etc., polyvinyl acetal resin, alcohol-soluble copolymer polyamide, modified polyamide, etc. It is preferable because it shows good dispersibility and applicability.

  The volume resistivity of the undercoat layer is not particularly limited, but is preferably lower than the volume resistivity of the photosensitive layer in terms of electrical characteristics (particularly residual potential).

  The mixing ratio of the particles to the binder resin can be arbitrarily selected, but it is preferably used in the range of 10% by weight to 500% by weight in terms of the stability of the dispersion and the coating property. The thickness of the undercoat layer can be arbitrarily selected, but is usually preferably 0.1 μm or more and 20 μm or less from the characteristics of the electrophotographic photosensitive member and the applicability of the dispersion. The undercoat layer may contain a known antioxidant or the like.

<Other layers>
The electrophotographic photosensitive member of the present invention may have other layers as needed in addition to the conductive support, photosensitive layer, protective layer and undercoat layer described above.

<Use of electrophotographic photoreceptor>
The type or the like of the image forming apparatus in which the electrophotographic photosensitive member of the present invention is used is not particularly limited, and can be applied to a known image forming apparatus. The exposure wavelength of the photosensitive layer is not particularly limited and is usually monochromatic light having a wavelength of 700 nm or more and 800 nm or less, monochromatic light having a wavelength of 600 nm or more and 700 nm or less, and monochromatic light having a wavelength of 380 nm or more and 600 nm or less. It can be. Among these, in particular, when reducing the aperture of exposure light, it is preferable to set the wavelength to 380 nm or more and 600 nm or less, more preferably 500 nm or less.

<Image forming apparatus>
Next, an image forming apparatus using the electrophotographic photosensitive member of the present invention will be described. The configuration of the image forming apparatus in the present invention is not particularly limited as long as it includes the above-described electrophotographic photosensitive member.
The image forming apparatus provided with the electrophotographic photosensitive member performs high-definition image formation in a target pattern with little decrease in surface potential even when the electrophotographic photosensitive member is repeatedly used for image formation. It is possible.

A description will be given below with reference to FIG. However, the embodiment is not limited to the following description, and can be arbitrarily modified without departing from the gist of the present invention.
As shown in FIG. 1, an image forming apparatus 100 includes an electrophotographic photosensitive member 1, a charging unit 2, an image exposing unit 3, a developing unit 4, and a transfer unit 5, and a cleaning unit 6 and a fixing unit 7 as necessary. Is provided.

  In the image forming apparatus 100 of the present invention, an image is recorded as follows. The electrophotographic photoreceptor 1 is rotationally driven at a predetermined peripheral speed around a predetermined axis (not shown). In the rotation process, the surface (photosensitive layer) of the electrophotographic photosensitive member 1 is charged to a predetermined potential (for example, +600 V) of a positive or negative predetermined potential by the charging unit 2. Subsequently, the exposure light intensity-modulated in response to the time-series electric digital image signal of the target image information output from the image exposure means 3 is received. As a result, electrostatic latent images corresponding to target image information are sequentially formed on the surface (photosensitive layer) of the electrophotographic photoreceptor 1.

  The formed electrostatic latent image is then visualized as a transferable particle image (toner image) by regular development or reversal development with toner in the developing means 4. Specifically, the developing unit 4 thins the toner T supplied by the supply roller 43 by a regulating member (developing blade) 45 and has a predetermined polarity (here, the same polarity as the charging potential of the photoreceptor 1). And negatively charged), conveyed while being carried on the developing roller 44, and brought into contact with the surface of the electrophotographic photosensitive member 1. When the charged toner T carried on the developing roller 44 contacts the surface of the electrophotographic photoreceptor 1, a toner image corresponding to the electrostatic latent image is formed on the photosensitive surface of the electrophotographic photoreceptor 1.

  Thereafter, the electrophotographic photosensitive member 1 is transferred to the transfer target (recording paper) P fed from the paper feeding unit P between the electrophotographic photosensitive member 1 and the transfer means 5 in synchronization with the rotation of the electrophotographic photosensitive member 1. The toner images formed and supported on the surface of the toner are sequentially transferred by the transfer means 5. At this time, a bias voltage having a polarity opposite to the charge held in the toner is applied to the transfer means from a bias power source (not shown).

  The transferred material (recording paper) P that has received the transfer of the toner image is separated from the surface of the electrophotographic photosensitive member 1 and conveyed to the fixing means 7 to undergo the fixing process of the toner image, thereby forming an image formed product (print, copy). ) Is printed out of the apparatus.

  The surface of the electrophotographic photoreceptor 1 after the transfer of the toner image is cleaned by removing the deposits such as toner remaining after the transfer by the cleaning means 6. In recent years, a cleaner-less system has been studied, and a configuration in which a transfer residual toner is directly collected by a developing device or the like can be employed. In addition to the above-described configuration, the image forming apparatus 100 may include a static elimination unit (not shown) that can neutralize an electrophotographic photosensitive member (static elimination process), for example.

The image forming apparatus may be further modified. For example, the image forming apparatus may be configured to perform a pre-exposure process, an auxiliary charging process, or the like, or may be configured to perform offset printing. A full-color tandem system configuration using toner may be used.
Hereinafter, each configuration of the image forming apparatus will be described.

[Electrophotographic photoconductor]
The electrophotographic photosensitive member in the image forming apparatus may be the one described in the above-mentioned “electrophotographic photosensitive member”. FIG. 1 shows, as an example, a drum-shaped photoreceptor in which the above-described photosensitive layer is formed on the surface of a cylindrical conductive support. A charging unit 2, an image exposure unit 3, a developing unit 4, a transfer unit 5, and a cleaning unit 6 are disposed along the outer peripheral surface of the electrophotographic photosensitive member 1.

  In many cases, the electrophotographic photosensitive member 1 and the charging unit 2 described later are designed to be removable from the main body of the image forming apparatus as a cartridge having both of them (hereinafter, referred to as an electrophotographic cartridge as appropriate). For example, when the electrophotographic photosensitive member 1 or the charging unit 2 deteriorates, the electrophotographic cartridge can be detached from the image forming apparatus main body, and another new electrophotographic cartridge can be mounted on the image forming apparatus main body. Is done. In addition, for example, an electrophotographic cartridge having a configuration including the electrophotographic photosensitive member 1, the charging unit 2, and the transfer unit 5 described later can be used.

[Charging means]
The charging unit 2 is not particularly limited as long as it can charge the electrophotographic photosensitive member 1 and can uniformly charge the surface of the electrophotographic photosensitive member 1 to a predetermined potential. In FIG. 1, a roller-type charging unit (charging roller) is shown as an example of the charging unit 2, but a corona charging unit such as a corotron or a scorotron, a contact type charging unit such as a charging brush, and the like are often used. As a material for the contact-type charging means, an elastic body imparted with conductivity is generally used.

  The voltage applied to the contact charging means may be only a DC voltage or an oscillating voltage obtained by superimposing an AC voltage on a DC voltage. The vibration voltage here is a voltage whose voltage value periodically changes with time, and the AC voltage has a peak-to-peak voltage that is at least twice the charging start voltage of the photosensitive member when only the DC voltage is applied. preferable.

[Image exposure means]
The image exposure means 3 is applied to the electrophotographic photosensitive member 1 with, for example, monochromatic light with a wavelength of 700 nm or more and 800 nm or less, monochromatic light with a wavelength of 600 nm or more and 700 nm or less, and a short wavelength of 380 nm or more and 600 nm or less. The type is not particularly limited as long as it can perform image exposure by irradiating monochromatic light and can form an electrostatic latent image on the photosensitive surface of the electrophotographic photosensitive member 1. Specific examples include a halogen lamp, a fluorescent lamp, a semiconductor laser, and an LED. Further, the exposure may be performed by a photoreceptor internal exposure method.

[Development means]
The developing means 4 is not particularly limited as long as it can form a toner image by attaching toner to the electrostatic latent image formed on the electrophotographic photoreceptor 1. For example, dry development methods such as cascade development, magnetic one-component contact development, magnetic one-component non-contact development, non-magnetic one-component contact development, non-magnetic one-component non-contact development, magnetic two-component contact development, magnetic two-component non-contact development Alternatively, any means such as a wet development method can be used. Further, a conductive toner may be used. In FIG. 1, the developing unit 4 includes a developing tank 41, an agitator 42, a supply roller 43, a developing roller 44, and a regulating member 45, and has a configuration in which toner T is stored inside the developing tank 41. .
Further, a replenishing device (not shown) for replenishing toner T may be attached to the developing unit 4 as necessary. The replenishing device is configured to be able to replenish toner T from a container such as a bottle or a cartridge.

  In many cases, the toner T is stored in a toner cartridge and is designed to be removable from the main body of the image forming apparatus. It is possible to replenish the toner T by adopting a configuration in which when the toner T in the toner cartridge in use runs out, the toner cartridge can be removed from the main body of the image forming apparatus and another new toner cartridge can be mounted. From the viewpoint of convenience and the like.

  The supply roller 43 is formed from a conductive sponge or the like. The developing roller 44 is formed of a metal roll such as iron, stainless steel, aluminum, or nickel, or a resin roll obtained by coating such a metal roll with a silicone resin, a urethane resin, a fluorine resin, or the like. The surface of the developing roller 44 may be smoothed or roughened as necessary.

  Normally, the developing roller 44 is disposed between the electrophotographic photosensitive member 1 and the supply roller 43 and is in contact with the electrophotographic photosensitive member 1 and the supply roller 43, respectively. The supply roller 43 and the developing roller 44 are rotated by a rotation drive mechanism (not shown). The supply roller 43 carries the stored toner T and supplies it to the developing roller 44. The developing roller 44 carries the toner T supplied by the supply roller 43 and contacts the surface of the electrophotographic photosensitive member 1.

  The regulating member 45 is formed of, for example, a resin blade such as a silicone resin or a urethane resin, a metal blade such as stainless steel, aluminum, copper, brass, phosphor bronze, or a blade obtained by coating such a metal blade with a resin. The regulating member 45 contacts the developing roller 44 and is pressed against the developing roller 44 side with a predetermined force by a spring or the like (a general blade linear pressure is 5 to 500 gf / cm). If necessary, the regulating member 45 may be provided with a function of imparting charging to the toner T by frictional charging with the toner T.

  The agitator 42 is rotated by a rotation driving mechanism, and agitates the toner T and conveys the toner T to the supply roller 43 side. A plurality of agitators 42 may be provided with different blade shapes and sizes.

  The type of the toner T is arbitrary, and besides the pulverized toner, a polymerized toner using a suspension polymerization method, an emulsion polymerization method, or the like can be used. In particular, when a polymerized toner is used, a toner having a small particle diameter of about 4 to 8 μm is preferable, and the toner particles are used in various shapes ranging from a nearly spherical shape to a shape outside the spherical shape on the potato. be able to. The polymerized toner is excellent in charging uniformity and transferability and is suitably used for high image quality. The toner suitably used in the present invention will be described in detail later.

[Transfer means]
The transfer unit 5 is not particularly limited as long as it can transfer the toner image formed on the electrophotographic photosensitive member 1 to the transfer target, and corona transfer, roller transfer, belt transfer. It is possible to use any method such as an electrostatic transfer method, a pressure transfer method, an adhesive transfer method, or the like. For example, the transfer means 5 can be composed of a transfer charger, a transfer roller, a transfer belt, and the like disposed so as to face the electrophotographic photoreceptor 1. The transfer unit 5 applies a predetermined voltage value (transfer voltage) having a polarity opposite to the charging potential of the toner T, and transfers the toner image formed on the electrophotographic photosensitive member 1 to a transfer target (recording paper) P. .

[Cleaning means]
The cleaning unit 6 scrapes the residual toner adhering to the electrophotographic photosensitive member 1 with a cleaning member and collects the residual toner. The type is not particularly limited, and any cleaning means such as a brush cleaner, a magnetic brush cleaner, an electrostatic brush cleaner, a magnetic roller cleaner, and a blade cleaner can be used. However, when there is little or almost no toner remaining on the surface of the cleaning unit 6 and the photosensitive member, the cleaning unit 6 may be omitted.

[Fixing means]
The fixing means 7 can be constituted by, for example, an upper fixing member (pressure roller) 71 and a lower fixing member (fixing roller) 72. Usually, the fixing member 71 or 72 includes a heating device. 73 is usually provided. FIG. 1 shows an example in which a heating device 73 is provided inside the upper fixing member 71. The upper and lower fixing members 71 and 72 include a fixing roll in which a metal base tube made of stainless steel, aluminum or the like is coated with silicon rubber, a fixing roll in which Teflon (registered trademark) resin is coated, a fixing sheet, or the like. A member can be used. Further, the fixing members 71 and 72 may be configured to supply a release agent such as silicone oil in order to improve the releasability, or may be configured to forcibly apply pressure to each other by a spring or the like.

When the toner transferred onto the transfer target (recording paper) P passes between the upper fixing member 71 and the lower fixing member 72 heated to a predetermined temperature, the toner is heated to a molten state, and after passing, The toner is fixed on the transfer target (recording paper) P by being cooled.
The type of fixing means is not particularly limited, and fixing means of any type such as those used here, heat roller fixing, flash fixing, oven fixing, pressure fixing, and the like can be provided.

[Static elimination means]
The neutralizing means is not particularly limited as long as it is a means capable of neutralizing the electrophotographic photosensitive member. Examples of the static elimination method include a method of irradiating the electrophotographic photosensitive member with energy using a fluorescent lamp, LED or the like. In many cases, the light used in the static elimination step is light having an exposure energy that is at least three times that of exposure light at the time of image exposure.

<Electrophotographic cartridge>
Next, an electrophotographic cartridge using the electrophotographic photosensitive member will be described. The configuration and the like of the electrophotographic cartridge are not particularly limited as long as the electrophotographic cartridge includes the above-described electrophotographic photosensitive member. For example, the above-described electrophotographic photosensitive member, charging means for charging the electrophotographic photosensitive member, image exposure means for performing image exposure on the charged electrophotographic photosensitive member to form an electrostatic latent image, and forming on the electrophotographic photosensitive member Developing means for forming a toner image by attaching toner to the electrostatic latent image formed, transfer means for transferring the toner image on the electrophotographic photosensitive member to the transfer target, and remaining on the electrophotographic photosensitive member after the transfer of the toner image At least one of a charge eliminating unit that removes the electric charge and a cleaning unit that removes the toner remaining on the electrophotographic photosensitive member after the transfer of the toner image.

  The electrophotographic photosensitive member, charging unit, image exposing unit, developing unit, transfer unit, neutralizing unit, and cleaning unit used in the electrophotographic cartridge are described in the above-mentioned “electrophotographic photosensitive unit” and “image forming apparatus”, respectively. It can be the same as that.

  In general, the electrophotographic photosensitive member cartridge can be configured to be detachable from a main body of an image forming apparatus such as a copying machine or a laser beam printer. In this case, for example, when the electrophotographic photosensitive member or other member deteriorates, the electrophotographic cartridge is removed from the image forming apparatus main body, and another new electrophotographic cartridge is mounted on the image forming apparatus main body, thereby forming an image. Equipment maintenance and management are easy.

  In the electrophotographic cartridge using the electrophotographic photosensitive member, even when the electrophotographic photosensitive member is repeatedly used for image formation, the initial potential can be reduced little, and the target image can be obtained. High definition can be formed. Therefore, the electrophotographic cartridge of the present invention can be suitably used for an image forming apparatus as described in “Image forming apparatus”. In such an image forming apparatus, stable and high-quality image formation can be performed. Is possible.

<Toner>
The toner used in the image forming apparatus may be manufactured by any method, but toner particles manufactured in an aqueous medium, so-called polymerization toner is preferable. Examples of the polymerization toner include suspension polymerization toner and emulsion polymerization aggregation toner. In particular, the emulsion polymerization aggregation method is a method of producing a toner by aggregating polymer resin fine particles and a colorant in a liquid medium, and the toner particle diameter and circularity can be adjusted by controlling the aggregation conditions. It is preferable because it is possible. In order to improve releasability, low-temperature fixability, high-temperature offset resistance, filming resistance, etc., a method of incorporating a low softening point substance (so-called wax) into the toner has been proposed. In the melt-kneading pulverization method, it is difficult to increase the amount of wax contained in the toner, and the limit is about 5% with respect to the binder resin. On the other hand, the polymerized toner contains a low softening point substance in a large amount (5 to 30% by weight) as described in, for example, JP-A-59-194393 and JP-A-03-194560. It is said.

Hereinafter, the toner produced by the emulsion polymerization aggregation method will be described in more detail.
When a toner is produced by an emulsion polymerization aggregation method, it usually has a polymerization step, an aggregation step, a fusion step, and a washing / drying step. That is, generally, a dispersion containing primary polymer particles obtained by emulsion polymerization is mixed with a dispersion of a colorant, wax, charge control agent, etc., if necessary, and an aggregating agent is added to the dispersion. The primary particles are agglomerated to form particle agglomerates, and if necessary, fine particles and the like are adhered, and then the particles obtained by fusing are washed and dried to obtain mother particles.
The materials used in each step carried out by the emulsion polymerization aggregation method will be described in detail.

<Polymerization process>
The binder resin fine particles (polymer primary particles) used in the emulsion polymerization aggregation method are not particularly limited, but a polymerizable monomer is polymerized in a liquid medium by a suspension polymerization method, an emulsion polymerization method, or the like. Fine particles obtained are preferred, and those using wax as a seed in polymerization methods, particularly emulsion polymerization methods, and in particular, emulsion polymerization are preferred. In addition, you may use the microparticles | fine-particles obtained by grind | pulverizing binder resin as a polymer primary particle.
When wax is used as a seed in emulsion polymerization, fine particles having a shape in which a binder resin encloses the wax can be produced. According to this method, since the wax can be contained without being exposed on the surface of the toner, there is no inhibition of pigment particle adhesion by the wax particles. Further, it is possible to improve the low-temperature fixing property, high-temperature offset property, filming resistance, releasability, etc. of the toner without impairing the charging property of the toner.

Hereinafter, the fine particles of the binder resin obtained by emulsion polymerization using wax as a seed will be described.
The emulsion polymerization method may be performed according to a conventionally known method. Usually, wax is dispersed in a liquid medium in the presence of an emulsifier to form wax fine particles, which have a polymerization initiator and a polymerizable monomer that gives a binder resin by polymerization, that is, a polymerizable carbon-carbon double bond. The polymer is waxed by carrying out the polymerization in the presence of the compound, and optionally a chain transfer agent, a pH adjuster, a polymerization degree adjuster, an antifoaming agent, a protective colloid, an internal additive, etc. It is possible to obtain an emulsion in which binder resin fine particles having a shape enveloping are dispersed in a liquid medium. Examples of the shape in which the polymer wraps the wax include a core-shell type, a phase separation type, and an occlusion type, and the core-shell type is preferable.

  Below, the wax, monomer, surfactant, and other components (polymerization initiator, chain transfer agent, crosslinking agent) used in the above method will be described.

(wax)
As the wax, any known wax that can be used for this purpose can be used. Specifically, olefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene and copolymer polyethylene; paraffin wax; silicone wax having an alkyl group; fluororesin wax such as low molecular weight polytetrafluoroethylene; higher grades such as stearic acid Fatty acids; Long-chain aliphatic alcohols such as eicosanol; Ester waxes having long-chain aliphatic groups such as behenyl behenate, montanate ester, stearyl stearate; Ketones having long-chain alkyl groups such as distearyl ketone; Water Plant waxes such as soy castor oil and carnauba wax; esters or partial esters obtained from polyhydric alcohols such as glycerin and pentaerythritol and long chain fatty acids; higher fatty acid amides such as oleic acid amide and stearic acid amide; Polyester, and the like. Especially, what has at least 1 the endothermic peak by a differential thermal analysis (DSC) in 50-100 degreeC is preferable.

  In addition, olefin waxes such as ester wax, paraffin wax, low molecular weight polypropylene, copolymer polyethylene, silicone wax, and the like are preferable because a release effect can be obtained in a small amount.

  When wax is used, it is preferably used in a proportion of 3 parts by weight or more with respect to 100 parts by weight of the binder resin. Of these, 5 parts by weight or more is preferable. The upper limit is usually 40 parts by weight or less, preferably 30 parts by weight or less.

(Polymerizable monomer)
Although it does not specifically limit as a polymerizable monomer, Styrenes, (meth) acrylic acid ester, acrylamides, the monomer which has a Bronsted acidic group (henceforth abbreviated as "acidic monomer" only) Monofunctional monomers such as a monomer having a Bronsted basic group (hereinafter sometimes simply referred to as “basic monomer”) are mainly used. Further, a monofunctional monomer can be used in combination with a polyfunctional monomer.

Examples of styrenes include styrene, methyl styrene, chlorostyrene, dichlorostyrene, p-tert-butyl styrene, pn-butyl styrene, pn-nonyl styrene, and the like.
As (meth) acrylic acid ester, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, hydroxyethyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate , Propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, hydroxyethyl methacrylate, and 2-ethylhexyl methacrylate.
Examples of acrylamides include acrylamide, N-propyl acrylamide, N, N-dimethyl acrylamide, N, N-dipropyl acrylamide, N, N-dibutyl acrylamide, and the like.
These polymerizable monomers may be used alone or in combination of two or more.

Examples of acidic monomers include monomers having a carboxyl group such as acrylic acid, methacrylic acid, maleic acid, fumaric acid and cinnamic acid, monomers having a sulfonic acid group such as sulfonated styrene, and sulfonamide groups such as vinylbenzenesulfonamide. And the like.
Basic monomers include aromatic vinyl compounds having an amino group such as aminostyrene, nitrogen-containing heterocycle-containing monomers such as vinylpyridine and vinylpyrrolidone, and amino groups such as dimethylaminoethyl acrylate and diethylaminoethyl methacrylate (meth) Examples include acrylic acid esters. The acidic monomer and basic monomer may exist as a salt with a counter ion.

  Examples of multifunctional monomers include divinylbenzene, hexanediol diacrylate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, diallyl phthalate, etc. Can be mentioned. It is also possible to use a monomer having a reactive group such as glycidyl methacrylate, N-methylolacrylamide, or acrolein. Among these, radically polymerizable bifunctional monomers, particularly divinylbenzene and hexanediol diacrylate are preferable.

  Among these, at least styrenes, (meth) acrylic acid esters, and preferably composed of an acidic monomer having a carboxyl group are preferable. Particularly, styrenes as styrenes, butyl acrylate as carboxylates (meth) acrylates, carboxyl groups It is preferable that it is acrylic acid as an acidic monomer which has this.

  When emulsion polymerization is performed using wax as a seed, it is preferable to use an acidic monomer or a basic monomer and a monomer other than these in combination. When an acidic monomer or a basic monomer is used for polymerization, it is usually used in an amount of 0.05 part by weight or more with respect to 100 parts by weight of the total polymerizable monomer. Of these, 0.5 parts by weight or more, particularly 1 part by weight or more is preferable. The upper limit is usually 10 parts by weight or less, preferably 5 parts by weight or less. By using an acidic monomer or a basic monomer in combination, the dispersion stability of the binder resin can be improved.

  When a polyfunctional monomer is used in combination, the blending amount is usually 0.005 part by weight or more with respect to 100 parts by weight of the polymerizable monomer. Of these, 0.1 parts by weight or more, more preferably 0.3 parts by weight or more is preferable. The upper limit is usually 5 parts by weight or less, preferably 3 parts by weight or less, more preferably 1 part by weight or less. By using a polyfunctional monomer, the fixability of the toner can be improved.

(Polymerization initiator)
The polymerization initiator used is not particularly limited, but persulfates such as sodium persulfate and ammonium persulfate, and organic peroxides such as t-butyl hydroperoxide, cumene hydroperoxide, and p-menthane hydroperoxide. And inorganic peroxides such as hydrogen peroxide. Of these, inorganic peroxides are preferred. These may be used alone or in combination of two or more.
These are usually used at a ratio of 0.05 to 2 parts by weight with respect to 100 parts by weight of the polymerizable monomer.

  Also, persulfates, organic or inorganic peroxides, reducing organic compounds such as ascorbic acid, tartaric acid and citric acid, reducing inorganic compounds such as sodium thiosulfate, sodium bisulfite, sodium metabisulfite, etc. Can also be used as a redox initiator. In this case, the reducing inorganic compounds may be used alone or in combination of two or more.

(emulsifier)
The emulsifier used is not particularly limited. For example, any of nonionic, anionic, cationic and amphoteric surfactants can be used.

  Nonionic surfactants include polyoxyalkylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyalkylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether, sorbitan fatty acid esters such as sorbitan monolaurate, etc. Is mentioned.

  Examples of the anionic surfactant include fatty acid salts such as sodium stearate and sodium oleate, alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, and alkyl sulfate esters such as sodium lauryl sulfate.

Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride.
Examples of amphoteric surfactants include alkylbetaines such as lauryl betaine.
Among these, nonionic surfactants and anionic surfactants are preferable. The emulsifier may be used alone or in combination of two or more.
An emulsifier is normally used in the ratio of 1-10 weight part with respect to 100 weight part of polymerizable monomers.

(Other)
Any known chain transfer agent can be used. Specific examples include t-dodecyl mercaptan, 2-mercaptoethanol, diisopropyl xanthogen, carbon tetrachloride, trichlorobromomethane, and the like. These may be used alone or in combination of two or more. The chain transfer agent is usually used at a ratio of 5 parts by weight or less with respect to 100 parts by weight of the polymerizable monomer.
As the protective colloid, any known colloid that can be used in this application can be used. Specifically, polyvinyl alcohols such as partially or completely saponified polyvinyl alcohol, and cellulose derivatives such as hydroxyethyl cellulose. And the like.
Examples of the internal additive include those for modifying the adhesiveness, cohesiveness, fluidity, chargeability, surface resistance, and the like of toner such as silicone oil, silicone varnish, and fluorine oil.

  The liquid medium is usually water and is used in an amount of about 1 to 20 times by weight with respect to the polymerizable monomer. The reaction temperature of the emulsion polymerization reaction is not particularly limited, but the polymerization temperature is usually 50 ° C. or higher, preferably 60 ° C. or higher, more preferably 70 ° C. or higher. Moreover, it is 120 degrees C or less normally, Preferably it is 100 degrees C or less, More preferably, it is 90 degrees C or less.

The method of mixing the polymerizable monomer into the liquid medium is not particularly limited, and any of batch mixing, continuous mixing, and intermittent mixing may be used, but continuous mixing is preferable from the viewpoint of reaction control. Moreover, when using several polymerizable monomer together, each polymerizable monomer may be mixed separately, and may be mixed after mixing beforehand. Furthermore, you may mix, changing the composition of a monomer mixture. The emulsifier is preferably premixed in the liquid medium, but may be continuously mixed in the liquid medium.
As the fine particles of the binder resin, one kind may be used, or two or more kinds produced with different raw materials and reaction conditions may be used in combination.

  The binder resin emulsion obtained by emulsion polymerization may be mixed with fine particles of the binder resin obtained by a method other than emulsion polymerization. Examples of the fine particles obtained by a method other than emulsion polymerization include fine particles obtained by suspension polymerization or pulverization. As such a resin, in addition to the monomer (co) polymer used for the emulsion polymerization described above, a single monomer such as vinyl acetate, vinyl chloride, vinyl alcohol, vinyl butyral, vinyl pyrrolidone, etc. Polymers or copolymers, saturated polyester resins, polycarbonate resins, polyamide resins, polyolefin resins, polyarylate resins, polysulfone resins, polyphenylene ether resins, and other thermoplastic resins, and unsaturated polyester resins, phenol resins, epoxy resins, urethane resins And particles composed of a thermosetting resin such as rosin-modified maleic resin, and these may be used alone or in combination of two or more. The proportion of fine particles obtained by a polymerization method other than emulsion polymerization in the total fine particles of the binder resin is usually 5% by weight or less.

(Binder resin fine particles (polymer primary particles))
As the binder resin (polymer primary particles) obtained by the above method, it is preferable to use those having a volume average particle diameter of usually 0.02 μm or more. It is more preferable to use those having a volume average particle size of 0.05 μm or more, and more preferably 0.1 μm or more. The upper limit is usually preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1 μm or less. If the volume average particle size is too small, it may be difficult to control the aggregation rate. If the volume average particle size is too large, the particle size of the toner obtained by agglomeration tends to be large, and it may be difficult to obtain a toner having a target particle size. The volume average particle diameter can be measured with a particle size analyzer using a dynamic light scattering method described later.

  It is preferable that at least one of the peak molecular weights in the gel permeation chromatography is in the range of 3000 to 100,000 in the binder resin. In particular, the peak molecular weight is more preferably 10,000 or more, more preferably 30,000 or more, and 70,000 or less, and even more preferably 60,000 or less. When the peak molecular weight is in the above range, the durability, storage stability, and fixability of the toner tend to be good. Here, as the peak molecular weight, a value in terms of polystyrene is used, and components insoluble in a solvent are excluded in measurement.

  In particular, when the binder resin is a styrene resin, the lower limit of the number average molecular weight in gel permeation chromatography is preferably 2000 or more, more preferably 2500 or more, and even more preferably 3000 or more. The upper limit is preferably 50,000 or less, and more preferably 40,000 or less.

The lower limit of the weight average molecular weight is preferably 20,000 or more, and more preferably 30,000 or more. The upper limit is preferably 1,000,000 or less, more preferably 500,000 or less.
A toner using a styrene resin in which at least one of the number average molecular weight and the weight average molecular weight, preferably both are in the above range, has good durability, storage stability and fixability. Further, the molecular weight distribution may have two main peaks. The styrene-based resin preferably refers to those in which styrenes account for 50% by weight or more, and more preferably 65% by weight or more.

  The softening point of the binder resin (hereinafter sometimes abbreviated as “Sp”) is not particularly limited, but it is preferably 150 ° C. or less, particularly 140 ° C. or less from the viewpoint of low energy fixing, 80 ° C. or more, particularly 100 ° C. The above is preferable in terms of high temperature offset resistance and durability. Here, Sp is a flow tester, when a 1.0 g sample is measured under conditions of a nozzle of 1 mm × 10 mm, a load of 30 kg, a preheating time of 50 ° C. for 5 minutes, and a heating rate of 3 ° C./min. It can be determined as the temperature at the midpoint of the strand from end to end.

  The glass transition point (hereinafter sometimes abbreviated as “Tg”) of the binder resin is preferably 80 ° C. or less, particularly preferably 70 ° C. or less. If Tg is too high, there is a possibility that low energy fixing cannot be performed. Moreover, it is preferable that the minimum of Tg is 40 degreeC or more, especially 50 degreeC or more. If Tg is too low, the blocking resistance may decrease. Here, Tg is obtained by drawing a tangent line at the start of transition (inflection) of a curve measured with a differential scanning calorimeter (DTA-40 manufactured by Shimadzu Corporation) at a temperature rising rate of 10 ° C./min. It can be determined as the temperature of the intersection. The Sp and Tg of the binder resin can be adjusted to the above ranges by adjusting the resin type, monomer composition ratio, molecular weight, and the like.

<Aggregation process>
The agglomeration step is mainly performed by adding an aqueous dispersion of colorant particles such as pigment particles to the emulsion in which fine particles of the binder resin prepared in the above step are dispersed, and agglomerating the emulsion containing the binder resin and the pigment. It is the process of obtaining. In that case, you may coexist a charge control agent, a mold release agent, an internal additive, etc. as needed. In order to maintain the stability of the pigment particle dispersion, the above-mentioned emulsifier may be added.
First, materials (colorant particles, charge control agents, etc.) used in the aggregation process will be described in detail below.

(Colorant particles)
The colorant particles are more uniformly aggregated when the density difference from the polymer primary particles (about 1.1 to 1.3 g / cm ³ as resin particles) in the emulsion polymerization aggregation method is smaller, and is obtained as a result. The toner performance is improved. Therefore, it is preferable that the true density of the colorant particles measured by the pycnometer method specified in JIS K 5101-11-1: 2004 is less than 2.0 g / cm ³ , and 1.2 to 1.9 g / more preferably from cm ^3, and particularly preferably from 1.3~1.8g / cm ^3. When the true density is too large, the sedimentation property in an aqueous medium tends to deteriorate. In addition, in consideration of storage stability and sublimation properties, the colorant is preferably carbon black or an organic pigment.

The colorant to be used is not particularly limited, and any of an inorganic pigment, an organic pigment, an organic dye, or a combination thereof may be used. The colorant may be chromatic or achromatic. Examples thereof include the following yellow pigments, magenta pigments, and cyan pigments. As the black pigment, carbon black or a mixture of the following yellow pigment / magenta pigment / cyan pigment mixed with black is used.
Among these, carbon black as a black pigment exists as an aggregate of very fine primary particles, and when dispersed as a pigment dispersion, coarsening of particles due to reaggregation tends to occur. According to the study by the present inventors, the degree of reagglomeration of the carbon black particles is correlated with the amount of impurities contained in the carbon black (the degree of residual undecomposed organic matter). There was a tendency for coarsening due to re-aggregation. As a quantitative evaluation of the amount of impurities, the ultraviolet absorbance of the toluene extract of carbon black measured by the following method is preferably 0.05 or less, and more preferably 0.03 or less. Generally, carbon black produced by the channel method tends to have a large amount of impurities, and therefore, carbon black produced by the furnace method is preferred as the carbon black in the present invention.

  The ultraviolet absorbance (λc) of carbon black is determined by the following method. First, 3 g of carbon black was sufficiently dispersed and mixed in 30 ml of toluene. Filter using 5C filter paper. Thereafter, the filtrate was put in a quartz cell having a 1 cm square light absorption part, and the value (λs) measured for absorbance at a wavelength of 336 nm using a commercially available ultraviolet spectrophotometer, and the value obtained by measuring the absorbance of toluene alone as a reference using the same method. From (λo), the ultraviolet absorbance is obtained by λc = λs−λo. Examples of commercially available spectrophotometers include an ultraviolet-visible spectrophotometer (UV-3100PC) manufactured by Shimadzu Corporation.

  As the yellow pigment, for example, a compound represented by a condensed azo compound, an isoindolinone compound, or the like is used. Specifically, C.I. I. Pigment Yellow 12, 13, 14, 15, 17, 62, 74, 83, 93, 94, 95, 109, 110, 111, 128, 129, 147, 168, 180, 185 and the like are preferably used.

  Examples of magenta pigments include condensed azo compounds, diketopyrrolopyrrole compounds, anthraquinones, quinacridone compounds, basic dye lake compounds, naphthol compounds, benzimidazolone compounds, thioindigo compounds, and perylene compounds. Specifically, C.I. I. Pigment Red 2, 3, 5, 6, 7, 23, 48: 2, 48: 3, 48: 4, 57: 1, 81: 1, 122, 144, 146, 166, 169, 177, 184, 185, 202, 206, 207, 209, 220, 221, 238, 254, C.I. I. Pigment Violet 19 or the like is preferably used. Among them, C.I. I. Pigment red 122, 202, 207, 209, C.I. I. A quinacridone pigment represented by pigment violet 19 is particularly preferred. This quinacridone pigment is suitable as a magenta pigment because of its clear hue and high light resistance. Among the quinacridone pigments, C.I. I. The compound represented by CI Pigment Red 122 is particularly preferable in view of dispersibility.

  As the cyan pigment, copper phthalocyanine and its derivatives, anthraquinone compounds, basic dye lake compounds and the like can be used. Specifically, C.I. I. Pigment Blue 1, 7, 15, 15: 1, 15: 2, 15: 3, 15: 4, 60, 62, 66 and the like can be used particularly preferably.

It is preferable to prepare a colorant dispersion in which the above-mentioned pigments are uniformly dispersed in advance in a liquid medium using a surfactant or the like and mix this with an emulsion of binder resin fine particles. As the surfactant used for the preparation of the colorant dispersion, the above-mentioned surfactants are used, and in particular, nonionic surfactants, anionic surfactants such as alkylaryl sulfonates such as sodium dodecylbenzenesulfonate, polymers A system surfactant or the like is preferably used.
The proportion of the colorant in the colorant dispersion is usually 10 to 50% by weight.

  The amount of the colorant particles used in the colorant dispersion is preferably 3 parts by weight or more, more preferably 5 parts by weight or more, and preferably 50 parts by weight or less, more preferably 100 parts by weight of water. 40 parts by weight or less. When the amount of the colorant exceeds the above range, the concentration of the colorant is high, which is not preferable because the probability of reaggregation of the particles is increased during the dispersion. Since it becomes difficult to obtain a particle size distribution, it is not preferable.

  Various known wet mills have been proposed as a method for obtaining a particle size by dispersing the pigment, and any of them can be used preferably. Examples of this type include ball mills, attritors, sand mills, and bead mills, and conditions may be selected as appropriate. The outline of each method is as follows.

Ball mill: A method in which a wet dispersion medium, a material to be pulverized, and media beads of about 10 to 30 mm are placed in a drum-like container, and the drum is rotated to grind the material to be crushed between the beads and the beads and the drum.
Attritor: A method in which a wet dispersion medium and an object to be crushed are placed in a tank, media beads of about 3 to 15 mm are placed, and the mixture is forcibly stirred and ground with an agitator arm such as alumina.
Sand mill: A system in which media beads of about 1 to 5 mm are added to a premixed wet dispersion medium and the material to be crushed, and then a sand disk is immersed and rotated and moved at a specified speed.
・ Bead mill (annular type): Filling media beads of about 1 to 3 mm between the rotor and stator of the container, and rotating the rotor at a high speed to give a flow rate difference between the beads, shear stress and shearing force A method of grinding and dispersing by friction.

In the present invention, the volume particle size distribution of the pigment particles in the pigment dispersion is measured by a dynamic light scattering method. In this method, a particle size distribution is obtained by irradiating particles with laser light and detecting scattering (Doppler shift) of light having different phases according to the speed of Brownian motion of finely dispersed particles. The value of the volume particle size of these pigment particles is a value when the colorant particles are stably dispersed in the aqueous system, and does not mean the particle size of the pigment or wet cake as the powder before dispersion. In actual measurement, the above volume particle size can be measured with the following settings using an ultrafine particle size distribution measuring apparatus using a dynamic light scattering method (UPA-EX150, manufactured by Nikkiso Co., Ltd.).
Measurement upper limit: 6.54 μm
Measurement lower limit: 0.0008 μm
Number of channels: 52
Measurement time: 100 sec.
Particle permeability: Absorbing particle refractive index: N / A (not applicable)
Particle shape: non-spherical density (g / cm ³ ): 1
Dispersion medium type: WATER
Dispersion medium refractive index: 1.333

At the time of measurement, the colorant dispersion was diluted with pure water so that the sample concentration index was in the range of 0.01 to 0.1, and measured with a sample subjected to dispersion treatment with an ultrasonic cleaner.
Note that the particle size distribution of the wax dispersion and the polymer dispersion can also be measured by the same method as described above.
Further, the ratio of the amount of the pigment to the binder resin is usually 1% by weight or more, preferably 3% by weight or more, and usually 20% by weight or less, preferably 15% by weight or less.

  The water quality of the binder resin particles and the pigment particle dispersion is also related to the coarsening due to reaggregation of each particle. When the conductivity is high, the dispersion stability with time tends to deteriorate. Therefore, it is preferable to use ion-exchanged water or distilled water that has been desalted so that its conductivity is preferably 10 μS / cm or less, more preferably 5 μS / cm or less. The conductivity is measured at 25 ° C. using a conductivity meter (personal SC meter model SC72 and detector SC72SN-11 manufactured by Yokogawa Electric Corporation).

(Charge control agent)
The charge control agent is used as necessary, and any known charge control agent can be used. Examples of the positive charge control agent include nigrosine dyes, quaternary ammonium salts, triphenylmethane compounds, imidazole compounds, and polyamine resins. Negatively charged charge control agents include azo complex compound dyes containing atoms such as Cr, Co, Al, Fe, and B, metal salts or metal complexes of salicylic acid or alkylsalicylic acid, curixarene compounds, metal salts of benzylic acid Alternatively, metal complexes, amide compounds, phenol compounds, naphthol compounds, phenol amide compounds, and the like can be given. Among them, it is preferable to select a colorless or light-colored toner in order to avoid a color tone failure as a toner. Particularly, as a positively chargeable charge control agent, a quaternary ammonium salt or an imidazole compound is preferable, and as a negatively chargeable charge control agent. Is preferably an alkyl salicylic acid complex compound or a curixarene compound containing atoms such as Cr, Co, Al, Fe, and B. The charge control agent may be used alone or in combination of two or more.
The ratio of the charge control agent is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, and preferably 10 parts by weight or less, more preferably 5 parts by weight with respect to 100 parts by weight of the binder resin. It is as follows.
In the emulsion polymerization aggregation method of the present invention, it is preferable to add the charge control agent in the state of being emulsified in an aqueous medium at the time of aggregation.

(Aggregation method)
Examples of the aggregation method of the emulsion in the present invention include methods such as heat treatment, mixing an electrolyte, and adjusting pH. Especially, the method of mixing electrolyte is preferable.
Examples of the electrolyte in the case of performing aggregation by adding and mixing the electrolyte to Elmajon include chlorides such as NaCl, KCl, LiCl, MgCl ₂ and CaCl ₂ , Na ₂ SO ₄ , K ₂ SO ₄ , Li ₂ SO _4. Inorganic salts such as sulfate such as MgSO ₄ , CaSO ₄ , ZnSO ₄ , Al ₂ (SO ₄ ) ₃ , Fe ₂ (SO ₄ ) ₃ , and organic salts such as CH ₃ COONa and C ₆ H ₅ SO ₃ Na Can be mentioned. Of these, inorganic salts having a divalent or higher polyvalent metal cation are preferred.

  The amount of electrolyte mixed varies depending on the type of electrolyte, but is usually 0.05 parts by weight or more, preferably 0.1 parts by weight or more, and usually 25 parts by weight or less, based on 100 parts by weight of the solid component in the emulsion. Preferably it is 15 weight part or less, More preferably, it is 10 weight part or less. In the case of agglomerating by mixing the electrolyte, if the amount of the electrolyte is too small, the progress of the agglutination reaction is delayed, and fine particles of 1 μm or less remain after the agglomeration reaction, or the average particle size of the obtained agglomerates is the target. The particle size may not be reached. Moreover, when there is too much mixing amount of electrolyte, since agglomeration reaction will occur rapidly, control of a particle size will become difficult, and a coarse powder and an amorphous thing may be contained in the obtained aggregate.

  The conditions for aggregating by heating are not particularly limited, but are usually 15 ° C. or higher, preferably 20 ° C. or higher, and usually Tg or lower, preferably 55 ° C. of the binder resin. The stirring is usually performed for 10 minutes or longer, preferably 60 minutes or longer, and within 300 minutes, preferably within 180 minutes. The stirrer is not particularly limited, but preferably has a double helical blade.

<Resin coating layer forming step (encapsulation step)>
The obtained agglomerated particles may proceed directly to the next step of forming a resin coating layer (also referred to as an encapsulation step), or continue to the fusion process by heating in a liquid medium and then proceed to the encapsulation step. But you can. Preferably, after the aggregation step, the encapsulation step is performed, and then the aggregated primary particles and the encapsulated resin fine particles are combined and heated at a temperature equal to or higher than the glass transition point of the encapsulated resin fine particles to perform the fusion step. This is preferable because the process can be simplified and toner performance degradation (such as thermal degradation) does not occur.

The step of forming a resin coating layer on the aggregated particles (encapsulation step) is to obtain a toner in which the surface of the toner particles is formed of a resin and the colorant is not substantially exposed on the surface of the toner particles. The thickness of the coating layer at this time is preferably in the range of 0.01 to 0.5 μm.
The method for forming the resin coating layer is not particularly limited, and examples thereof include a spray drying method, a mechanical particle composite method, an in-situ polymerization method, and a liquid particle coating method.
The method for forming the resin coating layer by the spray drying method is, for example, by dispersing agglomerated particles forming the inner layer and resin fine particles forming the resin coating layer in an aqueous medium to prepare a dispersion, and spraying the dispersion. In this method, a resin coating layer is formed on the surface of the aggregated particles by spraying and drying.
The resin coating layer is formed by the mechanical particle composite method. For example, the aggregated particles forming the inner layer and the resin fine particles forming the resin coating layer are dispersed in the gas phase, and mechanical force is applied in a narrow gap. This is a method of forming resin fine particles on the surface of aggregated particles. For example, apparatuses such as a hybridization system (manufactured by Nara Machinery Co., Ltd.) and a mechano-fusion system (manufactured by Hosokawa Micron) can be used.

In the in-situ polymerization method, for example, agglomerated particles are dispersed in water, a monomer and a polymerization initiator are allowed to coexist, adsorbed on the surface of the agglomerated particles, and heated to polymerize the monomer. In this method, a resin coating layer is formed on the surface of certain aggregated particles.
The submerged particle coating method is a method in which aggregated particles forming an inner layer and resin fine particles forming an outer layer are reacted or bonded in an aqueous medium to form a resin coating layer on the surface of the aggregated particles forming the inner layer. is there.

The resin fine particles used for forming the outer layer are not particularly limited as long as they are particles composed of a polymer, but from the viewpoint that the thickness of the outer layer can be controlled, polymer primary particles, aggregated particles, or fused particles of aggregated particles It is preferable that The polymer primary particles, aggregated particles and fused particles constituting the outer layer are produced by the same production method using the same polymers as the polymer primary particles, aggregated particles and fused particles used in the inner layer. be able to.
The amount of resin fine particles to be used is usually preferably 1% by weight or more, more preferably 5% by weight or more, usually 50% by weight or less, more preferably 25% by weight or less based on the toner particles. The resin fine particles mean particles having a particle size smaller than that of toner particles and mainly composed of a resin component, and those having a particle size of about 0.04 to 1 μm are preferably used in order to effectively fix or fuse them.

  As a glass transition point (Tg) of the polymer component used for a resin coating layer, 60 degreeC or more is preferable normally, More preferably, it is 70 degreeC or more, and normally an upper limit has preferable 110 degreeC. Especially, it is preferable that it is 5 degreeC or more higher than the glass transition point of a polymer primary particle, and it is more preferable that it is 10 degreeC or more higher. If Tg is too low, storage in a general environment is difficult, and if it is too high, sufficient meltability cannot be obtained, which is not preferable.

<Fusion process>
In the fusion step after the formation of the resin coating layer, the binder resin constituting the aggregate and the resin coating layer on the surface thereof are formed by heat treatment at a temperature equal to or higher than the glass transition point of the polymer component forming the resin coating layer. As a result of fusion and integration, toner particles having a nearly spherical shape can be obtained. Thereby, a form in which the pigment particles are not substantially exposed on the surface is obtained.

  The temperature of the heat treatment in the fusion step is preferably a temperature equal to or higher than the glass transition point of the polymer component forming the resin coating layer (of course, equal to or higher than the glass transition temperature of the polymer primary particles constituting the aggregate). More preferably, the glass transition temperature of the polymer component forming the resin coating layer +5 (° C.) or higher. The upper limit is preferably not higher than the glass transition temperature of the polymer component forming the resin coating layer +50 (° C.). The time for the heat treatment is usually 0.5 to 6 hours although it depends on the treatment capacity and the production amount.

<Washing and drying process>
When the toner particles used in the present invention are produced by forming a resin coating layer on the surface of the aggregated particles in an aqueous medium, the aqueous dispersion of the encapsulated toner particles is dehydrated and dried to form a powder. The resin-coated toner particles can be obtained to obtain the toner used in the present invention.

<Toner>
The volume average particle diameter Dv of the toner particles used in the present invention is preferably 4 μm or more, more preferably 5 μm or more, and preferably 10 μm or less, more preferably 8 μm. Further, the value (Dv / Dn) obtained by dividing the volume average particle diameter (Dv) of the obtained toner by the number average particle diameter (Dn) is preferably 1.0 or more. Further, it is preferably 1.25 or less, more preferably 1.20 or less, and particularly preferably 1.15 or less. The value of Dv / Dn represents the state of the particle size distribution. The closer this value is to 1.0, the sharper the particle size distribution is, and the chargeability of the toner becomes uniform.
The volume fraction of toner having a particle size of 25 μm or more is preferably 1% or less, and more preferably 0.5% or less. This value is preferably as small as possible, and is preferably 0.1% or less, and more preferably 0.05% or less. This means that the ratio of the coarse powder contained in the toner is small, and it is preferable that the coarse powder is small because the amount of toner consumed during continuous development is small and the image quality is stabilized. It is preferable that there is no coarse powder having a particle size of 25 μm or more, but it is difficult in actual production, and usually it is not necessary to make it 0.005% or less.

Further, the volume fraction of toner having a particle size of 15 μm or more is preferably 2% or less, particularly 1% or less, and further preferably 0.1% or less. It is preferable that there is no coarse powder having a particle size of 15 μm or more, but it is difficult in actual production, and it is usually not necessary to make it 0.01% or less.
Further, the number fraction of the toner having a particle diameter of 5 μm or less is preferably 15% or less, and more preferably 10% or less, since it is effective for improving the image fog.

  Here, as a toner particle size measuring device, a Coulter counter Multisizer II type (manufactured by Beckman Coulter) was used, and an interface for outputting the number distribution and volume distribution and a general personal computer were connected, and electrolysis was performed. Isoton II is used as the liquid. As a measuring method, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution, and further 2 to 20 mg of a measurement sample is added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and measured using a Coulter counter Multisizer II type with a 100 μm aperture. The number and volume of the toner are measured to calculate the number distribution and the volume distribution, respectively, and the number average diameter and the volume average diameter are obtained, respectively.

  Further, the shape of the toner used in the present invention, particularly the toner produced by the emulsion polymerization aggregation method, is preferably close to a sphere, and the average circularity is preferably 0.940 or more, more preferably 0.950 or more, and further Preferably it is 0.960 or more. The closer the shape is to a sphere, the less the charge amount is localized in the particles, and the developability tends to be uniform. On the other hand, since poor cleaning is likely to occur and it is difficult to produce a perfect spherical toner, the average circularity is preferably 0.995 or less, more preferably 0.990 or less.

The circularity in the present invention is used as a simple method for quantitatively expressing the particle shape. In the present invention, the circularity is measured by using a flow type particle image analyzer FPIA-2000 manufactured by Sysmex Corporation. The circularity of the obtained particles is obtained by the following equation (1).
Circularity a = L ₀ / L (1)
[In the formula, L ₀ represents the perimeter of a circle having the same projected area as the particle image, and L represents the perimeter of the particle image when image processing is performed. ]

The circularity used in the present invention is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is perfectly spherical, and the circularity becomes smaller as the surface shape becomes more complicated.
As a specific measurement method, a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 20 ml of water from which impurities in the container have been removed in advance, and about 0.05 g of a measurement sample is further added. The suspension in which the sample is dispersed is irradiated with ultrasonic waves for 30 seconds, the dispersion concentration is set to 3.0 to 8.0 thousand pieces / μl, and the above flow-type particle image measuring apparatus is used. The circularity distribution of particles having an equivalent circle diameter is measured.

  The softening point (Sp) of the toner is preferably 150 ° C. or lower, particularly 140 ° C. or lower from the viewpoint of fixing with low energy. Further, from the viewpoint of high temperature offset resistance and durability, those having a softening point of 80 ° C. or higher, particularly 100 ° C. or higher are preferable.

Further, it is preferable that the toner has a glass transition point (Tg) of 80 ° C. or lower, particularly 70 ° C. or lower because fixing can be performed with low energy. The glass transition point is preferably 40 ° C. or higher, particularly 50 ° C. or higher, from the viewpoint of blocking resistance.
The measurement of the softening point and glass transition point of the toner is in accordance with the method for measuring the binder resin described above.

  Since the softening point and glass transition point of the toner are greatly affected by the type and composition ratio of the binder resin, they can be adjusted by appropriately optimizing them. Moreover, it can adjust also with the kind and compounding quantity of low melting-point components, such as molecular weight of a binder resin, a gel content, and wax.

  When the toner contains a wax, the dispersed particle size of the wax in the toner particles is preferably 0.1 μm or more as an average particle size, more preferably 0.3 μm or more, and the upper limit is preferably 3 μm or less, particularly 1 μm or less. More preferred. If the dispersed particle size is too small, it is difficult to obtain the effect of improving the filming resistance of the toner. If the dispersed particle size is too large, the wax is likely to be exposed on the surface of the toner, and the chargeability and heat resistance may decrease. The dispersed particle size of the wax is determined by observing an electron microscope by slicing the toner, or by eluting the binder resin of the toner with an organic solvent that does not dissolve the wax and filtering it with a filter. It can be confirmed by the measurement method.

  Further, the proportion of the wax in the toner is usually preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and usually preferably 20% by weight or less, more preferably 15% by weight or less. .

(Externally added fine particles)
In order to improve toner fluidity, charging stability, anti-blocking property at high temperatures, and the like, external additive fine particles may be added to the surface of the toner particles.

  The method of adhering the externally added fine particles to the toner particle surface is a method in which the toner particles and the externally added fine particles are mixed in a liquid medium and then heated to fix the externally added fine particles on the toner particles. And a method in which externally added fine particles are mixed or fixed in a dry manner to toner particles obtained by drying.

  Examples of the mixer used when the toner particles and the externally added fine particles are mixed in a dry process include a Henschel mixer, a super mixer, a Nauter mixer, a V-type mixer, a Redige mixer, a double cone mixer, and a drum type mixer. Among them, it is preferable to use a high-speed agitation type mixer such as a Henschel mixer or a super mixer, and appropriately stir and mix by appropriately setting the blade shape, the number of revolutions, the time, the number of times of driving and stopping, and the like.

  Examples of the apparatus used when the toner particles and the externally added fine particles are fixed by a dry method include an apparatus that can apply a compressive shear stress and an apparatus that can melt the particle surface.

  A compression shearing apparatus generally has a narrow gap portion composed of a head surface and a head surface, a head surface and a wall surface, or a wall surface and a wall surface that move relatively while maintaining a gap, and particles to be processed are disposed in the gap. By being forced to pass through the portion, compressive stress and shear stress are applied to the particle surface without substantial pulverization. An example of such a compression shearing apparatus is a mechanofusion apparatus manufactured by Hosokawa Micron.

In general, the particle surface melting apparatus is configured so that a mixture of base fine particles and externally added fine particles can be instantaneously heated above the melting start temperature of the base fine particles by using a hot air stream or the like to fix the externally added fine particles. Examples of such a particle surface melting apparatus include a surfing system manufactured by Nippon Pneumatic Co., Ltd.
As the externally added fine particles, known fine particles that can be used for this purpose can be used, and specific examples include inorganic fine particles and organic fine particles.

  Examples of inorganic fine particles include silicon carbide, boron carbide, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, tantalum carbide, niobium carbide, tungsten carbide, chromium carbide, molybdenum carbide, calcium carbide, boron nitride, titanium nitride, Nitrides such as zirconium nitride and silicon nitride, borides such as zirconium boride, silica, colloidal silica, titanium oxide, aluminum oxide, calcium oxide, magnesium oxide, zinc oxide, copper oxide, zirconium oxide, cerium oxide, talc, hydro Oxides and hydroxides such as talcite, calcium titanate, magnesium titanate, strontium titanate, various titanate compounds such as barium titanate, tricalcium phosphate, calcium dihydrogen phosphate, calcium monohydrogen phosphate, phosphoric acid Phosphorus compounds such as substituted calcium phosphates, some of which are replaced by anions, sulfides such as molybdenum disulfide, fluorides such as magnesium fluoride and carbon fluoride, aluminum stearate, calcium stearate, zinc stearate, Various types of carbon black such as metal soap such as magnesium stearate, talc, bentonite, and conductive carbon black can be used. Furthermore, magnetic substances such as magnetite, maghematite, and an intermediate between magnetite and maghematite may be used.

Organic fine particles include styrene resins, acrylic resins such as polymethyl acrylate and polymethyl methacrylate, epoxy resins, melamine resins, tetrafluoroethylene resins, trifluoroethylene resins, polyvinyl chloride, polyethylene, and polyacrylonitrile. Fine particles such as these can be used.
Among these externally added fine particles, silica, titanium oxide, alumina, zinc oxide, carbon black and the like are preferably used. The external fine particles may be used alone or in combination of two or more.

In addition, the surface of these inorganic or organic fine particles may be a silane coupling agent, titanate coupling agent, silicone oil, modified silicone oil, silicone varnish, fluorine silane coupling agent, fluorine silicone oil, amino group or fourth group. Surface treatment such as hydrophobization may be performed by a treatment agent such as a coupling agent having a secondary ammonium base. One type of processing agent may be used or two or more types may be used in combination.
The number average particle diameter of the externally added fine particles is usually 0.001 μm or more, preferably 0.005 μm or more, and usually 3 μm or less, preferably 1 μm or less. A plurality of those having different average particle diameters may be blended. The average particle size of the externally added fine particles can be determined by observation with an electron microscope, conversion from the value of the BET specific surface area, or the like.
The proportion of the externally added fine particles in the toner is preferably 0.1% by weight or more. More preferably, it is 0.3% by weight or more, and more preferably 0.5% by weight or more. The upper limit is preferably 10% by weight or less, more preferably 6% by weight or less, and even more preferably 4% by weight or less.

The charging characteristics of the toner may be negatively charged or positively charged, and can be set according to the method of the image forming apparatus used. The charging characteristics of the toner can be adjusted by the selection and composition ratio of toner base particle components such as a charge control agent, the selection and composition ratio of externally added fine particles, and the like.
The toner can be used as a one-component developer or mixed with a carrier to be used as a two-component developer.

When used as a two-component developer, the carrier that is mixed with the toner to form the developer may be a known magnetic substance such as an iron powder, ferrite, or magnetite carrier, or a resin coating on the surface thereof. Or a magnetic resin carrier can be used. As the carrier coating resin, generally known styrene resins, acrylic resins, styrene acrylic copolymer resins, silicone resins, modified silicone resins, fluorine resins, and the like can be used, but are not limited thereto. It is not a thing. The average particle size of the carrier is not particularly limited, but preferably has an average particle size of 10 to 200 μm. These carriers are preferably used in a ratio of 5 to 100 parts by weight with respect to 1 part by weight of the toner.
Formation of a full-color image by electrophotography can be carried out in a conventional manner using magenta, cyan, and yellow color toners and, if necessary, black toner.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the following examples are given for the purpose of illustrating the present invention in detail, and the present invention is not limited to the examples shown below unless it is contrary to the gist thereof. In addition, the description of “parts” in the following examples and comparative examples indicates “parts by weight” unless otherwise specified.

<Method for producing dispersion for forming undercoat layer>
The undercoat layer dispersion A was produced as follows. Mixing 20 parts of oxytitanium phthalocyanine and 280 parts of 1,2-dimethoxyethane, characterized in that the Bragg angle (2θ ± 0.2) shows a strong diffraction peak at 27.3 ° in X-ray diffraction by CuKα ray. Then, the mixture was pulverized with a sand grind mill for 1 hour to carry out atomization dispersion treatment. Subsequently, 10 parts of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name “Denkabutyral” # 6000C) was added to 255 parts of 1,2-dimethoxyethane, 4-methoxy-4- A binder liquid obtained by dissolving in 85 parts of a mixture of methyl-2-pentanone and 230 parts of 1,2-dimethoxyethane were mixed to prepare dispersion A for forming an undercoat layer.

<Method for producing protective layer-forming dispersion>
The protective layer-forming dispersion was produced as follows. That is, a rutile type titanium oxide having an average primary particle size of 40 nm (“TTO55N” manufactured by Ishihara Sangyo Co., Ltd.) and 3% by weight of methyldimethoxysilane (“TSL8117” manufactured by Toshiba Silicone Co., Ltd.) with respect to the titanium oxide were flowed at high speed. The mixture was added to a type mixing kneader (“SMG300” manufactured by Kawata Corporation). Hydrophobic oxidation by dispersing the surface-treated titanium oxide obtained by high-speed mixing at a rotational peripheral speed of 34.5 m / sec in a mixed solvent having a methanol / 1-propanol weight ratio of 7/3 by a ball mill. A titanium dispersed slurry was obtained. The dispersion slurry, a mixed solvent of methanol / 1-propanol / toluene, and ε-caprolactam [compound represented by the following formula (A)] / bis (described in Examples of JP-A-4-31870) / bis ( 4-amino-3-methylcyclohexyl) methane [compound represented by the following formula (B)] / hexamethylenediamine [compound represented by the following formula (C)] / decamethylene dicarboxylic acid [represented by the following formula (D) Compound] / octadecamethylene dicarboxylic acid [compound represented by the following formula (E)] having a composition molar ratio of 60% / 15% / 5% / 15% / 5%, While stirring, the polyamide pellets were dissolved by mixing. Thereafter, by performing ultrasonic dispersion treatment, the solid content containing methanol / 1-propanol / toluene in a weight ratio of 7/1/2 and hydrophobized titanium oxide / copolymerized polyamide in a weight ratio of 3/1. A dispersion for forming a protective layer having a concentration of 18.0% was prepared.

<Method for producing coating solution for forming photosensitive layer>
Pigment dispersion liquid 7 parts of oxytitanium phthalocyanine, characterized by showing a strong diffraction peak at 27.3 ° in Bragg angle (2θ ± 0.2) in X-ray diffraction by CuKα ray, represented by the following structural formula 10.5 parts of the perylene compound and 227 parts of toluene were dispersed in a sand grind mill for 1 hour, and the resulting dispersion was diluted with toluene to prepare a pigment dispersion having a solid content concentration of 5% by weight.

-Charge transport material solution 105 parts of polycarbonate resin having the following repeating structure (viscosity average molecular weight, about 40,000), 63 parts of a hydrazone compound represented by the following structural formula, 1 part of an amine compound represented by the following structural formula, the following structure A charge transport material solution was prepared by mixing 17 parts of a phenol compound represented by the formula, 0.03 part of silicone oil (silicone oil KF96 manufactured by Shin-Etsu Chemical Co., Ltd.) and 494 parts of toluene.

  210 parts of the pigment dispersion and 683 parts of the charge transport material solution were mixed for 30 minutes with a TK homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. to prepare a coating solution for forming a photosensitive layer.

<Manufacture of electrophotographic photoreceptor>
[Example 1]
An aluminum iron tube having an outer diameter of 30 mm, a length of 244 mm, and a thickness of 0.75 mm, which was prepared by ironing an aluminum extruded tube, was dip-coated in the undercoat layer dispersion A, and the dry film thickness was 1 An undercoat layer was provided so as to have a thickness of 25 μm.
Next, the aluminum cylinder provided with the undercoat layer was dip-coated in the photosensitive layer forming coating solution, and the photosensitive layer was provided so that the dry film thickness was 25 μm. Further, the protective layer forming dispersion was applied as a protective layer by dip coating on the photosensitive layer, and a protective layer was provided so that the dry film thickness was 0.5 μm. Thus, an electrophotographic photoreceptor 1 was produced.

[Example 2]
An electrophotographic photosensitive member 2 was produced in the same manner as in Example 1 except that the thickness of the protective layer was changed to 1.0 μm in Example 1.

[Example 3]
An electrophotographic photoreceptor 3 was produced in the same manner as in Example 1, except that the composition of the coating solution for forming the protective layer in Example 1 was such that the weight ratio of hydrophobized titanium oxide and copolymer nylon was 4/1.

[Comparative example]
An electrophotographic photosensitive member 4 was produced in the same manner as in Example 1 except that the protective layer was not provided on the photosensitive layer used in Example 1.

<Volume resistivity>
The coating solution for forming the photosensitive layer and the coating solution for forming the protective layer used in Examples 1 to 3 and Comparative Example were each applied to an aluminum sheet by about 15 μm and dried, and Hiresta UP (MCP-) of Dia Instruments Co., Ltd. was used. 450), a voltage of 100 V was applied for 1 minute in an environment of a temperature of 25 ° C. and a relative humidity of 50%, and the volume resistivity was measured. The results are shown in Table 1 below.

<Electrical characteristics test>
The electrophotographic photoreceptors 1 to 4 are mounted on an electrophotographic characteristic evaluation apparatus manufactured according to the electrophotographic society measurement standard (basic and applied electrophotographic technology, edited by the Electrophotographic Society, Corona, pages 404 to 405). The electrical property test was conducted. The electrophotographic photosensitive member is rotated at a constant speed of 30 rpm, a scorotron charging unit is used for charging, the grid voltage is adjusted so that the initial surface potential of the photosensitive member becomes +700 V, and monochromatic light of 660 nm is removed as neutralizing light. Exposure was performed at 0.0 μJ / cm ² . Under these conditions, charging and discharging were repeated 3000 times, and then charged again under the same conditions, and the surface potential of the electrophotographic photosensitive member was measured to obtain an initial surface potential (V ₀ ) after repetition. In addition, after charging the initial surface potential after repetition, the surface potential (V ₁ ) after being left in the dark for 5 seconds is measured, and the ratio of the potential to the initial surface potential expressed as a percentage is retained. and the rate _(V 1 / V _0). The measurement was performed in an environment at a temperature of 25 ° C. and a relative humidity of 50%. The results are shown in Table 1 below.

<Image characteristics test>
(Image memory evaluation)
Each of the electrophotographic photoreceptors 1 to 4 is mounted on a monochrome laser printer (product name: HL-5040) manufactured by Brother Industries, Ltd., and image characteristics are obtained by non-magnetic one-component development using toner (product name: TN-36J). A test was conducted. In the image characteristic test, a solid black image of 6 cm × 3 cm is printed in the center of the first third of the area in the paper feeding direction of A4 paper, and a halftone image is printed on the entire area of the rear second third. This was done by printing 1000 test images. It was visually determined whether or not an image memory derived from a black solid image was observed in a halftone image printed in a two-thirds area on the rear side with respect to the paper feeding direction of A4 paper.
(Evaluation of fog and sunspot)
After the above evaluation, a test image for printing a white background image was printed and visually observed for fogging and black spots.
Evaluation criteria for “image memory” and “fogging and black spots” are as follows.

The evaluation of the “image after printing (fogging, black spots)” was performed according to the following criteria.
A: Neither fog nor black spots are seen in the image.
B: A slight fog or black spot is seen in the image, but there is no practical problem.
C: A fog or a black spot is clearly seen in the image, and there is a problem in practical use.
The evaluation of the “image after printing (image memory)” was performed according to the following criteria.
A: No image memory is seen in the image.
B: Image memory is slightly seen in the image, but there is no practical problem.
C: Image memory is clearly seen in the image, which is problematic in practice.

  When any one of the electrophotographic photoreceptors 1 to 3 as the electrophotographic photoreceptor of the present invention was mounted, no practical image memory was observed, but when the electrophotographic photoreceptor 4 was mounted. Two image memories were clearly observed in the halftone image.

  The electrophotographic photosensitive member of the present invention has a small initial voltage drop when repeatedly used, and even when the photosensitive cycle is repeated, an unnecessary image is not formed, and a high-quality image is stably formed. be able to. Therefore, the present invention can be suitably used in the fields of copiers, printers, printing machines, and the like.

1 Photoconductor 2 Charging device (charging roller)
DESCRIPTION OF SYMBOLS 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 6 Cleaning apparatus 7 Fixing apparatus 41 Developing tank 42 Agitator 43 Supply roller 44 Developing roller 45 Control member 71 Upper fixing member (pressure roller)
72 Lower fixing member (fixing roller)
73 Heating device 100 Image forming device T Toner P Transfer object

Claims (4)

  In an electrophotographic photosensitive member having a photosensitive layer containing a charge generating substance and a charge transporting substance in the same layer on a conductive support, a protective layer is provided on the photosensitive layer, and the volume resistivity of the protective layer is An electrophotographic photosensitive member characterized by having a volume resistivity lower than that of the photosensitive layer. 2. The electrophotographic photosensitive member according to claim 1, wherein the protective layer has a volume resistivity of 10 ¹⁰ to 10 ¹⁵ (Ω · cm).   An electrophotographic cartridge comprising the electrophotographic photosensitive member according to claim 1.   An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1.

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