JP2003287915A - Electrophotographic organic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic organic photoreceptor free from image fog in which irregular conductivity of an intermediate layer is significantly decreased. <P>SOLUTION: In the electrophotographic photoreceptor having an organic photosensitive layer formed on a conductive substrate with an intermediate layer interposed, the intermediate layer is formed by dispersing at least pigment particles in a binder resin. The pigment particles are grafted by a polymer having at least a reactive group which can react with functional groups on the surface of the pigment particles. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic organic photoconductor used in an image forming apparatus such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a composite machine having these functions. is there.

[0002]

2. Description of the Related Art In the image forming apparatus described above, a charge generating agent that generates an electric charge by light irradiation, a charge transferring agent that transfers the generated electric charge, and a binder resin that forms a layer in which these substances are dispersed are used. So-called organic photoconductors are widely used. Organic photoreceptors are roughly classified into those having a single-layer type photosensitive layer containing a charge generating agent and a charge transporting agent in the same layer, a charge generating layer containing a charge generating agent, and a charge transporting layer. A photoreceptor having a laminated type photosensitive layer in which a charge transport layer containing an agent is laminated is generally used.

However, the above-mentioned photoconductor has the following problems. 1. In the charging step at the time of outputting an image, either positive or negative charges are added to the surface of the photoconductor, but at that time, charges having the opposite polarity to the surface of the photoconductor are generated on the side of the supporting substrate. If there is no intermediate layer, the charge on the supporting substrate side is injected into the photosensitive layer, which causes a decrease in the charge on the surface of the photosensitive member and causes image fog. 2. When the photosensitive layer is directly coated on the supporting substrate, the photosensitive layer may not be sufficiently bound on the supporting substrate depending on the type of binder resin and the coating conditions. 3. If there are defects such as scratches on the surface of the supporting substrate, black spots are generated on the image.

In order to solve the above problems, there is a method in which an intermediate layer containing a binder resin is provided on a supporting substrate and a photosensitive layer is provided thereon. That is, by providing the intermediate layer, the charge on the supporting substrate side is prevented from being easily injected into the photosensitive layer, and the photosensitive layer is firmly bound on the supporting substrate to cover the defects on the supporting substrate surface. It can be smoothed.

However, in the case where the intermediate layer is composed of only the binder resin, the electrical conductivity is low. Therefore, unless the thickness of the intermediate layer is set to the submicron level, the problem of image fog occurs. This is because in the exposure step during image output, charges of both positive and negative polarities are generated in the exposed part by the charge generating agent, but the charges to be transported to the supporting substrate side (charges of the same polarity as the surface of the photoconductor) are intermediate. This is because it is blocked by the layer and remains on the photosensitive layer. Furthermore, it becomes impossible to eliminate the charge on the surface of the photoconductor in the charge eliminating step after the transferring step, which causes a rise in residual potential, which is also a cause of image fog. On the other hand, if the intermediate layer is made thin, it becomes difficult to cover the defects on the surface of the supporting substrate.

Therefore, it is possible to increase the conductivity of the intermediate layer to secure the film thickness. For example, JP-A-59-934
JP-A-6-202366 describes that a titanium oxide powder whose surface is treated with tin oxide or alumina is contained in the intermediate layer in JP-A No. 6-202366.

However, while the coating solution in which the metal oxide particles such as titanium oxide are dispersed is applied onto the supporting substrate, dried and solidified to form the intermediate layer, the metal oxide aggregates to generate aggregated particles. Resulting in. Therefore, the conductivity of the intermediate layer as a whole increases, but the conductivity becomes uneven, and the charges are trapped in the low conductivity portion. As a result, the residual potential becomes high and the same problem as described above occurs.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above technical problems, to remarkably reduce the unevenness of the conductivity of the intermediate layer as compared with the prior art, and to provide an electrophotographic organic photoreceptor without image fog. is there.

[0009]

In order to achieve the above object, the inventors of the present invention have earnestly studied, and as a result, an electrophotographic organic photosensitive material in which an organic photosensitive layer is formed on a conductive substrate with an intermediate layer interposed therebetween. In the body, the intermediate layer is formed by dispersing at least pigment particles in a binder resin, and the pigment particles are grafted with a polymer having at least a reactive group capable of reacting with a functional group on the surface of the pigment particles. It has been found that the electrophotographic organic photoconductor characterized in that there is not much unevenness in the conductivity of the intermediate layer and there is no image fog. In particular, the reactive group of the polymer is preferably at least one kind or two or more kinds selected from an epoxy group, a thioepoxy group, an aziridine group, an oxazoline group, an isocyanate group, and an N-hydroxyalkylamide group.

[0010]

The function of the present invention The "pigment particles grafted with a polymer" described in the present specification mean pigment particles in which a polymer portion (polymer chain) is grafted to the pigment particles. The polymer is grafted to the primary particles of pigment particles or to several aggregates. Furthermore, "grafting" as defined in this specification means Jean-Baptiste.
Donnet et al. In their book "Carbon Black"
(Kodansha 1978) is the irreversible addition of a polymer to a substrate such as pigment particles. By carrying out an irreversible addition reaction, the polymer portion can be chemically bonded to the pigment particle surface portion.

Specifically, "a pigment particle grafted with a polymer" has a pigment particle and a reactive group having reactivity with a functional group such as a hydroxy group or a carboxyl group on the surface of the pigment particle. It is a reaction with a polymer.

[0012] The pigment particles added to the intermediate layer function as a resistance adjusting agent for the intermediate layer as described in the above-mentioned prior art, but generally have a dispersibility in a binder resin solution. Since it is bad, it easily aggregates, and unevenness in the conductivity of the intermediate layer easily occurs.

Therefore, the present inventors utilize a functional group on the surface of the pigment particle to graft a polymer having a reactive group capable of chemically reacting with the functional group onto the surface of the pigment particle, whereby the polymer is It was found that the polymer chemically binds to the surface of the pigment particles, the polymer acts as a dispersant, the affinity between the pigment particles and the binder resin is improved, and the dispersibility in the binder resin is significantly improved. It was

FIG. 1 shows an outline of pigment particles grafted with a polymer.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The electrophotographic organic photoreceptor of the present invention comprises:
It suffices that the organic photosensitive layer is formed on the conductive substrate through the intermediate layer containing the pigment particles grafted with the binder resin and the polymer, and the organic photosensitive layer includes the binder resin, the charge generating agent and the charge transporting material. It may be either a single layer type containing an agent or a layered type having a charge generating layer containing a binder resin and a charge generating agent and a charge transporting layer containing a binder resin and a charge transferring agent.

The constitution or constituent materials of the electrophotographic organic photoreceptor of the present invention will be described in detail below.

<Intermediate Layer> As the pigment particles used in the intermediate layer of the electrophotographic organic photoreceptor of the present invention, conventionally known organic pigments or inorganic pigments can be used, but the average particle diameter is 1. 0 μm or less, more preferably an average particle size of 300
Inorganic pigments or metal oxides having a particle size of not more than nm such as carbon black, titanium oxide, aluminum oxide, silicon carbide, zirconia oxide, zinc oxide and tin oxide are preferably used.
If the average particle size exceeds 1.0 μm, the pigment particles grafted with the obtained polymer may not be able to impart sufficient dispersibility.

Among the pigment particles, acidic carbon black has many functional groups such as carboxyl groups on the surface and is easy to be grafted. Moreover, the electrical properties of the pigment particles for the intermediate layer are excellent. Even neutral carbon black can be easily converted into acidic carbon black by oxidation treatment. Any type of carbon black such as furnace black, channel black, acetylene black and lamp black can be used, but furnace black is preferred.

When a metal oxide is used as the pigment particles, the electrical characteristics of the intermediate layer are excellent. Among the metal oxides, titanium oxide particles are particularly excellent. The titanium oxide particles may be crystalline or amorphous. The crystalline form of crystalline titanium oxide is most commonly rutile, but it may be anatase, brookite, or the like. The pigment particles of the metal oxide are preferably not subjected to an organic surface treatment with polysiloxane or the like. When the treatment rate of the organic surface treatment is high, the grafting rate of the polymer is lowered and sufficient dispersibility cannot be imparted. However, for example, there is no particular problem with respect to the inorganic surface treatment in which the surface of titanium oxide is coated with an inorganic material such as alumina, silica, or zirconia.

All of the above pigment particles are used alone or
A blend of two or more species can be used.

The polymer that reacts with the pigment particles has a high affinity for the target medium (dispersion medium or binder resin for forming an intermediate layer to be added later) and a higher affinity for the target medium than the segment (B). Having a low segment (A), and only the segment (A) has a reactive group capable of reacting with the surface functional group of the pigment particle to be grafted. Grafting is preferably carried out in a dispersion medium liquid comprising a medium having properties (polarity) close to.

The polymer produced by the above method and reacted with the pigment particles is composed of the segment (A) having a reactive group and the segment (B) having an affinity for the target medium as described above. B) is oriented in the dispersion medium liquid, and the segment (A) surrounds the surface of the pigment particles, and the pigment particles can be grafted.

Generally, a method for obtaining a graft type polymer is, for example, solution polymerization, emulsion polymerization, bulk polymerization or polymerization of a polymerization initiator and a polymerizable monomer in the presence of a high molecular weight polymer which becomes a graft chain. A method of polymerizing a polymer which becomes a main chain by suspension polymerization is known. However, when the high molecular weight product does not have a radically polymerizable functional group, the resulting graft copolymer contains a large amount of ungrafted polymer, which has the drawback of low grafting efficiency. There is. Therefore, it is preferable to use a radical-polymerizable polymer as the polymer.
Such a radically polymerizable high molecular weight substance is generally called a "macromonomer", and has a radically polymerizable group at one end,
For example, it is a high molecular weight product having a (meth) acryloyl group, a styryl group, etc., and is obtained by reacting a polymer having a carboxyl group at one end with a radical polymerizable monomer having a glycidyl group in an organic solvent. It is what is done. JP-B-43-11224 discloses that a prepolymer obtained by radical polymerization of a radical-polymerizable monomer in the presence of mercaptoacetic acid in an organic solvent is reacted with glycidyl methacrylate in the presence of a dimethyllaurylamine catalyst. A method of obtaining the same is disclosed.

That is, a reactive group capable of reacting with the functional group on the surface of the pigment particle is intramolecularly present in the presence of the above radically polymerizable high molecular weight compound (b) as a component forming the main chain of the segment (B). It is obtained by adding a radical polymerization catalyst to the polymerizable monomer (a) contained in (1) and the polymerizable monomer (c) forming the skeleton of the segment (A) which is optionally mixed ( (See FIG. 1).

[1] Polymerizable monomer (a) having a reactive group capable of reacting with the functional group on the surface of the pigment particle in the molecule: In order to make grafting more reliable and stable, a covalent bond is used. It is desired to irreversibly bond to the pigment particles via, and examples of the bond include an ester bond, a thioester bond, an amide bond, an amino bond, an ether bond, a thioether bond, a carbonyl bond, a thiocarbonyl bond and a sulfonyl bond. Can be mentioned. The reactive group is an epoxy group, a thioepoxy group, an aziridine group, N-
It is desirable that it is at least one kind or two or more kinds selected from the group consisting of a hydroxyacrylamide group and an oxazoline group. However, the reactive groups for the pigment particles are not necessarily limited to these. Specific examples of the polymerizable monomer (a) are shown below.

<Epoxy group-containing polymerizable monomer>

[Chemical 1] (R _{1 to} R ₈ in the formula represent hydrogen or a methyl group, and n is 0
Alternatively, it is an integer of 1 to 20. )

<Thioepoxy group-containing polymerizable monomer>

[Chemical 2] (R _{9 to} R ₁₂ in the formula represent hydrogen or a methyl group, and n is 0 or an integer of 1 to 20.)

<Aziridine group-containing polymerizable monomer>

[Chemical 3]

[Chemical 4] (R _{13 to} R ₃₉ in the formula represent hydrogen or a methyl group, and n
Is 0 or an integer of 1 to 20. )

<Oxazoline group-containing polymerizable monomer> 2-
Vinyl-2-oxazoline, 2-vinyl-4-methyl-
2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl-4-ethyl-2-oxazoline, 2-vinyl-5-ethyl-2-oxazoline, 2-
Isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-4-ethyl-2-oxazoline, 2-isopropenyl -5-ethyl-2-oxazoline, 2-isopropenyl-4,5-dimethyl-2-oxazoline

<N-hydroxyalkylamide group-containing polymerizable monomer> N-hydroxymethyl acrylamide, N
-Hydroxyethylacrylamide, N-hydroxybutylacrylamide, N-hydroxyisobutylacrylamide, N-hydroxy-2-ethylhexylacrylamide, N-hydroxycyclohexylacrylamide, N-hydroxymethylmethacrylamide, N-hydroxyethylmethacrylamide, N-hydroxybutyl Methacrylamide, N-hydroxyisobutylmethacrylamide, N-hydroxy-2-ethylhexylmethacrylamide, N-hydroxycyclohexylmethacrylamide

[2] Polymerizable monomer (c) forming the skeleton of the segment (A): A polymerizable monomer (c) that can be used as necessary to form the segment (A) into a desired skeleton.
Is not particularly limited as long as it is copolymerizable with the monomer (a) and the radically polymerizable high molecular weight compound (b) as a component forming the segment (B) as described below, Depending on the molecular structure of the segment (A) to be represented by, for example, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene,
p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-
Styrene-based monomers such as chlorostyrene and p-chlorostyrene; acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, stearyl acrylate, 2-acrylic acid acrylate Acrylic acid such as ethylhexyl, methacrylic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate. Alternatively, a methacrylic acid-based monomer; one or two monomers such as ethylene, propylene, butylene, vinyl chloride, vinyl acetate, acrylonitrile, acrylamide, methacrylamide, and N-vinylpyrrolidone. It can be used as appropriate over.

[3] Radical-polymerizable polymer (b) as a component forming the main chain of the segment (B): The radical-polymerizable polymer (b) (macromonomer) is, for example, in an organic solvent. It is obtained by reacting a polymer having a carboxyl group at one terminal with a radical polymerizable monomer having a glycidyl group. Examples of the main chain of the segment (B) component include polysiloxane-based structures, poly (meth) acrylic-based structures, polyether-based structures such as polyalkylene glycols, polyester-based structures, polyalkylene-based structures, polyamide structures, Examples thereof include a polyimide structure, a polyurethane structure, a fluororesin structure and the like, and these have a reactive group at one end of the polymer chain.

Specifically, examples of the radical-polymerizable high molecular weight compound (b) having a polysiloxane structure include (meth) acryloyl group-containing polydimethylsiloxane,
Styryl group-containing polydimethylsiloxane (meth) acryloyl group-containing partial octyl-substituted polydimethylsiloxane, styryl group-containing partial octyl-substituted polydimethylsiloxasan, styryl group-containing partial phenyl-substituted polydimethylsiloxane, tris (trimethylsiloxy) silylpropyl (meth) Polymerizable polysiloxanes such as acrylates may be mentioned, and one or more of them may be used, and examples thereof include those having the following structures.

[0034]

[Chemical 5] (In the formula, B represents —COO— or a phenylene group, and R
¹ is a hydrogen atom or a methyl group, R ² is an alkylene group having 1 to 6 carbon atoms, R ^{3 to} R ¹³ are the same or different and are an aryl group, an alkyl group having 1 to 6 carbon atoms or 1 to 10 carbon atoms.
, And a and b are the same or different and each represents an integer of 0 to 10, and n represents an integer of 0 to 200. )

The segment (B) is polymetha (acrylic)
When it has a system structure, a radically polymerizable high molecular weight compound (b)
For example, the compounds shown below are used.

[Chemical 6] (In the formula, R ¹ and R ² are the same or different and each represents a hydrogen atom or a methyl group, R ³ represents an alkyl group having 1 to 25 carbon atoms, X represents an arbitrary connecting chain, and Y represents an initiator terminal. Alternatively, H atom and n represent an integer of 0 to 500.)

[0036]

[Chemical 7] (In the formula, R ¹ , R ² and R ⁴ are the same or different and represent a hydrogen atom or a methyl group, R ³ and R ⁵ are the same or different and represent an alkyl group having 1 to 25 carbon atoms, and X is an arbitrary group. It is a connecting chain, Y is an initiator terminal or an H atom, and m and n are the same or different and each represents an integer of 0 to 500.)

[0037]

[Chemical 8] (In the formula, R ¹ and R ² are the same or different and each represents a hydrogen atom or a methyl group, R ³ represents an alkylene group having 1 to 25 carbon atoms, and R ⁴ represents an alkyl group having 1 to 25 carbon atoms, X
Is any linking chain, Y is the initiator terminus or H atom,
n and m are the same or different and each represents an integer of 0 to 500. )

When the segment (B) has a polyalkylene glycol type structure, the radical-polymerizable high molecular weight compound (b) is, for example, a compound shown below.

[Chemical 9] (In the formula, R ¹ , R ² , and R ³ are the same or different and each represents a hydrogen atom or a methyl group, and n represents an integer of 0 to 500.)

[0039]

[Chemical 10] (In the formula, R ¹ , R ² , R ³ , and R ⁴ are the same or different and represent a hydrogen atom or a methyl group, and n and m are the same or different and represent an integer of 0 to 500.)

When the segment (B) has a polystyrene type structure, the radical-polymerizable high molecular weight compound (b) is, for example, a compound shown below.

[Chemical 11] (In the formula, R ¹ represents a hydrogen atom or a methyl group, X is an arbitrary connecting chain, Y is an initiator terminal or H atom, Z is a hydrogen atom, a halogen substituent or an alkyl group having 1 to 8 carbon atoms. , N represents an integer of 0 to 500.)

The linking chain X shown in the above formula group is described, for example, in "Chemistry and Industry of Macromonomers" (supervised by Yuya Yamashita, published by PC Corporation, September 2, 1989).
0 days) and any of them can be used.

As the radical catalyst, any one can be used as long as it is usually used for the polymerization of vinyl monomers. Typical examples include azo compounds such as 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, di-tert-butyl. Peroxide, ter
Examples thereof include peroxide compounds such as t-butyl peroctoate and tert-butyl peroxy-2-ethylhexanoate, which are usually 0.2 to 10 parts by weight, preferably 100 parts by weight of the monomer. Is used in the range of 0.5 to 5 parts by weight. Further, the solvent is appropriately selected depending on the type of the monomer and the radical-polymerizable high molecular weight substance used.

The molecular weight of the graft or block type polymer obtained as described above is not particularly limited, but the average molecular weight is 1 in view of the effect of grafting on the pigment particles and the workability during the reaction with the pigment particles. , 00
It is preferably in the range of 0 to 1,000,000,
More preferably, it is in the range of 5,000 to 100,000.

The molecular weights of the segment (A) and the segment (B) in the graft or block type polymer are not particularly limited, and depend on the types of polymer chains constituting these segments. From the viewpoint of grafting efficiency to the pigment particles, the segment (A) preferably has an average molecular weight in the range of 300 to 100,000, more preferably 5,000 to 50,000. From the viewpoint of the effect of improving the dispersibility, the segment (B) preferably has an average molecular weight of 500 to 100,000, more preferably 1,000 to 50,000. Further, the number of reactive groups contained in the segment (A) of the graft or block type polymer is not particularly limited, but it is 1 to 5 on average per molecule of the polymer.
It is preferably 0, more preferably about 1 to 20.

With respect to the pigment particles grafted with the polymer, the ratio of the graft polymer to the pigment particles is 100.
The amount is preferably 1 to 200 parts by weight, and particularly preferably 5 to 100 parts by weight, based on parts by weight. When the amount of the graft polymer is less than 1 part by weight, the obtained pigment particles aggregate with each other. Further, when the amount of the graft polymer exceeds 200 parts by weight, the polymer is grafted more than necessary, and the coating solution for forming an intermediate layer prepared by using the pigment particles grafted with this polymer. It deteriorates the coating performance, the physical properties of the formed intermediate layer, and the electrical characteristics of the electrophotographic photosensitive member formed by containing the intermediate layer.

The coating liquid for forming the intermediate layer comprises pigment particles having a polymer grafted thereon, a binder resin and a solvent, and the average molecular weight of the binder resin in the intermediate layer is 1.00.
It is preferably in the range of 0 to 1,000,000,
Furthermore, the range of 5,000 to 200,000 is more preferable. The amount ratio of the pigment particles obtained by grafting the polymer and the binder resin is 5 to 500 parts by weight, especially 20 to 20 parts by weight of the binder resin to 100 parts by weight of the grafted pigment particles.
It is preferably 0 part by weight. When the amount of the binder resin is less than 5 parts by weight, the formed intermediate layer does not have sufficient film formability, and when the amount of the binder resin is 500 parts by weight or more, the intermediate layer does not have sufficient electric characteristics.

As the binder resin used in the intermediate layer of the electrophotographic organic photoreceptor of the present invention, various resins used in conventionally known photosensitive layers can be used. Particularly, a polyamide resin, a polyvinyl acetal resin, a phenol resin, a melamine resin, a polyester resin, a silicone resin, and an acrylic resin are preferable. Further, the binder resins may be used alone or as a mixture of two or more kinds.

In addition to the pigment particles grafted with a polymer in the intermediate layer of the electrophotographic photosensitive member of the present invention, an organic pigment having a certain degree of conductivity such as a metal oxide or a perylene tetracarboxylic acid diimide derivative is added. It may be added separately. In this case, the pigment particles grafted with the polymer also serve as a dispersion aid for the separately added pigment, and the dispersibility of the separately added pigment is also improved, which is effective.

With respect to the polymer-grafted pigment particles, the segment (B) has at least one kind or two or more kinds selected from the group consisting of unsaturated double bond groups, hydroxyl groups, carboxyl groups and alkoxysilyl groups. You may have. Regarding the intermediate layer when the curable resin is used as the binder resin, by using the pigment particles grafted with the polymer having the reactive group,
An intermediate layer that can contribute to the curing of the intermediate layer composition in the course of curing and, as a result, forms a high-strength film and is more excellent in film-forming properties and physical properties such as electrical properties. You can

The intermediate layer of the electrophotographic organic photoreceptor of the present invention is
In addition to the pigment particles grafted with the polymer in the binder resin, it may be contained in combination with conventionally known electron transfer agents, hole transfer agents, pigments, additives and the like. Moreover, you may use these compounds individually or in mixture of 2 or more types. Examples of the additives include plasticizers such as phthalates, antioxidants such as hindered amines and hindered phenols, radical scavengers, ultraviolet absorbers, thickeners and the like.

In the case of forming the intermediate layer, first, the binder resin exemplified above and the constituent materials such as pigment particles grafted with a polymer together with an appropriate dispersion medium are subjected to a known method such as roll mill, ball mill, attritor,
A coating liquid is prepared by dispersing and mixing using a paint shaker, an ultrasonic disperser or the like. Then, this coating solution may be applied by a known means such as a blade method, a dipping method, or a spray method, and dried / cured.

As the dispersion medium for preparing the coating liquid, conventionally known organic solvents can be mentioned. For example, alcohols such as methanol, ethanol, isopropanol and butanol; aliphatic hydrocarbons such as n-hexane, octane and cyclohexane; aromatic hydrocarbons such as benzene, toluene and xylene, dichloromethane, dichloroethane, chloroform and carbon tetrachloride. , Halogenated hydrocarbons such as chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; ketones such as acetone, methyl ethyl ketone, cyclohexanone; esters such as ethyl acetate, methyl acetate; dimethyl formaldehyde, Examples thereof include dimethylformamide and dimethylsulfoxide. Further, a surfactant, a leveling agent, etc. may be used.

The thickness of the intermediate layer is 0.1 to 50 μm, preferably 1 to 30 μm. Improving coatability between the intermediate layer and the photosensitive layer, preventing penetration (of coating liquid for charge generating agent),
A resin layer may be provided within a range that does not impede charge transport control in order to improve drying properties and electrophotographic properties (image fog, image unevenness, repeatability, etc.).

<Supporting Substrate> As the supporting substrate used in the present invention, various conductive materials can be used. For example, iron, aluminum, copper, tin, platinum, silver,
Metal element such as vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, brass, etc., or a plastic material in which the metal is vapor-deposited or laminated, aluminum iodide, tin oxide, indium oxide, etc. Examples thereof include a resin substrate in which glass, carbon black and the like are dispersed.

The shape of the supporting substrate may be sheet-like, drum-like or the like depending on the structure of the image forming apparatus used, and the substrate itself has conductivity or the surface of the substrate is conductive. You only have to have Further, the supporting substrate is preferably one having sufficient mechanical strength when used.

If necessary, the surface of the supporting substrate may be subjected to surface treatment such as surface roughening treatment, oxidation treatment and etching treatment.

<Photosensitive Layer> The photosensitive layer in the electrophotographic organic photoreceptor of the present invention is classified into a single layer type and a laminated type depending on its constitution. The single-layer type photoreceptor has a single photosensitive layer containing at least a binder resin, a charge transporting agent and a charge generating agent on a supporting substrate. The laminated-type photoreceptor includes a charge generating layer containing a binder resin and a charge generating agent and a charge transporting layer containing a binder resin and a charge transferring agent, which are laminated on a conductive substrate in this order or in the reverse order. It was done.

As the charge-generating agent and charge-transporting agent (hole-transporting agent, electron-transporting agent) binder resin contained in the photosensitive layer, conventionally known compounds can be used alone or in combination of two or more kinds.

In the single-layer type photosensitive layer, the charge generating agent is added in an amount of 0.1 to 50 parts by weight, particularly 0.5 to 30 parts by weight, and the hole transfer agent is added to 5 parts by weight with respect to 100 parts by weight of the binder resin. ˜500 parts by weight, especially 25 to 200 parts by weight, respectively. When the electron transfer agent is contained, it is preferably contained in a ratio of 5 to 100 parts by weight, particularly 10 to 80 parts by weight, based on 100 parts by weight of the binder resin. When the hole transport material and the electron transport material are used in combination, the total amount thereof is 100% of the binder resin.
20-500 parts by weight, especially 30-200 parts by weight
Parts by weight are preferred. The thickness of the single-layer type photosensitive layer is 5 to 100 μm.
m, especially about 10 to 50 μm is preferable.

In the laminated type photosensitive layer, it is preferable to add the charge generating agent in an amount of 5 to 1000 parts by weight, particularly 30 to 500 parts by weight, based on 100 parts by weight of the binder resin. In the charge transport layer, the binder resin 1
When the electron transfer agent is contained with respect to 00 parts by weight,
0.1 to 250 parts by weight of the electron transfer agent, particularly 0.5 to
When the hole transport agent is contained at a ratio of 150 parts by weight, the hole transport agent is contained in an amount of 10 to 500 parts by weight, particularly 25
It is preferable that each of them is contained in a proportion of about 200 parts by weight. The thickness of the laminated photosensitive layer is 0.01 to 5 for the charge generation layer.
μm, particularly about 0.1 to 3 μm, and the charge transport layer is 2 to 10
It is preferably 0 μm, particularly preferably about 5 to 50 μm.

In addition to the above-mentioned components, various additives such as fluorene compounds, ultraviolet absorbers, plasticizers, surfactants and leveling agents may be added to the photosensitive layer. Further, in order to improve the sensitivity of the photoconductor, a sensitizer such as terphenyl, halonaphthoquinones and acenaphthylene may be added. A protective layer may be formed on the surface of the electrophotographic organic photoreceptor of the present invention.

[0062]

EXAMPLES The present invention will be described below based on Examples and Comparative Examples. The following embodiments are examples of embodying the present invention, and do not limit the technical scope of the present invention.

<Preparation of Coating Liquid for Intermediate Layer><Manufacturing Example 1> A polyamide macromonomer (segment (B)) was placed in a separable flask equipped with a stirrer, an inert gas introducing tube, a reflux cooling tube, and a thermometer. 40 parts by weight of a styrene monomer (corresponding to the radically polymerizable high molecular weight polymer (b) as a component forming the main chain) (segment (A))
(Corresponding to the polymerizable monomer (c) forming the skeleton), 7.5 parts by weight, 2- (1-aziridinyl) ethyl methacrylate (having a reactive group capable of reacting with the functional group on the surface of the pigment particle in the molecule) 5 parts by weight of the polymerizable monomer (a) and 5 parts by weight of azoisobutyronitrile as an initiator were dissolved in 75 parts by weight of ethanol (reaction solvent for grafting). Polymerization reaction was carried out at 90 ° C for 4 hours under nitrogen stream, and
After polymerizing at 0 ° C. for 2 hours, it was cooled to obtain a polymer solution A having a nonvolatile content of 40%.

Further, in a separable flask equipped with a stirrer and a reflux condenser, 16 parts by weight of carbon black (MA-600 manufactured by Mitsubishi Kasei) not surface-treated, 10 parts by weight of the polymer solution A, ethanol (grafted Reaction solvent) and 750 parts by weight of zirconia beads. 100 ° C with stirring at a rotation speed of 800 rpm,
The grafting reaction was carried out for 1.5 hours, the zirconia beads were separated, then the mixture was cooled while kneading while stirring at 100 rpm, and pulverized to obtain a dispersion liquid of polymer-grafted carbon black (carbon black / graft). Polymer / ethanol = 16/4/80).

Dissolve 100 parts by weight of the above polymer-grafted carbon black dispersion, 12 parts by weight of solvent-soluble polyamide (Toresin MF-30 manufactured by Teikoku Kagaku Sangyo) as a binder resin for the intermediate layer, and 108 parts by weight of methanol. Dispersion was performed to prepare an intermediate layer coating liquid.

<Manufacturing Examples 2 to 5> In Manufacturing Example 1, a radical-polymerizable high molecular weight compound (b) as a component forming the main chain of the segment (B) and a polymerization forming the skeleton of the segment (A). A polymerizable monomer (c), a polymerizable monomer (a) having a reactive group capable of reacting with a functional group on the surface of the pigment particle in the molecule, the pigment particle, a reaction solvent for grafting, and a binder resin for the intermediate layer. Substituting the materials shown in Table 1 to prepare an intermediate layer coating solution.

[0067]

[Table 1] Titanium oxide: Sakai Chemical rutile type titanium oxide STR-60
N

[Production of Single-Layer Photoreceptor] <Single-Layer Photoreceptor Examples 1 to 5> The coating solution for the intermediate layer obtained in the above Production Examples 1 to 5 was applied to a φ30 aluminum base pipe (supporting substrate). ) Is applied by the dip coating method, and
It was dried at 0 ° C. for 30 minutes to form an intermediate layer having an average film thickness of 10 μm.

Then, 3.5 parts by weight of a charge generating agent (X type metal-free phthalocyanine) and 35 parts of an electron transporting agent (ETM-1).
Parts by weight, 55 parts by weight of a hole transporting agent (HTM-1), 100 parts by weight of a bisphenol Z-type polycarbonate resin having a weight average molecular weight of 100,000, and tetrahydrofuran 8
It was dispersed or dissolved together with 00 parts by weight in a ball mill for 24 hours to prepare a single layer type photosensitive layer coating solution. This coating solution was applied on the above intermediate layer by a dip coating method to prepare a single-layer type photoreceptor having an average film thickness of 35 μm.

Comparative Example 1 of Single Layer Type Photoreceptor A coating solution for an intermediate layer was prepared in the same manner as in Production Example 1 except that untreated carbon black was used as the pigment particles. A single-layer type photoreceptor was prepared in the same manner as in 1 to 5.

<Single-Layer Photosensitive Member Comparative Example 2> A coating solution for an intermediate layer was prepared in the same manner as in Production Example 3 except that untreated titanium oxide was used as the pigment particles. A single-layer type photoreceptor was prepared in the same manner as in 1 to 5.

[Production of Laminated Photoreceptor] <Comparative Examples 1 to 5 of Laminated Photoreceptor> On the intermediate layers obtained in the above Production Examples 1 to 5, solvent-soluble polyamide (Tresin MF manufactured by Teikoku Chemical Industry Co., Ltd.) was further added. -30) A solution prepared by dissolving 2 parts by weight of methanol in 98 parts by weight is applied by a dip coating method and dried at 150 ° C. for 30 minutes to give a film thickness of 0.1.
A μm barrier layer was formed.

Then, 100 parts by weight of a charge generating agent (Y-type titanyl phthalocyanine) was added to 3900 parts by weight of ethyl cellosolve as a dispersion medium, and primary dispersion was performed using an ultrasonic disperser. To this dispersion was further added a solution prepared by dissolving 100 parts by weight of polyvinyl butyral (BM-1 manufactured by Sekisui Chemical Co., Ltd.) as a binder resin in 900 parts by weight of ethyl cellosolve, and the ultrasonic disperser was used again. Secondary dispersion was performed to prepare a coating solution for the charge generation layer. Next, this coating solution was applied onto the barrier layer prepared above by a dip coating method and dried at 110 ° C. for 5 minutes to form a charge generation layer having a thickness of 0.4 μm.

Next, 6 parts by weight of an electron transfer material (ETM-2), 90 parts by weight of a hole transfer material (HTM-1), and 100 parts by weight of a bisphenol Z type polycarbonate as a binder resin are added to 800 parts by weight of tetrahydrofuran. And mixed and dispersed to obtain a coating liquid for the charge transport layer. Then, this coating solution was applied onto the charge generation layer by dip coating and dried at 110 ° C. for 30 minutes to form a charge transport layer having a film thickness of 33 μm.

<Layered Photoreceptor Comparative Example 1> A coating solution for an intermediate layer was prepared in the same manner as in Production Example 1 except that untreated carbon black was used as the pigment particles. In the same manner as in 5, a laminated type photoreceptor was prepared.

<Layered Photoreceptor Comparative Example 2> A coating solution for an intermediate layer was prepared in the same manner as in Production Example 3 except that untreated titanium oxide was used as the pigment particles. In the same manner as in 5, a laminated type photoreceptor was prepared.

<HTM-1>

[Chemical 12]

<ETM-1>

[Chemical 13]

<ETM-2>

[Chemical 14]

[Evaluation of Image] The single-layer type photoreceptor having the intermediate layer obtained in each of the examples and comparative examples of the single-layer type photoreceptor was mounted on a modified laser printer HL-1670 manufactured by Brother Industries, Ltd. Then, 160 sheets of black and white belt-shaped images were continuously printed in an environment of a temperature of 50 ° C. and a humidity of 90%. And 1
The image fog on the 60th sheet was visually judged.

On the other hand, the laminated photoreceptor having the intermediate layer obtained in the above-mentioned laminated photoreceptor examples and comparative examples was mounted on a laser printer LBP-450 manufactured by Canon Inc.,
Image fog was evaluated in the same manner as in the case of the single-layer type photoreceptor.

Table 2 shows the image evaluation results.

[Table 2]

The image evaluation criteria are as follows. B: Image fog cannot be visually confirmed. Δ: Image fog is confirmed. ×: Image fogging occurred at a glance, and the degree was severe.

From the above evaluation results, by using the electrophotographic organic photoreceptor of the present invention having the intermediate layer containing the pigment particles grafted with the polymer, the unevenness of the conductivity of the intermediate layer is remarkably reduced. It is possible to obtain a good image without fog. Further, it is considered that the reason why the unevenness of the conductivity of the intermediate layer is reduced is that the dispersibility of the pigment particles grafted with the polymer in the binder resin or the resin solution used for the intermediate layer is good. .

[0085]

As described above, by using the electrophotographic organic photoreceptor of the present invention, the unevenness of the conductivity of the intermediate layer is remarkably reduced, and a good image free from fog can be obtained.

[0086]

[Brief description of drawings]

FIG. 1 is a schematic diagram showing pigment particles grafted with a polymer.

Claims (4)

[Claims] 1. An electrophotographic organic photoreceptor in which an organic photosensitive layer is formed on a conductive substrate via an intermediate layer, wherein the intermediate layer is formed by dispersing at least pigment particles in a binder resin, An electrophotographic organic photoreceptor, wherein the pigment particles are grafted with a polymer having at least a reactive group capable of reacting with a functional group on the surface of the pigment particle. 2. The reactive group of the polymer is at least one group selected from an epoxy group, a thioepoxy group, an aziridine group, an oxazoline group, an isocyanate group and an N-hydroxyalkylamide group. The electrophotographic organic photoreceptor according to claim 1, wherein 3. The segment (A) having a reactive group capable of reacting with a functional group on the surface of the pigment particle, the polymer comprising:
The electrophotographic organic photoreceptor according to claim 1 or 2, which is a block-type or graft-type copolymer comprising a segment (B) having a structure different from that of the segment. 4. The segment (B) comprises at least a polysiloxane structure, a poly (meth) acrylic acid structure, a polyether structure, a poly (meth) acrylonitrile structure, a polyester structure, a polyalkylene structure, and a polyamide. 4. The electrophotographic organic photoreceptor according to claim 3, which has a structure selected from a system structure, a polyimide structure, a polyurethane structure, and a fluororesin structure.