JPH0772635A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To improve carrier forming efficiency, to improve the sensitivity on a long wavelength side and to obtain the excellent balance of spectral sensitivity and repeating characteristics by consisting a charge generating material of a combination of respectively specific P type and N type charge generating pigments. CONSTITUTION:This electrophotographic photoreceptor has a conductive substrate and a photosensitive layer contg. the charge generating material and the charge transfer material. The charge generating material consists of the combination of the P type charge generating pigment and the N type charge generating pigment and at least a part of the P type and the N type charge generating pigments exist in the form of respective flocs in the photosensitive layer. The flocs of the P type and the N type charge generating pigments existing in the photosensitive layer have the flocculated structure in which plural pieces of the particles of the P type (or N type) charge generating pigments are flocculated via the particles of the N type (or P type) charge generating pigments. These flocs have preferably a grain size of 0.2 to 2mum in general.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to a sensitized electrophotographic photoreceptor.

[0002]

2. Description of the Related Art As an electrophotographic photoreceptor, a function-separated photoreceptor having a photosensitive layer containing a charge generating agent and a charge transporting agent provided on a conductive substrate is widely used. Are roughly classified into a so-called single dispersion layer type in which a charge generating agent is dispersed in a medium containing a charge transporting agent, and a charge generating layer and a charge transporting layer on a conductive substrate, in this order or the reverse order. Is known as a so-called laminated type.

As the charge generating agent, many types such as P type charge generating pigments such as phthalocyanine pigments and N type charge generating pigments such as perylene pigments and azo pigments have been used. In general, the spectral sensitivity is poorly balanced, and particularly when only N-type charge generating pigments such as perylene pigments and azo pigments are used, the sensitivity on the long wavelength side of wavelengths 600 to 700 nm is low and problems such as fog on yellow base paper occur. there were. Further, in order to design a photoconductor that can be commonly used for halogen, a fluorescent lamp, and a laser light source, a photoconductor having a panchromatic spectral sensitivity is desired, but there is no pigment suitable for this, and a plurality of types as shown below are available. Techniques using these pigments have been proposed.

For example, Japanese Patent Application Laid-Open No. 2-2 filed by the present applicant
No. 22961 discloses a laminate type in which a charge transport layer and a charge generation layer are provided in this order on a conductive substrate, and an N-type pigment (dibromoanthanthrone) and P are used as a charge generation agent.
40/60 with type pigment (metal-free phthalocyanine)
It is described to be used in an amount ratio of ˜90 / 10.

Further, JP-A-2-228670 discloses that 1.25 to 3.
The use of 75 parts by weight of X-form metal-free phthalocyanine in combination is described.

[0006]

[Problems to be Solved by the Invention]
222961), the combined use of an N-type pigment and a P-type pigment is such that when the photosensitive member is positively charged by corona discharge, the P-type pigment in an electrically neutral state is discharged from the corona discharge. The electric field generated by the action acts to inject hot holes from the P-type pigment into the charge transport layer to neutralize the negative charges induced on the substrate side. In addition, negative space charges are present in the outermost charge generation layer, and the negative space charges enhance the electric field together with the positive charges on the surface of the photoconductor to enhance the generation efficiency of photocarriers. Is. However, this is an effect that can be obtained only in the configuration in which the charge transport layer and the charge generation layer are provided in this order on the conductive substrate, and is still unsatisfactory in terms of improving the generation efficiency of photocarriers. The combined use of an N-type pigment and a P-type pigment found in the above proposal (Japanese Patent Laid-Open No. 2-228670) sensitizes the red light to some extent, but the P-type main pigment in the binder resin is used. The N-type pigment (perylene pigment) is simply added to the pigment (X-type metal-free phthalocyanine) and co-dispersed, which is insufficient from the viewpoint of improving the generation efficiency of photocarriers. It is still unsatisfactory for the purpose of providing a photoconductor suitable for use in printers and the like.

The present inventors have found that the N-type charge-generating pigment and the P-type charge-generating pigment form an aggregate under specific conditions, and that at least a part of these pigments is in the form of an aggregate in the photosensitive layer. It has been found that, when it is included, the carrier generation efficiency is remarkably improved, the sensitivity on the long wavelength side is remarkably improved, and the spectral sensitivity of the photosensitive layer is excellent in balance.

That is, the object of the present invention is to significantly improve carrier generation efficiency in a photoconductor containing a charge generating agent and a charge transporting agent, to significantly improve the sensitivity on the long wavelength side, and to balance and repeat the spectral sensitivity. An object is to provide an electrophotographic photoreceptor having excellent characteristics.

[0009]

According to the present invention, in an electrophotographic photoreceptor having a conductive substrate and a photosensitive layer containing a charge generating agent and a charge transporting agent, the charge generating agent is P
Photoreceptor comprising a combination of an N-type charge-generating pigment and an N-type charge-generating pigment, wherein at least a part of the P-type and N-type charge-generating pigments are present in the photosensitive layer in the form of their aggregates. Will be provided.

In the aggregate of the P-type and N-type charge generating pigments present in the photosensitive layer of the present invention, a plurality of particles of the P-type (or N-type) charge-generating pigment generate N-type (or P-type) charge. It is desirable that the pigment has an agglomerated structure that is agglomerated through particles of the pigment, and that the agglomerate generally has a particle diameter of 0.2 to 2 μm.

The existence and agglomeration structure of the agglomerates of fine pigment particles in the photosensitive layer of the present invention are confirmed by the combined use of a transmission electron micrograph and energy dispersive X-ray spectroscopy, as will be described later. The particle size in the present specification is defined as a value of 1/2 of the sum of the major axis of the particle and the minor axis of the particle.

[0012]

FIG. 1 of the accompanying drawings is a transmission electron microscope photograph of a photosensitive layer of the present invention, and FIG. 2 is a transmission electron microscope photograph of a conventional co-dispersion photosensitive layer. In the figure, the hatched particles represent the P-type charge generating pigment (phthalocyanine), and the doted particles represent the N-type charge generating pigment (perylene).

Referring to these figures, in the conventional photosensitive layer, the P-type charge generating pigment and the N-type charge generating pigment are dispersed in the resin medium (continuous phase) in the form of individual particles. In the photosensitive layer of the present invention, P-type charge generation pigment particles and N
Type charge generating pigment particles and aggregate form, especially P type (N type)
It is clear that a plurality of the charge generation pigment particles have an aggregation structure in which they are aggregated through the N-type (P-type) charge generation pigment particles, and the aggregation growth of the particles occurs. Incidentally, in the specific example shown in FIG. 1, a part of the N-type charge generation pigment having a large amount ratio is present in the form of an individual particle dispersion other than the agglomerate.
It is also understood that most of the P-type charge generating pigments having a small amount ratio are present in the form of the above aggregate.

According to the present invention, since at least a part of the P-type charge-generating pigment and the N-type charge-generating pigment are in the form of the above-mentioned aggregate, they can be used alone or in combination. Even co-dispersion (dispersion that does not form aggregates)
As compared with the above case, the carrier generation efficiency is remarkably improved, and significant advantages are brought about in terms of an increase in sensitivity on the long wavelength side and a balance of spectral sensitivity of the photosensitive layer.

See the examples below. For example, when the N-type charge generating pigment (perylene) is used alone (Comparative Example 1), a certain sensitivity can be obtained on the relatively short wavelength side (500 nm), but it is almost on the long wavelength side (700 nm). When the P-type charge generation pigment (phthalocyanine) is used alone (Comparative Examples 2 and 3), the sensitivity is tentatively obtained at a relatively long wavelength side, but is almost not at a relatively short wavelength side. They have no sensitivity, and all of them have a drawback that the spectral sensitivities are out of balance (the sensitivities referred to here are the half exposure amount and the potential decay rate).

Even if the P-type charge-generating pigment and the N-type charge-generating pigment are used in combination, the one having a co-dispersed structure in which each particle is dispersed individually (Comparative Example 4) is noted in terms of sensitivity. Then, the result obtained by simply connecting the N-type charge generating pigment (perylene) alone (Comparative Example 1) and the P-type charge generating pigment (phthalocyanine) alone (Comparative Example 2) Therefore, the carrier generation efficiency is not improved, the sensitivity is particularly insufficient on the long wavelength side, and further, the fluctuation of the surface potential (both the initial potential and the residual potential after exposure) increases due to repetition.

On the other hand, according to the present invention, an agglomerate is formed in advance from the P-type charge-generating pigment and the N-type charge-generating pigment, and the agglomerate is present in the photosensitive layer (Example 1).
Despite the mixing ratio of the P-type charge generating pigment and the N-type charge generating pigment in the photosensitive layer being the same as in Comparative Example 4, this photosensitive layer has a good spectral sensitivity balance at each wavelength, and has a long wavelength. The sensitivity on the side is remarkably improved, which is considered to be due to the increase in carrier generation efficiency, and the excellent effect that the fluctuation of the surface potential due to repetition can be suppressed to a small range is exerted. Further, a P-type charge generating pigment (phthalocyanine) and an N-type charge generating pigment (perylene) are combined at a ratio of 3 parts by weight: 10 parts by weight to form an agglomerate in advance, and the agglomerate is allowed to exist in the photosensitive layer. (Example 5) and 10 parts by weight of the P-type charge generating pigment (phthalocyanine) were used alone (Comparative Example 3), the sensitivity level (700 nm) was noted, and the levels were substantially the same. I understand. This is because Example 5 forms an aggregate, and therefore the carrier generation efficiency is improved by the micro PN junction even if the amount of the P-type charge generation pigment added is 3 parts by weight. The same effect is obtained as when 10 parts by weight of the charge-generating pigment (phthalocyanine) is used alone. Furthermore, it has a co-dispersion structure and has the same sensitivity (500 nm) as the structure in which aggregates are present in the photosensitive layer.
And 700 nm), it is necessary to increase the amount of the P-type charge generation pigment added (Comparative Example 8). However, in this case, the fluctuation of the surface potential (initial potential and residual potential after exposure) due to repetition was significantly large.

Further, 1 part by weight of P-type charge generating pigment (phthalocyanine) and N-type charge generating pigment (zinc oxide): 1
When 0 parts by weight were combined to form an agglomerate in advance, and the agglomerate was present in the photosensitive layer (Example 8), P
Comparing the case of using 1 part by weight of the charge-generating pigment (phthalocyanine) alone (Comparative Example 2) and the case of using 10 parts by weight of the N-type charge-generating pigment (zinc oxide) alone (Comparative Example 9) Focusing on the surface (700 nm), although not halved in both comparative examples, it was 13.5 in Example 8.
It can be seen that the sensitivity is as high as μJ / cm ² . This is because in Example 8 where the zinc oxide is not sensitive to 500 nm and 700 nm, it forms aggregates.
It can be considered that even if the amount of the P-type charge generating pigment added is 1 part by weight, the carrier generation efficiency is improved by the micro PN junction.

The above-mentioned improvement in the photosensitive layer according to the present invention has been found as a phenomenon as a result of numerous experiments by the present inventors, and the reason therefor is beyond speculation. The present inventors consider the following.

That is, in the photosensitive layer according to the present invention, the P-type charge-generating pigment particles or the N-type charge-generating pigment particles have an agglomerated structure in which they are agglomerated via the counterpart pigment particles. Many micro P-N junctions (PN junctions) are formed at the interfaces between the primary particles. It is believed that in the photosensitive layer according to the present invention, the formation of the P—N junction improves the carrier generation efficiency in a wide wavelength range including the long wavelength side and increases the sensitivity.

[0021]

Preferred Embodiment of the Invention

[Photoreceptor] In the photoreceptor of the present invention, the photosensitive layer may contain a charge generating agent and a charge transporting agent in a laminated type or a single layer dispersed type. However, since the single-layer dispersion type has a lower pigment concentration in one layer, the effect of positively forming a micro PN junction at the interface between the primary particles is most prominent.

In FIG. 3 showing an example of this electrophotographic photoreceptor, this one comprises a conductive base 1 and a single-layer type photosensitive layer 2 containing a charge generating agent and a charge transporting agent in a single layer. . The charge generation / charge transport layer 2 is a charge transport material (CTM).
And a dispersed phase of a particular charge generating agent (CGM), which is dispersed in the continuous phase and is described in detail below.

In FIG. 4, which shows another example of the electrophotographic photosensitive member, the photosensitive member comprises a conductive substrate 1, a charge generating layer (CGL) 3 containing a specific charge generating agent described in detail below, and a charge. The transport layer (CTL) 4 is provided in this order.

FIG. 5 showing still another example of the electrophotographic photoreceptor.
In this photoreceptor, a charge transport layer (CTL) 5 and a charge generation layer (CGL) 6 containing a specific charge generation agent described in detail below are provided in this order on a conductive substrate 1.

In these photoreceptors, the charge transport material (CTM) of the photosensitive layer 2 or the charge transport layer 4 or 5 may be a hole transport material, an electron transport material, or a combination of both.

Although not shown in FIGS. 3 to 5, in the photoreceptor of the present invention, a protective layer known per se, for example, a protective layer containing a charge transfer agent and / or conductive fine powder is provided on the uppermost layer. May be provided.

[Charge Generating Agent] In the present invention, a combination of a P-type charge generating pigment and an N-type charge generating pigment is used as a charge generating agent, and at least a part of them is used in the form of an aggregate in the photosensitive layer. To exist inside. In this aggregate, P
A plurality of particles of the type (or N-type) charge generating pigment are agglomerated via the particles of the N-type (or P-type) charge generating pigment to be contrasted with. There are many P-N junctions in.

As the P-type charge generating pigment constituting the aggregate of the present invention, organic and inorganic P-type charge generating pigments known per se are used. Examples thereof include phthalocyanine pigments, naphthalocyanine pigments and other porphyrin pigments. Mention may be made of pigments. These porphyrin-based pigments have a skeleton represented by the following formula (1).

[0029]

[Chemical 1]

In the above formula, Z is a nitrogen atom or a CH group, R ¹ and R ² are substituted or unsubstituted monovalent hydrocarbon groups having 12 or less carbon atoms, and these groups R ¹ and R ² May be linked to each other to form a substituted or unsubstituted benzene ring or naphthalene ring together with the bonding carbon atom, and M is H
₂ or a metal atom, which may be an oxide.

The following are examples of particularly suitable ones. The metal-free phthalocyanine, oxotitanyl phthalocyanine, and the P-type charge generating pigment are generally 0.1%.
It is desirable to have a particle size of 1 to 1 μm.

As the N-type charge-generating pigment constituting the aggregate, organic and inorganic N-type charge-generating pigments known per se are used, and in particular, perylene pigment, azo pigment, squarylium salt pigment or polycyclic quinone. Based pigments, zinc oxide, titanium oxide and the like are used.

The perylene pigment is represented by the following formula (2)

[0034]

[Chemical 2]

In the formula, each of R ³ and R ⁴ has 18 carbon atoms.
Examples thereof include the following substituted or unsubstituted alkyl groups, cycloalkyl groups, alkyl groups, aryl groups, or aralkyl groups, and examples of the substituents include an alkoxy group and a halogen atom.

As the azo pigment, any of monoazo pigments, disazo pigments, trisazo pigments and the like which have been conventionally used as charge generating pigments can be used.

The squarylium salt-based pigment is represented by the following formula (3)

[0038]

[Chemical 3]

In the formula, each of R ⁵ and R ⁶ is an alkyl group,
Alkoxy groups, halogen atoms, R ⁷ , R ⁸ ,
R ⁹ and R ¹⁰ are each an alkyl group, a cycloalkyl group,
Examples thereof include an alkoxy group, a halogen atom, an aryl group, and an aralkyl group, and each group may have an alkyl group, an alkoxy group, a halogen atom or the like as a substituent.

Examples of the polycyclic quinone pigments include anthanthuron pigments, quinacridone pigments, perinone pigments, quinophthalone pigments, flavantron pigments, pyranthrone pigments, violanthrone pigments, anthrone pigments and indanthrone pigments. Is exemplified.

The N-type charge generating pigment used in the present invention generally preferably has a particle size of 0.1 to 1 μm.

Aggregates of the P-type charge generating pigment and the N-type charge generating pigment cannot be formed by simply co-dispersing the P-type charge generating pigment and the N-type charge generating pigment in the resin solution. It is important to perform pretreatment in advance to form aggregates.

The pretreatment for producing the aggregates includes a wet method and a dry method. In the wet method, a specific polar solvent, for example, a solvent such as tetrahydrofuran or dichloromethane is used.
The P-type charge generating pigment and the N-type charge generating pigment are finely dispersed to form an aggregate. By finely dispersing both pigments in these solvents, the P-type charge-generating pigment particles are positively charged, while the N-type charge-generating pigment particles are negatively charged, and the formation of aggregates is effectively performed. .

According to the experiments by the present inventors, even if both pigments are mixed in an organic solvent, alcohols, cyclohexane,
It was confirmed that the dispersibility of individual pigments was not stable with toluene, dioxane, etc., and the efficiency of aggregate formation was extremely reduced. The formation of aggregates by the wet method is performed by a ball mill,
Wet grinding using a colloid mill, dispersion mill, homomixer, etc. is effective.

In the dry method, a P-type charge generating pigment and an N-type charge generating pigment are mixed and the mixture is co-ground. Also by this mechanochemical method, the crushing of each pigment into primary particles and the agglomeration of the crushed primary particles with each other occur, and the aggregates grow. Dry method pulverization can be performed using a ball mill or a vibration mill.

In the present invention, the amount ratio of the P-type charge generating pigment to the N-type charge generating pigment is generally 10: 0.1 to 0.
1:10 weight ratio, especially 10: 0.5 to 0.5: 10
Is appropriately selected from the weight ratio of.

When the amount ratio of the P-type charge-generating pigment and the N-type charge-generating pigment is biased to either side, the larger pigment particles are as shown in FIG. Although it may exist in the form, the presence of such free particles does not have any adverse effect in terms of sensitivity.

The agglomerate used in the present invention is composed of a plurality of particles of the P-type (N-type) charge generating pigment which are agglomerated through the particles of the N-type (P-type) charge generating pigment. The aggregates should have a particle size of 0.2 to 2 μm. If this particle size exceeds 2 μm, the sensitivity and chargeability of the photoconductor tend to decrease. It is considered that this is because the pigment particles at the center of the aggregate are hidden and the light receiving area is further reduced. In addition, it is considered that the presence of the giant particles facilitates charge leakage in the photosensitive layer and reduces the charging ability.
On the other hand, when the particle size of the aggregate is smaller than the above range, the balance of the spectral sensitivity is lowered and the long wavelength side sensitivity is also reduced as compared with the case where the particle size is within the above range.

[Single-Layer Photoreceptor] In the single-layer photoreceptor, the agglomerates of the P-type and N-type charge generating pigments and the charge transfer agent are
A binder resin solution for forming a photosensitive layer is dispersed and the coating composition is provided on a conductive substrate to obtain a single-layer photoreceptor.
Incidentally, in order to form the coating liquid, a conventionally known method, for example,
It may be prepared by using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, or the like, and coated and dried by a conventionally known coating means.

As the charge transfer agent, any electron transfer agent or hole transfer agent known per se is used, and for example, the following ones are used. These charge transfer agents may be used alone or in combination of two or more. For example, the electron transfer material may be used in combination with a small amount of hole transfer material, or conversely, the hole transfer material may be used in combination with a small amount of electron transfer material.

Suitable examples of the electron transfer agent include the following. 2,6-dimethyl-2 ', 6'-di-t-butyldiphenoquinone, 2,2'-dimethyl-6,6'-di-t-butyldiphenoquinone, 2,6'-dimethyl-2', 6-t
-Butyldiphenoquinone, 2,6,2'6'-tetramethyldiphenoquinone, 2,6,2 ', 6'-tetra-t-
Butyldiphenoquinone, 2,6,2 ', 6'-tetraphenyldiphenoquinone, 2,6,2', 6'-tetracyclohexyldiphenoquinone, chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane , 2,4,7-trinitro-9-fluorenone, 2,
4,5,7-tetranitro-9-fluorenone, 2,
4,7-trinitro-9-dicyanomethylenefluorenone, 2,4,5,7-tetranitroxanthone, 2,
4,8-Trinitrothioxanthone.

Suitable examples of the hole transfer material include the following. N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-phenylhydrazino-3-methylidene-9-carbazole, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N, N
-Diphenylhydrazino-3-methylidene-10-ethylphenothiazine, N, N-diphenylhydrazino-3
-Methylidene-10-ethylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, p-diethylaminobenzaldehyde-α-naphthyl-N-phenylhydrazone, p-pyrrolidinobenzaldehyde-N, N-diphenyl Hydrazone, 1,
3,3-Trimethylindolenine-ω-aldehyde-
N, N-diphenylhydrazone, p-diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,5-bis (p-diethylaminophenyl)-
1,3,4-oxazizole, 1-phenyl-3- (p
-Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [quinonyl (2)]-3
-(P-Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (p-diethylaminostyryl) -5-
(P-Diethylaminophenyl) pyrazoline, 1- [6
-Methoxy-pyridyl (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl)
Pyrazoline, 1- [pyridyl (3)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [lepidyl (3)]-3- (p
-Diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3
-(P-Diethylaminostyryl) -4-methyl-5-
(P-Diethylaminophenyl) pyrazoline, 1- [pyridyl (2)]-3- (α-methyl-p-diethylaminostyryl) -3- (p-diethylaminophenyl) pyrazoline, 1-phenyl-3- (p -Diethylaminostyryl) -4-methyl-5- (p-diethylaminophenyl) pyrazoline, 2- (p-diethylaminostyryl) -3-diethylaminobenzoxazole, 2-
(P-Diethylaminophenyl) -4- (p-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole, 2- (p-diethylaminostyryl) -6-diethylaminobenzothiazole, bis (4-diethylamino-2) -Methylphenyl) phenylmethane, 1,1-
Bis (4-N, N-diethylamino-2-methylphenyl) heptane, 1,1,2,2-tetrakis (4-N,
N-dimethylamino-2-methylphenyl) ethane,
N, N'-diphenyl-N, N'-bis (methylphenyl) benzdiene, N, N'-diphenyl-N, N'-bis (ethylphenyl) benzidine, N, N'-diphenyl-N, N'-bis ( Propylphenyl) benzidine,
N, N'-diphenyl-N, N'-bis (butylphenyl) benzidine, N, N'-bis (isopropylphenyl) benzidine, N, N'-diphenyl-N, N'-bis (secondary butylphenyl) Benzidine, N, N'-diphenyl-N, N'-bis (tertiary butylphenyl) benzidine N, N'-diphenyl-N, N'-bis (chlorophenyl) benzidine, triphenylamine, poly-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylarucdin, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole formaldehyde resin.

Various resins can be used as the resin medium in which the above-mentioned charge transport agent or charge generating agent is dispersed, and examples thereof include styrene polymers, acrylic polymers, styrene-acrylic polymers and ethylene- Vinyl acetate copolymer,
Olefin polymers such as polypropylene and ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone Resin, polyvinyl butyral resin,
Examples include various polymers such as polyether resins, phenol resins, and photocurable resins such as epoxy acrylate. These binder resins may be used alone or in combination of two or more. Suitable resins include styrene polymers, acrylic polymers, styrene-acrylic polymers,
Polyester, alkyd resin, polycarbonate, polyarylate and the like.

As the solvent used to form the coating liquid, various organic solvents can be used, and alcohols such as methanol, ethanol, isopropanol, butanol,
Aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, Ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, ketones such as cyclohexanone, ethyl acetate, esters such as methyl acetate, dimethylformamide, dimethyl sulfoxide, etc. Used as a mixture.

The composition of the photosensitive layer is not particularly limited, but it is generally preferable that the charge generating pigment accounts for 75 to 1% by weight, particularly 20 to 3% by weight, based on the dry matter. On the other hand, the charge transfer agent is 80 to 10% by weight, especially 60 to 3% by weight.
It is preferably present at 0% by weight. When the amount of the charge generating agent or the charge transporting agent is less than the above range, sufficient sensitivity cannot be obtained, and when the amount is more than the above range, the charge amount is decreased,
Printing durability of the photosensitive layer tends to decrease. Generally, the solid content concentration of the coating liquid is preferably 5 to 50% by weight.
The composition for forming a photoreceptor of the present invention contains various compounding agents known per se, such as an antioxidant, a radical scavenger, a singlet quencher, and UV absorption, within a range that does not adversely affect electrophotographic properties. Agents, softeners, surface modifiers, defoamers, extenders, thickeners, dispersion stabilizers, waxes, acceptors,
A donor etc. can be mix | blended.

As the conductive substrate on which the photosensitive layer is provided, various conductive materials can be used, such as aluminum, copper, tin, platinum, gold, silver, vanadium, molybdenum,
Chromium, cadmium, titanium, nickel, indium,
Examples include simple metals such as stainless steel and brass, plastic materials in which the above metals are vapor-deposited or laminated, and glass covered with aluminum iodide, tin oxide, indium oxide and the like. Generally, it is preferable to use an aluminum tube, particularly an anodized tube having a film thickness of 1 to 50 μm.

In the case of a monodisperse type photosensitive layer, its thickness is generally in the range of 5 to 100 μm, preferably 10 to 50 μm. If the thickness is smaller than the above range, the surface potential tends to be low, while if it is larger than the above range,
The sensitivity tends to decrease and the residual potential tends to increase.

[Layered Photoreceptor] Among the laminated photoreceptors of the present invention shown in FIG. 4, a charge generation layer is provided on the conductive substrate. The coating composition for forming the charge generation layer is the above-mentioned resin solution in which the charge generation agent is dispersed, and the charge generation agent is applied in an amount of 99 to 1% by weight, particularly 80 to 50% by weight, based on the solid content. It is preferable to contain it, and the thickness thereof is preferably in the range of 0.01 to 10 μm, 0.1 to 5 μm. Next, a charge transport layer is provided on the charge generation layer. This charge transport layer is a dispersion of the above-described charge transport agent in the above-mentioned resin solution, and is 80 to 10% by weight, particularly 60 to 30% by weight based on the total solid content of both.
It should contain the derivative in an amount of% by weight. The thickness is preferably in the range of 1 to 100 μm and 5 to 50 μm. As the charge transfer agent in the charge generation agent, one having an electron transfer agent as a main component for positive charging and one having a hole transfer agent as a main component for negative charging is used.

In the laminated type photoreceptor of the present invention shown in FIG. 5, a charge transport layer is provided on the conductive substrate, and a charge generation layer is provided thereon. The composition and thickness of the charge transport layer and the charge generation layer may be the same as those described above.

[0060]

The present invention will be further described in the following examples. The measurements in the examples were performed as follows.

Initial characteristics electrostatic copying tester (Kawaguchi Electric Co., EPA-
8100), the initial surface potential SP1 of the sheet-shaped electrophotographic photosensitive members prepared in Examples and Comparative Examples
The flow-in current was adjusted so that (V) was +700 V, and charging was performed. After that, from the xenon lamp, which is the exposure light source, using an interference filter,
Only the light of the wavelength
Irradiation (10 μw) for 2 seconds was performed to measure the half-exposure amount of each. That is, the time until the initial surface potential + 700V becomes 1/2 is obtained, and the half-exposure amount (μJ
/ Cm ² ) was determined. Further, the surface potential at the time point 3 seconds after the start of exposure was determined as the initial residual potential RP1 (V), and the potential decay rate (%) was calculated using the following formula.

Repetitive Characteristics The sheet-shaped electrophotographic photosensitive members prepared in the above Examples and Comparative Examples were subjected to the above electrostatic copying tester (Kawaguchi Denki EPA, EPA).
-8100), the charging process, the exposure process (the same as the above except that the interference filter is not used) in which the flow-in current value adjusted above is maintained in the initial stage, the charge removal process (1000 Lux
White light irradiation) for 1 second repeatedly 100 times, and then the surface potential SP100 (V) and the residual potential RP100.
(V) was measured in the same manner as above, and the difference between the initial surface potential and the initial residual potential was calculated using the following formula. ΔSP = (SP100)-(SP1) ΔRP = (RP100)-(RP1)

(Example 1) Perylene pigment (the following formula (4)) and X-type metal-free phthalocyanine (the following formula (5))
Was dispersed in 100 parts by weight of THF at a ratio of 10 parts by weight to 1 part by weight in a ball mill for 1 hour, and then D was used as a charge transfer agent.
50 parts by weight of EH (the following formula (6)) and 100 parts by weight of polycarbonate (manufactured by Mitsubishi Gas Chemical Co., Ltd.) as a binder resin were added, and 1 part of the coating solution was uniformly dispersed in a ball mill for 1 hour.
After heat treatment at 20 ° C. for 1 hour, the film thickness is 20 μm
Was applied onto an aluminum substrate (sheet-like) so as to be (agglomerate particle size: 0.2 to 2 μm). The dispersion structure in this photosensitive layer was as shown in FIG.

[0064]

[Chemical 4]

[0065]

[Chemical 5]

[0066]

[Chemical 6]

Example 2 Aggregates were formed in the same manner as in Example 1 except that the perylene pigment was replaced with an azo pigment (the following formula (7)) (aggregate particle size: 0.2 to 2 μm). A photoconductor was formed.

[0068]

[Chemical 7]

Example 3 Aggregates were formed in the same manner as in Example 1 except that the perylene pigment was replaced with a polycyclic quinone pigment (the following formula (8)) (aggregate particle size: 0.2). ~ 2μ
m) A photoreceptor was formed.

[0070]

[Chemical 8]

Example 4 Except that the X-type metal-free phthalocyanine was replaced with naphthalocyanine (the following formula (9)),
Aggregates were formed in the same manner as in Example 1 (aggregate particle size:
0.2 to 2 μm) A photoreceptor was formed.

[0072]

[Chemical 9]

(Example 5) The procedure of Example 1 was repeated except that the amount ratio of the perylene pigment to the X-type metal-free phthalocyanine was 10 parts by weight to 3 parts by weight to form an aggregate (aggregate particle size: 0 0.2-2 μm) A photoconductor was formed.

Example 6 The procedure of Example 1 was repeated except that the amount ratio of the perylene pigment to the X-type metal-free phthalocyanine was set to 10 parts by weight to 0.2 parts by weight to form the aggregate. : 0.2-2 μm) A photoreceptor was formed.

Example 7 The same procedure as in Example 1 was conducted except that the perylene pigment and the X-type metal-free phthalocyanine were ball-milled in THF for 100 hours to form an aggregate (aggregate particle diameter: 0.2 to 2 μm). ) A photoreceptor was formed.

Example 8 Aggregates (aggregate particle size 0.2 to 2 μm) were formed in the same manner as in Example 1 except that the perylene pigment was replaced with zinc oxide to form a photoreceptor.

Comparative Example 1 A photoconductor was formed in the same manner as in Example 1 except that 10 parts by weight of perylene pigment was used alone.

(Comparative Example 2) The procedure of Example 1 was repeated except that 1 part by weight of X-type metal-free phthalocyanine was used alone.
A photoconductor was formed.

Comparative Example 3 A photoconductor was formed in the same manner as in Example 1 except that 10 parts by weight of X-type metal-free phthalocyanine was used alone.

Comparative Example 4 A photoconductor was formed in the same manner as in Example 1 except that the perylene pigment and the X-type metal-free phthalocyanine were co-dispersed with the charge transfer agent and the binder resin without pre-dispersion. The dispersion structure of this photosensitive layer is
As shown in FIG. 2, formation of aggregates was not observed.

Comparative Example 5 A photoconductor was formed in the same manner as in Example 1 except that the ball mill treatment was carried out for 5 minutes as the predispersion of the perylene pigment and the X-type metal-free phthalocyanine. In this photoreceptor, it was confirmed that the formation of metal-free phthalocyanine aggregates in the photosensitive layer was incomplete.

Comparative Example 6 A photoconductor was formed in the same manner as in Example 1 except that toluene was used for the predispersion of the perylene pigment and the X-type metal-free phthalocyanine. No aggregate was formed in this photosensitive layer. This is probably because the polarities of the solvent are weak and it is difficult to form aggregates.

Comparative Example 7 A photoconductor was formed in the same manner as in Example 1 except that benzene was used for the predispersion of the perylene pigment and the X-type metal-free phthalocyanine. No aggregate was formed in this photosensitive layer. This is probably because the polarities of the solvent are weak and it is difficult to form aggregates.

Comparative Example 8 A photoconductor was formed in the same manner as in Comparative Example 4 except that 10 parts by weight of each of the perylene pigment and the X-type metal-free phthalocyanine were used.

Comparative Example 9 A photoconductor was formed in the same manner as in Example 1 except that 10 parts by weight of zinc oxide was used alone. The results obtained are shown in the table below.

[0086]

[Table 1]

[0087]

According to the present invention, at least a part of the P-type charge-generating pigment and the N-type charge-generating pigment is in the form of an aggregate, and in particular, a plurality of P-type (N-type) charge-generating pigment particles are N-type. (P
Type) Coexisting in the form of an agglomerated structure aggregated through the charge generation pigment particles in the photosensitive layer, even if any one of them is used alone or in combination (dispersion that does not form an aggregate) As compared with the above case, the carrier generation efficiency is increased, the long-wavelength side sensitivity is remarkably increased, and the spectral sensitivity of the photosensitive layer can be made excellent.
Further, the photoconductor of the present invention is remarkably excellent in repeatability.

[Brief description of drawings]

FIG. 1 is a drawing of a transmission electron micrograph of a photosensitive layer of the present invention.

FIG. 2 is a drawing of a transmission electron micrograph of a conventional co-dispersion type photosensitive layer.

FIG. 3 is a sectional view showing an example of a single dispersion layer type electrophotographic photoreceptor.

FIG. 4 is a cross-sectional view showing an example of a laminated electrophotographic photoconductor.

FIG. 5 is a cross-sectional view showing another example of a laminated electrophotographic photoconductor.

[Explanation of symbols]

 1 Conductive Substrate 2 Single Layer Type Photosensitive Layer Containing Charge Generating Agent and Charge Transporting Agent 3 Charge Generating Layer (CGL) 4 Charge Transporting Layer (CTL) 5 Charge Transporting Layer (CTL) 6 Charge Generating Layer (CGL)

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G03G 5/06 384

Claims (6)

[Claims] 1. A photoconductor for electrophotography comprising a conductive substrate and a photosensitive layer containing a charge generating agent and a charge transporting agent, wherein the charge generating agent comprises a P-type charge generating pigment and an N-type charge generating pigment. An electrophotographic photoreceptor comprising a combination, wherein at least a part of the P-type and N-type charge generating pigments are present in the photosensitive layer in the form of their aggregates. 2. A photoreceptor for electrophotography according to claim 1, wherein the P-type charge generating pigment is a pigment selected from the group consisting of phthalocyanine pigments, naphthalocyanine pigments and other porphyrin pigments. 3. The photoconductor for electrophotography according to claim 1, wherein the N-type charge generating pigment is a pigment selected from the group consisting of perylene pigments, azo pigments, squarylium salt pigments and polycyclic quinone pigments. 4. A photoreceptor for electrophotography according to claim 1, wherein the P-type charge generating pigment and the N-type charge generating pigment are present in a weight ratio of 10: 0.1 to 0.1: 10. 5. The agglomerate comprises an agglomerate of a plurality of particles of a P-type (N-type) charge generating pigment that are agglomerated via particles of an N-type (P-type) charge generating pigment, and the agglomerate is 0. The electrophotographic photoreceptor according to claim 1, having a particle size of 0.2 to 2 μm. 6. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer is a single dispersion type photosensitive layer containing a charge generating agent and a charge transporting agent.