JP2002341570A - Electrophotographic sensitive body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic sensitive body where the film thickness of an intermediate layer is uniformized and by which image fogging is prevented. SOLUTION: Binding resin and a charge transporting agent whose molecular weight is >=400 are incorporated in the intermediate layer provided on supporting base substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art In the above-described image forming apparatus, a charge generating agent which generates charges by light irradiation, a charge transporting agent which transfers generated charges, and a binder resin constituting a layer in which these substances are dispersed are used. The so-called organic photoreceptors are widely used. Organic photoreceptors are roughly divided 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 agent. A photoreceptor having a laminated photosensitive layer in which a charge transport layer containing an agent is laminated is generally used.

However, these photoconductors have the following problems. 1. In the charging step at the time of image output, either positive or negative charge is added to the surface of the photoreceptor, and at this time, charge having a polarity opposite to that of the surface of the photoreceptor is generated on the supporting substrate side. If there is no intermediate layer, the charge on the supporting substrate side is injected into the photosensitive layer, which causes a reduction in the charge on the surface of the photosensitive member, and image fogging occurs. 2. When the photosensitive layer is directly applied on the supporting substrate, the photosensitive layer may not be sufficiently bound on the supporting substrate depending on the type of the binder resin and the application conditions. 3. If there is a defect such as a scratch on the surface of the supporting substrate, a black spot occurs 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, while preventing the charge on the supporting substrate side from being easily injected into the photosensitive layer, the photosensitive layer is strongly bound on the supporting substrate,
Defects on the surface of the supporting substrate can be covered and smoothed.

[0005] However, when the intermediate layer is formed only of the binder resin, the electric conductivity is low, and unless the thickness of the intermediate layer is set to a submicron level, a problem such as image fogging occurs. This is because in the exposure step at the time of image output, both the positive and negative charges are generated by the charge generating agent in the exposed portion, but the charges to be transported to the support substrate side (charges of the same polarity as the photoreceptor surface) are intermediate. This is because it is blocked by the layer and remains in the photosensitive layer. Furthermore, in the charge removal step after the transfer step, the charge on the surface of the photoconductor cannot be removed, and the increase in the residual potential also causes image fog.

On the other hand, if the thickness of the intermediate layer is reduced, defects on the surface of the supporting substrate cannot be covered.

Therefore, it is conceivable to increase the conductivity of the intermediate layer to secure the film thickness. For example, JP-A-59-93453 describes that a surface of the titanium oxide powder is treated with tin oxide or alumina, and JP-A-6-202366 describes that an intermediate layer contains non-conductive titanium oxide particles. Have been.

However, during the application of a coating liquid in which metal oxide particles such as titanium oxide are dispersed on a supporting substrate, drying and solidification to form an intermediate layer, the metal oxides aggregate to form aggregated particles. Resulting in. For this reason, the conductivity of the entire intermediate layer is increased, but unevenness is caused in the conductivity, and charges are trapped in a portion having low conductivity. As a result, the residual potential is increased, and the same problem as described above occurs.

A charge transporting compound can be considered as a material capable of smoothly removing charges in the intermediate layer and hardly causing aggregation. For example, JP-A-6-202366 describes that an electron-accepting material is contained in an intermediate layer, and JP-A-10-73942 describes that an intermediate layer has an electron-withdrawing compound.

[0010] However, when the compound described in the above-mentioned publication is contained in the intermediate layer, another problem occurs. That is, because the viscosity of the coating liquid for the intermediate layer is low,
When an attempt is made to form an intermediate layer having a large thickness, the coating liquid drips below the support base after being applied onto the support base and before being cured / dried. Due to this dripping, the intermediate layer becomes thinner above the support base and thicker below. When the film thickness becomes nonuniform, the thin portion of the intermediate layer cannot cover the defects on the surface of the support substrate, or the effect of preventing the injection of charges on the support substrate side is reduced. Also,
Since the conductivity is low in the thick portion of the intermediate layer, the charge on the photosensitive layer side cannot be removed. These things are
As described above, this causes image fogging. further,
Since the thickness of the photosensitive layer provided on the intermediate layer also becomes non-uniform, problems such as image unevenness and insufficient durability of the photosensitive member occur.

In order to smooth the intermediate layer, it is considered to increase the viscosity of the coating solution by using a thickener such as an organic amide compound, a modified castor oil derivative, a modified polyolefin wax-based material, and an organic clay derivative. Can be However, by including a thickener in the intermediate layer, the charge removal by the charge transporting compound may be inhibited,
The effect of improving the electrical properties of the intermediate layer is reduced.

The viscosity of the coating solution can also be increased by increasing the content of the charge transporting compound in the coating solution. However, in this case, the conductivity increases as the thickening effect improves. Therefore, in order to avoid unnecessary charge removal, the thickness of the intermediate layer must be excessively large, and the effect of increasing the viscosity to make the thickness uniform cannot be expected much.

Accordingly, an object of the present invention is to solve the above-mentioned technical problems, to make the thickness of the intermediate layer uniform and to improve the electrical characteristics as compared with the prior art, so that an electrophotographic photosensitive member free from image fog can be obtained. Is to provide the body.

[0014]

Means for Solving the Problems In order to solve the above problems, the present inventors have paid attention to the fact that as the molecular weight of the charge transporting agent contained in the intermediate layer increases, the viscosity of the coating solution increases. Further, when the correlation between the thickness difference between the upper and lower support substrates and the molecular weight of the charge transporting agent was strictly investigated, the following was found. FIG. 1 shows the relationship between the difference in film thickness between the upper and lower portions of the support base and the molecular weight (for detailed experimental conditions, see Examples 1 to 8 described later). As shown in FIG. 1, up to a molecular weight of 400, the molecular weight increases and the film thickness difference decreases, but when the molecular weight exceeds 400, the film thickness difference decreases.
It turned out that it changes almost stably at 0.6 μm. Each of the charge transporting compounds used for the intermediate layer described in the above publication has a molecular weight of less than 400, and the thickness of the intermediate layer becomes uneven. For example, the charge transporting agent (CT-3) used in Comparative Example 4 described later is p-benzoquinone (molecular weight: 108) described in JP-A-6-202366. Had a large image fog of 1.8 μm.

As described above, by setting the molecular weight of the charge transporting agent contained in the intermediate layer to 400 or more, the viscosity of the coating solution can be increased without increasing the content of the charge generating agent more than necessary. become.

Accordingly, the electrophotographic photoreceptor of the present invention has a support base, an intermediate layer and a photosensitive layer provided on the support base, and the intermediate layer comprises a binder resin and a charge transport agent having a molecular weight of 400 or more. It is characterized by containing.

The molecular weight of the charge transporting agent defined in the present invention is a value obtained by calculating the atomic weights of the atoms constituting the charge transporting agent as the following numerical values and rounding off the result to the nearest whole number. Carbon: 12.011, hydrogen: 1.00079, oxygen: 15.999, nitrogen: 14.007.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the electrophotographic photosensitive member of the present invention will be described.

The electrophotographic photoreceptor of the present invention has an intermediate layer containing a binder resin and a charge transport agent having a molecular weight of 400 or more on a supporting substrate, and further comprises a charge generator or a charge transport agent in the binder resin. And a photosensitive layer having a single layer structure or a laminated structure including a layer in which is dispersed. The components of the electrophotographic photosensitive member of the present invention will be described below. << Intermediate Layer >><Charge Transport Agent> In the intermediate layer of the electrophotographic photoreceptor of the present invention, a charge transport agent having a molecular weight of 400 or more can be used. The charge transport agent includes an electron transport agent that transports electrons and a hole transport agent that transports holes. In the present invention, any of them can be used. When a charge transporting agent for transporting charges of the same polarity as that of the photoreceptor surface is contained, it acts to transport the charges transported from the photosensitive layer to the intermediate layer side to the support substrate side. On the other hand, when a charge transporting agent that transports charges of the opposite polarity to that of the photoreceptor surface is contained, the charges generated on the support substrate side are transported to the interface between the intermediate layer and the photosensitive layer, and are transported from the photosensitive layer side. It acts to neutralize the accumulated charge.

As the kind of the charge transporting agent, one having a good charge transporting ability and matching with the binder resin can be selected from conventionally known ones, and one kind or a mixture of two or more kinds can be used. (Electron transporting agent) As the electron transporting agent to be contained in the intermediate layer, among various conventionally known electron transporting compounds, those having a molecular weight of 40
Any one of 0 or more can be used.

In particular, benzoquinone compounds, diphenoquinone compounds, naphthoquinone compounds, dinaphthoquinone compounds, malononitrile compounds, thiopyran compounds, fluorenone compounds, dinitrobenzene compounds, dinitroanthracene compounds, dinitroacridine compounds, nitroanthraquinone Compound, succinic anhydride, maleic anhydride, dibromomaleic anhydride, nitrofluorenone imine compound, ethylated nitrofluorenone imine compound, trypto anthrin compound,
Tryptoantolinimine compounds, azafluorenone compounds, dinitropyridoquinazoline compounds, thioxanthene compounds, α-cyanostilbene compounds, nitrostilbene compounds, and salts of cations with anion radicals and cations of benzoquinone compounds An electron-withdrawing compound such as is preferred.

Specific examples of the electron transporting agent to be contained in the intermediate layer include the following general formulas (ET-1) to (ET-4) (hereinafter, charge generating agents (ET-1) to (ET-4)) The compound represented by the formula: In addition, the molecular weight (MW) is also described in the general formula.

[0023]

Embedded image

In the present invention, only one electron transport agent may be used, or two or more electron transport agents may be used in combination. (Hole transporting agent) As the hole transporting agent to be contained in the intermediate layer, among conventionally known various hole transporting compounds, those having a molecular weight of 40
Any one of 0 or more can be used.

In particular, benzidine compounds, phenylenediamine compounds, naphthylenediamine compounds, phenanthrylenediamine compounds, oxadiazole compounds, styryl compounds, carbazole compounds, pyrazoline compounds, hydrazone compounds, triphenyl Amine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds,
Thiadiazole compounds, imidazole compounds, pyrazole compounds, triazole compounds, butadiene compounds, pyrene-hydrazone compounds, acrolein compounds, carbazole-hydrazone compounds, quinoline-hydrazone compounds, stilbene compounds, stilbene-hydrazone compounds Compounds and diphenylenediamine compounds are preferably used.

Specific examples of the hole transporting agent to be contained in the intermediate layer include compounds represented by the following formulas (HT-1) to (HT-31) (hereinafter, charge generating agents (HT-1) to (HT-1)). HT-31)).

[0027]

Embedded image

[0028]

Embedded image

[0029]

Embedded image

[0030]

Embedded image

[0031]

Embedded image

[0032]

Embedded image

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

[0036]

Embedded image

[0037]

Embedded image

In the present invention, only one hole transport agent may be used, or two or more hole transport agents may be used in combination. The charge transport agent is 5 to 500 parts by weight based on 100 parts by weight of the binder resin,
Preferably, it may be blended at a ratio of 20 to 250 parts by weight. When the compounding ratio is within these ranges, the conductivity of the intermediate layer does not become too small or too large, and the ratio of the binder resin is sufficient to firmly bind the photosensitive layer.

When the molecular weight of the charge transporting agent contained in the intermediate layer is 1,000 or less, the compatibility with the binder resin is particularly good, and aggregation is less likely to occur in the coating solution.

Further, in order to adjust the charge transporting ability together with the above-mentioned charge transporting agent, the intermediate layer may contain a normal charge transporting agent having a molecular weight of less than 400 among the above-mentioned types of charge transporting agents. The content ratio of the ordinary charge transporting agent is preferably 2 to 50 parts by weight based on 100 parts by weight of the binder resin.
More preferably, it is 5 to 30 parts by weight. <Binder Resin> As the binder resin used for the intermediate layer of the electrophotographic photosensitive member of the present invention, various resins conventionally used for the photosensitive layer can be used. For example, styrene-butadiene copolymer, styrene-acrylonitrile nitrile copolymer,
Styrene-maleic acid copolymer, acrylic copolymer, styrene-acrylic copolymer, polyethylene, ethylene-
Vinyl acetate copolymer, chlorinated polyethylene, polyvinyl chloride, polypropylene, ionomer, vinyl chloride-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, polycarbonate, polyarylate, polysulfone, diallyl phthalate, ketone resin, polyvinyl Thermoplastic resins such as butyral resin, polyether resin and polyester resin; silicone resin,
Epoxy resins, phenol resins, urea resins, melamine resins, and other cross-linkable thermosetting resins; resins such as epoxy acrylates and urethane-acrylates and other photocurable resins can be used.

From these, it is necessary to select one which does not dissolve in the dispersion medium (such as an organic solvent) of the photosensitive layer coating solution applied on the intermediate layer. In this respect, acrylic resin, alkyd resin, polyurethane Resins that form a three-dimensional network structure such as melamine resin, epoxy resin, phenol resin, urea resin, polyamide, polyester, maleic acid resin, isocyanate resin, and silicone resin are preferably used. In particular, a phenol resin is optimal because it has excellent adhesion to a support substrate, solvent resistance, and compatibility with a charge transport agent.

In the laminated intermediate layer, a thin resin layer may be separately provided so as not to affect the conductivity. In this case, as the resin to be used, polyvinyl alcohol, polyvinyl pyridine, polyvinyl pyrrolidone,
Examples include water-soluble resins such as polyethylene oxide, polyacrylic acids, methylcellulose, ethylcellulose, polyglutamic acid, casein, gelatin, and starch, and resins such as polyamide resins, phenolic resins, polyvinylformal, and alkyd resins. <Pigment> The intermediate layer of the electrophotographic photoreceptor of the present invention may contain a pigment in order to adjust the conductivity of the intermediate layer and to prevent the occurrence of interference fringes. Known organic pigments and inorganic pigments can be used as the pigment used in the present invention. As organic pigments, for example, various phthalocyanine pigments, polycyclic quinone pigments, azo pigments, perylene pigments, indigo pigments, quinacridone pigments, azurenium salt pigments,
Squarylium pigment, cyanine pigment, pyrylium dye,
Thiopyrylium dyes, xanthene dyes, quinone immun dyes, triphenylmethane dyes, styryl dyes, anthanthrone-based pigments, pyrylium salts, triphenylmethane-based pigments, slen-based pigments, toluidine-based pigments, pyrazoline-based pigments, and the like. Examples of the inorganic pigment include titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), aluminum oxide (Al ₂ O ₃ ), zinc oxide (ZnO), indium-tin oxide, indium-titanium oxide, and the like. In addition to metal oxides, alkaline earth metal salt compounds such as calcium carbonate (CaCO ₃ ), barium carbonate (BaCO ₃ ), and barium sulfate (BaSO ₄ ) can be mentioned. Those obtained by doping these inorganic pigments with antimony oxide or the like, or those coated with tin oxide or indium oxide may be used. In addition, various treatments can be applied to the surface of the particles as long as the volume resistivity is not reduced. For example, aluminum, silicon, zinc, nickel, antimony, chromium, etc. are used as a treating agent, and Al ₂ O ₃ , S
An oxide film such as iO ₂ or ZnO can be coated. In addition, if necessary, dispersibility can be improved by a surface treating agent such as a coupling agent, stearic acid, or an organic siloxane, and water repellency can be imparted. These pigments can be used alone or in combination of two or more. Of these, metal oxides, particularly titanium oxide, tin oxide, and zinc oxide are preferably used. << 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, vanadium,
Molybdenum, chromium, cadmium, titanium, nickel,
Examples thereof include simple metals such as palladium, indium, stainless steel, and brass, plastic materials on which the metal is deposited or laminated, and glass coated with aluminum iodide, tin oxide, indium oxide, and the like.

The shape of the supporting substrate may be on a sheet, on a drum, or the like, depending on the structure of the image forming apparatus to be used, and the substrate itself has conductivity or the surface of the substrate has conductivity. It is sufficient if it has. Further, the support base preferably has sufficient mechanical strength when used.

The surface of the supporting substrate may be subjected to a surface treatment such as a surface roughening treatment, an oxidation treatment and an etching treatment, if necessary. << Formation of Intermediate Layer >> In the intermediate layer of the electrophotographic photoreceptor of the present invention, the charge transporting agent is 5 to 500 parts by weight based on 100 parts by weight of the binder resin.
It may be added in a ratio of 20 parts by weight, preferably 20 to 250 parts by weight. If the intermediate layer contains a pigment, the binder resin 100
The amount may be 5 to 500 parts by weight, preferably 20 to 250 parts by weight based on parts by weight.

The thickness of the intermediate layer is 0.1 to 50 μm, preferably 1 to 30 μm.

Between the intermediate layer and the photosensitive layer,
Resin layer within the range that does not hinder charge transport control to prevent penetration (of coating solution for charge generating agent), improve drying properties, and improve electrophotographic characteristics (image fog, image unevenness, repetition characteristics, etc.) May be provided.

When the intermediate layer is formed, first, the binder resin described above, the charge generating agent, and, if necessary, the pigment together with a suitable dispersion medium are used together with a known method such as a roll mill, a ball mill, an attritor, a paint shaker, and the like. The coating liquid is prepared by dispersing and mixing using an ultrasonic disperser or the like. Next, the coating liquid may be applied by a known method, for example, a blade method, a dipping method, or a spray method, and dried / cured. Among them, the immersion method is most effective according to the present invention because the difference in film thickness between the upper and lower ends of the coating region is likely to be large.

As a dispersion medium for preparing the coating liquid, a conventionally known organic solvent can be used. 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 and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethyl formaldehyde; Dimethylformamide, dimethylsulfoxide and the like.

Further, in order to improve the dispersibility of the charge transporting agent and the charge generating agent and the smoothness of the surface of the photosensitive layer, a surfactant is used.
A leveling agent or the like may be used. << Photosensitive layer >> The photosensitive layer in the electrophotographic photoreceptor of the present invention is
It is divided into a single-layer type and a laminated type according to its configuration. The single-layer type photoreceptor is provided with a single photosensitive layer containing at least a binder resin, a charge transport agent and a charge generation agent on a support base. The laminated photoreceptor includes a charge generating layer containing a binder resin and a charge generating agent, and a charge transport layer containing a binder resin and a charge transporting agent on a conductive substrate in this order, or vice versa. Are laminated.

As the binder resin and the charge transporting agent to be contained in the photosensitive layer, the same as those for the above-mentioned intermediate layer can be used alone or in combination of two or more.

Examples of the charge generating agent include various crystals of phthalocyanine compounds such as powders of inorganic photoconductive materials such as selenium, selenium-tellurium, selenium-arsenic, cadmium sulfide, α-silicon, and metal-free phthalocyanines and titanyl phthalocyanines. Phthalocyanine-based pigments, azo-based pigments, bisazo-based pigments, perylene-based pigments, anthanthrone-based pigments, indigo-based pigments, triphenylmethane-based pigments, slen-based pigments, toluidine-based pigments comprising crystals having a type,
Various conventionally known pigments such as pyrazoline pigments, quinacridone pigments, and dithioketopyrrolopyrrole pigments are exemplified.

The charge generators can be used alone or in combination of two or more so that the photosensitive layer has sensitivity in a desired wavelength range.

In particular, a digital optical image forming apparatus such as a laser beam printer or a plain paper facsimile apparatus utilizing infrared light such as a semiconductor laser requires a photosensitive member having a sensitivity in a wavelength region of 700 nm or more. Therefore, a phthalocyanine-based pigment among the above examples is preferably used as the charge generating agent.

In the single-layer type photosensitive layer, the charge generating agent is used in an amount of 0.1 to 50 parts by weight, especially 0.5 to 50 parts by weight, based on 100 parts by weight of the binder resin.
It is preferable to contain 30 parts by weight of a hole transporting agent as a charge transporting agent in an amount of 5 to 500 parts by weight, particularly 25 to 200 parts by weight. When the electron transporting agent is contained, it is preferably contained in an amount of 5 to 100 parts by weight, particularly 10 to 80 parts by weight based on 100 parts by weight of the binder resin.

At this time, the total amount of the hole transporting agent and the electron transporting agent is preferably 20 to 500 parts by weight, particularly preferably 30 to 200 parts by weight, based on 100 parts by weight of the binder resin.

The thickness of the single-layer type photosensitive layer is 5 to 100 μm, especially 1 to 100 μm.
About 0 to 50 μm is preferable.

In the laminated photosensitive layer, the charge generating agent is used in an amount of 5 to 1000 parts by weight, especially 30 to 100 parts by weight, based on 100 parts by weight of the binder resin.
It is preferable to contain it at a ratio of 500 parts by weight.

In the charge transport layer, the binder resin 100
Parts by weight, when the electron transporting agent is contained, the electron transporting agent is 0.1 to 250 parts by weight, particularly 0.5 to 150 parts by weight. It is preferable to add the agent in an amount of 10 to 500 parts by weight, particularly 25 to 200 parts by weight.

The thickness of the laminated photosensitive layer is 0.01
-5 μm, especially about 0.1-3 μm, and the charge transport layer is 2-100
μm, particularly preferably about 5 to 50 μm.

In addition to the above components, various additives such as a fluorene compound, an ultraviolet absorber, a plasticizer, a surfactant, and a leveling agent can be added to the photosensitive layer. In order to improve the sensitivity of the photoreceptor, a sensitizer such as terphenyl, halonaphthoquinones, and acenaphthylene may be added.

In the case of a single-layer type photoreceptor, between the support substrate and the photosensitive layer, and in the case of the laminated type photoreceptor, between the support substrate and the charge generation layer, between the support substrate and the charge transport layer, or between the support and the charge transport layer. A barrier layer may be formed between the generation layer and the charge transport layer as long as the characteristics of the photoreceptor are not impaired. Also,
A protective layer may be formed on the surface of the photoconductor.

[0062]

The present invention will be described below with reference to examples and comparative examples. << Formation of Intermediate Layer >> [Example 1] As a binder resin, 60 parts by weight of a phenol resin (TD447 manufactured by Dainippon Ink), 20 parts by weight of a charge transport agent (ET-1), and 100 parts by weight of methanol as a dispersion medium. The mixture was mixed and dispersed in a ball mill (φ1 zirconia beads) for 24 hours to prepare a coating solution for the intermediate layer. Next, one of the open ends of the φ30 aluminum base tube (support base) was set as an upper end, and the base tube was immersed in the coating solution while being kept sealed from the inside. At this time, the base tube was lowered at a speed of 5 mm / sec until the upper end of the tube was immersed in the coating solution, and was immersed for 3 seconds in a stationary state. Then, the base tube was pulled up at a speed of 5 mm / sec and applied. Thereafter, the film was dried at 150 ° C. for 30 minutes to form an intermediate layer having an average film thickness of 10 μm. Thus, an intermediate of the electrophotographic photoreceptor of Example 1 was produced. [Examples 2 to 8] Examples 2 to 8 were carried out in the same manner as in Example 1 except that the charge transporting agents shown in Table 1 were used instead of the charge transporting agents (ET-1). An intermediate of the electrophotographic photoreceptor was prepared. Comparative Example 1 An intermediate for the electrophotographic photoreceptor of Comparative Example 1 was prepared in the same manner as in Example 1 except that the charge transporting agent (ET-1) was not used. [Comparative Examples 2 to 13] Instead of the charge transport agent (ET-1), the following general formulas (CT-1) to (CT-12):

[0063]

Embedded image

[0064]

Embedded image

Example 1 except that the charge transporting agents represented by the following formulas (hereinafter referred to as charge transporting agents (CT-1) to (CT-10)) were used as shown in Table 1. In the same manner as in the above, intermediates of the electrophotographic photosensitive members of Comparative Examples 2 to 13 were produced. Example 9 A ball mill (φ1 zirconia) was prepared by using 60 parts by weight of a phenol resin (J325 manufactured by Dainippon Ink and Chemicals) as a binder resin, 20 parts by weight of a charge transport agent (HT-7), and 100 parts by weight of methanol as a dispersion medium. (Beads) for 24 hours to prepare a coating solution for the intermediate layer. Next, one of the open ends of the φ30 aluminum base tube (support base) was set as an upper end, and the base tube was immersed in the coating solution while being kept sealed from the inside. At that time, the base tube was lowered at a speed of 5 mm / sec until the upper end of the tube was immersed in the coating solution, and was immersed for 3 seconds at rest, and then the base tube was pulled up at a speed of 4 mm / sec and applied. Then 150 ℃
For 30 minutes to form an intermediate layer having an average film thickness of 10 μm. Thus, an intermediate of the electrophotographic photoreceptor of Example 9 was produced. [Example 10] Example 9 except that the charge transport agents shown in Table 2 were used instead of the charge transport agents (HT-7).
In the same manner as in the above, intermediates of the electrophotographic photosensitive members of Examples 10 to 11 were produced. [Comparative Example 14] Except not using the charge transport agent (HT-7),
In the same manner as in Example 9, an intermediate of the electrophotographic photosensitive member of Comparative Example 14 was produced. [Comparative Examples 15 to 17] Comparative Examples 15 to 17 were performed in the same manner as in Example 9 except that the charge transport agents shown in Table 2 were used instead of the charge transport agents (HT-7). An intermediate of the electrophotographic photoreceptor was prepared. << Measurement of Interlayer Thickness Difference >> The thickness difference of the intermediate layers of the intermediates of the electrophotographic photosensitive members produced in the above Examples and Comparative Examples was measured by the following method.

At the time of the above coating, a film thickness difference of 20 mm from the upper end of the aluminum tube and 20 mm from the lower end was measured. Measurement of the film thickness is performed using a contact type eddy current film thickness meter to measure the outer diameter at the above-mentioned position of the intermediate having the intermediate layer at 36 points in the circumferential direction (30 rad interval, 3 times each point measurement × 12 points) ) And the average was determined. Next, the difference between the average values of the outer diameters at respective positions of 20 mm from the upper and lower ends was determined, and the difference was defined as the film thickness difference.

Table 1 shows the measurement results of the difference in the thickness of the intermediate layer and the molecular weight of the charge transporting agent.
Shown in

[0068]

[Table 1]

As shown in Table 1, Example 1 having a molecular weight of 400 or more was obtained.
The charge transporting agent used in ~ 8 has a thickness difference of 0.59 ~ 0.65μm
It was found that the value was almost constant. Also, from FIG. 1, the difference in film thickness decreases with increasing molecular weight up to a molecular weight of 400.
It turned out that it changes almost stably at 0.6 μm.

For the intermediates produced in Examples 9 to 11 and Comparative Examples 14 to 17, the difference in the thickness of the intermediate layer was measured in the same manner as described above. The results are shown in Table 2 and FIG.

[0071]

[Table 2]

As shown in Table 2 and FIG. 2, for the intermediate containing a charge transporting agent having a molecular weight of less than 400, the difference in film thickness decreases as the molecular weight increases.
It was found that there was almost no change in the film thickness difference, and the same tendency as in Table 1 was exhibited.

As described above, the molecular weight of the charge transporting agent contained in the intermediate layer can be reduced by 40% even if the conditions for forming the intermediate layer such as the application conditions of the coating solution and the heat treatment conditions and the type of the binder resin are changed.
By setting it to 0 or more, it is possible to minimize the difference in thickness of the intermediate layer. (Formation of Laminated Photosensitive Layer) First, 1 part by weight of Y-type titanyl phthalocyanine as a pigment was added to 39 parts by weight of ethyl cellosolve as a dispersion medium, and subjected to primary dispersion using an ultrasonic disperser. To this dispersion, a solution prepared by dissolving 1 part by weight of polyvinyl butyral (BM-1 manufactured by Sekisui Chemical Co., Ltd.) as a binder resin in 9 parts by weight of ethyl cellosolve was added. And secondary dispersion to prepare a coating solution for the charge generation layer of the laminated photosensitive layer. Next, this coating solution was dip-coated on the intermediates prepared in Examples 1 to 8 and Comparative Examples 1 to 13, respectively, and dried at 110 ° C. for 5 minutes to form a 0.5 μm-thick charge generation layer. .

Next, the electron transporting agent 3,3 ′, 5,5′-
0.05 parts by weight of tetra-tert-4,4′-difequinone and 0.8 parts by weight of a hole transporting agent N, N, N ′, N′-tetrakis (3-methylphenyl) -1,3-diaminobenzene Z-type polycarbonate as binder resin (Taijin Kasei's Panrai
0.95 parts by weight of TS2050) and 0.05 parts by weight of a polyester resin (RV200 manufactured by Toyobo) were mixed and dispersed together with 8 parts by weight of tetrahydrofuran to obtain a coating liquid for a 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 thickness of 30 μm, thereby producing respective layered electrophotographic photosensitive members. << Evaluation of Images >> Each of the photoconductors obtained in Examples and Comparative Examples was set in an internal unit of a laser printer (LBP-450 manufactured by Canon Inc.), and 10 black-and-white belt-shaped images were continuously printed. The tenth (initial) image fog was visually checked. The criteria for the judgment were as follows.

：: Image fog cannot be visually confirmed.

Δ: Image fog is confirmed.

×: The occurrence of image fogging can be recognized at a glance, and the degree is severe.

Table 1 shows the image evaluation results of the photosensitive members produced in the above Examples and Comparative Examples.

Table 1 shows that no image fogging was observed for the photoreceptors of Examples 1 to 8. On the other hand, with respect to the photoreceptors of Comparative Examples 1 to 13, generation of image fog was observed. Particularly, when the intermediate layer contained a charge transporting agent having a molecular weight of 100 or less, generation of image fog was remarkable.

[0080]

As described above, the electrophotographic photoreceptor of the present invention has a small difference in the thickness of the intermediate layer and can provide a good image without image fog.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the difference in the thickness of an intermediate layer and the molecular weight of a charge transport agent in Examples 1 to 8 and Comparative Examples 1 to 13.

FIG. 2 is a diagram showing the relationship between the difference in the thickness of the intermediate layer and the molecular weight of the charge transport agent in Examples 9 to 11 and Comparative Examples 14 to 17.

Claims (7)

[Claims] An electrophotograph comprising a support substrate, an intermediate layer and a photosensitive layer provided on the support substrate, wherein the intermediate layer contains a binder resin and a charge transport agent having a molecular weight of 400 or more. Photoconductor. 2. The electrophotographic photoreceptor according to claim 1, wherein the charge transporting agent has a molecular weight of 1,000 or less. 3. The electrophotographic photosensitive member according to claim 1, wherein said binder resin is a phenol resin. 4. The electrophotographic photoreceptor according to claim 1, wherein said intermediate layer contains a pigment. 5. The electrophotographic photosensitive member according to claim 4, wherein said intermediate layer contains a metal oxide. 6. The electrophotographic photosensitive member according to claim 1, wherein said photosensitive layer has a single layer structure containing a binder resin, a charge generating agent and a charge transporting agent. 7. The photosensitive layer has a laminated structure having a charge generation layer containing a binder resin and a charge generator, and a charge transport layer containing a binder resin and a charge transport agent. The electrophotographic photosensitive member according to claim 1.