JPH09190001A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent productivity and obtain performance preferable in electrical and image characteristics by laminating a electron transfer layer which is formed by dispersing (n) type semiconductor pigments into a resin and has a specific film thickness and a charge generating layer which is formed by dispersing hole transfer material and charge generating materials into a resin and has a specific film thickness, thereby constituting a photosensitive layer. SOLUTION: The photosensitive layer 2 formed on a conductive substrate 1 is formed of the structure obtd. by laminating the electron transfer layer 7 which is formed by dispersing the (n) type semiconductor pigments 4 into the resin 4 and has 1 to 20μm film thickness and the charge generating layer 8 which is formed by dispersing the hole transfer material and charge generating materials 5 into the resin 6 and has 5 to 50μm film thickness. In such a case, disazo pigments, perylene pigments, anzanthrone pigments and perynone pigments are used preferably in terms of dispersibility and electrical characteristics as the (n) type semiconductor pigments 3 used for the charge transfer layer 7. Further, desired film thicknesses are easily obtd. as the film thicknesses of the electron transfer layer 7 and the charge generating layer 8 by adjusting a coating speed and various properties, such as viscosity and shearing force, of coating materials in the case of formation of these layers by dip coating.

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 an electrophotographic photoreceptor having excellent productivity, high sensitivity, and excellent image quality.

[0002]

2. Description of the Related Art Generally, an electrophotographic photosensitive member is formed by forming a photosensitive layer made of a photoconductive material on a conductive substrate. The photosensitive layer is a charge generating layer. A function-separated laminated type electrophotographic photoreceptor comprising a charge transport layer is often used.

The history of the development of organic photoreceptors for electrophotography shows that poly-
Single-layer type electrophotographic photoconductor using N-vinylcarbazole / trinitrofluorenone complex (US Pat. No. 34842)
37), U.S. Pat. No. 3,397,086, and a phthalocyanine resin-dispersed electrophotographic photoconductor, "Journal of Applied Physics".
(Journal of Applied Physics) Vol. 49, No. 11, No. 5
As can be seen in electrophotographic photoreceptors and the like in which a eutectic of a thiapyrylium salt and a polycarbonate resin is used in combination with a triphenylmethane-based charge-transporting material as disclosed in pp. 543-5564 (1978) and the like, various types of electrophotographic photoreceptors are initially used. Although development has been carried out exclusively for single-layer electrophotographic photoreceptors, these single-layer type electrophotographic photoreceptors have problems such as many material restrictions, insufficient sensitivity, and insufficient durability. However, since then, a laminated electrophotographic photoreceptor comprising a charge generation layer and a charge transport layer, which can solve these problems, has become widespread due to its advantages, and thus it is hardly used at present.

In the case of a general laminated type electrophotographic photosensitive member, the most problematic point in production is to form a thin layer of usually 1 μm or less in order to satisfy the electric characteristics of the charge generation layer. In point. However, it is difficult to form a stable coating film without defects, and the productivity is lowered at present. Further, in the case of the electrophotographic photoreceptor having such a layer structure, it is known that the characteristics of the electrophotographic photoreceptor significantly change depending on the electrical bonding state between the conductive substrate and the charge generation layer. Problems with characteristics tend to occur.

For example, it is known that if there is no good electrical barrier between the photosensitive layer and the substrate, charges will be injected from the substrate and the charging ability will be poor. In addition, defects caused by scattering on the tube, crystallization of impurities, impurities in the coating film, etc.
It is also known that a local potential drop occurs, and it tends to appear as a defect on an image particularly in the reversal development method.

The problems of such a conventional electrophotographic photoreceptor are improvement from the material side, development of functional layers such as a barrier layer, an intermediate layer and a surface protective layer, and further an effort to reexamine the layer structure itself. Although improvements have been investigated by the above, they have not been able to sufficiently meet the demand.

For example, Japanese Patent Laid-Open No. 59-49545 discloses a technique of providing a charge transport layer in which a hole transport substance is resin-dispersed between a layer containing a charge generating substance and a charge transport substance and a conductive substrate. Is disclosed. This is basically an attempt to achieve positive charging by reversing the stacking order of the conventional stacking type electrophotographic photoreceptor. Therefore, the charge transport layer used in the electrophotographic photoreceptor proposed in this publication is a resin containing a hole transport substance such as a hydrazone compound in a solid solution state, and has a hole transport ability. However, it does not show any electron transporting ability, and the electrophotographic photosensitive member proposed in this publication can be used only by positive charging. Further, in principle, this type of electrophotographic photoreceptor has a hole transport layer provided under a single-layer type electrophotographic photoreceptor of charge generating substance / charge transporting substance / resin dispersion system. Therefore, the basic characteristics of the positively charged electrophotographic photosensitive member are very close to those of the single-layer type electrophotographic photosensitive member having only the upper layer.

In recent years, electrophotographic photoconductors have been required to have low cost in accordance with the competition of low price, high image quality and long life of electrophotographic devices such as copying machines and printers. However, in order to respond to these two contradictory points, that is, high functionality, the conventional obsolete layered structure cannot sufficiently cope with the above, and a new concept of electrophotographic photoreceptor design is required.

[0009]

SUMMARY OF THE INVENTION The problem to be solved by the present invention is to provide a novel photosensitive layer structure which is different from the conventionally proposed electrophotographic photosensitive member, and thereby has excellent productivity and electrical properties. To provide a photoconductor for electrophotography, which has preferable performance in terms of physical and image characteristics.

[0010]

In order to solve the above-mentioned problems, the present invention provides an electrophotographic photosensitive member comprising a conductive substrate and a photosensitive layer formed on the conductive substrate. An electron transport layer having a film thickness of 1 to 20 μm dispersed, and a film thickness 5 having a hole transport material and a charge generating material dispersed in a resin.
Provided is an electrophotographic photoreceptor, which has a structure in which a charge generation layer having a thickness of ˜50 μm is laminated.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the structure of a photosensitive layer of an electrophotographic photosensitive member according to the present invention. The exemplified electrophotographic photoreceptor is one in which an electron transport layer in which an n-type semiconductor pigment is dispersed in a resin and a charge generation layer in which a charge generating substance and a hole transporting substance are dispersed in a resin are laminated in this order on a conductive substrate. . The thickness of the electron transport layer is preferably in the range of 1 to 20 μm, and the thickness of the charge generation layer is preferably in the range of 5 to 50 μm. If the thickness of the electron transport layer is smaller than 1 μm, not only the effect of concealing defects of the substrate is significantly deteriorated but also coating unevenness is likely to occur in production. Since it becomes too long, transportability is lowered and environmental characteristics are deteriorated, which is not preferable. If the thickness of the charge generation layer is smaller than 5 μm, the characteristics change due to abrasion of the film becomes large during repeated use, which is not preferable, and if it is larger than 50 μm, not only the productivity is deteriorated but also the migration distance of holes is long. Since it becomes too much, the environmental characteristics are deteriorated and become unpractical, which is not preferable. The thicknesses of the electron transport layer and the charge generation layer can be easily adjusted to desired thicknesses by adjusting various properties such as coating speed, coating viscosity, shearing force and the like when formed by dip coating. .

Examples of the conductive support used in the electrophotographic photoreceptor of the present invention include metals or alloys such as aluminum, copper, zinc, stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold and platinum. The used metal plate, metal drum, metal belt, or conductive polymer, conductive compound such as indium oxide, aluminum, palladium, gold or other metal or alloy coated, vapor deposited or laminated paper, plastic film, belt, etc. Can be mentioned.

Examples of the n-type semiconductor pigment used in the electron transport layer include azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, bisbenzimidazole pigments, quinacridone pigments, and quinoline pigments. Various organic pigments such as pigments, lake pigments, azo lake pigments, anthraquinone pigments, oxazine pigments, dioxazine pigments and triphenylmethane pigments, or inorganic materials such as titanium oxide, zinc oxide, cadmium sulfide, zinc sulfide and silicon carbide. Among the pigments, those capable of confirming the n-type semiconductor characteristics can be used, and in particular, disazo pigments,
The use of perylene pigments, anzanthuron pigments, and perinone pigments is preferable from the viewpoint of dispersibility and electric characteristics.

The ratio of the n-type semiconductor pigment in the electron transport layer is
Within the range where the electron transport in the electron transport layer is sufficient, the range where the film strength is obtained is preferable. Usually, the ratio of the pigment to the total weight of the electron transport layer is preferably 10 to 90% by weight. If it is less than 10% by weight, the electrons generated in the photosensitive layer are not sufficiently transported to the conductive substrate side, and the residual potential tends to increase, which is not preferable.
When the content is more than 0% by weight, the proportion of the binder in the electron transport layer becomes small, and mechanical properties such as adhesiveness tend to be insufficient, which is not preferable.

As the binder used in the electron transport layer, a high molecular polymer capable of forming an electrically insulating film is preferable.
Examples of such high molecular weight polymers include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile polymer, and chloride. Vinyl-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-
Alkyd resin, phenol-formaldehyde resin,
Styrene-alkyd resin, poly-N-vinylcarbazole, polyvinyl butyral, polyvinyl formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenol resin, polyamide, carboxy-methyl cellulose, vinylidene chloride polymer latex, polyurethane and the like. However, it is not limited thereto. These binders may be used alone or in combination of two or more.

Examples of the charge generating substance used in the charge generating layer include azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, bisbenzimidazole pigments, phthalocyanine pigments, quinacridone pigments, Quinoline pigments, lake pigments, azo lake pigments, anthraquinone pigments, oxazine pigments,
Dioxazine pigments, triphenylmethane pigments, azurenium dyes, squarium dyes, pyrylium dyes, triallylmethane dyes, xanthene dyes,
Various organic pigments such as thiazine dyes and cyanine dyes,
Dyes, and further amorphous silicon, amorphous selenium, tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide, can be listed as inorganic materials such as zinc sulfide, among these, titanyl phthalocyanine, or titanyl phthalocyanine and The reaction product with 2,3-butanediol is particularly preferred.

The charge-generating substance used in the charge-generating layer is not limited to those listed here, and when used, it may be used alone, but a mixture of two or more types of charge-generating substances may be used. It can also be used.

The proportion of the charge generating material in the charge generating layer is preferably in the range of 0.2 to 5% by weight based on the total weight of the charge generating layer. The reason will be described in detail in the section of action.

As the hole transporting substance which can be used in the charge generating layer, examples of low molecular weight compounds include pyrene type, carbazole type, hydrazone type, oxazole type, oxadiazole type, pyrazoline type, arylamine type, Examples thereof include aryl methane-based, benzidine-based, thiazole-based, stilbene-based and butadiene-based compounds. Examples of the polymer compound include poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, ethylcarbazole- Formaldehyde resin, triphenylmethane polymer, polysilane, etc. may be mentioned.

The ratio of the hole transporting material in the charge generating layer depends on the hole transporting ability of the hole transporting material to be used.
The range of ˜60% by weight is preferred. When the amount is less than 10% by weight, the charge transport is not sufficiently performed, resulting in insufficient sensitivity and the residual potential tends to increase. Since the content of the resin becomes small, the mechanical strength of the charge generation layer tends to decrease, which is not preferable. However,
When a polymer compound such as poly-N-vinylcarbazole is used as the hole transporting substance, the hole transporting substance itself has a function as a binder. You can also

These materials are usually dispersed or dissolved in a solvent together with a binder and then applied by a dip coating method or the like to be used for the charge generation layer. The charge generating substance and the charge transporting substance used in the electrophotographic photoreceptor of the present invention are not limited to those listed here, and may be used alone or in combination of two or more kinds. it can.

In addition to these materials, it is desirable to add an electron accepting substance to the charge generation layer in order to effectively prevent trapping of electrons in the charge generation layer. As the electron accepting substance, for example, an organic compound such as benzoquinone-based, tetracyanoethylene-based, tetracyanoquinodimethane-based, fluorenone-based, xanthone-based, phenanthraquinone-based, phthalic anhydride-based, diphenoquinone-based You can

As the material used for the binder of the charge generation layer, the materials mentioned as the binder of the electron transport layer may be used alone or in combination of two or more kinds.

In addition to these binders, additives such as dispersion stabilizers, plasticizers, surface modifiers, antioxidants and photodegradation inhibitors can also be used.

Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons. Can be mentioned.

Examples of the surface modifier include silicone oil and fluororesin.

Examples of the antioxidant include phenol-based, sulfur-based, phosphorus-based and amine-based compounds.

Examples of the photodeterioration preventing agent include benzotriazole compounds, benzophenone compounds, hindered amine compounds and the like.

When the electron transport layer or the charge generating layer is formed by dip coating, a mixture of the above n-type semiconductor pigment, charge generating substance, charge transporting substance and the like with a binder or the like is dissolved or dissolved in a solvent. Use dispersed paint. The solvent that dissolves the binder varies depending on the type of the binder, but is preferably selected from those that do not dissolve the lower layer.
Examples of such organic solvents include alcohols such as methanol, ethanol and n-propanol;
Ketones such as acetone, methyl ethyl ketone and cyclohexanone; amides such as N, N-dimethylformamide and N, N-dimethylacetamide; ethers such as tetrahydrofuran, dioxane and methyl cellosolve; esters such as methyl acetate and ethyl acetate; dimethyl Sulfoxides and sulfones such as sulfoxide and sulfolane;
Aliphatic halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride and trichloroethane; aromatics such as benzene, toluene, xylene, monochlorobenzene and dichlorobenzene.

[0030]

The electrophotographic photoreceptor of the present invention has a very unique layer structure, but the electrostatic operation principle is also characteristic. The operation will be described in detail below, and the reason why the electrophotographic photoreceptor of the present invention can exhibit excellent electrical and image quality will be clarified.

First, the charge generation mechanism of the electrophotographic photoreceptor of the present invention will be described. Needless to say, the charge generation in the electrophotographic photoreceptor of the present invention is due to the charge generating substance contained in the upper charge generating layer. However, the generation mechanism thereof is significantly different from the charge generation of a normal laminated type or single layer type electrophotographic photoreceptor. That is, in the conventional electrophotographic photoreceptor, the charge generation is the surface of the functional layer that absorbs light, for example, in the laminated electrophotographic photoreceptor, the charge generation layer surface, and in the single-layer electrophotographic photoreceptor. Electric charges are generated on the surface of the photosensitive layer. On the other hand, in the electrophotographic photoreceptor of the present invention, when negatively charged, the charges generated near the interface with the electron transport layer under the charge generation layer contribute to the sensitivity. The mechanism of this charge generation is rather similar to the charge generation at the time of negative charging in the above-mentioned thiapyrylium salt / polycarbonate eutectic / triphenylmethane type single-layer type electrophotographic photoreceptor. The reason for the mechanism of such charge generation is that the charge transport in the charge generation layer is mainly due to the hole transport substance contained in the resin in a solid solution state, and the electron transport ability is changed to the hole transport ability. Since it is extremely small, the generated charge is deactivated by recombination and the like even if light absorption occurs in the middle part of the layer, and electrons are injected and transported to the lower electron transport layer only near the interface with the lower layer. Therefore, effective charge generation can be achieved.

Therefore, in the electrophotographic photoreceptor of the present invention, the concentration of the charge generating substance in the charge generating layer needs to be sufficiently low so that effective light can reach the vicinity of the interface, but it is too low. Then, the absolute amount of the charge generating substance that contributes to the charge generation becomes insufficient, so it is necessary to control to an appropriate value in consideration of these. This appropriate value varies somewhat depending on the type and dispersion state of the charge generating substance used, but it is appropriate that the ratio of the charge generating substance is within the range of 0.2 to 5% by weight based on the total weight of the charge generating layer. is there.

In the electrophotographic photoreceptor of the present invention, the light energy absorbed in the intermediate portion of the charge generation layer is not always lost by radiation deactivation, and the excitation energy is at the phonon level. Unless it is considered that they are transmitted to the vicinity of the interface with the lower layer and contribute to the generation of electric charges, the reason why the electrophotographic photoreceptor of the present invention has high sensitivity cannot be explained, as shown in the examples.

Further, needless to say, the electron transport in the lower layer of the electrophotographic photoreceptor of the present invention depends on the electron transport characteristics of the n-type semiconductor pigment itself dispersed in the layer.
That is, the electron transport layer itself has the characteristics of an n-type semiconductor.

The charge generating layer laminated on the electron transporting layer having the characteristics of an n-type semiconductor is a layer containing both a hole transporting substance and a charge generating substance. The charge transporting in this charge generating layer is as follows. Mainly due to the hole transport material,
This charge generation layer has the characteristics of a p-type semiconductor in terms of charge transport characteristics.

By the way, a structure in which an n-type semiconductor and a p-type semiconductor are in contact with each other is called a so-called pn junction diode.
Shows excellent rectification characteristics. It is explained that this is because an insulating layer called a depletion layer, which is filled with space charges, is formed at the junction interface, and charge transfer cannot be performed in the opposite polarity. In addition, it is generally considered that a much larger local electric field is generated inside the depletion layer than an externally applied electric field, which further improves the efficiency of charge generation. As a result, the electrophotographic photoreceptor of the present invention can simultaneously realize excellent barrier properties and high sensitivity.

In the laminated electrophotographic photoreceptor of the present invention, since the n-type semiconductor layer is laminated on the lower layer and the p-type semiconductor layer is laminated on the upper layer, the above-mentioned pn junction prevents the charge injection. It works when the photoreceptor is negatively charged.
Further, since the electron transporting layer containing the n-type semiconductor pigment on the substrate side has an electron transporting property, it is electrons, that is, negative charges, injected into the substrate from the electrophotographic photosensitive member. The photoreceptor is essentially expected to be used with a negative charge. However, in practice, the electrophotographic photoreceptor of the present invention can exhibit good sensitivity even in positive charging. Because, when positively charged, the pn
The electric field to the junction is in the forward direction, the interface barrier is lowered, and electrons are easily injected from the substrate into the electron transport layer, so that the electron transport layer is filled with negative charges, and the charge generation layer is exposed by light irradiation. This is because the positive charge generated in 1 is easily neutralized. Therefore, the electrophotographic photoreceptor of the present invention can be put to practical use as a positive and negative bipolar electrophotographic photoreceptor.

In the conventional laminated type electrophotographic photoreceptor, charge injection is blocked by a rectifying junction represented by a Schottky junction between the substrate and the charge generating layer or by an electric resistance of an independent barrier layer. Therefore, a large change in characteristics may occur due to a delicate contact state between the substrate and the photosensitive layer. For example, if there are stains or defects on the substrate, effective barrier formation is impeded, and the probability of appearance as defects on the image becomes very large. However, in the electrophotographic photoreceptor of the present invention, it is not necessary to set delicate conditions for forming a barrier, and the charge injection is separated from the substrate surface which is the interface between the electron transport layer and the charge generation layer. Since it is blocked in the part, it is less affected by the substrate, and high quality image characteristics can be obtained. Therefore,
The electrophotographic photoreceptor of the present invention basically has an advantage that an independent barrier layer is unnecessary.

Further, in the electrophotographic photoreceptor of the present invention, unlike the case where the defect is concealed by providing the conventional laminated type electrophotographic photoreceptor with a thick barrier layer, the charge from the electron transport layer to the substrate is changed. Since there is no barrier to injection, deterioration of electrical characteristics such as increase in residual potential is not observed, and excellent performance can be obtained.

Further, since the electrophotographic photoreceptor of the present invention has an excellent barrier property against the injection of electric charges from the substrate as described above, the contact charging method using a roller, a brush or the like which has started to spread in recent years. Even if it is used in the electrophotographic device, there is an advantage that an image defect due to a charge leak hardly occurs.

Furthermore, since the electrophotographic photoreceptor of the present invention is composed of the resin dispersion film of the lower and upper co-pigments, an electrophotographic apparatus for forming a latent image by exposure with coherent light such as a laser printer. In the above, there is also an effect that it is possible to prevent the occurrence of interference fringes on the image due to the mutual interference of the reflected light on the surface of the base and the reflected light on the surface of the photosensitive layer, because the irradiation light is almost diffused and absorbed inside the photosensitive layer.

[0042]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. In addition, "part" in the following synthetic examples, examples and comparative examples means "part by weight".

(Synthesis Example 1) 20 parts of β-type titanyl phthalocyanine and (2R, 3R) -2,3-butanediol 2.
Two parts were reacted in 240 parts of α-chloronaphthalene with stirring at 200 ° C. for 1.5 hours. After cooling this to room temperature, the reaction product was filtered off, washed with benzene, methanol, dimethylformamide (hereinafter abbreviated as DMF) and water in this order, and then dried under reduced pressure to obtain a phthalocyanine compound.

The phthalocyanine compound thus obtained had a mass spectrum of m / Z = 648 and m / Z = 648.
Since a peak was shown at Z = 576, the formula (1)

[0045]

Embedded image

It was a mixed composition of the compound represented by and unreacted titanyl phthalocyanine. The X-ray diffraction spectrum of this mixed composition is shown in FIG.

As can be seen in FIG. 2, the present mixed composition comprises
At Bragg angle 2θ, 8.3 °, 24.7 ° and 2
It had a characteristic strong peak at 5.1 °.

Example 1 5 parts of a phenol resin (“Priophene 5010” manufactured by Dainippon Ink and Chemicals, Inc.) and methyl ethyl ketone (hereinafter abbreviated as MEK).
In a resin solution consisting of 40 parts, the formula (2)

[0049]

Embedded image

After mixing 10 parts of the disazo pigment represented by the formula (1), the mixture was dispersed for 6 hours using a ball mill to obtain a coating material A for an electron transport layer.

This coating material A was applied by dip coating to the outer peripheral surface of an aluminum drum having a diameter of 30 mm so that the film thickness after drying would be 5 μm, and then heat-dried at 150 ° C. for 30 minutes for electron transport. Layers were formed.

Next, 0.3 part of the mixed composition of the phthalocyanine obtained in Synthesis Example 1 and the formula (3)

[0053]

Embedded image

10 parts of the arylamine compound represented by and 14 parts of a polycarbonate resin ("Upilon Z-200" manufactured by Mitsubishi Gas Chemical Co., Inc.) were dissolved in 76 parts of chloroform and dispersed using a vibration mill to form a charge generation layer. A coating material B was prepared.

This coating material B was applied onto the above electron transport layer by dip coating so that the film thickness after drying was 15 μm, and then dried to form a charge generation layer, and a drum-shaped electron was formed. A photographic photoreceptor was obtained.

(Example 2) N, N'-di (3,5-dimethylphenyl) perylene-3,4,9,10-tetracarboxydiimide ("Novoperm Red BL" manufactured by Hoechst) ) 1 part and a polyamide resin ("CM-8000" manufactured by Toray Industries, Inc.) 1 part in a mixed solvent consisting of 7 parts of methanol and 7 parts of n-butanol, and dispersed for 1 hour using a sand mill to form an electron transport layer. A coating material C was obtained.

In Example 1, coating material A for electron transport layer
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the coating material C for the electron transport layer was used instead of the above, and the electron transport layer was formed so that the film thickness after drying was 3 μm.

Example 3 Dibromoanzanthuron (I
CI's "Monolite Red" 2
Y ") and 1 part of a phenoxy resin (" PKHH "manufactured by Union Carbide Co.) are mixed with a mixed solvent consisting of 7 parts of 1-acetoxy-2-methoxyethane and 7 parts of MEK and dispersed for 1 hour using a sand mill. Then, the coating material D for the electron transport layer was prepared.

In Example 1, coating material A for electron transport layer
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the coating material D for the electron transport layer was used instead of the above, and the electron transport layer was formed so that the film thickness after drying was 5 μm.

(Example 4) In Example 3, instead of dibromoanthanthrone, trans-bis (benzimidazole) perinone ("Hostapalm.
A coating material E for an electron transport layer was obtained in the same manner as in Example 3 except that 1 part of orange (Hostaperm Orange GR) was used.

In Example 1, coating material A for electron transport layer
An electrophotographic photoreceptor was obtained in the same manner as in Example 1 except that the coating material E for electron transport layer was used instead of the above, and the electron transport layer was formed so that the film thickness after drying was 5 μm.

(Comparative Example 1) 1 part of α-type titanyl phthalocyanine was mixed with a resin solution consisting of 1 part of polyvinyl butyral resin and 48 parts of methylene chloride and dispersed for 2 hours using a paint shaker to prepare a charge generation layer. A paint F was obtained.

This coating material F was applied by dip coating to the outer peripheral surface of the same aluminum drum as that used in Example 1 so that the film thickness after drying would be 0.4 μm, followed by heating and drying to obtain a charge. A generator layer was formed.

Then, 10 parts of the arylamine compound represented by the formula (3) used in Example 1 and 14 parts of the polycarbonate resin used in Example 1 were mixed with chloroform 76.
A coating material G for the charge transport layer was obtained which was dissolved in the area.

This coating material G is applied onto the above-mentioned charge generation layer by dip coating so that the film thickness after drying is 15 μm, and then dried to form a charge transport layer, which is of a negative charging type. To prepare a laminated type electrophotographic photoconductor.

(Comparative Example 2) The procedure of Example 1 was repeated except that the electron transport layer was not provided and the charge generation layer was provided directly on the outer peripheral surface of the aluminum drum. A layered electrophotographic photoreceptor was obtained.

(Comparative Example 3) 1 part of a polyamide resin ("CM-8000" manufactured by Toray Industries, Inc.), 7 parts of methanol and n-
A coating material H was obtained which was composed of a resin solution dissolved in a mixed solvent containing 7 parts of butanol.

In Example 1, instead of the electron transport layer,
An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that a barrier layer having a film thickness of 1 μm made of the coating material H was provided and a charge generation layer was provided on the barrier layer.

(Comparative Example 4) The aluminum drum used in Example 1 was anodized to form a porous oxide film having a thickness of 6 µm on the surface, and then the aluminum drum was sealed with nickel acetate.

In Example 1, an aluminum drum that had been subjected to anodizing treatment and sealing treatment was used, and the electron transport layer was not provided on the outer peripheral surface of this aluminum drum.
A single-layer type electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the charge generating layer made of the coating material B for the charge generating layer was directly provided.

Comparative Example 5 An electrophotographic photosensitive member was obtained in the same manner as in Example 1, except that the thickness of the electron transport layer was 0.8 μm.

(Electrical Properties) In order to evaluate the electrical properties of the electrophotographic photoconductors obtained in each of the examples and the comparative examples, each electrophotographic photoconductor was tested with an electrophotographic photoconductor testing device (manufactured by Gentec). "Cynthia-30") was used to measure the electrophotographic characteristics. The measuring method was as follows. First, the electrophotographic photosensitive member was charged at a voltage of +6 kV by corona discharge while rotating at 60 rpm in the dark, and the surface potential immediately after this was used as the initial potential V ₀ for evaluation of the charging ability. Then 10 in the dark
The potential after standing for 2 seconds was measured and defined as V ₁₀ . here,
The potential holding ability was evaluated by V ₁₀ / V ₀ . Then 7
The exposure intensity on the surface is 1μ with monochromatic light of 80 nm.
Set to be W / cm ^2, for 15 seconds with light irradiation in the photosensitive layer, was recorded decay curve of the surface potential. Here by measuring the surface potential after 15 seconds, was it a residual potential V _R. The surface potential by light irradiation determined amount of exposure until reduced to 1/2 of V _10, were evaluated sensitivity as half decay exposure E _1/2. Furthermore, the same measurement was performed under the condition of negative charging by corona discharge with an applied voltage of -6 kV. The results are summarized in Tables 1 and 2.

[0073]

[Table 1]

[0074]

[Table 2]

As is clear from the results shown in Tables 1 and 2, the electrophotographic photoconductors obtained in Examples 1 to 4 of the present invention show excellent charging ability and sensitivity at any charging polarity. It was On the other hand, the negative charging type electrophotographic photoconductor having the conventional structure in which the charge generation layer and the charge transport layer obtained in Comparative Example 1 were laminated in this order was compared with the electrophotographic photoconductors obtained in each Example.
The sensitivity was inferior even when negatively charged, and of course it did not show any sensitivity when positively charged. Comparative Example 2
The electrophotographic photoreceptor without the electron transport layer obtained in
Compared with the electrophotographic photoreceptors obtained in each example, the potential holding ability and the residual potential were significantly inferior. Further, the electrophotographic photoreceptors provided with the barrier layer in place of the electron transport layer obtained in Comparative Examples 3 and 4 showed improvement in charging property as compared with the electrophotographic photoreceptor obtained in Comparative Example 2. However, the sensitivity and residual potential were inferior to those of the electrophotographic photoreceptors obtained in the respective examples. Further, the electrophotographic photoreceptors obtained in Comparative Example 5 in which the thickness of the electron transport layer was made smaller than 1 μm achieved almost the same sensitivity as the electrophotographic photoreceptors obtained in the respective examples, but slightly. The chargeability tended to be low.

(Image Characteristics) For the evaluation of the image characteristics, a commercially available laser printer (“Laser Jet III Si” manufactured by Hewlett-Packard Co.) corresponding to a negatively charged drum-shaped electrophotographic photoreceptor is used. Attach the prototype drum-shaped electrophotographic photoconductor to the
The printing test was performed in the environment of No. 1 and the image was evaluated. The evaluation results are summarized in Table 2. For the evaluation of background stain, a printed white background document is observed with a magnifying glass of 50 times to find the area ratio of toner adhered in a square of 2 mm × 2 mm, and the following evaluation criteria are used: ◎, ○, △,
The grade was evaluated in four grades.

A: The maximum value of the above area ratio is less than 0.1% regardless of the printing area. ：: The maximum value of the area ratio is 0.1 irrespective of the printing area
% Or more and less than 0.5%. Δ: The maximum value of the area ratio was 0.5 regardless of the printing area.
% Or more and less than 1.0%. ×: The maximum value of the area ratio was 1.0 regardless of the printing area.
%that's all.

The image density was obtained by measuring the print density of the black background portion of the image with a densitometer (Model RD918 manufactured by Macbeth Co.).

[0079]

[Table 3]

As is clear from the results shown in Table 3, each of the electrophotographic photoconductors obtained in Examples 1 to 4 had no background stain, and an image of sufficient print density was obtained. The electrophotographic photoconductors obtained in Comparative Examples 1 and 2 were significantly inferior in the background stain evaluation, and the electrophotographic photoconductors having the barrier layers obtained in Comparative Examples 3 and 4 had a degree of background stain. However, it was inferior to the results of the electrophotographic photoreceptors of the respective examples. Further, it is understood that the electrophotographic photoreceptors of Comparative Examples 2 to 4 having the single-layer structure of only the charge generation layer are inferior in sensitivity and residual potential, so that the image density is significantly low and not practical. it can. Furthermore, the electrophotographic photoreceptor having a thin electron transport layer obtained in Comparative Example 5
It can be understood that in comparison with the electrophotographic photoreceptors obtained in Examples, the background stain evaluation is inferior and a sufficient defect concealing power cannot be expected.

[0081]

INDUSTRIAL APPLICABILITY The electrophotographic photoconductor of the present invention is excellent in productivity and can realize high image quality in which defects on the image do not appear, and good electrostatic characteristics exhibiting excellent sensitivity and chargeability. It is a preferable electrophotographic photoreceptor.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating an example of a layer configuration of an electrophotographic photoconductor of the present invention.

[Explanation of symbols]

 1 Conductive Substrate 2 Photosensitive Layer 3 n-Type Semiconductor Pigment 4 Resin 5 Charge Generating Material 6 Hole Transport Material / Resin 7 Electron Transport Layer 8 Charge Generation Layer

2 is a mixture composition X of the reaction product of the titanyl phthalocyanine represented by the formula (1) and (2R, 3R) -2,3-butanediol obtained in Synthesis Example 1 and unreacted titanyl phthalocyanine. It is a line diffraction spectrum.

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Claims (7)

[Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer formed on a conductive substrate, wherein the photosensitive layer comprises an electron transporting layer having a film thickness of 1 to 20 μm and comprising at least an n-type semiconductor pigment dispersed in a resin. An electrophotographic photoreceptor having a structure in which a charge generation layer having a film thickness of 5 to 50 μm, which is obtained by dispersing a hole transport material and a charge generation material in a resin, is laminated. 2. The ratio of the charge generating substance contained in the charge generating layer is 0.2 to 5% by weight based on the total weight of the charge generating layer.
The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor is in the range of 1. 3. The photoconductor for electrophotography according to claim 1, wherein the charge generation layer contains an electron accepting substance. 4. The n-type semiconductor pigment contains at least one pigment selected from the group consisting of disazo pigments, perylene pigments, anzanthron pigments and perinone pigments. Electrophotographic photoreceptor. 5. The charge-generating substance contained in the charge-generating layer is titanyl phthalocyanine, titanyl phthalocyanine, or 2,
The electrophotographic photoreceptor according to claim 1, further comprising at least one material selected from the group consisting of reaction products with 3-butanediol. 6. The electrophotographic photoconductor according to claim 1, which is used in an electrophotographic apparatus which forms a latent image by exposure with coherent light. 7. The electrophotographic photosensitive member according to claim 6, wherein the electrophotographic apparatus is a laser printer.