JP2000242006A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrophotographic photoreceptor excellent in productivity, having favorable electrical properties and image characteristics and adaptable to a reversal developing system by providing a structure formed by dispersing an electric charge generating material having characteristics of an n-type semiconductor in a resin to an electric charge generating layer and specifying the thickness of the layer. SOLUTION: An electric charge generating layer 6 having >=5 μm thickness formed by dispersing an electric charge generating material 3 having characteristics of an n-type semiconductor in a resin and an electric charge transferring layer 7 formed by dispersing a hole transferring material 5 in the resin are laminated in this order on an electrically conductive substrate 1 to obtain the objective electrophotographic photoreceptor. The thickness of the electric charge transferring layer 7 is preferably >=5 μm from the viewpoint of electrification ability and durability and <=50 μm from the viewpoint of productivity, the amounts of the materials used and electrical responsiveness. The desired thickness of each of the electric charge generating layer 6 and the electric charge transferring layer 7 is easily attained by adjusting coating speed and various physical properties such as the viscosity and shearing force of a coating material in the case of formation 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 photosensitive member for reversal development, and more particularly to an electrophotographic photosensitive member having excellent productivity, high image quality, and excellent repetition stability. .

[0002]

2. Description of the Related Art Generally, an electrophotographic photoreceptor is formed by forming a photosensitive layer made of a photoconductive material on a conductive support. And a charge-transporting layer, and a function-separated type laminated electrophotographic photoreceptor is often used.

[0003] The most problematic point in production of a general lamination type electrophotographic photoreceptor is that, in order to satisfy the electrical characteristics of the charge generation layer, the charge generation layer must usually be formed as a thin layer of 1 μm or less. On the point. However, it is difficult to form a stable film without defects, and the current situation is that productivity is reduced. Also, in the case of an electrophotographic photoreceptor having such a layer configuration, it is known that the characteristics thereof are greatly changed depending on the electrical bonding state between the conductive support and the charge generation layer. The above-mentioned problems in characteristics are also likely to occur.

[0004] For example, it is known that if there is no good electrical barrier between the photosensitive layer and the support, charges are injected from the support, resulting in poor charging ability. Further, due to defects scattered on the support, crystallization of impurities, impurities in the coating film, etc., a local drop in potential occurs, particularly in a reversal development method, a fatal black spot on an image, It is also known that it tends to appear as a defect such as background dirt.

[0005] Problems of such conventional electrophotographic photoreceptors include improvement in material, development of functional layers such as a barrier layer, an intermediate layer and a surface protective layer, and efforts to review the layer structure itself. Have been studied for improvement, but have not been able to adequately meet the demands.

The common sense that the thickness of the charge generation layer must be 1 μm or less in the conventional photoreceptor structure is caused by a phthalocyanine-based compound widely used as a charge generation material in a reversal development photoreceptor. And squarium-based compounds are generally p-type semiconductors, and when they are formed on an aluminum support, an energy barrier called a Schottky barrier is formed at the interface, which prevents charge injection from the support. Bring charging ability,
One of the major factors is that the characteristics of the photoreceptor greatly depend on contributing to charge generation. In this case, when the thickness of the charge generation layer is increased, the amount of charges thermally dissociated increases in proportion to the film thickness, and holes do not have an injection barrier from the charge generation layer to the charge transport layer. The charge is transported to cause a decrease in chargeability, and at the same time, the amount of negative charges trapped in the charge generation layer also increases, which further increases the charge injection from the support and causes the chargeability to deteriorate. .

[0007] Further, the development tendency of the charge transport material has a great relation in this regard. Conventionally, as the charge transport material, the smaller the ionization potential, the more advantageous the charge injection from the charge generation material and the improvement in sensitivity can be expected. Therefore, materials having a small ionization potential have been mainly developed. Therefore, the charge injection barrier between the charge generation layer and the charge transport layer is reduced, and the charge injected from the support side or the thermal dissociation charge is easily injected into the charge transport layer, and the chargeability is reduced when the film thickness is increased. The trend becomes more pronounced,
It has been found that it is more difficult to thicken the charge generation layer. Therefore, due to such findings, the charge generating substance itself having the n-type semiconductor characteristics has been conventionally known,
There has been no sufficient study of increasing the thickness of the film or the merits thereof, particularly in the reversal development system.

In recent years, the characteristics required of electrophotographic photoreceptors have been to reduce costs in accordance with the competition between electrophotographic devices such as copiers and printers, which are lower in price, higher in image quality and longer in life. Therefore, there is a demand for a design of an electrophotographic photoreceptor based on a new concept in order to respond to the two contradictory points.

[0009]

The problem to be solved by the present invention is to provide a novel photosensitive layer structure different from the conventionally proposed electrophotographic photoreceptor, thereby improving productivity and improving electrical performance. It is an object of the present invention to provide an electrophotographic photosensitive member compatible with a reversal development system having favorable performance in terms of target and image characteristics.

[0010]

In order to solve the above-mentioned problems, the present invention provides a reversal developing method in which a single charge generation layer and a hole transport type charge transport layer are laminated on a conductive support in this order. In the electrophotographic photoreceptor used for (1), the charge generation layer comprises n
Provided is an electrophotographic photoreceptor having a structure in which a charge generating substance having a mold semiconductor characteristic is dispersed in a resin, and having a thickness of 5 μm or more. Here, the work function of the charge transport layer is preferably larger than the work function of the charge generation layer, and the difference is more preferably 0.2 eV or more. Further, the charge generating substance is preferably at least one pigment selected from the group consisting of disazo pigments, perylene pigments, anzanthrone pigments and perinone pigments. The electrophotographic photoreceptor of the present invention is preferably used in an electrophotographic apparatus for forming a latent image by exposure to coherent light, and more preferably the electrophotographic apparatus is a laser printer.

[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 illustrated electrophotographic photoreceptor has a charge generation layer having a thickness of 5 μm or more in which a charge generation material having n-type semiconductor characteristics is dispersed in a resin on a conductive support, and a charge transport layer in which a hole transport material is dispersed in a resin. These are sequentially laminated. Here, the thickness of the charge transport layer is preferably 5 μm or more from the viewpoint of chargeability and durability, and is preferably 50 μm or less from the viewpoint of productivity, the amount of material used, and electrical response characteristics. When the thickness of the charge generation layer and the charge transport layer is formed by dip coating, the thickness can be easily adjusted to a desired thickness by adjusting various physical properties such as a coating speed, a viscosity of the coating, and a shearing force. it can.

As the conductive support used in the electrophotographic photoreceptor of the present invention, for example, a metal or alloy such as aluminum, copper, zinc, stainless steel, chromium, nickel, molybdenum, vanadium, indium, gold, platinum and the like can be used. Metal plates, metal drums, metal belts used, or papers, plastic films, belts, etc. coated, deposited or laminated with conductive compounds such as conductive polymers and indium oxide or metals or alloys such as aluminum, palladium and gold No.

The charge generation material having n-type semiconductor characteristics used in the charge generation layer means a material having a better electron transporting property than a hole transporting property. This characteristic can be easily determined by measuring the photocurrent of the sandwich cell in which the sample is sandwiched between the electrodes. Such materials include, for example, azo pigments, quinone pigments, perylene pigments, indigo pigments, thioindigo pigments, bisbenzimidazole pigments, quinacridone pigments, quinoline pigments, lake pigments, azo lake pigments, anthraquinone N-type semiconductor characteristics from various organic pigments such as pigments, oxazine pigments, dioxazine pigments, and triphenylmethane pigments, or inorganic pigments such as titanium oxide, zinc oxide, cadmium sulfide, zinc sulfide, and silicon carbide. Although it is possible to use those which can be confirmed, it is particularly preferable to use disazo pigments, perylene pigments, anzanthrone pigments, and perinone pigments from the viewpoint of dispersibility and electrical characteristics.

The charge generating substance having n-type semiconductor properties used in the electrophotographic photoreceptor of the present invention is not limited to those listed here.
Alternatively, two or more kinds can be used in combination.

The proportion of the charge generating material having n-type semiconductor properties in the charge generating layer is preferably in a range where the charge generation and electron transport in the charge generating layer are sufficient and the strength of the film is obtained. Usually, the ratio of the pigment to the total weight of the charge generation layer is preferably 10% by weight or more from the viewpoint of charge generation efficiency and electron transportability, and is preferably 90% by weight or less from the viewpoint of mechanical properties such as adhesion.

As the binder used in the charge generation layer, a polymer capable of forming an electrically insulating film is preferable.
Examples of such high-molecular 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-vinyl carbazole, polyvinyl butyral, polyvinyl formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenol resin, polyamide, carboxy-methyl cellulose, vinylidene chloride-based polymer latex, polyurethane and the like. However, the present invention is not limited to these. These binders are used alone or in combination of two or more.

The thickness of the charge generation layer of the present invention needs to be 5 μm or more. When the film thickness is smaller than 5 μm, the effect of preventing an abnormal portion on the support from appearing in the image in the reversal development system, which is one of the features of the electrophotographic photoreceptor of the present invention, is not sufficiently obtained. In addition, interference fringes easily occur in the exposure method using coherent light. The upper limit of the thickness of the charge generation layer is not particularly limited as long as the effect of the present invention can be obtained, but is determined in consideration of the balance between productivity, cost, and the like. From such a viewpoint, the practical optimum value is 20 μm or less, and more preferably 10 μm or less.

Examples of the hole transporting substance usable in the charge transporting layer include low molecular weight compounds such as pyrene, carbazole, hydrazone, oxazole, oxadiazole, pyrazoline, arylamine, and the like. Examples include arylmethane-based, benzidine-based, thiazole-based, stilbene-based, and butadiene-based compounds. Examples of the polymer compound include poly-N-vinyl carbazole, halogenated poly-N-vinyl carbazole, polyvinyl pyrene, polyvinyl anthracene, polyvinyl acridine, pyrene-formaldehyde resin, ethyl carbazole-formaldehyde resin, and ethyl carbazole. Formaldehyde resin, triphenylmethane polymer, polysilane and the like can be mentioned.

The ratio of the hole transporting substance in the charge transporting layer depends on the hole transporting ability of the hole transporting substance used. In the case of a low molecular weight compound, the charge transporting property is based on the total weight of the charge transporting layer. Is preferably 10% by weight or more from the viewpoint of the above, and is preferably 60% by weight or less from the viewpoint of the mechanical strength of the charge transport layer.
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, so that the whole amount can be used as the hole transporting substance.

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

As the material used for the binder of the charge transport layer, those listed as the binder of the charge generation layer can be used alone or in combination of two or more.

Further, together with these binders, a plasticizer,
Additives such as a surface modifier, an antioxidant, and a photo-deterioration inhibitor can also be used.

Examples of the plasticizer include biphenyl, biphenyl chloride, terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenylphosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene, and various fluorohydrocarbons. No.

Examples of the surface modifier include silicone oil, fluororesin and the like.

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

Examples of the photo-deterioration inhibitor include benzotriazole compounds, benzophenone compounds, hindered amine compounds and the like.

When the charge generation layer or the charge transport layer is formed by dip coating, a charge generation material having the above-mentioned n-type semiconductor characteristics, a charge generation material, or a charge transport material mixed with a binder or the like is used. Is dissolved or dispersed in a solvent. The solvent for dissolving 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, for example, alcohols such as methanol, ethanol, n-propanol; acetone, methyl ethyl ketone,
Ketones such as 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 sulfoxide, sulfolane and the like Sulfoxides and sulfones; aliphatic halogenated hydrocarbons such as methylene chloride, chloroform, carbon tetrachloride, and trichloroethane; and aromatics such as benzene, toluene, xylene, monochlorobenzene, and dichlorobenzene.

The work function defined in the present invention means the absolute value of the Fermi level of a material from the vacuum level. As a method of measuring such a work function, a method of obtaining the work function from a contact potential difference with respect to a reference electrode is generally used. Usually, this measurement requires a precise measuring means called the Kelvin method, but recently, for example, a simple application of the method such as a Fermi level measuring device (trade name, FAC-1) manufactured by Riken Keiki Co., Ltd. Devices are also commercially available. Also in the examples of the present invention, the absolute values of the work functions of the charge generation layer and the charge transport layer were measured using the same apparatus.

In the photoreceptor of the present invention, the work function of the charge generation layer is preferably smaller than the work function of the charge transport layer, and the difference is more preferably 0.2 eV or more. Such a combination is substantially determined by the types of the charge generating substance and the hole transporting substance having the n-type semiconductor characteristics to be used. However, since the absolute value of the work function varies somewhat depending on the binder resin, the mixing ratio, and the like, It is desirable to perform measurement using a sample on which a film is formed.

[0030]

The present inventors have studied the relationship between the thickness of the charge generation layer and its electrophotographic characteristics. In particular, in a system using a material having a clear n-type semiconductor characteristic as a charge generation material,
It is possible to form a thick charge generation layer that exceeds the thickness of the conventional common sense, and it is not only superior in productivity than the conventional thin film charge generation layer, but it is also used for reversal development type electrophotography. It has been found that when used as a photoreceptor, an excellent effect of improving electrical and image characteristics can be obtained. The details of the operation will be described below, and the reason why the electrophotographic photosensitive member of the present invention can exhibit excellent electrical and image quality will be clarified.

First, the generation of charges in the electrophotographic photoreceptor of the present invention is, of course, due to the charge generation material having n-type semiconductor properties contained in the lower charge generation layer. However, there is a remarkable difference in the film thickness from the conventional laminated photoreceptor. In a general thin charge generation layer, the entire charge generation layer is considered as a site of charge generation, and it is necessary to consider the charge transport characteristics itself. In contrast, in the case of a charge generation layer as thick as 5 μm or more as in the present invention, incident light is almost absorbed near the surface of the layer. Without involvement,
Only charge transport will be performed. Therefore, it is noted that a single charge generation layer has a function separation of an upper layer for charge generation and a lower layer for charge transport. This gives a great feature in the characteristics of the electrophotographic photosensitive member of the present invention.

This feature is effective only when a charge injection barrier exists at the interface between the charge generation layer and the charge transport layer. That is, when there is no barrier between the charge generation layer and the charge transport layer, as described in the section of the prior art, when the charge generation layer is thickened, the charge transport layer of the heat dissociated charge and the charge injected from the support is obtained. And the charging ability decreases, so that a practical photoconductor cannot be obtained. The charge generation layer in the electrophotographic photoreceptor of the present invention is an n-type semiconductor resin dispersion film and therefore has an electron transporting property. Since the charge transporting layer has a hole transporting property, the charge transport layer has a discontinuity in its transport characteristics. It is considered that there is a charge injection barrier, and even if the charge generation layer is thickened, its adverse effect is unlikely to occur.

Further, in the electrophotographic photoreceptor of the present invention, the work function of the n-type semiconductor pigment used as the charge generating material is generally smaller than the work function of the hole transporting material used in the charge transporting layer. It is believed that the barrier is effectively provided. This is because the n-type semiconductor has a small work function because its Fermi level is in a region near the conduction band in the forbidden band, and the hole transport material is a p-type semiconductor, so that its Fermi level is forbidden. This is because it is in a region near the valence band in the band, and the work function is generally large. Therefore, when a film composed of both is laminated, a depletion layer corresponding to the difference in work function is formed at the interface between the charge generation layer and the charge transport layer, and this forms a Schottky barrier between the p-type semiconductor pigment and the aluminum support. Similarly, it is conceivable that it acts as a barrier against charge injection from the support side, and the local electric field formed thereby contributes to the dissociation of ion pairs, thereby exhibiting the effect of increasing the charge generation efficiency. It has been found that such an effect is particularly effective when the difference between the work functions of the charge generation layer and the charge transport layer is 0.2 eV or more, as shown in Examples described later.

The main causes of image defects in the reversal development system are defects in the support at the interface between the support and the charge generation layer in the conventional photoreceptor structure, and the presence of abnormal substances serving as nuclei for charge injection such as impurities. The injected charges neutralize the charged charges on the photosensitive layer, causing local discharge of charges, and appear as defects such as fatal black spots and background stains on images in reversal development. In order to suppress the influence of such an abnormal substance, formation of a barrier layer using an undercoat layer or the like has been studied, but if the layer thickness is too large, sensitivity is reduced, and the effect is limited. In the photoconductor of the present invention, the lower part of the charge generation layer having a large thickness functions as a semiconductive layer,
Since the barrier for charge injection exists at a portion of the interface between the charge generation layer and the charge transport layer at a distance of 5 μm or more from the support surface, the influence of the above-mentioned abnormal substances is extremely effectively eliminated, and high quality image characteristics are obtained. Can be obtained. Therefore, the electrophotographic photoreceptor of the present invention has an advantage that an independent barrier layer is basically unnecessary.

Further, in the electrophotographic photoreceptor of the present invention, unlike the conventional multilayer electrophotographic photoreceptor in which a thick barrier layer is provided to cover defects, the charge generation layer is transferred from the charge generating layer to the support. Since there are few barriers to charge injection, no deterioration in electrical characteristics such as an increase in residual potential is observed.
It is also possible to obtain excellent performance.

Furthermore, in the electrophotographic photoreceptor of the present invention, since the charge generation layer is formed of a resin dispersion film of a thick pigment, the latent image is formed by exposure to coherent light from a laser printer or the like. In the device, the irradiation light is almost diffused and absorbed inside the charge generation layer,
There is also an effect that occurrence of interference fringes on an image due to mutual interference of reflected light on the surface of the support and the surface of the photosensitive layer can be prevented.

[0037]

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 the following Synthesis Examples, Examples and Comparative Examples, “parts” indicates “parts by weight”.

(Example 1) A resin solution comprising 1 part of polyvinyl butyral resin ("ESLEC BH-3" manufactured by Sekisui Chemical Co., Ltd.), 10 parts of methanol and 15 parts of toluene was used.
Equation (1)

[0039]

Embedded image

After mixing 2 parts of the disazo pigment represented by the formula (1), the mixture was dispersed using a ball mill for 6 hours to obtain a paint for a charge generation layer.

Using this paint, it was applied on a 30 mm-diameter aluminum drum by dip coating so that the film thickness after drying was 5 μm, and then dried to form a charge generating layer.

Similarly, the work function of the coating film formed on the measuring cell was measured using a Fermi level measuring apparatus (“FAC-1” manufactured by Riken Keiki Co., Ltd.), and it was 4.67 eV.

Further, as a result of photocurrent measurement of this coating film, it was confirmed that electron transport was dominant and that the charge generation material had n-type semiconductor characteristics.

Next, equation (2)

[0045]

Embedded image

10 parts of the arylamine compound represented by the formula and 14 parts of a polycarbonate resin ("Iupilon Z-200" manufactured by Mitsubishi Gas Chemical Co., Ltd.) were dissolved in 76 parts of chloroform to prepare a paint for a charge transport layer.

Using this paint, dip coating was performed on the charge generation layer so that the film thickness after drying was 20 μm, and then dried to form a charge transport layer. A photoreceptor was obtained. The work function of this charge transport layer was found to be 4.88 eV as a result of the same measurement as that of the charge generation layer.

Comparative Example 1 The procedure of Example 1 was repeated except that the charge generation layer coating material was diluted three times and redispersed, and the thickness of the dried charge generation layer was changed to 0.4 μm. In the same manner as in Example 1, an electrophotographic photoconductor was obtained.

(Embodiment 2) In the embodiment 1, the formula (2)
N, N′-di (3,5-dimethylphenyl) perylene-3,4,9,10-tetracarboxydiimide (“Paliogen Red K-3580 manufactured by BASF”) ") An electrophotographic photoreceptor was obtained in the same manner as in Example 1, except that two parts were used and the charge generation layer was formed so that the film thickness after drying was 6 µm.

As a result of the same measurement as in Example 1, it was found that the present charge generating substance was an n-type semiconductor, and the work function of the charge generating layer of this photosensitive member was 4.56 eV.

Comparative Example 2 An electrophotographic photosensitive member was obtained in the same manner as in Example 2, except that the thickness of the charge generation layer was changed to 0.6 μm.

Example 3 Dibromoanzanthrone (I
"Monolite Red 2" manufactured by CI
Y ”) and 2 parts of a phenoxy resin (“ PKHH ”manufactured by Union Carbide Co., Ltd.) are mixed with a mixed solvent consisting of 7 parts of 1-acetoxy-2-methoxyethane and 7 parts of methyl ethyl ketone, and are mixed for 1 hour using a sand mill. This was dispersed to prepare a paint for the charge generation layer.

The charge generation layer was formed using the charge generation layer paint so that the film thickness after drying was 8 μm. As a result of performing the same measurement as in Example 1, the charge generation material was an n-type semiconductor, and the work function of the charge generation layer was 4.62.
eV.

Next, equation (3)

[0055]

Embedded image

7 parts of a styryl compound and a polycarbonate resin ("PANLITE C-1" manufactured by Teijin Chemicals Ltd.)
400 ") 10 parts were dissolved in 83 parts of chloroform to prepare a paint for a charge transport layer.

Using this paint, dip coating was performed on the above-mentioned charge generating layer so that the film thickness after drying was 25 μm, and then dried to form a charge transporting layer. A photoreceptor was obtained. The work function of the charge transport layer was measured to be 4.90 eV as a result of the same measurement as that of the charge generation layer.

Comparative Example 3 An electrophotographic photosensitive member was obtained in the same manner as in Example 3, except that the thickness of the charge generation layer was changed to 0.8 μm.

(Example 4) In Example 3, trans-bis (benzimidazole) perinone ("Hostapalm.RTM." Manufactured by Hoechst) was used in place of dibromoanzanthrone.
Orange (Hostaperm Orange GR)) was used in the same manner as in Example 3 except that 2 parts of orange was used to obtain a paint for a charge generation layer.

As a result of the same measurement as in Example 1, it was found that the charge generation material was an n-type semiconductor and the work function of the charge generation layer was 4.49 eV.

An electrophotographic photoreceptor was obtained in the same manner as in Example 3 except that the charge generation layer coating was used to form a charge generation layer having a thickness of 5 μm after drying.

Comparative Example 4 An electrophotographic photosensitive member was obtained in the same manner as in Example 4, except that the thickness of the charge generation layer was changed to 0.4 μm.

(Comparative Example 5) A resin solution consisting of 1 part of polyvinyl butyral resin (“S-LEC BH-3” manufactured by Sekisui Chemical Co., Ltd.), 40 parts of methanol and 60 parts of toluene was prepared.
Two parts of α-type titanyl phthalocyanine were mixed, and a paint for a charge generation layer was obtained in the same manner as in Example 1.

This paint was placed on the same aluminum drum as used in Example 1 and dried to a thickness of 0.3 μm.
m, and then heated and dried to form a charge generation layer. As a result of performing the same measurement as in Example 1,
This charge generation material was a p-type semiconductor, and the work function of this charge generation layer was found to be 5.02 eV.

Next, the same coating material for a charge transport layer as in Example 1 was applied on the above-mentioned charge generation layer to a thickness of 20 μm after drying.
And then dried to form a charge transport layer, thereby producing a negatively charged laminated electrophotographic photoreceptor.

Comparative Example 6 An electrophotographic device was prepared in the same manner as in Example 1, except that a 5-μm-thick charge generating layer was formed using α-type titanyl phthalocyanine instead of the disazo pigment. A photoreceptor was obtained.

Comparative Example 7 One part of a polyamide resin (“CM-8000” manufactured by Toray Industries, Inc.) was mixed with 7 parts of methanol and n-
A paint consisting of a resin solution dissolved in a mixed solvent consisting of 7 parts of butanol was obtained.

An electrophotographic photosensitive member was prepared in the same manner as in Comparative Example 1 except that a 1 μm-thick barrier layer made of the coating material was provided, and a charge generation layer was provided on the barrier layer. Obtained.

Comparative Example 8 A 6 μm-thick porous oxide film was formed on the surface of the aluminum drum used in Example 1 by anodizing, followed by sealing with nickel acetate.

In Comparative Example 1, an aluminum drum subjected to anodizing treatment and sealing treatment was used, and a charge generating layer was provided on the outer peripheral surface of the aluminum drum. Thus, a photoconductor for electrophotography was obtained.

Comparative Example 9 An electrophotographic photosensitive member was obtained in the same manner as in Example 1, except that the thickness of the charge generation layer was changed to 3 μm.

(Electrical Characteristics) In order to evaluate the electrical characteristics of the electrophotographic photosensitive members obtained in each of the examples and comparative examples, each of the electrophotographic photosensitive members was subjected to an electrophotographic photosensitive member test apparatus (manufactured by Gentec Corporation). Of "Cynthia-90"). The measurement method was as follows. First, the electrophotographic photoreceptor was charged by corona discharge at an applied voltage of −6 kV while rotating at 60 rpm in a dark place, and the surface potential immediately after this was used as an initial potential V ₀ and used for evaluation of charging ability. . Next, in a dark place
The potential after leaving seconds was measured and the V _10. here,
The potential holding ability was evaluated by V ₁₀ / V ₀ . Then 5
50nm monochromatic light, exposure intensity on the surface is 1μ
W / cm ² , the photosensitive layer was irradiated with light for 15 seconds, and the decay curve of the surface potential was recorded. 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. After charging, 2,000 lux white light was applied to 0.1 lux.
Immediately after repeating the process of irradiating for 100 seconds and removing electricity 100 times,
The same measurement was performed, and the repeated stability was evaluated. 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 photosensitive members obtained in Examples 1 to 4 of the present invention were obtained in Comparative Examples 1 to 4 having the corresponding conventional structures. Compared with the electrophotographic photoreceptor, when considering the difference in characteristics depending on the type of charge generating material, it is clear that all of the initial characteristics are relatively excellent in sensitivity, and furthermore, in the repetition stability. A clear improvement was seen. On the other hand, in the electrophotographic photoreceptors obtained in Comparative Examples 5 and 6 using the p-type semiconductor pigment for the charge generation layer, the charge generation layer was 5 μm in comparison with Comparative Example 5 in which the charge generation layer was thin. In Comparative Example 6, significant degradation was exhibited in any of the characteristics. Further, the electrophotographic photoreceptors obtained in Comparative Examples 7 and 8, in which a barrier layer was provided between the substrate and the charge generation layer, showed a slight improvement in the chargeability, but the residual potential and the repetition stability were different from those of the present invention. Was inferior to the electrophotographic photoreceptor. In addition,
The characteristics of the electrophotographic photoconductor obtained in Comparative Example 9 in which the thickness of the charge generation layer was 3 μm were almost intermediate between those of Example 1 and Comparative Example 1.

(Image Characteristics) For evaluation of image characteristics, a commercially available laser printer (Laser Jet 3Si manufactured by Hewlett-Packard Company) compatible with a reversal development system using a drum photosensitive member was used. However, the semiconductor laser used as the exposure source was changed to a laser beam having a wavelength of 532 nm obtained by performing SHG modulation on an LD-excited Nd: YVO ₄ laser. A drum-shaped electrophotographic photoconductor was mounted on this, and the temperature was 23 ° C. and 50% R.
A printing test was performed in the environment of H, and the image was evaluated. The evaluation results are summarized in Tables 3 and 4. The evaluation of the background stain was performed by observing a printed white background document with a magnifying glass of 50 times, calculating the area ratio of the toner adhered in a 2 mm × 2 mm square, and using the following evaluation criteria, ◎, ○, Δ, × The degree was evaluated in four steps.

A: The maximum value of the area ratio is 0.1 regardless of the printing area.
%Less than. ：: 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.

In the evaluation of interference fringes, the irradiation amount was adjusted in accordance with each photoconductor so that the surface potential after the entire surface exposure became half the initial potential in the developing section.
The degree of interference fringes in the output image was evaluated according to the following criteria.

：: No interference fringes are seen. Δ: Slight interference fringes are observed. X: Clear interference fringes are observed.

[0080]

[Table 3]

[0081]

[Table 4]

As is evident from the results shown in Tables 3 and 4, each of the electrophotographic photoconductors obtained in Examples 1 to 4 was free from background stains and excellent in no interference fringes. Although a high quality image was obtained, the electrophotographic photoreceptors having the thin charge generation layers obtained in Comparative Examples 1 to 5 were not only poorly evaluated for background contamination but also showed clear interference fringes. Also,
The electrophotographic photoreceptor having a thick charge-generating layer of the p-type semiconductor pigment obtained in Comparative Example 6 was inferior in chargeability, and thus had poor background smear and was not practical. Comparative Example 7
In the electrophotographic photoreceptor having the barrier layer obtained in Examples 8 and 9, the degree of background contamination was improved, but the results were inferior to the results of the electrophotographic photoreceptor of each Example. The effect of preventing the occurrence was hardly expected. Further, in the electrophotographic photoreceptor having a charge generation layer thickness of 3 μm obtained in Comparative Example 9, the interference fringes were improved to a level that did not cause a problem compared to the photoreceptor of Comparative Example 1. In comparison with the electrophotographic photoreceptor, the evaluation of background contamination was inferior, and the ability to conceal defects was not yet sufficient.

[0083]

The photoreceptor for electrophotography of the present invention has high productivity, high image quality in which no defects appear on the image, and good electrostatic properties showing excellent sensitivity and repetition stability. More preferred is an 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]

 REFERENCE SIGNS LIST 1 conductive support 2 photosensitive layer 3 charge generating substance having n-type semiconductor properties 4 resin 5 hole transporting substance / resin 6 charge generating layer 7 charge transporting layer

Claims (6)

[Claims] 1. A single charge generation layer on a conductive support,
In an electrophotographic photoreceptor used for reversal development in which a hole transport type charge transport layer is laminated in order, the charge generation layer is
An electrophotographic photosensitive member having a structure in which a charge generating substance having n-type semiconductor characteristics is dispersed in a resin, and having a film thickness of 5 μm or more. 2. The electrophotographic photoconductor according to claim 1, wherein the work function of the charge transport layer is larger than the work function of the charge generation layer. 3. The electrophotographic photoconductor according to claim 2, wherein the difference between the work function of the charge transport layer and the work function of the charge generation layer is 0.2 eV or more. 4. The charge-generating substance is at least one pigment selected from the group consisting of disazo pigments, perylene pigments, anzanthrone pigments and perinone pigments. The photoconductor for electrophotography according to the above. 5. The electrophotographic photoconductor according to claim 1, wherein the electrophotographic photoconductor is used in an electrophotographic apparatus that forms a latent image by exposure with coherent light. 6. The electrophotographic photoconductor according to claim 5, wherein the electrophotographic apparatus is a laser printer.