JPH027459B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to electrophotographic photoreceptors, and more particularly to electrophotographic photoreceptors having a carrier transport layer combined with a layer of material that absorbs light and generates charge carriers. To date, carrier generation layers (hereinafter referred to as ``CGL'') containing a carrier generation substance (hereinafter referred to as ``CGM'') that absorbs visible light and generates charged carriers (hereinafter simply referred to as ``carriers''). )
and a carrier transport layer (hereinafter referred to as "CTL") containing a carrier transport material (hereinafter referred to as "CGM") that transports either or both of the positive and negative carriers generated in this CGL. It has been proposed that a photosensitive layer of an electrophotographic photoreceptor can be constructed by combining these materials. in this way,
By assigning the two basic functions necessary for the photosensitive layer, carrier generation and transport, to separate layers, the range of materials that can be used in the composition of the photosensitive layer is widened, and each function can be optimized. By doing so, it becomes possible to independently select materials or material systems that achieve the desired properties in the electrophotographic process, such as a high surface potential when charged, a large charge retention ability, and a high resistance to light. It becomes possible to construct an electrophotographic photoreceptor having excellent characteristics such as high sensitivity and great stability in repeated use. Conventionally, as such a photosensitive layer, the following ones are known, for example. (1) Consisting of amorphous selenium or cadmium sulfide
A structure in which CGL and CTL made of poly-N-vinylcarbazole are laminated. (2) Consisting of amorphous selenium or cadmium sulfide
A structure in which CGL and CTL containing 2,4,7-trinitro-9-fluorenone are laminated. (3) A structure in which a CGL made of a perylene derivative and a CTL containing an oxadiazole derivative are laminated (see US Pat. No. 3,871,882). (4) A structure in which a CGL made of chlordiane blue or methylscalyllium and a CTL containing a pyrazoline derivative are laminated (Japanese Patent Application Laid-Open No. 1973-
(See Publication No. 90827). (5) CGL made of amorphous selenium or its alloy;
A structure in which CTL containing a polyarylalkane-based aromatic amino compound is laminated (patent application)
52-147251). (6) A structure in which CGL containing a perylene derivative and CTL containing a polyarylamkane-based aromatic amino compound are laminated (Patent application 1973-
19907 specification). As described above, many types of photosensitive layers are known, but in conventional electrophotographic photoreceptors having such photosensitive layers, the electricity of the photosensitive layer when repeatedly subjected to electrophotographic processes is limited. It has the disadvantage of severe mechanical fatigue and a very short service life. That is,
Although it is necessary to eliminate the charge in the photosensitive layer when one electrophotographic process is completed and the photosensitive layer is used for the next electrophotographic process,
In this type of photosensitive layer, the discharge speed at the final stage of discharge is extremely low, so even if the static electricity is removed by exposure to a large amount of light, it is impossible to completely eliminate the static electricity, and a fairly high residual potential remains. The potential increases cumulatively each time the electrophotographic process is repeated, and eventually, after a small number of continuous copies, the residual potential exceeds its permissible limit and the electrophotographic photoreceptor becomes unusable. It is certainly possible to restore some types of photoreceptors to a usable state, but in order to recover, it is necessary to leave the photoreceptor in a dormant state for a considerable period of time, or to perform appropriate heat treatment. Moreover, the residual potential cannot be restored to a sufficiently lowered state, and therefore, the number of consecutive copies that can be made before the next unusable state is reached is greatly reduced. It is an object of the present invention to eliminate the above-mentioned drawbacks and provide an electrophotographic photoreceptor that exhibits little fatigue deterioration even when subjected to repeated electrophotographic processes, and therefore has a long continuous service life. The present inventors have completed the present invention as a result of intensive research to achieve the above object, and its characteristics include a conductive support and a structure provided on the conductive support. a photosensitive layer consisting of a laminate of CGL and CTL, wherein the CTL contains a carbazole derivative represented by the following general formula, and
The point is that at least one of CTL or CGL contains an electron-accepting substance. general formula (In the formula, R ₁ represents a substituted or unsubstituted aryl group, R ₂ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group,
represents an amino group, substituted amino group or hydroxyl group,
R ₃ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted thienyl group, or a substituted or unsubstituted carbazolyl group. ) That is, in the present invention, the carbazole derivative represented by the above general formula is used as CTM to be contained in CTL of the photosensitive layer, and an electron-accepting substance is contained in one or both of CTL and CGL, and combined with CGM. As a result, a photosensitive layer of a so-called functionally separated photoreceptor in which carrier generation and transport are performed using separate substances, respectively, is formed.
This makes it possible to provide an electrophotographic photoreceptor that exhibits stable characteristics with little fatigue deterioration even after repeated use. Specific examples of carbazole derivatives represented by the above general formula that can be effectively used in the present invention include those having the following structural formula, but are of course not limited to these. Structural formula Examples of the electron-accepting substance to be contained in at least one of CGL or CTL include succinic anhydride, maleic anhydride, dibromaleic anhydride, phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, and 3-nitroanhydride. Phthalic acid, 4-nitrophthalic anhydride, pyromellitic anhydride, mellitic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene, 1,3,5-trinitrobenzene, paranitrobenzo nitrile,
Picryl chloride, quinone chlorimide, chloranil, bromanil, dichlorodicyanoparabenzoquinone, anthraquinone, dinitroanthraquinone, 2,7-dinitrofluorenone, 2,4,
7-trinitrofluorenone, 2,4,5,7-
Tetranitrofluorenone, 9-fluorenylidene-[dicyanomethylenemalonodinitrile], polynitro-9-fluorenylidene-[dicyanomethylenemalonodinitrile], picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, 3,5-dinitro Benzoic acid, pentafluorobenzoic acid, 5-
Examples include nitrosalicylic acid, 3,5-dinitrosalicylic acid, phthalic acid, mellitic acid, and other compounds with high electron affinity. Among these electron-accepting substances, in the present invention, as will be understood from the examples described below,
In particular, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, picryl chloride, 2,4,7-
Trinitrofluorenone or 3,5-dinitrobenzoic acid is preferred, and when these are used, the effect of reducing electrical deterioration can be further enhanced. Next, the mechanical structure of the electrophotographic photoreceptor of the present invention will be explained. In one example of the present invention, as shown in FIG. 1, a CGL 2 containing CGM (described later) as a main component is formed on a conductive support 1.
A CTL 3 containing CTM as a main component, which will be described later, is laminated and formed on the CGL 2.
2 and CTL 3 constitute a photosensitive layer 4. Here, as the material of the conductive support 1, for example, a sheet of metal such as aluminum, nickel, copper, zinc, paldium, silver, indium, tin, platinum, gold, stainless steel, or brass can be used. However, the invention is not limited to these. For example, as shown in FIG. 2, a conductive layer 1B may be provided on an insulating substrate 1A to constitute the conductive support 1. In this case, the substrate 1A may be Suitable materials include paper, plastic sheets, and other materials that are flexible and have sufficient strength against stress such as bending and tension. The conductive layer 1B can also be provided by laminating metal sheets, vacuum depositing metal, or by other methods. The CGL 2 can be formed by CGM alone, which will be described later, by adding a suitable binder resin to it, or by adding a substance having a high mobility toward carriers of specific or non-specific polarity, that is, CTM. can. As a specific method, CGM is placed on the support.
Examples include a method in which CGM is vacuum-deposited, and a method in which CGM is dissolved or dispersed in a suitable solvent and then applied and dried. In this latter method, a binder resin or CTM may be added to CGM, and in that case, the ratio of CGM: binder resin: CTM is 1:0 to 100:0 to 500 by weight, particularly 1:0.
-0:0-50 is preferable. As CGM, any inorganic pigment or organic dye can be used as long as it absorbs visible light and generates free carriers. In addition to inorganic pigments such as amorphous selenium, trigonal selenium, selenium-arsenic alloy, selenium-tellurium alloy, cadmium sulfide, cadmium selenide, cadmium selenide sulfide, mercury sulfide, lead oxide, and lead sulfide, the following representative examples Organic dyes such as those shown in may also be used. (1) Azo dyes such as monoazo dyes, polyazo dyes, metal complex azo dyes, pyrazolone azo dyes, stilbene azo dyes, and thiazole azo dyes. (2) Perylene dyes such as perylene anhydride and perylene imide. (3) Anthraquinone or polycyclic quinone dyes such as anthraquinone derivatives, anthanthrone derivatives, dibenzpyrenequinone derivatives, pyrantrone derivatives, violanthrone derivatives, and isoviolanthrone derivatives. (4) Indigoid dyes such as indigo derivatives and thioindigo derivatives. (5) Phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine. (6) Carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, xanthene dyes, and acridine dyes. (7) Quinoneimine dyes such as azine dyes, oxazine dyes, and thiazine dyes. (8) Methine dyes such as cyanine dyes and azomethine dyes. (9) Quinoline dyes. (10) Nitro dyes. (11) Nitroso dyes. (12) Benzoquinone and naphthoquinone dyes. (13) Naphthalimide dyes. (14) Perinone dyes such as bisbenzimidazole derivatives. (15) Quinacridone dyes. Among these organic dyes, polycyclic quinone dyes are particularly preferred because they bond well with the carbazole derivative used as CTM in the present invention and provide high sensitivity. Binder resins that can be contained in CGL include, for example, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin,
Addition polymer resins such as silicone resins and melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more repeating units of these resins, such as vinyl chloride-vinyl acetate copolymers In addition to insulating resins such as polymer resins and vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, poly-N-
Examples include polymeric organic semiconductors such as vinyl carbazole. High mobility for carriers of specific or non-specific polarity that can be added to the CGL
As the CTM, the CTM used in the configuration of CTL 3 and the like in the present invention can be used as a part or whole thereof, but other CTMs may be used in consideration of the performance as an electrophotographic photoreceptor. Furthermore, this CGL can contain one or more electron-accepting substances for the purpose of improving sensitivity, reducing residual potential, or reducing fatigue during repeated use. When CGL contains an electron-accepting substance, the content ratio is CGM:electron-accepting substance = 100:0.01 to 100, preferably 100:0.1 to
It is 50. If the electron-accepting substance is less than 0.01 part by weight, the image background potential (white paper potential) will increase significantly;
If it exceeds 100 parts by weight, the image potential (black paper potential) decreases significantly and stable repeatability cannot be obtained. The thickness of the CGL 2 formed as described above is preferably 0.005 to 20 microns, particularly preferably 0.05 to 5 microns. If it is less than 0.005 microns, sufficient photosensitivity cannot be obtained, and if it exceeds 20 microns, sufficient charge retention cannot be obtained. In addition, CTL3 can be prepared by using the carbazole derivative represented by the above-mentioned general formula as CTM, dissolving or dispersing it in an appropriate solvent together with an appropriate binder resin as needed, applying a coating liquid obtained by applying it, and drying it, or by other methods. It can be formed by a method. Examples of binder resins that can be contained in CTL in the present invention include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, and polycarbonate. Addition polymer resins such as resins, silicone resins, and melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more repeating units of these resins, such as vinyl chloride-vinyl acetate copolymer resins. Examples include insulating resins such as polymer resins and vinyl chloride-vinyl acetate-maleic anhydride copolymer resins, as well as polymeric organic semiconductors such as poly-N-vinylcarbazole. In the present invention, the content ratio of the binder resin and carbazole derivative used in CTL is 20 to 20 parts by weight of the carbazole derivative per 100 parts by weight of the binder resin.
The amount is 400 parts by weight, preferably 50 to 200 parts by weight. If it is less than 20 parts by weight, sufficient photosensitivity cannot be obtained,
Moreover, if it exceeds 400 parts by weight, the strength of the CTL film will decrease significantly. In the present invention, the electron-accepting substance may be contained in the CTL for the purpose of improving sensitivity, reducing residual potential, and reducing fatigue during repeated use. In this case, the content ratio is 0.001 to 10 parts by weight of the electron accepting substance, preferably 100 parts by weight of CTM.
It is 0.01 to 5 parts by weight. The thickness of the CTL 3 thus formed is between 2 and 100 microns, preferably between 5 and 30 microns. If it is less than 2 microns, a sufficient acceptance potential for image formation cannot be obtained, and if it exceeds 100 microns, the electric field strength applied to the photosensitive layer decreases, making it impossible to obtain sufficient sensitivity. The present invention has been explained above according to the specific configuration example shown in FIG. 1 or FIG. 2, but in the present invention,
The CTL combined with the CGL may contain a carbazole derivative, and at least one of the CGL or the CTL may contain an electron-accepting substance, and the mechanical structure of the electrophotographic photoreceptor can be arbitrarily selected. For example, as shown in FIG. 3, a suitable intermediate layer 5 is provided on a conductive support 1, and a CGL2
may be formed, and CTL3 may be formed on this CGL2. This intermediate layer 5 has a function of preventing free carriers from being injected from the conductive support 1 into the photosensitive layer 4 when the photosensitive layer 4 is charged;
Alternatively, it can function as an adhesive layer that integrally adheres the photosensitive layer 4 to the conductive support. Materials for the intermediate layer 5 include metal oxides such as aluminum oxide and indium oxide, acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, polyurethane resins, phenolic resins, polyester resins,
Polymer materials such as alkyd resin, polycarbonate resin, silicone resin, melamine resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, etc. can be used. Further, as shown in FIG. 4, on the conductive support 1,
The photosensitive layer 4 may be constructed by forming the CTL 3 with or without the intermediate layer 5 and forming the CGL 2 on the CTL 3. Since the electrophotographic photoreceptor of the present invention has the above-described configuration, as will be understood from the examples described later, even when it is repeatedly used in electrophotographic processes, it has little electrical fatigue, and therefore has good characteristics. can be obtained stably over a long period of time, resulting in a long continuous service life. Although it is not clear why the electrophotographic photoreceptor of the present invention exhibits good characteristics after repeated use, it is clear that a charge transfer complex is formed by the carbazole derivative and the electron-accepting substance at the interface between CGL and CTL, and this charge It is presumed that this is because the transfer complex acts to suppress the accumulation of charge, that is, the increase in residual potential during repeated use. Therefore, it is understood that the electron-accepting substance may be contained in at least one of CGL and CTL. Examples of the present invention will be described below, but the present invention is not limited thereto. Example 1 A conductive support made of polyethylene terephthalate with a thickness of 100 microns on which aluminum was vapor-deposited was coated with vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.). An intermediate layer with a thickness of about 0.1 micron was provided, and 4,10-dibromanthanthrone "Monolite Red 2Y" (CI No. 59300I.C), a polycyclic quinone dye, was applied in a vacuum atmosphere of 2 to 3 x ^{10 -4} Torr. .
I. Co., Ltd.) was evaporated by heating at 350 DEG C. for 3 minutes, and deposited on the intermediate layer to form a CGL with a thickness of approximately 0.5 microns. On the other hand, carbazole derivatives represented by structural formula (3)
11.25 g, picrylic chloride 0.028 g, and 15 g of polycarbonate resin "Panlite L-1250" (manufactured by Teijin Kasei) were dissolved in 100 ml of 1,2-dichloroethane, and the resulting solution was placed on the CGL using a doctor blade. It was coated and dried at a temperature of 80° C. for 1 hour to form a CTL with a thickness of 12 microns, thereby producing an electrophotographic photoreceptor of the present invention. This will be referred to as "Sample 1". Example 2 A CGL with a thickness of about 0.5 micron was prepared in the same manner as in Example 1, except that 11.25 g of the compound represented by the structural formula (7) was used as the carbazole derivative and 0.11 g of tetrabromophthalic anhydride was used as the electron-accepting substance. , and a CTL with a thickness of 12 microns were formed, thereby producing an electrophotographic photoreceptor of the present invention. This will be referred to as "Sample 2." Example 3 2 g of polycarbonate resin and 0.2 g of tetrabromophthalic anhydride were added to 100 ml of 1,2-dichloroethane.
Add 4 g of 4,10-dibromanthanthrone to the resulting solution and perform ultrasonic dispersion.
The resulting dispersion was coated onto a conductive support having an intermediate layer similar to that in Example 1, with a thickness of 1 micron.
Formed CGL. On the other hand, 11.25 g of the carbazole derivative represented by the structural formula (14) and the polycarbonate resin "Panlite L
-1250'' (manufactured by Teijin Chemicals) in 100 ml of 1,2-dichloroethane, the resulting solution was applied onto the CGL using a doctor blade, and dried at a temperature of 80°C for 1 hour to form a thick layer. A CTL with a diameter of 12 microns was formed, thereby producing an electrophotographic photoreceptor of the present invention. This will be referred to as "Sample 3." Example 4 2 g of polycarbonate resin and 0.2 g of tetrabromophthalic anhydride were added to 100 ml of 1,2-dichloroethane.
Add 4 g of 4,10-dibromanthanthrone to the resulting solution and perform ultrasonic dispersion.
The resulting dispersion was coated onto a conductive support having an intermediate layer similar to that in Example 1, with a thickness of 1 micron.
Formed CGL. On the other hand, 11.25 g of the carbazole derivative represented by structural formula (14), 0.056 g of 3,5-dinitrobenzoic acid, and 15 g of polycarbonate resin "Panlite L-1250" (manufactured by Teijin Kasei) were mixed in 1,2-dichloroethane.
The resulting solution was applied onto the CGL using a doctor blade, and dried at a temperature of 80° C. for 1 hour to form a CTL with a thickness of 12 microns. was created.
This will be referred to as "Sample 4." Example 5 5 g of poly-N-vinylcarbazole "Rubican M170" (manufactured by BASF) as a polymeric organic semiconductor was dissolved in 50 ml of monochlorobenzene, and then the structural formula (7)
6g of carbazole derivative shown by , 3.5g of polycarbonate resin "Panlite L-1250" (manufactured by Teijin Chemicals), and 2,4,7-trinitrofluorenone
0.038 g was dissolved in 40 ml of 1,2-dichloroethane, and the resulting solution was added to the monochlorobenzene solution and mixed thoroughly. The obtained solution was applied onto CGL formed in the same manner as in Example 1, and the temperature was
Dry at 80℃ for 1 hour to a thickness of 13 microns.
A CTL was formed to produce an electrophotographic photoreceptor of the present invention. This will be referred to as "Sample 5." Example 6 On a conductive support made of polyethylene terephthalate with a thickness of 100 microns on which aluminum was vapor-deposited, selenium was vapor-deposited at a temperature of 300°C for 1 minute in a vacuum atmosphere of 2 to 3 × 10 ^-5 Torr to form a thick film. A CGL made of amorphous selenium with a diameter of 1 micron was formed. On the other hand, 11.25 g of the carbazole derivative represented by structural formula (14), 0.056 g of 3,5-dinitrobenzoic acid, and 15 g of polycarbonate resin "Panlite L-1250" (manufactured by Teijin Kasei) were mixed in 1,2-dichloroethane.
The resulting solution was applied onto the CGL using a doctor blade, and dried at a temperature of 40°C for 24 hours to form a CTL with a thickness of 12 microns. was created.
This will be referred to as "Sample 6." Comparative Examples 1 to 6 Comparative electrophotographic photoreceptors were produced in the same manner as in Examples 1 to 6, except that no electron accepting substance was used in Examples 1 to 6. These will be referred to as "Comparative Sample 1" to "Comparative Sample 6", respectively. Samples 1 to 6 and Comparative Samples 1 to 6 according to the above Examples and Comparative Examples were transferred to a dry type electronic copying machine "U-
The black paper potential Vb (V) and white paper potential Vw (V) at an exposure aperture value of 2.5 were measured using an "Electrostatic Voltmeter 144D-1D model". (manufactured by Monroe Electronics, Inc.) and was measured immediately before development. The results are shown in Table 1. The black paper potential here refers to the surface potential of the photoreceptor when the above-mentioned copying cycle is performed using black paper with a reflection density of 1.3 as the original, and the white paper potential refers to the surface potential of the photoreceptor when the original is a blank paper. Represents surface potential.

[Table] (However, in the table, △Vb (V) and △Vw (V) are the black paper potential Vb (V) and the white paper potential Vw (V), respectively.
Indicates the amount of change, + represents an increase and 1 represents a decrease. ) From the results in Table 1, for samples 1 to 6, the initial black paper potential and white paper potential
After 10,000 copies, the amount of variation in both potentials is small and stable, but in all comparative samples 1 to 6, the amount of variation in both potentials is large, and in particular, background fogging occurred in the copied image due to ink movement of the blank paper potential. .

[Brief explanation of drawings]

FIG. 1 is an explanatory sectional view showing an example of the structure of the electrophotographic photoreceptor of the present invention, FIG. 2 is an explanatory sectional view showing another example of the structure of the electrophotographic photoreceptor of the invention, and FIGS. 3 and 4 2A and 2B are explanatory cross-sectional views showing still other structural examples of the electrophotographic photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 1... Conductive support, 2... Carrier generation layer (CGL), 3... Carrier transport layer (CTL), 4... Photosensitive layer, 5... Intermediate layer, 1A... Insulating substrate, 1B... Conductive layer.

Claims (1)

[Scope of Claims] 1. A photosensitive layer comprising a conductive support and a laminate of a carrier generation layer and a carrier transport layer provided on the conductive support, the carrier transport layer having the following general formula: An electrophotographic photoreceptor comprising the carbazole derivative shown below, and at least one of the carrier transport layer and the carrier generation layer contains an electron-accepting substance. general formula (In the formula, R ₁ represents a substituted or unsubstituted aryl group, R ₂ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkoxy group,
represents an amino group, substituted amino group or hydroxyl group,
R ₃ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted thienyl group, or a substituted or unsubstituted carbazolyl group. ) 2 The electron-accepting substance is tetrachlorophthalic anhydride, tetrabromophthalic anhydride, picryl chloride, 2,4,7-trinitrofluorenone,
The electrophotographic photoreceptor according to claim 1, which is at least one selected from the group of 3,5-dinitrobenzoic acid. 3. Claim 1, wherein the carrier generating substance in the carrier generating layer is a polycyclic quinone dye.
The electrophotographic photoreceptor according to item 1 or 2. 4. Claim 1, 2 or 3, wherein the content of the electron-accepting substance is 0.001 to 10 parts by weight, preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the carrier transport substance. The electrophotographic photoreceptor described above. 5. Claim 1, 2 or 3, wherein the content of the electron-accepting substance is 0.01 to 100 parts by weight, preferably 0.1 to 50 parts by weight, based on 100 parts by weight of the carrier generating substance. The electrophotographic photoreceptor described above.