JPS6319867B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing a carrier-generating substance and a carrier-transporting substance. Conventionally, electrophotographic photoreceptors having photosensitive layers containing inorganic photoconductors such as selenium, zinc oxide, and cadmium sulfide as main components have been widely known. However, these are not necessarily satisfactory in terms of properties such as thermal stability and durability, and furthermore, there are problems in manufacturing and handling due to toxicity. On the other hand, electrophotographic photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, and easy to handle, and generally compared to selenium photoreceptors. It has many advantages, including excellent thermal stability, and has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is the most well-known such organic photoconductive compound, and a charge transfer complex formed from poly-N-vinylcarbazole and a Lewis acid such as 2,4,7-trinitro-9-fluorenone is Electrophotographic photoreceptors having a photosensitive layer as a main component have already been put into practical use. On the other hand, electrophotographic photoreceptors are known that have a laminated type or dispersion type functionally separated photosensitive layer in which the carrier generation function and the carrier transport function of the photoconductor are respectively assigned to separate substances. Electrophotographic photoreceptors having a photosensitive layer consisting of a carrier generation layer consisting of a thin layer of amorphous selenium and a carrier transport layer containing poly-N-vinylcarbazole as a main component have already been put into practical use. However, since poly-N-vinylcarbazole lacks flexibility, its coating is hard and brittle, and is prone to cracking and peeling. Therefore, electrophotographic photoreceptors using it have poor durability. If a plasticizer is added to improve this drawback, the residual potential will increase when subjected to the electrophotographic process, and with repeated use, the residual potential will accumulate and gradually cause fog on the copied image. It has drawbacks that come to arise. In addition, since low-molecular organic photoconductive compounds generally do not have film-forming ability, they are used in combination with any binder, and therefore the film can be formed by selecting the type and composition ratio of the binder used. Although it is preferable in that it allows the physical properties or electrophotographic properties to be controlled to a certain extent, the types of organic photoconductive compounds that have high compatibility with binders are limited, and in reality, electrophotographic sensitization is difficult. The reality is that there are not many materials that can be used to construct the photosensitive layer of the body. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole described in U.S. Pat. No. 3,189,447 is usually preferred as a material for the photosensitive layer of an electrophotographic photoreceptor. Since it has low compatibility with the binder used, if it is mixed with a binder such as polyester or polycarbonate in the proportion required to obtain favorable electrophotographic properties to form a photosensitive layer, Oxadiazole crystals begin to precipitate at temperatures of 50° C. or higher, which has the disadvantage of deteriorating electrophotographic properties such as charge retention and sensitivity. On the other hand, the diarylalkane derivative described in U.S. Patent No. 3,820,989 does not usually have a problem with its compatibility with binders, but its stability against light is low, so it cannot be charged or exposed to light. When used in the construction of the photosensitive layer of a photoreceptor for repetitive transfer electrophotography, where
This has the disadvantage that the sensitivity of the photosensitive layer gradually decreases. The reality is that a carrier transport material having practically preferable characteristics for producing an electrophotographic photoreceptor has not yet been found. An object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and low residual potential. Another object of the present invention is to maintain stable characteristics over a long period of time with little fatigue deterioration due to repeated use when used as a photoreceptor for repetitive transfer type electrophotography in which charging, exposure, development, and transfer steps are repeated. An object of the present invention is to provide an electrophotographic photoreceptor that has excellent durability over a long period of time. As a result of intensive research to achieve the above object, the present inventors discovered that the object could be achieved by using a specific triarylamine derivative as a carrier transport material of a functionally separated photoreceptor, and the present invention is provided. This is the completed version. The above object is achieved by using a triarylamine derivative represented by the following general formula as a carrier transport material constituting a functionally separated photoreceptor. general formula Ar ₁ and Ar ₂ may be the same or different, and each represents a substituted or unsubstituted phenyl group. Ar ₃ represents a substituted or unsubstituted arylene group. Preferably used arylene groups are phenylene and naphthylene groups. Ar ₄ represents a substituted or unsubstituted aryl group, a substituted or unsubstituted furyl group, or a substituted or unsubstituted thienyl group. Preferred aryl groups include phenyl, naphthyl, and anthryl groups. Preferred substituents for Ar ₁ , Ar ₂ , and Ar ₃ groups include halogen atoms, substituted or unsubstituted alkyl groups, alkoxy groups, substituted or unsubstituted amino groups, hydroxyl groups, and aryloxy groups. They can be different or the same. Preferred substituents for the Ar ₄ group include an alkyl group, an alkoxy group, an aryloxy group, a hydroxyl group, and a halogen atom. That is, in the present invention, the carrier transport ability of the triarylamine derivative represented by the above general formula is utilized, and this is used as a carrier in the photosensitive layer of a so-called functionally separated photoreceptor in which carrier generation and transport are performed using separate substances. When used as a transport material, it has excellent film properties, excellent electrophotographic properties such as charge retention, sensitivity, and residual potential, and has little fatigue deterioration even after repeated use.
It is possible to create an electrophotographic photoreceptor that exhibits stable characteristics without any change in the above-mentioned characteristics. Specific examples of triarylamine derivatives represented by the above general formula that are effective in the present invention include those having the following structural formula, but are not limited thereto. The above triarylamine derivatives can be easily synthesized by known methods. For example, Organic Reactions vol.25, p.73 (John
Wiley & Sons, Inc.), an aromatic aldehyde represented by the following general formula [] and a dialkyl phosphonate represented by the following general formula [] are combined with N,
It can be easily obtained by condensation in a solvent such as N-dimethylformamide in the presence of a base such as sodium alkoxide or sodium hydride. Here, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ represent the same as in the general formula [], and R ₁ represents an alkyl group or an aryl group. Next, a typical method for synthesizing the triarylamine derivative used in the present invention will be specifically explained. Synthesis Example 1 (Synthesis of Exemplary Compound A-(6)) Diethyl p-methoxybenzylphosphonate 5.2
g (0.02mol) of N,N-dimethylformamide
Dissolve in 60 ml and add 2.2 g (0.04 mole) of sodium methoxide while cooling on ice. A solution of 6 g (0.02 mole) of 4-(p,p'-ditollylamino)benzaldehyde dissolved in 40 ml of N,N-dimethylformamide was added dropwise, and after the dropwise addition,
Stir for an additional hour while cooling on ice. After standing overnight at room temperature, 40 ml of ice water was added, the precipitated crystals were collected by filtration, and recrystallized twice with acetonitrile. Yield 6.3g (78.0%) Melting point 155-156℃ Synthesis example 2 (Synthesis of exemplified compound A-(5)) Diethyl p-methylbenzylphosphonate 3.6g
(0.015mole) of N,N-dimethylformamide
Dissolve in 10 ml and add 1.6 g (0.03 mole) of sodium methoxide while cooling on ice. A solution of 4.5 g (0.015 mole) of 4-(p,p'-ditollylamino)benzaldehyde dissolved in 30 ml of N,N-dimethylformamide was added dropwise, and after the dropwise addition, the mixture was further stirred for 1 hour while cooling with ice. After standing at room temperature overnight, add 10 ml of ice water, collect the precipitated crystals by filtration, and recrystallize twice with acetonitrile. Yield: 4.8 g (82.9%) Melting point: 132 to 133°C The carrier transport material of the present invention can effectively constitute an electrophotographic photoreceptor in combination with any carrier generating material. Carrier generating substances used in the present invention include inorganic photoconductors such as selenium, selenium alloys and amorphous silicon, as well as organic dyes and pigments having carrier generating ability. Particularly preferred organic dyes/pigments include polycyclic quinone pigments and azo dyes such as monoazo dyes, bisazo dyes, and trisazo dyes. Since the triarylamine derivative of the present invention does not have film-forming ability, when it is used to form a photosensitive layer, it is preferably used together with a binder. Preferred binders used in the present invention are hydrophobic and
It is an electrically insulating film-forming polymer with a high dielectric constant. Examples of such polymers include the following. B-(1) Polystyrene B-(2) Polyvinyl chloride B-(3) Polyvinylidene chloride B-(4) Polyvinyl acetate B-(5) Acrylic resin B-(6) Mectaryl resin B-(7) Polyester B -(8) Polycarbonate B-(9) Phenol formaldehyde resin These binders may be used alone or in combination of two or more types, or copolymers containing at least one type of monomer constituting the above polymer. Although used as a binder, the binder used in the present invention is not limited to these. As shown in FIG. 1, FIG. 2, FIG. 3, and FIG. a carrier transport layer 3 is provided adjacent to the layer;
A photoreceptor having the best electrophotographic properties can be obtained when the photosensitive layer is composed of two layers, but as shown in FIGS. 5 and 6, an intermediate layer 5 is optionally provided on the conductive support 1. A photoreceptor in which fine particles 7 of a carrier-generating substance are dispersed in a photosensitive layer 6 mainly containing a carrier-transporting substance can also be effectively used in the present invention. When the photosensitive layer 4 has a two-layer structure, which of the carrier generation layer 2 and the carrier transport layer 3 should be the upper layer is determined by whether the charging polarity is positive or negative. In other words, when used with negative charge,
It is advantageous for the carrier transport layer 3 to be the upper layer,
This is because the triarylamine derivative of the present invention in the carrier transport layer is a substance that has a high ability to transport holes. The carrier generation layer 2 constituting the two-layered photosensitive layer 4 may be formed directly on the conductive support 1 or the carrier transport layer 3, or provided with an intermediate layer such as an adhesive layer or a barrier layer as necessary. It can be formed on the top by the following method. (C-1) Vacuum evaporation method (C-2) Dissolve the carrier generating substance in a suitable solvent,
Coating method (C-3) The carrier generating substance is made into fine particles in a dispersion medium using a ball mill, homomixer, sand mill, colloid mill, etc., and if necessary, the dispersion obtained by mixing and dispersing with a binder. Method of applying the liquid The carrier generation layer 2 formed in this way preferably has a thickness of 0.01 to 5 microns,
More preferably, it is 0.05 to 3 microns. Further, the thickness of the carrier transport layer 3 can be changed as necessary, but it is usually preferably 5 to 30 microns. The composition ratio in this carrier transport layer 3 is such that the binder is added to 1 part by weight of the carrier transport material whose main component is the triarylamine derivative mentioned above.
The amount of the binder is preferably 0.8 to 10 parts by weight, but when forming the photosensitive layer 4 in which a fine powder carrier-generating substance is dispersed, the amount of the binder is 5 parts by weight or less per 1 part by weight of the carrier-generating substance. It is preferable to use it in Further, when the carrier generating layer 2 is constructed as a dispersed type layer using a binder, it is preferable to use an adhesive in an amount of 5 parts by weight or less per 1 part by weight of the carrier generating substance. The conductive support 1 used in the construction of the electrophotographic photoreceptor of the present invention may be a metal plate, or a conductive compound such as a conductive polymer or indium oxide.
Alternatively, paper, plastic film, or the like can be used that has been made conductive by coating, vapor depositing, or laminating a thin layer of metal such as aluminum, palladium, or gold. In addition to the polymer used as the binder, the intermediate layer 5 such as an adhesive layer or barrier layer may be made of an organic polymer such as gelatin, casein, starch, polyvinyl alcohol, vinyl acetate, ethyl cellulose, carboxymethyl cellulose, or the like. Aluminum oxide or the like is used. The electrophotographic photoreceptor of the present invention has the above-described structure, and as is clear from the examples described later, it has excellent charging characteristics, sensitivity characteristics, image characteristics, etc. Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited thereto. Example 1 Selenium was evaporated onto a conductive support consisting of a polyester film laminated with aluminum foil to form a carrier generating layer with a thickness of 0.5 microns. On top of that, 6 parts by weight of Exemplified Compound (1) and 10 parts by weight of polycarbonate "Panlite L-1250" (manufactured by Teijin Chemicals) were added to 1,2-dichloroethane.
90 parts by weight, and the film thickness after drying this solution is
A carrier transport layer was formed by coating to a thickness of 11 microns, and the electrophotographic photoreceptor of the present invention was thus prepared. The electrophotographic properties of this electrophotographic photoreceptor were measured by a dynamic method using an electrostatic copying paper tester "SP-428 model" (manufactured by Kawaguchi Denki Seisakusho Co., Ltd.). That is, the surface of the photosensitive layer of the photoreceptor is charged with a voltage of -
The surface potential V _A when charged at 6 KV for 5 seconds, then the amount of exposure required to attenuate the surface potential V _A by half by irradiating the photoreceptor with light from a tungsten lamp so that the illumination intensity on the photoreceptor surface is 35 lux. (Half exposure amount) E1/2 (lux・sec) and 30lux・
Surface potential (residual potential) after irradiation with an exposure dose of sec
V _R was calculated for each. The same measurement was repeated 100 times. The results are shown in Table 1.

[Table] As is clear from this table, the electrophotographic photoreceptor of the present invention has sufficient charge retention ability, high sensitivity, low residual potential, and maintains good characteristics even after repeated use. It has excellent physical properties. Comparative Example 1 Example 1 except that 9-(p-diethylaminostyryl)anthracenone having the following structural formula was used instead of Exemplified Compound (1) as a carrier transport substance.
same as A comparative photoreceptor was prepared. When this photoreceptor was measured in the same manner as in Example 1, the results shown in Table 2 were obtained.

[Table] As is clear from the above results, the comparative photoreceptor was significantly inferior to the photoreceptor of the present invention of Example 1 in terms of sensitivity and stability during repeated use. Examples 2 to 4 Example 1 except that exemplified compounds (2), (3), and (4) were used instead of exemplified compound (1) as carrier transport substances.
An electrophotographic photoreceptor of the present invention was prepared in the same manner as described above. The initial characteristics of these photoreceptors were measured in the same manner as in Example 1, and the results shown in Table 3 were obtained.

[Table] Example 5 Vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" was placed on a conductive support made of polyester film with aluminum vapor-deposited.
(manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.05 microns, and on top of that, 1 part by weight of dibromoanthron "Monolite Red 2Y" (CI No. 59300, manufactured by ICI) was added to 30 parts by weight of 1,2-dichloroethane, and then milled in a ball mill. 1.5 parts by weight of polycarbonate "Panlite L-1250" (manufactured by Teijin Kasei) was dissolved in the resulting dispersion, and the thoroughly mixed coating solution was applied so that the film thickness after drying was 2 microns. A carrier generation layer was formed. On top of that, 6 parts by weight of exemplified compound (5) and 10 parts by weight of polyester "Pylon 200" (manufactured by Toyobo Co., Ltd.),
A carrier transport layer was formed by applying a coating solution dissolved in 90 parts by weight of 1,2-dichloroethane to a dry film thickness of 10 microns, thereby forming an electrophotographic photoreceptor of the present invention. When this photoreceptor was measured in the same manner as in Example 1, the results shown in Table 4 were obtained.

[Table] Comparative Example 2 A comparative photoreceptor was prepared in the same manner as in Example 5, except that a carbazole derivative having the following structural formula was used instead of Exemplary Compound (5) as a carrier transport material. When this comparative photoreceptor was measured in the same manner as in Example 1, the results shown in Table 5 were obtained.

[Table] As is clear from the above results, the comparative photoreceptor was significantly inferior to the photoreceptor of the present invention in sensitivity and repeated stability. Example 6 Same as Example 5 except that dibromoviolanthrone represented by the following structural formula was used instead of dibromoanthrone as the carrier generating substance. An electrophotographic photoreceptor of the present invention was prepared. Regarding this photoreceptor, the same procedure as in Example 1 was carried out,
When I measured the initial characteristics, VA=-932V, E1/2
=3.8lux・sec, V _R =0V. In addition, this photoreceptor was used in an electrophotographic copying machine "U-
Bix200R (manufactured by Konishiroku Photo Industry Co., Ltd.) and conducted a live-action test, the resulting reproduced images were faithful to the original, had high contrast, excellent gradation, and were clear. Even after repeating this method 1000 times, it gave a good copy image that was as good as the initial one. Example 7 The intermediate layer used in Example 5 was provided on a conductive support made of a polyester film laminated with aluminum foil. On top of that, 1 part by weight of a bisazo pigment represented by the following structural formula is added to ethylenediamine. A carrier generation layer was formed by applying a solution dissolved in 100 parts by weight to a dry film thickness of 0.5 microns. Furthermore, 6 parts by weight of the exemplary compound (6) and 10 parts by weight of polycarbonate "Iupilon S-1000" (manufactured by Mitsubishi Gas Chemical Co., Ltd.) were added to 90 parts by weight of 1,2-dichloroethane.
The electrophotographic photoreceptor of the present invention was prepared by coating a solution dissolved in parts by weight so that the film thickness after drying was 15 microns to form a carrier transport layer. When this photoreceptor was measured in the same manner as in Example 1, the results shown in Table 6 were obtained.

[Table] As is clear from the results, the photoreceptor of the present invention is extremely excellent in sensitivity and repeated stability. Example 8 A 0.1 micron thick intermediate layer made of polyester "Vylon 200" (manufactured by Toyobo Co., Ltd.) was provided on a conductive support made of a polyester film laminated with aluminum foil. On top of that, a liquid containing 1 part by weight of a bisazo pigment represented by the structural formula below as a carrier generating substance was dispersed in 60 parts by weight of 1,2-dichloroethane, and the film thickness after drying was It was applied to a thickness of 0.3 microns to form a carrier generation layer. Furthermore, 6 parts by weight of exemplified compound (7) and polycarbonate "Panlite L-1250"
(manufactured by Teijin Chemicals) in 90 parts by weight of 1,2-dichloroethane, the film thickness after drying was 15%.
A carrier transport layer was formed by coating in a micron thickness to produce an electrophotographic photoreceptor of the present invention. The initial characteristics of this photoreceptor were measured in the same manner as in Example 1. VA=-1060V, E1/2=
It was 1.4lux·sec, and V _R =0V. In addition, this photoreceptor was used in an electrophotographic copying machine "U-
Bix2000R (manufactured by Konishiroku Photo Industry Co., Ltd.) and conducted a live-action test, the resulting reproduced images were faithful to the original, had high contrast, excellent gradation, and were clear. Even after repeating this process 1000 times, a copy image as good as the initial one was obtained. Example 9 An electrophotographic photoreceptor of the present invention was prepared in the same manner as in Example 8 except that a bisazo pigment represented by the following structural formula was used as a carrier generating substance. The initial characteristics of this photoreceptor are V _A = -1120V, E1/2
=2.1lux・sec, V _R =0V. This was attached to an electrophotographic copying machine "U-Bix2000R" (manufactured by Konishiroku Photo Industry Co., Ltd.), and a photocopying test was conducted, and even after repeating 1000 times, a good copy image was obtained that was as good as the initial copy. Example 10 An electrophotographic photoreceptor of the present invention was prepared in the same manner as in Example 8, except that a bisazo pigment represented by the following structural formula was used as a carrier generating substance. The initial characteristics of this photoreceptor are V _A = -985V, E1/2
= 1.8 lux・sec, V _R = 0V. This was attached to an electrophotographic copying machine "U-Bix2000R" (manufactured by Konishiroku Photo Industry Co., Ltd.), and a photocopying test was conducted, and even after repeating 1000 times, a good copy image was obtained that was as good as the initial copy.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views showing examples of the mechanical structure of the electrophotographic photoreceptor of the present invention, respectively. 1... Conductive support, 2... Carrier generation layer,
3... Carrier transport layer, 4... Photosensitive layer, 5... Intermediate layer, 6... Layer containing a carrier transport substance, 7
...Carrier generating substance.

Claims (1)

[Scope of Claims] 1. A functionally separated electrophotographic photoreceptor comprising a photosensitive layer containing a carrier-generating substance and a carrier-transporting substance provided on a conductive support, in which the carrier-transporting substance is represented by the following general formula []. An electrophotographic photoreceptor comprising a triarylamine derivative. General formula [] (However, in the formula, Ar ₁ and Ar ₂ may be the same or different and represent a substituted or unsubstituted phenyl group, Ar ₃ represents a substituted or unsubstituted arylene group, and Ar ₄ represents a substituted or unsubstituted aryl group. , frill group,
Represents a thienyl group, with an alkyl group as a substituent,
One or more of the group consisting of an alkoxy group, an aryloxy group, a hydroxyl group, and a halogen atom are used in combination. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is constituted by a laminate of a carrier generation layer containing a carrier generation substance and a carrier transport layer containing a carrier transport substance.