JPH0466505B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention provides an electrophotographic photoreceptor using a charge generating substance and a charge transporting substance, which has the following general formula (), which has the property of effectively functioning as a charge transporting substance. (In the formula, Ar ₁ is an amino-substituted aromatic hydrocarbon group that may have a substituent or an N-substituted carbazole group, and Ar ₂ represents an aromatic hydrocarbon group that may have a substituent.) 1,1,4,4-tetraaryl-
The present invention relates to an electrophotographic photoreceptor containing a 1,3-butadiene derivative. [Prior art and its problems] In recent years, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been widely known as electrophotographic photosensitive materials, while organic photoconductive materials There are various photoconductive polymers including poly-N-vinylcarbazole and polyvinyl anthracene as materials. However, these have the disadvantage that they do not have sufficient film formability or flexibility, and that if they are left in the form of a film, they may crack or peel. Therefore, it has been proposed to add plasticizers, binders, etc. to compensate for these drawbacks, but while this improves flexibility,
It has been extremely difficult to obtain a practical photoreceptor because of the drawback that electrophotographic properties such as sensitivity and residual potential are reduced. In addition, although low-molecular organic photoconductive compounds do not have film-forming ability by themselves, films can be formed by appropriately selecting a polymeric binder such as polyester resin, polyvinyl chloride resin, or polycarbonate resin. Although it has become possible to obtain a photoreceptor with excellent film formability and flexibility, it is still not sufficient. In addition to methods using these photoconductive materials,
In recent years, many proposals have been made to use separate organic compounds to perform the two functions of photoconductive materials, that is, to generate charge carriers and to transport the generated charges (for example, U.S. Patent No.
No. 3791826). In this method, a highly sensitive electrophotographic photoreceptor may be obtained by combining a substance with high charge carrier generation efficiency and a substance with high charge transport ability. However, this does not mean that it is necessarily possible to simultaneously satisfy the various characteristics required of an electrophotographic photoreceptor, such as high surface charge, high charge retention ability, high photosensitivity, and almost no residual potential. isn't it. In order to obtain a practical photoreceptor with such characteristics, it is necessary to have high generation efficiency of charge carriers in the charge generation material and rapid transport of charge carriers in the charge transport material. It is also an important factor that charge carriers are injected from the photoreceptor into the charge transport material, or that charges are efficiently injected from the charge generation layer to the charge transport layer in the case of a laminated photoreceptor. Attempts have been made to explain this injection efficiency in terms of its correlation with the ionization potential of the charge transport material, but it still lacks generality and a unified explanation for charge transport materials in general has yet to be achieved. do not have. Charge injection depends on the characteristics of the interface between the charge generation material (or charge generation layer) and the charge transport material (or charge transport layer), and is not uniform among various materials. In an electrophotographic photoreceptor having a functionally separated type photosensitive layer, high sensitivity may be obtained by selecting and combining substances with each function as described above. When photographic photoreceptors are repeatedly used in an electrophotographic process, they have drawbacks such as a decrease in their ability to recover their original charging characteristics or a decrease in photosensitivity, which shortens the life of the photoreceptor. ing.
In other words, when the actual electrophotographic process of charging, exposure, and cleaning is repeated many times, one or more of the following may occur: fluctuations in surface charge after charging, decrease in charge retention ability, decrease in photosensitivity, increase in residual potential, etc. Two or more photofatigue phenomena occur, significantly deteriorating the performance of electrophotography, and are a major problem in practical use. Furthermore, as electrophotographic copying machines and printers have become faster in recent years, photoreceptors are required to have faster response. The response speed of a photoreceptor depends on the mobility of charge carriers in a charge transport material, and there is a strong desire to develop a charge transport material with high mobility. On the other hand, regarding the use of 1,1,4,4-tetraaryl-1,3-butadiene derivatives related to the present invention in electrophotographic photoreceptors, see, for example, M. Kleinerman et al., J. Chem. Phys. ,37,
1825 (1962) and JP-A No. 52-24248, 1,1,
4,4-tetraphenyl-1,3-butadiene has been reported. However, this 1,1,4,4-tetraphenyl-1,3-butadiene and its derivatives are known alkyl, alkoxy, and halogen-substituted 1,1,4,4-tetraphenyl-1,3-
Butadiene has extremely low sensitivity and poor solubility in binder polymers. In addition, as an alkylamino group-containing derivative, 1,1,4,4-tetrakis(p-dimethylphenyl)-1,3-butadiene is used.
Chem. by CEHBawn et al.
Commun., 599, (1968), and JP-A-62-30255 discloses a tetraphenylbutadiene derivative represented by the following general formula (). (In the formula, R represents a lower alkyl group.) However, the 1,1,4,4-tetrakis(p-dimethylphenyl)-1,3-butadiene compound does not have the ability to retain an electrostatic charge and is substantially photosensitive. There is a drawback that it cannot be used as a body, and also,
The compound disclosed in No. 30255 does not have sufficient photoresponsiveness,
Furthermore, materials with excellent photoresponsiveness are desired. [Means for Solving the Problems] In view of the current situation, the present inventors developed 1,1,4,4-tetraaryl-1,3 as a charge transport substance.
- Focusing on butadiene derivatives, we conducted extensive research to find compounds suitable for creating even higher-performance electrophotographic photoreceptors.As a result, we found that an aryl group or a carbazole group having an amino group at the 1st and 4th positions. The 1,1,4,4-tetraaryl-1,3-butadiene derivative substituted with The present invention was completed based on the discovery that the present invention has low resistance, durability, and high response speed. That is, the present invention is based on the following general formula () (In the formula, Ar ₁ is an aromatic hydrocarbon group substituted with a dimethylamino group, a diethylamino group, a di-n-propylamino group, a di-n-butylamino group, a diphenylamino group, or a dibenzylamino group, or an N-substituted 1,1,4,4-tetraaryl-, which is a carbazole group, and _Ar2 represents an aromatic hydrocarbon group optionally substituted with an alkyl group or an alkoxy group)
The present invention provides an electrophotographic photoreceptor containing a 1,3-butadiene derivative as a charge transport material. In the compound () of the present invention, the substituent of the group Ar ₁ may be further substituted with a substituted amino group or may be substituted with an aromatic hydrocarbon group. Specific examples of the group Ar ₁ include dialkylaminophenyl group, diphenylaminophenyl group, dibenzylaminophenyl group, N-alkyl substituted carbazole group, N-phenyl substituted carbazole group, dialkylaminotolyl group, etc. can be mentioned. Also, the base
Specific examples of Ar ₂ include phenyl group, alkylphenyl group, alkoxyphenyl group, and the like. 1,1,4,4-tetraaryl- of the present invention
The 1,3-butadiene derivative (1) can be synthesized, for example, by the method of L. Horner et al. [Chem. Ber., 95, 581 (1962)] as follows. That is, diarylketone () and ethylene bisdiphenylphosphinoxide () are reacted in the presence of a base to form 1,1,
4,4-tetraaryl-1,3-butadiene () is obtained. This reaction formula is abbreviated below. (In the formula, Ar ₁ and Ar ₂ have the above-mentioned meanings.) This reaction is carried out under general reaction conditions, such as alcohols such as methanol and ethanol, ether, 1,2-dimethoxyethane, tetrahydrofuran, dioxane, etc. ethers, toluene,
Hydrocarbons such as xylene, aprotic polar solvents such as dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, potassium t-butoxide, sodium methoxide,
It is carried out in the presence of a base such as sodium ethoxide, sodium hydride, sodium amide.
The reaction may be carried out at 0 to 150°C for about 5 to 50 hours. Representative examples of the 1,1,4,4-tetraaryl-1,3-butadiene derivatives () obtained in this manner are illustrated below. Exemplary compound (1) 1,4-diphenyl-1,4-bis(4'-dimethylaminophenyl)-1,3-butadiene (2) 1,4-diphenyl-1,4-bis(4'-diethylamino phenyl)-1,3-butadiene (3) 1,4-di-p-tolyl-1,4-bis(4'-diethylaminophenyl)-1,3-butadiene (4) 1,4-bis- (4'-methoxyphenyl)-
1,4-bis(4″-diethylamino-2″-methylphenyl)-1,4-butadiene (5) 1,4-diphenyl-1,4-bis(4′-dipropylaminophenyl)-1,3 -Butadiene (6) 1,4-diphenyl-1,4-bis(4'-diphenylaminophenyl)-1,3-butadiene (7) 1,4-diphenyl-1,4-bis(4'- dibenzylaminophenyl)-1,3-butadiene (8) 1,4-diphenyl-1,4-bis(N-ethyl-3-carbazolyl)-1,3-butadiene (9) 1,4-diphenyl- 1,4-bis(N-methyl-3-carbazolyl)-1,3-butadiene (10) 1,4-di-m-tolyl-1,4-bis(N
-Methyl-3-carbazolyl)-1,3-butadiene (11) 1,4-diphenyl-1,4-bis(N-
Phenyl-3-carbazolyl)-1,3-butadiene (12) 1,4-bis-(p-methoxyphenyl)-
1,4-bis(N-phenyl-3-carbazolyl)-1,3-butadiene The compound according to the present invention has various isomers. For example, exemplified compound (2) is (trans,
There are three types: trans), (trans, cis), and (cis, cis), but even if it is one of these or a mixture of them in any ratio, it is not suitable for the purpose of the present invention. available for. The compound (2) of the present invention obtained as described above has excellent properties as a charge transport material in an electrophotographic photoreceptor in which the charge generation substance and the charge transport substance are each composed of separate substances. Next, an electrophotographic photoreceptor using the compound of the present invention will be explained by giving basic examples. FIG. 1 shows an example of an electrophotographic photoreceptor of the present invention, in which a charge generation layer 3 mainly composed of a charge generation substance 2 and a compound of the present invention () are uniformly coated on a conductive support 1. A photosensitive layer 5 comprising a charge transport layer 4 containing a photosensitive layer 5 is provided. That is, in the photoreceptor shown in FIG. 1, light transmitted through the charge transport layer reaches the charge generation substance dispersed in the charge generation layer and generates a charge, and the charge transport layer absorbs the injection of this charge. It receives the goods and transports them. To create the photoreceptor shown in Figure 1, first, a charge-generating substance is vacuum-deposited onto a conductive support, and a dispersion obtained by mixing and dispersing fine particles of the charge-generating substance with a binder as necessary is prepared. The charge generation layer is formed by applying a solution of a charge generation substance dissolved in a suitable solvent. After drying, if necessary, the layer thickness can be adjusted by surface finishing, for example, by a method such as puff polishing. Next, a solution containing the compound () of the present invention and a binder is applied onto this charge generation layer and dried to form a charge transport layer. Application is carried out using conventional means, such as a doctor blade, wire bar, etc. The thickness of the charge generation layer is 5μ or less, preferably 2μ
The thickness of the charge transport layer is 3 to 50μ, preferably 5 to 20μ. In addition, the compounding ratio of the compound of the present invention () in the charge transport layer is 10 to 90% by weight.
(hereinafter simply expressed as "%"), preferably 30 to 70%. FIG. 2 shows another example of the photographic photoreceptor of the present invention. A photosensitive layer 5 is provided by applying and drying a coating liquid in which the compound () is uniformly dissolved. The thickness of the photosensitive layer in this case is 5~
50μ, preferably 10-25μ. As the conductive support, a metal plate such as aluminum, a metal foil or a metal tube, a plastic film on which metal such as aluminum is vapor-deposited, or paper subjected to conductive treatment may be used. As the binder, polyester resin, polyvinyl chloride resin, acrylic resin, methacrylic resin, polystyrene resin, polycarbonate resin, etc. are used, and among them, polyester resin and polycarbonate resin are preferred. Examples of charge-generating substances include inorganic materials such as amorphous selenium, arsenic selenide, cadmium sulfide, and amorphous silicon; examples of organic materials include bisazo pigments; trisazo pigments;
Examples include phthalocyanine pigments; indigo pigments; perylene pigments; squalium pigments; polycyclic quinone pigments; and pyrylium dyes. The photoreceptor of the present invention obtained as described below has excellent characteristics such as extremely high sensitivity, high flexibility, no change in characteristics due to charging exposure, and high durability. [Example] Next, the present invention will be explained in detail with reference to Synthesis Examples, Examples, and Comparative Examples. Synthesis Example 1 Synthesis of 1,4-diphenyl-1,4-bis(4'-diethylaminophenyl)-1,3-butadiene (Exemplary Compound-2); Method of L. Horner et al. [Chem.Ber., 95 ,581
(1962)], 2.15 g of ethylene bisdiphenylphosphinoxide, 5 g of 4-diethylaminobenzophenone, and 3 g of potassium t-butoxide.
g to 100ml of dimethylformamide, and
After reacting at 60-120°C for 24 hours, it was poured into water. Extract with benzene, wash the benzene layer with water,
After drying over magnesium sulfate, benzene was distilled off under reduced pressure to obtain 5.8 g of crude product. This was purified by silica gel column chromatography to obtain 3 g of crystals (theoretical yield: 60.7%). Further, it was recrystallized from ethyl acetate to obtain 2.4 g of purified crystals with a temperature of mp 191-2°C. Synthesis Example 2 Synthesis of 1,4-diphenyl-1,4-bis(N-ethyl-3-carbazolyl)-1,3-butadiene (exemplified compound-8); N-ethyl-3-benzoylcarbazole 4.55
g, ethylene bisdiphenylphosphinoxide
3.3 g of potassium tert-butoxide and 3.36 g of potassium t-butoxide were reacted in 100 ml of dimethylformamide for 24 hours and then poured into water. After extraction with benzene, the benzene layer was washed with water, dried over magnesium sulfate, and then benzene was distilled off under reduced pressure to obtain 5.0 g of a crude product.
This was purified using silica gel column chromatography,
2.6 g of crystals were obtained (theoretical yield 28.9%). Further, recrystallize from ethyl acetate to obtain purified crystals at mp276℃ 2.0
I got g. Example 1 () 0.2 g of chlordian blue was mixed with 4 g of a dichloroethane solution containing 5% polycarbonate resin ("Iupilon E-2000" manufactured by Mitsubishi Gas Chemical Co., Ltd.), and after adding 20 ml of dichloroethane, a vibrating mill was added. A dispersion of the charge carrier-generating pigment is prepared by crushing the pigment to less than 1 μm using a wire bar, and this is applied onto a polyester film coated with aluminum using a wire bar, dried at 45°C, and then dispersed to a thickness of about 1 μm. A charge carrier generation layer was created.
On the other hand, 0.1 g of Exemplified Compound (2) was added to dichloroethane solution 2 containing 5% of the above polycarbonate resin.
A charge transport layer forming liquid is prepared by dissolving the charge transport layer forming liquid in the above charge carrier generating layer using a doctor blade so that the dry film thickness is approximately 15 μm, and is dried at 45°C. It was created. (2) The electrophotographic properties of this photoreceptor were measured by a static method using an electrostatic copying paper testing device "Model SP-428" (manufactured by Kawaguchi Denki Seisakusho). That is, the photoreceptor was charged by -6KV corona discharge for 5 seconds, and the surface potential Vo
(unit - volt), hold it for 5 seconds in a dark place, and then irradiate it with light with an illuminance of 5 lux using a tungsten lamp, and the amount of exposure necessary to attenuate the surface potential by 1/2 and 1/6. E _1/2 (lux·sec) and E 1/6 (lux·sec), and the surface residual potential V _R (volt) after irradiation with light at an illuminance of 5 lux for 20 seconds were measured. The results are shown in Table 1 below. Examples 2 to 4 Photoreceptors were prepared in the same manner as in Example 1 using Exemplary Compounds (3), (6), and (8), and their performance as photoreceptors was examined. The results are shown in Table 1. Examples 5 to 8 The chlordian blue used in Examples 1 to 4 was converted to γ-phthalocyanine (Toyo Ink Manufacturing Co., Ltd.).
A photoreceptor was prepared using exemplified compounds (2), (3), (6) and (8) in the same manner as in Example-1, except that the compound was changed to
The characteristics as a photoreceptor were investigated. The results are shown in Table 1. Examples 9 to 13 Titanyl phthalocyanine (Sanyo dye) was deposited on an aluminum film deposited on a polyester film.
Co., Ltd.) was vapor-deposited to a thickness of 0.1μ at 10 ⁻⁶ Torr. Furthermore, exemplified compound (1),
A charge transport layer forming liquid prepared by dissolving 0.1 g each of (2), (4), (5), and (7) was applied using a doctor blade to a dry film thickness of about 15 μm. 45
A photoreceptor was prepared by drying at ℃. The electrophotographic properties of these photoreceptors were measured in the same manner as in Example-1. The results are shown in Table 1. Comparative example 1 K. Takagi et al. [Bull.Chem.Soc.Jpn., 57, 1887
(1984)] method and W. Todros [J.Chem.Soc.,
1954, 2966], 1,1,4,4-tetraphenyl-1,3-butadiene (comparative compound-1) was synthesized. A photoreceptor was prepared in the same manner as in Example 1, except that Comparative Compound-1 was used instead of Exemplified Compound (2). Although the obtained photoreceptor was cloudy due to precipitation of Comparative Compound-1 over the entire surface of the film, its performance as a photoreceptor was investigated. The results are shown in Table 1. Comparative Example 2 1,1,4,4-tetrakis(p-methoxyphenyl)-1,3-butadiene (comparative compound-2) was synthesized by the method of Comparative Example-1, and this was synthesized in Example-
Similar to 1, an attempt was made to dissolve the polycarbonate resin in a dichloroethane solution containing the resin, but the resin did not dissolve and a photoreceptor could not be prepared. Comparative Example 3 CEH Bown et al. (Chem.Commun.599 (1968))
1,1,4,4-tetrakis(p-dimethylaminophenyl)-1,3- synthesized by the method of
A photoreceptor was prepared in the same manner as in Example-1 using butadiene (comparative compound-3), and its performance as a photoreceptor was examined. The results are shown in Table 1. Comparative Example 4 1,1- disclosed in JP-A-62-30255
Diphenyl-4,4-bis(4'-diethylaminophenyl)-1,3-butadiene (comparative compound-
A photoreceptor was prepared in the same manner as in Example 5 using 4), and its characteristics were investigated. The results are shown in Table 1.

〔Effect of the invention〕

The present invention provides 1,1,4,4-tetraaryl-
The present invention provides a 1,3-butadiene derivative which has properties useful as a material for electrophotographic photoreceptors, such as excellent electrostatic charge retention ability. However, the electrophotographic photoreceptor using the compound of the present invention is the best in the field of electrophotographic processes because it has high sensitivity, low residual potential, little optical fatigue even after repeated use, and excellent durability. It has the required properties and is industrially advantageous.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view of an example of the electrophotographic photoreceptor of the present invention. FIG. 2 is an explanatory cross-sectional view of another example of the electrophotographic photoreceptor of the present invention. FIG. 3 is a surface potential-exposure relationship curve for the compound (2) of the present invention and the comparative compound (4). 1... Conductive support, 2... Charge generating substance, 3
... Charge generation layer, 4 ... Charge transport layer containing a 1,1,4,4-tetraaryl-1,3-butadiene derivative, 5 ... Photosensitive layer.

Claims (1)

[Claims] 1. In an electrophotographic photoreceptor in which a photosensitive layer containing a charge-generating substance and a charge-transporting substance is provided on a conductive support, the charge-transporting substance has the following general formula (), (In the formula, Ar ₁ is an aromatic hydrocarbon group substituted with a dimethylamino group, a diethylamino group, a di-n-propylamino group, a di-n-butylamino group, a diphenylamino group, or a dibenzylamino group, or an N-substituted 1,1,4,4-tetraaryl-, which is a carbazole group, and _Ar2 represents an aromatic hydrocarbon group optionally substituted with an alkyl group or an alkoxy group)
An electrophotographic photoreceptor comprising a 1,3-butadiene derivative.