JPH0336223B2 - - Google Patents

Description

[Detailed description of the invention]

Regarding the photoreceptor for electrophotography of the present invention, more specifically, a layer containing a substance that generates charge carriers (hereinafter referred to as a charge-generating substance) when irradiated with light (hereinafter referred to as a charge-generating substance)
A multilayer electrophotographic photosensitive layer consisting of a charge generation layer) and a layer containing a substance (hereinafter referred to as a charge transport material) that receives and transports charge carriers generated by the charge generation layer (hereinafter referred to as a charge transport layer). Regarding the body. Conventionally, there have been inorganic photoreceptors for electrophotography, such as those using selenium and its alloys, or photoreceptors with dye-sensitized zinc oxide dispersed in a binder resin, and organic photoreceptors. So,
A typical example is one using a charge transfer complex of 2,4,7-trinitro-9-fluorenone (hereinafter referred to as TNF) and poly-N-vinylcarbazole (hereinafter referred to as PVK). but,
Although these photoreceptors have many advantages, it is also true that they also have various disadvantages. For example, the currently widely used selenium photoreceptor has difficult manufacturing conditions and high manufacturing costs, is difficult to process into a belt shape due to its lack of flexibility, and is sensitive to heat and mechanical shock. Therefore, care must be taken when handling it. Zinc oxide photoreceptors are low in cost because they can be manufactured by applying inexpensive zinc oxide to a support, but they generally have low sensitivity and poor surface smoothness, hardness, tensile strength, and abrasion resistance. It has mechanical drawbacks such as durability, and as a photoreceptor for plain paper copying that is normally used repeatedly, there are many problems such as durability. Furthermore, a photoreceptor using a charge transfer complex of TNF and PVK has low sensitivity and is unsuitable as a photoreceptor for high-speed copying machines. In recent years, extensive research has been carried out to eliminate the drawbacks of these photoreceptors, and in particular, various organic photoreceptors have been proposed. Among them, a thin film of organic pigment is formed on a conductive support (charge generation layer),
Laminated photoreceptors, in which a layer mainly composed of a charge transporting material (charge transport layer) is formed, generally have higher sensitivity and stable chargeability compared to conventional organic photoreceptors. Since then, it has been attracting attention as a photoreceptor for plain paper copying machines, and some are in practical use. Conventional laminated photoreceptors of this type include: (1) one in which a thin layer of a perylene derivative vacuum-deposited is used as a charge generation layer and an oxadiazole derivative is used as a charge transport layer (see U.S. Pat. No. 3,871,882); ), (2) Using a thin layer formed by coating an organic amine solution of chlordian blue as the charge generation layer,
(3) A thin layer formed by coating an organic solvent dispersion of a distyrylbenzene-based disazo compound as a charge generation layer, One in which a hydrazone compound is used in the charge transport layer (see Japanese Patent Application Laid-open No. 84943/1983) is known. However, it is true that conventional laminated photoreceptors of this type have many advantages, but also have various drawbacks. That is, the photoreceptor using the perylene derivative and oxadiazole derivative shown in (1) has a high manufacturing cost because its charge generation layer is formed by vacuum evaporation, and even if there is no practical problem, it is faster to manufacture. There are problems such as insufficient sensitivity as a photoreceptor for copying machines. The photoreceptor using chlordiane blue and a hydrazone compound shown in (2) has good sensitivity, but requires the use of organic amines (e.g. ethylenediamine), which are generally difficult to handle, as a coating solvent to form the charge generation layer. Yes, there are many drawbacks in making photoreceptors. Furthermore, since the visible wavelength range extends from approximately 450 to 660 nm, image reproducibility of red originals is poor. Therefore, when actually implemented in a copying machine, a filter is required to cut out red light, which is disadvantageous in the design of the copying machine. The photoreceptor using a distyrylbenzene-based disazo compound and a hydrazone compound shown in (3) is very advantageous in terms of manufacturing because a charge generation layer can be easily formed by coating a dispersion of the disazo compound. , (2), its photosensitive wavelength range extends from approximately 450 to 700 nm, so it has the disadvantage of poor image reproducibility for red originals. etc. In view of the above drawbacks, the present inventor has developed a laminated photoreceptor that is easy to manufacture, has high sensitivity, and has a photosensitive wavelength range in the short wavelength range (that is, has excellent image reproducibility for red originals). As a result of extensive research with the aim of developing a photoreceptor, we discovered that a laminated photoreceptor in which the charge generation layer was constructed using a specific disazo compound as a charge generation substance could achieve the above objectives. It is a completed invention. That is, the electrophotographic photoreceptor of the present invention is a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, wherein the charge generation layer has the general formula (). (In the formula, X represents a substituted or unsubstituted aromatic ring or heterocycle, and Ar represents a substituted or unsubstituted aromatic ring or heterocycle.) . Specific examples of the aromatic ring in X in general formula () include benzene ring, naphthalene ring, etc.
Specific examples of the heterocycle include an indole ring, a carbazole ring, and a benzofuran ring. Further, specific examples of the aromatic ring in Ar include a benzene ring, a naphthalene ring, etc., and specific examples of the hetero ring include a dibenzofuran ring, a carbazole ring, etc. Substituents on the aromatic ring or heterocycle include lower alkyl groups such as methyl, ethyl, propyl, and butyl; lower alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy; fluorine; Halogen atoms such as chlorine, bromine, and iodine, halomethyl groups such as trifluoromethyl, carboxyl groups or lower alkyl esters such as ethyl ester thereof, lower alkylamino groups such as dimethylamino and diethylamino groups, cyano groups, nitro group, sulfonic acid (-SO ₃ Na) group, and the like. The laminated photoreceptor of the present invention is easy to manufacture, has high sensitivity, and has a sensitive wavelength range in the short wavelength range (450 to 600 nm), making it an excellent photoreceptor for copying machines. be. The present invention will be explained in more detail below. First, specific examples of the charge-generating substance used in the charge-punching layer in the present invention, that is, the disazo compound represented by the general formula () above, are as follows.

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[Table] These disazo compounds are 2,7-diaminoanthraquinones that can be synthesized according to the method described in the literature (Ryohei Oda, Industrial Chemistry Magazine 42, pp. 895-903 (1939) published by the Chemical Society of Japan). A tetrazonium salt obtained by diazotizing by a conventional method,
The corresponding couplers (naphthol ASs) can be easily produced by carrying out a coupling reaction with a base in a suitable organic solvent such as N,N-dimethylformamide (DMF). As an example, below is the above No. 1-13.
An example of the production of a disazo compound is shown below, but other disazo compounds can also be easily produced according to this production example, except for changing the coupler. Production example: 36% in 4.76g of 2,7-diaminoanthraquinone
Add 34 ml of HCl, cool the mixture to -5°C, add 3.0 g of 97% sodium nitrite to 10 ml of water.
ml solution was added dropwise over about 15 minutes. After the dropwise addition was completed, the mixture was stirred for another 20 minutes at approximately 0°C, and then
The reaction mixture was poured into 200 ml of cold water and the insoluble portion was separated. Subsequently, add 42% hydroborofluoric acid to the solution 10
ml of anthraquinone-2,7-bisdiazonium bistetrafluoroborate was collected as a precipitate, washed with methanol, and dried under reduced pressure to obtain 4.56 g (52.3
%) was obtained. The infrared absorption spectrum (KBr tablet method) of this product was as follows: V N2 2275 cm ^-1 V _CO 1690 cm ^-1 . 2.18 g of tetrazonium salt obtained as above
and 3.63 g of 2-hydroxy-3-phenylcarbamoylnaphthalene (naphthol AS).
Dissolve in 300ml of DMF and add 1.64ml of sodium acetate to this.
A solution prepared by dissolving G in 14 ml of water was added dropwise at room temperature (about 20°C) over about 5 minutes. After the dropwise addition was completed, the mixture was further stirred at the same temperature for 2 hours, and then precipitated crystals were collected. Next, 300 ml of DMF was added to the crystals and stirred at 80°C for 2 hours, then the crystals were collected again and this operation was repeated twice. Thereafter, the crystals were washed with water and dried at 80°C under reduced pressure. 2.75 g (70.0%) of disazo compound No. 1-13 was obtained as a purple-red powder. The physical properties of this disazo compound No. 1-13 were as follows. (a) Melting point; 300℃ or higher (b) Elemental analysis results;

[Table] (c) Infrared absorption spectrum (KBr tablet method); V _NH (secondary amide) 3250 cm ^-1 V _CO 1675 cm ^-1 Next, show specific examples of charge transport substances used in the charge transport layer in the present invention. The example is as follows.

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[Table] In addition to the above-mentioned exemplified compounds, polymer substances such as poly-
N-vinylcarbazole, halogenated-poly-N
- vinyl carbazole, polyvinylpyrene, or bromopyrene-formaldehyde condensation resin,
Condensation resins such as N-ethylcarbazole-formaldehyde condensation resin, and low molecular weight substances such as oxazole derivatives, oxadiazole derivatives, and nitro derivatives of fluorenone are all effective. FIG. 1 is an enlarged sectional view of an electrophotographic photoreceptor showing an embodiment of the present invention. This photoreceptor is constructed such that a charge generation layer 22 and a charge transport layer 33 are provided on a conductive support 11 to form a photosensitive layer 44 . The conductive support used in the present invention includes a metal plate, metal drum, or metal foil made of aluminum, nickel, chromium, etc.;
Plastic films provided with a thin layer of tin oxide, indium oxide, chromium, palladium, etc., and paper or plastic films coated with or impregnated with a conductive substance are used. The charge generation layer 22 is made of a liquid in which a specific disazo compound represented by the general formula () shown above is made into fine particles by means such as a ball mill, and dispersed in a suitable solvent, or if necessary, a binder resin is added thereto. A dissolved dispersion liquid is coated onto a conductive support 11, and if necessary, the surface is finished by a method such as puff polishing, and the film thickness is adjusted. The thickness of the charge generation layer 22 is 0.01 to 5 μm, preferably 0.05 to 2 μm, and the proportion of the disazo compound in the charge generation layer 22 is 10 to 100% by weight, preferably 30 to 95% by weight. The thickness of the charge generation layer 22 is
If it is 0.01 μm or less, the sensitivity is poor, and if it is 5 μm or more, the potential retention is poor. Furthermore, if the proportion of the disazo pigment in the charge generation layer is less than 10% by weight, the sensitivity is poor. The charge transport layer 33 is formed by coating the charge generation layer with a solution in which the various charge transport substances described above and a binder resin are dissolved in a suitable solvent such as tetrahydrofuran. Here, the ratio of the charge transport substance contained in the charge transport layer 33 is 10 to
The amount is 80% by weight, preferably 25 to 75% by weight, and the film thickness is 2 to 100 μm, preferably 5 to 40 μm. If the proportion of the charge transport substance contained in the charge transport layer 33 is less than 10% by weight, the sensitivity will be poor, and if it is more than 80% by weight, the film will become brittle or crystals will precipitate, making the charge transport layer 33 cloudy, which is undesirable. Furthermore, if the thickness of the charge transport layer 33 is 2 μm or less, the potential is not maintained well;
If the thickness is 100 μm or more, the residual potential becomes high. Examples of the binder resin for the charge generation layer 22 used here include polyester resin, butyral resin, ethyl cellulose resin, epoxy resin, acrylic resin, vinylidene chloride resin, polystyrene,
Examples include polybutadiene and copolymers containing at least one of these monomers, which may be used alone or in a mixture of two or more. Further, as the binder resin for the charge transport layer 33, polycarbonate resin, polyester resin,
Examples include polystyrene, polyurethane resin, epoxy resin, acrylic resin, silicone resin, and copolymers containing at least one of these monomers, which may be used alone or in a mixture of two or more. Furthermore, various additives can be added to the charge transport layer 33 for the purpose of improving flexibility or durability. Examples of additives used for this purpose include halogenated paraffin, dialkyl phthalate, and silicone oil. barrier layer,
An intermediate layer may be provided between the charge generation layer 22 and the charge transport layer 33, and an overcoat layer may be provided on the charge transport layer 33. Further, the disazo compound of the general formula () according to the present invention can be used as a dispersed photoreceptor by dispersing it as fine particles in a binder resin (a charge transporting substance may be added if necessary). You can also do that. The structure of the present invention is as described above, and as is clear from the Examples and Comparative Examples described later, the electrophotographic photoreceptor of the present invention is easier to manufacture than the conventional laminated type photoreceptor, and The photosensitive wavelength range is in the short wavelength range (approximately 450 to 600 nm), and it has excellent properties such as high sensitivity and stable characteristics even when the photoreceptor is used repeatedly. EXAMPLES Next, the present invention will be specifically explained using Examples, but the embodiments of the present invention are not limited thereby. Example 1 76 parts by weight of disazo compound No. 1-13, 1260 parts by weight of a tetrahydrofuran solution (solid content concentration 2%) of polyester resin (Vylon 200, manufactured by Toyobo Co., Ltd.), and 3700 parts by weight of tetrahydrofuran were placed in a ball mill. The resulting dispersion was applied using a doctor blade onto the aluminum surface of an aluminum-deposited polyester base (conductive support) and air-dried to form a charge generation layer with a thickness of about 1 μm. did. On the other hand, charge transport material No. 2-327 was
Part by weight, polycarbonate resin (Panlite
After mixing and dissolving 2 parts by weight of K1300 (manufactured by Teijin Ltd.) and 16 parts by weight of tetrahydrofuran to form a solution,
This was applied onto the charge generation layer using a doctor blade and dried at 80°C for 2 minutes and then at 100°C for 5 minutes to form a charge transport layer with a thickness of about 20 μm, and the laminated photoreceptor shown in FIG. Created No.1. Examples 2 to 39 In place of disazo compound No. 1-13 and charge transport substance No. 2-327 used in Example 1, the following table-
Photoreceptors Nos. 2 to 39 were prepared in the same manner as in Example 1 except that the disazo compound and charge transport substance shown in Example 1 were used.
It was created. These photoconductors No. 1 to 39 were negatively charged by performing -6KV corona discharge for 20 seconds using an electrostatic copying paper testing device (manufactured by Kawaguchi Electric Seisakusho Co., Ltd., model SP 428). After that, the surface potential was left in a dark place for 20 seconds, and the surface potential Vpo (V) was measured. Then, the surface was irradiated with light using a tungsten lamp at an illuminance of 4.5 lux, and the surface potential was determined to be Vpo.
Find the time (seconds) it takes for the exposure to become 1/2 of E.
1/2 (lux·sec) was calculated. The results are shown in Table-1.

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[Table] Comparative Example 1 A laminated photoreceptor described in US Pat. No. 3,871,882 using a perylene derivative as a charge generation layer and an oxadiazole derivative as a charge transport layer was prepared as follows. N,N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide as a charge generating substance was deposited on an aluminum plate under the conditions of a vacuum degree of 10 ^-5 mmHg, a deposition source temperature of 350°C, and a deposition time of 3 minutes. A charge generation layer was formed by vacuum evaporation. Next, on this charge generation layer, 5 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole and 5 parts by weight of polyester resin (manufactured by DuPont, Polyester Adhesive 49000) were added. and a solution consisting of 90 parts by weight of tetrahydrofuran,
It was dried at 120° C. for 10 minutes to form a charge transport layer with a thickness of about 10 μm, thereby producing Comparative Photoreceptor No. 1. Comparative Example 2 A laminated photoreceptor described in Japanese Patent Publication No. 55-42380, using chlordiane blue as the charge generation layer and a hydrazone compound as the charge transport layer, was prepared as follows. A solution consisting of 25 parts by weight of Chlordiane blue, 1240 parts by weight of ethylenediamine, 990 parts by weight of n-butylamine and 2740 parts by weight of tetrahydrofuran was applied onto the aluminum surface of the aluminum-deposited polyester base with a wet gap of 25 μm using a doctor blade and dried. , a charge generation layer was formed. Next, a solution consisting of 10 parts by weight of 4-diethylaminobenzaldehyde 1,1-diphenylhydrazone, 10 parts by weight of polycarbonate resin (the same resin used in Example 1), and 80 parts by weight of tetrahydrofuran was then applied onto the charge generating layer. , applied using a doctor blade and dried to a thickness of approximately 18μ
Comparative laminated photoreceptor No.
2 was created. Comparative Example 3 A laminated photoreceptor described in JP-A-55-84943 using a distyrylbenzene-based disazo compound as the charge generation layer and a hydrazone compound as the charge transport layer was prepared as follows. did. 4′,4″-bis[2-hydroxy-3-(2,4
-dimethylphenylcarbamoyl)-1-naphthylazo]-1,4-distyrylbenzene 20 parts by weight,
Polyvinyl butyral (Denka Butyral #4000
-1, manufactured by Tokyo Denki Kagaku Co., Ltd.), 7 parts by weight of polymethyl methacrylate (Dyanal BR-80, manufactured by Mitsubishi Rayon Co., Ltd.), and 300 parts by weight of tetrahydrofuran were milled in a ball mill for 3 hours. After diluting this dispersion with 2,700 parts by weight of tetrahydrofuran, it was applied onto the aluminum surface of an aluminum-deposited polyester base (conductive support) using a doctor blade and dried to form a charge generation layer with a thickness of approximately 0.3 μm. Formed. Then, 9-ethylcarbazole-3-aldehyde-
10 parts by weight of 1-methyl-1-phenylhydrazone,
10 parts by weight of polycarbonate resin (same resin used in Example 1) and 80 parts by weight of tetrahydrofuran
A solution consisting of parts by weight was applied using a doctor blade and dried to form a charge transport layer having a thickness of about 13 μm, thereby producing a laminated comparative photoreceptor No. 3. The spectral sensitivities of these comparative photoreceptors Nos. 1 to 3 and photoreceptors No. 10 and No. 19 of the present invention were measured in accordance with the following measurement procedure in order to examine their sensitive wavelength ranges. First, the photoreceptor is charged to a surface potential of -800 volts or more by corona discharge in a dark place, dark decayed until the surface potential reaches -800 volts, and when the surface potential reaches -800 volts, the monochromator The photoreceptor was irradiated with monochromatic light of 1 μW/cm ² using a spectrophotometer. Then, the time (seconds) until the surface potential attenuated to -400V was determined, and the half-reduced exposure amount (μW·sec/cm ² ) was calculated. On the other hand, the potential difference actually obtained by exposure is determined by subtracting the potential attenuation due to dark decay from the apparent potential difference of 400 volts obtained by exposure, and the light decay rate is calculated from this potential difference and the above-mentioned halved exposure amount. (Volt・cm ²・μW ⁻¹・sec ⁻¹ ) was calculated and defined as the sensitivity. The results are shown in FIG. In FIG. 2, ○ indicates photoconductor No. 10 of the present invention, ◎ indicates photoconductor No. 19 of the present invention, × indicates comparative photoconductor No. 1,

[Table] represents comparative photoreceptor No. 2, and ▲ represents comparative photoreceptor No. 3. From the results shown in Table 1 and FIG. 2, it can be seen that the photoreceptor of the present invention has high sensitivity, and its sensitive wavelength range is about 460 to 600 nm. In addition, in producing the electrophotographic photoreceptor of the present invention, the vacuum evaporation method used in producing comparative photoreceptor No. 1 or the organic amine used in producing comparative photoreceptor No. 2 was used. Since there is no need to use
It is also advantageous in terms of manufacturing. Further, photoconductors No. 10 and No. 19 of the present invention were installed in a copier P-500 manufactured by Ricoh Co., Ltd., and image production was repeated 10,000 times. As a result, clear images were obtained from all photoreceptors. From this, it can be understood that the photoreceptor of the present invention has extremely excellent durability.

[Brief explanation of drawings]

FIG. 1 is an enlarged sectional view showing an example of the structure of the electrophotographic photoreceptor of the present invention. FIG. 2 is a graph showing the spectral sensitivity characteristics of the photoreceptor of the present invention and a comparative photoreceptor. 11... Conductive support, 22... Charge generation layer,
33... Charge transport layer, 44... Photosensitive layer.

Claims (1)

[Scope of Claims] 1. A laminated photosensitive layer comprising a charge generation layer and a charge transport layer is provided on a conductive support, the charge generation layer having the following general formula: (In the formula, X represents a substituted or unsubstituted aromatic ring or heterocycle, and Ar represents a substituted or unsubstituted aromatic ring or heterocycle.) Photoreceptor for electrophotography.