JPH0243174B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photoreceptor for electrophotography, and more specifically, a layer containing a substance (hereinafter referred to as a charge-generating substance) that generates charge carriers when irradiated with light (hereinafter referred to as a charge-generating substance).
This is called the charge generation layer. ) and the charge generation layer accepts the generated charge carriers and transports them (hereinafter referred to as
It is called a charge transport material. ) (hereinafter referred to as a charge transport layer). Conventionally, photoconductors for electrophotography include inorganic photoconductors that use selenium and its alloys, photoconductors that have dye-sensitized zinc oxide dispersed in a binder resin, and organic photoconductors. 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). be. 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 due to its lack of flexibility, and is susceptible to heat and mechanical shock. It is sensitive and must be handled with care. In addition, zinc oxide photoreceptors are low in cost because they can be manufactured by coating zinc oxide onto a support, but they generally have low sensitivity, poor surface smoothness, hardness, tensile strength, and durability. It has mechanical drawbacks such as abrasion, and as a photoreceptor for plain paper copying machines, which is normally used repeatedly, there are many problems with durability. Also, TNF and
Photoreceptors using PVK charge transfer complexes have low sensitivity and are unsuitable as photoreceptors 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 laminated photoreceptor in which a thin film of organic pigment is formed on a conductive support (charge generation layer), and a layer mainly composed of a charge transport substance (charge transport layer) is formed on top of this, is different from conventional organic-based photoreceptors. Compared to photoconductors, photoconductors are attracting attention as photoconductors for plain paper copying machines because they generally have higher photosensitivity and stable chargeability, and some of them 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 Unexamined Patent Publication No. 84943/1983) is known. However, it is true that conventional laminated photoreceptors of this type have many advantages, but also have various drawbacks. Photoreceptors using perylene derivatives and oxadiazole derivatives shown in (1) have high manufacturing costs because their charge generation layer is formed by vacuum deposition, and even if there are no practical problems, they can be used for faster copying. There are problems such as insufficient sensitivity as a photoreceptor for machines. The photoreceptor using chlordiane blue and 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. , there are many drawbacks in the production of photoreceptors. In addition, the visible wavelength range is approximately
Since the wavelength ranged from 450 to 660 nm, image reproducibility of red originals was 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. Like the photoreceptor (2), its photosensitive wavelength range extends from approximately 450 to 700 nm, so it has the disadvantage of poor image reproducibility for red originals. 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 having a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer is a disazo compound represented by the following general formula (1). This is an electrophotographic photoreceptor characterized by comprising a layer containing a compound. General formula (1) [In the formula, A is

【formula】

[Formula] Or, (Here, R represents a bromine atom, NO ₂ or a CN group.) ] The laminated photoreceptor of the present invention is easy to manufacture, has high photosensitivity, and has a short wavelength range (450 to 660 nm), so it is excellent as a photoreceptor for copying machines. It is. The present invention will be explained in more detail below. First, specific examples of the charge generating substance used in the charge generating layer in the present invention, that is, the disazo compound represented by the general formula (1) above, are as follows.

【table】

[Table] The above disazo compound is commercially available 2,6-diaminoanthraquinone (Aldrich Chemical Co., Ltd.,
A coupling reaction is carried out by reacting a tetrazonium salt obtained by diazotizing (Milwankee) and the corresponding coupler (naphthol AS) with a base in a suitable organic solvent, such as N,N-dimethylformamide (DMF). It can be easily manufactured by carrying out the following steps. As an example, the production example of the disazo compound No. 1-1 is shown below, but other disazo compounds can also be easily produced according to this production example, except for changing the coupler. Production example: 35% in 14.3g of 2,6-diaminoanthraquinone
155 ml of HCl was added and the mixture was cooled to -5°C.
A solution of 9.0 g of 97% sodium nitrite dissolved in 30 ml of water was added dropwise to this over about 20 minutes. After finishing dropping -
The reaction mixture was stirred for an additional 2 hours at 5-0°C.
After pouring it into cold water, some insoluble matter was separated, and 40 ml of 42% hydroborofluoric acid was added to it. The precipitate was collected, washed with methanol, and then dried under reduced pressure to give a pale brown color. 22.6 g (86.3%) of anthraquinone-2,6-bisdiazonium bistetrafluoroborate was obtained as crystals. νN ₂ 2310cm ^-1 νC=0 1695cm ^-1 2.18g of tetrazonium salt obtained as above
and 3.42 g of 2-hydroxy-3-(m-bromphenylcarbamoyl)naphthalene in 300 ml of DMF.
Dissolve 1.64 g of sodium acetate in 14 ml of water.
was added dropwise over a period of about 5 minutes at room temperature (about 20°C). 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. Then, the crystals were washed with water and placed under reduced pressure for 80 min.
Dry at °C. 3.22g (68.2g) as a purple-red powder
%) of disazo compound No. 1-1 was obtained. Melting point: 300℃ or higher Elemental analysis results: Actual value Calculated value C (%) 60.92 61.03 H (%) 2.83 2.99 N (%) 8.74 8.90 Infrared absorption spectrum (KBr tablet method): νNH (secondary amide) 3250cm ^-1 νCO 1670cm ^-1 Next, specific examples of the charge transporting substance used in the charge generation layer in the present invention are as follows.

【table】

【table】

【table】
\

_CH3

【table】

【table】

【table】

【table】 \

C ₂ H ₅

【table】

【table】

【table】 \
C ₂ H ₅

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】 \

CH
₃

【table】

【table】

【table】

【table】 / /
2−331 1 −N −N
\ \
CH ₃ CH ₃
In addition to the above-mentioned exemplified compounds, among polymer substances, 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 supports used in the present invention include metal plates, metal drums, or metal foils made of aluminum, nickel, chromium, etc., and plastic films provided with thin layers of aluminum, tin oxide, indium oxide, chromium, palladium, etc. Paper or plastic film coated with or impregnated with a conductive substance is also used. The charge generation layer is made of a liquid in which a specific disazo compound represented by the general formula (1) shown above is made into fine particles by means such as a ball mill, and dispersed in an appropriate solvent.
Alternatively, if necessary, a dispersion in which a binder resin is dissolved is coated on a conductive support, and if necessary, the surface may be finished by a method such as buffing, or the film thickness may be changed. It has been adjusted. The thickness of this charge generation layer is 0.01 to 5 μm, preferably 0.05 to 2 μm, and the proportion of the disazo compound in the charge generation layer is 10 to 100% by weight, preferably 30 to 95% by weight.
Weight%. If the thickness of the charge generation layer is 0.01 μm or less, sensitivity is poor, and if it is 5 μm or less, potential retention is poor. In addition, the proportion of disazo pigment in the charge generation layer is 10
Sensitivity is poor below % by weight. The charge transport layer is formed by applying a solution of the various charge transport materials described above and a binder resin dissolved in a suitable solvent such as tetrahydrofuran onto the charge generation layer. Here, the proportion of the charge transport substance contained in the charge transport layer is 10 to 80% by weight,
Preferably it is 25 to 75% by weight, and the film thickness is 2 to 75% by weight.
It is 100 μm, preferably 5 to 40 μm. If the proportion of the charge transport substance contained in the charge transport layer 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 and the charge transport layer will become cloudy, which is not preferable. Further, if the thickness of the charge transport layer is 5 μm or less, the potential is not maintained well, and if the thickness is 40 μm or more, the residual potential becomes high. Examples of binder resins for the charge generation layer used herein include polyester resins, butyral resins, ethyl cellulose resins, epoxy resins, acrylic resins, vinylidene chloride resins, polystyrene, polybutadiene, and copolymers thereof. They may be used alone or in a mixture of two or more. Examples of binder resins for the charge transport layer include polycarbonate resins, polyester resins, polystyrene resins, polyurethane resins, epoxy resins, acrylic resins, silicone resins, and copolymers thereof. It is used in a mixture of more than one species. Furthermore, various additives can be added to the charge transport layer for the purpose of improving flexibility or durability. Examples of additives used for this purpose include halogenated paraffin, dialkyl phthalate, silicone oil, etc. In the photoreceptor of the present invention, if necessary, a barrier layer is provided between the conductive layer and the charge generation layer. An intermediate layer may be provided between the layer and the charge transport layer, and an overcoat layer may be provided on the charge transport layer. Further, the disazo compound of the general formula (1) 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). It can also be used. 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 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 A tetrahydrofuran solution (solid content concentration 2%) of polyester resin (Byron 200 manufactured by Chayobo Co., Ltd.) containing 76% of disazo compound No. 1-1 (solid content concentration 2%) 1260% by weight
parts by weight and 3,700 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto the aluminum surface of an aluminum-deposited polyester base (conductive support) using a doctor blade, and air-dried. , a charge generation layer with a thickness of about 1 μm was formed. On the other hand, charge transport material No. 2-5 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 with a doctor blade at 80°C for 2 minutes, then at 100°C for 5 minutes. A charge transfer layer having a thickness of about 20 μm was formed by drying for a minute, and a laminated photoreceptor No. 1 as shown in FIG. 1 was prepared. Examples 2 to 9 Example 1 except that the disazo compound and charge transport substance shown in Table 1 below were used instead of disazo compound No. 1-1 and charge transport substance 2-5 used in Example 1. Photoreceptors Nos. 2 to 9 were prepared in the same manner as described above. These photoreceptors No. 1 to 9 were negatively charged by performing -6KV corona discharge for 20 seconds using an electrostatic copying paper testing device (Kawaguchi Electric Seisakusho Co., Ltd., model SP428). Leave it in the dark for 20 seconds, measure the surface potential Vpo (V) at that time, then irradiate the surface with light using a tungsten lamp at an illumination intensity of 20 lux until the surface potential is 1/1 of Vpo.
Find the time (seconds) until it becomes 2, and calculate the exposure amount E1/2
(lux/second) was calculated. Table 1 shows the results.
Shown below.

[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. As a charge generation layer, N,N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide was deposited on an aluminum plate under 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, 5 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole,
A solution consisting of 5 parts by weight of polyester resin (manufactured by DuPont, Polyester Adhesive 49000) and 90 parts by weight of tetrahydrofuran was applied,
It was dried at ℃ for 10 minutes to form a charge transport layer with a thickness of about 10 μm, and Comparative Photoreceptor No. 1 was prepared. 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 using a doctor blade with a wet gap of 25μ, 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. A charge transport layer having a thickness of about 18 μm was formed by applying the coating using a doctor blade and drying to form a laminated comparative photoreceptor No. 2. 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 about 0.3μ. Formed. Then, on this charge generation layer,
9-ethylcarbazole-3-aldehyde 1-
A solution consisting of 10 parts by weight of methyl-1-phenylhydrazone, 10 parts by weight of polycarbonate resin (the same resin used in Example 1) and 80 parts by weight of tetrahydrofuran was applied using a doctor blade, dried and thickened. A charge transport layer having a thickness of approximately 13 μm was formed to prepare a laminated comparative photoreceptor No. 3. The spectral sensitivities of these comparative photoreceptors Nos. 1 to 3 and photoreceptors Nos. 3, 6, and 9 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, find the time (seconds) until the surface potential decays to -400 volts,
The half-reduced exposure amount (μW·sec/cm ² ) was calculated. on the other hand,
The potential difference actually obtained by exposure is obtained 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 (Volt・cm ²・μW ^-1・sec ^-1 ) was calculated and used as the sensitivity. The results are shown in FIGS. 2 to 5. Fig. 2: Photoconductor No. 3 Fig. 3: Photoconductor No. 6 Fig. 4: Photoconductor No. 9 Fig. 5 □・: Comparative photoconductor No. 1 ○・: Comparative photoconductor No. 2 △・: Comparative Photoreceptor No. 3 The results shown in Table 1 and FIGS. 2 to 5 show that the photoreceptor of the present invention has high sensitivity and its sensitive wavelength range is about 460 to 600 nm. In addition, in manufacturing the electrophotographic photoreceptor of the present invention, the vacuum evaporation method used to create Comparative Photoreceptor No. 1 or the organic amine used to create Comparative Photoreceptor No. 2 was used. Since there is no need to do this, it is also advantageous in terms of manufacturing. Reference Examples 1-3 In Example 1, 2-5 as the charge transport substance
Photoreceptors of Reference Examples 1 to 3 were prepared in the same manner as above, except that compounds having the following three types of substitutions as substitution A in general formula (1) of the present application were used as charge generating substances. When the Vo and E1/2 characteristics of Reference Examples 1 to 3 were measured, the results shown in Table 2 were obtained. From the results in Tables 1 and 2, it was found that the sensitivity of the photoreceptor of the present invention was significantly superior to that of the comparative photoreceptor.

[Table] Further, photoreceptors Nos. 3, 6, and 9 of the present invention were installed in a copying machine Ricopy 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. 2 to 5 are graphs 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 layered electrophotographic photoreceptor having a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer contains a disazo compound represented by the following general formula (1). An electrophotographic photoreceptor comprising: General formula (1) [In the formula, A is [Formula] [Formula] or, (Here, R represents a bromine atom, NO ₂ or a CN group.) ]