JPH026047B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photosensitive layer containing a novel organic photoconductive material comprising a hydrazone compound. Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide are known as photoconductive materials used in electrophotographic photoreceptors. These photoconductive materials have a number of advantages, such as being able to be charged to an appropriate potential in the dark, having little charge dissipation in the dark, or quickly dissipating the charge when irradiated with light. However, it also has various drawbacks. For example, selenium-based photoreceptors easily crystallize due to factors such as temperature, humidity, dust, and pressure. Especially when the ambient temperature exceeds 40°C, crystallization becomes significant, resulting in decreased charging performance and white spots on images. There is a drawback when this occurs. Furthermore, selenium-based photoreceptors and cadmium sulfide-based photoreceptors have the disadvantage that stable sensitivity and durability cannot be obtained when used under high humidity over time. In addition, zinc oxide photoreceptors require the sensitizing effect of sensitizing dyes such as rose bengal, but such sensitizing dyes cause charge deterioration due to corona charging and photobleaching due to exposure light, so it may take a long time. It has the disadvantage that it cannot provide a stable image over a long period of time. On the other hand, various organic photoconductive polymers including polyvinylcarbazole have been proposed, but these polymers are superior in terms of film formability and lightness compared to the inorganic photoconductive materials mentioned above. However, the practical application of photoconductive materials to date has been hampered by the fact that sufficient film formation properties have not yet been achieved, and inorganic photoconductive materials have poor sensitivity, durability, and stability against environmental changes. This was because it was inferior to the material. Also, US Patent Nos. 4150987 and 4278747
No. 2939483, British Publication No. 2034493, European Patent Publication No. 2034493, European Patent Publication No.
Low-molecular organic photoconductive materials such as hydrazone compounds disclosed in Publication No. 13172 have been proposed. By appropriately selecting the binder used, these low-molecular-weight organic photoconductive materials can overcome the film-forming problems that had been a problem in the field of organic photoconductive polymers. However, it has drawbacks such as a low initial potential and large dark decay. Also, after keeping it in a bright place for a certain period of time,
Due to its poor ability to recover its original charge characteristics (photo memory) when returned to a dark place, it causes various problems in practical use. An object of the present invention is to provide a new electrophotographic photoreceptor that eliminates the above-mentioned drawbacks or disadvantages. Another object of the invention is to provide new organic photoconductive materials. Another object of the present invention is to provide an electrophotographic photoreceptor with improved initial potential characteristics and dark decay. Another object of the present invention is to provide an electrophotographic photoreceptor having improved photo memory properties. Another object of the present invention is to provide a novel compound suitable as a charge transport material for use in a photosensitive layer having a laminated structure of a charge generation layer and a charge transport layer. This object of the present invention is achieved by an electrophotographic photoreceptor having a layer containing a hydrazone compound represented by the following general formula (1). General formula (1) In the formula, Ar represents a polycyclic aromatic hydrocarbon ring group, such as a naphthyl group, an anthralyl group, or a pyrenyl group. These aromatic rings include, for example, halogen atoms such as chlorine atoms and bromine atoms, alkyl groups such as methyl, ethyl, propyl, and butyl groups, alkoxy groups such as methoxy, ethoxy, propoxy, and butoxy groups, It can also be substituted with a di-substituted amino group such as a dimethylamino group, a diethylamino group, a dipropylamino group, a dibutylamino group, a dibenzylamino group, a diphenylamino group, and the like. R ₁ , R ₂ and R ₃ are
Alkyl groups (e.g., methyl, ethyl, propyl, butyl, amyl, hexyl, octyl, etc.), substituted alkyl groups (e.g., 2-chloroethyl, 3-chloropropyl, 2-hydroxyethyl) , 3-hydroxypropyl group, 2
-methoxyethyl group, 3-methoxypropyl group,
4-methoxybutyl group, 2-ethoxyethyl group,
3-ethoxypropyl group, 4-ethoxybutyl group, etc.), aralkyl group (e.g., benzyl group, phenethyl group, naphthylmethyl group, etc.), substituted aralkyl group (e.g., methoxybenzyl group, dimethoxybenzyl group, methylbenzyl group, ethyl benzyl group, chlorobenzyl group, dichlorobenzyl group, dimethylaminobenzyl group, diethylaminobenzyl group, etc.), aryl group (phenyl group,
naphthyl group, etc.) or substituted aryl group (tolyl group, xylyl group, ethyl phenyl group, diethylphenyl group, methoxyphenyl group, ethoxyphenyl group, dimethylaminophenyl group, diethylaminophenyl group, dipropylaminophenyl group) , chlorophenyl group, dichlorophenyl group, etc.). n is 0 or 1. Representative examples of the hydrazone compound represented by the general formula (1) are shown below. hydrazone compound These compounds can be used alone or in combination of two or more. These hydrazone compounds represented by the general formula (1) are represented by the general formula (In the formula, R ₂ and R ₃ are synonymous with the above.) A hydrazone represented by the general formula (In the formula, Ar, R ₁ and n are synonymous with the above.) It can be easily synthesized by a condensation reaction with a ketone represented by the following. Next, methods for synthesizing representative compounds among the hydrazone compounds used in the present invention will be shown. Synthesis Example 1 (Synthesis of the above-mentioned hydrazone compound No. (1)) In a 200 ml three-necked flask, 40 ml of ethanol was added.
ml, acetic acid 40ml, N,N-diphenylhydrazine
2.2g (0.012mol) and structural formula Inject 2.0 g (0.012 mol) of the ketone shown in
The reaction was allowed to proceed at room temperature for 1 hour. Next, water was added to form a precipitate, which was then separated and washed repeatedly with water. Next, recrystallization from a solution consisting of methyl ethyl ketone and ethanol gave 1.17 g of yellow crystals (yield 29%). Elemental analysis: Molecular formula C ₂₄ H ₂₀ N ₂ Calculated value (%) Experimental value (%) C 87.71 85.76 H 5.95 5.93 N 8.34 8.31 Other hydrazone compounds used in the present invention can be synthesized in the same manner. The electrophotographic photoreceptor containing the hydrazone compound represented by the general formula (1) can be applied to any type of electrophotographic photoreceptor using an organic photoconductive substance, but preferable types include (1) electron-donating photoreceptors; A charge transfer complex formed by a combination of a magnetic substance and an electron-accepting substance. (2) An organic photoconductor sensitized by adding a dye. (3) Pigment dispersed in a hole matrix. (4) Functionally separated charge generation layer and charge transport layer. (5) Those whose main components are a eutectic complex consisting of a dye and a resin and an organic photoconductor. (6) A charge transfer complex containing an organic or inorganic charge generating material. Among them, types (3) to (6) are desirable. Furthermore, in the case of a photoreceptor of type (4), that is, a hydrazone compound represented by general formula (1) is used as a charge transport material for the charge transport layer of a photoreceptor that is functionally separated into two layers: a charge generation layer and a charge transport layer. When used, the sensitivity of the photoreceptor is particularly improved and the residual potential is low. Further, in this case, a decrease in sensitivity and an increase in residual potential during repeated use can be suppressed to a practically negligible level. Therefore, we will discuss type (4) photoreceptor in detail. The layer structure requires a conductive layer, a charge generation layer, and a charge transport layer, and the charge generation layer can be either above or below the charge transport layer, but in electrophotographic photoreceptors of the type that are used repeatedly, it is mainly From the standpoint of physical strength and, in some cases, incidental properties, it is desirable to laminate a conductive layer, a charge generation layer, and a charge transport layer in this order. An adhesive layer may be provided as necessary for the purpose of improving the adhesiveness between the conductive layer and the charge generation layer. The charge transport layer used in the present invention is preferably formed by applying a solution of the hydrazone compound represented by the general formula (1) and a binder dissolved in a suitable solvent and drying the solution. Examples of the binder used here include polysulfone, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin,
Examples include polyester resins, alkyd resins, polycarbonates, polyurethanes, and copolymer resins containing two or more repeating units of these resins, with polyester resins and polycarbonates being particularly preferred. Furthermore, photoconductive polymers that themselves have charge transporting ability, such as poly-N-vinylcarbazole, can also be used as binders. The blending ratio of this binder and charge transport compound is
Preferably, the charge transport compound is contained in an amount of 10 to 500 parts by weight per 100 parts by weight of the binder. The thickness of this charge transport layer is between 2 and 100 microns, preferably between 5 and 30 microns. In addition, as a coating method used when providing a charge transport layer, a conventional method such as a blade coating method, a Mayer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, etc. is used. be able to. Further, the solvent used in forming the charge transport layer of the present invention includes many useful organic solvents. Typical examples include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, and chlorobenzene, acetone,
- Examples include ketones such as butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform, and ethylene chloride, cyclic or linear ethers such as tetrahydrofuran and ethyl ether, and mixed solvents thereof. can. The charge transport layer of the present invention can contain various additives. Such additives include diphenyl, diphenyl chloride, O-terphenyl,
P-terphenyl, dibutyl phthalate, dimethyl glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, dilaurylthiopropionate, 3,5-dinitrosalicylic acid,
Various fluorocarbons, silicone oil, silicone rubber or dibutylhydroxytoluene,
2,2'-methylene-bis-(6-t-butyl-4
-methylphenol), α-tocopherol, 2
-t-octyl-5-chlorohydroquinone,
Examples include phenolic compounds such as 2,5-di-t-octylhydroquinone. As the charge generation material used in the charge generation layer, any material can be used as long as it absorbs light and generates charge carriers with extremely high efficiency. Preferred materials include selenium, selenium/tellurium, Inorganic substances such as selenium, arsenic, cadmium sulfide, amorphous silicon, pyrylium dyes,
Thiopyrylium dyes, triarylmethane dyes, thiazine dyes, cyanine dyes, phthalocyanine pigments, perylene pigments, indigo pigments,
Examples include organic substances such as thioindigo pigments, quinacridone pigments, squaric acid pigments, azo pigments, and polycyclic quinone pigments. Representative examples of charge generating substances that can be used in the present invention are shown below. Charge generating substances (1) Amorphous silicon (2) Selenium-tellurium (3) Selenium-arsenic (4) Cadmium sulfide (58) Methine squarate dye (59) Indigo dye (CI No. 78000) (60) Thioindigo dye (CI No. 78800) (61) β-type copper phthalocyanine These pigments are used singly or in combination of two or more. be able to. Further, the crystal form of these pigments may be α type, β type, or any other type, but β type is particularly preferred. The electrophotographic photoreceptor of the present invention can be obtained by coating a charge generation layer containing the pigment described above on a suitable support;
It can be produced by using a photosensitive layer having a structure in which a charge transport layer is laminated on the charge generation layer. In this type of electrophotographic photoreceptor, an intermediate layer may be provided on a suitable support, a charge generation layer containing the aforementioned pigment may be formed thereon, and a charge transport layer may be formed thereon. This intermediate layer prevents the injection of free charges from the conductive support to the photosensitive layer when the photosensitive layer having a laminated structure is charged, and also serves as an adhesive that holds the photosensitive layer integrally bonded to the conductive support. It shows the action as a layer. This intermediate layer is made of metal oxide such as aluminum oxide, polyethylene, polypropylene, acrylic resin,
Methacrylic resin, vinyl chloride resin, phenolic resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane, polyimide resin, vinylidene chloride resin, vinyl chloride-vinyl acetate copolymer, casein, gelatin, polyvinyl alcohol, nitrocellulose, water-soluble A polyethylene-acrylic acid copolymer or the like can be used. The thickness of this intermediate layer or adhesive layer is 0.1μ~
A suitable value is 5μ, preferably 0.5 to 3μ. Further, a laminated structure may be used in which the charge generation layer is provided on the charge transport layer, and in this case, an appropriate surface protection layer may be formed. The charge generation layer can be provided by means such as vacuum deposition, sputtering, glow discharge or coating depending on the type of charge generation material used. When coating, the charge generating material is used as a binder.
There are cases where it is provided free, cases where it is provided as a resin dispersion, and cases where it is provided as a homogeneous solution of a binder and a charge generating material. When dispersing pigments, known methods such as ball mills and attritors can be used to disperse pigment particles.
It is desirable that the thickness be 5 μ or less, preferably 2 μ or less, and most preferably 0.5 μ or less. The pigment can also be applied by dissolving it in an amine solvent such as ethylenediamine. Conventional methods such as blade, Mayer bar, and spray dipping are used for application. The thickness of the charge generation layer used in the present invention is suitably 5 microns or less, preferably 0.01 micron to 1 micron. Examples of the binder for dispersing the charge generating substance include polyvinyl butyral, polymethyl methacrylate, polyester, polyvinylidene chloride, polyamide, chlorinated rubber, polyvinyltoluene, polystyrene, polyvinyl chloride, ethylcellulose, polyvinylpyridine, and styrene. Examples include maleic anhydride copolymers.
The proportion of such a binder in the charge generation layer is 80% by weight or less, preferably 50% by weight or less of the total weight of the charge generation layer.
It is desirable that the amount is less than % by weight. Further, if necessary, the surface of the charge generation layer can be polished to a mirror finish in order to uniformly inject carriers into the charge transport layer above the charge generation layer. The hydrazone compound used in the present invention has hole transport properties, and when using a photoreceptor in which a conductive layer, a charge generation layer, and a charge transport layer are laminated in this order, the surface of the charge transport layer must be negatively charged.・When exposed to light, holes generated in the charge generation layer are injected into the charge transport layer in the exposed area, and then reach the surface to neutralize the negative charge, causing a decrease in surface potential and creating an electrostatic contrast between the exposed area and the unexposed area. arise. Various conventionally used developing methods can be used for visualization. As another specific example of the electrophotographic photoreceptor of the present invention, for example, the above-mentioned hydrazone compound is used as a charge transport material, and an insulating binder (the binder itself is a charge transport material such as poly-N-vinylcarbazole) is used. A photosensitive layer may be formed on the conductive layer by dispersing the pigment described above in a charge transporting medium comprising: As the insulating binder and charge transport material used in this case, those disclosed in, for example, Japanese Patent Publications No. 52-1667, 47-30328, and 47-18545 can be used. The support used in the electrophotographic photoreceptor of the present invention may be any type of conductive layer conventionally used as long as it is imparted with conductivity. Specifically, metal sheets or metals such as aluminum, panadium, molybdenum, chromium, cadmium, titanium, nickel, copper, zinc, palladium, indium, tin, platinum, gold, stainless steel, and brass are vapor-deposited or laminated. Examples include plastic sheets. The electrophotographic photoreceptor of the present invention can be used not only for electrophotographic copying machines, but also for laser printers,
It can also be widely used in electrophotographic applications such as CRT printers and electrophotographic plate making systems. According to the present invention, the initial potential is higher than that of electrophotographic photoreceptors using conventional organic photoconductive materials;
Moreover, it has the advantage of reducing dark decay. Furthermore, the electrophotographic photoreceptor of the present invention has better photo memory properties than conventional ones, and is therefore practically effective. Hereinafter, the present invention will be explained according to examples. Example 1 Ammonia aqueous solution of casein (11.2 g of casein, 1 g of 28% ammonia water, 222 ml of water) on an aluminum plate.
Coated with Meyer bar and dried, coating amount 1.0g/m ²
An adhesive layer was formed. Next, 5 g of bisazo pigment having the following structure, Butyral resin (degree of butyralization 63 mol%) 2
After dispersing g with a solution dissolved in 95 ml of ethanol, it was coated on the adhesive layer and the coating amount after drying was 0.2 g/
A charge generation layer of m ² was formed. Next, 5 g of the exemplified hydrazone compound No. (1)
and poly-4,4'-dioxydiphenyl-2,
2′-propane carbonate (viscosity average molecular weight
30000) dissolved in 150 ml of dichloromethane was applied onto the charge generation layer and dried until the coating amount was 10 g/
An electrophotographic photoreceptor was prepared by forming a charge transport layer of ^m2 . The initial potential, sensitivity, dark decay, and photo memory properties of the electrophotographic photoreceptor prepared in this way were measured using the electrostatic copying paper tester "Model SP-" manufactured by Kawaguchi Electric Co., Ltd.
408". At this time, corona charging was performed at -5K volts using a static method, and the charging potential at this time was taken as the initial potential (V ₀ ). The dark decay (V ₅ ) is
After corona charging, the charged potential was measured when the sample was held in a dark place for 5 seconds. Sensitivity is measured by the amount of exposure (E1/2 lux seconds) required for the potential (V ₅ ) after dark decay to attenuate by half, and photo memory property is measured by exposing the photoreceptor to 1000 lux. After holding for 5 minutes,
Evaluation was made by measuring the time required to recover the original charging characteristics. These results are shown in Table 1. Table 1 V ₀ : -590 volts V ₅ : -570 volts P _M : 2 minutes E1/2: 4.8 Lux・sec Comparative Examples 1 to 3 In place of hydrazone compound No. (1) used in Example 1, A comparative electrophotographic photoreceptor (Comparative Sample 1) was prepared in the same manner except that diethylaminobenzaldehyde-N,N-diphenylhydrazone of the following formula (A) was used. Similarly, Comparative Samples 2 and 3 were substituted with the following formula (B) in place of hydrazone compound No. (1) used in Example 1.
and (C). The charging characteristics of each of Comparative Samples 1 to 3 were measured in the same manner as in Example 1. These results are shown in Table 2.

[Table] An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 1, except that the hydrazone compounds listed in Table 3 below were used in place of hydrazone compound No. (1) used in Example 1. Then, its charging characteristics were measured. These results are also listed in Table 4.

[Table] Example 15 5 g of the above-exemplified hydrazone compound No. (5) and 5 g of copolyester of bisphenol A and terephthalic acid-isophthalic acid (molar ratio of terephthalic acid and isophthalic acid 1:1) were added to 150 ml of dichloromethane. 1.0 g of β-type copper phthalocyanine was added to the dissolved solution, and after dispersion, it was applied onto the casein layer of the aluminum plate provided with the casein layer used in Example 1, and the coating amount after drying was 10 g/m ² . did. The charging of the photoreceptor thus prepared was measured in the same manner as in Example 1. The results are shown in Table 4. However, the charging polarity was taken into account. Table 4 V ₀ : +520 Volts V ₅ : +490 Volts P _M : 4 minutes E1/2 : 12.7 Lux・sec Comparative Example 4 In place of hydrazone compound No. (5) used in Example 15, Comparative Example 2 was used. A photoreceptor was prepared in exactly the same manner as in Example 15, except that the hydrazo compound used was used, and its charging characteristics were examined. The results are shown in Table 5. Table 5 V ₀ : +340 volts V ₅ : +230 volts P _M : 40 minutes E1/2: 37 Lux・sec Example 16 The following pigments were vacuum deposited on a 100μ thick aluminum plate,
A charge generation layer with a thickness of 0.15μ was formed. Next, polyester resin (Byron 200 Toyobo
Co., Ltd. and 5 g of the above-mentioned exemplary hydrazone compound No. (21) dissolved in 150 ml of dichloromethane were applied onto the charge generation layer and dried to form a charge transport layer with a coating weight of 11 g/m ² . The charging characteristics of the electrophotographic photoreceptor thus prepared were examined in the same manner as in Example 1. The results are shown in Table 6. Table 6 V ₀ : -560 volts V ₅ : -550 volts P _M : 2 minutes E1/2 : 5.4 Lux・sec Comparative example 5 Comparative example in place of hydrazone compound No. (21) used in Example 16 A photoreceptor was prepared in exactly the same manner as in Example 16, except that the hydrazone compound used in Example 3 was used, and its charging characteristics were measured. The results are shown in Table 7. Table 7 V ₀ : -390 volts V ₅ : -280 volts P _M : 20 minutes E1/2: 11.7 lux sec Example 17 Selenium/tellurium (10% tellurium) was vacuum deposited on an aluminum plate, and the thickness A charge generation layer of 0.8μ was formed. Next, the same charge transport layer as used in Example 1 was coated and dried to give a coating weight of 11 g/m ² . The charging characteristics of the electrophotographic photosensitive plate thus prepared were examined in the same manner as in Example 1. The results are shown in Table 8. Table 8 V ₀ : -590 volts V ₅ : -570 volts P _M : 2 minutes E1/2 : 3.3 Lux・sec Example 18 Glow discharge evaporation of a 0.2 mm thick molybdenum plate (substrate) with a cleaned surface It was fixed at a predetermined position in the tank. Next, the inside of the tank was evacuated to a vacuum level of approximately 5×10 ⁻⁶ torr. After that, the input voltage of the heater was increased to stabilize the molybdenum substrate temperature at 150℃. After that, hydrogen gas and silane gas (15% by volume relative to hydrogen gas) were introduced into the tank and stabilized at 0.5 torr by adjusting the gas flow rate and the main valve of the deposition tank. Next, 5MHz high-frequency power was applied to the dielectric coil to generate a glow discharge inside the coil in the tank, resulting in an input power of 30W. An amorphous silicon film was grown on the substrate under the above conditions, and the same conditions were maintained until the film thickness reached 2 μm, after which glow discharge was discontinued. Then the heating heater,
The high frequency power supply was turned off, and after waiting for the substrate temperature to reach 100°C, the hydrogen gas and silane gas outflow valves were closed, and after the inside of the tank was once lowered to below 10 ^-5 torr, the pressure was returned to atmospheric pressure, and the substrate was taken out. Next, a charge transport layer was formed on this amorphous silicon layer in exactly the same manner as in Example 1. The photoreceptor thus obtained was placed in a charging exposure experimental device, charged with corona at 6 kV, and immediately irradiated with a light image. The light image was illuminated through a transmission test chart using a tungsten lamp light source. Thereafter, a good toner image was obtained on the photoreceptor surface by immediately cascading a charged developer (including toner and carrier) onto the photoreceptor surface. Example 19 An aqueous solution of hydroxypropyl cellulose was applied to an aluminum plate and dried to form an adhesive layer with a coating weight of 0.6 g/m ² . Next, 5 g of poly-N-vinylcarbazole, 5 g of the exemplified hydrazone compound No. (1), and 0.1 g of 2.4.7-trinitrofluorenone were dissolved in 150 ml of dichloromethane, and then 1.0 g of the bisazo pigment used in Example 1 was dissolved. After dispersion, the photosensitive layer was coated on the adhesive layer and dried to form a photosensitive layer with a coating weight of 11 g/m ² . The charging of the photoreceptor thus prepared was measured in the same manner as in Example 1. The results are shown in Table 9. However, the charging polarity was taken into account. Table 9 V ₀ : +510 volts V ₅ : +480 volts P _M : 3 minutes E1/2: 13.7 Lux・sec

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a layer containing at least one hydrazone compound represented by the following general formula (1). General formula (1) (In the formula, Ar represents an optionally substituted polycyclic aromatic hydrocarbon ring group. _{R 1} , R ₂ and R ₃ are substituted or unsubstituted alkyl groups, substituted or unsubstituted aralkyl groups, or substituted or represents an unsubstituted aryl group. n is 0 or 1.)