JPS6310418B2 - - 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 substance 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, it has been difficult to put them into practical use to date because sufficient film-forming properties have not yet been achieved, and inorganic photoconductive materials lack sensitivity, durability, and stability against environmental changes. This was because it was inferior compared to. In addition, hydrazone compounds disclosed in U.S. Pat. No. 4,150,987, triarylpyrazoline compounds described in U.S. Pat. Low-molecular organic photoconductive materials have been proposed, such as the 9-styrylanthracene compound described above and the 4-chlorooxazole compound described in JP-A-55-53278. 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 cannot be said to be sufficient in terms of sensitivity. SUMMARY OF THE INVENTION An object of the present invention is to provide a new electrophotographic photoreceptor that overcomes the above-mentioned drawbacks or disadvantages. Another object of the present invention is to provide novel organic photoconductive materials. Another object of the present invention is to provide a compound suitable as a charge transport substance 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 at least one hydrazone compound represented by the following general formula (1). General formula (1) In the formula, X ₁ represents an atomic group necessary to complete an aromatic hydrocarbon ring such as a benzene ring, a naphthalene ring, an anthracene ring, etc. X ₂ represents an atomic group necessary to complete a heterocycle such as a thiazoline ring, thiazole ring, benzothiazole ring, naphthothiazole ring, oxazoline ring, oxazole ring, benzoxazole ring, naphthoxazole ring, or quinoline ring. These aromatic hydrocarbon rings and heterocycles include halogen atoms such as chlorine atom, bromine atom, and iodine atom, alkyl groups such as methyl group, ethyl group, propyl group, butyl group, and amyl group, benzyl group,
Aralkyl groups such as phenethyl group, α-naphthylmethyl group, β-naphthylmethyl group, methoxy group,
Alkoxy groups such as ethoxy, propoxy and butoxy groups, dimethylamino groups, dialkylamino groups such as diethylamino, dipropylamino and diptylamino groups, diphenylamino groups,
Diarylamino groups such as ditolylamino groups and dixylylamino groups, dialkylamino groups such as dibenzylamino groups and diphenethylamino groups, cyclic amino groups such as morpholino groups, pyrrolidino groups, and piperidino groups, acetyl groups, propionyl groups, It can also be substituted with an acetyl group such as a butyryl group, benzoyl group, or trioyl group, or an aryl group such as a phenyl group, tolyl group, or xylyl group. R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms, substituted or unsubstituted alkyl groups (e.g. methyl group, ethyl group, propyl group, butyl group, amyl group, octyl group, 2-chloroethyl group, 3 -Chloropropyl group, 2-bromoethyl group, 3-bromopropyl group, 2-methoxyethyl group, 3-bromopropyl group, 2-methoxyethyl group, 3-methoxypropyl group, 4-methoxybutyl group, 2-ethoxyethyl group group, 3-ethoxypropyl group, 4-ethoxybutyl group, 2-hydroxyethyl group, 3-hydroxypropyl group, 3-sulfopropyl group, etc.), substituted or unsubstituted aralkyl group (for example, benzyl group, phenethyl group, chlorobenzyl group, dichlorobenzyl group, methoxybenzyl group, dimethoxybenzyl group, α-naphthylmethyl group, β-naphthylmethyl group) or substituted or unsubstituted aryl group (e.g. phenyl group, tolyl group, xylyl group, biphenyl group) group, chlorophenyl group, dichlorophenyl group, trichlorophenyl, methoxyphenyl group, dimethoxyphenyl group, α-naphthyl group, β-naphthyl group, etc.). Specific examples of the hydrazone compound represented by the general formula (1) are listed below. Compound example These compounds can be used alone or in combination of two or more. The hydrazone compound represented by the general formula (1) is, for example, represented by the general formula (In the formula, R ₁ , R ₂ , R ₃ and X ₁ have the same meanings as above) and the aldehyde represented by the general formula (In the formula, R ₄ and X ₂ have the same meanings as above.) It can be easily synthesized by a conventional method using a hydrazone represented by the following. Next, the hydrazone compound used in the present invention will be specifically explained using synthesis examples. Synthesis Example (Synthesis of the Exemplified Hydrazone Compound H-(1)) In a 200 ml three-necked flask, in general formula (2), the atomic group necessary for X ₁ to complete the benzene ring, and R ₁ ,
4.31 g (0.021 mol) of aldehyde where R ₂ and R ₃ are each a methyl group, 3.84 hydrazine where X ₂ is the atomic group necessary to complete the benzothiazole ring in general formula (3), and R ₄ is a methyl group g (0.021
mol), 30 ml of ethanol, and 2 ml of acetic acid were added and reacted at 60°C for 30 minutes. Next, this reaction solution was poured into the water from step 4 and neutralized with sodium carbonate, and the resulting precipitate was separated, washed with water, and dried. This precipitate was repeatedly recrystallized with acetone, with a melting point of 157.0°C to 159.0°C.
3.42 g of yellow crystals (yield 45% based on aldehyde)
I got it. Elemental analysis Molecular formula C ₂₁ H ₂₂ N ₄ S Calculated value Analytical value C 69.57% 69.48% H 6.13% 6.20% N 15.46% 15.43% 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 the preferred type is 1 Electron-donating substance A charge transfer complex is formed by a combination of and an electron-accepting substance. 2 Organic photoconductor sensitized by adding dye. 3 Pigment dispersed in a hole matrix. 4 Functionally separated into 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. etc., among which types 3 to 6 are desirable. Furthermore, in the case of four types of photoreceptors, in other words, 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. In this case, 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, the four types of photoreceptors will be described 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 viewpoint of physical strength and, in some cases, chargeability, it is preferable 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,
Examples include vinyl acetate resin, phenol resin, epoxy resin, polyester resin, alkyd resin, polycarbonate, polyurethane, and copolymer resins containing two or more of the repeating units of these resins. In particular, polyester resin and polycarbonate are used. This is preferable. Furthermore, a photoconductive polymer that itself has charge transporting ability, such as poly-N-vinylcarbazole, can also be used as a binder. 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. Further, as the coating method used when providing the charge transport layer, conventional methods such as blade coating method, Mayer bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain coating method, etc. are 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, naphthalene, toluene, xylene, mesitylene, and chlorobenzene;
Ketones such as acetone and 2-butanone, halogenated aliphatic hydrocarbons such as methylene chloride, chloroform and ethylene chloride, cyclic or linear ethers such as tetrahydrofuran and ethyl ether, or mixed solvents thereof. can be mentioned. 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, triarylmetal dyes, thiazine dyes, cyanine dyes, phthalocyanine pigments, perylene pigments, indigo pigments, thioindigo pigments, quinacridone pigments,
Examples include organic substances such as 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 These pigments can be used alone or in combination of two or more. 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 is produced by coating a charge generation layer containing the pigment described above on a suitable support,
A structure in which a charge transport layer is laminated on this charge generation layer can be created by using a photosensitive 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~
5μ, preferably 0.5 to 3μ is suitable. 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. Binders for dispersing the aforementioned compounds include polyvinyl butyral, polymethyl methacrylate, polyester, polyvinylidene chloride, polyamide, chlorinated rubber, polyvinyltoluene, polystyrene, polyvinyl chloride, ethyl cellulose,
Examples include polyvinylpyridine, styrene-maleic anhydride copolymer, and the like. The proportion of such a binder in the charge generation layer is preferably 80% by weight or less, preferably 50% by weight or less of the total weight of the charge generation layer. 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 substance, and an insulating binder (the binder itself is a charge transport substance 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, Japanese Patent Application Laid-open No. 47-30328, and Japanese Patent Publication No. 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 application fields such as CRT printers and electrophotographic plate making systems. According to the present invention, the sensitivity is significantly higher than that of electrophotographic photoreceptors using conventional organic photoconductive materials, and moreover, repeated charging and exposure are not required.
There is no increase in bright area potential and no decrease in dark area potential even when the test is performed over 10,000 times. 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 a disazo pigment having the following structure, Butyral resin (butyralization degree 63 mol%) 2g
After dispersing it 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 hydrazone compound H-(1), poly-
A solution prepared by dissolving 5 g of 4,4'-dioxydiphenyl-2,2-propane carbonate (viscosity average molecular weight 30,000) in 150 ml of dichloromethane was applied onto the charge generation layer and dried to produce a charge transport coating with a coating weight of 10 g/ ^m2 . formed a layer. The electrophotographic photoreceptor thus prepared was statically charged with corona at 5KV using Kawaguchi Electric Co., Ltd.'s electronic copying paper tester Model SP-428, held in a dark place for 10 seconds, and then exposed at an illuminance of 5lux. The charging characteristics were investigated. The charging characteristics of this photoreceptor are shown using the initial potential Vo (V), the potential retention rate for 10 seconds in the dark as Rv (%), and the half-attenuation exposure amount E _1/2 (lux·sec). Vo: 520V Rv: 88% E _1/2 : 4.8lux·sec Examples 2 to 10 The following pigments were vacuum-deposited on an aluminum plate with a thickness of 100μ to form a charge generation layer with a thickness of 0.15μ. Next, 5 g of polyester resin (Vylon 200: Toyobo Co., Ltd.) and the above-mentioned hydrazone compound H
-(2)~H-(10) 5g each in dichloromethane
Apply the solution dissolved in 150ml onto the charge generation layer and dry it.
A charge transport layer with a coating weight of 11 g/m ² was formed. The charging characteristics of the electrophotographic photoreceptor thus prepared were examined in the same manner as in Example 1, and the results are shown in Table 1.
It was shown to.

【table】

[Table] Example 16 Selenium-tellurium (10% tellurium) was vacuum deposited on an aluminum plate to form a charge generation layer with a thickness of 0.8 μm. 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, and the results are shown below. Vo: 600V Rv: 86% E _1/2 : 3.4lux・sec Example 17 Hydrazone compound H-(1)5 used in Example 1
g and poly-N-vinylcarbazole (molecular weight 30
1.0g of β-type copper phthalocyanine was added to a solution of 5g) dissolved in 150ml of dichloromethane, and after dispersion, it was applied on the casein layer of the aluminum plate with the casein layer used in Example 1, and after drying. Amount: 10g/
^m2 . Charge measurement of the photoreceptor thus prepared was carried out in the same manner as in Example 1, and the results are shown below. However, the charging polarity was determined. Vo: 510V Rv: 78% E _1/2 : 17.8lux·sec Example 18 A 0.2 mm thick molybdenum plate (substrate) whose surface was cleaned was fixed at a predetermined position in a glow discharge deposition 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 induction coil to generate 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,
After turning off the high frequency power supply and 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.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a layer containing at least one compound represented by the following general formula (1). General formula (1) (In the formula, X ₁ represents _the atomic group necessary to complete the optionally substituted aromatic hydrocarbon ring.
Indicates the atomic groups necessary to complete the optionally substituted heterocycle. R ₁ , R ₂ , R ₃ and R ₄ are hydrogen atoms,
It represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aralkyl group, or a substituted or unsubstituted aryl group. )