JPH0434741B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an organic photoconductor made of a specific Schiff base type compound, and particularly to an electrophotographic photoconductor containing this organic photoconductor in a photosensitive layer. Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been widely used in the photosensitive layer of electrophotographic photoreceptors. Photoreceptors using such inorganic photoconductors have several advantages as well as various disadvantages. Production costs are high due to difficult conditions and wear and tear of raw materials, and the selenium vapor-deposited film itself is extremely susceptible to heat and mechanical shock, and is extremely susceptible to crystallization depending on environmental conditions. In the case of cadmium sulfide, it is sensitive to humidity and poses a pollution problem except for photoreceptors coated with an insulating layer. In the case of zinc oxide, it is sensitized with a dye with low fastness, such as rose bengal, so there are problems such as deterioration due to electrical conduction and photofading due to corona charging. Furthermore, since the zinc oxide particles are a resin dispersion system, the surface smoothness, hardness, abrasion resistance, etc. of the photosensitive layer are also poor. On the other hand, compared to inorganic photoconductive materials, organic photoconductive materials
Many proposals have been made in recent years due to the advantages that the photosensitive layer is highly flexible, easy to manufacture, and a photoreceptor with stable electrophotographic characteristics can be obtained at a lower cost. Types of photoreceptors using organic photoconductive materials include (1) those in which a charge transfer complex is formed by a combination of an electron-donating compound and an electron-accepting compound (e.g., USP 3484237); (2) organic photoconductive materials; (3) conductors sensitized by adding dyes (for example, Japanese Patent Publication No. 48-25658); (3) pigments dispersed in hole- or electron-active matrices (for example, Japanese Patent Publication No. 47-30328; (1989-18545)), (4) functionally separated charge generation layer and charge transport layer (e.g., JP-A-49-105537), (5) eutectic complex consisting of dye and resin. components (e.g., JP-A-47-10785); (6) charge-transfer complexes containing organic pigments or inorganic charge-generating materials (e.g., JP-A-49-91648); (7) Others. Although some of these photoreceptors are practical, the current situation is that further improvements in sensitivity, durability, environmental stability, etc. are desired. Organic photoconductive materials used in such photoreceptors include high molecular materials such as poly-N-vinylcarbazole and low molecular materials such as the hydrazone compound described in JP-A No. 54-59143. .
Polymer type coatings generally have brittle coatings and have problems with film formability, flexibility, etc. If plasticizers are added to solve this problem, problems such as decreased sensitivity arise. On the other hand, for low-molecular type products, an appropriate binder can be selected and the above-mentioned drawbacks of high-molecular type products can be covered. As a result of research, it was discovered that a specific Schiff base type compound can be used as an organic photoconductive substance, eliminating the above-mentioned drawbacks, and having extremely excellent properties, thereby completing the present invention. That is, an object of the present invention is to provide an organic photoconductor and an electrophotographic photoreceptor having the same. The Schiff base type compound in the present invention is represented by the following general formula (1). In the formula, A and A' represent an optionally substituted aromatic ring group or an optionally substituted heterocyclic group, and B represents an optionally substituted aromatic ring group. The aromatic ring group of A is represented by a monovalent residue derived from benzene, naphthalene, etc., and the heterocyclic group is represented by a monovalent residue derived from carbazole, indole, etc., and these are lower alkyl, lower alkoxy,
It may be substituted with lower alkylamino, diphenylamino, ditolylamino, dibenzylamino, halogen, or the like. Similarly, the aromatic ring group of B is represented by a monovalent residue derived from benzene, naphthalene, etc., and these may be further substituted with lower alkyl, lower alkoxy, etc. The compound represented by the general formula (1) is synthesized, for example, as follows. Synthesis example 9.4 g of benzoguanamine and 14.9 g of P-dimethylaminobenzophenone were added to 120 ml of glacial acetic acid and refluxed for a total of 4 hours. The reaction solution was poured into 500 ml of water to remove the precipitate, which was dried and then reconsolidated with ethanol and then with benzene to obtain 18.3 g of the target compound S-1. Melting point 272-274℃. Compounds S-2 and below (described later) are also synthesized by subjecting a benzoguanamine derivative and various aldehydes to a dehydration condensation reaction according to the above synthesis method. Next, representative compounds are illustrated. The Schiff base type compound represented by general formula (1) is 1
Because of the basic effect and planar structure of the regularly arranged nitrogen atoms, it becomes a good charge transport agent and provides a highly sensitive and stable electrophotographic photoreceptor. That is, as an electrophotographic photoreceptor having a photosensitive layer containing a Schiff base type compound represented by general formula (1),
It can be applied to any of the photoreceptor types (1) to (7) using organic photoconductive substances described above. Among these, types (3) to (6) are desirable. Furthermore(4)
In particular, when a compound represented by the 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, it is particularly photosensitive. The body becomes more sensitive and the residual potential is lower. In this case, the decrease in sensitivity and increase in residual potential during repeated use can be reduced 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 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. This charge transport layer is preferably formed by applying a solution prepared by dissolving the compound represented by the general formula (1) and a binder in an appropriate solvent and drying the solution. Examples of the binder used here include polystyrene, polysulfone, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, polyester resin, alkyd resin, polycarbonate,
Examples include polyurethane and copolymer resins containing two or more repeating units of these resins, with polyester resins and polycarbonates being particularly preferred. Also, poly-N
- Photoconductive polymers which themselves have charge transport capabilities, such as vinyl carbazole, 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, the coating methods used when providing the charge transport layer include blade coating method,
Conventional methods such as Mayer bar coating, spray coating, dip coating, bead coating, air knife coating, curtain coating, etc. can be used. Further, the solvent used when forming this charge transport layer includes many useful organic solvents. Typical examples include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, and chlorobenzene, ketones such as acetone and 2-butanone, and halogenated aliphatic carbons such as methylene chloride, chloroform, and ethylene chloride. Examples include hydrogens, cyclic or linear ethers such as tetrahydrofuran and ethyl ether, and mixed solvents thereof. This charge transport layer can contain various additives. Such additives include diphenyl, diphenyl chloride, 0-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 dibutyl hydroxy toluene, 2, 2
-methylene-bis-(6-t-butyl-4-methylphenol), α-tocopherol, 2-t-
Octyl-5-chlorohydroquinone, 2,5-
Examples include phenolic compounds such as 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 at an extremely high rate. Preferred materials include selenium and selenium/tellurium. , selenium, arsenic, cadmium sulfide, amorphous silicon and other inorganic substances, pyrylium dyes,
Thiopyrylium dyes, triarylmethane 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 are shown below. Charge generating substances (1) Amorphous silicon (2) Selenium-tellurium (3) Selenium-arsenic (4) Cadmium sulfide (58) Methine squaritate dye (59) Indigo dye (CI No. 78000) (60) Thioindigo dye (CI No. 78800) (61) α, β, ε-type copper phthalocyanine 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. An electrophotographic photoreceptor is produced by using a photosensitive layer having a structure in which a charge generation layer containing the pigment described above is coated on a suitable support, and a charge transport layer is laminated on top of this charge generation layer. can be created by
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, phenol 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 ethylene-acrylic acid copolymer, etc. can be used. The thickness of this intermediate layer or adhesive layer is suitably 0.1 to 5 microns, preferably 0.5 to 3 microns. 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 this charge generation layer is suitably 5 microns or less, preferably 0.01 micron to 1 micron. Binders for dispersing the above 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 compound used in the present invention has hole-transporting 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, and charging/exposure is necessary. Then, in the exposed area, holes generated in the charge generation layer are injected into the charge transport layer, and then reach the surface to neutralize the negative charges, causing attenuation of the surface potential and creating an electrostatic contrast with the unexposed area. Various conventionally used developing methods can be used for visualization. Another specific example of an electrophotographic photoreceptor is
For example, using the above-mentioned compound as a charge transport substance,
A photosensitive layer consisting of the above pigment dispersed in a charge transport medium consisting of this and an insulating binder (the binder itself may be a charge transport material such as poly-N-vinylcarbazole) is used as a conductive layer. It may be formed on top. The insulating binder and charge transport material used in this case are:
For example, Japanese Patent Publication No. 52-1667, Japanese Patent Publication No. 47-30328,
Those disclosed in 47-18545 and the like can be used. The support used in the electrophotographic photoreceptor 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, vanadium, 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. According to the present invention, the sensitivity is significantly higher than that of electrophotographic photoreceptors using conventional organic photoconductors, and even when repeated charging and exposure are performed more than 10,000 times, the bright area potential increases and the dark area increases. No potential drop occurs. The organic photoconductor of the present invention can be used not only as an electrophotographic photoreceptor in an electrophotographic copying machine, but also in a wide range of electrophotographic application fields such as laser printers, CRT printer photoreceptors, and electrophotographic plate-making systems. be able to. This invention will be explained in detail below using specific 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 (degree of butyralization 63 mol%) 2
After dispersing g with a solution of 95 ml of ethanol, it was coated on the adhesive layer, and the coating amount after drying was 0.2
A charge generation layer of g/m ² was formed. Next, 5g of the compound S-1 was added to poly-4,4'-
A solution prepared by dissolving 5 g of dioxydiphenyl-2,2-propane carbonate (viscosity average molecular weight 30,000) in 150 ml of dichloromethane is applied onto the charge generation layer and dried to form a charge transport layer with a coating weight of 10 g/ ^m2 . did. The electrophotographic photoreceptor thus prepared was statically charged with corona at 5KV using an electrostatic copying paper tester Model SP-428 manufactured by Kawaguchi Electric Co., Ltd.
After holding it in the dark for 10 seconds, it was exposed to light at an illuminance of 5 lux to examine the charging characteristics. The charging characteristics of the electrophotographic 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 as E1/2 (lex.sec). Vo: 580V, Rv: 94%, E1/2: 8.2lux.sec Examples 2 to 8 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 Schiff base type compound S-2 described above were added.
A solution prepared by dissolving 5 g of ~7 in 150 ml of dichloromethane was applied onto the charge generation layer, dried, and the amount of coating was determined.
A charge transport layer 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 below.

[Table] Example 9 Selenium-tellurium (10% tellurium) was vacuum deposited on an aluminum plate to form a charge generation layer with a thickness of 0.8μ. 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 photoreceptor thus prepared were examined in the same manner as in Example 1, and the results are shown below. Vo: 610V, Rv: 89%, E1/2: 5.5lux.sec Example 10 5g of Schiff base compound (S-1) used in Example 1
and poly-N-vinylcarbazole (molecular weight 300,000)
Add 1.0 g of β-type copper phthalocyanine to a solution of 5 g dissolved in 150 ml of dichloromethane, and after dispersion, apply it on the casein layer of the aluminum plate with the casein layer used in Example 1, and after drying, the coating amount is 10 g. / ^m2 . The electrostatic charge of the electrophotographic photoreceptor thus prepared was measured in the same manner as in Example 1, and the results are shown below. However, the charging polarity was determined. Vo: 500V,
Rv: 77%, E1/2: 27.5lux.sec Example 11 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 assilion 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 electrophotographic photoreceptor thus prepared 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. Immediately thereafter, a positively charged developer (including toner and carrier) was cascaded onto the surface of the electrophotographic photoreceptor to obtain a good toner image on the surface of the photoreceptor.

Claims (1)

[Claims] 1. General formula (In the formula, A and A' represent an optionally substituted aromatic ring group or an optionally substituted heterocyclic group, and B represents an optionally substituted aromatic ring group.) .