JPH0566581B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to an electrophotographic photoreceptor and an electrophotographic method, and particularly to an electrophotographic photoreceptor suitable for a laser beam printer and an electrophotographic method. [Background of the Invention] Conventionally, charge generating substances for electrophotographic photoreceptors include organic substances such as phthalocyanine pigments disclosed in Japanese Patent Application Laid-open No. 59-15253, and tellurium to arsenic substances disclosed in Japanese Patent Publication No. 50-15137. -Many glassy selenium-based inorganic substances have been proposed. On the other hand, as a charge transport material, JP-A-52-
Various compounds have been proposed, such as poly N-vinylcarbazole compounds as shown in Japanese Patent Publication No. 77730 and pyrazoline derivatives as shown in Japanese Unexamined Patent Publication No. 105537/1983, and have already been put to practical use as photoconductors for copying machines. In recent years, a method of printing using an electrophotographic method using a laser as a type of high-speed printer has been devised. In particular, when a semiconductor laser is used as a light source, the light source section can be made very small.
This has the advantage that the printer can be made smaller, its power consumption can be greatly reduced, and it can print at high speed. Furthermore, organic photoreceptors have the advantage that they can be disposed of by incineration after use. However, conventional organic photoreceptors have lower surface hardness than inorganic photoreceptors, and therefore have a drawback of inferior wear resistance.
Therefore, when used repeatedly over a long period of time, the photoconductive layer wears out and the film thickness decreases, resulting in a drawback in the long-term stability of electrophotographic properties. For electrophotographic photoreceptors, for example, Japanese Patent Publication No. 59-9905
As described in the above publication, there is a proposal in which the polymer material used for the protective layer is characterized by being soluble in lower alcohols, and melamine resin is described among various polymers. However, matters related to the properties of melamine resin, such as the number of bound formaldehyde,
No consideration is given to the number of butyl ether groups, the number of methylol groups, the number average molecular weight, etc. According to the conventional concept, melamine resins are thermosetting resins that are insoluble in lower alcohols. In fact, the publication does not mention any examples in which melamine resin is used. In addition, as the binder resin for the charge generation layer, polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic esters, and methacrylic esters are used, as described in JP-A-58-7642. , phenoxy resin, polysulfone, polyvinyl acetal, polycarbonate, polyester,
Examples include various polymers such as cellulose ester, cellulose ether, urethane resin, and epoxy resin. Generally, insulating and adhesive resin is used. In a composite electrophotographic photoreceptor, a charge-transporting layer coating is usually applied during formation of the charge-transporting layer in order to form a charge-generating layer on a conductive support and further form a charge-transporting layer thereon. Depending on the solvent contained in the liquid,
There was a problem that the binder resin of the charge generation layer was easily eluted and the electrophotographic properties were deteriorated, and it was necessary to take this point into consideration during production. [Object of the Invention] The object of the present invention is to provide an electrophotographic photoreceptor with excellent adhesiveness and abrasion resistance (durability) using a resin composition with excellent solvent resistance, and a reversal development method using the same. A method of electrophotography is provided. [Summary of the Invention] In the electrophotographic photoreceptor of the present invention, the resin that binds the photoconductive substance of the organic photoconductive layer contains an alkyl etherified melamine/formaldehyde resin alone or a resin that can be cured by reacting with the resin. It is characterized by the fact that it is Furthermore, in the electrophotographic method of the present invention, the electrophotographic photoreceptor is charged to impart photosensitivity, exposed to light to create an electrical latent image of the original image, and then developed with toner to visualize this latent image. The method is characterized in that the toner image is then transferred onto a sheet of paper, and the residual surface charge on the photoreceptor is erased by irradiating it with erase light. The organic photoconductive layer to which the present invention is applied may be divided into a charge transport layer and a charge generation layer, and in that case, at least one layer may contain the above-mentioned melamine resin. Further, an intermediate layer may be provided between the two layers, an intermediate layer may be provided between the support and the photoconductive layer, or a protective layer may be provided on the photoconductive layer. It may also be a melamine resin-containing composition. In general, factors that determine the lifespan of electrophotographic photoreceptors, especially organic photoreceptors, due to long-term repeated use are factors other than corona discharge of the charge transport material and deterioration due to light, etc., as well as friction with paper (transfer paper) and developer. Examples include the occurrence of external scratches due to oxidation and a decrease in film thickness due to abrasion. In particular, since the surface of an organic photoreceptor is mainly composed of a charge transport substance and a binder resin,
The surface hardness is significantly lower than that of inorganic photoreceptors.
Therefore, wear and the occurrence of external scratches due to long-term repeated use are unavoidable, and are a major factor in reducing the lifespan. However, it has been conventionally known to form a protective layer containing resin as a main component on an organic photoconductor for the purpose of improving surface hardness. However, the conventional ones had drawbacks such as insufficient hardness and electrophotographic properties, particularly sensitivity, which were significantly reduced by the formation of the protective layer. As a result of various studies based on this fact, the present inventors have determined that alcohol-soluble melamine resin or melamine resin can be applied to an inorganic or organic photoconductor or a photoconductor using a combination thereof, directly or through an intermediate layer, or to a curing reaction with melamine resin. It was discovered that the above-mentioned problems could be overcome by applying and curing a composition consisting of a melamine resin and a melamine resin, and this became the impetus for obtaining the present invention. (Melamine resin) The melamine resin used in the present invention is an alkyl etherified melamine/formaldehyde resin, but a butyl etherified melamine/formaldehyde resin is particularly suitable. In particular, the number average molecular weight is 1500 or less, the number of formaldehyde bound per melamine nucleus is 2 to 4, and the number of methylol groups is 1 to 1.
A resin with two pieces is desirable. This resin can be used alone, but it can also be used in combination with a curable resin that reacts with the resin. This melamine resin or its combination with other resins is used as a binder resin for photoconductive materials when applied to charge generation layers and charge transport layers, but when used as other layers, melamine resins are used as binder resins for photoconductive materials. A single layer of a resin or a combination of a melamine resin and another resin (that is, a layer that does not contain a photoconductive substance) may be formed. Resins with number average molecular weights exceeding 1500 have poor reactivity and must be cured at high temperatures, leading to a decline in electrophotographic properties. If the number of bound formaldehydes per melamine nucleus exceeds 4, the reactivity is poor and it is difficult to obtain desired electrophotographic properties. In particular, when lamination is performed by coating, the resin in the lower layer (for example, charge generation layer) is eluted, resulting in surface defects in the lower layer, leading to a decrease in photosensitivity. Conversely, if the number of bound formaldehydes per melamine nucleus is less than 2, the pot life of this mixture will be short when used in combination with other resins (that is, curable resins that react with this melamine resin). Become. If the number of methylol groups per melamine nucleus exceeds 2, the storage stability of this resin will be poor, and when it is dissolved in an organic solvent to prepare a coating liquid for a photoconductive layer,
It becomes cloudy during storage. Furthermore, if the number of methylol groups is less than one, the reactivity is poor and the above-mentioned film surface defects are likely to occur during coating. In the butyl etherified melamine/formaldehyde resin, bound formaldehyde exists as the above-mentioned methylol group, and most of it is etherified with butanol and exists as butoxymethyl group, and the number of bound formaldehyde is about 1 to 3 per melamine nucleus. It is individual. In addition, a small portion of the bound formaldehyde becomes a bridging group between melamine nuclei through condensation of methylol groups. In addition, in this specification, the number average molecular weight is determined by gel permeation chromatography.
It was determined using a standard polystyrene calibration curve. The manufacturing method for butyl etherified melamine/formaldehyde resin is to dissolve melamine in butanol,
There is a method in which addition and butyl etherification reaction is carried out while formaldehyde is added dropwise thereto, and a method in which melamine and formaldehyde are dissolved in butanol and this is heated to carry out addition and etherification reaction. Here, the reaction is preferably carried out under acidic conditions (preferably pH 3 to 6) by adding an acidic catalyst such as nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, para-toluenesulfonic acid, etc., and the reaction temperature is the reflux temperature of butanol. Preferably, the temperature is 90 to 100°C. Also,
The amount of raw materials to be charged is 4 to 5 moles of butanol and 3 to 7 moles of formaldehyde per 1 mole of melamine.
Preference is given to using moles. The numbers of bound formaldehyde, butyl ether groups, and methylol groups per melamine nucleus in the butyl etherified melamine formaldehyde resin thus obtained may be determined by nuclear magnetic resonance (NMR) spectroscopy.
It can also be found as follows. The number of bound formaldehydes can be determined from the difference between the charged amount and the unreacted formaldehyde determined by the sodium sulfite method. The butyl ether group can be determined by adding an internal standard substance to the reaction solution, determining the amount of butanol (unreacted butanol amount) in the reaction solution by gas chromatography, and subtracting this from the amount of butanol charged. The methylol group utilizes this number of butyl ether groups,
It can be determined from the area intensity ratio based on butyl ether groups and methylol groups in the NMR spectrum. (Resin suitable for use in combination with melamine resin) Examples of resins that can react with the melamine resin and harden include conventionally known resins containing hydroxyl groups, such as vinyl compounds such as acrylic esters and methacrylic esters. Conventionally known polymers and copolymers, acrylic resins, alkyd resins, alkyd-modified alkyd resins, acrylic resins/alkyd-modified alkyd resins, modified crosslinked fluororesins, vinyl-modified fluororesins, polyesters, and the like can be used. These preferably have a hydroxyl value of 15 to 200 in order to react with the butyl etherified melamine/formaldehyde resin. The higher the hydroxyl value, the higher the curability, and the lower the hydroxyl value, the higher the water resistance. The alkyd resin is, for example, a polyhydric carboxylic acid,
It is a resin obtained by reacting a polyhydric alcohol and, if necessary, oil or fat or its fatty acid. Polyhydric carboxylic acids include phthalic acid, isophthalic acid,
These include terephthalic acid, tetrahydrophthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid. These may be used in the form of ester-forming derivatives such as acid anhydrides and methyl esters. Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1,6-hexanediol, trimethylene glycol, glycerin, trimethylolpropane, and triethylene glycol. Examples include methylolethane and pentaerythritol. Examples of the oil include tung oil, linseed oil, soybean oil, dehydrated castor oil, safflower oil, castor oil, coconut oil, and tall oil. The production of alkyd resin is
This can be carried out by a known method, and when oil is used, the oil and polyhydric alcohol are reacted at 200 to 260°C in the presence of a transesterification catalyst such as lithium hydroxide, and then the polybasic acid and the remaining polyhydric alcohol are reacted. There are methods such as adding alcohol and reacting at 180 to 250°C, and when not using oil, mixing raw materials and reacting at 180 to 250°C. Acrylic resins include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,
It is obtained by copolymerizing α, β-ethylenically unsaturated monomers having hydroxy groups such as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate and other unsaturated monomers. Other unsaturated monomers include α,β-monoethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, and acrylic acid. Alkyl esters of α, β-monoethylenically unsaturated carboxylic acids such as 2-ethylhexyl acid, methyl methacrylate, n-butyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide α, such as acrylamide derivatives, glycidyl acrylate, glycidyl methacrylate, etc.
Examples include glycidyl esters of β-monoethylenically unsaturated carboxylic acids, vinyl esters of saturated carboxylic acids such as vinyl acetate and vinyl propionate, and aromatic unsaturated monomers such as styrene, α-methylstyrene, and vinyltoluene. The above copolymerization is
It can be carried out by heating to 90 to 160°C in the presence of a radical catalyst such as azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, or cumene hydroperoxide. The alkyd resin-modified acrylic polymer can be obtained by polymerizing monomers that are raw materials for the acrylic resin in the presence of the alkyd resin. The raw material composition of the alkyd resin, acrylic resin, and alkyd resin-modified acrylic polymer is preferably adjusted so that the hydroxyl value is 15 to 200.
In addition, if the hydroxyl value is too small, the curability will be poor, and if it is too large, the water resistance of the coating film will be poor. Furthermore, when the charge transport layer is multilayered, the butyl etherified melamine/formaldehyde resin may be combined with a conventionally known resin. That is,
silicone resin, phenolic resin, urea resin,
Furan resin, epoxy resin, silicone resin, vinyl chloride-vinyl acetate copolymer, xylene resin, toluene resin, urethane resin, vinyl acetate-methacrylic copolymer, acrylic resin, phenoxy resin, polymethyl methacrylate resin, polycarbonate resin, polyester -A charge transport layer is formed using a binder resin of a known resin such as a carbonate copolymer, a polyester resin, a polyarylate resin, a polyolefin resin, or a polyamide resin, either alone or in combination of two or more, and then A charge transport layer using the butyl etherified melamine formaldehyde resin as a binder resin can be formed directly or via an intermediate layer. Melamine resin and the above resins are usually the former/
It is desirable that the latter be blended in a weight ratio of 5/95 to 50/50. (Charge generating substance) The charge generating substance used in the present invention includes, for example, phthalocyanine pigments such as metal phthalocyanine and metal-free phthalocyanine, anthraquinone pigments,
Known materials include indigoid pigments, quinacrivane pigments, perylene pigments, polycyclic quinone pigments, methine squaritcate pigments, monoazo and disazo pigments, selenium and selenium compounds, cadmium sulfide, zinc oxide, amorphous silicon and amorphous silicon compounds. These pigments can be used alone or in combination of two or more. (Charge Transport Substance) The charge transport substance used in the present invention includes, for example, oxadiazole, triazole, imidazolone, oxazole, pyrazoline, imidazole, imidazolidine, benzothiazole, benzoxazole, triphenylamine, and derivatives of these substances. These charge transport substances can be used alone or in combination of two or more types. (Catalyst, organic solvent) The thermosetting resin composition related to the butyl etherified melamine/formaldehyde resin includes hydrochloric acid,
A catalyst such as phosphoric acid or para-toluenesulfonic acid may be added. The amount used is preferably 1% by weight or less based on the butyl etherified melamine formaldehyde resin. In addition, the thermosetting resin composition related to the butyl etherified melamine/formaldehyde resin can be cured with an appropriate organic solvent such as various alcohols such as xylene, toluene, butyl cellosolve, ethyl cellosolve, n-butanol, isobutanol, isopropanol, and methanol. It is used in solid form. (Conductive Support) The conductive support preferably has a conductive layer having a volume resistance of ¹⁰ Ωcm or less, such as aluminum, aluminum to other metal alloys, steel, iron, lead,
Metal plates such as copper, metal compound plates such as tin oxide, indium oxide, copper iodide (CuI), chromium oxide, conductive plastic plates, and plastics,
It is possible to use paper, glass, etc., which have been imparted with conductivity by vapor deposition, sputtering, etc., and these supports may be cylindrical, sheet, etc., and are not limited to any shape. (Application of the above-mentioned melamine-based resin to the charge-transporting layer) When applying the melamine-based resin to the charge-transporting layer, the concentration of the charge-transporting substance is desirably 90% or less, particularly 70% or less. Further, there is no restriction at all even if the charge transport layer is formed on the conductive support side of the photoreceptor and the charge generation layer is formed on the surface side. In addition, it can be used as a film-forming aid or sensitizing aid to improve film-forming properties when forming a charge transport layer, or as a dye or pigment that increases or decreases a desired wavelength range, or as an effect for various special improvements in electrophotographic properties. There are no restrictions on the addition of various additives such as auxiliary agents. Furthermore, conventionally known techniques can be used for the protective layer formed on the photoreceptor. In addition, after curing, the binder resin in the charge transport layer
Although at least some crosslinking is required, there are no restrictions on the curing conditions. Preferably, the binder resin composition is one that hardens at a temperature equal to or lower than the melting point of the charge transport material plus 20°C. The charge transport layer may be formed in one layer or in multiple layers. When forming multiple layers, the coating method for each layer may be the same or different.
A known coating method can be used. In addition, when forming multiple layers, there are no restrictions on the types of binder resins, charge transport substances, etc. for each layer, and the addition of various film-forming aids and aids that impart effects on electrophotographic properties. It is not something that will be done. It is desirable that the concentration of the charge transporting substance contained in each layer is made smaller toward the outer layer (the closer to the surface), and in particular, if the concentration of the charge transporting substance in the outermost layer is small, the effect as a protective layer is significantly exhibited. Further, it is preferable that each charge transport material is of the same type. Next, a typical example of a method for forming a charge generation layer and a charge transport layer on a conductive support will be described.
First, the charge generation layer disperses the charge generation substance well;
Alternatively, an organic solvent that easily dissolves the resin and additives used as necessary, such as tetrahydrofuran,
A coating liquid of the charge generating material is prepared by thoroughly mixing and stirring with ethyl acetate, acetone, methyl ethyl ketone, halogenated hydrocarbon, etc. The conductive support is immersed in this liquid, or this liquid is dropped onto the conductive support and coated with a bar coater, roll coater, applicator, casting method, dipping method, etc., and then applied with heat, light, etc. It is formed by drying or crosslinking reaction. As the resin, a known three-dimensional curing resin or thermoplastic resin can be used. The charge transport layer is
(1) A charge transport substance and a known binder resin are mixed and stirred in a known organic solvent to dissolve them, and various auxiliary agents are added to prepare a coating liquid. Using that coating liquid,
A charge transport () is formed on the charge generation layer. (2)
The charge transport substance and the above butyl etherified melamine
A coating solution prepared by dissolving a formaldehyde resin and various auxiliary agents in a known organic solvent can be applied alone onto the charge generation layer to form a charge transport layer, or alternatively, coating and curing can be repeated using this coating solution. Alternatively, the liquid (2) can be used to coat the charge transport layer formed in step (1) above to form multiple charge transport layers with different binder resins. can be formed. When forming a large amount of charge transport layer, two or more known charge transport substances as mentioned above may be used in combination or may be different for each coating liquid or for each layer, but it is preferable to use the same substance. good. The coating method is bar coater,
Known techniques such as a roll coater, an applicator, a casting method, and a dipping method can be used. Further, after coating, the charge transport layer can be dried or cured by conventional methods such as heat and light. If the melamine resin of the present invention is used as a binder, the charge transport layers can be directly bonded to each other, and the charge generation layer and the charge transport layer can also be directly bonded. (Application of the above melamine resin to the charge generation layer) The charge generation layer is usually prepared by coating, so a charge generation substance, the above-mentioned binder resin, an organic solvent and, if necessary, a leveling agent are used. A coating liquid consisting of the following is prepared, applied using a bar coater, applicator, spray, dipping, etc., and then subjected to a drying (curing) process. The blending amount of the charge generating substance and the binder resin (melamine resin alone or a composition containing this resin) is as follows:
The weight ratio of the former/latter is preferably in the range of 1/0.2 to 1/5; if the latter is less than 1/0.2, the adhesive force with the conductive support decreases, and when forming a charge transport layer, the conductive It tends to peel off easily from the support. Moreover, when the latter amount is more than 1/5, the characteristics as an electrophotographic photoreceptor, that is, the photosensitivity tends to deteriorate. The thickness of the charge generation layer is usually
It is preferably 10 μm or less, particularly preferably 3 μm or less. By forming a charge transport layer on the charge generation layer thus obtained, a composite type electrophotographic photoreceptor can be obtained. The method for forming the charge transport layer is as follows:
Similar to the charge generation layer, coating is usually carried out by preparing a coating liquid in which a charge transport material and a binder resin are dissolved in an organic solvent, and coating is carried out using a bar coater, an applicator, spraying, dipping, etc. The binder for the charge generation layer exhibits a remarkable effect when coating using the coating liquid for the charge transport layer, especially when coating is carried out by dipping. If the melamine resin of the present invention is used as a binder,
The charge generation layer and the conductive support layer can be directly bonded, and the charge generation layer and the charge transport layer can be bonded directly. (Application of the above-mentioned melamine resin to intermediate layer) A leveling agent may be included for the purpose of improving film formability as a coating film as an intermediate layer. The thickness of the intermediate layer is usually 5 μm or less, particularly preferably 1 μm or less, and if it is 5 μm or more, it will adversely affect electrophotographic properties, particularly light attenuation, resulting in poor photosensitivity. The intermediate layer is manufactured by coating using a bar coater, applicator, spraying, coating, etc.
This is accomplished by baking at a predetermined temperature. If the photoconductive layer does not require the use of a binder resin, it may be used. Further, when using a binder resin, it is not necessary to use a melamine resin. The photoconductive layer is formed on the intermediate layer by any suitable means such as vapor deposition, sputtering or coating. In the case of coating, a coating liquid is prepared by adding a binder, a plasticizer, a sensitizer, and a solvent to the photoconductor, if necessary. The intermediate layer according to the present invention exhibits remarkable effects, particularly when this coating is used to form a photoconductor layer. The intermediate layer may be located between the conductive support and the photoconductive layer, or between adjacent photoconductive layers in the case of two or more photoconductive layers. (Application of the above-mentioned melamine resin to the protective layer) A charge transporting substance can be contained in the protective layer if necessary, and preferably 30% or less. The thickness of the protective layer is not particularly limited and can be changed as necessary, but is preferably 20 μm or less. In addition, it is possible to add film-forming aids, sensitization aids, dyes and pigments that have the effect of increasing or decreasing the desired wavelength of light, or inorganic and organic fillers to the protective layer, and these may be added as necessary. can be added. Moreover, although the resin forming the protective layer of the present invention needs to be crosslinked after curing, the curing conditions are not restricted at all. When heat curing is performed, the curing is preferably carried out at a temperature equal to or lower than the melting point of the substance with the highest melting point among the charge transporting substances used plus 20°C. Next, the formation of the protective layer will be described. A protective layer is formed directly or via an intermediate layer on a photoreceptor consisting of a photoconductor layer or a charge generation layer and a charge transport layer on a conductive support. The polymer used for the protective layer reacts with the butyl etherified melamine/formaldehyde resin or its resin to form a curable thermosetting resin composition, such as xylene, toluene,
It is dissolved in a common organic solvent such as tetrahydrofuran, ethyl acetate, acetone, methyl ethyl ketone, halogenated hydrocarbon, various alcohols, or a mixed solvent thereof. The liquid may contain a charge transporting substance, various auxiliary agents, etc., if necessary. This liquid can be applied onto the photoreceptor described above using a known coating method such as a bar coater, a roll coater, an applicator, or a dipping method to form a protective layer. Solvent evaporation and curing reaction after coating can be carried out by conventional methods such as heating. [Examples of the Invention] In the following description, parts and % indicate parts by weight and % by weight, respectively. (Production of alkyl etherified melamine/formaldehyde resin) Production example 1 In a flask equipped with a stirrer, reflux condenser, and thermometer, 126 g of melamine, 444 g of n-butanol, and
Weigh out 0.2g of 61% nitric acid aqueous solution and raise the temperature to 100℃,
169 g of paraformaldehyde was added at equal intervals in 6 portions over 30 minutes, and then the mixture was allowed to react at reflux temperature for 30 minutes to remove moisture, and desolubization was performed so that the heating residue was 50%. The viscosity at this time is (Gardona 25℃)
It was B. Production Example 2 Using the same equipment as Production Example 1, 126g of melamine,
Weigh out 296g of n-butanol and 0.2g of 61% nitric acid.
Raise the temperature to 100℃. Here is 148g of n-butanol
A solution in which 169 g of paraformaldehyde was dissolved was added dropwise over 30 minutes using a dropping pump. after that,
The reaction was carried out at reflux temperature for 30 minutes to remove water, and then the residue on heating was dropped to 50%. The viscosity at this time was (Gardner/25°C) B. Production Example 3 Using the same equipment as Production Example 1, 126g of melamine,
444 g of n-butanol, 0.2 g of 61% nitric acid, and 169 g of paraformaldehyde were mixed and charged, heated to 100°C, and reacted for 30 minutes. Further, reflux dehydration was carried out for 30 minutes to remove water and the solvent was removed so that the heating residue was 50%. The viscosity at this time was C in Gardner (25°C). Production Example 4 126 g of melamine, 370 g of n-butanol, and 112.5 g of paraformaldehyde were reacted in the same manner as in Production Example 1. The solution was removed so that the heating residue was 50%. The viscosity at this time was (Gardna/25°C)C. Production Example 5 Using the same equipment as Production Example 1, 217.5 g of paraformaldehyde, 444 g of n-butanol, and melamine were prepared.
126 g was weighed out and an addition reaction was carried out at 90 to 100°C for 30 minutes. Thereafter, the mixture was cooled to 40 to 45°C, 0.1 g of phthalic acid was added, and reflux dehydration and dissolution were performed under acidic conditions.
After this, the heating residue was adjusted to 60%. This product was adjusted with xylene to have a heating residue of 50%. The viscosity at this time is (Gardna/25℃) B
It was hot. Production Example 6 Using the same equipment as Production Example 1, 310 g of paraformaldehyde, 450 g of n-butanol, and melamine were added.
130g was weighed out and an addition reaction was carried out at 100°C for 30 minutes. Thereafter, the mixture was cooled to 40 to 45°C, 0.15 g of phthalic acid was added, and reflux dehydration and dissolution were performed under acidic conditions.
After this, the heating residue was adjusted to 60%.
This product was adjusted with xylene to have a heating residue of 50%. The viscosity at this time is (Gardna/25℃)
It was B. Production Example 7 The composition was the same as in Production Example 6 except for the addition of 590 g of n-butanol, and the production conditions were also the same as in Production Example 6. Production Example 8 A product having the same composition as Production Example 1 was reacted at 100°C for 90 minutes. Further, reflux dehydration was performed for 60 minutes to remove water and desolubilization was performed such that the heating residue was 50%. The viscosity at this time was B in Gardner (25°C). Production Example 9 Using the same equipment as Production Example 1, 320 g of paraformaldehyde, 470 g of n-butanol, and melamine were added.
130g was weighed out and an addition reaction was carried out at 90-100°C for 30 minutes. Then cool to 40-45℃ and phthalic acid 0.15g
was added, and reflux dehydration and dissolution were performed under acidic conditions. After this, the heating residue was adjusted to 60%. This product was adjusted with xylene to have a heating residue of 50%. The viscosity at this time is (Gardna/25
℃）B. Production Example 10 The composition was the same as in Production Example 6 except for 590 g of n-butanol, and the production conditions were also the same as in Production Example 9. Production Example 11 A product having the same composition as Production Example 9 was reacted at 100°C for 120 minutes. Further, reflux dehydration was performed for 60 minutes to remove water and desolubilization was performed such that the heating residue was 50%. The viscosity at this time was B in Gardner (25°C). Table 1 shows the number of formaldehyde bound per melamine nucleus, the number of butyl ether groups, the number of methylol groups, and the number average molecular weight of the butyl etherified melamine formaldehyde resins obtained in Production Examples 1 to 11. However, the number of bound formaldehyde is determined by measuring the amount of unreacted formaldehyde using the charged amount and the sodium sulfite method, and the number of butyl ether groups is determined by measuring the amount of butanol charged and the unreacted butanol amount by gas chromatography using sec-butyl butanol as an internal standard solution. The methylol group is determined by the above-mentioned number of butyl ether groups and NMR
Obtained from the spectrum. In addition, the number average molecular weight is
The measurement was carried out by gel permeation chromatography under the following measurement conditions using a standard polystyrene calibration curve. [Measurement conditions] Column: Hitachi Chemical Co., Ltd. trade name, GELKO R-
420, R-430 and R-440 connected in series (number of theoretical plates 17000 plates/piece) Solvent: Tetrahydrofuran Flow rate: 1.77ml/min Temperature: 23℃ Sample concentration: 300mg/5ml Injection volume: 200μ Detector: Differential refractometer

【table】

[Table] Production Example 12 Using the same equipment as Production Example 1, 126g of melamine,
Methanol 256g, paraformaldehyde 187.5g,
Weigh out 0.1g of 30% sodium hydroxide aqueous solution.
The temperature was raised to 60°C and addition reaction was carried out for 30 minutes. after that,
The mixture was cooled to 40 to 45°C, 0.3g of 61% nitric acid aqueous solution was added, and the mixture was reacted under acidic conditions at 65°C for 60 minutes. Then 30%
After neutralization with an aqueous sodium hydroxide solution, desolvation was performed under reduced pressure. After this, the heating residue was adjusted to 50% with isobutanol and isopropanol. The viscosity at this time was A (Gardner/25°C). In this way, a methylated melamine resin was produced. Production Example 13 Using the same equipment as Production Example 1, 126g of melamine,
322g of ethanol, 187.5g of paraformaldehyde,
Then, 0.1 g of a 30% aqueous sodium hydroxide solution was taken out, heated to 60° C., and an addition reaction was carried out for 30 minutes. Thereafter, the mixture was cooled to 40 to 45°C, 0.3 g of a 61% nitric acid aqueous solution was added, and the mixture was reacted under acidic conditions at 70°C for 60 minutes. after that
After neutralization with a 30% aqueous sodium hydroxide solution, desolubization was performed under reduced pressure. After this, so that the remaining amount after heating is 50%,
Adjusted with isobutanol and isopropanol. The viscosity at this time was A (Gardner/25°C). In this way, an ethylated melamine resin was produced. Production Example 14 Using the same equipment as Production Example 1, 126g of melamine,
Isopropanol 360g, paraformaldehyde
187.5 g and 0.1 g of 30% aqueous sodium hydroxide solution were weighed out, heated to 60° C., and an addition reaction was performed for 30 minutes. Then cool to 40-45℃ and use 61% nitric acid aqueous solution.
0.3g was added and reacted under acidic conditions at 70°C for 60 minutes.
Thereafter, the mixture was neutralized with a 30% aqueous sodium hydroxide solution and desolubilized under reduced pressure. After this, the mixture was adjusted with isobutanol and isopropanol so that the heating residue was 50%. The viscosity at this time is (Gardana/25℃) and A
It was hot. In this way, a propylated melamine resin was produced. Table 2 shows the properties of the alkyl etherified melamine/formaldehyde resins prepared in Production Examples 12 to 14 above.

[Table] (Application of melamine resin to protective layer) Examples 1 to 11 A charge generation layer was formed on a 100 μm aluminum plate using the composition shown in Table 3, and heated to 140°C.
hardened with. The thickness of the charge generation layer was 1 μm or less.

[Table] A charge transport layer was coated thereon by a dipping method using a coating solution having the composition shown in Table 4, and dried at 110°C to form a charge transport layer. The thickness of the charge transport layer was 15 μm.

[Table] Furthermore, coating liquids of the compositions shown in Tables 5 and 6 were applied thereon and cured at 120°C to form a protective layer. The thickness of the protective layer was 0.5 to 10 μm.

【table】

[Table] The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording tester (Kawaguchi Electric, Model SP-428). In addition, the abrasion characteristics of the photoreceptor were determined by fixing the photoreceptor on the table of a fixability tester (Suga Test Instruments) and rubbing it 100,000 times with a polyurethane blade (Toei Sangyo). I asked for it. The results are shown in Table 7. Incidentally, the oxazole compound (A) represented by the following structural formula was used.

【table】

[Table] Examples 12 to 14 In addition to forming a charge generation layer and a charge transport layer in the same manner as in Example 1, a protective layer of the composition shown in Table 8 was formed by a casting method. The curing reaction was carried out at 120°C, and the thickness of the obtained protective layer was 3 μm. As in Example 1, the electrophotographic properties and abrasion test results are shown in Table 9.

【table】

【table】

[Table] Example 15 The three-necked flask of 1 was equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux condenser. 245 parts by weight of distilled and dried xylene was placed in this flask, and heated to 136°C with a mantle heater while slowly flowing nitrogen. Next, 50 parts by weight of styrene,
A mixture of 85 parts by weight of methyl methacrylate, 100 parts by weight of 2-ethylhexyl acrylate, 25 parts by weight of oxyethyl methacrylate and 5 parts by weight of di-tert-butyl peroxide was added over a period of 1 hour. Maintain the temperature between 136-140°C by adjusting the mantle heater or blowing air, and keep the temperature at 136-140°C for about 2 hours after adding the monomer mixture.
After cooling, a thermosetting acrylic polymer solution was obtained. The solids content of this solution was 50% by weight and the number average molecular weight was 10,000. Next, 67 parts by weight of commercially available 37% formaldehyde (1/3.3, molar ratio) and 14 parts by weight of water were added to 31.5 parts by weight of melamine.
Parts by weight were added, and the mixture was heated and stirred at 70° C. for 1 hour under a counterflow condenser. Note that NaOH was added to adjust the pH of the solution to maintain it at 9.0 during the reaction. After cooling, a portion of this solution was taken out, and free formaldehyde was measured using the sodium sulfite method, and its composition was investigated using paper chromatography. As a result, it was found that hexamethylolmelamine was mainly produced. Therefore, this reaction solution was poured into 2 to 3 times the volume of cold methanol to precipitate crystals, and after over-drying, xylene and butanol (volume ratio 7/3) were added.
A 50% by weight solution of methylolmelamine was obtained. Using the above thermosetting acrylic polymer and curing agent, the binder resin for the charge transport layer was prepared using the blending ratio shown in Table 10 below, and toluene/methyl ethyl ketone =
7/3 (volume ratio) to create a solution with a solid content of 20% by weight, binder resin: oxazole compound
(A) was added at a ratio of 5:1 (weight ratio) and dissolved by stirring to obtain a coating liquid for a protective layer. This coating liquid was applied and cured in the same manner as in Example 1 on the same charge transport layer as in Example 1 to form a protective layer. The thickness of this layer was 4 μm. The electrophotographic properties and abrasion properties measured in the same manner as in Example 1 are shown in Table 10.

[Table] According to Examples 1 to 15, the electrophotographic photoreceptor has excellent electrophotographic properties and greatly improved abrasion resistance, and is particularly excellent for long-term repeated use. I understand. (Application of melamine resin to charge transport layer) Examples 16 to 23 The compositions shown in Table 11 were placed in a glass container and stirred with an ultrasonic vibrator for 20 hours to prepare a charge generation layer coating liquid. . The compositions shown in Table 12 were similarly stirred to prepare respective coating liquids.
The oxazole compound (A) used in Table 4 is represented by the above structural formula. First, a charge generation layer of the composition shown in Table 11 was coated on an aluminum plate having a thickness of 100 μm by a dipping method, and the layer was placed in a hot air dryer at 140° C. to be cured.
The thickness of the charge generation layer was 1.0 μm or less.

[Table] Next, the composition in Table 12 was applied thereon with an applicator and cured in a hot air dryer at 120°C to form a charge transport layer. The thickness of the charge transport layer is 10 μm.

[Table] Table 13 shows the results of the photoreceptor thus obtained. The electrophotographic characteristics are based on electrostatic recording paper equipment (SP).
−428, Kawaguchi Electric).

[Table] Examples 24 to 28 A charge generation layer was formed in the same manner as in Example 16. Next, a coating solution prepared by stirring and mixing the compositions shown in Table 14 and completely dissolving them was applied onto the above-mentioned charge generation layer by a dipping method, and dried in a hot air dryer at 100°C.
A charge transport layer () was formed. Charge transport layer ()
The film thickness is 15 μm.

[Table] Next, a coating solution of the composition shown in Table 15 was applied onto the charge transport layer (2) by a dipping method and cured at 120°C to form a charge transport layer (2). The thickness of the charge transport layer ( ) is 3 μm.

[Table] Abrasion characteristics were determined by fixing a photoreceptor specimen on a table for a taper abrasion test and polishing it with a polyurethane plate (Toei Sangyo) for 5 hours. The results are shown in Table 16 together with the electrophotographic characteristics.

[Table] Comparative Examples 1 to 3 A charge generation layer was formed in the same manner as in Example 16. Next, a coating solution having the composition shown in Table 17 was applied onto the charge generation layer by a dipping method and cured at 120°C to form a charge transport layer. The thickness of the charge transport layer was 15 μm. Table 18 shows the properties of the obtained specimens.

【table】

[Table] The three-necked flask of Example 29 1 was equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux condenser. 245 parts by weight of distilled and dried xylene was placed in this flask, and heated to 136°C with a mantle heater while slowly flowing nitrogen. Next, 50 parts by weight of styrene,
A mixture of 85 parts by weight of methyl methacrylate, 100 parts by weight of 2-ethylhexyl acrylate, 25 parts by weight of oxyethyl methacrylate and 5 parts by weight of di-tert-butyl peroxide was added over a period of 1 hour. Maintain the temperature between 136-140°C by adjusting the mantle heater or blowing air, and keep the temperature at 136-140°C for about 2 hours after adding the monomer mixture.
After cooling, a thermosetting acrylic polymer solution was obtained. The solids content of this solution was 50% by weight and the number average molecular weight was 10,000. Next, 67 parts by weight of commercially available 37% formaldehyde (1/3.3, molar ratio) and 14 parts by weight of water were added to 31.5 parts by weight of melamine.
Parts by weight were added, and the mixture was heated and stirred at 70° C. for 1 hour under a counterflow condenser. Note that NaOH was added to adjust the pH of the solution to maintain it at 9.0 during the reaction. After cooling, a portion of this solution was taken out, and free formaldehyde was measured using the sodium sulfite method, and its composition was investigated using paper chromatography. As a result, it was found that hexamethylolmelamine was mainly produced. Therefore, this reaction solution was poured into 2 to 3 times the volume of cold methanol to precipitate crystals, and after over-drying, xylene and butanol (volume ratio 7/3) were added.
A 50% by weight solution of methylolmelamine was obtained. Using the above thermosetting acrylic polymer and curing agent, the binder resin for the charge transport layer was prepared in the proportions shown in Table 19 below, and toluene/methyl ethyl ketone =
7/3 (volume ratio) to create a solution with a solid content of 20% by weight, and add a charge transport material (manufactured by Nippon Kanko Shiki Kenkyusho Co., Ltd., NK-1343) shown by the following structural formula. The binder resin/charge transport material was added at a ratio of 2:1 (weight ratio) and dissolved by stirring to obtain a charge transport layer coating liquid. This coating liquid was applied on the same charge generation layer as in Example 16 and cured in the same manner as in Example 1 to form a charge transport layer. The thickness of this layer is
It was approximately 15 μm. The results of investigating the electrophotographic properties of the composite electrophotographic plate thus obtained are as follows.
Shown in Table 19.

[Table] According to Examples 16 to 29, the electrophotographic photoreceptor has excellent electrophotographic properties and greatly improved wear resistance, and is excellent for long-term repeated use. Recognize. (Application of melamine resin to charge generation layer) Example 30 1 part by weight of τ-type metal-free phthalocyanine (manufactured by Toyo Ink Manufacturing Co., Ltd.) as a charge generation substance, 37 parts by weight of tetrahydrofuran, and KP-323 as a leveling agent.
(manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and vibration was applied for 1 hour using an ultrasonic cleaner (manufactured by Shinmeidai Kogyo Co., Ltd., model UA-100) to disperse the τ-type metal-free phthalocyanine. Thereafter, 2 parts by weight of the butyl etherified melamine/formaldehyde resin of Production Example 1 was added to this dispersion, and the mixture was again subjected to ultrasonic vibration for 1 hour.
A coating liquid for a charge generation layer was obtained. Thickness of this coating liquid
100 μm, 70 x 100 mm square aluminum foil,
It was coated using an automatic applicator (manufactured by Toyo Seiki Co., Ltd.) and baked at 110°C for 1 hour to obtain a charge generation layer. The obtained charge generation layer was immersed in tetrahydrofuran and methylene chloride for 2 minutes, and then the surface was wiped with gauze and the appearance was examined. The results are shown in Table 20, and there was no change in appearance at all. Examples 31 to 34 Using the same coating liquid preparation method as in Example 30, coating liquids were obtained by changing the binder resin to Production Examples 2 to 5.
A charge generation layer was obtained by the same method as in No. 30. The resulting charge generation layer was examined for solvent resistance in the same manner as in Example 30. The results are shown in Table 20, and it was found that the product of Production Example 5 with a molecular weight exceeding 1500 was at risk of being immersed in the solvent.

[Table] ○ No change, △ Slight immersion Example 35 Saturated polyester resin (manufactured by Toyobo Co., Ltd., Byron
200) 10 parts by weight, KP-323 as in Example 30,
After dissolving 0.01 part by weight in 80 parts by weight of tetrahydrofuran, 10 parts by weight of a charge transport substance having the following structural formula was added and dissolved by stirring to obtain a coating liquid for a charge transport layer. Next, the charge generation layers obtained in Examples 30 to 34 were immersed in the charge transport layer coating solution described above for 30 seconds, and then pulled up at a rate of
Dipping was performed under the conditions of 15 mm/s, and the temperature was 110°C.
The mixture was dried for 1 hour to form a charge transport layer, thereby obtaining a composite electrophotographic photoreceptor. The electrophotographic properties of the photoreceptor were measured using an electrostatic recording paper tester (manufactured by Kawaguchi Electric Co., Ltd., model SP-428). Measurement is done in dynamic mode.
Corona charging at 5KV was performed for 10 seconds, and after being left in the dark for 30 seconds, exposure was performed using a tungsten lamp. During this time,
Record the potential of the photoreceptor surface, and the potential after corona charging is V ₀ , the potential after being left in the dark for 30 seconds, V ₃₀ , and V ₃₀ is 1/2
Half-reduced exposure amount (light sensitivity) until E ₅₀ (x・
s) was read. The results are shown in Table 21.

[Table] Example 36 The three-necked flask of 1 was equipped with a stirrer, a nitrogen inlet tube, a thermometer, and a reflux condenser. 245 parts by weight of distilled and dried xylene was placed in this flask, and heated to 136°C with a mantle heater while slowly flowing nitrogen. Next, 50 parts by weight of styrene,
85 parts by weight of methyl methacrylate, 100 parts by weight of 2-ethylhexyl acrylate, 25 parts by weight of oxyethyl methacrylate and 5 parts by weight of peroxide - No. 3
The butyl mixture was added over 1 hour. Maintain the temperature between 136-140°C by adjusting the mantle heater or blowing air, and keep the temperature between 136-140°C for about 2 hours after adding the monomer mixture. It was cooled to obtain an acrylic polymer solution. The heating residue of this solution is 50%, and the number average molecular weight is
It was 10,000. 14 parts by weight of this resin solution and 6 parts of the resin solution of Production Example 1
Parts by weight were mixed to form a binder resin for charge generation layer. As a charge-generating substance, 1 part by weight of a disazo pigment having the following structural formula (the manufacturing method is disclosed in JP-A No. 52-55643) is mixed with 0.1 to 0.1 to 1% of the above binder resin.
Add 10 parts by weight and further add xylene. After adding the mixture so that the heat residue was 5%, the mixture was kneaded in a ball mill for 5 hours to obtain a charge generation layer coating liquid. A charge generation layer was obtained using this coating liquid in the same manner as in Example 30. Next, 25 parts by weight of methylene chloride was added to 2 parts by weight of polycarbonate resin (Lexan 141, manufactured by GE) and dissolved, and then 0.7 parts by weight of the same charge transport material as in Example 30 was added and dissolved. A coating liquid for a charge transport layer was obtained. This coating liquid was subjected to dipping and drying in the same manner as in Example 35 to obtain a composite type electrophotographic photoreceptor. The electrophotographic properties of this photoreceptor were examined in the same manner as in Example 35. The results are shown in Table 22.

[Table] According to Examples 30 to 36, there is no elution of the charge generation layer during coating during preparation of the charge transport layer, and a composite type electrophotographic photoreceptor with excellent photosensitivity can be obtained. Examples 37 to 39 A charge generation layer and a charge transport layer () were formed on plate A in the same manner as in Examples 24 to 28. The thickness of the charge transport layer is 20 μm. Next, the coating liquid shown in Table 23 was applied onto the charge transport layer (2018) by a dipping method, and 130
C. to form a charge transport layer (). The thickness of the charge transport layer ( ) is 4 μm. Electrophotographic characteristics are shown in Example 1, and wear characteristics are shown in Example 24.
It was obtained in the same manner as ~28. The results are shown in Table 24.

【table】

【table】

〔Effect of the invention〕

According to the present invention, a new melamine resin (composition) with excellent solvent resistance is used to provide an electrophotographic photoreceptor with excellent adhesiveness and abrasion resistance, and an electrophotographic method using the same. It has the effect of being

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor comprising an organic photoconductive layer provided on a conductive support, the resin that binds the photoconductive substance of the organic photoconductive layer is an alkyl etherified melamine/formaldehyde. A photoreceptor for electrophotography, characterized in that it contains a resin alone or further contains a resin that can be cured by reacting with the resin. 2. In claim 1, the organic photoconductive layer comprises a charge transport layer and a charge generation layer, and the alkyl etherified melamine/formaldehyde resin comprises at least one of the charge transport layer and the charge generation layer. A photoreceptor for electrophotography, characterized in that it is applied to a binding resin. 3. The electrophotographic photoreceptor according to claim 1, characterized in that an intermediate layer is provided between the conductive support and the organic photoconductive layer. 4. An electrophotographic photoreceptor according to claim 2, characterized in that an intermediate layer is provided between the charge transport layer and the charge generation layer. 5. The electrophotographic photoreceptor according to claim 1, characterized in that a protective layer is provided on the organic photoconductive layer. 6. The electrophotographic photoreceptor according to claim 3 or 4, wherein the intermediate layer is a layer containing an alkyl etherified melamine/formaldehyde resin alone or further containing another resin. 7. The electrophotographic photoreceptor according to claim 5, wherein the protective layer is a layer containing an alkyl etherified melamine/formaldehyde resin alone or further containing another resin. 8. An electrophotographic photoreceptor comprising an organic photoconductive layer provided on a conductive support is charged to impart photosensitivity, exposed to light to form an electrical latent image of the original image, and then developed with toner. In an electrophotographic method, the electrical latent image is visualized using a photoreceptor, the toner image is then transferred to paper, and the residual surface charge on the photoreceptor is erased by irradiating the toner image with erase light. An electrophotographic method characterized in that the binder resin contains an alkyl etherified melamine/formaldehyde resin alone or a resin that can be cured by reacting with the resin.