JP2013246307A - Electrophotographic photoreceptor, and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor capable of improving durability against ozone and nitrogen oxide generated in an image forming apparatus to provide stable images for a long period.SOLUTION: A laminated-type photoreceptor is formed of a charge generating layer including a charge generating material, a charge transporting layer including a charge transporting material, and an optional surface protective layer laminated in this order on a conductive support. The laminated-type photoreceptor includes an outermost layer containing a long-chain alkyl benzene dicarboxylic acid represented by the following general formula (I), where Rand Rmutually independently represent a liner alkyl group having 12 to 30 carbon atoms.

Description

The present invention relates to an electrophotographic photosensitive member and an image forming apparatus using the same.
More particularly, the present invention can prevent the image defects due to oxidizing gases such as ozone and NO _x efficiently, electrophotographic photoreceptor containing a benzene dicarboxylic acid dialkyl having excellent gas barrier properties and it The present invention relates to an image forming apparatus provided.

2. Description of the Related Art An electrophotographic image forming apparatus (hereinafter also referred to as an electrophotographic apparatus) that forms an image using electrophotographic technology is widely used in a copying machine, a printer, a facsimile apparatus, and the like.
In recent years, electrophotographic technology has been used not only in the field of copying machines but also in the fields of printing plate materials, slide films, microfilms, and the like in which silver salt photographic technology has been conventionally used.
For example, the electrophotographic technology is also applied to a high-speed printer using a laser, a light emitting diode (abbreviated as LED), a cathode ray tube (abbreviated as CRT), or the like as a light source.

  With the expansion of the application range of electrophotographic technology, the demand for photoreceptors is becoming advanced and wide.

  As a photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductive material such as selenium, zinc oxide or cadmium sulfide has been widely used. However, at present, an organic photoconductive material is used. Organic photoconductors using these materials have been used.

  Organic photoconductive materials have been widely researched and developed in recent years, and are used not only for electrostatic recording elements such as photoreceptors, but also for sensor elements, organic electroluminescent (abbreviated as OEL) elements, etc. I'm starting.

  Organic photoconductors using organic photoconductive materials have good film-forming properties, excellent flexibility, light weight, good transparency, and a wide wavelength range by appropriate sensitization methods. However, it has been developed as the main force of the photoconductor, because it has an advantage that the photoconductor showing good sensitivity can be easily designed.

  Organic photoreceptors initially had drawbacks in sensitivity and durability, but these drawbacks were the development of function-separated photoreceptors in which the charge generation function and charge transport function were shared by different substances. Is significantly improved.

  In addition to the above-mentioned advantages of the organic photoconductor, this function-separated type photoconductor also has the advantage that a wide range of materials can be selected for the photosensitive layer and a photoconductor having arbitrary characteristics can be produced relatively easily. Have.

  Such an organic photoconductor may have a single-layer structure in which both a charge generation material and a charge transport material (also referred to as “charge transfer material”) are dispersed in a binder resin on a conductive support, or a conductive material. A laminated structure or reverse two-layer type in which a charge generation layer in which a charge generation material is dispersed in a binder resin and a charge transport layer in which a charge transport material is dispersed in a binder resin are formed in this order or in reverse order on a support. A structure such as a laminated structure has been proposed.

  Among these, the function separation type photoconductor in which a charge transport layer is laminated on a charge generation layer as a photosensitive layer is excellent in electrophotographic characteristics and durability, and can design various characteristics of the photoconductor from the high degree of freedom of material selection. Has been widely used since.

  Thus, the photoreceptor having the above-described configuration is required to have various performances such as high speed, durability, and sensitivity stability. In particular, in recent digital copying machines and laser printers, an electrophotographic apparatus having a reversal development method, that is, a double-sided printing function, is becoming popular. In response to this situation, the electrophotographic photosensitive member is compatible with both high sensitivity corresponding to high speed as a photosensitive member characteristic and durability having wear resistance and sensitivity stability, that is, long life. It is requested. In addition, higher image reliability and repetitive stability are required for photoreceptors used in laser printers and the like.

  However, it has generally been considered that one of the major disadvantages of organic photoreceptors is that they are less durable than inorganic photoreceptors. This durability is roughly classified into durability of electrophotographic physical properties such as sensitivity, residual potential, charging ability, and image blur, and mechanical durability such as abrasion and scratches on the surface of the photoreceptor due to rubbing.

The main causes of the decrease in the physical durability of the electrophotographic photosensitive member are ozone generated by corona discharge, NO _x (nitrogen oxide), and charge contained in the charge transport layer, which is the surface layer of the photosensitive member, by light irradiation. It is known that the transport material is deteriorated. In order to prevent such ozone, NO _x and light irradiation, many charge transport materials having various skeletons have been proposed and are being improved considerably in terms of durability, but are still not sufficient. Is the current situation.

  The above oxidizing gas chemically changes the material in the photosensitive layer, resulting in various characteristic changes, that is, a decrease in charging potential, an increase in residual potential, and a decrease in resolving power due to a decrease in surface resistance. Image blurring such as white spots and black belts occurs on the top, remarkably lowering the image quality, and shortening the life of the photoreceptor.

  For such a phenomenon, proposals to incorporate measures to efficiently exhaust and replace the gas around the corona charger to avoid direct gas influence on the photoreceptor, and antioxidants and stabilizers in the photosensitive layer There is also a proposal to prevent deterioration by adding.

For example, a hindered phenol-based additive has been proposed as an antioxidant (Patent Document 1).
The antioxidant traps and deactivates radical cations that cause deterioration of the photoreceptor material, thereby preventing deterioration of the photoreceptor.
However, since such an antioxidant becomes a trap with respect to charge transport, it often has an adverse effect on the electrophotographic characteristics, and there is a drawback that it is difficult to adjust the optimum addition amount.

On the other hand, there is a method for preventing deterioration without allowing ozone and NO _x gas, which cause deterioration, to pass through the inside of the photoreceptor.
It is believed that the phthalate ester improves the gas barrier properties by filling the gaps between the polymer compounds constituting the resin.

Specific examples of this method include, for example, addition of dialkyl terephthalate (Patent Document 2) and a method of adding a phthalate ester (Patent Document 3).
Phthalate esters are generally well-known as plasticizers for resins. In this case, phthalate diesters having a relatively low molecular weight of about 1 to 8 carbon atoms are usually used, but these are liquid at room temperature. There are many cases.

It has been pointed out that when such a compound is used for an electrophotographic photoreceptor, these compounds are vaporized in the heating and drying process at the time of production of the photoreceptor and do not work effectively (Patent Document 4).
Moreover, when these compounds have low volatility, they may be scattered in the air as fine droplets, and in recent years, these compounds are considered to be one cause of sick house syndrome.
In particular, low molecular weight dioctyl phthalate and dibutyl phthalate are defined in the indoor chemical concentration standards of the Ministry of Health, Labor and Welfare, and their use is restricted.

Then, the method of suppressing vaporization and scattering by making high molecular weight using an alicyclic alkyl group is proposed (patent document 5).
Although these certainly reduce vaporization and scattering, the annular portion is bulky, resulting in inferior gas barrier properties as compared with the above low molecular weight ones.

Japanese Patent Laid-Open No. 1-1118137 JP-A-5-323633 JP 2000-275880 A JP 2007-279446 A JP 2011-197646 A

As described above, the present situation is that an effective means for maintaining gas barrier properties while solving the problems of vaporization and scattering of additives has not yet been found.
In particular, in recent years, the peripheral portion of the electrophotographic photosensitive member has been downsized in the image forming apparatus, and due to the progress of colorization, the image forming apparatus has a tandem structure, and there are image forming processes for each of four colors of black, yellow, cyan, and magenta. As ozone and nitrogen oxides generated from the charging device are likely to stay at high concentrations, the influence of ozone and nitrogen oxides has become an increasingly important issue.

Also, the use of a surface protective layer has been advanced due to the necessity of improving the durability of the photoreceptor.
A high-strength thermosetting surface protective layer requires a high-temperature heat treatment because it is necessary to polymerize monomers constituting the polymer. Therefore, the vaporization at the time of manufacture of the material to be used has been an issue.

  As a result of intensive researches, the present inventors have found that long-chain dialkyl benzenedicarboxylate is an additive having excellent ozone resistance while having excellent gas barrier properties and no problems of vaporization and scattering. As a result, the present invention has been completed.

Thus, according to the present invention, in a laminated photoreceptor in which a charge generating layer containing a charge generating material, a charge transporting layer containing a charge transporting material, and an optional surface protective layer are laminated in this order on a conductive support. And at least the outermost surface layer has the following general formula (I):
(In the formula, R ₁ and R ₂ independently represent a linear alkyl group having 12 to 30 carbon atoms)
An electrophotographic photosensitive member characterized by containing a long-chain dialkyl benzenedicarboxylate represented by the formula:

  Further, according to the present invention, the electrophotographic photosensitive member, a charging means for charging the electrophotographic photosensitive member, an exposure means for exposing the charged electrophotographic photosensitive member, and an electrostatic formed by exposure. Development means for developing the latent image, transfer means for transferring the toner image to the medium, cleaning means for removing and collecting the toner remaining on the photoreceptor, fixing means for fixing the toner image on the medium, and surface charge remaining on the photoreceptor There is provided an image forming apparatus comprising a charge removing unit for removing charge.

  The image forming apparatus is characterized in that the charging means for charging the electrophotographic photosensitive member is a corona charger.

The electrophotographic photosensitive member according to the present invention has gas resistance properties against ozone and NO _x , has high image quality, and does not impair repeated electrical properties after long-term use, and has high durability.

FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the multilayer photoreceptor of the present invention. FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the multilayer photoreceptor of the present invention. FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the multilayer photoreceptor of the present invention. FIG. 2 is a schematic cross-sectional view showing a configuration of a main part of the multilayer photoreceptor of the present invention. 1 is a schematic side view illustrating a configuration of an image forming apparatus of the present invention.

The electrophotographic photoreceptor according to the present invention is a laminated photoreceptor in which a charge generation layer containing a charge generation material, a charge transport layer containing a charge transport material and an optional surface protective layer are laminated in this order on a conductive support. In which at least the outermost surface layer has the following general formula (I):
(In the formula, R ₁ and R ₂ independently represent a linear alkyl group having 12 to 30 carbon atoms)
It contains the long-chain dialkyl benzenedicarboxylic acid represented by these.

  The electrophotographic photoreceptor according to the present invention is characterized in that the benzenedicarboxylic acid long-chain dialkyl is at least one selected from phthalic acid long-chain dialkyl, isophthalic acid long-chain dialkyl and terephthalic acid long-chain dialkyl. To do.

In the electrophotographic photosensitive member according to the present invention, the long-chain dialkyl benzenedicarboxylate has the following general formula (II):
(In the formula, R ₁ and R ₂ independently represent a linear alkyl group having 12 to 30 carbon atoms)
It is characterized by being a long-chain dialkyl phthalate represented by:

  In the electrophotographic photoreceptor according to the present invention, the long-chain dialkyl benzenedicarboxylate is dihexadecyl phthalate, dioctadecyl phthalate, dieicosadecyl phthalate, didocosyl phthalate, ditetradocosyl phthalate, or dihexadocosyl phthalate. To do.

  The electrophotographic photosensitive member according to the present invention is characterized in that the benzenedicarboxylic acid long-chain dialkyl is contained in an amount of 0.1 to 10% by weight based on the binder resin.

  Furthermore, in the electrophotographic photoreceptor according to the present invention, the outermost surface layer is a charge transport layer or a surface protective layer, and the benzenedicarboxylic acid long chain dialkyl is a charge transport layer, a surface protective layer or a charge transport layer and a surface protective layer. It is characterized by being included in two layers with a layer.

Next, the configuration of the photoreceptor of the present invention will be specifically described.
1 to 4 are schematic cross-sectional views showing the configuration of the main part of the photoreceptor of the present invention.
1 to 4 show a multilayer photosensitive body (hereinafter referred to as “functional separation type photosensitive layer”) in which the photosensitive layer is a multilayer photosensitive layer (hereinafter also referred to as “function separation type photosensitive layer”) composed of a charge generation layer and a charge transport layer. FIG. 2 is a schematic cross-sectional view illustrating a configuration of a main part of the body. The photoreceptor of the present invention may have a reverse two-layered laminated structure in which a charge generating layer and a charge transporting layer are formed in reverse order, but the laminated type is preferred.

In the photoreceptor 15 of FIG. 1, a laminated photosensitive layer 7 in which a charge generation layer 3 and a charge transport layer 4 are laminated in this order is formed on the surface of a conductive support 1.
2 includes a laminated photosensitive layer 7 in which the charge generation layer 3 and the charge transport layer 4 are laminated in this order on the surface of the conductive support 1, and the surface protective layer 5 in this order. Is formed.
3 is formed on the surface of the conductive support 1 with an intermediate layer 6, and a laminated photosensitive layer 7 in which the charge generation layer 3 and the charge transport layer 4 are laminated in this order. Has been.
4 includes an intermediate layer 6, a charge generating layer 3 and a charge transport layer 4 laminated in this order on the surface of the conductive support 1, and a surface protective layer 5. Are formed in this order.

Conductive support 1 (element tube for photoconductor)
The constituent material of the conductive support is not particularly limited as long as it is a material used in this field.
Specifically, metallic materials such as aluminum, aluminum alloys, copper, zinc, stainless steel, titanium: substrate surface made of polymer materials such as polyethylene terephthalate, polyamide, polyester, polyoxymethylene, polystyrene, hard paper, glass, etc. And metal foil laminated, metal material deposited, conductive polymer, tin oxide, indium oxide or other conductive compound layer deposited or applied.

The shape of the conductive support is not limited to a sheet shape as shown in FIGS. 1 to 4, and may be a cylindrical shape, a columnar shape, an endless belt shape, or the like.
If necessary, the surface of the conductive support 1 is irregularly reflected within a range that does not affect the image quality, such as anodized film treatment, surface treatment with chemicals, hot water, coloring treatment, or roughening the surface. It may be processed.

  The irregular reflection treatment is particularly effective when the photoreceptor according to the present invention is used in an electrophotographic process using a laser as an exposure light source. That is, in the electrophotographic process using a laser as an exposure light source, the wavelength of the laser beam is uniform, so the laser beam reflected on the surface of the photoconductor and the laser beam reflected inside the photoconductor cause interference, Interference fringes due to this interference may appear in the image and cause image defects. Therefore, by performing irregular reflection processing on the surface of the conductive support, it is possible to prevent image defects due to interference of laser light having a uniform wavelength.

Multilayer photosensitive layer 7
The laminated photosensitive layer is composed of a charge generation layer 3 and a charge transport layer 4.

Charge generation layer 3
The charge generation layer 3 contains a charge generation material and a binder resin.
As the charge generation material, a compound used in this field can be used.

  Specifically, azo pigments (monoazo pigments, bisazo pigments, trisazo pigments, etc.), indigo pigments (indigo, thioindigo, etc.), perylene pigments (perylene imide, perylene acid anhydride, etc.), polycyclic quinone pigments Organic pigments or dyes such as pigments (anthraquinone, pyrenequinone, etc.), phthalocyanine pigments (various metal phthalocyanines, oxotitanium phthalocyanines, X-type metal-free phthalocyanines, etc.), squarylium dyes, pyrylium salts, thiopyrylium salts, triphenylmethane dyes, and more Examples thereof include inorganic materials such as selenium and amorphous silicon. These charge generating materials can be used alone or in combination of two or more.

Among these charge generation materials, phthalocyanine pigments such as metal phthalocyanine and X-type metal-free phthalocyanine are preferable, and oxotitanium phthalocyanine is particularly preferable.
Since phthalocyanine pigments have high charge generation efficiency and charge injection efficiency, they generate a large amount of charge by absorbing light, and in the single layer type photosensitive layer without accumulating the generated charge in the molecule. Since charges are efficiently injected into the contained charge transport material and smoothly transported, a highly sensitive and high resolution photoreceptor can be obtained. This effect is the same for the laminated type photoconductor described later.

The charge generating material can be used in combination with a sensitizing dye.
Examples of such sensitizing dyes include triphenylmethane dyes typified by methyl violet, crystal violet, knight blue and victoria blue; acridines typified by erythrosine, rhodamine B, rhodamine 3R, acridine orange and frappeosin. Dyes; thiazine dyes typified by methylene blue and methylene green; oxazine dyes typified by capri blue and meldra blue; cyanine dyes; styryl dyes; pyrylium salt dyes and thiopyrylium salt dyes.

  As the binder resin, for example, a resin having a binding property that is used for the purpose of improving the mechanical strength, durability, and the like of the charge generation layer can be used.

  Specifically, vinyl resins such as polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyester, polyester carbonate, polysulfone, polyarylate, polyamide, methacrylic resin, acrylic resin, polyether, polyacrylamide, polyphenylene oxide, etc. Thermoplastic resin: Thermosetting resin such as phenoxy resin, epoxy resin, silicone resin, polyurethane, phenol resin, alkyd resin, melamine resin, phenoxy resin, polyvinyl butyral, polyvinyl formal, partially cross-linked products of these resins, these resins Copolymer resins containing two or more of the structural units contained in (vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, acrylo Tolyl - insulating resin such as styrene copolymer resin). These binder resins can be used alone or in combination of two or more.

In particular, polyvinyl butyral having good dispersibility of the charge generating material is preferable.
The use ratio of the charge generation material and the binder resin is not particularly limited. Preferably, the charge generation material is contained in an amount of 10 to 99% by weight in the total amount of the charge generation material and the binder resin, and the balance is the binder resin. It is.

  If the ratio of the charge generation material is less than 10% by weight, the sensitivity may be lowered. Conversely, if the ratio of the charge generation material exceeds 99% by weight, not only the film strength of the charge generation layer is decreased, but also the charge generation. This is called a black spot where the dispersibility of the substance decreases and the coarse particles increase, the surface charge other than that which should be erased by exposure decreases, and image defects, especially toner adheres to the white background and minute black spots are formed. There is a possibility that a lot of fogging of the image occurs.

  In addition to the two essential components, the charge generation layer may be one or more selected from a hole transport material, an electron transport material, an antioxidant, a dispersion stabilizer, a sensitizer, and the like, if necessary. Each may contain an appropriate amount. As a result, the potential characteristics are improved, the stability of the coating solution for forming a charge generation layer, which will be described later, is increased, fatigue deterioration during repeated use of the photoreceptor is reduced, and durability can be improved.

  The charge generation layer 3 is prepared by dissolving or dispersing a charge generation material, a binder resin and, if necessary, other additives in an appropriate organic solvent to prepare a coating solution for forming a charge generation layer. It can be formed by applying to the surface of the body 1 or the surface of the intermediate layer 6 formed on the conductive support 1, and then drying to remove the organic solvent. More specifically, for example, a charge generating layer forming coating solution is prepared by dissolving or dispersing a charge generating substance and other additives as required in a resin solution obtained by dissolving a binder resin in an organic solvent. To do.

  Examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetralin, diphenylmethane, dimethoxybenzene, and dichlorobenzene; halogenated hydrocarbons such as dichloromethane, dichloroethane, and tetrachloropropane; tetrahydrofuran (THF) , Ethers such as dioxane, dibenzyl ether, dimethoxymethyl ether, 1,2-dimethoxyethane; ketones such as methyl ethyl ketone, cyclohexanone, acetophenone, isophorone; esters such as methyl benzoate, ethyl acetate, butyl acetate, diphenyl sulfide Sulfur-containing solvents such as: Fluoro-based solvents such as hexafluoroisopropanol; aprotic electrodes such as N, N-dimethylformamide and N, N-dimethylacetamide Solvent and the like, which may be used alone or as a mixed solvent. A mixed solvent obtained by adding alcohols, acetonitrile, or methyl ethyl ketone to such a solvent can also be used.

Prior to dissolving or dispersing the constituent materials in the resin solution, the charge generating material and other additives may be pre-ground.
The preliminary pulverization can be performed using, for example, a general pulverizer such as a ball mill, a sand mill, an attritor, a vibration mill, or an ultrasonic disperser.

The dissolution or dispersion of the constituent materials in the resin solution can be performed using, for example, a general disperser such as a paint shaker, a ball mill, or a sand mill. At this time, it is preferable to appropriately set the dispersion condition so that impurities are generated from the container and the members constituting the disperser due to wear and the like and are not mixed into the coating liquid.
Examples of the method for applying the charge generation layer forming coating solution include roll coating, spray coating, blade coating, ring coating, and dip coating.

  The film thickness of the charge generation layer 3 is not particularly limited, but is preferably 0.05 to 5 μm, and particularly preferably 0.1 to 1 μm. This is because if the thickness of the charge generation layer is less than 0.05 μm, the light absorption efficiency may be reduced and the sensitivity may decrease. Conversely, if the thickness of the charge generation layer exceeds 5 μm, In this case, the charge transport in this process becomes a rate-determining step in the process of erasing the charge on the surface of the photoreceptor, and the sensitivity may be lowered.

Charge transport layer 4
The charge transport layer 4 usually contains a charge transport material, a long-chain dialkyl benzenedicarboxylate according to the present invention, and a binder resin.
One or more of the long-chain dialkyl benzenedicarboxylates of the present invention can be used.
The charge transport material includes a hole transport material and an electron transport material having an ability to accept and transport charges generated in the charge generation material.

  However, when the surface protective layer 5 is formed on the charge transport layer 4 and the surface protective layer contains dialkyl benzenedicarboxylate, the charge transport layer 4 may or may not contain dialkyl benzenedicarboxylate. May be.

As the hole transport material, a compound used in this field can be used.
Specifically, carbazole derivatives, pyrene derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, many Ring aromatic compounds, indole derivatives, pyrazoline derivatives, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, triarylmethane derivatives, phenylenediamine derivatives, stilbene derivatives , Enamine derivatives, benzidine derivatives, polymers having groups derived from these compounds in the main chain or side chain (Polymers) -N- vinylcarbazole, poly-1-vinylpyrene, ethylcarbazole - formaldehyde resins, triphenylmethane polymers, poly-9-vinyl anthracene, etc.) and the like.

Moreover, as an electron transport substance, the compound used in the said field | area can be used.
Specific examples include benzoquinone derivatives, tetracyanoethylene derivatives, tetracyanoquinodimethane derivatives, fluorenone derivatives, xanthone derivatives, phenanthraquinone derivatives, phthalic anhydride derivatives, diphenoquinone derivatives, and the like. These charge transport materials can be used alone or in combination of two or more.

As the binder resin, one or more of the same binder resins as those contained in the charge generation layer can be used.
In addition to the three components, the charge transport layer may contain additives such as an antioxidant similar to those contained in the charge generation layer, if necessary.

  The charge transport layer 4 is prepared by dissolving or dispersing a charge transport material, a long-chain dialkyl benzenedicarboxylate, a binder resin and other additives as required in a suitable organic solvent to prepare a charge transport layer forming coating solution, The coating liquid can be applied to the surface of the charge generation layer 3 and then dried to remove the organic solvent. More specifically, for example, by dissolving or dispersing a charge transport material, a long-chain dialkyl benzenedicarboxylate of the present invention and other additives as required in a resin solution obtained by dissolving a binder resin in an organic solvent. Then, a coating liquid for forming a charge transport layer is prepared.

Other processes and conditions are in accordance with the formation of the charge generation layer.
The thickness of the charge transport layer 4 is not particularly limited, but is preferably 5 to 50 μm, and particularly preferably 10 to 40 μm. If the thickness of the charge transport layer is less than 5 μm, the charge holding ability on the surface of the photoreceptor may be lowered. Conversely, if the thickness of the charge transport layer exceeds 50 μm, the resolution of the photoreceptor may be lowered.

  As the binder resin, for example, a resin having a binding property used in the field, which is used for the purpose of improving the mechanical strength and durability of the charge transport layer, can be used, and the benzenedicarboxylic acid long chain dialkyl of the present invention. What is excellent in compatibility with is preferable.

  Specifically, vinyl resins such as polymethyl methacrylate, polystyrene, polyvinyl chloride, polycarbonate, polyester, polyester carbonate, polysulfone, polyarylate, polyamide, methacrylic resin, acrylic resin, polyether, polyacrylamide, polyphenylene oxide, etc. Thermoplastic resin: Thermosetting resin such as phenoxy resin, epoxy resin, silicone resin, polyurethane, phenol resin, alkyd resin, melamine resin, phenoxy resin, polyvinyl butyral, polyvinyl formal, partially cross-linked products of these resins, these resins Copolymer resins containing two or more of the structural units contained in (vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, acrylo Tolyl - insulating resin such as styrene copolymer resin). These binder resins can be used alone or in combination of two or more.

Among these resins, polystyrene, polycarbonate, polyarylate and polyphenylene oxide are particularly excellent in compatibility with amine compounds, and further have a volume resistance of 10 ¹³ Ω or more, excellent electrical insulation, and film formability. Since it is excellent also in an electrical potential characteristic etc., it is preferable and a polycarbonate can be used especially suitably.
When the surface protective layer is not provided on the charge transport layer, it is preferable to use a thermosetting resin as the charge transport layer forming resin in order to improve mechanical durability.

The ratio of the benzenedicarboxylic acid long chain dialkyl used in the charge transport layer 4 is not particularly limited, but the benzenedicarboxylic acid long chain dialkyl is preferably 0.1 to 10% by weight based on the binder resin.
When the amount of the benzenedicarboxylic acid long chain dialkyl of the present invention used for the binder resin is less than 0.1% by weight, the ozone resistance effect and the nitrogen oxide resistance effect due to the benzenedicarboxylic acid long chain dialkyl may be extremely small.

  On the other hand, if the amount of the benzenedicarboxylic acid long-chain dialkyl of the present invention used for the binder resin exceeds 10% by weight, the relative amount ratio of the benzenedicarboxylic acid long-chain dialkyl to the binder resin increases, resulting in a decrease in film strength. May be present.

  In addition, the charge transport layer may contain an additive such as an antioxidant used in this field. Such an additive is preferable because the stability as a coating solution for forming a photosensitive layer is increased and the life of the solution is extended, and the photoreceptor produced with the coating solution is also reduced in oxidizing impurities and improved in durability.

Examples of the antioxidant include hindered phenol compounds and hindered amine compounds.
The proportion of the antioxidant used in combination with the charge transport material is not particularly limited, but is preferably 0.1 to 10% by weight with respect to the charge transport material.
When the amount of the antioxidant used is less than 0.1% by weight, the effect of improving the stability of the coating solution for forming a photosensitive layer, which will be described later, and the durability of the photoreceptor may be insufficient. If exceeded, the electrical characteristics of the photoreceptor may be adversely affected.

Surface protective layer 5
The surface protective layer 5 has a function of improving the durability of the photoreceptor and includes a long-chain dialkyl benzenedicarboxylate and a binder resin, but further contains a charge transport material or a binder resin having a charge transport ability. Can be used.
As the charge transport material, one or more of the same charge transport materials as those contained in the laminated photosensitive layer can be used.

As the binder resin, one or more of thermosetting resins can be used.
For example, the surface protective layer 5 is prepared by dissolving or dispersing the charge transport material and the binder resin monomer component in an appropriate organic solvent to prepare a surface protective layer-forming coating solution, and the surface protective layer-forming coating solution is laminated. It can apply | coat to the surface of the photosensitive layer 7, and can form by thermosetting, photocuring, etc. As the organic solvent used here, the same organic solvent used for forming the photosensitive layer 2 can be used.

The ratio of the benzenedicarboxylic acid long chain dialkyl used in the surface protective layer 5 is not particularly limited, but the benzenedicarboxylic acid long chain dialkyl is preferably 0.1 to 10% by weight based on the binder resin.
When the amount of the benzenedicarboxylic acid long chain dialkyl of the present invention used for the binder resin is less than 0.1% by weight, the ozone resistance effect and the nitrogen oxide resistance effect due to the benzenedicarboxylic acid long chain dialkyl may be extremely small.

  On the other hand, if the amount of the benzenedicarboxylic acid long-chain dialkyl of the present invention to the binder resin exceeds 10% by weight, the relative amount ratio of the benzenedicarboxylic acid long-chain dialkyl to the binder resin increases, and the film strength of the surface protective layer decreases. May exhibit phenomena such as.

As a coating method of the coating solution for forming the surface protective layer, dip coating is inappropriate and roll coating, spray coating, blade coating, ring coating, etc. are preferable in order to avoid dissolution of the already formed charge transport layer.
In the case of a thermosetting resin, the thermosetting conditions are preferably 140 ° C to 160 ° C.
This is because if the temperature is lower than 140 ° C., thermal curing tends to be insufficient, and if the temperature is higher than 160 ° C., the charge transport material is deteriorated.

As the organic solvent, one or more of the same solvents as those used for preparing the coating liquid for forming the charge transport layer can be used.
The thickness of the surface protective layer 5 is not particularly limited, but is preferably 0.5 to 10 μm, and particularly preferably 1 to 5 μm. If the thickness of the surface protective layer 5 is less than 0.5 μm, the surface resistance of the photoreceptor is inferior and the durability may be insufficient. Conversely, if it exceeds 10 μm, the resolution of the photoreceptor may be reduced. There is.

Intermediate layer 6
The photoreceptor of the present invention preferably has an intermediate layer between the conductive support and the laminated photosensitive layer.
The intermediate layer has a function of preventing charge injection from the conductive support to the laminated photosensitive layer. That is, a decrease in chargeability of the laminated photosensitive layer is suppressed, a decrease in surface charge other than a portion to be erased by exposure is suppressed, and occurrence of image defects such as fog is prevented. In particular, during image formation by the reversal development process, it is possible to prevent the occurrence of image fogging called black spots in which minute black dots made of toner are formed on a white background portion.

In addition, the intermediate layer covering the surface of the conductive support with the intermediate layer reduces the degree of unevenness, which is a defect on the surface of the conductive support, and makes the surface uniform, thereby improving the film formability of the multilayer photosensitive layer. The adhesion (adhesiveness) between the conductive support and the laminated photosensitive layer can be improved.
The intermediate layer is formed, for example, by dissolving a resin material in an appropriate solvent to prepare a coating solution for forming an intermediate layer, applying this coating solution to the surface of the conductive support, and removing the organic solvent by drying. it can.

Examples of the resin material include natural polymeric materials such as casein, gelatin, polyvinyl alcohol, and ethyl cellulose in addition to the same binder resin as that contained in the multilayer photosensitive layer. Can be used.
Examples of the solvent for dissolving or dispersing the resin material include water, alcohols such as methanol, ethanol and butanol, glymes such as methyl carbitol and butyl carbitol, and mixed solvents in which two or more of these solvents are mixed. Can be mentioned.
Other processes and conditions thereof are in accordance with the formation of the laminated photosensitive layer.

Moreover, the coating liquid for intermediate | middle layer formation may contain the metal oxide particle.
The metal oxide particles can easily adjust the volume resistance value of the intermediate layer, can further suppress the injection of charges into the laminated photosensitive layer, and can maintain the electrical characteristics of the photoreceptor in various environments.
Examples of the metal oxide particles include titanium oxide, zinc oxide, aluminum oxide, aluminum hydroxide, and tin oxide.

  When the total content of the resin material and the metal oxide particles in the coating liquid for forming the intermediate layer is C and the content of the solvent is D, the volume ratio (C / D) of both is 1/99 to 40/60. (Weight ratio = 0.01 to 0.67) is preferable, and 2/98 to 30/70 (weight ratio = 0.02 to 0.43) is particularly preferable.

The volume ratio (E / F) between the resin material content (E) and the metal oxide particle content (F) is 1/99 to 90/10 (weight ratio = 0.01 to 9.0). ) Is preferred, and 5/95 to 70/30 (weight ratio = 0.05 to 2.33) is particularly preferred.
Although the film thickness of an intermediate | middle layer is not specifically limited, 0.01-20 micrometers is preferable, and 0.1-10 micrometers is especially preferable. When the film thickness of the intermediate layer is less than 0.01 μm, the intermediate layer substantially does not function, and there is a possibility that a uniform surface cannot be obtained by covering the defects of the conductive support, and the film thickness of the intermediate layer is 20 μm. If it exceeds 1, it is difficult to form a uniform intermediate layer, and the sensitivity of the photoreceptor may be lowered.
In addition, when the constituent material of the conductive support is aluminum, a layer containing an alumite (alumite layer) can be formed to form an intermediate layer.

Image forming apparatus 20
An image forming apparatus according to the present invention includes a photosensitive member according to the present invention, a charging unit that charges the photosensitive member, an exposure unit that exposes the charged photosensitive member, and an electrostatic latent image formed by exposure. And developing means for developing.
The image forming apparatus of the present invention will be described with reference to the drawings, but is not limited to the following description.

FIG. 5 is a schematic side view showing the configuration of the image forming apparatus of the present invention.
An image forming apparatus 20 shown in FIG. 5 includes a photoconductor 21 (for example, any one of the photoconductors 15 to 18 shown in FIGS. 1 to 4), a charging unit (charger) 24, an exposure unit 28, a developing unit ( Developing unit) 25, transfer unit 26, cleaner 27, and fixing unit 31. Reference numeral 30 denotes a transfer sheet.

The photoconductor 21 is rotatably supported by the main body of the image forming apparatus 20 (not shown), and is driven to rotate in the direction of the arrow 23 around the rotation axis 22 by a driving unit (not shown).
The driving means is configured to include, for example, an electric motor and a reduction gear, and can transmit the driving force to a conductive support constituting the core of the photosensitive member 21, thereby rotating the photosensitive member 21 at a predetermined peripheral speed. .

  The charging unit (charger) 24, the exposure unit 28, the developing unit 25, the transfer unit 26, and the cleaner 27 are arranged in this order along the outer peripheral surface of the photoconductor 21, and the rotation direction of the photoconductor 21 indicated by an arrow 23. It is provided from the upstream side toward the downstream side.

The charger 24 is a charging unit that charges the outer peripheral surface of the photoconductor 21 to a predetermined potential. In the present embodiment, the charger 24 is realized by a non-contact type corona charger 24a and a bias power source 24b that applies a voltage to the corona charger 24a.
Although a charging roller can be used as the charging means, the electrophotographic photosensitive member of the present invention exhibits particularly excellent ozone resistance even in a corona charger that generates a lot of ozone.

  The exposure unit 28 includes, for example, a semiconductor laser as a light source, and is charged by irradiating light 28 a such as a laser beam output from the light source between the charger 24 and the developing unit 25 of the photosensitive member 21. The outer peripheral surface of the photoconductor 21 is exposed according to image information. The light 28a is repeatedly scanned in the main scanning direction in the direction in which the rotation axis 22 of the photoconductor 21 extends, and accordingly, electrostatic latent images are sequentially formed on the surface of the photoconductor 21.

  The developing unit 25 is a developing unit that develops an electrostatic latent image formed on the surface of the photoreceptor 21 by exposure with a developer. The developing unit 25 is provided facing the photoreceptor 21, and applies toner to the outer peripheral surface of the photoreceptor 21. A developing roller 25a to be supplied and a casing 25b for supporting the developing roller 25a so as to be rotatable around a rotation axis parallel to the rotation axis 22 of the photosensitive member 21 and containing a developer containing toner in the internal space thereof.

  The transfer device 26 supplies a toner image, which is a visible image formed on the outer peripheral surface of the photoconductor 21 by development, between the photoconductor 21 and the transfer device 26 from the direction of the arrow 29 by a conveying unit (not shown). It is a transfer means for transferring onto the transfer paper 30 as a recording medium. The transfer unit 26 is, for example, a non-contact type transfer unit that includes a charging unit and transfers the toner image onto the transfer paper 30 by applying a charge having a polarity opposite to that of the toner to the transfer paper 30.

  The cleaner 27 is a cleaning unit that removes and collects toner remaining on the outer peripheral surface of the photoconductor 21 after the transfer operation by the transfer device 26, and includes a cleaning blade 27 a that peels off toner remaining on the outer peripheral surface of the photoconductor 21, and a cleaning device. A recovery casing 27b for storing the toner separated by the blade 27a. The cleaner 27 is provided together with a charge eliminating lamp (not shown).

  Further, the image forming apparatus 20 is provided with a fixing device 31 as fixing means for fixing the transferred image on the downstream side where the transfer paper 30 that has passed between the photoreceptor 21 and the transfer device 26 is conveyed. . The fixing device 31 includes a heating roller 31a having a heating unit (not shown), and a pressure roller 31b that is provided to face the heating roller 31a and is pressed by the heating roller 31a to form a contact portion.

  The image forming operation by the image forming apparatus 20 is performed as follows. First, when the photosensitive member 21 is rotationally driven in the direction of the arrow 23 by the driving means, the photosensitive member 24 is provided by the charger 24 provided on the upstream side in the rotational direction of the photosensitive member 21 with respect to the imaging point of the light 28a by the exposure means 28. The surface of 21 is uniformly charged to a predetermined positive or negative potential.

  Next, light 28 a corresponding to image information is irradiated from the exposure unit 28 to the surface of the photoconductor 21. With this exposure, the surface charge of the portion irradiated with the light 28a is removed from the photosensitive member 21, and a difference occurs between the surface potential of the portion irradiated with the light 28a and the surface potential of the portion not irradiated with the light 28a. An electrostatic latent image is formed.

  Toner is supplied to the surface of the photosensitive member 21 on which the electrostatic latent image is formed from a developing unit 25 provided on the downstream side in the rotation direction of the photosensitive member 21 with respect to the image forming point of the light 28a by the exposure means 28, and electrostatic latent The image is developed to form a toner image.

  In synchronization with the exposure of the photosensitive member 21, the transfer paper 30 is supplied between the photosensitive member 21 and the transfer device 26. The transfer device 26 applies a charge having a polarity opposite to that of the toner to the supplied transfer paper 30, and the toner image formed on the surface of the photoreceptor 21 is transferred onto the transfer paper 30.

  The transfer paper 30 onto which the toner image has been transferred is conveyed to a fixing device 31 by a conveying means, and is heated and pressurized when passing through a contact portion between a heating roller 31a and a pressure roller 31b of the fixing device 31, and toner The image is fixed on the transfer paper 30 and becomes a robust image. The transfer paper 30 on which the image is formed in this way is discharged to the outside of the image forming apparatus 20 by the conveying means.

  On the other hand, the toner remaining on the surface of the photoconductor 21 even after the transfer of the toner image by the transfer unit 26 is separated from the surface of the photoconductor 21 by the cleaner 27 and collected. The charge on the surface of the photoconductor 21 from which the toner has been removed in this manner is removed by the light from the static elimination lamp, and the electrostatic latent image on the surface of the photoconductor 21 disappears. Thereafter, the photosensitive member 21 is further driven to rotate, and a series of operations starting from charging again is repeated to continuously form images.

  Since the image forming apparatus 20 according to the present invention includes the photosensitive member 21 having the photosensitive layer in which the long-chain dialkyl benzenedicarboxylate is uniformly dispersed, it is possible to form a high-quality image without image defects such as white spots. .

  The present invention will be specifically described below with reference to production examples, examples and comparative examples, but the present invention is not limited to these synthesis examples and examples.

Moreover, the chemical structure and molecular weight of each compound obtained in the following production examples were measured by the following apparatus and conditions.
Molecular Weight Analyzer: LC-MS (Liquid Chromatography-Mass Spectrometry) (Thermoquest
(Finegan LCQ Deca Mass Spectrometer System)
LC column GL-Sciences Inertsil ODS-3 2.1 × 100mm
Column temperature 40 ° C
Eluent methanol: water = 90: 10
Sample injection volume 5 μl
Detector UV254nm and MS ESI

Production Example 1
Preparation of dihexadecyl phthalate (compound 1, C ₁₆ ) 12.06 g (2.02 equivalents) of hexadecanol and 5.23 g (2.10 equivalents) of triethylamine were dissolved in 50 ml of methylene chloride, and 0 ° C. or lower in an ice bath. Cool down. While sufficiently stirring with a stir bar, from a dropping funnel, 5.0 g (1.0 equivalent) of phthaloyl chloride dissolved in 20 ml of methylene chloride is gradually added dropwise.
When dripping is completed, the ice bath is removed and the reaction is continued at room temperature for 2-3 hours. After confirming the completion of the reaction by TLC (thin layer chromatography), a crude product was obtained by extraction. The obtained crude product was purified by silica gel column chromatography (eluent: a mixture of toluene: ethyl acetate 5: 1 to 1: 5) to obtain 14.39 g of the target compound 1.

When the obtained compound was analyzed by LC-MS, a peak corresponding to the molecular ion [M + H] ⁺ in which a proton was added to the target long-chain dialkyl (C ₁₆ ) phthalate (theoretical value: 614.98) was found. Since it was observed at 615.9, the following formula:

It was found to be Compound 1 having
Moreover, from the analysis result of LC-MS, it turned out that the purity of the obtained compound 1 is 98.7%.
The melting point was 42 ° C.

Production Example 2
Production of dioctadecyl phthalate (Compound 2, C ₁₈ ) Compound 2 was collected in the same manner as in Production Example 1, except that 1-octadecanol was used instead of 1-hexadecanol in Production Example 1 above. Obtained at a rate of 92%.

When Compound 2 was analyzed by LC-MS, a peak corresponding to the molecular ion [M + H] ⁺ in which a proton was added to Compound 2 (theoretical value: 671.09) was observed at 672.4, and the LC-MS analysis result From the results, it was found that the purity of the obtained compound 2 was 98.6%.

Production Example 3
Production of dieicosadecyl phthalate (Compound 3, C ₂₀ ) Compound 3 was obtained in the same manner as in Production Example 1 except that 1-eicosanol was used in place of 1-hexadecanol in Production Example 1 and the yield was 90%. I got it.
When Compound 3 was analyzed by LC-MS, a peak corresponding to the molecular ion [M + H] ⁺ in which a proton was added to Compound 3 (theoretical value: 727.19) was observed at 728.5, and the LC-MS analysis results From the results, it was found that the purity of the obtained compound 3 was 99.1%.

Production Example 4
Production of zidocosyl phthalate (Compound 4, C ₂₂ ) Compound 4 was obtained in exactly the same manner as in Production Example 1, except that 1-docosanol was used instead of 1-hexadecanol in Production Example 1.

Production Example 5
Production of ditetradocosyl phthalate (Compound 5, C ₂₄ ) Compound 5 was obtained in exactly the same manner as in Production Example 1, except that 1-tetracosanol was used instead of 1-hexadecanol in Production Example 1 above. .

Production Example 6
Production of dihexadocosyl phthalate (Compound 6, C ₂₆ ) Compound 6 was obtained in exactly the same manner as in Production Example 1, except that 1-hexacosanol was used instead of 1-hexadecanol in Production Example 1. .

Analytical data of compounds 1 to 6 obtained in Production Examples 1 to 6 are shown in the following table.

Example 1
In the following manner, a photoreceptor in which the charge transport layer contained Compound 1 produced in Production Example 1 was produced.
7 parts by weight of titanium oxide (trade name: Taibake TTO55A, manufactured by Ishihara Sangyo Co., Ltd.) and 13 parts by weight of copolymer nylon resin (trade name: Amilan CM8000, manufactured by Toray Industries, Inc.), 159 parts by weight of methyl alcohol and 1,3- In addition to a mixed solvent with 106 parts by weight of dioxolane, the mixture was dispersed for 8 hours with a paint shaker to prepare a coating solution for forming an intermediate layer (3 kg). The coating solution for forming the intermediate layer is filled in a coating tank, and an aluminum cylindrical conductive support having a diameter of 30 mm and a length in the longitudinal direction of 340 mm is immersed in the coating layer, and then pulled and dried to obtain a film thickness of 1 A 0.0 μm intermediate layer was formed on the conductive support.

  Next, 1 part by weight of titanyl phthalocyanine and 1 part by weight of butyral resin (trade name: # 6000-C, manufactured by Denki Kagaku Kogyo Co., Ltd.) are mixed with 98 parts by weight of methyl ethyl ketone, and dispersed by a paint shaker to form a charge generation layer. A forming coating solution (3 kg) was prepared. This charge generation layer forming coating solution was applied onto the intermediate layer by the same dip coating method as that for the previously formed intermediate layer, and dried to form a charge generation layer having a thickness of 0.1 μm.

Subsequently, 2.5 parts by weight of dihexadecyl phthalate of Compound 1 produced in Production Example 1, 100 parts by weight of charge transport material 1 represented by the following structural formula, and polycarbonate resin (trade name: Iupilon Z400, manufactured by Mitsubishi Gas Chemical Company, Inc.) ) 180 parts by weight were mixed, and a coating solution for forming a charge transport layer (3 kg) having a solid content of 20% by weight was prepared using THF as a solvent. This coating solution for forming a charge transport layer is applied onto the previously formed charge generation layer by the same dip coating method as that for the previously formed intermediate layer, and then dried at a temperature of 130 ° C. for 1 hour. The charge transport layer was formed so as to be 20 μm.

Example 2
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on the conductive support in the same manner as in Example 1 except that Compound 2 was used instead of Compound 1 which is a long-chain dialkyl phthalate according to the present invention. A laminated photoreceptor according to the present invention having a laminated structure was produced.

Example 3
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on the conductive support in the same manner as in Example 1 except that Compound 3 was used instead of Compound 1 which is a long-chain dialkyl phthalate according to the present invention. A laminated photoreceptor according to the present invention having a laminated structure was produced.

Example 4
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on the conductive support in the same manner as in Example 1 except that Compound 4 was used instead of Compound 1 which is a long-chain dialkyl phthalate according to the present invention. A laminated photoreceptor according to the present invention having a laminated structure was produced.

Example 5
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on the conductive support in the same manner as in Example 1 except that Compound 5 was used instead of Compound 1 which is a long-chain dialkyl phthalate according to the present invention. A laminated photoreceptor according to the present invention having a laminated structure was produced.

Example 6
An intermediate layer, a charge generation layer, and a charge transport layer were sequentially laminated on the conductive support in the same manner as in Example 1 except that Compound 6 was used instead of Compound 1 which is a long-chain dialkyl phthalate according to the present invention. A laminated photoreceptor according to the present invention having a laminated structure was produced.

Comparative Example 1
A laminated photoreceptor was prepared in the same manner as in Example 1 except that the long-chain dialkyl phthalate of the present invention was not used.

Comparative Example 2
A laminated photoreceptor was prepared in the same manner as in Example 1 except that dioctyl terephthalate (DNOP) was used instead of the long-chain dialkyl phthalate of the present invention.

Comparative Example 3
Instead of the long-chain dialkyl phthalates of the invention, the following structure:
A laminated photoconductor was produced in the same manner as in Example 1 except that a Sumitizer BHT (made by Sumitomo Chemical Co., Ltd.) having the same composition was used.

  For each of the photoreceptors of Examples 1 to 6 and Comparative Examples 1 to 3 manufactured as described above, (a) ozone gas resistance and (b) stability of electrical characteristics were evaluated as follows. c) A comprehensive determination of the photoreceptor performance was made.

(A) Evaluation by ozone gas resistance evaluation apparatus The photoconductors of Examples 1 to 6 and Comparative Examples 1 to 3 were mounted on a test copying machine, respectively, at a temperature of 25 ° C. and a relative humidity of 50%. N: The surface potential V ₁ (V) of the photoconductor immediately after charging and the surface potential V ₂ (V) of the photoconductor after 3 seconds from charging were measured in a normal temperature / normal humidity environment. In the test copying machine, the surface potential of the photosensitive member in the image forming process is set inside a commercially available copying machine (trade name: AR-450S, manufactured by Sharp Corporation) equipped with a corona discharge charger as charging means for the photosensitive member. What provided the surface electrometer (brand name: CATE751, the Gentec company make) so that it could measure was used. The measured surface potential V ₁ (V) immediately after charging and the surface potential V ₂ (V) after 3 seconds from charging are substituted into the following formula (I) to calculate the charge retention ratio DD (%). was the initial charge retention rate DD _0.

Next, using an ozone generation / control device (trade name: OES-10A, manufactured by Directec), each photoconductor is subjected to ozone concentration of about 15 ppm (confirmed by an ozone concentration meter MODEL1200 (trade name) manufactured by Directec). Exposure to ozone in a conditioned sealed container for 164 hours. After exposure to ozone, each photoconductor was left in a room temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50% for 2 hours, and then the charge retention ratio DD (% ) And obtained as the charge retention ratio DD ₀₂ after ozone exposure.

The value obtained by subtracting the charge retention ratio DD ₀₂ after ozone exposure from the charge retention ratio before exposure to ozone, that is, the initial charge retention ratio DD ₀ , is obtained as a charge retention ratio change amount ΔDD (= DD ₀ -DD ₀₂ ). Was used as an evaluation index.

Evaluation by actual machine Each of the actual machine evaluation photoreceptors of Examples 1 to 6 and Comparative Examples 1 to 3 is a commercially available copying machine (trade name: AR-450S manufactured by Sharp Corporation) equipped with a corona discharge charger as a charging means for the photoreceptor. The test images of a predetermined pattern were photographed on 50,000 sheets of recording paper in a normal temperature / normal humidity (N / N) environment at a temperature of 25 ° C. and a relative humidity of 50%. The operation of the copying machine was stopped for 1 hour after the end of the 50,000 actual shots, and then a halftone image was copied on the recording paper, which was used as the first evaluation image. Next, a test image of a predetermined pattern is photographed on 50,000 sheets of recording paper again in an N / N environment at a temperature of 25 ° C. and a relative humidity of 50%, and the copying machine operates for one hour from the point when 50,000 sheets are photographed. Then, a halftone image was copied on the recording paper, and this was used as a second evaluation image.

  The formed first evaluation image and second evaluation image were visually observed, and the toner image was transferred from the portion of the photoconductor that was placed close to the corona discharge charger when the operation of the copying machine was stopped. The image quality of the portion of the recording paper corresponding to the portion was determined based on the degree of occurrence of image defects such as white spots and black bands, and used as an evaluation index for ozone gas resistance. The criteria for determining image quality are as follows.

VG (very good): no image defect occurs in any of the first evaluation image and the second evaluation image;
G (good): Some image defects have occurred in one or both of the first evaluation image and the second evaluation image, but are negligible;
NB (not bad): Some image defects have occurred in one or both of the first evaluation image and the second evaluation image, but there is no problem in practical use;
B (bad): A large number of image defects occur in one or both of the first evaluation image and the second evaluation image and cannot be actually used.

The above-described value of the charge retention rate change ΔDD and the image quality determination result were combined to evaluate the ozone gas resistance of the photoreceptor. The evaluation criteria for ozone gas resistance are shown below.
VG (very good): ΔDD is less than 20% and image quality is VG;
G (good): ΔDD is 20% or more and less than 30% and image quality is VG, or ΔDD is less than 30% and image quality is G;
NB (not bad): No problem in practical use (ΔDD is less than 30% and image quality is NB;
B (bad): ΔDD is 30% or more, or the image quality is B.

(B) Stability of electrical characteristics The photoconductors of Examples 1 to 6 and Comparative Examples 1 to 3 were mounted on a test copying machine, respectively, at room temperature / normal humidity (N / N) at a temperature of 25 ° C. and a relative humidity of 50%. Under the environment, the stability of electrical characteristics was evaluated as follows. In the test copying machine, the surface potential of the photosensitive member in the image forming process is set inside a commercially available copying machine (trade name: AR-450S, manufactured by Sharp Corporation) equipped with a corona discharge charger as charging means for the photosensitive member. What provided the surface electrometer (brand name: CATE751, the Gentec company make) so that it could measure was used. The copying machine AR-450S is a negatively charged image forming apparatus that performs an electrophotographic process by negatively charging the surface of the photoreceptor.

Using the test copying machine on which each of the photoconductors of Examples 1 to 6 and Comparative Examples 1 to 3 is mounted, the surface potential of the photoconductor immediately after the charging operation by the charger is measured as a charging potential V0 (V). It was the charging potential V0 ₁ early. The measured surface potential of the photosensitive member immediately after subjected to exposure by a laser beam as a residual potential Vr (V), which was used as the initial residual potential Vr _1.

Then, after copying successively the test image of a predetermined pattern on the recording paper 30 million copies, the initial and in the same manner by measuring the charge potential V0 and residual potential Vr, the charge potential V0 ₂ and after repeated use of these The residual potential Vr ₂ after repeated use was set. The absolute value of the difference between the initial charging potential V0 ₁ and the charging potential V0 ₂ after repeated use was determined as a charging potential change amount ΔV0 (= | V0 ₁ −V0 ₂ |). Further, the absolute value of the difference between the initial residual potential Vr ₁ and the residual potential Vr ₂ after repeated use was determined as a residual potential change amount ΔVr (= | Vr ₁ −Vr ₂ |). The stability of the electrical characteristics was evaluated using the charging potential change amount ΔV0 and the residual potential change amount ΔVr as evaluation indexes.

The evaluation criteria for the stability of electrical characteristics are shown below.
VG (very good): ΔV0 is 35V or less and ΔVr is 55V or less;
G (good): ΔV0 is 35V or less and ΔVr is more than 55V and 80V or less, or ΔV0 is more than 35V and 75V or less and ΔVr is 55V or less;
NB (not bad): No problem in actual use. ΔV0 exceeds 35V and 75V or less, and ΔVr exceeds 55V and 80V or less;
B (bad): ΔV0 exceeds 75V, or ΔVr exceeds 80V.

(C) Comprehensive Judgment of Photoreceptor Performance A comprehensive judgment of the photoreceptor performance was made by combining the evaluation result of ozone gas resistance and the comprehensive evaluation result of stability of electrical characteristics. The criteria for comprehensive judgment are as follows: VG (very good): ozone gas resistance and electrical property stability are both VG;
G (good): One of ozone gas resistance and electrical property stability is G, and the other is VG or G;
NB (not bad): No problem in actual use (either ozone gas resistance or electrical property stability is no problem in actual use (NB) and the other is not B)
B (bad): One or both of ozone gas resistance and electrical property stability are B.

The above evaluation results are shown in Table 2.

The photoreceptors according to Examples 1 to 6 were good in both ozone gas resistance and repeated electrical characteristics.
On the other hand, the photoconductor according to Comparative Example 1 was a case where no additive was used, but it was greatly deteriorated by exposure to ozone gas and could not withstand repeated use.
The photoreceptor according to Comparative Example 2 was better than the case where no additive was used, but the ozone gas resistance and the repeated electrical characteristics were insufficient.
The photoreceptor according to Comparative Example 3 had deteriorated ozone gas resistance. Further, since the melting point of the added BHT is as low as 69 ° C. and is volatile, it is partially vaporized by heat treatment at a high temperature of 130 ° C. during the formation of the charge transport layer, and the remaining amount inside the photoreceptor is the original added amount It seems that less desired effects could not be obtained.

The electrophotographic photosensitive member using the long-chain dialkyl benzenedicarboxylate of the present invention is an image forming apparatus capable of improving the durability against ozone and nitrogen oxides generated in the image forming apparatus and obtaining a stable image over a long period of time. Realize.
In addition, environmental pollution can be prevented without causing harmful substances to vaporize or scatter during manufacturing.

DESCRIPTION OF SYMBOLS 1 Conductive support 3 Charge generation layer 4 Charge transport layer 5 Surface protective layer

6 Intermediate Layer 7 Multilayer Type Photosensitive Layer 15-18, 21 Photoconductor 20 Image Forming Device 22 Rotation Axis

23, 29 Arrow 24 Charging means (charger)
24a Corona charger 24b Bias power supply 25 Developing means (developer)

25a Developing roller 25b Casing 26 Transfer device 27 Cleaner 27a Cleaning blade

27b Recovery casing 28 Exposure means 28a Light 30 Transfer paper 31 Fixing device 31a Heating roller 31b Pressure roller

Claims (9)

In a laminate type photoreceptor in which a charge generation layer containing a charge generation material, a charge transport layer containing a charge transport material and an optional surface protective layer are laminated in this order on a conductive support, at least the outermost surface layer is the following: General formula (I):
(In the formula, R ₁ and R ₂ independently represent a linear alkyl group having 12 to 30 carbon atoms)
An electrophotographic photoreceptor comprising a long-chain dialkyl benzenedicarboxylate represented by the formula:   The electrophotographic photosensitive member according to claim 1, wherein the long-chain dialkyl benzenedicarboxylate is at least one selected from a long-chain dialkyl phthalate, a long-chain dialkyl isophthalate, and a long-chain dialkyl terephthalate. The long-chain dialkyl benzenedicarboxylate has the following general formula (II):
(In the formula, R ₁ and R ₂ independently represent a linear alkyl group having 12 to 30 carbon atoms)
The electrophotographic photosensitive member according to claim 1, which is a long-chain dialkyl phthalate represented by the formula:   The electron according to any one of claims 1 to 3, wherein the long-chain dialkyl benzenedicarboxylate is dihexadecyl phthalate, dioctadecyl phthalate, dieicosadecyl phthalate, didocosyl phthalate, ditetradocosyl phthalate or dihexadocosyl phthalate. Photoconductor.   The electrophotographic photosensitive member according to any one of claims 1 to 4, wherein the benzenedicarboxylic acid long-chain dialkyl is contained in an amount of 0.1 to 10% by weight with respect to the binder resin.   The electrophotographic photosensitive member according to claim 1, wherein the outermost surface layer is a charge transport layer or a surface protective layer.   The electrophotographic photosensitive member according to any one of claims 1 to 6, wherein the long-chain dialkyl benzenedicarboxylate is contained in two layers of a charge transport layer, a surface protective layer, or a charge transport layer and a surface protective layer.   The electrophotographic photosensitive member according to claim 1, a charging unit that charges the electrophotographic photosensitive member, an exposure unit that exposes the charged electrophotographic photosensitive member, and formed by exposure. Developing means for developing the electrostatic latent image, transfer means for transferring the toner image to the medium, cleaning means for removing and collecting the toner remaining on the photosensitive member, fixing means for fixing the toner image on the medium, and residual on the photosensitive member An image forming apparatus, comprising: a discharging unit that discharges the surface charge. 9. The image forming apparatus according to claim 8, wherein the charging means for charging the electrophotographic photosensitive member is a corona charger.