JPH0560859B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor with excellent durability that can be widely used in electrophotographic application fields such as electrophotographic copying machines, laser beam printers, CRT printers, and electrophotographic engraving systems. [Prior Art] In recent years, various organic photoconductive materials have been developed as photoconductive materials for electrophotographic photoconductors, and in particular, functionally separated photoconductors in which a charge generation layer and a charge transport layer are laminated have already been put into practical use and are used in copying machines and other applications. installed in the printer.
However, one major drawback of these photoreceptors has been that they generally have low durability. Durability is broadly divided 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 photoreceptor surface due to rubbing. It is a major factor that determines the lifespan of the body. Among these, the durability of electrophotographic physical properties, especially image blur, is caused by the deterioration of the charge transport material contained in the photoreceptor surface layer due to active substances such as ozone and _NOx generated from the corona charger. It has been known.
In addition, regarding mechanical durability, paper,
It is known that this is caused by physical contact and rubbing between cleaning members such as blades/rollers, toner, etc. In order to increase the durability of electrophotographic physical properties, it is important to use charge transport materials that are resistant to deterioration by active substances such as ozone and _NOx .
It is known to select a charge transport material with a high oxidation potential. In addition, in order to improve mechanical durability, it is necessary to increase the lubricity of the surface and reduce friction in order to withstand the rubbing caused by paper and cleaning materials, and to improve the surface separation in order to prevent toner filming and fusing. It is important to improve moldability, and Japanese Patent Application Laid-Open No. 56-25746, Japanese Patent Application Laid-open No. 56-25749,
As described in JP-A-61-123850, etc., it is known to incorporate lubricants such as fluorine resin powder, graphite fluoride, and polyolefin resin powder into the surface layer. Furthermore, Japanese Patent Application Laid-Open No. 63-30850 proposes a combination of the above-mentioned measures, and it has been found that this improves the durability and greatly extends the life of the photoreceptor. [Problems to be Solved by the Invention] However, as the life of the photoreceptor has been greatly extended, it has been found that a new problem arises in that the photoreceptor pause memory phenomenon is more likely to occur. The dormant memory phenomenon is basically a deterioration phenomenon caused by corona products, but after copying is complete, the rotation of the photoreceptor stops and the charging ability of the part that is stuck directly under the corona charger decreases. In the case of normal development, the image density decreases in that area and white spots appear on the image, whereas in the case of reverse development, the image density increases and black spots appear on the image. This phenomenon tends to occur after the photoreceptor is used for a long period of time, and becomes more noticeable as the life of the photoreceptor is extended by the above measures. By improving the intake and exhaust mechanism of the image forming apparatus itself and the shape of the charger, some improvement can be seen in this phenomenon, but it is not perfect, especially in small copying machines and copies with cartridge-type photoreceptors. Currently, there are problems with the equipment. That is, an object of the present invention is to provide a photoreceptor that has the above-mentioned electrophotographic physical durability and mechanical durability and does not cause the pause memory phenomenon when used in an actual image forming apparatus. Another object of the present invention is to provide a photoreceptor that can always produce stable, high-quality images with little potential fluctuation. [Means for Solving the Problems] As a result of extensive studies in accordance with the above objective, the present inventors found that a lubricant powder, a charge transport substance with an oxidation potential of 0.6V or more, and a general formula () It has been found that a photoreceptor having a surface layer containing a compound represented by the above has the ability to meet the above requirements. That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer on a conductive support, in which the surface layer comprises a lubricant powder, a charge transport substance having an oxidation potential of 0.6 V or more, and the general formula () [However, X ₁ , X ₂ and X ₃ are -H or -
Indicates CH ₃ , X ₄ and X ₅ are

[Formula] Also teeth

[Formula] is shown. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following. In the present invention, by adding lubricant powder, the mechanical properties such as the slipperiness and abrasion resistance of the surface layer and the mold releasability against deposits are improved. By using a charge transport material of
This is intended to stabilize electrophotographic characteristics. Furthermore, in the present invention, the compound of the general formula () is used to prevent the photoreceptor stop memory phenomenon that occurs newly when the life of the photoreceptor is extended by these means. The lubricant powder used in the present invention includes tetrafluoroethylene resin, trifluorochloride ethylene resin, hexafluoroethylene propylene resin, difluorodichloride ethylene resin, vinylidene fluoride resin, and copolymers thereof. Examples include fluorine resin powders such as fluorine resin powders, polyolefin resin powders such as polyethylene, polypropylene, polyhexene, and their copolymers, and even fluorinated graphite powders, and two or more types may be used in combination. good. Among these, ethylene tetrafluoride resin and vinylidene fluoride resin are preferred from the viewpoint of slipperiness, abrasion resistance, and mold releasability. Examples of charge transport substances with an oxidation potential of 0.6 V or higher used in the present invention include hydrazone compounds, stilbene compounds, carbazole compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, and polyarylalkane compounds. Selected from categories, etc. Further, two or more types of charge transport materials may be used in combination. The higher the oxidation potential, the better the durability performance.
The effect becomes more pronounced when the voltage exceeds 0.7V. Examples of the compound represented by the general formula () used in the present invention include the following. These compounds are one of the phenol derivatives known as radical scavengers or antioxidants for plastics, rubber, etc. Two or more of these compounds may be used in combination. The surface layer in the present invention is a charge transport layer when the photosensitive layer has a structure in which a charge generation layer and a charge transport layer are laminated in this order on a conductive support,
In addition, in the case of a structure in which a charge generation layer is laminated on a charge transport layer, the charge generation layer contains a charge transport substance, and in the case of a single layer structure in which a charge generation substance and a charge transport substance are mixed in the same layer. This is a single layer. Charge transport materials generally have a low molecular weight and cannot be used to form a film by themselves, so a resin having film-forming properties is used as a binder to form a photosensitive layer in which lubricant powder is dispersed. The binder resin may be any polymeric compound that has film-forming properties, but polymethacrylate, polycarbonate, polyarylate, polyester, and polysulfone are recommended because they have a certain degree of hardness even when used alone and do not interfere with carrier transport. etc. are preferable. The content of the lubricant powder is suitably 1 to 30% by weight, particularly preferably 2 to 20% by weight, based on the material constituting the surface layer of the photosensitive layer. If the content is less than 1% by weight, the surface modification effect by dispersing the lubricant powder will not be sufficient, while if it exceeds 30% by weight, the light transmittance will decrease, and the carrier mobility will also decrease. The amount of the compound represented by the above general formula () to be added is based on 100 parts by weight of the material constituting the surface layer of the photosensitive layer.
0.1% to 30% by weight is suitable, particularly preferably 0.2% to 10% by weight. Added amount is 0.1% by weight
If it is less than 30, the hibernation memory prevention effect is not sufficient.
If it exceeds % by weight, the residual potential tends to increase. When producing the electrophotographic photoreceptor of the present invention, the conductive support may be one that itself has conductivity, such as aluminum, aluminum alloy, stainless steel, etc. In addition, aluminum, aluminum alloy, stainless steel, etc. can be used. Plastics having a layer formed of indium oxide, tin oxide, indium oxide-tin oxide alloy, etc. by vacuum evaporation, and supports in which conductive particles are coated on plastic or the above-mentioned conductive support with a suitable binder. , a support made of plastic or paper impregnated with conductive particles, a plastic containing a conductive polymer, etc. can be used. A subbing layer having barrier and adhesive functions can also be provided between the conductive support and the photosensitive layer.
The undercoat layer is made of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyvinyl butyral, phenolic resin, polyamide (nylon 6, nylon 66, nylon
610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the undercoat layer is 0.1 to 40 μm, preferably 0.3 to 40 μm.
3 μm is appropriate. As charge generating substances, selenium-tellurium, pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthrone pigments, dibenzpyrenequinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanine, Quinocyanine and the like can be used, and it is also possible to use a mixture of various charge generating substances in order to obtain an appropriate spectral sensitivity. As a dispersion method for lubricant powder, general dispersion means,
That is, a homogenizer, an ultrasonic wave, a ball mill, a vibration mill, a sand mill, an attritor, a roll mill, etc. can be used. The lubricant powder is added to the binder dissolved in a suitable solvent, and then dispersed by the above-mentioned dispersion method. A surface layer coating liquid containing a lubricant can be obtained by mixing an appropriate amount of this with a solution in which a binder, a charge transport substance, and a compound represented by the above general formula (2) are dissolved in a solvent. Coating can be performed using a coating method such as a dip coating method, a spray coating method, a Meyer bar coating method, or a blade coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying is
It can be carried out at 30° C. to 300° C. for a time ranging from 5 minutes to 2 hours, either stationary or under ventilation. The oxidation potential in the present invention is obtained by sweeping the potential of the working electrode with a potential sweeper using a saturated calomel electrode as a reference electrode and a 0.1N (n-Bu) ₄ N ⁺ ClO ^- ₄ acetonitrile solution as an electrolyte. The peak position of the current-potential curve was directly determined as the value of the oxidation potential. For more information, sample at 0.1N (n-Bu)N ⁺ ClO ^- ₄
Dissolve in an electrolytic solution of acetonitrile solution to a concentration of 5 to 10 mmol%. Then, a voltage is applied to this sample solution, and a current change is measured when the voltage is changed linearly from a low potential to obtain a current-potential curve. The potential value corresponding to the first inflection point of the current value in this current-potential curve was defined as the oxidation potential in the present invention. Example 1 An 80φ x 360mm aluminum cylinder was used as a conductive support, and polyamide resin (product name:
A 5% methanol solution of Amilan CM-8000 (manufactured by Toray Industries) was applied by dipping to form a 1 μm thick undercoat layer. Next, add 10 parts (by weight) of the disazo pigment with the structural formula below. 100 parts of cyclohexanone were dispersed for 20 hours using a sand mill apparatus using 1φ glass beads. 50 to 100 (appropriate) parts of tetrahydrofuran were added to this dispersion and applied onto the undercoat layer, followed by drying at 100° C. for 5 minutes to form a charge generation layer with a thickness of 0.15 μm. Next, a polyethylene resin powder (trade name: Frozen 13142 manufactured by Seitetsu Kagaku Co., Ltd.) was used as a polyolefin-based lubricant powder, and a compound with an oxidation potential of 0.67 (V) having the following structural formula was used as a charge transport substance. A compound with the following structural formula, (IRGANOX1330: manufactured by Ciba Geigy Japan) and bisphenol Z type polycarbonate resin (manufactured by Teijin Kasei) were prepared as a binding agent binder. First, 20 parts of the polycarbonate resin, 20 parts of the above charge transport substance, and 0.2 parts of the above compound for suppressing dormant memory were dissolved in 100 parts of monochlorobenzene, and 6 parts of the above polyethylene resin powder was added to this, and the mixture was heated in a stainless steel ball mill for 50 hours. The mixture was dispersed and 20 parts of dichloroethane was further added to prepare a charge transport layer coating solution. Apply this solution on the generation layer,
A charge transport layer having a thickness of 20 μm was formed by drying with hot air at ℃ for 90 minutes, and photoreceptor 1 was manufactured. Comparative Example 1 The following structural formula as a charge transport material Photoreceptor 2 was produced in the same manner as in Example 1 except that a compound having an oxidation potential of 0.54 (V) was used. Comparative Example 2 Photoreceptor 3 was produced in the same manner as in Example 1 except that polyethylene resin powder was not added as the lubricant powder. Comparative example 3 Compound for measures against dormant memory Photoreceptor 4 was manufactured in the same manner as in Example 1 except that . Blade penetration depth is 1.0mm for photoconductors of
Installed in a Canon copier NP-3525 that was modified to have a cleaning roller relative speed of 106%.
Table 1 shows the results of a 100,000-sheet durability evaluation.

[Table] In Table 1, potential fluctuations are -650V for dark area potential (V _D ), -150V for light area potential (V _L ) at the initial stage of durability,
Set the residual potential (V _R ) at that time to −10V,
This shows the change in absolute value after 100,000 sheets of printing. In addition, the pause memory refers to the change in image density between the area immediately below the corona charger and other areas, or the potential ( _V
It is expressed as the change in . As shown in Table 1, the photoreceptor of Example 1 has small potential fluctuations and small scratches of the surface layer even after 100,000 sheets, and no pause memory occurs, indicating high practical durability. On the other hand, in Comparative Example 1, which used a charge transport material with a low oxidation potential, the potential fluctuation was large;
For those that do not use a lubricating material, the surface layer is extremely abraded, and potential fluctuations occur as a result. In addition, scratches have also occurred on the surface of the photoreceptor, which are also visible on the image. Furthermore, the photoconductor of Comparative Example 3 to which the compound for counteracting dormant memory was not added was as good as Example 1 in terms of potential fluctuations and scraping, but the dormant memory was
90V is also generated, which is clearly recognized in the image. Example 2 An 80φ x 360mm aluminum cylinder was used as a conductive support, and a 5% methanol solution of polyamide resin (product name: Amilan CM-8000, manufactured by Toray Industries, Ltd.) was applied by dipping to a 0.5 μm thick layer. A pull layer was provided. Next, add 10 parts of trisazo pigment with the following structural formula. Polyvinyl butyral resin (Product name: ESLETSUKU)
6 parts of BL-S (manufactured by Sekisui Chemical) and 50 parts of cyclohexanone were dispersed using a sand mill device using glass beads. Add methyl ethyl ketone to this dispersion.
100 parts was added and coated on the undercoat layer to form a charge generation layer with a thickness of 0.2 μm. Next, tetrafluoroethylene resin powder (trade name: Lubron L-2 manufactured by Daikin Industries) was used as the fluorine-based resin powder, and a compound of the following structural formula was used as the charge transport material. (Oxidation potential: 0.81 (V)), the compounds shown in Table 2 as compounds for preventing dormant memory, and bisphenol Z type polycarbonate resin (manufactured by Teijin Kasei) as a binding agent binder were prepared.

【table】

[Table] Below, 20 parts of charge transport material, 20 parts of binding agent binder
A photoreceptor was produced using the compounds listed in Table 2 in the same manner as in Example 1. The amount of fluorine-based resin powder added is 2 parts, and the amount of the compound for suppressing dormant memory is 0.2 parts, but Compound No. 1 is 0.05 parts (0.125 parts by weight based on 100 parts by weight of the surface layer constituent material). ), 0.1 part (equivalent to 0.25% by weight), 0.5 part (equivalent to 1.25% by weight), 1.0 part (equivalent to 2.5% by weight)
(equivalent to 100% by weight), 4.0 parts (equivalent to 100% by weight). Table 3 shows the results of evaluating the above photoreceptors. For the evaluation, we used an image scan reversal development type laser beam printer equipped with a semiconductor laser with an oscillation wavelength of 780 nm, a cleaning blade with a penetration depth of 0.1 mm, and a two-component developer consisting of toner and carrier. In the table above, potential fluctuation refers to the change in absolute value after 100,000 sheets of printing when the dark area potential is set to -600V, the light area potential is -150V, and the residual potential is -10V at the beginning of durability. It is something that Also, regarding hibernation memory, the actual

[Table] The measurement method is the same as in Example 1, but since reversal development is used, the change in image density appears in the direction of increase in density, contrary to Example 1. As can be seen from Table 3, the system to which the compound having the structure described in the present invention is added clearly has a better effect on preventing rest memory than additives having other structures.
In addition, there are few negative effects such as potential fluctuations. Example 3 An 80φ x 360mm aluminum cylinder was used as a conductive support, and polyamide resin (product name:
A 5% methanol solution of Amilan CM-8000 (manufactured by Toray Industries) was applied by dipping to form a 1 μm thick undercoat layer. Next, add 10 parts of the disazo pigment with the following structural formula. Polyvinyl butyral resin (Product name: ESLETSUKU)
6 parts of BL-S (manufactured by Sekisui Chemical) and 50 parts of cyclohexanone were dispersed using a sand mill device using glass beads. Add methyl ethyl ketone to this dispersion.
100 parts was added and coated on the undercoat layer to form a charge generation layer with a thickness of 0.2 μm. Next, graphite fluoride (manufactured by Daikin Industries, Ltd.) was used as a carbon fluoride powder, the same compound as in Example 1 was used as a compound for preventing dormant memory, the compound shown in Table 4 was used as a charge transport substance, and the binder was used as a binder. Bisphenol Z type polycarbonate resin (manufactured by Teijin Kasei) was prepared.

【table】

[Table] Photoreceptors were manufactured using the charge transport materials listed in Table 4 in the same manner as in Example 1 using 20 parts of the charge transport material and 20 parts of the binder. The amount of graphite fluoride powder added was 2 parts, and the amount of the compound for suppressing dormant memory was 0.2 parts. The above photoreceptors were evaluated in the same manner as in Example 1, and the results are shown in Table 5.

【table】

[Table] As is clear from the table, charge transport materials whose oxidation potential is lower than 0.6 (V) are superior in terms of rest memory, but when using charge transport materials whose oxidation potential is higher than 0.6 (V), It can be seen that it is large in comparison. Example 4 An 80φ x 360mm aluminum cylinder was used as a conductive support, and polyamide resin (product name:
A 5% methanol solution of Amilan CM-8000 (manufactured by Toray Industries) was applied by dipping to form a 1 μm thick undercoat layer. Next, add 10 parts of the disazo pigment with the following structural formula. Polyvinyl butyral resin (Product name: ESLETSUKU)
BXL (manufactured by Sekisui Chemical) and 100 parts of cyclohexanone were dispersed for 20 hours using a sand mill device using glass beads. 50 to 100 parts of tetrahydrofuran was added to this dispersion, which was coated on the undercoat layer and dried at 100° C. for 5 minutes to form a charge generation layer with a thickness of 0.15 μm. Next, tetrafluoroethylene resin powder (trade name: Lubron L-2 manufactured by Daikin Industries) was used as the fluorine-based resin powder, and a compound of the following structural formula was used as the charge transport material. (Oxidation potential: 0.66 (V)), the same compound as in Example 1 as a compound for counteracting dormant memory, and bisphenol Z type polycarbonate resin (manufactured by Teijin Kasei) as a binding agent binder. Hereinafter, using the same method as in Example 1 using 20 parts of the charge transport substance and 20 parts of the binder, the amount of the tetrafluoroethylene resin powder added was adjusted to 1.0 by weight relative to the surface layer constituent material (charge transport substance + binder). weight%, 10.0 weight%,
Photoreceptors were manufactured with three levels of 30% by weight. The above photoreceptors were evaluated in the same manner as in Example 1, and the results are shown in Table 6.

[Table] Example 5 In the same manner as in Example 4, layers up to the undercoat layer were coated on a conductive support. Next, a solution prepared by dissolving 15 parts of the charge transport material used in Example 1 and 10 parts of polycarbonate Z resin in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied onto the undercoat layer to form a charge transport layer with a thickness of 15 μm. . Next, 4 parts of the disazo pigment used in Example 1, 10 parts of polycarbonate Z resin,
Charge generation layer dispersion 1 was prepared by dispersing 50 parts of cyclohexanone for 20 hours in a sand mill using 1φ glass beads. Next, a tetrafluoroethylene resin powder, a fluorine-based acrylic oligomer as a dispersant, the above hydrazone compound, and polycarbonate Z resin were prepared. First, 10 parts of polycarbonate resin, 4 parts of hydrazone compound
and 0.15 parts of fluorine-based acrylic oligomer are dissolved in 10 parts of dichloromethane and 40 parts of monochlorobenzene. Next, add tetrafluoroethylene resin powder to this.
1.5 parts were added and dispersed in a stainless steel ball mill for 40 hours. Furthermore, the additives used in Example 1 were added to this liquid.
Charge transport layer liquid 1 was prepared by adding 0.3 parts. A paint obtained by mixing the charge generation layer dispersion 1 and the charge transport layer liquid 1 was applied onto the charge transport layer to form a charge generation layer having a thickness of 5 μm, thereby producing a photoreceptor. The copying machine used in Example 1 was modified so that it could be positively charged, and this photoreceptor was evaluated in the same manner as in Example 1, but even after 100,000 copies, potential fluctuations, photoreceptor scraping, and pause memory were small and high. A quality copy was obtained. Comparative Example 4 As a comparative example of Example 5, a photoreceptor without additives was manufactured and the same evaluation was performed. After 100,000 copies, a pause memory appeared on the image, and electrically △Vd
fluctuated significantly to -160V. Example 6 An 80φ×360mm aluminum cylinder was prepared as a conductive support. On the other hand, 100 parts of conductive powder coated with tin oxide containing 10% of antimony oxide so that the amount of titanium oxide was 75% by weight was mixed with resol-based phenolic resin.
100 parts and 30 parts of methanol, 100 parts of methyl cellosolve
The mixture was added to a solution consisting of 50% of the total amount of water and dispersed well using a ball mill to form a paint. This coating material was dip coated onto a conductive support and cured by heating at 140° C. for 30 minutes to form a conductive undercoat layer of 20 μm. On top of this, 1 part of polyamide resin (6-66-610-124 original nylon copolymer) and 8-nylon resin (methoxymethylated 6-nylon methoxylation rate 30
%) dissolved in a solvent consisting of 50 parts of methanol and 40 parts of phthanol, and applied by dipping.
After drying at 70°C for 10 minutes, a 0.5 μm thick undercoat layer was formed. Next, add 10 parts of the disazo pigment with the following structural formula. 6 parts of polyvinylbenzal resin and 50 parts of cyclohexanone were dispersed for 20 hours using a sand mill device using glass beads (Dispersion 1). Next, 10 parts of trisazo pigment with the following structural formula, 6 parts of polyvinylbenzal resin and 50 parts of cyclohexanone were dispersed for 20 hours using a sand mill device using glass beads (Dispersion 2). Mix 30 parts of this dispersion 1 and 10 parts of dispersion 2,
Furthermore, 50 to 60 parts of tetrahydrofuran was added, coated on the undercoat layer, and dried at 100°C for 5 minutes to a thickness of 0.25 μm.
A thick charge generation layer was formed. Next, we used tetrafluoroethylene resin powder as a fluorine-based resin powder, a fluorine-based acrylic oligomer as a dispersion aid, a compound with the following structural formula (oxidation potential 0.81V) as a charge transport substance, and a compound for counteracting dormant memory. The same compound as in Example 1 was prepared as a material, and bisphenol Z type polycarbonate resin was prepared as a binder. A photoreceptor was manufactured in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 7.

〔Effect of the invention〕

As mentioned above, the lubricant powder and the oxidation potential are 0.6V.
According to the electrophotographic photoreceptor of the present invention containing the above-mentioned charge transporting substance and a compound having a specific structure, it has excellent electrophotographic physical properties and mechanical durability, and stable high-quality images can always be obtained. I can do it.

Claims (1)

[Scope of Claims] 1. In an electrophotographic photoreceptor having a photosensitive layer on a conductive support, the surface layer includes a lubricant powder and an oxidation potential.
A charge transport material with a voltage of 0.6V or more and the general formula () [However, X ₁ , X ₂ and X ₃ are -H or -
CH ₃ is represented, and X ₄ and X ₅ represent [Formula] or [Formula]. ] An electrophotographic photoreceptor comprising a compound represented by the following. 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer, and the charge transport layer is coated on the charge generation layer. . 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer, and the charge generation layer is coated on the charge transport layer. . 4. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer is a single layer containing a charge generating substance and a charge transporting substance. 5. The electrophotographic photoreceptor according to claim 1, wherein the lubricant powder is a fluorine resin powder, a polyolefin powder, or a fluorinated carbon powder.