JP2644273B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high sensitivity and durability widely used in electrophotographic application fields such as electrophotographic copying machines, laser beam printers, CRT printers, and electrophotographic plate making systems. The present invention relates to an electrophotographic photoreceptor excellent in the above.

[Prior art] In recent years, various organic photoconductive materials have been developed as photoconductive materials for electrophotographic photoreceptors. Among photoreceptors using these organic photoconductive materials, particularly, a charge generation layer and a charge transport layer have been already used. The stacked function-separated type is commercialized and installed in copiers and printers. However, these photoreceptors generally have reduced durability, fluctuations in residual potential, reduced charging ability, durability of electrophotographic characteristics against image blur, and mechanical durability against abrasion and scratches due to rubbing of the surface of the photoreceptor. The life of these photoconductors was not satisfactory because of their poor properties.

Poor durability due electrophotographic properties face, particularly the cause of image blur, ozone generated from the corona charger, it is known that due to the deterioration of the charge transport material of the photosensitive member surface layer by NO _X, etc., electrophotographic In order to improve the durability of the characteristics,
Ozone, high oxidation potential materials are known as difficult to charge transport material is degraded by the NO _X or the like.

The cause of poor mechanical durability is known to be caused by paper, cleaning members such as blades and rollers, toner, etc. contacting and rubbing on the surface of the photosensitive layer. To a surface layer that improves the lubricity of the surface of the photoreceptor, reduces friction so that the surface can withstand rubbing, and improves releasability to prevent toner filming and fusing. Lubricants such as fluororesins, fluorinated graphite and polyolefin resins have been proposed as additives (Japanese Patent Application Laid-Open Nos. 56-25746, 56-25749 and 61-25749).
123850).

Further, it has been proposed to apply a combination of the above-mentioned techniques for improving the durability of the electronic characteristics and the mechanical durability (Japanese Patent Laid-Open No. 30850/1988). be able to.

[Problems to be Solved by the Invention] However, it has been pointed out that the above-mentioned technology easily causes a photoreceptor pause memory phenomenon as a new problem. The pause memory phenomenon is basically one of the degradation phenomena caused by corona products, but after the copy is completed, the rotation of the photoconductor stops, and the charging ability of the photoconductor in the portion stopped near the corona charger decreases. However, in the case of normal development, the image density is reduced only in that portion, and in the case of the reversal phenomenon, the image density is increased. This phenomenon is likely to occur after the photoconductor has been used for a long period of time, and becomes more conspicuous as the above-described improvement extends the life of the photoconductor. By improving the air intake / exhaust mechanism and charger shape of the image forming apparatus main body, a slight improvement in the sleep memory can be seen, but it is not perfect, especially in a small copy apparatus, a copy apparatus having a cartridge type photoconductor. It becomes.

Accordingly, it is an object of the present invention to provide a photoreceptor which has both durability of electrophotographic characteristics and mechanical durability, and which does not cause a pause memory phenomenon when used in an actual image forming apparatus. .

[Means for Solving the Problems] The problem is that, in an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, at least one kind of lubricant powder and an oxidation potential The problem was solved by an electrophotographic photoreceptor characterized by containing at least one charge transport material of 0.6 V or more and a compound represented by the following general formula (1).

General formula (1) [Where R is Where n is a positive integer and X ₁ is Or X ₂ is a hydrogen atom, in an alkenyl group is present invention alkyl or 2 to 10 carbon atoms having 1 to 10 carbon atoms, (i) the addition of lubricant powder surface layer slipperiness and abrasion resistance of Has an effect on the improvement of mechanical properties such as releasability from attachments, and (ii) the use of a charge transport material having a high oxidation potential of 0.6 V or more improves the durability against corona products, It contributes to stabilization of electrophotographic characteristics such as sensitivity, residual potential, and image blur. (Iii)
Further, the compound of the general formula (1) has an effect of preventing the photoreceptor pause memory phenomenon which newly occurs because the photoreceptor life is extended by the means of (i) and (ii).

As the lubricant powder used in the present invention, for example, ethylene tetrafluoride resin powder, ethylene trifluoride resin powder, hexafluoroethylene propylene resin powder, ethylene difluoride ethylene chloride resin powder, fluoride Fluorinated resin powders such as vinylidene resin powders and copolymers of monomers composing these polymers; polyethylene resin powders, polypropylene resin powders, polyhexene resin powders, and copolymers of monomers composing these polymers Polyolefin resin powders such as;
And carbon fluoride powder.

Examples of the charge transport material having an oxidation potential of 0.6 V or more used in the present invention include hydrazone compounds, stilbene compounds, carbazole compounds, pyrazoline compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, and polyaryl compounds. Alkanes and the like. The higher the oxidation potential of the charge transporting material, the more the durability of the photoreceptor is improved. In particular, when the oxidation potential is 0.7 V or more, the effect becomes more remarkable.

Since the charge transporting substance generally has a low molecular weight, it cannot form a film by itself, and a resin having a film forming property is used as a binder to form a photosensitive layer in which the lubricant powder is dispersed. The binder resin is not particularly limited as long as it is a polymer compound having a film-forming property.However, in view of the fact that the binder resin has a certain degree of hardness and does not hinder carrier transport, the number of polymethacrylates, polycarbonate, poly Preferred are arylate, polyester, polysulfone and the like.

The binder resin contained in the layer farthest from the substrate is usually used in an amount of about 50 to 300 parts by weight based on 100 parts by weight of the charge transporting substance.

The content of the lubricant powder dispersed in the layer farthest from the substrate is based on the total amount of the charge transporting substance and (if the layer contains a charge generating substance, further, the charge generating substance) the binder. 1.0 to 30% by weight is suitable, and 2.0 to 20% by weight is particularly preferable.

If the content is less than 1.0% by weight, the surface modification effect by the dispersion of the lubricant powder is not sufficient, while if it exceeds 30% by weight, the light transmittance tends to decrease, and the mobility of the carrier tends to decrease.

Examples of the compound represented by the general formula (1) used in the present invention include the following compounds.

The content of the compound represented by the general formula (1) contained in the layer furthest from the substrate is determined by the amount of the charge-transporting substance and (if the layer contains a charge-generating substance, further, the charge-generating substance) Usually, 0.1 to 30% by weight, and particularly preferably 0.2 to 10% by weight, based on the total amount of Addition amount
If the amount is less than 0.1% by weight, the effect of preventing the resting memory is insufficient, and if it exceeds 30% by weight, the residual potential tends to increase.

When the electrophotographic photoreceptor of the present invention is manufactured, a substrate having conductivity itself, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold Or platinum can be used, and in addition, aluminum, aluminum alloy, indium oxide, tin oxide,
A substrate having a layer in which an indium oxide-tin oxide alloy or the like is formed by a vacuum evaporation method (for example, carbon black, silver particles, etc.) coated on a plastic together with a suitable binder, and conductive particles on a plastic or paper. For example, an impregnated substrate, a plastic having a conductive polymer, or the like can be used.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive layer 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, copolymer nylon, alkoxymethyl nylon, etc.), polyurethane, gelatin, aluminum oxide and the like.

The thickness of the undercoat layer is suitably 0.1 to 40 microns, preferably 0.3 to 3 microns.

Selenium-tellurium, pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthantrone pigments, dibenzpyrene quinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines as charge generation substances Quinocyanine and the like can be used.

As a method of dispersing the lubricant powder, general dispersing means such as a homogenizer, an ultrasonic wave, a ball mill, a vibration mill, a sand mill, an attritor, and a roll mill can be used. After the lubricant powder is added to the binder dissolved in an appropriate solvent, it is dispersed by the above dispersion method. This is mixed with an appropriate amount of a solution obtained by dissolving a binder, a charge transporting substance and the compound represented by the general formula (1) in an appropriate solvent to obtain a surface layer coating solution containing a lubricant powder.

The coating can be performed by a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a Meyer bar coating method, a blade coating method, a roller coating method, a curtain coating method and the like.
Drying is preferably performed by touch drying at room temperature and then heating and drying. The heating and drying can be performed at 30 ° C. to 200 ° C. for 5 minutes to 2 hours in a stationary or blown state.

 In the present invention, the oxidation potential refers to the saturated calomel electrode.
Electrode, 0.1N (n-Bu)_FourN ClO_Four Acetone solution into electrolyte
Used as the working electrode by the potential sweeper
Of the resulting current-potential curve.
The position was directly obtained as the value of the oxidation potential.

Hereinafter, the present invention will be described with reference to examples. Parts in Examples are parts by weight.

Example 1 An aluminum cylinder of 80φ × 360 mm was used as a base, and a 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray) was applied by dipping to form an undercoat layer having a thickness of 1 μm.

Next, 10 parts of a disazo pigment having the following structural formula 6 parts of vinyl butyral resin (trade name: Esrec BXL, manufactured by Sekisui Chemical Co., Ltd.) and 100 parts of cyclohexanone
The mixture was dispersed for 20 hours by a sand mill using φ glass beads. Add this dispersion to tetrahydrofuran 50-100 (as appropriate)
Then, the mixture was applied onto the undercoat layer and dried at 100 ° C. for 5 minutes to form a 0.15 μm thick charge generation layer.

Next, a polyethylene resin powder (trade name: FLOWSEN 13142, manufactured by Iron and Steel Chemical) as a lubricating powder (polyolefin-based powder), and an oxidation potential of 0.67 of the following structural formula as a charge transporting substance.
The compound of V, the following structural formula (corresponding to the above general formula (1)) for preventing dormant memory And a bisphenol Z-type polycarbonate resin (manufactured by Teijin Chemicals Ltd.) was prepared as a binder.
First, 20 parts of the polycarbonate resin and the charge transport material 20
And 0.2 parts of the above compound for preventing quiescent memory were dissolved in 100 parts of monochlorobenzene, and 6 parts of the above polyethylene resin powder was added thereto.
After time dispersion, 20 parts of dichloroethane was added to prepare a charge transport layer coating solution. This liquid was applied on the above-mentioned generation layer, and hot-dried at 100 ° C. for 90 minutes to form a 20 μm thick charge transport layer.

Comparative Example 1 Photosensitivity was obtained in the same manner as in Example 1 except that a compound having an oxidation potential of 0.54 V having the following structural formula was used as a charge transporting substance. Created body.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 1, except that no lubricant powder was added.

Comparative Example 3 A photoconductor was prepared by the same way as that of Example 1 except that no compound for preventing quiescent memory was added.

The above photoreceptor was mounted on a Canon copier NP-3525 modified so that the blade penetration amount was 1.0 mm and the relative speed of the cleaning roller was 106%, and a 100,000-sheet durability test was performed. Table 1 shows the results.

In Table 1, the term “potential fluctuation” refers to a state in which the dark part potential (V _D ) is −650 V, the light part potential (V _L ) is −150 V, and the remaining potential (V _R ) at that time is −10 V at the beginning of the durability test. 3 shows the change in the absolute value after the 100,000-sheet durability test. Also, the pause memory stops the rotation of the photoconductor after the durability test for 100,000 sheets.
This is expressed by a change in image density between a portion immediately below the corona charger and another portion after 10 hours, or a change in potential (V _D ).

As can be seen from Table 1, the photoreceptor of Example 1 showed a small variation in potential and abrasion of the surface layer even after the 100,000-sheet durability test, and showed no high-speed memory and high durability in practice. On the other hand, in the case of using the charge transporting substance having a low oxidation potential of Comparative Example 1, the potential fluctuation was large, and in the case of using no lubricant powder of Comparative Example 2, the surface layer was greatly scraped. Voltage fluctuations occur. The surface of the photoreceptor is also scratched, and the effect appears on the image. Further, in the photoreceptor of Comparative Example 3 to which the compound for preventing a resting memory was not added, potential fluctuation and abrasion were excellent as in Example 1, but the resting memory generated 90 V in potential, resulting in an image on an image. The effect is also remarkably recognized.

Example 2 An aluminum cylinder of 80 mm x 360 mm was used as a conductive substrate, and a polyamide resin (trade name: Amiran)
A 5% methanol solution of CM-8000 (manufactured by Toray Industries, Inc.) was applied by an immersion method to form an undercoat layer having a thickness of 0.5 μm.

Next, 10 parts of a trisazo pigment having the following structural formula Rivinyl butyral resin (trade name: Eslec BL-S,
6 parts of Sekisui Chemical Co., Ltd.) and 50 parts of cyclohexanone were dispersed by a sand mill using glass beads. To this dispersion, 100 parts of methyl ethyl ketone was added and coated on the undercoat layer to form a 0.2 μm thick charge generation layer.

Next, a tetrafluoroethylene resin powder (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) as a lubricating powder (fluorine-based resin powder), and a compound of the following structural formula (oxidation potential 0.81) as a charge transporting substance. For prevention of sleep memory Compounds shown in Table 2 were prepared as compounds, and bisphenol Z-type polycarbonate resin (manufactured by Teijin Chemicals Ltd.) was prepared as a binder.

Hereinafter, a photoreceptor was prepared in the same manner as in Example 1 using the compounds listed in Table 2. With respect to 20 parts of the charge transport material and 20 parts of the binder binder, the addition amount of the fluorine-based resin powder is 2 parts, and the addition amount of the compound for preventing sleep memory is 0.2 parts. 0.05 parts, 0.1 parts, 0.5 parts,
Five levels of 1.0 and 4.0 parts.

Table 3 shows the results of the evaluation of the above photoreceptors. For the evaluation, a laser beam printer of an image scan reversal development system using a two-component developer composed of a toner and a carrier, equipped with a semiconductor laser having an oscillation wavelength of 780 nm, a cleaning blade having a penetration amount of 1.0 mm, and a toner was used. Table 3
In the potential fluctuation in the endurance test early in the dark part potential -600V,
The change in the absolute value after a 100,000-sheet durability test was set, with the bright part potential set to −150 V and the residual potential at that time set to −10 V. The rest memory is the same measurement method as in the first embodiment, but the image density change appears in the direction of the density increase contrary to the first embodiment because of the reversal development.

As can be seen from Table 3, in the system to which the compound corresponding to the general formula (1) is added, the effect of preventing the rest memory is clearly superior to the case of adding the compound having another structure, and the adverse effect on the potential fluctuation and the like. Few. Further, even when the amount of the compound corresponding to the general formula (1) is changed, the effect of preventing the memory from being inactive is high, and the potential stability is high without increasing the residual potential.

Example 3 An aluminum cylinder of 80φ × 360 mm was used as a base,
A 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray) is applied to this by an immersion method, and 1 μm
A thick undercoat layer was provided. Next, 10 parts of a disazo pigment having the following structural formula Six parts of a nilbutyral resin (trade name: Eslec BL-S, manufactured by Sekisui Chemical) and 50 parts of cyclohexanone were dispersed in a sand mill using glass beads. 100 parts of methyl ethyl ketone is added to this dispersion and applied on the undercoat layer,
A charge generation layer having a thickness of 0.2 μm was formed.

Next, fluorinated graphite (manufactured by Daikin Industries, Ltd.) as a carbon fluoride-based powder, the same compound as in Example 1 as a compound for preventing sleep memory, a compound shown in Table 4 as a charge transport material,
A bisphenol Z-type polycarbonate resin (manufactured by Teijin Chemicals Ltd.) was prepared as a binder.

Hereinafter, a photoreceptor was prepared in the same manner as in Example 1 using the charge transporting substances listed in Table 4. The addition amount of the fluorinated graphite powder was 2 parts,
0.2 parts.

Table 5 shows the evaluation results of the above photoreceptors in the same manner as in Example 1.

As can be seen from the table, those having an oxidation potential of less than 0.6 of the charge transport material are superior in terms of preventing resting memory,
It can be seen that the potential fluctuation is larger than that in the case of using the one with 0.6 V or more.

Example 4 An aluminum cylinder of 80φ × 360 mm was used as a base,
A 5% methanol solution of a polyamide resin (trade name: Amilan CM-8000, manufactured by Toray) is applied to this by an immersion method, and 1 μm
A thick undercoat layer was provided. Next, 10 parts of a disazo pigment having the following structural formula 6 parts of a vinyl butyral resin (trade name: Esrec BXL, manufactured by Sekisui Chemical) and 100 parts of cyclohexanone at 1φ
The dispersion was performed for 20 hours using a sand mill using glass beads. To this dispersion, 50 to 100 parts of tetrahydrofuran was added and applied on the undercoat layer.
A charge generation layer having a thickness of 5 μm was formed.

Next, a tetrafluoroethylene resin powder (trade name: Lubron L-2, manufactured by Daikin Industries, Ltd.) as a fluorine-based resin powder, a compound of the following structural formula (oxidation potential: 0.66 V) as a charge transporting substance,
Compound for preventing sleep memory The same compound as in Example 1 was prepared, and bisphenol Z-type polycarbonate resin (manufactured by Teijin Chemicals Ltd.) was prepared as a binder. Hereinafter, in the same manner as in Example 1, the addition amount of the tetrafluoroethylene resin powder was changed to three levels of 1.0, 10.0, and 30% by weight based on the total amount of the charge transport material and the binder in the surface layer. A photoreceptor was made.

Table 6 shows the evaluation results of the above photoreceptors in the same manner as in Example 1.

As can be seen from the table, even when the amount of the lubricant powder is changed, the effect of preventing the photoreceptor from being scraped is high, the surface is not easily scratched, and the image stain due to the toner filming is hardly generated. The stability of the potential is good without increasing the residual potential.

Example 5 In the same manner as in Example 4, an undercoat layer was applied on an 80φ cylinder substrate. Next, 15 parts of the hydrazone compound used in Example 1, A solution prepared by dissolving 10 parts of a polycarbonate Z resin in 50 parts of dichloromethane and 10 parts of monochlorobenzene was applied on the undercoat layer to form a 15 μm-thick charge transport layer. Next, 4 parts of the disazo pigment used in Example 1 and 10 parts of the polycarbonate Z resin were used. And 50 parts of cyclohexanone were dispersed in a sand mill using 1φ glass beads for 20 hours to prepare a CG dispersion.

Next, polytetrafluoroethylene resin powder, a fluorine-based acrylic oligomer as a dispersant, the above-mentioned hydrazone compound, and polycarbonate Z resin were prepared. First, 10 parts of a polycarbonate resin, 4 parts of a hydrazone compound, and 0.15 part of a fluorinated acrylic oligomer are dissolved in 10 parts of dichloromethane and 40 parts of monochlorobenzene. Then, 1.5 parts of polytetrafluoroethylene resin powder was added thereto, and the mixture was dispersed in a stainless steel ball mill for 40 hours. Further, 0.3 parts of the resting memory preventing compound used in Example 1 was added to this solution to prepare a CT solution. This C
A paint in which the G dispersion and the CT solution were mixed at a ratio of 1: 1 was applied on the charge transport layer to form a charge generation layer having a thickness of 5 μm.

The copier used in Example 1 was modified so that it could be positively charged.
The photoreceptor was evaluated in the same manner as in Example 1. However, even after the 100,000-sheet durability test, the potential fluctuation, the photoreceptor scraping, and the rest memory were small, and a high-quality copy was obtained.

Comparative Example 4 As a comparative example of Example 5, a photoreceptor to which no resting memory preventing compound was added was prepared, and the same evaluation was performed. As a result, the resting memory appeared on the image after a 100,000-sheet durability test, and the potential was ΔV _D.
= -160V.

[Effects of the Invention] According to the present invention, since the electrophotographic characteristics are excellent in durability, the potential fluctuation of the photoreceptor is small, and the mechanical durability is excellent, so that the photoreceptor is hardly scraped, and the life of the photoreceptor is small. , And furthermore, the photoreceptor resting memory is remarkably suppressed, so that an excellent electrophotographic photoreceptor can be obtained in which an obtained image does not have a partial density abnormality.

Claims (5)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, wherein at least a layer farthest from the substrate includes at least one kind of lubricant powder and at least one kind of charge transporting substance having an oxidation potential of 0.6 V or more. , And a compound represented by the following general formula (1): General formula (1) [Where R is Where n is a positive integer and X ₁ is Or X ₂ is a hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms] 2. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure composed of a charge generation layer and a charge transport layer, and the charge transport layer is provided on the charge generation layer. 3. The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure comprising a charge generation layer and a charge transport layer, and the charge generation layer is provided on the charge transport layer. 4. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer comprises 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 fluororesin powder, a polyolefin resin powder or a carbon fluoride powder.