JPH05224435A - Photosensitive body for contact charge - Google Patents

Abstract

PURPOSE:To prevent the deterioration of resolution even if the photosensitive body is used for electrophotographic process by contact charge system by containing an antioxidant and/or a charge transfer agent much more in the vicinity of a surface. CONSTITUTION:A layer part which is in the vicinity of the surface of an organic photosensitive layer 4 formed on a conductive substrate 5 and is sensitive to ozone degradation is called the 2nd layer zone 2 and a layer zone below the 2nd layer zone is called the 1st layer zone. A surface protective layer is provided if necessary. The antioxidant and/or large quantity of the charge transfer agent are contained in the 2nd layer zone. If the content of the antioxidant is excess, the charge transferring function of the photosensitive layer is obstructed to cause sensitivity deterioration and if the content of the antioxidant is too little, it is impossible to effectively prevent ozone degradation. The content of the charge transfer agent is excess, chargeability is lowered by lowering of film resistance and on the contrary if the content of the charge transfer agent is too little, an adequate charge transferring ability is not obtained and sensitivity deterioration is liable to be generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor used in a contact charging type electrophotographic process.

[0002]

2. Description of the Related Art A photoreceptor used in an electrophotographic process is charged by a corona charging method or a contact charging method. The contact charging method has an advantage in that it produces less ozone than the corona charging method. However, in the corona discharge, the electric force lines are concentrated in the vicinity of the discharge wire, whereas in the contact charging, the electric force lines are concentrated in a gap of only several tens of microns between the charging member and the surface of the photoconductor. However, the surface of the photoconductor is always exposed to the discharge active species that emit light, and the discharge is performed. Specifically, in corona charging using a scorotron, about 700 V / 1 mm = 7 KV / c
In contrast to m, contact charging is about 1000 V / 20
The electric field is as strong as about 2 digits of μm = 500 KV / cm. Therefore, the photoconductor is liable to deteriorate due to ion bombardment or impact of discharge products. Since the surface of the deteriorated photoconductor has low resistance, there is a problem that the resolution is lowered.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoreceptor which does not cause a reduction in resolution even when used in a contact charging type electrophotographic process. To do.

[0004]

That is, the present invention is used in an electrophotographic process employing at least a contact charging method, and is characterized by containing a large amount of an antioxidant and / or a charge transport agent in the vicinity of the surface. A charging photoreceptor is provided. The photoreceptor used for the contact charging of the present invention has a composition containing a large amount of an antioxidant and / or a charge transport agent near the surface. Hereinafter, for convenience of description, as shown in FIG. 1, a layer portion close to the surface of the organic photosensitive layer (4) formed on the conductive substrate (5), in which ozone deterioration easily occurs, is referred to as a second layer. The area (2) is called, and the layer area below the layer area is the first area.
It is called a layer region (1). In addition, (3) represents a surface protective layer provided as necessary.

The second layer region is a region up to about 5 μm below the surface of the organic photosensitive layer where abrasion of the photosensitive layer occurs in actual use, and specifically about 1 to 4 μm. The first layer region may be considered to mean a region of the organic photosensitive layer other than the second layer region. In the present invention, the second layer region contains an antioxidant and / or a large amount of charge transport agent.

Antioxidants usable in the present invention include N-isopropyl-N'-phenyl-paraphenylenediamine, N- (1,3-dimethylbutyl) -N'-phenyl-paraphenylenediamine and N-. (1-methylheptyl) -N′-phenyl-paraphenylenediamine,
N, N'-diphenyl-paraphenylenediamine, N, N '
-Di-2-naphthyl-paraphenylenediamine, octylated diphenylamine, Antigen P (Sumitomo Chemical Co., Ltd.),
Amines such as Mark LA-63 (manufactured by Adeka Agass Chemical Co., Ltd.) and Nocrac 224 (manufactured by Ouchi Shinko Chemical Co., Ltd.); 2,2,4-trimethyl-1,2-dihydroquinoline, 2,5-di-t-
Butylhydroquinone, 2,5-di-t-octylhydroquinone, 2,6-di-n-dodecylhydroquinone, 2-n-
Hydroquinones such as dodecylhydroquinone and 2-t-octyl-5-methylhydroquinone; styrenated phenol, 2,6-di-t-butyl-4-methylphenol,
2,2'-methylene-bis (4-methyl-6-t-butylphenol), 2'-methylene-bis (4-ethyl-6-
t-butylphenol), 4,4'-thiobis (3-methyl-6-t-butylphenol), 4,4'-butylidene-bis- (3-methyl-6-t-butylphenol), α-tocophenol-octadecyl Phenols such as -3- (3,5-di-t-butyl-4-hydroxyphenol) -propionate; hydroxyanisole such as butylhydroxyanisole and dibutylhydroxyanisole;
2-mercaptobenzimidazole, dilauryl-3,
Sulfur compounds such as 3-thiodipropionate; known chemical substances such as triphenylated phosphorus, tris (nonylphenyl) ated phosphorus, tricresylated phosphorus and other organic phosphorus compounds can be exemplified.

The content of the antioxidant in the second layer region is 1/10 to 3, preferably 1/5 to 2, represented by the ratio of the weight of the antioxidant to the weight of the resin constituting the photosensitive layer. If the content of the antioxidant is too large, the charge transport function of the photosensitive layer is hindered and the sensitivity is lowered. On the other hand, if the content of the antioxidant is too small, ozone deterioration cannot be effectively prevented. In the first layer region, ozone deterioration is almost completely prevented in the second layer region, and therefore, it is not always necessary to include an antioxidant, but a small amount may be included. Specifically, the content of the antioxidant in the first layer region, expressed in the same ratio as above, is sufficient to be 0 to 1/2, preferably 0 to 1/10.

It should be noted that the content of the antioxidant in the first and second layer regions is in the range partially overlapping in the above description (that is, 1/10 to 10 which is the content of the antioxidant in the second layer region). 3 and that in the second layer region are 0 to
It is ½, and the contents overlap in the range of 1/10 to ½). This depends on the type of charge transport material used in the photosensitive layer, the type of antioxidant, etc. In the present invention, the second layer region that is more susceptible to ozone deterioration contains a larger amount of antioxidant than the first layer region. To do. In the case of containing a large amount of charge transfer agent, a known charge transfer agent can be used, and the addition amount thereof is 1 to 9 in terms of the ratio of the charge transfer material agent to the weight of the resin constituting the photosensitive layer. , Preferably 2 to 7.
If the content of the charge transport agent is too large, the charge resistance is lowered due to the reduction of the film resistance of the photosensitive layer. On the other hand, if the content of the charge transport agent is too small, a suitable charge transport property cannot be obtained, and the sensitivity tends to be lowered.

In the first layer region, ozone deterioration is almost completely prevented in the second layer region, and the ozone deterioration does not reach the first layer region. Therefore, the charge transfer agent is contained more than necessary. You don't have to. Specifically, the content of the charge transport agent in the first layer region, expressed in the same ratio as above, is sufficient to be about 1/3 to 3, preferably 1/2 to 2. In addition, the content of the charge transfer agent in the first and second layer regions is a range that partially overlaps in the above description (that is, 1/3 to 3, which is the content of the antioxidant in the first layer region, In the second layer area it is 1
9 and the contents are overlapped in the range of 1 to 3). This is because it is necessary to appropriately select the contents depending on the type of the charge transfer agent used in the photosensitive layer. Therefore, in the present invention, the second
The layer region of 1 contains more charge transport material than the first layer region.

In order to add a large amount of the antioxidant and / or the charge transport agent to the surface side of the photosensitive layer, (i) a photosensitive layer containing a low concentration of the antioxidant and / or the charge transport agent in the step of coating the photosensitive layer. The coating liquid is applied, and then the coating liquid having a higher concentration of the antioxidant and / or the charge transport agent is applied. (ii) A photosensitive coating solution containing an antioxidant and / or a charge transporting agent at various concentrations is used for multiple coatings from a low concentration to a high concentration; (iii) In a photosensitive coating solution using a spray method. In addition, the content of the antioxidant and / or the charge transport agent is mixed in the pipe before the spray nozzle so as to be gradually increased;

The antioxidant and / or charge transport agent contained in the second layer region formed by the above method may have various distribution states, but in the present invention, the antioxidant and / or charge are used. The transport agent is contained more in the region closer to the surface. The distribution state in the second layer region of the antioxidant and / or the charge transport agent is illustrated in FIGS. In each figure, the horizontal axis indicates the density (arbitrary scale), and the vertical axis A indicates the position of the surface of the photosensitive layer, and the lower the point A, the closer to the substrate. FIG. 2 shows a distribution state when a layer having a constant high content is formed to have a constant thickness and a layer having a low content is provided below the layer. Such a distribution state well represents a state that can be taken by the method (i).
FIG. 3 shows a distribution state in the case where the region having a low content rate of the antioxidant is not provided in FIG. 4 and 5 show
2 and 3 show distribution states when a concentration gradient is provided in a layer having a high content of an antioxidant and / or a charge transfer agent. Such a concentration gradient well represents the distribution state that can be taken when the method (ii) is used. The distribution states shown in FIGS. 6 to 9 show the case where the concentration gradient is continuous rather than stepwise as shown in FIGS. Such a concentration gradient is
The distribution state that can be obtained when the film is formed by the above method (iii) is well represented. In any case, the thickness of each layer region and the concentration of the antioxidant and / or the charge transfer agent should be within the ranges described above.

The organic photosensitive layer according to the present invention is not particularly limited as long as it can obtain the desired sensitivity and charging ability of the photosensitive member. The internal structure of the organic photosensitive layer may be a function-separated structure in which a charge generation layer and a charge transport layer are laminated, or a charge generation agent and a charge transport agent are dispersed in a binder material. It may have a binder-type structure or a structure other than these. Also,
The charging polarity of the photoconductor may be any of negative charging type, positive charging type and bipolar type, and is not particularly limited.

10 and 11 show specific examples of the constitution of the photoconductor to which the present invention can be applied. FIG. 10 shows a conductive substrate
(5) A photoreceptor having a photosensitive layer (4) on which a charge generating agent (9) and a charge transporting agent (8) are mixed with a binder. Photosensitive layer (4)
A surface protective layer (3) is formed on the top. The second layer region containing an antioxidant and / or a large amount of charge transport agent is formed below the surface of the photosensitive layer (4). FIG. 11 shows a function-separated type photoreceptor having a charge generation layer (6) and a charge transport layer (7) as a photosensitive layer. The charge transport layer is formed on the charge generation layer (6).
(7) is formed. In the charge transport layer, a layer containing an antioxidant and / or a large amount of charge transport agent is formed in a region near the surface. In the photoreceptor having the structure shown in FIG. 11, the thickness of the charge transport layer is usually 5 to 50 μm,
Considering the simplification of the production method, the antioxidant- and / or charge-transporting agent-containing layer is formed in the charge-transporting layer (7), and it is not usually formed over the charge-generating layer (6).

Further, in the photoreceptor shown in FIGS. 10 to 11, an undercoat layer (intermediate layer) may be formed on the substrate (5). Generally, as a material used for producing the organic photosensitive layer,
As a charge generating agent that contributes to charge generation, for example, a phthalocyanine pigment, an azo pigment, a perylene pigment, or the like is used, and as a charge transporting agent that contributes to charge transport, for example,
Triphenylmethane-based compounds, triphenylamine-based compounds, hydrazone-based compounds, styryl-based compounds, pyrazoline-based compounds, oxazole-based compounds, oxadiazole-based compounds and the like are used, as a binder material for dispersing and coating these, For example, polyester resin, polyamide resin, polyvinyl butyral resin, vinyl chloride resin, polycarbonate resin, polyacrylate resin, phenoxy resin, styrene acrylic resin, cellulose ester resin, acrylic resin, epoxy resin Resins such as urethane resins, silicone resins, phenol resins, melamine resins, alkyd resins, ethylene acetic acid copolymers and ethylene butadiene copolymers are used. Here, it is desirable that the resin as the binding material has a volume resistance of 1 × 10 ¹⁴ Ω or more when measured alone.

To prepare the photosensitive layer of the photoreceptor according to the present invention, for example, dip coating method, spray coating method, spinner coating method, wire bar coating method, blade coating method, roller coating method, curtain coating method and the like are applied. Any method can be used. The photosensitive layer formed by such a coating method is preferably preliminarily dried at room temperature and then dried by heating. The heat drying can be performed at a temperature of 30 to 200 ° C. for a time in the range of about 5 minutes to 2 hours while still or under blowing air. The photoreceptor obtained as described above is used by being incorporated in a contact charging type copying machine or printer. In particular, the present invention is effective for a charging method in which the surface of the photoconductor is exposed at the discharge portion accompanied by light emission. FIG. 12 shows a configuration example of a printer adopting the contact charging method. The printer shown in FIG. 12 is provided with a photosensitive drum (10), which is an electrostatic latent image carrier, in the central portion, and this drum is rotationally driven in the direction of arrow a by a driving means (not shown). Around the drum (10), a charging device (12), a developing device (13),
A transfer charger (14) is arranged, and a cleaning device and an eraser are arranged in that order. Charging device (1
2) is a charging device adopting a contact charging method.

Above the photoconductor drum (10), an optical system (1
7) is arranged, and this optical system is such that a semiconductor laser generator, a polygon mirror, a toroidal lens, a half mirror, a spherical mirror, a folding mirror, a reflection mirror, etc. are arranged in a housing (71). 71)
An exposure slit (72) is formed in the floor of the photoconductor drum, and an image can be exposed on the photoconductor drum (10) from here through a space between the charging device (12) and the developing device (13). Photoconductor drum
A timing roller pair (81), an intermediate roller pair (82), and a sheet feeding cassette (83) are sequentially arranged on the right side of (10) in the figure, and the sheet feeding cassette (83) has a sheet feeding roller (84). Is facing. Further, a fixing roller pair (91) and a paper discharge roller pair (92) are sequentially arranged on the left side of the photosensitive drum (10) in the figure, and a paper discharge tray (93) is provided in the paper discharge roller pair (92). Is facing.

Each of the above-described parts is the printer body (10
It is installed in 0). The main body (100) is a lower unit (10
1) and the upper unit (102), the charging device (12), the developing device (13), the cleaning device,
An eraser, an optical system (17), an upper roller of the timing roller pair (81), an upper roller of the intermediate roller pair (82),
Paper feed roller (84), upper roller of fixing roller pair (91),
The paper discharge roller pair (92) and the paper discharge tray (93) are both provided in the upper unit (102). The upper unit has a shaft bar (103) provided at the left end of the printer in the drawing, and the end on the paper feed side can be opened and closed vertically, thereby enabling jam processing and various maintenance. ing.

According to this printer, the photosensitive drum (1
(0) The surface is uniformly charged to a predetermined potential by the charging device (12), and an electrostatic latent image is formed by imagewise exposing the charged area from the optical system (17). The electrostatic latent image thus formed is developed by the developing device 13 to become a toner image, and the toner image is transferred to the transfer area facing the transfer charger 14. On the other hand, the transfer paper is pulled out from the paper feeding cassette (83) by the paper feeding roller (84), and passes through the intermediate roller pair (82) and the timing roller pair.
At (81), the toner image on the drum (10) is sent to the transfer area in synchronization therewith. Thus, in the transfer area, the toner image on the drum (10) is transferred onto the transfer paper by the action of the transfer charger (14), and the transfer paper reaches the fixing roller pair (91) where the toner image is fixed and then discharged. The paper is discharged to the paper discharge tray (93) by the paper roller pair (92).
After the toner image is transferred to the transfer paper, the photosensitive drum (1
0) Toner remaining on the cleaning device (not shown)
The residual charge is erased by an eraser (not shown).

In the above printer, the type equipped with a cleaner has been described, but the photoconductor of the present invention can be used in a cleanerless process which does not cause deterioration of image quality even if the amount of wear is small. In such a cleanerless process, the ozone-deteriorated surface layer is not scratched or scraped by a cleaner blade or a fur brush. Therefore, in the case of the conventional photoconductor, the ozone deterioration layer is accumulated and the image quality is significantly deteriorated. However, when the photoconductor according to the present invention is used, since it contains an antioxidant and / or a large amount of a charge transport material near the surface, even if the ozone-deteriorated layer due to cleanerless is accumulated, it is It is possible to prevent such remarkable deterioration of image quality. A film type charging device, a brush type charging device, or the like can be used as the contact type charging device (12) used in the above printer and applicable to the photoconductor of the present invention. First, the basic structure of the film type charging device is shown in FIG.
3 shows.

As shown in FIG. 13, the charging device (12) has
A conductive support plate (21) (for example, an aluminum support plate) for supporting the film and one end portion (22) thereof
1) is supported and is on the free end side (222), that is, from the end P1 of the film support area to the free end P2 of the film.
A part of (222) is provided with a charging film (22) which comes into contact with the photosensitive drum (10). The support plate (21) is a drum that is separated from the surface of the photosensitive drum (10) by a certain distance.
The film (22) also extends in the width direction of the drum (10). A DC power source (23) for applying a negative voltage for charging is connected to the support plate (21). Also, if an AC power source (24) is used together as a power source,
Although the halftone reproducibility of an image is improved, it is not always essential. Since this flexible film is used for charging, it has conductivity or low electrical resistance (preferably 10 ³ to 1).
It is preferably a film having a thickness of 0 ⁸ Ωcm).

Examples of possible materials for the film are as follows. As the metal material, aluminum, gold, copper, iron, silver, chromium, nickel, platinum, tin,
Metals such as titanium, or alloys of these. Examples of synthetic resin materials include polyolefin resins such as polyethylene and polypropylene; polyacetal resins such as polyvinyl alcohol and polyvinyl acetate; ethylene-vinyl acetate copolymers, polymethyl methacrylate, acrylonitrile-
Acrylic resins such as methyl acrylate copolymer; polycarbonate, polystyrene, acrylonitrile-butadiene-styrene copolymer, ethylene polyterephthalate,
Polyurethane elastomer; Cellulose resin such as viscose rayon, cellulose nitrate, cellulose acetate, cellulose triacetate, cellulose propionate, cellulose acetate butyrate, ethyl cellulose, regenerated cellulose; nylon 6, nylon 66, nylon 11, nylon 12, nylon 46, etc. Polyamide-based resin; polyimide, polysulfone, polyether sulfone; polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, vinylidene chloride-vinyl chloride copolymer, polytetrafluoroethylene, polychlorofluoroethylene, poly Polyvinyl halide resin such as vinyl fluoride and polyvinylidene fluoride; Conductive material is dispersed in resin material such as vinyl nitrile rubber alloy, and the surface of the resin material is treated to be conductive to make it conductive appropriately. Or a low-resistance material.

In particular, when the resin contains metal powder, metal whiskers, carbon black, carbon fiber, etc., it is possible to obtain a low resistance material of about 10 ³ to 10 ⁸ Ωcm which is not even conductive. You can When applying a voltage for charging to the flexible film for charging,
A direct current, an alternating current, or a voltage resulting from the superposition thereof can be applied. Further, in order to adjust the mechanical strength of the film, the longitudinal and lateral mechanical strength of the film is made anisotropic, the crystallinity of the film material is appropriately changed, and an anisotropic material such as a liquid crystal polymer is used. You may use. Next, FIG. 14 shows a basic configuration example of the brush type charging device. In the brush type charging device shown in FIG. 14, the charging brush (30) is composed of a belt-shaped pile cloth. The pile cloth can be obtained, for example, by weaving the brush bristles (31) made of conductive fibers having a denier of 3 to 10 into the base cloth (32), and further coating the back surface of the base cloth portion with a conductive adhesive.
In addition, for example, 50 to 100 brush bristles are bundled in FIG.
As shown in FIG. 5, the warp yarns (32a) of the base fabric (32) can be woven in a V shape, or in a W shape as shown in FIG.

The material of the brush bristles is not particularly limited as long as it has appropriate conductivity. Examples of such a conductive material include metal wires such as tungsten, stainless steel, gold, platinum, iron, copper and aluminum. Further, as a conductive resin material, fibers such as rayon, nylon, acetate, copper ammonia, vinylidene, vinylon, fluorinated ethylene, promix, benzoate, polyurethane, polyester, polyethylene, polyvinyl chloride, polyclar, polynosic, polypropylene, etc. It is possible to use a material in which a resistance adjusting agent such as carbon black, carbon fiber, metal powder, metal whiskers, metal oxide, or semiconductor material is dispersed. in this case,
A desired resistance value can be appropriately obtained by the amount of dispersion. Further, the resistance adjusting agent may be coated on the surface of the fiber instead of being dispersed inside the fiber. The brush-type charger shown in FIG. 14 is of a fixed type, and the brush-type charger shown in FIG.
It is used in the mode shown in FIG. In addition, power supply (23), (24)
Since the above is the same as that described in FIG. 13, the description thereof is omitted here.

On the other hand, a rotating brush type charger can also be used. As shown in FIG. 18, the rotary brush type charger can be obtained by winding a cloth (33) woven on a base cloth around a conductive shaft (34). The mounted state of the rotary brush charger is as shown in FIG. The rotary brush (36) is installed at a distance H ′ from the center of the rotary brush (36) and the surface of the photoconductor (10), and is rotatable by a drive motor (35). H'is set to be slightly shorter than the natural length of the brush so as to contact the surface of the photosensitive drum 10 with an appropriate nip width. The power supplies (23) and (24) are shown in FIG.
The description is omitted because it is the same as in 3 and 17. As another contact charger, a blade type structure (for example, Japanese Patent Laid-Open No. 64-64
No. 93760), a roller type structure (for example, JP-A-64)
No. 73365), a brush type configuration (for example, USP4
55171), a porous structure (for example, JP-A-2-28).
669), a semiconductor type structure (for example, Japanese Patent Laid-Open No. 1-29)
2358), a magnetic brush type structure (for example, Japanese Patent Laid-Open No.
3-187267) and the like, and the photoconductor of the present invention is also applicable to a charger having such a contact structure.

Preparation of Photoreceptor First, as a photoreceptor for a comparative example, a photoreceptor having sensitivity to long-wavelength light (780 nm) was prepared as follows.

Preparation of Charge Generation Layer First, 1 part by weight of τ (tau) type metal-free phthalocyanine, 2 parts by weight of polyvinyl butyral resin and 100 parts by weight of tetrahydrofuran were placed in a ball mill pot and dispersed for 24 hours to obtain a photosensitive coating solution. At this time, the viscosity of the photosensitive coating liquid is 20 ° C.
It was 15 cp. As the polyvinyl butyral resin, one having an acetylation degree of 3 mol% or less, a butylation degree of 70 mol% and a polymerization degree of 1000 was used. This coating solution was applied to the surface of an aluminum cylindrical substrate having an outer diameter of 30 mm, a length of 240 mm and a wall thickness of 0.8 mm by a dipping method to form a charge generation layer having a film thickness after drying of 0.4 μm. The cylindrical substrate used here was an aluminum alloy containing 0.7% by weight of magnesium and 0.4% by weight of silicon. The drying condition was 30 minutes in circulating air at 20 ° C.
The τ-type metal-free phthalocyanine has a black angle (2θ) when CuKα / Ni X-ray with a wavelength of 1.541Å is used.
± 0.2 degrees) is 7.6, 9.2, 16.8, 17.4,
It has an X-ray diffraction pattern showing strong peaks at 20.4 and 20.9 degrees. In particular, in the infrared absorption spectrum, between 700~760cm ^-1 751 ± 2cm ^-1
Has four strongest absorption bands, two absorption bands of approximately the same strength between 1320 and 1340 cm ^-1 , and 3288
It has a characteristic absorption at ± 3 cm ^-1 .

Preparation of Charge Transport Layer Next, on this charge generation layer, 8 parts by weight of a hydrazone compound represented by the following structural formula and an orange dye (Sumiplast Or
ange12; Sumitomo Chemical Co., Ltd.) 0.1 part by weight, polycarbonate resin (Panlite L-1250; Teijin Chemicals Co., Ltd.) 10
A coating solution prepared by dissolving 180 parts by weight of tetrahydrofuran in a solvent of 180 parts by weight is applied by a dipping method,
After drying, a charge transport layer having a film thickness of 28 μm was formed. The viscosity of the coating liquid at this time was 240 cp at 20 ° C. The drying condition was 30 minutes in circulating air at 100 ° C.

[0028]

[Chemical 1]

As described above, a photoconductor was prepared in which a charge generation layer and a charge transport layer were sequentially laminated on a conductive substrate. The photoconductor is a photoconductor consisting only of the first layer region.

Of a photoreceptor having a first layer region and a second layer region
Manufacture This photoconductor is the same as the above-mentioned comparative photoconductor, except that the charge transport layer is added at the ratio of each addition amount shown in Tables 1 and 2 below.
A comparative photoconductor was prepared in the same manner as the comparative photoconductor, except that it was formed by coating twice. At this time, the antioxidant is Nocrac 224
(Manufactured by Ouchi Shinko Kagaku Co., Ltd.) was used and mixed and dispersed at the same time when the coating was prepared. The constitution of each photoconductor thus prepared is summarized in Tables 1 and 2.

[0031]

[Table 1]

[0032]

[Table 2]

The photoconductor obtained as described above is shown in FIG.
It was incorporated into the printer shown in. As a charging device,
The following film type charging device and brush type charging device were used.

Film type charging device (Fig. 13 ) Young's modulus is 7.0 × 10 ⁸ [g / cm] as a charging film.
The film thickness was 60 μm. As a material, a polypropylene film containing 8 wt% of conductive carbon powder and a resin film having an electric resistivity of 10 ⁷ Ωcm was used. Then, the power supply (23) produces a DC voltage of -800 V and the AC power supply (24) produces a peak-to-peak value of 12
A voltage obtained by superimposing a rectangular wave alternating voltage having a frequency of 800 Hz at 00 V was applied to charge the surface of the photoconductor to −800 V. The length between the end P1 of the support area of the film (22) and the free end P2 of the film was 15 mm. Support plate (21)
The distance H from the surface of the photosensitive drum (10) was 5 mm.

Brush type charger (FIG. 14) As the brush bristle material, 6 denier rayon fiber having an electric resistivity of about 1 × 10 ⁵ Ω · cm and containing 12 wt% of conductive carbon powder was adopted. .. As shown in FIG. 20, this fiber (31) is woven into a base cloth (32) having a thickness of 0.5 mm by using W weave as shown in FIG. 16, and the length L in the width direction of the photoconductor drum is L = 230 mm. Width W = 9mm, height h1 =
Form a charging brush (30) having a fiber density of 15000 filaments / cm ^{2 in} the center of 7 mm, coat the back surface of the base cloth (32) with a conductive adhesive, and thicken the base cloth (32) with the adhesive. T = 1m
It was fixed to an aluminum back plate (37) of m.
Then, a DC voltage of -1.1 KV was applied by the power source (23) to charge the surface of the photoconductor to -800V.
The AC power supply (24) was not operated.

Rotating brush type charger (FIG. 19) A brush cloth made of W-woven cloth was attached on an aluminum shaft in the same manner as the fixed type charger, and the charging was performed as shown in FIG.
A rotary brush having the dimensions shown in was obtained. When using,
The peripheral speed of the brush is rotated at 3 times the peripheral speed of the drum,
It was charged in the same manner as the fixed charger. The printer system speed (photosensitive drum peripheral speed) is 3.5 cm.
/ Sec, the developing device (13) is a one-component contact developing device and performs reversal development. The toner used in the following evaluations is a negatively charged type, 100 parts by weight of bisphenol A type polyester resin, 5 parts by weight of carbon black MA # 8 (manufactured by Mitsubishi Kasei Co., Ltd.), Bontron S-34 (Orient Chemical Industry). (Manufactured by the same company) and 2.5 parts by weight of Viscor TS-200 (manufactured by Sanyo Kasei Co., Ltd.) were kneaded, pulverized and classified by a known method to have an average particle size of 8 μm.
To produce toner particles in which 80% by weight is distributed in a particle size range of 6 to 11 μm, and a hydrophobic silica (Tanolux 500 manufactured by Tarco Co., Ltd.) is added to the toner particles as a fluidizing agent.
80% by weight was added and mixed and stirred by a homogenizer. Such toner was stored in the developing device (13), and the DC power supply (23) was used to develop under a developing bias of -300V. The AC power supply (24) was not operated.

Evaluation The following items were evaluated using the above printer. Chargeability chargeability was expressed in the amount of current required of the photosensitive member surface to -800V charging. Then, it is preferable that the rate of increase in the amount of current required as compared with the photoconductor of Comparative Example 1 is within 10%, and if the rate of increase is within 20%, there is no practical problem.

Half-exposure amount The half-exposure amount is the half-exposure amount in the printer shown in FIG.
The amount of light required to attenuate the photoreceptor surface potential to -400V, which is half of the initial -800V, was measured by changing the laser light amount by inserting a D filter.

Sensitivity Sensitivity was measured by the rate of increase in half-exposure amount and evaluated by comparing with the photoconductor of Comparative Example 1. And, those having an increase rate of 10% or less are preferable, and those having an increase rate of 20% or less are regarded as practically no problem. The evaluation results are shown in the table.

The resolution laser optical system (17) is set to 600 dpi, and 1 dot line pair, 2 dot line pair, 3 dot as shown in FIG.
Dot line pairs and 4 dot line pairs were drawn to obtain print samples, which were evaluated after printing 5,000 sheets. It should be noted that, in the figure, the shaded area represents a solid image.

The obtained print sample was applied to a densitometer (Sakura Microdensitometer Model Del PDM-5 Type-
BR) was used for analysis. Then, as shown in FIG. 23, if the white line has fallen to the density of the transfer paper, it is determined that the dot line pair has been resolved, and if it has not fallen to the density of the transfer paper as shown in FIG. (B) It was decided that it was not resolved. As an evaluation, when 3 dots line pairs or more are resolved but 1 dot line pair and 2 dots line pairs or more are not resolved, 3 dots line pair is described as clear. Then, after printing out 5,000 sheets, it was judged that those that clear within 3 dot line pairs had no practical problems, and those that clear 2 dot line pairs were suitable. The above evaluation results are shown in Table 3 to
Summarized in 6.

[0042]

[Table 3]

[0043]

[Table 4]

[0044]

[Table 5]

[0045]

[Table 6]

[0046]

The photoconductor of the present invention exhibits good photoconductor characteristics for a long period in a contact charging type copying machine.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a photoreceptor for explaining a region in which an antioxidant and / or a charge transport agent are contained in the photoreceptor.

FIG. 2 Second antioxidant and / or charge transport agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 3 Second Antioxidant and / or Charge Transport Agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 4 Second antioxidant and / or charge transport agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 5: Second antioxidant and / or charge transport agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 6 Second Antioxidant and / or Charge Transport Agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 7 shows a second antioxidant and / or charge transport agent.
It is a figure which shows the distribution state in a layer area | region.

FIG. 8: Second antioxidant and / or charge transport agent
It is a figure which shows the distribution state in a layer area | region.

FIG. 9 shows a second antioxidant and / or charge transport agent.
It is a figure which shows the distribution state in a layer area | region.

FIG. 10 is a cross-sectional view showing a schematic configuration of a photoconductor.

FIG. 11 is a cross-sectional view showing a schematic configuration of a photoconductor.

FIG. 12 is a schematic configuration diagram of a printer adopting a contact charging method.

FIG. 13 is a schematic configuration diagram of a film type charging device.

FIG. 14 is a diagram illustrating a schematic configuration example of a fixed charger.

FIG. 15 is a diagram for explaining how to weave brush bristles.

FIG. 16 is a diagram for explaining how to weave brush bristles.

FIG. 17 is a diagram for explaining a method of using the brush type charger.

FIG. 18 is a diagram showing a schematic configuration of a rotary brush type charger.

FIG. 19 is a view for explaining a method of using a rotary brush type charger.

FIG. 20 is a diagram showing a schematic configuration of a fixed charger used in Examples.

FIG. 21 is a diagram showing a schematic configuration of a rotary charger used in Examples.

FIG. 22 is a diagram for explaining a punto sample used for resolution evaluation.

FIG. 23 is a diagram for explaining a method of evaluating resolution.

FIG. 24 is a diagram for explaining an evaluation method of resolution.

[Explanation of symbols]

1: First Layer Area 2: Second Layer Area 3: Surface Protection Layer 4: Organic Photosensitive Layer 5: Substrate 6: Charge Generation Layer
7: Charge Transport Layer 8: Charge Transport Agent 9: Charge Generating Agent 10: Drum 12: Charging Device 13: Developing Device 14: Transfer Charger 17: Optical System 2
1: Support plate 22: Film for charging 23: Power supply
24: Power supply 30: Charging brush 31: Brush bristles 32: Base fabric 32a: Warp 33: Fabric 3
4: Conductive shaft 35: Drive motor 36: Rotating brush 71: Housing 72: Exposure slit 81: Timing roller 8
2: Intermediate roller 83: Paper feeding cassette 84: Paper feeding roller 91: Fixing roller 92: Paper discharging roller 93: Paper discharging tray 100: Printer body 10
1: Lower unit 102: Upper unit 221: One side end 222: Free end side

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Iino 2-3-13 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Akito Hitoshi, Chuo-ku, Osaka-shi, Osaka 2-3-13 Azuchi-cho, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Iyosei Osawa-cho 2-3-3 Azuchi-cho, Osaka City Osaka Prefecture International Building Minolta Camera Co., Ltd.

Claims (3)

[Claims] 1. A photoconductor for contact charging, which is used in an electrophotographic process adopting a contact charging system and contains a large amount of an antioxidant near the surface. 2. A contact charging photoreceptor which is used in an electrophotographic process employing a contact charging method and contains a large amount of a charge transfer agent near the surface. 3. The photoconductor according to claim 1, wherein the electrophotographic process adopts a cleanerless system.