JPH03276158A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To stabilize electrostatic chargeability even after repeated use and to prevent a change of sensitivity or potential by electrification due to a change of temp. or humidity by using an inorg. pigment and a binding resin in a prescribed ratio in a middle layer and incorporating a specified antioxidant into a photosensitive layer. CONSTITUTION:When a middle layer and a photosensitive lyaer are successively laminated on an electrically conductive substrate to obtain a sensitive body, an inorg. pigment and a binding resin are used in 1/1-3/1 volume ratio in the middle layer and a compd. represented by formula I is incorporated into the photosensitive layer. In the formula I, each of R1-R4 is H, hydroxyl, alkyl, etc., one or more among R1-R4 are hydroxyl and each of R5 and R6 is H, alkenyl or alkyl. Titanium oxide may be used as the inorg. pigment, alkyd resin and melamine resin may be used in combination as the binding resin and a compd. represented by formula II may be used as the antioxidant represented by the formula I.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and particularly relates to an electrophotographic photoreceptor that has excellent charging stability even during repeated use over a long period of time. .

[Conventional technology]

Conventionally, in order to improve the charging properties of electrophotographic photoreceptors,
A method has been proposed in which an intermediate layer mainly made of resin is provided between a conductive support such as aluminum and a photoconductive layer.

As this intermediate layer, it was proposed to provide a layer made only of resin, but in order to obtain a uniform film of resin without pinballs, a certain degree of thickness is required, and because of this, the characteristics of the photoreceptor depend on the environment. This resulted in problems such as an increase in residual potential at low humidity and a decrease in chargeability at high humidity.

For this reason, the intermediate layer is blended with a conductive polymer (Japanese Patent Laid-Open No. 58-95744), and the intermediate layer is made of a resin in which conductive powder is dispersed (Japanese Patent Laid-Open No. 58-9306).
3) etc. have been proposed. However, these photoreceptors
Although the photoreceptor exhibits good characteristics when used repeatedly up to about 10,000 times, it has the disadvantage that charging performance deteriorates when used over a longer cycle. At present, only by providing an intermediate layer as described above, a photoreceptor that has excellent electrical stability, satisfies durability, and is less dependent on the environment cannot be obtained.

[Problem to be solved by the invention]

An object of the present invention is to provide an electrophotographic photoreceptor that exhibits good chargeability even after repeated use, has low environmental dependence, and has excellent durability.

[Means to solve the problem]

As a result of intensive study on how to improve this point, the inventors found that
When the inorganic pigment and binder resin in the intermediate layer are used in a specific ratio and a specific antioxidant is added to the photosensitive layer, it is possible to prevent a decrease in charging performance even after repeated use, and it has excellent durability. It was discovered that an electrophotographic photoreceptor can be obtained, and the present invention was completed.

That is, according to the present invention, in an electrophotographic photoreceptor in which an intermediate layer and a photoconductive layer are sequentially provided on a conductive support, the intermediate layer is composed of an inorganic pigment (P) and a binder resin (R). Ratio P/
An electrophotographic photoreceptor is provided, wherein R is in a volume ratio of 1/1 to 371, and the photoconductive layer contains a compound represented by the following general formula (1).

1 (in the formula, R 1 R 2 1 R 3 and R 4 represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an alkyl group, provided that at least one of R 1 R 2 t R 3 and R 2 is a hydroxyl group), R 9 and R 6 are hydrogen atoms , represents an alkenyl group or an alkyl group. ) Hereinafter, the present invention will be explained in more detail.

Conductive supports include metals such as aluminum, nickel, and stainless steel; plastics with conductive pigments such as carbon dispersed; metals deposited on insulating supports (such as plastics or plastic films) or conductive paints. An example is a coated one.

Any suitable binder resin (R) can be used for the intermediate layer, but considering that a photosensitive layer is coated on top of it with a solvent, it is recommended that the binder resin (R) has high solvent resistance to general organic solvents. Resin is preferred. Such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate; alcohol-soluble resins such as copolymerized nylon and methoxymethylated nylon; polyurethane,
Examples include curable resins that form a three-dimensional network structure, such as melamine camphor resin and epoxy resin.

Further, as the inorganic pigment (P), it is desirable to use a white color or a color close to this, which has almost no absorption in visible light and near-infrared light, in consideration of increasing the sensitivity of the photoreceptor.

Examples of such inorganic pigments include white pigments such as titanium oxide, zinc white, zinc sulfide, white lead, and lithopone, and extender pigments such as alumina, calcium carbonate, and barium sulfate. Particularly in the case of photoreceptors used in laser printers and the like that write images using coherent light such as laser light, it is better to use a white pigment with a high refractive index in order to prevent the occurrence of moiré.

The ratio P/R of the inorganic pigment (P) and the binder resin (R) used in the intermediate layer is in the range of 171 to 3/1 in terms of volume ratio.

When the P/R ratio of the intermediate layer is less than 1, the intermediate layer is influenced by the properties of the binder resin, and in particular, the characteristics of the photoreceptor change with changes in temperature and humidity. Further, when the P/R ratio exceeds 3, the intermediate layer has many voids and air accumulates therein. This becomes bubbles when the photoconductive layer is applied and dried, causing coating defects.

In addition, the thickness of the intermediate layer is 0.1 to 50, preferably 0.3
~20IA is appropriate.

The photoconductive layer used in the present invention includes (1) a charge transfer complex formed by a combination of an electron-donating compound and an electron-accepting compound (described in US Pat. No. 3,484,237); (2)
Organic photoconductor sensitized by adding dye (Special Publication Act 4
8-25658), (3) Pigment dispersed in a hole- or electron-active matrix (Japanese Patent Laid-Open No. 47
-30328, JP-A-47-18545, etc.), (4) functionally separated charge generation layer and charge transport layer (described in JP-A-49-405537),
(5) Those whose main component is a eutectic chain consisting of a dye and a resin (described in JP-A-47-10785), (6) Those in which an organic pigment or an inorganic charge-generating material is added to a charge transfer complex. It may be formed of any conventionally known organic photoconductor such as (described in JP-A-49-91648).

However, among these, the laminated photoreceptor of type (4) is particularly preferred in the present invention because it has high sensitivity and allows a variety of materials to be selected depending on the function.

In this case, the charge generation layer is a charge generation material such as an azo pigment, a phthalocyanine pigment, a square pigment, an indigo pigment, a perylene pigment, a selenium powder, a selenium alloy powder, an amorphous silicon powder, a zinc oxide powder, or a cadmium sulfide powder. is dispersed in a solution of a binder resin such as polyester, polycarbonate, polyvinyl butyral, or acrylic resin, and this is coated onto the intermediate layer. The thickness of the charge generation layer is set to 0.0 to prevent deterioration of the photoreceptor characteristics such as a decrease in chargeability during repeated use.
One or two voices is appropriate.

The charge transport layer is an α-phenylstilbene compound (Japanese Patent Application Laid-open No.
8-198043), hydrazone compounds (
A charge transporting substance such as those described in JP-A No. 55-46760 is dissolved in a film-forming resin such as polyester, polysulfone, polycarbonate, polymethacrylic acid ester, polystyrene, etc., and this is applied onto the charge generation layer. It may be applied to a thickness of about 10 to 40R. The film-forming resin is used here because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself.

Furthermore, a photoreceptor for positive charging can be obtained by reversing the stacking order of the charge generation layer and the charge transport layer.

The present invention is characterized in that, as described above, the compound represented by the general formula (I) is added to the photoconductive layer.

Specific examples of the compound represented by the general formula (I) that can be used in the present invention include the following compounds.

α-tocopherol (5,7,8 trimethyl docol)
δ-Tocopherol (8-Methyltocol) Among these, α-tocopherol is preferably used, especially from the viewpoint of effectiveness. These compounds may be used alone or in combination.
It can be used as a mixture of more than one species.

In addition, the compound represented by the general formula (I) is the compound represented by the above (4).
For photoconductive layers other than that, it is added to the entire layer, but (4)
In the case of a photoconductive layer, a charge generation layer or a charge transport layer,
It may be added to at least one of them.

When adding the compound of general formula (I) to a photoconductive layer of a type other than (4), it is preferably added in an amount of 0.001 to 50.0% by weight based on the entire photoconductive layer.

In the case of the (4) type photoconductive layer, the addition to the charge generation layer is preferably from 0.01 to 50.0% by weight based on the charge generation substance. The photoreceptor thus manufactured is suitable for repeated use, and if necessary, a protective layer similar to conventional methods can be provided on the surface of the photoreceptor layer.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that all parts are based on weight.

Example 1 The following intermediate layer coating solution was applied onto an aluminum drum having a diameter of 80+ am and a length of 360 mm to form an intermediate layer having a thickness of 2 tones.

[Intermediate layer coating liquid]

Alkyd resin [Pesocozol 1307-60EL solid content 60% (Dainippon Ink & Chemicals)] 115 parts Melamine resin Super Beckamin G-821-60 solid content 60% (Dainippon Ink & Chemicals) 110 parts Methyl ethyl ketone 50
Partial titanium oxide powder (Tiebake R-680 manufactured by Ishihara Sangyo)
90 parts of the above ingredients were dispersed in a ball mill for 12 hours,
An intermediate layer coating solution was prepared. In this intermediate layer, the specific gravity of titanium oxide is 4.2 and the specific gravity of binder resin is 1.4, so the volume ratio of pigment (P)/binder resin (R) is 2/1.

Next, butyral resin [S-LEC BLS (Made by Block Chemical)
] 5 parts was dissolved in 150 parts of cyclohexanone, 10 parts of a trisazo pigment having the following structural formula was added thereto, and the mixture was dispersed in a ball mill for 48 hours.

Furthermore, 210 parts of cyclohexanone was added and dispersion was carried out for 3 hours. This was diluted with cyclohexanone while stirring so that the solid content was 1.5 wt%. The charge generation layer coating liquid thus obtained was applied onto the intermediate layer and dried to form a charge generation layer having a thickness of about 0.2 mm.

Furthermore, 8 parts of a charge transport substance having the following structural formula, 11 parts of a polycarbonate resin [Panlite-1300 (manufactured by Kijin Kasei)]
0 parts silicone oil (KF-50 (manufactured by Shin-Etsu Chemical))
]0002 parts and 0.5 parts of α-tocopherol were dissolved in 85 parts of methylene chloride.

Table 1 The thus obtained charge transport layer coating liquid was applied onto the charge generation layer and dried to form a charge transport layer with a thickness of 29 mm, thereby producing an electrophotographic photoreceptor.

Example 2 An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that α-tocopherol was replaced with β-tocopherol.

Example 3 An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that α-tocopherol was replaced with γ-tocopherol.

Comparative Examples 1 to 3 Photoreceptors were prepared in exactly the same manner as in Example 1, except that α-tocopherol, which was an additive to the charge transport layer in Example 1, was replaced with the compound shown in Table 1.

100,000 copies of the photoreceptor obtained above were made using Imagi No. 320 (manufactured by Ricoh Co., Ltd.), and the initial image quality and image quality after 100,000 copies were evaluated. Also, before the initial image copy and lO
After copying 10,000 sheets, a surface electrometer was attached to the developing position to measure the surface potential of the exposed and non-exposed areas. The evaluation results are shown in Table-2. The measurement environment was 20° C. and 50% R).

Table 2 Examples 4 to 6, Comparative Examples 4 and 5 Alcohol-soluble copolymer nylon [Amilan CM-8
000 (manufactured by Toshiku Co., Ltd.) (specific gravity 1.1)) 11 parts to 20
Titanium oxide TA-3 was dissolved in 0 parts of methanol.
00 (manufactured by Fuji Titanium Industry Co., Ltd.) (specific gravity 3.9)
3, and dispersed in a ball mill for 12 hours to obtain a coating solution for an intermediate layer.

Table 3 Next, the intermediate layer coating solution obtained above was dip coated on the surface of an aluminum drum with a diameter of 40 mm and a length of 250 mm, and dried at 120°C for 5 minutes to form an intermediate layer with a thickness of 2.5 prm. .

Next, butyral resin [S-LEC BLS Sekisui Chemical (
Co., Ltd.] was dissolved in 150 parts of cyclohexanone, 6 parts of a bisazo pigment having the structural formula below was added thereto, and the mixture was dispersed for 48 hours using a ball mill.
10 parts were added and dispersed for 12 hours.

This was placed in a container, and further cyclohexanone was added so that the solid content was 1 wt%. Furthermore, 8% by weight of α-tocopherol was added to the above bisazo pigment to obtain a coating liquid for a charge generation layer.

This was dip-coated onto the intermediate layer and dried at 120°C for 5 minutes to provide a charge generation layer with a thickness of about 0.31A.

Furthermore, 10 parts of -1300 [manufactured by Ondai Kasei Co., Ltd.] 0.002 parts of silicone oil KF-50 [manufactured by Shin-Etsu Chemical Co., Ltd.] were added to the charge transport material polycarbonate resin Panlite having the following structural formula. The charge transporting coating liquid prepared above was dip coated onto the charge generation layer and dried at 120° C. for 15 minutes to form a charge transporting layer having a thickness of 25R, thereby producing an electrophotographic photoreceptor.

The photoreceptor thus obtained was rotated at 1100 Orp, the photoreceptor was charged with a corona discharger, and the characteristics of the photoreceptor were measured using a measuring stand equipped with a surface electrometer and means for exposing the photoreceptor through a slit width of 3 nm. I did it.

In addition, the measurement was performed after charging for 10 seconds, dark decay for 10 seconds, and light decay for 15 seconds.
It was conducted under conditions of seconds.

(1) Charging potential: Potential after 10 seconds of charging Dark decay Potential after 10 seconds (2) Potential retention rate = Potential after 10 seconds of charging (3) Sensitivity: Necessary for the potential to decrease to 1/2 after exposure In addition, the photoreceptor is a laser printer LP-1060-
5P3 [manufactured by Ricoh Co., Ltd.]'s laser light writing optical system was modified to an optical system using a halogen lamp and lens for copying machines, and the image was copied at a fatigue rate of 150,000 revolutions, and then exposed again. Body characteristics were measured. In Comparative Example 5, bubbles were generated during the production of the photoreceptor (CTL coating), so characteristics were not evaluated.

〔Effect of the invention〕

Since the electrophotographic photoreceptor of the present invention has the above-mentioned structure, it exhibits stable charging performance even after repeated use, and has excellent practical value with no change in charging potential or sensitivity even when the environment such as temperature and humidity changes. It is something that

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor in which an intermediate layer and a photoconductive layer are sequentially provided on a conductive support, the intermediate layer contains an inorganic pigment (P
) and the binder resin (R), the ratio P/R is 1/1 to 1/1 by volume.
3/1, and the photoconductive layer contains a compound represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (In the formula, R_1, R_2, R_3, and R_4 represent a hydrogen atom, a hydroxyl group, an alkoxy group, or an alkyl group (However, R_1, R_2, R_3, and R_4 at least one is a hydroxyl group), R_5 and R_
6 represents a hydrogen atom, an alkenyl group or an alkyl group. )