JPH02259764A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent deterioration of sensitivity and rise of residual potential due to addition of an antioxidant by adding a specified antioxidant within a specified thickness from the surface of an electric charge transfer layer. CONSTITUTION:This photosensitive body is formed by successively laminating on a conductive substrate a charge generating layer containing a charge generating material, such as polycyclic pigments, and the charge transfer layer containing a charge transfer material, such as hydrazone derivatives, and as the antioxidant, at least one of a phenol type antioxidant, such as a compound of formula I, and a tocol type antioxidant, such as compounds of formula II is contained within the range of 0.5 - 50% of the total thickness of the charge transfer layer from its surface. This charge transfer layer can be formed by forming the layer of a desired thickness containing no antioxidant on the charge generating layer and then, the rest of the charge transfer layer containing the antioxidant of the desired thickness on the layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor used in electrophotographic apparatuses such as electrostatic transfer copying machines and laser printers.

[Conventional technology]

Currently, electrophotographic photoreceptors (hereinafter referred to as photoreceptors) are used.

) can be roughly divided into those using inorganic materials and those using organic materials.

Typical inorganic photoreceptors include amorphous selenium (a-3e) and amorphous selenium arsenide (a-As, S
), dye-sensitized zinc oxide (Z
nO) or cadmium sulfide (CdS) dispersed in a binder resin, and amorphous silicon (a-3
There are some that use t).

In addition, as a typical organic photoreceptor, 2,4°7-
Dolinitro-9-fluorenone (TNF) and poly-N-
Examples include those using a charge transfer complex with vinyl carbazole (PVK).

While these photoreceptors have many advantages, they also have disadvantages. For example, photoreceptors using selenium and Cds have problems with heat resistance and storage stability, and are also toxic, so they cannot be easily disposed of and must be recovered.

ZnO resin dispersion type photoreceptors are currently hardly used due to their low sensitivity and lack of durability.

Although the a-3i photosensitive material has excellent advantages such as high sensitivity and high durability, it suffers from high manufacturing costs due to the complexity of its manufacturing process and image defects due to film defects specific to the a-3i. I have a problem. Furthermore, these materials do not have satisfactory flexibility and have drawbacks such as difficulty in being easily processed into various shapes such as drum shapes and sheet shapes.

On the other hand, since organic photoreceptors have a wide variety of organic materials, problems such as storage stability and toxicity can be avoided by appropriately selecting them. It is attracting attention as one of the most important photoreceptors because it can be manufactured at low cost.

However, this photoreceptor has a problem of low sensitivity, and improvements are being made. PVK mentioned earlier
-TNF charge transfer complex system was one of the improvements, but it did not reach the point where it had sufficient sensitivity.

Various other sensitization methods have been proposed, including a layer containing a substance that generates charge carriers (hereinafter referred to as ``charge generation material'') when irradiated with light (hereinafter referred to as ``charge generation layer''). ), and the charge generation layer accepts the generated charge carriers,
The substance that transports it (hereinafter referred to as "charge transport substance")
A laminated photoreceptor (hereinafter referred to as a "functionally separated photoreceptor") consisting of a layer mainly composed of (hereinafter referred to as a "charge transport layer")
shows excellent sensitization and is currently the mainstream of organic photoreceptors.

However, the above-mentioned photoreceptor has a problem in potential stability because the dark area potential and bright area potential fluctuate greatly during repeated use. In particular, the organic charge transport layer is
When using the photoconductor repeatedly, corona discharge (ozone,
Deterioration occurs due to collisions of charged particles, ultraviolet rays, etc.), image exposure, and neutralizing light. This is considered to be a factor that causes the potential of the photoreceptor to fluctuate.

For this reason, in conventional organic photoreceptors, various additives are added to the charge transport layer to improve potential stability during repeated use.

[Problem to be solved by the invention]

However, in the conventional electrophotographic photoreceptor described above, when an additive to improve potential stability is added to the charge transport layer, this additive becomes a trap, leading to a decrease in sensitivity and an increase in residual potential. I have a problem.

Therefore, in the present invention, by preventing the decrease in sensitivity and increase in residual potential that would occur when additives are included in the charge transport layer, high sensitivity can be maintained and potential stability during repeated use can be extremely improved. The aim is to make it excellent.

[Means to solve the problem]

In order to solve the above-mentioned problems, the electrophotographic photoreceptor according to the present invention includes, on a conductive support, a charge generation layer having a charge generation substance that generates charge carriers, and a charge carrier generated from the charge generation layer. In an electrophotographic photoreceptor in which a charge transport layer having a charge transport substance that accepts and transports charges is formed in this order, the charge transport layer has a thickness of 0.5 from the layer surface with respect to the layer thickness of the charge transport layer. % or more and less than 50% of the layer thickness, and is characterized by containing at least one phenolic antioxidant and one or more tocol antioxidants.

[Function] According to the above structure, the charge transport layer has at least one kind of phenolic antioxidant and tocol antioxidant in the surface layer portion. This prevents the charge transport material in the charge transport layer from being oxidized and deteriorated by corona discharge or the like. Therefore, even if the electrophotographic photoreceptor is used repeatedly, the charge transport material will not deteriorate due to oxidation, and as a result, the electrophotographic photoreceptor will have excellent potential stability.

In addition, the above phenolic antioxidant or tocol antioxidant is limited to a layer thickness of 0.5% to 50% of the layer thickness of the charge transport layer from the layer surface of the charge transport layer. Contains Therefore, the charge transport material is prevented from decreasing sensitivity and increasing residual potential.

As a result, the electrophotographic photoreceptor has high sensitivity and excellent repetition stability.

〔Example] An embodiment of the present invention will be described below.

Photoreceptor for electrophotography according to the present invention (hereinafter referred to as photoreceptor)
has a conductive support. A charge generation layer containing a charge generation substance that generates charge carriers is formed thereon. Furthermore, a charge transport layer is formed on the charge generation layer, and includes a charge transport substance and a binder that receive and transport charge carriers generated from the charge generation layer.

Further, the above-described charge transport layer contains an antioxidant as an additive in a layer thickness ranging from 0.5% to 50% from the layer surface with respect to the layer thickness of the charge transport layer.

Aluminum vapor-deposited polyethylene terephthalate (Metal Me #100-TS; manufactured by Toshiku Co., Ltd.) is used for the above-mentioned conductive support.

In addition, the charge generation substance of the charge generation layer includes a polycyclic quinone pigment (Monoite Re
d2Y;1. (manufactured by C01) is used.

(Left below) A hydrazone compound represented by the following structural formula is used as a charge transport material in the charge transport layer.

Cz Hl ■ Polycarbonate resin (Kneepilon; manufactured by Mitsubishi Gas Chemical Co., Ltd.) is used as the binder.

In addition, the inventors of the present invention presumed that corona discharge and the like degraded the charge transport material near the surface of the charge transport layer by oxidation, and that this was the cause of the potential fluctuation, and thus came to use an antioxidant as an additive.

α-tocopherol shown by the following structural formula is used as an antioxidant.

Note that each of the above compounds is not limited to each compound having the above structural formula. In other words, the conductive support is, for example,
As the base itself has conductivity, aluminum,
It may be made of aluminum alloy, copper, zinc, stainless steel, nickel, etc., or it may be made of plastic having a layer formed by coating aluminum alloy, indium oxide, etc. by vacuum evaporation method or the like. Furthermore, the above-mentioned conductive support may be one in which plastic or paper is impregnated with conductive particles, or may be a plastic or the like containing conductive particles.

Examples of the charge-generating substance include polycyclic quinone pigments other than those shown in the above structural formula, bisazo pigments such as chlorocycloampurus, perylene compounds, quinacritone compounds, phthalocyanine compounds, and azulenium salt compounds. It's okay.

Examples of the charge transport substance include heterocyclic compounds such as carbazole, oxadiazole, thiazole, oxazole, imidazole, and pyrazoline, and low molecules such as hydrazone derivatives, aniline derivatives, and arylamine derivatives other than those shown in the above structural formulas. compounds, or polymeric compounds such as poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, and polyvinylanthracene.Furthermore, the charge transport substance may be one or two of these compounds. It may be a mixture of more than one species.

Note that when a low-molecular compound is used as the above charge transport material, it is mixed with a suitable binder to form a charge transport layer. On the other hand, when using a polymer compound with film-forming properties, the charge transport layer may be formed using only this polymer compound, or the charge transport layer may be formed by mixing this polymer compound into a binder. You may do so.

The above binders include, for example, polycarbonate resin, acrylic resin, polyester resin, polystyrene resin, melamine resin, silicone resin, polyvinyl butyral resin,
It may also be a polyamide resin. The binder may also be a copolymer resin containing two or more of the repeating units of the above resins, such as an insulating resin such as vinyl chloride-vinyl acetate copolymer resin, acrylonitrile-styrene copolymer resin, etc. However, without being limited to these, all commonly used resins may be used alone or in a mixture of two or more.

As the antioxidant, it is preferable to use a phenol compound or a tocol compound.

Specific examples of the above phenolic antioxidants include hydroquinone, hydroquinone monomethyl ether, 2.5-
Di-t-butylhydroquinone, L-butylcatechol,
Styrenated phenol, 2,6-di-butylphenol, BHTXBHA.

2-methyl-4,6-di-t-butylphenol, 2.
2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6
-t-butylphenol), 4.4°-methylenebis(2,6-di-t-butylphenol), 4.4°-butylidenebis(3-methyl-6-t-butylphenol), 2.6-di( Examples include methylbenzyl)-P-cresol.

Next, specific examples of tocol-based antioxidants include tocol derivatives such as β-tocopherol and T-tocopherol in addition to α-tocopherol shown in the above structural formula.

Furthermore, the antioxidant may be one type of the above-mentioned antioxidants or a mixture of two or more types.

In the above configuration, a method for manufacturing the present photoreceptor will be described below.

First, 2 parts by weight of a polycyclic quinone pigment, which is a charge-generating substance shown by the above structural formula, and a phenoxy tree Jll (PKH
H, manufactured by Union Carbide Co.) and 1 part by weight, and 1.4-
A dispersion liquid was prepared by dispersing 97 parts by weight of dioxane using a ball mill disperser for 12 hours.

Then, this dispersion was applied onto an aluminum vapor-deposited polyethylene terephthalate support, using a Baker applicator, and dried at room temperature for 1 hour to form a charge generation layer with a thickness of 1 p.

Next, 1 part by weight of a hydrazone compound which is a charge transporting substance shown by the above structural formula, 1 part by weight of a polycarbonate resin as a binder, and 8 parts by weight of dichloromethane were mixed and dissolved by stirring with a stirrer. .

This mixed solution was applied onto the charge generation layer using a Baker applicator and dried at 80° C. for 1 hour to form a charge transport layer with a thickness of 15 Jna.

Furthermore, 0.05 parts by weight of α-tocopherol, which is an antioxidant represented by the above structural formula, was mixed and stirred and dissolved in the mixture containing the above charge transport substance.

Then, this mixed solution was applied onto the above charge transport layer using a Baker applicator, and then dried at 80°C for 1 hour to form a charge transport layer having a thickness of 5 μm and having an antioxidant.

The content of the antioxidant is 0.0% relative to the charge transport substance.
01% to 20% by weight, preferably 0.1% to 1% by weight
0% by weight is good. That is, when the antioxidant content is less than 0.01% by weight, the antioxidant has no effect, and when the antioxidant content exceeds 20% by weight, the antioxidant has a negative effect on the charge transport substance. .

The photoreceptor produced by the method described above was designated as Sample 1.

Next, Samples 2 to 5 were produced in the same manner as Sample 1, as shown below.

Sample 2 is the same photoreceptor as Sample 1, except that in the charge transport layer, the thickness of the layer that does not contain an antioxidant is 19ttIIl, and the thickness of the layer that contains an antioxidant is 1-. did.

Sample 3 had only a charge transport layer that did not contain an antioxidant and had a layer thickness of 20 mm. In other respects, the photoreceptor was the same as Sample 1.

In sample 4, in the charge transport layer, the layer thickness of the layer not containing the antioxidant was 10-1, and the layer thickness of the layer containing the antioxidant was 1-1.
The photoreceptor was the same as Sample 1 except that it was 0-closed.

In sample 5, the charge transport layer contained an antioxidant throughout the charge transport layer having a layer thickness of 2<0>.

In other respects, the photoreceptor was the same as Sample 1.

Furthermore, except for the antioxidant shown by the following structural formula, sample 1
Samples 6 to 9 having the same structure as above were prepared. The antioxidant of Sample 6 is a monohydric phenol compound represented by the following structural formula.

The antioxidant of Sample 7 is a dihydric phenol compound represented by the following structural formula.

The antioxidant of Sample 9 is a tocol compound represented by the following structural formula.

The antioxidant of Sample 8 is a dihydric phenol compound represented by the following structural formula.

(The following is a blank space.) Next, the charging characteristics of Samples 1 to 9 and potential fluctuations during repeated use were measured by the method shown below.

First, samples 1 to 9 were tested using an electrostatic copying paper tester (EPA:M
Corona charging was carried out at 15 kV in static mode using an Odel 5P-428 (manufactured by Kawaguchi Denki Co., Ltd.) and held for 5 seconds in a dark place. After this, the above samples 1 to 9 were exposed to the illuminance of 5f.
x exposure to charge characteristics, i.e., initial potential (■0) and 5
The exposure amount (Bu/z) required to attenuate the potential to 1/2 when the dark decay is performed for 5 seconds, the residual potential (Vr) after 5 seconds from the start of exposure, and the residual potential (Vr) when the dark decay is performed for 5 seconds. The potential retention rate (Vk) was measured.

The measurement results of the charging characteristics of Samples 1 to 9 obtained by the above method are shown in Table 1.

Note that d4 is the layer thickness of the charge transport layer containing the antioxidant.

Table 1 Samples 1 to 9 were then loaded into a copying machine (SF-8100; manufactured by Sharp Corporation). As for the potential fluctuation during repeated use, samples 1 to 9 were measured at the initial stage and after 10,000 uses.
The dark area potential (Vd) and light area potential (VL) were measured.

The measurement results of potential fluctuations during repeated use of the above samples 1 to 9 are shown in Table 2.

(Margin below) Table 2 As is clear from Table 1 above, Sample 4 and Sample 5
The exposure amount (
This results in a deterioration in sensitivity (El/R) and an increase in residual potential (Vr).

This revealed that the antioxidant acts as a trap when contained in the charge transport layer in a range of 50% or more of the layer thickness of the charge transport layer.

In addition, as is clear from Table 2 above, sample 3 shows potential fluctuations during repeated use (after 10,000 times), especially dark area potential (Va), compared to samples 1 and 2 and samples 4 to 9.
There are large fluctuations. As a result, it was found that in a photoreceptor in which only a charge transport layer not containing an antioxidant was formed, the charge transport material deteriorated by oxidation due to corona discharge, resulting in large potential fluctuations.

Therefore, in the photoreceptor, the charge transport layer containing the antioxidant is 0.5% to 50% of the layer thickness of the charge transport layer from the layer surface.
%, preferably in the range of 5% to 25%, a decrease in sensitivity and an increase in residual potential can be prevented, and it has been found that the potential stability during repeated use is extremely excellent.

Next, as is clear from Samples 6 to 9 in Tables 1 and 2, the antioxidant contained in the charge transport layer decreases sensitivity and increases residual potential in phenolic compounds and tocol compounds. It has been found that it is possible to prevent this, and furthermore, the potential stability during repeated use is extremely excellent.

〔Effect of the invention〕

As described above, the electrophotographic photoreceptor according to the present invention includes a charge generation layer having a charge generation substance that generates charge carriers on a conductive support, and receives and transports charge carriers generated from the charge generation layer. In an electrophotographic photoreceptor in which a charge transport layer having a charge transport material that is At least 1 in a layer thickness of less than %
It has a structure containing more than one kind of phenolic antioxidant and tocol antioxidant.

This prevents the decrease in sensitivity and increase in residual potential that would occur when additives are included in the charge transport layer, maintaining high sensitivity and providing extremely excellent potential stability during repeated use. It has the effect of being able to

Claims (1)

[Scope of Claims] 1. Charge transport comprising a charge generation layer having a charge generation substance that generates charge carriers and a charge transport substance that receives and transports charge carriers generated from the charge generation layer on a conductive support. In the electrophotographic photoreceptor in which the charge transport layer and the charge transport layer are formed in this order, the charge transport layer has a layer thickness in the range of 0.5% or more and less than 50% from the layer surface with respect to the layer thickness of the charge transport layer. An electrophotographic photoreceptor comprising at least one phenolic antioxidant and tocol antioxidant.