JPS60218655A - electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To prevent fluctuation of electric resistivity due to change of humidity by incorporating an electron donor in an undercoat layer. CONSTITUTION:An electron donor, such as polymers, e.g., poly-N-vinyl-carbazole, or poly-1-vinylpyrene, or polyacenaphthylene; or monomers, such as carbazole, pyrene, or fluorene, is incorporated in the underlayer of an electrophotographic sensitive body having the underlayer and a photosensitive layer formed on a substrate in an amt. of 1-50,000, preferably, 10-1,000ppm. As the binder of the underlayer, polyamide type reins, such as nylon-6, nylon-66, casein, and gelatin, are preferable. The figures illustrate the cases in which positive charge is injected in the dark, and it is injected in the conventional layers, as shown in (1), but the underlayer hinders the injection of charge, as shown in the case (2) of this invention.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor having an undercoat layer containing an electron-donating substance.

An electrophotographic photoreceptor basically consists of a substrate and a photosensitive layer. However, improvements in adhesion between the substrate and photosensitive layer, improvement in coating properties of the photosensitive layer, protection of the substrate, covering defects on the substrate, protection against electrical breakdown of the photosensitive layer, improvement of charge injection from the substrate to the photosensitive layer, etc. Therefore, it is effective to provide an undercoat layer between the substrate and the photosensitive layer.

Conventionally known materials for the undercoat layer include polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, and polyamide.

The first characteristic required of the undercoat layer is electrical characteristics. Since it is used in an electrophotographic photoreceptor, it is important not to affect the electrophotographic properties, and for this purpose it is necessary to have low electrical resistance. When the electrical resistance is high, a charged potential is applied to the undercoat layer, and fogging occurs in the image as a so-called residual potential.

Furthermore, it is necessary that the electrical resistance is unaffected by changes in the external environment, in particular by changes in atmospheric humidity. For example, when electrical resistance increases due to low humidity, fogging can occur.

On the other hand, when a material whose electrical resistance decreases under high humidity conditions is used, charge injection from the substrate or from the undercoat layer itself to the photosensitive layer tends to occur. If charge injection occurs over the entire area of the photosensitive layer, the dark area potential will decrease, and if there are extremely fine irregularities or defects in the film, it will appear as a solid black area on the image copied by a normal copying machine. It appears as a white smudge.

Furthermore, in microreader printers and laser beam printers that apply a so-called reversal development process, in which the potential on the photoconductor and the area where the toner is attached and appears are reversed, the above-mentioned defects occur when the image (image) is This is a big problem because it causes black fog or black spots on the white background.

To summarize the above explanation, it is necessary to develop an undercoat layer material that has a volume resistivity of 10 to 10 Ω·α in the entire environmental range in which the photoreceptor is used.

This is extremely difficult.

Incidentally, the aforementioned increase in residual potential under low humidity, the degree of fogging under high humidity, etc. are not necessarily determined only by the electrical resistance of the undercoat layer.

The characteristics of charge transfer, trapping, injection, etc. in the undercoat layer are largely involved.

The main object of the present invention is to provide an electrophotographic photoreceptor with extremely stable environmental % properties. In particular, the purpose is to provide an electrophotographic photoreceptor with improved high-humidity characteristics (measures against white background fog in reversal development systems) by modifying a vinyl resin that is stable in a low-humidity environment as an undercoat layer material. do.

The present invention relates to an electrophotographic photoreceptor having an undercoat layer and a photosensitive layer on a substrate, wherein the undercoat layer contains an electron-donating substance. .

That is, the present invention uses as an undercoat layer a resin in which an electron-donating substance is added to the resin used for the undercoat layer in order to prevent the charge injection that occurs as shown in FIG. 2-(6) especially under high humidity. There is a slight AK%.

That is, the added electron-donating substance functions as a blocking layer for positive charge injection, as shown in Figure 3-(2). Charge injection during dark charging is due to a very small number of positive charges (7 leak carriers), and in order to prevent this, a small amount of carrier tra- All you have to do is form a whelk. Also, since a considerable number of positive charges are generated during exposure, the addition of an electron-donating substance to the resin layer does not reduce the sensitivity at all.

Historically speaking, there is a concern about the increase in residual potential under low humidity, but the addition of electron-donating substances actually reduces the so-called electrical resistance, and the increase in residual potential under low humidity is caused by the resin layer This is due to its own characteristics and has no effect at all. Moreover, the behavior under high humidity also contributes to a very small change in minority carriers, and the so-called electrical resistance hardly changes.

The amount of electron donating substance added can range from 1 to 50,000 ppm, but 10 to 1000 ppm is effective.
Moreover, there are few disadvantages (decreased sensitivity, increased memory, etc.).

Next, white background fog due to high humidity (reverse development (2) system)? Explain the principle behind this occurrence.

Figure 1 shows an example of the layer structure of a functionally separated electrophotographic photoreceptor. The photoreceptor is charged with (1)-order negative charge, (217
90nm infrared laser exposure, (3) about 1 second later, (4
(1) to (4) when used in a repeated process of reversal tM by negative toner, <5) transfer by positive band movement, (6) cleaning, and (7) erasing residual 5th place by strong exposure. The situation is shown in Figure 2. That is, Vd (
The positive charge injected into the dark area potential causes fogging. Particularly in high humidity, charge injection occurs because the resistance of the resin layer changes from 1/10 to 1/100.

The present invention will be explained with reference to the case where polyamide resin is used as the undercoat layer material. Polyamide resins include Nylo76, Nylon66, Nylo/610, Nyloyl
1, nylon 12, etc., but they are poorly soluble in solvents and difficult to handle. An example of a solvent-soluble polyamide resin is Amilan (Toshiku Co., Ltd.).

Zytel (Duboy), UItramid
(BASF).

Copolymerized nylon such as Mavanyl (ICI),
BCI (Belding-Corticalli)
Type 8 nylon such as , ) resin (Runishi Sangyo Co., Ltd.), and natural polyamides such as casein and gelatin.

Examples of electron-donating substances include polymers having polynuclear aromatic hydrocarbons as repeating units, such as poly-N-vinylcarbazole and poly-1-vinylvinylcarbazole.

Poly-9-vinylandracene/, poly-9-vinylphenylanthracene, polyacenaphthalene/, poly-'9-
(4-ben/tenyl)carbal/poly-9-(5-
(hexyl)carbazole, N-substituted acrylic acid amide polymer of polymethylene bire/or pyrene, and alkyl, nitro, amine, halogen or hydroxy substituted products of this polymer can be used as n'l:N-vinylcarbazole and A copolymer of methyl acrylate, a condensation polymer of 1- and nylpyrene and formaldehyde, and a block copolymer of 1-vinylpyrene and Poutadier can also be used.

Furthermore, examples of monomers that are not polymers include carbazole, N-ethylcarbazole, pyrene,
Tetrafen, 1-acetylpyrene, 2.3-benzochrysene, 6.7-benzopyrene, 1-bromopyrene, 1
-Ethylpyrene, 1-methylpyrene, perylene, 2-phenylindole, tetracene, bicene, 1.3,6.
8-tetraphenylbire/, chrysene, fluorene, phenanthrene, 2,3-benzopyrene, anthraquinone, dibenzothiophene, naphthalene/ and 1-phenylnaphthalene/, tris(dialkylaminophenyl)methaneleuco, bis(dialkylaminophenyl) ) methane, bis(dialkylaminophenyl)ether, 2. ．．
5-bis(dialkylaminophenyl)-1,3,5-
Examples include oxadiazole and pyrazoline derivatives.

To explain the electrophotographic photoreceptor of the present invention in more detail, first, the substrate is made of metal such as aluminum, brass, or stainless steel, or polyethylene terephthalate, polybutylene terephthalate, phenolic resin, polypropylene, etc.
It is made of polymeric materials such as iron, iron, polystyrene, and hard paper into a cylindrical shape, or it is used as a film or foil.

In the case of an insulator, it is necessary to conduct a conductive treatment, which includes methods such as impregnation with a conductive substance, lamination with metal foil, and metal vapor deposition. Furthermore, if the surface roughness of the substrate is large, a conductive paint may be applied to smooth the surface. Conductive paints include metal powders such as aluminum, copper, silver, gold, and nickel, metal oxide powders such as tin oxide, indium oxide, anotemon oxide, titanium oxide, and zinc oxide, and carbon powders. Powder alone or in combination with polyurethane, epoxy, alkyd, polyester, acrylic, melamine, silicone,
It is produced by dispersing it in a binder resin such as phenol resin. The thickness of the conductive layer 1* coated with the conductive paint is preferably at least the square of the surface roughness of the base.

The undercoat layer of the present invention is formed by coating on the substrate or a conductive layer formed on the surface of the substrate. Its thickness is 0.1
The thickness is preferably about 10μ.

A photosensitive layer is formed on this.

The photosensitive layer is made of CdS dye-sensitized zinc oxide, selenium powder, amorphous silicon powder, polyvinyl carbazo/l/,
Organic pigments such as phthalocyanine pigments and oxadiazole are coated together with a binder resin as required.

In addition, when using organic photoconductive materials, an effective method for improving properties is to combine a charge generation layer that generates charge carriers with four lights and a charge transport layer that has the ability to move the generated charge carriers. Sometimes.

The charge generation layer is made of azo pigments such as Sudan Red, Diamond/Blue, and Jenas Green B, Algol Yellow,
Quinone pigments such as pyrenequinone and indanthrene brilliant violet RRP, quinone anine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, bisbenzimidazole pigments such as India First Orange toner, phthalone anine pigments such as copper phthalocyanine, quinacridore pigments, It is formed by dispersing a charge generating substance such as a biryllium dye in a binder resin such as polyester, polystyrene, polyvinyl acetate, acrylic, polyvinyl butyral, polyvinylpyrrolidone, methylcellulose, hydroxyglopyl methylcellulose, or cellulose esters.

Alternatively, it can also be formed by vapor deposition or the like.

The thickness of the charge generation layer is approximately 0.05 to 0.5 μm.

In addition, the charge transport layer contains polycyclic aromatic compounds such as anthracene, pyrene, zena/threne, coronennato (1), indole, carbazole, oxazole, etc. in the main chain or side chain.
Compounds containing nitrogen-containing cyclic compounds such as isoxazole, thiazole, imidazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, and triazole, and hole-transporting substances such as hydrazone compounds are dissolved in resins that have film-forming properties. be done. This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. Seven X eel resins include polycarbonate,
Polyarylate, polystyrene, polymethacrylate esters, styrene-methyl methacrylate copolymer, polyester, styrene-acrylonitrile copolymer,
Examples include polysulfone. The thickness of the charge transport layer is 5~
The resistance is about 60μ.

Regarding the specific compounding ratio and composition of the photosensitive layer, please refer to the actual IA.
fliK will explain in detail.

Example 1 A case in which 100 ppm of anthraquino/ is blended into copolymerized nylon Amilan cM-8000 (Toshiku Co., Ltd.) is shown below.

The size is 60φ x 260m The above 0
M8000 kl 0 parts, anthraquino/o, ooi
(100 ppm) was dissolved in a mixed solution of 60 parts of methanol and 40 parts of butanol, and the solution was dip coated onto the above substrate to form a polyamide resin layer with a thickness of 1 μm.

Next, ε type steel phthalocyanine (Lionol Blue ES,
1 part of Toyo I/K Seizo Co., Ltd.), 1 part of butyral resin (S-LEC BM-2; manufactured by Sekisui Chemical Co., Ltd.), and 10 parts of 7chlorohexanone were mixed in a sand mill dispersion machine containing I ynmφ glass beads for 20 minutes. After time dispersion, the mixture was diluted with 20 parts of methyl ethyl ketone.

This liquid was dip coated onto the previously formed polyamide resin layer and dried to form a charge generation layer.

The film thickness at this time was 0.6μ.

Next, 10 parts of a hydrazone compound having the following structural formula, 15 parts of styrene/-methacrylic methyl copolymer resin (trade name: MS2 [ ] 0 ; manufactured by Steel Chemical Co., Ltd.), and 80 parts of toluene were dissolved. This liquid was applied onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer with a thickness of 16 μm.

This laminated photosensitive drum was attached to a laser printer (electrification is negative polarity) equipped with a gallium-aluminum arsenide semiconductor laser (emission wavelength 780 nm, output 5 mW) and placed in an environment of 65°C and 85% carp. After leaving it for a day and night, an image was produced using one reversal phenomenon, and no white background fog was observed on the solid white image 11.

For comparison, a photosensitive drum containing no anthraquinone was prepared in the same manner, and an image was produced in the same manner.
A fog on white background corresponding to +0.01 was observed in the scale (Type 341 manufactured by Macbeth).

Example 2 Under the same conditions as Example 1, as an undercoat layer material.

10 parts of Toresin gF30T (manufactured by Runishi Sangyo Co., Ltd.), which is an example of nylon type 801, and 10.01 parts (1000 ppm) of 1-acetyl bire were mixed with 6 parts of methanol and 4 parts of butanol.
The solution was dissolved in 0 parts of the mixed solution and applied by dip coating onto the same substrate as in Example 1 at 0.degree. C. to form a polyamide resin layer with a thickness of 1 .mu.m.

The subsequent steps are exactly the same as in Example 1.

For comparison, a photosensitive drum provided with an undercoat layer containing no 1-acetylpyrene was prepared in the same manner.

When the same apparatus as in Example 1 was used and image output was evaluated under the same environmental conditions, no fog occurred on the photosensitive drum of the present invention, and a fog equivalent to 10.03 was observed on the comparative drum. .

[Brief explanation of drawings]

Figure 1 shows an example of the layer structure of an electrophotographic photoreceptor made by Functional Separation.・Figure 2 shows the reversal development process (infrared laser beam plink).
), (1) is primary charging (approximately -700V) (2J&'!, exposure (790nm laser light) (3
) is the time lag (about 1 second) to move from (2) to (4)
(4) is +! Number 11 (reverse manifestation 18 to minus toner
+), Figure 116 shows positive charge injection in the dark area, (1) is a comparative example (conventional example) in which considerable charge injection is observed, (2+ is the inventive example in which the undercoat layer blocks charge injection). The case is shown below.Patent Applicant Canon Co., Ltd. Agent Yu Kano, Patent Attorney Figure 1, Figure 2 (3) (1) Figure (4) Figure (2)

Claims (2)

[Claims] (1) An electrophotographic photoreceptor comprising an undercoat layer and a photosensitive layer on a substrate, wherein the undercoat layer contains an electron-donating substance. (2) The electrophotographic photoreceptor according to claim 1, wherein the undercoat layer material is a polyamide resin.