JPS60218660A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent fluctuation of electric resistivity due to change in humidity by incorporating polystyrene and an electron donor in an undercoat layer. CONSTITUTION:An electron donor, such as poly-N-vinyl-carbazole, poly-1-vinylpyrene, ethyl carbazole, fluorene, or pyrazoline, is incorporated in the underlayer formed between a substrate and a photosensitive layer and made of a solvent- soluble hardenable type polystyrene type resin, such as polystyrene, styrene- sulfonic resin, or styrene-acrylic resin, having an electric resistivity of <=10<15> OMEGA.cm. The electron donor is added, preferably, in an amt. of 1-50,000ppm. The figures illustrate the cases in which positive electrostatic charge is injected in the dark, and it is injected conventionally as shown in (1), but the underlayer hinders the injection, 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.

The undercoat layer is conventionally made of polyvinyl alcohol, vinyl methyl ether, poly N-vinylimidasol. Ethylcellulose, methylcellulose.

Ethylene-acrylic acid copolymers, casein, gelatin, polyamides, etc. are known.

The first characteristic required of the skin is electrical properties. Since it is used in an electrophotographic photoreceptor, it is important that the electrophotographic properties are not affected, and for this purpose it is necessary that the electrical resistance is low. If the electrical resistance is high, a charging potential of the undercoat layer VC is applied, and fogging occurs in the image as a so-called residual potential.

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

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 injection occurs over the entire area of the photosensitive layer, the dark area potential will decrease, and if there is a partial [extremely fine, H unevenness, defect, etc. It appears as a white spot.

Historically, so-called reversal development (acid process) in which the potential on the photoconductor and the area to which toner is attached and developed is reversed, causes the above-mentioned defects in microreader printers, torsor beam printers, etc. This is a big problem because the upper white background is left blank.

To summarize the above explanation, it is necessary to develop an undercoat layer material having a volume resistivity of 10 to 10 Ω·a in all two environmental ranges in which the photoreceptor is used. This is extremely difficult.

By the way, as mentioned above, the residual potential increases under low humidity.

The degree of fogging under crystal humidity is not necessarily determined only by the electrical resistance of the undercoat layer.

M% properties such as charge transfer, trapping/injection, and the like in the undercoat layer are greatly involved.

The main object of the present invention is to provide an electrophotographic photoreceptor with extremely stable environmental characteristics. In particular, we modified polystyrene resin, which is stable in low humidity environments, as the material for the undercoat layer.
An object of the present invention is to provide an electrophotographic photoreceptor with improved wet characteristics (particularly, measures against white background fog in a reversal development system).

The present invention provides an electrophotographic photoreceptor having an undercoat layer and a photosensitive layer on a substrate, characterized in that the undercoat layer is made of a polystyrene resin with an electron-donating substance added thereto. It consists of an electrophotographic photoreceptor.

The present invention is characterized in that a styrene-based resin containing an electron-donating substance is used as an undercoat layer for the purpose of preventing the charge injection that occurs in Figure 2 (3) particularly under high humidity. .

That is, the added electron-donating substance functions as a layer for blocking positive charge injection, as shown in Figure 3 (2).

Charge injection during dark charging is caused by a very small number of glass charges (free carriers) K, and in order to prevent this, a small amount of glass charge (free carriers) must be added by adding a small amount of electron donating substance. - Just form a trap. Also, during forging exposure,
Since a significant number of positive charges are generated, there is no decrease in sensitivity due to the addition of electron-donating substances in the styrene layer.

To explain further, there is a concern about the increase in residual potential under low humidity, but the addition of an electron donating substance actually reduces the so-called electrical resistance, and the increase in residual potential under low humidity is caused by the resin layer itself. This is due to the characteristics of , 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 the electron donating substance to be added can range from 1 to 50,000 ppm, but 10 to 10001)I)m is effective and has few negative effects (decreased sensitivity, increased memory, etc.).

Next, the principle of occurrence of white background fog (reversal development system) at high humidity will be explained.

Figure 2.1 shows an example of the layer structure of a functionally separated photoreceptor. The photoreceptor is subjected to (1) -order negative fluoroelectron, (2) 790 nm
Infrared laser exposure, (3) after about 1 second, (4) reversal development with minus toner, (transfer with 51 plus charge), (6) cleaning/greasing, (7) erasure of residual potential with string sound light. (1) to (4) when used in the rolling process
The state of No. 7 is shown in Figure 2. That is, Va (dark potential)
The positive charge injected into the area causes fog.

Particularly in high humidity, charge injection occurs because the resistance of the polystyrene resin layer changes from 1/10 to 1/100.

Examples of the polystyrene resin used in the present invention include polystyrene resin, styrene/sulfonic acid resin, styrene-acrylic copolymer, etc.
It is limited to less than 0.0% and is solvent-soluble and hardening type.

Examples of electron-donating substances include polymers having polynuclear aromatic hydrocarbons as repeating units, such as poly-N-vinylcarbasol, poly-1-vinylbire/, poly-9-vinylanthracene, and poly-9-vinylphenyl. Anthrace/,
Polyacenaphthalene, Bo1J-9-(4-pentenyl)
Carbazole, Bo! J-9-(5-hexyl)carbazole, polymethylene/pyrene, or bire/N-substituted acrylic A/acid amide polymer and alkyl of this polymer,
Mention may be made of nitro, amino, halogen or hydroxy substitutes. Also usable are a copolymer of N-vinylcarbazole and methyl acrylate, a condensation polymer of 1-vinylpyrene and formaldehyde, and a block copolymer of 1-vinylpyrene and butadiene. Furthermore, examples of non-polymer monomers such as carbazole, N-
Ethylcarbazole, pyrene, tetraphere, 1-acetyl bire/, 2,3-be/zochrysene, 6,7-benzopyrene, 1-bromopyrene, 1-etherpyrene, 1-methyl bire/, perylene, 2-phenylindole, tetracene, bicene , 1,3,6.8-tetraphenylpyrene, chrysene, fluorene, phenanthre/, 2.3-
be/zobilene, anthraquino/, dibenzothiophene,
Naphthalene and 1-phenylnaphthalene, tris(dialkylaminophenyl)methane leuco, bis(dialkylaminophenyl)methane, bis(dialkylaminophenyl/I/) ether, 2.5-bis(dialkylaminophenyl)-1,3 , 5-oxadiazole, pyrazoline derivatives and the like.

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, polyethylene terephthalate, phenol resin, polypropylene,
It is used by molding polymeric materials such as nylon and polystyrene, or materials such as hard paper into a cylindrical shape, or by making it into 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, antimony oxide, titanium oxide, and zinc oxide, and carbon powders. The body may be made of polyurethane, epoxy, alkyd, polyester, acrylic, melamine, silicone,
A dispersion in a binder resin such as a phenol resin is used. The thickness of the applied conductive layer, such as a conductive paint, is preferably at least the square of the surface roughness of the substrate.

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.

On top of this, a photosensitive layer is formed.

The photosensitive layer is made of organic pigments such as CdS color sensitized zinc oxide, selenium powder, amorphous silicon powder, polyvinylcarbazole, phthalonanine pigment, oxadiazole, etc., and a binder as necessary. It is formed along with fat.

Furthermore, when using organic photoconductive materials, an effective method for improving properties is to combine a charge generation layer that generates charge carriers upon exposure to light and a charge transport layer that has the ability to move the generated charge carriers. There is also.

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 Pyrenequino/, Inta/Threne Brilliant Violet RRP, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, bisbenzimidazole pigments such as India First Orange Toner, and phthalocyanine M such as copper phthalocyanine.
Charge-generating substances such as R, quinacridone pigments and pyrylium dyes are added to binder resins such as polyester, polystyrene, polyvinyl acetate, acrylic, polyvinyl butyral, polyhinylpyrrolidone, methylcellulose, hydroxypropylmethylcellulose, and cellulose esters. Formed in a dispersed manner.

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

The thickness of the charge generation layer is approximately 05 to 0.5 μm thick.

Further, the charge transport layer contains anthracef, pyrene, zena/trene, coronenenatonopolycyclic aromatic compound, or indole, carbazole, oxazole, inoxazole, or thiazole in the main chain or side chain.

Imidazole, pyrazole, oxadiazole.

It is formed by dissolving a hole-transporting substance such as a compound having a nitrogen-containing cyclic compound such as pyrazoli/, thiadiazole, or triazole, or a hydrazone compound in a resin that has film-forming properties. This is because the charge transporting substance generally has a low molecular weight and has poor film-forming properties by itself. Such resins include polycarbonate, polyarylate, polystyrene, polymethacrylic acid esters, styrene-methyl methacrylate copolymer, polyester, styrene-
Examples include acrylonitrile copolymer, polysulfone, and the like. The thickness of the charge transport layer is approximately 5 to 60 microns.

Regarding the specific blending ratio and composition of the photosensitive layer.

This will be explained in detail using actual gun examples.

Example 1 A case in which 100 ppm of anthraquinone was blended with Oligo 2 (manufactured by Yasugawa Paper Co., Ltd.) as a styrene-sulfo/acid compound is shown below.

10 parts of the above oligo and anthraquinone [J, 001 parts (
10,0 ppm) with 60 parts of methanol and 4 parts of butanol.
0 parts of the mixed solution and dip-coated it onto the above substrate to obtain 1
A μ-thick polyamide resin layer was formed.

Next, ε-type copper phthalocyanine (Lionol Blue ES,
1 part of Toyo Ink Manufacturing Co., Ltd.), 1 part of butyral resin (Eslec BM-2: Tanemizu Kagaku Co., Ltd.), and 710 parts of cyclohexano were dispersed for 20 hours using a sand mill dispersion machine containing 1 dia. glass beads. It was then diluted with 20 parts of methyl ethyl ketone.

This liquid was applied by dip coating onto the previously formed polyamide resin layer and dried to form a charge generation layer. The film thickness at this time is 0
．． It was 6μ.

Next, 10 parts of a hydrazone compound having the following structural formula and 15 parts of a styrene-methyl methacrylate copolymer resin (trade name: MS200: manufactured by Tetsutsu Kagaku Co., Ltd.) were dissolved in 80 parts of toluene. Coat it on the layer and dry it with hot air at 100℃ for 1 hour.
A charge transport layer with a thickness of μ was formed.

This laminated photosensitive drum was attached to an experimental laser printer (charged with negative polarity) equipped with a gallium-aluminum semiconductor laser (emission wavelength: 780 nm, output: 5 mw) and left in an environment of 65°C and 85°C for one day and night. After that, when an image was formed by reversal development, no white background fog was observed on the solid white RFII image.

As a comparative example, a photosensitive drum containing no anthraquinone was prepared, and when an image (elevation) was performed in the same manner, the densitometer (
A white background fog corresponding to +0.02 was observed in Macbeth X Type 341).

Example 2 Under the same conditions as Example 1, 10 parts of Stylon (manufactured by Asahi Dow Co., Ltd.) and 7 parts of 1-acetylvinylene were used as undercoat layer materials.
0.01 part (1, [I[JOppm)] was dissolved in a mixed solution of 60 parts of monochlorobenzene and 40 parts of ethyl acetate, and the solution was dip-coated onto the above substrate to form a polyamide resin layer with a thickness of 1 μm.

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

As a comparative example, a photosensitive drum provided with an undercoat layer not containing 1-acetyl bire/ was prepared in the same manner.

When the image output was evaluated using the same apparatus as in Example 1 and under the same environmental conditions, no fog occurred on the photosensitive drum of the present invention, and fog equivalent to +0.03 was observed on the comparative drum.

[Brief explanation of drawings]

Figure 1 shows an example of the layer structure of a resin-separated electrophotographic photoreceptor, where a is the substrate, O is the undercoat layer, C is the charge generation layer (CGL), and d is the charge transport layer (CTL). is an inversion phenomenon process (infrared laser beam,
printer). (1) is primary charging (approximately -700V) (2) is exposure (790nm laser source) (3) is (2
) to (4) (about 1 second). Comparative example (conventional example) % (2) shows the case of the present invention in which the undercoat layer prevents charge injection. Patent applicant: Canon Co., Ltd. Representative Patent attorney Yu Kano (1st cause) 1) (2) 2nd (3) 3rd (1) Figure (4) Figure (2)

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor having an undercoat layer and a photosensitive layer on a substrate, the special feature is that the undercoat layer is made of a polystere/based resin with an electron-donating substance added thereto. Electrophotographic photoreceptor.