JPH03196082A - Electrophotograsphic copying device - Google Patents

Abstract

PURPOSE:To restrain the lowering of sensitivity caused by the durability of an organic electrophotographic photosensitive body for positive electrostatic charging and to obtain an excellent image by providing a destaticizing and electrostatic charging device which makes the surface potential of the OPC photosensitive body for positive electrostatic charging negative. CONSTITUTION:The image is formed by using the organic electrophotographic photosensitive body 1 at stages, at least, such as primary electrostatic charging, exposure, development, transfer, cleaning, destaticization, and fixation. In such a case, the device has such a mechanism that the destaticization is performed by superposing an alternating current on a direct current having a negative polarity and impressing it to make the surface potential of the photosensitive body negative. Thus, the remaining positive charge is eliminated and normal photocarrier is kept being generated, thereby preventing the lowering of sensitivity caused by the durability of the OPC photosensitive body for positive electrostatic charging.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic apparatus.

[Prior Art] Electrophotographic devices use organic photoconductors (OPC), which are inexpensive and easy to manufacture, as well as cadmium sulfide-resin dispersion systems, zinc oxide-resin dispersion systems, selenium vapor deposition systems, selenium-tellurium vapor deposition systems, and amorphous silicon systems. ) Copies are obtained by performing the basic steps of charging, exposing, developing, transferring, cleaning, neutralizing, and fixing each photoreceptor in the system.

The charging process at this time requires a higher voltage (
DC voltage of about 5 to 8 KV) is applied, and charging is performed by the generated corona.

However, OPC photoreceptors have lower potential stability than inorganic photoreceptors, especially OPC photoreceptors for negative charging, which are currently widely used.
When a PC photoreceptor has a large potential fall (a phenomenon in which the bright area potential and dark area potential decrease with durability), image defects such as a decrease in density during normal development and fogging during reversal development occur.

In order to suppress this drop in potential, a method is used in which a scorotron device is provided with a discharge current control member (hereinafter referred to as grid 2) to increase the value of the current flowing through the charging wire.

However, by increasing the current value, corona products such as ozone and NOx increase due to the negative charge, and electrophotography using OPC photoreceptors, which have lower chemical stability than inorganic photoreceptors. In the case of equipment, there have been cases where problems such as image blurring and image deletion have occurred, and these ozone and NO
The increase in x cannot be ignored as it has an impact on the environment around the electrophotographic device.In order to solve these problems such as ozone and NOx, we developed a positive charging OPC photoreceptor.
Commercialization is underway.

However, there are various problems with OPC photoreceptors for positive charging.
In particular, no definitive solution to the decrease in sensitivity due to chu/ku has been found.

[Problems to be Solved by the Invention] An object of the present invention is to suppress a decrease in sensitivity due to durability of a positively charging organic electrophotographic photoreceptor and provide a good image.

[Means and effects for solving the problem] In an electrophotographic device in which an image is formed in the fixing process and the primary charge is positive, static electricity is removed by superimposing alternating current and negative polarity direct current on the surface of the photoreceptor. It consists of an electrophotographic device characterized by a mechanism that makes the potential negative.

In the positively charging electrophotographic photoreceptor of the present invention, the photosensitive layer is composed of an organic photoconductor, and the organic photoconductor used in the photosensitive layer is an organic photoconductive polymer such as polyvinylcarbazole. thing.

There are also those using a low molecular weight organic photoconductive substance and an insulating polymer as a binder.

Among these, a functionally separated type photoreceptor in which 81 layers are formed from the conductive support side, including a charge transport layer and then a charge generation layer, or a single layer type photoreceptor in which a charge transport material and a charge generation material are bound together with the same binder. It doesn't matter which one you use.

The laminated organic electrophotographic photoreceptor used in the present invention has the following configuration.

The photosensitive layer is provided on a conductive support.

As the support, for example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum, etc., which are conductive in themselves, can be used, and other materials such as aluminum and aluminum alloy can be used. , indium oxide-tin oxide alloys, etc., formed on the surface of plastic materials such as polyethylene, polypropylene, polyvinyl chloride, acrylic resin, polyfluoroethylene, etc., by vacuum deposition, carbon black, tin oxide particles, etc., together with a suitable binder. Plastic or paper impregnated with a conductive binder can be used.

An undercoat layer having a barrier function and a VC adhesion function can be provided between the conductive support and the photosensitive layer.

The undercoat layer is made of casein, polyvinyl alcohol nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon, nylon 6, nylon 66, nylon 6).
10, copolymerized nylon, etc.), polyurethane, gelatin, aluminum oxide, etc. The thickness of the layer is 5 pm or less, preferably 0.5 to 3 pm, and it functions well as a rear layer. Therefore, it is desirable that the specific resistance is 107Ω or more.

The charge transport layer is formed by dissolving a charge transport substance in a resin having film-forming properties.

Examples of a charge transport substance include pyrene, N-ethylcarbazole, N-isopropylcarbazole N-methyl-N
-Phenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, N,N-diphenylhydrazino-3-methylidene-1O-ethylphenothiazine N,N -diphenylhydrazino-3-methylidene-
10-Nitylphenoxazine, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, P-diethylaminobenzaldehyde-N-α-naphthyl-N
-Phenylhydrazone, p-pyrrolidi/benzaldehyde-N,N-diphenylhydracin, 1,3.5-trimethylindolenine-ω-aldehyde-N,N-diphenylhydrazone, P-diethylbenzaldehyde-3-
Hydrazone compounds such as methylbenzthiazolinone-2-hydrazone, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole, 1-phenyl-3-(p-diethylaminostyryl)- 5-(p-
diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3(p-diethylaminostyryl)-5
-(p-diethylaminophenyl)pyrazoline, 1-[
pyridyl(2)]-3-(p-diethylaminostyryl)-5-(p-diethylami/phenyl)pyrazoline,
l-[6-medoxypyridyl(2)]-3-(p-diethylaminostyryl)-5-(p-diethylami/styryl)pyrazoline, 1[pyridyl(3)]-3-(
p-diethylaminostyryl)-5-(p-diethylami/phenyl)pyrazoline, 1-(levidyl(2)]-
3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-(pyridyl(2
)] -3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminostyryl)pyrazoline, l-[pyridyl(2)]3-(α-methyl-p-diethylaminostyryl)-5-( p-diethylaminophenyl) bilazoline, l-phenyl-3-(p-diethylaminostyryl)-4-methyl-5-(p-diethylaminophenyl)pyrazoline, l-phenyl-3(α-
benzyl-p-diethylaminostyryl)-5-(p-
Pyrazoline compounds such as diethylaminophenyl)pyrazoline, 2-(p-diethylaminostyryl)-6-
Oxazole compounds such as ethylaminobenzoxazole, 2-(p-diethylaminophenyl)-4-(p-diethylaminophenyl)5-(2-chlorophenyl)oxazole, 2-(p-diethylaminostyryl)-6-dinityl Thiazole compounds such as aminobenzothiazole, triallylmethane compounds such as bis(4-diethylamino-2-methyl-2enyl)-phenylmethane, 1,1-bis(4-N,N-dimethylamino-2-methyl) Polyallylalkane compounds such as phenyl)ethane, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethylcarbazole-formaldehyde resin, It is possible to use one kind or a combination of two or more kinds selected from the following.

As a binder, phenoxy resin, polyacrylic 7
polyvinyl butyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenolic resin, epoxy resin, polyester, alkyd resin, polycarbonate, polyurethane, or repeating units of these resins. Examples of copolymers containing two or more of these include styrene-butadiene copolymer, styrene-acrylonitrile copolymer, and styrene-maleic acid copolymer.

It can also be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

The thickness of the charge transport layer is 5 to 50 μm, preferably 8 to 20 μm.
μm, and the weight ratio of the charge transport material to the binder is 5:1 to 1:5, preferably 3:1 to 1:3.

Coating methods include dip coating, spray coating, spinner coating, bead coating,
Mayer bar coating method, blade coach ink method, roller coating method, curtain coating method, etc. can be used.

As the charge generation layer, Sudan Red, Guianpuru-
, azo pigments such as Jenas Green B, quinone pigments such as Algol Yellow, Pyrenequinone, and Indanthrene Brilliant Violet RR, indigo pigments such as quinocyanine pigments, perylene pigments, indigo and thioindigo pigments, and bisbenzimidazoles such as Indofast Orange Toner. It is formed by vapor deposition of one or more pigments, phthalocyanine pigments such as copper phthalocyanine, quinacridone pigments, or by dispersion coating together with a suitable binder as necessary.

The binder can be selected from insulating resins or organic photoconductive polymers, such as polyvinyl butyral, polyarylate (condensation polymer of bisphenol A and phthalic acid, etc.), polycarbonate polyester, phenoxy resin, polyvinyl acetate, acrylic resin, polyacrylamide. , polyamide, polyvinylpyridine, cellulose resin.

Examples of the organic conductive polymer include urethane resin, epoxy resin, casein, polyvinyl alcohol, and polyvinylpyrrolidone. Examples of the organic conductive polymer include poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene.

The thickness of the charge generation layer is 0.01 to 15 gm, preferably 0.05 to 57 gm, and the weight ratio of the charge generation material to the binder is 1oaf"1:20.

The solvent used for the charge generation layer-like paint shall be selected taking into account the solubility and dispersion stability of the resin and charge transport substance used, and specifically alcohols such as methanol, ethanol, isopropanol, etc. Acetone, methyl ethyl ketone, cyclohexanone, N,N-diethylformamide, sulfoxides such as N,N-dimethylsulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, esters such as methyl acetate, ethyl acetate, chloroform, chloride Aliphatic halogenated compounds such as methylene, dichloroethylene, carbon tetrachloride, and trichloroethylene) & aromatic hydrocarbons such as hydrogen hydride, benzene, toluene, xylene ligroin, chlorobenzene, and dichlorobenzene, etc. can be used.

Coating methods include dip coating method, spray coating method, spinner coating method, bead coach ink method,
Mayer bar coating method, blade coating method, roller coating method, curtain coating method, etc. can be used.

Further, the single-layer organic electrophotographic photoreceptor used in the present invention can be prepared by mixing the above-mentioned charge transporting substance and charge-generating substance with the above-mentioned binder and binding the mixture onto a conductive support.

Dyes, pigments, organic charge transport substances, etc. are generally exposed to ultraviolet light,
Because it is susceptible to dirt from ozone, oil, etc., and metals, etc.
It is also possible to provide a protective layer if necessary.

Now, the market for electrophotographic photoreceptors (OPC photoreceptors) composed of these organic photoconductors is rapidly developing because they are inexpensive, easy to manufacture, and non-toxic. In particular, it is important to develop a positively charging OPC photoreceptor that is advantageous in dealing with ozone and NOx problems.

However, positively charging OPC photoreceptors have several major problems. One of these is a decrease in sensitivity due to durability. This phenomenon causes image defects such as image fogging in the case of a normal development system and light density in the case of a reversal development system.

It is no exaggeration to say that this phenomenon is unique to OPG photoreceptors, and the mechanism is thought to be related to the carrier mobility of OPG photoreceptors.

A possible mechanism for the decrease in sensitivity of the laminated positive charging OPC photoreceptor is that positive charge is not completely injected from the charge generation layer to the charge transport layer, so the residual positive charge increases with durability, and the charge It is presumed that this inhibits the generation of photocarriers in the generation layer, causing a gradual decrease in sensitivity.

Furthermore, it is thought that the same phenomenon occurs in the case of a single-layer positive charging OPC photoreceptor due to the presence of hole traps.

The present invention eliminates this residual positive charge by applying an external electric field, maintains normal generation of photocarriers, and prevents a decrease in sensitivity due to the durability of the positively charged OPC photoreceptor.

The external electric field is provided by superimposing alternating current and negative polarity direct current in the static elimination process. Hereinafter, this will be referred to as static elimination.

The type of charger has a corona discharge electrode connected to a high voltage power source,
A corotron device consisting of a shield plate surrounding the corona discharge electrode or a scorotron device in which a grid is provided on the corotron device, and direct charging in which a conductive member is brought into contact with a photoreceptor and a voltage is applied to the conductive member to charge it. Any format can be used.

The strength of the static electricity removal charge depends on the ability of the primary charger and the charging ability of the charge setting photoreceptor, but the surface potential of the photoreceptor after static electricity removal charging is O to -1000V, preferably -100V to -
About 300V.

[Example] Example 1 As a conductive support, 60φX260 with a wall thickness of 0.5 mm
A mm aluminum cylinder was prepared.

4 parts of copolymerized nylon (trade name: CM8000, manufactured by Toshi ■) and type 8 nylon (trade name: Laccamite 5003)
, manufactured by Dainippon Ink Co., Ltd.) was dissolved in 50 parts of methanol and 50 parts of n-butanol.

A 0.67 part m thick polyamide undercoat layer was formed on the above support by dip coating.

And polycarbonate Z resin (manufactured by Mitsubishi Gas Chemical)
10 parts of a compound having a weight average molecular weight of 120,000 were prepared and dissolved in 80 parts of chlorobenzene together with 10 parts of a hydrazine compound having the following structural formula.

This coating liquid was applied onto the undercoat layer to form a charge transport layer of 16 JLm.

Next, add 10 parts of a disazo pigment having the following structural formula.

10 parts of polyvinyl butyral (trade name Kosuretsuku BM2, manufactured by Tsukiki Kagaku ■) was dispersed with 120 parts of cyclohexanone in a sand mill for 10 hours.

Adding 30 parts of methyl ethyl ketone to the dispersion and coating it on the charge transport layer to form a charge generation layer with a thickness of 2.04 parts,
It was used as an electrophotographic photoreceptor.

A copying machine 41jl (PC-20, manufactured by Canon Corp.) with a positive development method was modified for positive charging, and the pre-exposure unit was removed and placed in that position as shown in FIG.

(FIG. 1 is a cross-sectional view of the area around the drum of the copying machine used in this example and a comparative example, where 1 is an organic electrophotographic photoreceptor for positive charging, and 2 is a primary charger.

Reference numeral 3 denotes a static eliminator, 4 a cleaning blade, 5 a transfer charger, and 6 a developing device.) A static eliminator 3 (Corotron system M) is provided, and is connected to a power source that superimposes direct current on alternating current. Using a photographic photoreceptor, the potential after pre-charging is 1100V.
, 1,000 sheets of paper passed at -300V setting,
The potential and images of the photoreceptor were observed before and after durability.

The results will be described later.

Example 2 As a conductive support, 60φX260 with a wall thickness of 0.5 mm
A mm aluminum cylinder was prepared.

4 parts of copolymerized nylon (trade name CM8000, made by Toshiyoshi Co., Ltd.) and type 8 nylon (trade name Laccamite 5003)
．． (manufactured by Dainippon Ink) was dissolved in 50 parts of methanol and 50 parts of n-butanol, and the solution was applied onto the above support by dip coating to form a polyamide undercoat layer with a thickness of 0.6 pm.

Then, 15 parts of a stilbene compound having the following structural formula and 10 parts of polycarbonate (trade name Panlite L-1250, manufactured by Teijin Kasei ■) were dissolved in 50 parts of dichloromethane and 10 parts of chlorobenzene. This coating solution was applied onto the undercoat layer to form a charge transport layer of 15 lumen.

Next, 10 parts of a disazo pigment with the following structural formula, 1 part of polyvinyl butyral (trade name Kosuretsu BM2, manufactured by Sekisui Chemical Co., Ltd.)
1 part in a sand mill with 120 parts of cyclohexanone
Dispersed for 0 hours.

Add 30 parts of methyl ethyl ketone to the dispersion and apply it on the charge transport layer to form a charge stopping layer with a thickness of 2.0 pm,
It was used as an electrophotographic photoreceptor.

The same copying machine as in Example 1 was used, and evaluation was conducted in the same manner. The results will be described later.

Comparative Example 1 The same copying machine and electrophotographic photoreceptor as in Example 1 were used, except that pre-charging was not performed, and the same evaluation as in Example 1 was performed. The results will be described later.

Comparative Example 2 The same copying machine and electrophotographic photoreceptor as in Example 2 were used, except that pre-charging was not performed, and the same evaluation as in Example 2 was performed. Show the results.

Example 1 -100 300 Example 2 -100 300 Comparative example 1O Comparative example 20 650 200 650 200 650 200 650 200 650 200 650 200 Fog■ Potential after 1,000 sheets VL Example 1 640 220 0650
220 0 Example 2 650 240 Q650
220 Q Comparative Example 1 650 400 Δ Comparative Example 2
650 360 Δ*v? −p=l
OOOV f=1500Hz [Effects of the Invention] The electrophotographic device with 151 non-emissions is about 3000 Hz when the static electricity is removed.

By providing a static eliminator that makes the surface potential of the positively charged phase oPC photoreceptor negative, it is possible to prevent a decrease in sensitivity due to the durability of the photoreceptor and to provide a high-quality image, which is a remarkable effect.

[Brief explanation of drawings]

Figure i1 is a sectional view around the drum of the copying machine used in the present example and comparative example. Symbol 1 is a positive charging electrophotographic photoreceptor, 2 is a primary band ffj,
3 is a charger, 4 is a cleaning blade, 5 is a transfer charger, and 6 is a developer.

Claims (1)

[Claims] 1. In an electrophotographic apparatus in which an organic electrophotographic photoreceptor is used to form an image through at least the steps of primary charging, exposure, development, transfer, cleaning, neutralization, and fixing, and the primary charging is of positive polarity, An electrophotographic apparatus characterized in that static elimination is a mechanism in which the surface potential of a photoreceptor is made negative by applying an alternating current and a direct current of negative polarity in a superimposed manner.