JPS62296180A - Electrophotographic method - Google Patents

Abstract

PURPOSE:To cause a photosensitive body to maintain stable performance to the environment of temperature, moisture, etc., so that the photosensitive body hardly receives any influences of ozone, etc., by using the photosensitive body while the ambient temperature of the body is maintained within a prescribed range. CONSTITUTION:By repeating processes of electrostatic charging, picture exposure, development, transfer, and cleaning to an electrophotographic photosensitive body provided with a photosensitive layer containing an organic photoconductive substance on a conductive supporting body, picture formation is carried out. The photosensitive body is used while its ambient temperature is maintained within a range of 30-50 deg.C. As a result, a decline in sensitivity and increase in residual electric charge caused by a drop in electric charge movability in a low-temperature environment can be prevented.

Description

[Detailed description of the invention] 3. Detailed description of the invention [Industrial use! 7] The present invention relates to an electrophotographic method using an electrophotographic photoreceptor in which a photosensitive layer containing an organic photoconductor is provided on a conductive support, and more specifically, the present invention relates to an electrophotographic method using an electrophotographic photoreceptor in which a photoreceptor layer containing an organic photoconductor is provided on a conductive support. By keeping it.

The present invention relates to an electrophotographic method for stably maintaining the I distance of a photoreceptor.

[Prior Art] Electrophotographic photoreceptors using inorganic photoconductors such as selenium, cadmium*, and zinc oxide as photoreceptor components have been known.

On the other hand, since the discovery that certain organic compounds exhibit photoconductivity, many organic photoconductors have been developed. In addition to low-molecular organic photoconductors such as , anthracene, pyrazolines, oxadiazoles, hydrazones, and polyarylalkanes, phthalocyanine pigments, azo pigments, cyanine dyes, and polycyclic quinone pigments 1. Organic pigments and dyes such as perylene pigments, indigo dyes, thioindigo dyes or squaric acid methine dyes are known. In particular, photoconductive organic pigments and dyes are easier to synthesize than inorganic materials, and the ability to select compounds that exhibit photoconductivity in an appropriate wavelength range has expanded.
Many have been proposed. For example, U.S. Patent No. 412327
No. 0, No. 4247614, No. 4251613,
Same No. 4251614, Same No. 4256821, Same No. 4
No. 260672, No. 4268596, No. 4278
As disclosed in No. 747 and No. 4293628, an electrophotographic photoreceptor using a disazo pigment exhibiting photoconductivity as a charge generation substance in a photosensitive layer functionally separated into a charge generation layer and a charge transport layer. It has been known.

The characteristics of such organic photoconductors change depending on the environment,
In low-temperature conditions, charge mobility decreases, sensitivity deteriorates, and residual charge accumulates. In addition, especially in the case of a photoreceptor in which the surface layer is formed of a layer containing a charge generating substance,
Surface potential tends to become unstable due to adsorption of ozone and other ionic products generated by corona discharge.

[51 Purpose and Overview] The purpose of the present invention is to provide an electrophotographic method that solves the above-mentioned drawbacks, maintains stable characteristics in the environment such as temperature and humidity, and is less susceptible to the effects of ozone, etc. It's about doing.

The above object of the present invention is to form an image on an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support by repeating the processes of exposure, development, transfer, and cleaning for one charged image. In the electrophotographic method performed,
This is achieved by a photographic method characterized in that the photoreceptor is used while maintaining the humidity near the surface of the photoreceptor in the range of 30 to 50''C.

[Detailed Description of the Invention and Examples] In the present invention, an electrophotographic photoreceptor containing an organic photoconductor is constructed as follows.

A photosensitive layer is provided on a substrate having a conductive layer. Examples of substrates having a conductive layer include those in which the substrate itself is conductive;
For example, aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium,
Nickel, indium, gold, platinum, etc. can be used, and in addition, plastics (for example, polyethylene, conductive particles (e.g. carbon flag, silver).

It is possible to use a substrate in which plastic is coated with particles (such as particles) together with a suitable binder, a substrate in which plastic or paper is impregnated with conductive particles, or a plastic containing a conductive polymer.

Barrier and adhesive functions are provided between the conductive layer and the photosensitive layer.
A subbing layer may also be provided. The subbing layer is casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610.3 (combined nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin,
It can be formed from aluminum oxide, etc. The thickness of the undercoat layer is suitably 5W or more, preferably 0.5 to 3W.

In order to make the most of its potential, the barrier layer must be lO″Ω
It is desirable that it is c11 or higher.

The photosensitive layer is formed by coating a photoconductor such as a butalocyanine pigment or an azo pigment, together with a binder if necessary. Furthermore, when using an organic photoconductor, a photosensitive layer consisting of a combination of a charge generation layer that generates charge carriers upon exposure to light and a charge transport layer that has a residual force that transports the generated charge carriers can also be effectively used.

The charge generation layer is made of azo pigments such as Sudan Red, Diane Blue, and Chenas Green B, Algol Yellow,
Quinone pigments such as pinone quinone and indanthrene brilliant violet RRP, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, bisbenzimitazole pigments such as Indofairth l-olene toner, phthalocyanine pigments such as copper phthalocyanine, and quinacridones. It can be formed by dissolving one or more charge-generating substances such as pigments, or by dispersing them together with a suitable binder (or without a binder), and by coating. The binder can be selected from a wide variety of insulating resins or organic photoconductive polymers. For example, insulating resins include polyvinyl butyral polyarylate (condensation product of bisphenol A and phthalic acid, etc.), polycarbonate, polyester, phenoxy resin, polyvinyl acetate acrylic resin, polyacrylamide resin, polyamide, polyvinylpyridine, cellulose resin, urethane. Examples include resin, epoxy resin, casein, polyvinyl alcohol, polyvinylpyrrolidone, and the like. Examples of organic photoconductive polymers include poly-N-vinylcarbazole, polyvinylanthracene, and polyvinylpyrene. The thickness of the charge generation layer is 0.01 to 15
w is preferably from 0.05 to 5, and the weight ratio of the charge generating substance to the binder is from 10:1 to 1:20.

The solvent used in the paint for the charge generation layer is selected based on the solubility and dispersion stability of the resin and charge transport material used. Specific examples of aqueous solvents include alcohols such as methanol, ethanol, and isopropanol; Amides such as acetone, methyl ethyl ketone, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, sulfoxides such as dimethyl sulfoxide, ethers such as tetrahydrofuran, dioxane, ethylene glycol monomethyl ether, methyl acetate, ethyl acetate esters such as chloroform, methylene chloride,
dichloroethylene, tetrachloride), aliphatic halogenated carbonized wood such as trichlorethylene, or benzene,
Aromatic compounds such as toluene, xylene, ligroin, monochlorobenzene, dichlorobenzene, etc. can be used.

Coating is done by dip coating method, spray coating method,
Spinner coating method, beat coating method, Mayer bar coating method, Flede coating method,
This can be carried out using a coach ink method such as a roller coach ink method or a curtain coating method.

It is preferable to carry out drying by drying to the touch at room temperature and then heating. Drying by heating can be carried out at a temperature of 30 to 20° C. for a period of from 5 minutes to 2 hours, either stationary or under ventilation.

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

Examples of the organic substances used in the present invention 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-IO-ethylphenothiazine, N,N-
Diphenylhydrazino-3-methylidene-IO-ethylphenoxazine, P-ethylaminobenzaldehyde N, N-diphenylhydrazone, P-diethylaminobenzaldehyde N-α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde -N, N-
Hydrazones such as diphenylhydrazone, 1,3.5-trimethylindolenine-ω-aldehyde-N, N-diphenylhydrazone, and P-quelinone-2-hydrazone, 2,5-bis-(P-diethylaminophenyl)-
1,1,4-oxadiazole, l-phenyl-3-(
P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, ■-[quinolyl (2)-3
-(P-diethylaminostyryl)-s-(p-diethylamino, nophenyl)pyrazoline, l-[pyridyl(2
)]-3-(P-diethylaminostyryl)-5-(P
-diethylaminophenyl)pyrazoline, 1-[6-medoxypyridyl(2)] -3-(P-diethylaminostyryl) -5-(T'-diethylaminophenyl)pyrazoline, 1-[pyridyl(3)]-3- (P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[lepidyl (2)] -3-
(-diethylaminostyryl)-5-CP-diethylaminophenyl)pyrazoline, 1-[pyridyl(2)co-3-(P-diethylaminostyryl)-4-methyl-5
-(P-diethylaminophenyl)pyrazoline, 1-[
Pyridyl (2)] -3-(α-Methyl-P-diethylaminostyryl)-s-(p-diethylaminophenyl)pyrazoline, 1-phenyl-3-(P-diethylaminostyryl)-4-methyl-5-(P -diethylaminophenyl)pyrazoline, l-phenyl-3-(α-pencyl-P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, spiropyrazoline and other pyrazolines, 2-(P-diethylaminostyryl)-6- Dinithylaminobenzoxazole, 2-(P
Oxazole compounds such as -diethylaminophenyl)-4-(P-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, thiazole compounds such as 2-(P-diethylaminostyryl)-6-dinithylaminobenzothiazole , triarylmethane compounds such as bis(4-diethylamino-2-methylphenyl)-phenylmethane, 1.1-L's(4-N,N-
diethylamino-2-methylphenyl)-hebutane,
1.1,2.2-Tetrakis(4-N,N-dimethylamino-2-methylphenyl)ethane and other polyarylalkanes, triphenylamine, poly-N-vinylcarbazole, polyvinylpyrene.

Examples include polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, and ethylcarbazole formaldehyde resin. Further, these charge transport substances can be used alone or in combination of two or more.

Examples of the binder used in the charge transport layer include phenoxy resin, polyacrylamide, polyvinyl phthyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, phenol resin, Epoxy resin, polyester, alkyd resin, polycarbonate, polyurethane or two of the repeating units of these resins
Examples include styrene-butadiene copolymers, styrene-acrylonitrile copolymers, styrene-maleic acid copolymers, and the like. It may also be selected from organic photoconductive polymers such as poly-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and the like. The thickness of the charge transport layer is 5 to 50u.
L is preferably 8 to 20, and the weight ratio of charge transporting W to binder is 5:1 to 1:5, preferably 3:1 to 1:3.
It is the degree of species.

When forming a layer by coating, dip coating method, spray coating method, spinner coating method, beat coating method, Meyer bar coating method, plate coach ink method, roller coating method,
This can be done using a coating method such as a curtain coating method.

Furthermore, dyes, pigments, organic charge transport substances, and the like are generally susceptible to ultraviolet rays, ozone, stains caused by oil, etc., chips of metal, etc., and therefore a protective layer (insulating layer) is provided as necessary.

In order to form an electrostatic latent image on this protective layer, it is desirable that the surface resistivity be 10 11 Ω or more.

The five layers used in the present invention are resins such as polyvinyl butyral, polyester, polycarbonate, acrylic resin, methacrylic resin, nylon, polyimide, polyarylate, polyurethane, styrene-butadiene copolymer, styrene-acrylic acid copolymer, styrene-acrylonitrile copolymer, etc. The photosensitive layer can be formed by dissolving the photosensitive layer in an appropriate organic solvent and coating the photosensitive layer with the solution and drying it. At this time, the thickness of the protective layer is generally in the range of 0.05 to 20 mm. This protective layer may contain an ultraviolet absorber or the like.

The photoreceptor with the above structure has a temperature near the surface of 30°C to 50°C.
By heating it to ℃ and using it, the problems of decreased sensitivity and increased residual electric charge due to decreased charge mobility in low-temperature environments can be solved.

A decrease in charge mobility, a decrease in sensitivity, and an increase in residual charge in a low-temperature environment are especially caused when the content of a charge transport substance in the charge transport layer is less than 60%, or when the charge at 60% at 23°C is Mobility is l, Ox 10-6cra”/V-sec
(at 100V) This is often seen in the following cases, in which case the electrophotographic method described in the text IJ+ is highly effective.In recent years, copying machines and laser printers using organic photoconductors have become faster. When organic photoconductors are used at high process speeds (circumferential speeds) or short recirculation times (time for one cycle of charging, exposure, development, transfer, and cleaning processes), sensitivity decreases at low humidity and residual prints occur. Accumulation is a major problem.

High process speed (peripheral speed) e.g. 150am/
The electrophotographic method according to the present invention is highly effective when used at a repetition time of 2 seconds or more and 2 seconds or less.

The temperature near the surface of the photoreceptor is suitably in the range of 30°C to 50°C. This is because if the temperature is below 30°C, the effect of improving low-temperature properties will be diminished, and if the temperature is above 50°C, problems such as fusion of the developer will occur.

Ozone and ions generated during the charging process used in the electrophotographic process are adsorbed to the surface of the photoreceptor and form polar groups, and the charge during charging is transferred to the electrostatic charge formed during the image exposure process. The surface potential becomes unstable by electrically attracting or repelling the charge of the latent image. Such problems are caused by ``ionic particles'' on the surface,
It can be reduced to some extent by using some kind of polishing process to remove dirt and ozone adsorbents, but
A polishing process with a weak abrasive power, such as a developer with a weak abrasive power, or a blade cleaning method is not sufficient, and the present invention is more effective in this case.

In addition, when the surface layer is formed of a layer containing a charge-generating substance, for example, in the case of a photoreceptor formed by coating a charge-generating substance and a charge-transporting substance dispersed together with a binder and formed into a paint, or a conductive layer, a charge-transporting layer, etc. The present invention is particularly effective in the case of a photoreceptor in which a charge generation layer is formed in order of a charge generation layer and a charge generation layer.

Charge-generating substances such as ozone and ionic products are easily adsorbed.
Although phenomena such as a decrease in the charging level and unstable potential occur easily, the present invention is particularly effective because ozone and ionic products become difficult to adsorb due to the heating of the photoreceptor.

In the method of the present invention, any means can be used to heat the vicinity of the surface of the photoreceptor as long as the temperature near the surface falls within the above range.For example, a method of providing a heat source near or inside the surface of the photoreceptor The temperature near the zero surface can be adjusted by blowing hot air onto the surface of the photoreceptor from the fixing device 22 or the like using a known temperature adjustment member such as a thermostat.

In the method of the present invention, charging,! Processes such as Ij image exposure, development, transfer, and cleaning may be any method known in the field of electrostatic photography, and the type of developer is not limited to any particular one.

Further, the electrophotographic method of the present invention can be widely used not only in copying machines but also in electrophotographic applications such as laser printers and CRT printers.

The following is an example of the present invention: sl is used.

Example 1 A planar heater was evenly attached to the inner surface of an organic photoconductor photosensitive drum of a copy IaPC1O made by Canon, and the brush 1C pole was slid on both ends of the tram so that a constant voltage could be applied to the heater even when the drum was rotating. Contact with the terminal and heat to 40℃
It was heated to .

As Comparative Example 1, a photoreceptor without heating means was prepared.
Table 1 shows the sensitivity of each drum under various temperature and humidity environments and the change in remaining paper after 5,000 sheets. The sensitivity is the exposure t required to attenuate the surface potential to 172 or I/6 after applying a corona discharge of 15 kV to the photoreceptor and leaving it in the dark for 1 second: (El/2. El/61 ux-sec ) was evaluated by keeping the value constant.

Table 1 As is clear from Table 1, Example 1 exhibited stable characteristics in any environment, and neither the decrease in sensitivity nor the increase in residual paper as seen in Comparative Example 1 was observed.

Example 2 An ammonia aqueous solution of casein (11.2 g of casein) was placed on an aluminum cylinder for a Canon copier PCTO.
, 1 g of 28% ammonia water, and 222% water (222% seal pattern) was coated by dip coating method, and dried to give a coating percentage of 1. Og/m”
A subbing layer was formed.

Next, a charge generating substance lif of the following general formula [I], a dipping part,
5 parts by weight of a charge transport substance of the following general formula [11] and polysulfone resin (P1700: Union Carbide Co., Ltd. m>6)
41 parts by weight of monochlorobenzene and 40 parts by weight of monochlorobenzene were dispersed for 4 hours using a ball mill disperser. This dispersion was applied onto the previously formed subbing layer by dip coating. The film thickness was 15 l.

A Canon copier PC10 was modified so that it could be positively charged, and a heater was placed inside the cylinder in the same way as in Example 1 to heat it. Table 2 shows the temperature near the drum surface and the And about its characteristics, is the charge retention rate durable for 3000 sheets? & The retention rate of the dark area' potential after a 30-minute break with respect to the dark area potential before the break was expressed as a percentage.

Table 2 As is clear from Table 2, when we measured the charging capacity after 30 minutes of continuous copying of 3,000 sheets, we found that without the heater, the charging ability deteriorated due to the adsorption of ozone and ionic products. When the temperature is raised to 30° C. or higher using a heater, there is no decrease in charging ability.

Example 3 An undercoat layer was formed in the same manner as in Example 2.

Next, 1 part by weight of a charge transport substance shown in the following general formula [ml],
1 part by weight of polycarbonate resin (Panlite L-1250) and 6 parts by weight of dioxane were stirred and dissolved, and this coating solution was applied by dip coating and dried to form a charge transport layer. At this time, the film thickness was 15 mm.

Further, 11 parts by weight of the charge generator If of the general formula [I] and 8 parts by weight of polycarbonate resin (Panlite L-1250)
4 parts by weight and 10 parts by weight of dioxane using a ball mill disperser.
Spread out time. This dispersion was applied onto the previously formed heavy transport layer by a spray coating method and dried to give a film thickness of 5AL.

As in Example 2, a copying machine was modified, a heater was placed inside the cylinder, and the temperature near the drum was varied by 50°C, and 3000 sheets were continuously copied in an environment of 23°C and 60%. Thereafter, the battery was rested for 30 minutes, and its charging ability was measured. As a result, when the temperature near the drum was set to 30° C. or higher, there was no decrease in charging and luster, and 3,000 clear images were obtained. When the temperature was 25° C. or lower, the charge retention rate near 1 was measured after 30 minutes of rest after 3000 sheets, and it was 40% or less.

Example 4 A planar heater was attached to the inner surface of the organic photoconductor photosensitive drum of a Canon copier NP3525 to heat it to 40°C. The circumferential speed of the drum was set to 100 in a low temperature environment of 15℃.
Using the drum heater, the speed was varied from mII/see to 500 am/sec, and the increase in remaining paper after 10,000 continuous copies was compared with and without the drum heater.

As is clear from Table 3, the higher the process speed, the greater the decrease in sensitivity in low-temperature environments and the accumulation of residual electricity after durability, and the greater the decrease in sensitivity and accumulation of residual electricity when using the photoreceptor at 40 degrees Celsius. The effect is great.

Example 5 A subbing layer was formed in the same manner as in Example 2. Next, a dispersion of the charge generating substance used in Example 4 was coated by a nine-layer coating method and dried to a film thickness of 3 μL. Furthermore, the general formula [ml
0.5 parts and 1 part of the charge transporting substance shown by were stirred and dissolved in 1 part by weight of polycarbonate resin (Panlite L-1250) and 6 parts by weight of dioxane, and this solution was dip-coated on the charge generation layer. It was then dried to a film thickness of 20 mm.

As in Example 2, a copying machine was modified, a drum heater was installed inside the cylinder in an environment of 15°C, and the humidity near the drum was reduced to 3.
Sensitivity was evaluated at 5°C. The results and the charge mobility at 23°C are shown in Table 4 in comparison with the α-3i photoreceptor.

Table 4 Compared to a photoreceptor with a high charge mobility such as α-3i, a drum heater has a greater effect on a photoreceptor with a low charge mobility such as an organic photoconductor.

[Effects of the Invention] As explained above, a photosensitive layer containing an organic photoconductor that is easily influenced by the environment, ozone, ionic products, etc.
Stable performance can be maintained by performing the electrophotographic process while maintaining the temperature near the surface in the range of 30° to 50°C.

Claims (2)

[Claims] (1) Charging, image exposure, development, and
An electrophotographic method in which an image is formed by repeating transfer and cleaning processes, characterized in that the photoreceptor is used while maintaining the temperature near the surface of the photoreceptor in a range of 30 to 50°C. . (2) The electrophotographic method according to claim 1, wherein the surface layer of the photosensitive layer containing the organic photoconductor is formed of a layer containing a charge generating substance.