JPH01191888A - Method for recovering electrophotographic sensitive body from fatigue - Google Patents

Abstract

PURPOSE:To satisfactorily recover a photosensitive body having an org. photosensitive layer from its fatigue and to prevent the image deterioration at the time of a high temp. and low temp. by subjecting the above-mentioned photosensitive body to a required heating treatment for a prescribed period. CONSTITUTION:The photosensitive body having the org. photosensitive layer is rapidly recovered from the deteriorated characteristics such as degraded electrostatic chargeability based on its fatigue at the time of iterative use if the above-mentioned photosensitive body is subjected to the heating treatment at >=50 deg.C-150 deg.C of the range where no influence is exerted to a toner and the org. photosensitive layer in the preheating period of an image forming device. The relative humidity at the time of a high temp. and high humidity, is simultaneously lowered and the generation of dew condensation at the time of a low temp. and image scumming at the time of a low temp. and low humidity is prevented. As a result, the photosensitive body is satisfactorily recovered from its fatigue and the high-quality image formation is executed while the unequal densities, degraded densities and scumming are prevented.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to an image forming apparatus using an electrophotographic photoreceptor;
More specifically, the present invention relates to an improvement in a method for recovering from fatigue of an electrophotographic photoreceptor.

[Prior art]

In recent years, photoreceptors used in electrophotographic copying machines have begun to be made of organic photosensitive materials, which have the advantages of low cost, productivity, and non-polluting properties.

Organic electrophotographic photoreceptors include photoconductive resins such as polyvinylcarbazole (PVK), and PVK-TNF.
There are charge transfer complex type photoreceptors represented by (2,4,7 trinitrofluorenone), pigment dispersion types represented by phthalocyanine binders, and functionally separated type photoreceptors that use a combination of a charge generating substance and a charge transporting substance. In particular, functionally separated type photoreceptors are attracting attention.

When such an organic photoreceptor is applied to the Carlson process, it has low chargeability and poor charge retention (high dark decay), and these characteristics deteriorate significantly with repeated use, causing problems such as Uneven density.

It has the drawbacks of fogging and, in the case of reversal development, background smearing.

That is, the chargeability of organic photoreceptors decreases due to pre-exposure fatigue. This pre-exposure fatigue is mainly caused by light absorbed by the charge-generating material, so the longer the charges generated by light absorption remain in the photoconductor in a mobile state, the more the number of charges increases. It is thought that the lower the chargeability becomes, the more the chargeability decreases due to pre-exposure fatigue. In other words, even if a charging operation is performed while the charge generated by light absorption remains, the surface charge will be neutralized by the movement of the remaining carriers, so the surface potential will increase until the residual charge is consumed. Therefore, the rise in surface potential is delayed by the amount of pre-exposure fatigue, and the apparent charge level 4 becomes lower.

As a method to improve these drawbacks, a layer of Sin, Afi, 0.00. and other inorganic materials.

Methods such as vapor deposition, sputtering, and anodic oxidation are known to provide a charge generation layer with an AQ of 0. (Japanese Unexamined Patent Publication No. 55-142354), and it is also known to include metal powder in the charge generation layer (Japanese Unexamined Patent Publication No. 60-214364).

In addition, polyamide resin (Japanese Unexamined Patent Publication No. 58-30
No. 757, Japanese Patent Application Laid-Open No. 1967-739), Alcohol-soluble nylon resin
Publication No.), water-soluble polyvinyl butyral resin (Japanese Unexamined Patent Publication No. 6
0-232553) and polyvinyl butyral resin (Japanese Unexamined Patent Publication No. 106549/1982).

However, there are no improvement measures on the photoreceptor side regarding the deterioration of chargeability and charge retention due to repeated use.

Sufficient photoreceptors were not obtained.

JP-A-51-111338 discloses As, Se,
It is disclosed that the rate of fatigue (dark decay) is slowed down when the photoreceptor is maintained at a temperature of 10-30% above room temperature and no more than 40°C.

On the other hand, even in the operating environment of a copying apparatus, under high temperature and high humidity conditions, single image blurring, image distortion, etc. occur, and at low temperatures, there are problems such as dew condensation on the photoreceptor and scumming.

Regarding this environmental dependence, JP-A-61-7843 discloses that the relative humidity of the photoreceptor under high temperature and high humidity can be reduced by heating the support of the photoreceptor layer at a relatively low temperature using a planar heating element. , JP-A-62-121483 discloses a method of blowing hot or cold air onto a photoreceptor, which is a method that can prevent dew condensation on the photoreceptor at low temperatures and prevent deterioration of the photoreceptor at high temperatures. has been disclosed, but the method was not necessarily satisfactory.

〔the purpose〕

The present invention provides a method for recovering from fatigue of an electrophotographic photoreceptor, which can improve the chargeability of the photoreceptor, reduce relative humidity under high temperature and high humidity conditions, and prevent dew condensation on the photoreceptor at low temperatures. The purpose is to provide.

〔composition〕

According to the present invention, in an image forming apparatus including a device that charges and exposes an electrophotographic photoreceptor comprising at least an organic photoreceptor layer on a conductive support to form an electrostatic latent image, A method for recovering from fatigue of an electrophotographic photoreceptor is provided, which comprises heating during preheating of a forming apparatus.

The present inventors have investigated the problem of deterioration in chargeability of electrophotographic photoreceptors, which are formed by providing at least an organic photoreceptor layer on a conductive support. It has been found that when heated during preheating, charging characteristics with no delay in the rise of the 4th position of charging, which is equivalent to that before repeated use, are exhibited.

The preheating time in the present invention is a function associated with a copying machine, etc., in which when the main switch of the copying machine is turned on, the power is turned off after a certain period of time, except for the heating power supply for the fixing section.
It means that state.

According to the research conducted by the present inventors, when the heating temperature during preheating is at least room temperature, preferably at least 40°C, and more preferably at least 50°C, a good improvement in charging is observed. It was found that the faster the rate of improvement, the faster the improvement. However, when heating at high temperatures, organic substances in the photosensitive layer may undergo oxidation or other deterioration, or the toner in the developing area may melt.
In order to cause sticking etc., in the present invention, the photoreceptor,
Although there are some differences depending on the constituent materials such as toner, 15
It is desirable to perform the heat treatment at a temperature of 0°C or lower, preferably 120°C or lower.

In addition, as a heating means, an electric resistance heater (Unexamined Japanese Patent Publication No. 51
-111338 Publication), a method of blowing warm air (Japanese Patent Application Laid-open No. 51-111338, Japanese Patent Application Laid-Open No. 62-12148)
2), using a sheet heating element as a support (Japanese Unexamined Patent Publication No. 61-7843), and pasting a sheet heating element on the inside of the support, but are not limited to these. Never.

The present invention provides an organic photoreceptor and an image forming apparatus using the same, which uses a heating means for the organic photoreceptor, an actuating means (for example, a relay, etc.) for the heating means, and, if necessary, a temperature detection means. As another configuration, in addition to the above-mentioned configuration requirements, a cooling means and a means for operating the cooling means may be used. When cooling down to a certain temperature, it is useful to employ a cooling means.

In this case, the cooling method is to blow cooling air (
Examples include, but are not limited to, methods using a refrigerant (Japanese Unexamined Patent Publication No. 62-121482) and a method using a refrigerant.

In addition, as an example of the use of the cooling means, if there is a risk that the temperature of the photoreceptor will rise too much when the heating means is activated, the cooling means may also be activated in the same way as the heating means to prevent overheating. It is possible.

The heating means and cooling means described above may be installed inside the photoreceptor, and/or one or more of them may be installed at appropriate positions outside the photoreceptor at the same time.

In addition, the heating time during preheating of the present invention is determined by considering the frequency of use by the user, waiting time, etc., but in practice, the heating time during preheating is set at a relatively low temperature that does not pose a problem when using the photoreceptor. Preferably, a method is employed in which the photoreceptor is heated continuously at a temperature of 100° C. or a method in which the photoreceptor is heated at a relatively high temperature for a short period of time during preheating, and then used after the photoreceptor is cooled to a usable temperature.

Examples of the temperature detection means include, but are not limited to, temperature detection methods using thermocouples and infrared detectors, gas thermometers, bimetal thermometers, and the like.

Next, the electrophotographic photoreceptor used in the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view showing an example of the structure of a photoreceptor used in the present invention, in which a photoreceptor layer 15 is provided on a conductive support 11. As shown in FIG.

FIGS. 2A and 2A are cross-sectional views showing another example of the structure, in which the photosensitive layer is composed of a stack of a charge generation layer 21 and a charge transport layer 23. FIG.

3 and 4 are cross-sectional views showing still another example of the structure, and FIG. 3 shows an intermediate IC between the conductive support 11 and the photosensitive layer 15! 13, and FIG. 4 shows the photosensitive layer 1
A protective layer 17 is provided on top of the protective layer 5.

The conductive support 11 may be one that exhibits conductivity with a volume resistance of 10 ioΩl or less, such as metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, and platinum, and metal deposits such as tin oxide and indium oxide. by vapor deposition or sputtering to coat a film or cylindrical plastic or paper, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc., or a plate thereof, 1. I. It is possible to use a pipe that has been made into a blank pipe by extrusion, drawing, etc., and then surface-treated by cutting, superfinishing, polishing, etc.

Next, the photosensitive layer 15 will be explained, but first, the laminated photosensitive layer will be described.

The charge generation layer 21 is a layer mainly made of a charge generation substance,
A binder resin may be used if necessary.

Binder resins include polyamide, polyurethane,
Polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, poly-N-vinylcarbazole, polyacrylamide, etc. are used.

Examples of the charge generating substance include CI Pigment Blue 25 [Color Index (CI) 21180],
CI Pigment Red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (CI 45210), and a phthalocyanine pigment having a porphyrin skeleton,
Azo pigments having a carbazole skeleton (JP-A-53-95)
033), an azo pigment having a distyrylbenzene skeleton (described in JP-A-53-133455)
, an azo pigment having a triphenylamine skeleton (Japanese Unexamined Patent Publication No. 5
3-132547), an azo pigment having a dibenzothiophene skeleton (described in JP-A-54-21728), an azo pigment having an oxadiazole skeleton (described in JP-A-54-12742), Azo pigments having a fluorenone skeleton (described in JP-A No. 54-22834), azo pigments having a bisstilbene skeleton (described in JP-A-54-17733), azo pigments having a distyryloxadiazole skeleton ( Japanese Patent Publication No. 54-2129
Azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-17734), CI Pigment Blue 16 (CI 7410)
0), C.I. Butt Brown 5 (CI 73410), C.I. Butt Dye (CI
73030), and perylene pigments such as Argo Scarlet B (manufactured by Violet) and Indance Scarlet R (manufactured by Bayer).

Among these charge generating substances, azo pigments are preferred.

These charge generating substances may be used alone or in combination of two or more.

The binder resin is suitably used in an amount of 0 to 100 parts by weight, preferably 0 to 100 parts by weight, based on 100 parts by weight of the charge generating substance.
~50 parts by weight.

The charge generation layer is prepared by dispersing a charge generation substance together with a binder resin if necessary using a ball mill, attritor, sand mill, etc. using a solvent such as tetrahydrofuran, cyclohexane, dioxane, dichloroethane, etc., and diluting the dispersion liquid appropriately and applying it. It can be formed by Application can be performed using a dip coating method, a spray coating method, a bead coating method, or the like.

The thickness of the charge generation layer is 0. Approximately 01 to 5 pa is appropriate, and preferably 0.1 to 2 tones.

The charge transport layer 23 can be formed by dissolving or dispersing a charge transport substance and a binder resin in a suitable solvent, coating the solution on the charge generation layer, and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added if necessary.

Charge transport materials include hole transport materials and electron transport materials.

Examples of hole transport substances include poly-N-vinylcarbazole and its derivatives, poly-γ-rubazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, polyvinylpyrene, and oxazole derivatives. , oxadiazole derivatives, imidazole derivatives,
Triphenylamine derivatives, 9-(ρ-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene derivatives, benzidine derivatives Examples include charge-donating substances such as.

Examples of electron transport substances include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinone dimethane, 2,4,7-dolinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,
2,4,5.7-titranitroxanthone, 2.4.8
- Trinidrothioxanthone, 2,6.8-trinitro-4H-indeno(1,2-b)thiophene-4-
1.3.7-trinitrodibenzothiophene-5
, 5-dioxide and other electron-accepting substances.

These charge transport substances may be used alone or in a mixture of two or more.

Binder resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester,
Polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin.

Examples include thermoplastic or thermosetting resins such as ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenolic resin, and alkyd resin. It will be done.

As the solvent, tetrahydrofuran, dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. are used.

The thickness of the charge transport layer 23 is suitably about 5 to 50 mm.

Next, a case where the photosensitive layer 15 has a single layer structure will be described.

In this case as well, most of the materials are of a functionally separated type consisting of a charge generating substance and a charge transporting substance.

That is, the compounds shown above can be used as the charge generating substance and the charge transporting substance.

A single-layer photosensitive layer can be formed by dissolving or dispersing a charge generating substance, a charge transporting substance and a binder resin in a suitable solvent, coating the solution and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added if necessary.

As the binder resin, in addition to using the binder resin mentioned above for the charge transport layer 23 as is, the binder resin for the charge generation layer 2
The binder resins listed in 1 may be used in combination.

The single-layer photosensitive layer is formed by dipping coating, spray coating, bead coating, etc. using a coating solution in which a charge generating substance, a charge transporting substance, and a binder resin are dispersed using a dispersion machine using a solvent such as tetrahydrofuran, dioxane, dichloroethane, or cyclohexanone. Can be formed by coating.

The thickness of the single photosensitive layer is 5 to 50. The degree is appropriate.

In addition, in the present invention, photosensitive W! It is also possible to further provide an insulating layer on top of 15.

Also, as shown in FIG. 3 in one aspect of the present invention.

By providing an intermediate layer 1'3 between the conductive support and the photosensitive layer, it is possible to further improve the first effect of the present invention, and it is also possible to improve adhesion.

The intermediate layer 13 may be made of an inorganic material such as Sin or AQ203 provided by vapor deposition, sputtering, or anodization, or may be made of polyamide resin (Japanese Unexamined Patent Application Publication No. 58-30757, JP-A No. 58-98739). , alcohol-soluble nylon resin (JP-A-60-196766), water-soluble polyvinyl butyral resin (JP-A-60-2325)
No. 53), polyvinyl butyral resin (Japanese Unexamined Patent Publication No. 58
106549), a resin layer made of polyvinyl alcohol, etc. can be used.

Furthermore, a resin intermediate layer in which pigment particles such as ZnO1Tie2 and ZnS are dispersed can also be used as the intermediate layer.

Furthermore, as the intermediate layer 13 of the present invention, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, etc. can also be used.

The appropriate thickness of the intermediate layer 13 is 0-51A.

As the resin used for the protective layer 17, ABS resin, A
C3 resin, olefin vinyl copolymer resin, chlorinated polyether, allyl resin, phenolic resin, polyacetal, polyamide, polyamideimide.

polyarylate, polyallylsulfone, polybutylene,
Polybutylene terephthalate, polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, methacrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene resin, polyurethane, polyvinyl chloride, polyvinylidene chloride , epoxy resin, etc.

In addition, from the viewpoint of wear resistance, polytetrafluoroethylene resin, fluorine resin, and silicone resin can be added as additives to lower the wear coefficient and improve wear resistance and scratch resistance. The wear resistance can also be improved by dispersing inorganic compounds such as , tin oxide, and potassium titanate into the resin.

The thickness of this surface protective layer is 0.5 to 10 pm, preferably 1 to 5 pm.

〔Example〕

EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples.

Example 1 On an aluminum cylinder with an outer diameter of 40 mm and a length of 250 mm, a charge generation layer coating liquid and a charge transport layer coating liquid having the following compositions were applied and dried to form a charge generation layer (0, 2) and a charge transport layer. (20pm) was formed.

[Charge generation layer coating liquid]

Trisazo pigment with the following structural formula 2 parts by weight Polyvinyl butyral 0.5〃 (Denki Kagaku Kogyo ■
Denka Butyral #4000-1) Cyclohexanone 150 parts by weight 2-butanone
50 II [Charge Transport Layer Coating Solution] Charge transport substance having the following structural formula 100 parts by weight Tetrahydrofuran 800 The organic photoreceptor prepared as above was placed on a laser printer (Ricoh PC Laser 6000), and immediately after charging The probe of the surface electrometer was set at a position where the surface potential of the photoreceptor could be measured. Further, an electric resistance heater was set inside the photoreceptor, and the photoreceptor was set to be heated to 55° C. only during preheating. Using this printer, 500
Continuous printing of sheets → preheating state (15 minutes) was repeated to print up to 3,000 sheets.

Comparative Example 1 Printing was carried out in the same manner as in Example 1 except that the electric resistance heater was not activated.

FIG. 5 shows the surface potentials measured in Example 1 and Comparative Example 1.

Example 2 An intermediate layer coating solution having the following composition was applied and dried on an aluminum cylinder with an outer diameter of 40 mm and a length of 250 mm to form an intermediate layer (
2is) was formed.

[Intermediate layer coating liquid]

Titanium dioxide 10 parts by weight Polyvinyl butyral 1 (Tanezu Chemical Industry)
S-LEC BL-1) Toluylene-2,4-diisocyanate 0.2 parts by weight 2-butanone
100〃4-methyl-2-pentanone
60 Then, 0.2. A thin film was provided as a charge generation layer.

Further, a charge transport layer coating solution having the following composition was applied thereon and dried to form a charge transport layer (18tna).

[Charge transport layer coating liquid]

Charge transporting substance having the following structural formula: 90 parts by weight Methylene chloride 900 The organic photoreceptor prepared above was placed on a laser printer (Ricoh PC Laser 6000), and as in Example 1, the surface electrometer probe and electric I installed a resistance heater. When preheating the laser printer, the heater was controlled to heat the photoreceptor at a maximum temperature of 90° C. for 5 minutes, and then air (room temperature) was blown into the cylinder using a separately provided fan to cool the photoreceptor.

The above printer (10℃, 65%), (20%, 6
300%) and (30°C, 90%) environmental conditions.
Continuous printing of sheets→preheating state (10 minutes) was repeated to print up to 3,000 sheets.

Comparative Example 2 Printing was carried out in the same manner as in Example 2 except that the heater and cooling fan were not operated.

Table 1 shows the surface potentials and image characteristics of the 3000th sheet of the photoreceptors of Example 2 and Comparative Example 2.

x: Density decreases significantly, and background stains also become noticeable.

Example 3 A charge generation layer coating solution having the following composition was applied on a polyethylene terephthalate film support having an aluminum conductive layer.
A charge transport layer coating solution is applied, dried, and a charge generation layer (0,2
μs) and a charge transport layer (18 tan) were sequentially formed.

[Charge generation layer coating liquid]

Disazo pigment having the following structural formula: 2 parts by weight Tetrahydrofuran 80〃Ethyl Celsolve 120〃[Charge transport layer coating liquid] Charge transport material having the following structural formula: 100 parts by weight Tetrahydrofuran 800〃Next, a conductive layer is coated on this electrophotographic photoreceptor. , and belt bonding were performed to prepare a photoreceptor for mounting.

The organic photoreceptor prepared as described above is copied to the copier Ricopy-FT2.
050, and a surface electrometer probe was set so that the surface potential of the photoreceptor immediately after charging could be measured. In addition, a fan was installed during cleaning and charging so that hot air at 60° C. could be blown onto the surface of the photoreceptor, and the photoreceptor was heated for 12 minutes only when the copying machine was started.

Using the copying machine set as above, under the same environment as in Example 2, the process of continuously printing 300 sheets and preheating state (15 minutes) was repeated to make up to 3,000 copies.

Comparative Example 3 Copying was carried out in the same manner as in Example 3 except that hot air was not blown onto the surface of the photoreceptor.

Example 4 Each photoreceptor used in Comparative Example 3 was then used in Example 3.
Table 0-2, which was copied in the same manner as Example 3.
The surface potentials and image characteristics of the 3000th sheet of Sample No. 4 and Comparative Example 3 are described below.

x: Density decreases significantly, and background stains also become noticeable.

Example 5 A charge transport layer coating solution, a charge generation layer coating solution, and a protective layer coating solution having the following compositions were sequentially applied onto an ugly aluminum cylinder with an outer diameter of 80 m and a length of 340 m, and dried to form a charge transport layer ( 20t
s ), charge generation layer (0,3Iia), protective layer (3II
m) was established.

[Charge transport layer coating liquid]

Charge transport substance with the following structural formula: 80 parts by weight Tetrahydrofuran 800〃[Charge generation layer coating liquid] Disazo pigment with the following structural formula: 3 parts by weight Tolylene-2,4-diisocyanate 0.1〃Cyclohexanone 100〃Tetrahydrofuran
200 [Protective layer coating liquid] Conductive titanium (manufactured by Mitsubishi Metals) 100 n toluene 240 Butanol
The organic photoreceptor prepared as above was mounted on a copying machine, Ricopy-FT5510, and a surface electrometer probe was set so that the surface potential of the photoreceptor could be measured immediately after charging. In addition, a planar heating element is attached to the inside of the photoconductor, and the photoconductor is heated to a maximum temperature of 100% when preheating the copying machine.
After controlling the planar heating element to heat it at .degree. C. for 7 minutes, air (room temperature) was blown onto the surface of the photoreceptor using a separately provided fan to cool it down. The above copier was operated under the same environmental conditions as in Example 2.
Continuous copying of 00 sheets → preheating state (10 minutes) was repeated until 5000 sheets were copied.

Comparative Example 4 Copying was carried out in the same manner as in Example 5 except that the sheet heating element and cooling fan were not operated.

Table 3 shows the surface potential of Example 5 and Comparative Example 4 and 50
Describe the image characteristics of the 00th sheet.

x: Density decreases significantly, and background stains also become noticeable.

Example 6 An intermediate layer coating liquid having the following composition, a charge generation layer coating liquid,
The charge transport layer coating solution is sequentially applied and dried to form an intermediate layer (0,37
All), charge generation layer (0,21Ja), charge transport layer (
20 pa) was formed.

(Intermediate layer coating liquid) Water 150 parts by weight Methanol 200 [Charge generation layer coating liquid] Disazo pigment with the following structural formula 2 parts by weight cyclohexanone 160 2-butanone
40 [Charge transport layer coating liquid] Following structural formula (40 parts by weight of charge transport substance of 13)
[■] 40〃Tetrahydrofuran 800〃The organic photoreceptor prepared as above was mounted on a copying machine Ricobi-FT5510 modified for negative charging, so that the surface potential of the photoreceptor immediately after charging could be measured. A surface electrometer probe was set. Furthermore, warm air at 45° C. was allowed to be blown inside the photoreceptor, and the air was blown only during preheating. This copying record was repeated under the same environmental conditions as in Example 2 for 500 sheets in a continuous manner → in a preheated state (20 minutes) until a total of 5,000 sheets were copied.

Comparative Example 5 Copying was carried out in the same manner as in Example 6 except that hot air was not blown.

Table 4 shows the surface potential of Example 6 and Comparative Example 5 and 50
Describe the image characteristics of the 00th sheet.

x: Density decreases significantly, and background stains also become noticeable.

〔effect〕

Since the method of the present invention has the above-mentioned configuration, it has the following remarkable effects.

(1) Deterioration of charging characteristics after repeated use of the organic photoreceptor can be prevented.

That is, good images without background stains can be obtained when image density decreases, image density unevenness occurs in copying machines, printers, etc., or during reversal development.

(2) It is possible to lower the relative temperature of the photoreceptor atmosphere under high temperature and high humidity conditions, thereby preventing image distortion.

(3) It is possible to prevent dew condensation on the photoreceptor at low temperatures and background smearing of images at low temperatures and low humidity.

[Brief explanation of the drawing]

1, 2a, 2b, 3 and 4 are schematic cross-sectional views of the electrophotographic photoreceptor of the present invention, and FIG. 2 is a graph showing the relationship between the number of prints and the surface potential when printing using an electrophotographic photoreceptor. 11... Conductive support, 13... Intermediate layer, 15...
- Photosensitive layer, 17... Protective layer, 21... Charge generation layer,
23... Charge transport layer. Patent applicant Rico Co., Ltd. - Figure 1 Figure 2 (a) Figure 2 (b) Figure 3 Figure 4 Figure 5 Printed sheet! L (sheets) Procedure name RL? Official document (spontaneous) 1. Indication of the case Patent Application No. 18307 filed in 1989 2. Name of the invention Method for recovering from fatigue of electrophotographic photoreceptors 3. Relationship with the person making the amendment Patent applicant address Ota-ku, Tokyo Nakamagome 1-3-6 Name
(674) Rico Co., Ltd. - Representative Hama
1) Hiro 4, Agent 〒151 5, Date of amendment order Voluntary 6, Number of claims increased by amendment 07, Subject of amendment Column 8 of “Detailed Description of the Invention” of the specification, Contents of amendment The following amendments will be made in the specification. (1) In the first line of page 7, replace ``Means such as attachment, etc.'' with ``A method of attachment, a method using an infrared lamp, a heating medium (the medium is water, oil, air, other gas, etc.) Methods include methods using heating elements, methods using heating elements with PTC characteristics, methods heating by high frequency induction heating, etc.. (2) 5th row directly below the 9th row (7) rD,, 1.1.
, J wo, rD, 1. ,I. 1. Correct to J. (3) Delete "on the charge generation layer" in the 5th line from the bottom of Section 12. (4) Correct the chemical structural formula on page 30, line 5 as follows.

Claims (1)

[Claims] (1) In an image forming apparatus including a device that charges and exposes an electrophotographic photoreceptor comprising at least an organic photoreceptor layer on a conductive support to form an electrostatic latent image, the photoreceptor is A method for recovering from fatigue of an electrophotographic photoreceptor, the method comprising heating during preheating.