JPS6045424B2 - Multiple copy method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining multiple identical copies from a single electrostatic latent image formed on an electrophotographic photoreceptor.

2. Description of the Related Art A method is known in which a large number of identical copies are obtained from one electrostatic latent image using electrophotography.

This method involves forming an electrostatic latent image on an electrophotographic photoreceptor using a conventional method, that is, charging and exposing it to light, and then developing this latent image with a two-component dry developer consisting of toner and carrier. and the process of transferring the obtained image is repeated (for example, Japanese Patent Publication Nos. 44-30233 and 46).
-778 hours). In such a multi-sheet copying method, it is most important that the potential of the latent image on the photoreceptor be maintained constant without attenuation or leakage while the desired number of copies is obtained. To this end, various improvements have been made to developers and photoreceptors. For example, as for the developer, it has been proposed to use a magnetic carrier whose surface is insulated with a resin or the like (Japanese Patent Publication No. 17298/1983). However, this proposed method does not take into account charging caused by friction between the carrier surface and the photoreceptor surface during development, so depending on the surface material of the photoreceptor, the latent image potential may gradually attenuate as the number of copies increases. Another disadvantage is that toner adheres to the background portion of the copy, degrading the image quality. An object of the present invention is to provide a method for copying multiple copies without attenuation of latent image charge or deterioration of image quality by preventing frictional charging between the surface of a carrier and the surface of a photoreceptor.

That is, in the multi-sheet copying method of the present invention, after forming an electrostatic latent image on an electrophotographic photoreceptor having a resin layer or a resin-containing layer on the surface, the same resin as the resin is applied to the latent image. This method is characterized by repeating the steps of developing with a two-component dry developer containing a magnetic carrier coated with a magnetic carrier and transferring the obtained image.

The frictional electrification mechanism of materials is one of the academic fields that has not yet been theoretically elucidated, but when two different materials are rubbed together, it is possible to systematically determine whether the two materials become positively or negatively charged. Many research reports have been published, and charge series for many substances have been reported (for example, J,
44Triboe1ectr by Hennicker
icityinpolymers'', Nature1
96, p174 (1962)).

It is also known that, in general, when two different materials are brought into contact and separated repeatedly, the amount of triboelectrification of these materials increases as the relative speed of the two materials or the number of times of contact increases. By the way, in the magnetic brush development method using a magnetic carrier, in order to obtain a high-density image, the feeding speed of the photoreceptor (
Since the rotational speed of the magnetic brush roller is set high relative to the copying speed (the ratio of the former to the latter is a surface linear velocity ratio of about 1 to 5), the amount of developer supplied to the surface of the photoreceptor is large.
Furthermore, the number of times the developer comes into contact with the surface of the photoreceptor is large. Therefore, when developing with a magnetic brush development method, the material of the photoreceptor surface layer is separated from the material of the magnetic carrier surface by a large distance due to the charging sequence in the Carlson process, in which one development step and one transfer step are performed for one latent image. The amount of triboelectric charge that accumulates on the photoreceptor is almost negligible even when the photoconductor is in use, but in a multi-sheet copying method in which the development and transfer steps are repeated for one latent image, this amount of triboelectricity accumulates on the photoconductor each time it is developed. gradually accumulates and reaches a level that cannot be ignored (50 to 100 V). If this electrical charge level is added to the exposed and non-exposed areas (latent image areas) of the photoreceptor, it will have a serious effect on copying a large number of sheets. That is, if the polarity of the frictional charge accumulated on the photoreceptor is opposite to that of the latent image, the potential of the latent image will be significantly attenuated, making it impossible to copy the desired number of sheets, and the friction accumulated on the photoreceptor will If the polarities of the charges are the same, the potential of the exposed area increases, and toner adheres to the background area of the resulting copy, resulting in a decrease in image quality. The present inventors focused on the fact that frictional electrification does not occur between two objects if the charging series is the same, and in a multi-sheet copying method applying the magnetic brush method, the surface material of the photoreceptor and the surface material of the magnetic carrier are It has been found that by making them the same, the objects of the present invention can be achieved without affecting the characteristics of the photoreceptor and developer, particularly the life span of the developer and the photosensitivity of the photoreceptor.

Various types of electrophotographic photoreceptors have been known in the past, and the photoreceptor used in the present invention has a resin layer or a resin-containing layer on its surface. Examples of such photoreceptors include: 1) a photoconductive layer formed on a conductive support, the photoconductive layer being mainly composed of an inorganic photoconductive substance or an organic photoconductive substance and a resin binder, and 2) a photoconductive layer formed on a conductive support. A charge generating layer mainly composed of an inorganic photoconductive substance or a charge generating pigment and a charge transporting layer mainly composed of an electron accepting substance or an electron donating substance and a resin binder are sequentially provided on the 3) conductive layer. 4) A photoconductive layer consisting of an inorganic photoconductive substance or an organic photoconductive substance and a resin binder on a conductive support. There are also those in which resin protective layers are sequentially provided. In the single-layer photoreceptor of 1), examples of inorganic photoconductive substances include selenium, zinc oxide, cadmium sulfide, cadmium selenide, etc., and examples of organic photoconductive substances include polyvinylcarbazole, oxadiazole, and derivatives thereof. It will be done. In addition, resin binders are generally highly insulating (specific resistance 1013-1016 ΩC).
77, such as polyethylene (1015 ΩCm), polystyrene (1016 Ωα or more), polymer or copolymer of acrylic ester or methacrylic ester, polyester, polycarbonate (1016 ΩCrfl), polyamide, epoxy resin, urethane resin, silicone resin, alkyd resin There are many such things. In addition to the above materials, the photoconductive layer may contain sensitizers such as methylene blue and crystal violet in the case of inorganic photoconductive substances, and sensitizers such as 2,4,7-trinitrofluorenone in the case of organic photoconductive substances. A sensitizing agent may also be included. In the laminated photoreceptor described in 2), the electron-accepting substance is a compound having an electron-accepting core structure such as a carboxylic acid anhydride, an ortho or paraquinoid structure, or an electron-accepting substitution such as a nitro group, a nitroso group, or a cyano group. There are aliphatic cyclic compounds, aromatic compounds, and heterocyclic compounds having groups, and more specifically, maleic anhydride, phthalic anhydride, tetrachlorophthalic anhydride,
Tetrabromo phthalic anhydride, naphthalic anhydride, pyromellitic acid, chlorop-benzoquinone, 2,5-dichloropenzoquinone, 2,6-dichloropenzoquinone, 5
, 8-dichloronaphthoquinone, 0-chloranyl, 0-
Bromoanil, p-chloranyl, p-bromoanil,
p-iodoanil, tetracyanoquinodimethane, 5,6
-quinolinedione, coumarin-2,2-dione, oxindilpine, oxindico, 1,2-dinitroethane, 2,2-dinitropropane, 2-nitro-2-nitrosopropane, iminodiacetonitrile, succinonitrile, tetracyanoelethin , 1,1,1,3,3-tetracyanoprobenide, 0-, m- or p-dinitrobenzene, 1,2,3-trinitrobenzene, 1,2,
4-trinitrobenzene, 1,3,5-trinitrobenzene, dinitrodibendinitro-1,2-dimethylbenzene, 3-nitroso-2-nitrotoluene, 2-nitroso-3,5-dinitrotoluene, 01,m1 or p -Nitronitrosobenzene, phthalonitrile, terephthalonitrile, isophthalonitrile, benzoyl cyanide, brombenzyl cyanide, quinoline cyanide, 0 cyanide
-xylylene, 0-, m- or p-nitrobenzyl cyanide, 3,5-dinitropyridine, 3-nitro-2-pyridone, 3,4-dicyanopyridine, α-, β- or γ
-cyanopyridine, 4,6-dinitroquinone, 4-nitroxanthone, 9,10-dinitroanthracene, 1-
Nitroanthracene, 2-nitrophenanthrenequinone, 2,5-dinitrofluorenone, 2,6-dinitrofluorenone, 3,6-dinitrofluorenone, 2,7-
dinitrofluorenone, 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone,
3,6-dinitrofluorenone mandinonitrile, 3
-Nitrofluorenone mandenonitrile, tetracyanopyrene, etc.

Examples of electron-donating substances include compounds containing at least one of an alkyl group such as a methyl group, an alkoxy group, an amino group, an imino group, and an imide group, or compounds containing anthracene, pyrene, phenanthrene, coronene, etc. in the main chain or side chain. There are compounds having ring aromatic compounds or nitrogen-containing cyclic compounds such as indole, carbazole, oxazole, isoxazole, thiazole, imidazole pyrazole, oxadiazole, thiadiazole, and triazole. Specifically, as a low molecular weight compound, hexamethylene diamine,
N-(4-aminobutyl)cadaverine, As-didodecylhydrazine, p-toluidine, 4-amino-0-xylene, N,N''-diphenyl-1,2-diaminoethane, o-, m- or p-ditolyl amino, tri Phenylamine, diurene, 2-bromo-3,7-dimethylnaphthalene, 2,3,5-trimethylnaphthalene, N″-(3
-bilomphenyl)-N-(β-naphthyl)urea, N″
-Methyl-N-(α-naphthyl)urea, N,N″-diethyl-N-(α-naphthyl)urea, 2,6-dimethylanthracene, anthracene, 2-phenylanthracene, 9,10-diphenylanthracene, 9,9 ″-pianthranil, 2-dimethylaminoanthracene, phenanthrene, 9-aminophenanthrene, 3,6-dimethylphenanthrene, 5,7-dibromo-2-phenylindole, 2,3-dimethylindoline, 3-indolylmethylamine, carbazole, 2-methylcarbazole, N-ethylcarbazole, 9-phenylcarbazole, 1,'-dicarbazole, 3-(p-methoxyphenyl)oxazolidine, 3,4,5-trimethylisoxazole, 2-anilino-4,5-diphenylthiazole, 2,4,5-trinitrophenylimidazole,
4-Amino-3,5-dimethyl-1-phenylpyrazole, 2,5-diphenyl-1,3,4,oxadiazole, 1,3,5-triphenyl-1,2,4-triazole, 1-amino-5-phenyltetrazole , bis-
Diethylaminophenyl-1,3,6-oxadiazole, etc., and high molecular weight ones such as poly N-vinylcarbazole and its derivatives (for example, those containing halogens such as chlorine and bromine, methyl groups, amino groups, etc. in the carbazole core) polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymers, and derivatives thereof (for example, those having a substituent such as a nitrogen such as bromine or a nitro group on the pyrene skeleton).

The resin binder may be the same as in the case of the photoreceptor in 1).
Note that the charge generation layer can contain a similar binder. Further, in the laminated photoreceptor of 3) and 4), the resin of the resin protective layer may be the same as the resin binder described above. Examples of inorganic or organic photoconductive materials are mentioned above. The resin protective layer is made thinner than the photoconductive layer. (Usually less than a few μm)
. Note that any of the above photoreceptors can be easily produced by a known coating method (or sputtering method or vapor deposition method as the case may be).

In any of the photoreceptors, the conductive support used is a plastic film or a glass plate, a metal plate, or a metal plate which has been insulated by metal oxidation or the like after being subjected to conductive treatment (including metal vapor deposition). On the other hand, for two-component dry developers, the resin-coated carrier is made of iron, chromium, cobalt, or alloys of these seven materials, magnetic particles such as various ferrites, and the same as that used for the resin layer or resin-containing layer of the photoreceptor. Those coated with resin are used.

Such a resin-coated carrier can be easily produced by conventional methods such as coating and impregnation. In addition, two-component system 2
Dry developers include a resin-coated carrier as well as a toner. The toner may be a known toner. Examples are shown below.

Example 1 As shown in FIG. 1, an aluminum substrate 4 was anodized to form an insulating layer 3 of aluminum oxide having a thickness of 500 mm, thereby forming a conductive support.

Next, a cadmium sulfide layer with a thickness of 1 μm is provided as a charge generation layer 2 on the insulating layer 3 of this conductive support by high-frequency sputtering method, and on top of this, a polymethyl methacrylate layer with a weight ratio of 1:1 is formed as a charge transport layer 1. A solution of ~2,4,7-trinitro-9-fluorenone mixture in a dry thickness of 1
5 μml of this was applied and dried to obtain the laminated photoreceptor described in 2) above. On the other hand, the average particle size is 100P7T1. After applying a 10% solution of polymethyl methacrylate to iron particles using a fluidized bed to create a carrier with a 2 μm thick resin coating layer, this was coated with a commercially available dry toner (PPC9 manufactured by Ricoh Co., Ltd.).
A two-component dry developer was prepared by adding and mixing 2% by weight of OO toner for copying machines). Next, after forming an electrostatic latent image on the photoreceptor by a conventional method, the supply speed of the photoreceptor was increased to 40-/S in surface linear velocity.
Magnetic brush development was performed under the following conditions: EC and the rotational speed of the magnetic brush roller at a surface linear velocity of 500 mm/Sec.

The resulting image was then transferred onto plain paper. This development and transfer process was repeated 20 times for the same latent image, and the second copy obtained was of the same high quality as the first copy, and no decay in the latent image potential was observed. It was found that there was almost no frictional electrification with the carrier. The relationship between the potential of the non-exposed area on the photoreceptor (initial potential of 600 V) and the number of copies is shown by A in FIG. 1 at this time. On the other hand, as a comparative example, when the same multi-sheet copying method was repeated on a photoreceptor prepared in the same manner as in this example except that polystyrene was used as the binder in the charge transport layer, the potential of the latent image attenuated as the number of copies was repeated. It was found that the frictional electrification with the carrier gradually increased. The relationship between the potential of the non-exposed area on the photoreceptor and the number of copies is shown by B in FIG. 2 at this time.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the laminated photoreceptor used in Example 1;
The figure is a diagram showing the relationship between the potential of the non-exposed area and the number of copies of the photoreceptor of the present invention used in Example 1 and the comparative photoreceptor. DESCRIPTION OF SYMBOLS 1... Charge transport layer, 2... Charge generation layer, 3... Insulating layer, 4... Substrate, A...
... Photoreceptor of the present invention, B... Photoreceptor for comparison.

Claims (1)

[Claims] 1. After forming an electrostatic latent image on an electrophotographic photoreceptor having a resin layer or a resin-containing layer on the surface, a two-component layer containing a magnetic carrier coated with the same resin as the above-mentioned resin is applied to this latent image. A multi-sheet copying method characterized by repeating a step of developing with a system dry developer and a step of transferring the obtained image.