JPS6313536B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electrophotographic method capable of arbitrarily erasing and reproducing an image of one color of a two-color original. The applicant of the present application has so far made numerous proposals as two-color image reproduction methods. The outline of this method is to use a photoreceptor having at least two photoconductive layers with different spectral sensitivities on a conductive substrate, and to apply primary and secondary charging to the surface of the photoreceptor with opposite polarities. A light image of a two-color original is irradiated to form two latent images with opposite polarities, and these are developed with two-color toner charged with opposite polarities. This was born out of the need to faithfully reproduce the black image of documents in which parts of the document to be particularly emphasized are expressed in red, which are used for general office purposes. However, recently, if the part to be particularly emphasized is a secret matter, there has been a demand to reproduce it by erasing that part. For example, this is the answer part of an exam question. Conventionally,
When copying and distributing test questions and their answers, it was necessary to create two originals of the questions and answers separately. For example, if you want to create one original in which the question is expressed in black and the answer is expressed in red, and you want to copy only the black part of the question,
If you want to delete the red answer part and copy only the red answer part, you can erase the black problem part, which is extremely convenient and saves you the trouble of creating an original. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic method that can arbitrarily erase and reproduce an image of one color of a two-color original. Hereinafter, the present invention will be described with reference to the attached drawings. FIG. 1 shows an example of the process in the two-color reproduction method, and FIG. 2 shows the transition of the photoreceptor surface potential in each process. The photoreceptor P has a first photoconductive layer 2, a very thin translucent intermediate insulating layer 3, and a second photoconductive layer 4 laminated in this order on a conductive substrate 1. The first photoconductive layer 2 has panchromatic spectral sensitivity,
The second photoconductive layer 4 has spectral sensitivity to red light and has the property of not transmitting it. First, in step (1), the surface of the photoreceptor is uniformly and primarily charged by the corona charger 5 while the entire surface is exposed to red light. As a result, the second photoconductive layer 4 is made conductive, and the positive charge given to the surface is transferred to the second photoconductive layer 4.
The conductive substrate 1 is injected with a negative charge equal to the positive charge, and moves within the conductive substrate 1 to reach the surface of the intermediate insulating layer 3.
The first photoconductive layer 2 will be positively charged. In this step, the entire surface may be exposed to red light after charging. Next, in step (2), on the photoreceptor surface,
A corona discharger 6 uniformly charges the battery negatively,
Turns the photoreceptor surface potential negative. This allows the second
The photoconductive layer 4 will be negatively charged. A light image of a two-color original 7 having red and black images on a white background is irradiated onto the surface of such a photoreceptor. Since no light acts on the photoreceptor area Pa corresponding to the black portion 7a of the document 7, the photoreceptor surface potential in this area Pa is maintained at a negative potential that is approximately the same value as at the end of secondary charging. On the other hand, in the photoreceptor area Pb corresponding to the red portion 7b of the original, the negative charge stored in the second photoconductive layer 4 is discharged by the red light from the original, so that the photoreceptor in this area 4b is discharged. The surface potential turns positive. On the other hand, in the photoreceptor area Pc corresponding to the white portion 7c of the original, the second photoconductive layer 4 is exposed to white light from the original.
Since both the negative and positive charges stored in the first photoconductive layer 2 are discharged, the surface potential of the photoreceptor in this region Pc becomes almost zero. First, negatively charged red toner is supplied to the surface of the photoreceptor to develop the photoreceptor area Pb into red color.
Subsequently, positively charged black toner is supplied to develop black on the photoreceptor area Pa, thereby reproducing a two-color image on the photoreceptor. If the photoreceptor is not to be reused, this two-color image will be fixed on the photoreceptor as is.
If it is to be reused, it is transferred to transfer paper and then permanently fixed on the transfer paper. In such a process, the present invention shifts the entire latent image to one polarity side by controlling the charging potential of primary charging and secondary charging so that the latent image potential of one side of the image approaches zero. It is characterized by causing For example, when erasing a red image and reproducing only a black image, as shown in FIG. 1
By lowering the charging potential of the photoconductive layer and increasing the negative secondary charging voltage in step (2), the charging potential of the second photoconductive layer, which is the basis of the latent image potential corresponding to the black area, is increased, and the surface potential of the photoreceptor is increased. is shifted to the negative side as a whole. When such a photoreceptor is irradiated with two-color light images in step (3), the latent image potential in the area corresponding to the red area Pb approaches zero, and the potential in the area corresponding to the black area approaches zero.
The latent image potential at Pa becomes higher on the negative side.
At this time, the charging voltage must be controlled so that the potential of the latent image corresponding to the red portion is lower than the potential at which development can be started by the red toner. Even if negatively charged red toner is supplied to the surface of such a photoreceptor, the red corresponding area Pb is not developed, and only the black corresponding area Pa is developed by the positively charged black toner.
At this time, the potential in the white corresponding area Pc has also shifted to the negative side, so in order to prevent the positively charged black toner from being adsorbed in this area, the developing electrode provided opposite to the surface of the photoreceptor is It is preferable to apply a bias voltage of the same polarity that is slightly higher than the potential. Similarly, when erasing the black image and reproducing only the red image, as shown in Figure 4, the primary charging voltage is increased in step (1) and the secondary charging voltage is lowered in step (2). In step (3), the charged potential of the photoreceptor is shifted to the positive side as a whole.
By the image exposure in , the photoreceptor surface potential in the black corresponding area Pa approaches zero, and the photoreceptor surface potential in the red corresponding area Pb is pushed up to the positive side. When black toner and red toner are supplied to the surface of such a photoreceptor, only the red corresponding area Pb having a high potential is developed with the red toner. At this time, it is preferable to apply a bias voltage to the developing electrode in order to similarly prevent red toner from adhering to the white corresponding area Pc. In this way, by bringing the latent image potential of an image of one of the two colors close to zero, it is possible to make development of that color impossible. Toner of that color should not be supplied to the surface of the photoreceptor. If toner of the color of the image to be erased is not supplied, it is possible to eliminate the need to shift the photoreceptor potential as in the present invention.
It is possible to erase an image of one color using the conventional method, but by shifting the potential as in the present invention, the latent image potential of the image to be reproduced is further increased. can be reproduced with even higher density. The photoreceptor used in carrying out this invention is as follows:
As a conductive substrate, a material having conductivity with a volume resistance of 10 ¹⁰ Ωcm or less, such as a metal plate such as Al, Cu, or Pb, or a metal compound plate such as SnO ₂ , In ₂ O ₃ , CuI, or CrO ₂ , or A plastic film or paper coated with the above compound by vapor deposition or sputtering is used, and the first photoconductive layer is an inorganic pigment such as amorphous selenium, ZnO, or CdS, or Sudan Red, Jenas Green B, etc. Colored photoconductive particles are used in which colored photoconductive particles made of azo pigments, quinone pigments such as pyrenequinone, indigo pigments such as thioindigo, bisbenzimidazole pigments such as India First Orange Toner, and organic pigments such as quinacridin pigments are used. Binder materials for the first photoconductive layer include polyethylene, polystyrene, polybutadiene, styrene-butadiene copolymers, polymers and copolymers of acrylic esters or methacrylic esters, polyesters, polyamides, polycarbonates, epoxy resins, Urethane resin, silicone resin, alkyd resin, cellulose resin and poly
Anything that can be used for electrophotography can be used, such as polymeric electron-donating compounds such as N-vinylcarbazole and its derivatives, polyvinylpyrene, polyvinylasothracene, pyrene-formaldehyde condensation polymer and its derivatives, and blends thereof. . In addition, diphenylmethane dye, xanthene dye, acridine dye,
Azine dyes, thiazine dyes, etc. can be used as spectral sensitizers, and as chemical sensitizers, compounds or main chains containing at least one of alkyl groups, alkoxy groups, amino groups, imino groups, and imide groups can be used. or a low-molecular electron-donating compound having a polycyclic aromatic compound or a nitrogen-containing cyclic compound in its side chain, or a compound having an electron-accepting host structure such as a carboxylic acid anhydride, ortho- or para-quinoid structure, Electron-accepting compounds such as aliphatic cyclic compounds, aromatic compounds, and heterocyclic compounds having electron-accepting substituents such as nitro, nitroso, and cyano groups can be used. In addition, a plasticizer such as dibutyl phthalate or dioctyl phthalate can be used in combination with the resin binder.
The amount used is approximately 5 to 30% by weight based on the resin. Furthermore, the ratio of the colored photoconductive particles to the entire first photoconductive layer constituent material is from 1 to 1.
A suitable amount is 70% by weight, preferably 5 to 40% by weight, and the amount of the spectral sensitizer and chemical sensitizer to be added may be determined as necessary so that the entire low-molecular compound including the plasticizer and colored photoconductive particles is 1 Approximately for the entire photoconductive layer constituent material
It can be used until it becomes 70% by weight or less.
The thickness of the entire first photoconductive layer is 3 to 100 μm.
m, preferably from 5 to 70 μm. As the translucent intermediate insulating layer, any of the binder resin materials used for the first photoconductive layer can be used,
Its thickness is 0.01 to 5μm, preferably 0.1 to 2μm
It is about m. The materials used for the second photoconductive layer are as follows. First, in the case of the positively charged type, pyrylium dyes such as thiapyrylium salts such as 4-(4-dimethylaminophenyl)-2,6-diphenylthiapyrylium perchlorate, pyrylium salts, and selenapyrylium salts and polycarbonate are used. When the eutectic complex with the resin is of a negatively charged type, 1-phenyl-3-(P-dimethylaminostyryl)-5-(P-dimethylaminophenyl)pyrazoline, 1, 1-bis(4-N,N dibenzylaminophenyl)ethylmethane, 3-(9
-fluorenisodene)-N-ethylcarbazole,
Photoconductive substances such as 9-(P-diethylaminostyryl)anthracene, 2,3-bis(4'-diethylaminophenyl-1')-1,3,4-oxadiazole, and polyesters, vinyl butyral resins, etc. It is possible to use one with a binder added. The thickness of this second photoconductive layer is from 3 to 100 μm,
Preferably, the diameter is from 5 to 70 μm, and the proportion of pyrylium dye in the eutectic complex is from about 20 to 1% by weight. FIG. 5 shows an example of an electrophotographic apparatus implementing the method of the present invention. Photosensitive drum P
is selenium on the aluminum drum 11.
The first photoconductive layer 12 is vacuum-deposited with tellurium (tellurium 6 wt%) to a thickness of 20 μm, and on top of that, a 20 wt% solution of phenolic resin in methanol is coated by a dipping method to a thickness of 1 μm.
An intermediate insulating layer 13 heated and cured at 50° C. for 1 hour;
On top of that, 4-P-dimethylaminophenyl-
2 parts by weight of 2,6-diphenylthiapyrylium perchlorate, 4,4-bis(diethylamino)
-4 parts by weight of 2,2'-dimethyltriphenylmethane, polycarbonate (Teijin Panlite K-
1300) and 80 parts by weight of methylene chloride, the second photoconductive layer 14 was coated to a thickness of 25 μm using a dipping method. The first photoconductive layer 12 has a punctuate spectral sensitivity, and the second photoconductive layer 14 has a property of being sensitive to red light and not transmitting it. Around the photoreceptor drum P, from the top along the counterclockwise rotation direction, there are provided a first open-top corona discharger 15 for primary charging, a second corona discharger 16 for secondary charging, and a first developer. A device 17, a second developing device 18, a corona discharger for adjustment 19, a corona discharger for transfer 20, a corona discharger for static elimination 21, and a cleaning device 22 are arranged, respectively. An exposure lamp having an incandescent lamp 23 having an illuminance of 50 _lux and a red filter (R-64 manufactured by Hoya Glass Co., Ltd.) 24 disposed in front of the incandescent lamp 23 is attached to the upper part of the first corona discharger 15. A positive variable high voltage power source 25 is connected to the corona electrode of the first corona discharger 15, and a negative variable high voltage power source 26 is connected to the corona electrode of the second corona discharger 16. The first developing device 17 and the second developing device 18 are conventional magnetic brush developing devices, and the first developing device 17 includes:
A two-component red developer 27 made of red toner and positively charged iron powder is stored, and a two-component black developer 28 made of black toner and negatively charged iron powder is stored in the second developing device 18. The red toner is negatively charged and the black toner is positively charged due to friction with each iron powder. A positive variable bias power supply 30 is connected to a non-magnetic sleeve 29 that accommodates a stationary magnet in the first developing device 17 and rotates in a counterclockwise direction, and accommodates a stationary magnet in the second developing device 18. A negative variable bias power source 32 is connected to the non-magnetic sleeve 31 which rotates clockwise. The adjusting charger 19 is used to align images developed with toners charged with opposite polarities to the same polarity before transfer. connected via. The corona electrode of the transfer corona discharger 20 is connected to two power supplies 35 and 36 with different polarities via a switch 37 so that only one toner image can be transferred. An AC power source 38 is connected to the corona electrode. The cleaning device 22 is of a normal type equipped with a fur brush 39.
Other types may also be used. Although not shown, a known image exposure device is attached to the main body of the apparatus. In this electrophotographic apparatus, in order to perform the process as shown in FIG. A voltage of +6.8KV is applied to perform primary charging. Next, a voltage of -4.2 KV is applied from the power supply 26 to the second charger 16 to perform secondary charging. Then, a light image 40 of the two-color original is irradiated onto the surface of the photoreceptor using a 300W halogen lamp to form a positive latent image corresponding to a red image and a negative latent image corresponding to a black image. The latent image corresponding to red is developed with negatively charged red toner supplied from the first developing device 17, and the latent image corresponding to black is developed with positively charged black toner supplied from the second developing device 18. is supplied for black development. At this time, the first
The bias voltage applied to the sleeve 29 of the developing device 17 is zero V, and the bias voltage applied to the sleeve 29 of the second developing device 18 is zero V.
The bias voltage applied to 1 is -50V. Next, apply +4.5KV from the power supply 33 to the adjustment charger 19.
is applied to align the polarities of the two-color toner images, and then the transfer corona discharger 20 is connected to the power source 35.
A two-color toner image is transferred onto the transfer paper 41 by applying 5.5 KV. The transfer paper is then peeled off from the photoreceptor surface by a separating device (not shown), and then
The transfer image is permanently fixed on the transfer paper by the fixing device. On the other hand, after the charges remaining on the surface and inside of the photosensitive drum P are erased by the static eliminating corona discharger 21, the cleaning device 22
The residual toner remaining on the surface after transfer is removed. In this electrophotographic apparatus, when performing the process shown in FIG. 3 to erase the red image and reproduce only the black image, a voltage of +5.0 KV is applied to the first charger 15 from the power supply 25. , -4.5KV is applied from the power supply 26 to the second charger 16, and the first
The developing device 17 is stopped, a bias voltage of -100V is applied from the power source 32 to the sleeve 31 of the second developing device 18, the adjustment charger 19 is turned off, and the −100 V bias voltage is applied to the sleeve 31 of the second developing device 18 from the power source 35. 5.5KV
It is sufficient to apply a voltage of . In addition, a process as shown in Figure 4 is carried out,
When erasing the black image and reproducing only the red image, apply a voltage of +6.8KV from the power supply 25 to the first charger 15, and apply a voltage of -3.9KV from the power supply 26 to the second charger 16. A bias voltage of +50V is applied from the power supply 30 to the sleeve 29 of the first developing device 17, the second developing device 18 is stopped, the adjustment charger 19 is turned off, and the transfer corona discharger 20 is turned off. This can be done by applying +5.0KV. When these are tabulated, it looks like the following.

[Table] As a result of copying in this way, the density of the reproduced image in the case of two colors of red and black is 0.7 for red and 0.7 for black.
1.1, resolution is 3 lines/mm for red and 4.2 lines/mm for black.
It was hot. Further, the density of the reproduced image in the case of only black was 1.2 and the resolution was 4 lines/mm, and the density of the reproduced image in the case of only red was 0.8 and the resolution was 3 lines/mm. The reason why the image density in the case of monochrome is higher than in the case of two colors is that the potential of each latent image is shifted and increased by the method according to the present invention. Although this invention has been explained above with reference to a specific two-color electrophotographic process, the present invention is not limited to such two-color electrophotographic process, but can also be applied to intermediates as photoreceptors. It can be applied within the spirit of the invention to processes that do not use an insulating layer or to various other two-color electrophotographic processes, and the apparatus can be modified in various ways by appropriately utilizing known techniques. It is.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing an example of a two-color electrophotographic process to which the present invention is applied, FIG. 2 is a diagram showing changes in the photoreceptor surface potential in each step of FIG. 1, and FIGS. FIG. 4 is a diagram showing the transition of the surface potential of a photoreceptor in an embodiment of the present invention, and FIG. 5 is a schematic diagram showing the configuration of an example of an electrophotographic apparatus implementing the method of the present invention. P...photoreceptor, 1...conductive substrate, 2...first
photoconductive layer, 3... translucent intermediate insulating layer, 4... second
Photoconductive layer, 7...Two-color original.

Claims (1)

[Claims] 1 Using a photoconductor having at least two photoconductive layers with different spectral sensitivities on a conductive substrate, the surface of the photoconductor is subjected to primary charging and secondary charging of opposite polarity, and then a two-color original is charged. By irradiating the light image of
In an electrophotographic method in which two latent images with opposite polarities are formed and developed with two-color toners charged with opposite polarities, the charging potentials of the primary charging and secondary charging are controlled. An electrophotographic method in which the entire latent image potential is shifted to one polarity side so that the potential of the one latent image approaches zero potential.