JP3597254B2 - Cleanerless full-color image forming method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a full-color image forming method using a toner for developing an electrostatic image such as electrophotography, electrostatic recording, and electrostatic printing, and more particularly to a full-color image forming method using a reversal developing method without a cleaner mechanism.
[0002]
[Prior art]
In the conventional electrophotographic process, image formation is performed by repeating respective steps of charging, exposure, development, transfer, cleaning, and fixing. In recent years, in the reversal development method, since the polarity in the charging step and the polarity of the toner are the same, a simultaneous development cleaning process in which the toner on the photosensitive member is also cleaned in the development step has been proposed and put into practical use. The Journal of the Institute of Electrophotography, Vol. 30, No. 3, (1991) describes the mechanism of a simultaneous cleaning process using a one-component non-magnetic developing method using a reversal developing method.
[0003]
However, in a full-color development method in which a plurality of colors are repeatedly developed on one photoconductor, a mixture of toners of different colors occurs, resulting in poor color tone reproducibility. In addition, since there is an image writing exposure step before the transfer residual toner is cleaned in the developing step, if the transfer residual toner becomes large such as when the humidity is high or when the image is transferred onto thick paper, the exposure is hindered by the transfer residual toner and the residual image is prevented. Is generated. However, in order to improve the residual image, it has been proposed to disturb the transfer residual toner before the charging step or simultaneously with the charging (JP-A-5-241423, JP-A-5-241425, JP-A-5-281850, No. 6-51612, Japanese Patent Publication No. 5-50747). Nevertheless, in the full-color developing system for developing a plurality of colors on one photoconductor, the problem of color mixing still remains because the disturbance member is contaminated with the toners of a plurality of colors.
[0004]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to solve these problems, and to significantly reduce the occurrence of afterimages due to shading due to transfer residual toner without causing a decrease in color tone reproducibility due to color mixing. It is an object of the present invention to provide a cleaner-less full-color image forming method capable of achieving, with high reliability, advantages such as downsizing, effective use of toner, and user maintenance free.
[0005]
[Means for Solving the Problems]
(1) In a full-color developing system that performs multi-color development on one photoconductor by a reversal development method, a black toner developing unit does not provide a cleaning device for removing toner remaining on the photoconductor after transfer. a cleanerless color image forming method of recovering transfer residual toner, using a toner that is colored by oil-soluble dyes or disperse dyes no absorption in the wavelength of the exposure light source for forming an electrostatic latent image on the photoreceptor cleanerless color image forming method, characterized in that.
(2) In a full-color developing system in which a plurality of colors are developed on one photoconductor by a reversal development method, each toner is simultaneously developed in each color developing unit without providing a cleaning device for removing toner remaining on the photoconductor after transfer. Cleaning is performed, but the developer contacts the photoconductor only during development and cleaning.After development is completed, the photoconductor is charged for one or more rounds with the developer in contact, but the photoconductor is cleaned with a developing device without exposure. After that, the developer is brought into non-contact, and then the other colors are developed and cleaned in the same manner.A cleaner-less full-color image forming method , wherein an exposure light source for forming an electrostatic latent image on a photoreceptor is used. cleanerless color image shape and it is characterized by using a toner which has colored with oil-soluble dyes or disperse dyes no absorption in the wavelength Method.
[0006]
Hereinafter, the present invention will be described in more detail.
The image forming process used in the present invention is a reversal developing method used in a conventional full-color laser printer, a full-color digital copying machine, and the like. Charging method, exposure method, developing method and transfer method can be used. As the exposure light source, there are a laser, an LED, a fluorescent lamp, an EL, and the like, and a laser or an LED having no absorption in the visible region is preferably used.
[0007]
1 and 2 schematically show two examples of devices useful for implementing the method of the present invention.
FIG. 1 shows an example of a method in which a plurality of transfer residual toners of a plurality of colors are collected in a black toner developing unit 4. A photoconductor 1 is charged to a negative polarity by a charging charger 2, for example. After an electrostatic latent image is formed by exposure 3, development is performed in a black developing section 4 in which a developer always contacts the photoconductor 1. The developing units 5, 6, and 7 are color developing units that are not in contact with the photoreceptor 1 and that prevent black toner from being mixed. Next, each color toner and black toner are transferred by the transfer charger 10 to the transfer paper 8 carried by the transfer paper carrier 9. After the toner is transferred from the photoreceptor 1 to the charge removing lamp 12, the photosensitive drum 1 is subjected to black toner development of the developing unit 8 and color development of the developing units 5, 6, and 7 in the same process. However, the developing bias is set so that the black developing unit 4 at the time of performing the color developing works as if it were a magnetic brush cleaning device. That is, a bias having the same polarity as that of the toner is applied to the black developing portion, but a bias having a polarity opposite to that of the toner is applied.
[0008]
By adopting such means in the apparatus shown in FIG. 1, the black developing section contains yellow, magenta, and cyan residual toners, but the mixture of these three colors becomes black and the quantity is small. There is no problem with the color tone as blacker.
In principle, the color developing units 5, 6, and 7 develop the photoconductor 1 in a non-contact manner in order to prevent color mixing. However, in some cases, it is necessary to make a non-contact after the contact development. As the means, a known non-contact developing method and techniques such as movement of a developing section and cutting of a developer are used.
[0009]
FIG. 2 shows an example of a system in which each toner is simultaneously developed and cleaned in each color developing unit. In this system, when one color is subjected to contact development, the other developing unit is not in contact, thereby preventing color mixing. I have. As shown in FIG. 2, there are means for moving the rotary developing unit and the developing unit, and cutting the developer. Further, in this method, it is necessary to sufficiently clean the photosensitive member after development and before developing the next color.
[0010]
In the present invention, magnetic brush cleaning is performed by a simple method utilizing the fact that the charge of the photosensitive member and the charge of the toner have the same polarity. In other words, after the charge of the same polarity is surely given to the photosensitive member and the toner in the charging step, the toner is collected in the developing section by utilizing the electrostatic repulsion without exposing the photosensitive member and the toner. At this time, the cleaning property can be improved by setting the developing bias to an electric field opposite to that of the developing. In the post-development cleaning, it is necessary to perform at least one rotation of the photoconductor. The developing method can be used for both the one-component developing method and the two-component developing method.
[0011]
As can be inferred from the above description, in the cleaner-less full-color image forming method of the present invention, charging and exposure are performed in a state where untransferred residual toner, which has not been transferred in the transfer step, is present on the photoconductor. The transfer residual toner is 5 to 30% of the developed toner, depending on the conditions, hinders exposure, and in conditions where transfer is unfavorable, such as high humidity conditions or thick paper transfer, the surface potential of the photoreceptor is sufficient due to light shielding by the transfer residual toner. The image before one round of the photoreceptor may appear in the image portion as a low density without lowering, and an afterimage may occur. Although the light shielding by the transfer residual toner may be caused by scattering, the influence of the absorption by the colorant is large, and by using the toner using the colorant having no absorption at the wavelength of the exposure light source, the transmittance of the exposure is increased and the afterimage is increased. Is significantly improved.
[0012]
The toner used in the full-color image forming method of the present invention uses a specific colorant and contains a binder resin, and a charge control agent, a release agent, and an additive may be added as necessary. it can.
As the colorant for full color, three colors of yellow, magenta and cyan, and four colors including black are used. The colorant no absorption in the wavelength of the exposure light source of the present invention, various pigments or dyes other than carbon black is used, no absorption in the near infrared wavelength region, such as a laser or LED, is less more internal scattering In particular, oil-soluble dyes and disperse dyes are used.
[0013]
(Example of oil-soluble dye)
CI. Solvent Yellow 6, 9, 17, 31, 35, 58, 100, 102, 103, 105, CI. Solvent Orange 2, 7, 13, 14, 66, CI. Solvent Red 5, 16, 17, 18, 19, 22, 23, 143, 145, 146, 149, 150, 151, 157, 158, CI. Solvent Violet 31, 32, 33, 37, CI. Solvent Blue 22, 63, 78, 83, 84, 85, 86, 91, 94, 95, 104, CI. Solvent Green 24, 25, CI. Solvent Brown 3, CI. Solvent Black3 etc.
[0014]
(Example of disperse dye)
CI. Disperse Yellow 3, 7, 33, 42, 64, 82, 237, CI. Disperse Orange 3, 13, 29, 30, CI. Disperse Red 1, 17, 50, 54, 56, 60, 65, 72, 73, 88, 91, 92, 110, 135, 145, 146, 154, 167, 177, 207, 258, 283, CI. Disperse Violetl, 4, 26, 28, 35, 38, 43, 77, CI. Disperse Blue 3, 7, 56, 60, 73, 79, 81, 91, 94, 96, 102, 106, 128, 139, 146, 148, 149, 165, 183, 186, 187, 197, 201, 205, 207 , 214, 257, 266, 268, 291, 341, 354, 358, CI. Disperse Brown 1, CI. Disperse Black1 and so on.
[0015]
These colorants can be used as a mixture of two or more kinds. The amount of the colorant used varies depending on the color, charge amount, particle size and the like of the toner, but is about 0.5 to 10% in the toner.
[0016]
Examples of the binder resin used in the toner of the present invention include styrene, parachlorostyrene, vinyl toluene, vinyl chloride, vinyl acetate, vinyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate, and (meth) acrylate. ) Propyl acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tertiary butyl (meth) acrylate, dodecyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acryl Lauryl acid, 2-hydroxyethyl (meth) acrylate, glycidyl (meth) acrylate, hydroxypropyl (meth) acrylate, benzyl (meth) acrylate, furfuryl (meth) acrylate, 2-chloroethyl (meth) acrylate, (meth) ) Acrylonitrile, (meth) ac Polymer of monomers such as amide, (meth) acrylic acid, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl methyl ethyl ketone, N-vinyl pyrrolidone, N-vinyl pyridine, butadiene, or a polymer of these monomers Copolymers composed of two or more kinds, or mixtures thereof, may be mentioned. In addition, polyester, polyurethane, polyamide, epoxy resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin and the like can be used alone or in combination.
[0017]
Examples of the charge control agent include, in the case of negative charge, metal chelates of alkyl salicylic acid and naphthoic acid, and fluorine compounds described in JP-A-55-76353 and JP-A-3-213877. In the case of chargeability, quaternary ammonium salts and alkyl metal oxides described in JP-A-56-164350 can be used.
Examples of the release agent include low molecular weight polyolefins such as low molecular weight polyethylene, low molecular weight polypropylene and polyethylene oxide: natural waxes such as beeswax, carnauba wax and montan wax: higher fatty acids such as palmitic acid stearate and myristic acid And metal salts of higher fatty acids, higher fatty acid amides and the like.
[0018]
Examples of other additives include fine particles of silica, titanium dioxide, alumina, etc., which have been subjected to a hydrophobic treatment to improve transferability and fluidity, and these may be added externally.
[0019]
Next, the present invention will be described more specifically with reference to examples.
[0020]
Example 1
A developer consisting of a black toner and a ferrite carrier was put in the black developing section 4 of the copying machine having the configuration shown in FIG. 1, and yellow, magenta and cyan toners were put in the developing sections 5, 6, and 7, respectively. The developing unit 4 is a two-component magnetic brush contact developing system, and the developing units 5, 6, and 7 are a one-component non-contact developing system. The toner of each color uses a negatively chargeable toner for a digital full-color copying machine PRETER750 manufactured by Ricoh Company, a colorant uses a pigment, and a black toner uses carbon black.
Exposure 3 uses a semiconductor laser having an oscillation wavelength of 780 nm. The photoconductor 1 is an organic photoconductor (OPC) whose spectral sensitivity is adjusted to this wavelength. The surface potential of the photoconductor charged by the charging charger 2 is -700 V, and the developing bias of the black developing section is -550 V.
[0021]
First, the toner is developed with black toner, transferred, and then subjected to static elimination, charging, and exposure in a state where untransferred toner is present on the photoreceptor without cleaning. In the case of reversal development, since the toner polarity and the photoconductor charging polarity are the same, the charging polarity of the toner does not change, and the portion where the photoconductor surface potential is reduced by exposure is developed by the potential difference from the developing bias. At this time, the untransferred portion of the toner that has not been exposed receives an electrostatic force toward the developing unit during development, so that it is cleaned.
The transfer residual toner adhering to the exposed portion is the original developed portion and is not cleaned, but there is no problem. However, after the black toner development is completed, before the next color toner development is performed, only the cleaning is performed without exposing one or more rounds of the photoconductor.
[0022]
Subsequently, the yellow, magenta, and cyan color toners are sequentially developed. At this time, it is advantageous to set the bias voltage of the black developing section to about +150 V and perform magnetic brush cleaning. The color toner is developed by non-magnetic one-component non-contact development to prevent color mixing.
[0023]
When an image test was conducted using this method and apparatus, a good full-color image was stably obtained despite the absence of a cleaning device. However, under a forcible condition using a high humidity and thick paper of 30 ° C. and 90% RH, a slight black afterimage was generated.
[0024]
Example 2
The same toner as in Example 1 was put in the developing units 4 to 7 of the printer having the configuration shown in FIG. Each of the developing units 4 to 7 is a contact-type one-component developing system using a soft developing roller, and changes the developing unit that performs development by rotating. The exposure and the photoreceptor are the same as in the first embodiment. The photoreceptor surface potential is -700 V, the developing bias is -500 V, and the method of cleaning at the same time as the development is the same as that in the first embodiment. However, in this method, the transfer residual toner of each color is cleaned by each developing unit. Therefore, after the development is completed, the developer is kept in contact with the developer and charged one or more times.The toner adhered to the photoconductor is cleaned by a developing device without exposing or applying a developing bias, and then the next development is performed. Do. In the image test, a good full-color image was stably obtained. However, a slight black afterimage was generated under the conditions of high humidity and heavy paper.
[0025]
Example 3
The same test as in Example 1 was conducted except that the colorant of the black toner used in Example 1 was changed from carbon black to oil black 806 (oil-soluble dye manufactured by Orient Chemical Co.).
In the image test, a good full-color image was stably obtained, and no image lag was generated even under the high-humidity and forced conditions of thick paper.
[0026]
Example 4
The same test as in Example 2 was performed except that the black toner used in Example 3 was used.
In the image test, a good full-color image was stably obtained, and no afterimage was generated even under the high humidity and forced conditions of thick paper.
[0027]
【The invention's effect】
(1) In the cleanerless full-color image forming method of the first aspect, since the transfer residual toner of a plurality of colors is collected in the black toner developing section by utilizing the feature of the reversal development, a conventionally used cleaner mechanism is not required. The image forming apparatus can be reduced in size and simplified. Further, since the transfer residual toner is not collected by the cleaner, the toner can be effectively used, and the trouble of discarding the collected toner is eliminated. Since the performing further color development with a non-contact, which does not occur reduction in color reproducibility due to color mixing of the toner each other, and using a toner which is colored with a colorant which does not absorb in the wavelength of the exposure light source Therefore, occurrence of an afterimage due to interruption of writing exposure by the transfer residual toner can be remarkably improved .
(2) In the cleaner-less full-color image forming method of the second aspect, since a simultaneous development cleaning is performed in each color developing unit, a cleaner mechanism is not required, and the same advantage as the first aspect is obtained. Further, after the completion of development after the photosensitive member more than a round cleaned with developing unit, and a non-contact, which does not cause a reduction in color reproducibility due to color mixture of the toner for performing other development, the absorption in the wavelength of the exposure light source Since a toner colored with a colorant not used is used, generation of an afterimage due to interruption of writing exposure by transfer residual toner can be remarkably improved .
[Brief description of the drawings]
FIG. 1 is a schematic view of an example of an image forming apparatus useful for performing a method of the present invention.
FIG. 2 is a schematic view of another example of an image forming apparatus useful for performing the method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charger 3 Exposure 4 Black developing part 5, 6, 7 Color developing part 8 Transfer paper 9 Transfer paper carrier 10 Transfer charger 11 Static elimination charger 12 Static elimination lamp

Claims (2)

In a full-color developing system in which a plurality of colors are developed on one photoconductor by a reversal development method, the transfer residual toner of a plurality of colors is provided in a black toner developing unit without providing a cleaning device for removing the toner remaining on the photoconductor after the transfer. Cleaner-less full-color image forming method , characterized by using a toner colored with an oil-soluble dye or a disperse dye having no absorption at a wavelength of an exposure light source for forming an electrostatic latent image on a photoreceptor. Cleaner-less full-color image forming method. In a full-color developing system that performs multi-color development on one photoconductor by a reversal development method, each color developing unit cleans each toner at the same time without providing a cleaning device that removes toner remaining on the photoconductor after transfer. When the developer is in contact with the photoreceptor only during development and cleaning, and after the development is completed, the photosensitive drum is charged over one or more turns in a state where the developer is in contact with the developer, but after the photoreceptor is cleaned without being exposed by a developing device, A cleanerless full-color image forming method in which the developer is brought into non-contact, and then other colors are developed and cleaned in the same manner , and absorbs at the wavelength of an exposure light source for forming an electrostatic latent image on a photosensitive member. cleanerless color image forming method according to, characterized by using a toner which has colored with oil-soluble dyes or disperse dyes without a "

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