JPS62296167A - Image forming method - Google Patents

Abstract

PURPOSE:To easily obtain a color image having high resolving power and sharp color tones by incorporating a specific red pigment or blue pigment at a prescribed ratio into a color toner of a two-component developer. CONSTITUTION:At least one kind of the red pigment selected from monoazo, diazo, xanthene, anthraquinone, indigoid, thioindigoid and perylene pigment or at least one kind of the blue pigment selected from diazo, triphenylmethane, phthalocyanine, anthraquinone and indigoid pigment are incorporated as a coloring agent into the color toner of the two-component developer for developing the electrostatic image formed by a digital system. The contrast ratio of the red or blue color toner is specified to 10-80%, more preferably 35-70%. The content of the toner in the red or blue pigment is specified to 1-30wt%, more preferably 3-20wt% by the weight of the binder resin of the toner. The overlap of the color toner particles or color dots is specified to <=50%, more preferably <=30%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming color images, and particularly to a method for forming red, blue, and optionally black color images.

[Conventional technology]

In recent years, most magazines, advertisements, catalogs, literature, and business-use horoscopes are partially or entirely colored in four colors, and even color CIt T display devices for computer use; δ, Videotex terminal devices. With the development of color image equipment such as, the demand for color hard copies is increasing.

Methods for obtaining the color hard copy include, for example, a wire tod matrix recording method, an inkjet recording method, a thermal transfer recording method, an electrophotographic method, etc.
The electrophotographic method is the best in terms of recording speed, noise, failure, image quality, cost, etc.

As examples of electrophotographic printers that have been put to practical use, there are known color copying machines such as the Xerox 6500 manufactured by Xerox Corporation, the NP-Color T1 manufactured by Canon Corporation, and the Noriko Color 5000 manufactured by Ricoh Corporation.

The image forming process in such a color copying machine is as follows:
For example, after a photoreceptor is charged with corona, an original image is exposed through a green (G) filter and developed with a magenta (M) developer, and the resulting magenta visible image is once transferred onto a transfer material.

Next, in the same manner as above, the photoreceptor is exposed with a blue (B) filter, and the yellow visible image obtained after being developed with a yellow (Y) phenomenon agent is aligned with the magenta image already transferred onto the transfer material. transcribe. Furthermore, the same process as above is repeated using a red (R) filter and a cyan developer, transferring the cyan visible image in line with the previous two images, fixing the resulting image, and finally producing a color print. obtain.

That is, according to this method, the original image is subjected to BGR color separation, exposed to a photoreceptor for each color, YMC development is performed for each color, and the obtained toner materials of each color are superimposed and transferred onto a transfer material. It produces full, color images. Moreover, a significant amount of one layer of toner of each color toner image is overlapped to form a subtractive color image.

That is, in the conventional color image, one layer of cyan (C) toner and one layer of magenta (M) toner are overlapped, and one place is mainly blue (B), and one layer of cyan (C) toner and one layer of magenta (M) toner are overlapped.
Y) The area where one layer of toner overlaps is mainly green (G), the area where one layer of magenta (M) toner and one layer of yellow (Y) toner overlap is mainly red (R), and cyan (C) toner 1 [
Color reproduction is performed by a so-called subtractive color method so that the area where one layer of magenta (M) toner and one layer of yellow (Y) toner overlap becomes mainly black (Bk). In addition, as a coloring agent for the color toner at that time, for example, a yellow (Y) coloring agent such as olamine or benzidine yellow, a magenta (M) coloring agent such as rhodamine B or quinacridone, a cyan (C) coloring agent such as malachite green, phthalocyanine, or crystal violet. ) Colorants etc. are used.

[Problems to be solved by the invention]

However, in the conventional technique, since toner images of each color are transferred, there is a drawback that transfer misalignment occurs, resulting in poor resolution and image quality of the resulting color image.

Furthermore, in the color image produced by subtractive color reproduction, the lower layer color toner image is hidden by the upper layer color toner image.
There are drawbacks such as color mixing between the upper and lower layers, resulting in color gaps, poor color tone, lack of color density, and disordered color balance.Furthermore, color correction is required to correct these defects. There are also drawbacks, such as the need for a circuit and the complexity of the control mechanism and device.

By the way, in normal office copying, there are very few cases of full-color images as mentioned above, but rather images of simple colors such as red, blue, black, etc., or a combination thereof, and moreover, the toner layer of each color toner image is Most of the images are images that do not overlap with each other or have a low overlap rate, such as text images with color marks, graphics, illustrations, and the like.

Therefore, it is desired to develop a practical image forming method that can easily produce color copies with high density and clear tone for office copying, and furthermore, it is desired to select colorants for color toners used in this image forming method.

[Means for solving problems]

(Object of the Invention) An object of the present invention is to provide an image forming method suitable for office copying, in which a color image with high resolution and clear dark tones can be easily obtained.

(Structure of the Invention) The above object is to form an electrostatic image on an image forming member in a digital manner, and develop the electrostatic image with a two-component developer containing color toners to form a toner image of each color on the image forming member. The coloring agent contained in the color toner includes Monoazo type, Disazo type, Xa
nLhcne series, Anthraquinone series, In
digoid series, Thioindigoid series and Pc
At least one red pigment selected from rylene series, Disazo series, Triphenyl Metha
ne series, Phthalo cyanine series, AnL-
Hraquinone series and! A color toner containing at least one blue pigment selected from the ndigoid group, and preferably the red pigment or blue pigment, has a hiding rate of preferably 10 to 80%, more preferably 35 to 70%, based on the measurement method described in the text. %, and the overlap of each color toner particle or dot constituting each color toner image is achieved by an image forming method of 50% or less, preferably 30% or less.

[Detailed description of the invention]

In the image forming method of the present invention, an original image is a red-based original such as red, orange, or pink, an original with fruits and vegetables such as blue, cyan, green, or ultramarine, an original with black thread such as gray or black, or an original with black thread such as gray or black, or an original with thread of each color. A combination manuscript with few color overlaps and no continuous gradation is selected. For example, character images with color marks, graphic images, illustration images, colored graphs, etc. are targeted, and the image method of the present invention using such originals is, for example, the digital electrophotographic method described below.

In such a digital electrophotographic system, a large number of components are used, including an image processing section including a reading system and a writing system, and a recording section that forms a color image via an image forming body based on the optical signal obtained in the image processing section. .

The reading system uses two types of filters, a gicroic mirror, or a glyphroic mirror, which separates the optical information obtained by optically scanning the original image into, for example, cyan (C), blue (B) and red (R). Color separation information is obtained by color separation into the two colors using an ichroic prism. These color separation information are photoelectrically converted by a photoelectric conversion element such as a COD image sensor to obtain an image signal, and further A/D converted to a digital signal.

These digital signals are subjected to arithmetic processing, separated into colors based on the results, and binarized to produce, for example, a first color signal (R), a second color signal (B), or a third color signal ( Bk
) is obtained. The color signal is transmitted through an optical fiber (OF), for example.
T), liquid crystal (I, CD), light emitting diode (LED),
A laser beam or the like, preferably a semiconductor laser, converts the signal into an optical signal into an optical signal.

First, during the first rotation of the image forming body, writing is performed on the image forming body, which has been corona-charged in advance, using an optical signal obtained by electro-optical conversion of the first color signal (R), and an electrostatic image is formed. , a red toner image is formed by developing with a two-component developer containing red toner.

Next, in the second rotation of the image forming body, writing is performed using an optical signal obtained by electro-optical conversion of the first and second color signals (B) obtained in the same manner as described above, and development is performed using a two-component developing agent containing blue toner. A blue toner image is formed superimposed on the red toner image.

Next, in the third rotation of the image forming body, writing is performed using an optical signal obtained by electro-optical conversion of the third color signal (Bk) obtained in the same manner as above, and writing is performed using a two-component developer containing black toner. Development is performed, and a black toner image is formed superimposed on the toner images of the respective colors to obtain a multicolor toner image.

This multicolor toner image is transferred by a transfer means such as electrostatic transfer, pressure transfer, or adhesive transfer via an intermediate transfer member, and fixed by pressure or heat to obtain a color image. Here, the original image used in the image forming method is preferably a simple image of red, blue, black, etc., as seen in ordinary office copying, as described above, and the toner image of each of these colors is The overlapped area (intermediate color area) is 3 of the entire image.
It is preferably 0% or less.

Next, the developer containing the color toner will be explained below.

Here, in the image forming method of the present invention: A magnetic carrier and a non-magnetic toner are used because it is easy to control triboelectrification of toner particles and a color toner without color turbidity caused by a magnetic material can be obtained. A two-component developer is used.

The magnetic carrier used in the present invention may be used as a magnetic material as it is, coated with a resin or the like, or mixed with a resin as a fine powder. Extremely strongly magnetized substances, such as metals such as iron, cobalt, nickel, alloys or compounds containing ferromagnetic elements such as iron, cobalt, nickel, etc., including ferrite, magnetite, hematite, etc., or ferromagnetic substances. Examples include alloys which exhibit ferromagnetism by appropriate heat treatment, such as Heusler alloys containing manganese and copper such as manganese-copper-aluminum or manganese-copper-tin, or chromium dioxide. When the particle size of the magnetic material is used as is, the average particle size is 5 to 5.
The thickness is about 80 μm, preferably about 5 to 45 μm, and approximately the same level if the surface is coated with a resin or the like.

However, when preparing magnetic fine powder for dispersion type, those having an average particle size of about 0.05 to 3 μm are used.

In addition, in order to improve the delicate points, lines, or gradation of the image obtained by development, the carrier particles may be particles made of a magnetic material and resin, such as resin-dispersed particles of magnetic fine powder and resin. Preferably, the resin-coated magnetic particles are composed of particles having an average particle diameter of preferably 80 μm or less, particularly preferably 40 μm or less and 5 μm or more. In addition, in order to prevent carriers from adhering to the image forming surface where charges are injected into the carriers by the bias voltage, and to prevent the bias voltage from leaking and causing the latent image charges to disappear, the resistivity of the carrier is set to 106 Ωcm or more. Preferably +o13Ω
Insulating material of cm or more, more preferably 1014Ωc
m or more is better.

The specific resistance of the carrier is determined by placing the particles in a container with a cross-sectional area of 0.5cm'', tapping it, applying a load of IKg/cm' on the packed particles, Apply a voltage that generates an electric field of 102 to 105 V/cm between the two, read the current value flowing at that time,
It is obtained by performing predetermined calculations.

At this time, the thickness of the carrier particle layer is approximately 1 m+++. Furthermore, in the resin-coated carrier or resin-dispersed carrier, it is possible to improve the fluidity of the developer using the carrier, improve the triboelectric charging property between the carrier and the toner, and prevent blocking between carrier particles or between the carrier and the toner. It is preferable to make it spherical in order to make it difficult.

In order to obtain such a spherical carrier, for example, in the case of a resin-coated carrier, magnetic particles formed into spherical shapes in advance may be coated with a thin layer of resin, or in the case of a resin-dispersed carrier, fine magnetic powder is coated with a resin. The dispersed particles may be heat-treated to make them spherical, or spherical particles may be directly produced by a spray drying method.

Next, the nonmagnetic toner used in the present invention is as follows.

The toner used in the present invention is manufactured by applying a known method. That is, for example, a binder resin, a colorant, a fluidity improver, and other substances added as necessary are premixed using a ball mill, etc., and then uniformly dispersed, and then kneaded using heated rolls. Cool and crush, divide into plates as necessary to obtain particles with an average particle size of 1 to 20 μm,
The thickness is preferably 3 to 15 μm, and if necessary, heat treatment is performed to obtain a spherical toner.

Furthermore, a granulation polymerization method can also be used as a toner manufacturing method. When a toner with a small particle size, for example, a toner particle size of 1 to 20 μm, is produced by a granulation polymerization method, a spherical toner can be obtained and can be applied to the present invention.

As the binder resin for toner of the present invention, various thermoplastic resins can be used, including styrene resin,
Styrene-acrylic resin, styrene-butadiene resin,
Additive resins such as acrylic resins, polyester resins,
Condensation polymerization resins such as polyamide resins, and Epoquine resins are used.

Among these resins, monomers for forming addition polymerization type resins include styrenes such as styrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene, and 3,4-diglorstyrene; ethylene; , propylene, butylene, isobutylene, and other ethylenically unsaturated monoolefins: vinyl chloride, vinylidene chloride, vinyl bromide,
Vinyl halides such as vinyl fluoride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, methacrylate α such as phenyl acrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, etc.
- Methylene aliphatic monocarboxylic acid esters: Acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, etc.: Vinyl ethers such as vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether: vinyl methyl ketone, vinyl hequinle ketone, methyl Vinyl ketones such as isopropenyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone; monoolefins such as vinylnaphthalenes! ; 1 body; propadiene, butadiene, isoprene, chlorobrene, pentagene,
Diolefin monomers such as hexadiene can be mentioned.

These monomers can be used alone or in combination of two or more.

In addition, monomers for forming the condensation type resin include ethylene glycol, triethylene glycol, 1.3-
Examples include propylene glycol.

Also, resins suitable for pressure fixing toners that are plastically deformed and adhered to paper with a force of about 1 to 20 kg/am include waxes, polyolefins, ethylene vinyl acetate copolymers, polyurethanes, adhesive resins such as rubber, etc. To be elected. Capsule toners can also be used.

When producing the toner of the present invention, various additives are added together with the binder resin described in item 1 to give the toner characteristics as a color toner.

First, in order to give the toner characteristics as a color toner, 20wt of the red pigment or blue pigment described below is added to the toner.
% or less is added.

Such coloring pigments are selected so that they can be dispersed in the binder resin in the form of uniform fine particles to provide a color toner with high concentration and clear color tone.

A material is selected that does not impede electrophotographic properties such as triboelectrification properties with the carrier and charge acceptance properties.

Further, the image forming method of the present invention often requires a black toner, and known pigments such as carbon black, furnace black, aniline black, and lamp black can be used as the coloring agent.

Furthermore, it does not inhibit the coloring property of color images, for example, JP-A-59-88745, JP-A-59-88743, JP-A-59-79256, JP-A-59-78362, JP-A-5
9-228259, JP-A-59-124344 (negative charge control agent), JP-A-51-9456, JP-A-59-204851, JP-A-59-204850, JP-A-59-177571. A charge control agent described in each publication (positive charge control agent) is added to the toner in an amount of 5vt% or less.

In addition, fluidizing agents such as hydrophobic silica, colloidal silica, and silicone varnish, and cleaning aids such as fatty acid metal salts and fluorine-based surfactants may also be added to promote the fluidity of the developer. Can be done.

The red pigment or blue pigment according to the present invention has a high concentration and
In order to obtain clear color images, the hiding rate of the toner containing the pigment as measured by the following measuring method is 0 to 80%,
Preferably, it is selected from 35 to 70%.

Here, if the hiding rate of the IFi toner is less than 10%, the base appears to be hidden and a high-density, clear image cannot be obtained.

Furthermore, the upper limit of the concealment rate is set at 80% due to cost and manufacturing limitations.

Further, in order to ensure such a hiding rate, the content a of the 11ri pigment in the toner is in the range of 1% to 30% by weight, preferably 3% to 20% by weight based on the binder resin of the toner. .

Method for measuring hiding rate: Toner 259 to be tested was dissolved and dispersed in 150 mC of methyl ethyl ketone, applied onto a 100 μm thick polyester film using a wire bar to a dry film thickness of about 10 μm, and dried.

The obtained sample is brought into close contact with white paper (lightness approximately 85) and black paper (lightness approximately 5), and the brightness of each is measured from the sample side using a CMS-1000s high-speed spectrocolorimeter (manufactured by Murakami Color Research Co., Ltd.).

The concealment rate is displayed using the following formula.

Y8: Brightness on black paper W.

Y, Brightness on white paper The hiding power of the toner layer is low and if the black paper placed on the back side is seen through, the apparent brightness of the sample decreases and the above value decreases.

Red toner colorants useful in the present invention are listed below.

[A] Red pigment Colorants for blue toner useful in the present invention are listed below.

[B] [Kidney Pigment The average particle size of the carrier and toner is a weight average particle size, and is measured with a Coulter Counter manufactured by Coulter. Further, the resistivity of the toner is 10"Q cm or more,
Preferably 1013 Ωcm or more, more preferably 10
″Ωcff1 or more, and the resistivity is measured in the same manner as in the case of the carrier.

In the image forming method of the present invention, it is preferable to use a non-contact developing method to develop the electrostatic image formed on the image forming body using the two-component developer.

In this non-contact developing method, an alternating current electric field is formed in the developing area, and the toner is caused to fly by the alternating electric field without rubbing the image forming member and the developer layer to perform development. This will be explained in detail below.

With repeated development using an alternating current electric field as described above, it is possible to repeat development several times on an image forming body on which a toner image has already been formed, but if appropriate development conditions are not set, problems may occur during subsequent development. This may disturb the toner image formed on the image forming body in the previous stage, or the toner already attached to the image forming body may enter the developing device in the latter stage, which contains a developer of a different color from the developer in the previous stage. There are problems with doing so. To prevent this, basically, the developer layer on the sleeve should be operated without making any sliding contact with the image forming member. The gap between the former and the sleeve is kept larger than the thickness of the developer layer in the development area on the sleeve. In order to more completely avoid the above-mentioned problems and further form each toner image with sufficient image density, it is preferable to pay attention to the following points. That is, as development is repeated, (1) toners with a larger charge amount are sequentially used;

■ Gradually reduce the amplitude of the electric field strength of the AC component of the developing bias.

■ Sequentially increase the frequency of the AC component of the developing bias.

It is preferable to employ these methods alone or in any combination.

In other words, the more charged the toner particles are, the more they are affected by the electric field. Therefore, if highly charged toner particles adhere to the image forming member during the initial development, these toner particles may return to the sleeve during the subsequent development.

The above method (2) uses toner particles with a small amount of charge in the initial development to prevent the toner particles used in the previous stage from returning to the sleeve during the subsequent development. Method (2) is a method in which the toner particles already attached to the image forming body are prevented from returning by decreasing the intensity of the IllEi electric field as development is repeated (that is, as development progresses to later stages). As a specific method to reduce the electric field strength,
There is a method in which the voltage of the alternating current component is gradually lowered, and a method in which the gap d between the image forming member and the sleeve is made wider as the developing stage progresses. Further, (2) is a method in which the frequency of the alternating current component is sequentially increased as development is repeated to prevent the toner particles already attached to the image forming body from returning.

These ■■■ methods are effective when used alone, but they are even more effective when used in combination, for example, as the phenomenon is repeated, the toner charge amount is sequentially increased and the AC bias is decreased by one order. be. Further, when the above three methods are adopted, appropriate image density or color balance can be maintained by adjusting the DC bias respectively.

As the image forming body used in the image forming method of the present invention, Z
Photoreceptors with a photosensitive layer in which nO, CdS, etc. are dispersed in a bindu resin, photosensitive layers with vapor-deposited Se, 5eAs, 5eTe, etc., photoreceptors with an organic photosensitive layer, photoreceptors with an amorphous silicon germanium photosensitive layer, etc. be.

By the way, in the image forming method of the present invention which is a digital method, the writing system is preferably performed using an energy-saving semiconductor laser having a simple structure. The image forming bodies used for this purpose include a photoreceptor having a phthalocyanine photosensitive layer having a long-wavelength absorption range, a photoreceptor having an amorphous silicon germanium photosensitive layer, As, Te, etc.
It is preferable to use a photoreceptor having a Se photosensitive layer doped with Se or the like at a high concentration, or a photoreceptor having a bisazo or triazo photosensitive layer. Further, the present invention provides toner images of each color on the image forming body.
Since this is an image forming method in which R is overlapped, it is preferable to use non-contact development and reversal development. Therefore, in the case of a digital method and an overlapping method, it is best to use so-called reversal development in which each color toner image is developed in the area irradiated with a dot-shaped laser beam. A color toner image is obtained.

〔Example〕

EXAMPLES The present invention will be specifically explained below with reference to Examples, but the embodiments of the present invention are not limited thereto.

FIGS. 1, 2, 3, and 4 are diagrams for explaining this embodiment, and FIG. 1 shows digital optical system, +'? , black 3
Figure 2 is a cross-sectional view of the color copying machine incorporated in the color copying machine shown in Figure 4. Figure 4 is a block diagram of the original image reading and 12-imprint system. FIG. 2 is a side view of a color separation and photoelectric conversion device.

A color image forming method using a color copying machine will be described below.

A three-color graphic original 2 of red, blue, and black is scanned on a document table I by moving an exposure lamp 3 and a reflecting mirror 6 at the same linear speed as the 0PC (phthalon-anine-based) photoconductor 4,
．． 8 to 1! The exposure lamp η is moved at a speed of
, LC and introduced into the photoelectric conversion device 30.

1111 device 30 includes an optical lens 31.11, as shown in detail in FIG. Prism 32a1 Prism 32b
1 Daikurobukumira-33, CCD image sensor-3
5. It is composed of a base plate 34 of the sensor 35, a CCD image sensor 37, and a base plate 36 of the sensor 37.

That is, as shown in FIG. 3 and FIG.
A guichroic mirror 33 provided at the junction of the parts b separates the red light into R and cyan light Lc, which are photoelectrically converted by the COD image sensors 35 and 37, and then amplified 7A39R (39c), A/I) Conversion A
It is converted into a digital signal at -1- step 38 including 40R (40c).

This digital signal is compared with predetermined red (R) and blue (B) digital values stored in the memory 43R (43c) by a comparator 42R (42c), and the pixel data D8 (1)
n) is obtained, but when pixel data "!" is set as a printing level, black pixel data DBk is output when both DR and DB are rlJ or higher.

The thus obtained red pixel data DR.

Among the fruit and vegetable pixel data DR and the black pixel data 〇uk, the red data signal DJ (DJ) is selected during the first rotation of the photoreceptor 4 and output to the writing step 44.The writing step 44 is performed using a semiconductor laser light source. The red data signal DR is input to 45, and the laser beam modulated by the signal is sent to the reflection mirror 46.4?, motor 4.
8, the photoreceptor 4, which has been uniformly charged in advance by the charger II, is scanned through the polygon mirror 49 rotating at high speed and the r-theta lens 50, and an electrostatic image is formed. This electrostatic image is developed in a non-contact and reversal manner by a red developing device 12 having a structure shown in FIG. 2, which will be described later, while applying a bias from a power source 12b to a developing roll +2a, thereby forming a red toner image.

This red toner image is rotated with the transfer and cleaning processes etc. inactive, and is written on by a laser beam L based on the data signal Dn of the fruits and vegetables in the 2-rpm counter of the photoreceptor 4 to form an electrostatic image. is formed and 1. !
? Non-contact, reversal development is performed by the developing roll 13a of the developing device 13 under bias application from the power source +3b, and a blue toner image is formed on the red toner image [iη]. Furthermore, in the same manner, at the third rotation of the photoconductor 4, the laser beam is injected into the IY based on the black data signal, and the power is supplied by the developing roll 14a of the black developing device 14! Non-contact, reversal development is performed under the application of a bias from 4b, and a black toner image is formed on each of the 11ζi color toner images to obtain a multicolor toner image.

This multicolor toner image is transferred easily by the transfer 1) η charger 15, and then transferred by the transfer pole 18 onto the transfer material P fed by the paper feed roll 17 from the cassette 16, and then transferred by the separation pole 19. Separated and transported by. The separated and conveyed transfer material P''2 multicolor toner image is transferred to the heat roll 21 of the fixing device 2o.
The paper is heated and fixed by and is ejected: The paper is ejected from l<22 and becomes red,
111, a color image consisting of three colors, black, is obtained.

The photoreceptor 4 after transfer is cleaned by a static eliminator 23
After the toner is neutralized and made easier to clean, it is cleaned by the cleaning blade 25 of the cleaning device 24, the auxiliary cleaning brush 26, the cleaned toner collection roll 27, and the like, and is then provided for the next image formation.

FIG. 2 is a sectional view showing the configuration of the developing units 12, 13 and 14, in which 12a is a developing roll consisting of a sleeve rotating in the direction of the arrow and a magnet body rotating in the opposite direction. Developing is performed without contact with the rotating photoreceptor 4.

12c and 12d rotate in the direction of the arrow to agitate the developer in the vertical and horizontal directions and supply the developer to the developing roll 12a, and 12e rotates in the direction of the arrow to agitate the developer in the developer tank 12r. The impeller 12g is a sponge roller for alleviating and reducing uneven supply of the developer.

If a developing device with such a configuration is used, each color developing device can be connected to the photoreceptor 4.
The developer can be disposed compactly in a limited area, and the developer can be sufficiently stirred and mixed to achieve uniform development without color unevenness.

The following developers are used for the image formation.

Red toner: Styrene-butyl methacrylate (75:25) copolymer resin 100 parts of heavy charge Salicylic acid derivative (negative charge control agent) 0.5 parts by weight C, 1,124
90 (C, 1, Pigfficnt Red5)
8-weight polypropylene with a softening point of 120℃
After stirring and mixing the above materials in a ball mill for 5 hours, the mixture is kneaded with two rolls at 150°C. Next, after cooling naturally, it was roughly pulverized with a cutter mill, further pulverized with a pulverizer using a jet stream, and classified using an air classifier to obtain a non-magnetic insulating toner with an average particle size of 10 μl.
Negative chargeability). The toner hiding rate was 37.

Mata i! / For I.na, C01,4 is used as a coloring agent.
It was obtained in the same manner as the red toner except that 2052 (C, 1, Ac1d Blue5) was used, and its hiding rate was 52. The black toner can be obtained in the same manner as the toners described above, except that carbon black is used as the colorant.

Carrier: 100 parts by weight of styrene-methyl meccrylate (1:l) copolymer resin 100 parts by weight of magnetite powder with an average diameter of 0.1 μm 100 parts by weight 11 yen The above materials were mixed, ground, cooled and ground, classified and then heat treated. Thus, a carrier having an average particle size of 30 μm is obtained.

The developer of this example is obtained by mixing the carrier and toner in a weight ratio of 90:10, and adding 0.5% hydrophobic silica to the toner.

Tables 1 to 5 below using the image forming method and developer described above.
Image formation is performed under the conditions shown in the table.

Three-color images of red, blue, and black were formed under the conditions shown in Table 1, Table 2, Table 3, Table 4, Table 5, and each color had high density and clarity.

(Example l) 10 types of red toner and 10 types of blue toner belonging to the present invention as shown in Table 6, and the following 3 types not belonging to the present invention.
The hiding rates of each type of red toner and three types of blue toner were measured and are shown in Table 6.

Furthermore, an image was formed using the same image forming method as in Example I (digital development of three colors of red, blue, and black) using 26 types of developing agents using the 26 types of toners and the black toner developer of Example 1. A color image was formed, and its image quality (color tone and color density) was evaluated using the "○" and "x" system, and the results are shown in Table 6.

Red and blue colorants for comparison It can be seen that the dot images characteristic of digital color images are higher density and clearer than those using dyes.

〔Effect of the invention〕

As is clear from the above explanation, according to the color image forming method of the present invention, it is possible to obtain a digital color image with high density and clear brown tone using an extremely simple method, and it is effective for use in office color copying. be done.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a digital color copying machine, and Figure 2 is a cross-sectional view of a digital color copying machine.
FIG. 3 is a side view of a unit including a color separation device and a photoelectric conversion device incorporated in the color copying machine shown in FIG. FIG. 1 is a block diagram and a sectional view of a laser exposure apparatus. 1...Document stand 2...Document 3...Exposure lamp 4
...Image forming body (OPC photoreceptor) 8.7.8...Reflection mirror II...Charging electrode 12.13.14...
・Developer +2a, 13a, 14a-Developer roll 12
c, 12d - stirring roll 12e...developer supply roll 12h, L3h, 14h...bias power supply 15...transfer charger 16...cassette 18...transfer pole 19...separation pole 20...・Fixer 23... Pre-cleaning static eliminator 24... Cleaning device 33... Guicroic mirror 35.37... CCD image sensor 39R, 39
c・Amplifier 40R, 40c...A/D converter 42R, 42c・Comparator 43R, 43c...Memory 45...Laser light source 49...Rotating polygon mirror

Claims (4)

[Claims] (1) Multicolor, in which an electrostatic image is formed digitally on an image forming body, and the electrostatic image is developed with a two-component developer containing color toner, so that each color toner image is superimposed on the image forming body. The coloring agent contained in the color toner includes a step of forming a toner image.
ne series, Anthraquinone series, Indigo
id series, Thioindigoid series and Peryle
At least one red pigment selected from the ne series or Di
sazo type, triphenyl methane type,
Phthalo cyanine series, Anthraqu
An image forming method characterized by using at least one type of blue pigment selected from inone-based and indigoid-based blue pigments. (2) The image forming method according to claim 1, wherein the color toner containing the red pigment or the blue pigment has a hiding rate of 10 to 80%, preferably 35 to 70%, based on the measurement method described in the main text. . (3) The ratio of the red pigment or blue pigment contained in the color toner to the binder resin of the toner is 1 to 30.
% by weight, preferably from 3 to 20% by weight. (4) Image formation according to any one of claims 1 to 3, wherein the overlapping of each color toner particle or each color dot in the multicolor toner image is 50% or less, preferably 30% or less. Method.