JP2003114547A - Color image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming method by which the scattering of toner is made inconspicuous and also whose color reproduction range is wide as a method for forming a color image by an electrophotographic system. SOLUTION: In this color image forming method, developer consisting of toner of four colors, black, yellow, cyan and magenta, and carrier is used, a latent image on an electrostatic latent image holding body is developed by one color with toner of four colors, and the toner is transferred from the electrostatic latent image holding body to an intermediate image holding body in order of respective colors so that an image obtained by superposing the toner of four colors is formed, then the image is transferred from the intermediate transfer body to a final image holding body and fixed on the final image holding body. The order of the colors of the toner transferred from the electrostatic latent image holding body to the intermediate image holding body is such order as black, cyan, magenta and yellow or as black, magenta, cyan and yellow.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing machine, a copying machine,
The present invention relates to a color image forming method using an electrophotographic method or an electrostatic recording method used in printers, facsimiles and the like.

[0002]

2. Description of the Related Art In a dry electrophotographic process, a toner having a small particle size is widely used in order to obtain a high definition image quality. For example, Japanese Patent No. 3021277 describes that in a full color process, it is possible to obtain a high definition image quality by using a small particle size toner. However, in the full-color process, there are four colors, black, yellow, magenta, and cyan.
Since various colors are produced by superimposing color toners, the use of a small particle size toner increases the number of toner layers in a unit thickness, and toner scattering has become a problem.

In full-color image formation using an electrostatic latent image, four color toners of black, yellow, magenta, and cyan are used, and the four color toners need to be superposed on the final image carrier such as paper or sheet. There is. The following two methods are mainly used as a method of superposing four color toners.

The first is to develop the latent image on the electrostatic latent image carrier by the toner of four colors of black, yellow, magenta, and cyan for each color, and to retain the final image from the electrostatic latent image carrier in the order of each color. This is a method in which the toner is transferred to the body and four color toners are directly superposed on the final image holding body (hereinafter referred to as a direct transfer system). The second is to develop the latent image on the electrostatic latent image holding member by the toner of four colors of black, yellow, magenta and cyan one by one, and in order of each color, toner is transferred from the electrostatic latent image holding member to the intermediate image holding member. This is a method of transferring, superimposing four color toner images on the intermediate image carrier, and transferring the image from the intermediate image carrier to the final image carrier (hereinafter referred to as an intermediate transfer system). In both of the above two methods, the toner on the final image carrier is fixed to the final image carrier by heat or pressure.

In the direct transfer method, a separate electrostatic latent image holding member is used for each color, or one electrostatic latent image holding member is sequentially developed with four color toners, and the final image holding member is a cylinder or the like. A method in which the final image carrier is transferred after being fixed to the sheet is often used. Although a method using a separate electrostatic latent image carrier for each color enables high-speed output, the apparatus itself becomes large-scale and the cost increases. In addition, since each of the four latent image holding members is provided, it is difficult to control the overlap when the four colors are overlapped.
Color shift is likely to occur. In particular, the misalignment of the four-color stack is likely to occur due to thermal expansion and distortion of the image forming machine body. Further, the method of sequentially developing with four color toners using one electrostatic latent image carrier, fixing the final image carrier to a rigid cylinder or the like, and transferring the final image carrier is accurate with respect to color misregistration. Since the final image carrier is fixed to a cylinder or the like, there are many restrictions on the shape, size, rigidity, etc. of the final image carrier. Also, since the machine has a cylinder or the like for fixing the final image carrier, there is little freedom in the layout inside the machine, and the volume of the machine body increases,
The mechanism becomes complicated.

In the intermediate transfer system, there is often used a method in which one electrostatic latent image holding member is sequentially developed with four color toners and transferred onto the intermediate image holding member. This method has high accuracy with respect to color misregistration, and if a belt or the like is used for the image intermediate holding member, the machine layout has a high degree of freedom and space can be saved.

However, in order to obtain a full-color image by any method, the toner is transferred from the electrostatic latent image carrier to the final image carrier or from the electrostatic latent image carrier to the intermediate image carrier, It is necessary to stack four color toners, and when the toners are stacked, the toners scatter, the resolution is lowered, and bleeding occurs. Further, when the full-color image is fixed on the final transfer member, the color reproduction range, the hue of the black portion of the image, and the like differ depending on the order in which the toners overlap.

[0008]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a method for forming a color image by an electrophotographic system or an electrostatic recording system so as to make toner scattering less noticeable and color An object of the present invention is to provide a color image forming method having a wide reproduction range.

[0009]

As a result of intensive studies on the above problems, the present inventors have found that in the method of forming a color image by the above-mentioned intermediate transfer system, toner is transferred from an electrostatic latent image holding member to an intermediate image holding member. The inventors have found that the above-mentioned objects can be achieved by defining the order of the transfer when they are transferred onto the body, and have reached the present invention. That is, according to the present invention,
First, in claim 1, black, yellow, cyan,
Using a developer consisting of four magenta toners and a carrier, the latent image on the electrostatic latent image carrier is developed with four color toners in a single color, and the toners are transferred in order from the electrostatic latent image carrier to each color. In a color image forming method of transferring an image onto an image carrier to form an image in which four color toners are overlapped, and transferring and fixing the image from an intermediate image carrier to a final image carrier, an electrostatic latent image is retained. There is provided a color image forming method characterized in that the color order of toners transferred from the body to the intermediate image carrier is black, cyan, magenta, yellow in order or black, magenta, cyan, yellow in order. .

Second, in the color image forming method according to the first aspect, the weight average particle diameters of the four color toners are each 7.5 μm or less. Will be provided.

Thirdly, in the third aspect of the present invention, in the color image forming method according to the first or second aspect, the degree of haze when yellow, magenta, and cyan toners are fixed on the transparent sheet in a single color, respectively, There is provided a color image forming method characterized by increasing in order of magenta, cyan, and yellow, or cyan, magenta, and yellow.

Fourthly, in a fourth aspect, in the color image forming method according to any one of the first to third aspects,
As a main colorant of yellow toner, C.I. I. Pigme
There is provided a color image forming method using ntYellow 180.

Fifth, the fifth aspect of the present invention is the color image forming method according to any one of the first to third aspects,
As a main colorant of yellow toner, C.I. I. Pigme
A color image forming method is provided, which uses ntYellow 155.

Sixth, in a sixth aspect, in the color image forming method according to any one of the first to third aspects,
As a main colorant of yellow toner, C.I. I. Pigme
A color image forming method is provided, which uses ntYellow 74.

[0015]

To transfer toner from the electrostatic latent image carrier to the image carrier, toner is charged and a voltage is applied between the electrostatic latent image carrier and the image carrier to move the toner. . The toner on the image carrier is not fixed at this point and is only adhered to the image carrier by cohesive force or electrostatic force, and is physically peeled off and unstable.
In addition, the toner itself is charged, and the portion of the image carrier on which the toner is attached is electrostatically unstable. When the toner is overlaid, if the toner is present on the image carrier after the second and subsequent transfers, the transfer point is in an electrostatically and physically unstable state, and the transferred toner tends to scatter. . Further, the transferred toner is more likely to scatter because it is moved than the toner existing at the transfer point. That is, the toner having a color in the later transfer order is more likely to be scattered during the transfer. Therefore, a toner of a color that is transferred from the electrostatic latent image holding member to the image holding member earlier has a sharper and better image with less scattering. This applies to both the intermediate transfer method and the direct transfer method. This line of dust is conspicuous in the line or character portion where the toners of two or more colors are overlapped, and the quality of the full-color image is deteriorated.

Further, in order to improve the quality of the full-color image, the weight average diameter of the toner is preferably 7.5 μm or less. By reducing the particle size of the toner, it becomes possible to reproduce even a fine electrostatic latent image, and as a result, the resolution is improved and the granularity and roughness of the halftone portion and high tone portion are reduced. However,
On the contrary, in the high density image portion, the toner particle size is reduced, so that the number of toner layers is increased and dust during transfer is likely to occur.

Normally, when forming a full-color image, four color images of yellow, magenta, cyan and black are superposed. For human eyes and image recognition, magenta, cyan,
It is known that the disorder and details of the yellow image can hardly be recognized compared to black. Therefore, by bringing yellow as the toner of the color finally transferred from the electrostatic latent image holder onto which the image is apt to be disturbed, it is possible to make the disturbance of the image and the dust of the toner inconspicuous. Further, when the three colors of magenta, cyan, and black are compared, black is the most likely to experience image distortion in terms of human eyes and image recognition among these three colors. Therefore, in the transfer from the latent image holding member to the image holding member, it is possible to make the image disturbance less likely to be felt when black is first performed.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
As a colorant for yellow, magenta, cyan and black toners, all known dyes and pigments can be used. From the viewpoints of cost, light resistance, transparency, electrostatic characteristics, and resistance to contamination of surrounding members, it is preferable to use the pigment type rather than the dye type.

As a colorant for a conventional yellow toner,
C. I. Pigment Yellow 14 and C.I. I. Pigment Yellow 17 has been mainly used, but it may be decomposed by heat or the like to generate benzidine which is a carcinogen. Recently, C.I. I. PigmentY
ellow 180, C.I. I. Pigment Yel
low 155, C.I. I. Pigment Yellow
w 74 is used. In the present invention, it is preferable to use any of the latter three pigments from the viewpoint of safety.

As the colorant for the magenta toner, C.I. I. PigmentRed 57: 1 is the most suitable, and C.I. I. P
igment Red 122 is preferred. In addition, C.I.
I. Pigment Red 57: 1 is strongly negatively charged by rosin which is a treating agent, and C.I. I. Pigmen
The t Red 122 has a strong positive charge due to its surface structure. To obtain good chargeability as a toner, C.I. I. P
igment Red 184, C.I. I. Pigmen
t Red 146, C.I. I. Pigment Red
Naphthol based pigments such as 269 are also preferred.

As the colorant for the cyan toner, a copper phthalocyanine pigment is preferable in terms of cost, light resistance and color tone.

Further, for yellow, magenta and cyan pigments, the average particle diameter of the pigment is 0.2 μm or less and the average dispersed particle diameter is 0.2 μm in order to ensure the transmission of visible light.
The following are preferred.

Carbon black or iron oxide is preferably used as the colorant for the black toner in terms of cost and color. When carbon black is used, absorption in the long wavelength side of visible light is weak due to the absorption characteristics of carbon black, so that the halftone portion is reddish to yellowish. For this reason, it is preferable to use a coloring material that absorbs the long wavelength side in carbon black as a complementary colorant. Similarly, iron oxide also tends to be reddish, so that a good black toner can be obtained by introducing a complementary color agent or reducing the iron oxide.

In a full color system, in order to reproduce a wide range of colors, black, yellow, magenta, and cyan toners are overlaid on the final image carrier at various ratios. Naturally, the toners are deposited on the final image carrier in a certain order, but of the three toners of yellow, magenta, and cyan, the toner having a high light transparency has a better color reproduction range. Get wider

So far, the yellow pigment has been C.I. I. Pig
ment Yellow 14, C.I. I. Pigmen
Although t Yellow 17 has been used, its light resistance is poorer than that of the magenta pigment and cyan pigment described above, and therefore the pigment particles are made larger to increase the light resistance. Therefore, compared to magenta pigment and cyan pigment,
Poor transparency. In addition, recently, C. I. Pigment Yellow 18
0, C.I. I. Pigment Yellow 155,
C. I. Pigment Yellow 93, C.I.
I. Pigment Yellow 74 is used, but the dispersibility in the resin is C.I. I. Pigment Yel
low 14, C.I. I. Pigment Yellow
It is even worse than No. 17, and the transparency is further inferior as compared with the magenta pigment and the cyan pigment.

Regarding black, theoretically, it can be obtained by stacking toners of three colors of yellow, magenta and cyan, but it is not completely black due to the characteristics of the colorant. Moreover, the toners of three colors of yellow, magenta, and cyan are layered, so that the thickness of the toner on the transfer body becomes large, which causes image disturbance at the time of transfer. Therefore, the black portion of the full-color image is either black toner, four toners of black, yellow, magenta, and cyan are overlaid, or three colors of yellow, magenta, and cyan are overlaid. make use of,
Depending on the characteristics of the image, it is classified and output.

When four color toners of black, yellow, magenta, and cyan are overlapped to output a black image, the black toner is the highest on the final transfer member as compared with the other cases. Appears blacker, and the overall image is tighter. This is because when the yellow toner, the magenta toner, or the cyan toner, or the two colors or the three colors are overlapped on the black toner, the respective color toners do not completely transmit light and are not completely transmitted on the toner surface or inside the toner. There is some reflection, and the color of the toner is dull with black, and it does not look like perfect black. In addition, black is often used for the lines of characters and figures, and even if there is a background color, the black toner should be on the top of the final transfer body, or the image with a darker black outline. can get. That is, the toner on the final transfer member has a wide color reproduction range and a black image portion becomes blacker when the yellow, magenta, cyan, and black are overlapped from the final transfer member or in the order of yellow, cyan, magenta, and black. An image is obtained. Furthermore, by adding an intermediate transfer superposition method, the order of transfer when superposing the toners is black, cyan, magenta, yellow or black, magenta, cyan,
The image becomes yellow, and it is possible to obtain an image in which the image disorder is the least likely to be felt and the black image portion is blacker and has a rough outline.

The haze degree is used as an index showing the transparency of the toner. Here, the haze degree is generally defined as “percentage of transmitted light intensity obtained by integrating all light within an angle β> 2.5 ° with respect to incident light intensity”. When the toner is fixed on a transparent sheet or the like, a small value can be obtained if the toner is transparent.

The following points should be taken into consideration when measuring the haze in the present invention. In the present invention, the haze value is used to rank the transparency of yellow, magenta, and cyan toners. Therefore, any method can be used as long as the haze degree of yellow, magenta and cyan toners is measured under the same conditions. However, since the transparency of the toner is mainly evaluated, it is preferable that the image fixed on the transparent sheet be as flat as possible in order to prevent light scattering on the surface.

The present inventor measured the haze degree as follows. An OHP sheet subjected to solid development with a toner of 0.6 mg / cm ² was passed through a remodeling machine of a fixing unit of Ricoh Co., Ltd., a color copying machine, Pretail 550, and the above sample was fixed under the following conditions. In addition, in order to make the fixing surface as flat as possible, the fixing speed is 1/2 (90 mm
/ S). Furthermore, the above fixing sample was directly read by Suga Test Instruments Co., Ltd. Haze computer HGM-2DP
The haze degree was measured by setting the haze degree in a mold.

The latent image forming method on the electrostatic latent image holding member uses an electrophotographic method in which a photocharge generating material is used as the electrostatic latent image holding member to form a latent image by charging and exposure, and an electrostatic latent image holding member. Any method such as a method in which a non-conductive material is used as the material and an applied voltage is applied to the electrode needle to charge the surface to form a latent image can be used. Among these, the electrophotographic method is easy to control by exposure, and thus the gradation and resolution required for a full-color image can be relatively easily achieved. Also,
In the present invention, the overlapping of yellow, cyan, and magenta may be replaced with black in some cases, so it is better to use a digital method for processing the latent image.

The toner is roughly classified into a wet type in which it is dispersed in a liquid and a dry type in the form of powder. In the present invention, both wet toner and dry toner can be used. Particularly in the dry toner, it is relatively easy to disperse the pigment in the resin to 0.2 μm or less, so that the color reproduction range becomes wider than that of the wet toner.

As the binder resin used for the toner, all those which have been used as the binder for toner so far can be applied. Specifically, styrene such as polystyrene, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, styrene-butadiene copolymer Including resin, polyester resin,
Examples thereof include epoxy resin, phenol resin, maleic acid resin, coumaronic acid resin, chlorinated paraffin, xylene resin, vinyl chloride resin, polypropylene and polyethylene. It goes without saying that two or more kinds of these binder resins may be appropriately mixed and used. Among these, it is advantageous to use polyester resin, polystyrene, styrene resin and epoxy resin.

If desired, the toner used in the present invention may contain a charge control agent, a fluidizing agent or a releasing agent. As the charge control agent, there are nigrosine dyes, quaternary ammonium salts, basic dyes, amino acid-containing polymers, etc. that impart positive polarity to the toner.
In addition, as a substance imparting a negative polarity, a chromium-containing monoazo dye, a chlorinated organic dye, a metal salt of a salicylic acid derivative, and the like can be mentioned. Examples of the fluidizing agent include inorganic oxides such as SiO ₂ and TiO ₂ whose surfaces are hydrophobized, inorganic fine particles such as SiC, and metallic soaps such as zinc stearate. As the release agent, low molecular weight polyethylene,
In addition to synthetic waxes such as polypropylene, plant waxes such as candelilla wax, carnauba wax, rice wax, wood wax and jojoba oil; animal waxes such as beeswax, lanolin and whale wax; montan wax, ozokerite, etc. Mineral waxes; oil-based waxes such as hydrogenated castor oil, hydroxystearic acid, fatty acid amides, and phenol fatty acid esters.

The Coulter counter method is used to measure the particle size of the toner. Coulter counter TA-II and Coulter Multisizer II (both manufactured by Coulter Co., Ltd.) are examples of measuring devices for measuring the particle size distribution of toner particles by the Coulter counter method. The measuring method is described below. First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an electrolytic aqueous solution. Here, the electrolytic solution is an about 1% NaCl aqueous solution prepared using sodium chloride, and for example, ISOTON-II (manufactured by Coulter) can be used. Here, the measurement sample is further 2 to 20 m.
Add g. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of toner particles or toner is measured by the measuring device using a 100 μm aperture as an aperture, Calculate volume distribution and number distribution.

[0036]

EXAMPLES Next, the present invention will be described in more detail by way of examples. However, the present invention is not limited to the following examples. In the examples, all parts are parts by weight. In the following Examples and Comparative Examples, the Ricoh digital copying machine PRETER550 was modified so that the order of development and transfer could be changed. Further, although this apparatus uses the intermediate transfer method, it is modified so that the direct transfer superposition method, which is a comparative example, can be performed. In the case of the direct transfer superposition method, the paper is manually wound and removed, so that the image is fixed by external fixing. Further, the toners used in Examples and Comparative Examples were obtained by melt-kneading a mixture having the following composition, cooling and coarsely pulverizing with a hammer mill, and then finely pulverizing with a fine pulverizer by an air jet system. The finely pulverized product obtained was classified to obtain particles having an average particle size of 6 μm and 9 μm. 0.7 part of silica fine powder obtained by subjecting 100 parts of the present particles to hydrophobic treatment and 0.7 part of titania fine powder were treated.
The toner of the present invention was obtained by adding and mixing 7 parts. In order to improve the dispersibility of the pigment, the following colorant and binder resin were kneaded in advance in a ratio of 1: 1 with two rolls.

[0037] [Examples and Comparative Examples] Black toner   Binder resin (polyester resin) 100 parts   Colorant     Carbon black       (Nipex 60 manufactured by Degussa Hüls Japan) 6 parts     C. I. Pigment Blue 15: 3       (Clariant Japan Toner Cyan BG) 0.5 part     Charge control agent (salicylic acid derivative zinc salt) 2 parts Yellow toner 1   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Yellow 180     (Clariant Japan Toner Yellow HG) 7 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts Yellow toner 2   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Yellow 155     (Clariant Japan Co., Ltd. Toner Yellow 3GP) 8 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts Yellow toner 3   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Yellow 74     (Fast Yellow 7410 manufactured by Sanyo Dye Company) 8 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts Yellow toner 4   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Yellow 17       (Fast Yellow F5G made by Sanyo Dye Company) 7 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts Magenta toner   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Red 122     (Clariant Japan Toner Magenta E02) 6 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts Cyan toner   Binder resin (polyester resin) 100 parts   Colorant     C. I. Pigment Blue 15: 3     (Clariant Japan Toner Cyan BG) 4 parts   Charge control agent (salicylic acid derivative zinc salt) 2 parts

The haze of each toner is shown in Table 1 below.

[0039]

[Table 1]

Next, combinations of Examples and Comparative Examples and evaluation results are shown in Table 2-1, Table 2-2, Table 3-1, and Table 3-2. For the evaluation of dust in the character part, a printer controller is connected to the PRETER550 and blue (those with magenta and cyan overlapped), green (those with yellow and cyan overlap), and red (those with yellow and magenta overlap) are selected. Characters of 10 points in color were output, and the degree of character bleeding was visually evaluated. If the bleeding of the characters could not be confirmed, the Chile evaluation was ○, and if the bleeding of the characters could be confirmed, the Chile evaluation was ×. Regarding the color reproduction range, there are six colors of yellow, magenta, cyan, blue (magenta and cyan overlap), green (yellow and cyan overlap), and red (yellow and magenta overlap). The printer controller outputs 2 squares of 2 cm x 2 cm for each color, and 6 colors of L * a * b.
The color of * was measured (average value of 10 pieces), and the area of the hexagon of the a * b * coordinate was used for evaluation. X-RE for colorimetry
L * a * with D65 light using ITE colorimeter 938
b * was measured. Regarding the black portion of the natural image, the Electrophotographic Society Test Chart No. 5-2 was copied, and the hair portion was visually evaluated for color.

[0041]

[Table 2] *: Example Y: Yellow, M: Magenta, C: Cyan, K: Black

[0042]

[Table 3] Y: Yellow, M: Magenta, C: Cyan, K: Black

[0043]

[Table 4] Y: Yellow, M: Magenta, C: Cyan, K: Black

[0044]

[Table 5] Y: Yellow, M: Magenta, C: Cyan, K: Black

Table 4-1 shows a comparison between 6 μm toner and 9 μm toner. Electrophotographic Society Test Chart No. 5-
2 was copied and the rough feeling of the person's clothes and the face part (halftone part) was visually evaluated. Those with no graininess were marked with ○, and those with graininess were marked with ×.

[0046]

[Table 6]

[0047]

As described above, according to the color image forming method of the first aspect, the color order of the toner transferred from the electrostatic latent image carrier to the intermediate image carrier is cyan, magenta and yellow. Alternatively, since the order is black, magenta, cyan, and yellow, it is possible to make the disturbance of the toner image superimposed on the final image holding member less likely to be felt, and to form a sharp image with a wide color reproduction range.

According to the color image forming method of claim 2,
Since the weight average diameter of each of the four color toners is 7.5 μm or less, even a fine electrostatic latent image can be reproduced, the resolution is improved, and the granularity and roughness of the halftone portion and the high tone portion are sensed. Can be made smaller.

According to the color image forming method of claim 3,
In the above color image forming method, the haze degree when fixing each toner of yellow, magenta, and cyan in a single color on the transparent sheet increases in the order of magenta, cyan, and yellow or in the order of cyan, magenta, and yellow. Therefore, when an image is formed on a transparent sheet, an image having excellent transparency and a wide color reproduction range can be formed.

According to the color image forming method of claim 4,
In the above color image forming method, C.I. I. Pigment Yellow
Since 180 is used, a more safe image can be formed.

According to the color image forming method of claim 5,
In the above color image forming method, C.I. I. Pigment Yellow
Since 155 is used, an image with higher safety can be formed as in the above.

According to the color image forming method of claim 6,
In the above color image forming method, C.I. I. Pigment Yellow
Since 74 is used, a more safe image can be formed as in the above case.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an image forming process of a copying machine used for image formation in an example (intermediate transfer system).

FIG. 2 is a schematic diagram of an image forming process used in a comparative example (direct transfer method).

[Explanation of symbols]

1 electrification 2 exposure 3 potential sensor 4 development department 5 P sensor 6 OPC drum 7 PCC 8 Sweeper brush 9 drum clean 10 Static elimination lamp 11 transcription 12 separation 13 Intermediate transfer belt 14 paper 15 Paper support drum 16 Belt cleaning

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yasuo Asahina             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Kazuhiko Umemura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Hideki Sugiura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Kosuke Suzuki             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Tomomi Tamura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H005 AA21 CA21 EA05 EA10                 2H030 AD01 AD16 BB42 BB63

Claims (6)

[Claims] 1. A latent image on an electrostatic latent image holding member is developed with four color toners by using a developer composed of four color toners of black, yellow, cyan, and magenta and a carrier, and each color is developed in order. Toner is transferred from the electrostatic latent image carrier to the intermediate image carrier to form an image in which four color toners are superposed, and the image is transferred from the intermediate image carrier to the final image carrier and fixed. In the color image forming method, the color order of the toner transferred from the electrostatic latent image carrier to the intermediate image carrier is black, cyan, magenta, yellow in order or black, magenta, cyan, yellow in order. A characteristic color image forming method. 2. The color image forming method according to claim 1, wherein the four color toners each have a weight average particle diameter of 7.5 μm or less. 3. The color image forming method according to claim 1 or 2, wherein when the yellow, magenta, and cyan toners are fixed in a single color on the transparent sheet, the haze degree is in the order of magenta, cyan, and yellow, or cyan,
A color image forming method characterized by increasing in order of magenta and yellow. 4. The color image forming method as claimed in claim 1, wherein C.I. I. Pigment Yellow 18
A method for forming a color image, wherein 0 is used. 5. The color image forming method according to claim 1, wherein C.I. I. Pigment Yellow 15
5. A color image forming method, characterized in that No. 5 is used. 6. The color image forming method according to claim 1, wherein C.I. I. Pigment Yellow 74
A method for forming a color image, comprising: