WO1991006044A1

WO1991006044A1 - Color image forming method

Info

Publication number: WO1991006044A1
Application number: PCT/JP1990/001312
Authority: WO
Inventors: Sadao Masubuchi
Original assignee: Citizen Watch Co., Ltd.
Priority date: 1989-10-12
Filing date: 1990-10-11
Publication date: 1991-05-02
Also published as: EP0447566B1; EP0447566A4; DE69014600T2; EP0447566A1; DE69014600D1

Abstract

A one-shot color image forming system for producing a color image with one exposure, characterized in that three kinds of color toners capable of transmitting cyan, magenta and yellow therethrough, respectively and adapted to develop colors identical with those of the transmitted light are used, and red, green and blue light, the quantities of exposure light energy of which can be varied, being applied to the color toners on a photosensitive member to vary the combination of the light of these colors and the quantity of exposure light energy in order to selectively remove the color toners from the photosensitive member.

Description

Specification

Color image forming method

[Technical field ]

The present invention relates to an electrophotographic image forming method, and more particularly, to a method of forming an image by a one-shot color method in which an electrostatic latent image corresponding to a color image is obtained by one exposure.

[Background Art]

In response to the increase in the information processing capabilities of consumers, there is a strong demand for improved peripheral device functions. In printers that convey processed information to humans in the form of prints, color printing of prints is required to express more complex information accurately and intuitively.

A color image forming method using an electrophotographic method has been proposed as a method for responding to the above demand. There are two methods, a multi-process method and a one-shot method.

The multi-process electrophotographic process is as follows. Prepare cyan, magenta, yellow, and black as color toners. First, an electrostatic latent image corresponding to cyan is formed on the surface of the electrophotographic photosensitive member, and a cyan toner image is formed. Transfers cyan toner on the surface of the electrophotographic photosensitive member to a transfer drum. The magenta, yellow, and black toner images are sequentially superimposed on the transfer drum in the same process. When the transfer of the four color toners onto the transfer drum is completed, the toner image is transferred to paper. Fixing to obtain a color print image In the method using the normal color toner, a color toner image for one page is formed and then transferred to paper at a time. Since a transfer drum having a large diameter is required, there is a disadvantage that the apparatus becomes large. The disadvantage is that the printing speed is slow because the photoreceptor rotates four times, corresponding to the number of color toner types, in this case four times. In addition, when the color toner is superimposed on the transfer drum, misregistration causes a significant decrease in image quality, and a high-precision mechanical alignment mechanism is required, resulting in heavy and expensive equipment. .

As a method for solving these disadvantages, a one-shot color method using an electrophotographic method has been proposed. For example, Japanese Patent Publication No. 55-27341 discloses a method using a special color toner. This one-shot color system is characterized by using a special toner having a color filter core described below. A special donor is composed of two elements with different functions. One is a color filter that selectively controls the color, and the other is a color filter that reacts with a developer applied to the surface of recording paper to generate a complementary color to the transmitted color of the color filter. It is the best. The color former is transparent before reacting with the developer. A color filter that consists of a color filter that transmits red, green, and blue, and a color former that reacts with a developer to produce cyan, magenta, and yellow, which are complementary colors of red, green, and blue, respectively. It is a kind of special toner.

First, the photoreceptor is charged, the special toner is adhered to the surface of the photoreceptor, and the special toner is exposed with a combination of red light, linear light, and blue light depending on image data. When the exposure is completed, the electrostatic attraction between the photoreceptor and the special toner including the color filter that transmits the color of the exposure is reduced. For example, red exposure light passes through a special toner including a color filter that transmits red light, reaches the surface of the photoconductor, and reduces the amount of charge on the surface of the photoconductor. On the other hand, special toners containing color filters that control blue and blue absorb red, so red exposure light does not reach the surface of the photoconductor, and the amount of charge on the surface of the photoconductor does not decrease. . Next, in the developing step, only a toner having a weak electrostatic attraction is separated from the photoreceptor to form a color toner image on the surface of the photoreceptor. The special toner remaining on the photoreceptor is transferred to recording paper coated with a developer and fixed to obtain a color image. As shown in the above example, when exposing in red, the special toners of magenta and yellow remain on the surface of the photoreceptor, so these two types of special toner are transferred to the paper, and a red image is formed on the recording paper. It is formed. By combining and exposing light in different wavelength ranges, images of eight colors including white and black can be obtained.

The conventional one-shot color method has the following problems due to the use of a special toner. .

(a) Handling of recording paper is troublesome.

(b) Special toner is expensive.

(c) Special scum is generated.

(d) The color density of the image is insufficient.

(a) is due to the necessity of special paper coated with a color developer as the recording paper in order to develop the color former of the special toner. With plain paper used in an ordinary electrophotographic image forming apparatus, the color former does not develop color and an image cannot be obtained. Special paper is difficult to obtain, and it is necessary to improve the storage environment to prevent deterioration of the color developer.

(b) is due to the complexity of the special toner manufacturing process. In other words, the special toner forms a core of a color filter for selecting a transmission color and is manufactured by a complicated process of coating a color former on the core, so that it is expensive.

In (c), the color of the color filter that constitutes the special toner is complementary to the color that the color former produces, so the image becomes black when the color filter is fixed to the paper in the fixing process. Without This is because it is designed to remain on the paper surface. Action is required to remove this residue.

In (d), most of the volume of the special toner is occupied by the color filter member, and the ratio of the color former is small.

A one-shot method using cyan, magenta, and yellow power rasters without a color filter nucleus is disclosed in Japanese Patent Application Laid-Open No. 63-2855656. The color of the unit is only a combination of three colors of red, blue, and blue, and as a color printer, the number of expression colors is insufficient. Also, the one-shot method using red, yellow, and red color toners _ disclosed in Japanese Patent Publication No. 40 — 284997 can only express red, yellow, and blue, and the number of expression colors Is inadequate.

* The invention is a simple configuration that eliminates the above-mentioned problems by using an ordinary color toner without the core of a color filter and devising the exposure method. An object of the present invention is to provide an electrophotographic image forming method for obtaining an electrostatic latent image corresponding to an image, obtaining a large number of expression colors, and obtaining a high-quality color image on ordinary paper.

[Disclosure of the Invention] The invention provides a one-shot color system for forming a color image by one exposure, in order to achieve the above-mentioned object, each color of cyan, magenta and yellow as a color toner. Using three types of color toners that emit the same color as the color of the transmitted light, and irradiating red, red, and blue light with variable light energy for exposure to the color toner on the photoreceptor, It is characterized in that the color toner is selectively separated from the photoconductor by changing the combination of light of each color and the amount of light energy of exposure. [Single description of drawings]

Fig. 1 (a), (b), and (c) are diagrams explaining the principle of the exposure method according to the present invention. Fig. 2 is a chromaticity diagram explaining the hue of the expression color of an image. Fig. 3 FIG. 4 is a configuration diagram showing a configuration of an electrophotographic image forming apparatus according to the present invention, and FIG. 4 is an explanatory diagram illustrating a permeation vector of a color toner and an optical writing wavelength.

[Best Mode for Carrying Out the Invention]

Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

(Example 1)

Fig. 1 shows a method for controlling the electrostatic force between the color toner and the electrophotographic photoreceptor using the exposure method of the invention.

The electrophotographic photosensitive member used an organic optical semiconductor layer having sensitivity to red light, recording light, and blue light. The surface of the electrophotographic photosensitive member 1 is charged, and cyan toner C that transmits blue light and blue light and absorbs red light, and magenta toner M that transmits blue light and red light and absorbs blue light, and red light. Ye penetrates and absorbs blue light. Toner Y is uniformly applied to each color. Color toner is composed mainly of a colorant that determines the spectral transmission spectrum of the toner, a binder resin for fixing to recording paper, and a charge control agent that controls the charging characteristics of the toner. Is done. As the colorant, a pigment, a dye, a sublimable dye or the like is used. The core of the color filter for selecting the transparent color, which was required for the special toner described in the previous section on zono title, is not required in the invention.

The light intensities I _H , IG, and IB indicate that the surface potential of the electrophotographic photoreceptor is sufficiently increased when light is written on the electrophotographic photoreceptor on which the toner is formed using red, blue, and blue light. It is the light intensity required to separate the toner corresponding to each color by lowering it. It depends on the light time and the sensitivity characteristics of the photoconductor.

This can be expressed by the following equation.

(2 X I R) X T R X Δ t = E R

(2 XIG) XT G X Δt = E G,

(2 XIB) XTB x At = E _B

Here TH, T _G ,, TB is described in detail later, Ri permeable遏率der for each light color toner, A t is the exposure time, E _H, EG, EB are red, blue color This is the photoenergy for each color required to sufficiently lower the surface potential of the electrophotographic photoreceptor when the electrophotographic photoreceptor to which the color toner has not adhered is exposed to this light.

The meaning of the above relation is as follows. Exposure from the color toner side at twice the light intensity of I H, I G, I B gives the light intensity

When the value obtained by multiplying the transmittance of the color toner by twice the value of IR, IG, and IB reaches the surface of the electrophotographic photoreceptor, and this exposure is continued for At time, the electrophotographic photoreceptor is exposed to the surface. Obtain the light energy necessary to lower the potential sufficiently.

Next, the wavelengths of the red, blue and blue writing light (exposure) and the transmittance of each color toner will be described with reference to FIG.

The transmission spectrum of cyan toner is shown as 12, the magenta toner is shown as 13, and the yellow toner is shown as 14. In red light red exposure magenta toner and yellow toner transmittance center wavelength of 6 4 0 nm equal Hopo, exposure of籙色the cyan toner and the transmittance of the Yellow toner is equal Hopo ₅ Blue light with a center wavelength of 3 O nm is used, and blue exposure is performed with blue light having a center wavelength of 4 15 nm, where the transmittances of cyan and magenta toners are almost equal.

TR is the transmittance of magenta toner and yellow toner for the above-described red exposure light. TG is the transmittance of cyan and yellow toners to light of blue exposure. T _B is the transmittance of cyan and magenta toner for blue exposure light.

Figure 1 (a) is a case where the exposure is籙光red light and the light intensity I s of the light intensity I _H. Since cyan toner C absorbs red light and transmits only blue light, the blue light reaches the surface of the electrophotographic photoreceptor and slightly reduces the charge on the surface of the electrophotographic photoreceptor. Slightly reduces the electrostatic force between electrophotographic photoreceptors. However, the light intensity ₁₆ is 1 to 2 of the amount of exposure light required to reduce the electrostatic force to an extent sufficient to spread cyan toner from the electrophotographic photoreceptor in the development process. One is strongly attracted to the electrophotographic photoreceptor and is not peeled off in the developing process. With magenta toner M, recording light is absorbed and only red light is transmitted. Since the light intensity I _H is one half of the amount of exposure required to provide a sufficient reduction in electrostatic force to remove the magenta toner from the electrophotographic photoreceptor in the development process, the magenta toner is Not received from photoconductor.

On the other hand, since both yellow light and red light are transmitted by the yellow toner Y, the surface of the electrophotographic photosensitive member under the yellow toner Y is exposed by both the recording light and the red light. The yellow toner is transferred to the surface of the electrophotographic photoreceptor because two of the light of 1/2 of the amount of exposure light required to provide a sufficient reduction in electrostatic force to separate the yellow toner from the electrophotographic photoreceptor. Provide sufficient electrostatic force drop from photoreceptor.

That is, the color toner that transmits only one of the two types of exposure wavelength light is not separated from the electrophotographic photosensitive member in the developing process, and only the color toner that transmits both wavelength light is electrophotographic photosensitive device in the developing process. Separated from body.

When the exposure in the blue light of the red light and the light intensity I _B of the light intensity I _R, magenta door Since only the toner emits both red light and blue light, only the electrostatic force between the electrophotographic photosensitive member and the magenta toner is greatly reduced, and only the magenta toner is used for the electrophotographic photosensitive member during the developing process. Easy separation from the surface o

When exposed with blue light of籙光and the light intensity I _B of the light intensity I s, cyan Bok - since only toner transmits light of both綠光and blue light, the electrostatic force of only the cyan toner In the development process, only cyan toner can be easily removed from the surface of the electrophotographic photosensitive member.

In other words, when monochromatic exposure is performed with two wavelengths of light, one to two times the amount of exposure light necessary to sufficiently reduce the electrostatic force, one type of color toner that controls the two wavelengths of exposure is used. Only is selected and easily separated from the electrophotographic photosensitive member in the developing process.

Next, a method for selecting two types of color toners will be described. In Fig. 1 (b), shows the case of exposing the electrophotographic sensitive optical member from the color toner side red light of the light intensity 2 XI _H. Since cyan toner C absorbs red light, the surface potential of the electrophotographic photosensitive member under the cyan toner hardly decreases. The surface potential of the electrophotographic photosensitive member under the magenta toner M and the yellow toner Y, which transmit red light, is greatly reduced. Since the light intensity 2 XI _R is sufficient to cause a decrease in electrostatic force enough to separate the toner from the electrophotographic photosensitive member in the developing process, the magenta toner M and the yellow toner Y are electrophotographically used in the developing process. Peelable from photoreceptor.

Exposure to sunlight with a light intensity of 2 XI _S reduces the electrostatic force between the cyanogen that controls the sunlight and the electrophotographic photoreceptor of yellow toner. Only the magenta toner, which can be easily separated and does not transmit the recording light, remains on the surface of the electrophotographic photosensitive member.

Exposure with blue light at a light intensity of 2 × 1B reduces the electrostatic force between the cyan toner that controls blue light and the electrophotographic photoreceptor of magenta toner. In the image process, the electrophotographic photosensitive member can be easily removed from the electrophotographic photosensitive member, and only the yellow toner which does not penetrate blue remains on the surface of the electrophotographic photosensitive member.

In other words, when the monochromatic exposure is performed at a light intensity that sufficiently reduces the electrostatic force, two types of color toners that transmit the color of the exposure are selected and easily separated from the electrophotographic photoreceptor in the development process, and the exposure is performed. One type of color toner that does not permeate the color remains on the surface of the electrophotographic photosensitive member.

One to select three kinds of Color Camera toner Te to base the trick, as shown in FIG. 1 (c), the red light of the light intensity I _H, twill light of the light intensity I _e, strongly light of IB Exposure with blue light. As described above, the light intensity of the exposure of each color does not cause a sufficient decrease in electrostatic force with a single color, but when exposed with at least two colors, the electrostatic intensity is sufficient to separate toner in the developing process. This is the light intensity that causes the drop. The electrophotographic photoreceptor under the cyan toner C is irradiated with blue light and shining light, and causes a sufficient decrease in electrostatic force to be applied in the developing process. The electrophotographic photoreceptor under magenta toner M is illuminated with blue and red light, causing a reduction in electrostatic force sufficient to separate it in the development process. The electrophotographic photoreceptor under yellow toner Y is irradiated with red light and red light, causing a reduction in electrostatic force sufficient to be experienced in the development process. That is, all three types of color toners can be easily obtained from the electrophotographic photosensitive member in the developing step.

The color toner built from the electrophotographic photoreceptor in the developing process is transferred to recording paper in the transfer process, spreads two-dimensionally in the fixing process, and the color toners overlap and mix.

Summarizing the above, ①: the type and intensity of light to be exposed, ② the type of color toner separated from the electrophotographic photoreceptor during the development process, and ③: の the color toner that was transferred and fixed Table 1 shows the relationship between the color of the image, ：: the type of color toner remaining on the electrophotographic photoconductor, and ：: the color of the image when the color toner remaining on the electrophotographic photoconductor was transferred and fixed. Show.

The color of the S image obtained by transferring and fixing the color toner maintained from the electrophotographic photoreceptor and the color of the image obtained by transferring and fixing the color toner remaining on the electrophotographic photoreceptor are complementary colors. It is in. In each case, combining white and black produces an 8-color image.

table 1

Light exposure, the light intensity I _B IGIB and 2 times the light intensity of them is required. There are a method of changing the light intensity of optical writing and a method of changing the time of optical writing. If the optical writing device is a self-emission type such as a laser and performs point scanning, the emission intensity itself is changed, or the light emitted from the laser is changed using an optical modulator. The emission time may be changed while keeping the emission intensity constant.

Self-luminous arrays such as LEDs and fiber optical tubes W

In the case of the mold, the luminous intensity of the luminous dots constituting the array is changed. The emission time may be changed while keeping the emission intensity constant. In the case of a shutter type such as a liquid crystal shutter or PLZT (lead-lanthanum-zircone-to-titanate) shutter, the transmittance of the pixels constituting the shutter changes. Let it. The transmittance of the shutter may be kept constant, and the light transmission time may be changed.

(Example 2)

Intermediate colors other than blue, cyan, green, yellow, red, and magenta can be obtained by the following three methods. The first method is to use area gray scale using a plurality of dots, although the resolution of the pixel is reduced. One dot is composed of multiple dots, for example, 4 x 4 dots. The cyan, magenta, and yellow color toners are placed independently in 4x4 dots according to the color that the picture element should represent. When one pixel is composed of 4 X 4 = 16 dots, one pixel can represent 16 gradations of cyan, magenta, and yellow, respectively. Color can be expressed. In this example, each dot of 4 X 4 = 16 is composed of picture elements, and in the case of three types with one type of cyan toner, magenta toner, and yellow toner, two types are used. If there are three cases, all are present, all are not, it will be in one of the eight cases. Since these eight cases correspond to the eight colors described above, intermediate colors can be obtained by the basic exposure methods shown in Table 2.

The second method is to express the intermediate colors by performing area gradation for each color within one dot. In the first method described above, for one dot, each color toner has only two states, that is, the entire area of one dot and none at all. In the second method, There is also an intermediate state, that is, a state where a certain area of one dot is attached. This second approach can be embodied in digital and analog approaches. The digital method reduces the shape of the exposure light to less than one dot, further divides the time during which the photoconductor moves by one dot, and uses the divided time as the unit for exposure. It is a technique to control the time of the city. After determining the toner color to be selected, determine the exposure light according to Table 1, and control the exposure time for each exposure color according to the Y, C toner ratio. For example, if yellow toner is selected for 50% of the area of one dot and magenta toner is selected for 30% of the area of one dot, the time required for the electrophotographic photosensitive member to move by one dot is selected. 30% time, table

Select Y, トナー toner in the exposure of (4) of 1

In the exposure of (1), only the toner needs to be selected.

The analog approach is as follows. The location distribution of light energy obtained by integrating the exposure light within one dot is a Gaussian distribution with a light energy beak at the center of one dot. By setting the threshold value to an appropriate value of the light energy value, it becomes possible to change the image area of the color toner for each dot depending on the light intensity of the exposure. For example, at a light intensity of I _K (IG, IΒ), a color toner image cannot be formed, and at a light intensity of 2 XI _H (2 XI _G , 2 XI _B ), the color toner image covers almost the entire area of one dot. The electrophotographic process can be designed such that the image is formed, and the light intensity in the middle varies the area where the color toner image is formed, depending on the light intensity. This is the process used for analog color copiers. By exposing with two wavelengths of light and changing the ratio of the light intensity of the two wavelengths of light, the color of the image obtained when only one wavelength of light is exposed with strong light, and only the other wavelength of light A color that is intermediate between the colors of the rooster image obtained when exposed to strong light is obtained. Table 2 shows that, when exposed with red light and recording light, ①: the intensity of light to be exposed, ② the intensity of light reaching the surface of the electrophotographic photoreceptor under each color toner, and ③: the intensity of light ② The ratio of the color toner to the minimum light intensity required to form an image, ：: the type of color toner separated from the electrophotographic photoreceptor, ⑤: the color of the image when the separated color toner is transferred and fixed Is shown for a typical ratio of the light intensity of red light and blue light. When the value of ① in ③ is larger than 1, the area of the part of the color toner which is printed from the surface of the electrophotographic photoreceptor depends on the value of ② in ③, and the value of 2 Fill almost the whole area of one dot with. In (5), (0.5) means that the color toner occupies half the area of one dot. As the light intensity increases, the color of the image changes to red, orange, yellow, yellow, and red.

Table 3 shows the colors of images when exposed in combination of blue light and blue light, and blue light and red light in the same format as in Table 2. In Tables 2 and 3, the symbols (A) to (F) indicated by ⑤ in (1) indicate the positions in the CIE chromaticity diagram of FIG.

(Hereinafter the margin)

Table 3

5-By the exposure method described above, a color composed of two types of color toners can be obtained.

To further expand the range of color representation of the image, the image may be composed of three types of color toners. Table 4 shows the colors of the image when exposed with a combination of red, recording and blue light in the same format as Tables 2 and 3. However, here, the ⑤ ⑤ in Tables 2 and 3 is omitted. In Table 4, the ratio of the light intensity of each light was changed while keeping the sum of the light intensity of the three wavelength lights constant and making the red light and the aya light the same light intensity.

The third way to represent neutral colors is a combination of the first and second ways. Since the picture element is composed of multiple dots while producing an intermediate color in one dot, more subtle colors can be expressed.

(Example 3)

Example 1 obtained eight colors by the extinction method. In this practice, three basic colors are used, and these three colors are additively mixed to form three more colors, for a total of eight colors including white and black. As shown in Fig. 1 (b), exposure is performed using light in one wavelength range to obtain three basic colors. The results are (4), (5) and (6) in Table 1.

When an image is formed with a color toner separated from the electrophotographic photoreceptor in the development process, red, lines, and blue are obtained as the three colors of the base *, as shown in (1) of (3) in Table 1. The three base colors are additively mixed to produce cyan, magenta, and yellow. Divide one dot into one dot and two dots, and place the three basic colors that are different for each one dot. Alternatively, one dot is composed of two dots, and three different base colors are placed in each dot. For example, red and 綠 are arranged in a descending manner, and if they are additively mixed, they become yellow. The image is darker than when a yellow image is formed using only the yellow toner, but the color can be distinguished sufficiently. When red and blue are tangently arranged, magenta can be expressed by additive color mixing, and when blue and blue are tangently arranged, cyan can be expressed.

Red light of the light intensity 2 XI _H, the light intensity 2 xls of籙光, or less blue light of the light intensity 2 X 'I _B is also selected to expose the two wavelength light, in FIG. 1 (c) as shown, by exposing a light blue light籙光+ light intensity I _B of the red light + light intensity I _s of the light intensity I _H, to obtain a black. White without exposure. By the above method, you can get 8 colors of cyan, magenta, yellow, red, green, blue, white and black.

When the color toner remaining on the electrophotographic photoreceptor is transferred and fixed after the development process to form an S image, the three basic colors are cyan, magenta, and yellow as shown in the black box in Table 1. There are three colors. The three base colors are additively mixed to create red, aya, and blue. For example, cyan and magenta Arranged adjacent to each other and added to give a blue color. Compared to blue obtained by subtractive color mixing with cyan and magenta superimposed, the saturation is low but the colors can be distinguished sufficiently. If magenta and yellow are adjacent to each other, red can be expressed by additive color mixing, and if cyan and yellow are arranged in close contact, ¾ can be expressed.

Red light of the light intensity 2 XI _R, recording light of the light intensity 2 XI _e, or less blue light of the light intensity 2 XI _B also choose to expose the two wavelength light, shown in FIG. 1 (c) as, by exposing a light blue light綠光+ light intensity I _B of the red light + light intensity I _c of the light intensity I _H, to obtain a white. Black without exposure. In the above way, you get eight colors: cyan, magenta, yellow, red, green, blue, white and black.

(Example 4) ''

FIG. 3 shows the configuration of an electrophotographic color printer using the above-described exposure method as an exposure step. The surface of the OPC photosensitive drum 2 having panchromatic spectral sensitivity characteristics is charged entirely by the charger 3.

A photosensitive drum must have a sufficiently sharp y characteristic of a latent image in order to form a good electrostatic latent image by an unexposed exposure method. As detailed in real ¾ Example 1, for example, when exposed with red and blue light intensity I _B of the light intensity I _H, photosensitive under the magenta preparative Na first red light and blue light is transmitted through the magenta toner Only blue light reaches the photoreceptor under cyan toner and only red light reaches the photoreceptor under yellow toner. In order to obtain a good image, it is desirable that the surface potential of the photoconductor under the magenta toner is sufficiently reduced and the surface potential of the photoconductor under the cyan toner and the yellow toner is hardly reduced. . The light intensity that reaches the surface of the electrophotographic photosensitive member through the color toner is 2 in the light intensity ratio between the selected color toner and the non-selected color toner. Therefore, in order to obtain high quality images, When the contrast ratio of light reaching the surface is 2, it is desirable that the photoreceptor has a y-characteristic that can obtain a sufficiently large difference in surface potential. For example, as a photosensitive member, a photosensitive member for digital light input disclosed in Japanese Patent Application Laid-Open No. 1-164954 is effective.

Next, a cyan toner, a magenta toner, and a yellow toner are formed on the surface of the photosensitive drum 2 by the color toner applicator 4 to form one layer of toner on the charged photoconductor. In order to form only one layer of color toner, it is effective to coat the surface of the color toner with a conductive film such as iodide and to make the surface of the color toner conductive.

The image data is subjected to data processing in the image processing unit 5 and is converted into a signal which fluctuates J and D 6 to optical writing. A liquid crystal shutter was used for the optical writing head. In order to independently control red light, blue light and blue light with a liquid crystal shutter, for example, as disclosed in Japanese Patent Application Laid-Open No. 59-139730, red light and blue light are used. In addition, a color filter that controls blue light may be provided for each liquid crystal pixel constituting the liquid crystal shutter, and the light transmittance of the liquid crystal pixel may be controlled independently. In Japanese Patent Laid-Open No. 59-137930, liquid crystal pixels having a color filter that transmits red light, blue light, and blue light are provided one by one in the moving direction of the photosensitive drum. In the actual example, in order to increase the printing speed, a liquid crystal pixel having a color filter that emits red light, blue light, and blue light is moved in the moving direction of the photosensitive drum in each of the transparent colors. Two were arranged.

To print color on A4 paper with a dot resolution of 300 dpi, it is necessary to use 7600 liquid crystal pixels, which is three times the size of the 2560 liquid crystal pixels required for optical writing on a monochrome printer. is necessary. When this liquid crystal pixel is statically operated, a large number of driving ICs are required, so that the volume and cost of the optical writing head increase. To reduce the number of automatic ICs, it is effective to operate the liquid crystal pixels in a time-division manner. Enable light energy A liquid crystal capable of storing an optical state when driven in a time-division manner is suitable for use. If the response speed of the liquid crystal pixels is high, high-speed printing can be performed. For this reason, a ferroelectric liquid crystal having a fast response and a memory effect was used.

Further, as disclosed in Japanese Patent Application Laid-Open No. 61-52630, the ferroelectric liquid crystal is driven by an analog voltage so that the light transmission rate is completely transparent. An analog town can be controlled in the middle of transmission. * In this example, the drive timing is stored separately in the capacitors provided for each output terminal in the drive IC, with the charges corresponding to the positive analog voltage and the negative analog voltage that drive the liquid crystal pixels, respectively. Switching in synchronization with this, connected to a buffer amplifier provided for each output terminal in the drive IC, and driven the liquid crystal pixels. Exposure according to the image data with the liquid crystal shutter head, controls the charge on the photoconductor under the selected color toner, and controls the electrostatic force between the selected color toner and the photoconductor. did. Light intensity of exposure IH is a liquid crystal pixel in a half-open state, the light intensity 2 XI _H of exposure, the liquid crystal pixels in the status of all open, provided a difference in exposure amount. Further, the intermediate light intensity was obtained by changing the analog voltage applied to the liquid crystal pixels. Also, an intermediate value of light intensity was obtained by the time gradation method. The liquid crystal pixels are only in the two states of fully open or closed, and the liquid crystal pixels are in a light-transmissive state for one to two times of the time that the electrophotographic photosensitive member moves by one line. The liquid crystal pixels were kept closed for the time of 1-2. Further, the intermediate light intensity was obtained by changing the ratio of the time for which the liquid crystal pixel was in a light transmitting state to the time for which the liquid crystal pixel was not transmitting light. In addition, the amount of exposure light can be more finely controlled by combining the time gradation and the analog gradation.

The color toner, whose electrostatic force has been reduced, is transferred to a charged transfer drum 7 and is transferred to a recording paper 9 using a transfer corona unit 8, and is then transferred to a heat fixing unit. At 10 it settled on the paper. The color toner remaining on the surface of the photoconductor 2 without being removed from the photoconductor 2 was scraped off by the cleaner 11. The scraped color toner was sent to the color toner applicator 4 for reuse. Instead of using the transfer drum 7 to transfer the image to the recording paper, the image may be directly transferred to the recording paper without using the transfer drum.

Although an image was formed using color toner having reduced electrostatic force with the electrophotographic photosensitive member, an image may be formed using the color toner remaining on the surface of the electrophotographic photosensitive member after the development process. . However, since the complementary color of the exposed light becomes an image, the signal for operating the optical writer is transmitted in the opposite way when using a color toner separated from the electrophotographic photoreceptor and when opening and closing the liquid crystal pixels. Need to be

Since the consumption amounts of the three types of color toners are different, the percentage of the amount of each color toner in the color toner attaching device 4 changes as the number of prints increases. Using the light emitting diode and the light receiving sensor, the amount of each color toner in the color toner attaching device 4 is measured, and the color toner is automatically adjusted so that the ratio between each color toner becomes constant. Was replenished. The consumption of each color toner may be calculated from the print data and replenished.

* The optical writing by the liquid crystal shutter in the actual example may be done by a color fiber optical tube. Alternatively, the light emitted from the white gas laser may be decomposed into red, red, and blue, and then scanned and written with a polygon. Also, a combination of a semiconductor laser and a high haze wave generator may be used. In other words, the laser light of wavelength 1.06 itm obtained by exciting the YAG laser with the first semiconductor laser and semiconductor laser that emit red light, and the blue light obtained by passing through a double harmonic generator. the second semiconductor laser and emission wavelength of the emission _0. _{8 3 / tm} a semiconductor laser emitting light of a third semiconductor laser obtained blue emission through _second harmonic generator which Each scanning may be performed for exposure.

According to the present invention, since an image can be formed by one-shot exposure, a transfer drum for transferring a toner image is not required, and high-precision mechanical alignment is not required. become. In addition, since a special color toner is used as the color toner instead of a special color toner, a normal color toner that does not require the core of the color filter is used, the paper does not need special paper, and plain paper which can be easily obtained and stored can be used. it can. In addition, since optical writing is performed using an optical writing head with no moving parts and high dot position accuracy, high quality image printing with high image position accuracy is possible. It is possible to obtain an electrophotographic color printer that can print.

Claims

The scope of the claims

1. Apply a plurality of phototransmissive color toners on the electrophotographic photoreceptor at a time, expose from the color toners, develop, and transfer them to a transfer drum or recording paper in one go. In a color image forming method for obtaining an image, three types of color toners that transmit cyan, magenta, and yellow, respectively, and emit the same color as the transmitted light are used as the color toners. By using red, blue, and blue light, which can vary the amount of light energy of exposure, to the color toner on the photoreceptor, and changing the combination of light of each color and the light energy of exposure 露光, A color image forming method characterized by separating toner from a selective photoreceptor.

2. When light of each color of red, green, and blue is exposed to each of the toners of cyan, magenta, and yellow, which control each color, it is necessary to separate each toner from the photoreceptor. Gives the amount of energy of the light intensity of each light

2. The color image forming method according to claim 1, wherein the light energy of exposure is changed by combining light having a light intensity of 12 as a unit.

3. Red light whose center wavelength is equal to the transmittance of magenta toner and yellow toner, blue light whose center wavelength is the wavelength where cyan toner and yellow toner have the same transmittance, and cyan toner whose center wavelength is 2. The color image forming method according to claim 1, wherein the exposure is performed using blue light having a wavelength at which the permeation rate of the magenta toner is equal.