JPS58100140A - Color electrophotography - Google Patents

Abstract

PURPOSE:To obtain good color reproductivity, by controlling each toner concn. in 3 color developers independently to adjust color reproduction balance, and regulating an amt. of each color toner to be attached easily and securely. CONSTITUTION:When toners have characteristics as shown in the figure, a desirable amt. balance of each of Y, M, and C toner to be attached for obtaining good color reproductivity is Y:M:C=0.5-1:1.0:0.7-1.0 by wt. in ratio of attachment amt. on the black part, thus permitting toner concn. of each color developer to be easily obtained by independent control. Amts. of toners to be attached to a photoreceptor are expressed by formulae (1), thus amts. of toners to be attached M to be inversely proportional to toner charge quantitites (q/m), so these ratios to be controlled to Y:M:C=1/0.7:1:1/0.9.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention separates a document into three colors to create three types of latent images, develops them with a developer containing yellow, magenta, and cyan toner, and superimposes them on the same transfer paper. This invention relates to an electrophotographic method for obtaining color images by transferring images.

In this type of color electrophotography, three color filters, blue, green, and red, are installed in the document exposure system in a switchable manner, and three types of latent images are sequentially separated by these filters onto the photoreceptor. The latent image formed by the light transmitted through the blue filter is a developer containing yellow toner, and the latent image formed by light transmitted through the green filter is a developer containing magenta toner.
The latent images formed by the light transmitted through the red filter are developed with a developer containing cyan toner, and the toner images of each color are superimposed and transferred onto the same transfer paper and fixed, thereby producing a color copy similar to the original. Created.

As the above color separation filter, for example, the blue filter is a bandpass filter B manufactured by Fuji Photo Film Co., Ltd.
PB45 is used for the green filter, the same company's bandpass filter BPB53 is used for the green filter, and the same company's sharp cut filter SC60 is used for the red color filter. The characteristic curves of these filters are shown in FIG. In the figure, the horizontal axis shows the wavelength in 0 and 1, and the vertical axis shows the spectral transmittance in 2. As the color separation filter, it is also possible to use a filter equivalent to the above, such as a Latten filter manufactured by Kodak.

Now, the color tone reproduction of the image on the copy changes depending on the ratio of the adhesion amount of each color toner of yellow, magenta, and cyan (hereinafter abbreviated as Y, M, and C) on the transfer paper, so in order to reproduce the color tone of the original, It is necessary to specify the amounts of Y, M, and C color toners that adhere to the paper. If a copy image is simply created by placing equal amounts of fi, Y, M, and C toners on transfer paper, the color reproducibility will be far from the color tone of the original. Therefore, it is necessary to set in advance the amounts of Y, M, and C toners that adhere to each latent image on the photoreceptor to obtain a good color image.

The above-mentioned methods for setting the toner adhesion amount include a method of controlling the surface potential of each latent image by adjusting the charging conditions and exposure conditions of the photoreceptor, and a method of controlling the developing bias of the developing device for each color of Y, M, and C. , Y, M, and C color developing devices are known. By these methods, the adhesion amount of each toner can be changed in various ways. Additionally, color reproducibility can also be controlled freely.

An object of the present invention is to provide a color electrophotographic method that can reliably control the amount of toner adhesion of each color in a cylinder and obtain good color 4'lA properties using a method different from these methods.

Hereinafter, the present invention will be explained in detail using examples.

The spectral reflectance characteristics of general three-color toners used in the above-mentioned color electrophotography method are as shown in FIG. In the figure, the horizontal axis shows the wavelength in nm, and the vertical axis shows the spectral reflectance of the toner in chi. When using toner with the characteristics shown in this figure, good color reproducibility can be obtained.The balance of adhesion amount of Y, M, and C toners is determined from the experimental results. It was found that the order of M)C)Y should be used (the amount of adhesion becomes the maximum value).

The preferred adhesion amount ratio of Y, M, and C toners is Y:M:
C=0.5-1.0:1:, 0:0.7-1.0 (weight ratio).

The balance of the above adhesion amount is 1. This can be easily obtained by independently controlling the toner concentration in each color developer.

Now, the amount of toner adhering to the latent image on the photoreceptor is expressed by the following equation.

ε M=Ku・ξ・DōrokuT<v, −Vk)・・・・・・・・・
・Co., Ltd. M: Toner adhesion amount m: Toner mass q: Toner charge amount ξ: Replenishment amount of developer to the photoreceptor ε0: Dielectric constant in vacuum D: Effective thickness of the photoreceptor L) b = Development Effective thickness of the agent vo: Surface potential of the image area on the photoreceptor Vk: Development start voltage.

Further, it is known that the relationship between toner concentration and toner charge amount is as shown in FIG. The horizontal axis of the figure shows the toner concentration in weight%, and the vertical axis shows the toner charge amount q/m in μc/
It is indicated by g.

From the above equation (1), toner adhesion amount M and toner charge amount q
It can be seen that it is inversely proportional to /m. Therefore, Y, M,
The preferable M'kl ratio of each color toner of C is Y:M:
If C=0.7:1:0.9 (weight ratio), the toner charge amount ratio will be the reciprocal of the ratio.

That is, 1. 1 Y:M:C=-:　　　　　　　,.

0.7 =1.42: 1: 1.11 And it is sufficient.

Now, when using a toner whose relationship between toner concentration and toner charge amount is shown by the solid line in Figure 3, if the charge amount of M toner is set to 10 μc/g, the toner concentration will be approximately 10 μc/g. 7% by weight, the charge amount of Y toner is 14.2μC/
g%) From Figure 3, the toner concentration is approximately 2% by weight, the charge amount of C toner is 11.1 μC/g, and the toner concentration is approximately 5.5.
It turns out that it is sufficient to control it to m%.

That is, if the control conditions for the toner density of each color developer are set as described above, a good image with well-balanced color can be obtained. As a method for controlling the toner concentration of the developer in the developing device for each color, various known methods such as reactance measurement, bulk density detection, and development ability detection can be employed.

As described above, according to the present invention, color copies with good color reproducibility can be obtained by a simple method.

[Brief explanation of the drawing]

Figure 1 shows an example of the characteristic curve of a color separation filter used in color electrophotography, and Figure 2 shows an example of the spectral reflectance characteristic curves of three color toners used in color electrophotography. 3 are characteristic curve diagrams showing the relationship between the toner concentration of the developer and the toner charge amount. Figure 1 Wavelength fnml 2nd r\I wave length (nml Figure 3 Top - 6A-II (sv1%)

Claims (2)

[Claims] (1) Separate the original into three colors to create three types of latent images, develop each with a developer containing yellow, magenta, and cyan toner, and transfer them onto the same transfer paper in layers to create a color image. A color electronic photographic method characterized in that the toner concentration in the three color developers described above is independently controlled to control the color reproduction balance. (2) The toner concentration in the above three color developers is set to decrease in the order of magenta, cyan, and yellow so that the amount of toner adhering to each latent image is in the same order. A color electrophotographic method according to claim 1.