JPS63301068A - Method for exposing image of colored electrophotography - Google Patents

Abstract

PURPOSE:To execute the exposure of an image with high contrast without increasing power consumption by illuminating an original with fluorescent lamp obtained by mixing plural kinds of phosphors having different light emission peak wavelengths respectively at the time of separating the color of original. CONSTITUTION:By illuminating the original 1 with the fluorescent lamp 3 obtained by mixing plural kinds of phosphors respectively having different light emission peak wavelengths, at the time of separating the color of the original, the difference of density between desired color and undesired color of color substance of the original in the respective light emission peak wavelengths can be enlarged. Then, potential contrast between the desired color and undesired color in a sensitive substance to which the light beam from the original is radiated becomes high. Thus, the mixture of undesired color into desired color after developing is reduced and the turbidity of color can be improved. By selecting the light emission peak wavelength of a light source itself, the loss of light quantity can be made extremely small and the power consumption at the time of separating color can be suppressed low.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an image exposure method for color electrophotography, and in particular,
The present invention relates to a color separation image exposure method for forming a latent image on a sensitive material in color electrophotography.

[Conventional technology]

As one of the color image recording methods, a method is known in which monochrome electrophotography is repeated as many times as necessary. for example,
Using yellow, magenta, and cyan toners, processes such as exposure and development are repeated three times to obtain a color image. According to this electrophotographic method, color images can be obtained more easily and in a shorter time than with printing methods or color photography methods. However, the image quality is generally inferior to that of printing methods and color photography methods.

The reason for this is that sufficient contrast cannot be obtained between necessary and unnecessary colors at the stage of latent image formation, and that color correction called masking, which is widely used in printing, cannot be easily performed. Can be mentioned.

The conventional color electrophotographic method will be explained below with reference to FIGS. 4 to 6.

FIG. 4 shows the image forming process of a conventional color electrophotographic method using a powder development method.

The sensitive material is first uniformly charged by a charger.

Next, the color original image is irradiated with a fluorescent lamp, and the colors are separated by a color separation filter having transmission characteristics as shown in FIG. Ru. In addition, in Fig. 5, IOB, IO
G and IOR are respectively blue.

The characteristics of the filter for green and red separation are shown.

Next, this color latent image is developed with toner of a complementary color to the color of the color separation filter, and then a toner image on the sensitive material is formed on paper in a transfer process.

The above-mentioned series of cycles is repeated a number of times for the necessary colors to transfer the necessary engraving onto the paper, and then fix the toner on the paper. Usually, the number of repetitions is red separation/cyan toner development, green separation/magenta toner development.

There are three times: blue separation and yellow toner development, and black toner development may be added depending on the case.

For example, let's consider a case where a printed matter becomes an original image, and consider negative decomposition and development.

FIG. 6 shows the reflection characteristics of process ink during each color separation, and in FIG. 6(a), IIC, IIY! J C Reflection characteristics of the overlapping part of cyan ink, yellow ink, and magenta ink during red separation, in the same figure (b), 11M.

11CY is the reflection characteristic of the overlapping part of magenta ink, cyan ink, and yellow ink during green separation. In the same figure (C), llMC', IIY is the reflection of the overlap of magenta ink and cyan ink during blue separation, and the reflection of yellow ink. Show characteristics.

In this FIG. 6, the two reflection characteristics in each color separation indicate the colors that should be developed, or necessary colors, and the colors that should not be developed, or unnecessary colors, in each color separation. For example, during red separation, cyan becomes a necessary color, and yellow and magenta become unnecessary colors.

During color separation, the three color filters having the characteristics shown in FIG. 5 are sequentially exposed to light, so that the photosensitive material is illuminated with an amount of light corresponding to the average reflectance of the original image in the transmission range of each filter. Decrease the potential on the sensitive material. Therefore, the post-exposure potential on the photosensitive material is determined for the necessary color and unnecessary color from the above steps, and the potential difference becomes the contrast.

In the developing step, the developing bias in the developing device is set between the necessary color potential and unnecessary color potential so that the necessary color portion is developed with toner and the unnecessary color portion is not developed with toner.

At this time, if the contrast on the photosensitive material is not sufficient, the latitude of the development bias setting will be narrow, and changes in development characteristics due to fluctuations in temperature, humidity, etc. will easily appear in the image quality. Therefore, there is a problem that stability of image quality is impaired.

Now, if we think about red resolution exposure, we can see Figure 5.

According to FIG. 6(a), the necessary color is cyan, and the unnecessary colors are yellow and magenta, that is, red, and the difference in average reflectance between the two during red separation exposure is relatively large. At this time, for example, a wavelength of 570 nm or more is transmitted, but if this wavelength is set on the long wavelength side, this difference becomes even larger.

However, during green separation exposure and blue separation exposure, as shown in FIGS. 6(b) and (C), the green color of the process ink appears.

The unnecessary absorption of blue is large, and the transmission band of the filter during color separation is 5Q nm at half value of green exposure and 11 nm at half value of pre-exposure.
00n, the average reflectance difference between the necessary color and unnecessary color is small, and the contrast is not sufficient, indicating that it is necessary to optimize the peak wavelength of color separation.

The above can be said about the solid portion of the original image, but the contrast is further reduced in the line image portion. In the case of a line image, due to the resolution of the lens, light from the surrounding non-image area wraps around the line image area, and the amount of light illuminated on the photosensitive material is greater than that of a solid area, resulting in the required color sensitivity. This is because the potential on the material is lower than that in the solid part.

Therefore, in terms of image quality, it is the highly colored red of the original painting.

Problems arise in that color mixing occurs in the green and body parts, resulting in a loss of vividness, low-density solid parts, and even thin lines that are not reproduced.

In order to deal with this, in the past, an adjustment section was provided that could adjust the exposure rate, development bias, etc. according to the characteristics of the original image, and the operator made adjustments according to a certain adjustment procedure to a certain degree of satisfaction. The method is to adjust the image quality to the best possible level.

[Problem that the invention seeks to solve]

However, such a method not only requires a complicated adjustment mechanism, but also requires a dedicated operator for adjustment. That is, it is difficult for general customers to obtain satisfactory image quality with simple adjustments. Also,
Without sufficient contrast between necessary and unnecessary colors,
Since color correction is performed in the entire adjustment section, it has the disadvantage that it is difficult to maintain stability in image quality.

In order to improve this point, a method can be considered in which a halogen lamp having spectroscopically smooth emission characteristics is used as a light source, and a color separation filter is combined with this to optimize the transmission band of the filter.

However, in this case, since it is necessary to narrow the transmission band of the filter, there is a large loss and an excessive amount of light is required. This increases the power consumption of the lamp, which in turn increases the power consumption of the entire copying machine, and causes problems such as not being able to use a commercial power source with a power capacity of 1.5 to ν^.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to perform image exposure with high contrast without increasing power consumption.

[Failure to solve the problem]

In order to achieve the above object, the image exposure method for color electrophotography of the present invention includes illuminating the original with a fluorescent lamp containing a mixture of multiple types of phosphors each having a different emission peak wavelength during color separation of the original. Accordingly, the difference in density between the necessary color and unnecessary color of the coloring material of the document at each of the emission peak wavelengths is increased.

The plurality of types of phosphors can be used for noble exposure, green exposure, and red exposure, respectively, and their emission peak wavelengths can be set to the following wavelengths.

For front light: 445±10nm For green exposure: 515±10nm For red exposure: 620±10nm or more Also, as a phosphor for red exposure, 3.5! Jg 0.0.51Jg
It is preferable to use Fz.GeO2:Mn.

[Effect]

First, the principle of the present invention will be explained.

The inventors first investigated the color characteristics of process inks used in various printed materials in order to understand the color characteristics of the original images. At this time, we introduced an index called color separation efficiency as an index to quantify the influence of process ink color characteristics on contrast. Here, the color separation efficiency E is given by the following equation.

However, DW (λ): Required color density DU (λ): Unnecessary color density D (λ) = -LOG (R (λ)) R (λ): Process ink spectral reflectance Here, the required color, unnecessary color, and is, for red decomposition,
This is the overlapping area between yellow and magenta, the overlapping area between magenta, cyan and yellow during green separation, and the overlapping area between yellow and magenta and cyan during blue separation.

Here, the color separation efficiency E(
λ), the results shown in FIG. 1 were obtained. In the figure, 88.8G and 8R indicate blue, green, and red decomposition efficiencies, respectively.

The following can be seen from Figure 1.

Due to the color characteristics of the original printed matter, that is, the unnecessary absorption of the original color materials, the maximum contrast that can be obtained during color separation is
It is largest during red decomposition, and decreases in the order of green decomposition and blue decomposition. Therefore, the contrast expansion effect obtained by selecting the color separation wavelength range also follows this order.

Further, the peak wavelengths at which the color separation efficiency is maximum are 445 nm for blue separation, 515 nm for green separation, and 6200 m or more for red separation. In other words, taking into consideration the color characteristics of the coloring material of the original,
The maximum contrast can be obtained by matching the peak wavelength of the wavelength band during color separation to the wavelength at which the color separation efficiency is maximized.

Therefore, by performing image exposure using a fluorescent lamp containing a mixture of a plurality of types of phosphors each having a peak emission at the above-mentioned wavelength, the difference between the necessary color density and unnecessary color density in each color separation increases. As a result, the potential contrast between the necessary color and unnecessary color in the photosensitive material is increased, and color mixing into pure color portions on the image is greatly improved.

〔Example〕

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, features of the present invention will be specifically described based on examples with reference to the drawings.

FIG. 2 shows an embodiment of the present invention.

The document 1 placed on the platen glass 2 is irradiated with direct light from the fluorescent lamp 3 and indirect light via the reflector 6 . The reflected light from the original 1 is filtered through the color separation filter 7.
B, 7G, and 7H, for example, is exposed to light on a sensitive material (not shown) through a blue color separation filter 7B and a lens (not shown) to form an electrostatic latent image. The fluorescent lamp 3
In order to stabilize the light output, a lamp heater 4. A heat sink 5 is provided, and the mercury vapor pressure is controlled by a temperature control device (not shown).

The inner wall of the fluorescent lamp 3 is coated with a phosphor, and in this embodiment, a mixture of the following three types of phosphors at a certain ratio is used.

Blue BaMg, 2AQ+s O2t: [iL+
(445nm peak) Green BaMgzAI)+sO□t
:εu, Mn (515nm peak) Red 3.5Mg
()0.5MgF2・Ge0z:Mn (658nm peak) The mixing ratio is determined from the spectral transmittance of the optical system, the spectral sensitivity of the photosensitive material, the white paper reflectance, and the dark potential/bright potential contrast of the photosensitive material. It is defined by the ratio of the peak luminescence amount of each color phosphor.

Blue: Green: Red = 0.22: 0.36: 1, that is,
The amount of each phosphor is selected to obtain the above ratio.

FIG. 3 shows a system response curve obtained by multiplying the spectral transmittance of the fluorescent lamp and optical system thus obtained and the spectral sensitivity of the sensitive material. This curve is normalized and displayed with the peak luminescence value of each color as 100%.

At this time, as filters, IOB and IOG shown in Fig. 5 are used.
.

10R was used, but since the phosphor itself emits light in a specific wavelength band, the filter has less influence on color separation than when using a white light source such as a halogen lamp. Therefore, the present invention is not necessarily limited to the filter having the characteristics shown in FIG.

In addition, in this embodiment, rather than applying a narrow band color separation filter to the halogen lamp, the emission peak wavelength of the fluorescent lamp 3 itself is selected, so that the amount of light emission that does not contribute to color separation is extremely small. There is less attenuation in the filter.

Therefore, there is no need to increase the amount of light from the fluorescent lamp 3, and power consumption during color separation can be kept low.

Next, the results of imagewise exposure according to the embodiments of the present invention will be explained in comparison with the results of imagewise exposure according to the conventional method.

Now, the dark potential of the sensitive material is set to 1200 V for red, green, and blue, and the bright potential is set to 150 V for red, green, and blue.
Table 1 shows the results of measuring the potential contrast between the required colors using an electrostatic electrometer.

Table 1 Here, the conventional example is a case where the color separation filter shown in FIG. 5 is used in a halogen lamp with a color temperature of 3000 K.
This example uses the fluorescent lamp and the color separation filter shown in FIG. 5, and all other factors involved in the system response are the same.

As can be seen from Table 1, in this example, 2
An expansion of electrostatic contrast of about 00V was confirmed. As a result, the amount of cyan toner mixed into highly colored red originals, the amount of magenta toner mixed into green originals, and the amount of yellow toner mixed into blue originals has been reduced, and as shown in Table 2, the mixing of unnecessary colors has been significantly improved. It has become possible to improve color turbidity in highly chromatic reproduction.

Table 2 As can be seen from Table 2, the improvement effect on red is particularly large, but red is an important color as seen in vermillion, etc., and by clearly reproducing red, there is a visual improvement effect. becomes large. The degree of improvement regarding blue is small, but it is not a big problem since blue is originally difficult to distinguish from black.

As described above, in this embodiment, in the color electrophotography method in which one color copy is obtained through multiple copying steps, the light source for illuminating the original to be copied is a fluorescent lamp containing a mixture of multiple types of phosphors. . This phosphor is for blue, green, and red, and its emission peak wavelength is around 445 nm, 51
By setting the wavelength to around 5 nm and at least 620 nm, image exposure with high contrast became possible, and color mixture in pure color areas on the image could be improved. In particular, 3.5Mg O・0, 5Mg F 2 ・Ge O2 as a red phosphor
: When Mn is used, the emission peak wavelength is 658 nm, so as can be seen from FIG. 1, the red contrast is further improved. Note that the emission peak wavelength of each phosphor is ±1
It was possible to provide a width of 0 nm and 100 nm, and even in this case, image exposure with high contrast was possible.

〔Effect of the invention〕

As described above, in the present invention, the original is illuminated with fluorescent light, etc., which is a mixture of multiple types of phosphors each having a different emission peak wavelength, taking into account the color characteristics of the coloring materials used in the original. There is.

As a result, the difference between the density of the necessary color and the density of the unnecessary color of the coloring material during each color separation becomes large, and the potential contrast between the unnecessary color and the necessary color on the sensitive material irradiated with light from the original increases. Therefore, mixing of unnecessary colors into necessary colors after development is reduced, and color turbidity can be improved.

Furthermore, in the present invention, since the emission peak wavelength of the light source itself is selected, the loss of light amount is extremely small compared to the method of applying a narrow band color separation filter to a halogen lamp.
Power consumption during color separation can be kept low.

[Brief explanation of drawings]

Fig. 1 is a graph showing color separation efficiency for printing process inks, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a graph showing optical response in an embodiment of the present invention, and Fig. 4 is a graph showing the optical response in an embodiment of the present invention. FIG. 5 is a graph showing the spectral transmission characteristics of a color separation filter, and FIG. 6 is a graph showing unnecessary colors and necessary colors in process ink. l: Original 2 nibs Latin glass 3 2 fluorescent lamps 4: Lamp heater 5: Heat sink
6: Reflector 78, 7G, 7R: Color separation filter patent applicant Fuji Xeronsys Co., Ltd.
Masato Kobori (and 2 others)
name) 10th 445') +5 620 wavelength (nm) -2 to father-in-law 3 Figure 4 Diagram 5 =

Claims (1)

[Scope of Claims] 1. During color separation of an original, by illuminating the original with a fluorescent lamp containing a mixture of multiple types of phosphors each having a different emission peak wavelength, the original at each of the emission peak wavelengths can be separated. An image exposure method for color electrophotography characterized by increasing the difference in density between necessary colors and unnecessary colors of color materials. 2. The plurality of types of phosphors are for blue exposure, green exposure,
2. The image exposure method for color electrophotography according to claim 1, which is for red exposure and has a peak emission wavelength as shown below. For blue exposure 445±10nm For green exposure 515±10nm For red exposure 620±10nm or more 3. As the phosphor for red exposure, 3.5MgO.0.
The image exposure method for color electrophotography according to claim 2, characterized in that 5MgF_2.GeO_2:Mn is used.