JPH063560B2 - Color electrophotographic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application range] The present invention relates to a means for correcting unevenness in the exposure amount in the longitudinal direction of an exposure slit of a color electrophotographic apparatus.

[Conventional technology]

In the case of a PPC type color electrophotographic apparatus, for example, a drum provided with an electrophotographic photosensitive member is subjected to color separation exposure of an original using a color separation filter, and the resulting color separation latent image is
The process of developing with a toner of a corresponding color and transferring the obtained toner image onto a transfer paper is repeated 3 to 4 times to superimpose the toner image on the transfer paper and further perform post-fixing to obtain a full-color image.

In the above apparatus, a color separation filter provided with a multi-layered thin film on a transparent glass substrate is conventionally used as a color separation filter in order to improve the color separation property and increase the amount of transmitted light. A dichroic mirror that cuts light (hereinafter referred to as a multilayer film filter or the like) is used.

This multilayer film filter or the like is formed by alternately depositing a high-refractive index material (eg CeO ₂ , refractive index n = 2.25) and a low-refractive index material (eg MgF ₂ , n = 1.38) on a glass substrate or the like for 10 to 2
A thin film of 0 layer is provided.

[Problems to be solved by the invention]

When this multi-layer filter or the like is used in a color electrophotographic apparatus, uneven deposition (uneven thickness) or angular characteristics (3rd
As shown in Figure (a), when the incident angle θ of the light to the multilayer filter X etc. becomes large, the transmission wavelength shifts to the short wavelength side like the spectral transmittance of the multilayer film edge color filter in Figure 3 (b). To do. ), In the longitudinal direction of the exposure slit, the photoconductor Y
Exposure unevenness may occur on the top. As a result, uneven density or uneven color (uneven color tone caused by uneven density of each color) may occur in the copied image. In the figure, Z is the original and Y
Is a photoconductor, and V is a platen glass.

This is because it is difficult to form a vapor-deposited film having a uniform film pressure over the entire surface of the glass substrate during manufacture when the filter has a large vapor deposition unevenness. If a color separation filter is provided near the shooting lens, the area of the filter can be reduced and uneven deposition can be reduced, but on the other hand, if the surface accuracy of the glass substrate is not made extremely high, the prism effect will appear and the difference in the refractive index due to each color light will become large, and each color will become large. The position of the light image of is different and causes a color shift, which is not practical. Therefore, it is necessary to provide the color separation filter near the exposure slit, and the size of the filter becomes close to the size of the exposure slit, which increases the size.

For example, in a 40 mm × 240 mm edge-colored multi-layer film filter required to obtain an exposure width that covers the A4 size longitudinal direction, the film thickness tends to be thicker in the central portion and thinner in both end portions, and thus the vertical The wavelength of light transmitted is shifted to the shorter wavelength side by about 10 nm at both ends as compared with the central portion.

Further, due to the above angle characteristics, in the above filter, each incident light (θ) at the end is 1 as shown in FIG. 3 (b).
It becomes 5 °, and the transmittance is 50% compared to the central part (θ = 0 °)
The wavelength of about 6 nm shifts to the short wavelength side.

Due to the above problems, uneven exposure occurs on the photoconductor in the longitudinal direction of the exposure slit. Especially when a photoconductor with a relatively low spectral sensitivity of a short wavelength is used, or when an illumination lamp with a relatively short spectral energy of a small wavelength is used, the effect of the short wavelength shift of the transmitted light becomes large. Problems occur with copied images. Note that the wavelength shift of the transmitted light may have an influence on the color separation property, but in the actual copy image, the influence of uneven density or uneven color due to uneven exposure is dominant. It has been confirmed that the problem due to the difference in color separation in the longitudinal direction of the exposure slit can be ignored if the wavelength shift width of the transmitted light is large.

Generally, in a black-and-white electrophotographic copying apparatus, a method is known in which a mask plate is provided in the scanning direction at the exposure slit to adjust the exposure amount in order to correct the exposure unevenness.

However, in a color electrophotographic copying machine, it is possible to perform exposure using three color separation filters for blue, edge, and red, and to perform monochromatic color copying by white light exposure without using a color separation filter. In addition, since the dichroic mirror is commonly used for each exposure to correct the color separation filter characteristics, it is extremely difficult to correct the exposure unevenness in each color separation exposure with the mask plate provided in the exposure slit part. Difficult to do. This is because the unevenness of vapor deposition of a multi-layer film filter and the unevenness of exposure on the photosensitive member due to the angle characteristic are not the same for each color of blue, edge, and red (including white in some cases).

[Object of the Invention]

The present invention provides a color electrophotographic apparatus provided with an exposure unevenness correcting means improved in view of the above problems.

[Means for Solving Problems] In order to solve the above problems, the present invention has a plurality of color separation filters for color-separating color image light, and image light obtained by slit exposure of an original is In a color electrophotographic apparatus which forms an image on a photoconductor through a color separation filter, a correction means for correcting uneven exposure of image light from a document in a slit longitudinal direction is provided in the color separation filter. It is characterized by being.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples shown in the drawings.

FIG. 4 shows an example of a transfer type color electrophotographic copying apparatus to which the present invention is applicable.

In FIG. 4, reference numeral 1 denotes a photosensitive drum having a three-layered photosensitive member including an insulating layer, a CdS photoconductive layer, and a conductive layer, which is rotatably supported by a shaft 2 and in the direction of an arrow 3 by a copy command. To start rotating. When the photosensitive drum 1 rotates to a fixed position, the original O placed on the original table glass 4 is illuminated by the halogen lamp 5. The reflected light is reflected by the first scanning mirror 6 and the second scanning mirror 7, passes through the lens 8 and the third mirror 9, and is color-separated by the multilayer blue filter 101 of the color separation filter group 10, and further the fourth mirror. (Dichroic mirror with a multilayer film that reflects visible light and transmits near-infrared light) removes the near-infrared light component in the optical image that reduces the color separation that cannot be suppressed by the multilayer film filter. Only the light component is imaged on the photosensitive drum 1 by the exposure unit 12. At the same time, a uniform exposure of near-infrared light is given to the exposure unit 12 through the fourth mirror 11 by the plurality of tungsten beans L arranged in the axial direction of the drum 1. The uniform exposure is performed for the improvement of l _og E (exposure amount logarithmic) -V S _(surface potential) characteristics of power saving latent image.

The photosensitive drum 1 is uniformly discharged by the AC charger 13 and the pre-exposure lamp 14, and then charged by the primary charger 15 to a positive polarity, and then by the secondary charger 16 a blue color separation image at the exposure unit 12. At the same time as the exposure (slit exposure) is applied, the negative polarity charge is removed. A large number of grid wires are provided in the casing opening of the secondary charger to control the static elimination potential. Further, by exposing the entire surface with the entire surface exposure lamp 17, a blue color separation latent image is formed on the drum 1.

The electrostatic latent image on the photosensitive drum 1 is next developed by the developing device group 18.
It is visualized as a donor image. The developing device group 18 includes yellow 18a, magenta 18b, cyan 18c, and black 18d.
It consists of four developing units, and the developing unit designated corresponding to the color separation filter used for exposure works to obtain the toner image of the required color. The latent image is developed by the yellow developing device 18a.

The transfer material 20 in the cassette 19 is fed into the machine by a paper feed roller 21, and the tip of the transfer material is the gripper 2 of the transfer drum 23.
It is grasped by 31. The mesh screen 232, which is the transfer material carrying sheet of the transfer drum 23, has the charges on the front and back sides of the screen removed in advance by the AC charging devices (separation charging devices) 234 and 235 for separation.

The transfer material held by the gripper 231 of the transfer drum 23 is conveyed while being wound around the screen 232 as the transfer drum 23 rotates, and transferred to the transfer charger 232 and the photosensitive drum 1.
While the transfer material passes through the gap, the yellow toner image on the photosensitive drum is transferred onto the transfer material and the transfer material is held on the screen surface by electrostatic attraction.

The transfer drum 23 grips the front end of the transfer paper 20 by the gripper 231 and rotates a required number of times while being electrostatically attracted to the mesh screen, and the toner image of the required number of colors is transferred. That is, in the case of a full-color copy, a magenta toner image is formed by color separation exposure using a multilayer film edge color filter after the transfer of the yellow toner image described above, and the magenta toner image is aligned and transferred onto the transfer paper. Furthermore, the red filter of the dye film combined with the transparent glass (for the red filter, it is not necessary to use a multi-layer film filter in terms of color separation and the amount of light passing therethrough. Cyan toner image is formed by the color separation exposure using the () which does not occur) and is aligned and transferred onto the transfer paper.

After the transfer of the three color toner images is completed, the gripper 231 is released when the front end of the transfer material approaches the separation position, and the separation charger 234 is released.
And 235 work, the transfer material and the screen are both discharged, and the transfer material is separated by the approach of the separation claw 236 to the screen.

After the transfer material is separated, the transfer belt 27 guides the transfer material to the heat roller fixing device 28 to define the heat, and then discharges it to the tray 30. The surface of the photosensitive drum 1 after the transfer is cleaned by a cleaning device 31 composed of an elastic blade, and the process proceeds to the next cycle.

It should be noted that the apparatus shown in FIG. 4 can also perform monochromatic color copying by exposure to white light. When this copying is performed, exposure is performed through the transparent glass plate in the color separation filter group 10 to form a latent image and then development. Development is performed by a one-color developing device in the device group 18.

FIG. 1 is an explanatory view of an exposure mask M provided on a color separation filter or a transparent glass plate (hereinafter referred to as a color separation filter) F in the color separation filter group 10 of the apparatus shown in FIG. In the figure, a is an effective exposure area in the longitudinal direction of the exposure slit, and b is an effective exposure area in the exposure scanning direction. As the exposure mask M, a black paper or the like is directly attached to the color separation filter or the like so as to correct the unevenness of exposure. Alternatively, as shown in FIG. 2, an adjustable thin metal plate mask m provided near a color separation filter or the like.
An exposure frame S having 1 to m3 (the masks m1 and m2 are fulcrums P
Is adjustable in the direction of the arrow with respect to the center and can be fixed with the screw N together with the mask m3).

[Effect]

According to the present invention, a good color copy image having no density unevenness or color unevenness can be obtained with the above-described simple structure.

[Brief description of drawings]

1 and 2 are front views of an exposure correction mask used in combination with the color separation filter of the present invention, and FIGS. 3 (a) and 3 (b) are explanatory views of angular characteristics of spectral transmittance of a multilayer thin film filter. FIG. 4 is a sectional view of a color electrophotographic copying machine to which the present invention is applied. In the figure, 1 ... Photosensitive drum, 4 ... Original platen glass, 10 ... Color separation filter group, 11 ... Dichroic mirror, 23 ... Transfer drum.

Claims (1)

[Claims] 1. A color electrophotographic apparatus having a plurality of color separation filters for color-separating color image light, wherein image light obtained by slit exposure of an original is imaged on a photoconductor through the color separation filter. The color electrophotographic apparatus is characterized in that the apparatus has a correction means for correcting unevenness of exposure of image light from a document in a slit longitudinal direction, and the correction means is provided in the color separation filter.