JPH01180573A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the generation of a moire by inclining the direction of a dot point of a dot image on a photosensitive body and the direction in which color separation function elements of the photosensitive body are arranged in the shortest period. CONSTITUTION:As for the filter arrangement shape of R, G, B, etc., in the color separation layer 3a of an insulating layer 3, a mosaic-like arrangement is used mostly. Also, the arrangement direction of the shortest period or the arrangement direction of the period being near said period is Xi-Xi (i=1-3). Subsequently, the arrangement shape of a mosaic is determined so that the direction of a dot point for making 45 deg. against an original avoids the direction of the substantially shortest period of a mosaic arrangement shape. That is, the mosaic arrangement is determined so that the direction of the shortest period of the mosaic arrangement is inclined against the dot point direction which is projected at an angle of + or -45 deg. against the direction being parallel to the rotary axis of a photosensitive body 4. In such a way, no moire is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a color image forming apparatus, and in particular, the present invention relates to a color image forming apparatus, and in particular, the present invention relates to a color image forming apparatus that has a color separation function member in its surface and uniformly applies electric discharge to a photoreceptor whose surface is an insulating layer. After performing charging, forming a primary latent image by imagewise exposure and discharging, forming an electrostatic image by uniform exposure to specific light and developing with the corresponding color toner are repeated to synthesize a color toner image. The present invention relates to an apparatus for forming color images.

[Background of the invention]

The present inventors have previously completed various inventions regarding the above-mentioned image forming apparatus (Japanese Patent Application No. 185440, No. 59, No. 187044, No. 229524, No. 60, etc.). According to such an image forming apparatus, a color image can be formed on a photoreceptor without color shift, and a monochrome image can also be formed with the same image density and resolution as in a monochrome copying machine. However, when reproducing a document image composed of halftone dots, moiré may occur. The cause of this was investigated as follows.

The halftone dot image of printed matter is 60 to 6 on coarse materials such as newspapers.
A mesh of 5IiI, that is, a halftone dot array pitch of 423 to 390 μml lines, a mesh of 85 to 100 lines, that is, a halftone dot array pitch of 298 to 254 μm/line in general books,
For fine prints such as fine art prints, a dot registration pitch of 133 to 175 lines, ie, 190 to 145 μm/line, is used. On the other hand, the color separation function member of the photoreceptor is manufactured using printing, vapor deposition, or photoresist technology in order to form an image with sufficient resolution and density, with a unit size of 20 to 200 μm and a period of 50 to 500 μm. It is formed by an array of color separation functional elements. That is, the arrangement period of the color separation functional members on the photoreceptor is also comparable to the halftone dot arrangement pitch of the halftone image of the printed matter. Therefore, if the array direction and period of the halftone dots of the halftone dot image of the printed matter projected onto the photoreceptor match the arrangement direction and period of the color separation function member of the photoreceptor, moiré may become noticeable. Ru. In most cases, the direction in which the halftone dots are arranged in the halftone image of a printed matter, that is, the screen angle, is determined to be 45° for a monochrome image, and 45° for a black color image. However, yellow m, magenta concave, cyan (there are various cases regarding CI, Y is Oo, M
is 15° and C is 75°. When the 45° direction in black of this monochromatic image or color image comes to match the arrangement direction and period of the color separation function members of the photoreceptor, noticeable moiré will occur, and Y/M of the color image
- It was found that the direction in which the halftone dots such as C are arranged does not have much to do with the occurrence of noticeable moiré.

[Purpose of the invention]

The present invention has been made based on the above-mentioned knowledge, and has been made for the purpose of providing an image forming apparatus using a photoreceptor having a color separation function member that does not cause moiré.

[Structure of the invention]

The present invention uses a photoreceptor having a color separation function member in its surface, and after charging the photoreceptor and imagewise exposure, uniform exposure and development of the electrostatic image formed thereby are performed. In the image forming apparatus, the direction of the halftone dots of the halftone dot image on the photoreceptor is tilted to the direction in which the color separation functional elements of the photoreceptor are arranged at substantially the shortest period. This configuration achieves the above object.

〔Example〕

The present invention will be explained below using illustrated examples.

1 to 4 are schematic partial cross-sectional views showing examples of the layer structure of a photoreceptor used in the image forming apparatus of the present invention, and FIGS. 5 and 6 are filters of color separation filter layers of the photoreceptor, respectively. A partial plan view showing an example of the arrangement shape, and FIGS. 7 and 8 are schematic configuration diagrams showing an example of the image forming apparatus of the present invention, respectively.

In FIGS. 1 to 4, 1 is a conductive member formed into an appropriate shape as required, such as a cylindrical shape or an endless belt shape, and 2 is a light guide 1! made of an inorganic photoconductor or an organic photoconductor. Layer 3 is a layer consisting of minute color separation filters such as red (R1, green (G), blue CB1, etc.) formed from various polymers, resins, etc. and colorants such as dyes and pigments, that is, an array of color separation functional elements. 3a, that is, an insulating layer containing a color separation function member.The insulating layer 3 of the photoreceptor 4 in FIG. The insulating layer 3 of the photoreceptor 4 shown in FIG. The insulating layer 3 of the body 4 has a transparent insulating layer on top of the insulating layer 3 in FIG. 2, and the insulating layer 3 of the photoreceptor 4 in FIG. It is like having a transparent insulating layer on the top.

R and G in the color separation layer 3a of these insulating layers 3.

As filter array shapes such as B, mosaic arrays as shown in FIGS. 5 and 6 are often used because they are suitable for reproducing delicate multicolor images.

In the arrangement shapes shown in Figures 5 and 6, the arrangement direction with the shortest period or the arrangement direction with a period close to it is Xl-Xl.
In the arrangement direction of the shortest period shown by (i = 1 to 3), the size of each unit filter is 11 + t2 /-1 = V'
In the arrangement shape shown in Fig. 5, which has a regular hexagonal shape at t2,
-X, + X2- In Figure 5 of 3 t, = 3 fi
t2, 3t in FIG. 6, = 312, and since the ratio is 1.2 or less in the direction of the shortest period, this is the direction that is substantially regarded as the direction of the shortest period with respect to moiré.

Since the direction of the halftone dots forming the black image of the original is 45°, in the above-mentioned FIG.

-x, direction and x2-X2 direction, X2- X2 direction and X3- X, direction, or X, -X3 direction and X
, -X1 direction. Similarly, in FIG. 6, x,
-X1 direction and X2- Between X2 direction + X2- Between X2 direction and X, -X3 direction, X, -X3 direction and Xl-
The direction of mosaic arrangement is set so that the direction of the halftone dots falls somewhere between the X2 directions. In addition, as understood from the above explanation, in the arrangement shape of FIG. 5, t, < JTt2
, or t in the configuration shown in FIG.

<If t2, in addition to xl-X1 direction, Y, -
The Y direction may also need to be considered as the direction of the shortest period. Conversely, in Figure 5, 1. >JT t2
, when 11>12 in Figure 6, x, -x2 and X
It is preferable to set the arrangement direction of the mosaic so that the direction of the halftone dots is between the directions of 3-X3.

As described above, the mosaic arrangement shape is determined so that the direction of the halftone dots forming an angle of 45° with respect to the original document avoids the direction of substantially the shortest period of the mosaic arrangement shape. That is, the mosaic arrangement is determined such that the direction of the shortest cycle of the mosaic arrangement is inclined with respect to the direction of the halftone dots projected at an angle of ±45° with the direction parallel to the rotation axis of the photoreceptor 4.

Note that increasing the ratio between tl and t2 is not preferable because the directionality will depend on the shape of the filter. It is preferable that this ratio is set within 3f times in FIG. 5, and within 3 times in FIG.

The image forming apparatus shown in FIGS. 7 and 8 includes a charger 5, an image exposure device 6, a uniform exposure device 7B, 7Cr, 7
The R1-component or two-component developer is formed to a layer thickness that does not contact the surface of the photoreceptor 47, and non-contact development is performed in which an AC bias is used as the development bias to cause the toner to fly to the developer layer. Developing devices 8Y, 8M, 8C, 8K, or dischargers 9Y, 9M for smoothing the surface potential of the photoreceptor 4 after development, white light or infrared light that can pass through the toner layer. A transfer pretreatment device 10 using an exposure lamp and a corona discharger, a transfer device 11, a separator 12,
Alternatively, a pre-cleaning static eliminator 13 and a cleaning device 14 using an exposure lamp and a corona discharger are further provided to form a color image or a monochrome image on the photoreceptor 4 through the steps described below.

The photoreceptor 4 rotates in the direction of the arrow shown in FIGS. 7 and 8,
A charger 5 performs corona discharge to uniformly charge the surface of the photoreceptor 4. When the photoreceptor 4 uses an n-type semiconductor such as cadmium sulfide for the photoconductive layer 2, the corona discharge of the charger 5 is a positive discharge; If it is, it is a negative discharge. As a result, reflected light from a document placed on a document table by the image exposure device 6 is incident on the surface of the charged photoreceptor 4 as an image exposure process. This image exposure device 6 performs slit exposure using reflected light or transmitted light irradiated onto a document, in which either an optical system or a document table moves back and forth, or a document passes through a platen. Then, as the image light beam enters, the discharger 61 of the image exposure device 6 performs alternating current or direct current corona discharge of substantially opposite polarity to the charger 5. As a result, a primary latent image consisting of charge density is formed on the photoreceptor 4. This secondary latent image does not function as an electrostatic latent image to be developed. A uniform exposure device 7B uniformly applies blue light to this surface on which a latent image is formed.

Due to this uniform exposure to the blue light, a potential pattern is generated on the surface of the B filter portion of the photoreceptor 4 from the previously formed primary latent image. This potential pattern is developed by the developing device 8Y containing yellow toner to form a yellow toner image made of the yellow toner adhered to the surface of the B filter portion. The potential of the surface on which this yellow toner image is formed is set to
Smoothing is performed by a discharger 61 in the device shown in the figure, and by a discharger 9Y in the device shown in FIG. 8, and green light is uniformly incident on the smoothed surface by a uniform exposure device 7G.

As a result, a potential pattern is generated on the surface of the G filter portion of the photoreceptor 4, and this potential pattern is developed by the developing device 8M containing magenta toner, resulting in a magenta toner image consisting of magenta toner adhered to the surface of the G filter portion. form. The potential of the surface on which this magenta toner image has been formed is again smoothed by the discharger 61 in the apparatus shown in FIG. 7, and by the discharger 9M in the apparatus shown in FIG. When light is incident uniformly, a potential pattern is generated on the surface of the R filter portion of the photoconductor 4. This potential pattern is developed by the developing device 8C containing cyan toner, and the cyan toner adhering to the R filter portion is developed. A cyan toner image is formed.

As a result, yellow and magenta are printed on the photoreceptor 4.

If the color image formed by combining cyan toner images or the original image is a monochrome image, an image that appears to be a monochrome image is formed. Therefore, these toners are made easy to transfer by the transfer pre-processing device 10, and are transferred by the Hg device 11 onto the recording material P fed by the paper feed device 15.

The recording material P onto which the toner has been transferred is separated from the photoreceptor 4 by the separator 12 and transferred to the fixing device 1 by the conveying means 16.
7, the toner is fixed by the fixing device 17, and the toner is discharged outside the machine. On the other hand, the surface of the photoreceptor 4 to which the toner has been transferred is neutralized by a pre-cleaning static eliminator 13 provided as necessary, and then a cleaning blade or a cleaning roller of the cleaning device 14 is removed from the surface of the photoreceptor 4.
The remaining toner is removed by contacting the surface of the toner, and the toner is subjected to the next image forming process.

For example, in the image forming apparatus as described above, the photoreceptor 4
has a color separation layer 3a consisting of regular hexagonal color separation function elements shown in FIG. 5, and the rotation axis is x3-x of the color separation layer 3a,
The document is tilted at an angle of 15 degrees in the x and -x directions, so that the direction of the original halftone dots projected onto the photoreceptor 4 is X3-X.
, and the direction of Then, a newspaper with a black image with a 65-line mesh, a re-examination with a color image with a 100-line mesh, and an art print with a color image with a 175-line mesh are used as manuscripts, and these are placed on the manuscript table as an A-4 size manuscript. The document image is reproduced for each of the predetermined placement states, including a predetermined placement state in which the document is placed, and a placement state in which the projection on the photoreceptor rotates clockwise by 10° up to 90° from that state. In that case, depending on the angle at which the document is placed, the first
As shown in the table, moiré may or may not occur in the reproduced image, and even when rotated by 30 degrees, moiré occurs.

Table 1 In Table 1, ◯ indicates that no moire was observed, △ indicates that slight moire was observed, and × indicates that moire was clearly observed.

Table 1 shows that the tl of each microfilter shown in FIG. 5 is 50.
This is a case where a photoreceptor 4 of .mu.m is used. As can be seen from Table 1, the halftone dot inclination force X of the original projected onto the photoreceptor,
As the image approaches the X, +X2, X2+, and X3X directions, moiré begins to occur. This is the photoreceptor 4 for black images in newspapers, color images in books or art prints.
This is considered to be because the arrangement direction and period of the black halftone dots incident on the photoreceptor 4 coincide with the Xl-X direction in which they are arranged at a relatively short period in the mosaic arrangement in the color separation layer 3a of the photoreceptor 4.

Therefore, in the image forming apparatus shown in FIGS. 7 and 8, when the color separation layer 3a of the photoreceptor 4 has the distribution shape shown in FIG. , so that it deviates from the direction of the halftone dot that forms an angle of ±45° with respect to the rotation axis of the photoreceptor 4 projected on the photoreceptor 4, in practice, the angle is ±15°.
It is preferable that the mosaic arrangement is set to be more inclined than that. This is because when placing a document in a predetermined state on a document table, it is placed along the side of the document table, so that the direction of the halftone dots on the document is inclined by 45 degrees to this side. That is, it is preferable that the direction of the shortest period of the mosaic is the most distant from the halftone dots projected at an angle of 45 degrees to the rotation axis of the photoreceptor. Practically speaking, they should be separated by 15 degrees or more. As a result, when an original is placed on the document table in a predetermined state (parallel or perpendicular to the rotation axis of the photoreceptor) and image exposure 1 is applied to the photoreceptor 4 by the image exposure device 6, there will be moiré in the reproduced image. will no longer occur. Also when the color separation layer 3a of the photoreceptor 40 has the distribution shape shown in FIG.
Xi force direction 15 with respect to the halftone dot direction projected on the photoreceptor 4
If you use a mosaic photoreceptor 4 whose direction is deviated by more than 2 degrees,
The occurrence of moire can be prevented.

When forming a monochrome image with the same resolution and image density as in a monochrome copying machine using the image forming apparatus shown in Fig. 7 or 8, after image exposure, uniform exposure to blue, green, red light or white light is required. As a result, a potential pattern is formed on all the color separation filters B, G, and R portions of the photoconductor 4, and the potential pattern is applied to one or two of the developing devices 8Y, 8M, and 8G or to the black toner. The image may be developed in the developing device 8 containing the image data.

〔Effect of the invention〕

The image forming apparatus of the present invention uses a photoreceptor having a color separation layer in which color separation functional elements are distributed, and can form a color image on the photoreceptor without color shift, and can prevent moiré from occurring in the formed image. It has an excellent effect of being free of oxidation. Further, the image forming apparatus of the present invention can also form a monochrome image with the same resolution and image density as in a monochrome copying machine.

In the present invention, the color separation function member is not limited to a distribution of color separation filters, but the photoconductive layer may have a color separation function (% Application No. 59-201085, No. 60
-245177). Further, the image forming apparatus described in Japanese Patent Application No. 1995-1987 uses a photoreceptor in which a color separation function member consisting of a distribution of color separation filters is provided on the opposite side of the photoelectric layer to the side receiving the corona discharge of the charger. It can also be applied to

[Brief explanation of the drawing]

1 to 4 are schematic partial cross-sectional views showing examples of the layer structure of a photoreceptor used in the image forming apparatus of the present invention, and FIGS. 5 and 6 are filters of color separation filter layers of the photoreceptor, respectively. A partial plan view showing an example of the arrangement shape, and FIGS. 7 and 8 are schematic configuration diagrams showing an example of the image forming apparatus of the present invention, respectively. 1... Conductive member, 2... Photoconductive layer, 3...
- Insulating layer, 3a... Color separation layer, 4...
Photoreceptor, 5... Charger, 6...11!
Exposure device, 7B, 7G, 7R... Uniform exposure device, 8Y, 8M, 8
0.8K...Developing device. Patent Applicant Roku Konishi Photo Industry Co., Ltd. Agent Patent Attorney Haru Yasutaka 2-゛)ノ' Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 6

Claims (2)

[Claims] (1) Using a photoreceptor that has a color separation functional member within its surface,
In an image forming apparatus that charges the photoreceptor and imagewise exposes it, then uniformly exposes it and develops the electrostatic image formed thereby, the direction of the halftone dot image on the photoreceptor and the direction of the halftone dot image on the photoreceptor and the An image forming apparatus characterized in that the color separation function elements of the photoreceptor are arranged at substantially the shortest period in a direction that is inclined. (2) Claim 1, wherein the inclination is 15° or more
The image forming apparatus described in .