JPH0257366A - color printer - Google Patents

Abstract

PURPOSE:To prevent deviations of colors by providing a long photosensitive drum formed by scanning each monochromatic image by a laser optical system for sequentially continuously scanning each chromatic image during one main scanning to form latent images of each monochromatic image longitudinally continuously. CONSTITUTION:A laser optical system 17 continuously forms latent images of four monochromatic images simultaneously on a rotating photosensitive drum 18, and further rotates to pass the latent images under developing units 71 - 74 thereby to form the monochromatic images in parallel. On the other hand, a single slip 8 placed on a tray 23 is horizontally sub scanned synchronously with the rotation of the drum 18 by transferring means to transfer a yellow image. Thereafter, the tray 23 which places the slip 8 is returned to the initial position, and the drum 18 is reversibly rotated synchronously therewith. Then, the slip 8 is moved in a main scanning direction by positioning means, and held at a position corresponding to the second monochromatic image. Similarly magenta, cyan, black color images are sequentially lap printed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a color printer for paper sheets that forms a color image by overprinting a plurality of monochrome images.

Prior Art First, a first conventional example of a color printer will be described with reference to FIG. First, this color printer 1 includes, as its main parts, a laser optical system 3 that sequentially exposes a plurality of monochrome images with laser light 2 using a dot matrix method, a photosensitive drum 4, a transfer drum 5 that comes into contact with this, yellow, magenta ,cyan.

It is composed of developing units 71 to 74 that house black color toners 61 to 64, respectively. Here, these developing units 71 to 74 are arranged facing each other in the circumferential direction of the photosensitive drum 4, and on the other hand, a paper feed tray 9 that stores the cut paper 8, and a fixing unit that also serves as a cut paper delivery device are provided. The container 10 is provided to face the transfer drum 5.

In this configuration, the photosensitive drum 4 rotates once,
One of the monochromatic images, for example, a latent image of a yellow image (not shown) is formed by the laser beam 2 in a dot matrix method, and a yellow 1-toner 61 is applied to this F to form a yellow image (not shown). is formed. Therefore, on the cut paper 8 wound around the transfer drum 5 which rotates in synchronization with this,
The image is pressed and the yellow image is transferred.

After this, the cut paper 8 further rotates together with the transfer drum 5,
Each monochrome image of magenta, cyan, and black is sequentially overprinted every rotation. Then, the cut sheet 8 released from the transfer drum 5 is pressurized and heated by a fixing device 10 to complete a color image.

Next, a second conventional example of a color printer will be explained based on FIG. 3. Note that the same parts as those in the color printer 1 described above are given the same names and symbols.

Explanation will also be omitted. In this color printer 11, instead of the transfer drum 5, an endless belt-shaped transfer belt 12 is stretched approximately horizontally, and four photosensitive drums 41 to 44 are mounted on the upper surface of the belt.
are placed opposite to each other.

Moreover, so as to face these photosensitive drums 41 to 44,
Four laser optical systems 31 each forming one monochromatic image
~:34. Four developing devices 71 to 74 are provided.

Furthermore, a paper feed tray 9 is attached so as to face the front end of the transfer belt ]-2, and a fixing device 1o is attached so as to face the rear end.

In such a configuration, each of the laser optical systems 31 to 34 operates in sequence in synchronization with the transfer of the transfer bell 1 to 12 that conveys the placed cut sheet 8, and each of the photosensitive drums 41 to 44
7, each monochrome image is formed.

Then, each photosensitive drum 41 to
44 monochrome images are sequentially printed one on top of the other to form a color image.

Next, a third conventional example of a color printer will be explained based on FIG. 4. The configuration of this color printer 13 is similar to that of the color printer 1 described above, except that four laser optical systems 31 to 34 and developing devices 71 to 74 are arranged in parallel.

In such a configuration, for example, first, a yellow image is formed on the rotating photosensitive drum 4 by the laser optical system 31 and the developing device 71, and this is transferred onto the cut paper 8 wound around the transfer drum 5. .

Thereafter, the laser optical systems 32 to 34 and the developing devices 72 to 74 operate in sequence for each rotation of the photosensitive drum 4, and each monochrome image is overprinted on the cut paper 8, thereby completing a color image. do.

Next, a fourth conventional example of a color printer will be explained based on FIG. 5. This color printer 14 includes - laser optical systems 3 and a mirror 1 that reflects the laser beam 2 irradiated from the laser optical system 3 onto each of the photosensitive drums 41 to 44.
The color printer 11 has the same configuration as the color printer 11 described above except that 51 to 154 are provided.

In such a configuration, the laser optical system 3 operates continuously to sequentially form latent images on the photosensitive drums 41 to 44F,
A color image is formed on the conveyed cut sheet 8 in substantially the same manner as the color printer 11 described above.

The problems to be solved by the invention and the color printers 1, 11, 13, 14 as described above are as follows:
For example, four types of color toner 61~
64 etc., it is possible to obtain a variety of color images.
It is effective. However, multiple laser optical systems 3
1 to 34 have characteristic differences due to manufacturing errors in the laser light source and polygon mirror, which are single-tone generating members. Further, the plurality of photosensitive drums 41 to 44 also have dimensional errors, sensitivity differences, and the like. In other words, multiple laser optical systems 3
1 to 34, or a plurality of photosensitive rams 114.41 to 4 due to various errors as described above.
Electrostatic intensity differences, positional deviations, etc. have occurred in the latent image formed in 4. Therefore, the quality of the first print is low because color balance is likely to be disrupted and color deviations are likely to occur. in this way.

It has been found that it is desirable for a color printer to have a structure in which members such as the laser optical system 3 and the photosensitive drum 4, which are directly involved in forming one image, are integrated into one. Here, the above-mentioned color printer 1- has a structure using - laser optical systems 3 and photosensitive drums 1. However, in this color printer 1-, the laser optical system 3 is connected to the photosensitive drum lz
Since one monochromatic image is formed every rotation of the photosensitive drum 4, the start timing of image scanning and the rotation of the photosensitive drum 4 must be precisely synchronized. However, this is difficult in reality, and misalignment is likely to occur between the photosensitive drum 4 and the transfer drum 5 as they rotate once. Therefore, images printed by such a color printer 1 tend to have color shift, especially in the sub-scanning direction.

Means for Solving the Problem A single laser optical system is provided that sequentially scans each monochromatic image during one main scan, and the latent image of each monochromatic image is scanned by this laser optical system in the longitudinal direction. A long photosensitive drum is provided which continuously forms latent images on the photosensitive drum, and a plurality of developing devices each containing a different color 1 hener are provided opposite the position of each latent image on the photosensitive drum. A positioning means is provided for sequentially positioning each latent image on the photosensitive drum, and a transfer means is provided for moving the fit slip in a sub-scanning manner with respect to each latent image on the photosensitive drum.

Function: By providing a single laser optical system that scans each iB color image sequentially and continuously during one main scan, the laser optical system that scans the latent image of each qt color image is the same, so multiple One long photosensitive drum is provided, which has no characteristic differences that exist between individual laser optical systems, and which is scanned by the laser optical system to form a latent image of each monochromatic image continuously in the longitudinal direction. Since the photosensitive drum on which each latent image is formed is the same, there is no sensitivity difference or dimensional error that exists between multiple photosensitive drums, so the electrostatic strength of the latent image of each jli color image is Differences and positional deviations are less likely to occur, and since the latent images of a plurality of monochrome images are simultaneously formed on one photosensitive drum, the positions of the latent images of each monochrome image precisely match.

Embodiment An embodiment of the color printer of the present invention will be described with reference to FIG. Note that the same reference numerals and names are used for the same parts as in the conventional example described above, and explanations thereof will be omitted.

First, this color printer 16 includes a laser optical system 17,
A long photosensitive drum 18, four developing units 71 to 74 degrees connected in the longitudinal direction of the photosensitive drum 18, a transfer means (not shown) for moving the cut paper 8 in the sub-scanning direction, and a transfer means (not shown) for moving the cut paper 8 in the main scanning direction. It is comprised of a positioning means (not shown) that moves in the direction and positions it at the position of a latent image of each monochromatic image, which will be described later. The laser optical system 17 includes a half-four body laser 1
9, various lens groups 20, a polygon mirror 2], a correction lens 22, etc. Here, for example, if the color printer 16 is about 21. A of OX300 (mm)
4 size! lj, slip 8 When m-color images on upper paper 8 are to be overprinted, what is the correction lens 20 and the photosensitive I to plum 8?

The length is approximately 4×210=840 (own). Further, the positioning means is provided to position the cut sheet 8 placed on the tray 23 at the position of each latent image on the photosensitive drum 18 using a position sensor or the like. Furthermore, the transfer means 1 transfers the a
It is provided to move the cut paper 8 which has been subjected to Vl in the sub-scanning direction in synchronization with the rotation of the photosensitive drum 18.

In this configuration, the laser optical system 17 of the color printer 16 simultaneously forms four m-color latent images in succession on the rotating photosensitive drum 18. Therefore, this photosensitive drum 18 further rotates, and each latent image is transferred to each developing device 7.
1 to 74, each monochrome image is formed in parallel.

On the other hand, the tB placed on the tray 23 waiting at the initial position
The slip 8 is the first one of the photosensitive drums 18! 31° opposite the position of the color image. and by means of transcription.

This cut sheet 8 is moved horizontally in sub-scanning in synchronization with the rotation of the photosensitive drum 18, and, for example, a yellow image is transferred thereto.

Thereafter, the tray 23 on which the cut paper 8 has been placed returns to its initial position, and in synchronization with this, the photosensitive drum 18 is also reversed.

Next, the paper cut 8 is moved by the positioning means in the main scanning direction, which is the longitudinal direction of the photosensitive drum 18, and is held at a position corresponding to the second monochrome image.
Single-color images of magenta, cyan, and black are sequentially printed one on top of the other. Then, the upper paper 8 is pressurized and heated by a fixing ri (not shown) to complete a color image.

Effects of the Invention The present invention provides a laser optical system that scans the latent image of each monochromatic image by providing one laser optical system that sequentially and continuously scans each monochromatic image during one main scan as described above. Since the system is the same, there is no characteristic difference that exists in multiple laser optical systems, and the latent image of each Qi color image is formed continuously in the longitudinal direction by scanning with this laser optical system. By providing one long photosensitive drum, each latent image is formed on the same photosensitive drum, so there is no sensitivity difference or dimensional error that exists between multiple photosensitive drums, so each monochrome image can be Electrostatic intensity differences and positional deviations of the latent images occur.Furthermore, since the latent images of multiple monochrome images are simultaneously formed on one photosensitive drum, the position of the latent image of each monochrome image is Since the colors match precisely, it is possible to perform beautiful, high-quality printing without any misalignment of the five colors or loss of color balance.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a color printer according to an embodiment of the present invention;
FIG. 2 is a vertical side view of the first conventional color printer;
FIG. 3 is a vertical side view of a second conventional color printer;
FIG. 4 is a vertical side view of a second conventional color printer;
FIG. 5 is a longitudinal sectional side view of a fourth conventional color printer. 61-64...Color toner, 71-74...Developer, 8...Slip paper 516...Color printer, 17
・Laser optical system, 18...photosensitive drum

Claims (1)

[Claims] In a color printer that forms a color image by overprinting a plurality of monochrome images on a cut sheet, a single laser optical system is installed that sequentially and continuously scans each monochrome image during one main scan. A long photosensitive drum was provided on which latent images of the monochromatic images were continuously formed in the longitudinal direction by being scanned by the system, and different color toners were stored opposite the positions of the respective latent images on the photosensitive drum. A plurality of developing devices are provided, a positioning means is provided for sequentially positioning the cut paper at the position of each latent image on the photosensitive drum, and the cut paper is moved in a sub-scanning direction with respect to each latent image on the photosensitive drum. A color printer characterized by being provided with a transfer means.