JPS6381375A - Laser beam printer - Google Patents

Abstract

PURPOSE:To obtain a laser beam printer with a low piece, miniaturized, and capable of fast printing, by using half mirrors for the other reflecting mirrors other than the reflecting mirror on the rearmost end of the optical path of a laser beam out of plural reflecting mirrors. CONSTITUTION:The laser beam generated from a laser unit 1 is polarized by a scanner unit, and scans a first photosensitive drum 9, and a second photosensitive drum 10 through the half mirror 5, and a mirror 6 simultaneously. At this time, if a first shutter 7 is closed, no laser beam arrives at the first photosensitive drum 9, therefore, no image is formed on the first photosensitive drum 9, and also, a same result occurs on the second photosensitive drum 10 if a second shutter 8 is closed. In other words, laser scanning by an arbitrary picture signal can be performed selectively on the photosensitive drums 9 and 10, by controlling the first and the second shutters 7 and 8, and color printing of two colors an be produced easily.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a laser beam printer, particularly a laser beam printer having a plurality of photosensitive drums, and a laser beam printer having a plurality of photosensitive drums. The present invention relates to a so-called multi-drum laser beam printer that obtains images.

(Background of the Invention) Conventionally, in a laser beam printer using electrophotography, a laser beam modulated by an image signal is reflected by a rotating reflecting mirror (hereinafter referred to as a scanner), and the electrophotographic photosensitive Image formation is performed by scanning over the body. In this case, drum-shaped photoreceptors are often used. When this method is applied to a multi-color or full-color printer, it is necessary to superimpose a plurality of images of different colors on recording paper. The main configurations for achieving this superimposition technology are as follows.

In one configuration, a first color image signal is scanned onto a photoreceptor drum to form a latent image, and a developer is attached for visualization.
This is transferred onto a recording paper, after which the photosensitive drum is cleaned and the second color image signal is scanned again onto the same photosensitive drum to form a latent image, and the same process as the first process is performed. However, the second color developer is used. 3rd color, 4th color
. . . If there is an n-th color, the same process is repeated for the third color image signal, fourth color image signal, . . . for the n-th color image signal. In this way, one image is recorded by superimposing the development multiple times on the same recording paper.

In another configuration, the same number of photosensitive drums are provided for a plurality of image signals, a latent image is created on the photosensitive drum in one-to-one correspondence for each color image signal, and a latent image is formed using a developer of a different color. Visualization development is performed and the images are sequentially transferred onto recording paper. In this case, it is common to prepare one laser, one scanner, and one photosensitive drum for one image signal, and therefore, the same number of lasers and the same number of scanners as the image signals (number of colors) to be superimposed. The same number of photosensitive drums are required.

By the way, in the first configuration, a series of electrophotographic processes including charging, exposure, development, transfer, and cleaning must be performed multiple times in chronological order. Therefore, it has the disadvantage that it takes a very long time to print one sheet. The second configuration is characterized by being able to print in a shorter time than the first configuration, but as mentioned above, it is necessary to prepare the same number of laser scanner drums as the number of color image signals. However, the disadvantage is that the equipment becomes larger and more expensive.

The present invention eliminates the drawbacks of the conventional example, especially the problems with the second configuration, and achieves low cost by using a single laser and a single scanner to perform laser scanning on a plurality of photosensitive drums. The objective is to obtain a laser beam printer that is small and capable of high-speed printing.

(Summary of the Invention) A laser beam printer according to the present invention includes a plurality of latent image carriers, a laser unit that irradiates each image carrier with laser light modulated by an image signal, and a laser beam printer that deflects the laser light from the laser unit. A scanner unit is provided corresponding to each city image carrier on the optical path of the laser beam from the laser scanner unit, and the laser beam is scanned along the width direction of each city image carrier. The plurality of reflecting mirrors include a reflecting mirror that guides the laser beam to the latent image carrier, and a shutter that is provided between each of the reflecting mirrors and each of the image carriers and allows the laser beam to pass or not pass through the latent image carrier. Among them, the other reflecting mirrors except the one at the rearmost end of the optical path of the laser beam are half mirrors.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail according to embodiments shown in the drawings.

FIG. 1 is a schematic diagram showing the configuration of an embodiment of a laser beam printer according to the present invention.

In the figure, 1 is a laser unit that generates a laser beam modulated by an image signal, 2 is a scanner unit that deflects and scans the laser beam generated from the laser unit, and 3
9 is an fθ lens; 4 is a laser beam modulated by the image signal and further deflected and scanned by the scanner unit 2;
．． 10 is a first photosensitive drum and a second photosensitive drum on which an image is formed by laser scanning light; 5 is a drum that transmits 1/2 of the laser beam 4; and the remainder 172 is configured to scan on the second photosensitive drum 10. The reflecting half mirror 16 is half mirror 6
A mirror 7.8 that reflects the laser beam that has passed therethrough so as to scan it onto the first photoreceptor drum 9 blocks the laser beam that should reach the first photoreceptor drum 9EL and the second photoreceptor drum 10. Or let it pass. The first shutter, the second shutter, and 11 are the first photosensitive drum and the second/! This is a recording paper onto which the image formed on the five-light drum 10 is transferred. in fact,
The areas around the first and second photosensitive drums 9 and 10 are equipped with a charging device, a developing device, a transfer device, a cleaning device, etc. necessary for the electrophotographic process. These are omitted.

The operation of the laser beam printer according to FIG. 1 will be explained below. A laser beam generated from a laser unit 1 is polarized by a scanner unit and simultaneously scans a first photosensitive drum 9 and a second photosensitive drum 10 via a half mirror 5 and a mirror 6. However, this is the case where the first shutter 8 and the second shutter 8 are both in between (in a state where the laser beam can pass through).

Conversely, if the first shutter is closed, the laser light will not reach the first photosensitive drum 9, and no image will be formed on the first photosensitive drum 9. The same applies to the second photosensitive drum 10 when the second shutter 8 is closed. That is, by controlling the first shutter and the second shutter 8, it is possible to selectively perform laser scanning on the photosensitive drum 9.10 using an arbitrary image signal.

Therefore, it can be seen that two-color multicolor printing can be easily performed by changing the color of the toner in the developing device provided on the first photosensitive drum 9 and the toner provided on the second photosensitive drum 10. . That is, as shown in FIG. 2, when transmitting the image signal for the first color to the laser unit 1, the second shutter 8 is opened and the first shutter is closed, and the image of the negative color is transmitted to the second photosensitive drum 10. Form on top. Next, when the first color image signal-page is completed and the second color image signal is to be sent to the laser unit l, the second shutter 8 is closed and the first shutter is opened, contrary to the first color image signal. A second color image is formed on the first photosensitive drum 9. Then, when the above control is transferred to the recording paper 11,
The image writing position in the sub-scanning direction (circumferential direction of the photosensitive drum) should be the same for the first color and the fifth color for the second color.

On the other hand, in the configuration shown in FIG. 1, the center distance between the first photosensitive drum 9 and the second photosensitive drum 10 is set to be longer than the length of the recording paper 11 in the sub-scanning direction. Therefore, as described above, since the first color image signal and the second color image signal are sent out separately for each page, it is sufficient to open and close the first and second shutters 8 for each page. However, the present invention is not limited to this condition.For example, the first! f! , when the center distance between the optical drum 9 and the 275th optical drum 10 is shorter than the length of the recording paper 11 in the sub-scanning direction, the output timing of the first color image signal and the output of the second color image signal When the timings overlap, these image signals can be output in a time-division manner for each main scanning line, and the first and second shutters 8 can also be opened and closed for each line.

Furthermore, in the configuration shown in FIG. 1, by setting the distance from the laser unit 1 to each photosensitive drum 9, 10 to be equal, the laser scanning speed (linear velocity) on each photosensitive drum 9, 10 becomes equal. Therefore, images can be formed on each photosensitive drum 9 and 10 at the same image frequency. However, this also does not limit the present invention.

Although the present invention has been described above based on an embodiment using two photosensitive drums, the present invention is not limited to this, and is applicable to all cases where two or more plural drums are used.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of a laser beam printer according to the present invention, and FIG. 2 is a diagram showing image signals and shutter opening/closing timing. 1...Laser unit 2...Scanner unit 3...Fθ lens 4...Laser beam 5...Half mirror 6...Mirror 7.8-...Shutter 9.10...Photosensitive drum 1
1... Recording paper

Claims (1)

[Claims] a plurality of latent image carriers, a laser unit that irradiates each of the latent image carriers with laser light modulated by an image signal, and a laser unit that deflects the laser light from the laser unit in the width direction of each of the latent image carriers; a scanner unit that scans along the laser scanner unit; a reflecting mirror that is provided on the optical path of the laser beam from the laser scanner unit corresponding to each of the latent image carriers and guides the laser beam to the latent image carrier; A shutter is provided between each reflecting mirror and each of the latent image carriers to allow the laser beam to pass through or not pass through the latent image carrier, and the shutter is provided at the end of the optical path of the laser beam among the plurality of reflecting mirrors. A laser beam printer characterized in that the other reflecting mirrors except for the end reflecting mirror are half mirrors.