JPH06118743A - Image forming device - Google Patents

Abstract

PURPOSE:To miniaturize a printer engine. CONSTITUTION:This device adopts a rear light exposure system. A liquid crystal printing head 13 is used for an exposure unit. In the internal structure, optical paths are provided so that light from a light source 14 reaches the development side and the fixing side. One of the optical paths is used for the formation of a development image, and the other is for fixing toner on recording paper in a part of a photosensitive drum 1 by utilizing the photothermal energy of the light source. Since the photosensitive drum 1 acts as a part of a heat roller, an independent transfer means is not necessary. Additionally, space in the photosensitive drum 1 can be efficiently used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus.

[0002]

2. Description of the Related Art In a conventional electrophotographic image forming apparatus, as shown in FIG. 4, a charger B, an exposure section C, a developing section D, a transfer section E and a charge eliminator F are arranged around a photosensitive drum A. , And the cleaning unit G in this order. In such an image forming apparatus, the surface of the photosensitive drum A is uniformly charged by the charging device B, an electrostatic latent image is formed by the exposure part C, a toner image is formed by the toner of the developing device D, and a transfer part E is formed. Then, the toner image is transferred onto the recording paper, and the latent image remaining on the drum after the transfer is erased by the static eliminator F. The cleaning unit G cleans the residual toner, and the toner image transferred onto the recording paper is fixed by the fixing device H. An image is formed in the above steps.

[0003]

In the case of the image forming apparatus, it is very difficult to downsize the image forming unit because the respective units are independently provided around the photosensitive drum. Further, it is necessary to separately provide a fixing device (means).

[0004]

In order to achieve the above-mentioned object, a backside light system in which charging, exposure, development, cleaning and charge removal are performed in almost one process is used, and the charging used in the conventional electrophotographic system is used. The container, cleaning unit, and static eliminator are omitted. Further, a liquid crystal printer head is used as the exposure means, and one light source in the head is used for image writing exposure and fixing. Therefore, the fixing device (means) is also configured as a part of the above process.

[0005]

The liquid crystal print head is used as the exposing means in the light backside method which is characterized by means for exposing from the inside of the photosensitive drum. There is a light source such as a fluorescent lamp in the liquid crystal print head, and on the developing side, the light is exposed through the liquid crystal shutter array, and the electrostatic latent image is formed on the surface of the photosensitive drum by the control of the liquid crystal shutter array based on the image information. To form.
Then, the toner of the developing means acts on the latent image portion to form a toner image. At the same time, an optical path is provided on the fixing side, and the light from the light source generates photothermal energy via the light collecting lens. Using the heat, the entire drum is set to 1 when fixing the toner.
It also functions as one heat roller.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, regarding an outline of an image forming apparatus to which the present invention is directed. FIG. 1 is an embodiment of the present invention and shows an example of application to a facsimile apparatus using a plain paper roll.

A developing device 2, a transfer roller 4, and a fixing roller 5 are provided adjacent to the photosensitive drum 1, and the recording paper P is conveyed by a feeding roller 12 to a position before the transfer roller 4. When printing is started, the recording paper P is fed between the photosensitive drum 1 and the transfer roller 4, and the photosensitive drum starts to rotate. The photosensitive drum 1, the transfer roller 4, and the fixing roller 5 are driven by one pulse motor (not shown).

Inside the photosensitive drum 1, a liquid crystal printer head, which is an exposure device 3, is supported and fixed to a body frame.
The exposed portion causes an electrostatic latent image on the outer surface of the photosensitive drum 1, and the conductive magnetic toner from the developing device 2 moves to the outer surface of the photosensitive drum 1. The toner imaged on the outer surface of the photosensitive drum 1 by the transfer roller 4 is transferred onto the recording paper P. Then, the toner image on the recording paper is fixed by the pressure action of the silicon roller 5 (fixing roller) and the photosensitive drum 1 and the photothermal energy from the exposing means. Then, the toner on the surface of the photosensitive drum 1 is peeled off, the recording paper P is cut by the recording paper cutter 6, and is discharged to the recording paper receiving tray 7.

Image information of the original is read by the contact image sensor 8 in the original reading section. The read image information is directly stored in the RAM of the electronic circuit board 10 and sent to the transmitting side. The feed roller 9 driven by a pulse motor (not shown) is attached to the contact image sensor 8
The original R is read in the meantime and is ejected by the ejection roller 11.

FIG. 2 is a schematic view of the developing section and the exposing section in FIG. Conventionally, the exposure device C was provided along the outer side of the photosensitive drum (see FIG. 1). However, in the back exposure method, which is the main method, as shown in FIG. 2, the liquid crystal print head (exposure device) 1
3 is inside the photosensitive drum, and a developing device is provided on the side opposite to the exposure position. A developing bias and a transfer bias are applied to the sleeve and the transfer roller, respectively.

In order to allow light from the light source 14 (fluorescent lamp) in the liquid crystal print head 13 to pass therethrough, one is provided on the developing section side and the other is provided on the transfer section side. On the developing side, the light from the fluorescent lamp 14 is reflected by the first mirror 15 and the second mirror 16. The liquid crystal shutter array 17 is on / off controlled for each dot based on image information. The light emitted to the liquid crystal shutter array 17 is transmitted or blocked according to the control for each dot. One line of dots is formed in the main scanning direction along the print width, and one dot line is exposed in the sub scanning direction. The light that has passed through the rod lens 18 reaches the photosensitive drum 1. A light collecting lens 20 is provided in the optical path on the fixing side.
Is provided to generate heat around the fixing unit due to photothermal energy from the light source 14. The heat causes the toner on the recording paper P to be fixed. Also, 1
Reference numeral 9 is a control circuit board for the photosensitive drum 1, and 21 is a dustproof glass.

Next, the optical back surface type recording principle used in the present invention will be described. FIG. 3 is an enlarged view of the exposed portion of FIG. The photosensitive drum 1 is composed of multiple layers of a transparent support 23 (glass or resin), a transparent electrode layer 24, and a photoconductive layer 25 (eg, amorphous silicon), and is controlled via a liquid crystal shutter array based on image information. The light I is emitted from the inner surface of the photosensitive drum. A developing bias is applied to the sleeve 22 formed of the conductive magnetic toner layer 26, and the photoconductive layer 25 and the toner layer 26, which are in contact with the toner, have the same potential. When the charge of the toner moves to the photoconductive layer 25 and the toner layer 26 of the sleeve 22 and the photoconductive layer 25 are exposed to each other immediately before the exposure, the positive charge due to the photoexcitation moves to the surface of the photoconductive layer 25 and the photoconductive layer 25 is exposed. The surface potential drops. Then, the toner adheres to the photoconductive layer 25. The toner attached at this position is immediately separated from the sleeve 22, so that there is no time to be charged through the toner and the electric force remains strong, so that the visible image J remains attached to the photoconductive layer 25 without returning to the sleeve 22. And the visible image J
Is transferred onto the recording paper P by the transfer roller 5, and the visible image J is fixed by the pressing force of the fixing roller 5 and the heat generation of the light source 19 (see FIG. 2).

By using amorphous silicon for the photoconductive layer 25, it is possible to withstand heat of about 200 ° C., and it is possible to sufficiently cope with the heat generated during fixing.

In the above embodiments, the light source is a fluorescent lamp, but if a light source such as a halogen lamp that generates a large amount of heat and a large amount of light is used, the light collecting lens becomes unnecessary. Although the case of a facsimile machine is assumed, the invention can be applied to other machines having a printer function.

[0015]

As described above, according to the present invention, the liquid crystal print head is provided as the exposing means in the photosensitive drum. The size can be made smaller than before, and the space inside the photosensitive drum can be effectively used. Further, by utilizing the photothermal energy of the light source in the liquid crystal printer head, the heat roller used for fixing is eliminated. This is because a part of the photosensitive drum functions as a heat roller, and an independent space as a fixing unit is not necessary. This made it possible to make the body itself compact.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a facsimile apparatus to which the present invention is applied.

FIG. 2 is an enlarged view of an exposed portion of a light backside system used in the present invention.

FIG. 3 is an enlarged view of an exposed portion of FIG.

FIG. 4 is a schematic view of an image forming apparatus using a conventional electrophotographic method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Developing means 13 Liquid crystal print head 14 Light source 17 Liquid crystal shutter array 23 Transparent support 24 Transparent electrode layer 25 Photoconductive layer

Claims (1)

[Claims] 1. A photosensitive drum in which a transparent electrode layer and a photoconductive layer are provided in this order on the surface of a cylindrical transparent support, an exposing means installed in the photosensitive drum, and a photosensitive drum arranged in contact with the drum surface. Developing means, wherein the exposing means includes one light source and two
An image forming apparatus having two optical paths, one of which is directed to the developing means side through the liquid crystal shutter array and the other of which is directed to the other inner surface of the photosensitive drum.