KR20070017723A - Trilevel Process Scanning Unit and Color Image Forming Apparatus Having the Same - Google Patents

Abstract

A triple level scanning unit and a color image forming apparatus having the same are disclosed. The triple level scanning unit may include: a first electrode part including fine electrodes disposed at a predetermined distance from the photosensitive member along a length direction of the photosensitive member; And a second electrode part which is insulated from the first electrode part by an insulator and surrounds the first electrode part. The color image forming apparatus includes: a photosensitive member whose surface is uniformly charged by a charger; And a triple level scanning unit configured to form positive and negative corona discharges on the photoreceptor to form an electrostatic latent image.

Image forming apparatus, printer, trilevel, triple level, potential, scanning apparatus

Description

Trilevel scanning unit and color image forming apparatus having the same {Trilevel Process Scanning Unit and Color Image Forming Apparatus Having the Same}

1 is a block diagram of a conventional electrophotographic color image forming apparatus;

FIG. 2 is a schematic configuration diagram of the laser scanning unit of FIG. 1;

3 is a perspective view of a triple level scanning unit of the present invention,

4 is a circuit diagram of FIG.

Figure 5 is a graph of the photosensitive drum surface potential change for explaining the concept of electrostatic latent image formation by the general triple level method,

6 is a graph showing potential change of the photosensitive drum by the triple level scanning unit of the present invention.

<Description of the symbols for the main parts of the drawings>

1: first electrode portion 2: second electrode portion

2a: shield 2b: grid

2c: insulator 11: photosensitive drum

12: charger 20: laser scanning unit

The present invention relates to a color image forming apparatus, and more particularly, a scanning unit capable of forming an electrostatic latent image on a photoreceptor by simultaneously using positive and negative corona discharges, and a color image forming apparatus having the same. It is about.

In general, in the electrophotographic color image forming apparatus, for example, the color laser printer 10, as shown in FIG. 1, when the charger 12 charges an optical photographic drum 11 which is a photosensitive member, the laser scanning unit (laser scanning unit; hereinafter referred to simply as 'LSU') 20 scans the photon to form an electrostatic latent image on the surface of the photosensitive drum 11.

Specifically, in the charger 12, when the photosensitive drum 11 is charged through a charging roller or corona discharge, the photosensitive drum 11 has a certain amount of electric charge. The polarity of the charge is the same as that of the toner, and the size has a value between approximately -500V and -900V. The photosensitive drum 11 having a constant size of charge is irradiated with light to a desired portion, that is, an image portion by using a laser, and only the portion reduces the size of the charge. The image formed on the photosensitive drum due to such a difference in charge is an electrostatic latent image.

The LSU 20 is an apparatus for generating an electrostatic latent image by irradiating light generated by a laser to a desired position on the photosensitive drum 11 and changing the amount of charge of the irradiated portion from the amount of surrounding charge. A schematic configuration for a typical LSU 20 is shown in FIG. 2.

Referring to the drawings, the LSU 20 scans a light source 21 capable of emitting a laser beam according to data, a modulator 22 that controls input and output of the laser beam, and a laser beam on the photosensitive drum 11. The note consists of a rotating polygon mirror (23). The rotating mirror 23 varies depending on the data processing speed, but is generally rotated at tens of thousands of rpm. Although not shown, a lens may be added after the multi-face mirror in order to obtain more optical accuracy.

As the output speed of the color image forming apparatus has recently increased, it is necessary to increase the data processing speed of the LSU 20. To this end, the speed of the multi-faceted mirror 23 must be faster, and the optical design must be more precise. However, increasing the speed of the multi-faceted mirror 23 not only increases noise but also causes vibration, causing periodic band-shaped image contamination of the image. In addition, for precise optical design, the precision of each component used in the LSU, such as a lens, a mirror, and a motor, must also be improved. In particular, in the tri-level process, the LSU beam size is generally used because not only the exposure potential but also the surface potential is used as the image area to develop two color toners in one photosensitive drum. There is a problem in that 1 × 1 latent image potential cannot be formed by using. In addition, in order to form a 1 × 1 latent image potential, when the beam size is reduced to 50 μm or less, there is a problem that an intermediate potential to be used as a non-image region may become unstable.

The present invention has been proposed in order to solve the above-mentioned problems, and its object is to use a triple level method using a positive and negative corona discharge simultaneously without using a conventional laser scanning unit. The present invention provides a scanning unit capable of forming an electrostatic latent image on a photosensitive member.

Another object of the present invention is to provide a color image forming apparatus having such a scanning unit.

In order to achieve the above object, a triple level scanning unit according to the present invention includes: a first electrode part including fine electrodes arranged at a predetermined distance from the photosensitive member along a length direction of the photosensitive member; And a second electrode part insulated from the first electrode part and an insulator and surrounding the first electrode part.

The first electrode part is made of an electrode material having a diameter of several μm or less, preferably 1 μm or less, and a specific resistance thereof is preferably 10 ⁻³ μm cm or less.

A shield insulated from the first electrode part by an insulator; And a grid installed in the opening of the shield.

In addition, the color image forming apparatus of the present invention, the photosensitive member whose surface is uniformly charged by the charger; And a triple level scanning unit configured to form positive and negative corona discharges on the photoreceptor to form an electrostatic latent image.

Hereinafter, a triple level scanning unit of the present invention will be described in detail with reference to the accompanying drawings.

3 is a perspective view of a triple level scanning unit of the present invention, Figure 4 shows a circuit diagram of FIG.

Referring to the drawings, the triple level scanning unit according to the present invention includes a first electrode portion 1 and a second electrode portion (2).

The first electrode part 1 is composed of microelectrodes provided at a predetermined distance from the photosensitive drum 11 along the length of the photosensitive member, for example, the photosensitive drum 11. The first electrode portion 1 is made of an electrode material having a diameter of several μm or less, preferably 1 μm or less, and the specific resistance thereof is preferably 10 ⁻³ μm cm or less.

As shown in FIG. 4, the microelectrodes of the first electrode part may be independently applied with a voltage, so that the ions formed by corona discharge may change the latent potential only for a small area on the photoreceptor due to the microelectrodes. do. That is, the first electrode part 1 forms a '+' (FIG. 4B) or a '-' (FIG. 4A) corona discharge by using a material of a sub-micro size as an electrode, whereby the photosensitive drum 11 The latent image potential of the local part of the phase is controlled to the desired size. Through this, a three-level latent image potential is formed on the photosensitive drum 11, and '+' or '-' toner is developed on one photosensitive drum 11.

The second electrode part 2 is composed of a shield 2a and a grid 2b. The shield 2a is insulated from the first electrode part 1 by an insulator 2c and surrounds the first electrode part 1. The insulator is to insulate between the electrode material and the ground, and it is preferable to use a material having excellent insulation such as alumina or mica. The grid 2b is installed in the opening of the shield and causes corona discharge.

The color image forming apparatus of the present invention also includes the triple level scanning unit described above. The scanning unit is installed in the vicinity of the photosensitive drum 11 in place of the laser scanning unit. The photosensitive member is provided with a charger 12 in advance of the triple level scanning unit.

Hereinafter, with reference to the accompanying drawings, it will be described in detail the operation and effect of the three-level scanning unit according to the present invention.

First, the latent potential of the photosensitive drum according to the polarity of the voltage applied to the first electrode portion in the dark room was measured while charging the photosensitive drum to -450V using a charger equipped with a charging roller. At this time, the latent potential of the photosensitive drum was measured using a non-contact surface electrometer manufactured by TREK and an oscilloscope (Agilent).

The photosensitive drum was u1.5g6H2_21 made by Mitsubishi Caul, Japan, -3.5kV was applied to the first electrode for (-) corona discharge, and + 3.5kV was applied to the first electrode for (+) corona discharge. In the case of (-) corona, -900V is applied to the shield and grid, and (+) corona is applied to the shield and grid + 100V. Voltage is applied to the first electrode, shield and grid by TREK. One high voltage supplier was used. 5 is a graph of photoelectric drum surface potential change by the charging device.

As shown in FIG. 5, when (-) corona was used, the surface potential of the photosensitive drum became -900V, and when (+) corona was used, the surface potential of the photosensitive drum became + 100V. This shows that the simultaneous use of the positive and negative corona can form triple-level latent image potentials.

Meanwhile, in the triple level scanning unit according to the present invention, a 1 × 1 latent potential is formed by applying a negative voltage to the odd-numbered fine electrodes and a positive voltage to the even-numbered fine electrodes. . 6 is a graph of such photosensitive drum surface potential change.

As shown in FIG. 6, it can be seen that by using the positive and negative corona simultaneously, the 1 × 1 latent image potential required when developing two colors side by side is easily obtained.

As described above, according to the charging apparatus according to the present invention, it is possible to easily obtain the 1 × 1 latent image potential required when developing two colors side by side without using an LSU.

As described above, according to the three-level scanning unit of the present invention, jitter and LSU ghost or left and right concentration variations that may occur using the LSU without using the existing LSU as the exposure apparatus, etc. The same image defect factor can be eliminated.

In addition, according to the scanning unit of the present invention, since the 1 × 1 latent image potential required for developing two colors side by side can be easily obtained, it can be applied to various electrophotographic image forming apparatuses such as a laser printer, a facsimile machine, and a copy machine. .

In the above, certain preferred embodiments of the present invention have been illustrated and described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made by those skilled in the art without departing from the spirit and spirit of the present invention as claimed in the claims. And modifications will be possible.

Claims (5)

A first electrode part including fine electrodes disposed at a predetermined distance from the photosensitive member along a length direction of the photosensitive member; And And a second electrode part insulated from the first electrode part and an insulator and surrounding the first electrode part. The method of claim 1, The first electrode unit is a triple-level scanning unit, characterized in that consisting of a plurality of electrodes having a diameter of 1㎛ or less. The method of claim 1, A shield insulated from the first electrode by the insulator; And Triple-level scanning unit, characterized in that consisting of a grid (grid) provided in the opening of the shield. The method of claim 1, The three-level scanning unit of the first electrode portion, characterized in that the voltage is independently applied. A photosensitive member whose surface is uniformly charged by a charger; And And a triple level scanning unit configured to form a latent electrostatic image by performing positive and negative corona discharge on the photoreceptor.

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