JPH03180871A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To widely reduce the toner filming of the surface of a photosensitive body and to prolong the life of the photosensitive body by interposing a reflection mirror in an exposing means and vibrating it by means of a movable means. CONSTITUTION:The reflection mirror 24 is arranged between a rotary mirror 22 and the photosensitive body 1, an optical image 3 scans in parallel to the rotary shaft of the cylindrical photosensitive body 1 from the A of a light source 21 while being reflected on the B of a mirror 22, is reflected on the C of a rear mirror stopped by a lens system 23, and formed on the surface D of the photosensitive body 1. The mirror 24 whose the central part in a transverse direction is rotatively supported varies a reflection angle by the moving means 25 composed of a piezoelectric body 26, etc. Therefore, the mirror 24 is synchronized with an one-format cycle by the means 25, or is vibrated asynchronizing with the rotational cycle of the photosensitive body. The home position of the optical image 3 made incident on the surface of the photosensi tive body 1 is irregularly changed, and the signs of the toner filming are prevented.

Description

[Detailed Description of the Invention] [Summary] An electrophotographic apparatus, which aims to reduce toner filming that occurs on a photoreceptor, includes a photoreceptor and an exposure means, the photoreceptor is The exposure means is made of a highly insulating material and has a cylindrical shape. and is configured such that the reflection angle can be varied by a movable means.

[Industrial application field]

The present invention relates to an electrophotographic apparatus, and more particularly to an electrophotographic apparatus having an exposure means for reducing toner filming that occurs on a photoreceptor.

As for electrophotography, the method described in US Pat. No. 2,297,691 and the like is well known.

This method involves uniformly charging a highly insulating photoreceptor in the dark, irradiating it with light to form an electrostatic latent image, and then developing it with colored fine powder called toner to create a visible image. , a photographic process in which a record is obtained by transferring it to paper, etc.

The main processes of electrophotography are generally divided into four major processes: pre-charging, latent image formation, development, and transfer, and the procedures of this process themselves are almost obsolete.

However, the various technologies associated with this process, such as photoconductor materials, light image irradiation, toner and its development method, photoconductor cleaning, and post-transfer fixation, still require improvements in recording performance and recording quality. Various studies are being conducted toward this goal.

[Conventional technology]

FIG. 7 is a schematic diagram of an example of an electrophotographic process.

In the figure, l is a photoreceptor, 2 is an exposure means, 3 is a light image, 4 is a charger, 5 is a developer, 6 is a transfer device, 7 is a transfer medium, 8 is a fixing device, and 9 is a cleaner.

The photoreceptor l may be belt-shaped or sheet-shaped, but
Since they generally have a cylindrical shape, which is convenient for performing the recording process in a cyclical manner, they are commonly called photosensitive drums or photocon drums.

The photoreceptor 1 is made of a photosensitive and highly insulating material, and recently, amorphous Si has been frequently used, including Se-based materials, which are well known as inorganic materials. In addition, in the case of organic materials, OPC (Organ
For example, phthalocyanine dyes and azo dyes are used.

These photosensitive materials are, for example, vapor-deposited or coated onto a drum made of AA or plastic to form the photoreceptor 1.

First, the surface of the photoreceptor 1 is uniformly charged by the charger 4 in a dark place.

The charger 4, also called a corona charger, is a corona discharge generating device that generates corona discharge in the atmosphere with an electric field applied with a high voltage of several thousand volts. If the corona discharge is emitted, the entire surface will be charged and the static charge 41 will be maintained.

Charging efficiency is better when the polarity of corona charging is the same as that of the majority carriers of the photoreceptor 1. For example, in the case of Se, which is a P-type semiconductor, a positive electrostatic charge 41 is charged by a positive direct current corona.

For example, in the case of a copying machine, the light image 3 is reflected while scanning an original, passes through an optical system, and is incident on a photoreceptor l that moves in synchronization with the scanning of the original.

For example, in the case of a so-called laser printer that uses a laser beam that has become popular recently, a light source 21 such as a semiconductor laser, and a polygonal rotating mirror 22 called a polygon mirror that scans the beam in the width direction of the photoreceptor l. and a lens system 23 that narrows the beam and corrects distortion in the scanning width direction, and an optical image 3 is formed by the exposure means 2, which is incident on the photoreceptor l that moves synchronously. . If the light source 21 is a gas laser or the like, a modulator is used to intermittent the beam, but recently semiconductor lasers have been widely used, and since the light source 21 is directly modulated, no modulator is used.

In this way, the electrostatic charge 41 on the photoreceptor 1 at the portion where the optical image 3 is incident is discharged, and an electrostatic latent image 42 is formed on the photoreceptor 1.

There are various types of developing device 5, but when the toner 51 is a powder, magnetic Vlasov development is generally used. This is a brush 53 in which iron powder 52 is attracted to a cylindrical magnet and becomes fuzzy.

Add an appropriate amount of toner 51 to this iron powder 52 and swirl it around to create a toner St.
to be charged. The charge polarity of the toner 51 is determined by the material of the toner 51, the surface treatment of the iron powder 52, etc. Generally, since so-called positive development is performed, the charge polarity of the toner 51 is opposite to that of the electrostatic charge 41 held on the photoreceptor l. ing.

Then, when the bristles of the rotating brush brush 53 touch and stroke the surface of the photoreceptor I, the toner 51 is electrostatically attracted to the electrostatic latent image 42 formed on the photoreceptor I and developed. . Then, a so-called toner image 54 (powder image) is formed.

The transfer device 6 has a similar configuration to the charger 4 and is disposed on the back surface of the transfer medium 7 that comes into contact with the toner image 54 formed on the photoreceptor 1 . Then, an electric field having a polarity opposite to that of the toner 51 is applied to attract the toner image 54 to the transfer medium 7 and transfer it. This transfer process is performed while the transfer medium 7 is moved in synchronization with the movement of the photoreceptor 1 so that the transfer medium 7 does not rub the surface of the photoreceptor 1.

The transfer medium 7 onto which the toner image 54 has been transferred is fixed on the surface of the transfer medium 7 by the fixing device 8, thereby completing a so-called hard copy. This fixing method includes, in addition to the commonly used heat fixing, for example, pressure bonding, solvent welding, and the like.

On the other hand, since the toner 51 remains on the surface of the photoreceptor l after the toner image 54 has been transferred without being transferred, it is cleaned by passing through the cleaner 9.

There are various methods for this cleaning; Those affected will be given an AC corona shower to eliminate static electricity. Thereafter, this toner 51 is rubbed off with a fluffy material such as a fur brush so as not to damage the surface of the photoreceptor i.

In this way, a series of electrophotographic processes is completed, but in the case of a drum-shaped photoreceptor, each means is arranged in accordance with the order of each process so as to surround the drum, and this process is an endless cycle. It will be held on.

[Problem to be solved by the invention]

As described above, in a normal photosensitive photo process, a series of processes are performed cyclically, so that the photoreceptor must be returned to its initial state after cleaning and entering the first pre-charging process. In other words, it is necessary to thoroughly clean the photoreceptor so that no foreign matter such as toner or static charge remains on the photoreceptor.

On the other hand, in order to damage the surface of the photoconductor or deteriorate the electrophotographic characteristics of the photoconductor itself, shortening its lifespan, cleaning to clean the surface of the photoconductor, such as neutralization or toner removal using Blasof, is necessary. It is not advisable to scrub the area too thoroughly.

However, when the same light image, such as a vertical ruled line, is continuously incident on the same spot on the surface of the photoreceptor, the toner that could not be removed by the cleaning cycle gradually fuses and sticks to the surface of the photoreceptor. Eventually, so-called toner filming occurs.

It is difficult for light images to be incident on the same spot repeatedly because it is rare for the repetition of horizontal ruled lines to exactly match the period in the rotational direction of the drum-shaped photoreceptor. Since the originals are arranged manually, it is rare for the vertical ruled lines of the originals to be completely parallel to the direction of movement of the photoreceptor.

However, when the light image is electronically controlled, such as in a laser printer, the position where the light image enters the surface of the photoreceptor is strictly determined, so it is necessary to Ruled lines are inserted repeatedly.

This toner filming destroys the original performance of the photoreceptor, causing problems such as fogging and processes such as latent image formation and transfer not being able to be performed properly.

An object of the present invention is to provide an electrophotographic apparatus having an exposure means that reduces such toner filming that occurs on the surface of a photoreceptor.

[Means to solve the problem]

The above-mentioned problem includes a photoreceptor and an exposure means, the photoreceptor is made of a photosensitive highly insulating material and has a cylindrical shape, and the exposure means is arranged on the photoreceptor. A beam-shaped optical image is incident on the electrophotographic device, which has a light source, a rotating mirror, a lens system, and a reflecting mirror, and is configured so that the reflection angle can be varied by a movable means. be related to

[For production]

As mentioned above, in conventional electrophotographic equipment, it is difficult to perform this process thoroughly due to the fear of scratching the surface of the photoreceptor, but on the other hand, in laser printers etc. ) is repeatedly incident on the same spot on the surface of the photoreceptor, then that spot is repeatedly developed, and then that spot is repeatedly cleaned, toner filming occurs on that spot. However, in the present invention, the optical image is prevented from repeatedly entering the same location on the photoreceptor.

In other words, conventionally, the scanning starting point of the incident light image while scanning on the photoconductor, that is, the home position, was fixed at a fixed position, but in the present invention, A reflecting mirror whose reflection angle can be minutely varied is installed in between, and this reflecting mirror is slightly tilted and vibrated to swing the home position of the beam-shaped light image back and forth in the scanning width direction. There is.

FIG. 3 is a layout diagram of the standardized exposure means, and FIG. 4 is a partially enlarged view of FIG. 3.

In the figure, the position of the reflecting mirror 24 is designated as B, and the optical image 3 incident from B onto the central portion C of the reflecting mirror 24 is reflected and incident on D of the photoreceptor l. Further, when the reflecting mirror 24 is tilted by a small angle θ0 with C as the center, the optical image 3 or the D of the photoreceptor 1
Assuming that the light is incident at the position o, the following relationship holds true.

DD' = CD' s in θ0 ■ Since θ0 is a small angle, CD'#CD ■ sin θ0
#πθ/180 It can be approximated as ■
Substituting the formula and the ■formula into the ■formula, DD' = CD·πθ/180 ■.

On the other hand, when the reflecting mirror 24 is tilted by a small angle θ0, the reflecting mirror 24
When the longitudinal end C'' of 4 moves to C'', C'C'
#CC's inθ #cc' ・πθ/180 ■Therefore, by substituting the formula ■ into the formula ■, C'C″=cc'·DD' /CD ■.

According to the equation (2), if the length of the reflecting mirror 24 (CC" x 2) and the distance (CD) between the reflecting mirror 24 and the photoreceptor 1 are determined in advance, the light image incident on the surface of the photoreceptor 1 can be 3 by a minute distance (DD"), the end of the reflector 24 is displaced (
C'C'').

FIG. 5 is a diagram showing the relationship between the continuous vibration of the reflecting mirror and the light image on the photoreceptor.

When the fine vibration of the reflecting mirror 24 is a continuous operation, the fine vibration is made so that the period of one rotation of the drum-shaped photoreceptor 1 and the vibration of the reflecting mirror 24 are not synchronized. Then,
As shown in the figure, on the surface of the photoreceptor l, the incident position is different between the home position 31 of the optical image 3 of the first rotation and the home position 32 of the optical image 3 of the second rotation.

FIG. 6 is a diagram showing the relationship between the intermittent vibration of the reflecting mirror and the optical image on the photoreceptor.

When the micro-vibration of the reflecting mirror 24 is an intermittent operation, for example, the home position 3132 of the optical image 3 is vibrated in synchronization with the period of each format. Then, as shown in the figure, the respective home positions 3I and 32 of the optical image 3 will be different between one format 33 and the next format 34 on the surface of the photoreceptor l.

By doing this, when recording a large number of documents of the same format, the light image is not repeatedly incident on the same location on the photoreceptor.

Furthermore, when recording a large number of documents of the same format, the light image will not be repeatedly incident on the same location on the photoreceptor.

As a result, an electrostatic latent image is not repeatedly formed, developed, transferred, and cleaned at the same location on the photoreceptor, so toner filming can be reduced.

Figure 2 is an enlarged view of the reflecting mirror.

In the figure, 1 is a photoreceptor, 2 is an exposure means, 21 is a light source, 22 is a rotating mirror, 23 is a lens system, 24 is a reflecting mirror, and 3 is an optical image.

For example, the photoreceptor L has a diameter of 110 mm and a diameter of 300 mm.
A photosensitive drum is used, which has a cylindrical surface made of aluminum and has amorphous Si sputtered thereon.

The exposure means 2 emits 200 beams of light with a wavelength of 780 nm.
A light source 21 consisting of a semiconductor laser that modulates at kHz to form an optical image 3, a rotating mirror 22 consisting of an octahedral polygon mirror that rotates 30,000 times per minute, and a 1008 m
A lens system 23 that forms a light image 3 of m, and a reflecting surface of A
Reflector 24 made by I and capable of changing the reflection angle by a minute angle θ0
It is composed of. With this exposure means 2, it is possible to record 50 sheets per minute in terms of A4 size.

The reflecting mirror 24 is arranged between the rotating mirror 22 and the photoreceptor l. The light image 3 is transmitted from A of the light source 21 to the rotating mirror 22.
It is scanned parallel to the rotation axis of the cylindrical photoreceptor I while being reflected by B of the photoreceptor I, and after being focused by the lens system 23, it is reflected by C of the reflecting mirror 24, and condensed while scanning D of the surface of the photoreceptor I. It's like a statue.

In this\, for example, distance BC is 100m, m, distance CD
is 6 Hmm, and when the rotating mirror 22 rotates, the optical image 3 swings on the surface of the photoreceptor 1 with a width of 300 mm.

In FIG. 2, the reflecting mirror 24 has a width of 50 mm and a height of 1
It is made of 0mm aluminum and has a mirror-finished surface. In addition, the center part in the width direction is rotatably supported on the back side.
The reflection angle is made variable by the movable means 25.

This movable means 25 includes, for example, a means for providing a member at one end of the reflecting mirror 24, which is made of a piezoelectric material 26 laminated with electrodes sandwiched therebetween, and whose length expands and contracts when a voltage is applied.

Alternatively, a method may be adopted in which the center of the reflecting mirror 24 is supported by a shaft, and the shaft is driven to vibrate electromagnetically, for example.

The reflecting mirror 24 is swung by the movable means 25 in synchronization with the cycle of the l format, and the home position of the optical image 3 incident on the surface of the photoreceptor 1 is varied for each l format.

Alternatively, it is swung asynchronously with the rotation period of the drum-shaped photoreceptor 1, and the home position of the optical image 3 incident on the surface of the photoreceptor 1 is irregularly varied.

Now, the optical image 3 is formed on the surface of the photoreceptor 1! D to 0
．． If we move it by 3mm and set it as D゛, that is, if we move the home position by 0.3mm, then in the equation (2), C'C''#cc'・DD' /CD, CC' = 25mm, CD = 600mm.

Since DD' = 0.3mm, C' C'' = 0.0125 mm.

In other words, one end surface of the reflecting mirror 24 is
Just shake it 2.5 μm. If this is replaced by the minute angle θ0 at which the reflecting mirror 24 is tilted, then the equation (2), C'C''=cc' ・From πθ/180, θ#
180・C′ C”/πCC゛, and θ is approximately 0.
It becomes 03°.

In this way, the reflector 2 is synchronized with the A4 format.
4, recording was performed through a series of electrophotographic processes installed around a drum-shaped photoreceptor l as shown in FIG.

As a result, the vertical ruled line that appears for each format is 0.3 m.
The deviation in m could not be visually determined.

Furthermore, even after recording in the same format 500 times in a row, no signs of toner filming were observed.

In 2\, the reflecting mirror was placed behind the rotating mirror via the lens system, but for example, it may be placed directly behind the rotating mirror and the lens system behind it, and various modifications are possible. It is.

Furthermore, various modifications can be made to the movable means for vibrating the reflecting mirror.

Furthermore, the type of light source, the distance of arrangement of the exposure means, the amount of movement of the home position of the light image on the surface of the photoreceptor,
Various modifications can be made to the material, shape, etc. of the photoreceptor.

〔Effect of the invention〕

In the conventional electrophotographic process, when recording a large number of images in the same format, toner filming occurs from time to time, whereas in the electrophotographic apparatus of the present invention, a reflecting mirror is interposed in the exposure means. ing.

The reflecting mirror is vibrated by a movable means to appropriately shift the home position of the optical image formed on the surface of the photoreceptor.

Then, if records of the same format are consecutive,
Even in cases where there are particularly severe vertical ruled lines, the home position can be moved for each format or moved irregularly on the surface of the photoreceptor, greatly reducing toner filming. can be reduced to

As a result, the present invention greatly contributes to prolonging the life of photoreceptors in terms of electrophotographic processes.

Figure 2 is an enlarged view of the reflector, Figure 3 is a standardized layout of the exposure means, Figure 4 is a partially enlarged view of Figure 5, and Figure 5 is the continuous vibration of the reflector and the surface on the photoreceptor. FIG. 6 is a diagram showing the relationship between the intermittent vibration of the reflecting mirror and the light image on the photoreceptor, and FIG. 7 is a schematic diagram of an example of the electrophotographic process.

In the figure, l is a photoreceptor, 21 is a light source, 23 is a lens system, 25 is a movable means, 2 is an exposure means, 22 is a rotating mirror, 24 is a reflecting mirror, 3 is a light image, and 10 is a starting point. Main rabbit's strabismus origin 1 month gray shooting mirror n enlargement cheering 2 eyes fu 4 Mi I 1 shi Oshi 1 Ko 1 Go Hiroshi + P negative placement color] Field
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Claims (1)

[Scope of Claims] It has a photoreceptor (1) and an exposure means (2), the photoreceptor (1) is made of a highly insulating photosensitive material and has a cylindrical shape; The exposure means (2) makes a beam-shaped light image (3) incident on the photoreceptor (1), and includes a light source (21).
), rotating mirror (22), lens system (23), and reflecting mirror (24)
), and the reflection angle can be varied by a movable means (25).