JPH0943940A - Optical scanning device and electrophotographic recording device using the same - Google Patents

Abstract

(57) [Abstract] [Purpose] To eliminate the floating toner that pollutes the optical system of the laser beam printer. [Structure] A conductive transparent film is formed on the surface of a laser beam emission window of an optical system, a transparent electrode is provided, another electrode is provided in the vicinity of the transparent electrode, and an electric field is applied between the two electrodes so that the toner is emitted to the laser beam emission window. Prevent adhesion. [Effect] By adding the toner adhesion preventing function of the present invention to the laser beam emission window, the risk of contaminating the lens and the laser beam emission window with toner is greatly reduced. As a result, the characteristics of the optical system can always be kept constant,
The stability of the printing performance of the laser beam printer is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical scanning device, and more particularly to an optical scanning device provided with a mechanism for eliminating floating toner which can deteriorate the performance of an optical scanning optical system, and an electrophotographic recording device using the same. Regarding

[0002]

2. Description of the Related Art In a conventional electrophotographic apparatus, a scanning optical system is arranged near a photoconductor or a developing unit because of its structure. Therefore, after the transfer, residual toner that could not be cleaned in the cleaning process floats and adheres to the surface of optical elements such as lenses arranged in the scanning optical system to reduce the condensing characteristics of the optical system and the optical characteristics such as a decrease in transmittance. It is fully conceivable that it will cause deterioration of characteristics. To prevent toner from adhering to this optical system, JP-A-55-1305
In the publication No. 61, the transparent electrode layer is provided so as to cover at least the end face of the focused light transmission body array facing the photoconductor, at least the slit-shaped area portion constituted by the aggregated surface of the minute end faces of the focused light transmission body. The transparent electrode layer is provided with an electric potential of the same polarity as that of the electrostatic latent image visualization toner, and another electrode is provided around the transparent electrode layer, and the other electrode has a polarity opposite to that of the toner. By applying the electric potential, it becomes difficult for the toner to adhere to the transparent electrode, and the toner easily adheres to the surrounding electrodes.

Recently, in order to reduce the cost of the apparatus, as shown in JP-A-59-204001, a plastic lens is often used as the lens 6 constituting the scanning optical system. ing.

[0004]

By the way, when a plastic lens is used for the optical system, the plastic is a material which is very easily charged, and the toner floating beside the optical system is generally negatively charged. ing. Therefore, the plastic lens easily attracts the charged floating toner, and the toner once attached to the lens is difficult to peel off. Therefore, in a laser printer equipped with a plastic lens, the amount of residual toner adhering to an optical element such as a plastic lens increases with the increase of the operating time of the device depending on the arrangement of the lens in the optical system, and the optical characteristics Is expected to progress. Therefore, especially when a plastic lens is used for the scanning optical system of a laser printer, it is an important problem to be solved to eliminate the floating toner that is likely to pollute the optical system. According to the conventional measures for preventing the adhesion of the floating toner, the floating toner is adhered to the vicinity of the emission port of the optical system, and when the adhered amount increases, the emission port is also blocked. Further, simply applying a charge having the same polarity as that of the toner to the emission port may generate toner of the opposite polarity, which is not a sufficient measure.

Therefore, it is an object of the present invention to provide a laser beam printer having a function of solving these conventional problems and maintaining optical characteristics.

[0006]

To achieve the above object, a transparent film having conductivity is provided on the surface of a laser beam emission window, and a predetermined voltage is applied so that the laser beam emission window has the same polarity as the toner. However, the toner adhered to the laser beam emission window is removed electrostatically, and the electrostatic field is provided between the emission port and the electrode provided near the emission port, so that the floating toner does not enter the optical system path. It was done like this.

[0007]

The recording information formed on the surface of the photosensitive drum is developed by the toner charged positively or negatively and fixed on the paper. In general, toner is often negatively charged, so the present invention will be described when floating toner is negatively charged. A laser beam emitting window provided with a transparent conductive film of tin oxide or indium oxide based thin film on the light transmitting surface and a predetermined interval in the direction perpendicular to the surface of the emitting window so that the optical path is not blocked in parallel with the surface. A voltage is applied between the two electrodes provided on the output window so that the emission window has a negative polarity. A small amount of toner that does not participate in fixing and cannot be completely eliminated even in the cleaning process and floats inside the apparatus is negatively charged. On the other hand, since the laser beam emitting window has a negative polarity, electrostatic repulsion acts between them to prevent the floating toner from adhering to the surface of the laser beam emitting window. Further, a barrier for electrostatic force is formed between the exit window and two electrodes provided on the front surface thereof so as to be separated by a predetermined distance, and it becomes difficult for the floating toner to enter the path of the laser beam.

[0008]

First, the construction of an optical system of an electrophotographic apparatus will be described with reference to FIG.

As shown in the figure, the scanning optical system for modulating and deflecting the laser light emitted from the light source 8 to form an optical pattern on the photoconductor 15, and the scanning optical system for the photoconductor 1
5 is composed of an image forming system for making a hard copy of the light pattern formed on the surface 5 by using an electrophotographic process (not shown).

In FIG. 4, the light source 8 is generally a gas laser or a semiconductor laser. As the modulator 27, an A that uses an acousto-optic (A / O) element is used.
/ O modulators are commonly used. The A / O modulator is
An ultrasonic wave is allowed to pass through the A / O element, and the incident laser light is diffracted by the synchronous change in the refractive index generated by the ultrasonic wave to perform intensity modulation. A beam compressor 18 that narrows the incident beam diameter in order to increase the modulation speed by the A / O element.
a) A beam expander 18b used to obtain a small image spot on the photoconductor is used, and a collimator lens for converting a divergent beam emitted from a semiconductor into a parallel beam is used. A rotary polygon mirror (polygon mirror) 10 is used as a deflector for scanning the photosensitive member with laser light. A laser printer using a hologram instead of the rotary polygon mirror has also been proposed.

Since the rotary polygon mirror 10 rotates at a constant speed,
The reflected laser light is deflected at a constant angular velocity. The imaging lens (Fθ lens) 6 has an action of forming an image of the deflected laser light on one plane on the surface of the photoconductor, and also imparts an optical distortion to incident light of a constant angular velocity so that the surface of the photoconductor at a constant velocity. It has a function of converting so as to scan the upper part (fθ characteristic).

The photoconductor 15 has a two-layer structure in which a photoconductor layer is provided on a conductive support. In advance, uniformly charge the surface of the photoconductor in the dark by discharging corona, etc.
When laser light is applied to this, the resistance of the light conductor in the light-exposed portion is lowered, and the charged electric charge flows to the ground, and the surface of the photoconductor 15 has no electric charge remaining and no electric charge remains. Part arises. That is, a potential difference is generated in the photoconductor 15 by irradiating the laser beam. This potential difference becomes an electrostatic latent image. The formed electrostatic latent image is made visible by toner attached by a developing device (not shown). The present invention relates to the part of the optical system.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of a scanning optical system having a toner removing mechanism according to the present invention. The laser beam emitting window 3 is made of a glass plate, and an ITO (Indium Tin Oxside) film is formed on the laser beam transmitting surface to form the transparent electrode 1. Two electrodes 2 made of a metal plate were provided in the vicinity of the laser beam emission window 3 having the transparent electrode 1 at an interval larger than the laser beam diameter. By the way, the transparent electrode 1
The space between the metal electrode 2 and the metal electrode 2 needs to be made small to some extent in order to apply an electric field therebetween. Therefore, in this example, the transparent electrode 1
The distance d between the metal electrode 2 and the metal electrode 2 was 400 μm. The magnitude of the voltage applied to the electrodes was 1 kV.

In the case of the present embodiment, since the floating toner 7 which is separated from the photoconductor 15 and floats in the vicinity of the optical system is negatively charged, the transparent electrode 1 side becomes negative and the metal electrode 2 side becomes positive. Voltage is applied to.

It is expected that the amount of floating toner 7 generated will be the maximum when the photoconductor 15 is rotated, that is, when the laser beam is scanned in the optical system. Therefore, an electric field is applied between the transparent electrode 1 and the metal electrode 2 in synchronization with the scanning of the laser beam. The laser beam is scanned, the photoconductor 15 is rotated accordingly, and the floating toner (negatively charged) 7 generated from the surface of the photoconductor 15 partially tries to adhere to the surface of the laser beam emission window 3. However, since an electric field is generated between the transparent electrode 1 provided on the surface of the laser beam emission window 3 and the metal electrode 2 facing the transparent electrode 1 in association with the scanning of the laser beam, it is attempted to adhere to the laser beam emission window 3. The floating toner 7 is prevented from moving to the laser beam emission window 3 due to an electrostatic force acting from the transparent electrode 1 side toward the metal electrode 2 side, so that the floating toner cannot be attached. The material of the electrode provided in the vicinity of the transparent electrode 1 has been described by using the metal material in this embodiment, but any material having conductivity may be used.

Although not shown in the figure, a charger for uniformly charging the surface of the photosensitive drum is provided around the photoconductor 15, and information inputted after being uniformly charged by the charger. The light emitting element is driven based on the above, and an electrostatic latent image is formed by exposure of the optical system. The formed electrostatic latent image is
A developing device for developing with toner is arranged. The toner image on the photoconductor 15 developed by the developing device is applied with a transfer voltage at the transfer position, and is transferred to a recording medium, that is, a sheet. The sheet on which the toner image is transferred is conveyed to the fixing device. Then, it is heated and pressed to fix the toner on the paper,
Then, it is discharged to the outside of the recording apparatus. The toner remaining on the photosensitive drum after the transfer is cleaned by the drum cleaner. The floating toner which is a problem in the present invention is generated in the developing process, the transferring process and the cleaning process.

Next, another embodiment will be described below.

An example in which the long cylinder lens 5 is arranged at the position of the laser beam emission window will be described. An ITO (Indium
Tin Oxside) film was formed and the transparent electrode 1 was provided.

Cylinder lens 5 having this transparent electrode 1
Is provided at the position of the laser beam emission window. Further, two metal electrodes 2 are provided near the cylinder lens 5. The distance between the two metal electrodes is larger than the diameter of the laser beam. The distance between the transparent electrode 1 and the metal electrode 2 was 400 μm. Since the cylinder lens 5 provided with the transparent electrode 1 has a predetermined radius of curvature, when the metal electrode 2a has a flat plate shape,
As shown in FIG. 3A, the distance between the two electrodes is locally different, and it becomes difficult to apply an electric field of uniform magnitude. Therefore, as shown in FIG. 3B, the metal electrode 2b
The radius of curvature of the surface facing the cylinder lens 5 is substantially the same as that of the cylinder lens 5 so that the distance between the transparent electrode 1 and the metal electrode 2b is uniform.

The magnitude of the voltage applied to the electrodes is 1 kV.
And The operation of preventing the floating toner 7 from adhering to the surface of the cylinder lens 5 is such that an electric field is applied between the transparent electrode 1 and the metal electrode 2 in conjunction with the scanning of the laser beam, as described in the first embodiment. Transparent electrode 1 side to metal electrode 2
Since the electrostatic force acts toward the side, the floating toner 7 that tends to adhere to the surface of the cylinder lens 5 is prevented from moving to the surface of the cylinder lens 5, and the adhesion of the floating toner becomes impossible. As described above, the cylinder lens 5 having the toner adhesion preventing function is also used as the laser beam emission window 3, so that the number of components of the optical system can be reduced. By using the plastic cylinder lens instead of the glass cylinder lens, the cost of the lens can be reduced.

Another embodiment of the present invention is shown in FIG.

In this embodiment, there is a first opening between the laser beam emission window 3 and the photoconductor 15 and having an opening larger than the diameter of the laser beam passing through the emission window 3 with a predetermined gap therebetween. 2 and the second electrode 2-1 having an opening larger than the diameter of the laser beam passing therethrough is provided in front of the first electrode 2 at a predetermined interval.

A voltage is applied to the first electrode 2 and the second electrode 2-1 so as to have polarities different from each other with reference to the voltage of the transparent electrode 1 provided on the front surface of the emission window 3. There is.

As described above, by providing the first electrode 2 and the second electrode 2-1 having different polarities at positions apart from the emission window 3, the toner floating around the emission window can be separated from the first electrode. It is adsorbed to the electrode 2 or the second electrode 2-1. In general, it is not known which polarity of dust is charged in the floating toner. Therefore, by configuring as in the present embodiment, the effect of preventing contamination of the exit window is greater than that in the above-described embodiment.

[0026]

As described above, according to the present invention, it is possible to effectively eliminate the toner floating inside the apparatus, which causes the optical system of the laser printer to become dirty. In particular, by using a plastic cylinder lens having a toner adhesion preventing function also as a laser beam emission window, it is possible to prevent contamination of the optical system by the toner and to realize a low cost optical system.

[Brief description of drawings]

FIG. 1 is a diagram showing an optical system having a toner adhesion preventing mechanism according to an embodiment of the present invention.

FIG. 2 is a diagram showing an optical system having a toner adhesion preventing mechanism according to another embodiment of the present invention.

FIG. 3 is an enlarged view of an emission port of the optical system of the present invention.

FIG. 4 is a block diagram of an optical system of a general laser beam printer.

FIG. 5 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Transparent electrode, 2 ... Metal electrode, 3 ... Laser beam exit window, 4 ... Laser beam, 5 ... Cylinder lens, 6 ... Fθ
Lens, 7 ... Floating toner, 8 ... Light source, 9 ... Optical system frame, 10 ... Polygon mirror, 15 ... Photoconductor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Susumu Saito 2-6-2 Otemachi, Chiyoda-ku, Tokyo Inside Nititsu Koki Co., Ltd. (72) Kenji Mochizuki 2--6, Otemachi, Chiyoda-ku, Tokyo No. 2 Nitto Koki Co., Ltd. (72) Inventor Kenichi Hisagai No. 2-6-2 Otemachi, Chiyoda-ku, Tokyo Nitate Koki Co., Ltd.

Claims (3)

[Claims] 1. An optical scanning device for forming a latent image on a recording medium through light emitted from a light source according to input information through an optical system having a scanning means, and used as a window for emitting scanning light. Transparent transparent film is provided, an electrode having an opening larger than the diameter of the light is provided near the front surface of the exit window, and the conductive transparent film has the same polarity as the floating toner between the conductive transparent film and the electrode. An optical scanning device having a configuration for applying a voltage as described above. 2. An optical scanning device according to claim 1, wherein a SnO ₂ or In ₂ O ₃ based material is used as the conductive transparent film material. 3. A recording medium is uniformly charged, and a light emitted from a light source according to input information is formed on the recording medium through an optical system having a scanning means to form a latent image on the recording medium. In a recording device, which develops the information on a medium surface using a developer, transfers a developed image on the recording medium to a recording medium, and then fixes the developed image on the recording medium,
A conductive transparent film is provided on the transmission surface of the scanning light emission window, and an opening larger than the diameter of the scanning emission light is provided between the emission window and the recording medium at a position spaced from the emission window by a predetermined distance. An electrophotography characterized in that an electrode is provided, and a voltage is applied between the conductive transparent film and the electrode so that the surface of the conductive transparent film is always kept in the same polarity as the developer particles. Recording device.