JPH09300688A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out the stabilized static recording in compliance with photo- emission. SOLUTION: In the constitution of an image forming device, an image carrier 2 having a dielectric layer 23 formed on a conductive layer 21 and a photoelectric conversion device 9 forming a photoelectric conversion layer 14 on the conductive layer 12 are so disposed as to make the dielectric layer 23 and the photoelectric conversion layer 14 facing each other, and the image exposure is performed on the photoelectric conversion layer 14 in the state of forming the potential difference between both conductive layers 12 and 21, and a latent image is formed on a traveling latent image carrier 2 by the discharge between the photoelectric conversion device 9 and the image carrier 2. In that case, a float electrode 16 constituted of a conductive body for fixing a discharge point formed on a surface facing the conductive layer 23 of the photoelectric conversion layer 14 is provided, and an auxiliary electrode 18 forming a discharge electric field between the auxiliary electrode and the float electrode 16 is provided on the same face as the photoelectric conversion layer 14 on which the float electrode 16 is also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an electrostatic latent image on an image carrier.

[0002]

2. Description of the Related Art Conventionally, as a method for forming an electrostatic latent image on a charge holding medium to form an image, for example, Japanese Patent Laid-Open No.
The method described in Japanese Patent No. 293358 has been proposed. In this image forming method, as shown in FIG. 4, a photoreceptor 101 made of small pieces and a cylindrical charge holding medium 102 are separately provided. The photoconductor 101 includes a photoconductive layer support 103, a photoconductor electrode 104, and a photoconductive layer 105, which are sequentially stacked. On the other hand, the charge holding medium 102 is
The insulating layer support 106, the charge holding medium electrode 107, and the insulating layer 108 are sequentially stacked. This photoconductor 1
01 and the charge holding medium 102 are arranged so that the photoconductive layer 105 and the insulating layer 108 face each other with a gap therebetween.

Then, a voltage is applied between the photoconductor electrode 104 and the charge holding medium electrode 107, and the photoconductor 101 is placed in a dark place.
When light is incident on the charge carrier 102 to scan it in the axial direction (main scanning direction), the portion of the photoconductive layer 105 on which light is incident exhibits conductivity, and that portion and the insulating layer 108 of the charge carrier medium 102 are A discharge is generated during this period, and charges are accumulated in the insulating layer 108 of the charge holding medium 102 that has been rotated in the direction of arrow b in the figure to form an electrostatic latent image. The formed electrostatic latent image is developed by the developing device 109 to become a toner image,
The toner image is transferred to paper or film by the transfer charger 110.

[0004]

However, when an image is formed by the apparatus shown in FIG. 4 described above, a dot-shaped image is formed or the rear end portion of the image is extended to obtain a stable image. Was difficult. This is the photoconductor 10.
It is considered that the electric discharge from No. 1 to the charge holding medium 102 is not promptly and stably performed, and the electrical discharge is performed intermittently, or the electrical discharge is continued after the exposure is completed. The present invention, the discharge is interrupted in this way,
It is an object of the present invention to provide an electrostatic recording head that eliminates continuous discharge after exposure and discharges quickly and stably.

Therefore, the inventors of the present invention have found that the image is interrupted,
As a result of examining the phenomenon of trailing edge extension, the discharge point of the photoconductor was not stable and the charge was discharged to a position different from the desired position on the image carrier, which is a charge-holding medium. It has been found that the above-described image discontinuity and trailing edge extension occur due to the fact that the latent image has already been formed on the image carrier and the discharge does not occur.

[0006]

The present invention has been made on the basis of the above findings, and the electric charges generated by the exposure of the photoconductor are stably and repeatedly discharged to desired positions on the image carrier. It was done like this.

That is, the image forming apparatus of the present invention includes an image carrier having a dielectric layer formed on a conductive layer, a photoelectric conversion device having a photoelectric conversion layer formed on the conductive layer, and a dielectric layer and a photoelectric conversion layer. Are arranged so that they oppose each other, image exposure is performed on the photoelectric conversion layer in a state where a potential difference is formed between both conductive layers, and an image that forms a latent image on the running image carrier by discharge between the photoelectric conversion device and the image carrier In the forming device, the photoelectric conversion layer has an electrically floating float electrode made of a conductor for fixing a discharge point on a surface of the photoelectric conversion layer facing the dielectric layer, and the photoelectric conversion layer having the float electrode It has an auxiliary electrode that forms a discharge electric field with the float electrode on the same surface.

In the image forming apparatus having such a structure, when the photoelectric conversion layer is exposed while the electric field is formed in the photoelectric conversion layer, carriers are generated by irradiation of light. By providing a float electrode made of a conductor in contact with the photoelectric conversion layer, the carriers generated by light irradiation in the photoelectric conversion layer move to the float electrode, and are concentrated in the portion closest to the auxiliary electrode. To do. Due to this action, the potential of the float electrode rises, discharge is generated between the float electrode and the auxiliary electrode, and a part of it discharges onto the image carrier to perform electrostatic recording. In this way, electrostatic recording is performed on the image carrier in accordance with the optical signal.

At this time, since discharge is performed between the end portion of the float electrode on the photoelectric conversion layer and the auxiliary electrode, the discharge position of the photoelectric conversion device is specified and the electrostatic latent image to be continuously formed on the image carrier. There is no possibility that the image will be discontinuous or that an electrostatic latent image will be formed even if the position is not irradiated with light. Therefore, the carriers generated in the photoelectric conversion layer are discharged from a predetermined position, and an electrostatic latent image that is faithful to a desired image can be formed. Also,
By providing the auxiliary electrode, concentration of carriers is promoted and stable discharge is performed. Furthermore, since the discharge is performed between the auxiliary electrode and the float electrode, a wide gap can be secured between the photoelectric conversion device and the image bearing pair, and the allowable range thereof is widened. Will be easier. In addition, since the float electrode and the auxiliary electrode may be formed on the same plane, the photoelectric conversion device itself can be easily manufactured, and the cost can be reduced.

In the electrostatic recording head of the present invention, it is preferable that the float electrode is provided corresponding to a pixel at the time of image exposure, and the auxiliary electrode is formed in a comb shape corresponding to the float electrode. By forming in this way,
The discharge between the float electrode and the auxiliary electrode is stable, and the manufacture is easy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a conceptual diagram of the image forming apparatus 1 according to the first embodiment.
Shows a partially enlarged sectional view of the photoelectric conversion device 9 and the image carrying belt 2 which are essential parts.

At the center of the image forming apparatus 1, an image bearing belt 2 which is an image bearing member is arranged. The image bearing belt 2 is rotated in the direction of arrow a by a driving roller 3 which is rotated by a driving device (not shown) and a heating roller 4 which is provided in parallel with the driving roller 3.

As shown in FIG. 2, the image bearing belt 2 has a dielectric layer 23 formed on the surface of a base 21 which is a conductive layer. Specifically, it is a structure in which a dielectric layer 23 made of polyethylene terephthalate having a thickness of about 10 μm is provided on a base 21 made of a conductive film having a width of 25 cm and a circumference of 30 cm. The base 21 is connected to the second power supply 25. An electrostatic recording head 5, a developing device 6, and a transfer roller 7 are provided around the image bearing belt 2 as indicated by an arrow a in the figure.
Are sequentially arranged in the direction.

The electrostatic recording head 5 comprises an optical system 8 and a photoelectric conversion device 9 arranged between the optical system 8 and the image carrying belt 2. The optical system 8 has a semiconductor laser generator, a collimator lens, a polygon mirror, an Fθ lens, a reflection mirror, and the like arranged in a housing. Laser light generated by semiconductor laser generator 8
1 is configured so that the photoelectric conversion device 9 is irradiated with light from a slit formed in the housing and image exposure can be performed. The direction in which the laser beam 81 scans and exposes is the width direction of the image bearing belt 2 (front and back directions in FIG. 1), and this direction is hereinafter referred to as the main scanning direction, and the traveling of the image bearing belt 2 orthogonal to this main scanning direction. The direction is called the sub-scanning direction.

In the photoelectric conversion device 9, as shown in FIG. 2, a transparent conductive layer 12 extending in the main scanning direction from the end portion 10a in the range of about one third in the sub scanning direction is provided on the transparent substrate 10. The photoelectric conversion layer 14 is formed on the surface formed of the transparent conductive layer 12 and the transparent substrate 10, and the float electrode 16 and the auxiliary electrode 18 are further formed thereon. . The photoelectric conversion device 9 and the image bearing belt 2 are arranged so that the float electrode 16 and the dielectric layer 23 face each other with a space of 200 μm therebetween.

The translucent substrate 10 has a width of 30 in the main scanning direction.
mm, the width in the sub-scanning direction is 250 mm, and the thickness is 3 mm. The transparent conductive layer 12 is composed of an ITO film as a conductive material and a polyamide resin film as an injection preventing layer. The first power supply 13 is connected to the ITO film of the translucent conductive layer 12.

The photoelectric conversion layer 14 is a function-separated type having good sensitivity to long-wavelength light such as semiconductor laser light (wavelength 780 nm) and LED light (wavelength 680 nm), and is a charge having a carrier pair generation function. Generation layer (CGL) and charge transport layer (CTL) having a function of transporting free carriers
Consists of The photoelectric conversion layer 14 is provided such that its charge generation layer is in contact with the injection prevention layer of the transparent conductive layer 12.

As is apparent from FIGS. 2 and 3, the float electrode 16 has a distance of about 3 minutes in the sub-scanning direction on the side where the transparent conductive layer 12 is formed on the photoelectric conversion layer 14 (end 10a side). Of 2
Are arranged in parallel with each other in the main scanning direction with a predetermined length and are in contact with the charge transport layer of the photoelectric conversion layer 14, and each of them is provided at the time of printing. Corresponds to the pixel.

On the other hand, the auxiliary electrode 18 has a plurality of protrusions 19
It has a comb-like shape composed of a base portion 20 and a base portion 20, and a tip portion 19 a of the protruding portion corresponding to the tip of the protruding portion 19 faces the end portion 17 of each float electrode 16 with a distance of 10 μm. The auxiliary electrode 18 is formed on the side of the photoelectric conversion layer 14 where the translucent conductive layer 12 is not formed, and is grounded by the conductive line 27.

Here, the potential relationship among the transparent conductive layer 12, the base 21 and the auxiliary electrode 18 is such that the potential of the transparent conductive layer 12> the potential of the auxiliary electrode 18 ≧ the potential of the base 21, or The potential of the photoconductive layer 12 <the potential of the auxiliary electrode 18 ≤ the potential of the base 21. In the case of the present embodiment, the first power supply 13 applies a voltage of 1.2 kV to the translucent conductive layer, and the second power supply 25 applies a voltage of −2.0 kV to the base 21 to form an auxiliary electrode. Since 18 is grounded, the potential relationship is such that the potential of the transparent conductive layer 12> the potential of the auxiliary electrode 18> the potential of the base 21.

The developing device 6 includes a toner accommodating portion 61 for accommodating a negatively-charged one-component developer (hereinafter referred to as toner).
And a developing sleeve 62 arranged in proximity to the image carrying belt 2, and a supply roller 6 for agitating the toner accommodated in the toner accommodating portion 61 and supplying the toner to the developing sleeve 62.
It consists of 3. An appropriate developing bias voltage is applied to the developing sleeve 62 in order to prevent background fogging.

The transfer roller 7 faces the heating roller 4 with the image bearing belt 2 in between, and the image bearing belt 2
It is arranged in pressure contact with. The recording paper S is passed between the transfer roller 7 and the image carrying belt 2.

In the image forming apparatus 1 configured as described above, the process of latent image formation will be described first.
The light-transmitting conductive layer 12 of the photoelectric conversion device 9 has the first power supply 1
The voltage of 1.2 kV (V _C ) is applied by 3
A voltage of minus 2.0 kV is applied to the base 21 of the image bearing belt 2 by the second power supply 25. Therefore, 3.2 is provided between the translucent conductive layer 12 and the base 21.
An electric field is formed by the voltage difference of kV.

The laser beam 8 emitted by the optical system 8 to the photoelectric conversion device 9 in the state where the electric field is formed as described above.
1 is irradiated and exposed, the laser beam 81 emits the laser beam 81.
0, the light passes through the transparent conductive layer 12 and reaches the photoelectric conversion layer 14. In the charge generation layer of the photoelectric conversion layer 14, when light is absorbed in the presence of an electric field, a carrier pair is generated. Among the generated carrier pairs, the free carriers have the property of moving in the opposite electrode directions of opposite polarities. At this time, the freed positive carriers move to the float electrode 16 through the charge transport layer. Thereby, the float electrode 16
When the electric field between the auxiliary electrode 18 and the auxiliary electrode 18 rises and exceeds the threshold value determined by the passion law, the float electrode 1
Discharge occurs between the end 17 of No. 6 and the tip 19a of the protruding portion of the auxiliary electrode 18. Part of the generated discharge is drawn by the image bearing belt 2 to form an electrostatic latent image on the dielectric layer 23.

Here, the potential difference between the float electrode 16 and the image bearing belt 2 is the float electrode 16 and the auxiliary electrode 18.
The discharge is generated between the float electrode 16 and the auxiliary electrode 18 even though the potential difference between the float electrode 16 and the auxiliary electrode 18 is large.
00 μm) is much larger than the distance (10 μm) between the float electrode 16 and the auxiliary electrode 18, so the threshold value determined by the Paschen's law is set to the float electrode 16 and the auxiliary electrode 18.
This is because the electric field between and exceeds first.

By providing such an auxiliary electrode 18, the distance between the float electrode 16 and the other electrode (auxiliary electrode 18) that generates a discharge is always constant, so that the distance between the float electrode 16 and the image carrying belt 2 is increased. That is, since the distance between the photoelectric conversion device 9 and the image carrying belt 2 can be widened and the allowable width thereof can be widened, unevenness or deformation of the image carrying belt 2 occurs and the distance between the photoelectric converting device and the image carrying belt 2 is increased. Can be changed to some extent, and stable discharge can be obtained.
Therefore, the work at the design stage and the manufacturing stage becomes easy,
Cost reduction can be achieved.

The float electrode 16 is formed in a strip shape extending in the sub-scanning direction, as is apparent from FIGS. Therefore, when the laser beam 83 is irradiated and exposed, even if the irradiation light is deviated in the sub-scanning direction due to a surface accuracy error of the polygon mirror or the like, as long as it is within the existing range of the float electrode 16, it moves into the float electrode 16. Carrier is float electrode 1
Since it freely moves in 6 and discharges concentratedly at the end closest to the auxiliary electrode 18, regardless of the shift of the exposure position,
An electrostatic latent image can be formed on the image bearing belt 2 at a specific position. In addition, by intentionally varying the irradiation light in the sub-scanning direction and using it, the frequency of use of a specific region of the photoelectric conversion layer 14 can be reduced, and as a result, the life of the photoelectric conversion device can be extended. You can

Next, the process after the latent image formation will be described. The electrostatic latent image formed on the image bearing belt 2 is conveyed to a developing unit facing the developing device 6 by the rotation of the driving roller 3 and the heating roller 4, and is developed by the developing device 6 with toner. After that, the toner image formed on the image carrying belt 2 is further conveyed by the rotation of the driving roller 3 and the heating roller 4, and the heating element 11 provided inside the heating roller 4 is conveyed.
At the same time, the transfer roller 7 transfers the heat to the recording paper S. At this time, the toner image is melted and transferred, so that the toner does not remain on the image bearing belt 2 and is almost completely transferred to the recording paper S and is fixed at the same time.

The photoelectric conversion device 9 of the above-described embodiment
As the material, one manufactured by the following method is used. First, a transparent conductive layer 12 is formed on the surface of a transparent glass plate which is a transparent substrate 10 serving as a support for the photoelectric conversion device 9.
Are formed on the entire surface in the main scanning direction by 10 mm from the end 10a in the sub scanning direction. The translucent conductive layer 12 is formed by forming an ITO film by a known ion plating method to a thickness of about 0.2 μm (the area resistance of the ITO film is about 100 Ω / □), and further forming an injection prevention layer of about 0 μm thereon. A 0.5 μm polyamide resin layer is applied by the dipping method.

Subsequently, the photoelectric conversion layer 14 is formed by applying the following photosensitive coating on the surface of the transparent conductive layer 12 of the substrate and the transparent substrate 10 by the dipping method, and the film thickness after drying is A 0.4 μm charge generation layer is formed. τ (tau)
1 part by weight of a metal-free phthalocyanine, 2 parts by weight of polyvinyl butyral resin, and 100 parts by weight of tetrahydrofuran are put in a ball mill pot and dispersed for 24 hours to obtain a photosensitive coating. The viscosity of the photosensitive coating at this time is 15 cp at 20 ° C.
It is. As the polyvinyl butyral resin, a resin having an acetylation degree of 3 mol% or less, a butylation degree of 70 mol% and a polymerization degree of 1000 was used. Although the charge generation layer is formed by applying a solution of a photosensitive material in a solvent, it may be formed by vapor deposition of the photosensitive material.

Then, a coating solution prepared by dissolving 8 parts by weight of a hydrazone compound, 0.1 part by weight of an orange dye, and 10 parts by weight of a polycarbonate resin in a solvent consisting of 180 parts by weight of tetrahydrofuran on the charge generation layer was prepared by a depping method. And then dried to form a charge transport layer having a film thickness of 21 μm.

Next, a plurality of float electrodes 16 are formed in parallel with the main scanning direction as shown in FIG. 3 on the surface of the photoelectric conversion layer 14, more specifically, the surface of the charge transport layer. A plurality of the float electrodes 16 are formed in a strip shape by screen-printing a conductive paste. At this time, the float electrodes 16 are formed flat with a pitch of 80 μm in the main scanning direction, a width of 50 μm in the main scanning direction, a length of 20 mm in the sub scanning direction, and a film thickness of 5 μm.

Simultaneously with the formation of the float electrode 16, a base portion 20 extending in the main scanning direction as shown in FIG. 3 is formed on the surface of the photoelectric conversion layer 14, more specifically, the surface of the charge transport layer, and each float electrode 16 is formed from the base portion 20. A comb-shaped auxiliary electrode 18 including a plurality of protrusions 19 extending in the sub-scanning direction is applied toward the end portion 17 by screen printing with a conductive paste to form a film thickness of 5 μm. Like the float electrode 16, the protrusions 19 have a pitch of 80 μm in the main scanning direction.
The width in the main scanning direction is 50 μm, and the length in the sub scanning direction is 5 mm
And The auxiliary electrode 18 can be formed on the same plane as the float electrode 16 at the same time, and can be formed without increasing the number of production steps.

With respect to the structure of the photoelectric conversion layer 14, in addition to the function separation type described above, it may be an inverse laminated type or a single layer type. Further, as the charge generating material, the charge transporting material, the binder resin, the additive, etc., known materials may be appropriately selected according to the purpose. In addition, the photosensitive material is not limited to the organic material, and an inorganic material such as zinc oxide, cadmium sulfide, selenium alloy, amorphous silicon alloy, amorphous germanium alloy may be used. Further, a publicly known undercoat layer may be provided for the purpose of improving charging performance, image quality, adhesion to a substrate and the like. The transparent substrate 10 is not particularly limited as long as it is a substrate that is transparent to the light to be exposed and serves as a support.

For the float electrode 16 and the auxiliary electrode 18, a known conductive oxide film, a metal material or the like can be used in addition to the conductive paste. The float electrode 16 and the auxiliary electrode 18 are not particularly limited as long as they are electrically conductive, but since they are directly exposed to discharge, it is preferable to use a material that does not easily oxidize.

The method of forming the float electrode 16 and the auxiliary electrode 18 is not limited to this, and the electrodes may be formed by a method such as vapor deposition, ion plating or sputtering instead of screen printing.
In this case, a mask sheet is used or a pattern is formed by photolithography.

Instead of the ITO film used for the transparent conductive layer 12, a transparent conductive material may be used. However, in order to avoid a voltage drop, it is preferable to use a material having a sheet resistance of 1000 Ω / □ or less. The method for forming the conductive layer is not limited to the method described above, and the conductive material layer may be formed by a method such as printing or sputtering instead of the ion plating method or vapor deposition. Further, the injection preventing layer is not limited to the polyamide resin, and a known material having a light transmitting property may be used.

In the above embodiment, a voltage (V _C ) of 1.2 kv is applied to the transparent conductive layer 12, the auxiliary electrode 18 is grounded (0 V), and the image carrying belt 2 is used.
Although a negative voltage of 2.0 kv is applied to the base 21, the negative voltage is applied to the base 21 between the end 17 of the float electrode 16 and the protruding end 19a of the auxiliary electrode 18. This is for securely capturing a part of the discharge on the image bearing belt 2, and may be grounded like the auxiliary electrode 18.

Although the semiconductor laser has been shown as a light source for exposing the photoelectric conversion device 9, the invention is not limited to this, and an LED system or a liquid crystal shutter system may be used as long as the electrostatic recording head 5 can be appropriately exposed. A known exposure method such as the PLZT method can be used. Needless to say, the non-exposed area can be developed without developing the exposed area by changing the characteristics of the developer. The configuration of the image carrier is not limited to such a belt, and may be drum-shaped.

[0040]

As is apparent from the above description, according to the present invention, the charges generated corresponding to the optical information are concentrated on the float electrode, and the float electrode and the auxiliary electrode which are the specific positions of the photoelectric conversion device. A stable discharge is performed from between
A desired electrostatic recording can be achieved without interruption of the image or extension of the trailing edge. In addition, since the gap between the photoelectric conversion device and the image carrier can be set wide, and the setting allowable range is wide,
The degree of freedom in design can be increased, productivity can be improved, and stable image formation can be performed for a long period of time. It becomes easy to set the irradiation position of the optical information from the light source to the photoelectric conversion device, and the cost can be reduced.

Further, in the case where the auxiliary electrode is provided in a comb-teeth shape, a discharge is generated between the end of the float electrode and the tip of the comb-teeth-shaped protrusion, so that the discharge position is further stabilized. At the same time, it becomes easy to make the potential of the auxiliary electrode constant.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 is an enlarged view of a main part of the image forming apparatus shown in FIG.

FIG. 3 is a view showing a surface of the photoelectric conversion device shown in FIG.

FIG. 4 is a diagram showing a conventional image forming apparatus.

[Explanation of symbols]

1 ... Image forming apparatus, 2 ... Image bearing belt (image bearing member), 8
... Optical system, 9 ... Photoelectric conversion device, 12 ... Translucent conductive layer (conductive layer), 13 ... First power source, 14 ... Photoelectric conversion layer, 16
... Float electrode, 18 ... Auxiliary electrode, 19 ... Projection part, 21
... Base (conductive layer), 23 ... Dielectric layer.

Claims (2)

[Claims] 1. An image carrier having a dielectric layer formed on a conductive layer, and a photoelectric conversion device having a photoelectric conversion layer formed on the conductive layer are arranged so that the dielectric layer and the photoelectric conversion layer face each other.
In an image forming apparatus that performs image exposure on a photoelectric conversion layer in a state where a potential difference is formed between both conductive layers and forms a latent image on a running image carrier by discharge between the photoelectric conversion device and the image carrier, A float electrode made of a conductor for fixing a discharge point on the surface of the layer facing the dielectric layer, and the float electrode is formed on the same surface of the photoelectric conversion layer on which the float electrode is formed. An image forming apparatus comprising: an auxiliary electrode that forms a discharge electric field between the electrodes. 2. The float electrode is provided corresponding to each pixel at the time of image exposure, and the auxiliary electrode is formed in a comb shape corresponding to the float electrode. The image forming apparatus according to item 1.