JPH0664372B2 - Image recording apparatus and image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline of the Invention] A voltage is applied between a photoreceptor having an island-shaped microelectrode on its surface and a first developing device for development, and then image exposure is performed from the back surface side to trap charge. An image is formed, and then a reverse bias is applied to the second developing machine to remove the background toner.

[Industrial application field]

The present invention relates to an image recording apparatus and an image forming method used for a printer or the like, and in particular, image recording for forming a toner image on a bright portion (exposure portion) on a photosensitive member irradiated with image light based on an image pattern to be formed. The present invention relates to an apparatus and an image forming method.

[Conventional technology]

Figure 2 shows charging, exposure, development, and
FIG. 7 is a schematic diagram of a conventional so-called electrophotographic recording type image forming apparatus that is configured to perform operations such as transfer. A recording drum 1 provided with a photoconductive layer 2 such as selenium as shown in FIG.
The upper surface is uniformly charged by the initial charging corona discharger 3. Next, the photoconductive layer 2 is exposed by exposure means 4 such as a laser corresponding to image information to form an electrostatic latent image. Further, a toner image is formed by electrostatically adhering the toner of black fine particles charged to the same polarity by the developing device 5 to the electrostatic latent image by the electric field by the developing machine 5. Then, the toner image on the photoconductive layer 2 is transferred by the transfer corotron 6 onto the recording paper 10 charged with an electric charge having a polarity opposite to that of the toner. The toner image transferred in this manner is fixed on the recording paper 10 by heat fixing, pressure fixing, or the like in the fixing device 7. On the other hand, the toner remaining on the photoconductive layer 2 is easily cleaned and removed by the fur brush cleaner 9 through a neutralizing step of neutralizing the charge on the photoconductive layer 2 and the charge on the photoconductive layer 2 by the static elimination corotron 8. The surface potential of the photoconductive layer 2 is made substantially zero. Image recording is completed by such a series of processes from initial charging to cleaning of residual toner. Hereinafter, the above recording process is repeated.

As described above, in the electrophotographic method, the corona discharger is required for charging and discharging the photoconductor. To this corona discharger, a high voltage of several KV must be applied to the corona wire, a high voltage power supply for this is required, and the corona discharger is susceptible to humidity, dust, etc. and has high reliability. Inferior.
Further, ozone generated by the corona discharger produces an odor and also has an effect on the human body. further,
Charge, exposure, development, transfer, charge removal, cleaning 6
It has the disadvantage of requiring two processes, which makes the equipment complicated and bulky.

Recently, instead of the conventional electrophotographic process, an image forming method which does not use a corona discharger has already been disclosed as an electrophotographic display in Japanese Patent Application Laid-Open No. 57-119375. This device is shown in FIG. 3A. A transparent conductive layer 12 made of ITO is provided on a transparent substrate 11, a photosensitive layer 13 made of a CdS binder binder layer having a thickness of 65 μm is provided thereon, and a white insulating layer 14 having a certain resistance value is further provided thereon. A conductive magnetic toner developing machine 1 is formed on a recording film 15 having a laminated structure.
6 are arranged facing each other, and while applying a voltage between the developing machine 16 and the transparent conductive layer 12, image exposure is performed through the semiconductor laser 17, the polygon scanner 18, and the f _θ lens 19. Since the voltage is applied between the developing roller and the ITO, the light beam is irradiated as shown in FIG. 3B, and the photocharge runs to the toner side in the photosensitive layer CdS portion where the resistance is lowered, resulting in the toner. The toner is attracted to the photoreceptor by the clonal force by attracting the induced opposite charge. On the other hand, in the portion not irradiated with light, the thickness of the insulating layer is sufficiently large, so that the electric adhesion is weak and the toner does not adhere to the photoconductor. As a result, the toner image 2 corresponding to the exposure
0 or formed on the photoreceptor. After the image formation, the photocharge and the charge induced in the toner are discharged through the surface layer within one cycle of the image display. As a result, when the image is formed next time, it is held again on the developing roller. On the other hand, image exposure is performed without any trouble, and a new image can be formed. In this method, since the image is formed by utilizing the difference in Coulomb force exerted on the toner in the exposed portion and the non-exposed portion, it is necessary to considerably increase the film thickness of the photoconductor.
However, it is difficult to produce a thick photoconductor uniformly, and
As the amount of the photoconductor material used increases and the film thickness increases, the recording voltage increases and the photosensitivity decreases. Further, when the image forming method is applied to a hard copy device, there is a drawback that transfer to plain paper is difficult because the toner is a conductive toner.

It is an object of the present invention to provide an image recording apparatus and an image forming method that solve the above drawbacks.

[Means for solving problems]

According to the present invention, the above-mentioned problems are caused by a photosensitive member in which a transparent conductive film and a photoconductive layer are sequentially arranged on a transparent substrate, and an image exposing means arranged so as to face the transparent substrate through the photosensitive member. And an developing device disposed opposite to the photoconductive layer surface, which conveys charged toner between the developing device and a photoconductor and applies a voltage between the developing device and the transparent conductive film. A first developing machine having a plurality of island-shaped microelectrodes disposed on the photoconductive layer, the developing machine facing the island-shaped microelectrodes, and a predetermined distance from the first developing machine. And a second developing machine which is arranged facing the island-shaped microelectrodes.

Further, according to the present invention, the above-mentioned problems are caused by applying a voltage between the first developing device and the transparent electrode to form a charged toner layer on the island-shaped microelectrodes by using the above-mentioned device and at the same time, to the transparent conductive film. After inducing an electric charge, the photosensitive member is moved to expose the photosensitive member to light by irradiating the photosensitive member with light corresponding to an image pattern from the substrate side, and the electric charge induced on the transparent conductive film is exposed to the light. What is the voltage applied to the first developing machine to the second developing machine, which is trapped on the exposed surface of the photoconductive film of the body and then moved to the second developing machine facing the island electrode? By applying a voltage of opposite polarity to electrostatically remove the charged toner adhering to the non-exposed portion, and forming a toner image corresponding to the light irradiation pattern on the surface of the photoconductor by an image forming method. Is also solved.

Before describing the present invention, the recording principle of the previously proposed novel image forming method will be described below with reference to FIGS. 4A, 4B and 4C. A transparent conductive film 22 and a photoconductive layer 23 are provided on the transparent substrate 21. A two-component developer composed of an insulating toner and a carrier is conveyed onto the photoconductive layer 23, and a voltage is applied between the sleeve of the magnetic brush developing machine 25 and the transparent conductive layer 22. In FIG. 4, a positive voltage V _b1 is applied. Development is performed in this state to form a uniform charged toner layer.

At this time, the photoconductive layer 23 functions as a capacitor, and negative charges having the opposite polarity are induced in the transparent conductive film 22 corresponding to the charges of the toner layer 26 attached to the photoconductive film 23. Adhering toner amount Mi in the I developing process shown in FIG. 4A
Is expressed by the following equation.

Here, δ is the mass of the toner, p is the filling rate per unit volume of the toner, ρ _i is the volume charge density of the adhered toner layer in the image area, ε ₀ is the dielectric constant of vacuum, and ε _r is the relative dielectric constant of the toner layer. rate,
d is the thickness of the photoconductive film. The charge amount Q of the toner layer at this time is expressed by the following equation.

However, q / m is the specific charge of the toner.

Next, after moving the photosensitive member, as shown in FIG. 4B, exposure is performed by irradiating laser light in the direction of arrow B corresponding to the image pattern to be printed. Then, the charges 27 induced in the transparent conductive film 22 move to the surface of the photoconductive film 23 because the resistance of the photoconductive film 23 is reduced by the irradiation of the laser beam.

When the exposure is stopped here, the resistance of the photoconductive film 23 returns to the original resistance of the substantially perfect insulator. Therefore, the photoconductive film 23
The charges 27 that have moved to the surface of the above become trap charges 28 and cannot move, and this becomes latent image charges.

After the photoconductor is further moved, in the II developing step shown in FIG. 4C, the DC developing bias voltage V _b2 is positive on the transparent conductive film 22 side and in the II magnetic step, contrary to the case of the I developing step. The voltage is applied so that the brush developing machine 29 becomes negative.

Then, the positively charged charged toner in the non-image portion where the latent image charge is not formed is generated in the second magnetic brush developing device 29 by the electric field of the second magnetic brush developing device 29 and the transparent conductive film 22. Collected inside. At the same time, the negative electrons 27 having negative charges induced in the transparent conductive film 22 gradually move to the ground electrode side, and finally the free electrons induced in the transparent conductive film 22 completely disappear. To do.

On the other hand, in the image forming portion irradiated with light, a part of the charged toner is discharged from the second magnetic brush developing device 29 and the transparent conductive film 22.
Recovered by the electric field between. At this time, the charges 28 trapped on the surface of the photoconductive film 23 cannot move because the photoconductive film 23 is an insulator, and the photoconductive film 2 is not charged.
By the same operation as the condenser of No. 3, the transparent conductive film 22 corresponds to the charge amount of the charged toner collected by the electric field.
A positive charge 30 of the same polarity is induced on top. Since the capacity of the photoconductive film 23 when light is not irradiated is small, the surface potential on the photoconductive film 23 is greatly changed even with a slight positive charge 30 of the transparent conductive film 22. The voltage is balanced with the voltage _Vb2, and the toner in the image area no longer is electrostatically collected.

In this way, the charged toner 31 remains only in the image portion,
A toner image is formed. Adhering toner amount Mo at this time
i is a process of developing the trapped charge Q obtained in the I-th developing step with the developing bias voltage V _b2 , and thus is expressed by the following equation.

However, Q depends on the second equation.

The fourth term of the formula (3) represents the latent image charge due to the trap charges. Normally, the amount of adhered toner Moi has a positive value, so that by keeping this latent image potential higher than the developing bias potential V _b2 in the second developing step, sufficiently dark printing can be obtained in the second developing step.

In the above image forming method, the trap charge plays an important role. Therefore, the present inventors have clarified how the trap charges are distributed in the photoconductor. The result is shown in FIG. FIG. 5 shows the relationship between the surface potential Vt on the toner layer in the exposed portion after the I-th development and the photosensitive member surface potential Vs immediately after the charged toner is blown off with N ₂ gas. Is. The Δ mark in FIG. 5 indicates
The results of measuring the trap voltage Vs in the case of using a photoconductor in which a transparent conductive film is provided on a transparent substrate and a photoconductive film is further provided thereon are shown. Further, the solid line is a theoretical value obtained by assuming that trap charges corresponding to the charge amount of the adhered toner are distributed at the interface of the photoconductor. Further, the broken line is a theoretical value obtained by assuming that the trap charges corresponding to the charge amount of the adhered toner are uniformly distributed inside the photoconductor. From this, it is considered that the theoretical value and the experimental value of the broken line are in good agreement, and that the trapped charges are evenly distributed in the photoconductor after the charged toner layer is removed.

This apparently corresponds to the doubling of the photoconductor capacity, and in order to obtain a constant density, the recording voltage should be about twice or more than that of the trap charge distributed on the surface of the photoconductor. It means that it must be raised.

In order to solve this drawback, the present inventors have devised a method of forming the trapped charges on the outer surface of the photoconductor and on the surface of the photoconductor. The mark ◯ in FIG. 5 is obtained by the method of the present invention.
It shows the trap voltage immediately after blowing the adhered toner layer developed on the u foil with N ₂ gas. From this, it was revealed that when the Cu foil was provided on the surface of the photoconductor, trap charges were formed on the surface of the photoconductor.

As described above, in the interface charge distribution in which the trap charges are present on the surface of the photoconductor and the bulk charge distribution in which the trap charges are evenly distributed inside the photoconductor, the amount of adhered toner obtained after the second development is different from each other by the following formula.

In Equations (4) and (5), the fourth term represents the latent image potential (trap voltage) due to the trap charges. From the comparison of both formulas, it can be seen that the amount of adhered toner increases in the formula (4) according to the present invention if the trap charge amount Q is the same.

An embodiment of the present invention when applied to a hard copy device will be described with reference to FIG.

The photoconductor film 32 includes the transparent substrate 21 and the transparent conductive film 2.
2, a film having a four-layer structure including a photoconductive layer 23 and an island-shaped microelectrode 33. The transparent substrate 21 is a polyethylene terephthalate film having a thickness of 75 μm, the transparent conductive film 22 is an indium oxide vapor deposition film, and the photoconductive film 23 is an organic semiconductor having a thickness of 10 μm. A mesh pattern of several μm squares was brought into close contact with the film thus constructed, and nickel was vapor-deposited on the mesh pattern to form the island-shaped microelectrodes 33. The island-shaped microelectrode 33 is 1 dot, 100
About 2 or 3 pieces per μm are preferable.

Two magnetic brush developers 3 in contact with the island-shaped microelectrode surface
4, 35 are provided. The magnetic brush developing machine 34 and the magnetic brush developing machine 35 are integrated and incorporated in one housing 36. Between the magnetic brush developing machine 34 and the magnetic brush developing machine 35, and further, on the transparent substrate side, an LED 37 and a self-fox lens 38 were installed as a light source for exposure. Further, a conductive rubber roller 41 is provided as a transfer means for transferring the toner image 39 onto the recording paper 40. Further, a fur brush cleaner 43 for removing the toner 42 remaining on the photoconductor film is provided, and a charge eliminating lamp 44 for removing trap charges and surface charges is provided.

Both the magnetic brush developing machines 34 and 35 are sleeve rotating,
The sleeve peripheral speed is 30 cm / s. The developer is a two-component developer in which a non-magnetic insulating toner having a particle size of about 10 μm and a carrier of iron powder of about 10 to 15 μm are mixed at a weight ratio of 20%. The specific charge of the toner was 10 μC / g.

The operation of this embodiment will be described below.

Endless speed of photoconductor film in the direction of arrow 10 cm / s
To run.

A developing bias voltage V _b1 = 300 V is applied between the transparent conductive film 22 and the magnetic brush developing device 34 to perform development to form a uniformly charged toner layer. At this time, negative charges of opposite polarity corresponding to the amount of adhered toner are induced on the transparent conductive film.
After that, the LED 37 is controlled according to the image information, and negative exposure is performed via the sec-focal lens 38. In the exposed portion, photocarriers are generated in the photoconductive layer 23, electrons reach the island-shaped microelectrode 33 through the photoconductive layer, and the potentials of the transparent conductive layer and the island-shaped microelectrode become almost the same. At this time, negative charges having the same polarity as the charges on the charged toner layer developed by the magnetic brush developing machine 34 move to the island-shaped microelectrode surface through the transparent conductive layer 22 and the photoconductive layer 23. To do. Then, when the exposure is complete, the photoconductive layer becomes highly resistive and can no longer move.

Next, a developing bias voltage _Vb2 = -100V, which is the reverse of that of the magnetic brush developing machine 34, is applied to the magnetic brush developing machine 35 to develop. Then, in the image portion, a part of the charged toner is collected by the action of the electric field. However, at this time, the electrons trapped on the island-shaped microelectrode cannot move,
Depending on the amount of charge of the collected charged toner, the transparent conductive layer 2
A positive charge having the same polarity as the charged toner is induced on the surface 2. Since the capacitance of the photoconductive layer in the dark area is small, the surface potential of the photoconductive layer surface is greatly displaced even with a slight positive charge,
Balance with development bias voltage V _b2 . Then, the toner in the image area is no longer collected. On the other hand, the positively charged toner in the non-image area gradually develops due to the electric field.
It begins to be recovered within 5. At the same time, the transparent conductive film 22
The electrons induced above also gradually move to the ground side, and finally the free electrons induced on the charged toner layer and the transparent conductive layer disappear completely. Along with this, the toner attached to the non-image portion is completely collected in the developing machine 35.

The toner image 39 thus formed is electrostatically transferred onto the recording paper 40 by the conductive rubber roller 41 to which a voltage having a polarity opposite to that of the charged toner is applied. The fur brush cleaner removes the residual toner remaining on the photoreceptor layer without being transferred. Then, the trap charges and the surface charges on the surface of the photoconductor are discharged by the discharge lamp 44. Printing is continuously performed by repeating the above process.

In this way, in this example, dark print without fog having the print density OD = 1.0 or more and the fog density OD = 0.02 or less was obtained. On the other hand, in the previously proposed novel image forming method (Japanese Patent Application No. 59-173636), the developing bias voltage V _b1 = 700 V or more is required to obtain OD = 1.0 or more. However, the method of the present invention has an advantage that the recording voltage can be reduced to about 1/2. Further, since the island-shaped microelectrodes are used, there is a secondary effect that the edge effect effectively acts even on a solid black image.

Further, in comparison with the case where the conventional image forming method shown in FIG. 3A is applied to a hard copy apparatus, the photoconductive layer thickness is about 10 μm (about 1/5 or less of the conventional method) in this embodiment. Therefore, the manufacturing cost of the photoconductor film can be reduced.

The photosensitivity increases with a thin photoconductor.

Insulating toner can be used and transfer to plain paper is easy.

It has various features such as.

〔The invention's effect〕

As described above, according to the present invention, since it is not necessary to use a corona discharger, a high voltage is unnecessary, and
Reliability is improved because it is less affected by humidity and dust.
In addition, there is an advantage that the recording can be performed with a lower voltage than the previously proposed novel image forming method (Japanese Patent Application No. 59-173636) by a simple process. Further, in the present invention, since the insulating toner can be used, when the present invention is applied to a hard copy device, there is an advantage that transfer to plain paper is possible.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment in which the present invention is applied to a hard copy device, and FIG. 2 is a schematic diagram for explaining an image forming device of a conventional electrophotographic recording system, 3A and 3b are schematic views for explaining an electrophotographic display device which is an example of another conventional recording method, and FIG. 4 is a novel image previously proposed by the present inventors. It is a figure for demonstrating the printing principle of a formation method, and FIG. 5 is a figure for demonstrating the principle of this invention. DESCRIPTION OF SYMBOLS 1 ... Recording drum, 2 ... Photoconductive layer, 3 ... Corona discharger, 4 ... Exposure means, 5 ... Developing machine, 6 ... Transfer corotron, 7 ... Fixing device, 8 ... Static elimination corotron, 9,43 ... Far brush cleaner, 10,40 ... Recording paper, 11,21 ... Transparent substrate, 12 ... Transparent conductive layer, 13 ... Photosensitive layer, 14 ... White insulating layer, 15 ... Recording film, 16 ... Developer, 17 ... Semiconductor laser, 18 ... Polygon scanner, 19 ... f _theta lens, 20,39 ... toner image, 22 ... transparent conductive film, 23 ... photoconductive layer, 26 ... toner layer, 27 ... charge, 28 ... trapped charge, 30 ... positive charge, 31 ... charged toner , 32 ... Photosensitive film, 33 ... Island-shaped microelectrodes, 34, 35 ... Magnetic brush developing machine, 36 ... Housing, 37 ... LED (light emitting diode), 38 ... Selfoc lens, 41 ... Conductive rubber roller, 44 ... Static elimination lamp.

Claims (2)

[Claims] 1. A photoconductor in which a transparent conductive film and a photoconductive layer are sequentially arranged on a transparent substrate, an image exposing means and a photoconductive layer surface which are arranged to face the transparent substrate through the photoconductor. And a developing device disposed opposite to the image forming device, wherein the developing device and the photoconductor convey a charged toner and a voltage is applied between the developing device and the transparent conductive film. A plurality of island-shaped microelectrodes are arranged on the upper surface of the developing machine, and the developing machine has a first developing machine arranged to face the island-shaped microelectrodes and has a predetermined distance from the first developing machine. An image recording apparatus comprising a second developing device arranged so as to face the island-shaped microelectrodes. 2. A photoconductor in which a transparent conductive film and a photoconductive layer are sequentially arranged on a transparent substrate, and an image exposing means and a photoconductive layer surface which are arranged to face the transparent substrate through the photoconductor. An image recording device for transporting charged toner between the developing device and a photoconductor and applying a voltage between the developing device and the transparent conductive film. A first developing machine in which a plurality of island-shaped microelectrodes are arranged on a layer, and the developing machine is arranged to face the island-shaped microelectrodes; and a first developing machine having a predetermined distance from the first developing machine. An image forming method using an image recording device, wherein the second developing device is arranged so as to face the island-shaped microelectrodes, and a voltage is applied between the first developing device and the transparent electrode to charge the image. A toner layer is formed on the island-shaped microelectrodes and electric charges are induced in the transparent conductive film, and thereafter, The photoconductor is moved to expose the photoconductor by irradiating the photoconductor with light corresponding to an image pattern from the substrate side, and exposing the photoconductive film of the photoconductor with the charges induced on the transparent conductive film. Then, the photosensitive member is moved, and a voltage having a polarity opposite to that of the voltage applied to the first developing device is applied to the second developing device facing the island-shaped electrode. An image forming method characterized in that the charged toner attached to the non-exposed portion is electrostatically removed and a toner image corresponding to a light irradiation pattern is formed on the surface of the photoconductor.