JPH0118424B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement for obtaining high quality recorded images at low cost in an electrostatic recording method.

Conventionally, when performing electrostatic recording on recording media using pin electrodes, etc., there was a problem that only recorded images with low resolution could be obtained due to abnormally large recording dot diameters, etc.This problem was solved. Several proposals have already been made for this purpose.

FIG. 1A is a schematic diagram showing the electrostatic latent image forming method proposed in the past (Japanese Patent Application Laid-Open No. 147532/1983), and FIG. 1B is a circuit diagram showing its electrical equivalent circuit. It is. Refer to the same figure. The latent image forming body is made by coating a conductive base material 3 with a layer having a low capacitance C ₂ and an intermediate resistance R ₂ as a first dielectric layer 4, and then applying a charge. As a recording layer on which a latent image is formed, a two-layer structure is used, in which a recording layer 5 of high capacitance C ₁ is formed of a second dielectric layer, and a driver 2 is connected to a pin electrode 1.
A latent image is formed on the recording layer 5 by applying a pulse voltage. The capacitance C ₂ of the underlayer 4 is selected to be lower than the capacitance C ₁ of the recording layer 5, and at least a fraction of the capacitance C 1 . Then, when a pulse voltage is applied from the pin electrode 1, the discharge current is intermittent multiple times at a period determined by the time constant C ₂ R ₂ during the application, and a good latent image dot can be obtained. However, this conventional example has a drawback in that it is practically difficult to realize the underlayer 4 having a capacitance C ₂ lower than the capacitance C ₁ of the recording layer 5. Generally, when a resin is mixed with carbon or the like to impart conductivity, the capacitance becomes extremely large, and therefore it can be said that it is practically difficult to realize the above-mentioned base layer 4.

FIG. 2 is a circuit diagram of an electrostatic recording device according to a conventional proposal (Japanese Patent Publication No. 19414/1983). In the figure, a back electrode 6, a front electrode 7,
A high voltage power source 8, an electrostatic recording medium 9, and a protruding portion 10 of the front electrode are arranged as shown in the figure, and a resistor r is interposed between the back electrode 6 and the ground terminal of the high voltage power source 8. With this circuit configuration, the resistance value of resistor r is
When a voltage pulse was applied between electrodes 7 and 6 with the resistor set at 100 kΩ or more and 30 MΩ or less, better electrostatic recording was obtained than in the case where the resistor r did not exist. However, as in this conventional example, the resistance r
If it is connected to an external circuit, the recording speed will be slow due to the stray capacitance, which has the disadvantage that it is not suitable for high-speed recording. By the way, if the stray capacitance is 100PF and the resistance is 10MΩ, the time constant is 100×10 ^-12 ×10×
10 ⁶ = 10 ^-3 seconds.

FIG. 3 is a schematic cross-sectional view of an electrostatic recording medium according to a conventional proposal (Japanese Unexamined Patent Publication No. 152733/1983). The one shown in the figure has a resistance of 10 ⁶ to 10 ¹² Ω·cm between the conductive substrate 11 and the electrostatic recording layer 12 made of a dielectric material.
The recording medium has a semiconductive intermediate layer 13 interposed therebetween and has a volume resistivity of several μ to several + μ, and specifically, the conductive substrate 11 is made of aluminum, This is a recording medium in which a semiconductive intermediate layer 13 is formed by alumite treatment on the aluminum substrate, and a dielectric layer 12 is provided on top of the semiconductive intermediate layer 13, and when electrostatic recording is performed using such a recording medium, This means that image quality can be improved. However, in this case as well, as in the case of the conventional example described with reference to FIG. 1, there is a drawback in that, as a practical matter, it is difficult to realize the dielectric layer 12 with the intermediate layer 13 as described above. Furthermore, forming the intermediate layer by alumite treatment has the drawback that the resistance value is too high and the efficiency of electrostatic recording is poor.

FIG. 4 is a schematic diagram showing an electrostatic recording method similarly proposed in the past (printed at the 42nd research discussion session of the Electrophotography Society, November 16, 1978). In the figure, a recording medium is used in which a conductive layer 17 made of a metal vapor deposition film is arranged between a base 18 made of a polyester film or the like and a dielectric layer 16 made of a polyester resin with pigment added, and a voltage is applied to the recording electrode 14. This method performs electrostatic recording by applying voltage V ₁ and voltage V ₂ to the control electrode 15, but this method is a so-called single-sided recording method and has the drawback of slow recording speed. That is, this method has the disadvantage that it is suitable for slow recording at a recording speed of several m ³ /line or more, but is not suitable for high-speed recording.

In addition, the surface of the dielectric layer on which the electrostatic latent image is formed is opposed to the pin electrode in a non-contact manner, and a voltage is applied to the pin electrode to cause discharge between the two, thereby creating an electrostatic latent image on the surface of the dielectric layer. In the case of an electrostatic recording device in which the surface of the dielectric layer and the pin electrode are not in contact (there is a gap between them), discharge will not occur unless the voltage applied to the pin electrode is increased. Under these circumstances, if the voltage applied to the pin electrode is increased,
It is difficult to arrange the pin electrodes in a high density arrangement due to the withstand voltage between the pin electrodes, which makes it impossible to increase the recording density and make it impossible to obtain high-quality recorded images.
Similarly, when the voltage applied to the pin electrode increases, the influence of the induced voltage on the adjacent electrode increases, resulting in the problem that a high quality recorded image cannot be obtained. Furthermore, if the voltage applied to the pin electrode is increased, circuit elements with high withstand voltages are required, resulting in an increase in cost. In order to solve these problems, the electrostatic recording device previously proposed (Japanese Patent Application Laid-Open No. 158336/1983) uniformly charges the surface of the dielectric layer in advance to reduce the electric field strength necessary for discharge.
The voltage applied to the pin electrode was reduced by sharing the voltage applied to the pin electrode with the dielectric layer surface voltage caused by the charged charges.
However, in this recording device, as a method for pre-charging the surface of the dielectric layer, a method is used in which a corona discharge is generated separately and the resulting charge is charged, which tends to cause uneven charging on the surface of the dielectric layer.
Therefore, there is a drawback that the quality of recorded images is unstable.

This invention was made in order to solve the drawbacks of the conventional proposals as described above, and the purpose of this invention is to enable high-speed recording and to prevent the recording dot diameter from increasing. An electrostatic recording method that has high resolution due to its normal size, is easy to implement in practice, and can reduce the voltage applied to the recording electrode without destabilizing the quality of the recorded image. Our goal is to provide the following.

The main point of the structure of the present invention is that in a recording medium in which a resistance layer made of a conductive resistor is arranged between a recording layer made of a dielectric material and an insulating layer made of an insulator, one end of the resistance layer is A recording electrode is connected to a potential source, and a recording electrode is opposed to the recording layer, and a discharge current is passed between the recording electrode and the constant potential source through the recording layer and the resistance layer to generate an electrostatic charge in the recording layer. A latent image is formed, at which time the electric field strength necessary to form the electrostatic latent image is shared between a constant potential voltage applied to the resistive layer and a voltage applied to the recording electrode, and The capacitance due to the gap between the recording electrode and the recording layer is smaller than the capacitance of the recording layer, and the surface resistance of the resistance layer is 10 ⁵ to 10.
10 ¹² Ω/□.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 5 is a schematic diagram showing one embodiment of the present invention, FIG. 6 is a schematic diagram showing another embodiment, and FIG. 7 is a circuit diagram showing an electrical equivalent circuit thereof.

Please refer to FIG. The recording medium is composed of a recording layer 19 made of a dielectric material or the like, an insulating layer 21 made of an insulator or the like, and a conductive resistance layer 20 placed between them. The electrode 22 is in contact with or in contact with the recording layer 19.
They face each other with a minute gap of 100 μm or less (hereinafter simply referred to as non-contact), but the fifth
The figure shows the case of contact. Further, the recording medium is supported by an insulated roller 24. One end of the conductive resistance layer 20 is grounded via a power supply VB. When a pulse voltage is applied to the recording electrode 22 from a pulse voltage source 23 whose one end is grounded, a closed circuit in which a discharge current flows as shown by the dotted line is created. That is, a closed circuit is formed from the pulse voltage source 23 through the recording electrode 22, the recording layer 19, the resistive layer 20, and the power source VB and returning to the pulse voltage source 23. The magnitude of the discharge current is determined by the surface resistance value of the conductive resistance layer 20. In addition, the discharge voltage is the voltage from the pulse voltage source 23 and the power supply.
It is shared by the voltage of VB.

Please refer to FIG. Recording electrode 22 and recording layer 19
This embodiment differs from the embodiment shown in FIG. 5 in that it is non-contact and the recording medium is supported by a metal drum 25.
Similarly, the discharge current during discharge is defined by the surface resistance value of the resistance layer 20, and the discharge voltage is shared by the voltage from the pulse voltage source 23 and the voltage from the power supply VB.

Please refer to FIG. In the equivalent circuit shown in the figure, capacitance C _a is the capacitance due to the microgap between the recording electrode 22 and the recording layer 19, C _b is the capacitance of the recording layer 19 made of dielectric material, The resistance R is the surface resistance of the resistance layer 20. Also capacitance
C _n is the capacity that occurs when the metal drum 25 is used to support the recording medium, that is, in the case of the embodiment shown in FIG. 6, and is the capacity that does not occur in the case of the embodiment shown in FIG. It is represented by a broken line for its meaning.

In the configuration of the embodiment of the present invention as described above, the electrostatic charge in the recording layer 19 can be reduced by changing the surface resistance value R of the conductive resistance layer 20 or by adjusting the grounding position of the resistance layer 20. Factors that degrade the resolution of recorded images, such as enlargement of latent image dots, blurring, and blurring, can be easily removed. Furthermore, it is preferable and easy to make the capacitance C _b larger than C _a . A suitable surface resistance of the resistance layer 20 is 10 ⁵ to 10 ¹² Ω/□ (here, □
generally represents a square with sides of 1 cm).

Next, to describe a specific example, the recording layer 19 is as follows:
A polyester film with a thickness of about 10 to 30 μm is suitable, but if the capacitance is increased by a method such as dispersing particles with a high dielectric constant therein, the recording efficiency will not decrease even if the film thickness is further increased. Additionally, durability can be improved by adding an abrasion resistant layer to the surface. conductive resistive layer 2
0, a metal such as palladium, indium oxide, or a vapor-deposited film of a metal oxide may be used, and a suitable surface resistance is 10 ⁵ to ^{10 12} Ω/□.
It is also possible to use sputtering other than vapor deposition or ion conductive resin. Insulating layer 21
A suitable thickness of polyester is 200 μm, but any other insulating material may be used, and the film thickness may be selected as appropriate. However, as in the case of the embodiment shown in FIG. 6, when a metal body is located below, it is possible to improve the recording efficiency by appropriately selecting the film thickness. In other words, the effect of the capacitance C _n in the equivalent circuit can be seen.

FIG. 8 is a graph showing temporal changes in the voltage VG applied between the recording electrode and the ground (GND).
In the same figure, when the voltage of power supply VB is VB=0,
Discharge starts at time _t2 when voltage VG exceeds discharge threshold voltage Vth, but when an appropriate voltage VB
(≠0), the voltage VG exceeds the discharge threshold voltage Vth at time _t1 . In other words, the start time of electrostatic recording is advanced. However, in this case,
It is necessary that VB<Vth. In addition, VP is
Represents the voltage applied to the recording electrode.

FIG. 9 is a voltage level comparison diagram showing a comparison of the levels of each voltage. Referring to the same figure, voltage VB
How to determine the optimum value of will be explained using the case of negative charging as an example. In principle, the voltage VB can be equal to the discharge threshold voltage Vth, but in reality,
It is preferable to set VB so that the sum of voltages Vi and VB induced in the pin electrode when a recording voltage is applied to another pin electrode does not exceed Vth. The smaller Vi is, the closer VB can be to Vth, so the recording efficiency increases. To lower Vi,
This can be achieved by taking measures such as reducing the capacitance between pins.

As explained above, according to the present invention, in order to obtain clear recorded dots with high resolution in an electrostatic recording method, it is easy to realize a recording medium necessary for this purpose, and moreover, it is possible to maintain high-speed recording. Furthermore, since the voltage applied to the recording electrodes can be reduced, the dielectric strength of the recording electrode drive circuit can be reduced, reducing costs accordingly.The distance between the recording electrodes can be narrowed, making high-density recording possible and stable. It has advantages such as high quality image recording.

[Brief explanation of drawings]

FIG. 1A is a schematic diagram showing an example of a conventional electrostatic latent image forming method, B is a circuit diagram showing its electrical equivalent circuit, FIG. 2 is a circuit diagram of a conventional electrostatic recording device, FIG. 3 is a schematic cross-sectional view of a conventional electrostatic recording medium, and FIG. 4 is a schematic diagram showing a conventional electrostatic recording method.
FIG. 5 is a schematic diagram showing an embodiment of the present invention, and FIG.
The figure is a schematic diagram showing another embodiment of the present invention, FIG. 7 is a circuit diagram showing an electrical equivalent circuit of the above embodiment, and FIG. 8 is a diagram showing temporal changes in the voltage applied between the recording electrode and the ground. The graph in FIG. 9 is a voltage level comparison diagram showing a comparison of the levels of various voltages. In the figure, 1 is a pin electrode, 2 is a pin electrode driver, 3 is a conductive base material, 4 is a base layer that is a first dielectric layer, 5 is a recording layer that is a second dielectric layer, 6
is the back electrode, 7 is the front electrode, 8 is the high voltage power supply, 9
10 is the electrostatic recording medium, 10 is the protruding part of the front electrode,
11 is a conductive substrate, 12 is an electrostatic recording layer, 13 is a semiconductive layer, 14 is a recording electrode, 15 is a control electrode, 1
6 is a dielectric layer, 17 is a conductive layer, 18 is a base, 19
20 is a recording layer, 20 is a conductive resistance layer, 21 is an insulating layer, 22 is a recording electrode, 23 is a pulse voltage source, 24
indicates an insulated roller, and 25 indicates a metal drum.

Claims (1)

[Scope of Claims] 1. A recording medium in which a resistive layer made of a conductive resistor is arranged between a recording layer made of a dielectric material and an insulating layer made of an insulating material, wherein one end of the resistive layer is placed at a constant potential. A recording electrode is placed opposite to the recording layer, and a discharge current is passed between the recording electrode and the constant potential source through the recording layer and the resistance layer to generate an electrostatic latent in the recording layer. In this case, the electric field strength necessary for forming an electrostatic image is divided between a constant voltage applied to the resistive layer and a voltage applied to the recording electrode, and the recording The capacitance due to the gap between the electrode and the recording layer is smaller than the capacitance of the recording layer, and the surface resistance of the resistance layer is 10 ⁵ to 10.
An electrostatic recording method characterized by 10 ¹² Ω/□.