JPH02244062A - Method for sensitizing image recording - Google Patents

Abstract

PURPOSE:To enhance contrast by uniformly precharging electric charge reverse in polarity to imagewise charge before imagewise exposure. CONSTITUTION:For example, a corona discharge electrode 10 is moved in a state of opposing the electrode 10 to a charge retaining medium 1 and prescribed voltage is applied from a power supply E between the electrode 1b of the medium 1 and the electrode 10, and an insulating layer 1a is precharged to a polarity opposite to that of the imagewise charge formed by imagewise exposure to give uniform reverse charge 11. Then, it is uniformly reversely charged and the charge retaining medium 1 is opposed to a photosensitive body 2, and a prescribed voltage is applied between both electrodes, to imagewise expose the photosensitive body, thus permitting contrast to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high-resolution image recording method, and particularly to an image recording sensitization method that improves contrast.

[Conventional technology]

A photoreceptor having a conductive layer and a photoconductive layer formed on a support and a charge retention medium having a conductive layer and an insulating layer formed on a support are placed close to each other, and a voltage is applied between both conductive layers. We have already proposed a method for recording and reproducing images on a charge-retaining medium by exposing the photoreceptor to light without applying a charge-retaining medium and generating a corona discharge between the photoreceptor and the charge-retaining medium.
It has been filed as No. 121592. According to this method, extremely high-resolution analog recording is possible, and it is possible to semi-permanently retain an electrostatic latent image on a charge-retaining medium.

[Problem to be solved by the invention]

By the way, in the above-mentioned image recording method, when the voltage in the gap between the photoreceptor and the charge holding medium exceeds the firing voltage of Paschen discharge, a constant potential is generated on the charge holding medium even when no exposure is performed. There was a problem in that it became a background and lowered the contrast.

The present invention is intended to solve the above problems, and provides an image recording sensitization method that can improve contrast by pre-charging with charges of opposite polarity to the image charge prior to image exposure. With the goal.

[Means to solve the problem]

FIG. 1 is a diagram for explaining the image recording aggravation method of the present invention, in which 1 is a charge retention medium, 1a is an insulating layer, 1b is a charge retention medium electrode, lc is an insulating layer support, and 2 is a photosensitive body, 2
a is a photoconductive layer support, 2b is a photoreceptor electrode, 2c is a photoconductive layer, E is a power source, 1° is a corona discharge electrode, and 11 is a charged charge.

In the present invention, first, as shown in FIG.
A predetermined voltage is applied by E, and the insulating layer 1a is uniformly pre-charged with charges 11 having a polarity opposite to the image charge due to image exposure. For this purpose, in FIG. 1(a), the corona discharge electrode 10 is moved in a state facing the charge retention medium 1.

Further, as shown in FIG. 1(b), an electrode 20 having a shape facing the charge holding medium 1 on the entire surface is arranged, a predetermined voltage is applied between the electrode 20 and the charge holding medium electrode 1b, and the insulation II
It may be possible to uniformly charge the surface of la.

Furthermore, as shown in FIG. 1(c), the photoreceptor 2 and the charge holding medium 1 are arranged facing each other, and a predetermined voltage is applied between the electrodes 2b and 1b to expose the entire surface from the photoreceptor side, thereby uniformly exposing the photoreceptor to light. The charge-retaining medium 1, which may be electrically charged, and the photoreceptor 2, which have been uniformly charged, are placed facing each other as shown in FIG. 2, and a predetermined voltage is applied between the two electrodes to perform image exposure. .

As a result, the exposed portion of the photoconductive layer 2c of the photoreceptor 2 becomes conductive, and the charges injected into the photoconductive layer 2c from the electrode 2b move to the surface of the photoconductive layer 2c, causing ionized ions in the voids. The charge in the void having the opposite polarity to the bonded ion is attracted by the electric field of the void and is charged on the insulating layer lc,
Image recording is performed.

In such image recording, the photoreceptor 2 can be thought of as a conductor while it is irradiated with light, and as an insulator when it is not irradiated with light, and a voltage determined by Paschen's discharge characteristics is applied to the air layer. The discharge gap can be considered a conductor if a voltage exceeding Further, the charge retention medium 1 may be considered to be an insulator at all times.

Therefore, the system shown in FIG. 2 can be considered as an equivalent circuit as shown in FIG. 3(a). In FIG. 3(a), ■ is the power supply voltage applied between the photoreceptor and the charge holding medium, C, R,
are the resistance and capacitance of the photoreceptor, C8 and R2 are the resistance and capacitance of the air layer, Vg is the Paschen discharge starting voltage, and C3 is the capacitance of the charge holding medium.

When the voltage of the air gap exceeds the discharge starting voltage Vg, the voltage of the air gap saturates at Vg. The equivalent circuit when no light is irradiated and the voltage of the gap exceeds the discharge starting voltage is as shown in Figure 3(b), where the power supply voltage decreases by Vg and the photoreceptor and charge retention medium can be considered as an equivalent circuit in which capacitances C+ and Cs are connected in series. Then, when light is irradiated from the photoreceptor side and the photoreceptor becomes a conductor, as shown in Figure 3 (C
) can be considered as an equivalent circuit.

Now, if the charge retention medium 1 is pre-charged uniformly and the potential becomes ■゛, then the charge retention medium 1 will have Q=C, V'...
This means that the charge in (1) is charged. If the voltages distributed to the capacitors C8 and C1 when the voltage of the air gap exceeds the discharge starting voltage g are V, , V, then the following simultaneous equations hold true.

V, +V, kov-v g CIV+ +Cs Vs =Cs V'By solving this second, Vl -cs (V-Vg)/ (c+ +cs)
-Cs V'/ (CI + Cs) ・
...(2)v, -Ct (V-Vg)/(C
I +C3)+CsV”/(C++CI −−・−
-(3) The first term on the right side of equation (2) is the voltage applied to the photoreceptor in the dark state, and the second term is the voltage generated on the photoreceptor due to pre-charging. Furthermore, in equation (3), the first term on the right side is the fog potential of the unexposed portion, and the second term is the voltage generated by pre-charging.

Next, when image exposure is performed and the photoreceptor becomes a conductor, that is, when the equivalent circuit becomes as shown in FIG. 3(C), the potential on the charge holding medium is V -Vg. Therefore, the potential difference between the exposed part and the unexposed part on the charge holding medium, that is, the contrast potential is V-Vg Vl -CI (V-Vg)/(CI +Cs)ci V
'/(CI +Cs)"""(4), (
It can be seen from equation 4) that when a negative potential is applied to V', the contrast potential increases. This can be understood from the fact that in equation (3), the fog potential of the unexposed portion is canceled out by pre-charging, and in equation (2), the voltage applied to the photoreceptor increases due to pre-charging. Since the voltage applied to the photoreceptor increases in this way, using a photoreceptor material whose sensitivity depends on the electric field strength, such as selenium, can increase the quantum efficiency and increase the sensitivity.

[Effect]

In the present invention, prior to image exposure, a charge holding medium is uniformly pre-charged with a charge having a polarity opposite to that of the image charge, and then image exposure is performed to reduce the fogging potential of the unexposed area and to reduce the potential of the photoreceptor. As a result, the contrast potential can be increased and sensitivity can be improved.

C Example 1] Using a charge holding medium charged to a surface potential of -600 V with a corona voltage of 4 KV, that is, an aluminum electrode provided on a glass substrate, and coated with TSR-144 manufactured by Toshiba Silicon Co., Ltd., The photoreceptor was a-3e photoreceptor (film thickness i0u) fabricated on Nesa glass by vacuum evaporation method.
m), the air layer was set to 9 μm, and voltage application exposure was performed by applying a voltage of +750 V between the photoreceptor and the charge holding medium, and the bright area potential was 280 ■, the dark area potential was 110 V, and the contrast potential was 17 QV. .

Compared to the case where voltage is applied and exposed under the above conditions without pre-charging, the bright area potential is unchanged, but the dark area potential is 60%.
This means that the contrast voltage has improved by 6OV.

[Example 2] In addition, as a pre-charging method, an aluminum electrode plate was placed facing the charge-holding medium with an air layer of 9 μm in between, and the charge-holding medium was charged by applying a voltage of IKV. The voltage became 1600V. Then, when the same voltage application exposure as in [Example 1] was performed, the same effect was obtained.

[Example 3] Under the same conditions as the voltage application exposure in [Example 1], the photoreceptor was irradiated with −-like light, and a voltage of ~750 μm with the opposite polarity to that during voltage application exposure was applied. 128 on the charge holding medium
A potential of 0■ was applied. At this point, stop applying the voltage,
When the photoreceptor electrode was grounded while being exposed to --like light to release the charge on the surface of the photoreceptor, and then exposure was performed by applying a voltage, the dark area potential was 140 Å, and the contrast potential was improved by 30 Å.

〔Effect of the invention〕

As described above, according to the present invention, by uniformly pre-charging the image belt with a charge of opposite polarity to the charge prior to image exposure, the fogging potential of the unexposed area is reduced, and the potential of the photoreceptor is increased. As a result, the contrast potential can be improved, and it becomes possible to record images with good resolution.

[Brief explanation of drawings]

1 and 2 are diagrams for explaining the image recording method of the present invention, and FIG. 3 is a diagram showing an equivalent circuit. 1... Charge retention medium, ■a... Insulating layer, 1b...
Charge retention medium electrode, 1c...Insulating layer support, 2...
Photoreceptor, 2a... Photoconductive layer support, 2b... Photoconductor electrode, 2c... Photoconductive layer, E... Power source, 10... Corona discharge electrode, 1... Charged charge. Applicant Dai Nippon Printing Co., Ltd.

Claims (4)

[Claims] (1) A photoconductor with a conductive layer and a photoconductive layer formed on the surface of the support and a charge retention medium with a conductive layer and an insulating layer formed on the support are placed facing each other, and between the conductive layers In an image recording method in which an electrostatic latent image is recorded on a charge-retaining medium by imagewise exposure from the photoreceptor side while applying a voltage, a charge of opposite polarity to the image charge due to imagewise exposure is uniformly pre-charged before imagewise exposure. An image recording sensitization method characterized by: (2) The image recording sensitization method according to claim 1, wherein the pre-charging is performed by corona discharge. (3) Image recording according to claim 1, characterized in that an electrode is provided opposite to the charge holding medium, and a voltage is applied between the electrode and the conductive layer of the charge holding medium to cause discharge and pre-charging. Sensitization method. (4) The image recording sensitization method according to claim 1, wherein the photoreceptor and the charge holding medium are disposed facing each other, and the photoreceptor is fully exposed to light from the photoreceptor side to perform precharging.