JPH09269547A - Picture exposure device using liquid crystal display panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a liquid crystal display panel from being deteriorated by voltage impression in the case of intercepting light for recording in a picture exposure device using an always opening type liquid crystal display panel. SOLUTION: As for this picture exposure device provided with a light source 10 emitting the recording light L for exposing a photosensitive material 14, and the liquid crystal display panel 12 provided wit plural liquid crystal cells arranged in an array state and spatially modulating the light L; a shutter 16 is provided which is capable of selectively taking either the condition that the light L is intercepted or the condition that the light L is not intercepted and the shutter 16 is set in the condition that the light L is intercepted and the voltage is stopped being impressed on the respective liquid crystal cells of the panel 12 by a control means 20 at least a part of a term when the panel 12 does not perform modulation operation based on a picture signal S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display panel, and more particularly to an image exposure apparatus using a normally open liquid crystal display panel.

[0002]

2. Description of the Related Art Conventionally, a large number of liquid crystal cells, which change the light transmittance according to the voltage application, are arranged in an array, and a liquid crystal display panel which spatially modulates the light transmitted through each liquid crystal cell to display an image. Are variously provided. Further, recently, as disclosed in, for example, Japanese Patent Application Laid-Open No. 1-133041, a gradation image displayed on a liquid crystal display panel is formed on a photosensitive material, and this image is recorded on the photosensitive material. Has been.

The above-mentioned liquid crystal display panel is roughly classified into a normally closed type in which a liquid crystal cell is normally closed and opens when a voltage is applied thereto, and a normally closed type in which the liquid crystal cell is always open. It is divided into a normally open type that closes when a voltage is applied to it.
Since the latter type of liquid crystal display panel generally has a higher extinction ratio than the former type, it is suitable for use in an image exposure device that exposes a gradation image. Incidentally, FIG. 4 shows an outline of the applied voltage-transmittance characteristic of the liquid crystal display panel of the normally open type.

[0004]

By the way, when the normally open type liquid crystal display panel is used, when the recording light must be completely blocked in order to prevent fogging of the photosensitive material, for example, the image exposure described above. When the photosensitive material is set to the exposure position or discharged from the device,
A high voltage must be applied to all liquid crystal cells to fully close them.

For these reasons, when a high voltage is applied to the liquid crystal cell for a long time, the liquid crystal is likely to deteriorate.
Since this problem is remarkable when the applied voltage is a DC voltage, it is generally A for a normally open type liquid crystal display panel.
The C voltage is applied. However, even if the liquid crystal display panel is AC-driven as described above, the DC component may be accumulated in the liquid crystal when the driving time becomes long, and the liquid crystal may deteriorate as in the case of the DC drive.

The present invention has been made in view of the above circumstances, and in an image exposure apparatus using a normally open liquid crystal display panel, it is possible to prevent deterioration of the liquid crystal display panel due to voltage application when recording light is cut off. To aim.

[0007]

An image exposure apparatus using a liquid crystal display panel according to the present invention comprises a light source for emitting recording light for exposing a photosensitive material, and a normally open type liquid crystal display panel as described above. In the image exposure apparatus, a shutter that can selectively take one of a state where the recording light is blocked and a state where the recording light is not blocked, and at least a part of a period in which the liquid crystal display panel does not perform a modulation operation based on an image signal,
A control means is provided for setting the shutter to a state in which recording light is blocked and for stopping voltage application to each liquid crystal cell of the liquid crystal display panel.

[0008]

In the image exposure apparatus of the present invention having the above-described structure, the voltage application to each liquid crystal cell is stopped to fully open the liquid crystal display panel during at least a part of the period in which the normally open liquid crystal display panel does not perform the modulation operation. Therefore, the liquid crystal is prevented from being deteriorated due to the application of the high voltage for a long time, and the life of the liquid crystal is extended.

At this time, the recording light cannot be blocked by the liquid crystal display panel, but instead the recording light is blocked by the shutter. Therefore, work such as setting of the photosensitive material can be performed in the same manner as in the conventional apparatus without causing fogging of the photosensitive material.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows an image exposure apparatus which is one embodiment of the present invention. As shown in the figure, this image exposure apparatus has a light source 10 for emitting a recording light L for exposing a color photosensitive material 14, and a light source 10 arranged so that the light source 10 is near a focal position. A condensing lens 11 for collimating the light L and a large number of liquid crystal cells are arranged in a two-dimensional array, and the liquid crystal display panel 12 is arranged in a direction substantially perpendicular to the optical axis O of the condensing lens 11. An imaging lens 13 arranged at a position where the recording light L passing through the liquid crystal display panel 12 is incident, and a liquid crystal display panel
In front of 12, a color filter 15 and a black shutter 16 which are inserted in the optical path of the recording light L are provided. In addition, a parallel plate 17 is provided between the liquid crystal display panel 12 and the imaging lens 13 for performing pixel shift, which will be described later.

The light source 10 comprises, for example, a halogen lamp that emits white light, and the center of its filament is a condenser lens 11.
Are arranged so as to be located on the optical axis O of the. Further, the black shutter 16 is driven by the driving unit 16D and selectively takes one of a state of entering the optical path of the recording light L and a state of exiting from the optical path. The parallel plate 17 is driven by the drive unit 17D.
It is swung in the direction of arrow A in the figure and in the direction around the axis B.

On the other hand, the liquid crystal display panel 12 is driven by a drive circuit 18 which receives an image signal S indicating a gradation image, and spatially modulates the recording light L to display a gradation image. That is, each of a large number of liquid crystal cells arranged two-dimensionally in the liquid crystal display panel 12 is applied with the AC voltage according to the image signal S by the drive circuit 18, and the recording light is applied according to the value of the applied voltage. The liquid crystal display panel is changed by changing the transmittance of L.
A gradation image is displayed on 12. As the liquid crystal display panel 12, the normally open type described in detail above, that is, the type in which the liquid crystal cell is normally open and closed when a voltage is applied thereto is used.

The image forming lens 13 forms an image of the gradation image formed on the liquid crystal display panel 12 as described above on the photosensitive material 14, and exposes the photosensitive material 14. The photosensitive material 14 in this example is a long color photographic printing paper (color paper), and is fed by the conveying means 19 by one frame.

The color filter 15 comprises a B (blue) filter, a G (green) filter and an R (red) filter. Then, the respective color filters are sequentially inserted into the optical path of the recording light L by the driving unit 15D, and the liquid crystal display panel 12 is driven based on the respective color image signals corresponding to the respective colors while the respective color filters are being inserted. In this way, the color light-sensitive material 14 is sequentially exposed to the modulated blue, green and red light, and a color photographic latent image is recorded therein.

The operations of the drive units 15D, 16D and 17D, the drive circuit 18, and the conveying means 19 are controlled by the control circuit 20 in synchronization with each other. It should be noted that FIG. 2 shows the respective processings based on these operations, that is, the timings of switching of the color filters and pixel shifting described below.

Next, the pixel shift will be described. During the period in which one of the color filters is inserted in the optical path of the recording light L, the direction of the parallel plate 17 is changed in four ways, and the image exposure is performed based on each color image signal corresponding to the color filter each time. Is done. That is, for example, B
When the (blue) filter is inserted in the optical path of the recording light L, the liquid crystal display panel 12 is driven with the parallel plate 17 first placed in the first position. At this time, the liquid crystal display panel 12 is driven based on the blue image signals relating to the pixels in the odd rows and the odd columns of the image to be exposed. Thereby the photosensitive material
The exposure dot D is recorded in 10 as shown by adding "1" in (1) of FIG. In addition, in FIG. 3, the shape of the exposure dot D is schematically shown as a circle.

Next, the parallel plate 17 is swung by a predetermined amount in the direction of arrow A in FIG. 1 and is placed at the second position, and the liquid crystal display panel 12 is driven in this state. At this time, the liquid crystal display panel 12
It is driven based on a blue image signal relating to pixels in odd rows and even columns of an image to be exposed. As a result, the exposure dot D as indicated by "2" in FIG. 3B is recorded on the photosensitive material 10.

Next, the parallel flat plate 17 is swung by a predetermined amount about the axis B in FIG. 1 and placed at the third position, and the liquid crystal display panel 12 is driven in this state. At this time, the liquid crystal display panel 12
Are driven on the basis of a blue image signal for pixels in even rows and columns of the image to be exposed. As a result, the exposure dots D as indicated by "3" in FIG. 3C are recorded on the photosensitive material 10.

Next, the parallel plate 17 is swung by a predetermined amount in the direction of arrow A in FIG. 1 (the direction opposite to the direction in which the plate is moved from the first position to the second position) and is placed at the fourth position. The display panel 12 is driven. At this time, the liquid crystal display panel 12 is driven based on the blue image signal relating to the pixels in the even rows and the odd columns of the image to be exposed. Thereby the photosensitive material
The exposure dots D are recorded in 10 as shown by adding "4" in (4) of FIG. After that, the parallel plate 17 is
While the G (green) filter is being inserted in the optical path of the recording light L instead of the (blue) filter, it is returned to the first position.

As described above, the liquid crystal display panel 12 is set to 1 in each of the pixel arrangement directions X and Y which are orthogonal to each other.
Since the pixel shifting is performed one by one, the exposure dots D that are twice as many as the number of pixels arranged side by side in the liquid crystal display panel 12 are recorded in both of these directions X and Y, and a high-definition image is exposed. .

The above-described pixel shifting operation is similarly performed when the G (green) filter and the R (red) filter are inserted in the optical path of the recording light L to perform image exposure. Then photosensitive material
No. 10 is subjected to normal development processing, whereby the exposed image is visualized.

As shown in (1) of FIG. 2, the photosensitive material 14 (color paper) is stopped during the exposure of one image, and when the exposure of one image is completed, a predetermined value is set. One frame is moved over time. In synchronism with the movement of the photosensitive material 14, that is, between the end of the exposure of one image and the start of the exposure of the next one image, the black shutter 16 is set as shown in FIG. Control circuit
A closed state, that is, a state of entering the optical path of the recording light L is provided by 20.

The control circuit 20 applies the AC voltage to all the liquid crystal cells of the liquid crystal display panel 12 during the period when the black shutter 16 is completely closed, that is, during the period shown by the broken line in FIG. Stop. LCD panel
12 has the maximum transmittance over the entire surface, and the recording light L is satisfactorily transmitted through the liquid crystal display panel 12. However, at this time, since the black shutter 16 is inserted in the optical path of the recording light L as described above, the photosensitive material 14 is not irradiated with the unnecessary light, and the fog is not caused.

The AC voltage application to the liquid crystal cells of the liquid crystal display panel 12 is stopped during most of the period when the image exposure is not performed, that is, the period when the liquid crystal display panel 12 does not perform the modulation operation based on the image signal S. Even if the liquid crystal display panel 12 is driven for a long period of time, the DC component does not accumulate in the liquid crystal and deteriorate.

In this example, the liquid crystal display panel 12 is fully closed in all pixels during the switching period of each color filter, but the liquid crystal display panel 12 is not only moved during the moving period of the photosensitive material 14 but also during the switching period of this color filter. The black shutter is used to stop the recording light L by stopping the voltage application to the display panel 12.
16 may be used.

Further, although the image exposure apparatus of the above-described embodiment exposes a color image by switching the color filters, the present invention spatially modulates recording light of three colors by separate liquid crystal display panels. However, the present invention can be similarly applied to an image exposure apparatus of a type in which a light-sensitive material is simultaneously irradiated with those lights to perform image exposure.

[Brief description of drawings]

FIG. 1 is a side view of an image exposure apparatus that is an embodiment of the present invention.

FIG. 2 is a timing chart showing timings of various operations in the image exposure apparatus.

FIG. 3 is an explanatory diagram illustrating pixel shift in the image exposure apparatus.

FIG. 4 is a graph showing applied voltage versus transmittance characteristics of a normally open type liquid crystal display panel according to the present invention.

[Explanation of symbols]

 10 Light source 11 Condenser lens 12 Liquid crystal display panel 13 Imaging lens 14 Photosensitive material 15 Color filter 16 Black shutter 17 Parallel plate for pixel shift 18 Liquid crystal display panel drive circuit 19 Photosensitive material transport means 20 Control circuit L Recording light

Claims (1)

[Claims] 1. A liquid crystal display panel comprising a light source for emitting recording light for exposing a photosensitive material, a plurality of normally open liquid crystal cells arranged in an array, and spatially modulating the recording light based on an image signal. In an image exposure apparatus having, a shutter capable of selectively taking one of a state of blocking the recording light and a state of not blocking the recording light, and at least a part of a period during which the liquid crystal display panel does not perform a modulation operation based on an image signal, An image exposure apparatus using a liquid crystal display panel, which is provided with a control means for setting a shutter to a state in which the recording light is blocked and for stopping voltage application to each liquid crystal cell of the liquid crystal display panel. .