JPH02141724A - Lcd printer - Google Patents

Abstract

PURPOSE:To make light leaked at the time of printing with electric field as little as possible and to prevent the distinctness of an image or fogging from occurring even if a temperature is changed by changing the direction of a polarizing plate according to the temperature. CONSTITUTION:A frame 20 in which the polarizing plate 3 is fitted is turnably supported on a pedestal 12 by a supporting shaft 11. A temperature sensor 13 is attached to the proper spot of an LCD array 2 and it detects the temperature of the liquid crystal cell 5 of the LCD array 2 and transmits a temperature signal to a direction control signal generation circuit 14. An action central temperature signal is also inputted in the direction control signal generation circuit 14. Then, the temperature signal is compared with the action central temperature signal to generate a motor driving control signal, so that an eccentric cam 18 is rotated through a motor 16 and an encoder 17 and the polarizing direction of the polarizing plate 3 is changed. Therefore, the crossed angle of the polarizing direction of the polarizing plate with that of the liquid crystal cell can be kept within an allowable range centering 90 deg. even if the temperature is changed. Thus, the light leaked at the time of shielding the light is made little and the distinct high-contrast image is recorded.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention uses an array of liquid crystal shutters and selectively opens and closes each liquid crystal shutter according to image information to expose an image onto a recording medium. L CD (Liq
(uid Crystal Display) printer.

(Background of the invention) FIG. 4 is a diagram showing the configuration of the LCD printer.

1 is a rod-shaped light source, and the direction perpendicular to the paper surface is the axial direction.

2' is an LCD array, and 3' is a polarizing plate and cover glass.
, an electrode 4, a liquid crystal cell 5, an electrode 6, and a cover glass 7 are integrated into a liquid crystal shutter array (LCD array) in which a large number of liquid crystal shutters are arranged along the longitudinal direction of the rod-shaped light source 1.
It consists of

The light emitted from the rod-shaped light source 1 passes through or is prevented from passing by selectively opening and closing each liquid crystal shutter of the LCD array 2', and the passed light passes through 5LA (Selfoc lens array) 8. An image is formed on the recording medium 9.

The light emitted from the rod-shaped light source 1 passes through a polarizing plate and cover glass (
The direction of polarization can be uniformly aligned by the polarizing plate 3' (hereinafter simply referred to as a polarizing plate). In other words, the light that reaches the liquid crystal cell 5 has a constant polarization direction.

On the other hand, the liquid crystal cell 5 is in a state where no electric field is applied (electrical [!4.
6), it does not have a specific polarization direction, but when an electric field is applied, it becomes polarized. By setting the angle (intersection angle) between the polarization direction of the liquid crystal cell 5 and the polarization direction of the polarizing plate 3' to 90°, the transmittance of the liquid crystal cell when an electric field is applied can be made almost zero. A large number of such liquid crystal shutters are arranged and the liquid crystal shutters are turned on and off according to image signals, and the recording medium 9
An LCD printer exposes an image to light and records an image.

(Problems to be Solved by the Invention) However, in conventional LCD printers, the polarizing plate is integrally fixed to the liquid crystal cell and the direction of polarization is fixed, resulting in the following problems.

The polarization direction of a liquid crystal cell changes depending on the temperature, as shown in the example of FIG. 5. For example, if the temperature rises or falls by ±5°C around 35°C, the polarization direction changes by 3°.

Due to this change in the polarization direction, the transmittance ratio (hereinafter referred to as contrast) of the liquid crystal cell between 0N and OFF changes as shown in Figure 6. For example, in the case of green light, the contrast is 180 at 35°C, but it is 200 at 30°C.
However, at 40°C, it drops to about 500.

This is because the polarization direction of the liquid crystal cell changes and the intersection angle deviates from 90°, which increases leakage light when an electric field is applied. If recording is performed in such a state, the image will be unclear, resulting in inconveniences such as, for example, in the case of negative recording, areas that should be white appear gray.

In view of the above-mentioned problems of the prior art, an object of the present invention is to minimize leakage light when an electric field is applied and to prevent temperature changes by making it possible to change the orientation of a polarizing plate according to the temperature. It is an object of the present invention to provide an LCD printer that does not cause blurring or fogging.

(Means for Solving the Problems) The present invention has the following means configuration to achieve the above object.

That is, the first LCD printer of the present invention uses an array of liquid crystal shutters composed of polarizing plates and liquid crystal cells, and selectively opens and closes each liquid crystal shutter according to image information to expose an image onto a recording medium. and an LCD printer for recording an image, comprising: a polarizing plate attached so as to be variably oriented;
A temperature sensor that directly or indirectly detects the temperature of the liquid crystal cell and outputs a temperature signal; and orientation adjustment means that receives the temperature signal and changes the orientation of the polarizing plate in accordance with the temperature. It is something to do.

A second LCD printer of the present invention uses an array of liquid crystal shutters composed of a polarizing plate and a liquid crystal cell, and selectively opens and closes each liquid crystal shutter according to image information to expose an image onto a recording medium, An LCD printer that records images; a polarizing plate that is attached in a variable direction; a photosensor that detects leakage light from the liquid crystal shutter and outputs a leakage light signal; and a photo sensor that detects leakage light from the liquid crystal shutter and outputs a leakage light signal; and a direction adjustment means for changing the direction according to the amount of leaked light.

(Function) Hereinafter, the function of the LCD printer of the present invention having the above means configuration will be explained.

Once the liquid crystal cell to be used is determined, the fifth
The temperature characteristics of the polarization direction as shown in the figure can be known in advance.

In the present invention, the orientation of the polarizing plate can be changed with respect to the liquid crystal cell, and the angle of intersection between the polarization direction of the polarizing plate and the polarization direction of the liquid crystal cell is adjusted to be 1 degree and 90 degrees at a temperature. can do.

This temperature will now be referred to as the operating center temperature. When the temperature of the liquid crystal cell changes from the operating center temperature to another temperature, it can be determined in which direction and how many times the polarization direction of the liquid crystal cell changes from the temperature characteristics of the polarization direction.

Therefore, the crossing angle can be maintained at 90° by making the direction of the polarizing plate follow that amount. Since the temperature characteristics of the polarization direction of a liquid crystal cell are determined by the liquid crystal cell, if the setting is made as described above, the angle to be followed with respect to the temperature of the liquid crystal cell is also determined.

In the present invention, a temperature sensor detects the temperature of the liquid crystal cell and sends a temperature signal to the orientation adjustment means. The relationship of the adjustment angle of the orientation adjustment means to the input temperature signal can be freely designed, so by designing this to be the same as the relationship of the angle to be followed with respect to the temperature of the liquid crystal cell, the orientation adjustment means can adjust the angle of the polarizing plate. The polarization direction can be adjusted so that the crossing angle is 90° even if the temperature of the liquid crystal cell changes.

Furthermore, when using a photosensor, the orientation control means does not operate if the amount of leaked light is less than a predetermined value, and if it exceeds a predetermined value, the orientation of the polarizing plate is changed to one of the predetermined values. If the amount of leaked light decreases, it will continue to operate, and if the amount of leaked light falls below a predetermined value, it will stop operating, and conversely, if it is detected that the amount of leaked light is increasing, it will continue to operate. If the direction is reversed and the operation continues, the operation will stop when the amount of leaked light becomes less than a predetermined value.

In this way, the intersection angle between the polarization direction of the polarizing plate and the polarization direction of the liquid crystal cell settles to an angle within a permissible range centered around 90°.

(Embodiments) Hereinafter, embodiments of the LCD printer of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of a polarizing plate orientation adjustment mechanism according to an embodiment of the present invention using a temperature sensor.

A frame 20 into which the polarizing plate 3 is fitted is rotatably supported on a base 12 by a support shaft 11.

The LCD array 2 is fixed, and temperature sensors 13 are attached to appropriate locations. Temperature sensor 13 is LC
The temperature of the liquid crystal cell 5 of the D array 2 is detected and a temperature signal is sent to the orientation control signal generation port Ft1114. An operating center temperature signal is also input to the direction control signal generating circuit 14, and the temperature signal is compared with this operating center temperature signal. A motor drive control signal is generated based on this difference signal and sent to the motor drive circuit 115. Motor drive circuit 15 rotates motor 16 and encoder 17 by a predetermined angle based on this control signal. An eccentric cam 18 is attached to the rotating shaft of the encoder 17, the peripheral edge of the cam 18 is in contact with the side surface of a frame 20, and the frame 20 is pressed against the eccentric cam 18 by a pressing spring 19. Therefore, when the eccentric cam 18 rotates, the frame 20 rotates about the support shaft 11 as shown by the arrow. As a result, the polarization direction of the polarizing plate is LC
It can be changed with respect to the polarization direction of the liquid crystal cells of the D array 2.

Now, for example, using a liquid crystal cell with temperature characteristics as shown in Fig. 5, when the temperature of the liquid crystal cell is 35°C, the direction of polarization of the polarizing plate 3 is set at exactly 90 degrees with respect to the direction of polarization of the liquid crystal cell. When set, a temperature signal of 35°C is input to the direction control signal generation circuit 14 as the operating center temperature signal, and if the temperature signal from the temperature sensor 13 is 35°C, no motor drive control signal is generated, and the motor 16 is not rotated, and the orientation of the polarizing plate 3 remains as it was initially set.

On the other hand, when the temperature of the liquid crystal cell becomes 30° C., the polarization angle of the liquid crystal cell changes from 21.5° to 23.5°, an increase of 2°. On the other hand, a temperature signal of 30° C. is sent from the temperature sensor 13 to the orientation control signal generation circuit 14. Here, the orientation control signal generation circuit 14 generates a control signal for increasing the orientation of the polarizing plate 3 by 2 degrees based on the difference between the operating center temperature signal and the 30° C. temperature signal, and sends it to the motor drive circuit 15. Conversely, when the temperature of the liquid crystal cell becomes 40℃, the polarization angle of the liquid crystal cell becomes 21.
．． It becomes 20.5° from 5°, which is 1° smaller.

A temperature signal of 40°C is sent from the temperature sensor 13 to the direction control signal generation circuit 14, which generates a control signal to reduce the direction of the polarizing plate 3 by 1° based on the difference with the operating center temperature signal, and controls the motor. The signal is sent to the drive circuit 15. Once the liquid crystal cell to be used is determined, the temperature characteristics of its polarization angle can be known in advance, so at what temperature should the polarizing plate be changed from its initial setting state and in which direction? It can be known in advance. On the other hand, the direction control signal generation circuit 14
In addition, it is possible to freely design output characteristics such as in which direction and how many times to rotate with respect to the input temperature signal, so the design can be made in accordance with the temperature characteristics of the liquid crystal cell. In this way, even if the temperature of the liquid crystal cell changes, the polarization direction of the polarizing plate 3 can always be kept at 90 degrees with respect to the polarization direction of the liquid crystal cell, and leakage light can be minimized.

FIG. 2 is a diagram of an embodiment in which the direction of the polarizing plate 3 is changed by detecting leaked light from a liquid crystal cell using a photosensor. If the intersection angle between the polarization direction of the polarizing plate and the first light direction of the liquid crystal cell deviates from the 90° angle, the liquid crystal shutter will become light-blocking! Even if it is turned off (off), light still leaks out. Therefore, the fact that there is light leakage is 9
This means that it is away from 0°. Therefore, by detecting this leaked light, the direction of the polarizing plate can be controlled so that the intersection angle is 90°.

In this embodiment, an electric field is constantly applied to the liquid crystal cells at the ends of the LCD array 2 that are not used for image formation.
OFF), and a photosensor 21 is placed below it to constantly detect leakage light and send a leakage light signal to the orientation control signal generation circuit 14'.

FIG. 3 is a diagram showing how the photosensor 21 is attached to the LCD array 2. Here, if the level of the leakage light signal is greater than a predetermined threshold, a control signal is output to rotate the eccentric cam 18 in one predetermined direction. If the level of the leakage light signal from the photosensor 21 decreases as the motor 16 rotates, this indicates that the intersection angle is approaching 90'', so continue the operation until it drops below the dark value and the operation will stop. On the other hand, if it is detected that the leakage light signal level is increasing as the motor rotates, the motor rotation is reversed and the motor stops when the leakage light signal level falls below the threshold. In this way, the orientation of the polarizing plate 3 is such that the level of the leaked light signal is smaller than the determined darkness value, that is, the intersection angle is 90°.
The angle is controlled to fall within the permissible angle centered at °.

(Effects of the Invention) As explained above, the LCD printer of the present invention is capable of changing the orientation of the polarizing plate that constitutes the liquid crystal shutter, and even if the polarization direction of the liquid crystal cell changes due to temperature changes, it is possible to change the orientation of the polarizing plate constituting the liquid crystal shutter. The direction of the polarizing plate can be changed depending on the temperature characteristics of the liquid crystal cell, or the direction of the polarizing plate can be adjusted so that the leakage light from the liquid crystal cell is detected and the amount of leakage light is below a predetermined threshold. Even if the temperature changes, the intersection angle between the polarization direction of the polarizing plate and the polarization direction of the liquid crystal cell can be maintained within a permissible range centered around 90 degrees, and leakage light when light is blocked can be maintained. It has the advantage of being able to record clear images with high contrast and less turbulence.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a polarizing plate orientation adjustment mechanism in an embodiment of the LCD printer of the present invention, FIG. 2 is a diagram showing the configuration of another embodiment, and FIG. 3 is a diagram showing the configuration of a photosensor to an LCD array. FIG. 4 is a diagram showing the configuration of the LCD printer, FIG. 5 is a temperature characteristic diagram of the polarization direction of the liquid crystal cell, and FIG. 6 is a contrast temperature characteristic diagram. 1... Rod-shaped light source, 2,2'...LC
D array, 3...I! Light plate, 3'...
・Polarizing plate and cover glass, 4... Electrode, 5.
...Liquid crystal cell, 6...Electrode, 7...
...Cover glass, 8...SLA, 9.
...Recording medium, 11...Spindle, 1
2... Base, 13... Temperature sensor,
14.14' River... Direction control signal generation circuit, 15.
...Motor drive circuit, 16...Motor,
17... Encoder, 18...
Eccentric cam, 19...pressing spring, 2o...
...Frame, 21...Photo sensor. Agent: Patent Attorney Yoshihiro Hachiman! Senara 4 figure number? Figure diagram

Claims (2)

[Claims] (1) An LCD printer that uses an array of liquid crystal shutters made up of polarizing plates and liquid crystal cells to expose images onto a recording medium and record images by selectively opening and closing each liquid crystal shutter according to image information. There is a polarizing plate whose orientation is variable; a temperature sensor that directly or indirectly detects the temperature of the liquid crystal cell and outputs a temperature signal; and a temperature sensor that detects the temperature of the liquid crystal cell directly or indirectly and outputs a temperature signal; An LCD printer comprising: an orientation adjusting means for changing the orientation; (2) An LCD printer that uses an array of liquid crystal shutters consisting of a polarizing plate and a liquid crystal cell to selectively open and close each liquid crystal shutter according to the image information to expose the recording medium and record the image. There is a polarizing plate whose orientation is variable; a photosensor that detects leakage light from the liquid crystal shutter and outputs a leakage light signal; and a photo sensor that detects leakage light from the liquid crystal shutter and outputs a leakage light signal;
An LCD printer comprising: orientation adjusting means for changing the orientation of a polarizing plate in accordance with the amount of leaked light.