JPH06230344A - Liquid crystal device - Google Patents

Abstract

PURPOSE:To prevent deterioration in picture quality and the crystallization of liquid crystal in emergency with necessary minimum of power consumption by controlling electric power to be supplied to a heater panel depending upon environmental temperature, by a heater control circuit. CONSTITUTION:The liquid crystal device has a liquid crystal panel 1 which displays information, a heater 11 which heats the liquid crystal pane 1 to raise its temperature, and a heater control circuit 15 which controls the heater 11; when the environment temperature is lower than a prescribed stand-by temperature, the heater 11 is controlled by the heater control circuit 15 which lets the temperature of the liquid crystal panel 1 be the stand-by temperature when the liquid crystal device is not in operation and also lets the temperature of the liquid crystal panel 1 be a prescribed operation temperature when the liquid crystal device is in operation. The heater panel is controlled according to the environmental temperature, so the power consumption in the heater panel can be minimized, excessive heat is applied to neither members nor circuits, and their deterioration can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device for displaying information using a ferroelectric liquid crystal, and more particularly to controlling the panel temperature of a liquid crystal panel.

[0002]

2. Description of the Related Art In recent years, attention has been focused on a ferroelectric liquid crystal, which has a high-speed response and bistability and can be used for a large-screen liquid crystal device, in place of the nematic liquid crystal that has been widely used.
However, this ferroelectric liquid crystal property strongly depends on temperature,
The threshold value at which liquid crystal molecules switch greatly changes with temperature, and the response speed becomes slower as the temperature becomes lower. Furthermore, a ferroelectric liquid crystal has a narrow temperature range in which a chiral smectic phase exhibiting ferroelectricity exists stably, and undergoes a phase transition to a crystal phase near zero degrees. Then, once crystallized, even if it returns to the temperature range where it shows a chiral smectic phase, it does not return to the original state until the alignment state of liquid crystal molecules (at the time of fabrication, it is set to a chiral smectic phase with a uniform layer structure). , It may not be suitable for display.

Therefore, a liquid crystal device having a flat heating element as shown in FIG. 11 has been proposed. In the figure, 5
Reference numeral 01 is a liquid crystal panel in which a ferroelectric liquid crystal is sealed, and an upper polarizing plate 502 and a lower polarizing plate 503 are fixed to both surfaces thereof with an adhesive. Further, 508 is a liquid crystal panel 501.
Is a back light device for illuminating from the back surface, and a flat heating element 505 is adhered and stuck to the surface thereof, and the back light device 508 is supported by a support 509.

The flat heating element 505 is formed by forming a transparent conductive layer on one surface of a glass plate and providing extraction electrodes at both ends. Reference numeral 510 denotes a circuit board, which has a liquid crystal drive circuit and a planar heating element control circuit, and is connected to the liquid crystal panel 50 with leads 504.
1 and the lead heating element 505 by the lead 506. The flat heating element control circuit of the circuit board 510 is the temperature detecting element 5 attached to the liquid crystal panel 501.
The amount of heat generated by the flat heating element 505 is controlled by the signal from 07.

FIG. 5 shows an example of the temperature characteristic of one scanning line writing frequency of the ferroelectric liquid crystal according to this embodiment of the present invention described later. As can be seen from this example, higher image quality can be displayed when the value of one scanning line writing frequency (which indicates the response speed of the ferroelectric liquid crystal) is larger. That is, the ferroelectric liquid crystal has a tendency that the higher the temperature is, the faster the response speed becomes and the higher the image quality is.

Therefore, in order to fully exhibit the display capability of the liquid crystal device, it is necessary to control the flat heating element 505 with a certain high temperature as a set value.

[0007]

However, in order to prevent the crystallization of the ferroelectric liquid crystal, the flat heating element 505 is always used.
Has a problem that the liquid crystal device is energized, consumes unnecessary power, and heats peripheral members, electronic circuits, and the like, which accelerates deterioration of quality of the liquid crystal device and shortens the life of the liquid crystal device.

Therefore, the present inventors have tried to keep the temperature setting lower by taking into consideration the reliability of members and electronic circuits and the power consumption of the flat heating element, but as described above. It has been found that it is difficult to satisfactorily avoid the above problems because the liquid crystal device cannot exert its ability because the response speed decreases and the image quality deteriorates when the temperature is lowered.

Further, while the liquid crystal panel 501 is made of a material such as glass having a large heat capacity and a poor heat conduction, the temperature sensing element 507 has a small heat capacity and a metal or the like has a good heat conduction. To be composed of materials,
When cold air or the like is blown into the liquid crystal device from the outside, the temperature detecting element 507 reacts sensitively and the liquid crystal panel 5
The temperature of 01 and the temperature detected by the temperature detecting element 507 may not always match.

In view of the above, the present invention does not cause deterioration of image quality at the beginning of use and during use, and when not in use, crystallization of the liquid crystal is prevented with less power consumption and deterioration of members and electronic circuits arranged in the periphery is prevented. It is an object of the present invention to provide a highly reliable liquid crystal device by speeding up the temperature detection and making the temperature detection by the temperature detection element accurate.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a liquid crystal panel for displaying information, and a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel. A heater control circuit for controlling the heater, the temperature of the liquid crystal panel when the liquid crystal device is not operating is set to the standby temperature when the ambient temperature is lower than a predetermined standby temperature. At the same time, the heater control circuit controls the heater so that the temperature of the liquid crystal panel during operation of the liquid crystal device becomes a predetermined operating temperature.

A liquid crystal device having a liquid crystal panel for displaying information, a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel, and a heater control circuit for controlling the heater When the ambient temperature is higher than a predetermined standby temperature and lower than a predetermined operating temperature, the heater control circuit controls the heater to set the temperature of the liquid crystal when the liquid crystal device is operating to the predetermined operating temperature. Will be done
It is characterized by

Further, in a liquid crystal device having a liquid crystal panel for displaying information, a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel, and a heater control circuit for controlling the heater. When the ambient temperature is higher than a predetermined operating temperature, the heater control circuit shuts off the power supply to the heater panel.

Further, the liquid crystal panel has a temperature detecting means for detecting a temperature of the liquid crystal panel, and the temperature detecting means is attached to a slowly changing temperature region above the liquid crystal panel. To do.

Further, the upper part of the liquid crystal panel to which the temperature detecting means is attached is set to a higher temperature than the lower part to suppress convection on the surface of the liquid crystal panel.

Further, the liquid crystal panel has two transparent substrates, and ferroelectric liquid crystal is sandwiched between the transparent substrates.

[0017]

Based on the above configuration, the electric power supplied to the heater panel depending on the environmental temperature is controlled by the heater control circuit to suppress the required minimum electric power consumption.

Further, the temperature detecting means is attached to the slowly changing temperature region of the liquid crystal panel where the temperature change is gentle, and the temperature of the upper part of the liquid crystal device is made warmer than that of the lower part to suppress convection.

[0019]

Embodiments of the present invention will be described with reference to the drawings. Figure 1
FIG. 2 is a cross-sectional view of the liquid crystal device, and FIG. 2 is a plan view of the liquid crystal device when a protective plate described later is removed. The liquid crystal device has a liquid crystal panel 1 in which two glass substrates sandwich a liquid crystal, a backlight device 20, and a heater panel 11. LCD panel 1
Is the fixing plate 4 via the silicone adhesive 14 having elasticity.
The protective plate 10 having an upper polarizing plate (not shown) is attached to the fixed plate 4. A drive element 3 for driving the liquid crystal panel 1 and a wiring board 2 are provided adjacent to each other. A heater panel 11 is provided on the lower surface of the liquid crystal panel 1.
Are attached to the liquid crystal panel 1 with a silicon adhesive 14 at a predetermined interval. Further, a backlight device 20 is provided below the heater panel 11. The heater control circuit 1 for controlling the heater panel 11
5 is provided on the back surface of the backlight device 20, and a temperature detection element 16 (temperature detection means) for detecting the temperature of the liquid crystal panel 1 is provided on the upper surface side end (slow change temperature region) of the liquid crystal panel 1. .

FIG. 3 shows a sectional view of the liquid crystal panel 1, which has a glass substrate 25 having a thickness of 1.1 mm, and a plurality of strip-shaped transparent electrodes 26 are formed on the glass substrate 25. In ₂ O ₃ or ITO is used for the transparent electrode 26, and its film thickness is set to about 1500 Å.

After that, as the insulator film 27 for preventing short circuit, SiO ₂ was formed by 1000 Å by the sputtering method. As the insulator film 27, in addition to SiO ₂ , Ta ₂
An inorganic insulating material such as O ₅ may be used, and Si, Ti, T
It is also possible to use an inorganic insulating film obtained by coating and firing an organometallic compound containing at least one element of a, Zr, Al and the like. Also, the film thickness is 200Å ~ 3000Å
It should be in the range of.

Further, a polyimide forming liquid was applied on the insulator film 27 by a spinner and heated at 270 ° C. for 1 hour to form a polyimide orientation control film 28 of about 200 Å.
As the orientation control film 28, polyvinyl alcohol,
Polyimide, polyamide imide, polyester imide,
Organic insulating substances such as polyparaxylylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyamide, polystyrene, cellulose resin, melamine resin, urea resin and acrylic resin may be used, and the film thickness is 50 Å to 1000 Å. It only needs to be in the range. Then, by rubbing the surface of the orientation control film 28 in one direction with a nylon rubbing cloth,
A uniaxial orientation axis that serves as an orientation regulating force substantially in the same direction as the rubbing direction is provided.

The glass substrate 25 produced in this way
On one of the glass substrates 25, a bead spacer 29 (silica beads, alumina beads, etc.) having an average particle size of about 1.5 μm.
And a sealing adhesive 30 which is an epoxy resin adhesive is formed on the other glass substrate 25 by a screen printing method, and these two glass substrates 25 are 0.1 μm to 3 μm.
The seal adhesive 30 was solidified by heat treatment by holding it at the intervals of 2 and facing each other. After that, the ferroelectric liquid crystal 31 was injected.

Further, the backlight device 20 has a light source lamp 8, a diffusion plate 7 and a reflection plate 5, and the light emitted from the light source lamp 8 is reflected / reflected by the reflection plate 5 and the diffusion plate 7.
It is configured so that the luminance distribution in the display area of the liquid crystal panel 1 is diffused and becomes uniform. In addition, 9 is a lower polarizing plate.

Further, the heater panel 11 has a heater (not shown) made of a transparent conductive layer on one surface of the glass plate, and the heater control circuit 15 controls the temperature by a signal from the temperature detecting element 16 attached to the liquid crystal panel 1. Are in control.

FIG. 4 is a circuit diagram of the heater control circuit 15.
Reference numeral 01 is a circuit for generating a signal corresponding to the first set temperature on the high temperature side according to the operating temperature, and the output signal thereof is compared with the temperature signal from the temperature detection element 107 by the first comparator 202. Reference numeral 203 denotes a temperature signal generation circuit corresponding to the second set temperature on the low temperature side according to the standby temperature, and the sled output signal is compared with the signal from the temperature detection element 107 by the second comparator 204. Comparison result by the first comparator 202 and the second comparator 2
The comparison result of 04 is the selection circuit 2 according to the external signal.
Either of them is selected in 05 and the switch 20 of the power supply of the heater is selected.
Control 6

In the above structure, the temperature control is set as described later. FIG. 5 shows the temperature dependence of one scanning line writing frequency (hereinafter simply referred to as writing frequency) of the liquid crystal device. Referring to FIG. 5, if the liquid crystal temperature is 30 ° C. or higher, high speed writing (the higher the speed, the better the image quality) becomes possible. However, if the temperature is too high, the temperature margin for the phase transition of the ferroelectric liquid crystal becomes narrow, and the power supplied to the heater increases, which is not a good idea.

From a practical point of view, the writing frequency is 1OK.
It is sufficient if it is about Hz or higher. Therefore, the temperature setting during use is preferably around 30 ° C. (operating temperature). Also, the lowest allowable writing frequency is about 6 KHz, that is, 1
It is 5 ° C (standby temperature). This means that the temperature of the liquid crystal panel 1 needs to be heater-controlled to this temperature even when the liquid crystal device is not used. Therefore, the guaranteed temperature of the liquid crystal device is set to about 5 to 35 ° C.
The allowable waiting time from the startup of the liquid crystal device to the normal image quality is set to 5 minutes.

6 to 8 show that when the detected environmental temperature is 5 ° C. or higher and lower than 15 ° C. (FIG. 6), 15 ° C. or higher and lower than 30 ° C. (FIG. 7), 30 ° C. or higher (FIG. 8). 3 shows the temperature distribution of the liquid crystal panel 1 under the heater control of FIG. The environmental temperature referred to here is a temperature to be detected which is a reference of a use state, and is the temperature of the liquid crystal panel 1 before operating the liquid crystal panel 1, the backlight device 20, or the heater panel 11 or the vicinity of the panel corresponding thereto. Is the temperature of.

When the ambient temperature is 5 ° C. or higher and lower than 15 ° C. (FIG. 6), the liquid crystal panel 1 is preheated by the heater panel 11 when the liquid crystal device is not used, and the liquid crystal panel 1 maintains 15 ° C. Then, at the same time when the liquid crystal device is started (point S in FIG. 6), the heat generation amount of the heater panel 11 is increased and the heat generation of the backlight device 20 and the liquid crystal panel 1 itself is increased so as to reach 30 ° C. within the allowable waiting time (5 minutes). Therefore, the temperature rises and reaches a predetermined operating temperature of 30 ° C. After that, the heat generation amount of the heater panel 11 is controlled so as to constantly maintain 30 ° C. (at startup (S
The amount of heat generation is reduced compared to point)).

When the environmental temperature is 15 ° C. or higher and lower than 30 ° C. (FIG. 7), the environmental temperature is 15 ° C. or higher, so that the heater panel 11 is not preheated. At the same time as the startup, the heater panel 11 is turned on to bring the temperature to 30 ° C. within a predetermined time. In the steady state, the temperature rises by about 10 ° C. due to the liquid crystal panel 1 and the backlight device 20, so that heat generation corresponding to the temperature of 5 ° C. is sufficient. Therefore, when the liquid crystal panel 1 reaches 30 ° C., the heater panel 11
The calorific value of becomes small and it becomes a steady state.

Further, when the environmental temperature is 30 ° C. or higher (FIG. 8)
Since the operating temperature has reached 30 ° C. from the beginning, the heater panel 11 remains in the OFF state, and no power is consumed.

The temperature correction for the temperature distribution of the liquid crystal panel is performed based on the temperature detected by the temperature detecting element 16 based on the correction data of the heater control circuit 15.

By the temperature control described above, it is possible to save electric power when the liquid crystal device is not used and used, as compared with the conventional continuous heat generation. As a result, it is possible to prevent the resin material, the upper polarizing plate, the lower polarizing plate, and the electronic parts from being rapidly deteriorated by heat.

Next, an embodiment for monitoring the actual value of the liquid crystal panel 1 by the temperature detected by the temperature detecting element 16 will be described. FIG. 9 shows an example of an information processing device using the liquid crystal device 50, and the liquid crystal device 50 is normally used upright.

Some of the electronic components used in the liquid crystal device 50 need to radiate heat. Therefore, the housing of the liquid crystal device 50 is provided with heat dissipation ports 51 and 52. Therefore, convection occurs around the heat generating sources such as the backlight device 20 and the heater panel 11.

In such a situation, cold air or the like may enter the liquid crystal device 50 (arrow in FIG. 9). Then, the previous convection is disturbed and the temperature distribution of the liquid crystal panel 1 described above changes. In such a case, since the heat capacity of the temperature detecting element 16 is small and the heat conduction is good, it is more sensitive to the outside air than the liquid crystal panel 1 and the accurate temperature cannot be detected.

Therefore, in the present invention, the rapid temperature change in the liquid crystal device 50 is suppressed by suppressing the convection. Specifically, the liquid crystal device 50 shown in FIG.
The upper heat radiating port 51 is smaller than the lower heat radiating port 52, and the upper heat radiating port 51 is provided with a louver structure or a warp structure so that hot air from the backlight device or the like does not flow directly to the outside through the upper heat radiating port 51. A window structure is adopted to provide a temperature difference between the upper part and the lower part (the upper part and the lower part in FIG. 9) of the liquid crystal panel 1. That is, since convection occurs when cold air is heated and flows upward, convection is suppressed by warming the upper part of the liquid crystal panel 1. This prevents the temperature of the liquid crystal panel 1 from changing and prevents the cool air from directly hitting the temperature detecting element 16.

Further, since the outside air mainly enters through the low temperature portion of the liquid crystal device 50, that is, the lower heat radiation port 52, the lower portion of the upper and lower portions of the liquid crystal panel 1 is more easily affected by the outside air. Figure 10
4 shows the temperature distribution of the liquid crystal panel 1 when steady information is displayed at an ambient temperature of 35 ° C. As you can see from this figure, the temperature changes drastically in the dense isotherms.
It is easily affected by the outside air. Therefore, as shown in FIG. 10, the temperature detecting element 16 is a side of the liquid crystal panel 1 where the driving element 3 is not provided, and a glass is formed at a side end portion (a region where temperature change is small) slightly lower than the upper end of the panel 1. It is attached by abutting the end face of the substrate 25. The reason why the liquid crystal device 50 is attached slightly downward from the upper end is to avoid the influence from the upper heat radiation port 51 of the liquid crystal device 50.

Although the above description has been made only when the outside air is cold, the same explanation can be made when the outside air is warmer than the device.

[0041]

As described above, since the heater panel is controlled by the ambient temperature, it is possible to minimize the power consumption in the heater panel, and this causes excessive heat to be applied to the members and circuits. It has become possible to suppress these deteriorations.

Further, the reliability of the liquid crystal device is improved by warming the upper part of the liquid crystal device and mounting the temperature detecting element on the upper part of the liquid crystal panel to achieve a liquid crystal device and a temperature detecting device which are not easily affected by the outside air. It was

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a liquid crystal device applied to the description of an embodiment of the present invention.

FIG. 2 is a plan view of a liquid crystal device applied to the description of an embodiment of the present invention.

FIG. 3 is a sectional view of a liquid crystal panel applied to the description of an embodiment of the present invention.

FIG. 4 is a circuit diagram of a heater control circuit applied to the description of the embodiment of the present invention.

FIG. 5: Environmental temperature 5 applied to the description of the embodiment of the present invention
Heater panel Fence Hita LCD panel in case of ℃ to 15 ℃

FIG. 6 is a diagram showing a relationship between a writing frequency and a liquid crystal panel temperature applied to the description of the embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a writing frequency and a liquid crystal panel temperature applied to the description of the embodiment of the present invention.

FIG. 8 is a diagram showing a relationship between a writing frequency and a liquid crystal panel temperature applied to the description of the embodiment of the present invention.

FIG. 9 is a perspective view of the information processing apparatus showing the flow of outside air applied to the description of the embodiment of the present invention.

FIG. 10 is a diagram showing a temperature distribution of a liquid crystal panel applied to the description of the embodiments of the present invention.

FIG. 11 is a cross-sectional view of a liquid crystal device applied to the description of the related art.

[Explanation of symbols]

 1 Liquid Crystal Panel 11 Heater Panel 15 Heater Control Circuit 16 Temperature Detector (Temperature Detector)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeki Yabu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A liquid crystal device comprising a liquid crystal panel for displaying information, a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel, and a heater control circuit for controlling the heater. When the environmental temperature is lower than a predetermined standby temperature, the temperature of the liquid crystal panel when the liquid crystal device is not operating is set to the standby temperature, and the temperature of the liquid crystal panel when the liquid crystal device is operating is set to a predetermined operating temperature. A liquid crystal device, wherein the heater control circuit controls the heater. 2. A liquid crystal device comprising a liquid crystal panel for displaying information, a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel, and a heater control circuit for controlling the heater. When the ambient temperature is higher than a predetermined standby temperature and lower than a predetermined operating temperature, the heater control circuit controls the heater to set the temperature of the liquid crystal panel at the time of operating the liquid crystal device to the predetermined operating temperature. A liquid crystal device characterized by being controlled. 3. A liquid crystal device comprising a liquid crystal panel for displaying information, a heater for heating the liquid crystal panel to raise the temperature of the liquid crystal panel, and a heater control circuit for controlling the heater. The liquid crystal device, wherein the heater control circuit shuts off power supply to the heater panel when the ambient temperature is higher than a predetermined operating temperature. 4. The liquid crystal panel, comprising temperature detecting means for detecting the temperature of the liquid crystal panel, wherein the temperature detecting means is attached to a slowly changing temperature region above the liquid crystal panel. Liquid crystal device. 5. The liquid crystal device according to claim 4, wherein an upper part of the liquid crystal panel to which the temperature detecting means is attached is set to a higher temperature than a lower part thereof to suppress convection on the surface of the liquid crystal panel. 6. The liquid crystal panel has two transparent substrates,
The liquid crystal device according to claim 1, wherein a ferroelectric liquid crystal is sandwiched between the transparent substrates.