JPH1054985A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the heat transfer between a panel heater for temperature compensation of a liquid crystal panel using a smectic liquid crystal and a light diffusing plate, and forcibly center the light diffusing plate by an air cooling device. Provided is a liquid crystal device that suppresses uneven temperature distribution of a panel heater, which is a cause of uneven temperature of a liquid crystal panel, by air cooling. A light diffusion plate (31A) is attached to a panel heater (20). The light reflecting plate 38 is mounted on the light reflecting plate 31A via the band-shaped buffer member 37. Air cooling device 40
Is attached to the wall portion 38b of the light reflection plate 38 from the outside thereof.
The air is blown through 8e toward the center of the light diffusion plate 31A. The outside air blown into the light reflecting plate 38 is supplied to both through holes 38.
The light flows out of the light reflecting plate 38 through c and 38f.

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 having a liquid crystal panel using a smectic liquid crystal.

[0002]

2. Description of the Related Art Among liquid crystal devices of this type, for example, in a liquid crystal display device for a vehicle, as shown in FIG. 4, a liquid crystal panel 10, a translucent panel heater 20 for temperature compensation, and
There is one configured with a backlight unit 30. Here, the liquid crystal panel 10 includes two electrode substrates 11, which are overlapped with each other via a seal, a spacer, and adhesive fine particles.
An antiferroelectric liquid crystal 13 is sealed between the electrodes 12 and a polarizing plate 14 (corresponding to the surface of a liquid crystal panel) is adhered to the surface of the electrode substrate 11, while a polarizing plate 15 (liquid crystal) is (Equivalent to the back of the panel)
It is configured.

The panel heater 20 is attached to the surface of the polarizing plate 15 (the surface on the other side from the electrode substrate 12) with an adhesive. The backlight unit 30 is disposed so as to face the polarizing plate 15 via the panel heater 20. The backlight unit 30 includes the panel heater 2
The light diffusing plate 31 is provided in parallel to 0, and a predetermined distance g is provided between the light diffusing plate 31 and the panel heater 20. The panel heater 20 is formed by patterning a transparent electrode for heater on the surface of a glass plate or a resin film.

The backlight unit 30 has a plurality of backlights 32 to 35 parallel to each other.
On the inner surface side (the surface opposite to the panel heater 20)
In FIG. 4, they are arranged orthogonally to the plane of the paper, and project light to the light diffusion plate 31. For this reason, the light diffusion plate 31 is
, And light from a light reflection plate 36 described later is diffused and incident on the liquid crystal panel 10. Here, both backlights 33 and 34 face the center of the panel heater 20 in the left-right direction in FIG. The backlight 3
As 2 to 35, long cold cathode tubes are used.

The backlight unit 30 has a light reflecting plate 36 having a substantially U-shaped cross section.
Is mounted on the light diffusion plate 31 so as to cover the backlights 32 to 35, and reflects light from the backlights 32 to 35 toward the light diffusion plate 31, as shown in FIG.

[0006]

By the way, in the above-mentioned liquid crystal display device, when the ambient temperature is low, the panel heater 20 is not used.
Raises the temperature of the liquid crystal panel 10 to an optimum value due to the heat generation, and plays a role of maintaining the display performance of the liquid crystal panel 10 in a favorable state. However, the heat generated by the panel heater 20 escapes from the outer periphery of the panel heater 20 to the outside air. Therefore, the temperature of the outer peripheral portion of the panel heater 20 is less likely to rise than that of the central portion, and
As shown in FIG. 5, a temperature difference occurs between the central portion and the outer peripheral portion.

[0007] Accordingly, the temperature of the outer peripheral portion of the liquid crystal panel 10 is hard to rise as compared with the central portion, and a temperature difference similar to that of the panel heater 20 occurs between the central portion and the outer peripheral portion of the liquid crystal panel 10. When using a nematic liquid crystal that is not sensitive to temperature unevenness like a conventional liquid crystal panel,
Although the above temperature difference is not a problem, the antiferroelectric liquid crystal 1
In No. 3, the change in the display characteristics due to the temperature change is large.

Therefore, if there is a temperature difference between the central portion and the outer peripheral portion of the panel heater 20 as described above, this temperature difference becomes
The display characteristics of the antiferroelectric liquid crystal 13 are adversely affected. As a result, display unevenness of the liquid crystal panel 10 is caused, and the display performance is significantly reduced. Generally, the human eye changes continuously2
The range in which one color cannot be identified is said to be within 10 color differences. Then, when the range in which the temperature unevenness is allowed was obtained by an experiment, it was found that it is necessary to suppress the temperature unevenness in the display area of the liquid crystal panel to 2 ° C. or less as shown in FIG.

This is a considerably severe condition compared to a nematic liquid crystal, and poses a very serious problem in commercializing a liquid crystal panel using an antiferroelectric liquid crystal. In addition, as shown in Japanese Utility Model Laid-Open No. 6-43625, there is a light reflection plate having a heat dissipation structure and forced air cooling by an air cooling fan. In this case, the temperature of the entire light reflection plate is reduced. Just lowering it does not provide a structure that aims to make the temperature of the entire liquid crystal panel uniform.

In order to cope with the above, the present invention improves the heat transfer between a light-diffusing plate and a panel heater for temperature compensation of a liquid crystal panel using a smectic liquid crystal, and uses an air-cooling device. An object of the present invention is to provide a liquid crystal device in which the center of a light diffusing plate is forcibly air-cooled so as to suppress unevenness in heat energy distribution of a panel heater, which is a cause of temperature unevenness of a liquid crystal panel.

[0011]

According to the first to third aspects of the present invention, a light diffusion plate of a backlight unit is provided on an outer surface of a panel heater mounted on a back surface of a liquid crystal panel. Is pasted on. In addition, an air cooling device is provided outside the wall facing the central portion of the panel heater of the reflection plate, and the air cooling device blows outside air through an outside air introduction port in the reflection plate. .

Therefore, when operating the liquid crystal device in a state where the ambient temperature is low, the panel heater heats the liquid crystal panel and raises the temperature of the liquid crystal panel to an optimum temperature. Along with this, the air cooling device blows outside air through the outside air introduction port into the light reflection plate. For this reason, the central part of the light reflection plate is forcibly cooled by the external airflow. With the air cooling at the central portion of the light reflecting plate, the corresponding central portions of the panel heater and the liquid crystal panel are forcibly cooled.

In this case, as described above, since the light diffusion plate is attached to the panel heater, the temperature change of the light diffusion plate can be directly and efficiently transmitted to the panel heater. For this reason, as the temperature of the central portion of the light reflecting plate decreases, the temperatures of the central portions of the panel heater and the liquid crystal panel also decrease sequentially and efficiently. Therefore, since the heat generated at the outer peripheral portion of the panel heater escapes to the outside air, even if the central portion of the panel heater tends to be higher than the outer peripheral portion, the temperature drop due to forced air cooling at the central portion of the light reflecting plate. Accordingly, the temperature at the center of the panel heater approaches the temperature at the outer periphery of the panel heater.

As a result, the temperature difference between the central portion and the outer peripheral portion of the liquid crystal panel is suppressed to be small, and even in the liquid crystal panel using the smectic liquid crystal, the display unevenness due to the temperature unevenness at the time of low-temperature operation is ensured. Can be suppressed. Here, if the outside air inlet is formed in the opposite wall of the reflector behind the backlight as in the invention according to claim 2, light diffusion from the reflector to light from the backlight is performed. No uneven reflection on the plate occurs. For this reason, light diffusion unevenness due to the light diffusion plate does not occur.

According to the third aspect of the present invention, the outside air outlet of the outside air in the reflection wall is located behind the backlight.
The reflector is formed at a position different from the outside air inlet. Therefore, the outside air in the reflection plate can be efficiently discharged to the outside from the outside air introduction port while preventing the occurrence of uneven reflection of the light from the backlight from the reflection plate to the light diffusion plate. This makes it possible to more efficiently cool the central portion of the light diffusion plate without causing uneven light diffusion by the light diffusion plate.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG. 1 and 2 show a liquid crystal display device according to the present invention. In the present embodiment, the same components as those of the liquid crystal display device of FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 shows a liquid crystal display device according to this embodiment.
In this liquid crystal display device, a backlight unit 30A is employed instead of the backlight unit 30. The backlight unit 30A includes a light diffusing plate 31.
A (corresponding to the light diffusing plate 31), and the light diffusing plate 31A is attached to the outer surface of the panel heater 20 (the surface opposite to the polarizing plate 15) as shown in FIG. Have been. As a result, the light diffusion plate 31A uniformly adheres to the panel heater 20 and is integrated with the panel heater 20. The light diffusing plate 31A is formed of a translucent resin.

The backlight unit 30A is provided with a light reflecting plate 38 (corresponding to the light reflecting plate 36) having a substantially U-shaped cross section. 37, at both flange portions 38a thereof,
It is mounted on both sides of the light reflecting plate 31A. Light reflector 3
As shown in FIGS. 1 and 2, through holes 38c to 38f are formed in the wall portion 38b parallel to the eight light reflecting plates 31A, respectively, behind the backlights 32 to 35, respectively.

The air cooling device 40 includes a wall 38 of the light reflecting plate 38.
b from outside thereof, and this air cooling device 4
Reference numeral 0 denotes an annular casing 41 and an air-cooling fan 42 disposed coaxially in the casing 41. Here, the casing 41 has two through holes 3 inside thereof.
It is mounted on the wall 38b of the light reflection plate 38 so as to position 8d and 38e. Then, the air cooling fan 42
By the operation, the outside air is introduced into the casing 41 and is blown through the through holes 38d and 38e toward the center of the light diffusing plate 31A in the light reflecting plate 38.

The outside air blown into the light reflecting plate 38 is
The light flows out of the light reflection plate 38 through the through holes 38c and 38f. Therefore, both through holes 38d and 38e serve as outside air introduction ports, while both through holes 38c and 38e
38 f serves as an outside air outlet in the light reflection plate 38. In the present embodiment configured as above, when operating the liquid crystal display device in a state where the ambient temperature is low, the panel heater 20 heats the liquid crystal panel 10 due to the heat generated, and the temperature of the liquid crystal panel 10 is adjusted to the optimum temperature. Up to

Along with this, the air-cooling fan 42 introduces outside air into the casing 41 as outside air, and blows the air through the through holes 38d and 38e into the light reflection plate 38. Then, this outside air flow passes near both backlights 33 and 34,
In FIG. 1, it flows in the direction of arrow a, and reaches the central portion (see reference numeral b in FIG. 1) of the light reflecting plate 31A. Thereby, the central portion b of the light reflecting plate 31A is forcibly cooled by air. With the cooling of the central portion of the light reflecting plate 32A, the central portion of the panel heater 20 and the liquid crystal panel 10
Are also forcibly cooled in order. Also, the light diffusion plate 3
As shown by the arrow c in FIG.
8f flows out.

In this case, as described above, the light diffusing plate 31A
However, unlike the case of FIG. 4, the temperature change of the light diffusion plate 31 </ b> A can be directly and efficiently transmitted to the panel heater 20 because it is attached to the panel heater 20. For this reason, as the temperature of the central portion of the light reflecting plate 31A decreases, the temperature of the central portion of the panel heater 20 also decreases efficiently, and the liquid crystal panel 10 attached to the panel heater 20 by the polarizing plate 15. Similarly, the temperature at the central portion of the slab decreases efficiently.

Therefore, since the heat generated at the outer peripheral portion of the panel heater 20 escapes to the outside, the panel heater 2
Even when the central part of 0 tends to be higher than its outer peripheral part, the temperature of the central part of the panel heater 20 decreases efficiently due to forced air cooling with the temperature decrease of the central part of the light diffusion plate 31A, The temperature of the outer peripheral portion of the panel heater 20 approaches.

As a result, the temperature difference between the central portion and the outer peripheral portion of the liquid crystal panel 10 is suppressed as shown in FIG.
However, the display unevenness due to the temperature unevenness during the low-temperature operation can be reliably suppressed. Also, since the light diffusion plate 31A is attached to the panel heater 20, the light diffusion plate 31A
There is no need to provide an outside air inlet at For this reason, the light diffusion unevenness by the light diffusion plate 31A for the light from the backlights 32 to 35 does not occur.

As described above, each of the through holes 38d, 3d
8e is located behind each of the backlights 33 and 34, and the through holes 38c and 38f are located behind each of the backlights 32 and 35. Accordingly, since there is no uneven reflection of the light from each backlight from the reflection plate 38 to the light diffusion plate 31A, the reflection plate 38 can reflect the light from the backlight to the light diffusion plate 31A as uniform reflected light. . As a result, light diffusion unevenness due to the light diffusion plate 31A does not occur.

The present invention is not limited to the antiferroelectric liquid crystal 13 but may be implemented by using a smectic liquid crystal such as a ferroelectric liquid crystal. In practicing the present invention, for example, a single backlight having a wide light-emitting surface (facing each of the through holes 38c to 38f) may be employed instead of the backlights 32 to 35.

In practicing the present invention, the liquid crystal display device is not limited to a vehicle, but may be various types of liquid crystal display devices (using a smectic liquid crystal) such as home electric appliances, aircraft, ships, and the like. Various liquid crystal devices such as a liquid crystal shutter may be used without being limited to the liquid crystal display device.
Further, in the practice of the present invention, the present invention may be applied such that when an increase in display luminance is required, the thermal energy trapped in the light reflection plate is forcibly discharged to the outside.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a liquid crystal display device according to the present invention.

FIG. 2 is a rear view of the liquid crystal display device of FIG.

FIG. 3 is a plan view showing a temperature distribution of the panel heater.

FIG. 4 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 5 is a plan view showing a temperature distribution of the panel heater of FIG.

FIG. 6 is a graph illustrating a relationship between a color difference and a temperature for explaining an allowable range of temperature unevenness in a display area of a liquid crystal panel.

[Explanation of symbols]

Reference Signs List 10: liquid crystal panel, 13: antiferroelectric liquid crystal, 20: panel heater, 30A: backlight unit, 31A: light diffusion plate, 32 to 35: backlight, 38: reflection plate,
38b: wall portion, 38c to 38f: through hole.

Claims (3)

[Claims] 1. A liquid crystal panel (10) enclosing a smectic liquid crystal (13); a panel heater (20) mounted on the back of the liquid crystal panel to compensate for the temperature of the liquid crystal panel; A backlight (32 to 35) disposed on the outer surface so as to project light to the liquid crystal panel through the panel heater, and a light diffused from the backlight attached to an outer surface of the panel heater. A light diffusing plate (31A) to be incident on the panel heater and a box-shaped reflecting plate attached to the light diffusing plate so as to cover the backlight and reflecting light of the backlight toward the light diffusing plate (31A). And a cooling unit (40) disposed outside a wall (38b) of the reflector that faces the center of the panel heater. A liquid crystal device, wherein the air cooling device blows outside air through the outside air inlets (38d, 38e) provided in the opposed wall portion in the reflection plate. 2. The liquid crystal device according to claim 1, wherein the outside air introduction port is formed in the opposite wall of the reflector behind the backlight. 3. An outside air outlet (38c, 38f) through which outside air inside the reflection wall flows out to the outside is formed in the reflection plate at a position different from the outside air introduction port, behind the backlight. The liquid crystal device according to claim 1, wherein: