JP2000105359A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element capable of obtaining the uniform contrast ratio of the liquid crystal element by keeping the temperature of the liquid crystal element almost constant. SOLUTION: This device has a heating means 18 arranged on the rear side of a liquid crystal display element 13. The heating means 18 has a 1st heat generation part 27 arranged at a part far from a light source 15 lighting the liquid crystal display element 13 and a 2nd heat generation part 28 which is arranged at a part near the light 15 and generates heat at a temperature lower than the 1st heat generation part 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device having a heater for heating a liquid crystal display element.

[0002]

2. Description of the Related Art Conventionally, there is a liquid crystal display device using a liquid crystal display element 1 as shown in FIG. The liquid crystal display element 1 is a device in which polarizing plates (not shown) are attached to both sides of a liquid crystal cell in which liquid crystal is sealed in a pair of translucent substrates 2 provided with a transparent electrode film. The liquid crystal display element 1 is connected to a tape carrier package 3 (hereinafter referred to as TCP).
The TCP 3 has a flexible circuit board 4 on which a drive circuit 5 for driving the liquid crystal display element 1 is provided. A hard wiring board 6 is connected to the TCP 3, and a microcomputer 7 for controlling the drive circuit 5 is provided on the hard wiring board 6.

The liquid crystal display element 1 is a light receiving type display element which cannot emit light by itself, and is provided with a light source 8 such as a cold-cathode tube to illuminate the liquid crystal display element 1 so that good visibility can be obtained. I have to. A reflection member 9 is provided behind the liquid crystal display element 1, and light from the light source 8 is reflected by the reflection member 9 toward the liquid crystal display element 1. A translucent sheet heater 10 is provided on the rear surface side of the liquid crystal display element 1 to prevent the viscosity coefficient of the liquid crystal from increasing when the liquid crystal display device is used in a cold place, thereby preventing the response from being lowered. I have.

[0004]

In the liquid crystal display device, when the liquid crystal display element 1 is of a negative display type, only the illuminated pixels 11 (pixels to which an on-drive voltage is applied) transmit the light of the light source 8 to provide a desired liquid crystal display device. Display characters and figures. However, when the temperature of the liquid crystal of the liquid crystal display element 1 becomes high, the transmittance of the unlit pixels 12 (pixels to which the off-drive voltage is applied) also increases. In this case, the drive voltage is lowered to adjust the contrast ratio. . However, the portion of the liquid crystal display element 1 near the light source 8 has a relatively high temperature due to the heat of the light source 8,
The transmittance of the unlit pixel 12 is also increased, and the contrast ratio is deteriorated at a position near the light source 8 of the liquid crystal display element 1 (see FIG. 5). In this case, when the driving voltage is reduced, the ON driving voltage of the lighting pixel 11 becomes insufficient at a location far from the light source 8 of the liquid crystal display element 1, and the transmittance of the lighting pixel 11 decreases. The contrast ratio deteriorates at a location far from the camera (see FIG. 6).

That is, when the temperature of the liquid crystal display element 1 is not uniform, a uniform contrast ratio cannot be obtained even if the driving voltage is adjusted. SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device capable of obtaining a uniform contrast ratio of the liquid crystal display device by keeping the temperature of the liquid crystal display device substantially uniform.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a liquid crystal display element, a light source provided behind the liquid crystal display element for illuminating the liquid crystal display element, and a liquid crystal display element. The liquid crystal display device further includes a first heat generating portion for heating, and a second heat generating portion disposed closer to the light source than the first heat generating portion and for heating the liquid crystal display element.

Further, according to the present invention, there is provided a liquid crystal display element, heating means disposed behind the liquid crystal display element for heating the liquid crystal display element, and illuminating the liquid crystal display element disposed behind the heating means. A light source, wherein the heating means has a first heat generating portion provided at a location far from the light source and a lower temperature than the first heat generating portion provided at a location near the light source. And a second heat-generating section that generates heat.

Further, the present invention provides a liquid crystal display device comprising a control means for turning on / off the first heat generating part and the second heat generating part based on the temperature detected by the temperature detecting means.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device has a liquid crystal display element 1 according to the present invention.
3 has a heating means 18 provided on the rear surface side. The heating unit 18 includes a first heating unit 27 provided at a location far from the light source 15 that illuminates the liquid crystal display element 13, and a light source 15.
, And a second heat generating portion 28 that generates heat at a lower temperature than the first heat generating portion 27. Although the heat from the light source 15 is applied to a portion near the light source 15, the second heat generating portion 28 generates heat at a lower temperature than the first heat generating portion 27, so that the temperature of the liquid crystal display element 13 becomes substantially uniform, and uniform contrast is obtained. It can be displayed as a ratio.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view of a liquid crystal display device, FIG. 2 is a front view of a translucent sheet heater, and FIG. 3 is a block diagram.

Reference numeral 13 denotes a liquid crystal display element. The liquid crystal display element 13 has a liquid crystal cell in which liquid crystal is sealed in a pair of translucent substrates 14 and a polarizing plate (not shown) attached to both front and rear surfaces. The liquid crystal display element 13 is of the so-called STN (super twisted nematic) type.
Reference numeral 3 denotes a dot matrix type in which many pixels are arranged in a matrix. A cold cathode tube (light source) 15 illuminates the liquid crystal display element 13 from behind.

Reference numeral 16 denotes a reflecting member.
Is disposed behind the liquid crystal display element 13. Reflecting member 16
Is a laminate of a polyethylene terephthalate (PET) film having a silver coating on an aluminum substrate, and reflects light emitted from the cold cathode tube 15 to the liquid crystal display element 13. Reference numeral 17 denotes a light guide member, and the light guide member 17 is provided between the liquid crystal display element 13 and the reflection member 16. The light guide member 17 is made of a translucent resin (for example, acrylic) and has a wedge shape. Reference numeral 18 denotes a translucent sheet heater (heating means). The translucent sheet heater 18 is disposed on the rear side of the liquid crystal display element 13 to heat the liquid crystal display element 13.

Reference numeral 19 denotes a reflector, and the reflector 19 reflects light emitted from the cold-cathode tube 15 to the reflecting member 16. Reference numeral 20 denotes a frame on which the liquid crystal display element 13, the cold cathode tube 15, the reflection member 16 and the like are mounted. Reference numeral 21 denotes a TCP. The TCP 21 has a structure in which a drive circuit 23 is provided on a flexible wiring board 22. One end of the flexible wiring board 22 is an anisotropic conductive film (not shown)
Is connected to the liquid crystal display element 13. Reference numeral 24 denotes a hard wiring board, on which a microcomputer 25 for controlling the drive circuit 23 is provided. The other end of the flexible wiring board 22 is connected to the hard wiring board 24. 26
Is a temperature sensor (temperature detecting means), and the temperature sensor 26 is disposed on the hard wiring board 24.

Next, the translucent sheet heater 18 will be described in detail with reference to FIG. The translucent sheet heater 18 is formed by forming a first heat generating portion 27 and a second heat generating portion 28 on a translucent resin sheet such as polyethylene terephthalate (PET). The first heating section 27 and the second heating section 28 are made of ITO (indium tin oxide) formed by a vapor deposition method. First heating section 27, second heating section 2
8 has a first terminal 27a and a second terminal 28a, respectively.
9 (see FIG. 3). The first heating section 27,
The second heat generating section 28 generates heat by applying a voltage to the first terminal 27a and the second terminal 28a, respectively.

The translucent sheet heater 18 is arranged such that the first heating section 27 is far from the cold cathode tube 15 and the second heating section 28 is near the cold cathode tube 15. The width W2 of the second heating section 28 is smaller than the width W1 of the first heating section 27, and the resistance value of the second heating section 28 is larger than the resistance value of the first heating section. Therefore, even if the same voltage is applied to the first terminal 27a and the second terminal 28a, the current flowing through the second heat generating portion 28 becomes small, and the second heat generating portion 28 is more than the first heat generating portion 27. Generates heat at low temperatures.

FIG. 3 shows that the transparent sheet heater 18 is turned on / off.
FIG. 3 is a block diagram illustrating a control unit that is turned off. 3
Reference numeral 1 denotes a power supply circuit, and this power supply circuit 31 adjusts the voltage of a battery (or commercial power supply) and supplies power to the microcomputer 25 and the heater circuit 29. The control means 30 comprises a microcomputer 25 and a heater circuit 29, and turns on the translucent sheet heater 18 when the temperature detected by the temperature sensor 26 becomes 0 degrees Celsius or less,
Transparent sheet heater 18 when the temperature reaches 5 degrees Celsius or more
Turn off.

According to the embodiment described above, the heat of the light source 15 is applied to the portion close to the light source 15, but the second heat generating portion 28 generates heat at a lower temperature than the first heat generating portion 27. The temperature of the element 13 becomes substantially uniform, and display can be performed with a uniform contrast ratio. In addition, for example, by providing two translucent sheet heaters, the first heat generating section 27 and the second heat generating section 28 may be separated from each other, but as in this embodiment, one translucent sheet is provided. It is desirable that the heater 18 be provided with the first heat generating portion 27 and the second heat generating portion 28, and the number of components can be reduced.

It is desirable that the translucent sheet heater 18 be disposed as close to the liquid crystal display element 13 as possible, and it is more desirable that the heater 18 be in close contact with the liquid crystal display element 13. Further, in the present embodiment, the first heat generating portion 27 and the second heat generating portion 28 are provided in the translucent sheet heater 18.
A third heat generating portion that generates heat at a lower temperature than the first heat generating portion 28 and at a higher temperature than the second heat generating portion 28 may be provided between the seventh heat generating portion 28 and the second heat generating portion 28. The temperature sensor 26 is disposed on the hard wiring board 24,
May be adhered to.

[0019]

According to the present invention, there is provided a liquid crystal display element, a light source disposed behind the liquid crystal display element for illuminating the liquid crystal display element, a first heating section for heating the liquid crystal display element, And a second heat generating portion that is disposed closer to the light source than the heat generating portion and that heats the liquid crystal display element.The temperature of the liquid crystal display element is substantially uniform, and the liquid crystal display element has a uniform contrast ratio. Can be displayed.

The present invention also provides a liquid crystal display element, heating means disposed behind the liquid crystal display element for warming the liquid crystal display element, and illuminating the liquid crystal display element disposed behind the heating means. A light source, wherein the heating means has a first heat generating portion provided at a location far from the light source and a lower temperature than the first heat generating portion provided at a location near the light source. And a second heat generating portion that generates heat in the liquid crystal display element, the temperature of the liquid crystal display element becomes substantially uniform, display can be performed with a uniform contrast ratio, and the number of components can be further reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a front view of a translucent sheet heater showing the embodiment.

FIG. 3 is a block diagram showing the embodiment.

FIG. 4 is a sectional view showing a conventional example.

FIG. 5 is a display explanatory diagram showing a conventional example.

FIG. 6 is a display explanatory view showing a conventional example.

[Explanation of symbols]

 Reference Signs List 13 liquid crystal display element 15 cold cathode tube (light source) 18 translucent sheet heater (heating means) 26 temperature sensor (temperature detecting means) 27 first heating section 28 second heating section 30 control section

Claims (3)

[Claims] 1. A liquid crystal display element, a light source disposed behind the liquid crystal display element and illuminating the liquid crystal display element, a first heating unit for heating the liquid crystal display element, and a first heating unit A liquid crystal display device, further comprising: a second heat generating portion disposed near the light source for heating the liquid crystal display element. 2. A liquid crystal display element, heating means disposed behind the liquid crystal display element for warming the liquid crystal display element, and a light source disposed behind the heating means for illuminating the liquid crystal display element. A liquid crystal display device, wherein the heating means is provided at a location far from the light source and a first heating section provided at a location close to the light source and generates heat at a lower temperature than the first heating section. A liquid crystal display device comprising: a second heat generating portion. 3. The liquid crystal display device according to claim 1, wherein the control means for turning on / off the first heating unit and the second heating unit based on the temperature detected by the temperature detection unit. A liquid crystal display device comprising: