JP2000231093A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation of a liquid crystal due to heat generation and to prolong the life of a liquid crystal display device when the substrate includes a heat generating source such as a driving circuit. SOLUTION: A driving circuit 4 including a heat generating source is formed on a glass substrate 1, where a liquid crystal is to be sealed. Then a heat radiating plate 8 is attached to prevent heating of the liquid crystal. A sealing layer 9 is formed between the heat radiating plate 8 and the glass substrate 1 so as to increase the thermal conduction. The heat radiating plate 8 is fixed by pressing between enclosures 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display (Li)
More particularly, the present invention relates to an LCD in which a driving circuit including a heating element such as a level shifter is integrally formed.

[0002]

2. Description of the Related Art In recent years, a so-called system-on-glass system has been proposed in which a driver circuit is formed on a glass substrate of an LCD by driving each electrode for controlling a screen display by applying a voltage. FIG. 4A is a sectional view of a system-on-glass LCD module, and FIG. 4B is a perspective view thereof. An LCD in which liquid crystal is sealed between two glass substrates 1 and 2 is provided with a display region 3 in which pixel electrodes and a common electrode are formed, and a driver circuit for applying a voltage to the electrodes. A drive circuit region 4 is formed. The LCD is housed in housings 5 and 6 made of metal such as aluminum. The housings 5 and 6 are fixed to each other with the LCD sandwiched from above and below. An area facing the display area 3 of the housing 5 is opened,
The display area 3 of the LCD can be visually recognized. The area facing the display area 3 of the housing 6 is also opened, and a backlight (not shown) or a reflector that reflects light from the upper surface is provided to irradiate light from the back of the LCD to visually recognize the display area 3. It can be so. The drive circuit area 4 is a housing 5,
6 and cannot be seen from outside. A flexible lead 7 that can be freely bent and extended is provided from the drive circuit area 4 to the outside of the housings 5 and 6, so that it can be connected to external terminals such as a power supply and a video signal.

FIG. 5 is a plan view of the LCD. A display area 3 is formed on a glass substrate 1 and includes a pixel group formed in a matrix. A vertical drive circuit 10 composed of a shift register and the like and a horizontal drive circuit 11 are formed around the display area 3. The horizontal and vertical drive circuits 10 and 11 are connected to a flexible lead 7 via a level shifter 12. In the cross-sectional view of FIG. 4A, the drive circuits 10 and 11 are combined with the level shifter 12 and the wiring connecting them to form the drive circuit region 4. The level shifter 12 receives, for example, 5
The V clock signal is boosted to 15 V, and the drive circuit 10,
11 is output.

[0004]

When a driver circuit is formed integrally with a glass substrate, the driver circuit and the liquid crystal are arranged in contact with or near the liquid crystal. The driver circuit often includes a circuit, such as the level shifter 12, that generates heat with its operation. like this,
When the liquid crystal is in contact with the heat generating circuit, the generated heat denatures the surrounding liquid crystal and shortens the life of the LCD. It is expected that drive circuits having more functions and more heating elements will be formed on the glass substrate 1 in the future.

In particular, in recent years, there has been an increasing demand for installing an LCD in a car, for example, in a car navigation system. However, the temperature inside the automobile during summer may become high, and the liquid crystal inside the LCD may be denatured or its characteristics may be deteriorated.

For example, a vertical alignment type LCD using a liquid crystal having a negative dielectric anisotropy generally has a temperature (denaturation temperature) at which heat denaturation occurs, as compared with a liquid crystal having a positive dielectric anisotropy. ) Is low and denatures at approximately 80 ° C. The denaturation temperature of a liquid crystal having a positive dielectric anisotropy is about 100 ° C. In such an LCD, the above-mentioned problems appear more prominently.

Accordingly, an object of the present invention is to achieve a longer life of an LCD using a liquid crystal having a low heat denaturation temperature.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and has a first substrate on which a drive circuit is formed, a second substrate opposed thereto, and a first substrate. And a liquid crystal display device including a liquid crystal sealed in a second substrate, wherein the driving circuit includes a level shifter, and a heat sink is provided in a region of the first substrate where the level shifter is formed.

[0009] An adhesion layer is provided between the heat sink and the first substrate.

[0010] Further, there is provided a housing for covering the first substrate, and the radiator plate is sandwiched and crimped between the first substrate and the housing.

The first substrate has a heat radiating area formed adjacent to a heat source of the drive circuit.

A first substrate on which a drive circuit is formed; a second substrate facing the first substrate;
In a liquid crystal display device having liquid crystal sealed in a substrate, the driving circuit includes a level shifter, and the first substrate includes:
This is a liquid crystal display device in which a heat dissipation area provided adjacent to a level shifter is formed.

[0013]

FIG. 1A is a sectional view of an LCD module according to a first embodiment of the present invention, and FIG. 1B is a perspective view thereof. An LCD in which liquid crystal is sealed between two glass substrates 1 and 2 has a display area 3 in which pixel electrodes and a common electrode are formed, and a drive circuit area 4 in which a driver circuit for driving display is formed. Are formed. The LCD is housed in housings 5 and 6 made of metal such as aluminum, and the area facing the display area 3 of the housing 5 is opened so that the display area 3 of the LCD can be viewed. The area facing the display area 3 of the housing 6 is also opened, and a backlight (not shown) or a reflector that reflects light from the upper surface is provided to irradiate light from the back of the LCD to visually recognize the display area 3. It can be so. The drive circuit area 4 is covered by the housings 5 and 6, and cannot be visually recognized from the outside. A flexible lead 7 that can be bent and extended is provided from the drive circuit area 4 to the outside of the housings 5 and 6, so that it can be connected to an external terminal such as a power supply. A heat radiating plate 8 made of a metal having high thermal conductivity, for example, stainless steel, is provided on a region of the drive circuit region 4 where a circuit that generates heat is formed.

The drive circuit region 4 is formed on the glass substrate 1, and the heat radiating plate 8 is fixed on the glass substrate 1 on which the drive circuit 4 is formed, directly above a heat generating circuit such as a level shifter. The heat generated from the circuit is
From the liquid crystal to the surroundings, thereby preventing heating of the liquid crystal. The material of the radiator plate 8 may be any material as long as it has a high thermal conductivity. However, the radiator plate 8 is exposed outside the housing, and therefore requires a certain strength. Therefore, the material of the heat sink 8 is optimally a metal.

The radiator plate 8 is pressed between the housings 5 and 6 and the glass substrate 1. An adhesion layer 9 made of a soft metal such as indium or aluminum is provided between the glass substrate 1 and the heat radiating plate 8 to enhance the adhesion between the heat radiating plate 8 and the glass substrate 1. It is necessary to increase the adhesion between the heat sink 8 and the glass substrate 1 so that air does not enter. This is because when air enters, the thermal conductivity at the interface between the heat radiating plate 8 and the glass substrate 1 is greatly reduced, and the heat radiating ability is reduced. Therefore, when the pressure bonding with the glass substrate 1 is made of a soft metal such as indium or aluminum, the glass substrate 1 is deformed and adheres to even minute irregularities on the surface of the glass substrate 1.
Adhesion is not impaired. However, a soft metal has insufficient strength and is broken by bending, so that it cannot be used as the material of the heat sink 8. Therefore, the heat radiating plate 8 was formed of a material having high strength, and a soft metal was inserted as the adhesion layer 9.

If the LCD module having the above configuration is incorporated as an on-vehicle LCD monitor and the radiator plate 8 is disposed at the outlet of the ventilation port, heat can be efficiently radiated.

Incidentally, the heat sink 8 may be fixed to the glass substrate 1 with an adhesive such as epoxy. However, since an adhesive layer is formed between the glass substrate 1 and the heat radiating plate 8 and the thermal conductivity may be reduced here, it is preferable to perform pressure bonding with a housing.

FIG. 2 (a) shows the L of the second embodiment of the present invention.
It is a top view of CD. A display area 3 is formed on a glass substrate 1 and includes a pixel group formed in a matrix. A vertical drive circuit 10 composed of a shift register and the like and a horizontal drive circuit 11 are formed around the display area 3. The horizontal and vertical drive circuits 10 and 11 are connected to a flexible lead 7 via a level shifter 12. Level shifter 12 and horizontal / vertical drive circuit 1
0, 11 and the display area 3 are connected by wiring made of a metal such as an aluminum alloy or a chromium alloy. An insulating film is formed between the wires that intersect each other. The drive circuit area 4 has a configuration in which the drive circuits 10 and 11 are combined with the level shifter 12 and a wiring connecting these. The level shifter 12 boosts a clock signal of, for example, 5 V input from the outside to 15 V, and outputs the boosted clock signal to the drive circuits 10 and 11.

A heat radiation region 13 made of metal is formed adjacent to the level shifter 12. The heat dissipation area 13 is a heat capacity formed around the drive circuit area 4, and the heat generated by the level shifter 12 is absorbed by the heat dissipation area 13. The heat radiation area 13 has a larger area than other elements.

The radiator plate 8 shown in FIG.
2 and the heat radiating region 13, the heat radiating efficiency is further improved.

As shown in FIG. 2B, the level shifter 1
When the heat radiation area 14 is provided between the drive circuit 2 and the drive circuit 10, heat conduction to the drive circuit 10 can be prevented. Also, L
When the heat dissipation area 15 is formed around the CD, the heat capacity of the heat dissipation area can be further increased.

Next, the structure of the LCD of the present invention will be described. FIG. 3A is a plan view of a vertical alignment type LCD, and FIG.
(B) is a sectional view thereof. A pixel electrode 55 made of ITO (indium tin oxide) connected to a thin film transistor (TFT) 53 is formed on a glass substrate 50, and an organic material such as polyimide or a silane material is formed on the pixel electrode 55. A vertical alignment film 56 made of such an inorganic material is formed. On a second glass substrate 60 arranged opposite to the glass substrate 50, a common electrode 61 is formed so as to cover the plurality of pixel electrodes 55.
On the common electrode 61, the same vertical alignment film 62 as the first substrate 50 side is provided. An alignment control window 63 is provided in the common electrode 61 at a position corresponding to the pixel electrode 55. The orientation control window 63 is an electrode-free region where the common electrode is opened, and has a shape in which the letter “Y” is connected upside down, for example, as illustrated.

The first substrate 50 and the second substrate 6
Between 0, the liquid crystal 70 is sealed, and the orientation of the liquid crystal molecules, that is, the orientation of the liquid crystal molecules is controlled according to the electric field intensity formed by the voltage applied between the pixel electrode 55 and the common electrode 61.
Outside the first substrate 50 and the second substrate 60, a polarizing plate (not shown) is arranged with the polarization axes orthogonal to each other.
The linearly polarized light passing between the polarizers is modulated when passing through the liquid crystal 70 controlled to have a different orientation for each display pixel, and is controlled to have a desired transmittance.

The liquid crystal 70 has a negative dielectric anisotropy, that is, has a property of being oriented so as to be inclined with respect to the direction of the electric field. The vertical alignment films 56 and 62 control the initial alignment of the liquid crystal 70 in the vertical direction. In this case, when no voltage is applied, the liquid crystal molecules are perpendicular to the vertical alignment films 56 and 62, and the linearly polarized light that has passed through one polarizing plate passes through the liquid crystal layer 70 and is blocked by the other polarizing plate. The display is recognized as black. With this configuration, the pixel electrode 55 and the common electrode 61
When a voltage is applied therebetween, electric fields 66 and 67 are formed, and the liquid crystal molecules are tilted. At the end of the pixel electrode 55, an electric field 66
Has a shape obliquely inclined from the pixel electrode 55 toward the common electrode 61 side. Similarly, since no electrode is present at the end of the alignment control window 63, the electric field 67 has a shape inclined toward the pixel electrode 55. Since the alignment direction of the liquid crystal is controlled so as to be perpendicular to the inclined electric field, the liquid crystal molecules are inclined toward the inside of the pixel electrode 55 and toward the alignment control window 63. As a result, the linearly polarized light that has passed through one polarizing plate undergoes birefringence in the liquid crystal layer 70, changes to elliptically polarized light, passes through the other polarizing plate, and the display approaches white.

In this embodiment, the liquid crystal is a liquid crystal having a negative dielectric anisotropy, and therefore has a low denaturation temperature. However, since the liquid crystal is provided with the heat sink 8, the life of the liquid crystal can be extended.

[0026]

According to the present invention, since the heat sink is provided in the area of the first substrate where the level shifter is formed, the liquid crystal can be prevented from being denatured or deteriorated by the heat from the heat source, and the life of the LCD can be reduced. Can be longer.

Further, since the adhesive layer is provided between the heat sink and the first substrate, the heat sink and the first substrate are in close contact with each other, so that the heat conduction between the first substrate and the heat sink is improved. The rate is high and heat can be dissipated more efficiently.

Further, since the heat radiating plate is sandwiched and pressed between the first substrate and the housing, no adhesive or the like is interposed between the heat radiating plate and the first substrate. The heat conductivity between the heat sinks is high, and the heat can be more efficiently dissipated.

Since the first substrate is provided with a heat radiating region provided adjacent to the heat source of the drive circuit,
The heat conductivity between the drive circuit and the first substrate is high, and heat can be dissipated more efficiently.

[Brief description of the drawings]

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

FIG. 2 is a plan view of the embodiment of the present invention.

FIG. 3 is a plan view and a cross-sectional view of a vertical alignment type liquid crystal display device.

FIG. 4 is a cross-sectional view and a perspective view of a conventional liquid crystal display device.

FIG. 5 is a plan view of a conventional liquid crystal display device.

[Explanation of symbols]

1, 2: glass substrate, 3: display area, 4 drive area,
5, 6: housing, 7: flexible lead, 8: heat sink, 9: adhesion layer

Continued on the front page (72) Inventor Kiyoshi Yoneda 2-5-5 Keihanhondori, Moriguchi-shi, Osaka F-term (reference) in Sanyo Electric Co., Ltd. 2H089 HA40 JA10 KA15 QA16 RA03 2H093 NA16 NC21 NC80 ND44 ND47 NF04 NG03 5C006 BB16 EA01 EC08 FA19 FA33

Claims (5)

[Claims] 1. A liquid crystal display comprising: a first substrate on which a drive circuit is formed; a second substrate facing the first substrate; and a liquid crystal sealed in the first and second substrates. A liquid crystal display device, wherein a level shifter for supplying a boosted voltage to the drive circuit is formed on the first substrate, and a heat sink is provided in a region where the level shifter is formed. 2. The method according to claim 1, wherein the heat sink and the first substrate are provided between the heat sink and the first substrate.
The liquid crystal display device according to claim 1, wherein an adhesion layer is provided. 3. The liquid crystal display device further includes a housing that covers the first substrate, and wherein the heat sink is pressed between the first substrate and the housing. The liquid crystal display device according to claim 1. 4. The liquid crystal display device according to claim 1, wherein a heat radiation area provided adjacent to the level shifter is formed on the first substrate. 5. A liquid crystal display comprising: a first substrate on which a drive circuit is formed; a second substrate facing the first substrate; and a liquid crystal sealed in the first and second substrates. 2. A liquid crystal display device according to claim 1, further comprising a level shifter for supplying a boosted voltage to said drive circuit, wherein said first substrate is provided with a heat radiation region provided adjacent to said level shifter.