JP2002341319A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device with high performance and high reliability adaptive to variation of surrounding temperature and variation of pressure. SOLUTION: A housing 9 protects a backlight 10 and a liquid crystal cell 100. The housing 9 is a dual structured plate body of which the inside is evacuated. Also a display window 14 composed of a transparent member is formed on part of the housing 9 confronting the display surface of the liquid crystal cell 100. Furthermore, the housing 9 and the display window 14 hermetically seal the inside of the housing 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display device utilizes the fact that light transmittance can be controlled by applying a voltage to liquid crystal.

According to this liquid crystal display device, the luminance (transmittance)
The optical characteristics such as the response speed, the contrast, and the contrast depend on the physical property parameters (such as the refractive index and the dielectric constant) of the liquid crystal material.

[0004] It is known that such physical properties are temperature-dependent, and the display state of the liquid crystal display device greatly changes depending on the environment (temperature, pressure, etc.).

[0005] A conventional liquid crystal display device will be described with reference to FIGS. 9 and 10. FIG. 9 is a schematic cross-sectional view of a transmission type liquid crystal display device, and FIG. 10 is a cross-sectional view of a liquid crystal cell which is a main part of the liquid crystal display device.

Reference numeral 10 denotes a backlight, 100 denotes a liquid crystal cell, and the backlight 10 and the liquid crystal cell 100
Is protected by a housing 9 made of metal or the like.

The backlight 10 includes a light guide plate, a CFL tube provided on an end face of the light guide plate, a light reflection film formed on one main surface of the light guide plate, and a light diffusion layer on the other main surface. , CF
The irradiation light of the L tube enters through the end face of the light guide plate, and is emitted through the light diffusion layer while being reflected by the light reflection film, and the emitted light irradiates the liquid crystal cell 100.

As shown in FIG. 10, the liquid crystal cell 100 has a structure in which two opposing transparent glasses 3 are bonded to each other.
An ITO electrode 4 and an alignment film 5 are sequentially formed on the inner surface of the glass substrate 3 on the display unit side, and a retardation plate 2 and a polarizing plate 1 are sequentially provided on the outer surface.

A color filter layer 8, an ITO electrode 4, and an alignment film 5 are sequentially formed on the inner surface of the other glass substrate 3, and a retardation plate 2 and a polarizing plate 1 are sequentially provided on the outer surface. .

Then, both glass substrates 3 are provided with a liquid crystal layer 6.
This is a structure that is arranged to face each other via the. In addition, by including the spacer 7 in the liquid crystal layer 6, the thickness of the layer is made uniform in a plane.

However, in the liquid crystal display device having the above structure, the physical property parameters also change due to a change in the temperature of the liquid crystal material itself due to a change in the temperature of the surrounding atmosphere, thereby changing the liquid crystal display state. As a result, a favorable display state cannot be obtained depending on environmental conditions.

In particular, in a high temperature state, the contrast is lowered, while in a low temperature state, the display quality is lowered such as the response speed.

Further, depending on the atmospheric pressure, temperature, and other conditions of the surrounding environment, bubbles (air layers generated in the liquid crystal layer 6) and alignment disorder of the liquid crystal are generated, thereby deteriorating the display quality.

In order to solve such a problem, a structure in which a liquid crystal cell is sandwiched between glass substrates (or acrylic plates) having a gap layer, and a gap layer is provided inside both glass substrates (acryl substrates). Thus, a technique has been proposed in which heat from the outside is blocked, and a liquid crystal cell sandwiched between glass substrates having such a heat insulating effect is protected from surrounding heat (see Japanese Patent Application Laid-Open No. 5-80315).

On the other hand, a transparent material mixed with a tin oxide-based additive is applied to the outer surfaces of the upper and lower glass substrates and the outer surface of the sealing material forming the conventional liquid crystal cell, whereby a heat insulating effect can be obtained. A technique has been proposed in which a liquid crystal cell is surrounded by a transparent material to protect the liquid crystal cell from a change in surrounding heat (Japanese Patent Laid-Open No. Hei 8-
334760).

[0016]

As described above, in a liquid crystal display device, when the temperature environment changes, the contrast decreases in a high temperature state, the response speed decreases in a low temperature state, and the crosstalk characteristic deteriorates. Furthermore, when the atmospheric pressure of the surrounding environment changes, display defects such as bubbles may occur.

However, according to the liquid crystal display device proposed above, provision of a member having a heat insulating effect is intended to cope with a temperature change in the surrounding environment, but it has not been improved to a satisfactory degree.

That is, according to the liquid crystal display devices proposed in JP-A-5-80315 and JP-A-8-334760, the device is exposed to a high or low temperature state for a long period of time, so that the device is once in a high (low) state. In this case, the longer the heat insulation from the surroundings, the longer it takes to return to the normal state (room temperature state), and as a result, the display quality rapidly changes from a high temperature (low temperature) state to a normal temperature state. I was unable to do it.

For example, as an example, according to a liquid crystal display device mounted on a car, a forklift, or the like that has been left for a long time at a poor environmental temperature, a good display cannot be obtained immediately upon starting.

In addition, when used or stored in an environment where the air pressure is significantly changed from the time of manufacturing the liquid crystal panel, such as air transportation and high altitude, bubbles in the liquid crystal layer are generated,
As a result, the display quality may be degraded.

The present invention has been completed in view of the above, and it is an object of the present invention to provide a high-performance and highly-reliable liquid crystal display device that responds to changes in environmental temperature.

Another object of the present invention is to provide a high-performance and high-reliability liquid crystal display device that responds to environmental pressure changes.

Another object of the present invention is to provide a liquid crystal display device which can always obtain a good display state for a long period of time even under poor environmental conditions.

[0024]

According to the liquid crystal display device of the present invention, a liquid crystal cell is installed inside a housing constituted by a plate-like body having a double structure whose inside is evacuated, and a display surface of the liquid crystal cell is provided. A display window made of a transparent member is formed in a part of the housing facing the device, and the inside of the housing is hermetically sealed with the housing and the display window.

[0025]

In the liquid crystal display device of the present invention, the liquid crystal cell is constituted by a plate member having a double structure in which the inside is evacuated, instead of using a member having a heat insulating effect as in the prior art. The hermetically sealed inside of the housing makes it unaffected by changes in temperature and pressure in the environment, whereby a good display state can always be obtained even under poor environmental conditions.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal display device according to the present invention will be described with reference to FIGS. FIG. 1 is a schematic sectional structure of a liquid crystal display device, and FIG. 2 is a sectional view of a main part of a housing. 3 and 4 show examples of the configuration of the spacer arranged in the housing. 5 and 6 show a manufacturing method (assembly method) of the liquid crystal display device, FIG. 5 is a process diagram, and FIG. 6 is a sectional view of a main part thereof.
7 and 8 show a method of manufacturing the housing, FIG. 7 is a process diagram thereof, and FIG. 8 is a sectional view of a main part thereof. FIG. 11 shows a specific example of the liquid crystal cell 100.

(Outline of Liquid Crystal Display) The liquid crystal display will be described with reference to FIGS.

In this example, a transflective liquid crystal display device is shown, 10 is a backlight, 100 is a liquid crystal cell, and these backlight 10 and liquid crystal cell 100 are protected by a casing 9 made of metal or the like. Have been.

The housing 9 is made of a metal material such as an electrogalvanized steel plate or stainless steel.

Further, such a housing 9 is a plate-like body having a double structure whose inside is evacuated, and spacers 13 are arranged and formed at predetermined intervals in order to keep the interval of the internal space constant. Good to do.

The spacer 13 is made of a material such as a glass spacer or a plastic spacer. Further, as shown in FIG. 3, there is a spherical or rod-shaped member which is disposed in a plate-like body (metal case) having a double structure.
In addition, as shown in FIG. 4, one plate of a plate-like body (metal case) having a double structure may be provided with irregularities, and thus may be used as a spacer.

The backlight 10 includes a light guide plate, a CFL tube provided on an end face of the light guide plate, a light reflection film formed on one main surface of the light guide plate, and a light diffusion layer on the other main surface. , CF
The irradiation light of the L tube enters through the end face of the light guide plate, and is emitted through the light diffusion layer while being reflected by the light reflection film, and the emitted light irradiates the liquid crystal cell 100.

Further, a display window 14 made of a transparent member is formed in a part of the housing 9 facing the display surface of the liquid crystal cell 100, and the inside of the housing 9 is hermetically sealed by the housing 9 and the display window 14. Stopped.

As the transparent member, there are a glass material and an acrylic synthetic resin.

In the liquid crystal cell 100, a printed circuit board is juxtaposed on an end face of an STN type simple matrix type display portion as a main component, and a driving IC is mounted on the printed circuit board.

A specific example of the structure of the display portion will be described with reference to FIG. A retardation plate 53 made of polycarbonate or the like and an iodine-based polarizing plate 54 are sequentially stacked on the outer surface of a glass substrate 52, and a retardation plate 56 made of polycarbonate or the like and an iodine-based polarizing plate 57 are placed on the outer surface of the glass substrate 55.
Are sequentially stacked. These are attached using an adhesive made of an acrylic material.

Further, a backlight 10 is provided below the polarizing plate 57 in FIG. The backlight 10 is a light guide plate 5
A light source 60 such as a CFL tube or an LED is arranged on the end face of 9,
The light emitted from the light source 60 is introduced into the light guide plate 59, and the light guide plate 5
From 9, light is emitted to the liquid crystal cell 100.

In the liquid crystal cell 100, the glass substrate 5
2, a signal electrode 61 and an alignment film (not shown) made of a polyimide resin rubbed in a certain direction are sequentially formed. It should be noted that SiO ₂ is provided between the signal electrode 61 and the alignment film.
An insulating layer made of such as may be interposed.

A semi-transmissive film 62 is formed on the inner surface of the glass substrate 55, and a color filter 63 is provided on the semi-transmissive film 62. Further, a black matrix which is a light shielding film formed of a thin film made of a metal such as aluminum or chromium or a photosensitive resist may be formed between the color filters 63.

Then, the SiO 2 on the color filter 63
₂ and an overcoat layer 64 made of resin, and a scanning electrode 65 and an alignment film (not shown) made of polyimide resin rubbed in a certain direction on the overcoat layer 64
Are sequentially formed. This scanning electrode 65 is a signal electrode 6
It is orthogonal to 1. Note that an insulating layer made of SiO ₂ or the like may be provided between the scanning electrode 65 and the alignment film.

The semi-transmissive film 62 has both light transmissive and light reflective properties, and prevents a phase difference from occurring when sandwiched between two polarizing plates. Further, the semi-transmissive film 62 may be specular or scattering.
In order to produce the semi-transmissive film 62 having a scattering property, it is only necessary to form an uneven shape with a resin and form a semi-transmissive film thereon.

The color filter 63 is of a pigment dispersion type,
That is, a photosensitive resist prepared in advance with a pigment (red, green, blue, or the like) is applied on a substrate and formed by photolithography.

Each of the glass substrates 52, 5 thus formed
5 are bonded together with a sealing material 67 via a liquid crystal layer 66 made of chiral nematic liquid crystal twisted at an angle of, for example, 200 to 270 °. Further, a large number of spacers 68 are arranged between the two glass substrates 52 and 55 in order to keep the thickness of the liquid crystal layer 66 constant.

In the liquid crystal display device provided with the semi-transmissive film 62 as described above, when used as a reflection type (reflection mode), irradiation light from external illumination such as sunlight or a fluorescent lamp is not emitted. The light sequentially passes through the polarizing plate 54, the retardation plate 53, and the liquid crystal panel. Light incident on the inside of the liquid crystal panel passes through the color filter 63, reaches the semi-transmissive film 62, and then passes through the semi-transmissive film 62. The light is reflected, passes through the liquid crystal panel, passes through the phase difference plate 53 and the polarizing plate 54, and is emitted.

On the other hand, when the liquid crystal display device is set to the transmission mode, the light emitted from the backlight 10 passes through the polarizing plate 57, the phase difference plate 56, and the glass substrate 55 of the liquid crystal panel in order, and becomes a semi-transmissive film. 62, the color filter 63
Through the liquid crystal panel and the retardation plate 53
And the light is emitted through the polarizing plate 54.

Further, by forming the semi-transmissive film 62 on the glass substrate 55, in the reflection mode, particularly by increasing the reflectance, a brighter display can be obtained, and in the transmission mode, a high contrast can be obtained. The reflection mode and the transmission mode can be enhanced to the extent that both functions of the reflection mode and the transmission mode can be satisfied.The panel used in the reflection mode can be used in the transmission mode under the same conditions. In each case, stable and vivid color display was achieved.

The semi-transmissive film 62 is made of a metal thin film such as aluminum, chromium, SUS, aluminum alloy, silver alloy, etc. However, as the film thickness increases, the light transmittance decreases and the light reflectivity decreases. growing. The thickness of such a metal thin film has a different light absorption coefficient depending on the type of metal, and is also determined by which of the reflection mode and the transmission mode is required to improve performance. , Usually 50 to 500 °, preferably 100 to 400 °. Thereby, characteristics as a transflective liquid crystal display device having a reflectivity of 30 to 70% and a transmittance of 5 to 50% can be obtained.

For example, when the semi-transmissive film 62 is formed of an aluminum metal thin film having a thickness of 250 °, the reflectivity becomes 6
5% and the transmittance is 15%.

Further, the semi-transmissive film 62 may be formed of a dielectric material to have a laminated structure of a low refractive index layer and a high refractive index layer.

Then, for the liquid crystal display device having the above configuration,
When the semi-transmissive film 62 is specular, a light scattering plate between the glass substrate 52 of the liquid crystal panel and the retardation plate 53 may be further formed. For example, IDS (Internal Diffusin) manufactured by Dai Nippon Printing Co., Ltd.
g Sheet), which contains beads and the like in the resin. In addition, light scattering irregularities may be provided on the surface of the flat plate.

By providing such a light scattering film between the liquid crystal panel and the phase difference plate 53, when used in the reflection mode, the reflected light reflected by the semi-transmissive film 62 becomes positive by the light scattering film. The light is also scattered in directions other than the reflection direction, thereby increasing the viewing angle of the image display and widening the recognition area of the image display.

Thus, according to the liquid crystal display device having the above-described configuration, the liquid crystal cell 100 is hermetically sealed in the housing 9 so that the liquid crystal cell 100 is not affected by environmental temperature changes and pressure changes. , A good display state can always be obtained.

Next, a method of assembling the liquid crystal display device will be described with reference to FIGS.
This will be described below.

As shown in FIG. 5, the process comprises steps A to D as a flowchart. Each step will be described sequentially.

Step A: A flat plate, which is a plate having a double structure and whose inside is evacuated, is prepared.

Step B: The above flat plate is processed into the structure of the housing 9.

Step C: The backlight 10 and the liquid crystal cell 100 are arranged inside the casing 9 and fixed.

Step D: A display window 14 made of a transparent member is provided at an open portion of the housing 9. Then, the inside of the housing 9 is hermetically sealed by the housing 9 and the display window 14.

The display window 14 is sealed with a vacuum adhesive p such as an araldite between the housing 9 and the display window 14 to keep a vacuum state.

FIG. 6 is an enlarged view of the portion S shown in FIG. 5D.

A method of manufacturing the housing 9 will be described with reference to FIGS.

As shown in FIG. 7, the process comprises steps A to D which are flowcharts. The casing 9 obtained through these steps is subjected to the above steps B to D shown in FIG.

Hereinafter, each step will be described sequentially.

Step A: A flat plate which is a plate having a double structure and is kept at a predetermined interval by the spacer 13 is prepared. A spacer 13 made of a heat insulating material is interposed in the plate.

In a later step, the housing 9 is preferably made of a metal such as SUS in consideration of the deformation of the shape during vacuum evacuation and the ease of processing.

Step B: The above-mentioned flat plate is processed into the structure of the housing 9. However, the interior is not in a vacuum state and is in an open state.

Step C: The open end h of the housing 9 is sealed.
This is done with brazing.

[0068] Brazing is a method in which a metal having a lower melting point is put between two metals to be joined and heated and melted for joining. The joining surface is cleaned with a flux or the like to prevent oxidation. I have to.

Step D: A small hole having a diameter of 0.2 to 2.0 mm is provided in the outer or inner wall of the housing 9, and the air in the gap between the inner and outer walls is exhausted from the small hole to create a vacuum state. The site where this small hole is formed is indicated by m.

FIG. 8 shows the state of the portion m.

To create a vacuum state, a vacuum pump is prepared according to the value of the degree of vacuum to be set.
At a vacuum of 10 ^-1 Pa, a rotary pump is suitable. 10 ^- In ¹ to 10 ^-4 Pa degree of vacuum, an oil diffusion pump or the like is generally used.

As shown in FIG. 8A, an appropriate sealing material such as a solid brazing filler metal or a metal brazing filler metal is disposed at an appropriate position around the small hole, and as shown in FIG. The stopper is melted to seal the small holes. This method is a method used when creating a thermos or the like, and is not a special method but a commonly used method.

As described above, when the liquid crystal display unit has a high sealed space, the liquid crystal cell 100 in the liquid crystal display unit can always maintain a constant atmospheric pressure and temperature state for a long period regardless of the external environment. As a result, the display quality could be kept constant.

The present inventor sets the degree of vacuum to 0.1 Pa or 100 Pa when hermetically sealing the inside of the housing 9 with the housing 9 and the display window 14. When a liquid crystal display device in a thermal equilibrium state of 100 ° C. was placed in a thermal bath having an ambient temperature of 100 ° C., the time change of the temperature of the liquid crystal display device was measured. (Correlation diagram of the time until the material reaches the thermal equilibrium state).

From these results, it is desirable to set the air pressure in the closed space including the liquid crystal cell to 0.1 Pa or less.

The operation guarantee time of a general liquid crystal display device is as follows.
When it is tens of thousands of hours and the degree of vacuum in the closed space is 0.1 Pa or less, the heat insulation can be maintained within that time. Furthermore, it can be said that the larger the degree of vacuum in the heat insulating layer, the higher the heat insulating property of the liquid crystal display device, and the longer the storage time of the liquid crystal display device.

Thus, according to the present invention, it was possible to provide a liquid crystal display device having a constant display quality regardless of the external environment (temperature and pressure).

[0078]

As described above, according to the liquid crystal display device of the present invention, a liquid crystal cell is installed inside a housing composed of a plate-like body having a double structure whose inside is evacuated and evacuated. A display window made of a transparent material is formed in a part of the housing facing the display surface, and the inside of the housing is hermetically sealed with the housing and the display window, so that it is not affected by environmental temperature changes or pressure changes. ,
As a result, a good display state can always be obtained even under poor environmental conditions, and as a result, a high-performance and highly reliable liquid crystal display device that responds to changes in environmental temperature and pressure can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a liquid crystal display device of the present invention.

FIG. 2 is a sectional view of a main part of a housing according to the liquid crystal display device of the present invention.

FIG. 3 is a schematic cross-sectional view illustrating a configuration example of a spacer arranged in a housing.

FIG. 4 is a schematic cross-sectional view showing another configuration example of the spacer disposed in the housing.

FIGS. 5A, 5B, 5C, and 5D are process diagrams illustrating a manufacturing method (assembly method) of the liquid crystal display device of the present invention.

FIG. 6 is a sectional view of a main part of the liquid crystal display device of the present invention.

FIGS. 7A, 7B, 7C, and 7D are process diagrams illustrating a method of manufacturing a housing.

8A and 8B are cross-sectional views of main parts of the housing.

FIG. 9 is a schematic sectional view of a conventional liquid crystal display device.

FIG. 10 is a sectional view showing a specific example of a liquid crystal cell.

FIG. 11 is a cross-sectional view showing a specific example of a liquid crystal cell.

FIG. 12 is a diagram illustrating a correlation between an environmental temperature and a time required for a liquid crystal display device to reach a thermal equilibrium state.

[Explanation of symbols]

 9 ... housing 10 ... backlight 13 ... spacer 14 ... display window 100 ... liquid crystal cell

Claims (1)

[Claims] 1. A liquid crystal cell is installed inside a housing formed of a plate member having a double structure whose inside is evacuated, and a transparent member is formed on a part of the housing facing the display surface of the liquid crystal cell. A liquid crystal display device, wherein a display window is formed, and the housing is hermetically sealed with the housing and the display window.