JP2000131692A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device preventing entering of humidity and a foreign matter in an atmosphere and having a thin, light weight and less secular change light source by improving flatness of a backlight irradiation surface opposite to a liquid crystal display element and making it an airtight structure. SOLUTION: This liquid crystal display device is provided with a backlight irradiating light onto a liquid crystal panel 2. The backlight irradiates light as a surface light source by the light from a lamp, and is provided with a structure laminating a light transmission plate 7m and optical sheets 7r, 7p, 7n, 7s, and is constituted as the airtight structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

BACKGROUND OF THE INVENTION A liquid crystal display device, in particular, a liquid crystal display device having a structure in which a liquid crystal display element itself is hermetically installed inside a vacuum tube or a pressure reducing tube is used as a display element for a liquid crystal display device having a relatively narrow operating temperature range. Used for obtaining stable display characteristics over a wide temperature range.

The above-mentioned liquid crystal display device is disclosed in, for example,
No. 9-231514. JP 59
In the liquid crystal display device disclosed in JP-A-231514, a liquid crystal display element is hermetically mounted at least inside a vacuum tube or a pressure reducing tube having a transparent display surface. This type of liquid crystal display device has an additional temperature compensation circuit. Without doing
The use temperature range of the liquid crystal display device is improved without using a liquid crystal material having little temperature dependency.

[0004] That is, the above-mentioned Japanese Patent Application Laid-Open No. 59-2315.
According to the liquid crystal display device disclosed in Japanese Patent Application Publication No. 14, the entire liquid crystal display element is sealed in a glass tube, and the inside of the glass tube is sealed with 0.1%.
By maintaining the liquid crystal display element in a state where the liquid crystal display element is completely shut off from the outside air by maintaining the low pressure state of Pa or lower, the operating temperature range, that is, the crosstalk in the high temperature region, the temperature range that causes a decrease in contrast in the low temperature region. It is to make it wider.

However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 59-231514, there is a problem that the weight increases and the thickness of the entire apparatus increases.

Meanwhile, a general liquid crystal display device is composed of two glass substrates and a liquid crystal material. One glass substrate is formed with pixel electrodes corresponding to each of RGB colors, and the other glass substrate is formed. Are formed with a filter of three primary colors of RGB. The two glass substrates are bonded to each other at a constant interval at the peripheral edge, and a gap is filled with a liquid crystal material.

As the thickness and weight of the device have been promoted, the weight of the glass substrate has been reduced by making the peripheral portion of the liquid crystal display element narrower (hereinafter referred to as “narrower frame”). About 1/3 of the total. To reduce the pressure in the gap between adjacent glass substrates, arranging a highly rigid glass substrate that covers the entire liquid crystal display device is disadvantageous not only in terms of the weight of the device but also on both the display surface and the back surface. Because of the need to cover, there are also thickness and optical problems.

[0008] For example, Japanese Patent Application Laid-Open No. 23358/1990 describes a technique for a close contact baking method in a photomechanical process and an apparatus therefor. In this technique, a decomposition positive film and a photosensitive material are arranged above, and the film is exposed from below.

The technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 23358/1990 is intended to cover the glass with a vacuum sheet and reduce the pressure in the sheet to improve the adhesion between the films and the paper and the glass plate. It is optimal to use.

The technique disclosed in Japanese Patent Laid-Open No. 23358/1990 cannot cover a vacuum sheet and depressurize the inside thereof to maintain airtightness permanently. In the shape, since it is a sheet of a single plane, if there is a thick member such as wiring in a peripheral frame portion requiring airtightness, it is impossible to maintain close contact between the sheet and the glass, It is difficult to apply the above technology to a liquid crystal display device.

Japanese Patent Application Laid-Open No. 9-96800 discloses a backlight which realizes weight reduction as shown in FIG.

As shown in FIG. 6, an optical sheet 73 having a four-layer structure including a diffusion sheet 7r, a lens sheet 7p, a lens sheet 7z, and a diffusion sheet 7n is arranged on the front side of the light guide plate 7m. On the back side of 7 m, a reflection sheet (not shown) is arranged.

On one side of a side surface in the thickness direction of the light guide plate 7m, a lamp assembly 7 in which a lamp (not shown) and cables 7f and 7h for supplying power to the lamp are incorporated.
1 are arranged, and at the ends of the cables 7f and 7h,
Connector 7g is attached. Connector 7g is
Only when the insertion direction is correct, the structure can be electrically connected.

The thickness of the light guide plate 7m depends on the lamp assembly 7
1 is the thickest on the side where it is disposed, and has a cross-section such that the thickness decreases as the distance from the lamp assembly 71 side increases. At this time, the thick side of the light guide plate 7m has a thickness of 2 to 5m.
m, the thin side has a thickness of about 0.5 to 2 mm.

Four-layer optical sheet 7 of diffusion sheet 7r, lens sheet 7p, lens sheet 7z and diffusion sheet 7n
The light guide plate 7m on which the light guide plate 3 is disposed, and the lamp assembly 71 disposed on the side surface of the light guide plate 7m are positioned and housed by a frame of a back shield 74, and a frame body 72 is disposed on the upper surface side.

The frame 72 has an opening at the center, and a tongue 72b having a width of 1 to 5 mm which presses down the outer edge of the optical sheet 73 is formed on the periphery of the opening 72a.
The light for backlight is emitted from the illuminating surface 7d of the optical sheet 73 located in the opening 72a of the frame 72.

[0017]

However, in the liquid crystal display device disclosed in Japanese Unexamined Patent Application Publication No. 9-96800 shown in FIG. 6, the optical sheet 73 is held by the frame 72, so that only the peripheral portion is fixed. The central portion is not held, and the sheets and the reflection sheet cannot be supported by a uniform pressure, and wrinkles may be generated on the illumination surface 7d.

Therefore, the optical sheet 73 (7r, 7p,
7z, 7n), the gaps are naturally formed between the sheets and between the light guide plate 7m and the optical sheet 73. Therefore, there is a problem that the optical sheet 73 is wrinkled in a humid environment or when heat is applied. In addition, there is a problem that a Newton's ring is generated when a path difference of light due to an air layer generated between the sheets becomes an integral multiple of the wavelength of light.

Furthermore, the light guide plate 7m used in the backlight 7 cannot be neglected due to the difference in moisture absorption between the front and back surfaces in a humid environment, and the backlight itself is warped. Not maintain the flatness, which affects the assemblability, permanent deformation remaining after removing humidity,
Deformation under high humidity not only does not keep the luminance uniformity as a surface light source, but also has the problem that Newton rings occur.

The reason is that a resin material such as acrylic, which is used as a material of the light guide plate 7m, having high transparency and good moldability, has a difference in humidity, particularly in a wet environment, or This is because if the resin density during resin molding varies, the amount of warpage increases, and deformation after the drying step is unavoidable, making it difficult to obtain a necessary planar light source.

Generally, since a cold cathode tube or a hot cathode tube is used as a light source, the temperature distribution applied to the resin-made optical system components (light guide plate, optical sheet) is non-uniform in the plane. In addition, it is necessary to uniformly press the entire illumination surface.

Furthermore, in the prior art, when narrowing the frame, there is a problem that the optical sheets cannot be prevented from protruding from the frame when an impact is applied, and the impact resistance is deteriorated.

The reason is that, in a narrow frame structure in which the screen size and the outer size are almost the same, the outer shape of the frame 72 and the outer shape of the optical sheet 73 are almost the same, so that the amount of overlap between the frame and the sheet is large. This is because, when an impact is applied, the optical sheet 73 jumps out toward the illuminating surface 7d side of the frame 72, and the possibility of occurrence of display abnormality increases.

An object of the present invention is to improve the flatness of a backlight illuminating surface facing a liquid crystal display element and to prevent the invasion of humidity and foreign substances in the atmosphere by using an airtight structure, thereby making it thin and lightweight. Another object of the present invention is to provide a liquid crystal display device having a light source with little aging.

[0025]

In order to achieve the above object, a liquid crystal display device according to the present invention is a liquid crystal display device having a backlight for irradiating a liquid crystal panel with light,
The backlight performs light irradiation as a surface light source based on light from a lamp, and has a structure in which a light guide plate and optical sheets are stacked, and further, the backlight has a sealed structure. It was done.

In the backlight, the pressure in the closed structure is reduced.

[0027] The backlight sealing structure may further include a back support having a recess for receiving the laminated structure;
An optical sheet for closing the opening of the recess is provided.

The back support is formed of a thin sheet-like molded product.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is an exploded perspective view showing a liquid crystal display device according to an embodiment of the present invention.

A liquid crystal display device 100 according to the embodiment of the present invention shown in FIG. 1 includes a panel assembly 20 including a liquid crystal panel 2, a backlight 7, a shield plate 1, and a protection plate 8.
And

The panel assembly 20 includes the liquid crystal panel 2
, A gate driver 5 and a source driver 6.

The liquid crystal panel 2 has a structure of a transmission type liquid crystal display element. The gate driver 5 and the source driver 6 drive the liquid crystal panel 2 and have flexibility. Transmissive liquid crystal display elements include TFT, ST
Although there are N and DSN type structures, any of these structures using the backlight 7 can be used as the liquid crystal panel 2.

The source driver 6 has a tape carrier package (TCP) structure including a semiconductor element for driving the liquid crystal panel 2, and uses an anisotropic conductive connection material such as ACF for the liquid crystal panel 2. The terminals provided are electrically and mechanically connected to the signal processing board 3 by soldering. The connection may be made electrically or mechanically by another connection method instead of soldering.

The gate driver 5 has a tape carrier package (TCP) structure including a semiconductor element for driving the liquid crystal panel 2, and includes a terminal provided on the short side of the liquid crystal panel 2, the connection substrate 4, Is electrically and mechanically connected to

The backlight 7 is disposed on the back surface opposite to the display surface of the liquid crystal panel 2.
Is designed to project white light from the illumination surface 7d to the back surface of the display unit of the liquid crystal panel 2.

The signal processing board 3 connected to the liquid crystal panel 2 via the source driver 6
Is bent by the source driver section due to its flexibility, and is disposed on the back surface of the illumination surface 7 d of the backlight 7.

The connection substrate 4 is disposed on the back side of the backlight 7 by utilizing the flexibility of the gate driver 5.
The signal processing board 3 and the connection board 4 are electrically connected by the FPC 4a mounted on the connection board. In this case, the substrates 3 and 4 are electrically and mechanically connected by soldering, ACF or a connector.

The shield plate 1 is disposed on the front side of the liquid crystal panel 2 and has an opening 1e at a position corresponding to the display surface of the liquid crystal panel 2. The protection plate 8 is made of sheet metal, resin, or the like, and is disposed on the back side of the liquid crystal panel 2. The shield plate 1 and the protection plate 8 hold the liquid crystal panel 2 and the backlight 7 therebetween.

The shield plate 1 has a fitting claw 1 on the short side.
a and 1b are each provided with a fitting claw 1c on the long side, and the protection plate 8 is provided with a fitting claw 8b on the short side and a fitting claw 8c on the long side. Backlight 7
Has a fitting claw 7a on the short side.

The liquid crystal panel 2 and the backlight 7 are butted together. As a structure in which the liquid crystal panel 2 and the backlight 7 are brought into contact with each other, the liquid crystal panel 2 is attached to the periphery of the backlight 7 with an adhesive tape, or projections are provided at four corners of the backlight 7, and the projections of the backlight 7 A structure in which a corner of the panel 2 is abutted can be used. The liquid crystal panel 2 and the backlight 7 which are brought into contact with each other by the above-described structure are combined with the shield plate 1 and the protection plate 8.
And the fitting claw 1a of the shield plate 1, the fitting claw 7a of the backlight 7, the fitting claw 1b of the shield plate 1, the fitting claw 8b of the protection plate 8, and the fitting claw of the shield plate 1. 1c and the fitting claw 8c of the protection plate 8 are fitted to each other, whereby the liquid crystal display device 100 is constructed.

FIG. 2 is a perspective view showing the backlight 7 used in the embodiment of the present invention, and FIG. 3 is a sectional view taken along line AA of FIG.

As shown in FIG. 2, the backlight 7 is provided with a high-voltage side cable 7f and a low-voltage side cable 7h for supplying power to the lamp, and a connector 7g is attached to the ends of the cables 7f and 7h. Have been. The connector 7g has a structure in which a wrong polarity is prevented by a key groove or the like so as not to make a wrong polarity.

As shown in FIG. 3, the backlight 7 comprises a diffusion sheet 7r, a lens sheet 7p, and a diffusion sheet 7 from the side of the illuminating surface 7d as optical system components for obtaining a required luminance.
n are sequentially arranged one above another, and further below the light guide plate 7.
m and the reflection sheet 7s on the back surface of the light guide plate are arranged in an overlapping manner. At this time, the periphery of only the diffusion sheet 7r protrudes from the periphery of the other sheets 7p, 7n, 7s and the light guide plate 7m by about 2 to 10 mm.

Further, as shown in FIG.
The back support 7j is arranged on the back side of the reflection sheet 7s. The back surface support 7j has a bottom surface and a wall surface 7k standing upright on the bottom surface, and a tongue portion 7e is provided on an upper edge of the wall surface so as to protrude in the horizontal direction in parallel with the bottom surface. The tongue 7e of the backlight 7 has a width of 2 to 10 mm,
The four sides of the backlight 7 are formed in a frame shape.

The back support 7j is provided with a diffusion sheet 7r, a lens sheet 7p, a diffusion sheet 7n, and a light guide plate 7 of the backlight 7 in a recess formed by the bottom surface and the wall surface 7k.
m and the reflection sheet 7s on the back surface of the light guide plate are received and surrounded, and the tongue 7e of the back surface support 7j is adhered to the diffusion sheet 7r of the backlight 7 by welding or bonding all around.

When the tongue 7e of the back support 7j is welded or bonded to the diffusion sheet 7r of the backlight 7, the air pressure in the closed space sealed by the diffusion sheet 7r and the back support 7j is reduced by the external pressure ( 1.013 HPa) and the diffusion sheet 7 r and the lens sheet 7 using the low-pressure air pressure in the closed space.
The clearance between the p, the diffusion sheet 7n, the light guide plate 7m, and the reflection sheet 7s on the back surface of the light guide plate is appropriately maintained.

In selecting the air pressure in the closed space sealed by the diffusion sheet 7r and the back support 7j, the air pressure which does not cause the deterioration of the characteristics of the optical sheet (physical collapse of the lens sheet, etc.) is determined. Check the matching with the physical strength of the sheet and select.

As a material of the diffusion sheet 7r, as a material having excellent heat-fusibility, low hygroscopicity, and high moldability, polyethylene terephthalate (PET) and polycarbonate (PC) having a thickness of 0.05 to 1 mm are used. , Polyolefin and the like can be used. The diffusion sheet 7r is made of a sheet-shaped raw material and the same material having a diameter of 8 μm to 20 μm.
μ microspheres (beads) are fixed to the surface by a binder layer having a thickness of 10 to 50 μ to obtain a diffusion effect.

The material of the lens sheet 7p is as follows.
A resin such as polyethylene terephthalate (PET), polycarbonate (PC), or polyolefin having a thickness of 0.05 to 1 mm is used.
Pitch 10-100 with an isosceles triangular cross section of 0 °
The structure is such that it has a μ-striped surface and obtains the effect of condensing light in a direction perpendicular to the streaks and the surface.

In the case where the tongue 7e of the back support 7j and the diffusion sheet 7r of the backlight 7 are fused, the same material can be used to obtain a strong adhesive force. The material of the diffusion sheet 7r to be
It is desirable to select from the requirements of the optical design, and the material of the back support plate 7j is desirably selected in accordance with the material of the diffusion sheet 7r. Can be adjusted.

In order to fuse the tongue 7e of the back support 7j and the diffusion sheet 7r of the backlight 7, the peripheral portion is heated by ultrasonic welding, high-frequency heating, or the like.
Perform fusion.

In the above case, the case where the back support 7j and the diffusion sheet 7r are joined with the same material has been described. However, when the backlight itself requires rigidity, the back support 7j is made of a thin plate such as a metal plate. In this case, it is bonded to the diffusion sheet 7r in an airtight state by bonding.

FIG. 4 is a partial perspective view showing a configuration in which a wiring portion for supplying power to an optical system according to the embodiment of the present invention is a sealed structure, and FIG. 5 is a cross-sectional view taken along the line BB 'of FIG. .

A tongue 7e on which the fused portion is formed projects outward from the illuminating surface 7d of the backlight 7, and a high-voltage cable extends from the fused portion of the tongue 7e near the corner of the back support 7j. 7f and the low-voltage cable 7h are pulled out while maintaining airtightness.

The low-voltage-side cable conductor 7t is covered with a low-voltage-side cable insulator 7y, and is pulled out from the fusion portion of the tongue 7e. The cross-sectional shape of the low-voltage side cable insulator 7y is
The side in contact with the diffusion sheet 7r forming the illuminating surface 7d has a planar shape, and the side in contact with the back surface support 7j has an arc shape. Back surface support 7j corresponding to the arc side
The shape can be obtained by projecting a corresponding male mold into an arc shape at the time of molding the back support 7j and processing and forming an arc-shaped depression in the corresponding female mold. Thereby, the flatness required optically can be maintained and the airtightness can be obtained on the diffusion sheet 7r side.

The high-voltage-side cable conductor 7u is covered with a high-voltage-side cable insulator 7x, and is drawn out from the fusion portion of the tongue 7e. The cross-sectional shape of the high voltage side cable insulator 7x is
The side in contact with the diffusion sheet 7r forming the illuminating surface 7d has a planar shape, and the side in contact with the back surface support 7j has an arc shape. Back surface support 7j corresponding to the arc side
The shape can be obtained by projecting a corresponding male mold into an arc shape at the time of molding the back support 7j and processing and forming an arc-shaped recess in the corresponding female mold. Thereby, the flatness required optically can be maintained and the airtightness can be obtained on the diffusion sheet 7r side.

Here, since the applied voltage of the low voltage side cable 7f is low, the insulation coating is FPC or FF.
C, the thickness of the cable including the insulating coating is thin, and it is easy to maintain airtightness with respect to the fused portion of the tongue 7e. However, in the high-voltage side cable 7h, a backlight using a cold cathode tube is used. In the case of (3), the insulation withstand voltage of 3 KV or more is required, so that the insulator 7x needs to have the thickness of the insulating material, and it is necessary to form the depression as described above.

As described above, according to the embodiment of the present invention,
The fused portion between the tongue 7e of the diffusion sheet 7r and the back support 7j is connected to two high voltage side cables 7f for supplying power to the optical system.
In addition, airtightness is maintained and joined over the entire circumference including the location of the low-voltage side cable 7h.

In order to reduce the pressure in the closed space sealed by the diffusion sheet 7r and the back support 7j, the back support 7j is formed of a thin sheet (or thin plate). The part is the illumination surface 7d
Move toward the side, and each sheet 7r, 7p, 7n,
The light guide plate 7m and the reflection sheet 7s are uniformly pressed on the illumination surface 7d. Thereby, the sheets 7r, 7p,
Unnecessary clearance between the light guide plate 7n, the light guide plate 7m, and the reflection sheet 7s can be eliminated.

Further, the diffusion sheet 7r and the back support 7
Since the backlight 7 is incorporated in the enclosed space enclosed by the j, the backlight 7 is shielded from the outside, and it is possible to protect the light guide plates and sheets having the characteristic of causing warpage in a partially-humid state from the outside air. it can. Further, when a thin structure is adopted, the dimensional instability of the backlight 7 can be suppressed by utilizing the low pressure in the closed space, and the entire thickness can be stabilized.

In view of the restrictions on the thickness and required luminance, a sheet structure in which a lens sheet is used on the front side and a lens sheet, a lens sheet, and a diffusion sheet are stacked from the illuminating surface 7d side may be used.

Further, by using a material having a polarizing property as the material of the illuminating surface 7d, a polarizing plate normally attached to the illuminating surface side of the liquid crystal display element can be arranged on the backlight side.

Further, in accordance with the demand for surface uniformity and a large screen,
In some cases, a lamp holder used when light is incident on the light guide plate is made of metal. In this case, the entire backlight can be covered with a resin, and an insulating structure can be ensured all around the fused portion of the tongue portion 7e. It is possible to increase the dielectric strength.

[0065]

As described above, according to the present invention, the dust between the optical sheets of the backlight, in which dust easily enters during assembly, is covered with a resin sheet in the sub-ASS step to hermetically seal the dust. Can be prevented from entering.

Furthermore, by evacuating the inside of the sealed structure surrounding the backlight, it is possible to prevent the occurrence of warpage or the like due to swelling of the optical sheets and the resin constituting the light guide.

Further, unnecessary members between the optical sheets can be filled by making the members constituting the closed structure flexible members and evacuating the inside of the closed structure.
Furthermore, it is possible to avoid that the air layer in the thickness direction, which is naturally generated between the optical sheets, becomes an integral multiple of the path difference of the light, which causes a display defect due to the generation of Newton rings (interference fringes) and an optical sheet. A display defect due to swelling and thermal deformation can be avoided, and a thin, good liquid crystal display device can be obtained.

Since the illuminating surface is constituted by a single layer or an optical sheet as in the conventional case, there is no disadvantage in terms of luminance and the like. Further, the illuminating surface is made of a material having a polarizing property or a lens sheet as in the related art, and does not require any additional members. Therefore, there is no disadvantage in brightness, weight, and outer shape.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a backlight used in the embodiment of the present invention.

FIG. 3 is a sectional view taken along line A-A ′ of FIG. 2;

FIG. 4 is a partial perspective view illustrating a configuration in which a wiring unit that supplies power to an optical system according to an embodiment of the present invention has a sealed structure.

FIG. 5 is a sectional view taken along line B-B ′ of FIG. 4;

FIG. 6 is a perspective view showing a backlight according to a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 shield plate 2 liquid crystal panel 7 backlight 7 d illuminating surface 7 e tongue 7 j back support 7 m light guide plate 7 n diffusion sheet 7 p lens sheet 7 r diffusion sheet 7 s reflection sheet

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Claims (4)

[Claims] 1. A liquid crystal display device having a backlight that irradiates a liquid crystal panel with light, wherein the backlight irradiates light as a surface light source based on light from a lamp. A liquid crystal display device having a structure in which optical sheets are laminated, and wherein the backlight is configured as a closed structure. 2. The liquid crystal display device according to claim 1, wherein the backlight has a reduced pressure in a closed structure. 3. The closed structure of the backlight is characterized by comprising a back support having a concave portion for receiving the laminated structure, and an optical sheet for closing an opening of the concave portion. The liquid crystal display device according to claim 2. 4. The back support according to claim 3, wherein the back support is formed of a thin sheet-like molded product.
3. The liquid crystal display device according to 1.