JPH1124071A - Back light for color liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a back light for a color liquid crystal device which can make small the width of the edge part of its case and equalize the sizes of three light sources. SOLUTION: The three light sources 6, 7, and 8 are arranged in the thickness direction A of a light guide body 4, so the width W of the edge part 18 of the case 3 behind which the light sources 6, 7, and 8 are hidden can be made small, and the designability of the back light 2 can be improved. The light sources 6, 7, and 8 are of the same size and in the same shape, so the same machine and jig are usable for the manufacture and assembly and only one kind of packing is needed, which is advantageous in manufacture, assembly, and packing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a backlight for a color liquid crystal display.

[0002]

2. Description of the Related Art Recently, OA of personal computers and the like has been developed.
2. Description of the Related Art A color liquid crystal display device is used for a display of a home appliance such as a device or a television. As this type of color liquid crystal display device, a TFT type color liquid crystal display device is widely known. That is, a color filter corresponding to the three primary colors (red (R), green (G), and blue (B)) and a color liquid crystal cell including a thin film transistor (TFT) are combined with a backlight of a white light source to form each color. The liquid crystal corresponding to the filter is opened by a drive circuit to allow light to pass therethrough, so that mosaic color mixture by a combination of red (R), green (G), and blue (B) colors is obtained.

Such a TFT type color liquid crystal display device can obtain a clear full color image, but requires a color filter and a thin film transistor for each pixel (liquid crystal cell). Processing is required, and there are also problems such as difficulty in color balance adjustment.

In view of this, a color filter-less color liquid crystal display device has recently been proposed in which a monochrome liquid crystal cell which does not require a color filter or a thin film transistor is combined with a backlight of three primary colors (see, for example, Japanese Patent Application Laid-Open No. Hei 6 (1994) -106).
-13859). That is, the light sources of the three primary colors are sequentially and periodically pulse-emitted, and the liquid crystal is opened at the same timing as the emitted light, so that red (R) and green (G) are emitted.
-An afterimage color mixture is obtained by a combination of blue (B) colors.

The backlight used in the color filter-less color liquid crystal display device has three primary colors along two or three surfaces adjacent to each other among four end surfaces around one light guide plate. Are independent L-shaped or U-shaped light sources arranged along the plane of the light guide plate. That is, the three light sources sequentially increase in size from the inside to the outside, and the light sources are arranged on the same plane along the plane direction of the light guide plate. The light guide plate is housed in the case, and most of the light guide plate except the end face is located inside the opening of the case, and the end face of the light guide plate and the light source are hidden by the edge around the opening. .

[0006]

However, in such a conventional backlight for a color liquid crystal display device, the width of the edge of the case is increased in order to cover a light source arranged in a plane direction. Required, and the degree of freedom in design is limited. A case with a large edge has an old design feeling, and the design is impaired.

[0007] Further, the size of the three light sources is different (the larger the size on the outer side), and it is necessary to change the setting of the bending process of the manufacturing machine for each light source, which is disadvantageous in terms of mass productivity of the light sources.

Furthermore, the different sizes of the light sources require three types of assembling machines, jigs, and packages for the light sources, and it is not possible to use a common machine and packaging.

The present invention has been made by paying attention to such a conventional technique, and is intended for a color liquid crystal display device in which the width of an edge of a case can be reduced and three light sources can be made the same size. The backlight is provided.

[0010]

According to the first aspect of the present invention,
A reflecting mirror having a cross-sectional shape with an opening on the light guide plate side is provided along two or three surfaces adjacent to each other among four end surfaces around one light guide plate, and a pulse is sequentially and periodically provided in the reflector. An independent L-shaped or U-shaped light source of the three primary colors that emits light is arranged, and most of the light guide plate except for the end face is positioned inside the opening of the case, and the end face of the light guide plate and the light source are positioned around the opening. A backlight for a color liquid crystal display device obscured by a portion, wherein two or three adjacent surfaces of the light guide plate are inclined at 45 ° with the front surface side inclined inward, and the reflecting mirror is inclined. Three light sources having the same L-shape or U-shape are arranged along the thickness direction of the light guide plate in the reflecting mirror, with the cross-sectional shape opened to the closer back end,
Further, an extension portion for covering the inclined surface is formed on the reflecting mirror.

According to the first aspect of the present invention, since the three light sources are arranged in the thickness direction of the light guide plate, the width of the edge of the case that hides the light sources can be reduced, and the design of the backlight can be improved. Can be improved. Even if the light source is arranged in the thickness direction of the light guide plate in this manner, the light is reliably guided into the light guide plate by the 45 ° inclined surface formed on the end surface of the light guide plate and the extension of the reflecting mirror covering the end surface. be able to. Further, since the shape and size of the light source are the same, the same machine and jig can be used for manufacturing and assembling, and only one kind of packing is required, which is advantageous in terms of manufacturing, assembling and packing. .

According to a second aspect of the present invention, a diffusion sheet is provided on the front surface of the light guide plate, and a reflection sheet is provided on the rear surface via halftone printing.

According to the second aspect of the present invention, since the diffusion sheet, the halftone dots, and the reflection sheet are provided, the light incident on the light guide plate is diffused and emitted, and the luminance can be made uniform. it can.

According to a third aspect of the present invention, an auxiliary reflection sheet is provided on an end face of the light guide plate where no light source is disposed.

According to the third aspect of the present invention, since the auxiliary reflection sheet is provided on the end surface of the light guide plate on which the light source is not disposed, the luminance is prevented from attenuating in a portion far from the light source, and the luminance is made uniform. Can be planned.

According to a fourth aspect of the present invention, the light source is a cold-cathode tube and color light is emitted from each phosphor.

According to the fourth aspect of the present invention, since the three primary colors are generated from the phosphors of the respective cold cathode tubes, the color film on the light source side provided for color development can be eliminated.
The number of parts can be reduced.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to FIGS.

The color liquid crystal display device according to this embodiment includes a liquid crystal panel 1, a backlight 2, a case 3,
And a control circuit (not shown). The liquid crystal panel 1 is incorporated in the backlight 2, and a control circuit is also installed in the backlight 2.

The liquid crystal panel 1 is formed of liquid crystal cells corresponding to one pixel. In each liquid crystal cell, liquid crystal (STN) is sealed between two glass substrates, and the liquid crystals are arranged in a matrix. ON via transparent conductive film (ITO film)
A known one that is turned off can be used. Since this liquid crystal cell is for monochrome and does not require a color filter or a thin film transistor, the structure is simple.

The backlight 2 includes one light guide plate 4, a reflecting mirror 5, three light sources 6, 7 and 8, a diffusion sheet 9,
It is composed of a halftone dot (dot pattern) 10, a reflection sheet 11, and an auxiliary reflection sheet 12.

As the light guide plate 4, a transparent resin plate or a molded product having six smooth surfaces can be used. As the transparent resin, an acrylic plate, a polyester plate, a vinyl chloride plate and the like are preferable. The cross-sectional area (that is, thickness) of the end surface (light incident surface) of the light guide plate 4 is an important factor for effectively introducing light from the light sources 6, 7, 8; Although the light can enter the light plate 4, if it is too thick, light loss is also caused. The backlight 2 of this embodiment includes a light guide plate 4
Since only one sheet is required, the structure is simple, which is advantageous in reducing the size and thickness of the apparatus.

Of the four end surfaces around the light guide plate 4, three adjacent end surfaces except one are inclined surfaces 13, 14, and 15 of 45 ° whose front surfaces are inclined inward.
The remaining end surface 16 is a right angle surface.

At the end of the back surface of the light guide plate 4 corresponding to the inclined surfaces 13, 14, 15, a reflecting mirror 5 having a U-shaped cross section opened to the back surface is provided.
It is formed in a U-shape along 3, 14, and 15. Also, from the outer end of the reflecting mirror 5, each inclined surface 13, 1
An extension 5a covering the fourth and the fourth 15 is also formed. A silver mirror surface having a high reflectivity is formed on the inner surface of the reflecting mirror 5 in order to efficiently introduce light from the light sources 6, 7, 8 into the light guide plate 4 and prevent the light from leaking outside. I have.

In the reflecting mirror 5, light sources 6, 7, and 8 having the same U-shape are arranged in the thickness direction of the light guide plate 4 (the direction A in FIG. 2).
Are arranged along. The light source 6 is for red (R), the light source 7 is for green (G), and the light source 8 is for blue (B), each using a cold cathode tube. The light sources 6, 7, and 8 emit light from the phosphor itself coated on the inner surface of the cold-cathode tube to display three primary colors, and do not require a color filter.
The light sources 6, 7, and 8 are continuously lit at a constant pulse cycle, and do not require an optical shutter or the like.

Printed on the back surface of the light guide plate 4 are white dots 10. The dot 10 is for scattering light, and is formed by printing an ink in which a filler having a high refractive index is mixed with an organic resin in a dot shape.

The reflection sheet 11 is a sheet made of a white high-reflectance material, and is formed by depositing a metal film such as aluminum or silver by vapor deposition or the like. A metal tape such as aluminum or silver may be adhered to the side surface.

Attached to one of the remaining end surfaces 16 is an auxiliary reflection sheet 12, and by providing the auxiliary reflection sheet 12, it is possible to prevent the luminance from declining in portions far from the light sources 6, 7, and 8. Thus, the brightness can be made uniform.

The diffusion sheet 9 is a roughened surface having a satin finish on the sheet surface, and is for scattering and transmitting light transmitted from the light guide plate 4.

The case 3 has an opening 17 on the upper surface, and the periphery of the opening 17 and the ends of the liquid crystal panel 1 and the light guide plate 4 and the light source 6.
An edge 18 for hiding 7 and 8 is formed.

Next, the operation of the color liquid crystal display device will be described. Each light source 6, 7, 8 is controlled by a control circuit (not shown).
Is output. The pulse waveform for the R light source 6 has a duty set to １ ／ to avoid simultaneous lighting with other colors (mixing colors). Next, the G light source 7,
Regarding the B light source 8 as well, a pulse is caused to rise just in a form shifted by 1/3 cycle.

The color light emitted from the light sources 6, 7, 8 is directly or reflected by the reflecting mirror 5, and enters the light guide plate 4 once from the back surface of the light guide plate 4, and the light entering the light guide plate 4 is: The light is reflected by the extension 5 a of the reflecting mirror 5 attached to the inclined surfaces 13, 14 and 15 of the light guide plate 4, and is introduced into the light guide plate 4 along the plane direction of the light guide plate 4. A part of the light guided into the light guide plate 4 hits the halftone dot 10 on the back surface and is scattered, so that the light is emitted to the liquid crystal panel 1 side. A part of the light hitting the halftone dot 10 is reflected in the light guide plate 4 and then hits the reflection sheet 11 to be guided again to the liquid crystal panel 1 side.

Light entering the liquid crystal panel 1 from the light guide plate 4 passes through the diffusion sheet 9. Light passing through the diffusion sheet 9 becomes scattered light due to minute irregularities and satin finish on the surface, so that an effect of uniformly illuminating the entire surface can be obtained.

While the light sources 6, 7, and 8 in the backlight 2 emit pulses sequentially at a high speed as described above, the liquid crystal in the liquid crystal panel 1 opens at the same timing as the color to be emitted. Therefore, the color at the timing when the liquid crystal opens is transmitted through the liquid crystal panel 1, and the color is displayed. Color mixing is performed by opening the liquid crystal at the timing of another color. For example, if the liquid crystal is opened at both timings of R and G, R and G
Is displayed, the liquid crystal is left open and R
-If three colors of G and B are mixed, white is displayed. This is afterimage color mixing that occurs because the pulses of the light sources 6, 7, and 8 are sufficiently faster than the afterimage time of the eyes. The white color adjustment is performed by adjusting the light amount (luminance) ratio of each of the light sources 6, 7, and 8.

In this embodiment, as described above,
Since the light sources 6, 7, 8 are all of the same shape, the light sources 6, 7,
The setting of the three pipe bending devices in the mass production of No. 8 can be shared, and the step change is unnecessary. Therefore, the manufacturing cost of the light sources 6, 7, and 8 can be reduced, and the effect of mass production about three times that of the related art can be obtained. The fact that the three light sources 6, 7, 8 have the same shape means that the automatic assembling apparatus, the assembling jig,
This is advantageous because the shape of the packaging can be shared.

Further, since the light sources 6, 7, 8 are all of the same size, the length of each of the light sources 6, 7, 8 can be made shorter than that of the conventional outermost one (conventionally, the tube). The spacing between the tubes was increased to avoid discharge between them, and the outer tubes were very long.) Since the voltage applied to the cold-cathode tube is proportional to the length of the tube, if the tube is long, the capacity of the output transformer of the inverter must be large, resulting in an increase in the size of the transformer and the accompanying cost.
In the present invention, it is not necessary to make the tube longer than necessary,
The conventional trouble does not occur.

Furthermore, since the light sources 6, 7, 8 are arranged in the thickness direction of the light guide plate 4, the width W of the edge 18 of the case 3 can be small. Therefore, the degree of freedom in design of the backlight 2 is improved, and the appearance is good.

In the above-described embodiment, three of the four end surfaces of the light guide plate 4 are inclined surfaces 13, 14, 15, and the U-shaped light sources 6, 7, 8 are arranged there. Is shown, but two adjacent end faces are inclined, and L
A light source of a shape may be arranged.

[0039]

According to the first aspect of the invention, since the three light sources are arranged in the thickness direction of the light guide plate, the width of the edge of the case that hides the light sources can be reduced, and the design of the backlight can be reduced. Performance can be improved. Even if the light source is arranged in the thickness direction of the light guide plate in this manner, the light is reliably guided into the light guide plate by the 45 ° inclined surface formed on the end surface of the light guide plate and the extension of the reflecting mirror covering the end surface. be able to. Further, since the shape and size of the light source are the same, the same machine and jig can be used for manufacturing and assembling, and only one kind of packing is required, which is advantageous in terms of manufacturing, assembling and packing. .

According to the second aspect of the present invention, since the diffusion sheet, the halftone dots, and the reflection sheet are provided, the light incident on the light guide plate is diffused and emitted, and the luminance can be made uniform. it can.

According to the third aspect of the present invention, since the auxiliary reflection sheet is provided on the end surface of the light guide plate on which the light source is not disposed, the luminance is prevented from attenuating in a portion far from the light source, and the luminance is made uniform. Can be planned.

According to the fourth aspect of the present invention, since the three primary colors are generated from the phosphors of the respective cold cathode tubes, the color film on the light source side provided for color development can be eliminated.
The number of parts can be reduced.

[Brief description of the drawings]

FIG. 1 is a plan view showing a color liquid crystal display device of the present invention.

FIG. 2 is a sectional view taken along line SA-SA shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight 3 Case 4 Light guide plate 5 Reflector 5a Extension part 6, 7, 8 Light source 9 Diffusion sheet 10 Halftone dot 11 Reflection sheet 12 Auxiliary reflection sheet 13, 14, 15 Inclined surface 17 Opening 18 Edge A Thickness direction W width

Claims (4)

[Claims] 1. A reflecting mirror having a cross-sectional shape with an opening on the light guide plate side is provided along two or three surfaces adjacent to each other among four end surfaces around one light guide plate. Independent L-shaped or U-shaped light sources of three primary colors that sequentially emit pulses in a periodic manner are arranged, and most of the light guide plate other than the end face is located inside the opening of the case, and the end face of the light guide plate and the light source are disposed. A backlight for a color liquid crystal display device, which is covered by an edge around an opening, wherein two or three adjacent surfaces of the light guide plate have a 45 ° inclined surface whose front surface is inclined inward, The same L-shaped or U-shaped three light sources are arranged along the thickness direction of the light guide plate in the reflecting mirror, with the reflecting mirror having a cross-sectional shape opened to the back end near the inclined surface. And the reflector has an extension to cover the inclined surface. Backlight for a color liquid crystal display device. 2. The backlight for a color liquid crystal display device according to claim 1, wherein a diffusion sheet is provided on the front surface of the light guide plate, and a reflection sheet is provided on the back surface via halftone printing. Backlight for color liquid crystal display. 3. A backlight for a color liquid crystal display device according to claim 1, wherein an auxiliary reflection sheet is provided on an end face of the light guide plate on which the light source is not arranged. For backlight. 4. The backlight for a color liquid crystal display device according to claim 1, wherein a light source is a cold cathode tube and color light is emitted from each phosphor. Backlight for a color liquid crystal display device.