JPH11305679A - Backlight for color liquid-crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the width of the edge of a case, to make three light sources equal to each other in size, and to display a virtual image in an undistorted state. SOLUTION: In this backlight 2, a reflection mirror 5 of a cross-sectional form open on the side of a light guide plate 4 is arranged along peripheral edge faces 4 of a sheet of the light guide plate 4, independent light sources 6, 7, 8 of three primary colors emitting pulses sequentially and periodically are arranged in the reflection mirror 5, the end faces of the light guide plate 4 and the light sources 6, 7, 8 are covered by the edge 18 of the periphery of an opening 17, the end face 4b of the light guide plate 4 is formed so as to be right-angled to a surface 4a of the light guide plate 4, the reflection mirror 5 is an integration of a general part 20 arranged along the thickness direction of the light guide plate 4 and a reflecting plane part 21 inclined inside by 45 degrees opposed to the end faces 4b of the light guide plate 4, and an L-shaped or U-shaped three light sources are arranged along with the thickness direction of the light guide plate 4 from the opening 22 of the general part 20 of the reflection mirror 5 toward a back side.

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. In addition, since the size of the three light sources is different, it is not possible to use a common light source driving inverter, and it is necessary to change each light source, which is disadvantageous in terms of mass productivity of the inverter.

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. The width of the edge of the case can be reduced, the three light sources can be made the same size, and the virtual image is not distorted. An object of the present invention is to provide a backlight for a color liquid crystal display device capable of displaying in a state.

[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 surfaces adjacent to each other of the light guide plate are formed so as to be perpendicular to the surface of the light guide plate; The reflecting mirror comprises a general portion arranged along the thickness direction of the light guide plate, and a 45 ° inclined reflecting surface portion inclined inward facing two or three surfaces of the light guide plate. One end of the opening of the general part of the reflecting mirror is The three L-shaped or U-shaped light sources are disposed at positions substantially facing the rear surface end of the light guide plate and the remaining openings are disposed at positions facing the reflection surface at an angle of 45 °. Is arranged along the thickness direction of the light guide plate from the opening of the general portion of the reflecting mirror toward the back side.

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, since the reflecting surface of the reflecting mirror arranged at the right-angled end surface of the light guide plate is inclined at 45 °, light is surely guided into the light guide plate. And the virtual image is not distorted. 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.

The light guide plate 4 may be a transparent resin plate or a molded product whose six surfaces are smooth and transparent surfaces. As the transparent resin, an acrylic plate, a polyester plate, a polyvinyl chloride plate and the like are preferable. End surface (light incident surface) 4 of light guide plate 4
The cross-sectional area (ie, thickness) of b is an important factor for effectively introducing light from the light sources 6, 7, 8;
A large amount of light can enter the light guide plate 4, but if too thick, it leads to light loss. Backlight 2 of this embodiment
Since only one light guide plate 4 suffices, the structure is simple, which is advantageous in reducing the size and thickness of the device.

Two or three adjacent surfaces around the light guide plate 4, that is, the light incident surface 4 b is formed so as to be perpendicular to the surface 4 a of the light guide plate 4.

The reflecting mirror 5 is inclined inward in opposition to the light guide surface 4b of the light guide plate 5 and a general portion 20 having a U-shaped cross section which is arranged along the thickness direction of the light guide plate 4. 45 °
And the inclined reflecting surface portion 21 are integrally 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.

One end 22a of the opening 22 of the general portion 20 of the reflecting mirror 5 is disposed at a position substantially opposite to the end of the back surface 4c of the light guide plate 4, and the remaining opening 22 is formed by the reflecting surface 2
1 at a 45 ° angle.

The three L-shaped or U-shaped light sources 6, 7 and 8 extend from the opening 22 of the general portion 20 of the reflecting mirror 5 to the back side, that is, in the thickness direction of the light guide plate 4 (see FIG. A in 2
Direction).

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.

The halftone dots 10 are printed on the back surface of the light guide plate 4. 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 of a white high-reflectance material, on which a metal film such as aluminum or silver is adhered by vapor deposition or the like. A metal tape such as aluminum or silver may be adhered to the side surface.

Attached to the end face 16 of the light guide plate 4 where the reflecting mirror 5 is not disposed is an auxiliary reflecting sheet 12, and by providing the auxiliary reflecting sheet 12, the light sources 6, 7,
The luminance can be made uniform by preventing the luminance from decay in a portion far from the position 8.

The diffusion sheet 9 is a roughened surface in which the surface of the sheet is roughened in a satin pattern, 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 has the ends of the liquid crystal panel 1 and the light guide plate 4, the light source 6, and the like.
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 red (R) light source 6 has a duty set to １ ／ to avoid simultaneous lighting with other colors (mixed colors). Next, the green (G) light source 7 and the blue (B) light source 8
The pulse rises in a form shifted by / 3 period.

The color light emitted from the light sources 6, 7, 8 is emitted from the opening 22 of the reflecting mirror 5, reflected by the reflecting surface 21, and is incident on the light guide plate 4 from the light incident surface 4b of the light guide plate 4.
The light that has entered the light guide plate 4 is introduced into the light guide plate 4 along the plane direction of the light guide plate 4. 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 toward the liquid crystal panel 1. Part of the light that hit the halftone dot 10 is
After being reflected in the light guide plate 4, the light strikes the reflection sheet 11 and is 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. The light passing through the diffusion sheet 9 is
Since the light becomes scattered light due to minute irregularities and satin finish on the surface, 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 is opened at the same timing as the emitted light. 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 red (R) and green (G), yellow which is a mixed color of red (R) and green (G) is displayed. If three colors of green (G) and blue (B) are mixed, white is displayed. This is an afterimage color mixture 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,
Even if the light sources 6, 7, 8 are arranged in the thickness direction of the light guide plate 4 in this way, the reflection surface portion 21 of the reflection mirror 5 disposed on the light incident surface 4b, which is the right-angled end surface of the light guide plate 4, becomes 45 °. Since the light is inclined, the light can be surely guided into the light guide plate 4 and the virtual image is not distorted. Further, the light incident surface 4 of the light guide plate 4
Since b is a right-angled end face, the light guide plate 4 can be simply cut out, so that the cost can be significantly reduced.

Further, since all of the light sources 6, 7, 8 have the same shape, the setting of the three tube bending devices in the mass production of the light sources 6, 7, 8 can be made common, 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
Advantageously, the shapes of the automatic assembling apparatus, assembling jig, and packaging can be shared.

Further, since the light sources 6, 7, and 8 are all the same size, the length of each of the light sources 6, 7, and 8 can be shorter than that of the conventional one located at the outermost position. The spacing between the tubes was increased to avoid discharge between them, and the outer tubes were very long.) 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 a corresponding increase in cost. According to the present invention, there is no need to make the pipe longer than necessary, so that the conventional problem 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 embodiment, the light guide plate 4 has four end surfaces, the three end surfaces of which 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.

[0042]

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 way, since the reflecting surface of the reflecting mirror disposed on the right-angled end surface of the light guide plate is inclined at 45 °,
Light can be reliably guided into the light guide plate, and the virtual image does not distort. 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 dot, 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 face of the light guide plate on which the light source is not disposed, the attenuation of the luminance at a portion far from the light source is prevented, 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.

DESCRIPTION OF SYMBOLS 1 Liquid crystal panel 2 Backlight 3 Case 4 Light guide plate 4a Surface of light guide plate 4b Light incident surface which is end face of light guide plate 4c Back surface of light guide plate 5 Reflecting mirror 6, 7, 8 Light source 9 Diffusion sheet 10 Net Point 11 Reflection sheet 12 Auxiliary reflection sheet 17 Opening 18 Edge 20 General part of reflecting mirror 21 Reflecting surface of reflecting mirror 22 Opening of reflecting mirror 22a One end of opening A Thickness direction W width

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Tsuchiya Kimura 80 Itado, Isehara-shi, Kanagawa Prefecture Ichihara Industrial Co., Ltd.

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 are formed so as to be perpendicular to the surface of the light guide plate. The reflector has a general portion disposed along the thickness direction of the light guide plate, and a 45 ° inclined shape inwardly facing two or three surfaces of the light guide plate. An opening in a general part of the reflecting mirror; The one end is disposed at a position substantially facing the rear end of the light guide plate, and the remaining opening is disposed at a position facing the reflection surface at an angle of 45 °, and the L-shaped or U-shaped is formed. A backlight for a color liquid crystal display device, wherein the three light sources are arranged along the thickness direction of the light guide plate from the opening of the general part of the reflector to the back side. 2. The backlight for a color liquid crystal display device according to claim 1, wherein a diffusion sheet is provided on a 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 devices. 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 where no light source is arranged. Back light for equipment. 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.