JP2002090736A - Backlight for flanar display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart sufficient strength to the frame structure of a direct backlight used for a large-sized liquid crystal display device or the like without increasing a manufacturing cost practically even in the case of a large-sized narrow frame, and to prevent the breakage of a tubular light source (fluorescent lamp) 3 due to excessive deflection caused by a external mechanical impact to a backlight 10. SOLUTION: A metal base frame 1 constituting a rectangular exit opening 15 is provided with a flange-like overhang 11 overhung from an inner edge along the exit opening 15 to a rear side. A deformation regulating member 6 with a reverse U shape consisting of transparent rubber is disposed at a nearly central part in the longitudinal direction of each tubular light source 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight used for a flat panel display such as a liquid crystal display. in particular,
The present invention relates to a direct-type backlight used for a large-sized liquid crystal display device having a diagonal size exceeding 20 inches.

[0002]

2. Description of the Related Art Recently, a large liquid crystal display device having a diagonal size of a display screen exceeding 20 inches has been developed and used as a display device of a workstation, a CAD device or other desktop personal computers, or a large television or video image reproducing device. As a device, it is about to spread rapidly. In such a large liquid crystal display device, a cathode ray tube (C
(RT), a luminance that is not inferior to that of (RT) is required.

[0003] For this reason, the required brightness may not be achieved with an edge light type backlight which is mainly used in a liquid crystal display device having a diagonal dimension of 20 inches or less. Further, the luminance may be lower at the center of the display screen than at the ends, and the luminance distribution may be non-uniform. An edge light type backlight is one in which a light source such as a cold cathode fluorescent tube is arranged on an end face of a light guide plate made of an acrylic plate or the like, and a light source cannot be arranged except for a portion along the end face of the light guide plate. It is.

On the other hand, a large-sized liquid crystal display device having a diagonal dimension of more than 20 inches is used by being placed on a desk or the like, and is not required to have a high degree of thinness and lightness required for a notebook personal computer.

Therefore, in designing such a large-sized liquid crystal display device, a direct-type backlight is often adopted. As illustrated in FIG. 2, a direct-type backlight includes a plurality of tubular light sources 3 (fluorescent tubes) arranged in parallel at a position corresponding to immediately below (a back side of) a display panel without using a light guide plate. 3 is emitted directly to the back side of the display panel. A reflecting plate 5 is arranged on the back side of the plurality of light sources, and a diffusing plate 4 for dispersing the direction of the light flux from the light sources to realize uniform light emission is arranged on the emission surface. In addition, the plurality of tubular light sources 3 are usually held from the metal frame 1 via the support members 2 and 25 that grasp both ends thereof.

In a direct type backlight used for a large liquid crystal display device, the frame structure needs to have a high strength. As the area of the emission surface increases, the opening 15 of the frame corresponding to the emission surface also increases accordingly, and the distance between the opposed beam portions 14 (the span between the beam portions).
Because it becomes bigger. In order to ensure that the frame has sufficient strength even when the size is increased, it is necessary to improve the strength of each beam portion 14 forming the exit aperture.

[0007]

However, if a separate reinforcing member is added or the thickness of each beam portion is increased, the cost of the material and processing of the frame increases. Further, the weight of the backlight is increased, which is not preferable.

Further, when the width of each beam portion is increased, there is a problem that the width of the frame portion of the backlight, that is, the width of the peripheral non-light emitting region where the backlight is not emitted is increased. .

[0009] On the other hand, when the direct backlight becomes large, the tubular light source usually has a longer length. However, since the tubular light source is generally held only by the electrode portions at both ends, the tubular light source may be damaged by excessive bending deformation when the backlight receives a mechanical shock from the outside.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a direct-type back which can impart sufficient strength to a frame structure without increasing the manufacturing cost, even if the frame is large and narrow. It provides light. It is another object of the present invention to provide a direct-type backlight capable of preventing a long tubular light source from being damaged by excessive bending deformation even when it receives a mechanical shock.

[0011]

According to a first aspect of the present invention, there is provided a backlight including a light source group comprising a plurality of tubular light sources arranged in parallel, and a light source support member for supporting these tubular light sources at electrode portions at both ends thereof. A reflector disposed on the back side of the light source group to guide light from the light source group to an emission surface; and a diffusion plate arranged on the emission surface for diffusing and emitting light from the light source group. And a metal frame that holds them, wherein the metal frame includes a window frame-shaped portion for forming one emission opening corresponding to the emission surface. And a flange-like overhanging portion projecting from the edge to the back surface side.

According to the above configuration, a sufficient strength can be imparted to the frame structure without increasing the manufacturing cost and the width of the frame region.

According to a second aspect of the present invention, the metal frame is obtained by sheet metal processing of a metal plate, and the flange-shaped overhang is formed by drawing.

With such a configuration, a frame having a sufficient strength can be easily obtained.

According to a third aspect of the present invention, in the backlight, the reflection plate is connected to a side surface of the light source group and inclined to an outside toward the emission surface and to an edge of the inclination plate portion. The metal frame includes a window frame-like portion and a mounting flange portion that is fixed by being overlapped with the metal frame, wherein the flange-like overhanging portion extends along the inclination of the inclined plate portion.

With such a configuration, even when the flange-shaped overhanging portion is applied to the light emitting area on the light emitting surface, the light emitting characteristics are not impaired.

According to a fourth aspect of the present invention, in the backlight, the light emitting portion extending between the electrode portions at both ends of the tubular light source is provided with a deformation restricting member for restricting a positional shift due to deformation of the light emitting portion. Features.

With this configuration, even when the backlight receives a mechanical shock from the outside, it is possible to prevent the tubular light source from being damaged due to excessive bending deformation.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Flat display devices such as liquid crystal display devices have been used as image display devices for televisions, various computers, car navigation systems and the like. The liquid crystal display device includes a liquid crystal panel having a liquid crystal layer held between a pair of transparent substrates, and a liquid crystal panel arranged on a back surface (a surface opposite to an image display surface) of the liquid crystal panel to supply light to the liquid crystal panel. And a guiding backlight (surface light source device on the back side).

The backlight can be roughly classified into a direct type in which a plurality of tubular light sources such as fluorescent lamps are arranged in parallel under a display panel (back side), and a tubular light source arranged on an end face of a light guide plate. There is a side light type (edge light type) in which light is emitted from the upper surface (main surface) of the light guide plate.

The backlight of the early flat panel display was of a direct type, but the edge light type is now the mainstream. This is because, in order to further reduce the thickness and size of the flat display device, it is necessary to achieve the reduction in the thickness of the surface light source device.

However, recently, large-size stationary LCD monitors having a diagonal size exceeding 20 inches have been manufactured and sold, and as described in the prior art, in order to easily achieve high luminance, the direct-type LCD monitor has to be used again. Was used. That is, a direct-type backlight is employed in a large transmissive display panel having a diagonal width of more than 20 inches, which has recently been manufactured and marketed.

However, depending on the conditions of use of the flat panel display, such as those used under outdoor sunshine, it is considered that a smaller type may be suitable for the direct type. Further, it is considered that the possibility of use in a smaller flat panel display device may arise due to technological innovation such as a tubular light source.

An embodiment of the present invention will be described with reference to FIG. FIG. 1 is an exploded cross-sectional perspective view schematically illustrating the entire configuration of a direct-type backlight according to an embodiment.

The backlight 10 is used for a transmissive liquid crystal panel 20 having a diagonal size of an effective display area of 21 inches, and has an equivalent effective light emitting area. In the following description, for convenience, the side of the emission surface of the backlight, that is, the side on which a display panel such as a liquid crystal panel is arranged, will be described as an upper side.

The backlight 10 includes a plurality of tubular light sources 3 arranged in parallel, and a light source supporting member 2 for supporting these together.
5, a metal reflecting plate (reflector) 5 combined with the light source supporting member 25 from below, a diffusion plate 4 disposed above, and a metal basic frame (base frame) 1 holding these components. Become.

The basic frame 1 is obtained by processing a metal plate into a sheet metal. The basic frame 1 has a window frame-like portion 12 formed by combining four elongated beam-like horizontal plates 14 into a rectangular window frame.
And four side walls 13 projecting vertically downward from the outer edge of each beam-shaped horizontal plate 14. A rectangular opening 15 is formed inside the window frame portion 12, and the light of the tubular light source 3 passes through the opening 15 and is emitted upward through the diffusion plate 4 placed on the window frame portion 12. Is done. Each side wall 13 is in the shape of a relatively wide rectangular plate, and is omitted at four corners of the window frame-shaped portion 12. In the illustrated example, the vertical dimension of each side wall 13 is set to be substantially the same as or slightly larger than the thickness dimension of the reflector 5 described later.

From the inner edge of the window frame portion 12 along the opening 15, a flange-like protrusion 11 projects over the entire periphery of the opening 15 toward the back side, that is, toward the tubular light source 3. The angle between the overhang portion 11 and the window frame-shaped portion 12 is larger than 90 degrees, and the inclined plate portion 5 of the reflection plate 5 described later is used.
It is set so as to coincide with the inclination of 1. The overhang 11 remarkably increases the strength of the basic frame 1 with a simple configuration. This flange-shaped overhang 1
1 can be easily manufactured by drawing when a sheet metal is processed from a metal plate.

The reflection plate 5 is obtained by bending a metal plate, and is formed on the horizontal bottom plate portion 53 disposed on the back side of the tubular light source 3 and on both ends in the parallel direction of the tubular light source 3. An inclined plate portion 51 and a mounting flange portion 52 protruding further outward from the upper end of the inclined plate portion 51 are provided.

The mounting flange portion 52 is fixed to the window frame-like portion 12 of the basic frame 1 by being overlapped from the back side. In such a fixed state, the basic frame 1
Of the reflecting plate 5 so as to be almost in close contact with the upper end of the inclined plate portion 51 of the reflecting plate 5.

As described above, when the reflecting plate 5 is combined with the basic frame 1 to form the frame structure of the backlight 10, the flange-like overhanging portion 11 plays a role in remarkably increasing the resistance to bending and torsional stress on the frame structure. I have. Moreover, the flange-like overhang portion 1
1 is pressed against the inclined plate 51 of the reflection plate 5, so that the use efficiency of light from the tubular light source 3 is not reduced, and the display characteristics of the display panel are not adversely affected.

On the other hand, an inverted U-shaped stopper 6 made of transparent rubber is arranged at a substantially central portion in the longitudinal direction of each tubular light source 3. The stoppers 6 have their lower ends 61 fixed to the bottom wall of the reflector 5, and are arranged so as to form a predetermined clearance between the top and the left and right ends of the light emitting surface of the tubular light source 3. In the illustrated example, the stoppers 6 arranged for each of the tubular light sources 3 are continuous with each other in the parallel direction of the tubular light sources 3.

The stopper 6 is formed, for example, by bending one ribbon tape-shaped transparent rubber and heat setting the same, and then attaching the same to the horizontal bottom plate portion 53 of the reflection plate 5 on which the tubular light source 3 is disposed by using an adhesive. Can be provided. As the material of the stopper 6, for example, a material having high transparency can be selected from silicon rubber and used.

The stopper 6 prevents the light emitting portion of the tubular light source made of glass from bending beyond a certain limit, thereby preventing the light emitting portion from being damaged.

Specific examples of dimensions and the like are as follows.

The tubular light source 3 is a cold cathode tube having a diameter of 3 mm. In a state where twelve tubular light sources 3 are arranged in parallel and cap-shaped members 2 are fitted at both ends of each tubular light source 3,
The light source supporting member 25 made of plastic is assembled and supported. The light source support member 25 is joined to the reflection plate 5 made of an aluminum plate having a thickness of 1 mm by screwing. The metal basic frame 1 is also made of a 1 mm thick aluminum plate,
The diffusion plate 4 mounted thereon is made of an acrylic plate having a thickness of 2 mm. A diffusion sheet made of polycarbonate (PC) having a thickness of 0.2 mm is stacked on the diffusion plate 4. Here, the overhang dimension of the flange-like overhang portion 11 is, for example, 2 to 3 mm.

With the configuration of the above embodiment, the strength of the frame structure of the backlight can be significantly increased.
Moreover, the increase in manufacturing cost and weight is small.

Further, with the configuration of the above embodiment, the resistance of the tubular light source to damage due to mechanical impact can be significantly increased.

In the above embodiment, the flange-shaped overhang portion 11 has been described as having the same inclination angle as the inclined plate 51 of the reflecting plate 5 and being in close contact with the upper surface of the inclined plate 51. However, the inclined angles are not necessarily the same. There is no need to
There is no need to adhere to each other. Flange overhang 1
1 and the tip of the overhang portion 11 and the diffusion plate 4
By setting the distance between them to an appropriate range, an appropriate interval may be formed between the diffusion plate 4. If set in this way, the flange-shaped overhang 11
Can be prevented from appearing in the display image of the display panel even when the light source is located within the emission area of the backlight 10 and within the effective display area placed on the backlight. .

In the above embodiment, a description has been given assuming that one stopper is provided for each tubular light source, but several stoppers may be provided if necessary. Further, the stopper may be provided by a lip portion made of plastic or metal instead of a rubber material. Further, the clearance can be provided without providing a clearance between the stopper and the light emitting surface of the tubular light source.

Although the stopper is made of a material that is transparent or has a high light transmittance, the material of the stopper is made of a material that is translucent or has a certain degree of light transmittance. The loss can be made sufficiently small.

[0042]

As described above, in a direct type backlight used for a transmissive liquid crystal display device or the like, even if the frame is large and has a narrow frame, sufficient strength can be imparted to the frame structure without substantially increasing the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is an exploded cross-sectional perspective view schematically illustrating the entire configuration of a direct-type backlight according to an embodiment.

FIG. 2 is an exploded cross-sectional perspective view corresponding to FIG. 1, schematically showing the entire configuration of a direct-type backlight according to a conventional example.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 window frame basic frame (base frame) forming emission opening 10 direct backlight 11 flange-shaped overhang from edge of emission opening 12 window frame portion of basic frame 13 side wall 15 emission opening formed by basic frame 2 cap Shaped Member 25 Light Source Supporting Member 3 Tubular Light Source 35 Electrodes at Both Ends of Tubular Light Source 4 Diffusion Plate 5 Metal Reflection Plate Forming Part of Frame Structure 6 Reverse U-Shaped Stopper Made of Transparent Rubber

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H091 FA14Z FA31Z FA42Z FC14 FD01 FD03 FD11 FD13 LA02 5G435 AA07 AA18 BB12 BB15 EE26 FF03 FF06 GG24 GG26 KK05

Claims (9)

[Claims] 1. A light source group comprising a plurality of tubular light sources arranged in parallel, a light source support member for supporting these tubular light sources at electrode portions at both ends thereof, and a light source supporting member arranged on the back side of the light source group. A reflector that guides light from the light source group to the display panel arrangement side; a diffusion plate that is arranged on the display panel arrangement side to diffuse and emit light from the light source group; and a window that supports these. In a backlight for a flat panel display device comprising a metal frame including a frame portion, the metal frame is directed from an inner edge of a window frame portion for emitting light from the tubular light source to a side of the reflection plate. A backlight for a flat panel display device, comprising a flange-shaped overhang portion. 2. A flat display device according to claim 1, wherein said window frame-like portion is formed of a horizontal plate, and an inclination angle of said flange-like projection with respect to said window frame-like portion is 20 to 80 degrees. For backlight. 3. The backlight for a flat panel display according to claim 1, wherein the metal frame is obtained by sheet metal working of a metal plate, and the flange-shaped overhang is formed by drawing. . 4. The inclined plate portion disposed on a side surface of the light source group and inclined outward toward the display panel arrangement side, the reflector plate being connected to an edge of the inclined plate portion and being provided on the metal frame. A window frame-shaped portion and a mounting flange portion that is fixed by being overlapped with the window frame-shaped portion; The backlight for a flat panel display according to claim 1, wherein 5. The backlight for a flat panel display according to claim 1, wherein the light emitting portion of the tubular light source is provided with a deformation restricting member for restricting a bending deformation of the light emitting portion. 6. A light source group comprising a plurality of tubular light sources arranged in parallel, a light source support member for supporting these tubular light sources at electrode portions at both ends thereof, and a light source supporting member arranged on the back side of the light source group. A reflection plate for guiding light from the light source group to the display panel arrangement side; a diffusion plate arranged on the display panel arrangement side for diffusing and emitting the light from the light source group; A backlight for a flat panel display device, comprising: a light-emitting portion of the tubular light source provided with a flexible deformation restricting member for restricting bending deformation of the light-emitting portion. For backlight. 7. The backlight according to claim 6, wherein the deformation restricting member is made of a light transmissive material. 8. The deformation restricting member, when not deformed,
7. The backlight according to claim 6, wherein the backlight is arranged to have a predetermined clearance with respect to the light emitting unit. 9. The backlight according to claim 6, wherein the deformation restricting member is fixed to the reflection plate.