JPH06273760A - Backlight unit - Google Patents

Abstract

PURPOSE:To provide a backlight unit capable of performing back illumination more uniformly by preventing the warp of a light diffusing part. CONSTITUTION:This unit is provided with a light source 14, a reflection part 13 reflecting light from the light source, and the light diffusing parts 11, 34 and 35 arranged on the front side of the light source and diffusing the light directly made incident from the light source or the light guided after reflecting the light from the light source by the reflection part. Illumination for an equipment arranged on the front side is performed through the light diffusing part in the unit. A light reflection pattern is formed on the light diffusing parts 11, 34 and 35 corresponding to a distance to the light source 14, and the light diffusing plate is supported so that a relative position between the light source and the light diffusing parts may not be deviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit for illuminating, for example, a liquid crystal display unit incorporated in a liquid crystal display device from the rear.

[0002]

2. Description of the Related Art Conventionally, such a backlight unit is constructed, for example, as shown in FIG. Figure 5
FIG. 1 is a cross-sectional view showing a schematic structure of a conventional backlight unit, in which the backlight unit 1 is
In a case 2 formed to be relatively thin, a reflection plate 3 and a fluorescent tube 4 which is a light source arranged on the front side of the reflection plate 3 are housed. A circuit board (not shown) for driving the fluorescent tube 4 is provided.

Further, two light diffusion plates 6 and 7 and a diffusion sheet 8 are provided on the front side (upper side in the figure) of the fluorescent tube 4.
A light diffusing member such as the above is disposed, and light from the fluorescent tube 4 or light reflected by the reflective plate 3 is incident from the fluorescent tube 4 toward the reflective plate 3. As a result, the two light diffusion plates 6 and 7
The diffusion sheet 8 diffuses these lights into uniform planar illumination light, and irradiates it on the front side (upper side in the figure).

Thus, the liquid crystal display unit (not shown) arranged on the front side (upper side in the drawing) of the backlight unit 1 is illuminated from behind to raise the display and enhance the visibility. Has become.

Here, when the liquid crystal display unit or the like is back-illuminated as described above, it is necessary to uniformly illuminate the entire display surface of the liquid crystal display unit with illumination light.
That is, if there is unevenness in the illumination light, the brightness of the liquid crystal screen is dispersed, resulting in uneven display on the screen, making it difficult to visually recognize the display content.

Further, in the case of the backlight unit 1, even if it is attempted to diffuse the light from the fluorescent tube 4 only by the light diffusing plates 6 and 7 and the diffusing sheet 8, the specific region such as the light diffusing plate and the fluorescent tube 4 are provided. Due to the difference in the distance between and, uneven brightness occurs.

Therefore, as shown in FIG. 6, the surface of the light diffusion plate 6 facing the fluorescent tube 4 is provided with a masking 9 such as white ink on the surface 6a by printing or the like.

At this time, the white ink is printed, for example, in a dot shape, and the closer to the fluorescent tube 4, the more dots are formed. As a result, in the light diffusion plate 6, the fluorescent tube 4 is
Since the number of white ink dots is larger and the density thereof is higher at a position closer to, the light from the light source 4 is reflected by that much and it becomes difficult to transmit the light. As a result, the light diffusion plate 6 as a whole is provided with less unevenness in brightness and more uniform back illumination is performed.

[0009]

The light diffusing plates 6 and 7 and the sheet 8 are, as shown in FIG.
Only the peripheral edge portion is held only by the outer frame of the case 2. For this reason, when these light diffusion plates 6 and 7 warp, this cannot be regulated.

Therefore, when the light diffusing plates 6 and 7 are warped, the masking pattern 9 for reflection shown in FIG.
Then, there is a problem that the positional relationship with the fluorescent tube 4 is distorted, and it becomes difficult to perform uniform back lighting in the initially designed state. In particular, when the display area S of the display screen of the liquid crystal display device or the like to be back-illuminated by the backlight unit 1 becomes relatively large, the areas of the light diffusion plates 6 and 7 also become large and warpage occurs. At this time, the positional relationship between the reflection masking pattern 9 and the fluorescent tube 4 is greatly deviated.

In view of the above points, it is an object of the present invention to provide a backlight unit capable of preventing the light diffusing portion from being warped and performing back illumination more uniformly.

[0012]

According to the present invention, the above object is to provide a light source, a reflector for reflecting light from the light source,
The light source is disposed on the front surface side of the light source, and has a light diffusing portion that diffuses the light that is directly incident from the light source or the light from the light source that is reflected by the reflecting portion and guided.
In a backlight unit for illuminating a device arranged on the front side through the light diffusing section, a light reflecting pattern is formed in the light diffusing section in correspondence with the distance to the light source, and This is achieved by a backlight unit that supports the light diffusing plate so that the relative position of the light diffusing portion is not displaced.

Preferably, the backlight unit of the present invention may be configured so that it serves as both a fixing member for the light source and a supporting member for the light diffusing section.

Further, preferably, in the backlight unit of the present invention, the light diffusing section includes two light diffusing plates arranged on the front side of the light source, and the light diffusing plates are positioned and supported. .

Further, instead of the two light diffusing plates, one thick light diffusing plate may be arranged.

[0016]

According to the above construction, the light diffusing portion of the backlight unit of the present invention is constructed so as not to shift the positional relationship with the light source. Therefore, in the light diffusion portion, the reflection pattern formed according to the distance to the light source, between the light source,
It is prevented that the correspondence that should be maintained according to the mutual distance is out of order.

[0017]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The examples described below are
Since it is a preferred specific example of the present invention, various technically preferable limitations are attached, but the scope of the present invention is, unless otherwise stated to limit the present invention, in the following description.
It is not limited to these modes.

FIG. 1 is an exploded perspective view for explaining the overall configuration of the backlight unit of this embodiment. First, the overall configuration of the backlight unit will be described with reference to this figure. In the figure, the backlight unit 10
Is a reflection plate 13 as a reflection portion housed in a relatively thin case 12 whose front surface (upper surface in the drawing) is open.
And a U-shaped fluorescent tube 14 as a light source arranged on the front side of the reflection plate 13, and the U-shaped fluorescent tube 1
Radiating rubbers 31, 31 are attached to the fixed portions at both ends of 4.

The case 12 is made of, for example, thermoplastic resin Iupylene, lexan, etc.
A circuit board 15 for driving the light source 14 is provided, and the circuit board 15 is covered with a cover 32.

A light diffusing plate 11 as a light diffusing portion is fitted and fixed in the open portion of the case 12. As a result, the light diffusion plate 11 covers the front side of the light source 14. Although one light diffusing plate 11 is used in FIG. 1, as shown in FIG. 2, another light diffusing plate 35 may be attached to the front side to provide two or more light diffusing plates. Well, and as will be described later in detail, the mounting position is supported so as not to shift.

The reflection plate 13 is constructed by using, for example, a metal plate such as white resin or aluminum, or a white plate coated on the metal plate. This reflector 13
In this embodiment, as shown in FIG.
It is arranged behind (lower side in the figure) the fluorescent tube 14 formed in a letter shape, and has a shape that reflects the light from this fluorescent tube 14 to the front side (upper side in the figure). A shield plate 33, preferably made of metal, is arranged on the back side of the reflection plate 13 or the case 12.

The light diffusing plate 11 is preferably an acrylic plate or opalescent plate, for example, and diffuses the light incident from the back (back side) thereof and irradiates it to the front side. A diffusion sheet 34, which is formed by, for example, subjecting a polycarbonate to an embossing process, is attached to the front surface side (upper surface side in the drawing) of the light diffusion plate 11. Thereby, the light from the light diffusion plate 11 can be condensed and the brightness of the back illumination can be increased.

Further, in this embodiment, similarly to the conventional backlight unit described in FIG. 6, the surface of the light diffusing plate 11 that faces the fluorescent tube 14, that is, the back surface side in the figure, is, for example, A dot-shaped reflection pattern of white ink is formed.

Specifically, this reflection pattern is formed by forming dots 17 of white ink along the shape of the fluorescent tube 14 which is a light source, and the density of the dot is closer to the fluorescent tube 14 which is a light source. Is high.

As a result, when the light emitted from each fluorescent tube 14 reaches the light diffusing plate 11 directly or the light emitted from each fluorescent tube 14 is reflected by the reflecting plate 13, the light diffusing plate is formed. When the light is guided to 11, the amount of light increases toward the light source.
The amount of light reflected by and transmitted through the light diffusion plate 11 is made uniform.

Further, in this embodiment, the light diffusing plate 11 is used.
A support portion for the light diffusing plate 11 is provided so that the mounting position of the light diffusing plate 11 does not shift even when the warp or the like occurs. FIG. 2 and FIG. 3 show one aspect of the specific configuration thereof. In the drawings, the support portion 41 is a boss having a certain elasticity provided so as to stand upright from the reflector 13, for example. .

The supporting portions 41, 41 are preferably provided in the vicinity of the fluorescent tube 14 and two on both sides of the fluorescent tube 14,
As shown in the drawing, holding claws 42, 42 that surround a part of the outer circumference of the fluorescent tube 14 from above are provided in the middle thereof. Further, the tip of the support portion 41 is configured to penetrate through a through hole 11a formed in the light diffusion plate 11 in advance. The tip portion 43 penetrating above the light diffusing plate 11 has a hemispherical shape with an R shape on the tip side so that it can be easily inserted into the through hole 11a. Further, the lower surface of the tip portion 43 is a flat contact surface so as not to come into contact with the peripheral portion of the through hole 11a and come out.

As a result, the supporting portion 43 can hold the fluorescent tube 14 by the holding claws 42 so that the fluorescent tube 14 does not come off, and the light diffusing plate 11 moves laterally or vertically in the figure. To prevent it from slipping, it is necessary to regulate the mounting. Therefore, the reflection pattern (not shown) previously formed by the white ink dots or the like on the light diffusion plate 11 and the fluorescent tube 14 as the light source can maintain the positional correspondence as originally designed.

Therefore, the light diffusing plate 11 can diffuse the light entering from the fluorescent tube 14 and the light entering from the reflecting plate 13 as originally designed, and it is possible to prevent variations in luminance among products, Uniform back lighting can be performed. Further, since the light diffusing plate 11 is less likely to warp as compared with the conventional one because it is held by the supporting portion 41, it is not required that the light diffusing plate has high rigidity, and as a result, the light diffusing plate having a thin plate thickness is used. Therefore, the backlight unit can be easily reduced in weight and thickness.

Moreover, since the through hole 11a formed in the light diffusing plate 11 is formed in the vicinity of the fluorescent tube 14 in the example shown in the figure, this area is originally a dot forming the reflection pattern. High density. Therefore, when viewed from the front side of the backlight unit 10, the through hole 1
The 1a, the support portion 41, and the tip portion 43 thereof are hardly visible due to being reflected in the reflection pattern, and the uniformity of the back illumination is hardly impaired.

FIG. 4 shows another example of the support portion 41. The support portion 41 is a column portion 1 on which the diffusion plate 11 is placed.
42 and a rib piece 143 having an engaging claw on the tip side 144. Even with such a supporting portion 142, the height of the light diffusing plate 11 is kept constant while the light diffusing plate 1 is held.
1 can be supported so as not to be displaced.

As described above, according to this embodiment, since the light diffusing plate 11 is supported by the supporting portions 41 and 141, warpage does not occur, and in particular, a liquid crystal display device having a large display screen is used as a back light. Even in the case of a backlight unit that illuminates, it is possible to prevent the light diffusion portion from warping.
Therefore, the light diffusing unit can diffuse the light entering from the fluorescent tube 14 and the light entering from the reflecting plate 13 as originally designed, and it is possible to prevent the brightness from varying for each product and to achieve uniform back lighting. Can be done.

The present invention is not limited to the above embodiment. Although a fluorescent tube is used as the light source in the illustrated embodiment, it goes without saying that the light may be diffused by using another light source, for example, a light source such as an LED or a miniature bulb. Further, for example, in the above-described embodiment, the structure for supporting only the light diffusion plate 11 is shown, but the light diffusion plate 35 and the diffusion sheet 34 can be supported by adding a similar support structure.

In addition to the position shown in the figure, the support portion 41 is
The light diffusing plate or the diffusing sheet can be provided at a predetermined position to be fixed, and the supporting portion 41 does not necessarily have to be formed integrally with the reflecting plate 13. For example, it may be configured to stand up from the case 12 and penetrate the reflection plate 13 and the light diffusion plate 11.

Furthermore, the shape of the tip of the support portion is not limited to the illustrated example, and various shapes can be adopted. That is,
Any shape may be used as long as it can hold down the diffusion portion such as the light diffusion plate 11, and for example, the boss-shaped support portion made of resin is passed through the through hole formed in the diffusion portion, and the tip side is heated to be enlarged. You may do it.

[0036]

As described above, according to the present invention, it is possible to provide a backlight unit capable of preventing the light diffusion portion from warping and performing the back illumination more uniformly.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an overall configuration of a preferred embodiment of a backlight unit of the present invention.

FIG. 2 is a schematic cross-sectional view of the backlight unit of FIG.

3 is an enlarged view showing an example of a main part of the backlight unit shown in FIG.

FIG. 4 is an enlarged view showing another example of the main part of the backlight unit of FIG.

FIG. 5 is a schematic sectional view showing an example of a conventional backlight unit.

6 is an enlarged cross-sectional view of the backlight unit of FIG.

[Explanation of symbols]

 10 Backlight Unit 11,35 Light Diffusing Plate 12 Case 13 Reflecting Plate 14 Fluorescent Tube 15 Circuit Board 41.141 Supporting Part

Claims (4)

[Claims] 1. A light source, a reflector for reflecting the light from the light source, and a light source, which is disposed on the front side of the light source and which is directly incident from the light source or the light from the light source is reflected by the reflector. And a light diffusing section that diffuses the guided light.
In a backlight unit for illuminating a device arranged on the front side through the light diffusing section, a light reflecting pattern is formed in the light diffusing section in correspondence with the distance to the light source, and A backlight unit, characterized in that a light diffusing plate is supported so that the relative position of the light diffusing portion is not displaced. 2. The backlight unit according to claim 1, wherein the light source fixing member also serves as a supporting member for the light diffusion portion. 3. The light diffusing section includes two light diffusing plates arranged on the front side of the light source, and the light diffusing plates are positioned and supported. Backlight unit. 4. The backlight unit according to claim 3, wherein a single thick light diffusing plate is arranged in place of the two light diffusing plates. .