JPH11223812A - Lighting system and display device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the uniformity of the luminance of the light emission surface of a display member from being lost even in the case of variation in temperature and humidity in in-use environment. SOLUTION: The entire surface of the display member is irradiated uniformly by transmitting the light from a linear light source 1, arranged right below the display member, through a diffusion plate 4 provided with a light homogenizing pattern 2. In this case, support parts 8b form a gap between the diffusion plate 4 and light-diffusing or light-converging sheets 5, 6, and 7 arranged on the light emission surface side of the diffusion plate 4. Consequently, the light emission surface side and light source side of the diffusion plate 4 are brought into direct contact with the outside air, so even if the humidity rises or falls, both the surfaces of the diffusion plate 4 are held in the same moisture absorption state and are free of differences in shrinkage or expansion, so that the diffusion plate 4 will not deform concavely or convexly to the display member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device used for a display device such as a liquid crystal device, and more particularly to an illuminating device for suppressing deformation of a diffusion plate due to a change in humidity due to the environment and a display device using the same. Things.

[0002]

2. Description of the Related Art Conventionally, various transmission type liquid crystal devices having an illumination device have been proposed. These are classified into a so-called direct type in which a light source is disposed immediately below a liquid crystal panel as a display member, and a so-called edge type in which a light source is disposed at an edge portion of the liquid crystal panel.

[0003] The direct lighting device shown in FIG. 4 will be described below. In the figure, reference numeral 1 denotes a fluorescent lamp as a line light source,
Reference numeral 3 denotes a reflecting plate for reflecting light rays backward of the fluorescent lamp 1 forward, and 4 denotes a diffusing plate on which a white mesh-like light uniforming pattern 2 is printed for uniform luminance. The diffusion sheets 5 and 7 are stacked with the prism sheet 6 interposed therebetween.

The diffusion sheets 5 and 7 and the prism sheet 6 laminated on the light exit surface side of the diffusion plate 4 are selected according to the luminance and the viewing angle required by the lighting device.
Some of them have only one sheet, others have a combination with the prism sheet 6, and the stacking order is variously configured.

Further, as a material of the diffusion plate 4, an acrylic resin mixed with a diffusion material is often used. In addition, since the outer dimensions of the diffusion plate 4 shrink or expand depending on the temperature and humidity conditions of the environment in which the liquid crystal device in which the lighting device is incorporated is used, the diffusion plate 4 and a supporting member that supports the diffusion plate 4 are provided. Is provided with a gap.

The outer diameter of the diffusion plate 4 contracts or expands due to changes in the temperature and humidity of the environment. However, the deformation of the outer diameter of the diffusion plate 4 is caused by the light uniform pattern 2.
Does not cause uneven brightness because all the mesh areas are similarly contracted or expanded.

[0007]

However, in the case of the direct lighting device shown in FIG. 4, when the humidity is reduced in an environment in which the lighting device is used, the diffusion plate 4 has a convex shape with respect to the liquid crystal panel surface. When the humidity rises, the diffusion plate 4 is deformed into a concave shape with respect to the liquid crystal panel surface. Diffusing plate 4
When such a deformation occurs, the positional relationship between the light uniform pattern 2 printed on the diffusion plate 4 and the fluorescent lamp 1 is broken, and the brightness uniformity of the lighting device is lost.

That is, when the humidity of the environment rises, the diffusion sheets 5, 7 and the prism sheet 6 are laminated so as to be in close contact with the light emitting surface (front surface) of the diffusion plate 4, so that the surface of the diffusion plate 4 Does not come into direct contact with the outside air containing humidity, but the light source side surface (back surface) of the diffusion plate 4 is in contact with the air layer, so that it comes into contact with the outside air containing moisture.
There is a difference in the degree of moisture absorption between the front and back surfaces of the diffusion plate 4, and the front surface side of the diffusion plate 4 is deformed into a concave shape as shown in FIG.

When the environmental humidity decreases, the diffusion plate 4
Dried outside air flows into the back side of the diffusion plate 4, and the back side dries faster than the surface of the diffusion plate 4, so that the front side of the diffusion plate 4 is contracted and deformed into a convex shape as shown in FIG.

In other words, the center position of the light uniformizing pattern 2 is usually determined under the condition of normal temperature and normal humidity. The positional relationship between the diffuser plate 4 on which the light uniform pattern 2 is printed and the fluorescent lamp 1 is determined in the vertical and horizontal directions (x, y).
Direction) or a change in the distance between the fluorescent lamp 1 and the diffuser 4 causes uneven brightness.

For this reason, there is a problem that the liquid crystal display quality of the liquid crystal device in which the lighting device is incorporated is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is intended to prevent the luminance uniformity of the light emitting surface from being impaired even when the temperature or humidity changes under the use environment. And a display device using the same.

[0013]

In order to achieve the above object, in the lighting device according to the first aspect of the present invention, the light from the linear light source (1) is provided with a light uniform pattern (2). One or both of a light-diffusing or light-collecting sheet (5, 6, 7) is arranged on the light-emitting surface side of the diffusion plate (4) so that uniform light is irradiated from the entire surface. And a support member (8b) for forming a gap between the diffusion plate (4) and the sheets (5, 6, 7).

According to a second aspect of the present invention, the light from the linear light source (1) is diffused to a light uniformizing pattern (2).
A light diffusing or condensing sheet (5,
6, 7) is arranged to irradiate uniform light from the entire surface, and the sheet (5, 6, 7) is placed on the light emitting surface side of the diffusion plate (4). A light-transmitting sheet (9) is adhered to the diffuser plate (4) on the side of the line light source on the diffuser plate (4).

According to a third aspect of the present invention, the light from the linear light source (1) is provided with a light uniformizing pattern (2).
A light diffusing or condensing sheet (5,
One or both of (6) and (7) are arranged so as to irradiate uniform light from the entire surface, and the diffusion plate (4) is formed of a material having low hygroscopicity.

In this case, it is preferable that the diffusion plate (4) is formed of a polycarbonate resin.

Further, the lighting device according to any one of claims 1 to 4 may be arranged directly below the display member.

[0018]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a sectional view showing a lighting device according to an embodiment of the present invention, FIG. 2 (a) is a perspective view of the same, and FIG.
FIG. 3 is a plan view, and FIG. 3 is a sectional view showing a lighting device according to another embodiment of the present invention. Note that the same components as those shown in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.

The illumination device of the first embodiment shown in FIGS. 1 and 2 transmits light from a linear light source 1 disposed immediately below a display member through a diffusion plate 4 provided with a light uniforming pattern 2. This causes the entire surface of the display member to be uniformly irradiated with light, and the light-diffusing or condensing sheet 5 disposed on the light-exiting surface side of the light-diffusing plate 4 and the light-diffusing plate 4.
A support member 8b that forms a gap between the diffusion plate 4 and the sheets 5, 6, 7 is provided.

The illumination device according to the second embodiment shown in FIG. 3 transmits light from a linear light source 1 disposed immediately below a display member through a diffusion plate 4 provided with a light uniforming pattern 2. Light is uniformly applied to the entire surface of the display member, and light diffusing or condensing sheets 5, 6, 7 provided on the light emitting surface side of the diffusion plate 4 are brought into close contact with each other, A light transmitting sheet 9 is closely attached to the light source side of the diffusion plate 4.

In the lighting device according to the third embodiment, the light from the linear light source 1 disposed immediately below the display member is transmitted through the diffusion plate 4 on which the light uniformizing pattern 2 has been formed, so that the display member The light is irradiated uniformly on the entire surface, and the diffusing plate 4 is formed of a material having low hygroscopicity.

In this case, the diffusion plate 4 made of a material having low hygroscopicity
It is preferable to use a polycarbonate resin.

Next, the operation and effect of this embodiment will be described.

According to the first embodiment, the supporting member 8b is interposed between the diffusion plate 4 and the light diffusion sheet 5, so that the light exit surface side and the light source side of the diffusion plate 4 are both in direct contact with the outside air. With this configuration, even if the environment changes and the humidity rises or falls, the moisture absorption state on both sides of the diffusion plate 4 becomes the same, so that there is no difference in contraction or expansion on both sides of the diffusion plate 4, The diffusion plate 4 is not deformed into a concave shape or a convex shape with respect to the display member, and therefore, there is no possibility that uneven brightness occurs on the light emitting surface of the display member due to a change in environmental humidity.

Further, according to the second embodiment, the light diffusing sheet 5 is brought into close contact with the light emitting surface side of the diffusion plate 4 and the transmission sheet 9 is brought into close contact with the light source side of the diffusion plate 4. Therefore, even if there is a change in the environment and the humidity rises or falls, both surfaces of the diffusion plate 4 do not directly contact the outside air, so it is possible to suppress unevenness deformation caused by a difference in moisture absorption between the front and back surfaces of the diffusion plate 4, There is no possibility that uneven brightness occurs on the light emitting surface of the display member.

Further, according to the third embodiment, since the diffusion plate 4 is made of a material having a small hygroscopic property, the water absorption rate can be kept small even if the humidity changes due to environmental changes. In addition, the amount of uneven deformation of the diffusion plate 4 can be reduced, and the luminance unevenness of the light emitting surface of the display member becomes very small.

[0028]

<First Embodiment> A lighting device according to a first embodiment of the present invention includes a frame 8 for supporting a diffusion plate 4, diffusion sheets 5, 7 and a prism sheet 6 in a stacked manner as shown in FIGS. Are attached to the upper end of the reflecting plate 3 and slits 8a for allowing the outside air to flow are formed in the four surfaces of the frame 8, and diffusion sheets 5 are formed at four corners continuously with the slits 8a.
A support portion 8b as a support member for supporting the prism sheet 7 and the prism sheet 6 is provided in a protruding manner. Thus, the support portion 8b is interposed between the diffusion sheet 5 and the diffusion plate 4 to form an air layer.

According to this embodiment, the same effects as those of the above-described embodiment can be obtained. <Second Embodiment> As shown in FIG. 3, a lighting device according to the present embodiment is configured such that a diffusion sheet 5 is brought into close contact with a light exit surface of a diffusion plate 4 and a light transmissive sheet is provided on the light source side of the diffusion plate 4. Since the transparent film 9 is adhered, the back surface of the diffusion plate 4 does not come into direct contact with the outside air, similarly to the front surface.

According to this embodiment, the same effects as those of the above-described embodiment can be obtained. <Third Embodiment> A lighting device according to the present embodiment is a diffusion plate 4 on which a light uniform pattern 2 in the structure shown in FIG. 1 (first embodiment) or the structure shown in FIG. 3 (second embodiment) is printed. Is changed from an acrylic resin material having relatively high hygroscopicity to a polycarbonate resin material having low hygroscopicity.

As a result, for example, the water absorption (ASTMD570) of methacrylic resin of an acrylic resin material becomes 0.3
%, The water absorption of the polycarbonate resin can be reduced to about 0.15%.

Therefore, by changing the material of the diffusion plate 4 from the conventional acrylic resin material to the polycarbonate resin, the amount of unevenness deformation on the light emitting surface of the diffusion plate 4 can be reduced.

[0033]

As described above, according to the present invention,
With the above-described configuration, changes in the temperature and humidity of the use environment of the lighting device, in particular, shrinkage of both surfaces of the diffuser plate on which a light uniform pattern that leads to uneven brightness of the light emitting surface of the display member caused by the change in humidity are printed. Alternatively, the difference in expansion does not occur, and the deformation of the light-emitting surface of the display member into a concave shape or a convex shape can be suppressed. Therefore, there is no possibility that uneven brightness occurs on the light-emitting surface of the display member due to a change in environmental humidity. Further, when the lighting device of the present invention is provided in a display device, it is possible to avoid a problem that display quality is deteriorated.

Further, since the front and back surfaces of the diffusion plate are not directly in contact with the outside air, it is possible to suppress uneven deformation caused by a difference in moisture absorption between the front and back surfaces of the diffusion plate, thereby causing uneven brightness on the light emitting surface of the display member. There is no danger of doing so. When the lighting device of the present invention is provided in a display device, it is possible to avoid a problem that display quality is deteriorated.

Further, the diffusion plate is formed of a material having a small hygroscopic property, so that even if the environment changes and the humidity rises, the water absorption rate can be kept small, and the amount of unevenness of the diffusion plate can be kept small. This has an effect that the luminance unevenness of the light emitting surface of the member is very small. When the lighting device of the present invention is provided in a display device, it is possible to avoid a problem that display quality is deteriorated.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a lighting device according to a first embodiment of the present invention.

FIGS. 2A and 2B show the lighting device according to the first embodiment, wherein FIG. 2A is an exploded perspective view and FIG. 2B is a plan view.

FIG. 3 is a cross-sectional view illustrating a lighting device according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating an example of a conventional lighting device.

5A and 5B show a problem based on the above lighting device, wherein FIG. 5A is a cross-sectional view illustrating a state in which the diffusion plate is deformed into a concave shape due to environmental humidity, and FIG. FIG. 4 is a cross-sectional view illustrating a state in which it is performed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Line light source (fluorescent lamp) 2 Light uniform pattern 4 Diffusion plate 5 Diffusion sheet 6 Prism sheet 8b Support member (support part) 9 Light transmissive sheet (transmissive film)

Claims (5)

[Claims] 1. A light diffusing or condensing sheet or both sheets are arranged on a light exit surface side of a diffusion plate on which a light from a linear light source is provided with a light uniforming pattern, and uniform light is emitted from the entire surface. An illuminating device adapted to irradiate, comprising: a supporting member that forms a gap between the diffusion plate and the sheet. 2. A light diffusing or condensing sheet or both sheets are arranged on the light exit surface side of a diffusion plate on which a light from a linear light source is provided with a light uniforming pattern, and uniform light is emitted from the entire surface. In the lighting device configured to irradiate, the sheet is brought into close contact with the light exit surface side of the diffusion plate, and a light transmissive sheet is brought into close contact with the line light source arrangement side of the diffusion plate. Lighting equipment. 3. A light diffusing or condensing sheet, or both, is disposed on the light emitting surface side of a diffusion plate on which a light from a linear light source is provided with a light uniforming pattern, and uniform light is emitted from the entire surface. An illumination device for irradiating, wherein the diffusion plate is formed of a material having low hygroscopicity. 4. The lighting device according to claim 3, wherein the diffusion plate is formed of a polycarbonate resin. 5. A display device, comprising: the lighting device according to claim 1 disposed directly below a display member.