JP2539334B2 - Light guide plate for backlight - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate for a backlight, which is formed so as to cope with high brightness and thinness of a color liquid crystal display, and more specifically, a side light system (edge light system) and a light source. The present invention relates to a light guide plate for a backlight of a type that uses a single-lamp linear light source.

[0002]

2. Description of the Related Art Heretofore, as a light guide plate of this type, for example, the back surface is curved so as to warp toward the front side as it goes away from the linear light source, or is formed into an inclined surface so that the thickness is kept away from the linear light source. There is one that is gradually thinned in accordance with the above (see, for example, the prior art described in Japanese Patent Laid-Open No. 2-247686, Japanese Utility Model Laid-Open No. 63-26874).

[0003]

When the light source is a linear light source such as a cold cathode fluorescent lamp, the structure of this type of light source causes
It is unavoidable that the illuminance at both ends of the light source is lower than the illuminance at the center. However, in the conventional light guide plate, a measure for such characteristics of the light source of this kind is not usually provided. Therefore, when the conventional product is used, the position corresponding to the central part of the linear light source becomes brighter than both sides, and uneven brightness occurs in the longitudinal direction of the linear light source.

Thus, in the past, for example, the actual exploitation Sho 62-7428.
As in the device described in Japanese Patent Laid-Open No. 2 (1994), a technique has been proposed in which a concavo-convex pattern is formed on the side surface opposed to a linear light source, and thereby the above problem is solved. However, in the case of this conventional product, there is a problem that the light emitting surface becomes a dead space by the amount corresponding to the depth of the uneven surface because it is necessary to form the uneven pattern on the side surface. Generally, it is desirable that the light guide plate of this type is originally formed so that the light emitting surface can be effectively and widely used as much as possible so that the liquid crystal display can be downsized and the space can be saved. Therefore, in the case of the above-mentioned conventional product, it is possible to prevent uneven brightness in the longitudinal direction of the linear light source, but it is difficult to sufficiently exhibit the function in response to the demand for miniaturization of the display.

[0005] The present invention is to solve such a problem of the conventional product. Therefore, the technical problem of the present invention is to form not only the direction orthogonal to the linear light source but also the luminance unevenness in the longitudinal direction of the linear light source,
A light guide plate for a backlight, which is designed to equalize and average the brightness of the entire light emitting surface, and is formed so that the entire light emitting surface can be effectively used to meet the demand for downsizing of liquid crystal displays. To provide.

[0006]

The present invention employs the following technical means in order to solve the above problems. That is, according to the present invention, the back surface 1 is curved so as to warp toward the front surface 4 side as the distance from the linear light source 2 increases, and the cross section parallel to the linear light source 2 is formed in a plano-convex lens shape having a convex curvature on the back surface 1 side. , One side portion 3 on which the linear light source 2 is arranged on the back surface 1
To the opposite side portion 5, a plurality of grooves 6 are formed in parallel with each other, and the grooves 6 are formed gradually deeper and wider from the one side portion 3 to the opposite side portion 5, and the starting end thereof is formed. 6a is positioned on the arc line 7 that is concavely curved with respect to the linear light source 2.

[0007]

In the case of the present invention, the light from the linear light source 2 is guided to the side portion 5 opposite to the light source 2 not only in the light guide plate but also by the optical path 6b formed by the groove 6. In this case, the light is less likely to be attenuated in the optical path 6b of the air layer as compared with transmitting while being reflected in the light guide plate, so that the light can be efficiently guided far from the light source 2.

The groove 6 is formed so that the depth and the width thereof gradually increase as the distance from the light source 2 increases. Therefore, the area of the light guided by the groove 6 is irregularly reflected from the starting end 6a to the leading end, and the amount of light reflected on the surface 4, which is the light emitting surface, is also increased accordingly. Further, in the case of the present invention, the back surface 1 is warped as the distance from the light source 2 increases, and the thickness is formed thin. Therefore, in the present invention, the luminance in the orthogonal direction of the light source 2 becomes uniform in combination with the above-described action of the groove 6.

In the light guide plate of the present invention, the start end 6a of the groove 6 is positioned on the arc line 7 in consideration of the characteristics of the light source 2. Therefore, the starting end 6a of the groove 6 at the center and the grooves 6 on both sides are
The starting end 6a of is a point light source having the same amount of light. Further, in the present invention, since the cross section is formed into a plano-convex lens shape so that the thickness of the central portion is thicker than both sides, the light amount reflected on the surface 4 side is the same between the central portion and both sides of the light guide plate. . As a result, in the present invention, the luminance of the light emitting surface corresponding to the longitudinal direction of the light source 2 becomes uniform.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. Reference numeral 1 is a back surface of the light guide plate according to the present invention, and 2 is a linear light source such as a cold cathode tube disposed on one side portion 3 side.

The back surface 1 is curved so as to warp back to the front surface 4 which is a light emitting surface as the distance from the linear light source 2 increases. In this case, the curvature of the back surface 1 is set to a value that allows the incident light from the linear light source 2 to be uniformly reflected on the front surface 4 and also serves as a reflecting surface that guides the incident light from one side portion 3 to the opposite side portion 5. It has been selected. Further, as shown in FIG. 1C, etc., the cross section parallel to the linear light source 2 is formed in a plano-convex lens shape having a convex curve on the back surface 1 side.

Reference numeral 6 is a groove having an inverted V-shaped cross section. This groove 6 is formed on the back surface 1 on one side 3 on the side of the linear light source 2.
To the opposite side portion 5 are formed in parallel to each other, and in this embodiment, a plurality of them are formed at equal intervals. Further, the groove 6 is formed so as to be gradually deeper and has a divergent shape from one side portion 3 to the opposite side portion 5, and the start end 6 thereof is formed.
a is positioned on the arc line 7 that is concavely curved with respect to the linear light source 2. In this case, the number of grooves 6, the depth, the opening width, and the curvature of the arc line 7 are appropriately selected according to various conditions such as the size and thickness of the light guide plate and the illuminance required as a backlight. 6b (see FIGS. 3 and 8) is an optical path formed by the groove 6. The light guide plate of this embodiment is made of an acrylic resin material and is formed by injection molding.

Reference numeral 8 (see FIG. 7) is a reflector disposed on the back surface 1 side. The reflecting plate 8 is formed of, for example, a mirror-finished aluminum plate material or the like. Reference numeral 9 is a light diffusing film that is in close contact with the surface 4, and 10 is a liquid crystal display element. In the light guide plate according to this embodiment, the portions 11 and 11 (see FIG. 2 and the like) corresponding to both ends of the linear light source 2 are formed in a side wall shape.

Next, the operation of this embodiment will be described. First,
Part of the light that has entered the light guide plate from the light source 2 is guided by the one side portion 3 to the opposite side portion 5 in the optical path 6b while being diffusely reflected by the inner surface of the groove 6. A part of the light is reflected by the curved surface of the back surface 1 directly to the front surface 4 side. Then, as shown in FIG. 8A, the light reflected by the inner surface of the groove 6 and reaching the reflecting plate 8 is totally reflected by the reflecting plate 8. Also, as shown in FIG.
The light refracted from the back surface 1 and reaching the reflection plate 8 is also totally reflected by the reflection plate 8, emitted from the front surface 4 together with the direct light from the light source 2, and diffused by the light diffusion film 9.

In this case, since the groove 6 is formed so that the depth and the width thereof gradually increase as the distance from the light source 2 increases, the area of the light guided by the groove 6 irregularly reflects from the starting end 6a to the leading end. The amount of light reflected on the surface 4, which is the light emitting surface, also increases accordingly. Further, since the back surface 1 is warped as it becomes farther from the light source 2 and is formed to have a smaller thickness, the brightness of the light source 2 in the orthogonal direction is made uniform, in combination with the above action of the groove 6. Therefore, one side portion 3 of the surface 4 which is a light emitting surface and the side portion 5 on the opposite side emit light uniformly.

Further, in the present invention, the starting end 6a of the groove 6 is positioned on the arc line 7 in consideration of the characteristics of the light source 2. Therefore, the starting ends 6a of the grooves 6 in the central portion of the light guide plate and the starting ends 6a of the grooves 6 on both sides form a point light source having the same amount of light. Further, in the light guide plate of the present invention, in consideration of the characteristic of the seed linear light source 2 that the light amount differs between the central portion and both end portions of the light source 2, the transmitted light amount to the surface 4 is equalized in the central portion of the light guide plate and on both sides. Be able to,
A cross section parallel to the light source 2 is formed in a plano-convex lens shape with different thicknesses. Therefore, according to the present invention, the amount of light reflected on the front surface 4 side is uniform between the central portion of the light guide plate and both sides. As a result, in the present invention, the brightness is made uniform not only in the direction orthogonal to the linear light source 2 but also in the longitudinal direction of the linear light source 2, that is, in the central portion and both sides of the light guide plate.

In the above, in the case of the present invention, the cross-sectional shape of the groove 6 is arbitrary. That is, the cross section of the groove 6 is not limited to the inverted V shape as in the above example, but may be, for example, a polygonal cross section. In the present invention, the grooves 6 may be formed with different intervals, for example, roughly at the center of the light guide plate and densely on both sides. In the present invention,
The surface 4 is subjected to, for example, light diffusion processing, and the above-mentioned light diffusion film 9
May be omitted.

[0018]

As described above, the light guide plate of the present invention is
The back surface is curved so that the thickness is gradually reduced, and a groove for guiding light to the back surface is formed so as to be gradually deeper and wider as the distance from the light source increases. Therefore, in the present invention, the light can be guided by the inside of the light guide plate and the groove. In this case, the light guided by the groove has a smaller attenuation amount than the inside of the light guide plate, and the diffused reflection area gradually increases from the start end of the point light source shape. Will be guided. Therefore, according to the present invention, light is efficiently transmitted in the direction orthogonal to the linear light source, and the luminance in the same direction can be made uniform.

Further, in the present invention, the cross section parallel to the linear light source is formed in the shape of a plano-convex lens having a convex curve on the back side.
The amount of reflected light to the front surface side becomes uniform between the central part of the light guide plate and both sides. Further, in the case of the present invention, since the starting end of the groove is positioned on the arc line which is concavely curved with respect to the light source, the starting end of the groove at the central part of the light guide plate and the starting ends of the grooves on both sides are at the same light quantity. Turn it into a light source. Therefore, according to the present invention, it is possible to prevent luminance unevenness of the light emitting surface in the longitudinal direction of the linear light source, and to achieve uniformization and averaging of the luminance of the entire light emitting surface.

Further, according to the present invention, the shape of the back surface of the light guide plate, the structure of the groove, and the like are used to uniformize the luminance in the longitudinal direction of the linear light source, so that the entire light emitting surface is effectively used. As a result, there is an advantage that the liquid crystal display can be downsized.

[Brief description of drawings]

FIG. 1 shows a preferred example of the present invention, in which A is a bottom view, B is a sectional view taken along line BB of A, and C is a sectional view taken along line CC of A.

FIG. 2 is a perspective view of the present invention.

FIG. 3 is a bottom view of a main part with a part cut away of the present invention.

FIG. 4 is a front view of a main part of the present invention with a part cut away.

5 is a sectional view taken along line VV of FIG.

6 is a cross-sectional view taken along line VI-VI in FIG.

FIG. 7 is a vertical cross-sectional view of a central portion showing a usage state of the present invention.

FIG. 8 is an explanatory diagram illustrating a light reflecting action in both A and B.

[Explanation of symbols]

 1 Back surface 2 Linear light source 3 One side part 4 Front surface 5 Opposite side part 6 Groove 6a Start end 7 Arc line

Claims (1)

(57) [Claims] 1. A back surface is curved so as to warp to the front side as it moves away from the linear light source, and a cross section parallel to the linear light source is formed into a plano-convex lens shape having a convex curvature on the back surface side. A plurality of grooves are formed in parallel with each other from one side portion on the side of the light source to the side portion on the opposite side, and the grooves are formed in a gradually widening and divergent shape from the one side portion to the opposite side portion. At the same time, the light guide plate for a backlight is characterized in that its start end is positioned on an arc line which is concavely curved with respect to the linear light source.