JPH06281928A - Illuminator and liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent respective projections from being visible from an out-going surface even when a light transmission body is formed thin and to make the light transmission body passible to be made thin by forming plural projections projecting to the outside and whose sectional shape is a nearly semi-circular shape on the bottom surface of the light transmission body. CONSTITUTION:Plural semi-spherical shaped projections 16 projecting to the outside are formed overall on the bottom surface 13b of the light transmission body 13. The density of these semi-spherical shaped projections 16 is formed so as to become denser gradually from a pair of left and right fluorescent lamps 14a, 14b. The incident beams from the left and right ends of the light transmission body 13 propagating to central part are refracted by respective semi-spherical shaped projections 16 and emitted to the outside and reflected irregularly by a reflection sheet 15. Then, almost all of the reflected beams are made incident on the inside of the light transmission body 13 again from the bottom surface 13b of the body 13, and the incident beams on the outgoing surface 13a at a crtical angle or below are emitted to the outside from the outgoing surface 13a. Thus, since the peripheral parts of respective semi-spherical shaped projections 16 are bright when respective semi-spherical shaped projections 16 are seen from the outgoing surface 13a of the light transmission body 13, the shapes of respective semi-spherical shaped projections 16 are faded and hard to be visible from the outgoing surface 13a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LCD (liquid crystal display device).
The present invention relates to a lighting device and a liquid crystal display device suitable for a backlight for illuminating the back surface of a panel and the like, and more particularly to a lighting device and a liquid crystal display device capable of achieving a thinner light guide.

[0002]

2. Description of the Related Art Conventionally, an example of this type of illumination device is disclosed in Japanese Patent Application Laid-Open No. 3-81906. This illuminating device is called a side (edge) light system, and as shown in FIG. 6, a light guide 2 in the shape of, for example, a rectangular plate, is provided in a lamp case 1 in which almost the entire inner surface 1a is formed as a reflecting surface. A pair of left and right, for example, straight fluorescent lamps 3a and 3b, which are arranged side by side at the left and right ends, are built in, and a diffusion plate or the like is provided on the light emitting surface 3a on the upper surface of the light guide 2 in the figure. An LCD (Liquid Crystal Display) panel (not shown) is placed and fixed via the above. Then, as shown in FIG. 7, a plurality of grooves 4 and 4 each having a triangular cross section are arranged in the width direction on the outer bottom surface 2b of the light guide.

Further, in the lighting device disclosed in Japanese Utility Model Laid-Open No. 3-92627, a plurality of conical recesses 5 are formed on the outer bottom surface 2b of the light guide 2 as shown in FIGS. 8 and 9. .

[0004]

However, in such a conventional illuminating device, the triangular groove 4 and the conical concave portion 5 illuminate with a considerably high brightness by the light from the pair of lamps 3a and 3b, so that the light guiding body has a certain degree of brightness. If there is no thickness, the shapes of the triangular groove 4 and the conical concave portion 5 are projected on the light exit surface 2a, and thus there is a limit to the thinning of the light guide 2.

Further, in the triangular groove 4 and the conical recess 5, there is a problem that the sharp-pointed tip portion of the tip portion is not illuminated and is projected as a black spot on the light emitting surface 2a and is visually recognized.

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to provide an illuminating device and a liquid crystal display device capable of achieving a thinner light guide.

[0007]

The present invention is configured as follows to solve the above problems.

The invention according to claim 1 of the present application (hereinafter, referred to as the first
Of the invention), a light source, a light guide that receives light from the light source and guides the light to the light exit surface, and a reflector that is disposed on the bottom surface side of the light guide opposite to the light exit surface. And a plurality of protrusions having a semi-circular cross-section that are convex outward are formed on the bottom surface of the light guide.

The invention according to claim 2 of the present application (hereinafter referred to as the second invention) is characterized in that the protrusions are hemispherical.

Further, the invention according to claim 3 of the present application (hereinafter referred to as the third invention) is characterized in that the projection is a string-like projection having a substantially semicircular cross section.

Further, in the invention according to claim 4 of the present application (hereinafter referred to as the fourth invention), the density of the plurality of protrusions is formed so as to become denser as the distance from the light source increases. Characterize.

The invention according to claim 5 of the present application (hereinafter referred to as the fifth invention) is any one of claims 1 to 4.
And a liquid crystal display panel which is illuminated by light from the illumination device.

[0013]

[Action]

<First to Third Inventions> When the light from the light source propagates in the light guide body and is incident on a protrusion such as a hemispherical protrusion or a hemispherical cord-shaped protrusion,
Here, while a part of the light is totally reflected, most of it is refracted, goes out from the bottom surface of the light guide, and is diffusely reflected by the reflector,
The light again propagates in the light guide body from the bottom surface toward the light emitting surface and is emitted outward from the light emitting surface.

Therefore, when the projections are viewed from the light exit surface of the light guide, the projections and their peripheral parts appear to be bright, and the shapes of the projections are blurred and almost invisible.

For this reason, even if the light guide is formed thin,
Since each protrusion cannot be seen from the light exit surface, the light guide can be made thinner.

<Fourth Invention> In the fourth invention, the density of the plurality of protrusions is set to be gradually higher as the distance from the light source increases. Originally, the brightness is relatively high, but the brightness is suppressed because the density of the protrusions is relatively sparse.

On the other hand, in the portion of the light guide near the light source, the brightness is originally relatively low, but since the protrusions are dense, the brightness is high. Therefore, the brightness on the entire light emitting surface of the light guide can be flattened regardless of the distance of the light source, and the brightness uniformity can be improved.

<Fifth Invention> Since the illumination device according to any one of the first to fourth inventions, which can make the light guide thinner, is incorporated as a backlight of a liquid crystal display panel, a liquid crystal display device is provided. The overall thickness can be reduced.

[0019]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a vertical sectional view of an embodiment including the first, second, and fourth inventions of the present application.
In the lamp case 12, a rectangular plate-shaped light guide 13 and a pair of left and right fluorescent lamps 14a and 14b arranged side by side at the left and right ends of the light guide 13 are incorporated.

The lamp case 12 has a reflection surface 12a formed on almost the entire inner surface thereof, and a relatively large opening 1 is formed on the upper surface in the figure.
2b is formed, on the inner bottom surface of the lamp case 12,
Reflection sheet 1 slightly larger than the bottom surface 13b of the light guide body 13
5 is arranged to reflect the light from the bottom surface 13b of the light guide body 13.

The light guide 13 has a light emitting surface 13a on the upper surface in the figure.
In addition, the left and right ends of the light guide 13 are sandwiched by the ends of the opening 12b of the lamp case 12 in the vertical direction in the figure, while the bottom surface 13b of the light guide 13 is substantially convex outward. A plurality of hemispherical projections 16 such as hemispheres are formed on almost the entire surface. These hemispherical protrusions 16 form a part of a substantially hemispherical equal spherical body, and the density of these hemispherical protrusions 16 is as follows as the distance from the pair of left and right fluorescent lamps 14a and 14b increases.
In other words, it is formed so that it gradually becomes denser toward the central part. Therefore, the density of the hemispherical protrusions 16 is maximum at the middle portion of the light guide 13 in the left-right direction in the drawing, and is lowest at the left and right ends thereof.

For this purpose, a pair of left and right fluorescent lamps 14 are provided.
Light from a and 14b is directly or in the lamp case 12
After being reflected by the reflection surface 12a of the above, the light enters the light guide 13 from the left and right ends in the figure and propagates toward the central portion, but most of the light incident on each hemispherical protrusion 16 The light is refracted by the projections 16 and goes out, and is diffusely reflected by the reflection sheet 15, and most of the reflected light is again on the bottom surface 13b of the light guide body 13.
The light that has entered the light emitting surface 13a from the light emitting surface 13a at the critical angle or less is emitted to the outside from the light emitting surface 13a.

Therefore, when the hemispherical projections 16 are viewed from the light emitting surface 13a of the light guide 13, the respective hemispherical projections 1
Since the peripheral portion of 6 is shining, the shape of each hemispherical projection 16 is blurred from the light emitting surface 13a and becomes almost invisible.

For this reason, even if the light guide 13 is made thin, the shape of each hemispherical protrusion 16 cannot be seen from the light emitting surface 13a, so that the light guide 13 can be made thin.

Further, in a portion near the pair of left and right fluorescent lamps 14a, 14b of the light guide body 13, which is originally relatively bright, the density of the plurality of hemispherical projections 16 is higher than that of the central portion. Since it is rare, the hemispherical projection 16 in this part
From the light emitting surface 13a, the amount of light emitted from the light emitting surface 13a to the outside is reduced, and the brightness is suppressed accordingly.

On the other hand, in the middle portion of the light guide 13, since it is farthest from the pair of left and right fluorescent lamps 14a, 14b, the luminance should be relatively low by that amount, but the hemispherical projection 16
These hemispherical protrusions 16 have the highest density of each other.
Then, the amount of light that has once exited to the outside, is reflected by the reflection sheet 15 and returns to the outside from the light exit surface 13a, and the brightness is improved accordingly. As a result, the brightness of the entire light emitting surface 13a of the light guide 13 can be flattened.

FIG. 4 is a perspective view showing a part of a longitudinal section of one embodiment of the fifth invention of the present application, and a liquid crystal display device 21 of this embodiment.
The liquid crystal display panel 22 is attached to the light exit surface 13a of the light guide 13 of the illuminating device 11 with the back surface thereof in close contact with each other.
It is characterized in that the liquid crystal display panel 22 is supported by a and 23b, and the drive circuit of the liquid crystal display panel 22 is omitted in the drawing.

In the liquid crystal display device 21, as described above, the shape of the hemispherical projection 16 is not projected onto the light exit surface 13a of the light guide 13, and the liquid crystal display device 21 uses the thin illumination device 11 for the light guide 13. Since the back surface of the display panel 22 is illuminated, the liquid crystal display device 21 as a whole can be thinned.

The liquid crystal display panel 22 may be replaced with a display plate such as a guide plate having a required display, a signboard, or the like to form a guide light, a signboard light, or the like. Further, in the above embodiment,
Although the case where the hemispherical projection 16 is formed in the shape of an approximately half of a sphere has been described, the present invention is not limited to this, and for example, as shown in FIG. 5A, the cross section has a semicircular shape. 5 may be arranged in parallel on the outer bottom surface 13b of the light guide 13 in the width direction at a required pitch.
As shown in (B), one spherical projection 31 may be formed by connecting a plurality of small hemispherical projections 31a, 31a ... These small hemispherical protrusions 31
The a and 31a can also be formed by a method of printing resin on the light guide 13 by screen printing or the like.

[0031]

As described above, according to the first to third inventions of the present application, since a plurality of hemispherical or semicircular string-like projections are formed on the bottom surface of the light guide, the light is incident on these projections. These projections and their peripheral portions shine due to light, and the shapes of the projections are almost invisible from the light exit surface of the light guide, so that the light guide can be made thinner.

Further, according to the fourth aspect of the invention, since the density of the projections is set to be higher as the distance from the light source increases, the uniformity of the light exit surface of the light guide can be increased.

Further, according to the fifth aspect of the invention, since the illuminating device capable of reducing the thickness of the above-mentioned light guide body is incorporated as a backlight, the overall thickness of the liquid crystal display device can be reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment of a lighting device including the first, second, and fourth inventions of the present application.

FIG. 2 is a bottom view of a main part of FIG.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a perspective view showing, in a vertical cross section, a part of an embodiment of a liquid crystal display device according to the fifth invention of the present application.

5A is a perspective view of an essential part of an embodiment of the third invention of the present application, and FIG. 5B is a longitudinal sectional view of an essential part of another embodiment shown in FIG.

FIG. 6 is a vertical sectional view of a conventional example.

7 is a partially enlarged bottom view of FIG.

FIG. 8 is a vertical cross-sectional view of another conventional example.

9 is a bottom view showing a part of the bottom surface of FIG. 8. FIG.

[Explanation of symbols]

 11 Lighting Device 12 Lamp Case 12a Reflective Surface 12b Opening 13 Light Guide 13a Light Emitting Surface 13b Bottom 14a, 14b Pair of Fluorescent Lamp 15 Reflective Sheet 16 Hemispherical Protrusion 21 Liquid Crystal Display 22 Liquid Crystal Display Panel 23 Lamp Case 23a, 23b Opening End 30 String-shaped protrusion

Claims (5)

[Claims] 1. A light source, a light guide that receives light from the light source and guides the light to a light exit surface, and a reflector that is disposed on the bottom surface side of the light guide opposite to the light exit surface. An illumination device, comprising: a plurality of protrusions having an outwardly convex and substantially semicircular cross section formed on the bottom surface of the light guide. 2. The lighting device according to claim 1, wherein the projection has a hemispherical shape. 3. The illumination device according to claim 1, wherein the protrusion is a string-shaped protrusion having a substantially semicircular cross section. 4. The lighting device according to claim 1, wherein the density of the plurality of protrusions is gradually increased as the distance from the light source increases. 5. A liquid crystal display device comprising: the illuminating device according to claim 1; and a liquid crystal display panel illuminated by light from the illuminating device.