JP2002270019A - Lighting system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting system capable of eliminating both brightness irregularity of a luminous surface possibly occurring in a region close to a light source and lack of luminous energy of the luminous surface possibly occurring in a region distant from the light source, and easy to improve display quality. SOLUTION: A first groove 31 positioned in the vicinity of the light source 4 within multiple grooves formed on the back face of a light guide body 3 is formed into a rounded groove shape with its wall surface 31a smoothly continued, and its groove depth is set smaller than those of cross-sectionally triangular second grooves 30. Thereby, when the light from the light source 4 is reflected by the bent wall surface 31a of the first groove 31 in the vicinity thereof, the light is significantly spread and advances to the luminous surface 3a, so that a dark band-like part never appears on the luminous surface 3a in front of the grooves 30. When the depth of the first groove 31 positioned in the vicinity of the light source 4 is small, much light can be delivered to the thin part of the guide body 3 distant from the light source 4, so that the lack of luminous energy never occurs even in the region of the luminous surface 3a distant from the light source 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminating device suitable for use as a backlight of a liquid crystal display element or the like having a relatively large light emitting surface of a light guide.

[0002]

2. Description of the Related Art FIG. 3 is a cross-sectional view showing a conventional illuminating device, and FIG. 4 is an explanatory view showing an enlarged portion A of FIG. 3, which is used as a backlight of a liquid crystal display element. is there. The illumination device generally indicated by reference numeral 1 in FIG. 3 is a reflection case 2 made of a resin material such as white having a high light reflectance.
A light guide 3 having a flat light-emitting surface 3a on the front surface and a curved back surface, and a light source 4 such as a small light bulb mounted on a substrate 5.
The light guide 3 is mounted on the inner bottom surface 2 a of the reflection case 2, and the light source 4 is arranged to face one thick side of the light guide 3. The light from the light source 4 is radiated to the inside of the light guide 3 and reflected on the back surface thereof, so that the light emitting surface 3a emits light. A large number of grooves 30 having a triangular cross section are provided in substantially the entire region on the back surface of the light guide 3. As shown in FIG. 4, the light source 4 of the chevron wall forming each
The wall surface 30a facing the side (the left side in the figure) reflects the light L coming from the light source 4, and the front (upper side in the figure) light emitting surface 3a
Performs the function of moving to Further, light leaking from the back surface of the light guide 3 to the outside is also reflected by the inner bottom surface 2a of the reflection case 2 curved along the back surface, so that the light is returned to the inside of the light guide 3 again to emit light. 3a can emit light.

However, since the distance from the light emitting surface 3a of the light guide 3 to the light source 4 varies depending on the location, the intensity of light traveling directly from the light source 4 to the light emitting surface 3a increases as the distance from the light source 4 increases (FIG. 3).
On the right side). However, in this type of illuminating device 1, the back surface of the light guide 3 and the inner bottom surface 2 a of the reflection case 2 are curved so as to rise as the distance from the light source 4 increases, so that the light guide 3 moves away from the light source 4. The thinner part, the groove 3
Thus, the light reflected by the inner bottom surface 2a is easily supplied. Therefore, the light emitting surface 3a is located in a region far from the light source 4,
It is possible to emit light with the same brightness as the region close to.

[0004] The upper opening 2b of the reflection case 2 has
A liquid crystal display element 7 is incorporated via a diffusion sheet 6 in a state of being close to the light emitting surface 3a of the light guide 3, and the liquid crystal display element 7 is illuminated from behind by the light emitting surface 3a. The diffusion sheet 6 is required to have appropriate translucency, and the light diffusion effect has a limit. Therefore, if the light emitting surface 3a of the light guide 3 has uneven brightness, the brightness varies depending on the location. In addition, the display screen of the liquid crystal display element 7 also has uneven brightness, which degrades the display quality.

[0005]

In the above-described conventional illuminating device 1, the light reflected by the inner bottom surface 2a of the reflection case 2 is not supplied much to the area of the light emitting surface 3a close to the light source 4, and Light direct from 4 to the light emitting surface 3a;
The region emits light due to the light reflected by the wall surface 30a of the groove 30 provided at the rear. That is, the light emitting surface 3
5A, the reflected light from the wall surface 30a of the rear groove 30 is relatively strong in the region close to the light source 4, and as shown in the plan view of FIG. 5A and the sectional view of FIG. The front of the other wall surface 30b of the groove 30 (the wall surface on the side of the blind spot with respect to the light source 4) 30b becomes a relatively dark band-shaped portion D and is easily noticeable.
For this reason, there is a problem that a relatively dark band-shaped portion is easily visually recognized in a region near the light source 4 also on the display screen of the liquid crystal display element 7 using the illumination device 1 as a backlight.

Further, since the rear surface of the light guide 3 hardly rises in the vicinity of the light source 4, the other groove 30 located on the side opposite to the light source 4 is formed by the groove 30 located in the vicinity of the light source 4. A phenomenon occurs in which light traveling toward the inner bottom surface 2a is blocked. As a result, sufficient light may not reach the thin portion of the light guide 3 far away from the light source 4, which is an obstacle in preventing uneven brightness of the light emitting surface 3 a.

The present invention has been made in view of such a situation of the prior art, and an object of the present invention is to solve the problem of uneven brightness of a light emitting surface which is concerned in a region close to a light source and a problem in a region far from the light source. Insufficient light quantity on the light emitting surface
An object of the present invention is to provide an illumination device in which display quality can be easily improved.

[0008]

SUMMARY OF THE INVENTION According to the present invention, among a number of grooves provided on the back surface of a light guide, a groove located near a light source has a rounded groove shape whose wall surface is smoothly continuous. And the depth of the groove is made shallower than the other grooves. That is, when the light from the light source is reflected by the curved wall surface of the neighboring groove, the light spreads greatly toward the light-emitting surface, so that there is no possibility that a dark band-shaped portion appears on the light-emitting surface in front of the groove. Also, if the groove located near the light source is shallow, more light can reach the other groove located on the side opposite to the light source or the inner bottom surface of the reflection case, etc.
Light from the light source can be easily supplied to the light emitting surface far from the light source.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a lighting device according to the present invention, a light guide whose front surface is a light emitting surface and whose back surface is curved by gradually reducing the plate thickness from one side to the other side, and this light guide. A light source disposed opposite to the one side of the light guide, and the light of the light source applied to the inside of the light guide, a plurality of grooves provided on the back surface of the light guide. In the illuminating device, which is reflected on a wall surface and guides the light to the light-emitting surface, the plurality of grooves are located near the light source, and the first wall has a smoothly rounded wall surface, And a second groove having a triangular cross section positioned farther from the light source than the first groove, and the depth of the first groove is shallower than that of the second groove.

As described above, if the groove located near the light source among the grooves provided on the back surface of the light guide is formed as a shallow first round groove, the groove is formed on the side opposite to the light source. Not only the blind spot area is reduced, but also the light of the light source reflected on the wall of the groove can be directed to a wide range of the light emitting surface, so that a dark band corresponding to the blind spot area is formed on the light emitting surface near the light source. There is no fear of appearing. Further, if the first groove close to the light source is shallow, the amount of light traveling toward the opposite side of the light source without being blocked by the groove increases, and it becomes easier to supply the light of the light source to the thin portion of the light guide. Therefore, it is possible to avoid a shortage of light quantity, which is concerned in a region of the light emitting surface far from the light source. Therefore, it is possible to greatly reduce luminance unevenness over the entire area of the light emitting surface.

[0011]

Embodiments will be described with reference to the drawings.
FIG. 1 is a sectional view of an illumination device according to an embodiment, and FIG.
FIG. 4 is an enlarged view showing a portion, and portions corresponding to those in FIGS. 3 and 4 used in the description of the conventional example are denoted by the same reference numerals.

In FIG. 1, an illuminating device generally indicated by reference numeral 10 has a reflective case 2 made of a resin material such as white having a high light reflectivity, a flat light emitting surface 3a on the front surface, and a curved back surface. The light guide 3 is schematically constituted by a light guide 3 mounted on the inner bottom surface 2a of the reflection case 2 and a light source 4 such as a small light bulb mounted on the substrate 5 and irradiating one side of the light guide 3 with light. And is used as a backlight of the liquid crystal display element 7. The shape of the light guide 3 is such that one side where the light source 4 is disposed to face is thick, and the plate thickness gradually decreases as the distance from the light source 4 increases.
The other side is thin. On the back of the light guide 3,
A number of grooves for reflecting light from the light source 4 toward the light emitting surface 3a are provided. Of these, a plurality of first grooves 31 located in the vicinity of the light source 4 include other grooves. The groove shape and the depth of the groove are different from those of the second groove 30. That is, the second groove 30 located at a certain distance from the light source 4
Is formed as a groove having a triangular cross section as in the conventional example, but as shown in FIG.
1 is formed as a rounded shallow groove whose wall surface 31a is smoothly continuous. The dashed line in FIG. 2 indicates a triangle corresponding to the second groove 30, and the first groove 31 has a rounded shape by chamfering a corner of the second groove 30. You can see that it is.

Therefore, when the light L entering from the light source 4 toward the first groove 31 is reflected by the inclined portion of the wall surface 31a on the light source 4 side, the second groove 30
The light L from the light source 4 is directed toward the light-emitting surface 3 a along the same path as that reflected on the light source 4 side wall surface.
Is reflected by the top of the wall surface 31a, and the reflected light changes its course largely to the upper side in the drawing or to the upper right in the drawing. Therefore, the light emitting surface 3a is located behind the first light emitting surface 3a.
Reflected by the top of the wall 31a of the groove 31
A wide area including the front of the blind spot generated on the side opposite to the light source 4 of the groove 31 emits light, and there is no possibility that a dark strip corresponding to the blind spot appears on the light emitting surface 3a.
That is, it is possible to avoid the uneven brightness of the light emitting surface 3a, which has been a concern in a region near the light source 4. The first
Since the groove 31 is a shallow groove and has a small blind spot area with respect to the light source 4, it is possible to reliably cover the front of the blind spot area by the reflected light at the top of the wall surface 31 a of the groove 31.

Further, since the first groove 31 located near the light source 4 is shallow and does not block much the light traveling toward the side opposite to the light source 4, the first groove 31 and the inner bottom surface 2 a of the reflection case 2 are formed. The light from the light source 4 can easily reach. In other words, since the amount of light supplied to the thin portion of the light guide 3 far from the light source 4 increases, the light quantity shortage of the light emitting surface 3a, which has been conventionally concerned in a region far from the light source 4, can be solved.

The upper opening 2b of the reflection case 2 has
A liquid crystal display element 7 is incorporated via a diffusion sheet 6 in a state of being close to the light emitting surface 3a of the light guide 3, and the liquid crystal display element 7 is illuminated from behind by the light emitting surface 3a. Therefore, as described above, the display quality of the liquid crystal display element 7 can be significantly improved by using the illuminating device 10 that can significantly reduce the luminance unevenness over the entire area of the light emitting surface 3a as a backlight. .

[0016]

The present invention is embodied in the form described above, and has the following effects.

Of the many grooves provided on the back of the light guide,
The groove located near the light source is an illuminating device whose wall has a smoothly continuous rounded groove shape and the depth of the groove is shallower than other grooves. When the light is reflected by the curved wall surface of the groove, the light spreads greatly toward the light emitting surface, and there is no possibility that a dark band-shaped portion appears on the light emitting surface in front of the groove. Also, if the groove located near the light source is shallow, more light can reach the other groove located on the side opposite to the light source or the inner bottom surface of the reflection case, so the light emitting surface far from the light source In addition, the light from the light source can be easily supplied, and shortage of the light amount can be avoided. As described above, since the illuminating device can greatly reduce the luminance unevenness over the entire area of the light emitting surface, if the illuminating device is used as a backlight of a liquid crystal display element, the display quality can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an illumination device according to an embodiment.

FIG. 2 is an explanatory diagram showing a portion B in FIG. 1 in an enlarged manner.

FIG. 3 is a cross-sectional view of an illumination device according to a conventional example.

FIG. 4 is an explanatory diagram showing an enlarged portion A of FIG. 3;

FIG. 5 is an explanatory diagram for explaining a problem of the related art.

[Explanation of symbols]

 2 Reflective case 2a Inner bottom surface 3 Light guide 3a Light emitting surface 4 Light source 5 Substrate 6 Diffusion sheet 7 Liquid crystal display element 10 Illumination device 30 Second groove 31 First groove 31a Wall surface

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) // F21Y 101: 02 F21Y 101: 02 F-term (Reference) 2H038 AA55 BA01 2H042 DA11 DC08 DD10 DE04 2H052 BA03 BA09 BA11 2H091 FA14Z FA23Z FA41Z LA18

Claims (1)

[Claims] 1. A light guide having a front surface serving as a light-emitting surface and having a back surface curved by gradually reducing a plate thickness from one side to another side, and facing the one side of the light guide. Disposed on the light guide, the light of the light source emitted to the inside of the light guide is reflected by the wall surfaces of a number of grooves provided on the back surface of the light guide to the light emitting surface. In the illumination device, the plurality of grooves are located near the light source, and the first wall has a smoothly rounded wall surface that is smoothly continuous, and is farther from the light source than the first groove. An illumination device comprising: a second groove having a triangular cross-section positioned at a right angle; and a depth of the first groove is smaller than a depth of the second groove.