JP2001332114A - Surface lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface lighting device applicable to a front light and the like of high brightness and capable of reducing thickness. SOLUTION: This surface lighting device includes a light guide plate 2 that introduces light from an outside and after forming a micro prism 2c on an observation surface, irradiates light to opposite side of the observation surface. The light guide plate 2 is formed of a luminous part 2b forming the micro prism 2c and an introduction part 2a projecting obliquely downward in line with the luminous part 2b. A light source unit 3 is arranged on a side surface of the introduction part 2a and a diffusion layer 2d diffusing light from the light source unit 3 and entering it into the luminous part 2b is formed on an upper surface of the introduction part 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface illumination device used for a front light or the like which can be suitably used for a reflection type color liquid crystal display.

[0002]

2. Description of the Related Art In recent years, a color liquid crystal display has been used for a display portion of a cellular phone or the like. However, a backlight is eliminated to reduce power consumption and to reduce the weight and thickness of the display. There is a movement to cope with the combination of the front lighting type surface lighting device. This front-light type surface illumination device is basically the same as the conventional backlight in that surface emission is performed, and there is, for example, one described in Japanese Patent Application Laid-Open No. 11-184386.

In the front light type surface illumination device described in the above-mentioned publication, chip-type LEDs are arranged so as to face one end side of a surface-emitting light guide plate, and light from these LEDs is transmitted to the light guide plate. The light is made to enter from the end face, and light is irradiated to the liquid crystal panel side by a microprism formed on the emission observation surface side of the light guide plate. Then, a diffusion layer is arranged between the LED and the end face of the light guide plate so that the light is uniformly diffused from the LED and enters the light guide plate. In such a configuration, even if the LED is a point light source, since the LED is provided with a diffusion layer, a linear light is radiated from the LED in a direction perpendicular to the groove of the microprism and the liquid crystal looks non-uniform. And a substantially uniform surface illumination device can be realized.

[0004]

However, in a configuration having a diffusion layer between the LED and the light guide plate, light from the LED passes through the diffusion layer from the air layer to the air layer again, and the light is introduced into the light guide plate. Is done. In this case, since the light from the LED is attenuated in the air layer, the efficiency of light incidence on the light guide plate decreases, and the light emission luminance of the light guide plate also decreases.

It is natural that the larger the area of light incident from the LED to the light guide plate, the higher the luminance. However, since the light incident surface is the end surface of the light guide plate, the only way to increase the area of this end surface is to increase the thickness of the light guide plate. Accordingly, there is a problem that the light guide plate becomes thick and cannot be made thinner when combined with a liquid crystal display panel or the like.

An object of the present invention is to provide a surface illumination device which can be applied to a front light or the like which has a high light emission luminance and can be made thin.

[0007]

According to the present invention, there is provided a surface illuminating apparatus including a light guide plate which receives light from the outside, forms a microprism on an observation surface, and irradiates light on the side opposite to the observation surface. The light plate is formed from a light emitting portion having the microprism formed therein and an introduction portion projecting obliquely downward in connection with the light emitting portion, and a light source unit is disposed on a side surface of the introduction portion, and the light source unit is disposed on an upper surface of the introduction portion. A diffusion layer for diffusing light from the light source unit and guiding the light to the light emitting unit is formed.

According to the present invention, it is possible to obtain a surface illuminating device which has a high emission luminance and can be made thin.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention according to a first aspect of the present invention relates to a surface illuminating device including a light guide plate for introducing light from the outside, forming a microprism on an observation surface, and irradiating light to the opposite side to the observation surface. The light guide plate is formed from a light emitting unit on which the microprism is formed and an introduction unit protruding obliquely downward connected to the light emission unit, and a light source unit is disposed on a side surface of the introduction unit, and A surface illumination device, wherein a diffusion layer that diffuses light from the light source unit and guides the light to the light emitting unit is formed on an upper surface, and the diffusion layer covers a wide area of an upper surface of the introduction unit that protrudes obliquely downward. Can be formed, the light from the light source unit can be sufficiently reflected and refracted to be introduced into the light emitting section, and the luminance of the light emitting section can be increased.

[0010] According to a second aspect of the present invention, the diffusion layer includes:
2. The surface lighting device according to claim 1, wherein the light source unit has a substantially triangular planar shape whose width increases as the width near the light source unit decreases. There is an effect that the light can be led to the inside, that is, to the light emitting portion, and light of uniform luminance can be obtained.

According to a third aspect of the present invention, there is provided the surface illuminating device according to the first or second aspect, wherein the periphery of the introduction portion is covered with a reflection cover with an air layer interposed therebetween. Since the light that escapes outside can be collected by the reflection cover and made incident on the light emitting unit, the brightness of the light emitting unit can be further improved.

According to a fourth aspect of the present invention, the light source unit comprises an LED buried on a side surface of the introduction portion and a flexible substrate conductively mounting the LED. The surface lighting device described in the above item (1), wherein the LED is embedded in the light guide plate, so that the efficiency of light incidence on the introduction portion can be increased, and the brightness of the light emitting portion is increased.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a side view showing an example in which the surface illumination device of the present invention is provided as a front light of a reflection type liquid crystal display panel, and FIG. 2 is a front view as viewed from a light emission observation surface side.

As shown in FIG. 1, a reflection plate 22 is arranged on the back side of a liquid crystal display panel 21 in which liquid crystal is sealed, and a surface illumination device 1 of a front light type is arranged on the front side. This surface illumination device 1 mainly includes a light guide plate 2 formed of a transparent acrylic resin, and has an LED on one side surface.
Is provided with the light source unit 3 in which is embedded.

The light guide plate 2 includes an introduction portion 2a into which light from the light source unit 3 is introduced, and a light emitting portion 2b formed to be continuous with the introduction portion 2a and covering the surface of the liquid crystal display panel 21. The light emitting unit 2b forms a microprism 2c on the light emission observation surface side, and irradiates light toward the liquid crystal display panel 21 using reflection and refraction by the microprism 2c. The microprism 2c has, like a conventional light guide plate for a front light, a scalene triangular wave shape having a peak angle of about 165 °, a peak height of about 7 μm, and a pitch of about 300 μm, for example. It was done.

The introduction part 2a is inclined obliquely downward with respect to the flat light emitting part 2b, and a diffusion layer 2d is formed on the surface side. The diffusion layer 2d is formed by silk printing or pasting a reflection sheet, and diffuses light from the light source unit 3 and makes the light enter the light emitting unit 2b. Diffusion layer 2
d has an elongated triangular planar shape whose width is narrower near the light source unit 3 and becomes wider as the distance from the light source unit 3 increases. Further, since the introduction part 2a is inclined and the diffusion layer 2d is formed on the surface thereof, the area of the diffusion layer 2d can be made larger than when the introduction part 2a is not inclined, and the light source unit 3 Can be sufficiently diffused to be incident on the light emitting section 2b.

Further, a light source unit 3 is provided around the introduction portion 2a.
Are covered by the reflective cover 4 except for the end face where the. The reflection cover 4 is made of a material having a high reflectance such as white resin, aluminum, or stainless steel.
Are arranged with the interposition.

In the above configuration, when the LED included in the light source unit 3 emits light, it is incident on the introduction section 2a.
Since the diffusion layer 2d is formed on the surface of the introduction section 2a, light is uniformly introduced into the light emitting section 2b from the entire introduction section 2a. Here, assuming that the diffusion layer 2d is not formed in a slender triangular shape as shown in the figure but is formed on the surface of the introduction portion 2a as a uniform width, the brightness near the light source unit 3 is high, and the light source unit 3 Since the luminance decreases as the distance from the light guide plate 2 increases, uneven diffused light enters the inside of the light guide plate 2, that is, the light emitting portion 2b. On the other hand, by forming the elongated triangular diffusion layer 2d as in the present embodiment, the degree of diffusion increases as the distance from the light source unit 3 increases, so that the amount of light incident on the light emitting unit 2b is reduced. The light can be made to enter the light emitting unit 2b as substantially uniform light from a portion close to the unit 3 to a portion far from the unit 3.
Therefore, the light emitting section 2b can irradiate the liquid crystal display panel 21 with uniform light emission luminance without generating a local bright line.

Further, by providing the reflection cover 4, light that is going to escape from the introduction portion 2a is collected by reflection, and a decrease in light emission luminance is suppressed. Here, if the configuration is such that the reflection cover 4 comes into close contact with the surface of the introduction section 2a, the reflection cover 4 plays the same role as the diffusion layer. For this reason, the brightness decreases in a portion where the brightness near the light source unit 3 side is high and far away.
On the other hand, since the reflection cover 4 is arranged via the air layer 5, the reflection cover 4 does not function as a diffusion layer, and reflects light that is going to escape from the introduction part 2a toward the light emitting part 2b. Therefore, the light emitting portion 2b can emit light with uniform luminance by the elongated triangular distribution of the diffusion layer 2d, and at the same time, the light emission luminance can be increased by collecting the light by the reflection cover 4.

As described above, in the present embodiment, the diffusion layer 2d is formed over a wide area on the surface of the introduction portion 2a inclined with respect to the flat light-emitting portion 2b. Light incidence is performed more efficiently. Since the diffusion is promoted without increasing the thickness of the light guide plate 2, the overall thickness when combined with the liquid crystal display panel 21 can be suppressed, and the thickness can be sufficiently reduced.

FIG. 3 is a plan sectional view of a main part showing another embodiment of the light source unit.

The light source unit in the illustrated example includes an LED 6a conductively mounted on a flexible substrate 6 and an introduction portion 2a.
Is embedded in a concave portion 2a-1 formed on an end surface of the substrate and sealed with a sealing resin 6b such as epoxy.

With such a light source unit, an LED
6a is incorporated in the light guide plate 2, so that the LED 6
The light from a can be made incident on the introduction section 2a without interposing an air layer. For this reason, the incident efficiency from the LED 6a is improved, and the light emission luminance of the light emitting unit 2b can be increased. Further, since the flexible substrate 6 is used, the overall bulk is reduced, so that not only a reduction in thickness but also a reduction in size can be achieved.

Although the above embodiment has been described as a front light for irradiating a liquid crystal display panel, it can also be used as a thin illuminating device for displaying a picture, a poster, or the like.

[0026]

According to the present invention, since the introduction portion is projected obliquely downward and connected to the flat light emitting portion of the light guide plate to form a diffusion layer on the upper surface thereof, the diffusion layer can be formed without increasing the thickness of the light guide plate. Can be formed widely. Therefore, since the light from the light source unit can be sufficiently diffused and introduced into the light emitting unit, the light emission luminance of the light emitting unit can be increased, and the overall bulk can be reduced even when used as a front light of a liquid crystal display panel or the like. be able to. Also, optimize the planar shape of the diffusion layer,
By providing a reflection cover around the introduction section or burying an LED as a light source unit in the introduction section, the luminance of the light emitting section can be further improved.

[Brief description of the drawings]

FIG. 1 is a side view showing an example in which a surface lighting device of the present invention is arranged as a front light of a liquid crystal display panel.

FIG. 2 is a front view of the light guide plate viewed from its light emission observation surface side.

FIG. 3 is a plan cross-sectional view of a main part showing an example in which an LED is incorporated in an introduction part of a light guide plate.

[Explanation of symbols]

 1 surface illumination device 2 light guide plate 2a introduction unit 2b light emitting unit 2c micro prism 2d diffusion layer 3 light source unit 4 reflection cover 5 air layer 6 flexible substrate 6a LED 6b sealing resin 21 liquid crystal display panel 22 reflection plate

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02B 5/08 G02B 5/08 B 6/00 331 6/00 331 G02F 1/13357 G09F 9/00 336B G09F 9/00 336 F21Y 101: 02 // F21Y 101: 02 G02F 1/1335 530 F term (reference) 2H038 AA52 AA55 BA06 2H042 BA03 BA20 CA12 DD01 2H091 FA14X FA14Y FA21X FA23X FA31X FA45X FD05 LA11 5G435 FB0312 FF08 GG03 GG23 LL07 LL08

Claims (4)

[Claims] 1. A surface illumination device including a light guide plate for introducing light from the outside to form a microprism on an observation surface and irradiating light to a side opposite to the observation surface, wherein the light guide plate is formed with the microprism. Formed from a light-emitting part and an introduction part projecting obliquely downward in connection with the light-emitting part, the light source unit is arranged on the side surface of the introduction part, and light from the light source unit is diffused on the upper surface of the introduction part. And a diffusion layer for guiding light to the light emitting portion. 2. The surface lighting device according to claim 1, wherein the diffusion layer has a substantially triangular planar shape whose width on the side closer to the light source unit is narrower and wider. 3. A reflection cover is provided around the introduction section with an air layer interposed therebetween.
Or the surface lighting device according to 2. 4. The surface lighting device according to claim 1, wherein the light source unit includes an LED embedded in a side surface of the introduction section and a flexible substrate in which the LED is electrically mounted. .