JP2003045213A - Plane illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve high luminance by a simple and low cost construction. SOLUTION: A plurality of protrusions (22) are formed on the emitting face (12b) of a light-guiding plate (12) and a semi-spherical face (22a) is formed on the outer face of each protrusion (22). The light reflected at the semi- spherical face (22a) and the light transmitted the semi-spherical face (22a) are turned in the prescribed direction regularly, therefore, scattering of lights does not happen. And since the light emitted from the semi-spherical face (22a) has directivity of inclining to a prescribed angle to the emitting face (12b), almost all the lights that are irradiated to the lens sheet (20) can be modified in the direction crossing the emitting face (12b) at right angles. Thereby, high luminance is achieved as well as it is condensed by the lens sheets (20).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface lighting device used as a backlight for a liquid crystal display panel.

[0002]

2. Description of the Related Art A conventional surface illumination device of this type shown in FIG.
(1) is for illuminating the liquid crystal display panel (A) from the back side and includes a light guide plate (2) having a plurality of dot patterns (2b) printed on the non-light emitting surface (2a). And the light entrance surface (2c) of the light guide plate (2)
The light source (3) and the reflector (4) are arranged in close proximity to the light emitting surface (2) and the reflector (5) is arranged in close proximity to the non-light emitting surface (2a).
On the d) side, the diffuser plate (6), the first lens (7), the second lens (8)
And the diffusion sheet (9) is arranged in this order. The first lens (7) and the second lens (8) have protrusions (7
a) and ridges (8a) are formed.

When the light source (3) is turned on, the light from the light source (3) enters the light guide plate (2) from the light incident surface (2c) directly or through the reflector (4), and the dot pattern (2b). ) Is diffused and emitted from the light exit surface (2d), diffused by the diffuser plate (6), and then directionally corrected by the first lens (7) and the second lens (8). Then, after being further diffused by the diffusion sheet (9), the liquid crystal display panel (A) is irradiated.

[0004]

In the prior art, since a plurality of dot patterns (2b) were used to diffusely reflect light, there was a problem that the loss due to light scattering was large. Therefore, the brightness must be increased by increasing the output of the light source (3) or increasing the number of the light sources (3), which causes a problem that the entire device becomes large and the cost becomes high.

Therefore, a main object of the present invention is to provide a surface illuminating device which can easily achieve high brightness without increasing the size of the device.

[0006]

According to the present invention, there are provided two light entrance surfaces facing each other, a light exit surface orthogonal to the light entrance surface, a plurality of hemispherical surfaces formed on the light exit surface, and a light exit surface. A light guide plate having a non-light emitting surface facing each other, a light source arranged along each of the light incident surfaces, a reflector for reflecting light from the light source to the light incident surface, a light arranged along the non light emitting surface and leaking from the light guide plate. A reflection plate that reflects the emitted light to the light guide plate side, and a plurality of first ridges having a triangular cross section that are arranged along the light exit surface of the light guide plate and that extend parallel to the light entrance surface on the surface facing the light exit surface. It is a surface illuminating device provided with the lens sheet which has.

When the light source is turned on, the light from the light source enters the light guide plate from the light incident surface directly or through the reflector. The light in the light guide plate passes through the wall surface and is emitted to the outside when the incident angle with respect to the wall surface of the light guide plate satisfies a predetermined condition. The light emitted from the non-light emitting surface is reflected by the reflecting plate and returned to the inside of the light guide plate, and the light emitted from the light emitting surface is incident on the lens sheet. The light incident on the lens sheet is rectified by the first ridge in a direction orthogonal to the light exit surface, and this light is applied to the liquid crystal display panel.

Since the light reflected by the hemispherical surface of the light emitting surface and the light transmitted through the hemispherical surface are regularly directed in a predetermined direction, light scattering as in the conventional dot pattern does not occur. In addition, since the light emitted from the hemispherical surface is inclined at a predetermined angle with respect to the light emitting surface and exhibits directivity, almost all of the light incident on the lens sheet is corrected in a direction orthogonal to the light emitting surface. Can be done. Therefore, the brightness is dramatically improved in combination with the light being condensed by the lens sheet.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Referring to FIG. 1, a surface illumination device (10) of an embodiment of the present invention is a backlight for illuminating a liquid crystal display panel (A) such as a TV receiver or a computer display from the back. Used as a light, light guide plate
(12), light source (14), reflector (16), reflector (18) and lens sheet (20).

The light guide plate (12) is made of a light transmissive material such as acrylic resin, and the light incident surface (12a) is formed on the opposite side end faces thereof.
Is formed, and a light emitting surface (12b) is formed on the upper surface (meaning the upper surface in FIG. 1. The same applies hereinafter) and the lower surface (see FIG. 1).
Means the lower surface of. same as below. ), A non-light emitting surface (12c) is formed. Further, a plurality of protrusions (22) are formed on the light emitting surface (12b), and the outer surface of each protrusion (22) is a smooth hemispherical surface.
(22a). The distribution density and size of the protrusions (22) are
The light amount is set to be uniform over the entire surface of the light exit surface (12b). For example, the central portion of the light exit surface (12b) has a high density and a large diameter, and the light density becomes small and small toward the end. The protrusions (22) are formed integrally with the main body portion when the light guide plate (12) is injection-molded.

Then, a light source (14) is provided along each light incident surface (12a).
Are arranged, the reflection plate (18) is arranged along the non-light emitting surface (12c), and the lens sheet (20) is arranged along the light emitting surface (12b). In addition, the reflector (1
6) is placed.

The light source (14) is for irradiating the entire surface of the light incident surface (12a) with light. In this embodiment, one light source is provided for each light incident surface (12a). A cold cathode discharge tube is arranged as the light source (14). As shown in FIG. 2, the output of the light source (14) is set so that the maximum light reaching distance is substantially equal to the distance from the light source (14) to the light incident surface (12a) on the opposite side. This eliminates the waste of light and allows the light to be used efficiently. As the light source (14), a fluorescent lamp or a halogen lamp may be used instead of the cold cathode discharge tube.

The reflector (16) is for reflecting the light from the light source (14) and guiding it to the light incident surface (12a), and is a regular reflection member such as a metal foil or a white PET film. It is formed in a semi-cylindrical shape by such a diffuse reflection member.

The reflection plate (18) is for reflecting the light leaking from the light guide plate (12) toward the light guide plate (12) side, and is formed of a regular reflection member or a diffuse reflection member.

The lens sheet (20) directs light in the direction of the light guide plate (1
It is for correcting in a direction substantially orthogonal to the light emitting surface (12b) of 2), and is formed of a light transmissive material such as acrylic resin. On the lower surface of the lens sheet (20), that is, the surface facing the light exit surface (12b) of the light guide plate (12), a plurality of ridges (20a) having a triangular cross section are provided on the light entrance surface (12a) of the light guide plate (12). The protrusions (20a) are formed so as to extend in parallel to each other, and the direction of light is changed.

On the back surface of the liquid crystal display device (A), a surface lighting device (1
(0) is placed and the light source (14) is turned on, the light from the light source (14) enters the light guide plate (12) from the light incident surface (12a) directly or via the reflector (16) and is guided. It advances while being reflected by the wall surface of the light plate (12). The light inside the light guide plate (12) passes through the wall surface and is emitted to the outside when the incident angle with respect to the wall surface of the light guide plate (12) satisfies a predetermined condition. The light emitted from the non-light emitting surface (12c) is reflected by the reflection plate (18) and returned to the inside of the light guide plate (12), and the light emitted from the light emitting surface (12b) passes through the lens sheet (20). LCD panel (A) after the orientation is corrected
Is irradiated.

Since the light reflected by the hemispherical surface (22a) of the projection (22) formed on the light emitting surface (12b) and the light emitted from the hemispherical surface (22a) are regularly oriented in a predetermined direction, No loss due to light scattering occurs on the hemisphere (22a). Further, as shown in FIG. 3 (A), the light emitted from the hemispherical surface (22a) has a predetermined angle (about 7 degrees) with respect to the light emitting surface (12b).
The lens sheet (20)
Almost all of the light incident on can be redirected in a direction orthogonal to the light exit surface (12b). Therefore, high brightness is achieved in combination with the light being condensed by the lens sheet (20).

The light incident on the lens sheet (20) is condensed in a direction (hereinafter referred to as "X direction") orthogonal to the ridge (20a) as shown in FIG. Since the light is not condensed in the parallel direction (hereinafter referred to as “Y direction”), when this light is applied to the liquid crystal display panel (A), the viewing angle becomes narrow in the X direction (A) and the wide viewing angle in the Y direction. It becomes a corner (B).

According to this embodiment, high brightness can be easily achieved without increasing the output of the light source (14) or increasing the number of light sources (14). Therefore, if the brightness is the same, the light source (14) can be downsized, and the area lighting device (1
0) can be downsized and the cost can be reduced.

Another embodiment of the surface illumination device (24) shown in FIG.
Is an improvement of the surface illumination device (10) of the embodiment of FIG. In this surface lighting device (24), the non-light emitting surface of the light guide plate (12) is
A plurality of ridges (hereinafter referred to as “second ridges”) (12d) extending in a direction orthogonal to the light incident surface (12a) are further formed in (12c), and the upper surface of the lens sheet (20), that is, A diffusion sheet (26) is arranged along the light emitting surface. The ridge (hereinafter referred to as the "first ridge") (20a) of the lens sheet (20) is a light-incident surface.
Since it is formed so as to extend parallel to (12a), the first protrusion
(20a) and the second protrusion (12d) are orthogonal to each other. However, the respective second protrusions (12d) may be formed continuously with each other or may be formed intermittently.

In this surface illumination device (24), the light incident on the light guide plate (12) is condensed in the Y direction by the ridges (12d). Then, this light is output under a predetermined condition.
The light is emitted from (12b), and is applied to the liquid crystal display device (A) through the lens sheet (20) and the diffusion sheet (26). Since the lens sheet (20) collects light in the X direction as described above, in this embodiment, the viewing angle is narrow in both X and Y directions, and the luminance in the direction orthogonal to the light exit surface (12b) is obtained. Is more enhanced. When the light transmitted through the lens sheet (20) is incident on the diffusion sheet (26), the directivity of the light is relaxed and the intensity of the light is made uniform over the entire surface of the diffusion sheet (26).

Another embodiment of the surface illumination device (28) shown in FIG.
4 is an improvement of the surface illumination device (24) of FIG. 4 embodiment, in which a reflective polarizing film (30) is further arranged along the light exit surface of the lens sheet (20). Reflective Polarizing Film (30)
Has a function of transmitting one polarization component (P-polarization wave or S-polarization wave) of the incident light and reflecting the other polarization component (S-polarization wave or P-polarization wave). Therefore,
From the reflective polarizing film (30), as shown in FIG.
Only one of the polarized wave and the S-polarized wave is emitted in a superimposed form, and the brightness in the direction orthogonal to the light exit surface (12b) is further increased.

In each of the above embodiments, the light exit surface (12b)
A plurality of protrusions (20) are formed on the
(20a), instead of this, a plurality of holes may be formed in the light output surface (12b) and the inner surface of each hole may be a hemispherical surface. Even in this case, the light can be regularly directed in the predetermined direction, so that the light can be prevented from being scattered and the brightness can be increased.

[0024]

Since the hemispherical surface regularly reflects and transmits light, it is possible to prevent loss due to light scattering. Further, since the hemispherical surface can be integrally formed with the main body portion of the light guide plate, it is not necessary to separately prepare special parts. Therefore, it is possible to easily achieve high brightness without increasing the cost, and it is possible to easily meet the demand for a larger screen.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the distance from a light source and the amount of light.

FIG. 3 is an illustrative view showing a state of light transmitted through a hemispherical surface and a lens sheet.

FIG. 4 is a perspective view showing another embodiment of the present invention.

FIG. 5 is a perspective view showing another embodiment of the present invention.

FIG. 6 is an illustrative view showing a state in which one component of light is superimposed in the embodiment of FIG. 5;

FIG. 7 is a perspective view showing a conventional technique.

[Explanation of symbols]

(A) ... Liquid crystal display panel (10), (24), (28) ... Surface lighting device (12) ... Light guide plate (12a) ... Light incident surface (12b) ... Idemitsu side (12c) ... Non-light emitting surface (12d) ... ridge (14)… Light source (16)… Reflector (18) ... Reflector (20)… Lens sheet (20a) ... Ridge (22)… Protrusion (22a) ... hemisphere (26)… Diffusion sheet (30) ... Reflective polarizing film

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02F 1/1335 520 520 1/13357 1/13357 // F21Y 103: 00 F21Y 103: 00 ( 72) Inventor Yusumi Taguchi 3-7-17 Nitta-Cho, Niihama, Niihama, Ehime Prefecture Nihon Chemtech Co., Ltd. (72) Inventor Nozomi Mito 3-7-17 Nitta-cho, Niihama, Ehime Nikko Chemtech Co. (72) Inventor Masaya Suzuki 3-7-17 Nitta-cho, Niihama-shi, Ehime F-Term in Nihon Chemitec Corporation (reference) 2H042 BA04 BA12 BA14 BA20 2H091 FA14Z FA23Y FA26X FA41Z LA30

Claims (5)

[Claims] 1. Two light entrance surfaces facing each other, a light exit surface orthogonal to the light entrance surface, a plurality of hemispherical surfaces formed on the light exit surface, and a non-light exit surface opposed to the light exit surface. A light guide plate having, a light source arranged along each of the light entrance surfaces, a reflector for reflecting light from the light source to the light entrance surface, and a light guide plate arranged along the non-light exit surface and leaking from the light guide plate. A plurality of triangular sections, which are arranged along the light exit surface of the light guide plate and reflect the emitted light to the light guide plate side, and which extend in parallel to the light entrance surface on the surface facing the light exit surface. A surface illumination device comprising a lens sheet having a first ridge. 2. A plurality of second ridges each having a triangular cross section orthogonal to the first ridges are formed on the non-light emitting surface, and a diffusion sheet is arranged along the light emitting surface of the lens sheet. The planar lighting device according to claim 1. 3. The reflection type polarizing film which transmits one polarization component of the light from the lens sheet and reflects the other polarization component is arranged along the light emitting surface of the lens sheet. Surface lighting device. 4. The plurality of protrusions are formed on the light emitting surface, and the outer surface of the protrusion is the hemispherical surface.
4. The surface illumination device according to any one of 3 to 3. 5. The surface lighting device according to claim 1, wherein a plurality of holes are formed in the light output surface, and an inner surface of the hole is the hemispherical surface.