JP2003115209A - Linear lighting system and planar lighting system using linear light guide body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear lighting system relieving high luminance and luminance irregularity and to provide a planar lighting system using it. SOLUTION: In this linear lighting system, point-like light sources 3, 3 are disposed on light entering surfaces 21 and 23 of a linear light guide body 2, and linear light is emitted from a light emitting surface 24 perpendicular to or nearly perpendicular to the entering surfaces 21 and 23 of the guide body 2. The linear lighting system is characterized by forming a diffraction pattern 22a formed by setting the cross section of one pattern asymmetrical on at least one surface 22 of the guide body 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear lighting device and a planar lighting device using a linear light guide for converting a point light source into a linear light source.

[0002]

2. Description of the Related Art In recent years, techniques for reducing the weight, size and power consumption of electronic equipment have been remarkably developed. In the flow of this technology, by using a non-emissive display device typified by a liquid crystal display device, electronic devices have been reduced in weight, size, and power consumption.

The liquid crystal display device is classified into a transmissive type and a reflective type. The transmissive liquid crystal display device is provided with an illuminating device for illuminating the liquid crystal display device from the back side, that is, a so-called backlight, and the reflective liquid crystal display The device is provided with a lighting device that illuminates the liquid crystal display device from the front side, that is, a so-called front light.

An edge light type light guide plate used as a light source for a liquid crystal display device is widely used because the thickness of the light guide plate can be reduced and the structure can be simplified.

In the above lighting device, a cold cathode tube lamp is used at the end of the planar light guide plate, but from the viewpoint of low power consumption, the light emitting diode (LED) consumes less power than the cold cathode tube lamp. ) One using a point light source such as a light source has been put into practical use.

When a plurality of LED chips are arranged at the end of the planar light guide plate, there is a problem that firefly-like unevenness and light streaks are generated in the vicinity of the LED chips. Therefore, a linear illumination device that converts a point light source such as an LED into a linear light source using a light guide has come to be used.

A linear illumination device for converting a point light source such as a light emitting diode (LED) light source into a linear light source by a light guide is known as shown in FIG. This linear lighting device includes both end face portions 211 of a linear light guide 210,
Point light sources 250, 250 are arranged at 211. Then, a method of forming a plurality of, for example, V-shaped grooves 225 in the longitudinal direction of the linear light guide 210 on the reflecting surface 216 facing the light emitting surface 213 on one side in the longitudinal direction of the light guide 210 is described. Are known. The linear light guide 210 has a light emitting surface 21.
3, the reflecting surface 216 and both side surfaces 212 orthogonal to these surfaces,
It is configured in a square pole shape with 215.

In this system, a part of the light rays that have entered the linear light guide 210 from the point light source 250 is a slope 22 of the V-shaped groove 225 provided directly on the reflecting surface 216.
6 and reaches the light emitting surface 213 by being reflected by the slope 226.
Reaches the light emitting surface 213 at an angle equal to or less than the critical angle of
Emit from 13. Further, another part of the incident light ray is repeatedly reflected until the angle between the light emitting surface 213 and the reflecting surface 216 becomes equal to or less than the critical angle. In this principle, V
By setting the distribution of the pitch or depth of the V-shaped groove 225 to an appropriate value, the light quantity distribution of the light emitted from the light emitting surface 213 can be made substantially uniform, and as a result, a linear light source can be obtained. .

Japanese Unexamined Patent Publication No. 2000-11723 discloses a planar illumination device that uses a light source composed of a point light source and a linear light guide as a linear light source of an illumination device of a liquid crystal display device. There is.

In the light source described in this publication, a point light source is arranged close to the end portion of the light guide on which the optical path changing means is formed. The optical path changing means is composed of, for example, groove portions having a substantially triangular cross section and flat portions formed between the groove portions. As one example of the optical path changing means, the gap between one groove and the adjacent groove is constant,
It is shown that the cutting depth of the groove is set so as to gradually increase as the distance from the point light source increases. Further, as another example of the optical path changing means, there is shown one in which the groove is formed so that the cutting depth is constant and the interval for forming the groove is gradually narrowed as the distance from the point light source increases. Has been done.

Further, the planar illumination device described in this publication uses a light source having two point light sources in which two point light sources are arranged close to each other at both ends of a linear light guide. There is shown that the surface of the light guide body is arranged so as to face the one end surface of the transparent substrate.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Japanese Patent No. 11723 discloses a method of converting a point light source into a linear light source using a rod-shaped light guide,
In order to reduce uneven brightness and the like, a reflective pattern such as a V-shaped groove is provided on one surface of the linear light guide. However, in the configuration in which only a reflection pattern such as a V-shaped groove is provided,
The uneven brightness could not be sufficiently eliminated.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a linear illumination device and a planar illumination device that can achieve high brightness and eliminate uneven brightness.

[0014]

According to the linear lighting device of the present invention, a point light source is arranged on a light entrance surface of a linear light guide, and the light entrance surface of the linear light guide is orthogonal to or substantially equal to the light entrance surface. In a linear illumination device that emits linear light from orthogonal light emitting surfaces, a diffraction pattern in which a cross section of one pattern is asymmetric is provided on at least one surface of the linear light guide. To do.

It is preferable that a reflection type diffraction pattern is provided on a reflection surface of the linear light guide facing the light exit surface.

Further, it is preferable to provide a transmission type diffraction pattern on the light entrance surface of the linear light guide.

Further, according to the present invention, point light sources are arranged at both ends of the linear light guide, and whether the diffraction pattern has a smaller diffraction pitch or a shallower depth as the distance from the point light source increases. Is set to at least one of the above, and the diffraction pitch becomes smaller as the distance from the point light source increases, the linear light guide is formed so as to have a minimum at approximately the center, and the depth of the diffraction pitch increases as the distance from the point light source increases. In the case of shallower depth, it is preferable that the linear light guide is formed so as to have the minimum depth at the approximate center thereof.

The planar lighting device of the present invention is constructed by disposing the above-mentioned linear lighting device near the side surface of a planar light guide plate made of a translucent material.

Further, in the surface illumination device of the present invention, a light entrance surface on which the light from the point light source is incident is provided on the side surface side of the surface light guide plate, and the light entrance surface is reflected orthogonally or substantially orthogonally to the light entrance surface. A surface is provided, a transmissive diffraction pattern in which the cross section of one pattern is asymmetrical is provided on the light entrance surface, and a reflective diffraction pattern in which the cross section of one pattern is asymmetrical is provided on the reflective surface. The light incident from the light incident surface is guided to the reflection surface side by the transmission type diffraction pattern, and is converted into linear light by the reflection type diffraction pattern of the reflection surface to guide the light into the planar light guide plate. Characterized by giving guidance.

A planar light guide plate made of a translucent material and a planar lighting device in which a lighting device composed of a plurality of point light sources is arranged near the light entrance surface of the planar light guide plate. A planar illuminating device characterized in that a diffraction pattern in which the cross section of one pattern is asymmetric is provided on all or part of the light surface.

A diffractive pattern having a non-symmetrical cross section may be provided on the surface of the light guide plate facing the light exit surface.

As described above, the point light source can be efficiently converted into the linear light source by using the linear light guide having the diffraction pattern in which one pattern cross section is asymmetrical. Can be improved.

Further, unevenness in brightness can be improved by providing a diffraction pattern in which one pattern cross section is asymmetrical on a part or all of the light entrance surface of the planar light guide plate and controlling the direction of light. it can.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. 1 is an exploded perspective view of a planar lighting device according to an embodiment of the present invention, FIG. 2 is a perspective view of a linear lighting device according to an embodiment of the present invention, and FIG. 3 is a linear lighting according to an embodiment of the present invention. 4 is a plan view of the apparatus, FIG. 4 is a schematic view showing a conventional symmetrical diffraction pattern, FIG. 5 is a schematic view showing a non-symmetrical diffraction pattern used in the present invention, and FIG. 6 is a schematic view showing a diffraction state by a diffraction grating. Yes, (a) shows the diffraction state when the target diffraction pattern is used, and (b) shows the diffraction state when the non-target diffraction pattern is used.

The planar lighting device according to the present invention mainly includes a planar light guide plate 1, a linear light guide 2, a point light source 3 including an LED chip, and a light source reflection plate 4. Consists of

The planar light guide plate 1 is formed of a transparent member such as transparent acrylic resin or polycarbonate resin in a substantially flat plate shape, and is a linear light source so as to face one end surface thereof. The linear light guide 2 is provided. Further, on the side opposite to the light guide plate 1 of the linear light guide 2, the linear light guide 2 and the point light source 3 are substantially U-shaped in cross section so as to substantially cover the non-light guide plate side, and the inner surface side is highly reflective. The light emitted from the linear light guide 2 in a direction other than the end face of the light guide plate 1 is used as the light guide plate 1.
The light source reflection plate 4 is arranged so as to be reflected by the end face of the light guide plate 1 and guided to the inside of the light guide plate 1.

The linear light guide 2 of this embodiment has a quadrangular prism shape, and as shown in FIGS. 2 and 3, the first light entrance surface 21,
A second light entrance surface 23, a first light entrance surface 21, a light exit surface 24 of light formed on one side surface in the longitudinal direction orthogonal to the second light entrance surface 23,
It has a reflecting surface 22 facing the light emitting surface, a light emitting surface 24, and surfaces 25 and 26 orthogonal to the reflecting surface 22. The height (H) of the linear light guide 2, that is, the distance between the surfaces 25 and 26 is smaller than the width (W), that is, the distance between the surfaces 22 and 24. Also. In FIG. 2, L indicates the length of the linear light guide 2, that is, the distance in the longitudinal direction of the light output surface 24.

A first point light source 3 such as an LED chip is arranged near the first light incident surface 21, which is one end surface portion of the linear light guide 2, and the other end surface portion is the first point light source 3. 2 incident surface 2
A second point light source 3 is arranged in the vicinity of 3.

At least one surface of the linear light guide 2 is provided with a diffraction pattern in which the cross section of one pattern is asymmetric. This diffraction pattern is a reflection type diffraction pattern, and is set to at least one of a smaller diffraction pitch and a smaller depth as the distance from the point light source 3 increases. Then, when the diffraction pitch becomes smaller as the distance from the point light source 3 increases, the linear light guide 2 is formed so as to have a minimum at almost the center, and the depth of the diffraction pitch becomes shallower as the distance from the point light source 3 increases. In such a case, the linear light guide 2 is formed so that the depth of the linear light guide 2 is at the minimum.

In this embodiment, the reflecting surface 22 facing the light emitting surface 24 is provided with a diffraction pattern 22a in which the cross section of the above-mentioned one pattern is asymmetrical.
Further, although not shown, the linear light guide 2 is provided with a transmission type diffraction pattern. This diffraction pattern is also a diffraction pattern in which the cross section of the above-mentioned one pattern is asymmetrical. That is, in this embodiment, a reflection type diffraction pattern and a transmission type diffraction pattern are provided. The diffraction pattern 22a is formed into a non-diffraction pattern whose cross section is as shown in FIG.

As shown in FIG. 3, the light emitted from the point light source 3 enters the linear light guide 2 through the light entrance surface 21 and the light entrance surface 23, and is guided by the diffraction pattern 22a. Light output surface 2
4 is diffracted in a direction substantially perpendicular to the light, and the light is emitted from the light emitting surface 24.

As described above, the light entrance surface 21 of the linear light guide 2 is
The light from the point light source 3 that has entered from
The emission direction is efficiently controlled by a and is diffracted, so that the emission surface 2
The light is emitted from No. 4 without uneven brightness.

4 and 5 show examples of diffraction patterns.
FIG. 4 is a conventional symmetrical diffraction pattern, and FIG. 5 is an asymmetrical diffraction pattern used in the present invention. In the case of the symmetrical diffraction pattern, as shown in FIG. 6A, multi-order diffraction occurs and the diffraction efficiency is poor. Therefore, in this embodiment, an asymmetrical pattern as shown in FIG. 5 is used to optimize the depth to improve the diffraction efficiency. Figure 6 (b)
As shown in, in the case of the asymmetric pattern, the diffracted light of a desired order can be concentrated.

As for the diffraction pattern, at least one of the diffraction pitch becomes smaller and the depth becomes smaller as the distance from the light source increases. As shown in FIG. 3, when the point light sources 3 are arranged at both ends of the linear light guide 2, the diffraction pattern 22a has a minimum diffraction pitch at approximately the center in the length direction of the linear light guide 2. Or the depth is minimized.

Next, another embodiment of the present invention will be described with reference to FIG.
Will be described with reference to. The embodiment shown in FIG. 7 has a white LE
A plurality of point light sources 31 made of D or the like are installed on the substrate 30, and the light sources are arranged close to the end 11 of the planar light guide plate 1. When a light source provided with a plurality of point light sources 31 is arranged at the end of the light guide plate 1 so that light is incident, as shown in FIG. 8, the space between the point light sources 31, 31 becomes dark and the dark portion 1a becomes dark. Occurs.

Therefore, in the embodiment shown in FIG.
The diffraction pattern 11a is formed on the end portion 11 of the light guide plate 1 on which light is incident from the point light source 31. With this diffraction pattern 11a, it is possible to convert a point light source into a line light source on the light incident surface.
It is possible to eliminate the occurrence of the dark portion 1a as shown in FIG. The diffraction pattern 11a may be provided on the entire surface of the end 11 which is the light incident surface as shown in FIG. 7, or may be provided on only a part thereof. When only a part is applied, it is effective to form a diffraction pattern at a portion corresponding to the dark portion 1a shown in FIG.

Next, still another embodiment of the present invention will be described with reference to FIG. The embodiment shown in FIG.
The point light sources 3 and 3 are arranged on both end portions 21 and 23 of the linear light guide 2, and the transmission type diffraction pattern 21a is applied to the end portions on which the light is incident from the point light source 3 respectively. Has been done. Further, the reflective surface 22 of the linear light guide 2 is provided with a reflective diffraction pattern 22a. By providing the diffraction pattern in two stages in this way, the diffraction can be controlled more efficiently.

FIG. 10 shows a different embodiment of the present invention. In the embodiment shown in FIG. 10, the linear light guide is eliminated, and the light from the point light sources 3 is converted into linear light only by the planar light guide plate 1a, and the planar light guide plate 1a is provided with a light exit surface 15. The light is emitted from the light emitting surface 15 by repeating reflection with the reflecting surface 14. Therefore, both side surfaces 11 of the planar light guide plate 1a,
Transmission type diffraction patterns 11a and 13a in which the cross section of one pattern is asymmetrical are provided on the end side of 13.
The spots on which the transmission type diffraction patterns 11a and 13a are provided serve as a light entrance surface, and the point light sources 3 and 3 are arranged respectively. Since the rear end face 12 that is orthogonal or substantially orthogonal to the light incident face has a function as a reflecting face,
A reflective diffraction pattern 12a is provided in which the cross sections of the two patterns are asymmetric.

Transmission type diffraction pattern 11 from point light sources 3 and 3
The light incident through a and 13a is transmitted through the transmission type diffraction pattern 1
The emission direction is efficiently controlled by 1a and 13a and is diffracted and given to the reflection type diffraction pattern 12a of the end face 12. Then, the emitting direction is efficiently controlled by the reflection type diffraction pattern 12a, and the light is diffracted as linear light to form the light guide plate 1a.
Light is given inside. The linear light is repeatedly reflected in the planar light guide plate 1a between the light emitting surface 15 and the reflecting surface 14, and the light emitting surface 1
Light is emitted from 5.

FIG. 11 shows still another embodiment. In the embodiment shown in FIG. 11, in addition to the structure of the embodiment shown in FIG. 7, the reflecting surface 14 of the light guide plate 1 is provided with an asymmetrical diffraction pattern 14a as shown in FIG. In this way, by providing the diffraction pattern 14a on the reflection surface 14,
The light emitted from the light guide plate 1 can be efficiently controlled, and uneven brightness and the like can be eliminated.

In the planar lighting device shown in FIGS. 1, 9 and 10, by applying an asymmetric diffraction pattern to the reflection surface of the light guide plate 1 facing the light exit surface, as in FIG. Similarly, the light emitted from the light guide plate 1 can be efficiently controlled.

As the material of the linear light guide 2, acrylic resin or polycarbonate resin is used, but a light guide containing a scattering material may be used.

Further, in the planar lighting device shown in FIG. 1, the light source reflection plate 4 is provided. However, by applying silver or aluminum plating to the reflection surface of the linear light guide 2, It is also possible to omit the reflector 4.

In the above embodiment, the point light sources are provided on both end faces of the light guide and the light guide plate, but they may be provided only on one end face.

[0045]

As described above, according to the present invention, by forming a diffraction pattern in which the cross section of one pattern is asymmetric on the surface of the rod-shaped light guide or the planar light guide plate, It is possible to provide a lighting device in which the emission direction can be efficiently controlled, and high brightness and uneven brightness can be eliminated.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a planar lighting device according to an embodiment of the present invention.

FIG. 2 is a perspective view of the linear lighting device according to the embodiment of the present invention.

FIG. 3 is a plan view of the linear lighting device according to the embodiment of the present invention.

FIG. 4 is a schematic diagram showing a conventional symmetrical diffraction pattern.

FIG. 5 is a schematic diagram showing an asymmetric diffraction pattern used in the present invention.

FIG. 6 is a schematic diagram showing a diffraction state by a diffraction grating,
(A) shows the diffraction state when a target diffraction pattern is used, and (b) shows the diffraction state when an asymmetric diffraction pattern is used.

FIG. 7 is an exploded perspective view of a planar lighting device according to another embodiment of the present invention.

FIG. 8 is a schematic diagram showing a problem when a conventional point light source is used.

FIG. 9 is an exploded perspective view of a planar lighting device according to still another embodiment of the present invention.

FIG. 10 is a perspective view of a planar lighting device according to a different embodiment of the present invention.

FIG. 11 is an exploded perspective view of a planar lighting device according to still another embodiment of the present invention.

FIG. 12 is a plan view showing a conventional linear lighting device.

[Explanation of symbols]

1 Light guide plate 2 linear light guide 3 point light source 4 Light source reflector 22 Reflective surface 22a diffraction pattern 24 Light emitting surface

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Claims (8)

[Claims] 1. A linear shape in which a point light source is arranged on a light entrance surface of a linear light guide, and linear light is emitted from a light exit surface orthogonal or substantially orthogonal to the light entrance surface of the linear light guide. In the illuminating device, a linear illuminating device characterized in that a diffraction pattern in which the cross section of one pattern is asymmetric is provided on at least one surface of the linear light guide. 2. The linear illumination device according to claim 1, wherein a reflective diffraction pattern is provided on a reflective surface of the linear light guide facing the light emitting surface. 3. The linear lighting device according to claim 1, wherein a transmissive diffraction pattern is provided on a light entrance surface of the linear light guide. 4. A point light source is arranged at both ends of the linear light guide, and the diffraction pattern has a smaller diffraction pitch or a shallower depth as the distance from the point light source increases. If the diffraction pitch becomes smaller as the distance from the point light source increases, the linear light guide is formed so as to have a minimum at approximately the center, and the depth of the diffraction pitch becomes shallower as the distance from the point light source increases. The linear lighting device according to any one of claims 1 to 3, wherein the linear light guide is formed so as to have a minimum depth substantially at the center thereof. 5. A planar lighting device in which the linear lighting device according to any one of claims 1 to 4 is arranged near a side surface of a planar light guide plate made of a translucent material. 6. A light entrance surface on which light from a point light source is incident is provided on a side surface side of the planar light guide plate, and a reflection surface is provided orthogonal to or substantially orthogonal to the light entrance surface. Is provided with a transmission type diffraction pattern in which the cross section of one pattern is asymmetrical, and a reflection type diffraction pattern in which the cross section of one pattern is asymmetrical is provided on the reflection surface, and is incident from the light incident surface. A planar shape characterized in that light is guided to the reflection surface side by the transmission type diffraction pattern, and is converted into linear light by the reflection type diffraction pattern of the reflection surface to guide the light into the planar light guide plate. Lighting equipment. 7. A planar illuminating device comprising a planar light guide plate made of a translucent material, and an illuminating device comprising a plurality of point light sources arranged near the light incident surface of the planar light guide plate. A planar illuminating device characterized in that a diffraction pattern having a non-symmetrical cross section of one pattern is provided on all or part of a light incident surface. 8. The surface pattern according to claim 5, wherein a diffractive pattern having a non-symmetrical cross section is provided on a surface of the light guide plate facing the light exit surface. Lighting equipment.