JPH09145934A - Illuminator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the surface luminance of a light guide plate at minimum cost. SOLUTION: This illuminates is equipped with a light guide plate 1 which has a diffuse reflection part 2 on its reverse surface side and a light projection part on its top surface side, a lamp 3 as a linear light source which faces the end surface of the light guide late 1, and a reflecting plate 4 which surrounds the lamp 3 and directs reflected light to the said end surface of the light guide plate 1. The end surface of the light guide plate 1 which faces the lamp 3 is formed into an uneven surface 5 where projections which are sectioned triangularly along the length of the lamp 3 are arrayed. When the surface facing the lamp 3 is flat, light which is not made incident on the light guide plate 1 because of total reflection can be made incident.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an edge light type lighting device used for a thin illuminated light, an advertisement display device, a guide light, a back lamp of a liquid crystal display device, or the like.

[0002]

2. Description of the Related Art An edge light type illuminating device comprises a light guide plate which is made of a light-transmitting material such as an acrylic plate and whose back side is a diffuse reflection part, and one end face of the light guide plate.
Alternatively, a lamp which is a linear light source facing a plurality of end faces (usually a cold cathode tube lamp is used), a reflector having a U-shaped or C-shaped cross section for directing light emitted from the lamp to the light guide plate, and a light guide plate And a back reflector that reflects the light traveling toward the back side toward the front side to the front side, and the light entering the light guide plate from the lamp is emitted from the entire front surface of the light guide plate by being reflected by the diffuse reflection section on the back side of the light guide plate.

In such an illuminating device, it is required to increase the brightness of the surface of the light guide plate while keeping it thin, and to maintain uniform brightness over the entire surface. To raise the height, all the light emitted from the lamp may enter the light guide plate and reach the diffuse reflection section. However, the following problems exist here.

That is, the incident loss due to total reflection, the reflectivity of the reflector and the light transmittance of the incident end face of the light guide plate are 100, respectively.
%, Loss due to reflection plate shape, loss due to solid angle, loss due to re-absorption of light by the lamp. Regarding the incident loss due to total reflection, of the light emitted from the lamp, the incident light having an angle larger than the total reflection angle with respect to the incident end face of the light guide plate has a larger reflected component than the component incident on the light guide plate. In an edge light type illuminating device using a linear light source lamp, this loss often occurs in the longitudinal direction of the lamp.

Regarding the light-collection loss due to the shape of the reflector,
In the case of a U-shaped or C-shaped reflector, the center (focus) of the arc will be aligned or close to the center of the lamp, and the light guide plate side will be almost parallel to the front and back surfaces of the light guide plate. Of the light emitted from the lamp of the reflection plate, reflected by the light guide plate and then directed to the light guide plate, a large amount of light is totally reflected. Even if the light enters the light guide plate, the light will reach only the diffuse reflection surface near the incident end face of the light guide plate, or the light will go out directly from the surface near the incident end face of the light guide plate. Simply increasing the surface brightness in the vicinity increases the problem in terms of brightness uniformity. Further, a portion of the lamp opposite to the portion facing the incident end surface of the light guide plate faces the outer peripheral surface of the lamp at a short distance, so that it is re-incident on the lamp to increase loss due to reabsorption.

Further, the loss due to the solid angle needs to efficiently collect the light of the lamp on the diffuse reflection part on the back surface of the light guide plate, whereas in the conventional edge light panel, the center of the thickness of the light guide plate is required. This is because almost the same amount of light is directed to the front surface and the back surface of the light guide plate because the center of the lamp and the center of the lamp are substantially aligned with each other. In order to reduce such loss, especially the loss due to total reflection, Japanese Patent Application Laid-Open No.
Japanese Patent Laid-Open No. 127160 proposes disposing a mirror frame that is finely divided in the longitudinal direction of the lamp between the lamp and the incident end surface of the light guide plate.
In Japanese Patent No. 289077, it is proposed to seal the lamp house and the incident end face of the light guide plate and fill the inside thereof with a liquid having a refractive index almost equal to that of the light guide plate.

[0007]

However, in the former case, since the mirror frame as described above is newly provided, the cost is inevitably increased, and in the latter case, liquid leakage should be prevented. The cost is also increased because it is essential.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an edge light type lighting device capable of improving the surface brightness of a light guide plate at a minimum cost. There is.

[0009]

SUMMARY OF THE INVENTION The present invention, however, provides a light guide plate having a diffuse reflection portion on the back surface side and a light emission portion on the front surface side, and a linear light source facing the end surface of the light guide plate. In an edge-light type illumination device including a lamp and a reflector that surrounds the lamp and directs reflected light to the end face of the light guide plate, at least the end face of the light guide plate facing the lamp has a triangular cross section at least in the longitudinal direction of the lamp. It is characterized in that it has an uneven surface in which projections having a shape are arranged. When the surface facing the lamp is a flat surface, light that does not enter the light guide plate can be made incident by total reflection.

It is more preferable that the uneven surface of the light guide plate is such that projections having a triangular cross section are arranged in the thickness direction of the light guide plate. It is also preferable that the end surface of the light guide plate provided with the uneven surface is a surface forming an obtuse angle with respect to the surface of the light guide plate. A transparent material having a refractive index higher than that of air may be sandwiched between the lamp and the reflection plate, or an uneven surface may be coated with a reflection suppressing layer. It may be formed as a flat surface inclined with respect to the back surface, or the lamp may be arranged at a position closer to the front surface side in the thickness direction of the light guide plate and in contact with the end surface of the light guide plate.

Further, it is preferable that the lamp is held by a lamp holding portion integrally extended from a side end portion of the light guide plate.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An example of an embodiment of the present invention will be described. In FIG. 1, a conductor whose one end face is opposed to a lamp 3 formed of a cold cathode tube surrounded by a reflection plate 4 having a U-shaped cross section. The light plate 1 is made of a transparent acrylic resin having a high light transmittance, and the diffuse reflection portion 2 is provided on the back side thereof by printing a dot pattern or integrally molding. Further, the one end surface of the light guide plate 1 which is a surface facing the lamp 3 is formed as an uneven surface 5. The concave-convex surface 5 here is formed by arranging concave-convex portions having a regular triangular cross section in the longitudinal direction of the lamp 3, but the sectional shape may be as shown in FIG. As shown in FIG. 3, it may not be parallel to the thickness direction of the light guide plate 1. However, the ridgeline should not be parallel to the longitudinal direction of the lamp 3.

The light emitted from the lamp 3 toward the one end face (incident end face) of the light guide plate 1 is a total reflection angle (light enters the acrylic resin from the air, which is determined by the refractive index of air and the refractive index of the light guide plate 1). In this case, as shown in FIG. 14, when the angle is larger than 82 °), the amount of reflected light is larger than the amount of light incident on the light guide plate 1, but in the case of a flat surface, Even when the incident angle with respect to the light guide plate 1 exceeds the total reflection angle, if the uneven surface 5 is provided as described above, the incident angle is less than or equal to the total reflection angle, so that the incident loss due to the total reflection is greatly reduced. In particular, in the case where irregularities having a triangular cross section are arranged in the longitudinal direction of the lamp 3, it is effective to reduce the loss in the longitudinal direction of the lamp 3.

FIG. 4 shows another example. Here, the end face on the side having the maximum thickness of the light guide plate 1 having a wedge-shaped cross section is an incident end face facing the lamp 3, and the uneven surface 5 provided on the incident end face has a shape in which square pyramids are arranged in a grid pattern. It is formed as. In the illustrated example, the triangle is a quadrangular pyramid that is a regular triangle when cut by a plane that passes through the vertices and is perpendicular to the bottom surface, as shown in FIG. 5, but is not limited to this. It may be present, or the side piece / bus bar may be curved. Further, instead of being arranged in a grid pattern, they may be arranged so that they are staggered by half. Further, the line connecting the vertices of adjacent pyramids may be oriented in any direction, but it is preferable that the line is not parallel to the longitudinal direction of the lamp 3.

In this case, not only the longitudinal direction of the lamp 3 but also the total reflection loss in the thickness direction of the light guide plate 1 can be reduced, and moreover, a lens or a lens can be formed on each conical protrusion forming the uneven surface 5. Since it can have a function as a prism, the distribution of light after entering the light guide plate 1 can be controlled, and the light is directed to the diffuse reflection part 2 on the back surface side of the light guide plate 1. be able to. In addition, 6 in FIG.
Is a reflection plate disposed further on the back side of the diffuse reflection part 2, and 7 is a display / diffusion plate such as a milky white panel disposed on the front side of the light guide plate 1. The light guide plate 1 has a wedge-shaped cross section. Is for light distribution to the diffuse reflection part 2.

FIG. 6 shows another example. Here, the angle α formed between the incident end surface, which is the uneven surface 5 of the light guide plate 1, and the surface of the light guide plate 1 is an obtuse angle. In this case, the amount of light emitted from the lamp 3 and directly distributed to the diffuse reflection part 2 on the back surface side of the light guide plate 1 can be increased as compared with the case where the angle α is a right angle. The brightness of the surface of the light guide plate 1 can be improved, and at the same time, control by the diffuse reflector 2 for uniforming the brightness distribution of the surface becomes easy.

In the structure shown in FIG. 7, a flexible sheet-shaped transparent material 8 having a refractive index higher than that of air is sandwiched between a side of the lamp 3 not facing the light guide plate 1 and the reflection plate 4. If the transparent material 8 is formed of a sheet made of the same acrylic resin as the light guide plate 1, the total reflection angle when light goes from the air to the acrylic resin is 82 °, whereas the acrylic resin changes to air. The total reflection angle when the light goes is 42
Since the light enters the transparent material 8 at an angle of 42 ° or more, after multiple reflection is repeated inside the transparent material 8, the light travels from the end surface of the transparent material 8 to the light guide plate 1 side. This makes it possible to reduce the reabsorption loss of the light reflected by the reflection plate 4 and traveling toward the lamp 3 by the lamp 3.
The transparent material 8 may be a bundle of plastic optical fibers as shown in FIG. 8, and in this case, the optical fibers of the lamp 3 and the reflector 4 are arranged so that each optical fiber intersects the longitudinal direction of the lamp 3. Place in between.

In order to suppress reflection occurring at the incident end surface of the light guide plate 1, a material having a refractive index smaller than that of the light guide plate 1, for example, magnesium fluoride (refractive index 1.38) is ¼.
When the antireflection layer 9 formed by coating with a wavelength thickness is formed on the incident end face of the light guide plate 1 as shown in FIG. 9, a better result can be obtained. The reflectance on the acrylic resin surface when the antireflection layer 9 is not provided is about 4% in the case of vertical incidence, and the reflected light component when obliquely incident is further increased. The reflectance on the surface can be suppressed to 2% or less, and the reflectance can be further suppressed if the antireflection layer 9 is so-called multicoat.

The reflection plate 4 is not U-shaped or C-shaped in cross section, but has a flat plate shape at least at both ends as shown in FIG. 10 and is inclined with respect to the front and back surfaces of the light guide plate 1. It is good to U-shaped cross section or C
In the case of a letter shape, the reflection plate 4 is substantially parallel to the front surface and the back surface of the light guide plate 1 on the side close to the light guide plate 1, so that the reflected light at this portion has a total reflection angle with respect to the incident end surface of the light guide plate 1. In addition, even if the light is incident on the light guide plate 1, it contributes only to the brightness of the portion of the surface of the light guide plate 1 closer to the incident end face, but the reflection plate 4 is at least a required angle with respect to the front and back surfaces of the light guide plate 1. If the light guide plate 1 is tilted at, the reflected light can be incident at a larger angle with respect to the incident end face of the light guide plate 1.
At the same time that the efficiency of incidence on the light is increased, the light can be efficiently guided to the back of the light guide plate 1.

As shown in FIG. 11, even if the lamp 3 is brought closer to the incident end face, preferably, the lamp is brought into contact with the incident end face, and the lamp 3 is arranged so as to be displaced to the surface side in the thickness direction of the light guide plate 1, only the direct light is emitted. Not only that, the reflected light from the reflection plate 4 can also be efficiently condensed and incident on the back surface side and the depth direction of the light guide plate 1, and the uniformity of the brightness of the display surface can be improved.

An example of a concrete embodiment is shown in FIG.
An acrylic resin light guide plate 1 having a wedge-shaped cross section and a dot pattern 20 integrally formed on the back surface side.
Has an end face having the largest thickness as an incident end face, and this end face is an uneven surface 5 in which pyramidal protrusions are arranged. Further, the incident end face is about 11 with respect to the surface of the light guide plate 1.
It is a surface forming an angle of 0 °. The sheet-like reflection 6 covers the back surface side and both side surfaces of the light guide plate 1 and the end surface opposite to the incident end surface, and a display surface / diffusing plate 7 made of a milky white acrylic plate is arranged on the surface of the light guide plate 1. ing.

The cold-cathode tube lamp 3 as a linear light source facing the incident end face of the light guide plate 1 is held at both ends by holding parts 15 and 15 extended from both end parts of the light guide plate 1, respectively. The light guide plate 1 is arranged near the front side in the thickness direction of the light guide plate 1 so as to be in contact with the incident end face, and surrounds the lamp 3 and has a plurality of reflection plates 4 whose inner surface side is mirror-finished with silver or the like. The shape is a combination of flat surfaces (the cross-sectional shape shown in FIG. 11).

The dot pattern 20 forming the diffuse reflection portion 2 on the back surface of the light guide plate 1 is formed on the back surface of the light guide plate 1 as minute grooves (depth 50 μm, width 150 μm, total length x) shown in FIG. The total length x of the groove here is the light guide plate 1
Is short on the side close to the incident end face, and becomes long as it goes away, and the pitch at which the grooves are provided also becomes small as it goes away from the incident end face.

In such a structure, the thickness of the light guide plate 1 on the incident end face side is 5 mm, the thickness on the other end side is 2 mm, and the length on the surface side from the incident end face side to the other end is 2.
When the cold cathode fluorescent lamp 3 having a diameter of 2.6 mm is used in addition to the one having a diameter of 10 mm, the incident end face is perpendicular to the surface, the incident end face is formed as a flat surface, and the reflection plate 4 is used.
In comparison with a lamp having a U-shaped cross section and having the lamp 3 positioned at the center of the light guide plate 1 in the thickness direction, an improvement in incidence efficiency of about 20% could be obtained.

[0025]

As described above, in the present invention, since the end surface of the light guide plate facing the lamp is an uneven surface in which projections having a triangular cross section at least in the longitudinal direction of the lamp are lined up, it is possible to form the lamp with the lamp. When the opposing surface is a flat surface, light that does not enter the light guide plate can also be made incident by total reflection, which can improve the surface brightness of the light guide plate, and the uneven surface can guide light. Since the light plate can be integrally formed at the time of molding, the cost can be reduced.

Further, if the projections having a triangular cross section are arranged in the uneven surface of the light guide plate also in the thickness direction of the light guide plate, the surface brightness can be further improved. Further, if the end surface of the light guide plate provided with the uneven surface is an obtuse angle with respect to the surface of the light guide plate, the amount of direct light to the diffuse reflection section on the back side of the light guide plate can be increased,
It is possible to improve surface brightness and brightness uniformity.

If a transparent material having a refractive index higher than that of air is sandwiched between the lamp and the reflector, the amount of light that is re-absorbed by the lamp can be suppressed and the surface brightness of the light guide plate can be reduced. The surface brightness of the light guide plate can be similarly improved by coating the antireflection layer on the uneven surface. If the light guide plate side of the reflector is formed by a plane inclined with respect to the front surface or the back surface of the light guide plate,
The brightness can be improved by increasing the amount of light incident on the light guide plate, and the uniformity of brightness can be improved because the amount of light reaching the back of the light guide plate can be increased.

Even when the lamp is arranged at a position closer to the surface side in the thickness direction of the light guide plate and in a position in contact with the end face of the light guide plate, the amount of light incident on the light guide plate can be increased to improve the brightness. In addition, since the amount of light reaching the back of the light guide plate can be increased, the uniformity of brightness can be improved. Further, if the lamp is held by the lamp holding portion that is integrally extended from the side end of the light guide plate, the lamp holding structure can be simplified and the cost can be reduced. It can be reliably held at an advantageous position in terms of improving the surface brightness.

[Brief description of the drawings]

FIG. 1 shows an example of an embodiment of the present invention, in which (a)
FIG. 3A is a cutaway perspective view, and FIG. 3B is an enlarged perspective view of an uneven surface.

FIG. 2 shows another example of the uneven surface, and (a) and (b) are cross-sectional views, respectively.

FIG. 3 is an end view showing another example of an uneven surface.

4A and 4B show another example, FIG. 4A is a cross-sectional view, and FIG. 4B is an enlarged perspective view of an uneven surface.

FIG. 5 is an enlarged perspective view of the uneven surface of the same.

FIG. 6 is a cross-sectional view showing another example.

FIG. 7 is a sectional view showing still another example.

FIG. 8 is a perspective view showing another example of a transparent material.

FIG. 9 is a cross-sectional view showing another example.

FIG. 10 shows still another example, (a) is a sectional view,
(b) is an enlarged sectional view.

FIG. 11 is a cross-sectional view of another example.

FIG. 12 shows a specific example, (a) is a cutaway perspective view, (b)
[Fig. 3] is a side view of a light guide plate.

FIG. 13 is a perspective view showing a diffuse reflection portion of the same as above, (a) is an enlarged perspective view and (b) is a bottom view of the light guide plate.

FIG. 14 is an explanatory diagram of a ratio of incident light and reflected light depending on an incident angle when light enters the acrylic resin plate from air.

[Explanation of symbols]

 1 Light guide plate 2 Diffuse reflection part 3 Lamp 4 Reflector plate 5 Uneven surface

Claims (8)

[Claims] 1. A light guide plate having a diffuse reflection part on the back surface side and a light emission part on the front surface side, a lamp as a linear light source facing the end surface of the light guide plate, and a reflected light surrounding the lamp. In an edge-light type illumination device provided with a reflection plate facing the end face of the light guide plate, an end face facing the lamp in the light guide plate has a concavo-convex surface where at least projections having a triangular cross section in the longitudinal direction of the lamp are arranged. The lighting device characterized in that. 2. The illuminating device according to claim 1, wherein the uneven surface of the light guide plate is provided with protrusions having a triangular cross section in the thickness direction of the light guide plate. 3. The lighting device according to claim 1, wherein the end surface of the light guide plate provided with the uneven surface is formed as an obtuse surface with respect to the surface of the light guide plate. 4. The lighting device according to claim 1, wherein a transparent material having a refractive index larger than that of air is sandwiched between the lamp and the reflector. 5. The illumination device according to claim 1, wherein the uneven surface is coated with a reflection suppressing layer. 6. The lighting device according to claim 1, wherein the light guide plate side of the reflection plate is formed by a flat surface inclined with respect to the front surface or the back surface of the light guide plate. 7. The lamp according to claim 1, wherein the lamp is arranged at a position closer to a surface side in a thickness direction of the light guide plate and at a position in contact with an end face of the light guide plate. Lighting equipment. 8. The lighting device according to claim 1, wherein the lamp is held by a lamp holding portion integrally extended from a side end portion of the light guide plate.