JP2001043721A - Surface light source device and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device capable of presenting uniform luminance without providing special both-surface tapes by using a point light source as a light source and suppressing the number of point light sources to be provided and to provided a display device with satisfactory display performance using the surface light source device. SOLUTION: By partially providing both-surface tapes 4 for fixing one end of a reflection sheet 3 at a plurality of corresponding positions between an LED 1 and an LED 1, in the vicinity of an incident plane 2 on an outgoing plane 22 and forming each of the both-surface tapes 4 into a tapered shape according to spreading of light from each of the LEDs 1, light quantity insufficiency between the LEDs 1 can be compensated, securing luminance by efficient utilization of light from the LEDs 1. The number of the LEDs 1 to be provided is suppressed, and luminance uneveness can be eliminated and luminance of outgoing light can be made uniform without using special both-surface tapes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface light source device and a display device using the surface light source device.
The present invention relates to a point light source such as an ED, and a method for bonding and fixing a reflection sheet for reflecting light from the point light source to the light guide plate with a double-sided tape or the like.

[0002]

2. Description of the Related Art In a non-light-emitting display device represented by a liquid crystal display device, for example, when it is incorporated into a product such as a digital still camera, a video camera, or a liquid crystal television, a surface is provided on the rear surface of the device for illumination. A backlight unit as a light source device is provided. As one structure of the backlight unit, a light source, a light guide plate that receives light from the light source from the side and emits light from the entire surface, and condenses light emitted from the light guide plate surface (emitted light) within a viewing angle. There is known a lens sheet for improving the brightness and a reflector provided on the back side of the light guide plate and returning the light that has escaped from the back surface to the inside of the light guide plate again. Then, in order to introduce the light from the light source into the light guide plate, a reflection sheet (light source light reflection sheet) is provided around the light source except for the end surface facing the light guide plate.
Is installed. This reflection sheet is usually fixed with a double-sided tape around the light introduction end face of the light guide plate (for example, the end face on the light incident face side of the light exit face and the rear face).

When light from a light source is introduced from the side of a light guide plate, a linear light source such as a cold cathode fluorescent lamp or a point light source such as an LED is used as a light source. When a point light source such as an LED is used as a light source, a plurality of point light sources are arranged side by side with respect to the light incident surface of the light guide plate. A point light source such as an LED can reduce cost and power consumption as compared with a linear light source such as a cold cathode fluorescent lamp. In this case, there is a problem that the portion between the portions becomes dark and uneven brightness occurs. It is possible to reduce this uneven brightness by reducing the distance between the point light sources, but this requires many point light sources,
The advantage of using a point light source is diminished.

[0004] Further, uneven brightness is also caused by fixing a reflection sheet provided around a light source with a double-sided tape. When the reflective sheet is fixed with a double-sided tape, the double-sided tape is non-transparent because it is based on a nonwoven fabric. Some parts glowed abnormally brightly, causing uneven brightness. To cope with the uneven brightness caused by the double-sided tape, for example, Japanese Patent Application Laid-Open No. 8-54624 discloses a method of using a double-sided tape for fixing a reflective sheet, which is colored to absorb light or to which graphite is added. The unevenness is reduced.

[0005]

As described above, in order to reduce luminance unevenness, when a point light source such as an LED is used as a light source, many point light sources are required, or light is absorbed. Needed a special double-sided tape to do. Further, if light is absorbed by a special double-sided tape in order to reduce luminance unevenness, light from a light source cannot be used efficiently, and there is a possibility that illumination luminance may be reduced. These may increase the cost of the surface light source device and the display device, and may reduce the competitiveness in the market.

[0006] The present invention has been made in view of such a point. When a point light source is used as a light source, the number of point light sources to be provided can be reduced, and a special double-sided tape can be provided.
It is an object of the present invention to provide a surface light source device capable of exhibiting uniform luminance, and further to provide a display device having good display performance using the surface light source device.

[0007]

According to a first aspect of the present invention, there is provided a surface light source device comprising: a plurality of point light sources; an incident surface on which the plurality of point light sources are arranged to face each other and light incident from the point light sources; A light guide plate having an emission surface for emitting light incident from the light source, and a reflecting member for causing light from the point light source to enter the incidence surface, and one end of the reflection member is provided on the emission surface in the vicinity of the incidence surface. It is characterized in that a plurality of portions corresponding to between the point light sources are bonded.

According to a second aspect of the present invention, there is provided the surface light source device according to the first aspect, wherein one end of the reflecting member is adjusted to the spread of light from the point light source at a plurality of portions on the emission surface. It is characterized by being tapered.

According to a third aspect of the present invention, in the surface light source device according to the second aspect, the plurality of portions where one end of the reflecting member and the emission surface are bonded are arranged in a direction perpendicular to the incidence surface. It is characterized by having an inclination of approximately 42.2 °.

According to a fourth aspect of the present invention, in the surface light source device according to any one of the first to third aspects, one end of the reflecting member is adhered on the light emitting surface with a light-diffusing adhesive. It is characterized by having.

According to a fifth aspect of the present invention, there is provided a display device comprising the surface light source device according to any one of the first to third aspects, and a non-light emitting display means provided on an emission surface side of the light guide plate. Features.

[0012]

FIG. 1 is a schematic structural view of a surface light source device according to the present invention and a display device using the same.

Reference numeral 1 denotes an LED as a point light source.
D1 is juxtaposed on the substrate 11 so as to be separated from each other.

Reference numeral 2 denotes a light guide plate made of a translucent material such as an acrylic resin. A plurality of LEDs 1 provided on a substrate 11 are arranged to face each other, and an incident surface 21 on which light from the LEDs 1 is incident.
And an emission surface 22 for emitting the incident light, and a back surface 23 facing the emission surface, and the other three surfaces are reflection surfaces so that the incident light does not leak in a mirror state.
A reflector is provided as needed. The thickness of the light guide plate 2, that is, the distance between the emission surface 22 and the back surface 23 is formed smaller as the distance from the incidence surface 21 increases in order to improve the emission efficiency of the emitted light. For example, the back surface 23 is formed on a surface inclined with respect to the emission surface 22 or in a stepwise manner so as to present a surface parallel to the diffuser plate or the liquid crystal display panel. Although not shown, a diffusion pattern may be formed on the back surface 23 as a diffusion unit that is designed so that incident light is emitted from the emission surface 22 with uniform luminance. Such a light guide plate is
Usually, since it is formed by injection molding using a thermoplastic resin, such a light guide plate can be integrally and easily formed by a general molding process using a mold, even if the light guide plate has a diffusion pattern. Is done.

Reference numeral 3 denotes a reflection sheet as a reflection member for causing light from the LED 1 to enter the incident surface 21. The reflection surface is formed of a white or silver reflection surface, and the inner surface is formed of LE.
It is provided so as to cover D1 and face the reflection surface 21.
Reference numerals 4 and 41 denote a double-sided tape as an adhesive for fixing the reflection sheet 3. The double-sided tape 4 has one end of the reflection sheet 3 on the output surface 22, and the double-sided tape 41 has a reflection end on the other end of the reflection sheet 3. Each is stuck to fix it on a board. The double-sided tape 4 is stuck on the output surface 22.
As shown in (1), it is partially provided at a plurality of positions corresponding to between the LEDs 1 in the vicinity of the incident surface 21. Each of the double-sided tapes 4 is formed in a tapered shape in accordance with the spread of light from the LED 1. Double-sided tape 4
Is preferably formed in a tapered shape, preferably, for example, when the light guide plate 2 is made of an acrylic resin and the refractive index is n = 1.49, assuming that the angle with respect to the direction perpendicular to the incident surface 21 is θ, sin θ / sin 90 ° = 1 / 1.49, that is, a tapered shape having an inclination of θ = 42.155 ° (approximately 42.2 °).

Reference numeral 5 denotes a reflection plate which is disposed to face the back surface 23 and has a surface facing the back surface 23 serving as a reflection surface, and is for returning light leaked from the back surface 23 into the light guide plate 2 again. 6
Reference numeral denotes a diffusion plate provided opposite to the emission surface 22 for uniformly distributing the emitted light. Reference numeral 7 denotes a transmission type liquid crystal display panel provided as a non-light emitting display means provided on the emission surface 22 side via the diffusion plate 6. It is. Although not shown, a lens sheet may be provided between the liquid crystal display panel 7 and the diffusion plate 6 or between the diffusion plate 6 and the light guide plate 2 if necessary. Are appropriately provided according to the characteristics of

The light from the LED 1 is directly or reflected by the reflection sheet 3 and enters the light guide plate 2 from the entrance surface 21. At this time, the amount of light incident on the incident surface 21 is large in a portion where the LED 1 is opposed, and small in a portion corresponding between the LED 1 and the LED 1. However, the incident light is reflected by the reflection sheet 3 on the exit surface 22.
In the part which is in contact with the double-sided tape 4 for fixing
It is diffused more than the part without the double-sided tape 4. Due to this diffusion, light is also supplied to a portion corresponding to between the LEDs 1, and the light amount of this portion is compensated.

The area where light travels from the double-sided tape 4 due to the diffusion at the portion where the double-sided tape 4 is adhered (the incident surface 2).
(On the side opposite to 1), uniform light can be supplied. And
The light that has been diffused at the portion where the double-sided tape 4 is adhered, while the incident light propagates through the light guide plate 2, some are reflected directly or on another surface, and some are temporarily
Then, the light is reflected by the reflection plate 5, enters the light guide plate 2 again, and is emitted from the emission surface 22. The light emitted from the emission surface 22 is
The liquid crystal display panel 7 is illuminated from behind via the diffusion plate 6.

As described above, the double-sided tape 4 for fixing one end of the reflection sheet 3 is partially provided at a plurality of positions corresponding to between the LEDs 1 in the vicinity of the incident surface 21. Is formed in a tapered shape in accordance with the spread of the light from the LED 1, it is possible to compensate for the insufficient light amount between the LEDs. As a result, uneven brightness can be eliminated, and the brightness of emitted light can be made uniform. In addition, it is possible to provide a surface light source device having good illumination performance with less luminance unevenness, and further to provide a display device having excellent display performance.

In addition, since the shortage of the light amount between the LEDs can be compensated for while ensuring the luminance by efficiently using the light from the LEDs, the distance between the LEDs can be increased, and the distance between the LEDs can be increased. There is no need to provide many LEDs for light amount compensation. Further, an ordinary double-sided tape may be used as the double-sided tape to which the reflection sheet 3 is fixed, and the cost can be reduced.

In this embodiment, the adhesive between the reflecting sheet 3 and the exit surface is fixed by using an adhesive such as a double-sided tape. However, the present invention is not limited to this. For example, they may be bonded with an adhesive. At this time, a transparent adhesive may be used as long as the reflection sheet causes white light diffusion, and if the reflection sheet does not cause light diffusion, an adhesive having light diffusion may be used. The effect of the invention can be sufficiently obtained.

[0022]

As is apparent from the above description, the present invention provides a double-sided tape for fixing one end of a reflection sheet.
By providing a plurality of double-sided tapes in a tapered shape in accordance with the spread of light from the LEDs, the light emitting surface is partially provided at a plurality of positions corresponding to between the LEDs near the light incident surface on the light emitting surface. Insufficient light quantity between the LEDs can be compensated for while ensuring the luminance by efficiently using the light from the LED. As a result, the number of LEDs to be provided can be suppressed, and uneven brightness can be eliminated and the brightness of emitted light can be made uniform without using a special double-sided tape. In addition, it is possible to provide a surface light source device that can reduce costs and has good illumination performance with less luminance unevenness, and further can provide a display device that has excellent display performance.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of one embodiment according to the present invention.

FIG. 2 is a schematic top view for explaining one embodiment according to the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 LED (point light source) 11 substrate 2 light guide plate 21 incident surface 22 emission surface 23 back surface 3 reflection sheet (reflection member) 4 double-sided tape (adhesive material) 5 reflection plate 6 diffusion plate 7 liquid crystal display panel (non-light emitting display means)

Claims (5)

[Claims] A light guide plate having a plurality of point light sources, an incident surface on which the plurality of point light sources are arranged facing each other, on which light from the point light sources is incident, and an emission surface for emitting light incident from the incident surface; A reflecting member for causing light from the light source to enter the incident surface, and one end of the reflecting member is bonded on the emitting surface at a plurality of portions corresponding to between the point light source and the point light source near the incident surface. A surface light source device. 2. The surface light source according to claim 1, wherein one end of the reflection member is bonded to the emission surface in a plurality of portions in a tapered shape corresponding to the spread of light from the point light source. apparatus. 3. A plurality of portions where one end of the reflection member and the emission surface are bonded to each other in a direction substantially perpendicular to the incidence surface.
The surface light source device according to claim 2, wherein the surface light source device has an inclination of 2 degrees. 4. The surface light source device according to claim 1, wherein one end of the reflection member is adhered to the light exit surface with an adhesive having a light diffusing property. 5. A display device, comprising: the surface light source device according to claim 1; and a non-light-emitting display unit provided on an emission surface side of the light guide plate.