JP2001028202A - Light source for front light - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive light source for a front light, which has a spot-like light source, which is capable of efficiently guiding light beams from the light source into a light guide with directivity of the light source considered and uniformly illuminating to a light outgoing surface in a plane form, thereby realizing reduction in cost for the light source and power consumption. SOLUTION: In this light source, an LED 3 composed of a spot-like light source is arranged nearby to one side surface of a light guide 2, having an approximately rectangular parallelepiped shaped, which is made of a transparent plastic material. On one side of a wide surface of the light guide member 2, a light-diffusing surface 2b is formed by forming narrow linear grooves 2a approximately parallel to the irradiation direction from the LED 3, angles obtusely, and concentrically semi-circled. Light beams impinging onto the grooves 2a are reflected gently, resulting in being the reflected light beams from the light diffusing surface 2b outgoing from a light output surface 2c with a degree of light reflection immediately above the LED 3 reduced to form a uniform light. Thus illumination without luminance unevenness is obtained. The loss of light is reduced, so that low cost and space saving are attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a front light source for a display device which requires a reflective panel to be illuminated from the front side.

[0002]

2. Description of the Related Art Conventionally, a front light source (illumination device)
Is arranged on the front side of the liquid crystal display panel, and a reflection plate is arranged on the back side of the liquid crystal display panel to constitute a reflection type liquid crystal display device. For example, Japanese Patent Application Laid-Open No. Hei 6-324331 discloses the technique. Hereinafter, the outline will be described with reference to FIG.

In FIG. 3, reference numeral 10 denotes a front light source. The front light source 10 has a function of projecting a light beam on the liquid crystal display panel 11 side and transmitting the light beam reflected by the reflector 12 with little dispersion. Reference numeral 13 denotes a linear light source, which is disposed on at least one end surface of the light guide 14. The light guide 14 has a rib-shaped projection 15 provided on one surface of a transparent plate substantially in parallel with the linear light source 13, and each surface of the projection 15 is substantially perpendicular to a plane substantially parallel to the light-emitting side plane 16. It consists only of faces. The light rays from the linear light source 13 enter the end face 18 as shown by the light rays 17a and 17b, and then repeatedly undergo total reflection in the light guide 14 and emit only from the side surfaces of the projections 15. From the liquid crystal display panel 11 can be illuminated. The linear light source 13
Is provided with a fluorescent tube, a cold cathode tube, an LED array and the like.

When there is sufficient external light, the front light source 10 is turned off and used. In this case, the front light source 10 acts as a mere transparent plate, so that the visibility is not lowered and the display quality is not affected. It is especially effective. When used in a dark place where external light is not sufficient, the front light source 10 illuminates the liquid crystal display panel 11 and the light reflected by the reflector 12 is reflected by the front light source 1.
0 functions as a mere transparent plate and transmits light as it is in the same manner as in the case of turning off the light, which is effective for maintaining high visibility.

FIG. 4 shows a point light source L on one side of a light guide.
FIG. 5 is an image diagram of an optical path in which light having a high light intensity when viewed from above a light guide is a front light source having an ED light source. In FIG. 4, reference numeral 20 denotes a front light source, which includes a light guide 21 and an LED 22 as a point light source. The light guide 21 has a substantially rectangular parallelepiped shape made of a transparent plastic member, and has a wide surface, that is, a lower surface, as a radiating means for reflecting light from the light source to the upper surface facing the light guide 21. A plurality of thin linear grooves 21
a (or unevenness) is drawn from the left side to the right side of the light guide 21 so as to be substantially orthogonal to the radiation direction of the LED 22 to form a light diffusion surface. The light emitted from the point light source LED 22 repeats total reflection in the light guide 21 and emerges from the light diffusion surface having the groove 21a to illuminate a liquid crystal display panel (not shown). LED2
When the light source 2 is a point light source, the light of the LED 22 is naturally strong immediately above, so that the light guide 21 has a linear groove 2 drawn from the left side to the right side.
1a, the light hitting the groove 21a is of course the LED 22
4 becomes stronger, and this appears as a band-like unevenness 25 as shown by oblique lines in FIG.

In order to use the LED 22 as a linear light source in order to eliminate the above-mentioned band-like unevenness 25, the LED 2
An acrylic plate or the like is disposed between the light guide 2 and the light guide 11 to provide a linear light source, or a linear light source such as a cold cathode tube, a fluorescent tube, or an LED array is used.

FIG. 5 shows another front light source having an LED light source as a point light source on one side of the light guide.
5A is an image diagram of an optical path in which light having a high light intensity travels when viewed from above the light guide, and FIG. 5B is an image diagram in which light traveling in a cross-sectional direction is reflected by a groove and emitted from the light guide. It is. In FIG. 5, reference numeral 30 denotes a front light source, which includes a light guide 31 and an LED 22 as a linear light source. The light guide 31 has a plurality of thin linear grooves 31a formed on its lower surface as a radiating means for reflecting light from the light source to the upper surface facing the light guide 31 so that the light is substantially oblique to the light from the point light source. The light diffusing surface 3 is drawn from the left side to the right side of the light guide 31.
1b is formed. Light from the LED 22 enters the light guide 31, is diffused by the light diffusion surface 31b having the groove 31a, and exits from the light emission surface 31c. Finally, a liquid crystal display panel (not shown) is illuminated. When the linear groove 31a extending from the left side to the right side of the light guide 31 has an inclination, when light strikes the inclined groove 31a, the light band is inclined according to Snell's law. This appears as a band-like unevenness 35 as shown by oblique lines in FIG.

In order to use the point light source as a linear light source, an acrylic plate or the like is provided between the LED and the light guide, as described with reference to FIG. A linear light source such as a cold cathode tube, a fluorescent tube, an LED array, or the like is directly used by disposing the light source via an acrylic plate.

[0009]

As described above, FIG.
In the front light source described above, the contrast is reduced unless all the light emitted from the light guide is emitted to the liquid crystal display panel side. In addition, since a linear light source is used as the light source, there is a problem that cost and power consumption increase.

A point light source (LE) shown in FIGS.
In the case of D), in terms of the directivity of the LED, brightness unevenness occurs when used for illumination of a liquid crystal display panel or the like that requires uniform illumination. If the number of LEDs is increased to compensate for this, or if another linear light source is used, there has been a problem that the increase in cost and the reduction in power consumption are hindered as described above.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a front light source using a point-like light source, in which light from the light source is efficiently guided in consideration of the directivity of the light source. And illuminate it uniformly on the light exit surface. An object of the present invention is to provide an inexpensive front light source by realizing a reduction in light source cost and power consumption.

[0012]

In order to achieve the above object, a front light source according to the present invention has a thin linear groove formed on one wide surface of a substantially rectangular parallelepiped light guide made of a transparent plastic member. A front light source for a panel having a light diffusion surface having a light source disposed close to a side surface of the light guide, wherein a point light source is disposed close to a side surface of one side of the light guide. The light guide is formed by forming a groove on one wide surface of the light guide in a radiation direction from the point light source, and allowing the light from the point light source to directly enter the light guide. The reflected light from the formed light diffusion surface is characterized in that reflection of light immediately above the point light source is reduced, and the light is emitted from the light emission surface as uniform light.

Further, the point light source is an LED.

Further, the groove is a thin linear groove substantially parallel to a radiation direction from a point light source.

Further, the groove is a thin linear groove obtuse in the direction of radiation from the point light source.

Further, the groove is a thin linear groove having a substantially concentric semicircle in a radiation direction from the point light source.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A front light source according to the present invention will be described below with reference to the drawings. FIG. 1 relates to a first embodiment of the present invention, FIG. 1A is a front view of a front light source having an LED light source as a point light source on one side of a light guide, and FIG. FIG. 2 is an enlarged view of a section B taken along the line AA of FIG.

In FIG. 1, reference numeral 1 denotes a front light source, which comprises a light guide 2 and an LED 3 which is a point light source. The light guide 2 has a substantially rectangular parallelepiped shape made of a transparent plastic member.
That is, a linear thin groove 2a extending from the upper side to the lower side of the light guide 2 substantially in parallel with the radiation direction of the LED 3 is provided on the lower surface as a radiation means for reflecting the light from the light source to the upper surface facing the LED 3, The light diffusion surface 2b is formed. The light emitted from the LED 3 is incident on the light guide 2, is totally reflected repeatedly in the light guide 2, is diffused by the light diffusion surface 2 b provided with the groove 2 a, and is emitted from the light emission surface 2 c. Eventually, a liquid crystal display panel (not shown) is uniformly illuminated to provide illumination without luminance unevenness.

FIG. 2 relates to a second embodiment of the present invention, and FIG.
Front view of front light source having D light source, FIG. 2 (b)
FIG. 3 is an enlarged view of a section D taken along the line CC in FIG. FIG.
, 1A is a front light source. Light guide 4
As the light emitting means of the LED 3, a linear thin groove 4 a radially extending from the left, right, and upper sides of the light guide 4 toward the center of the lower side where the LED 3 is provided is arranged at an obtuse angle in the emission direction of the LED 3. The light diffusion surface 4b is formed. LED
Light emitted from 3 hits the groove 4a and is gently reflected,
Light is uniformly emitted from the light emitting surface 4c onto the surface. Other configurations are the same as those of the first embodiment. Finally, a liquid crystal display panel (not shown) is uniformly illuminated.

FIG. 3 is a front view of a front light source having an LED light source as a point light source on one side of a light guide according to a third embodiment of the present invention. In FIG. 3, 1B
Is a front light source. The light guide 5 is provided with a thin linear groove 5a (having a saw-like or semi-circular shape) of substantially concentric semicircle in a radiation direction of the LED 3 as a light radiating means of the LED 3, and a light diffusing surface 5b. Form. The light emitted from the LED 3 hits the groove 5a and is gently reflected, and is uniformly emitted from the light emitting surface onto the surface. Other configurations are the same as those of the above-described first and second embodiments. Finally, a liquid crystal display panel (not shown) is uniformly illuminated.

As described above, as in the first, second, and third embodiments, a thin linear line that is substantially parallel, obtuse angle, or concentric semicircle in the direction of light emission from the LED as a point light source. By digging the groove, the light hitting the groove is gently reflected. Light reflection immediately above the point light source is reduced, and uniform illumination without luminance unevenness is achieved.

In the first, second and third embodiments described above, the groove has a saw-like shape or a semi-circular shape, but is not limited to this, and may have an uneven shape.

At present, in the case of an emboss type front light, since the light guide having a linear light source is a linear groove extending from the left side to the right side, the light guide is rotated by 90 degrees to be parallel to the radiation direction of the LED. Alternatively, the groove can be easily formed by forming the groove at an obtuse angle, and the band-shaped unevenness that has conventionally occurred can be eliminated.

[0024]

As described above, according to the present invention,
Conventionally, when an LED light source (dot-like) is used as a front light source, the LED light source is converted into a linear light source via an acrylic plate or the like and then is incident on the light guide, or a plurality of L light sources
Used as an LED array (linear light source) on which EDs are arranged. According to the present invention, an LED, which is a point light source, is directly incident on the light guide, so that light loss is small, it is not necessary to use a linear light source, and the number of LEDs can be reduced. Can be reduced. In addition, it is not necessary to use a cold cathode tube required for an inverter board, and low cost and
Space saving can be realized. Further, it is possible to use a conventional linear grooved front light simply by changing the LED entrance. Therefore, it has become possible to provide a front light source which has a simple structure, saves space, is low in cost, and has no luminance unevenness.

[Brief description of the drawings]

FIG. 1 relates to a first embodiment of the present invention;
1A is a front view of a front light source, and FIG. 1B is an enlarged view of a section B taken along the line AA of FIG. 1A.

FIG. 2 relates to a second embodiment of the present invention;
2A is a front view of a front light source, and FIG. 2B is an enlarged view of a section D taken along the line CC in FIG. 2A.

FIG. 3 is a front view of a front light source according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a conventional reflective liquid crystal display device.

FIG. 5 is an image diagram of an optical path in which light having a high light intensity travels when viewed from above a conventional light guide.

6A is an image diagram of an optical path in which light having a high light intensity travels when viewed from above in a conventional light guide, and FIG. 5B.
FIG. 4 is an image diagram in which light traveling in a cross-sectional direction is reflected by a groove and emitted from a light guide.

[Explanation of symbols]

 1, 1A, 1B Front light source 2, 4, 5 Light guide 2a, 4a, 5a Groove 2b, 4b, 5b Light diffusing surface 2c, 4c Light emitting surface 3 LED

Claims (5)

[Claims] 1. A light diffusing surface having a thin linear groove is formed on one wide surface of a substantially rectangular parallelepiped light guide made of a transparent plastic member, and is disposed close to a side surface of the light guide. In a front light source for a panel having a light source, a point light source is disposed close to a side surface of one side of the light guide, and a radiation direction from the point light source is provided on one wide surface of the light guide. The light from the light diffusing surface formed on the light guide is a reflection of light immediately above the point light source by forming a groove in the The front light source is characterized in that the light is reduced and uniform light is emitted from the light emitting surface. 2. The front light source according to claim 1, wherein the point light source is an LED. 3. The front light source according to claim 1, wherein the groove is a thin linear groove substantially parallel to a radiation direction from the point light source. 4. The front light source according to claim 1, wherein the groove is a thin linear groove obtuse at an angle in a radiation direction from the point light source. 5. The front light source according to claim 1, wherein the groove is a thin linear groove having a substantially concentric semicircle in a radiation direction from the point light source.