JP2004014365A - Plane luminescent light source, downright backlight, and signal light using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plane luminescent light source capable of uniformly emitting light with a small number of light sources, a downright backlight and a signal light using the same. <P>SOLUTION: With the plane luminescent light source provided with a light guide plate having a top face and a bottom face opposing each other and a plurality of light sources emitting light of the light source incident from the bottom face side of the light guide plate from the top face side, the light guide plate is provided with a plurality of light-incident parts optically separated and a diffusion part having in common the light coming in from the light-incident parts, each light-incident face for the plurality of the light sources is in opposition to each of the plurality of the light sources. Like this, by separating functions of the light-incident parts and the diffusion part capable of emitting uniform light, light of each light source of the limited number is made the most use of to a maximum degree, while, an extent of mixture is enhanced, and thus a luminous observation face with a high brightness and uniformity can be obtained. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a planar light source used for a liquid crystal backlight, a panel meter, an indicator lamp, a surface light switch, and the like, and more particularly to a planar light source capable of uniformly emitting a complicated light emitting surface with a small number of light sources.
[0002]
[Prior art]
Today, light emitting diodes capable of emitting RGB colors and light emitting diodes capable of emitting white light with high luminance have been developed, and as a result, LED indicator lamps configured by arranging a plurality of light emitting diodes have been used in various fields. ing.
[0003]
For example, as shown in FIG. 4, a plurality of LED light sources and a light guide plate for guiding the light sources are used as the planar light source, and the light guide plate is arranged on the plurality of LED light sources. A planar light source that receives light from one surface, diffuses the light, emits light from the other surface facing the one surface, diffuses the light, and emits light from the upper surface as a planar light source is considered.
[0004]
On the other hand, in recent years, as the brightness of each light emitting diode has been increased, the number of light emitting diode arrays in the LED display has been reduced, and the cost of the LED display has been reduced.
[Problems to be solved by the invention]
[0005]
However, when the number of light emitting diodes arranged in the direct type planar light emitting light source having the planar light emitting light source having the above-described configuration is reduced, the dot feeling that the light emission of each light emitting diode is recognized as a sparse dot increases, and the display quality is reduced. The problem of lowering has arisen, and further improvement is required.
[0006]
Therefore, the present invention solves the above problems and provides a planar light source capable of emitting light with high luminance and uniformity even with a small number of light sources.
[0007]
[Means for Solving the Problems]
A planar light emitting light source according to the present invention includes a light guide plate having an upper surface and a lower surface facing each other, and a plurality of light sources, and emits light from the light source incident from a lower surface side of the light guide plate from an upper surface side. A light emitting plate, wherein the light guide plate has a plurality of optically separated light incident portions, and a diffusion portion for sharing light incident from the light incident portions, and The light-entering surface of the unit is individually opposed to the plurality of light sources.
[0008]
As described above, in the light guide member that guides light, the light source is individually provided for each light source, and the diffusion unit that shares and diffuses the light incident from the light input unit is provided, thereby reducing the number of light sources. As a result, a planar light-emitting light source that can emit light with high luminance and evenly can be obtained.
[0009]
Further, the light emitting device includes a light guide plate having an upper surface and a lower surface opposed to each other, and a plurality of light sources, and a planar light emitting device that emits light from the light source incident from the lower surface side of the light guide plate from a light emitting surface on the upper surface side. A light source, wherein the upper surface of the light guide plate has a light emission observation surface that emits light corresponding to a desired display figure, and a substantially parallel region facing the light emission observation surface is divided into a plurality of light entrance parts. Wherein each of the light incident portions has a light incident surface, and one light source is disposed in an outer frame of the one light incident surface. Are arranged.
[0010]
With this configuration, it is possible to obtain a planar light source capable of uniformly emitting a complicated display figure.
[0011]
In addition, it is preferable that a separation wall is provided between the light incident portions, whereby each light source can be efficiently guided to the corresponding light incident region, and a more uniform light emitting surface can be obtained.
[0012]
Preferably, the light incident portion is separated by a groove having two separation walls, and a surface of the light incident portion facing the light source and a side surface form an obtuse angle. The point light source applied to the end face can be efficiently turned into a planar light source in the light incident area. As a result, a planar light source having more excellent uniformity can be obtained.
[0013]
Further, the plurality of light sources are optically separated by a storage body capable of individually storing the light sources, and each light source storage part of the storage body is two-dimensionally mounted on a light emission observation surface. It is characterized by having. Thereby, the light source can be freely arranged according to the shape of the light guide plate having a desired display shape, and even when the display shape is complicated, the planar light emission capable of uniformly emitting light to the corners. A light source is obtained.
[0014]
Further, it is preferable that the inner wall of the light source storage unit and the side surface of the light entrance unit form one plane. That is, a surface that is the side surface of the light incident portion and the separation wall is disposed at a position where the inner wall of the light source storage portion is extended upward. In this way, by making the light reflection angle in the light source storage section substantially equal to the light reflection angle in the light entrance section, the efficiency of using a point light source as a surface light source can be further increased.
[0015]
When the light incident portion has a convex portion protruding toward the light source on the surface facing the light source, the point light source incident from the incident surface can be more efficiently a planar light source. On the other hand, if a concave portion capable of accommodating the light source is provided on the incident surface of the light guide plate, light can be effectively used when a light source that emits light in all directions is used.
[0016]
Further, the length in the thickness direction of the diffusion portion is preferably substantially equal to or longer than the length in the thickness direction of the light incident portion, whereby light that has been made planar in each light incident portion, A planar light source capable of mixing well in the diffusion portion and uniformly emitting light over the entire surface is obtained.
[0017]
Further, the direct backlight of the present invention is a direct backlight including a plurality of light sources and a light guide plate optically connected to the light sources, wherein the light guide plate receives light from the plurality of light sources. It is characterized in that it has a light-entering portion for individually introducing the light and a diffusing portion for diffusing the introduced light in a planar manner.
[0018]
In this way, by separating the function of the light input part for introducing light and the diffusion part capable of uniform light emission, high brightness and uniformity can be obtained even when incident from the outside such as sunlight when used as a light source for signals. A planar light source capable of emitting light can be used.
[0019]
In addition, the surface emitting light source includes a plurality of light sources and a light guide plate optically connected to the light source, and emits incident light in a direction directly below the light guide plate. It has a plurality of substantially parallel surfaces facing the emission observation surface, and the plurality of surfaces are formed in a convex shape from the emission observation surface side to a surface side connected to a plurality of light sources. .
[0020]
As described above, by dividing the light incident area corresponding to the light emission observation surface into a plurality, it is possible to uniformly and clearly display a complicated figure.
[0021]
Further, the plurality of light sources may be optically separated by a housing capable of individually storing the light sources. By arranging the respective light source storage sections of the storage body two-dimensionally with respect to the light emission observation surface, it becomes possible to uniformly emit a more complicated display figure on the light emission observation surface.
[0022]
Further, a diffusion sheet may be provided above. As a result, a direct-type backlight light source capable of emitting light more uniformly can be obtained.
[0023]
Further, the signal light of the present invention is a signal light in which a direct-type backlight having a plurality of light sources and a light guide plate optically connected to the light source is disposed in a housing, wherein the light guide plate includes a plurality of light sources. It is characterized by having a light-entering section for individually introducing light from a light source and a diffusing section for diffusing the introduced light in a planar manner. Thus, a signal lamp capable of emitting light uniformly without being affected by the external environment is obtained.
[0024]
Also, a signal lamp in which a direct-type backlight having a plurality of light sources and a light guide plate optically connected to the light source is disposed in a housing, wherein the light guide plate includes a light emission observation surface and the light emission observation surface. And a plurality of substantially parallel surfaces facing each other, and the plurality of surfaces have a convex shape from the emission observation surface side to a surface side connected to a plurality of light sources.
[0025]
This makes it possible to uniformly and clearly display both a human figure and a complicated figure.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
As a result of various experiments, the present inventor has found that a plurality of LED light sources are used, and that a light emitted from a light source is introduced into a light guide plate to emit light in a planar manner. The present invention has been found that, by separating the function of the diffusion part and the diffusion part capable of uniform light emission, a high-luminance and uniform light emission observation surface can be realized regardless of the use environment, the number of light sources used, and optical characteristics. Was reached. Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
[0027]
<First embodiment>
FIG. 1 is a schematic cross-sectional view of a planar light source according to an embodiment of the present invention. The plurality of LED light sources 2 are electrically connected on the wiring board 6. The light guide plate 1 is mounted above so as to cover these LED light sources. The light guide plate of the present invention is characterized in that it has a light input section for individually introducing light from a plurality of light sources, and a diffusion section for diffusing the introduced light in a planar manner. In the present embodiment, each light incident portion is separated by a groove having a substantially V-shaped cross section. Hereinafter, each component will be described in detail.
[0028]
(Light source 2)
In the present embodiment, an LED light source is used as the light source 2. As the LED light source, an SMD type light emitting diode using a blue light emitting LED chip whose light emitting layer is made of a nitride semiconductor is preferably used, but a plurality of LED chips are directly flipped by soldering or the like on a substrate on which a wiring pattern is formed. It may be mounted on a chip. In addition, in order to make effective use of light, a common side wall may be provided for a plurality of LED chips mounted on the board, or a side wall may be provided on a board having a plurality of through holes corresponding to the LED chips. You can also. Here, the nitride semiconductor indicates various nitrogen-containing compound semiconductors such as InAlGaN, InGaN, and GaN doped with various impurities, and preferably includes a III-V nitride semiconductor.
[0029]
Examples of the SMD light emitting diode include the following. Using a package having a recess and insert-molding such that the tip surfaces of a pair of lead electrodes are exposed from the bottom surface of the recess, an LED chip is electrically connected to the bottom surface of the recess, and then an optical chip is formed in the recess. A translucent member having a functional function is provided. The outer lead portions of the pair of lead electrodes are processed into a J-shape or a gull-wing shape so that they can be connected to the surface of the wiring board.
[0030]
When a light emitting diode is used as a light source, a single LED chip is not necessarily used to correspond to one light source unit, but a plurality of LED chips capable of emitting light having different wavelengths from each other (for example, It is also possible to mount a red light emitting LED chip and a blue green light emitting LED chip) or a plurality of LED chips capable of emitting similar colors (for example, two or more blue green LED chips). In the former case, by selecting variously the LED chips to be lit in one light source section, various luminescent colors can be displayed in one planar light source.
[0031]
(Wiring board 3)
Such SMD type light emitting diodes are arranged at predetermined intervals on a wiring board 3 having external electrodes wired on the board to establish electrical continuity. The substrate member of the wiring board preferably has excellent thermal conductivity, and an aluminum base substrate, a ceramics base substrate, or the like can be used. When a glass epoxy substrate or a paper phenol substrate having poor heat conductivity is used, it is preferable to take measures against heat radiation such as a thermal pad and a thermal via. Further, the light emitting diode and the wiring board can be electrically connected by a conductive member such as solder. In consideration of heat dissipation, it is preferable to use a silver paste.
[0032]
(Light guide plate 1)
The light guide plate 1 of the present invention has a light input section 1a for individually introducing light from a plurality of light sources, and a diffusion section 1b for diffusing the introduced light in a planar manner. As described above, in a planar light source that guides and emits incident light in a parallel direction, a light incident part for introducing light and a diffusion part capable of uniformly emitting light are used as a signal light source by separating the functions. A planar light source capable of emitting light with high luminance and uniformity even when the light enters from the outside such as sunlight.
[0033]
(Light incident part 1a)
The light incident portion may be optically divided. The method of division is not particularly limited, and a slit or a groove may be provided on a flat plate, or injection molding may be performed using a mold having a desired shape in advance.
[0034]
An LED chip made of a nitride semiconductor tends to have a high luminous intensity in the direction of the end face, and an emission surface of an LED light source using such an LED chip reflects uneven luminous intensity of the LED chip, resulting in uneven light emission. It tends to be. According to the invention of the present application, since the light guide plate is provided with one light incident portion corresponding to one light source, the color unevenness of each LED light source can be improved in the light incident portion region. By sharing and diffusing the improved light source by the diffusion unit, it is possible to improve the unevenness of the light emission observation surface due to the uneven color of the LED light source.
[0035]
(Diffusion section 1b)
In the present invention, it is preferable that the thickness of the diffusion portion be substantially equal to or larger than the thickness of the light incident portion. Thereby, the light guided from the light entrance can be diffused favorably. Each light guided to the diffusion unit is provided with directivity by the light entrance unit. That is, the end portion of the light emission is a dark portion compared to the central portion of the light emission. In the present invention, the diffusion unit can share and diffuse the dark portions of these adjacent light sources to have the same brightness as the central portion of each. Thus, a planar light source having uniform luminance on one surface can be realized.
[0036]
In addition, LED chips made of a nitride semiconductor tend to have wavelength variations among the LED chips in manufacturing. Such a variation in the wavelength is easily observed to the human eye when other light such as extraneous light is buffered. However, according to the present invention, the respective wavelengths can be mixed well by sharing and diffusing the dark portions of the adjacent light sources, and when used as a signal light source, high luminance can be obtained even when external light such as sunlight enters. In addition, a planar light source capable of emitting light uniformly can be provided.
[0037]
The material of the light guide plate is preferably excellent in light transmittance and moldability, and an organic member such as an acrylic resin, a polycarbonate resin, an amorphous polyolefin resin, or a polystyrene resin, or an inorganic member such as glass can be used. . The surface of the light guide plate preferably has a surface accuracy Ra of 25 μm or less (see JIS standard) or less in order to improve the transmittance and the total reflection light ratio.
[0038]
Such a light guide plate is mounted so that each LED light source and each light input section face each other. As a method for mounting the light guide plate, it is possible to use a method such as screwing, bonding, welding, etc., which can be easily positioned and reliably obtains bonding strength, and can be selected according to specifications and requirements. In the embodiment of the present invention, a claw portion (fitting portion) is provided at an end portion of the light guide plate, a through hole is provided at a corresponding portion of the wiring board, and the claw portion is engaged with the bottom surface of the front fluorescent substance wiring board. Is fixed.
[0039]
(Diffusion sheet 4)
In the planar light source of the present invention, the diffusion sheet 4 can be provided above. As described above, the planar light source of the present invention can be used as a direct-type backlight source for irradiating another member such as a diffusion sheet disposed above. The choice of the diffusion sheet affects the thickness and performance of the light guide plate. Therefore, it is preferable to perform verification and selection each time according to specifications and requirements. In this embodiment, a diffusion sheet having a haze value of 88% to 90% (see the JIS standard) and a film thickness of about 100 μm is used for a light guide plate made of polycarbonate having excellent heat resistance and a film thickness of 20 mm. Thereby, the space between dots of each light source is further reduced, and uniform light emission is obtained. Such a diffusion sheet can be attached to the light guide plate directly by bonding or welding. When a cover lens is provided above, it can be fixed by being sandwiched between the cover lens and the light guide plate. The distance between the diffusion sheet and the light guide plate is preferably 0 mm to 10 mm, and it is most preferable that these interfaces are in close contact. As the material of the diffusion sheet, PET is mainly used, but there is no particular limitation as long as the material does not deform or deteriorate due to heat generation of the light emitting diode.
[0040]
The planar light source obtained in this manner can emit uniform and high-luminance light over the entire light-emitting surface.
[0041]
On the other hand, as shown in FIG. 4, when a light guide plate having flat upper and lower surfaces is used, the light sources of the respective light emitting diodes are sparsely observed, and bright and dark portions are observed on the light emitting surface.
[0042]
<Embodiment 2>
FIG. 2 is a schematic cross-sectional view of the planar light source according to Embodiment 2 of the present invention. The light guide plate according to the present embodiment is characterized in that the light guide plate has a concave portion capable of accommodating a light source at a front end of a light incident portion for individually introducing light from a plurality of light sources. The LED light source used in the present embodiment is an SMD type light-emitting diode with a lens using the same LED chip as in the embodiment. An SMD light emitting diode with a lens is obtained by transfer molding a pair of lead electrodes with a transparent member. Since such an SMD light-emitting diode with a lens is entirely made of a transparent member, it emits light not only in the upper surface but also in four directions. Therefore, in the present embodiment, the light use efficiency is increased by housing the SMD light-emitting diodes with lenses in the respective recesses and facing each other. The opposing surfaces of the outer wall of the LED light source and the inner wall of the recess are preferably substantially parallel, so that the inner wall of the recess can be evenly irradiated with light.
[0043]
<Embodiment 3>
FIG. 3 is a schematic cross-sectional view of the planar light source according to Embodiment 3 of the present invention. The planar light source according to the present embodiment is characterized in that it has a housing 5 that can individually house each light source on the wiring board. This makes it possible to reduce the thickness of the light incident portion. Thereby, a light guide plate having a desired shape can be formed with high reliability.
[0044]
(Storage 5)
The housing 5 can be made of various materials capable of optically separating each light source, such as metals such as Al, Ag, Cu, and Fe, and resins such as PP, PC, and ABS. . The surface of the storage body, particularly the inner wall of each storage section having a curvature, is desirably not more than Ra 25 μm (see JIS standard) in order to improve the reflection efficiency. Further, in the housing formed of resin, the inner wall of the housing can be coated with a metal coat of Ag, Ni, Al or the like.
[0045]
The container can be fixed to the wiring board by various methods such as screwing, bonding, welding, etc., according to specifications and requirements. In this embodiment, the mounting is performed by providing a claw portion (fitting portion) on the base body side and providing a through-hole on the wiring board side capable of engaging the claw portion. Thereby, the manufacturing process is simplified, and a planar light source having excellent mass productivity can be obtained.
[0046]
【The invention's effect】
As described in detail above, the planar light source, the direct-type backlight, and the signal lamp of the present invention each include a light input unit for individually introducing light from a plurality of light sources, and diffuse the introduced light in a planar shape. By using a light guide plate having a diffusing part and separating the function of the light entering part for introducing light and the diffusing part capable of uniform light emission, the light of each light source can be effectively utilized even with a small number of light sources, and It is possible to obtain a light emission observation surface with high mixing and high luminance and uniformity. In addition, high luminance and uniform light emission can be obtained without being affected by the special optical characteristics of the light source or the influence of sunlight when used as a signal light source.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a planar light source according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view of a planar light source according to another embodiment.
FIG. 3 is a schematic cross-sectional view of a planar light source according to another embodiment.
FIG. 4 is a schematic cross-sectional view of a planar light-emitting light source used as a comparative example.
FIG. 5 is an exploded view of a planar light source according to an embodiment of the present invention.
6 (a) is a schematic elevation view showing a state where a light source is placed on the storage body shown in FIG. 5, and FIG. 6 (b) is a sectional view taken on line AA of FIG. 6 (a). It is a typical sectional view in the 'line.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light guide plate 1a ... Light input part 1b ... Diffusion part 2 ... Light source 3 ... Wiring board 4 ... Diffusion sheet 5 ... Housing

Claims (16)

A light guide plate having an upper surface and a lower surface facing each other, and a plurality of light sources, a planar light emitting light source that emits light from the light source incident from the lower surface side of the light guide plate from the upper surface side,
The light guide plate has a plurality of optically separated light incident portions, and a diffusion portion that shares light incident from the light incident portion,
A light-emitting surface of the plurality of light-entering sections, wherein the light-entering surfaces individually face the plurality of light sources, respectively. A light guide plate having an upper surface and a lower surface opposed to each other, and a plurality of light sources, and a planar light emitting light source that emits light of the light source incident from the lower surface side of the light guide plate from the light emitting surface on the upper surface side. So,
The upper surface of the light guide plate has a light emission observation surface that emits light corresponding to a desired display figure,
A substantially parallel region facing the light emission observation surface is divided into a plurality of light incident portions,
The planar light emitting source, wherein each of the light incident portions has a light incident surface, and one light source is arranged in an outer frame of the one light incident surface. The planar light source according to claim 1, further comprising a separation wall between the light incident portions. 4. The planar light source according to claim 1, wherein the light incident portion is divided by a groove having two separation walls. The surface light emitting light source according to claim 1, wherein the front light incident portion has an obtuse angle between a surface facing the light source and a side surface. The plurality of light sources are optically separated by a storage body capable of individually storing the light sources, and each light source storage part of the storage body is two-dimensionally mounted on a light emission observation surface. The planar light source according to any one of claims 1 to 5, wherein: The planar light-emitting light source according to claim 1, wherein an inner wall of the light source housing and an end face of the light-entering portion form one plane. The planar light source according to claim 1, wherein the light incident portion has a convex shape from the light emission observation surface side to the light source side. The planar light emitting light source according to claim 1, wherein the light incident portion has a concave portion capable of storing the light source. The planar light emitting source according to claim 1, wherein a length of the diffusion portion in a thickness direction is substantially equal to or longer than a length of the light incident portion in a thickness direction. A direct backlight having a plurality of light sources and a light guide plate optically connected to the light sources,
The direct-type backlight according to claim 1, wherein the light guide plate includes a light input unit that individually introduces light from a plurality of light sources, and a diffusion unit that diffuses the introduced light in a planar shape. A direct backlight having a plurality of light sources and a light guide plate optically connected to the light sources,
The light guide plate has a plurality of substantially parallel surfaces facing the light emission observation surface and the light emission observation surface,
A direct-type backlight, wherein the plurality of surfaces have a convex shape from the emission observation surface side to a surface side connected to the plurality of light sources. The plurality of light sources are optically separated by a storage body capable of individually storing the light sources, and each light source storage part of the storage body is two-dimensionally mounted on a light emission observation surface. 13. The direct-type backlight according to claim 11, wherein: 14. The direct backlight according to claim 11, wherein an upper surface of the light guide plate has a diffusion sheet. A signal light in which a direct-type backlight having a plurality of light sources and a light guide plate optically connected to the light sources is disposed in a housing,
The signal light according to claim 1, wherein the light guide plate includes a light input unit for individually introducing light from a plurality of light sources, and a diffusion unit for diffusing the introduced light in a planar shape. A signal light in which a direct-type backlight having a plurality of light sources and a light guide plate optically connected to the light sources is disposed in a housing,
The light guide plate has a plurality of substantially parallel surfaces facing the light emission observation surface and the light emission observation surface,
A signal lamp, wherein the plurality of surfaces are formed in a convex shape from the emission observation surface side to a surface side connected to the plurality of light sources.

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