JP2006344450A - Linear light source and surface light emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bright and reliable linear light source and a surface light emitting device by preventing both short-time luminance degradation and long-term luminance degradation. <P>SOLUTION: In this linear light source, a light emitting element is covered and sealed with glass. Since the light emitting element is sealed with glass in which an amount of permeation of water or oxygen is smaller than in a resin, or practically zero, the light emitting element may not be deteriorated with water or oxygen. Since it is glass without being deteriorated in quality by light like a resin, light emitting efficiency of a sealing material is not declined even in long term lighting of the light emitting element, and transmissivity of water or oxygen in the sealing material does not increase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linear light source and a surface light emitting device used in a liquid crystal display device such as a computer display, a television display, and a portable information communication device.

  A transmissive liquid crystal display device is generally used as the liquid crystal display device. The transmissive liquid crystal display device includes a surface light emitting device called a backlight, and forms an image by spatially modulating illumination light from the surface light emitting device using a liquid crystal panel.

  As a surface light emitting device, a method of using a cold cathode tube which is a substantially linear light source and entering from a side surface of a light guide plate is currently widely used. Light incident from the side surface of the thin plate-like light guide plate propagates while repeating total reflection between opposing main surfaces. At this time, it is common to form a part of the propagating light by forming a diffuse reflection layer or reflection unevenness having a specific density distribution and size on the surface opposite to the surface to be the exit surface. It is. By appropriately setting the density distribution, size distribution, and the like that form the diffuse reflection layer or the reflection irregularities, it is possible to perform substantially uniform illumination over the entire surface of the liquid crystal panel.

  More recently, the performance of light-emitting elements such as light-emitting diodes has been improved, and it has been proposed to use this as a light source for liquid crystal backlights. For small screens such as cellular phones, light-emitting elements are used instead of conventional cold-cathode tubes. It is mainly used as a light source. As shown in FIG. 6, the light emitting element package 61 in which the light emitting element chip, the wiring, and the sealing resin are integrally assembled is individually arranged in the vicinity of the side surface of the light guide plate 63 one by one. In this method, the light emitting device package is relatively large, which is an obstacle to reducing the overall size and thickness of the light emitting device package, and the brightness unevenness that the light emitting device package is bright and dark between adjacent light emitting device packages is disadvantageous. There is.

  On the other hand, in order to reduce the unevenness in size and brightness, a plurality of light-emitting elements 71 are disposed on a thin wiring board 73 as shown in FIG. There has been proposed a structure in which a resin 72 is disposed to seal a light emitting element.

As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
JP 2004-235139 A

  However, in the conventional light source, the light emitting element is sealed with a resin material in order to prevent it from being deteriorated by oxygen or water present in the vicinity. However, although the resin is small, it transmits oxygen and water. There is a problem that the deterioration of the light-emitting element proceeds over a long period of time.

  Also, the sealing resin material itself is deteriorated and deteriorated by the light emitted from the light emitting element. Therefore, the resin is discolored, and the efficiency of the light emitted from the light emitting element through the sealing resin is emitted. There is a problem of reduction, and there is a problem that the amount of permeation of water and oxygen increases to accelerate deterioration of the light emitting element.

  Further, part of the electric energy supplied to the light emitting element is changed to heat, and the temperature of the light emitting element and its peripheral portion is increased. Due to this temperature rise, there is a problem that the sealing resin further deteriorates, and that the luminous efficiency of the light emitting element is lowered and the luminance is lowered when the temperature becomes high even after a short time after lighting.

  The above problems are solved by the following linear light source and surface light emitting device.

  A linear light source comprising: a wiring board; a plurality of light emitting elements arranged on the wiring board; and a glass material that is formed on the wiring board and covers the light emitting elements.

  The linear light source and the light guide plate, and the light from the linear light source is incident from the side surface of the light guide plate and propagated across the entire surface while reflecting between the opposing main surfaces, and one of the main surfaces A surface light-emitting device that emits light from a certain light exit surface.

  Since the light-emitting element is sealed with glass that is smaller and substantially zero in water and oxygen permeation than the resin, the light-emitting element is not deteriorated by water and oxygen.

  In addition, since the glass does not deteriorate due to light like resin, even when the light emitting element is lit for a long time, the light emission rate of the sealing material does not decrease, and the water and oxygen transmittance of the sealing material increases. There is nothing.

  The thermal conductivity of the sealing resin is about 0.2 W / m · K, whereas the glass is as high as about 1 W / m · K. A decrease in luminous efficiency due to a small increase and a high temperature can be reduced.

  Due to the synergistic effect of the above effects, the linear light source of the present invention can provide both a bright and highly reliable light source that prevents both a short-time luminance decrease and a long-time luminance decrease.

  A structure in which a reflecting member is arranged between the light emitting elements and the opening of the reflecting surface facing the light emitting element is sealed with glass so as to cover the light emitting elements is also sealed. It is possible to reduce the luminance unevenness and improve the luminance in the longitudinal direction by reflecting in the direction of the exit surface of the stop glass, and the amount of sealing glass can be reduced.

  By using the linear light source and the light guide plate, a similarly bright and highly reliable surface light emitting device can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
The linear light source concerning Embodiment 1 of this invention is demonstrated using FIG.

  1 is a perspective view of a linear light source according to Embodiment 1. FIG. The wiring board 3 has an elongated plate shape, and although not shown in the drawing, electrical wiring for transmitting and receiving power and signals from the power source to the light emitting element is formed, and a light emitting diode is formed in the longitudinal direction of the board. A plurality of light emitting elements 1 represented by the above are arranged at a predetermined interval. The light emitting element is not a light emitting element package integrated with a sealing material such as the light emitting element package 61 of FIG. 6, but a light emitting element chip itself. And the glass 2 is formed as a sealing material so that the light emitting element 1 may be coat | covered on the surface of a wiring board.

  The sealing glass does not need to be formed on the entire mounting surface of the wiring board, and the end of the wiring board may be excluded as shown in FIG. 1, or may be formed only around the light emitting element. As the glass, a low melting point glass can be heat-softened and press-molded, a powdery glass can be heated and melted, and a forming method such as a sol-gel method can be used.

  Since the transmittance of water and oxygen in glass is substantially zero, the light-emitting element covered and sealed with glass does not react with water or oxygen and deteriorate. Glass does not change its structure due to light energy unlike resin, so even if the light-emitting element is lit for a long time and exposed directly to light, the light transmittance decreases or the water and oxygen transmittance increases and emits light. It can suppress that quantity reduces.

  While the light emitting element generates heat during lighting, glass has a thermal conductivity approximately five times greater than that of conventional resins, so that the amount of heat emitted from the light emitting element is increased and the temperature rise of the light emitting element can be suppressed. For this reason, it is possible to suppress a decrease in the light emission efficiency that has occurred in a short time after lighting by suppressing a decrease in the light emission efficiency of the light emitting element.

  Unlike conventional light emitting device packages, wiring and package frames are not required, and it is integrated with the wiring board, so that the overall size can be reduced and thinned, and the brightness unevenness is reduced by reducing the light emitting device pitch. It becomes easy.

(Embodiment 2)
A linear light source according to a second embodiment of the present invention will be described with reference to FIG.

  FIG. 2 is a longitudinal sectional view of the linear light source. The first wiring board 23 is the same as the wiring board 3 of the first embodiment, and a plurality of light emitting elements 21 are arranged at predetermined intervals in the longitudinal direction of the first wiring board.

  Glass 22 is formed as a sealing material so as to cover the light emitting element 21 on the surface of the first wiring substrate 23. This is the light emitting element array module 25. In this embodiment, the linear light source has a configuration in which a plurality of light emitting element array modules are arranged on the surface of the second wiring board 26 longer than the first wiring board.

  Transmission and reception of power and signals to each light emitting element are performed by the wiring circuit of the first wiring board, and the second wiring board transmits and receives power and signals to the first wiring board.

  As an example, in the case of a linear light source used for a 12-inch display, a configuration in which six light emitting element array modules having a length of about 50 mm in which eight light emitting elements are arranged is arranged on the second wiring board can be formed. The number of the arrays is an example, and the number of light emitting elements, the pitch of the light emitting elements, the length of the light emitting element array modules, and the number of the arrays are appropriately determined depending on factors such as required brightness and low brightness unevenness and ease of manufacturing the light emitting element array module I can decide.

  When all wirings, light emitting elements, and sealing glass are mounted on a single wiring board, a process of mounting and sealing a large number of light emitting elements on a very elongated substrate is required. This is a difficult manufacturing operation that requires man-hours and precision, and if the original light emitting device is defective or has some mounting failure, the entire linear light source becomes defective and causes great damage.

  On the other hand, according to this embodiment, since the number of mounting and sealing of the light emitting elements on one first wiring board is small, the manufacturing becomes easy. Furthermore, the assembly of the first wiring board and the second wiring board can be easily performed because only a small number of wiring connections and a large board are joined as compared with mounting of a light emitting element and a sealing material.

  As a result, an inexpensive linear light source can be easily obtained with a good yield. And since it seals with glass, it is the same as that of Embodiment 1 that a bright thing is obtained as a linear light source in the short term and the long term.

(Embodiment 3)
Next, a linear light source according to Embodiment 3 of the present invention will be described with reference to FIG.

  FIG. 3 is a perspective view of a linear light source according to the third embodiment. The wiring board 33 has an elongated plate shape, and although not shown in the drawing, electrical wiring for transmitting and receiving power and signals from the power source to the light emitting element is formed, and the light emitting element extends in the longitudinal direction of the substrate. A plurality of lines 31 are arranged at predetermined intervals. A reflective member 34 is arranged between the light emitting elements.

  The reflection surface 35, which is a surface facing the light emitting element 31 of the reflecting member 34, has a larger opening between the reflection surfaces facing each other across the light emitting element as it goes upward in the figure, which is the emission direction of the light emitting element. It has a shape that is inclined to become. And the glass 32 is formed as a sealing material so that the light emitting element 31 may be coat | covered on the surface of the wiring board 33 between the reflective surfaces 35 which oppose.

  The direction of the light emitted from the light emitting element is not only in the upward direction in the figure but also in the lateral direction, and this lateral light hits the reflection surface of the reflecting member and can be reflected and emitted upward. Therefore, compared to a linear light source that emits directly upward from a light emitting element, light emitted in the horizontal direction can be effectively emitted upward and the emitted light can be expanded in the horizontal direction. A light source can be realized. Further, since the sealing member does not require a sealing material, the amount of sealing glass used can be reduced, and the treatment at a relatively high temperature in the sealing process can be completed in a short time and the influence on other members can be suppressed.

  And since it seals with glass, it is the same as that of Embodiment 1 that a bright thing is obtained as a linear light source in the short term and the long term.

(Embodiment 4)
Next, a linear light source according to Embodiment 4 of the present invention will be described with reference to FIG.

  FIG. 4 is a cross-sectional view in the longitudinal direction of the linear light source according to the fourth embodiment. The first wiring board 43 is the same as the wiring board 3 of the first embodiment, and a plurality of light emitting elements 41 are arranged at predetermined intervals in the longitudinal direction of the first wiring board. A reflective member 44 is arranged between the light emitting elements. The reflection surface, which is the surface of the reflection member 44 that faces the light emitting element 41, has a larger opening between the reflection surfaces facing each other across the light emitting element as it goes upward in the figure, which is the emission direction of the light emitting element. The shape is slanted. And the glass 42 is formed as a sealing material so that the light emitting element 41 may be coat | covered on the surface of the 1st wiring board 43 between the reflective surfaces which oppose. This is the light emitting element array module 45. In this embodiment, the linear light source has a configuration in which a plurality of light emitting element array modules are arranged on the surface of the second wiring board 46 longer than the first wiring board. Transmission and reception of power and signals to each light emitting element are performed by the wiring circuit of the first wiring board, and the second wiring board transmits and receives power and signals to the first wiring board.

  The light emitted from the light emitting element 41 is not only directly emitted upward, but the lateral light is reflected by the reflecting surface of the reflecting member 44 and emitted upward, thereby obtaining a bright linear light source with reduced luminance unevenness. be able to. As described in the second embodiment, a linear light source with a high yield is realized compared with the case where a very large number of light emitting elements, reflecting members, and sealing glass are mounted on a single very thin wiring board. And because it is sealed with glass, it can be bright in both the short and long term.

(Embodiment 5)
Next, a surface light emitting device according to Embodiment 5 of the present invention will be described with reference to FIG.

  5A is a plan view of the surface light emitting device according to Embodiment 5, and FIG. 5B is a cross-sectional view. A light source array module in which a light emitting element 51 and a reflecting member 54 are arranged on a first wiring board 53 is constituted by a linear light source in which a second wiring board 56 is arranged, and a light guide plate 57 having a wedge shape. Light emitted from the light emitting element 51 is transmitted through the sealing glass and emitted, enters the incident surface 58 that is the side surface of the light guide plate 57, and faces the output surface 59 that is the main surface of the light guide plate, and the output surface 59. This is a surface light emitting device that emits light that is propagated to the entire surface while being reflected between the other inclined main surfaces and reflected forward from the inclined main surface as planar light from the emission surface.

  In this light-emitting device, since the light-emitting element is sealed with glass, there is no problem such as a decrease in light transmittance of the sealing material and a decrease in water and oxygen transmittance, and bright light emission can be achieved in the short and long term. Therefore, it is possible to realize a small and thin surface light emitting device as compared with a conventional one using a package type light emitting element. This light-emitting device is not limited to this embodiment, and it is also effective to install all light-emitting elements, wiring, and sealing glass on a single wiring board, or to include no reflective member between the light-emitting elements. It is.

  The linear light source and the surface light-emitting device of the present invention are small and thin and can emit bright light in the short term and in the long term, and are useful as light sources for displays.

1 is a perspective view of a linear light source according to Embodiment 1. FIG. Sectional drawing of the longitudinal direction of the linear light source which concerns on Embodiment 2 The perspective view of the linear light source which concerns on Embodiment 3. FIG. Sectional drawing of the longitudinal direction of the linear light source which concerns on Embodiment 4 (A) The top view of the surface emitting device which concerns on Embodiment 5, (b) Sectional drawing (A) Top view of a conventional surface light emitting device, (b) Side view of a conventional surface light emitting device. Partial sectional view of a conventional linear light source

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Glass 3 Wiring board 25 Light emitting element array module 26 2nd wiring board 34 Reflective member

Claims (4)

A wiring board;
A plurality of light emitting elements arranged on the wiring board;
A linear light source comprising a glass material formed on the wiring board and covering the light emitting element. A first wiring board;
A plurality of light emitting elements arranged on the first wiring board;
A linear light source having a configuration in which a plurality of light-emitting element array modules, which are formed on the first wiring board and have a glass material covering the light-emitting elements, are arranged on the second wiring board. A reflective member is arranged between the light emitting elements arranged on the wiring board,
3. The linear light source according to claim 1, wherein a reflection surface, which is a surface facing the light emitting element of the reflecting member, has a shape inclined so that an opening becomes larger toward an emission direction of the light emitting element. A linear light source according to any one of claims 1 to 3 and a light guide plate,
Light from the linear light source is incident from the side surface of the light guide plate and propagates to the entire surface while being reflected between opposing main surfaces, and is emitted from an output surface that is one of the main surfaces to emit planar light. A surface emitting device.

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