JP2012138345A - Edge-light type surface light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an edge-light type surface light-emitting device in which deterioration of luminous efficiency and possibility of breakage due to thermal expansion of a light guide plate are eliminated.SOLUTION: The edge-light type surface light-emitting device 1 is provided with at least a resin-made light guide plate 2 of a rectangular shape in plane view, a light source 3 arranged along an end face 2A of the light guide plate 2, and a housing body 4 which supports the light source 3 and the light guide plate 2 surrounding them. Light from the light source 3 enters from the end face 2A of the light guide plate 2, is reflected in the light guide plate 2, and is emitted from an emitting face of the light guide plate 2. The housing body 4 is constructed so as to have gaps 51, 52, 53 against the end faces 2B, 2C, 2D of the light guide plate 2; an elastic member 61 is installed at least in the gap 52, and the elastic member 61 is established so as to push the light guide plate 2 to the light source 3 and to absorb the expansion of the light guide plate 2.

Description

  The present invention relates to an edge light type surface light emitting device. This surface light-emitting device is useful for lighting bodies used indoors in offices or in vehicles such as bullet trains, backlight units used in liquid crystal displays, signboards, and the like.

  The edge light type surface light emitting device generally includes at least a light source, a light guide plate for surface emitting light incident from the light source, and a housing body surrounding and supporting the light source and the light guide plate. As the light guide plate, a resin plate such as methacrylic resin is typically used.

JP 2010-177077 A JP-A-6-186433 JP 2006-185724 A

  By the way, since the light guide plate is made of resin, it expands due to heat from the light source and changes in temperature and humidity under the usage environment. Therefore, conventionally, in consideration of expansion of the light guide plate, a gap for absorbing the expansion is secured in advance between the light guide plate and the light source and / or between the light guide plate and the housing body. It was.

  However, when a gap is secured between the light guide plate and the light source in advance, a part of the light from the light source leaks out of the light guide plate, which causes a problem that the light emission efficiency is low. Further, when a gap is secured in advance between the light guide plate and the housing body, there is a problem that the light guide plate is unstable in the housing body and the light guide plate or the light source may be damaged.

  An object of the present invention is to provide an edge light type surface light emitting device capable of solving both the above-mentioned problems.

  The present invention includes at least a resin-made light guide plate having a rectangular shape in plan view, a light source disposed along one end surface of the light guide plate, and a housing body that surrounds and supports the light source and the light guide plate. In an edge light type surface light emitting device in which light enters from the end face of the light guide plate, is reflected within the light guide plate, and exits from the light exit face of the light guide plate, the housing body is other than the end face of the light guide plate. An elastic member is provided in the gap between the housing body and at least the end face facing the end face of the light guide plate, and an elastic member is provided. The member is characterized in that it is set so as to press the light guide plate toward the light source and absorb the expansion of the light guide plate.

As the elastic member, for example, the following members can be used.
(A) The elastic member is a block body made of an elastic material, and is provided in the gap at appropriate intervals.
(B) The elastic member is a spring and is provided in the gap at an appropriate interval.
(C) The elastic member is a spring piece formed by cutting and raising the housing body, and is provided at an appropriate interval in the gap.

  According to the present invention, the elastic member can absorb the expansion of the light guide plate due to heat while maintaining the state where the end face of the light guide plate is pressed against the light source. Therefore, the luminous efficiency can be improved and the light guide plate can be stably held in the housing body to prevent the light guide plate and the light source from being damaged.

  According to said structure (A)-(C), an elastic member can be set easily.

It is sectional drawing of the edge light type surface emitting device of one Embodiment of this invention, and is a figure corresponded to the II cross section of FIG. It is an II-II arrow line view of FIG. It is a fragmentary figure which shows an example of the modification of an elastic member. It is a fragmentary figure which shows another example of the modification of an elastic member.

  FIG. 1 is a cross-sectional view of an edge light type surface light emitting device according to an embodiment of the present invention. 2 is a view taken in the direction of arrows II-II in FIG. 1 corresponds to the II cross section of FIG. The surface light emitting device 1 includes at least a light guide plate 2, a light source 3, and a housing body 4.

  A plurality of light sources 3 are provided and are arranged at equal intervals toward one end surface 2A of the light guide plate 2 and along the end surface 2A. The light source 3 is fixed on the substrate 30. As the light source 3, an LED, a fluorescent lamp, a cold cathode tube or the like can be used, and in particular, an LED can be preferably used.

  The light guide plate 2 is a rectangular plate in plan view and is made of resin as a main component. As the resin, for example, at least one selected from the group consisting of (meth) acrylic resin, polystyrene resin, polyolefin resin, polycarbonate resin, polyvinyl chloride resin, and (meth) acrylic acid ester-styrene resin is preferable, Particularly preferred is a (meth) acrylic resin. These resins may be used as a mixture of two or more, or may be used so as to laminate two or more. The thickness of the light guide plate 2 is usually 1 to 10 mm, preferably 1.5 to 8 mm, and more preferably 2 to 5 mm. If the light guide plate 2 is too thin, the light from the light source 3 may be difficult to be incident. If the light guide plate 2 is too thick, the light emission efficiency may be insufficient. Is too heavy, so it is not preferable that it is too thin or too thick.

  An irregular reflection layer 21 is formed on the reflection surface 2 </ b> X of the light guide plate 2. The irregular reflection layer 21 is formed by subjecting the reflective surface 2X to direct processing with a laser in a dot shape or a stripe shape, screen printing or vapor deposition of ink, or ink jet printing. Yes. In particular, a dot shape is preferable. As a form of a dot, for example, a substantially circular shape, a substantially triangular shape, a substantially rectangular shape, a substantially hexagonal shape and the like are preferable. As a method of forming the irregular reflection layer 21 in the form of dots, (1) a method of applying unevenness to the portion corresponding to the dots or attaching ink or the like, and (2) a portion of the ground other than the dots On the other hand, there is a method of performing uneven processing or attaching ink or the like. The method (1) is referred to as “positive pattern”, and the method (2) is referred to as “negative pattern”. In the case of a positive pattern, the dot distribution is preferably such that the area occupied by dots per unit area gradually increases from the end surface 2A side toward the end surface 2C. In the case of a negative pattern, It is preferable that the area occupied by dots per unit area gradually decreases from the end surface 2A side toward the end surface 2C.

  A reflective film 22 is further provided on the surface of the irregular reflection layer 21. A reflective film 22 is attached to the end surface 2C of the light guide plate 2. The thickness of the reflective film 22 is usually 50 to 400 μm. As the reflective film 22, for example, a low-foamed film made of white polyester, a film made of glass or plastic, and a metal having a high reflectance deposited thereon can be used.

  A light diffusion plate 23 is installed on the light exit surface 2Y side of the light guide plate 2. The light diffusion plate 23 is a plate having a light diffusion function or a light collecting function. The light diffusing plate 23 is a plate made of a resin composition containing a light diffusing agent, a plate made of a resin composition and having a concavo-convex shape on the surface, or a resin composition containing a light diffusing agent and a surface. It is comprised with the board | plate with which uneven | corrugated shape was given to. As resin which comprises the light diffusing plate 23, it selects from the group which consists of (meth) acrylic resin, polystyrene resin, polyolefin resin, polycarbonate resin, polyvinyl chloride resin, and (meth) acrylic acid ester-styrene resin, for example. At least one type is preferable, and a (meth) acrylic resin is particularly preferable. These resins may be used as a mixture of two or more, or may be used so as to laminate two or more. Examples of the light diffusing agent that can be included in the light diffusion plate 23 include organic fine particles such as acrylic crosslinked beads and (meth) methyl acrylate-styrene copolymer (MS) crosslinked beads, silica, titanium oxide, Inorganic fine particles such as barium sulfate can be used, and two or more of these may be used simultaneously. In particular, organic fine particles are preferable. Similar to the light guide plate 2, the light diffusion plate 23 may be a rectangular plate in plan view. The thickness is usually about 0.1 to 5 mm, preferably 0.15 to 4 mm. If the light diffusing plate 23 is too thin, wrinkles are likely to occur in the light diffusing plate 23 itself. If the light diffusing plate 23 is too thick, the entire surface light emitting device becomes heavy. It is not preferable. Also, a clear protective plate (not shown) having a rectangular shape in plan view is installed on the light exit surface 2Y side of the light diffusing plate 23 so as to cover the light diffusing plate 23 in order to suppress the generation of wrinkles on the light diffusing plate 23. It is preferable to do this.

  The housing body 4 includes a main body surface portion 41 that covers the light guide plate 2 from the reflective surface 2X side, and four side surface portions 421 and 422 that extend downward from the four sides of the main body surface portion 41 so as to cover the peripheral edge portion of the light guide plate 2. , 423, 424 and four edge surface portions extending inwardly from the lower edge of each side surface portion. In FIG. 1, only two edge portions 431 and 433 are shown.

  As shown in FIG. 2, the size of the housing body 4 is such that substantially the same gaps 51, 52, and 53 are provided between the three end surfaces 2 </ b> B, 2 </ b> C, and 2 </ b> D of the light guide plate 2 with respect to the housed light guide plate 2. Is set to have.

  An elastic member 61 is provided in the gaps 51, 52, 53. The elastic member 61 is a block body made of an elastic material. Examples of the elastic material that can be used include silicone rubber, acrylic rubber, nitrile rubber, urethane rubber, ethylene propylene rubber, chloroprene rubber, styrene-butadiene rubber, and fluorine rubber.

  A plurality of elastic members 61 are provided at appropriate intervals. The elastic member 61 is set so as to press the light guide plate 2 toward the light source 3 and absorb the expansion of the light guide plate 2.

  In the housing body 4, the four edge surfaces extend inward by a dimension that can prevent the light guide plate 2 accommodated in the internal space of the housing body 4 from falling from the housing body 4.

  In the surface light emitting device 1 having the above-described configuration, the light emitted from the light source 3 enters the light guide plate 2 from the end surface 2A, and is diffusely reflected at the dots of the irregular reflection layer 21 while being repeatedly reflected in the light guide plate 2 and the dots. In the meantime, the light is reflected by the reflection film 22 and is diffused and emitted from the light exit surface 2Y by the light diffusion plate 23. That is, the light exit surface 2Y emits light by the light emitted from the light source 3. Thereby, the surface emitting device 1 exhibits a surface emitting function. The surface light-emitting device 1 having the above configuration has a sufficient illuminance, and is particularly suitable as an indoor lighting device.

  By the way, in the surface light emitting device 1 having the above configuration, the end surface 2 </ b> A of the light guide plate 2 is pressed against the light source 3 by the elastic member 61 provided in the gap 52. Therefore, there is no gap between the end face 2A and the light source 3. Therefore, the light emitted from the light source 3 enters the end face 2A more efficiently than when there is a gap. Therefore, the light emission efficiency by the light guide plate 2 can be improved.

  On the other hand, the light guide plate 2 expands in the direction of arrow A due to heat from the light source, temperature change or humidity change in the usage environment, but the expansion is received by the elastic member 61 provided in the gaps 51, 52, 53. It is done. That is, the expansion of the light guide plate 2 is absorbed by the elastic member 61. Therefore, even when the light guide plate 2 is expanded, it is stably held in the housing body 4. Therefore, the light guide plate 2 and the light source 3 can be prevented from being damaged by the expansion of the light guide plate 2. Moreover, even when the light guide plate 2 expands, the end surface 2A is pressed against the light source 3. Therefore, even if the light guide plate 2 expands, the light emitted from the light source 3 efficiently enters the end surface 2A. Therefore, even when the light guide plate 2 expands, the light emission efficiency of the light guide plate 2 can be maintained.

In addition, as an elastic member, you may employ | adopt the following modifications.
(1) As shown in FIG. 3, an elastic member 62 made of a spring can be used. Similarly to the elastic member 61, the elastic member 62 is set so as to press the light guide plate 2 toward the light source 3 and absorb the expansion of the light guide plate 2.

(2) As shown in FIG. 4, an elastic member 63 made of a spring piece can be used. The elastic member 63 is formed by cutting and raising the housing body 4. Similarly to the elastic member 61, the elastic member 63 is set so as to press the light guide plate 2 toward the light source 3 and absorb the expansion of the light guide plate 2.

  Moreover, in the said embodiment, it is elastic to all the clearance gaps 51, 52, and 53 between end surface 2B, 2C, 2D other than end surface 2A in which the light source 3 is arrange | positioned, and the housing body 4 of the light-guide plate 2. The member 61 is provided, but the elastic member 61 may be provided at least in the gap 52 between the end surface 2C facing the end surface 2A and the housing body 4.

[Example 1]
It is the surface emitting device 1 which has the structure of FIG.1 and FIG.2. The specific configuration of each part is as follows.
Light guide plate 2: A (meth) acrylic resin plate having a product name “SUMIPEX E005” manufactured by Sumitomo Chemical Co., Ltd. was used. The dimensions are 4 mm in thickness, 50 mm in width, and 300 mm in length. “SUMIPEX” is a registered trademark of Sumitomo Chemical Co., Ltd.
-Diffuse reflection layer 21: formed by printing a reflective ink by a screen printing method. The reflective ink is composed of volatile curable resin ink, acrylic beads, silica fine particles, and phosphor. The print pattern is a negative pattern, the dot shape is substantially circular, and the dot pitch (center-to-center distance) is constant. The negative pattern is set so that the printed portion per unit area is small in the vicinity of the light source and increases as the distance from the light source increases so that the luminance when used as illumination is uniform. Considering that the incident light is reflected by the reflection film 22 on the end face 2C, the print portion is set to be the largest just before the end face 2C.
Reflective film 22: The product name “E60” manufactured by Toray Industries, Inc. was used.
-Light diffusion plate 23: An acrylic resin plate having a product name "Sumipex EM090" manufactured by Sumitomo Chemical Co., Ltd. was used. The thickness is 2 mm.
LEDs 28 are arranged on the long side end surface 2A of the light guide plate 2.
Elastic member 61 is a block body made of silicone rubber.
In Example 1, the LED is pressed against the end surface 2A by the elastic member 61, so that there is no gap between the LED and the end surface 2A.

[Comparative Example 1]
Only the point which does not have the elastic member 61 differs from Example 1. FIG. In Comparative Example 1, the reflection film 22 on the end surface 2C is bonded to the side surface portion 423 of the housing body 4 with a double-sided tape, and a gap of 1.0 mm is provided between the LED and the end surface 2A. .

[performance test]
The surface light-emitting device 1 of Example 1 was installed at the center of a large integrating sphere for measuring total luminous flux. Then, the surface light emitting device 1 was caused to emit light by applying power of 8.9 W, and the total luminous flux was measured with a diode array spectroscope.
For the surface light emitting device of Comparative Example 1, the total luminous flux was measured in the same manner.
The results are shown in Table 1.
As a large integrating sphere for measuring the total luminous flux, a model 1500 type spherical luminous meter manufactured by Nemtech Co., Ltd. was used. As a diode array spectrometer, DAS-2100 manufactured by Labsphere was used.

  As is clear from Table 1, the surface light emitting device 1 of Example 1 is excellent in luminous efficiency.

  The edge light type surface light emitting device of the present invention can absorb the expansion of the light guide plate due to heat and can realize high luminous efficiency, and thus has great industrial utility value.

  DESCRIPTION OF SYMBOLS 1 Edge light type surface emitting device 2 Light guide plate 2A End surface 3 Light source 4 Housing body 51, 52, 53 Crevice 61, 62, 63 Elastic member

Claims (4)

A resin-made light guide plate having a rectangular shape in plan view;
A light source disposed along one end surface of the light guide plate;
A housing body that surrounds and supports the light source and the light guide plate;
In the edge light type surface light emitting device, the light of the light source is incident from the end face of the light guide plate, reflected in the light guide plate and emitted from the light exit surface of the light guide plate.
The housing body is configured so as to have a gap between the light guide plate and an end face other than the end face,
An elastic member is provided in the gap between the housing body and at least the end surface facing the end surface of the light guide plate,
The elastic member is set so as to press the light guide plate toward the light source and absorb the expansion of the light guide plate.
An edge light type surface light emitting device characterized by the above. The elastic member is a block body made of an elastic material, and is provided at appropriate intervals in the gap.
The edge light type surface emitting device according to claim 1. The elastic member is a spring and is provided at an appropriate interval in the gap.
The edge light type surface emitting device according to claim 1. The elastic member is a spring piece formed by cutting and raising the housing body, and is provided at appropriate intervals in the gap.
The edge light type surface emitting device according to claim 1.

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