JP2009076329A - Plane light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plane light source device that has more superior light uniformity in a wide range. <P>SOLUTION: In the plane light source device 1, a light source 3, a light guide body 2, a prism sheet 4, and an adhesive member 6 are included, in which one part of one side part 7 side of a light-emitting face 8 of the light guide body 2 is adhered by the adhesive member 6 with a part opposing to one part of the outer edge part of the prism sheet 4. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, light from an LED element that is a point light source is incident from one side of a light guide, propagates inside the light guide, and is emitted from the main surface of the light guide. The present invention relates to a surface light source device that emits light.

  2. Description of the Related Art A surface light source device that emits light from an LED element that is a point light source in a planar shape is used as a light source such as a liquid crystal backlight. The surface light source device is configured to allow light emitted from the light emitting diode to enter from the light incident end surface of the light guide plate and to emit light from the entire light emitting surface of the light guide plate. In this surface light source device, it is important to output light uniformly from the light emitting surface, and various structures have been proposed to realize this uniformity.

  In the surface light source device according to the first conventional technique, in order to achieve uniformity, the light-shielding tape covers and hides the part where the brightness difference is generated, and the part where the luminance unevenness is generated is outside the effective area, that is, the invalid area. (See, for example, Patent Document 1).

  In the surface light source device of the second conventional technique, a tape for fixing the reflection sheet is used to improve uniformity, and one end of the reflection sheet is a point light source near the incident surface on the exit surface. And a structure in which a plurality of corresponding portions are bonded to each other between the light source and the point light source (see, for example, Patent Document 2).

JP-A-10-293202 JP 2001-43721 A

  In the first conventional technique, the light-shielding tape covers the portion where the light and dark differences are generated, which leads to expansion of the ineffective area and becomes an obstacle to downsizing the surface light source device.

  In the second conventional technique, a double-sided tape is provided in the dark area near the light source to improve the brightness of the dark area and reduce the contrast between the light sources, but the brightness of the bright area is not lowered. Remains large. As a result, the vicinity of the light source side is brighter than the other ranges. That is, the uniformity of the entire effective range cannot be improved.

  Accordingly, an object of the present invention is to provide a surface light source device that is more excellent in light uniformity over a wide range.

The present invention includes a light source that emits light;
A light guide that is incident from one side, diffuses light incident from one side, and exits from at least one main surface;
At least one optical member provided to face one main surface of the light guide;
A surface light source device comprising: an adhesive member that bonds a portion of an outer edge portion of one main surface of the light guide to a portion facing the outer edge portion of the optical member.

  According to the present invention, the surface light source device includes a light source, a light guide, an optical member, and an adhesive member. The adhesive member bonds a portion of the outer edge portion of the one main surface of the light guide to a portion facing a portion of the outer edge portion of the optical member. In the surface light source device configured as described above, inconvenient light causing uneven brightness near one side of the light guide is emitted and scattered by a part of the adhesive member obtained by bonding the light guide and the optical member. By doing so, it is possible to reduce the range in which the luminance in the vicinity of the light source on one side of the light guide is extremely larger than that of other portions. In addition, since the adhesive member bonds the one main surface of the light guide to the optical member, when light transmitted through the light guide is incident on the adhesive member, the light is diffusely reflected and guided again into the light guide. be able to. As a result, light reaching the adhesive member can be used more effectively than simply blocking light with a light shielding tape or the like as in the prior art. Thereby, uniform light can be emitted over a wide range from one main surface of the light guide.

  Hereinafter, a plurality of embodiments for carrying out the present invention will be described with reference to the drawings. Portions corresponding to the matters described in the preceding forms in each embodiment are denoted by the same reference numerals, and overlapping description may be omitted. When only a part of the configuration is described, the other parts of the configuration are the same as those described in the preceding section. Not only the combination of the parts specifically described in each embodiment, but also the embodiments can be partially combined as long as the combination does not hinder.

  FIG. 1 is an enlarged perspective view showing a part of a surface light source device 1 according to a first embodiment of the present invention. FIG. 2 is a plan view showing the surface light source device 1 in a simplified manner. In FIG. 2, a part is virtually shown for easy understanding. The surface light source device 1 is a device for illuminating an object with illumination light, and is provided in, for example, a transmissive liquid crystal display device (not shown) and illuminates a liquid crystal display panel (not shown). Used as In the liquid crystal display device, the surface light source device 1 is provided to face the liquid crystal display panel, and illuminates the liquid crystal display panel that is the object from the side opposite to the side on which the operator of the liquid crystal display device views the display screen. The surface light source device 1 is not limited to the illumination of the liquid crystal display panel, and may be used for illumination of other objects or illumination. The surface light source device 1 includes a light guide 2, a light source 3, a prism sheet 4, a reflection sheet 5, and an adhesive member 6. The surface light source device 1 according to the present embodiment is an edge light type surface light source device 1 in which a light source 3 is provided to face one side portion 7 of the light guide 2.

  First, the light source 3 will be described. The light source 3 includes at least one light emitting element (not shown) and a support portion (not shown) that supports the light emitting element. The light emitting element included in the light source 3 emits light radially toward the one side portion 7 of the light guide 2 based on power supplied from a power source (not shown). A light emitting element is implement | achieved by the light emitting diode (abbreviation LED), for example. The support portion is provided so as to cover the outside of the remaining portion excluding the region where the light emitting element emits light. The support portion is used for positioning and fixing the light emitting element at a predetermined position of the one side portion 7 of the light guide 2. The emission direction of the light emitting element is arranged so as to be directed to one side portion 7 of the light guide 2.

The light-emitting element includes a semiconductor element (not shown) and a translucent resin (not shown) that covers the semiconductor element. The translucent resin absorbs light generated from the semiconductor element and A phosphor that generates light having a wavelength different from the absorbed light can be included. When light generated from the semiconductor element is ultraviolet light, a phosphor that is excited by the ultraviolet light and generates ultraviolet light or visible light can be used. Further, a semiconductor element capable of emitting visible light may be used, and a fluorescent substance capable of absorbing visible light from the semiconductor element and emitting visible light having a longer wavelength may be combined. When a semiconductor element is used in combination with a phosphor, it is possible to emit mixed colors of various tones. Moreover, as a semiconductor element, it is a nitride compound semiconductor, for example, Comprising: The thing of the general formula (I) shown next is used suitably.
In _i Ga _j Al _k N (I)

  Here, in the formula (I), i, j, and k represent atomic ratios of In, Ga, and Al, respectively, are values of 0 or more, and are values that satisfy i + j + k = 1.

  As nitride compound semiconductors, there are various types including InGaN and GaN doped with various impurities. This semiconductor element is formed by growing a semiconductor such as InGaN and GaN as a light emitting layer on a substrate by MOCVD or the like. Examples of the structure of the semiconductor element include a homostructure, a heterostructure, and a double heterostructure having a MIS junction, a PIN junction, and a pn junction. The nitride semiconductor layer can have various emission wavelengths depending on the material and the crystallinity. In addition, the semiconductor active layer may be a single quantum well structure or a multi-quantum well structure formed by a thin film that produces a quantum effect.

  In addition, the fluorescent substance converts the wavelength of light from the light-emitting element, and light emitted to the outside can be converted by including the fluorescent substance in a translucent resin that covers the light-emitting element. When light from the light emitting element is high-energy short-wavelength visible light, nitrogen activated by at least one of perylene-type derivatives, organic phosphors such as ZnCdS: Cu and YAG: Ce, and Eu and Cr Various inorganic phosphors such as containing CaO—Al 2 O 3 —SiO 2 are suitably used. In particular, when a YAG: Ce phosphor is used, light from a light emitting element that emits blue light depending on its content and a yellow color that partially absorbs the light to emit light can be emitted, and a white color is relatively This is preferable because it can be easily formed with high reliability. Similarly, when an inorganic phosphor is used, depending on its content, it is possible to emit blue light and red light which is a complementary color by partially absorbing the light, so the white light is relatively easy and reliable. It is preferable to form.

  Next, the light guide 2 will be described. The light guide 2 is translucent and has a flat plate shape in the present embodiment, and has a substantially rectangular cross section in the XY plane, which is a virtual plane perpendicular to the thickness direction, and more specifically, a substantially rectangular shape. It is. The light guide 2 has principal surfaces 8 and 9 on both surfaces in the thickness direction. The light guide 2 diffuses light incident from the one side portion 7, and exits from at least one of the two main surfaces 8, 9, in this embodiment, one main surface 8. To do. Hereinafter, one main surface 8 from which the light is emitted is referred to as an emission surface 8, and the other main surface 9 opposite to the emission surface 8 is referred to as a back surface 9.

  The direction parallel to the thickness direction of the light guide 2 is defined as the Z direction, the direction perpendicular to the Z direction and parallel to the short direction of the light guide 2 is defined as the X direction, and in the Z direction and the X direction. A direction perpendicular to the longitudinal direction of the light guide 2 is defined as the Y direction. In each figure, these X, Y, and Z directions are represented by arrows X, Y, and Z.

  The light exit surface 8 and the back surface 9 of the light guide 2 are configured so that light incident on the light exit surface 8 and the back surface 9 from the inside of the light guide 2 is guided along the Y direction along the light guide 2. The light exit surface 8 and the back surface 9 of the light guide 2 are configured by a large number of prism rows (not shown) that extend substantially parallel to the Y direction and have slopes with an average tilt angle of 120 degrees or more and 180 degrees or less.

  The light guide 2 has at least translucency, and preferably has excellent moldability, such as translucent resin such as acrylic resin, polycarbonate resin, cycloolefin polymer, polystyrene resin, and functional norbornene resin. Formed of a translucent material. These materials for the light guide 2 have different refractive indexes, but the direction in which the light travels can be controlled by selecting the shape of the exit surface 8 and the back surface 9 of the light guide 2. There is no restriction by the rate. For example, when the light guide 2 is made of an acrylic resin or a polycarbonate resin, the refractive index of the light guide 2 is about 1.49 to 1.59.

  Next, the prism sheet 4 will be described. The prism sheet 4 is an optical member, and is provided to face the light exit surface 8 of the light guide 2 as shown in FIG. The prism sheet 4 is arranged so that the light emitted from the emission surface 8 of the light guide 2 is substantially parallel to the Z direction of the light guide 2 on the opposite surface facing the emission surface 8 of the light guide 2. It has a guiding prism portion (not shown). The prism portion is realized by arranging triangular prisms extending in the X direction at regular intervals in the Y direction, for example. In the plurality of prism portions extending substantially parallel to the X direction, the prism unit pitch, which is a dimension between adjacent prisms, is set to, for example, 20 μm to 5 mm, and the prism apex angle is set to, for example, 50 degrees to 120 degrees. The

  The prism sheet 4 is preferably manufactured using a material having a high visible light transmittance and a relatively high refractive index. For example, an acrylic resin, a polycarbonate resin, a vinyl chloride resin, an active energy ray curable resin, and the like. Preferably, an active energy ray-curable resin is used from the viewpoint of scratch resistance, handleability, productivity and the like of the lens sheet.

  Next, the reflection sheet 5 will be described. As shown in FIG. 1, the reflection sheet 5 is provided to face the back surface 9 of the light guide 2. The reflection sheet 5 has light reflectivity such that light emitted from the back surface 9 of the light guide 2 is reflected inside the light guide 2. The reflection sheet 5 is formed so as to have a reflectance close to about 1.0 with respect to incident light. As the material of the reflection sheet 5, a material having high light reflectivity and a reflectance close to 1.0 is used. Examples of such a material include silver (Ag) and aluminum (Al). The reflection sheet 5 is realized by a thin film having a reflectance close to 1.0, for example. By providing such a reflection sheet 5, it is possible to prevent light from being undesirably emitted from the back surface 9.

  Next, the adhesive member 6 will be described. The bonding member 6 bonds a portion of the outer edge portion of the main surfaces 8 and 9 of the light guide 2 and a portion of the prism sheet 4 facing a portion of the outer edge portion of the light guide 2. The adhesive member 6 bonds the light guide 2 and the prism sheet 4 at a part outside the effective light emitting portion. The light-emitting portion is a region where light emitted from the light exit surface 8 of the light guide has a predetermined luminance or higher. The predetermined luminance varies depending on the device in which the surface light source device 1 is used, and is set to a visible luminance when used in a liquid crystal display device. The adhesive member 6 is a part of the outer edge part of the light exit surface of the light guide 2, preferably a part adjacent to one side part 7 of the light guide 2 and a part facing a part of the outer edge part of the prism sheet 4. And glue. Therefore, the adhesive member 6 adheres the light guide 2 and the prism sheet 4 at a part outside the effective light emitting portion on the side 7 of the light guide 2. In other words, the adhesive member 6 is provided on the emission surface 8 which is an emission region of light emitted from the light source 3. The number of contact points between the adhesive member 6 and the light guide 2 is preferably two or more. In the present embodiment, the adhesive member 6 has a tape shape as shown in FIG. 1, and is provided along one side portion 7 of the emission surface 8 of the light guide 2. Therefore, there are a plurality of contact points between the adhesive member 6 and the light guide 2. Since such an adhesive member 6 has adhesiveness on both sides in the Z direction, the light guide 2 and the prism sheet 4 can be bonded. Adhesive member 6 preferably has at least one of translucency or light absorption, and has translucency in the present embodiment.

  Next, the first embodiment of the present invention will be specifically described with reference to the first embodiment, but the present invention is not limited to the following description. FIG. 3 is an enlarged side view showing a part of the surface light source device 1 of the first embodiment. The surface light source device 1 of this embodiment is suitably used for the surface light source device 1 for liquid crystal mounted on a mobile device such as a 2.4-inch mobile phone. The example of the surface light source device 1 shown in FIG. 1 was manufactured, and the luminance measurement using the manufactured surface light source device 1 was performed. The light guide 2 was produced so that the dimension in the Y direction was about 55 mm, the dimension in the X direction was about 39 mm, and the dimension in the Z direction was about 0.6 mm. A pattern for diffusing light may be applied to one side portion 7 of the light guide 2, but here the one side portion 7 is assumed that the light source 3 can sufficiently reduce luminance unevenness in the vicinity of the light source 3. It is flat.

  On the emission surface 8 and the back surface 9, a V-groove pattern is formed, and a prism-like pattern is arranged so that the ridge line is parallel to the Y direction for the purpose of raising or spreading light traveling in the Y direction.

  The reflection sheet 5 is laminated on the back surface 9 of the light guide 2, and the downward prism sheet 4 is laminated on the emission surface 8. The light guide 2 and the prism sheet 4 were bonded on the one side 7 side of the emission surface 8 using an adhesive member 6 (transparent double-sided adhesive tape CS9621 manufactured by Nitto Denko). The size of the adhesive member 6 was about 39 mm in the X direction and about 1 mm in the Y direction.

  The dimension of the adhesive 6 in the Y direction may be, for example, about twice or more the thickness of the light guide 2 and may be equal to or less than the length from the light source to the effective area.

  The light guide 2 and the prism sheet 4 bonded together, the light source 3, and the reflection sheet 5 are packaged using a resin frame 10 and a light-shielding tape 11 (Nitto Denko light-reflection reflective double-sided adhesive tape No. 5680W) ( At this time, the distance L1 from the light source 3 in the portion where the vicinity of the light source 3 is covered with the light shielding tape 11 is about 3 mm, and the effective range is 49 mm (L2) × 37 mm (W1)). did. The resin frame 10 and the light shielding tape 11 are virtually shown in FIG.

  The light source 3 is a type of linear light source 3 in which four 1.5 cd light emitting elements are arranged, and the light emitting elements are arranged side by side with a pitch p1 of 9 mm. These four LEDs were connected in series, and a current of 20 mA was applied. As the reflection sheet 5, a reflection sheet (ESR) manufactured by Sumitomo 3M was used. The prism sheet 4 is a Mitsubishi Rayon prism sheet (M168YS) configured to include a large number of prisms having a prism unit pitch of 18 μm and a prism apex angle of 68 degrees.

  FIG. 4 is an enlarged side view showing a part of the surface light source device 1 of the comparative example. As shown in FIG. 4, as a comparative example of the light guide 2, the surface light source device 1 in which the light guide 2 and the prism sheet 4 are not bonded by the adhesive member 6 was created. The remaining configuration of the light guide 2 of the comparative example is the same as the configuration of the light guide 2 of the above-described embodiment.

  When the surface light source device 1 of the example and the surface light source device 1 of the comparative example were turned on, the bright portion continued to 4 mm from the end of the effective range in the surface light source device 1 of the comparative example, but effective in the surface light source device 1 of the example. The bright part disappeared at 1 mm from the end of the range, and the range of luminance unevenness became a quarter.

  Moreover, the luminance measurement was performed for the surface light source device 1 of the example and the surface light source device 1 of the comparative example. As shown by dots in FIG. 2, the measurement position is a position where a distance L3 of 4 mm from the light source 3 is opened, and measurement is performed at a plurality of locations with the measurement interval p2 being 0.5 mm along the X direction. . For luminance measurement, a spectral luminance measuring device SR-3A (not shown) manufactured by Topcon was used, and the luminance at the measurement position described above was measured at a measurement angle of 0.1 degrees and a measurement distance of 500 mm.

  FIG. 5 is a graph showing an example of the front luminance distribution using the surface light source devices 1 of the present example and the comparative example. In the front luminance point measurement, in the surface light source device 1 (shown by a solid line in FIG. 6) of the present embodiment, the luminance unevenness on the light source 3 side than the surface light source device 1 of the comparative example (shown by a broken line in FIG. 6). Was able to be suppressed. As described above, by manufacturing the surface light source device 1 of the present embodiment, the range of extreme luminance unevenness near the light source 3 could be reduced.

  As described above, according to the surface light source device 1 of the present embodiment, the adhesive member 6 faces a portion of the outer edge portion of one main surface of the light guide 2 and a portion of the outer edge portion of the prism sheet 4. Adhere to the part to be. Thus, since the adhesive member 6 is provided at the outer edge portion of one main surface of the light guide 2, it is possible to block light emitted from the output surface 8 that is one main surface of the light guide 2. Can be prevented. Further, since the adhesive member 6 bonds the light exit surface 8 of the light guide 2 and the prism sheet 4, when light transmitted through the light guide 2 is incident on the adhesive member 6, as shown in FIG. Can be diffused and guided again into the light guide 2. Accordingly, as described in the surface light source device of the comparative example (see FIG. 4), the light reaching the adhesive member 6 can be used more effectively than simply blocking the light with the light shielding tape 11 or the like. Thereby, uniform light can be emitted over a wide range from the emission surface 8 of the light guide 2.

  In other words, in the present embodiment, inconvenient light that causes luminance unevenness in the vicinity of one side portion 7 of the light guide 2 is caused by a part of the adhesive member 6 in which the light guide 2 and the prism sheet 4 are bonded. As shown in FIG. 3, by emitting and scattering light, it is possible to reduce a range in which the luminance in the vicinity of the light source 3 on the one side portion 7 of the light guide 2 is extremely higher than that of other portions.

  In the surface light source device 1 of the comparative example, as shown in FIG. 4, there is not less than an air layer between the light guide 2 and the prism sheet 4, and the light guide 2 having a higher refractive index than air is present inside the light guide 2. Among certain lights, light having an incident angle greater than the total reflection angle does not exit.

  In contrast, in the present embodiment, the light guide 2 and the prism sheet 4 are bonded together by the adhesive member 6 as shown in FIG. It is filled with a substance (adhesive member 6) having a higher refractive index. Therefore, total reflection is less likely to occur than when an air layer is present, and more light is emitted. Further, light is scattered by a scattering effect caused by bubbles or the like present in a large amount in the vicinity of the adhesive member 6 and the adhesive member 6. As a result, the light that causes the luminance unevenness can be emitted and scattered at a portion having no influence, and the range of the extreme luminance unevenness can be reduced.

  Moreover, in this Embodiment, since the adhesive member 6 is united when adhering the adhesive member 6 partially in several places, it can attain simplification in a manufacturing process.

  Next, the surface light source device 1A according to the second embodiment of the present invention will be described. FIG. 6 is an enlarged perspective view showing a part of the surface light source device 1A according to the second embodiment of the present invention. FIG. 7 is a plan view schematically showing the surface light source device 1A. The surface light source device 1A of the present embodiment is characterized in that it is divided into two or more adhesive members 6 and four in the present embodiment. The adhesive member 6 is provided at least in a portion facing the emission region of each light source 3. Accordingly, the light-emitting body 2 is provided so as to cover the emission surface 8 in the region that becomes the bright portion of the one side portion 7 of the light guide 2. In the present embodiment, since there are four light sources 3, four adhesive members 6 are provided.

  Next, the second embodiment of the present invention will be specifically described with reference to a second example, but the present invention is not limited to the following description. In the second embodiment, only a part of the configuration will be described, and the remaining configuration is the same as that of the first embodiment.

  The light guide 2 and the prism sheet 4 were bonded on the one side 7 side of the emission surface 8 using an adhesive member 6 (Nitto Denko's transparent double-sided adhesive tape CS9621). At this time, as for the size of the adhesive member 6, four dimensions of about 4 mm in the X direction and about 1 mm in the Y direction are prepared, and the center of each light source 3 and the center of the adhesive member 6 are approximately in the X direction. Affixed so as to be in the same position (the term “substantially identical” includes the same).

  As described in the first embodiment, the surface light source device 1A of this embodiment has an effect of reducing the range of uneven brightness and the adhesive member 6 is disposed only in the bright portion of uneven brightness. Since the brightness can be lowered only in the bright part and the brightness in the dark part is not lowered, the uniformity of the brightness is improved as compared with the surface light source device 1 described in the first embodiment.

  Moreover, in this Embodiment, it is possible to eliminate the sticking to the excess part of the adhesive member 6, and to reduce material.

  As described above, in the surface light source device 1 of the present embodiment, the range of extreme luminance unevenness in the vicinity of the light source 3 can be reduced, and the luminance uniformity of the effective light emitting portion can be further improved.

  Next, the surface light source device 1B according to the third embodiment of the present invention will be described. FIG. 8 is an enlarged perspective view showing a part of the surface light source device 1B according to the third embodiment of the present invention. FIG. 9 is a plan view schematically showing the surface light source device 1B. The surface light source device 1 </ b> B of the present embodiment is characterized in that the adhesive member 6 is provided integrally with the prism sheet 4. Therefore, the prism sheet 4 has an adhesive function, and this adhesive function is an alternative to the adhesive member 6 described above. The adhesive member 6 provided integrally with the prism sheet 4 is provided on the prism sheet 4 so as to be positioned at least in a portion facing the emission region of each light source 3. Therefore, when the prism sheet 4 is laminated on the emission surface 8, the adhesive member 6 is provided so as to cover the emission surface 8 in a region that becomes a bright portion of the one side portion 7 of the light guide 2. In the present embodiment, since there are four light emitting elements, the four adhesive members 6 are integrally provided on the prism sheet 4.

  Next, the third embodiment of the present invention will be specifically described with reference to a third example. However, the present invention is not limited to the following description. In the third embodiment, only a part of the configuration will be described, and the remaining configuration is the same as that of the second embodiment.

  The prism sheet 4 has a bonding function at the end on the light source 3 side, that is, an bonding member 6, and the bonding function is only at four positions that are substantially the same as the position of the light source 3. The size of 6 is about 4 mm in the X direction and about 1 mm in the Y direction. The adhesive member 6 is added with a light absorbing material (not shown). Therefore, the adhesive member 6 has light absorption. The light absorbing material is preferably a material that absorbs visible light, and examples thereof include black nickel. However, the light absorbing material used in the present invention is not limited to this.

  Since the surface light source device 1B of the present example is only in the immediate vicinity of the light source 3 in the bright part where the unevenness of luminance is present, the same effects as those of the second embodiment described above can be obtained. Further, since the bonding function is integrated with the prism sheet 4, the number of parts can be reduced, and simplification can be achieved in the manufacturing process.

  In addition, the added light absorbing material prevents the light emitted at the adhesion point from being reflected by the light shielding tape 11 and returning into the light guide 2, so that the light that causes the unevenness emitted at the adhesion point can be reduced. This can be eliminated more effectively, and the luminance uniformity can be improved than the surface light source devices 1 and 1A of the first and second embodiments.

  Thus, in the surface light source device 1B of the present embodiment, the range of extreme luminance unevenness in the vicinity of the light source 3 can be reduced, and the uniformity of the luminance of the effective light emitting portion can be further improved. Moreover, simplification can be achieved in the manufacturing process.

  Each above-mentioned embodiment is only illustration of this invention, and can change a structure within the scope of the present invention. The surface light source device 1 is preferably configured to include the light guide 2, the light source 3, and the prism sheet 4, but is not limited to such a configuration, and as another optical member, for example, a light diffusion sheet , And a plurality of prism sheets 4 may be included. The light source 3 is not limited to the configuration using the linearized LED as the light source 3, but is not limited to the type of the light source 3 such as a configuration in which a plurality of individual LEDs are arranged or a cold cathode tube. Further, the one side portion 7 of the light guide 2 is not limited to a flat shape, and may be used to reduce unevenness in brightness by forming irregularities on the one side portion 7 according to the emission form of the light source 3. In addition, the light exit surface 8 and the back surface 9 of the light guide 2 may be configured by an arbitrary shape, for example, a large number of lens rows having a curved slope.

  In the above-described embodiment, the surface light source device 1 is used in a liquid crystal display device, but is not limited to a liquid crystal display device, and can be applied to a panel meter, a display lamp, a surface emitting switch, and the like.

It is a perspective view which expands and shows a part of surface light source device 1 of the 1st Embodiment of this invention. It is a top view which simplifies and shows the surface light source device. It is a side view which expands and shows a part of surface light source device 1 of a 1st Example. It is a side view which expands and shows a part of surface light source device 1 of a comparative example. It is a graph which shows an example of a front luminance distribution using the surface light source device 1 of a present Example and a comparative example. It is a perspective view which expands and shows a part of surface light source device 1A of the 2nd Embodiment of this invention. It is a top view which simplifies and shows the surface light source device 1A. It is a perspective view which expands and shows a part of surface light source device 1B of the 3rd Embodiment of this invention. It is a top view which simplifies and shows the surface light source device 1B.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A, 1B Surface light source device 2 Light guide 3 Light source 4 Prism sheet 5 Reflective sheet 6 Adhesive member 7 One side part 8 Output surface 9 Back surface 10 Resin frame 11 Light shielding tape

Claims (8)

A light source that emits light;
A light guide that is incident from one side, diffuses light incident from one side, and exits from at least one main surface;
At least one optical member provided to face one main surface of the light guide;
A surface light source device comprising: an adhesive member that bonds a portion of an outer edge portion of one main surface of the light guide to a portion of the optical member facing a portion of the outer edge portion.   The adhesive member is a part of an outer edge part of one main surface of the light guide, a part adjacent to one side part of the light guide, and a part facing a part of the outer edge part of the optical member; The surface light source device according to claim 1, wherein:   The surface light source device according to claim 1, wherein the adhesive member is divided into two or more.   The surface light source device according to claim 1, wherein the adhesive member is provided in an emission region of light emitted from a light source.   The surface light source device according to claim 1, wherein the adhesive member and the light guide have two or more contacts.   The surface light source device according to claim 1, wherein the adhesive member has light absorptivity.   The surface light source device according to claim 1, wherein the adhesive member has translucency.   The surface light source device according to claim 1, wherein the adhesive member is provided integrally with the optical member.

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