JP2014130832A - Surface light source device, liquid crystal display apparatus and mobile equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device which reduces light quantity leaking from a light guide plate.SOLUTION: A light source is arranged oppositely to a light incident edge surface of a light guide plate. A diffusion sheet and a prism sheet are overlapped on an upper surface of the light guide plate and a rim sheet is overlapped on the overlapped diffusion sheet and prism sheet. The edge of the light source side of the diffusion sheet is extended more than the edge of the prism sheet, and at least one side surface of the extended part of the diffusion sheet is covered with a light shielding member. The light guide plate has a directivity conversion pattern 112 for converting the directivity. On the left side area of the light source center C, when a normal N is erected on each pattern slant 114a, 114b toward an outer part from an inner part of the light guide plate, the sum of such a lateral width D2 of pattern slant 114b inclined that the normal N is inclined to the light source center side becomes larger than the sum of such a lateral width D1 of pattern slant 114a that the normal N is inclined to the side opposite to the light source center.

Description

  The present invention relates to a surface light source device, a liquid crystal display device, and a mobile device. In particular, the present invention relates to a surface light source device that can improve light emission quality by reducing light leakage in an effective light emission region.

  FIG. 1 shows a cross section of a conventional surface light source device. In the surface light source device 11, the light guide plate 13 is housed in the frame 12, and the light source 15 is disposed so as to face the end surface (light incident end surface 14) of the light guide plate 13. The light guide plate 13 is obtained by continuously forming the light introducing portion 16 at the end of the light guide plate main body 17. The light introducing portion 16 has an inclined surface 16 a and has a thickness larger than that of the light guide plate main body 17. The light guide plate body 17 occupies most of the area of the light guide plate 13. The light source 15 is mounted on the lower surface of the flexible printed circuit board 18. The flexible printed circuit board 18 is bonded to the upper surface of the frame 12 and the light introducing portion 16 with an adhesive 19, whereby the light source 15 is fixed at a position facing the light incident end surface 14.

  Three optical sheets, that is, a diffusion sheet 20 and two prism sheets 21 and 22 are overlaid on the upper surface of the light guide plate body 17. A rim sheet 23 (light-shielding plate) is pasted on the flexible printed circuit board 18, the frame 12, and the prism sheet 22, and an effective light emitting area of the light guide plate body 17 is exposed from the opening window 24 of the rim sheet 23. In addition, the effective light emission area | region of the light-guide plate 13 is an area | region where the light utilized as the light of the surface light source device 11 is radiate | emitted, and is an area | region where the light used in order to irradiate a liquid crystal display panel etc. comes out ( Usually, the area other than the effective light emission area is covered with a rim sheet or the like so as not to be emitted from the surface light source device). A reflection sheet 25 is disposed on the lower surface of the light guide plate 13.

  In such a surface light source device 11, the light emitted from the light source 15 can be incident into the light introducing portion 16 from the light incident end surface 14 having substantially the same height as the light source 15. The light incident on the light introducing portion 16 is guided to the light guide plate main body 17 having a small thickness by being reflected by the lower surface of the light introducing portion 16 and the inclined surface 16a. Therefore, according to such a surface light source device 11, the light from the light introducing portion 16 is efficiently incident into the light guide plate 13 to emit light in the effective light emitting region of the light guide plate 13 with high luminance, and at the same time. Can be made thinner.

  However, in the surface light source device 11 having the structure as shown in FIG. 1, light of three paths is likely to leak from the opening window 24 of the rim sheet 23. The first leakage light is light L1 that leaks directly from the light source 15. That is, the light L1 does not enter the light guide plate 13 but passes through the transparent adhesive 19 that bonds the flexible printed circuit board 18 to the light introducing portion 16 and enters the end face of the optical sheet. The second leaked light is the light L2 that leaks from the inclined surface 16a of the light introducing portion 16. That is, the light L2 is light that enters the light introducing portion 16 from the light incident end surface 14, immediately exits from the inclined surface 16a, and enters the end surface of the optical sheet. The third leakage light is reflected by the inclined surface 16a, travels downward, is further reflected by the reflection sheet 25, leaks from the upper surface of the light guide plate body 17, and enters the end surface and the lower surface of the optical sheet.

  Since these lights L1, L2, and L3 are not controlled light like the light that is guided through the light guide plate body 17 and emitted from the effective light emitting area, the effective light emitting area is caused to illuminate non-uniformly in the vicinity of the light source 15. Worsen the appearance. For example, when leakage light leaks through the edge of the opening window 24 in front of the light source 15 like the light A shown in FIG. 2, an eye-shaped light emission P appears at the edge of the effective light emitting region as shown in FIG. The uniformity of luminance in the effective light emitting region is impaired. 2 enters the optical sheet from the end face of the optical sheet and gradually leaks while being guided while being reflected in the optical sheet, as shown in FIG. Bright lines Q are generated, and the uniformity of luminance in the effective light emitting region is impaired.

  As a method for solving the above problems, there is a method of extending the diffusion sheet 20 toward the light introducing portion 16 as shown in FIG. 5 (see, for example, Patent Document 1). If the diffusion sheet 20 is extended to the light introduction part 16 side and the inclined surface 16a is covered with the diffusion sheet 20, the light L2 leaking from the inclined surface 16a can be diffused by the diffusion sheet 20, and therefore uneven from the vicinity of the light source 15 It is possible to reduce light leaking to the surface. However, with such a method, it is not possible to eliminate even the eyeball-like light emission P due to leaked light as shown in FIG.

  In addition, as shown in FIG. 6, there is a method of extending the prism sheet 21 toward the light introducing section 16 (see, for example, Patent Document 2). According to this method, the light L2 emitted from the inclined surface 16a of the light introducing portion 16 enters the optical sheet, and light that gradually leaks from the optical sheet can be absorbed by the rim sheet 23, thereby preventing the bright line Q from being generated. be able to. However, in this method, the distance DS from the edge of the prism sheet 21 (the distance to the edge of the opening window 24) DS must be sufficiently long. If the distance DS is short, the effect cannot be obtained. Therefore, the effective light emission area of the surface light source device tends to be narrowed. Further, this method is not effective for the light L1 leaked directly from the light source 15, and the leaked light L1 leaks from the edge of the opening window 24 to generate the eye-shaped light emission P.

JP 2006-93015 A JP2012-14909

  An object of the present invention is to provide a surface light source device capable of reducing the amount of light leaking from a light guide plate.

  A surface light source device according to the present invention includes a light guide plate that introduces light from an end surface and emits light from a light output surface, a light source that is disposed at a position facing the end surface of the light guide plate, and a light source plate disposed on the light guide plate. In the surface light source device comprising the plurality of optical sheets thus formed and a light shielding plate disposed so as to cover the light source, a light shielding member different from the light shielding plate is disposed on the end surface of the light guide plate and the light source plate. The light guide plate has a light introduction part for confining light from the light source incident from the end face, and a thickness smaller than a maximum thickness of the light introduction part. A light guide plate body that is provided so as to be continuous with the introduction portion and that allows the confined light to be emitted from the light emission surface to the outside by the light emission means, and the light introduction portion includes a light emission side of the light guide plate On at least one of the other side and the other side The light guide plate has an inclined surface that is inclined from the surface of the portion thicker than the light guide plate main body toward the end of the surface of the light guide plate main body, and the light guide plate has at least one of the light emitting side surface and the opposite surface. The surface has a directivity conversion pattern for converting the directivity spread in the thickness direction of the light guide plate of light incident on the light introducing portion into a directivity characteristic inclined toward a direction parallel to the surface direction of the light guide plate. The directivity conversion pattern is configured to alternately repeat ridge lines and valley lines along the width direction of the light guide plate, and among the cross sections of the directivity conversion pattern cut in parallel with the end face, A portion located in front of the light source and within a region having the same width as the light source connects one of the ridge lines of the directivity conversion pattern and one valley line adjacent to the ridge line. The slope, the ridgeline and the The slope connecting the other valley line adjacent to the line is asymmetric with respect to a straight line passing through the ridge line and perpendicular to the light emitting surface, and at least one set of the asymmetric shape portions having different shapes on both sides of the light source center. It is characterized by the existence. The light shielding member herein may be any member that can prevent light outside the design from leaking from the surface light source device by absorbing or reflecting light.

  In an embodiment of the surface light source device according to the present invention, in a cross section of the directivity conversion pattern cut in parallel with the end face, the area is located in front of the light source and has a width equal to the light source. The normal line is inclined toward the light source center side in at least one of the regions on both sides sandwiching the light source center when a normal line is set on each of the inclined surfaces from the inside to the outside of the light guide plate. The sum of the lateral widths of the slopes in the one region is larger than the sum of the lateral widths of the slopes whose normals are inclined to the opposite side of the light source center in the one region.

  Another embodiment of the surface light source device according to the present invention is such that the light shielding member is below the light shielding plate and emits light at a portion of the light guide plate that covers the light source in the end face and the light shielding plate. It is provided between the edge on the surface side.

を満たすことを特徴とする。 Still another embodiment of the surface light source device according to the present invention includes: an end of the light shielding member on the side far from the light source; and a light emitting surface side edge of the portion of the light shielding plate that covers the light source. When the distance in the direction parallel to the light exit surface is De and the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

It is characterized by satisfying.

を満たすことを特徴とする。 Still another embodiment of the surface light source device according to the present invention is the light source side display area in the display area of the liquid crystal panel disposed above the optical sheet and the end of the light shielding member on the side far from the light source. The distance in the direction parallel to the light exit surface between the edges is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness of the glass plate on the lower surface side of the liquid crystal panel When the refractive index is tm and Nm, respectively,

It is characterized by satisfying.

  Still another embodiment of the surface light source device according to the present invention is such that the light shielding member is formed at an end portion of at least one surface of the lowermost optical sheet, and the extended end of the lowermost optical sheet. The portion is fixed to a wiring board on which the light source is mounted.

  Still another embodiment of the surface light source device according to the present invention is such that the light shielding member is formed at an end portion of at least one surface of the lowermost optical sheet, and the extended end of the lowermost optical sheet. The portion is fixed to the light shielding plate.

  Still another embodiment of the surface light source device according to the present invention is such that the light shielding member is formed at an end portion of at least one surface of the lowermost optical sheet, and the extended end of the lowermost optical sheet. The portion is fixed to the uppermost optical sheet.

  In another embodiment of the surface light source device according to the present invention, one end of the light shielding member is fixed to a wiring board on which the light source is mounted, and the other end of the light shielding member is fixed to the optical sheet. It is characterized by.

  In another embodiment of the surface light source device according to the present invention, one end of the light shielding member is fixed to the uppermost optical sheet, and the other end of the light shielding member is attached to the optical sheet in the lower layer portion. It is fixed.

  Still another embodiment of the surface light source device according to the present invention is such that the end portion of the optical sheet in the lowermost layer extends to the light source side than the end of the other optical sheet, and the upper surface of the optical sheet in the lowermost layer The above-described light shielding member is provided on the surface.

  Still another embodiment of the surface light source device according to the present invention is characterized in that the upper surface of the light shielding member is fixed to the lower surface of the light shielding plate.

  Yet another embodiment of the surface light source device according to the present invention is characterized in that the upper surface of the light shielding member is fixed to the lower surface of the wiring board on which the light source is mounted.

を満たすことを特徴とする。なお、条件１が満たされていれば、条件３も満たされる。 Still another embodiment of the surface light source device according to the present invention includes: an end of the light shielding member on the side far from the light source; and a light emitting surface side edge of the portion of the light shielding plate that covers the light source. When the distance in the direction parallel to the light exit surface is De and the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

It is characterized by satisfying. If condition 1 is satisfied, condition 3 is also satisfied.

を満たすことを特徴とする。なお、条件２が満たされていれば、条件４も満たされる。 Still another embodiment of the surface light source device according to the present invention is such that the end portion of the optical sheet in the lowermost layer extends to the light source side than the end of the other optical sheet, and the upper surface of the optical sheet in the lowermost layer The light shielding member is provided, and the light shielding member between the end of the light shielding member far from the light source and the display area end on the light source side in the display area of the liquid crystal panel disposed above the optical sheet, The distance in the direction parallel to the light exit surface is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness and refractive index of the glass plate on the lower surface side of the liquid crystal panel are tm and When Nm, the following conditions

It is characterized by satisfying. If condition 2 is satisfied, condition 4 is also satisfied.

  Still another embodiment of the surface light source device according to the present invention is such that the light guide plate has a light introducing portion for introducing light of the light source from an end surface, and is thinner than a maximum thickness of the light introducing portion, and the light emitting surface The light guide plate body having a thickness is continuously formed, and the ratio of the thickness of the light guide plate body to the maximum thickness of the light introducing portion is 0.75 or less.

  The liquid crystal display device according to the present invention includes the surface light source device according to the present invention and a liquid crystal panel.

  The mobile device according to the present invention includes the surface light source device according to the present invention.

  The means for solving the above-described problems in the present invention has a feature in which the above-described constituent elements are appropriately combined, and the present invention enables many variations by combining such constituent elements. .

  According to the present invention, since the light shielding member is provided between the end face of the light guide plate and the opening window of the light shielding plate, the light leaked directly from the light source, the light leaked from the slope of the light guide plate, or the slope of the light guide plate The light that is reflected by the light source and further reflected from the lower surface of the light guide plate is less likely to leak from the opening window of the light shielding plate, so that it is possible to suppress eye-shaped light emission and bright lines generated at the edge of the opening window.

  Further, according to the present invention, by making the pattern elements constituting the directivity conversion pattern asymmetrical, the light from the directivity conversion pattern is compared with the case where the pattern elements of the directivity conversion pattern are symmetrical. Leakage can be suppressed, and the light utilization efficiency can be improved.

  Further, if any one of the above conditions 1 to 4 is satisfied, even when the light shielding member is provided on the lower surface side of the light shielding plate, the light shielding member is not seen through the opening of the light shielding plate, and the surface light source The quality of the apparatus can be improved.

FIG. 1 is a schematic cross-sectional view showing a conventional surface light source device. FIG. 2 is a schematic diagram for explaining the appearance of eye-shaped light emission and bright lines in the surface light source device of FIG. FIG. 3 is a plan view of the surface light source device showing eye-shaped light emission generated in the surface light source device of FIG. FIG. 4 is a plan view of the surface light source device showing bright lines generated in the surface light source device of FIG. FIG. 5 is a schematic cross-sectional view of a surface light source device showing one method for reducing leakage light. FIG. 6 is a schematic cross-sectional view of a surface light source device showing another method for reducing leakage light. FIG. 7 is a cross-sectional view of the surface light source device according to Embodiment 1 of the present invention. FIG. 8A is a cross-sectional view of a surface light source device according to Embodiment 1 (modified example) of the present invention. FIG. 8B is a diagram for explaining condition 1, and a part of FIG. 8A is enlarged. 9A and 9B are schematic cross-sectional views showing the light shielding member in the surface light source device of FIG. 7 in an enlarged manner. FIG. 9C and FIG. 9D are schematic cross-sectional views showing the light shielding member in the surface light source device of FIG. FIG. 10 is a cross-sectional view showing a liquid crystal display device using the surface light source device according to Embodiment 1 of the present invention. FIG. 11 is a cross-sectional view showing a surface light source device according to another modification of Embodiment 1 of the present invention. FIG. 12 is a sectional view showing a surface light source device according to Embodiment 2 of the present invention. FIG. 13: is sectional drawing which shows the surface light source device by the modification of Embodiment 2 of this invention. FIG. 14 is a sectional view showing a surface light source device according to Embodiment 3 of the present invention. FIG. 15: is sectional drawing which shows the surface light source device by the modification of Embodiment 3 of this invention. FIG. 16: is sectional drawing which shows the surface light source device by Embodiment 4 of this invention. FIG. 17: is sectional drawing which shows the surface light source device by the modification of Embodiment 4 of this invention. FIG. 18: is sectional drawing which shows the surface light source device by another modification of Embodiment 4 of this invention. FIG. 19 is a cross-sectional view showing a surface light source device according to still another modification of Embodiment 4 of the present invention. FIG. 20 is a sectional view showing a surface light source device according to Embodiment 5 of the present invention. FIG. 21 is a sectional view showing a surface light source device according to a modification of the fifth embodiment of the present invention. FIG. 22 is a cross-sectional view showing a surface light source device according to Embodiment 6 of the present invention. FIG. 23A and FIG. 23B are schematic enlarged cross-sectional views showing a method of fixing the light shielding member on the diffusion sheet. FIG. 24 is a cross-sectional view showing a surface light source device according to a modification of the sixth embodiment of the present invention. FIG. 25 is a cross-sectional view showing a surface light source device according to Embodiment 7 of the present invention. FIG. 26 is a cross-sectional view showing a surface light source device according to Embodiment 8 of the present invention. FIG. 27 is a perspective view of a light guide plate used in the surface light source device of the eighth embodiment. FIG. 28 is a plan view of a light guide plate used in the surface light source device of the eighth embodiment. FIG. 29 is a cross-sectional view taken along the line XX of FIG. FIG. 30 is an explanatory diagram of the operation of the directivity conversion pattern shown in FIG. FIG. 31A is a plan view showing a surface light source device according to Embodiment 9 of the present invention. FIG. 31B is a cross-sectional view of the surface light source device of the ninth embodiment. FIG. 32 is a diagram showing the relationship between the ratio of the thickness of the light guide plate body to the thickness of the light introduction portion of the light guide plate (step ratio) and the luminance efficiency of the surface light source device. FIG. 33 is a plan view of a mobile device using the surface light source device according to the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various design changes can be made without departing from the gist of the present invention.

(Embodiment 1)
7 and 8A are cross-sectional views showing the surface light source device 31 according to Embodiment 1 of the present invention. In the surface light source device 31 of Embodiment 1, the end of the diffusion sheet 43 extends to the light source side, and a sheet-like or film-like light shielding member 49 is formed on at least one surface of the extended portion. Are fixed to a flexible printed circuit board 41. The light shielding member 49 may be provided on both the upper and lower surfaces of the diffusion sheet 43 as shown in FIG. 7, or may be provided only on the lower surface of the diffusion sheet 43 as shown in FIG.

  Hereinafter, the surface light source device 31 according to Embodiment 1 of the present invention will be described with reference to FIGS. 7 and 8A. In the surface light source device 31 according to the first embodiment, the light guide plate 33 is housed in a frame 32 having a frame shape, and a plurality of light sources 40 are arranged to face the end surface (light incident end surface 36) of the light guide plate 33. The light source 40 incorporates an LED and is mounted on the lower surface of the flexible printed board 41.

  The light guide plate 33 is obtained by continuously and integrally forming the light introducing portion 34 at the end of the light guide plate main body 35. The light guide plate 33 is formed of a transparent and high refractive index material such as polycarbonate resin, polymethyl methacrylate (PMMA resin), or glass. The light introducing portion 34 has a larger maximum thickness than the light guide plate main body 35, and the inclined surface 37 provided on the light guide plate main body side upper surface of the light introducing portion 34 does not cause a stepped step with the light guide plate main body 35. So that it is continuous. The inclined surface 37 extends in a strip shape from one end of the light guide plate 33 to the other end. The light guide plate body 35 occupies most of the area of the light guide plate 33. The upper surface of the light guide plate main body 35 is a light emitting surface 39 for emitting light for illumination, and a light emitting means, that is, a large number of microscopic parts, is provided on the lower surface of the light guide plate 33 facing the light emitting surface 39. A light deflection pattern 38 is provided.

  In FIG. 7, a triangular groove-shaped light deflection pattern 38 is shown as the light emitting means. However, sandblasting, a photographic printing of diffusion ink, a diffraction grating pattern, an arbitrary uneven pattern, etc. may be used. It may be provided on the light exit surface 39 of the light guide plate body 35 or on both the light exit surface 39 and the opposite surface.

  The flexible printed circuit board 41 is bonded to the upper surface of the frame 32 and the light introducing portion 34 with an adhesive 42 (including an adhesive). The plurality of light sources 40 mounted on the lower surface of the flexible printed circuit board 41 are arranged at regular intervals at positions facing the light incident end face 36 of the light guide plate 33 (light introduction part 34).

  A plurality of optical sheets, that is, a diffusion sheet 43 and two prism sheets 44 and 45 are overlaid on the upper surface (light emitting surface 39) of the light guide plate body 35. The prism sheets 44 and 45 have a large number of prism-like patterns formed in parallel on the surface thereof, and the prism sheets 44 and 45 are overlapped so that the extending directions of the prism-like patterns are orthogonal to each other.

  The light source side end of the diffusion sheet 43 protrudes longer than the ends of the prism sheets 44 and 45. The light source side end portion of the diffusion sheet 43 extends toward the light source side, and a light shielding member 49 is provided on at least one surface. In FIG. 7, the light shielding members 49 are provided on both the upper and lower surfaces of the diffusion sheet 43, but the light shielding members 49 may be provided only on the lower surface of the diffusion sheet 43 as shown in FIG.

  9A and 9B show the case where the light shielding members 49 are provided on both surfaces of the diffusion sheet 43. FIG. FIG. 9A shows a case where the light shielding member 49 is printed on the surface of the diffusion sheet 43 (for example, silk printing). FIG. 9B shows a case where a light shielding member 49 including a base material 49a and an adhesive 49b is used. The light shielding member 49 is attached to the surface of the diffusion sheet 43 by the adhesive 49b. When printing the light shielding member 49 as shown in FIG. 9A, the light shielding member 49 may be formed of a monochrome material. Further, when the light shielding member 49 is bonded with the adhesive 49b as shown in FIG. 9B, the adhesive 49b may be formed of a monochrome material, and the base material 49a is formed of a monochrome material. Also good. Here, the monochrome material is black, white, or a gray material having an intermediate color.

  9C and 9D show the case where the light shielding member 49 is provided only on the lower surface of the diffusion sheet 43, but the case of one side is the same as the case of both sides.

  On the other hand, a cutout portion 50 is provided along the width direction on the upper surface of the end portion of the flexible printed circuit board 41 on the light guide plate side. The distal end portion of the extended portion of the diffusion sheet 43 is accommodated in the notch 50 and is fixed to the upper surface of the flexible printed circuit board 41 with an adhesive or the like.

  A light shielding plate, that is, a rim sheet 46 is overlaid on the light source 40 and the prism sheet 45, and the lower surface of the rim sheet 46 is bonded to the upper surface of the flexible printed board 41 and the upper surface of the prism sheet 45. From the opening window 24 of the rim sheet 23, a portion corresponding to the effective light emitting region of the light guide plate body 35 is exposed. A reflection sheet 48 is disposed on the lower surface of the light guide plate 33.

  In the surface light source device 31, when the light emitted from the light source 40 enters the light introducing portion 34 from the light incident end surface 36, a part of the light directly enters the light guide plate body 35 or a part thereof. Is guided to the light guide plate body 35 while being reflected by the inclined surface 37 and the reflection sheet 48. The light guided through the light guide plate body 35 is reflected from the light deflection pattern 38 to be emitted from the light exit surface 39, passes through the optical sheets 43 to 45, and is uniformly irradiated upward from the opening window 47. The

  In such a surface light source device 31, the light from the light source 40 may leak to the upper surface side of the light guide plate 33 through the adhesive 42 and the like, as the light L <b> 1 shown in FIGS. 7 and 8A. Further, like the light L <b> 2, the light may not be reflected by the inclined surface 37 but may pass through the inclined surface 37 and leak to the upper surface side of the light guide plate 33. Further, like the light L <b> 3, the light may be totally reflected by the inclined surface 37 and further reflected by the reflection sheet 48, and then leak from the upper surface of the light guide plate body 35. As described above, these leakage lights L1, L2, and L3 cause eyeball-like light emission P (see FIG. 3) and bright lines Q (see FIG. 4).

  However, in the surface light source device 31 according to the first embodiment of the present invention, the space between the upper surface of the light introducing portion 34 and the opening window 47 is partitioned by the diffusion sheet 43, and at least one surface of the diffusion sheet 43, for example, the lower surface (light source) A light shielding member 49 is provided on the side facing the surface. Therefore, these leakage lights L1, L2 and L3 are absorbed or reflected by the light shielding member 49 (in the case of the printing type), the adhesive 49b or the base material 49a (in the case of the adhesion type), and leak from the opening window 24. Is prevented. Therefore, eye-shaped light emission and bright lines due to leaked light leaking from the opening window 24 can be prevented.

  In addition, when the light shielding member 49 (or the base material 49a and the adhesive 49b) is a black resin, the light L1, L2, and L3 are absorbed by the light shielding member 49, so that it is difficult to leak from the opening window 47. On the other hand, when the light shielding member 49 (or the base material 49a and the adhesive 49b) is a white resin, the light L1, L2, and L3 are reflected and may be emitted from the opening window 47. As a result of scattering by the light shielding member 49, the light emission and bright lines do not become eyeballs. On the contrary, it can be said that it is preferable because the luminance of the surface light source device 31 is improved. When the light shielding member 49 is gray, the situation is intermediate between the case of white and the case of black. Further, when the light shielding members 49 are provided on both surfaces of the diffusion sheet 43, the diffusion sheets 43 having different colors may be provided on the upper surface and the lower surface of the diffusion sheet 43. If light shielding members 49 are provided on both surfaces of the diffusion sheet 43 and at least one of the light shielding members 49 is made of a light-absorbing material such as a black material, light entering the diffusion sheet 43 from the end surface of the diffusion sheet 43 is While light is repeatedly reflected in the diffusion sheet 43, it is absorbed by the light-absorbing light shielding member 49.

  The cutout portion 50 of the flexible printed circuit board 41 is not always necessary, but by providing the cutout portion 50, it is possible to prevent the rim sheet 46 from expanding and the surface light source device 31 from increasing in thickness. .

を満たしていれば、光遮蔽部材４９が透けて見えることを防止できる。これは、ｉ番目の光学シートで光が、Ｓi＝ｔi×tan〔arcsin（１／Ｎi）〕だけ水平方向にずれるので、下面の光遮蔽部材４９の端から出た光はリムシート４６の下面では、全体として条件１の右辺（ΣＳi）だけ水平方向にずれて入射する。この入射点がリムシート４６で隠されているための条件が、上記条件１である。 As described above, when the light shielding member 49 such as black or white is provided in the extended portion of the transparent diffusion sheet 43, the light shielding member 49 may be seen through the opening window 47 of the rim sheet 46. In order to prevent the light shielding member 49 from being seen through the opening window 47, the following condition 1 may be satisfied. Now, as shown in FIG. 8B, it is assumed that n optical sheets are stacked on the upper surface of the light guide plate main body 35, and the i-th optical sheet (i = 1, 2,..., N) from the bottom. The thickness is ti and the refractive index is Ni. A light emission surface 39 measured from the end of the light shielding member 49 far from the light source 40 to the light source side opening end of the opening window 47 (the light emission surface side edge of the portion of the rim sheet 46 covering the light source 40); A distance De in a parallel direction (hereinafter, a direction parallel to the light emitting surface 39 is referred to as a horizontal direction) is:

If the above condition is satisfied, the light shielding member 49 can be prevented from being seen through. This is because light is shifted in the horizontal direction by Si = ti × tan [arcsin (1 / Ni)] on the i-th optical sheet, so that the light emitted from the end of the light shielding member 49 on the lower surface is on the lower surface of the rim sheet 46. As a whole, only the right side (ΣSi) of Condition 1 is incident in the horizontal direction. The condition for the incident point to be hidden by the rim sheet 46 is the condition 1 described above.

  FIG. 10 shows a cross section of a liquid crystal display device 61 in which a liquid crystal panel 63 is overlaid on the surface light source device 62 of the first embodiment (the same as that shown in FIG. 8A). The liquid crystal panel 63 is formed by surrounding a space between a pair of glass plates 64 with a spacer 65 and placing a liquid crystal material or an electrode in a space (display area K) surrounded by the spacer 65 to form a large number of pixels. . In this example, the spacer 65 extends to the outside of the glass plate 64 and covers the light source 40 and the light introduction part 34.

  In addition, the rim sheet | seat 46 can be abbreviate | omitted when the upper part of the light source 40 and the light introduction part 34 is covered with the spacer 65 of the liquid crystal panel 63 like FIG.

を満たしていれば、光遮蔽部材４９が透けて見えることを防止できる。 In this case, in order to hide the light shielding member 49 through the glass plate 64, the following condition 2 may be satisfied. In this case, before the light reaches the height of the lower surface of the spacer 65, the light shift due to the glass plate 64 on the lower surface side is further added. As shown in FIG. 10, assuming that the thickness of the lower glass plate 64 is tm and the refractive index of the lower glass plate 64 is Nm, the shift of light by the lower glass plate 64 is tm × tan [arcsin ( 1 / Nm)]. Therefore, the horizontal distance Da measured from the end of the light shielding member 49 on the side far from the light source 40 to the display area end on the light source side in the display area K of the liquid crystal panel 63 is

If the above condition is satisfied, the light shielding member 49 can be prevented from being seen through.

  A surface light source device 71 shown in FIG. 11 is a modification of the first embodiment of the present invention. In this surface light source device 71, a light shielding member 49 is provided on at least one surface of the extended portion of the diffusion sheet 43, and the end of the extended portion of the diffusion sheet 43 is bonded and fixed to the flexible printed circuit board 41. Yes. In the surface light source device 71, the end portion of the flexible printed circuit board 41 is curved along the inclined surface 37, and the end portion of the diffusion sheet 43 is fixed to the upper surface of the curved portion of the flexible printed circuit board 41. Even with such a configuration, it is possible to prevent the rim sheet 46 from being swollen by the diffusion sheet 43 and the surface light source device 71 from becoming thick.

(Embodiment 2)
FIG. 12 is a cross-sectional view showing a surface light source device 81 according to Embodiment 2 of the present invention. In this surface light source device 81, a light shielding member 49 is provided on at least one surface of the extended portion of the diffusion sheet 43 extending to the light source side, and the extended portion of the diffusion sheet 43 is adhered to the lower surface of the rim sheet 46. It is fixed. Even with such a structure, the space between the upper surface of the light introducing portion 34 and the opening window 47 can be partitioned by the light shielding member 49, so that eye-shaped light emission and bright lines can be suppressed.

  FIG. 13 is a cross-sectional view showing a surface light source device 83 according to a modification of the second embodiment of the present invention. In this modification, the light source 40 is mounted on the upper surface of the flexible printed circuit board 41, the flexible printed circuit board 41 is positioned on the lower surface of the light guide plate 33, and the light source 40 is opposed to the light incident end surface 36. This modification shows that the extending portion of the diffusion sheet 43 can be fixed in the same manner regardless of whether the flexible printed circuit board 41 is on the upper surface or the lower surface of the light source 40. Although FIG. 3 shows a case where the extending portion of the diffusion sheet 43 is fixed to the lower surface of the rim sheet 46, the flexible printed circuit board 41 can be disposed on the lower surface side in other embodiments.

(Embodiment 3)
FIG. 14 is a cross-sectional view showing a surface light source device 91 according to Embodiment 3 of the present invention. In the surface light source device 91, the light shielding member 49 is provided on at least one surface of the extended portion of the diffusion sheet 43 extended to the light source side, and the extended portion of the diffusion sheet 43 is bent so as to be folded upward. The upper surface of the diffusion sheet 43 is fixed to the upper surface of the prism sheet 45 with an adhesive. Even with such a structure, the space between the upper surface of the light introducing portion 34 and the opening window 47 can be partitioned by the light shielding member 49, so that eye-shaped light emission and bright lines can be suppressed.

  FIG. 15 is a cross-sectional view showing a surface light source device 92 according to a modification of the third embodiment of the present invention. In this modification, the extended portion of the diffusion sheet 43 is bent into a substantially rectangular shape along the end surfaces of the prism sheets 44 and 45.

(Embodiment 4)
FIG. 16 is a sectional view showing a surface light source device 93 according to Embodiment 4 of the present invention. In the surface light source device 93, the light source side end of the diffusion sheet 43 is retracted from the ends of the prism sheets 44 and 45. The light shielding member 94 is formed in a sheet shape from a flexible black, white, or gray material (monochrome material), and is a separate member from the diffusion sheet 43. One end of the light shielding member 94 is bonded and fixed to the cutout 50 of the flexible printed circuit board 41. The other end of the light shielding member 94 is inserted and fixed under the prism sheet 44 or is bonded and fixed to the lower surface of the prism sheet 44. Even with such a structure, the space between the upper surface of the light introducing portion 34 and the opening window 47 can be partitioned by the light shielding member 94, so that it is possible to suppress eye-shaped light emission and bright lines.

  FIG. 17 is a cross-sectional view showing a surface light source device 95 according to a modification of the fourth embodiment of the present invention. In the surface light source device 95, the light source side end of the diffusion sheet 43 protrudes beyond the ends of the prism sheets 44 and 45. One end of the light shielding member 94 is bonded and fixed to the cutout 50 of the flexible printed circuit board 41. The other end of the light shielding member 94 is inserted and fixed under the diffusion sheet 43, or is overlapped and adhered to the protruding portion of the diffusion sheet 43. In this modified example, since no gap is generated between the light shielding member 94 and the diffusion sheet 43, the effect of suppressing leakage light is enhanced.

  FIG. 18 is a cross-sectional view showing a surface light source device 96 according to another modification of Embodiment 4 of the present invention. In the surface light source device 96, the light source side end of the diffusion sheet 43 is retracted from the ends of the prism sheets 44 and 45. The light shielding member 94 is formed in a sheet shape from a flexible black, white, or gray material (monochrome material), and is a separate member from the diffusion sheet 43. One end of the light shielding member 94 is bonded and fixed to the lower surface of the flexible printed circuit board 41. The other end of the light shielding member 94 is inserted and fixed under the prism sheet 44 or is bonded and fixed to the lower surface of the prism sheet 44.

  FIG. 19 is a cross-sectional view showing a surface light source device 97 according to still another modification of Embodiment 4 of the present invention. In the surface light source device 97, the light source side end portion of the diffusion sheet 43 protrudes beyond the ends of the prism sheets 44 and 45. One end of the light shielding member 94 is bonded and fixed to the lower surface of the flexible printed circuit board 41. The other end of the light shielding member 94 is inserted and fixed under the prism sheet 44, or is overlapped and adhered to the protruding portion of the diffusion sheet 43.

(Embodiment 5)
FIG. 20 is a cross-sectional view showing a surface light source device 98 according to Embodiment 5 of the present invention. In the surface light source device 98, the sheet-shaped light shielding member 94 is curved in an arc shape, and one end of the light shielding member 94 is inserted and fixed under the prism sheet 44, or adhered to the lower surface of the prism sheet 44. Are fixed. The other end of the light shielding member 94 is bonded and fixed to the upper surface of the prism sheet 45. Even in such a structure, since the space between the upper surface of the light introducing portion 34 and the opening window 47 can be partitioned by the light shielding member 94, it is possible to suppress eye-shaped light emission and bright lines.

  FIG. 21 is a cross-sectional view showing a surface light source device 99 according to a modification of the fifth embodiment of the present invention. In the surface light source device 99, the sheet-shaped light shielding member 94 is bent into a rectangular shape, and one end of the light shielding member 94 is inserted and fixed under the prism sheet 44, or is adhered to the lower surface of the prism sheet 44. It is fixed. The other end of the light shielding member 94 is bonded and fixed to the upper surface of the prism sheet 45.

(Embodiment 6)
FIG. 22 is a sectional view showing a surface light source device 101 according to Embodiment 6 of the present invention. In the surface light source device 101, the light source side end of the diffusion sheet 43 protrudes beyond the ends of the prism sheets 44 and 45, and the upper surface of the protruding portion of the diffusion sheet 43, that is, the upper surface of the diffusion sheet 43 and the lower surface of the rim sheet 46. Between them, a rod-shaped light shielding member 102 is provided. The light shielding member 102 includes a base material 102a and an adhesive 102b, and the light shielding member 102 may be adhered to the upper surface of the diffusion sheet 43 with an adhesive 102b as shown in FIG. As in B), the light shielding member 102 may be bonded to the lower surface of the rim sheet 46 by the adhesive 102b. In this embodiment, the member in contact with the diffusion sheet 43 among the base material 102a and the adhesive 102b is preferably a light-absorbing material such as a black material. The other member may be white or gray material.

In this embodiment, since the light shielding member is not provided on the lower surface of the diffusion sheet 43, the conditions for preventing the light shielding member 102 from being seen from the opening window 47 and the display area, that is, the above conditions 1 and 2 are Correction is required. When the light shielding member 102 is provided on the upper surface of the diffusion sheet 43, the light that exits from the end of the lower surface of the light shielding member 102 that is far from the light source and travels toward the opening window 47 is the lowermost optical sheet (diffusion). Since the sheet 43) does not pass, the term relating to the optical sheet in the lowermost layer may be excluded from the condition 1. Therefore, the condition for preventing the light shielding member 102 from being seen through the opening window 47 is as follows. The symbols are the same as in condition 1.

When the liquid crystal panel is overlaid on the surface light source device 101 (see FIG. 10), the condition for preventing the light shielding member 102 from being seen through the display area of the liquid crystal panel is as the following condition 4 become. The symbols are the same as in condition 2.

  FIG. 24 is a sectional view showing a surface light source device 104 according to a modification of the sixth embodiment of the present invention. In the modified example, the end portion of the diffusion sheet 43 extends to the light source side, and the flexible printed circuit board 41 extends to the upper surface of the light guide plate body 35, and the light shielding member 102 is connected to the upper surface of the diffusion sheet 43 and the flexible printed circuit board 41. It is bonded and fixed to the lower surface.

(Embodiment 7)
FIG. 25 is a cross-sectional view showing a surface light source device 106 according to Embodiment 7 of the present invention. In the surface light source device 106, a light shielding member 49 is provided on at least one surface of the extended portion of the diffusion sheet 43 extending toward the light source side, and the extended portion of the diffusion sheet 43 is along the inclined surface 37. . Further, the rim sheet 46 is loosened to bond the lower surface of the rim sheet 46 and the upper surface of the extended portion of the diffusion sheet 43. Even with such a structure, the space between the upper surface of the light introducing portion 34 and the opening window 47 can be partitioned by the light shielding member 49 and the rim sheet 46, so that it is possible to suppress eye-shaped light emission and bright lines. it can.

(Embodiment 8)
FIG. 26 is a cross-sectional view of the surface light source device 111 according to Embodiment 8 of the present invention. The surface light source device 111 has substantially the same structure as that of the first embodiment except for the structure of the light guide plate 33.

  27 and 28 are a perspective view and a plan view showing the structure of the light guide plate 33 used in the surface light source device 111. FIG. A directivity conversion pattern 112 is formed on the inclined surface 37 of the light introducing portion 34. The directivity conversion pattern 112 is a pattern in which a plurality of pattern elements having a mountain shape or a V-groove shape are arranged along the width direction of the light introducing portion 34. That is, in the directivity conversion pattern 112, ridge lines and valley lines are alternately arranged. When the directivity conversion pattern 112 is viewed from a direction perpendicular to the light emitting surface 39, the pattern elements or ridge lines and valley lines are arranged in parallel to the direction perpendicular to the light incident end face 36. They are parallel to each other along the width direction. Each pattern element has an asymmetric shape in a cross section parallel to the light incident end face 36. Further, at least one set of asymmetric pattern elements having different shapes are present in the regions on both sides of the light source center. The directivity conversion pattern 112 reflects the light incident on the light introducing portion 34 so that the directivity spread in the light guide plate thickness direction of the light incident on the light introducing portion 34 is parallel to the surface direction of the light guiding plate 33. It has a function of converting to a directional characteristic inclined toward the.

  A lenticular lens 113 extending in a direction perpendicular to the light incident end surface 36 is formed on the upper surface (light emitting surface 39) of the light guide plate body 35.

  FIG. 29 shows the cross-sectional shape of the directivity conversion pattern 112 in the XX line cross section of FIG. That is, FIG. 29 shows an area (in other words, a light source width W) that is located in front of the light source 40 and has a width (light source width W) equal to that of the light source 40 in the cross section of the directivity conversion pattern 112 cut parallel to the light incident end face 36. , A portion within the area W / 2 from the light source center C to the left and right sides). Here, the light source center C is a plane that passes through the light emission center 40 a of the light source 40 and is perpendicular to the light incident end surface 36 and the light emitting surface 39 of the light guide plate 33. The light source width W does not mean the width of the light source 40 package but the width of the light emitting surface. In FIG. 29, the directivity conversion pattern 112 has a symmetrical shape with respect to the light source center C, but is not necessarily symmetrical.

  In the surface light source device 111 of the eighth embodiment, the directivity conversion pattern 112 has the following structure or characteristics in the region of the light source width W in the cross section parallel to the light incident end face 36. The region outside the light source width W may have the same structure or characteristics as the region of the light source width W. However, in the region away from the light source 40, the amount of light supplied and the light intensity are small. The structure of the directivity conversion pattern 112 is not particularly limited outside the width W.

  In the region of the light source width W in the cross section parallel to the light incident end face 36, most or all of the pattern elements constituting the directivity conversion pattern 112 have an asymmetric shape. That is, the pattern slope 114a connecting a certain ridge line (maximum point of the cross section) and one valley line (minimum point of the cross section) adjacent to the ridge line, and the other valley line (minimum of the cross section) adjacent to the ridge line and the ridge line. The pattern slope 114b connecting the point) is asymmetrical with respect to a straight line passing through the ridge line and perpendicular to the light emitting surface 39. However, some pattern elements (for example, the pattern element at the position of the light source center C) may be symmetrical. Here, the pattern slopes 114a and 114b are surfaces of the directivity conversion pattern 112 located between adjacent ridge lines and valley lines. In the directivity conversion pattern 112 shown in FIG. 29, the pattern slopes 114a and 114b are flat surfaces, but may be curved surfaces or bent surfaces.

  Further, in the light source center C and the area W / 2 to the left side from the light source center C (hereinafter referred to as the left side area of the light source center C), the pattern slopes 114a and 114b are extended from the inside of the light guide plate 33 to the outside. When the line N is erected, the sum of the lateral widths D2 of the pattern slopes 114b in which the normal line N is inclined toward the light source center (the total value in the left region of the width W / 2 of the lateral width D2 of each pattern slope 114b) is The sum of the width D1 of the pattern slope 114a in which the line N is inclined to the side opposite to the light source center (the total value in the left region of the width W / 2 of the width D1 of each pattern slope 114a) is larger (condition 5). : ΣD1 <ΣD2).

  Similarly, in the light source center C and an area W / 2 on the right side from the light source center C (hereinafter referred to as the right area of the light source center C), the pattern slopes 114a and 114b extend from the inside of the light guide plate 33 to the outside. When the normal line N is set, the sum of the lateral widths D2 of the pattern slopes 114b inclined toward the light source center side (the total value of the lateral widths D2 of the respective pattern slopes 114b in the right region of the width W / 2) However, the sum N of the width D1 of the pattern slope 114a in which the normal N is inclined to the opposite side of the light source center (the total value in the right region of the width W / 2 of the width D1 of each pattern slope 114a) is larger. (Condition 5: ΣD1 <ΣD2).

  In order to realize such a configuration, in two adjacent pattern slopes 114a and 114b (pattern elements), the horizontal width D2 of the pattern slope 114b in which the normal line N is inclined toward the light source center side, and the normal line N is the light source. It may be larger than the lateral width D1 of the pattern slope 114a inclined to the side opposite to the center or may be the same in part (condition 6: D1 ≦ D2). It is only necessary that at least a part of the pattern elements in the region of the light source width W satisfy the condition 6. It is preferable that as many pattern elements as possible satisfy the condition 6, but not all pattern elements are required.

  In the surface light source device 111, in each of the left and right regions of the light source center C, the sum of the lateral widths D2 of the pattern slopes 114b in which the normal line N is inclined toward the light source center side, It is larger than the sum of the width D1 of the slope 114a (condition 5). In particular, in many pattern elements, the width D2 of the pattern slope 114b in which the normal line N is inclined toward the light source center side is larger than the width D1 of the pattern slope 114a in which the normal line N is inclined to the side opposite to the light source center, or It is the same for some pattern elements (condition 6). As a result, as shown in FIG. 30, the area of the pattern slope 114a where the light L1 emitted obliquely from the light emission center 40a enters at an angle close to the vertical is that the pattern element is a directional conversion pattern that is symmetric. In comparison, it becomes narrower and light is less likely to leak from the pattern slope 114a. Further, since the inclination angle of the pattern slope 114a in which the normal N is inclined to the side opposite to the light source center C is increased, the pattern slope pattern 114a is incident on the pattern slope 114a as compared with the case where the pattern elements of the directivity conversion pattern are symmetrical. The incident angle of the light L1 is increased, and the light L1 is difficult to leak from the pattern slope 114a. As a result, according to the surface light source device 111, leakage of light from the directivity conversion pattern 112 can be suppressed, and light utilization efficiency is improved.

  The main structure of the light guide plate 33 disclosed in the eighth embodiment of the present invention is an international patent application (PCT / JP2012 / 056182) filed by the applicant of the present invention. Although the basic structure has been described here, any configuration disclosed in the international patent application (PCT / JP2012 / 056182) may be implemented in addition to or in addition to the surface light source device 111 of the eighth embodiment of the present invention. It can replace with the surface light source device 111 of the form 8, and can be applied.

(Embodiment 9)
FIG. 31A is a plan view of a surface light source device 116 according to Embodiment 9 of the present invention. FIG. 31B is a cross-sectional view of the surface light source device 116. The rim sheet 46 is not limited to the one having a frame shape as in the above embodiments and having an opening window. In the surface light source device 116 according to the ninth embodiment, the light emitting surface side edge of the rim sheet 46 that covers only the light source 40 and the light introduction part 34 by using the substantially rectangular rim sheet 46 and covers the light source 40. A light shielding member 49 having an appropriate structure is provided between the light incident end face 36 and the light incident end face 36.

  FIG. 32 shows the relationship between the ratio of the thickness of the light guide plate body to the thickness of the light introducing portion of the light guide plate (step ratio) and the luminance efficiency of the surface light source device. The step ratio on the horizontal axis is the ratio t / T of the thickness t of the light guide plate body 35 to the maximum thickness T of the light introducing portion 34, and the surface light source device is made thinner as the step ratio is smaller. The luminance efficiency is a percentage of how much of the light incident on the light introducing portion 34 is emitted from the light exit surface 39. Empirically, it is known that when the luminance efficiency is higher than 97%, the appearance of the surface light source device is deteriorated. Therefore, according to FIG. 32, the step ratio of the light guide plate is desirably 0.75 or less. Therefore, in any embodiment of the present application, the step ratio is desirably 0.75 or less.

(Embodiment 10)
FIG. 33 is a plan view of a mobile device using the surface light source device or the liquid crystal display device of the present invention, that is, a smartphone 121, and includes a liquid crystal display device 122 with a touch panel on the front. If the surface light source device of the present invention is used for such a smartphone, eyeball-like light emission and bright lines are less likely to occur, so that the quality of the display screen is improved. The surface light source device of the present invention can be applied to mobile devices such as tablet computers, electronic dictionaries, and electronic book readers in addition to mobile phones such as smartphones.

31, 71, 81, 91, 92, 93, 95 to 99 Surface light source device 101, 104, 106, 111, 116 Surface light source device 33 Light guide plate 34 Light introducing portion 35 Light guide plate main body 36 Light incident end surface 37 Inclined surface 38 Light Deflection pattern 39 Light exit surface 40 Light source 41 Flexible printed circuit board 42 Adhesive 43 Diffusion sheet 44, 45 Prism sheet 46 Rim sheet 47 Open window 48 Reflective sheet 49, 94, 102 Light shielding member 49a, 102a Base material 49b, 102b Adhesive 50 Notch 61 Liquid crystal display device 62 Surface light source device 63 Liquid crystal panel 64 Glass plate 65 Spacer

を満たすことを特徴とする。 Still another embodiment of the surface light source device according to the present invention includes: an end of the light shielding member on the side far from the light source; and a light emitting surface side edge of the portion of the light shielding plate that covers the light source. When the distance in the direction parallel to the light exit surface is De and the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

It is characterized by satisfying.

を満たすことを特徴とする。 Still another embodiment of the surface light source device according to the present invention is the light source side display area in the display area of the liquid crystal panel disposed above the optical sheet and the end of the light shielding member on the side far from the light source. The distance in the direction parallel to the light exit surface between the edges is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness of the glass plate on the lower surface side of the liquid crystal panel When the refractive index is tm and Nm, respectively,

It is characterized by satisfying.

を満たすことを特徴とする。なお、条件１が満たされていれば、条件３も満たされる。 Still another embodiment of the surface light source device according to the present invention includes: an end of the light shielding member on the side far from the light source; and a light emitting surface side edge of the portion of the light shielding plate that covers the light source. When the distance in the direction parallel to the light exit surface is De and the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

It is characterized by satisfying. If condition 1 is satisfied, condition 3 is also satisfied.

を満たすことを特徴とする。なお、条件２が満たされていれば、条件４も満たされる。 Still another embodiment of the surface light source device according to the present invention is such that the end portion of the optical sheet in the lowermost layer extends to the light source side than the end of the other optical sheet, and the upper surface of the optical sheet in the lowermost layer The light shielding member is provided, and the light shielding member between the end of the light shielding member far from the light source and the display area end on the light source side in the display area of the liquid crystal panel disposed above the optical sheet, The distance in the direction parallel to the light exit surface is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness and refractive index of the glass plate on the lower surface side of the liquid crystal panel are tm and When Nm, the following conditions

It is characterized by satisfying. If condition 2 is satisfied, condition 4 is also satisfied.

を満たしていれば、光遮蔽部材４９が透けて見えることを防止できる。これは、ｉ番目の光学シートで光が、Ｓi＝ｔi×tan〔arcsin（１／Ｎi）〕だけ水平方向にずれるので、下面の光遮蔽部材４９の端から出た光はリムシート４６の下面では、全体として条件１の右辺（ΣＳi）だけ水平方向にずれて入射する。この入射点がリムシート４６で隠されているための条件が、上記条件１である。 As described above, when the light shielding member 49 such as black or white is provided in the extended portion of the transparent diffusion sheet 43, the light shielding member 49 may be seen through the opening window 47 of the rim sheet 46. In order to prevent the light shielding member 49 from being seen through the opening window 47, the following condition 1 may be satisfied. Now, as shown in FIG. 8B, it is assumed that n optical sheets are stacked on the upper surface of the light guide plate main body 35, and the i-th optical sheet (i = 1, 2,..., N) from the bottom. The thickness is ti and the refractive index is Ni. A light emission surface 39 measured from the end of the light shielding member 49 far from the light source 40 to the light source side opening end of the opening window 47 (the light emission surface side edge of the portion of the rim sheet 46 covering the light source 40); A distance De in a parallel direction (hereinafter, a direction parallel to the light emitting surface 39 is referred to as a horizontal direction) is:

If the above condition is satisfied, the light shielding member 49 can be prevented from being seen through. This is because light is shifted in the horizontal direction by Si = ti × tan [arcsin (1 / Ni)] on the i-th optical sheet, so that the light emitted from the end of the light shielding member 49 on the lower surface is on the lower surface of the rim sheet 46. As a whole, only the right side (ΣSi) of Condition 1 is incident in the horizontal direction. The condition for the incident point to be hidden by the rim sheet 46 is the condition 1 described above.

を満たしていれば、光遮蔽部材４９が透けて見えることを防止できる。 In this case, in order to hide the light shielding member 49 through the glass plate 64, the following condition 2 may be satisfied. In this case, before the light reaches the height of the lower surface of the spacer 65, the light shift due to the glass plate 64 on the lower surface side is further added. As shown in FIG. 10, assuming that the thickness of the lower glass plate 64 is tm and the refractive index of the lower glass plate 64 is Nm, the shift of light by the lower glass plate 64 is tm × tan [arcsin ( 1 / Nm)]. Therefore, the horizontal distance Da measured from the end of the light shielding member 49 on the side far from the light source 40 to the display area end on the light source side in the display area K of the liquid crystal panel 63 is

If the above condition is satisfied, the light shielding member 49 can be prevented from being seen through.

In this embodiment, since the light shielding member is not provided on the lower surface of the diffusion sheet 43, the conditions for preventing the light shielding member 102 from being seen from the opening window 47 and the display area, that is, the above conditions 1 and 2 are Correction is required. When the light shielding member 102 is provided on the upper surface of the diffusion sheet 43, the light that exits from the end of the lower surface of the light shielding member 102 that is far from the light source and travels toward the opening window 47 is the lowermost optical sheet (diffusion). Since the sheet 43) does not pass, the term relating to the optical sheet in the lowermost layer may be excluded from the condition 1. Therefore, the condition for preventing the light shielding member 102 from being seen through the opening window 47 is as follows. The symbols are the same as in condition 1.

When the liquid crystal panel is overlaid on the surface light source device 101 (see FIG. 10), the condition for preventing the light shielding member 102 from being seen through the display area of the liquid crystal panel is as the following condition 4 become. The symbols are the same as in condition 2.

Claims (18)

A light guide plate that introduces light from the end face and emits light from the light exit face;
A light source disposed at a position facing the end face of the light guide plate;
A plurality of optical sheets disposed on the light guide plate;
In a surface light source device comprising a light shielding plate arranged so as to cover the light source,
A light shielding member different from the light shielding plate, between the end face of the light guide plate and the light emitting surface;
The light guide plate is provided so as to be continuous with the light introduction portion with a light introduction portion for confining light from the light source incident from the end face and a thickness smaller than the maximum thickness of the light introduction portion. A light guide plate main body adapted to emit light confined by the light emitting means to the outside by the light emitting means,
The light introducing portion is directed to at least one of the light emitting side surface of the light guide plate and the opposite surface thereof, from the surface of the portion having a larger thickness than the light guide plate body toward the end of the surface of the light guide plate body. Having an inclined surface,
The light guide plate has a directivity spread in the thickness direction of the light guide plate of light incident on the light introducing portion parallel to the surface direction of the light guide plate on at least one of the light emitting side surface and the opposite surface. It has a directivity conversion pattern for converting to a directivity characteristic inclined toward the direction,
The directivity conversion pattern is configured to alternately repeat ridge lines and valley lines along the width direction of the light guide plate,
Of the cross section of the directivity conversion pattern cut parallel to the end face, a portion located in front of the light source and within a region having a width equal to the light source is the ridge line of the directivity conversion pattern. A slope connecting one of the ridge lines and one valley line adjacent to the ridge line, and a slope connecting the ridge line and the other valley line adjacent to the ridge line pass through the ridge line and are perpendicular to the light emitting surface. A surface light source device characterized in that it is asymmetric with respect to a straight line, and at least one set of the asymmetric shape portions having different shapes is present on both sides of the center of the light source.   Of the cross section of the directivity conversion pattern cut parallel to the end face, the inclined surface is located in front of the light source and has the same width as the light source, from the inside of the light guide plate to the outside. When the normal line is set to each of the above, in at least one of the regions on both sides sandwiching the light source center, the total width in the one region of the lateral width of the slope in which the normal line is inclined toward the light source center side, 2. The surface light source device according to claim 1, wherein a normal line is larger than a total sum in the one region of a lateral width of the inclined surface inclined to the opposite side to the light source center.   The light shielding member is provided below the light shielding plate and between the end surface of the light guide plate and a light emitting surface side edge of a portion of the light shielding plate covering the light source. The surface light source device according to claim 1, wherein the surface light source device is characterized. De is the distance in the direction parallel to the light exit surface between the end of the light shield member that is far from the light source and the light exit surface side edge of the light shield plate that covers the light source. When the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

The surface light source device according to claim 1, wherein: A direction parallel to the light emitting surface between the end of the light shielding member on the side far from the light source and the display area end on the light source side in the display area of the liquid crystal panel disposed above the optical sheet. When the distance is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness and refractive index of the glass plate on the lower surface side of the liquid crystal panel are tm and Nm, respectively,

The surface light source device according to claim 1, wherein: The light shielding member is formed at an end of at least one surface of the optical sheet in the lowermost layer,
6. The surface light source device according to claim 4, wherein an extended end portion of the lowermost optical sheet is fixed to a wiring substrate on which the light source is mounted. The light shielding member is formed at an end of at least one surface of the optical sheet in the lowermost layer,
5. The surface light source device according to claim 4, wherein an extended end portion of the lowermost optical sheet is fixed to the light shielding plate. The light shielding member is formed at an end of at least one surface of the optical sheet in the lowermost layer,
6. The surface light source device according to claim 4, wherein an extended end of the lowermost optical sheet is fixed to the uppermost optical sheet. 7.   The one end portion of the light shielding member is fixed to a wiring board on which the light source is mounted, and the other end portion of the light shielding member is fixed to the optical sheet. Surface light source device.   The one end portion of the light shielding member is fixed to the uppermost optical sheet, and the other end portion of the light shielding member is fixed to the optical sheet of the lower layer portion. The surface light source device described in 1.   An end portion of the optical sheet in the lowermost layer extends to the light source side than an end of the other optical sheet, and the light shielding member is provided on the upper surface of the optical sheet in the lowermost layer. Item 2. A surface light source device according to Item 1.   The surface light source device according to claim 11, wherein an upper surface of the light shielding member is fixed to a lower surface of the light shielding plate.   The surface light source device according to claim 11, wherein an upper surface of the light shielding member is fixed to a lower surface of a wiring board on which the light source is mounted. De is the distance in the direction parallel to the light exit surface between the end of the light shield member that is far from the light source and the light exit surface side edge of the light shield plate that covers the light source. When the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively,

The surface light source device according to claim 11, wherein: The end of the lowermost optical sheet extends to the light source side than the end of the other optical sheet, and the light shielding member is provided on the upper surface of the lowermost optical sheet,
A direction parallel to the light emitting surface between the end of the light shielding member on the side far from the light source and the display area end on the light source side in the display area of the liquid crystal panel disposed above the optical sheet. When the distance is Da, the thickness and refractive index of the i-th optical sheet from the bottom are ti and Ni, respectively, and the thickness and refractive index of the glass plate on the lower surface side of the liquid crystal panel are tm and Nm, respectively,

The surface light source device according to claim 5, wherein: The light guide plate has a light introduction portion for introducing light from the light source from an end surface, and a light guide plate body having the light emission surface, which is thinner than a maximum thickness of the light introduction portion, and is continuously formed. ,
6. The surface light source device according to claim 1, wherein a ratio of a thickness of the light guide plate main body to a maximum thickness of the light introducing portion is 0.75 or less.   A liquid crystal display device comprising the surface light source device according to claim 1 and a liquid crystal panel.   A mobile device comprising the surface light source device according to claim 1.

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