JP5499458B2 - Light guide, light guide plate, backlight unit, and liquid crystal display device including the same - Google Patents

Description

  The present invention relates to a backlight unit that illuminates light on the back side of a liquid crystal panel, a light guide provided in the backlight unit, and a light guide plate in which a plurality of light guides are arranged. The present invention relates to a light guide body and a light guide plate that are provided with a concave portion that has an inclined surface having an inner surface reflecting action on the surface side, and a backlight unit including the light guide body or the light guide plate.

  A backlight unit used in a liquid crystal display device includes a light source that illuminates light on the back side of a liquid crystal panel, a light guide plate that guides light from the light source, and the like. The backlight unit is roughly classified into a sidelight system in which light sources are arranged on one or both end faces of the light guide plate and a direct type in which a plurality of light sources are arranged on the back surface of the light guide plate. Sidelight type backlight units are mainly used for small display devices, and direct type backlight units are mainly used for large display devices.

  However, the conventional direct type backlight unit has a high luminance directly above the light source and a low luminance between the light sources, that is, uneven luminance. In view of this, there have been provided a backlight unit and a liquid crystal display device using the backlight unit that are less likely to cause uneven brightness.

  For example, Patent Document 1 discloses various types of liquid crystal display devices. As shown in FIGS. 8A and 8B, each of the liquid crystal display devices has one or more on the back surface of the effective display area. A substantially flat light guide plate 2 in which the groove 1 is formed, a linear light source 3 such as a cold cathode fluorescent tube arranged in the groove 1 of the light guide plate 2, and a liquid crystal arranged on the surface side of the light guide plate 2 A V-shaped inclined surface 4 having a display element (not shown) and having an inner surface reflecting action is formed on the surface in the vicinity of the groove 1.

  In the liquid crystal display device shown in FIG. 8A, the back (front side) of the groove 1 is a bowl-shaped inclined surface 1 a and the flat portion 4 a is provided at the center of the bottom of the inclined surface 4 of the light guide plate 2. It is a feature. This liquid crystal display device is formed such that light L incident from the light source 3 into the light guide plate 2 is reflected mainly along the inclined surface 4 of the light guide plate 2.

  In the liquid crystal display device shown in FIG. 8B, the back (front side) of the groove 1 has a substantially bowl-shaped slope, and the center of the back of the groove 1 is rounded 1 b. It is characterized in that the bottom of the inclined surface 4 is also rounded 4b. In this liquid crystal display device, the luminous intensity distribution of the light L incident on the light guide plate 2 from the central portion of the groove 1 changes so as to be dense just above the light source 3 and gradually become sparse as it goes away, so that no bright line is generated. Has been.

  Further, Patent Document 2 discloses a backlight unit including a substantially flat light guide plate 5, a light source 6, a reflecting member (not shown), and a diffusion plate 9, as shown in FIG. Yes. In this backlight unit, the light guide plate 5 is formed by dispersing a light diffusing agent in a transparent resin, and a light source recess 7 for housing the light source 6 is formed on the back surface of the light guide plate 5. An inclined surface 8 having a V-shaped cross section is formed on the surface of the light guide plate 5.

The light L incident from the light source 6 into the light guide plate 5 is diffused by the light diffusing agent in the light guide plate 5 and partially reflected by the inclined surface 8. The reflected light propagates in the light guide plate 5 toward an end far from the light source 6 or another light source 6 adjacent thereto, and is evenly emitted from the surface of the light guide plate 5 on the far side of the reflecting member.
Japanese Patent Laid-Open No. 2001-133779 JP 2006-286217 A

  In the liquid crystal display device shown in FIGS. 8A and 8B and the backlight unit shown in FIG. 8C, the light L is not evenly emitted by the light guide plate 2 alone, and luminance unevenness can be eliminated. Can not. Therefore, those equipped with these light guide plates 2 and 5 are provided with a reflection plate (not shown) on the back side of the light guide plates 2 and 5, and with a diffusion plate 9 on the surface side of the light guide plate 2 and reflected. The light L is uniformly emitted by the cooperation of the plate and the diffusion plate 9.

  However, in order to emit the light L evenly, it is necessary to increase the distance between the reflecting plate and the diffusing plate 9 (in the apparatus and unit shown in FIGS. 8A and 8B, 10. 9 mm, 8.4 mm in the unit shown in FIG. 8C), and cannot be thinned.

  Accordingly, the present invention provides a light guide, a light guide plate, a backlight unit, and a liquid crystal display device including the same, which can emit light uniformly and can be thinned. Is an issue.

Light guide according to the present invention, the rear side groove-like recess or depression-like recess for accommodating is provided a linear light source or a point light source, recess so gradually deeper from the surface toward the center of the recess-free In addition, a light guide body having an inclined surface formed with a curved surface portion having substantially the same shape as the concave portion at a peripheral portion , wherein the inclined surface emits light incident from the light source to the inside from the inclined surface. An inclined or non-inclined transmission part and a reflection part that is inclined or non-inclined so as to be reflected from the inclined surface are alternately provided continuously, and the width and reflection of the transmission part at the center side are provided. The ratio of the width of the reflection part is smaller than the ratio of the width of the transmission part on the peripheral side and the width of the reflection part, and the width of the reflection part is larger than the width of the transmission part on the center side. The width is made larger than the width of the reflecting portion .

According to this light guide, the light incident on the inside of the light guide from the light source is emitted from the light guide at the transmission part provided on the inclined surface, and is reflected into the light guide by the reflection part. The ratio of the width of the transmissive part on the center side to the reflective part is smaller than the ratio of the width of the transmissive part to the width of the reflective part on the peripheral side, so that the amount of light emitted from the central side is reduced. It is relatively less than the amount of light emitted from the peripheral side. However, a diffusion plate is disposed on the surface side of the light guide, and light is emitted after entering the diffusion plate. This light is incident in a vertical direction at a portion facing the center of the light guide, and is incident obliquely at a portion facing the periphery of the light guide. Therefore, the light on the center side enters the diffuser plate in a narrow range, the light on the peripheral side enters the diffuser plate in a wide range, and the amount of light at the diffuser plate is relatively even on the center side and the peripheral side. Therefore, the light is evenly emitted from the diffusion plate over the entire surface. Further, according to this light guide, the width of the reflection part is larger than the width of the transmission part on the center side, and the width of the transmission part is larger than the width of the reflection part on the peripheral side, so that the light is centered. Since the light is reflected more on the side and less reflected on the peripheral side, the density of the light amount is made uniform between the central side and the peripheral side. Furthermore, according to this light guide, light is emitted from the light guide over a wide range by providing the same transmission part and reflection part on the curved part having substantially the same shape as the concave part provided in the peripheral part. can do.

  The light guide plate according to the present invention is characterized in that any one of the light guides described above is arranged and integrated with the substrate in a state where the recesses are opened.

  According to this light guide plate, since the plurality of light guides are integrated with the substrate, the plurality of light guides can be positioned and the assembly workability can be improved.

  Further, the backlight unit according to the present invention includes any one of the plurality of light guides according to the present invention that is not provided with the substrate, a light source accommodated in a recess of each light guide, and each light guide. And a diffusion plate disposed on the surface side of the substrate.

  According to this backlight light source, light is uniformly incident on the entire surface from the inclined surface of the light guide to the diffuser plate, and is uniformly emitted from the diffuser plate over the entire surface.

  Further, the backlight unit different from the above according to the present invention includes a light guide plate according to the present invention in which the light guide and the substrate are integrated, a light source housed in a recess of each light guide, and each light guide. And a diffusion plate arranged on the surface side of the body.

  According to this backlight light source, light is uniformly incident on the entire surface from the inclined surface of the light guide of the light guide plate into the diffuser plate, and is uniformly emitted from the diffuser plate over the entire surface.

  In addition, according to the liquid crystal display device according to the present invention, the light guide plate according to the present invention in which the light guide and the substrate are integrated, the light source stored in the recess of each light guide, and each light guide. And a diffusion plate disposed on the surface side of the substrate.

  According to this liquid crystal display device, light is uniformly incident on the entire surface of the diffusion plate from the inclined surface of the light guide of the light guide plate, and is uniformly emitted from the diffusion plate to the entire surface of the liquid crystal panel.

  According to the present invention, it is possible to provide a light guide and a light guide plate having no luminance unevenness. In the present invention, the backlight unit thickness (FIG. 8 (a) (b)) using the conventional light guide plate ( 10.9 mm) can be reduced to 70% or less, and a backlight unit thinner than the conventional one can be provided. Therefore, the present invention can favorably illuminate the liquid crystal panel of the liquid crystal display device and contribute to the thinning of the liquid crystal display device.

  A first embodiment of a light guide according to the present invention will be described with reference to FIGS. 1 and 2. The light guide 11 is provided with a groove-like or hollow-like recess 12 for accommodating the linear light source 10 or the point light source 10 (hereinafter also referred to as “light source”) on the back side, and the recess 12 from the surface. An inclined surface 13 is formed so as to be gradually deeper toward the center. The center of the recess 12 and the bottom of the inclined surface 13 are close to each other.

  For example, the light guide 11 provided with the groove-like recess 12 to accommodate the linear light source 10 in which cold cathode fluorescent tubes and light-emitting diodes are arranged in a line is naturally a long rod-like body. Yes. In addition, the light guide 11 provided with the recessed portion 12 for accommodating the point light source 10 such as one light emitting diode is a bottomed cylindrical body formed in a bottomed cylindrical shape.

  Any of the concave portions 12 is not limited to a cross-sectional shape such as a square shape, a cross-sectional shape not shown, or a pentagonal shape having two parallel sides. The pentagonal concave portion 12 may be rounded on the back side or pointed in the back direction (in the drawing, in a letter-like shape), but is pointed in the back direction because of the reflection direction of the light L (in the drawing, It is not preferable to have a V shape or an inverted W shape.

  The inclined surface 13 has an internal reflection effect and is macroscopically formed in a curved surface shape. However, as shown in the partial enlarged view of FIG. They are provided alternately and continuously. The reflector 14 is inclined or not inclined so that the light L incident from the light source 10 to the inside of the light guide 11 is reflected from the inclined surface 13 to the inside. Further, the transmissive portion 15 is inclined or not inclined so that the light L incident from the light source 10 into the light guide 11 is emitted from the inclined surface 13.

  Here, the width of the reflection part 14 on the center side (not the length but the interval between the perpendiculars when the vertical lines are taken from both ends to the back surface; the same applies hereinafter) is A1, and the width of the transmission part 15 is B1. When the width of the reflection part 14 is A2 and the width of the transmission part 15 is B2, the inclined surface 13 is (B1 / A1) ≦ (B2 / A2), that is, the width of the transmission part 15 on the center side and the reflection part 14 The width ratio is formed smaller on the peripheral side than the ratio of the width of the transmission portion 15 and the width of the reflection portion 14.

  Further, the inclined surface 13 has B1 / A1 ≦ 1 and B2 / A2 ≧ 1, that is, the width of the reflection part 14 is larger than the width of the transmission part 15 on the center side, and the width of the transmission part 15 on the peripheral side. It is preferable that the reflection part 14 is formed to be larger than the width. For example, A1 = 0.06 mm, B1 = 0.04 mm, A2 = 0.01 mm, and B2 = 0.09 mm at the position where the enlarged view of FIG. 1 is drawn.

  Further, the inclined surface 13 in the first embodiment is provided with a curved surface portion 16 rounded at the peripheral portion, and the transmissive portion 15 and the reflective portion 14 are alternately and continuously provided on the curved surface portion 16. Yes.

  The light guide 11 according to the first embodiment emits light L emitted from the light source 10 with a small amount of light on the center side and a large amount of light on the peripheral side as shown in FIG.

  When viewed locally, since the transmissive part 15 and the transmissive part 15 are in the relationship of the above formula, the transmissive part 15 transmits the light from the light guide 11 on the center side shown in FIG. The light L to be transmitted is less than the light L reflected in the light guide 11 by the reflection portion 14, and is transmitted from the light guide 11 by the transmission portion 15 in the middle between the center side and the peripheral side shown in FIG. In the curved surface portion 16 on the peripheral side shown in FIG. 2D, most of the light L is transmitted from the light guide 11 through the transmission portion 15 and guided by the reflection portion 14. The light L reflected in the light body 11 becomes small.

  Next, a second embodiment will be described with reference to FIGS. As in the first embodiment, the light guide 21 of the second embodiment is provided with a groove-like or hollow-like recess 22 that houses the linear light source 10 or the point light source 10 on the back side, and is long. It is a rod-shaped body or a bottomed cylindrical body.

  The light guide 21 of the second embodiment is also formed with an inclined surface 23 that is recessed from the surface so as to gradually become deeper toward the center of the concave portion 22, and the inclined surface 23 is microscopically reflected by the reflecting portion. 24 and the transmission part 25 are provided alternately and continuously. The width of the reflecting portion 24 and the width of the transmitting portion 25 are provided according to the relationship of the above formula. For example, A1 = 0.05 mm, B1 = 0.01 mm, A2 = 0.05 mm, and B2 = 0.08 mm at the position where the enlarged view of FIG. 2 is drawn. Note that, unlike the first embodiment, the inclined surface 23 of the second embodiment is not provided with a curved surface portion at the periphery.

  However, in the light guide 21 in the second embodiment, the light L emitted from the light source 10 is emitted from the transmission part 25 of the inclined surface 23 and reflected by the reflection part 24 as in the first embodiment. Accordingly, as shown in FIG. 4, the light is emitted with a small amount of light on the center side and with a large amount of light on the peripheral side.

  In both the first and second embodiments, the backlight unit is provided in a state in which a plurality of light guides 11 and 21 are arranged. That is, if the light guides 11 and 21 are rod-like bodies, a plurality of them are arranged in parallel, and if they are bottomed cylindrical bodies, they are arranged in a matrix.

  In any case, the light guides 11 and 21 are positioned and assembled by using the light guide plate 31 integrated with the substrate 30 with the plurality of light guides 11 and 21 opening the recesses 12 and 22. Can be improved.

  The light guide plate 31 is, for example, as shown in FIG. 5 if the light guide bodies 11 and 21 are rod-shaped bodies (FIG. 5 and FIG. 6 below show the light guide body 21 of the second embodiment. Although it is shown, the same applies to the light guide 11 of the first embodiment.) The substrate is disposed below the side portions of the light guides 11 and 21 so that the upper portions of the side portions of the light guides 11 and 21 are exposed. 30 and may be integrated with the substrate 30 with the same width as the side portions of the light guides 11 and 21, as shown in FIG.

  Further, in the light guide plate 31, if the light guides 11 and 21 are cylindrical with bottoms, the light guides 11 and 21 may be arranged at intersections of square squares as shown in FIG. 7. However, although not shown, the light guides 11 and 21 may be arranged at the intersections of the equilateral triangular meshes.

  In any case, the backlight unit is configured by disposing the diffusion plate 9 adjacent to the inclined surfaces 13 and 23 of the light guides 11 and 21. In the backlight unit, a reflector (not shown) may be disposed on the back side of the light guides 11 and 21.

  As described above, the light L entering the light guides 11 and 21 from the light source 10 is emitted from the light guides 11 and 21 with a small amount of light on the center side of the inclined surfaces 13 and 23 and a large amount of light on the peripheral side. Is done. However, the diffuser plate 9 disposed on the front surface side of the light guides 11 and 21 is vertically incident at a portion facing the center side of the light guides 11 and 21, and is on the peripheral side of the light guides 11 and 21. The light is incident obliquely at the part facing the line. Therefore, when viewed in a direction perpendicular to the surface of the diffusion plate 9, the density of the light amount emitted on the center side of the inclined surfaces 13 and 23 and the density of the light amount emitted on the peripheral side are generally uniform. To be.

  For this reason, the liquid crystal display device in which the liquid crystal panel is disposed on the surface side of the diffusion plate 9 is illuminated uniformly on the entire surface of the liquid crystal panel by the backlight unit, and high image quality can be achieved.

  In addition, this invention can be variously changed without being limited to the said embodiment. Needless to say, the above dimensions are merely examples.

  The light guide and the light guide plate according to the present invention can be effectively used as components constituting a backlight unit, and the backlight unit is a display device such as a mobile phone, a digital camera, a personal computer, a liquid crystal display device, etc. Can be used effectively as a component of

The front view of the light guide in 1st Embodiment which concerns on this invention, and the partially expanded front view of a light guide The one side half of the light simulation of the light guide in the 1st Embodiment concerning this invention is shown, (a) is the whole front view, (b) is the front view of the center side, (c) is the center side and the periphery Middle front view of the side, (d) is the front view of the peripheral side The front view of the light guide in 2nd Embodiment which concerns on this invention, and the partially expanded front view of a light guide Whole front view showing a half of one side of light simulation of a light guide in the first embodiment of the present invention The perspective view which shows 1st Embodiment of the light-guide plate which concerns on this invention. The perspective view which shows 2nd Embodiment of the light-guide plate which concerns on this invention. The top view which shows 3rd Embodiment of the light-guide plate which concerns on this invention. (A) (b) (c) is a front view showing different conventional light guide plates

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Diffusing plate 10 Linear light source 10 Point light source 11 Light guide 12 Recessed part 13 Inclination surface 14 Transmission part 15 Reflection part 16 Curved surface part 21 Light guide body 22 Recessed part 23 Inclination surface 24 Transmission part 25 Reflection part 30 Substrate 31 Light guide plate L light

Claims (5)

Rear side groove-like recess or depression-like recess for accommodating is provided a linear light source or a point light source, progressively deeper so as to recess Mutotomoni from the surface toward the center of the recess, the recess substantially in the peripheral portion A light guide having an inclined surface provided with a curved surface portion having the same shape , wherein the inclined surface is inclined or not inclined so that light incident from a light source is emitted from the inclined surface. And reflecting portions that are inclined or not inclined so as to be reflected from the inclined surface, and the ratio of the width of the transmitting portion and the width of the reflecting portion on the center side is The width of the transmissive part on the side is smaller than the ratio of the width of the reflective part, the width of the reflective part is larger than the width of the transmissive part on the center side, and the width of the transmissive part is larger than the width of the reflective part on the peripheral side. A light guide characterized by being enlarged . A plurality of light guides according to claim 1 are arranged, and the plurality of light guides are integrated by a substrate that connects portions other than the inclined surface without closing the recess. Light guide plate. A plurality of light guides according to claim 1 are arranged , and a light source housed in a recess of each light guide and a diffusion plate arranged on the surface side of each light guide are provided. Backlight unit. Backlight unit and claim 2, wherein the light guide plate, a light source housed in the recess of the light guide, characterized in that is provided with a diffusion plate disposed on the surface side of the light guide. A liquid crystal display device comprising the backlight unit according to claim 3.

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