WO2005114046A1

WO2005114046A1 - Optical waveguide, planar illuminating device using the same and liquid crystal display device

Info

Publication number: WO2005114046A1
Application number: PCT/JP2005/009245
Authority: WO
Inventors: Osamu Iwasaki
Original assignee: Fuji Photo Film Co., Ltd.
Priority date: 2004-05-21
Filing date: 2005-05-20
Publication date: 2005-12-01

Abstract

In a transparent waveguide (18), an orthogonal direction cross section shape of a leading edge part of a parallel groove (18f), which is formed on a thick part (18b) of the optical waveguide and stores a bar-shaped light source, is tapered symmetrically to the center line, toward a rectangular light projecting plane (18a). A relationship between an inclination angle (Φ1) of an inclined rear plane part (18d) to a light projecting plane (18a) and a distance (W) between the both outermost edges satisfies an inequality of Φ1[rad]×W[mm] ≤200[mm]. Illuminance or brightness at a part equivalent to the parallel groove (18f) on the light projecting plane (18a) can be adjusted, and generation of emission lines can be suppressed. When the optical waveguide (18) having a large size light projecting plane is constituted by connecting a plurality of the optical waveguides (18), generation of emission lines at the connecting parts can be suppressed. As a result, the large size optical waveguide (18) which can project uniform illuminating light with less irregularity and higher brightness from the light projecting plane, a planar illuminating device (2) which uses the optical waveguide and has a large size illuminating surface, and a liquid crystal display device (10) having a large size display screen such as a wall-hung TV can be provided.

Description

Specification

Light guide plate, planar lighting device and liquid crystal display device using the same

Technical field

The present invention relates to a transparent light guide plate that diffuses light incident from a rod-shaped light source in a plane direction and emits more uniform illumination light from a light exit surface, a planar lighting device using the same, and a liquid crystal display device.

Background art

[0002] A backlight unit that illuminates a liquid crystal panel (LCD) with light from the rear side thereof to illuminate the liquid crystal panel is used in the liquid crystal display device. The backlight unit uses a light source for illumination, a light guide plate for diffusing the emitted light and illuminating the liquid crystal panel, and a prism sheet and a diffusion sheet for uniformizing the light emitted from the light guide plate. Composed

At present, a backlight unit of a large liquid crystal television is a so-called direct type in which a light guide plate is disposed immediately above a light source for illumination, as disclosed in Japanese Utility Model Laid-Open No. 5-4133. Is the mainstream. In this method, a plurality of cold-cathode tubes, which are light sources, are arranged on the back of a liquid crystal panel, and the inside is used as a white reflective surface to ensure a uniform light amount distribution and required luminance. However, this method requires a thickness of about 30 mm in the vertical direction of the liquid crystal panel in order to make the light quantity distribution uniform in principle.

[0004] In recent years, there has been a demand for thinner, lower power consumption, and larger liquid crystal display devices. With the above-described direct-type backlight unit, a thickness of 10 mm or less cannot realize the viewpoint of unevenness in light intensity. Therefore, light guide plates of various shapes have been proposed in order to realize a thin liquid crystal display device, low power consumption, and large size! (Japanese Patent Laid-Open No. 9-304623, 8-62426). JP-A-10-133027, JP-A-5-249320 and JP-A-2001-42327).

FIG. 43 is a schematic sectional view of a surface light source device having a light guide plate 100 disclosed in Japanese Patent Application Laid-Open No. 9-304623.

The surface light source device (backlight unit) shown in FIG. After embedding, it is formed by arranging a reflection sheet 104 on the back surface of the light guide plate 100 and stacking a transmission light amount correction sheet 106, a light diffusion plate 108, and a prism sheet 110 on the emission surface of the light guide plate 100.

The light guide plate 100 has a substantially rectangular shape, and is formed using a resin into which fine particles that diffuse illumination light are dispersed and mixed. In addition, the upper surface of the light guide plate 100 is flat, and is allocated to the emission surface. Further, a U-shaped cross section groove 100a for embedding the fluorescent lamp 102 is formed on the back surface (the surface opposite to the emission surface) of the light guide plate 100, and the emission surface of the light guide plate 100 is formed just above the fluorescent lamp 102. By avoiding this, a light quantity correction surface 100b that promotes emission of illumination light is formed.

As described above, Japanese Patent Application Laid-Open No. 9-304623 discloses that a light guide plate 100 is formed by mixing fine particles, and a light amount correction surface formed on a part or all of an emission surface except a portion right above a fluorescent lamp 102. It is described that by promoting the emission of the illumination light by 100b, the overall thickness can be reduced and unnatural luminance unevenness of the emitted light can be reduced.

[0006] Further, Japanese Patent Application Laid-Open No. 8-62426 discloses a liquid crystal display that can realize a small and lightweight liquid crystal display device without reducing the irradiation amount of a knock light, a thinner liquid crystal display device, and a reduction in cost and power consumption. In order to obtain the backlight of the device, a rectangular irradiation surface, a rectangular section with a rectangular section cut out in the center of the short side in parallel with the long side and for inserting a light source, and the long side sandwiching this groove There is disclosed a light guide plate having a back surface formed such that the plate thickness gradually decreases toward both side surfaces of the light guide plate.

[0007] Further, Japanese Patent Application Laid-Open No. Hei 10-133027 discloses that a light source is arranged in order to obtain a bright backlight unit that can make the frame of a liquid crystal display device narrower and thinner, and has high light use efficiency. A light guide (light guide plate) having a parabolic shape in which the cross section parallel to the width direction of the concave portion is parallel to the depth direction is disclosed.

[0008] Further, Japanese Patent Application Laid-Open No. 5-249320 discloses that in order to keep the in-plane brightness of the display panel uniform and to provide high-luminance illumination, the light is sequentially refracted on a C-shaped high reflection layer. There is disclosed a light guide plate in which a plurality of plate-shaped optical waveguide layers are stacked so as to increase the efficiency, and the light diffusion layer is brightened by light emitted from each light emitting end face. Here, the concave portion for arranging the light source has a triangular shape. The light guide plates disclosed in each of the above publications are used to reduce the thickness, size, and weight of the liquid crystal display device, reduce power consumption, and reduce costs. One or a plurality of grooves are provided, and the rod-shaped light source is housed in the grooves. Preferably, the groove force is formed so that the plate thickness is gradually reduced toward the end face, and the thickness is reduced. I have.

[0009] Also, Japanese Patent Application Laid-Open No. 2001-42327 discloses that in order to improve a liquid crystal backlight for a large liquid crystal display surface of a wall-mounted television, a plurality of light guide plates are arranged in parallel, and a predetermined number of light guide plates are provided between the light guide plates. By arranging the linear light source, high brightness and high uniformity, large-scale backlighting is realized.

Patent Document 1: Japanese Utility Model Application No. 5-4133

Patent Document 2: Japanese Patent Application Laid-Open No. 9-304623

Patent Document 3: JP-A-8-62426

Patent Document 4: JP-A-10-133027

Patent Document 5: JP-A-5-249320

Patent Document 6: JP 2001-42327 A

Disclosure of the invention

Problems to be solved by the invention

In the light guide plate 100 disclosed in Japanese Patent Application Laid-Open No. Hei 9-304623, the light output surface of the light guide plate 100 is not directly above the light source (fluorescent lamp) 102 but has a rough surface or a micro prism surface. A supplementary front face 100b is formed to promote the emission of illumination light that enters the emission surface at an angle greater than the critical angle. However, as shown in FIG. Since the luminance N2 of the illumination light from the light guide plate 100 having the light amount correction surface 10 Ob indicated by the solid line shown by the dotted line with respect to the luminance N1 of the illumination light from the light plate is slight, the light amount compensation front 100b The effect of improving the luminance by the light source is large. The efficiency of the use of the light source light is low. The light source light is insufficiently diffused, so that there is a problem that uniform and high-luminance light cannot be emitted.

[0011] Further, in the light guide plate 100 disclosed in Japanese Patent Application Laid-Open No. 9-304623, a light source (fluorescent lamp) 102 is embedded in a groove 100a having a circular cross section, and as shown in FIG. Luminance peaks remain as they are. It is necessary to remove the unnatural luminance unevenness on the emission surface by using the transmitted light amount correction sheet 106, the light diffusion plate 108, and the prism sheet 110 arranged on the emission side of the plate. There is a problem that is up.

[0012] Further, in the backlight of the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. H8-62426, components on the electronic circuit board are arranged in gaps created by tilting the back surface of the light guide plate, thereby reducing costs. Thus, the size and weight of the liquid crystal display device can be reduced and the thickness of the liquid crystal display device can be reduced. However, the unevenness of the illumination light emitted from the emission surface of the light guide plate is not considered at all.

[0013] Further, in the backlight unit of the liquid crystal display device disclosed in Japanese Patent Application Laid-Open No. 10-133027, the cross-sectional shape of the concave portion on the groove provided in the light guide (light guide plate) is made parabolic, so that the light guide Light is incident on the light guide where the diffusion of light in the body is almost uniform, and the efficiency of light utilization is said to be improved. V, it is considered at all! /.

Further, the light guide plate disclosed in Japanese Patent Application Laid-Open No. 5-249320 has a complicated structure in which a plurality of plate-shaped optical waveguide plates are stacked, so that the brightness attenuation is reduced and uniform brightness is reduced as compared with the related art. It has the problem that the manufacturing cost is high.

In the light guide plate disclosed in Japanese Patent Application Laid-Open No. 2001-42327, a transmission suppression pattern for suppressing transmission of light from the linear light source is provided in order to increase the luminance immediately above the linear light source. The light from the linear light source must be transmitted inside the light guide plate from one end to the other end in the in-plane direction. Was not enough.

[0016] A first object of the present invention is to solve the above-mentioned problems of the prior art, to be thin and light, and to have a uniform and less uneven light output surface force even when a plurality of light emitting devices are configured in parallel. An object of the present invention is to provide a light guide plate capable of emitting high-luminance illumination light with high efficiency.

Further, another object of the present invention is to provide a light guide plate capable of providing a light emitting surface of a larger size, in addition to the first object.

[0017] A second object of the present invention is to solve the above-mentioned problems of the prior art, and to make it thinner than a direct type. And can be manufactured at lower cost, can emit more uniform, less uneven, and higher-intensity illumination light, and can have a large-sized illumination surface, or Another object of the present invention is to provide a planar lighting device that can be applied to a liquid crystal display device such as a wall-mounted television.

[0018] A third object of the present invention is to solve the above-mentioned problems of the prior art, to be thin and lightweight, to be able to be manufactured at lower cost, to be more uniform, to have less unevenness, and to be more efficient. It is an object of the present invention to provide a liquid crystal display device which can perform bright display, can have a large-sized display screen, or can be of a wall-mounted type such as a wall-mounted television.

Means for solving the problem

[0019] In order to solve the above first problem, a first mode of the first aspect of the present invention is a transparent light guide plate, comprising a rectangular light exit surface, and a rectangular light exit surface. A pair of thick portions parallel to one side and located at a substantially central portion of a rectangular shape; and a pair of thick portions located outside the thick portion in a direction orthogonal to the one side and formed parallel to the thick portion. A parallel groove formed between the thin end portion and the bar-shaped light source and located between the pair of thick portions and opposite to the side on which the rectangular light emitting surface is formed and parallel to the one side. And symmetrical with respect to a plane including the axis of the rod-shaped light source and perpendicular to the rectangular light emitting surface, and extending from the thick portion toward the pair of thin ends in a direction orthogonal to the one side. A pair of inclined back surfaces that form an inclined back surface that is inclined with respect to the rectangular light exit surface so that the wall thickness is reduced, The row groove has a cross-sectional shape in a direction perpendicular to the rectangular groove, and a leading end portion of the parallel groove is symmetrically narrowed toward the rectangular light emitting surface with respect to a center line of the parallel groove perpendicular to the rectangular light emitting surface. A light guide plate in which the relationship between the angle Φ 1 (rad) of the inclined back surface with respect to the rectangular light exit surface and the distance W between both extreme ends satisfies Φ 1 XW ≤ 200 (mm). Things.

[0020] In order to solve the above-mentioned other problems, a second embodiment of the first embodiment of the present invention includes a plurality of light guide plates according to the first embodiment of the first embodiment of the present invention. Another object of the present invention is to provide a light guide plate characterized in that one of the pair of thin ends is connected to each other so that the rectangular light exit surfaces are in the same direction. In order to solve the above-mentioned other problems, a third embodiment of the first aspect of the present invention is directed to a third embodiment in which each of the light guide plates is used as a repeating unit and a plurality of repeating units are used. It is intended to provide a light guide plate having a structure in which the connecting portions are seamlessly integrated and arranged in parallel.

[0021] In the light guide plate according to the first aspect of the present invention, it is preferable that the shape of the cross section perpendicular to the parallel groove in the connecting portion when a plurality of the light guide plates are connected has an arc shape or a polygon shape. No.

Further, it is more preferable that the light guide plate having this shape is a repetition unit, and it is more preferable that the light guide plate has a structure in which a plurality of repetition units are seamlessly united and arranged in parallel. Angle of the inclined back surface with respect to the rectangular light exit surface 0> 2 (rad

) Preferably satisfies Φ 2 and Φ 1.

[0022] In the cross-sectional shape of the parallel groove, the tip portion is a portion in which the center force of the rod-shaped light source is directed to the rectangular light emitting surface and the angle with respect to the perpendicular is 90 degrees on both sides. Is preferred.

Further, in the cross-sectional shape of the parallel groove, it is preferable that the front end portion is a portion where an angle with respect to a vertical force perpendicular to the central force of the rod-shaped light source is 60 degrees on both sides. Further, it is preferable that the angle is substantially 20 degrees or more in consideration of the thickness of the light guide plate and the arrangement of the bar-shaped light sources.

[0023] It is preferable that the cross-sectional shape of at least the distal end portion of the parallel groove is a part of two straight lines or curves symmetrical with respect to the center line, each having one sharp intersection point intersecting with each other.

Further, it is preferable that a cross-sectional shape of at least the distal end portion of the parallel groove or a cross-sectional shape of the parallel groove is a triangle.

In addition, it is preferable that the two curves, which are the cross-sectional shapes of at least the distal end portion of the parallel groove, are convex or concave toward the center of the parallel groove.

Further, at least the cross-sectional shape of at least the distal end portion of the parallel groove or the two curves that are the cross-sectional shape of the parallel groove is convex or concave toward the center of the parallel groove, and the shape is 10 or more. The curve, which is preferably a curve approximated by the following function, is more preferably a part of a circle, ellipse, parabola, or hyperbola.

[0024] Further, the cross-sectional shape of the top of the tip portion of the parallel groove may be between the two symmetrical straight lines. Preferably, the shapes are connected by a straight line or a curve symmetrical with respect to the center line before the curves intersect.

Further, it is preferable that a cross-sectional shape of the top portion of the distal end portion of the parallel groove is a shape having a portion parallel to the rectangular light exit surface where the one sharp intersection is chamfered.

Also, the cross-sectional shape of at least the tip portion of the parallel groove or the cross-sectional shape of the parallel groove is triangular, and the cross-sectional shape of the top of the tip portion of the parallel groove with respect to the center line. Preferably, it has a symmetric trapezoidal shape.

In the above description of the cross-sectional shape, triangles and trapezoids indicate shapes that can be seen when the open part of the groove is complemented by a straight line when the line forming the cross-section of the parallel groove is constituted by a straight line. And

[0025] It is preferable that a cross-sectional shape of a top portion of the distal end portion of the parallel groove is a curved shape that is convex or concave with respect to the rectangular light emission surface and is symmetric with respect to the center line.

Further, the cross-sectional shape of the top of the tip portion of the parallel groove may be a circle, an ellipse, a parabola, or a hyperbolic shape in which the one point of intersection is symmetrically rounded with respect to the center line. Preferably it is.

[0026] Preferably, at least the cross-sectional shape of the distal end portion of the parallel groove is an elliptical shape or a part of a hyperbola.

Further, it is preferable that the top portion of the tip portion of the parallel groove is a grit surface. Further, it is preferable that the rectangular light emitting surface has a halftone dot at a portion corresponding to the top of the tip portion of the parallel groove.

[0027] In the present invention, a surface force perpendicular to the rectangular light exit surface and including a central axis of the rod-shaped light source is a distance from the thin end portion to an end surface, L (mm), and the rod-shaped light source is ΔL (mm), the light transmittance of the light-transmitting resin is t%, the distance from the center of the rectangular light exit surface to the intersection with the inclined back surface is ΔL (mm). When the distance to the rectangular light emitting surface in a direction perpendicular to the light emitting surface is D (mm), it is preferable that the following formula be satisfied.

t = {l -kl X (D / L- AL)} X 100 0 <kl≤2

The total light flux on the light exit surface when the incident light is emitted from the rod-like light source is represented by I I.

BLU, when the total luminous flux on the surface of the rod-shaped light source is CFL, the distance L (mm) from the surface perpendicular to the rectangular light exit surface and including the center axis of the rod-shaped light source to the end surface of the thin end portion ) 1S It is preferable to satisfy the following equation.

L = k2 X (I / \)

CFL BLU

l≤k2≤160

[0029] Further, in the present invention, in a first portion corresponding to the parallel groove of the rectangular light emitting surface, relative illuminance or relative illuminance formed by the emission light of the rod-like light source housed in the parallel groove. The peak value of relative brightness The cross section of the parallel groove in the orthogonal direction so that the relative brightness or the average value of relative brightness formed by the emitted light in the second portion corresponding to the inclined back surface portion is 3 times or less. In the shape, it is preferable that a tip end portion of the parallel groove is symmetrically narrowed toward the rectangular light emission surface with respect to a center line of the parallel groove perpendicular to the rectangular light emission surface.

Further, the peak of the relative illuminance or relative luminance of the first portion of the rectangular light exit surface is preferably 3 times or less of the average value of the relative illuminance or relative luminance of the second portion, and is preferably 2 times or less. Is more preferable.

[0030] In the present invention, relative illuminance or relative illuminance formed by the rod-like light source power emitted from the rod-shaped light source housed in the parallel groove in the first portion corresponding to the parallel groove on the rectangular light emission surface. According to the ratio of the peak value of the luminance to the relative illuminance or the average value of the relative luminance formed by the emitted light in the second portion corresponding to the inclined back surface, the parallel groove has a cross-sectional shape in the orthogonal direction. It is preferable that the parallel groove is designed so that the leading end of the parallel groove is symmetrically narrowed toward the rectangular light emitting surface with respect to a center line perpendicular to the rectangular light emitting surface. In addition, the parallel light is adjusted so that a peak value of relative illuminance or relative luminance of the first portion of the rectangular light exit surface is three times or less of an average value of relative illuminance or relative luminance of the second portion. U, It is preferable to design the groove tip symmetrically thin.

[0031] In order to solve the second problem, a second aspect of the present invention is directed to the first aspect. Each light guide plate, a rod-shaped light source housed in the parallel groove of the light guide plate, a reflector provided behind the rod-shaped light source so as to close the parallel groove, and both sides of the thick portion of the light guide plate And a reflecting sheet attached to the inclined back surface of the inclined back portion.

Here, it is preferable that the light guide plate further includes a diffusion sheet disposed on the rectangular light emission surface of the light guide plate, and is disposed between the rectangular light emission surface of the light guide plate and the diffusion sheet. It is preferable to have a prism sheet.

Further, in a first portion corresponding to the parallel groove of the rectangular light exit surface of the light guide plate, relative illuminance or relative luminance formed by emission light of a rod-like light source force housed in the parallel groove. The ratio of the peak value to the average value of relative illuminance or relative luminance formed by the emitted light in the second portion corresponding to the inclined back surface portion is the ratio between the rectangular light emitting surface of the light guide plate and the diffusion sheet. It is preferable that the distance is set in accordance with the interval allowed between the two or the thickness allowed in the planar lighting device.

[0032] In order to solve the third problem, a third aspect of the present invention is directed to a backlight unit which also has the surface illumination device power of the second aspect, and a light exit surface of the backlight unit. The present invention provides a liquid crystal display device comprising: a liquid crystal display panel disposed on a side thereof; and a drive unit for driving the backlight unit and the liquid crystal display panel.

The invention's effect

According to the first aspect of the present invention, since the light source can be accommodated in the parallel groove formed in the light guide plate, the light guide plate can be made thinner and lighter than before, and By satisfying the relational force Φ 1 XW≤200 (mm) between the angle Φ 1 (rad) of the inclined surface with respect to the exit surface and the distance W between the two extreme ends, the light exit surface force is more uniform and uneven. It is possible to emit less and higher brightness illumination light.

Furthermore, by reducing the cross-sectional shape of the parallel groove toward the light exit surface and toward the tip, the peak of illuminance or luminance can be reduced, and the illuminance or luminance at the light exit surface can be further improved. The uniformity can be achieved, and the uniformity required for the light exit surface can be achieved. In addition, even if a plurality of light guide plates are connected, it is necessary to reduce the occurrence of bright lines at the connection portions. Can do.

[0034] Further, according to the second mode of the first mode of the present invention, by connecting the thin end portions of the light guide plate of the first mode to each other, the size of the light exit surface of the light guide plate can be further increased. It can be large. Further, according to the third aspect of the first aspect of the present invention, since the thin end portions of the light guide plate of the first aspect are integrally connected to each other, the size of the light exit surface of the light guide plate is reduced. It is possible to increase the size and to suppress the generation of bright lines at the connecting part. A part of the light is emitted by the adjacent repetitive unit force, so that the change of the light emission amount near the connection part is suppressed.

Further, according to the second aspect of the present invention, by using the light guide plate of the first aspect, the light guide plate can be manufactured to be thinner and lighter, can be manufactured at lower cost, and can be made more uniform and uneven. A planar lighting device capable of emitting less and higher-intensity illumination light, having a larger illumination surface, or being applicable to a liquid crystal display device such as a wall-mounted television. Can be provided.

[0036] Further, according to the third aspect of the present invention, by using the spread illuminating apparatus of the second aspect described above, it is possible to manufacture the thin and light-weight device at a lower cost, and to reduce the cost. Provided is a liquid crystal lighting device which can perform display with less unevenness and higher brightness, can have a large display screen, or can be a wall-mounted type such as a wall-mounted television. be able to.

Brief Description of Drawings

FIG. 1 is a schematic cross-sectional view of a configuration in which a plurality of light guide plates of the present invention are arranged in parallel.

2A and 2B are a schematic perspective view and a schematic sectional view, respectively, of a liquid crystal display device using a backlight unit having the light guide plate of the present invention, and FIG. 2C is a schematic sectional view of the light guide plate. It is.

FIG. 3A is a schematic cross-sectional view showing a state in which a prism sheet is disposed between a reflection sheet and an inclined surface of a light guide plate, and FIG. FIG. 3 is a schematic plan view and a schematic cross-sectional view of the prism sheet disposed therebetween viewed from the light guide plate side. is there.

FIG. 4A is a partially enlarged cross-sectional view near the extreme end when the cross-sectional shape near the extreme end of the inclined surface to which the light guide plates are connected when a plurality of light guide plates are connected is curved. Fig.4B is a partial enlarged cross-sectional view near the extreme end when the cross-sectional shape near the extreme end of the inclined surface where the light guide plates are connected when a plurality of light guide plates are connected is polygonal. is there.

FIG. 5 is a diagram for explaining the principle of light emission of the light guide plate of the present invention.

6A to 6E are graphs each showing a luminance distribution on a light emitting surface of a light guide plate when three light guide plates are connected. FIG.

FIG. 7 is a graph collectively showing the graphs of FIGS. 6A to 6E.

[FIG. 8] FIGS. 8A to 8D show three light guide plates in which the angle Φ 2 of the inclined surface with respect to the light exit surface at the connecting portion is smaller than the angle Φ 1 of the inclined surface other than the connecting portion. 5 is a graph of a luminance distribution on the light exit surface of FIG.

FIG. 9 is a diagram collectively showing the graphs shown in FIGS. 8A to 8D.

FIG. 10A to FIG. 10E are graphs showing luminance distribution on a light exit surface when six light guide plates are connected.

FIG. 11 is a diagram collectively showing the graphs shown in FIGS. 10A to 10E.

FIG. 12A to FIG. 12C are graphs showing a luminance distribution on a light exit surface when nine light guide plates are connected.

[FIG. 13] FIGS. 13D and 13E are graphs showing the brightness distribution on the light exit surface when nine light guide plates are connected, where the inclination angles are different from the graphs shown in FIGS. 12A to 12C. It is.

FIG. 14 is a view collectively showing the graphs shown in FIGS. 12A to 12C, FIG. 13D, and FIG. 13E.

FIG. 15 is a schematic cross-sectional view of the light guide plate when the cross-sectional shape perpendicular to the length direction of the parallel groove is hyperbolic.

FIG. 16 is a schematic cross-sectional view of the light guide plate when the cross-sectional shape perpendicular to the length direction of the parallel groove is elliptical.

[FIG. 17] FIG. 17 shows that the cross-sectional shape perpendicular to the length direction of the parallel groove passes through the center of the parallel groove and guides the light. FIG. 4 is a schematic cross-sectional view of a light guide plate formed by partially forming two arc curves symmetric with respect to a center line perpendicular to a light exit surface of the plate.

[Figure 18] Figure 18 shows a part of two parabolas whose cross section perpendicular to the length direction of the parallel groove is symmetrical with respect to the center line passing through the center of the parallel groove and perpendicular to the light exit surface of the light guide plate. FIG. 4 is a schematic sectional view of a light guide plate formed by force.

[FIG. 19] FIG. 19 is a schematic cross-sectional view of a light guide plate in which a cross-sectional shape perpendicular to the length direction of a parallel groove is formed with two curved forces convex toward the center of the parallel groove.

[FIG. 20] FIG. 20 shows that the cross-sectional shape perpendicular to the length direction of the parallel groove has a curved force formed by combining a convex curve and a concave curve toward the center of the parallel groove. It is a schematic sectional view.

FIG. 21 is an example of a halftone dot pattern formed on the light exit surface side of a light guide plate.

FIG. 22 is a graph showing the illuminance distribution of light emitted from the light exit surface of the light guide plate when the cross-sectional shape of the parallel groove of the light guide plate is changed to various shapes.

FIG. 23 is a graph showing the illuminance distribution of light emitted from the light guide plate when the deepest portion of the parallel groove is flattened and the length of the flat portion is changed to various values. It is a graph shown.

[FIG. 24] FIGS. 24A to 24D are schematic cross-sectional views of the light guide plate when the flat portions at the deepest portions of the parallel grooves are 1.5 mm, 1. Omm, 0.5 mm, and 0.25 mm, respectively. It is.

[FIG. 25] FIG. 25 is a graph showing the light exit surface force of the light guide plate when the shape of the deepest portion of the parallel groove is a curved surface having a radius of curvature R and the radius of curvature of the curved surface is changed to various values. It is a graph which shows illuminance distribution.

[FIG. 26] FIGS. 26A to 26D are schematic diagrams of light guide plates when the radii of curvature at the apexes of parallel grooves having a triangular cross section are 0.25 mm, 0.5 mm, 1.0 mm, and 1.5 mm, respectively. It is sectional drawing.

FIG. 27A is a configuration example in which a reflector is disposed on the side surface of the light guide plate of the present invention, and FIG. 27B is a configuration example in which the reflector is disposed on the side surface of the light guide plate when the light guide plates of the present invention are arranged in parallel. This is an example of the configuration in which they are arranged.

[FIG. 28] FIG. 28 is a schematic configuration diagram of a housing for housing the knock light unit.

[FIG. 29] FIG. 29 is a schematic oblique view of a housing accommodating a backlight unit and a liquid crystal display panel. FIG.

FIG. 30 is a schematic cross-sectional view of a housing containing a backlight unit and a liquid crystal display panel.

FIG. 31 is a schematic enlarged cross-sectional view of both ends of the housing shown in FIG. 30.

FIG. 32A is a schematic sectional view showing an example of a light source used in the backlight unit of the present invention, FIG. 32B is a schematic perspective view showing an example of a light source positioning means, and FIG. FIG. 32B is a schematic sectional view of the light source shown in FIG. 32A and FIG. 32B.

FIG. 33 is a schematic diagram of a light guide plate in which ribs are formed in parallel grooves to prevent a light source from being in direct contact with the parallel grooves.

34] FIG. 34A and FIG. 34B are a plan view and a side view schematically showing a configuration in which a reflection sheet and a light guide plate including a light source are integrated, respectively. FIG. 34C is a CC line of FIG. 34A. FIG. 34D is a view taken in the direction of the arrow, and FIG. 34D is a view taken in the direction of the arrow DD in FIG. 34A.

FIG. 35 is a schematic diagram showing a state in which a halftone sheet having halftone dots formed thereon is arranged so as to cover the light exit surfaces of a plurality of connected light guide plates.

36A is a configuration example of a light guide plate of the present invention in which a reflector is disposed on a side surface in the longitudinal direction of a light source, and FIG. 36B is a cross-sectional view of FIG. 36A.

FIG. 37A is a schematic perspective view showing another example of the light guide plate of the present invention, FIG. 37B is a sectional view taken along line BB of FIG. 37A, and FIG. 37C is a sectional view taken along line C—B of FIG. 37A. FIG. 37D is a sectional view taken along line C-D, and FIG. 37D is a sectional view taken along line DD in FIG. 37A.

FIG. 38 is a schematic cross-sectional view showing another example of a light guide plate in which a plurality of light guide plates having different widths are connected.

FIG. 39 is a schematic sectional view showing an example of a light guide plate having a light exit surface having an R shape.

FIG. 40A is a schematic cross-sectional view showing an example of a shape in which the end of the light guide plate in the longitudinal direction of the light source has an inclination. FIG. 40B is parallel to the light exit surface and in the longitudinal direction of the light source. FIG. 40C is a schematic perspective view showing an example of a shape in which the end of the light guide plate in a direction perpendicular to FIG. 40 is inclined, and FIG. 40C is a cross-sectional view taken along line CC in FIG. 40B.

[FIG. 41] FIG. 41A is a schematic perspective view showing an example of a light guide plate having a gentle curved surface in which a light emitting surface has a curved cross-sectional shape in the longitudinal direction of a light source. FIG. 41B is a light emitting surface. Light source FIG. 4 is a schematic perspective view showing an example of a light guide plate having a rib with a minute height extending in a direction perpendicular to the longitudinal direction.

FIG. 42 is a schematic perspective view of the knock light unit as viewed from the rear side.

FIG. 43 is a schematic sectional view of a surface light source device having a conventional light guide plate.

[FIG. 44] FIG. 44 is a graph of luminance at an emission surface of a light guide plate of the surface light source device of FIG. 43. BEST MODE FOR CARRYING OUT THE INVENTION

A light guide plate, a planar lighting device and a liquid crystal display device using the same according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a schematic cross-sectional view of a planar lighting device 1 (hereinafter, also referred to as a backlight unit) according to a second embodiment of the present invention in which a plurality of light guide plates 18 according to the first embodiment of the present invention are arranged in parallel. The figure is shown. Such a planar illumination device 2 is used as a knock light cut of the liquid crystal display device according to the third embodiment of the present invention. FIGS. 2A and 2B are a schematic partial perspective view and a schematic partial cross-sectional view of a portion of one light guide plate 18 of the backlight unit 2 shown in FIG. 1 and a liquid crystal display device 10 using the backlight unit 2. Show. FIG. 2C shows a schematic cross-sectional view of the light guide plate of the present invention. As shown in FIGS. 2A and 2B, the liquid crystal display device 10 basically includes a backlight unit 2, a liquid crystal display panel 4 arranged on the light emission surface side of the backlight unit 2, and a drive unit for driving the liquid crystal display panel 4. Drive unit 6. The knock light unit 2 includes a cold cathode tube 12, a diffusion sheet 14, prism sheets 16, 17, a light guide plate 18, a reflector 20, and a reflection plate 22.

In the liquid crystal display device shown in FIGS. 2A and 2B, the liquid crystal display panel 4 includes, for example, GH, PC, TN, STN, ECB, PDLC, IPS (In-Plane Switching), VA (Vertical). Various types of liquid crystal display panels (MVA, PVA, EVA), OCB, ferroelectric liquid crystal, antiferroelectric liquid crystal, and other liquid crystal display modes can be used. The driving method of the liquid crystal display panel 4 is not particularly limited, and a known driving method such as a simple matrix method or an active matrix method can be used.

The backlight unit 2 is a planar illumination device for irradiating the entire surface of the liquid crystal display panel 4 with uniform light from behind the liquid crystal display panel 4. It has substantially the same light emitting surface (light emitting surface). As shown in FIGS. 2A to 2C, the backlight unit 2 basically includes a light source 12, a diffusion sheet 14, two prism sheets 16 and 17, a light guide plate 18, a reflector 20, And a reflection sheet 22.

[0042] The method of driving the backlight unit 2 is not particularly limited. For example, the backlight unit 2 may be driven so as to monitor the surrounding environment and perform luminance modulation. For example, the luminance may be modulated according to the brightness or the temperature by providing an external light sensor to detect the surrounding brightness, or by providing a temperature sensor to detect the surrounding temperature. The driving method of the knock light unit 2 is not particularly limited. For example, R (red), G (green), and B (blue) light sources (for example, LED light sources) are used, and these light sources are used. It may be driven by a field sequential method in which the liquid crystal display panel 4 is sequentially turned on in accordance with the display, or may be driven by an intermittent lighting method in which light is emitted or turned off sequentially or simultaneously with the scanning display of the liquid crystal. If the backlight unit 2 is driven using the field sequential method, the R, G, and B color filters can be removed, so that the loss of light amount due to the color filters can be eliminated. In addition, if the light source is turned on for a short time according to the intermittent lighting method, it is possible to improve the display performance of moving images.

The above-mentioned constituent members constituting the knock light unit 2 are arranged in a housing 280 as shown in FIG. 28, and are fixed from the rear side of the knock light unit 2 to be integrated. It may be configured as a single unit. As shown in FIG. 28, the housing 280 has a box-shaped structure with one surface opened, and a rectangular opening is formed on the side where the light emission surface of the backlight unit is located. I have.

Examples of such a housing 280 include a box-shaped housing made of resin or metal, a frame of a skeleton structure made of metal, and a box-shaped structure made of a rigid resin other than metal. And a frame having a skeletal structure, a metal and a rigid resin, and a rib having a rib extending in a direction perpendicular to the parallel groove of the light guide plate 18.

When the constituent members of the backlight unit 2 are incorporated in the housing 280 made of a resin, as shown in FIG. 28, a housing 281 for holding the backlight unit is provided on the housing 280. In the section 281, the reflection sheet 22 of the knock light unit 2 can be inserted. FIG. 28 shows a configuration in which the constituent members of the backlight unit 2 are disposed in the housing 280, but a configuration in which the backlight unit and the liquid crystal display panel are disposed in one housing. It may be. Fig. 29 to Fig. 31 show the configuration examples of the housing that houses the knock light unit and the liquid crystal display panel. FIG. 29 is a schematic perspective view of a housing 290 accommodating a knock light unit (not shown) and the liquid crystal display panel 4, and FIG. 30 is a housing accommodating the backlight unit 2 and the liquid crystal display panel. 290 is a schematic sectional view of FIG. FIG. 31 is a schematic enlarged cross-sectional view of both ends of the housing 290 shown in FIG.

The housing that houses the knock light unit and the liquid crystal display panel has a configuration in which the backlight unit is housed in a dedicated housing, and the backlight unit and the liquid crystal display panel that are housed in the housing for the backlight unit are housed. Alternatively, the knock light unit and the liquid crystal display panel may be fixed and accommodated without accommodating the knock light unit in the housing for the backlight unit.

2A and 2B, the light source 12 is a small-diameter rod-shaped cold cathode tube, and is used to illuminate the liquid crystal display panel 4. The light source 12 is arranged in a parallel groove 18f formed in the light guide plate 18, and is connected to the drive unit 6. Here, a cold cathode tube is used as the light source 12, but the present invention is not limited to this, and any rod-shaped light source may be used. As the light source 12, for example, a light source such as a normal fluorescent tube, a cold cathode tube, a hot cathode tube, an external electrode tube, a light emitting diode (LED), or a semiconductor laser can be used. Alternatively, a light emitting diode is preferred.

Further, a cylindrical or prismatic transparent light guide having the same length as the parallel groove 18f of the light guide plate 18 is used, and an LED light source having LEDs arranged on the top and bottom surfaces of the light guide is used as the light source 12. It may be used instead. In such an LED light source, the light of the LED can be incident from the top and bottom surfaces of the light guide, and the lateral force of the light guide can also emit the LED light.

As the light source, an aperture-type lamp as shown in FIG. 32A may be used. In the present invention, an aperture-type lamp is provided with a high-reflectance member at a portion other than an angle at which light is to be emitted, that is, a high-reflectance member is provided at a portion where light is not emitted, and a predetermined angle is provided. Refers to a rod-like light source that increases the amount of light emitted from the light source. FIG. 32C shows a cross-sectional view of an aperture-type lamp. In FIG. 32C, the area 320 emits light. Area. By using an aperture-type lamp, the light use efficiency can be further improved. Further, it is not always necessary to provide a reflection sheet (reflector) disposed on the back side of the light source, so that the configuration of the apparatus can be simplified, and the occurrence of uneven brightness due to a mounting error of the reflection sheet can be prevented.

Here, various materials such as metal and nonmetal can be used as the member having high reflectance, and it is particularly preferable to use nonmetal material. By using a nonmetallic material as a member having a high reflectivity, the leakage current can be reduced.

[0047] Further, when a one-aperture type lamp is used, it is preferable to provide a positioning means in at least one place. As the positioning means, for example, as shown in FIG. 32B, a bent portion 322 is provided in the terminal portion of the lamp, a groove 326 is formed in the support member 324 for supporting the lamp, and the bent portion 322 is formed in the groove 326 of the support member 324. There is a method of fixing the lamp by inserting the lamp. Further, the angle of the bent portion 322 provided in the terminal portion of the lamp may be any angle as long as it can be specified with respect to the parallel groove of the light guide plate. It is preferable that the bent portion 322 is provided so that the light emission region 320 of one type of lamp is bisected. In addition, the shape of the bent portion can be any shape that can fix the position of the lamp and the direction of arrangement of the member having high reflectivity with respect to the parallel groove and does not hinder the arrangement in the parallel groove. Any shape is acceptable.

Thus, by providing the positioning means, the center of the opening of the light source can be easily aligned with the center of the parallel groove of the light guide plate, and light can be efficiently incident on the light guide plate.

Further, in the present invention, as shown in FIG. 33, when the light source is arranged in the parallel groove 18f of the light guide plate 18, the light source 12 and the parallel groove 18f formed in the light guide plate 18 are directly connected. The light source 12 may be disposed in the parallel groove 18 of the light guide plate 18f by partially providing a rib 330 or the like in the parallel groove 18f of the light guide plate 18 so as not to make contact.

By adopting such a configuration, the heat generated in the light source 12 is suppressed from being directly transmitted to the light guide plate 18, an excessive rise in the temperature of the light guide plate 18 is suppressed, and the cold-cathode tube as the light source is partially Cooling can be avoided. Such a rib 330 may have, for example, a convex shape with a width of lmm or less and a height of about 0.5 mm, and may be formed in a parallel groove of the light guide plate. It is preferable to provide a part in the direction of the center line of 18f.

Further, an opening may be provided on the side surface of the backlight unit corresponding to an extension of the parallel groove of the light guide plate 18 in the center line direction, and the light source 12 may be exchanged through the opening. By doing so, the life of the light source 12 or the replacement of the light source in the event of a failure can be facilitated, and a configuration that does not require a separate guide member to replace the light source 12 can be achieved.

[0049] In order to regulate the position of the light source 12 with respect to the reflection sheet 22, the reflection sheet 22 is formed of a rigid metal material or a resin material, and the reflection sheet 22 and the light guide plate 18 including the light source 12 are integrated. It is preferable to adopt a sloping configuration. In this case, as shown in FIGS. 34A to 34D, one of the light guide plate 18 and the reflection sheet 22 is provided with a concave portion and the other is provided with a convex portion, and is fitted or fixed with screws. Alternatively, the light guide plate 18 and the reflection sheet 22 may be integrally formed.

When the reflection sheet 22 is formed of a metal material in order to secure sufficient rigidity with respect to the thinning of the knock light unit, a floating capacitance occurs depending on the combination of the metal material and the cold cathode tube. It is known. On the other hand, stray capacitance can be reduced by providing an elongated hole in the portion of the reflection sheet that faces the cold cathode tube.

In FIG. 2A to FIG. 2C, the diffusion sheet 14 is for diffusing the light emitted from the light exit surface 18a of the light guide plate 18 to make it uniform, for example, PET (polyethylene terephthalate), Optically transparent, such as PP (polypropylene), PC (polycarbonate), PMMA (polymethinolemethacrylate), benzyl methacrylate, MS resin, other acrylic resins, or COP (cycloolefin polymer) It is formed by giving light diffusivity to a flat member made of a resin. Although the method is not particularly limited, for example, the surface of the above-mentioned plate-shaped member is subjected to surface roughening by fine irregularity processing or polishing (hereinafter, the surface subjected to these treatments is referred to as “sand rubbing surface”) to impart diffusivity. Or a pigment such as silica, titanium oxide, zinc oxide or the like, or beads such as resin glass, zirconia, etc., which scatter light on the surface, is coated with a binder, or light is scattered in the resin described above. It is formed by kneading the aforementioned pigments and beads. In the present invention, as the diffusion sheet 14, a diffusion sheet of a mat type or a coating type can be used. In the present invention, as the diffusion sheet 14, it is also preferable to use a film-like member having a thickness of 500 μm or less, which is made of the above-mentioned material and has light diffusing properties.

The diffusion sheet 14 is preferably disposed at a predetermined distance from the light exit surface 18 a of the light guide plate 18, and the distance is appropriately determined according to the light amount distribution from the light exit surface 18 a of the light guide plate 18. Can change. By separating the diffusion sheet 14 from the light exit surface 18a of the light guide plate 18 by a predetermined distance in this way, the light force emitted from the light exit surface 18a of the light guide plate 18 can be changed between the light exit surface 18a and the diffusion sheet 14. Further mixing (mixing). Thereby, the illuminance of the light passing through the diffusion sheet 14 and illuminating the liquid crystal display panel 4 can be made more uniform. As a method of separating the diffusion sheet 14 from the light exit surface 18a of the light guide plate 18 by a predetermined distance, for example, a method of providing a spacer between the diffusion sheet 14 and the light guide plate 18 can be used.

[0053] In particular, when the thickness of the knock light unit 2 may be slightly increased, the light exit surface 18a of the light guide plate 18 corresponding to the parallel groove 18f may be formed depending on the cross-sectional shape of the parallel groove 18f of the light guide plate 18. It is not necessary to sufficiently reduce the peak value of the illuminance, and the light emitted from the diffusion sheet 14 is provided by providing a gap between the diffusion sheet 14 and the light exit surface 18a of the light guide plate 18. The light may have a uniform illuminance distribution. In addition, there is a limit to the improvement of the cross-sectional shape of the parallel groove 18f of the light guide plate 18 (the tapering of the tip of the parallel groove), and the peak value of the illuminance at the light exit surface 18a of the light guide plate 18 corresponding to the parallel groove 18f is limited. Even if the reduction cannot be achieved completely or cannot be sufficiently reduced, a gap is provided between the diffusion sheet 14 and the light exit surface 18a of the light guide plate 18 to make the illuminance distribution of the illumination light emitted from the diffusion sheet 14 uniform. May be.

The prism sheets 16 and 17 are transparent sheets formed by arranging a plurality of prisms in parallel. The prism sheets 16 and 17 increase the light condensing property of light emitted from the light exit surface 18 a of the light guide plate 18 and increase the brightness. Can be improved. One of the prism sheets 16 and 17 is arranged so that the direction in which the prism rows extend is parallel to the parallel groove 18f of the light guide plate 18, and the other is arranged so as to be vertical. That is, the prism sheets 16 and 17 are arranged so that the directions in which the prism rows extend are perpendicular to each other. The prism sheet 16 is disposed such that the apex angle of the prism faces the light exit surface 18a of the light guide plate 18. Here, the arrangement order of the prism sheets 16 and 17 is such that a prism sheet 16 having a prism extending in a direction parallel to the parallel groove of the light guide plate is arranged immediately above the light guide plate, and the prism sheet is arranged. A prism sheet having a prism extending in a direction perpendicular to the parallel groove 18f of the light guide plate 18 may be arranged on the light guide plate 16, or vice versa.

In the illustrated example, a prism sheet is used, but a sheet in which optical elements similar to prisms are regularly arranged may be used instead of the prism sheet. In addition, a sheet regularly provided with an element having a lens effect, for example, an optical element such as a lenticular lens, a concave lens, a convex lens, or a pyramid type can be used instead of the prism sheet.

In the present invention, as shown in FIGS. 3A and 3B, a prism sheet 19 is further provided between the reflection sheet 22 and the inclined surface 18d of the light guide plate 18 opposite to the light exit surface 18a. It is preferred that FIG. 3A is a schematic cross-sectional view showing a state in which a prism sheet 19 is arranged between the reflection sheet 22 and the inclined surface 18d of the light guide plate 18, and FIG. 3B is a sectional view of the reflection sheet 22 and the light guide plate 18. FIG. 9 is a schematic plan view and a schematic cross-sectional view of the prism sheet 19 disposed between the inclined surface 18d and the light guide plate when viewed from the side of the light guide plate. The prism sheet 19 provided between the reflection sheet 22 and the inclined surface 18d of the light guide plate 18 is arranged so that the direction in which the prism 19a extends is perpendicular to the parallel groove 18f of the light guide plate 18, and It is preferable that the apex angle of 19a is arranged so as to face the inclined surface 18d of the light guide plate 18.

Here, a force using a prism sheet An optical element having a lens effect that can be obtained by using an optical element having the same effect as the prism sheet, for example, an optical element such as a lenticular lens, a concave lens, a convex lens, or a pyramid type A sheet in which elements are regularly arranged may be provided.

In the illustrated example, the prism sheets 16 and 17, and more preferably the prism sheet 19, are used.However, when the illuminance on the light exit surface 18a by the parallel grooves 18f of the light guide plate 18 is more uniform, Of course, the prism sheet 19 is unnecessary, and one or both of the prism sheets 16 and 17 need not be used. The apparatus cost can be reduced by reducing the number of expensive prism sheets used or by omitting the use of prism sheets.

2A to 2C, the reflection sheet 22 reflects light leaking from the rear surface (the lower surface in the figure) of the light guide plate 18 and makes the light enter the light guide plate 18 again. Usage efficiency can be improved. The reflection sheet 22 is formed so as to cover the lower surface (inclined surface) of the light guide plate 18. Made. The reflector 20 is provided behind the light source 12 so as to close the parallel groove 18f of the light guide plate 18. The reflector 20 reflects the light of the lower surface of the light source 12 as well as the light of the side wall surface of the parallel groove 18f of the light guide plate 18.

[0059] The reflection sheet 22 may be made of any material as long as it can reflect light leaking from the back surface (the lower surface in the figure) of the light guide plate 18, for example, PET or PP ( A resin sheet in which the reflectance is increased by forming voids by kneading a filler into (polypropylene) or the like, and a sheet in which a mirror surface is formed on the surface of a transparent or white resin sheet by aluminum evaporation or the like as described above; It can be formed of a metal foil of aluminum or the like, a resin sheet carrying the metal foil, or a metal thin plate having a sufficiently reflective surface. Further, the reflector 20 can be formed of, for example, the same material as the above-mentioned reflection sheet, that is, a resin material, a metal foil or a metal plate having a surface with sufficient reflectivity.

[0060] Further, the reflection sheet may be directly attached to a portion of the light guide plate opposite to the light exit surface except for the parallel groove, for example, an inclined surface. Further, the present invention is not limited to directly applying the reflection sheet to the light guide plate, and a paint having the same function as the reflection sheet may be directly applied to the light guide plate.

As described above, by directly attaching the reflection sheet or directly applying the paint, the emission efficiency can be improved, and the occurrence of luminance unevenness due to a mounting error of the reflection sheet can be prevented.

The backlight unit in the present invention is not limited to the configuration shown in FIGS. 2A and 2B. For example, in order to improve the brightness of light emitted from light guide plate 18, a reflective polarizing film In addition, a brightness enhancement sheet such as a cholesteric polarizing film or a scattering polarizing film may be provided. In FIG. 2A and FIG. 2B, such a brightness enhancement sheet is preferably disposed between the light guide plate 18 and the liquid crystal display panel 4 (lower polarizer), particularly, for the liquid crystal display panel 4 (lower polarizer). It is preferable to dispose it on the surface on the light incident side.

[0062] Further, in the present invention, an optical compensation film for widening the viewing angle may be provided. As the optical compensation film, for example, an optical compensation film using a discotic liquid crystal / nematic liquid crystal, an optical compensation film using a collimating film, or the like can be used. The optical compensation film is shown in FIGS. 2A and 2B. It is preferable to be provided by being attached to the upper surface or the lower surface of the nozzle 4.

In addition, an optical member having a function such as diffusion, light collection, scattering, or diffraction is connected to the light exit side of the light guide plate 18 in FIGS. 2A and 2B, for example, the light exit surface of the light guide plate 18 or the light guide plate 18. And the liquid crystal display panel 4. As such an optical component, only one optical component having any one of the above functions may be arranged, or a plurality of optical members having the same or different functions may be arranged in combination. When a plurality of optical components are used in combination, the order of arrangement of the plurality of optical components is arbitrary, and the order of arrangement can be appropriately adjusted according to desired optical characteristics.

[0064] Each of the above-described optical members such as the diffusion film, the prism sheet, and the brightness enhancement sheet may be used one by one or a plurality of them. Further, such optical members can be used by being bonded to each other. Further, it can be attached directly to the light guide plate, or it can be attached to the light incident side surface of the liquid crystal display panel. Further, the arrangement of the prism sheet is not particularly limited. For example, when the light emission direction is upward, the prism may be disposed upward !, or may be disposed downward, and two prisms may be disposed. It is used to stack sheets.

In FIGS. 2A and 2B, between the light guide plate 18 and the liquid crystal display panel 4, as described above, the optical components such as the diffusion sheet 14 and the prism sheets 16 and 17 are arranged. The configuration of the optical component is not limited to such a configuration example, and may be, for example, a configuration as described below. For example, on a light exit surface side of a light guide plate, a diffusion sheet in which halftone dots for suppressing generation of bright lines are formed by printing, a prism sheet, and the above-described brightness improvement sheet are sequentially arranged. can do. In this case, it is preferable that halftone dots are formed on the light incident side surface of the diffusion sheet, that is, the surface facing the light exit surface of the light guide plate, and the prism row is arranged on the light exit side in the prism sheet. Is preferred.

Further, as another configuration example, a configuration can be adopted in which a diffusion sheet in which halftone dots are formed by printing and a brightness enhancement sheet are arranged on the light exit surface side of the light guide plate. In this case, it is preferable that a halftone dot is formed on the light incident side surface of the diffusion sheet as described above. Further, as another configuration example, a halftone dot is formed by printing on the light exit surface of the light guide plate, and a diffusion sheet and a brightness enhancement sheet are arranged in this order on the light exit surface side of the light guide plate. You can also. In this case, since halftone dots are formed on the light exit surface of the light guide plate, halftone dots are formed, and a diffusion sheet is used.

Further, halftone dots are formed on the light exit surface of the light guide plate by printing, and two diffusion sheets having the same or different characteristics and one brightness enhancement sheet are provided on the light exit surface side of the light guide plate. May be arranged in order. Further, a configuration may be adopted in which two diffusion sheets and one brightness enhancement sheet are sequentially arranged on the light exit surface side of the light guide plate. In this case, halftone dots are not printed on the light exit surface of the light guide plate, but are printed on the surface of the diffusion sheet located closer to the light guide plate, facing the light exit surface of the light guide plate. It is preferable to form by.

In the above configuration example, from the viewpoint that the number of parts is small and the manufacturing cost can be reduced, halftone dots are formed on the light exit surface of the light guide plate by printing, and a diffusion sheet and a diffusion sheet are provided on the light exit surface side of the light guide plate. A configuration in which the brightness enhancement sheets are arranged in this order is preferable.

Here, the structure of the light guide plate 18 of the present invention will be described in more detail.

As shown in FIG.2B, the light guide plate 18 is formed with a rectangular light exit surface 18a, a pair of thick portions 18b parallel to one side thereof, and on both sides of the thick portions 18b parallel to the one side. A thin end portion 18c, a slanted back portion 18e that becomes thinner from the thick portion 18b toward the thin end portions 18c on both sides in a direction orthogonal to the one side and forms an inclined surface 18d, and a thick portion. 18b has a parallel groove 18f formed in parallel with the one side and for accommodating the light source 12. That is, the light guide plate 18 is a plate-like member having a rectangular outer shape on the surface, and is formed of transparent resin. The light exit surface 18a of the light guide plate 18 is flat, and the surface on the opposite side is inclined with respect to the light exit surface 18a so that the thickness of the light guide plate 18 becomes smaller in accordance with the direction of one side.

Further, in the light guide plate of the present invention, as shown in FIG. 2C, the distance from the surface X perpendicular to the light exit surface 18a and including the central axis O of the light source 12 to the end surface 18h of the thin portion is determined. L [mm], a linear light source is arranged in the parallel groove, and the total luminous flux on the light exit surface when light incident from the linear light source exits from the light exit surface is I, and the total luminous flux on the light source surface is I Then, L is

BLU CFL

Preferably, it is formed to be within the range.

L = k2 X (I / \)

CFL BLU

[0068] The lower limit value of I / \, which indicates the emission efficiency, is the average value required for PC monitors and LCD TVs. The brightness and the upper limit are determined from the viewpoint of Fresnel loss at the light guide plate interface, transmittance of the light guide plate, and reflectivity of the reflective film.

0.3 ≤ 1 / \ ≤ 0.9 Preferred LCD LCD or outdoor monitor

BLU CFL

Since high average luminance is required, it is preferable that the ratio is 0.6≤1 / \ ≤0.8.

BLU CFL

K2 is a parameter that represents the shape of the light guide path.From the viewpoint of the average luminance required for PC monitors and liquid crystal TVs, k2 should be 1≤1 ^ 2≤160, and 9≤k2≤40. Is preferable.

A desired light flux can be obtained by forming the light guide plate with the L obtained in this manner.

In the present invention, as shown in FIG. 2C, the inclined surface 18d of the light guide plate 18 has a relational force of 1 between the inclined angle Φ1 with respect to the light exit surface 18a and the distance W between the two extreme ends 18h. rad] XW [mm] ≤200 (mm) (Φ 1 [°] XW [mm] ≤11459 (mm)) As shown in FIG. 1, a plurality of light guide plates 18 having an angle in such a range are connected so that the end surfaces 18h of the thin end portions 18c are in close contact with each other to form a light guide having a large light exit surface. If formed, the light of the cold cathode tube 12 incident from the light incident portion 18g of the parallel groove 18f is reflected by the inclined surface 18d inside the light guide plate 18, then exits from the light exit surface 18a, and the brightness unevenness at the connection portion is obtained. Can be reduced. The angle of inclination Φ1 is such that the light emitted from the cold cathode tube partially reflects inside the light guide plate 18 and propagates the light to the connecting portion, and the ratio of the relative luminance to the light incident portion is less than twice. To satisfy the relationship with the distance W between both ends, for example, when W = 300, O (rad) ≤ 1 ≤ 0.35 (rad) (0 ° ≤ Φ 1 ≤ 20 ° ) Is preferable, and it is more preferable to satisfy O (rad) ≤ 1 ≤ 0.175 (rad) (0 ° ≤ Φ 1 ≤ 10 °). In addition, in the case where the connecting portion is integrally formed without a joint, it is preferable that the connecting portion is formed so as to have an inclination angle different from the above-mentioned inclination angle Φ1 in order to prevent reflection of the connection surface near the connection portion. When the different angle is Φ 2, the inclination angle Φ 2 is set to satisfy Φ 1> Φ 2 in order to increase the relative brightness at the connection portion to 3 times or less, preferably 2 times or less of the average brightness ratio. It is preferable to satisfy the conditions. When the connecting portion is a curved surface as shown in Fig. 4Α, the angle between the connecting portion and the tangential direction is Φ2.

Here, a plurality of light guide plates 18 in which the inclined surfaces 18d of the light guide plates 18 are formed as flat surfaces are connected. The cross-sectional shape near the extreme end (hereinafter, referred to as the inclined end) of the inclined surface 18d where the light guide plates are connected to each other when the light guide plates are connected to each other is formed into a curved shape or a polygonal shape as shown in FIGS.4A and 4B. It is preferable that the inclined surface 18d of one light guide plate 18A is continuously connected to the inclined surface 18d of the other light guide plate 18B. For example, as shown in FIG.4A, when the shape of the end portion of the inclined surface is curved, the connecting portion 120 on the surface opposite to the light exit surface 18a of each of the light guide plates 18A and B is used. Preferably, the inclination angle with respect to the light exit surface 18a is set to zero, and the inclination surface 18d other than the vicinity of the connecting portion 120 is preferably set so as to fall within the range of the inclination angle. Further, as shown in FIG. 4B, when a polygon is used, the polygon may include a curve.

As shown in FIG. 4B, in the case where the shape of the end portion of the inclined surface 18d is polygonal, the shape of the surface opposite to the light exit surface 18a of each of the light guide plates 18A and 18B is used. It is preferable that the connecting portion 120 is formed of a plane whose angle with respect to the light exit surface 18a is gradually inclined from zero, and that the inclined surface 18d other than the connecting portion 120 is formed so as to be in the range of the above-mentioned inclined angle. At this time, the angle at the connecting portion 120 formed by the inclined surface near the extreme end of each of the inclined surfaces 18d of the light guide plates 18A and 18B may be zero. It is sufficient that the angle is gentler than the angle of the surface. With such a configuration, when a plurality of light guide plates 18 are arranged in parallel, it is possible to further reduce the occurrence of luminance at the connecting portion 120 of the light exit surface of each light guide plate. When the shape of the end portion of the inclined surface 18d is a polygonal shape, as shown in FIG. 4B, Φ 2 is the angle of the inclined surface close to the end portion.

Here, the light emission principle of the light guide plate of the present invention will be described with reference to FIG. In FIG. 5, components such as the reflector, the reflector, and the prism sheet shown in FIG. 2B are omitted for convenience of description.

In the present invention, the relationship between the inclination angle Φ1 of the inclined surface 18d of the light guide plate 18 and the distance W between the two extreme ends satisfies 1 [ _rad ] XW [mm] ≤ 200 [mm]. are doing. When the backlight unit is configured by arranging a plurality of such light guide plates 18 in parallel, a part of the light emitted from the cold cathode tubes 12 provided in the parallel grooves 18f of the predetermined light guide plate 18A is After being reflected by the inclined surface 18d inside A, the light reaches the end face 18h of the light guide plate 18A. So Then, the light enters the interior of the light guide plate 18B from the end surface 18h of the adjacent light guide plate 18B connected to the end surface 18h, and exits from the light exit surface 18a of the adjacent light guide plate 18B.

Further, by changing the inclination angle Φ2 near the connecting portion, it is possible to adjust the amount of light moving to the adjacent light guide plate.

[0073] In the present invention, a plurality of light guide plates 18 are continuously arranged in this way, and light from the cold cathode tubes 12 arranged on the adjacent light guide plate 18 can also be used. As a result, the light emission efficiency can be increased. The structure of the integrated repeating unit has an advantage that a more uniform luminance can be obtained because an increase in the intensity of the bright line at each end when the repeating unit is continued without being integrated. . Further, the cross-sectional shape of the light guide plate 18 adjacent to each other at the end opposite to the light exit surface 18a is formed into a curved shape or a polygonal shape as shown in FIG. 4A and FIG. The generation of luminance in the portion can be further suppressed.

Next, the dependency of the inclination angle of the bright line on the light exit surface when a plurality of the light guide plates of the present invention were connected was examined by simulation. First, we examined the case where three light guide plates were connected. 6A to 6E respectively show graphs of emission lines when the inclination angles are different. In the simulation, the brightness at the light exit surface 18a was calculated by changing the thickness T of the outermost portion 18i to a small value while maintaining the thickness of the thick portion 18b of the light guide plate 18 shown in FIG. 2B constant. did. The diameter of the cold cathode tube 12 is 3 mm, the width of the light guide plate 18 perpendicular to the axis of the cold cathode tube 12 is 30 mm, the maximum thickness of the thick portion 18b is 5.5 mm, and the thickness of T was changed to 1. Omm, 1.5 mm, 2. Omm, 2.5 mm, 3. Omm. The graphs shown in FIGS. 6A to 6E show the light emission surface when the thickness T of the outermost portion 18i is 1.Omm, 1.5 mm, 2.Omm, 2.5 mm, and 3.Omm, respectively. 6 is a graph of luminance at. Here, the light guide plate having a thickness T force of 1.Omm, 1.5mm, 2.Omm, 2.5mm, 3.Omm at the end 18i has an inclination angle Φ1 of the inclined surface of FIG. 380 [rad] (about 21.8 °), about 0.335 [rad] (about 19.2 °;), about 0.390 [rad] (about 16.6 °;), about 0.246 [ rad] (about 14.1 °) and about 0.204 [rad] (about 11.7 °). In the graphs shown in FIGS.6A to 6E, the luminance on the vertical axis represents a value obtained by converting the luminance of the cold cathode fluorescent lamp to 1 lumen, and the horizontal axis represents a value in a direction perpendicular to the axis of the cold cathode fluorescent lamp. The distance between the three light guide plates The distance from the axis of the cold cathode tube provided on the central light guide plate is shown. In addition, Fig. 7 summarizes the graphs shown in Figs. 6A to 6E into one to show how the emission line changes according to the angle of the inclined surface, that is, to clearly show the dependence of the emission line on the inclination angle. Shown.

[0075] As shown in the graphs of Figs. 6A to 6E, it can be seen that bright lines are generated at the connection portions of the light guide plates. Then, as shown in FIG. 7, it can be seen that the luminance at the connection portion changes according to the angle of the inclined portion of the inclined surface. In particular, as the angle of inclination of the inclined surface of the light guide plate becomes gentler, the luminance at the connecting portion becomes lower, and it can be seen that the luminance unevenness is reduced. When the distance between the two extreme ends is 300 mm, by setting the inclination angle Φ 1 of the inclined surface of the light guide plate to 0.349 [rad] (about 20 °) or less, the relationship with the distance W between the extreme ends is It satisfies 1 [rad] XW [mm] ≤ 200 (1 [°] XW [mm] ≤ 11459 [mm]), and it can be seen that the brightness at the joint is reduced.

8A to 8D, the angle Φ 2 of the inclined surface with respect to the light exit surface at the connecting portion is set to Φ 1, and Φ 2 is set to Φ 1Ζ2, so that the angle Φ 1 of the inclined surface other than the connecting portion is larger than Φ 1. A graph of the luminance distribution when three light guide plates of reduced size (Φ 2 Φ 1) are connected is shown. FIGS. 8A to 8D show the results when the thickness T of the outermost end 18i of the light guide plate 18 is set to 1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm, respectively. Also, FIG. 9 shows how the bright line changes according to the angle of the inclined surface, that is, the graphs shown in FIGS. 8A to 8D are combined into one in order to clearly show the inclination angle dependence of the bright line. Indicated. Also in this case, as in the above, a bright line is generated at the connection portion of the light guide plate, and as the inclination angle of the inclined surface of the light guide plate becomes gentler, the brightness at the connection portion becomes lower, and the brightness unevenness is reduced. It can be seen that it has been reduced.

By using this light guide plate, the thickness of the combination of the cold cathode fluorescent lamp (CCFL) and the light guide plate can be 5 mm or less, and the thickness of the backlight unit (BLU) can be 10 mm or less. It is possible to reduce the thickness of the direct-type backlight unit, which has the above-mentioned performance, to a thickness of 20 to 30 mm.

[0077] Figs. 10A to 10E show graphs of the luminance distribution on the light exit surface when six light guide plates are connected. 10A to 10E show the luminance distribution when the thickness T of the outermost end 18i of the light guide plate 18 is 1.Omm, 1.5mm, 2.Omm, 2.5mm, and 3.Omm, respectively. You. FIG. 11 shows how the bright line changes in accordance with the angle of the inclined surface, that is, the bright line The graphs shown in FIGS. 10A to 10E are collectively shown in order to clearly show the inclination angle dependency of FIG. Also in this case, similarly to the above, the bright line is generated at the connecting portion of the light guide plate, and as the inclination angle of the inclined surface of the light guide plate becomes gentler, the brightness at the connecting portion becomes lower and the uneven brightness is reduced. You can see that it is.

FIGS. 12A to 12C, 13D, and 13E show graphs of luminance distribution on the light exit surface when nine light guide plates are connected. The graphs shown in FIGS.12A to 12C, FIG.13D, and FIG.13E respectively show the thickness T of the outermost portion 18i of the light guide plate 18 as 1.Omm, 1.5mm, 2.Omm, 2.5mm, 3. This is the result when Omm is set. In addition, Fig. 14 shows how the bright line changes according to the angle of the inclined surface, that is, Fig. 12A to Fig. 12C, Fig. 13D, and Fig. The graphs are summarized below. Even in the case where nine light guide plates are connected in this way, similarly to the above, bright lines are generated at the connection portions of the light guide plates, and as the inclination angle of the inclined surface of the light guide plate becomes gentle, the connection portions are connected. It can be seen that the luminance of the image becomes lower, and the luminance unevenness is reduced.

By the way, parallel grooves 18f for accommodating the light source 12 are provided in the longitudinal direction on the side opposite to the light exit surface 18a of the thick portion 18b of the light guide plate 18 so that the force shown in FIGS. It is formed to extend. The depth of the parallel groove 18f is determined so that a part of the light source 12 does not protrude from the lower surface of the light guide plate 18, and preferably the dimensions of the light source 12, the mechanical strength of the light guide plate 18, and the change with time. Preferably, it is determined in consideration of the above. The thickness of the thick portion 18b and the thin end portion 18c of the light guide plate 18 can be arbitrarily changed according to the dimensions of the light source 12. Here, the parallel groove 18f of the light guide plate 18 may be formed in a direction perpendicular to the longitudinal direction of the light guide plate 18, but in order to increase the efficiency of using light from the light source 12 housed in the parallel groove 18f. Is preferably formed in the longitudinal direction.

In the light guide plate 18 having the structure shown in FIG. 2B, of the light emitted from the light source 12 disposed in the parallel groove 18f, the light enters the light guide plate 18 from the side wall force forming the parallel groove 18f. The reflected light is reflected from the inclined surface 18d of the light guide plate 18 and then exits from the light exit surface 18a. At this time, some light leaks from the lower surface force of the light guide plate 18, but the leaked light is reflected by the reflection sheet 18 formed on the inclined surface 18 b side of the light guide plate 18, and again inside the light guide plate 18. And exits from the light exit surface 18a. Thus, the uniform light is emitted from the light exit surface 18a of the light guide plate 18. Is emitted.

The light guide plate 18 is manufactured by, for example, a method of molding a heated raw resin by extrusion molding or injection molding, or a casting polymerization method of polymerizing monomers, oligomers and the like in a mold and molding. Can be. Examples of the material of the light guide plate 18 include acrylic resins such as polycarbonate and PMMA (polymethylmethacrylate), PET (polyethylene terephthalate), PP (polypropylene), PC (polycarbonate), and PMMA (polymer It is possible to use transparent resins such as cinnamate methacrylate, benzyl metathallate, MS resin, other acrylic resins, or COP (Shikiguchi Refin Polymer). Fine particles for dispersing light may be mixed in the transparent resin. This makes it possible to further enhance the efficiency of light emission from the light exit surface 18a. When fine particles for scattering light are mixed into the transparent resin, the fine particles may have isotropic properties or may have anisotropy.

[0082] It is also possible to adjust the color tone of the emitted light by mixing a color tone correction agent into the light guide plate. Further, instead of mixing a color tone correcting agent into the light guide plate, a color correction filter may be provided to correct the color tone of light incident on the liquid crystal display panel. Further, a light guide plate mixed with a color tone correcting agent and a color correction filter for correcting the color tone can be used in combination.

Here, it is preferable to use a material that easily transmits blue light for the transparent member used for the light guide plate. For example, when the light source is a rod-shaped light source such as a cold-cathode tube, the color temperature of the light emitting surface of the liquid crystal display panel is lower than the color temperature of the light source due to the spectral characteristics of the transmission member. Therefore, the color temperature of the light source must be set higher. However, if the color temperature of the light source is set to a high value, the luminance efficiency may decrease. By using a material that easily transmits blue light for the transparent member used for the light guide plate, the color temperature of the light source and the color temperature of the liquid crystal display surface can be made equal. Thus, high-luminance light emitted from the light source can be emitted from the liquid crystal display panel without lowering the color temperature. As a result, power consumption can be reduced, the light source can have a longer life, and the number of light sources and inverters can be reduced to reduce costs.

Further, a charge removing material or a conductive material may be applied to the light exit surface side of the light guide plate. This makes it difficult for dust to accumulate inside the backlight due to static electricity.

When the above transparent resin is selected, as shown in FIG. 2C, the light emitting surface 18a is opposed to the light emitting surface 18a. The distance from the plane X including the center axis 0 of the rod-shaped light source 12 to the end face 18h of the thin-walled end is L (mm), and is inclined parallel to the light exit surface 18a from the center 0 of the rod-shaped light source 12 AL (mm) is the distance to the intersection P with the surface 18d, t is the light transmittance of the light transmitting resin, and the distance from the intersection P to the light exit surface 18a in the direction perpendicular to the light exit surface 18a. When D is set to D (mm), it is preferable to select at least the following expression.

t = {l -kl X (D / L- A L)} X 100

Here, kl is a parameter representing the attenuation rate of light inside the light guide plate, and is preferably set to 0 <kl ≦ 2 from the viewpoint of the internal transmittance of the material used for the light guide plate.

Here, the light guide plate of the present invention will be described in detail with respect to the preferred shape and shape of the parallel groove.

2A to 2C, the parallel groove 18f of the light guide plate 18 has a triangular cross-sectional shape perpendicular to the length direction of the parallel groove 18f (hereinafter, simply referred to as the cross-sectional shape of the parallel groove! /). It is formed as follows. Here, the cross-sectional shape of the parallel groove 18f is triangular, but in the present invention, the cross-sectional shape of the parallel groove 18f is such that the light exits from the light guide plate 18f through the deepest portion or the center of the parallel groove 18f. Any shape that is symmetrical with respect to the center line perpendicular to the surface and narrows toward the light exit surface 18a may be used.For example, as shown in FIGS. 15 and 16, the shape may be a hyperbolic shape or an elliptical shape. be able to. Alternatively, the cross-sectional shape of the parallel groove 18f of the light guide plate 18 may be a catenary shape.

[0086] Further, in the present invention, the cross-sectional shape of the parallel groove is such that the deepest part (connection part of the side wall forming the parallel groove) of the parallel groove is a point. You can also. In other words, the cross-sectional shape of the leading end of the parallel groove has two sharp curves, each having one sharp intersection, which are symmetrical with respect to the center line perpendicular to the light exit surface of the light guide plate through the center of the parallel groove. A straight line partial force can also be formed. In the present invention, even if the cross-sectional shape of the parallel groove of the light guide plate is any of the above shapes, uniform light can be emitted from the light exit surface of the light guide plate.

[0087] FIG. 17 shows that the cross-sectional shape of the tip portion of the parallel groove is different from the center line perpendicular to the light exit surface of the light guide plate passing through the center of the parallel groove 18f, which has one sharp intersection point intersecting with each other. An example of the case where the partial force of the two symmetrical curves is also shown. The light guide plate 50 shown in FIG. Two curves 54a and 54b symmetrical with respect to a center line X perpendicular to the light exit surface 52 of the light guide plate 50 through the center of the row groove are the case of arcs. In this case, as shown in FIG. 17, the center position of the arc 54a corresponding to one side wall forming the parallel groove 18f is different from the center position of the arc 54b corresponding to the other side wall. . As a result, the portion 56 where the arc-shaped side walls intersect has a pointed shape as shown in FIG.

Further, FIG. 18 shows that the cross-sectional shape force of the front end portion of the parallel groove has a sharp point of intersection with one another and passes through the center of the parallel groove and is perpendicular to the center line perpendicular to the light exit surface of the light guide plate. Another example is shown in which the partial force of two symmetric curves is also obtained. In the light guide plate 60 shown in FIG. 18, two curves 64a and 64b symmetric with respect to a center line X passing through the center of the parallel groove 18f and perpendicular to the light exit surface of the light guide plate are parabolic. In FIG. 18, the side wall of the parallel groove 18f is formed such that the focus of the parabola 64a forming one side wall of the parallel groove 18f and the focus of the parabola 64b forming the other side wall 22b are different from each other.

As shown in FIG. 18, when the cross-sectional shape of the tip of the parallel groove is formed from two curves 64a and 64b intersecting at the intersection 66, a curve corresponding to one side wall of the parallel groove 18f The angle が between the tangent at the intersection (cusp) 66 of the point 64a and the tangent at the intersection 64 of the curve 64b corresponding to the other side wall of the curve 64b is preferably 90 degrees or less, more preferably 60 degrees or less.

FIGS. 1 to 18 show examples of the light guide plate in which the side wall of the parallel groove is concave toward the center of the parallel groove in the cross-sectional shape of the parallel groove. Another embodiment of the light guide plate of the present invention is shown in FIGS. FIG. 19 is an example of a light guide plate 70 in which the cross-sectional shape of the parallel groove 18f is formed from two curves 72a and 72b that are convex toward the center of the parallel groove 18f, and FIG. 20 is a cross-sectional view of the parallel groove 18f. This is an example of the light guide plate 80 having a shape formed by combining curves 82a and 82b convex toward the center of the parallel groove 18f and curves 84a and 84b concave. The light guide plates 70 and 80 having parallel grooves having a cross-sectional shape as shown in FIGS. 19 and 20 can also emit light with sufficient light emission surface power while suppressing the generation of bright lines.

As described above, in the present invention, in the cross-sectional shape of the parallel groove of the light guide plate, the portion corresponding to the parallel groove has a convex or concave curve directed toward the center of the parallel groove. Shape or linear And a combination thereof. These curves are not limited to the arcs in the illustrated example, and may be any part of a curve such as an ellipse, a parabola, or a hyperbola that is convex or concave toward the center of the parallel groove. Further, in the present invention, if the cross-sectional shape of the tip portion of the parallel groove is tapered as described later, the curve constituting the parallel groove will be a circle or a convex or concave toward the center of the parallel groove. If it is a part of a curve such as an ellipse, a parabola, or a hyperbola, it is preferable that the curve be a curve that can be approximated by a 10th order function.

In the light guide plate of the present invention, as shown in FIG. 21, the density of the halftone dots is high at a certain center line X, and as the halftone dot moves toward both sides (perpendicular to the center line) from the center line X, as shown in FIG. Next, a halftone dot pattern 92 having a low halftone dot density may be formed on the light exit surface 18a of the light guide plate 18, for example, by printing. By forming such a halftone dot pattern 92 on the light exit surface 18a of the light guide plate 18 so that the center line X of the halftone dot pattern coincides with the position corresponding to the center line of the parallel groove of the light guide plate 18, The generation and unevenness of bright lines on the light exit surface 18a of the light guide plate 18 can be suppressed. Instead of printing the halftone dot pattern 92 on the light guide plate 18, a thin sheet having the halftone dot pattern formed thereon may be laminated on the light exit surface. The shape of the halftone dot can be an arbitrary shape such as a rectangle, a circle, and an ellipse, and the density of the halftone dot can be appropriately selected according to the intensity and spread of the bright line. Instead of forming such a halftone dot pattern by printing, a portion corresponding to the halftone dot pattern may be roughened as a sand rubbing surface. Such a sand rubbing surface may be formed on the deepest portion or the side wall of the parallel groove of the light guide plate.

[0093] Next, the illuminance distribution of light emitted from the light exit surface of the light guide plate when the cross-sectional shape of the parallel groove of the light guide plate was changed to various shapes was examined. First, as an example of the light guide plate according to the present invention, the parallel groove 18f has a triangular or hyperbolic cross-sectional shape as shown in FIGS. 2A to 2C and FIG. 15, and a conventional light guide plate has a parabolic cross-sectional shape. , And a semicircular shape. FIG. 22 shows the relative illuminance distributions on the light exit side surfaces of the light guide plates. In FIG. 22, the vertical axis indicates the relative illuminance, and the horizontal axis indicates the distance from the center position of the light guide plate (the center of the parallel groove). Here, the relative illuminance was measured as follows.

[0094] A light source is incorporated in the light guide plate of the present invention, and light enters the light guide plate to emit light from the light exit surface. Then, fix the illuminometer so that it is perpendicular to the emission surface of the light guide plate. Then, the illuminance is measured at the position of the light exit surface by the illuminometer to obtain information of the illuminance regarding the specific position of the light exit surface of the light guide plate.

Then, by moving the XY stage, the relationship between the position on the light emitting surface and the illuminance is determined, and the average value of the entire surface is calculated. The ratio of the illuminance at each position divided by the average value of the illuminance, respectively, is the relative illuminance at that position.

In addition, by measuring one axis perpendicular to the axial direction of the parallel groove and representing the value, it is possible to easily compare the cross-sectional shapes.

When measuring the relative luminance, a luminance meter may be used instead of the illuminometer, whereby the relative luminance distribution on the light emission side surface of the light guide plate can be obtained.

[0095] As can be seen from Fig. 22, when the cross-sectional shape of the parallel groove of the light guide plate is hyperbolic, the peak value of relative illuminance at the portion corresponding to the parallel groove is due to the emitted light of the inclined back surface force. Therefore, the illuminance of the light emitting surface is almost uniform. On the other hand, in a conventional light guide plate having a semicircular or parabolic cross section, the relative illuminance is high at the center of the parallel groove, that is, at a position immediately above the light source, as shown in FIG. It can be seen that a bright line is generated. That is, in the conventional light guide plate having a semicircular or parabolic cross section, the illuminance on the light irradiation surface is not uniform.

[0096] In a light guide plate in which the cross-sectional shape of the parallel groove is triangular, the relative illuminance at the center is low. When the cross-sectional shape of such a parallel groove is triangular, as shown below, the force for flattening the apex with a predetermined width and the illuminance on the light exit surface are obtained by forming the curved surface with a relatively small radius of curvature. Can be made uniform.

FIG. 23 shows that, when the cross-sectional shape of the parallel groove of the light guide plate is triangular, the deepest portion of the parallel groove (the apex of the triangular parallel groove) is flattened, and the length of the flat portion is varied. It shows the illuminance distribution of the emitted light when the light exit surface force of the light guide plate is changed. In FIG. 23, the vertical axis indicates the relative illuminance, and the horizontal axis indicates the distance from the center of the parallel groove formed in the light guide plate. Here, in order to simplify the calculation, the diameter of the cold cathode tube was 3 mm, and the length of the flat part was 1.5 mm, 1.0 mm, 0.5 mm, and 0.25 mm. Figures 24A to 24D In the case where the cross-sectional shape of the parallel groove is triangular, the schematic cross-sectional views of the light guide plate with the flat part at the deepest part of the parallel groove being 1.5 mm, 1. Omm, 0.5 mm, 0.25 mm are shown, respectively. Was.

[0098] As shown in the graph of Fig. 23, it can be seen that the relative illuminance at a portion corresponding to the parallel groove of the light guide plate changes according to the length of the flat portion. Here, in the present invention, the illuminance can be increased by lengthening the flat end portion at the deepest portion of the parallel groove. However, if the length is too long, there is a possibility that a bright line is formed. The diameter is preferably 20% or less of the diameter of the tube, more preferably 10% or less.

[0099] Fig. 25 shows that in the light guide plate in which the cross-sectional shape of the parallel groove of the light guide plate is triangular, the shape of the deepest portion of the parallel groove is a curved surface having a radius of curvature R, and the radius of curvature of the curved surface is varied. The light exit surface power of the light guide plate when the light guide plate was transformed was shown as the illuminance distribution of the emitted light. Here, the radius of the cold-cathode tube was 3 mm, and the radii of curvature at the apexes were measured at 0.25 mm, 0.5 mm, 1.0 mm, and 1.5 mm. Figures 26A to 26D show schematic cross-sectional views of light guide plates with the radii of curvature at the vertices of 0.25mm, 0.5mm, 1.Omm, and 1.5mm, respectively, when the cross-sectional shape of the parallel groove is triangular. Was. From the graph of Fig. 25, the relative illuminance at the portion corresponding to the parallel groove of the light guide plate changes according to the radius of curvature of the vertex portion of the parallel groove. It can be seen that the relative illuminance on the light exit surface is substantially uniform.

[0100] From the above, it is apparent that the shape of the tip of the parallel groove of the light guide plate greatly depends on the illuminance of the light exit surface force. That is, the illuminance on the light exit surface of the light guide plate can be optimally adjusted and made uniform only by designing the shape of the parallel grooves of the light guide plate to have the shape shown in the present invention. .

On the surface of the light guide plate, illuminance and luminance can be handled in substantially the same manner. Therefore, from the relative illuminance graphs of FIGS. 23 and 25, it is inferred that in the present invention, there is a similar tendency in luminance. Therefore, it is considered that by designing the shape of the parallel groove of the light guide plate so as to have the shape shown in the present invention, the luminance on the light exit surface of the light guide plate can also be made uniform.

The cross-sectional shape of the top (deepest) of the tip of the parallel groove is such that one point of intersection that is sharply symmetrical with respect to the center line of the parallel groove is a chamfered flat shape or a rounded circular shape. Needless to say, the shape may be elliptical, parabolic, or hyperbolic. In addition, as described above, the peak (the deepest part) of the tip of the parallel groove may be a sand rubbing surface to reduce the illuminance or luminance peak value.

[0101] As described above, in the light guide plate of the present invention, the average value of the illuminance formed on the light exit surface 18a of the light guide plate 18 other than the parallel groove 18f, that is, on the portion (second portion) corresponding to the inclined back surface 18d. In accordance with the ratio of the peak value (peak value of illuminance) of the bright line formed in the portion (first portion) corresponding to the parallel groove 18f on the light exit surface 18a of the light guide plate 18, It is preferable to taper the tip shape, that is, to control the degree of tapering of the tip shape of the parallel groove 18f of the light guide plate 18 according to the value of this ratio. In this case, the ratio is preferably 3 or less, more preferably 2 or less.

[0102] This ratio depends on the thickness of the knock light unit 2 (the distance between the light exit surface 18a of the light guide plate 18 and the diffusion sheet 14) and the diffusion sheet used in the knock light unit 2. It is preferable to set according to the diffusion efficiency and the number of sheets of 14, and the diffusion efficiency and the number of sheets used of the prism sheets 16, 17 and 19. That is, the thickness of the knock light unit 2 (the distance between the light emitting surface 18a of the light guide plate 18 and the diffusion sheet 14) can be increased (or increased) to some extent, or the diffusion sheet used in the knock light unit 2 can be increased. If the diffusion efficiency of 14 can be increased and the number of used sheets can be increased, or the diffusion efficiency of prism sheets 16, 17 and 19 can be increased, the light emitted from the light exit surface 18a of the light guide plate 18 can be used. A light-emitting surface of the light guide plate 18 with respect to the average value of the illuminance of the second portion of the light guide plate 18a, which is a high cost because light diffusion (mixing, etc.) can be performed sufficiently. The ratio of the peak values of the illuminance of the first portion of 18a can be set to a somewhat large value. However, if this is not the case, it is necessary to set the value of this ratio small enough to achieve low cost.

[0103] In the light guide plate of the present invention, the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate 18 is equal to the average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate 18. It is preferable to taper the tip shape of the parallel groove 18f of the light guide plate 18 so as to be three times or less, more preferably two times or less. Here, the reason why the peak value of the illuminance of the first portion of the light exit surface 18a of the light guide plate 18 is three times or less the average value of the illuminance of the second portion of the light exit surface 18a of the light guide plate 18 is as follows. The illuminance distribution of the illumination light emitted from the light exit surface 18a of the light guide plate 18 is more uniform than before. As a result, the illumination light emitted from the light exit surface 18a of the light guide plate 18 does not need to be sufficiently diffused (mixing, etc.), and the diffusion efficiency is extremely high. The use of the diffusion sheet 14 is possible, the number of sheets used can be reduced, and the use of the expensive prism sheets 16, 17, and 19 itself can be stopped. This is because the prism sheets 16, 17 and 19 can be used and the number of sheets used can be reduced.

In the light guide plate according to the first embodiment of the present invention, in the cross-sectional shape of the parallel groove 18 f of the light guide plate 18, the tapered tip portion of the parallel groove 18 f has a central force of the rod-shaped light source 12. Direction force on the emission surface 18a Angular force with respect to the perpendicular (X) Both sides are preferably within 90 degrees, more preferably within 60 degrees. That is, in the present invention, in order to reduce the peak value of the illuminance of the first portion corresponding to the parallel groove 18f of the light exit surface 18a of the light guide plate 18, the portion where the parallel groove 18f is tapered is the parallel groove 18f. The whole may be used, but if the peak value can be reduced, a predetermined tip may be used.

[0105] In the present invention, the parallel groove 18f of the light guide plate 18 is shaped as described above, and the inclination angle Φ1 of the inclined surface and the inclination angle Φ2 at the extreme end of the inclined surface are as described above. In addition, by satisfying Φ 2 and Φ 1, when a plurality of light guide plates are connected, it is possible to suppress the generation of bright lines from each of the light guide plates and also to suppress the generation of bright lines at the connected portions. In the present invention, by arranging a plurality of light guide plates side by side, a knock light unit having a large-sized light irradiation surface in which the light quantity distribution of the light flux emitted from the light emission surface is uniform and the generation of bright lines is suppressed. be able to. A backlight unit having such a large-sized light irradiation surface can be applied to a liquid crystal display device having a large-sized display screen, and is particularly suitable for a wall-mounted liquid crystal display device such as a wall-mounted television. is there.

As described above, the light guide plate of the present invention, the backlight unit including the same, and the liquid crystal display device have been described in detail. However, the present invention is not limited to the above-described embodiment, and is not departed from the gist of the present invention. Of course, various improvements and changes may be made

For example, in the above embodiment, a light guide plate having a shape as shown in FIG. Although the configuration in which a plurality of the light guide plates are connected to form a large light guide plate has been described, in order to enhance the uniformity of emitted light, a shape in which two or more light guide plates of the present invention are connected is described. It is preferable to form the structure integrally and use the structure as one light guide plate. In particular, from the viewpoint of improving the manufacturing efficiency, it is preferable to integrally form as many light guide plates as necessary for illuminating the liquid crystal panel according to the screen size of the liquid crystal display panel to be used. With such a configuration, with a single light guide plate, the light quantity distribution of the luminous flux emitted from the light exit surface is uniform, and a thin knob having a large-sized light irradiation surface with suppressed generation of bright lines is provided. A light unit can be realized. Further, such an integrated light guide plate can be easily manufactured by using, for example, an extrusion molding method.

Further, as shown in FIG. 1, when a plurality of light guide plates of the present invention are connected to each other, when light is transmitted toward one light guide plate, In such a case, light scattering may occur. However, in a light guide plate formed by integrating a plurality of light guide plates, such light scattering does not occur at the end face, so that the efficiency of use of light from the light source is further improved. Can be.

In the above embodiment, the light exit surfaces of the plurality of connected light guide plates are flat, that is, the light exit surfaces of the respective light guide plates are necessarily flat. The light guide plate may be configured such that the entire light exit surface of the light guide plate when a plurality of light guide plates are connected has the same curved surface. It may be configured to have a curved surface. Alternatively, each light guide plate may be configured such that undulations with a constant period are formed on the entire light exit surface of the light guide plate when a plurality of light guide plates are connected. Also, a sand rubbing surface, a large number of dimples or a large number of minute projections, or a large number of scatterers may be formed by printing on the entire surface or a part of the light exit surface. Such a sand rubbing surface, dimples, protrusions, and scatterers tend to suppress the generation of bright lines on the light exit surface of the light guide plate.

As shown in FIG. 35, when a large-sized backlight unit is formed by connecting a plurality of light guide plates 18, the brightness unevenness on the light emitting surface of the connected light guide plates 18 is reduced. It is preferable that one halftone sheet 350 on which halftone dots for suppressing the occurrence of light are formed is arranged so as to cover the light exit surfaces of the plurality of connected light guide plates 18. Such a dot The sheet 350 can have various sizes according to the number of the light guide plates 18 to be connected, and the halftone dots of the halftone sheet 18 are arranged at the positions where the bright lines on the light exit surface of the light guide plate 18 are generated. . As the material of the halftone sheet 350, the same material as that of the light guide plate 18 or a material having substantially the same thermal expansion coefficient and high transmittance and diffusion effect is used from the viewpoint of suppressing the influence of thermal change. Is preferred. By forming a halftone sheet using such a material, the position of the halftone dot of the halftone dot sheet will be different from the position of the bright line on the light exit surface of the light guide plate due to changes in temperature and humidity due to the manufacturing environment and use environment. Deviation is suppressed, and a change in the illuminance distribution of light emitted from the light exit surface of the light guide plate unit can be suppressed.

[0111] Further, the light guide plate may have a structure such that it is divided along the center line of the parallel groove for arranging the light source in light guide plate 18 shown in FIG. 2B. When a light guide plate having such a structure is used, the light guide plates are connected to each other at a portion corresponding to the parallel groove 18f of the light guide plate 18 having the structure shown in FIG. 2B. It is preferable to arrange the halftone sheets so as to coincide with the portion having the highest density of halftone dots in the dot sheet. Furthermore, when connecting a plurality of light guide plates, some light guide plates are configured with a structure divided along the center line of the parallel groove, and the other light guide plates are as shown in Fig. 2B. When configured with a structure, it is preferable to form a halftone dot pattern of a halftone dot sheet so as to increase the density of halftone dots at a position corresponding to the center line of the parallel groove of the light guide plate other than the connection portion, . By forming such a dot pattern, when a plurality of light guide plates are connected to manufacture a large-sized knock light unit, generation and unevenness of a bright line at a connection portion of the plurality of light guide plates are suppressed. be able to. Such a dot sheet can be bonded to the light guide plate by laminating an adhesive layer on the back surface.

When such a halftone sheet is arranged on the light emitting surface of a plurality of connected light guide plates, the position of the halftone dot pattern formed on the halftone sheet is determined by the center of the parallel groove of the light guide plate. In order to accurately and reliably match the position corresponding to the line, for example, an area not used as a light emitting area on the light emitting surface of the light guide plate and a position of the dot sheet corresponding to the position are used for positioning. It is preferable to form holes. By passing a fixing tool such as a pin through these positioning holes, it is possible to accurately and reliably position the bright line generating position of the light guide plate and the position of the halftone dot of the halftone dot sheet. The position of the hole for positioning is The area is not particularly limited as long as it is not used.However, in order to reduce the shift between the halftone dot pattern and the position corresponding to the center line of the parallel groove of the light guide plate due to the influence of temperature and humidity changes, the parallel groove of the light guide plate is used. It is preferable to form a hole at the substantially end of the light exit surface in the direction perpendicular to the center line of the parallel groove of the light guide plate on the end side in the length direction.

[0113] Further, it is desirable that the position of the halftone dot sheet is regulated with respect to the light guide plate in the vicinity of the center of the combined light guide plate, and that the outer peripheral portion is fitted with a gap only by its thickness.

Further, in the light guide plate of the present invention, the reflection plate 24 may be arranged on the side surface of the light guide plate 18 as shown in FIG. 27A in consideration of the area of the side surface and the like. Further, as described above, when a plurality of light guide plates 18 are arranged, as shown in FIG. 27B, the reflection plate 24 may be arranged on the side surface of the outermost light guide plate 18. By arranging such a reflection plate 24 on the side surface, it is possible to prevent light from leaking from the side surface of the light guide plate 24, and it is possible to further enhance the light use efficiency. The reflecting plate 24 can be formed using the same material as the above-mentioned reflecting sheet or reflector.

Further, as shown in FIG. 36A and FIG. 36B, a reflective plate 362 made of the same material as the above-described reflective sheet 22 and reflector may be disposed on a side surface of the light guide plate 18 in the longitudinal direction of the light source 12. As a result, the emission efficiency can be further improved, and the uneven brightness at the end of the light guide plate 18 in the longitudinal direction of the light source 12 can be reduced.

When the brightness distribution of the light source is not flat in the longitudinal direction of the light source, there is also a method of adjusting the shape of the parallel groove of the light guide plate, particularly the angle of the tip portion, according to the position in the longitudinal direction of the light source. . For example, in the case where the brightness of the light source increases from the end to the center in the longitudinal direction of the light source, as shown in FIGS. 37A to 37D, the light guide plate 18 extends in the longitudinal direction of the light source 12. The shape may be such that the angle of the tip of the parallel groove 18f of the light guide plate 18 increases from the end (see FIGS. 37B and 37D) toward the center (see FIG. 37C).

On the other hand, in a direction parallel to the light exit surface of the light guide plate and perpendicular to the longitudinal direction of the light source, the luminance distribution of the light source is not flat, or the brightness of light emitted from the light exit surface of the light guide plate. In the case where the distribution is not flat or the like, the arrangement interval of the plurality of light sources may be changed, that is, the width of each light guide plate may be adjusted according to the arrangement position. For example, parallel to the light exit surface If the brightness increases from the end of the light guide plate toward the center in the direction perpendicular to the longitudinal direction of the light source, as shown in the lower part of FIG. 38, the light exit surface 18a of the light guide plate 18 In a direction parallel to and perpendicular to the longitudinal direction of the light source 12, the distance between the light sources 12 may be narrower as the center of the light guide plate 18 is further away.

[0118] Further, the light exit surface of the light guide plate is formed into a curved surface shape having a curved cross-sectional shape in a plane perpendicular to the longitudinal direction of the light source, and is formed in a direction parallel to the light exit surface and perpendicular to the longitudinal direction of the light source. In this case, the luminance distribution of the light source or the light exit surface force of the light guide plate may also make the luminance distribution of the emitted light flat. For example, if the brightness increases from the end of the light guide plate toward the center in a direction parallel to the light exit surface and perpendicular to the longitudinal direction of the light source, the light guide plate 18 is moved to the light source as shown in FIG. A cross-sectional shape in a plane orthogonal to the longitudinal direction of the light source 12 is convex to the side of the light source 12 as an R-shaped curved surface in a direction parallel to the light exit surface of the light guide plate 18 and orthogonal to the longitudinal direction of the light source. Then, the shape may be such that the distance between the light source disposed on each light guide plate and the liquid crystal display panel 4 increases from the end of the light guide plate toward the center.

When the luminance distribution near the longitudinal end of the light source is different from that of the other portions, as shown in FIG. 40A, the end 402 of the light guide plate 18 in the longitudinal direction of the light source 12 is A shape having a predetermined angle of inclination from a direction perpendicular to the light exit surface may be used. Furthermore, when the luminance distribution near the end of the light guide plate in a direction parallel to the light exit surface and perpendicular to the longitudinal direction of the light source is different from that of the other portions, as shown in FIG. 40B and FIG. The end of the light guide plate in a direction parallel to the surface and perpendicular to the longitudinal direction of the light source may have a shape having a predetermined angle of inclination from a direction perpendicular to the light exit surface of the light guide plate. In this way, by adjusting the shape of the light guide plate according to the light source, uniform light can be emitted from the light exit surface.

Further, when it is possible to increase the thickness of the knock light, for example, as shown in FIG. 41A, the light exit surface of the light guide plate 18 is formed into a gently curved surface having a curved cross-sectional shape in the longitudinal direction of the light source 12. Alternatively, as shown in FIG. 41B, a minute height rib 412 extending in a direction orthogonal to the longitudinal direction of the light source 12 may be provided on the light exit surface of the light guide plate 19 as shown in FIG. 41B. This can prevent the light guide plate from bending in a direction perpendicular to the longitudinal direction of the light source. Further, the rib 412 is provided between the light guide plate 18 and a sheet-like member constituting a backlight unit such as a diffusion sheet. The liquid crystal display panel also functions as a spacer for forming a predetermined gap, thereby making the illuminance of the light illuminating the liquid crystal display panel more uniform.

[0121] Further, as shown in Fig. 42, a reflection sheet is attached to the inclined surface of the light guide plate 18, and the reflection sheet is extended to the parallel groove of the light guide plate to regulate the position of the light source or to temporarily fix the light source. Or just a little.

By regulating the position of the light source, the position of the light source with respect to the light guide plate becomes constant, and luminance unevenness can be reduced. Further, by temporarily fixing the light source, the assemblability of the knock light unit can be improved.

[0122] As shown in Fig. 42, when a cold cathode tube is used as a light source, an elastic member that embraces the cold cathode tube, for example, a transparent O-ring is attached to the end of the cold cathode tube. It may be provided. By providing such an elastic member, the elastic member acts as a cushioning material. Therefore, when the cold cathode tube is arranged in the parallel groove of the light guide plate, the cold cathode tube collides with the parallel groove and the cold cathode tube is turned on. Damage can be prevented. Further, by fixing the elastic member to the cold cathode tube, handling in the assembly and manufacturing process is improved. Furthermore, as shown in FIG. 42, by providing electrode covers at both ends of the cold cathode tube, it is possible to easily attach and detach the cold cathode tube from the housing that houses the knock light unit.

[0123] Further, by holding the longitudinal end of the cold-cathode tube with a sponge or the like and closing the longitudinal side surface of the parallel groove of the light guide plate, dust enters the parallel groove of the light guide plate from the outside. In addition to preventing the cold cathode tube from entering, the cold cathode tube may be prevented from being partially cooled. As described above, the light guide plate, the planar lighting device and the liquid crystal display device using the same according to the present invention have been described in detail. However, the present invention is not limited to the above-described embodiments, and the present invention is not limited thereto. Of course, various improvements and changes may be made, of course.

Industrial applicability

As described in detail above, the light guide plate of the present invention can accommodate the light source in the parallel groove formed therein, so that it can be made thinner and lighter than before, and When the relationship between the angle Φ 1 (rad) of the inclined surface with respect to the surface and the distance W between the two extreme ends satisfies Φ 1 XW ≤ 200 (mm), the cross-sectional shape of the parallel groove is By narrowing the tip toward the surface, it is possible to reduce the peak of illuminance or brightness, and to increase the light output surface power. It is possible to emit uniform, less uneven and higher-luminance illumination light, and furthermore, even if a plurality of light guide plates are connected, it is possible to reduce the occurrence of bright lines at the connection portions. As a result, in the light guide plate of the present invention, the size of the light exit surface of the light guide plate can be made larger. In addition, the spread illuminating device of the present invention is thin and lightweight, can be manufactured at lower cost, can emit more uniform, less uneven, and higher-luminance illumination light. In addition, the lighting surface can be made large, so that it can be applied to a liquid crystal display device such as a wall-mounted television.

Further, the liquid crystal display device of the present invention is thin and lightweight, can be manufactured at lower cost, can provide a more uniform, less uneven, and higher-luminance display. The screen can be large and can be a wall-mounted type such as a wall-mounted television.

Claims

The scope of the claims

[1] a transparent light guide plate,

A rectangular light exit surface;

A pair of thick portions parallel to one side of the rectangular light exit surface and positioned at a substantially central portion of the rectangular shape, and located outside the thick portion in a direction orthogonal to the one side and parallel to the thick portion. A pair of thin ends formed,

A parallel groove formed therein, in which a rod-shaped light source is housed and positioned between the pair of thick portions and opposite to the side on which the rectangular light emission surface is formed, and parallel to the one side;

The thick portion is symmetrical with respect to a plane including the axis of the rod-shaped light source and perpendicular to the rectangular light exit surface, and the thick portion force is directed to the pair of thin ends in a direction orthogonal to the one side. And a pair of inclined rear portions forming an inclined rear surface inclined with respect to the rectangular light exit surface, so that

The parallel groove is symmetrical in its cross section in the orthogonal direction with respect to a center line perpendicular to the rectangular light exit surface of the parallel groove toward the rectangular light exit surface. It is thin,

A light guide plate satisfying a relational force Φ 1 XW ≦ 200 (mm) between an angle Φ 1 (rad) of the inclined back surface with respect to the rectangular light exit surface and a distance W between both end portions.

[2] A plurality of the light guide plates according to claim 1, wherein one of the pair of thin end portions is connected to each other such that the rectangular light exit surfaces are in the same direction. Light guide plate.

[3] A light guide plate having a structure in which the light guide plate according to claim 1 is used as a repeating unit, and a connecting portion of the plurality of repeating units is arranged seamlessly and integrally in parallel.

[4] Furthermore, the cross section perpendicular to the parallel groove in the connecting portion when a plurality of connecting portions are connected is an arc shape

4. The light guide plate according to claim 1, wherein the light guide plate has a polygonal shape.

5. The light guide plate according to claim 4, further comprising an angle φ 2 (rad) force Φ 2 <Φ 1 of the inclined rear surface with respect to the rectangular light exit surface in the connection portion when a plurality of the connection portions are connected.

[6] In the cross-sectional shape of the parallel groove, the tip portion is located forward of the center of the rod-shaped light source. The light guide plate according to any one of claims 1 to 5, wherein an angular force with respect to a perpendicular directed to the rectangular light exit surface is a portion that is within 90 degrees on both sides.

[7] Claims 1 to 6, wherein the cross-sectional shape of at least the distal end portion of the parallel groove has a part of two straight lines or curves symmetric with respect to the center line, each having one sharp intersection point intersecting with each other. The light guide plate according to any one of the above.

[8] The light guide plate according to any one of claims 1 to 7, wherein a cross-sectional shape of at least the distal end portion of the parallel groove or a cross-sectional shape of the parallel groove is triangular.

[9] The light guide plate according to claim 7, wherein the two curves each having a cross-sectional shape of at least the end portion of the parallel groove are convex or concave toward the center of the parallel groove.

[10] A circle, an ellipse, or a parabola, wherein at least the cross-sectional shape of the tip portion of the parallel groove or the two curves that are the cross-sectional shape of the parallel groove are convex or concave toward the center of the parallel groove. 10. The light guide plate according to claim 7 or 9, which is a part of a hyperbola.

[11] The cross-sectional shape of the top portion of the tip portion of the parallel groove is a shape in which the two symmetrical straight lines or curves are connected to each other by a symmetrical straight line or a curve with respect to the center line before intersecting. 7 to: The light guide plate according to any of L0.

12. The guide according to claim 11, wherein a cross-sectional shape of the top portion of the distal end portion of the parallel groove has a portion parallel to the rectangular light exit surface in which the sharp intersection point is chamfered. Light board.

[13] The cross-sectional shape of at least the tip portion of the parallel groove or the cross-sectional shape of the parallel groove is triangular, and the cross-sectional shape of the top portion of the tip portion of the parallel groove is different from the center line. 13. The light guide plate according to claim 11, wherein the light guide plate has a symmetrical trapezoidal shape.

14. The cross-sectional shape of the top portion of the tip portion of the parallel groove is a curved shape that is convex or concave with respect to the rectangular light exit surface and is symmetric with respect to the center line. Light guide plate.

[15] The cross-sectional shape of the top portion of the tip portion of the parallel groove is a circle, an ellipse, a parabola, or a hyperbola in which the one point of intersection is rounded symmetrically with respect to the center line. The light guide plate according to claim 11.

[16] The cross-sectional shape of at least the tip portion of the parallel groove is an ellipse or a part of a hyperbola. The light guide plate according to any one of claims 1 to 3, wherein

[17] A light guide plate comprising the light-transmitting resin according to any one of claims 1 to 16,

The distance from a plane perpendicular to the rectangular light emitting surface and including the central axis of the rod-shaped light source to the end face of the thin end portion is L (mm), and the rectangular light emission is performed from the center of the rod-shaped light source. The distance parallel to the plane and the intersection with the inclined back surface is ΔL (mm), the light transmittance of the light transmitting resin is t%, and the direction perpendicular to the rectangular light exit surface from the intersection is When the distance to the rectangular light exit surface in the above is defined as D (mm), the following equation is obtained.

t = {l -kl X (D / L- A L)} X 100

0 <kl≤2

A light guide plate characterized by satisfying the following.

[18] The light guide plate according to any one of [1] to [17], wherein the total light flux amount on the light exit surface when the light incident from the rod-shaped light source exits from the exit surface is I.

BLU, the total luminous flux on the rod-shaped light source surface

When CFL is used, the surface force perpendicular to the rectangular light exit surface and including the central axis of the rod-shaped light source is expressed by the following formula: L (mm) to the end surface of the thin end portion: L = k2 X (I / \)

CFL BLU

l≤k2≤160

A light guide plate characterized by satisfying the following.

[19] The light guide plate according to any one of claims 1 to 18, wherein a top portion of the tip portion of the parallel groove is a gravel surface.

[20] The light guide plate according to any one of claims 1 to 19, wherein the rectangular light exit surface has a halftone dot at a portion corresponding to a top of the tip portion of the parallel groove.

[21] The light guide plate according to any one of claims 1 to 20,

A rod-shaped light source housed in the parallel groove of the light guide plate;

A reflector provided behind the rod-shaped light source so as to close the parallel groove, and a reflection sheet attached to the inclined rear surface of the inclined rear portion on both sides of the thick portion of the light guide plate. Surface illumination device.

[22] The planar lighting device according to claim 21,

A light diffusing sheet disposed on the rectangular light exit surface of the light guide plate. Area lighting device.

23. The spread illuminating apparatus according to claim 22, further comprising a prism sheet disposed between the rectangular light exit surface of the light guide plate and the diffusion sheet.

[24] In a first portion corresponding to the parallel groove of the rectangular light exit surface, a peak value of relative illuminance or relative luminance formed by the emission light of the rod-shaped light source force stored in the parallel groove. The ratio of the relative illuminance or relative luminance formed by the emitted light in the second portion corresponding to the inclined back surface portion to the average value is allowed between the rectangular light emitting surface of the light guide plate and the diffusion sheet. 24. The spread illuminating device according to claim 22 or 23, wherein the spread illuminating device is set according to an interval to be set or a thickness allowed for the spread illuminating device.

[25] A knock light unit which also has the power of the planar lighting device according to any one of claims 21 to 24, a liquid crystal display panel arranged on a light emission surface side of the knock light unit, and the backlight unit and A liquid crystal display device comprising: a driving unit that drives the liquid crystal display panel.