JP4403121B2 - Light guide plate and backlight device - Google Patents

Description

  The present invention relates to a light guide plate for spreading light from a light source over the entire light emitting surface and emitting light, and a backlight device using such a light guide plate.

  Recently, as a light source for a backlight of a liquid crystal display device, a light emitting diode element (LED) or a cold cathode tube is used to generate light, and light from the light emitting diode element or the cold cathode tube is emitted in a planar shape. The device is used. In such a surface light-emitting device, light-emitting diode elements and the like are usually arranged on one side surface of the light guide plate, and the light incident from the side surface is reflected by one main surface of the light guide plate and faces the opposite side. Ejected from the main surface. A plurality of dots for reflection are formed on one main surface of the light guide plate that performs reflection, and light incident from the side surface is reflected by the plurality of dots to the exit surface.

  As a light guide plate in which such dots for reflection are formed, the dots are arranged so that a band-like area defined as an area having a constant distribution density is formed, and there is an interval formed by the dots in each band-like area. A technique is known in which generation of bright lines is suppressed by setting the area different from the adjacent band-like areas (see, for example, Patent Document 1). As a light diffusing dot pattern on the reflection surface of the light guide plate, there is also known a technique in which the area of the dots is sequentially enlarged as the distance from the light source increases, and the area for light diffusion in a region further away from the light source is increased. (For example, refer to Patent Document 2). Further, there is also known a configuration in which a light guide plate itself having a slope is adopted so that light emitted from the side surface can be reflected at a dispersed position on the exit surface and the entrance surface (see, for example, Patent Document 3). .) In addition, there is also known a technique of forming a V-shaped groove that is thin at the central portion to solve the problem that light does not reach the central portion (see, for example, Patent Document 4).

JP 2003-43266 A JP-A-8-271893 JP-A-6-314069 JP 2001-228477 A

  6 to 9 are a plan view and a cross-sectional view showing an example of a conventional light guide plate. 6 and 7 are examples of the light guide plate 101 in which the shape of one dot is circular, the reflection surface on the back side is an inclined surface, the plate thickness is increased on the side surface 103 side, and the plate is formed on the side surface 104 side. The thickness is reduced. In this light guide plate 101, the side surface 103 side is the side closer to the light source, and the side surface 104 is the side farther from the light source. As for the dots formed on the reflection surface, a relatively small dot 102a is formed on the side surface 103 near the light source, and a relatively large dot 102b is formed on the side surface 104 near the light source.

  8 and 9 show an example of the light guide plate 110 in which the shape of one dot is a pyramid shape. The exit surface on the front surface side is an inclined surface, the plate thickness is increased on the side surface 113 side, and the side surface 114 side is increased. The plate thickness is reduced. In this light guide plate 111, the side surface 113 side is the side close to the light source, and the side surface 114 is the side far from the light source. As for the dots formed on the reflection surface, a relatively small pyramidal dot 112a is formed on the side surface 113 near the light source, and a relatively large pyramidal dot 112b is formed on the side surface 114 near the light source. .

  The light incident from the side surface is reflected by the circular or pyramidal dots 102 and 112 to the output surface side. In particular, the dot formed in a portion far from the light source has a relatively large area, and light The amount of diffusion is also designed to increase, and thus functions to compensate for a shortage of light in a portion far from the light source.

  In the above-described technique, the area of the dots used for light diffusion is increased as the distance from the light source increases, so that irregular reflection is increased, and as a whole, the shortage of light in the portion away from the light source is compensated. However, for example, when processing the light guide plate shown in FIG. 6 to FIG. 9 or the light guide plate having a slope as shown in Patent Document 3, either the slope side or the face facing the slope becomes the machining surface, Compared with the case of processing on a flat surface, the number of processes is increased and it is not easy to maintain high processing accuracy. In addition, the inclined surface and the transparent synthetic resin plate on one side of the plate material are more expensive than the flat resin plate. There is also a problem that product prices increase and market competitiveness declines.

  Accordingly, in view of the above technical problems, the present invention provides a light guide plate that can sufficiently perform a required function with a component that does not reduce the processing accuracy and is not expensive while compensating for a shortage of light in a portion away from the light source. With the goal. Another object of the present invention is to provide a backlight device using such a light guide plate.

In order to solve the above technical problem, the light guide plate of the present invention is reflected by the side surface on which the light beam introduced from the light source is incident, the reflection surface that reflects the incident light beam, and the reflection surface. A plurality of reflective members having substantially the same depth in a direction away from the side surface of the reflective member. One set of recesses is provided, and each set is provided with a plurality of sets so as to become deeper as the distance from the side surface increases, and the recesses are formed by ultrasonic processing .

  According to the light guide plate of the present invention, the reflective surface is formed such that the plurality of concave portions for reflection become deeper as the distance from the incident side surface increases. When viewed, an effect that does not overlap with each other is obtained, and each concave portion can exhibit a light diffusing function, so that it is possible to reliably compensate for a shortage of light in a portion away from the light source without using a slope.

  According to a preferred embodiment of the present invention, the concave portion can be configured such that the opening area at the reflecting surface increases as the depth increases, and the concave portion is formed by ultrasonic processing, hot press processing, high frequency processing. It is also possible to process and form by a method selected from among the processes. In addition, the reflective concave portion can be configured to form a pair having the same depth with the adjacent concave portion, and the shape of the concave portion is selected from a pyramid shape, a cone shape, a cylindrical shape, or a prism shape. can do.

  Further, the backlight device of the present invention has a light source that generates a required light beam, an emission surface and a reflection surface that face each other, and the light beam introduced from the light source is incident from the side surface of the plate-like member and is reflected. A light guide plate having a plurality of concave portions for reflection which is reflected from the surface to the output surface and becomes deeper as the distance from the incident side surface increases, and a reflective plate disposed to face the reflection surface It is characterized by having.

  According to the backlight device of the present invention, since the light guide plate as described above is used, it is possible to obtain an effect such that they do not overlap each other when viewed from the side surface direction, in the same manner as when formed on a slope. Since each concave portion can exhibit a light diffusing function, it is possible to surely compensate for a shortage of light in a portion away from the light source without using a slope.

  According to the light guide plate of the present invention, it is possible to reliably compensate for a shortage of light in a portion away from the light source without using a slope, and it is not necessary to process the slope or a surface facing the slope, thereby increasing the processing accuracy of a recess or the like. be able to. In addition, it is not necessary to use a synthetic resin plate having a slope as a component, the final product price can be kept low, and the competitiveness in the market can be improved.

  A preferred embodiment of the light guide plate of the present invention will be described with reference to the drawings. 1 and 2 show a cross-sectional view and a plan view of the light guide plate of the present embodiment. As shown in FIGS. 1 and 2, the light guide plate 10 of the present embodiment is composed of a plate-like member made of a transparent synthetic resin having an emission surface 14 and a reflection surface 13 facing each other as main surfaces, and particularly on the bottom side. The reflective surface 13 that is the main surface is formed with a plurality of reflective recesses 12a to 12k that become deeper as the distance from the side surface 16 on which light enters.

  The bottom surface side of the light guide plate 10 is a reflective surface 13, and the concave portions 12 a to 12 k that function as a plurality of reflective dots are arranged in a matrix from the surface of the reflective surface 13 in a substantially quadrangular pyramid shape. Here, the recesses 12a to 12k are formed so as to be deeper as the distance from the side surface 16 on which light is incident becomes longer. For example, the recess 12a closest to the side surface 16 on the incident side is formed with a considerably shallow depth. The concave portion 12k on the side farthest from the side surface 17 on the most incident side is formed to have the deepest depth. The concave portions 12a to 12k are similar in shape, the concave portion 12a closest to the side surface 16 on the incident side has a small formation area, and the concave portion 12k on the side far from the side surface 16 on the incident side and close to the side surface 17 on the opposite side is The formation area is increased. The recesses between the recesses 12a and 12k are formed such that the formation area increases and the depth increases as the distance from the side surface 17 increases. A broken line 15 is an asymptote in the depth direction, and is formed so as to be inclined with respect to the reflecting surface 13 which is a bottom surface in accordance with a tendency that the concave portions 12a to 12k become deeper gradually.

  Each of the recesses 12a to 12k has a similar pyramid shape, but the shape of the recess may be a columnar shape such as a cylinder, a bell shape, or a prism, or another pyramid shape such as a cone, a triangular pyramid, or a hexagonal pyramid. Or a combination of them. Further, the positions of the recesses 12a to 12k are not limited to those arranged in an orderly manner in a matrix. For example, the recesses are formed near the center of the reflection surface or in a region far from the side surface on which the light is incident so that the distribution of the reflected light is uniform. A pattern in which 12a to 12k are densely arranged may be used. Moreover, as what is formed in a reflective surface, you may form not only the reflective dot which consists of a recessed part but the groove | channel for reflection, the protruding part etc. which formed the recessed part continuously.

  Examples of the material of the light guide plate 10 include polyester resin, amorphous polyester resin, acrylic resin such as polymethyl methacrylate (PMMA), polycarbonate resin, polystyrene resin (PS), styrene / acrylonitrile resin (SAN), urethane resin, cyclo resin. Use various transparent polymer materials such as olefin resin, alicyclic polyolefin resin, cyclic polyolefin resin, alicyclic acrylic resin, amorphous fluororesin, epoxy resin, polyimide resin, polyamide resin, vinyl ester resin, etc. It may be a combination of these modified materials and a plurality of resin materials. Moreover, you may have a structure which contains a fluorescent material in a part or whole surface of the light-guide plate 10. FIG.

  The surface side of the light guide plate 10 is an emission surface 14, and light is emitted in a planar shape from the emission surface 14. On the light output surface 14 of the light guide plate 10, a protrusion or the like that functions like a lens obtained by curing a photocurable resin may be formed. It is also possible to increase the light scattering effect by applying surface processing to the reflecting surface 13 and the emitting surface 14 of the light guide plate 10 to form, for example, a satin surface.

  The recesses 12a to 12k formed in the reflecting surface 13 on the bottom surface side of the light guide plate 10 can be formed by, for example, uneven processing by ultrasonic rolls or ultrasonic processing, and are formed by melting by local heating. . Moreover, you may make it process using the pressing member etc. which made high temperature using the high frequency for formation of the recessed part 12. FIG. In order to gradually change the depth of the concave portion, the shape of the convex portion to be embossed may be changed gradually, and control is performed while gradually changing the voltage and current applied to the heater built in the heat roll. You may do it. Further, in order to gradually change the depth of the recess, control may be performed while gradually changing the voltage and current applied to the ultrasonic processing and high frequency processing apparatuses.

  FIG. 3 shows an image display device configured by incorporating a light guide plate 20 having concave portions 24a to 24k that are deepened as the distance from the side surface 16 on which light enters. In this image display device, a light source 21 such as an LED array or a cold cathode tube configured by arranging a plurality of LEDs is arranged on the side surface thereof, and the side of the light source 21 opposite to the side on which the light guide plate 20 is disposed. A reflective member or cover 22 is attached in such a shape as to cover the peripheral surface. The light guide plate 20 has a reflection surface side as a bottom surface side and an emission surface side as a surface side.

  On the reflective surface side of the light guide plate 20, prismatic concave portions 24 a to 24 k that function as a plurality of reflective dots are formed as described above, and these concave portions 24 a to 24 k become deeper as the distance from the light source 21 increases. In other words, the height from the bottom surface is increased as the distance from the light source 21 increases. Further, a reflecting plate 23 is attached to the bottom side of the reflecting surface. The reflection plate 23 has a function of reflecting the light emitted from the light guide plate 20 to the bottom surface side toward the light guide plate 20 side, and is configured by, for example, a resin plate bonded with a metal foil or the like.

  A prism sheet 25 is provided on the light exit surface side of the light guide plate 20, and a liquid crystal panel 26 is provided on the prism sheet 25 for arranging color cells in a matrix to display color or black and white according to a required image signal. It has been. The portion excluding the liquid crystal panel 26 functions as a backlight device. In the case where sufficient light is diffused by the prism-shaped concave portions 24a to 24k and the in-plane uniformity of the planar light beam incident on the liquid crystal panel 26 is sufficient, the prism sheet can be omitted without providing a prism sheet.

  In the image display device having such a structure, light from the light source 21 is incident from one side surface of the light guide plate 20, and a part of the incident light from the side surface is emitted by the recesses 24 a to 24 k formed on the reflection surface. Is reflected from the light guide plate 20 and emitted from the light guide plate 20 toward the liquid crystal panel 26. At this time, the recesses 24a to 24k formed on the reflection surface can surely compensate for the light quantity shortage particularly in the region far from the light source 21 due to its depth and size, so that a uniform surface emission distribution can be realized as a whole. . Further, when such a light guide plate 20 is incorporated as one component of the image display device, there is no portion formed as an inclined surface, so that the assembly accuracy when the components are stacked is also improved.

  FIG. 4 is a cross-sectional view of a light guide plate showing a modification of the previous embodiment. The light guide plate 30 shown in FIG. 4 is made of a plate-shaped member made of a transparent synthetic resin having the emission surface 34 and the reflection surface 33 facing each other as main surfaces, and in particular, the reflection surface 33 that is the main surface on the bottom surface side includes A plurality of reflective recesses 32a to 32k are formed which become farther away from the side surface 36 where the light enters and approach the side surface 37 on the opposite side. Each of 32a to 32k is a prismatic or cylindrical recess. The concave portion 32a on the side closest to the side surface 36 on the incident side is formed to have a considerably shallow depth, and the concave portion 32k on the side farthest from the side surface on the most incident side is formed to have a relatively deepest depth.

  In such a light guide plate 30 as well, in the same way as the light guide plate described above, it is possible to reliably compensate for a shortage of light particularly in a region far from the light source, and to achieve a uniform surface emission distribution as a whole. Also, the area occupied by the reflecting surface can be increased in a region far from the light source, as in the above-described light guide plate, and may be the same area regardless of the distance from the light source. .

  FIG. 5 is a cross-sectional view of a light guide plate showing still another modification of the previous embodiment. The light guide plate 40 shown in FIG. 5 is made of a plate-like member made of a transparent synthetic resin having an emission surface 44 and a reflection surface 43 that face each other as main surfaces, and in particular, the reflection surface 43 that is a main surface on the bottom surface side includes: A plurality of prismatic or columnar concave portions 42a to 42d are formed which become farther away from the side surface 46 where light enters and approach the side surface 47 on the opposite side. Each of the respective 42a to 42d forms a group having the same depth by three as illustrated, and in the illustrated example, a group of recesses having four different depths is formed.

  Similarly, in such an example in which a set of recesses having different depths is formed, it is possible to reliably compensate for a shortage of light quantity in a portion away from the light source, and it is not necessary to process the slope or a surface facing the slope. For this reason, it is possible to increase the processing accuracy of the recesses and the like. Further, since it is not necessary to change the processing conditions for the same set of recesses, the processing accuracy can be maintained high, and the production throughput can be increased.

It is sectional drawing of the light-guide plate of one Embodiment of this invention. It is a top view of the light-guide plate of FIG. It is a schematic sectional drawing which shows the image display apparatus using the light-guide plate of embodiment of this invention. It is sectional drawing of the modification of the light-guide plate of one Embodiment of this invention. It is sectional drawing of the other modification of the light-guide plate of one Embodiment of this invention. It is sectional drawing of an example of the conventional light-guide plate. It is a top view of an example of the conventional light guide plate shown in FIG. It is sectional drawing of another example of the conventional light-guide plate. It is a top view of an example of the conventional light guide plate shown in FIG.

Explanation of symbols

10, 20, 30, 40 Light guide plates 12a-12k, 24a-24k, 32a-32k, 42a-42d Recesses 13, 33, 43 Reflecting surfaces 14, 34, 44 Outgoing surfaces 16, 17, 36, 37, 46, 47 Side 21 Light source 23 Reflector 26 Liquid crystal panel

Claims (5)

Comprising a plate-like member having a side surface on which a light beam introduced from a light source is incident, a reflective surface that reflects the incident light beam, and an output surface that emits the reflected light beam facing the reflective surface;
The reflecting surface of the plate-like member is formed as a set of a plurality of reflecting recesses having substantially the same depth in the direction away from the side surface, and the depth increases as the distance from the side surface increases. A light guide plate , wherein a plurality of sets are provided so that the concave portion is formed by ultrasonic processing . The light guide plate according to claim 1, wherein the concave portion is formed by melting the reflection surface of the plate-like member by local heating by the ultrasonic processing.   The light guide plate according to claim 1, wherein the reflection recesses form a set having the same depth together with the adjacent recesses.   The light guide plate according to claim 1, wherein the concave portion has a shape selected from a pyramid shape or a conical shape. A backlight device comprising the light guide plate according to claim 1.