JP2005063913A - Light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate for restraining the occurrence of a dark part at a light guide part side of a light take-in part corresponding to a front part of point light sources and of a bright part at an area between the point light source and itself, by uniformizing the direction and amount of the light incident on the light take-in part through the light guide part. <P>SOLUTION: The light guide plate 14 comprises a light introducing part 18 which diffuses the light incident from the point-like light source 15 and a light outgoing face 23 from which the light incident from the light introducing part 18 is emitted, and a reflecting part 24 which reflects the light incident from the point light source 15 into the lighting part 19 toward the outgoing face 23 is formed. A plurality of projected lines 26 of prism-shape are provided at the outgoing face 23 so as to extend in the direction crossing at right angles the extending direction of the lighting face 25a. A part of the projected lines 26 provided on the outgoing face 23 extends up to the above of the light introducing part 18. The projected lines 26 extended up to the above of the light introducing part 18 extend in the range wider than the range corresponding to the width of each point light source 15. The length of the extended part 26a is formed all in the same length. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a light guide plate, and more particularly to a light guide plate that emits light emitted from a point light source such as an LED (light emitting diode) and emits the light in a planar shape.

  As a liquid crystal display device, there is one in which a surface light source device is disposed as a backlight on the back surface (surface opposite to the display surface) of a liquid crystal display panel (liquid crystal panel). As this type of surface light source device, a device in which a fluorescent tube (cold cathode tube) is arranged along an end surface of a light guide plate formed of a material having high translucency is used. However, as the liquid crystal display device becomes thinner, the diameter of the fluorescent tube needs to be very small, and the fluorescent tube is easily damaged by a small impact. In addition, since a high voltage is required to cause the fluorescent tube to emit light as a light source, there is a problem that a complicated lighting circuit is required. Therefore, instead of a configuration using a fluorescent tube as a light source, the LED is arranged to face the end face of the light guide plate, and light is emitted in a planar shape from the surface of the light guide plate (the face facing the liquid crystal panel). Edge light type (side light type) devices have been proposed. However, since LEDs have strong directivity, it is difficult to make light uniformly incident on a wide light guide plate with a single LED. Therefore, a light guide plate for emitting light from the light guide plate in a uniform plane using one or a small number of LEDs has been proposed (see, for example, Patent Document 1 and Patent Document 2).

The light guide plate described in Patent Literature 1 and Patent Literature 2 includes a square plate-shaped daylighting portion (light emitting portion) and a trapezoidal introduction portion (light guide portion), and the introduction portion penetrates the introduction portion in the thickness direction. A light diffusion hole is formed. A part of the light emitted from the LED light source and incident on the introducing portion is separated into light that is totally reflected by the peripheral surface of the light diffusion hole and light that is transmitted (penetrated) near the center of the light diffusion hole. Thus, the light that has entered the light guide plate is in a state of spreading in the width direction of the light guide plate, so that the luminance distribution of the daylighting unit is made uniform.
JP 2000-149635 A (paragraphs [0023] to [0025] in FIG. 1, FIG. 1) JP 2002-169034 A (paragraphs [0045] to [0049] of the specification, FIG. 1)

  However, in the configurations of Patent Document 1 and Patent Document 2, the light incident on the introduction part from the LED light source has a problem that the amount of light incident on the daylighting part decreases because there is light that passes through the light diffusion hole in the vertical direction. There is. There is also a problem that a dark portion is generated at the end of the daylighting portion side of the portion corresponding to the rear of the light diffusion hole, that is, the front of the LED (point light source).

  The present invention has been made in view of the above problems, and its purpose is to suppress the occurrence of a dark portion at the end portion of the daylighting portion side of the portion corresponding to the front surface of the point light source, and the point shape. An object of the present invention is to provide a light guide plate that can suppress the occurrence of bright portions in a region corresponding to between light sources.

  In order to achieve the above object, the invention according to claim 1 is a light guide plate that receives light emitted from a plurality of point light sources and converts the light into a planar shape, and emits the light. A plate-shaped daylighting unit having an introduction part for diffusing light, an emission surface that is formed continuously with the introduction part, emits light introduced from the introduction part, and a reflection part formed on the back surface on the opposite side. It has. Plural prism-like or lens-like ridges are provided on the emission surface so as to extend in a direction perpendicular to the end surface on the introduction part side of the daylighting part, and a part of the ridges extend to the introduction part. ing.

  In this invention, since the light from the point light source is diffused by the introducing portion, it is easy to guide the light through the entire light guide plate. In addition, since the prism-like or lens-like ridges are formed on the exit surface side of the light guide plate so as to extend in a direction orthogonal to the end face on the introduction portion side of the daylighting portion, incident light can be used without using a prism sheet. Can be efficiently emitted to the front of the emission surface. Since a part of the prism-like or lens-like ridge extends to the introduction part, a part of the light guided between the point light sources in the introduction part is provided in the introduction part. The light is deflected by the ridge and guided to the front of the point light source. The directivity and amount of light incident on the daylighting unit from the introduction unit are made uniform, and the occurrence of a dark portion at the introduction unit side end of the daylighting unit corresponding to the front surface of the point light source is suppressed. It is possible to suppress the occurrence of a bright portion in a region corresponding to between light sources.

  According to a second aspect of the present invention, in the first aspect of the present invention, the ridge extending to the top of the introduction portion is extended in a range wider than the range corresponding to the width of each point light source. Yes. Here, the “width of the point light source” means the width of the portion corresponding to the light emitted in parallel among the light emitted from the point light source. In the present invention, the upper surface of the introduction portion of the light incident on the light extraction portion of the light guide plate through the introduction portion as compared with the configuration in which the ridges extend to the introduction portion in a range narrower than the width of each point light source. It is possible to deflect most of the light reaching the light by the ridges, and it is difficult to produce a dark portion at the end portion side end portion of the daylighting portion corresponding to the front surface of the point light source. It is possible to suppress the occurrence of a bright portion in a region corresponding to between light sources.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the reflection portion formed on the back surface extends in parallel with the end surface and emits the incident light from the emission surface. A plurality of grooves constituting the daylighting surface to be reflected in the direction to be formed are formed. In this invention, the light incident from the end face is reflected by the lighting surface while being guided in the light guide plate toward the end face opposite to the end face, and most of the reflected light is directed to the exit face. The direction of travel is deflected. And it is radiate | emitted through the protruding item | line provided in the output surface. Therefore, the variation in the direction of light emitted from the exit surface can be reduced as compared with the case where dots are provided on the back surface and scattered by the dots.

  According to the present invention, it is possible to suppress the occurrence of a dark portion at an end portion side end portion of the daylighting portion of the portion corresponding to the front surface of the point light source, and to suppress generation of a bright portion in a region corresponding to the point light source. be able to.

(First embodiment)
Hereinafter, a first embodiment in which the present invention is embodied in a light guide plate of a surface light source device used for a sidelight type backlight of a liquid crystal display device will be described with reference to FIGS. 1A is a schematic perspective view showing the relationship between the light guide plate and the point light source, FIG. 1B is a schematic plan view showing the relationship between the introducing portion and the point light source, and FIG. FIG. 2 is a schematic perspective view of a liquid crystal display device. Moreover, Fig.3 (a), (b) is a schematic diagram which shows the effect | action of a lighting surface and a protruding item | line.

  As shown in FIG. 2, the liquid crystal display device 11 includes a liquid crystal panel 12 and a surface light source device 13 serving as a backlight disposed on the back surface (surface opposite to the display surface). The surface light source device 13 includes a light guide plate 14 and a plurality of point light sources 15 arranged at positions facing one end of the light guide plate 14. As the point light source 15, an LED (light emitting diode) is used.

  The surface light source device 13 is located on the opposite side of the liquid crystal panel 12 with the light guide plate 14 interposed therebetween, and a reflective member (reflective sheet) for returning the light leaking from the light guide plate 14 to the light guide plate 14 and using it as outgoing light 16 is provided. A diffusion sheet 17 is disposed between the light guide plate 14 and the liquid crystal panel 12.

  Next, the light guide plate 14 will be described in detail. The light guide plate 14 is made of a highly transparent material such as an acrylic resin. As shown in FIG. 1A and FIG. 2, the light guide plate 14 is formed continuously with the introduction portion 18 that diffuses the light incident from the point light source 15 and the introduction portion 18, and is introduced from the introduction portion 18. And a daylighting unit 19 for emitting the emitted light in a planar shape. A plurality of introduction portions 18 (two are shown in FIG. 1A) are formed adjacent to each other.

  The introduction unit 18 includes an incident unit 20 and a reflection unit 21. As shown in FIG. 1B, the introduction portion 18 is formed in a symmetrical shape that spreads from the light incident side toward the daylighting portion 19 side of the light guide plate 14, and the width K (in the drawing) of the incident side end portion. The length in the left-right direction is larger than the width of the point light source 15. The incident part 20 faces the point light source 15 and is parallel to the plane 22 extending in the width direction of the introduction part 18, and a V-shaped groove 20 b as a diffusion part for diffusing light from the point light source 15. Are alternately repeated at equal intervals. The value of the angle θ formed by the surface constituting the V-shaped groove 20b and the plane 20a in the incident portion 20 is a value between 120 degrees and 150 degrees.

  The reflection part 21 is formed so as to reflect the light diffused by the V-shaped groove 20 b toward the daylighting part 19. The reflection part 21 is planar. The value of the angle β formed by the reflecting portion 21 and the surface 22 extending in the width direction of the introducing portion 18 is a value between 35 degrees and 65 degrees.

  The daylighting unit 19 is formed in a substantially square plate shape, and includes an emission surface 23 that emits light incident from the introduction unit 18, and a reflection unit 24 that is formed on the back surface opposite to the emission surface 23. The reflection part 24 is configured by a plurality of parallel grooves 25 formed so as to extend along a virtual end surface 19a (illustrated in FIGS. 1B and 2) on the introduction part 18 side of the daylighting part 19. . In FIG. 1B, the end face 19a coincides with the face 22.

  In the groove 25, a daylighting surface 25a that rises and inclines from the end surface 19a toward the opposing surface 19b side and a waveguide surface (inclined surface) 25b that inclines and descends from the end surface 19a to the opposing surface 19b side are connected alternately. Is provided. That is, the grooves 25 are formed adjacent to each other so that a cross-sectional shape by a plane orthogonal to the end surface 19a is a sawtooth shape.

  The daylighting surface 25 a is incident on the daylighting unit 19 from the introduction unit 18, and the light that has reached the daylighting surface 25 a comes into contact with the apex of each ridge 26 formed on the exit surface 23, which will be described later (FIG. 3B). ) Is formed at an angle at which the light is totally reflected in the direction of the exit surface 23 at an angle close to a right angle. As shown in FIG. 3A, the groove 25 has a predetermined angle in which the angle θ1 formed by the daylighting surface 25a and a plane parallel to the virtual plane P1 is, for example, 35 ° to 50 °, preferably 40 ° to 45 °. In addition, an angle θ2 formed by the waveguide surface 25b and a plane parallel to the virtual plane P1 is formed at a predetermined angle in a range of 0.3 degrees to 2.5 degrees, for example.

  Plural prism-like ridges 26 are provided on the emission surface 23 so as to extend in a direction orthogonal to the direction in which the daylighting surface 25a extends, that is, in a direction orthogonal to the end surface 19a. Each ridge 26 is formed in the shape of an isosceles triangle in the cross section at the cutting plane orthogonal to the longitudinal direction, and is formed in the same height. Each ridge 26 is formed so that the end face is substantially perpendicular to the virtual plane P1. Moreover, each protruding item | line 26 is formed so that it may mutually adjoin, and the output surface 23 becomes the structure by which the protruding item | line 26 which has a pair of inclined surface extended in the direction orthogonal to the end surface 19a was formed repeatedly. The width of the ridge 26 is formed to a predetermined size in the range of 10 to 500 μm, preferably 50 to 300 μm, and the width of the point light source 15 is formed to 3 mm, for example.

  A part of the ridges 26 provided on the emission surface 23 extends to the introduction portion 18. The ridges 26 extending to the top of the introduction part 18 are extended in a range wider than the range corresponding to the width of each point light source 15 of the introduction part 18. In this embodiment, the lengths of the extending portions 26a are all the same.

  In this specification, the ratio of the size of the point light source 15 and the ridge 26 is different from the actual for convenience of illustration, and the number of the point light sources 15 (the number of the introduction portions 18) is also different from the actual. Only two cages are shown. For convenience of illustration, the protrusion 26 is not shown in FIG.

  The length of the extending portion 26a is the value of the apex angle of the ridge 26, the angle θ1 that the lighting surface 25a forms a plane parallel to the virtual plane P1, and the angle θ2 that the waveguide surface 25b forms a plane parallel to the virtual plane P1. The appropriate length may vary depending on the directivity of the point light source 15. Therefore, the length of the extending portion 26a is set to a length in which light from the point light source 15 is incident on the light guide plate 14 by simulation or test, and the luminance unevenness generated in the daylighting portion 19 is suppressed.

  Next, the operation of the light guide plate 14 configured as described above will be described. For example, as shown in FIG. 2, the light guide plate 14 is used by being incorporated in a surface light source device 13 as a backlight unit of a transmissive liquid crystal display device 11.

  When the point light source 15 is turned on, the light emitted from the point light source 15 enters the light guide plate 14 from the introduction portion 18, and the incident light is emitted from the light exit surface 23 of the light guide plate 14 toward the liquid crystal panel 12. Then, the light enters the liquid crystal panel 12 through the diffusion sheet 17. The user of the liquid crystal display device 11 visually recognizes the display on the liquid crystal panel 12 by the emitted light.

  The operation of the light guide plate 14 will be described in detail. Most of the light emitted from the point light source 15 reaches the incident portion 20. A part of the light reaching the incident part 20 is incident on the introduction part 18 from a plane 20 a parallel to the surface 22 extending in the width direction of the introduction part 18. Most of the light incident on the introduction unit 18 from the plane 20a parallel to the surface 22 extending in the width direction of the introduction unit 18 is refracted so that the traveling direction of the plane 20a approaches a direction perpendicular to the plane 20a. 19 enters.

  On the other hand, the remaining part of the light reaching the incident part 20 is refracted toward the reflection part 21 by the V-shaped groove 20b and is incident on the introduction part 18. And most of the light is reflected in the reflecting portion 21 so as to approach a direction perpendicular to the width direction of the daylighting portion 19. The light reflected by the reflecting unit 21 enters the daylighting unit 19.

  The light incident on the daylighting unit 19 is guided in the daylighting unit 19. Of these, the light that has reached the daylighting surface 25 a is totally reflected in the direction of the exit surface 23 and exits from the exit surface 23 as shown in FIG.

  The light that has entered the daylighting unit 19 from the end surface 19a does not always travel straight toward the daylighting surface 25a, and the light that reaches the daylighting surface 25a is totally reflected by the waveguide surface 25b and the exit surface 23 while being daylighted. There is also light that reaches the daylighting surface 25a after being guided inside. The waveguide surface 25b is formed so as to be inclined downward from the end surface 19a side toward the opposing surface 19b side. For this reason, while repeating the optical waveguide other than the light guided directly toward the daylighting surface 25a, it approaches the direction parallel to the virtual plane P1, and as a result, the daylighting surface 25a efficiently and totally reflects in the direction of the emission surface 23. Can do.

  As shown in FIG. 3B, when the light emitted from the point light source 15 toward the front is compared with the light emitted obliquely from the point light source 15 with respect to the lighting surface 25a, the latter one is compared. After the light is totally reflected by the daylighting surface 25a and proceeds into the ridge 26, the ratio of the light emitted from the surface of the ridge 26 toward the liquid crystal panel 12 is large. This is due to the following reason.

  That is, the light emitted from the point light source 15 to the front is reflected substantially perpendicularly to the virtual plane P1 by the lighting surface 25a, and the light emitted obliquely from the point light source 15 to the virtual plane P1 by the lighting surface 25a. On the other hand, it is reflected obliquely. Since the former light has a large angle with the normal of the slope of the ridge 26, the ratio of the light reflected by the ridge 26 and guided to the inside is large. Since the latter light has a small angle with the normal line of the slope of the ridge 26, the ratio of the light emitted from the ridge 26 to the outside is large. And when it radiate | emits outside from the protruding item | line 26, the advancing direction of the latter light approaches the direction perpendicular | vertical to the virtual plane P1 by the refraction in the slope of the protruding item | line 26. FIG.

  For this reason, in the oblique direction from the point light source 15, when the ridge 26 is present, the ratio of the light emitted to the front surface of the emission surface 23 is increased, and when the ridge 26 is not present, the emission surface is provided. The ratio of the light emitted to the front of 23 is reduced. On the contrary, in the front direction of the point light source 15, when the ridge 26 is present, the ratio of the light emitted to the front of the emission surface 23 is reduced, and when the ridge 26 is not present, the emission surface 23. The ratio of the light emitted to the front of is increased.

  Therefore, depending on the directivity of the point light source 15, the apex angle of the ridges 26, and the values of the angles θ1 and θ2, when the ridges 26 having the same shape and the same length are formed on the light guide plate 14, the adjacent point shapes A region corresponding to the space between the light sources 15 may be a bright portion, and a portion corresponding to the front of the point light source 15 may be a dark portion. This is because, in the daylighting unit 19, light emitted from the point light sources 15 on both sides is guided in a region corresponding to between the adjacent point light sources 15, and a region (part) where the emitted light overlaps is bright. It is because it is easy to become a part.

  However, in this embodiment, a part of the ridge 26 extends to the introduction part 18. Therefore, when the ridge 26 does not extend to the introduction portion 18, the light that has entered the introduction portion 18 from the point light source 15 and has formed a bright portion in a region corresponding to the space between the point light sources 15. However, the light is totally reflected by the slope of the extending portion 26 a and proceeds toward the daylighting portion 19. As a result, the light that has conventionally formed the bright portion is guided to the portion corresponding to the front of the point light source 15, and the portion corresponding to the front of the point light source 15 is suppressed from becoming a dark portion, Occurrence of bright portions in the corresponding region between the point light sources 15 is suppressed.

  Further, since the extending portion 26a exists on the introducing portion 18 in a range wider than the portion corresponding to the front surface of the point light source 15, a part of the light that is obliquely guided in the introducing portion 18 extends. The traveling direction is deflected to the side corresponding to the front of the point light source 15 by being totally reflected by the slope of the extending portion 26a. Accordingly, the direction and amount of light incident on the daylighting unit 19 are further uniformed, and as a result, the occurrence of the dark part and the bright part as described above can be further suppressed.

This embodiment has the following effects.
(1) The light guide plate 14 is incident on the light emitted from the point light source 15 and diffuses the incident light, and is formed continuously from the introduction unit 18 and introduced from the introduction unit 18. And a plate-shaped daylighting portion 19 having a reflection portion 24 formed on the rear surface opposite to the emission surface 23 for emitting the emitted light. Therefore, since the light from the point light source 15 is diffused by the introduction part 18, it becomes easier to guide the light to the entire daylighting part 19 compared to the case where the introduction part 18 is not provided.

  (2) A plurality of prismatic ridges 26 are provided on the emission surface 23 so as to extend in a direction orthogonal to the end surface 19 a on the introduction portion 18 side of the daylighting portion 19, and a part of the ridges 26 extends to the top of the introduction portion 18. It has been extended. Therefore, incident light can be efficiently emitted in front of the emission surface 23 without using a prism sheet. Further, by deflecting a part of the light that enters the daylighting unit 19 of the light guide plate 14 through the introduction unit 18 by the ridges 26 provided on the introduction unit 18, the direction and amount of light are made uniform. It is possible to suppress the occurrence of a dark part at the end of the daylighting unit 19 in the portion corresponding to the front surface of the light source 15 and to suppress the occurrence of a bright part in the region corresponding to the point light source 15. it can. As a result, luminance unevenness is suppressed.

  (3) The ridges 26 extended to the top of the introduction portion 18 are extended in a range wider than the range corresponding to the width of each point light source 15. Therefore, in comparison with a configuration in which the ridge 26 extends to the introduction portion 18 in a range narrower than the width of each point light source 15, out of the light incident on the daylighting portion 19 of the light guide plate 14 through the introduction portion 18. The amount of light that can be deflected by the ridges 26 provided on the introduction portion 18 increases. As a result, it is possible to suppress the occurrence of a dark portion at the end of the daylighting portion 19 corresponding to the front surface of the point light source 15 and the occurrence of a bright portion in a region corresponding to the point light source 15. .

  (4) Since it is not necessary to use a prism sheet, the number of parts constituting the surface light source device 13 is reduced, the number of assembling steps can be reduced, and the manufacturing cost can be reduced. It is necessary to form the ridges 26 on the light guide plate 14. However, since the light guide plate 14 is manufactured by injection molding using a mold, the cost of the mold is slightly increased. However, by manufacturing a large number of light guide plates 14, the number of light guide plates 14 per sheet can be increased. The manufacturing cost can be lower than the sum of the manufacturing cost of the light guide plate without the ridges 26 and the unit price of the prism sheet.

  (5) On the back surface of the daylighting unit 19, a plurality of grooves 25 are formed that constitute the daylighting surface 25a that extends along the end surface 19a and reflects the light incident from the introduction unit 18 in the direction of exiting from the exit surface 23. Yes. Therefore, the variation in the direction of the light emitted from the emission surface 23 can be reduced as compared with the case where dots are provided on the back surface.

  (6) The introduction portion 18 is formed with a concave V-shaped groove 20b in the direction toward the daylighting portion 19 as a diffusion portion for diffusing light from the point light source 15. Therefore, the light from the point light source 15 can be effectively diffused with a simple shape, and the number of steps required for designing and manufacturing the light guide plate 14 can be reduced.

  (7) The surface light source device 13 includes a diffusion sheet 17. Therefore, even when the bright portion cannot be completely prevented in the light guide plate 14, when the light emitted from the light guide plate 14 passes through the diffusion sheet 17 and enters the liquid crystal panel 12, the bright portion cannot be identified with the naked eye. Can be in a state.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. In this embodiment, in addition to the configuration of the first embodiment, the length of the ridges 26 arranged at positions corresponding to between the point light sources 15 is shortened on the introduction part 18 side. This is different from the embodiment. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. FIG. 4 is a schematic perspective view showing the relationship between the light guide plate 14 and the point light source 15 of the second embodiment.

  The length of at least some of the ridges 26 of the ridges 26 arranged at positions corresponding to between the point light sources 15 is formed to be shorter on the introduction portion 18 side. That is, the ridge 26 is formed in a state where one end is retracted from a position corresponding to the end face 19a. In this embodiment, the ridges 26 formed short are not the same length, and as shown in FIG. 4, the ridges 26 (2 in the figure) are arranged at positions corresponding to the center between the adjacent point light sources 15. The individual ridges 26) are formed to be the shortest. And the length of the protruding line 26 arranged on both sides of the protruding line 26 becomes longer as the protruding line 26 is closer to the point light source 15, and is symmetrical about the central protruding line 26 (symmetrical in FIG. 4). It is formed to become. The length of each ridge 26 is the value of the apex angle of the ridge 26, the angle θ1 that the daylighting surface 25a forms with a plane parallel to the virtual plane P1, and the angle θ2 that the waveguide surface 25b forms with a plane parallel to the virtual plane P1. The appropriate length varies depending on the directivity of the point light source 15. Therefore, the length is set such that the luminance unevenness is suppressed by causing light from the point light source 15 to enter the light guide plate 14 by simulation or a test, and eliminating the bright and dark portions generated in the light guide plate 14.

  As described in the first embodiment, light is emitted so as to have uniform brightness over the entire surface of the daylighting unit 19 only by setting the apex angles and the angles θ1 and θ2 of the ridges 26 to specific values. It is difficult to do so. In this embodiment, the ridge 26 provided in the portion corresponding to between the point light sources 15 is formed short in the daylighting portion 19 as described above. As a result, the amount of light emitted from the emission surface 23 is reduced in the region without the ridges 26, and the brightness of the region that is a bright portion is reduced. Therefore, the amount of light emitted from the area where the light emitted from the adjacent point light sources 15 overlaps is reduced, and the area is suppressed from becoming a bright portion. As a result, luminance unevenness as a whole of the daylighting unit 19 is suppressed.

This embodiment has the following effects in addition to the same effects as (1) to (7) of the first embodiment.
(8) The length of at least a part of the ridges 26 among the ridges 26 provided in the portion corresponding to between the point light sources 15 is formed short on the introduction portion 18 side. Accordingly, the amount of light emitted from the region where the light emitted from the adjacent point light sources 15 overlaps is reduced, the region is prevented from becoming a bright portion, and the luminance unevenness of the light guide plate 14 is suppressed.

The embodiment is not limited to the above, and may be embodied as follows, for example.
O When extending the protrusion 26 formed on the lighting part 19 of the part corresponding to the front of each point light source 15 to the introduction part 18, the length of each extension part 26a is not restricted to the same. For example, as shown in FIG. 5A, there are two types of extending portions 26a, and a plurality of extending portions 26a arranged adjacent to the center are formed long, and short extending portions on both sides thereof. A plurality of 26a are arranged adjacent to each other. As shown in FIG. 5B, a plurality of extending portions 26a arranged adjacent to the center are formed long, and short extending portions 26a and long extending portions 26a are alternately arranged on both sides thereof. It is good also as a structure to be made.

  As shown in FIG. 6 (a), a plurality of adjacent extending portions 26a are formed at the shortest position at a position corresponding to the center of the point light source 15, and are arranged on both sides of the extending portion 26a. The length of the extended portion 26a is longer as the extended portion 26a is farther from the center, and the number of the extended portions 26a having the same length is reduced, and is symmetrical about the central extended portion 26a. You may form in. Moreover, as shown in FIG.6 (b), the extension part 26a arrange | positioned in the position corresponding to the center of the point light source 15 is formed the longest, and the extension part arrange | positioned at the both sides of the extension part 26a The length of the extended portion 26a far from the center may be shortened, and the length of the extended portion 26a may be symmetric with respect to the extended portion 26a at the center. Moreover, as shown in FIG.6 (c), the extension part 26a arrange | positioned in the position corresponding to the center of the point light source 15 is formed shortest, and the extension part arrange | positioned at the both sides of the extension part 26a The length of the extended portion 26a far from the center may be longer, and the length of the extended portion 26a may be symmetric with respect to the extended portion 26a at the center. In FIGS. 6A to 6C, illustration of the ridge line of the extending portion 26a is omitted.

  ○ The length of the extension part 26a corresponds to the directivity of the point light source 15, the apex angle of the ridge 26, the angles θ1, θ2, etc., and the arrangement of the extension parts 26a having different lengths is appropriate. A pattern is set. Accordingly, the length and the arrangement pattern of the extending portions 26a are set as appropriate. The range in which the extending part 26 a is provided may be a range narrower than the width of the point light source 15.

  ○ As for the pattern for changing the length of the ridge 26 corresponding to between the adjacent point light sources 15, the ridge 26 located at the center is the shortest as in the second embodiment, and the ridges are arranged on both sides. The pattern is not limited to the pattern in which the stripes 26 become gradually longer. For example, all the short ridges 26 have the same length, every other pattern has a different length, or there are two types of lengths. Various modifications can be made in the same manner as the arrangement pattern of the extending portions 26a, such as a pattern longer than the protruding ridges 26. That is, the appropriate value of the length of the ridge 26 also varies depending on how the luminance unevenness is generated in a state where all the ridges 26 are arranged over the entire length of the daylighting portion 19, and the ridge 26 Depending on the apex angle, width, and values of the angles θ1 and θ2.

  ○ In the second embodiment, the length of the ridge 26 arranged at a position corresponding to between the point light sources 15 is shortened on the introduction part 18 side, but without changing the length of the ridge 26, A part of the ridge 26 may be cut out on the introduction part 18 side. For example, as shown to Fig.7 (a), it is good also as a shape where the edge part of the protruding item | line 26 was cut | disconnected by the plane which cross | intersects the protruding item | line 26 in the upper end of the end surface 19a of the lighting part 19. FIG. That is, the ridges 26 are slopes 26b that are inclined so that the end face on the introduction part 18 side is not parallel or flush with the end face 19a and the top part of the isosceles triangle approaches the facing face 19b side. Then, by changing the angle formed between the intersecting plane and the end face 19a, the area of the slope 26b of the ridge 26 is changed, and the same effect as when the length of the ridge 26 is changed is obtained. For example, if the area of the slope 26b is increased, the same effect as when the length of the ridges 26 is shortened can be obtained.

  O The notch shape at the time of notching the edge part of the protruding item | line 26 is not restricted to the shape cut | disconnected by the plane which cross | intersects the protruding item | line 26 in the upper end of the end surface 19a of the lighting part 19. FIG. For example, as shown in FIG. 7 (b), the end is cut by a surface parallel to the bottom surface and a surface parallel to the end surface 19a, or as shown in FIG. It is good also as a shape cut | disconnected by the plane which cross | intersects. Moreover, as shown in FIG.7 (d), the shape cut | disconnected by the downward convex curved surface which cross | intersects the protruding item | line 26 in the upper end of the end surface 19a of the lighting part 19, or as shown in FIG.7 (e) It is good also as a shape cut | disconnected by the convex curved surface which cross | intersects the protruding item | line 26 in the middle of the end surface 19a of the item | strip | row 26. FIG. Moreover, as shown in FIG.7 (f), it is good also as a shape cut | disconnected by the convex curved surface which cross | intersects the protruding item | line 26 in the upper end of the end surface 19a of the lighting part 19. FIG.

○ Instead of shortening the length of the extending part 26a, a part of the extending part 26a may be cut out. The shape of the notch can be arbitrarily selected from the various shapes described above.
The incident part 20 provided in the introduction part 18 has alternately a plane 20a parallel to the surface 22 extending in the width direction of the introduction part 18 and a V-shaped groove 20b as a diffusion part for diffusing the light from the point light source 15. For example, the V-shaped groove 20b may be continuously repeated.

  The ridge 26 is not limited to a prism having an isosceles triangle cross section, and may be a prism having another cross sectional shape, or may be a lens without being limited to a prism. For example, as shown in FIG. 8A, each ridge 26 has its apex located on the virtual plane P <b> 1, and the surface of each ridge 26 has a convex curved surface on the back side of the daylighting unit 19. You may form in a shape. Therefore, in the ridge 26, the angle formed between the surface of the groove 27 existing between the adjacent ridges 26 and the virtual plane P1 in contact with the apex of each of the ridges 26 is in contact with the surface of the groove 27. The side closer to the back surface is formed to be smaller. Since the light emitted from the point light source 15 and incident on the daylighting unit 19 has a spread, the angle at which it is totally reflected by the daylighting surface 25a varies depending on the location. As a result, when the ridge 26 is a prism, that is, when the emission surface 23 is a flat surface, light incident on the lighting surface 25a at a specific angle is emitted to the front of the light guide plate 14 when emitted from the ridge 26. Therefore, bright lines are easily generated.

  However, when the ridge 26 is a lens whose surface is formed in a shape in which a convex curved surface is continuous with the rear surface side of the daylighting portion 19, the two inclined surfaces 26c of each ridge 26 are each composed of one curved surface. In addition, the angle formed between the surface in contact with the surface constituting the inclined surface 26c and the virtual plane P1 is formed so that the side closer to the back surface becomes smaller. As a result, in the case of the prism, not only the light incident on the inclined surface 26c at a specific angle that refracts and proceeds toward the front of the daylighting unit 19, but also the light emitted from the front of the light having a angle other than the specific angle is the ridge 26. Exists within.

  In addition, light that is not reflected by the lighting surface 25a but is incident on the inclined surface 26c with a small angle with the virtual plane P1 has a convex surface on the back surface 26 because the surface of the ridge 26 is convex on the back surface side. Only the region where the angle formed with the plane P1 is small and does not correspond to the region where the angle formed with the virtual plane P1 is large. Therefore, light incident on the inclined surface 26c in a state where the angle formed with the virtual plane P1 is small is totally reflected to the back surface side without passing through the inclined surface 26c. After being reflected to the back surface side, it is reflected by the waveguide surface 25b and enters the inclined surface 26c at a large angle, and is emitted so as to proceed toward the front of the daylighting unit 19. Therefore, the light emitted without going to the front of the daylighting unit 19 is reduced, and the efficiency is improved.

  ○ When the ridge 26 is formed in a lens shape, the surface thereof is not limited to a shape in which a convex curved surface is continuous on the back side of the daylighting portion 19 as shown in FIG. In this case, the angle formed between the surface that is in contact with the surface constituting the slope 26c and the virtual plane P1 does not have to be smaller as the side closer to the back surface. For example, as shown in FIG. 8B, the shape of the ridge 26 is not limited to a shape in which a convex curved surface is continuous on the back surface side of the daylighting unit 19, but a concave curved surface on the back surface side on the tip side. It may be a configured shape.

  The ridges 26 may have a shape in which the slope 26c is configured by only a plurality of planes having different angles with the virtual plane P1, or a shape in which the slope 26c is configured by a plane and a curved surface. Even in these configurations, substantially the same effect can be obtained as in the case where the entire slope 26c has a shape in which convex curved surfaces are continuous on the back surface side of the daylighting unit 19.

  In the case where the ridges 26 are formed in a lens shape, the shape is not limited to the shape having the inclined surface 26c formed on the back surface side of the light guide plate 14 but a concave curved surface on the back surface side such as a semicircular cross section. It is good also as the formed shape.

  O When manufacturing the light guide plate 14, not only injection molding using a mold, but also adjustment of suppression of luminance unevenness may be performed by cutting the protrusion 26 of the intermediate product that has been injection molded. That is, the apex angle of the ridge 26, the angle θ1 formed by the daylighting surface 25a with the plane parallel to the virtual plane P1, the angle θ2 formed with the plane parallel to the virtual plane P1 and the directivity of the point light source 15 An appropriate length of the ridge 26 corresponding to the above is obtained in advance by simulation or test, and injection molding is first performed so that the length is slightly longer than that value. Next, light is incident on the light guide plate 14 from the point light source 15 and the light emission state from the emission surface 23 is observed. And when the suppression state of luminance unevenness is insufficient, the extending portion 26a on the introduction portion 18 is shortened, or the ridge 26 is cut with a blade so as to cut out a part thereof, thereby Adjust and finish so as to suppress uneven brightness. In this case, the light guide plate 14 in which luminance unevenness is suppressed can be reliably manufactured. The same effect can be obtained not only in the adjustment of the extending part 26a on the introduction part 18 but also in the case of the ridge 26 located on the daylighting part 19 corresponding to between the point light sources 15.

  ○ The thickness of the daylighting unit 19 is not constant when viewed macroscopically, but is substantially wedge-shaped and gradually thickened from the end surface 19a side toward the opposing surface 19b side when viewed macroscopically. It may be formed.

  The configuration in which the light incident from the introduction unit 18 is emitted from the emission surface 23 of the lighting unit 19 is not limited to the configuration in which the reflection unit 24 having the configuration in which the lighting surface 25a and the waveguide surface 25b are continuous in a sawtooth shape is provided on the back surface. For example, you may provide the lighting means using volume scattering. The daylighting means using volume scattering means light (visible light) by dispersing bubbles or beads made of a material having a refractive index different from that of the material of the light guide plate 14 in a highly transparent material constituting the light guide plate 14. Means having a function of reflecting or refracting. A reflective sheet is disposed on the back side of the daylighting unit 19. When this configuration is adopted, the daylighting portion 19 is preferably formed in a substantially wedge shape whose thickness gradually decreases from the end surface 19a side to the opposing surface 19b side when viewed macroscopically.

  The diffusion sheet 17 may be omitted from the surface light source device 13. The provision of the diffusion sheet 17 can reduce the luminance unevenness of the entire emission surface of the surface light source device 13. However, depending on the definition of the display unit required for the display device using the surface light source device 13, even if the diffusion sheet 17 is omitted, it is possible to suppress the brightness unevenness from being noticed.

  The liquid crystal display device 11 uses the transmissive liquid crystal panel 12 and uses the surface light source device 13 as a front light as shown in FIG. 9 as well as the configuration using the surface light source device 13 as a backlight. In addition, a configuration using a reflective liquid crystal panel 28 may be employed. Also in this configuration, the emission surface 23 is provided on the side facing the liquid crystal panel 28. However, unlike the configuration used as a backlight, the reflecting member 16 is not provided outside the reflecting portion 24. When the outside of the liquid crystal display device 11 is bright, external light is incident from the reflection unit 24 side of the daylighting unit 19, passes through the daylighting unit 19, is emitted from the exit surface 23, and irradiates the liquid crystal panel 28. The light that irradiates the liquid crystal panel 28 is reflected by the liquid crystal panel 28, enters the daylighting unit 19 again, passes through the light guide plate 14, exits from the surface opposite to the exit surface 23 (reflecting unit 24), and is visually recognized by the eyes. The A large number of ridges 26 are formed on the exit surface 23. By narrowing the width of the ridges 26, the image on the liquid crystal panel 28 can be normally visually confirmed. When the external environment is dark, the point light source 15 is turned on, and light incident from the introduction unit 18 is emitted from the emission surface 23 in the same manner as in the above embodiment, and illuminates the liquid crystal panel 28.

The following technical idea (invention) can be understood from the embodiment.
(1) A surface light source device comprising the light guide plate according to any one of claims 1 to 3 and a point light source.

(2) In the invention according to any one of claims 1 to 3, the ridge is constituted by a pair of curved surfaces whose front surface is convex toward the back surface side.
(3) An introduction part for diffusing incident light; a reflection part formed continuously on the introduction part and emitting the light introduced from the introduction part; and a reflection part formed on the back surface on the opposite side A plurality of prism-like or lens-like ridges are provided on the exit surface so as to extend in a direction perpendicular to the end surface on the introduction portion side of the daylighting portion. A method of manufacturing a light guide plate in which a portion extends to the top of the introduction portion, and after forming the ridges on the light guide plate to be longer than the optimum state, light is experimentally transmitted from the point light source to the light guide plate. If the vicinity of the end face corresponding to the front surface of the point light source is dark when the incident state of light is observed after being incident, at least a part of the protrusions provided on the portion corresponding to the front surface Is adjusted to suppress the luminance unevenness of the light guide plate, and the luminance unevenness of the light guide plate is adjusted. The manufacturing method of the light-guide plate which adjusts and finishes so that it may suppress.

(A) is a schematic perspective view which shows the relationship between the light guide plate of 1st Embodiment, and a point light source, (b) is a schematic top view which shows the relationship between an introducing | transducing part and a point light source, (c) is the back surface of a light guide plate. The partial model perspective view which looked at from the output surface side. 1 is a schematic diagram of a liquid crystal display device. (A) is a schematic diagram which shows the effect | action of a lighting surface, (b) is a schematic perspective view which shows the effect | action of a lighting surface and a protruding item | line. The model perspective view which shows the relationship between the light-guide plate of 2nd Embodiment, and a point light source. (A), (b) is a partial model perspective view of the introduction part vicinity of another embodiment. (A)-(c) is a partial schematic diagram of the introduction part vicinity of another embodiment. (A) is a partial schematic perspective view of the vicinity of the introduction part of another embodiment, and (b) to (f) are partial schematic views of the ridges of another embodiment. (A), (b) is a schematic diagram which shows another embodiment of a protruding item | line. The schematic diagram of the liquid crystal display device of another embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 14 ... Light guide plate, 15 ... Point light source, 18 ... Introduction part, 19 ... Daylighting part, 19a ... End face, 23 ... Outgoing surface, 24 ... Reflection part, 25 ... Groove, 25a ... Daylighting face, 26 ... Projection, 26a ... extension part.

Claims (3)

A light guide plate that receives light emitted from a plurality of point light sources, converts the light into a planar shape, and emits the light.
A plate-like shape having an introduction part for diffusing incident light, an emission surface formed continuously from the introduction part and emitting light introduced from the introduction part, and a reflection part formed on the back surface on the opposite side And a plurality of prism-like or lens-like ridges are provided on the exit surface so as to extend in a direction perpendicular to the end surface on the introduction portion side of the daylighting portion. A light guide plate extending up to the introduction part.   The light guide plate according to claim 1, wherein the ridge extending to the top of the introduction portion extends in a range wider than a range corresponding to the width of each point light source.   The reflecting portion formed on the back surface is formed with a plurality of grooves that form a daylighting surface that extends in parallel with the end surface and reflects the incident light in a direction of exiting from the exit surface. Item 3. The light guide plate according to Item 2.

Images