JP3115861U - Light guide plate and backlight unit having the same - Google Patents

Abstract

To provide a light guide plate with high diffusion efficiency and sufficient luminance.
SOLUTION: Incident end faces 8 and 12 on which light from cold cathode fluorescent lamps 16 and 18 are incident, an outgoing face 4 that emits light introduced from the incident end faces 8 and 12, and a position opposite to the outgoing face 4 A light guide plate having a back surface 6. A diffusion pattern 20 is applied to the back surface 6 of the light guide plate 2, and the diffusion pattern 20 is composed of a plurality of quadrangular pyramid-shaped convex portions 22 (or concave portions) arranged irregularly. In addition, a prism pattern 24 can be provided on the light exit surface 4 of the light guide plate 2, and this prism pattern is composed of peaks and valleys having V-shaped cross sections arranged alternately and continuously. The part is provided in a straight line substantially perpendicular to the incident end faces 8 and 12. The diffusion pattern 20 may be provided on the emission surface 4 of the light guide plate 2.
[Selection] Figure 1

Description

  The present invention relates to a light guide plate used for surface illumination of a liquid crystal display and a backlight unit including the same.

  A liquid crystal display for displaying image information and the like is composed of a liquid crystal unit and a backlight unit for illuminating the liquid crystal unit, and the liquid crystal unit is disposed facing the surface side of the backlight, that is, the emission surface. Is done. The liquid crystal unit adjusts the amount of transmitted light by a liquid crystal cell, does not emit light itself, and the backlight unit functions as a light source for displaying image information and the like on the liquid crystal display.

  The backlight unit includes a primary light source such as a cold cathode fluorescent lamp, a light guide plate for guiding light, a reflection sheet, and a diffusion sheet. One end surface (or both opposing end surfaces) of the light guide plate functions as an incident end surface, and a primary light source is disposed facing the incident end surface. Further, one surface substantially perpendicular to the incident end surface of the light guide plate functions as an exit surface, a diffusion sheet is disposed facing the exit surface, and a liquid crystal unit is disposed facing the diffusion sheet. Furthermore, in the light guide plate, the back surface is located on the side opposite to the light exit surface, and a reflection sheet is disposed facing the back surface. With this configuration, the light from the cold cathode fluorescent lamp is guided into the light guide plate through the incident end surface, reflected by the reflection sheet on the back side of the light guide plate, propagated in the light guide plate, and emitted from the output surface. The light is emitted toward the liquid crystal unit. The light from the emission surface is diffused as required in the diffusion sheet, and the diffused light uniformly illuminates the entire area from the back side of the liquid crystal unit.

  In the backlight unit for illuminating the liquid crystal unit, it is required to illuminate the liquid crystal unit with high brightness from the back side and to uniformly illuminate the display area of the liquid crystal unit. It is required that the light introduced from the light source through the incident end face is efficiently emitted through the emission surface, and the light emitted from the emission surface is substantially uniform over the entire area.

  In order to solve such a problem, a light guide plate having a concave pattern (or a convex pattern) on the emission surface has been proposed (see, for example, Patent Document 1). In this light guide plate, the concave pattern (or convex pattern) is composed of a large number of irregularly arranged concave parts (or convex parts), and these convex parts (or concave parts) are formed in a truncated cone shape, for example. Yes. Also, a prism pattern is formed on the back surface opposite to the exit surface, and the prism pattern is composed of peaks and valleys having a V-shaped cross section in which the prism patterns are alternately and continuously arranged. In such a light guide plate, the light can be bent as required by the prism pattern on the back side and guided to the exit surface side to increase the propagation efficiency, and the projection pattern (or recess pattern on the exit surface side) ) Can diffuse the light to uniformly illuminate the liquid crystal unit.

Utility Model Registration No. 3108745

  However, the above-described light guide plate and the backlight unit including the same have the following problems to be solved. That is, in the light guide plate, the concave pattern (or convex pattern) provided on the exit surface is an irregular frustoconical convex portion (or an inverted frustoconical concave portion), so that the light from the primary light source Diffusion efficiency is not high enough. Therefore, sufficient brightness as a backlight unit cannot be obtained. To increase the brightness, it is necessary to increase the brightness of the light source, which increases power consumption. Also, there is a problem that heat is generated.

  In the backlight unit using such a light guide plate, a reflection sheet is provided on the back side of the light guide plate, and a first diffusion sheet, a prism sheet, and a second diffusion sheet are arranged in this order on the emission surface side. Therefore, various sheets are required to uniformly illuminate the liquid crystal unit, which causes a problem in that the configuration of the backlight unit is complicated and the manufacturing cost is high.

An object of the present invention is to provide a light guide plate having high diffusion efficiency and sufficient luminance.
Another object of the present invention is to provide a backlight unit that can obtain a sufficient luminance and can uniformly illuminate a liquid crystal unit with a relatively simple configuration.

  A light guide plate according to a first aspect of the present invention is a light guide plate used in a backlight unit of a liquid crystal display, and is substantially perpendicular to the incident end surface on which light from a primary light source is incident. An exit surface that emits light introduced from the incident end surface, and a back surface that is located on the opposite side of the exit surface, and a diffusion pattern is applied to the exit surface or the back surface, The diffusion pattern is composed of a plurality of quadrangular pyramid-shaped convex portions or concave portions arranged irregularly.

  In the light guide plate according to claim 2 of the present invention, the diffusion pattern is provided on the exit surface of the light guide plate, a prism pattern is provided on the back surface of the light guide plate, and the prism patterns are alternately arranged. The crests and the troughs extend in a straight line substantially perpendicularly to the incident end face.

  The light guide plate according to claim 3 of the present invention is characterized in that the diffusion pattern is provided on the exit surface of the light guide plate, and the back surface of the light guide plate is formed on a flat surface. .

  Further, in the light guide plate according to claim 4 of the present invention, the diffusion pattern is provided on the back surface of the light guide plate, and a prism pattern is provided on the exit surface of the light guide plate, and the prism patterns are alternately arranged. The crests and the troughs extend in a straight line substantially perpendicularly to the incident end face.

  The light guide plate according to claim 5 of the present invention is characterized in that the diffusion pattern is provided on the back surface of the light guide plate, and the emission surface of the light guide plate is formed as a flat surface. .

  In the light guide plate according to claim 6 of the present invention, the plurality of convex portions or concave portions of the diffusion pattern are substantially the same size as a regular pyramid, and the size of one side of the bottom portions of the convex portions or concave portions. Is 30 to 100 μm, and its height or depth is 15 to 50 μm.

  In the light guide plate according to claim 7 of the present invention, the primary light source is composed of a cold cathode fluorescent lamp or a plurality of LEDs arranged in a predetermined direction, and a convex portion or a concave portion per unit area in the diffusion pattern. Is higher in the corner region on the primary light source side of the light guide plate, and is lower than the density of the corner region in regions other than the corner region of the light guide plate.

  In the light guide plate according to claim 8 of the present invention, the peak and valley of the prism pattern have substantially the same shape, and the peak angle of the peak and the valley angle of the valley are 80 to 120. The pitch between the peaks is 30 to 100 μm.

  A backlight unit according to a ninth aspect of the present invention is a backlight unit of a liquid crystal display including the light guide plate according to the third or fifth aspect, wherein an incident end face on which light is incident and light is emitted. A light guide plate having an exit surface and a back surface opposite to the exit surface, a primary light source disposed to face the incident end surface of the light guide plate, and disposed on the back side of the light guide plate And a reflection sheet.

  In the backlight unit according to claim 10 of the present invention, a first prism sheet is provided to face the light exit surface of the light guide plate, and the first prism sheet has a surface facing the light guide plate; A first prism pattern is formed on the opposite surface, and the first prism pattern is composed of peaks and valleys having a V-shaped cross section arranged alternately and continuously. The optical plate extends in a straight line substantially perpendicular to the incident end face of the optical plate.

  In the backlight unit according to claim 11 of the present invention, a second prism sheet is further provided on the light exit surface side of the light guide plate, and the second prism sheet faces the light guide plate. A second prism pattern is formed on a surface opposite to the surface, and the second prism pattern is composed of a peak portion and a valley portion of a V-shaped cross section arranged alternately and continuously, The first prism pattern and the second prism pattern of the second prism sheet extend substantially crossing each other.

  A backlight unit according to a twelfth aspect of the present invention is a backlight unit of a liquid crystal display including the light guide plate according to the second or fourth aspect. A light guide plate having an exit surface and a back surface opposite to the exit surface, a primary light source disposed opposite to the incident end surface of the light guide plate, and a reflection disposed on the back surface of the light guide plate And a sheet.

  Further, in the backlight unit according to claim 13 of the present invention, a prism sheet is further disposed so as to face the emission surface of the light guide plate, and the prism sheet is opposite to the surface facing the light guide plate. A prism pattern is applied to the surface of the side, and the prism pattern is composed of peaks and valleys of a V-shaped cross section that are alternately arranged continuously and extend linearly in a predetermined direction, and the prism pattern of the light guide plate And the prism pattern of the prism sheet extend substantially perpendicularly to each other.

  According to the light guide plate according to claim 1 of the present invention, a diffusion pattern is applied to the light exit surface or the back surface of the light guide plate, and the diffusion pattern is irregularly arranged from a plurality of quadrangular pyramid-shaped convex portions or concave portions. Because it is configured, the light from the back surface is sufficiently diffused and guided to the exit surface, and the brightness of the light exiting from this exit surface can be sufficiently increased, and the light from the exit surface is spread over the entire area. It can be made substantially uniform.

  According to the light guide plate of the present invention, a diffusion pattern having a specific shape is provided on the exit surface of the light guide plate, and a prism pattern is provided on the back surface thereof. Since it is composed of a crest and a trough of the cross section, the light from the primary light source incident from the incident end surface is refracted and reflected as required on the back side of the light guide plate and guided to the exit surface side, Further, the light that is propagated through the light guide plate and emitted from the exit surface is sufficiently diffused by the plurality of quadrangular pyramid-shaped convex portions or concave portions. Therefore, in this light guide plate, the propagation efficiency and the diffusion efficiency can be improved by combining the prism pattern of the specific shape on the back side and the diffusion pattern on the exit surface side, and sufficient luminance can be obtained. Brightness can be obtained.

  According to the light guide plate of the present invention, a diffusion pattern comprising a plurality of quadrangular pyramid-shaped convex portions or concave portions is provided on the exit surface of the light guide plate, and the back surface thereof is formed on a flat surface. Therefore, even with a light guide plate having a relatively simple structure having a diffusion pattern of a specific shape, sufficient luminance can be obtained and light emitted from the light exit surface can be made uniform.

  According to the light guide plate of the present invention, a specific-shaped diffusion pattern is provided on the back surface of the light guide plate, and a prism pattern is provided on the exit surface of the light guide plate. The light is sufficiently diffused on the back surface of the light guide plate and guided to the exit surface side, and the light thus guided is the exit surface of the light guide plate. On the side, the light is refracted and reflected as required. Therefore, also in this light guide plate, the propagation efficiency and the diffusion efficiency can be improved by combining the diffusion pattern having a specific shape on the back surface and the prism pattern having a specific shape on the output surface, and sufficient luminance can be obtained, and the entire light guide plate can be uniformly distributed. Brightness can be obtained.

  In the light guide plate according to claim 5 of the present invention, the back surface of the light guide plate is provided with a diffusion pattern composed of a plurality of quadrangular pyramid-shaped convex portions or concave portions, and its emission surface is formed on a flat surface. Therefore, even with a light guide plate having a relatively simple structure having a diffusion pattern of a specific shape, sufficient luminance can be obtained and light emitted from the light exit surface can be made uniform.

  In the light guide plate according to claim 6 of the present invention, the plurality of convex portions (or concave portions) of the diffusion pattern are formed in a regular quadrangular pyramid shape having substantially the same size, and the size is within a predetermined range. Therefore, the diffusion efficiency is high, and the light emitted from the exit surface of the light guide plate can have uniform brightness over the entire exit surface.

  According to the light guide plate of the present invention, the density of the convex portions (or concave portions) per unit area in the diffusion pattern is high in the corner region on the primary light source side of the light guide plate. In areas other than the area, the density is lower than the density of the corner area, so the brightness of the corner area on the primary light source side of the light guide plate where the brightness tends to decrease is increased, and the brightness of the entire exit surface of the light guide plate is substantially increased. The top can be equal.

  According to the light guide plate of claim 8 of the present invention, the peak and valley of the prism pattern have substantially the same specific size, so that light from the primary light source is desired in the prism pattern. The light propagation efficiency can be increased by refraction and reflection as described above.

  According to the backlight unit of claim 9 of the present invention, since the plurality of quadrangular pyramid-shaped convex portions or concave portions are provided on the exit surface or the back surface of the light guide plate, the liquid crystal unit is irradiated from the backlight. The brightness of the emitted light can be increased and the brightness can be made uniform.

  In the backlight unit according to claim 10 of the present invention, the first prism sheet is provided so as to face the emission surface of the light guide plate, and the first prism patterns are arranged alternately and continuously. It is composed of crests and troughs with a cross-section, and these crests and troughs extend in a straight line substantially perpendicular to the incident end face of the light guide plate. The light emitted from the backlight unit can be made more uniform by being refracted and reflected by the first prism sheet.

  According to the backlight unit of claim 11 of the present invention, the second prism sheet is provided on the light exit surface side of the light guide plate, and the second prism patterns of the second prism sheet are arranged alternately and continuously. Since the first prism pattern of the first prism sheet and the second prism pattern of the second prism sheet extend substantially intersecting each other, the first prism pattern of the first prism sheet and the second prism pattern of the first prism sheet extend from the light guide plate. The emitted light can be refracted and reflected as required by the first and second prism sheets, and the light emitted from the backlight unit can be made more uniform.

  According to the backlight unit of the twelfth aspect of the present invention, a large number of quadrangular pyramid-shaped convex portions or concave portions are provided on the back surface or the exit surface of the light guide plate, and peaks and troughs are formed on the exit surface or the back surface. Since the prism pattern is provided, the brightness of the light emitted from the backlight to the liquid crystal unit can be increased by combining the diffusion pattern of the specific shape on the light guide plate and the prism pattern, and the brightness can be increased. It can be made uniform.

  According to the backlight unit of the thirteenth aspect of the present invention, the prism sheet is provided so as to face the exit surface of the light guide plate, and the prism sheet extends in the direction in which the peaks and valleys of the prism pattern of the light guide plate extend. Since the direction in which the peaks and valleys of the prism pattern extend substantially perpendicularly, the light from the exit surface of the light guide plate is refracted by these prism patterns and becomes uniform light and is guided to the liquid crystal unit. Therefore, the liquid crystal unit can be illuminated more uniformly.

  Hereinafter, embodiments of a light guide plate and a backlight unit including the same according to the present invention will be described with reference to the accompanying drawings. 1 is a partially cutaway perspective view showing an embodiment of a light guide plate according to the present invention, and FIG. 2 is a partially enlarged rear view showing an enlarged part of the back surface of the light guide plate of FIG. 3 is a cross-sectional view taken along line III-III in FIG.

  1 and 2, the illustrated light guide plate 2 is formed in a rectangular plate shape. In FIG. 1, the upper surface 4 on the upper side and the lower surface 6 on the lower side, and the four side end surfaces 8 and 10 that connect the upper surface 4 and the lower surface 6. , 12 and 14. In this embodiment, the side end surfaces 8 and 12 that face each other are longer than the other side end surfaces 10 and 14 that face each other, and a pair of side end surfaces in the longitudinal direction, that is, side end surfaces 8 (the side end surfaces on the lower left side in FIG. 1). And cold cathode fluorescent lamps 16 and 18 as primary light sources are disposed opposite to the side end face 12 (upper right side end face in FIG. 1) facing the side end face 8. Light is guided into the light guide plate 2 from the side end face 8, and light from the other cold cathode fluorescent lamp 18 is guided into the light guide plate 2 from the side end face 12 on the opposite side, and these side end faces 8, 12 are the light guide plate 2. It functions as the incident end face.

  In addition, a liquid crystal unit (not shown) is disposed so as to face the upper surface 4 of the light guide plate 2, and light introduced into the light guide plate 2 from the cold cathode fluorescent lamps 16 and 18 is emitted from the upper surface 4 to be liquid crystal. The unit is irradiated from the back side, and the upper surface 4 functions as an exit surface. Such a light guide plate 2 is formed of a thermoplastic resin, such as an acrylic resin or a polycarbonate resin.

  Referring also to FIG. 3, in this embodiment, the upper surface 4 (outgoing surface) of the light guide plate 2 is formed in a substantially flat flat surface, preferably in a mirror surface. On the other hand, a diffusion pattern 20 (a part of which is shown in FIG. 1 and enlarged in FIG. 2) is provided on the lower surface 6 of the light guide plate 2 (the rear surface facing the upper surface 4). As shown in an enlarged view in FIG. 2, the diffusion pattern 20 is composed of a large number of quadrangular pyramid-shaped convex portions 22, and is irregularly disposed over substantially the entire lower surface 6 (back surface). The density of the convex portions 22 of the diffusion pattern 20 is configured as follows. That is, the density of the protrusions 22 per unit area in the diffusion pattern 20 is such that the corner region on the primary light source side of the light guide plate 2, in this embodiment, the corner region on the cold cathode fluorescent lamp 16 side and the other cold cathode fluorescent lamp 18. It is high in the corner region on the side, and is lower than the density of these corner regions in the region other than these corner regions in the light guide plate 2. The diffusion efficiency in the region is increased, the luminance of the region where the light from the cold cathode fluorescent lamp 16 is weak can be increased, and the luminance of the upper surface 4 (emission surface) of the light guide plate 2 can be made substantially uniform.

  Each convex part 22 of the diffusion pattern 20 has substantially the same shape, and is formed in a regular quadrangular pyramid shape in this embodiment. The size L (see FIG. 2) of one side of the bottom of the convex portion 22 is 30 to 100 μm, preferably 40 to 70 μm, and the height H (see FIG. 3) is 15 to 50 μm, preferably 20 to 35 μm. is there. By making the convex part 22 of the diffusion pattern 20 into a small regular quadrangular pyramid shape, it is possible to increase the diffusion efficiency and increase the brightness.

  In this embodiment, as shown in FIG. 2, the convex portions 22 of the diffusion pattern 20 have a vertical direction (a direction perpendicular to the axial direction of the cold cathode fluorescent lamps 16 and 18) and a horizontal direction (the cold cathode fluorescent lamp 16). However, the arrangement is not limited to this arrangement, and may be configured as shown in FIG. FIG. 4 is a rear view showing a part of another embodiment of the light guide plate. In the following embodiments, substantially the same members are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 4, the protrusions 22A of the diffusion pattern 20A are arranged to some extent in the vertical direction and to some extent in the zigzag form in the horizontal direction. Thus, the quadrangular pyramidal projections 22A are arranged in this way. However, the same effect is achieved. In addition, you may make it arrange many protrusions of a diffusion pattern irregularly in the vertical direction and a horizontal direction.

  In this embodiment, the diffusion pattern 20 (20A) is composed of a large number of convex portions 22 (22A), but instead of these convex portions 22 (22A), it is composed of a large number of concave portions as shown in FIG. You may make it do. In FIG. 5, which shows a part of another embodiment of the light guide plate, in this embodiment, the diffusion pattern 20B is composed of a large number of concave portions 27 having a quadrangular pyramid shape, and is irregularly distributed over substantially the entire lower surface 6 (back surface). It is arranged. The concave portions 27 of the diffusion pattern 20B are configured in substantially the same manner as the convex portions 22 (22A) described above, and the density per unit area of the concave portions 27 is the corner region (cold cathode) on the primary light source side of the light guide plate 2B. The corner area on the fluorescent lamp 16 side and the corner area on the other cold cathode fluorescent lamp 18 side) are high, and the area other than these corner areas on the light guide plate 2B is lower than the density of these corner areas. Is done. Moreover, each recessed part 27 of the diffusion pattern 20B is formed in substantially the same shape, and in this embodiment, it is formed in a regular quadrangular pyramid shape. The size of one side of the bottom of the concave portion 27 (one side of the opening of the concave portion 27) is 30 to 100 μm, preferably 40 to 70 μm, and its depth H1 is 15 to 50 μm, preferably 20 to 35 μm. By forming 20B from a large number of quadrangular pyramid-shaped recesses 27, the same effect as when formed from a large number of quadrangular pyramid-shaped projections 22 (22A) is achieved.

  The light guide plate can also be configured as shown in FIGS. FIG. 6 is a perspective view showing still another embodiment of the light guide plate. FIG. 7 is a partially enlarged cross-sectional view showing a part of the light guide plate in FIG.

  6 and 7, in this embodiment, a prism pattern 24 is provided on the upper surface (outgoing surface) of the light guide plate 2C. The prism pattern 24 is composed of peak portions 26 and valley portions 28 having V-shaped cross sections that are alternately and continuously arranged. The peak portions 26 and the valley portions 28 correspond to the side end surfaces 8 and 12 (incident end surfaces). Extend substantially vertically in a straight line. These peaks 26 and valleys 28 have substantially the same shape, and the apex angle α (see FIG. 7) of the peaks 26 and the valley angle β (see FIG. 7) of the valleys 28 are 80 to 120 degrees, preferably The pitch P between the ridges 26 (see FIG. 7) is 30 to 100 μm, preferably 40 to 70 μm. By making the prism pattern 24 into small crests 26 and troughs 28, light can be refracted and reflected as desired on the upper surface 4 (outgoing surface) side of the light guide plate 2C to make the luminance uniform. The other configuration of this embodiment is substantially the same as that of the embodiment shown in FIGS.

  Since the basic form of the light guide plate 2C is substantially the same as that shown in FIGS. 1 to 3, the same effect as described above can be achieved. In addition, since the prism pattern 24 having a predetermined shape is provided on the upper surface (outgoing surface) of the light guide plate 2C, the outgoing light from the outgoing surface can be made more uniform. Note that the diffusion pattern 20 on the lower surface 6 (rear surface) combined with the prism pattern 24 on the upper surface 4 (outgoing surface) may have, for example, the form shown in FIG.

  FIG. 8 is a partially enlarged sectional view showing a part of still another embodiment of the light guide plate. In this embodiment, as in the embodiment shown in FIG. 5, in this embodiment, the diffusion pattern 20 </ b> D is composed of a large number of quadrangular pyramid-shaped recesses 27 </ b> D and is irregularly arranged over substantially the entire lower surface 6 (back surface). Has been. The diffusion pattern 27D may be the same as the diffusion pattern 27 shown in FIG. In this embodiment, the prism pattern 24 on the upper surface 4 (outgoing surface) and the diffusion pattern 20D on the lower surface 6 (back surface) are used in combination, and the embodiment shown in FIGS. The same effect is achieved.

  Such a light guide plate 2 (2A to 2D) is manufactured by a hot press transfer molding method. FIG. 9 is a cross-sectional view schematically showing an embodiment of a hot press transfer molding apparatus for performing the hot press transfer molding method. For example, the manufacture of the light guide plate 2C will be described with reference to FIG.

  In FIG. 9, the illustrated hot press transfer molding apparatus 52 includes a fixed-side mold 54 that is fixedly attached and a movable-side mold 56 that is moved relative to the fixed-side mold 54. The The stationary mold 54 is provided with a recess 58, and a temperature adjustment plate 64 is attached to the recess 58 via a heat insulating member 60 and a thin film heater 62. The movable die 56 is similarly provided with a recess 66, and a temperature control plate 72 is attached to the recess 66 via a heat insulating member 68 and a thin film heater 70.

  A flow path 74 is provided in the temperature control plates 64 and 72, and a special fluid for heating / cooling is circulated through the flow path. A heating fluid supply source (not shown) for supplying a heating fluid and a cooling fluid supply source (not shown) for supplying a cooling fluid are provided. The heating fluid from the source is circulated through the flow path 74 of the temperature control plates 64 and 72, and when cooling, the cooling fluid from the cooling fluid supply source is circulated through the flow path 74 of the temperature control plates 64 and 72. .

  In this embodiment, a fixed stamper 76 having a shape corresponding to the prism pattern 24 on the upper surface 4 of the light guide plate 2 is attached to the surface of the temperature adjustment plate 64 of the fixed side mold 54, and the temperature of the movable side mold 56 is set. A movable stamper 78 having a shape corresponding to the diffusion pattern 20 on the lower surface 6 of the light guide plate 2 is attached to the surface of the adjustment plate 74. A stamper having a shape corresponding to the prism pattern 24 may be provided in the movable mold 56 and a stamper having a shape corresponding to the diffusion pattern 20 may be attached to the fixed mold 54.

  When manufacturing the light guide plate 2, the plate 80 formed of thermoplastic resin is placed on the fixed stamper 76 of the fixed mold 54, and then the movable mold 56 is moved relative to the fixed mold 54. These molds 54 and 56 are closed. In the state where the molds 54 and 56 are closed, the air in the recesses 58 and 66 of the molds 54 and 56 is sucked and discharged by the vacuum pump 82, and the spaces in the recesses 58 and 66 are kept in a vacuum state. Be drunk. For example, a seal member 84 is provided in the vicinity of the opening of the concave portion 58 of the fixed mold 54 so as to maintain the vacuum state in this way.

  Thereafter, a heating liquid heated to a predetermined heating temperature (for example, about 150 ° C.) is supplied from a heating fluid supply source (not shown) to the temperature adjustment plates 64 and 72 of the stationary mold 54 and the movable mold 56. The plate 80 is heated for a predetermined heating time (for example, about 15 seconds), and hot press transfer is performed on the plate 80 while being heated. That is, the stamper 76 of the fixed mold 54 acts on the lower surface of the plate 80, the pattern of the stamper 76 is transferred to form the prism pattern 24, and the stamper of the movable mold 56 is applied to the upper surface of the plate 80. 78, the pattern of the stamper 78 is transferred, and the diffusion pattern 20 is applied.

  After the pattern is transferred, the cooling liquid cooled to a predetermined cooling temperature (for example, about 23 ° C.) is supplied to the temperature adjustment plates 64 and 72 from a cooling liquid supply source (not shown), and the plate 80 is After cooling for a predetermined cooling time (for example, about 15 seconds), the prism pattern 24 and the diffusion pattern 22 thermally transferred during the cooling are fixed to the plate 80, and thus the light guide plate 2 described above is manufactured.

  As can be understood from the above description, the light guide plate 2 (2A, 2B, 2D) can be manufactured in the same manner as described above, but the light guide plate 2 (2A) manufactured by the fixed stamper and the movable stamper, respectively. , 2B, 2D).

The light guide plate 2 shown in FIGS. 1 to 3 is assembled as a backlight as shown in FIG. 10, for example. FIG. 10 is an exploded perspective view showing the backlight unit in an exploded manner.
In FIG. 10, in addition to the light guide plate 2 described above, the backlight unit 102 includes a reflection sheet 104 for reflecting light, first and second prism sheets 106 and 107 for refracting light, and a protection sheet 108. It is composed of The reflection sheet 104 is disposed to face the lower surface 6 (the surface on which the diffusion pattern 20 is applied) of the light guide plate 2 and reflects light guided to the lower surface 6 side of the light guide plate 2 to the upper surface 4 side.

  The first prism sheet 106 is disposed to face the upper surface 4 of the light guide plate 2. A first prism pattern 110 is formed on the upper surface of the first prism sheet 106 (the surface opposite to the surface facing the light guide plate 2). The first prism pattern 110 is formed of the light guide plate shown in FIGS. Similarly to the prism pattern 24 applied to 2C, the prism pattern 24 is composed of peak portions 114 and valley portions 116 having V-shaped cross-sections arranged alternately and continuously. The shape of the peak portion 26 and the valley portion 28 may be the same. The crests 114 and the troughs 116 of the first prism pattern 110 are provided in a straight line substantially perpendicular to the incident end face on which light from the cold cathode fluorescent lamps 16 and 18 is incident (the cold cathode fluorescent lamps 16, 18 is disposed opposite to the side end surface 8 on the near side with respect to the paper surface in FIG. 10 and the side end surface 12 on the back side with respect to the paper surface).

  The second prism sheet 107 is disposed to face the upper surface of the first prism sheet 106 (the surface on which the first prism pattern 110 is provided). A second prism pattern 118 is applied to the upper surface of the second prism sheet 107 (the surface opposite to the surface facing the first prism sheet 106). The second prism pattern 118 is applied to the first prism sheet 106. Similarly to the first prism pattern 110, the ridges 120 and the valleys 122 having V-shaped cross sections arranged alternately and continuously are formed. The shapes of the ridges 120 and the valleys 122 are the first prism pattern. 110 may have the same shape as the peaks 114 and valleys 116. The crest 120 and the trough 122 of the second prism pattern 118 are provided substantially parallel to the incident end face of the light guide plate 2, and accordingly, the crest 120 of the second prism pattern 118 of the second prism sheet 107. The direction in which the troughs 122 extend and the direction in which the crests 114 and troughs 116 of the first prism pattern 110 of the first prism sheet 106 extend substantially vertically intersect as shown in FIG. With this arrangement, the illumination light from the backlight unit 102 to the liquid crystal unit (not shown) can be made uniform.

  The protection sheet 108 is disposed on the surface side of the second prism sheet 107 (that is, facing the second prism pattern 118), and protects the surface side of the backlight unit 102. Note that the first prism sheet 106 and / or the second prism sheet 107 can be omitted according to the required high luminance level and luminance uniformity level. A diffusion plate may be disposed between the light guide plate 2 and the first prism sheet 106.

In the backlight unit 102, light from the cold cathode fluorescent lamp is introduced into the light guide plate 2 from the incident end surface, and the light thus introduced is reflected by the reflection sheet 104 on the lower surface 6 side of the light guide plate 2 and is reflected on the upper surface. 4 (outgoing surface) side, and is emitted from the upper surface 4 of the light guide plate 2. The emitted light is illuminated from the back side of the liquid crystal unit (not shown) through the first prism sheet 106, the second prism sheet 107, and the protective sheet 108, and the liquid crystal unit is uniformly illuminated with sufficient luminance. By using two cold cathode fluorescent lamps with a diameter of 2.5 to 3.0 mm as the primary light source, the luminance of the light emitted from the backlight unit 102 can be about 5500 cd / m ² , which is sufficient Brightness can be obtained.

  For example, the light guide plate 2C shown in FIGS. 6 and 7 is assembled as a backlight unit as shown in FIG. FIG. 11 is an exploded perspective view showing an exploded backlight unit according to another embodiment.

  In FIG. 11, the backlight unit 102C includes a reflection sheet 104, a prism sheet 132, and a protection sheet 108 in addition to the light guide plate 2C described above. The reflective sheet 104 and the protective sheet 108 may be the same as those in the embodiment shown in FIG. 10, and are arranged in the same manner as described above.

  In the backlight unit 102C, the diffusion pattern 20 is applied to the lower surface 6 of the light guide plate 2, and the prism pattern 24 is applied to the upper surface thereof. The prism sheet 132 is disposed between the light guide plate 2C and the protective sheet 108, and a prism pattern 134 is applied to the upper surface (the surface opposite to the surface facing the light guide plate 2C). Similarly to the prism pattern 24 provided on the upper surface 4 of the light guide plate 2C, the peak pattern 136 and the valley portion 138 having V-shaped cross sections arranged alternately and continuously are formed. The shape may be the same as the shape of the peaks 26 and valleys 28 of the prism pattern 24. As shown in FIG. 11, the extending direction of the crests 26 and troughs 28 of the prism pattern 24 of the light guide plate 2 </ b> C and the extending direction of the crests 136 and troughs 138 of the prism pattern 134 of the prism sheet 132 are substantially vertical. By arranging in this way, it is possible to make the illumination light from the backlight unit 102C to the liquid crystal unit (not shown) uniform with high brightness. Note that the prism sheet 132 can be omitted according to the required high luminance level and luminance uniformity level.

In the backlight unit 102C, the same effect as described above is achieved. In addition, since the prism pattern 24 is provided on the upper surface 4 of the light guide plate 2C, the light from the upper surface 4 (exiting surface) has higher brightness, and a cold cathode fluorescent light of 2.5 to 3.0 mm as a primary light source. By using two lamps, the luminance of the light emitted from the backlight unit 102C can be about 5800 cd / m ^2, and further sufficient luminance can be obtained.

  FIG. 12 shows still another embodiment of the backlight unit using the light guide plate 2D shown in FIG. In FIG. 12, in this embodiment, a diffusion pattern 20E is provided on the upper surface 4 of the light guide plate 2E, and a prism pattern 24E is provided on the lower surface 6 thereof. The diffusion pattern 20E on the upper surface 4 may have the same configuration as the diffusion pattern 20 provided on the lower surface 6 of the light guide plate 2 shown in FIGS. 1 to 3, and a large number of quadrangular pyramid (for example, regular square) convex portions. It may be comprised from many recessed parts of square pyramid shape. Also, the prism pattern 24D on the lower surface 6 may have the same configuration as the prism pattern 24 provided on the upper surface 4 of the light guide plate 2 in FIGS. It consists of a part and a valley part. In the light guide plate 2E of this embodiment, the prism pattern 24E and the diffusion pattern 20E are provided upside down with respect to the light guide plate 2 of the embodiment shown in FIGS.

  The other configuration of the backlight unit 102E of this embodiment is the same as that of the backlight unit 102 shown in FIG. 11. Also in this backlight unit 102E, the peaks and valleys of the prism pattern 24E of the light guide plate 2E extend. The direction and the direction in which the peaks and valleys of the prism pattern 134 of the prism sheet 132 extend are configured to intersect substantially vertically as shown in FIG. Since the basic configuration of the backlight unit 102E having such a configuration is the same as that of the above-described embodiment, the same operation and effect as described above can be achieved, and the liquid crystal unit can be uniformly illuminated with sufficient luminance. Can do. Note that such a method of applying the light guide plate can also be performed on the light guide plate 2 shown in FIGS. 1 to 3, the light guide plate 2A shown in FIG. 4, the light guide plate 2B shown in FIG. 5, and the light guide plate 2D shown in FIG. it can.

  As mentioned above, although various embodiment of the light-guide plate according to this invention and a backlight unit provided with this was described, this invention is not limited to these embodiment, Various deformation | transformation is carried out, without deviating from the scope of the present invention. Or it can be modified.

  For example, in the light guide plate 2 (2A to 2E) of the above-described embodiment, the cold cathode fluorescent lamps 16 and 18 are disposed to face the two side end surfaces 8 and 12 (functioning as the incident end surfaces), respectively. However, the present invention is not limited to such a configuration, and the cold cathode fluorescent lamp may be disposed so as to face either one of the side end surfaces 8 and 12, and in such a case, the light guide plate 2 (2A to 2E) It is desirable to form a wedge shape so that the thickness gradually decreases from the side end surface (incident end surface) facing the cold cathode fluorescent lamp toward the side end surface facing the cold cathode fluorescent lamp.

  Further, for example, in the backlight unit 102 (102C, 102E) of the above-described embodiment, the primary light source is composed of the cold cathode fluorescent lamps 16, 18, but is not limited thereto, and is disposed in a predetermined direction, for example. You may make it comprise from several LED (light emitting diode) made.

The perspective view which cuts off and shows one Embodiment of the light-guide plate according to this invention. The partial expansion rear view which expands and shows a part of back surface of the light-guide plate of FIG. The expanded sectional view by the III-III line in FIG. The partial expanded rear view which expands and shows a part of other embodiment of a light-guide plate. The partial expanded sectional view which expands and shows a part of other embodiment of a light-guide plate. Furthermore, the perspective view which partially cuts and shows the light-guide plate of other different embodiment. The partial expanded sectional view which shows a part of light-guide plate of FIG. 6 in a cross section. Furthermore, the partial expanded sectional view which shows a part of light-guide plate of other embodiment in a cross section. Sectional drawing which shows simply one Embodiment of a hot press transfer molding apparatus. The disassembled perspective view which decomposes | disassembles and shows one Embodiment of a backlight unit. The disassembled perspective view which decomposes | disassembles and shows the backlight unit of other embodiment. The disassembled perspective view which decomposes | disassembles and shows the backlight unit of other embodiment.

Explanation of symbols

2, 2A, 2B, 2C, 2D, 2E Light guide plate 4 Upper surface (outgoing surface)
6 Bottom (back)
8,12 side end face (incident end face)
16, 18 Cold cathode fluorescent lamp (primary light source)
20, 20B, 20C, 20D, 20E Diffusion pattern 22 Convex part 24, 24D, 24E Prism pattern 26 Mountain part 28 Valley part 52 Hot press transfer molding device 102, 102C, 102E Backlight unit 104 Reflective sheet 106 First prism sheet 107 Second prism sheet 108 Protection sheet 132 Prism sheet

Claims (13)

  A light guide plate used in a backlight unit of a liquid crystal display, which is an incident end face into which light from a primary light source is incident, and a plane substantially perpendicular to the incident end face, and is introduced from the incident end face A plurality of quadrangular pyramids provided with an exit surface for emitting light and a back surface located on the opposite side of the exit surface, wherein the exit surface or the back surface is provided with a diffusion pattern, and the diffusion pattern is irregularly arranged; A light guide plate comprising a convex portion or a concave portion.   The diffusion pattern is provided on the exit surface of the light guide plate, a prism pattern is provided on the back surface of the light guide plate, and the prism patterns are alternately and continuously arranged with ridges of V-shaped cross sections and 2. The light guide plate according to claim 1, wherein the light guide plate includes a valley portion, and the peak portion and the valley portion extend linearly substantially perpendicular to the incident end face.   The light guide plate according to claim 1, wherein the diffusion surface is provided on the emission surface of the light guide plate, and the back surface of the light guide plate is formed as a flat surface.   The diffusion pattern is provided on the back surface of the light guide plate, and a prism pattern is provided on the light exit surface of the light guide plate. 2. The light guide plate according to claim 1, wherein the light guide plate includes a valley portion, and the peak portion and the valley portion extend linearly substantially perpendicular to the incident end face.   The light guide plate according to claim 1, wherein the diffusion pattern is provided on the back surface of the light guide plate, and the emission surface of the light guide plate is formed as a flat surface.   The plurality of convex portions or concave portions of the diffusion pattern have substantially the same size as a regular quadrangular pyramid, the size of one side of the bottom portions of these convex portions or concave portions is 30 to 100 μm, and the height or depth thereof is It is 15-50 micrometers, The light-guide plate in any one of Claims 1-5 characterized by the above-mentioned.   The primary light source is composed of a cold cathode fluorescent lamp or a plurality of LEDs arranged in a predetermined direction, and the density of convex portions or concave portions per unit area in the diffusion pattern is a corner portion on the primary light source side of the light guide plate. The light guide plate according to any one of claims 1 to 6, wherein the light guide plate is high in a region and lower than the density of the corner region in a region other than the corner region in the light guide plate.   The crests and valleys of the prism pattern have substantially the same shape, the apex angle of the crests and the trough angle of the troughs are 80 to 120 degrees, and the pitch between the crests is 30 to 100 μm. It exists, The light-guide plate in any one of Claims 1-6 characterized by the above-mentioned.   A backlight unit for a liquid crystal display comprising the light guide plate according to claim 3, wherein the light guide plate includes an incident end surface on which light is incident, an exit surface from which light exits, and a back surface opposite to the exit surface. A backlight unit comprising: an optical plate; a primary light source disposed to face the incident end surface of the light guide plate; and a reflection sheet disposed on the back side of the light guide plate.   A first prism sheet is provided to face the emission surface of the light guide plate, and a first prism pattern is applied to the first prism sheet on a surface opposite to the surface facing the light guide plate, and the first prism sheet is provided. The prism pattern is composed of crests and troughs having V-shaped cross-sections arranged alternately and continuously, and the crests and troughs extend in a straight line substantially perpendicular to the incident end face of the light guide plate. The backlight unit according to claim 9.   A second prism sheet is further provided on the light exit surface side of the light guide plate, and the second prism sheet is provided with a second prism pattern on the surface opposite to the surface facing the light guide plate, The second prism pattern is composed of peaks and valleys having V-shaped cross sections that are alternately and continuously arranged, and the first prism pattern of the first prism sheet and the second prism pattern of the second prism sheet. The backlight unit according to claim 10, wherein and extend substantially crossing each other.   5. A backlight unit of a liquid crystal display comprising the light guide plate according to claim 2, wherein the light guide plate has an incident end surface on which light is incident, an exit surface from which the light exits, and a back surface opposite to the exit surface. A backlight unit comprising: an optical plate; a primary light source disposed to face the incident end surface of the light guide plate; and a reflection sheet disposed on the back surface of the light guide plate.   A prism sheet is further disposed opposite to the light exit surface of the light guide plate. The prism sheet is provided with a prism pattern on a surface opposite to the surface facing the light guide plate, and the prism patterns are alternately arranged. The prism pattern of the light guide plate and the prism pattern of the prism sheet intersect each other substantially vertically. The peak pattern and the valley portion of the V-shaped cross section are arranged continuously and extend linearly in a predetermined direction. The backlight unit according to claim 12, wherein the backlight unit extends.

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