JP3120071U - Light guide plate and backlight unit having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide plate capable of obtaining uniform luminance over substantially the entire area of an emission surface.
A light guide plate used in a backlight unit of a liquid crystal display, which is an incident end surface into which light from a primary light source is incident, and a surface substantially perpendicular to the incident end surface, which is introduced from the incident end surface. A light guide plate comprising an emission surface for emitting the emitted light and a back surface located on the opposite side of the emission surface. A diffusion pattern 20 is applied to the rear surface 6 of the light guide plate, and the diffusion pattern 20 is composed of a plurality of irregularly arranged quadrangular pyramidal projections 22, and the top of the projections is formed in an arc shape. . It is preferable that the plurality of quadrangular pyramid-shaped convex portions 22 are formed in a circular arc shape from the apex portion P to 5 to 15 μm in the height direction.
[Selection] Figure 2

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 is used 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.

  Moreover, what comprised the recessed part pattern (or convex part pattern) of the output surface of a light-guide plate from many square pyramid-shaped recessed parts (or convex part) is proposed (for example, refer patent document 2). In this light guide plate, the concave pattern (or convex pattern) is composed of a large number of concave portions (or convex portions) having a specific shape irregularly arranged, so that the luminance of the light guide plate can be further increased. As a result, the image plane of the liquid crystal display can be brightened.

Utility Model Registration No. 3108745 Utility Model Registration No. 3115861

  However, the light guide plate in which the concave pattern (or the convex pattern) is formed of a quadrangular pyramid concave (or convex) and the backlight unit including the same have the following problems to be solved. That is, since the concave portion (or convex portion) is a quadrangular pyramid, the light diffused by the concave portion pattern (or convex portion pattern) tends to gather at the bottom (or the tip portion) of each concave portion (or convex portion), Therefore, it is difficult to obtain uniform brightness over the entire light guide plate, and the bright areas are partially scattered. In addition, when forming a light guide plate with a concave pattern (or convex pattern) by injection molding, hot press transfer molding, etc., the bottom (or tip) of the concave part (or convex part) of the concave pattern (or convex part pattern) It is difficult to form the shape neatly, and if the bottom (or the tip) of some of them is distorted or missing, the brightness at these missing parts and the brightness at other parts will be different. It becomes impossible to make it uniform.

An object of the present invention is to provide a light guide plate capable of obtaining uniform luminance over substantially the entire area of the exit surface.
Another object of the present invention is to provide a light guide plate capable of greatly reducing the occurrence of distortion and defects even when formed by molding or the like.

  Still 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 irregularly arranged convex or concave portions of a quadrangular pyramid, and the top of the convex portion or the bottom of the concave portion is formed in a spherical shape.

  In the light guide plate according to claim 2 of the present invention, the plurality of quadrangular pyramid-shaped convex portions or concave portions of the diffusion pattern have a portion from the apex portion or the bottom portion to 5 to 15 μm in the height direction. It is formed in an arc shape.

  In the light guide plate according to claim 3 of the present invention, the plurality of quadrangular pyramidal projections or recesses of the diffusion pattern are substantially the same size as a regular pyramid, and the bottoms of the projections or recesses One side is 30-100 micrometers, and the height or depth of these convex parts or recessed parts is 20-50 micrometers.

In the light guide plate according to claim 4 of the present invention, the surface roughness of the inclined side surfaces of the plurality of quadrangular pyramidal projections or recesses of the diffusion pattern is 20 nmRy or less.
A light guide plate according to a fifth aspect of the present invention is a light guide plate used in a backlight unit of a liquid crystal display, and substantially includes an incident end face on which light from a primary light source enters and the incident end face. An upper vertical surface that includes 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 conical convex portions or concave portions arranged irregularly, and the top portion of the convex portion or the bottom portion of the concave portion is formed in an arc shape.

  Further, in the light guide plate according to claim 6 of the present invention, the plurality of conical convex portions or concave portions of the diffusion pattern are circular in a height direction from a top portion or a bottom portion to 5 to 15 μm. It is formed in an arc shape.

  In the light guide plate according to claim 7 of the present invention, the plurality of conical convex portions or concave portions of the diffusion pattern have substantially the same size, and the diameter of the bottom portion of the convex portions or concave portions is 30 to 30. The height or depth of these convex portions or concave portions is 20 to 50 μm at 100 μm.

The light guide plate according to claim 8 of the present invention is characterized in that the surface roughness of the inclined peripheral side surfaces of the plurality of conical convex portions or concave portions of the diffusion pattern is 20 nmRy or less.
Furthermore, the backlight unit according to claim 9 of the present invention is a backlight unit of a liquid crystal display including the light guide plate according to any one of claims 1 to 8, wherein an incident end face on which light is incident, light A light guide plate having an exit surface from which the light exits 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 a light source plate disposed on the back side of the light guide plate. And a reflection sheet provided.

  According to the light guide plate described in claim 1 (or claim 5) of the present invention, a plurality of quadrangular pyramids (or conical shapes) in which the diffusion patterns formed on the exit surface or the back surface of the light guide plate are irregularly arranged. ), The diffusion efficiency in the diffusion pattern is enhanced, and the brightness of light emitted from the exit surface can be sufficiently increased by sufficiently diffusing on the exit surface or the back surface. At the same time, the light from the exit surface can be made substantially uniform over the entire area. In particular, since the tops or bottoms of the plurality of convex portions or concave portions are formed in an arc shape, the focusing of light at the top portions or the bottom portions can be suppressed, and the brightness of the exit surface can be made more uniform. Further, by forming in this way, when forming by molding such as injection molding, it is possible to greatly reduce the occurrence of distortion and defects at the top or bottom of the convex portion or concave portion.

  According to the light guide plate described in claim 2 (or claim 6) of the present invention, the quadrangular pyramid (or conical) convex part or concave part of the diffusion pattern is 5 to 5 from the apex part or the bottom part. Since the region up to 15 μm is formed in an arc shape, the light focusing at the top or bottom is more effectively suppressed, and the brightness of the exit surface can be made more uniform.

  In the light guide plate according to claim 3 (or claim 7) of the present invention, the plurality of convex portions or concave portions of the diffusion pattern are formed in a regular quadrangular pyramid shape (or conical shape) having substantially the same size. Since the size is within a predetermined range, the diffusion efficiency is very high, and the light emitted from the exit surface of the light guide plate can be made uniform brightness over the entire exit surface.

  In addition, according to the light guide plate according to claim 4 (or claim 8) of the present invention, the surface roughness of the inclined side surface (or the inclined peripheral side surface) of the convex portion or the concave portion of the quadrangular pyramid (or conical shape). Since it is 20 nm Ry or less, the reflection efficiency in such a convex part or a recessed part is improved, and the brightness | luminance of the light radiate | emitted from the output surface of a light-guide plate can be raised further.

  According to the backlight unit of the present invention, a plurality of quadrangular pyramid (or conical) convex portions or concave portions are provided on the exit surface or the back surface of the light guide plate, and the top portions of these convex portions. Alternatively, since the bottom of the concave portion is formed in an arc shape, the luminance of light emitted from the backlight to the liquid crystal unit can be increased and the brightness can be made uniform.

  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). It is important that the convex portions 22 of the diffusion pattern 20 have cross-sectional shapes formed at the top portions 23 in an arc shape. The density of the plurality of convex portions 22 is high in the corner region on the primary light source side of the light guide plate 2, in this embodiment, in the corner region on the cold cathode fluorescent lamp 16 side and in the corner region on the other cold cathode fluorescent lamp 18 side. In the regions other than these corner regions in the light guide plate 2, the density of these corner regions is lower than that. By configuring the density of the convex portions 22 in this way, the diffusion efficiency in the above-described corner regions is high. Thus, the luminance of the weak region of light from the cold cathode fluorescent lamp 16 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 20 to 50 μm, preferably 20 to 35 μm. The convex portion 22 is formed in an arc shape in the height direction from the apex portion P to the distance h, that is, from the apex portion P to 5 to 15 μm. The distance h from the apex portion formed in a circular arc shape increases when the height H of the quadrangular pyramid-shaped convex portion 22 is high, and this distance h is 20 to 50% of the height H, preferably 20 to 35. % Is set to the size of the percentage. By making the convex portion 22 of the diffusion pattern 20 into a small regular quadrangular pyramid shape, it is possible to increase the diffusion efficiency and brighten the brightness, and by forming the portion from the vertex portion P to a predetermined range in an arc shape, The gathering of light to the part P can be suppressed and the brightness of the exit surface 4 can be made more uniform. When the distance h from the apex P exceeds 15 μm, the diffusion efficiency decreases and the luminance of the exit surface 4 is somewhat reduced. When the distance h from the apex P is less than 5 μm, the apex of the convex portion 22 Light easily collects at P, and luminance unevenness is likely to occur on the exit surface 4.

  The surface roughness (average surface roughness) of each inclined side surface 25 of the convex portion 22 is formed to be 20 nm (nanometer) Ry or less, preferably 15 nm Ry or less. By increasing the surface roughness in this manner, the diffusion efficiency of the inclined side surface 25 of the convex portion 22 is increased, and thereby the luminance on the emission surface 4 can be further increased. When the surface roughness of the inclined side surface 25 of the convex portion 22 is greater than 20 nmRy, the diffusion efficiency on the inclined side surface 25 decreases, and the luminance of the exit surface 4 decreases somewhat.

  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). , 18 (in the direction of the axial line), but are arranged irregularly to some extent. However, the arrangement is not limited to this, and the arrangement may be arranged irregularly in the vertical and horizontal directions.

  In this embodiment, the diffusion pattern 20 is provided on the upper surface 4 of the light guide plate 2. On the contrary, a diffusion pattern may be provided on the lower surface 6. Further, in this embodiment, the diffusion pattern is composed of a large number of convex portions, but instead of these convex portions, it may be composed of a large number of concave portions as shown in FIG.

  In FIG. 4 showing a part of another embodiment of the light guide plate, in this embodiment, the diffusion pattern 20A is composed of a large number of quadrangular pyramid-shaped concave portions 27, and is irregularly formed over substantially the entire lower surface 6 (back surface). It is arranged. The concave portion 27 of the diffusion pattern 20A is configured in substantially the same manner as the convex portion 22 described above, and the density per unit area of the concave portion 27 is a corner region (cold cathode fluorescent lamp 16 on the primary light source side of the light guide plate 2A. The corner area on the side and the corner area on the other cold cathode fluorescent lamp 18 side), and the area other than these corner areas in the light guide plate 2A is configured to be lower than the density of these corner areas.

  Further, the respective concave portions 27 of the diffusion pattern 20A are formed in substantially the same shape, and in this embodiment, are 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 20 to 50 μm, preferably 20 to 35 μm. 27, a portion from the bottom point P1 to the distance h1 in the height direction, that is, a portion from the bottom point P1 to 5 to 15 μm is formed in a circular arc shape. The distance h1 from the bottom portion formed in an arc shape increases when the depth H1 of the concave portion 27 having a quadrangular pyramid shape is high, and this distance h1 is 20 of the depth H1 as in the above-described embodiment. It is set to a size of ˜50%, preferably 20-35%. Even in such a configuration, as in the above-described embodiment, the luminance of the emission surface 4 can be increased by increasing the diffusion efficiency of the diffusion pattern 20A, and by forming such a portion in an arc shape, It is possible to suppress the collection of light to the bottom point portion P1 and make the brightness of the emission surface 4 more uniform.

  Also in this embodiment, the surface roughness (average surface roughness) of each inclined side surface 29 of the concave portion 27 of the diffusion pattern 20A is formed to be 20 nmRy or less, preferably 15 nmRy or less. By doing so, the diffusion efficiency of the inclined side surface 29 of the concave portion 27 is enhanced, whereby the luminance on the exit surface 4 can be further enhanced. In this way, when the diffusion pattern 20A is formed from a large number of quadrangular pyramid-shaped concave portions 27, the same effect as when formed from the quadrangular pyramid-shaped convex portions 22 is achieved.

  The light guide plate can also be configured as shown in FIGS. FIG. 5 is a perspective view in which still another embodiment of the light guide plate is partially cut away, and FIG. 6 is a partially enlarged cross-sectional view showing a part of the light guide plate in FIG. 6 in cross section.

  5 and 6, in this embodiment, a prism pattern 24 is provided on the upper surface (outgoing surface) of the light guide plate 2B. 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. The peak portion 26 and the valley portion 28 have substantially the same shape, and the apex angle α (see FIG. 6) of the peak portion 26 and the valley angle β (see FIG. 6) of the valley portion 28 are 80 to 120 degrees, preferably The pitch R between the ridges 26 (see FIG. 6) 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 2B to make the luminance uniform. Other configurations of this embodiment are substantially the same as those of the embodiment shown in FIGS. 1 to 3, and a plurality of quadrangular pyramid-shaped convex portions 22 (the top portion 23 of which has an arc shape) are formed on the lower surface 6 of the light guide plate 2B. The diffusion pattern 20 is formed.

  Since the basic form of the light guide plate 2B 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 2B, 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 be, for example, in the form shown in FIG.

  In this embodiment, the prism pattern 24 is provided on the upper surface 4 of the light guide plate 2B, and the diffusion pattern 20 is provided on the lower surface 6. On the contrary, the diffusion pattern 20 is provided on the upper surface 4 of the light guide plate 2B, A prism pattern 24 may be provided on the lower surface 6.

  7 and 8 show a part of still another embodiment of the light guide plate, and FIG. 7 is an enlarged rear view showing a part of the light guide plate of still another embodiment. These are the expanded sectional views by the VIII-VIII line in FIG.

  7 and 8, the diffusion pattern 20C of this embodiment is composed of a large number of conical convex portions 22C, and it is important that the top portion 23C is formed in an arc shape in cross section. Each protrusion 22C of the diffusion pattern 20C is formed in substantially the same shape. The diameter D (see FIG. 7) of the bottom of the convex portion 22C is 30 to 100 μm, preferably 40 to 70 μm, and its height H2 (see FIG. 8) is 20 to 50 μm, preferably 20 to 35 μm. Similarly to the above, the convex portion 22C is formed such that a portion from the apex portion P to the distance h2 in the height direction, that is, a portion from the apex portion P2 to 5 to 15 μm is formed in a circular arc shape. This distance h2 is set to a size of 20 to 50%, preferably 20 to 35% of the height H2. By making the convex portion 22C of the diffusion pattern 20C into a small conical shape, as described above, the diffusion efficiency can be increased and the luminance can be increased, and the range of the distance h2 from the apex portion P2 is formed in an arc shape. By doing so, it is possible to suppress the collection of light to the apex P and make the brightness of the exit surface 4 more uniform.

  When the diffusion pattern 20C is composed of such conical convex portions 22C, the surface roughness (average surface roughness) of the inclined peripheral side surface 25C of these convex portions 22C is formed to be 20 nmRy or less, preferably 15 nmRy or less. By configuring in this way, the luminance on the emission surface 4 can be further increased as described above.

  As shown in FIG. 9, this diffusion pattern may be composed of a large number of recesses. In FIG. 9 which shows a part of still another embodiment of the light guide plate, in this embodiment, the diffusion pattern 20D is composed of a large number of conical recesses 27D, and is irregularly formed over substantially the entire lower surface 6 (back surface). It is arranged. The concave portion 27D of the diffusion pattern 20D is formed in substantially the same shape, and the diameter D3 of the bottom of the concave portion 27D (the diameter of the opening of the concave portion 27D) is 30 to 100 μm, preferably 40 to 70 μm, and the depth H3 is The recess 27D is formed in an arc shape in the height direction from the bottom point P3 to the distance h3, that is, from the bottom point P3 to 5 to 15 μm. Has been. The distance h3 from the bottom point P3 formed in an arc shape is set to a size of 20 to 50%, preferably 20 to 35% of the depth H3, as described above. By configuring, the same effect as described above is achieved. Further, the surface roughness (average surface roughness) of the inclined circumferential side surface 29D of the conical recess 27D of the diffusion pattern 20D is formed to be 20 nmRy or less, preferably 15 nmRy or less. As described above, the diffusion efficiency of the inclined circumferential side surface 29D of the recess 27D can be increased.

  Also in the light guide plate 2C (or the light guide plate 2D shown in FIG. 9) having the form shown in FIGS. 7 and 8, the diffusion pattern 20C (or 20D) is provided in the same manner as the light guide plate 2B shown in FIGS. A prism pattern may be integrally provided on the surface opposite to the surface on which the light is present.

  Such a light guide plate 2 (2A to 2D) is manufactured by, for example, a hot press transfer molding method. FIG. 10 is a cross-sectional view schematically showing an embodiment of a hot press transfer molding apparatus for carrying out the hot press transfer molding method. Referring to FIG. 10, for example, the light guide plate 2 (FIGS. 1 to 3). Will be described.

  In FIG. 10, 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, 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, 72. .

  In this embodiment, a fixed stamper 76 having a shape corresponding to the upper surface 4 of the light guide plate 2 (that is, a substantially flat shape) is attached to the surface of the temperature adjustment plate 64 of the fixed side mold 54, and the movable side 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 temperature adjustment plate 74 of the mold 56. A stamper having a shape corresponding to the upper surface 4 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, and the stamper 78 of the movable mold 56 acts on the upper surface of the plate 80 to apply the diffusion pattern 20.

  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. Instead of the above-described molding method, it may be formed by an injection molding method or the like in which a molten resin is poured into a mold at a predetermined pressure.

  In the light guide plate 2 (2A to 2D) of this embodiment, the quadrangular pyramid-shaped convex portions 22 (the quadrangular pyramid-shaped concave portion 22A, the conical convex portion 22C, the conical shape of the diffusion pattern 20 (20A, 20C, 20D) Since the top part 23 (bottom part, top part 23C, bottom part) of the concave part 22D) is formed in a circular arc shape in cross section, even if it is formed by molding such as hot press transfer molding or injection molding, the convex part 22 having a quadrangular pyramid shape (four The generation of distortion and defects in the pyramidal concave portion 22A, the conical convex portion 22C, and the conical concave portion 22D) can be suppressed very little, and this type of light guide plate 2 (2A to 2D) can be made relatively easily. It can be manufactured with high accuracy.

The light guide plate 2 shown in FIGS. 1 to 3 is assembled as a backlight as shown in FIG. 11, 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, 11 is disposed opposite to the side end surface 8 on the near side with respect to the paper surface in FIG. 11 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. 11 and the direction in which the peaks 114 and the valleys 116 of the first prism pattern 110 of the first prism sheet 106 extend intersect substantially vertically 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. Can do.

  When the light guide plate 2B shown in FIGS. 5 and 6 is used, the first prism sheet 106 in FIG. 11 is omitted because the prism pattern 24 is integrally provided on the exit surface 4 of the light guide plate 2B. Accordingly, the configuration of the backlight unit 102 can be simplified and the thickness thereof can be reduced.

  1 to 3 is a light guide plate having a regular pyramid-shaped convex portion formed as a diffusion pattern, and a reflectance measurement experiment using a top portion of each convex portion having an arc-shaped cross section. As a result, the experimental results shown in FIG. 12 were obtained. The solid line in FIG. 12 shows the experimental result of the light guide plate A in which the surface roughness of each inclined side surface of the convex portion of the diffusion pattern is 14 nm Ry, and the reflectance increases as the wavelength of the propagating light increases. Moreover, the broken line in FIG. 12 shows the experimental result of the light guide plate B in which the surface roughness of each inclined side surface of the convex portion of the diffusion pattern is 65 nm Ry, and the reflectance increases as the wavelength of the propagating light increases. The reflectance was about 10 to 20% smaller than that of the light guide plate A. From this experimental result, it has been found that by reducing the surface roughness of the inclined side surface of the convex portion of the diffusion pattern to about 15 nm or less, the reflectance of the light guide plate can be increased and the luminance of the exit surface can be increased.

  Although various embodiments of the light guide plate according to the present invention and the backlight unit including the light guide plate have been described above, the present invention is not limited to these embodiments, and various modifications can be made without departing from the scope of the present invention. Or it can be modified.

  For example, in the light guide plate 2 (2A to 2D) of the above-described embodiment, the cold cathode fluorescent lamps 16 and 18 are disposed so as to face the two side end surfaces 8 and 12 (functioning as incident end surfaces), respectively. However, the present invention is not limited to such a configuration, and a cold cathode fluorescent lamp may be arranged to face either one of the side end surfaces 8 and 12, and in such a case, the light guide plate 2 (2A to 2D) 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 of the above-described embodiment, the primary light source is composed of the cold cathode fluorescent lamps 16 and 18, but is not limited to this, for example, a plurality of LEDs arranged in a predetermined direction. You may make it comprise from (light emitting diode).

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 sectional view which expands and shows a part of other embodiment of a light-guide plate. The perspective view which cuts off and shows further another embodiment of a light-guide plate. The partial expanded sectional view which expands and shows a part of light-guide plate of FIG. The partial expanded rear view which expands and shows a part of back surface of further another embodiment of a light-guide plate. Sectional drawing by the VIII-VIII line in FIG. The partial expanded sectional view which expands and shows a part of other embodiment from which light guide plate differs further. 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 figure which shows the relationship between the wavelength of the light propagated through a light guide plate, and the reflectance of the light guide plate.

Explanation of symbols

2, 2A, 2B, 2C, 2D 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, 20A, 20C, 20D Diffusion pattern 22, 22C Convex part 23 Top part 25, 29 Inclined side face 25C, 29D Inclined peripheral side face 27, 27D Concave part 52 Hot press transfer molding apparatus 102 Backlight unit 104 Reflective sheet 104 First prism sheet 107 Second prism sheet P, P2 Vertex P1, P3 Bottom point

Claims (9)

  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, wherein a top portion of the convex portion or a bottom portion of the concave portion is formed in an arc shape.   The plurality of quadrangular pyramid-shaped convex portions or concave portions of the diffusion pattern are formed such that a portion from the apex portion or the bottom portion to 5 to 15 µm is formed in an arc shape in the height direction. The light guide plate described in 1.   The plurality of quadrangular pyramidal convex portions or concave portions of the diffusion pattern are substantially the same size as a regular quadrangular pyramid, and one side of the base of the convex portions or concave portions is 30 to 100 μm, and the height of the convex portions or concave portions is The light guide plate according to claim 1, wherein the thickness or depth is 20 to 50 μm.   4. The light guide plate according to claim 1, wherein a surface roughness of an inclined side surface of the plurality of quadrangular pyramidal convex portions or concave portions of the diffusion pattern is 20 nm Ry or less.   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 light emitting surface for emitting light; and a back surface located on the opposite side of the light emitting surface, wherein the light emitting surface or the back surface is provided with a diffusion pattern, and the diffusion pattern is irregularly arranged in a plurality of conical shapes. The light guide plate is characterized in that the top part of the convex part or the bottom part of the concave part is formed in an arc shape.   The plurality of conical convex portions or concave portions of the diffusion pattern are formed such that a portion from the apex portion or the bottom portion to 5 to 15 μm is formed in an arc shape in the height direction. The light guide plate described.   The plurality of conical convex portions or concave portions of the diffusion pattern have substantially the same size, the diameter of the bottom portions of these convex portions or concave portions is 30 to 100 μm, and the height or depth of these convex portions or concave portions is It is 20-50 micrometers, The light-guide plate of Claim 5 or 6 characterized by the above-mentioned.   8. The light guide plate according to claim 5, wherein a surface roughness of the inclined circumferential side surface of the plurality of conical convex portions or concave portions of the diffusion pattern is 20 nm Ry or less.   A backlight unit for a liquid crystal display comprising the light guide plate according to claim 1, wherein an incident end face to which light enters, an exit surface from which light exits, and a back surface opposite to the exit surface. A light guide plate, a primary light source disposed opposite to the incident end surface of the light guide plate, and a reflective sheet disposed on the back side of the light guide plate. Light unit.

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