JP2007214001A - Light guide plate, mold for forming light guide plate, manufacturing method of mold for forming light guide plate, and manufacturing method of light guide plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate, a mold for forming the light guide plate, a manufacturing method of the mold for forming the light guide plate, and the manufacturing method of the light guide plate capable of stably improving emission efficiency of light from a light source. <P>SOLUTION: The light guide plate 110 includes a light emission surface 110A for emitting light, which is emitted from the light source and is incident from a side surface, and a light reflection surface 110B for reflecting the light. At least one of the light emission surface 110A and the light reflection surface 110B is provided with diffusion dots 111 which are a plurality of first light diffusion parts formed in a concave shape or convex shape in a thickness direction of the light guide plate 110 and formed in a pattern in a surface direction to diffuse the light, and a rough surface 112 which is a second light diffusion part formed so as to have approximately equal plane roughness over an entire surface between the plurality of the diffusion dots 111. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is used in an illumination device provided in various display devices such as a liquid crystal display device, and includes a light emitting surface on which light from a light source is incident from a side surface and emits the light, and a light reflecting surface that reflects the light. The present invention relates to a light guide plate, a light guide plate forming mold, a light guide plate forming mold manufacturing method, and a light guide plate manufacturing method, and in particular, a light guide plate capable of improving light emission efficiency from a light source, and a light guide plate forming metal mold. The present invention relates to a mold, a method for manufacturing a light guide plate mold, and a method for manufacturing a light guide plate.

  In recent years, various display devices such as liquid crystal display devices often used for televisions and personal computers are equipped with illumination devices such as so-called backlights in order to ensure the brightness of images actually displayed and to display them clearly. It has been. Such an illuminating device generally includes a light source that emits light and a light guide plate that guides the light emitted from the light source to the display device side.

  In such an illuminating device, the light emitted from the light source enters the inside of the light guide plate, for example, from the side and exits from the surface on the display device side (hereinafter referred to as “light emitting surface”). The light is repeatedly reflected on a surface opposite to the surface (hereinafter referred to as “light reflecting surface”) and finally emitted from the light emitting surface to the outside.

  Here, when the light emitting surface of the light guide plate is formed in a flat mirror shape over the entire area, most of the light from the light source is totally reflected at the boundary surface between the light emitting surface and the outside air, and thus the display device The irradiation efficiency with respect to (that is, the emission efficiency from the light guide plate) decreases. For this reason, in an illuminating device, usually, a number of fine irregularities are formed on the light emitting surface or light reflecting surface of the light guide plate, and the light path in the light guide plate is changed to improve the light emission efficiency. .

  In order to manufacture such a light guide plate, a mold for forming a light guide plate is usually used, and the following method is known as a manufacturing method for manufacturing this mold for forming a light guide plate. It has been. That is, for example, a method of manufacturing a light guide plate molding die for injection molding a light guide plate that emits light incident from a side surface from a light exit surface different from the side surface, and includes a first step to a third step. is doing.

  Among them, in the first step, a plurality of depressions are formed by etching a processed surface to be a surface for forming a light emitting surface of the plate-shaped member as a material. In the second step, the processed surface is blasted to roughen the region including the inner surface of each recess in the processed surface. In the third step, the processed surface is polished to selectively mirror a part of the processed surface other than the inner surface of the recess. The light guide plate manufactured using the mold for forming the light guide plate manufactured as described above is configured to improve the light emission efficiency from the light output surface (for example, Patent Document 1). reference.).

JP 2004-216705 A

  However, in the light guide plate molding die manufactured by the conventional manufacturing method described in Patent Document 1, a part of the region other than the inner surface of the recess of the processed surface is mirror-finished. In the optical plate, there is a problem that a part of the light entering from the light source and going to the light exit surface is totally reflected by the mirrored portion, and it is difficult to improve the light exit efficiency more stably.

  The present invention has been made to solve the above problems, and can manufacture a light guide plate, a light guide plate molding die, and a light guide plate molding die capable of stably improving the light emission efficiency from the light source. It is an object to provide a method and a method for manufacturing a light guide plate.

  In order to solve the above-described problems, a light guide plate according to the present invention is a light guide plate having a light exit surface that emits light from a light source and emits the light, and a light reflection surface that reflects the light. And at least one of the light emitting surface and the light reflecting surface is formed in a concave or convex shape in the plate thickness direction of the light guide plate, and a plurality of the light diffused in the dot pattern formed in the surface direction. A first light diffusing portion and a second light diffusing portion formed so as to have substantially the same surface roughness over the entire surface between the plurality of first light diffusing portions.

  According to the present invention, a plurality of concave or convex first light diffusing portions for diffusing light on at least one of the light emitting surface and the light reflecting surface of the light guide plate, and between the plurality of first light diffusing portions. And a second light diffusing portion formed to have substantially the same surface roughness over the entire surface.

  As a result, the light incident on the light guide plate is diffused by the second light diffusing portion formed between the plurality of first light diffusing portions and emitted to the light emitting side. Compared with the conventional light guide plate which has, the emission efficiency of the light from a light source can be improved stably.

  In addition, the plurality of first light diffusion portions of the light guide plate of the present invention are roughened so that each concave or convex surface has a plurality of fine irregularities.

  According to the present invention, since the concave or convex surfaces of the plurality of first light diffusion portions are each roughened so as to have a plurality of fine irregularities, the light incident on the light guide plate can be efficiently diffused. Can do.

  In addition, the plurality of first light diffusion portions of the light guide plate of the present invention are formed so that the density per unit area increases from the side closer to the light source to the side farther from the light source.

  According to the present invention, the density of the plurality of first light diffusing sections increases per unit area from the side closer to the light source to the side farther away, so that the amount of emitted light near the light source and the amount of emitted light away from the light source are made uniform. Therefore, so-called luminance unevenness can be suppressed.

  The plurality of first light diffusion portions of the light guide plate of the present invention have a diameter of about 0.1 mm to about 0.5 mm and a vertex height of about 0. It is characterized by being formed in a circular shape in the range of 02 mm to approximately 0.1 mm.

  According to the present invention, since the shape of the plurality of first light diffusing portions has a circular shape designed in the above numerical range, the first light diffusing portion has flexibility in the pattern design of the first light diffusing portion in the light guide plate. It becomes possible to easily improve the emission efficiency by the diffusion unit.

  Further, the second light diffusion portion of the light guide plate of the present invention is characterized in that the surface roughness Ra is formed to be approximately 10 μm or less.

  According to the present invention, since the surface roughness Ra of the second light diffusing section is formed to be approximately 10 μm or less, the second light diffusing section in the light guide plate can be formed uniformly, and the second It is possible to easily design the pattern of the first light diffusion portion based on the surface roughness Ra of the second light diffusion portion while improving the emission efficiency by the two light diffusion portions.

  A light guide plate molding die according to the present invention is a guide for injection molding a light guide plate having a light emitting surface that emits light from a light source and a light reflecting surface that reflects the light. An optical plate molding die, which is formed in a concave or convex shape in a direction orthogonal to the surface direction on at least a processing surface to be a surface for molding the light reflecting surface, and is patterned in the surface direction. A plurality of first light diffusing portion forming dots and a second light diffusing portion forming rough surface formed so as to have substantially the same surface roughness across the entire processed surface between the first light diffusing portion forming dots. And.

  According to the present invention, a plurality of concave or convex first light diffusing portion forming dots for diffusing light on at least a processed surface to be a surface for forming a light reflecting surface of the light guide plate, and the plurality of these A second light diffusion portion forming rough surface is formed between the first light diffusion portion forming dots so as to have substantially the same surface roughness over the entire surface.

  As a result, the light incident on the light guide plate formed by the light guide plate forming mold is, together with the plurality of first light diffusion portions formed by the plurality of first light diffusion portion forming dots, the second light diffusion portion. The light from the light source is diffused by the second light diffusing portion formed by the forming rough surface and emitted to the light emitting side, so that the light from the light source is compared with the conventional light guide plate molding die having the rough surface and the mirror surface. It is possible to manufacture a light guide plate that can stably improve the light emission efficiency.

  In addition, the first light diffusing portion forming dots of the light guide plate forming mold of the present invention are each roughened so that each concave or convex surface has a plurality of fine irregularities. .

  According to the present invention, the concave or convex surfaces of the plurality of first light diffusing portion forming dots are each roughened so as to have a plurality of fine irregularities. Thus, it is possible to efficiently diffuse the incident light by the first light diffusion portion of the light guide plate formed thereby.

  Further, the first light diffusing portion forming dots of the light guide plate molding die of the present invention are formed so that the density on the processed surface gradually increases from one end side to the other end side of the processed surface. It is characterized by being.

  According to the present invention, the density on the processed surface of the plurality of first light diffusing portion forming dots gradually increases from one end side to the other end side of the processed surface, so in the light guide plate formed thereby, The amount of emitted light near the light source and the amount of emitted light away from the light source can be made uniform, and so-called luminance unevenness can be suppressed.

  The first light diffusing portion forming dots of the light guide plate forming mold of the present invention have a diameter of approximately 0.1 mm to approximately 0.5 mm, respectively, when viewed in a direction orthogonal to the processed surface. It is characterized by being formed in a circular shape having a vertex height of about 0.02 mm to about 0.1 mm with respect to the processed surface.

  According to the present invention, the plurality of first light diffusing portion forming dots forming the plurality of first light diffusing portions of the light guide plate have a circular shape designed in the above numerical range, and thus formed. In the light guide plate, it is possible to easily improve the emission efficiency by the first light diffusion portion.

  Further, the rough surface for forming the second light diffusing portion of the light guide plate forming mold of the present invention is formed so that the surface roughness Ra is about 10 μm or less.

  According to the present invention, the surface roughness Ra of the rough surface for forming the second light diffusing portion forming the second light diffusing portion is formed to be approximately 10 μm or less. The second light diffusing portion can be formed uniformly, and the pattern design of the first light diffusing portion is based on the surface roughness Ra of the second light diffusing portion while improving the emission efficiency by the second light diffusing portion. Can be done easily.

  In the method for manufacturing a light guide plate molding die according to the present invention, light from a light source is incident from a side surface, and a light guide plate having a light emitting surface for emitting the light and a light reflecting surface for reflecting the light is injection molded. A method of manufacturing a light guide plate molding die for forming a concave or convex shape in a direction perpendicular to the surface direction by etching or casting on at least a surface of a metal base material to be a surface for molding the light reflecting surface And a step of forming a rough surface having substantially the same surface roughness over the entire surface by grinding or blasting between the plurality of dots. .

  According to the present invention, a plurality of concave or convex dots are formed by etching or casting on the surface of the metal base material to be a surface for forming at least the light reflecting surface of the light guide plate, and between the plurality of dots. A rough surface having substantially the same surface roughness is formed over the entire surface by grinding or blasting.

  As a result, a light guide plate molding die having a plurality of dots and a rough surface formed on the surface can be obtained, and by using this light guide plate molding die, the emission efficiency of incident light can be stabilized. It becomes possible to manufacture a light guide plate that can be improved.

  The light guide plate manufacturing method according to the present invention includes a step of injection molding the light guide plate using the light guide plate forming mold manufactured by the light guide plate forming mold described above. And

  According to the present invention, it is possible to stably improve the emission efficiency of incident light by injection molding using the light guide plate molding die manufactured by the above-described light guide plate molding die manufacturing method. A light guide plate can be obtained.

  Exemplary embodiments of a light guide plate, a light guide plate forming mold, a light guide plate forming mold, and a light guide plate manufacturing method according to the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment)
FIG. 1 is an exploded perspective view showing an example of a configuration of a light guide plate unit using the light guide plate according to the present embodiment. FIG. 2 is a side view showing an example of the configuration of the light guide plate unit shown in FIG. As shown in FIGS. 1 and 2, the light guide plate unit 100 is configured in a rectangular plate shape, for example, and includes prism sheets 101 and 102, a diffusion sheet 103, a light guide plate 110, a reflection sheet 104, and a light source cover 105. , And a light source 106.

  The prism sheets 101 and 102 have a structure in which, for example, a prism made of an acrylic resin is disposed on a polyester film layer, and condenses light emitted from the light emitting surface 110A side of the light guide plate 110 in the emitting direction. Similar to the prism sheets 101 and 102, the diffusion sheet 103 condenses light emitted from the light exit surface 110A side of the light guide plate 110 in the exit direction.

  The reflection sheet 104 is disposed so as not to leak light incident on the light guide plate 110 from the light reflection surface 110 </ b> B side or the side surface side of the light guide plate 110. The light source cover 105 is disposed so as to cover the light source in order to efficiently transmit the light from the light source 106 from the side surface of the light guide plate 110. The light source 106 includes a fluorescent tube such as a cold cathode tube and a light emitting element such as an LED (Light Emitting Diode). In addition, each sheet | seat 101-104 and the light source cover 105 are comprised by various resin materials, such as an acrylic type and a polyethylene type, for example.

  The light guide plate 110 is made of, for example, a thermoplastic resin material such as polycarbonate (PC), polymethyl methacrylate (PMMA), or cyclic olefin copolymer (COC), or a transparent material such as glass, and has high light transmittance and low birefringence. It has. The light guide plate 110 is formed by a processing method such as injection molding or heat press, for example, and a light exit surface 110A that emits light incident on the light guide plate 110 from the light source 106 through the side surface and the light exit surface 110A. And a light reflecting surface 110B that reflects to the side.

  That is, in the light guide plate unit 100 configured in this way, light from the light source 106 repeats reflection in the light guide plate 110 and is emitted from the light exit surface 110A side, and a part of the light leaks from the light guide plate 110 by the reflection sheet 104. Thus, the light reflected from the light exit surface 110 </ b> A is emitted in the direction substantially perpendicular to the light reflection surface 110 </ b> B through the diffusion sheet 103 and the prism sheets 101 and 102.

  The light exit surface 110A of the light guide plate 110 is, for example, a flat surface or a rough surface roughened with a certain roughness, and the light reflecting surface 110B is, for example, a first light formed in a concave shape or a convex shape described later. A diffusion dot that is a diffusion part and a rough surface that is a second light diffusion part formed between the diffusion dots are provided.

  FIG. 3 is a front view of the light reflecting surface 110 </ b> B of the light guide plate 110. 4 is a cross-sectional view taken along the line AA in FIG. FIG. 5 is an enlarged view of a range indicated by M in FIG. As shown in FIGS. 3 and 4, the light reflecting surface 110 </ b> B of the light guide plate 110 includes a plurality of diffusion dots 111 and a rough surface 112 formed between the plurality of diffusion dots 111.

  Here, the plurality of diffusion dots 111 are formed in a circular convex shape protruding outward from the light reflecting surface 110B, and the diameters D1 and D2 of the diffusion dots 111 are, for example, about 0.1 mm to 0.5 mm, respectively. It is appropriately formed in the range. Here, each diffusion dot 111 is formed so that the diameter D1 of the diffusion dot 111 closer to the light source 106 <the diameter D2 of the diffusion dot 111 farther from the light source 106.

  Each diffusing dot 111 is formed so as to gradually protrude from the light reflection surface 110B in a range of about 0.02 mm to about 0.1 mm from the side closer to the light source 106 to the side farther from the light source 106. Further, the pitch P between the diffusion dots 111 is formed to be about 0.03 mm in the narrowest case. On the other hand, the rough surface 112 has a depth of about 0.01 mm from the light reflecting surface 110B and is formed over the entire surface of the light reflecting surface 110B with a uniform surface roughness.

  Here, the relationship between the diffusing dots 111 and the rough surface 112 on the light reflecting surface 110B of the light guide plate 110 formed in this way is diffused around a predetermined range M of the light reflecting surface 110B, for example, as shown in FIG. Assuming that the area of the dot 111 is S1 and the unit area within the predetermined range M is T1, the area ratio R for realizing the desired amount of emitted light can be derived from the relational expression S1 / T1 = R.

  FIG. 6 is a graph showing the relationship between the area ratio R and the distance L from the light source 106. As described above, the relationship between the area ratio R and the distance L needs to be adjusted so that the area ratio R increases as the distance L from the light source 106 increases as represented by the curve 600. Next, a manufacturing process of a light guide plate forming mold for manufacturing the light guide plate 110 will be described.

  FIG. 7 is a process diagram showing a manufacturing process of a light guide plate forming mold for manufacturing the light guide plate 110. In the following description, the same reference numerals are given to the same portions as those already described, and description thereof is omitted. First, as shown in FIG. 7A, a light guide plate molding die 700 of a plate-like member made of a metal base material is prepared and subjected to degreasing, washing, and the like. Next, as shown in FIG. 7B, a resist 701 is formed on the processed surface of the light guide plate molding die 700 other than the diffusion dot 111 formation portion, and the diffusion dot formation region 702 and the rough surface formation region are formed. 703 is determined.

  Next, as shown in FIG. 7C, the processed surface of the light guide plate molding die 700 is subjected to an etching process so that a diffusion dot transfer recess 711 having a fine rough surface in the diffusion dot formation region 702 is formed. Then, as shown in FIG. 7D, the resist 701 is removed to expose the rough surface forming region 703. Finally, as shown in FIG. 7E, for example, a grindstone is applied to the work surface using a grindstone 719 that rotates in the direction indicated by the arrow E in the figure and moves in the direction indicated by the arrow F in the figure. A rough surface transfer portion 712 is formed in the surface forming region 703 to form a light guide plate molding die 700 having a molding surface 710 having a diffusion dot transfer recess 711 and a rough surface transfer portion 712.

  Here, the conditions for the etching process are set so that the diffusion dot transfer depression 711 has a hemispherical shape with a diameter of 0.11 mm to 0.47 mm and a depth of 0.02 mm to 0.1 mm, for example. As the grinding conditions, for example, a surface grinder can be used, and a general grindstone, a diamond grindstone, a CBN grindstone, or the like can be selected as the grindstone 719. Further, as grinding conditions of the surface grinder, for example, the X-axis feed rate is preferably set to 20 m / min, the Y-axis feed rate is set to 4 mm per pitch, and the cutting depth is set to 0.01 mm.

  As dressing conditions, grinding is performed by applying a single crystal diamond grindstone 719 at an acute angle (less than 90 °) with respect to the processed surface of the light guide plate molding die 700, and the surface roughness is slightly finely adjusted. When grinding, grinding is performed by applying a grindstone 719 at an obtuse angle (90 ° or more). The tip of the grindstone 719 may be a polygon such as a pentagon, and the surface to be applied for each dress may be changed.

  By setting the conditions for the etching process and the grinding process in this way, the light guide plate molding die 700 having the rough surface transfer portion 712 having a surface roughness Ra of about 8 μm ± 1 μm, that is, a surface roughness Ra of 10 μm or less. Can be manufactured. In addition, it is also possible to change surface roughness Ra to about 6 micrometers-14 micrometers by changing the cutting depth of grinding. Next, a process of manufacturing the light guide plate 110 using the light guide plate forming mold 700 manufactured as described above will be described.

  8 and 9 are explanatory views for explaining a manufacturing process of the light guide plate 110. FIG. 10 is a side view showing the manufactured light guide plate 110. 8 to 10, the shape of the molding surface 710 of the light guide plate molding die 700 is omitted. First, as shown in FIG. 8, the upper mold 801 having the injection gate 801a formed thereon, the side molds 802 and 803, and the light guide plate molding mold 700 are appropriately combined, and the plasticized state from the injection cylinder 804 is obtained. The resin material is injected and filled. And each metal mold | die 700,801-803 is cooled and the filled resin material is solidified.

  Next, as shown in FIG. 9, for example, the upper mold 801 is removed in the direction of the white arrow in the figure, and the light guide plate 110 provided with the runner 110C is die-cut in the direction of the white arrow in the figure. Then, the runner 110C is cut to manufacture the light guide plate 110 having the diffusion dots 111 and the rough surface 112 as shown in FIG.

  The light guide plate 110 manufactured using the above-described light guide plate molding die 700 has the configuration of having the diffusing dots 111 and the rough surface 112 on the light reflecting surface 110B side. May be formed. Note that only the rough surface 112 may be formed on the light exit surface 110A side. In this case, specifically, for example, a rough surface may be formed on the processed surface of the upper mold 801 by grinding, and this may be transferred when the light guide plate 110 is formed.

  FIG. 11 is a side view showing another light guide plate. As described above, when a rough surface is formed and transferred on the processed surface of the upper mold 801, the rough surface 1112 is provided on the light emitting surface 1110A side, and the diffusing dots 1111 and the rough surface 1112 are provided on the light reflecting surface 1110B side. It is possible to obtain a light guide plate 1110 having The conditions for forming the diffusion dots 1111 and the rough surface 1112 are preferably set in the same manner as the light guide plate 110 described above. As described above, the light guide plates 110 and 1110 are provided with the diffusion dots 111 and 1111 having a fine rough surface and the rough surfaces 112 and 1112 formed between the diffusion dots 111 and 1111. For this reason, the occurrence of uneven brightness, which is a disadvantage of these, compared to the conventional method of improving the luminance by the rough surface and mirror surface formation, or the method of improving the luminance only by the dot arrangement mode, etc. Can be further suppressed by combining the diffusion dots 111 and 1111 and the rough surfaces 112 and 1112, while reliably suppressing the diffusion dots 111 and 1111 and the rough surfaces 112 and 1112.

  12 and 13 are graphs showing the relationship between the luminance B and the relative position L where the light source 106 is 0 in a general light guide plate. FIG. 14 is a graph showing the relationship between the luminance B in the light guide plate 110 of the present embodiment and the relative position L where the light source 106 is zero. As shown in FIG. 12, when a general light guide plate is ground and a rough surface 112 is formed on at least one surface, the luminance B increases as the relative position L from the light source 106 increases as shown by a curve 1200. Less. For this reason, the brightness B is not uniform.

  Therefore, as shown in FIG. 13, a diffused dot 111 is patterned on at least one side of a general light guide plate, and the luminance B increases as the relative position L from the light source 106 increases as shown by the curve 1300. If the diffusion dots 111 are formed and combined, the luminance B can be made uniform. Therefore, as shown in FIG. 14, in the case of the light guide plate 110 of the present embodiment, stable emission as indicated by the curve 1400 within the range from the luminance Min to the luminance Max regardless of the relative position L from the light source 106. The amount of light can be obtained. At this time, the ratio of luminance Min / luminance Max is preferably 80% or more.

  According to the experiment by the applicant of the present invention, the following results could be obtained. That is, a cold cathode tube of φ1.8 is used as the light source 106 of the light guide plate 110, the thickness of the light guide plate is unified to 2.15 mm, and only one of the diffusion dots 111 and the rough surface 112 is a light exit surface. The center luminance and the luminance unevenness of the light guide plate 110 were compared between the case where the light guide plate 110 is formed on the light reflecting surface 110B and the case where the light reflection surface 110B is formed in combination.

As a result, in the former case, the center luminance was 3,780 cd / m ² and the luminance unevenness was 81.5%, whereas in the latter case, the central luminance was 4,994 cd / m ² and the luminance unevenness was 80%. The result was 0.0%. Therefore, when the diffusing dots 111 and the rough surface 112 are combined in the light guide plate 110, the luminance unevenness is approximately the same as when only one of them is formed, but the luminance is about 1 .3 times improvement was able to be obtained. For this reason, according to the light guide plate 110 of the present invention, it can be said that the emission efficiency can be stably improved.

  As described above, according to the light guide plate 110 of the embodiment of the present invention, a plurality of concave or convex shapes that diffuse light on at least one of the light emitting surface 110A and the light reflecting surface 110B of the light guide plate 110. And a rough surface 112 formed between the plurality of diffusion dots 111 so as to have substantially the same surface roughness over the entire surface. Accordingly, the light incident on the light guide plate 110 is diffused by the rough surface 112 formed between them together with the plurality of diffusion dots 111 and is emitted to the light emitting side, so that the conventional light having a rough surface and a mirror surface is provided. Compared with the light guide plate, the emission efficiency of light from the light source 106 can be stably improved as compared with the case where the emission efficiency is improved only by the arrangement or formation of dots or rough surfaces.

  In addition, since the concave or convex surfaces of the plurality of diffusion dots 111 are each roughened so as to have a plurality of fine irregularities formed by, for example, an etching process, light incident on the light guide plate 110 can be efficiently Can diffuse. Furthermore, since the density of the plurality of diffusion dots 111 increases per unit area from the side closer to the light source 106 to the side farther from the light source 106, the emitted light amount near the light source 106 and the emitted light amount far from the light source 106 can be made uniform. It is possible to suppress so-called luminance unevenness.

  Moreover, since the shape of the plurality of diffusion dots 111 has a circular shape (hemispherical shape) designed in the above numerical range, the emission efficiency of the diffusion dots 111 is made flexible while allowing the pattern design of the diffusion dots 111 on the light guide plate 110 to be flexible. Can be easily improved. Furthermore, since the surface roughness Ra of the rough surface 112 is formed to be approximately 10 μm or less, the rough surface 112 in the light guide plate 110 can be uniformly formed based on this surface roughness, It is possible to easily design the pattern of the diffusing dots 111 based on the surface roughness Ra of the rough surface 112 while improving the emission efficiency by the surface 112.

  In addition, according to the light guide plate molding die 700 of the embodiment of the present invention, at least a processed surface to be a surface for forming the light reflecting surface 110B of the light guide plate 110, a concave shape or a convex shape that diffuses light. A plurality of diffusion dot transfer depressions 711 and a rough surface transfer portion 712 formed between the diffusion dot transfer depressions 711 so as to have substantially the same surface roughness over the entire surface. Thereby, the light incident on the light guide plate 110 formed by the light guide plate molding die 700 is formed by the rough surface transfer unit 712 together with the plurality of diffusion dots 111 formed by the plurality of diffusion dot transfer depressions 711. Since the light is diffused by the rough surface 112 and emitted to the light exit side, the light emission efficiency from the light source 106 can be stably compared with a conventional mold for forming a light guide plate having a rough surface and a mirror surface. It becomes possible to manufacture the light guide plate 110 that can be improved.

  Further, since the concave or convex surfaces of the plurality of diffusion dot transfer depressions 711 are each roughened so as to have a plurality of fine irregularities, the light is incident by the diffusion dots 111 of the light guide plate 110 formed thereby. The diffused light can be diffused efficiently. Further, the density of the plurality of diffusion dot transfer depressions 711 on the processing surface gradually increases from one end side to the other end side of the processing surface, and thus the light guide plate 110 formed thereby emits light near the light source 106. The amount of light and the amount of light emitted from the light source 106 can be made uniform, and so-called luminance unevenness can be suppressed.

  Moreover, since the shape of the plurality of diffusion dot transfer depressions 711 for forming the plurality of diffusion dots 111 of the light guide plate 110 has a circular shape (hemispherical shape) designed in the above numerical range, the light guide plate 110 formed thereby. In this case, it is possible to easily improve the emission efficiency by the diffusing dots 111. Furthermore, since the surface roughness Ra of the rough surface transfer part 712 for forming the rough surface 112 is formed to be approximately 10 μm or less, the rough surface 112 in the light guide plate 110 formed thereby has the surface roughness. It is possible to form uniformly based on this, and it is possible to easily design the pattern of the diffusing dots 111 based on the surface roughness Ra of the rough surface 112 while improving the emission efficiency by the rough surface 112.

  In addition, according to the method of manufacturing light guide plate molding die 700 of the embodiment of the present invention, at least the surface of the metal base material to be a surface for forming light reflecting surface 110B of light guide plate 110 is etched or cast. Thus, a plurality of concave or convex diffusion dot transfer depressions 711 are formed, and a rough surface transfer portion 712 having substantially the same surface roughness is formed between the plurality of diffusion dot transfer depressions 711 by grinding or blasting. Is done. As a result, a light guide plate molding die 700 having a plurality of diffusion dot transfer depressions 711 and a rough surface transfer portion 712 formed on the surface can be obtained. It is possible to manufacture the light guide plate 110 that can stably improve the emission efficiency of the emitted light.

  Furthermore, according to the manufacturing method of the light guide plate 110 of the embodiment of the present invention, the incidence is performed by injection molding using the light guide plate molding die 700 manufactured by the above-described manufacturing method of the light guide plate molding die 700. It is possible to obtain the light guide plate 110 that can stably improve the emission efficiency of the emitted light.

The disassembled perspective view which shows an example of a structure of a light-guide plate unit. The side view which shows an example of a structure of a light-guide plate unit. The front view of the light reflection surface of a light-guide plate. AA sectional drawing of FIG. The enlarged view of the range shown by M of FIG. The graph which shows the relationship between the area ratio R and the distance L from a light source. Process drawing which shows the manufacturing process of the metal mold | die for light-guide plate shaping | molding. Explanatory drawing for demonstrating the manufacturing process of a light-guide plate. Explanatory drawing for demonstrating the manufacturing process of a light-guide plate. The side view which shows the manufactured light-guide plate. The side view which shows another light-guide plate. The graph which shows the relationship between the brightness | luminance in a common light-guide plate, and a relative position. The graph which shows the relationship between the brightness | luminance in a common light-guide plate, and a relative position. The graph which shows the relationship between the brightness | luminance and relative position in the light-guide plate of embodiment.

Explanation of symbols

100 light guide plate unit, 101, 102 prism sheet, 103 diffusion sheet, 104 reflection sheet, 105 light source cover, 106 light source, 110, 1110 light guide plate, 110A, 1110A light exit surface, 110B, 1110B light reflection surface, 111, 1111 diffusion Dot, 112, 1112 Rough surface, 700 Light guide plate mold

Claims (12)

A light guide plate having a light exit surface from which light from a light source is incident and emits the light and a light reflection surface that reflects the light,
At least one of the light emitting surface and the light reflecting surface is formed in a plurality of first shapes that diffuse concavely or convexly in the plate thickness direction of the light guide plate and that have a dot pattern formed in the surface direction. 1 light diffusion part;
A second light diffusion portion formed so as to have substantially the same surface roughness across the entire surface between the plurality of first light diffusion portions;
A light guide plate comprising:   2. The light guide plate according to claim 1, wherein each of the plurality of first light diffusion portions is roughened so that each concave or convex surface has a plurality of fine irregularities.   3. The light guide plate according to claim 1, wherein each of the plurality of first light diffusion portions is formed so that a density per unit area increases from a side closer to the light source to a side farther from the light source.   The plurality of first light diffusion portions have a diameter of about 0.1 mm to about 0.5 mm and a vertex height of about 0.02 mm to about 0.1 mm with respect to the formation surface when viewed in the thickness direction. The light guide plate according to claim 1, wherein the light guide plate is formed in a circular shape.   5. The light guide plate according to claim 1, wherein the second light diffusion portion is formed to have a surface roughness Ra of approximately 10 μm or less. A light guide plate molding die for injection molding a light guide plate having a light exit surface from which light from a light source is incident and emits the light and a light reflection surface that reflects the light,
For forming a plurality of first light diffusion portions formed in a concave or convex shape in a direction orthogonal to the surface direction on a processing surface to be a surface for forming the light reflecting surface, and patterned in the surface direction Dots and
A second light diffusion portion forming rough surface formed so as to have substantially the same surface roughness across the entire processed surface between the first light diffusion portion forming dots;
A mold for forming a light guide plate, comprising:   7. The light guide plate molding die according to claim 6, wherein the first light diffusing portion forming dots are roughened so that each concave or convex surface has a plurality of fine irregularities. .   The first light diffusing portion forming dots are formed so that the density on the processed surface gradually increases from one end side to the other end side of the processed surface. The light guide plate molding die described.   The first light diffusing portion forming dots have a diameter of about 0.1 mm to about 0.5 mm and a vertex height of about 0.02 mm to about 0.5 mm when viewed in a direction orthogonal to the processing surface. The light guide plate molding die according to any one of claims 6 to 8, wherein the light guide plate molding die is formed in a circular shape in a range of 0.1 mm.   10. The light guide plate molding according to claim 6, wherein the rough surface for forming the second light diffusing portion is formed so that the surface roughness Ra is about 10 μm or less. Mold. A method for manufacturing a light guide plate molding die for injection molding a light guide plate having a light exit surface that emits light from a light source and a light exit surface that emits the light and a light reflection surface that reflects the light,
Forming a plurality of dots that are concave or convex in a direction perpendicular to the surface direction by etching or casting on the surface of the metal base material that should be a surface for forming at least the light reflecting surface;
Forming a rough surface having substantially the same surface roughness over the entire surface by grinding or blasting between the plurality of dots;
A method for manufacturing a light guide plate molding die, comprising: A method for manufacturing a light guide plate, comprising the step of injection molding a light guide plate using the light guide plate forming die manufactured by the method for manufacturing a light guide plate forming die according to claim 11.

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