JP4637732B2 - Light guide plate and manufacturing method thereof - Google Patents

Description

  The present invention relates to a light guide plate constituting a surface illumination device used for a backlight or the like of a liquid crystal display panel and a method for manufacturing the same.

  As shown in FIG. 9, a conventional light guide plate 1 constituting a surface illumination device includes a light incident surface 2 on which light is incident, a light output surface 3 from which light incident from the light incident surface 2 is emitted, A light exit surface 3 and a non-light exit surface 4 are provided, and a plurality of light deflection sections 5 are formed on at least one of the light exit surface 3 and the non-light exit surface 4. When the light guide plate 1 is used, the light source 6 is disposed along the light incident surface 2, and the light emitted from the light source 6 is taken into the light guide plate 1 from the light incident surface 2. The light is deflected by the light deflector 5 and emitted from the light exit surface 3.

In such a light guide plate 1, since it is important that the brightness of the light exit surface 3 is uniform over the entire surface, conventionally, by adjusting the density and size of the light deflection unit 5, The emitted light quantity was made uniform. Further, in the light guide plate described in Patent Document 1, unevenness in brightness is eliminated by forming a rough surface pattern that diffuses light on at least one of the light exit surface and the non-light exit surface.
JP 2004-31031 A

  Conventionally, the brightness of the light exit surface 3 is made uniform over the entire surface by changing the size of the light deflection unit 5 (FIG. 9) or forming a rough surface pattern (Patent Document 1). In these methods, the shadow 6 a of the light source 6 arranged along the light incident surface 2 cannot be prevented from being reflected on the light exit surface 3.

  In other words, the conventional light deflecting unit 5 and the rough surface pattern are designed mainly for “making the brightness uniform when the light exit surface 3 is viewed from the front”. No sufficient countermeasure has been taken for the “reflection” problem that the shadow 6 a of the light source 6 is reflected on the light exit surface 3 when viewed from an oblique direction. When this “reflection” occurs, the shadow 6a portion appears brighter than the other portions, and thus the brightness of the light exit surface 3 is uneven.

  Therefore, a main object of the present invention is to provide a light guide plate that can eliminate unevenness in brightness on the light exit surface by preventing the shadow of the light source from appearing on the light exit surface.

The invention described in claim 1 is described as follows: “a light incident surface 10a on which light is incident, a light exit surface 10b from which light incident from the light incident surface 10a is emitted, and a non-light exit surface that faces the light exit surface 10b” In the light guide plate 10 in which a plurality of light deflection portions 26 that emit light from the light exit surface 10b are formed on at least one of the light exit surface 10b and the non-light exit surface 10c, the light exit surface 10b Further, at least one of the non-light-emitting surfaces 10c except for the light deflecting portion 26, a plurality of streaky light diffusing portions 28 for diffusing light are arranged in the traveling direction of the light incident from the light incident surface 10a. The light guide plate 10 "is characterized by being inclined at an arbitrary angle with respect to the light guide plate 10".

  In the present invention, when light hits the plurality of streaky light diffusing portions 28, the light is diffused in a direction substantially orthogonal to the longitudinal direction of the light diffusing portions 28, that is, in the width direction. That is, in the streak-like light diffusion portion 28, although there is almost no change in shape in the longitudinal direction, the change in shape in the width direction is steep, so that light is diffused over a wide range in the width direction.

  The invention described in claim 2 is characterized in that, in the “light guide plate 10” described in claim 1, “the light diffusion portion 28 is a groove or a protrusion”.

  In the present invention, the shape of the light diffusion portion 28 is limited to a groove or a protrusion.

According to the third aspect of the present invention, "a plurality of light deflecting portions 26 that emit light from the light exit surface 10b are provided on at least one of the light exit surface 10b and the non-light exit surface 10c. A plurality of streaky light diffusing portions 28 for diffusing light in a portion excluding the light deflecting portion 26 in at least one of the non-light exiting surfaces 10c is at an arbitrary angle with respect to the traveling direction of the light incident from the light incident surface 10a. a method of manufacturing a light guide plate 10 in inclined are formed, preparing a base material that is formed in (a) pattern corresponding to the light deflection unit 26 and the light diffusing portion 28 is a surface, (b A replica plate is formed by growing a metal layer on the surface of the base material by electroforming, (c) the replica plate removed from the base material is placed in a mold cavity, and (d) the gold plate Inside mold cavity The resin is injected, a method of manufacturing the light guide plate 10 ".

  This invention is a manufacturing method of a light-guide plate used for manufacturing the light-guide plate 10 described in Claims 1-3.

  According to the first to third aspects of the present invention, the light incident from the light incident surface 10a is diffused by the streaky light diffusion portion 28 in a direction substantially orthogonal to the longitudinal direction of the light diffusion portion 28. Can do.

  Therefore, if the longitudinal direction of the light diffusing portion 28 is aligned with a direction substantially orthogonal to the light traveling direction, the shadow 14a of the light source 14 reflected on the light exit surface 10b is effectively diffused in the light traveling direction. Can be blurred.

  According to the invention described in claim 4, the light guide plate 10 according to the invention described in claims 1-3 can be manufactured easily and inexpensively.

  FIG. 1 is a perspective view showing a light guide plate 10 to which the present invention is applied, and FIG. 2 is a plan view (A) and a bottom view (B) showing the light guide plate 10. 3 is a front view showing the surface illumination device 12 in which the light guide plate 10 is incorporated, and FIG. 4 is an exploded perspective view showing the surface illumination device 12.

  The surface illumination device 12 (FIGS. 3 and 4) is used as a backlight for irradiating a liquid crystal display panel such as a car navigation system, a TV receiver, or a computer display from the back, and includes a light guide plate 10, a light source 14, The reflector 16, the reflection plate 18, the diffusion plates 20 a and 20 b, the light guide lens 22, and the like are included.

  The light guide plate 10 (FIGS. 1 and 2) is a wedge-shaped member made of a light-transmitting material such as transparent acrylic resin (PMMA) or polycarbonate (PC). A surface 10a is formed, a light exit surface 10b is formed on the front surface (upper surface in FIG. 1), and a non-light exit surface 10c is formed on the back surface, that is, the surface opposite to the light exit surface 10b (lower surface in FIG. 1). ing. The non-light-emitting surface 10c is provided with a plurality of light deflecting portions 26 that emit light from the light-emitting surface 10b, and a plurality of light-diffusing portions on the non-light-emitting surface 10c except for the light deflecting portions 26 are diffused. The streak-like light diffusing portion 28 is formed.

  The light deflecting unit 26 in this embodiment is a dot-like “concave portion”, and the size of the light deflecting unit 26 is from the light incident surface 10a so that the amount of emitted light is uniform over the entire surface of the light emitting surface 10b. It is set to increase as you move away.

  The light deflecting unit 26 may have any function as long as it has a function of emitting light from the light exit surface 10b, and the shape thereof is not particularly limited. That is, the shape of the light deflection unit 26 may be a dot-like “projection”, “projection”, “strip”, or the like in addition to the dot-like “recess”. The more specific shape of “” may be “hemispherical” or “quadrangular pyramid”.

  The light diffusion portion 28 is a fine “groove”, and is formed to extend in a direction substantially orthogonal to the traveling direction of the light incident from the light incident surface 10a.

  The distribution density, depth, and the like of the light diffusion portion 28 are determined depending on the surface pattern of the base material used in the manufacturing process to be described later, but the portion corresponding to the light diffusion portion 28 in the surface pattern of the base material Is formed by a polishing process by a polishing machine. Therefore, the state of the light diffusion portion 28 can be expressed as surface roughness (JIS standard) by polishing treatment. In this embodiment, the arithmetic average roughness Ra is 0.03 to 0.30 μm, and the ten-point average The light diffusion portion 28 is formed with a surface roughness such that the roughness Rz is 0.10 to 0.70 [mu] m and the average interval Sm between the irregularities is 20 to 600 [mu] m. However, these values are measured in a direction orthogonal to the direction in which the light diffusion portion 28 extends.

  The light diffusing unit 28 may have any function of diffusing light, and the shape thereof may be a “protrusion” in addition to the “groove”.

  The light source 14 provides light to the light guide plate 10 and is disposed along the light incident surface 10a. The light source 14 in this embodiment is a rod-like cold cathode tube, but instead of this, a plurality of LEDs (light emitting diodes) with low power consumption may be used.

  The reflector 16 reflects a part of the light emitted from the light source 14 and gives it to the light incident surface 10 a, and is disposed on the back of the light source 14 so as to cover it.

  The reflection plate 18 returns light leaking from the light guide plate 10 to the light guide plate 10, and is formed of a material having excellent light reflectivity such as white PET, and is disposed in the vicinity of the non-light exit surface 10c. ing.

  The diffusing plates 20a and 20b are for diffusing light to eliminate uneven brightness, and are formed by mixing light diffusing means such as transparent resin particles in a translucent material such as acrylic resin. . The light guide lens 22 is for correcting the direction of light in a direction substantially orthogonal to the light exit surface 10b of the light guide plate 10, and is formed of a translucent material such as acrylic resin. Then, the diffusion plate 20a, the light guide lens 22, and the diffusion plate 20b are arranged in layers in this order adjacent to the light exit surface 10b.

  When the surface illumination device 12 is disposed on the back surface of a liquid crystal display panel (not shown) and the light source 14 is turned on, the light from the light source 14 enters the light guide plate 10 from the light incident surface 10 a directly or via the reflector 16. Incident light travels while being reflected by the wall surface of the light guide plate 10. When the light hits the light deflecting unit 26, the light is deflected in a predetermined direction, so that the light is emitted to the outside of the light guide plate 10 without being diffused or reflected to the inside of the light guide plate 10.

  On the other hand, when light hits the light diffusing unit 28, the light is diffused in a direction substantially orthogonal to the longitudinal direction of the light diffusing unit 28, that is, in the width direction. That is, in the streak-like light diffusion portion 28, although there is almost no change in shape in the longitudinal direction, the change in shape in the width direction is steep, so that light is diffused over a wide range in the width direction. Therefore, as shown by the two-dot chain line in FIG. 1, the shadow 14a of the light source 14 reflected on the light exit surface 10b can be diffused in the light traveling direction and effectively blurred.

  In addition, as a method of manufacturing the light guide plate 10, “a method of directly forming a predetermined optical pattern by irradiating a resin plate with laser light”, “machining a pattern corresponding to the predetermined optical pattern on a mold, "Method of injection molding using the mold" or "Method of forming a replica plate having a pattern corresponding to a predetermined optical pattern by electroforming, and placing the replica plate in the mold and injection molding" However, since it is necessary to form the streak-like light diffusing portion 28 with high accuracy, “a replica plate manufactured by an electroforming method is disposed in a mold and injection molded. Method (hereinafter referred to as “replica method”) ”is desirable.

  When the light guide plate 10 is manufactured using the replica method, first, (a) a groove corresponding to the streak-shaped light diffusion portion 28 by polishing the surface of a base material made of metal such as stainless steel with a polishing machine. In addition, a minute concave portion corresponding to the light deflection unit 26 is formed by blasting (that is, a method of spraying a projection material on the surface of the base material), etching, machining, or the like. That is, a pattern corresponding to a predetermined optical pattern composed of the light deflection unit 26 and the light diffusion unit 28 is formed on the surface of the base material.

  Then, (c) a metal layer made of a metal such as nickel or copper is grown by electroforming on the surface of the base material on which the patterns (strips and recesses) are formed, thereby forming a replica plate on which the patterns are transferred. Thereafter, (d) the replica plate removed from the base material is placed in the mold cavity, (e) the resin is injected into the mold cavity, and a predetermined optical pattern (the light deflection unit 26 and the light diffusion unit 28). A light guide plate 10 having the following is obtained.

  In the light guide plate 10 described above, as shown in FIG. 2, the light diffusion portion 28 is formed only on the non-light-emitting surface 10c, but the light diffusion portion 28 is at least one of the light-emitting surface 10b and the non-light-emitting surface 10c. As long as it is formed in a portion excluding the light deflection portion 26 in FIG. Therefore, as shown in FIG. 5 or FIG. 6, the light diffusion portion 28 may be formed on both the light exit surface 10b and the non-light exit surface 10c, or the light diffusion portion only on the light exit surface 10b as shown in FIG. 28 may be formed. Further, the light deflection unit 26 may be formed on at least one of the light exit surface 10b and the non-light exit surface 10c.

  Further, as shown in FIG. 8, the light diffusion portion 28 may be formed to be inclined at an arbitrary angle (45 ° in FIG. 8) with respect to the traveling direction of the light incident from the light incident surface 10a. In this case, you may form so that the light-diffusion part 28 formed in each of the light-emitting surface 10b and the non-light-emitting surface 10c may mutually cross | intersect. For example, when the diffusing direction by the light diffusing unit 28 and the deflecting direction by the light guide lens 22 are in a relationship of mutual interference, the traveling direction of the light incident from the light incident surface 10a is canceled so as to eliminate the interference. You may set the inclination-angle of the light-diffusion part 28. FIG.

  Further, the overall shape of the light guide plate 10 may be a flat plate shape having a uniform thickness or other shapes in addition to the wedge shape as in the above-described embodiment.

  Furthermore, the light incident surfaces 10a may be formed on both end surfaces of the light guide plate 10, and the light sources 14 may be disposed along the respective light incident surfaces 10a. In this case, the distribution density and size of the light deflection unit 26 are set so that the light incident from each light incident surface 10a is uniformly emitted from the light output surface 10b, and the surface of the light diffusion unit 28 Roughness etc. are set.

The perspective view which shows the light-guide plate of one Example of this invention. 1 is a plan view and a bottom view showing the light guide plate of the embodiment 1 is a front view showing a surface illumination device using the light guide plate of the embodiment of FIG. 1 is an exploded perspective view showing a surface illumination device using the light guide plate of FIG. 1 embodiment. The top view and bottom view which show the light-guide plate of another Example. The top view and bottom view which show the light-guide plate of another Example. The top view and bottom view which show the light-guide plate of another Example. The top view and bottom view which show the light-guide plate of another Example. A perspective view showing a conventional light guide plate

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Light guide plate 10a ... Light entrance surface 10b ... Light exit surface 10c ... Non-light exit surface 12 ... Plane type illuminating device 14 ... Light source 14a ... Shadow 16 ... Reflector 18 ... Reflector plate 20a, 20b ... Diffuser plate 22 ... Light guide lens 26 ... Light deflection unit 28 ... Light diffusion unit

Claims (3)

A light incident surface on which light is incident, a light exit surface from which light incident from the light incident surface is emitted, and a non-light exit surface facing the light exit surface, wherein at least one of the light exit surface and the non-light exit surface On one side, in the light guide plate in which a plurality of light deflecting portions that emit light from the light exit surface are formed,
A portion of at least one of the light exit surface and the non-light exit surface excluding the light deflection portion has a plurality of streaky light diffusion portions for diffusing light with respect to the traveling direction of the light incident from the light incident surface. The light guide plate is formed to be inclined at an arbitrary angle .   2. The light guide plate according to claim 1, wherein the light diffusion part is a groove or a protrusion. A portion except at least one of the light exit surface and the non-light exit surface is provided with a plurality of light deflectors for emitting light from the light exit surface on at least one of the light exit surface and the non-light exit surface. In addition, a light guide plate manufacturing method in which a plurality of streaky light diffusing portions for diffusing light is formed at an arbitrary angle with respect to a traveling direction of light incident from a light incident surface,
(A) preparing a base material on which a pattern corresponding to the light deflection section and the light diffusion section is formed;
(B) forming a replica plate by growing a metal layer on the surface of the base material by electroforming;
(C) placing the replica plate removed from the base material in a mold cavity;
(D) A method for manufacturing a light guide plate, in which a resin is injected into the mold cavity.

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