JP2006261064A - Light guide plate and backlight device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide plate superior in uniform surface light emission performance and light utilization efficiency. <P>SOLUTION: The reflecting surface 13 has a plurality of first optical grooves 14 formed in horizontal direction of the light guide plate 10 and a plurality of second optical grooves 15 formed in vertical direction of the light guide plate 10 from an incident face 11 over a prescribed distance, and an outgoing face 12 has an anisotropic diffusion pattern by hologram. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light guide plate that guides light emitted from an LED light source, and a backlight device that includes the light guide plate and irradiates a liquid crystal display element or the like from the back.

  2. Description of the Related Art Conventionally, in order to illuminate a liquid crystal display device such as a cellular phone, a light guide plate that guides light emitted from a light source to the liquid crystal display device and a backlight device that includes the light guide plate and illuminates the liquid crystal display device from the back are provided. .

  FIG. 13 is a diagram showing the appearance of a conventional light guide plate (see, for example, Patent Document 1). FIG. 13A shows a perspective view, and FIG. 13B shows a top view. In FIG. 13A, the light emitting diode 120 of the light source is also shown.

  The light guide plate 110 is made of a transparent material such as PMMA or polycarbonate and has a substantially plate-like flat shape. The upper and lower surfaces are an emission surface 112 and a reflection surface 113, respectively, and one side surface is an incidence surface 111. On the reflection surface 113, a deflection pattern is formed by a plurality of deflection pattern elements 114 in order to reflect the light incident from the incident surface 111 toward the emission surface 112. As described above, the light guide plate 110 that emits light incident from the incident surface 111 on the side surface from the emission surface 112 on the main surface is referred to as a side edge method, and is widely used in mobile phones and the like.

  Here, the deflection pattern elements 114 are arranged with a space therebetween, and the longitudinal direction thereof is perpendicular to the traveling direction of light from the light source 120. When a plurality of light sources 120 are arranged apart from each other, the reflecting surface 113 is divided into regions corresponding to the respective light sources 120 so as to be perpendicular to the traveling direction of light from the corresponding light sources 120 for each region. The deflection pattern element 114 is disposed on the substrate.

  When the light emitted from the light source 120 enters the light guide plate 110 from the incident surface 111 and is reflected in the longitudinal direction of the deflection pattern element 114 formed on the reflection surface 113, the light is deflected in the direction of the emission surface 112 and emitted. The light is emitted from the surface 112. Further, when the light is reflected in the short direction of the deflection pattern element 114, the traveling direction of the light is changed, so that it acts as a diffusion effect that weakens the directivity of the light source 120 (light emitting diode) and suppresses the generation of bright lines. That is, in this case, the deflection pattern element 114 has both a reflection function for deflecting in the direction of the emission surface 112 and a diffusion function for suppressing the generation of bright lines.

  In this method, since the deflection pattern elements 114 are arranged at intervals, there is a problem that the efficiency of deflecting by the reflection surface in the longitudinal direction is low, and the utilization efficiency of the light emitted from the light source is low. In the case of a plurality of light sources, the arrangement of the deflection pattern elements 114 is very complicated as shown in FIG.

  FIG. 14 is a diagram illustrating how the conventional light guide plate and backlight device are used.

  The light guide plate 110 is disposed immediately below the liquid crystal display device 140 such that the emission surface 112 faces the lower surface 141 of the liquid crystal display device 140. The light emitted from the light emitting diode 120 enters the light guide plate 110 from the incident surface 111.

  The light incident on the light guide plate 110 from the incident surface 111 is deflected and reflected by the deflection pattern element 114 formed on the reflecting surface 113 facing the output surface 112 and is raised in the direction of the liquid crystal display device 140 to be emitted. The light is emitted from the surface 112.

On the other hand, there has conventionally been provided a hologram in which a photosensitive film is exposed through a rectangular opening having a diffuser to form a large number of speckles at random (US Pat. No. 5,365,354). No. 5,534,386). In this hologram, the speckle has a substantially elliptical shape, and the major axis and minor axis of the ellipse have a relationship of Fourier transform with the short side and long side of the rectangle of the opening. When this hologram laser beam is incident, the laser beam is scattered by each speckle and reproduces a rectangular opening used for exposure. By using such a hologram, incident light can be diffused anisotropically.
Japanese Patent No. 3151830

  By the way, when a point light source such as an LED is used, the maximum refraction angle of light incident from the incident surface of the light guide plate is about 42 degrees. Therefore, the incident angle of light that is directly incident on the exit surface from the incident surface is at least about 48 degrees, which is larger than the critical angle. Therefore, the light incident on the light guide plate from the point light source is not directly emitted, but is totally reflected on the emission surface and the reflection surface and then emitted on the emission surface.

  For this reason, in the region of a distance of several mm from the incident surface in the light guide plate, the amount of light emitted from the emission surface is small, and a dark portion is generated in this region, resulting in luminance unevenness. Further, in the backlight device including the downward prism, there is a problem that the amount of light collected from the light exiting surface of the light guide plate by the downward prism is small in the region, and a dark portion is generated in the region to cause luminance unevenness. .

  This invention is proposed in view of the above-mentioned subject, and it aims at providing the light-guide plate and backlight apparatus excellent in uniform planar light emission property and light utilization efficiency.

  In order to solve the above-described problems, a light guide plate according to the present invention has one side as an incident surface, an output surface orthogonal to the incident surface, and a reflective surface facing the output surface, and the incident surface. A light guide plate in which light rays are incident on the incident surface from a plurality of light sources arranged along the longitudinal direction of the surface, wherein the reflecting surface is normal to the exit surface incident on the incident surface from the light source A plurality of first optical grooves formed in the longitudinal direction of the incident surface that receive a light beam having a certain angle and reflect a light beam having a reduced angle with the normal line; A plurality of second optical grooves formed in a direction perpendicular to the longitudinal direction of the incident surface over a predetermined distance from the incident surface, which reflects at least a part of the incident surface at a different angle with respect to the normal line. The exit surface is normal to the normal of the exit surface An anisotropic diffusion pattern that diffuses and transmits light incident from the reflecting surface at an angle equal to or smaller than a constant angle, and the diffusion width of the incident light in the longitudinal direction of the incident surface is the longitudinal direction And an anisotropic diffusion pattern that diffuses so as to be larger than the diffusion width in the direction orthogonal to the.

  The first optical groove preferably has a first surface that forms an angle of 88 degrees or more with the incident surface.

  The light emitting surface of the light source faces the incident surface, and the thickness of the incident surface between the emitting surface and the reflecting surface is preferably within ± 50 μm with respect to the length of the light emitting surface in the thickness direction. .

  The predetermined distance at which the second optical groove is formed is preferably not more than 10 times the thickness of the entrance surface between the exit surface and the reflection surface.

  In the anisotropic diffusion pattern, the diffusion width in the longitudinal direction of the incident surface with respect to the diffusion width in the direction orthogonal to the incident surface is preferably 1:30 or more.

  A ratio L / P between the distance P between the light sources along the incident surface and the distance L between the incident surface and the light source is preferably 0.474 or less.

  The backlight device according to the present invention includes the light guide plate.

  It is desirable to provide an optical film that deflects light emitted from the light guide plate in the normal direction of the output surface of the light guide plate.

  It is desirable that the optical film has a plurality of prismatic deflection elements formed on the surface facing the light exit surface of the light guide plate.

  The light guide plate according to the present invention is excellent in uniform planar light emission and light utilization efficiency, and is suitable for a backlight device that irradiates a liquid crystal display element or the like from the back. In addition, the backlight device according to the present invention is excellent in uniform surface light emission and light utilization efficiency.

BEST MODE FOR CARRYING OUT THE INVENTION

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a light guide plate and a backlight device according to the present invention will be described in detail with reference to the drawings.

  The light guide plate of the present embodiment is made of a transparent resin having a substantially rectangular plate shape, and one side surface thereof is used as an incident surface, and one main surface orthogonal to the incident surface is used as an output surface. The other principal surface that faces the surface in parallel is defined as a reflecting surface.

  This light guide plate is formed by, for example, injection molding using a mold subjected to precision processing, for example. As the transparent resin, for example, polycarbonate (PC), polymethyl methacrylate (PMMA), zeonore, polystyrene, and vinyl chloride can be applied. Among these, from the viewpoint of precision molding, PC, PMMA, and ZEONOR are preferable, and PC is more preferable.

  The light guide plate is formed by such a transparent resin so that a predetermined optical pattern is formed on the reflection surface and an anisotropic diffusion pattern is formed on the emission surface.

  As the optical pattern of the reflecting surface, there are dots, V-shaped grooves, U-shaped grooves, random roughening, etc., but in this embodiment, from the viewpoint of the direction control (alignment) of light rays reflected by this optical pattern. Adopt excellent V-shaped groove. The continuity of the optical pattern may be continuous or discontinuous. In this embodiment, a continuous optical pattern that is excellent in terms of mold workability is employed.

  In the present embodiment, a plurality of V-shaped first optical grooves are formed on the reflecting surface in parallel with the longitudinal direction of the incident surface (hereinafter referred to as the lateral direction).

  The first optical groove has a first surface facing the incident surface and a second surface facing the first surface. The first surface preferably has an angle of 88 degrees or more with respect to the incident surface, and more preferably 88 to 89.2 degrees. When this angle is less than 88 degrees, a large amount of light tends to be emitted to the incident surface side, and when it exceeds 89.2 degrees, light tends to escape to the surface side facing the incident surface.

  The interval between the first optical grooves is preferably 100 to 200 μm, and more preferably 120 to 160 μm. If this interval is less than 100 μm, interference is likely to occur with the prism sheet placed facing the exit surface, and interference fringes tend to be generated during light emission. When this interval exceeds 200 μm, the groove shape tends to be visually recognized.

  In the present embodiment, the reflecting surface has a plurality of second optical grooves formed over a predetermined distance from the incident surface in a direction orthogonal to the longitudinal direction of the incident surface (hereinafter referred to as the vertical direction).

  The second optical groove preferably has an inclined surface with an angle of 30 to 60 degrees with respect to the normal line of the reflecting surface, and the inclined surface is more preferably 50 degrees. If the angle of the inclined surface is less than 30 degrees, the amount of light emitted in the vicinity of the surface facing the incident surface is reduced, and the uniform light emission tends to be impaired. If the angle of the inclined surface exceeds 60 degrees, the amount of light emitted from the reflecting surface is reduced, and therefore a portion that does not shine tends to occur and unevenness tends to occur.

  In the present embodiment, the thickness of the light guide plate between the exit surface and the reflection surface on the entrance surface (hereinafter referred to as the thickness of the light guide plate) is the entrance surface in a plurality of light sources arranged in the lateral direction facing the entrance surface. Is within ± 50 μm with respect to the length in the thickness direction of the light emitting surface facing the light source (hereinafter referred to as the thickness of the light source). More preferably, the thickness of the light guide plate is the same as the thickness of the light source.

  If the thickness of the light guide plate is less than −50 μm with respect to the thickness of the light source, the light emitted from the light source cannot be sufficiently taken into the light guide plate, the amount of light is insufficient, the light emitted from the light guide plate is reduced, and the luminance decreases. Tend. On the other hand, when the thickness of the light guide plate exceeds +50 μm with respect to the thickness of the light source, the light emitted from the light source can be sufficiently taken into the light guide plate, but the light that is not emitted more than that is generated and emitted from the light guide plate. There is a tendency for unevenness to occur.

  In the present embodiment, the second optical groove is formed in the longitudinal direction of the light guide plate on the reflection surface over a length within 10 times the thickness of the light guide plate from the incident surface. As a result, the influence of light reflection by the second optical groove is kept at a predetermined distance from the incident surface, so that there is no influence of light unevenness on the display area where characters, images, etc. are displayed on the liquid crystal display element. .

  In the present embodiment, the light diffusion ratio in the horizontal direction with respect to the vertical direction of the anisotropic diffusion pattern formed on the exit surface is preferably 1:30 to 1:60, and more preferably 1:60. When this ratio is less than 1:30, the diffusion angle in the lateral direction of the light guide plate is small, and the light does not spread and tends to cause unevenness. On the other hand, if this ratio exceeds 1:60, the light tends to spread too much in the lateral direction of the light guide plate on the incident surface side, and the brightness tends to be lowered.

  In this embodiment, light is incident from a point light source such as an LED arranged at substantially equal intervals in the lateral direction of the light guide plate along the incident surface, and the distance P between the light sources and the distance L between the incident surfaces and the light sources are The ratio L / P is 0.474 or less. When the light source is arranged according to such a ratio, the unevenness of light on the incident surface side of the light guide plate is reduced by the action of the second optical groove.

  The backlight device according to the present embodiment has an optical sheet that rises in the direction perpendicular to the light exit surface, and the light output from the light guide plate across the optical sheet. A liquid crystal display element is provided facing the surface.

  The optical sheet is a prism sheet on which a prism-shaped optical deflection element is formed, and the surface on which the optical deflection element is formed is arranged to face the emission surface of the light guide plate (downward prism). For this prism sheet, for example, diamond art made by Mitsubishi Rayon can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this Example shows an example of this invention and this invention is not limited only to this.

  FIG. 1 is a diagram showing an outline of the light guide plate of this embodiment. A light emitting diode (LED) of the light source is also shown. 1A is a bottom view of the light guide plate, FIG. 1B is a longitudinal side view of the light guide plate, and FIG. 1C is a perspective view of the light guide plate.

  The light guide plate 10 is made of a transparent material having a constant refractive index, such as PMMA, polyolefin, or polycarbonate, and has a substantially plate shape having a substantially rectangular upper surface and a lower surface. Then, one side surface is an incident surface 11 on which light from the LED 20 is incident, and a lower surface orthogonal to the incident surface 11 is a reflection surface 13 that reflects incident light from the incident surface 11 or reflected light from the output surface 12. An upper surface that is orthogonal to the incident surface 11 and parallel to the reflecting surface 13 is defined as an emitting surface 12 that emits light.

  A plurality of LEDs 20 are arranged at substantially constant intervals in the lateral direction of the light guide plate 10 so as to face the incident surface 11. The LED 20 has a light emitting surface facing the incident surface 11 at a predetermined distance from the incident surface 11.

  The incident surface 11 has a thickness within ± 50 μm with respect to the thickness of the light emitting surface of the LED 20. Further, the incident surface 11 has a groove shape extending in the thickness direction. Due to this groove shape, light from the LED 20 is efficiently incident into the light guide plate 10.

  Note that a plurality of partial cylindrical shapes extending in the thickness direction can be formed on the incident surface 11 instead of the groove shape. Further, the incident surface 11 can be a flat surface. In this case, this plane is preferably parallel to the light emitting surface of the LED 20, for example.

  The reflecting surface 13 has a plurality of first optical grooves 14 extending in the lateral direction of the light guide plate 10. In addition, a plurality of second optical grooves 15 extending in the longitudinal direction of the light guide plate 10 over a predetermined distance from the incident surface 11 are provided.

  The light guide plate 10 according to the present embodiment has the first optical groove 14 and the second optical groove 15 so that the light incident from the incident surface 11 can be efficiently emitted without causing unevenness in the region on the incident surface 11 side. It can be emitted from.

  FIG. 2 is a side view of the main part of the longitudinal direction of the light guide plate. This figure is an enlarged view of a main part of the side view of the light guide plate 10 shown in FIG.

  The first optical groove 14 formed on the reflecting surface 13 has a first surface 14a that faces the incident surface 11 and a second surface 14b that faces the first surface 14a. The angle α formed by the first surface 14a and the incident surface 11 is 88 degrees or more.

  In addition, the angle β formed by the perpendicular of the second surface 14b and the reflecting surface 13 is 5 to 60 degrees, preferably 5 to 55 degrees so that the light guide plate 10 can be easily removed from the mold.

  The interval p between the adjacent first optical grooves 14 can be constant, preferably 30 to 300 μm, and more preferably 60 to 260 μm. In addition, since the appearance of moire may appear due to interference with the cell arrangement of the liquid crystal display element when the interval p is constant, the interval p can be intentionally set at random.

  FIG. 3 is a vertical cross-sectional view of the main part of the light guide plate for explaining the operation of the first optical groove.

  A light beam incident on the incident surface 11 from the LED 20 at an incident angle φ0 is raised in the direction of the emission surface 12 by the first surface 14 a of the first optical groove 14. This light ray enters the position x1 of the emission surface 11 at an incident angle ψ1, and is totally reflected because it does not reach the critical angle. This light beam is further raised in the direction of the emission surface 12 by the first surface 14 a, enters the position x 2 of the emission surface 12 with an incident angle ψ 2 smaller than the critical angle, and is emitted from the emission surface 12.

  As described above, the light ray incident on the light guide plate 10 from the incident surface 11 repeats total reflection between the reflecting surface 13 and the first surface 14a, and is emitted from the emitting surface 12 when the incident angle to the emitting surface 12 becomes smaller than the critical angle. Is done.

  Here, the closer the angle formed by the incident surface 11 and the first surface 14a is to 90 degrees, the closer the first surface 14a and the exit surface 12 are to be parallel, and the light beam that repeats total reflection between the first surface 14a and the exit surface 12 is The incident angle or the emission angle of light that is gradually raised in the direction of the emission surface 12 and emitted from the emission surface 12 is always substantially equal to the critical angle. Therefore, the direction of the light emitted from the emission surface 12 is aligned.

  FIG. 4 is a lateral side view of the light guide plate.

  A plurality of second optical grooves 15 are formed in the reflection surface 13 in the longitudinal direction of the light guide plate 10. The second optical groove 15 has a first inclined surface 15a, a second inclined surface 15b, and a third inclined surface 15c. The angle γ formed by the first inclined surface 15a and the second inclined surface 15b with the reflecting surface 13 is preferably 40 degrees.

  FIG. 5 is a cross-sectional view of the main part in the horizontal direction of the light guide plate showing the operation of the second optical groove.

  The first inclined surface 15 a, the second inclined surface 15 b, and the third inclined surface 15 c of the second optical groove 15 make the light incident from the incident surface 11 at an incident angle ψ 3 with respect to the output surface 12. To a light beam having an incident angle ψ4 with respect to.

  As described above, the first inclined surface 15 a and the second inclined surface 15 b of the second optical groove 15 are at an angle with respect to the normal line of the exit surface 12 in the entrance surface 11 with respect to at least a part of the light rays incident on the light guide plate 10. It has the effect of reflecting and changing. By this action, the second optical groove 15 spreads in the lateral direction of the light guide plate 10 and acts to alleviate light unevenness in the vicinity of the incident surface 11 which is particularly problematic.

  The third inclined surface 15c is desirably as small as possible from the viewpoint of the reflection effect of raising the light incident on the second optical groove 15 in the direction of the exit surface 12, but it is easy to fill the resin when the light guide plate 10 is molded. In view of the properties, a width of 0 to 10 μm is preferable. More preferably, it is 0-5 micrometers.

  6 and 7 are enlarged views showing details of the hologram formed on the exit surface.

  The hologram 22 serves as an anisotropic diffusion pattern that anisotropically diffuses light incident on the exit surface 12. This hologram 22 is called a surface relief hologram in order to distinguish it from a hologram formed three-dimensionally.

  FIG. 6 is an enlarged view in which the hologram is enlarged 200 times, and FIG. 7 is an enlarged view in which the hologram is further enlarged.

  As shown in FIG. 6, the hologram 22 is a large number of linear speckles or random speckles extending in the longitudinal direction of the light guide plate 10 (or a very thin ellipse) when viewed at 200 times magnification. A region (for example, a region having higher (or lower) transmittance than other regions) (random grooves or unevenness) 22a is provided.

  The random speckle 22a has a shape and a position that are not constant throughout the hologram 22, and has randomness.

  As will be described later, the light incident on the hologram 22 is strongly diffused in the vertical and horizontal directions of the light guide plate 10 by the linear speckles 22a. The diffusion ratio with respect to the vertical and horizontal directions of the light guide plate 10 is determined by the dimensions of the major and minor axes of the speckle.

Further, due to the randomness of the speckle 22a, the incident light to the hologram 22 is
Scattered or transmitted in random directions. Therefore, the hologram has a function as a diffuser.

  FIG. 8 is a diagram for explaining the operation of the hologram.

  FIG. 8A is a top view showing the angle dependence of the intensity of light emitted from the point P1 of the emission surface 12 of the light guide plate 10. FIG. FIG. 8B is a perspective view three-dimensionally showing the intensity distribution of light emitted from the point P <b> 2 on the emission surface 12 of the light guide plate 10.

  Here, for convenience of explanation, the direction of the first optical groove 14 is the X axis, the direction orthogonal to the first optical groove 14 where the incident light from the incident surface 11 travels is the Y axis, and the direction in which light is emitted from the emission surface 12. An orthogonal coordinate system with the Z axis is introduced.

The light emitted from the point P1 on the exit surface 12 of the light guide plate 10 is laterally compared with the longitudinal direction (Y direction) of the light guide plate 10 by the hologram 22 formed on the exit surface 12 as shown by an ellipse E1. It is strongly diffused in the direction (X direction). That is, a relationship of Φ _X >> Φ _Y is established between the half widths Φ _X and Φ _{Y in} the xy direction of light diffusion by the hologram 22. That is, the half value width Φ _{X in} the horizontal direction (X direction) of the light guide plate 10 is sufficiently larger than the half value width Φ _{Y in} the vertical direction (Y direction).

The half width Φ _{Y in} the longitudinal direction (Y direction) of the light guide plate 10 is preferably 0 <Φ _Y ≦ 5 degrees, and more preferably 0 <Φ _Y ≦ 1 degrees. On the other hand, the half width Φ _{X in} the horizontal direction (X direction) of the light guide plate 10 is desirably 30 to 70 degrees, more desirably 40 to 70 degrees, and further desirably 50 to 70 degrees.

The ratio between the half width Φ _Y and the half width Φ _X is preferably in the range of 1:30 or more.

  Due to the anisotropic diffusion action of the hologram 22, a uniform intensity distribution of emitted light in the lateral direction (X direction) of the light guide plate 10 is realized in the light guide plate 10. Therefore, the appearance of bright lines in the light emitted from the emission surface 12 is prevented.

  Moreover, according to the said structure, the fluctuation | variation of the critical angle of the vertical direction (Y direction) by the hologram 22 as a diffuser is suppressed by suppressing the diffusion angle of the emitted light in the vertical direction (Y direction) of the light-guide plate 10. FIG. Thus, the uniformity of the emission angle is maintained.

  FIG. 9 is a schematic diagram showing an outline of a hologram manufacturing apparatus.

  This apparatus has a laser light source (not shown) that emits laser light having a predetermined wavelength in the Z direction, a first shielding plate 81 having a slit-like (for example, 1 mm width) first opening 81a in the X direction, and an Y direction. A second shielding plate 82 having a triangular second opening 82a, a third shielding plate 83 having a triangular third opening 83a opened in the -Y direction, and a photosensitive film 84 made of, for example, a photopolymer are fixed. A table 85, a support member 87 that supports the table 85, a first slider 88 that fixes and supports the support member 87, a second slider 89 that supports the first slider 88 movably in the Z-axis direction, and a second And a base 90 that supports the slider so as to be movable in the Y-axis direction. An appropriate focusing lens (not shown) is provided between the shielding plates 82 and 83.

  The opening 81a is provided with a diffuser such as polished glass that diffuses and transmits the laser light L.

  The combination of the first and second openings 81a and 82a acts as a linear opening (or elongated rectangular opening) having a predetermined length with respect to the laser light. In other words, the linear opening (or elongated rectangular opening) has the width of the first opening 81a as the short side and the distance in the X direction where the second opening 82a overlaps the opening 81a as the long side.

  The linear opening is moved by moving the second slider 89 in the Y-axis direction relative to the base 90 or by moving the shielding plate 82 in the Y-axis direction relative to the second slider 89. The length can be changed.

  With the above-described configuration, light rays emitted from the linear opening (or elongated rectangular opening) and incident on the photosensitive film 84 generally have a plurality of specifications in which each cross-sectional shape has a horizontally long linear shape (or elongated elliptical shape). A light beam with

  The third shielding plate 83 transmits a light beam located in the third opening 83a among the light beams. Accordingly, a light spot is formed at the position of the photosensitive film 84 by the light beam transmitted through the opening 83a.

  With the above configuration, the light spot can be formed at a desired position β1 (FIG. 10) of the photosensitive film 84 with respect to the support member 87.

  Therefore, by positioning the support member 87 to a desired position in the Y-axis direction, a laser light spot can be formed in the desired region 84a (FIG. 10) of the photosensitive film.

  Incidentally, the laser light L is diffused by the diffuser when passing through the first opening 81a.

  The laser light diffused by the diffuser forms a large number of approximately elliptical (or linear) random speckles on the photosensitive film 84. The average dimensions of the short axis and the long axis of the random speckle correspond to the dimensions of the long side and the short side of the rectangle, respectively, and the directions of the long axis and the long side are orthogonal. More specifically, assuming that the long side and the short side are L and W, the average dimensions of the short axis and the long axis are λh / L and λh / W. Here, λ is the wavelength of the laser beam, and h is the distance between the opening 81a and the photosensitive film.

  Accordingly, by irradiating the desired area 84a of the photosensitive film shown in FIG. 10 with the light diffused by the diffuser, the large number of random speckles can be formed in the desired area 84a. The random speckle has a general shape, a linear shape, or an elongated elliptical shape.

  In manufacturing the hologram, multiple exposure is repeated for each region 84a to expose the entire photosensitive film 84.

  When the exposed hologram is developed, a master hologram in which speckles are formed by unevenness is obtained. The master hologram produced in this way is transferred to the exit surface of the mold used for molding the light guide plate. Then, the hologram can be integrally formed on the exit surface of the light guide plate by injection molding the light guide plate using a mold to which the master hologram is transferred.

  FIG. 11 is a diagram illustrating a part of a backlight device (or a surface light source device) having a light guide plate and an optical sheet.

In the backlight device having the light guide plate 10 and the optical sheet (prism film) 50, the light emitted from the light exit surface 12 of the light guide plate 10 is light L ₁ , L having components with small angles γ 1 and γ 2 formed with the light exit surface 12. ₂ is included. The optical sheet 50 has a flat upper surface 51 and a prism-shaped lower surface 52. When light L ₁ and L ₂ having a small angle with the light exit surface 12 of the light guide plate 10 is incident from the lower surface 52, the optical sheet 50 is larger than the upper surface 51. The light is deflected to form an angle (L ₁ ′, L ₂ ′). Thus, the optical sheet 50 improves the front intensity of the light emitted to the liquid crystal display device.

  FIG. 12 is a top view showing the optical sheet.

The optical sheet (prism film) 50 is made of a transparent material such as PMMA, polyolefin, or polycarbonate, for example, and has a reflective surface 53 that forms a continuous prism-like structure on a lower surface 52 that faces the upper surface 51. The optical sheet 50 is installed on the light emission surface 12 of the light guide plate 10 so as to be parallel to the first optical grooves 14 formed on the reflection surface 13 of the light guide plate 10.

  The backlight device (or surface light source device) can be used as a backlight in a liquid crystal display device such as a mobile phone or an electronic notebook.

It is a figure which shows the outline of a light-guide plate. It is a longitudinal direction principal part side view of a light-guide plate. It is a longitudinal direction principal part sectional drawing of the light-guide plate explaining the effect | action of a 1st optical groove. It is a horizontal direction side view of a light-guide plate. It is a horizontal direction principal part sectional drawing of the light-guide plate which shows the effect | action of a 2nd optical groove. It is the enlarged view which expanded the hologram 200 times. It is the enlarged view which expanded the hologram further. It is a figure explaining the effect | action of a hologram. It is a schematic diagram which shows the outline of the manufacturing apparatus of a hologram. It is a figure which shows the photosensitive film which forms a hologram. It is a figure which shows a part of backlight apparatus. It is a top view which shows an optical sheet. It is a figure which shows the external appearance of the conventional light-guide plate. It is a figure which shows the usage condition of the conventional light-guide plate and a backlight apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light guide plate 11 Incident surface 12 Outgoing surface 13 Reflecting surface 14 1st optical groove 15 2nd optical groove 20 Light source

Claims (9)

The incident surface is formed of a plurality of light sources arranged along the longitudinal direction of the incident surface, the incident surface being one incident surface, an exit surface orthogonal to the incident surface, and a reflective surface facing the exit surface. A light guide plate on which light is incident,
The reflecting surface receives a light beam having an angle with respect to a normal line of the exit surface incident on the incident surface from the light source and reflects a light beam having a reduced angle with the normal line. A plurality of first optical grooves formed in a longitudinal direction, and reflecting at least a part of the incident light beam at a predetermined distance from the incident surface by reflecting at least a part of the incident light beam at an angle with respect to the normal line in the incident surface; A plurality of second optical grooves formed in a direction perpendicular to the longitudinal direction of the surface;
The exit surface is an anisotropic diffusion pattern that diffuses and transmits light incident from the reflective surface at an angle of a predetermined angle or less with respect to the normal of the exit surface, and the incident light A light guide plate having an anisotropic diffusion pattern that diffuses so that a diffusion width in a longitudinal direction of the incident surface is larger than a diffusion width in a direction orthogonal to the longitudinal direction.   The light guide plate according to claim 1, wherein the first optical groove has a first surface that forms an angle of 88 degrees or more with the incident surface.   The light emitting surface of the light source faces the incident surface, and the thickness of the incident surface between the emitting surface and the reflecting surface is within ± 50 μm with respect to the length of the light emitting surface in the thickness direction. The light guide plate according to claim 1 or 2.   The said predetermined distance in which the said 2nd optical groove is formed is 10 times or less of the thickness between the said output surface of the said incident surface, and the said reflective surface, The Claim 1 thru | or 3 characterized by the above-mentioned. Light guide plate.   5. The anisotropic diffusion pattern according to claim 1, wherein a diffusion width in a longitudinal direction of the incident surface with respect to a diffusion width in a direction orthogonal to the incident surface is 1:30 or more. The light guide plate described in 1.   The ratio L / P between the distance P between the light sources along the incident surface and the distance L between the incident surface and the light source is 0.474 or less. Light guide plate.   A backlight device comprising the light guide plate according to claim 1.   The backlight device according to claim 7, further comprising an optical film that deflects the light beam emitted from the light guide plate in a normal direction of an emission surface of the light guide plate. 9. The backlight device according to claim 8, wherein the optical film has a plurality of prismatic deflecting elements formed on a surface facing the light exit surface of the light guide plate.