JP4411997B2 - Light guide and surface light source device - Google Patents

Description

  The present invention relates to a light guide that guides light emitted from a light source and a surface light source device that includes the light guide to illuminate a liquid crystal display element, a liquid crystal display device, and the like from the back.

  Conventionally, in order to illuminate a liquid crystal display device such as a mobile phone, a light guide that guides light emitted from the light source to the liquid crystal display and a surface light source device that includes the light guide and illuminates the liquid crystal display from the back are provided. ing.

  FIG. 1 is a perspective view showing the appearance of a conventional light guide (see, for example, Patent Document 1). In the drawing, the light source 120 is also shown.

  The light guide 110 is made of a transparent material such as PMMA or polycarbonate, and has a substantially flat plate 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 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 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. The light is emitted from the emission surface 112. Further, when the light is reflected in the short direction of the deflection pattern element 114, the light traveling direction is changed, so that it acts as a diffusion effect that weakens the directivity of the light source 120 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 120 is low. Further, when there are a plurality of light sources 120, the arrangement of the deflection pattern elements 114 becomes very complicated as shown in FIG.

  FIG. 2 is a diagram illustrating how the conventional light guide and the surface light source device are used.

  The light guide 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 source 120 enters the light guide 110 from the incident surface 111.

  The light incident on the light guide 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. The light is emitted from the emission surface 112.

On the other hand, there has conventionally been provided a hologram obtained by exposing a photosensitive film to a photosensitive film through a rectangular opening having a diffuser to randomly form a large number of speckles (see Patent Documents 2 and 3). 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 the incident laser light to the hologram, the laser light is scattered by the speckle reproduces the rectangular opening that is used during exposure. By using such a hologram, incident light can be diffused anisotropically.

Japanese Patent No. 3151830 US Pat. No. 5,365,354 US Pat. No. 5,534,386

  In the conventional light guide, the ratio of the light emitted from the exit surface is small in the light incident from the entrance surface, and most of the light not emitted from the exit surface is from the side surface opposite to the portion where the light source is arranged. There was a problem in terms of light utilization efficiency.

  The present invention has been proposed in view of the above-described circumstances, and an object thereof is to provide a light guide having high light use efficiency and a surface light source device provided with such a light guide.

In order to solve the above-described problems, a light guide according to the present invention has at least one side surface as an incident surface, a light guide having a rectangular exit surface orthogonal to the entrance surface, and a reflective surface facing the exit surface. The reflecting surface is a body that receives light incident at an angle with respect to the normal of the light exit surface from the light incident surface or light exit surface, and emits light having a reduced angle with the normal. The deflection pattern has a linear deflection pattern element or a curved polarization pattern element substantially parallel to the incident surface , and the exit surface has an angle less than a predetermined critical angle with respect to the normal of the exit surface. has anisotropic diffusion pattern Ru is transmitted by diffusing rays incident from the deflection pattern form, the anisotropic diffusion pattern is a direction perpendicular to light beams incident from the deflection pattern ridge of the linear deflection pattern Parallel to the ridgeline rather than the diffusion width of It is intended to spread as diffuse width direction becomes large.

  The thickness of the light guide is 10 to 400 μm, the thickness of the light guide is preferably 10 to 200 μm, the thickness of the light guide is more preferably 10 to 100 μm, and the thickness of the light guide is 10 to 70 μm. It is particularly preferable that the range is By setting it as such light guide body thickness, the light quantity which leaks from the reflective side surface of the part which has arrange | positioned the light source can be reduced, and the utilization efficiency of the emitted light from a light source improves.

  Preferably, the inclination angle α1 of the linear deflection pattern element or the curved polarization pattern element with respect to the light guide plane is such that the light incident from the incident surface on the side surface is reflected by the exit surface and the reflection surface a predetermined number of times and then exits. When the incident angle of the light beam with respect to the surface is equal to or smaller than the critical angle, the angle is 0.5 to 45 degrees so that the light is emitted from the emission surface.

  Preferably, the anisotropic diffusion pattern has a surface relief hologram.

  Preferably, the surface relief hologram has a plurality of linear random speckle regions that are long in the radial direction of concentric circles.

  Preferably, the surface relief hologram of the previous period is integrally formed on the exit surface of the light guide plate.

  Preferably, the aspect ratio of the luminous flux of the diffused light is in the range of 1: 180 to 1: 3.

  Preferably, the incident surface has a fine uneven shape such as a prism or a hairline for spreading light.

The surface light source device according to the present invention includes the light guide.
In addition to the light guide, the surface light source device according to the present invention may have an optical film that deflects light emitted from the light guide in the normal direction of the light guide plane.

  Preferably, the optical film is a prism film having a plurality of refractive surfaces.

  Preferably, the optical film is an optical film on which a diffraction grating or a hologram is formed.

  Preferably, the light guide has substantially one or more light emitting points on or near the incident surface thereof.

  Preferably, substantially one or more light emitting points each consist of one LED.

According to the present invention, by reducing the thickness of the light guide, light leaking from the side surface opposite to the portion where the light source of the light guide is disposed can be reduced, and the light use efficiency can be increased. In addition, production efficiency is increased because continuous production is possible in the form of a film. As a result, a thin light guide and a surface light source device with low power consumption and high luminance can be provided at low cost.

  Hereinafter, embodiments of a light guide and a surface light source device according to the present invention will be described in detail with reference to the drawings.

  In the present embodiment, for the sake of simplicity, the same members are indicated by common reference numerals in several different drawings. The drawings of the present embodiment are used to explain the contents of the present invention and do not accurately reflect the ratio of dimensions of each part.

  For convenience of reference, an xyz orthogonal coordinate system is set in the drawing. That is, the x axis and the y axis are set along the two sides of the upper surface or the lower surface of the light guide in the light traveling direction in the light guide, and the z axis is set in the normal direction of the emission surface. Further, the positive and negative directions of the z axis are referred to as up and down.

  FIG. 3 shows an outline of the light guide according to the present embodiment. In the figure, four light emitting diodes 20 serving as light sources are also shown. As the light source, in addition to a plurality of light emitting diodes as shown in FIG. 3, a fluorescent tube such as a cold cathode tube can be used.

  3A is a top view of the light guide 10, FIG. 3B is a front view of the light guide 10, and FIG. 3C is a perspective view of the light guide 10.

  The light guide 10 reflects an incident surface 11 on which light from the light emitting diode 20 is incident, an output surface 12 that emits light from the light guide, and incident light from the incident surface 11 or reflected light from the output surface 12. And at least a reflecting surface 13.

  More specifically, the light guide 10 has a substantially plate shape having a substantially rectangular upper surface and lower surface. As the material, for example, a transparent material having a certain refractive index such as PMMA, polyolefin or polycarbonate can be used, but any material satisfying this requirement may be used.

  The entrance surface 11 is substantially orthogonal to the reflection surface 13 and the exit surface 12. Light emitted from the plurality of light emitting diodes 20 arranged in a straight line at substantially equal intervals so as to face the incident surface 11 enters the light guide 10 from the incident surface 11.

  A prism extending in the thickness direction of the light guide may be formed on the incident surface 11, and the prism shape has a substantially triangular, semi-elliptical or smooth wave shape as shown in FIG. A fine uneven shape may be formed.

  The reflective surface 13 is generally formed on a lower surface parallel to the xy plane of the light guide 10.

FIG. 5 is a diagram showing a reflection groove 14 formed on the reflection surface 13 for changing the traveling direction of light. The reflection grooves 14 are formed in a direction substantially parallel to the incident surface 11, and a plurality of reflection grooves 14 are continuously formed from the incident surface 11 to a surface facing the incident surface 11. The interval between adjacent grooves may be constant or may vary. The distance of each reflection groove 14 from the incident surface 11 may be expressed as a function. By adjusting the interval between adjacent grooves, characteristics such as the reflection efficiency of the light guide 10 can be finely adjusted.

  Since most of the reflection groove 14 is used for light reflection, the reflection surface 13 formed with the reflection groove 14 as in this embodiment has a high efficiency in reflecting incident light in the direction of the emission surface 12 and is guided. The light utilization efficiency of the light body 10 is increased.

  FIG. 6 shows a detailed cross section of the light guide 10 including the reflective grooves 14.

As shown in FIG. 6A, the reflection groove 14 has a first surface 14 a on the incident surface 11 side and a second surface 14 b on the surface side facing the incident surface 11 of the light guide 10. With respect to the emission surface 12 , the first surface 14a has a certain finite angle α1 (inclination angle), and the second surface 14b has a certain finite angle α2 (inclination angle). α1 and α2 may be constant in all the reflection grooves 14 or may be different in some or all of the reflection grooves 14. In addition, you may provide a plane part between reflection grooves as shown in FIG.6 (b). In this case, instead of the reflective groove (concave shape with respect to the light guide), a reflective ridge (convex shape with respect to the light guide) may be used.

  FIG. 7 shows the operation of the first surface 14a.

  As shown in FIG. 7, the first surface 14 a raises the light incident on the incident surface 11 at an angle ψ 1 with the emission surface 12 to light having an angle ψ 2 with respect to the emission surface 12. That is, light incident on the first surface 14a at an angle with respect to the normal of the exit surface 12 on the incident surface 11 is emitted with a reduced angle with the normal.

  The light launched on the first surface 14a is emitted from the emission surface 12 when the angle formed with the normal line of the emission surface 12 is smaller than the critical angle (point X1 in FIG. 7).

  The angle α1 (inclination angle) formed by the first surface 14a and the emission surface 12 is 0.5 to 45 degrees.

  The second surface 14b does not have the reflecting action and is preferably as large as possible from the viewpoint of the reflecting action. Degrees or less are desirable. The second surface 14b is preferably 30 to 90 degrees, and more preferably 35 to 88 degrees.

  Moreover, when there is no plane part between the reflective grooves 14 as shown in FIG. 6A, the interval p between the adjacent reflective grooves 14 can be constant, preferably 1 to 100 μm, more preferably It is 2-80 micrometers, More preferably, it is 5-60 micrometers. If the interval p is constant, moire may appear due to interference with the cell arrangement of the liquid crystal display element. Therefore, the interval can be intentionally set at random. When there is a plane portion between the reflection grooves 14 as shown in FIG. 6B, the interval p ′ between the adjacent reflection grooves 14 is changed for each place according to the distance from the light source so that the outgoing light distribution is uniform. May be. Alternatively, the interval p ′ may be constant, and the width p of the reflective groove or the reflective bulge may be changed for each location according to the distance from the light source. In this case, the depth of the reflective groove or the height of the reflective bulge varies from place to place.

  The thickness of the light guide 10 is constant, 10 to 400 μm, preferably 10 to 200 μm, more preferably 10 to 100 μm, and particularly preferably 10 to 70 μm.

  With the above configuration, as shown in FIG. 7, the light incident on the incident surface 11 of the light guide 10 from the light emitting diode 20 is reflected from the output surface 12 until the angle formed with the normal line of the output surface 12 reaches a critical angle. It advances inside the light guide 10 while repeating total reflection on the surface 13.

  The emission surface 12 is formed on the upper surface of the light guide 10 parallel to the xy plane.

  A hologram as an anisotropic diffusion pattern having anisotropy is formed on the emission surface 12. This hologram is referred to as a surface relief hologram to distinguish it from a three-dimensionally formed hologram.

  8 and 9 are enlarged views showing details of the hologram 22 formed on the exit surface.

  FIG. 8 is an enlarged view in which the hologram is enlarged 200 times, and FIG. 9 is an enlarged view in which the hologram is further enlarged.

As shown in FIG. 8, the hologram is a linear (or very thin ellipse) extending along the direction from the incident surface 11 toward the surface facing the incident surface 11 when viewed at 200 times magnification. A large number of random speckles or random speckle regions (for example, regions having higher or lower transmittance than other regions) (random grooves or irregularities) 22a are provided. The random speckle 22a has a shape and a position that are not constant throughout the hologram, and has randomness.

As will be described later, the linear speckle 22 a causes the light incident on the hologram to be strongly diffused in a direction perpendicular to the direction from the incident surface 11 toward the surface facing the incident surface 11. The diffusion ratio of the diffusivity in each direction is determined by the major and minor axis dimensions of the speckle.

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

  FIG. 10 is a diagram for explaining the operation of the hologram.

  FIG. 10A is a top view showing the angle dependence of the intensity of light emitted from the point P1 on the emission surface 12 of the light guide 10. FIG. FIG. 10B is a perspective view three-dimensionally showing the intensity distribution of light emitted from the point P <b> 1 on the emission surface 12 of the light guide 10.

  The light emitted from the point P1 on the exit surface 12 of the light guide 10 is strongly diffused in the θ direction compared to the r direction by the hologram formed on the exit surface 12 as shown by an ellipse E1.

FIG. 11 shows the intensity distribution of the emitted light. FIG. 11A shows the intensity distribution of the emitted light in the θ direction, and FIG. 11B shows the intensity distribution of the emitted light in the r direction.

As described above, it is diffused more strongly in the θ direction than in the r direction, and the half width Φ _θ0 of the diffusion angle Φ _{θ in} the _{θ direction} is larger than the half width Φ _r0 of the diffusion angle Φ _{r in} the r direction. It is large enough (Φ _θ0 >> Φ _r0 ).

The half width Φ _{r0 in the} r direction is preferably 0 <Φ _r0 ≦ 5 degrees, and more preferably 0 <Φ _r0 ≦ 1 degree. On the other hand, the half width Φ _θ0 in the θ direction is preferably 5 to 70 degrees, more preferably 5 to 30 degrees, and further preferably 5 to 10 degrees.

The ratio of the half width Φ _θ0 and the half width Φ _r0 is preferably in the range of half width Φ _r0 : half width Φ _θ0 = 1: 180 to 1: 3.

  For reference, a point C1 in FIG. 10 indicates an intensity distribution of light emitted from the point P1 when an isotropic diffusion element is provided on the emission surface 12. In this case, the light emitted from the emission surface has an isotropic intensity distribution represented by a circle C1.

In short, the hologram diffuses and transmits the light emitted from the emission surface 12 in the θ direction compared to the r direction.

  Due to the anisotropic diffusion action of the hologram, a uniform intensity distribution of emitted light in the θ direction is realized in the light guide 10. In particular, the appearance of bright lines in the outgoing light from the outgoing surface 12 is prevented.

  FIG. 12 shows bright lines appearing in the light emitted from the exit surface 12 when the isotropic diffusing element is provided on the exit surface.

  The light reflected by the continuous reflecting grooves 14 on the reflecting surface 13 has a number of paths that reach the viewpoint V0. Therefore, when the light guide 10 is viewed from the viewpoint V0, the bright line BL appears on the line connecting the light emitting diode 20 and the viewpoint V0.

  In the light guide 10 of the present embodiment, the hologram 22 formed on the exit surface 12 diffuses light more anisotropically in the θ direction than in the r direction. Accordingly, when the light source direction is viewed from the viewpoint V0, the light intensity toward the viewpoint V0 is suppressed, and the appearance of the bright line BL is prevented.

  Further, according to the above configuration, by suppressing the diffusion angle of the outgoing light in the r direction, the fluctuation of the critical angle in the r direction due to the hologram as the diffuser is suppressed, and the uniformity of the outgoing angle is maintained.

  FIG. 13 is a schematic diagram showing an outline of the hologram 22 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 rotating table 85, a support member 87 that supports the table 85 rotatably about the optical axis L0, a first slider 88 that fixes and supports the support member 87, and the first slider 88 is movable in the Z-axis direction. And a base 90 for supporting the second slider movably in the Y-axis direction. An appropriate focusing lens (not shown) is provided between the shielding plates 82 and 83.

  The first 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 the desired circumferential position β1 (FIG. 14) of the photosensitive film 84 by rotating the table 85 with respect to the support member 87. Further, by moving the second slide 89 in the Y-axis direction with respect to the base 90, the light spot can be formed roughly at a desired radial position r1 (FIG. 14) of the photosensitive film 84.

  Therefore, by rotating the table 85 to a desired position and positioning the support member 87 at a desired position in the Y-axis direction, a light spot of laser light can be formed in the desired region 84a (FIG. 14) of the photosensitive film. I can do it.

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

  The laser light diffused by the diffuser generates a large number of random substantially elliptical (or linear) bright spots on the photosensitive film 84. This bright spot becomes a random speckle. 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.

  Therefore, by irradiating the desired region 84a of the photosensitive film shown in FIG. 14 with the light diffused by the diffuser, the large number of random speckles can be formed in the desired region 84a. The random speckle generally has a linear or elongated elliptical shape extending in the radial direction of a circle centering on a point of the photosensitive film intersecting with the optical axis L0.

  A depression is formed in the bright spot portion of the random speckle, and this depression becomes a relief-type speckle pattern, and light is diffused when many are formed on the material surface.

  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. By taking the electro-mold of the master hologram thus produced and making it into a roll mold, the hologram can be integrally formed on the exit surface of the light guide by roll transfer.

  FIG. 15 is a diagram illustrating a part of a surface light source device having a light guide and an optical sheet.

  In the surface light source device having the light guide 10 and the optical sheet 50, the light emitted from the emission surface 12 of the light guide 10 includes light L 1 and L 2 having components with small angles γ 1 and γ 2 formed with the emission surface 12. Yes. The optical sheet 50 has a flat upper surface 51 and a non-flat lower surface 52. When light L1 and L2 having a small angle with the light exit surface 12 of the light guide 10 are incident from the lower surface 52, the optical sheet 50 has a large angle with the upper surface 51. The light is deflected so as to form (L1 ′, L2 ′). Thus, the optical sheet 50 improves the front intensity of the light emitted to the liquid crystal display device.

  FIG. 16 is a top view showing the optical sheet 50.

  The optical sheet 50 is made of a transparent material such as PMMA, polyolefin, or polycarbonate, for example, and has a lower surface 52 that faces the upper surface 51, and has a prism-shaped surface, and the ridge line 53 of the prism is linear or curved. Is continuous. The optical sheet 50 is installed on the light emission surface 12 of the light guide 10 so as to be substantially parallel to or tilted by a predetermined angle with the linear or curved reflection groove 14 formed on the reflection surface 13 of the light guide 10. The

  Even when the lower surface 52 of the optical sheet 50 is oriented in the direction opposite to the light guide side, the front intensity of light emitted to the liquid crystal display device is improved by appropriately selecting the shape (vertical angle) of the lower surface 52. be able to.

  The above-described embodiment shows one specific example of the present invention, and the present invention is not limited to this. The present invention can be applied to various objects without departing from the scope of the present invention. The numerical values shown in the text are only examples, and the present invention is not limited to these.

  The surface light source device can be used as a backlight in liquid crystal display devices such as mobile phones, game machines, and electronic notebooks. In addition, since the light guide is thin and filmy, it is excellent in mass productivity and can be provided at low cost.

It is the schematic of the conventional surface light source device. It is a figure which shows the usage condition of the conventional surface light source device. It is the schematic of the surface light source device of this invention. 3 is a top view showing the shape of a light incident surface 11 of the light guide 10. FIG. It is a figure which shows the reflective groove. It is a figure which shows the detailed cross section of the light guide 10 of this embodiment. It is a figure which shows the effect | action of the 1st surface 14a of the reflective groove 14. FIG. 3 is an enlarged view of a hologram 22. FIG. 3 is an enlarged view of a hologram 22. FIG. It is a figure explaining the effect | action of the hologram. It is a figure which shows intensity distribution of the emitted light from the hologram. FIG. 4 is a diagram showing bright lines appearing on an emission surface 12. 2 is a schematic diagram showing an outline of a manufacturing apparatus for a hologram 22. FIG. It is a figure which shows the desired area | region of a photosensitive film. It is a figure which shows a part of surface light source device which has the light guide and the optical sheet. 3 is a top view showing an optical sheet 50. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Light guide 11 Incident surface 12 Output surface 13 Reflective surface 14 Reflective groove 14a First surface 14b Second surface 20 Light emitting diode 22 Hologram 22a Speckle 50 Optical sheet 51 Upper surface 52 Lower surface 53 Ridge line 81 First shielding plate 81a First opening 82 Second shielding plate 82a Second opening 83 Third shielding plate 83a Third opening 84 Photosensitive film 84a Desired region 85 of photosensitive film Table 87 Support member 88 First slider 89 Second slider 90 Base 110 Light guide 111 Incident surface 112 Outgoing surface 113 Reflecting surface 114 Deflection pattern element 120 Light source 140 Liquid crystal display device 141 Lower surface

Claims (5)

A light guide (10) having at least one side surface as an incident surface (11), an upper surface orthogonal to the incident surface as an output surface (12), and a lower surface facing the output surface as a reflective surface (13),
Provided on the reflecting surface and receiving light incident on the reflecting surface from the incident surface or the emitting surface at an angle with respect to the normal of the emitting surface, and the angle formed with the normal decreases. A deflection pattern having a linear or curved continuous deflection pattern element (14) that emits light rays and is parallel to the incident surface;
Provided on the exit surface, the light beam emitted from the deflection pattern so as to form an angle less than a critical angle with respect to the normal line of the exit surface is more incident than the diffusion width in the direction perpendicular to the entrance surface. An anisotropic diffusion pattern (22) for diffusing and transmitting so as to increase the diffusion width in a direction parallel to the surface,
A light guide having a thickness between the emission surface and the reflection surface of 10 to 400 μm. The light guide according to claim 1, wherein the deflection pattern has one or a plurality of concave or convex deflection pattern elements on the reflection surface . The deflection pattern element has a triangular cross section, and has an inclined surface (14a) in which a normal line directed to the exit surface intersects the entrance surface, and an inclination angle (α1) between the inclined surface and the exit surface is 0. It is 5 degrees-45 degrees, The light guide of Claim 1 or 2 characterized by the above-mentioned. The anisotropic diffusion pattern is a hologram pattern having a plurality of linear random speckles (22a) having random shapes and positions and extending in a direction perpendicular to the incident surface . 4. The light guide according to any one of 3 above. The light guide according to any one of claims 1 to 4 ,
A light source (20) disposed opposite to the incident surface
A surface light source device comprising:

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