JPWO2005073625A1 - Light guide for surface light source device, method for manufacturing the same, and surface light source device - Google Patents

Abstract

As a surface light source device in which uneven luminance in the vicinity of the light incident end face near the light guide end due to the thinning of the light guide is difficult to be visually recognized and specific light emission in the oblique direction near the light incident end face is small, the primary light source 1 and light A surface light source device including a plate-shaped light guide 3 having an incident end face 31 and a light exit surface 33 is provided. Here, the light guide light emitting surface 33 is a rough surface, and in the specific region A in the vicinity of the light incident end surface 31, the average inclination angle θa of the surface is the boundary with the general region B other than the specific region and the light. A maximum value θa1 larger than the average value θa0 of the average inclination angle of the general area B is taken between the boundary with the incident end face 31, and the average value θa0 of the average inclination angle of the general area B is taken near the boundary with the light incident end face 31. It is a small θa2. The maximum value θa1 of the average inclination angle is in the range of 2.2 ° to 4.0 °. The average value θa0 of the average inclination angle in the general region is in the range of 1.4 ° or more and less than 2.4 °.

Description

  The present invention relates to an edge light type surface light source device, a light guide used therefor, and a method for manufacturing the same, and more particularly to a surface light source device intended to reduce the visibility of luminance unevenness and a light guide used therefor. is there. The surface light source device of the present invention is, for example, a backlight of a liquid crystal display device used as a display unit of a monitor such as a portable notebook personal computer or a liquid crystal television or a video integrated liquid crystal television, or a portable type such as a mobile phone. For backlights of relatively small liquid crystal display devices used as display panels for electronic devices and indicators of various devices, or for backlights of liquid crystal display devices used as information display boards and signs in stations and public facilities Alternatively, it is suitable for a backlight of a liquid crystal display device used as a marking device such as a traffic sign on a highway or a general road.

  Liquid crystal display devices have been widely used as monitors for portable notebook personal computers or the like, as display units for liquid crystal televisions and video integrated liquid crystal televisions, and in various other fields. A liquid crystal display device basically includes a backlight and a liquid crystal display element. As the backlight, an edge light type is often used from the viewpoint of making the liquid crystal display device compact. Conventionally, as an edge light type backlight, at least one end face of a rectangular plate-shaped light guide is used as a light incident end face, and a linear or rod-like shape such as a straight tube fluorescent lamp is provided along the light incident end face. A primary light source is disposed, light emitted from the primary light source is introduced from the light incident end surface of the light guide into the light guide, and the light exit surface is one of the two main surfaces of the light guide. What is emitted from the projector is widely used.

  Incidentally, in recent years, liquid crystal display devices are required to increase the display efficiency by increasing the ratio of the display screen dimensions to the external dimensions as much as possible. Therefore, also in the surface light source device, the ratio of the light emitting surface dimension to the outer dimension is made as large as possible, that is, the size of the structural part (sometimes referred to as a “frame”) existing in a frame shape around the light emitting surface is made as small as possible. Is required to do.

  On the other hand, the surface light source device is also required to be thin, and in order to meet this demand, it is necessary to reduce the thickness of the light guide. As the light guide becomes thinner (for example, about 0.5 mm to 3 mm in thickness), the light emitted from the primary light source becomes two at the light guide ridge line that forms the boundary between the light incident end face and the light exit face of the light guide. The influence of functioning as the next light source appears in the luminance of the light emitting surface of the surface light source device. This effect is noticeable mainly in a region near the light incident end face. This phenomenon is not particularly a problem in practice when the frame width is large, but in the surface light source device having the small frame width as described above, the luminance unevenness due to this influence is particularly easily recognized.

  As one form of easily recognizing the luminance unevenness of the light emitting surface, in a region close to the light incident end surface, a high luminance portion (bright line or bright band) and a low luminance portion (dark line or dark band) Is generated at a specific interval and is visually recognized as a plurality of light and dark lines extending substantially parallel to the light incident end face.

As a technique for preventing such luminance unevenness in the vicinity of the light incident end face, for example, in Japanese Patent Application Laid-Open No. 10-153778 (Patent Document 1), an area adjacent to the light incident end face of the light emitting face is placed adjacent to the area. It is disclosed that a band-like light diffusion region having a higher light scattering property is provided. In order to achieve the same object, for example, Japanese Patent Application Laid-Open No. 2002-216530 (Patent Document 2) describes the average inclination angle of the surface in the vicinity of the light incident end face of the light exit surface as another region of the light exit surface. Making it larger is disclosed.
JP-A-10-153778 JP 2002-216530 A

  According to the methods of Patent Document 1 and Patent Document 2, the light scattering property or the light diffusing property in the region near the light incident end surface of the light emitting surface is strengthened, and the amount of emitted light in this region is increased. The band is made inconspicuous to reduce brightness unevenness.

  However, the problems associated with thinning the light guide in a surface light source device having a small frame width exist in addition to the above. In other words, the light incident from the primary light source functions as a secondary light source at the ridge line of the light guide that forms the boundary between the light incident end face of the light guide and the light exit surface. In the vicinity of the end face, a specific strong light is emitted from the light emitting surface of the surface light source device in an oblique direction inclined with respect to the normal direction, and when used as a backlight of a liquid crystal display device, the display image quality is improved. May decrease.

  Such a phenomenon cannot be sufficiently suppressed by the methods of Patent Document 1 and Patent Document 2 described above.

  The present invention provides a surface light source device in which luminance unevenness in the region near the light incident end surface of the light guide associated with the thinning of the light guide is less visible, and less specific light emission in the oblique direction near the light incident end surface, and a light source used therefor An object is to provide a light body.

According to the present invention, as a solution to the above problems,
A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
At least one of the light exit surface and the back surface is a rough surface. In the light exit surface and / or the back surface, which is a rough surface, an average inclination angle of the surface is close to the light entrance end surface toward the light entrance end surface. A light guide for a surface light source device, characterized in that there is an inclined angle decreasing region gradually decreasing by 0.5 ° or more,
Is provided.

  In one aspect of the present invention, the thickness of the light guide at the edge on the light incident end face side is d, and at least part of the inclined angle decreasing region has a distance from the light incident end face of 0.1 mm. It exists in the region from 2d to 2d. In one aspect of the present invention, at least part of the inclined angle decreasing region is present in a region having a distance from the light incident end surface of 0.2 mm to 4 mm.

Further, according to the present invention, as a solution to the above problems,
A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
At least one of the light exit surface and the back surface is a rough surface. In the light exit surface and / or the back surface, which is a rough surface, in a specific region near the light incident end surface, an average inclination angle of the surface is the specific surface. A maximum value larger than the average value of the average inclination angle of the general region between the boundary with the general region other than the region and the boundary with the light incident end surface, and in the vicinity of the boundary with the light incident end surface, A light guide for a surface light source device, characterized by being smaller than an average value of an average inclination angle;
Is provided.

  In one aspect of the present invention, the thickness at the light incident end face side edge of the light guide is d, and the position where the average inclination angle has a maximum value is the distance from the light incident end face of the specific region. The distance to the boundary exists in a region in the range of d to 3d. In one aspect of the present invention, the maximum value of the average inclination angle in the specific region is in the range of 2.2 ° to 4.0 °. In one aspect of the present invention, the average value of the average inclination angle in the general region is in the range of not less than 1.4 ° and less than 2.4 °. In one aspect of the present invention, the specific region has a distance from a boundary with the general region to a boundary with the light incident end surface that is 10 mm of a thickness at an edge of the light guide on the light incident end surface side. It is in the range of times to 30 times. In one aspect of the present invention, the specific region has a distance from the boundary with the general region to the boundary with the light incident end surface within a range of 10 mm to 70 mm.

  Furthermore, according to the present invention, the primary light source is disposed so as to face the light incident end surface of the light guide for a surface light source device as described above, in order to solve the above-described problem. A surface light source device is provided.

  In one aspect of the present invention, the surface light source device is further disposed on a light emitting surface of the light guide, and a light incident surface on which light emitted from the light emitting surface of the light guide enters and An optical deflection element having a light exit surface on the opposite side is provided. In one aspect of the present invention, the light deflection element includes a plurality of prism rows that extend along the light incident end surface of the light guide and are arranged in parallel to each other on the light incident surface. Each has a first prism surface on which light from the light exit surface of the light guide is incident and a second prism surface on which the incident light is internally reflected. In one aspect of the present invention, the primary light source is a linear light source.

Furthermore, according to the present invention, as a solution to the above problems,
A method for manufacturing a light guide for a surface light source device as described above, wherein a first mold member having a first transfer surface for transferring and forming the light emitting surface and a second transfer for transferring and forming the back surface are provided. Forming a translucent synthetic resin using a second mold member having a surface, wherein the first transfer surface and / or the transfer surface of the rough surface of the light exit surface and the back surface; When forming the second transfer surface, the first rough surface is provided with a shielding effect on the vicinity of the edge corresponding to the boundary between the light incident end surface and the light exit surface of the light guide in the transfer surface region. A method of manufacturing a light guide for a surface light source device, characterized in that
Is provided.

  In one aspect of the present invention, in forming the first transfer surface and / or the second transfer surface for transfer formation of a rough surface of the light exit surface and the back surface, the general transfer The second roughening is performed with the shielding effect applied to the transfer surface area corresponding to the area. In one aspect of the present invention, the second roughening also provides a shielding effect on the vicinity of the edge in the transfer surface area corresponding to the specific area. In one embodiment of the present invention, the first roughening and / or the second roughening is performed by an etching process. In one embodiment of the present invention, the first roughening and / or the second roughening is performed by blasting. In one aspect of the present invention, the shielding effect is imparted by arranging a shielding member, and the shielding member is arranged away from the first transfer surface or the second transfer surface.

  According to the present invention as described above, at least one of the light exit surface and the back surface of the light guide for the surface light source device is formed of a rough surface, and the rough surface is in the vicinity of the light incident end surface and has an average inclination angle of the surface. Since there is a slope angle decreasing region that gradually decreases by 0.5 ° or more toward the light incident end surface, or the average inclination angle in the specific region near the light incident end surface is other than the specific region Takes a maximum value larger than the average value of the average inclination angle of the general area between the boundary with the general area and the boundary with the light incident end face, and further averages the average inclination angle of the general area in the vicinity of the boundary with the light incident end face. Because it is made smaller, the luminance unevenness in the region near the light incident end face on the light exit surface due to the light guide thinning is less visible, and the surface with less specific light emission in the oblique direction near the light incident end face A light source device is provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic perspective view showing one embodiment of a surface light source device according to the present invention, and FIG. 2 is a partial sectional view thereof. As shown in the drawing, the surface light source device of the present embodiment includes a light guide 3 having at least one side end surface as a light incident end surface 31 and a light exit surface 33 as one surface substantially orthogonal thereto. A linear primary light source 1 disposed facing the light incident end surface 31 of the light guide 3 and covered with the light source reflector 2, a light deflection element 4 disposed on the light exit surface of the light guide 3, and a light guide The light reflecting element 5 is disposed so as to face the back surface 34 opposite to the light emitting surface 33 of the light body 3.

  The light guide 3 is arranged in parallel with the XY plane and has a rectangular plate shape as a whole. The light guide 3 has four side end surfaces, and at least one of the pair of side end surfaces parallel to the YZ plane is a light incident end surface 31. The light incident end face 31 is disposed to face the primary light source 1, and the light emitted from the primary light source 1 enters the light guide 3 from the light incident end face 31. In the present invention, for example, the light source may be disposed opposite to another side end face such as the side end face 32 opposite to the light incident end face 31.

  Two main surfaces that are substantially orthogonal to the light incident end surface 31 of the light guide 3 are respectively positioned substantially parallel to the XY plane, and one of the surfaces (the upper surface in the drawing) serves as the light emitting surface 33. By providing a rough directional light emitting mechanism on at least one of the light emitting surface 33 or the back surface 34 thereof, the light incident from the light incident end surface 31 is guided through the light guide 3. However, light having directivity is emitted from the light emitting surface 33 within the light incident end surface 31 and a surface (XZ surface) orthogonal to the light emitting surface 33. The angle between the peak direction (peak light) of the emitted light luminous intensity distribution in the XZ in-plane distribution and the light emitting surface 33 is defined as α. The angle α is, for example, 10 to 40 degrees, and the full width at half maximum of the emitted light luminous intensity distribution is, for example, 10 to 40 degrees. Details of the rough surface formed on the light emitting surface 33 or the back surface 34 of the light guide 3 will be described later.

  In addition, the other main surface to which the directional light emitting mechanism is not provided is light in order to control the directivity on a surface (YZ surface) parallel to the primary light source 1 of the light emitted from the light guide 3. It is preferable to form a lens surface in which a large number of lens rows extending in a direction substantially perpendicular to the incident end surface 31 (X direction) are arranged. In the embodiment shown in FIG. 1, a lens array comprising a plurality of lens arrays in which a rough surface is formed on the light emitting surface 33 and the back surface 34 extends in a direction substantially perpendicular to the light incident end surface 31 (X direction). A forming surface is formed. In the present invention, contrary to the embodiment shown in FIG. 1, a lens array forming surface may be formed on the light emitting surface 33, and the back surface 34 may be a rough surface.

  As shown in FIG. 1, when a lens array forming surface is formed on the back surface 34 or the light emitting surface 33 of the light guide 3, the lens array includes a prism array, a lenticular lens array, a V-shape extending substantially in the X direction. However, it is preferable that the YZ cross-sectional shape is a substantially triangular prism array.

  In the present invention, when a prism row forming surface is formed on the back surface 34 of the light guide 3 as a lens row forming surface, the apex angle is preferably in the range of 85 to 110 degrees. This is because the light emitted from the light guide 3 can be appropriately condensed by setting the apex angle within this range, and the luminance as the surface light source device can be improved, and more preferably It is in the range of 90 to 100 degrees.

  In the light guide of the present invention, the desired prism array shape is accurately produced, and stable optical performance is obtained, and for the purpose of suppressing prism top wear and deformation during assembly work and use as a light source device, A flat portion or a curved surface portion may be formed at the top of the prism row.

  In the present invention, a directional light emitting mechanism by mixing and dispersing light diffusing fine particles inside the light guide in combination with the light emitting mechanism formed on the light emitting surface 33 or the back surface 34 as described above. May be added.

  The light incident end face 31 is preferably roughened in order to adjust the spread of light in the XY plane and / or the XZ plane. Examples of the rough surface forming method include a method of cutting with a milling tool or the like, a method of polishing with a grindstone, sandpaper, buff or the like, a method of blasting, electric discharge machining, electrolytic polishing, chemical polishing or the like. Blasting particles used for blasting include spherical particles such as glass beads and polygonal particles such as alumina beads, but the use of polygonal particles has a greater effect of spreading light. It is preferable because the surface can be formed. An anisotropic rough surface can also be formed by adjusting the processing direction of cutting or polishing. In order to adjust the spread of light in the XY plane, a Z-direction machining direction can be adopted to form a streak-like uneven shape in the Z direction, and to adjust the spread of light in the XZ plane. Can adopt a processing direction in the Y direction to form a streak-like uneven shape in the Y direction. This rough surface processing can be performed directly on the light incident end face of the light guide, but a portion corresponding to the light incident end face of the mold can be processed and transferred at the time of molding.

  The degree of roughening of the light incident end face 31 is, in the light guide thickness direction, an average inclination angle θa of 1 to 5 degrees, a centerline average roughness Ra of 0.05 to 0.5 μm, and a ten-point average roughness. Rz is preferably 0.5 to 3 μm. This is because, by setting the degree of roughening of the light incident end face 31 within this range, it is possible to suppress the occurrence of bright bands or dark bands on the light exit surface and to make the bright lines and dark lines difficult to see. Because. The average inclination angle θa is more preferably in the range of 2 to 4.5 degrees, particularly preferably 2.5 to 3 degrees. The center line average roughness Ra is more preferably in the range of 0.07 to 0.3 μm, particularly preferably in the range of 0.1 to 0.25 μm. The ten-point average roughness Rz is more preferably in the range of 0.7 to 2.5 μm, particularly preferably 1 to 2 μm. The degree of roughening of the light incident end face 31 is, in the longitudinal direction, for the same reason as described above, the average inclination angle θa is 1 to 3 degrees, the centerline average roughness Ra is 0.02 to 0.1 μm, The ten-point average roughness Rz is preferably 0.3 to 2 μm. The average inclination angle θa is more preferably in the range of 1.3 to 2.7 degrees, particularly preferably 1.5 to 2.5 degrees. The centerline average roughness Ra is more preferably in the range of 0.03 to 0.08 μm, particularly preferably 0.05 to 0.07 μm. The ten-point average roughness Rz is more preferably in the range of 0.4 to 1.7 μm, particularly preferably 0.5 to 1.5 μm.

  The light guide 3 is not limited to the shape shown in FIG. 1, and various shapes such as a rust shape with a thicker light incident end face can be used.

  The light deflection element 4 is disposed on the light emitting surface 33 of the light guide 3. The two main surfaces 41 and 42 of the light deflection element 4 are arranged in parallel with each other as a whole, and are located in parallel with the XY plane as a whole. One of the main surfaces 41 and 42 (the main surface located on the light emitting surface 33 side of the light guide 3) is a light incident surface 41, and the other is a light emitting surface 42. The light exit surface 42 is a flat surface parallel to the light exit surface 33 of the light guide 3. The light incident surface 41 is a prism row forming surface in which a large number of prism rows extending in the Y direction are arranged in parallel to each other. The prism row forming surface may be provided with a bottom flat portion having a relatively narrow width between adjacent prism rows (for example, a flat portion having a width equal to or smaller than the dimension in the X direction of the prism row). It is preferable to arrange the prism rows continuously in the X direction without providing a flat bottom portion in order to improve the utilization efficiency of the prism.

  FIG. 3 schematically shows the state of light deflection by the light deflection element 4. This figure shows an example of the traveling direction of the peak light (light corresponding to the peak of the outgoing light distribution) from the light guide 3 in the XZ plane. The peak light emitted obliquely at an angle α from the light emitting surface 33 of the light guide 3 is incident on the first prism surface of the prism row and is totally reflected by the second prism surface so as to be substantially equal to the light emitting surface 42 method. Emits in the direction of the line. Further, in the YZ plane, the luminance in the direction of the normal line of the light exit surface 42 can be sufficiently improved in a wide area by the action of the prism row on the light guide back surface 34 as described above.

  The shape of the prism surface of the prism row of the light deflection element 4 is not limited to a single plane, and can be, for example, a convex polygonal shape or a convex curved surface shape, thereby achieving high brightness and narrow field of view. it can.

  In the light deflection element 4, a prism array is formed for the purpose of accurately producing a desired prism shape, obtaining stable optical performance, and suppressing wear and deformation of the prism top during assembly work and use as a light source device. A top flat portion or a top curved surface portion may be formed on the top of the top. In this case, the width of the top flat part or the top curved surface part is preferably 3 μm or less from the viewpoint of suppressing the occurrence of a non-uniform luminance pattern due to a decrease in luminance or a sticking phenomenon as the surface light source device. The width of the top flat part or the top curved part is 2 μm or less, more preferably 1 μm or less.

  The primary light source 1 is a linear light source extending in the Y direction. As the primary light source 1, for example, a fluorescent lamp or a cold cathode tube can be used. In this case, as shown in FIG. 1, the primary light source 1 is not only installed to face one side end face of the light guide 3, but is further placed on the opposite side end face as necessary. You can also.

  The light source reflector 2 guides the light from the primary light source 1 to the light guide 3 with little loss. As the material, for example, a plastic film having a metal-deposited reflective layer on the surface can be used. As shown in the figure, the light source reflector 2 avoids the light deflecting element 4 and passes from the outer surface of the light reflecting element 5 to the light emitting surface edge of the light guide 3 through the outer surface of the primary light source 1. It is wrapped around. On the other hand, the light source reflector 2 can be wound from the outer surface of the light reflecting element 5 to the light emitting surface edge of the light deflecting element 4 through the outer surface of the primary light source 1. A reflection member similar to the light source reflector 2 can be attached to the side end face other than the light incident end face 31 of the light guide 3.

  As the light reflecting element 5, for example, a plastic sheet having a metal vapor deposition reflecting layer on the surface can be used. In the present invention, it is also possible to use a light reflecting layer or the like formed by metal vapor deposition or the like on the back surface 34 of the light guide 3 instead of the reflecting sheet as the light reflecting element 5.

  The light guide 3 and the light deflection element 4 of the present invention can be made of a synthetic resin having a high light transmittance. Examples of such synthetic resins include methacrylic resins, acrylic resins, polycarbonate resins, polyester resins, and vinyl chloride resins. In particular, methacrylic resins are optimal because of their high light transmittance, heat resistance, mechanical properties, and molding processability. Such a methacrylic resin is a resin mainly composed of methyl methacrylate, and preferably has a methyl methacrylate content of 80% by weight or more. When forming a surface structure such as a rough surface of the light guide 3 and the light deflecting element 4 or a surface structure such as a prism array or a lenticular lens array, the transparent synthetic resin plate is heated using a mold member having a desired surface structure. You may form by pressing, and you may give a shape simultaneously with shaping | molding by screen printing, extrusion molding, injection molding, etc. The structural surface can also be formed using heat or a photocurable resin. Furthermore, the surface of a transparent substrate such as a polyester resin, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or the like, or a rough surface made of an active energy ray curable resin is used. A structure or a lens array arrangement structure may be formed, or such a sheet may be bonded and integrated on a separate transparent substrate by a method such as adhesion or fusion. As the active energy ray-curable resin, polyfunctional (meth) acrylic compounds, vinyl compounds, (meth) acrylic acid esters, allyl compounds, (meth) acrylic acid metal salts, and the like can be used.

  On the light emitting surface (the light exit surface 42 of the light deflection element 5) of the surface light source device including the primary light source 1, the light source reflector 2, the light guide 3, the light deflection element 4, and the light reflection element 5 as described above, As shown in FIG. 3, a liquid crystal display device using the surface light source device of the present invention as a backlight is configured by arranging the transmissive liquid crystal display element 8. The liquid crystal display device is observed by an observer from above in FIG.

  Next, the rough surface constituting the light emitting mechanism of the light guide 3 will be described. FIG. 4 is a schematic diagram showing the relationship between the primary light source 1 and the light guide light exit surface 33 and the distribution of the average inclination angle θa of the light exit surface 33. The rough surface formed on the light emitting surface 33 is not uniformly formed as a whole, but is composed of two regions, that is, a specific region A and a general region B, which are divided by the distribution form of the average inclination angle θa. The specific area A is an area having a width (dimension in the X direction) x1 in the vicinity of the light incident end face 31, and the general area B is the other area. The general area B is a large area including the central portion of the light emitting surface 33, and the specific area A has a width x1, for example, a thickness at an edge on the light incident end face side of the light guide 3 d ( 2), it is within a range of 10d to 30d, specifically, for example, within a range of 10 mm to 70 mm, and is a relatively narrow region with respect to the general region B. In addition, the thickness d at the edge on the light incident end face side of the light guide 3 is in the range of 0.5 mm to 3 mm, for example.

  The average inclination angle θa can be obtained according to ISO 4287 / 1-1984 using a surface roughness / contour shape measuring instrument (for example, Surfcom [trade name] manufactured by Tokyo Seimitsu Co., Ltd.). In other words, the coordinate in the measurement direction is x, and can be obtained from the obtained gradient function f (x) using the following equations (1) and (2). Here, L is the measurement length, and Δa is the tangent of the average inclination angle θa.

実際の測定に際しては、導光体３の表面をＹ方向に測定し、その測定をＸ方向に一定ピッチ（例えば１ｍｍピッチ）ごとにずらしてθａを求め、特定領域Ａ及び一般領域ＢにおけるＸ方向の平均傾斜角θａの分布形態を得ることができる。

In actual measurement, the surface of the light guide 3 is measured in the Y direction, the measurement is shifted in the X direction at a constant pitch (for example, 1 mm pitch) to obtain θa, and the X direction in the specific area A and the general area B The distribution form of the average inclination angle θa can be obtained.

  As shown in FIG. 4, in the general region B, the distribution pattern of the average inclination angle θa is relatively gentle, and the average value of the entire range in the X direction of the average inclination angle θa is θa0. On the other hand, in the specific region A, the distribution pattern of the average inclination angle θa is relatively varied, and the average inclination angle θa takes the maximum value θa1 at the position of the distance x2 from the boundary with the light incident end face 31. This maximum value θa1 is larger than the above θa0. That is, in the specific region A, the average inclination angle θa first increases gradually from θa0 toward the boundary with the light incident end face 31 from the boundary with the general region B, and takes a local maximum value θa1. In general, it gradually decreases. The average inclination angle θa of the specific region is smaller than θa0 in the vicinity of the boundary with the light incident end face 31, and θa2 (<θa0) at the boundary with the light incident end face 31. As described above, in the specific region A, by providing a region in which the average inclination angle θa is larger than that of the general region B, the surface light source device emission surface in the region near the light incident end surface 31 due to the light guide thinning. The effect of making it difficult to visually recognize uneven brightness is obtained. Further, by making the average inclination angle θa smaller than θa0 in the vicinity of the boundary with the light incident end face 31, the oblique direction from the light emitting surface of the surface light source device in the vicinity of the light incident end face 31 due to the light guide thinning. An effect of suppressing specific light emission is obtained.

  θa0 is in the range of not less than 1.4 ° and less than 2.4 °, for example. Further, θa1 is in the range of 2.2 ° to 4.0 °, for example. θa2 is in the range of not less than 0.8 ° and not more than 2.0 °, for example. The position at which the average inclination angle θa takes the maximum value θa1 is preferably present in a region where the distance x2 to the boundary with the light incident end face 31 is in the range of d to 3d. This is because the bright line can be blurred by the position where the maximum value θa1 is in this range.

  In the specific region A, an inclination angle in which the average inclination angle θa gradually decreases toward the light incident end face 31 by 0.5 ° or more in the vicinity of the light incident end face 31 within the range from the light incident end face 31 to the distance x2. A decreasing area exists. It is preferable that at least a part of the inclined angle decreasing region exists in a band-shaped region whose distance from the light incident end face 31 is 0.2d to 2d. For example, at least a part of the decreasing tilt angle region exists in a band-shaped region whose distance from the light incident end face 31 is 0.2 mm to 4 mm. Since such an inclination angle decreasing region having an average inclination angle decreasing amount of 0.5 ° or more exists in the vicinity of the light incident end face 31, light emission from the surface light source device in the vicinity of the light incident end face 31 due to the light guide thinning. An effect of suppressing specific light emission in an oblique direction from the surface is obtained.

  An example of a manufacturing method of the light guide 3 having the light emitting surface 33 as described above will be described with reference to FIG.

  Here, as shown in FIG. 5A, the light guide 3 includes a first mold member 330 having a first transfer surface 33 ′ for transferring and forming the light emitting surface 33, and a back surface 34. It is produced by molding a translucent synthetic resin using a second mold member 340 having a second transfer surface 34 ′ for transfer formation. As the molding method, hot pressing, injection molding, or the like can be used. In FIG. 5 (a), only the first and second mold members 330 and 340 are shown as the mold apparatus, but the light incident end face and other side end faces of the light guide disposed around these mold members. A cylinder-shaped member having a transfer side wall surface for transferring and forming an end surface corresponding to is also used.

  The second mold member 340 can be produced by mechanical cutting on the surface of a metal flat plate such as a stainless steel plate or a copper alloy plate. Moreover, the 1st type | mold member 330 can be produced by the blast process or the etching process with respect to the surface of metal flat plates, such as a stainless steel board and a copper alloy board.

  The case where the first mold member 330 is manufactured by blasting will be described below. First, as shown in a schematic cross-sectional view in FIG. 5B, in the vicinity of the edge E corresponding to the boundary with the light incident end surface of the transfer surface area A ′ corresponding to the specific area A of the light guide light exit surface. On the other hand, the first roughening is performed by spraying the blast particles toward the surface of the metal flat plate under the first condition in a state where the shielding effect is imparted by the shielding member M1. As a result, the roughening of the first transfer surface 33 'other than the region of about half the distance x2 in the vicinity of the edge E is performed. The first condition is that the material of the blast particles, the particle size, the spraying speed, the spraying distance, the arrangement of the shielding member M1, etc., so that a transfer surface capable of transferring and forming the surface of the average inclination angle θa0 is obtained by this roughening. Is appropriately set. Next, as shown in a schematic cross-sectional view in FIG. 5C, in a state where the shielding effect is imparted to the transfer surface area B ′ corresponding to the general area B of the light guide light exit surface by the shielding member M2. The second roughening is performed under the second condition. As a result, roughening is performed on the transfer surface area A ′. The second condition is that the material of the blast particle, the particle size, the injection speed, the injection distance, and the shielding member are set so that a transfer surface capable of transferring and forming the specific region A of the average inclination angle distribution is obtained by this roughening. The arrangement and the like are appropriately set. In the second roughening, the shielding member M3 provides a shielding effect to the vicinity of the edge E in the transfer surface area A ′ (an area about half the distance x2 in the vicinity of the edge E). You can also. This facilitates formation of a transfer surface that can transfer and form the specific region A having an average inclination angle distribution in which the average inclination angle θa in the vicinity of the boundary with the light incident end face 31 is smaller than θa0. The blasting process can be performed by moving the jet nozzle parallel to the surface of the mold member and scanning while jetting blast particles from the jet nozzle.

  As shown in FIGS. 5 (b) and 5 (c), the shielding members M1 to M3 are arranged apart from the mold member transfer surface 33 ′ in the blasting process as described above, thereby obtaining an average inclination angle distribution. A gentle change can be realized. On the other hand, by arranging the shielding members M1 to M3 close to the mold member transfer surface 33 'during the blasting process, a steep change in the average inclination angle distribution can be realized. What is necessary is just to set the distance of a shielding member and a mold member transfer surface suitably according to desired average inclination-angle distribution.

  Using the first and second mold members 330 and 340 obtained as described above, the first and second transfer surfaces using the molding method such as injection molding as described with reference to FIG. By transferring the surface shapes of 33 ′ and 34 ′ onto the surface of the translucent synthetic resin material, the light guide 3 having the light emitting surface 33 and the back surface 34 of the required surface form is obtained.

  The transfer surface 33 'can be formed by etching instead of blasting. In this etching process, the light guide light emitting surface 33 having a desired average inclination distribution is transferred and formed by appropriately setting the concentration of the etching solution, the processing time, the arrangement of the shielding member in contact with the mold member transfer surface, and the like. A transfer surface 33 'that can be formed can be formed.

  Hereinafter, the present invention will be described with reference to examples and comparative examples.

[Example 1]
In this example, the light guide described in the embodiment of FIGS. 1 to 4 and the surface light source device using the same were manufactured.

  In order to produce the first mold member 330, the surface of a stainless steel plate having a mirror-finished effective area of 309 mm × 234 mm and a thickness of 3 mm is made of glass beads having a particle diameter of 75 μm or less (J-220 manufactured by Potters Barrodini Co., Ltd.). [Product Name]), the distance from the stainless steel plate to the spray nozzle was 320 mm, and the first roughening was performed by blasting almost the entire surface at a spray pressure of 0.1 MPa. At that time, as shown in FIG. 5 (b), the shielding member M1 is placed so as to float from the stainless steel plate, so that only the region in the vicinity of the edge (one long side) E is not roughened. The degree of blasting continuously changed at the boundary between the region near the edge E and other regions, and the change was steep.

  Next, the spray nozzle was moved along the edge of the shielding member and blasted in a state in which the shielding member M1 was floated from the stainless steel plate so that the region near the edge E was not roughened. Specifically, the blasting process was performed by moving the spray nozzle six times on the same line at a spray pressure of 0.30 MPa on the band-shaped region adjacent to the region near the edge E.

  Further, as shown in FIG. 5C, the shielding members M2 and M3 are arranged with a gap so as to form a slit having a width of 3 mm, and the center of the slit is the maximum value of the average inclination angle of the specific region. Blasting by moving the spray nozzle three times at a spray pressure of 0.15 MPa on the line directly above the slit in a state where the position is 4.5 mm from the edge E and placed above the stainless steel plate. did.

  On the other hand, in order to fabricate the second mold member 340, a prism array having an effective area of 309 mm × 234 mm and a thickness of 3 mm with a mirror finish on the surface of a stainless steel plate having an apex angle of 100 °, an apex tip radius of curvature of 15 μm, and a pitch of 50 μm. A transfer surface for transferring and forming the prism pattern provided continuously was formed by cutting.

  Transparent acrylic resin is injection-molded using the first and second mold members 330 and 340 obtained as described above, and is a 307 mm × 230 mm rectangle having a thickness opposite to the light incident end face 31 side. A light guide 3 having a wedge shape continuously changing from 2.2 mm to 0.7 mm toward the end surface, the light emitting surface 33 being roughened, and a prism pattern formed on the back surface 34 was obtained.

  The average inclination angle distribution of the specific area A (area from the light incident end face to 40 mm) and the general area B of the light emitting surface 33 of the obtained light guide 3 is shown in FIG. The distribution is enlarged and shown in FIG. The average inclination angle at a position where the distance from the light incident end face is 0.5 mm is 1.55 °, and the average inclination angle at a position where the distance from the light incident end face is 1.5 mm is 2.00 °. The average inclination angle at the position where the distance from the light incident end face is 2.5 mm is 2.46 °, and the average inclination angle at the position where the distance from the light incident end face is 3.5 mm is 2.67 °. there were.

  The primary light source 1 made of a cold cathode tube was disposed along the longitudinal direction of the light guide 3 so as to face the light incident end face 31 of the light guide 3 and covered with the light source reflector 2. The light reflecting element 5 made of a light scattering reflection sheet is arranged so as to face the back surface 34 of the light guide 3 to which the prism pattern is applied, and a large number of prism rows are made to face the light emitting surface 33 made of a rough surface. The surface light source device as shown in FIG. 2 was manufactured by arranging the light deflection elements 4 made of prism sheets formed in parallel arrangement so that the prism array formation surface is on the light guide light emission surface side. . As the prism sheet of the light deflection element 4, a prism sheet having one convex surface having a convex curved surface shape with a radius of curvature of 1000 μm and the other prism surface having a planar shape and arranged in parallel at a pitch of 50 μm was used.

  When the primary light source 1 of the obtained surface light source device was turned on and the vicinity of the light incident end face 31 on the light emitting surface was observed, the bright and dark lines and the bright and dark bands that caused uneven brightness were not visible. Further, when the vicinity of the light incident end face 31 of the light emitting surface was observed from an oblique direction (that is, as if looking into the light incident end face 31), specific light emission in the oblique direction was not visually recognized.

  When the luminance distribution on the light emitting surface of the surface light source device was measured, as shown in FIG. 8, it gradually decreased from the center to the light guide light incident end surface side, which was consistent with the above observation result.

Comparative Example 1:
Except not using shielding member M1 and not performing blasting using shielding members M2 and M3, the same steps as in Example 1 were performed to obtain a light guide. The average inclination angle distribution of the light exit surface of the obtained light guide is shown in FIGS. The average inclination angle at a position where the distance from the light incident end face is 0.5 mm is 2.76 °, and the average inclination angle at a position where the distance from the light incident end face is 1.5 mm is 2.81 °. Yes, the average inclination angle at the position where the distance from the light incident end face is 2.5 mm is 2.68 °, and the average inclination angle at the position where the distance from the light incident end face is 3.5 mm is 2.57 °. there were.

  Using the obtained light guide, a surface light source device was produced in the same manner as in Example 1. When the primary light source of the surface light source device was turned on and the vicinity of the light incident end face of the light emitting surface was observed, a light / dark line and a light / dark band causing uneven brightness were slightly recognized. Further, when the vicinity of the light incident end face of the light emitting surface was observed from an oblique direction (that is, from a direction looking into the light incident end face), specific light emission in the oblique direction was visually recognized.

  When the luminance distribution on the light emitting surface of the surface light source device was measured, the luminance change was larger than that in Example 1 particularly in the vicinity of the light guide light incident end surface as shown in FIG.

[Example 2]
In order to produce the first mold member 330, the surface of a stainless steel plate having an effective area of 336 mm × 214 mm and a thickness of 3 mm, which is mirror-finished, is made of glass beads having a particle size of 75 μm or less (Potters Barodini Co., Ltd. J-220 [ Product name]), the distance from the stainless steel plate to the spray nozzle was set to 320 mm, and the first roughening was performed by blasting almost the entire surface at a spray pressure of 0.1 MPa. At that time, as shown in FIG. 5 (b), the shielding member M1 is placed so as to float from the stainless steel plate, so that only the region in the vicinity of the edge (one long side) E is not roughened. The arrangement of the shielding member M1 with respect to the stainless steel plate, that is, the overlapping width of the shielding member M1 with respect to the stainless steel plate in a plane parallel to the stainless steel plate was made smaller than that in Example 1. As a result, the change in the degree of the blasting process at the boundary between the area near the edge E and the other area was more gradual than in the first embodiment.

  Next, the spray nozzle was moved along the edge of the shielding member and blasted in a state in which the shielding member M1 was floated from the stainless steel plate so that the region near the edge E was not roughened. Specifically, the blasting process was performed by moving the spray nozzle six times on the same line at a spray pressure of 0.30 MPa on the band-shaped region adjacent to the region near the edge E.

  On the other hand, in order to fabricate the second mold member 340, a prism array with an apex angle of 100 °, apex tip radius of curvature of 15 μm, and a pitch of 50 μm is provided on the surface of a stainless steel plate having an effective area of 336 mm × 214 mm and a thickness of 3 mm that is mirror-finished. A transfer surface for transferring and forming the prism pattern provided continuously was formed by cutting.

  Using the first and second mold members 330 and 340 obtained as described above, injection molding of transparent acrylic resin is performed, and the rectangular shape is 336 mm × 213 mm, and the thickness is opposite from the light incident end face 31 side. A light guide 3 having a wedge shape continuously changing from 2.6 mm to 0.7 mm toward the end surface, the light emitting surface 33 being roughened, and a prism pattern formed on the back surface 34 was obtained.

  The average inclination angle distribution in the specific area A of the light emitting surface 33 of the obtained light guide 3 is shown in FIG. The average inclination angle at the position where the distance from the light incident end face is 0.2 mm is 1.92 °, and the average inclination angle at the position where the distance from the light incident end face is 1 mm is 2.32 °, The average inclination angle at a position where the distance from the light incident end face was 2 mm was 2.53 °.

  The primary light source 1 made of a cold cathode tube was disposed along the longitudinal direction of the light guide 3 so as to face the light incident end face 31 of the light guide 3 and covered with the light source reflector 2. The light reflecting element 5 made of a light scattering reflection sheet is arranged so as to face the back surface 34 of the light guide 3 to which the prism pattern is applied, and a large number of prism rows are made to face the light emitting surface 33 made of a rough surface. The surface light source device as shown in FIG. 2 was manufactured by arranging the light deflection elements 4 made of prism sheets formed in parallel arrangement so that the prism array formation surface is on the light guide light emission surface side. . As the prism sheet of the light deflection element 4, a prism sheet having one convex surface having a convex curved surface shape with a radius of curvature of 1000 μm and the other prism surface having a planar shape and arranged in parallel at a pitch of 50 μm was used.

  When the primary light source 1 of the obtained surface light source device was turned on and the vicinity of the light incident end face 31 on the light emitting surface was observed, the degree of expression of bright and dark lines and bright and dark bands that caused uneven brightness was small. Further, when the vicinity of the light incident end face 31 of the light emitting surface was observed from an oblique direction (that is, so as to look into the light incident end face 31), the degree of specific light emission in the oblique direction was small.

  When the luminance distribution on the light emitting surface of the surface light source device was measured, as shown in FIG. 10, it gradually decreased from the center toward the light guide light incident end surface side, which was consistent with the above observation result.

Comparative Example 2:
Except not using shielding member M1, the same process as Example 2 was performed and the light guide was obtained. FIG. 9 shows a part of the average inclination angle distribution of the light exit surface of the obtained light guide. The average inclination angle at a position where the distance from the light incident end face was 1 mm was 3.11 °, and the average inclination angle at a position where the distance from the light incident end face was 2 mm was 2.84 °.

  Using the obtained light guide, a surface light source device was produced in the same manner as in Example 2. When the primary light source of the surface light source device was turned on and the vicinity of the light incident end face of the light emitting surface was observed, a light / dark line and a light / dark band causing uneven brightness were slightly recognized. Further, when the vicinity of the light incident end face of the light emitting surface was observed from an oblique direction (that is, from a direction looking into the light incident end face), specific light emission in the oblique direction was visually recognized.

  When the luminance distribution on the light emitting surface of the surface light source device was measured, as shown in FIG. 10, the luminance change was larger than that in Example 2 particularly in the vicinity of the light guide light incident end surface, which was consistent with the above observation result.

FIG. 1 is a schematic perspective view showing one embodiment of a surface light source device according to the present invention.
FIG. 2 is a partial cross-sectional view of the surface light source device of FIG.
FIG. 3 is a schematic diagram showing a state of light deflection by the light deflection element.
FIG. 4 is a schematic diagram showing the relationship between the primary light source and the light guide light exit surface and the average inclination angle distribution of the light exit surface.
FIG. 5 illustrates an example of a method for manufacturing a light guide.
FIG. 6 is a diagram showing an average inclination angle distribution of light guide light exit surfaces obtained in Example 1 and Comparative Example 1.
FIG. 7 is an enlarged view showing a part of the average inclination angle distribution of FIG.
FIG. 8 is a diagram showing the luminance distribution on the light emitting surface of the surface light source devices obtained in Example 1 and Comparative Example 1.
FIG. 9 is an enlarged view showing a part of the average inclination angle distribution of the light guide light exit surfaces obtained in Example 2 and Comparative Example 2.
FIG. 10 is a diagram showing the luminance distribution on the light emitting surface of the surface light source devices obtained in Example 2 and Comparative Example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Primary light source 2 Light source reflector 3 Light guide 31 Light incident end surface 32 Side end surface 33 Light emission surface 34 Back surface 4 Light deflection element 41 Light incident surface 42 Light emission surface 5 Light reflection element 8 Liquid crystal display element A Specific area B General area 330 1st 1 mold member 33 ′ first transfer surface 340 second mold member 34 ′ second transfer surface A ′ transfer surface region B ′ transfer surface region E mold member edge M1, M2, M3 shielding member

Claims (19)

A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
At least one of the light exit surface and the back surface is a rough surface. In the light exit surface and / or the back surface, which is a rough surface, an average inclination angle of the surface is close to the light entrance end surface toward the light entrance end surface. And a light source for a surface light source device, characterized in that there is a gradually decreasing inclination angle region that gradually decreases by 0.5 ° or more. The thickness of the light guide at the edge on the light incident end face side is d, and at least a part of the inclined angle decreasing region is within a region whose distance from the light incident end surface is 0.2d to 2d. The light guide for a surface light source device according to claim 1, wherein the light guide is present. 2. The light guide for a surface light source device according to claim 1, wherein at least a part of the inclined angle decreasing region exists in a region having a distance from the light incident end face of 0.2 mm to 4 mm. . A light guide for a surface light source device that is used to configure a surface light source device in combination with a primary light source and guides light emitted from the primary light source,
A light incident end surface on which light emitted from the primary light source is incident, a light emitting surface from which guided light is emitted, and a back surface opposite to the light emitting surface;
At least one of the light exit surface and the back surface is a rough surface. In the light exit surface and / or the back surface, which is a rough surface, in a specific region near the light incident end surface, an average inclination angle of the surface is the specific surface. A maximum value larger than the average value of the average inclination angle of the general region between the boundary with the general region other than the region and the boundary with the light incident end surface, and in the vicinity of the boundary with the light incident end surface, A light guide for a surface light source device, wherein the light guide is smaller than an average value of an average inclination angle. Assuming that the thickness of the light guide at the edge on the light incident end face side is d, the position where the maximum value of the average tilt angle is at a distance from the boundary of the specific region to the light incident end face is d to 3d. It exists in the area | region of the range of this, The light guide for surface light source devices of Claim 4 characterized by the above-mentioned. The light guide for a surface light source device according to claim 4, wherein the maximum value of the average inclination angle in the specific region is in a range of 2.2 ° to 4.0 °. The light guide for a surface light source device according to claim 4, wherein an average value of an average inclination angle in the general region is in a range of 1.4 ° or more and less than 2.4 °. In the specific region, the distance from the boundary with the general region to the boundary with the light incident end surface is within a range of 10 to 30 times the thickness at the edge on the light incident end surface side of the light guide. The light guide for a surface light source device according to claim 4, wherein the light guide is provided. 5. The light guide for a surface light source device according to claim 4, wherein the specific region has a distance from a boundary with the general region to a boundary with the light incident end surface within a range of 10 mm to 70 mm. . The said surface light source device by which the said primary light source is arrange | positioned facing the light-incidence end surface of the light guide for surface light source devices in any one of Claims 1-9. And a light deflection element disposed on the light exit surface of the light guide and having a light entrance surface on which light emitted from the light exit surface of the light guide enters and a light exit surface on the opposite side. The surface light source device according to claim 10, wherein: The light deflection element includes a plurality of prism rows that extend along the light incident end surface of the light guide and are arranged in parallel to each other on the light incident surface, and each of the prism rows is light of the light guide. The surface light source device according to claim 11, further comprising: a first prism surface on which light from the emission surface is incident; and a second prism surface on which incident light is internally reflected. The surface light source device according to claim 10, wherein the primary light source is a linear light source. It is a method of manufacturing the light guide for a surface light source device according to any one of claims 1 to 9, wherein the first mold member having a first transfer surface for transferring and forming the light emitting surface and the back surface are provided. A translucent synthetic resin is molded using a second mold member having a second transfer surface to be transferred, and the first member for transfer formation of a rough surface of the light emitting surface and the back surface is formed here. When forming the first transfer surface and / or the second transfer surface, a shielding effect is provided for the vicinity of the edge corresponding to the boundary between the light incident end surface and the light emitting surface of the light guide in the transfer surface region. A method of manufacturing a light guide for a surface light source device, wherein the first roughening is performed in a state. When forming the first transfer surface and / or the second transfer surface for transfer formation of a rough surface of the light emitting surface and the back surface, a transfer surface region corresponding to the general region is further formed. The method for producing a light guide for a surface light source device according to claim 14, wherein the second roughening is performed in a state where a shielding effect is imparted. The light guide for a surface light source device according to claim 15, wherein a shielding effect for the vicinity of the edge of the transfer surface region corresponding to the specific region is also provided during the second roughening. Manufacturing method. 15. The method of manufacturing a light guide for a surface light source device according to claim 14, wherein the first roughening and / or the second roughening is performed by an etching process. 15. The method of manufacturing a light guide for a surface light source device according to claim 14, wherein the first roughening and / or the second roughening is performed by blasting. 19. The surface light source device according to claim 18, wherein the shielding effect is imparted by arranging a shielding member, and the shielding member is arranged away from the first transfer surface or the second transfer surface. Manufacturing method of light guide.

Images