JP2012203081A - Light deflecting element and surface light source device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface light source device balanced between a viewing angle and brightness and a light deflecting element for use in the same.SOLUTION: The surface light source device includes a primary light source 1, a light guide 3, and a light deflecting element 4. The light deflecting element 4 has a light incident surface and a light emission surface located on the side opposite to the light incident surface, and a plurality of prism arrays each of which comprises a pair of prism surfaces are arranged in parallel on the light incident surface. The prism surface farther from the primary light source 1, out of the pair of prism surfaces of each prism array, comprises two or more planes of which the inclination angles with respect to a normal direction of the light emission surface in a cross section orthogonal to an extension direction of the prism array are different from each other. The inclination angle of a plane nearest to the front end part of the prism array is within a range from 35° to 42°, and the inclination angle of a plane nearest to a valley part of the prism array is within a range from 25° to 30°. When a length in a prism array arrangement direction of the prism surface farther from the primary light source 1 is denoted as 1, a length of the plane nearest to the valley part of the prism array is within a range from 0.45 to 0.85.

Description

  The present invention relates to an edge light type surface light source device that constitutes a liquid crystal display device used as a display unit in a portable information terminal, a notebook computer, a monitor, a television, and the like, and a light deflection element used therefor.

  In recent years, color liquid crystal display devices have been widely used in various fields as monitors for portable notebook computers, personal computers, etc., or as display units for liquid crystal televisions. In addition, with the increase in the amount of information processing, diversification of needs, compatibility with multimedia, and the like, liquid crystal display devices have been increased in screen size and definition.

  The liquid crystal display device basically includes a backlight unit and a liquid crystal display element unit. As the backlight unit, there are a direct type with a light source arranged directly under the liquid crystal display element unit and an edge light type with a light source arranged so as to face the side end face of the light guide. From the viewpoint of making it easier, an edge light type is widely used.

  In recent years, from the viewpoint of reducing power consumption, in order to effectively use the amount of light emitted from the primary light source as an edge light type backlight unit, the spread angle of the light beam emitted from the light emitting surface is made as small as possible to obtain the required angle. Those that emit light in a concentrated manner are used. For example, a high-luminance surface light source device can be realized by using a light deflection element disclosed in Japanese Patent No. 4323189 (Patent Document 1) and Japanese Patent Application Laid-Open No. 2004-233938 (Patent Document 2).

Japanese Patent No. 4323189 Japanese Patent Laid-Open No. 2004-233938

  By the way, in a display unit such as a monitor or a television, it is necessary to secure an appropriate viewing angle. If the light is concentrated in a narrow angle range, it can be seen only in a specific angle range, which is inconvenient. .

  However, in the surface light source device using the light deflecting element described in Patent Document 1 and Patent Document 2, light is concentrated in a required angle range, and the spread angle of the light beam emitted from the light emitting surface is made as small as possible. Thus, since the high luminance is realized by effectively using the light amount emitted from the primary light source, it is difficult to widen the viewing angle while maintaining the luminance appropriately.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source device having a wide viewing angle and maintaining appropriate luminance, that is, a balanced viewing angle and luminance, and an optical deflection element used therefor.

The optical deflecting element of the present invention that achieves the above object is
It has a light incident surface on which light is incident and a light output surface on the opposite side from which incident light is emitted, and the light incident surface has a plurality of prism rows arranged in parallel in a pair of prism surfaces. An optical deflection element,
One prism surface of the pair of prism surfaces is composed of two or more planes having different inclination angles with respect to the normal direction of the light exit surface in a cross section orthogonal to the extending direction of the prism row,
The inclination angle of the plane closest to the tip of the prism row in the cross section is in the range of 35 to 42 degrees;
The inclination angle of the plane closest to the valley of the prism row in the cross section is in the range of 25 degrees to 30 degrees;
The length of the one prism surface in the arrangement direction of the prism rows is 1, and the length of the plane closest to the valley of the prism rows in the cross section is in the range of 0.45 to 0.85. ,
It is characterized by that.

The surface light source device of the present invention that achieves the above object is as follows.
A light guide having a primary light source, a light incident end surface on which light emitted from the primary light source is incident, a light emitting surface that guides the incident light and emits at least part of the guided light And the light deflection element disposed adjacent to the light exit surface of the light guide,
The light deflecting element is configured such that the light incident surface faces the light emitting surface of the light guide, and the prism array has the one prism surface far from the primary light source and the other prism surface. It is arranged on the side close to the primary light source.

  According to the present invention, it is possible to provide a surface light source device having a wide viewing angle and maintaining appropriate luminance, that is, a balanced viewing angle and luminance, and an optical deflection element used therefor.

It is a typical perspective view which shows embodiment of the surface light source device by this invention. It is explanatory drawing of the cross-sectional shape of the prism row | line | column in embodiment of the optical deflection | deviation element by this invention. It is a figure which shows an example of the outgoing light luminous intensity distribution of the light guide in the surface light source device by this invention dependent on the outgoing angle. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection | deviation element in Example 1 of this invention. It is a figure which shows the cross-sectional shape of the prism row | line | column of the optical deflection | deviation element in Example 2 of this invention. It is a figure which shows the cross-sectional shape of the prism row | line | column of the optical deflection | deviation element in Example 3 of this invention. It is a figure which shows the cross-sectional shape of the prism row | line | column of the optical deflection | deviation element in Example 4 of this invention. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection element in the comparative example 2. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection element in the comparative example 3. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection element in the comparative example 4. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection element in the comparative example 5. It is a figure which shows the cross-sectional shape of the prism row | line | column of the light deflection element in the comparative example 6.

  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. As shown in FIG. 1, the surface light source device of this embodiment includes a light guide 3 having a light incident end surface 31 as one side end surface and a light exit surface 33 as one surface substantially orthogonal thereto. The primary light source 1 disposed facing the light incident end surface 31 of the light guide 3, the light deflecting element 4 and the light diffusing element 6 disposed on the light emitting surface 33 of the light guide 3, and the light guide The light reflecting element 5 is disposed so as to face the back surface 34 on the side opposite to the light emitting surface 33 of the 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 one side end surface of the pair of side end surfaces parallel to the YZ plane is defined as a light incident 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 incident end face 31 and is introduced into the light guide 3.

  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. At least one of the light emitting surface 33 and the back surface 34 located on the opposite side thereof has a directional light emitting function portion formed of a rough surface, a prism array, a lenticular lens array, a V-shaped groove, and the like. By providing a directional light emitting function unit composed of lens surfaces in which lens rows are formed in parallel, the light incident on the light incident end surface 31 is guided through the light guide 3 while the light incident end surface 31 is exposed to the light incident end surface. In the outgoing light distribution in the plane (XZ plane) orthogonal to both 31 and the light emitting surface 33, light having directivity is emitted. When the angle formed by the peak direction of the outgoing light distribution in the XZ plane and the light outgoing surface 33 is a, this angle a is preferably 10 to 40 degrees, and the full width at half maximum of the outgoing light distribution is 10 to 40 degrees. It is preferable that

  In the present invention, light diffusing fine particles are mixed and dispersed in the light guide instead of or in combination with the light emitting surface 33 or the back surface 34 as described above. What provided the directional light emission function may be used. Further, the light guide 3 is not limited to a substantially parallel plate shape (that is, the XZ cross-sectional shape is rectangular) as shown in FIG. 1, but at least in a portion adjacent to the light incident end surface. Those having a wedge shape in which the thickness gradually decreases as the distance from the head is increased, or those having various XZ cross-sectional shapes such as a hull shape can be used.

  The light guide 3 of the present invention can be composed 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 the surface structure such as the rough surface of the light guide 3 is formed, the transparent synthetic resin plate may be formed by hot pressing using a mold member having a desired surface structure, screen printing, extrusion molding. Alternatively, the shape may be imparted simultaneously with molding by injection molding or the like. The structural surface can also be formed using heat or a photocurable resin. Furthermore, on a transparent substrate such as a polyester film, acrylic resin, polycarbonate resin, vinyl chloride resin, polymethacrylamide resin, or other transparent substrate or rough surface structure made of an active energy ray curable resin. May be formed on the surface, 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.

  FIG. 2 is an explanatory diagram of a cross-sectional shape orthogonal to the prism array extending direction of the light deflection element 4. FIG. 2 corresponds to the XZ section in FIG. One of the main surfaces of the light deflection element 4 is a light incident surface 41 and the other surface is a light output surface 42. A large number of prism rows are arranged in parallel on the light incident surface 41, and each prism row is a first prism surface 44 positioned on the side closer to the primary light source 1 and a second prism positioned on the side farther from the primary light source 1. It consists of two prism surfaces (a pair of prism surfaces) with the prism surface 45.

  The second prism surface 45 is composed of a plurality of planes. The plurality of planes have different inclination angles with respect to the normal direction (Z direction) of the light exit surface 42 in a cross section (XZ cross section) orthogonal to the extending direction (Y direction) of the prism rows. The inclination angle of the plane closest to the tip of the prism row (corresponding to the top of the prism row) in the XZ cross section is in the range of 35 to 42 degrees, preferably 35 to 40 degrees. Further, the inclination angle of the plane closest to the valley of the prism row (corresponding to the prism bottom located near the boundary with the adjacent prism row) in the XZ section is 25 degrees to 30 degrees, preferably 27 degrees to 29 degrees. Is in the range of up to.

  Assuming that the normal direction of the light exit surface 42 of the light deflecting element 4 is 0 degree, the side closer to the primary light source 1 is a negative angle, and the side far from the primary light source 1 is a positive angle, as shown in FIG. The peak in the emission direction of the light totally reflected by the plane close to the column tip is inclined to the positive side. On the other hand, the peak in the emission direction of light totally reflected by a plane close to the prism row valley is inclined to the negative side. The inclination angle of the plane closest to the prism array tip is in the range of 35 to 42 degrees with respect to the normal direction of the light output surface 42, and the inclination angle of the plane closest to the prism array valley is the output surface 42. A surface light source device in which the viewing angle is wide and the appropriate brightness is maintained, that is, the viewing angle and the brightness are balanced by being within a range from 25 degrees to 30 degrees with respect to the normal direction Can be realized.

  Further, the length in the prism row arrangement direction [prism row pitch direction] (X direction) of the plane closest to the prism row valley is 0.45 times or more the length of the second prism surface 45 in the prism row arrangement direction. 0.85 times or less, preferably 0.55 times or more and 0.8 times or less. That is, assuming that the length of the second prism surface 45 in the prism array arrangement direction is 1, the length of the plane closest to the prism array valley in the XZ section is from 0.45 to 0.85, preferably from 0.55. Within the range of up to 0.8. This is because the amount of light per unit area is less in the prism row valley than in the prism row tip, and if there is no length in the X direction above a certain level in the plane closest to the prism row valley, This is because the amount of light totally reflected on the near surface, that is, light emitted to the negative side is reduced. On the other hand, if the plane close to the prism row tip is too short, the amount of light totally reflected by the plane near the prism row tip is reduced, and as a result, the emitted light is biased to the negative side.

  In the embodiment shown in FIG. 2, the first prism surface 44 is composed of one plane, and the second prism surface 45 is composed of two planes. The second prism surface 45 can easily control the light distribution of the light emitted from the light deflection element 4 if the number of planes constituting the second prism surface 45 is increased. It is difficult to produce a transfer mold member for transferring and forming the surface 41. Therefore, it is appropriate that the second prism surface 45 is composed of at most four or two planes.

  In the embodiment shown in FIG. 2, the first prism surface 44 preferably has an angle of 5 degrees to 40 degrees with respect to the normal direction of the light exit surface 42. When this angle is smaller than 5 degrees, it becomes difficult to manufacture the light deflection element 4, particularly the transfer mold member for transferring and forming the light incident surface 41 which is the prism array forming surface. On the other hand, when the angle is larger than 40 degrees, the amount of light hitting the second prism surface 45 is reduced, and sufficient luminance cannot be obtained.

  The arrangement pitch P of the prism rows is not particularly limited, but is preferably about 10 to 100 μm. However, a value that can avoid moiré with the liquid crystal panel (liquid crystal display element) may be selected.

  As the primary light source 1, for example, a point light source such as an LED light source, a halogen lamp, or a metal halide lamp, or a linear light source extending in the Y direction such as a fluorescent lamp or a cold cathode tube can be used. A plurality of point light sources may be arranged in the Y direction. If necessary, a light source reflector may be installed so as to surround the primary light source 1. The light source reflector reflects light that has not been incident on the light incident end surface 31 of the light guide 3 out of the light emitted from the primary light source 1 toward the light incident end surface 31. As a material of the light source reflector, for example, a plastic film having a metal vapor deposition reflecting layer on the surface can be used. A reflection member similar to such a light source reflector may be attached to a side end face other than the side end face 31 that is the light incident end face of the light guide 3.

  The light reflecting element 5 is disposed so as to face the back surface 34 on the side opposite to the light emitting surface 33 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 on the back surface 34 of the light guide 3 by metal vapor deposition or the like, instead of the reflecting sheet, as the light reflecting element 5. Thereby, the light leaked from the light guide 3 can be returned again into the light guide, and the amount of light emitted from the primary light source 1 can be used effectively.

  The light diffusing element 6 may be integrated with the light deflecting element 4 on the light exiting surface side of the light deflecting element 4, or the light diffusing element 6 may be individually placed on the light exiting surface of the light deflecting element 4. good. When the light diffusing element 6 is individually mounted, the surface adjacent to the light deflecting element 4 of the light diffusing element 6, that is, the incident surface is provided with an uneven structure to prevent sticking with the light deflecting element 4. It is preferable to give. Similarly, it is necessary to consider sticking between the light diffusing element 6 and the liquid crystal display element disposed thereon, and it is preferable to provide a concavo-convex structure on the light emitting surface. When this concavo-convex structure is provided only for the purpose of preventing sticking, the average inclination angle according to ISO 4287 / 1-1984 described in paragraphs [0018] to [0019] of the specification of Patent Document 1 is 0. It is preferable to have a structure of 7 degrees or more, more preferably 1 degree or more, and more preferably 1.5 degrees or more.

  The light diffusing element 6 may be omitted.

  A liquid crystal display device is configured by disposing a liquid crystal display element on the light emitting surface of the surface light source device as described above. The liquid crystal display device is observed by an observer through the liquid crystal display element from above in FIG.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

  In addition, the preparation method of the light guide used in the following examples and comparative examples and the measurement method of each physical property are shown below.

[Production of light guide]
A stainless steel plate with an effective area of 195 mm (dimension in the X direction) x 307 mm (dimension in the Y direction) and a thickness of 3 mm is used as the mold material, and stainless steel using glass beads (J220 manufactured by Potters Valotini). Blasting was performed with the distance from the plate to the blast nozzle being 32 cm. As a result, a first mold member was obtained.

  On the other hand, a mirror-finished effective area of 195 mm (dimension in the X direction) x 307 mm (dimension in the Y direction) and a 3 mm thick nickel-phosphorus plated plate is used as the mold material, and the back surface of the light guide consisting of the lens array forming surface is used. The shape transfer surface for forming the film by transfer was formed by cutting. As a result, a second mold member was obtained. The lens array on the lens array forming surface had a top tip radius of curvature of 135 μm, an array pitch of 100 μm, and an aspect ratio of 10. Further, the extending direction of the lens array was set to be a direction (X direction) perpendicular to the long side of the stainless steel plate.

  A transparent acrylic resin composition is injection-molded by using the above two molding mold members, and has a rectangular shape with a short side of 195 mm and a long side of 307 mm, a constant thickness of 0.8 mm, and one surface (light emitting surface) A light guide 3 made of a transparent acrylic resin having a rough surface 33) and a lens array forming surface on the other surface (back surface 34) was obtained.

[Measurement of luminous intensity distribution of light guide]
54 LEDs (E1S62-YWOS7-07 manufactured by Toyoda Gosei Co., Ltd.) at equal intervals along the long side as the primary light source 1 so as to face the long side end surface (light incident end surface 31) of the light guide. And a light source reflector. Further, a light scattering reflection sheet (E6SP manufactured by Toray Industries, Inc.) was disposed as the light reflecting element 5 so as to face the back surface 34 of the light guide 3.

  In the structure obtained by removing the light deflecting element 4 and the light diffusing element 6 from the configuration shown in FIG. 1, the primary light source 1 is turned on, and the light emitting surface 33 of the light guide 3 has a 3 mmφ diameter. A black paper having a pinhole was fixed so that the pinhole was positioned at the center of the light emitting surface 33. The luminous intensity distribution of the emitted light was measured with a luminance meter while tilting at an interval of 1 ° within the range of + 85 ° to −85 ° in the XZ plane with the normal direction of the light emitting surface 33, that is, the Z direction as 0 °. The angle was negative on the side close to the primary light source 1 and positive on the opposite side. The measurement result of the luminous intensity distribution of this light guide is shown in FIG. 3 (luminous intensity is shown as a relative value). The light emitted from the light exit surface 33 of the light guide 3 is 20 degrees in the angle between the direction of the distribution peak and the light exit surface 33 in a plane orthogonal to both the light incident end surface 31 and the light exit surface 33. Yes, the full width at half maximum of the distribution was 26 degrees.

[Measurement of peak luminance and full width at half maximum of luminance distribution of surface light source device]
In the configuration shown in FIG. 1, the primary light source 1 was turned on, the viewing angle of the luminance meter was set to 1 degree, and the measurement position was adjusted to be in the center of the surface light source device. The luminance distribution of the emitted light is measured with a luminance meter while tilting at an interval of 1 ° within the range of + 45 ° to −45 °, with the normal direction of the light exit surface 42 of the light deflecting element 4, that is, the Z direction being 0 °, The full width at half maximum of the peak brightness and the brightness distribution (the spread angle of the brightness value distribution that is 1/2 or more of the peak brightness value) was determined. The angle was negative on the side close to the primary light source 1 and positive on the opposite side.

Example 1:
The surface light source device belonging to the embodiment of FIGS. 1 and 2 was produced as follows.

  First, the light guide 3 having the emitted light luminous intensity distribution (luminous intensity is shown as a relative value) shown in FIG. 3 was produced. On the light emitting surface 33 of the light guide 3, the light deflection element 4 manufactured using an acrylic ultraviolet curable resin having a refractive index of 1.506 was placed. The light deflection element 4 is a prism sheet in which a large number of prism rows are formed on the light incident surface 41, and the cross-sectional shape of each prism row (the cross-sectional shape perpendicular to the extending direction of the prism rows) is as shown in FIG. there were.

  FIG. 4 shows the dimension value and angle value of each part of the prism row. In FIG. 4, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 27 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of three planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 39.06 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 5.60 μm. The plane closest to the valley of the prism row has an inclination angle of 27 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 15.68 μm. A plane located between these two planes has an inclination angle of 34.85 degrees with respect to the light exit surface normal, and a length in the prism array arrangement direction of 5.50 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.59. The arrangement pitch P of the prism rows is 50.00 μm.

  This prism sheet was placed so that the light incident surface 41 formed of the prism row forming surface faces the light emitting surface 33 of the light guide 3. Further, the primary light source 1 and the light reflecting element 5 were arranged to obtain a surface light source device.

  The emission light luminance distribution of this surface light source device is measured, and the value of the peak luminance ratio and the value of the full width at half maximum of the luminance distribution (in units of degrees [°; deg]) are obtained based on Comparative Example 1 described later. The results are shown in Table 1.

Example 2:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of each prism row was as shown in FIG.

  FIG. 5 shows the dimension value and angle value of each part of the prism row. In FIG. 5, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 27 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 37.03 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 5.56 μm. The plane closest to the valley of the prism row has an inclination angle of 29 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 21.20 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.79. The arrangement pitch P of the prism rows is 50.00 μm.

  The luminance distribution of the emitted light of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution were obtained with reference to Comparative Example 1 described later. The results are shown in Table 1.

Example 3:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of each prism row was as shown in FIG.

  FIG. 6 shows the dimension value and angle value of each part of the prism row. In FIG. 6, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 27 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism array has an inclination angle of 36.50 degrees with respect to the light exit surface normal, and the length in the prism array arrangement direction is 10.00 μm. The plane closest to the valley of the prism row has an inclination angle of 28.50 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 17.08 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.63. The arrangement pitch P of the prism rows is 50.00 μm.

  The luminance distribution of the emitted light of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution were obtained with reference to Comparative Example 1 described later. The results are shown in Table 1.

Example 4:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of each prism row was as shown in FIG.

  FIG. 7 shows the dimension value and angle value of each part of the prism row. In FIG. 7, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 38 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of three planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 40.0 degrees with respect to the light exit surface normal and a length in the prism row arrangement direction of 4.00 μm. The plane closest to the valley of the prism row has an inclination angle of 27.0 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 12.09 μm. The plane located in the middle of these two planes has an inclination angle of 35 degrees with respect to the light exit surface normal, and the length in the prism array direction is 5.5 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.56. The arrangement pitch P of the prism rows is 50.00 μm.

  The luminance distribution of the emitted light of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution were obtained with reference to Comparative Example 1 described later. The results are shown in Table 1.

Comparative Example 1:
In the XZ cross-sectional shape, when the coordinates of the vertices of the prism rows are (X [μm], Z [μm]) = (0, 0), the shape of each prism row is (X, Z) = (− 25 , 38.94) and the vertex and (X, Z) = (25, 38.94), except that the shape is an isosceles triangle, a surface light source device was obtained in the same manner as in Example 1. . Here, both the first prism surface 44 located on the side closer to the primary light source 1 and the second prism surface 45 located on the side far from the primary light source 1 have an inclination angle of 32.7 degrees with respect to the light emitting surface normal. It is. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 1.0.

  The emitted light luminance distribution of this surface light source device was measured, the peak luminance was set to 1.000, the value of the full width at half maximum of the luminance distribution was obtained, and the results are shown in Table 1.

Comparative Example 2:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of the prism row was as shown in FIG.

  FIG. 8 shows the dimension value and angle value of each part of the prism row. In FIG. 8, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 27 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 45 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 8.00 μm. The plane closest to the valley of the prism array has an inclination angle of 29 degrees with respect to the light exit surface normal, and the length in the prism array arrangement direction is 19.76 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.71. The arrangement pitch P of the prism rows is 50.00 μm.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution when Comparative Example 1 was used as a reference were obtained. The results are shown in Table 1.

Comparative Example 3:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of the prism row was as shown in FIG.

  FIG. 9 shows the dimension value and angle value of each part of the prism row. In FIG. 9, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 10 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 39 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 19.51 μm. The plane closest to the valley of the prism array has an inclination angle of 31 degrees with respect to the light exit surface normal, and the length in the prism array arrangement direction is 20.29 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.51. The arrangement pitch P of the prism rows is 50.00 μm.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution when Comparative Example 1 was used as a reference were obtained. The results are shown in Table 1.

Comparative Example 4:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of the prism row was as shown in FIG.

  FIG. 10 shows the dimension values and angle values of each part of the prism row. In FIG. 10, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 10 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of three planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 39 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 12.53 μm. The plane closest to the valleys of the prism rows has an inclination angle of 28 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 12.25 μm. The plane located between these two planes has an inclination angle of 34 degrees with respect to the light exit surface normal and a length in the prism array direction of 14.61 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.31. The arrangement pitch P of the prism rows is 50.00 μm.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution when Comparative Example 1 was used as a reference were obtained. The results are shown in Table 1.

Comparative Example 5:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of the prism row was as shown in FIG.

  FIG. 11 shows the dimension value and angle value of each part of the prism row. In FIG. 11, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 27 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 35 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 3.00 μm. The plane closest to the valley of the prism array has an inclination angle of 30 degrees with respect to the light exit surface normal, and the length in the prism array arrangement direction is 23.81 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.89. The arrangement pitch P of the prism rows is 50.00 μm.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution when Comparative Example 1 was used as a reference were obtained. The results are shown in Table 1.

Comparative Example 6:
A surface light source device was obtained in the same manner as in Example 1 except that the shape of the prism row was as shown in FIG.

  FIG. 12 shows the dimension values and angle values of each part of the prism row. In FIG. 12, the vertical direction corresponds to the normal direction of the light exit surface 42, that is, the Z direction. A normal line of the light exit surface 42 is indicated by a one-dot chain line, and a value of an inclination angle (unit: degrees [°; deg]) with respect to the light exit surface normal is indicated. The first prism surface 44 located on the side closer to the primary light source 1 has an inclination angle of 45 degrees with respect to the light exit surface normal. The second prism surface 45 located on the side far from the primary light source 1 is composed of two planes having different inclination angles with respect to the light exit surface normal direction. The plane closest to the tip of the prism row has an inclination angle of 40 degrees with respect to the light exit surface normal, and the length in the prism row arrangement direction is 8.00 μm. The plane closest to the valley of the prism array has an inclination angle of 29 degrees with respect to the light exit surface normal, and the length in the prism array arrangement direction is 11.58 μm. Accordingly, the ratio of the “length in the prism array arrangement direction of the plane closest to the prism array valley” to the “length of the second prism surface 45 in the prism array arrangement direction”, that is, the prism array of the second prism surface 45. When the length in the arrangement direction is 1, the length of the plane closest to the prism row valley is 0.59. The arrangement pitch P of the prism rows is 50.00 μm.

  The emission light luminance distribution of this surface light source device was measured, and the peak luminance ratio value and the full width at half maximum of the luminance distribution when Comparative Example 1 was used as a reference were obtained. The results are shown in Table 1.

1 Primary light source 3 Light guide 31 Light incident end face
33 Light exit surface 34 Back surface 4 Light deflection element 41 Light incident surface 42 Light exit surface 44 First prism surface 45 Second prism surface 5 Light reflection element 6 Light diffusion element

Claims (4)

It has a light incident surface on which light is incident and a light output surface on the opposite side from which incident light is emitted, and the light incident surface has a plurality of prism rows arranged in parallel in a pair of prism surfaces. An optical deflection element,
One prism surface of the pair of prism surfaces is composed of two or more planes having different inclination angles with respect to the normal direction of the light exit surface in a cross section orthogonal to the extending direction of the prism row,
The inclination angle of the plane closest to the tip of the prism row in the cross section is in the range of 35 to 42 degrees;
The inclination angle of the plane closest to the valley of the prism row in the cross section is in the range of 25 degrees to 30 degrees;
The length of the one prism surface in the arrangement direction of the prism rows is 1, and the length of the plane closest to the valley of the prism rows in the cross section is in the range of 0.45 to 0.85. ,
An optical deflection element for a surface light source device.   The other prism surface of the pair of prism surfaces has an inclination angle with respect to the normal direction of the light exit surface in a cross section orthogonal to the extending direction of the prism row in a range of 5 degrees to 40 degrees. The light deflection element for a surface light source device according to claim 1, wherein A light guide having a primary light source, a light incident end surface on which light emitted from the primary light source is incident, a light emitting surface that guides the incident light and emits at least part of the guided light And the light deflection element according to claim 1 or 2 disposed adjacent to the light exit surface of the light guide.
The light deflecting element is configured such that the light incident surface faces the light emitting surface of the light guide, and the prism array has the one prism surface far from the primary light source and the other prism surface. A surface light source device arranged on a side closer to the primary light source.   In the distribution in the plane orthogonal to both the light incident end face and the light exit surface, the angle between the direction of the distribution peak and the light exit surface is 10 for the light emitted from the light exit surface of the light guide. 4. The surface light source device according to claim 3, wherein the surface light source device is in a range from 40 degrees to 40 degrees, and a full width at half maximum of the distribution is in a range from 10 degrees to 40 degrees.