JP2007335182A - Surface light source element, light control member used therefor, and image display device using surface light source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high light use efficiency, high luminance uniformity, and high color uniformity in an edge-light surface light source element with color reproducibility improved by using a point-like light source such as an LED. <P>SOLUTION: The surface light source element is composed so that a generally-used fine-particle diffuser plate is replaced with at least one light control member, so as to reduce a light source image by a means that is provided to the light control member in order to control a light beam direction. The light control member has a function to obtain the high luminance uniformity and color uniformity. It is possible to reduce light absorption or light emission in an unwanted direction while preventing an increase in density of fine particles by using the light control member. Consequently, it is possible to achieve energy saving while improving light use efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface light source element having a plurality of point light sources, a sheet-like light control member provided in the surface light source element, and an image display apparatus using the same, and particularly requires a large size, high luminance and luminance uniformity. In particular, the present invention relates to a direct-type surface light source element used in an illumination signage device, a liquid crystal display device, and the like, a light control member provided in the surface light source element, and an image display device using the same.

  For example, surface light source elements used in image display devices include an edge light method and a direct light method. The edge light method is a method of taking out light from a light source arranged on the end face of the light guide plate in a front direction from the main surface orthogonal to the end face by the light guide plate, and the direct method is arranging a plurality of light sources on the back of the device, In this method, light is incident on a diffuser plate, the light is made uniform by the diffuser plate, and the light is extracted to an exit surface opposite to the incident surface (see Patent Document 1, for example).

  In an image display device used for a mobile phone or a mobile personal computer, thinness of the device is required. Therefore, an edge light method that is advantageous for thinning is mainly used by providing a light source at a side end of the device. On the other hand, with respect to television and personal computer monitors, there are increasing demands for larger image display devices, higher brightness, and lower power consumption. In a large screen, the ratio of the length of the peripheral portion to the screen area is reduced, and sufficient luminance cannot be obtained. In addition, the light guide plate becomes thick and the weight increases. Therefore, the direct type is the mainstream for large surface light source elements.

  In the direct-type surface light source element, improvement in luminance uniformity, improvement in front luminance, reduction in thickness, and reduction in power consumption, that is, energy saving are required. The luminance uniformity is particularly important for eliminating the light / dark difference in the screen due to the light source image, and is important for applications such as image display devices and illuminated signboards.

  The direct-type surface light source element includes a light source, a reflection plate, a diffusion plate, a diffusion sheet, and the like. The reflection plate reflects light emitted from the light source to the back side in the front direction, and the diffusion plate has a function of reducing the image of the light source in which fine particles that diffuse light are dispersed.

  As a light source, a fluorescent lamp, which is a linear light source, has been used, but there are problems such as poor color reproducibility and load on the environment due to the use of mercury. In view of this, it has been proposed that a point light source such as a light emitting diode (LED) that does not use mercury with good color reproducibility is arranged in a plane and used as a planar light source (see, for example, Non-Patent Document 1). .

  However, when the point light source is arranged in a plane, the contrast between the light source images is generated two-dimensionally. Furthermore, the light emission of the LED has a strong directivity, and it is more difficult to obtain high luminance uniformity than when a linear light source is used. In addition, when using LEDs of each color such as red, blue, and green in order to widen the color coordinates, it is difficult to obtain color uniformity. It is possible to increase brightness uniformity and color uniformity by increasing the fine particles of the diffuser plate, but because light absorption and light emission in unnecessary directions increase, light use efficiency decreases. From the viewpoint of energy saving, it is not preferable.

Japanese Patent Laid-Open No. 2-17 Nikkei Business Publications, Inc. Flat-Panel Display2004 Business Edition p170

  Therefore, in the present invention, for example, a direct-type surface light source element used in an image display device or the like, which uses a point light source such as an LED, enables high color reproducibility, high brightness, and uniform brightness. An object of the present invention is to provide a surface light source element capable of realizing energy saving because of high color uniformity and high light utilization efficiency, a sheet-like light control member provided in the surface light source element, and an image display device using the surface light source member.

  In the present invention, high luminance uniformity and high color uniformity are obtained by replacing the diffusion plate in which fine particles for diffusing light are dispersed with at least one sheet-like light control member. To solve.

That is, the present invention
One of the normals of the XY plane parallel to the X axis and the Y axis perpendicular to the X axis as a front direction, at least an emission surface parallel to the XY plane, a plurality of point light sources, and at least A sheet-like light control member, wherein the plurality of point light sources are periodically arranged in a virtual plane parallel to the XY plane in the X-axis and Y-axis directions; Parallel to the XY plane and in the front direction of the plurality of point light sources, the emission surface is arranged on the front direction side of the light control member, and the light control member is in the light beam direction. The means for controlling the light beam direction controls at least the light beam direction along the X axis and the Y axis, and is parallel to the X axis of the array of the plurality of point light sources on the exit surface. In a range surrounded by one period along the vertical direction and one period along the direction parallel to the Y-axis Kicking color coordinates (x, y) the difference between the maximum value and the minimum value as (Δx, Δy),
| Δx | <0.01
| Δy | <0.01
And
Assuming that the maximum value of the luminance L is Lmax and the minimum value is Lmin,
Lmin / Lmax> 0.9
It is a surface light source element characterized by being.

The present invention also provides:
In the sheet-like light control member provided with means for controlling the light beam direction, a plurality of hook-shaped convex portions parallel to the X-axis direction and perpendicular to the Y-axis direction are arranged on the surface side from which light is mainly emitted. The first light control member, and a second light control member in which a plurality of hook-shaped convex portions orthogonal to the X-axis direction and parallel to the Y-axis direction are arranged on the surface side mainly emitting light. This is a surface light source element.

The present invention also provides:
The surface light source element according to claim 1, wherein the means for controlling the light beam direction in the sheet-like light control member comprises a dot-like lens array disposed mainly on a light emitting surface side.

The present invention also provides:
It is a sheet-like light control member which has a light control means which controls a light beam direction along an X-axis or a Y-axis with which a surface light source element as described in any one of Claims 1-3 is provided.

The present invention also provides:
It is an image display apparatus characterized by arrange | positioning a transmission type display apparatus in the said front direction of the surface light source element as described in any one of Claims 1-3.

  The sheet-like light control member used in the present invention has a function of reducing the light source image by means for controlling the light beam direction and obtaining high luminance uniformity and color uniformity. By using the light control member, it is possible to prevent the concentration of the light diffusing fine particles from increasing, and light absorption and light emission in unnecessary directions are reduced, so that the light use efficiency of the lighting device of the present invention is increased, Energy saving can be realized.

  One period of the arrangement of the light sources refers to a unit of arrangement of the light sources arranged repeatedly in the X-axis direction and the Y-axis direction, and the intensity, relative arrangement, color, etc. of each light source in each of the X-axis direction and the Y-axis direction. The array of point light sources is reproduced by repeating this unit including all the elements relating to the uniformity of color and brightness. In the direct-type surface light source element, by arranging the point light sources periodically in the X-axis direction and the Y-axis direction, high luminance uniformity and high color uniformity in the range of one cycle of the array of light sources on the emission surface. As a result, high luminance uniformity and high color uniformity can be obtained over the entire emission surface of the surface light source element.

  The light control member has a function of reducing the point light source image and obtaining high luminance uniformity and color uniformity. On the light incident surface of the light control member, the light from the light source travels in the front direction at the positions in the X-axis direction and Y-axis direction where the point light source is arranged, while the point light source and point light At the intermediate position of the light source, the light from the light source travels in an oblique direction. Therefore, the light incident on the light control member is high in luminance at the position in the X direction and Y direction where the point light source is arranged in the front direction, and low in the middle position between the point light source and the point light source. The light emission characteristics are shown.

  By using the light control member, it is possible to direct light emitted obliquely in the X-axis direction and the Y-axis direction to the vicinity of the front, and increase the luminance in the front direction at an intermediate position between the point light source and the point light source. Thus, the brightness difference due to the light source image is reduced, and high luminance uniformity and color uniformity are obtained.

  The light control member including means for controlling the light beam direction is a first light control in which a plurality of hook-shaped convex portions parallel to the X-axis direction and perpendicular to the Y-axis direction are arranged on the surface side where light is mainly emitted. This can be realized by including a member and a second light control member in which the hook-shaped convex portion that is orthogonal to the X-axis direction and parallel to the Y-axis direction is disposed mainly on the surface side from which light is emitted. The first light control member can control the light beam direction along the Y-axis direction, and can improve luminance uniformity and color uniformity in the Y-axis direction. Further, the light direction can be controlled along the X-axis direction by the second light control member, and luminance uniformity and color uniformity in the X-axis direction can be improved.

  Further, the means for controlling the direction of the light beam can be realized by a dot-shaped lens array disposed mainly on a light emitting surface of the light control member. With the dot-shaped lens array, the light beam directions in the X-axis direction and the Y-axis direction can be controlled simultaneously, and luminance uniformity in the X-axis direction and the Y-axis direction can be obtained.

  The principle on which high brightness uniformity and color uniformity can be obtained by the light control member of the present invention will be described below.

FIG. 1 shows a cross section of a light control member of the present invention and a traveling direction of a part of light incident on the light control member. A part of the light incident in the oblique direction is refracted by the light control member and is emitted in the vicinity of the front direction. Here, the slope inclined with respect to the XY plane with the X axis as the rotation axis can deflect light incident obliquely along the Y axis to the front, and is a point light source in the Y axis direction. It is possible to improve the uniformity of brightness and the uniformity of color in the Y-axis direction by deflecting light incident in an oblique direction at an intermediate position between the light source and the point light source in the front direction. In addition, the slope inclined with respect to the XY plane with the Y axis as the rotation axis can deflect light incident obliquely along the X axis to the front, and a point light source in the X axis direction Light incident in an oblique direction at an intermediate position of the point light source can be deflected in the front direction, and the luminance uniformity and color uniformity in the X-axis direction can be enhanced.
Accordingly, at the intermediate position between the point light source and the point light source in the X-axis direction and the Y-axis direction, the brightness difference due to the image of the point light source is eliminated, high luminance uniformity is obtained, and color uniformity is obtained. Is possible.

  The hook-shaped convex portion provided in the first light control member has a slope inclined with respect to the XY plane with the X axis as a rotation axis, and light incident obliquely along the Y axis direction is directed to the front. It is possible to deflect. Further, the hook-shaped convex portion provided in the second light control member has a slope inclined with respect to the XY plane with the Y axis as a rotation axis, and the light incident in the oblique direction along the X axis direction. It can be deflected to the front. By using the first and second light control members, it is possible to efficiently control the light beam direction in the X-axis direction and the Y-axis direction, and high brightness uniformity and high color uniformity can be achieved. Obtainable.

  The dot-shaped lens array has a slope inclined with respect to the XY plane with the X axis as a rotation axis, and a slope inclined with respect to the XY plane with the Y axis as a rotation axis. Light incident obliquely along the X-axis direction and the Y-axis direction can be simultaneously deflected to the front. By using a light control member including the dot-shaped lens array, it is possible to simultaneously reduce the number of members and achieve high brightness uniformity and color uniformity.

  Here, the surface light source element of the present invention may include a plurality of sheet-like light control members of the present invention. For example, the first light control member and the second light control member can be used. By using a plurality of the light control members of the present invention, the effects such as improvement of effects and light control in a plurality of directions are changed. When a plurality of light control members of the present invention are used, these may have the same shape or different shapes. If it is the same shape, productivity will become high. Further, if a combination of different shapes is used, more precise light control is possible.

  The light incident on the light control member from the light source is incident at an angle inclined in the oblique direction from the front as the X-direction position and the Y-direction position from the light source are further away. In order to refract the light and direct it in the front direction, a slope inclined from the XY plane is required.

  Accordingly, the light control member is orthogonal to the first light control member in which a plurality of hook-shaped convex portions parallel to the X-axis direction and orthogonal to the Y-axis direction are arranged on the surface side mainly emitting light. And a second light control member that is arranged on the surface side that mainly emits light, and includes a plurality of hook-shaped protrusions parallel to the Y-axis direction. The aspect ratio H1 / L1 which is the ratio between the height H1 and the width L1, and the aspect ratio H2 / L2 which is the ratio between the height H2 and the width L2 of the flange-shaped convex portion provided in the second light control member are the X axis of the light source When the relationship between the direction period D1 and the Y-axis direction period D2 is D1> D2, H1 / L1 <H2 / L2, and when the relationship between D1 and D2 is D1 <D2, H1 / L1> H2 / L2. .

  Further, in the case where the light control member includes a dot-shaped lens array disposed mainly on the light exiting side as a means for controlling the light beam direction, the dot-shaped lens is parallel to the X-axis direction and the Y-axis. The aspect ratio H1 / P1, which is the ratio of the lens height H1 to the lens width P1 in the direction orthogonal to the direction, and the lens height relative to the lens width P2 in the direction orthogonal to the X-axis direction and parallel to the Y-axis direction The aspect ratio H2 / P1, which is the ratio of the height H2, is H1 / P1 <H2 / P2 when the relationship between D1 and D2 is D1> D2, and H1 / P1 when the relationship between D1 and D2 is D1 <D2. > H2 / P2. Here, the dot-shaped lens width P1 is the maximum value of the lens width parallel to the X-axis direction and orthogonal to the Y-axis direction, and P2 is parallel to the Y-axis direction and orthogonal to the X-axis direction. The maximum lens width.

  Further, the image display device of the present invention is configured by disposing a transmissive display device in the front direction of the surface light source element, and can display a bright and high-quality image because of high luminance and high luminance uniformity. . Here, the image display device of the present invention is a display module in which a surface light source element and a display element are combined, and is a device having at least an image display function using the display module, and includes a television, a personal computer monitor, and the like.

  An example of the best mode of the present invention is shown in FIGS. One of the normal lines of the XY plane parallel to the X axis and the Y axis orthogonal to the X axis is defined as the front direction, the emission surface parallel to the XY plane, a plurality of point light sources, and at least one sheet This is a surface light source element in which a plurality of point light sources, a light control member, and an emission surface are arranged in this order in the front direction.

  With the surface light source element of the present invention, high color uniformity and high luminance uniformity can be realized. That is, the lower values of | Δx | and | Δy | are more preferable, but | Δx | <0.01. When | Δy | <0.01, the color uniformity of the surface light source element, which is one of the objects of the present invention, is achieved. | Δx | and | Δy | are more preferably 0.008 or less, more preferably 0.005 or less, and in particular, for applications such as high-quality image display devices that require high color uniformity. Is desirably 0.003 or less. Further, Lmin / Lmax is preferably as high as possible, but when Lmin / Lmax> 0.9, luminance uniformity of the surface light source element, which is one of the objects of the present invention, is achieved. Lmin / Lmax is more preferably 0.92 or more, and further preferably 0.94 or more. In particular, in applications such as high-quality image display devices that require high luminance uniformity, 0.96. More preferably, it is more preferable that it is 0.98 or more.

Although there is no restriction | limiting in particular as a point light source, LED etc. can be used. Examples of the LED include a white LED and LEDs of each color such as red, blue, and green. However, only white is used, and each color LED is periodically arranged. Further, a plurality of light sources having the same color may be arranged within one cycle according to the color required on the emission surface.
It is desirable that the distance between adjacent point light sources is narrow, because the luminance uniformity and color uniformity are good and high luminance can be obtained. However, if the interval is too narrow, the number of point light sources increases, resulting in an increase in power consumption and a problem of heat generation. The interval between the point light sources is preferably 7 mm to 70 mm. More desirably, the thickness is 15 mm to 50 mm.

  A longer distance between the point light source and the light control member is desirable because of high luminance uniformity and color uniformity. However, if the length is too long, the thickness of the entire apparatus increases, which is not preferable. The distance between the point light source and the light control member is preferably 5 mm to 50 mm. More desirably, the thickness is 10 mm to 30 mm.

  Width L1 of the ridge-shaped protrusion provided on the emission surface side of the first light control member, Width L2 of the ridge-shaped protrusion provided on the emission surface side of the second light control member, or the emission surface of the light control member The width P1 in the X-axis direction and the width P2 in the Y-axis direction of the dot-shaped lens array provided on the side are preferably 10 μm to 500 μm. If it is larger than 500 μm, the pattern itself is visually recognized from the exit surface, and the appearance quality is lowered. On the other hand, if it is smaller than 10 μm, it is colored by the diffraction phenomenon and the appearance quality is lowered. More preferably, the thickness is 20 μm to 400 μm, and further desirably 40 μm to 300 μm. In this range, it is difficult to observe the pattern itself, and it is easy to produce and the productivity is improved. Furthermore, in the image display device in which the transmissive display device is provided on the exit surface side of the surface light source element of the present invention, L1, L2 or P1, P2 is 1/100 to 1 / 1.5 of the pixel pitch of the transmissive display device. It is desirable to be in the range. If it is larger than this, interference fringes with the pixel pitch are generated and the appearance quality is lowered.

  Although it is desirable that the thickness of the light control member is thin, in the surface light source element of the present invention which is a direct type, since a space is provided between the light source and the light control member, the light control member arranged closest to the light source side It is desirable that the thickness has a strength without bending or deformation. The light control member arranged closest to the light source differs depending on the size of the surface light source element, but the thickness is preferably 0.5 mm to 5 mm. If it is thinner than this, the light control member will be bent or deformed, the point light source will come into contact with the light control member, and the appearance quality will deteriorate. If it is thicker than this, the surface light source element becomes thick and the weight also increases. More desirably, the thickness is 1 mm to 4 mm, and more preferably 1.5 mm to 2.5 mm. In this range, the strength is maintained, and it is possible to suppress an increase in manufacturing cost due to an increase in the amount of base material used per main surface area.

  When the light control member is not disposed closest to the light source, the thickness of the light control member may be set in consideration of the strength, productivity, and the like of the light control member itself. When used as a normal surface light source element, the vicinity of the end surface is fixed together with the light control member arranged closest to the light source, so that even a thin sheet is unlikely to be bent. Therefore, the light control member that is not closest to the light source can be made thinner than the light control member that is closest to the light source. The light control member that is not closest to the light source is preferably thin in order to reduce the thickness of the entire apparatus. Although the thickness varies depending on the size of the surface light source element, the thickness is preferably 0.05 mm to 1 mm. If it is thinner than this, the strength of the light control member itself is lowered, and the quality is lowered due to deformation or the like. On the other hand, if it is thicker than this, the surface light source element becomes thick and the weight also increases. Furthermore, in order to prevent the light control member from being deformed by heat and to obtain high productivity by extrusion molding or the like, 0.1 mm to 0.7 mm is desirable, and 0.2 mm to 0.5 mm is further desirable.

  Examples of the method for manufacturing the light control member include extrusion molding, injection molding, and 2P (Photo Polymerization) molding using an ultraviolet curable resin. When a convex portion is provided, the size of the convex portion, the shape of the convex portion, etc. A suitable molding method may be selected in consideration of mass productivity. Extrusion molding is suitable when the main surface is large.

  As a material for the light control member, any optically transparent material can be used. For example, methacrylic resin, polystyrene resin, polycarbonate resin, cycloolefin resin, methacryl-styrene copolymer resin, cycloolefin-alkene copolymer resin and the like can be mentioned.

  In order to use more light, a reflector or the like may be used on the back surface of the light source. By using the reflector, the light emitted from the light source in the back direction and the light emitted from the light control member in the back direction can be directed to the front direction so that more light can be used and high brightness can be obtained. It is.

  The reflection plate has a function of reflecting light emitted from the light source to the back side in the front direction. A reflectance of 95% or more is desirable because of high light utilization efficiency. Examples of the material of the reflecting plate include metal foils such as aluminum, silver, and stainless steel, white coating, and foamed PET resin. In order to increase the light utilization efficiency, it is desirable that the material has a high reflectance. This includes silver, foamed PET, and the like. In order to improve luminance uniformity, the material is preferably diffusely reflected. This includes foamed PET and the like.

  Further, in order to further improve the luminance uniformity and the color uniformity, the light control member of the present invention may be provided with a light diffusion means. As the light diffusion means, a method of providing random irregularities such as embossing or embossing on the main surface of the light control member, a method of providing fine particles that diffuse a small amount of light inside the structure, a diffusion sheet as the incident surface of the light control member The method of providing in the side and / or the output surface side, or the method which combined these is mentioned.

  Random irregularities can be realized by applying a solution in which fine particles are dispersed to the main surface by spraying, molding by extrusion of a resin in which fine particles are dispersed, and transferring from a mold having irregularities. As for the degree of unevenness, the arithmetic average roughness Ra is desirably 3 μm or less. If it is larger than this, the front luminance is lowered because the diffusion effect becomes too large.

  When fine particles that diffuse light are provided inside the structure, the concentration of the fine particles can be kept very low compared to a normal diffusion plate, and the fine particle base material and particle size are normal light diffusing materials. Can be suitably used as long as they are used in a fine particle diffusion plate or the like. The preferred concentration of fine particles varies depending on the material, and examples thereof include dispersing 0.4% by weight of siloxane polymer particles in a methyl methacrylate-styrene copolymer.

  Further, a diffusion sheet may be used in order to obtain more uniform brightness and color uniformity, and a prism sheet, a deflection separation film, or the like may be used in order to obtain high brightness in the front direction.

  The light control member of the present invention can be used for light sources other than a plurality of point light sources. For example, by using it for a single point light source, it is possible to obtain uniform and high luminance in a wider range. Further, the means for controlling the light beam direction of the light control member of the present invention includes a plurality of linear light sources arranged in a virtual plane parallel to the XY plane and parallel to the X axis direction and along the Y axis, or It is possible to control the direction of light rays from a plurality of linear light sources arranged parallel to the Y-axis direction and along the X-axis, and high luminance uniformity can be realized. As these linear light sources, it is also possible to use a linear light source configured by linearly arranging point light sources such as fluorescent lamps and LEDs at narrow intervals.

  In addition, a transparent support substrate made of resin, glass, or the like may be provided on the light source side of the light control member. By disposing the support substrate, the light control member can be supported even if the light control member is thinned, for example, from 0.1 mm to 1 mm. By reducing the thickness of the light control member, molding by extrusion molding or the like is further facilitated, and productivity is improved. In addition, it becomes easy to support the light control member that becomes increasingly difficult as the surface light source element becomes larger. The thickness of the support substrate is not particularly limited, but is usually 1 mm to 5 mm, and more preferably in the range of 2 mm to 4 mm, usually in view of weight reduction and strength. The support substrate may be improved in diffusibility by dispersing fine particles that diffuse light inside, embossing on the surface, or applying fine particles. In the case of dispersing fine particles inside or embossing on the surface, it is preferable for production that the base material is a thermoplastic resin, and a suitable material is equivalent to the light control member. Further, the support substrate may be bonded to the light control member, for example, can be bonded with a transparent adhesive or the like, thereby simplifying the assembly process of the surface light source element, and further, the shift of the light control member and wrinkles Occurrence can be prevented.

  Moreover, the 1st light control member provided with the hook-shaped convex part which controls a light beam direction along a Y-axis is the 2nd light control member provided with the hook-shaped convex part which controls a light beam direction along an X-axis. For example, the first light control member produced by extrusion molding is used for the first light control member along the X axis by using 2P molding or the like with an ultraviolet curable resin having a refractive index different from that of the flange-like convex portion on the exit surface side. It is obtained by forming a hook-shaped convex part provided in the second light control member for controlling the light beam direction. Thereby, the assembly process of the surface light source element can be simplified, the surface light source element can be thinned, and further, the shift of the light control member can be prevented.

  Further, the image display device of the present invention is realized by providing a transmissive display device on a surface light source element, and a transmissive liquid crystal panel or the like can be given as the display device. As a result, an image display device with high display surface brightness, good color reproducibility, and excellent brightness uniformity and color uniformity can be obtained.

Examples of the present invention will be described below, but the present invention is not limited thereto.
In order to obtain a means for controlling the light beam direction of the light control member of the present invention, a polystyrene resin (thickness 2 mm) made of UV curable resin from a mold in which groove-like recesses having a width of 60 μm are continuously formed in parallel by cutting. Refractive index 1.60) A first light control member was produced by forming hook-shaped protrusions on the substrate. A second light control member was produced by the same method.

  In order to obtain a plurality of point light sources of the present invention, as shown in FIG. 5, red, blue, and green LEDs are arranged in a cycle of 30 mm in the X-axis direction, and this LED array is arranged at intervals of 30 mm in the Y-axis direction. . Here, the period refers to the interval from the red LED to the red LED.

  In carrying out the present invention, the light control member was disposed at a position of 15 mm in the front direction from the light source. A reflector was installed on the back side of the light source.

  With respect to the implemented configuration, the luminance in the front direction and the color coordinates were measured at intervals of 1 mm over a range of one cycle of the point light source in the X-axis direction and one cycle in the Y-axis direction. The brightness and color coordinates in the front direction were measured using a luminance meter (BM-7 manufactured by Topcon Techno House Co., Ltd.) with a measurement angle range of 0.2 degrees and a constant measurement distance. For the obtained luminance for one period, average luminance Lave, maximum value Lmax and minimum value Lmin of luminance were obtained, and ΔL = Lmin / Lmax was obtained. Further, regarding the color coordinates, the difference (Δx, Δy) between the maximum value and the minimum value of (x, y) was obtained.

Table 1 shows the configuration of each example and comparative example and the results of luminance measurement.

  The configuration of Example 1 is shown in FIG. From Example 1, when a diffusion sheet is used on the light exit surface side of the light control member of the present invention for a plurality of point light sources, the luminance is uniform, and Δx and Δy are 0.01 or less in color. A uniform surface light source element was obtained. Compared with Comparative Example 1, the light utilization efficiency was high and high luminance was realized.

  The configuration of Example 2 is shown in FIG. From Example 2, by using a prism sheet on the exit surface side of the light control member of the present invention, higher color uniformity, higher luminance uniformity, and higher luminance were obtained.

As Comparative Example 1, evaluation was carried out in the case of using an ordinary fine particle-containing diffusion plate and the light control sheet of the present invention. The diffusion plate was prepared by extruding a methyl methacrylate-styrene copolymer resin in which 1.9% by weight of cyclohexane polymer particles were dispersed as fine particles for diffusing light. Evaluation was performed in the case where a diffusion sheet was disposed on the exit surface side of the diffusion plate. In this case, since the light source image is not sufficiently reduced, the color uniformity and the luminance uniformity are low. Furthermore, the light use efficiency is low, and high brightness is not obtained.

It is a figure showing the advancing direction of a part of incident light, showing the principle that high luminance uniformity and high color uniformity can be obtained with the light control member of the present invention. It is a figure which shows an example of the best form of this invention. It is a figure which shows the structure of the Example of this invention. It is a figure which shows the structure of the Example of this invention. It is a figure which shows a part of arrangement | sequence of the several point light source of the Example of this invention.

Explanation of symbols

1: Light control member 2: Means for controlling the light beam direction 3: Point light source 4: First light control member 5 having a hook-shaped convex portion for controlling light in the Y-axis direction: Control light in the X-axis direction Second light control member 6 having a ridge-shaped convex portion: Light control member 7 having a dot-shaped lens array as means for controlling the light beam direction 7: Diffusing sheet 8: Reflecting sheet 9: Prism sheet 10: Light control Light obliquely incident on the member from the front direction 11: Light emitted from the light control member 12: Light totally reflected by means for controlling the light beam direction of the light control member 13: Red LED
14: Blue LED
15: Green LED
Δx: difference between the maximum value and the minimum value of the color coordinate x in a range surrounded by one cycle of the X coordinate of the point light source and one cycle of the Y coordinate Δy: one cycle of the X coordinate of the point light source Difference between maximum value and minimum value of color coordinate y in a range surrounded by one cycle of Y coordinate L: luminance in a range surrounded by one cycle of X coordinate of the point light source and one cycle of Y coordinate Lmin: Minimum value of L Lmax: Maximum value of L

Claims (5)

One of the normals of the XY plane parallel to the X axis and the Y axis perpendicular to the X axis is defined as the front direction,
at least,
An emission surface parallel to the XY plane, a plurality of point light sources, and at least one sheet-like light control member,
The plurality of point light sources are periodically arranged in the X-axis and Y-axis directions in a virtual plane parallel to the XY plane,
The light control member is disposed in parallel to the XY plane and in front of the plurality of point light sources,
The exit surface is disposed on the front direction side of the light control member,
The light control member comprises means for controlling the light beam direction,
The means for controlling the ray direction controls the ray direction along at least the X-axis and the Y-axis;
On the exit surface, the color coordinates (x in the range surrounded by one period along the direction parallel to the X axis and one period along the direction parallel to the Y axis of the array of the plurality of point light sources are arranged. , Y) as the difference between the maximum value and the minimum value (Δx, Δy),
| Δx | <0.01
| Δy | <0.01
And
Assuming that the maximum value of the luminance L is Lmax and the minimum value is Lmin,
Lmin / Lmax> 0.9
A surface light source element. The sheet-like light control member provided with means for controlling the light beam direction,
A plurality of hook-shaped convex portions parallel to the X-axis direction and perpendicular to the Y-axis direction, the first light control member disposed on the surface side from which light is mainly emitted;
A plurality of hook-shaped convex portions that are orthogonal to the X-axis direction and parallel to the Y-axis direction, and a second light control member that is disposed on the surface side that mainly emits light,
The surface light source element according to claim 1. Means for controlling the light beam direction in the sheet-like light control member,
Arranged mainly on the side that emits light,
Consisting of a dot-shaped lens array,
The surface light source element according to claim 1.   The sheet-like light control member which has the light control means which controls the light beam direction along an X-axis or a Y-axis with which the surface light source element as described in any one of Claims 1-3 is equipped. A transmissive display device is disposed in the front direction of the surface light source element according to claim 1.

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