JP2007163615A - Surface light emitting device, method for uniformizing luminance, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light emitting device with which split distances between light source images are easily controlled, a method for uniformizing luminance, and a liquid crystal display device. <P>SOLUTION: In the surface light emitting device 10, linear protrusions 16a on a prism sheet 16 as a light source image split sheet and linear light sources 12 are arranged in such a way that a direction of ridge lines of the linear protrusions 16a and an extending direction of the linear light sources 12 are intersecting with each other, and thereby image distances of the light source images split with the prism sheet 16 are optimized so as to improve uniformity of in-plane luminance distribution. The image distances of the light source images are adjusted with an angle between the direction of the ridge lines of the linear protrusions 16a on the prism sheet 16 and an extending direction of the linear light sources 12. Consequently only by adjusting the corresponding angle, most suited distances between the light source images are materialized in accordance with required luminance characteristics, and luminance uniformization is more simply materialized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a surface light emitting device, a luminance uniformizing method, and a liquid crystal display device suitable for use in, for example, a direct type backlight device in a liquid crystal display device.

  2. Description of the Related Art Conventionally, as a display device such as a word processor or a laptop personal computer, a liquid crystal display device having a thin and easy-to-read backlight (surface light emitting device) has been used. As a backlight for such a liquid crystal display device, a linear light source such as a fluorescent tube is disposed at a side end of a transparent plate (light guide plate) in order to reduce the weight and size. An edge light type backlight in which a liquid crystal display panel is installed via a light diffusing sheet or the like has been the mainstream.

  However, with the recent increase in size of display devices, the brightness of the edge-light type backlight described above often becomes insufficient, so a linear light source and a light diffusing sheet are arranged directly under the liquid crystal panel. A direct type backlight of the form is used.

  FIG. 14 is a perspective view showing a schematic configuration of a conventional direct type backlight device. In FIG. 14, the backlight device 1 includes a linear light source 2 such as a fluorescent tube, a reflection plate 3, and a diffusion plate 4 and a diffusion sheet 5 as light diffusing sheets. A reflection plate 3 is disposed below the linear light source 2, a diffusion plate 4 is disposed above the linear light source 2, and a diffusion sheet 5 is disposed above the diffusion plate 4. The diffusion plate 4 and the diffusion sheet 5 form a light exit surface of the backlight device.

  In such a backlight device 1, the light beam emitted from the linear light source 2 exits from the diffusion plate 4 and the diffusion sheet 5. However, the luminance of the irradiation light beam of the backlight device 1 is high at a position directly above the light source 2 as shown in FIG. 15A and is low at an upper position in the middle portion between the light sources 2.

  For this reason, as shown in FIG. 15B, a method of dividing a light source image (bright line) by providing a prism sheet 6 between the light source 2 and the diffusion sheet 5 is known (see Patent Documents 1 to 3 below). . 15B shows an example in which a prism sheet 6 is installed as a light source image division sheet instead of the diffusion plate 4 in FIG. 15A. This prism sheet 6 has a plurality of triangular protrusions (prisms) 6a continuously formed at equal pitches on the front surface or the back surface, and has been generally used as a brightness enhancement film. It is an optical film.

  The prism sheet 6 is arranged so that the ridge line direction of the linear protrusion 6 a is parallel to the extending direction of the linear light source 2. As a result, the light source image of the irradiation light beam emitted from the diffusion sheet 5 as shown in FIG. 15B is doubled as compared with the case where there is no prism sheet as shown in FIG. 15A, and the luminance distribution is made uniform. I have to.

JP-A-5-333333 JP-A-6-250178 Japanese Patent Laid-Open No. 10-283818

  In the method of dividing the light source image using the prism sheet 6 described above, it is necessary to divide the two main light source images at short intervals in order to effectively equalize the luminance. For this reason, it is necessary to consider the relationship between the distance between the prism sheet 6 and the light source 2, the refractive index of the prism sheet 6, and the base angle of the linear protrusion 6a of the prism sheet 6, making the design complicated and difficult to adjust. There is a problem that there is.

  Here, FIG. 16A is an optical path diagram showing the relationship between the prism sheet 6 and the light source 2. The light L1 emitted from the light source 2 in the normal direction of the prism sheet 6 is totally reflected by the inclined surface (prism surface) of the linear protrusion 6a of the prism sheet 6, returned to the light source 2 side, and recycled. Further, the light L2 incident on the prism sheet 6 at a certain angle is raised and emitted in the front direction (normal direction) by the linear protrusion 6a, and the light source image LA appears. Furthermore, the light L3 incident on the prism sheet 6 at a larger angle is reflected by the lower surface of the prism sheet 6 and returned to the light source 2 side. Therefore, the light source image LA that appears on the front side of the prism sheet 6 with respect to one light source 2 is divided into two.

  In this case, the distance between the divided light source images LA varies depending on the difference in the distance from the light source 2 to the prism sheet 6. For example, when the distance from the light source 2 to the prism sheet 6 is S1 as shown in FIG. 16A, the distance between the light source images LA is T1, whereas the prism sheet having the same configuration from the light source 2 as shown in FIG. 16B. When the distance up to 6 is S2 shorter than S1, the distance T2 between the light source images is also shorter than T1. That is, the shorter the distance from the light source 2 to the prism sheet 6, the shorter the distance between the light source images LA.

  Similarly, as shown in FIGS. 17A and 17B, even if the distance from the light source 2 to the prism sheet 6 is constant, the difference in the base angle θ (θ1> θ2) of the linear protrusion (prism) 6a of the prism sheet 6 is caused. The distance between the divided light source images LA changes. That is, the smaller the base angle θ, the shorter the distance between the light source images.

  Further, as shown in FIGS. 18A and 18B, even if the distance from the light source 2 to the prism sheet 6 and the base angle of the linear protrusion 6a of the prism sheet 6 are constant, the refractive index of the prism sheet 6 as a whole is the same. Due to the difference, the distance between the divided light source images LA changes. That is, the smaller the refractive index of the prism sheet 6, the shorter the distance between the light source images LA.

  As described above, when the distance between the light source images LA divided using the prism sheet 6 is controlled, the distance from the light source 2 to the prism sheet 6, the base angle of the linear protrusion 6 a of the prism sheet 6 (that is, the linear protrusion). 6a), the refractive index of the prism sheet 6 needs to be adjusted to an optimum value, and there is a problem that the design becomes very complicated.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a surface light emitting device, a luminance uniformizing method, and a liquid crystal display device that can easily control the distance between divided light source images.

  In solving the above problems, in the present invention, the ridge line direction of the linear protrusion on the light source image dividing sheet and the extending direction of the linear light source are arranged so as to intersect each other, thereby dividing the light source image dividing sheet. By optimizing the image interval of the light source image, the in-plane luminance distribution is improved.

  That is, the surface light-emitting device of the present invention includes a diffusive sheet that forms a light-emitting surface, a reflective plate that is disposed to face the diffusive sheet, and a linear shape that is disposed between the diffusive sheet and the reflective plate. A light source, and a light source image dividing sheet disposed between the diffusive sheet and the linear light source. The light source image dividing sheet has linear protrusions on the front surface and / or back surface of the light source image dividing sheet. The ridge line direction is arranged so as to intersect the extending direction of the linear light source.

  Further, a diffusive sheet that forms a light-emitting surface, a reflector disposed opposite to the diffusible sheet, a linear light source disposed linearly between the diffusible sheet and the reflector, and diffusibility A method for leveling luminance of a surface light emitting device including a light source image division sheet disposed between a sheet and a linear light source and having linear protrusions on a front surface and / or a back surface thereof, in the extending direction of the linear light source On the other hand, the luminance distribution of the light beam emitted from the light exit surface is controlled by adjusting the angle at which the ridge line directions of the linear projections of the light source image division sheet intersect.

  In the present invention, the image interval of the light source image is adjusted by the angle formed by the ridge line direction of the linear protrusion on the light source image dividing sheet and the extending direction of the linear light source. Therefore, only by adjusting the angle, it is possible to realize the optimum distance between the light source images according to the required luminance characteristics, and it is possible to more easily realize luminance uniformity. Of course, not only the angle adjustment of the light source image division sheet described above but also the distance between the light sources, the shape of the linear protrusion, the refractive index, etc. may be adjusted together.

  The diffusive sheet is a broad concept including a relatively thick diffusion plate, a film-like diffusion sheet, and the like, and refers to a general film having a function of diffusing light emitted from a light source over a certain angle. The diffusion plate and the diffusion sheet may be used alone or in combination.

  The light source image division sheet can be constituted by, for example, a prism sheet having linear protrusions having a triangular cross section. A triangular base angle or apex angle, pitch, height, etc. are not limited. The linear protrusions may be formed on the sheet surface side, may be formed on the back surface side, or may be formed on both the front and back surfaces. There may be at least one light source image division sheet, and two or more light source image division sheets may be used in combination according to the specification.

  The linear protrusion is not limited to a prism shape, and may be a curved surface shape such as a circular cross section or an elliptical shape, or may have a lens function added thereto. Further, a flat portion parallel to the sheet surface may be provided between the linear protrusions, or a similar flat portion may be provided on a part of the linear protrusion (for example, the top portion).

  The light source is not limited to a linear light source such as a fluorescent tube, and may be a plurality of point light sources such as LEDs (Light Emitting Diodes) arranged in a linear shape. Similarly in this case, the distance between the light source images can be adjusted by intersecting the ridge line direction of the linear protrusion on the light source image dividing sheet with the arrangement direction of the point light sources.

  That is, the surface light-emitting device of the present invention is linearly arranged between the diffusive sheet forming the light exit surface, the reflector disposed opposite to the diffusive sheet, and the diffusive sheet and the reflector. A plurality of point light sources, and a light source image division sheet disposed between the diffusive sheet and the point light source, the light source image division sheet having linear protrusions on the front surface or the back surface thereof, and the line The ridge line direction of the projections is arranged so as to intersect the arrangement direction of the point light sources.

  In addition, another brightness equalization method of the present invention includes a diffusive sheet that forms a light exit surface, a reflective plate disposed opposite to the diffusive sheet, and a linear shape between the diffusive sheet and the reflective plate. A plurality of point light sources arranged in a row, and a light source image dividing sheet disposed between the diffusive sheet and the point light source and having linear protrusions on the front surface and / or the back surface, in the array direction of the point light sources On the other hand, the luminance distribution of the light beam emitted from the light exit surface is controlled by adjusting the angle at which the ridge line directions of the linear projections of the light source image division sheet intersect.

  The protrusion formed on the light source image division sheet is not limited to a linear protrusion. For example, in-plane such as a plurality of linear projections divided in the ridge direction, a planar fly-eye lens, a pyramidal projection such as a triangular pyramid or a quadrangular pyramid, or an elliptical cone-shaped projection in plan view In the present invention, a projection having a shape anisotropy can be applied to the present invention. In this case, an angle at which the projection formation direction (ridge line direction, major axis direction, base direction, etc.) intersects the extending direction of the linear light source or the array direction of the point light sources arranged in a plurality of lines is set. By adjusting, the same luminance distribution control function can be obtained.

  Further, by configuring the surface light emitting device having the above-described configuration as a backlight for a liquid crystal display device, for example, luminance unevenness of an image formed by the liquid crystal display panel can be eliminated and image quality can be improved.

  As described above, according to the present invention, the distance between the light source images can be easily achieved by intersecting the linear protrusions on the light source dividing sheet with the extending direction of the linear light sources or the arrangement direction of the point light sources. Therefore, it is possible to easily control the luminance uniformity.

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view showing a schematic configuration of a surface light emitting device 10 according to a first embodiment of the present invention. The surface light emitting device 10 constitutes a direct type backlight device for a liquid crystal display device, for example.

  A surface light emitting device 10 according to the present embodiment accommodates a linear light source 12, a reflecting plate 13, a diffusive sheet 14 made of a diffusing plate or a diffusing sheet, a prism sheet 16 as a light source image dividing sheet, and these. And a housing 11. The reflection plate 13 and the diffusive sheet 14 are arranged to face each other, and a plurality of linear light sources 12 are arranged in parallel at an equal pitch between the reflection plate 13 and the diffusive sheet 14.

  As the linear light source 12, various conventionally known light sources, for example, fluorescent tubes such as cold cathode tubes and hot cathode tubes can be used. The reflecting plate 13 is not particularly limited as long as it has a property of reflecting light, and those made of aluminum, foamed PET (polyethylene terephthalate), and polycarbonate can be used. Specific examples include a reflective sheet E60L (trade name) manufactured by Kimoto Co., Ltd. and crystal white (trade name) manufactured by Nippon Sky Aluminum Co., Ltd.

  The diffusive sheet 14 forms a light exit surface of the surface light emitting device 10 to further diffuse the light source image divided by the prism sheet 16 and to irradiate the surface of the irradiated light beam emitted from the light exit surface, as will be described later. The internal brightness is made uniform. A liquid crystal display panel (not shown) is disposed on the light exit surface side of the surface light emitting device 10, and the liquid crystal display panel can be irradiated with illumination light with uniform luminance. Thereby, the image quality can be improved by eliminating the light source image from the image formed by the liquid crystal display panel.

  The diffusive sheet 14 is not particularly limited as long as it has a translucency and a function of diffusing light, such as a diffusion plate and a film-like diffusion sheet that are widely used conventionally. Examples of the diffusing plate include those made of acrylic or polycarbonate, and specific examples include DR-60C (trade name) manufactured by Nitto Resin Co., Ltd. and NB01 (trade name) manufactured by Mitsubishi Rayon Co., Ltd. Further, the diffusion sheet is used to assist light diffusion, and can be exemplified by a product made of PET. Specifically, D114 (trade name) manufactured by Tsujiden Co., Ltd., D511 manufactured by Enomoto Electric Co., Ltd. (Trade name), and Lightup 100S (trade name) manufactured by Kimoto Co., Ltd. are available. Note that at least one of the diffusion plate and the diffusion sheet may be used, and these may be laminated and used.

  Next, details of the prism sheet 16 as the light source image division sheet according to the present invention will be described.

  FIG. 2 is a plan view when the prism sheet 16 is viewed from the light emitting surface side. The prism sheet 16 is disposed between the linear light source 12 and the diffusive sheet 14. In the present embodiment, the prism sheet 16 has linear protrusions (prisms) 16 a having a triangular cross section on the surface, and is arranged so that the direction of the ridge line 16 b intersects the extending direction of the linear light source 12. Yes. The angle α formed by the ridge line direction D1 of the prism sheet 16 and the extending direction D2 of the linear light source 12 has a certain angle, and is optimal according to specifications such as the light source position, light emission intensity, and required light distribution. The correct angle is set.

  By changing the crossing angle α (hereinafter also referred to as “axial angle”) of the ridge line direction D1 of the linear protrusion 16a on the prism sheet 16 with respect to the extending direction D2 of the linear light source 12, the prism sheet 16 The image interval of the light source image divided into two can be adjusted. FIG. 3 is an explanatory diagram of the principle, A shows when the shaft angle is 0 °, B shows when the shaft angle is 45 °, and C shows when the shaft angle is 90 °. FIG. 4 shows image division photographs in the case of axial angles of 0 °, 45 °, and 90 °.

  Compared with the case where the shaft angle is 0 °, the base angle of the linear protrusion 16a on the prism sheet 16 is apparently smaller when the shaft angle is 45 °, so that the image interval of the divided light source images is shorter. Become. When the azimuth direction D1 of the prism sheet 16 and the extending direction D2 of the linear light source 12 are orthogonal to each other, the image division effect by the prism does not work and the light source image is not divided and is directly below. A light source image LB corresponding to the linear light source 12 appears.

  The optimum value of the axial angle depends on the arrangement pitch of the linear light sources 12, the distance between the linear light sources 12 and the prism sheet 16, the cross-sectional shape of the linear protrusions 16a on the prism sheet 16, the refractive index of the prism sheet 16, and the like. Depending on the required specifications, such as light distribution characteristics and luminance distribution, etc. are appropriately adjusted.

  That is, according to the present embodiment, after the prism sheet 16 having the predetermined bright line division characteristic is manufactured, in addition to the adjustment of the distance between the linear light source 12 and the prism sheet 16, the ridge line direction D1 of the prism sheet 16 And adjusting the crossing angle (axial angle) between the linear light source 12 and the extending direction D2 of the linear light source 12 makes it possible to obtain optimum luminance distribution characteristics. Accordingly, since it is not necessary to redesign the prism shape or review the refractive index, the degree of freedom in designing the prism sheet 16 is increased, and fine adjustment of characteristics can be easily performed. As a result, the luminance distribution characteristics of the surface light emitting device 10 can be easily controlled, and luminance uniformity can be easily improved. Further, according to the present embodiment, it is possible to make the luminance distribution uniform without using a thick diffuser plate, so that it is possible to reduce the light amount loss and improve the luminance.

  The prism sheet 16 is not particularly limited as long as it has linear protrusions having a cross-sectional shape as shown in FIG. The linear protrusion 16a1 shown in FIG. 5A corresponds to the linear protrusion 16a in the present embodiment, and prism-shaped linear protrusions are continuously formed.

  The linear protrusion 16a2 shown in FIG. 5B shows an example in which the slopes of the linear protrusions forming the prism surface are configured by combining a plurality of slopes with different inclination angles. Further, the linear protrusion 16a3 shown in FIG. 5C has a curved surface shape such as a circular shape or an elliptical cross section, and has, for example, a cylindrical lens shape. The linear protrusion 16a4 shown in FIG. 5D is an example in which a convex and concave compound lens is configured by providing a curved concave portion 16c between the protrusions and having a substantially triangular cross section with a curved top. A linear protrusion 16a5 shown in FIG. 5E shows an example in which a flat portion 16d is formed on the top of a prism, and FIG. 5F shows an example in which a flat portion 16d is provided between adjacent prisms 16a6.

  Note that the shape of the linear protrusion 16a shown in FIG. 5 is merely an example, and shapes other than the above are naturally applicable. All the linear protrusions 16a are not limited to the same shape, and a plurality of kinds of protrusions having different shapes, pitches, heights, and the like may be formed on the same surface. These linear protrusions 16a are not limited to being formed on the front surface side (diffusive sheet 14 side) of the prism sheet 16, but are formed on the back surface side (light source 12 side) of the prism sheet 16. In some cases, it may be formed on both the front and back surfaces. When the linear protrusions 16a are formed on the front and back surfaces of the sheet, the shape, pitch, refractive index and the like can be made different on each surface, and the ridge line directions of the protrusions can be made different from each other.

  The prism sheet 16 can be formed of a translucent resin material. At this time, as shown in FIG. 6A, the linear protrusion 16a and the base material 16p supporting the linear protrusion 16a can be produced by integral molding of a thermoplastic resin. Typical examples of the thermoplastic resin include polycarbonate, PMMA (polymethyl methacrylate), and polystyrene. However, the thermoplastic resin is not particularly limited as long as it is a translucent resin. Further, as shown in FIG. 6B, it is also possible to transfer and form the linear protrusions 16a with an energy ray (for example, ultraviolet ray) curable resin on a light-transmitting substrate 16p such as PET. The size and interval of the linear protrusions 16a are appropriately set according to the size of the light source to be used, the arrangement interval, and the like.

(Second Embodiment)
Next, as a second embodiment of the present invention, a surface light emitting device using a prism sheet 26 having a linear protrusion 16a (16a6) having the shape shown in FIG. 5F as a light source image division sheet will be described. The other constituent elements other than the prism sheet 26 are the same as those in the first embodiment.

  FIG. 7 shows a light source image photograph of an irradiation light beam transmitted through the prism sheet 26 when the prism sheet 26 having the above configuration is applied. 7A shows the case where the axial angle of the ridge line direction of the linear protrusion 16a with respect to the extending direction of the linear light source 12 is 0 °, and FIGS. 7B and 7C show the case where the axial angle is 45 ° and 90 °, respectively. Show.

  By providing a flat portion 16d (FIG. 5F) parallel to the sheet surface between the linear protrusion 16a and the linear protrusion 16a, the inter-image distance of the light source image is changed as compared with the case where there is no flat portion (FIG. 4). be able to. Further, by adjusting the axial angle of the linear protrusion 16a, the distance between the light source images can be changed.

  As schematically shown in FIG. 8, by providing a flat portion 16d between the prismatic linear protrusions 16a having a triangular cross section, light that is incident from the light source 12 in the normal direction of the prism sheet 26 is allowed to enter the flat portion 16d. The light source image LB can appear on the front side without being totally reflected at the formation position. Therefore, not only the light source image LA divided by the linear protrusion 16a but also the light source image LB that appears by transmitting through the flat portion 16d is added, and as a result, the main light source image is divided into three. become.

  FIG. 9 is a luminance distribution diagram when the prism sheet 26 with the flat portion 16d is installed at an axial angle of 45 °. In the figure, B1 is the luminance distribution of only the linear light source, and the peak-to-peak distance corresponds to the arrangement interval of the linear light sources. On the other hand, B2 in the figure is a luminance distribution when the prism sheet 16 is installed, and although the peak luminance is lowered, the bright line of one light source is divided into three.

  Therefore, according to the present embodiment, the ridge line direction of the linear protrusion 16a on the prism sheet 26 intersects the extending direction of the linear light source 12 as in the first embodiment described above. The distance between the images of the light source image can be arbitrarily adjusted, and the flat portion 16d is provided between the adjacent linear protrusions 16a, thereby increasing the number of divisions of the light source image and shortening the distance between the images. be able to. As a result, the luminance distribution control can be performed with high accuracy.

  The formation width of the flat portion 16d is not particularly limited, and is appropriately selected according to required luminance distribution characteristics. In the present embodiment, the formation width of the flat portion 16d is set to be half or less of the formation width of the linear protrusion 16a.

(Third embodiment)
FIG. 10 is a perspective view showing a schematic configuration of a surface light emitting device 30 according to the third embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The surface light emitting device 30 according to the present embodiment accommodates a point light source 32, a reflection plate 13, a diffusive sheet 14 made of a diffusion plate or a diffusion sheet, a prism sheet 16 as a light source image division sheet, and these. And a housing 11. The reflection plate 13 and the diffusive sheet 14 are arranged to face each other, and a plurality of point light sources 32 arranged in a line between the reflection plate 13 and the diffusive sheet 14 are respectively arranged in a plurality of rows. Interspersed.

  The point light source 32 is composed of an LED, an organic EL, or the like, and point light sources of each color of RGB (red, green, and blue) are arranged in a line in one direction in a predetermined order. Of course, each point light source 32 may be formed of a white LED.

  FIG. 11 is a plan view when the prism sheet 16 is viewed from the light emitting surface side. The prism sheet 16 is disposed between the point light source 32 and the diffusive sheet 14. In the present embodiment, the prism sheet 16 has a linear protrusion (prism) 16 a having a triangular cross section on the surface, and the direction of the ridge line 16 b is arranged so as to intersect the arrangement direction of the point light sources 32. . The angle β formed by the ridge line direction D1 of the prism sheet 16 and the arrangement direction D3 of the point light sources 32 has a fixed angle, and is optimal according to specifications such as the light source position, light emission intensity, and required light distribution. An angle is set.

  Also in the present embodiment configured as described above, the ridge line direction of the linear protrusions 16a on the prism sheet 16 with respect to the arrangement direction D3 of the point light sources 32, as in the first embodiment described above. By changing the intersection angle β of D1, the image interval of the light source image divided into two by the prism sheet 16 can be adjusted. As a result, the luminance distribution characteristics of the surface light emitting device 30 can be easily controlled, and luminance uniformity can be easily improved.

  Examples of the present invention will be described below.

Example 1
Using the surface light emitting device described in the first embodiment, luminance uniformity was tested under the following conditions. The obtained result is shown in FIG.
・ Diffusion sheet 14: Diffusion sheet D114 (manufactured by Tsujiden Co., Ltd.)
・ Linear light source 12, reflector 13: LCD TV KDL-S19A10 (manufactured by Sony Corporation)
The linear projection 16a of the prism sheet 16: an angle α formed by the ridge line direction D1 of the prism / linear projection 16a and the extending direction D2 of the linear light source 12 is 45 °.
-Distance from the linear light source 12 to the prism sheet 16: 10 mm
Luminance meter: RISA-COLOR (manufactured by Highland)

The prism sheet 16 was produced by the following method.
Using a metal emboss for hot pressing as a master, a right-angled isosceles triangle having an apex angle of 90 °, a base of 50 μm, and a height of 25 μm in a cross-sectional shape was regularly engraved at an interval of 50 μm. As a thermoplastic resin, a 200 μm polycarbonate resin sheet (FE2000 manufactured by Mitsubishi Engineering Plastics) was obtained at 180 ° C. for 10 minutes under a pressing condition of 9.8 MPa (100 kgf / cm ² ).

(Comparative Example 1)
The same luminance uniformity test was performed by arranging the ridge line direction D1 of the prism sheet 16 used in Example 1 in parallel with the extending direction D2 of the linear light source 12 (α = 0 °). The result is shown in FIG.

(Comparative Example 2)
The same luminance uniformity test was performed by arranging the ridge line direction D1 of the prism sheet 16 used in Example 1 perpendicularly to the extending direction D2 of the linear light source 12 (α = 90 °). The result is shown in FIG.

  From the result of FIG. 12, in Example 1 using the present invention, a good surface emitting device having no luminance unevenness and excellent luminance uniformity is obtained. On the other hand, in Comparative Examples 1 and 2, the light source image was not optimized, the luminance unevenness was large, and the luminance uniformity was not obtained.

(Example 2)
Using the surface emitting device described in the second embodiment, luminance uniformity was tested under the following conditions. The obtained result is shown in FIG.
・ Diffusion sheet 14: Diffusion sheet D114 (manufactured by Tsujiden Co., Ltd.)
・ Linear light source 12, reflector 13: LCD TV KDL-S19A10 (manufactured by Sony Corporation)
Prism sheet 26: flat part 16d: formation width 15 μm
Linear protrusion 16a: Angle α: 45 ° formed by the ridge line direction D1 of the prism / linear protrusion 16a having a base of 50 μm and an apex angle of 90 ° and the extending direction D2 of the linear light source 12
-Distance from the linear light source 12 to the prism sheet 16: 10 mm
Luminance meter: RISA-COLOR (manufactured by Highland)

The prism sheet 26 was produced by the following method.
Using a metal emboss for hot pressing as a master, a combination of a right-angled isosceles triangle with a top angle of 90 °, a base of 50 μm, and a height of 25 μm and a flat part of a width of 15 μm is regularly arranged at an interval of 65 μm. The one engraved was used. As a thermoplastic resin, a 200 μm polycarbonate resin sheet (FE2000 manufactured by Mitsubishi Engineering Plastics) was obtained at 180 ° C. for 10 minutes under a pressing condition of 9.8 MPa (100 kgf / cm ² ).

(Comparative Example 3)
The same luminance uniformity test was performed by arranging the ridge line direction D1 of the prism sheet 26 used in Example 2 in parallel to the extending direction D2 of the linear light source 12 (α = 0 °). The result is shown in FIG.

(Comparative Example 4)
The same luminance uniformity test was performed by arranging the ridge line direction D1 of the prism sheet 26 used in Example 2 perpendicularly to the extending direction D2 of the linear light source 12 (α = 90 °). The result is shown in FIG.

  From the result of FIG. 12, in Example 1 using the present invention, a good surface emitting device having no luminance unevenness and excellent luminance uniformity is obtained. On the other hand, in Comparative Examples 1 and 2, the light source image was not optimized, and the luminance unevenness was large and the luminance uniformity was not obtained.

  As mentioned above, although each embodiment of this invention was described, of course, this invention is not limited to these, A various deformation | transformation is possible based on the technical idea of this invention.

  For example, in the above embodiment, the protrusion 16a constituting the light source image division sheet is formed in a linear shape, but instead, the shape of the protrusion is shape anisotropy in a plane such as a triangular pyramid or a quadrangular pyramid. You may comprise with a pyramid with. Also in this case, the same effect as that of the above-described embodiment can be obtained by adjusting the angle at which the formation direction of the projection of the cone structure intersects the extending direction of the linear light sources or the arrangement direction of the point light sources. Can do.

  In addition, in the prism sheets 16 and 26 having the above-described configuration, the back side of the sheet on which the linear protrusions 16a are not formed is subjected to roughening processing such as embossing, so that the back side is damaged when the sheet is handled. It is possible to alleviate the deterioration of the optical characteristics caused by.

  In the above embodiment, one sheet of prism sheets 16 and 26 as light source image division sheets is used as the surface light emitting device 10, but the present invention is not limited to this, and two or more prism sheets may be used. In this case, the occurrence of moire (interference fringes) can be suppressed by changing the ridge line direction of each prism sheet.

  Further, the surface light emitting device according to the present invention is not limited to use as a backlight device for a liquid crystal display device. In addition, by using a diffusion plate provided with a dot pattern as the diffusive sheet, it is possible to reduce the thickness of the obtained surface light emitting device by an appropriate combination.

1 is a perspective view showing a schematic configuration of a surface light emitting device 10 according to a first embodiment of the present invention. FIG. 3 is a plan view of the surface light emitting device 10 when viewed from the light emitting surface side of the prism sheet 16. It is the top view and side view of the prism sheet 16 explaining the light source image when changing the ridgeline direction of the prism sheet 16 and the extending direction of the linear light source 12, respectively. It is a light source image photograph when the ridge line direction of the prism sheet 16 and the extending direction of the linear light source 12 are respectively changed. FIG. 6 is a side view showing a modified example of the configuration of the prism sheet 16. It is explanatory drawing of the structure of the prism sheet. It is a light source image photograph when the ridge line direction of the prism sheet 26 and the extending direction of the linear light source 12 are each changed, which will be described in the second embodiment of the present invention. 4 is a side view for explaining the principle of light source image division by the prism sheet 26. FIG. It is a figure which compares and shows the luminance distribution of the linear light source 12, and the luminance distribution when the prism sheet 26 is used. It is a perspective view which shows schematic structure of the surface emitting device 30 by the 3rd Embodiment of this invention. 3 is a plan view of the surface light emitting device 30 when viewed from the light emitting surface side of the prism sheet 16. FIG. It is a measurement result of the brightness | luminance equalization test of the surface emitting apparatus demonstrated in Example 1 of this invention. It is a measurement result of the brightness | luminance equalization test of the surface emitting apparatus demonstrated in Example 2 of this invention. It is a perspective view which shows schematic structure of the conventional surface light-emitting device 1. FIG. It is a side view explaining the structure and luminance distribution of the conventional surface light-emitting device, A shows the example which has arrange | positioned the diffuser plate 4 and the diffusion sheet 5 on the light source 2, B shows the light source image division sheet on the light source 2. As an example, a prism sheet 6 and a diffusion sheet 5 are arranged. FIG. 5 is an optical path diagram of light passing through the prism sheet 6 and shows how the distance between the light source images varies depending on the distance between the light source and the prism sheet. It is an optical path figure of the light which passes through the prism sheet 6, and has shown the mode of the change of the distance between light source images by the difference in prism shape. FIG. 4 is an optical path diagram of light passing through the prism sheet 6 and shows how the distance between the light source images varies depending on the refractive index of the prism sheet.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10,30 ... Surface light-emitting device, 11 ... Housing | casing, 12 ... Linear light source, 13 ... Reflecting plate, 14 ... Diffusing sheet, 16, 26 ... Prism sheet (light source image division sheet), 16a ... Linear protrusion, 16b ... ridge line, 16d ... flat part, 32 ... point light source, D1 ... ridge line direction of linear projection on prism sheet, D2 ... extension direction of linear light source, D3 ... arrangement direction of point light source, LA, LB ... Light source image (image)

Claims (9)

A diffusive sheet that forms a light exit surface; a reflector disposed opposite the diffusive sheet; a linear light source disposed between the diffusible sheet and the reflector; and the diffusive sheet. A surface light emitting device comprising a light source image division sheet disposed between the linear light source,
The light source image division sheet has linear protrusions on the front surface and / or back surface thereof,
The surface light-emitting device is characterized in that the ridge line direction of the linear protrusion is arranged to intersect the extending direction of the linear light source. The surface light-emitting device according to claim 1, wherein the light source image division sheet is a prism sheet having linear protrusions having a triangular cross section. The surface light-emitting device according to claim 1, wherein the light source image division sheet is a lens sheet having a lens-shaped linear protrusion. The surface light emission according to claim 1, wherein the light source image division sheet is provided with a flat portion parallel to the sheet surface between adjacent linear protrusions or a part of the linear protrusions. apparatus. A diffusive sheet that forms a light exit surface; a reflector disposed opposite to the diffusive sheet; and a plurality of point light sources arranged linearly between the diffusive sheet and the reflector; A surface light emitting device including a light source image dividing sheet disposed between the diffusive sheet and the point light source,
The light source image division sheet has linear protrusions on the front surface and / or back surface thereof,
The surface light emitting device, wherein the ridge line direction of the linear protrusions is arranged to intersect with the arrangement direction of the point light sources. A diffusive sheet forming a light exit surface; a reflector disposed opposite to the diffusible sheet; a linear light source disposed linearly between the diffusible sheet and the reflector; and the diffusion A method of uniformizing luminance in a surface light emitting device including a light source image division sheet disposed between a light-sensitive sheet and the linear light source and having a linear protrusion on a front surface and / or a back surface,
The brightness distribution of the light beam emitted from the light exit surface is controlled by adjusting the angle at which the ridge line direction of the linear protrusion on the light source image dividing sheet intersects the extending direction of the linear light source. Luminance equalization method. A diffusive sheet that forms a light exit surface; a reflector disposed opposite to the diffusive sheet; and a plurality of point light sources arranged linearly between the diffusive sheet and the reflector; A brightness uniformizing method in a surface light emitting device including a light source image division sheet disposed between the diffusive sheet and the point light source and having linear protrusions on the front surface and / or the back surface,
The brightness distribution of the light beam emitted from the light exit surface is controlled by adjusting the angle at which the ridge line direction of the linear protrusion on the light source image dividing sheet intersects the array direction of the point light sources. Brightness uniformity method. A diffusive sheet that forms a light-emitting surface, a reflective plate disposed to face the diffusive sheet, and a linear light source or a linear shape disposed linearly between the diffusive sheet and the reflective plate A plurality of point-like light sources arranged on the surface, and a light source image dividing sheet disposed between the diffusive sheet and the light source and having protrusions having shape anisotropy in the in-plane direction on the front surface and / or the back surface A brightness uniformizing method in a surface light emitting device comprising:
The brightness of the light beam emitted from the light exit surface is adjusted by adjusting the angle at which the projection formation direction on the light source image dividing sheet intersects the extending direction of the linear light source or the arrangement direction of the point light sources. A luminance uniforming method characterized by controlling the distribution. A liquid crystal display panel and a surface light emitting device that illuminates the liquid crystal display panel from the back side,
The surface light emitting device is linearly disposed between a diffusive sheet that forms a light exit surface, a reflective plate disposed to face the diffusive sheet, and the diffusive sheet and the reflective plate. In a liquid crystal display device comprising a linear light source or a plurality of point light sources arranged in a line, and a light source image division sheet disposed between the diffusive sheet and the light source,
The light source image division sheet has linear protrusions on the front surface and / or back surface thereof,
The liquid crystal display device, wherein a ridge line direction of the linear protrusions is arranged so as to intersect an extending direction of the linear light sources or an arrangement direction of the point light sources.