JP2012190582A - Lighting unit, lighting device, and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting unit that improves front luminance while optical deflection elements of a light guide plate are made hardly visible.SOLUTION: In the lighting unit 7 including a surface light source device 2 having a light source 11, the light guide plate 10 with an incident end surface, an emitting surface, and an optical deflection surface, and a reflection sheet 9, a diffusion sheet 3, and a diffusion and condensing sheet 4 for coping with both of diffusion of light and improvement of luminance, the optical deflection elements 13 provided on an optical deflection surface 12 are extended in a first direction in parallel with the end surface, and are arranged in one-dimensional array arranged in a second direction perpendicular to the end surface. The light guide plate 10 is divided into two zones such as the zone A wherein an arrangement pitch of the optical deflection elements is 500 μm or more and the zone B wherein the arrangement pitch of the optical deflection elements is less than 500 μm. The diffusion and condensing sheet 4 diffuses light emitted from the zone A in one-dimensional direction or two-dimensional direction at an angular distribution wider than the light emitted from the zone B.

Description

  The present invention relates to an illuminating unit, an illuminating device, and a display device that include a diffusing and condensing sheet mainly used for illuminating optical path control.

  In recent large-sized liquid crystal televisions, flat panel displays, etc., direct type illumination devices and edge light illumination devices are mainly employed. In the direct type illumination device, a plurality of cold cathode tubes and LEDs (Light Emitting Diodes) are regularly arranged as light sources on the back surface of the panel. A light diffusing plate is used between the image display element such as a liquid crystal panel and the light source so that a cold cathode tube or LED as a light source is not visually recognized.

  On the other hand, in an edge light type lighting device, a plurality of light sources such as cold cathode tubes and LEDs are arranged on an end face of a light-transmitting plate called a light guide plate. In general, a light deflection surface that efficiently guides incident light incident from the end surface of the light guide plate to the exit surface is formed on the surface opposite to the exit surface of the light guide plate (the surface facing the image display element). The light deflecting elements formed on the light deflecting surface include various light deflecting elements for efficiently leading to the exit surface, such as those printed with a white dot pattern or those provided with a lens shape. Proposed.

  However, since the edge light system has a structure in which the light source is disposed only on the end face of a light-transmitting plate called a light guide plate, the number of light sources installed is limited. Therefore, as the liquid crystal display device becomes larger, it becomes difficult to brighten the entire display, and the role of the optical sheet for improving the brightness becomes important.

As means for improving the brightness of a liquid crystal display screen, BEF (Brightness Enhancement Films), which is a registered trademark of 3M Corporation (Minnesota Mining and Manufacturing Company), is widely used as a lens sheet.
7 and 8 are diagrams showing brightness enhancement films described in Patent Documents 1 and 2 below, and FIG. 7 is a schematic cross-sectional view for explaining the configuration of a conventional liquid crystal display device using BEF. is there. Schematically, a surface light source 182, a BEF 185 as a brightness enhancement film on which light indicated by an arrow emitted from the surface light source 182 is incident, and a liquid crystal panel 184 are disposed. FIG. 8 is a perspective view of the BEF 185 shown in FIG. 7, and the BEF 185 is an optical film in which a plurality of prisms 187 having a triangular cross section are periodically arranged in one direction on a transparent substrate 186. The unit width of the prism 187 is larger than the wavelength of the light, and the arrangement pitch is larger than the wavelength of the light. The condensed light is emitted in the direction indicated by the block arrow F ′. can do.

  FIG. 6 is a cross-sectional view of an essential part showing an arrangement configuration of a liquid crystal display device including a BEF according to a conventional technique using an edge light type illumination device in which a light source 101 is arranged on an end face of a light guide plate 100. For example, a lens sheet 191 using BEF collects light from “off-axis” and redirects this light “on-axis” toward the viewer. Or it can be “recycled”. That is, BEF can increase the on-axis brightness by reducing the off-axis brightness when using the liquid crystal display device (when observing). Here, “on-axis” is a direction that coincides with the visual direction F of the observer in FIG. 6, and is generally a normal direction to the display screen of the liquid crystal panel 184.

  Incidentally, as described above, the light guide plate 100 used in the edge light system includes the light deflection surface 100b at a position facing the exit surface 100a, and the light deflection surface 100b has a white dot pattern or a microlens (concave, convex). Mold) and other lens-shaped light deflection elements 102 are formed. As the light deflecting element 102, a minute reflecting element is formed by grooves or protrusions arranged in a one-dimensional direction or two-dimensional direction, and light is reflected toward the light exit surface side by total reflection of these minute reflecting elements. Various variations of the light guide plate 100 related to luminance improvement have been proposed, such as a configuration in which light is emitted toward the visual direction F side.

  However, since any light deflection element 102 is formed of a reflective layer or a structure that is regularly or quasi- irregularly arranged with regularity, the regularity as described above. There is a problem of moire interference fringes due to interference and unevenness of the light deflection surface 100b with a lens sheet 191 represented by a BEF having a structure having the above. As a solution, a method of using a diffusion sheet 190 as shown in Patent Document 3 between the light guide plate 100 and the lens sheet 191 is common.

  The diffusion sheet 190 is disposed between the light guide plate 100 and the lens sheet 191 when a lens sheet 191 represented by BEF is used using a diffusion film in which a diffusion filler is applied on a transparent substrate. In addition, it is possible to make uniform light incident on the plane of the lens sheet 191 while suppressing luminance unevenness of the light emitted from the exit surface 100 a of the light guide plate 100.

  However, in particular, when the light deflecting elements 102 are grooves or protrusions arranged in a one-dimensional direction and their pitch is large, the light plane is uniformized using the diffusion sheet 190 as described above. Even in the illustrated case, the light deflection element 102 may be visually recognized on the visual direction F side. That is, an illumination unit in which the light deflection element is not visually recognized and high brightness is obtained cannot be easily obtained.

Japanese Patent Publication No. 1-378001 JP-A-6-102506 JP 2004-295080 A

  The present invention is proposed in view of the above problems, and the problem to be solved by the present invention is to conceal the light deflection element formed on the light deflection surface of the light guide plate from the visual direction and to increase the front luminance. It is an object to provide an illumination unit and an illumination device that can be improved, and a display device using the illumination device.

As means for solving the above-mentioned problems, the invention according to claim 1 is directed to a light source, an end face on which light emitted from the light source is incident, an emission surface on which incident light is emitted to the observation side, and incident light. A surface light source device comprising: a light guide plate provided with a light deflection surface that guides the light to the exit surface; and a reflection sheet that reflects light emitted from the surface of the light guide plate excluding the exit surface to guide the light guide plate; A diffusion sheet that is provided on the exit surface side of the surface light source device and diffuses incident light in a two-dimensional direction, and a diffusion condensing sheet that is provided on the observation side of the diffusion sheet to achieve both diffusion of light and improvement in luminance. In the illumination unit, the light guide plate includes, on the light deflection surface, a light deflection element that guides light incident on the light guide plate to the exit surface side, and the light deflection element is in a first direction parallel to the end surface. It is arranged in a one-dimensional arrangement that extends and is arranged in a second direction perpendicular to the end face. The arrangement pitch of the light deflection elements and more areas A 500 [mu] m 5
Divided into two areas of area B less than 00 μm, the diffusion condensing sheet diffuses the light emitted from area A in a one-dimensional direction or two-dimensional direction with a wider angular distribution than the light emitted from area B It is the lighting unit characterized by doing.

  According to the illumination unit including the diffusion condensing sheet according to the present invention, when the illumination unit is viewed from the observation side, an image of the light deflection element formed on the light deflection surface of the light guide plate is diffused. Since the image of the deflection element cannot be visually recognized, there is little illumination unevenness and the front luminance can be improved.

  Further, in the invention according to claim 2, a plurality of lenses formed by cylindrical curved surfaces are first in a region facing the region A in the light exit surface facing the observation side of the diffusion condensing sheet. A plurality of prisms having a triangular cross section are arranged in a first direction in a region facing the region B out of the light exit surface facing the observation side of the diffusion condensing sheet. The lighting unit according to claim 1, wherein the lighting unit is arranged to extend.

  The invention according to claim 3 is arranged such that a plurality of prisms having a triangular cross section extend in the first direction on the light exit surface facing the observation side of the diffusion condensing sheet, and the region A 2. The illumination unit according to claim 1, wherein a light diffusion layer is formed on the surfaces of the plurality of prisms arranged in the region of the diffusion condensing sheet opposed to the light.

  In the invention according to claim 4, a plurality of lenses formed by cylindrical curved surfaces are arranged on the light exit surface facing the observation side of the diffusion condensing sheet so as to extend in the first direction. 2. The illumination unit according to claim 1, wherein a light diffusion layer is formed on surfaces of a plurality of lenses arranged in a region of the diffusion condensing sheet facing the region A. 3.

  The invention according to claim 5 is characterized in that a rough surface is formed in a region facing the region A in the light incident surface facing the diffusion sheet side of the diffusion condensing sheet. The lighting unit according to 1.

  In the invention according to claim 6, a directional diffusion layer for diffusing light in the second direction is provided in a region facing the region A in the light incident surface facing the diffusion sheet side of the diffusion condensing sheet. The lighting unit according to claim 1, wherein the lighting unit is formed.

  The invention according to claim 7 is an illumination characterized in that the illumination unit according to any one of claims 1 to 6 is provided with a reflective polarization separation sheet that polarizes light emitted from the illumination unit. Device.

  According to the illuminating device of the present invention, by including the reflective polarization separation sheet, it is possible to selectively transmit a specific polarization component and reflect other polarization components in the light emitted from the illumination unit. As a lighting device for a liquid crystal display device, it is possible to efficiently increase luminance along with the reduction of uneven illumination by the lighting unit of the present invention.

  The invention described in claim 8 is characterized in that any one of the illumination unit according to claims 1 to 6 or the illumination device according to claim 7 is provided in an image display element that defines a display image. Display device.

  According to the display device of the present invention, when viewed from the observation side, the light emitted from the surface light source device is concealed so that the light deflection element formed on the light deflection surface of the light guide plate cannot be visually recognized by the diffusion condensing sheet. Thus, it is possible to provide a bright display device that displays a non-uniform screen and has improved front luminance.

According to the illumination unit including the diffusion condensing sheet according to the present invention, when the illumination unit is viewed from the observation side, an image of the light deflection element formed on the light deflection surface of the light guide plate is diffused. Since the image of the deflection element cannot be visually recognized, there is little illumination unevenness and the front luminance can be improved.
Further, according to the illumination device of the present invention, in addition to the effects of the illumination unit described above, a specific polarization component can be selectively transmitted among the light emitted from the illumination unit by using a reflective polarization separation sheet. In addition, since other polarization components are reflected, the luminance can be efficiently increased as an illumination device for a liquid crystal display device.
Furthermore, according to the display device according to the present invention, when viewed from the observation side, the light emitted from the surface light source device cannot be viewed with the light deflection element formed on the light deflection surface of the light guide plate by the diffusion condensing sheet. It is possible to provide a display device that displays a screen with no unevenness by concealing, displays a bright image with high image quality, and improves front luminance.

It is principal part sectional drawing for showing the example of arrangement structure of the liquid crystal display device containing the illumination unit provided with the diffusion condensing sheet | seat by embodiment of this invention. It is principal part explanatory drawing showing the light deflection | deviation element arranged on the light deflection surface of a light-guide plate. It is a schematic cross section which shows two types of light guide plates, (a) is a figure showing the light deflection | deviation element arranged on a light deflection surface in case a light source is arranged on the two end surfaces of a light guide plate. is there. (B) is a figure showing the light deflection | deviation element arranged on a light deflection surface in case a light source is arranged on one end surface of a light-guide plate. It is a perspective view of the illumination unit provided with the diffusion condensing sheet | seat shown in order to demonstrate the division of the area | region by embodiment of this invention. It is a schematic cross section showing the example of the diffusion condensing sheet | seat of this invention, Comprising: (a) is an example which arranges a lens or a prism according to an area | region. (B) is an example in which a rough surface is selectively formed by a region. It is principal part sectional drawing which shows the arrangement configuration of the liquid crystal display device by a prior art. It is a schematic cross section for demonstrating the structure of the conventional liquid crystal display device using BEF. It is a perspective view of BEF shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a longitudinal sectional view of an essential part showing a liquid crystal display device 1 for displaying a liquid crystal image as a representative example of a display device according to an embodiment of the present invention. The liquid crystal display device 1 includes a surface light source device 2 that emits light from a light source 11, a diffusion sheet 3 that is provided on the exit surface side of the surface light source device and diffuses incident light in a two-dimensional direction, and the observation side of the diffusion sheet A diffusion condensing sheet 4 that achieves both diffusion of light and brightness improvement, a reflective polarization separating sheet 5 that reflects a specific polarization component of incident light, and a liquid crystal image as, for example, a liquid crystal display element 6 Image display elements are sequentially provided in the light traveling direction. A further forward direction of light of the liquid crystal display element 6 is a visual direction F corresponding to the observation side.
In the liquid crystal display device 1, the surface light source device 2, the diffusion sheet 3, and the diffusion condensing sheet 4 constitute an illumination unit 7, and the illumination unit 7 and the reflective polarization separation sheet 5 constitute an illumination device 8. In FIG. 1, a reduced view of each component is schematically shown and does not match the actual one.

In the surface light source device 2, a light source 11 is disposed adjacent to an end surface 10 a in the thickness direction of a light-transmitting light guide plate 10 having a flat plate shape, and incident light from the light source 11 enters the light guide plate 10 from the end surface 10 a. It enters and is transmitted to the far side and is emitted from the exit surface 10b to the observation side, and the exit surface 1 of the light guide plate
An edge light system having a configuration in which a light deflection surface 12 that efficiently guides incident light to the exit surface is formed on the surface opposite to 0b. The surface light source device 2 also includes a reflection sheet 9 that mainly reflects the light emitted from the surface of the light guide plate excluding the exit surface and guides it back to the light guide plate, mainly on the back side opposite to the observation side of the light guide plate 10. Is provided.

  For example, a point light source is used as the light source 11. For example, an LED is used as the point light source, and a white LED, RGB-LED, organic EL light source, or the like can be employed as the LED. Alternatively, the light source 11 may be a fluorescent tube represented by a cold cathode tube (CCFL). Although FIG. 1 shows an example in which the light source 11 is arranged on one end surface 10a in the thickness direction facing the light guide plate 10, the present invention is not limited to this, and the light source 11 may be arranged on two end surfaces 10a. The shape of the light guide plate 10 may be a wedge shape or the like instead of the flat plate shape.

  The light deflection surface 12 described above is formed on the surface of the light guide plate 10 opposite to the exit surface 10b in the visual direction F. The light deflection surface 12 is formed with a light deflection element 13 that deflects light incident on the light guide plate 10 from the light source 11 toward the emission surface 10b. As the light deflection element 13, for example, a groove having a triangular cross section is an end face. They are arranged extending in a direction parallel to 10a. Further, as another example of the light deflection element 13, a groove having a curved cross section may be formed. Alternatively, instead of the groove, a protruding structure may be arranged in parallel with the end face 10a.

  FIG. 2 is a view showing the light deflection surface 12 of the light guide plate 10 in the present embodiment, and the light deflection elements 13 are arranged on the light deflection surface 12 so as to extend in a direction parallel to the end surface 10a. Here, in a plane parallel to the light deflection surface 12, the direction parallel to the end surface 10a of the light guide plate 10 is referred to as a first direction, and the direction perpendicular to the end surface 10a is referred to as a second direction. In FIG. 2, the cross section of the light deflection element 13 is shown as a curved surface shape, but is not limited to a curved surface, and may be a triangular shape or a polygonal shape. In FIG. 2, a first direction and a second direction that exist in a plane parallel to the light deflection surface 12 and are orthogonal to each other are indicated by arrows. The light deflection elements 13 extend in a direction parallel to the first direction and are arranged at a pitch P (L) in the second direction. Here, L represents the distance from the end face 10a, and the pitch P (L) indicates that it is a function of the distance from the end face 10a.

  By the way, it is desirable that the light deflection elements 13 formed on the light guide plate 10 be arranged in a pattern so that the pitch in the vicinity of the end surface 10a of the light guide plate 10 is large and the pitch at a position away from the end surface 10a is small. When the cross section of the light deflection element 13 is semicircular and the radius and the arrangement pitch are uniformly equal, the amount of incident light is closer to the vicinity of the end surface 10a of the light guide plate 10 facing the light source 11 than to a position far from the light source. Because there are many, a lot of light is scattered. As a result, the front luminance near the central portion of the light guide plate 10 is lowered, and luminance unevenness is strongly generated. Therefore, in order to eliminate the above phenomenon, the arrangement pitch of the light deflection elements 13 is widened so that light is not scattered much in the vicinity of the end face 10a with a large amount of light, and the pitch becomes smaller as the distance from the end face 10a of the light guide plate 10 increases. By forming the light deflection element 13 in the light, it becomes easy for light to propagate to the central portion of the light guide plate, and the front luminance near the central portion of the light guide plate 10 can be increased, and uneven brightness can be eliminated.

3A and 3B show examples of arrangement patterns of the light sources 11 arranged facing the end face 10a of the light guide plate 10 and the light deflection elements 13 arranged on the light deflection surface 12. FIG.
In FIG. 3A, the light source 11 is arranged facing the two end faces 10 a of the light guide plate 10, and the pattern pitch decreases as the distance from the light source 11 in the second direction becomes smaller. It is a figure showing the arrangement pattern of the light deflection | deviation element 13 that the pitch of becomes the minimum.
In FIG. 3B, the light source 11 is arranged facing one end face 10 a of the light guide plate 10, and the pattern pitch decreases as the distance from the light source 11 in the second direction becomes closer to the light source 11. It is a figure showing the arrangement pattern of the optical deflection | deviation element 13 in which the pitch of a pattern becomes the minimum in the optical deflection surface near the end surface on the opposite side to the end surface 10a.

  Here, if the pitch of the arrangement of the light deflection elements 13 is increased too much in the vicinity of the end face 10a that is close to and opposed to the light source 11, the diffusion sheet 190 or BEF described above with reference to FIG. Even if the lens sheet 191 or the reflective polarization separation sheet 5 is placed, the light deflection element 13 may be visually recognized as a bright bright line. On the other hand, in the illumination unit according to the present invention, it is possible to make the light deflection element 13 of the light guide plate 10 invisible by disposing the diffusion condensing sheet 4 described later instead of the BEF 185 and the similar lens sheet 191. It becomes possible.

  FIG. 4 is a perspective view of an illumination unit including a diffusing and condensing sheet, which is shown for explaining the division of regions according to the embodiment of the present invention. As shown in FIG. 4, a region where the pitch of the light deflection elements 13 arranged on the light deflection surface 12 of the light guide plate 10 is 500 μm or more is a region A, and a region where the pitch is less than 500 μm is a region B. In general, because of the limitation of the resolution of the human eye with respect to the display device, an image having a size of 500 μm or more is positioned as a boundary value that is easier to visually recognize than a smaller image. Are divided by 500 μm.

  According to the above description regarding the propagation and scattering of light in the light guide plate, in order to eliminate luminance unevenness due to the tendency of scattered light in the edge light method, a region close to the end surface 10a that takes light from the light source 11 to the light guide plate is lighted. As the region A where the pitch of the deflecting elements 13 is large, it is appropriate that the region away from the light source is the region B where the pitch of the light deflecting elements 13 is small. The diffusion condensing sheet 4 provided on the observation side of the light guide plate to achieve both the diffusion of light and the improvement in luminance prevents the light deflection element 13 in the region A having a pitch of 500 μm or more, which is generally easily visible, from being visible. As an object, the present invention is characterized in that light emitted from the region A is diffused in a one-dimensional direction or a two-dimensional direction with a wider angular distribution than the light emitted from the region B. In other words, the light of the arrangement pattern that is easily visible that is emitted from the area A is diffused more strongly than the other areas by the diffusion condensing sheet 4, so that the image of the light deflection element 13 that is generated in the area A and is conspicuous due to the large pitch. Can be diffused and made inconspicuous. On the other hand, in the region B, since the pitch of the light deflection elements 13 is originally narrow, even if the light emitted from the region B is not diffused so much by the condensing diffusion sheet 4, the image of the light deflection elements 13 is not conspicuous.

  FIG. 5 is a schematic cross-sectional view showing an example of the diffusing and condensing sheet 4 in the present invention in relation to the region A and the region B of the light guide plate. FIG. 5A is an example in which lenses or prisms are arranged according to the region. Yes, (b) is an example in which a rough surface is selectively formed by a region.

  As shown in FIG. 5A, as an example of the diffusing and condensing sheet 4, when a region facing the region A on the light exit surface of the diffusing and condensing sheet 4 is A ′, a cylindrical shape is formed on the region A ′. A plurality of lenses formed by curved surfaces are arranged so as to extend in parallel to the first direction. Furthermore, when the region facing the region B on the light exit surface of the diffusing and condensing sheet 4 is B ′, a plurality of prisms having a triangular cross section extend in parallel to the first direction on the region B ′. Arrange. Since the curved lens is arranged in the area A ′, the light emitted from the area A can be diffused and the image of the light deflection element 13 can be made inconspicuous. Since the prisms arranged in the region B ′ have an effect of collecting light without diffusing light, it contributes to an increase in luminance of the diffusing and collecting sheet 4.

  Alternatively, a plurality of prisms having a triangular cross section are arranged so as to extend in parallel with the first direction on the entire surface of the light exit surface of the diffusing and condensing sheet 4, and on the surfaces of the plurality of prisms on the region A ′, A light diffusion layer may be formed. By the light diffusing layer on the prism surface, the region A ′ can diffuse the light emitted from the region A and make the image of the light deflection element 13 inconspicuous. Even if the light diffusing layer is not formed on the prisms arranged in the region B ′, the light deflection elements 13 are not visually recognized because the pitch of the light deflection elements 13 in the facing region B is narrow. Further, the light collecting effect of the prisms arranged in the region B ′ contributes to an increase in luminance of the diffusing light collecting sheet 4.

  Alternatively, a plurality of lenses formed by a cylindrical curved surface are arranged on the entire light exit surface of the diffusion condensing sheet 4 so as to extend in parallel with the first direction, and the plurality of lenses on the region A ′ are arranged. A light diffusion layer may be formed on the surface. Since the light emitted from the region A is diffused by both the diffusion effect of the lens and the diffusion effect of the light diffusion layer, the light deflection elements 13 arranged in the region A can be effectively made inconspicuous. In addition, the plurality of lenses arranged in the region B ′ has a light condensing effect although not as much as a prism, and thus contributes to an improvement in front luminance.

  Alternatively, as illustrated in FIG. 5B, a rough surface may be formed on the region A ″ facing the region A in the light incident surface of the diffusion condensing sheet 4. The rough surface is formed. Thus, since the light emitted from the region A is diffused in the region A ″, the light deflection element 13 in the region A can be made inconspicuous. The region B ″ facing the region B may be a completely flat surface, or a rough surface having a lower diffusibility than the region A ″ may be formed. In addition, as in this example, in the method of making a difference in image diffusibility by selectively forming a rough surface, the function of the brightness enhancement surface of the diffusion condensing sheet 4 is the same as in the above example. realizable. That is, a plurality of prisms having a triangular cross section are arranged on the entire surface of the light exit surface of the diffusion light collection sheet 4 so as to extend parallel to the first direction, or the light emission surface of the diffusion light collection sheet 4 By arranging a plurality of lenses formed by cylindrical curved surfaces on the entire surface so as to extend in parallel with the first direction, it is possible to give a certain light collection effect to the diffusion light collection sheet, This can contribute to improvement of the brightness of the unit.

  Alternatively, a directional diffusion layer having diffusivity in the second direction may be formed on the region A ″ facing the region A in the light incident surface of the diffusion condensing sheet 4 instead of the rough surface. .

  The light guide plate 10 included in the illumination unit 7 according to the present embodiment is preferably made of a highly transparent acrylic material, and in particular, PMMA (polymethyl methacrylate) is preferable because of its high transparency. However, the material is not limited to this as long as the material has high transparency. The light guide plate 10 is molded by an extrusion molding method, an injection molding method, or a hot press molding method well known in this technical field. The light deflection element 13 formed on the light deflection surface 12 of the light guide plate 10 can be integrally molded by these methods. The light deflection element 13 uses, for example, a mold plate in which a prism shape or a lens shape is formed by mechanical cutting or the like, or a resin plate die in which a lens shape is molded using a UV curable resin or a radiation curable resin. Alternatively, a method may be employed in which the resin material to be molded and the mold of the resin plate are pressure bonded.

  The diffusion condensing sheet 4 included in the illumination unit 7 according to the present embodiment is molded using a UV curable resin, a radiation curable resin, or the like, or PET (polyethylene terephthalate), PC (polycarbonate), PMMA (polymethyl methacrylate). ), COP (cycloolefin polymer), PAN (polyacrylonitrile copolymer), AS (acrylonitrile styrene copolymer), etc., which are well known in this technical field such as extrusion molding, injection molding, or heat It can be formed integrally by a press molding method. Alternatively, a resin plate mold in which a lens shape is formed using a UV curable resin, a radiation curable resin, or the like may be used, and the resin material to be molded and the resin plate mold may be pressed and extruded.

  As a method of selectively forming the light diffusion layer on the surface of the prism or curved lens in the area A ′, a blasting process such as sand blasting is selectively applied to a mold obtained by cutting the prism or curved lens by mechanical cutting or the like. There is a method of forming a rough surface by performing the above. Since the prism having a rough surface or the curved lens has diffusibility, the light deflection element 13 can be effectively made inconspicuous. Alternatively, the diffusion layer may be formed by selectively coating the surface of the molded diffusion condensing sheet 4 on the prism or curved lens with a layer mixed with a diffusion filler.

  As the rough surface formed in the region A ″, for example, a two-dimensional rough surface formed by blasting such as sandblasting may be formed, or a microlens made of a part of a sphere may be formed. In addition, as the directional diffusion layer, a linear concavo-convex structure formed with a fine pitch such as a hairline, a microlens formed of a part of an ellipsoid, or a corrugated shape arranged in parallel to each other. An uneven structure may be formed, or a method of coating needle-shaped fillers with their directions aligned with each other may be used.

  The image display element exemplified as the liquid crystal display element 6 is preferably an element that displays an image by transmitting / blocking light in pixel units. If the image is displayed by transmitting / blocking light in pixel units, the illumination unit 7 according to the present embodiment improves the luminance of the image transmitted through the image display element in the visual direction F, and the light intensity is viewed. Angle dependency is reduced. Furthermore, the illumination unit 7 according to the present embodiment makes it impossible to visually recognize the light deflection element 13, and an image with high image quality can be displayed.

  Further, the illumination device 8 is configured by placing a reflective polarization separation sheet on the illumination unit 7. As the reflective polarization separation sheet, for example, a reflective polarization separation sheet represented by DBEF (registered trademark of 3M) can be used. Reflective polarized light separation sheet reflects the light with the polarization component absorbed by the polarizing plate of the liquid crystal panel and transmits only the light with the polarization component that passes through the polarizing plate. Can be enhanced.

  The image display element is preferably a liquid crystal display element 6. As shown in FIG. 1, the liquid crystal display element 6 is configured by laminating polarizing plates 23 and 23 before and after a liquid crystal panel 22. The liquid crystal display element 6 is a typical element that transmits / shields light in pixel units and displays an image. The liquid crystal display element 6 can improve image quality as compared with other display elements and can reduce manufacturing costs. it can.

  In addition, the diffusion condensing sheet 4 in the present invention can be used not only as the liquid crystal display device 1 such as a television but also for indoor and outdoor lighting applications, for example. In particular, the illumination unit 7 incorporating the diffusion condensing sheet 4 can emit light with high front brightness without unevenness in brightness, and therefore can illuminate a specific indoor or outdoor space uniformly and brightly.

  Next, as examples of the present invention, the diffused condensing sheet 4 according to Examples 1 to 3 and the diffused condensing sheet 4 according to Comparative Example 1 were manufactured, and each was incorporated into the illumination device 8 of the liquid crystal display device 1. Evaluation of luminance and visibility of the light deflection element 13 were performed.

<Production of surface light source device 2>
The surface light source device 2 was produced as follows.
First, a 3 mm-thick light guide plate 10 having a groove having a triangular cross section formed on the light deflection surface 12 is prepared, and a plurality of LEDs are opposed to the end surface 10 a in the thickness direction of one side of the light guide plate 10 as the light source 11. Arranged in a row. The light guide plate 10 was a plate having a length of 550 mm on the side facing the LED and a length of 310 mm on a side perpendicular to the LED.
On the light deflection surface 12 of the light guide plate 10, a plurality of grooves having an apex angle of 90 ° and a triangular cross section were arranged so as to extend in a direction parallel to the end surface 10a facing the LED. The groove pitch is designed to decrease linearly as the distance from the LED side increases, and the groove pitch is 800 μm in the vicinity of the end face 10a on the LED side and 60 μm in the vicinity of the end face 10a opposite to the LED. did. The width of the groove having a triangular cross section was 50 μm, and the depth of the groove was 25 μm.
PMMA resin was used as the material of the light guide plate 10, and the light deflection element 13 of the light guide plate 10 was integrally molded by extrusion molding of PMMA resin. The light deflection element 13 was produced by pressing and molding a resin plate on which protrusions having a triangular cross section were formed against molten PMMA resin. The resin plate was produced by transferring the inverted shape onto a PET substrate with a UV curable resin from a roll in which prismatic grooves were formed by mechanical cutting.
The surface light source device 2 was obtained by arranging the reflection sheet 9 on the back surface of the light guide plate 10 on the light deflection surface 12 side.

<Preparation of diffusion condensing sheet 4>
A polycarbonate resin was used as the material of the diffusion condensing sheet 4. Since the polycarbonate resin has a high refractive index of about 1.59, it is possible to obtain the diffusion condensing sheet 4 having high front luminance. The diffusion condensing sheet 4 was formed by extrusion molding using a polycarbonate resin.
Specific configurations of the diffusion condensing sheets 4 according to Examples 1 to 3 and Comparative Example 1 will be described later.

<Production of lighting device 8>
The lighting device 8 was produced as follows.
First, the diffusing sheet 3 is arranged on the light emitting surface side of the surface light source device 2, and the diffusing and condensing sheet 4 is arranged on the light emitting surface side to produce the illumination unit 7. The diffusion sheet 3 was a film having a total light transmittance of 60% and Hz of 85%, and a coating of diffusion fine particles on a PET substrate.
Further, a diffusion condensing sheet 4 was disposed on the diffusion sheet 3. Furthermore, DBEF (made by 3M company) was arrange | positioned as the reflection type polarization separation sheet 5 on it, and the illuminating device 8 was obtained.

The production conditions of the diffusion condensing sheet 4 according to Examples 1 to 3 and Comparative Example 1 are as follows.
Example 1
A curved lens having a pitch of 50 μm, a height of 23 μm, and a top radius of curvature of 12 μm was formed in the region A ′ of the light exit surface of the diffusion condensing sheet 4. In the region B ′, prisms having a pitch of 50 μm and a height of 25 μm were formed. The light incident surface of the diffusion condensing sheet 4 was a flat surface.
(Example 2)
A prism having a pitch of 50 μm and a height of 25 μm was formed on the entire surface of the light exit surface of the diffusion condensing sheet 4. A rough surface having a surface roughness Rz of 6.0 μm was formed in the region A ″ of the light incident surface. The region B ″ was a flat surface.
(Example 3)
A prism having a pitch of 50 μm and a height of 25 μm was formed on the entire surface of the light exit surface of the diffusion condensing sheet 4. On the light incident surface, a directional diffusion layer was formed in the region A ″. As the directional diffusion layer, a curved surface having an aspect ratio (height / pitch) of 0.08, a pitch of 20 μm, and a cross section consisting of a part of a circle. The lenses were arranged in a direction parallel to the end face 10a. The region B ″ was a flat surface.

(Comparative Example 1)
A prism having a pitch of 50 μm and a height of 25 μm was formed on the entire surface of the light exit surface of the diffusion condensing sheet 4. Further, a rough surface having a surface roughness Rz of 6.0 μm was formed over the entire light incident surface.

<Evaluation of front brightness>
Next, as the illuminating device 8, the diffusion sheet 3 is mounted on the surface light source device 2, and the diffusion condensing sheets 4 according to Comparative Example 1 and Examples 1 to 3 are mounted on the light exit surface side, respectively, and the reflective polarized light is mounted thereon. DBEF was mounted as the separation sheet 5 and the lighting devices 8 were assembled.
And the external appearance evaluation of the illuminating device 8 by a comparative example and Examples 1-3 and the measurement of front luminance were performed. When measuring the front luminance, a spectral radiance meter SR3 manufactured by Topcon Corporation was used as a luminance measuring device.
At the time of evaluation, the measured value of the front luminance of the lighting device 8 using the comparative example was set to 1.

As a result of measuring the front luminance of Example 1, 1.075 was obtained.
As a result of measuring the front luminance of Example 2, 1.040 was obtained.
As a result of measuring the front luminance of Example 3, 1.055 was obtained.
As a result of the external appearance evaluation of the lighting device 8 in Examples 1 to 3, the light deflection element 13 was not visually recognized in all.

  From the measurement results of Examples 1 to 3 and Comparative Example 1 above, the front luminance of the illuminating device 8 incorporating the diffusing and condensing sheet 4 in Examples 1 to 3 is the front luminance compared to that incorporating the Comparative Example 1. It was proved that the luminance increased and the light deflection element 13 was not visually recognized.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device 2 ... Surface light source device 3 ... Diffusion sheet 4 ... Diffusion condensing sheet 5 ... Reflection type polarization separation sheet 6 ... Liquid crystal display element 7 ... Illumination unit ,
DESCRIPTION OF SYMBOLS 8 ... Illuminating device 9 ... Reflective sheet 10 ... Light guide plate 10a ... End surface 10b ... Ejection surface 11 ... Light source 12 ... Light deflection surface 13 ... Light deflection element 22- .. Liquid crystal panel 23... Polarizing plate 100... Light guide plate 100 a.・ Liquid crystal display element 185... BEF
186: Transparent substrate 187 ... Prism 190 ... Diffusion sheet 191 ... Lens sheet (BEF)
200: Liquid crystal display device

Claims (8)

A light source;
A light guide plate comprising an end face for incident light emitted from a light source, an emission surface for emitting incident light to the observation side, and a light deflection surface for guiding incident light to the emission surface;
A reflection sheet that reflects light emitted from the surface of the light guide plate excluding the exit surface and guides it to the light guide plate;
A surface light source device comprising:
A diffusion sheet that is provided on the exit surface side of the surface light source device and diffuses incident light in a two-dimensional direction;
A diffusion condensing sheet that is provided on the observation side of the diffusion sheet to achieve both light diffusion and brightness improvement;
A lighting unit comprising:
The light guide plate includes, on the light deflection surface, a light deflection element that guides light incident on the light guide plate to the exit surface side, the light deflection element extending in a first direction parallel to the end surface, Arranged in a one-dimensional arrangement arranged in a second vertical direction, the light guide plate is divided into two areas, an area A in which the arrangement pitch of the light deflection elements is 500 μm or more and an area B in which the arrangement pitch is less than 500 μm.
The diffusion condensing sheet diffuses light emitted from the region A in a one-dimensional direction or a two-dimensional direction with a wider angular distribution than the light emitted from the region B.   Of the light exit surface facing the observation side of the diffusion condensing sheet, in a region facing the region A, a plurality of lenses formed by a cylindrical curved surface are arranged to extend in the first direction, Of the light exit surface facing the observation side of the diffusion condensing sheet, a plurality of prisms having a triangular cross section are arranged so as to extend in the first direction in a region facing the region B. The lighting unit according to claim 1.   A plurality of prisms having a triangular cross section are arranged to extend in the first direction on the light exit surface facing the observation side of the diffusion condensing sheet, and arranged in the region of the diffusion condensing sheet facing the region A The illumination unit according to claim 1, wherein a light diffusion layer is formed on surfaces of the plurality of prisms.   A plurality of lenses formed by a cylindrical curved surface are arranged to extend in the first direction on the light exit surface facing the observation side of the diffusion condensing sheet, and the diffusion condensing sheet facing the region A The illumination unit according to claim 1, wherein a light diffusion layer is formed on surfaces of the plurality of lenses arranged in the region.   2. The illumination unit according to claim 1, wherein a rough surface is formed in a region facing the region A in the light incident surface facing the diffusion sheet side of the diffusion condensing sheet.   The directional diffusion layer for diffusing light in the second direction is formed in a region facing the region A in the light incident surface facing the diffusion sheet side of the diffusion condensing sheet. The lighting unit according to 1.   An illumination apparatus comprising: the illumination unit according to any one of claims 1 to 6; and a reflective polarization separation sheet that polarizes light emitted from the illumination unit.   A display device comprising the illumination unit according to claim 1 or the illumination device according to claim 7 in an image display element that defines a display image.

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