JP2008304700A - Optical sheet, illumination device and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet that can be made thin without deteriorating use efficiency of light and to provide an illumination device and a display device equipped with the sheet. <P>SOLUTION: The optical sheet 1 is provided with a plurality of convexes 10, and each convex 10 has a surface form that is a superposition of a surface form expressed by a function f(x) in one direction (x-direction) within the sheet plane and a surface form expressed by a function g(y) in a y-direction orthogonal to the x-direction. The surface form expressed by the function f(x) is, for example, an aspheric form, while the surface form expressed by the function g(y) is, for example, a prism form. In the x-direction within the plane, light is divided by the aspheric form, which reduces luminance irregularity , while the light is directed to the front direction by the prism form in the y-direction, which contributes to improvement of front luminance. Thus, luminance irregularity can be decreased as well as the front luminance can be improved with a single optical sheet. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light transmissive optical sheet, an illumination device including the same, and a display device.

  In recent years, liquid crystal display devices for television and the like have become widespread, and demands for higher image quality and thinner thickness are increasing. These display devices, for example, perform display based on light emitted from a backlight installed on the back surface of the display panel. As the backlight, a display in which a plurality of linear light sources such as CCFLs are usually arranged is usually used. Used.

In general, such a display device is required to have, for example, high backlight luminance and no luminance unevenness. Usually, since the linear light sources are installed at regular intervals, large luminance unevenness occurs in the direction in which the linear light sources are arranged. For this reason, a diffusion plate or the like for diffusing light is disposed above the linear light source. Further, in order to improve the luminance, a lens sheet or the like in which a plurality of triangular prisms are arranged is disposed above the diffusion plate.
JP 2007-11292 A JP 2002-352611 A

  As described above, conventionally, optical sheets such as a diffusion sheet and a lens sheet are provided for each function, and a plurality of objects are achieved by superimposing them. However, when an optical sheet is provided for each function as described above, it is necessary to dispose many optical sheets between the light source and the display panel. For this reason, a boundary surface and an air layer increase on the optical path, which causes a decrease in light use efficiency as a whole apparatus and becomes a factor that hinders a reduction in thickness.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical sheet that can be thinned without lowering the light use efficiency, an illumination device including the optical sheet, and a display device. Is to provide.

  The first optical sheet according to the present invention has a plurality of three-dimensional shapes in the same plane, and each three-dimensional shape represents a surface shape in one direction x in the plane as a function f (x) and is orthogonal to the direction x. When the surface shape in the direction y is represented by a function g (y), the surface shape is represented by f (x) + g (y). The surface shape represented by the function f (x) is a columnar shape including an aspherical surface or a polygonal columnar shape, and the surface shape represented by the function g (y) is a triangular prism shape. The “triangular prism shape” is not limited to a literal triangular prism shape, and may be any shape having two inclined surfaces on the side surface, for example, a concept including a shape having a curved surface at the apex portion of the triangular prism. And

  The second optical sheet according to the present invention has a plurality of three-dimensional shapes in the same plane, and each three-dimensional shape represents a surface shape in one direction x in the plane as a function f (x) and is orthogonal to the direction x. When the surface shape in the direction y is represented by a function g (y), the surface shape is represented by f (x) + g (y). The surface shapes represented by the function f (x) and the function g (y) are respectively columnar shapes including aspheric surfaces or polygonal columnar shapes.

  The third optical sheet according to the present invention has a plurality of three-dimensional shapes in the same plane, and each three-dimensional shape represents a surface shape in one direction x in the plane as a function f (x) and is orthogonal to the direction x. When the surface shape in the direction y is represented by a function g (y), the surface shape is represented by f (x) + g (y).

  A first illumination device according to the present invention includes a plurality of line light sources and an optical sheet that transmits light emitted from the line light sources, and the optical sheet has a configuration similar to that of the first optical sheet. It is.

  A second illumination device according to the present invention includes a plurality of point light sources and an optical sheet that transmits light emitted from the point light sources, and the optical sheet has a configuration similar to that of the second optical sheet. It is.

  A first display device according to the present invention includes a plurality of line light sources, an optical sheet that transmits light emitted from the line light source, and a display panel that displays an image based on the light transmitted through the optical sheet. The configuration is the same as that of the first optical sheet.

  A second display device according to the present invention includes a plurality of point light sources, an optical sheet that transmits light emitted from the point light source, and a display panel that displays an image based on the light transmitted through the optical sheet. The second optical sheet has a configuration similar to that of the second optical sheet.

  In the first optical sheet, the first illumination device, and the first display device according to the present invention, each solid shape is represented by a function f (x) and a surface shape represented by a function g (y). And the surface shape represented by the function f (x) has a columnar shape including an aspherical surface or a polygonal columnar shape, so that light in the x direction is a plurality of planes of a polygonal columnar shape. Or it is divided into a plurality of parts by an aspherical surface.

  On the other hand, since the surface shape represented by the function g (y) is a triangular prism shape, incident light having an angle that does not cause total reflection at the prism slope is refracted by the prism surface, and the light rises in the front direction. . When a light reflector is provided below the optical sheet, light incident on the prism slope at a predetermined angle (front light) is totally reflected by the two slopes and reaches the reflection sheet and diffuses. By doing so, it becomes light with various angles (recycling effect). A part of the recycled light is raised in the front direction due to the refraction effect of the prism surface, and part of the light is totally reflected and returned to the light reflecting plate side again. By repeating this action, the luminance in the front direction is improved. Furthermore, this recycling effect increases optical mixing, and uneven brightness is effectively reduced. Therefore, the function of reducing the luminance unevenness and the function of improving the front luminance are simultaneously exhibited with one optical sheet.

  In particular, in the first lighting device and the first display device, the first optical sheet is disposed on the plurality of line light sources, and the extending direction of the line light sources is equal to the y direction. The surface shape represented by the function f (x) is exhibited in the arrangement direction, and the surface shape represented by the function g (y) is exhibited in the extending direction of the line light source. Conventionally, since the line light sources are arranged at regular intervals, a large luminance unevenness occurs in the arrangement direction due to the light source image formed by each line light source. In the present invention, the light source image is divided in the arrangement direction of the line light sources. Therefore, the function of reducing luminance unevenness in the x direction is effectively exhibited. Further, the light mixing is enhanced by the recycling effect due to the shape of the linear light source in the extending direction (y direction), and the luminance unevenness reducing function is more effectively exhibited.

  In the second optical sheet, the second illumination device, and the second display device according to the present invention, each solid shape is represented by a function f (x) and a surface shape represented by a function g (y). And the surface shape represented by the function f (x) and the function g (y) has a columnar shape including an aspherical surface or a polygonal columnar shape, so that the incident light is in the x direction and It is divided into a plurality of parts in both directions in the y direction. Therefore, in one optical sheet, the luminance unevenness is reduced two-dimensionally on the plane including the x direction and the y direction.

  In particular, in the second lighting device and the second display device, the second optical sheet is disposed on the plurality of point light sources, thereby effectively reducing luminance unevenness caused by the arrangement of the point light sources. it can.

  The third optical sheet according to the present invention has a plurality of three-dimensional shapes in the same plane, and each three-dimensional shape is represented by a surface shape represented by a function f (x) and a surface shape represented by a function g (y). Are superimposed on each other, the functions based on the respective surface shapes are simultaneously exhibited in each of the x direction and the y direction.

  According to the first optical sheet, the first illumination device, and the first display device according to the present invention, the three-dimensional shape provided on the optical sheet is expressed by the surface shape represented by the function f (x) and the function g. The surface shape represented by (y) is superimposed on the surface shape, and the surface shape represented by the function f (x) is a columnar shape including an aspherical surface or a polygonal columnar shape, and the function g ( Since the surface shape represented by y) has a triangular prism shape, the surface shape represented by the function f (x) exhibits a function of reducing luminance unevenness, while represented by the function g (y). The surface shape to be displayed exhibits a function of improving the front luminance. Therefore, two functions are compatible with one optical sheet, and compared to the case of using two optical sheets, a diffusion sheet for reducing luminance unevenness and a lens sheet for increasing front luminance as in the prior art. As a result, the area that becomes the air layer and the boundary surface on the optical path is reduced, and the number of parts is reduced. Therefore, it is possible to reduce the thickness of the entire apparatus without reducing the light utilization efficiency.

  In particular, when a light reflecting plate is provided below the optical sheet, light mixing is enhanced by the recycling effect of the triangular prism shape, so that the luminance unevenness is effectively reduced, which is advantageous for thinning.

  In particular, in the first lighting device and the first display device, the first optical sheet is disposed on a surface light source including a plurality of line light sources, and the extending direction of the line light sources is equal to the y direction. Then, the function of reducing the luminance unevenness is exhibited in the arrangement direction of the line light sources, and the function of improving the front luminance is exhibited in the extending direction of the line light sources. Therefore, these two functions are more effectively exhibited.

  According to the second optical sheet, the second illumination device, and the second display device according to the present invention, each three-dimensional shape is represented by a surface shape represented by a function f (x) and a function g (y). A column shape including an aspherical surface or a polygonal column shape, and a surface shape represented by a function f (x) and a surface shape represented by a function g (y). In one optical sheet, luminance unevenness is reduced two-dimensionally on a plane including the x direction and the y direction. Therefore, since it is not necessary to stack a plurality of diffusion sheets, the area that becomes an air layer or a boundary surface on the optical path is reduced, and the number of parts is reduced. Therefore, it is possible to reduce the thickness of the entire apparatus without reducing the light utilization efficiency.

  In particular, according to the second illumination device and the second display device, the second optical sheet is arranged on the plurality of point light sources, and thus the function of reducing the luminance unevenness in the in-plane two-dimensional direction. Is effectively exhibited, and uniform surface emission can be obtained.

  According to the third optical sheet of the present invention, a plurality of three-dimensional shapes are provided in the same plane, and each three-dimensional shape is represented by a surface shape represented by a function f (x) and a function g (y). By having a surface shape obtained by superimposing the surface shape, a function based on each surface shape is simultaneously exhibited in each of the x direction and the y direction. Therefore, it is not necessary to stack a plurality of optical sheets for each function, and the area that becomes an air layer or a boundary surface on the optical path is reduced, and the number of parts is reduced. Therefore, it is possible to reduce the thickness of the entire apparatus without reducing the light utilization efficiency.

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

[First Embodiment]
FIG. 1 is a perspective view illustrating a schematic configuration of an optical sheet (optical sheet 1) according to the first embodiment of the present invention. The optical sheet 1 includes a plurality of convex portions 10 arranged in a matrix on the same plane. For example, the optical sheet 1 is disposed and used immediately above a surface light source formed by arranging a plurality of line light sources such as fluorescent tubes or a surface light source formed by arranging a plurality of point light sources such as LEDs (Light Emitting Diodes). It is what is done.

  The optical sheet 1 is made of a translucent resin material, for example, polycarbonate, PMMA (polymethyl methacrylate), or a polystyrene-based thermoplastic resin. In addition, the magnitude | size, arrangement | positioning space | interval, the number, etc. of the some convex part 10 provided in the optical sheet 1 are not necessarily limited to what was shown in FIG. 1, and are determined by the specification aspect of an optical sheet.

  The convex portion 10 has a surface shape represented by a function f (x) where y is not a variable, where x is one direction in the sheet plane and y is a direction perpendicular to the x direction, Has a surface shape obtained by superimposing the surface shapes represented by a function g (y) that does not take as a variable. That is, each convex portion 10 has a surface shape represented by Z = f (x) + g (y), where Z is the overall surface shape.

  For example, the entire surface shape of each convex portion 10 is an optical sheet 1x provided with a plurality of convex portions 10x in which the surface shape in the x direction as shown in FIG. 2A is represented by a function f (x). The optical sheet 1y provided with a plurality of convex portions 10y whose surface shape in the y direction is represented by the function g (y) as shown in FIG. 2B is superposed. In particular, the surface shape represented by the function f (x) is a column shape including an aspheric surface (hereinafter simply referred to as “aspheric surface shape”), and the surface shape represented by the function g (y). Is a triangular prism shape, preferably an isosceles triangular prism shape with an apex angle of 90 °, which is highly recyclable.

  Such an optical sheet 1 can be easily produced by, for example, a mask imaging method. In the mask imaging method, an image formed by a mask is transferred to an object to be processed through a lens using an excimer laser, a carbon dioxide gas laser, or the like. In particular, in the biaxial dragging mask imaging method, it is possible to perform fine laser processing independently on each of the two axes of the workpiece. For this reason, it is suitable for preparation of the optical sheet 1 which has the surface shape mutually independent in the x direction and the y direction. For example, in the case of forming the surface shape as shown in FIG. 1, for example, masks 100a and 100b as shown in FIGS. 3A and 3B are used.

  The mask 100a is a mask for forming a surface shape represented by a function f (x), that is, an aspheric shape, and has a plurality of openings 101a having a shape represented by the function f (x). The mask 100b is a mask for forming a surface shape represented by the function g (y), that is, a prism shape, and has a plurality of openings 101b having a shape represented by the function g (y). Note that the number of openings 101a and 101b provided in the masks 100a and 100b is not particularly limited, but a desired shape can be formed in a shorter time as the number increases. Further, an area in which an opening pattern having a shape represented by a function f (x) is formed on one mask and an area in which an opening pattern having a shape represented by a function g (y) is formed. It is also possible to use different pattern areas depending on the direction of processing.

  First, as shown in FIG. 4, the mask 100a is placed above the sheet 1a in the direction shown in the figure, and dragging is performed in the y direction using a lens (not shown), as shown in FIG. A convex portion 10x having a surface shape represented by a function f (x) in the x direction is formed. At this time, the sheet 1a may be fixed and the mask 100a may be shifted and irradiated with the laser beam B. Conversely, the mask 100a may be fixed and the sheet 1a may be shifted and irradiated with the laser beam B. May be. Further, the optical system for irradiating the laser beam B may be shifted.

  Next, as shown in FIG. 5, the mask 100b is placed above the sheet 1b in the direction shown in the figure, and dragging is performed in the x direction, so that the function g (y) in the y direction as shown in FIG. The surface shape represented by y) is superimposed, and the optical sheet 1 shown in FIG. 1 is completed.

  As described above, it is preferable to first form the surface shape (aspherical shape) of the function f (x) and then superimpose the surface shape (prism shape) of the function g (y) thereon. . That is, it is better to form a duller surface shape first. Thereby, the surface shape represented by the function f (x) and the function g (y) can be formed with high accuracy, and a desired shape can be easily obtained.

  Next, operations and effects of the optical sheet 1 of the present embodiment will be described with reference to FIGS. 6 and 7. In the optical sheet 1, each convex portion 10 is a surface in which the surface shape represented by the function f (x) in the x direction in the sheet surface and the surface shape represented by the function g (y) in the y direction are superimposed. By having the shape, the function based on each surface shape is exhibited simultaneously in each of the x direction and the y direction.

  In particular, as shown in FIG. 6, the light (L1) in the x direction out of the light incident on the optical sheet 1 is mainly due to the aspherical surface shape represented by the function f (x). It is divided into a plurality of parts (for example, L1a) under the action of refraction. Therefore, luminance unevenness is reduced in the x direction.

  On the other hand, as shown in FIG. 7, the light in the y direction out of the light incident on the optical sheet 1 represented by the function g (y) has a triangular prism shape in the surface shape represented by the function g (y). As a result, the light L2 incident on the slope of the prism at a predetermined angle is raised in the front direction by the action of refraction (L2a). In addition, the light L3 incident on the optical sheet 1 at a perpendicular or near-perpendicular angle is totally reflected on the surface of the optical sheet 1 (interface between the optical sheet and the air layer) and then below the optical sheet 1 (L3a). Returned (recycling effect). At this time, when a reflection sheet is provided below the optical sheet 1 (below the light source), the light L3a is diffusely reflected at various angles by the reflection sheet, and a part of the light is raised in the front direction. And a part is returned downward again. By repeating this, the front luminance is improved. In addition, since the light mixing is improved by repeating the diffuse reflection by the reflection sheet, the function of reducing the luminance unevenness is assisted (assist effect).

  As described above, since the optical sheet 1 has a surface shape in which the aspherical shape in the x direction and the prism shape in the y direction are superimposed, the function of reducing luminance unevenness in the x direction is exhibited. On the other hand, the function of improving the front luminance is exhibited in the y direction. Therefore, two functions are compatible with one optical sheet. Compared to the case of using two optical sheets, a diffusion sheet for reducing luminance unevenness and a lens sheet for increasing front luminance, as in the prior art, there is an area that becomes an air layer or a boundary surface on the optical path. As it decreases, the number of parts decreases. Therefore, it is possible to reduce the thickness of the entire apparatus without reducing the light utilization efficiency. Moreover, since the brightness unevenness reduction effect is enhanced by the assist effect, the distance from the optical sheet (diffusion plate) can be shortened, and the thickness can be further reduced.

(Modification 1)
Next, Modification 1 (convex portion 20, convex portion 30, convex portion 40) of each convex portion of the optical sheet 1 of the present embodiment will be described with reference to FIGS.

  8A and 8B are perspective views illustrating schematic configurations of the convex portion 20 and the convex portion 30, respectively. The convex part 20 and the convex part 30 have the same configuration as the convex part 10 except that the combination of the surface shapes in the x direction and the y direction is different. The convex portion 20 has a pentagonal prism shape whose surface shape is represented by a function f (x) in the x direction, and a triangular prism shape whose surface shape is represented by a function g (y) in the y direction. . The convex portion 30 has a pentagonal prism shape in the surface shape represented by the function f (x) in the x direction, and the top surface of the triangular prism shape in the surface shape represented by the function g (y) in the y direction. The corner portion has a curved surface.

  As shown in FIG. 8A, the surface shape represented by the function f (x) may be a polygonal column shape having three or more surfaces. In this case, as the number of slopes of the convex portion increases, the number of divisions of the luminous flux of incident light increases, so that the luminance unevenness is more effectively reduced. Therefore, it is preferable that the number of faces in the surface shape represented by the function f (x) is large. With such a configuration, the function of reducing luminance unevenness is exhibited in the x direction, while the function of improving front luminance is exhibited in the y direction. Therefore, the luminance unevenness can be reduced and the front luminance can be improved with one optical sheet.

  As shown in FIG. 8B, the surface shape represented by the function g (y) may be a triangular prism shape having a curved surface at the apex portion. Even with such a surface shape, the front luminance can be improved by condensing in the front direction or by light mixing.

  FIG. 9 is a perspective view illustrating a schematic configuration of the convex portion 40. The convex part 40 is an array in which convex parts 40a and convex parts 40b are alternately adjacent to each other. Thus, you may make it comprise by arranging the convex parts 40a and 40b which have mutually different surface shape. Thereby, since the number of planes (slopes) can be increased, the number of divisions of light is increased, and luminance unevenness is more effectively reduced. The convex portions 40a and 40b do not necessarily have to be adjacent to each other. For example, you may make it arrange | position alternately every two so that it may become 40a, 40a, 40b, 40b ... in order. Moreover, you may arrange | position the convex parts 40a and 40b at random. Further, the surface shapes to be combined are not limited to two, and three or more surface shapes may be combined.

  Next, an application example of the optical sheet according to the present invention will be described taking the optical sheet 1 shown in FIG. 1 as an example.

  FIG. 10 is a perspective view illustrating a schematic configuration of the illumination device 2 using the optical sheet 1. The illumination device 2 includes the optical sheet 1 immediately above the plurality of line light sources 11, and a reflector 200 is provided below the line light sources 11. The linear light source 11 is arranged so that its extending direction is equal to the y direction of the optical sheet 1.

  The linear light source 11 includes a linear light source such as a fluorescent tube, for example, a cold cathode fluorescent lamp called a cold cathode fluorescent lamp (CCFL). In the illuminating device 2, a plurality of linear light sources 11 arranged at regular intervals are used as light sources for obtaining surface light emission. The reflection plate 200 diffuses and reflects the light reflected by the optical sheet 1 and returning to the line light source 11 side.

  In such an illuminating device 2, the optical sheet 1 of the present embodiment is provided on the plurality of line light sources 11, and in particular, the extending direction of the line light source 11 and the y direction of the optical sheet 1 are equal. The function of the surface shape represented by the function f (x) is exhibited in the direction orthogonal to the extending direction of the line light source 11 (hereinafter referred to as the arrangement direction), and in the extending direction of the light source 11, the function g ( The function of the surface shape represented by y) is exhibited. Usually, since the line light sources 11 are arranged at regular intervals, large luminance unevenness occurs in the arrangement direction. However, in the illumination device 2, the luminance unevenness is reduced in the arrangement direction of the line light sources 11, and the line light source is reduced. The front luminance is improved in the extending direction of 11. Therefore, each function in the x direction and the y direction of the optical sheet 1 is effectively exhibited, and surface emission with uniform and high front luminance can be realized.

  In addition, in the y direction, the light L3 (see FIG. 7) incident on the optical sheet 1 at an angle that is perpendicular or nearly perpendicular is totally reflected by the prism-shaped slope (light L3a) and then returned to the line light source 11 side. . The light L3a is diffused and reflected by the reflecting plate 200 and is incident on the optical sheet 1 again. Thus, the light incident on the optical sheet 1 again is raised in the front direction under the action of refraction depending on the incident angle, or returned to the light source side under the action of total reflection. Thus, by making the light totally reflected by the optical sheet 1 incident on the optical sheet 1 again by the reflection plate 200 (recycling effect), the light utilization efficiency is improved and the front luminance is further improved as a whole.

  Furthermore, since light mixing occurs due to the light recycling effect in the y direction, the effect of reducing luminance unevenness in the x direction is assisted. Therefore, the luminance unevenness reducing function in the x direction can be more effectively exhibited by a combination of an aspherical shape in the x direction and a prism shape in the y direction.

  FIG. 11 is a perspective view illustrating a schematic configuration of the display device 3 using the optical sheet 1 illustrated in FIG. 1. The display device 3 is a backlight type liquid crystal display device that emits light from the back surface of a display panel such as a liquid crystal panel. For example, the optical sheet 1, the diffusion sheet 12, and the brightness enhancement film 13 are disposed above the line light source 11. The polarizing plate 14, the liquid crystal panel 15, and the polarizing plate 16 are arranged in this order, and a reflecting plate 200 is provided below the line light source 11. Further, in the display device 3, the line light source 11 is placed vertically with respect to the display surface, and is configured to extend in the vertical direction when viewed from the viewer. In the display device 3, the optical sheet 1, the line light source 11, and the reflection plate 200 correspond to the illumination device 2. Therefore, below, description about the optical sheet 1 and the illuminating device 2 is abbreviate | omitted suitably.

  The diffusion sheet 12 has translucency and is provided for light collection or light diffusion. The diffusion sheet 12 is a concept including a wide range from a plate-like relatively thick to a film-like relatively thin, and these may be used alone or in combination. May be. The diffusion sheet 12 is made of, for example, acrylic or polycarbonate, and specifically, DR-60C (manufactured by Nitto Resin Co., Ltd .: trade name), NB01 (manufactured by Mitsubishi Rayon Co., Ltd .: trade name), or the like is used. .

  The brightness enhancement film 13 is, for example, a multilayer film having an anisotropic refractive index, and transmits only a certain amount of polarized light and reflects polarized light having a component orthogonal thereto. Since the polarization transmission axis of the brightness enhancement film 13 is arranged to be equal to the polarization transmission axis of the polarizing plate 14 described later, the light absorbed by the polarizing plate 14 is returned to the reflecting plate 200 to be diffused and reflected. Can be recycled.

  The polarizing plates 14 and 16 are optical films that allow only incident polarized light and outgoing light of the liquid crystal panel 15 to pass therethrough. These polarizing plates 14 and 16 are arranged so that their polarization axes are orthogonal to each other, whereby light from the light source 11 side is transmitted or blocked via the liquid crystal panel 15.

  The liquid crystal panel 15 includes, for example, a TFT (Thin Film Transistor) substrate 151, a CF (Color Filter) substrate 153, and a liquid crystal layer 152 provided between the TFT substrate 151 and the CF substrate 153. I have. The TFT substrate 151 includes, for example, a TFT switching element including a plurality of pixel electrodes arranged in a matrix on a transparent substrate, and includes a gate, a source, a drain, and the like that respectively drive the plurality of pixel electrodes. A gate line, a source line, and the like (not shown) connected to the element are provided. The CF substrate 153 includes a color filter in which, for example, red (R), green (G), and blue (B) filters are provided in a stripe pattern on a transparent substrate, and a counter electrode over almost the entire effective display area. And are arranged. The liquid crystal layer 152 is composed of nematic liquid crystal having a driving method such as a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, and an IPS (In Place Switching) mode. Note that an alignment film or the like for regulating the alignment state of the liquid crystal layer 152 may be further provided at each interface between the TFT substrate 151 and the CF substrate 153 and the liquid crystal layer 152.

  In the display device 3, the extending direction of the line light source 11 of the lighting device 2 is equal to the vertical direction viewed from the viewer (hereinafter simply referred to as the vertical direction). That is, the y direction of the optical sheet 1 is equal to the vertical direction. Here, in the optical sheet 1, the light in the y direction is raised in the front direction by the surface shape represented by the function g (y), that is, the prism shape. In general, in a liquid crystal television application, the extending direction of the line light source is often horizontal when viewed from the viewer. For this reason, when the line light source 11 is arranged in the horizontal direction and the extending direction of the line light source 11 is made equal to the y direction, the viewing angle characteristic in the horizontal direction may be deteriorated. In general, it is not preferable that the viewing angle in the horizontal direction becomes narrow in television applications. As a solution in such a case, as shown in FIG. 11, the extending direction of the line light source 11 is equal to the vertical direction. It is possible to be. Thereby, a favorable viewing angle characteristic can be maintained.

[Second Embodiment]
FIG. 12 is a perspective view illustrating a schematic configuration of an optical sheet (optical sheet 4) according to the second embodiment of the present invention. The optical sheet 4 includes a plurality of convex portions 50 arranged in a matrix on the same plane. For example, the optical sheet 4 is used by being arranged on a light source that emits surface light by arranging a plurality of point light sources such as a surface light source such as a fluorescent tube or a line light source such as an LED (Light Emitting Diode). It is what is done.

  The optical sheet 4 is made of a resin material having translucency, for example, polycarbonate, PMMA (polymethyl methacrylate), or a polystyrene-based thermoplastic resin. In addition, the magnitude | size, arrangement | positioning space | interval, the number, etc. of the some convex part 50 provided in the optical sheet 4 are not necessarily limited to what was shown in FIG. 12, but are determined by the specification aspect of an optical sheet.

  The convex portion 50 has a surface shape represented by a function f (x) where y is not a variable, where x is one direction in the sheet plane and y is a direction perpendicular to the x direction, Has a surface shape obtained by superimposing the surface shapes represented by a function g (y) that does not take as a variable. That is, each convex part 50 has a surface shape represented by Z = f (x) + g (y), where Z is the overall surface shape.

  For example, the entire surface shape of each convex portion 50 is an optical sheet 4x provided with a plurality of convex portions 50x in which the surface shape in the x direction as shown in FIG. 13A is represented by a function f (x). The optical sheet 4y provided with a plurality of convex portions 50y whose surface shape in the y direction is represented by the function g (y) as shown in FIG. 13B is superposed. In particular, the surface shape represented by the function f (x) and the surface shape represented by the function g (y) are each aspherical.

  In the optical sheet 4 of the present embodiment, each convex portion 50 has a surface shape represented by a function f (x) in the x direction in the sheet surface and a surface shape represented by a function g (y) in the y direction. And the surface shapes represented by the function f (x) and the function g (y) are aspherical, respectively, so that light in each of the x direction and the y direction can be obtained. Is divided into a plurality of parts under the action of refraction. Therefore, luminance unevenness is reduced two-dimensionally in a plane including the x direction and the y direction. Accordingly, it is not necessary to stack a plurality of diffusion sheets and the like, so that the area that becomes the air layer and the boundary surface on the optical path is reduced and the number of parts is reduced. Thereby, it is possible to reduce the thickness of the entire apparatus without reducing the light utilization efficiency.

(Modification 2)
Next, modification 2 (convex portion 60, convex portion 70) of each convex portion of the optical sheet 4 of the present embodiment will be described with reference to FIG.

  14A and 14B are perspective views illustrating schematic configurations of the convex portion 60 and the convex portion 70, respectively. The convex portion 60 and the convex portion 70 have the same configuration as the convex portion 50 except that the combination of the surface shapes in the x direction and the y direction is different. In the convex portion 60, the surface shape represented by the function f (x) in the x direction is an aspherical shape, and the surface shape represented by the function g (y) in the y direction is a pentagonal prism shape. . The convex portion 70 has a hexagonal columnar surface shape represented by a function f (x) in the x direction, and a pentagonal columnar shape represented by a function g (y) in the y direction. .

  Next, the illuminating device 6 using the optical sheet 4 shown in FIG. 12 is demonstrated with reference to FIG.

  FIG. 15 is a perspective view illustrating a schematic configuration of the illumination device 6 using the optical sheet 4. The illuminating device 6 includes the optical sheet 4 immediately above a surface light source on which a plurality of point light sources 21 are arranged, and a reflector 200 is provided below the point light source 21. The point light source 21 is configured by a point light source such as an LED or an organic EL (Electro Luminescence).

  Such an illuminating device 6 has the function of causing the point light source 21 to express the surface shape represented by the function f (x) and the function g (y) by including the optical sheet 4 of the present embodiment. Are demonstrated at the same time. Normally, when a plurality of point light sources 21 are arranged, luminance unevenness occurs in both the x direction and the y direction. However, in this embodiment, the luminance unevenness is reduced in each of the x direction and the y direction. Therefore, uniform surface emission can be obtained with one optical sheet.

  The optical sheet 4 shown in FIG. 12 can also be applied to the display device 7 as shown in FIG. The display device 7 has the same configuration as the display device 3 of the first embodiment except that the configuration of the optical sheet and the light source is different. Further, the optical sheet 4, the point light source 21, and the reflection plate 200 correspond to the lighting device 6.

  Next, examples of the present invention will be described.

(Example 1-1)
As Example 1-1, the following simulation was performed about the illuminating device 2 using the optical sheet 1 of 1st Embodiment. Specifically, in the illumination device 2 shown in FIG. 10, the luminance distribution and luminance orientation of light emitted from above the optical sheet 1 were measured. At this time, the distance d1 between the line light sources 11 is 27.8 mm, the distance d2 between the line light source 11 and the optical sheet 1 is 16.9 mm, the thickness of the optical sheet 1 is 2 mm, and the pitch Px in the x direction of each convex portion 10 is 100 μm. The pitch Py in the y direction of each convex portion 10 was 50 μm. Moreover, it arrange | positioned so that the extension direction of the line light source 11 and the y direction of the optical sheet 1 may become equal.

  Further, the surface shape in the x direction of each convex portion 10 is an aspherical shape represented by the function f (x) shown in FIG. 17A, and the surface shape in the y direction is shown in FIG. 17B. The triangular prism shape represented by the function g (y) (the isosceles triangular prism shape having an apex angle of 90 °) was used. In addition, the unit of the numerical value in FIG. 17 shall be micrometer (micrometer).

  FIG. 21 shows a simulation result for the luminance orientation (viewing angle characteristics) in the x direction and the y direction, and FIG. 25 shows a simulation result for the luminance distribution in the illuminating device having such a configuration. In FIG. 21, the positions indicated by dotted lines (−27.8, 0, 27.8) indicate the positions where the light sources are arranged.

(Comparative Example 1-1)
As Comparative Example 1-1 of Example 1-1, as shown in FIG. 18, an optical sheet 102 having an aspheric shape represented by a function f (x) only in the x direction of each convex portion was used. A simulation was performed on the lighting device. At this time, as the function f (x), the same function as in FIG. 17A is used, except that only one surface in the x direction has a surface shape represented by the function f (x). As the same conditions as in Example 1-1, the luminance orientation and the luminance distribution were measured. In Comparative Example 1-1, the y direction and the extending direction of the light source 11 were arranged to be equal. FIG. 22 shows the simulation result for the luminance orientation of Comparative Example 1-1, and FIG. 25 shows the simulation result for the luminance distribution together with the result of Example 1-1.

(Comparative Example 1-2)
As Comparative Example 1-2 of Example 1-1, a simulation of luminance orientation and luminance distribution was performed for an illumination device using the optical sheet 103 as shown in FIG. The optical sheet 103 of Comparative Example 1-2 has a surface shape represented by Z = max {f (x), g (y)} where Z is the entire surface shape of each convex portion. Except for this, the configuration is the same as in Example 1-1. FIG. 23 shows the result of the luminance alignment of Comparative Example 1-2, and FIG. 25 shows the result of the luminance distribution together with the result of Example 1-1.

  In addition, the surface shape in the comparative examples 1-1 and 1-2 is a shape that can be easily processed by a conventionally used cutting method. By this cutting method, for example, an aspherical shape and a triangular prism shape are used. Is a shape generally recalled when considering superposition.

(Comparative Example 1-3)
As Comparative Example 1-3 of Example 1-1, a simulation of luminance orientation and luminance distribution was performed for a lighting device using the optical sheet 104 as shown in FIG. The optical sheet 104 of Comparative Example 1-3 has a surface shape represented by Z = min {f (x), g (y)} where Z is the entire surface shape of each convex portion. Except for this, the configuration is the same as in Example 1-1. FIG. 24 shows the result of the luminance alignment of Comparative Example 1-3, and FIG. 25 shows the result of the luminance distribution together with the result of Example 1-1.

  FIG. 26 shows a summary of front luminance (average value of in-plane distribution) for Example 1-1 and Comparative Examples 1-1 to 1-3.

  From the results of FIGS. 21 and 22, the luminance in the vicinity of the viewing angle of 0 °, that is, the front luminance is improved in Example 1-1 in both the x direction and the y direction in comparison with Comparative Example 1-1 (17 .8% improvement). In addition, from the result of FIG. 25, in Example 1-1 in which the prism shape is arranged in the y direction, the luminance unevenness is further reduced and uniform compared to Comparative Example 1-1 in which the prism shape is not arranged in the y direction. It can be seen that the state is maintained. That is, in Example 1-1 and Comparative Example 1-1, Example 1-1, in which the prism shape is arranged in the y direction, although the surface shape in the x direction is the same aspherical shape, As a result, the luminance unevenness was reduced. This indicates that light mixing occurs due to the recycling effect in the prism shape in the y direction, and the luminance unevenness reducing function in the aspherical shape in the x direction is more effectively exhibited.

  From the results of FIGS. 23 to 26, it can be seen that in Example 1-1, the front luminance is improved and the luminance unevenness is reduced as compared with Comparative Example 1-2. On the other hand, in Comparative Example 1-3, it can be seen that although the front luminance is high, the luminance unevenness is hardly reduced. Therefore, when the overall surface shape of each convex portion is Z, the surface shape represented by Z = f (x) + g (y), that is, the surface where each convex portion is represented by the function f (x). It was shown that the respective functions in the x direction and the y direction can be exhibited simultaneously by superimposing the shape and the surface shape represented by the function g (y).

(Example 2-1)
Next, as Example 2-1, a simulation of luminance orientation and luminance distribution for an illuminating device (FIG. 27) using an optical sheet 5 having convex portions 40 (convex portions 40a, convex portions 40b) according to a modification. Went. At this time, the distance d1 between the line light sources 11 is 33.0 mm, the distance d2 between the line light source 11 and the optical sheet 5 is 15.5 mm, the thickness of the optical sheet 5 is 2 mm, and the pitch Pxa of the convex portions 40a in the x direction is 100 μm. The pitch Pxb in the x direction of the protrusions 40b was 75 μm, and the pitch Py in the y direction of the protrusions 40a and 40b was 50 μm. Further, the surface shape in the x direction of each of the convex portions 40a and 40b is a polyhedral shape represented by the function f (x) shown in FIG. On the other hand, the surface shape in the y direction is an isosceles triangular prism shape as shown in FIG. For other conditions, a simulation was performed in the same manner as in Example 1, and the results for the luminance orientation are shown in FIG. 30, and the results for the luminance distribution are shown in FIG.

(Comparative Example 2-1)
As Comparative Example 2-1 of Example 2-1, as shown in FIG. 29, an optical sheet 105 having a polygonal column shape represented by a function f (x) only in the x direction of each convex portion was used. A simulation was performed on the lighting device. At this time, the function f (x) is the same as that shown in FIG. 28, except that the surface shape represented by the function f (x) is attached to only one axis in the x direction. As conditions similar to 2-1, luminance distribution and luminance orientation were measured. In Comparative Example 2-1, the y direction and the extending direction of the light source 11 were arranged to be equal. FIG. 31 shows the result of the luminance / luminance orientation of Comparative Example 2-1, and FIG. 32 shows the result of the luminance distribution together with the result of Example 2-1.

  From the results of FIGS. 30 and 31, it can be seen that in both the x direction (vertical direction) and the y direction (horizontal direction), the viewing angle is near 0 °, that is, the front luminance is improved. In addition, it can be seen from the results of FIG. 32 that both the example 2-1 and the comparative example 2-1 maintain a uniform state without uneven luminance due to the arrangement of the line light sources 11. In particular, in Example 2-1, the front luminance was improved by 4.5% compared to Comparative Example 2-1. Accordingly, even when a polygonal prism shape in the x direction and a triangular prism shape in the y direction are superposed on the line light source extending in the y direction, the respective functions can be exhibited at the same time. It was shown that two functions are compatible.

  From the above, in the illuminating device in which the optical sheet is provided immediately above the plurality of line light sources 11, each convex portion has a surface shape represented by the function f (x) in the x direction and a function g (y in the y direction. The surface shape represented by the function f (x) is an aspherical shape, and the surface shape represented by the function g (y) is a triangular prism shape. As a result, the luminance unevenness can be reduced and at the same time the front luminance can be improved. Therefore, it is possible to achieve both the function of reducing luminance unevenness and the function of improving front luminance with a single optical sheet.

  Although the embodiments and examples of the present invention have been described above, the present invention is not limited to these embodiments and the like, and various modifications are possible.

  For example, in the above-described embodiment, light is applied to the optical sheet 1 in which the surface shape represented by the function f (x) is an aspherical shape and the surface shape represented by the function g (y) is a triangular prism shape. The light source to be incident has been described by taking as an example one in which a plurality of line light sources 11 are arranged at a constant interval, but the type of light source is not limited to this, and a two-dimensional surface including the x direction and the y direction The effect of the present invention can be achieved if it is intended for surface light emission. Similarly, a plurality of point light sources 21 are arranged as light sources for the optical sheet 4 in which the surface shape represented by the function f (x) and the surface shape represented by the function g (y) are each aspherical. Although an example has been described, the type of light source is not limited to this.

  In addition, by applying a roughening process such as embossing to the surface side on which no protrusion is formed in the optical sheet, it is possible to prevent scratches during handling and to alleviate deterioration of optical characteristics. . Further, the present invention is not limited to use as a backlight device for a liquid crystal display device. Further, by using a diffusion plate provided with a dot pattern as the diffusive sheet, the apparatus can be thinned by an appropriate combination.

  Moreover, although the method for producing the optical sheet 1 using the mask imaging method has been described, the invention is not limited to this, and the optical sheet 1 can be produced by other methods. For example, it is formed by integral molding (hot pressing) of a thermoplastic resin using a master disk in which a desired shape is cut in the x and y directions, or an energy ray (for example, ultraviolet ray) curable resin on a sheet May be transferred to form a convex portion. In addition, it can be formed by various transfer methods such as melt extrusion and injection molding.

  In the display device 3, the line light source 11 has been described with an example in which the extending direction is equal to the vertical direction viewed from the viewer. However, the arrangement direction of the line light source 11 is of course limited to this. It is not done. The effect of the present invention can be achieved even when the extending direction of the line light source 11 is equal to the horizontal direction as in a general liquid crystal television.

  Further, as the optical sheet, a material mixed with a diffusing material or the like may be used. By doing in this way, the function which reduces a brightness nonuniformity can be improved.

It is a perspective view which shows schematic structure of the optical sheet which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the surface shape of the x direction of the optical sheet shown in FIG. 1, and the y direction. It is a top view of the mask used when producing the optical sheet shown in FIG. It is a perspective view for demonstrating the preparation methods of the optical sheet shown in FIG. It is a perspective view for demonstrating the preparation methods of the optical sheet shown in FIG. It is a figure for demonstrating the effect | action of the incident light in the x direction of the optical sheet shown in FIG. It is a figure for demonstrating the effect | action of the incident light in the y direction of the optical sheet shown in FIG. It is a perspective view which shows schematic structure of the convex part which concerns on the 1st modification of this invention. It is a perspective view which shows schematic structure of the convex part which concerns on the 1st modification of this invention. It is a perspective view which shows schematic structure of the illuminating device which concerns on the 1st Embodiment of this invention. 1 is a perspective view illustrating a schematic configuration of a display device according to a first embodiment of the present invention. It is a perspective view which shows schematic structure of the optical sheet which concerns on the 2nd Embodiment of this invention. It is a figure for demonstrating the surface shape of the x direction of the optical sheet shown in FIG. 12, and the y direction. It is a perspective view which shows schematic structure of the convex part which concerns on the 2nd modification of this invention. It is a perspective view which shows schematic structure of the illuminating device which concerns on the 2nd Embodiment of this invention. It is a perspective view which shows schematic structure of the display apparatus which concerns on the 2nd Embodiment of this invention. It is a figure which shows the function showing the surface shape of each convex part of the optical sheet of Example 1-1. It is a perspective view which shows schematic structure of the illuminating device of the comparative example 1-1. It is a perspective view which shows schematic structure of the illuminating device of Comparative Example 1-2. It is a perspective view which shows schematic structure of the illuminating device of Comparative Example 1-3. It is a characteristic view about the brightness | luminance orientation of Example 1-1. It is a characteristic view about the luminance orientation of Comparative Example 1-1. It is a characteristic view about the luminance orientation of Comparative Example 1-2. It is a characteristic view about the luminance alignment of Comparative Example 1-3. It is a characteristic view about the luminance distribution of Example 1-1 and Comparative Examples 1-1 to 1-3. It is the figure put together about Example 1-1 and the front luminance of Comparative Examples 1-1 to 1-3. It is a perspective view which shows schematic structure of the illuminating device of Example 2-1. It is a characteristic view showing the function f (x) of each convex part of the optical sheet of Example 2-1. It is a perspective view which shows schematic structure of the illuminating device of the comparative example 2-1. It is a characteristic view about the luminance orientation of Example 2-1. It is a characteristic view about the luminance orientation of Comparative Example 2-1. It is a characteristic view about the luminance distribution of Example 2-1 and Comparative Example 2-1.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,4,5 ... Optical sheet | seat, 2,6 ... Illuminating device, 3,7 ... Display apparatus 10, 20, 30, 40, 50, 60, 70 ... Convex part 11,21 ... Light source, 12 ... Diffusing sheet , 13 ... brightness enhancement film, 14, 16 ... polarizing plate, 15 ... liquid crystal panel.

Claims (14)

A plurality of three-dimensional shapes are provided in the same plane,
The three-dimensional shape is expressed as f (x) when the surface shape in one direction x in the plane is represented by a function f (x), and the surface shape in a direction y orthogonal to the direction x is represented by a function g (y). ) + G (y)
The surface shape represented by the function f (x) is a columnar shape including an aspherical surface or a polygonal columnar shape,
The surface shape represented by the function g (y) is a triangular prism shape. The optical sheet according to claim 1, wherein the surface shape represented by the function g (y) is an isosceles triangular prism shape. The optical sheet according to claim 1, wherein the surface shape represented by the function g (y) is an isosceles triangular prism shape having an apex angle of 90 °. The optical sheet according to claim 1, wherein the plurality of three-dimensional shapes are arranged in a matrix. A plurality of three-dimensional shapes are provided in the same plane,
The three-dimensional shape is expressed as f (x) when the surface shape in one direction x in the plane is represented by a function f (x), and the surface shape in a direction y orthogonal to the direction x is represented by a function g (y). ) + G (y)
The surface shape represented by the function f (x) and the surface shape represented by the function g (y) are each a columnar shape including an aspherical surface or a polygonal columnar shape. A plurality of three-dimensional shapes are provided in the same plane,
The three-dimensional shape is expressed as f (x) when the surface shape in one direction x in the plane is represented by a function f (x), and the surface shape in a direction y orthogonal to the direction x is represented by a function g (y). 2) An optical sheet characterized by having a surface shape represented by + g (y). Multiple line light sources;
An optical sheet that transmits light emitted from the line light source,
The optical sheet is
A plurality of three-dimensional shapes are provided in the same plane,
Each of the three-dimensional shapes represents a surface shape in one direction x by a function f (x), and when a surface shape in a direction y orthogonal to the direction x is represented by a function g (y), f (x) + g ( y) having a surface shape represented by
The surface shape represented by the function f (x) is a columnar shape including an aspherical surface or a polygonal columnar shape,
The surface shape represented by the function g (y) is a triangular prism shape. The lighting device according to claim 8, wherein the linear light source is arranged so that an extending direction thereof is equal to the direction y. The lighting device according to claim 7, further comprising a light reflecting plate on the line light source side of the optical sheet. Multiple point sources,
An optical sheet that transmits the light emitted from the point light source,
The optical sheet is
A plurality of three-dimensional shapes are provided in the same plane,
Each of the three-dimensional shapes represents a surface shape in one direction x by a function f (x), and when a surface shape in a direction y orthogonal to the direction x is represented by a function g (y), f (x) + g ( y) having a surface shape represented by
The surface shape represented by the function f (x) and the surface shape represented by the function g (y) are each a columnar shape including an aspherical surface or a polygonal columnar shape. Multiple line light sources;
An optical sheet that transmits the light emitted from the line light source; and a display panel that displays an image based on the light transmitted through the optical sheet.
The optical sheet is
A plurality of three-dimensional shapes are provided in the same plane,
Each of the three-dimensional shapes represents a surface shape in one direction x by a function f (x), and when a surface shape in a direction y orthogonal to the direction x is represented by a function g (y), f (x) + g ( y) having a surface shape represented by
The surface shape represented by the function f (x) is a columnar shape including an aspherical surface or a polygonal columnar shape,
The display device characterized in that the surface shape represented by the function g (y) is a triangular prism shape. The display device according to claim 11, wherein an extending direction of the line light source is equal to a vertical direction on a display surface of the display panel. The display device according to claim 11, further comprising a light reflection plate on a side of the line light source of the optical sheet. Multiple point sources,
An optical sheet that transmits light emitted from the point light source, and a display panel that displays an image based on the light transmitted through the optical sheet,
The optical sheet is
A plurality of three-dimensional shapes are provided in the same plane,
Each of the three-dimensional shapes represents a surface shape in one direction x by a function f (x), and when a surface shape in a direction y orthogonal to the direction x is represented by a function g (y), f (x) + g ( y) having a surface shape represented by
The display device, wherein the surface shape represented by the function f (x) and the surface shape represented by the g (y) are each a columnar shape including an aspherical surface or a polygonal columnar shape.

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