JP5614128B2 - Optical sheet, backlight unit and display device - Google Patents

Description

  The present invention relates to a liquid crystal in which a transmissive or non-transmissive lens sheet and a display optical sheet in pixel units, or an optical sheet, and a display element in which a display pattern is defined according to a transparent state or a scattering state are arranged. The present invention relates to a backlight unit that illuminates a panel from the back side, or a display device including an optical sheet and a backlight unit.

In recent years, display devices using TFT-type liquid crystal panels and STN-type liquid crystal panels have been commercialized mainly in color notebook PCs (personal computers) in the OA field, for example.
In such a liquid crystal display device, a so-called backlight method is employed in which a light source is arranged on the back side of the liquid crystal panel (opposite to the observer side) and the liquid crystal panel is illuminated with light from this light source. ing.

  As a backlight unit employed in this type of backlight system, a light source lamp such as a cold cathode fluorescent lamp (CCFT) is roughly divided into a flat light guide plate made of an acrylic resin having excellent light transmittance. There are a “light guide plate light guide method” (edge light method) for multiple reflection and a “direct type” method that does not use a light guide plate.

  As a liquid crystal display device on which a light guide plate light guide type backlight unit is mounted, for example, the one shown in FIG. 11 is generally known. In addition, FIG. 11 is a figure which shows schematic structure of the display apparatus by which the backlight unit of a light-guide plate light guide system is mounted.

  As shown in FIG. 11, the display device 1 in which the light guide plate light guide type backlight unit is mounted includes a liquid crystal element 10 sandwiched between a front side polarizing plate 6 and a back side polarizing plate 8. A light guide plate 40 is installed on the lower surface (light incident side) of 10.

The light guide plate 40 is formed of a substantially rectangular plate-like PMMA (polymethyl methacrylate) or a transparent base material such as acrylic.
A diffusion film 44 (diffusion layer) is provided between the upper surface (light emitting side) of the light guide plate 40 and the back-side polarizing plate 8.

  Further, the light introduced into the light guide plate 40 is scattered and reflected on the back side of the light guide plate 40 (the lower surface side in FIG. 11) so as to be uniformly uniform in the direction of the liquid crystal element 10. The scattering reflection pattern portion (not shown) is provided by printing or the like. A reflective film 46 (reflective layer) is provided on the lower side (the lower surface side in FIG. 11) of the scattering reflection pattern portion.

  A light source 20 is attached to one side end of the light guide plate 40, and a high-reflectance lamp reflector 22 is provided so as to cover the back side of the light source 20. The lamp reflector 22 is a member for allowing the light from the light source 20 to enter the light guide plate 40 efficiently.

  The above-described scattering reflection pattern portion is formed by printing a mixture of white titanium dioxide (TiO2) powder in a transparent adhesive or the like, printing it in a predetermined pattern (for example, a dot pattern), and drying it. Thus, directivity is imparted to the light incident on the light guide plate 40 and guided to the light exit surface side, thereby increasing the brightness.

  As a liquid crystal display device on which a light guide plate light guide type backlight unit is mounted, in addition to the one shown in FIG. 11, for example, the one shown in FIG. 12 is generally known. In addition, FIG. 12 is a figure which shows schematic structure of the display apparatus by which the backlight unit of a light-guide plate light guide system is mounted.

  As shown in FIG. 12, the display device 1 in which the light guide plate light guide type backlight unit having a configuration different from that shown in FIG. 11 is mounted between the diffusion film 44 and the liquid crystal element 10. Two prism films 48 (prism layers) having a light collecting function are provided. The configuration of the display device 1 shown in FIG. 12 is the same as the configuration of the display device 1 shown in FIG. 11 except that two prism films 48 are provided.

The two prism films 48 condense light emitted from the light exit surface of the light guide plate 40 and diffused by the diffusion film 44 onto the effective display area of the liquid crystal element 10 with high efficiency. This is a member for improving the brightness and increasing the brightness.
However, in the display device 1 shown in FIG. 12, the control of the viewing angle is left only to the diffusibility of the diffusing film 44, which is difficult to control, so that the center is bright when viewed from the front of the display. The characteristics that become darker toward the periphery are inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

  Further, in the display device 1 using the prism film 48 shown in FIG. 12, since two prism films 48 are required, not only the light amount is greatly reduced due to the absorption of the prism film 48 but also the number of members is increased. It was also the cause of the cost increase.

  On the other hand, the direct type backlight unit is used in a display device such as a large liquid crystal TV in which it is difficult to use a light guide plate. As a liquid crystal display device on which a direct type backlight unit is mounted, for example, the one shown in FIG. 13 is generally known. FIG. 13 is a diagram showing a schematic configuration of a display device on which a direct type backlight unit is mounted.

  As shown in FIG. 13, the display device 1 in which the direct type backlight unit is mounted includes a liquid crystal element 10 sandwiched between a front-side polarizing plate 6 and a back-side polarizing plate 8. A plurality of light sources 20 made of fluorescent tubes or the like are provided on the lower surface (light incident side) side. The plurality of light sources 20 are arranged in a direction orthogonal to the thickness direction (vertical direction in FIG. 13) of the liquid crystal element 10.

  A diffusion film 44 (diffusion layer) is provided between the light source 20 and the back side polarizing plate 8.

  And the light radiate | emitted from the light source 20 is diffused with the diffusion film 44, and is condensed on the effective display area of the liquid crystal element 10 with high efficiency. In addition, a lamp reflector 22 is disposed on the back surface of the light source 20 in order to efficiently use light from the light source 20 as illumination light.

  However, also in the display device 1 shown in FIG. 13, since the control of the viewing angle is left only to the diffusibility of the diffusion film 44, and the control is difficult, the central portion is viewed from the front of the display. The characteristic that it becomes bright and becomes darker as it goes to the periphery is inevitable. For this reason, when the liquid crystal screen is viewed from the side, the luminance is greatly reduced, and the light utilization efficiency is reduced.

  Furthermore, even in a display device equipped with a direct-type backlight unit, since two prism films are required when using a prism film, not only the amount of light is greatly reduced due to absorption of the film, but also the number of members. It was also the cause of the increase in cost due to the increase.

  Further, in the display device 1 shown in FIG. 13, if the distance between the adjacent light sources 20 is too wide, luminance unevenness is likely to occur on the screen. This was a cause of increase and cost increase.

  By the way, in the liquid crystal display device (display device) as described above, light weight, low power consumption, high luminance, and thinning are strongly demanded as market needs. The number of liquid crystal display devices used is increasing rapidly.

  In the case of the edge light method described above, the dot pattern printed on the light guide plate becomes more visible as the brightness of the screen increases. Therefore, the optical sheet has a high brightness that makes it difficult to see the dot pattern. Uniformity is required.

On the other hand, in the case of the direct type, the LED is often arranged as a point light source.
So far, the cold cathode tube most used as a light source is a line light source, which requires luminance uniformity only in the direction orthogonal to the direction in which the cold cathode tube is arranged. .

  On the other hand, since the LED is a point light source and has a large distance from the adjacent light source in all directions, a difference in brightness between the point light source and its periphery tends to occur. In recent years, the number of LEDs used has been reduced due to the tendency of low power consumption, and the distance between point light sources has become wider than ever, so that the optical sheet has even more uniform brightness. Is required.

At present, as a means for achieving two functions of luminance uniformity and luminance improvement, a method of combining a plurality of diffusion sheets and lens sheets is generally used.
The diffusion sheet scatters light by at least one of an internal diffusion in which a diffusing agent having a different refractive index is added and a surface diffusion due to surface irregularities, thereby improving luminance uniformity. Therefore, it has a high light diffusing effect, and is extremely excellent with respect to the uniformity of the luminance of the light source and the decrease in the visibility of the dot pattern of the light guide plate.

On the other hand, since the diffusion sheet has a low light condensing effect, the luminance improving effect, which is important as the performance of the optical sheet, is characterized by being lower than that of the lens sheet.
In the case of a lens sheet, light is condensed and diffused by the lens shape to improve luminance and improve luminance uniformity.

The most typical example of the lens sheet is a prism sheet.
The prism sheet has the advantage that the brightness improvement effect is very high, but on the other hand, since the uniformity of brightness is low and the light diffusibility is low, the edge light method using a light guide plate has a dot pattern. In particular, in the display device, the image quality performance is deteriorated. Therefore, there is a demand for an optical sheet that has low dot pattern visibility, that is, a very low dot pattern concealing effect.

  Therefore, as described in Patent Document 1, as a method for improving the luminance uniformity of the lens sheet, minute irregularities are formed by mat processing on a large number of regular parallel corrugated shapes on the light exit surface. A method of applying a shape has been proposed.

  If this method is used, the light output surface is subjected to minute unevenness processing, thereby producing a light scattering effect that cannot be obtained only with a normal corrugated lens sheet, and it is possible to improve luminance uniformity. Become. In addition, the effect of easing the abrupt viewing angle dependence, which is a characteristic of the lens sheet, is exhibited.

  However, in the method described in Patent Document 1, the surface of the lens shape that is important for the luminance improvement effect of the lens sheet collapses, which causes a problem that the light condensing effect is reduced and a large luminance improvement cannot be obtained. There is a fear. In addition, the method described in Patent Document 1 is highly effective in eliminating the light / dark difference in the range where the distance is close, but when the distance is long and the luminance uniformity over a wide range is required, It is hard to say that it is an effective method. In particular, it is difficult to obtain a great effect as the uniformity of the luminance of the point light source by the direct LED type or the like and the dot pattern concealing property of the light guide plate having a dot pattern with a large pitch interval.

In addition to the method described in Patent Document 1, Patent Document 2 discloses a method of exhibiting the same effect by providing a micro uneven surface and a diffusion layer that exhibit a light scattering effect at an intermediate interface of a prism sheet. Has been proposed.
Although the method proposed in Patent Document 2 is highly effective, it is difficult to use a lens sheet that requires a large number of members and processes and is required to reduce costs.

In addition to the methods described in Patent Documents 1 and 2, Patent Document 3 has been proposed as a method for obtaining a similar effect by applying a minute uneven shape to the light incident surface itself.
Compared with the method proposed in Patent Document 2, the method proposed in Patent Document 3 has a smaller number of members and steps, and can be reduced in cost.

  However, since the lens sheet is often used in a display device such as a liquid crystal television and an illumination device, the required light scattering effect differs because the alignment characteristics required in the horizontal direction and the vertical direction are different. In addition, the dot pattern of the light guide plate is often regular in arrangement, and the light scattering effect necessary for concealing the dot pattern varies depending on the directionality.

In addition, since the light scattering effect reduces the light condensing effect, the isotropic light scattering effect such as the methods described in Patent Document 2 and Patent Document 3 reduces the brightness enhancement effect of the optical sheet and increases the efficiency. It is hard to say that the light scattering effect is obtained.
Therefore, at present, the function of uniformity of luminance is ensured by a diffusion sheet, and the enhancement of luminance is ensured by a lens sheet, thereby ensuring two functions of uniformity of luminance and enhancement of luminance.

  When providing an optical sheet having both functions of brightness uniformity and optical performance of an optical sheet, it is common to use a combination of a diffusion sheet having high brightness uniformity and a lens sheet having high optical performance. It is.

Japanese Patent No. 2562265 Japanese Patent Laid-Open No. 8-335044 Japanese Patent No. 3607759

As described above, the optical sheet is required to have more uniform brightness due to low power consumption, thinning, and the like. At present, the number of diffusion sheets and lens sheets is increased to meet this requirement. This is the situation.
However, the method of increasing the number of diffusion sheets and lens sheets is a method contrary to the current demand for cost reduction and thickness reduction.

  An object of the present invention is to provide an optical sheet capable of having two functions of luminance uniformity and high luminance, a backlight unit including the optical sheet, and a display device.

Of the present invention, the invention described in claim 1 is an optical sheet in which a three-dimensional shape is formed on a light emitting surface and a light incident surface of a translucent substrate,
An uneven shape for forming the three-dimensional shape is formed along two directions on the light incident surface,
Ra (x) is the average roughness of the light incident surface along the first direction parallel to the light incident surface, and Sm (x) is the average interval between the concave and convex shapes along the first direction. The average roughness of the light incident surface along the second direction parallel to the surface and perpendicular to the first direction is Ra (y), and the average interval between the concave and convex shapes along the second direction is Sm (y). In case,
30Ra (x) ≧ Ra (y)> 2Ra (x) and Sm (y) ≧ 0.5Sm (x) are established ,
An optical element is formed on the light exit surface,
Wherein the optical element is triangular prism-shaped, square pyramid prisms, polygonal pyramid prism shape, or those characterized by der Rukoto that the semi-elliptical cylindrical lens is formed in a one-dimensional direction or two-dimensional direction It is.

Next, among the present inventions, the invention described in claim 2 is the invention described in claim 1, wherein the uneven shape has one flat surface and a plurality of concave portions formed on the flat surface. It is characterized by being formed from.
Next, among the present inventions, the invention described in claim 3 is the invention described in claim 1 or 2 , wherein the uneven shape is an irregular shape. is there.
Next, among the present inventions, the invention described in claim 4 is the invention described in any one of claims 1 to 3, and is a portion protruding from the light incident surface of the uneven shape. The tip of is rounded.

Next, among the present inventions, the invention described in claim 5 is the invention described in any one of claims 1 to 4 , and is an average of the uneven shape along the second direction. The interval is 500 μm or less.
Next, among the present inventions, the invention described in claim 6 is the invention described in any one of claims 1 to 5 , wherein the optical sheet is manufactured from a single material. It is characterized by that.

Next, among the present inventions, the invention described in claim 7 is disposed on the light incident surface side of the optical sheet described in any one of claims 1 to 6 and the optical sheet. And a light source.
Next, among the present inventions, the invention described in claim 8 is the invention described in claim 7 , wherein the light source is one of an LED, a cold cathode tube, an EL, and a semiconductor laser. It is a feature.

Next, of the present invention, the invention described in claim 9 is the backlight unit described in claim 7 or claim 8 and the light emitting surface side of the backlight unit, and the backlight An image display element that displays an image using light from the unit as display light.

  According to the present invention, an optical element for realizing high brightness is formed on the light exit surface side of the optical sheet, and the unevenness is formed on the light incident surface side of the optical sheet so as to have a high brightness uniformity effect. Form a shape. Then, by establishing the above relationship, it is possible to achieve both high brightness improvement and high light guide plate dot pattern concealment by providing anisotropy to the uneven shape.

It is a figure which shows schematic structure of the display apparatus in 1st embodiment of this invention. It is an overhead view of an optical sheet. It is explanatory drawing of uneven | corrugated shape. It is a figure which shows schematic structure of the extruder used for general extrusion molding. It is a figure which shows schematic structure of the display apparatus in the modification of 1st embodiment of this invention. It is an overhead view of an optical sheet, and is a figure which shows schematic structure of the optical sheet in the modification of 1st embodiment of this invention. It is an overhead view of an optical sheet, and is a figure which shows schematic structure of the optical sheet in the modification of 1st embodiment of this invention. It is an overhead view of an optical sheet, and is a figure which shows schematic structure of the optical sheet in the modification of 1st embodiment of this invention. It is explanatory drawing of the uneven | corrugated shape in the modification of 1st embodiment of this invention. It is explanatory drawing of the uneven | corrugated shape in the modification of 1st embodiment of this invention. It is a figure which shows schematic structure of the display apparatus by which the backlight unit of a light-guide plate light guide system is mounted. It is a figure which shows schematic structure of the display apparatus by which the backlight unit of a light-guide plate light guide system is mounted. It is a figure which shows schematic structure of the display apparatus by which the direct type backlight unit is mounted.

(First embodiment)
Hereinafter, a first embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described with reference to the drawings.
(Constitution)
Hereinafter, the optical sheet according to the present embodiment will be described together with a backlight unit and a display device including the optical sheet.

(Configuration of display device)
First, the configuration of the display device 1 according to the present embodiment will be described with reference to FIG.
FIG. 1 is a diagram showing a schematic configuration of a display device 1 in the present embodiment.
The display device 1 of the present embodiment is a direct type display device and includes an image display element 2 and a backlight unit 4 as shown in FIG. In FIG. 1, the size comparison between the display device 1 and each member included in the display device 1 may not match the actual size.

The image display element 2 is formed by a liquid crystal panel (liquid crystal display element). That is, the display device 1 of the present embodiment is a liquid crystal display device.
The image display element 2 includes a front side polarizing plate 6, a back side polarizing plate 8, and a liquid crystal element 10, and the liquid crystal element 10 is sandwiched between the front side polarizing plate 6 and the back side polarizing plate 8. Has been. Thereby, the front side polarizing plate 6, the back side polarizing plate 8, and the liquid crystal element 10 are laminated in the order of the front side polarizing plate 6, the liquid crystal element 10, and the back side polarizing plate 8.

  In the present embodiment, the display device 1 is a liquid crystal display device, but the type of the display device 1 is not limited to this. That is, the display device 1 may be other than a liquid crystal display device such as a projection screen device, a plasma display device, an EL display device, or the like. In short, any type of display device 1 may be used as long as it is a display device that displays an image with light.

(Configuration of backlight unit)
The backlight unit 4 includes a lamp house 12, a diffusion plate 14, two condensing sheets 16, and an optical sheet 18.

The lamp house 12 is disposed on the back surface of the optical sheet 18 and includes a plurality of light sources 20 and a lamp reflector 22. The back surface of the optical sheet 18 is the surface of the optical sheet 18 opposite to the surface facing the lens sheet 8 (the surface below the optical sheet 18 in FIG. 1).
The plurality of light sources 20 are each formed of an LED, and are arranged at predetermined intervals in a direction orthogonal to the thickness direction of the optical sheet 18.

In the present embodiment, the light source 20 is an LED, but the configuration of the light source 20 is not limited to this, and the light source 20 may be a cold cathode tube (CCFL), an EL, a semiconductor laser, or the like. .
The lamp reflector 22 is disposed on the back surface of the light source 20 and reflects light from the light source 20.

The diffusion plate 14 is disposed on the front side of the light irradiation direction of the light source 20 (above the light source 20 in FIG. 1), and forms a light diffusion layer that diffuses light entering from the light source 20.
The two light collecting sheets 16 are composed of the same type of sheet, and are disposed between the diffusion plate 14 and the image display element 2.

  Each condensing sheet 16 is formed using an appropriate condensing optical sheet. Examples of the condensing optical sheet include a quadrangular prism sheet, a polygonal prism sheet, a triangular prism sheet, a semi-elliptical cylindrical lens, a micro lens sheet, and a diffusion sheet.

In the present embodiment, the configuration of the backlight unit 4 includes two condensing sheets 16. However, the number of the condensing sheets 16 is not limited to this, and one condensing sheet is used. The structure provided with the sheet | seat 16 and the structure provided with the three or more light collection sheet | seats 16 may be sufficient.
Moreover, in this embodiment, although the two condensing sheets 16 were comprised with the same kind of sheet | seat, it is not limited to this, The two condensing sheets 16 are comprised with a different kind of sheet | seat. Also good.

  Moreover, in this embodiment, although the structure of the backlight unit 4 was set as the structure provided with the condensing sheet 16, it is not limited to this, The structure of the backlight unit 4 is not provided with the condensing sheet 16. It is good also as a structure.

(Schematic configuration of optical sheet)
The optical sheet 18 is disposed between the diffusing plate 14 and the condensing sheet 16, and condenses and diffuses light transmitted through the diffusing plate 14. The optical sheet 18 and the light collecting sheet 16 are used by freely combining directions and types depending on desired luminance and viewing angle characteristics.

The optical sheet 18 is a sheet in which a desired three-dimensional shape is formed on the front and back surfaces of the translucent substrate.
Specifically, an optical element 24 for forming a desired three-dimensional shape is formed in a one-dimensional direction on the light emitting surface side of the optical sheet 18 that is the surface side of the translucent substrate. The detailed configuration of the optical element 24 will be described later.

  On the other hand, on the light incident surface side of the optical sheet 18, which is the back surface side of the translucent substrate, minute uneven shapes 26 for forming a desired three-dimensional shape are formed in two directions. The detailed configuration of the concavo-convex shape 26 will be described later.

  In this embodiment, the condensing sheet 16 is disposed between the diffusion plate 14 and the image display element 2, that is, above the optical sheet 18 (in FIG. 1, the direction of the optical sheet 18 toward the image display element 2). However, the present invention is not limited to this. That is, the condensing sheet 16 may be disposed between the optical sheet 18 and the diffusion plate 14, that is, below the optical sheet 18 (in the direction of the optical sheet 18 on the diffusion plate 14 side in FIG. 1). Further, the condensing sheet 16 may be disposed both above and below the optical sheet 18.

(Detailed configuration of optical sheet)
Hereinafter, the detailed configuration of the optical sheet 18 will be described with reference to FIG. 1 and FIG. 2 and FIG. 3.
FIG. 2 is an overhead view of the optical sheet 18.
As shown in FIG. 2, the optical sheet 18 includes a base material portion 28, an optical element 24, and an uneven shape 26. The optical sheet 18 may have a single layer structure or a multilayer structure, and may include a transparent layer.

The base material portion 28 is formed in a plate shape using a translucent resin material.
The optical element 24 is formed in a prism shape having a one-dimensional direction on the light emitting surface side of the optical sheet 18 that is the surface side of the base material portion 28.

The concavo-convex shape 26 is formed of a large number of concave portions on the light incident surface side of the optical sheet 18 that is the back surface side of the base material portion 28.
Further, the tip of the portion of the concavo-convex shape 26 protruding from the light incident surface of the optical sheet 18 is rounded.

  Hereinafter, the optical element 24 formed on the light emitting surface side of the optical sheet 18 is formed into a prism shape having a one-dimensional direction, and the uneven shape 26 formed on the light incident surface side of the optical sheet 18 is formed into a large number of concave portions. Will be described.

  Conventionally, the concavo-convex shape 26 is often irregularly placed on the entire surface of the light incident surface by sandblasting or the like. For this reason, it is difficult to impart a shape with anisotropy in the plane of the light incident surface, and it is difficult to exhibit anisotropy in the light diffusion effect only with the uneven shape 26. .

  As a method of effectively exhibiting anisotropy in the light diffusion effect with only the concavo-convex shape 26, there is a method of imparting a lens shape or the like to the light incident surface of the optical sheet 18. In many cases, a light effect is also required. For this reason, if it is going to exhibit the light-diffusion effect with a lens shape, the light condensing effect will fall correspondingly and the performance of an optical sheet will fall.

  Therefore, in order to have both an efficient light condensing function and a diffusing function, the light exit surface side of the optical sheet 18 is provided with a shape having a high condensing function, and the light incident surface of the optical sheet 18 is provided. On the side, it is best to give a shape having high brightness uniformity. For this purpose, the optical element 24 formed on the light emitting surface side of the optical sheet 18 is formed into a prism shape having a one-dimensional direction, and the uneven shape 26 formed on the light incident surface side of the optical sheet 18 is formed with a number of concave portions. It is preferable to do.

  For the reasons described above, in the present embodiment, the optical element 24 formed on the light emitting surface side of the optical sheet 18 has a prism shape formed in a one-dimensional direction, and the uneven shape formed on the light incident surface side of the optical sheet 18. 26 is a number of recesses.

(Resin material used as optical sheet material)
The optical sheet 18 is made of a single material.
As the material of the optical sheet 18, that is, the resin material used as the material of the base material portion 28, a resin material having light transmittance with respect to the wavelength of light emitted from the light source 20 is used. As such a resin material, for example, a plastic material that can be used for an optical member is used.

  Specific examples of plastic materials that can be used as the material of the base material 28 include polyester resin, acrylic resin, polycarbonate resin, polystyrene resin, MS (acrylic and styrene copolymer) resin, polymethylpentene resin, cyclohexane. Examples thereof include thermoplastic resins such as olefin polymers, oligomers such as polyester acrylate, urethane acrylate, and epoxy acrylate, and transparent resins such as radiation curable resins made of acrylates.

  Further, depending on the use of the optical sheet 18, fine particles may be dispersed in the transparent resin used as the material of the base material portion 28.

As the fine particles dispersed in the transparent resin, transparent particles made of an inorganic oxide or transparent particles made of a resin can be used.
As the transparent particles made of an inorganic oxide, for example, particles made of silica, alumina, titanium oxide or the like can be used.

  The transparent particles made of resin include, for example, acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, melamine-formalin condensate particles, PTFE (polytetrafluoroethylene), PFA (perfluoroalkoxy resin), FEP. It is possible to use fluorine-containing polymer particles such as (tetrafluoroethylene-hexafluoropropylene copolymer), PVDF (polyfluorovinylidene), and ETFE (ethylene-tetrafluoroethylene copolymer), and silicon resin particles. is there. The fine particles described above may be used as a mixture of two or more.

(Detailed configuration of uneven shape)
The uneven shape 26 is formed in an irregular shape on the light incident surface of the optical sheet 18. That is, a large number of recesses forming the uneven shape 26 are irregularly arranged on the light incident surface of the optical sheet 18.

Hereinafter, the reason why the irregular shape 26 is formed in an irregular shape on the light incident surface of the optical sheet 18 will be described.
When the concave and convex shapes 26 are irregularly arranged on the light incident surface of the optical sheet 18 and the irregular shapes 26 are irregularly formed, the optical elements on the light incident surface and the light emitting surface side are arranged. There is an advantage that moire can be easily avoided. In particular, when the optical sheet 18 is used in combination with the condensing sheet 16 that is another optical sheet in the display device 1, the pitch of the lens of the condensing sheet 16, the pitch of the dot pattern of the light guide plate, a liquid crystal panel, or the like There is a high possibility that moire occurs due to interference with the pixel pitch.

Here, the occurrence of the above moire can be avoided by optimizing the pitch and optimizing the direction of the lens. Further, the visibility of moire can be reduced by a method of reducing the strength of moire or a method of reducing the moire generation pitch.
However, since the pixel pitch and orientation of the liquid crystal panel including the optical sheet 18 greatly affect the optical performance of the display device 1, it is difficult to set freely.

Therefore, in order to avoid the moire described above, it is desirable to form the uneven shape 26 in an irregular shape on the light incident surface of the optical sheet 18.
Further, as shown in FIG. 3, the uneven shape 26 is formed so that the cross-sectional shape along the thickness direction of the optical sheet 18 in the portion closest to the light incident surface side is an elliptical shape. FIG. 3 is an explanatory diagram of the concavo-convex shape 26. In FIG. 3, only the outer periphery of the portion of the concavo-convex shape 26 that is closest to the light incident surface side is indicated by a dotted line.

  Specifically, the concavo-convex shape 26 is formed so that the long side direction of the elliptical shape is parallel to a first direction to be described later. Thereby, the uneven | corrugated shape 26 has acquired the light scattering effect which is different in the 1st direction and the 2nd direction mentioned later.

(Detailed configuration of light incident surface)
Hereinafter, a detailed configuration of the light incident surface of the optical sheet 18 will be described.
On the light incident surface, the following relational expressions (1) and (2) are established.
30Ra (x) ≧ Ra (y)> 2Ra (x) (1)
Sm (y) ≧ 0.5 Sm (x) (2)
Here, in the above relational expression (1),
Ra (x): average roughness of the light incident surface along the first direction parallel to the light incident surface Ra (y): light incident surface along the second direction parallel to the light incident surface and orthogonal to the first direction Is the average roughness.

In the relational expression (2),
Sm (x): Average interval of the uneven shape 26 along the first direction Sm (y): Average interval of the uneven shape 26 along the second direction.

  The average roughness of the light incident surface is an average value of the surface roughness of the light incident surface along the linear direction on the light incident surface, and is a numerical value defined for the Japanese Industrial Standard JISB0601. Moreover, average roughness Ra (x) and Ra (y) have shown that the grade of roughness is so large that a numerical value is large.

In the present embodiment, the first direction is a direction parallel to the prism shape forming the optical element 24, as shown in FIG. Accordingly, in the present embodiment, the second direction is a direction orthogonal to the prism shape forming the optical element 24 as shown in FIG.
The units of Ra (x), Ra (y), Sm (x), and Sm (y) are all [μm].

Hereinafter, the reason why the relational expressions (1) and (2) are established on the light incident surface will be described.
The above relational expressions (1) and (2) have different surface roughnesses in the first direction and the second direction on the light incident surface, and light in the first direction and the second direction. It shows that the scattering effect and the diffusion effect are different.

  Here, the average roughness Ra (x) and Ra (y) tend to increase as the size of the uneven shape 26 itself increases.

On the other hand, the average intervals Sm (x) and Sm (y) of the uneven shape 26 are greatly affected by the size and density of the uneven shape 26.
Specifically, when the size of the concavo-convex shape 26 is large, the values of the average intervals Sm (x) and Sm (y) are likely to increase, and the size of the concavo-convex shape 26 is small and the ratio of the concavo-convex shape 26 present is small. As the value increases, the average intervals Sm (x) and Sm (y) become smaller.

For this reason, the light scattering effect and the diffusion effect become larger as the average roughness Ra (x) and Ra (y) are larger and the values of the average intervals Sm (x) and Sm (y) are smaller.
Therefore, by controlling the average roughness Ra (x) and Ra (y) and the average intervals Sm (x) and Sm (y) in the in-plane direction of the light incident surface, an optical device having high brightness and high diffusibility. The sheet 18 can be obtained.

As described above, the optical sheet 18 of the present embodiment needs to have a low light diffusion effect due to the surface roughness in the first direction and a strong light diffusion effect due to the surface roughness in the second direction.
However, since the numerical values of both the average roughness Ra (x) and Ra (y) and the average intervals Sm (x) and Sm (y) change when the size and ratio of the concavo-convex shape 26 are changed, the average roughness It is difficult to individually control the depth Ra (x) and Ra (y) and the average intervals Sm (x) and Sm (y).

Specifically, when Ra (y) ≦ 2Ra (x), the difference between the diffusion effects in the first direction and the second direction is small, and the average roughness Ra (x) and Ra (y) are small. Since there is no sufficient light scattering effect, it is not possible to ensure brightness uniformity.
In addition, when the average roughness Ra (x) and Ra (y) are large, the uniformity of luminance can be ensured, but the luminance is greatly reduced. Further, when the uneven shape 26 is irregularly arranged, the average roughness Ra (x) in the first direction needs to be very small in order to achieve 30Ra (x) ≧ Ra (y).

  That is, the surface roughness in the first direction is very small, and not only the average roughness Ra (x) in the first direction but also the average interval Sm (x) in the first direction varies. For this reason, the average interval Sm (x) in the first direction tends to increase. Then, in the first direction, the distance between the adjacent concavo-convex shapes 26 is increased, and as a result, a phenomenon in which the luminance uniformity is reduced occurs.

  Further, when focusing only on the average spacing Sm (x) in the first direction, considering only the light diffusion effect, the light diffusive effect is exhibited when the value of the average spacing Sm (x) in the first direction is small. Easy to be. For this reason, the larger the average interval Sm (x) in the first direction, the lower the light diffusibility and the lower the luminance.

  However, it is known that when the average roughness Ra (x) in the first direction is small, the light scattering effect is low even if the average interval Sm (x) in the first direction is small. Further, when a large number of the same uneven shapes are arranged on the entire light incident surface by using sandblasting or the like, it is difficult to maintain the average interval Sm (x) in the first direction as being large.

  Therefore, if the above relational expression (1) holds, even if the average interval Sm (x) in the first direction is smaller than the average interval Sm (y) in the second direction, Sm (x) and Sm (y ) Is within the range in which the above relational expression (2) is established, the light scattering effect in the first direction is small, and no significant reduction in luminance occurs.

(Average interval of uneven shape)
In the present embodiment, the average interval Sm (y) of the uneven shape 26 along the second direction is set to 500 [μm] or less.

Hereinafter, the reason why the average interval Sm (y) of the uneven shape 26 along the second direction is set to 500 [μm] or less will be described.
The optical sheet 18 of the present embodiment is mainly used for the purpose of reducing the uniformity of the luminance of the point light source and the hiding property of the dot pattern of the light guide plate.
In general, the dot pattern of a conventional light guide plate is formed by arranging white ink in a circular shape in a hexagonal close-packed manner by screen printing or the like. The dot diameter is about 0.5 [mm] at a minimum to about 2 [mm] at a maximum.

  Therefore, in particular, in order to have dot pattern concealment even at the minimum dot diameter, the average interval Sm (y) of the concavo-convex shape 26 along the second direction must be 500 [μm] or less.

  On the other hand, the average interval Sm (x) of the uneven shape 26 along the first direction need not be limited to 500 [μm] or less. This is because, in the present embodiment, the shape of the light exit surface of the optical sheet 18, the light diffusing effect due to the combination with another optical sheet (light collecting sheet 16) when used in the display device 1, This is because the concealment effect can be used. At present, at least one lens sheet is generally used for the other optical sheet (light collecting sheet 16) of the display device 1.

  Although the shape of the lens sheet is not limited, as an example, when the light exit surface side is a triangular prism shape having an apex angle of 90 °, from the optical characteristics of the prism shape, the direction of the prism shape is aligned. Since there is a light splitting effect in the orthogonal direction, the pattern arrangement changes so that the interval between adjacent dots is reduced.

  On the other hand, since there is no split effect as described above in a direction orthogonal to the direction in which the prism shapes are arranged, no change in the visibility of the dot pattern is observed. Also, in the case of a cylindrical lens shape instead of a prism shape, because of the lens effect, dots and point light sources have the effect of uniformly diffusing the luminance in a direction perpendicular to the direction in which the cylindrical lenses are arranged, The strong diffusion effect by the uneven shape 26 formed on the light incident surface is not always necessary.

  Therefore, depending on the lens shape of another optical sheet (light condensing sheet 16) and the shape of the light exit surface of the optical sheet 18 of this embodiment, only the direction in which the concealment property and the uniformity of luminance are most necessary is required. In order to obtain the diffusion effect with the uneven shape 26 formed on the light incident surface, the surface roughness in the first direction orthogonal to the second direction is made as low as possible, thereby reducing the light scattering effect and making the luminance uniform. The brightness improvement effect which is in a trade-off relationship with the property is obtained.

(Optical sheet manufacturing method)
Hereinafter, a method for manufacturing the optical sheet 18 in the present embodiment will be described with reference to FIGS. 1 to 3.
The optical sheet 18 can be manufactured by an extrusion method, a casting method, or an injection method.

In the present embodiment, the optical sheet 18 is manufactured by pouring the above-described resin material into a mold in a molten state and solidifying it into a plate shape or a belt shape.
At this time, the thickness of the optical sheet 18 is set to 12 [μm] or more and 1 [mm] or less. This is because when the thickness of the optical sheet 18 is less than 12 [μm], there is no rigidity that can withstand the processing by the manufacturing method described above, and when the thickness of the optical sheet 18 exceeds 1 [mm] This is because there is no flexibility to withstand.

Here, the mold into which the melted resin material is poured is composed of a mold for forming the optical element 24 and a mold for forming the concavo-convex shape 26.
The mold for forming the optical element 24 has a three-dimensional portion formed in a shape opposite to the shape of the optical element 24 (prism shape). The three-dimensional part formed in the shape opposite to the shape (concave portion) of the concavo-convex shape 26 is formed.

  The optical sheet 18 can be produced using materials, structures, processes, etc. other than those described above as long as the optical characteristics required for the optical sheet 18 of the present embodiment can be achieved. It is also possible to do.

(Method of forming mold)
Examples of a method for forming a mold for forming the optical element 24 include a cutting method. When forming a mold for forming the optical element 24 by a cutting method, a diamond tool having the same shape as the optical element 24 is used to form a mold for forming the optical element 24. The mold roll is cut, and a three-dimensional portion having a shape opposite to the prism shape of the optical element 24 is formed in a portion corresponding to the optical element 24 in the optical element side mold roll.

  On the other hand, as a method of forming a mold for forming the concavo-convex shape 26, for example, blasting is performed on the concavo-convex shape side mold roll itself constituting the mold for forming the concavo-convex shape 26, There is a method by corrosion.

  When using the method of hitting the blast against the concave / convex side mold roll itself, the concave / convex shape 26 can be adjusted by adjusting the shape and size of the blast, and the pressure and number of times that the blast is blown against the concave / convex side mold roll. Although it is possible, in this method, it is difficult to form the regular uneven shape 26.

On the other hand, when the method using chemical corrosion is used, the shape of the concavo-convex shape 26 can be adjusted by the location where the chemical is applied, the corrosion time, and the number of times of corrosion. In particular, in the case of this method, both regular and irregular concavo-convex shapes 26 can be produced.
It should be noted that when forming a mold for forming the concavo-convex shape 26 in both the method of hitting the blast to the concavo-convex shape side mold roll itself and the method by chemical corrosion, the shape opposite to the concave portion of the concavo-convex shape 26 is formed. A three-dimensional part is formed in the part corresponding to the uneven | corrugated shape 26 among uneven | corrugated shaped side metal rolls.

  In addition, when forming a mold for forming the concavo-convex shape 26 by either the method of hitting the blast to the concavo-convex shape side mold roll itself or the method by chemical corrosion, the light incidence of the optical sheet 18 having the concavo-convex shape is performed. A mold for forming the concavo-convex shape 26 is formed so that the tip of the portion protruding from the surface is rounded. As a result, it is possible to reduce damage to the optical sheet 18 and the diffusion plate 14 caused by the contact between the optical sheet 18 and the diffusion plate 14.

(Example)
The results of manufacturing the optical sheet 18 described in the first embodiment and evaluating the physical properties thereof will be described with reference to FIGS. 1 to 3 and FIG. 4.

Hereinafter, a specific configuration, an experimental method, and an experimental result of the manufactured optical sheet 18 will be described. Since two types of experiments were performed on the manufactured optical sheet 18, the two types of experiments are described as “Experiment 1” and “Experiment 2”, respectively, in the following description.
First, Experiment 1 will be described.

(Experiment 1: Examination of surface roughness of uneven shape 26)
In order to examine the surface roughness of the concavo-convex shape 26 formed on the light incident surface of the optical sheet 18, a plurality of types (comparative examples and examples) of optical sheets 18 having different properties of the concavo-convex shape 26 on the light incident surface were prepared. The luminance and the concealment property were evaluated for each optical sheet 18.

As a comparative example, an optical sheet 18 whose light incident surface is a mirror (mirror surface) was used.
The irregular shape 26 was an irregular mat shape formed on the entire surface of the light incident surface by sandblasting. At this time, the optical element 24 formed on the light emitting surface has a prismatic prism lens shape with a height of 50 [μm] and a pitch of 100 [μm] and an apex angle of 90 °.
(Experiment 1: Method for Producing Optical Sheet 18)
A mold for forming the uneven shape 26 was produced by spraying blast on a mold roll to form a desired three-dimensional shape corresponding to the uneven shape 26. At this time, in order to make the surface roughness anisotropic with respect to the light incident surface, the nozzle was moved in one direction and blasting was performed.

The mold for forming the optical element 24 is a prism shape with an apex angle of 90 ° corresponding to the optical element 24 by setting a mold roll in a precision cutting machine and cutting with a diamond tool having a prism shape at the tip. A mold roll for molding the optical sheet 18 was prepared.
The optical sheet 18 itself was produced by an extrusion method using the extruder shown in FIG. In addition, FIG. 4 is a figure which shows schematic structure of the extruder used for general extrusion molding.

As shown in FIG. 4, the extruder 30 includes a die 32, a first roll 34, a second roll 36, and a third roll 38.
The die 32 discharges the molten resin obtained by melting the thermoplastic polycarbonate resin into a gap formed between the first roll 34 and the second roll 36.
The first roll 34 is a mold roll that forms a mold for forming the concavo-convex shape 26, and the second roll 36 is a mold roll that forms a mold for forming the optical element 24.

  When the optical sheet 18 is formed using the extruder 30 having such a configuration, the first roll 34 and the second roll 36 apply a narrow pressure to the molten resin discharged from the die 32. An optical sheet 18 having a desired shape is obtained. The thickness of the optical sheet 18 was set to 320 [μm] for both the comparative example and the example.

In addition, all the optical sheets 18 used in Experiment 1 are produced by an extrusion method using a thermoplastic polycarbonate resin of Teijin Chemicals Ltd. The elastic modulus E of this thermoplastic polycarbonate resin is 2400 [MPa], and the specific gravity is 1.2 [g / cm ³ ]. This optical sheet 18 has a very good transfer rate from the mold, and its shaping rate is 99% or more.
Further, the surface roughness of the light incident surface of the extruded optical sheet 18 was measured using a small surface roughness measuring machine Surf Test SJ-201 manufactured by Mitutoyo Corporation.

(Experiment 1: Evaluation of luminance)
Luminance evaluation was performed on the optical sheets 18 of the comparative example and the example obtained by the method described above.

  When evaluating the luminance, the optical sheet 18 of the comparative example and the example is mounted on the LED edge light type liquid crystal television, and the luminance is measured using the spectroradiometer SR-3A manufactured by Topcon Corporation. went. As the liquid crystal television, a 40-inch liquid crystal television manufactured by Sony Corporation was used.

At this time, the light guide plate mounted on the liquid crystal television is used as it is, and the optical sheet 18 of the present invention, the prism sheet manufactured by Sumitomo 3M, and the retroreflective sheet DBEF manufactured by Sumitomo 3M are installed in this order. ing.
And the brightness | luminance was measured from the front of the liquid crystal television, and if the measured brightness | luminance was 0.8 or more with respect to the comparative example, it was set as the pass ((circle)), and if less than 0.8, it was set as the disqualification (x).

(Experiment 1: Evaluation of luminance uniformity)
Furthermore, with respect to the optical sheets 18 of the comparative example and the example obtained by the method described above, evaluation of luminance uniformity was performed.

When evaluating the uniformity of brightness, the optical sheet 18 of the comparative example and the example was mounted on an LED edge light type liquid crystal television, and evaluated by a brightness unevenness measuring machine and visual evaluation. As the liquid crystal television, a 40-inch liquid crystal television manufactured by Sony Corporation was used.
The light guide plate used in the liquid crystal television is used as it is. On the light guide plate, the optical sheet 18 of the present invention, the prism sheet BEFIII manufactured by Sumitomo 3M, and the retroreflective sheet manufactured by Sumitomo 3M. DBEF was installed in order.

Then, using ProMetric made by Cybernet as a brightness unevenness measuring device, the brightness unevenness was measured from the front of the liquid crystal television, and the brightness unevenness in the plane was quantified.
Evaluation by the brightness unevenness measuring machine was set to pass (◯) if the measured numerical value had less brightness unevenness than the target configuration. Here, in order from the light guide plate, the target configuration is a microlens sheet PTR873H manufactured by MNTech, a prism sheet BEFIII manufactured by Sumitomo 3M, and Sumitomo 3M.
It consists of a company-made retroreflective sheet DBEF.

  Moreover, visual evaluation confirmed whether the dot of the light-guide plate was visible within the viewing angle of 60 degrees C from the front of the liquid crystal television, and it was set as the pass. The uniformity of luminance was determined to be acceptable (◯) in the final judgment when both luminance unevenness evaluation and visual evaluation were acceptable.

  The evaluation results of Experiment 1 are shown in Table 1. Table 1 is a table showing experimental results in Experiment 1.

  In Experiment 1, the average interval of the concavo-convex shape 26 is not significantly different between the first direction and the second direction, but the relationship between the average roughness Ra (x) and the average roughness Ra (y) described above is 30 Ra ( x) ≧ Ra (y)> 2Ra (x) In a state where the relationship is established, as shown in Table 1, the decrease in luminance due to the surface roughness of the concavo-convex shape 26 is low, and the luminance uniformity is low. It was confirmed that it improved.

Next, Experiment 2 will be described.
(Experiment 2: Examination of surface roughness of minute uneven shape 26)
In order to examine the surface roughness of the concavo-convex shape 26 formed on the light incident surface of the optical sheet 18, a plurality of types (comparative examples and examples) of optical sheets 18 having different properties of the concavo-convex shape 26 on the light incident surface were prepared. For each, brightness and concealment were evaluated.

In this experiment, a plurality of types of optical sheets 18 having different anisotropy of the uneven shape 26 were produced.
When forming the concavo-convex shape 26, a hemispherical concave portion is irregularly formed in a film as a material by laser irradiation, and then the film is stretched in one direction to form a portion closest to the light incident surface side. The film which has the recessed part from which the cross-sectional shape along the thickness direction of the optical sheet 18 becomes elliptical shape was obtained (refer FIG. 3).

  When stretching the film, the amount of stretching was adjusted to produce films having different light incident surface shapes. At this time, the optical element 24 formed on the light emitting surface has a prismatic prism lens shape with a height of 50 [μm] and a pitch of 100 [μm] and an apex angle of 90 °.

(Experiment 2: Manufacturing method of optical sheet 18)
Since the manufacturing method of the optical sheet 18 used in Experiment 2 is the same as the manufacturing method of the optical sheet 18 used in Experiment 1 described above, description thereof is omitted.
Further, the surface roughness of the light incident surface of the optical sheet 18 was measured using a small surface roughness measuring machine Surf Test SJ-201 manufactured by Mitutoyo Corporation as in Experiment 1 described above.

(Experiment 2: Evaluation of luminance)
Luminance evaluation was performed on the optical sheets 18 of the comparative example and the example obtained by the method described above.
When evaluating the luminance, the optical sheet 18 of the comparative example and the example is mounted on the LED edge light type liquid crystal television, and the luminance is measured using the spectroradiometer SR-3A manufactured by Topcon Corporation. went. As the liquid crystal television, a 40-inch liquid crystal television manufactured by Sony Corporation was used.
At this time, the light guide plate mounted on the liquid crystal television is used as it is, and the optical sheet 18 of the present invention, the prism sheet manufactured by Sumitomo 3M, and the retroreflective sheet DBEF manufactured by Sumitomo 3M are installed in this order. ing.

  And the brightness | luminance was measured from the front of the liquid crystal television, and if the measured brightness | luminance was 0.8 or more with respect to the comparative example, it was set as the pass ((circle)), and if less than 0.8, it was set as the disqualification (x).

(Experiment 2: Evaluation of luminance uniformity)
Furthermore, with respect to the optical sheets 18 of the comparative example and the example obtained by the method described above, evaluation of luminance uniformity was performed.

When evaluating the uniformity of brightness, the optical sheet 18 of the comparative example and the example was mounted on an LED edge light type liquid crystal television, and evaluated by a brightness unevenness measuring machine and visual evaluation. As the liquid crystal television, a 40-inch liquid crystal television manufactured by Sony Corporation was used.
The light guide plate used in the liquid crystal television is used as it is. On the light guide plate, the optical sheet 18 of the present invention, the prism sheet BEFIII manufactured by Sumitomo 3M, and the retroreflective sheet manufactured by Sumitomo 3M. DBEF was installed in order.
Then, using ProMetric made by Cybernet as a brightness unevenness measuring device, the brightness unevenness was measured from the front of the liquid crystal television, and the brightness unevenness in the plane was quantified.

Evaluation by the brightness unevenness measuring machine was set to pass (◯) if the measured numerical value had less brightness unevenness than the target configuration. Here, in order from the light guide plate, the target configuration is a microlens sheet PTR873H manufactured by MNTech, a prism sheet BEFIII manufactured by Sumitomo 3M, and Sumitomo 3M.
It consists of a company-made retroreflective sheet DBEF.

  Moreover, visual evaluation confirmed whether the dot of the light-guide plate was visible within the viewing angle of 60 degrees C from the front of the liquid crystal television, and it was set as the pass. The uniformity of luminance was determined to be acceptable (◯) in the final judgment when both luminance unevenness evaluation and visual evaluation were acceptable.

  The evaluation results of Experiment 2 are shown in Table 2. Table 2 is a table showing experimental results in Experiment 2.

In Experiment 2, by stretching the film, a sample in which the average interval of the uneven shape 26 is greatly different in the first direction and the second direction was created.
At this time, the above-described average interval Sm (x) is sufficiently large. In particular, the relationship between the above-described average roughness Ra (x) and the average roughness Ra (y) and the above-described average interval Sm (x) and the average As shown in Table 2, when the relationship with the interval Sm (y) is satisfied by the relationship of 30Ra (x) ≧ Ra (y)> 2Ra (x) and Sm (y) ≧ 0.5Sm (x) In addition, it was confirmed that the uniformity of luminance was improved without causing a large decrease in luminance.

(Application examples)
Hereinafter, application examples of the first embodiment will be listed.
(1) In the first embodiment, the display device 1 is a direct type display device. However, the display device 1 is not limited to this. As shown in FIG. 5, the display device 1 is an edge light type display device. It is good. FIG. 5 is a diagram illustrating a schematic configuration of the display device 1 according to a modification of the first embodiment.

  As shown in FIG. 5, the edge light type display device 1 has the same configuration as the direct type display device 1 except for the configuration of the backlight unit 4. That is, the backlight unit 4 included in the edge light type display device 1 includes a light guide plate 40 and a plurality of light sources 20 made of LEDs arranged at both ends of the light guide plate 40. In addition, the backlight unit 4 included in the edge light type display device 1 has a plurality of reflective dots 42 arranged on the back side of the light guide plate 40.

(2) In the first embodiment, as shown in FIG. 2, the concavo-convex shape 26 is formed from a large number of concave portions, but the configuration of the concavo-convex shape 26 is not limited to this, and the concavo-convex shape 26 is For example, as shown in FIG. 6, you may form from many convex parts. FIG. 6 is a bird's-eye view of the optical sheet 18 and shows a schematic configuration of the optical sheet 18 in a modification of the first embodiment.

(3) In the first embodiment, as shown in FIG. 2, the optical element 24 is formed in a one-dimensional direction. However, the configuration of the optical element 24 is not limited to this, and for example, FIG. Alternatively, as shown in FIG. 8, the optical element 24 may be formed in a two-dimensional direction. 7 and 8 are overhead views of the optical sheet 18, and are diagrams showing a schematic configuration of the optical sheet 18 in a modification of the first embodiment. Further, the optical sheet 18 shown in FIG. 7 and the optical sheet 18 shown in FIG. 8 are different from each other in the direction in which the concavo-convex shape 26 is arranged by 90 °. The arrangement is different.

Further, the configuration of the optical element 24 is not limited to the prism shape composed of the one-dimensional direction shown in FIG. 2 or the two-dimensional direction shown in FIGS. A quadrangular pyramid prism shape, a polygonal pyramid prism shape, a semi-elliptical cylindrical lens, a microlens, or the like may be used.
In addition, two or more types of optical elements 24 having different shapes may be formed on the light exit surface of the optical sheet 18.

  In this case, as the optical element 24, a prism shape that easily secures luminance, a cylindrical lens shape that easily obtains luminance uniformity, and the like can be freely arranged on the light emitting surface. In addition, optical elements 24 having different heights may be arranged, and a scratch resistance effect may be obtained by providing minute unevenness and minute protrusions. In short, the optical element 24 may have any shape as long as it satisfies the required performance.

(4) In the first embodiment, as shown in FIG. 3, the concavo-convex shape 26 is such that the cross-sectional shape along the thickness direction of the optical sheet 18 at the portion closest to the light incident surface side is an elliptical shape. However, the configuration of the concavo-convex shape 26 is not limited to this. That is, for example, as shown in FIG. 9, the concavo-convex shape 26 is formed so that the cross-sectional shape along the thickness direction of the optical sheet 18 at the portion closest to the light incident surface side is linear. Also good. In addition, FIG. 9 is explanatory drawing of the uneven | corrugated shape 26 in the modification of 1st embodiment. In FIG. 9, only the portion closest to the light incident surface side of the concavo-convex shape 26 is indicated by a dotted line.

  Further, for example, as shown in FIG. 10, the concavo-convex shape 26 is formed so that the cross-sectional shape along the thickness direction of the optical sheet 18 at the portion closest to the light incident surface side is a curved shape. Also good. In addition, FIG. 10 is explanatory drawing of the uneven | corrugated shape 26 in the modification of 1st embodiment. In FIG. 10, only the portion closest to the light incident surface side in the concavo-convex shape 26 is indicated by a dotted line.

When the cross-sectional shape along the thickness direction of the optical sheet 18 at the portion closest to the light incident surface side of the concavo-convex shape 26 is linear or curved, the longitudinal direction of the concavo-convex shape 26 is particularly preferably By arranging it relatively parallel to the direction, a high light scattering effect in the second direction can be obtained.
Here, the shape of the uneven shape 26 is not limited to these shapes. Further, the density and arrangement method of the uneven shape 26 are not particularly limited, and it is only necessary that the relationship between the surface roughness in the first direction and the second direction is established.

Further, the concave / convex shape 26 may be a concave portion or a convex portion alone, or a concave portion and a convex portion may be mixed.
When the ratio of the uneven shape 26 is small with respect to the light incident surface, different effects such as improvement of scratch resistance can be obtained when the uneven shape 26 is formed as a convex portion.

On the other hand, when there are a large number of uneven shapes 26, even if scratches are generated, the visibility of the scratches is reduced due to the scattering effect of the uneven shapes 26, and as a result, scratch resistance on the light incident surface of the optical sheet 18. There may be an improvement in sex.
(5) In the first embodiment, the optical sheet 18 is manufactured by pouring a molten resin material into a mold and solidifying it into a plate shape or a belt shape. However, the method for manufacturing the optical sheet 18 is limited to this. For example, the optical sheet 18 may be manufactured by a UV curing method.

  When the optical sheet 18 is manufactured by the UV curing method, a mold having a desired shape is pressed against the UV curable resin applied on the base material portion 28 which is a sheet-like base material. Then, UV (ultraviolet light) is irradiated to the UV curable resin pressed against the mold to obtain the optical sheet 18 including the base material portion 28, the optical element 24, and the uneven shape 26.

  Here, as the material of the base material portion 28, it is possible to use a PET (polyethylene terephthalate), polycarbonate, acrylic, polypropylene film or the like well known in the field of the present invention.

  At this time, the optical element 24, the base material portion 28, and the concavo-convex shape 26 may be formed as separate bodies or may be formed as a single body. Further, when the optical element 24 and the base material portion 28 are molded, it is also possible to mold by dispersing a diffusing agent such as a filler therein.

DESCRIPTION OF SYMBOLS 1 Display apparatus 2 Image display element 4 Backlight unit 6 Front side polarizing plate 8 Back side polarizing plate 10 Liquid crystal element 12 Lamphouse 14 Diffuser plate 16 Condensing sheet 18 Optical sheet 20 Light source 22 Lamp reflector 24 Optical element 26 Uneven shape 28 Base material part 30 Extruder 32 Die 34 First Roll 36 Second Roll 38 Third Roll 40 Light Guide Plate 42 Reflective Dot 44 Diffusion Film 46 Reflective Film 46 Prism Film

Claims (9)

An optical sheet in which a three-dimensional shape is formed on the light emitting surface and the light incident surface of the translucent substrate,
An uneven shape for forming the three-dimensional shape is formed along two directions on the light incident surface,
Ra (x) is the average roughness of the light incident surface along the first direction parallel to the light incident surface, and Sm (x) is the average interval between the concave and convex shapes along the first direction. The average roughness of the light incident surface along the second direction parallel to the surface and perpendicular to the first direction is Ra (y), and the average interval between the concave and convex shapes along the second direction is Sm (y). In case,
30Ra (x) ≧ Ra (y)> 2Ra (x) and Sm (y) ≧ 0.5Sm (x) are established ,
An optical element is formed on the light exit surface,
Wherein the optical element is triangular prism-shaped, square pyramid prisms, polygonal pyramid prisms, or optical, characterized in der Rukoto that the semi-elliptical cylindrical lens is formed in a one-dimensional direction or two-dimensional direction Sheet. The optical sheet according to claim 1, wherein the uneven shape is formed of one flat surface and a plurality of concave portions formed on the flat surface. The uneven shape, the optical sheet according to claim 1 or claim 2, characterized in that an irregular shape. The optical sheet according to any one of claims 1 to 3 , wherein a tip of a portion protruding from the light incident surface of the concavo-convex shape is rounded. The optical sheet according to any one of claims 1 to 4 , wherein an average interval of the concavo-convex shape along the second direction is 500 µm or less. The optical sheet according to any one of claims 1 to 5 , wherein the optical sheet is made of a single material. A backlight unit comprising: the optical sheet according to any one of claims 1 to 6 ; and a light source disposed on the light incident surface side of the optical sheet. The backlight unit according to claim 7 , wherein the light source is one of an LED, a cold cathode tube, an EL, and a semiconductor laser. The backlight unit according to claim 7 or 8 , and an image display element that is disposed on the light emission surface side of the backlight unit and displays an image using light from the backlight unit as display light, A display device comprising:

Images