JP2010266856A - Optical sheet, method of manufacturing the same, and light source device including the same, and display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical sheet for liquid crystal display panels, enabling improvement of the luminance ratios at the center points between linear light sources arranged next to each other and positions directly above the linear light sources, and uniform luminance distribution, and also to provide a method of manufacturing the optical sheet, a direct-type light source, and a liquid crystal display device. <P>SOLUTION: This optical sheet includes a convex lens group formed in linear ridge shapes on its surface. The lens group has at least two kinds of unit lenses having different shapes of the outer lines of the convex parts in the cross section taken perpendicularly to their lengthwise directions of the unit lenses, and the unit lenses are arranged on a light exit surface at a constant ratio. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical sheet, a method for manufacturing the optical sheet, a light source device including the optical sheet, and a display device.

  In recent years, a display device has been replaced by a liquid crystal display from a display using a cathode ray tube, and the screen has been enlarged. The light source of the liquid crystal display device includes an edge light type and a direct type, but a large type liquid crystal display device generally uses a direct type light source in which a plurality of cold cathode tubes are arranged as the light source.

  On the screen of a liquid crystal display device using a direct light source, there is a luminance unevenness in which a portion where a cold cathode tube is present is bright and a portion where the cold cathode tube is not present is relatively dark, and the cold cathode tube is reflected on the screen. There is. Therefore, by arranging various optical sheets between the cold cathode fluorescent lamp and the liquid crystal panel, light emitted from the cold cathode fluorescent lamp is uniformly diffused over the entire screen.

  Liquid crystal display devices are required to be further thinned. For this reason, the distance between the cold cathode tube and the screen has to be reduced, and it has become difficult to sufficiently diffuse the light from the cold cathode tube. Yes. Further, in order to reduce the cost, the number of cold cathode tubes is also reduced, and it is difficult to uniformly diffuse light from the cold cathode tubes as the interval between the cold cathode tubes is increased. Therefore, under such severe conditions, as a method of eliminating luminance unevenness and improving luminance, select an optical sheet with a lens as the optical sheet placed closest to the light source and adjust the lens shape. Has been done. Further, from the viewpoint of luminance, at least one prism sheet is selected as the second and subsequent optical sheets with respect to the direction from the light source to the liquid crystal panel. In such a combination of a plurality of optical sheets, what is becoming a problem is that, firstly, the portion where the cold cathode tube exists is bright, but the portion where it does not exist is relatively dark, and secondly, the luminance unevenness is eliminated. It is also possible to eliminate new brightness unevenness caused by the low brightness portion near the cold cathode tube, which is generated by using a diffusion sheet with a lens or a prism sheet.

  In order to make the luminance distribution uniform while preventing a reduction in illumination efficiency, for example, in the direct light source device disclosed in Patent Literature 1 and Patent Literature 2, a plurality of prism lenses having a triangular cross section are arranged in parallel. A prism sheet and a lenticular lens sheet in which a plurality of cylindrical lenses having a cylindrical convex surface are arranged in parallel are used as an alternative to the conventional optical sheet. The prism sheet and lenticular lens sheet have a smaller number of incident light beams that are repeatedly reflected and refracted compared to optical sheets using conventional light diffusing agents. Can be improved. However, although the prism sheet can improve the luminance, there is a limit to the uniform distribution thereof. Although the lenticular lens sheet can also increase the uniformity of the luminance distribution as compared to the prism sheet, it is difficult to completely eliminate the luminance unevenness under the severe cold cathode tube installation conditions as described above.

Japanese Patent Laid-Open No. 10-283818 JP 2004006256 A

  An optical sheet having lenses arranged in a straight bowl on the light exit surface is arranged at a position closest to the light source, and at least one prism is provided on the optical sheet arranged second or later in the direction from the light source to the liquid crystal panel. When using a sheet or the like, the light diffusibility is enhanced by the effect of the prism, and the front luminance can be increased. Therefore, an optical sheet configuration for a light source that is optimal for thinning the liquid crystal television and reducing the number of cold cathode tubes It is considered.

  However, although such an optical sheet configuration can diffuse sufficient light between cold cathode tubes with originally low brightness, light with a small incident angle from the optical sheet to the prism sheet is optically reflected by the prism sheet. Since the sheet is returned to the sheet, a dark line is generated on the cold cathode tube. Even if the pattern of the cold-cathode tube can be erased, this dark line remains, resulting in new brightness unevenness.

  An object of the present invention is to reduce luminance unevenness at an intermediate point between line light sources (for example, cold-cathode tubes) arranged in parallel with each other and immediately above the line light source. It is an object to provide an optical sheet that can obtain a uniform luminance distribution by combination with an optical sheet, a method for manufacturing the optical sheet, a light source device including them, and a liquid crystal display device.

  As a result of intensive studies to solve the above problems and the problems of the prior art, the inventors have found that each unit lens in the lens group formed in a linear bowl shape on the surface of the optical sheet is perpendicular to its length direction. The cross-sectional shape has found that the above-mentioned problems can be solved when it includes two different shapes having a specific ratio of the outer peripheral line portion having a tangential angle within a specific range, and has completed the invention. In order to describe the lens of the present invention and the surface shape of the lens, a cross-section (vertical cross-section) perpendicular to the linear scission direction (lens length direction) of the lens arranged in a straight scissor shape on the optical sheet. The form will be described below using (shape) (see FIG. 6).

  The first embodiment is an optical sheet having a convex lens group formed on the surface in a straight bowl shape, and the lens group has the following shape 1 as a vertical cross-sectional shape with respect to the length direction of the unit lens. 5 is an optical sheet (see, for example, FIGS. 2 to 4) having a unit lens having a shape and a unit lens having a shape 2.

≪Shape 1≫
A portion (R1) in which an outer peripheral line is a curve or a straight line and an angle θ1 formed by a tangent line or a straight line at all points on the curve and a base line of the unit lens cross-sectional shape is 25 ° ≦ θ1 ≦ 35 ° In addition, the total length (r1) of the portion (R1) projected onto the base line of the unit lens cross-sectional shape is 90% or more with respect to the total length of the base part of the unit lens cross-sectional shape. shape.

≪Shape 2≫
The total length (r2) projected on the base line of the unit lens shape of the portion (R2) represented by a single quadratic curve, the outer peripheral line is mainly composed of a curved portion, is the unit lens shape. A curve that is 90% or more with respect to the total length of the base line, and an angle (θ3) between the tangent line and the base line at all points on the curve is θ3 ≧ 40 ° as a part of the portion (R2). A shape characterized in that the total length (r3) of the curved portion (R3) projected onto the base line of the lens cross-sectional shape is 20% or more with respect to the total length of the base line.

  The second embodiment is a method for producing the optical sheet of the present invention, and the third embodiment is a light source device for a liquid crystal display device which essentially comprises the optical sheet of the present invention. The fourth embodiment is a display device including the light source device for a liquid crystal display device of the present invention.

  By using the form of the present invention described in the above solution, the luminance in the viewing angle direction in the region immediately above the cold cathode tube of the light source device and the luminance in the viewing angle direction in the intermediate region of the adjacent cold cathode tubes are obtained. Each can be adjusted independently, and in various apparatus settings (apparatus configuration, light source apparatus conditions, combinations with optical sheets other than the present invention), high brightness uniformity on the light-emitting surface side in the settings can be realized.

It is a schematic diagram which shows the structure of a display apparatus. It is explanatory drawing of an example of the unit lens cross-sectional shape 1 of the optical sheet of this invention. It is explanatory drawing of an example of the unit lens cross-sectional shape 2 of the optical sheet of this invention. It is explanatory drawing of an example of the unit lens cross-sectional shape 1 of the optical sheet of this invention. It is explanatory drawing of an example of the unit lens cross-sectional shape of the optical sheet of this invention. It is explanatory drawing of the name of each part of the optical sheet of this invention. It is explanatory drawing of an example of the matrix which faces directly for forming the surface shape used for the manufacturing method of this invention.

  The following description is made with reference to the drawings and the like, but the present invention is not limited to the embodiments of the drawings.

  In the present specification, the first optical sheet refers to an optical sheet arranged first in the direction from the light source to the liquid crystal panel, and the second and subsequent optical sheets are the second, third, and fourth, respectively. And the optical sheets in the order of arrangement (see FIG. 1). The optical sheet closest to the front panel corresponds to the fourth optical sheet denoted by reference numeral 6 in FIG. If these optical sheets can achieve the purpose of installation (for example, improvement in luminance) without causing any hindrance (for example, significant increase in thickness and cost), there is no upper limit on the number of sheets.

  Hereinafter, first, the physical configuration such as the surface shape of the optical sheet according to the present invention will be described, and then the chemical composition, the method of combining other sheets, the apparatus configuration, etc. will be described.

<Surface shape of the optical sheet of the present invention>
In the optical sheet of the present invention, a convex lens group formed in a linear bowl shape is formed on at least one surface, and the lens group serves as a convex portion outer peripheral line in a vertical cross-sectional shape with respect to the length direction of the unit lens. And a unit lens having the following shape 1 and a unit lens having the shape 2.

≪Shape 1≫
A portion (R1) in which an outer peripheral line is a curve or a straight line and an angle θ1 formed by a tangent line or a straight line at all points on the curve and a base line of the unit lens cross-sectional shape is 25 ° ≦ θ1 ≦ 35 ° In addition, the total length (r1) of the portion (R1) projected onto the base line of the unit lens cross-sectional shape is 90% or more with respect to the total base line length of the unit lens cross-sectional shape. shape.

≪Shape 2≫
The total length (r2) projected on the base line of the unit lens shape of the portion (R2) represented by a single quadratic curve, the outer peripheral line is mainly composed of a curved portion, is the unit lens shape. A curve that is 90% or more with respect to the total length of the base line, and an angle (θ3) between the tangent line and the base line at all points on the curve is θ3 ≧ 40 ° as a part of the portion (R2). A shape including the portion (R3), and a total length (r3) of the curved portion (R3) projected onto the base line of the lens cross-sectional shape is 20% or more with respect to the total length of the base line .

  The surface shape of the entire lens shaping surface of the optical sheet is configured by arranging at least two different types of unit lenses substantially parallel to each other. The arrangement of the two different types of unit lenses may be arranged randomly without regularity, or may be arranged with a certain regularity. Further, the unit lenses may be arranged without a gap, or may be arranged with an interval. In order to fully exhibit the optical performance of the unit lens, it is preferable not to leave a gap. However, as long as it does not affect the performance of the optical sheet as an assembly of unit lenses, an interval may be provided for ease of molding. In order to provide optical performance different from that of the unit lenses, the unit lenses may be spaced apart. In that case, the planar shape between the unit lenses may be a surface shape that achieves the object to be imparted at a sufficient interval to achieve the object to be imparted.

  In the optical sheet of the present invention, these surface shapes are set on the light exit surface side. On the other hand, the surface shape configuration on the light incident surface side of the optical sheet of the present invention is not particularly limited and can be appropriately selected from flat surfaces, embossed surfaces, mat surfaces, surfaces having optical elements such as lenses, etc. An embossed surface and a mat surface are preferably used from the viewpoints of preventing sticking, preventing sound noise, and exhibiting a light scattering effect.

<Unit lens structure>
The unit lens structure arranged in the shape of a straight bowl on the optical sheet of the present invention is a unit lens in which the lens group has at least the following shape 1 as a convex portion outer peripheral line in a vertical cross-sectional shape with respect to the length direction of the unit lens. And a unit lens having shape 2.
≪Shape 1≫
A portion (R1) in which an outer peripheral line is a curve or a straight line and an angle θ1 formed by a tangent line or a straight line at all points on the curve and a base line of the unit lens cross-sectional shape is 25 ° ≦ θ1 ≦ 35 ° In addition, the total length (r1) of the portion (R1) projected onto the base line of the unit lens cross-sectional shape is 90% or more with respect to the total base line length of the unit lens cross-sectional shape. shape.
≪Shape 2≫
The total length (r2) projected on the base line of the unit lens shape of the portion (R2) represented by a single quadratic curve, the outer peripheral line is mainly composed of a curved portion, is the unit lens shape. A curve that is 90% or more with respect to the total length of the base line, and an angle (θ3) between the tangent line and the base line at all points on the curve is θ3 ≧ 40 ° as a part of the portion (R2). A shape including the portion (R3), and a total length (r3) of the curved portion (R3) projected onto the base line of the lens cross-sectional shape is 20% or more with respect to the total length of the base line .

  The shape 1 includes a portion (R1) where an angle (θ1) between a tangent or straight line and a base line at all points on the curve is 25 ° ≦ θ1 ≦ 35 °, and this portion (R1) The ratio of the total length (r1) projected onto the convex portion base line to the total base line length is 90% or more. When the ratio of the total (r1) is less than 90%, in order to increase the luminance in the viewing angle direction, when a commonly used optical sheet such as a prism sheet or a diffusion sheet with a lens is superposed, a cold cathode The luminance of the tube upper area is lowered, and it becomes difficult to eliminate luminance unevenness. The ratio of the total (r1) is more preferably 95% or more, and further preferably 100%.

  The portion (R1) is composed of a straight line or a curve, and may be a combination of a plurality of straight lines and curves. For example, a so-called prism shape composed of two straight lines is one of the preferred embodiments of the present invention. In the case of a curve, it is preferably a part of a quadratic curve, more preferably a part of a hyperbola, from the viewpoints of design easiness, workability, and optical performance. In addition, the unit lens having the shape 1 may have a left-right asymmetric shape, but is preferably left-right symmetric in order to reduce a luminance unevenness difference due to a viewing angle.

  The shape 2 has a portion (R2) represented by a single quadratic curve, and the quadratic curve is preferably an ellipse or a part of a hyperbola. When the part (R2) is a part of an ellipse, the eccentricity is preferably 0.50 to 0.95, more preferably 0.70 to 0.93, and further preferably 0.80 to 0.90. . The shape 2 includes a curved portion (R3) in which the angle (θ3) between the tangent line and the base line at all points on the curved line satisfies θ3 ≧ 40 °. The curved portion (R3) The ratio of the total length (r3) projected onto the base line is preferably 20% or more. When the ratio of the total (r3) is less than 20%, the light diffusion to the intermediate portion of the cold cathode tube array is reduced, the luminance in the viewing angle direction at the intermediate portion is lowered, and it is difficult to eliminate luminance unevenness. Become. The shape 2 may be an asymmetric shape, but is preferably left-right symmetric in order to reduce luminance unevenness due to viewing angle.

  In addition, the shape 1 and the shape 2 as the vertical cross-sectional shape with respect to the length direction of the unit lens in the optical sheet of the present invention do not need to be a single shape as long as the shape satisfies the above-described conditions. There may be a plurality of types of shapes 2 that satisfy the above-mentioned conditions.

  In the unit lens having the shape 1 and the unit lens having the shape 2, the area ratio of the unit lens having the shape 1 and the unit lens having the shape 2 (shape 1 / shape 2) is the sum of the projected areas of the entire light exit surface. ) Is preferably 0.05 to 2.0. In order to increase the luminance in the viewing angle direction when the area ratio is less than 0.05, when an optical sheet such as a commonly used prism sheet or a diffusion sheet with a lens is overlapped, Luminance decreases, and it becomes difficult to eliminate luminance unevenness. On the other hand, when the area ratio exceeds 2.0, the light diffusion to the intermediate portion of the cold cathode tube array is reduced, and the luminance in the viewing angle direction at the intermediate portion is lowered, making it difficult to eliminate luminance unevenness. The area ratio is more preferably 0.1 to 1.5, still more preferably 0.15 to 1.0, and most preferably 0.2 to 0.75.

  In addition, as the arrangement of the shape 1 and the shape 2, it is preferable that the lenses belonging to the shape 1 and the shape 2 are successively adjacent to each other while satisfying the above-described area ratio, and preferably 20 or less. More preferably. When the lenses belonging to the shape 1 and the shape 2 are continuously adjacent to each other more than the above range, the uniformity of the optical performance of the entire optical sheet is impaired, and the luminance leveling may be insufficient. In order to level the luminance, it is preferable that the overall ratio is substantially uniform while satisfying the ratio of the area ratio (shape 1 / shape 2). From the viewpoint of creating a master mold, it is most preferable to repeat the same arrangement pattern because it is easy to create and the uniformity of the entire optical sheet is easy to design.

  By disposing the unit lens having the shape 1 and the unit lens having the shape 2 as described above, the light from the light source can be sufficiently diffused to the intermediate portion of the cold cathode tube array, and the viewing angle direction in the intermediate portion The brightness can be improved. In addition, in order to increase the luminance in the viewing angle direction, even when a commonly used optical sheet such as a prism sheet or a diffusion sheet with a lens is superposed, the luminance in the upper area of the cold cathode tube can be sufficiently secured, and the thickness is further reduced. Increasing the distance between the line light sources due to the closer distance between the line light source and the optical sheet and the reduction in the energy consumption of liquid crystal display devices and the reduction in the number of line light sources for cost reduction will become increasingly difficult. Even in liquid crystal display panels, it has become possible to eliminate the uneven brightness.

[Unit lens height H and width P]
The length (P) of the base line of the outer periphery of the convex portion in the vertical cross-sectional shape with respect to the length direction of the unit lens is the length of the unit lens having the shape 1 (L1) and the length of the unit lens having the shape 2 ( L2) is preferably 30 to 300 μm, more preferably 40 to 200 μm, and even more preferably 50 to 150 μm. When the length (P) exceeds the above range, the luminance uniformity in the viewing angle direction tends to decrease, or a moire pattern tends to occur depending on the combination with the optical sheet to be superimposed. On the other hand, when the length (P) is less than the above range, when the optical sheet of the present invention is manufactured by transferring the lens shape using a matrix facing the lens shape, the separation after the lens shape transfer is performed. Mold may be difficult.

  In addition, the height (H) from the base portion of the convex portion outer peripheral line to the lens apex in the vertical cross-sectional shape with respect to the length direction of the unit lens has the height (H1) of the unit lens having the shape 1 and the shape 2. The unit lens height (H2) is preferably 15 to 100 μm, more preferably 20 to 85 μm, and even more preferably 25 to 65 μm. When the height (H) exceeds the above range, when the optical sheet of the present invention is manufactured by transferring the lens shape using a matrix facing the lens shape, the mold release after the lens shape transfer May become difficult. On the other hand, if the height (H) is less than the above range, the light diffusing effect of the lens is reduced, and the luminance uniformity may be reduced.

  The ratio (H / P) between the height (H) and the length (P) is not particularly limited, but as a unit lens having the shape 1, the ratio (H1 / L1) = 0.20 to 0.40. It is preferable that it is 0.22-0.35. On the other hand, as a unit lens having the shape 2, the ratio (H2 / L2) = 0.25 to 0.75 is preferable, and 0.30 to 0.65 is more preferable. When the ratio (H / P) is less than the above range, the light diffusing effect of the lens is reduced, and the brightness uniformity may be reduced. On the other hand, when the ratio (H / P) exceeds the above range, There is a possibility that the light diffused by the unit lens enters the adjacent unit lens again and does not exit in the direction of the front panel, resulting in a decrease in luminance.

<Combination of unit lens structures>
[Disposition ratio of unit lenses on the optical sheet plane]
In the optical sheet of the present invention, the unit straight lens having the shape 1 and the unit lens having the shape 2 are optimally shaped and combined to achieve high brightness uniformity. Therefore, usually other unit lens structures may be included. In order to exhibit preferable performance as the entire optical sheet, it is preferable that 80 area% or more of the entire light exit surface of the optical sheet is composed of a unit lens having shape 1 and a unit lens having shape 2 and is 90 area% or more. Is more preferable, and a configuration of 95 area% or more is more preferable. The other unit lens structures may be the same combination or a plurality of combination structures.

[Method of arranging unit lenses on the optical sheet plane]
In the optical sheet of the present invention, it is preferable that the interval between the apexes of the convex portion outer peripheral lines of adjacent unit lenses is 300 μm or less in a vertical cross section with respect to the length direction of the unit lenses. When the distance exceeds 300 μm, the luminance uniformity in the viewing angle direction is lowered, or a moire pattern is likely to be generated depending on the combination with the optical sheet to be overlapped. The arrangement of the lens groups arranged in the shape of the straight saddle is only required to be the arrangement ratio of the entire optical sheet, and the unit lens having the shape 1 and the unit lens having the shape 2 are arranged at the above intervals. Other unit lenses (for example, a lenticular shape or a prism shape) may be adjacent to each other.

  In the optical sheet of the present invention, the configuration of the connecting portion between adjacent unit lenses is not particularly limited as long as the target optical performance is not affected. For example, when it is desired to achieve only the optical performance as designed for the unit lens with the entire optical sheet, ideally, the lowest part of the outer peripheral line of the convex part in the vertical cross section with respect to the length direction of the unit lens is the base line. It is preferable that the unit lenses are aligned, that is, the unit lenses are arranged without gaps.

  However, a gap may be provided between the unit lenses as long as the optical performance of the entire optical sheet is not affected. For example, in the step of transferring the lens shape of the optical sheet of the present invention, a slight gap is given so as to facilitate release after the lens shape transfer. With respect to the cross-sectional shape between the unit lenses given to the optical sheet of the present invention by this slight gap, any shape such as a straight line, a concave curve, or a V-shape can be used as long as the optical performance is not affected. The invention is synonymous with no gap.

  On the contrary, in order to assist or strengthen the optical performance of the unit lens of the present invention, or to supplement other optical performance, the minimum portions of the adjacent unit lenses are separated from each other, and the shape according to the purpose is provided therebetween. May be added.

<Configuration of optical sheet of the present invention>
[Transparent thermoplastic resin]
The thermoplastic resin constituting the optical sheet of the present invention is not particularly limited as long as it is transparent and has an appropriate strength as a main component of the optical sheet. For example, polycarbonate resin; acrylic resin such as polymethyl methacrylate; styrene resin such as polystyrene, polyvinyl toluene and poly (p-methylstyrene); MS resin (copolymer of methyl methacrylate and styrene); norbornene resin Polyolefin resin; Polyarylate resin; Polyethersulfone resin Among these, two or more kinds of mixed resins can be used. A polycarbonate resin, a styrene resin, or a norbornene resin is preferably used. Among these, polycarbonate resin is particularly preferable as a resin for an optical sheet because it is excellent in transparency, heat resistance, and workability and has a good balance. In addition, an ultraviolet absorber, a fluorescent brightening agent, a flame retardant, and the like may be included as necessary.

[Light diffusion layer]
The optical sheet of the present invention may be composed of only a transparent resin, but in order to adjust the light diffusibility, a light diffusing layer made of particles having a light diffusing ability may be provided. The light diffusing layer may be uniformly or randomly dispersed in the entire optical sheet, only the lens portion, the entire portion other than the lens portion, only the light exit surface layer, only the light entrance surface layer, or the intermediate layer. In the light diffusion layer, light diffusing particles (light diffusing agent) having a refractive index of 0.01 or more different from that of the transparent resin are dispersed in the thermoplastic resin, and the diffusion direction of the light diffusion by the lens And adjusting the diffusion ratio and the like, it is possible to further increase the luminance uniformity in the viewing angle direction.

  The thickness of the optical sheet of the present invention can be appropriately adjusted and is not particularly limited, but can usually be about 0.3 mm or more and 10 mm or less. If the thickness is less than 0.3 mm, the light diffusing action may not be sufficiently exerted, or the rigidity may be insufficient to maintain the shape stability. On the other hand, if the thickness exceeds 10 mm, the entire apparatus to which the optical sheet of the present invention is applied. It is because there is a possibility that cannot be made compact. The thickness of the optical sheet is more preferably 0.5 mm or more and 5 mm or less. In addition, the thickness of an optical sheet is the sum total of the thickness of a base part, and unit lens height in FIG.

[Light diffusing agent]
Examples of the material of the light diffusing particles (fine particles) include (meth) acrylic resins, styrene resins, polyurethane resins, polyester resins, silicone resins, fluorine resins, and synthetic resins such as copolymers thereof. Glass; clay compounds such as smectite and kaolinite; inorganic oxides such as silica and alumina; and the like. Of these materials, (meth) acrylic resins, silicone resins, and silica are particularly suitable. As the light diffusing agent, any one of these exemplified materials, a single material mixture, a mixed material, and a mixed material mixture may be used. In the present application, (meth) acryl means acryl and / or methacryl.

  The average particle size of the light diffusing particles is preferably from 0.1 to 50 μm, more preferably from 0.3 to 10 μm, still more preferably from 0.5 to 5 μm. When the average particle diameter of the light diffusing particles is out of the above range, there is a possibility that sufficient light diffusibility cannot be exhibited. Here, the average particle diameter of the light diffusing particles is a volume-based median diameter measured by a particle size distribution measuring device (Coulter counter).

  The ratio between the thermoplastic resin and the light diffusing particles may be adjusted as appropriate. For example, if the light diffusing particles are added in an amount of 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin. Good. If the light diffusing particles are less than 0.01 part by mass with respect to 100 parts by mass of the thermoplastic resin, the luminance leveling adjustment by the light diffusing agent cannot be sufficiently performed. On the other hand, when the amount exceeds 10 parts by mass, the transparency of the light diffusion layer is lowered and the transmitted light is reduced, which may reduce the luminance of the entire light source device.

  In the case where the optical sheet of the present invention needs to have higher anisotropic light diffusion performance as the optical performance, low crosslink density organic fine particles capable of exhibiting anisotropic light diffusibility during molding of the optical sheet are preferably used. Monomers used as raw materials for the low crosslink density organic fine particles include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl (meth) acrylate, n -Butyl (meth) acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, hydroxyethyl (meth) acrylate, (Meth) acrylates such as hydroxypropyl (meth) acrylate; styrenes such as styrene, p-methylstyrene, vinyltoluene, pt-butylstyrene; N-phenylmaleimide, N-cyclohexylmaleimide, N-benzyl Maleimides such as reimide; (meth) acrylamide, (meth) acrylamides such as N-methylol (meth) acrylamide; acrylonitriles such as (meth) acrylonitrile; N-vinylpyrrolidone; or two of these The above can be mixed and used.

  Examples of the crosslinking agent used as a raw material for the crosslinked organic fine particles include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) ) Acrylate, bishydroxyethyl bisphenol A polyfunctional (meth) acrylates such as di (meth) acrylate; radically polymerizable crosslinking agents such as divinyloxyethoxy (meth) acrylate, diallyl phthalate, allyl (meth) acrylate, divinylbenzene; Polyfunctional epoxy compounds such as bisphenol A diglycidyl ether, diethylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether; Or a polyfunctional isocyanate compound such as N-methylol melamine or N-methylol benzoguanamine; or a mixture of two or more thereof. it can.

  The crosslinking density of the crosslinked organic fine particles for producing anisotropic diffusion is preferably 0.001% or more and 0.12% or less. Such organic fine particles having a low crosslinking density are spherical or substantially spherical at the raw material stage, but are formed in an ellipsoidal shape or a rod shape at a predetermined position (layer, etc.) of the optical sheet due to heat, shearing force, etc. received during the optical sheet molding. When this shape is changed, anisotropic diffusivity is expressed. In addition, a crosslinking density is a numerical value calculated | required by following Formula (1).

Fn (c): number of functional groups of the crosslinking agent used for production of radical polymerized crosslinked fine particles, provided that Fn (c) ≧ 2
Mw (c): Molecular weight of the crosslinking agent used for the production of radical polymerized crosslinked fine particles W (c): Mass blending ratio (%) of the crosslinking agent used for the production of radical polymerized crosslinked fine particles
W (m): Mass blending ratio (%) of monomer used for production of radical polymerized crosslinked fine particles
However, W (m) + W (c) = 100

[Antioxidant]
An antioxidant may be further added to at least one of the organic fine particles including the low crosslink density organic fine particles of the present invention and the thermoplastic resin. Since the antioxidant can suppress coloring of the thermoplastic resin and organic fine particles due to oxidation and deterioration during thermoforming, the luminance of the light source device to which the optical sheet of the present invention is applied can be more reliably exhibited.

  A conventionally well-known thing can be used as antioxidant. For example, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] or octadecyl-3- (3,5-di-t-butyl-1-hydroxyphenyl) propionate Hindered phenolic antioxidants; tris (2,4-di-t-butylphenyl) phosphite and tris [2-[[2,4,8,10-tetra-t-butyldibenzo [d, f] [ Phosphorous antioxidants such as 1,3,2] dioxaphosphin-6-yl] oxy] ethyl] amine; thiodiethylenebis [3- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate] and the like having no aromatic ring, pentaerythrityltetrakis (3-laurylthiopropionate) Sulfur-based antioxidants such as; lactone-based antioxidants such as the reaction product of 3-hydroxy-5,7-di-t-butyl-furan-2-one and o-xylene; Hydroxylamine antioxidants such as oxidation products of alkylamines; 3,4-dihydro-2,5,7,8-tetramethyl-2- (4,8,12-trimethyltridecyl) -2H-benzopyran- Vitamin E antioxidants such as 6-ol can be used.

  Although the usage-amount of antioxidant may be adjusted suitably, normally, what is necessary is just to add about 0.005 mass% or more and 0.3 mass% or less with respect to a thermoplastic resin.

<About optical sheet manufacturing method and optical sheet molded by the manufacturing method>
The optical sheet of the present invention can be manufactured using a matrix that faces the surface shape described in the claims of the present invention. The shape of the matrix is a shape for realizing the surface shape described in <Surface shape of the optical sheet of the present invention>, <Unit lens structure> and <Combination of unit lens structures> in the section of the description of the invention. That is, it is sufficient if the convex portions of these surface structures are concave and the concave portions are convex. In the present invention, the matrix of these structures is referred to as “a matrix facing directly to form the surface shape”. "(FIG. 7).

  The optical sheet of the present invention can be manufactured by a manufacturing process having the matrix. Specifically, a transparent thermoplastic resin or a transparent thermoplastic resin can be blended with fine particles having light diffusibility and obtained by known extrusion molding or injection molding. When a laminated body is used to adjust optical performance and other physical properties, for example, when a light diffusing layer is installed only on a specific layer such as a light incident side or a lens side, or for improving the light resistance of an optical sheet. In the case of installing an absorber blending layer or an antistatic layer for preventing dust from adhering to the optical sheet due to static electricity, the extrusion method is particularly preferable from the viewpoint of productivity. In particular, when molding a lens shape with a narrow pitch, it is particularly preferable to use the method described in International Application No. (PCT / JP2009 / 0666525).

  Whether or not a molded product according to the design of the present invention can be manufactured can be confirmed by obtaining r1, r2, and r3 from the molded product. Specifically, a vertical cross-sectional shape with respect to the length direction of the unit lens is photographed with an electron microscope or the like, and an appropriate curve (may be a combination of two or more) is fitted to the outer peripheral line of the convex part, and the tangent line is the basis. It is possible to obtain from the range of the outer peripheral line in which the angle formed with the line is a predetermined angle.

  With these various manufacturing methods, the optical sheet manufactured so that the configuration of the sheet has the configuration described in <Configuration of optical sheet of the present invention> is the <surface shape of optical sheet of the present invention>, <unit lens It becomes an excellent optical sheet having substantially the same shape and optical and mechanical characteristics as the optical sheet having the lens shape described in “Structure> and <Combination of Unit Lens Structures”.

<Combination with the second optical sheet and other optical sheets>
The optical sheet of the present invention is preferably used as the first optical sheet in order to efficiently use its high optical performance adjustment capability in other optical sheets and apparatus settings. By using it as the first optical sheet, the effect of improving the luminance in the viewing angle direction in the intermediate region of the adjacent cold cathode tubes of the light source device and the luminance in the viewing angle direction in the region immediately above the cold cathode tube are improved. The effect can be utilized to the maximum. In addition, when used as the first optical sheet, as the other optical sheet, a prism sheet, a diffusion sheet, a diffusion sheet with a lens, a reflective polarizing film, etc. can be used, and the combination thereof is more suitable depending on the conditions of the light source device. In this case, as the optical sheet closest to the front panel, it is preferable to use a diffusion sheet or a diffusion sheet with a lens. In particular, the use of at least one prism sheet for the second and subsequent optical sheets eliminates dark lines generated near the cold cathode tube and achieves high brightness and brightness uniformity on the light exit surface immediately before the front panel. It becomes possible.

  The optical sheet manufactured according to the present invention can diffuse light in a desired direction and, as a result, can maintain the uniformity of the light, so that the power consumption reduction and the manufacturing cost of the liquid crystal display device, which are in increasing demand, are increased. It is extremely useful industrially because it can contribute to the reduction in the thickness of the liquid crystal display device as it can exhibit high brightness while reducing. Therefore, by applying the optical sheet of the present invention and the direct light source device having the optical sheet to a liquid crystal display device or the like, it is possible to reduce power consumption and manufacturing cost. Furthermore, the liquid crystal display device can be made thin.

  Next, practical examples of the present invention will be described in Tables 1 and 2, but the present invention is not limited to these examples.

<Method for measuring surface of optical sheet>
Using polycarbonate as a raw material, an optical sheet having an embossed surface (arithmetic average roughness Ra = 2 to 6 μm) on the light incident surface and a linear rod-shaped lens group having various cross-sectional shapes on the light output surface was manufactured by extrusion molding. The cross-sectional shapes of the produced various optical sheets were confirmed using a scanning electron microscope. Table 1 shows the observation results of the surface shape.

<Evaluation of uneven brightness>
A white reflector is provided on the inner surface of a plastic case with an inner dimension of 690 mm, depth of 390 mm, and depth of 10 mm, and 19 cold cathode fluorescent tubes with a diameter of 3 mm are spaced 20.5 mm apart from the bottom of the reflector. The optical sheets of the present invention having various shapes were arranged on the direct type light source device arranged in parallel so that the lens processing surface was up and the longitudinal direction of the lens was parallel to the longitudinal direction of the cold cathode tube. On this optical sheet, a commercially available light diffusion sheet (CH273 manufactured by Hiroshige Kogyo (Suzhou) Co., Ltd.), prism sheet (BEF II 90/50 manufactured by Sumitomo 3M: apex angle 90 degrees, pitch 50 μm), micro lens sheet ( Made by Hiroshige Kogyo (Suzhou) Co., Ltd. ML24M: an optical sheet with a hemispherical convex lens group arranged finely on one surface) as shown in Table 2, and in each combination, the direct light source device The luminance unevenness was visually observed from a position 400 mm away from the center in the vertical direction. The brightness unevenness is evaluated in 10 stages, and the larger the value, the less the brightness unevenness, indicating that the lamp image of the cold cathode tube is not noticeable. The evaluation results are shown in Table 1.

  By using the form of the present invention, the first optical sheet capable of improving the luminance ratio at the intermediate point between the line light sources arranged in parallel to each other and / or directly above the cold cathode tube and obtaining a uniform luminance distribution, and Type light source devices and liquid crystal display devices can be provided, which is extremely useful in industry.

1: Cold cathode tube lamp 2: Reflective film 3: 1st optical sheet 4: 2nd optical sheet 5: 3rd optical sheet 6: 4th optical sheet 7: Front panel P: Lens part width H: Lens portion height θ1: Angle formed by the tangent of the straight line or curved portion of the R1 portion and the base line θ3: Angle formed by the tangent of the curved portion R3 and the base line R1: Linear portion or curved line satisfying 25 ° ≦ θ1 ≦ 35 ° Part R2: Curved part R3 represented by a single quadratic curve: Curved parts r1, r2, r3 satisfying θ3 ≧ 40 °: Projection length to the base line corresponding to each of the outer peripheral line parts R1, R2, R3

Claims (10)

An optical sheet having a convex lens group formed in a linear bowl shape on the surface,
An optical sheet, wherein the lens group includes a unit lens having the following shape 1 and a unit lens having the shape 2 as convex portion outer peripheral lines having a vertical cross-sectional shape with respect to the length direction of the unit lens.
≪Shape 1≫
A portion (R1) in which an outer peripheral line is a curve or a straight line and an angle θ1 formed by a tangent line or a straight line at all points on the curve and the base line of the unit lens cross-sectional shape satisfies 25 ° ≦ θ1 ≦ 35 °. And the total length (r1) of the portion (R1) projected onto the base line of the unit lens cross-sectional shape is 90% or more with respect to the total base line length of the unit lens cross-sectional shape. shape.
≪Shape 2≫
The total length (r2) projected on the base line of the unit lens shape of the portion (R2) represented by a single quadratic curve, the outer periphery of which is mainly composed of a curved part, is the unit lens shape. 90% or more of the total length of the base line,
In addition, as a part of the portion (R2), an angle (θ3) formed by a tangent line and a base line at all points on the curve includes a curved portion (R3) where θ3 ≧ 40 °, and the curved portion ( A shape in which the total length (r3) projected onto the base line of the lens cross-sectional shape of R3) is 20% or more with respect to the total length of the base line.   The optical sheet according to claim 1, wherein the total area of the base lines of the unit lens having the shape 1 and the unit lens having the shape 2 is 80 area% or more of the entire light exit surface.   The area ratio (shape 1 / shape 2) of the unit lens having the shape 1 and the unit lens having the shape 2 as a sum of the respective projection areas on the entire light exit surface is 0.05 to 2.0. 2. The optical sheet according to 2.   The ratio (H1 / L1) of the base line length (L1) and the height (H1) from the base line to the lens apex in the vertical cross-sectional shape with respect to the length direction of the unit lens having the shape 1 is 0.20-0. .40, and the ratio (H2 / L2) of the length (L2) of the base line and the height (H2) from the base line to the top of the lens in the vertical cross-sectional shape with respect to the length direction of the unit lens having the shape 2 ) Is 0.25 to 0.75. The optical sheet according to any one of claims 1 to 3.   5. The lens group according to claim 1, wherein in the vertical cross-sectional shape with respect to the length direction of the unit lens, the distance between the apexes of the convex portion outer peripheral lines of adjacent unit lenses is 300 μm or less. Optical sheet. The material constituting the optical sheet contains a thermoplastic resin and fine particles having an average particle diameter different from that of the thermoplastic resin of 0.1 μm to 50 μm,
The optical sheet according to any one of claims 1 to 5, wherein the compounding amount of the fine particles is 0.01 to 10 parts by mass with respect to 100 parts by mass of the thermoplastic resin.   A method for manufacturing an optical sheet, comprising using a matrix that faces the surface for forming the surface shape of the optical sheet according to claim 1.   An optical sheet manufactured by the manufacturing method according to claim 7.   A light source device for a display device, comprising the optical sheet according to claim 1 and a prism sheet.   A display device comprising the light source device for a display device according to claim 9.