JP2008243637A - Light diffuser plate, surface light source apparatus and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface light source apparatus preventing the generation of annoying noise from an area of contact between a light diffuser plate and a lamp box. <P>SOLUTION: In this surface light source apparatus 1, a plurality of light sources 2 are disposed in the lamp box 5 made of a resin and having an open front side; a light diffuser plate 3 made of a resin is disposed in a state contacting at least a front surface 31a of an edge frame part 31 of the lamp box 5 to close the open surface of the box 5; at least a part of the back surface of the light diffuser plate 3 that contacts the front surface 31a of the edge frame part is formed on a mat surface; the mat surface has an arithmetic mean surface roughness Ra of 0.8-15 μm and a mean surface irregularity interval Rsm of 100-300 μm; a plurality of nearly-semicircular projecting parts 7 each having a cross-sectionally nearly-semicircular shape, are projected from the front surface of the light diffuser plate 3; a pitch interval P between the nearly-semicircular projecting parts 7 adjacent to each other is 10-500 μm; the height H of the nearly-semicircular projecting parts 7 is set to 3-500 μm; and H/P is 0.2-0.8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light diffusing plate, a surface light source device, and a liquid crystal display device that can prevent generation of unpleasant noise from a contact portion between a light diffusing plate and a lamp box.

  In this specification and claims, the term “arithmetic average roughness Ra” means an arithmetic average roughness Ra measured according to JIS B0601-2001, and “an average interval Rsm of unevenness”. "Means the average interval Rsm of the irregularities measured according to JIS B0601-2001.

As a liquid crystal display device, for example, a configuration in which a surface light source device is disposed as a backlight on a lower surface side (back surface side) of an image display unit in which a pair of polarizing plates is disposed on both upper and lower surfaces of a liquid crystal cell is known. As the surface light source device for the backlight, a surface light source device having a configuration in which a plurality of light sources are arranged in a lamp box and a light diffusion plate is arranged on the front side of these light sources is known (Patent Document 1). reference).
Japanese Unexamined Patent Publication No. 7-141908 (paragraph 0012, FIG. 1)

  By the way, the light diffusing plate is arranged and fixed in contact with the front surface of the edge frame portion of the lamp box, and unpleasant noise is generated due to friction between the front surface of the edge frame portion and the light diffusing plate. There are things to do. For example, when the power is turned on, the light diffusing plate expands due to a temperature rise inside the surface light source device, and at this time, an unpleasant sound may be generated due to a rubbing phenomenon between the front surface of the edge frame and the light diffusing plate. Such generation of unpleasant noise was remarkable when the edge frame of the lamp box was made of polycarbonate.

  The present invention has been made in view of such a technical background, and provides a light diffusing plate, a surface light source device, and a liquid crystal display device that can prevent generation of unpleasant noise from a contact portion between a light diffusing plate and a lamp box. The purpose is to provide.

  In order to achieve the above object, the present invention provides the following means.

[1] In a state where a plurality of light sources are spaced apart from each other in a resin lamp box whose front side is open and a resin light diffusion plate is in contact with the front surface of the edge frame portion of the lamp box. A surface light source device arranged to close an open surface of the lamp box,
A portion of the back surface of the light diffusing plate that contacts at least the front surface of the edge frame portion is formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval of the unevenness of the mat surface Rsm is 100 to 300 μm,
A plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. A surface light source device, wherein the height H of the semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.

[2] In a state in which a plurality of light sources are spaced apart from each other in a resin lamp box whose front side is open and a resin light diffusion plate is in contact with the front surface of the edge frame portion of the lamp box. A surface light source device arranged to close an open surface of the lamp box,
The entire back surface of the light diffusing plate is formed on a mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface is 100 to 300 μm,
A plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. A surface light source device, wherein the height H of the semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.

  [3] The substantially semicircular convex portion is a cylindrical lens-shaped convex strip portion, the light source is a linear light source, the length direction of the cylindrical lens-shaped convex strip portion and the length direction of the linear light source 3. The surface light source device according to item 1 or 2, wherein the surface light source device is configured so as to substantially match.

  [4] The surface light source device according to any one of items 1 to 3, wherein the light diffusion plate has a total light transmittance of 55 to 85%.

  [5] A liquid crystal display device comprising the surface light source device according to any one of items 1 to 4 and a liquid crystal panel disposed on a front surface side of the surface light source device.

[6] The matte surface has an arithmetic average roughness Ra of 0.8 to 15 μm, and the mat surface has irregularities. The average interval Rsm is 100 to 300 μm,
A plurality of substantially semicircular protrusions having a substantially semicircular cross-sectional shape projecting from the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular protrusions is set to 10 to 500 μm, A light diffusing plate, wherein the height H of the substantially semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.

[7] The one surface is made of a resin light-transmitting plate formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average roughness of the mat surface The interval Rsm is 100 to 300 μm,
A plurality of substantially semicircular protrusions having a substantially semicircular cross-sectional shape projecting from the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular protrusions is set to 10 to 500 μm, A light diffusing plate, wherein the height H of the substantially semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.

  In the invention of [1], at least a portion of the back surface of the light diffusing plate that is in contact with the front surface of the edge frame portion is formed on the mat surface, and the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm. Since the average distance Rsm is 100 to 300 μm, it is possible to prevent the generation of unpleasant noise due to the friction between the front surface of the edge frame portion of the lamp box and the light diffusion plate. In the conventional configuration, the generation of unpleasant noise was particularly noticeable when the edge frame portion of the lamp box was made of polycarbonate, but according to the present invention, when the edge frame portion of such a lamp box is made of polycarbonate, The generation of unpleasant noise can be sufficiently prevented.

  Further, a plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. Since the height H of the semicircular convex portion is set to 3 to 500 μm and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8, the luminance of the emitted light can be improved. .

  In the invention of [2], the entire back surface of the light diffusing plate is formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface is 100 to 300 μm. Therefore, it is possible to prevent generation of unpleasant noise due to friction between the front surface of the edge frame portion of the lamp box and the light diffusion plate. In the conventional configuration, the generation of unpleasant noise was particularly noticeable when the edge frame portion of the lamp box was made of polycarbonate, but according to the present invention, when the edge frame portion of such a lamp box is made of polycarbonate, The generation of unpleasant noise can be sufficiently prevented. In addition, since the entire back surface of the light diffusing plate is formed on the mat surface, the manufacturing efficiency can be improved and it is easy to cope with production of different sizes.

  Further, a plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. Since the height H of the semicircular convex portion is set to 3 to 500 μm and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8, the luminance of the emitted light can be improved. .

  Furthermore, due to the synergistic effect that the entire back surface of the light diffusing plate is formed on a specific mat surface and the substantially semicircular convex portion of the specific configuration is projected on the front surface of the light diffusing plate, It becomes possible to emit uniform light without uneven brightness. In addition, the brightness nonuniformity suppression effect by the said synergistic effect becomes larger when the structure (for example, 55 to 85%) with a high total light transmittance of a light diffusing plate is employ | adopted. In addition, the synergistic effect of suppressing luminance unevenness is particularly remarkable in a light diffusing plate containing a light diffusing agent (light diffusing particles) having a particle size of submicron. For example, when an image of a light source is transmitted through a light diffusing plate containing a light diffusing agent (light diffusing particles) having a particle size of sub-micron, a contour image of a colored light source is transmitted to the front side. Although the appearance is easy, in the invention of [2], the appearance of the contour image of the light source can be sufficiently suppressed by the synergistic effect.

  In the invention of [3], since the length direction of the cylindrical lens-shaped ridges and the length direction of the linear light source are substantially coincident with each other, an image of the light source transmitted through the light diffusing plate can be obtained. There is an advantage that it can be spread in the direction perpendicular to the length direction of the linear light source and the uniformity of the in-plane brightness can be improved.

  In the invention of [4], since the total light transmittance of the light diffusing plate is 55 to 85%, sufficient luminance is obtained, and the luminance unevenness suppressing effect due to the synergistic effect is sufficiently obtained.

  In the invention of [5], a liquid crystal display device capable of preventing generation of unpleasant noise from a contact portion between the light diffusion plate and the lamp box is provided.

  The invention (6) (light diffusing plate) comprises a resin light-transmitting plate in which at least a peripheral portion of one surface is formed on a mat surface, and an arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm. In addition, since the average interval Rsm of the unevenness of the mat surface is 100 to 300 μm, it is possible to prevent generation of unpleasant noise due to friction between the front surface of the edge frame portion of the lamp box and the light diffusion plate.

  In addition, a plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape are provided on the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. Since the height H of the substantially semicircular convex portion is set to 3 to 500 μm and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8, the brightness of the emitted light is improved. Can do.

  The invention of [7] comprises a resin light-transmitting plate in which the entire surface of one surface is formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the unevenness of the mat surface Since the average distance Rsm is 100 to 300 μm, it is possible to prevent the generation of unpleasant noise due to the friction between the front surface of the edge frame portion of the lamp box and the light diffusion plate. In addition, since the entire surface of one surface is formed on the mat surface, the manufacturing efficiency can be improved, and it is very easy to cope with production of different sizes.

  In addition, a plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape are provided on the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. Since the height H of the substantially semicircular convex portion is set to 3 to 500 μm and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8, the brightness of the emitted light is improved. Can do.

  Furthermore, the entire surface of one surface of the light diffusing plate is formed on a specific mat surface, and the substantially semicircular convex portion of the specific configuration is projected on the other surface of the light diffusing plate. Due to the synergistic effect, uniform light with no luminance unevenness can be emitted and the diffusivity of the light diffusion plate can be sufficiently improved.

  An embodiment of a liquid crystal display device according to the present invention is shown in FIG. In FIG. 1, (1) is a surface light source device (backlight), (10) is a liquid crystal panel, and (20) is a liquid crystal display device. The liquid crystal panel (10) includes a liquid crystal cell (11) and polarizing plates (12) and (13) disposed on both upper and lower sides of the liquid crystal cell (11).

  The said surface light source device (1) is arrange | positioned at the lower surface side (back side) of the polarizing plate (13) below the said liquid crystal panel (10). The surface light source device (1) includes a thin box-shaped lamp box (5) having a substantially rectangular shape in plan view and an open front surface (upper surface), and a lamp box (5) spaced apart from each other. A plurality of linear light sources (2) arranged, and a resin light diffusing plate (3) arranged on the front side (upper side) of the plurality of linear light sources (2) are provided. As shown in FIG. 1, the lamp box (5) has an edge frame portion (31) made of a side plate extending from the periphery of the rear plate (32) having a rectangular shape in plan view and extending toward the front side. The front side is open. The light diffusing plate (3) is disposed and fixed to the lamp box (5) so as to close the open surface on the front side. That is, the light diffusing plate (3) is configured such that the peripheral portion of the back surface (3a) of the light diffusing plate (3) is in contact with the front surface (31a) of the edge frame portion (31) of the lamp box (5). ) Is fixed to the lamp box (5). A light reflecting layer (not shown) is provided on the inner surface of the lamp box (5).

  As shown in FIG. 3, the light diffusing plate (3) is made of a resin light transmitting plate having the entire back surface (3a) formed on the mat surface (6). That is, the light diffusion plate (3) is arranged so that the surface (3a) formed on the mat surface (6) is on the light source (2) side (see FIG. 1). The arithmetic average roughness Ra of the mat surface (6) is set to 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface (6) is set to 100 to 300 μm. In the present embodiment, the entire surface of the back surface (3a) of the light diffusing plate (3) is formed on the mat surface (6). However, the present invention is not limited to such a configuration, and the light diffusing plate ( It is only necessary that at least a portion in contact with the front surface (31a) of the edge frame portion on the back surface (3a) of 3) is formed on the mat surface (6). For example, as shown in FIG. 4, the back surface of the light diffusion plate (3) It is also possible to adopt a configuration in which only the portion in contact with the edge frame front surface (31a) in (3a) is formed on the mat surface (6).

  In addition, the front surface (3b) of the light diffusing plate (3) is formed with a concavo-convex shape portion (4) formed by projecting a plurality of substantially semicircular convex portions (7) having a substantially semicircular cross section. Yes. That is, the surface (3b) on which the substantially semicircular convex portion (7) is formed in the light diffusing plate (3) is disposed on the liquid crystal panel (10) side (see FIG. 1). The pitch interval (P) between adjacent semicircular convex portions (7) is set to 10 to 500 μm, the height (H) of the substantially semicircular convex portion (7) is set to 3 to 500 μm, and the pitch The ratio (H / P) of the height (H) to the interval (P) is set to 0.2 to 0.8.

  In the present embodiment, the substantially semicircular convex portion (7) is a cylindrical lens-shaped convex strip portion (substantially semi-cylindrical shape) extending along one direction parallel to the surface of the light diffusion plate (3). Convex ridges) (8), and the longitudinal directions (axial direction) of the plurality of cylindrical lens-shaped ridges (8) are arranged substantially parallel to each other (see FIG. 2). The cylindrical lens shape means that a substantially cylindrical body is cut by a plane parallel to the axial direction (length direction) (a plane including the axis or a plane not including the axis). The shape corresponding to any one of the members is meant.

  In the present embodiment, the cylindrical lens-shaped convex strip portion (8) is a convex strip portion having a semi-cylindrical shape, that is, any one of the cylindrical body cut into two evenly on a plane including its axis. It is a protruding item | line part provided with the shape corresponded to one member (semi-cylindrical body).

  Further, in the present embodiment, a linear light source is used as the light source (2), and the length direction of the linear light source (2) and the cylindrical lens-shaped convex strip portion of the light diffusion plate (3) ( It is arranged so that the length direction of 8) substantially coincides. Further, the length direction of the cylindrical lens-shaped ridges (8) is arranged so as to substantially coincide with the longitudinal direction (N) of the light diffusion plate (3) (see FIG. 2).

  In the surface light source device (1) according to the above configuration, at least a portion of the back surface (3a) of the light diffusing plate (3) that contacts the front surface (31a) of the edge frame portion of the lamp box (5) is formed on the mat surface (6). Since the arithmetic average roughness Ra of the mat surface (6) is 0.8 to 15 μm and the average interval Rsm of the unevenness of the mat surface (6) is 100 to 300 μm, the edge of the lamp box (5) The contact between the frame front surface (31a) and the light diffusing plate (3) becomes a point contact or a state close to a point contact, and friction between both is reduced, thereby the edge frame front surface (31a) of the lamp box (5). ) And the light diffusion plate (3) can be prevented from generating unpleasant noise.

  Further, the pitch interval (P) between adjacent semicircular convex portions (7) is set to 10 to 500 μm, and the height (H) of the substantially semicircular convex portion (7) is set to 3 to 500 μm. Since the ratio (H / P) of the height (H) to the pitch interval (P) is set to 0.2 to 0.8, the brightness of the emitted light can be sufficiently increased.

  Furthermore, in this embodiment, the entire back surface (3a) of the light diffusing plate (3) is formed on the mat surface (6) with Ra of 0.8 to 15 μm and Rsm of 100 to 300 μm, Uniform light without uneven brightness can be emitted by a synergistic effect with the substantially semicircular protrusion (7) protruding from the front surface (3b) of the light diffusion plate (3). That is, the surface uniformity of luminance is excellent.

  Moreover, in this embodiment, since the whole surface of the back surface (3a) of the light diffusing plate (3) is formed on the mat surface (6), the manufacturing efficiency can be improved, and products of different sizes are produced. This has the advantage of being easy to handle.

  In the present invention, the mat surface (6) is formed on at least a portion of the back surface (3a) of the light diffusing plate (3) in contact with the front surface (31a) of the edge frame portion. The arithmetic average roughness Ra of 6) needs to be set in the range of 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface (6) needs to be set in the range of 100 to 300 μm. If Ra is less than 0.8 μm or Rsm exceeds 300 μm, the effect of preventing the generation of unpleasant noise cannot be sufficiently obtained. Further, a mat surface having an Ra of more than 15 μm and a mat surface having an Rsm of less than 100 μm are difficult to manufacture and the productivity is deteriorated. Among them, the arithmetic average roughness Ra of the mat surface (6) is preferably set in the range of 1.0 to 10 μm, and the average interval Rsm of the unevenness of the mat surface (6) is set in the range of 130 to 250 μm. It is preferable.

  Examples of the cross-sectional shape of the mat surface (6) include a substantially semicircular arc shape and a flat curve shape, but are not particularly limited thereto. That is, as long as the conditions of Ra: 0.8 to 15 μm and Rsm: 100 to 300 μm are satisfied, the cross-sectional shape of the mat surface (6) may be any shape.

  The formation method of the mat surface (6) is not particularly limited. For example, the mat surface may be formed by transferring irregularities using an embossing roll on the surface, or the mat surface may be formed by particle bulging on the surface by adding fine particles to the constituent resin. In particular, it is not limited to these methods.

  Further, in the present invention, a configuration is adopted in which a plurality of substantially semicircular convex portions (7) having a substantially semicircular cross section are provided on the front surface (3b) of the light diffusing plate (3). The pitch interval (P) between adjacent semicircular convex portions (7) is set to 10 to 500 μm, the height (H) of the substantially semicircular convex portion (7) is set to 3 to 500 μm, and the pitch The ratio (H / P) of the height (H) to the interval (P) needs to be set to 0.2 to 0.8. By setting to such a range, the brightness | luminance of emitted light can fully be improved. If the pitch interval (P) is less than 10 μm, it is difficult to accurately shape the shape. If the pitch interval (P) exceeds 500 μm, the shape of the substantially semicircular convex portion (7) is visually recognized as a streak. is there. Further, when the height (H) is less than 3 μm, when the substantially semicircular convex portion (7) is formed on the light diffusing plate, the shape of the convex portion (7) is easily melted by the heat of the plate itself, so that the desired shape is obtained. When the height (H) exceeds 500 μm, for example, the shape accuracy of a mold for transferring the shape of the substantially semicircular convex portion (7) to the light diffusing plate is deteriorated. Further, if the ratio (H / P) is less than 0.2, the luminance unevenness suppressing effect is not sufficient, and if the ratio (H / P) exceeds 0.8, it is difficult to perform shape processing with high accuracy. Especially, it is preferable that the pitch space | interval (P) of adjacent substantially semicircle convex parts (7) is set to 50-300 micrometers. Moreover, it is preferable that the height (H) of the said substantially semicircle convex part (7) is set to 25-250 micrometers. The ratio (H / P) of the height (H) to the pitch interval (P) is preferably set to 0.2 to 0.75.

  The method for forming the substantially semicircular convex portion (7) is not particularly limited. For example, a thermal transfer method using a mold, an injection molding method, a cutting method, a profile extrusion molding method, a melt extrusion transfer using an engraving roll. Examples include molding methods.

  Although the thickness (S) of the said light diffusing plate (3) is not specifically limited, It is preferable to set to the range of 1.0-5.0 mm.

  Moreover, it is preferable that the total light transmittance of the said light diffusing plate (3) is set to the range of 55 to 85%. By setting to such a range, sufficient luminance can be obtained, and the luminance unevenness suppressing effect by the above-described synergistic effect can be sufficiently obtained. Although such a total light transmittance is not specifically limited, For example, it can adjust by adding a light-diffusion agent. In addition, although the said total light transmittance is a total light transmittance measured based on JISK7361-1 (1997), in the case of a measurement, the substantially semicircular convex of the said light diffusing plate (3). The measurement is performed with the front surface (3b) side on which the portion (7) is formed facing the integrating sphere and the pitch interval direction toward the left and right sides.

  In the present invention, the light diffusing plate (3) is not particularly limited, but a single-layer plate made of a translucent resin and a different type of translucent resin on at least one surface of a base layer made of a translucent resin. A laminated plate or the like in which one or more other layers made of are laminated is used.

  Examples of the translucent resin include acrylic resin, styrene resin, polycarbonate, polyethylene, polypropylene, cyclic polyolefin, cyclic olefin copolymer, polyethylene terephthalate, MS resin (methyl methacrylate-styrene copolymer resin), Examples include ABS resin (acrylonitrile-butadiene-styrene copolymer resin), AS resin (acrylonitrile-styrene copolymer resin), and the like.

  The light diffusing plate (3) contains a light diffusing agent (light diffusing particles) as necessary. The light diffusing agent is not particularly limited as long as it is a particle having a refractive index different from that of the translucent resin constituting the light diffusing plate (3), and any material can be used. it can. The inorganic light diffusing agent is not particularly limited, and examples thereof include calcium carbonate, barium sulfate, titanium oxide, aluminum hydroxide, silica, glass, talc, mica, white carbon, magnesium oxide, and zinc oxide. May have been subjected to a surface treatment with a fatty acid or the like. The organic light diffusing agent is not particularly limited, and examples thereof include styrene polymer particles, acrylic polymer particles, and siloxane polymer particles. Among them, the weight average molecular weight is 500,000 to 5,000,000. High molecular weight polymer particles and crosslinked polymer particles having a gel fraction of 10% by mass or more when dissolved in acetone are preferably used. As the light diffusing agent, one of those exemplified above may be used, or a mixture of two or more of these may be used.

  The absolute value of the difference between the refractive index of the translucent resin and the refractive index of the light diffusing agent is preferably 0.02 or more from the viewpoint of light diffusibility, and the absolute value is 0.13 or less. Is preferable from the viewpoint of light transmittance. That is, the absolute value of the difference between the refractive index of the translucent resin and the refractive index of the light diffusing agent is preferably in the range of 0.02 to 0.13.

  The light diffusing plate (3) may contain various additives such as an ultraviolet absorber, a heat stabilizer, an antioxidant, a weathering agent, a light stabilizer, a fluorescent brightening agent, and a processing stabilizer. . In addition, when adding a ultraviolet absorber, it is preferable to add 0.1-3 mass parts of ultraviolet absorbers with respect to 100 mass parts of said translucent resins. By setting it in such a range, bleeding to the surface of the ultraviolet absorber can be suppressed, and the appearance can be favorably maintained. Further, when a heat stabilizer is also added, the heat stabilizer is preferably 2 parts by mass or less with respect to 1 part by mass of the UV absorber in the translucent resin, and in particular, the UV absorption in the translucent resin. It is particularly preferable to add 0.01 to 1 part by mass of a heat stabilizer with respect to 1 part by mass of the agent.

  Although it does not specifically limit as said light source (2), For example, point light sources, such as a light emitting diode, etc. other than linear light sources, such as a fluorescent tube, a halogen lamp, and a tungsten lamp, are mentioned.

  Moreover, it is preferable that the space | interval (L) of adjacent light sources (2) (2) is set to 10 mm or more from a viewpoint of power saving, and the said light diffusing plate (3) and the said light source (2). The distance (d) is preferably set to 50 mm or less from the viewpoint of thinning. D: L is preferably 1: 5 to 5: 1. Especially, it is more preferable that the space | interval (L) of the said adjacent light sources (2) (2) is set to 10-100 mm. The distance (d) between the light diffusing plate (3) and the light source (2) is particularly preferably set to 10 to 50 mm.

  In the above embodiment, the substantially semicircular convex portion (7) of the light diffusing plate (3) is formed by a cylindrical lens-shaped convex strip portion (8) extending along one direction parallel to the surface thereof. (One-dimensional type) (see FIG. 2) is not particularly limited to such a configuration. For example, the substantially semicircular convex portion (7) of the light diffusing plate has different two parallel to the surface thereof. It may be formed by a convex portion (8) having a cylindrical lens shape extending along a direction (for example, two directions orthogonal to each other) (that is, it may be a two-dimensional type).

  Moreover, in the said embodiment, although a substantially semicircle convex part (7) is a structure (refer FIG. 2) which consists of a cylindrical lens-shaped convex strip part (substantially semi-cylindrical convex strip part) (8), The configuration is not limited to such a configuration. For example, a large number of substantially semicircular convex portions (7) that are not continuous in the length direction (N) are arranged along the length direction (N) in a state of being separated from each other. It is also possible to adopt the configuration described above.

  Moreover, in the said embodiment, although the surface of a substantially semicircle convex part (7) is formed in the cross-sectional semicircular arc shape, it is not specifically limited to such a shape, For example, as shown in FIG. Further, it may have a shape corresponding to any one of the members cut by a plane that does not include the axis, or is formed in a shape such as a semi-elliptical arc shape in cross section or a flat curved line shape in cross section. The term “substantially semicircular convex portion” may be used to include a convex portion having such a shape.

  Moreover, in the said embodiment, although comprised so that it may have a flat surface part (9) between adjacent semicircle convex parts (7), it is not limited to such a structure in particular, For example, FIG. As shown in FIG. 6, a continuous configuration in which no flat surface portion is formed between adjacent semicircular convex portions (7) may be adopted. In addition, in the case of adopting a continuous configuration in which a flat surface portion is not formed between adjacent substantially semicircular protrusions (7), a cross section of a substantially V-shaped groove between adjacent approximately semicircular protrusions (7). The shape may be, for example, an R shape (arc shape) having a radius of about 5 μm as long as the luminance unevenness suppressing effect is not hindered. In addition, when employ | adopting the structure by which the flat surface part (9) was formed between adjacent substantially semicircle convex parts (7), the value of E / P is the groove width (E) of this flat surface part (9). It is preferably set to be less than 0.1.

  Moreover, in the said embodiment, as shown in FIG. 3, the cross-sectional shape of a substantially semicircle convex part (7) is a cross-sectional shape symmetrical with respect to the normal line (perpendicular line with respect to a horizontal surface) passing through the center of this circle. However, it is not particularly limited to such a configuration. For example, if the ratio H / P satisfies the condition of 0.1 to 0.8, the left arc is more than the right arc, for example. Alternatively, it may be formed in a non-axisymmetric cross-sectional shape that swells to the front surface side, or a right-side arc may be formed in a non-axisymmetric cross-sectional shape that swells to the front side of the left-side arc.

  Moreover, in the said embodiment, although the substantially semicircle convex part (7) is comprised so that all may become the same shape and the same magnitude | size, it is not limited to such a structure in particular, Adjacent substantially The pitch interval (P) between the semicircular convex portions (7), the height (H) of the substantially semicircular convex portion (7), the ratio (H / P) of the height (H) to the pitch interval (P), etc. The numerical value of at least one of the elements may vary and be different. For example, a configuration as shown in FIG. 5 may be adopted.

  In addition, if it is the range which does not inhibit the effect of this invention, as for the said uneven | corrugated shaped part (4), pitch space | interval (P) is set to 10-500 micrometers, height (H) is set to 3-500 micrometers, pitch It includes substantially semicircular convex portions other than the substantially semicircular convex portion (7) in which the ratio (H / P) of the height (H) to the interval (P) is set to 0.2 to 0.8. It may be a configuration.

  The light diffusing plate (3), the surface light source device (1) and the liquid crystal display device (20) according to the present invention are not particularly limited to those of the above-described embodiment, and the spirit thereof is within the scope of the claims. Any design changes are allowed as long as they do not deviate from.

  Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

<Raw materials>
Translucent resin A: Styrene resin (Toyo Styrene "HRM40", refractive index 1.59)
Translucent resin B: MS resin (“MS200NT” manufactured by Nippon Steel Chemical Co., Ltd., refractive index 1.57, styrene / methyl methacrylate = 80 parts by mass / 20 parts by mass)
Light diffusing agent A: PMMA crosslinked particles (“SUMIPEX XC1A” manufactured by Sumitomo Chemical Co., Ltd., refractive index 1.49, weight average particle diameter 35 μm)
Light diffusing agent B: “Tospearl 120” (refractive index 1.49, weight average particle diameter 2 μm) manufactured by Momentive Performance Materials Japan GK.

  Light diffusing agent master batch A: 75.8 parts by mass of translucent resin B, 23.0 parts by mass of light diffusing agent A, and 1.0 of LA-31 (manufactured by Asahi Denka Kogyo Co., Ltd.) as an ultraviolet absorber. After dry blending 0.2 parts by mass of Sumrizer GP (manufactured by Sumitomo Chemical Co., Ltd.) which is a mass part and a heat stabilizer, this blended product is put into a hopper of a 65 mm twin screw extruder and melt-mixed in a cylinder. A pellet-shaped light diffusing agent master batch A obtained by extruding into a strand and pelletizing. Extrusion was carried out by setting the temperature in the cylinder from the lower part of the hopper: 200 ° C. to the vicinity of the extrusion die: 250 ° C. so that the temperature gradually increased toward the downstream.

  Light diffusing agent master batch B: 86.0 parts by mass of translucent resin B, 10.0 parts by mass of light diffusing agent B, and 2.0 parts by mass of Sumisorb 200 (manufactured by Sumitomo Chemical Co., Ltd.), which is an ultraviolet absorber. After dry blending 2.0 parts by mass of Sumilizer GP (manufactured by Sumitomo Chemical Co., Ltd.), a heat stabilizer, this blended product is put into a hopper of a 65 mm twin screw extruder, melted and mixed in a cylinder, and then in a strand form A pellet-shaped light diffusing agent masterbatch B obtained by extruding into pellets. Extrusion was carried out by setting the temperature in the cylinder from the lower part of the hopper: 200 ° C. to the vicinity of the extrusion die: 250 ° C. so that the temperature gradually increased toward the downstream.

<Example 1>
After dry blending 97.5 parts by mass of translucent resin A and 2.5 parts by mass of light diffusing agent masterbatch B, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. To do. On the other hand, after dry blending 67.8 parts by mass of the light-transmitting resin B and 32.2 parts by mass of the light diffusing agent masterbatch A, the temperature in the cylinder is melt-kneaded in a second extruder having a temperature of 190 to 250 ° C. Feed the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). And co-extrusion molding from a multi-manifold die, and sandwiching and cooling with a polishing roll to form a two-layer laminate (base material layer 1.43 mm, back layer 0) having a width of 23.5 cm and a thickness of 1.5 mm. (.07 mm) was produced.

  In addition, since the gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, the light diffusing agent particles added to the resin are raised. Allowed (without being smoothed), the entire surface of the back layer is formed on the mat surface (6), that is, the entire surface of one surface (back surface) (3a) of the light diffusion plate (3). It is formed on the mat surface (6). The arithmetic average roughness Ra of the mat surface (6) was 1.10 μm, and the average interval Rsm of the unevenness of the mat surface (6) was 202 μm.

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIGS. 2 and 3). The height (H) of the substantially semicircular protrusions (7) is 35.2 μm, and the pitch interval (P) between adjacent approximately semicircular protrusions (7) is 102.4 μm, and the pitch interval is 72.4 μm. The height ratio (H / P) was 0.34.

<Example 2>
After dry blending 97.5 parts by mass of translucent resin A and 2.5 parts by mass of light diffusing agent masterbatch B, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. To do. On the other hand, after dry blending 67.8 parts by mass of the light-transmitting resin B and 32.2 parts by mass of the light diffusing agent masterbatch A, the temperature in the cylinder is melt-kneaded in a second extruder having a temperature of 190 to 250 ° C. Feed the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). And co-extrusion molding with a multi-manifold die, and sandwiching and cooling with a polishing roll to obtain a two-layer laminate (base layer 1.42 mm, back layer 0) having a width of 22.8 cm and a thickness of 1.49 mm. (.07 mm) was produced.

  In addition, since the gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of 1.49 mm of the laminated plate at the time of molding, the light diffusing agent particles added to the resin are raised. Allowed (without being smoothed), the entire surface of the back layer is formed on the mat surface (6), that is, the entire surface of one surface (back surface) (3a) of the light diffusion plate (3). It is formed on the mat surface (6). The arithmetic average roughness Ra of the mat surface (6) was 1.21 μm, and the average interval Rsm of the unevenness of the mat surface (6) was 210 μm.

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIGS. 2 and 3). The height (H) of the substantially semicircular protrusions (7) is 43.8 μm, and the pitch interval (P) between adjacent semicircular protrusions (7) is 149.6 μm, and the pitch interval is 79.6 μm. The height ratio (H / P) was 0.29.

<Example 3>
After dry blending 97.5 parts by mass of translucent resin A and 2.5 parts by mass of light diffusing agent masterbatch B, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. To do. On the other hand, after dry blending 67.8 parts by mass of the light-transmitting resin B and 32.2 parts by mass of the light diffusing agent masterbatch A, the temperature in the cylinder is melt-kneaded in a second extruder having a temperature of 190 to 250 ° C. Feed the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). Are co-extruded from a multi-manifold die, and sandwiched and cooled with a polishing roll to form a two-layer laminate (base layer 1.45 mm, back layer 0) having a width of 23.6 cm and a thickness of 1.5 mm. .05 mm) was produced.

  In addition, since the gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, the light diffusing agent particles added to the resin are raised. Allowed (without being smoothed), the entire surface of the back layer is formed on the mat surface (6), that is, the entire surface of one surface (back surface) (3a) of the light diffusion plate (3). It is formed on the mat surface (6). The arithmetic average roughness Ra of the mat surface (6) was 1.22 μm, and the average interval Rsm of the unevenness of the mat surface (6) was 205 μm.

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIG. 6). In addition, as shown in FIG. 6, it is the continuous shape in which the flat surface part is not formed between adjacent semicircle convex parts (7). The height (H) of the substantially semicircular protrusions (7) is 68.5 μm, and the pitch interval (P) between the adjacent semicircular protrusions (7) is 279.6 μm, and the pitch interval is 79.6 μm. The height ratio (H / P) was 0.24.

<Comparative Example 1>
After dry blending 97.5 parts by mass of translucent resin A and 2.5 parts by mass of light diffusing agent masterbatch B, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. To do. On the other hand, the translucent resin B is melt-kneaded by a second extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). And co-extrusion molding with a multi-manifold die, and sandwiching and cooling with a polishing roll to form a two-layer laminate (base layer 1.43 mm, back layer 0) having a width of 23.0 cm and a thickness of 1.5 mm (.07 mm) was produced.

  The gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, but the translucent resin B supplied to the second extruder Does not contain a light diffusing agent, so that the light diffusing agent particles do not rise, and the entire surface of the back layer is substantially smooth, that is, one surface (back surface) of the light diffusing plate (3) ( The entire surface of 3a) is substantially smooth. That is, the back surface (3a) of the light diffusing plate had an arithmetic average roughness Ra of 0.13 μm, and an average interval Rsm between the concaves and convexes was not measurable (Rsm is smaller than the measurement lower limit 0.04 μm).

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIGS. 2 and 3). The height (H) of the substantially semicircular protrusions (7) is 37.4 μm, and the pitch interval (P) between adjacent semicircular protrusions (7) is 102.8 μm, and the pitch interval is 72.8 μm. The height ratio (H / P) was 0.36.

<Comparative example 2>
After 99.8 parts by mass of the light-transmitting resin A and 0.2 parts by mass of the light diffusing agent B are dry blended, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. On the other hand, the translucent resin B is melt-kneaded by a second extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). Are co-extruded from a multi-manifold die, and sandwiched and cooled with a polishing roll, thereby obtaining a two-layer laminate (base layer 1.42 mm, back layer 0) having a width of 22.8 cm and a thickness of 1.5 mm. (.08 mm) was produced.

  The gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, but the translucent resin B supplied to the second extruder Does not contain a light diffusing agent, so that the light diffusing agent particles do not rise, and the entire surface of the back layer is substantially smooth, that is, one surface (back surface) of the light diffusing plate (3) ( The entire surface of 3a) is substantially smooth. That is, the back surface (3a) of the light diffusing plate had an arithmetic average roughness Ra of 0.11 μm, and an average interval Rsm between the concaves and convexes was not measurable (Rsm is smaller than the measurement lower limit 0.04 μm).

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIGS. 2 and 3). The height (H) of the substantially semicircular protrusions (7) is 46.2 μm, and the pitch interval (P) between adjacent semicircular protrusions (7) is 149.6 μm, and the pitch interval is 79.6 μm. The height ratio (H / P) was 0.31.

<Comparative Example 3>
After 99.8 parts by mass of the light-transmitting resin A and 0.2 parts by mass of the light diffusing agent B are dry blended, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. On the other hand, the translucent resin B is melt-kneaded by a second extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). And co-extrusion molding with a multi-manifold die, and sandwiching and cooling with a polishing roll to form a two-layer laminate (base layer 1.43 mm, back layer 0) having a width of 23.0 cm and a thickness of 1.5 mm (.07 mm) was produced.

  The gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, but the translucent resin B supplied to the second extruder Does not contain a light diffusing agent, so that the light diffusing agent particles do not rise, and the entire surface of the back layer is substantially smooth, that is, one surface (back surface) of the light diffusing plate (3) ( The entire surface of 3a) is substantially smooth. That is, the back surface (3a) of the light diffusing plate had an arithmetic average roughness Ra of 0.06 μm, and an average interval Rsm between the concaves and convexes was not measurable (Rsm is smaller than the measurement lower limit 0.04 μm).

  Moreover, since the surface of the outer peripheral surface of all three polishing rolls is mirror-finished, the entire surface of the other surface (front surface) (3b) of the light diffusion plate (3) is a smooth surface. That is, the substantially semicircular convex part (7) is not formed in the other surface (front surface) (3b) of the light diffusing plate (3).

<Comparative Example 4>
After dry blending 97.5 parts by mass of translucent resin A and 2.5 parts by mass of light diffusing agent masterbatch B, the mixture is melt-kneaded with a first extruder having a temperature in the cylinder of 190 to 250 ° C. and supplied to the feed block. To do. On the other hand, after dry blending 67.8 parts by mass of the light-transmitting resin B and 32.2 parts by mass of the light diffusing agent masterbatch A, the temperature in the cylinder is melt-kneaded in a second extruder having a temperature of 190 to 250 ° C. Feed the feed block.

  Extrusion resin temperature 250 ° C. so that the resin supplied from the first extruder to the feed block becomes a base layer and the resin supplied from the second extruder to the feed block becomes a back layer (surface on the back side). And co-extrusion molding with a multi-manifold die, and sandwiching and cooling with a polishing roll to form a two-layer laminate (base layer 1.43 mm, back layer 0) having a width of 23.2 cm and a thickness of 1.5 mm. (.07 mm) was produced.

  In addition, since the gap between the intermediate roll and the lower roll of the three polishing rolls is set to be larger than the thickness of the laminated plate at 1.5 mm during the molding, the light diffusing agent particles added to the resin are raised. Allowed (without being smoothed), the entire surface of the back layer is formed on the mat surface (6), that is, the entire surface of one surface (back surface) (3a) of the light diffusion plate (3). It is formed on the mat surface (6). The arithmetic average roughness Ra of the mat surface (6) was 1.23 μm, and the average interval Rsm of the unevenness of the mat surface (6) was 201 μm.

  In addition, since a plurality of grooves having a semicircular cross-sectional shape are formed in a stripe shape on the outer peripheral surface of the intermediate roll among the three polishing rolls, the cross-sectional shape is semicircular over the entire surface of the base material layer. A large number of substantially semicircular convex portions (7) are formed in a protruding manner, that is, a large number of cylindrical lens-shaped convex strip portions (8) are formed on the other surface (front surface) (3b) of the light diffusing plate (3). Individual protrusions are formed (see FIGS. 2 and 3). The height (H) of the substantially semicircular protrusions (7) is 10.0 μm, and the pitch interval (P) between adjacent semicircular protrusions (7) is 62.8 μm, and the pitch interval is 72.8 μm. The height ratio (H / P) was 0.16.

  Each light diffusion plate produced as described above was evaluated according to the following evaluation method. These results are shown in Table 1.

<Total light transmittance measurement method>
Based on JIS K7361-1 (1997), the total light transmittance (%) of the light diffusing plate was measured using a transmittance meter (“HR-100” manufactured by Murakami Color Research Laboratory). At the time of measurement, the measurement was performed with the front surface side where the substantially semicircular convex portion of the light diffusing plate was formed facing the integrating sphere side and the pitch interval direction toward the left and right sides.

<Luminance uniformity evaluation method>
After removing the liquid crystal panel, various optical films, and the light diffusing plate from the commercially available 20-inch type liquid crystal television, the frame of the polycarbonate lamp box (with a plurality of fluorescent tubes spaced apart from each other) The light diffusing plate (Example product / Comparative product) produced as described above was placed and fixed in a state where it was in contact with the front surface of the unit, thereby closing the open surface of the lamp box. Thereafter, the luminance was measured using a luminance meter (“Eye Scale-3WS” manufactured by I-System Co., Ltd.) with the light diffusing plate set. When the minimum luminance value is “C1” and the maximum luminance value is “C2”,
Brightness uniformity (%) = (C1 / C2) × 100
The value obtained by the above formula was defined as the luminance uniformity (%).

  The luminance measurement was performed as follows. That is, the liquid crystal television is placed on the floor in a dark room of constant temperature and humidity (temperature: 25.0 ° C., humidity: 50.0%) with the front side facing up (the back is in contact with the floor), The camera was placed facing downwards above the LCD TV so that the entire front surface of the LCD TV was reflected. At this time, the distance from the front surface of the liquid crystal television to the camera is set to 65.0 cm, and the measurement conditions of the luminance meter are set to SPEED: 1/500, GAIN: 1, aperture: 16, and the central portion of the front surface of the liquid crystal television is set. The luminance at each measurement spot was measured by designating a range of 60 mm × 60 mm centering on the measurement spot, and the luminance uniformity (%) was obtained from the minimum luminance value and the maximum luminance value among these measurement values.

  The commercially available 20-inch liquid crystal television has 12 light sources, a distance (L) between adjacent light sources of 26.0 mm, a light source diameter of 4.0 mm, and a distance (d) between the light diffusion plate and the light source. Was 12.0 mm, and the distance (f) between the light source and the reflector (the bottom of the lamp box) was 1.0 mm (see FIG. 1).

<Measurement method of diffusivity D of light diffusion plate>
What is the intensity distribution of transmitted light when light is incident on the light diffuser plate (example product / comparative example product) at a specified angle using an automatic variable angle photometer ("GP230" manufactured by Murakami Color Research Laboratory)? The diffusivity D (%) was determined by measuring whether or not it changes. The measurement was performed with the back surface of the light diffusing plate facing the light source (emitted light), the front surface of the light diffusing plate facing the integrating sphere, and the pitch (interval) direction of the substantially circular convex portions arranged on the left and right sides. The measurement conditions were a light beam stop: 1.7 mmφ, the intensity of emitted light and the sensitivity of light reception were constant, and the incident angle of light was 0 degree.

<Method for evaluating the prevention of unpleasant noise (sound)>
After removing the liquid crystal panel and light diffusion plate of the same commercially available 20-inch liquid crystal television used in the luminance uniformity evaluation method, a polycarbonate lamp box (with a plurality of fluorescent tubes spaced apart from each other). The light diffusing plate (Example product / Comparative product) produced as described above was placed and fixed in a state where it was in contact with the front surface of the edge frame portion), and the open surface of the lamp box was closed. After that, the liquid crystal panel is reset in this lamp box to reconfigure the liquid crystal television, and the liquid crystal television is shaken in the front-rear direction about 180 times in one minute while holding the normal vertical support state with both hands, The presence or absence of unpleasant noise was examined. The case where no unpleasant noise was generated was indicated as “◯”, the case where slight unpleasant sound was generated was indicated as “Δ”, and the case where no unpleasant noise was generated was indicated as “X”.

<Arithmetic mean roughness Ra measurement method>
Arithmetic mean roughness Ra was measured according to JIS B0601-2001. That is, the arithmetic average roughness Ra of the mat surface of the light diffusion plate was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 2.5 × 5 and measurement range: auto.

<Measuring method of average interval Rsm of unevenness>
Based on JIS B0601-2001, the average interval Rsm of the unevenness was measured. That is, the average interval Rsm of the unevenness of the mat surface of the light diffusion plate was measured using a surface roughness meter (“SJ-201P” manufactured by Mitutoyo). The measurement conditions of the surface roughness meter were set to cut-off value: 2.5 × 5 and measurement range: auto.

  As is apparent from the table, the surface light source device and the liquid crystal display device configured using the light diffusing plates of Examples 1 to 3 of the present invention were able to sufficiently suppress the generation of unpleasant noise.

  On the other hand, in Comparative Examples 1 to 3 that depart from the scope of the present invention, the generation of unpleasant noise could not be prevented. Further, in Comparative Example 4 where H / P is below the specified range of the present invention, the luminance unevenness suppressing effect was not sufficient.

  The light diffusing plate of the present invention is suitably used as a light diffusing plate for a surface light source device, but is not particularly limited to such applications. The surface light source device of the present invention is preferably used as a backlight for a liquid crystal display device, but is not particularly limited to such applications.

1 is a schematic view showing an embodiment of a liquid crystal display device according to the present invention. It is a typical perspective view which shows one Embodiment of the light diffusing plate which concerns on this invention. FIG. 3 is a schematic cross-sectional view of the light diffusing plate of FIG. 2. It is typical sectional drawing which shows other embodiment of the light diffusing plate of this invention. It is typical sectional drawing which shows other embodiment of the light diffusing plate of this invention. It is typical sectional drawing which shows other embodiment of the light diffusing plate of this invention. It is typical sectional drawing which shows other embodiment of the light diffusing plate of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Surface light source device 2 ... Light source 3 ... Light diffusing plate 3a ... Back surface (one surface)
3b ... Front side (the other side)
5 ... Lamp box 6 ... Mat surface 7 ... Semi-circular convex part 8 ... Cylindrical lens
DESCRIPTION OF SYMBOLS 10 ... Liquid crystal panel 20 ... Liquid crystal display device 31 ... Edge frame part (side plate)
31a ... front (front side end face of side plate)
H: Height of substantially semi-convex portion P: Pitch interval between adjacent semi-convex portions

Claims (7)

A plurality of light sources are disposed apart from each other in a resin lamp box whose front side is open, and the light box made of resin is in contact with the front surface of the edge frame portion of the lamp box. A surface light source device arranged so as to block the open surface of
A portion of the back surface of the light diffusing plate that contacts at least the front surface of the edge frame portion is formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval of the unevenness of the mat surface Rsm is 100 to 300 μm,
A plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. A surface light source device, wherein the height H of the semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8. A plurality of light sources are disposed apart from each other in a resin lamp box whose front side is open, and the light box made of resin is in contact with the front surface of the edge frame portion of the lamp box. A surface light source device arranged so as to block the open surface of
The entire back surface of the light diffusing plate is formed on a mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface is 100 to 300 μm,
A plurality of substantially semicircular convex portions having a substantially semicircular cross-sectional shape projecting from the front surface of the light diffusing plate, and a pitch interval P between adjacent semicircular convex portions is set to 10 to 500 μm. A surface light source device, wherein the height H of the semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.   The substantially semicircular convex part is a cylindrical lens-shaped convex part, the light source is a linear light source, and the length direction of the cylindrical lens-shaped convex part and the length direction of the linear light source are approximately The surface light source device according to claim 1, wherein the surface light source device is configured to match.   The surface light source device according to claim 1, wherein the light diffusing plate has a total light transmittance of 55 to 85%.   A liquid crystal display device comprising: the surface light source device according to claim 1; and a liquid crystal panel disposed on a front side of the surface light source device. The matte surface has an arithmetic mean roughness Ra of 0.8 to 15 [mu] m, and an average interval of the irregularities on the mat surface. Rsm is 100 to 300 μm,
A plurality of substantially semicircular protrusions having a substantially semicircular cross-sectional shape projecting from the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular protrusions is set to 10 to 500 μm, A light diffusing plate, wherein the height H of the substantially semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8. One surface is made of a resin light-transmitting plate formed on the mat surface, the arithmetic average roughness Ra of the mat surface is 0.8 to 15 μm, and the average interval Rsm of the unevenness of the mat surface is 100-300 μm,
A plurality of substantially semicircular protrusions having a substantially semicircular cross-sectional shape projecting from the other surface of the light transmission plate, and the pitch interval P between adjacent semicircular protrusions is set to 10 to 500 μm, A light diffusing plate, wherein the height H of the substantially semicircular convex portion is set to 3 to 500 μm, and the ratio of the height to the pitch interval (H / P) is 0.2 to 0.8.

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