JP2010072630A - Optical control sheet and surface light source device provided with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical control sheet capable of making a surface light source device, such as, backlight type liquid crystal display device that is smaller in thickness and higher-luminance, without causing a lamp image to develop. <P>SOLUTION: The optical control sheet includes; an optical diffusion sheet 48, which comprises an anisotropic diffusion layer 47 including a continuous phase 47a constituted of a transparent resin and particulate dispersion phases 47b, which have a refractive index different from that of the continuous phase and in which the major axis direction is aligned in one-side direction; and a prism part 46, which is formed on one face of the optical diffusion sheet and in which a plurality of prism units 46a are arranged regularly. In the prism part 46, trigonal prism units are arranged side by side adjacent to one another, and the transverse cross-sectional shape of the prism units may be an isosceles triangle shape whose apex angle is 50 to 120°. The continuous phase is, preferably, made of polycarbonate-based resin and the dispersion phase is preferably made of polypropylene-based resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a novel light control sheet used for a surface light source device in a display device (liquid crystal display device or the like) and a device including the same. More specifically, the present invention relates to a light control sheet suitable for a direct backlight type liquid crystal display device and a device including the same.

  In a direct backlight type display device (or liquid crystal display device or the like) that illuminates a display panel (liquid crystal display module or the like) from the back surface, a surface light source unit (or backlight unit) is disposed on the back surface of the display panel. Yes. In addition, in order to make the irradiation light to the display panel uniform as a surface light source and to increase the brightness of the front surface of the liquid crystal display device, a diffusion sheet, a prism sheet, a brightness enhancement sheet (a reflective polarizing plate, etc.) and the like are used. Further, in a liquid crystal display device, a polarizing plate, a retardation plate, a color filter, and the like are also used as constituent members of a liquid crystal cell.

  More specifically, for example, as a planar display device (flat display device) having a flat (planar) image display area, a planar display unit (such as a transmissive liquid crystal display unit) 5 as shown in FIG. And a surface light source unit for illuminating the unit from the back side are known. The surface light source unit has one or a plurality of fluorescent discharge tubes (cold cathode tubes) 1, and a reflection plate 2 for reflecting light is disposed on the back side of the fluorescent discharge tube 1. Between the discharge tube 1 and the display unit 5, there is disposed a diffusion plate 3 for diffusing light to uniformly illuminate the display unit 5, and a prism sheet 4 is laminated on the display unit side of the diffusion plate 3. Has been. In the case of a liquid crystal display unit, the surface display unit 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, and a first layer laminated on the electrode. The alignment film 9a, the liquid crystal layer 10, the second alignment film 9b, the second electrode 8b, the color filter 11, the second glass substrate 7b, and the second polarizing film 6b are sequentially stacked. . In such a display device, the display unit can be directly illuminated from the back by a built-in fluorescent discharge tube (cold cathode tube) 1.

  In the backlight system using such a rod-shaped (tubular) light source (lamp), the weight of the liquid crystal display device has become very high with the recent increase in size of the liquid crystal television. In recent years, in such a surface light source device, there is a tendency that the brightness of the light source is increased and the device is thinned. However, in the surface light source device having such a structure, a lamp image (in the shape of a lamp that is a light source). The resulting image and the image in which the presence of the lamp can be easily understood) are more likely to remain.

  In the backlight method, the luminance distribution in the axial direction of the rod-shaped light source is different from that in the direction perpendicular to the axial direction, and it is difficult to uniformly illuminate the display unit, so it is difficult to expand the viewing angle. . For this reason, an anisotropic light diffusion sheet having optically anisotropic scattering characteristics is used as the diffusion sheet, and the luminance is made uniform by utilizing the anisotropic scattering characteristics. For example, by arranging the long axis direction of the dispersed phase of the anisotropic light diffusing sheet toward the axial direction of the tubular light source, anisotropic scattering is possible even when using light sources having different luminance distributions in the long axis direction and the short axis direction. A method is known that can make the luminance of transmitted light uniform by utilizing the characteristics. However, even if a light diffusing sheet having such anisotropic scattering characteristics is used, the erasure of the lamp image is not sufficient.

  Furthermore, in the backlight system, since the rod-shaped light source is close to the display unit, the display unit is heated, and the diffusion sheet is also required to have heat resistance. A polycarbonate resin is known as a resin having high heat resistance and transparency. However, since the polycarbonate resin has low melt fluidity, it is difficult to industrially efficiently produce a light diffusion film by a melt molding method such as melt extrusion molding. Further, since the polycarbonate resin does not have a high affinity with the components of the dispersed phase, voids are easily generated at the interface with the dispersed phase, and it is difficult to form the dispersed phase uniformly.

  Japanese Patent No. 4115113 (Patent Document 1) as a light diffusion sheet used for a backlight system displays a tubular light source and light from the tubular light source incident from the side and emitted from a flat emission surface. A light guide member for illuminating the unit, and a plurality of anisotropic light scattering members disposed between the light guide member and the display unit, and for uniformly illuminating the display unit with light from the tubular light source A surface light source unit comprising a film, wherein the anisotropic light scattering film is composed of a laminated film in which transparent resin layers are laminated on both sides of an anisotropic light scattering layer, and the anisotropic light scattering layer is composed of a resin. And a continuous phase dispersed in the continuous phase with an average aspect ratio of 5 to 1000 and made of a resin having a refractive index different from that of the continuous phase resin. , A combination of a polypropylene resin and a styrene resin, or a combination of a polypropylene resin and a polycarbonate resin, and the transparent resin layer is the same resin as the continuous phase and has a glass transition temperature or melting point of 130. A surface light source unit is disclosed which is made of a transparent resin at 280 ° C., and in which a plurality of anisotropic light scattering films are arranged with different light scattering directions between the light guide member and the display unit. Has been.

  However, even in this surface light source unit, in recent backlight type display devices with high luminance and thinning, the luminance on the display surface is insufficiently uniform, and a lamp image remains. Furthermore, although the combination of polycarbonate-type resin and polypropylene-type resin is described, the details and specific preparation methods of both resins are not described. Therefore, in this film, in order to produce a film free from voids and having excellent light scattering characteristics, it is essential to add a compatibilizing agent, and it is difficult to prepare a sheet.

  On the other hand, as a method for improving light diffusibility, a method of shaping a plastic sheet into a lens shape is also known, and a method combining such a lens shape and a light diffusing function with a light diffusing agent has also been proposed. Yes. For example, in Japanese Patent Laid-Open No. 2003-16819 (Patent Document 2), in a diffusion plate used in a direct light source device, a prism row is formed on the surface of a resin plate mixed with a light diffusing agent. A high diffusion plate is disclosed in which both the convex portion and the concave portion are curved surfaces, and the concave portion curvature radius is smaller than the convex portion curvature radius. In this document, acrylic resin, polycarbonate resin, styrene resin, MS resin, MBS resin, PE, PET, SAN, alicyclic acrylic resin, alicyclic polyolefin resin, alternating olefin / maleimide are used as the base resin for the resin plate. Copolymers, cyclohexadiene polymers, amorphous polyester resins, amorphous fluorine resins, etc. are described, and as light diffusing agents, calcium carbonate, barium sulfate, titanium oxide, silicone fine particles, acrylic fine particles, styrenic fine particles, MS-based fine particles, glass-based fine particles and the like are described.

  However, this diffuser plate is not sufficiently uniform in brightness because the dispersed phase composed of the light diffusing agent is isotropic. Furthermore, since the heat resistance of the diffuser plate is low, the film will be deformed if the diffuser plate is used in a high temperature environment, such as a device that directly illuminates the light source from the back without using a light guide plate (direct type). In the case where the thermal stability of the matrix phase is low, the shape of the shrinkage or dispersed phase changes due to the strain accompanying stretching, so that the light diffusion characteristics change and the brightness of the transmitted light cannot be made uniform.

  Furthermore, Japanese Patent Laid-Open No. 2001-159704 (Patent Document 3) discloses a light scattering film that can scatter incident light in the light traveling direction, and has a scattering characteristic that indicates the relationship between the scattering angle θ and the scattered light intensity F. In F (θ), when the scattering characteristic in the X-axis direction of the film is Fx (θ) and the scattering characteristic in the Y-axis direction is Fy (θ), the formula: Fy (θ ) / Fx (θ)> 5 is disclosed. This document describes a film in which the continuous phase is composed of a crystalline olefin resin and the dispersed phase is composed of an amorphous polyester resin. Furthermore, a film is also described in which an uneven portion extending in the X-axis direction of the film is formed on the film surface.

  However, even in this anisotropic light scattering film, since the shape of the uneven portion on the surface is minute, the lens effect is not sufficient, the luminance on the display surface is insufficiently uniform, and a lamp image remains. Furthermore, since this anisotropic light scattering film also has low heat resistance, in a direct type apparatus, the light diffusion characteristics change, and the brightness of transmitted light cannot be made uniform.

Japanese Patent No. 4115113 (Claim 1) JP 2003-16819 A (Claim 1, paragraphs [0008] and [0009], Examples) JP 2001-159704 A (Claims 1, 6 and 12)

  Accordingly, an object of the present invention is to provide a light control sheet that can reduce the thickness and brightness of a surface light source device such as a backlight type liquid crystal display device without developing a lamp image (lamp image), and a device (surface) including the same. It is to provide a light source device or a display device such as a liquid crystal display device.

  Another object of the present invention is to provide a light control sheet and a device (a display device such as a surface light source device or a liquid crystal display device) including the light control sheet that can suppress a change in light diffusion characteristics even when used at high temperatures. It is in.

  Still another object of the present invention is to provide a light control sheet capable of forming a dispersed phase uniformly even when a polycarbonate resin having low fluidity and affinity is used, and anisotropically diffusing transmitted light, and an apparatus including the same (A display device such as a surface light source device or a liquid crystal display device).

  Another object of the present invention is to provide an optically anisotropic light control sheet and an apparatus (surface light source device, liquid crystal display device, or the like) that is optically anisotropic even when used at high temperatures despite being stretched. Display device).

  Still another object of the present invention is to provide a light control sheet that can cope with the thinning of a device even in a large liquid crystal display device and can be easily manufactured, and a liquid crystal display device including the same. .

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have regularly arranged a plurality of prism units on at least one surface of a light diffusion sheet having specific anisotropy and light diffusibility. When the prism portion is formed, it has been found that a surface light source device such as a backlight type liquid crystal display device can be made thin and high in brightness without developing a lamp image (lamp image), and the present invention has been completed.

  That is, the light control sheet of the present invention includes a different phase containing a continuous phase composed of a transparent resin and a particulate dispersed phase having a refractive index different from that of the continuous phase and having a major axis direction oriented in one direction. A light diffusing sheet composed of an isotropic diffusing layer; and a prism portion formed on at least one surface of the light diffusing sheet and provided with a plurality of prism units regularly. The light diffusion sheet may further include a transparent resin layer formed on at least one surface of the anisotropic diffusion layer, and a prism portion may be formed in the anisotropic diffusion layer and / or the transparent resin layer. . The prism unit may be an isosceles triangle having apex angles of 50 to 120 °, and triangular prism units are arranged adjacently and arranged in parallel. The major axis direction of the particulate dispersed phase may be parallel or orthogonal to the longitudinal direction of the prism unit. The average length of the minor axis of the particulate dispersed phase is about 0.01 to 1 μm, and the average aspect ratio of the particulate dispersed phase is about 2 to 20000. This light control sheet can scatter incident light in the light traveling direction, and has a scattering characteristic F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F in the X-axis (MD) direction of the sheet. When the scattering characteristic is Fx (θ) and the scattering characteristic in the Y-axis (width) direction is Fy (θ), Fx (θ) and Fy (θ) have patterns that attenuate as the scattering angle θ becomes wider. In the range of scattering angle θ = 4-30 °, 1.01 ≦ Fy (θ) / Fx (θ), and 1.1 <Fy (θ) / Fx (θ) at scattering angle θ = 18 °. There may be. In the light control sheet, the continuous phase may be composed of a polycarbonate resin, and the dispersed phase may be composed of a polypropylene resin. The light diffusing layer of this light diffusing sheet may be substantially free of a compatibilizing agent. The polycarbonate resin in the continuous phase may be a polycarbonate resin having a number average molecular weight of 15,000 to 25000, and the melt flow rate of the polycarbonate resin is 5 to 30 g at ISO 1133 (300 ° C., 1.2 kg load). / 10 minutes may be sufficient. The polypropylene resin in the dispersed phase may be a metallocene resin (polypropylene resin using a metallocene catalyst) or a polypropylene random copolymer, and the melt flow rate of the polypropylene resin is JIS K7210 ( 230 ° C., 2.16 kg load), it may be about 3 to 20 g / 10 minutes.

  The present invention also includes a surface light source device and a display device (such as a liquid crystal display device) provided with the light control sheet. In particular, the display device may be a direct type that directly illuminates the display unit from the back surface with a plurality of light sources arranged in parallel.

  In the present specification, “sheet” is used to mean including a film regardless of the thickness.

  In the present invention, a backlight type liquid crystal is formed by forming a prism portion in which a plurality of prism units are regularly arranged on at least one surface of a light diffusion sheet having specific anisotropy and light diffusibility. A surface light source device such as a display device can be reduced in thickness and brightness, and the appearance of a lamp image (lamp image) can be suppressed.

  In addition, when the matrix phase (continuous phase) is made of polycarbonate resin and the dispersed phase is made of polypropylene resin, it has high heat resistance and can suppress changes in light diffusion characteristics over a long period of time even when used at high temperatures. . Despite the use of a polycarbonate resin having low fluidity and affinity, a dispersed phase can be formed uniformly, and transmitted light can be diffused isotropically or anisotropically. Furthermore, even if it is stretched to give an optically anisotropic light diffusion property, or it is used at a high temperature, the optically anisotropic light diffusion property can be maintained.

  Furthermore, even a large-sized liquid crystal display device can cope with the thinning of the device and can be easily manufactured. That is, when the light control sheet of the present invention is used, a conventionally used combination of a diffusion sheet and a prism sheet (and its protective sheet as required) can be replaced with a single sheet. Therefore, it is possible to reduce the raw material cost of the surface light source device, reduce the assembly processing cost, reduce the defect rate such as contamination, and achieve a significant cost reduction of the surface light source device. Can be suppressed.

FIG. 1 is a schematic sectional view showing a surface light source device and a transmissive liquid crystal display device. FIG. 2 is a schematic cross-sectional view showing an example of a light diffusion sheet. FIG. 3 is a schematic sectional view showing another example of the light diffusion sheet. FIG. 4 is a conceptual diagram for explaining anisotropic scattering of the light diffusion sheet. FIG. 5 is a schematic diagram for explaining a method of measuring light scattering characteristics. FIG. 6 is a schematic perspective view showing an example of the light control sheet of the present invention. FIG. 7 is a schematic perspective view showing another example of the light control sheet of the present invention. FIG. 8 is a graph showing the relationship between the position of the CCFL and the luminance in the example.

[Light control sheet]
The light control sheet of the present invention includes a light diffusion sheet composed of an anisotropic diffusion layer including a continuous phase and a particulate dispersed phase, and a plurality of prism units formed on at least one surface of the light diffusion sheet. Are regularly arranged prism portions.

(Light diffusion sheet)
The light diffusion sheet is an anisotropic diffusion layer including a continuous phase composed of a transparent resin and a particulate dispersed phase having a refractive index different from that of the continuous phase and having a major axis direction oriented in one direction. It is configured.

  The transparent resin constituting the continuous phase includes thermoplastic resins (olefin resins, cyclic olefin resins, halogen-containing resins (including fluorine resins), vinyl alcohol resins, vinyl ester resins, vinyl ether resins, (meta ) Acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin, thermoplastic polyurethane resin, polysulfone resin (polyethersulfone, polysulfone, etc.), polyphenylene ether resin (2,6-xylenol heavy Coalescence), cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubber or elastomers (polybutadiene, polyisopropylene, etc.) Diene rubber such as styrene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylic rubber, urethane rubber, silicone rubber, etc.), and thermosetting resin (epoxy resin, unsaturated polyester resin, diallyl phthalate) Resin, silicone resin, etc.). These transparent resins can be used alone or in combination of two or more. Of these transparent resins, polycarbonate resins are preferred.

The polycarbonate-based resin includes aromatic polycarbonate based on bisphenols. Examples of bisphenols include biphenols such as dihydroxybiphenyl, bis (hydroxyaryl) alkanes such as bisphenol A, bisphenol F, and bisphenol AD, and bis (hydroxyaryl) cycloalkanes such as bis (hydroxyphenyl) cyclohexane. Di (hydroxyphenyl) ethers such as 4,4'-di (hydroxyphenyl) ether, di (hydroxyphenyl) ketones such as 4,4'-di (hydroxyphenyl) ketone, di (hydroxyphenyl) such as bisphenol S And bisphenol fluorenes such as sulfoxides, bis (hydroxyphenyl) sulfones, and 9,9-bis (4-hydroxyphenyl) fluorene. These bisphenols may be C _2-4 alkylene oxide adducts. These bisphenols can be used alone or in combination of two or more.

The polycarbonate resin may be a polyester carbonate resin obtained by copolymerizing a dicarboxylic acid component (such as an aliphatic, alicyclic or aromatic dicarboxylic acid or an acid halide thereof). These polycarbonate resins can be used alone or in combination of two or more. A preferred polycarbonate resin is a resin based on bis (hydroxyphenyl) C _1-6 alkanes, for example, a bisphenol A type polycarbonate resin.

  The number average molecular weight of the polycarbonate-based resin can be selected from a range of about 10,000 to 50,000 (for example, 15000 to 30000), for example, 12500 to 30000 (for example, 15000 to 25000), preferably 17000 to 25000 (for example, 18000 to 22000). ) When the molecular weight of the polycarbonate-based resin is too small, the strength of the sheet is lowered, and when the molecular weight is too large, the melt fluidity and the uniform dispersibility of the dispersed phase are liable to be lowered. When the polycarbonate resin and the specific polypropylene resin are combined, a dispersed phase having a high aspect ratio can be formed without generating voids without using a compatibilizing agent.

  The melt flow rate (MFR) of the polycarbonate resin is, for example, 3 to 30 g / 10 minutes (for example, 4 to 20 g / 10 minutes) in accordance with ISO 1133 (300 ° C., 1.2 kg load (11.8 N)). It can be selected from a range of about 5 to 30 g / 10 minutes (for example, 5 to 15 g / 10 minutes), preferably 6 to 25 g / 10 minutes (for example, 7 to 20 g / 10 minutes), and more preferably 8 to 15 g. / 10 minutes (for example, 9 to 12 g / 10 minutes).

  The melting point or glass transition temperature of the polycarbonate resin is, for example, about 130 to 280 ° C, preferably about 140 to 270 ° C, and more preferably about 150 to 260 ° C.

  Such polycarbonate resins are often classified as “medium viscosity products”, “low viscosity products”, and “high flow” grades in product catalogs.

  As the dispersed phase, among the transparent resins similar to the continuous phase, a resin having a refractive index different from that of the resin constituting the continuous phase can be used alone or in combination. Of these transparent resins, a polypropylene resin is preferable as the transparent resin forming the dispersed phase.

The polypropylene resin includes polypropylene (homopolymer) and a copolymer of propylene and a copolymerizable monomer. Copolymerizable monomers include olefins (in addition to ethylene, α-C _4-10 olefins such as butene, pentene, heptene, hexene, etc.), (meth) acrylic monomers (for example, (meth) Acrylic acid, (meth) acrylic acid C _1-10 alkyl ester, (meth) acrylic acid hydroxyalkyl ester, (meth) acrylic acid glycidyl ester, etc.), fatty acid vinyl esters (vinyl acetate, etc.), dienes and the like. . These copolymerizable monomers can be used alone or in combination of two or more. Of these copolymerizable monomers, α-olefins (ethylene, butene, etc.) are often used.

  In the propylene-based copolymer, the propylene content is often 80 mol% or more (80 to 100 mol%), preferably 85 mol% or more, and more preferably 90 mol% or more. The propylene-based copolymer may be a block copolymer or the like, but is usually a random copolymer in many cases.

  Preferred polypropylene resins are polypropylene homopolymer, propylene-ethylene copolymer, propylene-butene copolymer, propylene-ethylene-butene copolymer and the like. As a polypropylene resin, a polypropylene homopolymer and a propylene-ethylene copolymer are often used.

  The polypropylene resin may be a polymer using a Ziegler catalyst or the like, but is preferably a metallocene resin using a metallocene catalyst. The metallocene resin is characterized by a narrow molecular weight distribution and a small amount of low molecular weight components and low crystalline components. For this reason, the polypropylene resin phase (dispersed phase) can be uniformly dispersed in the matrix phase of the polycarbonate resin without using a compatibilizing agent.

In gel permeation chromatography (GPC), the molecular weight distribution of the polypropylene resin is, for example, weight average molecular weight Mw / number average molecular weight Mn = 1 to 2.5 (for example, 1.2 to 2.3), preferably 1. It is about 3 to 2 (for example, 1.5 to 1.8), and usually about 1.3 to 2.5 (for example, 1.5 to 2.0). The weight average molecular weight Mw of the polypropylene resin is, for example, 1 × 10 ^{4 to} 100 × 10 ⁴ , preferably 2 × 10 ⁴ to 75 × 10 ⁴ (for example, 3 × 10 ⁴ to 50 × 10 ⁴ ), more preferably. It may be about 3 × 10 ⁴ to 30 × 10 ⁴ . In GPC, the content of a low molecular weight component having a molecular weight of 10,000 or less is, for example, 1% by volume or less, preferably 0.5% by volume or less, and more preferably 0.3% by volume or less. The molecular weight and molecular weight distribution by GPC can be measured at a temperature of 135 ° C. using an apparatus: Waters Alliance GPCV-2000, a column: PL 20 μm MIXED-A, a detector: RI, and a solvent: o-dichlorobenzene. The molecular weight and molecular weight distribution are values in terms of polypropylene calibrated by a general calibration curve method using monodisperse polystyrene as a reference substance.

  The MFR of the polypropylene resin is, for example, 3 to 20 g / 10 minutes, preferably 4 to 15 g / 10 minutes, more preferably in accordance with JIS K7210 (230 ° C., 2.16 kg load (21.2 N)). Is about 5-10 g / 10 minutes.

  The polypropylene resin may be crystalline, and the crystallinity of the crystalline polypropylene resin is, for example, about 10 to 80%, preferably about 20 to 70%, and more preferably about 30 to 60%. Also good. The melting point (melting peak temperature in the differential scanning calorimeter DSC) of the polypropylene resin is, for example, about 100 to 140 ° C., preferably 110 to 135 ° C., more preferably about 115 to 130 ° C. (for example, 120 to 130 ° C.). is there.

  As the polypropylene resin, a copolymer (such as a propylene-ethylene random copolymer) or a metallocene resin using a metallocene catalyst, particularly a metallocene copolymer is preferable.

  When such a polypropylene-based resin is combined with the polycarbonate-based resin, a dispersed phase (such as a dispersed phase having a predetermined aspect ratio) does not generate voids even when substantially free of a compatibilizing agent as described above. Can be formed.

  The difference in melting point or glass transition temperature between the resin constituting the dispersed phase (for example, polypropylene resin) and the resin constituting the continuous phase (for example, polycarbonate resin) is, for example, 10 to 200 ° C., preferably 30 to 30 ° C. 150 degreeC, More preferably, about 50-120 degreeC may be sufficient.

  Further, the ratio of the MFR of the resin constituting the continuous phase (for example, polycarbonate resin) and the MFR of the resin constituting the dispersed phase (for example, polypropylene resin) is the former / the latter = 0.8 / 1. ~ 2.5 / 1 (e.g., 0.9 / 1 to 2.3 / 1), preferably 1/1 to 2/1, more preferably about 1.2 / 1 to 1.7 / 1. Also good.

  In order to impart light diffusibility, the continuous phase and the dispersed phase are composed of components having different refractive indexes. The difference in refractive index between the resin constituting the continuous phase (for example, polycarbonate resin) and the resin constituting the dispersed phase (for example, polypropylene resin) is, for example, 0.001 or more (for example, 0.001 to 0.001). About 3), preferably about 0.01 to 0.3, and more preferably about 0.01 to 0.1.

  In the anisotropic diffusion layer, the ratio between the continuous phase and the dispersed phase is, for example, the former / the latter (weight ratio) = 99/1 to 30/70 (depending on the type of resin, melt viscosity, light diffusibility, etc. For example, it can be selected from the range of about 95/5 to 40/60), for example, 99/1 to 50/50 (for example, 95/5 to 50/50), preferably 99/1 to 75/25 (for example, 93/7 to 70/30), more preferably about 95/5 to 60/40, particularly about 90/10 to 75/25.

  Combining the polycarbonate resin and polypropylene resin not only has practical thermal stability, but also easily disperses the dispersed phase at the orientation treatment temperature such as uniaxial stretching temperature, and diffuses the transmitted light anisotropically. Sheet to be obtained. In addition, the aspect ratio of the dispersed phase particles can be controlled by an orientation treatment such as draw ratio or uniaxial stretching in the extrusion molding process, and a dispersed phase having a large aspect ratio can be easily formed. Furthermore, since the continuous layer is composed of a polycarbonate-based resin, heat resistance and blocking resistance can be improved.

  The anisotropic diffusion layer preferably does not contain a compatibilizing agent, but may contain a compatibilizing agent as necessary depending on the type and purpose of the resin. By using a compatibilizing agent, the miscibility and affinity between the continuous phase and the dispersed phase can be increased, and defects (such as voids) can be prevented from being generated even when the sheet is subjected to orientation treatment. It is possible to prevent a decrease in sex. Furthermore, the adhesiveness between the continuous phase and the dispersed phase can be improved, and even if the sheet is uniaxially stretched, adhesion of the dispersed phase to the stretching apparatus can be reduced.

  Examples of the compatibilizer include a bisoxazoline compound, a modified olefin resin modified with a modifying group (such as a carboxyl group, an acid anhydride group, an epoxy group, or an oxazolinyl group), a diene, or a rubber-containing polymer [for example, butadiene, A homopolymer of a diene monomer such as isoprene, or a diene copolymer obtained by copolymerization of a diene monomer and a copolymerizable monomer (such as an aromatic vinyl monomer such as styrene). (Random copolymer, etc.); Diene-based graft copolymer such as acrylonitrile-butadiene-styrene copolymer (ABS resin); Styrene-butadiene (SB) block copolymer, Hydrogenated styrene-butadiene (SB) block copolymer Polymer, hydrogenated styrene-butadiene-styrene block copolymer (SEBS), hydrogenated (styrene-ethylene Diene-based block copolymers such as butylene-styrene) block copolymers or hydrogenated products thereof], diene or rubber-containing polymers modified with the above-described modifying groups (such as epoxy groups) (such as the above-mentioned block copolymers) Etc. can be exemplified. These compatibilizers can be used alone or in combination of two or more.

Examples of the diene monomer include conjugated dienes such as butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, piperylene (1,3-pentadiene), and 3-butyl-1. , 3-octadiene, phenyl-1,3-butadiene and the like, and a C _4-20 conjugated diene which may have a substituent. Conjugated dienes may be used alone or in combination of two or more. Of these conjugated dienes, butadiene and isoprene are preferred. Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyltoluene (such as p-methylstyrene), pt-butylstyrene, and divinylbenzene. Of these aromatic vinyl monomers, styrene is preferred. These monomers can be used alone or in combination of two or more.

  In addition, modification is a monomer corresponding to the modification group (for example, carboxyl group-containing monomer such as (meth) acrylic acid for carboxyl group modification, maleic anhydride for acid anhydride group modification, and (meta) for ester group modification. ) Acrylic monomer, maleimide group modification for maleimide group modification, and epoxy group-containing monomer such as glycidyl (meth) acrylate for copolymerization with epoxy modification. Epoxy modification may be performed by epoxidation of an unsaturated double bond.

  As a compatibilizer, a polymer (random, block or graft copolymer) usually having the same or common components as the constituent resin of the polymer blend system, a polymer having an affinity for the constituent resin of the polymer blend system (Random, block or graft copolymers) are used.

  Preferred compatibilizers are unmodified or modified diene copolymers, particularly modified block copolymers (eg, epoxidized diene block copolymers such as epoxidized styrene-butadiene-styrene (SBS) block copolymers). Or an epoxy-modified diene block copolymer). The epoxidized diene block copolymer not only has high transparency, but also has a relatively high softening temperature of about 70 ° C., so that a polycarbonate resin and a polypropylene resin can be compatibilized to uniformly disperse the dispersed phase. .

  The block copolymer can be composed of, for example, a conjugated diene block or a partially hydrogenated block thereof, and an aromatic vinyl block. In the epoxidized diene block copolymer, part or all of the double bond of the conjugated diene block is epoxidized. The ratio (weight ratio) between the aromatic vinyl block and the conjugated diene block (or its hydrogenated block) is, for example, the former / the latter = about 5/95 to 80/20 (for example, about 25/75 to 80/20). More preferably, it is about 10/90 to 70/30 (for example, about 30/70 to 70/30), and usually about 50/50 to 80/20.

  The number average molecular weight of the block copolymer can be selected from the range of, for example, about 5,000 to 1,000,000, preferably about 7,000 to 900,000, more preferably about 10,000 to 800,000. . The molecular weight distribution [ratio (Mw / Mn) of weight average molecular weight (Mw) and number average molecular weight (Mn)] is, for example, 10 or less (about 1 to 10), preferably about 1 to 5.

The molecular structure of the block copolymer may be linear, branched, radial, or a combination thereof. Examples of the block structure of the block copolymer include a multi-block structure such as a monoblock structure and a teleblock structure, a trichain radial teleblock structure, and a tetrachain radial teleblock structure. As such a block structure, when the aromatic vinyl block is X and the conjugated diene block is Y, for example, XY type, XYX type, YXY type, YXY -X type, X-Y-X-Y type, XY-X-Y-X type, Y-X-Y-X-Y type, (X-Y-) ₄ Si type, (Y-X- ) ₄ Si type can be exemplified.

  The proportion of the epoxy group in the epoxidized diene block copolymer is not particularly limited, but is, for example, 0.1 to 8% by weight, preferably 0.5 to 6% by weight, more preferably as the oxygen concentration of oxirane. About 1 to 5% by weight. The epoxy equivalent (JIS K 7236) of the epoxidized block copolymer may be, for example, about 300 to 1000, preferably about 500 to 900, and more preferably about 600 to 800.

  The refractive index of the compatibilizing agent (epoxidized block copolymer or the like) is approximately the same as that of the polypropylene resin (for example, the difference in refractive index from the polypropylene resin is about 0 to 0.01, preferably 0) About 0.005).

  As the epoxidized block copolymer, a diene block copolymer (or a partially hydrogenated block copolymer) is converted into a conventional epoxidation method, for example, an epoxidizing agent (peracid, It can be produced by epoxidizing the block copolymer with hydroperoxides or the like.

  The amount of the compatibilizer used is, for example, about 0.1 to 20% by weight, preferably about 0.5 to 15% by weight, and more preferably about 1 to 10% by weight with respect to the total amount of the polycarbonate resin and the polypropylene resin. You can select from a range. As described above, in the present invention, the dispersed phase can be uniformly dispersed by combining the specific polycarbonate resin and the specific polypropylene resin, even if the compatibilizer is not included. In addition, an anisotropic light diffusing sheet having no voids and high transmittance can be formed even if an orientation treatment such as uniaxial stretching is performed.

  In a preferable light diffusion sheet, the ratio of the continuous phase, the dispersed phase, and the compatibilizer is, for example, as follows.

(1) Continuous phase / dispersed phase (weight ratio) = about 99/1 to 50/50, preferably about 97/3 to 60/40, more preferably about 95/5 to 70/30, particularly 90/10 About 80/20 (2) Dispersed phase / Compatibilizer (weight ratio) = about 100/0 to 50/50, preferably about 99/1 to 70/30, more preferably about 98/2 to 80/20.

  In addition, in this invention, even if it does not contain a compatibilizing agent by combining the said polycarbonate-type resin and the said polypropylene-type resin, a dispersed phase can be disperse | distributed uniformly.

  If each component is used at such a ratio, the dispersed phase can be dispersed evenly by directly melting and kneading the pellets of each component without compounding each component in advance, and by an orientation treatment such as uniaxial stretching. Generation of voids can be prevented, and a light diffusion sheet having high transmittance and anisotropy can be obtained.

  More specifically, for example, when a resin composition containing the polycarbonate resin as a continuous phase and the polypropylene resin as a dispersed phase in the above ratio is used, compounding is easy and only the raw materials are fed. Thus, it is possible to form a melt while forming a compound, and to form an anisotropic light diffusion sheet free from voids even when uniaxially stretched.

  In addition to polypropylene resins, polyethylene resins, styrene resins, aromatic polyester resins (polyalkylene arylate homopolyesters such as polyalkylene terephthalate and polyalkylene naphthalate, the content of alkylene arylate units is 80 mol% or more. Copolyesters, liquid crystalline aromatic polyesters, etc.), polymers such as polyamide resins (aliphatic polyamides such as polyamide 46, polyamide 6 and polyamide 66), and inorganic particles such as silica are used as components of the dispersed phase. May be.

  Furthermore, the anisotropic diffusion layer contains conventional additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, light stabilizers, etc.), plasticizers, antistatic agents, flame retardants, and the like. It may be.

Examples of the antioxidant include phenolic antioxidants, hydroquinone antioxidants, quinoline antioxidants, and sulfur antioxidants. Phenol antioxidants include hindered phenols such as 2,6-di-tert-butyl-p-cresol, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2 Alkylphenol-based antioxidants such as' -thiobis (4-methyl-6-t-butylphenol); C ₁₀ such as n-octadecyl [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] _-35 alkyl [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxy) C _2-10 alkanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] such as phenyl) propionate]; Lumpur - bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) propionate] oxy C _2-4 alkylene diol such as - bis [3- (3,5-di -t- butyl - 4-hydroxyphenyl) propionate]; C _3-8 alkylenetriol-tris [3- (3,5-di) such as glycerol tris [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]. -T-butyl-4-hydroxyphenyl) propionate]; C _4-8 alkylenetetraol tetrakis [3- (3,3-di-t-butyl-4-hydroxyphenyl) propionate]; (3,5-di-t-butyl-4-hydroxyphenyl) propionate]; N, N′-hexamethylenebis (3,5-di-t-butyl) N, N′-C _2-10 alkylenebis (3,5-di-t-butyl-4-hydroxyhydrocinnamamide) such as til-4-hydroxyhydrocinnamamide) is preferable.

  Amine-based antioxidants include hindered amines such as 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane, phenylnaphthylamine, N, N′-diphenyl-1,4. -Phenylenediamine, N-phenyl-N'-cyclohexyl-1,4-phenylenediamine and the like are included.

  Examples of the hydroquinone antioxidant include 2,5-di-t-butylhydroquinone, and examples of the quinoline antioxidant include 6-ethoxy-2,2,4-trimethyl-1,2. -Dihydroquinoline and the like are included. Examples of the sulfur-based antioxidant include dilauryl thiodipropionate and distearyl thiodipropionate.

  Examples of the ultraviolet absorber include salicylic acid ester ultraviolet absorbers such as phenyl salicylate and 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate; 2- (2- Hydroxy-5-methylphenyl) benzotriazole, 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimido-methyl) -5-methylphenyl] benzotriazole, 2- (3-t-butyl -2-hydroxy-5-methylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-5-t-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-t-butyl) Phenyl) benzotriazole, 2- (2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl) benzotri Azole, octyl-3- [3-t-butyl-4-hydroxy- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3 Benzotriazole ultraviolet absorbers such as 3-tetramethylbutyl) phenol; 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,2′-dihydroxy-4-methoxy Benzophenone ultraviolet absorbers such as benzophenone; 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) -5-hydroxyphenyl and oxirane reaction product, 2- (2,4-dihydroxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine) and 2-ethylhexylglycidic acid ester, 2,4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) Examples thereof include hydroxyphenyl triazine-based ultraviolet absorbers such as -1,3,5-triazine.

Examples of the light stabilizer (HALS) include compounds having a 2,2,6,6-tetramethylpiperidine skeleton and a 1,2,2,6,6-pentamethyl-4-piperidine skeleton, such as N, N ′, N '', N '''-tetrakis (4,6-bis (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) triazin-2-yl) -4, 7-diazadecane-1,10-diamine, decanedioic acid bis (2,2,6,6-tetramethyl-1-octyloxy-4-piperidinyloxy) ester, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4 -Piperidinyl) sebacate, this C _4-20 alkane corresponding to the dicarboxylic acid ester of al - such as dicarboxylic acid esters (malonates, such as adipates) or array Nji carboxylate (terephthalate, etc.) can be exemplified.

  Examples of the thermal stabilizer include phosphite stabilizers (tris (branched alkylphenyl) phosphites such as tris (2,4-di-t-butylphenyl) phosphite), bis (alkylaryl) pentaerythritol diphosphites. And the like, phosphorus-based stabilizers (or phosphate esters), sulfur-based heat stabilizers, hydroxylamine-based heat stabilizers, and the like.

  These stabilizers (for example, light stabilizers) may be a low molecular weight type or a high molecular weight type. In addition, the stabilizer may be used alone or in a combination of two or more components (for example, a combination of an antioxidant and an ultraviolet absorber, a combination of an ultraviolet absorber and a light stabilizer, an antioxidant) And a combination of a UV absorber and a light stabilizer. The amount of each stabilizer used is 0.01 to 2.5 parts by weight, preferably 0.03 to 2 parts by weight (for example, 0.05 to 2 parts by weight) with respect to 100 parts by weight of the resin component constituting the anisotropic diffusion layer. 1.5 parts by weight), more preferably about 0.07 to 1 part by weight (for example, 0.1 to 0.7 part by weight), and usually about 0.07 to 0.5 part by weight (for example, 0.1 to 0.3 parts by weight). More specifically, the antioxidant is about 0.05 to 1 part by weight (for example, 0.08 to 0.3 part by weight) with respect to 100 parts by weight of the resin component, and the ultraviolet absorber is 100 parts by weight of the resin component. About 0.1 to 2 parts by weight (for example, 0.2 to 0.7 parts by weight) with respect to parts, and the light stabilizer is 0.03 to 0.5 parts by weight (for example with respect to 100 parts by weight of the resin component). 0.05 to 0.25 parts by weight). The total amount of the stabilizer may be 0.05 to 3 parts by weight (for example, 0.1 to 2 parts by weight), preferably about 0.1 to 1 part by weight with respect to 100 parts by weight of the resin component. Good. Further, when a plurality of stabilizers are used in combination, the ratio of the first stabilizer (for example, antioxidant) and the second stabilizer (for example, ultraviolet absorber) is the former / the latter (weight ratio) = It can be selected from a range of about 95/5 to 10/90 (for example, 90/10 to 30/70).

  When an alloy based on a combination of a polycarbonate resin and a polypropylene resin is melt-extruded or compounded, a part of the extrudate is in the form of eye boogers on the die lip (particularly the wall adjacent to the opening of the die lip). Gradually, the deposit grows and contacts the molten sheet extruded from the die lip, forming a non-uniform sheet. Therefore, it becomes impossible to produce a uniform sheet and film continuously. In such a case, when the stabilizer, particularly at least one selected from an antioxidant and an ultraviolet absorber (an antioxidant alone, an ultraviolet absorber alone, an antioxidant and an ultraviolet absorber, etc.) is contained, the deposition is performed. It is possible to remarkably prevent the production and growth of products, and to produce uniform sheets and films continuously. In addition, an antioxidant and / or an ultraviolet absorber), particularly at least an antioxidant, may be contained in the anisotropic diffusion layer in contact with the die lip. You may make it contain in the laminated | stacked transparent resin layer, and may make it contain in an anisotropic diffused layer and a transparent resin layer. In many cases, the anisotropic diffusion layer usually contains at least one selected from an antioxidant and an ultraviolet absorber.

  In the anisotropic diffusion layer, the form of the dispersed phase is such that the ratio of the average length L of the major axis to the average length W of the minor axis (average aspect ratio, L / W) is greater than 1, and the length of the dispersed phase particles The axial direction is oriented in one direction. The dispersed phase may be fibrous. The aspect ratio of the dispersed phase is usually larger than 1 (for example, 2 to 20000), for example, 3 to 20000 (for example, 5 to 15000), preferably 10 to 12000 (for example, 50 to 10,000), and more preferably 100. It is about -9000 (for example, 200-8000). In particular, in order to increase anisotropy, the aspect ratio of the dispersed phase may be about 50 to 20000 (for example, 100 to 15000), more preferably about 1000 to 10,000 (for example, 3000 to 8000). The larger the aspect ratio of such dispersed phase particles, the higher the anisotropic light scattering property. Such dispersed phase particles may have a football shape (such as a spheroidal shape), a fiber shape, or a rectangular shape. In the anisotropic diffusion layer, the long axis direction of the dispersed phase is oriented in a predetermined direction of the sheet, that is, the X-axis direction (take-up direction or machine direction) to form a particulate dispersed phase. In particular, in the present invention, high anisotropic scattering can be expressed by adjusting the aspect ratio of the dispersed phase particles of the anisotropic diffusion layer to be high, and the generated anisotropic diffused light can be efficiently directed to the front direction at the prism portion. Since the light can be condensed, the luminance uniformity can be improved even if the light diffusion sheet is thinned.

  The average length L of the long axis of the dispersed phase can be selected from a range of, for example, about 0.1 to 2000 μm, for example, about 1 to 1500 μm, preferably about 1 to 1200 μm (for example, about 1.5 to 1000 μm). ), Especially about 2 to 900 μm (for example, about 5 to 800 μm), and usually about 100 to 1000 μm (for example, 300 to 800 μm). Further, the average length W of the minor axis of the dispersed phase can be selected from a range of about 0.01 to 10 μm, for example, 0.01 to 1 μm, preferably 0.02 to 0.8 μm, and more preferably 0. 0.03 to 0.7 μm (particularly 0.05 to 0.5 μm).

  The orientation coefficient of the dispersed phase particles as the degree of alignment is, for example, 0.34 or more (about 0.34 to 1), preferably 0.4 to 1 (for example, 0.5 to 1), and more preferably 0.7. It may be about ˜1. Higher anisotropy can be imparted to the scattered light as the orientation coefficient of the dispersed phase particles is higher. The orientation coefficient can be calculated based on the following formula.

Orientation coefficient = (3 <cos ² θ> −1) / 2
(Wherein θ represents the angle between the long axis of the particulate dispersed phase and the X axis of the sheet (θ = 0 ° when the long axis and the X axis are parallel), and <cos ² θ> represents each The average cos ² θ calculated for the dispersed phase particles is shown by the following formula).

<Cos ² θ> = ∫n (θ) · cos ² θ · dθ
(In the formula, n (θ) represents the ratio (weight ratio) of dispersed phase particles having an angle θ in all dispersed phase particles).

  The light diffusion sheet may have the directivity of diffused light. That is, having directivity means that there is an angle at which the scattering intensity has a maximum in the direction of strong scattering in anisotropic diffused light. When the diffused light has directivity, when the diffused light intensity F is plotted with respect to the diffusion angle θ in the measurement apparatus of FIG. 5 described later, the plot curve shows a range of a specific diffusion angle θ (θ = It has a maximum or a shoulder (in particular, an inflection point such as a maximum) in an angle range other than 0 °. When imparting directivity to the anisotropic light diffusion sheet, the average length of the long axis of the dispersed phase particles is, for example, about 10 to 100 μm, preferably about 20 to 60 μm.

  The thickness of the anisotropic diffusion layer is about 3 to 500 μm (for example, 3 to 300 μm), preferably about 5 to 200 μm (for example, 10 to 200 μm), more preferably about 15 to 150 μm (for example, 30 to 120 μm). May be.

  The light diffusion sheet may be a single layer sheet or a film of the anisotropic diffusion layer alone (for example, an anisotropic light diffusion layer for anisotropically diffusing transmitted light). The laminated body comprised with the transparent resin layer laminated | stacked on one surface may be sufficient. Moreover, in the light-diffusion sheet which has a laminated structure, you may laminate | stack a transparent resin layer not only on one side of an anisotropic diffusion layer but on both surfaces. From the viewpoint of thinning the surface light source device, the prism portion may be formed directly on the anisotropic diffusion layer without forming the transparent resin layer.

  The transparent resin layer is a highly transparent resin, for example, a thermoplastic resin [olefin resin, cyclic olefin resin, halogen-containing resin (including fluorine resin), vinyl alcohol resin, fatty acid vinyl ester resin, (meta ) Acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin, thermoplastic polyurethane resin, polysulfone resin (polyethersulfone, polysulfone, etc.), polyphenylene ether resin (2,6-xylenol heavy Coalesced), cellulose esters, silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), elastomers (nitrile-butadiene copolymers, rubbers such as acrylic rubber, urethane rubber, silicone rubber, thermoplastic elastomers, etc.). ], And it includes a thermosetting resin (epoxy resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin or the like) and the like. A preferred resin is a thermoplastic resin. The highly transparent resin may be an amorphous resin.

Examples of olefin resins include polypropylene resins, copolymers of α-C _2-6 olefin and copolymerizable monomers (ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene- Examples include (meth) acrylic acid ester copolymers, ethylene- (meth) acrylic acid copolymers or salts thereof (for example, ionomer resins), etc. Examples of cyclic olefin resins include cyclic olefins (norbornene, Dicyclopentadiene) or a copolymer (for example, a polymer having an alicyclic hydrocarbon group such as sterically rigid tricyclodecane), a copolymer of the cyclic olefin and the copolymerizable monomer. Examples include polymers (ethylene-norbornene copolymer, propylene-norbornene copolymer, etc.) The polymer constituting the transparent resin layer The propylene-based resin may be different from the polypropylene-based resin constituting the light diffusion layer, the molecular weight and its distribution, the melt flow rate, etc., but the same type or the same system in which at least some copolymerization components are common ( Or the same resin).

  Examples of halogen-containing resins include vinyl halide resins (such as homopolymers of halogen-containing monomers such as polyvinyl chloride and polyvinyl fluoride, vinyl chloride-vinyl acetate copolymers, vinyl chloride- (meth) acrylate esters). A halogen-containing vinylidene monomer such as a copolymer of a halogen-containing monomer such as a polymer and a copolymerizable monomer), a vinylidene halide resin (a vinylidene chloride- (meth) acrylate copolymer) And other monomers).

  Examples of the fatty acid vinyl ester resins include vinyl ester monomers alone or copolymers (polyvinyl acetate, etc.), vinyl ester monomers and copolymerizable monomers (vinyl acetate-ethylene). Copolymer, vinyl acetate-vinyl chloride copolymer, vinyl acetate- (meth) acrylic ester copolymer, etc.) or derivatives thereof. Examples of the derivative of the fatty acid vinyl ester resin include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyvinyl acetal resin, and the like.

As the (meth) acrylic resin, a (meth) acrylic monomer alone or a copolymer, or a copolymer of a (meth) acrylic monomer and a copolymerizable monomer can be used. Examples of the (meth) acrylic monomer include (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Examples include (meth) acrylic acid C _1-10 alkyl; hydroxyalkyl (meth) acrylate; glycidyl (meth) acrylate; (meth) acrylonitrile; (meth) acrylate having an alicyclic hydrocarbon group such as tricyclodecane. . Examples of the copolymerizable monomer include styrene monomers. These monomers can be used alone or in combination of two or more.

  Examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer Examples thereof include methyl methacrylate, acrylic acid ester- (meth) acrylic acid copolymer, and (meth) methyl acrylate-styrene copolymer (such as MS resin). Preferable (meth) acrylic resins include methyl methacrylate resins containing methyl methacrylate as a main component (50 to 100% by weight, preferably about 70 to 100% by weight).

  Styrene resins include styrene monomers alone or copolymers (polystyrene, styrene-α-methylstyrene copolymer, styrene-vinyltoluene copolymer, etc.), styrene monomers and other polymerizable properties. Copolymers with monomers ((meth) acrylic monomers, maleic anhydride, maleimide monomers, dienes, etc.) are included. Examples of the styrene-based copolymer include a styrene-acrylonitrile copolymer (AS resin), a copolymer of styrene and a (meth) acrylic monomer [styrene-methyl methacrylate copolymer, styrene-methacrylic acid. Methyl- (meth) acrylic acid ester copolymer, styrene- (meth) acrylic acid ester copolymer such as styrene-methyl methacrylate- (meth) acrylic acid copolymer], styrene-maleic anhydride copolymer, etc. Is mentioned. Preferred styrenic resins include polystyrene, copolymers of styrene and (meth) acrylic monomers [copolymers based on styrene and methyl methacrylate such as styrene-methyl methacrylate copolymer], AS resin, styrene-butadiene block copolymer and the like are included.

Polyester resins include aromatic polyesters (homopolyesters such as poly C _2-4 alkylene terephthalates such as polyethylene terephthalate and polybutylene terephthalate and poly C _2-4 alkylene naphthalates, C _2-4 alkylene arylate units (C _{2 4} copolyester containing ₄ alkylene terephthalate and / or C _2-4 alkylene naphthalate unit) as a main component (for example, 50 mol% or more, preferably 75 to 100 mol%, more preferably 80 to 100 mol%), etc. Can be illustrated. As the copolyester, a part of C _2-4 alkylene glycol may be polyoxy C _2-4 alkylene glycol, C _6-10 alkylene glycol, alicyclic diol (cyclohexanedimethanol, hydrogenated bisphenol A, etc.), bisphenol A, Copolyesters substituted with bisphenol A-alkylene oxide adducts, etc.), asymmetric aromatic dicarboxylic acids such as phthalic acid and isophthalic acid, and aliphatic C _6-12 dicarboxylic acids such as adipic acid And copolyesters substituted with Polyester resins also include polyarylate resins, aliphatic polyesters using aliphatic dicarboxylic acids such as adipic acid, and homopolymers or copolymers of lactones such as ε-caprolactone. A preferred polyester resin is usually amorphous such as an amorphous copolyester (for example, C _2-4 alkylene arylate copolyester).

  Examples of the polyamide resin include aliphatic polyamides such as polyamide 6, polyamide 66, polyamide 610, polyamide 612, polyamide 11 and polyamide 12, dicarboxylic acid (eg terephthalic acid, isophthalic acid, adipic acid etc.) and diamine (eg hexa Polyamide (such as aromatic polyamide such as xylylenediamine adipate (MXD-6)) in which at least one component of methylenediamine or metaxylylenediamine) is an aromatic compound. The polyamide-based resin may be a lactone such as ε-caprolactone or a copolymer, and is not limited to a homopolyamide but may be a copolyamide.

Examples of the polycarbonate-based resin include the same resins as described above. The polycarbonate resin constituting the transparent resin layer may be different from the polycarbonate resin constituting the light diffusion layer in kind, molecular weight, melt flow rate, etc., but the same type or the same system (or common skeleton) If the same resin is used, the adhesion to the light diffusion layer may be improved. The polycarbonate resin is preferably a polycarbonate resin based on bis (hydroxyaryl) C _1-6 alkane such as bisphenol A.

Examples of the cellulose esters include aliphatic organic acid esters (cellulose acetates such as cellulose diacetate and cellulose triacetate; C _1-6 such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). Organic acid esters, etc.) and aromatic organic acid esters (C _7-12 aromatic carboxylic acid esters such as cellulose phthalate and cellulose benzoate), and mixed acid esters such as acetic acid and cellulose nitrate esters may be used.

  Preferable components constituting the transparent resin layer include olefin resins, (meth) acrylic resins, styrene resins, polyester resins, polyamide resins, polycarbonate resins, and the like. A preferred transparent resin layer can be composed of a polycarbonate resin. As the resin constituting the transparent resin layer, a resin that is the same as or different from the resin of the continuous phase and / or the dispersed phase constituting the anisotropic diffusion layer can be used as long as the adhesion and mechanical properties are not impaired. Usually, a resin that is the same or common (or the same system) as the resin of the continuous phase is preferred.

  The transparent resin constituting the transparent resin layer is preferably a heat-resistant resin (such as a resin having a high glass transition temperature or a melting point) or a crystalline resin in order to improve heat resistance or blocking resistance. The glass transition temperature or melting point of the resin constituting the transparent resin layer may be, for example, about 130 to 280 ° C, preferably about 140 to 270 ° C, and more preferably about 150 to 260 ° C.

  Further, the transparent resin layer contains conventional additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, light stabilizers, etc.), plasticizers, antistatic agents, flame retardants and the like. Also good. In particular, the transparent resin layer is composed of a stabilizer (antioxidant, ultraviolet absorber, light stabilizer), preferably at least one component selected from an ultraviolet absorber and a light stabilizer (ultraviolet absorber alone, light stabilizer alone). , Ultraviolet absorbers and light stabilizers), particularly preferably a resin layer containing an ultraviolet absorber and a light stabilizer. As the stabilizer, the same components as described above can be used, and the amount of each stabilizer used and the total amount of the stabilizer relative to 100 parts by weight of the resin component constituting the transparent resin layer is based on the resin component constituting the anisotropic diffusion layer. It can be selected from the same range as the ratio. Moreover, when using an ultraviolet absorber and a light stabilizer together, the ratio of both is from the range of the former / the latter (weight ratio) = 95 / 5-50 / 50 (for example, 90 / 10-70 / 30) grade. You can choose.

  Each transparent resin layer may have the same thickness as the anisotropic diffusion layer. For example, when the thickness of the anisotropic diffusion layer is about 3 to 300 μm, the thickness of the transparent resin layer is about 3 to 150 μm. You can choose from. The ratio of the thickness of the anisotropic diffusion layer and each transparent resin layer is, for example, anisotropic diffusion layer / transparent resin layer = 5/95 to 99/1, preferably 30/70 to 99/1, more preferably It is about 40/60 to 95/5. The thickness of the laminated sheet or film may be, for example, about 6 to 600 μm, preferably about 10 to 400 μm, and more preferably about 20 to 250 μm.

  Conventionally, a diffusion plate having a thickness of several millimeters has been used, but in the present invention, even a thin light diffusion sheet of several tens of microns can be effectively used without using such a thick diffusion plate. The light can be diffused and the luminance of the display device can be improved. In particular, even in a backlight type liquid crystal display device provided with a tubular light source, the luminance of the display device can be effectively improved.

  The total light transmittance of the light diffusion sheet (or anisotropic diffusion layer) is, for example, 50% or more (for example, 50 to 100%), preferably 60% or more (for example, 60 to 100%), particularly 70. It may be about -95% (for example, 75-90%). Furthermore, the haze value of the light diffusion sheet (or anisotropic diffusion layer) is 80% or more (for example, 80 to 99.9%), preferably 90% or more (for example, 90 to 99.8%), and more preferably. Is about 93 to 99.5%, particularly about 95 to 99%. If the total light transmittance is small, the luminance tends to decrease, and if the haze value is small, the light cannot be diffused uniformly and the display quality is deteriorated.

  The surface of the light diffusing sheet may be subjected to a surface treatment such as a corona discharge treatment from the viewpoint of improving the adhesion with the prism portion within a range not impeding the optical characteristics.

  FIG. 2 is a schematic cross-sectional view showing an example of a light diffusion sheet. The light diffusion sheet 17 having a single layer structure is composed of a plurality of resins having different refractive indexes, and has a phase separation structure (or sea island structure) in which the particulate dispersed phase 17b is dispersed in the continuous layer 17a. .

  FIG. 3 is a schematic sectional view showing another example of the light diffusion sheet. In this example, the light diffusion sheet 28 has a laminated structure composed of an anisotropic diffusion layer 27 and a transparent resin layer 29 laminated on at least one surface of the anisotropic diffusion layer. The anisotropic diffusion layer 27 is composed of a plurality of resins having different refractive indexes, and has a phase separation structure (or sea-island structure) in which the particulate dispersed phase 27b is dispersed in the continuous layer 27a. . In the light diffusing sheet having such a laminated structure, the transparent resin layer 29 protects the light diffusing layer 27 to prevent the dispersed phase particles from falling off and adhering, and the sheet can be improved in scratch resistance and manufacturing stability. Strength and handleability can be improved.

  FIG. 4 is a conceptual diagram for explaining the anisotropy of light diffusion. As shown in FIG. 4, the light diffusing sheet 37 is composed of a continuous phase 37 a made of a resin and an anisotropic dispersed phase 37 b dispersed in the continuous phase. The anisotropy of light diffusion is the scattering characteristic F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F. The scattering characteristic in the X-axis direction of the sheet or film is expressed as Fx (θ), X-axis direction When the scattering characteristic in the orthogonal Y-axis direction is Fy (θ), the scattering characteristics Fx (θ) and Fy (θ) (particularly Fy (θ)) indicate the light intensity as the scattering angle θ becomes wider. Shows a pattern of slowly decaying. In the range of the scattering angle θ = 4 to 30 °, the value of Fy (θ) / Fx (θ) is 1.01 or more, for example, about 1.01 to 200, preferably about 1.1 to 150. It is. Further, at the scattering angle θ = 18 °, the value of Fy (θ) / Fx (θ) is 1.1 to 400 (for example, 1.1 to 100), preferably 1.1 to 200, and more preferably. Is about 5 to 100 (especially 10 to 80).

  When a light diffusing sheet having such optical characteristics is used, the light diffusing sheet is arranged so as to scatter in a direction perpendicular to the axial direction of the rod light source, thereby erasing the lamp image in which the rod light source itself is recognized. A reduction in luminance can be achieved with a minimum. Note that if the value of Fy (θ) / Fx (θ) and the value of Fy (θ) / Fx (θ) at the scattering angle θ = 18 ° are too large, the appearance of the lamp image can be suppressed, but the luminance is reduced. On the other hand, when these values are too small, a decrease in luminance can be suppressed, but a lamp image appears.

  In order to prepare a sheet or film having such scattering characteristics, selection of components (particularly resins) constituting the continuous phase and dispersed phase, molding conditions, particularly extrusion temperature, draw ratio after molding and cooling temperature are important. Yes, a sheet or film having such light diffusion characteristics can be obtained by producing a sheet or film under the types and conditions described below.

  Note that the X-axis direction of the light diffusion sheet 37 is usually the long-axis direction of the dispersed phase 37b. Therefore, the X-axis direction of the light diffusion sheet is arranged in a direction substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. Note that the X-axis direction of the light diffusion sheet does not need to be completely parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit, for example, an angle ± 15 ° (eg, ± 10 °) In particular, it may be disposed in an oblique direction within a range of about ± 5 °.

  The scattering characteristic F (θ) can be measured using, for example, a measuring apparatus as shown in FIG. This apparatus measures the intensity of laser light that has passed through the light diffusion sheet 37 and a laser light irradiation apparatus (for example, NIHON KAGAKU ENG NEO-20MS) 38 for irradiating the anisotropic light diffusion sheet 37 with laser light. And a detector 39 for the purpose. Then, laser light is irradiated (perpendicularly) at an angle of 90 ° with respect to the surface of the light diffusion sheet 37, and the intensity (scattered light intensity) F of the light diffused by the sheet is measured (plotted) with respect to the scattering angle θ. ) To obtain light scattering characteristics.

  In the light diffusion sheet, when the anisotropy of light scattering is high, the angle dependency of scattering in a predetermined direction can be reduced, and therefore the angle dependency of luminance can also be reduced. In the light diffusing sheet, when an angle (90 °) perpendicular to the display surface is 0 °, a decrease in luminance can be suppressed even at an angle of 40 ° or more exceeding an angle of 20 ° with respect to the display surface.

(Prism part)
The prism portion (lens portion) is formed by arranging a plurality of prism units on at least one surface (one surface or both surfaces) of the light diffusion sheet. More specifically, these prism units may be formed in the anisotropic diffusion layer, or may be formed in the transparent resin layer laminated on the anisotropic diffusion layer. Usually, in many cases, a plurality of prism units are formed on at least the transparent resin layer. If it is desired to make the surface light source device thinner, the prism portion may be formed on the anisotropic diffusion layer without forming the transparent resin layer.

  The form of the prism unit is not particularly limited as long as the cross-sectional shape is a triangular shape, may be a quadrangular pyramid shape, or may be a column shape having a triangular cross section (triangular prism shape) extending linearly. Further, the plurality of prism units may be irregularly or independently formed, but are usually regularly arranged, for example, regularly arranged in parallel with each other, particularly in an adjacent form. ing. In a preferred embodiment, the plurality of prism units are often in the form of a column with a triangular cross section (triangular prism), and in parallel with each other, particularly adjacent to each other, prism columns (or triangular column prism arrays whose major axis directions are parallel to each other). Forming.

  The cross-sectional shape of the prism unit may be an isosceles triangle shape, but isosceles triangle shape, in particular, the apex angle is 50 to 120 ° (preferably 60 to 110 °, more preferably 70 to 100 °, particularly 80). It is preferably an isosceles triangle shape of about ~ 95 °. In the cross-sectional shape, the apex angle of the prism unit is usually about 90 ° ± 10 °, particularly about 90 ° ± 5 °, and if the apex angle is in this range (near 90 °), the luminance unevenness becomes high. Can be suppressed.

  The pitch of the prism unit can be selected from a range of, for example, about 5 to 100 μm, and may be generally 10 to 80 μm, preferably 20 to 60 μm, and more preferably about 30 to 50 μm.

  The height of the prism unit can be selected from a range of, for example, about 1 to 50 μm, and is usually 5 to 45 μm, preferably 10 to 40 μm (for example, 15 to 30 μm), and more preferably about 15 to 25 μm. .

  Each prism unit may be formed on a transparent resin layer or an anisotropic diffusion layer so that each unit is adjacent to each other, and each prism unit (prism region) is transparent resin layer or anisotropic through a base region. It may be formed on the conductive diffusion layer. In the former case, each prism unit constituting the prism portion is in contact with adjacent end portions (vertical corners of a triangular section), but each unit is independently a transparent resin layer or anisotropic diffusion. It is arranged directly on the layer without a base. On the other hand, in the latter case, the prism portion has an integral sheet shape in which each prism unit protrudes from the base region. In other words, the integrated sheet-like prism portion has a structure in which the surface of the sheet has a concavo-convex prism-like surface (prism area), a prism unit valley (or a triangle base), a transparent resin layer, or an anisotropy It differs from the structure in which each prism unit protrudes from the transparent resin layer or the anisotropic diffusion layer in that a base region is interposed between the diffusion layer and the diffusion layer. The height (thickness) of the base region is, for example, 0 to 30 μm (for example, 0.1 to 30 μm), preferably 1 to 20 μm, and more preferably about 3 to 15 μm.

  The plurality of prism units may be formed of a prism sheet or a lenticular lens. A plurality of prism units of the prism sheet or lenticular lens is formed by a method of forming a prism-like lens portion on the surface of a thermoplastic resin substrate sheet softened by a mold (or embossing), and a translucent by a transfer mold. A method of transferring a prism-shaped lens part to a base sheet and curing the lens part if necessary, an uneven part corresponding to a prism unit while applying or applying a photocurable resin composition to a translucent base sheet A roll mold having (a plurality of adjacent V-shaped grooves or the like) is rolled to form a prism-shaped lens portion, and this lens portion can be cured. Such a prism sheet or a lenticular lens may be laminated on a light diffusion sheet to prepare a light control sheet. Note that the presence or absence of the base region in the prism portion can be controlled by adjusting the amount of the resin composition used as a raw material.

  The plurality of prism units may be directly formed on the light diffusion sheet (transparent resin layer and / or anisotropic diffusion layer). For example, the photocurable resin composition is applied to a light diffusion sheet (transparent resin layer and / or anisotropic diffusion layer) or the roll mold is rolled while applying the lens portion in the form of a prism. A plurality of prism units may be formed by forming, irradiating light, and curing at the lens portion.

  The photocurable resin composition is prepared by using conventional components such as photocurable oligomers or resins [for example, (meth) acrylates of bisphenol A-alkylene oxide adducts, epoxy (meth) acrylates (bisphenol A type epoxy (meth) acrylates). , Novolak type epoxy (meth) acrylate, etc.), polyester (meth) acrylate (for example, aliphatic polyester type (meth) acrylate, aromatic polyester type (meth) acrylate, etc.), (poly) urethane (meth) acrylate (polyester type) Urethane (meth) acrylate, polyether type urethane (meth) acrylate, etc.), silicone (meth) acrylate, etc.], photopolymerization initiator (benzophenone photopolymerization initiator, etc.), and reactive diluent (vinyl pyrrolide if necessary) Monofunctional photopolymerizable monomers such as polyfunctional (meth) acrylate monomers having about 2 to 6 (meth) acryloyl groups such as trimethylolpropane tri (meth) acrylate), photopolymerization promotion An agent (sensitizer) or the like may be included. Moreover, in order to improve the shape or dimensional accuracy of the lens part, it may contain an adjusting agent (such as a viscosity adjusting agent) for adjusting the consistency (thixotropic properties, dilatancy, viscosity, etc.) of the photocurable resin composition. Good. Further, the photocurable resin composition may be a (semi) solid or viscous composition in the rolling process of coating or roll mold.

  The arrangement direction (or arrangement direction) of the plurality of prism units is not particularly limited with respect to the major axis direction of the particulate dispersed phase, and for example, a direction intersecting with the major axis direction of the particulate dispersed phase (a direction orthogonal thereto, It may be a direction crossing the oblique direction). For example, the major axis direction of the particulate dispersed phase and the arrangement direction of the prism units (ridge line or major axis direction) are, for example, substantially within a range of ± 15 ° (preferably ± 10 °, more preferably ± 5 °). May be substantially in the same direction (substantially parallel), for example, substantially orthogonal (crossed) in a range of ± 15 ° (preferably ± 10 °, more preferably ± 5 °). Good. In a preferred embodiment, the major axis direction of the particulate dispersed phase is directed to the extending direction of the prism unit (the ridge line or the major axis direction of the triangular prism unit) and is parallel to each other. When the long axis direction of the particulate dispersed phase is substantially parallel to the extending direction of the prism unit, the light collection effect on the front surface can be improved. On the other hand, when the major axis direction of the particulate dispersed phase is substantially orthogonal to the extending direction of the prism unit, there is an effect that the bright line and the dark line can be suppressed.

  When such a plurality of prism units are formed on the light diffusion sheet, the diffused light diffused anisotropically by the anisotropic diffusion layer can be condensed in the front direction, and the luminance distribution can be averaged. Therefore, the brightness of the front direction is improved, the image of the light source (lamp image) can be lost, and the display quality can be improved.

  FIG. 6 is a cross-sectional perspective view showing an example of the light control sheet of the present invention. In this example, the light control sheet includes a light diffusion sheet 48 formed of an anisotropic diffusion layer 47 and transparent resin layers 49 formed on both sides of the anisotropic diffusion layer, and one of the transparent resin layers. And a prism row (prism portion) 46 formed in the above. The prism portion has a base area. The anisotropic diffusion layer 47 is formed of a continuous phase (matrix) 47a formed of a thermoplastic resin and a thermoplastic resin having a refractive index different from that of the thermoplastic resin of the continuous phase. A particulate dispersed phase 47b oriented and dispersed in a predetermined direction, and the particulate dispersed phase 47b is formed in an elongated shape. That is, the long axis of the particulate dispersed phase 47 b is oriented in the longitudinal direction of the light diffusion sheet 48. In this example, the continuous phase (matrix) is formed of a resin having high translucency or transparency and high heat resistance, such as polycarbonate resin, and the particulate dispersed phase 47b is, for example, high in heat resistance. It is formed of an olefin resin, for example, a polypropylene resin (a polypropylene resin using a metallocene catalyst). The transparent resin layer 49 is formed of a resin having high transparency and heat resistance, such as a polycarbonate resin.

  The prism portion 46 formed in the one transparent resin layer 49 is formed of a plurality of prism units 46a having a triangular cross section. That is, each prism unit 46a is adjacent to each other, and the ridge line of each prism unit extends along the long axis direction of the particulate dispersed phase 47b to form a prism row 46. The prism portion 46 forms a curable resin unit having a shape corresponding to a plurality of triangular cross-sectional prism units 46a adjacent to each other on the transparent resin layer 49 without using an adhesive. The resin unit is directly formed on the transparent resin layer 49 by a method of curing these resin units).

  FIG. 7 is a cross-sectional perspective view showing another example of the light control sheet of the present invention. In this example, the light control sheet includes an anisotropic diffusion layer 57 including a continuous phase 57a and a particulate dispersed phase 57b without forming a transparent resin layer, and a prism formed on one side of the anisotropic diffusion layer. Part 56. Further, in the prism portion 56, the prism units 56a are formed adjacent to each other on the surface of the anisotropic diffusion layer 57 without interposing a base region.

  When such a light control sheet is used, the diffused light diffused anisotropically by the anisotropic diffusion layer can be collected in the front direction, and the luminance directly above the linear light source (such as a fluorescent tube) is reduced (that is, The luminance distribution corresponding to the linear light source can be eliminated), and the luminance distribution can be averaged. Therefore, the brightness of the front direction is improved, the image of the light source (lamp image) can be lost, and the display quality can be improved. Moreover, since the prism row is directly formed on the light diffusion sheet, the thickness of the light control sheet can be reduced and the accommodation space can be reduced as compared with the case where the prism sheet and the light diffusion sheet are used separately.

  In the light control sheet, the light diffusion sheet may be composed of at least an anisotropic diffusion layer, and the transparent resin layer is not necessarily required. Further, the transparent resin layer does not need to be formed on both surfaces of the anisotropic diffusion layer, and may be formed on at least one surface of the anisotropic diffusion layer, and may be formed on one surface of the anisotropic diffusion layer. Also good. Furthermore, the prism portion need not be formed in the transparent resin layer, and may be formed in the anisotropic diffusion layer. More specifically, the light control sheet is a sheet that does not include a transparent resin layer (for example, a sheet in which a prism portion is formed on one surface of an anisotropic diffusion layer), and a sheet that includes a transparent resin layer (anisotropic). A prism portion is formed on one surface of the anisotropic diffusion layer, a transparent resin layer is formed on the other surface of the anisotropic diffusion layer, and a transparent resin layer is formed on one surface of the anisotropic diffusion layer. A sheet in which a prism portion is formed on a transparent resin layer, a sheet in which a transparent resin layer is formed on both surfaces of an anisotropic diffusion layer, and a prism portion is formed on one transparent resin layer).

[Manufacturing method of light control sheet]
The light control sheet is formed by dispersing and orienting the components (resin component, fibrous component, etc.) constituting the dispersed phase in the resin constituting the continuous phase to form the light diffusing sheet, and then forming a prism on the light diffusing sheet. It can be obtained by forming a part.

  In the method for forming a light diffusion sheet, the dispersed phase can be usually obtained by a method in which the resin component constituting the dispersed phase is deformed and oriented. For example, a resin constituting a continuous phase (for example, a polycarbonate-based resin), a component constituting a dispersed phase (for example, a polypropylene-based resin), and a component such as a compatibilizing agent, if necessary, can be used by a conventional method (for example, , Melt blending method, tumbler method, etc.), melt mixing, extruding from a T die, ring die or the like to form a sheet or film to disperse the dispersed phase. Also, a coating method in which a composition composed of a light scattering component (for example, a polypropylene resin) and a binder resin (for example, a polycarbonate resin) is applied on a base film, or a laminating method for laminating the composition The film can be produced by forming using a conventional film forming method such as a casting method or an extrusion method. Usually, a light diffusing sheet is often prepared by forming a film by an extrusion method.

  The light diffusion sheet having a laminated structure composed of an anisotropic diffusion layer and a transparent resin layer laminated on at least one surface of the anisotropic diffusion layer is a component corresponding to the anisotropic diffusion layer. A co-extrusion molding method in which a resin composition composed of a resin composition composed of a component corresponding to the transparent resin layer and a resin composition composed of a component corresponding to the transparent resin layer are formed. It can be formed by a method of laminating layers by extrusion lamination, a dry laminating method of laminating an anisotropic diffusion layer and a transparent resin layer, respectively.

  In the anisotropic diffusion layer, for example, (1) a method of forming a film while drawing an extruded sheet, (2) a method of uniaxially stretching the extruded sheet, (3) the above (1) (4) A method of combining the above method and the method of (2), (4) a method of solution blending the above components and forming a film by a casting method.

  The melting temperature may be, for example, about 150 to 270 ° C, preferably about 200 to 260 ° C, and more preferably about 230 to 255 ° C.

  In order to develop an appropriate anisotropy, it is preferable to form a film while drawing an extruded sheet in a light diffusion sheet or melt film formation. In order to exhibit a predetermined anisotropic light diffusion characteristic, it is important to adjust the draw ratio after extrusion. The draw ratio (draw ratio) can be selected from a range of about 1.5 to 50 times depending on the opening degree of the die of the extruder, the type of resin, the layer structure, etc., and cannot be uniquely determined. In this case, for example, the anisotropic parameter is selected from the range of about 4 to 40 times, preferably 5 to 35 times, and more preferably 8 to 30 times (particularly 10 to 25 times). it can. In the case of a laminated body, since the anisotropy tends to be higher than that of a single layer, the draw ratio is, for example, 3.5 to 20 times, preferably 4 to 18 times, more preferably 5 to 16 times (particularly 6 times). (About 15 times).

  The cooling temperature by a cast roll etc. may be about 30-110 degreeC, for example, Preferably it is 40-100 degreeC, More preferably, about 60-90 degreeC may be sufficient. Furthermore, the light diffusion sheet may be stretched (uniaxial or biaxial stretching, particularly uniaxial stretching). The draw ratio of the light diffusion sheet can be selected according to the aspect ratio of the dispersed phase. For example, the draw ratio in one direction is 1.1 to 10 times, preferably 1.2 to 5 times, more preferably 1.5 to It may be about 3 times.

  As a method for forming the prism portion on the obtained light diffusion sheet, the prism-shaped lens portion is formed on the surface of the thermoplastic resin base sheet softened by the above-described method, for example, a mold (or embossing). A method of forming, a method of transferring a prism-shaped lens portion to a translucent substrate sheet by a transfer mold, and curing the lens portion as necessary, a photocurable resin composition being applied to or applied to the translucent substrate sheet However, there is a method of rolling a roll mold having uneven portions (adjacent plural V-shaped grooves or the like) corresponding to the prism unit to form a prism-shaped lens portion and curing the lens portion. Can be mentioned.

  In the light control sheet of the present invention, the anisotropic light diffusing effect by the light diffusing sheet and the lens effect by the prism portion are combined, whereby the luminance can be made highly uniform. Therefore, the light control sheet of the present invention can be used for various optical applications. In particular, since the brightness on the display surface can be made highly uniform, the appearance of a lamp image can be suppressed even if the surface light source device is made thinner and higher in brightness. Therefore, when applied to a display device such as a liquid crystal display device (particularly a backlight system), the entire display surface can be illuminated uniformly. Therefore, the light control sheet of the present invention is useful as a constituent member of a surface light source device or a display device (for example, a surface display device (flat display device) having a flat image display area such as a liquid crystal display device). is there. An example of a liquid crystal display device will be described with reference to FIG. 1 described above.

[Liquid Crystal Display]
In FIG. 1 which shows the outline of a liquid crystal display device, the liquid crystal display device includes a surface type display unit (such as a transmission type liquid crystal display unit or a liquid crystal display panel) 5 as an irradiated body including a liquid crystal cell in which liquid crystal is sealed. The surface light source unit is disposed on the back side of the display unit (or panel) and illuminates the display unit 5.

  The surface light source unit includes a tubular light source 1 such as a plurality of fluorescent discharge tubes (cold cathode tubes) arranged in parallel or directly below the display unit 5 and light from the tubular light source 1 in the forward direction (display unit). And a reflecting plate 2 for guiding the light to the display unit 5. In front of the tubular light source 1, a support plate (not shown) disposed in front of the tubular light source 1 and an emission surface side (light-emitting surface side of the surface light source unit) of the support plate are arranged to transmit transmitted light. A diffusion plate (for example, anisotropic light diffusion sheet) 3 for anisotropically scattering light, and a prism that is positioned on the display surface side of the diffusion plate 3 and in which micro prisms having a triangular cross section are formed in parallel in a predetermined direction Sheets 4 are sequentially stacked. The light from the tubular light source 1 is diffused and made uniform by the diffusion plate 3 and condensed forward by the prism sheet 4 to illuminate the display unit 5 with increased brightness. In addition, the said support plate is a transparent plate formed in order to protect the anisotropic light-diffusion film 3 which is a thin film. In the liquid crystal display device of the present invention, since the light control sheet has a prism function, the prism sheet 4 may be omitted in some cases.

  The surface type display unit (liquid crystal display unit) 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, and a first electrode laminated on the electrode. The first alignment film 9a, the liquid crystal layer 10, the second alignment film 9b, the second electrode 8b, the color filter 11, the second glass substrate 7b, and the second polarizing film 6b are sequentially stacked. Yes.

  In such a display device, the display unit can be directly illuminated from the back by a tubular light source 1 such as a built-in fluorescent discharge tube (cold cathode tube). For this reason, the backlight type surface light source device using a tubular light source (lamp) has become very heavy in the liquid crystal display device as the liquid crystal display screen of a liquid crystal television or the like in recent years increases in size.

  However, in general, the luminance distribution of the emitted light from the tubular light source 1 is not uniform, and the luminance distribution in the direction orthogonal to the axial direction of the tubular light source 1 is not uniform. In particular, the tubular light source itself disposed immediately below the display unit (liquid crystal display unit) 5 is recognized from the display surface side, and a lamp image remains on the display surface. Therefore, even when a tubular light source is used, it is necessary to make the luminance on the display surface uniform. In particular, since the light control sheet 3 as a diffusion plate is close to the tubular light source 1, the light control sheet 3 is required to have a stable light diffusibility over a long period of time.

  When the light control sheet 3 is used in a backlight type surface light source unit or a liquid crystal display device, the luminance on the display surface can be made uniform and the expression of the lamp image can be suppressed. That is, when the light control sheet 3 is arranged with the long axis direction of the dispersed phase aligned with the long axis direction of the tubular light source 1, the light from the tubular light source (fluorescent tube) 1 is transmitted to the rod-shaped light source due to anisotropic light scattering. The light can be scattered in the direction perpendicular to the length direction, and the display surface can be illuminated uniformly by making the brightness of the exit surface uniform while minimizing the decrease in brightness. In particular, a backlight that is required to be thin and have high brightness because the diffused light can be concentrated in the front direction and the brightness can be made uniform by the synergistic effect of the high anisotropic diffusion function and the lens function of the prism portion. The lamp image can be erased even with the mold unit. Furthermore, even on a thin sheet (for example, about 0.2 mm) with a thin anisotropic diffusion layer in the light control sheet, the luminance on the display surface of the backlight type liquid crystal display device can be improved. Furthermore, since the light diffusing sheet can be thinned and a prism sheet is not required, even a large liquid crystal display device can cope with the thinning of the device and can be easily manufactured. That is, even if the light control sheet of the present invention is thin, the display surface of a large-area liquid crystal display device can be illuminated uniformly with high luminance. In particular, since the continuous phase and the disperse phase are made of a predetermined resin, even a direct type surface light source unit that has high heat resistance, is located in the vicinity of the tubular light source 1 and is subjected to high temperatures can be used for a long time. A predetermined anisotropic light diffusion can be maintained.

  In the liquid crystal display device, the light control sheet may be interposed in the light path emitted from the light exit surface (exit surface) of the surface light source unit, that is, between the surface light source unit and the display unit, and if necessary, an adhesive. You may arrange | position with the lamination | stacking form laminated | stacked on the light emission surface (output surface) using. More specifically, the light control sheet may be disposed on the light exit surface (emission surface) side of the surface light source unit or the incident surface side of the display unit, and is disposed between the exit surface of the surface light source unit and the display unit. You may set up. In addition, it is not necessary to laminate | stack on the output surface of the said surface light source unit. The light control sheet may be used in combination (for example, laminated) with a brightness enhancement sheet, a retardation film, a polarizing film, a color filter, or the like.

  Furthermore, in the surface light source unit, the tubular light source does not have to be positioned directly below the display unit, and may be positioned on the side portion. In this case, the light from the side tubular light source may be incident from the side of the light guide plate, and may be emitted from the exit surface of the light guide plate formed to face the display unit to illuminate the display unit. . The number of tubular light sources is not particularly limited and can be selected according to the size of the display surface.

  The X-axis direction of the light control sheet is usually the long-axis direction of the dispersed phase of the anisotropic diffusion layer. Therefore, the light control sheet is disposed so that the X-axis direction thereof is substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. Note that the X-axis direction of the light control sheet does not have to be completely parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit, for example, an angle ± 15 ° (for example, ± 10 °) In particular, it may be disposed in an oblique direction within a range of about ± 5 °.

  The light control sheet of the present invention suppresses the appearance of a lamp image even when it is thin and has high brightness, has high heat resistance, and can suppress changes in light scattering characteristics over a long period of time even when used at high temperatures. The display unit can be uniformly illuminated by the backlight unit (surface light source unit). Therefore, it is useful as a member of a display device (liquid crystal display device or the like) or a backlight type light source device (surface light source device). In particular, a direct type backlight unit (surface light source unit) in which a light source is disposed directly below the display unit can be used for display devices having various screen sizes, particularly large screen display units. It is suitable as a constituent member of the display unit or the backlight unit. The screen size of the display unit is not particularly limited, and may be, for example, about 20 inches or more (for example, 23 to 300 inches, preferably 30 to 200 inches).

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the characteristics of the light control sheet used in Examples and Comparative Examples, the light diffusion sheet (anisotropic diffusion sheet) serving as the base, and the surface light source device using the light diffusion sheet were evaluated according to the following methods.

[Total light transmittance TT (%) and haze (%)]
Based on JIS K7301, the total light transmittance and haze of the light diffusion sheet were measured using a haze meter (NDH-500, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Anisotropy]
The scattered light intensity F with respect to the scattering angle θ was measured using the measuring apparatus shown in FIG. In addition, the extending | stretching direction of the anisotropic light-diffusion film was made into the X-axis direction, and the direction orthogonal to this direction was made into the Y-axis direction. Table 1 shows the value of R (θ) = Fy (θ) / Fx (θ) at θ = 18 ° as the degree of anisotropy.

[Aspect ratio of diffuser (particulate dispersed phase)]
The cross section of the anisotropic diffusion layer of the light control sheet is observed with a transmission electron microscope (TEM), and the major axis length and minor axis length of the dispersed phase particles are measured for the five dispersed phase particles, and the addition average is performed. The average aspect ratio was calculated.

[Quantitative evaluation of front luminance of surface light source device]
As the direct light source device for evaluation, a commercially available liquid crystal TV (Mitsubishi Electric Corporation, REAL-LCD-H32MX600) having the direct light source device on the back surface was modified and used. That is, the liquid crystal TV displays a liquid crystal display unit, a plurality of cold cathode tubes (CCFL) (φ2.6 mm) arranged in parallel immediately below the liquid crystal display unit, and light reflected from the CCFL. It has a reflection sheet (reflector) that leads to the unit side. In this test apparatus, in the liquid crystal display unit, in order to guide the direct light from the CCFL and the reflected light from the reflection sheet to the liquid crystal layer, from the CCFL side, a support (a transparent acrylic plate having a thickness of 2 mm), a light control sheet, a diffusion A sheet, a prism sheet, and a polarizing sheet (manufactured by 3M, trade name “DBEF”) were laminated in this order. In this apparatus, the distance between the reflective sheet and the liquid crystal display unit (support) was 10 mm, the distance between the reflective sheet and the upper end of each CCFL was 4 mm, and the center distance between adjacent CCFLs was 24 mm. .

And the sheet | seat of an Example and a comparative example is arrange | positioned as a light control sheet | seat of the said apparatus, Luminance meter (Konica Minolta Co., Ltd. product) brightness | luminance cd / m < ² > (maximum average brightness | luminance, minimum average brightness | luminance), and LMI (luminance unevenness). LS-110), the luminance at 100 points was measured at equal intervals on the center line in the longitudinal or width direction, and the luminance average value was obtained. LMI (luminance unevenness) is defined by the following equation as unevenness of the lamp image.

LMI = [Σ (average value between peak luminance / valley luminance) / number of peaks] − [Σ (average value between valley luminance / peak luminance) / number of valleys]
In the above formula, as shown in FIG. 8, the peak luminance and the valley luminance are “peak luminance” when the front luminance at the lamp position is highest, and the front luminance between the lamp and the lamp is the lowest. This brightness is the valley brightness. In this example, six central lamps were adopted as an effective evaluation range, and lamp images were generated for each of the six peak luminances. Therefore, the average value was evaluated. That is, the number of peaks in the above formula is 6, and the number of valleys is 5.

[Brightness unevenness (visual)]
In the backlight unit removed from the transmissive liquid crystal display device, instead of the protective sheet, the sheets obtained in the examples and comparative examples are arranged and turned on, and the luminance unevenness of the backlight unit surface is angled with respect to the front or the front. Visual observation was performed from an oblique direction (side surface) of 30 °, and evaluation was performed according to the following criteria.

○: No brightness unevenness Δ: Slight brightness unevenness is observed ×: Brightness unevenness is remarkably large.

Example 1
In order to produce a light diffusion sheet of two types and three layers (light diffusion sheet having an anisotropic light diffusion layer as an intermediate layer and transparent resin layers laminated on both sides of the intermediate layer), as a resin composition for a transparent resin layer, Using bisphenol A type polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., “Medium viscosity product Iupilon S-2000”, number average molecular weight 18000-20000, melt flow rate 9-12 g / 10 min) As a product, 92 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”) as a matrix resin, a polypropylene resin (manufactured by Nippon Polypro Co., Ltd.) as a resin constituting the dispersed phase, Wintech WFX-4 ”, a propylene random copolymer using a metallocene catalyst, 8 parts by weight) was used. The resin composition constituting each layer is mixed, and is melted and co-extruded from a die at a resin temperature of 250 ° C. and a die opening of 1.3 mm with a multilayer extruder, and the draw ratio (draw ratio) is set to 7.7 times. The oil temperature-controlled three-cast roll was cooled at 80 ° C., and a light diffusion sheet having a thickness of 175 μm (thickness ratio = 1: 3: 1) having a two-type three-layer structure was produced. This light diffusion sheet had a total light transmittance of 89% and an anisotropy of 14. Further, when the cross section was observed with a transmission electron microscope (TEM), in the light diffusion sheet, the polypropylene resin formed a scatterer (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase was It was in the shape of an ellipsoid (or elongated line), with an average length of the minor axis of 0.20 μm and an average length of the major axis of 133.3 μm (aspect ratio 667).

  An ultraviolet shaping method in which a transparent acrylic photocurable resin composition (manufactured by Daicel Cytec Co., Ltd., trade name “PETIA”) is applied on the light diffusion sheet, and a roll mold is rolled to irradiate ultraviolet rays. To form a prism row (pitch 40 μm, height approximately 20 μm, prism apex angle 90 °, distance between prism unit bottom surface and light diffusion sheet surface (transparent resin layer surface) (base region height) 20 μm), A light control sheet was obtained. The ridge line direction of the prism row was formed along the long axis direction of the particulate dispersed phase of the light diffusion sheet.

  As the light control sheet of the test apparatus, a light control sheet obtained with the prism surface facing the diffusion sheet is disposed on a support (a transparent acrylic plate having a thickness of 2 mm), and the longitudinal direction of the CCFL and the prism array The lamp image and average brightness were measured by placing the ridge line parallel to each other.

Example 2
An anisotropic diffusion layer (containing 92 parts by weight of polycarbonate-based resin as a matrix and 8 parts by weight of polypropylene-based resin as a dispersed phase) in the same manner as in Example 1 except that the draw ratio is 6.3 times. A light diffusion sheet (thickness ratio = 1: 3: 1) having a two-layer / three-layer structure having a transparent resin layer (polycarbonate resin) on both sides and having a thickness of 205 μm was prepared. This light diffusion sheet has a total light transmittance of 83%, an anisotropic degree of 10 and an aspect ratio of the particulate dispersed phase of 48.2 (average minor axis length of 0.48 μm and major axis average length of 23.2 μm). Had. A prism row was formed on one surface of the light diffusion sheet in the same manner as in Example 1 to obtain a light control sheet.

Example 3
An anisotropic diffusion layer (containing 92 parts by weight of a polycarbonate-based resin as a matrix and 8 parts by weight of a polypropylene-based resin as a dispersed phase) in the same manner as in Example 1 except that the draw ratio is 5.3 times. A light diffusion sheet (thickness ratio = 1: 3: 1) having a two-layer / three-layer structure with a transparent resin layer (polycarbonate resin) on both sides and having a thickness of 245 μm was prepared. This light diffusion sheet has a total light transmittance of 75%, an anisotropy of 2.8, and an aspect ratio of a particulate dispersed phase of 27.9 (average minor axis length of 0.58 μm and major axis average length of 16.1 μm). ). A prism row was formed on one surface of the light diffusion sheet in the same manner as in Example 1 to obtain a light control sheet.

Examples 4-6
In Examples 1 to 3, light control sheets were produced in the same manner as in Examples 1 to 3, except that the apex angle of the prism row was 60 °.

Examples 7-9
In Examples 1 to 3, light control sheets were produced in the same manner as in Examples 1 to 3, except that the apex angle of the prism rows was 100 °, the pitch was 40 μm, and the height was 16.8 μm.

Example 10
92 parts by weight of bisphenol A type polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., “medium viscosity product Iupilon S-2000”) as a resin constituting the continuous phase, and a polypropylene resin (Nippon Polypro ( "Wintech WFX-4" manufactured by Co., Ltd.) 8 parts by weight were mixed and extruded from a die at a resin temperature of 250 ° C. and a die opening of 0.82 mm, and draw ratio (draw ratio) Was 7.7 times, and cooled at 80 ° C. with a three-roll oil temperature controlled to produce a light diffusion sheet having a thickness of 110 μm and a single layer structure. This light diffusion sheet had a total light transmittance of 89% and an anisotropy of 14. In this light diffusion sheet, the polypropylene resin forms a scatterer (particulate dispersed phase), and the shape of the particulate dispersed phase is an ellipsoid (or elongated linear), and the average of the short axes. The length was 0.20 μm and the average length of the long axis was 133.3 μm (aspect ratio 667).

  On the light diffusing sheet, the prism array (pitch 40 μm, height approximately 20 μm, prism apex angle 90 °, no base area, and the bottom surface of the prism unit is light-transmitted by ultraviolet shaping in the same manner as in Example 1. A diffusion sheet (which is in contact with the anisotropic diffusion layer) was formed to obtain a light control sheet. The ridge line direction of the prism row was formed along the long axis direction of the particulate dispersed phase of the light diffusion sheet.

Example 11
As a resin composition for a transparent resin layer, a bisphenol A-type polycarbonate system is used to produce a two-type two-layer light diffusion sheet (a light diffusion sheet in which a transparent resin layer is laminated on one surface of an anisotropic diffusion layer). Using resin (Mitsubishi Engineering Plastics Co., Ltd., “Medium viscosity product Iupilon S-2000”, number average molecular weight 18000-20000, melt flow rate 9-12 g / 10 min), 92 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”) as a matrix resin, a polypropylene resin (Nippon Polypro Co., Ltd., “Wintech WFX” as a resin constituting the dispersed phase) -4 ", propylene-based random copolymer using metallocene catalyst, melt flow (7 g / 10 min) and 8 parts by weight were used. The resin composition constituting each layer is mixed, and is melted and co-extruded from a die at a resin temperature of 250 ° C. and a die opening of 1.3 mm with a multilayer extruder, and the draw ratio (draw ratio) is set to 7.7 times. The oil temperature control three cast rolls were cooled at 80 ° C. to prepare a light diffusion sheet having a two-layer / two-layer structure and a thickness of 175 μm (thickness ratio: transparent layer / anisotropic diffusion layer = 2: 3). This light diffusion sheet had a total light transmittance of 89% and an anisotropy of 14. Further, when the cross section was observed with a transmission electron microscope (TEM), in the light diffusion sheet, the polypropylene resin formed a scatterer (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase was It was in the shape of an ellipsoid (or elongated line), with an average length of the short axis of 0.2 μm and an average length of the long axis of 133.3 μm (aspect ratio 667).

  On the transparent resin layer of the light diffusing sheet, a prism array (pitch 40 μm, height about 20 μm, prism apex angle 90 °, no base area, prism base, as in Example 1 by ultraviolet shaping) The bottom surface of the unit was in contact with the light diffusion sheet (transparent resin layer) to obtain a light control sheet. The ridge line direction of the prism row was formed along the long axis direction of the particulate dispersed phase of the light diffusion sheet.

Example 12
In the same manner as in Example 11, a two-type two-layer light diffusion sheet was obtained. On the anisotropic diffusion layer of the light diffusing sheet, a prism array (pitch 40 μm, height about 20 μm, prism apex angle 90 °, base area is not obtained by ultraviolet shaping in the same manner as in Example 1. The bottom surface of the prism unit is in contact with the light diffusion sheet (anisotropic diffusion layer) to obtain a light control sheet. The ridge line direction of the prism row was formed along the long axis direction of the particulate dispersed phase of the light diffusion sheet.

Comparative Examples 1-3
The light diffusion sheets obtained in Examples 1 to 3 were used for the test without forming a prism row.

Comparative Example 4
100 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., trade name “Iupilon S-2000”) as a matrix resin, spherical cross-linked polystyrene resin particles (Sekisui Plastics Co., Ltd.) as a light diffusing agent, (Product name “SBX-6”) 1 part by weight was mixed and extruded from a die at a resin temperature of 300 ° C. and a die opening of 8 mm, and cooled at 150 ° C. A light diffusion plate having a thickness of 2 mm was prepared. The shape of the granular dispersed phase was spherical and had a diameter of 6 μm.

Comparative Example 5
A commercially available liquid crystal television (manufactured by Mitsubishi Electric Corporation, “LCD-H32MX600”) was disassembled and a diffusion plate therein was used. A structural analysis of the diffusion plate revealed that the material (cyclic olefin resin), thickness 2 mm, and surface shape were prisms (vertical angle 90 °, pitch 50 μm, prism height 30 μm).

Comparative Example 6
A commercially available liquid crystal television (manufactured by Mitsubishi Electric Corporation, “LCD-H37MX600”) was disassembled, and a diffusion plate therein was used. A structural analysis of the diffusion plate revealed that the material (polystyrene resin), thickness 2 mm, and surface shape were cylindrical lenses (pitch 70 μm, lens height 25 μm).

  The results are shown in Tables 1 and 2. In Table 1, symbol TT means total light transmittance (%).

  As is apparent from the table, when the light control sheet of the example is used, a high luminance can be obtained without the lamp image remaining. On the other hand, when the sheet of the comparative example is used, a lamp image remains or a significant decrease in luminance is confirmed.

1. Fluorescent discharge tube (cold cathode tube)
DESCRIPTION OF SYMBOLS 2 ... Reflecting plate 3 ... Diffusing plate 4 ... Prism sheet 5 ... Planar display unit 6a, 6b ... Polarizing film 7a, 7b ... Glass substrate 8a, 8b ... Electrode 9a, 9b ... Alignment film 10 ... Liquid crystal layer 11 ... Color filter 17 , 28, 48 ... light diffusion sheet 27, 37, 47, 57 ... anisotropic diffusion layer 17a, 27a, 37a, 47a, 57a ... continuous phase 17b, 27b, 37b, 47b, 57b ... dispersed phase 29, 49 ... transparent Resin layer 46, 56 ... Prism part 46a, 56a ... Prism unit

Claims (14)

  Light diffusion composed of an anisotropic diffusion layer comprising a continuous phase composed of a transparent resin and a particulate dispersed phase having a refractive index different from that of the continuous phase and having a major axis direction oriented in one direction A light control sheet comprising: a sheet; and a prism portion formed on at least one surface of the light diffusion sheet and having a plurality of prism units arranged regularly.   The light diffusion sheet further comprises a transparent resin layer formed on at least one surface of the anisotropic diffusion layer, and a prism portion is formed in the anisotropic diffusion layer and / or the transparent resin layer. The light control sheet as described.   3. The light according to claim 1, wherein the prism section is arranged in parallel with adjacent triangular prism units, and the cross-sectional shape of the prism units is an isosceles triangle having an apex angle of 50 to 120 °. Control sheet.   The light control sheet according to claim 3, wherein the major axis direction of the particulate dispersed phase is parallel or perpendicular to the longitudinal direction of the prism unit.   The light control sheet according to any one of claims 1 to 4, wherein the average length of the minor axis of the particulate dispersed phase is 0.01 to 1 µm, and the average aspect ratio of the particulate dispersed phase is 2 to 20000.   In the scattering characteristic F (θ) that can scatter incident light in the light traveling direction and shows the relationship between the scattering angle θ and the scattered light intensity F, the scattering characteristic in the X-axis (MD) direction of the sheet is expressed as Fx (θ ), When the scattering characteristic in the Y-axis (width) direction is Fy (θ), Fx (θ) and Fy (θ) show patterns that attenuate as the scattering angle θ becomes wider, and the scattering angle θ = 6. In a range of 4 to 30 °, 1.01 ≦ Fy (θ) / Fx (θ), and 1.1 <Fy (θ) / Fx (θ) at a scattering angle θ = 18 °. The light control sheet according to any one of the above.   The light control sheet according to any one of claims 1 to 6, wherein the continuous phase is composed of a polycarbonate resin and the dispersed phase is composed of a polypropylene resin.   The light control sheet according to claim 7, wherein the polycarbonate resin is a polycarbonate resin having a number average molecular weight of 15,000 to 25000, and the polypropylene resin is a metallocene resin.   The light control sheet according to claim 7 or 8, wherein the anisotropic diffusion layer substantially does not contain a compatibilizing agent, and the dispersed phase contains a polypropylene random copolymer.   The melt flow rate of the polycarbonate resin is 5 to 30 g / 10 min at ISO 1133 (300 ° C., 1.2 kg load), and the melt flow rate of the polypropylene resin is JIS K7210 (230 ° C., 2.16 kg load). The light control sheet according to claim 7, wherein the light control sheet is 3 to 20 g / 10 minutes.   A surface light source device comprising the light control sheet according to claim 1.   A display device comprising the light control sheet according to claim 1.   The display device according to claim 12, which is a direct type system in which the display unit is directly illuminated from the back surface by a plurality of light sources arranged in parallel.   The display device according to claim 12, which is a liquid crystal display device.

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