JP2003090906A - Anisotropic diffusing film and device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic diffusing film which can easily control the degrees of the anisotropy for diffusing light and which can uniformly display an image with a wide viewing angle in a liquid crystal display device. SOLUTION: The light diffusing layer of the diffusing film 7 is composed of a continuous phase and a dispersion phase. The dispersion phase is composed of spheric dispersion phase particles and dispersion particles in an irregular form having 1.5 average aspect ratio and having the major axes oriented along a specified direction so as to impart anisotropy to the transmitted light. The degrees of the anisotropy in the transmitted and diffused light can be controlled by varying the proportions of the dispersion phase particles. The diffusing film 7 is applicable for a display device 1 composed of a liquid crystal display unit 2 and a surface light source unit 3. The surface light source unit 3 is equipped with a tubular light source 4, light guide member 5, light diffusing film 7 and prism sheet 8. The light diffusing film 7 diffuses the light from the light source (fluorescent tube) of the surface light source device (back light) to uniformly illuminate the liquid crystal display unit 2 in the lateral direction and vertical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic diffusion film (sheet) useful for displaying a liquid crystal display device clearly at a predetermined viewing angle, a method for producing the same, and a device using the film ( Surface light source device and liquid crystal display device).

[0002]

2. Description of the Related Art In a backlight type display device (such as a transmissive liquid crystal display device), a surface light source unit (or a backlight unit) is arranged on the back surface of a display panel. Further, in order to uniformly illuminate the display panel, a diffusion sheet, a prism sheet, a brightness enhancement sheet (such as a reflective polarizing plate), etc. are used.

More specifically, for example, a surface light source unit for illuminating a rear surface of a transmissive liquid crystal display unit is
One or more fluorescent discharge tubes (cold-cathode tubes), a reflector plate provided on the back side of the fluorescent discharge tubes, and the fluorescent discharge tubes and the display unit are arranged so that the display unit is uniform. And a diffusion plate for illuminating. Further, as a surface light source unit, a tubular light source such as a fluorescent tube (cold-cathode tube) and a side surface adjacent to the tubular light source are disposed, and light from the tubular light source is incident on the side surface and emitted from the front surface. A unit composed of a light guide plate, a diffusion plate provided on the front surface (light emitting surface) of the light guide plate, and a reflection plate provided on the opposite side of the light guide plate to the display unit is also known. ing.

As the diffusion plate, a diffusion film in which spherical crosslinked resin beads are dispersed in a transparent resin matrix has been proposed. However, in the surface light source unit, the brightness distribution in the axial direction of the tubular light source is different from that in the direction orthogonal to the axial direction. Therefore, when the diffusion film is used, light is scattered isotropically, and it is difficult to uniformly illuminate the display unit and widen the viewing angle.

Therefore, an anisotropic diffusion sheet having an optically anisotropic scattering characteristic is used as the diffusion sheet, and the luminance is made uniform by utilizing the anisotropic scattering characteristic.

For example, in Japanese Patent Laid-Open No. 4-314522, a transparent matrix has an anisotropic shape with an aspect ratio of 15 to 30 and a minor axis length of 1 to 2 μm, and has a refractive index different from that of the transparent matrix. An anisotropic light-scattering material is described in which the transparent materials of a certain index are homogeneously dispersed in a positional relationship in which they are translated in an orderly manner. Specifically, low-melting point low-density polyethylene as a transparent matrix resin and high-melting point polystyrene or styrene-acrylonitrile copolymer as a transparent substance are kneaded, and the resulting composition is extruded and extruded. An anisotropic sheet is manufactured by a method in which a sheet-shaped molten resin is strongly drawn in the extrusion direction and cooled while being stretched. JP-A-7-114
No. 013 discloses that, in order to improve the viewing angle characteristics, the transparent resin matrix is formed of a transparent resin, the ratio of the major axis to the minor axis is 10 or more, and the average particle diameter is 0.5 to 70.
Films or sheets in which μm dispersed phase particles are dispersed are disclosed. In Japanese Patent Laid-Open No. 2001-31774, in a light-scattering sheet having a sea-island structure made of resins having different refractive indexes, the average particle diameter of the island polymer is 0.5 to 10.
μm, the ratio of sea polymer and island polymer is 70/30 ~
40/60 (weight ratio) and sheet thickness is 5 to 200
A transmission type light-scattering sheet having a thickness of μm is disclosed. This document also discloses that scattered light is directed and diffused within a scattering angle range of 5 to 50 °.

However, these diffusion films cannot illuminate a wide-angle region with a uniform intensity distribution because the anisotropy of transmitted light scattering intensity is strong. That is, for example, if the anisotropy of light scattering is used to increase the front brightness in the left-right direction of the display surface and the brightness from an oblique direction, the high-brightness area becomes narrower in the up-down direction of the display surface, and in a wide angle range. It cannot be brightened uniformly. Furthermore, in order to adjust the degree of anisotropy, it is necessary to control the type and combination of resins and the film molding conditions (melting temperature, extrusion rate, stretching conditions, etc.), and to control the degree of anisotropy easily and easily. Difficult to adjust easily.

[0008]

Therefore, an object of the present invention is to make it possible to easily adjust the degree of anisotropy of light scattering and to make the light scattering intensity uniform over a wide viewing angle. And a manufacturing method thereof, and an apparatus (a surface light source device, a liquid crystal display device) including the anisotropic diffusion film.

Another object of the present invention is to increase the viewing angle in a predetermined direction of the display surface and to make the display even brighter even in the direction intersecting with the above direction, which is useful for anisotropic display. A film and a method for manufacturing the film, and an apparatus (a surface light source device, a liquid crystal display device) including the anisotropic diffusion film.

[0010]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that dispersed phase particles dispersed in a continuous phase are spherical particles and anisotropic light particles involved in isotropic light scattering. By combining with anisotropic particles involved in scattering and adjusting the ratio of spherical particles to anisotropic particles, the degree of anisotropic light scattering can be easily controlled, and the brightness in the vertical direction as well as in the horizontal direction of the display surface can be controlled. The present invention has been completed based on the finding that the above can be improved and the viewing angle can be expanded.

That is, the anisotropic diffusion film of the present invention is composed of a light diffusion layer, and the light diffusion layer is composed of a continuous phase and a disperse phase having different refractive indexes and is capable of scattering transmitted light. Is. The dispersed phase is spherical dispersed phase particles,
It is composed of anisotropic dispersed phase particles whose major axis is oriented in a predetermined direction. The average aspect ratio of the spherical dispersed phase particles is, for example, about 0.8 to 1.2, and the average aspect ratio of the anisotropically shaped dispersed phase particles is 1.5 or more (for example, about 1.5 to 200). ). The ratio (weight ratio) of the spherical dispersed phase particles to the anisotropic dispersed phase particles is
The latter can be selected from the range of about 1/99 to 70/30. The anisotropic diffusion film of the present invention is composed of a continuous phase (matrix phase) composed of a transparent thermoplastic resin and a dispersed phase dispersed in the continuous phase. For example, it can be composed of spherical dispersed phase particles composed of a crosslinked resin) and anisotropic dispersed phase particles composed of a transparent thermoplastic resin. Examples of the transparent thermoplastic resin forming the continuous phase and anisotropic dispersed phase particles include a polyolefin resin, a (meth) acrylic resin, a styrene resin, a polyester resin, a polyamide resin, a polycarbonate resin, and a cellulose derivative. Can be exemplified.

The anisotropic diffusion film of the present invention is composed of a continuous phase and a disperse phase having different refractive indexes, and the disperse phase has a spherical disperse phase particle and an anisotropic shape in which the major axis is oriented in a predetermined direction. A method for producing a film composed of dispersed phase particles, comprising a transparent thermoplastic matrix resin constituting the continuous phase, transparent spherical particles non-deformable at the molding temperature of the matrix resin, and at the molding temperature. It can be produced by mixing a deformable transparent thermoplastic resin at the melting temperature of the matrix resin and forming a film.

In such an anisotropic diffusion film, the degree of anisotropy of transmitted diffused light (anisotropy of scattered light is adjusted) by adjusting the ratio of the spherical dispersed phase particles to the anisotropically shaped dispersed phase particles. The degree of sex) can be controlled.

The present invention also discloses a device (surface light source device and display device) using the light diffusion film. That is,
The present invention also discloses a surface light source device in which the anisotropic diffusion film is arranged on the light emitting surface side of a surface light source unit. In the surface light source device, the surface light source unit may include a tubular light source and a light guide plate which is disposed with its side portion adjacent to the tubular light source and which guides light from the light source. The major axis direction (X axis direction) of the dispersed phase particles of the anisotropic light diffusion sheet may be oriented in the longitudinal direction (X axis direction) of the tubular light source of the surface light source unit.

Further, the present invention also discloses a liquid crystal display device provided with the anisotropic diffusion film and the surface light source device.
The liquid crystal display device also discloses a transmissive display device (transmissive liquid crystal display device or the like) including a display unit and the surface light source device for illuminating the display unit.

In the present specification, the term "film" is used to mean a sheet regardless of its thickness.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The anisotropic diffusion film of the present invention comprises at least a light diffusion layer.
It is composed of a continuous phase and a dispersed phase having different refractive indexes, and is capable of scattering transmitted light. That is, the light diffusion layer can diffuse or scatter the incident light in the traveling direction of the light. The difference in refractive index between the continuous phase and the dispersed phase is, for example, 0.001 or more (for example, about 0.001 to 0.3), preferably 0.01.
Above (about 0.01 to 0.3), more preferably 0.
It is 03 or more (about 0.03 to 0.1).

In the present invention, in order to adjust the degree of light scattering anisotropy, the dispersed phase may be spherical dispersed phase particles (hereinafter, simply referred to as first dispersed phase particles or first dispersed phase). A) and anisotropically-shaped dispersed phase particles whose major axis is oriented in a predetermined direction (hereinafter, may be simply referred to as second dispersed phase particles or second dispersed phase).

The spherical dispersed phase particles may be substantially spherical, and the average aspect ratio of the spherical dispersed phase particles is, for example, 0.8 to 1.2, preferably about 0.9 to 1.1. In practice, spherical particles or beads having an average aspect ratio of substantially 1 are often used. The average particle size of the spherical dispersed phase particles is, for example, 0.5 to 25 μm, preferably 1 to 20 μm, more preferably about 1 to 10 μm, and usually about 2 to 15 μm. Such dispersed phase particles are mainly involved in isotropic light scattering.

On the other hand, the anisotropic dispersed phase particles have a ratio of the average length L of the major axis to the average length W of the minor axis (average aspect ratio, L / W) of more than 1, and in the major axis direction. The (X axis) is mainly oriented in the orientation direction of the light diffusion layer (X axis direction).
Usually, they are dispersed in the form of an ellipsoid (rugby ball shape) or a fibrous shape. The average aspect ratio of the anisotropically-shaped dispersed phase particles is, for example, 1.5 or more (for example, 1.5 to 200),
It may be preferably 2 to 200 (for example, 5 to 200), and more preferably about 10 to 100. Such second dispersed phase particles may have a football shape (spheroidal shape, etc.), a fiber shape, a rectangular shape, or the like. The larger the aspect ratio, the higher the anisotropic light scattering property can be.

The average length L of the long axis of the second dispersed phase particles is, for example, 0.5 μm or more (for example, 1 to 100 μm).
m), preferably 5 μm or more (for example, 5 to 100).
μm), and usually 2 to 100 μm (for example, 2
˜50 μm). The short-axis average length W of the second dispersed phase particles is, for example, 0.1 μm or more (0.1 to 0.1 μm).
100 μm), preferably 0.5 μm or more (0.5
.About.50 .mu.m), and usually about 0.3 to 10 .mu.m (for example, 0.5 to 5 .mu.m).

The orientation coefficient of the second dispersed phase particles as the degree of arrangement is, for example, 0.25 or more (about 0.25 to 1), and the closer to 1 as 0.7 to 1, the more preferable. The higher the orientation coefficient of the dispersed phase particles, the higher the anisotropy can be imparted to the scattered light. The orientation coefficient can be calculated based on the following formula.

Orientation coefficient = (3 <cos ² θ> −1) / 2 In the formula, θ represents the angle between the major axis of the second dispersed phase particles and the X axis of the film (the major axis and the X axis). If and are parallel, θ = 0
)), <Cos ² θ> indicates the average of cos ² θ calculated for the ^second dispersed phase particles, and is represented by the following formula.

<Cos ² θ> = ∫n (θ) · cos ² θ · dθ (where n (θ) is the value of the second dispersed phase particles having the angle θ in the second total dispersed phase particles) Anisotropic dispersed phase particles are mainly involved in anisotropic light scattering,
The scattered light intensity in the Y-axis direction is large in a wide scattering angle range. That is, in the scattering characteristic F (θ) showing the relationship between the scattering angle θ and the scattered light intensity F, the scattering characteristic in the X axis direction of the film is Fx (θ), and the scattering characteristic in the Y axis direction orthogonal to the X axis direction is Assuming that Fy (θ) is the light incident on the film in the vertical direction, the scattering characteristics Fx (θ) and Fy
(Θ) shows a pattern in which the light intensity gently attenuates as the scattering angle θ becomes wider with the incident angle as the center.
The anisotropic dispersed phase particles have a large light scattering intensity in a range of a wider scattering angle θ in the Y axis direction (short axis direction of the dispersed phase particles) than in the X axis direction (long axis direction) of the dispersed phase particles. .

Therefore, the degree of anisotropy of scattered light is adjusted by adjusting the ratio of the spherical dispersed phase particles involved in isotropic scattering properties and the anisotropic dispersed phase particles involved in anisotropic scattering properties. [Anisotropic scattering characteristic Fy (θ) / Fx (θ)] can be easily controlled. In particular, the degree of anisotropy can be controlled by the anisotropically shaped dispersed phase particles while maintaining the uniformity of high intensity scattering by the spherical dispersed phase particles in a wide angle range. Therefore, on the display surface of the display device, not only can the front luminance and the diagonal luminance in a predetermined direction (for example, the left-right direction) be improved, but also a direction that intersects with the direction (for example,
The brightness in the vertical direction can be made uniform, and the light scattering intensity can be made uniform in a wide angle range (viewing angle).

The ratio of the continuous phase to the dispersed phase is, for example,
Continuous phase / dispersed phase (weight ratio) = about 99/1 to 50/50, preferably about 95/5 to 60/40, and more preferably about 90/10 to 70/30.

Furthermore, the ratio of the spherical dispersed phase particles to the anisotropic dispersed phase particles is such that the former / the latter (weight ratio) = 1/99 to
It can be appropriately selected from the range of about 99/1, usually 5/9
5 to 95/5, preferably 10/90 to 90/10, more preferably 10/90 to 75/25, especially 10/9
It is about 0 to 50/50 (for example, 10/90 to 30/70). The total light transmittance of the anisotropic diffusion film is, for example, 80% or more, preferably 90% or more.

The continuous phase and the dispersed phase constituting the light diffusion layer are
The continuous phase can be usually composed of a transparent thermoplastic resin, and the dispersed phase can be composed of a transparent thermoplastic or non-thermoplastic material. Further, in the dispersed phase, the first dispersed phase particles are often composed of a thermoplastic or non-thermoplastic transparent substance, and the second dispersed phase particles are often composed of a transparent thermoplastic resin. In particular, the continuous phase is composed of a transparent thermoplastic matrix resin capable of being film-formed at a molding temperature through a heating and melting process such as extrusion molding, and the second dispersed phase particles are transparent and deformable at the molding temperature. It is preferable that the first dispersed phase particles are composed of a thermoplastic resin, and the first dispersed phase particles are composed of transparent spherical particles that are non-deformable at the molding temperature of the matrix resin.

As the transparent thermoplastic resin, an olefin resin (including a cyclic olefin resin), a halogen-containing resin (including a fluorine resin), a vinyl ester resin or a derivative thereof (including a vinyl alcohol resin), Vinyl ether resin, (meth) acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin, thermoplastic polyurethane resin, polysulfone resin (polyether sulfone, polysulfone, etc.), polyphenylene ether resin (2 , 6-xylenol polymers, etc.), cellulose derivatives (cellulose esters, cellulose carbamates, cellulose ethers, etc.), silicone resins (polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubbers or elastomers. Polybutadiene, diene rubbers such as polyisoprene, styrene - butadiene copolymer, acrylonitrile - butadiene copolymer, acrylic rubber,
Examples thereof include urethane rubber, silicone rubber, and thermoplastic elastomers (polyester elastomer, polyolefin elastomer, polyamide elastomer, styrene elastomer, etc.).

Examples of the olefin resin include homopolymers or copolymers of C _2-6 olefins (ethylene, ethylene, ethylene-propylene copolymer and other ethylene resins, polypropylene, propylene-ethylene copolymer, propylene-
Copolymerization with polypropylene resins such as butene copolymers (such as polypropylene resins with a propylene content of 90 mol% or more), poly (methylpentene-1), propylene-methylpentene copolymers, etc., C _2-6 olefins Copolymer with a polymerizable monomer (ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-
Examples thereof include (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid copolymers or salts thereof (for example, ionomer resins), and ethylene- (meth) acrylic acid ester copolymers. The alicyclic olefin resin is a homopolymer or copolymer of a cyclic olefin (norbornene, dicyclopentadiene, etc.) (for example, a polymer having an alicyclic hydrocarbon group such as sterically rigid tricyclodecane). Examples thereof include copolymers of the above-mentioned cyclic olefin and a copolymerizable monomer (ethylene-norbornene copolymer, propylene-norbornene copolymer, etc.). The alicyclic olefin resin is available, for example, under the trade name “ARTON” and the trade name “ZEONEX”.

Examples of the halogen-containing resin include vinyl halide resins (homopolymers of halogen-containing monomers such as polyvinyl chloride, polytetrafluoroethylene, polychlorotrifluoroethylene, and polyvinyl fluoride, tetrafluoroethylene-hexa). Fluoropropylene copolymers, copolymers of halogen-containing monomers such as tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride- (meth) acrylic acid ester copolymers , A copolymer of a halogen-containing monomer such as tetrafluoroethylene-ethylene copolymer and a copolymerizable monomer), a vinylidene halide resin (polyvinylidene chloride, polyvinylidene fluoride, vinylidene chloride- ( (Meth) acrylic acid ester copolymer Halogen-containing vinylidene monomer and other monomers, a copolymer) and the like.

The vinyl ester-based resin may be a homo- or copolymer of vinyl ester-based monomers (polyvinyl acetate,
Polyvinyl propionate, etc.), copolymers of vinyl ester monomers and copolymerizable monomers (vinyl acetate-ethylene copolymers, vinyl acetate-vinyl chloride copolymers, vinyl acetate- (meth) acrylics) Acid ester copolymers) or their derivatives. Derivatives of vinyl ester resins include polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polyvinyl acetal resins, and the like.

Examples of vinyl ether resins include vinyl C such as vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether and vinyl t-butyl ether.
_1-10 Alkyl ether homo- or copolymers, vinyl C
Examples thereof include copolymers of _1-10 alkyl ether and a copolymerizable monomer (such as vinyl alkyl ether-maleic anhydride copolymer).

As the (meth) acrylic resin, a homopolymer or copolymer of a (meth) acrylic monomer, 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, (meth)
Ethyl acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. C _1-10 alkyl (meth) acrylate; cycloalkyl (meth) acrylate such as cyclohexyl (meth); (meth) such as phenyl (meth) acrylate
Aryl acrylate; Hydroxy C _2-6 alkyl (meth) acrylate; Glycidyl (meth) acrylate;
Examples thereof include N, N-dialkylaminoalkyl (meth) acrylate; (meth) acrylonitrile; and (meth) acrylate having an alicyclic hydrocarbon group such as tricyclodecane. Examples of the copolymerizable monomer include styrene-based monomers, vinyl ester-based monomers, maleic anhydride, maleic acid and fumaric acid. These monomers can be used alone or in combination of two or more.

Preferred (meth) acrylic resins are poly (meth) acrylates such as poly (meth) acrylate.
Acrylic acid C _1-6 alkyl, in particular a main component methyl methacrylate (50 to 100 wt%, preferably 70 to 100
Methyl methacrylate-based resin, for example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid Examples thereof include ester copolymers, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymers, and (meth) acrylic acid ester-styrene copolymers (MS resin, etc.).

The styrene resin includes homopolymers or copolymers of styrene monomers (polystyrene, styrene-α-methylstyrene copolymer, styrene-vinyltoluene copolymer, etc.), styrene monomers and other And a copolymer with a polymerizable monomer ((meth) acrylic monomer, maleic anhydride, maleimide monomer, dienes, etc.).
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 Styrene- (meth) acrylic acid ester copolymers such as methyl- (meth) acrylic acid ester copolymer, 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 [of styrene and methyl methacrylate-based monomers such as styrene-methyl methacrylate copolymers]. Copolymer], AS resin, styrene-butadiene copolymer, and the like.

Polyester resins include terephthalic acid.
Aromatic polyester using which aromatic dicarboxylic acid
(Polyethylene terephthalate, polybutylene terephthalate
Poly C such as rate_2-4Alkylene terephthalate and
Re-C_2-4Homopolyester such as alkylene naphthalate
Le, C_2-4Alkylene arylate unit (C_2-4Alkylene
Terephthalate and / or C_2-4Alkylene naphthale
Unit as the main component (for example, 50 mol% or more, preferably
Is 70 to 98 mol%, more preferably 75 to 95 mol
%) Including as copolyester), liquid crystalline polyester
Tell, etc. can be illustrated. As copolyester, poly
C_2-4C among alkylene arylates_2-4Alalkylene
Part of the recall is polyoxy C_2-4Alkylene glyco
(Diethylene glycol, triethylene glycol
Etc.), C_2-10Alkylene glycol, alicyclic diol
(Cyclohexanedimethanol, hydrogenated bisphenol A
Etc.), diols with aromatic rings (fluorenone side chains
Having 9,9-bis (4- (2-hydroxyethoxy)
Phenyl) fluorene, bisphenol A, bispheno
A-alkylene oxide adduct, etc.)
Copolyester, aromatic dicarboxylic acid (terephthalate
Acid, naphthalenedicarboxylic acid), phthalic acid,
Asymmetric aromatic dicarboxylic acid such as sophthalic acid, adipine
Aliphatic C such as acid _6-12Copo substituted with dicarboxylic acid, etc.
Contains esters. In copolyester, C
_2-4Alkylene glycol and aromatic dicarboxylic acid components
It is only necessary that a part of
It may be replaced. Polyester resin
Aliphatic dicarboxylic acid such as relate resin and adipic acid
Aliphatic polyester, ε-caprolactone, etc.
The lactone homopolymers or copolymers are also included. Polyeste
The resin is usually an amorphous copolyester (for example,
C_2-4Alkylene arylate copolyester, etc.)
It may be amorphous in any way.

Polyamide resin is nylon 4
6, Nylon 6, Nylon 66, Nylon 610, Nylon 612, Nylon 11, Nylon 12 and other aliphatic polyamides, dicarboxylic acids (eg, terephthalic acid, isophthalic acid, adipic acid, etc.) and diamines (eg, hexamethylene diamine, meta Xylylenediamine) and a polyamide (eg, an aromatic polyamide such as xylylenediamine adipate (MXD-6)). The polyamide resin may be a lactam homopolymer or copolymer such as ε-caprolactam, and may be a copolyamide as well as a homopolyamide.

Polycarbonate resins include aromatic polycarbonates based on bisphenols (bisphenol A, etc.), aliphatic polycarbonates such as diethylene glycol bisallyl carbonate, and the like.

Among the cellulose derivatives, examples of the cellulose ester include aliphatic organic acid esters (cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate). _C1-6 organic acid ester such as rate), aromatic organic acid ester ( _C7-12 aromatic carboxylic acid ester such as cellulose phthalate, cellulose benzoate), inorganic acid ester (for example,
Cellulose phosphate, cellulose sulfate, etc.)
It may be a mixed acid ester such as acetic acid / nitric acid cellulose ester. Cellulose derivatives include cellulose carbamates (for example, cellulose phenyl carbamate), cellulose ethers (for example, cyanoethyl cellulose; hydroxy C _2-4 alkyl cellulose such as hydroxyethyl cellulose and hydroxypropyl cellulose; C _1- such as methyl cellulose and ethyl cellulose). ₆ alkyl cellulose; carboxymethyl cellulose or a salt thereof, benzyl cellulose, acetyl alkyl cellulose, etc.) are also included.

Preferred components constituting the continuous phase or the second dispersed phase include polyolefin resin (polypropylene resin etc.), (meth) acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin. And cellulose derivatives (such as cellulose esters).

The resin constituting the continuous phase and / or the second dispersed phase may be crystalline or amorphous. For example, one of the continuous phase and the dispersed phase (for example, the continuous phase) may be made of a crystalline resin, and the other phase (for example, the dispersed phase) may be made of an amorphous resin.

The first dispersed phase particles (spherical dispersed phase particles) are
Inorganic particles (glass, silica, alumina, zirconia, etc.), heat resistant organic particles (crosslinked resin particles, for example, crosslinked (meth) acrylic resin particles such as crosslinked polymethylmethacrylate, crosslinked styrene resin particles, crosslinked benzoguanamine resin , Cross-linked silicone resin, etc.).
These particles can be used alone or in combination of two or more kinds. The spherical dispersed phase particles usually have low thermal deformability, and it seems that the particles retain their initial shape even after being formed into a film.

The resin component may be modified (for example, rubber modified) if necessary. Alternatively, the resin component may form a continuous phase matrix, and the dispersed phase component may be grafted or block copolymerized on the matrix resin to form the first dispersed phase particles and / or the second dispersed phase particles. As such a graft or block polymer, for example, a rubber block copolymer (styrene-
Examples thereof include a butadiene copolymer (SB resin) and a rubber-grafted styrene resin (acrylonitributadiene-styrene copolymer (ABS resin)).

The light diffusion layer of the anisotropic diffusion film may contain a compatibilizer, if necessary. As a compatibilizer,
It can be selected from conventional compatibilizers depending on the type of the continuous phase and the dispersed phase, and examples thereof include an oxazoline compound, a modified resin modified with a modifying group (carboxyl group, acid anhydride group, epoxy group, oxazolinyl group, etc.), a diene. Or a rubber-containing polymer [for example, a diene-based monomer (eg, a random copolymer) obtained by homopolymerization of a diene-based monomer or copolymerization with a copolymerizable monomer (such as an aromatic vinyl monomer); Diene-based graft copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS resin); styrene-butadiene (SB) block copolymers, hydrogenated styrene-butadiene (SB) block copolymers, hydrogenated styrene-
Butadiene-styrene block copolymer (SEBS),
Diene-based block copolymers such as hydrogenated (styrene-ethylene / butylene-styrene) block copolymers or hydrogenated products thereof], and diene or rubber-containing polymers modified with the above-mentioned modifying groups (such as epoxy groups) Can be illustrated. These compatibilizers can be used alone or in combination of two or more.

As the compatibilizer, a polymer (random, block or graft copolymer) having a component which is the same as or common to the constituent resin of the polymer blend system, or an affinity for the constituent resin of the polymer blend system is usually used. A polymer (random, block or graft copolymer) or the like is used.

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

The modification is carried out by modifying the monomer corresponding to the modifying group (for example, a carboxyl group-containing monomer such as (meth) acrylic acid in the case of modifying the carboxyl group, maleic anhydride, modifying the ester group in the case of modifying the acid anhydride group). Then (meth) acrylic monomer, maleimide group modified maleimide monomer,
The epoxy modification can be performed by copolymerizing an epoxy group-containing monomer such as glycidyl (meth) acrylate. Further, the epoxy modification may be carried out by epoxidizing the unsaturated double bond.

Preferred compatibilizers are unmodified or modified diene copolymers, especially modified block copolymers (eg epoxidized styrene-butadiene-styrene (SB
S) an epoxidized diene-based block copolymer such as a block copolymer or an epoxy-modified diene-based block copolymer). The epoxidized diene block copolymer is
Not only is the transparency high, but the softening temperature is relatively high at about 70 ° C., and the resin can be compatibilized in many combinations of the continuous phase and the dispersed phase, and the dispersed phase can be uniformly dispersed.

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, some or all of the double bonds of the conjugated diene block are epoxidized. The ratio (weight ratio) of the aromatic vinyl block and the conjugated diene block (or its hydrogenated block) is, for example, former / latter = 5/95 to 80/20 (for example, 25/75 to
80/20), more preferably 10/90 to 70
It is about / 30 (for example, about 30/70 to 70/30), and is usually about 40/60 to 80/20. An epoxidized block copolymer having an aromatic vinyl block (styrene block etc.) content of about 60 to 80% by weight has a relatively high refractive index (for example, about 1.5%).
7) In addition, since it has a refractive index similar to that of the resin of the dispersed phase (such as amorphous copolyester), the dispersed phase can be uniformly dispersed while maintaining the light scattering property of the dispersed phase resin.

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

The molecular structure of the block copolymer is linear,
It may be branched, radial or a combination thereof. Examples of the block structure of the block copolymer include a multiblock 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 diene block is X and the conjugated diene block is Y, for example, XY type, XYX type, YXY type,
Y-X-Y-X type, X-Y-X-Y type, X-Y-X-Y
-X type, Y-X-Y-X -Y -type, (X-Y-) ₄ Si
Type, (YX-) ₄ Si type, and the like.

The proportion of epoxy groups in the epoxidized diene block copolymer is not particularly limited, but the oxygen concentration of oxirane is, for example, 0.1 to 8% by weight, preferably 0.5 to 6% by weight, More preferably 1 to 5% by weight
It is a degree. The epoxy equivalent of the epoxidized block copolymer (JIS K 7236) is, for example, 300 to 10.
It may be about 00, preferably about 500 to 900, and more preferably about 600 to 800.

The refractive index of the compatibilizing agent (epoxidized block copolymer etc.) is about the same as that of the dispersed phase resin (for example, the difference in refractive index from the dispersed phase resin is about 0 to 0.01,
Preferably about 0 to 0.005).

The epoxidized block copolymer may be prepared by converting a diene block copolymer (or a partially hydrogenated block copolymer) into a conventional epoxidation method, for example, in an inert solvent with an epoxidizing agent ( It can be produced by epoxidizing the block copolymer with peracids, hydroperoxides, etc.).

The amount of the compatibilizer used is, for example, 0.1 to 20% by weight, preferably 0.5 to 15% by weight, of the entire resin composition (a composition containing the constituents of the continuous phase and the dispersed phase).
More preferably, it can be selected from the range of about 1 to 10% by weight. The ratio of the compatibilizing agent to the dispersed phase (first dispersed phase particles and second dispersed phase particles) is, for example, dispersed phase /
Compatibilizer (weight ratio) = about 99/1 to 50/50, preferably about 99/1 to 70/30, and more preferably 9
It is about 8/2 to 80/20.

If necessary, the light diffusion layer may contain fibrous dispersed particles (organic fiber, inorganic fiber) as a light scattering factor, and the organic fiber is a heat-resistant organic fiber such as aramid fiber, It may be wholly aromatic polyester fiber, polyimide fiber, etc., and the inorganic fiber is fibrous filler (glass fiber, silica fiber, alumina fiber, inorganic fiber such as zirconia fiber), flaky filler (such as mica). May be.

The diffusion film is not limited to the single layer structure of the light diffusion layer alone, and may have a laminated structure. In the diffusion film having a laminated structure, at least one surface (one surface or both surfaces) of the light diffusion layer is covered with a transparent layer. This transparent layer may be a transparent substrate such as glass or may be formed of resin. The resin constituting the transparent layer may be the same or different resin as the resin of the continuous phase and / or the dispersed phase constituting the light diffusion layer, but is usually the same or common (or) resin as the resin of the continuous phase. Is preferably used. In particular, the transparent resin layer is preferably an isotropic resin having a small birefringence (the resin for the continuous phase) or a transparent base material (for example, glass).

The light diffusing layer and / or the transparent resin layer may contain various additives such as stabilizers (antioxidants, UV absorbers,
It may contain a heat stabilizer), a plasticizer, an antistatic agent, a flame retardant, a filler, and the like.

The anisotropic diffusion film has a thickness of 3 to 100.
0 μm, preferably 5 to 500 μm (for example, 30
~ 200 μm), more preferably 5-100 μm
(For example, 50 to 100 μm). In the anisotropic diffusion film having a laminated structure, the thickness ratio of the light diffusion layer and the transparent layer is, for example, light diffusion layer / transparent layer = 5/95 to 9
It is about 9/1, preferably about 50/50 to 99/1, and more preferably about 70/30 to 95/5.

The surface of the diffusion film may be coated with a release agent such as silicone oil or may be subjected to corona discharge treatment, as long as the optical characteristics are not impaired. Furthermore, the diffusion film having anisotropy may be formed with an uneven portion extending in the X-axis direction of the film (long-axis direction of the dispersed phase). By forming such uneven portions, it is possible to impart a higher anisotropic light scattering property to the film.

[Method for Producing Anisotropic Diffusion Film] In the anisotropic diffusion film, the components (resin component, etc.) constituting the dispersed phase are dispersed in the resin constituting the continuous phase to form the second dispersed phase particles. It can be obtained by orienting. For example,
The resin constituting the continuous phase and the components constituting the dispersed phase (first and second dispersed phase particles) are blended by a conventional method (for example, a melt blending method, a tumbler method, etc.), if necessary, to obtain a resin. The dispersed phase can be dispersed by melt-mixing the composition and extruding it from a T die, a ring die or the like to form a film. Further, a coating method of applying a composition composed of a light scattering component (first and second dispersed phase particle components) and a binder resin on a substrate film, a laminating method of laminating the composition, and a casting method. Law,
It can be produced by molding using a conventional film molding method such as an extrusion molding method. In a preferred method, a transparent thermoplastic matrix resin constituting the continuous phase, a non-deformable transparent spherical particles at the molding temperature of the matrix resin, and a transparent thermoplastic resin deformable at the molding temperature,
The anisotropic diffusion film can be produced by mixing at a melting temperature of the matrix resin and film-forming (film-forming by an extrusion molding method).

The diffusion film having a laminated structure composed of a light diffusion layer and a transparent resin layer laminated on at least one surface of the light diffusion layer was composed of components corresponding to the light diffusion layer. A resin composition and a resin composition composed of components corresponding to the transparent resin layer are coextrusion-molded to form a film, a coextrusion molding method, one layer prepared in advance and the other layer is extruded and laminated. Can be formed by, for example, a dry laminating method in which the light diffusion layer and the transparent resin layer that have been produced are laminated.

Further, the orientation treatment of the second dispersed phase particles includes, for example, (1) a method of forming a film while drawing the extruded sheet, (2) a method of uniaxially stretching the extruded sheet,
(3) A method of combining the method of (1) and the method of (2), (4) a method of solution-blending the above components and forming a film by a casting method, or the like.

In the film molding, the melting temperature of the resin is a temperature equal to or higher than the melting point of the resin component (continuous phase resin, second dispersed phase resin), for example, 150 to 290 ° C., preferably 2
The temperature is about 00 to 260 ° C. Draw ratio (draw magnification)
Is, for example, about 1.5 to 30 times, preferably 2 to 15 times.
It is about twice, more preferably about 3 to 10 times. Moreover, when performing a stretching process, the stretching ratio is, for example, 1.1.
It is about 30 times (for example, about 1.5 to 20 times), preferably about 1.5 to 10 times (for example, about 2 to 10 times). When combining drawing and stretching,
The draw ratio is, for example, about 2 to 10 times, preferably 2 to
The stretching ratio may be, for example, 1.1.
It may be about 10 to 10 times (for example, about 1.5 to 10 times), preferably about 2 to 10 times.

In order to control the aspect ratio of the second dispersed phase particles, a pair of rolls (2
Multiple rolls (for example, two rolls) are arranged in parallel, the film is inserted into each two rolls, and the film is stretched between the two rolls on the feeding side and the two rolls on the feeding side. Of stretching by increasing the feeding speed of the film on the feeding side than on the feeding side (inter-roll stretching), a method of inserting the film between a pair of rolls facing each other, and rolling the film with roll pressure (roll rolling) And so on. Especially according to roll rolling,
Not only the amorphous resin but also the crystalline resin can be easily stretched.

The rolling pressure is, for example, 1 × 10 ⁴
˜1 × 10 ⁷ N / m (about 0.01 to 10 t / cm), preferably 1 × 10 ⁵ to 1 × 10 ⁷ N / m (about 0.1)
It is about 10 t / cm). Roll rolling, for example,
Thickness reduction rate (reduction rate) is about 0.9 to 0.1, preferably about 0.77 to 0.2, and more preferably about 0.67.
It can be performed at about 0.33.

The orientation treatment temperature is, for example, 100 to 200.
℃ (110-200 ℃), preferably 110-18
It is about 0 ° C. (130 to 180 ° C.). Further, the temperature of the roll rolling, when the continuous phase resin is a crystalline resin, may be a temperature below the melting point of the resin and in the vicinity of the melting point, and when the continuous phase resin is an amorphous resin, below the glass transition temperature. Therefore, the temperature may be near the glass transition temperature.

In such a method, by adjusting the ratio of the spherical dispersed phase particles to the anisotropic dispersed phase particles, the degree of anisotropic light diffusivity of transmitted light (anisotropy of transmitted scattered light). Can be controlled. In addition, it is possible to improve the diagonal brightness with respect to the front brightness in a predetermined direction,
The light scattering brightness in the direction intersecting with the above direction can be improved, and the scattering high intensity can be made uniform over a wide angle range.

The ratio of the spherical dispersed phase particles to the anisotropic dispersed phase particles also changes depending on the film forming conditions (for example, melt kneading conditions, temperature conditions, extrusion rate, draw and / or centrifugal conditions, etc.). In some cases, the adjustment is often made mainly by the quantitative ratio of the crosslinked resin particles forming the first dispersed phase particles and the transparent thermoplastic resin forming the second dispersed phase particles.

[Application of Anisotropic Diffusion Film] The anisotropic diffusion film of the present invention not only imparts anisotropic scattering property to transmitted light but also controls the degree of anisotropy of scattered light, You can control the vertical and horizontal viewing angles of the surface. Therefore, the anisotropic diffusion film of the present invention is useful as a constituent member of a surface light source device or a liquid crystal display device. That is, by disposing the anisotropic diffusion film on the emission surface side of the surface light source unit of the surface light source device, it is possible to illuminate the irradiated object with uniform light while imparting anisotropic diffusivity to the transmitted light. Also,
The liquid crystal display surface can be uniformly illuminated with high brightness and can be displayed clearly with a wide viewing angle.

The use of the anisotropic diffusion film of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a schematic exploded perspective view showing an example of a surface light source device and a transmission type liquid crystal display device of the present invention.

In FIG. 1, the display device 1 includes a liquid crystal display unit (or a liquid crystal display panel) 2 as an irradiation target including a liquid crystal cell in which liquid crystal is sealed, and a rear side of the display unit (or panel). And a surface light source unit 3 for illuminating the display unit 2.

The surface light source unit 3 is composed of a tubular light source 4 such as a fluorescent tube (cold-cathode tube) and a translucent plate-like member, and the side portions thereof are adjacent to each other in the axial direction of the tubular light source substantially parallel to each other. A light guide member (light guide plate) 5 disposed as a member, a reflection mirror 6b disposed on the side of the tubular light source 4 and for reflecting light from the light source to the side surface of the light guide member 5, and It is provided on the back surface side of the light guide member 5 and is provided with a reflection member or a reflection layer 6 a for reflecting the light from the tubular light source 4 in the forward direction (display unit side) and guiding it to the display unit 2. The light from the tubular light source 4 enters from the side surface of the light guide member 5 and exits from the flat exit surface to illuminate the display unit. Generally, the luminance distribution of the light emitted from the tubular light source 4 is not uniform, and the luminance distribution in the direction (Y-axis direction) orthogonal to the axial direction (X-axis direction) of the tubular light source 4 is non-uniform. Therefore, even if light is emitted from the emission surface through the light guide member 5,
The display unit 2 cannot be illuminated uniformly.

FIG. 2 is a conceptual diagram for explaining the anisotropy of light diffusion. As shown in FIG. 2, the anisotropic light-diffusing film 7 is composed of a continuous phase 7a made of a resin, a spherical dispersed phase 7b dispersed in the continuous phase, and an anisotropic dispersed phase 7c. . Then, in the scattering characteristic F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F, the anisotropy of light diffusion is, as described above, the scattering characteristic in the X-axis direction of the film F.
x (θ), the scattering characteristic in the Y-axis direction orthogonal to the X-axis direction is F
When y (θ), it is represented by Fy (θ) / Fx (θ), and Fy (θ)> Fx (θ). The X-axis direction of the anisotropic light-diffusing film 7 is usually the long-axis direction of the dispersed phase 7c. That is, the spherical dispersed phase 7b causes X-axis and Y-axis.
The light scattering intensity in the axial direction can be improved isotropically, and the anisotropic dispersed phase 7c can improve the light scattering intensity in the Y-axis direction rather than in the X-axis direction.

Therefore, in the present invention, the light exit surface side of the light guide member 5 (light exit surface side of the surface light source unit) is anisotropic with respect to the axial direction (X-axis direction) of the tubular light source 4 of the surface light source unit. The X-axis direction (the major axis direction of the dispersed phase 7c) of the characteristic diffusion film 7 is arranged substantially parallel or aligned. Further, the anisotropic diffusion film 7 and a prism sheet 8 in which micro prisms having a triangular cross section are formed in parallel in a predetermined direction are sequentially arranged by stacking. Therefore, the light from the tubular light source 4 is diffused and uniformed by the diffusion film 7 via the light guide member 5, and is also condensed forward by the prism sheet 8 to enhance the brightness and to make the display unit 2 from the back surface. Can be illuminated. In particular, since the anisotropic diffusion film 7 can improve the light scattering intensity in the Y-axis direction, the front brightness in the Y-axis direction and the brightness in the oblique direction can be improved. Moreover, X
Since the light can be scattered isotropically and uniformly in the axial direction and the Y-axis direction, the scattering high intensity in the X-axis direction can be improved and uniformized even if an anisotropic diffusion film is used.

In the present invention, the light emitting surface (emission surface) of the surface light source unit may be disposed in the optical path, that is, on the light emission surface (emission surface) side of the surface light source unit. And the display unit, and it is not necessary to stack them on the emission surface of the surface light source unit. The X-axis direction of the anisotropic light-diffusing film does not need to be completely aligned with the axial direction (X-axis direction) of the tubular light source of the surface light source unit, and is, for example, an oblique direction within an angle range of ± 15 °. You may arrange toward.

The anisotropic diffusion film does not have to be used in combination with the prism sheet, and even when used in combination with the prism sheet, the positional relationship between the anisotropic diffusion film and the prism sheet is not particularly limited. For example, the light diffusion film may be arranged on the downstream side or the upstream side of the optical path with respect to the prism sheet. further,
On the back surface of the light guide member (light guide plate), various reflection means,
For example, the reflecting means is not limited to the above-mentioned reflective layer, and a reflecting means (a wedge-shaped reflecting groove) constituted by a groove having a wedge-shaped cross section may be formed.

As described above, the transmissive display device (particularly the transmissive liquid crystal display device) of the present invention comprises a display unit (a liquid crystal display unit or the like) and the surface light source unit for illuminating this display unit. Has been done. In this device, the anisotropic light diffusing film may be arranged in various directions, but when the horizontal direction of the display surface (liquid crystal display surface) is the Y axis, the anisotropic light diffusion film is It is preferable that the anisotropic light-diffusing film is arranged along the Y-axis (main light-scattering direction) or along the same direction. The Y-axis direction of the anisotropic light-diffusing film is the left-right direction (X
It does not need to be completely coincident with the axial direction), and may be arranged in an oblique direction within an angle range of ± 15 °, for example. By arranging the anisotropic light diffusion film in such a direction, the luminance distribution can be made uniform and the angular dependence of the luminance with respect to the display surface can be reduced, so that the luminance in the horizontal direction (horizontal direction) and the vertical direction (vertical direction) can be made uniform. Can be converted.

In the transmissive liquid crystal display device provided with the light source for illuminating the display surface from the back surface, the light sources of the liquid crystal display device are not limited to the tubular light sources adjacent to the side surface of the light guide plate, but are arranged in parallel with each other. Alternatively, the shape of the light source is not limited to a tubular shape. The liquid crystal display device of the present invention is not limited to the transmissive liquid crystal display device,
It may be a reflection type liquid crystal display device that illuminates the display surface by taking in external light or natural light and reflecting it by a reflection plate. Further, if necessary, the liquid crystal display device may include a polarizing plate or a retardation plate.

[0081]

According to the present invention, the degree of anisotropy of light scattering can be easily adjusted by the ratio of the first dispersed phase particles and the second dispersed phase particles, and the light scattering can be performed in a wide angle range. The strength can be made uniform. In particular, it is possible to widen the viewing angle in a predetermined direction (for example, the left-right direction) of the display surface, and also to uniformly brighten the direction that intersects with the direction (for example, the vertical direction). Therefore, when applied to a surface light source device, the viewing angle in the vertical and horizontal directions can be expanded in a liquid crystal display device, which is useful for displaying clearly.

[0082]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by these examples.

Example 1 Crystalline polypropylene resin PP (F133, manufactured by Grand Polymer Co., Ltd.) as a continuous phase resin, refractive index 1.50
3) 85 parts by weight, and polystyrene-based resin GPPS (general-purpose polystyrene-based resin, GPPS # 30 manufactured by Daicel Chemical Industries, Ltd., refractive index 1.589) as a dispersed phase resin 1
2.5 parts by weight, cross-linked polymethylmethacrylate (PMM
A) type fine particles (MBX-2 manufactured by Sekisui Chemical Co., Ltd.)
2.5 parts by weight were mixed with a tumbler type mixer for about 5 minutes, and melt-kneaded at a cylinder temperature of 220 to 230 ° C. using a twin-screw extruder (PCM30 manufactured by Ikegai Tekko KK) to prepare pellets. Using the obtained pellets, a single-screw extruder (Plastics Engineering Laboratory Co., Ltd., GT-25-A)
And coat hanger type single layer die (width 150 mm)
With a cylinder temperature of 220 to 230 ° C. and a die temperature of 220 ° C.
A μm film was prepared.

Comparative Example 1 85 parts by weight of a crystalline polypropylene resin PP (F133 manufactured by Grand Polymer Co., Ltd.) as a continuous phase resin, and a polystyrene resin GPPS (general purpose polystyrene resin, Daicel Chemical Industries, Ltd.) as a dispersed phase resin. Made GPPS
# 30) A film having a thickness of 120 μm was produced in the same manner as in Example 1 except that 15 parts by weight was used.

Comparative Example 2 75 parts by weight of a crystalline polypropylene resin PP (F133 manufactured by Grand Polymer Co., Ltd.) as a continuous phase resin, and a polystyrene resin GPPS (general purpose polystyrene resin, Daicel Chemical Industries Ltd.) as a dispersed phase resin. Made GPPS
# 30) A first film having a thickness of 60 μm was produced in the same manner as in Example 1 except that 25 parts by weight was used.

Also, 95 parts by weight of a crystalline polypropylene resin PP as a continuous phase resin and crosslinked polymethylmethacrylate (PMMA) type fine particles (manufactured by Sekisui Chemical Co., Ltd.,
A second film having a thickness of 60 μm was produced in the same manner as in Example 1 except that 5 parts by weight of MBX-2) was used.

Then, the first film and the second film were laminated to prepare a laminated film having a thickness of 120 μm. The composition of the entire laminated film was the same as that of the film of Example 1 except that PP / GPPS / PMMA was used.
= 85 / 12.5 / 2.5 (weight ratio).

Comparative Example 3 75 parts by weight of a crystalline polypropylene resin PP (F133 manufactured by Grand Polymer Co., Ltd.) as a continuous phase resin, and a polystyrene resin GPPS (general purpose polystyrene resin, Daicel Chemical Industries Ltd.) as a dispersed phase resin. Made GPPS
# 30) A film having a thickness of 60 μm was produced in the same manner as in Example 1 except that 25 parts by weight was used.

Comparative Example 4 95 parts by weight of a crystalline polypropylene resin PP (F133 manufactured by Grand Polymer Co., Ltd.) as a continuous phase resin, and crosslinked polymethyl methacrylate (PMM) as a dispersed phase resin.
A) fine particles (MBX-2, manufactured by Sekisui Chemical Co., Ltd.) 5
A thickness of 6 was obtained in the same manner as in Example 1 except that parts by weight were used.
A 0 μm film was made.

Then, the characteristics of the films obtained in Examples and Comparative Examples were evaluated as follows.

[Haze / Total Light Transmittance] Using a haze meter (NDH-300A, manufactured by Nippon Denshoku Industries Co., Ltd.), white light was incident from the normal direction of the film to measure optical characteristic values. The results are shown in the table together with the configurations of the films of Examples and Comparative Examples.

[0092]

[Table 1]

[Light scattering property] H from the normal direction of the film
An e-Ne laser beam was incident, the angle dependence of the intensity of the transmitted scattered light was measured by a photo multiplier mounted on a goniometer, and the scattering intensity (vertical axis) was plotted against the scattering angle (horizontal axis). Regarding the laminated film obtained in Comparative Example 2, laser light was made incident from the first film side or the second film side, and the scattering characteristic of transmitted light was examined.

The results are shown in FIG. The X-axis direction is a direction in which scattered light spreads widely, and the Y-axis direction is a direction perpendicular to the X-axis direction.

As is apparent from FIG. 3, for example, the embodiment
Comparing 1 with Comparative Example 1, although the difference in the angle dependence of the scattering intensity in the X-axis direction is small, the angle dependence of the scattering intensity in Example 1 is smaller in the Y-axis direction than in Comparative Example 1. I understand. That is, the degree of anisotropic scattering is larger in Example 1 than in Comparative Example 1, and the scattering pattern is more circular.

In order to evaluate the degree of such anisotropic scattering, the anisotropy ratio is calculated based on the following formula: anisotropy ratio = scattering intensity in X-axis direction / scattering intensity in Y-axis direction The anisotropy ratio (vertical axis) was plotted against the angle (horizontal axis). The results are shown in Fig. 4. Note that, in FIG. 4, the larger the slope to the right is, the larger the scattering anisotropy is.

In FIG. 4, the sheet of Comparative Example 2 obtained by stacking the sheets of Comparative Example 3 and the sheet of Comparative Example 4 and the sheet of Example 1 showed an anisotropic dispersed phase. By combining with a spherical dispersed phase, the degree of anisotropy can be easily controlled.

[Brief description of drawings]

FIG. 1 is a schematic exploded perspective view showing an example of a surface light source device and a transmissive liquid crystal display device of the present invention.

FIG. 2 is a conceptual diagram for explaining anisotropic scattering of a diffusion film.

FIG. 3 is a graph showing scattering patterns of diffusion films obtained in Examples and Comparative Examples.

FIG. 4 is a graph showing scattering characteristics (anisotropy ratio) of diffusion films obtained in Examples and Comparative Examples.

[Explanation of symbols]

1 ... Display device 2 ... Liquid crystal display unit 3 ... Surface light source unit 4 ... Tube light source 5 ... Light guide member 6a ... Reflective member or reflective layer 7 ... Anisotropic diffusion film 8 ... Prism sheet 7a ... continuous phase 7b ... Spherical dispersed phase 7c ... Anisotropic dispersed phase

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H042 BA02 BA14 BA15 BA20                 2H091 FA23Z FA31Z FA41Z FB12                       LA18 LA19                 5G435 AA02 AA03 BB12 BB15 DD09                       DD14 EE27 FF06 FF08 GG03                       GG24 KK07

Claims (10)

[Claims] 1. A light-scattering film comprising a continuous phase and a dispersed phase having different refractive indexes and a light diffusion layer capable of scattering transmitted light, wherein the dispersed phase is spherical dispersed phase particles. And an anisotropic dispersion-phase particle having a major axis oriented in a predetermined direction. 2. The anisotropy according to claim 1, wherein the spherical dispersed phase particles have an average aspect ratio of 0.8 to 1.2, and the anisotropic dispersed phase particles have an average aspect ratio of 1.5 or more. Diffusion film. 3. The ratio (weight ratio) of spherical dispersed phase particles to anisotropic dispersed phase particles is such that the former / the latter = 1/99 to 70 /
The anisotropic diffusion film according to claim 1, which is 30. 4. A continuous phase composed of a transparent thermoplastic resin and a dispersed phase dispersed in the continuous phase, the dispersed phase comprising spherical dispersed phase particles composed of a transparent substance, The anisotropic diffusion film according to claim 1, which is composed of anisotropically-shaped dispersed phase particles made of a transparent thermoplastic resin. 5. The continuous phase and anisotropic dispersed phase particles are selected from polyolefin resin, (meth) acrylic resin, styrene resin, polyester resin, polyamide resin, polycarbonate resin and cellulose derivative. Composed of at least one transparent thermoplastic resin,
The anisotropic diffusion film according to claim 4, wherein the spherical dispersed phase particles are composed of a crosslinked resin. 6. A continuous phase and a disperse phase having different refractive indexes from each other, and the disperse phase is composed of spherical disperse phase particles and anisotropic disperse phase particles having major axes oriented in a predetermined direction. A method for producing a film, comprising a transparent thermoplastic matrix resin which constitutes the continuous phase, transparent spherical particles which are not deformable at a molding temperature of the matrix resin, and a transparent thermoplastic resin which is deformable at the molding temperature. Is mixed at the melting temperature of the matrix resin to form a film, which is a method for producing an anisotropic diffusion film. 7. A method of adjusting the degree of anisotropy of transmitted light by a film having a light diffusion layer composed of a continuous phase and a dispersed phase having different refractive indexes, wherein the dispersed phase is
Spherical dispersed phase particles, the long axis is composed of anisotropically shaped dispersed phase particles oriented in a predetermined direction, and by adjusting the ratio of the spherical dispersed phase particles and anisotropically shaped dispersed phase particles,
A method of controlling the degree of anisotropy of transmitted and diffused light. 8. A surface light source device in which the anisotropic diffusion film according to claim 1 is disposed on the exit surface side of the surface light source unit. 9. A liquid crystal display device comprising the anisotropic diffusion film according to claim 1. 10. A transmissive liquid crystal display device comprising the surface light source device according to claim 8.