JP2004101641A - Anisotropic diffusion film and device having the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light diffusing film which can improve the display grade of a surface light source device and liquid crystal display device by using anisotropic light diffusion. <P>SOLUTION: A diffusing film 7 has a diffusion layer consisting of: a continuous phase of resin (a cyclic polyolefin system resin, etc.) of a low intrinsic double refraction index; and a dispersion phase of resin (non-crystalline polyester, styrene system resin, etc.) of a refractive index different from the refractive index of the continuous phase. The mean aspect ratio of the dispersion phase is greater than 41 in order to impart anisotropy to transmitted light. The diffusion film 47 is applicable to a display device 41 consisting of a liquid crystal display unit 42 and a surface light source unit 43. The unit 43 is provided with a tubular light source 44, a light guide member 45, the optical diffusion film 47, and a prism sheet 48. The film 47 diffuses the light from the light source (fluorescent lamp) of the surface light source device (back light) to uniformly illuminate the unit 42. <P>COPYRIGHT: (C)2004,JPO

Description

【０１１１】
実施例５
図５に示す面光源装置及び透過型液晶表示装置において、異方性拡散フィルム４７として実施例１で得られたフィルムを用いた面光源装置及び透過型液晶表示装置について、異方性及び正面輝度を測定した。その結果を表２に示す。
【０１１２】
比較例３
図５に示す面光源装置及び透過型液晶表示装置において、異方性拡散フィルム４７として比較例１で得られたフィルムを用いた面光源装置及び透過型液晶表示装置について、異方性及び正面輝度を測定した。その結果を表２に示す。
【０１１３】
【表２】

【０１１４】
【図面の簡単な説明】
【図１】図１は本発明のタッチパネル式液晶表示装置の一例を示す概略断面図である。
【図２】図２は本発明のインナー型タッチパネル式液晶表示装置の一例を示す概略断面図である。
【図３】図３は本発明の異方性拡散フィルムを液晶セルの電極基板として用いた液晶表示装置の一例を示す概略断面図である。
【図４】図４は本発明の異方性拡散フィルムをバックライト用拡散シートとして用いた液晶表示装置の一例を示す概略断面図である。
【図５】図５は本発明の面光源装置及び透過型液晶表示装置の一例を示す概略分解斜視図である。
【図６】図６は光拡散フィルムの異方的散乱を説明するための概念図である。
【符号の説明】
１，４１…液晶表示装置
４２…液晶表示ユニット
４３…面光源ユニット
４４…管状光源
４５…導光部材
４６ａ…反射部材又は反射層
４７…異方性拡散フィルム
４８…プリズムシート
４７ａ…連続相
４７ｂ…分散相[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light-scattering film (sheet) useful for clearly displaying high luminance in a liquid crystal display device, a method for manufacturing the same, and a device (a surface light source device or a liquid crystal display device) using the film.
[0002]
[Prior art]
In a backlight type display device (such as a transmission type liquid crystal display device), a surface light source unit (or a backlight unit) is provided 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) and the like are used. Further, in the liquid crystal display device, as a constituent member of the liquid crystal cell, a transparent conductive substrate, a polarizing plate, a retardation plate, and the like, which are disposed to face each other and enclose liquid crystal, are used.
[0003]
More specifically, for example, a surface light source unit for illuminating the transmission type liquid crystal display unit from the back side is provided with one or a plurality of fluorescent discharge tubes (cold cathode tubes) and on the back side of the fluorescent discharge tubes. And a diffusion plate disposed between the fluorescent discharge tube and the display unit for uniformly illuminating the display unit. Further, as a surface light source unit, a tubular light source such as a fluorescent tube (cold cathode tube) is disposed, and a side surface is arranged adjacent to the tubular light source, and light from the tubular light source is incident on the side surface and emitted from the front surface. There is also known a unit including 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 with respect to the display unit. ing.
[0004]
In such a surface light source unit, the brightness distribution in the axial direction of the tubular light source is different from the brightness distribution in the direction orthogonal to the axial direction, making it difficult to uniformly illuminate the display unit and increasing the viewing angle. Is difficult. Therefore, an anisotropic diffusion sheet having optically anisotropic scattering characteristics is used as the diffusion sheet, and the luminance is made uniform using the anisotropic scattering characteristics.
[0005]
For example, JP-A-4-314522 discloses that a transparent matrix has an anisotropic shape having 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. Anisotropic light-scattering materials are described in which the materials are homogeneously dispersed in an ordered, mutually translated positional relationship. Specifically, a low-melting-point low-density polyethylene as a transparent matrix resin and a high-melting-point polystyrene or a styrene-acrylonitrile copolymer as a transparent substance were kneaded, and the resulting composition was extruded and extruded. Anisotropic sheets are manufactured by a method in which a sheet-like molten resin is strongly drawn in the extrusion direction and cooled while being stretched.
[0006]
Japanese Patent Application Laid-Open No. 7-114013 discloses that in order to improve the viewing angle characteristics, a 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 0.1. Disclosed are films or sheets in which dispersed phase particles of 5 to 70 μm are dispersed.
[0007]
However, the anisotropic diffusion sheet has large birefringence due to high optical anisotropy.
Therefore, the display quality is deteriorated, and the display cannot be performed with high definition. Such a problem similarly occurs in a touch panel for detecting a touch position using a pair of transparent electrodes disposed to face each other and displaying the touch position on a display panel.
[0008]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a light diffusing film capable of improving display quality while maintaining light diffusing properties, a method for manufacturing the same, and a device including the film (a surface light source device or a transmission type liquid crystal display device). It is in.
[0009]
Another object of the present invention is to provide a conductive film having a light diffusing property and a conductive property, which is useful as a transparent substrate or the like in a functional element such as a liquid crystal cell or a touch panel, and a device (such as a liquid crystal display or a touch panel) provided with the film. ).
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, in an anisotropic light diffusion film having a phase separation structure in which a dispersed phase is dispersed in a continuous phase, a continuous phase resin having a low intrinsic birefringence and a specific dispersion. It has been found that, when combined with a phase resin, anisotropic light diffusivity can be imparted by an anisotropically shaped dispersed phase and a film having a small birefringence can be obtained, and the present invention has been completed.
[0011]
That is, the anisotropic diffusion film of the present invention is a diffusion film composed of a diffusion layer capable of scattering incident light in the light traveling direction, and has a scattering characteristic indicating a 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), Fy (θ) is in the range of the scattering angle θ = 4 to 30 °. /Fx(θ)>1.01 and a retardation R = Δnxd based on the refractive index difference Δn between the X-axis direction and the Y-axis direction and the thickness d of 50 nm or less. . The diffusion layer of the anisotropic diffusion film can be composed of a continuous phase and a dispersed phase having different refractive indexes, and the continuous phase can be composed of a resin having a low intrinsic birefringence (particularly, a transparent resin). The dispersed phase has an average aspect ratio of more than 1 in order to impart anisotropic diffusion to transmitted light, and the major axis direction of the dispersed phase is oriented in the direction in which the film is taken. At least the continuous phase of the continuous phase and the dispersed phase may be composed of a transparent resin having a low intrinsic birefringence, for example, a cyclic polyolefin-based resin. For example, a continuous phase composed of a cyclic polyolefin-based resin, and a non-crystalline polyester, a (meth) acrylic resin, a styrene-based resin and a poly (4-methylpentene-dispersed) dispersed in a particulate form in the continuous phase. 1) The anisotropic diffusion film may be composed of a dispersed phase composed of a transparent resin selected from a series of resins. The diffusion layer of the anisotropic diffusion film may further contain a compatibilizer for the continuous phase and the dispersed phase, for example, an epoxidized diene-based block copolymer. Further, the anisotropic diffusion film is not limited to a single layer film of the diffusion layer, and may be a laminated film, for example, a laminated film in which at least one surface of the diffusion layer is covered with a transparent resin layer.
[0012]
The anisotropic diffusion film can be manufactured by melt-extruding a resin constituting a continuous phase and a resin constituting a dispersed phase, and forming a film while taking off the resin.
[0013]
The present invention also discloses a conductive film having a transparent conductive layer formed on at least one surface of the anisotropic diffusion film. This conductive film is disposed to face each other, and various substrates constituting the functional element, for example, a pair of substrates disposed to face each other and constitute the functional element, at least one of The substrate can be used as a substrate for a resistive touch panel composed of the conductive film.
Further, in a touch panel including the substrate for a resistive touch panel, an inner touch panel in which a touch surface is formed of a polarizing plate may be configured.
[0014]
Furthermore, the present invention also discloses a surface light source device in which the anisotropic diffusion film is disposed on the exit surface side of the surface light source unit, and a liquid crystal display device including the anisotropic diffusion film. Furthermore, a liquid crystal display device including the conductive film as an electrode substrate of a liquid crystal cell, a liquid crystal including two polarizing plates, and the anisotropic diffusion film disposed between the two polarizing plates. A display device and a transmission type liquid crystal display device including the surface light source device are also disclosed.
[0015]
In this specification, the term “film” is used to include a sheet regardless of its thickness.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The diffusion film of the present invention is constituted by a diffusion layer capable of scattering incident light in the traveling direction of light, and imparts anisotropic light diffusion to transmitted light. That is, in 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 film is Fx (θ), and the scattering characteristic in the Y-axis direction is Fy (θ). At this time, it has an anisotropy (or anisotropic light scattering property) satisfying Fy (θ) / Fx (θ)> 1.01 in a range of the scattering angle θ = 4 to 30 °. The value of F = Fy (θ) / Fx (θ) is usually about 1.1 to 500 (for example, 10 to 500), preferably about 15 to 500, and more preferably about 50 to 500 (for example, 100 to 400). It is.
[0017]
In the production of an anisotropic film, a birefringence usually increases because a deformation orientation due to an external force acting upon the film forming and a refractive index difference between a stress direction and a direction perpendicular to the stress direction. The anisotropic diffusion film of the present invention is anisotropic with respect to light scattering characteristics, but has the characteristic of having a small birefringence and being substantially isotropic. That is, the retardation R = Δn × d based on the refractive index difference Δn between the X-axis direction (the film take-off direction) and the Y-axis direction of the anisotropic film and the thickness d is 50 nm or less (for example, 5 to 50 nm). It is preferably 30 nm or less (for example, 5 to 30 nm), and usually about 10 to 25 nm (particularly, 10 to 20 nm). For example, the retardation R can be measured at a wavelength of 550 nm. In addition, the thickness of the anisotropic diffusion film is, for example, about 5 to 300 μm, preferably about 10 to 200 μm, and more preferably about 50 to 150 μm.
[0018]
The anisotropic diffusion film of the present invention has a high light transmittance. That is, the total light transmittance of the anisotropic diffusion film is, for example, about 85 to 100%, preferably about 90 to 100% (practically 90 to 95%), and more preferably 87 to 95% (for example, 88). ９３93%).
[0019]
The diffusion layer constituting the anisotropic diffusion film of the present invention can be composed of a plurality of resins having different refractive indexes from each other, and has a phase separation structure composed of a continuous phase and a dispersed phase having different refractive indexes. The difference in the 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 about 0.01 to 0.3, and more preferably 0.01 to 0.3. It is about 0.1.
[0020]
In order to impart anisotropic light scattering, the dispersed phase has a ratio (average aspect ratio, L / W) of the average length L of the major axis to the average length W of the minor axis of greater than 1. The aspect ratio of the dispersed phase is, for example, 1.5 to 1000 (for example, 2 to 1000), preferably about 5 to 1000, more preferably about 5 to 500 (for example, 20 to 500), and usually about 2.5 to 2.5. About 500 (especially 10 to 300). Such dispersed phase particles may have a football shape (spheroidal shape or the like), a fiber shape, a rectangular shape, or the like. Note that the major axis direction (X-axis direction) of the dispersed phase is substantially oriented in the film take-off direction (X-axis direction).
[0021]
The average length L of the major axis of the dispersed phase is, for example, about 0.1 to 200 μm (for example, about 1 to 100 μm), preferably about 1 to 150 μm (for example, about 1 to 80 μm), particularly 2 to 100 μm. (For example, about 2 to 50 μm), and usually about 10 to 100 μm (for example, 30 to 100 μm, particularly 10 to 50 μm). The average length W of the minor axis of the dispersed phase is, for example, about 0.1 to 10 μm, preferably about 0.15 to 5 μm (for example, 0.5 to 5 μm), and more preferably 0.2 to 2 μm ( For example, it is about 0.5 to 2 μm).
[0022]
The orientation coefficient of the dispersed phase particles may be, for example, 0.5 or more (about 0.5 to 1), preferably about 0.7 to 1, and more preferably about 0.8 to 1. The higher the orientation coefficient of the dispersed phase particles, the higher the anisotropy can be given to the scattered light. The orientation coefficient can be calculated based on the following equation.
[0023]
Orientation coefficient = (3 <cos ² θ> -1) / 2
In the formula, θ indicates the angle between the major axis of the particulate dispersed phase and the X axis of the film (θ = 0 ° when the major axis and the X axis are parallel), and <cos ² θ> is the cos calculated for each dispersed phase particle ² Indicates the average of θ and is represented by the following equation.
[0024]
<Cos ² θ> = ∫n (θ) · cos ² θ ・ dθ
(In the formula, n (θ) indicates the ratio (weight) of the dispersed phase particles having the angle θ in all the dispersed phase particles)
The diffuse transmitted light from the anisotropic light diffusion film may have directivity. That is, having directivity means that there is an angle at which the scattering intensity shows a maximum among the directions in which the anisotropic diffused light has strong scattering. When the diffused light has directivity, when the diffused light intensity F is plotted against the diffused angle θ, the plotted curve has a maximum within a specific diffused angle θ range (an angle range excluding θ = 0 °). Or it has a shoulder (particularly, an inflection point such as a maximum).
[0025]
In the present invention, in order to make the diffusion layer have a small birefringence, it is preferable that at least one of the continuous phase and the dispersed phase (in particular, at least the continuous phase) is formed of a transparent resin having a low intrinsic birefringence. Examples of the transparent resin having a low intrinsic birefringence include cellulose esters, (meth) acrylic resins, cyclic polyolefin resins, and poly (4-methylpentene-1) resins.
[0026]
Examples of the cellulose esters include aliphatic organic acid esters (for example, cellulose acetate such as cellulose diacetate and cellulose triacetate; cellulose ester such as cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). _1-6 Organic acid esters, etc., aromatic organic acid esters (eg, cellulose phthalate, cellulose benzoate, etc.) _7-12 Examples thereof include aromatic carboxylic acid esters) and inorganic acid esters (for example, cellulose phosphate and cellulose sulfate), and may be a mixed acid ester such as acetic acid / cellulose nitrate ester.
[0027]
As the (meth) acrylic resin, a homopolymer or copolymer of a (meth) acrylic monomer and a copolymer of a (meth) acrylic monomer and a copolymerizable monomer can be used.
(Meth) acrylic monomers include, for example, (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, t-butyl (meth) acrylate, (Meth) acrylic acid C such as isobutyl (meth) acrylate, hexyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate _1-10 Alkyl; cycloalkyl (meth) acrylate such as cyclohexyl (meth) acrylate; norbornyl (meth) acrylate, adamantyl (meth) acrylate, tricyclodecanyl (meth) acrylate, and dicyclopentadienyl group (Meth) acrylates having a bridged or polycyclic aliphatic hydrocarbon group such as (meth) acrylates; hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate Acrylate; glycidyl (meth) acrylate; N, N-dialkylaminoalkyl (meth) acrylate; (meth) acrylonitrile and the like. Examples of the copolymerizable monomer include the styrene-based monomer, vinyl ester-based monomer, maleic anhydride, maleic acid, fumaric acid, and the like.
These monomers can be used alone or in combination of two or more.
[0028]
Examples of the (meth) acrylic resin include a poly (meth) acrylate such as polymethyl methacrylate, a methyl methacrylate- (meth) acrylic acid copolymer, and a methyl methacrylate- (meth) acrylate copolymer. Copolymer, methyl methacrylate-acrylate- (meth) acrylic acid copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group [methyl methacrylate -Cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.].
Preferred (meth) acrylic resins include poly (meth) acrylic acid C such as poly (meth) acrylate. _1-6 A methyl methacrylate resin containing alkyl, particularly methyl methacrylate as a main component (about 50 to 100% by weight, preferably about 70 to 100% by weight) is exemplified.
[0029]
As the cyclic polyolefin resin (alicyclic olefin resin), homo- or copolymers of cyclic olefins (norbornene, dicyclopentadiene, etc.) (for example, alicyclic hydrocarbon groups such as stereorigid tricyclodecane) Olefin-based polymers having a) a cyclic olefin and a copolymerizable monomer (α-C such as ethylene, propylene, butylene, etc.) _2-10 And olefins (e.g., ethylene-norbornene copolymer, propylene-norbornene copolymer, etc.). The alicyclic olefin-based resin is available, for example, under the trade name “ARTON”, under the trade name “ZEONEX”, or the like.
[0030]
Examples of the poly (4-methylpentene-1) -based resin include homopolymers (poly (4-methylpentene-1)) and copolymerizable monomers (α-C such as ethylene, propylene and butylene). _2-10 And olefins (e.g., propylene-4-methylpentene-1 copolymer).
[0031]
These resins having a low intrinsic birefringence can be used alone or in combination of two or more. Preferred low intrinsic birefringence resins include transparent resins selected from cellulose esters, (meth) acrylic resins and cyclic polyolefin resins.
Such a resin having a low intrinsic birefringence is suitable as a resin constituting a continuous phase.
[0032]
As the dispersed phase dispersed in the continuous phase in the form of particles, various transparent resins can be used as long as the type and the refractive index of the resin constituting the continuous phase are different, and the transparent resin (cellulose) constituting the continuous phase can be used. Esters, acrylic resins, styrene copolymer resins, cyclic polyolefin resins, poly (4-methylpentene-1) resins, non-crystalline polyesters, etc.). Further, the dispersed phase may be made of a transparent resin different from the above-described resin for the continuous phase. Examples of such a transparent resin include thermoplastic resins (olefin resins, halogen-containing resins, vinyl ester resins or derivatives thereof, vinyl ether resins, styrene resins, polyester resins, polyamide resins, polycarbonate resins, and the like). , Thermoplastic polyurethane resins, polysulfone resins (polyethersulfone, polysulfone, etc.), polyphenylene ether resins (2,6-xylenol polymers, etc.), cellulose derivatives (cellulose carbamates, cellulose ethers, etc.), silicone resins ( Polydimethylsiloxane, polymethylphenylsiloxane, etc.), rubber or elastomer (diene rubber such as polybutadiene, polyisoprene, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, Kurirugomu, urethane rubber, silicone rubber, etc.), etc.), and a thermosetting resin (epoxy resin, unsaturated polyester resin, diallyl phthalate resin, silicone resin, etc.) and the like. Preferred resins are thermoplastic resins. These disperse phase resins can be used alone or in combination of two or more.
[0033]
As the olefin resin, C _2-6 Olefin homo- or copolymer (ethylene-based resin such as polyethylene, ethylene-propylene copolymer, polypropylene-based resin such as polypropylene, propylene-ethylene copolymer, propylene-butene copolymer), C _2-6 Copolymers of olefins and copolymerizable monomers (ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid copolymer Examples thereof include a coalescence or a salt thereof (for example, an ionomer resin) and a copolymer such as an ethylene- (meth) acrylate copolymer.
[0034]
Examples of the halogen-containing resin include homopolymers of halogen-containing monomers such as polyvinyl chloride, copolymers of halogen-containing monomers such as tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and vinyl chloride-vinyl acetate copolymers. Examples include a copolymer of a halogen-containing monomer and a copolymerizable monomer such as a polymer, a vinyl chloride- (meth) acrylate copolymer, and a vinylidene chloride- (meth) acrylate copolymer. it can.
[0035]
Vinyl ester resins include homopolymers (such as polyvinyl acetate) and copolymers of vinyl ester monomers and copolymerizable monomers (vinyl acetate-ethylene copolymers, vinyl acetate-vinyl chloride copolymers). Polymer, vinyl acetate- (meth) acrylate copolymer, etc.), and examples of the vinyl ester resin derivative include polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and polyvinyl acetal resin.
[0036]
Vinyl ether resins include vinyl methyl ether and vinyl t-butyl ether such as vinyl C. _1-10 Homo- or copolymer of alkyl ether, vinyl C _1-10 Copolymers of an alkyl ether and a copolymerizable monomer (such as a vinyl alkyl ether-maleic anhydride copolymer) can be exemplified.
[0037]
Styrene-based resins include homo- or copolymers of styrene-based monomers (polystyrene, styrene-α-methylstyrene copolymer, styrene-vinyltoluene copolymer, etc.) and copolymerizable monomers with styrene-based monomers. Copolymers with monomers (such as the (meth) acrylic monomers, maleic anhydride, and maleimide monomers) can be exemplified. Examples of the styrene copolymer resin include a styrene-methyl methacrylate copolymer, a styrene-methyl methacrylate- (meth) acrylate copolymer, and a styrene-methyl methacrylate- (meth) acrylic acid copolymer. Styrene- (meth) acrylate copolymer, acrylonitrile-styrene copolymer (AS resin), styrene-maleic anhydride copolymer, styrene-butadiene copolymer, and the like.
[0038]
Polyester resins include aromatic polyesters using aromatic dicarboxylic acids such as terephthalic acid (especially poly-C such as polyethylene terephthalate and polybutylene terephthalate). _2-4 Alkylene terephthalate or poly C _2-4 C such as alkylene naphthalate _2-4 Examples thereof include homopolyesters, copolyesters, and liquid crystalline polyesters containing an alkylene arylate unit as a main component (for example, 50 mol% or more, preferably 75 to 100 mol%, more preferably 80 to 100 mol%). As a copolyester, poly C _2-4 Of the structural units of alkylene arylate, C _2-4 Part of the alkylene glycol is replaced with polyoxy C _2-4 Alkylene glycol, C _6-10 Alkylene glycol, alicyclic diol (cyclohexane dimethanol, hydrogenated bisphenol A, etc.), diol having an aromatic ring (9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene having a fluorenone side chain), bisphenol A , A bisphenol A-alkylene oxide adduct, etc.) and a portion of the aromatic dicarboxylic acid is converted to an asymmetric aromatic dicarboxylic acid such as phthalic acid and isophthalic acid, and an aliphatic C such as adipic acid. _6-12 Copolyesters substituted with dicarboxylic acids and the like are included. The polyester resin also includes a polyarylate resin, an aliphatic polyester using an aliphatic dicarboxylic acid such as adipic acid, and a homo- or copolymer of a lactone such as ε-caprolactone. Preferred polyester resins are usually amorphous copolyesters (eg, C _2-4 (E.g., alkylene arylate copolyester).
[0039]
Examples of the polyamide-based resin include aliphatic polyamides such as nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, and nylon 12, dicarboxylic acids (eg, terephthalic acid, isophthalic acid, adipic acid) and diamines. For example, polyamides (e.g., aromatic polyamides such as xylylenediamine adipate (MXD-6)) obtained from hexamethylenediamine and meta-xylylenediamine) are exemplified. The polyamide resin may be a homo- or copolymer of a lactam such as ε-caprolactam, and is not limited to a homopolyamide but may be a copolyamide.
[0040]
Polycarbonate resins include aromatic polycarbonates based on bisphenols (such as bisphenol A) and aliphatic polycarbonates such as diethylene glycol bisallyl carbonate.
[0041]
Cellulose derivatives include cellulose carbamates (eg, cellulose phenyl carbamate, etc.), cellulose ethers (eg, cyanoethyl cellulose; hydroxy C, such as hydroxyethyl cellulose and hydroxypropyl cellulose). _2-4 Alkyl cellulose; C such as methyl cellulose and ethyl cellulose _1-6 Alkylcellulose; carboxymethylcellulose or a salt thereof, benzylcellulose, acetylalkylcellulose, etc.).
[0042]
The resin components constituting the continuous phase and the dispersed phase may be modified (for example, rubber-modified) as necessary. Further, a continuous phase matrix may be constituted by the resin component, and the dispersed phase component may be grafted or block copolymerized to the matrix resin.
[0043]
If necessary, the dispersed phase (light scattering factor) may be a crosslinked resin having a different refractive index to the continuous phase resin (matrix resin), for example, a crosslinked styrene resin such as crosslinked polystyrene beads, a crosslinked polymethylmethacrylate or the like. It may be composed of crosslinked resin particles such as acrylic resin and crosslinked guanamine resin.
[0044]
Preferred resins constituting the dispersed phase are styrene-based resins and / or polyester-based resins (particularly non-crystalline copolyester-based resins). When the continuous phase is composed of the cyclic polyolefin-based resin or cellulose ester, in addition to the styrene-based resin and the polyester-based resin (particularly, the non-crystalline copolyester-based resin), a resin having a low intrinsic birefringence ( For example, (meth) acrylic resin, poly (4-methylpentene-1) resin, etc.) are also preferable as the resin constituting the dispersed phase.
[0045]
In the diffusion layer, the ratio between the continuous phase and the dispersed phase is, for example, the former / the latter (weight ratio) = 99/1 to 50/50 (for example, 95) depending on the type of resin, melt viscosity, light diffusivity, and the like. / 5 to 60/40), preferably about 90/10 to 60/40 (for example, 90/10 to 70/30), and more preferably 80/20 to 70/30 (80/20 to 60/40). It can be appropriately selected from the range of the degree.
[0046]
The light scattering sheet may contain a compatibilizer as needed. The use of a compatibilizer can enhance the miscibility and affinity between the continuous phase and the dispersed phase, prevent the generation of defects (voids and the like) even when the film is subjected to an orientation treatment, and make the film transparent. Can be prevented from decreasing. Further, the adhesiveness between the continuous phase and the dispersed phase can be improved.
[0047]
The compatibilizer can be selected from conventional compatibilizers according to the types of the continuous phase and the dispersed phase. For example, the compatibilizer is modified with an oxazoline compound, a modifying group (such as a carboxyl group, an acid anhydride group, an epoxy group, or an oxazolinyl group). Modified resin, diene or rubber-containing polymer [for example, a diene-based copolymer (random) obtained by copolymerization with a diene-based monomer alone or 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 copolymer, hydrogenated styrene-butadiene (SB) block copolymer , Hydrogenated styrene-butadiene-styrene block copolymer (SEBS), hydrogenated (styrene-ethylene / butylene-styrene) Click copolymer diene block copolymer or hydrogenated products thereof and the like, etc.], etc. The (such as an epoxy group) modifying groups modified with diene or rubber-containing polymer can be exemplified. These compatibilizers can be used alone or in combination of two or more.
[0048]
As the compatibilizer, a polymer (random, block or graft copolymer) having the same or a common component as the polymer blend-based constituent resin, a polymer having an affinity for the polymer blend-based constituent resin is usually used. (Random, block or graft copolymer) and the like are used.
[0049]
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, and phenyl-diene. C which may have a substituent such as 1,3-butadiene _4-20 Conjugated dienes are mentioned. 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 (such as p-methylstyrene), pt-butylstyrene, and divinylbenzenes. Of these aromatic vinyl monomers, styrene is preferred. These monomers can be used alone or in combination of two or more.
[0050]
The modification is performed 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 modification with a carboxyl group, maleic anhydride in the case of modification with an acid anhydride group, and ) An acrylic monomer, a maleimide monomer in the case of maleimide group modification, and an epoxy group-containing monomer such as glycidyl (meth) acrylate in the case of epoxy modification can be copolymerized. Epoxy modification may be performed by epoxidation of an unsaturated double bond.
[0051]
Preferred compatibilizers include unmodified or modified diene-based copolymers, especially epoxidized diene-based block copolymers (eg, epoxidized styrene-butadiene-styrene (SBS) block copolymers and the like). A diene-based block copolymer or an epoxy-modified diene-based block copolymer). The epoxidized diene-based block copolymer has not only high transparency but also a relatively high softening temperature of about 70 ° C., and compatibilizes the resin in many combinations of the continuous phase and the dispersed phase to form a dispersed phase. Can be dispersed uniformly.
[0052]
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-based 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 a hydrogenated block thereof) 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. An epoxidized block copolymer having a content of an aromatic vinyl block (styrene block or the like) of about 60 to 80% by weight has a relatively high refractive index (for example, about 1.57), and has a high dispersion index. Since it has a refractive index close to that of a resin (such as an amorphous copolyester), the dispersed phase can be uniformly dispersed while maintaining the light scattering property of the dispersed phase resin.
[0053]
The number average molecular weight of the block copolymer can be selected, for example, from the range of about 5,000 to 1,000,000, preferably about 7,000 to 900,000, and more preferably about 10,000 to 800,000. . The molecular weight distribution [the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn)] is, for example, 10 or less (about 1 to 10), preferably about 1 to 5.
[0054]
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 mono-block structure and a tele-block structure, a tri-chain radial tele-block structure, and a tetra-chain radial tele-block structure. As such a block structure, when an aromatic diene block is X and a conjugated diene block is Y, for example, XY type, XYX type, YXY type, YXY -X type, XYXY type, XYXYX type, YXYXXY type, (XY-) ₄ Si type, (YX-) ₄ An example is an Si type.
[0055]
Although the ratio of the epoxy group in the epoxidized diene-based block copolymer is not particularly limited, the oxygen concentration of oxirane is, for example, 0.1 to 8% by weight, preferably 0.5 to 6% by weight, more preferably It is about 1 to 5% by weight. The epoxy equivalent (JIS K 7236) of the epoxidized block copolymer may be, for example, about 300 to 1,000, preferably about 500 to 900, and more preferably about 600 to 800.
[0056]
The refractive index of the compatibilizer (epoxidized block copolymer or the like) is substantially the same as that of the dispersed phase resin (for example, the difference in the refractive index from the dispersed phase resin is about 0 to 0.01, preferably 0 to 0.01). To about 0.005).
[0057]
The epoxidized block copolymer is prepared by subjecting a diene-based block copolymer (or a partially hydrogenated block copolymer) to a conventional epoxidation method, for example, an epoxidizing agent (peracids, Epoxidation of the block copolymer with hydroperoxides or the like.
[0058]
The amount of the compatibilizer to be used can be selected, for example, from the range of about 0.1 to 20% by weight, preferably about 0.5 to 15% by weight, and more preferably about 1 to 10% by weight of the whole resin composition. The ratio (weight ratio) of the dispersed phase and the compatibilizer is the former / the latter = about 99/1 to 50/50, preferably about 99/1 to 70/30, and more preferably about 98/2 to 80/20. It is.
[0059]
The diffusion film is not limited to a single layer structure of the diffusion layer alone, and may have a laminated structure.
In the diffusion film having a laminated structure, at least one surface (one or both surfaces) of the diffusion layer is covered with a transparent layer. This transparent layer may be a transparent substrate such as glass or may be formed of a resin. As the resin constituting the transparent layer, a resin which is the same as or different from the resin of the continuous phase and / or the dispersed phase which constitutes the light diffusion layer can be used, but usually, the same or common resin as the resin of the continuous phase is preferably used. Is done. In particular, the transparent resin layer is preferably an isotropic resin having a small birefringence (the resin for the continuous phase) or a transparent substrate (for example, glass).
[0060]
In a laminated anisotropic diffusion film, protecting the diffusion layer with a transparent resin layer can prevent the dispersed phase particles from falling off or adhering, improve the film's scratch resistance and production stability, and improve the film's strength and handleability. Can be enhanced.
[0061]
The diffusion layer and / or the transparent resin layer contains various additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers), plasticizers, antistatic agents, flame retardants, fillers, and the like. You may.
[0062]
The thickness of the anisotropic diffusion film is about 3 to 1000 μm, preferably about 5 to 500 μm (eg, 30 to 200 μm), and more preferably about 5 to 100 μm (eg, 50 to 100 μm). In the anisotropic diffusion film having a laminated structure, the ratio of the thickness of the light diffusion layer to the thickness of the transparent layer is, for example, about 5/95 to 99/1, preferably 50/50 to 99/1. Degree, more preferably about 70/30 to 95/5.
[0063]
The surface of the diffusion film may be coated with a release agent such as silicone oil or corona discharge treatment as long as the optical characteristics are not impaired. Further, the light diffusing film having anisotropy may be formed with irregularities extending in the X-axis direction of the film (the major axis direction of the dispersed phase). By forming such an uneven portion, a higher anisotropic light scattering property can be imparted to the film.
[0064]
[Diffusion film manufacturing method]
The diffusion film, depending on the layer structure, casting method, a conventional film forming method such as extrusion molding method can be used, the diffusion film having a laminated structure, a resin composition composed of components corresponding to the diffusion layer and A resin composition composed of components corresponding to the transparent layer, a co-extrusion method of forming a film by co-extrusion, a method of coating one layer prepared in advance with the other layer, and laminating by extrusion lamination. It can be formed by a dry lamination method or the like in which a diffusion layer and a transparent layer prepared respectively are laminated. The anisotropic diffusion film can be obtained by dispersing and orienting a component (such as a resin component) constituting a dispersed phase in a resin constituting a continuous phase. For example, the resin constituting the continuous phase and the components constituting the dispersed phase (resin component, fibrous component, etc.) are blended by a conventional method (eg, a melt blending method, a tumbler method, etc.) as necessary, and then melted. The dispersed phase can be dispersed by mixing, extruding from a T-die, a ring die or the like to form a film.
[0065]
The birefringence depends on the polarizability anisotropy (intrinsic birefringence) based on the molecular structure and the molecular orientation due to molding, so that a diffusion layer can be formed without applying a relatively large external force or a film can be formed. Molding is preferred. Therefore, in a preferred method, the anisotropic diffusion film is manufactured by a method in which a resin constituting a continuous phase and a resin constituting a dispersed phase are melt-extruded and formed into a film while taking over. More specifically, the orientation treatment of the dispersed phase may be performed by, for example, a method of uniaxially stretching an extruded sheet, but a method of forming a film while drawing the extruded sheet, a solution blending of each of the above components, A method of forming a film by a casting method or the like is preferable.
[0066]
In the film forming, the melting temperature of the resin is a temperature equal to or higher than the melting point of the resin component (continuous phase resin, dispersed phase resin), for example, 150 to 290 ° C, preferably about 200 to 260 ° C. The draw ratio (draw magnification) is, for example, about 1.5 to 30 times, preferably about 2 to 15 times, and more preferably about 3 to 10 times. Further, although the stretching treatment is not necessary, when performing the stretching treatment, the stretching ratio is, for example, about 1.1 to 30 times (for example, about 1.5 to 20 times), preferably about 1.5 to 10 times. (For example, about 2 to 10 times).
[0067]
In the case where draw and stretching are combined, the draw ratio may be, for example, about 2 to 10 times, preferably about 2 to 5 times, and the draw ratio is, for example, about 1.1 to 10 times. (For example, about 1.5 to 10 times), preferably about 2 to 10 times.
[0068]
In order to suppress an increase in birefringence while controlling the aspect ratio of the dispersed phase, a plurality of pairs of rolls (two rolls) facing each other are arranged in a plurality of lines (for example, two lines), and each of the two rolls is arranged in parallel. A film is stretched by inserting the film between the two rolls on the feeding side and the two rolls on the feeding side while increasing the film feeding speed on the feeding side from the feeding side (roll). Stretching), a method of inserting a film between a pair of rolls facing each other, and rolling the film by roll pressure (roll rolling). In particular, according to roll rolling, not only non-crystalline resin but also crystalline resin can be easily stretched.
[0069]
The pressure of the roll rolling is, for example, 1 × 10 ⁴ ~ 1 × 10 ⁷ N / m (about 0.01 to 10 t / cm), preferably 1 × 10 ⁵ ~ 1 × 10 ⁷ N / m (about 0.1 to 10 t / cm). Roll rolling can be performed, for example, at a thickness reduction rate (reduction rate) of about 0.9 to 0.1, preferably about 0.77 to 0.2, and more preferably about 0.67 to 0.33.
[0070]
The alignment treatment temperature is, for example, about 100 to 200 ° C. (110 to 200 ° C.), and preferably about 110 to 180 ° C. (130 to 180 ° C.). In addition, the temperature of the roll rolling may be lower than or equal to the melting point of the resin when the continuous phase resin is a crystalline resin, and may be a temperature in the vicinity of the melting point, or lower than the glass transition temperature when the continuous phase resin is an amorphous resin. It may be a temperature near the glass transition temperature.
[0071]
[Use of anisotropic diffusion film]
Although the anisotropic diffusion film of the present invention imparts anisotropic scattering to transmitted light, the member itself is optically low in anisotropy and isotropic, so light transmission and reflection are involved. It can be used as various optical members. For example, it can be used not only as a light diffusion film for imparting light diffusion (particularly anisotropic light diffusion) to transmitted light or reflected light, but also as a substrate constituting a functional element. In particular, a touch panel (particularly a resistive touch panel) that is used in combination with a pair of electrode substrates that form a liquid crystal cell and is used in combination with the liquid crystal cell and that detects a contact position using electrical characteristics, dielectric characteristics, and the like. It can be used as a pair of electrode substrates. When the above-mentioned electrode substrate is used for such a functional element, it is not necessary to adjust the direction of the substrate with respect to the alignment direction or the optical axis of the liquid crystal or the liquid crystal cell because of low birefringence.
[0072]
Such an electrode substrate usually comprises the anisotropic diffusion film and a transparent conductive layer formed on at least one surface of the diffusion film, and forms a conductive film. Further, at least one of the pair of substrates disposed opposite to each other is formed of the conductive film. The electrode surfaces of the conductive films may be formed on the inner surface or the outer surface of the substrates facing each other, depending on the operation or function of the functional element. Further, the electrode may be formed on the entire surface of the anisotropic diffusion film, or may be formed in a dot shape, a strap shape, a matrix (or lattice) shape, or the like. Note that the electrode can be generally formed of a transparent conductive agent (for example, a conductive metal oxide such as tin oxide / indium ITO or the like) so as not to impair the transparency.
[0073]
Hereinafter, the use of the conductive film of the present invention will be described in detail with reference to the accompanying drawings. 1 and 2 are schematic sectional views of a touch panel type liquid crystal display device of the present invention.
[0074]
FIG. 1 is a schematic sectional view showing an example of a normal touch panel type liquid crystal display device. The liquid crystal display device 1 of FIG. 1 includes a pair of conductive electrodes 2a and 2b on the front side (liquid crystal display side) of a liquid crystal cell including polarizers 3 and 5 and a pair of electrodes 4a and 4b. A touch panel unit is provided, and light is emitted from the back surface by the backlight unit 6. The backlight unit 6 is usually a combined body such as a light source, a light guide plate, a diffusion plate, and a prism sheet. In the present invention, a resistive touch panel substrate formed of the conductive film can be used as at least one of the conductive electrodes 2a and 2b.
[0075]
FIG. 2 is a schematic sectional view showing an example of the inner type touch panel type liquid crystal display device. The liquid crystal display device 11 in FIG. 2 includes a polarizing plate 12 and a pair of conductive electrodes 13a and 13b on the front side (liquid crystal display side) of a liquid crystal cell including a polarizing plate 15 and a pair of electrodes 14a and 14b. The configured touch panel unit is provided, and light is emitted from the backlight surface by the backlight unit 16. In the present invention, a resistive touch panel substrate made of the conductive film can be used as at least one of the conductive electrodes 13a and 13b. The normal touch panel type liquid crystal display device shown in FIG. 1 is completed by arranging a separately manufactured touch panel portion on the already manufactured liquid crystal cell surface, whereas the inner type touch panel shown in FIG. 2 is completed. In the type display device, a polarizing plate exists on the front side of the touch panel (there is no polarizing plate between the liquid crystal cell and the touch panel), and the liquid crystal cell and the touch panel are integrated. With such a structure, in the inner type, reflection of light generated between the touch panel portion and the liquid crystal cell is suppressed, and the quality of the liquid crystal display is improved.
[0076]
The anisotropic diffusion film of the present invention is useful as a component of a surface light source device or a liquid crystal display device. That is, when the anisotropic diffusion film is provided on the emission surface side of the surface light source unit of the surface light source device, the object to be irradiated can be illuminated with uniform light while imparting anisotropic diffusion to transmitted light. In addition, the liquid crystal display surface can be uniformly illuminated with high luminance, and a clear display can be achieved with a wide viewing angle.
[0077]
Hereinafter, the use of the anisotropic diffusion film of the present invention will be described in detail with reference to the accompanying drawings. FIG. 3 is a schematic sectional view showing an example of a liquid crystal display device using the anisotropic diffusion film of the present invention as an electrode substrate of a liquid crystal cell. FIG. 4 is a schematic cross-sectional view showing an example of a liquid crystal display device using the anisotropic diffusion film of the present invention as a backlight diffusion sheet. As a more specific example, FIG. 5 is a schematic exploded perspective view showing an example of the surface light source device and the transmission type liquid crystal display device of the present invention.
[0078]
In FIG. 3, a liquid crystal display device 21 includes a liquid crystal cell including a pair of polarizing plates 22 and 24, electrodes 23a and 23b formed on opposing surfaces of the polarizing plate, and irradiates the liquid crystal cell from the back side. And a backlight unit 25 for performing the operation. In the present invention, the anisotropic diffusion film can be used as at least one electrode substrate of the conductive electrodes 23a and 23b.
[0079]
In FIG. 4, a liquid crystal display device 31 includes a liquid crystal cell including a pair of polarizing plates 32 and 34, electrodes 33a and 33b formed on opposing surfaces of the polarizing plate, and illuminates the liquid crystal cell from the back side. And a tubular light source 38b. Further, the display device 31 is provided with a light guide plate 38a disposed adjacent to the light source 38b in a direction substantially parallel to the axial direction thereof, and a light guide plate 38a disposed on the back side of the light guide plate 38a. A reflection sheet 39 for reflecting light in the front direction (display side) and guiding the light to the liquid crystal cell. The light from the light source 38b enters from the side surface of the light guide plate 38a and exits from the flat exit surface to illuminate the liquid crystal cell. Further, a diffusion film 37 for diffusing light to uniformly illuminate the liquid crystal cell is disposed between the light guide plate 38a and the liquid crystal cell. The protective film 35 is laminated on the front side of the prism sheet 36. In the present invention, the anisotropic diffusion film can be used as at least one of the diffusion film 37 and the protection film 35.
[0080]
In FIG. 5, a liquid crystal display device 41 is provided with a liquid crystal display unit (or liquid crystal display panel) 42 as an object to be irradiated provided with a liquid crystal cell in which liquid crystal is sealed, and is disposed on the back side of the display unit (or panel). And a surface light source unit 43 for illuminating the display unit 42.
[0081]
The surface light source unit 43 is composed of a tubular light source 44 such as a fluorescent tube (cold cathode tube) and a translucent plate-like member, and is disposed adjacent to the tubular light source in such a manner that its side portions are substantially parallel to each other in the axial direction. A light guide member (light guide plate) 45, a reflection mirror 46 b disposed on a side of the tubular light source 44 and reflecting light from the light source to a side surface of the light guide member 45, and the light guide member A reflection member or a reflection layer 46a is provided on the back side of the light source 45 and reflects the light from the tubular light source 44 forward (toward the display unit) and guides the light to the display unit 42. The light from the tubular light source 44 enters from the side surface of the light guide member 45 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 44 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 44 is not uniform. Therefore, even if light is emitted from the emission surface through the light guide member 45, the display unit 42 cannot be uniformly illuminated.
[0082]
FIG. 6 is a conceptual diagram for explaining anisotropy of light diffusion. As shown in FIG. 6, the anisotropic light-diffusing film 47 is composed of a continuous phase 47a made of resin and an anisotropic dispersed phase 47b dispersed in this continuous phase. In the scattering characteristic F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F, as described above, the anisotropy of light diffusion indicates that the scattering characteristic in the X-axis direction of the film is Fx (θ), When the scattering characteristic in the Y-axis direction orthogonal to the X-axis direction is Fy (θ), it is expressed as Fy (θ) / Fx (θ), and Fy (θ)> Fx (θ). The X-axis direction of the anisotropic light-diffusing film 47 is usually the long-axis direction of the dispersed phase 47b.
[0083]
Therefore, in the present invention, an anisotropic diffusion film is provided on the exit surface side (the light exit surface side of the surface light source unit) of the light guide member 45 with respect to the axial direction (X-axis direction) of the tubular light source 44 of the surface light source unit. The X-axis direction of 47 (the major axis direction of the dispersed phase) is arranged substantially parallel or coincident. Further, the anisotropic diffusion film 47 and a prism sheet 48 in which minute prisms having a triangular cross section are formed in parallel in a predetermined direction are sequentially laminated. Therefore, the light from the tubular light source 44 is diffused and uniformized by the diffusion film 47 via the light guide member 45, and is collected forward by the prism sheet 48 to increase the luminance and move the display unit 42 from the back surface. Can be illuminated. In particular, in the anisotropic diffusion film having high light scattering anisotropy, the angle dependence of scattering in a predetermined direction and the angle dependence of luminance can be further reduced.
[0084]
In the present invention, the surface light source unit may be disposed in an optical path of light emitted from the light emitting surface (light emitting surface), that is, on the light emitting surface (light emitting surface) side of the surface light source unit. , And need not be laminated on the emission surface of the surface light source unit. The X-axis direction of the anisotropic light-diffusing film does not need to completely match the axial direction (X-axis direction) of the tubular light source of the surface light source unit. It may be arranged facing.
[0085]
The anisotropic diffusion film does not need to be used in combination with the prism sheet, but the prism sheet is useful for collecting diffused light and illuminating the display unit. Further, even when the prism sheet and the light diffusion sheet are used in combination, the positional relationship between the anisotropic diffusion film and the prism sheet is not particularly limited. For example, the light diffusion film is located downstream of the optical path from the prism sheet. May be disposed on the upstream side or on the upstream side. Further, on the back surface of the light guide member (light guide plate), not only the reflection layer or the like but also various reflection means may be formed.
[0086]
As described above, the transmissive display device (particularly, transmissive liquid crystal display device) of the present invention includes a display unit (such as a liquid crystal display unit) and the surface light source unit for illuminating the display unit. . In this device, the anisotropic light-diffusing film may be arranged in various directions, but when the left-right direction of the display surface (liquid crystal display surface) is defined as the Y-axis, It is preferable that the anisotropic light-diffusing film is disposed along or coincident with the Y-axis (main light scattering direction). Note that the Y-axis direction of the anisotropic light-diffusing film does not need to completely coincide with the left-right direction (Y-axis direction) of the display unit. It may be provided. By disposing the anisotropic light diffusion film in such a direction, the luminance distribution can be made uniform and the angle dependence of the luminance on the display surface can be reduced, so that the luminance in the horizontal direction (horizontal direction) can be made uniform.
[0087]
In the transmission type liquid crystal display device provided with a light source for illuminating the display surface from the back surface, the light source of the liquid crystal display device is not limited to the tubular light source adjacent to the side surface of the light guide plate, but a plurality of light sources arranged in parallel with each other. It may be constituted by a tubular light source or the like, and the shape of the light source is not limited to a tubular shape. Further, the liquid crystal display device of the present invention is not limited to the transmissive liquid crystal display device, but may be a reflective liquid crystal display device that illuminates a display surface by taking in external light or natural light and reflecting the light by a reflector. Further, if necessary, the liquid crystal display device may include a polarizing plate or a retardation plate.
[0088]
【The invention's effect】
In the present invention, since the diffusion film has low birefringence and anisotropy with respect to light scattering, display quality can be improved while maintaining anisotropic light diffusion in a surface light source device or a liquid crystal display device. Further, when it has conductivity, it is useful as a transparent substrate in a functional element such as a liquid crystal cell or a touch panel.
[0089]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[0090]
The characteristics of the light diffusion films used in the examples and comparative examples, and the surface light source devices and transmission type liquid crystal display devices using the same were evaluated according to the following methods.
[0091]
[Retardation R]
At a wavelength of 550 nm, a retardation R = Δn × d (nm) based on the refractive index difference Δn between the X-axis direction (the film taking direction) and the Y-axis direction of the anisotropic film and the thickness d was determined.
[0092]
[anisotropy]
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 is Fy (θ). Fy (θ) / Fx (θ) when θ = 18 ° was obtained.
[0093]
Anisotropy: Of Fy (θ) / Fx (θ), describe the value of θ = 18 °
Further, in the surface light source device and the transmission type liquid crystal display device, the ratio of Fx (θ) when the scattering angle θ = 6 ° to Fy (θ) when the scattering angle θ = 2 ° was also obtained.
[0094]
[Film forming property]
The film forming property was evaluated according to the following criteria.
[0095]
：: stable melt film formation
△: Melt film formation is somewhat unstable
X: Melt film cannot be formed.
[0096]
[Front luminance]
With respect to the surface light source device and the transmission type liquid crystal display device shown in FIG. 5, the front luminance was measured by placing a luminance meter (LS-110, manufactured by MINOLTA) in front of the surface light source device and the transmission type liquid crystal display device.
[0097]
Example 1
95 parts by weight of a cyclic polyolefin resin (1060R, manufactured by Nippon Zeon Co., Ltd., refractive index: 1.53) as a continuous phase resin, and GPPS (general polystyrene resin, GPPS # 30 manufactured by Daicel Chemical Industries, Ltd., refraction) as a dispersed phase resin (Ratio 1.589) 5 parts by weight. The difference between the refractive indices of both resins is 0.059.
[0098]
The continuous phase resin and the dispersed phase resin were dried at 70 ° C. for about 4 hours and kneaded with a Banbury mixer. The kneaded product was melted at about 240 ° C. by an extruder, and extruded from a T-die at a draw ratio of about 6 times to a cooling drum having a surface temperature of 80 ° C. (melt film forming). Although this film formation was apt to cause thickness variation and was somewhat unstable, the thickness of the obtained film was about 150 μm. When the film was observed with a scanning electron microscope (SEM), the dispersed phase was in the form of a rugby ball. In the shape, the winding direction of the film was the major axis direction of the rugby ball, the length was about 10 μm, and the minor axis direction perpendicular thereto was about 1 μm. When the light scattering and the anisotropy of the obtained film were measured, as shown in Table 1, the film had a sufficient anisotropy and a very small retardation.
[0099]
Comparative Example 1
95 parts by weight of PP (polypropylene, F133 manufactured by Grand Polymer Co., Ltd., refractive index: 1.503) as a continuous phase resin, and GPPS (general-purpose polystyrene resin, GPPS # 30 manufactured by Daicel Chemical Industries, Ltd., refraction) as a dispersed phase resin (Ratio 1.589) 5 parts by weight. The difference between the refractive indices of both resins is 0.086.
[0100]
The continuous phase resin and the dispersed phase resin were dried at 70 ° C. for about 4 hours and kneaded with a Banbury mixer. The kneaded product was melted at about 240 ° C. using an extruder, and extruded from a T-die at a draw ratio of about 3 times onto a cooling drum having a surface temperature of 80 ° C. (melt film forming). Although this film formation was apt to cause variation in thickness and was somewhat unstable, the thickness of the obtained film was about 150 μm. When the film was observed with a scanning electron microscope (SEM), the dispersion layer was in the shape of a rugby ball. In the shape, the winding direction of the film was the major axis direction of the rugby ball, the length was about 20 μm, and the minor axis direction perpendicular thereto was about 0.8 μm. When the light scattering and the anisotropy of the obtained film were measured, as shown in Table 1, the film had a sufficient anisotropy, but the retardation was a large value.
[0101]
Example 2
95 parts by weight of a cyclic polyolefin resin (1060R, manufactured by Nippon Zeon Co., Ltd., refractive index: 1.53) as a continuous phase resin, and GPPS (general polystyrene resin, GPPS # 30 manufactured by Daicel Chemical Industries, Ltd., refraction) as a dispersed phase resin 4.689 parts by weight, epoxidized diene-based block copolymer resin (Epofriend AT202, manufactured by Daicel Chemical Industries, Ltd .; styrene / butadiene = 70/30 (weight ratio) as a compatibilizer) Epoxy equivalent 750 , About 1.57) 0.4 parts by weight.
[0102]
The continuous phase resin and the dispersed phase resin were dried at 60 ° C. for about 8 hours and kneaded with a Banbury mixer. The kneaded product was melted at about 240 ° C. by an extruder, and extruded from a T-die at a draw ratio of about 6 times to a cooling drum having a surface temperature of 80 ° C. (melt film forming). This film was extremely stable, hardly varied in thickness, and the thickness of the obtained film was about 150 μm, which was fairly uniform. When the film was observed by SEM, the dispersed phase was in the form of a rugby ball. The shape was such that the winding direction of the film was the major axis direction of the rugby ball, the length was about 12 μm, and the minor axis direction perpendicular thereto was about 1 μm. When the light scattering and the anisotropy of the obtained film were measured, as shown in Table 1, the film had a sufficient anisotropy and a very small retardation.
[0103]
Example 3
The resin formulation was the same as in Example 2, and the same kneading and melt film formation were carried out, except that the draw ratio was about three times, and a raw film having a thickness of about 300 μm was formed.
[0104]
The film was uniaxially stretched by roll stretching (120 ° C., stretching ratio 2 ×) to obtain a film having a thickness of 150 μm. Observation of the film by SEM revealed that the dispersed phase had an elongated, football-like shape with an average length of the major axis (roll stretching direction) of about 40 μm and an average length of the minor axis of about 0.4 μm. When the light scattering and anisotropy of the obtained film were measured, as shown in Table 1, the film had a large anisotropy and a relatively small retardation.
[0105]
Comparative Example 2
95 parts by weight of PP (polypropylene, F133 manufactured by Grand Polymer Co., Ltd., refractive index: 1.503) as a continuous phase resin, and GPPS (general-purpose polystyrene resin, GPPS # 30 manufactured by Daicel Chemical Industries, Ltd., refraction) as a dispersed phase resin 4.689 parts by weight, epoxidized diene-based block copolymer resin (Epofriend AT202, manufactured by Daicel Chemical Industries, Ltd .; styrene / butadiene = 70/30 (weight ratio) as a compatibilizer) Epoxy equivalent 750 , About 1.57) 0.4 parts by weight.
[0106]
The kneading and melt film formation were performed in the same manner as in Comparative Example 1, except that the draw ratio was about three times, and a raw material having a thickness of about 300 μm was formed. This film was uniaxially stretched in the same manner as in Example 3 by roll stretching (however, at 110 ° C. and a stretching ratio of 2) to obtain a film having a thickness of 150 μm. Observation of the film by SEM revealed that the dispersed phase had an elongated, football-like shape with an average major axis (roll stretching direction) length of about 50 μm and an average minor axis length of about 0.4 μm. When the light scattering and the anisotropy of the obtained film were measured, as shown in Table 1, the film had a large anisotropy and a very large retardation.
[0107]
Example 4
The cyclic polyolefin resin of Example 2 was 1600R manufactured by Nippon Zeon Co., Ltd. Other than that, a melt film was formed in the same manner as in Example 2 to obtain a film having the same draw ratio of 6 and a thickness of about 150 μm. Since 1600R is a resin having a high glass transition temperature, the obtained film showed a hard sheet shape.
[0108]
The continuous phase resin and the dispersed phase resin were dried at 70 ° C. for about 4 hours and kneaded with a Banbury mixer. The kneaded product was melted at about 240 ° C. by an extruder, and extruded from a T-die at a draw ratio of about 6 times to a cooling drum having a surface temperature of 80 ° C. (melt film forming). Although this film formation was apt to cause thickness variation and was somewhat unstable, the thickness of the obtained film was about 150 μm. When the film was observed by SEM, the dispersed phase was in the form of a rugby ball. In the shape, the winding direction of the film was the major axis direction of the rugby ball, the length was about 10 μm, and the minor axis direction perpendicular thereto was about 1 μm. When the light scattering and the anisotropy of the obtained film were measured, as shown in Table 1, the film had a sufficient anisotropy and a very small retardation.
[0109]
Table 1 summarizes the results of the examples and comparative examples.
[0110]
[Table 1]

[0111]
Example 5
In the surface light source device and the transmission type liquid crystal display device shown in FIG. 5, the anisotropic diffusion film 47 using the film obtained in Example 1 was used as the surface light source device and the transmission type liquid crystal display device. Was measured. Table 2 shows the results.
[0112]
Comparative Example 3
In the surface light source device and the transmission type liquid crystal display device shown in FIG. 5, the anisotropy and the front luminance of the surface light source device and the transmission type liquid crystal display device using the film obtained in Comparative Example 1 as the anisotropic diffusion film 47 are shown. Was measured. Table 2 shows the results.
[0113]
[Table 2]

[0114]
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing one example of a touch panel type liquid crystal display device of the present invention.
FIG. 2 is a schematic sectional view showing an example of an inner-type touch panel type liquid crystal display device of the present invention.
FIG. 3 is a schematic sectional view showing an example of a liquid crystal display device using the anisotropic diffusion film of the present invention as an electrode substrate of a liquid crystal cell.
FIG. 4 is a schematic sectional view showing an example of a liquid crystal display device using the anisotropic diffusion film of the present invention as a backlight diffusion sheet.
FIG. 5 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.
FIG. 6 is a conceptual diagram for explaining anisotropic scattering of a light diffusion film.
[Explanation of symbols]
1, 41: liquid crystal display device
42 ... Liquid crystal display unit
43… Surface light source unit
44 ... Tube light source
45 ... Light guide member
46a: reflective member or reflective layer
47 ... Anisotropic diffusion film
48 ... Prism sheet
47a: continuous phase
47b: Dispersed phase

Claims (18)

A diffusion film composed of a diffusion layer capable of scattering incident light in the traveling direction of light, and having a scattering characteristic F (θ) indicating a relationship between a scattering angle θ and a scattered light intensity F, in the X-axis direction of the film. When the scattering characteristic is Fx (θ) and the scattering characteristic in the Y-axis direction is Fy (θ), Fy (θ) / Fx (θ)> 1.01 is satisfied in the range of the scattering angle θ = 4 to 30 °. An anisotropic diffusion film having anisotropy and having a retardation R = Δnxd based on a refractive index difference Δn between the X-axis direction and the Y-axis direction and a thickness d of 50 nm or less. 2. The anisotropic diffusion film according to claim 1, wherein the diffusion layer is composed of a continuous phase and a dispersed phase having different refractive indexes, and the continuous phase is composed of a transparent resin having a low intrinsic birefringence. 3. The anisotropic diffusion film according to claim 2, wherein the average aspect ratio of the dispersed phase is larger than 1, and the major axis direction of the dispersed phase is oriented in the direction in which the film is taken. The anisotropic diffusion film according to claim 2, wherein the continuous phase is composed of a cyclic polyolefin resin. A continuous phase composed of a cyclic polyolefin-based resin, and a non-crystalline polyester, a (meth) acrylic-based resin, a styrene-based resin, and poly (4-methylpentene-1) dispersed in a particulate form in the continuous phase. The anisotropic diffusion film according to claim 2, comprising a dispersed phase composed of a transparent resin selected from a series resin. The anisotropic diffusion film according to any one of claims 2 to 5, wherein the diffusion layer further contains a compatibilizer for the continuous phase and the dispersed phase. The anisotropic diffusion film according to claim 6, wherein the compatibilizer is an epoxidized diene-based block copolymer. The ratio (weight ratio) between the continuous phase and the dispersed phase is the former / latter = 99/1 to 50/50, and the ratio (weight ratio) between the dispersed phase and the compatibilizer is the former / latter = 99/1 to 50/50. The anisotropic diffusion film according to claim 6 or 7, wherein the ratio is / 50. The anisotropic diffusion film according to claim 1, wherein at least one surface of the diffusion layer is covered with a transparent resin layer. The method for producing an anisotropic diffusion film according to claim 1, wherein the resin constituting the continuous phase and the resin constituting the dispersed phase are melt-extruded and formed while taking off the film. A conductive film having a transparent conductive layer formed on at least one surface of the anisotropic diffusion film according to claim 1. A substrate for a resistive touch panel, comprising: a pair of substrates disposed to face each other and constituting a functional element, wherein at least one of the substrates is composed of the conductive film according to claim 11. A touch panel comprising the touch panel substrate according to claim 12, wherein the touch surface is formed of a polarizing plate. A surface light source device, wherein the anisotropic diffusion film according to claim 1 is disposed on an emission surface side of the surface light source unit. A liquid crystal display device comprising the anisotropic diffusion film according to claim 1. A liquid crystal display device comprising the conductive film according to claim 11 as an electrode substrate of a liquid crystal cell. A liquid crystal display device comprising: two polarizing plates; and the anisotropic diffusion film according to claim 1 disposed between the two polarizing plates. A transmission type liquid crystal display device comprising the surface light source device according to claim 14.

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