JP4050564B2 - Method for producing anisotropic light scattering sheet - Google Patents

Description

【００８５】
表１から明らかなように、実施例のシートは、ドローにより製膜するだけでも分散相が異方的形状に変形され、Ｘ軸方向の散乱光の広がりが大きく、比較例１のシートに比べて高い異方性を示した。また、シートに球状粒子が存在する場合（実施例２及び３）には、Ｙ軸方向の半値角があまり変化しないのに対し、Ｘ軸方向の半値角は大きくなり、Ｘ軸方向の散乱光の広がりが増大し、さらに高い異方性を示した。さらに、実施例のシートでは、ドローにより製膜後、圧延工程を経た比較例２のシート並みの散乱異方性を示し、二次工程として圧延処理することなく、高い散乱異方性を有するシートを製造できた。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light scattering sheet having anisotropy and a method for producing the same.
[0002]
[Prior art]
Cellulose derivatives such as cellulose acetate are excellent film materials not only in optical properties such as transparency and gloss, but also in thermal properties such as high melting point and heat resistance, low thermal expansion coefficient and heat shrinkage. is there. In general, the cellulose acetate film is close to the thermal decomposition temperature and the melting temperature, and also has a high melting temperature. Therefore, the cellulose acetate film is not suitable for a molding method that requires a melt-kneading process such as an extrusion molding method. It is film-formed.
[0003]
On the other hand, in JP-A-4-314522, a transparent material having an anisotropic shape in a transparent matrix and having a refractive index different from that of the transparent matrix is arranged in a uniform manner in a positional relationship in which they are regularly translated. An anisotropic light scattering material characterized by being dispersed is disclosed. In this document, as a method of dispersing a transparent substance having an anisotropic shape and the transparent substance in a transparent matrix, a transparent resin constituting the transparent matrix and a transparent resin having a refractive index different from that of the transparent matrix are kneaded. A method is described in which the resulting composition is extruded and then stretched uniaxially. By this method, the transparent resin having an isotropic shape at the kneading stage is transformed into a spheroid anisotropic shape having a major axis in the stretching direction and dispersed in the transparent matrix.
[0004]
However, in this method, a drawing process is required to deform the dispersed phase into an anisotropic shape. Also by the above method, a combination of resins constituting the continuous phase (matrix) and the dispersed phase (for example, when the melt viscosity of the resin constituting the continuous phase and the resin constituting the dispersed phase is close, The resin constituting the dispersed phase may not be sufficiently deformed into an anisotropic shape depending on the case where the resin constituting the resin has a low melt viscosity. Furthermore, in this method, since the drawing process is performed, there is a possibility that the optical characteristics of the molded body are deteriorated (for example, the birefringence is increased).
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an anisotropic light scattering sheet having excellent optical characteristics and thermal characteristics in a simple molding process and a method for producing the same, without performing a high degree of orientation treatment (for example, stretching treatment). It is to provide.
[0006]
Another object of the present invention is to provide an anisotropic light scattering sheet that can maintain high anisotropy even when a wide range of thermoplastic resins are used as the dispersed phase, and a method for producing the same.
[0007]
Still another object of the present invention is to provide an anisotropic light scattering sheet that can be molded without degrading optical characteristics and thermal characteristics in the molding step, and a method for producing the same.
[0008]
[Means for Solving the Problems]
As a result of intensive investigations to achieve the above-mentioned problems, the inventors of the present invention have formed the dispersed phase into an anisotropic shape without performing a high degree of orientation treatment by constituting the continuous phase with a plasticized cellulose derivative. It was found that an anisotropic light scattering sheet having excellent optical properties can be obtained easily and efficiently, and the present invention was completed.
[0009]
That is, the anisotropic light scattering sheet of the present invention is composed of a cellulose derivative that constitutes a continuous phase and is plasticized, and a thermoplastic resin that has a refractive index different from that of the cellulose derivative and constitutes a dispersed phase. The dispersed phase has an anisotropic shape.
[0010]
The cellulose derivative may be a cellulose ester (in particular, at least one selected from cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate). Moreover, 1-3 may be sufficient as the average substitution degree of the said cellulose ester.
[0011]
The thermoplastic resin may be at least one selected from an olefin resin, a styrene resin, a (meth) acrylic resin, a polyester resin, and a polycarbonate resin.
[0012]
The cellulose derivative is a phthalate ester, C _6-12 C of aliphatic dicarboxylic acid ester, phosphoric acid ester and polyhydric alcohol _2-4 It may be plasticized with at least one plasticizer selected from alkyl carboxylic acid esters.
[0013]
In the anisotropic light scattering sheet, the ratio between the cellulose derivative and the thermoplastic resin may be the former / the latter (weight ratio) = 99/1 to 50/50, and the average aspect ratio of the dispersed phase is About 3 to 1000, the average length of the minor axis of the dispersed phase may be 10 μm or less.
[0014]
The present invention is to melt and knead a resin composition composed of a plasticized cellulose derivative and a thermoplastic resin having a refractive index different from that of the cellulose derivative, to form a film while drawing the anisotropic light scattering Including a method of manufacturing a sheet.
[0015]
In the draw, the draw ratio may be about 2 to 10 times.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
[Resin composition]
The anisotropic light-scattering sheet of the present invention is a resin comprising a continuous cellulose-plasticized cellulose derivative and a thermoplastic resin having a refractive index different from that of the cellulose derivative and constituting a dispersed phase. The composition can be produced as a molding material. In the resin composition, the dispersed phase and the continuous phase are usually incompatible.
[0017]
Examples of the cellulose derivative include cellulose esters, cellulose carbamates, and cellulose ethers. You may use a cellulose derivative individually or in combination of 2 or more types.
[0018]
Examples of cellulose esters include aliphatic organic acid esters (cellulose C such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, and cellulose acetate butyrate). _2-6 Alkyl carboxylic acid ester; alkyl cellulose ester such as acetyl alkyl cellulose; haloalkyl cellulose ester such as dichloromethyl cellulose ester, trichloromethyl cellulose ester and trifluoromethyl cellulose ester), aromatic organic acid ester (cellulose phthalate, cellulose benzoate, cellulose-4- C such as methylbenzoate _7-12 Organic acid esters such as aromatic carboxylic acid esters); inorganic acid esters such as cellulose phosphate and cellulose sulfate; and mixed acid esters of organic and inorganic acids.
[0019]
Examples of cellulose carbamates include cellulose aryl carbamates (such as cellulose phenyl carbamate) and cellulose ether carbamates (such as ethyl cellulose phenyl carbamate).
[0020]
Examples of cellulose ethers include cyanoalkyl cellulose (such as cyanoethyl cellulose), C _1-10 Alkylcellulose (C such as methylcellulose and ethylcellulose) _1-6 Alkyl cellulose, etc.), aralkyl cellulose (benzyl cellulose, etc.) _6-12 Aryl-C _1-4 Alkyl cellulose, etc.).
[0021]
Preferred cellulose derivatives include cellulose esters having at least an acetyl group among cellulose esters, for example, cellulose acetate (cellulose monoacetate, cellulose diacetate, cellulose triacetate), internally plasticized cellulose derivatives [acetyl C _3-6 Acyl cellulose (cellulose acetate propionate, cellulose acetate butyrate, etc.).
[0022]
The average degree of substitution of the cellulose ester can be selected according to the use of the resin composition, for example, 1 to 3, preferably 1.3 to 3, more preferably 1.5 to 3 (particularly 2 to 3). Degree. The acetyl C _3-6 In acyl cellulose, acetyl group and C _3-6 The ratio with the acyl group is, for example, the former / the latter (molar ratio) = about 90/10 to 5/95, preferably about 70/30 to 10/90, and more preferably about 50/50 to 15/85. .
[0023]
In the cellulose derivative, the average degree of polymerization of the cellulose derivative is not particularly limited, and is, for example, about 50 to 8000, preferably about 100 to 7000, and more preferably about 200 to 6000.
[0024]
As plasticization of the cellulose derivative, (a) cellulose acetate, C softener such as propionate group and butyrate group _3-6 A method of introducing an acyl group and internal plasticizing, (b) a method of adding a plasticizer to the cellulose derivative and external plasticizing, (c) a method of combining these methods (a) and (b), etc. Can be mentioned.
[0025]
The plasticizer is not particularly limited as long as the cellulose derivative can be plasticized. For example, phthalate ester, aliphatic ester, phosphate ester, epoxy derivative, polyhydric alcohol C _2-4 Examples thereof include alkyl carboxylic acid esters. These plasticizers may be used alone or in combination of two or more.
[0026]
Examples of phthalic acid esters include di-C such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, di (2-ethylhexyl) phthalate, dinonyl phthalate, and diisodecyl phthalate. _1-10 Di-C such as alkyl phthalate and dicyclohexyl phthalate _6-8 Examples thereof include alkyl-aralkyl phthalates such as cycloalkyl phthalate and butyl benzyl phthalate, and di (methoxyethyl) phthalate.
[0027]
Aliphatic esters include adipic acid diesters (dioctyl adipate, di (2-ethylhexyl) adipate, etc.), azelaic acid diesters (dioctyl azelate, di (2-ethylhexyl) azelate, etc.), sebacic acid diesters (dibutyl sebacate, dioctyl, etc.) C such as sebacate, di (2-ethylhexyl) sebacate), citric acid triester (acetyl triester such as triethyl acetyl citrate and tributyl acetyl citrate) _6-12 Aliphatic di- or tricarboxylic acid ester (C _6-12 Aliphatic di- or tricarboxylic acid C _2-8 Alkyl ester), methylacetylricinoleate and the like.
[0028]
Examples of phosphate esters include trialkyl phosphates [triethyl phosphate, tributyl phosphate, trioctyl phosphate, _1-10 Alkyl phosphate; halogen-containing tri-C such as trichloroethyl phosphate _1-10 Alkyl phosphate etc.], triaryl phosphate [triphenyl phosphate, tricresyl phosphate, tris (isopropylphenyl) phosphate, cresyl diphenyl phosphate, etc. _6-10 Aryl phosphate, etc.], alkyl-diaryl phosphate (octyl diphenyl phosphate, etc.), tri (butoxyethyl) phosphate, etc.
[0029]
Examples of the epoxy derivative include epoxidized fatty acid esters (alkyl epoxy stearate, diisodecyl-4,5-epoxytetrahydrophthalate, etc.) and the like.
[0030]
C of polyhydric alcohol _2-4 Examples of alkyl carboxylic acid esters include mono- or di-C of glycols (ethylene glycol, triethylene glycol, polyethylene glycol, etc.) _2-4 Glycerin C such as alkyl carboxylic acid esters (triethylene glycol diacetate, triethylene glycol dipropionate, etc.) and triacetin _2-4 Alkyl carboxylic acid ester, etc.).
[0031]
Other plasticizers include oligomer type plasticizers such as polyester.
[0032]
Preferred plasticizers include phthalate esters (particularly di-C such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate). _1-8 Alkyl phthalate), C _6-10 Alkanedi or tricarboxylic acid C _2-10 Alkyl esters (especially sebacic acid diesters such as dibutyl sebacate, citric acid triesters such as triethyl acetyl citrate), phosphoric acid esters (especially triaryl phosphates such as triphenyl phosphate), polyhydric alcohol acetates (such as triacetin) ).
[0033]
The ratio between the cellulose derivative and the plasticizer can be selected according to the type of the cellulose derivative and the like. For example, the former / the latter (weight ratio) = about 100/0 to 50/50, preferably 100/0 to 60/40. The degree is more preferably about 100/0 to 70/30.
[0034]
As the thermoplastic resin, a polymer having a (melting) viscosity smaller than that of the cellulose derivative and having a different refractive index can be suitably used. Since the cellulose derivative generally has a high (melt) viscosity, the thermoplastic resin constituting the dispersed phase can be selected within a wide range.
[0035]
Examples of such thermoplastic resins include olefin resins, halogen-containing resins, vinyl alcohol resins, vinyl ester resins, styrene resins, (meth) acrylic resins, polyester resins, polycarbonate resins, polyamide resins, Examples include polysulfone resins, polyphenylene resins, polyacetal resins, and thermoplastic elastomers.
[0036]
Examples of the olefin resin include C _2-6 Olefin homopolymers or copolymers (ethylene resins such as polyethylene and ethylene-propylene copolymers, polypropylene resins such as polypropylene, propylene-ethylene copolymers, propylene-butene copolymers, poly (methylpentene-1) , Propylene-methylpentene copolymer, etc.), C _2-6 Copolymers of olefins and copolymerizable monomers (ethylene- (meth) acrylic acid copolymers, ethylene- (meth) acrylic acid ester copolymers, etc.), aliphatic polycycles such as norbornene skeleton in the main chain Examples thereof include cyclic polyolefin resins containing a cyclic structure.
[0037]
Examples of halogen-containing resins include halogenated vinyl resins (homopolymers of halogen-containing monomers such as polyvinyl chloride and polyvinyl fluoride, tetrafluoroethylene-hexafluoropropylene copolymers, tetrafluoroethylene-perfluoroalkyl vinyl ethers). Halogen-containing monomers such as copolymers such as copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride- (meth) acrylic acid ester copolymers, tetrafluoroethylene-ethylene copolymers, etc. Copolymers with other copolymerizable monomers), vinylidene halide resins (polyvinylidene chloride copolymer, polyvinylidene fluoride, or other copolymerizable properties with vinylidene halide monomers) And a copolymer with a monomer).
[0038]
Examples of the vinyl alcohol resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Examples of vinyl ester resins include vinyl ester monomers alone or copolymers (polyvinyl acetate, etc.), vinyl ester monomers and copolymerizable monomers (ethylene-vinyl acetate copolymer). Polymer, vinyl acetate-vinyl chloride copolymer, vinyl acetate- (meth) acrylate copolymer, etc.).
[0039]
As the styrene resin, a styrene monomer alone or a copolymer (polystyrene, styrene-α-methylstyrene copolymer, etc.), a copolymer of a styrene monomer and another copolymerizable monomer Examples thereof include styrene-acrylonitrile copolymer (AS resin), styrene- (meth) acrylic acid ester copolymer, styrene-maleic anhydride copolymer, and the like.
[0040]
Examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as poly (meth) methyl acrylate, methyl methacrylate- (meth) acrylic acid copolymer, and methyl methacrylate- (meth) acrylic acid. Examples include ester copolymers, methyl methacrylate- (meth) acrylic acid esters- (meth) acrylic acid copolymers, (meth) acrylic acid ester-styrene copolymers (such as MS resin).
[0041]
Examples of polyester resins include homopolyesters or copolyesters (such as adipic acid) having alkylene terephthalate (ethylene terephthalate, butylene terephthalate, etc.) or alkylene naphthalate (ethylene naphthalate, butylene naphthalate, etc.) as a repeating unit. _6-12 Asymmetric aromatic dicarboxylic acids such as aliphatic dicarboxylic acid, phthalic acid, and isophthalic acid, C _2-6 Polyesters produced by the reaction of aromatic diols such as bisphenol A and aromatic dicarboxylic acids such as terephthalic acid, such as copolyesters having a copolymerization component of alkylene glycol, polyoxyalkylene glycol, bisphenol A, etc. Arylate resins), liquid crystalline polyesters, and lactones (e.g., ε-caprolactone) alone or copolymers.
[0042]
Examples of the polycarbonate-based resin include polycarbonates obtained by reacting dihydroxy compounds (such as bisphenol compounds such as bisphenol A and bisphenol S) with phosgene or carbonic acid diesters (such as dialkyl carbonates such as diphenyl carbonate and dimethyl carbonate).
Examples of polyamide resins include aliphatic polyamide (nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, etc.), aromatic polyamide [aromatic dicarboxylic acid (terephthalic acid etc.) and aliphatic diamine. Polyamides obtained by reaction with (such as hexamethylenediamine), polyamides obtained by reaction between aliphatic dicarboxylic acids (such as adipic acid) and aromatic diamines (such as metaxylylenediamine, paraxylylenediamine)], lactams (E-caprolactam or the like) homopolymer or copolymer may be mentioned. The polyamide-based resin is not limited to homopolyamide but may be copolyamide.
[0043]
Examples of the polysulfone resin include polysulfone and polyethersulfone.
[0044]
Examples of polyphenylene resins include polyphenylene oxide resins [poly (2,5-dimethyl-1,4-phenylene) oxide, poly (2,6-dimethyl-1,4-phenylene) oxide, poly (2-methyl-6). -Ethyl-1,4-phenylene) oxide, poly (2,6-di-n-propyl-1,4-phenylene) oxide, poly (2-methyl-6-chloroethyl-1,4-phenylene) oxide, etc. Homopolymers, modified polyphenylene oxide copolymers based on polyphenylene oxide blocks, modified graft copolymers in which styrene polymers are grafted onto polyphenylene oxide or copolymers thereof, etc.], polyphenylene sulfide resins ( Polyphenylene sulfide, polyphenylene sulfide ketone, polybiphenyle Sulfides, polyphenylene sulfide sulfone) and the like.
[0045]
Examples of the polyacetal resin include polyacetal (polyoxymethylene) and copolyacetal (for example, trioxane-ethylene oxide copolymer, trioxane-1,3-dioxolane copolymer).
[0046]
Examples of the thermoplastic elastomer include a hard phase such as a polyolefin-based thermoplastic elastomer, a polystyrene-based thermoplastic elastomer, a polyvinyl chloride-based thermoplastic elastomer, a polyurethane-based thermoplastic elastomer, a polyester-based thermoplastic elastomer, and a polyamide-based thermoplastic resin elastomer. A thermoplastic elastomer composed of a soft phase is exemplified.
[0047]
Preferable thermoplastic resins include olefin resins, styrene resins, (meth) acrylic resins, polyester resins, and polycarbonate resins.
[0048]
The thermoplastic resin may be a single resin or a combination of two or more resins, and may be modified (for example, rubber-modified) as necessary.
[0049]
The flowability (melt flow rate) of the thermoplastic resin is, for example, 1 to 100 g / 10 minutes, preferably 2 to 50 g / 10 minutes, more preferably 3 to 30 g at the temperature and load specified in JIS K 7210. / 10 minutes.
[0050]
The difference in refractive index between the cellulose derivative and the thermoplastic resin is, for example, 0.001 or more (for example, 0.001 to 0.3), preferably 0.01 or more (for example, 0.01 to 0.3). ), More preferably 0.03 or more (for example, 0.03 to 0.3).
[0051]
In the resin composition, the ratio between the cellulose derivative and the thermoplastic resin can be selected according to the type of the cellulose derivative, for example, the former / the latter (weight ratio) = about 99/1 to 50/50, preferably 95. / 5 to 60/40, more preferably about 95/5 to 70/30.
[0052]
The resin composition may further contain spherical particles. By appropriately adjusting the ratio between the thermoplastic resin and the spherical particles, the degree of light scattering anisotropy can be easily controlled.
[0053]
Examples of the spherical particles include heat-resistant organic particles [ultra high molecular weight (for example, number average molecular weight around 2 million) particles (for example, ultra high molecular weight polyethylene particles), crosslinked resin particles, for example, crosslinked polymethyl methacrylate, and the like. (Meth) acrylic resin particles, crosslinked styrene resin particles, crosslinked benzoguanamine resin, crosslinked silicone resin, etc.], inorganic particles (glass, silica, alumina, zirconia, etc.) and the like. These particles can be used alone or in combination of two or more. Spherical particles usually have low heat deformability and seem to retain their original shape even after sheet molding.
[0054]
The ratio of the thermoplastic resin to the spherical particles is, for example, the former / the latter (weight ratio) = about 100/0 to 50/50, preferably about 100/0 to 60/40, and more preferably 100/0 to 70. / 30 or so.
[0055]
If necessary, the resin composition may further include a compatibilizing agent and a conventional additive, for example, an antioxidant, an ultraviolet absorber, a stabilizer such as a heat stabilizer, a colorant (dye, pigment, etc.), a charging agent. You may contain an inhibitor, a flame retardant, surfactant, a filler, etc.
[0056]
The resin composition can be produced by mixing the cellulose derivative, the thermoplastic resin and, if necessary, the plasticizer. The mixing method is not particularly limited, but is usually mixed by a conventional mixing means (for example, a mixer such as a ribbon blender, a tumble mixer, a Henschel mixer, or a kneader such as an open roller, kneader, Banbury mixer, extruder). For example, a melt kneading method using a method may be used. The resin composition may be pre-dried before and after mixing.
[0057]
[Anisotropic light scattering sheet]
Since the resin composition can constitute a continuous phase with a cellulose derivative having a high molecular weight and (melt) viscosity, even if it is a wide range of thermoplastic resins, it can efficiently form an anisotropic shape by applying a shearing force. Can be dispersed as a dispersed phase. Therefore, the anisotropic light-scattering sheet of the present invention forms the resin composition using a conventional molding method (for example, a melt extrusion molding method) without performing an advanced orientation treatment such as stretching. Thus, it can be easily and efficiently produced while maintaining the excellent optical properties and thermal properties of the cellulose derivative.
[0058]
In the anisotropic light scattering sheet of the present invention, the dispersed phase has an anisotropic shape and is dispersed in the continuous phase. The anisotropic shape is not particularly limited as long as it has anisotropy, and examples thereof include a spheroid shape, a fiber shape, and a rectangular parallelepiped shape.
[0059]
The value of the aspect ratio of the dispersed phase (the ratio of the average length L of the major axis to the average length W of the minor axis (average aspect ratio, L / W)) is, for example, 3 to 1000, preferably 5 to 500, More preferably, it is about 10-300. The average length of the minor axis is 10 μm or less (for example, 0.1 to 10 μm), preferably 0.2 to 5 μm, and more preferably about 0.5 to 2 μm.
[0060]
The anisotropic phase of the dispersed phase is mainly involved in anisotropic light scattering. If the minor axis direction of the dispersed phase is the X-axis direction and the direction perpendicular to the minor axis direction is the Y-axis direction, scattering in the X-axis direction is performed. High light intensity. That is, in the scattering characteristics F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F, the scattering characteristics in the X-axis direction (short axis direction of the dispersed phase) of the sheet are expressed as Fx (θ) and Y-axis direction (dispersion). The scattering characteristic in the major axis direction of the phase is F _Y When (θ), when light is incident on the sheet from the vertical direction, the scattering characteristics Fx (θ) and F _Y (Θ) is Fx (θ)> F _Y The relationship of (θ) is shown.
[0061]
Further, in the scattering characteristic F (θ), the scattering angle at which the scattering intensity is F (2) / 2 with respect to the scattering intensity F (2) when the scattering angle θ = 2 ° is the half-value angle θ. _H Then, the larger the half-value angle, the larger the scattering spread, and the half-value angle θ in the X-axis direction _{X, H} And the half-value angle θ in the Y-axis direction _{Y, H} It shows that the light scattering anisotropy of a specific axial direction is so large that the variation of this is large. In the present invention, the spread in the X-axis direction is large, and the half-value angle θ in the X-axis direction _{X, H} Is, for example, about 7 or more (for example, 7 to 25), preferably about 10 or more (for example, 10 to 25).
[0062]
The total light transmittance of the anisotropic light scattering sheet is, for example, 70% or more (about 70 to 95%), preferably 75% or more (about 75 to 95%). The haze value of the anisotropic light scattering sheet is, for example, 70% or more (about 70 to 90%), preferably 80% or more (about 80 to 100%).
[0063]
The thickness of the anisotropic light scattering sheet is, for example, about 50 to 300 μm, preferably about 80 to 250 μm, and more preferably about 100 to 200 μm.
[0064]
Examples of the melt extrusion molding method include a method of melt-kneading the resin composition, extruding from a die (T die, ring die, etc.), and forming a film while drawing (drawing). Through this drawing process, the dispersed phase is more efficiently transformed into an anisotropic shape and dispersed in the continuous phase.
[0065]
In the melt extrusion molding method, the melting temperature can be adjusted according to the thermal properties (melting point, decomposition temperature, melt viscosity, etc.) of the cellulose derivative and the thermoplastic resin, the mixing ratio of the resin composition, etc. C., preferably 150 to 300.degree. C., more preferably about 170 to 250.degree.
[0066]
In the melt extrusion molding, the pressure applied to the resin composition can be appropriately selected, and is, for example, about 1 to 40 MPa, preferably 3 to 30 MPa, and more preferably about 5 to 20 MPa.
[0067]
In the draw step, the draw ratio (the clearance length of the discharge port of the extruder is t ₁ , The thickness of the sheet is t ₂ T ₁ / T ₂ Is, for example, 2 to 10 times, preferably 2 to 8 times, and more preferably about 2 to 5 times. In the resin composition, since the continuous phase is composed of a cellulose derivative having a high (melt) viscosity, the dispersed phase can be deformed with a high aspect ratio even with a relatively small draw ratio.
[0068]
The anisotropic light scattering film may be further subjected to secondary molding such as a calendering method or a stretching method, if necessary.
[0069]
According to the present invention, since the continuous phase is composed of a cellulose derivative having a high molecular weight and (melting) viscosity, the dispersed phase can be anisotropically easily and efficiently without performing an orientation treatment such as stretching. An anisotropic light-scattering sheet that can be deformed into a shape and has excellent optical properties (such as high transparency and gloss) and thermal properties (such as high heat resistance, low thermal expansion coefficient and low heat shrinkage) can be obtained. it can. Moreover, according to the anisotropic light-scattering sheet of this invention, even if it uses a wide range thermoplastic resin as a dispersed phase, the anisotropy of light scattering can be maintained to a high extent.
[0070]
The anisotropic light scattering sheet of the present invention can be used for display devices such as a transmissive liquid crystal display device, a reflective liquid crystal display device, an organic EL display device, and a projection television.
[0071]
【The invention's effect】
In the present invention, a disperse phase having an anisotropic shape can be generated by a simple molding process without performing an advanced orientation treatment such as a stretching treatment, and a different optical property and thermal properties can be obtained. An isotropic light scattering sheet can be provided. Moreover, even if a wide range of thermoplastic resins are used as the dispersed phase, high anisotropy can be maintained. Furthermore, since a stretching process or the like is not required, molding can be performed without deteriorating optical characteristics and thermal characteristics in the molding process.
[0072]
【Example】
Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.
[0073]
Example 1
As a resin constituting the continuous phase, 85 parts by weight of cellulose acetate propionate CAP (manufactured by Eastman Chemical Co., Ltd. 307E, refractive index 1.475 acetyl group amount 6.9%, propyl group amount 39.7%), As a resin constituting the dispersed phase, 15 parts by weight of polystyrene PS (HRM63X manufactured by Toyo Styrene Co., Ltd., refractive index 1.592) was melt-kneaded at 220 ° C. to obtain a resin composition. This resin composition was melt-kneaded at 220 ° C. by an extruder, extruded from a T die, and formed while drawing at a draw ratio of 4.7 to obtain a sheet having a thickness of 150 μm.
[0074]
Example 2
As a resin constituting the continuous phase, 85 parts by weight of cellulose acetate propionate CAP (manufactured by Eastman Chemical Co., Ltd. 307E, refractive index 1.475 acetyl group amount 6.9%, propyl group amount 39.7%), As the resin constituting the dispersed phase, 12.5 parts by weight of polystyrene PS (HRM63X manufactured by Toyo Styrene Co., Ltd., refractive index 1.592) and crosslinked polymethacrylate (PMMA) (Epaster MA1004 manufactured by Nippon Shokubai Co., Ltd.) (Rate 1.492) 2.5 parts by weight were melt-kneaded at 220 ° C. to obtain a resin composition. This resin composition was melt-kneaded at 220 ° C. by an extruder, extruded from a T die, and formed while drawing at a draw ratio of 4.7 to obtain a sheet having a thickness of 150 μm.
[0075]
Example 3
Cellulose acetate propionate CAP (manufactured by Eastman Chemical Co., Ltd. 307E, refractive index 1.475, acetyl group content 6.9%, propyl group content 39.7%) 85 parts by weight, PS (manufactured by Toyo Styrene Co., Ltd.) 13.25 parts by weight of HRM63X, refractive index 1.592) and 1.25 parts by weight of cross-linked polymethyl methacrylate (PMMA) (Epester MA1004, refractive index 1.492) manufactured by Nippon Shokubai Co., Ltd. were melt kneaded at 220 ° C. Then, the film was extruded from a T-die and formed while drawing at a draw ratio of 4.7 to obtain a sheet having a thickness of 150 μm.
[0076]
Comparative Example 1
As a resin constituting the continuous phase, 85 parts by weight of polypropylene (F109BA, refractive index 1.503) manufactured by Grand Polymer Co., Ltd., and as a resin constituting the dispersed phase, PS (HRM63X manufactured by Toyo Styrene Co., Ltd., refractive index 1) .592) 13.25 parts by weight of the mixture was melt-kneaded at 220 ° C. to obtain a resin composition. This resin composition was melt kneaded at 220 ° C. with an extruder, extruded from a T-die, and formed while drawing at a draw ratio of 4.7 to obtain a sheet having a thickness of 150 μm.
[0077]
Comparative Example 2
As a resin constituting the continuous phase, 80 parts by weight of polypropylene PP (F109BA, manufactured by Grand Polymer Co., Ltd., refractive index 1.503) and as a resin constituting the dispersed phase, polystyrene PS (HRM63X, manufactured by Toyo Styrene Co., Ltd., refraction) (Rate 1.592) 19 parts by weight and 1 part by weight of an epoxidized styrene-butadiene-styrene block copolymer (ESBS) compatibilizer (refractive index 1.567) are melt-kneaded at 220 ° C. to obtain a resin composition. Obtained. This resin composition was melt kneaded at 220 ° C. with an extruder and extruded from a T-die to obtain a sheet having a draw ratio of 2.0 and a thickness of 250 μm. This sheet was rolled with a pressure roll having a roll temperature of 120 ° C. to obtain a rolled film having a plate thickness reduction rate of 48.4 and a smooth surface of 129 μm. The plate thickness reduction rate was calculated based on the following formula.
[0078]
Sheet thickness reduction rate = (H-H ₁ ) / H × 100
H: Film thickness before rolling
H ₁ : The thickness of the film after rolling.
[0079]
The total light transmittance, the haze value, the lengths of the major and minor axes of the dispersed phase, and the scattering intensity of the sheets obtained in Examples and Comparative Examples were measured as follows.
[0080]
[Total light transmittance and haze value]
The total light transmittance and haze value of the sheets obtained in Examples and Comparative Examples are measured by using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH-300A) and white light is incident from the normal direction of the sheet. Was measured.
[0081]
[Length of major axis and minor axis of dispersed phase]
In the sheets obtained in Examples and Comparative Examples, the lengths of the short axis and long axis of the dispersed phase having an anisotropic shape were measured by a scanning electron microscope (SEM), and the average length and short axis of the long axis were measured. The aspect ratio was calculated from the ratio to the average length.
[0082]
[Scattering intensity]
Laser light is irradiated from the normal direction of one surface of the sheet obtained in the example and the comparative example, and the scattering characteristic F (θ) with respect to the scattering angle θ of the transmitted light by a photo multiplier mounted on the goniometer Is a scattering characteristic F with respect to the X-axis direction [direction orthogonal to the sheet draw direction (the minor axis direction of the dispersed phase having an anisotropic shape)]. _X (Θ) and scattering characteristics F in the Y-axis direction (direction perpendicular to the X-axis) _Y (Θ) was measured. Further, as an index of sheet anisotropy (the extent of spread of scattering), the scattering angle at which the scattering intensity is F (2) / 2 with respect to the scattering intensity F (2) when the scattering angle θ = 2 °. Half-value angle θ _H It was. The larger the half-value angle, the larger the scattering spread, and the half-value angle θ in the X direction _{X, H} And the half-value angle θ in the Y direction _{Y, H} The larger the variation, the greater the anisotropy of light scattering.
[0083]
The results are shown in Table 1.
[0084]
[Table 1]

[0085]
As is clear from Table 1, in the sheet of the example, the dispersed phase is deformed into an anisotropic shape just by forming a film by drawing, and the spread of scattered light in the X-axis direction is large, compared with the sheet of Comparative Example 1. Showed high anisotropy. When spherical particles are present in the sheet (Examples 2 and 3), the half-value angle in the Y-axis direction does not change much, whereas the half-value angle in the X-axis direction becomes large, and scattered light in the X-axis direction. And the anisotropy was further increased. Furthermore, in the sheet of the example, after forming the film by drawing, the sheet exhibits a scattering anisotropy similar to that of the sheet of Comparative Example 2 that has undergone a rolling process, and has a high scattering anisotropy without being subjected to a rolling process as a secondary process. Could be manufactured.

Claims (7)

The cellulose derivative comprising a continuous phase and a plasticized cellulose derivative, and a thermoplastic resin having a refractive index different from that of the cellulose derivative and constituting a dispersed phase , wherein the plasticized cellulose derivative is acetyl C _3-6 acyl cellulose, and a method of producing an anisotropic light-scattering sheet in which the dispersed phase have a anisotropic shape an average aspect ratio of 10 to 300, wherein the plasticized cellulose derivatives, wherein A method of producing an anisotropic light-scattering sheet by melt-kneading and extruding a resin composition composed of a thermoplastic resin, forming a film without drawing while drawing at a draw ratio of 2 to 5 times. The method according to claim 1, wherein the average degree of substitution of acetyl C _3-6 acylcellulose is 1 to 3. The method according to claim 1 or 2, wherein the thermoplastic resin is at least one selected from an olefin resin, a styrene resin, a (meth) acrylic resin, a polyester resin, and a polycarbonate resin. The cellulose derivative is plasticized with at least one plasticizer selected from phthalic acid esters, C _6-12 aliphatic dicarboxylic acid esters, phosphoric acid esters and C _2-4 alkyl carboxylic acid esters of polyhydric alcohols. Item 4. The production method according to any one of Items 1 to 3. The production method according to any one of claims 1 to 4, wherein a ratio of the cellulose derivative and the thermoplastic resin is the former / the latter (weight ratio) = 99/1 to 50/50. The production method according to claim 1, wherein an average length of minor axes of the dispersed phase is 10 μm or less. The production method according to claim 1 , wherein the resin composition further contains spherical particles.