JP2022168526A - Resin composition, optical film and laminated film - Google Patents

Abstract

[Problem] To provide a resin composition that exhibits negative birefringence, has high productivity, and is highly compatible with film-forming and stretching processes, and an optical film that contains the resin composition and has excellent retardation properties and compatibility with film-forming and stretching processes. [Solution] A resin composition that contains a fumaric acid ester polymer represented by formula (1) and a dibasic acid ester. JPEG2022168526000006.jpg4943 (R1 and R2 each independently represent an alkyl group having 1 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms) [Selected Figure] Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for producing an optical film that can be suitably used as a retardation film or the like, and more particularly to an optical film that is excellent in retardation properties and suitability for film-forming and stretching processes.

Liquid crystal displays are widely used in mobile phones, computer monitors, notebook computers, and televisions as the most important display devices in the multimedia society. Many optical films are used in liquid crystal displays to improve display characteristics. In particular, optical films play a major role in improving contrast when viewed from the front or obliquely and in compensating for color tone.

A retardation film can be cited as a typical example of optical films related to liquid crystal displays. A retardation film is used as an antireflection layer for a reflective liquid crystal display device, a touch panel, or an organic EL.

As conventional retardation films, polycarbonate and cyclic polyolefin are used, and both of these polymers are polymers having positive birefringence. Here, the positive and negative of birefringence are defined as follows.

The optical anisotropy of a polymer film that has been molecularly oriented by stretching or the like is determined by nx, the refractive index in the fast axis direction in the plane of the film when the film is stretched, and the refractive index in the in-plane direction (slow axis) of the film perpendicular to nx. It can be represented by a refractive index ellipsoid where ny is the index and nz is the refractive index in the thickness direction of the film.

In other words, in the uniaxial stretching of a polymer with negative birefringence, the refractive index in the stretching axis direction is small (fast axis: stretching direction), and in the uniaxial stretching of a polymer with positive birefringence, the axis perpendicular to the stretching axis direction The refractive index in the direction is small (fast axis: direction perpendicular to stretching direction).

Further, the in-plane retardation (Re) is expressed as a value obtained by multiplying the refractive index (ny) in the direction orthogonal to the fast axis direction - the refractive index (nx) in the fast axis direction by the thickness of the film.

Many polymers have positive birefringence. Polymers having negative birefringence include acrylic resins and polystyrene, but acrylic resins have a low retardation property and do not have sufficient properties as optical compensation films. Polystyrene has a large photoelastic coefficient in the room temperature region, and the phase difference changes with a slight stress, which is a problem with the stability of the phase difference. It is not currently used due to practical problems such as

The wavelength dependence of the phase difference means that the phase difference changes depending on the measurement wavelength, and the ratio of the phase difference (R450) measured at a wavelength of 450 nm and the phase difference (R550) measured at a wavelength of 550 nm is R450/ It can be expressed as R550. In general, macromolecules with aromatic structures tend to increase R450/R550, resulting in lower contrast and viewing angle characteristics in the low wavelength region.

A stretched polymer film that exhibits negative birefringence has a high refractive index in the thickness direction of the film, making it an optical compensation film that has never existed before. -LCD), in-plane alignment liquid crystal (IPS-LCD), reflective liquid crystal display, transflective liquid crystal display, etc. For compensating the viewing angle characteristics of retardation films and polarizing plates There is a strong market demand for retardation films that are useful as retardation films and have negative birefringence.

Various retardation films have been developed to meet such required properties.

A method for producing a film in which the refractive index in the thickness direction of the film is increased by using a polymer having positive birefringence has been proposed. One is a treatment method in which a heat-shrinkable film is adhered to one or both sides of a polymer film, the laminate is heated and stretched, and a shrinkage force is applied in the thickness direction of the polymer film (see, for example, Patent Documents 1 to 3). is. A method of uniaxially stretching a polymer film in-plane while applying an electric field has also been proposed (see, for example, Patent Document 4).

Further, a retardation film composed of fine particles having negative optical anisotropy and a transparent polymer has been proposed (see, for example, Patent Document 5).

Japanese Patent No. 2818983 JP-A-05-297223 JP-A-05-323120 JP-A-06-088909 JP 2005-156862 A

However, the methods proposed in Patent Documents 1 to 4 have the problem of poor productivity due to the extremely complicated manufacturing process. Also, the control of the uniformity of the retardation is much more difficult than the conventional control by stretching.

Further, the optical compensation film obtained in Patent Document 5 is a retardation film having negative birefringence due to the addition of fine particles having negative optical anisotropy. There are issues with transparency, etc.

There is a demand for a resin composition that exhibits negative birefringence, has high productivity, and is highly compatible with film-forming and stretching processes.

As a result of extensive studies by the present inventors, it was found that a resin composition using an ester resin having specific properties and an additive can solve the above problems, and a single film exhibiting negative birefringence and the film are provided. The inventors have found that it is possible to obtain a laminated film, and have completed the present invention.

That is, the present invention comprises 71 to 99.99% by weight of an ester resin containing 50 mol% or more of fumarate ester residue units represented by the following formula (1), and either an aliphatic dibasic acid ester or a phthalate. A resin composition containing 0.01 to 29% by weight of

(wherein R ₁ and R ₂ are each independently a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms. shows one species of the group)

According to the present invention, by using the resin composition of the present invention as a raw material, it is possible to obtain a film having a negative birefringence with high substrate peelability after film formation and high stretchability. Laminated films are also useful as optical films for liquid crystal displays and antireflection films.

FIG. 11 shows the element arrangement of a liquid crystal display device simulation model in Example 9. FIG. FIG. 11 shows the element arrangement of a liquid crystal display device simulation model in Example 10. FIG.

Hereinafter, a resin composition that is one embodiment of the present invention (hereinafter referred to as "the resin composition of the present invention") will be described in detail.

The resin composition of the present invention contains an ester-based resin containing 50 mol % or more of fumarate ester residue units represented by the formula (1).

The ester resin exhibits negative birefringence. Here, the positive and negative of birefringence are defined as follows.

A film made of a resin is represented by a refractive index ellipsoid where nx is the refractive index in the fast axis direction in the film plane, ny is the refractive index in the film in-plane direction perpendicular to it, and nz is the refractive index in the thickness direction of the film. be able to.

Negative birefringence means that the drawing direction is the fast axis direction, and positive birefringence means that the direction perpendicular to the drawing direction is the fast axis direction.

In other words, when uniaxially stretched, the refractive index in the direction perpendicular to the stretching axis is small (fast axis: the direction perpendicular to the stretching direction) is a resin that exhibits positive birefringence, and when uniaxially stretched, the refractive index in the stretching direction is small. (Fast axis: stretching direction) is called a resin exhibiting negative birefringence.

When a resin exhibiting positive birefringence and a resin exhibiting negative birefringence are stretched, a difference in refractive index occurs in the axial direction perpendicular to the stretching direction, and thus an in-plane retardation (Re) is developed. Re is represented by the following formula (a). In addition, a resin exhibiting positive birefringence has a small refractive index in the thickness direction perpendicular to the stretching direction, so that the out-of-plane retardation (Rth) is positively large. On the other hand, a resin exhibiting negative birefringence has a large refractive index in the thickness direction perpendicular to the stretching direction, so that the out-of-plane retardation (Rth) is negatively large. Rth is represented by the following formula (b).
Re=(ny−nx)×d(a)
Rth=[(nx+ny)/2−nz]×d (b)
(In formulas (a) and (b), d indicates the thickness of the film.)

In formula (1), R ₁ and R ₂ are each independently selected from a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms. It shows one of the group. The alkyl group may be substituted with a halogen group such as a fluorine atom or a chlorine atom; an ether group; an ester group or an amino group.

Specific examples of R ₁ and R ₂ include ethyl, isopropyl, s-butyl, t-butyl, s-pentyl, t-pentyl, s-hexyl, t-hexyl, cyclo A propyl group, a cyclopentyl group, a cyclohexyl group, etc., and among them, an ethyl group, an isopropyl group, a s-butyl group, a t-butyl group, a cyclopentyl group, and a cyclohexyl group because they form a retardation film having excellent heat resistance and mechanical properties. It is preferably one of the group consisting of groups, and is particularly preferably an isopropyl group because it provides a retardation film having an excellent balance between heat resistance and mechanical properties.

Here, the fumarate diester residue unit represented by formula (1) specifically includes diisopropyl fumarate residue, di-s-butyl fumarate residue, di-t-butyl fumarate residue, fumarate acid di-s-pentyl residue, di-t-pentyl fumarate residue, di-s-hexyl fumarate residue, di-t-hexyl fumarate residue, dicyclopropyl fumarate residue, di-fumarate residue Cyclopentyl residue, dicyclohexyl fumarate residue and the like, diisopropyl fumarate residue, di-s-butyl fumarate residue, di-t-butyl fumarate residue, dicyclopentyl fumarate residue, dicyclohexyl fumarate residue. A residue or the like is preferred, and a diisopropyl fumarate residue is particularly preferred.

The fumaric acid diester resin may contain one component of the residue unit represented by formula (1), or may contain two or more types of residue units represented by formula (1), that is, contain two or more components. You can stay.

As the fumaric acid ester-based resin used in the present invention, 50 mol% or more of the fumarate diester residue unit represented by the formula (1) and 50 mol% of the residue unit composed of a monomer copolymerizable with the fumarate diester. It is preferably a resin containing the following. Here, the residue unit comprising a monomer copolymerizable with fumarate diesters includes, for example, styrene residues, styrene residues such as α-methylstyrene residues; acrylic acid residues; methyl acrylate residues; acrylic acid ester residues such as groups, ethyl acrylate residues, butyl acrylate residues; methacrylic acid residues; methacrylic acid esters such as methyl methacrylate residues, ethyl methacrylate residues, and butyl methacrylate residues residue; vinyl ester residue such as vinyl acetate residue and vinyl propionate residue; acrylonitrile residue; methacrylonitrile residue; olefin residue such as ethylene residue and propylene residue; Two or more types can be mentioned. Among them, it is preferable that the fumaric acid diester residue unit represented by the formula (1) is 70 mol% or more, and the fumaric acid diester residue unit is preferable because it becomes a retardation film having excellent heat resistance and mechanical properties. It is preferably 80 mol % or more, more preferably 90 mol % or more.

Ester-based resins have particularly excellent mechanical properties and are excellent in moldability during film formation. The number average molecular weight (Mn) is preferably 1×10 ³ to 5×10 ⁶ , more preferably 5×10 ³ to 3×10 ⁵ .

The ester resin in the composition contained in the optical film of the present invention is 71 to 99.99% by weight, preferably 94% by weight, from the viewpoint of peelability from the substrate, improvement of stretchability, and in-plane retardation. 0 to 99.9% by weight, more preferably 95.5 to 98.0% by weight.

The ester resin may be produced by any method as long as the copolymer can be obtained, and the ester resin can be produced by radical polymerization.

As the radical polymerization method, for example, any of bulk polymerization method, solution polymerization method, suspension polymerization method, precipitation polymerization method, emulsion polymerization method and the like can be employed.

The resin composition of the present invention contains either an aliphatic dibasic acid ester or a phthalate as an additive in the ester resin represented by the formula (1). As a result, a film having high substrate releasability after film formation and high stretchability is obtained, so that the film is characterized by being highly compatible with film formation and stretching processes. In the present invention, it was found that these ester additives have high compatibility with specific ester-based resins exhibiting negative birefringence, and are easily intercalated between resin chains (easily mixed). Since the additive mixed in the resin chain has a flexible structure, it acts as a plasticizer to improve the flexibility of the resin composition. In addition, after forming a film made of a resin composition on a substrate, in the process of peeling the film from the substrate, the additive with a flexible and highly mobile structure reduces the adhesion to the substrate and causes Releasability from the substrate is improved by reducing the generated frictional force. As a result, it becomes possible to increase the peel speed and peel. In addition, since the flexibility of the resin composition is improved by the additive, stretchability is improved. As a result, the film can be stretched at a high magnification, and a thin film with high retardation performance can be exhibited.

Preferred examples of ester additives include adipate compounds, sebacate compounds, azelaate compounds, dodecanoate compounds, and phthalate compounds.

The ester additive preferably has a molecular weight of 350 to 5,000, preferably 400 to 3,000, from the viewpoint of peelability from the substrate, stretchability, in-plane retardation, and suppression of volatilization at high temperatures. is more preferable, and 400 to 1,000 is particularly preferable. Here, the molecular weight indicates the molecular weight of the additive if it is a low molecular weight compound that can be calculated from the chemical structure, and indicates the weight average molecular weight of standard polystyrene conversion if the additive is a polymer compound having repeating units.

The proportion of the additive in the composition contained in the optical film of the present invention is 0.01 to 29% by weight, preferably 0.01 to 29% by weight, from the viewpoint of peelability from the substrate, improvement of stretchability, and in-plane retardation. It is 0.1 to 6.0% by weight, more preferably 2.0 to 4.5% by weight.

Examples of ester additives include di-n-octyl adipate, bis(2-ethylhexyl) adipate, diisooctyl adipate, dicapryl adipate, dinonyl adipate, diisononyl adipate, didecyl adipate, diisodecyl adipate, adipate compounds such as diundecyl adipate, dilauryl adipate, ditridecyl adipate, normal octyl normal decyl adipate, normal heptyl normal nonyl adipate, bis[2-(2-butoxyethoxyethyl)] adipate; Sebacate compounds such as bis(2-ethylhexyl) sebacate, di-n-octyl sebacate and diisooctyl sebacate. Azelaic acid ester compounds such as bis(2-ethylhexyl) azelate, di-n-octyl azelate and diisooctyl azelate. Dodecanedioic acid ester compounds such as bis(2-ethylhexyl) dodecanedioate, di-n-octyl dodecanedioate, diisooctyl dodecanedioate, di-n-octyl phthalate, diisooctyl phthalate, bis(2-ethylhexyl) phthalate, phthalate dicapryl acid, dinonyl phthalate, diisononyl phthalate, didecyl phthalate, diisodecyl phthalate, diundecyl phthalate, dilauryl phthalate, ditridecyl phthalate, benzyloctyl phthalate, normal hexyl normal decyl phthalate, normal octyl normal decyl phthalate, Examples thereof include phthalate compounds such as bis(2-ethylhexyl) isophthalate and bis(2-ethylhexyl) terephthalate.

Among these, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, diisodecyl adipate, and ditridecyl adipate are selected from the viewpoint of peelability from the substrate, stretchability, in-plane retardation, and suppression of volatilization at high temperatures. , bis[2-(2-butoxyethoxyethyl)] adipate, bis(2-ethylhexyl) sebacate, bis(2-ethylhexyl) azelate, and bis(2-ethylhexyl) dodecanedioate.

Next, an optical film that is one embodiment of the present invention (hereinafter referred to as "the optical film of the present invention") will be described in detail.

The optical film of the invention contains the resin composition of the invention.

The thickness of the optical film of the present invention is preferably 80.0 μm or less, more preferably 0.1 μm or more and 50.0 μm or less, more preferably 1 μm or more and 20.0 μm or less, from the viewpoint of compatibility with thinning of optical members. 0 μm or less is most preferable.

Re measured at 589 nm represented by the above formula (b) of the optical film of the present invention is preferably 20 nm or more and 700 nm or less, more preferably 80 nm or more and 400 nm or less, because the retardation film has excellent optical properties. , particularly preferably 100 nm or more and 350 nm or less.

The Rth measured at 589 nm represented by the formula (a) of the optical film of the present invention is preferably -500 nm or more and -20 nm or less, more preferably - 300 nm or more and -40 nm or less, particularly preferably -200 nm or more and -65 nm or less.

The wavelength dispersion characteristics of the optical film of the present invention can be expressed as the ratio R450/R550 of the retardation (R450) measured at a wavelength of 450 nm and the retardation (R550) measured at a wavelength of 550 nm. Re (450) / Re (550) of the optical film of the present invention is Re (450) / Re (550) ≤ 1.04, preferably Re (450 )/Re(550)≦1.03. Here, the wavelength dispersion characteristic Re (450) / Re (550) is a value Re (450) measured under the conditions of a measurement wavelength of 450 nm using a general fully automatic birefringence meter, and under the conditions of a measurement wavelength of 550 nm Measured value is the calculated ratio of Re(550).

The laminated film that is one aspect of the present invention (hereinafter referred to as "laminated film of the present invention") will be described in detail below.

The optical film of the present invention (hereinafter referred to as "film (A)") exhibits excellent viewing angle characteristics by laminating it with a film exhibiting positive birefringence (hereinafter referred to as "film (B)"). do.

Since the Rth of the film (A) has a negative value and the Rth of the film (B) has a positive value, it is possible to adjust the Rth at the time of lamination to an arbitrary value.

The Re of the laminated film of the present invention can be controlled by adjusting the Re of the film (A) and the film (B). The thickness is preferably 0 nm or more and 400 nm or less, more preferably 20 nm or more and 300 nm or less, and particularly preferably 100 nm or more and 150 nm or less, because the laminated film of the present invention has excellent optical properties when used as a retardation film.

The Rth of the laminated film of the present invention can be controlled by adjusting the Rth of the film (A) and the film (B). When the laminated film of the present invention is used as a retardation film, the viewing angle compensation performance is excellent, so it is preferably -200 nm or more and 200 nm or less, more preferably -70 nm or more and 70 nm or less, and particularly preferably 0 nm or more and 40 nm or less.

Re of the film (B) is preferably 0 nm or more and 400 nm or less, more preferably 0 nm or more and 300 nm or less, because the film (A) and the film (B) are laminated to form a thin retardation film having excellent optical properties. , particularly preferably 0 nm or more and 150 nm or less.

The Rth of the film (B) is preferably 5 nm or more and 500 nm or less, more preferably 5 nm or more and 500 nm or less, more preferably Rth is 40 nm or more and 300 nm or less, particularly preferably 65 nm or more and 200 nm or less.

Such a film (B) can be obtained, for example, by uniaxially stretching a polymer having positive birefringence. The polymer having positive birefringence is not particularly limited as long as it is a polymer having positive birefringence. Preferred examples from the viewpoint of heat resistance and transparency include polycarbonate resins and polyether sulfone resins. , polyarylate resins, polyimide resins, cyclic olefin resins, cellulose resins, N-substituted maleimide resins, and the like. Among these resins, polycarbonate resins, polyimide resins, cyclic olefin resins, cellulose resins, and the like are preferable, since a retardation film having high environmental stability can be obtained when laminated with the film (A).

The angle formed by the fast axis of the film (A) and the fast axis of the film (B) can be set according to the purpose. It is preferably 0 degrees ±10 degrees or less, or 90 degrees ±10 degrees or less.

The optical film according to the present invention described above can be suitably used for liquid crystal display devices, organic electroluminescence (organic EL) displays, and the like.

The type of the liquid crystal display device is not particularly limited, and any type of transmissive type, reflective type, and reflective transflective type can be used. Examples of liquid crystal cells used in the liquid crystal display device include twisted nematic (TN) mode, super twisted nematic (STN) mode, horizontal alignment (ECB) mode, vertical alignment (VA) mode, and in-plane switching (IPS). There are various liquid crystal cells such as mode, bend nematic (OCB) mode, ferroelectric liquid crystal (SSFLC) mode, and antiferroelectric liquid crystal (AFLC) mode liquid crystal cells. Among these, the retardation film, optical film and polarizing plate according to the present invention are preferably used for TN mode, VA mode, IPS mode or OCB mode liquid crystal cells.

By using the optical film according to the present invention in such various liquid crystal cells, contrast, hue and viewing angle characteristics can be improved.

Film (A) and film (B) may contain an antioxidant to improve thermal stability. Examples of antioxidants include hindered phenol-based antioxidants, phosphorus-based antioxidants, sulfur-based antioxidants, lactone-based antioxidants, amine-based antioxidants, hydroxylamine-based antioxidants, and vitamins. Examples include E-based antioxidants and other antioxidants, and these antioxidants may be used alone or in combination of two or more.

Film (A) and film (B) may contain a hindered amine light stabilizer or an ultraviolet absorber to enhance weather resistance. Examples of ultraviolet absorbers include benzotriazole, benzophenone, triazine and benzoate.

Film (A) and film (B) may contain other polymers, surfactants, polymer electrolytes, conductive complexes, pigments, dyes, antistatic agents, antiblocking agents, lubricants, etc., within the scope of the invention. may contain.

The method for producing the film (A) and film (B) of the present invention is not particularly limited. It can be produced by stretching axially or more.

A method for producing the elongated film will be described below.

As a method for manufacturing the film, it is preferable to manufacture the film by a solution casting method. Here, the solution casting method is a method of casting a resin solution (generally referred to as a dope) on a support substrate and then heating to evaporate the solvent to obtain a film. A coating method is not particularly limited, and a usual method can be adopted. For example, T-die method, doctor blade method, bar coater method, slot die method, lip coater method, reverse gravure coating method, micro gravure method, spin coating method, brush coating method, roll coating method, flexographic printing method, and the like. The supporting substrate to be used is not particularly limited. Polymers composed of cellulose such as cellulose ether, polyvinyl alcohol, polyamide, polyimide, polyarylate, polysulfone, polyethersulfone, polyetherketone, phenolic resin, epoxy resin, aliphatic cyclic polyolefin, norbornene-based thermoplastic transparent resin, etc. Substrates include glass substrates such as glass plates and quartz substrates, metal substrates such as aluminum, stainless steel and ferrotype substrates, and inorganic substrates such as ceramics substrates. Preferably, the base material is polyester such as polyethylene terephthalate or polyethylene naphthalate, polypropylene, polyacryl, cellulose such as cellulose acetate or cellulose ether, polyimide, aliphatic cyclic polyolefin, norbornene-based thermoplastic transparent resin or the like. It is wood. Polymer substrates such as polyesters such as polyethylene terephthalate and polyethylene naphthalate, polypropylenes, polyimides, aliphatic cyclic polyolefins, and norbornene-based thermoplastic transparent resins are particularly preferred.

The peeling speed of the film in the substrate peeling step after film formation is preferably in the range of 0.1 m / min or more and 30 m / min or less in terms of productivity, machine accuracy, stability, etc., and more preferably 1 m / min or more and 30 m/min or less.

As the solvent used for solution casting, any solvent can be used as long as it is capable of dissolving the resin or the like. 170° C. or lower is more preferable.

Examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichlorethylene, tetrachlorethylene, chlorobenzene and dichlorobenzene; phenols such as phenol and chlorophenol; benzene, toluene and xylene. , methoxybenzene, mesitylene, dimethoxybenzene and other aromatic hydrocarbons; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, cyclopentanone, 2-pyrrolidone, N-methyl-2-pyrrolidone and other ketone solvents; ethyl acetate , ester solvents such as butyl acetate; t-butyl alcohol, glycerin, ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, 2-methyl-2,4-pentanediol alcohol solvents; amide solvents such as dimethylformamide and dimethylacetamide; nitrile solvents such as acetonitrile and butyronitrile; ether solvents such as diethyl ether, dibutyl ether and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cell Solv and the like may be used alone or in combination.

The viscosity of the resin solution when producing the film can be adjusted by the molecular weight, concentration, and type of solvent of each component. Although the viscosity of the resin solution is not particularly limited, it is preferably 100 to 30,000 cps, more preferably 300 to 20,000 cps, and particularly preferably 300 to 15,000 cps in order to facilitate film coating.

The drying method in the drying step of the coating solution is not particularly limited, and ordinary heating means can be employed. Examples include hot air blowers, heating rolls, and far infrared heaters.

In the film manufacturing method, the drying temperature may be only one step, or in order to maintain the appearance and shorten the drying time, the first step is dried at a low temperature, and the second step and later are dried at a high temperature. But I don't mind.

In the present invention, the concentration of the raw material resin relative to the dope is not particularly limited as long as dissolution and film formation are possible. The method of dissolving the resin composition may be carried out so that a predetermined concentration is obtained in the dissolution step, or a low concentration solution may be prepared in advance and then adjusted to a predetermined high concentration solution in the concentration step. good. Further, after preparing a high-concentration resin solution of the resin composition in advance, a predetermined low-concentration resin solution may be obtained by adding various additives.

The retardation is controlled by stretching the film uniaxially or biaxially, and the film (A) or film (B) constituting the laminated film of the present invention can be obtained. The uniaxial stretching method includes, for example, a free width uniaxial stretching method, a method of stretching with a tenter, and a method of stretching between rolls. Examples of the biaxial stretching method include a method of stretching with a tenter, and stretching by inflating into a tubular shape. There are methods. As for the stretching direction, the film is preferably stretched in the width direction or oblique direction.

The temperature during stretching is preferably 90° C. or higher and 300° C. or lower, particularly preferably 105° C. or higher and 250° C. or lower, because the retardation film is less likely to cause thickness unevenness and has excellent mechanical properties and optical properties. be.

The stretching ratio of the film (hereinafter referred to as "stretching ratio") is preferably 1.4 times or more and 4.0 times or less, more preferably 1.4 times or more and 4.0 times or less, since the resulting film is thin and exhibits good retardation properties. is 1.5 times or more and 3.8 times or less, particularly preferably 1.7 times or more and 3.5 times or less.

Thus, the in-plane retardation of the obtained stretched film can be controlled by adjusting the stretching temperature and stretching ratio.

The conveying speed of the resin film in the stretching step is preferably in the range of 0.5 m/min or more and 30 m/min or less, more preferably 1 m/min or more and 20 m/min or less in terms of mechanical accuracy, stability, etc. A range can be mentioned.

The production method of the present invention may have a shrinking step of performing a shrinking treatment on the film obtained by the stretching step. Specifically, the stretched resin film is shrunk in the direction opposite to the stretching direction. As a result, residual stress accumulated in the stretched resin film can be relaxed, and the resulting film exhibits a high retardation even after a long period of time.

The thickness of the resin composition film to be subjected to the stretching step is preferably 5 to 200 μm, more preferably 5 to 150 μm, particularly 5 to 100 μm, from the viewpoints of ease of stretching and suitability for thinning of optical members. preferable.

The film (A) and the film (B) preferably have a transmittance of 85% or more, more preferably 90% or more in the form of a film, in order to avoid a decrease in the amount of light in the image display device. Here, the light transmittance represents the total light transmittance, and is a value measured at a wavelength of 380 nm to 780 nm using a transmittance measurable device equipped with a white light source in accordance with JIS K 7361-1 (1997 version). . Here, the total light transmittance is a value measured by molding the composition contained in the optical film of the present invention into a film having a thickness of 20 μm.

The haze of film (A) and film (B) is preferably 3.0% or less, more preferably 1.0% or less. By controlling the haze within the above range, a high-contrast image can be obtained when incorporated as a retardation film into a display device. Here, the haze is a value measured at wavelengths from 380 nm to 780 nm using a general haze meter equipped with a white light source according to JIS-K 7136 (2000 edition).

Film (A) and film (B) can be further laminated with a film containing other resins, if necessary. Other resins include, for example, polyether sulfone, polyarylate, polyethylene terephthalate, polynaphthalene terephthalate, polycarbonate, cyclic polyolefin, maleimide-based resin, fluorine-based resin, and polyimide. It is also possible to laminate a liquid crystal layer, a hard coat layer, a gas barrier layer, and a layer with a controlled refractive index (low reflection layer).

The film (A) and the film (B) are suitably used in polarizing plates used for applications such as liquid crystal display devices and organic EL display devices. Moreover, the polarizing plate is preferably used as an image display device.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

Various physical properties shown in the examples were measured by the following methods.

<Analysis of polymer>
Structural analysis of the polymer was obtained by proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR) using a nuclear magnetic resonance spectrometer (manufactured by JEOL, trade name: JNM-GX270).
<Measurement of number average molecular weight>
Using a gel permeation chromatography (GPC) device (manufactured by Toso, trade name: C0-8011 (equipped with column GMH _HR -H)), tetrahydrofuran or dimethylformamide was used as a solvent, and measurement was performed at 40°C. and calculated as a standard polystyrene conversion value.
<Measurement of retardation characteristics>
Retardation properties of the optical film were measured using light with a wavelength of 589 nm using an automatic sample tilt type birefringence meter (trade name: KOBRA-21ADH, manufactured by Oji Scientific Instruments).
<Measurement of chromatic dispersion characteristics>
Using a sample tilting automatic birefringence meter (manufactured by Oji Scientific Instruments, trade name: KOBRA-21ADH, light source: halogen lamp (12 V 100 W)), the phase difference Re (450) by light with a wavelength of 450 nm and the phase difference by light with a wavelength of 550 nm The wavelength dispersion characteristic of the optical film was measured as a ratio of Re(550).
<Evaluation of peelability>
A rectangular film having a width of 35 mm and a length of 210 mm is cut from the film (resin composition) formed on the substrate with scissors to prepare a test piece. A rectangle having a width of 25 mm and a length of 190 mm is cut with a cutter in the film surface at the center of the cut test piece. From the cut end of the film, the film is peeled from the substrate by hand, taking care not to damage it, with a 100 mm gripping portion in the length direction. Using a Tensilon universal material testing machine (manufactured by Orientec, trade name: RTG-1210), the end of the test piece from which the film was removed was placed on the substrate side and clamped with a chuck. The edge of the gripped portion of the film peeled off from the base material is bent in the opposite direction so as to be peeled off 180° so as not to form a crease, and then sandwiched with the other chuck. Peeling is performed on a 90 mm long film that has not been peeled off from the substrate. The peeling speed is set at 0.1 m to 1.0 m/min. The film after peeling was visually checked, and when no tearing or cracking occurred, the film was evaluated as ◯.

Synthesis example 1
600 g of distilled water, 3.4 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metolose 60SH-50) as a dispersing agent, and diisopropyl fumarate were placed in a 1-liter reactor equipped with a stirrer, condenser, nitrogen inlet tube and thermometer. 387.5 g, 12.5 g of 3-ethyl-3-oxetanylmethyl acrylate (3.2 parts by weight per 100 parts by weight of diisopropyl fumarate) and 8.3 g of t-butyl peroxypivalate, an oil-soluble radical initiator was added, nitrogen bubbling was performed for 1 hour, and then radical suspension polymerization was performed by holding at 50° C. for 24 hours while stirring at 400 rpm. After completion of the polymerization reaction, the contents were recovered from the reactor, and the polymer was separated by filtration, washed twice with distilled water and twice with methanol, and dried under reduced pressure at 80° C. (yield: 73%).
The obtained fumaric acid ester polymer had a number average molecular weight of 147,000. According to ¹ H-NMR measurement, the polymer particles are diisopropyl fumarate residue units/3-ethyl-3-oxetanylmethyl acrylate residue units = 96.1/3.9 (mol%). Diisopropyl 3-ethyl fumarate -3-oxetanylmethyl acrylate copolymer.

Synthesis example 2
600 g of distilled water, 3.4 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metolose 60SH-50) as a dispersing agent, and diisopropyl fumarate were placed in a 1-liter reactor equipped with a stirrer, condenser, nitrogen inlet tube and thermometer. 400.0 g and 8.3 g of t-butyl peroxypivalate, which is an oil-soluble radical initiator, were added, and after bubbling with nitrogen for 1 hour, radical suspension was maintained at 50° C. for 24 hours while stirring at 400 rpm. Polymerization was carried out. After completion of the polymerization reaction, the contents were recovered from the reactor, and the polymer was separated by filtration, washed twice with distilled water and twice with methanol, and dried under reduced pressure at 80°C (yield: 77%). The obtained diisopropyl fumarate polymer had a number average molecular weight of 129,000.

Synthesis example 3
600 g of distilled water, 3.4 g of hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., trade name Metolose 60SH-50) as a dispersing agent, and diisopropyl fumarate were placed in a 1-liter reactor equipped with a stirrer, condenser, nitrogen inlet tube and thermometer. 350.9 g, 49.1 g of diethyl fumarate (14.0 parts by weight with respect to 100 parts by weight of diisopropyl fumarate), and 8.3 g of t-butyl peroxypivalate, which is an oil-soluble radical initiator, were added, and nitrogen bubbling was performed. After conducting for 1 hour, radical suspension polymerization was carried out by holding at 50° C. for 28 hours while stirring at 400 rpm. After completion of the polymerization reaction, the contents were recovered from the reactor, and the polymer was separated by filtration, washed twice with distilled water and twice with methanol, and dried under reduced pressure at 80°C (yield: 75%).
The obtained fumaric acid ester polymer had a number average molecular weight of 138,000. According to ¹ H-NMR measurement, the polymer particles are diisopropyl fumarate/diethyl fumarate copolymer with diisopropyl fumarate residue unit/diethyl fumarate residue unit=86.7/13.3 (mol %). It was confirmed.

Synthesis example 4
42 g of diisopropyl fumarate, 7.7 g of monoethyl fumarate, and 0.66 g of tert-butyl peroxypivalate, which is a polymerization initiator, were placed in a glass ampoule with a capacity of 75 mL. did. This ampoule was placed in a constant temperature bath at 55° C. and held for 24 hours to effect radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampoule and dissolved in 200 g of tetrahydrofuran. This polymer solution was dropped into 4 L of hexane for precipitation, and then vacuum-dried at 80° C. for 10 hours to obtain 27 g of a diisopropyl fumarate/monoethyl fumarate resin. The resulting resin had a number average molecular weight of 53,000, diisopropyl fumarate residue units of 82 mol %, and monoethyl fumarate residue units of 18 mol %.

Example 1
19.4 g of the fumarate ester resin obtained in Synthesis Example 1 and 0.6 g of diisodecyl adipate (molecular weight: 427) were dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution to obtain a 20% by weight resin solution. and The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 22 µm. did. After the film was formed, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. The resulting film was longitudinally uniaxially stretched 1.5 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 2
19.2 g of the fumarate ester resin obtained in Synthesis Example 2 and 0.8 g of diisodecyl phthalate (molecular weight: 447) were dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution to obtain a 20 wt% resin solution. and The solution was poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 17 µm. did. After the film was formed, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. The resulting film was longitudinally uniaxially stretched 1.4 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 3
A film having a thickness of 17 μm obtained by forming the film in Example 2 was longitudinally uniaxially stretched to 1.75 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 4
19.2 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.8 g of diisodecyl phthalate (molecular weight: 447) were dissolved in a methyl ethyl ketone solution to prepare a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 50°C, 80°C and 100°C to form a film (resin composition) having a thickness of 16 µm. did. After the film formation, the peelability from the substrate was evaluated at a peeling speed of 1.0 m/min. The obtained film was longitudinally uniaxially stretched by 1.75 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 5
18.8 g of the fumarate ester resin obtained in Synthesis Example 3 and 1.2 g of diundecyl phthalate (molecular weight: 475) were dissolved in a methyl ethyl ketone solution to prepare a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three stages at drying temperatures of 50°C, 80°C and 100°C to form a film (resin composition) having a thickness of 28 µm. did. After the film formation, the peelability from the substrate was evaluated at a peeling speed of 1.0 m/min. The resulting film was longitudinally uniaxially stretched 1.6 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 6
19.4 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.6 g of diisodecyl adipate (molecular weight: 427) were dissolved in a methyl ethyl ketone solution to prepare a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 50°C, 80°C and 100°C to form a film (resin composition) having a thickness of 18 µm. did. After the film formation, the peelability from the substrate was evaluated at a peeling speed of 1.0 m/min. The obtained film was longitudinally uniaxially stretched by 1.75 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 7
19.4 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.6 g of bis(2-ethylhexyl) sebacate (molecular weight: 427) were dissolved in a methyl ethyl ketone solution to prepare a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 50°C, 80°C and 100°C to form a film (resin composition) having a thickness of 22 µm. did. After the film formation, the peelability from the substrate was evaluated at a peeling speed of 1.0 m/min. The resulting film was longitudinally uniaxially stretched 1.4 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Example 8
19.4 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.6 g of bis(2-ethylhexyl) dodecanedioate (molecular weight: 455) were dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution. A 20% by weight resin solution was prepared. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 20 µm. did. After the film formation, the peelability from the substrate was evaluated at a peeling speed of 1.0 m/min. The resulting film was longitudinally uniaxially stretched 1.5 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had excellent viewing angle characteristics and was suitable as an optical film.

Comparative example 1
20 g of the fumaric acid ester resin obtained in Synthesis Example 1 was dissolved in a toluene/methyl ethyl ketone=4/6 (weight ratio) solution to obtain a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 24 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was uniaxially stretched 1.4 times in the longitudinal direction at 140° C. using a batch-type film biaxial stretching apparatus, and the film broke during the stretching. The obtained film was insufficient in substrate releasability and stretchability after film formation.

Comparative example 2
20.0 g of the fumaric acid ester resin obtained in Synthesis Example 3 was dissolved in a methyl ethyl ketone solution to prepare a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 50°C, 80°C and 100°C to form a film (resin composition) having a thickness of 20 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was uniaxially stretched 1.4 times in the longitudinal direction at 140° C. using a batch-type film biaxial stretching apparatus, and the film broke during the stretching. The obtained film was insufficient in substrate releasability and stretchability after film formation.

Comparative example 3
19.2 g of the fumaric acid ester resin obtained in Synthesis Example 2 and 0.8 g of silicone resin RSN-217 (Dow Corning) were dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution to obtain a 20% by weight solution. A resin solution was prepared. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 22 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was uniaxially stretched 1.4 times in the longitudinal direction at 140° C. using a batch-type film biaxial stretching apparatus, and the film broke during the stretching. The obtained film was insufficient in substrate releasability and stretchability after film formation.

Comparative example 4
19.4 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.6 g of tributyl trimellitate were dissolved in a toluene/methyl ethyl ketone=4/6 (weight ratio) solution to obtain a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 21 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was longitudinally uniaxially stretched 1.4 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had insufficient substrate releasability after film formation.

Comparative example 5
19.0 g of the fumaric acid ester resin obtained in Synthesis Example 1 and 1.0 g of silicone YR-3370 (Momentive Performance Materials Holdings Inc.) were dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution to obtain 20 weights. % resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 19 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was uniaxially stretched 1.4 times in the longitudinal direction at 140° C. using a batch-type film biaxial stretching apparatus, and the film broke during the stretching. The obtained film was insufficient in substrate releasability and stretchability after film formation.

Comparative example 6
19.4 g of the fumarate ester resin obtained in Synthesis Example 3 and 0.6 g of tricresyl phosphate were dissolved in a toluene/methyl ethyl ketone=4/6 (weight ratio) solution to obtain a 20% by weight resin solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 80°C, 120°C and 130°C to form a film (resin composition) having a thickness of 25 µm. did. After the film formation, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. To obtain a film for stretching, the film was carefully peeled from the substrate by hand at a peeling speed of less than 0.1 m/min. The resulting film was longitudinally uniaxially stretched 1.4 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had insufficient substrate releasability after film formation.

Comparative example 7
7.2 g of the fumarate ester resin obtained in Synthesis Example 4, 0.6 g of diisodecyl adipate (molecular weight: 427), ethyl cellulose (ETHOCEL standard 100 manufactured by Dow Chemical Co., molecular weight Mn = 55,000 , molecular weight Mw = 176,000, Mw / Mn = 3.2, total degree of substitution DS = 2.5) was dissolved in a toluene/methyl ethyl ketone = 4/6 (weight ratio) solution to obtain 12% by weight of resin. solution. The solution is poured onto a polyethylene terephthalate substrate (Lumirror T60 manufactured by Toray) using a coater and dried in three steps at drying temperatures of 50°C, 80°C and 130°C to form a film (resin composition) having a thickness of 29 µm. did. After the film was formed, the peelability from the substrate was evaluated at a peel speed of 0.1 m/min. The obtained film was longitudinally uniaxially stretched by 1.75 times at 140° C. using a batch-type film biaxial stretching apparatus. The film thickness, retardation characteristics, and wavelength dispersion characteristics of the obtained optical film were measured. The results are also shown in Table 1. The resulting film had a large Rth and insufficient viewing angle characteristics.

<Evaluation of laminated film>
A simulation was performed using a liquid crystal display simulator "LCDMASTER" manufactured by Shintech. With the transmissive liquid crystal display device and the liquid crystal cell in the dark state (black display), the calculation is performed every 5 degrees at a polar angle of 60 degrees and an azimuth angle of 0 degrees to 360 degrees to calculate the luminance during black display (black luminance). and find its maximum value.

Example 9
A simulation model of a liquid crystal display device comprising, from the light source side, a polarizer, an IPS liquid crystal cell (Re = 285 nm), a film (A) exhibiting negative birefringence, a film (B) exhibiting positive birefringence, and a polarizer in this order. As such, a simulation was performed. The arrangement of each element was as shown in FIG.
For the film (A), the Re and Rth measurement results of Examples 1 to 7 were entered. Re and Rth of the film (B) were set as shown in Table 2. Table 2 shows the simulation results.

<Evaluation of Single Film>
Example 10
A simulation was performed using a liquid crystal display device equipped with a polarizer, an IPS liquid crystal cell (Re=285 nm), a film (A) exhibiting negative birefringence, and a polarizer in this order from the light source side as a simulation model. The arrangement of each element was as shown in FIG.

For the film (A), the Re and Rth measurement results of Examples 5 and 7 were entered. Table 2 shows the simulation results.

Comparative example 8
A simulation was performed assuming a configuration in which neither the film (A) nor the film (B) was used, and the viewer-side polarizer, the liquid crystal cell, and the light source-side polarizer were arranged in this order.

Comparative example 9
The measurement results of Re and Rth of Comparative Example 7 were inputted to the film (A), and a simulation was performed with the configuration shown in FIG.
From Table 2, it can be seen that the black luminance in the oblique direction is reduced when the liquid crystal display device has the film (A) or the film (A) and the film (B).
From the above results, it can be seen that by using the film (A) or the film (A) and the film (B), a liquid crystal display device with low black brightness and high contrast even when viewed from an oblique direction can be obtained.

10 Light sources 20, 60 Polarizers 21, 61 Absorption axis of polarizer 30 Liquid crystal cell 31 Orientation direction of liquid crystal molecules 40 Film (A)
50 Film (B)
41 Fast axis of film (A) 51 Fast axis of film (B) 100 Liquid crystal display device

Claims (10)

71 to 99.99% by weight of an ester resin containing 50 mol% or more of fumaric acid ester residue units represented by the following formula (1), and 0.01 of either an aliphatic dibasic acid ester or a phthalic acid ester Resin composition containing ~29% by weight.

(wherein R ₁ and R ₂ are each independently a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms. shows one species of the group) 2. The resin composition according to claim 1, wherein the aliphatic dibasic ester or phthalate has a molecular weight of 400 or more and 5,000 or less. An optical film comprising the resin composition according to claim 1 . 4. The optical film according to claim 3, wherein the film has a thickness of 80 μm or less and an out-of-plane retardation Rth measured at a wavelength of 589 nm represented by the following formula (a) of −500 nm or more and −20 or less.
Rth=[(nx+ny)/2−nz]×d(a)
(Wherein, nx is the refractive index in the fast axis direction in the film plane, ny is the refractive index in the slow axis direction in the film plane, nz is the refractive index in the vertical direction out of the film plane, and d is the refractive index of the film. thickness.) Re measured at a wavelength of 589 nm represented by the following formula (b) is 20 nm or more and 700 nm or less, and the ratio of Re (R450) measured at a wavelength of 450 nm to Re (R550) measured at a wavelength of 550 nm (R450/R550) is 1. 5. The optical film according to claim 3, wherein the optical film has a refractive index of 0.4 or less.
Re=(ny−nx)×d(b) 6. The optical film according to any one of claims 3 to 5, wherein the film alone can be stretched 1.4 times or more at a stretching temperature of 250°C or less. After forming a film of the resin composition on a substrate, it can be peeled off from the substrate at a peel speed of 0.1 m/min or more in a 180 degree peel test without causing breakage or cracking. 7. The optical film according to any one of 3 to 6. A laminated film comprising the optical film (A) according to any one of claims 3 to 7 and a film (B) exhibiting positive birefringence. 9. The laminated film according to claim 8, wherein the film (B) exhibiting positive birefringence is a film having Re measured at a wavelength of 589 nm of 0 nm or more and 400 nm or less and Rth of 5 nm or more and 500 nm or less. 10. The laminate film according to claim 8, wherein Re measured at a wavelength of 589 nm is 0 nm or more and 400 nm or less, and Rth is -200 nm or more and 200 nm or less.

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