JP2008129465A - Retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film having a controlled wavelength dispersibility, and further to provide a retardation film having reverse wavelength dispersibility. <P>SOLUTION: The retardation film comprises a film (A) and a film (B). The film (A) consists of a fumaric acid ester resin and satisfies a relation: nx<ny≤nz, wherein nx denotes a refractive index in a film surface in a phase advancing axis direction, ny denotes a refractive index in a film in-plane direction perpendicularly intersecting the phase advancing axis direction, and nz denotes a refractive index in a film thickness direction. In the film (B), 3-dimensional refractive indexes of the film satisfy a relation: ny>nx≥nz or a relation: ny>nz≥nx, wherein nx denotes a refractive index in the film surface in the phase advancing axis direction, ny denotes a refractive index in a film in-plane direction perpendicularly intersecting the phase advancing axis direction and nz denotes a refractive index in a film thickness direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a retardation film having controlled wavelength dispersion, and further to a retardation film having reverse wavelength dispersion.

  Liquid crystal displays are widely used as the most important display devices in the multimedia society, from mobile phones to computer monitors, notebook computers, and televisions. Many optical films are used in liquid crystal displays to improve display characteristics. In particular, the retardation film plays a large role in improving contrast and compensating for color tone when viewed from the front or obliquely. As conventional retardation films, polycarbonate and cyclic polyolefin are widely used. By stretching these films, the retardation is adjusted and used as a retardation film.

  The phase difference has wavelength dependency (wavelength dispersion), and the value of the phase difference changes depending on the light of wavelengths from blue to red. Usually, the phase difference is set with light of around 550 nm (green), but generally the phase difference measured with short wavelength light is larger than the phase difference measured with long wavelength light. When viewing angle characteristics of a liquid crystal display, especially color correction, it is important to control the wavelength dispersion characteristics of the retardation film according to the characteristics of the liquid crystal material used, etc. Since it depends on the material used for the film, it is difficult to control them.

  Further, a retardation film in which the phase difference measured with short-wavelength light is smaller than the phase difference measured with long-wavelength light (reverse wavelength dispersion characteristic), particularly a film having a quarter-wavelength retardation, is a reflective liquid crystal Although it is useful as a display, an antireflection film, or a touch panel film, it has many problems such as complicated manufacturing processes and insufficient properties. For example, what formed by laminating | stacking two polymer films is mentioned (for example, refer patent documents 1-3). However, in the conventional laminated phase difference plate, for production, two kinds of single-wafer films are formed by cutting a stretched birefringent film stretched in one direction in directions different from each other in the stretch direction. And this film needs to be bonded and laminated with an adhesive. In addition, when bonding two films, not only the cost increase associated with adhesive coating, cutting, and bonding, but also the effects on performance such as performance degradation due to angular misalignment associated with film bonding are ignored. Can not.

  A stretched film made of a resin having a positive intrinsic birefringence value, a stretched film made of a resin having a negative intrinsic birefringence value, in particular, an oriented film made of a norbornene-based resin and an oriented film made of a styrene maleic anhydride resin, respectively. A retardation film that has been laminated so that the orientation directions coincide with each other has been proposed (see, for example, Patent Document 4). However, the styrene maleic anhydride resin has problems such as a large change in retardation due to low heat resistance and low mechanical strength, and cracking of the film.

JP-A-10-68816 JP-A-5-27118 JP-A-5-100114 JP 2003-90912 A

  An object of the present invention is to provide a retardation film having controlled wavelength dispersion, and further a retardation film having reverse wavelength dispersion.

  As a result of intensive studies in view of the above problems, the present inventors have found that a film (A) made of a specific fumarate-based resin and a film (B) having a specific relationship between the three-dimensional refractive index of the film. It has been found that the characteristic retardation film satisfies the above-mentioned problems, and the present invention has been completed.

  That is, the present invention is a film made of a fumarate ester resin, wherein the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film in-plane direction perpendicular to the film is ny, and the film thickness direction is A film (A) in which each relationship is nx <ny ≦ nz when the refractive index is nz, and a film in which the three-dimensional refractive index of the film is the refractive index in the fast axis direction in the film plane, nx, and a film orthogonal thereto When the refractive index in the in-plane direction is ny and the refractive index in the thickness direction of the film is nz, the film (B) has a relationship of ny> nx ≧ nz or ny> nz ≧ nx. The present invention relates to a retardation film.

  Hereinafter, the retardation film of the present invention will be described in detail.

  Examples of the fumaric acid ester resin used in the present invention include fumaric acid ester polymers, and among them, fumaric acid diester resin comprising 50 mol% or more of fumaric acid diester residue units represented by the following general formula (a). Is preferred.

(Here, R ₁ and R ₂ each independently represents a branched or cyclic alkyl group having 3 to 12 carbon atoms.)
R ₁ and R ₂ which are substituents of the fumaric acid diester residue unit are each independently a branched alkyl group or a cyclic alkyl group having 3 to 12 carbon atoms, such as a halogen group such as fluorine or chlorine, or an ether group. , May be substituted with an ester group or an amino group. Here, examples of the branched alkyl group having 3 to 12 carbon atoms include isopropyl group, s-butyl group, t-butyl group, s-pentyl group, t-pentyl group, s-hexyl group, and t-hexyl group. Examples of the cyclic alkyl group having 3 to 12 carbon atoms include a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group. Among these, an isopropyl group, s-butyl group, t-butyl group, cyclopentyl group, cyclohexyl group, and the like are preferable because the retardation film is excellent in heat resistance and mechanical properties, and particularly in balance of heat resistance and mechanical properties. An isopropyl group is preferred because it is an excellent retardation film.

  Specific examples of the fumaric acid diester residue unit represented by the general formula (a) include diisopropyl fumarate residue, di-s-butyl fumarate residue, di-t-butyl fumarate residue, and fumaric acid. Di-s-pentyl residue, di-t-pentyl fumarate residue, di-s-hexyl fumarate residue, di-t-hexyl fumarate residue, dicyclopropyl fumarate residue, dicyclopentyl fumarate Residue, dicyclohexyl fumarate residue, etc. Among them, diisopropyl fumarate residue, di-s-butyl fumarate residue, di-t-butyl fumarate residue, dicyclopentyl fumarate residue, fumaric acid A dicyclohexyl residue and the like are preferable, and a diisopropyl fumarate residue is particularly preferable.

  The fumaric acid ester resin comprising 50 mol% or more of the fumaric acid diester residue unit represented by the general formula (a), preferably used as the fumaric acid ester resin used in the present invention, is represented by the general formula (a). Resin consisting of 50 mol% or more of fumaric acid diester residue units and 50 mol% or less of residue units composed of other monomers copolymerizable with fumaric acid diesters, and other copolymerizable with fumaric acid diesters Residue units composed of other monomers include, for example, styrene residues such as styrene residues and α-methylstyrene residues; acrylic acid residues; methyl acrylate residues, ethyl acrylate residues, acrylic Acrylic acid ester residues such as butyl acid residues; methacrylic acid residues; methyl methacrylate residues, ethyl methacrylate residues, butyl methacrylate residues, etc. Methacrylic acid ester residues; Vinyl ester residues such as vinyl acetate residues and vinyl propionate residues; Acrylonitrile residues; Methacrylonitrile residues; Olefin residues such as ethylene residues and propylene residues; etc. 1 type or 2 types or more can be mentioned. Among them, the fumaric acid diester residue unit represented by the general formula (a) is preferably 70 mol% or more, and since it becomes a retardation film excellent in heat resistance and mechanical properties, the fumaric acid diester residue unit. Is preferably 80 mol% or more, more preferably 90 mol% or more.

The fumaric acid ester resin used in the present invention has a number average molecular weight (Mn) of 1 × 10 in terms of standard polystyrene obtained from an elution curve measured by gel permeation chromatography (hereinafter referred to as GPC). It is preferably ⁴ or more. Particularly, it is preferably 2 × 10 ⁴ or more and 2 × 10 ⁵ or less because it is a retardation film having excellent mechanical properties and excellent moldability during film formation.

  As a method for producing the fumaric acid ester resin constituting the retardation film of the present invention, any method may be used as long as the fumaric acid ester resin is obtained. For example, fumaric acid diesters, and in some cases fumaric acid ester It can be produced by performing radical polymerization or radical copolymerization using a monomer copolymerizable with acid diesters. Examples of the fumaric acid diesters include diisopropyl fumarate, di-s-butyl fumarate, di-t-butyl fumarate, di-s-pentyl fumarate, di-t-pentyl fumarate, and di-fumarate. -S-hexyl, di-t-hexyl fumarate, dicyclopropyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate, and the like. Examples of the monomer copolymerizable with fumaric acid diesters include styrene, Styrenes such as α-methylstyrene; Acrylic acid; Acrylic esters such as methyl acrylate, ethyl acrylate and butyl acrylate; Methacrylic acid; Methacrylic esters such as methyl methacrylate, ethyl methacrylate and butyl methacrylate Vinyl esters such as vinyl acetate and vinyl propionate; acrylonitrile ; Methacrylonitrile; can be exemplified one or two or more such, ethylene, olefins such as propylene.

  Further, as the radical polymerization method to be used, it can be carried out by a known polymerization method, for example, any of a bulk polymerization method, a solution polymerization method, a suspension polymerization method, a precipitation polymerization method, an emulsion polymerization method and the like can be adopted. is there.

  Examples of the polymerization initiator used in the radical polymerization method include benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, and dicumyl peroxide. , Organic peroxides such as t-butylperoxyacetate and t-butylperoxybenzoate; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-butyronitrile), 2 , 2′-azobisisobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile) and the like.

  And there is no restriction | limiting in particular as a solvent which can be used in a solution polymerization method, a suspension polymerization method, a precipitation polymerization method, and an emulsion polymerization method, For example, aromatic solvents, such as benzene, toluene, xylene; Methanol, ethanol, propyl alcohol, butyl alcohol Examples include alcohol solvents such as cyclohexane, dioxane, tetrahydrofuran (THF), acetone, methyl ethyl ketone, dimethylformamide, isopropyl acetate, water, and the like, and mixed solvents thereof.

  Moreover, the polymerization temperature at the time of performing radical polymerization can be suitably set according to the decomposition temperature of a polymerization initiator, and generally it is preferable to carry out in the range of 40-150 degreeC.

  The retardation film of the present invention is a film made of the fumarate ester resin, wherein the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film in-plane direction orthogonal to the film is ny, and the film When the refractive index in the thickness direction is nz, the relationship (nx) is nx <ny ≦ nz, and the three-dimensional refractive index of the film is the refractive index in the fast axis direction in the film plane, nx, The film (B) is in a relationship of ny> nx ≧ nz or ny> nz ≧ nx, where ny is the refractive index in the in-plane direction of the film perpendicular to it and nz is the refractive index in the thickness direction of the film. A retardation film characterized by the following.

  Here, when the film thickness is d, the film (A) preferably has an in-plane retardation (Re) of 50 to 2000 nm measured at a wavelength of 550 nm represented by the following formula (1). The thickness is preferably 100 to 600 nm, more preferably 120 to 300 nm.

Re = (ny−nx) × d (1)
Moreover, it is preferable that the in-plane phase difference of the film (B) used for the optical film of this invention measured at the wavelength of 550 nm shown by the said Formula (1) is 50-2000 nm.

  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 resin, polyimide resin, cyclic olefin resin, N-substituted maleimide resin and the like. Among these, a film having a large wavelength dispersion such as a polycarbonate resin or a polyether sulfone resin is preferable because a retardation film having reverse wavelength dispersion can be obtained.

  The retardation film of the present invention is a retardation film comprising a film (A) and a film (B), and the angle formed by the fast axis of the film (A) and the fast axis of the film (B) depends on the purpose. Among them, it is preferably 90 ° ± 20 ° or less, particularly preferably 90 ° ± 5 ° or less, and more preferably 90 ° from the viewpoint of wavelength dispersion control and productivity. Is preferred.

  The in-plane retardation of the retardation film comprising the film (A) and the film (B) of the present invention is the difference in retardation between the film (A) and the film (B), and has a quarter wavelength retardation. As a retardation film, so-called quarter wave plate, the difference between the in-plane retardation (Re) of the film (A) measured at 550 nm and the in-plane retardation (Re) of the film (B) is 100 to 100. It is preferable that it is 160 nm, and it is especially preferable that it is 130-150 nm. In addition, as a retardation film having a retardation of ½ wavelength, a so-called ½ wavelength plate, the in-plane retardation (Re) of the film (A) measured at 550 nm and the film of the film (B) are measured. The in-plane retardation (Re) difference is preferably 250 to 300 nm.

  The wavelength dispersibility of the retardation film of the present invention can be controlled by adjusting the retardation of the film (A) and the film (B). When used as a quarter-wave plate or a half-wave plate, the ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm is 1.0. The following is preferable, particularly preferably 0.99, and more preferably 0.98 or less. Further, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm and the phase difference (R550) measured at a wavelength of 550 nm is preferably 1.0 or more, particularly preferably 1.01 or more.

  There is no restriction | limiting in particular as a manufacturing method of the film (A) used for the retardation film of this invention, and a film (B). It can be produced by stretching beyond the axis.

  The solution casting method is a method in which, for example, a solution obtained by dissolving a fumarate ester resin in a solvent (hereinafter referred to as a dope) is cast on a support substrate, and then the solvent is removed by heating or the like to obtain a film. In this case, as a method for casting the dope on the support substrate, for example, a T-die method, a doctor blade method, a bar coater method, a roll coater method, a lip coater method or the like is used. Particularly, industrially, a method of continuously extruding a dope from a die onto a belt-like or drum-like support substrate is most common. Examples of the support substrate used include a glass substrate; a metal substrate such as stainless steel or ferrotype; and a plastic substrate such as polyethylene terephthalate. In the solution casting method, when forming a film having high transparency and excellent thickness accuracy and surface smoothness, the solution viscosity of the dope is a very important factor, and preferably 700 to 30000 cps. It is preferable that it is 1000-10000 cps. The melt casting method is a molding method in which a fumarate ester resin is melted in an extruder and extruded from a slit of a T die into a film shape, and then cooled and cooled with a roll or air.

  And the obtained film can be used as the film (A) and the film (B) used for the retardation film of the present invention by controlling the retardation by stretching uniaxially or biaxially. Examples of the uniaxial stretching method include a free-width uniaxial stretching method, a stretching method using a tenter, and a stretching method between rolls. The biaxial stretching method includes, for example, a stretching method using a tenter and a tube-like expansion. There are methods. As stretching conditions at that time, unevenness in thickness is unlikely to occur, and a retardation film having excellent mechanical properties and optical properties is obtained. Therefore, the stretching temperature is preferably 80 to 250 ° C, particularly preferably 120 to 220 ° C. Yes, the draw ratio is preferably 1.01 to 5 times, particularly preferably 1.01 to 2 times.

  The retardation film of the present invention can be produced, for example, by bonding the film (A) and the film (B). There is no restriction | limiting in particular about the method of bonding, Bonding with a sheet | seat is also possible, and it can bond especially the roll film of a film (A) and a film (B) using a well-known adhesive agent etc. preferable. In the pasting, the angle formed by the fast axis of the film (A) and the fast axis of the film (B) is preferably 90 ° ± 20 °. Since it is possible, it is preferably 90 ° ± 5 ° or less, and more preferably 90 °.

  It is also possible to produce the film (A) and the unstretched film (B) by forming them by coextrusion and then stretching them.

  In the retardation film of the present invention, it is preferable that an antioxidant is blended in order to increase the thermal stability of the retardation film itself or during film formation. Examples of the antioxidant include hindered phenol antioxidants, phosphorus antioxidants, and other antioxidants. These antioxidants may be used alone or in combination. And since an antioxidant effect | action improves synergistically, it is preferable to use together and use a hindered phenolic antioxidant and phosphorus antioxidant, for example, 100 weight part of hindered phenolic antioxidants in that case On the other hand, it is particularly preferable to use a phosphorus-based antioxidant mixed at 100 to 500 parts by weight. Moreover, as addition amount of antioxidant, 0.01-10 weight part is preferable with respect to 100 weight part of fumaric acid ester-type resin which comprises the retardation film of this invention, Especially 0.5-1 weight part is preferable. A range is preferable.

  Furthermore, as an ultraviolet absorber, for example, an ultraviolet absorber such as benzotriazole, benzophenone, triazine, or benzoate may be blended as necessary.

  The retardation film of the present invention is within the scope of the invention, and other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, dyes, antistatic agents, antiblocking agents, lubricants, etc. May be blended.

  Moreover, it can also laminate | stack with the retardation films of this invention, or other retardation films.

  The retardation film of the present invention is an antireflection film such as an organic EL display or a touch panel in addition to a circularly polarizing film formed by laminating and integrating a quarter wavelength plate and a polarizing plate, a retardation film of a reflective liquid crystal display, It is also useful for brightness enhancement films. Moreover, it can also be set as a composite polarizing plate by laminating | stacking with a polarizing plate.

  According to the present invention, a retardation film capable of improving viewing angle characteristics such as contrast and color compensation of a liquid crystal display, and a composite polarizing plate useful for an antireflection film and the like can be provided. Further, the retardation film is useful for improving the image quality of reflective and transflective mobile liquid crystal displays and various monitors, and various liquid crystal televisions such as VA mode, IPS mode, and OCB mode.

  EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise noted, commercially available reagents were used.

~ Measurement of number average molecular weight ~
Using gel permeation chromatography (GPC) (manufactured by Tosoh Corporation, trade name HLC-802A), THF was used as a solvent and a standard polystyrene conversion value was obtained.

-Measurement of light transmittance and haze of film-
The light transmittance and haze of the produced film were measured using a haze meter (trade name NDH2000, manufactured by Nippon Denshoku Industries Co., Ltd.).

-Measurement method of refractive index-
Measurement was performed using an Abbe refractometer (manufactured by Atago) in accordance with JIS K 7142 (1981 version).

-Measurement of retardation and three-dimensional refractive index of film-
Measurement was performed using a fully automatic birefringence meter (trade name KOBRA-21ADH, manufactured by Oji Scientific Instruments).

~ Positive birefringence ~
Positive and negative birefringence was determined from the three-dimensional refractive index of the stretched film.

Synthesis Example 1 (Production Example of Diisopropyl Fumarate Homopolymer)
A 30 liter autoclave was charged with 18 kg of distilled water containing 0.2% by weight of partially saponified polyvinyl alcohol, 3 kg of diisopropyl fumarate, and 7 g of dimethyl-2,2′-azobisisobutyrate as a polymerization initiator, and a polymerization temperature. The suspension radical polymerization reaction was carried out under the conditions of 50 ° C. and a polymerization time of 24 hours. The obtained particles were filtered, sufficiently washed with methanol, and dried at 80 ° C. to obtain diisopropyl fumarate homopolymer. The number average molecular weight of the obtained diisopropyl fumarate homopolymer was 160,000.

Film creation example 1
The diisopropyl fumarate homopolymer obtained in Synthesis Example 1 was dissolved in a THF solution to give a 22% solution, and tris (2,4) as a hindered phenol-based antioxidant was added to 100 parts by weight of the diisopropyl fumarate homopolymer. -Di-tert-butylphenyl) phosphite 0.35 parts by weight and pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) 0.15 as phosphorus antioxidant After adding 1 part by weight of 2- (2H-benzotriazol-2-yl) -p-cresol as an ultraviolet absorber, it was cast on a support substrate of a solution casting apparatus by T-die method, After drying at 80 ° C. and 120 ° C. for 10 minutes, a film having a width of 250 mm and a thickness of 105 μm was obtained.

  The obtained film had a light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.470.

Film creation example 2
The diisopropyl fumarate homopolymer obtained in Synthesis Example 1 was dissolved in a THF solution to form a 22% solution, and the film was cast on a support substrate of a solution casting apparatus by the T-die method in the same manner as in Film Production Example 1, and the width was 250 mm. A film having a thickness of 124 μm was obtained.

  The obtained film had a light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.470.

Film production example 3
A polycarbonate resin (manufactured by Aldrich) is dissolved in a methylene chloride solution to make a 25% solution. Further, with respect to 100 parts by weight of the polycarbonate resin, 0.35 weight of tris (2,4-di-t-butylphenyl) phosphite as an antioxidant. Parts and pentaerythritol-tetrakis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate) 0.15 parts by weight, 2- (2H-benzotriazol-2-yl)-as UV absorber After adding 1 part by weight of p-cresol, it is cast on a support substrate of a solution casting apparatus by the T-die method, dried at 40 ° C., 80 ° C. and 120 ° C. for 15 minutes, respectively, and then a film having a width of 250 mm and a thickness of 100 μm Got.

  The obtained film had a light transmittance of 91%, a haze of 0.6%, and a refractive index of 1.583.

Film creation example 4
A polycarbonate resin (manufactured by Aldrich) was dissolved in a methylene chloride solution to obtain a 25% solution, and a film having a width of 250 mm and a thickness of 85 μm was obtained in the same manner as in the film trial example 3.

  The obtained film had a light transmittance of 91%, a haze of 0.5%, and a refractive index of 1.583.

Example 1
The film obtained in Film Preparation Example 1 was cut into a square of 50 mm, and the temperature was 140 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.2 and stretched 1.2 times (hereinafter referred to as film A-1). As a result of measuring the three-dimensional refractive index of the stretched film (nx = 1.4673, ny = 1.4702, nz = 1.4725) (nx <ny <nz), the refractive index in the stretch axis direction is small, and The resulting film had negative birefringence. The in-plane retardation Re = (ny−nx) × d of the film was 283 nm.

  The polycarbonate film obtained in Film Preparation Example 3 was cut into a 50 mm square, and the temperature was 170 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was stretched by a factor of 1.5 by free-width uniaxial stretching (hereinafter referred to as film B-1). The three-dimensional refractive index of the obtained film was nx = 1.5827, ny = 1.5842, nz = 1.5827 (ny> nz = nx), and showed positive birefringence. The in-plane retardation (Re) of the film was 130 nm.

  Bonding was performed so that the fast axis of the film A-1 produced here and the fast axis of the film B-1 were orthogonal (angle 90 ° C.). The thickness of the laminated film was 186 μm, and the in-plane retardation (Re) of the film was 153 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.98. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.01.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Example 2
The film obtained in Film Preparation Example 2 was cut into a 50 mm square, and the temperature was 160 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.25 and stretched 1.25 times (hereinafter referred to as film A-2). As a result of measuring the three-dimensional refractive index of the stretched film (nx = 1.4660, ny = 1.4709, nz = 1.4731) (nx <ny <nz), the refractive index in the stretch axis direction is small, and The resulting film had negative birefringence. The in-plane retardation Re = (ny−nx) × d of the film was 531 nm.

  The polycarbonate film obtained in Film Preparation Example 4 was cut into a 50 mm square, and the temperature was 160 ° C. and the stretching speed was 20 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was stretched 1.5 times by free-width uniaxial stretching under the conditions (hereinafter referred to as film B-2). The three-dimensional refractive index of the obtained film was nx = 1.5811, ny = 1.5863, nz = 1.5819 (ny> nz> nx), and showed positive birefringence. The in-plane retardation (Re) of the film was 395 nm.

  The pasting was performed so that the fast axis of the film A-2 produced here and the fast axis of the film B-2 were orthogonal (angle 90 ° C.). The thickness of the laminated film was 185 μm, and the in-plane retardation (Re) of the film was 136 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.91. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.07.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Example 3
The film obtained in Film Prototype Example 4 was cut into a 50 mm square, and the temperature was 165 ° C. and the stretching speed was 20 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.5 and stretched 1.5 times (hereinafter referred to as film B-3). The three-dimensional refractive index of the obtained film was nx = 1.5820, ny = 1.5849, nz = 1.5819 (ny>nx> nz), and showed positive birefringence. The in-plane retardation (Re) of the film was 261 nm.

  Bonding was performed so that the fast axis of the film A-2 and the fast axis of the film B-3 produced here were orthogonal (angle 90 ° C.). The thickness of the laminated film was 199 μm, and the in-plane retardation (Re) of the film was 270 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.97. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.03.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a half-wave retardation, a so-called half-wave plate.

Example 4
A commercially available PES film (manufactured by Lonza) was cut into a 50 mm square, and a temperature of 245 ° C. and a stretching speed of 20 mm / min. The film was subjected to uniaxial stretching with a free width under the conditions of 1.5 and stretched 1.5 times (hereinafter referred to as film B-4). The three-dimensional refractive index of the obtained film was nx = 1.65887, ny = 1.6111, nz = 1.65887 (ny> nz = nx), and showed positive birefringence. The in-plane retardation (Re) of the film was 149 nm.

  Bonding was performed so that the fast axis of the film A-1 produced here and the fast axis of the film B-4 were orthogonal (angle 90 ° C.). The thickness of the laminated film was 161 μm, and the in-plane retardation (Re) of the film was 134 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.94. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.03.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Example 5
The film obtained in Film Preparation Example 2 was cut into a 50 mm square, and the temperature was 140 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was subjected to uniaxial stretching with a free width under the conditions of 1.21 times (hereinafter referred to as film A-3). As a result of measuring the three-dimensional refractive index of the stretched film (nx = 1.4671, ny = 1.4702, nz = 1.4725) (nx <ny <nz), the refractive index in the stretched axis direction is small and obtained. The resulting film had negative birefringence. The in-plane retardation Re = (ny−nx) × d of the film was 312 nm.

  The polycarbonate film obtained in Film Preparation Example 3 was cut into a 50 mm square, and the temperature was 170 ° C. and the stretching speed was 10 mm / min. With a biaxial stretching apparatus (manufactured by Imoto Seisakusho). The film was stretched by a factor of 1.5 by free-width uniaxial stretching (hereinafter referred to as film B-5). The three-dimensional refractive index of the obtained film was nx = 1.5827, ny = 1.5842, nz = 1.5827 (ny> nz = nx), and showed positive birefringence. The in-plane retardation (Re) of the film was 130 nm.

  Bonding was performed so that the fast axis of the film A-3 produced here and the fast axis of the film B-5 were orthogonal (angle 90 ° C.). The thickness of the laminated film was 177 μm, and the in-plane retardation (Re) of the film was 183 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.96. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.06.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Example 6
The fast axis of the produced film A-3 and the fast axis of the film B-5 were bonded so as to be 80 degrees. The in-plane retardation (Re) of the film was 181 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.97. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.03.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Example 7
The fast axis of the produced film A-3 and the fast axis of the film B-5 were bonded to 70 degrees. The in-plane retardation (Re) of the film was 181 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm was 0.98. Furthermore, the ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm to the phase difference (R550) measured at a wavelength of 550 nm was 1.02.

  From these results, the obtained film was suitable for the retardation film because the wavelength dispersion was controlled and it had reverse wavelength dispersion. It was also suitable as a retardation film having a quarter wavelength retardation, a so-called quarter wavelength plate.

Comparative Example 1
The in-plane retardation (Re) of the film A-1 was 283 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm is 1.04, measured at a phase difference (R650) measured at a wavelength of 650 nm and a wavelength of 550 nm. The ratio (R650 / R550) of the phase difference (R550) was 0.99.

  Since the film (B) was not used, the reverse wavelength dispersibility was poor.

Comparative Example 2
The in-plane retardation (Re) of the film B-1 was 130 nm. The ratio (R450 / R550) of the phase difference (R450) measured at a wavelength of 450 nm to the phase difference (R550) measured at a wavelength of 550 nm is 1.08, measured at a phase difference (R650) measured at a wavelength of 650 nm and a wavelength of 550 nm. The ratio (R650 / R550) of the phase difference (R550) was 0.96.

Since the film (A) was not used, the reverse wavelength dispersibility was poor.

Claims (11)

A film made of a fumarate-based resin, wherein the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film in-plane direction orthogonal thereto is ny, and the refractive index in the film thickness direction is nz. And the film (A) where nx <ny ≦ nz, and the three-dimensional refractive index of the film is nx the refractive index in the fast axis direction in the film plane, and the refraction in the film in-plane direction perpendicular to the film A retardation film comprising a film (B) having a relationship of ny> nx ≧ nz or ny> nz ≧ nx, where ny is the refractive index and nz is the refractive index in the thickness direction of the film. The film (B) has an in-plane retardation (Re) of 50 to 2000 nm measured at a wavelength of 550 nm represented by the following formula (1), where d is the thickness of the film. Item 2. A retardation film according to Item 1.
Re = (ny−nx) × d (1) 3. The retardation film according to claim 1, wherein an in-plane retardation (Re) of the film (A) measured at a wavelength of 550 nm indicated by the formula (1) is 50 to 2000 nm. The retardation film according to claim 1, wherein the fumaric acid ester-based resin comprises 50 mol% or more of a fumaric acid diester residue unit represented by the general formula (a).

(Here, R ₁ and R ₂ each independently represents a branched or cyclic alkyl group having 3 to 12 carbon atoms.) The retardation film according to any one of claims 1 to 4, wherein an angle formed by the fast axis of the film (A) and the fast axis of the film (B) is 90 degrees ± 20 degrees. The difference between the in-plane retardation (Re) of the film (A) measured at 550 nm and the in-plane retardation (Re) of the film (B) is 100 to 160 nm. 6. The retardation film according to any one of 5 above. The difference between the in-plane retardation (Re) of the film (A) measured at 550 nm and the in-plane retardation (Re) of the film (B) is 250 to 300 nm. 6. The retardation film according to any one of 5 above. 8. The ratio (R450 / R550) 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 1.0 or less. Retardation film. The ratio (R650 / R550) of the phase difference (R650) measured at a wavelength of 650 nm and the phase difference (R550) measured at a wavelength of 550 nm is 1 or more, and the position according to any one of claims 1 to 8, Phase difference film. The film (B) is a polycarbonate resin, a polyether sulfone resin, a polyarylate resin, a polyimide resin, a cyclic polyolefin resin, or an N-substituted maleimide resin, according to any one of claims 1 to 9. Retardation film. 11. A composite polarizing plate comprising the retardation film according to claim 1 laminated on a polarizing plate.