JP5625898B2 - Fumaric acid diester resin and retardation film using the same - Google Patents

Description

  The present invention relates to a fumaric acid diester resin, and more specifically, fumaric acid suitable for a retardation film having a high out-of-plane retardation even in a thin film and excellent optical characteristics such as low wavelength dependency. The present invention relates to a diester resin.

  A liquid crystal display is widely used as a most important display device in a multimedia society, such as a mobile phone, a computer monitor, a notebook computer, and a television. Many optical films are used in liquid crystal displays to improve display characteristics. In particular, retardation films play a large role in improving contrast and compensating for color tone when viewed from the front or obliquely. As the conventional retardation film, polycarbonate or cyclic polyolefin is used, and these polymers are polymers having positive birefringence. Here, the sign of birefringence is defined as shown below.

  The optical anisotropy of the polymer film molecularly oriented by stretching or the like can be represented by a refractive index ellipsoid shown in FIG. Here, the refractive index in the fast axis direction in the film plane when the film is stretched is represented by nx, the refractive index in the film in-plane direction orthogonal thereto is represented by ny, and the refractive index in the thickness direction of the film is represented by nz. The fast axis indicates an axial direction having a low refractive index in the film plane.

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

  That is, in the uniaxial stretching of the polymer having negative birefringence, the refractive index in the stretching axis direction is small (fast axis: stretching direction), and in the uniaxial stretching of the polymer having positive birefringence, the axial direction perpendicular to the stretching axis. Has a small refractive index (fast axis: a direction perpendicular to the stretching direction).

  Many polymers have positive birefringence. As a polymer having negative birefringence, there are acrylic resin and polystyrene. However, acrylic resin has a small retardation, and the properties as a retardation film are not sufficient. Polystyrene has a large photoelastic coefficient in the low-temperature region, so the phase difference changes due to slight stress, the problem of stability of the phase difference, the problem of optical properties such as the large wavelength dependence of the phase difference, and heat resistance However, it is not used at present.

  Here, the wavelength dependence of the phase difference means that the phase difference changes depending on the measurement wavelength. The phase difference measured at the wavelength of 450 nm (R450) and the phase difference measured at the wavelength of 550 nm (R550). The ratio can be expressed as R450 / R550. In general, a polymer having an aromatic structure has a strong tendency to increase R450 / R550, and the contrast and viewing angle characteristics in a low wavelength region are deteriorated.

  A stretched polymer film exhibiting negative birefringence has a high refractive index in the thickness direction of the film, resulting in an unprecedented retardation film. For example, a super twist nematic liquid crystal display (STN-LCD) or a vertically aligned liquid crystal As a retardation film for compensating viewing angle characteristics of a display such as a display (VA-LCD), an in-plane alignment type liquid crystal display (IPS-LCD), a reflection type liquid crystal display (reflection LCD), or a viewing angle compensation film of a polarizing plate There is a strong market demand for retardation films that are useful and have negative birefringence.

  A method for producing a film has been proposed in which a polymer having positive birefringence is used to increase the refractive index in the thickness direction of the film. One is a method of applying a shrinkage force in the film thickness direction of the polymer film by applying a heat-stretching treatment to the laminate by heat-stretching the film on one or both sides of the polymer film (see, for example, Patent Documents 1 to 3). It is. In addition, a method of uniaxial stretching in a plane while applying an electric field to a polymer film has been proposed (see, for example, Patent Document 4).

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

  However, the methods proposed in Patent Documents 1 to 4 have a problem that productivity is inferior because the manufacturing process becomes very complicated. In addition, the control of the uniformity of the phase difference and the like is significantly more difficult than the control by the conventional stretching. Further, when polycarbonate is used as the base film, there are problems that the photoelastic coefficient at room temperature is large, the phase difference is changed by a slight stress, and the wavelength dependency is large.

  The retardation film obtained in Patent Document 5 is a retardation film that exhibits negative birefringence by adding fine particles having negative optical anisotropy. From the viewpoint of simplification of production method and economical efficiency, fine particles are obtained. There is a need for retardation films that do not require the addition of.

  Moreover, the film which consists of a fumaric acid diester type resin is proposed (for example, refer patent document 6). Although the optical compensation film obtained in Patent Document 6 has a certain amount of out-of-plane retardation, a film having a higher retardation even in a thinner film is required.

Japanese Patent No. 2818983 JP-A-5-297223 JP-A-5-323120 JP-A-6-88909 JP 2005-156862 A JP 2008-112141 A

  The present invention has been made in view of the above-mentioned problems, and the object thereof is a material suitable for a retardation film having optical characteristics such as a high out-of-plane retardation even in a thin film and a small wavelength dependency. Is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have found that a specific fumaric acid diester resin can solve the above problems, and have completed the present invention. That is, the present invention is a fumaric acid diester-based resin comprising a diisopropyl fumarate residue unit, a ditertiary butyl fumarate residue unit, and a fumaric acid diester residue unit represented by a predetermined general formula, And a retardation film using the same.

  The present invention is described in detail below.

  The fumaric acid diester resin of the present invention includes a diisopropyl fumarate residue unit, a ditert-butyl fumarate residue unit, and a fumaric acid diester residue unit represented by the following general formula (1). It is.

（式中、Ａはそれぞれ独立して水素、又は炭素数１〜１２の直鎖状アルキル基若しくは分岐状アルキル基を示す。）
一般式（１）で表されるフマル酸ジエステル残基単位としては、例えば、フマル酸ジメチル、フマル酸ジエチル、フマル酸ジプロピル、フマル酸ジブチル、フマル酸ジペンチル、フマル酸ジヘキシル、フマル酸ジヘプシル、フマル酸ジオクチル、フマル酸ジノニル、フマル酸ジデシル、フマル酸ジウンデシル、フマル酸ジドデシル、フマル酸ジイソブチル、フマル酸ジ−２−エチルへキシル等が挙げられる。またこれらはフッ素、塩素などのハロゲン基、エーテル基、エステル基またはアミノ基で置換されていてもよい。これらは１種または２種以上含まれていてもよい。

(In the formula, each A independently represents hydrogen, or a linear or branched alkyl group having 1 to 12 carbon atoms.)
As the fumarate diester residue unit represented by the general formula (1), for example, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, dipentyl fumarate, dihexyl fumarate, diheptyl fumarate, fumaric acid Examples include dioctyl, dinonyl fumarate, didecyl fumarate, diundecyl fumarate, didodecyl fumarate, diisobutyl fumarate, di-2-ethylhexyl fumarate, and the like. These may be substituted with a halogen group such as fluorine or chlorine, an ether group, an ester group or an amino group. One or more of these may be contained.

  The composition of the diisopropyl fumarate residue unit, ditertiary butyl fumarate residue unit and the fumaric acid diester residue unit represented by the general formula (1) contained in the fumaric acid diester resin of the present invention is particularly limited. However, since the retardation characteristics and strength when used as a retardation film are excellent, diisopropyl fumarate residue units of 10 to 98 mol%, ditertiary butyl fumarate residue units of 1 to 45 mol%, and 1 to 45 mol% of the fumaric acid diester residue unit represented by the general formula (1) is preferable, and since the retardation property and strength when the retardation film is obtained, the diisopropyl fumarate residue unit 20 ~ 90 mol%, ditertiary butyl fumarate residue units 5 to 40 mol%, and a single fumaric acid diester residue represented by the general formula (1) More preferably 5 to 40 mol%.

  The fumaric acid diester resin of the present invention may contain other monomer residue units as long as it does not exceed the scope of the present invention. Examples of other monomer residue units include styrene residues. Styrene residue units such as group units and α-methylstyrene residue units; (meth) acrylic acid residue units; (meth) methyl acrylate residue units, (meth) ethyl acrylate residue units, (meth) (Meth) acrylate residue units such as butyl acrylate residue units; vinyl ester residue units such as vinyl acetate residue units and vinyl propionate residue units; acrylonitrile residue units, (meth) acrylonitrile residues Unit: vinyl ether residue unit such as methyl vinyl ether residue unit, ethyl vinyl ether residue unit, butyl vinyl ether residue unit; N-methylmaleimide residue unit, N-silane N-substituted maleimide residue units such as rohexylmaleimide residue units and N-phenylmaleimide residue units; olefin residue units such as ethylene residue units and propylene residue units; other than the fumarate diester residue units The fumaric acid diester residue unit and the like can be exemplified, and these residue units may be one kind or two or more kinds.

  Since the fumaric acid diester resin of the present invention has excellent film forming properties and retardation characteristics when used as a retardation film, it is a standard polystyrene obtained from an elution curve measured by gel permeation chromatography (GPC). The converted number average molecular weight is preferably from 50,000 to 500,000, and more preferably from 80,000 to 400,000 because the film forming property and retardation properties when used as a retardation film are more excellent.

  As a manufacturing method of the fumaric acid diester resin of the present invention, for example, it can be manufactured by radical polymerization of diisopropyl fumarate, ditertiary butyl fumarate and the fumaric acid diester represented by the general formula (1).

  For the radical polymerization, 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.

  Examples of the polymerization initiator used in radical polymerization include benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, ditertiary butyl peroxide, tertiary butyl cumyl peroxide, dicumyl peroxide, and tertiary oxide. Organic peroxides such as butyl peroxyacetate, tertiary butyl peroxybenzoate, and tertiary butyl peroxypivalate; 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis Examples thereof include azo initiators such as isobutyronitrile, dimethyl-2,2′-azobisisobutyrate, 1,1′-azobis (cyclohexane-1-carbonitrile), and the like.

  The polymerization temperature at the time of performing radical polymerization can be appropriately set according to the decomposition temperature of the polymerization initiator, and is generally preferably performed in the range of 30 to 150 ° C.

  When the fumaric acid diester resin of the present invention is used as an optical film, it has a high out-of-plane retardation even in a thin film and is excellent in optical properties such as small wavelength dependence. preferable. The retardation film is a retardation film that does not require addition of fine particles.

  In the retardation film of the present invention, the refractive index in the fast axis direction in the film plane is nx, the refractive index in the film plane orthogonal thereto is ny, and the refractive index in the thickness direction of the film is nz. Is preferably nx ≦ ny <nz. By satisfying nx ≦ ny <nz, a retardation film excellent in viewing angle compensation performance such as STN-LCD, IPS-LCD, reflective LCD, and transflective LCD can be obtained. In general, since the control of the three-dimensional refractive index of a film is performed by stretching the film and the like, the manufacturing process and quality control are complicated. Has been found to exhibit a specific behavior of high.

  In addition, since the retardation film of the present invention becomes a retardation film with more excellent optical properties, an out-of-plane retardation (Rth) measured at a wavelength of 550 nm represented by the following formula (a) is −50 to −2000 nm. It is preferable that it is -100--500 nm.

Rth = ((nx + ny) / 2−nz) × d (a)
(In the formula, d represents the thickness of the film.)
Since the retardation film of the present invention has a high out-of-plane retardation even in a thin film, the absolute value of out-of-plane retardation (Rth) / film thickness (μm) is preferably 4.7 nm / μm or more, 15 nm / μm is more preferable.

  The wavelength dependence of the phase difference can be expressed as a 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. In the retardation film of the present invention, R450 / 550 is preferably 1.1 or less, more preferably 1.08 or less, and particularly preferably 1.05 or less.

  The retardation film of the present invention has good image quality characteristics when used in a liquid crystal display element, so that the light transmittance is preferably 85% or more, and more preferably 90% or more. The haze (cloudiness) of the retardation film is preferably 2% or less, more preferably 1% or less.

  The retardation film of the present invention preferably contains an antioxidant during film formation or in order to increase the thermal stability of the retardation film itself. Examples of the antioxidant include hindered phenol antioxidants, phosphorus antioxidants, and other antioxidants, and these antioxidants may be used alone or in combination. And since an antioxidant effect | action improves synergistically, it is especially preferable to mix and use 100-500 weight part of phosphorus antioxidant with respect to 100 weight part of hindered phenolic antioxidant. Moreover, as addition amount of antioxidant, 0.01-10 weight part is preferable with respect to 100 weight part of fumaric-acid diester type resin which comprises the phase difference film of this invention, 0.5-1 weight part is preferable. Further preferred.

  The retardation film of the present invention may contain an ultraviolet absorber in order to improve light resistance. Examples of the ultraviolet absorber include benzotriazole, benzophenone, triazine, benzoate and the like.

  The retardation film of the present invention can be added within the scope of the invention without adding other polymers, surfactants, polymer electrolytes, conductive complexes, inorganic fillers, pigments, antistatic agents, antiblocking agents, lubricants, etc. An agent may be contained.

  Examples of the method for producing the retardation film of the present invention include methods such as a solution casting method and a melt casting method.

  The solution casting method is a method of obtaining a film by casting a solution in which a fumaric acid diester resin is dissolved in a solvent (hereinafter referred to as a dope) on a support substrate and then removing the solvent by heating or the like. In addition to the fumaric acid diester resin, the dope may be prepared by dissolving an antioxidant, an ultraviolet absorber, and other additives in a solvent as necessary. 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, the most common method is to continuously extrude a dope from a die onto a belt-like or drum-like support substrate. Examples of the support substrate used include a glass substrate, a metal substrate such as stainless steel and ferrotype, and a film 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 an extremely important factor, preferably 10 to 20000 cPs, More preferably, it is 10,000 cPs. In addition, the solvent used in that case is not particularly limited as long as the fumaric acid diester resin is dissolved. For example, aromatic hydrocarbons such as toluene and xylene; ketones such as acetone and methyl ethyl ketone; ethyl acetate and acetic acid Examples thereof include esters such as butyl; ethers such as tetrahydrofuran; halogenated hydrocarbons such as chloroform.

  In this case, the coating thickness of the fumaric acid diester resin is preferably 1 to 200 μm after drying, more preferably 5 to 100 μm, and particularly preferably 10 to 50 μm.

  The melt casting method is a molding method in which a fumaric acid diester resin is melted in an extruder and extruded from a narrow slit die such as a T die into a film shape and then cooled and cooled with a roll or air. At this time, the film thickness can be controlled with high accuracy by optimizing the flow path of the molten resin inside the die and controlling the clearance of the die lip.

  The retardation film of the present invention can be used by being peeled off from a glass substrate as a base material or another optical film, and can also be used as a laminate with a glass substrate as a base material or another optical film.

  The retardation film of the present invention can be laminated with a polarizing plate to be used as a circular or elliptical polarizing plate, and can be laminated with a polarizer containing polyvinyl alcohol / iodine or the like to form a polarizing plate. It is. Furthermore, the retardation films of the present invention can be laminated with each other or with other retardation films.

  According to the present invention, the refractive index in the thickness direction of a film useful as a compensation film or antireflection film for contrast and viewing angle characteristics of a liquid crystal display is large, the out-of-plane retardation is negatively large, and the wavelength dependency is small. A fumaric acid diester resin suitable for a retardation film having excellent optical properties can be provided.

  The fumaric acid diester resin of the present invention has a high out-of-plane retardation even in a thin film, has a large refractive index in the thickness direction of the film, and is excellent in optical characteristics such as a low wavelength dependency. It is an acid diester resin and is particularly suitable as an optical compensation film material for liquid crystal display elements.

It is a figure which shows the change of the refractive index ellipsoid by extending | stretching.

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

  Hereafter, the method used for evaluation and measurement of an Example is shown. Unless otherwise noted, commercially available reagents were used.

<Measurement of composition of fumaric acid diesters>
Using a nuclear magnetic resonance measuring apparatus (manufactured by JEOL, trade name JNM-GX270), it was determined by proton nuclear magnetic resonance spectroscopy ( ¹ H-NMR) spectrum analysis.

<Number average molecular weight>
Using a gel permeation chromatography (GPC) apparatus (trade name HLC-8320GPC (equipped with column SuperHM-H) manufactured by Tosoh Corporation) using tetrahydrofuran as a solvent, it was measured at 40 ° C. and obtained as a standard polystyrene equivalent value.

<Evaluation of transparency>
The total light transmittance and haze of the film were measured using a haze meter (trade name NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.).

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

<Film retardation and three-dimensional refractive index>
Measurement was performed using a fully automatic birefringence meter (trade name KOBRA-WR, manufactured by Oji Scientific Instruments).

Synthesis example 1
A 300 mL autoclave equipped with a stirrer and a thermometer was charged with 60 mL of ethylene glycol dimethyl ether, 20 g of maleic acid, and 4 g of sulfuric acid.

  80 mL of ethylene glycol dimethyl ether solution of ditertiary butyl maleate obtained by neutralizing and washing the reaction solution obtained in the above reaction and 0.3 g of piperidine were added to 150 mL equipped with a stirrer, a condenser and a thermometer. The reaction was carried out at 110 ° C. for 2 hours with stirring. As a result of GC analysis of the obtained reaction liquid, the isomerization rate to ditertiary butyl fumarate was 99%. After distilling off the solvent of the obtained reaction liquid, sublimation was performed to obtain 22 g of ditertiary butyl fumarate having a purity of 99%.

  Thereafter, the same synthesis as described above was performed 5 times to obtain 110 g of ditertiary butyl fumarate having a purity of 99%.

Example 1
In a glass ampule with a capacity of 75 mL, 50 g (0.25 mol) of diisopropyl fumarate, 1.9 g (0.008 mol) of ditertiary butyl fumarate obtained in Synthesis Example 1, and 2.8 g (0.016 mol) of diethyl fumarate ) And 0.24 g (0.0014 mol) of tertiary butyl peroxypivalate which is a polymerization initiator, and after repeating nitrogen substitution and depressurization, the mixture was sealed under reduced pressure. The ampoule was placed in a thermostat at 50 ° C. and kept for 48 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum-dried at 80 ° C. for 10 hours to obtain 48 g of a fumaric acid diester resin (yield: 88%).

The number average molecular weight of the obtained fumaric acid diester resin was 152,000. In addition, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 93/3/4.

Example 2
In a glass ampoule with a capacity of 75 mL, 10 g (0.05 mol) of diisopropyl fumarate, 26.6 g (0.117 mol) of ditertiary butyl fumarate obtained in Synthesis Example 1, and 28.7 g (0.166 mol) of diethyl fumarate ), And 1.16 g (0.007 mol) of tertiary butyl peroxypivalate as a polymerization initiator, and after repeating nitrogen substitution and depressurization, the mixture was sealed under reduced pressure. The ampoule was placed in a constant temperature bath at 57 ° C. and kept for 48 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum-dried at 80 ° C. for 10 hours to obtain 50 g of a fumaric acid diester resin (yield: 77%).

The number average molecular weight of the obtained fumaric acid diester resin was 53,000. Further, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 20/39/41.

Example 3
In a glass ampule with a capacity of 75 mL, 35 g (0.175 mol) of diisopropyl fumarate, 25.5 g (0.112 mol) of ditertiary butyl fumarate obtained in Synthesis Example 1, and 2.6 g (0.015 mol) of diethyl fumarate ), And 0.1 g (0.0005 mol) of tertiary butyl peroxypivalate as a polymerization initiator, and after repeating nitrogen substitution and depressurization, the mixture was sealed under reduced pressure. The ampoule was placed in a constant temperature bath at 35 ° C. and held for 120 hours for radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum dried at 80 ° C. for 10 hours to obtain 38 g of a fumaric acid diester resin (yield: 60%).

The number average molecular weight of the obtained fumaric acid diester resin was 402,000. In addition, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 61/34/5.

Example 4
In a glass ampule with a capacity of 75 mL, 60 g (0.3 mol) of diisopropyl fumarate, 3 g (0.013 mol) of ditertiary butyl fumarate obtained in Synthesis Example 1, 2.9 g (0.02 mol) of dimethyl fumarate, Then, 0.29 g (0.0017 mol) of tertiary butyl peroxypivalate as a polymerization initiator was added, and after nitrogen substitution and depressurization were repeated, the mixture was sealed under reduced pressure. The ampoule was placed in a constant temperature bath at 47 ° C. and kept for 48 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum dried at 80 ° C. for 10 hours to obtain 52 g of a fumaric acid diester resin (yield: 79%).

The number average molecular weight of the obtained fumaric acid diester resin was 155,000. In addition, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 91/5/4.

Example 5
In a glass ampule with a capacity of 75 mL, 44 g (0.220 mol) of diisopropyl fumarate, 14 g (0.061 mol) of ditertiary butyl fumarate obtained in Synthesis Example 1, 7 g (0.031 mol) of dinormal butyl fumarate and Tertiary butyl peroxypivalate 0.3g (0.0017mol) which is a polymerization initiator was added, and after nitrogen substitution and depressurization were repeated, it was sealed under reduced pressure. The ampoule was placed in a 45 ° C. constant temperature bath and held for 48 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum-dried at 80 ° C. for 10 hours to obtain 51 g of a fumaric acid diester resin (yield: 78%).

The number average molecular weight of the obtained fumaric acid diester resin was 194,000. Further, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / dinormal butyl fumarate residue unit = 70/23/7.

Example 6
The fumaric acid diester resin obtained in Example 1 was dissolved in methyl isobutyl ketone to form a 15% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 100 ° C. for 10 minutes to obtain a thickness. A retardation film of 14 μm fumaric acid diester resin was obtained.

  The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.466. The three-dimensional refractive index was nx = 1.642, ny = 1.6422, nz = 1.4697, and nx = ny <nz, indicating a large value of the refractive index in the thickness direction of the film. The out-of-plane retardation (Rth) was as negative as −77 nm, and the retardation ratio (R450 / R550) (wavelength dependence) was as small as 1.01. The out-of-plane retardation (Rth) / film thickness (μm) was 5.5 nm / μm.

  From these results, the obtained retardation film has negative birefringence, a large refractive index in the thickness direction, a large out-of-plane retardation, a small wavelength dependency, and a high surface even in a thin film. It had an external phase difference.

Example 7
The fumaric acid diester resin obtained in Example 2 was dissolved in methyl isobutyl ketone to form a 10% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 100 ° C. for 10 minutes to obtain a thickness. A retardation film of 13 μm fumaric acid diester resin was obtained.

  The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.439. The three-dimensional refractive index was nx = 1.4372, ny = 1.4372, and nz = 1.4426, and nx = ny <nz, indicating a large value of the refractive index in the thickness direction of the film. The out-of-plane phase difference (Rth) was as negative as −71 nm, and the phase difference ratio (R450 / R550) (wavelength dependence) was as small as 1.01. The absolute value of out-of-plane retardation (Rth) / film thickness (μm) was 5.5 nm / μm.

  From these results, the obtained retardation film has negative birefringence, a large refractive index in the thickness direction, a large out-of-plane retardation, a small wavelength dependency, and a high surface even in a thin film. It had an external phase difference.

Example 8
The fumaric acid diester resin obtained in Example 3 was dissolved in methyl isobutyl ketone to form a 10% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 100 ° C. for 10 minutes to obtain a thickness. A retardation film of 15 μm fumaric acid diester resin was obtained.

  The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.454. The three-dimensional refractive index was nx = 1.4521, ny = 1.4521, and nz = 1.4578, and nx = ny <nz and the value of the refractive index in the thickness direction of the film were large. The out-of-plane retardation (Rth) was as negative as −85 nm, and the retardation ratio (R450 / R550) (wavelength dependence) was as small as 1.01. The out-of-plane retardation (Rth) / film thickness (μm) was 5.7 nm / μm.

  From these results, the obtained retardation film has negative birefringence, a large refractive index in the thickness direction, a large out-of-plane retardation, a small wavelength dependency, and a high surface even in a thin film. It had an external phase difference.

Example 9
The fumaric acid diester resin obtained in Example 4 was dissolved in methyl isobutyl ketone to form a 15% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 100 ° C. for 10 minutes to obtain a thickness. A retardation film of 16 μm fumaric acid diester resin was obtained.

The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.466. The three-dimensional refractive index was nx = 1.644, ny = 1.644, nz = 1.4693, and nx = ny <nz, indicating a large value of the refractive index in the thickness direction of the film. Further, the out-of-plane retardation (Rth) was as negative as −78 nm, and the retardation ratio (R450 / R550) (wavelength dependence) was as small as 1.01. The absolute value of out-of-plane retardation (Rth) / film thickness (μm) was 4.9 nm / μm.
From these results, the obtained retardation film has negative birefringence, a large refractive index in the thickness direction, a large out-of-plane retardation, a small wavelength dependency, and a high surface even in a thin film. It had an external phase difference.

Example 10
The fumaric acid diester resin obtained in Example 5 was dissolved in methyl isobutyl ketone to give a 15% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 120 ° C. for 10 minutes to obtain a thickness. A retardation film of 17 μm fumaric acid diester resin was obtained.

  The obtained retardation film had a previous light transmittance of 93%, a haze of 0.3, and a refractive index of 1.467. The three-dimensional refractive indexes were nx = 1.4652, ny = 1.4652, and nz = 1.4706, and nx <ny = nz and a large refractive index in the thickness direction of the film were shown. Further, the out-of-plane phase difference (Rth) was as negative as -92, and the phase difference ratio (R450 / R550) (wavelength dependence) was as small as 1.01. The absolute value of out-of-plane retardation (Rth) / film thickness (μm) was 5.4 nm / μm.

  From these results, the obtained retardation film has negative birefringence, a large refractive index in the thickness direction, a large out-of-plane retardation, a small wavelength dependency, and a high surface even in a thin film. It had an external phase difference.

Synthesis example 2
Into a 75 mL glass ampule, 64 g (0.32 mol) of diisopropyl fumarate and 0.52 g (0.003 mol) of tert-butyl peroxypivalate as a polymerization initiator were added, and after nitrogen substitution and depressurization were repeated. Sealed under reduced pressure. The ampule was placed in a thermostatic bath at 50 ° C. and kept for 24 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum-dried at 80 ° C. for 10 hours to obtain 57 g of a fumaric acid diester resin (yield: 89%).

  The number average molecular weight of the obtained fumaric acid diester resin was 115,000.

Further, ¹ H-NMR measurement confirmed that the resin composition was diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 100/0/0.

Synthesis example 3
A glass ampule with a capacity of 75 mL was charged with 60 g (0.263 mol) of di-tert-butyl fumarate and 0.4 g (0.002 mol) of 2,2′-azobiscyclohexanecarbonitrile as a polymerization initiator, and replaced with nitrogen. After repeating the depressurization, it was sealed in a reduced pressure state. The ampoule was placed in a constant temperature bath at 80 ° C. and kept for 24 hours to carry out radical polymerization. After completion of the polymerization reaction, the polymer was taken out from the ampule and dissolved in 400 g of tetrahydrofuran. This polymer solution was dropped into 3 L of methanol and precipitated, and then vacuum dried at 80 ° C. for 10 hours to obtain 48 g of a fumaric acid diester resin (yield: 80%).

The number average molecular weight of the obtained fumaric acid diester resin was 48,000. ¹ H-NMR measurement confirmed that diisopropyl fumarate residue unit / ditertiary butyl fumarate residue unit / diethyl fumarate residue unit = 0/100/0.

Comparative Example 1
The fumaric acid diester resin obtained in Synthesis Example 2 was dissolved in methyl isobutyl ketone to form a 20% by weight resin solution, cast on a polyethylene terephthalate film with a coater, and dried at 100 ° C. for 10 minutes to obtain a thickness. A retardation film of 14 μm fumaric acid diester resin was obtained.

  The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.470. The three-dimensional refractive index was nx = 1.46889, ny = 1.4689, nz = 1.4723, and nx = ny <nz and the refractive index in the thickness direction of the film was large, but the out-of-plane retardation (Rth) was as negative as −48 nm, and the absolute value of out-of-plane retardation (Rth) / film thickness (μm) was as small as 3.4 nm / μm.

Comparative Example 2
The fumaric acid diester resin obtained in Synthesis Example 3 was dissolved in tetrahydrofuran to give a 20% by weight resin solution, cast on a polyethylene terephthalate film by a coater, and dried at 120 ° C. for 10 minutes to obtain a thickness of 14 μm. A phase difference film of a fumaric acid diester resin was obtained.

  The obtained retardation film had a total light transmittance of 93%, a haze of 0.3%, and a refractive index of 1.437. The three-dimensional refractive index was nx = 1.4364, ny = 1.4364, nz = 1.4381, and nx = ny <nz and the refractive index in the thickness direction of the film was large, but the out-of-plane retardation (Rth) was as negative as −24 nm, and the absolute value of out-of-plane retardation (Rth) / film thickness (μm) was also as small as 1.7 nm / μm.

nx: refractive index in the fast axis direction in the film plane ny: refractive index in the film in-plane direction orthogonal to nx nz: refractive index in the film thickness direction

Claims (8)

A fumarate diester resin comprising a diisopropyl fumarate residue unit, a ditertiary butyl fumarate residue unit, and a fumarate diester residue unit represented by the following general formula (1):

(In the formula, each A independently represents hydrogen, or a linear or branched alkyl group having 1 to 12 carbon atoms.) The diisopropyl fumarate residue unit is 10 to 98 mol%, the ditertiary butyl fumarate residue unit is 1 to 45 mol%, and the fumaric acid diester residue unit represented by the general formula (1) is 1 to 45 mol%. The fumaric acid diester resin according to claim 1, wherein The number average molecular weight is 50,000-500,000, The fumaric acid diester resin according to claim 1 or 2. A retardation film comprising the fumaric acid diester resin according to any one of claims 1 to 3. The relationship when 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 it is ny, and the refractive index in the thickness direction of the film is nz is nx ≦ ny <nz. The retardation film according to claim 4, wherein the retardation film is provided. The retardation film according to claim 4 or 5, wherein an out-of-plane retardation (Rth) measured at a wavelength of 550 nm represented by the following formula (a) is -50 to -2000 nm.
Rth = ((nx + ny) / 2−nz) × d (a)
(In the formula, d represents the thickness of the film.) The retardation film according to any one of claims 4 to 6, wherein an absolute value of out-of-plane retardation (Rth) / film thickness (µm) is 4.7 nm / µm or more. 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 1.1 or less, and any one of claims 4 to 7 The retardation film as described in the item.

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