JP2010058455A - Stretched film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film, which is excellent in flexibility and causes double refraction to hardly develop, and a method for manufacturing the film. <P>SOLUTION: A stretched film including amorphous thermoplastic resin under the state that the following conditions (i) and (ii) are simultaneously satisfied and the method for manufacturing the film are dealt. The condition (i) requires that the degree of in-plane orientation in polarized Raman spectrum measurement Dpl is ≥0.3 and ≤3.0. The condition (ii) requires that the degree of Z-direction orientation in the polarized Raman spectrum measurement Dth is ≥0.1 and ≤0.25 or ≥4 and ≤10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a stretched film which is suitable for an optical member and which does not cause birefringence and is made flexible by stretching, and a method for producing the stretched film.

Optical members used in image display devices that handle polarized light, such as liquid crystal display devices (LCDs), are optically transparent and have low birefringence and are required to have optical homogeneity. In particular, in the case of a polarizer protective film for protecting a polarizer or a film substrate for a plastic liquid crystal display device, it is required that the phase difference represented by the product of birefringence and thickness is small. Moreover, in the production process of the optical member, high flexibility is required in order to improve ease of handling.
Currently, a low birefringence film using an acrylic resin (acrylic polymer) having excellent optical properties has been studied, but the acrylic resin generally has a drawback of low flexibility. Then, the method of improving flexibility by giving vertical / horizontal biaxial stretching is disclosed (refer patent document 1).
However, when the vertical and horizontal stretch ratios are different, that is, when there is a large difference in the vertical and horizontal orientation degrees, it becomes a film that is easy to tear, and even if there is no large difference in the vertical and horizontal orientation degrees, Becomes a film that easily peels in the thickness direction. Peeling in the thickness direction means peeling as thin as mica, for example. Thus, the provision of flexibility by stretching largely depends on the stretching balance in the vertical and horizontal directions.

JP 2005-162835 A

  The present invention has been made in view of the above problems, and is intended to provide a stretched film having low birefringence, high flexibility, and low peelability in the thickness direction, which is suitable for optical applications. is there.

The present invention employs the following means in order to solve such problems. That is, the stretched film of the present invention is
(1) A stretched film containing an amorphous thermoplastic resin, wherein the following conditions (i) and (ii) are satisfied at the same time.
(I) The in-plane orientation degree Dpl in the deflection Raman spectrum measurement is 0.3 or more and 3.0 or less.
(Ii) The degree of thickness orientation Dth in the deflection Raman spectrum measurement is 0.1 or more and 0.25 or less, or 4 or more and 10 or less.
(2) The stretched film according to (1), wherein an in-plane retardation Re with respect to light having a wavelength of 589 nm is 10 nm or less.
(3) The stretched film according to (1) or (2), wherein a film thickness direction retardation Rth with respect to light having a wavelength of 589 nm is −10 to +10 nm.
(4) The stretched film according to any one of (1) to (3), wherein the amorphous thermoplastic resin is an acrylic polymer.
(5) The acrylic stretched film according to (4), wherein the glass transition temperature (Tg) of the acrylic polymer is 110 ° C. or higher and 200 ° C. or lower.
(6) The acrylic stretched film according to (4) or (5), wherein the acrylic polymer has a ring structure.
(7) The acrylic stretched film according to any one of (4) to (6), wherein the acrylic polymer has a ring structure in the main chain.
(8) The acrylic stretched film according to (7), wherein the ring structure is at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure. .
(9) The acrylic stretched film according to (7) or (8), wherein the ring structure is a lactone ring structure.
(10) A deflection Raman spectrum measurement is performed at the start of film production to calculate an in-plane orientation degree Dpl and a thickness orientation degree Dth, and any one of the following conditions (iii) to (v) is adjusted based on the results. A method for producing a stretched film.
(Iii) Stretching temperature (iv) Stretching ratio (v) Line speed

  According to the present invention, a stretched film having low birefringence, high flexibility, and low peelability in the thickness direction suitable for optical applications can be provided. For example, various covers, cameras, VTRs, projections can be provided. It can be used for a finder such as a TV, a filter, and the like, and can be used very suitably for a film for a liquid crystal display device such as a polarizer protective film, various optical disk substrate protective films and the like.

Hereinafter, the present invention will be described in detail. However, the scope of the present invention is not limited to these descriptions, and modifications other than the following examples can be made as appropriate without departing from the spirit of the present invention. In the present specification, the “main component” is intended to contain 50% by weight or more. In addition, “a to b” indicating the range indicates a range from a to b. The present invention is described in detail below.

The thermoplastic resin contained in the stretched film of the present invention is not particularly limited as long as it is amorphous, but is more preferably a cycloolefin (co) polymer, a cellulose resin, or an acrylic polymer. is there. The specific example of the thermoplastic resin used for this invention is shown.
(1. Cycloolefin (co) polymer)
The cycloolefin (co) polymer preferably comprises an olefin based on a norbornene structure, in particular norbornene, tetracyclododecene, optionally vinyl norbornene or norbornadiene. Also preferred are cycloolefins (copolymers) comprising polymerized units derived from α-olefins having for example 2 to 20 carbon atoms, particularly preferably acyclic olefins having terminal double bonds such as ethylene or propylene. ) Polymer. Particularly preferred are norbornene / ethylene copolymers and tetracyclododecene / ethylene copolymers.
(2. Cellulosic resin)
The cellulose resin is not particularly limited as long as the hydroxyl group of cellulose is substituted with various substituents, but is preferably a cellulose acylate substituted with an acyl group because birefringence hardly occurs. In addition, when the degree of substitution is low, positive birefringence is likely to be exhibited, and when the degree of substitution is high, negative birefringence is likely to occur and is likely to be exhibited. It is preferable that

Specific examples of such cellulose acylates have a plurality of acyl groups such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, and cellulose acetate benzoate. Things.
(3. Acrylic resin)
The acrylic resin is a resin obtained by polymerizing acrylic acid, methacrylic acid and derivatives thereof as a main component and derivatives thereof. For example, the general formula (1)

(In the formula, R 1 and R 2 each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. Specifically, the organic residue is a linear or branched chain having 1 to 20 carbon atoms. Preferred examples of the compound (monomer) having a structure represented by a chain or cyclic alkyl group, acrylic acid, methacrylic acid and derivatives thereof include methyl (meth) acrylate, (meth ) Ethyl acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, 2-chloroethyl (meth) acrylate, (Meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydroxyexyl and (meth) acrylic acid Such as Le acid 2,3,4,5-hydroxypentyl and the like. Among these, only 1 type may be used and 2 or more types may be used together. Of these, methyl (meth) acrylate is most preferred because of its excellent thermal stability.
In addition, from the viewpoint of heat resistance, methacrylic thermoplastic resins may be copolymerized with N-substituted maleimides such as phenylmaleimide, cyclohexylmaleimide and methylmaleimide, or in the molecular chain (in the main skeleton in the polymer). Alternatively, a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, or the like may be introduced into the main chain). Especially, the structure which does not contain a nitrogen atom from the point of the difficulty of coloring (yellowing) of a film is preferable. Moreover, the thing which has a lactone ring structure in a principal chain from the point which is easy to express a positive birefringence (positive phase difference) is preferable. Regarding the lactone ring structure in the main chain, a 4- to 8-membered ring may be used, but a 5- to 6-membered ring is more preferable, and a 6-membered ring is particularly preferable in terms of the stability of the structure. As described above, examples of the case where the lactone ring structure in the main chain is a 6-membered ring include a general formula (2) described later and a structure represented in Japanese Patent Application Laid-Open No. 2004-168882. When synthesizing a polymer before introducing a lactone ring structure into the polymer, it is possible to obtain a polymer having a high polymerization yield, a polymer having a high content of lactone ring structure with a high polymerization yield, methyl methacrylate, etc. It is preferable that it is a structure represented by General formula (2) at a point with good copolymerizability with (meth) acrylic acid ester.
Moreover, these acrylic resins may have a unit obtained by copolymerizing other monomer components that can be copolymerized within a range that does not impair the heat resistance. Specific examples of other monomer components that can be copolymerized include aromatic vinyl monomers such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile, vinyl esters such as vinyl acetate, and the like. Can be given. If the weight average molecular weight of the above acrylic resin is in the range of 50,000 or more and 2,000,000 or less, the effect of the invention for minimizing thickness unevenness can be exhibited, but preferably 70,000 or more, It is within the range of 000,000 or less, more preferably within the range of 90,000 or more and 500,000 or less.
What is necessary is just to superpose | polymerize the monomer composition containing (meth) acrylic acid ester as a method of manufacturing the said acrylic resin using a well-known method. The polymerization temperature and the polymerization time vary depending on the type of monomer (monomer composition) used, the ratio of use, and the like. Preferably, the polymerization temperature is in the range of 0 ° C. to 150 ° C., and the polymerization time is 0.00. It is in the range of 5 hours to 20 hours, more preferably, the polymerization temperature is in the range of 80 ° C. to 140 ° C., and the polymerization time is in the range of 1 hour to 10 hours. In the case of a polymerization form using a solvent, the polymerization solvent is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ether solvents such as tetrahydrofuran Etc., and only one of these may be used, or two or more may be used in combination. When producing the lactone ring-containing polymer described later, if the boiling point of the solvent used is too high, the residual volatile content of the lactone ring-containing polymer finally obtained increases, so the boiling point is 50 ° C. or higher and 200 ° C. Those within the following ranges are preferred.
During the polymerization reaction, a polymerization initiator may be added as necessary. Examples of the polymerization initiator include cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxyisopropyl carbonate, and t-amyl peroxy-2. -Organic peroxides such as ethylhexanoate; 2,2'-azobis (isobutyronitrile), 1,1'-azobis (cyclohexanecarbonitrile), 2,2'-azobis (2,4-dimethylvalero) Azo compounds such as nitrile), and the like. These may be used alone or in combination of two or more. What is necessary is just to set the usage-amount of a polymerization initiator suitably according to the combination of the monomer to be used, reaction conditions, etc.
When performing the polymerization, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 50% by weight or less in order to suppress gelation of the reaction solution. Specifically, when the concentration of the produced polymer in the polymerization reaction mixture exceeds 50% by weight, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture and controlled to be 50% by weight or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 45% by weight or less, still more preferably 40% by weight or less. Note that if the concentration of the polymer in the polymerization reaction mixture is too low, the productivity is lowered. Therefore, the concentration of the polymer in the polymerization reaction mixture is preferably 10% by weight or more, and more preferably 20% by weight or more. It is more preferable.
The form in which the polymerization solvent is appropriately added to the polymerization reaction mixture is not particularly limited, and the polymerization solvent may be added continuously or intermittently. By controlling the concentration of the produced polymer in the polymerization reaction mixture in this way, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, to increase the lactone ring content and improve the heat resistance. Even when the ratio of hydroxyl groups and ester groups in the molecular chain is increased, gelation can be sufficiently suppressed.
The polymerization solvent to be added may be the same type of solvent used during the initial charging of the polymerization reaction or may be a different type of solvent, but is the same as the solvent used during the initial charging of the polymerization reaction. It is preferable to use different types of solvents. Further, the polymerization solvent to be added may be only one type of solvent or a mixed solvent of two or more types. In the polymerization reaction mixture obtained when the polymerization reaction is completed, a solvent is usually contained in addition to the obtained polymer. In the case where the polymer is a lactone ring-containing polymer described in detail below, it is not necessary to completely remove the solvent and take out the polymer in a solid state. It is preferable to perform a polycondensation step. If necessary, after taking out in a solid state, a solvent suitable for the subsequent lactone cyclization condensation step may be added again.
The hue of the acrylic resin obtained by the polymerization reaction is not particularly limited, but it is preferable that it is transparent and has a small yellowing degree because it does not impair the original characteristics of the acrylic resin. For example, the acrylic resin has a haze value of 3 or less, more preferably 2 or less, and most preferably 1 or less when formed into a molded body having a thickness of 3 mm. The molded article has a YI (yellow index) value of 10 or less, preferably 5 or less.
(Lactone ring-containing polymer)
The acrylic resin has high transparency, heat resistance, and optical isotropy, and can fully exhibit the characteristics according to various optical applications. Therefore, the (meth) acrylic acid ester copolymer has an intramolecular ring. It is preferable to include a so-called lactone ring-containing polymer into which a lactone ring structure is introduced by a fluorination reaction, and it is particularly preferable to use a polymer as a main component. The lactone ring-containing polymer is not particularly limited, but preferably has a lactone ring structure represented by the following general formula (2).

(In the formula, R 3, R 4 and R 5 each independently represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.)
The content of the lactone ring structure represented by the general formula (2) in the lactone ring-containing polymer structure is preferably 5% by weight to 90% by weight, more preferably 10% by weight to 70% by weight, Preferably they are 10 weight% or more and 60 weight% or less, Especially preferably, they are 10 weight% or more and 50 weight% or less. When the content is less than 5% by weight, the heat resistance, solvent resistance and surface hardness may be insufficient, which is not preferable. On the other hand, when the content is more than 90% by weight, molding processability may be poor, which is not preferable.
The lactone ring-containing polymer may have a structure other than the lactone ring structure represented by the general formula (2). Examples of structures other than the lactone ring structure represented by the general formula (2) include, for example, (meth) acrylic acid esters, hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the following general formula (3). A polymer structural unit (repeating structural unit) constructed by polymerizing at least one selected from is preferred.

(Wherein R6 represents a hydrogen atom or a methyl group, X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an -OAc group, a -CN group, a -CO-R7 group, or -C-O) -R8 group, Ac group represents an acetyl group, R7 and R8 represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.) In particular, when the present invention is used for a lactone ring-containing polymer, An optical film made of a heat-resistant acrylic resin having uniform physical properties is obtained without causing defects such as cracks, surface unevenness, and streaks.

In the lactone ring-containing polymer, the content ratio of the structure other than the lactone ring structure represented by the general formula (2) is that of a polymer structural unit (repeating structural unit) constructed by polymerizing (meth) acrylic acid ester. In this case, it is preferably in the range of 10% to 95% by weight, more preferably in the range of 10% to 90% by weight, still more preferably in the range of 40% to 90% by weight, particularly preferably 50%. It is in the range of not less than 90% by weight.
In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing a hydroxyl group-containing monomer, the content ratio of the structure other than the lactone ring structure represented by the general formula (2) is preferably 0 weight. % To 30% by weight, more preferably 0% to 20% by weight, even more preferably 0% to 15% by weight, particularly preferably 0% to 10% by weight. Within the following range. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing an unsaturated carboxylic acid, the content of the structure other than the lactone ring structure represented by the general formula (2) is preferably 0% by weight. In the range of 30 wt% or less, more preferably in the range of 0 wt% or more and 20 wt% or less, more preferably in the range of 0 wt% or more and 15 wt% or less, particularly preferably in the range of 0 wt% or more and 10 wt% or less Is within the range.
In addition, in the case of a polymer structural unit (repeating structural unit) constructed by polymerizing the monomer represented by the general formula (3), inclusion of a structure other than the lactone ring structure represented by the general formula (2) The ratio is preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight, still more preferably in the range of 0 to 15% by weight, particularly preferably It is in the range of 0 wt% or more and 10 wt% or less.
The method for producing the lactone ring-containing polymer is not particularly limited. Preferably, after obtaining a polymer having a hydroxyl group and an ester group in the molecular chain by a polymerization step, the polymer is heat-treated. Can be obtained by conducting a lactone ring condensation reaction for introducing a lactone ring structure into the polymer.
By forming the lactone ring structure in the molecular chain of the polymer (in the main skeleton of the polymer), high heat resistance is imparted to the polymer. If the reaction rate of the cyclization condensation reaction leading to the lactone ring structure is insufficient, the heat resistance will not be improved sufficiently, or the condensation reaction will occur during the molding process due to the heat treatment during molding, and the resulting alcohol will be contained in the molded product. It is not preferable because it may exist as bubbles or silver streaks.
Regarding the method for heat-treating the polymer to perform the lactone ring condensation reaction, for example, the polymerization reaction mixture containing the solvent obtained by the polymerization step may be heat-treated as it is. Moreover, you may heat-process using a ring-closing catalyst as needed in presence of a solvent. Further, the heat treatment can be performed using a heating furnace or reaction apparatus having a vacuum apparatus or a devolatilizing apparatus for removing volatile components, an extruder having a devolatilizing apparatus, or the like.
In carrying out the cyclization condensation reaction, other acrylic resins may coexist in addition to the polymer. Further, when performing the cyclization condensation reaction, if necessary, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid generally used as a catalyst for the cyclization condensation reaction may be used. Organic carboxylic acids such as propionic acid, benzoic acid, acrylic acid, and methacrylic acid may be used as a catalyst. As disclosed in JP-A-61-254608 and JP-A-61-261303, basic compounds, organic carboxylates, carbonates and the like may be used.
In carrying out the cyclization condensation reaction, it is preferable to use an organic phosphorus compound as a catalyst. By using an organophosphorus compound as a catalyst, the cyclization condensation reaction rate can be improved, and coloring of the resulting lactone ring-containing polymer can be greatly reduced. Furthermore, by using an organophosphorus compound as a catalyst, it is possible to suppress a decrease in molecular weight that can occur when a devolatilization step described later is used in combination, and to impart excellent mechanical strength.
Examples of the organic phosphorus compound that can be used as a catalyst in the cyclocondensation reaction include alkyl (aryl) phosphonous acids such as methylphosphonous acid, ethylphosphonous acid, and phenylphosphonous acid (however, Tautomers (which may be alkyl (aryl) phosphinic acid) and diesters or monoesters thereof; dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid, etc. Dialkyl (aryl) phosphinic acids and esters thereof; alkyl (aryl) phosphonic acids such as methyl phosphonic acid, ethyl phosphonic acid, trifluoromethyl phosphonic acid, phenyl phosphonic acid, and their diesters or monoesters; Alkyl (aryl) phosphinic acids such as phosphoric acid, ethylphosphinic acid, phenylphosphinic acid and their esters; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, phosphorous acid Phosphorous acid diester or monoester or triester such as diethyl, diphenyl phosphite, trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, phosphorus Isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, phosphorus Diisostearyl acid, diphenyl phosphate, trimethyl phosphate , Phosphoric diesters or monoesters or triesters such as triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine, phenylphosphine, dimethyl Phosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine, etc. mono-, di- or trialkyl (aryl) phosphine; methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, Alkyl (aryl) halogen phosphines such as diphenylchlorophosphine; Sphine, phenylphosphine oxide, dimethylphosphine oxide, diethylphosphine oxide, diphenylphosphine oxide, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide, mono-, di- or trialkyl (aryl) phosphines; tetramethylphosphonium chloride, chloride And halogenated tetraalkyl (aryl) phosphonium such as tetraethylphosphonium and tetraphenylphosphonium chloride. Among these, alkyl (aryl) phosphonous acid, phosphorous acid diester or monoester, phosphoric acid diester or monoester, and alkyl (aryl) phosphonic acid are preferable because of high catalytic activity and low colorability. ) Phosphorous acid, phosphorous acid diester or monoester, phosphoric acid diester or monoester are more preferred, and alkyl (aryl) phosphonous acid, phosphoric acid diester or monoester is particularly preferred. These organic phosphorus compounds may use only 1 type and may use 2 or more types together.
The amount of the catalyst used in the cyclization condensation reaction is not particularly limited, but is preferably in the range of 0.001 to 5% by weight, more preferably 0.01 to 2.5% by weight with respect to the polymer. %, More preferably 0.01 to 1% by weight, particularly preferably 0.05 to 0.5% by weight. If the amount of the catalyst used is less than 0.001% by weight, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the other hand, if the amount exceeds 5% by weight, coloring may occur, This is not preferable because it may be difficult to melt and form by crosslinking of the coalesced. The addition timing of the catalyst is not particularly limited, and it may be added at the beginning of the reaction, during the reaction, or both.
It is preferable to carry out the cyclization condensation reaction in the presence of a solvent and to use a devolatilization step in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used throughout the cyclization condensation reaction and a mode in which the devolatilization step is not used throughout the entire cyclization condensation reaction and are used in only a part of the process. In the method using the devolatilization step in combination, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous for the production side.

  Next, the specific manufacturing method of the stretched film of this invention is shown.

  As a method of forming the film, any conventionally known method can be used. Examples thereof include a solution casting method (solution casting method) and a melt extrusion method, and any of them can be employed. For example, when trying to obtain a film using the solution casting method (solution casting method), the thermoplastic resin as the main component and, if necessary, other polymers and other additives are mixed in a good solvent with stirring. Then, it can be obtained as a uniform mixed solution, cast on a support film or drum and pre-dried until it has self-supporting properties, and then peeled off from the support film or drum and dried. Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol And alcohol solvents such as n-butanol and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, ethyl acetate, and diethyl ether. These solvents may be used alone or in combination of two or more.

Examples of the apparatus for performing the solution casting method (solution casting method) include a drum type casting machine, a belt type casting machine, and a spin coater.
In the melt extrusion method, an extruder equipped with a T-shaped die or the like, or an inflation method is used to extrude a thermoplastic resin or, if necessary, a thermoplastic resin previously kneaded with other polymers or other additives by heating and melting. By taking up the obtained film, a film having an arbitrary thickness can be obtained.

  As a stretching method for obtaining a stretched film according to the present invention, a conventionally known stretching method can be applied. For example, uniaxial stretching such as free-width uniaxial stretching and constant-width uniaxial stretching; biaxial stretching such as sequential biaxial stretching and simultaneous biaxial stretching; and a laminate by adhering a shrinkable film to one or both sides of the film during stretching A birefringent film in which molecular groups oriented in the stretching direction and the thickness direction are mixed by forming and heat-stretching the laminate and applying a shrinkage force in a direction perpendicular to the stretching direction to the film. Stretching to obtain. Biaxial stretching is preferable in that the bending resistance is improved. Furthermore, simultaneous biaxial stretching is preferred in that the bending resistance to any two orthogonal directions in the film plane is improved.

  Examples of the stretching apparatus include a roll stretching machine, an oven-type stretching machine, a tenter-type stretching machine, and a small experimental stretching apparatus such as a tensile tester, a uniaxial stretching machine, a sequential biaxial stretching machine, and a simultaneous biaxial stretching machine. The retardation film according to the present invention can be obtained using any of these apparatuses, but when the film is sequentially biaxially stretched in the flow direction (X direction) and the width direction (Y direction). It is desirable to use a roll stretching machine or a combination of an oven-type longitudinal stretching machine and a tenter-type stretching machine, but in the film flow direction (X direction) and width direction (Y direction) using a simultaneous biaxial stretching machine. You may extend | stretch simultaneously.

The thickness of the stretched film of the present invention is not particularly limited. This is because the Raman spectrum is used for the measurement, and is due to the characteristic that the focal point of the measurement and the depth inside the film can be focused, and it is 2 μm or more and 10 mm (1 cm) or less. It can be used without any problems. Moreover, even if it is a laminated | multilayer film, if the thickness of each layer is 2 micrometers or more, the orientation degree of arbitrary layers can be measured. However, when handling property as a film is considered, 5 μm or more and 500 μm or less are suitable. More preferably, they are 10 micrometers or more and 100 micrometers or less.
The stretched film of the present invention is a stretched film containing an amorphous thermoplastic resin that simultaneously satisfies at least the following conditions (i) and (ii).
(I) The in-plane orientation degree Dpl in the deflection Raman spectrum measurement is 0.3 or more and 3.0 or less.
(Ii) Thickness orientation degree Dth in deflection Raman spectrum measurement is 0.1 or more and 0.25 or less, or 4.0 or more and 10.0 or less.

Next, a method for evaluating the in-plane orientation degree Dpl and the thickness orientation degree Dth of the present invention will be described in detail. The evaluation method proceeds according to the following procedure.
[1] The Raman spectrum of the stretched film is measured without using a polarizing filter, and one peak attributed to a substituent oriented in a direction parallel or perpendicular to the main chain of the resin constituting the film is selected ( Let P _P. ). Also selects one peak attributed to a substituent that can not identify the orientation relative to the main chain (and P _S).
[2] the flow direction X direction of the film, the width direction of the film Y direction, the thickness direction of the film as the Z direction to measure the X-direction of the polarized Raman spectra of the XY plane, the intensity of the peak corresponding to P _P ( S _XY X _P) and to calculate the ratio _{(S XY X P / S XY} X S) of the intensity of the peak corresponding to _{P S (S XY X S)} , and _{S XY} X. In addition, when the flow direction and the width direction are not clear as in a cut film or the like, the polarization Raman spectrum in the XY plane is rotated in-plane every 10 °, and similarly measured in the range of 0 ° to 170 °. the direction in which P _P is the largest measured X direction, the direction in which P _P is the smallest measured and the Y direction. In the case resulted in no differences in P _P determined in an arbitrary direction in the X and Y directions.
[3] Similarly to measure the polarized Raman spectra of the XY plane Y-direction, the ratio of the intensity of the peak corresponding to _{P P (S} XY _{Y P)} and the intensity of the peak corresponding to _{P S (S XY Y S)} ( calculating the _{S XY Y P / S XY Y} S), and _{S XY} Y.
[4] Let (S _XY X / S _XY Y) be the in-plane orientation degree Dpl.
[5] polarized Raman spectra of X-direction in the XZ plane is measured, the ratio _{(S XZ} intensity peaks corresponding to _{P P (S} XZ _{X P)} and the intensity of the peak corresponding to _{P S (S} XZ _{X S)} X _P / S _XZ X _S ) is calculated and set as S _XZ X.
[6] polarized Raman spectrum of Z-direction in the XZ plane is measured, the ratio _{(S XZ} intensity peaks corresponding to _{P P (S} XZ _{Z P)} and the intensity of the peak corresponding to _{P S (S} XZ _{Z S)} Z _P / S _XZ Z _S ) is calculated and set as S _XZ Z.
[6] polarized Raman spectra of Y direction YZ plane was measured, the ratio _{(S YZ} intensity peaks corresponding to _{P P (S} YZ _{Y P)} and the intensity of the peak corresponding to _{P S (S} YZ _{Y S)} Y _P / S _YZ Y _S ) is calculated and set as S _YZ Y.
[7] polarized Raman spectrum of Z-direction of the YZ plane was measured, the ratio _{(S YZ} intensity peaks corresponding to _{P P (S} YZ _{Z P)} and the intensity of the peak corresponding to _{P S (S} YZ _{Z S)} Z _P / S _YZ Z _S ) is calculated and set as S _YZ Z.
[8] Let {(S _XZ X × S _YZ Y) ^1/2 } / {(S _XZ Z × S _YZ Z) ^1/2 } be the thickness orientation degree Dth.
When the orientation degree of the resin constituting the stretched film is equal in the X direction and the Y direction, the in-plane orientation degree Dpl is 1.
If in-plane orientation degree Dpl is less than 1, if the peak attributable to the substituents oriented direction parallel to P _P to the main chain of the resin are oriented in the Y direction, the direction perpendicular to the opposite When the peak is attributed to the facing substituent, it is oriented in the X direction. Also, if the in-plane orientation degree Dpl is greater than 1, are oriented in the X direction when the peak attributable to the substituents oriented direction parallel to the main chain of the resin P _P, perpendicular to the opposite The peak attributed to the substituent that faces the direction is oriented in the Y direction.
Note that the in-plane orientation degree Dpl is a value larger than zero.
When the in-plane orientation degree Dpl is smaller than 0.3 or larger than 3.0, the stretching ratio in the vertical and horizontal directions is not balanced, and the film is easy to tear and / or the film showing anisotropy in the vertical and horizontal directions Become. Preferably they are 0.6 or more and 2 or less, More preferably, they are 0.8 or more and 1.2 or less.
When the resin constituting the stretched film is not oriented, or the orientation degree of the resin is equal in the X direction, Y direction, and Z direction, or the average orientation degree of the resin in the X direction and the Y direction and the orientation degree in the Z direction are When equal, the thickness orientation degree Dth is 1.
If the thickness orientation Dth is less than 1, are oriented in the Z direction when the peak attributable to the substituents oriented direction parallel to P _P to the main chain of the resin, toward the direction perpendicular to the opposite When the peak is attributed to a substituent, the draw ratio (surface ratio) in the XY plane direction is high. Further, if the thickness orientation Dth is greater than 1, P _P and high when the peak attributed to the substituents oriented direction parallel to the main chain of the resin stretching ratio in the XY plane direction (plane ratio) is, Conversely, if the peak is attributed to a substituent that faces in the vertical direction, it is oriented in the Z direction.
Note that the thickness orientation degree Dth is also greater than zero.

  When the thickness orientation degree Dth is larger than 0.25 and smaller than 4.0, the effect of improving flexibility by stretching is small, and a brittle film is obtained. On the other hand, when it is smaller than 0.1 or larger than 10.0, the film is easily peeled in the thickness direction because the plane orientation is too strong. Preferably they are 0.11 or more and 0.2 or less, or 5 or more and 9 or less, More preferably, they are 0.13 or more and 0.17 or less, or 6 or more and 8 or less.

  When the in-plane orientation degree Dpl of the obtained stretched film is less than 0.3 or greater than 3.0, the stretching temperature and / or stretching is performed in order to match the stretching balance in the X direction and the Y direction. What is necessary is just to change magnification, and if it is a continuous film forming apparatus, the same effect will be acquired even if it changes line speed.

Furthermore, when the thickness orientation degree Dth of the obtained stretched film is larger than 0.25 and smaller than 4, it is because the stretching is insufficient, so the stretching temperature and / or the stretching ratio is changed to increase the surface magnification. Do it. Moreover, if it is a continuous film forming apparatus, the same effect can be obtained even if the line speed is lowered. If the thickness orientation degree Dth is smaller than 0.1 or larger than 10, it is because the film has been stretched too much. Therefore, the surface magnification may be lowered by changing the stretching temperature and / or the stretching ratio. Moreover, if it is a continuous film forming apparatus, the same effect can be obtained even if the line speed is increased.
Next, a method for measuring film properties will be described.
The physical properties in the present invention are measured by the following method. The same method was used in the examples and comparative examples.
<Glass transition temperature>
Although there are various measuring methods for the glass transition temperature, in this specification, it is defined as a temperature obtained by a midpoint method according to ASTM-D-3418 using a differential scanning calorimeter (DSC).
<Thickness of film>
Measurement was performed using a Digimatic Micrometer (manufactured by Mitutoyo Corporation).
<Phase difference>
The in-plane retardation value (Re) and thickness direction retardation value (Rth) of the film at a wavelength of 589 nm were measured using KOBRA-WR manufactured by Oji Scientific Instruments. The thickness direction retardation value (Rth) is the average refractive index of the film measured with an Abbe refractometer, the film thickness d, the slow axis as the tilt central axis, and the incident angle of 40 °, and the in-plane retardation value. (Re), thickness direction retardation value (Rth), retardation value measured by tilting 40 ° with slow axis as tilt axis (Re (40 °)), three-dimensional refractive index nx, ny, nz Was obtained from the following formula.
Thickness direction retardation Rth (nm) = d × {(nx + ny) / 2−nz}
<Bending test>
The film bending test was performed in two directions, ie, a direction in which the film was stretched and a direction perpendicular to the stretched direction. In the case of a biaxially stretched film, the test was performed in two orthogonal stretching directions. When bent at 180 ° at a bending radius of 1 mm in an atmosphere of 25 ° C. and 65% RH, “○” indicates that no cracks are generated in both directions, “△” indicates that cracks are generated in only one direction, and cracks in both directions. The state where the occurrence of was evaluated as “×”.

EXAMPLES The present invention will be described in further detail below with reference to examples, but the present invention is not limited thereto.
[Production Example 1]
A 1 m2 reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe is charged with 204 kg of methyl methacrylate (MMA), 51 kg of methyl 2- (hydroxymethyl) acrylate (MHMA), and 249 kg of toluene. Then, while the temperature was raised to 105 ° C. while refluxing nitrogen and refluxed, 281 g of tertiary amyl peroxyisononanoate (manufactured by Atofina Yoshitomi, trade name: Luperox 570) was added as a polymerization initiator. While a solution comprising a polymerization initiator and 5.4 kg of toluene was added dropwise over 2 hours, solution polymerization was performed under reflux (about 105 to 110 ° C.), followed by further aging for 4 hours.

  To the obtained polymer solution, 255 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 110 ° C.) for 5 hours. A condensation reaction was performed.

  Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 250 ° C., a rotation speed of 150 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent of 1 and a forevent of 4 It is introduced into a type screw twin screw extruder (Φ = 42 mm, L / D = 42) at a processing rate of 15 kg / hour in terms of the amount of resin, subjected to cyclization condensation reaction and devolatilization in the extruder, and then extruded. Thus, a transparent pellet was obtained.

Next, 90 parts of heat-resistant acrylic resin pellets, AS resin (Stylac AS783 manufactured by Asahi Kasei Chemicals Corporation) 10 using a single screw extruder of L / D = 36 consisting of a full flight type screw having a mixing part of Φ50 mm, multi-flight structure Part and 0.04 part of zinc acetate were melt-extruded at a cylinder set temperature of 270 ° C. at a processing rate of 50 kg / hour to prepare resin pellets (1A). The obtained resin pellet (1A) had a mass average molecular weight of 132,000, a lactone ring content of 28.5%, and a glass transition temperature of 125 ° C.
Example 1
The resin pellet (1A) obtained in Production Example 1 is melt-extruded at a temperature of 270 ° C. to form an unstretched film having a thickness of 180 μm, and then heated to a temperature of 130 ° C. to increase 1.9 times in the longitudinal direction. Stretching was performed. Further, as it is, 20 mm from both ends of the film is gripped with a 2 inch clip, supplied to a tenter, heated to 145 ° C., stretched 2.2 times, and stretched film having an average film thickness of 45 μm (1AF-1) Got.
About the obtained stretched film (1AF-1), the Raman spectrum was measured using Laser Raman Spectrophotometer JASCO NRS-3100 by JASCO Corporation, and in-plane orientation degree Dpl and thickness orientation degree Dth were computed. Measurement and calculation were performed according to the following procedure.
(1) The direction of film flow was the X direction, the width direction of the film was the Y direction, the thickness direction of the film was the Z direction, and a square measurement sample was accurately cut out by 10 mm in both the X and Y directions. The cut sample was set on the sample holder with the axes aligned so that the XY plane could be measured.
(2) Raman spectrum measurement was performed without using a polarizing filter. The peaks of the obtained Raman spectrum were assigned. 2960 cm ⁻¹ peak (C—H stretching) as a peak (P _P ) attributed to a substituent oriented in a direction perpendicular to the main chain, a peak attributed to a substituent whose direction cannot be specified with respect to the main chain A peak (CH ₂ variable angle) of 1460 cm ⁻¹ was selected as (P _S ).
(3) in the X direction polarized Raman spectra of the XY plane is measured, the ratio _{(S XY} intensity peaks corresponding to _{P P (S} XY _{X P)} and the intensity of the peak corresponding to _{P S (S} XY _{X S)} X) was calculated to be 5.64. It should be _noted that S _XY X = S _{XY XP} / S _XY X _S.
(4) The polarized Raman spectra of the XY plane Y-direction were measured, the ratio _{(S XY} intensity peaks corresponding to _{P P (S} XY _{Y P)} and the intensity of the peak corresponding to _{P S (S} XY _{Y S)} Y) was calculated to be 4.58. Note _that it is _{S XY Y = S XY Y P} / S XY Y S.
(5) Degree of in-plane orientation Dpl = (S _XY X / S _XY Y) = 1.23.
(6) The sample was cut into the sample holder and set so that the XZ plane (cut plane) of the sample could be measured, and the polarization Raman spectrum in the X direction of the XZ plane was measured. Was calculated the ratio of the intensity of the peak corresponding to _P P _(S XZ _X P) and the intensity of the peak corresponding to _{P S (S XZ X S)} (S XZ X), it was 0.95. Note _that it is _{S XZ X = S XZ X P} / S XZ X S.
(7) also measures the polarized Raman spectra of Z-direction in the XZ plane, the ratio of the intensity of the peak corresponding to _{P P (S} XZ _{Z P)} and the intensity of the peak corresponding to _{P S (S} XZ _{Z S)} (S _XZ Z) was calculated to be 6.10. Note that S _XZ Z = S _XZ Z _P / S _XZ Z _S.
(8) The sample was cut into the sample holder and set so that the YZ plane (cut plane) of the sample could be measured, and the polarization Raman spectrum in the Y direction of the YZ plane was measured. Was calculated the ratio of the intensity of the peak corresponding to _P P _(S YZ _Y P) and the intensity of the peak corresponding to _{P S (S YZ Y S)} (S YZ Y), it was 0.93. Note that S _YZ Y = S _YZ Y _P / S _YZ Y _S.
(9) also measures the polarized Raman spectra in the Z direction of the YZ plane, the ratio of the intensity of the peak corresponding to _{P P (S} YZ _{Z P)} and the intensity of the peak corresponding to _{P S (S} YZ _{Z S)} (S _YZ Z) was calculated to be 5.71. Note that S _YZ Z = S _YZ Z _P / S _YZ Z _S.
(10) Thickness orientation degree Dth = {(S _XZ X × S _YZ Y) ^1/2 } / {(S _XZ Z × S _YZ Z) ^1/2 } = 0.16.
The properties of the obtained stretched film (1AF-1) were as follows, and it was a stretched film excellent in flexibility.

In-plane retardation Re (nm): 1.6
Thickness direction retardation Rth (nm): 0.9
Bending test: ○
In-plane orientation degree Dpl: 1.23
Thickness orientation degree Dth: 0.16
(Example 2)
The resin pellet (1A) obtained in Production Example 1 was melt extruded at a temperature of 270 ° C. to form an unstretched film having a thickness of 180 μm, and an unstretched film having an average film thickness of 180 μm was obtained. Next, from the obtained unstretched film, a square unstretched film sample of 98 mm in both the flow direction (X direction) and the width direction (Y direction) was accurately cut out.
The cut unstretched film sample was sequentially biaxially stretched with a biaxial stretching apparatus (TYPE EX4 manufactured by Toyo Seiki Seisakusho) to obtain a stretched film (1AF-2) having an average film thickness of 60 μm. The first stage stretching is performed in the X direction at a stretching temperature of 150 ° C., a stretching ratio of 1.5 times, and a stretching speed of 1000% / min. The second stage of stretching is performed in the Y direction at a stretching temperature of 150 ° C. and a stretching ratio of 1.5%. The stretching speed was 1000% / min.
The properties of the obtained stretched film (1AF-2) were as follows, and it was a stretched film excellent in flexibility.

In-plane retardation Re (nm): 0.8
Thickness direction retardation Rth (nm): 3.1
Bending test: ○
In-plane orientation degree Dpl: 1.18
Thickness orientation degree Dth: 0.22
(Comparative Example 1)
A stretched film (1AF-3) was obtained in the same manner as in Example 1 except that the stretching conditions in the tenter were changed to 2.4 times. The properties of the obtained stretched film (1AF-3) were as follows, and it was a stretched film that was easy to tear in the Y direction.

In-plane retardation Re (nm): 1.5
Thickness direction retardation Rth (nm): 1.8
Bending test: △
In-plane orientation degree Dpl: 3.72
Thickness orientation degree Dth: 0.13
(Example 3)
In response to the result of Comparative Example 1, the stretched temperature of the tenter was increased by 5 ° C. to 150 ° C. to obtain a stretched film (1AF-4). The properties of the obtained stretched film (1AF-4) were as follows, and a stretched film excellent in flexibility could be obtained by changing the stretching conditions.

In-plane retardation Re (nm): 2.0
Thickness direction retardation Rth (nm): 1.3
Bending test: ○
In-plane orientation degree Dpl: 2.23
Thickness orientation degree Dth: 0.14
(Comparative Example 2)
A stretched film (1AF-5) was obtained in the same manner as in Example 2 except that the stretch ratio was changed to 1.2 times in both the first and second stages. The characteristics of the obtained stretched film (1AF-5) were as follows, and it was a stretched film inferior in flexibility.

In-plane retardation Re (nm): 0.0
Thickness direction retardation Rth (nm): 0.3
Bending test: ×
In-plane orientation degree Dpl: 1.11
Thickness orientation degree Dth: 0.74
(Comparative Example 3)
A stretched film (1AF-6) was obtained in the same manner as in Example 2 except that the stretch ratio was changed to 3.5 times in both the first and second stages. The properties of the obtained stretched film (1AF-6) were as follows. Although it was a stretched film excellent in flexibility, it was a film that was easily peeled off in the thickness direction.

In-plane retardation Re (nm): 1.9
Thickness direction retardation Rth (nm): 1.6
Bending test: ○
In-plane orientation degree Dpl: 1.11
Thickness orientation degree Dth: 0.09
The data of Examples and Comparative Examples are summarized in Table 1.

  The stretched film and / or its production method of the present invention is flexible like various optical films such as a protective film, an antireflection film, a retardation film, and a polarizing film, which are used in flat panel display devices such as liquid crystal display devices. It can be suitably used for film applications that are excellent in properties and hardly generate birefringence.

Claims (10)

A stretched film containing an amorphous thermoplastic resin, wherein the following conditions (i) and (ii) are satisfied at the same time.
(I) The in-plane orientation degree Dpl in the deflection Raman spectrum measurement is 0.3 or more and 3.0 or less.
(Ii) The degree of thickness orientation Dth in the deflection Raman spectrum measurement is 0.1 or more and 0.25 or less, or 4 or more and 10 or less. The stretched film according to claim 1, wherein an in-plane retardation Re for light having a wavelength of 589 nm is 10 nm or less. The stretched film according to claim 1 or 2, wherein a film thickness direction retardation Rth with respect to light having a wavelength of 589 nm is -10 to +10 nm. The amorphous thermoplastic resin is an acrylic polymer.
The stretched film according to any one of 3 above. The acrylic stretched film according to claim 4, wherein the acrylic polymer has a glass transition temperature (Tg) of 110 ° C. or more and 200 ° C. or less. The acrylic stretched film according to claim 4 or 5, wherein the acrylic polymer has a ring structure. The acrylic stretched film according to any one of claims 4 to 6, wherein the acrylic polymer has a ring structure in the main chain. The acrylic stretched film according to claim 7, wherein the ring structure is at least one selected from a lactone ring structure, a glutarimide structure, a glutaric anhydride structure, an N-substituted maleimide structure, and a maleic anhydride structure. The acrylic stretched film according to claim 7 or 8, wherein the ring structure is a lactone ring structure. The orientation of the stretched film is determined by performing deflection Raman spectrum measurement at the start of film production to calculate the in-plane orientation degree Dpl and the thickness orientation degree Dth, and adjusting any of the following conditions (iii) to (v) based on the results Production method.
(Iii) Stretching temperature (iv) Stretching ratio (v) Line speed