JP5715773B2 - Method for producing retardation film - Google Patents

Description

  The present invention relates to a method for producing a retardation film.

  The retardation film is required not only to exhibit desired retardation values, transparency, and heat resistance, but also to exhibit retardation stability under harsh usage environments. In particular, a retardation film used for a liquid crystal panel provided in a liquid crystal image device is required to have a retardation stability enough to withstand long-term severe use.

  As a retardation film, a polycarbonate (PC) retardation film and a cycloolefin resin (COP) retardation film are known.

  The PC-based retardation film has high heat resistance and high retardation development performance. However, the PC-based retardation film has a problem that the photoelastic coefficient is high and the retardation value changes greatly with a slight stress. For this reason, it becomes difficult to apply high tension at the time of bonding with another film. Moreover, when it is exposed to high temperature in the state where it is bonded and disposed, it has a problem that a phase difference value is shifted due to a stress generated due to heat and a problem that unevenness is likely to occur. Furthermore, there is a problem that the PC-based retardation film is inferior in weather resistance.

  The COP retardation film has high heat resistance, moderately high retardation development performance, low photoelastic coefficient, and low hygroscopicity. However, the COP retardation film has a problem of poor adhesion.

  On the other hand, acrylic retardation films represented by polymethyl methacrylate (PMMA) are also known as retardation films.

  The acrylic retardation film has high transparency and a low photoelastic coefficient. However, since the acrylic retardation film has low retardation development performance, it needs to be stretched at a large stretch ratio or stretched at a low temperature in order to exhibit a sufficient retardation. In addition, the stretched acrylic retardation film has a problem of low heat resistance. Further, the acrylic retardation film has a problem of high hygroscopicity.

  In order to solve the above problem, an acrylic retardation film having a ring structure introduced therein has been reported (see Patent Document 1). An acrylic retardation film having such a ring structure has high transparency, high heat resistance, large retardation development performance, and excellent adhesiveness. However, an acrylic retardation film having such a ring structure has a problem in that it does not have sufficient retardation stability to withstand long-term severe use.

JP 2008-9378 A

  An object of the present invention is a method for producing an acrylic retardation film, which is excellent in all of the desired retardation value expression, transparency, and heat resistance, and excellent in retardation stability under severe use environment. Is to provide.

  In the method for producing a retardation film of the present invention, after stretching a raw film mainly composed of an acrylic resin, the temperature is 40 ° C. or higher, the glass transition temperature of the acrylic resin or lower, and the humidity is 70% RH or higher. The exposure process is performed under conditions of 100% RH or less.

  In a preferred embodiment, the acrylic resin is an acrylic resin having a ring structure in the main chain.

  In a preferred embodiment, the ring structure is a lactone ring.

  According to the present invention, a method for producing an acrylic retardation film that is excellent in all of the desired retardation value expression, transparency, and heat resistance, and that is excellent in retardation stability under a severe use environment. Can be provided.

≪Acrylic resin≫
In the production method of the present invention, a raw film having an acrylic resin as a main component is used. Here, “having the acrylic resin as the main component” means that the content of the acrylic resin in the raw film is preferably 50% by weight or more, more preferably 70% by weight or more, more preferably 90% by weight. More preferably, it is 95% by weight or more, particularly preferably 98% by weight or more, and most preferably substantially 100% by weight. Here, “substantially 100% by weight” is an expression to the effect that components (additives, etc.) that do not impair the effects of the present invention may be included in the range of 1% by weight or less.

  As the acrylic resin that can be used in the present invention, a resin obtained by a polymerization reaction using any appropriate (meth) acrylic monomer can be adopted within a range that does not impair the effects of the present invention. Examples of such (meth) acrylic monomers include (meth) acrylic acid and (meth) acrylic acid esters. Such (meth) acrylic monomers may be used alone or in combination of two or more. In the description of the present invention, “(meth) acryl” means acryl and / or methacryl.

  The acrylic resin that can be used in the present invention is preferably an acrylic resin obtained by polymerizing a monomer composition containing (meth) acrylic acid ester as a main component. Here, “having (meth) acrylic acid ester as the main component” means that the content ratio of (meth) acrylic acid ester in the monomer composition is preferably 50% by weight or more, more preferably 60% by weight. More preferably, it is 70% by weight or more, particularly preferably 80% by weight or more, and most preferably 90% by weight or more.

  Examples of (meth) acrylic acid esters that can be used in the present invention include acrylic acrylates such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, and benzyl acrylate. Acid ester; methacrylate ester such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate; Monomer represented; and the like. Such (meth) acrylic acid ester may use only 1 type, and may use 2 or more types together.

（式中、Ｒ^４およびＲ^５は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を示す。有機残基は、酸素原子を含んでいる場合、または、含んでいない場合がある。有機残基は、好ましくは、直鎖若しくは分岐状のアルキル基、直鎖若しくは分岐状のアルキレン基、アリール基、−ＯＡｃ基、−ＣＮ基である。）

(Wherein 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 or may not contain an oxygen atom. The organic residue is preferably a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, an —OAc group, or a —CN group.)

  The (meth) acrylic acid ester that can be used in the present invention is particularly preferably a methacrylic acid ester or a monomer represented by the general formula (1) from the viewpoint of excellent heat resistance and transparency.

  Examples of the monomer represented by the general formula (1) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) normal butyl acrylate, and tertiary butyl 2- (hydroxymethyl) acrylate. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable in that the effect of improving heat resistance is high.

  In the said monomer composition for obtaining the acrylic resin which can be used by this invention, you may contain other monomers other than the said (meth) acrylic acid ester. Examples of such other monomers include a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a monomer represented by the following general formula (2).

（式中、Ｒ^６は水素原子またはメチル基を表し、Ｘは水素原子、炭素数１〜２０のアルキル基、アリール基、−ＯＡｃ基、−ＣＮ基、−ＣＯ−Ｒ^７基、又はＣ−Ｏ−Ｒ^８基を表し、Ａｃ基はアセチル基を表し、Ｒ^７及びＲ^８は水素原子または炭素数１〜２０の有機残基を表す。有機残基は、酸素原子を含んでいる場合、または、含んでいない場合がある。有機残基は、好ましくは、直鎖若しくは分岐状のアルキル基、直鎖若しくは分岐状のアルキレン基、アリール基、−ＯＡｃ基、−ＣＮ基である。）

(Wherein R ⁶ 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—R ⁷ group, or a C— Represents an O—R ⁸ group, an Ac group represents an acetyl group, and R ⁷ and R ⁸ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms, where the organic residue contains an oxygen atom, (The organic residue is preferably a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, an —OAc group, or a —CN group.)

  As said hydroxyl-containing monomer, arbitrary appropriate hydroxyl-containing monomers other than the monomer represented by General formula (1) can be employ | adopted. Examples of such a hydroxyl group-containing monomer include allyl alcohol such as methallyl alcohol, allyl alcohol, and 2-hydroxymethyl-1-butene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, and 2- (hydroxyethyl). ) 2- (hydroxyalkyl) acrylic acid ester such as methyl acrylate; 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid; and the like. Such a hydroxyl group-containing monomer may be used alone or in combination of two or more. It is also possible to construct a lactone ring by reacting a hydroxyl group in the molecular chain of a polymer obtained using such a hydroxyl group-containing monomer.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid, and maleic anhydride. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited. Such unsaturated carboxylic acid may use only 1 type, and may use 2 or more types together.

  Examples of the monomer represented by the general formula (2) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited. As for the monomer represented by the general formula (2), only one kind may be used, or two or more kinds may be used in combination.

  In order to further improve the heat resistance of the retardation film obtained by the production method of the present invention, N-substituted maleimides such as phenylmaleimide, cyclohexylmaleimide, and methylmaleimide are copolymerized in the monomer composition. Also good.

  In order to obtain a retardation film exhibiting wavelength dispersion (showing reverse wavelength dispersion) in which birefringence is reduced as the wavelength is shortened in the visible light region, the monomer described in WO2009 / 084663 may be contained. Good. Specifically, for example, N-vinyl-2-pyrrolidone, N-vinyl-ε-caprolactam, N-vinyl-2-piperidone, N-vinyl-4-methyl-2-pyrrolidone, N-vinyl-5-methyl -2-pyrrolidone, N-vinyl-ω-heptalactam, vinyl carbazole, vinyl pyridine, vinyl imidazole, vinyl thiophene and the like.

  In order to further improve the heat resistance of the retardation film obtained by the production method of the present invention, in the main chain (also referred to as molecular chain) of the acrylic resin that can be used in the present invention, a lactone ring structure, a glutaric anhydride structure, A glutarimide structure, an N-substituted maleimide structure (a structure obtained by copolymerizing an N-substituted maleimide), a maleic anhydride structure (a structure obtained by copolymerizing maleic anhydride), or the like may be introduced. In particular, it is preferable to introduce a structure that does not contain a nitrogen atom in the main chain, and it is more preferable to introduce a lactone ring structure in the main chain in that the retardation film is difficult to be colored (yellowing).

  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 more preferable from the viewpoint of structural stability. In addition, when the lactone ring structure in the main chain is a 6-membered ring, examples include a structure represented by the general formula (3) and a structure represented by Japanese Patent Application Laid-Open No. 2004-168882. The point of high polymerization yield when synthesizing the polymer before introducing the ring structure, the point that it is easy to synthesize the polymer having a high content of the lactone ring structure with high polymerization yield, and (meth) acrylic acid ester It is preferable that it is a structure represented by General formula (3) at a point with good copolymerizability.

（式中、Ｒ^１、Ｒ^２、Ｒ^３は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。なお、有機残基は、酸素原子を含んでいる場合、または、含んでいない場合がある。有機残基は、好ましくは、直鎖若しくは分岐状のアルキル基、直鎖若しくは分岐状のアルキレン基、アリール基、−ＯＡｃ基、−ＣＮ基である。）

(Wherein R ¹ , R ² and R ³ each independently represents a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue contains an oxygen atom, or (The organic residue is preferably a linear or branched alkyl group, a linear or branched alkylene group, an aryl group, an —OAc group, or a —CN group.)

  When the acrylic resin that can be used in the present invention is a resin obtained by polymerizing a monomer composition containing the monomer represented by the general formula (1), the acrylic resin has a lactone ring structure. More preferably. Hereinafter, an acrylic polymer having a lactone ring structure may be referred to as a “lactone ring-containing polymer”.

  The content of the lactone ring structure in the acrylic resin that can be used in the present invention is preferably within a range of 5 to 90% by weight, more preferably within a range of 20 to 90% by weight, and even more preferably 35 to 90% by weight. , Particularly preferably in the range of 40-80% by weight, most preferably in the range of 45-75% by weight. If the content of the lactone ring structure is more than 90% by weight, the moldability becomes poor. Moreover, there exists a possibility that the flexibility of the retardation film obtained may fall. When the content of the lactone ring structure is less than 5% by weight, it is difficult to obtain a necessary retardation when formed into a retardation film, and heat resistance, solvent resistance, and surface hardness may be insufficient. There is.

  In the lactone ring-containing polymer, the content ratio of the structure other than the lactone ring structure represented by the general formula (3) is that of a polymer structural unit (repeating structural unit) constructed by polymerizing (meth) acrylic acid ester. In the range of 10 to 95% by weight, more preferably in the range of 10 to 80% by weight, further preferably in the range of 10 to 65% by weight, particularly preferably in the range of 20 to 60% by weight, Preferably it is in the range of 25 to 55% by weight. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing a hydroxyl group-containing monomer, it 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. It is in the range of 0 to 15% by weight, particularly preferably in the range of 0 to 10% by weight. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing an unsaturated carboxylic acid, it is preferably in the range of 0 to 30% by weight, more preferably in the range of 0 to 20% by weight, and still more preferably 0. It is in the range of ˜15% by weight, particularly preferably in the range of 0 to 10% by weight. In the case of a polymer structural unit (repeating structural unit) constructed by polymerizing the monomer represented by the general formula (2), it is preferably in the range of 0 to 30% by weight, more preferably 0 to 20% by weight. More preferably, it is in the range of 0 to 15% by weight, particularly preferably in the range of 0 to 10% by weight.

  Regarding the method for producing a lactone ring-containing polymer, preferably, after obtaining a polymer having a hydroxyl group and an ester group in the main chain by a polymerization step, the lactone ring structure is polymerized by heat-treating the polymer. The lactone cyclocondensation step to be introduced into is carried out.

  A polymer having a hydroxyl group and an ester group in the molecular chain can be obtained by conducting a polymerization reaction of the monomer composition containing the monomer represented by the general formula (1) (polymerization step).

  The content ratio of the monomer represented by the general formula (1) in the monomer composition to be subjected to the polymerization step is preferably in the range of 5 to 80% by weight, more preferably in the range of 10 to 50% by weight. More preferably, it is in the range of 15 to 40% by weight. When the content ratio of the monomer represented by the general formula (1) in the monomer composition to be subjected to the polymerization step is less than 5% by weight, a necessary retardation is obtained when it is formed into a retardation film. May be difficult, and heat resistance, solvent resistance, and surface hardness may be insufficient. When the content of the monomer represented by the general formula (1) in the monomer composition to be subjected to the polymerization step is more than 80% by weight, gelation may occur during the polymerization reaction or lactone cyclization, There is a possibility that the flexibility of the resulting polymer is lowered and the molding processability becomes poor.

  The monomer composition used for the polymerization step may contain a monomer other than the monomer represented by the general formula (1). As such a monomer, for example, (meth) acrylic acid esters other than the monomer represented by the general formula (1) as described above, other than the monomer represented by the general formula (1) Hydroxyl group-containing monomers, unsaturated carboxylic acids, and monomers represented by the general formula (2).

  When a (meth) acrylic acid ester other than the monomer represented by the general formula (1) is used, the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. And preferably in the range of 20 to 95% by weight, more preferably in the range of 50 to 90% by weight, still more preferably in the range of 60 to 85% by weight.

  In the case of using a hydroxyl group-containing monomer other than the monomer represented by the general formula (1), the content ratio in the monomer composition to be subjected to the polymerization step is sufficient to exert the effect of the present invention. Preferably, it is 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, and particularly preferably in the range of 0 to 10% by weight.

  When using an unsaturated carboxylic acid, the content ratio in the monomer composition to be subjected to the polymerization step is preferably in the range of 0 to 30% by weight, more preferably, in order to sufficiently exhibit the effects of the present invention. It is in the range of 0 to 20% by weight, more preferably in the range of 0 to 15% by weight, particularly preferably in the range of 0 to 10% by weight.

  When the monomer represented by the general formula (2) is used, the content ratio in the monomer composition to be subjected to the polymerization step is preferably 0 to 30% in order to sufficiently exhibit the effects of the present invention. %, 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 in the range of 0 to 10% by weight.

  As a form of the polymerization reaction for polymerizing the monomer composition to obtain a polymer having a hydroxyl group and an ester group in the main chain, a polymerization form using a solvent is preferable, and solution polymerization is particularly preferable. .

  In the polymerization step, the polymerization temperature and the polymerization time vary depending on the type of monomer (monomer composition) to be used, the ratio of use, etc., but preferably the polymerization temperature is in the range of 0 to 150 ° C., the polymerization time. It is in the range of 0.5 to 20 hours, more preferably, the polymerization temperature is in the range of 80 to 140 ° C., and the polymerization time is in the range of 1 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 And the like. Moreover, since the residual volatile matter of the lactone ring containing polymer finally obtained will increase when the boiling point of the solvent to be used is too high, the thing whose boiling point is in the range of 50-200 degreeC is preferable. Such a polymerization solvent may use only 1 type and may use 2 or more types together.

  In the polymerization step, 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 isononano. , Organic peroxides such as t-amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2 ′ -Azo compounds such as azobis (2,4-dimethylvaleronitrile); Such polymerization initiators 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.

  In the polymerization step, it is preferable to control the concentration of the produced polymer in the polymerization reaction mixture to be 75% 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 75% by weight, it is preferable that the polymerization solvent is appropriately added to the polymerization reaction mixture to control it to 75% by weight or less. . The concentration of the produced polymer in the polymerization reaction mixture is more preferably 60% by weight or less, and still more preferably 50% 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.

  Arbitrary suitable addition forms can be employ | adopted as a form which adds a polymerization solvent to a polymerization reaction mixture suitably. For example, the polymerization solvent may be added continuously, or the polymerization solvent may be added intermittently. The polymerization solvent to be added may be the same type of solvent as that used in the initial charging of the polymerization reaction or may be a different type of solvent. Preferably, the same type of solvent as that used in the initial charge of the polymerization reaction is added. Such a polymerization solvent to be added may be used alone or in combination of two or more.

  By controlling the concentration of the generated polymer in the polymerization reaction mixture, the gelation of the reaction solution can be more sufficiently suppressed, and in particular, the heat resistance can be increased by increasing the content ratio of the lactone ring in the acrylic resin. Even if it is a case where the ratio of the hydroxyl group and ester group in a principal chain is raised in order to improve, gelatinization can fully be suppressed.

  When the monomer composition containing the monomer represented by the general formula (1) is polymerized, the polymer obtained in the polymerization step is a polymer having a hydroxyl group and an ester group. The weight average molecular weight of the polymer is preferably in the range of 1,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, still more preferably in the range of 10,000 to 500,000, and particularly preferably in the range of 50,000 to 500,000.

  In the polymer obtained by polymerizing the monomer composition containing the monomer represented by the general formula (1), in the subsequent lactone cyclization condensation step, the lactone ring structure is converted into the polymer by heat treatment. The lactone ring-containing polymer can be introduced.

  In the polymerization reaction mixture obtained when the polymerization step is completed, a solvent is usually contained in addition to the obtained polymer. In the case of introducing a lactone ring structure into the above polymer to obtain a lactone ring-containing polymer, it is not necessary to completely remove the solvent and take out the polymer in a solid state. It is preferable to perform a lactone cyclization condensation step. If necessary, after taking out in a solid state, a solvent suitable for the subsequent lactone cyclization condensation step may be added again.

  In the lactone cyclocondensation step, the reaction for introducing the lactone ring structure into the polymer is cyclized and condensed with a hydroxyl group and an ester group present in the main chain of the polymer to produce a lactone ring structure. This is a reaction, and alcohol is by-produced by the cyclocondensation. By forming the lactone ring structure in the main 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 may not be sufficiently improved, or a condensation reaction will occur during the molding due to the heat treatment during molding, and the alcohol produced will be in the film May exist as bubbles or silver streaks.

  The lactone ring-containing polymer obtained in the lactone cyclization condensation step preferably has a lactone ring structure represented by the general formula (3).

  Any appropriate method can be adopted as a method for heat-treating the polymer. For example, you may heat-process the polymerization reaction mixture containing the solvent obtained by the superposition | polymerization process 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.

  When performing the cyclization condensation reaction in the lactone cyclization condensation step, in addition to the above polymer, another acrylic polymer may coexist. 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. Further, basic compounds, organic carboxylates, carbonates and the like as disclosed in JP-A-61-254608 and JP-A-61-261303 may be used.

  In carrying out the cyclization condensation reaction in the lactone cyclization condensation step, 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 in the case of using a devolatilization step described later, and to impart excellent mechanical strength to the resulting acrylic resin. .

  Examples of the organic phosphorus compound that can be used as a catalyst in the cyclization condensation reaction in the lactone cyclization condensation process include alkyl (aryl) phosphonous acid such as methylphosphonous acid, ethylphosphonous acid, and phenylphosphonous acid. (However, these may be alkyl (aryl) phosphinic acids which are tautomers) and diesters or monoesters thereof; dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, Dialkyl (aryl) phosphinic acids such as phenylethylphosphinic acid and their esters; alkyl (aryl) phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid and their diesters Monoesters; alkyl (aryl) phosphinic acids such as methylphosphinic acid, ethylphosphinic acid, phenylphosphinic acid and their esters; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite , Phosphite diesters or monoesters or triesters such as diethyl phosphite, diphenyl phosphite, trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, phosphoric acid 2 -Ethylhexyl, isodecyl phosphate, lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, phosphoric acid Distearyl, diisostearyl phosphate, phosphorus Phosphoric diesters or monoesters or triesters such as diphenyl, trimethyl phosphate, triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine , Phenylphosphine, dimethylphosphine, diethylphosphine, diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine, etc. mono-, di- or trialkyl (aryl) phosphine; methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine Alkyl (aryl) halogen phosphines such as diethylchlorophosphine and diphenylchlorophosphine; Mono-, di- or trialkyl (aryl) phosphine oxides such as tilphosphine, ethyl phosphine oxide, phenyl phosphine oxide, dimethyl phosphine oxide, diethyl phosphine oxide, diphenyl phosphine oxide, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide; And halogenated tetraalkyl (aryl) phosphonium such as tetramethylphosphonium chloride, tetraethylphosphonium chloride, 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. Such an organic phosphorus compound may be used alone or in combination of two or more.

  Arbitrary appropriate amount can be employ | adopted for the usage-amount of the catalyst used in the case of cyclization condensation reaction in a lactone cyclization condensation process. For example, with respect to the polymer, preferably in the range of 0.001 to 5% by weight, more preferably in the range of 0.01 to 2.5% by weight, and still more preferably in the range of 0.01 to 1% by weight. In particular, it is preferably in the range of 0.05 to 0.5% by weight. If the amount of the catalyst used is less than 0.001% by weight based on the polymer, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. On the other hand, when the amount of the catalyst used exceeds 5% by weight with respect to the polymer, there is a possibility that coloring may be caused or it may be difficult to melt and form due to crosslinking of the polymer.

  Arbitrary appropriate time can be employ | adopted as a catalyst addition time. For example, it may be added at the beginning of the reaction, may be added during the reaction, or may be added both.

  In the lactone cyclization condensation step, it is preferable to perform 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 over the entire cyclization condensation reaction but only in 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.

  The devolatilization step refers to a step of removing volatile components such as a solvent and residual monomers and alcohol produced as a by-product by a cyclocondensation reaction leading to a lactone ring structure, if necessary under reduced pressure heating conditions. If this removal treatment is insufficient, the residual volatile matter in the produced resin increases, and there is a risk of coloring due to alteration during molding, or molding defects such as bubbles or silver streaks may occur.

  In the case of a form in which a devolatilization step is used throughout the cyclization condensation reaction in the lactone cyclization condensation step, any appropriate device can be adopted as the device to be used. For example, in order to carry out the present invention more effectively, a devolatilizing device or vented extruder composed of a heat exchanger and a devolatilizing tank, or those in which these devolatilizing device and an extruder are arranged in series are used. Is preferable, and it is more preferable to use a devolatilizer or a vented extruder comprising a heat exchanger and a devolatilization tank.

  The reaction treatment temperature in the case of using a devolatilizer comprising a heat exchanger and a devolatilization tank is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the reaction treatment temperature is lower than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. If the reaction treatment temperature is higher than 350 ° C., coloring or decomposition may occur.

  In the case of using a devolatilizer comprising a heat exchanger and a devolatilization tank, the pressure during the reaction treatment is preferably within a range of 931 to 1.33 hPa (700 to 1 mmHg), and 798 to 66.5 hPa (600 to 50 mmHg). Within the range is more preferable. If the pressure during the reaction treatment is higher than 931 hPa, volatile components including alcohol may easily remain. If the pressure during the reaction treatment is lower than 1.33 hPa, industrial implementation may be difficult.

  When using an extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  The reaction processing temperature when using an extruder with a vent is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the reaction treatment temperature is lower than 150 ° C., the cyclization condensation reaction may be insufficient and the residual volatile matter may increase. If the reaction treatment temperature is higher than 350 ° C., coloring or decomposition may occur.

  In the case of using an extruder with a vent, the pressure during the reaction treatment is preferably within a range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably within a range of 798 to 13.3 hPa (600 to 10 mmHg). If the pressure during the reaction treatment is higher than 931 hPa, volatile components including alcohol may easily remain. If the pressure during the reaction treatment is lower than 1.33 hPa, industrial implementation may be difficult.

  In the case of using the devolatilization step throughout the cyclization condensation reaction in the lactone cyclization condensation step, the physical properties of the lactone ring-containing polymer obtained may be deteriorated under severe heat treatment conditions, as will be described later. Is preferably carried out using a vented extruder or the like under the mildest conditions possible, using the above-described dealcoholization reaction catalyst.

  In the case of using the devolatilization step throughout the cyclization condensation reaction in the lactone cyclization condensation step, preferably, the polymer obtained in the polymerization step is introduced into the cyclization condensation reactor system together with the solvent. If necessary, it may be passed through the reactor system such as a vented extruder once again.

  In the lactone cyclization condensation step, the devolatilization step may not be used over the entire process of the cyclization condensation reaction but may be used only in a part of the process. For example, the apparatus for producing the polymer is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization condensation reaction to some extent in advance, and then the devolatilization step is used at the same time. In this mode, the cyclization condensation reaction is performed to complete the reaction.

  In the lactone cyclization condensation step, the devolatilization step is used throughout the cyclization condensation reaction. For example, when the polymer is heat-treated at a high temperature of about 250 ° C. or higher using a twin screw extruder. Depending on the difference in thermal history, partial decomposition or the like may occur before the cyclization condensation reaction occurs, and the physical properties of the resulting lactone ring-containing polymer may be deteriorated. Therefore, if the cyclization condensation reaction is allowed to proceed to some extent before the cyclization condensation reaction using the devolatilization step at the same time, the latter reaction conditions can be relaxed and the physical properties of the resulting lactone ring-containing polymer deteriorated. Is preferable. As a particularly preferred embodiment, the devolatilization step is started after a lapse of time from the start of the cyclization condensation reaction, that is, the hydroxyl group and ester group present in the polymer main chain obtained in the polymerization step are cyclized in advance. A form in which a condensation reaction is performed to increase the cyclization condensation reaction rate to some extent, and then a cyclization condensation reaction using a devolatilization step in combination is performed. Specifically, for example, a cyclization condensation reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a devolatilizer, for example, a heat Preferred is a mode in which the cyclization condensation reaction is completed with a devolatilizer comprising an exchanger and a devolatilization tank, an extruder with a vent, or the like. Particularly in this form, it is more preferable that a catalyst for the cyclization condensation reaction is present.

  In the lactone cyclocondensation step, the hydroxyl group and ester group present in the main chain of the polymer obtained in the polymerization step are preliminarily subjected to a cyclocondensation reaction to increase the cyclization condensation reaction rate to some extent, followed by devolatilization. The method of carrying out the cyclization condensation reaction using the steps at the same time is a preferred form for obtaining a lactone ring-containing polymer. With this configuration, a lactone ring-containing polymer having a higher cyclization condensation reaction rate, a higher glass transition temperature, and excellent heat resistance can be obtained. In this case, as a measure of the cyclization condensation reaction rate, the weight loss rate between 150-300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1.5% or less. More preferably, it is 1% or less.

  In the lactone cyclization condensation step, as a reactor that can be employed in the cyclization condensation reaction that is performed in advance before the cyclization condensation reaction that simultaneously uses the devolatilization step, for example, an autoclave, a kettle reactor, a heat exchanger, Preferred examples include a devolatilizer comprising a devolatilization tank, and a vented extruder suitable for a cyclization condensation reaction in which a devolatilization step is simultaneously used. More preferred are autoclaves and kettle reactors. However, even when using a reactor such as an extruder with a vent, by adjusting the temperature condition, barrel condition, screw shape, screw operating condition, etc. It is possible to carry out the cyclization condensation reaction in the same state as the reaction state in the kettle reactor.

  In the lactone cyclization condensation step, in the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time, preferably, a mixture containing the polymer and the solvent obtained in the polymerization step is used. (I) A method in which a catalyst is added and subjected to a heat reaction, (ii) a method in which a heat reaction is performed without a catalyst, and a method in which the above (i) or (ii) is performed under pressure are employed.

  In the lactone cyclization condensation step, the “mixture containing a polymer and a solvent” to be introduced into the cyclization condensation reaction may be the polymerization reaction mixture obtained in the polymerization step as it is, or once the solvent is used. It means that a solvent suitable for the cyclization condensation reaction may be added again after the removal.

  In the lactone cyclization condensation step, any appropriate solvent can be adopted as a solvent that can be re-added in the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step at the same time. For example, aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform; DMSO; tetrahydrofuran; Preferably, it is the same kind of solvent as the polymerization solvent that can be used in the polymerization step.

  Examples of the catalyst added in the method (i) include esterification catalysts such as p-toluenesulfonic acid or transesterification catalysts, basic compounds, organic carboxylates, and carbonates. In the present invention, it is preferable to use the organophosphorus compound described above.

  Arbitrary appropriate time can be employ | adopted for the addition time of a catalyst. For example, it may be added at the beginning of the reaction, may be added during the reaction, or may be added both. Any appropriate amount can be adopted as the amount of the catalyst to be added. For example, it is preferably in the range of 0.001 to 5% by weight, more preferably in the range of 0.01 to 2.5% by weight, still more preferably 0.01 to 0.1% by weight, based on the weight of the polymer. And particularly preferably in the range of 0.05 to 0.5% by weight.

  Arbitrary appropriate temperature and time can be employ | adopted as a heating temperature and heating time of the said method (i). For example, the heating temperature is preferably room temperature or higher, more preferably 50 ° C. or higher, and the heating time is preferably in the range of 1 to 20 hours, more preferably in the range of 2 to 10 hours. If the heating temperature is low or the heating time is short, the cyclization condensation reaction rate may be lowered. If the heating time is too long, the resin may be colored or decomposed.

  Examples of the method (ii) include a method of heating the polymerization reaction mixture obtained in the polymerization step as it is using a pressure-resistant kettle or the like. The heating temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. The heating time is preferably in the range of 1 to 20 hours, more preferably in the range of 2 to 10 hours. If the heating temperature is low or the heating time is short, the cyclization condensation reaction rate may be lowered. If the heating time is too long, the resin may be colored or decomposed.

  Both the above methods (i) and (ii) have no problem even under pressure depending on conditions. Moreover, in the case of the cyclization condensation reaction performed beforehand before the cyclization condensation reaction which used the devolatilization process simultaneously, even if a part of the solvent volatilizes naturally during the reaction, there is no problem.

  The weight loss rate between 150 and 300 ° C. in dynamic TG measurement at the end of the cyclization condensation reaction performed in advance before the cyclization condensation reaction simultaneously using the devolatilization step, that is, immediately before the start of the devolatilization step is Preferably it is 2% or less, More preferably, it is 1.5% or less, More preferably, it is 1% or less. When the weight reduction rate is higher than 2%, the cyclization condensation reaction rate does not rise to a sufficiently high level even if the cyclization condensation reaction is performed simultaneously with the devolatilization step, and the physical properties of the resulting lactone ring-containing polymer. May decrease. In addition, when performing cyclization condensation reaction, in addition to the said polymer, you may coexist other acrylic polymer.

  In the lactone cyclocondensation step, the hydroxyl group and ester group present in the main chain of the polymer obtained in the polymerization step are preliminarily subjected to a cyclocondensation reaction to increase the cyclization condensation reaction rate to some extent, followed by devolatilization. In the case of carrying out a cyclization condensation reaction in which the steps are used simultaneously, a polymer obtained by a cyclization condensation reaction carried out in advance (a polymer obtained by cyclization condensation reaction of at least a part of hydroxyl groups and ester groups present in the main chain) ) And the solvent may be separated from each other without separating the solvent from the solvent. In addition, if necessary, other treatments such as re-adding the solvent after separating the above polymer (a polymer in which at least a part of the hydroxyl group and ester group present in the main chain have undergone cyclization condensation reaction) are performed. After that, you may perform the cyclization condensation reaction which used the devolatilization process simultaneously.

  The devolatilization step may be completed simultaneously with the cyclization condensation reaction, or may be completed after a lapse of time from the completion of the cyclization condensation reaction.

  The weight average molecular weight of the obtained lactone ring-containing polymer is preferably in the range of 1,000 to 2,000,000, more preferably in the range of 5,000 to 1,000,000, still more preferably in the range of 10,000 to 500,000, and particularly preferably in the range of 50,000 to 500,000. Is within.

  The lactone ring-containing polymer has a weight loss rate of 150 to 300 ° C. in dynamic TG measurement, preferably 1% or less, more preferably 0.5% or less, and still more preferably 0.3%. It is as follows.

  In the lactone ring-containing polymer in the present invention, it is possible to avoid the disadvantage that bubbles and silver streaks enter the film after molding due to the high cyclization condensation reaction rate. Furthermore, since the lactone ring structure is sufficiently introduced into the polymer due to a high cyclization condensation reaction rate, the resulting lactone ring-containing polymer has sufficiently high heat resistance.

  The lactone ring-containing polymer has a coloration degree (YI) in a 15% by weight chloroform solution of preferably 6 or less, more preferably 3 or less, still more preferably 2 or less, and particularly preferably 1 It is as follows. If the coloring degree (YI) exceeds 6, transparency may be impaired due to coloring, and there is a possibility that it cannot be used for the intended purpose.

  The lactone ring-containing polymer has a 5% weight loss temperature in thermogravimetric analysis (TG) of preferably 330 ° C. or higher, more preferably 350 ° C. or higher, and further preferably 360 ° C. or higher. The 5% weight loss temperature in thermogravimetric analysis (TG) is an indicator of thermal stability, and if it is less than 330 ° C., sufficient thermal stability may not be exhibited.

  The lactone ring-containing polymer has a glass transition temperature (Tg) of preferably 110 ° C to 200 ° C, more preferably 115 ° C to 200 ° C, still more preferably 120 ° C to 200 ° C, and particularly preferably. It is 125 degreeC-190 degreeC, Most preferably, it is 130 degreeC-180 degreeC.

  The total amount of residual volatile components contained in the lactone ring-containing polymer is preferably 3000 ppm or less, more preferably 1500 ppm or less, and even more preferably 1000 ppm or less. When the total amount of residual volatile components is more than 3000 ppm, there is a risk of coloring due to alteration during molding, foaming, or molding defects such as silver streak.

  The lactone ring-containing polymer has a total light transmittance of 85% or more, more preferably 90% or more, as measured by a method according to ASTM-D-1003 of a molded product obtained by injection molding. Yes, more preferably 91% or more. The total light transmittance is a measure of transparency, and if it is less than 85%, the transparency is lowered and there is a possibility that it cannot be used for the intended purpose.

≪Other ingredients as raw film material≫
The material for the raw film in the present invention may contain the following other components.

  Examples of such other components include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing polymers such as vinyl chloride and chlorinated vinyl resins. Polymer; Styrenic polymer such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer; Polyester such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; Polyamide such as nylon 6, nylon 66, nylon 610 Polyacetal; Polycarbonate; Polyphenylene oxide; Polyphenylene sulfide; Polyetheretherketone; Polysulfone; Polyethersulfone; Polyoxybenzylene; Polyamideimide; Butadiene rubber or ABS resin containing an acrylic rubber, rubber-like polymer such as ASA resin; and the like. The rubbery polymer preferably has, on its surface, a graft portion having a composition compatible with the main component acrylic resin, and when the rubbery polymer is in the form of particles, its average particle size is: From the viewpoint of improving transparency when a retardation film is used, 300 nm or less is preferable, 150 nm or less is more preferable, and 100 nm or less is more preferable. Among the other components exemplified, because of excellent compatibility with the main component acrylic resin, a structural unit derived from a vinyl cyanide monomer and a structural unit derived from an aromatic vinyl monomer The copolymer which has is preferable. Examples of such a copolymer include a styrene-acrylonitrile copolymer.

  When the acrylic resin in the present invention is the lactone ring-containing polymer described above, since the lactone ring-containing polymer has a positive intrinsic birefringence, the original film is usually positive when the original film is stretched. Birefringence (positive phase difference) is shown. In order to increase the positive birefringence (positive retardation) and increase the retardation value, other components such as vinyl chloride, polycarbonate, and other polymers containing aromatic rings in the main chain are positive A polymer having intrinsic birefringence may be included. In addition, in order to increase the positive birefringence (positive phase difference) and increase the phase difference value, it contains a low molecular substance exhibiting positive birefringence (positive phase difference) as another component. Also good. Examples of such low molecular weight substances include low molecular weight substances having a molecular weight of preferably 5000 or less, more preferably 1000 or less, and specifically, for example, low molecular weight substances described in Japanese Patent No. 3696645. More specifically, for example, stilbene, biphenyl, diphenylacetylene, and usual liquid crystal substances can be mentioned.

  Further, since polymethyl methacrylate (PMMA) has a weak negative intrinsic birefringence, when the original film is stretched, the original film shows negative birefringence (negative retardation). Styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer having negative intrinsic birefringence are added to acrylic polymers such as PMMA and the above-mentioned lactone ring-containing polymers. An acrylic resin composition having negative intrinsic birefringence as a whole may be used. Usually, when the raw film obtained from this composition is stretched, a retardation film exhibiting negative birefringence can be obtained.

  In addition, in order to obtain a retardation film exhibiting wavelength dispersion (in which reverse wavelength dispersion is exhibited) in which birefringence is reduced as the wavelength is shortened in the visible light region, as described in WO2009 / 084663, positive A polymer having negative intrinsic birefringence may be added to the polymer having intrinsic birefringence. Specifically, for example, the above-mentioned lactone ring-containing polymer having a positive intrinsic birefringence or an acrylic polymer having a glutarimide structure contains a polymer having a vinylcarbazole unit having a negative intrinsic birefringence. May be.

  The content of other components in the retardation film obtained by the production method of the present invention (or the content of other components in the material of the raw film in the present invention) is preferably 0 in the case of the above polymer. -50% by weight, more preferably 0-40% by weight, still more preferably 0-30% by weight, particularly preferably 0-20% by weight. In addition, the content of other components in the retardation film obtained by the production method of the present invention is preferably 0 to 20% by weight, more preferably 0 to 10% by weight, and still more preferably, in the case of the low molecular weight substance. 0 to 5% by weight.

  The material for the raw film in the present invention may contain other additives. Examples of other additives include hindered phenol-based, phosphorus-based and sulfur-based antioxidants; light-resistant stabilizers, weather-resistant stabilizers, heat-stabilizers, and other stabilizers; reinforcing materials such as glass fibers and carbon fibers. UV absorbers such as phenyl salicylate, (2,2′-hydroxy-5-methylphenyl) benzotriazole, 2-hydroxybenzophenone; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide Flame retardants such as: antistatic agents such as anionic, cationic and nonionic surfactants; colorants such as inorganic pigments, organic pigments and dyes; organic fillers and inorganic fillers; resin modifiers; Inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants;

  The content of other additives in the retardation film obtained by the production method of the present invention (or the content of other additives in the material of the raw film in the present invention) is preferably 0 to 5% by weight. More preferably, it is 0 to 2% by weight, and further preferably 0 to 0.5% by weight.

≪Original film≫
The raw film in the present invention can be obtained by mixing an acrylic resin as a main component and, if necessary, other components and other additives by a conventionally known mixing method, and forming into a film shape. .

  Examples of the film forming method include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method such as a T-die method and an inflation method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  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, diethyl ether, and the like. 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 casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the film forming temperature at that time is preferably 150 to 350 ° C., more preferably 200 to 300 ° C. When forming a film by the T-die method, a T-die is attached to the tip of any appropriate single-screw extruder or twin-screw extruder, and the film extruded into a film is wound to obtain a roll-shaped film. be able to.

  A film-like product obtained by mixing an acrylic resin as a main component and, if necessary, other components and other additives by a conventionally known mixing method, and melt-extruding the obtained mixture from a T-die or the like. A method of forming a film by bringing at least one surface of the film into contact with a roll or a belt is preferable in that a film having good surface properties can be obtained. In particular, from the viewpoint of improving the surface smoothness and surface glossiness of the film, a method of forming a film by bringing both surfaces of a film-like product obtained by melt-extruding the mixture into contact with the roll surface or the belt surface is preferred.

≪Method for producing retardation film≫
In the method for producing a retardation film of the present invention, after stretching a raw film mainly composed of an acrylic resin, the temperature is 40 ° C. or higher, the glass transition temperature of the acrylic resin or lower, and the humidity is 70% RH or higher. The exposure process is performed under conditions of 100% RH or less. Here, RH is an abbreviation for relative humidity and means relative humidity.

  In the method for producing a retardation film of the present invention, first, a raw film is stretched to obtain a stretched film. In order to develop the retardation performance, it is important to orient the molecular chains in the retardation film. In the present invention, retardation performance is exhibited by stretching in terms of high production efficiency.

  Any appropriate stretching method can be adopted as the stretching method. 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; and the like. 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 two orthogonal directions in the plane include a direction parallel to the slow axis in the film plane and a direction perpendicular to the slow axis in the film plane. In addition, what is necessary is just to set extending | stretching conditions, such as a draw ratio, extending | stretching temperature, an extending | stretching speed, suitably according to a desired phase difference value and desired bending resistance.

  When the refractive index in the slow axis direction in the film plane is nx, the refractive index in the direction perpendicular to nx in the film plane is ny, and the refractive index in the film thickness direction is nz, nx> ny = nz or nx = nz Free width uniaxial stretching is preferred in that a retardation film satisfying> ny can be obtained. Biaxial stretching is preferred in that a retardation film satisfying nx = ny> nz or nx = ny <nz can be obtained. Furthermore, in order to obtain a retardation film satisfying 0 <(nx−nz) / (nx−ny) <1 when nx> ny, stretching that imparts a shrinkage force in a direction perpendicular to the stretching direction to the film is obtained. The method is preferred.

  Examples of the stretching apparatus include a roll stretching machine, an oven 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. Is mentioned.

  The stretching temperature is preferably around the glass transition temperature on the high temperature side of the film. Specifically, it is preferably performed at (glass transition temperature-30) ° C. to (glass transition temperature + 50) ° C., more preferably performed at (glass transition temperature−20) ° C. to (glass transition temperature + 20) ° C., It is more preferable to carry out at (glass transition temperature−10) ° C. to (glass transition temperature + 10) ° C. In particular, biaxial stretching is preferably performed at (glass transition temperature-5 ° C.) to (glass transition temperature + 15 ° C.).

  If the stretching temperature is lower than (glass transition temperature-30) ° C., a sufficient stretching ratio may not be obtained. If the stretching temperature is higher than (glass transition temperature + 50) ° C., resin flow may occur and stable stretching may not be performed.

  The draw ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.2 to 10 times, and still more preferably in the range of 1.3 to 5 times. When the draw ratio defined by the area ratio is smaller than 1.1 times, there is a possibility that the retardation performance accompanying the drawing and the toughness cannot be improved. When the draw ratio defined by the area ratio is larger than 25 times, there is a possibility that the effect of increasing the draw ratio is not recognized.

  When extending | stretching to a certain direction, the range of 1.05-10 times is preferable, the range of 1.0-5 times is more preferable, the range of 1.1-5 times is more preferable, and the range of 1.2-3 times is further more preferable. When the draw ratio is less than 1.05, a desired retardation value may not be obtained. If the stretching ratio is larger than 10 times, the effect of only increasing the stretching ratio may not be recognized, or the film may be broken during stretching.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If the stretching speed (one direction) is slower than 10% / min, it takes time to obtain a sufficient stretching ratio, which may increase the production cost. If the stretching speed (one direction) is faster than 20000% / min, the stretched film may be broken.

  The thickness of the stretched film is preferably 5 to 350 μm, more preferably 20 to 200 μm, still more preferably 30 to 150 μm, and particularly preferably 30 to 100 μm. If the thickness of the film after stretching is less than 5 μm, the strength is poor and it may be difficult to obtain a desired retardation value. If the film after stretching is thicker than 350 μm, it may be disadvantageous for thinning of a liquid crystal display device or the like.

  The thickness of the stretched film can be measured using a commercially available measuring instrument such as a Digimatic Micrometer (manufactured by Mitutoyo Corporation).

  In the method for producing a retardation film of the present invention, the stretched film is exposed to a temperature of 40 ° C. or higher and a glass transition temperature of the acrylic resin or lower, and a humidity of 70% RH or higher and 100% RH or lower. I do. By producing the above stretched film using the above raw materials and further performing this treatment, it is excellent in all of the desired retardation value expression, transparency, and heat resistance, and under severe use environment. It is possible to provide a method for producing an acrylic retardation film that is excellent in retardation stability.

  The lower limit of the treatment temperature is 40 ° C, preferably 45 ° C, more preferably 50 ° C. If the lower limit of the treatment temperature is lower than 40 ° C., a retardation film excellent in retardation stability may not be obtained, or an enormous amount of time is required to obtain a retardation film excellent in retardation stability. There is a risk of this (productivity may be reduced).

  The upper limit of the treatment temperature is the glass transition temperature of the acrylic resin, preferably (glass transition temperature of acrylic resin—10 ° C.), more preferably (glass transition temperature of acrylic resin—20 ° C.), more preferably. Is (glass transition temperature of acrylic resin -30 ° C), particularly preferably (glass transition temperature of acrylic resin -40 ° C). If the upper limit value of the treatment temperature is higher than the glass transition temperature of the acrylic resin, there is a possibility that the phase difference may be greatly reduced or the film may be deformed such as bending.

  The lower limit of the treatment humidity is 70% RH, preferably 75% RH, more preferably 80% RH. If the lower limit of the treatment humidity is lower than 70% RH, a retardation film having excellent retardation stability may not be obtained, or a huge amount of time is required to obtain a retardation film having excellent retardation stability. There is a risk that it will take (productivity may be reduced).

  The upper limit of the treatment humidity is 100% RH, preferably 98% RH, and more preferably 95% RH. If the upper limit of the treatment humidity is higher than 100% RH, the amount of water absorption increases, and the film may be deformed.

  Arbitrary appropriate time can be employ | adopted for the time (processing time) which performs the said process in the range which does not impair the effect of this invention.

  The lower limit of the treatment time is preferably 5 seconds, more preferably 1 minute, still more preferably 10 minutes, and particularly preferably 1 hour. If the lower limit of the treatment time is shorter than 5 seconds, a retardation film having excellent retardation stability may not be obtained.

  The upper limit of the treatment time is preferably 100 hours, more preferably 50 hours, and even more preferably 25 hours. If the upper limit of the treatment time is longer than 100 hours, the productivity may be reduced.

  The treatment can be performed in any appropriate environment as long as the temperature and humidity can be controlled. For example, the film is stored in a constant temperature and humidity chamber, the film is rewound onto another core under the above conditions, passed through an oven in a stretching machine under predetermined conditions, and passed through a coating drying line under predetermined conditions. , Etc.

≪Phase difference film≫
The retardation film obtained by the production method of the present invention is excellent in all of the desired retardation value, transparency, and heat resistance, and is excellent in retardation stability under a severe use environment.

  Examples of the phase difference include “in-plane phase difference (Re)” and “thickness direction phase difference (Rth)”. “In-plane retardation (Re)” refers to the retardation value in the retardation film (layer) plane measured at 23 ° C. with light having a wavelength of 589 nm. “Thickness direction retardation (Rth)” refers to a retardation value in the thickness direction of a retardation film (layer) measured at 23 ° C. with light having a wavelength of 589 nm. The slow axis direction is a direction in which the refractive index in the retardation film plane is maximum. In addition, a film having a large refractive index in the stretching direction is said to have positive birefringence, and a film having a large refractive index in the direction perpendicular to the stretching direction in the retardation film surface is said to have negative birefringence. . Whether the birefringence is positive or negative is determined by using a polarizing microscope described in “Introduction to Polarizing Microscopes for Polymer Materials” (Hiroshi Hiroya, Agne Technical Center Edition, Chapter 5, pp 78-82 (2001)). / 4 plate color addition determination method and whether or not the retardation film or a film obtained by heating and shrinking the retardation film is uniaxially stretched to increase the refractive index in the stretching direction.

  The in-plane retardation (Re) is defined by Re = (nx−ny) × d, and the thickness direction retardation (Rth) is defined by Rth = [(nx + ny) / 2−nz] × d. Here, “nx” is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), and “ny” is the direction perpendicular to the slow axis in the plane (ie, fast phase). The refractive index in the axial direction), “nz” is the refractive index in the thickness direction, and d is the thickness (nm) of the retardation film.

  The in-plane retardation (Re) of the retardation film obtained by the production method of the present invention can take any appropriate value depending on various factors such as the type of acrylic resin used, the conditions for film formation, and the stretching conditions. Preferably it is 20-1000 nm, More preferably, it is 20-500 nm, More preferably, it is 20-300 nm.

  The thickness direction retardation (Rth) of the retardation film obtained by the production method of the present invention can take any appropriate value depending on various factors such as the type of acrylic resin to be used, the conditions for film formation, and the stretching conditions. Preferably it is 50-500 nm or -50--500 nm, More preferably, it is 50-400 nm or -50--400 nm, More preferably, it is 50-300 nm or -50--300 nm.

  The retardation film obtained by the production method of the present invention is excellent in retardation stability under a severe use environment. That is, for example, changes in in-plane retardation (Re) and thickness direction retardation (Rth) before and after the durability test (stored in an atmosphere of 60 ° C. and 90% RH for 500 hours) described in the examples described later. The amount and rate of change are small.

  The retardation film obtained by the production method of the present invention has an in-plane retardation (Re) change amount before and after the durability test (Re after the durability test-Re before the durability test), Preferably it is 5 nm or less, More preferably, it is 3 nm or less, More preferably, it is 2 nm or less, Most preferably, it is 1 nm or less.

  The retardation film obtained by the production method of the present invention has a change rate of in-plane retardation (Re) before and after the durability test ([(Re-after durability test before Re- durability test)) / durability. The absolute value of Re] × 100) before the test is preferably 5% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less.

  The retardation film obtained by the production method of the present invention has an absolute value of the amount of change in the thickness direction retardation (Rth) before and after the durability test (Rth after the durability test-Rth before the durability test). Preferably it is 5 nm or less, More preferably, it is 3 nm or less, More preferably, it is 2 nm or less, Most preferably, it is 1 nm or less.

  The retardation film obtained by the production method of the present invention has a change rate of thickness direction retardation (Rth) before and after the durability test ([(Rth after durability test−Rth before durability test) / durability]. The absolute value of Rth] × 100) before the test is preferably 5% or less, more preferably 3% or less, still more preferably 2% or less, and particularly preferably 1% or less.

  The retardation film obtained by the production method of the present invention is excellent in heat resistance, and the glass transition temperature is preferably 100 ° C to 200 ° C, more preferably 110 ° C to 200 ° C, and further preferably 115 ° C to 200 ° C. More preferably, the temperature is 120 ° C to 200 ° C, particularly preferably 125 ° C to 190 ° C, and most preferably 130 ° C to 180 ° C. When the glass transition temperature is less than 100 ° C., the heat resistance is insufficient with respect to a severe use environment, and the film may be deformed to easily cause unevenness in retardation. When the glass transition temperature exceeds 200 ° C., an ultrahigh heat-resistant retardation film is obtained, but there is a possibility that the molding processability for obtaining the film is bad or the flexibility of the film is greatly reduced.

  The retardation film obtained by the production method of the present invention is excellent in transparency, and the total light transmittance is preferably 85% or more, more preferably 90% or more, and further preferably 91% or more. The total light transmittance is a measure of transparency, and if the total light transmittance is less than 85%, the transparency is lowered, which may be unsuitable as a retardation film.

  The retardation film obtained by the production method of the present invention is excellent in transparency, and the haze is preferably 5% or less, more preferably 3% or less, and further preferably 1% or less. Haze is a measure of transparency, and if haze exceeds 5%, the transparency is lowered and may not be suitable as a retardation film.

  The wavelength dispersion of the retardation film obtained by the production method of the present invention may be forward wavelength dispersion, flat dispersion, or inverse wavelength dispersion. Specifically, for example, in-plane retardation (Re ( 447)) and the in-plane retardation (Re (590)) at a wavelength of 590 nm (Re (447) / Re (590)) is preferably 0.65 to 1.5, more preferably 0.8. It is 8-1.2, More preferably, it is 0.85-1.1.

  The retardation film obtained by the production method of the present invention preferably has flexibility. More preferably, the film has flexibility in two orthogonal directions in the plane of the retardation film. Specifically, in the atmosphere of 25 ° C. and 65% RH, the bending film has a radius of 1 mm. When bent 180 ° in the direction parallel to the slow axis and in the direction perpendicular to the slow axis in the retardation film plane, it is preferable that no cracks occur in either direction. Here, the bending radius means the distance from the bending center of the retardation film to the end of the bent portion. A retardation film that does not cause cracks when bent 180 ° at a bending radius of 1 mm is very easy to handle and is industrially useful. A retardation film that cracks when bent at 180 ° at a bending radius of 1 mm under an atmosphere of 65% RH at 25 ° C. has insufficient flexibility and is difficult to handle. In addition, what is necessary is just to perform a bending test based on JIS. For example, it is preferable to carry out in accordance with K5600-5-1 (1999). The crack means, for example, a crack having a length of 1 mm or more.

  The retardation film obtained by the production method of the present invention can further control optical properties by being laminated with the same kind of optical material and / or different kind of optical material in addition to the use alone. As an optical material laminated | stacked in this case, arbitrary appropriate materials, such as a polarizing plate, the extending | stretching orientation film made from a polycarbonate, and a stretching orientation film made from cyclic polyolefin, are mentioned, for example.

  The retardation film obtained by the production method of the present invention is suitably used as an optical protective film such as an optical compensation member for a liquid crystal display device or a polarizer protective film used for a polarizing plate for a liquid crystal display device. Specifically, for example, retardation films for LCD such as STN type LCD, TFT-TN type LCD, OCB type LCD, VA type LCD, IPS type LCD, etc .; 1/2 wavelength plate; 1/4 wavelength plate; reverse wavelength Dispersion characteristic film; optical compensation film; color filter; laminated film with polarizing plate; polarizing optical compensation film.

  Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. In the following, “parts by weight” may be simply referred to as “parts” for convenience. In addition, “wt%” may be described as “wt%”. In addition, “liter” may be written as “L”.

[Polymerization reaction rate, polymer composition analysis]
The reaction rate during the polymerization reaction and the content of the specific monomer unit in the polymer were determined by gas chromatography (manufactured by Shimadzu Corporation, apparatus name: GC17A) based on the amount of unreacted monomer in the obtained polymerization reaction mixture. ) And measured.

[Weight average molecular weight and number average molecular weight]
The weight average molecular weight (Mw) and number average molecular weight (Mn) of the resin were determined according to the following measurement conditions using gel permeation chromatography (GPC).
Measurement system: Tosoh GPC system HLC-8220
Developing solvent: Chloroform (Wako Pure Chemical Industries, special grade)
Solvent flow rate: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Measurement side column configuration: guard column (manufactured by Tosoh, TSK guardcolumn SuperHZ-L), separation column (manufactured by Tosoh, TSK Gel Super HZM-M), two in series Reference side column configuration: reference column (manufactured by Tosoh, TSK gel SuperH) -RC)

[Glass-transition temperature]
The glass transition temperature (Tg) was determined in accordance with JIS K7121 regulations. Specifically, using a differential scanning calorimeter (Rigaku, Thermo plus EVO DSC-8230), a sample of about 10 mg was heated from room temperature to 200 ° C. (heating rate 20 ° C./min) in a nitrogen gas atmosphere. From the DSC curve obtained in this way, the starting point method was used for evaluation. Α-alumina was used as a reference.

[Phase difference]
The in-plane retardation (Re) and thickness direction retardation (Rth) of the film were left in a constant temperature and humidity chamber (23 ° C., 60% RH setting) for 1 hour, and then a phase difference measuring device (manufactured by Oji Scientific Instruments, KOBRA). -WR) at a measurement wavelength of 589 nm. Specifically, the incident angle dependency (single N calculation) is selected as the measurement item, the average refractive index of the film measured with an Abbe refractometer, with the tilt axis as the slow axis and the incident angle as 40 °, The film thickness d was input and measured.

[Durability test]
Conditions: Input into a durability test for 500 hours in an atmosphere of 60 ° C. and 90% RH, change in in-plane retardation (Re) over time, and change in thickness direction retardation (Rth) over time Evaluated.
Specifically, the retardation films obtained in the following Examples and Comparative Examples were cut into 40 mm × 40 mm, and using an acrylic optical adhesive sheet (Bikan Imaging Co., Ltd., transparent double-sided adhesive tape NCR65), After being attached to a micro slide glass (Matsunami Glass Industry Co., Ltd., product number: S200200, product type: water edge polishing, size: 45 mm × 50 mm × 1.3 mm), it was heated in an autoclave at 50 ° C. × 5 atm × 15 minutes. After the pressure treatment, the specimen was left for 24 hours in an atmosphere of constant temperature and humidity (23 ° C., 60% RH) to obtain a test piece.
The obtained test piece was left in an atmosphere of constant temperature and humidity (23 ° C., 60% RH) for 1 hour, and then the phase difference at the center of the sample was measured (initial value).
After the sample was stored in an atmosphere of 60 ° C. and 90% RH for 500 hours and then returned to an atmosphere of constant temperature and humidity (23 ° C., 60% RH), the phase difference was measured again after 1 hour. The amount of change and the rate of change of the phase difference were determined as the average of three test pieces.

[Film thickness]
Measurement was performed using a Digimatic Micrometer (manufactured by Mitutoyo Corporation).

[Total light transmittance and haze]
It measured using Nippon Denshoku Industries Co., Ltd. NDH-1001DP.

(Production Example 1)
In a 1000 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen gas introduction pipe, 30 parts of methyl methacrylate (MMA), 15 parts of methyl 2- (hydroxymethyl) acrylate (MHMA), and n methacrylate -5 parts of butyl (BMA), 50 parts of toluene, and 0.025 part of ADK STAB 2112 (manufactured by ADEKA) were charged. While introducing nitrogen gas into the reaction vessel, the temperature was raised to 105 ° C. and refluxed. As a polymerization initiator, 0.03 part of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi Corp., Luperox 570) At the same time, an initiator solution consisting of 0.06 part of t-amylperoxyisononanoate and 0.7 part of toluene was added dropwise over 6 hours while solution polymerization was performed under reflux (about 105 to 111 ° C.). And after the dropwise addition of the initiator solution, aging was performed for another 2 hours. The polymerization reaction rate was 96.2%, and the content (weight ratio) of structural units of MHMA in the polymer was 30.2%.
To the resulting polymer solution, 0.1 part of 2-ethylhexyl phosphate (manufactured by Sakai Chemical Industry, trade name: Phoslex A-8) was added as a cyclization catalyst, and the mixture was refluxed at about 85 to 105 ° C. for 12 hours. Cyclocondensation reaction (reaction in which the polymer is subjected to intramolecular dealcoholization reaction to form a lactone ring structure in the polymer molecule) was performed.
Subsequently, the polymer solution obtained by the cyclization condensation reaction was heated to 240 ° C. through a multi-tube heat exchanger, and provided with a leaf disk filter having a filtration accuracy of 5 μm, a barrel temperature of 250 ° C., and a rotation speed. Bent type screw biaxial with 170 rpm, degree of vacuum 13.3 to 400 hPa (10 to 300 mmHg), 1 rear vent, 4 fore vents (referred to as first, second, third and fourth vents from upstream) The product was introduced into an extruder (φ = 42 mm, L / D = 42) at a processing rate of 15 kg / hour in terms of resin amount, and cyclized condensation reaction and devolatilization treatment were performed in the extruder. At that time, using a high pressure pump after the first vent and using a high pressure pump after the first vent, zinc octylate (manufactured by Nippon Chemical Industry Co., Ltd., Nikka Octix zinc 18%): 9.8 parts, Ciba A solution consisting of Irganox 1010 manufactured by Specialty Chemicals: 0.8 part, Adeka Stub AO-412S manufactured by ADEKA: 0.8 part, and toluene: 88.6 parts was poured at a rate of 0.46 kg / hour.
Through this series of operations, a transparent pellet (A1) of an acrylic resin having a lactone ring structure in the main chain was obtained. The weight average molecular weight of the obtained pellet (A1) was 109000, and the glass transition temperature (Tg) was 132 ° C.

(Production Example 2)
The pellet (A1) obtained in Production Example 1 was dried at 80 ° C. for 5 hours, and melt-extruded from a T die at a temperature of 275 ° C. using a 65 mmφ single screw extruder equipped with a leaf disk filter having a filtration accuracy of 5 μm. An unstretched film having a thickness of about 250 μm was formed, and then stretched 2.2 times in the longitudinal direction (MD direction) in an oven at a temperature of 145 ° C. Subsequently, the film was stretched 2.4 times in the width direction (TD direction) at 135 ° C. using a tenter to obtain a stretched film (B1) having a thickness of 70 μm.
The stretched film (B1) had an in-plane retardation (Re) of 55.2 nm and a thickness direction retardation (Rth) of 122.6 nm.
The stretched film (B1) had a total light transmittance of 92.3% and a haze of 0.3%.

[Example 1]
A sample of 40 mm in each of the MD direction and the TD direction was cut out from the stretched film (B1) obtained in Production Example 2, and the sample was left to stand in an atmosphere of 60 ° C. and 90% RH for 24 hours to obtain a retardation film. (C1) was obtained.
The thickness of the retardation film (C1) was 70 μm, the in-plane retardation (Re) was 55.4 nm, and the thickness direction retardation (Rth) was 120.4 nm.
The retardation film (C1) had a total light transmittance of 92.3% and a haze of 0.3%.
A durability test was performed on the retardation film (C1). The results are shown in Table 1. As shown in Table 1, the retardation film (C1) was excellent in retardation stability.

[Comparative Example 1]
From the stretched film (B1) obtained in Production Example 2, a sample of 40 mm in each of the MD direction and the TD direction was cut out, and a durability test was performed without performing any special treatment. The results are shown in Table 1.

  The retardation film obtained by the production method of the present invention is excellent in all of the desired retardation value expression, transparency, and heat resistance, and is also excellent in retardation stability under harsh usage environments. It is suitably used as an optical protective film for a liquid crystal display device or an optical protective film such as a polarizer protective film used for a polarizing plate for a liquid crystal display device.

Claims (2)

After stretching a raw film mainly composed of an acrylic resin having a ring structure in the main chain, the temperature is 40 ° C. or higher and the glass transition temperature of the acrylic resin or lower, and the humidity is 70% RH or higher and 100% RH or lower. The manufacturing method of retardation film which performs the process exposed to 24 hours or more on these conditions.   The method for producing a retardation film according to claim 1, wherein the ring structure is a lactone ring.