JP2008216998A - Multilayer optical film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical film having a small absolute value of thickness-direction retardation (Rth). <P>SOLUTION: The multilayer optical film is obtained by stacking a film A whose thickness-direction retardation (Rth) is positive and a film B whose thickness-direction retardation (Rth) is negative. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical film used for optical materials such as a polarizing plate protective film and a retardation film.

  With the recent expansion of the thin display market represented by liquid crystal televisions, there is an increasing demand for clearer images at a lower price. What is important for realizing this is various optical films, and a polarizing plate protective film and a retardation film are representative.

Regarding a polarizing plate protective film and a retardation film for an IPS liquid crystal display device, a film having a small absolute value of its thickness direction retardation (Rth) is desired. However, the thickness direction retardation (Rth) of a triacetyl cellulose film or a norbornene-based resin film used as a polarizing plate protective film or retardation film for a conventional VA liquid crystal display device shows a large positive value, Necessary functions cannot be provided as protective films and retardation films for IPS liquid crystal display devices (Patent Document 1).
JP 2003-75638 A

  The subject of this invention is providing the optical film with a small absolute value of thickness direction retardation (Rth).

  As a result of intensive studies, the inventors of the present invention laminated a film A having a positive thickness direction retardation (Rth) and a film B having a negative thickness direction retardation (Rth) to obtain a thickness direction retardation (Rth). The inventors have found that an optical film having a small absolute value can be produced, and have completed the present invention.

  According to the present invention, an optical film having a small absolute value of thickness direction retardation (Rth) can be obtained, so that a film useful for a thin display market represented by a liquid crystal television can be provided.

Hereinafter, the present invention will be specifically described.
The present invention is a laminated optical film in which a film A having a positive thickness direction retardation (Rth) and a film B having a negative thickness direction retardation (Rth) are laminated.

1. Material constituting film A having positive thickness direction retardation (Rth) As a material constituting film A having positive thickness direction retardation (Rth) in the present invention, cellulose ester such as triacetyl cellulose, diacetyl cellulose, propionyl cellulose is used. , Butylcellulose, acetylpropionylcellulose, and nitrocellulose. Among these, triacetyl cellulose is preferable.

Moreover, norbornene-type resin is mentioned as another example of the material which comprises the film A with a positive thickness direction retardation (Rth).
Here, the norbornene-based resin refers to a resin containing a norbornene-based monomer as a monomer component, and the norbornene-based monomer refers to a monomer having a norbornene skeleton in its structure. Examples of norbornene resins include, for example, ring-opening polymers or ring-opening copolymers of norbornene monomers, or hydrogenated products thereof, addition polymers or addition copolymers of norbornene monomers, or hydrogens thereof. An additive etc. can be mentioned. Among these, a hydrogenated product of a norbornene-based monomer polymer can be suitably used because it has good film forming properties and excellent mechanical strength, heat resistance, and transparency.

Another example of the film A having a positive thickness direction retardation (Rth) is polycarbonate resin.
In the present invention, polycarbonate resins generally used in the field of optical films can be used as they are. Aromatic polycarbonate is preferred, and polybisphenol A carbonate is more preferred.

2. Material constituting film B having negative thickness direction retardation (Rth) As a material constituting film B having negative thickness direction retardation (Rth) in the present invention, styrene resin (B-1), acrylic resin (B -2).

  In the present invention, the styrene resin (B-1) refers to a polymer containing at least a styrene monomer as a monomer component. Here, the styrene monomer means a monomer having a styrene skeleton in its structure.

  Specific examples of the styrene monomer include nuclei such as o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, and p-tert-butylstyrene in addition to styrene. Examples thereof include vinyl aromatic compound monomers such as α-alkyl-substituted styrenes such as alkyl-substituted styrene, α-methylstyrene, and α-methyl-p-methylstyrene, and a typical one is styrene.

The styrene resin (B-1) may be one obtained by copolymerizing a styrene monomer component with another monomer component. Examples of the copolymerizable monomer include alkyl methacrylates such as methyl methacrylate, cyclohexyl methacrylate, methylphenyl methacrylate and isopropyl methacrylate; alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and cyclohexyl acrylate. Saturated carboxylic acid alkyl ester monomer; unsaturated carboxylic acid monomer such as methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid; maleic anhydride, itaconic acid, ethyl maleic acid, methyl itaconic acid Unsaturated dicarboxylic acid anhydride monomers such as chloromaleic acid; Unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; 1,3-butadiene, 2-methyl Conjugated dienes such as -1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, and the like are copolymerized. May be.
The copolymerization ratio of such other monomer components is preferably 50% by mass or less with respect to the styrene monomer component.

As the styrene resin (B-1), in particular, a styrene-acrylonitrile copolymer (B-1-1), a styrene-methacrylic acid copolymer (B-1-2), and a styrene-maleic anhydride copolymer. (B-1-3) is preferable because it has characteristics required for optical materials such as heat resistance and transparency.
Also, styrene-acrylonitrile copolymer (B-1-1), styrene-methacrylic acid copolymer (B-1-2), and styrene-maleic anhydride copolymer (B-1-3) are methacrylic acid. Since compatibility with a polymer containing methyl as a monomer component is high, it is particularly preferable when a polymer containing methyl methacrylate as a monomer component is used as the acrylic resin (B-2).

  In the case of the styrene-acrylonitrile copolymer (B-1-1), the copolymerization ratio of acrylonitrile in the copolymer is preferably 1 to 40% by mass. A more preferable range is 1 to 30% by mass, and an especially preferable range is 1 to 25% by mass. A copolymerization ratio of acrylonitrile in the copolymer of 1 to 40% by mass is preferable because of excellent transparency.

  In the case of a styrene-methacrylic acid copolymer (B-1-2), the copolymerization ratio of methacrylic acid in the copolymer is preferably 0.1 to 50% by mass. A more preferable range is 0.1 to 40% by mass, and a further preferable range is 0.1 to 30% by mass. When the copolymerization ratio of methacrylic acid in the copolymer is 0.1% by mass or more, the heat resistance is excellent, and when it is in the range of 50% by mass or less, the transparency is excellent, which is preferable.

In the case of the styrene-maleic anhydride copolymer (B-1-3), the copolymerization ratio of maleic anhydride in the copolymer is preferably 0.1 to 50% by mass. A more preferable range is 0.1 to 40% by mass, and a further preferable range is 0.1 to 30% by mass. A copolymerization ratio of maleic anhydride in the copolymer of 0.1% by mass or more is excellent in heat resistance, and a range of 50% by mass or less is preferable because of excellent transparency.
Among these, styrene-methacrylic acid copolymer (B-1-2) and styrene-maleic anhydride copolymer (B-1-3) are particularly preferable from the viewpoint of heat resistance.

As the styrene resin (B-1), a plurality of types of styrene resins having different compositions and molecular weights can be used in combination.
The styrenic resin (B-1) can be obtained by a known anion, block, suspension, emulsion or solution polymerization method. Moreover, the unsaturated double bond of the benzene ring of a conjugated diene or a styrene monomer may be hydrogenated in the styrene resin (B-1). The hydrogenation rate can be measured by a nuclear magnetic resonance apparatus (NMR).

  In this invention, acrylic resin (B-2) means the polymer which contains acrylic acid, methacrylic acid, or these derivatives as a monomer component.

  A preferred example of the acrylic resin (B-2) is a polymer (B-2-1) containing an alkyl acrylate ester or an alkyl methacrylate ester as a monomer component.

  Specific examples of the polymer (B-2-1) containing an alkyl acrylate ester or an alkyl methacrylate ester as a monomer component include alkyl methacrylates such as cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, and methyl methacrylate. Esters: those obtained by polymerizing one or more monomers selected from alkyl acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, 2-ethylhexyl acrylate, and the like.

Here, the polymer containing an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer component includes those obtained by copolymerization of monomers other than the methacrylic acid alkyl ester and the acrylic acid alkyl ester.
As monomers other than acrylic acid alkyl esters, methacrylic acid alkyl esters and methacrylic acid alkyl esters and acrylic acid alkyl esters, aromatic vinyl compounds such as styrene, vinyltoluene and α-methylstyrene; acrylonitrile Vinyl cyanides such as methacrylonitrile; maleimides such as N-phenylmaleimide and N-cyclohexylmaleimide; unsaturated carboxylic acid anhydrides such as maleic anhydride; unsaturated acids such as acrylic acid, methacrylic acid and maleic acid Etc. These may be used alone or in combination of two or more.
When monomer components other than methacrylic acid alkyl ester and acrylic acid alkyl ester are copolymerized, the copolymerization ratio is preferably less than 50% by mass with respect to methacrylic acid alkyl ester and acrylic acid alkyl ester. More preferably, it is 40 mass% or less, Most preferably, it is 30 mass% or less. Less than 50% by mass is preferable because optical properties such as total light transmittance are excellent.

Among polymers containing an alkyl acrylate ester or an alkyl methacrylate ester as a monomer component, a homopolymer of methyl methacrylate or a copolymer of methyl methacrylate and another monomer is heat resistant and transparent. It is preferable because it has properties required for optical materials such as optical properties.
As the monomer copolymerized with methyl methacrylate, acrylic acid alkyl esters are particularly preferable because they are excellent in thermal decomposition resistance and have high fluidity during molding of a methacrylic resin obtained by copolymerization thereof. The amount of alkyl acrylates used when copolymerizing alkyl methacrylates with methyl methacrylate is preferably 0.1% by mass or more from the viewpoint of thermal decomposition resistance, and 15 masses from the viewpoint of heat resistance. % Or less is preferable. The content is more preferably 0.2% by mass or more and 14% by mass or less, and particularly preferably 1% by mass or more and 12% by mass or less.
Among the alkyl acrylates, methyl acrylate and ethyl acrylate are preferable because only a small amount of methyl acrylate is copolymerized with a small amount of methyl methacrylate because the effect of improving the fluidity during the molding process described above can be obtained remarkably.

  In the present invention, isotactic polymethacrylate and syndiotactic polymethacrylate can be used simultaneously.

  The polymer (B-2-1) containing an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer component preferably has a mass average molecular weight of 50,000 to 200,000. The mass average molecular weight of the polymer (B-2-1) is preferably 50,000 or more from the viewpoint of the strength of the molded product, and preferably 200,000 or less from the viewpoint of molding processability and fluidity. A more preferable range is 70,000 to 150,000.

As a method for producing a polymer (B-2-1) containing an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer component, for example, cast polymerization, bulk polymerization, suspension polymerization, solution polymerization, emulsion polymerization, anionic polymerization A generally used polymerization method such as can be used. For optical applications, it is preferable to avoid contamination of minute foreign substances as much as possible. From this viewpoint, bulk polymerization or solution polymerization without using a suspending agent or an emulsifier is preferable.
When solution polymerization is performed, a solution prepared by dissolving a mixture of monomers in an aromatic hydrocarbon solvent such as toluene or ethylbenzene can be used. In the case of polymerization by bulk polymerization, the polymerization can be started by irradiation with free radicals generated by heating or ionizing radiation as is usually done.

As the initiator used in the polymerization reaction, any initiator used in radical polymerization can be used. For example, azo compounds such as azobisisobutylnitrile, benzoyl peroxide, lauroyl peroxide, t-butylperoxy An organic peroxide such as -2-ethylhexanoate can be used.
In particular, when polymerization is carried out at a high temperature of 90 ° C. or higher, solution polymerization is common, so that the 10-hour half-life temperature is 80 ° C. or higher and a peroxide that is soluble in the organic solvent used, An azobis initiator is preferred. Specifically, 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, 1, Examples thereof include 1-azobis (1-cyclohexanecarbonitrile) and 2- (carbamoylazo) isobutyronitrile.
These initiators are preferably used, for example, in the range of 0.005 to 5% by mass.

As the molecular weight regulator used as necessary for the polymerization reaction, any one generally used in radical polymerization can be used. Particularly preferred.
These molecular weight regulators are added in a concentration range such that the degree of polymerization of the polymer (B-2-1) is controlled within a preferable range.

  Among polymers (B-2-1) containing an alkyl acrylate ester or an alkyl methacrylate ester as a monomer component, methyl methacrylate homopolymer, methyl methacrylate-methyl acrylate copolymer, methyl methacrylate- An ethyl acrylate copolymer is preferable, and a methyl methacrylate-methyl acrylate copolymer is particularly preferable in that it has a good balance between fluidity and heat resistance during molding.

Further, another preferred example of the acrylic resin (B-2) is a ternary or higher copolymer obtained by copolymerizing a methacrylic acid ester and / or an acrylic acid ester with two or more other monomers. A polymer (B-2-2) is mentioned.
Examples of other monomer components copolymerized with methacrylic acid ester and / or acrylic acid ester include styrene, α-methyl styrene, o-methyl styrene, p-methyl styrene, o-ethyl styrene, p-ethyl styrene. And aromatic vinyl compounds such as pt-butylstyrene; vinyl cyanides such as acrylonitrile, methacrylonitrile, ethacrylonitrile; N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, N-phenyl Maleimides such as maleimide, acrylamide, methacrylamide, N-methylacrylamide, butoxymethylacrylamide, N-propylmethacrylamide; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; acrylic acid, methacrylic acid and croton Acid, α Unsaturated carboxylic acids such as substituted acrylic acid, α-substituted methacrylic acid and maleic acid; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate T-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2- (meth) acrylic acid 2- Such as hydroxyethyl, 3-hydroxypropyl (meth) acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate And unsaturated carboxylic acid alkyl esters.

  Among the ternary or higher copolymer (B-2-2), a heat-resistant acrylic resin (B-2-2-1) is particularly preferable.

  In the present invention, the heat-resistant acrylic resin (B-2-2-1) includes a methacrylic acid ester and / or an acrylic acid ester unit, an aromatic vinyl compound unit, and a compound unit represented by the following general formula [1]. It is a copolymer.

General formula [1]

(Wherein X represents O or N—R, O represents an oxygen atom, N represents a nitrogen atom, and R represents a hydrogen atom, an alkyl group, an aryl group or a cycloalkane group.)

  Specific examples of the methacrylic acid ester and / or acrylic acid ester that are the first monomer component of the heat-resistant acrylic resin (B-2-2-1) include, for example, methyl methacrylate, ethyl methacrylate, and methacrylic acid. Methacrylic acid ester such as propyl, n-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, acrylic acid 2 -Acrylic acid esters such as ethylhexyl. Of these, methyl methacrylate is preferred.

  Specific examples of the aromatic vinyl compound that is the second monomer component of the heat-resistant acrylic resin (B-2-2-1) include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, Examples include nuclear alkyl-substituted styrene such as 2,4-dimethylstyrene, ethylstyrene, and p-tert-butylstyrene; α-alkyl-substituted styrene such as α-methylstyrene and α-methyl-p-methylstyrene. Of these, styrene is preferable.

  Among the units represented by the general formula [1], which is the third monomer component of the heat-resistant acrylic resin (B-2-2-1), those in which X is O include maleic anhydride, itacon Examples thereof include unsaturated dicarboxylic acid anhydride monomer units which are anhydrides such as acid, ethylmaleic acid, methylitaconic acid and chloromaleic acid. Of these, maleic anhydride is most preferred. Examples of X being N—R include maleimide monomers such as N-phenylmaleimide and N-cyclohexylmaleimide.

The copolymerization ratio of the monomer units constituting the heat-resistant acrylic resin (B-2-2-1) is 40% by mass of methacrylic acid ester and / or acrylic acid ester unit from the viewpoint of heat resistance and photoelastic coefficient. It is preferably 90% by mass or less, 5% by mass or more and 40% by mass or less of the aromatic vinyl compound unit, and 5% by mass or more and 20% by mass or less of the compound unit represented by the general formula [1].
More preferably, the methacrylic acid ester and / or acrylic acid ester unit is 42% by mass to 83% by mass, the aromatic vinyl compound unit is 12% by mass to 40% by mass, and the compound represented by the above general formula [1] A unit is 5 mass% or more and 18 mass% or less.
More preferably, the methacrylic acid ester and / or acrylic acid ester unit is 45% by mass to 78% by mass, the aromatic vinyl compound unit is 16% by mass to 40% by mass, and the compound represented by the above general formula [1] A unit is 6 mass% or more and 15 mass% or less.

  Moreover, it is preferable that the ratio of the aromatic vinyl compound unit with respect to the copolymerization ratio of the compound unit represented by the general formula [1] is 1 to 3 times.

  The heat-resistant acrylic resin (B-2-2-1) includes a heat-resistant acrylic resin obtained by copolymerizing other monomers that can be copolymerized as necessary in addition to the above-described essential constituent monomer components. Are also included. Other copolymerizable monomers used here include unsaturated carboxylic acid monomers such as methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid and cinnamic acid; unsaturated monomers such as acrylonitrile and methacrylonitrile. Saturated nitrile monomers; 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, etc. Conjugated dienes and the like can be mentioned, and two or more of these can be copolymerized.

As a method for producing the heat-resistant acrylic resin (B-2-2-1), bulk polymerization using a radical initiator is suitable, but solution polymerization and emulsion polymerization can also be used.
Aqueous suspension polymerization is not recommended when maleic anhydride is used as a monomer component because it is highly water-soluble and it is difficult to maintain a stable suspension system throughout.

Among general radical initiators, among azo initiators such as azobisisobutyronitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), and peroxide initiators, benzoyl When peroxide is used for polymerization of the heat-resistant acrylic resin, the resulting polymer may be colored.
When lauroyl peroxide, decanoyl peroxide, or t-butylperoxy 2-ethylhexanoate is used as the peroxide initiator, the heat-resistant acrylic resin (B-3) is not colored. However, a polymer using t-butylperoxy 2-ethylhexanoate has low water resistance, a large weight increase when immersed in hot water, and the surface may be whitened.
Therefore, it is preferable to apply a diacyl peroxide such as lauroyl peroxide to the polymerization of the heat-resistant acrylic resin (B-2-2-1).

  As a preferable polymerization method of the heat-resistant acrylic resin (B-2-2-1), a method described in JP-B-63-1964 is exemplified.

  The melt index (ASTM D1238; condition I) of the heat-resistant acrylic resin (B-2-2-1) is preferably 10 g / 10 minutes or less from the viewpoint of the strength of the molded product. More preferably, it is 6 g / 10 minutes or less, More preferably, it is 3 g / 10 minutes or less.

  Another preferred example of the ternary or higher copolymer (B-2-2) is a methacrylic acid ester and / or an acrylic acid ester unit, an aromatic vinyl compound unit, and the following general formula [2]. A heat-resistant acrylic resin (B-2-2-2), which is a copolymer containing an acid anhydride unit having a 6-membered ring structure. The copolymer (B-2-2-2) containing an acid anhydride unit having a 6-membered ring structure is excellent in heat resistance, and the retardation design of a molded product obtained therefrom is easy. Is suitable.

General formula [2]

(In the formula, R ₁ and R ₂ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may be substituted with, for example, a hydroxyl group.)

  In the present invention, the monomer component before polymerization is referred to as “˜monomer” (however, “monomer” may be omitted and only the compound name may be described). The constituting unit is referred to as “˜monomer unit”.

  Specific examples of the methacrylic acid ester and / or acrylic acid ester that are the first monomer component of the heat-resistant acrylic resin (B-2-2-2) include the above-mentioned heat-resistant acrylic resin (B-2-2). -1) can be used, and methacrylic acid esters include, in particular, butyl methacrylate, ethyl methacrylate, methyl methacrylate, propyl methacrylate, isopropyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, methacrylic acid. Acid (2-ethylhexyl), methacrylic acid (t-butylcyclohexyl), benzyl methacrylate, methacrylic acid (2,2,2-trifluoroethyl) and the like can be preferably used, and typical ones are methyl methacrylate. It is.

  Examples of the acrylic ester include methyl acrylate, ethyl acrylate, butyl acrylate, isopropyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, acrylic acid (2-ethylhexyl), acrylic acid (t -Butylcyclohexyl), benzyl acrylate, acrylic acid (2,2,2-trifluoroethyl) and the like can be suitably used.

  The above methacrylic acid esters and acrylic acid esters may be used alone or in combination of two or more.

  The amount of methacrylic acid ester and / or acrylic acid ester charged is the total amount of monomers used for polymerization in consideration of the balance of heat resistance, optical properties, etc. of the heat-resistant acrylic resin (B-2-2-2). When the amount of the component is 100 parts by mass, it is preferably 5 parts by mass or more and 85 parts by mass or less, more preferably 20 parts by mass or more and 80 parts by mass or less, and further preferably 40 parts by mass or more and 80 parts by mass or less. .

  Specific examples of the aromatic vinyl compound that is the second monomer component of the heat-resistant acrylic resin (B-2-2-2) are exemplified in the above-mentioned heat-resistant acrylic resin (B-2-2-1). In particular, a compound represented by the following general formula [3] can be preferably used.

General formula [3]

(In the formula, R ₆ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may have, for example, a hydroxyl group as a substituent. And R ₇ independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and 1 to 1 carbon atoms. And each R ₇ may be the same or different, and each R ₇ may be bonded to each other to form a ring structure. May be.)

  Specific examples of the compound represented by the general formula [3] include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,4 -Styrene monomers such as dimethyl styrene, 3,5-dimethyl styrene, p-ethyl styrene, m-ethyl styrene, о-ethyl styrene, p-tert-butyl styrene, isopropenyl benzene (α-methyl styrene); 1-vinylnaphthalene, 2-vinylnaphthalene, 1,1-diphenylethylene, isopropenyltoluene, isopropenylethylbenzene, isopropenylpropylbenzene, isopropenylbutylbenzene, isopropenylpentylbenzene, isopropenylhexylbenzene, isopropenyloctylbenzene, etc. Mentioned Therefore, it can be appropriately selected according to the properties required for the copolymer. The preferred monomer is a styrene monomer, more preferably styrene, isopropenylbenzene, and still more preferably styrene.

  The said aromatic vinyl compound may be used independently and can also be used in combination of 2 or more type.

  The amount of the aromatic vinyl compound charged can be appropriately determined according to the optical characteristics, heat resistance, and workability required for the heat-resistant acrylic resin (B-2-2-2). When the amount of all monomer components used in the polymerization is 100 parts by mass, it is preferably 1 part by mass or more and 50 parts by mass or less, more preferably more than 3 parts by mass and 40 parts by mass. It is 3 parts by mass or more, more preferably 3 parts by mass or more and 30 parts by mass or less, particularly preferably 3 parts by mass or more and 25 parts by mass or less, and most preferably 5 parts by mass or more and 20 parts by mass or less.

  The acid anhydride unit having a 6-membered ring structure represented by the general formula [2], which is the third unit of the heat-resistant acrylic resin (B-2-2-2), is an unsaturated carboxylic acid monomer. And, if necessary, the unsaturated carboxylic acid ester monomer is polymerized and copolymerized with other monomer components such as methacrylic acid ester and / or acrylic acid ester and aromatic vinyl compound. The copolymer can be produced by heating in the presence or absence of a suitable catalyst to cause an intramolecular cyclization reaction by dealcoholization and / or dehydration. In this case, typically, the carboxyl group of the unsaturated carboxylic acid unit of 2 units is dehydrated by heating the copolymer, or the alcohol is removed from the adjacent unsaturated carboxylic acid unit and unsaturated carboxylic acid ester unit. Separation produces an acid anhydride unit having a 6-membered ring structure.

  Specific examples of the unsaturated carboxylic acid monomer for producing an acid anhydride unit having a 6-membered ring structure represented by the general formula [2] include compounds represented by the following general formula [4]. It is done.

General formula [4]

(In the formula, R ₅ represents a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group may have, for example, a hydroxyl group.)

For example, methacrylic acid, acrylic acid, itaconic acid, maleic acid, fumaric acid, cinnamic acid and the like, and unsaturated carboxylic acid alkyl ester monomers include, for example, methyl methacrylate, methyl acrylate and the like, Preferably, methacrylic acid or acrylic acid can be used, more preferably methacrylic acid can be used.
These unsaturated carboxylic acids may be used alone or in combination of two or more.

  The amount of the unsaturated carboxylic acid monomer charged is used in the polymerization in consideration of the heat resistance, workability, optical characteristics, productivity, etc. required for the heat-resistant acrylic resin (B-2-2-2). When the amount of all monomers is 100 parts by mass, it is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, and further preferably 10 parts by mass or more and 40 parts by mass or less. Hereinafter, it is particularly preferably 10 to 35 parts by mass, particularly preferably 15 to 35 parts by mass, and most preferably 20 to 30 parts by mass.

  The heat-resistant acrylic resin (B-2-2-2) is obtained by copolymerizing other monomers in the range not impairing the effects of the present invention in addition to the monomer components of the essential constituent units described above. Also included are heat resistant acrylic resins. As other monomers used here, for example, vinyl monomers other than the monomer of the essential constituent unit can be used. Other vinyl monomers used as monomers include vinyl cyanides such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; N-methylmaleimide, N -Maleimides such as ethylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide; and amides such as acrylamide and methacrylamide.

  In the case of containing other monomers, considering the optical properties, heat resistance, and processability of the heat-resistant acrylic resin (B-2-2-2), the amount charged is the total amount of monomers used in the polymerization. When the amount is 100 parts by mass, it is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 40 parts by mass, still more preferably 0.5 to 35 parts by mass, and particularly preferably 1 to 1 part by mass. 30 parts by mass, particularly preferably 1 to 25 parts by mass.

  The heat-resistant acrylic resin (B-2-2-2) is disclosed in JP-B-02-26641, JP-A-2006-266543, JP-A-2006-274069, JP-A-2006-274071, JP-A-2006. The composition ratio can be determined, manufactured, and evaluated by referring to the methods described in Japanese Patent Publication No.-283013 and Japanese Patent Application Laid-Open No. 2005-162835.

  As a polymerization method of the heat-resistant acrylic resin (B-2-2-2), conventionally known methods such as bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization, and precipitation polymerization can be used. Therefore, bulk polymerization, solution polymerization, and precipitation polymerization without using a suspending agent or an emulsifier are preferable. In consideration of productivity such as ease of control of molecular weight, bulk polymerization and solution polymerization are performed. preferable.

  In the production of the heat-resistant acrylic resin (B-2-2-2), a solvent can be used. The solvent can be appropriately selected in accordance with the polymerization method, and specific examples include aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; alcohols such as methanol, ethanol, and cyclohexanol; acetone, Examples include ketones such as methyl ethyl ketone, methyl isobutyl ketone, and diisobutyl ketone; hydrocarbons such as pentane, hexane, heptane, and cyclohexane; esters such as ethyl acetate and butyl acetate. These may be used alone. Two or more kinds can be used in combination.

When the heat-resistant acrylic resin (B-2-2-2) is produced, particularly when solution polymerization or bulk polymerization is performed, the copolymer is precipitated if the solubility of the resulting copolymer in the solvent is low. It may be difficult to achieve stable operation. Therefore, when selecting the solvent, it is preferable to consider the solubility of the copolymer in the solvent. Specifically, the solubility parameter δ of the solvent used is preferably 9.0 to 15.0 (cal / cm ³ ) ^1/2 . Preferably 9.2 to 14.0 (cal / cm ³ ) ^1/2 , more preferably 9.3 to 13.5 (cal / cm ³ ) ^1/2 , particularly preferably 9.4 to 13.0 ( cal / cm ³ ) ^1/2 , particularly preferably 9.7 to 12.8 (cal / cm ³ ) ^1/2 . The value of the solubility parameter and how to obtain the value are described in, for example, P. in “Journal of Paint Technology Vol. 42, No. 541, February 1970”. 76-P. K. posted on 118 L. Hoy “New Values of the Solubility Parameters From Vapor Pressure Data” For example, Brandrup et al., “Polymer Handbook Fourth Edition” P-VII / 675-P714 can be referred to. 1 (cal / cm ³ ) ^1/2 is approximately 0.49 (MPa) ^1/2 .

  When a heat-resistant acrylic resin (B-2-2-2) is produced using a solvent that does not contain a hydroxyl group, such as aromatic hydrocarbons and ketones, it is operated at a practically useful degree of polymerization when producing the copolymer. In this case, the degree of polymerization may not be increased because the molecular weight and molecular weight distribution tend to be difficult to control due to precipitation of high molecular weight components. In particular, the high molecular weight component tends to precipitate when the charging ratio of the unsaturated carboxylic acid monomer is 15% by mass or more. Therefore, when it is necessary to consider productivity, it is preferable to use a solvent having at least one hydroxyl group represented by the following general formula [5].

General formula [5]
R ₈ -OH
(Wherein, .R ₈ R ₈ is representing a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms is, for example, may be substituted with a hydroxyl group, or may contain an ether bond .)

  In addition, since unsaturated carboxylic acid monomers tend to be highly polymerizable, self-polymerization can be performed at room temperature to high temperature when a polymerization inhibitor is not added or when the amount of polymerization inhibitor is small. is there. When recycling the solvent and monomer recovered from the reaction system, separation operation may be performed using a rectifying column, but when polymerization of unsaturated carboxylic acid monomer proceeds in the rectifying column, In addition to being unable to recycle, the equipment may be damaged by the precipitation and solidification of the polymer. Therefore, it is preferable to use a solvent having at least one hydroxyl group also when the monomer or solvent is recovered from the reaction system and recycled.

  Specific examples of such a solvent having at least one hydroxyl group include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, capryl alcohol, lauryl alcohol, myristyl alcohol, cyclopentanol, cyclohexanol, and cycloheptanol. 2-methylcyclohexanol, 3-methylcyclohexanol, 4-methylcyclohexanol, 2-ethylcyclohexanol, 3-ethylcyclohexanol, 4-ethylcyclohexanol, 2,3-dimethylcyclohexanol, 2,4-dimethyl Cyclohexanol, 2,5-dimethylcyclohexanol, 2,6-dimethylcyclohexanol, 3,4-dimethylcyclohexanol, 3,5-dimethylcyclohexanol Alcohols having one hydroxyl group and the like; ethylene glycol, alcohols containing multiple hydroxyl groups such as glycerin; ether bond-containing alcohols such as methyl cellosolve.

  Among them, secondary alcohols are preferable, and alcohols having a cyclic structure are more preferable. Among them, cyclohexanol having excellent miscibility with an unsaturated carboxylic acid monomer is an unsaturated carboxylic acid monomer that is an organic acid. It is particularly preferable also from the viewpoint of preventing metal corrosion due to the nature (preventing the corrosiveness of pipes of equipment used for the polymerization liquid recycling process, polymerization liquid recycling process, etc.).

  Further, the amount of water contained in the solvent used in the production of the heat-resistant acrylic resin (B-2-2-2) is preferably 5% by mass or less, more preferably 3% by mass or less, still more preferably 0. 0.01 to 2% by mass, particularly preferably 0.1 to 2% by mass.

  In addition, unsaturated carboxylic acid monomers tend to have a higher boiling point than acrylic acid ester monomers and aromatic vinyl compound monomers, and are used at the bottom of the rectifying column when separating the recycle liquid. It tends to remain at a high concentration, and the self-polymerization of the unsaturated carboxylic acid monomer proceeds at the lower part of the rectifying column, which may impair the recyclability of the monomer or solvent. As described above, by using a solvent containing at least one hydroxyl group, self-polymerization of the unsaturated carboxylic acid monomer is reduced. However, when higher recyclability is required, the boiling point of the solvent is 100 ° C. The temperature is preferably 100 ° C. or higher and 200 ° C. or lower, more preferably 110 ° C. or higher and 200 ° C. or lower, particularly preferably 120 ° C. or higher and 190 ° C. or lower, and particularly preferably 130 ° C. or higher and 190 ° C. or lower.

  Furthermore, the difference (XY (° C.)) between the boiling point (X) of the monomer having the highest boiling point and the boiling point (Y) of the solvent to be used is −50 ° C. ≦ (X −Y) ≦ 40 ° C., more preferably −40 ° C. ≦ (XY) ≦ 30 ° C., further preferably −40 ° C. ≦ (X−Y) ≦ 20 ° C., particularly preferably −30 ° C. ≦ (XY) ≦ 20 ° C., particularly preferably −25 ° C. ≦ (XY) ≦ 15 ° C., and most preferably −15 ° C. ≦ (XY) ≦ 10 ° C.

  When solution polymerization or bulk polymerization is performed in the production of the heat-resistant acrylic resin (B-2-2-2), the heat-resistant acrylic resin (B-2-2-2-) with respect to the solvent to be used is considered in consideration of production stability. The solubility of 2) is preferably 0.1 g / 100 mL or more, more preferably more than 1 g / 100 mL. Further, it is preferably 2 g / 100 mL or more.

  In consideration of the recycling solution recovery process of the polymerization solution and the pipe corrosivity of the apparatus used for polymerization and recycling, the solubility of the solvent used in water is preferably 0.7 g / 100 mL or more and 100 g / 100 mL or less. . More preferably 1.0 g / 100 mL to 80 g / 100 mL, still more preferably 1.0 g / 100 mL to 50 g / 100 mL, particularly preferably 1.0 g / 100 mL to 25 g / 100 mL, particularly preferably 1.0 g / 100 mL or more 15 g / 100 mL or less, most preferably 1.0 g / 100 mL or more and 10 g / 100 mL or less.

  When the amount of the solvent used in the production of the heat-resistant acrylic resin (B-2-2-2) is too large, the monomer concentration in the polymerization solution decreases, and the productivity decreases. Since the viscosity of the polymerization solution increases, it is necessary to take measures such as increasing the temperature of the polymerization solution, which tends to increase production costs. Accordingly, the solvent addition amount itself can be appropriately determined within a polymerizable range, but considering the productivity and production cost, the amount of the solvent when the total of all the monomer components and the solvent is 100% by mass. Is preferably 5% by mass or more and 60% by mass or less. More preferably, they are 5 to 50 mass%, More preferably, they are 10 to 45 mass%, Most preferably, they are 15 to 40 mass%.

  The polymerization temperature in the production of the heat-resistant acrylic resin (B-2-2-2) may be any temperature at which polymerization proceeds, but is preferably 50 ° C. or higher and 200 ° C. or lower from the viewpoint of productivity. Is 90 ° C. or higher and 200 ° C. or lower. More preferably, they are 100 degreeC or more and 200 degrees C or less, More preferably, they are 100 degreeC or more and 180 degrees C or less, Especially preferably, they are 110 degreeC or more and 170 degrees C or less, Especially preferably, they are 120 degreeC or more and 160 degrees C. The polymerization time is not particularly limited as long as the required degree of polymerization can be obtained, but is preferably 0.5 hours or more and 6 hours or less, more preferably from the viewpoint of productivity. It is 1 hour or more and 5 hours or less, More preferably, it is 1 hour or more and 3 hours or less.

  In the production of the heat-resistant acrylic resin (B-2-2-2), the dissolved oxygen concentration in the polymerization solution is preferably 10 ppm or less. The dissolved oxygen concentration can be measured using, for example, a dissolved oxygen meter DO meter B-505 (manufactured by Iijima Electronics Co., Ltd.). As a method for lowering the dissolved oxygen concentration, a method of bubbling an inert gas in the polymerization solution, an operation of releasing the pressure after pressurizing the inside of the container containing the polymerization solution to about 0.2 MPa with an inert gas before the start of polymerization is performed. Methods such as a method of repeating and a method of passing an inert gas into a container containing a polymerization solution can be appropriately selected.

The molecular weight distribution range of the heat-resistant acrylic resin (B-2-2-2) is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) (Mw / Mn) from the viewpoint of processing fluidity and mechanical strength. It is preferable that it exists in the range of 1.5-3.0. More preferably, it is 1.6-2.7, More preferably, it is the range of 1.6-2.4.
In the present invention, the ratio (Mw / Mn) between the weight average molecular weight (Mw) and the number average molecular weight (Mn) refers to a value determined by PMMA conversion using gel permeation chromatography (GPC).

  The weight average molecular weight (Mw) measured by GPC of the heat-resistant acrylic resin (B-2-2-2) is preferably 50,000 to 300,000, more preferably from the balance of fluidity, heat resistance, stretching stability, and the like. Is 5 to 250,000, more preferably 7 to 220,000, and particularly preferably 80 to 200,000.

As described above, the acid anhydride unit having a 6-membered ring structure represented by the general formula [2] of the heat-resistant acrylic resin (B-2-2-2) includes an unsaturated carboxylic acid monomer and, if necessary, Accordingly, an unsaturated carboxylic acid ester monomer and other monomer components are polymerized to form a copolymer, and then the copolymer is heated in the presence or absence of a catalyst to produce an unsaturated carboxylic acid. By dehydration reaction from an acid monomer unit or dealcoholization reaction from an unsaturated carboxylic acid monomer unit and an unsaturated carboxylic acid ester unit (specifically, a methacrylic acid ester and / or an acrylic acid ester unit, etc.) It can be obtained by an intramolecular cyclization reaction.
The method for causing such an intramolecular cyclization reaction is not particularly limited. For example, a method using an extruder having a vent port or a devolatilization tank under an inert gas atmosphere such as nitrogen or argon or under reduced pressure is used. Methods and the like.

  Examples of the apparatus used for causing the intramolecular cyclization reaction include a flash tank, a twin screw extruder, a single screw extruder, a twin / single screw composite continuous kneading extruder, a multi-screw extruder having three or more axes, A kneader etc. are mentioned, These may use together 1 type, or 2 or more types.

  When the intramolecular cyclization reaction is caused by heat devolatilization, the temperature can be appropriately set according to the desired copolymer composition, the amount of unreacted monomer and the amount of solvent, and intramolecular cyclization. Although it will not be restrict | limited especially if it is temperature at which reaction occurs, Preferably it is 180-300 degreeC, More preferably, it is 200-300 degreeC, More preferably, it is 200-280 degreeC, Most preferably, it is 220-280 degreeC.

  Moreover, the heating time in the case of performing the heat devolatilization and / or cyclization reaction can be appropriately set according to the desired copolymer composition, and is usually 1 to 240 minutes, preferably 1 to 150 minutes, More preferably 1 to 120 minutes, particularly preferably 2 to 90 minutes, particularly preferably 3 to 60 minutes, and particularly preferably 5 to 60 minutes.

  When using an extruder, in order to ensure the heating time, the ratio of screw diameter (D) to screw length (L) is preferably L / D = 20 or more, more preferably 30 or more, particularly preferably. It is preferable to set it to 40 or more. Moreover, it is preferable that L / D is 120 or less practically.

  Further, when the heat devolatilization and / or cyclization reaction is carried out under reduced pressure, it is preferably 200 Torr or less, more preferably 150 Torr or less, still more preferably 100 Torr or less, particularly preferably 50 Torr, in view of devolatilization efficiency and the like. It is as follows. Moreover, it is preferable that it is 1 Torr or more practically.

In the heat-resistant acrylic resin (B-2-2-2), when forming an acid anhydride unit having a 6-membered ring structure represented by the general formula [2], in order to promote the cyclization reaction, As the catalyst, at least one selected from acids, alkalis and salts can be added. The amount of the cyclization catalyst added is not particularly specified as long as it does not impair the purpose of the present application, but is preferably smaller from the viewpoint of the transparency and mechanical strength of the resulting copolymer. Specifically, it is preferably 1 part by mass or less, more preferably 0.5 part by mass or less, and still more preferably 0.1 part by mass or less.
If an example of the catalyst used suitably is given, hydrochloric acid, a sulfuric acid, phosphoric acid, phosphorous acid, p-toluenesulfonic acid, phenylphosphonic acid etc. will be mentioned as an acid catalyst. Examples of the basic catalyst include metal hydroxides, amines, imines, alkali metal derivatives, alkaline earth metal derivatives, and the like. Examples of the salt catalyst include metal carbonates, metal sulfates, metal acetates, and metal stearates.

  From the viewpoint of the reaction promotion effect of the cyclization reaction, the transparency of the copolymer, and the colorability, a basic catalyst and a salt-based catalyst can be preferably used. The said cyclization catalyst may be used independently and can also be used in combination of 2 or more type.

  The copolymerization ratio of each structural unit of the heat-resistant acrylic resin (B-2-2-2) is not particularly limited as long as the effect of the present application can be achieved, but high heat resistance and optics required for the application of the present application. In the case where it is necessary to impart a high degree of balance with characteristics, when the total amount of all monomer units is 100% by mass, methacrylic acid ester and / or acrylate monomer units are 5% by mass or more and 85%. It is preferably no greater than 20% by mass, more preferably no less than 20% by mass and no greater than 80% by mass, even more preferably no less than 40% by mass and no greater than 80% by mass, and even more preferably no less than 50% by mass and no greater than 80% by mass. 2] The acid anhydride unit having a 6-membered ring structure is preferably 10% by mass or more and 35% by mass or less, more preferably 15% by mass or more and 33% by mass or less, and more preferably 1%. % By mass to 30% by mass, more preferably 17% by mass to 28% by mass, particularly preferably 17% by mass to less than 25% by mass, and the aromatic vinyl compound unit being 2% by mass to 50% by mass. More preferably, it is 4 mass% or more and 45 mass% or less, More preferably, it is 4 mass% or more and 30 mass% or less, Especially preferably, it is 5 mass% or more and 25 mass% or less, Most preferably, it is 5 mass% or more and 20 mass% or less. It is as follows.

  Furthermore, when the heat-resistant acrylic resin (B-2-2-2) contains an unsaturated carboxylic acid monomer unit, the copolymerization ratio is, when the total amount of all monomer units is 100% by mass, It is preferably 10% by mass or less, more preferably 1% by mass or more and 10% by mass or less, still more preferably 1% by mass or more and 8% by mass or less, and particularly preferably 2% by mass or more and 7% by mass or less.

  Further, in consideration of the balance of heat resistance, fluidity, processability, mechanical properties, and optical properties, it has a 6-membered ring structure represented by the general formula [2] with respect to the copolymerization ratio of unsaturated carboxylic acid monomer units. Ratio of copolymerization ratio of acid anhydride units (% by mass) is 2 ≦ copolymerization ratio of acid anhydride units having a 6-membered ring structure represented by the general formula [2]) / unsaturated carboxylic acid monomer It is preferable that the copolymerization ratio of units ≦ 30.

  In particular, when it is necessary to highly balance the optical properties such as the photoelastic coefficient and retardation, heat resistance, and process fluidity, the copolymerization of the aromatic vinyl compound unit with respect to the copolymerization ratio of the unsaturated carboxylic acid monomer unit. The ratio of the polymerization ratio is preferably 1 ≦ copolymerization ratio of aromatic vinyl compound unit / copolymerization ratio of unsaturated carboxylic acid monomer unit ≦ 10.

  In addition, the copolymerization ratio of each monomer unit of the heat-resistant acrylic resin (B-2-2-2) is generally determined by a method such as NMR method, infrared spectrophotometer, neutralization titration. Is possible.

  In the polymerization of the heat-resistant acrylic resin (B-2-2-2), a polymerization initiator may be used for the purpose of adjusting the degree of polymerization. In the present invention, examples of polymerization initiators that can be used include di-t-butyl peroxide, lauroyl peroxide, stearyl peroxide, benzoyl peroxide, and t-butyl peroxyneo when radical polymerization is performed. Decanate, t-butyl peroxypivalate, dilauroyl peroxide, dicumyl peroxide, t-butylperoxy-2-ethylhexanoate, 1,1-bis (t-butylperoxy) 3,3 Organic peroxides such as 5-trimethylcyclohexane and 1,1-bis (t-butylperoxy) cyclohexane, azobisisobutyronitrile, azobisisovaleronitrile, 1,1-azobis (1-cyclohexanecarbonitrile) ) 2,2′-azobis-4-methoxy-2,4-azobi Azo-based general radical polymerization initiators such as sisobutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis-2-methylbutyronitrile can be listed. . These may be used alone or in combination of two or more. A combination of these radical initiators and an appropriate reducing agent may be used as a redox initiator. These initiators can be appropriately selected in consideration of the polymerization temperature and the half life of the initiator.

  In particular, when polymerization is performed at a high temperature of 90 ° C. or higher, solution polymerization is common, so that the peroxide has a 10-hour half-life temperature of 80 ° C. or higher and is soluble in the organic solvent used. An azobis initiator is preferred. Specifically, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, cyclohexane peroxide, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, , 1-azobis (1-cyclohexanecarbonitrile), 2- (carbamoylazo) isobutyronitrile and the like.

These initiators are preferably used, for example, in the range of 0 to 1 part by mass with respect to 100 parts by mass of the total monomer mixture.
In addition, when performing the solution polymerization method, the type and amount of the polymerization initiator may be appropriately determined so that the solid content in the polymerization solution is 10 to 60% by mass in consideration of the viscosity of the polymerization solution and the like. .

  In the production of the heat-resistant acrylic resin (B-2-2-2), the molecular weight can be controlled within a range that does not impair the object of the present invention. For example, there are methods using chain transfer agents such as alkyl mercaptans, dimethylacetamide, dimethylformamide, and triethylamine; iniferters such as dithiocarbamates, triphenylmethylazobenzene, and tetraphenylethane derivatives. The molecular weight can be adjusted by adjusting the addition amount of these additives. When these additives are used, alkyl mercaptans are preferably used from the viewpoint of handleability and stability. Specific examples include n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan, and t-dodecyl mercaptan. N-tetradecyl mercaptan, n-octadecyl mercaptan, 2-ethylhexyl thioglycolate, ethylene glycol dithioglycolate, trimethylolpropane tris (thioglycolate), pentaerythritol tetrakis (thioglycolate) and the like.

These molecular weight modifiers can be appropriately added so that the molecular weight of the heat-resistant acrylic resin (B-2-2-2) becomes a desired value, but generally 100 parts by mass of the total monomer mixture. Is used in the range of 0.001 parts by mass to 3 parts by mass.
Examples of other molecular weight control methods include a method of changing the polymerization method, a method of adjusting the amount of the polymerization initiator, and a method of changing the polymerization temperature.
These molecular weight control methods may be used alone, or two or more methods may be used in combination.

  In the present invention, a plurality of types of acrylic resins (B-2) having different compositions and molecular weights can be used in combination.

  In the present invention, the above-described styrene resin (B-1) and acrylic resin (B-2) may be used alone as the material constituting the film B having a negative thickness direction retardation (Rth). When a resin composition containing both a styrene resin (B-1) and an acrylic resin (B-2) is used as a material constituting the film B, optical design of the film B, for example, control of in-plane retardation Etc. are preferable because they become easier.

  In this case, it is preferable that the styrene resin (B-1) and the acrylic resin (B-2) are compatible. For the compatibility, the composition (including the copolymer composition) of the styrene resin (B-1) and the acrylic resin (B-2), the blending ratio, the kneading temperature, the kneading pressure, the cooling temperature, the cooling rate, and the like are appropriately selected. Can be realized. The miscible is described in detail in “High Performance Polymer Alloy” (edited by the Society of Polymer Science, published by Maruzen Co., Ltd. in 1991). When the styrene resin (B-1) and the acrylic resin (B-2) are compatible, the film B made of a resin composition containing the styrene resin (B-1) and the acrylic resin (B-2) It is possible to increase the total light transmittance, and to produce a highly stable film B that does not cause phase separation during use and does not deteriorate transparency.

  Specifically, since the polymer (B-2-1) containing an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer component is highly compatible with the styrene resin (B-1), the acrylic resin As (B-2), it is particularly preferable to use a polymer (B-2-1) containing an acrylic acid alkyl ester or a methacrylic acid alkyl ester as a monomer component.

The content of the styrenic resin (B-1) in the resin composition is preferably 0.1 to 99.9% by mass, and preferably 0.2 to 90% by mass with respect to the entire resin composition. Is more preferable, and it is especially preferable that it is 20-80 mass%. The content of the acrylic resin (B-2) is preferably 0.1 to 99.9% by mass, more preferably 10 to 99.8% by mass with respect to the entire resin composition, and 20 It is especially preferable that it is -80 mass%.
Moreover, it is preferable that the sum total of content of a styrene resin (B-1) and an acrylic resin (B-2) is 70 mass% or more with respect to a resin composition, and it is 80 mass% or more. More preferably, it is particularly preferably 90% by mass or more.
Furthermore, the mass ratio ((B-1) / (B-2)) of the styrene resin (B-1) and the acrylic resin (B-2) is the styrene resin (B-1), the acrylic resin ( Although depending on the type of B-2), it is preferably 0.1 / 99.9 to 99.9 / 0.1, more preferably 20/80 to 80/20, and 40/60. Particularly preferred is ˜60 / 40.

In the present invention, the polymer constituting the film A and the film B can be mixed with another polymer other than those described above as long as the object of the present invention is not impaired. Polymers that can be mixed include polyolefins such as polyethylene and polypropylene, polyamides, polyphenylene sulfide resins, polyether ether ketone resins, polyesters, polysulfones, polyphenylene oxides, polyimides, polyether imides, polyacetals and other thermoplastic resins, and Examples thereof include thermosetting resins such as phenol resin, melamine resin, silicone resin, and epoxy resin.
When the polymer other than (B-1) and (B-2) is mixed with the film B, the ratio is 20 with respect to the total 100 parts by mass of (B-1) and (B-2). It is preferable that it is below mass parts.

Moreover, in this invention, a ultraviolet absorber can be mix | blended with the material which comprises the film A and the film B in the range which does not impair the objective of this invention.
Examples of ultraviolet absorbers that can be mixed include benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, oxybenzophenone compounds, phenol compounds, oxazole compounds, malonic ester compounds, cyanoacrylates. Compounds, lactone compounds, salicylic acid ester compounds, benzoxazinone compounds, hindered amine compounds, triazine compounds, and the like.

  Among these, benzotriazole compounds, benzotriazine compounds, benzoate compounds, benzophenone compounds, phenol compounds, oxazole compounds, malonic ester compounds, and lactone compounds are the light of the resin composition to which they are added. This is preferable because it has the effect of reducing the absolute value of the elastic modulus. Most preferred are benzotriazole compounds and benzotriazine compounds. These may be used alone or in combination of two or more.

The ultraviolet absorber is excellent in molding processability when the vapor pressure (P) at 20 ° C. is 1.0 × 10 ⁻⁴ Pa or less. A more preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁶ Pa or less, and a particularly preferable range is a vapor pressure (P) of 1.0 × 10 ⁻⁸ Pa or less. Here, being excellent in moldability means that, for example, the adhesion of the ultraviolet absorber to the roll is small during film formation. When the ultraviolet absorber adheres to the roll, for example, it adheres to the surface of the molded body and deteriorates the appearance and optical characteristics, and therefore it is not preferable as an optical material.

The ultraviolet absorber is preferably excellent in moldability when the melting point (Tm) is 80 ° C. or higher. A more preferable range is a melting point (Tm) of 130 ° C. or higher, and a particularly preferable range is a melting point (Tm) of 160 ° C. or higher.
The ultraviolet absorber is excellent in molding processability when the weight reduction rate when the temperature is increased from 23 ° C. to 260 ° C. at a rate of 20 ° C./min is 50% or less. A more preferable range is a weight reduction rate of 15% or less, and a particularly preferable range is a weight reduction rate of 2% or less.

  Film A and film B in the present invention preferably have a spectral transmittance at 380 nm of 5% or less and a spectral transmittance at 400 nm of 65% or more. The lower the spectral transmittance at 380 nm in the ultraviolet region, the lower the deterioration of the polarizer and the liquid crystal element, and the higher the 400 nm spectral transmittance in the visible region, the better the color reproducibility, so that it can be preferably used as an optical film. In order to design the spectral transmittance of the film within this range, the amount of the ultraviolet absorber is preferably 0.1% by mass or more and 10% by mass or less. When the content is more than 0.1% by mass, the spectral transmittance at 380 nm is small, and when it is less than 10% by mass, the increase in the photoelastic coefficient is small, and the molding processability and mechanical strength are also improved. A more preferable range of the amount of the ultraviolet absorber is 0.3% by mass or more and 8% by mass or less, and a further preferable range is 0.5% by mass or more and 5% by mass or less.

  The amount of the ultraviolet absorber is measured by proton NMR measured by a nuclear magnetic resonance apparatus (NMR) and obtained from a ratio of integral values of peak signals or extracted from a resin using a good solvent and then measured by a gas chromatograph (GC). It can be quantified by the method to do.

Moreover, in this invention, arbitrary additives can be mix | blended with the material which comprises the film A and the film B according to various objectives in the range which does not impair the objective of this invention. The additive that can be blended is not particularly limited as long as it is generally used for blending resins and rubber-like polymers.
Examples of such additives include inorganic fillers such as silicon dioxide; pigments such as iron oxide; lubricants such as stearic acid, behenic acid, zinc stearate, calcium stearate, magnesium stearate, and ethylene bisstearamide; Mold release agents: Softeners and plasticizers such as paraffinic process oil, naphthenic process oil, aromatic process oil, paraffin, organic polysiloxane, mineral oil; hindered phenolic antioxidants, phenolic compounds with acrylate groups Antioxidants such as antioxidants and phosphorus heat stabilizers; hindered amine light stabilizers; flame retardants; antistatic agents; reinforcing agents such as organic fibers, glass fibers, carbon fibers, metal whiskers; and colorants .

When the antioxidant is blended in the films A and B, it is preferably blended in the range of 0.01% by mass or more and 2% by mass or less with respect to the resin composition constituting the film, and 0.05% by mass or more. More preferably, it is blended in the range of 2% by mass or less, particularly preferably 0.1% by mass or more and 2.0% by mass or less.
When the blending amount of the antioxidant is less than 0.01% by mass, the thermal stability of the resulting film during high-temperature processing becomes poor, and the generation of foreign matters may not be sufficiently suppressed. On the other hand, when the blending amount exceeds 2% by mass, a large amount of volatile matter is produced, and the processability of the film may be lowered.

3. Production of Films A and B The production method of the resin composition as the material constituting the films A and B in the present invention is not particularly limited, and a known method can be used. For example, using a melt kneader such as a single screw extruder, twin screw extruder, Banbury mixer, Brabender, various kneaders, etc., adding a resin component, if necessary, adding a hydrolysis resistance inhibitor and the above other components to melt It can be produced by kneading.

Films A and B in the present invention can be formed by a known method such as injection molding, sheet molding, blow molding, injection blow molding, inflation molding, extrusion molding, foam molding, etc., such as pressure forming, vacuum forming, etc. The secondary processing molding method can also be used.
In addition, for example, an unstretched film can be extruded using an extruder or the like equipped with a T die, a circular die, or the like. When a molded product is obtained by extrusion molding, the components to be mixed and blended may be mixed and blended in advance, or may be mixed and blended at the time of extrusion molding.

  Films A and B can be formed not only by the above melting method but also by cast molding using a good solvent, for example, a solvent such as chloroform.

Further, if necessary, the unstretched film can be stretched uniaxially in the machine flow direction (MD) and uniaxially stretched in the direction (TD) perpendicular to the mechanical flow direction. For example, industrially, a uniaxial stretching method by roll stretching or tenter stretching, a sequential biaxial stretching method by a combination of roll stretching and tenter stretching, a simultaneous biaxial stretching method by tenter stretching, a biaxial stretching method by tubular stretching, etc. A stretched film can be produced. The final draw ratio can be determined from the heat shrinkage rate of the obtained film. The stretching ratio is preferably 0.1% or more and 300% or less in at least one direction, more preferably 1% or more and 200% or less, and particularly preferably 2% or more and 100% or less. By designing in this range, a stretched film preferable from the viewpoint of birefringence and strength can be obtained. The draw ratio can be determined from the following relational expression by shrinking the obtained stretched film at a temperature 20 ° C. or higher than the glass transition temperature. The glass transition temperature can be determined by a DSC method or a viscoelastic method.
Stretch ratio (%) = [(length before shrinkage / length after shrinkage) −1] × 100

  In the present invention, the thickness of the films A and B is preferably 1 μm or more, more preferably 5 μm or more.

4). Manufacture of a laminated optical film The lamination of the film A having a positive thickness direction retardation (Rth) and the film B having a negative thickness direction retardation (Rth) of the present invention may employ a method generally used industrially. it can. For example, a so-called dry lamination method in which each of films A and B is bonded using an adhesive, or a so-called T-die, in which a resin composition constituting the other film in a molten state is laminated on one film using a T-die. -The die method etc. are mentioned.

  When the film A and the film B are bonded together using an adhesive, it is preferable to use an acrylic pressure-sensitive adhesive that is optically transparent and has no anisotropy. In addition, it is preferable to use the same acrylic pressure-sensitive adhesive for bonding to a polarizing film and bonding to an LCD. The thickness of the pressure-sensitive adhesive is usually 15 μm to 30 μm.

  Moreover, when laminating film A and film B, if it is desired to add in-plane retardation of film A and in-plane retardation of film B, it is preferable to laminate so that both slow axes are parallel to each other. If it is desired to cancel the in-plane retardation of the film A and the in-plane retardation of the film B, it is preferable to laminate them so that their slow axes are perpendicular.

  That is, when film A and film B are laminated so that the slow axis is perpendicular, Re of the laminated film is the difference between Re of film A and film B, and the absolute value of Re of the laminated film becomes small. On the other hand, when film A and film B are laminated so that their slow axes are parallel, Re of the laminated film approaches the sum of Re of film A and film B. Thus, the Re value of the laminated film can be controlled by the Re value of the films A and B and the way of lamination.

In the present invention, film A and film B are laminated so that their slow axes are parallel to each other. The crossing angle of the slow axes in the film plane of film A and film B is 0 ° ± 10 °. It is more preferable that the angle is 0 ° ± 5 °. This is because if the crossing angle of the slow axes exceeds 0 ° ± 10 °, light leakage and a decrease in contrast tend to occur.
Further, “lamination so that the slow axes of both are perpendicular to each other” means that the laminating angles of the slow axes in the film plane of film A and film B are 90 ° ± 10 °.

  The laminated optical film of the present invention can be subjected to surface functionalization treatment such as antireflection treatment, transparent conductive treatment, electromagnetic wave shielding treatment, and gas barrier treatment.

5. Thickness direction retardation (Rth) of the film In the present invention, retardation in the plane direction (Re), retardation in the thickness direction (Rth), and Nz coefficient are defined as follows.
Re = (nx−ny) × d,
Rth = [(nx + ny) / 2−nz] × d
Here, nx is the refractive index in the slow axis direction in the film plane, ny is the refractive index in the direction perpendicular thereto, and nz is the refractive index in the thickness direction of the film. D is the thickness (nm) of the film.

  The preferable Rth value of the film A in the present invention is 500 nm to 1 nm, more preferably 450 nm to 5 nm, and particularly preferably 350 nm to 10 nm. The value of Rth can be adjusted by the draw ratio in the MD and TD directions and the thickness of the film.

  The preferable Rth value of the film B in the present invention is −500 nm to −1 nm, more preferably −450 nm to −5 nm, and particularly preferably −350 nm to −10 nm. The value of Rth can be adjusted by the draw ratio in the MD and TD directions, the film thickness, the mass ratio of the resin (B-1) and the resin (B-2).

The preferred Rth value of the laminated optical film obtained by laminating the film A and the film B in the present invention is −500 nm or more and 20 nm or less, more preferably −100 nm to 20 nm, and particularly preferably −20 nm to 20 nm. is there.
According to the study by the present inventors, it is found that Rth of the laminated film of film A and film B is the sum of Rth of film A and film B regardless of the value of the crossing angle of the slow axes of both. It was. Therefore, the value of Rth of the laminated optical film can be controlled by adjusting the Rth of film A and film B.
Specifically, if the positive and negative values of Rth of film A and film B are reversed, the Rth of both cancel each other, resulting in a smaller absolute value of Rth of the laminated film.

In the present invention, intrinsic birefringence is a value representing the magnitude of birefringence depending on orientation, and is defined by the following equation.
Intrinsic birefringence = npr−nvt
Here, npr is a refractive index in a direction parallel to the alignment direction of the polymer aligned with uniaxial order, and nvt is a refractive index in a direction perpendicular to the alignment direction.

  That is, in the present invention, a resin having a negative intrinsic birefringence means that when light is incident on a layer formed by orienting polymers constituting the resin in a uniaxial order, the light is refracted in the orientation direction. A resin whose rate is smaller than the refractive index of light in a direction perpendicular to the orientation direction.

Next, the present invention will be described specifically by way of examples.
The evaluation methods used in the present invention and examples will be described.
(1) Evaluation method

(I) Measurement of molecular weight i) Styrene resin (B-1)
GPC (measuring device: GPC-8020 manufactured by Tosoh Corp., detector: differential refraction detector (RI), column: Shodex K-805, 801 linked by Showa Denko) was used, the solvent was chloroform, and the measurement temperature was 40 ° C. The mass average molecular weight is determined in terms of commercially available standard polystyrene.
ii) Acrylic resin (B-2)
Tosoh Corporation Gel Permeation Chromatography (HLC-8120 + 8020) column, Tosoh Corporation TSK Super HH-M (2) and Super H2500 (1) are arranged in series, and a differential refraction detector is used as a detector. Use. 0.02 g of acrylic resin as a measurement sample was dissolved in 20 cc of a THF solvent, and the elution time and strength were measured at an injection amount of 10 ml and a development flow rate of 0.3 ml / min. Using a calibration curve with a monodisperse methacrylic resin of known weight average molecular weight manufactured by GL Sciences as a standard sample, obtain the weight average molecular weight (Mw) and number average molecular weight (Mn) of the acrylic resin of the measurement sample. The molecular weight distribution is calculated as Mw / Mn.
(II) Measurement of copolymerization ratio i) Measurement of copolymerization ratio of acrylonitrile in styrene-acrylonitrile copolymer A sample styrene-acrylonitrile copolymer was formed into a film using a hot press machine and manufactured by JASCO Corporation. Using FT-410, the absorbance derived from acrylonitrile groups at 1603 cm ⁻¹ and 2245 cm ⁻¹ of the film is measured. By using the relationship between the acrylonitrile content in the styrene-acrylonitrile copolymer previously determined using a styrene-acrylonitrile copolymer having a known acrylonitrile content and the absorbance ratio of 1603 cm ⁻¹ , 2245 cm ⁻¹ , the styrene-acrylonitrile copolymer The acrylonitrile content in the coalesced is quantified.
ii) Measurement of copolymerization ratio of maleic anhydride in styrene-maleic anhydride copolymer A styrene-maleic anhydride copolymer as a sample was dissolved in deuterated chloroform, and 1H-NMR (JNM ECA-500 manufactured by JEOL Ltd.) was dissolved. NMR measurement was performed at a frequency of 500 MHz and at room temperature. From the measurement results, the area ratio between the proton peak of the benzene ring in the styrene unit (near 7 ppm) and the proton peak of the alkyl group in the maleic anhydride unit (near 1 to 3 ppm), the styrene unit and maleic anhydride unit in the sample The molar ratio of is determined. From the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: maleic anhydride unit = 104: 98), the copolymerization ratio of maleic anhydride in the styrene-maleic anhydride copolymer is determined.
iii) Measurement of copolymerization ratio of methacrylic acid in styrene-methacrylic acid copolymer Dissolve styrene-methacrylic acid copolymer as a sample in deuterated chloroform, and use 1H-NMR (JNM ECA-500) manufactured by JEOL. NMR measurement is performed at a frequency of 500 MHz and at room temperature. From the measurement results, the molar ratio of the styrene unit and the methacrylic acid unit in the sample was determined from the area ratio of the proton peak of the benzene ring in the styrene unit (around 7 ppm) and the proton peak of the alkyl group in the methacrylic acid unit (around 1 to 3 ppm). Find the ratio. The copolymerization ratio of methacrylic acid in the styrene-methacrylic acid copolymer is determined from the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: methacrylic acid unit = 104: 86).

iv) Measurement of respective copolymerization ratios in methyl methacrylate-maleic anhydride-styrene copolymer Methyl methacrylate-maleic anhydride-styrene copolymer as a sample was dissolved in deuterated chloroform, and 1H- manufactured by JEOL Ltd. NMR measurement is performed using NMR (JNM ECA-500) at a frequency of 500 MHz and at room temperature. From the measurement results, the proton peak of the benzene ring in the styrene unit (around 7 ppm), the proton peak of the alkyl group in the maleic anhydride unit (around 1-3 ppm), and the proton peak of the methyl group in the methyl methacrylate unit (0. The molar ratio of styrene units, maleic anhydride units and methyl methacrylate units in the sample is determined from the area ratio of about 5 to 1 ppm. From the obtained molar ratio and the mass ratio of each monomer unit (styrene unit: maleic anhydride unit: methyl methacrylate = 104: 86: 100), each of the methyl methacrylate-maleic anhydride-styrene copolymers Obtain the copolymerization ratio.

v) Methyl methacrylate—an acid anhydride unit having a 6-membered ring structure—measurement of respective copolymerization ratios in the styrene copolymer Methyl methacrylate—an acid anhydride unit having a 6-membered ring structure—styrene copolymer 50 mg of the polymer was dissolved in 0.75 mL of deuterated dimethyl sulfoxide (d-DMSO), and NMR measurement was performed at a frequency of 500 MHz and 40 ° C. using 1H-NMR (JNM ECA-500) manufactured by JEOL.
From the measurement results, the integral value of the proton peak (near 7 ppm) of the benzene ring in the styrene unit and the integral value of the proton peak (near 12-13 ppm) of the carboxylic acid in the methacrylic acid unit were determined, and from these values, the styrene unit The molar ratio of methacrylic acid units to is determined.
Next, by subtracting the integrated value of the peak due to water in DMSO observed near 3.3 ppm from the total integrated value of the plurality of peaks near 2.7 to 4 ppm, the COOMe site of the methyl methacrylate unit is reduced. The integral value of the proton peak of the methyl group is obtained, and the molar ratio of the methyl methacrylate unit to the styrene unit is obtained from this value and the integral value of the proton peak (around 7 ppm) in the styrene unit.
The molar ratio of the acid anhydride unit having a 6-membered ring structure to the styrene unit is determined as follows. That is, a plurality of peaks in the vicinity of 0 to 2.2 ppm are represented by a methylene group contained in the main chain skeleton in the styrene unit, a methylene group contained in the main chain skeleton in the methacrylic acid unit, and a main clavicle in the methacrylic acid unit. It has a methyl group that is directly bonded, a methylene group contained in the main chain skeleton in the methyl methacrylate unit, a methyl group that is directly bonded to the main chain skeleton in the methyl methacrylate unit, and a six-membered ring structure Methylene group contained in main chain skeleton in acid anhydride unit, methylene group contained in 6-membered ring in acid anhydride unit having 6-membered ring structure, and acid anhydride having 6-membered ring structure It is recognized that it is derived from a methyl group directly bonded to the 6-membered ring in the unit. Therefore, the ratio of the sum of the integral values of a plurality of peaks near 0 to 2.2 ppm and the integral value of the proton peak (near 7 ppm) of the benzene ring in the styrene unit, the mole of the methacrylic acid unit relative to the styrene unit previously determined. The molar ratio of the acid anhydride unit having a 6-membered ring structure to the styrene unit is calculated using the ratio and the previously obtained molar ratio of the methyl methacrylate unit to the styrene unit.
From the molar ratio of each unit to the styrene unit thus determined, methyl methacrylate unit in the sample, acid anhydride unit having a 6-membered ring structure represented by the general formula [2], styrene unit, methacrylic acid unit The molar ratio of each of the monomer units (methyl methacrylate unit: acid anhydride unit having a 6-membered ring structure: styrene unit: methacrylic acid unit = 100: 154 (for example, heat-resistant acrylic resin) In the case of (B-2-2-2) 1): 104: 86), the respective copolymerization ratios in the acid anhydride unit-styrene copolymer having a methyl methacrylate-6-membered ring structure are determined.

(III) Measurement of optical properties i) Judgment of positive or negative intrinsic birefringence value Stretching while applying an extensional stress within the range of the glass transition temperature to the glass transition temperature + 50 ° C or lower, rapidly solidifying, and npr-nvt at 23 ° C. Measure. When npr-nvt is negative, it is determined that the intrinsic birefringence is negative, and when npr-nvt is positive, the intrinsic birefringence is positive.
ii) Measurement of in-plane retardation (Re) The thickness d (nm) of the film is measured using a thickness gauge. This value is input to a birefringence measuring apparatus RETS-100 manufactured by Otsuka Electronics Co., Ltd., a sample is placed so that the measurement surface is perpendicular to the measurement light, and in-plane retardation (Re ) Is measured and calculated.
iii) Measurement of thickness direction retardation (Rth) and Nz coefficient The average refractive index n of the optical film is measured at 23 ° C. using a laser refractometer Model 2010 manufactured by Metricon. And average refractive index n and film thickness d (nm) are inputted into Otsuka Electronics Co., Ltd. birefringence measuring apparatus RETS-100, and thickness direction retardation (Rth) and Nz coefficient are measured and calculated at 23 ° C. .
(IV) Glass transition temperature (Tg) measurement A differential scanning calorimeter DSC-7 type (manufactured by Perkin Elmer) was used and measured at a heating rate of 20 ° C./min in a nitrogen atmosphere.

(2) Preparation of raw materials (I) Preparation of film A having positive thickness direction retardation (Rth) i) Commercially available triacetyl cellulose (TAC) film A1
A triacetyl cellulose film (Fuji Photo Film Co., Ltd.) (100 μm) was used. The intrinsic birefringence value was positive.
ii) Norbornene resin film A2
A cycloolefin-based resin film was obtained as follows. Addition polymerization of ethylene and norbornene was performed as a cyclic polyolefin. This produced an ethylene-norbornene random copolymer (copolymerization ratio of ethylene: 65 mol%, MFR: 31 g / 10 min, number average molecular weight: 68000). 100 parts by mass of the resin obtained here was dissolved in a mixed solvent of 80 parts by mass of cyclohexane, 80 parts by mass of toluene, and 80 parts by mass of xylene, and a film having a thickness of 100 μm was produced by a casting method. The intrinsic birefringence value was positive.
iii) Norbornene resin film A3
Using the norbornene-based resin obtained in the same manner as in ii), a uniaxially stretched film was produced under the conditions shown in Table 1 in the same manner as in the production of film B in (II) described later. The intrinsic birefringence value was positive.
vi) Polycarbonate resin film A4
A polybisphenol A carbonate film was used. The intrinsic birefringence value was positive.
v) Polycarbonate resin film A5
A polybisphenol A carbonate film was prepared. The intrinsic birefringence value was positive.

(II) Preparation of film B having negative thickness direction retardation (Rth) (preparation of material constituting film B)
i) Styrene-acrylonitrile copolymer (B-1-1)
A monomer mixture composed of 72% by mass of styrene, 13% by mass of acrylonitrile, and 15% by mass of ethylbenzene was continuously fed into a complete mixing reactor equipped with a stirrer, and a polymerization reaction was performed at 150 ° C. and a residence time of 2 hours.
The obtained polymerization solution was continuously supplied to an extruder, and unreacted monomer and solvent were recovered by the extruder to obtain styrene-acrylonitrile copolymer (B-1-1) pellets.
The obtained styrene-acrylonitrile copolymer (B-1-1) was colorless and transparent, and as a result of compositional analysis, the copolymerization ratio of styrene was 80% by mass, the copolymerization ratio of acrylonitrile was 20% by mass, and conformed to ASTM-D1238. The melt flow rate value at 220 ° C. and 10 kg load was 13 g / 10 min. Further, the photoelastic coefficient (unstretched) at 23 ° C. was 5.0 × 10 ⁻¹² Pa ⁻¹ and the intrinsic birefringence was negative.

ii) Styrene-methacrylic acid copolymer (B-1-2)
Continuous solution polymerization was carried out using all the equipment made of stainless steel. 75.2% by mass of styrene, 4.8% by mass of methacrylic acid, and 20% by mass of ethylbenzene were used as a preparation liquid, and 1,1-tert-butylperoxy-3,3,5-trimethylcyclohexane was used as a polymerization initiator. This prepared solution was added at 1 L / hr. The mixture was continuously fed at a rate of 1 liter to a completely mixed polymerization reactor equipped with a stirrer with an internal volume of 2 L, and polymerization was carried out at 136 ° C.
A polymerization liquid containing 49% of solid content is continuously taken out, first preheated to 230 ° C., kept at 230 ° C., and supplied to a devolatilizer depressurized to 20 torr. It discharged continuously from the gear pump at the lower part of the volatilizer.
The obtained styrene-methacrylic acid copolymer (B-1-2) was colorless and transparent, and as a result of compositional analysis, the copolymerization ratio of styrene was 92% by mass and the copolymerization ratio of methacrylic acid was 8% by mass. The melt flow rate value measured at 230 ° C. under a load of 3.8 kg measured in accordance with ASTM-D1238 was 5.2 g / 10 minutes. The photoelastic coefficient (unstretched) at 23 ° C. was 4.8 × 10 ⁻¹² Pa ⁻¹ and the intrinsic birefringence was negative.

iii) Styrene-maleic anhydride copolymer (B-1-3)
Continuous solution polymerization was carried out using all the equipment made of stainless steel. A total of 100 parts by mass was prepared at a ratio of 91.7 parts by mass of styrene and 8.3 parts by mass of maleic anhydride. (However, the two are not mixed.) 5 parts by mass of methyl alcohol and 0.03 parts by mass of 1,1-tert-butylperoxy-3,3,5-trimethylcyclohexane as a polymerization initiator are mixed with styrene. It was set as the preparation liquid. 0.95 kg / hr. Was continuously fed to a jacketed complete mixing polymerization machine having an internal volume of 4 L.
On the other hand, maleic anhydride heated to 70 ° C. was used as the second preparation liquid at 0.10 kg / hr. Was fed to the same polymerization machine at a speed of When the polymerization conversion rate became 54%, the polymerization solution was continuously removed from the polymerization machine, first preheated to 230 ° C., kept at 230 ° C., and supplied to a devolatilizer reduced to 20 torr, with an average retention of 0 After 3 hours, it was continuously discharged from the lower gear pump of the devolatilizer to obtain a styrene-maleic anhydride copolymer (B-1-3).
The obtained styrene-maleic anhydride copolymer (B-1-3) was colorless and transparent. As a result of compositional analysis, the copolymerization ratio of styrene was 85% by mass and the maleic anhydride unit was 15% by mass. The melt flow rate value measured at 230 ° C. under a load of 2.16 kg measured according to ASTM-D1238 was 2.0 g / 10 min. The photoelastic coefficient (unstretched) at 23 ° C. was 4.1 × 10 ⁻¹² Pa ⁻¹ and the intrinsic birefringence was negative.

iv) Polymer (B-2-1) containing alkyl acrylate or alkyl methacrylate as monomer component
1,1-di-t-butylperoxy-3,3,3-trimethyl was added to a monomer mixture consisting of 89.2 parts by weight of methyl methacrylate, 5.8 parts by weight of methyl acrylate, and 5 parts by weight of xylene. 0.0294 parts by weight of cyclohexane and 0.115 parts by weight of n-octyl mercaptan were added and mixed uniformly. This solution is continuously supplied to a closed pressure-resistant reactor having an internal volume of 10 liters, polymerized with stirring at an average temperature of 130 ° C. and an average residence time of 2 hours, and then continuously sent to a reservoir connected to the reactor. The volatile matter was removed under certain conditions, and the mixture was continuously transferred to an extruder in a molten state to obtain acrylic resin (B-2) (methyl methacrylate / methyl acrylate copolymer) pellets. The copolymer obtained had a copolymerization ratio of methyl acrylate of 6.0%, a weight average molecular weight of 145,000, and a melt flow value measured at 230 ° C. and a load of 3.8 kg measured in accordance with ASTM-D1238 was 1. It was 0 g / min. The intrinsic birefringence value was negative.

v) Heat-resistant acrylic resin (B-2-2-1)
A methyl methacrylate-maleic anhydride-styrene copolymer was obtained using styrene, methyl methacrylate, and maleic anhydride by the method described in Japanese Patent Publication No. 63-1964.
The composition of the obtained methyl methacrylate-maleic anhydride-styrene copolymer was 74% by mass of methyl methacrylate, 10% by mass of maleic anhydride, and 16% by mass of styrene, and the copolymer melt flow rate value (ASTM- D1238; 230 ° C., 3.8 kg load) was 1.6 g / 10 min. The intrinsic birefringence value was negative.

vi) Heat-resistant acrylic resin (B-2-2-2)
1) Heat-resistant acrylic resin (B-2-2-2) 1 (for film B8)
53 parts by weight of methyl methacrylate, 5 parts by weight of styrene, 12 parts by weight of methacrylic acid, 30 parts by weight of cyclohexanol (water content: 2%, solubility parameter δ = 11.4), 1,1-di (tert-butyl par Oxy) A liquid mixture consisting of 50 ppm of cyclohexane and 1400 ppm of n-octyl mercaptan was prepared, and nitrogen gas was bubbled for 10 minutes. This mixture was continuously fed to a jacketed complete mixing reactor having an internal volume of 3 L at a rate of 1.5 L / hr for polymerization. When the reaction was conducted at a polymerization temperature of 135 ° C. for 2 hours, the polymer was completely dissolved, and the solid content of the polymer contained in the polymerization solution was 40% by mass. This polymerization solution was immediately and continuously passed through a heater and supplied to the devolatilization tank. In this devolatilization tank, the polymerization solution was allowed to stay at 255 ° C. and 25 Torr for 40 minutes, thereby generating an acid anhydride unit having a 6-membered ring structure along with removal of unreacted monomers and solvent. Unreacted monomers and solvent were recovered through a recovery line.
The composition of the obtained polymer was 70% by mass of methyl methacrylate units, 10% by mass of styrene units, 3% by mass of methacrylic acid units, and 17% by mass of acid anhydride units having a 6-membered ring structure. ASTM-D1238; 230 ° C., 3.8 kg load) was 0.9 g / 10 min, Mw / Mn = 1.9, and Tg was 130 ° C. The photoelastic coefficient at 23 ° C. was −2.8 × 10 ⁻¹² / Pa, and the intrinsic birefringence was negative. 2) Heat-resistant acrylic resin (B-2-2-2) 2 (for film B9)
51.8 parts by weight of methyl methacrylate, 3.5 parts by weight of styrene, 14.7 parts by weight of methacrylic acid, 30 parts by weight of cyclohexanol, 50 ppm of 1,1-di (tert-butylperoxy) cyclohexane, 1500 ppm of n-octyl mercaptan A mixed solution was prepared and nitrogen gas was bubbled for 10 minutes. This mixture was continuously fed to a jacketed complete mixing reactor having an internal volume of 3 L at a rate of 1.5 L / hr for polymerization. When the reaction was conducted at a polymerization temperature of 135 ° C. for 2 hours, the polymer was completely dissolved, and the solid content of the polymer contained in the polymerization solution was 40% by mass. This polymerization solution was immediately and continuously passed through a heater and supplied to the devolatilization tank. In this devolatilization tank, the polymerization solution was allowed to stay at 255 ° C. and 25 Torr for 30 minutes, thereby generating unreacted monomers and an acid anhydride unit having a 6-membered ring structure along with removal of the solvent. . Unreacted monomers and solvent were recovered through a recovery line.
The composition of the obtained polymer was 68.9% by mass of methyl methacrylate units, 6.8% by mass of styrene units, 3.2% by mass of methacrylic acid units, and 21.1% by mass of acid anhydride units having a 6-membered ring structure. The melt flow rate (ASTM-D1238; 230 ° C., 3.8 kg load) was 0.9 g / 10 min, Mw / Mn = 1.9, and Tg was 132 ° C. The photoelastic coefficient at 23 ° C. was −2.6 × 10 ⁻¹² / Pa, and the intrinsic birefringence was negative.
3) Heat-resistant acrylic resin (B-2-2-2) 3 (for film B10 and film B11)
A mixed liquid consisting of 35 parts by weight of methyl methacrylate, 21 parts by weight of styrene, 14 parts by weight of methacrylic acid, 30 parts by weight of cyclohexanol, 50 ppm of 1,1-di (tert-butylperoxy) cyclohexane, and 1200 ppm of n-octyl mercaptan is prepared. Then, nitrogen gas was bubbled for 10 minutes. This mixture was continuously fed to a jacketed complete mixing reactor having an internal volume of 3 L at a rate of 1.5 L / hr for polymerization. When the reaction was conducted at a polymerization temperature of 135 ° C. for 2 hours, the polymer was completely dissolved, and the amount of polymer solids contained in the polymerization solution was 42% by mass. This polymerization solution is immediately passed through a heater, set to a barrel temperature of 255 ° C., and continuously supplied to a twin-screw extruder with a vent reduced to 25 Torr, along with removal of unreacted monomers and solvent and a six-membered ring. Generation of an acid anhydride unit having a structure was carried out. Unreacted monomers and solvent were recovered through a recovery line. The obtained polymer was further passed through a vented twin screw extruder (L / D = 67) reduced to 50 Torr to remove unreacted monomers and solvent and an acid anhydride having a 6-membered ring structure. Completed unit generation.
The composition of the obtained polymer was 43% by mass of methyl methacrylate units, 33% by mass of styrene units, 7% by mass of methacrylic acid units, and 17% by mass of acid anhydride units having a 6-membered ring structure. ASTM-D1238; 230 ° C., 3.8 kg load) was 0.6 g / 10 min, Mw / Mn = 1.9, and Tg was 136 ° C. Further, its photoelastic coefficient at 23 ° C. was −0.1 × 10 ⁻¹² / Pa, and the intrinsic birefringence was negative.

(Manufacture of film B)
Using the resin or resin composition shown in Table 1, using a Technobel T-die mounting extruder (KZW15TW-25MG-NH type / width 150 mm T-die mounting / lip thickness 0.5 mm), screw rotation speed, An unstretched film was obtained by adjusting the resin temperature in the cylinder and the temperature of the T die to the conditions shown in Table 1 and performing extrusion molding. The flow (extrusion direction) of the film was defined as the MD direction, and the direction perpendicular to the MD direction was defined as the TD direction.
A part of the unstretched film was cut out to have a width of 50 mm, and uniaxial stretching (between chucks: 50 mm, chuck moving speed: 500 mm / min) was performed using a tensile tester under the conditions shown in Table 1. A uniaxially stretched film was obtained.
Further, some uniaxially stretched films were cut out so that the width was 50 mm, and uniaxially stretched (between chucks: 50 mm, chuck moving speed: 500 mm / min) under the conditions shown in Table 1 using a tensile tester. And unstretched, uniaxially stretched or biaxially stretched films B1 to B8 were obtained.
Table 1 shows the compositions, extrusion molding conditions, film thickness, in-plane retardation (Re), and thickness direction retardation (Rth) of films A1 to B5 and B1 to B10.

[Examples 1-13, Comparative Examples 1-2]
Films A and B were used in the combinations shown in Table 2, and these were laminated by pasting them together with an acrylic adhesive having a thickness of about 20 μm so that the slow axes were parallel. Thirteen laminated optical films were produced. Similarly, laminated optical films of Comparative Examples 1 and 2 were produced.
According to Table 2, the thickness direction retardation (Rth) of the laminated film is approximately the sum of the Rth of the first layer and the second layer, and as a result, the thickness A retardation (Rth) corresponding to the present invention is positive. And the film of Examples 1-13 which laminated | stacked the film B with a negative thickness direction retardation (Rth) are the 1st layer which comprises these, the single layer film of a 2nd layer, and the laminated film of Comparative Examples 1 and 2 It was confirmed that the absolute value of the thickness direction retardation (Rth) was smaller than that of.

[Examples 14 to 17]
Films A and B were used in the combinations shown in Table 3, and these were laminated by pasting them together with an acrylic adhesive having a thickness of about 20 μm so that the slow axis would be vertical. Seventeen laminated optical films were produced.
According to Table 3, the films of Examples 12 to 15 in which the film A having a positive thickness direction retardation (Rth) and the film B having a negative thickness direction retardation (Rth) are laminated are the first layer, the first It was confirmed that the absolute value of the thickness direction retardation (Rth) was smaller than that of the two-layer monolayer film.

The laminated optical film of the present invention includes a display front plate, a display substrate, a touch panel, a transparent substrate used for solar cells, etc., and other fields such as an optical communication system, an optical switching system, an optical measurement system, a waveguide, a lens, It can be used to manufacture various optical elements such as optical fibers, optical fiber coating materials, LED lenses, and lens covers.
In particular, the laminated optical film of the present invention is a polarizing plate protective film used for liquid crystal displays, plasma displays, organic EL displays, field emission displays, rear projection televisions, quarter wavelength plates, half wavelength plates. In order to produce a liquid crystal optical compensation film such as a phase difference plate, a viewing angle control film, and the like.
In particular, the laminated optical film of the present invention is preferably used for producing a polarizing plate protective film or retardation film for an IPS mode liquid crystal display device in which the absolute value of the thickness direction retardation (Rth) is desired to be small. Can do.

Claims (15)

  A laminated optical film in which a film A having a positive thickness direction retardation (Rth) and a film B having a negative thickness direction retardation (Rth) are laminated.   The laminated optical film according to claim 1, wherein the thickness direction retardation (Rth) is from -500 nm to 20 nm.   The laminated optical film according to claim 1, wherein the thickness direction retardation (Rth) is -20 nm or more and 20 nm or less.   The laminated optical film according to any one of claims 1 to 3, wherein the film A and the film B are laminated so that slow axes are parallel to each other.   The laminated optical film according to any one of claims 1 to 4, wherein the film B comprises a resin composition containing a styrene resin (B-1) and an acrylic resin (B-2).   The laminated optical film according to claim 5, wherein the styrene resin (B-1) is a styrene-acrylonitrile copolymer.   The laminated optical film according to claim 6, wherein a copolymerization ratio of acrylonitrile in the styrene-acrylonitrile copolymer is 1 to 40% by mass.   The laminated optical film according to claim 5, wherein the styrene resin (B-1) is a styrene-methacrylic acid copolymer.   The laminated optical film according to claim 8, wherein a copolymerization ratio of methacrylic acid in the styrene-methacrylic acid copolymer is 0.1 to 50% by mass.   The laminated optical film according to claim 5, wherein the styrene resin (B-1) is a styrene-maleic anhydride copolymer.   The laminated optical film according to claim 10, wherein a copolymerization ratio of maleic anhydride in the styrene-maleic anhydride copolymer is 0.1 to 50% by mass. The film B is represented by the following general formula [1]: 40 to 90% by mass of methacrylic acid ester and / or acrylate unit, 5 to 40% by mass of aromatic vinyl compound unit. The ratio of the copolymerization ratio of the aromatic vinyl monomer unit to the copolymerization ratio of the compound unit represented by the following general formula [1] (vinyl aromatic monomer) 5. The heat-resistant acrylic resin containing 1 to 3 times the copolymerization ratio of the body unit / copolymerization ratio of the compound unit represented by the general formula [1]. Laminated optical film.
General formula [1]

(In the general formula [1], X represents O or N—R, where O is an oxygen atom, N is a nitrogen atom, R is a hydrogen atom, an alkyl group, an aryl group, or a cycloalkane group. .) The film B has a methacrylic acid ester and / or an acrylate monomer unit of 30% by mass to 80% by mass, and an acid anhydride unit having a 6-membered ring structure represented by the following general formula [2]: 10% by mass The laminate according to any one of claims 1 to 4, comprising a heat-resistant acrylic resin which is a copolymer containing from 1% to 35% by weight and from 1% to 50% by weight of an aromatic vinyl compound unit. Optical film.
General formula [2]

(However, in the general formula [2], R ₁ and R ₂ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and the alkyl group is substituted with, for example, a hydroxyl group. May be.)   A polarizing plate protective film comprising the laminated optical film according to claim 1.   A retardation film comprising the laminated optical film according to claim 1.