JP6392090B2 - Thermoplastic resin film and method for producing the same, optical film, polarizer protective film, and retardation film - Google Patents

Description

The present invention relates to a thermoplastic resin film containing a methacrylic resin and a method for producing the same.
The present invention also relates to an optical film, a polarizer protective film, and a retardation film using the thermoplastic resin film.

Various optical films such as a polarizer protective film are used in the liquid crystal display device.
Conventionally, triacetyl cellulose is mainly used for the polarizer protective film. However, a film made of triacetyl cellulose has a high moisture permeability, and the quality of the polarizer tends to decrease as the film becomes thinner.
Therefore, a methacrylic resin has been studied as a material for a new polarizer protective film.
Conventionally, a resin film made only of a general methacrylic resin has insufficient mechanical properties such as toughness, and film-forming properties are not good.
It is known that when a film made of a methacrylic resin is stretched, toughness is increased (see Patent Document 1). However, since a conventional glass transition temperature (Tg) of a methacrylic resin is low and heat resistance is low, a stretched film made of a methacrylic resin is likely to be thermally contracted.

  In general, methacrylic resins are known to have higher glass transition temperature (Tg) and higher heat resistance as syndiotacticity increases. An anionic polymerization method is mentioned as a manufacturing method of a methacrylic resin with a high gindiotacticity (refer patent document 2, 3). However, a methacrylic resin having a high gindiotacticity has poor film-forming properties, and a film made of this methacrylic resin tends to be inferior in surface smoothness. Although the film forming property can be improved by lowering the molecular weight, the mechanical strength of the resulting film tends to decrease. For this reason, a film made of a methacrylic resin having high syndiotacticity has not yet been put into practical use.

In general, an optical film preferably has high transparency and low haze.
In an optical film such as a polarizer protective film, it is preferable that the retardation of the film can be adjusted to zero or a value close thereto.

Patent Documents 4 to 8 disclose a resin composition or a resin film obtained by blending a vinyl acetal resin such as a vinyl butyral resin with a conventional general methacrylic resin.
A vinyl acetal resin has good affinity with a methacrylic resin and a small difference in glass transition temperature (Tg). Various mechanical properties and film-forming properties can be improved by adding a vinyl acetal resin.
The vinyl acetal resin itself has a positive intrinsic birefringence, and by blending with a methacrylic resin having a negative intrinsic birefringence, the retardation of the film can be easily adjusted to a desired range.
For example, in applications such as a polarizer protective film, the phase difference of the film can be adjusted to zero or a value close thereto. In applications such as a retardation film, it can be adjusted to a desired value.
In Patent Document 7, the haze and in-plane direction retardation of the dumbbell specimen are suitable by adjusting the content of alkali metal and / or alkaline earth metal in the vinyl butyral resin and the moisture content to a specific range. It is described that it becomes inside.
However, in patent documents 4-8, since the conventional general methacryl resin is used, the heat resistant improvement effect is not acquired.

In the previous patent applications 9 and 10 (unpublished at the time of filing this application), the applicant of the present application is the first methacrylic resin and the triad with relatively high syndiotacticity (rr) of triplet display. A resin composition or a resin film including a second methacrylic resin having a relatively low syndiotacticity (rr) of a child display is proposed.
Heat resistance can be improved by using the first methacrylic resin. By using the second methacrylic resin, various mechanical properties and film forming properties can be improved.

Japanese Patent Publication No.57-32942 Japanese Patent Laid-Open No. 10-273505 Japanese Patent Laid-Open No. 2002-327012 JP 2008-133452 A (Patent No. 5535433) International Publication No. 2008/050738 International Publication No. 2009/130883 JP 2013-28670 A International Publication No. 2014/115883 International application number PCT / JP2014 / 063039 (unpublished at the time of filing this application) International application number PCT / JP2014 / 063040 (unpublished at the time of filing this application)

  The present invention has been made in view of the above problems, has good mechanical properties such as toughness, high transparency, low haze, high surface smoothness, high heat resistance, low heat shrinkage, The object is to provide a thermoplastic resin film capable of adjusting the phase difference.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have invented the following thermoplastic resin film and its production method, optical film, polarizer protective film, and retardation film.

(1) A methacrylic resin (A) having a syndiotacticity (rr) of triplet display of 58% or more and a vinyl acetal resin (B),
The total amount of methacrylic resin (A) and vinyl acetal resin (B) is 100 parts by mass, the content of methacrylic resin (A) is 95 parts by mass or less and more than 75 parts by mass, and the vinyl acetal resin (B) The content is 5 parts by mass or more and less than 25 parts by mass,
Thermoplastic resin film.

(2) Methacrylic resin (A)
The weight average molecular weight is 50,000 to 150,000,
The content of the component having a molecular weight of 200,000 or more is 0.1 to 10%,
The content of components having a molecular weight of less than 15000 is 0.2 to 5%.
The thermoplastic resin film according to (1).

(3) Methacrylic resin (A)
A first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more, and a second triplet display syndiotacticity (rr) of 45 to 58%. A methacrylic resin (X2),
For the total amount of 100 parts by mass of the first methacrylic resin (X1) and the second methacrylic resin (X2),
The content of the first methacrylic resin (X1) is 40 to 70 parts by mass,
The content of the second methacrylic resin (X2) is a methacrylic resin having a content of 60 to 30 parts by mass.
The thermoplastic resin film as described in (1) or (2).

(4) The methacrylic resin (A) has a content of structural units derived from methyl methacrylate of 99% by mass or more.
The thermoplastic resin film according to any one of (1) to (3).

(5) The methacrylic resin (A) has a melt flow rate of 0.1 to 10 g / 10 min measured at a temperature of 230 ° C. and a load of 3.8 kg.
The thermoplastic resin film according to any one of (1) to (4).

(6) An optical film comprising the thermoplastic resin film according to any one of (1) to (5).
(7) A polarizer protective film comprising the thermoplastic resin film according to any one of (1) to (5).
(8) A retardation film comprising the thermoplastic resin film according to any one of (1) to (5).

(9) A method for producing a thermoplastic resin film according to any one of (1) to (5),
A methacrylic resin (A) having a tridentate syndiotacticity (rr) of 58% or more, and a vinyl acetal resin (B),
The total amount of methacrylic resin (A) and vinyl acetal resin (B) is 100 parts by mass, the content of methacrylic resin (A) is 95 parts by mass or less and more than 75 parts by mass, and the vinyl acetal resin (B) Preparing a thermoplastic resin composition having a content of 5 parts by mass or more and less than 25 parts by mass;
Forming a film of the thermoplastic resin composition,
A method for producing a thermoplastic resin film.

(10) The methacrylic resin (A) includes one or more methacrylic resins,
Producing at least one methacrylic resin contained in the methacrylic resin (A) by an anionic polymerization method;
The method for producing a thermoplastic resin film according to (9).

(11) Methacrylic resin (A)
A first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more, and a second triplet display syndiotacticity (rr) of 45 to 58%. A methacrylic resin (X2),
The first methacrylic resin (X1) is produced by an anionic polymerization method,
Producing a second methacrylic resin (X2) by radical polymerization;
(9) The manufacturing method of the thermoplastic resin film as described in (10).

In this specification, “film” refers to what is generally called a film or sheet.

  According to the present invention, thermoplastic properties that have good mechanical properties such as toughness, high transparency, low haze, high surface smoothness, high heat resistance, low heat shrinkage, and adjustment of phase difference. A resin film can be provided.

  Hereinafter, the present invention will be described in detail.

"Thermoplastic resin film"
The thermoplastic resin film of the present invention contains a methacrylic resin (A) and a vinyl acetal resin (B).
The methacrylic resin (A) and the vinyl acetal resin (B) can be used alone or in combination of two or more.

(Methacrylic resin (A))

In the thermoplastic resin film of the present invention, a specific methacrylic resin (A) is used to improve heat resistance.
From the viewpoint of improving heat resistance, the methacrylic resin (A) has a lower limit of triplet-syndiotacticity (rr) of 58%, preferably 59%, more preferably 60%, particularly preferably 62%, most preferably Preferably it is 65%.

In the present invention, the heat resistance is improved by using a relatively high syndiotacticity methacrylic resin (A) having a triplet display syndiotacticity (rr) of 58% or more.
In general, the higher the syndiotacticity (rr) in triplet display, the higher the heat resistance of the methacrylic resin, while the mechanical properties such as toughness decrease, and the film-forming property tends to decrease.
In the present invention, by blending a vinyl acetal resin (B) described later with a relatively high syndiotacticity methacrylic resin (A), the mechanical properties such as toughness are improved, and the film forming property is improved. I am trying.

In the methacrylic resin (A), from the viewpoint of film forming properties, the upper limit of the triplet display syndiotacticity (rr) is preferably 99%, more preferably 85%, still more preferably 77%, particularly preferably. 76%, most preferably 75%.
When the syndiotacticity is within the above range, the heat shrinkage rate is suppressed, a film having a uniform thickness, excellent surface smoothness, and high surface hardness is easily obtained.

In this specification, the triplet display syndiotacticity (rr) (hereinafter sometimes simply referred to as “syndiotacticity (rr)”) is a chain of three consecutive structural units (3 This is a ratio in which the two chains (doublet, triad) of the triplet (triad) are both racemo (abbreviated as “rr” in this specification).
In the chain of molecular units (doublet, diad) in the polymer molecule, those having the same configuration are referred to as “meso”, and those opposite to each other are referred to as “racemo”, which are expressed as m and r, respectively.
The tridentate syndiotacticity (rr) (%) of the methacrylic resin was measured by measuring a ¹ H-NMR spectrum at 30 ° C. in deuterated chloroform, and TMS was 0 ppm from the spectrum. The area (X) of the region of 0.6 to 0.95 ppm and the area (Y) of the region of 0.6 to 1.35 ppm can be measured and calculated by the formula: (X / Y) × 100. .

  The methacrylic resin (A) can include a plurality of methacrylic resins having different syndiotacticity (rr) in triplet display.

For example, in the methacrylic resin (A), the first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more and the triplet display syndiotacticity (rr) And 45% to 58% of the second methacrylic resin (X2).
In this case, the content of the first methacrylic resin (X1) is 40 to 70 parts by mass with respect to 100 parts by mass of the total amount of the first methacrylic resin (X1) and the second methacrylic resin (X2). The content of the second methacrylic resin (X2) is preferably 60 to 30 parts by mass.
Each of the first methacrylic resin (X1) and the second methacrylic resin (X2) can be used alone or in combination of two or more.

As described above, the first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more and the triplet display syndiotacticity (rr) of 45 to 58%. By using the second methacrylic resin (X2), the syndiotacticity (rr) of triplet display is 58% or more, and a methacrylic resin (A) having various physical properties is stably obtained. It is done.
Heat resistance can be further improved by using the first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more. However, this resin alone has mechanical properties such as toughness. It tends to decrease and the film forming property tends to decrease. A first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more and a second methacrylic resin having a triplet display syndiotacticity (rr) of 58% or less. By using together with (X2), it is possible to improve the mechanical properties such as toughness and the film forming property while improving the heat resistance.

The methacrylic resin (A) has a weight average molecular weight (hereinafter sometimes abbreviated as “Mw”), preferably 50,000 to 150,000, more preferably 52,000 to 120,000, and particularly preferably 55,000 to 100,000.
When the Mw of the methacrylic resin (A) is in the above range, mechanical properties such as toughness are good, and a film having a uniform film thickness and excellent surface smoothness is easily obtained.

In the methacrylic resin (A), the ratio of Mw to the number average molecular weight (hereinafter sometimes abbreviated as “Mn”) (Mw / Mn, in the present specification, this value is defined as “molecular weight distribution”). However, it is preferably 1.2 to 2.0, more preferably 1.3 to 1.7.
When the molecular weight distribution (Mw / Mn) is in the above range, a film having good mechanical properties such as toughness and excellent surface smoothness can be easily obtained.
In the present specification, Mw and Mn are values obtained by converting a chromatogram obtained by gel permeation chromatography (GPC) into a molecular weight of standard polystyrene.
In this specification, GPC measurement is carried out by the method described in the section “Examples” below.

The methacrylic resin (A) has a content of a component having a molecular weight of 200,000 or more (defined as “high molecular weight component” in the present specification) in the range of 0.1 to 10%, preferably 0.5 to 5%. .
The methacrylic resin (A) has a content of a component having a molecular weight of less than 15000 (defined as “low molecular weight component” in the present specification) of 0.2 to 5%, preferably 1 to 4.5%.
When the content of the high molecular weight component and the low molecular weight component of the methacrylic resin (A) is in the above range, the film forming property is improved, and a film having a uniform film thickness is easily obtained.

In this specification, the content of a component having a molecular weight of 200,000 or more (high molecular weight component) is based on the retention time of standard polystyrene having a molecular weight of 200000 in the area surrounded by the chromatogram and baseline measured by GPC. Calculated as a percentage of the area of the early holding time portion.
The content of the component having a molecular weight of less than 15000 (low molecular weight component) is the area of the retention time portion that is slower than the retention time of the standard polystyrene having a molecular weight of 15000 out of the area surrounded by the chromatogram obtained by GPC and the baseline. As a percentage of

  The methacrylic resin (A) may be abbreviated as “MFR” (hereinafter referred to as “MFR”) measured at 230 ° C. under a load of 3.8 kg in accordance with JIS K 7210 from the viewpoint of film forming properties. Is preferably 0.1 g / 10 min or more, more preferably 0.1 to 30 g / 10 min, particularly preferably 0.5 to 20 g / 10 min, most preferably 1.0 to 10 g / 10 min. is there.

The methacrylic resin (A) is a resin containing a structural unit derived from a methacrylic acid ester.
Examples of methacrylic acid esters include:
Alkyl methacrylates such as methyl methacrylate, ethyl methacrylate, and butyl methacrylate;
Methacrylic acid aryl esters such as phenyl methacrylate;
And methacrylic acid cycloalkyl esters such as cyclohexyl methacrylate and norbornenyl methacrylate.
These can be used alone or in combination of two or more.
Among these, methacrylic acid alkyl ester is preferable, and methyl methacrylate (MMA) is particularly preferable.

In the methacrylic resin (A), the content of structural units derived from methacrylic acid esters with respect to all structural units is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 98% by mass or more, and particularly preferably. It is 99 mass% or more, Most preferably, it is 100 mass%.
Furthermore, in the methacrylic resin (A), the content of structural units derived from methyl methacrylate (MMA) with respect to all structural units is preferably 90% by mass or more, more preferably 95% by mass or more, and still more preferably 98% by mass. Above, particularly preferably 99% by mass or more, most preferably 100% by mass.

Methacrylic resin (A) can contain 1 type, or 2 or more types of structural units derived from other monomers other than methacrylic acid ester.
Examples of other monomers other than methacrylic acid esters that can be used in the methacrylic resin (A) include:
Alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate;
Acrylic acid aryl esters such as phenyl acrylate;
Acrylic acid cycloalkyl esters such as cyclohexyl acrylate and norbornenyl acrylate;
Aromatic vinyl compounds such as styrene and α-methylstyrene;
Examples thereof include vinyl monomers having only one polymerizable carbon-carbon double bond in one molecule such as (meth) acrylamide and (meth) acrylonitrile.
These can be used alone or in combination of two or more.

The glass transition temperature of the methacrylic resin (A) (hereinafter sometimes abbreviated as “Tg”) is preferably 110 ° C. or higher. The upper limit of the glass transition temperature (Tg) of the methacrylic resin (A) is usually 130 ° C. or lower.
When the glass transition temperature (Tg) is in the above range, deformation such as heat shrinkage of the film hardly occurs.
The glass transition temperature (Tg) can be controlled by adjusting the molecular weight or syndiotacticity (rr).
In the present specification, unless otherwise specified, the “glass transition temperature (Tg)” is a midpoint glass transition temperature measured by the method described in the section “Examples” below.

The production method of the methacrylic resin (methacrylic resin (A), first methacrylic resin (X1), or second methacrylic resin (X2)) is not particularly limited, and known polymerization methods such as radical polymerization method and anionic polymerization method are used. Can be applied.
Solvent-free continuous radical polymerization and anionic polymerization are preferred from the standpoint of obtaining a methacrylic resin having high thermal decomposition resistance, few foreign substances, and high transparency.
The anionic polymerization method is preferred from the viewpoint that there are few dimers and trimers of methacrylic acid esters and the appearance of the film is excellent.

  In the above known polymerization method, by adjusting the polymerization temperature, the polymerization time, the type or amount of the chain transfer agent, or the type or amount of the polymerization initiator, the Mw, the proportion of the high molecular weight component, the proportion of the low molecular weight component , And methacrylic resin whose properties such as syndiotacticity (rr) are in a desired range can be produced.

In general, a methacrylic resin having a relatively high syndiotacticity (rr) can be polymerized under conditions where the polymerization temperature is relatively low.
When polymerizing a methacrylic resin having a relatively high syndiotacticity (rr), the polymerization temperature is preferably 80 ° C. or lower, more preferably 70 ° C. or lower, and particularly preferably 60 ° C. or lower, regardless of the polymerization method.
However, in general, in the radical polymerization method, when the polymerization temperature is low, the polymerization initiator does not work effectively and the polymerization may not be efficiently started. In this case, anionic polymerization in which the polymerization initiator functions well also in low temperature polymerization is preferable.
From the viewpoint that a methacrylic resin (A) having high transparency and a relatively high syndiotacticity (rr) can be easily produced, at least one methacrylic resin constituting the methacrylic resin (A) is produced by an anionic polymerization method. It is preferable.
In particular,
A method for producing a methacrylic resin (A) whose properties satisfy a specified range by an anionic polymerization method;
A method of producing a methacrylic resin (A) whose characteristics satisfy a specified range by mixing a methacrylic resin produced by an anionic polymerization method and a methacrylic resin produced by radical polymerization;
and,
A method of producing a methacrylic resin (A) whose properties satisfy a specified range by mixing a plurality of types of methacrylic resins produced by an anionic polymerization method is preferred.
For example, when the methacrylic resin (A) includes the first methacrylic resin (X1) and the second methacrylic resin (X2), preferably, the first methacrylic resin (X1) is manufactured by an anionic polymerization method, The methacrylic resin (X2) 2 can be produced by a normal high temperature radical polymerization method.

  In the case of the anionic polymerization method, it is preferable to use alkyllithium such as n-butyllithium, sec-butyllithium, isobutyllithium, and tert-butyllithium as the polymerization initiator. Moreover, it is preferable to make an organoaluminum compound coexist from a viewpoint of productivity.

Examples of the organic aluminum include compounds represented by the following general formula.
AlR ¹ R ² R ³
(In the above formula, R ¹ , R ² and R ³ may each independently have an alkyl group which may have a substituent, an cycloalkyl group which may have a substituent, or a substituent. An aryl group, an aralkyl group which may have a substituent, an alkoxyl group which may have a substituent, an aryloxy group which may have a substituent, or an N, N-disubstituted amino group.
R ² and R ³ may be an aryleneoxy group which may have a substituent formed by bonding each other. )

  Specific examples of organoaluminum include isobutylbis (2,6-di-tert-butyl-4-methylphenoxy) aluminum, isobutylbis (2,6-di-tert-butylphenoxy) aluminum, and isobutyl [2,2 '-Methylenebis (4-methyl-6-tert-butylphenoxy)] aluminum and the like.

  In the anionic polymerization method, ether or a nitrogen-containing compound can be allowed to coexist in order to control the polymerization reaction.

  In the case of anionic polymerization of a methacrylic resin, an appropriate amount of a polymerization terminator is added in the middle of the polymerization reaction, or an appropriate amount of a polymerization initiator is additionally added in the middle of the polymerization reaction. Mn) etc. can be adjusted.

As a method for producing a methacrylic resin (A) containing a plurality of methacrylic resins having different compositions or various physical properties,
A method of melt-kneading a plurality of kinds of methacrylic resins prepared in advance by a known method;
and,
Examples thereof include a method of polymerizing other methacrylic resins in the presence of one or more kinds of methacrylic resins prepared in advance.
In the latter method, since the thermal history applied to the methacrylic resin (A) is shortened, thermal decomposition of the methacrylic resin (A) is suppressed, and a film with little coloring and foreign matter is easily obtained.

(Vinyl acetal resin (B))
In the thermoplastic resin film of the present invention, the vinyl acetal resin (B) is blended with the methacrylic resin (A) having high heat resistance.

  The vinyl acetal resin (B) has good affinity with the methacrylic resin (A), and the difference in glass transition temperature (Tg) is also small. Various mechanical properties and film-forming properties can be improved by adding the vinyl acetal resin (B).

The vinyl acetal resin (B) has a positive intrinsic birefringence and can be easily adjusted to a desired range of the retardation of the film by blending with the methacrylic resin (A) having a negative intrinsic birefringence. .
For example, in applications such as a polarizer protective film, the phase difference of the film can be adjusted to zero or a value close thereto. In applications such as a retardation film, it can be adjusted to a desired value.
Conventionally, in applications such as a polarizer protective film and a retardation film, the retardation is adjusted by blending polycarbonate with methacrylic resin. In the present invention, the phase difference can be easily adjusted without using polycarbonate.
Since the vinyl acetal resin (B) has a higher affinity with the methacrylic resin (A) than the polycarbonate, it can be added more than the polycarbonate, and the degree of freedom in adjusting the phase difference is great. Further, there is an advantage that various mechanical properties and film forming properties can be improved.

  The vinyl acetal resin (B) is a resin obtained by acetalizing a vinyl alcohol resin (hereinafter sometimes abbreviated as “PVA”) with one or more aldehydes.

  The vinyl acetal resin (B) includes a vinyl alcohol unit represented by the following formula (I), a vinyl ester unit represented by the following formula (II), and a vinyl acetal unit represented by the following formula (III) (adjacent to each other). Two matching vinyl alcohol units are units acetalized with aldehydes).

Each abbreviation in the above formulas (I) to (III) has the following meaning.
l is the molar ratio of vinyl alcohol units, and l ≧ 0.
m is a molar ratio of vinyl ester units, and m ≧ 0.
k is the molar ratio of vinyl alcohol units acetalized with aldehydes.
k / 2 is the molar ratio of vinyl acetal units, and k / 2> 0.
When the vinyl acetal resin (B) is composed only of a vinyl alcohol unit, a vinyl ester unit, and a vinyl acetal unit, k + 1 + m = 1.
The general formula of the aldehyde used for the acetalization of PVA is represented by R ^a -CHO.
^{R a} in formula (I) in ~ (III) is the same as ^{R a} in the aldehyde.
The general formula of vinyl ester is represented by R ^b COOCH═CH ₂ .
^{R b} in the formula (I) in ~ (III) is the same as ^{R b} in the vinyl ester _{^{(R b COOCH = CH 2)}} .
The arrangement order of each unit is not particularly limited.
Each unit may be arranged at random, may be arranged in a block shape, or may be arranged in a taper shape. Further, the bond between the repeating units may be Head-to-Tail or Head-to-Head.

The raw material vinyl alcohol resin (PVA) may be a homopolymer consisting only of vinyl alcohol units, or a copolymer obtained by using vinyl alcohol and a monomer copolymerizable therewith (hereinafter referred to as “PVA copolymer”). It may also be said.) Furthermore, it may be a modified vinyl alcohol resin having a functional group such as a carboxyl group introduced in the middle, end, or side chain of the molecular chain.
A vinyl alcohol resin (PVA) can use 1 type (s) or 2 or more types.

The manufacturing method in particular of vinyl alcohol resin (PVA) is not restrict | limited, A well-known method is applicable.
As a manufacturing method of vinyl alcohol resin (PVA), the method of saponifying 1 type, or 2 or more types of vinyl ester polymers, such as polyvinyl acetate, with an alkali, an acid, or aqueous ammonia, etc. are mentioned.
The vinyl ester monomers used for the polymerization of the above vinyl ester polymers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, and pivalin. Examples thereof include vinyl acid vinyl and versatic vinyl acid acid. Among these, vinyl acetate is preferable from the viewpoint of productivity of vinyl alcohol resin (PVA).

As a copolymerization monomer used for polymerization of PVA copolymer,
Α-olefins such as ethylene, propylene, 1-butene, isobutene, and 1-hexene;
(Meth) acrylic acid and its salts;
(Meth) acrylic acid esters such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and i-propyl (meth) acrylate;
(Meth) acrylamide derivatives such as (meth) acrylamide, N-methyl (meth) acrylamide, and N-ethyl (meth) acrylamide;
Vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether, and n-butyl vinyl ether;
Hydroxy group-containing vinyl ethers such as ethylene glycol vinyl ether, 1,3-propanediol vinyl ether, and 1,4-butanediol vinyl ether;
Allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, and hexyl allyl ether;
A monomer having an oxyalkylene group such as a polyoxyethylene group, a polyoxypropylene group, and a polyoxybutylene group;
Vinylsilanes such as vinyltrimethoxysilane;
Isopropenyl acetate, 3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, and 3-methyl-3 A hydroxy group-containing α-olefin such as buten-1-ol or an esterified product thereof;
N-vinylamides such as N-vinylformamide, N-vinylacetamide, and N-vinylpyrrolidone;
Monomers having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride, or itaconic anhydride;
A monomer having a sulfonic acid group derived from ethylenesulfonic acid, allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, or the like;
Vinyloxyethyltrimethylammonium chloride, vinyloxybutyltrimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium And monomers having a cationic group derived from allylethylamine such as chloride, methallyltrimethylammonium chloride, and dimethylallylamine.
These can be used alone or in combination of two or more.

  The content of these copolymerizable monomer units (hereinafter also referred to as “comonomer units”) is preferably 20 mol parts or less in 100 mol parts of all monomer units constituting the PVA copolymer. More preferably, it is 10 mol parts or less. In view of the copolymerization effect, the comonomer unit content is preferably 0.01 mol parts or more.

Examples of the polymerization method for the vinyl ester polymer include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among these, the bulk polymerization method and the solution polymerization method, which are methods of polymerizing without solvent or in a solvent such as alcohol, are preferable.
As the alcohol used as a solvent in the solution polymerization method, lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol are usually used.
As a polymerization initiator used in the above various polymerization methods,
azo compounds such as α, α′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethyl-valeronitrile);
and,
Examples thereof include benzoyl peroxide and peroxides such as n-propyl peroxycarbonate.
In the above various polymerization methods, the polymerization temperature is not particularly limited, and is usually 0 to 200 ° C.

As the saponification catalyst for the vinyl ester polymer, an alkaline substance is usually used.
Examples of the alkaline substance include potassium hydroxide and sodium hydroxide.
The usage-amount of an alkaline substance is 0.004-0.5, More preferably, it is 0.005-0.05 by molar ratio with respect to the vinyl ester unit in a vinyl ester-type polymer.
The alkaline substance may be added all at the beginning of the saponification reaction, or may be additionally added during the saponification reaction.
Examples of the solvent that can be used during the saponification reaction include methanol, methyl acetate, dimethyl sulfoxide, and dimethylformamide. Of these, methanol is preferred. A solvent whose water content is adjusted is preferable. The water content of the solvent is preferably 0.001 to 1% by mass, more preferably 0.003 to 0.9% by mass, and particularly preferably 0.005 to 0.8% by mass.

From the viewpoint of the thermal stability of the vinyl acetal resin (B), the saponification degree of the vinyl alcohol resin (PVA) is preferably higher, and is preferably completely saponified or close thereto.
The saponification degree of PVA is preferably more than 95 mol%, more preferably 98 mol% or more, particularly preferably 99 mol% or more.
If the degree of saponification is too low, the thermal stability of the vinyl acetal resin (B) will be insufficient, and thermal decomposition or cross-linking gelation may occur during film formation.

After the saponification reaction, the produced PVA is washed.
Examples of the cleaning liquid include methanol, acetone, methyl acetate, ethyl acetate, hexane, and water. Among these, methanol, methyl acetate, water, or a mixed solution thereof is preferable.
The amount of the cleaning liquid used is preferably set so as to satisfy the content of alkali metal and / or alkaline earth metal described later, and is preferably 300 to 10,000 parts by mass, more preferably 500 parts per 100 parts by mass of PVA. -5000 parts by mass.
The washing temperature is preferably 5 to 80 ° C, more preferably 20 to 70 ° C.
The washing time is preferably 20 minutes to 100 hours, more preferably 1 to 50 hours.

The content of alkali metal and / or alkaline earth metal in PVA is preferably 0.00001 to 1 part by mass with respect to 100 parts by mass of PVA.
PVA having an alkali metal and / or alkaline earth metal content of less than 0.00001 parts by mass is industrially difficult to produce. Further, if the content exceeds 1 part by mass, the content of alkali metal and / or alkaline earth metal remaining in the obtained vinyl acetal resin (B) increases, and thermal decomposition or cross-linking gelation occurs during film formation. May occur.
Examples of the alkali metal include sodium and potassium.
Examples of alkaline earth metals include calcium and barium.
Note that the content of alkali metal or alkaline earth metal can be determined by atomic absorption spectrometry or ICP emission analysis.

The vinyl alcohol resin (PVA) preferably has a viscosity average polymerization degree of 500 or more, more preferably 500 to 4,000, particularly preferably 500 to 3,000, and most preferably 500 to 2,000.
If the viscosity average polymerization degree of the vinyl alcohol resin (PVA) is too small, the mechanical properties of the resulting vinyl acetal resin (B) are insufficient, and the mechanical properties, particularly toughness, of the thermoplastic resin film of the present invention may be reduced. .
If the viscosity average polymerization degree of the vinyl alcohol resin (PVA) is excessive, the melt viscosity of the thermoplastic resin composition that is a raw material of the thermoplastic resin film of the present invention tends to be high.

In this specification, the viscosity average degree of polymerization (P) of vinyl alcohol resin (PVA) is measured according to JIS K 6726.
Specifically, after the vinyl alcohol resin (PVA) is completely re-saponified and purified, the intrinsic viscosity [η] (dl / g) is measured in water at 30 ° C., and the following formula is calculated from the value. The

P = ([η] × 10 ³ /8.29) ^{(1 / 0.62)}

The carbon number of the aldehyde used for acetalization is not particularly limited.
An aldehyde having 4 or more carbon atoms and / or an aldehyde having 3 or less carbon atoms can be used.

Examples of aldehydes having 3 or less carbon atoms include formaldehyde (including paraformaldehyde), acetaldehyde (including paraacetaldehyde), propionaldehyde, and glyoxal.
These can be used alone or in combination of two or more.
Among these, from the viewpoint of ease of production of the vinyl acetal resin (B), acetaldehyde and / or formaldehyde (including paraformaldehyde) are preferable, and acetaldehyde is particularly preferable.

Examples of the aldehyde having 4 or more carbon atoms include butyraldehyde, isobutyraldehyde, n-octylaldehyde, amylaldehyde, hexylaldehyde, heptylaldehyde, 2-ethylhexylaldehyde, cyclohexylaldehyde, furfural, glyoxal, glutaraldehyde, benzaldehyde, 2-methylbenzaldehyde , 3-methylbenzaldehyde, 4-methylbenzaldehyde, p-hydroxybenzaldehyde, m-hydroxybenzaldehyde, phenylacetaldehyde, and β-phenylpropionaldehyde.
These can be used alone or in combination of two or more.
Of these, butyraldehyde and the like are preferable from the viewpoint of ease of production of the vinyl acetal resin (B).

From the viewpoint of compatibility between the methacrylic resin (A) and the vinyl acetal resin (B), it is preferable to use one or more aldehydes containing at least an aldehyde having 3 or less carbon atoms.
That is, only one or two or more aldehydes having 3 or less carbon atoms are used, or one or more aldehydes having 3 or less carbon atoms and one or two or more aldehydes having 4 or more carbon atoms and It is preferable to use together.
When an aldehyde having 3 or less carbon atoms and an aldehyde having 4 or more carbon atoms are used in combination, acetaldehyde and butyl are used from the viewpoint of ease of production of the vinyl acetal resin (B), thermal stability of the vinyl acetal resin (B), and mechanical properties. A combination with an aldehyde is preferred.

The acetalization reaction of the vinyl alcohol resin (PVA) with an aldehyde can be performed by a known method.
An aqueous medium method in which an aqueous solution of vinyl alcohol resin (PVA) and an aldehyde are acetalized in the presence of an acid catalyst to precipitate resin particles;
and,
Solvent method in which vinyl alcohol resin (PVA) is dispersed in an organic solvent, acetalized with aldehyde in the presence of an acid catalyst, and this reaction solution is precipitated with water or the like as a poor solvent for vinyl acetal resin (B) Etc.
Of these, the aqueous medium method is preferred.

  The aldehyde used for acetalization may be charged at once, or may be charged in a plurality of times.

As an acid catalyst used for acetalization,
Organic acids such as acetic acid and p-toluenesulfonic acid;
Inorganic acids such as nitric acid, sulfuric acid and hydrochloric acid;
Gas that shows acidity when it is made into an aqueous solution such as carbon dioxide;
and,
Examples include cation exchangers and solid acid catalysts such as metal oxides.

  The randomness of the vinyl acetal unit in the vinyl acetal resin (B) can be changed by changing the addition order of the aldehyde and / or acid catalyst.

  The degree of acetalization of the vinyl acetal resin (B) is preferably 55 to 85 mol%, more preferably 55 to 83 mol%.

The degree of acetalization of the vinyl acetal resin (B) can be determined according to JIS K 6728 (1977).
First, the mass ratio (l ₀ ) of vinyl alcohol units that have not been acetalized and the mass ratio (m ₀ ) of vinyl acetate units are determined by titration. The mass ratio (k ₀ ) of the acetalized vinyl alcohol units is calculated by the formula: k ₀ = 1−l ₀ −m ₀ . From these, the molar ratio (l) of vinyl alcohol units that were not acetalized and the molar ratio (m) of vinyl acetate units were calculated, and acetalized vinyl alcohol units in the formula: k = 1-l-m The molar ratio (k) is calculated.

The degree of acetalization of the vinyl acetal resin (B) can also be determined by the following method.
Dissolve vinyl acetal resin (B) in deuterated dimethyl sulfoxide, measure ¹ H-MMR or ¹³ C-NMR, and determine molar ratio (l) of vinyl alcohol units not acetalized, vinyl ester The molar ratio (m) of units and the molar ratio (k) of acetalized vinyl alcohol units are calculated. Here, k ₀ + l ₀ + m ₀ = 1 and k + l + m = 1. Then, the degree of acetalization is calculated by the formula: {k / (k + 1 + m)} × 100.

In general, the molar proportion of vinyl alcohol units acetalized with butyraldehyde is referred to as the “degree of butyralization”.
Similarly, the molar proportion of vinyl alcohol units acetalized with acetaldehyde is referred to as “degree of acetoacetalization”.
Similarly, the molar proportion of vinyl alcohol units acetalized with formaldehyde is referred to as “degree of formalization”.

As an example, a vinyl acetal resin (B) obtained by acetalizing a vinyl alcohol resin (PVA) with butyraldehyde, acetaldehyde and formaldehyde will be specifically described.
The molar ratio of vinyl alcohol units acetalized with butyraldehyde is k _(BA) . The molar ratio of vinyl alcohol units acetalized with acetaldehyde is defined as k _(AA) . The molar ratio of vinyl alcohol units acetalized with formaldehyde is defined as k _(FA) . The molar ratio of vinyl alcohol units that are not acetalized is defined as l. Let the molar ratio of vinyl acetate units be m.
The degree of butyralization (mol%) is determined by the formula: k _(BA) / {k _(BA) + k _(AA) + k _(FA) + l + m} × 100.
The degree of acetoacetalization (mol%) is determined by the formula: k _(AA) / {k _(BA) + k _(AA) + k _(FA) + l + m} × 100.
The degree of formalization (mol%) is determined by the formula: k _(FA) / {k _(BA) + k _(AA) + k _(FA) + l + m} × 100.
In addition, the degree of acetalization for each aldehyde can be calculated by measuring the ratio of acetalized aldehyde by ¹ H-NMR or ¹³ C-NMR. However, k _(BA) + k _(AA) + k _(FA) + 1 + m = 1.

When a vinyl butyral resin is used as the vinyl acetal resin (B), the degree of acetalization (degree of butyralization) of the vinyl butyral resin is preferably 55 to 85 mol%, more preferably 55 to 75 mol%, particularly preferably. It is 55 to 65 mol%.
When the vinyl acetal resin (B) is a resin obtained by coacetalizing a vinyl alcohol resin (PVA) with an aldehyde having 3 or less carbon atoms and an aldehyde having 4 or more carbon atoms, the acetal of the vinyl acetal resin (B) From the viewpoint of continuous productivity, the degree of conversion is preferably 55 to 85 mol%, more preferably 60 to 83 mol%, and particularly preferably 70 to 83 mol%.
The vinyl acetal resin (B) having a degree of acetalization within the above range is easy to produce and easy to melt.

The amount of the vinyl ester unit constituting the vinyl acetal resin (B) is preferably less than 5 mol%, more preferably 2 mol% or less, and particularly preferably 1 mol% or less.
If the vinyl ester unit is excessive, the thermal stability and continuous productivity of the vinyl acetal resin (B) may be lowered.

Basically, the degree of polymerization does not change due to acetalization. For this reason, the degree of polymerization of the vinyl alcohol resin (PVA) and the vinyl acetal resin (B) obtained by acetalizing the vinyl alcohol resin (PVA) are basically the same.
Therefore, the viscosity average degree of polymerization of the vinyl acetal resin (B) is preferably 500 or more, more preferably 500 to 4,000, particularly preferably 500 to 3,000, most preferably, like the vinyl alcohol resin (PVA). 500-2,000.
If the degree of polymerization of the vinyl acetal resin (B) is too low, the mechanical properties of the vinyl acetal resin (B) are insufficient, and particularly the toughness may be insufficient. If the degree of polymerization of the vinyl acetal resin (B) is excessively high, the melt viscosity becomes high and film formation may be difficult.

Slurries produced in the aqueous medium method and the solvent method are usually acidic by an acid catalyst. The pH of this slurry is preferably adjusted to 5 to 9, more preferably 6 to 9, and particularly preferably 6 to 8 by a known method.
As a method for removing the acid catalyst,
A method of repeatedly washing the slurry with water;
A method of adding a neutralizing agent to the slurry;
and,
Examples thereof include a method of adding an alkylene oxide or the like to the slurry.

As a neutralizing agent,
Alkali metal compounds such as sodium hydroxide, potassium hydroxide, sodium acetate, sodium carbonate, sodium bicarbonate, and potassium carbonate;
Alkaline earth metal compounds such as calcium hydroxide;
and,
Ammonia or an aqueous solution thereof may be used.

As alkylene oxides,
Alkylene oxides such as ethylene oxide and propylene oxide;
and,
Examples thereof include glycidyl ethers such as ethylene glycol diglycidyl ether.

For the slurry whose acid catalyst has been removed by adjusting the pH, a catalyst residue, a neutralizing agent residue, a salt produced by neutralization, an aldehyde reaction residue, an alkali metal, an alkaline earth metal, and a by-product are obtained by a known method. Impurities such as these are removed to purify the vinyl acetal resin (B).
The purification method is not particularly limited, and a method of repeating washing with a washing solution and dewashing solution is usually used.
Examples of the cleaning liquid include water or a mixed liquid obtained by adding alcohol such as methanol and ethanol to water.

Since alkali metal and / or alkaline earth metal can be effectively reduced and vinyl acetal resin (B) can be stably produced, after neutralizing vinyl acetal resin (B), water and alcohol A method of repeating washing and dewashing liquid using a mixed washing liquid until the pH is in the above preferred range is particularly preferred.
The mixing ratio of water / alcohol in the cleaning liquid is preferably 50/50 to 95/5, more preferably 60/40 to 90/10 in terms of mass ratio.
When the ratio of water is too small, the vinyl acetal resin (B) tends to be eluted into the mixed cleaning liquid. When the proportion of water is excessive, the removal efficiency of alkali metal and / or alkaline earth metal tends to decrease.

The amount of alkali metal and / or alkaline earth metal in the vinyl acetal resin (B) is preferably small, preferably 100 ppm or less, more preferably 70 ppm or less, and particularly preferably 50 ppm or less.
When the amount of alkali metal and / or alkaline earth metal exceeds 100 ppm, gel is generated at a high temperature, and the continuous productivity of the thermoplastic resin film of the present invention tends to decrease.
Incidentally, the vinyl acetal resin (B) having an alkali metal and / or alkaline earth metal content of less than 0.1 ppm requires a long washing time to obtain it, resulting in an increase in production cost and industrial production. Production tends to be difficult.

  The water-containing vinyl acetal resin (B) from which impurities such as residues have been removed is dried as necessary, processed into powder, granules or pellets as necessary, and used as a film forming material. In this processing, it is preferable to reduce aldehyde reaction residue, moisture, and the like by degassing under reduced pressure.

The moisture content of the vinyl acetal resin (B) is preferably 0.005 to 2%, more preferably 0.01 to 1%.
If the moisture content is less than 0.005%, it is difficult to produce and may go through an excessive heat history. On the other hand, when the moisture content exceeds 2%, film formation may be difficult.
The moisture content can be measured by the Karl Fischer method.

(Compounding ratio of methacrylic resin (A) and vinyl acetal resin (B))
From the viewpoint that mechanical properties such as toughness of the thermoplastic resin film of the present invention, heat resistance, transparency, haze, and film-forming properties become good and the retardation of the film can be easily adjusted to be small, methacrylic resin (A) and vinyl The compounding ratio with the acetal resin (B) is as follows.
In the thermoplastic resin film of the present invention, the content of the methacrylic resin (A) is 95 parts by mass or less and 75 parts by mass with respect to 100 parts by mass of the total amount of the methacrylic resin (A) and the vinyl acetal resin (B). The content of the vinyl acetal resin (B) is more than 5 parts by mass and less than 25 parts by mass.
Preferably, the total amount of the methacrylic resin (A) and the vinyl acetal resin (B) is 100 parts by mass, and the content of the methacrylic resin (A) is 93 parts by mass or less and more than 80 parts by mass. The content of B) is 7 parts by mass or more and less than 20 parts by mass.
Particularly preferably, the total content of the methacrylic resin (A) and the vinyl acetal resin (B) is 100 parts by mass, and the content of the methacrylic resin (A) is 93 parts by mass or less and more than 84 parts by mass. The content of (B) is 7 parts by mass or more and less than 16 parts by mass.
In applications such as a polarizer protective film, the phase difference can be adjusted to zero or a value close to it by setting the blending ratio.
In applications such as a polarizer protective film, in the case of a uniaxially stretched film having a thickness of 200 μm, the thickness direction retardation (Rth) is preferably −15 to +15 nm.
In applications such as a retardation film, the retardation can be adjusted to a desired range by setting the blending ratio.
When the amount of the vinyl acetal resin (B) is less than 5 parts by mass, the mechanical properties such as the toughness of the film and the film forming property are deteriorated. Moreover, in applications such as polarizer protective films and optical films such as retardation films, it becomes difficult to adjust the retardation within a suitable range.
On the other hand, when the amount of the vinyl acetal resin (B) is 25 parts by mass or more, the transparency is lowered and the haze is increased. Moreover, in the use of optical films such as a polarizer protective film and a retardation film, it is difficult to adjust the retardation within a suitable range.

  The thermoplastic resin film of this invention can contain 1 type, or 2 or more types of arbitrary components other than a methacryl resin (A) and a vinyl acetal resin (B) as needed.

As an optional component,
Other polymers or resins;
and,
Fillers, antioxidants, thermal degradation inhibitors, UV absorbers, light stabilizers, lubricants, mold release agents, polymer processing aids, antistatic agents, flame retardants, dyes and pigments, light diffusion agents, organic dyes, matte Agents, impact modifiers, foaming agents, fillers, and various additives such as phosphors.

  The addition timing of the optional component is not particularly limited, and may be added during polymerization of the methacrylic resin (A) and / or the vinyl acetal resin (B), or the polymerized methacrylic resin (A) and / or the vinyl acetal resin. It may be added to (B), or may be added during or after kneading the methacrylic resin (A) and the vinyl acetal resin (B).

<Other polymers or resins>
Other polymers or resins include
Olefin resins such as polyethylene, polypropylene, polybutene-1, poly-4-methylpentene-1, and polynorbornene;
Ethylene ionomers;
Styrene resins such as polystyrene, styrene-maleic anhydride copolymer, high impact polystyrene, AS resin, ABS resin, AES resin, AAS resin, ACS resin, and MBS resin;
Methyl methacrylate-styrene copolymer;
Ester resins such as polyethylene terephthalate and polybutylene terephthalate;
Polyamides such as nylon 6, nylon 66, and polyamide elastomers;
Polycarbonate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymer, polyacetal, polyvinylidene fluoride, polyurethane, modified polyphenylene ether, polyphenylene sulfide, and silicone modified resin;
Acrylic rubber, acrylic thermoplastic elastomer, and silicone rubber;
Styrenic thermoplastic elastomers such as SEPS, SEBS, and SIS;
Examples thereof include olefinic rubbers such as IR, EPR, and EPDM.
These can be used alone or in combination of two or more.

  Each abbreviation in the above-mentioned other polymer or resin is commonly used by those skilled in the art as an abbreviation for the polymer or resin. For example, AS resin indicates acrylonitrile styrene resin, and ABS resin indicates acrylonitrile-butadiene-styrene copolymer resin.

The thermoplastic resin film of the present invention has the methacrylic resin (A) and the vinyl acetal resin (B), which are essential components, as main components, so that the operational effects of these blends are effectively expressed.
The total amount of other polymers or resins that can be contained in the thermoplastic resin film of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and particularly preferably 0% by mass.

<Filler>
Examples of the filler include calcium carbonate, talc, carbon black, titanium oxide, silica, clay, barium sulfate, and magnesium carbonate.
These can be used alone or in combination of two or more.
The amount of filler that can be contained in the thermoplastic resin film of the present invention is preferably 3% by mass or less, more preferably 1.5% by mass or less.

<Antioxidant>
The antioxidant alone has an effect of preventing oxidative deterioration of the resin in the presence of oxygen.
Examples thereof include phosphorus antioxidants, hindered phenol antioxidants, and thioether antioxidants.
As the antioxidant, an antioxidant containing a portion having the effect of a phosphorus antioxidant and a portion having the effect of a hindered phenol antioxidant in the same molecule can also be used.
These antioxidants can be used alone or in combination of two or more.
Among these, from the viewpoint of the effect of preventing deterioration of optical properties due to coloring, a phosphorus-based antioxidant and a hindered phenol-based antioxidant are preferable, and a combined use of a phosphorus-based antioxidant and a hindered phenol-based antioxidant is more preferable. .
When using together phosphorus antioxidant and hindered phenolic antioxidant, the usage-amount of phosphorus antioxidant: The usage-amount of hindered phenolic antioxidant is 1: 5-2 by mass ratio. 1 is preferable, and 1: 2 to 1: 1 is more preferable.

  Examples of phosphorus antioxidants include 2,2-methylenebis (4,6-di-t-butylphenyl) octyl phosphite (manufactured by ADEKA; trade name: ADK STAB HP-10), tris (2,4-di-t- Butylphenyl) phosphite (manufactured by BASF; trade name: IRGAFOS168) and 3,9-bis (2,6-di-tert-butyl-4-methylphenoxy) -2,4,8,10-tetraoxa3 9-diphosphaspiro [5.5] undecane (manufactured by ADEKA; trade name: ADK STAB PEP-36) and the like are preferable.

  As the hindered phenol-based antioxidant, pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (manufactured by BASF; trade name IRGANO01010), and octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate (manufactured by BASF; trade name IRGANO01076) is preferred.

  Antioxidants containing a portion having the effect of a phosphorus antioxidant and a portion having the effect of a hindered phenol antioxidant in the same molecule include 6- [3- (3-t-butyl-4-hydroxy -5-methyl) propoxy] -2,4,8,10-tetra-t-butyldibenz [d, f] [1,3,2] -dioxasphospine (manufactured by Sumitomo Chemical; trade name: Sumilizer) GP) and the like are preferable.

<Heat degradation inhibitor>
The thermal degradation inhibitor can prevent thermal degradation of the resin by scavenging polymer radicals generated when exposed to high heat in a substantially oxygen-free state.
As the thermal degradation inhibitor, 2-t-butyl-6- (3′-t-butyl-5′-methyl-hydroxybenzyl) -4-methylphenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumilyzer GM), and 2,4-di-t-amyl-6- (3 ′, 5′-di-t-amyl-2′-hydroxy-α-methylbenzyl) phenyl acrylate (manufactured by Sumitomo Chemical Co., Ltd .; trade name Sumitizer GS) and the like are preferable.

<Ultraviolet absorber>
The ultraviolet absorber is a compound having an ability to absorb ultraviolet rays. The ultraviolet absorber is a compound that is said to have a function of mainly converting light energy into heat energy.
Examples of the ultraviolet absorber include benzophenones, benzotriazoles, triazines, benzoates, salicylates, cyanoacrylates, succinic anilides, malonic esters, and formamidines.
These can use 1 type (s) or 2 or more types.
Among these, benzotriazoles, triazines, or ultraviolet absorbers having a maximum molar extinction coefficient ε _{max at a} wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less are preferable.

Benzotriazoles are highly effective in suppressing deterioration of optical properties such as coloring due to ultraviolet irradiation.
As benzotriazoles,
2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (manufactured by BASF; trade name TINUVIN329),
2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (manufactured by BASF; trade name TINUVIN234),
and,
2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4-tert-octylphenol] (manufactured by ADEKA; LA-31) is preferred.

The ultraviolet absorber having a maximum value ε _max of the molar extinction coefficient at a wavelength of 380 to 450 nm of 1200 dm ³ · mol ⁻¹ cm ⁻¹ or less can suppress the yellowness of the obtained thermoplastic resin film. Examples of such an ultraviolet absorber include 2-ethyl-2′-ethoxy-oxalanilide (manufactured by Clariant Japan, trade name: Sundebore VSU).

  Among the above-described ultraviolet absorbers, benzotriazoles and the like are preferably used from the viewpoint that resin degradation due to ultraviolet irradiation can be suppressed.

Further, when it is desired to efficiently absorb a wavelength around 380 nm, a triazine ultraviolet absorber is preferably used.
As such an ultraviolet absorber,
2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine (manufactured by ADEKA; LA-F70),
And hydroxyphenyltriazine-based ultraviolet absorbers (manufactured by BASF; TINUVIN477-D, TINUVIN460, and TINUVIN479) that are analogs thereof.

  Furthermore, when it is desired to particularly effectively absorb light having a wavelength of 380 to 400 nm, International Publication No. 2011/089794, International Publication No. 2012/124395, Japanese Unexamined Patent Application Publication No. 2012-012476, Japanese Unexamined Patent Application Publication No. 2013-023461, Heterocyclic structure arrangements disclosed in JP2013-112790A, JP2013-194037A, JP201462228A, JP2014-88542A, JP2014-88543A, and the like. It is preferable to use a metal complex having a ligand (for example, a compound having a structure represented by the following formula (A)) as an ultraviolet absorber.

In formula (A), M is a metal atom.
Y ¹ , Y ² , Y ³ and Y ⁴ are each independently a divalent group other than a carbon atom (oxygen atom, sulfur atom, NH, NR ^{5 and the} like). Here, R ⁵ is a substituent such as an alkyl group, an aryl group, a heteroaryl group, a heteroaralkyl group, and an araryl group. This substituent may further have a substituent on this substituent.
Z ¹ and Z ² are each independently a trivalent group (nitrogen atom, CH, CR ^{6 and the} like). Here, R ⁶ is a substituent such as an alkyl group, an aryl group, a heteroaryl group, a heteroaralkyl group, and an araryl group. This substituent may further have a substituent on this substituent.
R ¹ , R ² , R ³ and R ⁴ are each independently a hydrogen atom, alkyl group, hydroxyl group, carboxyl group, alkoxyl group, halogeno group, alkylsulfonyl group, monophorinosulfonyl group, piperidinosulfonyl group, Substituents such as a thiomorpholinosulfonyl group and a piperazinosulfonyl group. This substituent may further have a substituent on this substituent.
a, b, c and d each represent the number of R ¹ , R ² , R ³ and R ⁴ and are each an integer of 1 to 4;

  Examples of the heterocyclic ligand include 2,2′-iminobisbenzothiazole, 2- (2-benzothiazolylamino) benzoxazole, 2- (2-benzothiazolylamino) benzimidazole, (2 -Benzothiazolyl) (2-benzimidazolyl) methane, bis (2-benzoxazolyl) methane, bis (2-benzothiazolyl) methane, bis [2- (N-substituted) benzimidazolyl] methane, and derivatives thereof .

  As the central metal of the metal complex, copper, nickel, cobalt, and zinc are preferably used.

In order to use the metal complex as an ultraviolet absorber, it is preferable to disperse the metal complex in a medium such as a low molecular compound or a polymer.
The addition amount of the metal complex is preferably 0.01 to 5 parts by mass, more preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the thermoplastic resin film of the present invention.
Since the metal complex has a large molar extinction coefficient at a wavelength of 380 to 400 nm, the amount added to obtain a sufficient ultraviolet absorption effect is small. If the amount added is small, deterioration of the film appearance due to bleeding out or the like can be suppressed. Moreover, since the metal complex has high heat resistance, there is little deterioration or decomposition during film formation. Furthermore, since the metal complex has high light resistance, the ultraviolet absorption performance can be maintained for a long time.

In addition, the maximum value ε _max of the molar extinction coefficient of the ultraviolet absorber is measured as follows.
Add 10.00 mg of UV absorber to 1 L of cyclohexane and dissolve it so that there is no undissolved material by visual observation. This solution is poured into a 1 cm × 1 cm × 3 cm quartz glass cell, and the absorbance at a wavelength of 380 to 450 nm is measured using a U-3410 spectrophotometer manufactured by Hitachi, Ltd. The maximum value ε _max of the molar extinction coefficient is calculated from the molecular weight (M _UV ) of the ultraviolet absorber and the maximum value (A _max ) of the measured absorbance according to the following formula.

ε _max = [A _max / (10 × 10 ⁻³ )] × M _UV

<Light stabilizer>
The light stabilizer is a compound that is said to have a function of capturing radicals generated mainly by oxidation by light.
Suitable light stabilizers include hindered amines such as compounds having a 2,2,6,6-tetraalkylpiperidine skeleton.

<Lubricant>
Examples of the lubricant include stearic acid, behenic acid, stearamic acid, methylene bisstearamide, hydroxystearic acid triglyceride, paraffin wax, ketone wax, octyl alcohol, and hardened oil.
These can be used alone or in combination of two or more.

<Release agent>
As a mold release agent,
Higher alcohols such as cetyl alcohol and stearyl alcohol;
and,
Examples include glycerin higher fatty acid esters such as stearic acid monoglyceride and stearic acid diglyceride.
These can be used alone or in combination of two or more.

It is preferable to use a higher alcohol and a glycerin fatty acid monoester in combination as a mold release agent.
When higher alcohols and glycerin fatty acid monoester are used in combination, the ratio is not particularly limited, but the amount of higher alcohol used: the amount of glycerol fatty acid monoester used is 2.5: 1 to 3. 5: 1 is preferable, and 2.8: 1 to 3.2: 1 is more preferable.

<Polymer processing aid>
As the polymer processing aid, polymer particles having a particle diameter of 0.05 to 0.5 μm, usually produced by an emulsion polymerization method, are used. Such polymer particles may be single layer particles composed of a single composition and single intrinsic viscosity polymer, or may be multilayer particles composed of two or more polymers having different compositions or intrinsic viscosities. .
In particular, particles having a two-layer structure having a polymer layer having a relatively low intrinsic viscosity in the inner layer and a polymer layer having a relatively high intrinsic viscosity of 5 dl / g or more in the outer layer are preferable.
The polymer processing aid preferably has an intrinsic viscosity of 3 to 6 dl / g. If the intrinsic viscosity is too small or too large, the film forming property may be lowered.
Specific examples include the Metablene-P series manufactured by Mitsubishi Rayon Co., Ltd., Rohm and Haas Co., Ltd., Dow Chemical Co., Ltd., and Kureha Chemical Co., Ltd. paraloid series.
The amount of the polymer processing aid blended in the thermoplastic resin film of the present invention is preferably 0.00 with respect to 100 parts by mass of the total amount of the methacrylic resin (A) and the vinyl acetal resin (B). 1 to 5 parts by mass.
If the blending amount of the polymer processing aid is less than 0.1 parts by mass, the film forming property may be deteriorated, and if it exceeds 5 parts by mass, the surface smoothness of the film may be deteriorated.

<Impact resistance modifier>
As an impact resistance modifier,
A core-shell type modifier containing acrylic rubber or diene rubber as a core layer component;
and,
Examples thereof include a modifier containing a plurality of rubber particles.
These can be used alone or in combination of two or more.

<Organic dye>
As the organic dye, a compound having a function of converting ultraviolet light into visible light is preferably used.

<Light diffusing agent or matting agent>
Examples of the light diffusing agent or matting agent include glass fine particles, polysiloxane-based crosslinked fine particles, crosslinked polymer fine particles, talc, calcium carbonate, and barium sulfate.
These can be used alone or in combination of two or more.

<Phosphor>
Examples of the phosphor include a fluorescent pigment, a fluorescent dye, a fluorescent white dye, a fluorescent whitening agent, and a fluorescent bleaching agent.
These can be used alone or in combination of two or more.

The thermoplastic resin film of the present invention has the methacrylic resin (A) and the vinyl acetal resin (B), which are essential components, as main components, so that the operational effects of these blends are effectively expressed.
The total amount of the various additives is preferably 7 parts by mass or less, more preferably 5 parts by mass or less, and particularly preferably with respect to 100 parts by mass of the total amount of the methacrylic resin (A) and the vinyl acetal resin (B). 4 parts by mass or less.

(Method for producing thermoplastic resin film)
The method for producing the thermoplastic resin film of the present invention is not particularly limited.
For example, a plurality of raw material resins including a methacrylic resin (A) and a vinyl acetal resin (B) are prepared, and a thermoplastic resin composition is obtained by melting and kneading the plurality of raw material resins. A film forming method is preferred.

The melt kneading may be performed only once or may be performed in a plurality of times.
For example, a methacrylic resin (A), a vinyl acetal resin (B), and, if necessary, another polymer or resin can be melt-kneaded at a time.
Further, after the methacrylic resin (X1) and the methacrylic resin (X2) are melt-kneaded to obtain the methacrylic resin (A), the methacrylic resin (A), the vinyl acetal resin (B), and other heavy resins as necessary. The coalescence or resin may be melt kneaded.

The melt-kneading can be performed using, for example, a melt-kneader such as a kneader ruder, an extruder, a mixing roll, and a Banbury mixer. Among these, a twin screw extruder is preferable.
The kneading temperature is appropriately adjusted according to the softening temperature of the resin component, preferably in the range of 110 to 300 ° C, and more preferably in the range of 140 to 300 ° C.
Shear rate applied to the thermoplastic resin composition during melt-kneading is preferably at 100 sec ^-1 or more, more preferably 200 sec ^-1 or more.

  After carrying out melt-kneading at the above temperature, the obtained melt-kneaded product is cooled to a temperature of 120 ° C. or lower. The cooling is preferably rapid cooling rather than natural cooling. Examples of the rapid cooling method include a method of immersing a melted strand in a cold water tank.

In the thermoplastic resin film of the present invention, the continuous phase is preferably formed of a methacrylic resin (A).
By rapid cooling, the methacrylic resin (A) forms a continuous phase, and the dispersed phase formed by the vinyl acetal resin (B) can be kept in a very small state.

  The thermoplastic resin composition obtained by melt-kneading may be used for film formation in the molten state, and in order to enhance the convenience during storage, transportation or film formation, any of pellets, granules, powders, etc. You may make it the form.

The molding method (including the film molding method) of the thermoplastic resin composition is not particularly limited.
For example, T-die method (laminate method, co-extrusion method, etc.), inflation method (co-extrusion method, etc.), compression molding method, blow molding method, calendar molding method, vacuum molding method, pressure forming method, transfer molding method, rotation Melt molding methods such as molding method, powder slush method, and injection molding method (insert method, two-color method, press method, core back method, sandwich method, etc.);
And
The solution cast method etc. are mentioned.
Among these, the T die method, the inflation method, the injection molding method, and the like are preferable from the viewpoint of high productivity and cost.

Examples of the method for forming a thermoplastic resin composition (film molding method) include a solution casting method, a melt casting method, an extrusion molding method, an inflation molding method, and a blow molding method.
Of these, the extrusion method is preferable. According to the extrusion molding method, a film having high transparency, uniform thickness, and excellent surface smoothness can be obtained with relatively high productivity. The temperature of the thermoplastic resin composition discharged from the extruder is preferably set to 160 to 270 ° C, more preferably 220 to 260 ° C. From the viewpoint of removing foreign matter, the extruder is preferably equipped with equipment capable of removing impurities with a vent, and may be manufactured by installing a polymer filter. Moreover, in order to make thickness accuracy high, it is good to install and manufacture a gear pump.

From the viewpoint that a film having high surface smoothness and high specular gloss can be obtained, a thermoplastic resin composition containing a methacrylic resin (A) and a vinyl acetal resin (B) is extruded from a T-die in a molten state and extruded. An extrusion method including a step of bringing a mirror surface such as a mirror roll or a mirror belt into contact with at least one surface of the film-like material is preferable.
The mirror surface is preferably a metal mirror surface. Examples of the mirror metal include chromium.

  In the said process, it is preferable to press-clamp both surfaces of the extruded film-like material with a pair of mirror surfaces. The clamping pressure of the extruded film-like material by a pair of mirror surfaces is preferably high, and the linear pressure is preferably 2 N / mm or more, more preferably 10 N / mm or more, and particularly preferably 30 N / mm or more.

From the standpoint of obtaining a film having high surface smoothness and good surface gloss and low haze, at least one of the mirror surfaces sandwiching the extruded film-like material has a mirror surface temperature of 60 ° C. or higher, and both The mirror surface temperature is preferably 130 ° C. or lower.
When the mirror surface temperature of both of the pair of mirror surfaces sandwiching the extruded film-like material is less than 60 ° C., the surface smoothness of the obtained thermoplastic resin film may be lowered and haze may be increased. When the mirror surface temperature of both of the pair of mirror surfaces sandwiching the extruded film-like material is over 130 ° C., the film and the mirror surface are too close to each other, and the film surface becomes rough when the film is peeled off from the mirror surface. There is a possibility that the surface smoothness of the plastic resin film is lowered and haze is increased.

The thickness of the unstretched film obtained by the various film forming methods is preferably 10 to 500 μm, more preferably 50 to 300 μm, and particularly preferably 75 to 200 μm.
Films of less than 10 μm are difficult to manufacture.
When it is thicker than 500 μm, the secondary processability such as laminating property, handling property, cutting property, and punching property is lowered, and the material cost per unit area is also increased.
The haze of the unstretched film obtained by extrusion molding is preferably 0.5% or less, more preferably 0.3% or less at a thickness of 400 μm.

The unstretched film obtained by the various film forming methods described above may be stretched to give a stretched film.
The stretching process increases the mechanical strength, and a film that is difficult to crack can be obtained.
The stretching method is not particularly limited, and examples thereof include a simultaneous biaxial stretching method, a sequential biaxial stretching method, and a tuber stretching method.
The lower limit of the stretching temperature is preferably 10 ° C. higher than the glass transition temperature (Tg) of the thermoplastic resin composition, and the upper limit of the stretching temperature is preferably from the viewpoint that it can be uniformly stretched and a high-strength film can be obtained. The temperature is 40 ° C. higher than the glass transition temperature (Tg) of the thermoplastic resin composition.
The stretching speed is preferably 10 to 5000% / min.
A film with little heat shrinkage can be obtained by heat setting after stretching. The thickness of the stretched film is preferably 10 to 200 μm.
The haze at a thickness of 200 μm of the stretched film is preferably 0.5% or less, more preferably 0.3% or less.
By stretching, birefringence in the in-plane direction is effectively expressed.

  The unstretched film or stretched film having the above haze characteristics is excellent in surface gloss and transparency. For optical applications such as a liquid crystal protective film and a light guide film, the utilization efficiency of the light source is preferably increased. Furthermore, since it is excellent in the shaping precision at the time of surface shaping, it is preferable.

  According to the present invention, thermoplastic properties that have good mechanical properties such as toughness, high transparency, low haze, high surface smoothness, high heat resistance, low heat shrinkage, and adjustment of phase difference. A resin film can be provided.

The thermoplastic resin film of the present invention may be provided for various uses by providing various functional layers on the surface thereof.
Examples of the functional layer include a hard coat layer, an antiglare layer, an antireflection layer, an antisticking layer, a diffusion layer, an antiglare layer, an antistatic layer, an antifouling layer, and a slippery layer containing fine particles.

The thermoplastic resin film of the present invention may be provided for various uses by providing an adhesive layer on the surface thereof.
Examples of the adhesive constituting the adhesive layer include a water-based adhesive, a solvent-based adhesive, a hot-melt adhesive, and an active energy ray-curable adhesive.
Of these, water-based adhesives and active energy ray-curable adhesives are suitable.

Examples of the water-based adhesive include vinyl polymer, gelatin, vinyl latex, polyurethane, isocyanate, polyester, and epoxy.
The aqueous adhesive may contain a crosslinking agent, a catalyst such as an acid, and other additives as necessary.
Among them, the water-based adhesive is preferably an adhesive containing a vinyl polymer, and the vinyl polymer is preferably a vinyl alcohol resin (PVA).
Vinyl alcohol resin (PVA) can contain water-soluble crosslinking agents such as boric acid, borax, glutaraldehyde, melamine, and oxalic acid.
From the viewpoint of improving the durability of the adhesive effect, an adhesive containing a vinyl alcohol resin (PVA) having an acetoacetyl group is more preferable.
The aqueous adhesive is usually an aqueous solution containing a solid content of 0.5 to 60% by mass.

As the active energy ray-curable adhesive, those containing a curable component such as a compound having a monofunctional or bifunctional (meth) acryloyl group and a compound having a vinyl group can be used.
As the active energy ray-curable adhesive, an adhesive containing a photocationic curing component mainly composed of an epoxy compound or an oxetane compound and a photoacid generator can be used.
Examples of active energy rays include electron beams and ultraviolet rays.

"Use of thermoplastic resin film"
The thermoplastic resin film of the present invention has good mechanical properties, high transparency, low haze, high surface smoothness, high heat resistance, low heat shrinkage, and adjustment of phase difference.
The thermoplastic resin film of the present invention can be used for any application taking advantage of the above properties.

The thermoplastic resin film of the present invention can be preferably used for an optical device, an electronic device or the like because of properties such as transparency, heat resistance, and low birefringence.
For example, polarizer protective film, retardation film, liquid crystal protective plate, light guide plate, light guide film, prism film, diffusion plate, front plate of various displays, surface material of portable information terminal, display window protection of portable information terminal It is suitable for a film and a transparent conductive film having silver nanowires or carbon nanotubes coated on the surface.

Since the thermoplastic resin film of the present invention can adjust the retardation, it is particularly suitable as an optical film such as a polarizer protective film and a retardation film.
When the thermoplastic resin film of the present invention is used as a polarizer protective film or a retardation film, it can be laminated on one side or both sides of the polarizer film. When laminating | stacking with a polarizer film, it can laminate | stack via an adhesive layer or an adhesion layer as needed.
A well-known thing can be used for a polarizer film, The stretched film etc. which contain vinyl alcohol resin (PVA) and iodine are mentioned. The film thickness is preferably 1 to 100 μm.

  The thermoplastic resin film of the present invention has an IR (infrared light) cut film, a crime prevention film, an anti-scattering film, a solar cell back sheet, a flexible solar cell, in addition to the above-mentioned uses, from the characteristics such as transparency and heat resistance. It can be used for a front sheet, a shrink film, an in-mold label film, and the like.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.
In the following description, “part” represents “part by mass” and “%” represents “mass%” unless otherwise specified.

  Various evaluations of the resin or film were carried out by the following methods.

(Polymerization conversion)
The gas chromatograph GC-14A manufactured by Shimadzu Corporation was used as a column for GL Sciences Inc. Inert CAP 1 (df = 0.4 μm, ID = 0.25 mm, length = 60 m) was connected. The injection temperature was 180 ° C. and the detector temperature was 180 ° C. The column temperature was kept at 60 ° C. for 5 minutes, and then the temperature profile was raised from 60 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min, and held at 200 ° C. for 10 minutes. Measurement was performed under these conditions, and the polymerization conversion was calculated based on the obtained results.

(Weight average molecular weight (Mw), molecular weight distribution (Mw / Mn), content of high molecular weight component and low molecular weight component)
The weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the methacrylic resin were calculated by measuring the chromatogram under the following conditions by gel permeation chromatography (GPC) and converting it to the molecular weight of standard polystyrene.
“HLC-8320” manufactured by Tosoh Corporation was used as the GPC apparatus. A differential refractive index detector (RI detector) was used as a detector. As the column, a column in which two “TSKgel Super Multipore HZM-M” manufactured by Tosoh Corporation and “Super HZ4000” were connected in series was used. Tetrahydrofuran (THF) was used as the eluent. A solution in which 4 mg of resin was dissolved in 5 ml of tetrahydrofuran was used as a measurement sample. The eluent flow rate was 0.35 ml / min. The column temperature was 40 ° C. A chromatogram was measured by injecting 20 μl of the sample solution at an eluent flow rate of 0.35 ml / min.
The baseline of the chromatogram shows that the slope of the peak on the high molecular weight side of the GPC chart changes from zero to positive when viewed from the earlier retention time, and the slope of the peak on the lower molecular weight side is viewed from the earlier retention time. This is a line connecting points that change from minus to zero. If the chromatogram shows multiple peaks, connect the line connecting the point where the slope of the highest molecular weight peak changes from zero to positive and the point where the slope of the lowest molecular weight peak changes from negative to zero. Baseline.
From the integrated molecular weight distribution calculated using the calibration curve, the proportion of components having a molecular weight of 200,000 or more (high molecular weight components) and the proportion of components having a molecular weight of less than 15,000 (low molecular weight components) were calculated.
In addition, GPC measurement was performed using standard polystyrene having a molecular weight in the range of 400 to 5000000, and a calibration curve showing the relationship between the retention time and the molecular weight was created. A calibration curve was prepared using data of 10 standard polystyrene points.

(Syndiotacticity (rr) in triplet display)
The ¹ H-NMR spectrum of the methacrylic resin was measured using a nuclear magnetic resonance apparatus (ULTRA SHIELD 400 PLUS manufactured by Bruker) using deuterated chloroform as a solvent at room temperature under the conditions of 64 times of accumulation.
The area (X) of the region of 0.6 to 0.95 ppm and the area (Y) of the region of 0.6 to 1.35 ppm when TMS was 0 ppm was measured from the obtained spectrum, and the triplet The displayed syndiotacticity (rr) was calculated by the formula: (X / Y) × 100.

(Glass transition temperature (Tg))
Based on JIS K7121, the glass transition temperature (Tg) of the methacrylic resin was measured.
Using a differential scanning calorimeter (“DSC-50” manufactured by Shimadzu Corporation), the temperature of the sample was once raised to 230 ° C. and cooled to room temperature, and then increased again from room temperature to 230 ° C. at a rate of 10 ° C./min. The DSC curve was measured under the condition of raising the temperature at. The intermediate point obtained from the obtained DSC curve was defined as the glass transition temperature (Tg). When a plurality of shoulders appeared in the DSC curve, the glass transition temperature (Tg) was determined based on the shoulder on the highest temperature side.

(Melt flow rate (MFR))
Based on JIS K7210, the melt flow rate (MFR) of the methacrylic resin was measured under the conditions of 230 ° C., 3.8 kg load, and 10 minutes.

(Viscosity average degree of polymerization)
The viscosity average polymerization degree of the vinyl alcohol resin (PVA) was determined as follows.
Based on JIS K 6726, the relative viscosity of vinyl alcohol resin (PVA) based on water was measured, and the viscosity average degree of polymerization was calculated based on this measurement result.
Since the viscosity average polymerization degree of the vinyl acetal resin (B) is equal to the viscosity average polymerization degree of the vinyl alcohol resin (PVA) as a raw material, the viscosity average polymerization degree of the vinyl alcohol resin (PVA) is set to the same value.

(Acetalization degree, residual hydroxyl group content, residual OAc group content, saponification degree)
The composition analysis of the vinyl acetal resin (B) was performed by measuring a ¹³ C-NMR spectrum using a nuclear magnetic resonance apparatus (Lambda 500 manufactured by JEOL Ltd.).
Deuterated dimethyl sulfoxide (DMSO) was used as a solvent.
360 mg of vinyl acetal resin (B), 26 mg of chromium acetylacetonate, and about 3.0 ml of DMSO were mixed to obtain a sample having a concentration of 13 wt% / vol.
The ¹³ C-NMR spectrum was measured under the conditions of measurement mode SGNNE (addition of chromium acetylacetonate), measurement temperature of 80 ° C., and integration number of 30000 times.
From the obtained ¹³ C-NMR spectrum, mol% of each vinyl alcohol unit relative to all repeating units was calculated as the degree of acetalization of the vinyl acetal resin (B).
Specifically, mol% of vinyl alcohol units acetalized with butyraldehyde (hereinafter also referred to as “butyl acetal unit” or “BA unit”) with respect to all repeating units, and vinyl acetalized with acetaldehyde The mol% of the alcohol unit (hereinafter also referred to as “acetoacetal unit” or “AA unit”) relative to all repeating units was calculated.
From the obtained ¹³ C-NMR spectrum, mol% of the residual hydroxyl group not acetalized (hereinafter also referred to as “OH group”) with respect to all repeating units, and the residual saponified OAc group (here, OAc is a —OC (═O) CH ₃ group.) Mol% based on all repeating units was also calculated.
The saponification degree (mol%) of the vinyl acetal resin (B) was calculated by the formula: 100- [content of residual OAc group (mol%)].

(Alkali metal content)
The alkali metal content of the vinyl acetal resin (B) was measured as follows.
Place 2 mg of vinyl acetal resin (B) in a platinum crucible, add H ₂ SO ₄ and HNO ₃ and carbonize with a hot plate, then ash it in an electric furnace, dissolve the residue in 2 ml of hydrochloric acid, and add to a 50 ml volumetric flask. Moved up and messed up. Using this ICP emission analyzer (IRIS AP manufactured by Jarrel Ashe) for this solution, under the conditions of high frequency output 750 W, auxiliary gas flow rate (Ar) 1.5 L / min, nebulizer flow rate (Ar) 35 psi, and pump rotation speed 130 rpm. The content of Na which is an alkali metal was measured.

(Tensile elongation at break)
An unstretched film is obtained from Dumb Bell Ltd. It was punched with a super dumbbell cutter manufactured to obtain a dumbbell-shaped No. 2 test piece based on JIS K 6251. Using an autograph AG-5000B manufactured by Shimadzu Corporation, the obtained test piece was pulled at a speed of 5 mm / min. The tensile elongation at break was measured.

(Total light transmittance)
Based on JIS K 7361-1, the total light transmittance of the unstretched film and the uniaxially stretched film was measured using a haze meter (manufactured by Murakami Color Research Laboratory, HM-150).

(Haze)
Based on JIS K7136, the haze of the unstretched film and the uniaxially stretched film was measured using a haze meter (manufactured by Murakami Color Research Laboratory, HM-150).

(Surface smoothness)
The surface of the unstretched film was visually observed, and the surface smoothness was evaluated according to the following criteria.
○ (good): The surface is smooth.
X (defect): The surface has irregularities.

(Heat shrinkage)
A straight line having a length of 70 mm was drawn on the surface of the uniaxially stretched film, and the film was heated for 30 minutes in a forced hot air circulating constant temperature oven maintained at a temperature of 80 ° C. The length (L (mm)) after heating of the entered straight line was read with a scale, and the heat shrinkage rate was determined by the following formula.
Heat shrinkage rate (%) = (70−L) / 70 × 100

(Thickness direction retardation (Rth))
A 40 mm × 30 mm test piece was cut out from the stretched portion of the uniaxially stretched film. With respect to this test piece, an automatic birefringence meter (KOBRA-WR manufactured by Oji Scientific Co., Ltd.) was used, and the phase difference value at a wavelength of 590 nm and a tilt angle of 40 ° was measured at a temperature of 23 ± 2 ° C. and a humidity of 50 ± 5% did. Three-dimensional refractive indexes nx, ny, and nz were obtained from the obtained data, and thickness direction retardation Rth = ((nx + ny) / 2−nz) × d was calculated. The thickness d of the test piece was measured using a Digimatic Indicator (manufactured by Mitutoyo Corporation), and the refractive index n was measured using a digital precision refractometer (KPR New Optical Co., Ltd. KPR-20).

[Methacrylic resin]
(Production Example 1)
The inside of a 5 L glass reaction vessel equipped with a stirring blade and a three-way cock was replaced with nitrogen. To this, at room temperature, 1600 g of toluene, 2.49 g (10.8 mmol) of 1,1,4,7,10,10-hexamethyltriethylenetetramine, isobutylbis (2,6-dioxy) having a concentration of 0.45M. 5. 53.5 g (30.9 mmol) of a toluene solution of -t-butyl-4-methylphenoxy) aluminum and a solution of sec-butyllithium having a concentration of 1.3 M (solvent: cyclohexane 95%, n-hexane 5%) 17 g (10.3 mmol) was charged. While stirring, 550 g of distilled methyl methacrylate (MMA) was added dropwise at 20 ° C. over 30 minutes. After completion of dropping, the mixture was stirred at 20 ° C. for 90 minutes. The color of the solution changed from yellow to colorless. At this time, the polymerization conversion rate of methyl methacrylate (MMA) was 100%.
The obtained solution was diluted by adding 1500 g of toluene. Next, the obtained diluted solution was poured into 100 kg of methanol to obtain a precipitate. The obtained precipitate was dried at 80 ° C. and 140 Pa for 24 hours.

  By the above anionic polymerization method, the mass average molecular weight (Mw) is 81400, the molecular weight distribution (Mw / Mn) is 1.08, the content of the component having a molecular weight of 200000 or more (high molecular weight component) is 0.02%, The content of the component having a molecular weight of less than 15000 (low molecular weight component) is 0.19%, the syndiotacticity (rr) is 73%, the glass transition temperature (Tg) is 131 ° C., and the main dispersion peak temperature TαA is 136. The melt flow rate (MFR) measured at 230 ° C., 3.8 kg load, and 10 minutes is 0.9 g / 10 minutes, and the content of structural units derived from methyl methacrylate (MMA) ( Hereinafter, a methacrylic resin (X1-1) having a “MMA unit content” of 100% by mass was obtained.

  The methacrylic resin (X1-1) is a first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more.

  Table 1 shows the resin composition of the produced methacrylic resin (in this example, methacrylic resin (X1-1) alone) and various physical properties thereof.

(Production Example 2)
The inside of the autoclave equipped with the stirrer and the sampling tube was replaced with nitrogen. To this, 100 parts by weight of purified methyl methacrylate, 0.0052 parts by weight of 2,2′-azobis (2-methylpropionitrile (hydrogen abstraction capacity: 1%, 1 hour half-life temperature: 83 ° C.), and 0.225 parts by mass of n-octyl mercaptan was added and stirred to obtain a raw material liquid, and nitrogen was fed into the raw material liquid to remove dissolved oxygen in the raw material liquid.
The raw material liquid was put to 2/3 of the capacity in a tank reactor connected to the autoclave by piping. First, the polymerization reaction was started in a batch mode while maintaining the temperature at 140 ° C. When the polymerization conversion rate reaches 55% by mass, the raw material liquid is supplied from the autoclave to the tank reactor at a flow rate of an average residence time of 150 minutes, and the reaction liquid is supplied at a flow rate corresponding to the supply flow rate of the raw material liquid. It was extracted from the tank reactor, maintained at a temperature of 140 ° C., and switched to a continuous flow polymerization reaction. After switching, the polymerization conversion in the steady state was 55% by mass.
The reaction liquid withdrawn from the tank reactor in a steady state was heated by supplying it to a multi-tubular heat exchanger having an internal temperature of 230 ° C. at a flow rate with an average residence time of 2 minutes. Next, the heated reaction liquid was introduced into a flash evaporator, and volatile components mainly composed of unreacted monomers were removed to obtain a molten resin. The molten resin from which volatile components were removed was supplied to a twin-screw extruder having an internal temperature of 260 ° C., discharged into a strand, and cut with a pelletizer to obtain pellets.

  By the above high-temperature radical polymerization method, the mass average molecular weight (Mw) is 103600, the molecular weight distribution (Mw / Mn) is 1.81, and the content of the component having a molecular weight of 200000 or more (high molecular weight component) is 10.5%. The content of the component having a molecular weight of less than 15000 (low molecular weight component) is 2.28%, the syndiotacticity (rr) is 52%, the glass transition temperature (Tg) is 120 ° C., and the main dispersion peak temperature TαA is Content of structural unit derived from methyl methacrylate (MMA) at 125 ° C., melt flow rate (MFR) measured at 230 ° C., 3.8 kg load, 10 minutes, 1.4 g / 10 minutes A methacrylic resin (X2-1) having a (MMA unit content) of 100% by mass was obtained.

  The methacrylic resin (X2-1) is a second methacrylic resin (X2) having a syndiotacticity (rr) in a triplet display of 45 to 58%.

  Table 1 shows the resin composition of the produced methacrylic resin (in this example, methacrylic resin (X2-1) alone) and various physical properties thereof.

(Production Example 3)
57 parts by mass of the methacrylic resin (X1-1) obtained in Production Example 1 and 43 parts by mass of the methacrylic resin (X2-1) obtained in Production Example 2 were mixed with a twin-screw kneading extruder LABO PLASTOMILL 2D30W2 manufactured by Toyo Seiki. The mixture was biaxially kneaded under the conditions of a cylinder temperature of 240 ° C. and a screw rotation speed of 100 rpm.

  As described above, the mass average molecular weight (Mw) is 88600, the molecular weight distribution (Mw / Mn) is 1.32, the content of the component having a molecular weight of 200000 or more (high molecular weight component) is 4.50%, the molecular weight The content of the component (low molecular weight component) less than 15000 is 0.98%, the syndiotacticity (rr) is 62%, the glass transition temperature (Tg) is 126 ° C., and the main dispersion peak temperature TαA is 130 ° C. The melt flow rate (MFR) measured at 230 ° C. under a load of 3.8 kg for 10 minutes is 1.3 g / 10 minutes, and the content of structural units derived from methyl methacrylate (MMA) (MMA) A methacrylic resin (A-1) having a unit content of 100% by mass was obtained.

  The methacrylic resin (A-1) has a triplet display syndiotacticity (rr) of 58% or more, a weight average molecular weight (Mw) of 50,000 to 150,000, and a high molecular weight component content of 0.1. A methacrylic resin (A) having a content of 1 to 10% and a low molecular weight component of 0.2 to 5%.

  Table 1 shows the resin composition of the produced methacrylic resin (in this example, a blend of methacrylic resin (X1-1) and methacrylic resin (X2-1)) and various physical properties thereof.

[Vinyl acetal resin]
(Production Example 4)
A predetermined amount of butyraldehyde and acetaldehyde as aldehyde compounds are added to a 10% by mass aqueous solution of a vinyl alcohol resin (PVA, manufactured by Kuraray Co., Ltd.) having a viscosity average polymerization degree of 1000 and a saponification degree of 99 mol%, Acetalization reaction was performed by adding 220 ml of 20% hydrochloric acid as an acid catalyst to 100 g of PVA and stirring. After the resin was precipitated, the slurry was held at 30 ° C. for 60 minutes, and then the slurry containing the resin precipitate was taken out. The slurry was washed until the pH reached 6 by repeated charging into ion-exchanged water and filtration according to a known method, then suspended in an alkaline aqueous medium and stirred, and then washed until pH = 7. Then, the vinyl acetal resin (B-1) was obtained by drying until a volatile matter became 1.0%. Volatiles were determined by the mass before and after drying or by the Karl Fischer method.

The vinyl acetal resin (B-1) had a viscosity average polymerization degree of 1000 and a saponification degree of 99 mol%.
In the vinyl acetal resin (B-1), the molar ratio of butyl acetal units (BA units) to all repeating units was 29 mol%.
As for vinyl acetal resin (B-1), the molar ratio with respect to all the repeating units of an acetoacetal unit (AA unit) was 53 mol%.
The vinyl acetal resin (B-1) had a residual hydroxyl group (OH group) content of 17 mol% and an OAc group content of 1 mol%.
The vinyl acetal resin (B-1) had an alkali metal (Na) content of 39 ppm.
Table 2 shows main production conditions and various physical properties of the vinyl acetal resin (B-1).

(Production Example 5)
A vinyl acetal resin (B-2) was obtained in the same manner as in Production Example 4 except that the aldehyde used was only butyraldehyde and the amount used was changed.
Table 2 shows main production conditions and various physical properties of the vinyl acetal resin (B-2).

Example 1
Compounding 85 parts by weight of methacrylic resin (A-1) and 15 parts by weight of vinyl acetal resin (B-1), using Toyo Seiki's twin screw extruder LABO PLASTOMILL 2D30W2, conditions of cylinder temperature 240 ° C. and screw rotation speed 100 rpm A thermoplastic resin composition was obtained by biaxial melt kneading.
Table 3 shows the composition.

(Examples 2 to 4)
A thermoplastic resin composition was obtained in the same manner as in Example 1 except that the composition of the methacrylic resin (A) and the vinyl acetal resin (B) was as shown in Table 3.

(Comparative Example 1)
Without using the vinyl acetal resin (B), the methacrylic resin (A-1) was used for evaluation as it was.

(Comparative Example 2)
A thermoplastic resin composition was obtained in the same manner as in Example 1 except that the methacrylic resin (X2-1) was used instead of the methacrylic resin (A-1).

(Extrusion film formation and film stretching, and film evaluation)
About the thermoplastic resin composition or resin obtained in each Example and the comparative example, the following extrusion film forming and film stretching were implemented.
<Extrusion film formation>
After the thermoplastic resin composition or resin was dried at 80 ° C. for 12 hours, film formation was performed.
Using a GT-40 single screw extruder manufactured by Plastics Engineering Laboratory, the thermoplastic resin composition or resin was extruded from a 500 mm wide T die into a film at a resin temperature of 260 ° C., and 90 ° C. just below the T die. The unstretched film having a thickness of 400 μm was obtained by sandwiching and pulling with two metal mirror rolls adjusted in temperature at a pressing pressure of 50 N / mm.
<Film stretching>
A test piece of 50 mm × 40 mm was cut out from the unstretched film and set in a tensile tester (manufactured by Shimadzu Corporation, AG-IS 5 kN). The long side of the test piece was held with a pair of chucks. The distance between the pair of chucks was 20 mm. Stretching temperature is set to glass transition temperature (Tg) + 10 ° C., stretching is performed under the conditions of a stretching speed of 15% / min and a stretching ratio of 2 times in the tensile direction by a pair of chucks, and held for 10 seconds, then taken out at 25 ° C. This was cooled to room temperature, and a uniaxially stretched film having a stretched portion thickness of 200 μm was obtained.
In the present specification, “normal temperature” is defined as a temperature of 25 ± 5 ° C.
Further, since the portion gripped by the chuck and the vicinity thereof are not stretched or are not sufficiently stretched, the portion excluding this portion is defined as “stretched portion”. Unless otherwise specified, various parameter definitions for “stretched film” are for the stretched portion.

  In each Example and Comparative Example, various evaluations were performed on the stretched portions of the unstretched film and the uniaxially stretched film. The evaluation results are shown in Table 3.

(Evaluation results)
Examples 1 to 4 include a methacrylic resin (A) having a triplet display syndiotacticity (rr) of 58% or more and a vinyl acetal resin (B), and the methacrylic resin (A) and the vinyl acetal. The content of the methacrylic resin (A) is 95 parts by mass or more and more than 75 parts by mass, and the content of the vinyl acetal resin (B) is 5 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the total amount with the resin (B). The thermoplastic resin composition which is less than a mass part was manufactured.
As shown in Table 3, the unstretched films obtained in Examples 1 to 4 have high toughness (tensile elongation at break), high total light transmittance, low haze, and high surface smoothness. It was.
The unstretched films obtained in Examples 1 to 4 had a glass transition temperature (Tg) of 110 ° C. or higher and high heat resistance.
The stretched films obtained in Examples 1 to 4 had low heat shrinkage, high total light transmittance, and low haze.
The stretched films (thickness 200 μm) obtained in Examples 1 to 4 had a thickness direction retardation (Rth) in the range of −15 to 15 nm, and were suitable as a polarizer protective film or the like.

In Comparative Example 1, a film was formed using only the methacrylic resin (A).
The unstretched film obtained in Comparative Example 1 had low toughness (tensile elongation at break) as compared with Examples 1 to 4, and poor mechanical properties. The stretched film obtained in Comparative Example 1 had a poor heat shrinkage rate as compared with Examples 1 to 4, and was defective. Moreover, the stretched film obtained in Comparative Example 1 had a larger absolute value of retardation (Rth) in the film thickness direction than Examples 1 to 4, and was unsuitable for applications such as a polarizer protective film.

In Comparative Example 2, instead of the methacrylic resin (A), a second methacrylic resin (X2) having a triplet display syndiotacticity (rr) of 45 to 58% was used. A film was formed using the second methacrylic resin (X2) and the vinyl acetal resin (B).
The unstretched film obtained in Comparative Example 2 had a glass transition temperature (Tg) of less than 110 ° C. and poor heat resistance. The stretched film obtained in Comparative Example 2 had a large heat shrinkage compared to Examples 1 to 4, and was defective. Moreover, the stretched film obtained in Comparative Example 2 had a larger absolute value of retardation (Rth) in the film thickness direction than Examples 1 to 4, and was unsuitable for applications such as a polarizer protective film.

Claims (11)

A methacrylic resin (A) having a tridentate syndiotacticity (rr) of 58% or more, and a vinyl acetal resin (B),
The total amount of methacrylic resin (A) and vinyl acetal resin (B) is 100 parts by mass, the content of methacrylic resin (A) is 95 parts by mass or less and more than 75 parts by mass, and the vinyl acetal resin (B) The content is 5 parts by mass or more and less than 25 parts by mass,
Thermoplastic resin film. Methacrylic resin (A)
The weight average molecular weight is 50,000 to 150,000,
The content of the component having a molecular weight of 200,000 or more is 0.1 to 10%,
The content of components having a molecular weight of less than 15000 is 0.2 to 5%.
The thermoplastic resin film according to claim 1. Methacrylic resin (A)
A first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more, and a second triplet display syndiotacticity (rr) of 45 to 58%. A methacrylic resin (X2),
For the total amount of 100 parts by mass of the first methacrylic resin (X1) and the second methacrylic resin (X2),
The content of the first methacrylic resin (X1) is 40 to 70 parts by mass,
The content of the second methacrylic resin (X2) is a methacrylic resin having a content of 60 to 30 parts by mass.
The thermoplastic resin film according to claim 1. The methacrylic resin (A) has a content of structural units derived from methyl methacrylate of 99% by mass or more.
The thermoplastic resin film in any one of Claims 1-3. The methacrylic resin (A) has a melt flow rate of 0.1 to 10 g / 10 min measured at a temperature of 230 ° C. and a load of 3.8 kg.
The thermoplastic resin film in any one of Claims 1-4.   An optical film comprising the thermoplastic resin film according to claim 1.   A polarizer protective film comprising the thermoplastic resin film according to claim 1.   A retardation film comprising the thermoplastic resin film according to claim 1. A method for producing a thermoplastic resin film according to any one of claims 1 to 5,
A methacrylic resin (A) having a tridentate syndiotacticity (rr) of 58% or more, and a vinyl acetal resin (B),
The total amount of methacrylic resin (A) and vinyl acetal resin (B) is 100 parts by mass, the content of methacrylic resin (A) is 95 parts by mass or less and more than 75 parts by mass, and the vinyl acetal resin (B) Preparing a thermoplastic resin composition having a content of 5 parts by mass or more and less than 25 parts by mass;
Forming a film of the thermoplastic resin composition,
A method for producing a thermoplastic resin film. The methacrylic resin (A) contains one or more methacrylic resins,
Producing at least one methacrylic resin contained in the methacrylic resin (A) by an anionic polymerization method;
The method for producing a thermoplastic resin film according to claim 9. Methacrylic resin (A)
A first methacrylic resin (X1) having a triplet display syndiotacticity (rr) of 65% or more, and a second triplet display syndiotacticity (rr) of 45 to 58%. A methacrylic resin (X2),
The first methacrylic resin (X1) is produced by an anionic polymerization method,
Producing a second methacrylic resin (X2) by radical polymerization;
The method for producing a thermoplastic resin film according to claim 9 or 10.