JP6220293B2 - Optical film, polarizer protective film, polarizing plate, and image display device - Google Patents

Description

  The present invention relates to a thermoplastic resin composition. Moreover, this invention relates to the optical film comprised from a thermoplastic resin composition, a polarizer protective film provided with the said optical film, a polarizing plate, and an image display apparatus.

  As a thermoplastic resin used for the optical film, an acrylic resin having a ring structure in the main chain is known. For example, Patent Document 1 (Japanese Patent Laid-Open No. 2010-72135) discloses at least one ring structure selected from a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure. An acrylic resin having a main chain and an optical film composed of a thermoplastic resin composition containing the resin are disclosed. Patent Document 1 describes that the heat resistance of the optical film can be improved by introducing a ring structure into the main chain of the acrylic resin.

  It is known that the introduction of a ring structure into the main chain of an acrylic resin can control not only the heat resistance but also the optical properties of the optical film. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 6-25359) requires the existence of a structural unit derived from benzyl methacrylate or methyl benzyl methacrylate, but the coexistence of methyl methacrylate and a specific maleimide monomer. A low birefringence methacrylic molding material obtained by polymerization is disclosed. Patent Document 3 (International Publication No. 2011/149088) contains a repeating unit derived from a specific methacrylate monomer and two repeating units derived from a specific N-substituted maleimide monomer. “Acrylic thermoplastic resins are disclosed in which the birefringence (birefringence and photoelastic coefficient), which is an optical property, is highly controlled” (paragraphs 0016 and 0019).

JP 2010-72135 A JP-A-6-25359 International Publication No. 2011/149088

  The optical film is formed by, for example, melt molding of a thermoplastic resin composition, and the film forming property (film moldability) of the resin composition at that time is industrial production of the optical film, typically mass production. It is very important when considering gender. However, in each patent document mentioned above, the film forming property of the resin composition is not considered at all. In addition, Patent Document 1 describes that by introducing a ring structure into the main chain of the acrylic resin, the obtained film is hardened and easily breaks due to bending. The “hardness” of the resin composition molded body and the film forming property at the time of melt molding of the resin composition do not have a direct correspondence relationship. In addition, Patent Document 2 discloses a molding material used for a bulk molded body such as a lens, but there is no description about the film in the first place.

  One of the objects of the present invention is to provide a thermoplastic resin composition comprising an acrylic thermoplastic resin having a ring structure in the main chain, and having excellent film forming properties (film moldability). is there.

The thermoplastic resin composition of the present invention comprises: a structural unit (A) derived from an N-substituted maleimide monomer represented by the following formula (1), and a (meth) acrylate monomer represented by the following formula (2): , At least one monomer selected from a carboxylic acid vinyl ester monomer (carboxylic acid having 4 to 12 carbon atoms) and a maleic acid dialkyl ester monomer (alkyl group having 4 to 8 carbon atoms), The structural unit (B) derived from the monomer (M) having a glass transition temperature (Tg) of 20 ° C. or less when it is a homopolymer, and a (meth) acrylate monomer (the monomer (M) A structural unit (C) derived from a certain (meth) acrylate monomer), and a thermoplastic resin (D) having a Tg of 115 ° C. or higher and lower than 130 ° C .; a melt flow rate (MFR) 7.5-50 [g / 10 min In it, the thermal decomposition temperature (Td) is 300 ° C. or higher. In Formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and X is an alkyl group having 3 to 12 carbon atoms. A cycloalkyl group or an aryl group having 6 to 14 carbon atoms. In formula (2), R ³ is a hydrogen atom or a methyl group, when R ³ is a hydrogen atom R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, R ⁴ when R ³ is a methyl group the carbon It is a hydrocarbon group of formula 4-12.

  The optical film of the present invention is a film obtained by melt molding the thermoplastic resin composition of the present invention.

  The polarizer protective film of the present invention includes the optical film of the present invention.

  The polarizing plate of the present invention includes a polarizer and the polarizer protective film of the present invention.

  The image display device of the present invention includes the optical film of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, it is a thermoplastic resin composition containing the acrylic thermoplastic resin which has a ring structure in a principal chain, Comprising: The thermoplastic resin composition excellent in film forming property (film moldability) is provided. Thereby, for example, industrial manufacturability of a film such as an optical film composed of the resin composition, typically mass productivity, is increased.

The thermoplastic resin composition (E) of the present invention includes: a structural unit (A) derived from an N-substituted maleimide monomer represented by the following formula (1); and a (meth) acrylate represented by the following formula (2): And at least one monomer selected from a monomer, a carboxylic acid vinyl ester monomer (carboxylic acid having 4 to 12 carbon atoms), and a maleic acid dialkyl ester monomer (alkyl group having 4 to 8 carbon atoms). A structural unit (B) derived from a monomer (M) having a Tg of 20 ° C. or less when a homopolymer is obtained; and a (meth) acrylate monomer (a monomer (M) (meth) And a thermoplastic resin (D) having a structural unit (C) derived from (excluding an acrylate monomer). In Formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and X is an alkyl group having 3 to 12 carbon atoms. A cycloalkyl group or an aryl group having 6 to 14 carbon atoms. In formula (2), R ³ is a hydrogen atom or a methyl group, when R ³ is a hydrogen atom R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, R ⁴ when R ³ is a methyl group the carbon It is a hydrocarbon group of formula 4-12.

  The resin composition (E) has a Tg of 115 ° C. or higher and lower than 130 ° C., a melt flow rate (MFR) value of 7.5 to 50 [g / 10 minutes], and a thermal decomposition start temperature (Td) of 300. It is above ℃.

  When the resin (D) contains the structural unit (A) derived from the monomer represented by the formula (1), the resin (D) and the resin composition (E) have a high Tg of 115 ° C. or higher, and the resin The heat resistance of (D), the resin composition (E) and a molded article obtained by molding the composition (E), for example, an optical film, is improved.

  However, if the Tg of the resin (D) and the resin composition (E) is simply increased by introducing the structural unit (A), the film forming property of the composition (E) becomes insufficient. The specific factors are the increase in Tg due to the introduction of the structural unit (A), the decrease in fluidity during film formation that can be expressed by MFR, and the variation in the thermal decomposition start temperature (Td). The present inventors have found that the balance is lost.

  In this invention, Tg of a resin composition (E) shall be 115 degreeC or more and less than 130 degreeC. Although the Tg of 115 ° C. or more and less than 130 ° C. can be achieved by introducing the structural unit (A), the MFR of the resin (D) and the resin composition (E) is decreased by the introduction. Patent Document 1 mentions several types of ring structures including a lactone ring structure as ring structures capable of increasing the Tg of acrylic thermoplastic resins, but the ring structure (N-substituted) of the structural unit (A) is mentioned. The maleimide structure) has a particularly strong effect of lowering the MFR of an acrylic resin having the ring structure in the main chain. Moreover, Td of resin (D) and a resin composition (E) changes with introduction | transduction of a structural unit (A). When Tg increases, it is necessary to increase the film forming temperature when forming the resin composition (E) into a film. However, when the decrease in MFR relative to Td increases due to the introduction of the structural unit (A), Film formation at such a high film formation temperature becomes difficult.

  Considering these, in the present invention, the Td of the resin composition is set to 300 ° C. or higher, and the MFR value is set to 7.5 [g / 10 minutes] or higher. The resin composition (E) having such Tg, MFR and Td is excellent in balance among these three components from the viewpoint of film forming property. That is, the resin composition (E) is a resin composition containing an acrylic thermoplastic resin (D) having a ring structure in the main chain, and is excellent in film formability (film moldability).

[Structural unit (A)]
The structural unit (A) is a structural unit (N-substituted maleimide unit) derived from the N-substituted maleimide monomer represented by the above formula (1) (formed by polymerization of the monomer). In Formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and X is an alkyl group having 3 to 12 carbon atoms. A cycloalkyl group or an aryl group having 6 to 14 carbon atoms. R ¹ and R ² are preferably each independently a hydrogen atom, a methyl group, a benzyl group or a phenyl group, more preferably a hydrogen atom. X is a cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, phenyl group, chlorophenyl group, methylphenyl group, naphthylphenyl group, hydroxyphenyl group, methoxyphenyl group, nitrophenyl group, A carboxylphenyl group and a tribromophenyl group are preferable, and a cyclohexyl group, a phenyl group, and a benzyl group are more preferable.

  In the case where X is an aryl group, the structural unit (A) is, for example, N-phenylmaleimide, N-chlorophenylmaleimide, N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenyl. It is a structural unit derived from each monomer of maleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide, and N-tribromophenylmaleimide.

  In the case where X is a cycloalkyl group, the structural unit (A) is derived from, for example, each monomer of N-cyclohexylmaleimide, N-cyclopropylmaleimide, N-cyclobutylmaleimide, and N-cyclopentylmaleimide. It is.

  The structural unit (A) includes at least one monomer selected from N-phenylmaleimide, N-cyclohexylmaleimide, N-naphthylmaleimide, and N-tribromophenylmaleimide from the viewpoints of price, availability, and heat resistance. The structural unit derived from is preferable, and the structural unit derived from at least one monomer selected from N-phenylmaleimide and N-cyclohexylmaleimide is more preferable.

[Structural unit (B)]
In the resin composition (E), one of the factors that achieves an excellent balance of Tg, MFR and Td from the viewpoint of film forming property is the structural unit (B). The structural unit (B) is at least one monomer selected from a (meth) acrylate monomer, a carboxylic acid vinyl ester monomer, and a maleic acid dialkyl ester monomer represented by the above formula (2). , A structural unit derived from the monomer (M) having a glass transition temperature (Tg) of 20 ° C. or lower when formed as a homopolymer (formed by polymerization of the monomer). The Tg of a homopolymer (homopolymer) can be confirmed, for example, by literature such as “Polymer Handbook Fourth Edition” by J. Brandrup.

In the (meth) acrylate monomer represented by the formula (2), R ³ is a hydrogen atom or a methyl group, and when R ³ is a hydrogen atom, R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, R ³ When is a methyl group, R ⁴ is a hydrocarbon group having 4 to 12 carbon atoms. Regarding the carboxylic acid vinyl ester monomer, the carbon number of the carboxylic acid portion (the portion derived from the carboxylic acid used in the esterification reaction with the vinyl compound during formation of the carboxylic acid vinyl ester) is 4 to 12. For the maleic acid dialkyl ester monomer, the alkyl group has 4 to 8 carbon atoms.

  The monomer (M) from which the structural unit (B) is derived has a very low Tg compared to a resin generally used for an optical member, such as PMMA, when a homopolymer is formed. Specifically, the Tg of the homopolymer of monomer (M) is 20 ° C. or less. By having the structural unit (B) derived from a monomer that exhibits a low Tg when forming a homopolymer (hereinafter, also simply referred to as “low Tg monomer”), the resin (D) and The film forming property of the resin composition (E) is improved. One of the factors is that the structural unit (B) derived from the low Tg monomer exhibits an action similar to that of a plasticizer. However, with a normal plasticizer, only the fluidity of the resin is improved, but in the case of the structural unit (B), the balance between the Tg, MFR and Td of the resin having the structural unit (A) is improved. Further advantageous effects are realized. In this respect, the structural unit (B) and the mere plasticizer are greatly different.

  Paying attention to the point that the structural unit (B) is derived from a low Tg monomer, the resin composition (E) is a single unit that exhibits a Tg of 20 ° C. or lower when the homopolymer is formed with the structural unit (A). A thermoplastic resin (D) having a structural unit derived from a body and a structural unit (C) derived from a (meth) acrylate monomer (excluding the monomer having a Tg of 20 ° C. or lower). , Tg is 115 ° C. or more and less than 130 ° C., MFR is 7.5 [g / 10 minutes] or more and 50 [g / 10 minutes] or less, and Td is 300 ° C. or more.

For the illustrated (meth) acrylate monomer formula (2), the upper limit of the carbon number of R ⁴ is 12, preferably 10, 8 is more preferable.

The hydrocarbon group for R ⁴ is, for example, an alkyl group, a cycloalkyl group, a benzyl group, or a phenyl group. The hydrogen atom of each hydrocarbon group may be substituted with a halogen atom such as a chlorine atom.

The monomer (M) (meth) acrylate monomer is an acrylic ester (R ³ is a hydrogen atom), for example, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate. Hexyl acrylate, cyclohexyl acrylate, benzyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and methacrylic acid ester (R ³ is methyl group). For example, butyl methacrylate, pentyl methacrylate Hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate. Resin composition (E) having high copolymerization reactivity with the N-substituted maleimide monomer represented by formula (1) and less influence of coloring on resin (D) and resin composition (E) The (meth) acrylate monomer that is the monomer (M) is composed of methyl acrylate (MA) and methacrylic acid from the viewpoint that there is little influence on the retardation when a retardation film is formed using At least one selected from butyl (BMA) is preferred. The Tg of the homopolymer of methyl acrylate is 5 ° C., and the Tg of the homopolymer of butyl methacrylate is 20 ° C.

  The monomer (M) carboxylic acid vinyl ester monomer (having 4 to 12 carbon atoms) is not particularly limited, and examples thereof include vinyl isobutyrate, vinyl 2-ethylhexanoate, vinyl propionate, vinyl isooctanoate and versatic. The vinyl acid is preferably at least one selected from vinyl isobutyrate and vinyl 2-ethylhexanoate.

  The maleic acid dialkyl ester monomer (alkyl group having 4 to 8 carbon atoms) as the monomer (M) is not particularly limited, and examples thereof include dibutyl maleate and dioctyl maleate.

  The structural unit (B) is a (meth) acrylate monomer represented by formula (2) because of its high copolymerization reactivity with the N-substituted maleimide monomer represented by formula (1), and is a homopolymer. It is preferable that it is a structural unit derived from the monomer whose Tg is 20 degrees C or less.

[Structural unit (C)]
The structural unit (C) is a structural unit derived from a (meth) acrylate monomer. However, the said monomer excludes the (meth) acrylate monomer which is a monomer (M). More specifically, in the formula (2), when R ³ is a hydrogen atom or a methyl group, R ³ is a hydrogen atom, R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, and R ³ is methyl. In the case of a group, R ⁴ is a (meth) acrylate monomer which is a hydrocarbon group having 4 to 12 carbon atoms, and excludes the monomer having a Tg of 20 ° C. or less when it is a homopolymer. From the viewpoint of the Tg of the homopolymer described above, the structural unit (C) is a (meth) acrylate monomer having a Tg of more than 20 ° C., preferably 50 ° C. or more, more preferably 80 ° C. or more. A structural unit derived from the body.

  The structural unit (C) is, for example, a structural unit derived from each monomer of methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, and benzyl methacrylate, and a structural unit derived from MMA. (MMA unit) is preferred. In this case, the resin (D) having the structural unit (C), the resin composition (E) containing the resin (D), and the optical transparency of the molded product obtained by molding the composition (E) and The mechanical properties are enhanced, and a Tg of 115 ° C. or higher can be achieved with a content of the structural unit (A) that is smaller than that of the other structural unit (C), so that the above-described balance is more reliably ensured.

  In addition, since the MMA unit is weak, it has a function of giving negative intrinsic birefringence to the resin (D). Therefore, the structural unit (A) has a function of giving positive intrinsic birefringence to the resin (D). The resin (D) and the resin composition (E) exhibiting optical isotropy can be realized by canceling the action. A structural unit having an action of giving negative (or positive) intrinsic birefringence to a resin means that when the homopolymer of the unit is formed, the intrinsic birefringence of the formed homopolymer becomes negative (or positive). A structural unit.

[Thermoplastic resin (D)]
A thermoplastic resin (D) has a structural unit (A), a structural unit (B), and a structural unit (C) as a structural unit which comprises the said resin. The resin (D) has two or more structural units (A) or two or more structural units (B) or two or more structural units (C). It may be. The resin (D) preferably has one type of structural unit (C) from the viewpoint of ensuring the above-mentioned balance between the three properties relating to film forming properties more reliably. At this time, the structural unit (C) is in MMA units. More preferably.

  10 mass% or more and 40 mass% or less are preferable, as for the content rate of the structural unit (A) in resin (D), 12 mass% or more and 35 mass% or less are more preferable, and 15 mass% or more and 30 mass% or less are more preferable. 5 mass% or more and 40 mass% or less are preferable, as for the content rate of the structural unit (B) in resin (D), 8 mass% or more and 30 mass% or less are more preferable, and 8 mass% or more and 20 mass% or less are more preferable. 20 mass% or more and 85 mass% or less are preferable, as for the content rate of the structural unit (C) in resin (D), 35 mass% or more and 80 mass% or less are more preferable, and 50 mass% or more and 77 mass% or less are more preferable. Within these ranges, the balance between the above three factors relating to the film-forming property can be ensured more reliably, and the resin composition (E) having a better film-forming property can be obtained.

  Depending on the content of the structural unit (C) and the type and content of the structural unit (B), the content of the (meth) acrylate unit in the resin (D) is 30% by mass or more. At this time, the resin (D) is an acrylic resin. When the resin (D) is an acrylic resin, the content of the (meth) acrylate unit in the resin (D) is preferably 50% by mass or more.

  Regarding the resin (D), the ratio MFR / Td (unit: g / (10 minutes · ° C.)) of the melt flow rate (MFR) to the thermal decomposition starting temperature (Td) is preferably 0.023 or more. It is more preferably 040 or more, and further preferably 0.050 or more. Even when the Td of the resin (D) can be achieved at 300 ° C. or higher, if the MFR value is relatively lowered, the film forming property of the resin composition (E) is lowered. By setting the ratio MFR / Td to 0.023 or more for the resin (D), the balance between the above three factors relating to the film-forming property is more surely secured, and the resin composition (E) is more excellent in film-forming property. Can do. The ratio MFR / Td of 0.023 or more is preferable for the resin composition (E) containing the resin (D).

  For the resin (D), the ratio MFR / Tg (unit: g / (10 minutes · ° C.)) of the MFR to the glass transition temperature (Tg) is preferably 0.080 or more, and more preferably 0.100 or more. More preferably, it is more preferably 0.120 or more. Tg and MFR are not simply inversely related. Tg is a thermal characteristic of the resin (D) related to a required film forming temperature. By setting the ratio MFR / Tg to 0.080 or more for the resin (D), the balance between the above three factors relating to the film-forming property is more reliably ensured, and the resin composition (E) is more excellent in film-forming property. Can do. The ratio MFR / Tg of 0.080 or more is also preferable for the resin composition (E) containing the resin (D).

  The Tg of the resin (D) is 115 ° C. or higher and lower than 130 ° C., preferably 118 ° C. or higher and 128 ° C. or lower, more preferably 118 ° C. or higher and 125 ° C. or lower. In this case, the balance between the three factors relating to the film forming property is more reliably ensured. Moreover, when Tg is less than 115 degreeC, heat resistance of molded objects, such as an optical film comprised from the resin composition (E) containing resin (D), is insufficient. On the other hand, when Tg is 130 ° C. or higher, the introduction of the structural unit (A) tends to strongly lower the fracture energy E described later for the resin (D) and the resin composition (E). For example, the resin composition (E When the film is formed, the handling property is lowered, for example, the film is likely to be broken during line transportation or stretching after the film formation. The range of these preferable Tg is the same also about the resin composition (E) containing resin (D). Tg is a value evaluated by the method described later in the examples.

  The MFR (unit: g / 10 minutes) of the resin (D) is 7.5 or more and 50 or less. If the MFR is less than 7.5, sufficient fluidity during film formation cannot be ensured. On the other hand, if the MFR exceeds 50, the shape of the resin composition (E) cannot be maintained during melt molding, and film formation becomes difficult. The upper limit of MFR is preferably 40 or less, more preferably 30 or less, and particularly preferably 20 or less. The lower limit of MRF is preferably 10 or more. The range of these preferable MFR is the same also about the resin composition (E) containing resin (D). MFR is a value evaluated at a temperature of 240 ° C. and a load of 98 N (10 kgf) in accordance with JIS K7210 B method, as will be described later in Examples.

  The Td of the resin (D) is 300 ° C. or higher. When Td is less than 300 ° C., the resin composition (E) is likely to thermally decompose and foam during film formation, and these phenomena are obtained by molding the composition (E), for example. This leads to poor appearance in molded articles such as optical films. Td is preferably 300 ° C. or higher and lower than 370 ° C., more preferably 310 ° C. or higher and lower than 360 ° C., and further preferably 315 ° C. or higher and lower than 350 ° C. In these cases, the balance between the above three factors relating to film forming properties is more reliably ensured. The preferable range of Td is the same for the resin composition (E) containing the resin (D). Td is a value evaluated by the method described later in the examples.

  According to the present invention, the breaking energy E of the resin (D) and the resin composition (E) (breaking energy E when an unstretched film having a thickness of 100 μm) is equal in content of the structural unit (A). Therefore, it can be improved as compared with a conventional thermoplastic resin having no structural unit (B). Although the specific value of the fracture energy E is not limited, it is 4.5 mJ or more, for example, and can also be 7.0 mJ or more, 8.0 mJ or more, or 8.5 mJ or more. The fracture energy E is a value evaluated by the method described later in the examples.

According to the present invention, even when the stress optical coefficient (Cr) of the resin (D) and the resin composition (E) is reduced and the optical film is a stretched film, the optical isotropy is ensured. Can do. Cr (unit: × 10 ^-9 Pa ^-1 ) is, for example, from -0.14 to 0.14, preferably from -0.12 to 0.12, and preferably from -0.11 to 0.11. More preferred. Cr is a value evaluated by the method described later in the examples.

According to the present invention, the photoelastic coefficient (Cd) of the resin (D) and the resin composition (E) can be reduced, and the fluctuation of birefringence with respect to the stress as the optical film can be reduced. Cd (unit: × 10 ⁻¹² Pa ⁻¹ ) is, for example, 0 or more and 4.5 or less, preferably 0 or more and 4.4 or less, and more preferably 0 or more and 4.3 or less. Cd is a value evaluated by the method described later in the examples.

  As long as the effects of the present invention are obtained, the resin (D) may have a structural unit other than the structural units (A), (B), and (C). Examples of the structural unit include styrene, vinyltoluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, 4-methyl- It is a structural unit derived from each monomer of 1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, and N-vinyl carbazole.

  The weight molecular weight (Mw) of the resin (D) is preferably 100,000 or more and 400,000 or less, more preferably 180,000 or more and 300,000 or less. In this case, Tg and MFR can be adjusted to a preferable range at the same time, and the balance between the above three factors relating to the film-forming property is more reliably ensured, and the resin composition (E) having a better film-forming property can be obtained. Further, the breaking energy E of the resin (D) and the resin composition (E) can be adjusted to a preferable range.

  The formation method of resin (D) is not specifically limited. For example, an N-substituted maleimide monomer represented by the formula (1) that becomes a structural unit (A) by polymerization, a monomer that becomes a structural unit (B) by polymerization, and a structural unit (C) by polymerization ( A monomer group containing a (meth) acrylate monomer can be polymerized by various polymerization methods such as solution polymerization to form the resin (D). The polymerization may be performed according to a known method.

[Resin composition (E)]
The structure of the resin composition (E) other than the above will be described.

  Resin composition (E) contains resin (D). The resin composition (E) may contain two or more kinds of resins (D). The content rate of resin (D) in a resin composition (E) is 70 mass% or more normally, Preferably it is 80 mass% or more, More preferably, it is 90 mass% or more. Resin composition (E) may contain only resin (D) as resin, and may consist of resin (D).

  As long as the effect of this invention is acquired, the resin composition (E) can contain the further thermoplastic resins other than resin (D). However, when the molded product obtained by molding the resin composition (E) is used for optical applications such as an optical film, the compatibility between the resin (D) and the further resin is required in order to ensure necessary optical properties. It is necessary to pay attention to.

  Examples of the additional resin include olefin resins such as polyethylene, polypropylene, ethylene-propylene polymer, and poly (4-methyl-1-pentene); halogen-containing resins such as vinyl chloride and chlorinated vinyl resins; polyethylene terephthalate, poly Polyesters such as butylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetals; polycarbonates; polyphenylene oxides; polyphenylene sulfides; polyether ether ketones; Imide; a rubbery polymer. The resin composition (E) may contain two or more of these resins. The content of these resins in the resin composition (E) is preferably 10% by mass or less, more preferably 5% by mass or less.

  As long as the effect of this invention is acquired, resin composition (E) can contain materials other than a thermoplastic resin, for example, an additive. Additives include, for example, ultraviolet absorbers (UVA); stabilizers such as antioxidants, light stabilizers, weathering stabilizers, heat stabilizers; phase increase agents, phase difference reducers, phase difference stabilizers, etc. Phase difference adjusting agent; Reinforcing materials such as glass fiber and carbon fiber; Near infrared absorbing agent; Flame retardant such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; anionic, cationic and nonionic surfactants Including antistatic agents; coloring agents such as inorganic pigments, organic pigments, dyes; organic fillers, inorganic fillers, resin modifiers, plasticizers, lubricants. The content of additives (excluding UVA) in the resin composition (E) is preferably 5% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less.

  In the present invention, for example, the film forming temperature of the composition (E) can be lowered from the high film forming property of the resin composition (E). For this reason, even when the resin composition (E) contains UVA, scattering of UVA during film formation can be suppressed. If UVA is scattered at the time of film formation, the ultraviolet absorption ability as designed cannot be obtained, or the film forming apparatus (melt molding apparatus) is contaminated by UVA.

  UVA is not limited as long as it is a substance that has ultraviolet absorbing ability and is compatible with resin (D). It is preferable that UVA does not contain a repeating unit derived from a monomer (that is, it is not a polymer). In general, it is difficult to ensure compatibility with the resin (D) for the ultraviolet absorber that is a polymer, and depending on additives such as a polymerization initiator remaining in the polymer, the resin composition (E) and the composition Coloring may occur in a molded product obtained by further molding the product (E).

  As UVA, for example, at least one selected from a benzophenone compound, a silicate compound, a benzoate compound, a triazole compound, and a triazine compound can be used. Of these, UVA, which is a triazole compound and a triazine compound, is preferable because of its high ultraviolet absorption ability.

  Triazole compounds include, for example, 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3 5-Di-t-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl)- 4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-t-butylphenol, 2- [5-chloro (2H) -benzotriazole-2 -Yl] -4-methyl-6- (t-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-t-butylphenol, 2- (2H-ben Triazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6- (3,4,5, 6-tetrahydrophthalimidylmethyl) phenol, methyl-3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction product, 2 -(2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy- 3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-benzotriazol-2-yl) -5 (1,1-dimethylethyl) -4-hydroxy -C7-9-side and straight chain alkyl esters,. A triazole compound having a halogen atom, such as a chlorine atom, is preferred because of its high ultraviolet absorption ability.

  Examples of triazine compounds include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-ethoxy). Phenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-butoxy) Phenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy) -4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-triazine, , 4-Diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl) -1,3 , 5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3,5-triazine, 2,4-bis (2-hydroxy-4-butoxyphenyl) -6 (2,4-dibutoxyphenyl) -1,3-5-triazine, 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine, 2 , 4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-alkyloxy-2-hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (a Rukyloxy; UVA having a long-chain alkyloxy group such as octyloxy, nonyloxy, decyloxy). Among these, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-) has high compatibility with the resin (D) and excellent ultraviolet absorption performance. UVA having an alkyloxy-2-hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (alkyloxy; long-chain alkyloxy groups such as octyloxy, nonyloxy, decyloxy, etc.) is preferred.

  The molecular weight of UVA is not particularly limited, but is preferably 600 or more. The upper limit of the molecular weight of UVA is, for example, 10,000. When the molecular weight of UVA becomes excessively large, the compatibility with the resin (D) decreases, and the optical transparency of the resin composition (E) and a molded product obtained by molding the composition (E) decreases. . The upper limit of the molecular weight of UVA is preferably 8000, more preferably 5000.

  UVA may be a commercially available substance, such as ADK STAB LA-31, LA-F70 (manufactured by ADEKA), Tinuvin 1577, Tinuvin 460, Tinuvin 477 (manufactured by BASF Japan).

The UVA absorption ability of UVA is 10,000 (L · mol ⁻¹ · cm ⁻¹ ) in terms of a molar extinction coefficient (chloroform solution) for light having a wavelength within the wavelength range of 300 to 380 nm and maximum absorption by UVA. The above is preferable.

  UVA may be a mixture of two or more compounds.

  When the resin composition (E) contains UVA, the UVA content in the composition (E) is 100 parts by mass of the thermoplastic resin including the resin (D) contained in the resin composition (E). On the other hand, it is 0.1-5 mass parts, for example, 0.5-5 mass parts is preferable, and 0.7-3 mass parts, 1-3 mass parts, and 1-2 mass parts are more preferable. If the UVA content is excessively small, the desired ultraviolet absorbing ability cannot be obtained. On the other hand, when the UVA content is excessively large, the disadvantage of foaming or bleeding out during molding of the resin composition is greater than the advantage of obtaining ultraviolet absorption ability.

  The formation method of a resin composition (E) is not specifically limited. Additives such as UVA can be added to the resin composition (E) at any time and by any method. For example, the resin composition (E) may be formed by melt-kneading the resin (D) and the additive.

  When the resin composition (E) does not contain any material other than the resin (D), the resin (D) is the resin composition (E).

[Molded body]
The use of a molded body obtained by molding the resin composition (E), typically a molded body (melt molded body) obtained by melt molding is not limited, and is an optical member, for example. An example is an optical film such as a polarizer protective film.

  The optical film of the present invention is a film obtained by melt-molding the resin composition (E). The method for forming the optical film of the present invention is not particularly limited as long as the resin composition (E) is melt-molded. The melt molding of the resin composition (E) can be performed by a known method, for example, melt extrusion molding using a melt extruder and a die. At that time, a polymer filter may be used in combination.

  The optical film of the present invention has heat resistance based on the high Tg of the resin composition (E). Such an optical film having heat resistance is suitable for use in an image display device such as a liquid crystal display device (LCD) having a structure in which heating elements such as a light source, a power source, and a circuit board are integrated in a narrow space. is there. The Tg of the optical film of the present invention is, for example, 115 ° C. or higher and lower than 130 ° C., preferably 118 ° C. or higher and 128 ° C. or lower, more preferably 118 ° C. or higher and 125 ° C. or lower.

  The optical film of the present invention can be a film showing optical isotropy. The in-plane retardation Re and the absolute value | Rth | of the thickness direction retardation Rth of the optical film of the present invention (respectively, the retardation per film thickness of 100 μm with respect to light having a wavelength of 590 nm) is, for example, 10 nm or less. It can be 5 nm or less, and further 3 nm or less.

  The optical film of the present invention may be a stretched film such as a uniaxially stretched film or a biaxially stretched film. From the viewpoint of ensuring optical isotropy more reliably and increasing the flexibility of the optical film, a biaxially stretched film is preferable. The optical film which is a stretched film can be formed by stretching an unstretched film (original film) obtained by melt molding the resin composition (E) by a known method. Biaxial stretching may be either sequential biaxial stretching or simultaneous biaxial stretching.

  The thickness of the optical film of the present invention is, for example, 1 to 250 μm, preferably 10 to 100 μm, and more preferably 20 to 60 μm.

  The optical film of this invention can be used as a polarizer protective film which protects a polarizer, for example. The polarizer protective film of the present invention includes at least one optical film of the present invention. When used as a polarizer protective film, the optical film of the present invention is preferably a biaxially stretched film, and is preferably a film exhibiting optical isotropy.

  The polarizing plate of the present invention includes a polarizer and the polarizer protective film of the present invention. The polarizing plate of the present invention has, for example, a structure in which the polarizer protective film of the present invention is bonded to one side or both sides of the polarizer.

  The polarizer is not particularly limited. For example, a polarizer obtained by dyeing and stretching a polyvinyl alcohol film; a polyene polarizer such as dehydrated polyvinyl alcohol or dehydrochlorinated polyvinyl chloride; a multilayer laminate or a cholesteric liquid crystal Reflective polarizer used: a known polarizer such as a polarizer made of a thin film crystal film. Among these, a polarizer obtained by dyeing and stretching polyvinyl alcohol is preferable.

  A typical example of the structure of the polarizing plate of the present invention is that the polarizer is protected on one or both sides of a polarizer obtained by uniaxially stretching after dying a polyvinyl alcohol with a dichroic substance such as iodine or a dichroic dye. The film has a structure in which the optical film of the present invention is bonded.

  The structure of the image display device of the present invention is not particularly limited as long as it includes the optical film of the present invention. The image display device of the present invention is, for example, an LCD, and the image display unit of the LCD device includes the optical film of the present invention together with members such as a liquid crystal cell, a polarizing plate, and a backlight. The image display device of the present invention typically includes the optical film of the present invention as a polarizer protective film constituting a polarizing plate. The image display mode of the LCD is not particularly limited and is, for example, a VA mode, an IPS mode, or an OCB mode.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

  Initially, the evaluation method of the thermoplastic resin composition produced in a present Example is shown.

[Weight average molecular weight and number average molecular weight]
The weight average molecular weight Mw and the number average molecular weight Mn of the thermoplastic resin composition were determined in terms of polystyrene using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.
System: Tosoh GPC system HLC-8220
Measurement side column configuration:
Guard column (manufactured by Tosoh, TSK guard column Super HZ-L)
・ Two separation columns (manufactured by Tosoh, TSKgel SuperHZM-M) in series connection Reference side column configuration:
・ Reference column (manufactured by Tosoh Corporation, TSKgel SuperH-RC)
Developing solvent: Chloroform (Wako Pure Chemical Industries, special grade)
Flow rate of developing solvent: 0.6 mL / min Standard sample: TSK standard polystyrene (manufactured by Tosoh, PS-oligomer kit)
Column temperature: 40 ° C

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

[Pyrolysis start temperature (Td)]
The thermal decomposition start temperature (Td) of the thermoplastic resin composition was determined from dynamic TG measurement for the composition. Specifically, it is as follows. Using a differential type differential thermal balance device (Rigaku, Thermo Plus2 TG-8120), a 10 mg sample was heated from room temperature to 500 ° C. in a nitrogen gas atmosphere. At this time, when the sample mass reduction rate is 0.005% by mass / second or less, the rate of temperature increase is 10 ° C./min. When the sample mass decrease rate during temperature increase exceeds 0.005% by mass / second The temperature was increased by using stepwise isothermal control so that the speed was maintained at 0.005 mass% / second or less. The temperature at which stepwise isothermal control was first performed in order to maintain the mass reduction rate (the lowest temperature at which stepwise isothermal control was performed) was defined as Td of the resin composition.

[Melt flow rate (MFR)]
The melt flow rate (MFR) of the thermoplastic resin composition was evaluated at a temperature of 240 ° C. and a load of 98 N (10 kgf) in accordance with JIS K7210 B method.

[Stress optical coefficient (Cr)]
The stress optical coefficient (Cr) of the thermoplastic resin composition was determined as follows. First, the thermoplastic resin composition was melt-extruded to obtain a film (unstretched film) having a thickness of 100 μm. Next, the film is cut into a 60 mm × 20 mm rectangle to form a test piece, and when the film is attached to the film, a weight is selected so that a stress of 1 N / mm ² or less is applied to the film. Attached to one of the short sides of the piece. Next, the whole was stored in a constant temperature dryer (manufactured by ASONE, DOV-450A) maintained at Tg + 3 ° C. of the resin composition, and left for 30 minutes. When storing in the dryer, use a chuck to fix one side of the test piece that is opposite to the side to which the weight is attached. The weight is applied to the test piece, and the test piece is uniaxially stretched at the free end in the vertical direction. It was made to be. The distance between the chuck and the portion to which the weight was attached was 40 mm. Thereafter, the heater of the dryer is turned off, and after cooling at a cooling rate of about 1 ° C./min until the temperature in the dryer reaches Tg−40 ° C. of the resin composition, the test piece is taken out of the dryer, The length, thickness, in-plane retardation Re for light having a wavelength of 590 nm, and the weight of the weight used were measured. The measurement was further performed at four points while changing the mass of the weight.

  Next, based on the measurement result, the measurement described in “Front Line of Transparent Plastic” (Polymer Frontier 21 Series, edited by Polymer Society, NTS, Inc., issued October 2006), pages 37-44 Cr was calculated based on the method. Specifically, the measured in-plane retardation Re is divided by the thickness d of the test piece to obtain the birefringence Δn (= nx−ny, measurement wavelength 590 nm) of the test piece, The stress σ (Pa) applied to the test piece was obtained from the mass of the weight, and this was plotted on the x-axis, and the slope of the straight line of the plot was calculated by the least square method, which was defined as the Cr of the resin composition. . In addition, nx is a refractive index in the stretching direction (stress application method) in the plane of the film, and ny is a refractive index in a direction perpendicular to the stretching direction (stress application direction) in the plane of the film.

  The in-plane retardation Re for light having a wavelength of 590 nm was measured using a retardation film / optical material inspection apparatus RETS-100 (manufactured by Otsuka Electronics). Re is defined by Re = (nx−ny) × d.

[Photoelastic coefficient (Cd)]
The photoelastic coefficient (Cd) of the thermoplastic resin composition was determined as follows. First, the thermoplastic resin composition was melt-extruded to obtain a film (unstretched film) having a thickness of 100 μm. Next, the film was cut into a rectangle having a width of 7 mm to obtain a test piece. Next, the cut out test piece is mounted at a distance of 30 mm between chucks on a retardation film / optical material inspection apparatus RETS-100 (manufactured by Otsuka Electronics Co., Ltd.) equipped with a tensile tester stage, and an elongation stress ( (σR) was applied (chuck moving speed 5 mm / min), and its birefringence with respect to light having a wavelength of 590 nm was measured. From the relationship between the measured absolute value of birefringence (| Δn |) and the tensile stress (σR) applied to the test piece, the slope | Δn | / σR was determined by the least square method, and the photoelastic coefficient (Cd) was calculated. (Cd = | Δn | / σR). For the calculation of Cd, data in which the tensile stress is in the range of 2.5 MPa ≦ σR ≦ 10 MPa was used. | Δn | is | Δn | = | nx−ny |.

[Destruction energy E]
The breaking energy E of the thermoplastic resin composition was determined as follows. First, the thermoplastic resin composition was melt-extruded to obtain a film (unstretched film) having a thickness of 100 μm. Next, a test of dropping a ball having a mass of 0.0054 kg from a certain height on the film was carried out 15 times, and from the average value of the height (breaking height) when the film was broken, The breaking energy E was determined. Whether or not the film was destroyed was judged by visually confirming whether or not the film was deformed after falling on the film. If deformation was seen, the film was considered broken.
Fracture energy E (mJ) = sphere mass (kg) × fracture height average value (mm) × 9.8 (m / s ² )

[Film thickness]
The thickness of the film obtained by molding the thermoplastic resin composition was determined by a digimatic micrometer (Mitutoyo).

[Melt extrusion molding]
In the melt extrusion molding of the thermoplastic resin composition, the resin composition pellets prepared in each of the examples and comparative examples were introduced into a single screw extruder having a cylinder diameter of 20 mm, and the resin composition in a hot melt state in the extruder was obtained. It was carried out by discharging from a T die (width 120 mm) to a cooling roll having a temperature of 110 ° C. At this time, the temperature of the cylinder and the T-die (film forming temperature) was 280 ° C., thereby obtaining an unstretched film having a thickness of 100 μm.

Example 1
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, a nitrogen introduction tube, and a dropping funnel, 76 parts by mass of methyl methacrylate (MMA), 15 parts by mass of N-phenylmaleimide (PMI), methyl acrylate (MA) 9 parts by mass, an antioxidant (Adeka Stub 2112, manufactured by ADEKA) 0.05 part by mass, and 80.5 parts by mass of toluene were charged, and the content was heated to 105 ° C. while introducing nitrogen gas. At the start of the reflux due to the temperature rise, 0.103 parts by mass of t-amylperoxyisononanoate (manufactured by Arkema Yoshitomi, Luperox 570) was added as a polymerization initiator, and t-amylperoxy was added to 21 parts by mass of toluene. Solution polymerization was allowed to proceed while dropping 0.205 parts by mass of isononanoate over 2 hours, and after completion of the dropwise addition, aging was further performed for 6 hours.

  Next, the obtained polymerization solution was subjected to a barrel temperature of 240 ° C., a rotation speed of 100 rpm, a degree of vacuum of 10.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1 and a fore vent number of 4 (first and Introduced into a vent type screw twin screw extruder (φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin, Devolatilization was performed. At that time, the separately prepared antioxidant solution was added from behind the first vent at a charging rate of 0.03 kg / hr, and ion exchange water was fed from behind the third vent at a charging rate of 0.01 kg / hr. , Respectively. As the antioxidant solution, a solution obtained by dissolving 50 parts by mass of an antioxidant (manufactured by Sumitomo Chemical Co., Ltd., Sumilizer GS) in 235 parts by mass of toluene was used.

  After completion of devolatilization, the resin composition in the heat-melted state remaining in the extruder was discharged from the tip of the extruder and pelletized by a pelletizer to obtain a pellet of the resin composition (E-1).

(Example 2)
The amount of MMA charged in the reaction vessel was changed from 76 parts by mass to 71 parts by mass, 8 parts by mass of PMI and 11 parts by mass of cyclohexylmaleimide (CMI) were charged in the reaction vessel instead of 15 parts by mass of PMI, and instead of 9 parts by mass of MA. A pellet of the resin composition (E-2) was obtained in the same manner as in Example 1 except that 10 parts by mass of butyl methacrylate (BMA) was charged into the reaction vessel.

(Example 3)
The amount of MMA charged into the reaction vessel is 71 to 55 parts by mass, the amount of PMI is 8 to 13 parts by mass, the amount of CMI is 11 to 17 parts by mass, and the amount of BMA is 10 parts by mass. A pellet of the resin composition (E-3) was obtained in the same manner as in Example 2 except that the content was changed from 15 to 15 parts by mass.

(Comparative Example 1)
In the same manner as in Example 1 except that the amount of MMA charged into the reaction vessel was changed from 76 parts by mass to 100 parts by mass, and PMI and MA were not charged into the reaction vessel, pellets of the resin composition (F-1) were obtained. Obtained.

(Comparative Example 2)
The amount of MMA charged into the reaction vessel was changed from 76 parts by mass to 90 parts by mass, the amount of PMI was changed from 15 parts by mass to 10 parts by mass, and MA was not charged into the reaction vessel. A pellet of the resin composition (F-2) was obtained.

(Comparative Example 3)
A pellet of the resin composition (F-3) was obtained in the same manner as in Example 1 except that the amount of MMA charged into the reaction vessel was changed from 76 parts by mass to 85 parts by mass without charging MA into the reaction vessel. It was.

(Comparative Example 4)
A pellet of the resin composition (F-4) was obtained in the same manner as in Example 2 except that BMA was not charged in the reaction vessel, but instead the amount of MMA charged in the reaction vessel was changed from 71 parts by mass to 81 parts by mass. It was.

(Comparative Example 5)
A pellet of the resin composition (F-5) was obtained in the same manner as in Example 3 except that BMA was not charged into the reaction vessel, but instead the amount of MMA charged into the reaction vessel was changed from 55 parts by mass to 70 parts by mass. It was.

(Comparative Example 6)
Example 1 except that the amount of MMA charged into the reaction vessel was changed from 76 parts by weight to 86 parts by weight, the amount of PMI was changed from 15 parts by weight to 10 parts by weight, and the amount of MA was changed from 9 parts by weight to 4 parts by weight. Similarly, pellets of the resin composition (F-6) were obtained.

  The evaluation results of the resin compositions prepared in Examples 1 to 3 and Comparative Examples 1 to 6 are shown in Table 1 below.

  As shown in Table 1, the resin compositions of the examples exhibit high Td (high heat resistance) of 115 ° C. or higher, but also high Td (high heat decomposition characteristics) of 300 ° C. or higher, and MFR values. In addition, the ratio MFR / Td and the ratio MFR / Tg were high, and the resin composition was excellent in film formability. On the other hand, although the resin composition of each comparative example after comparative example 2 except comparative example 1 which used only MMA for superposition | polymerization has high Tg of 115 degreeC or more like an example, the value of MFR, As a result, the value of ratio MFR / Td and the value of ratio MFR / Tg were low, and the film forming property was inferior. Depending on the comparative example, Td was less than 300 ° C., which showed insufficient thermal decomposition characteristics for film formation of a resin composition having a high Tg.

  In addition to this, when the contents of N-substituted maleimide units were compared between the same samples, the value of the fracture energy E was greatly improved in the resin compositions of the examples as compared with the comparative examples. That is, the resin compositions of the examples were excellent in mechanical properties such as film handling properties and flexibility during film formation. Furthermore, it was a resin composition in which a value of Cr and Cd was small and a film (including a stretched film) excellent in optical isotropy was realized.

  The thermoplastic composition resin composition of the present invention can be used in various applications similar to conventional thermoplastic resin compositions. One of the uses is an optical film.

Claims (9)

An optical film obtained by melt-molding a thermoplastic resin composition,
The thermoplastic resin composition is
And shown in Equation (1) follows N- substituted maleimide monomer from which the structural unit (A),
Shown in the equation below (2) (meth) acrylate monomers, carboxylic acid vinyl ester monomer (4 to 12 carbon atoms in the carboxylic acid), and maleic acid dialkyl ester monomer (number of carbon atoms in the alkyl group 4 ~ 8), a structural unit (B) derived from the monomer (M) having a glass transition temperature (Tg) of 20 ° C. or lower when it is a homopolymer,
Include (meth) acrylate monomer thermoplastic resin having a structural unit derived from a (the monomeric (M) (meth) excluding acrylate monomer) (C), the (D),
Tg is less than 130 ° C. 115 ° C. or higher of the thermoplastic resin composition, main belt flow rate (MFR) of is from 7.5 to 50 [g / 10 min], the thermal decomposition temperature (Td) is 300 ° C. That's it,
Optical film.

In Formula (1), R ¹ and R ² are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 14 carbon atoms, and X is an alkyl group having 3 to 12 carbon atoms. A cycloalkyl group or an aryl group having 6 to 14 carbon atoms.

In formula (2), R ³ is a hydrogen atom or a methyl group, when R ³ is a hydrogen atom R ⁴ is a hydrocarbon group having 1 to 12 carbon atoms, R ⁴ when R ³ is a methyl group the carbon It is a hydrocarbon group of formula 4-12.
The glass transition temperature (Tg) is based on a DSC curve obtained in accordance with the provisions of JIS K7121, using a differential scanning calorimeter (DSC) under a nitrogen gas atmosphere and at a measurement rate of 20 ° C./min. It is a value evaluated by the starting point method.
The melt flow rate (MFR) is a value evaluated under measurement conditions of a temperature of 240 ° C. and a load of 98 N in accordance with JIS K7210 B method.
The thermal decomposition starting temperature (Td) is a value evaluated by dynamic TG measurement under a nitrogen gas atmosphere using a differential type differential thermal balance apparatus, and the mass reduction rate of the sample is 0.005 mass% / second. In the following cases, the rate of temperature increase is 10 ° C./min, and when the mass reduction rate exceeds 0.005% by mass / second, stepwise isothermal control is performed so that the rate of decrease is maintained at 0.005% by mass / second or less. As described above, after the start of temperature increase, the stepwise isothermal control is first performed in order to maintain the mass reduction rate of 0.005 mass% / second or less. The optical film of Claim 1 whose ratio MFR / Td of the melt flow rate (MFR) with respect to the thermal decomposition start temperature (Td) in the said thermoplastic resin composition is 0.023 or more. The optical film of Claim 1 or 2 whose ratio MFR / Tg of the melt flow rate (MFR) with respect to the glass transition temperature (Tg) in the said thermoplastic resin composition is 0.080 or more. The optical film in any one of Claims 1-3 whose content rate of the said structural unit (C) in the said thermoplastic resin (D) is 20 to 85 mass%. The optical film in any one of Claims 1-4 whose content rate of the said structural unit (A) in the said thermoplastic resin (D) is 10 to 40 mass%. The optical film in any one of Claims 1-5 whose content rate of the said structural unit (B) in the said thermoplastic resin (D) is 5 mass% or more and 40 mass% or less. Comprising an optical film according to claim 1, the polarizer protective film. A polarizing plate comprising a polarizer and the polarizer protective film according to claim 7 . It provided an optical film according to claim 1, the image display device.