Methacrylic resin composition and resin film

Abstract

To provide a methacrylic resin composition that has optical characteristics including transparency and color tone suitable for optical use and exhibits reduced thermal degradation during molding, as well as a resin film comprising the methacrylic resin composition.SOLUTION: The methacrylic resin composition according to the present invention comprises a methacrylic resin and diene-based crosslinked particles, wherein the proportion of the diene-based crosslinked particles is 0.01 to 3 pts.mass per 100 pts.mass of the total of the methacrylic resin and the diene-based crosslinked particles, and the methacrylic resin composition exhibits a thermal weight loss of less than 1.0% when held at 280°C for 15 minutes in a nitrogen gas atmosphere.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a methacrylic resin composition and a resin film. [Background technology]

[0002] Methacrylic resins are widely used in various fields due to their excellent transparency, weather resistance, processability, etc. In particular, resin films obtained by molding methacrylic resins are used in optical applications such as display devices due to their excellent optical properties. Known methods for producing resin films include a method in which molten methacrylic resin is extruded into a film shape and wound up (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-229901 Summary of the Invention [Problem to be solved by the invention]

[0004] However, methacrylic resins can sometimes cause foaming due to thermal decomposition during molding, and there is room for improvement in terms of thermal stability.

[0005] An object of the present invention is to provide a methacrylic resin composition that has optical properties such as transparency and color tone required for optical applications and is inhibited from thermal decomposition during molding processing, and a resin film containing the methacrylic resin composition. [Means for solving the problem]

[0006] Specific means for solving the above problems include the following embodiments. <1> A methacrylic resin composition containing a methacrylic resin and diene-based crosslinked particles, the proportion of the diene crosslinked particles in 100 parts by mass of the total of the methacrylic resin and the diene crosslinked particles is 0.01 to 3 parts by mass; The methacrylic resin composition has a thermal weight loss rate of less than 1.0% when exposed to 280°C in a nitrogen gas atmosphere for 15 minutes. <2> The diene-based crosslinked particles are core-shell type rubber graft copolymer particles having a core layer composed of a diene-based rubber polymer and a shell layer grafted to the core layer. <1> The methacrylic resin composition according to claim 1. <3> The diene rubber polymer is a butadiene rubber polymer. <2> The methacrylic resin composition according to claim 1. <4> The weight average molecular weight of the methacrylic resin is 70,000 to 250,000. <1> ~ <3> The methacrylic resin composition according to any one of the above. <5> The molecular weight distribution (Mw / Mn) of the methacrylic resin exceeds 1.5. <1> ~ <4> The methacrylic resin composition according to any one of the above. <6> Further containing an ultraviolet absorber, <1> ~ <5> The methacrylic resin composition according to any one of the above. <7> <1> ~ <6> A resin film comprising the methacrylic resin composition according to any one of claims 1 to 10. <8> The resin film is a polarizer protective film. <7> The resin film according to claim 1. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a methacrylic resin composition that has optical properties such as transparency and color tone required for optical applications and is inhibited from thermal decomposition during molding processing, and a resin film containing the methacrylic resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, one embodiment of the present invention will be described, but the present invention is not limited to this embodiment. In this specification, the notation "A to B" using numerical values ​​A and B means "A or more and B or less" unless otherwise specified. In such notation, when a unit is added only to numerical value B, the unit is also applied to numerical value A. Furthermore, in this specification, the term "(meth)acrylic acid" means both "acrylic acid" and "methacrylic acid", and the term "(meth)acrylate" means both "acrylate" and "methacrylate".

[0009] <Methacrylic resin composition> The methacrylic resin composition according to this embodiment contains a methacrylic resin and diene-based crosslinked particles, in which the proportion of the diene-based crosslinked particles in 100 parts by mass of the total of the methacrylic resin and the diene-based crosslinked particles is 0.01 to 3 parts by mass, and the methacrylic resin composition has a thermal weight loss rate of less than 1.0% when exposed to 280°C in a nitrogen gas atmosphere for 15 minutes.

[0010] Each component contained in the methacrylic resin composition according to this embodiment will be described in detail below. Note that each of the following components may be used alone or in combination of two or more.

[0011] <Methacrylic resin> Methacrylic resin refers to a resin in which the proportion of structural units derived from polymerizable monomers having a methacryloyl group is 50% by mass or more. Among polymerizable monomers having a methacryloyl group, methyl methacrylate is preferred from the viewpoints of optical properties and heat resistance. That is, the proportion of structural units derived from methyl methacrylate (hereinafter also referred to as "methyl methacrylate units") in the methacrylic resin is preferably 50% by mass or more, more preferably 70% by mass or more, and even more preferably 90% by mass or more. The methyl methacrylate units are represented by the following formula:

[0012] [ka]

[0013] The content of the methacrylic resin in the methacrylic resin composition according to this embodiment is preferably 80 to 99.99 mass %, more preferably 90 to 99.95 mass %, and even more preferably 95 to 99.9 mass %.

[0014] The methacrylic resin preferably has a weight-average molecular weight (Mw) of 70,000 to 250,000, and more preferably 90,000 to 150,000. When the weight-average molecular weight (Mw) of the methacrylic resin is 70,000 or more, the mechanical properties of the resulting molded article tend to be improved, and when the weight-average molecular weight (Mw) of the methacrylic resin is 250,000 or less, the moldability tends to be improved.

[0015] Furthermore, the methacrylic resin preferably has a molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), of more than 1.5, more preferably 1.6 to 2.5, and particularly preferably 1.7 to 2.2. When the molecular weight distribution (Mw / Mn) of the methacrylic resin exceeds 1.5, the flowability of the methacrylic resin tends to improve and it becomes easier to mold, and when the molecular weight distribution (Mw / Mn) of the methacrylic resin is 2.5 or less, the mechanical properties of the resulting molded article, such as impact resistance, toughness, and flex resistance, tend to improve.

[0016] The weight average molecular weight (Mw) and number average molecular weight (Mn) in this specification are values ​​measured by gel permeation chromatography (GPC) in terms of standard polystyrene, and are measured by the method described in the examples below.

[0017] The methacrylic resin can be produced by a known radical polymerization method. The methacrylic resin produced by the radical polymerization method contains terminal double bonds generated by a disproportionation termination reaction during polymerization, etc. Since the terminal double bonds affect the thermal stability of the resin, it is preferable that the proportion of terminal double bonds is small.

[0018] In the methacrylic resin, for example, the ratio of terminal double bonds to methyl methacrylate units is preferably less than 0.020 mol %, more preferably less than 0.015 mol %, even more preferably less than 0.010 mol %, and particularly preferably less than 0.006 mol %.

[0019] The ratio of terminal double bonds to methyl methacrylate units was determined in deuterated chloroform at 20°C and accumulated for 8192 cycles, as described in the Examples below. 1 The H-NMR spectrum is measured, and from the spectrum, the sum (X) of the areas of the peaks (5.47 to 5.53 ppm and 6.21 ppm) derived from the terminal double bonds of the methacrylic resin and the area (Y) of the peaks (0.50 to 1.25 ppm) derived from the α-methyl groups of the methacrylic resin are measured, and the RI can be calculated using the formula: [(3 × X) / (2 × Y)] × 100.

[0020] The methacrylic resin is preferably one having excellent heat resistance. Examples of methacrylic resins having excellent heat resistance include a methacrylic resin having a proportion of methyl methacrylate units of 98% by mass or more and a triad syndiotacticity (rr) of 54% or more (hereinafter also referred to as a "first methacrylic resin"), a methacrylic resin having a ring structure in the main chain (hereinafter also referred to as a "second methacrylic resin"), and the like. The first and second methacrylic resins will be described in detail below.

[0021] [First methacrylic resin] The first methacrylic resin is a resin in which the proportion of methyl methacrylate units is 98% by mass or more and the syndiotacticity (rr) expressed in triad notation is 54% or more.

[0022] The first methacrylic resin preferably has a proportion of methyl methacrylate units of 99% by mass or more and a proportion of other polymerizable monomer units other than methyl methacrylate units of 1% by mass or less, more preferably has a proportion of methyl methacrylate units of 99.5% by mass or more and a proportion of other polymerizable monomer units other than methyl methacrylate units of 0.5% by mass or less, and is even more preferably a homopolymer of methyl methacrylate.

[0023] Examples of polymerizable monomers other than methyl methacrylate include alkyl acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate; aryl acrylates such as phenyl acrylate; cycloalkyl acrylates such as cyclohexyl acrylate and norbornenyl acrylate; alkyl methacrylates other than methyl methacrylate such as ethyl methacrylate, propyl methacrylate, and n-butyl methacrylate; aryl methacrylates such as phenyl methacrylate; cycloalkyl methacrylates such as cyclohexyl methacrylate and norbornenyl methacrylate; aromatic vinyl monomers such as styrene and α-methylstyrene; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; acrylamide; methacrylamide; and the like.

[0024] The first methacrylic resin has a syndiotacticity (rr) expressed as a triad of 54% or more, preferably 55% or more, more preferably 56% or more, and even more preferably 57% or more. When the syndiotacticity (rr) expressed as a triad of 54% or more, the glass transition temperature (Tg) of the methacrylic resin tends to be high and the heat resistance tends to be improved. There is no particular upper limit for the syndiotacticity (rr), but from the viewpoints of the molding temperature and the toughness and secondary processability of the molded body, it is preferably 70% or less, more preferably 67% or less, even more preferably 65% ​​or less, and particularly preferably 63% or less.

[0025] Syndiotacticity (rr) is the proportion of two diads in a triad of three consecutive structural units that are both racemo (rr). Diads in polymer molecules with the same configuration are called meso, and those with the opposite configuration are called racemo, and are abbreviated as m and r, respectively.

[0026] As described in the Examples below, syndiotacticity (rr) was measured in deuterated chloroform at 22°C and 16 cycles. 1 The H-NMR spectrum is measured, and the area (X) of the region from 0.60 to 0.95 ppm and the area (Y) of the region from 0.60 to 1.25 ppm are measured from the spectrum when tetramethylsilane (TMS) is set to 0 ppm, and the amount of fluorine can be calculated using the formula: (X / Y) × 100.

[0027] The syndiotacticity (rr) and glass transition temperature (Tg) of the first methacrylic resin can be controlled by adjusting the polymerization temperature during synthesis of the first methacrylic resin. For example, lowering the polymerization temperature is preferable for increasing the syndiotacticity (rr) and glass transition temperature (Tg) of the first methacrylic resin. The glass transition temperature (Tg) can also be controlled by adjusting the molecular weight of the first methacrylic resin.

[0028] As a method for producing the first methacrylic resin, a conventionally known polymerization method can be used, for example, a radical polymerization method such as continuous bulk polymerization, solution polymerization, emulsion polymerization, emulsifier-free (soap-free) emulsion polymerization, or suspension polymerization. Among them, from the viewpoint of the degree of freedom in structural design of the methacrylic resin, simplicity of polymerization, productivity, etc., a production method involving aqueous polymerization is preferred, suspension polymerization and emulsion polymerization are more preferred, and suspension polymerization is even more preferred. The first methacrylic resin can be produced, for example, according to the method described in International Publication No. 2023 / 238885.

[0029] [Second methacrylic resin] The second methacrylic resin is a resin having a ring structure in its main chain. Examples of the ring structure include at least one ring structure selected from a glutarimide structure, a lactone ring structure, a maleic anhydride structure, an N-substituted maleimide structure, and a glutaric anhydride structure. Among these, a methacrylic resin having a glutarimide structure or a lactone ring structure in its main chain is preferred from the viewpoints of ease of production, cost, quality stability against moisture, etc.

[0030] (Methacrylic resin with glutarimide structure in the main chain) A methacrylic resin having a glutarimide structure in its main chain is, for example, a resin containing a glutarimide unit represented by the following formula (1) and a methyl methacrylate unit, and can be produced by heating and melting a polymethyl methacrylate resin and then treating it with an imidizing agent.

[0031] [ka] (In the formula, R 1 and R 2 each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms, and R 3 represents a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0032] The proportion of glutarimide units in the methacrylic resin is preferably 2 to 30% by mass. When the proportion of glutarimide units is 2% by mass or more, the desired heat resistance tends to be easily imparted. Furthermore, when the proportion of glutarimide units is 30% by mass or less, the amount of imidizing agent added can be reduced, odor due to residual volatile components can be suppressed, and the retardation of the resin film tends to be reduced.

[0033] R in the above formula (1) 3When is a methyl group, the proportion of glutarimide units in the methacrylic resin can be measured, for example, by the following method. First, the proportion of glutarimide units in the resin is measured using a nuclear magnetic resonance apparatus (AVANCEIII 400 MHz, manufactured by Bruker). 1 H-NMR measurement is performed. The molar ratio is calculated from the area A of the peak at around 3.5 to 3.8 ppm derived from the protons constituting the O-CH3 of methyl methacrylate and the area B of the peak at around 3.0 to 3.3 ppm derived from the protons constituting the N-CH3 of the glutarimide ring. The molar ratio is converted into weight to calculate the proportion of glutarimide units.

[0034] When producing polymethyl methacrylate resin, in addition to methyl methacrylate, other polymerizable monomers such as methyl acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, etc. may be used in combination. In addition to the above, it is also possible to use in combination vinyl cyanide monomers such as acrylonitrile and methacrylonitrile; maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide; aromatic vinyl monomers such as styrene; etc.

[0035] The structure of the polymethyl methacrylate resin is not particularly limited and may be any of a linear polymer, a block polymer, a core-shell polymer, a branched polymer, a ladder polymer, a crosslinked polymer, etc. In the case of a block polymer, it may be any of AB type, ABC type, ABA type, and other types. In the case of a core-shell polymer, it may be one consisting of a single core layer and a single shell layer, or each of the core and shell may be multi-layered.

[0036] The method for producing polymethyl methacrylate resin is not particularly limited, and radical polymerization methods such as emulsion polymerization, emulsion-suspension polymerization, suspension polymerization, bulk polymerization, and solution polymerization can be used. When used for optical applications, bulk polymerization and solution polymerization are preferred because they reduce impurities. Polymethyl methacrylate resin can be produced, for example, according to the methods described in JP-A-56-8404, JP-B-6-86492, JP-B-7-37482, and JP-B-52-32665.

[0037] The method for producing a methacrylic resin having a glutarimide structure in the main chain includes a step of heating and melting the above-mentioned polymethyl methacrylate resin, and then treating it with an imidizing agent (imidization step).

[0038] The imidizing agent is not particularly limited as long as it can generate the glutarimide unit represented by the above formula (1), and those described in International Publication No. 2005 / 054311 can be used. Specific examples of the imidizing agent include ammonia; aliphatic hydrocarbon group-containing amines such as methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine, isobutylamine, t-butylamine, and n-hexylamine; aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine, and trichloroaniline; and alicyclic hydrocarbon group-containing amines such as cyclohexylamine. Urea-based compounds that generate the above-listed amines upon heating, such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, can also be used. Among these, from the viewpoints of cost and physical properties, methylamine, ammonia, and cyclohexylamine are preferred, and methylamine is more preferred. Methylamine and the like, which are gaseous at room temperature, may be used in a dissolved state in an alcohol such as methanol.

[0039] In the imidization step, the ratio of glutarimide units and methyl methacrylate units in the resulting methacrylic resin can be adjusted by adjusting the amount of imidization agent added, and the physical properties of the resulting methacrylic resin can be adjusted by adjusting the degree of imidization.

[0040] The amount of imidizing agent added is preferably 0.5 to 20 parts by mass relative to 100 parts by mass of polymethyl methacrylate resin. When the amount of imidizing agent added is 0.5 parts by mass or more, the proportion of glutarimide units increases, which tends to improve the heat resistance of the methacrylic resin and prevent appearance defects after molding. When the amount of imidizing agent added is 20 parts by mass or less, the imidizing agent is less likely to remain in the methacrylic resin, which tends to prevent appearance defects and foaming after molding.

[0041] In the imidization step, a ring closure promoter (catalyst) may be added in addition to the imidization agent, if necessary.

[0042] The method for heating and melting the polymethyl methacrylate resin and treating it with an imidizing agent is not particularly limited, and for example, the methods described in JP-A Nos. 2008-273140 and 2008-274187 can be used.

[0043] The method for producing a methacrylic resin having a glutarimide structure in its main chain may include, in addition to the imidization step, a step of treating with an esterifying agent (esterification step). This esterification step allows the acid value of the resin obtained in the imidization step to be adjusted within a desired range.

[0044] Examples of the esterifying agent include dimethyl carbonate, 2,2-dimethoxypropane, dimethyl sulfoxide, triethyl orthoformate, trimethyl orthoacetate, trimethyl orthoformate, diphenyl carbonate, dimethyl sulfate, methyl toluene sulfonate, methyl trifluoromethyl sulfonate, methyl acetate, methanol, ethanol, methyl isocyanate, p-chlorophenyl isocyanate, dimethylcarbodiimide, dimethyl-t-butylsilyl chloride, isopropenyl acetate, dimethyl urea, tetramethylammonium hydroxide, dimethyldiethoxysilane, tetra-N-butoxysilane, dimethyl(trimethylsilane) phosphite, trimethyl phosphite, trimethyl phosphate, tricresyl phosphate, diazomethane, ethylene oxide, propylene oxide, cyclohexene oxide, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and benzyl glycidyl ether. Among these, dimethyl carbonate and trimethyl orthoacetate are preferred from the viewpoints of cost, reactivity, etc., and dimethyl carbonate is more preferred from the viewpoint of cost.

[0045] The amount of the esterifying agent added is preferably 0 to 20 parts by mass, more preferably 0 to 15 parts by mass, relative to 100 parts by mass of the polymethyl methacrylate resin. When the amount of the esterifying agent is within the above range, the acid value can be adjusted to an appropriate range, and unreacted esterifying agent tends to be less likely to remain in the resin.

[0046] In the esterification step, a catalyst may be used in addition to the esterifying agent. Examples of the catalyst include aliphatic tertiary amines such as trimethylamine, triethylamine, and tributylamine. Among these, triethylamine is preferred from the viewpoints of cost, reactivity, etc.

[0047] The method for treating the resin obtained in the imidization step with an esterifying agent is not particularly limited, and for example, the methods described in JP-A-2008-273140, JP-A-2008-274187, etc. can be used.

[0048] (Methacrylic resin with a lactone ring structure in the main chain) A methacrylic resin having a lactone ring structure in the main chain can be produced by polymerizing a methacrylic resin having a hydroxy group and an ester group in the molecular chain (polymerization step), and then heat-treating the resulting methacrylic resin to introduce a lactone ring structure into the methacrylic resin (lactone cyclization condensation step).

[0049] In the polymerization step, a polymerizable monomer component including a polymerizable monomer represented by the following formula (2) and a polymerizable monomer having a methacryloyl group is polymerized to obtain a methacrylic resin having a hydroxy group and an ester group in the molecular chain.

[0050] [ka] (In the formula, R 4 and R 5 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

[0051] Examples of the polymerizable monomer represented by the above formula (2) include methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, isopropyl 2-(hydroxymethyl)acrylate, n-butyl 2-(hydroxymethyl)acrylate, t-butyl 2-(hydroxymethyl)acrylate, etc. Among these, methyl 2-(hydroxymethyl)acrylate and ethyl 2-(hydroxymethyl)acrylate are preferred, and methyl 2-(hydroxymethyl)acrylate is more preferred from the viewpoint of a high effect of improving heat resistance.

[0052] The content of the polymerizable monomer represented by formula (2) in the polymerizable monomer component is preferably 5 to 50% by mass, more preferably 10 to 40% by mass, and even more preferably 10 to 30% by mass. When the content of the polymerizable monomer represented by formula (2) is 5% by mass or more, the heat resistance, solvent resistance, surface hardness, and other properties of the resulting methacrylic resin tend to be improved. Furthermore, when the content of the polymerizable monomer represented by formula (2) is 50% by mass or less, gelation due to a crosslinking reaction occurring during the formation of the lactone ring structure tends to be suppressed, and a decrease in fluidity tends to be suppressed. Furthermore, remaining unreacted hydroxy groups tends to further promote condensation during molding, resulting in the generation of volatile substances, which can cause silver streaks and increase the retardation of the resin film.

[0053] Examples of polymerizable monomers having a methacryloyl group include methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc. Among these, methyl methacrylate is preferred from the viewpoints of heat resistance and transparency.

[0054] The content of the polymerizable monomer having a methacryloyl group in the polymerizable monomer component is preferably 50 to 95% by mass, more preferably 60 to 90% by mass, and even more preferably 70 to 90% by mass.

[0055] <Diene-based crosslinked particles> The diene-based crosslinked particles are not particularly limited as long as they contain a diene-based rubber polymer such as polybutadiene, poly(styrene-butadiene), poly(acrylonitrile-butadiene), or butadiene-acrylic acid ester copolymer. Among the diene-based crosslinked particles, core-shell type rubber graft copolymer particles having a core layer composed of a diene-based rubber polymer and a shell layer grafted to the core layer are preferred. The core-shell type rubber graft copolymer particles will be described in detail below.

[0056] [Core layer] The core layer is composed of a diene rubber polymer such as polybutadiene, poly(styrene-butadiene), poly(acrylonitrile-butadiene), butadiene-acrylic acid ester copolymer, etc. As the diene rubber polymer, a butadiene rubber polymer is preferred, a (co)polymer of 50 to 100 mass % of 1,3-butadiene and 0 to 50 mass % of a polymerizable monomer other than 1,3-butadiene is more preferred, and a homopolymer of 1,3-butadiene is even more preferred.

[0057] Examples of polymerizable monomers copolymerizable with 1,3-butadiene include aromatic vinyl monomers such as styrene and α-methylstyrene; (meth)acrylic acid and (meth)acrylic acid alkyl esters such as acrylic acid, methacrylic acid, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate; and unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile. Furthermore, polyfunctional polymerizable monomers such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butylene dimethacrylate can also be used as appropriate.

[0058] In order to adjust the molecular weight and degree of crosslinking of the diene rubber polymer constituting the core layer, a chain transfer agent may be used during production of the diene rubber polymer. Examples of the chain transfer agent include alkyl mercaptans having 5 to 20 carbon atoms.

[0059] Shell layer The shell layer refers to a polymer layer located on the surface side of the polymer particle, and is preferably a layer in which at least a portion of a polymerizable monomer is graft-polymerized onto the core layer. When a portion of a polymerizable monomer that has not been graft-polymerized is present in the core layer, the ungraft-polymerized polymerizable monomer is also included in the polymer of the shell layer.

[0060] Examples of polymerizable monomers constituting the shell layer include vinyl cyanide compounds; unsaturated carboxylic acids; unsaturated carboxylic acid esters such as (meth)acrylate monomers; and aromatic vinyl monomers.

[0061] Examples of the vinyl cyanide compound include acrylonitrile and methacrylonitrile.

[0062] Examples of the unsaturated carboxylic acid include acrylic acid and methacrylic acid.

[0063] Examples of the (meth)acrylate monomer include alkyl acrylates having an alkyl group having 1 to 22 carbon atoms, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, and behenyl acrylate; glycidyl group-containing acrylates, such as glycidyl acrylate, 1-methyl-1,2-epoxy-ethyl acrylate, and 4-hydroxybutyl acrylate glycidyl ether; aromatic ring-containing acrylates, such as phenoxyethyl acrylate and benzyl acrylate; hydroxyalkyl acrylates, such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; alkoxyalkyl acrylates; and methyl methacrylates. Examples of suitable methacrylates include alkyl methacrylates having an alkyl group having 1 to 22 carbon atoms, such as acrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, dodecyl methacrylate, stearyl methacrylate, and behenyl methacrylate; glycidyl group-containing methacrylates, such as glycidyl methacrylate, 1-methyl-1,2-epoxy-ethyl methacrylate, and 4-hydroxybutyl methacrylate glycidyl ether; aromatic ring-containing methacrylates, such as phenoxyethyl methacrylate and benzyl methacrylate; hydroxyalkyl methacrylates, such as 2-hydroxyethyl methacrylate and 4-hydroxybutyl methacrylate; and alkoxyalkyl methacrylates. Among these, methyl methacrylate and butyl acrylate are preferred, with methyl methacrylate being more preferred.

[0064] Examples of aromatic vinyl monomers include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, t-butylstyrene, α-methylvinyltoluene, dimethylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, dibromostyrene, etc. Among these, styrene is preferred.

[0065] From the viewpoint of compatibility with the methacrylic resin, the content of the (meth)acrylate monomer in the polymerizable monomer component constituting the shell layer is preferably 50 to 100% by mass, and more preferably 60 to 100% by mass.

[0066] From the viewpoint of compatibility with the methacrylic resin, the amount of the shell layer is preferably 20 to 100 parts by mass, more preferably 25 to 55 parts by mass, and even more preferably 30 to 45 parts by mass, per 100 parts by mass of the core layer.

[0067] The rubber graft copolymer particles may further have an intermediate layer between the core layer and the shell layer. The intermediate layer is preferably a layer composed of a polymer and graft-bonded to the core layer. When the rubber graft copolymer particles have an intermediate layer, the intermediate layer covers at least a portion of the surface of the core layer, and the shell layer covers at least a portion of the surface of the intermediate layer.

[0068] [Method for producing rubber graft copolymer particles] The rubber graft copolymer particles can be produced by bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, etc. Among these, emulsion polymerization, i.e., emulsion graft polymerization, is preferred. Specifically, a preferred method involves adding a latex of a rubber polymer to form the core layer to a reaction vessel equipped with a stirrer, followed by adding a polymerizable monomer, a polymerization initiator, and water, and optionally adding a chain transfer agent and an oxidation-reduction agent, followed by heating and stirring.

[0069] There are no particular limitations on the types of polymerization initiator, chain transfer agent, and redox agent, and known agents can be used. There are also no particular limitations on the method for adding each raw material to a reaction vessel, and they may be added all at once before the start of polymerization, or they may be added in portions. The graft polymerization is carried out in one stage or two or more stages, and the composition of the polymerizable monomers in each stage may be the same or different. The polymerizable monomers may be added all at once, continuously, or in a combination thereof.

[0070] When emulsion polymerization is employed, known polymerization initiators, for example, thermal decomposition type polymerization initiators such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, ammonium persulfate, etc. Alternatively, redox type polymerization initiators can be used, which are obtained by combining peroxides such as organic peroxides such as t-butylperoxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-hexyl peroxide, and inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate, with reducing agents such as sodium formaldehyde sulfoxylate and glucose, transition metal salts such as iron (II) sulfate, chelating agents such as disodium ethylenediaminetetraacetate, and phosphorus-based flame retardants such as sodium pyrophosphate, as needed.

[0071] When a redox polymerization initiator is used, polymerization can be carried out even at a low temperature at which the peroxide does not substantially decompose thermally, and therefore the polymerization temperature can be set within a wide range, which is preferable. Among these, it is preferable to use an aromatic ring-containing peroxide such as cumene hydroperoxide or dicumyl peroxide as the redox polymerization initiator. The amount of the polymerization initiator used, and the amount of the reducing agent, transition metal salt, chelating agent, etc. used when a redox polymerization initiator is used, can be within known ranges.

[0072] Examples of polymerization emulsifiers that can be used in emulsion polymerization include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. These polymerization emulsifiers may be used alone or in combination of two or more. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used in combination.

[0073] Examples of anionic surfactants among the polymeric emulsifiers include fatty acid soaps such as potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid soda soap, semi-hardened beef tallow fatty acid soda soap, and castor oil potassium soap; alkyl sulfate ester salts such as sodium dodecyl sulfate, higher alcohol sodium sulfate, triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and sodium 2-ethylhexyl sulfate; and dodecyl sodium alkylbenzenesulfonates such as sodium benzenesulfonate; sodium dialkylsulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalenesulfonates; sodium alkyldiphenyletherdisulfonates; potassium alkylphosphates; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalenesulfonate-formaldehyde condensates; polycarboxylic acid type polymeric anions; sodium acyl (beef tallow) methyl taurate; sodium acyl (coconut) methyl taurate; sodium cocoyl isethionate; sodium α-sulfofatty acid ester salts; sodium amidoethersulfonate; oleyl sarcosine; sodium lauroyl sarcosine; rosin acid soap; and the like.

[0074] A preferred method for producing the rubber graft copolymer particles is, for example, (a) preparing a latex containing a rubber graft copolymer by polymerizing in the presence of an alkali metal salt of a phosphoric acid compound at a pH of 4.6 to 9.4 (preferably pH 5.0 to 9.0, more preferably pH 5.5 to 8.5); (b) adding an alkaline earth metal chloride solution to the latex containing the rubber graft copolymer to coagulate it; and (c) washing and drying the obtained coagulum Examples include:

[0075] The step (a) of preparing the latex usually comprises a core layer-forming step (a1) of polymerizing a polymerizable monomer in water in the presence of a polymerizing emulsifier to form a diene-based rubbery polymer (core layer), and a shell layer-forming step (a2) of grafting a polymerizable monomer onto the diene-based rubbery polymer (core layer) in water in the presence of a polymerizing emulsifier. The alkali metal salt of the phosphoric acid compound described above is used as a polymerizing emulsifier in at least one of the core layer-forming step (a1) and the shell layer-forming step (a2), and is preferably used in both the core layer-forming step (a1) and the shell layer-forming step (a2).

[0076] The alkali metal salt of a phosphoric acid compound is not particularly limited, and any conventionally known salt of a phosphoric acid compound and an alkali metal can be used, such as alkyl phosphates and alkylaryl phosphates.

[0077] From the viewpoint of ensuring stability during polymerization, the alkali metal salt of a phosphoric acid compound (e.g., alkyl phosphates, alkylaryl phosphates, etc.) is preferably a polyoxyalkylene alkyl phenyl ether phosphate or a polyoxyalkylene alkyl ether phosphate, more preferably a polyoxyethylene alkyl phenyl ether phosphate or a polyoxyethylene alkyl ether phosphate, and even more preferably a polyoxyethylene alkyl ether phosphate. The number of carbon atoms in the alkyl group of the polyoxyethylene alkyl ether phosphate is, for example, 1 to 20, preferably 5 to 18, more preferably 7 to 16, and even more preferably 10 to 16. The number of oxyethylene units in the polyoxyethylene alkyl ether phosphate is, for example, 2 to 14, preferably 2 to 10, more preferably 2 to 8, and even more preferably 2 to 6.

[0078] The concentration of the polymerization emulsifier is not particularly limited as long as it is a concentration that allows stable emulsion polymerization of the rubber graft copolymer, and for example, it is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, and even more preferably 0.5 to 2 parts by mass, relative to 100 parts by mass of the total amount of polymerizable monomers that constitute the diene-based rubbery polymer.

[0079] The solvent used during polymerization may be any solvent that allows emulsion polymerization to proceed stably, and for example, water can be suitably used.

[0080] The temperature during emulsion polymerization is not particularly limited as long as the polymerization emulsifier is uniformly dissolved in the solvent, and is, for example, preferably 40 to 75°C, more preferably 45 to 70°C, and even more preferably 49 to 65°C.

[0081] The rubber graft copolymer particles can be obtained by coagulating a latex containing the rubber graft copolymer obtained by emulsion polymerization with an alkaline earth metal chloride solution. For example, the rubber graft copolymer-containing latex is mixed with a divalent or higher metal salt such as calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, or calcium acetate, and then coagulated. The rubber graft copolymer particles can be separated from the aqueous medium by heat treatment, dehydration, washing, and drying according to known methods (also known as the coagulation method).

[0082] As the divalent or higher metal salt, calcium chloride and magnesium chloride are preferred because they are economically available at low cost and easy to handle. When it is desired to avoid even trace amounts of halogens from an environmental perspective, magnesium sulfate is preferably used as the divalent or higher metal salt.

[0083] The resulting rubber graft copolymer particles are preferably washed with water and / or a solvent.

[0084] Alternatively, the latex containing the rubber graft copolymer can be directly powdered by spray drying. In this case, the obtained powder can be washed with water and / or a solvent in the same manner as in the coagulation method described above, thereby obtaining the same effect. Alternatively, calcium chloride, magnesium chloride, magnesium sulfate, aluminum chloride, etc. can be added to the obtained powder, preferably as a solution such as an aqueous solution, and the powder can be re-dried as necessary, thereby obtaining the same effect.

[0085] The volume average particle diameter of the rubber graft copolymer particles is preferably 10 to 1000 nm, more preferably 20 to 800 nm, and even more preferably 50 to 600 nm, from the viewpoints of productivity of the rubber graft copolymer particles, stability of the particle polymerization system, and good dispersibility in the methacrylic resin.

[0086] From the viewpoint of the transparency of the resulting molded article, the refractive index of the rubber graft copolymer particles is preferably 1.47 to 1.55, more preferably 1.47 to 1.53, and even more preferably 1.48 to 1.52.

[0087] The proportion of the diene crosslinked particles in 100 parts by mass of the total of the methacrylic resin and the diene crosslinked particles is 0.01 to 3 parts by mass, preferably 0.05 to 2.5 parts by mass, and more preferably 0.1 to 2 parts by mass. When the proportion of the diene crosslinked particles is 0.01 part by mass or more, the thermal stability of the obtained molded article tends to be improved. Furthermore, when the proportion of the diene crosslinked particles is 3 parts by mass or less, the optical properties of the obtained molded article tend to be improved.

[0088] <UV absorber> The methacrylic resin composition according to the present embodiment may contain an ultraviolet absorber to further improve the light resistance of the resulting molded article. Examples of ultraviolet absorbers include benzotriazole compounds, triazine compounds, oxalic acid anilide compounds, cyanoacrylate compounds, salicylate compounds, and benzophenone compounds. Among these, triazine compounds are preferred from the viewpoint of light resistance.

[0089] Examples of triazine compounds include 2,4-diphenyl-6-(2-hydroxyphenyl-4-hexyloxyphenyl)-1,3,5-triazine, 2-[4,6-bis(2,4-dimethylphenyl)-1,3,5-triazin-2-yl]-5-(octyloxy)phenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[(hexyl)oxy]phenol, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol, and 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine. The alkoxy group contained in 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine is preferably a linear or branched alkoxy group having 1 to 10 carbon atoms. Specific examples of 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine include 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine.

[0090] Among these triazine compounds, 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol and 2,4,6-tris(2-hydroxy-4-alkoxy-3-methylphenyl)-1,3,5-triazine are preferred. 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-[2-(2-ethylhexanoyloxy)ethoxy]phenol is available as Adeka STAB LA-46 (manufactured by ADEKA Corporation). 2,4,6-tris(2-hydroxy-4-hexyloxy-3-methylphenyl)-1,3,5-triazine is available as Adeka STAB LA-F70 (manufactured by ADEKA Corporation).

[0091] When the methacrylic resin composition according to the present embodiment contains an ultraviolet absorber, the content thereof is preferably 0.1 to 5 parts by mass, and more preferably 0.2 to 3 parts by mass, relative to 100 parts by mass of the methacrylic resin. When the content of the ultraviolet absorber is 0.1 part by mass or more, the ultraviolet absorption effect tends to be improved. Furthermore, when the content of the ultraviolet absorber is 5 parts by mass or less, coloration of the obtained molded article tends to be suppressed, and deterioration of transparency due to an increase in haze of the molded article tends to be suppressed.

[0092] <Other ingredients> The methacrylic resin composition according to this embodiment may further contain known additives such as light stabilizers, heat stabilizers, matting agents, light diffusing agents, colorants, dyes, pigments, antistatic agents, heat reflective materials, lubricants, plasticizers, stabilizers, flame retardants, mold release agents, polymer processing aids, and fillers, as well as resins other than methacrylic resins. Examples of resins other than methacrylic resins include styrene-based resins such as acrylonitrile-styrene resins and styrene-maleic anhydride resins; polycarbonate resins; polyvinyl acetal resins; cellulose acylate resins; fluorine-based resins such as polyvinylidene fluoride and polyfluorinated alkyl (meth)acrylate resins; silicone-based resins; polyolefin-based resins; polyethylene terephthalate resins; and polybutylene terephthalate resins.

[0093] Furthermore, in order to adjust the orientation birefringence of the molded article, the methacrylic resin composition according to this embodiment may contain inorganic fine particles having birefringence as described in Japanese Patent No. 3648201, Japanese Patent No. 4336586, etc., or a low molecular weight compound having birefringence and a molecular weight of 5000 or less (preferably 1000 or less) as described in Japanese Patent No. 3696649.

[0094] <Physical properties and morphology of methacrylic resin composition> The methacrylic resin composition according to this embodiment exhibits a thermal weight loss rate of less than 1.0%, preferably 0.9% or less, and more preferably 0.8% or less, when exposed to 280°C in a nitrogen gas atmosphere for 15 minutes. This thermal weight loss rate is measured by the method described in the Examples below.

[0095] Furthermore, the methacrylic resin composition according to this embodiment preferably has a 5% weight loss temperature (Td5) of 335°C or higher, more preferably 336°C or higher, and even more preferably 337°C or higher.

[0096] Furthermore, the methacrylic resin composition according to this embodiment preferably has a glass transition temperature (Tg) of 118° C. or higher, more preferably 120° C. or higher, even more preferably over 120° C., and particularly preferably 121° C. or higher. There is no particular upper limit to the glass transition temperature (Tg), but from the viewpoints of molding temperature and secondary processability of molded articles, it is preferably 135° C. or lower, and may be 130° C. or lower.

[0097] The glass transition temperature (Tg) in this specification is the midpoint glass transition temperature determined from a DSC curve, and is measured by the method described in the examples below.

[0098] The form of the methacrylic resin composition according to this embodiment is not particularly limited, and may be a powder, granules, a powder-granule mixture containing both powder and granules, or pellets.

[0099] <Molded body> The methacrylic resin composition according to the present embodiment can be molded into a molded article by a known molding method, such as a melt molding method such as a T-die method (lamination method, co-extrusion method, etc.), an inflation method (co-extrusion method, etc.), a compression molding method, a blow molding method, a calendar molding method, a vacuum molding method, or an injection molding method (insert method, two-color method, press method, core-back method, sandwich method, etc.); a solution casting method;

[0100] <Resin film> The resin film according to this embodiment contains the methacrylic resin composition according to this embodiment described above. The resin film according to this embodiment is produced, for example, by a melt extrusion method using the methacrylic resin composition according to this embodiment. When producing a resin film by the melt extrusion method, the methacrylic resin composition according to this embodiment is first pre-dried, then fed to an extruder, heated and melted, and fed to a T-die. Next, the methacrylic resin composition fed to the T-die is extruded as a sheet-shaped molten resin, and cooled and solidified using a cooling roll or the like to obtain a resin film.

[0101] The thickness of the resin film according to this embodiment is, for example, preferably 500 μm or less, more preferably 300 μm or less, and even more preferably 200 μm or less. The thickness of the resin film according to this embodiment is, for example, preferably 10 μm or more, more preferably 30 μm or more, even more preferably 50 μm or more, and particularly preferably 60 μm or more. When the thickness of the resin film is within the above range, there is an advantage that the resin film is less likely to deform when vacuum forming is performed using the resin film, and breakage is less likely to occur at the deep-drawn portion. Another advantage is that a resin film with uniform optical properties and good transparency can be produced.

[0102] The total light transmittance of the resin film according to this embodiment is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. If the total light transmittance is within the above range, the transparency is high, and the film can be suitably used for optical applications that require light transmittance.

[0103] The haze of the resin film according to this embodiment is preferably 1.5% or less, more preferably 1.3% or less, and even more preferably 1.0% or less. The internal haze of the resin film is preferably 1.1% or less, more preferably 0.9% or less, even more preferably 0.5% or less, and particularly preferably 0.4% or less. When the haze and internal haze are within the above ranges, the film has high transparency and can be suitably used for optical applications requiring light transmittance. The haze consists of the haze inside the film and the haze on the film surface (external), and these are referred to as internal haze and external haze, respectively.

[0104] The yellowness index (YI) of the resin film according to this embodiment is preferably 1.4 or less, more preferably 1.2 or less, and even more preferably 1.0 or less. If the yellowness index is within the above range, the transparency is high, and therefore the film can be suitably used for optical applications that require light transmittance.

[0105] The resin film according to this embodiment may contain an ultraviolet absorber from the viewpoint of further improving light resistance. The ultraviolet absorber aims to improve light resistance by absorbing ultraviolet light having a wavelength of 400 nm or less. When the resin film according to this embodiment contains an ultraviolet absorber, the transmittance of the resin film at a wavelength of 380 nm is preferably 2 to 30%, more preferably 4 to 20%, and even more preferably 5 to 10%.

[0106] A resin film produced using the methacrylic resin composition according to this embodiment tends to have a lower static friction coefficient than a resin film produced from a methacrylic resin alone. The static friction coefficient of the resin film according to this embodiment is preferably 2.50 or less, more preferably 2.20 or less, even more preferably 1.80 or less, and particularly preferably 1.50 or less. If the static friction coefficient is within the above range, there is an advantage that wrinkles and wrinkle marks due to contact between films are less likely to occur when the film is wound into a roll.

[0107] The resin film according to this embodiment can be suitably used as an optical film such as a polarizer protective film. When the resin film according to this embodiment is used as a polarizer protective film, it is preferable that the optical anisotropy is small. In particular, it is preferable that not only the optical anisotropy in the in-plane directions (length direction and width direction) of the resin film but also the optical anisotropy in the thickness direction is small. In other words, it is preferable that the absolute values ​​of both the in-plane retardation and the thickness direction retardation are small. For example, when the measurement wavelength is 590 nm, the absolute value of the in-plane retardation is preferably 20 nm or less, more preferably 15 nm or less. Furthermore, the absolute value of the thickness direction retardation is preferably 50 nm or less, more preferably 20 nm or less, and even more preferably 15 nm or less.

[0108] The retardation is an index value calculated based on birefringence. The in-plane retardation (Re) and thickness direction retardation (Rth) can be calculated using the following formulas. In an ideal resin film that is completely optically isotropic in three-dimensional directions, both the in-plane retardation Re and thickness direction retardation Rth are 0.

[0109] Re=(nx-ny)×d Rth = [(nx + ny) / 2 - nz] × d In the above formula, nx, ny, and nz represent the refractive index in the respective axial directions, where the in-plane stretching direction (polymer chain orientation direction) is the X axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the resin film is the Z axis. Also, d represents the thickness of the resin film, and nx-ny represents the orientation birefringence. The MD direction of the film is the X axis, but in the case of a stretched film, the stretching direction is the X axis.

[0110] The resin film according to this embodiment preferably has an orientation birefringence value of −5.0×10 -4 ~5.0×10 -4 , more preferably -4.0 × 10 -4 ~4.0×10 -4 , and more preferably −3.8×10 -4 ~3.8×10 -4If the orientation birefringence is within the above range, birefringence does not occur during molding and stable optical properties tend to be obtained.

[0111] <Stretching> The resin film according to this embodiment may be further stretched, which can improve the mechanical strength and thickness accuracy of the resin film.

[0112] When stretching the resin film according to the present embodiment, an unstretched resin film is first formed from the resin composition according to the present embodiment, and then uniaxially or biaxially stretched, thereby producing a stretched film (uniaxially or biaxially stretched film).

[0113] The stretching ratio of the stretched film is not particularly limited and is determined appropriately depending on the mechanical strength, surface properties, thickness accuracy, etc. of the stretched film to be produced. Although it also depends on the stretching temperature, the stretching ratio is generally preferably selected from the range of 1.1 to 5, more preferably from the range of 1.3 to 4, and even more preferably from the range of 1.5 to 3. If the stretching ratio is within the above range, the mechanical properties of the film, such as elongation, tear propagation strength, and flexural fatigue resistance, tend to be significantly improved.

[0114] <Application> The resin film according to this embodiment can be used in various applications such as transportation equipment, solar cell components, civil engineering and construction components, daily necessities, electrical and electronic devices, optical components, and medical supplies. In particular, the resin film according to this embodiment has excellent heat resistance and optical properties, and is therefore suitable for optical applications. Examples of optical applications include front panels (cover windows) for various display devices, diffusion plates, polarizer protective films, polarizing plate protective films, retardation films, light diffusion films, and optically isotropic films.

[0115] Among these, the resin film according to the present embodiment can be suitably used as a polarizer protective film or a front panel (cover window) of a display device. When the resin film according to the present embodiment is used as a front panel (cover window) of various display devices, a functional coating layer such as a primer layer or a hard coat layer may be formed on at least one main surface of the resin film, if necessary. When the resin film according to the present embodiment is used as a polarizer protective film, the resin film according to the present embodiment is bonded to a polarizer to form a polarizing plate. The polarizer is not particularly limited, and any conventionally known polarizer can be used. This polarizing plate is used in display devices such as liquid crystal display devices and organic EL display devices. [Example]

[0116] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. In the following examples, "parts" means "parts by mass."

[0117] The methods for measuring various physical properties described in the examples and comparative examples are as follows.

[0118] (1) Polymerization conversion rate (conversion rate) (Methacrylic resin polymerization conversion rate) In the production of methacrylic resin (Resin A), the polymerization conversion rate was determined as follows. First, the residual methyl methacrylate in the methacrylic resin was determined using a gas chromatograph (Agilent Technologies, 7890B). A DB-1 analytical column (Agilent Technologies, 0.8 μm film thickness, 0.20 mm internal diameter, 30 m length) was used. Analysis was performed under conditions of an inlet temperature of 150 °C and a detector temperature of 320 °C. The column temperature was increased from 35 °C to 250 °C at a rate of 30 °C / min and held for 3 minutes. A calibration curve was created using the internal standard method with chlorobenzene as the internal standard, and the residual methyl methacrylate rate (Wm, mass%) in the methacrylic resin was calculated. The polymerization conversion rate was then calculated using the following equation: Polymerization conversion rate (%) = 100-Wm

[0119] (Polymerization Conversion Rate of Diene-Based Crosslinked Particles) In the production of diene-based crosslinked particles (2), the polymerization conversion rate was determined by the following method. First, a portion of the obtained latex was sampled and precisely weighed, and dried in a hot air dryer at 120°C for 1 hour. The weight after drying was precisely weighed as the solid content. Next, the ratio of the weighed results before and after drying was determined as the solid content ratio in the latex. Then, using this solid content ratio, the polymerization conversion rate was calculated by the following formula. Polymerization conversion rate (%) = (total weight of raw materials charged × solid content ratio - total weight of raw materials other than polymerizable monomers) / charged weight of polymerizable monomers × 100

[0120] (2) Calculation of the percentage of glutarimide units The proportion of glutarimide units contained in the methacrylic resin (Resin C) was calculated as follows. First, a nuclear magnetic resonance apparatus (Bruker, AVANCEIII 400 MHz) was used to measure the proportion of glutarimide units in the methacrylic resin. 1 H-NMR measurement was performed. The molar ratio was calculated from the area A of the peak derived from the protons constituting the O-CH3 of methyl methacrylate around 3.5 to 3.8 ppm and the area B of the peak derived from the protons constituting the N-CH3 of the glutarimide ring around 3.0 to 3.3 ppm. The molar ratio was then converted into weight to calculate the proportion of glutarimide units.

[0121] (3) Volume average particle size of diene-based crosslinked particles In the production of the diene-based crosslinked particles (2), the volume average particle diameters of the diene-based rubbery polymer and rubber graft copolymer particles were measured in the latex state. The volume average particle diameters (nm) were measured using a MICROTRAC UPA150 manufactured by Nikkiso Co., Ltd.

[0122] (4) Syndiotacticity (rr) Methacrylic resin 1The H-NMR spectrum was measured using a nuclear magnetic resonance spectrometer (Bruker, AVANCEIII 400MHz) in a deuterated chloroform solution at 22°C with 16 accumulations. From the spectrum, the area (X) of the region from 0.60 to 0.95 ppm and the area (Y) of the region from 0.60 to 1.25 ppm were measured when tetramethylsilane (TMS) was set to 0 ppm, and then the syndiotacticity (rr) in triad notation was calculated using the formula: (X / Y) × 100.

[0123] (5) Average molecular weight and molecular weight distribution The weight-average molecular weight (Mw), number-average molecular weight (Mn), and the ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), which is an index of molecular weight distribution, of the methacrylic resin were calculated by a standard polystyrene conversion method using gel permeation chromatography (GPC). Specifically, analysis was performed using a sample solution prepared by dissolving 4 mg of methacrylic resin in 2 mL of chloroform using the following equipment and conditions. Measuring equipment: HLC-8220GPC (manufactured by Tosoh Corporation) Detector: RI detector Guard column: KF-G 4A (manufactured by Resonac Co., Ltd.) Analytical column: KF-806M and KF-806L manufactured by Resonac Corporation connected in series Eluent: chloroform Eluent flow rate: 1 mL / min Measurement temperature: 40℃ Standard material for calibration curve: polystyrene

[0124] (6) Percentage of terminal double bonds As a pretreatment, the methacrylic resin was dissolved in methylene chloride, and the solution was dropped into methanol to precipitate and purify the resin. The precipitated resin was collected by suction filtration, dried, and then subjected to analysis. Note that the methacrylic resin (Resin D) was not subjected to the above purification treatment, and the resin after production was subjected to analysis as is. A solution of 20 mg of the dried methacrylic resin was prepared in 0.6 to 0.7 mL of deuterated chloroform, and the NMR spectrum was analyzed using a nuclear magnetic resonance spectrometer (Bruker, AVANCE NEO 700 MHz).1 H-NMR was measured. The measurement temperature was 20°C, the number of accumulations was 8192, and the peak derived from the methoxy group of the methacrylic resin (3.60 ppm, the value when the chemical shift of the solvent peak was set to 7.26 ppm) was eliminated using the Excitation Sculpting (ES) method, which is a type of solvent elimination method. 1 From the H-NMR spectrum, the total area (X) of the peaks (5.47 to 5.53 ppm and 6.21 ppm) derived from the terminal double bonds of the methacrylic resin and the area (Y) of the peaks (0.5 to 1.25 ppm) derived from the α-methyl groups of the methacrylic resin were measured, and then the proportion of the terminal double bonds of the methacrylic resin was calculated using the formula: [(3 × X) / (2 × Y)] × 100.

[0125] (7) Glass transition temperature (Tg) The glass transition temperature of the methacrylic resin composition pellets was measured using a differential scanning calorimeter (DSC; Hitachi High-Tech Science Corporation, DSC7000X). First, under a nitrogen flow rate of 40 mL / min, the sample was heated from 40°C to 160°C at a heating rate of 10°C / min for the first time, cooled to 40°C, and then heated from 40°C to 160°C at a heating rate of 10°C / min for the second time. DSC measurements were performed under these conditions. Then, from the DSC curve measured during the second heating, the midpoint glass transition temperature (the temperature at the point where the curve representing the stepwise change in the glass transition intersects with a line equidistant in the vertical direction from both a line extrapolating the baseline before the inflection point to the higher temperature side and a line extrapolating the baseline after the inflection point to the lower temperature side) was read.

[0126] (8) 5% weight loss temperature (Td5) The 5% weight loss temperature (Td5) of the methacrylic resin composition pellets was measured using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation). First, the sample was heated from 40°C to 190°C at a heating rate of 10°C / min under a nitrogen flow of 200 mL / min, then cooled to 40°C, and then heated a second time from 40°C to 500°C at a heating rate of 10°C / min. The 5% weight loss temperature (Td5) was determined from the thermogravimetric (TG) curve measured during the second heating run, and the temperature at which the sample weight decreased to 95% of the weight at the start of the second heating run.

[0127] (9) Retention thermal stability The retention thermal stability of the methacrylic resin composition pellets was evaluated using a thermogravimetric analyzer (STA7200, manufactured by Hitachi High-Tech Science Corporation). First, under a nitrogen flow of 200 mL / min, the sample was heated from 40°C to 190°C at a heating rate of 10°C / min, then cooled to 40°C, and then heated from 40°C to 280°C at a heating rate of 10°C / min, and held at 280°C for 30 minutes, and the weight change was recorded under these conditions. The weight when the sample temperature reached 280°C was X0, and the weight when held at 280°C for 15 minutes was X. 15 The formula is: (X0-X 15 The retention heat stability was evaluated from the weight loss rate calculated by [( ...

[0128] (10) Total light transmittance The total light transmittance of the stretched resin film was measured using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K7361-1.

[0129] (11) Haze and internal haze The haze of the stretched resin film was measured using a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K7136. The same measurement was also performed with both sides of the resin film sandwiched between glycerin and then glass, and the value obtained was taken as the internal haze. The obtained result was converted into a film thickness equivalent to 40 μm.

[0130] (12) Yellowness index (YI) The yellowness index (YI) of the stretched resin film was measured using a spectrophotometer (SC-P, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7373. The obtained results were converted into a film thickness equivalent to 40 μm.

[0131] (13)b * value b of the resin film after stretching * The values ​​were measured using a spectrophotometer (SC-P, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS Z8781-4.

[0132] (14) Light transmittance at a wavelength of 380 nm The light transmittance of the stretched resin film at a wavelength of 380 nm was measured using an ultraviolet-visible spectrophotometer (V-560, manufactured by JASCO Corporation).

[0133] (15) Coefficient of static friction The static friction coefficient of the stretched resin film was measured in accordance with JIS K7125. First, side A of the stretched resin film was fixed on a smooth stainless steel plate, and side B of the stretched resin film was attached to a 60 mm x 60 mm, 200 g sled with double-sided tape. The load when the sled was moved at a speed of 100 mm / min via a pulley was read with a load cell, and the static friction coefficient was calculated. The measurement was performed five times with a new film, and the average value was calculated.

[0134] (16) MIT bending resistance test The stretched resin film was cut into 15 mm wide strips to serve as test specimens. These test specimens were measured using a MIT flexible fatigue tester, Model D, manufactured by Toyo Seiki Co., Ltd., under the conditions of a test load of 1.96 N, a speed of 175 times / min, a bending clamp curvature radius R of 0.38 mm, and a bending angle of 135° to the left and right, to determine the number of reciprocal bendings required to break the test specimen. Three measurements were performed in each of the MD and TD directions, and the arithmetic average value was used as the MIT reciprocal bending number.

[0135] <Production of methacrylic resin (resin A)> A 5-liter glass reactor equipped with an H-shaped impeller stirrer was charged with 150 parts of deionized water, 0.20 parts of tribasic calcium phosphate (dispersant), 0.0075 parts of sodium α-olefin sulfonate, and 0.30 parts of sodium chloride. Under a nitrogen atmosphere, while stirring at 250 rpm, 100 parts of methyl methacrylate, 0.289 parts of n-octyl mercaptan (chain transfer agent), and 0.074 parts of 2,2'-azobis(isobutyrate)dimethyl ester (V-601, Fujifilm Wako Pure Chemical Industries, Ltd.) (polymerization initiator) were added to the reactor. The temperature of the liquid in the reactor was then raised to 70°C to initiate polymerization. Two hours after the start of polymerization, 0.10 parts of tribasic calcium phosphate was added to the reaction mixture. An exothermic peak associated with the gel effect was observed 4 hours and 20 minutes after the start of polymerization. Seven hours after the start of polymerization, the temperature was raised to 95°C. Two hours after the temperature reached 95°C, the reactor was cooled to room temperature to terminate the polymerization. The polymerization conversion rate at the end of the polymerization was 99%.

[0136] The methacrylic resin bead dispersion obtained by the above polymerization was washed with 1N hydrochloric acid in an amount 0.1 times by weight relative to the amount of polymerizable monomer charged, then washed with water to remove dispersants, etc., and further dehydrated and dried to obtain bead-shaped methacrylic resin (Resin A). The physical properties of the obtained methacrylic resin (Resin A) are shown in Table 1 below.

[0137] <Methacrylic resin (Resin B)> The methacrylic resin (resin B) used was Parapet HR-S (a copolymer of methyl methacrylate and methyl acrylate, methyl methacrylate / methyl acrylate = 98.9 / 1.1 (mass ratio)) manufactured by Kuraray Co., Ltd. The physical properties of the methacrylic resin (resin B) are shown in Table 1 below.

[0138] <Production of methacrylic resin (resin C)> A 40 mm diameter, co-rotating, intermeshing twin-screw extruder (L / D = 90) was used to produce methacrylic resin (resin c1). The extruder barrel temperature was set to 250-280°C, and the screw rotation speed was set to 85 rpm. Using a loss-in-weight feeder CE-T-2E (Kubota Corporation), polymethyl methacrylate resin was fed to the main feeder at a feed rate of 42.4 kg / h. The resin was melted and filled using a kneading block, and then 1.8 parts of monomethylamine (Mitsubishi Gas Chemical Company, Inc.) per 100 parts of resin was injected through a nozzle. A reverse flight was inserted at the end of the reaction zone to fill the zone with resin. The pressure at the vent port was reduced to remove reaction by-products and excess monomethylamine. The strand extruded from the extruder die was cooled in a water bath and then cut using a pelletizer to obtain pelletized methacrylic resin (resin c1).

[0139] Next, a 40 mm diameter co-rotating intermeshing twin-screw extruder (L / D = 90) was used to produce methacrylic resin (Resin C). The barrel temperature was set to 240-260°C, and the screw rotation speed was set to 102 rpm. Using a loss-in-weight feeder CE-T-2E (Kubota Corporation), methacrylic resin (Resin C1) was fed to the main feeder at a feed rate of 41 kg / h. The resin was melted and filled using a kneading block, and then 0.56 parts of dimethyl carbonate per 100 parts of resin was injected through a nozzle to reduce the carboxyl groups in the resin. A reverse flight was inserted at the end of the reaction zone to fill the resin. The pressure at the vent port was reduced to remove reaction by-products and excess dimethyl carbonate. The strand extruded from the extruder die was cooled in a water bath and then cut using a pelletizer to obtain pelletized methacrylic resin (Resin C). The methacrylic resin (resin C) had a glutarimide structure in the main chain, and the proportion of glutarimide units was 6% by mass.

[0140] <Production of methacrylic resin (resin D)> A methacrylic resin prepared in the same manner as in Production Example 1 of Japanese Patent No. 6827272 was extruded at a resin temperature of 265°C using a 15mm diameter intermeshing co-rotating twin-screw extruder (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D=45). The resin that emerged as strands from a die installed at the extruder outlet was cooled in a water tank and then cut with a pelletizer to obtain pelletized methacrylic resin (Resin D).

[0141] <Diene-based crosslinked particles (1)> Kane Ace M521 (methyl methacrylate-butadiene-styrene (MBS) resin) manufactured by Kaneka Corporation was used as the diene-based crosslinked particles (1).

[0142] <Production of Diene-Based Crosslinked Particles (2)> A pressure vessel equipped with a stirrer was charged with 200 parts of pure water, 0.002 parts of ethylenediaminetetraacetic acid disodium salt, 0.0012 parts of ferrous sulfate, 0.008 parts of ethylenediaminetetraacetic acid disodium salt, and 0.12 parts of polyoxyethylene alkyl ether sodium phosphate, followed by deacidification. Next, 100 parts of butadiene, 0.05 parts of sodium formaldehyde sulfoxylate, and 0.2 parts of paramenthane hydroperoxide were added, followed by dropwise addition of 1.4 parts of polyoxyethylene alkyl ether sodium phosphate over 6 hours. The pH of the reaction solution was then adjusted to 6.5-7.5 and maintained at 50°C for 124 hours, yielding a diene-based rubber polymer latex (2a) with a volume average particle size of 130 nm at a polymerization conversion of 98%.

[0143] While maintaining the temperature of the rubber latex (2a) (solid content: approximately 71 parts) obtained above at 60°C, 22 parts of methyl methacrylate and 7 parts of styrene as polymerizable monomers were added over 1 hour. Simultaneously with the addition of the polymerizable monomers, addition of 0.07 parts of t-butyl hydroperoxide and 0.1 parts of sodium formaldehyde sulfoxylate was started, and the entire amount was added over 2 hours while maintaining the pH of the reaction solution at 6.5 to 7.5 and the temperature at approximately 60°C. Thereafter, the reaction solution was maintained at approximately 60°C for 1 hour to obtain a rubber graft copolymer latex (2b) having a volume average particle diameter of 145 nm. Two parts of a phenolic antioxidant, IRGANOX-1076 [n-octadecyl-3-(3',5',di-t-butyl-4'-hydroxyphenyl)propionate], was added to this rubber graft copolymer latex (2b), and the mixture was coagulated with an aqueous calcium chloride solution, washed with water, dehydrated, and dried to obtain powdery diene-based crosslinked particles (2).

[0144] Example 1 A hand-blended mixture of 99.9 parts of methacrylic resin (resin A) and 0.1 parts of diene-based crosslinked particles (1) was extruded at a resin temperature of 255°C using a 15mm diameter intermeshing co-rotating twin-screw extruder (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D = 45). The resin that emerged as strands from the die at the extruder outlet was cooled in a water bath and then pelletized using a pelletizer to obtain resin composition pellets. The obtained resin composition pellets were dried at 90°C for 4 hours and then extruded at a resin temperature of 240°C using a 15mm diameter intermeshing co-rotating twin-screw extruder (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D = 45) equipped with a T-die at the extruder outlet. The sheet-like molten resin extruded from the T-die was cooled using a cooling roll to obtain a resin film with a width of 160 mm and a thickness of 160 μm. In this case, the surface that contacted the casting roll was defined as side B, and the other side was defined as side A. A small piece of 100 mm x 100 mm was cut from the obtained resin film so that two sides were parallel to the extrusion direction. The small piece was placed in a pantograph-type biaxial stretching device and simultaneously biaxially stretched at 135°C by 2 times in the direction parallel to the extrusion direction and 2 times in the direction perpendicular to the extrusion direction. The stretching speed in each direction was 100 mm / min. The piece was then removed to room temperature and quenched to obtain a stretched film with a thickness of 39 μm. The physical properties of the resin composition pellets and stretched film are shown in Table 1 below.

[0145] <Example 2> Resin composition pellets and a stretched film having a thickness of 41 μm were obtained in the same manner as in Example 1, except that 99.5 parts of methacrylic resin (resin A) and 0.5 parts of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 parts of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and the stretched film are shown in Table 1 below.

[0146] Example 3 Resin composition pellets and a stretched film having a thickness of 38 μm were obtained in the same manner as in Example 1, except that 99 parts of methacrylic resin (resin A) and 1 part of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and the stretched film are shown in Table 1 below.

[0147] Example 4 Resin composition pellets and a stretched film having a thickness of 41 μm were obtained in the same manner as in Example 1, except that 98 parts of methacrylic resin (resin A) and 2 parts of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and the stretched film are shown in Table 1 below.

[0148] <Example 5> Resin composition pellets and a 40 μm thick stretched film were obtained in the same manner as in Example 1, except that 97 parts of methacrylic resin (resin A) and 3 parts of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and stretched film are shown in Table 1 below.

[0149] Example 6 Resin composition pellets and a 40 μm thick stretched film were obtained in the same manner as in Example 1, except that 99 parts of methacrylic resin (resin A) and 1 part of diene-based crosslinked particles (2) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and stretched film are shown in Table 1 below.

[0150] Example 7 Resin composition pellets and a 40 μm-thick stretched film were obtained in the same manner as in Example 1, except that 99.9 parts of methacrylic resin (resin A), 0.1 parts of diene-based crosslinked particles (1), and 0.7 parts of an ultraviolet absorber (ADEKA CORPORATION, Adekastab LA-F70) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 parts of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and the stretched film are shown in Table 1 below.

[0151] Example 8 Resin composition pellets and a 40 μm thick stretched film were obtained in the same manner as in Example 1, except that 99 parts of methacrylic resin (resin B) and 1 part of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and stretched film are shown in Table 1 below.

[0152] Example 9 Resin composition pellets and a stretched film having a thickness of 36 μm were obtained in the same manner as in Example 1, except that 99 parts of methacrylic resin (resin C) and 1 part of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1, and the stretching temperature of the resin film was set to 145° C. The physical properties of the resin composition pellets and the stretched film are shown in Table 1 below.

[0153] <Comparative Example 1> Resin pellets and a stretched film having a thickness of 39 μm were obtained in the same manner as in Example 1, except that 100 parts of methacrylic resin (resin A) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 parts of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin pellets and stretched film are shown in Table 2 below.

[0154] As shown in Table 2, compared with Examples 1 to 9, the thermal stability (Td5, residence thermal stability) of the resin pellets was poor, and the static friction coefficient of the stretched film was high.

[0155] <Comparative Example 2> Resin composition pellets and a stretched film having a thickness of 41 μm were obtained in the same manner as in Example 1, except that 95 parts of methacrylic resin (resin A) and 5 parts of diene-based crosslinked particles (1) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 part of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and the stretched film are shown in Table 2 below.

[0156] As shown in Table 2, compared with Examples 1 to 9, the total light transmittance, haze, internal haze, YI, and b * The results were high.

[0157] <Comparative Example 3> 100 parts of methacrylic resin (resin B) pellets were dried at 90°C for 4 hours and then extruded at a resin temperature of 240°C using a 15mm diameter intermeshing co-rotating twin-screw extruder (manufactured by Technovel Corporation, KZW15TWIN-45MG, L / D = 45) equipped with a T-die at the extruder outlet. The sheet-shaped molten resin extruded from the T-die was cooled with a cooling roll to obtain a resin film with a width of 160 mm and a thickness of 160 μm. In this case, the surface contacting the casting roll was defined as side B, and the other side was defined as side A. From the obtained resin film, a small piece of 100 mm x 100 mm was cut so that two sides were parallel to the extrusion direction. The small piece was placed in a pantograph-type biaxial stretching device and simultaneously biaxially stretched at 135°C, twice in the direction parallel to the extrusion direction and twice in the direction perpendicular to the extrusion direction. The stretching speed in each direction was 100 mm / min. The resin pellets were then removed and rapidly cooled to room temperature to obtain a stretched film having a thickness of 37 μm. The physical properties of the resin pellets and the stretched film are shown in Table 2.

[0158] As shown in Table 2, compared to Examples 1 to 9, the thermal stability (Td5, residence thermal stability) of the resin pellets was inferior, the heat resistance (glass transition temperature) was insufficient, and the static friction coefficient of the stretched film was high.

[0159] <Comparative Example 4> Resin composition pellets and a 40 μm-thick stretched film were obtained in the same manner as in Example 1, except that 100 parts of methacrylic resin (resin B) and 0.5 parts of antioxidant (ADEKA CORPORATION, Adekastab AO-60) were used instead of 99.9 parts of methacrylic resin (resin A) and 0.1 parts of diene-based crosslinked particles (1) in Example 1. The physical properties of the resin composition pellets and stretched film are shown in Table 2 below.

[0160] As shown in Table 2, the static friction coefficient of the stretched film was higher than that of Examples 1 to 9.

[0161] <Comparative Example 5> A stretched film having a thickness of 39 μm was obtained in the same manner as in Comparative Example 3, except that 100 parts of pellets of methacrylic resin (resin C) were used instead of 100 parts of pellets of methacrylic resin (resin B) in Comparative Example 3, and the stretching temperature of the resin film was set to 145° C. The physical properties of the resin pellets and stretched film are shown in Table 2 below.

[0162] As shown in Table 2, the static friction coefficient of the stretched film was higher than that of Examples 1 to 9.

[0163] <Comparative Example 6> A stretched film having a thickness of 40 μm was obtained in the same manner as in Comparative Example 3, except that 100 parts of pellets of methacrylic resin (resin D) were used instead of 100 parts of pellets of methacrylic resin (resin B) in Comparative Example 3, and the stretching temperature of the resin film was set to 138° C. The physical properties of the resin pellets and stretched film are shown in Table 2 below.

[0164] As shown in Table 2, the static friction coefficient of the stretched film was higher than that of Examples 1 to 9.

[0165] [Table 1]

[0166] [Table 2]

[0167] As shown in Table 1, the methacrylic resin compositions of Examples 1 to 9 had excellent thermal stability. In particular, a surprising result was obtained: the Td5 of the resin composition pellets obtained by combining a methacrylic resin with diene-based crosslinked particles was higher than the Td5 of the methacrylic resin alone. Therefore, the methacrylic resin compositions of Examples 1 to 9 have the advantage of being less susceptible to thermal decomposition when molded in an extruder. Furthermore, the resin films of Examples 1 to 9 maintained the excellent optical properties (transparency, color tone) of the methacrylic resin and were useful as optical films. Furthermore, the resin films of Examples 1 to 9 had relatively low coefficients of static friction. Therefore, the resin films of Examples 1 to 9 were less likely to develop wrinkles or wrinkle marks due to contact between films when wound into a roll, and were considered to have good roll winding properties (smoothness). As shown in Example 7, the addition of an ultraviolet absorber also made it possible to impart excellent light resistance.

Claims

1. A methacrylic resin composition containing a methacrylic resin and diene-based crosslinked particles, the proportion of the diene crosslinked particles in 100 parts by mass of the total of the methacrylic resin and the diene crosslinked particles is 0.01 to 3 parts by mass; The methacrylic resin composition has a thermal weight loss rate of less than 1.0% when exposed to 280°C in a nitrogen gas atmosphere for 15 minutes.

2. The methacrylic resin composition according to claim 1, wherein the diene-based crosslinked particles are core-shell type rubber graft copolymer particles having a core layer composed of a diene-based rubber-like polymer and a shell layer grafted to the core layer.

3. 3. The methacrylic resin composition according to claim 2, wherein the diene rubber polymer is a butadiene rubber polymer.

4. The methacrylic resin composition according to claim 1, wherein the weight average molecular weight of the methacrylic resin is 70,000 to 250,000.

5. The methacrylic resin composition according to claim 1, wherein the molecular weight distribution (Mw / Mn) of the methacrylic resin exceeds 1.

5.

6. The methacrylic resin composition according to claim 1, further comprising an ultraviolet absorber.

7. A resin film comprising the methacrylic resin composition according to any one of claims 1 to 6.

8. The resin film according to claim 7 , which is a polarizer protective film.

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