JP2009160891A - Laminated acrylic resin film, polarizer protective film, polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated acrylic resin film, which is superior in optical characteristics, transparency, zero defect, heat resistance, tenacity and working capability, a polarizing plate protective film employed thereof, a polarizing plate and a liquid crystal display. <P>SOLUTION: This laminated acrylic resin film includes an acrylic resin α containing glutaric anhydride unit having structural formula (1) and acrylic elastomer particles β. When let a B layer be a layer including acrylic elastomer particles β and an A layer be a layer with no acrylic elastomer particles included, this resin film is so constituted as to be produced by alternately laminating the A layer and the B layer in the direction of thickness by at least three sets of layers and, at the same time, every surface of the set is composed of the A layer having at least 1 μm and the total thickness of the A layers is set to be ≤30% of the total thickness of the film. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laminated acrylic resin film, a polarizing plate protective film using the film, a polarizing plate and a liquid crystal display.

  Acrylic resin films are excellent in transparency, surface gloss and light resistance, so liquid crystal display sheets or films, optical materials such as light guide plates, vehicle interior materials and exterior materials, vending machine exterior materials, electrification It is used for the surface skins of products, interior materials for building materials and exterior materials, and is used in a wide range of fields such as the protection of skins such as polycarbonate and vinyl chloride.

  In recent years, these resin films have been expanded to harsh usage environment conditions that require weather resistance and heat resistance, such as outdoors and in automobiles, due to the widespread use of, for example, automobile navigation systems and handy cameras. Yes. When used under such severe environmental conditions, a sheet or film having an acrylic resin as a substrate has excellent transparency and weather resistance, but has a problem that deformation occurs due to low heat resistance. Also, in processing steps such as drying, coating, and sputtering after coating, flatness deteriorates due to low heat resistance, and single elongation tends to occur due to process tension at high temperatures when the processing speed is increased. There was a problem. Another problem is that the toughness represented by the elongation at break and impact resistance is low, so that it is easy to break in the conveying process during processing. For the purpose of improving the heat resistance of an acrylic resin film, a film having a glutaric anhydride unit represented by the following structural formula (1) is disclosed (see Patent Document 1 and Patent Document 2).

  However, if the heat resistance is simply improved by adjusting the composition of the acrylic resin film, the flexibility is insufficient and the film is easily cracked by bending stress, and sufficient toughness required during processing cannot be obtained.

  In addition, for the purpose of simultaneously improving the heat resistance and toughness of the acrylic resin film, a crosslinked elastic body is contained in an acrylic resin containing a methyl methacrylate unit, a glutaric anhydride unit represented by the following structural formula (2), and a styrene unit. Disclosed is a film (see Patent Document 3).

However, since this film contains styrene units in the acrylic resin, heat resistance and transparency are not sufficient, and flatness deteriorates when processed at high speed and high temperature and high tension to improve productivity, In applications where high light transmittance is required, such as for film, there is a problem that the performance is insufficient. Further, this crosslinked elastic body aggregates in the extrusion process of melt film formation, and the film surface portion is deformed using the aggregate as a core, resulting in a surface defect, which may not be used as a polarizing plate.
JP 7-268036 A (first page) Japanese Patent Laying-Open No. 2004-2711 (first page) JP 2000-178399 A (first page)

  The object of the present invention is to solve the above-mentioned problems of the conventional film and not only have excellent optical isotropy, but also have excellent transparency, defect-free properties, heat resistance, toughness, and excellent processability. An object of the present invention is to provide a polarizing plate protective film, a polarizing plate and a liquid crystal display using the film.

  The present invention for achieving the above object is a laminated acrylic resin film containing an acrylic resin α containing a glutaric anhydride unit represented by the following structural formula (1) and acrylic elastic particles β, When the layer containing 5% by mass or less of the elastic elastic particles β is A layer and the layer containing 7-40% of the acrylic elastic particles β is B layer, the A layer and the B layer are alternately arranged in the thickness direction. It is a laminated acrylic resin film that is laminated to at least three layers and is composed of an A layer having a thickness of at least 1 μm on any surface, and the total thickness of the A layer is 30% or less of the total film thickness. It is characterized by.

In said formula, R < ¹ >, R < ² > represents the same or different hydrogen atom or a C1-C5 alkyl group.

  Moreover, it is also preferable that this invention is a polarizer protective film which uses said laminated acrylic resin film, a polarizing plate, and a liquid crystal display.

  The present invention provides a laminated acrylic resin film excellent in transparency, defect-free property, heat resistance, toughness, and workability in addition to optical isotropy, a polarizing plate protective film, a polarizing plate and a liquid crystal display using the film. can do.

  The present invention is a laminated acrylic resin film containing an acrylic resin α containing a glutaric anhydride unit represented by the following structural formula (1) and acrylic elastic particles β, wherein the acrylic elastic particles β are 5 When the layer containing not more than mass% is the A layer and the layer containing 7-40% of the acrylic elastic particles β is the B layer, the A layer and the B layer are alternately laminated in at least three layers in the thickness direction. In addition, the laminated acrylic resin film is composed of an A layer having a thickness of at least 1 μm on any surface, and the total thickness of the A layer is 30% or less of the total film thickness.

In said formula, R < ¹ >, R < ² > represents the same or different hydrogen atom or a C1-C5 alkyl group.

  The film of the present invention preferably has 3 or more layers as the number of layers, more preferably 5 layers or more, and still more preferably 9 layers or more. When the number of layers is less than 3, sufficient transparency and defect-free properties may not be obtained. In particular, according to various findings by the present inventors, the upper limit of the number of layers is not particularly limited, and may be, for example, about several tens of layers, but about 3 to 30 layers from the viewpoint of production. It is good to do. Therefore, according to the knowledge of the present inventors, the preferred number of layers is 3 to 30 layers, more preferably 5 to 15 layers.

  Further, the content of the acrylic elastic particles β in the A layer is preferably 0 to 5% by mass, more preferably 0 to 2% by mass, and further preferably 0% by mass (not contained). When the content exceeds 5% by mass, sufficient transparency and defect-free properties may not be obtained. On the other hand, the content of the acrylic elastic particles β in the B layer is preferably 7 to 40% by mass, more preferably 12 to 25% by mass. If the amount is less than 7% by mass, sufficient toughness cannot be obtained, and if it exceeds 40% by mass, the frequency of defects tends to deteriorate due to aggregation of the elastic body, and the heat resistance tends to decrease.

  Moreover, although the surface (both front and back surfaces) of the laminated acrylic resin film is composed of an A layer, the thickness of the A layer on this surface is preferably 1 μm or more, and more preferably. Is 2 μm or more. Further, the ratio of the total thickness of the A layer to the total film thickness is preferably 30% or less, more preferably 10% or less.

  When the thickness of the A layer in the surface layer portion on either side of the A layer is less than 1 μm, the laminated thickness of the surface layer is insufficient, resulting in insufficient transparency and defect-free properties. On the other hand, when the ratio of the total thickness of the A layer to the total film thickness exceeds 30%, the toughness is insufficient, and the bending resistance and the slit property are insufficient.

  Further, all the A layers or the B layers preferably have the same thickness in order to exhibit tear resistance, but the thickness of each layer is within the range satisfying the number of laminations and the lamination ratio. If the difference between the maximum and the minimum is within 30% of the average thickness of each layer, there is no particular problem in performance. In addition, about the measuring method of the lamination | stacking thickness of each layer, an interface is recognized from the difference in contrast by the change state of particle concentration or the difference in a polymer by cross-sectional observation with an electron microscope etc., and the thickness of each layer is calculated | required. When this method is difficult, after the laminated polymer is peeled off, the laminated thickness is obtained using a thin film level difference measuring machine.

  Moreover, about a layer structure, it is preferable to laminate | stack by regular permutation, such as ABABA and ABABABA, for example. When it consists of 2 types of resin, it is preferable to have the structure where they were laminated | stacked alternately. Here, the layer which comprises both surface layers of a film needs to be A layer from a viewpoint on the use as a polarizing plate protective film. When the B layer is located on the surface layer, transparency and defect-free properties tend to deteriorate due to the influence of the acrylic elastic particles contained in the B layer.

  For example, even when the layer containing the acrylic resin α ′ having a different type of acrylic resin α is the A ′ layer and the layer containing the acrylic elastic particle β ′ having a different type from the acrylic elastic particle β is the B ′ layer, , ABA′B′A and BAB′ABA ′ are preferably stacked alternately.

  As content with respect to the acrylic resin (alpha) of the said glutaric anhydride unit, 20-40 mass% is preferable, More preferably, it is 25-35 mass%. By setting it to 20% by mass or more, excellent heat resistance, optical isotropy and chemical resistance can be obtained, and an acrylic resin having a high glass transition temperature can be obtained as described later. On the other hand, the fall of toughness can be prevented by setting it as 40 mass% or less.

In particular, from the viewpoint of heat resistance, in the above structural formula (1), R ¹ and R ² are preferably hydrogen or a methyl group, and particularly preferably a methyl group.

  The acrylic resin α preferably contains a vinyl carboxylic acid alkyl ester unit. By adopting a vinylcarboxylic acid alkyl ester unit as the basic structural unit of the acrylic resin, an acrylic resin that is stable against heat and water can be obtained.

Examples of the vinyl carboxylic acid alkyl ester unit include those represented by the following general formula (3). However, R ³ is a hydrogen atom or a C1-5 aliphatic or alicyclic hydrocarbon, R ⁴ is an aliphatic hydrocarbon having 1 to 5 carbon atoms.

  Preferable specific examples of the vinyl carboxylic acid alkyl ester unit include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and (meth) acrylic acid. t-butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) Examples include 3-hydroxypropyl acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth) acrylate and 2,3,4,5-tetrahydroxypentyl (meth) acrylate. 1 type may be included independently and 2 or more types may coexist. Of these, methyl (meth) acrylate is most preferred because of its excellent thermal stability.

  Moreover, as a mass mean molecular weight of acrylic resin (alpha), 80,000-150,000 are preferable. By setting it to 80,000 or more, the mechanical strength of the acrylic resin film can be maintained. Moreover, coloring of resin can be prevented by setting it as 150,000 or less.

  In addition, the glass transition temperature (Tg) of the acrylic resin α is preferably 120 ° C. or higher in terms of heat resistance. Moreover, it is preferable to set it as 160 degrees C or less from the point of the ease of a process.

  In order to set the glass transition temperature within the above range, the content of the glutaric anhydride unit represented by the structural formula (1) with respect to the acrylic resin α as described above is the constituent amount represented by this structural unit. Is preferably 20 to 40% by mass in terms of mass relative to the entire polymer composition. The glass transition temperature here is measured at a rate of temperature increase of 20 ° C./min using a differential scanning calorimeter (for example, DSC-7 manufactured by Perkin Elmer).

  Moreover, as content with respect to the acrylic resin film of the said acrylic resin (alpha), it is important to set it as 60-90 mass%. By setting it as 60 mass% or more, the acrylic resin film which utilized the characteristic of acrylic resin (alpha), such as transparency, can be obtained. On the other hand, the upper limit value corresponds to the lower limit value of the addition amount of acrylic elastic particles β described later.

  Next, it is important that the laminated acrylic resin film of the present invention contains acrylic elastic particles β. The acrylic resin film contains acrylic elastic particles β and is dispersed, whereby excellent toughness as an acrylic resin film can be obtained.

  The rubbery polymer constituting the acrylic elastic particle β has an acrylic component such as an ethyl acrylate unit or a butyl acrylate unit as an essential component, and other components preferably included include a dimethylsiloxane unit and a phenylmethylsiloxane unit. Silicone component, styrene component such as styrene unit and α-methylstyrene unit, nitrile component such as acrylonitrile unit and methacrylonitrile unit, conjugated diene component such as butanediene unit and isoprene unit, urethane component or ethylene component, propylene component, isobutene component And so on.

  Among these, those composed of an acrylic component, a silicone component, a styrene component, a nitrile component, and a conjugated diene component are preferable.

  A rubber elastic body composed of a combination of two or more of these components is also preferable. For example, a rubber elastic body composed of an acrylic component and a silicone component, a rubber elastic body composed of an acrylic component and a styrene component, Examples thereof include a rubber elastic body composed of an acrylic component and a conjugated diene component, and a rubber elastic body composed of an acrylic component, a silicone component and a styrene component.

  In addition to these components, those containing a crosslinkable component such as a divinylbenzene unit, an allyl acrylate unit, or a butylene glycol diacrylate unit are also preferred.

  Among these, a combination of an acrylic acid alkyl ester unit and an aromatic vinyl-based unit is preferable. Alkyl acrylate units, especially butyl acrylate, are extremely effective in improving toughness, and the refractive index of acrylic elastic particles β can be adjusted by copolymerizing aromatic vinyl units such as styrene. .

  The difference in refractive index between the acrylic elastic particles β and the acrylic resin α is preferably 0.01 or less. Thereby, transparency as an acrylic resin film can be obtained. In order to satisfy such a refractive index condition, a method of adjusting each monomer unit composition ratio of the acrylic resin α and / or a composition of the rubber polymer or monomer used for the acrylic elastic particle β By adjusting the ratio, the refractive index difference can be reduced, and an acrylic resin film excellent in transparency can be obtained. In particular, acrylic elastomer particles having a small refractive index difference from the acrylic resin A can be obtained by copolymerizing an aromatic vinyl-based unit such as styrene with an alkyl acrylate such as butyl acrylate and adjusting the copolymerization ratio. Obtainable.

  The average particle diameter of the acrylic elastic particles β is important to be 70 to 300 nm, preferably 100 to 200 nm. If it is less than 70 nm, the effect of improving toughness is not sufficient, and if it is more than 300 nm, the heat resistance is lowered.

  As content with respect to the acrylic resin film of acrylic elastic-body particle | grain (beta), it is preferable to set it as 7-40 mass%, More preferably, it is 12-20 mass%. When it is less than 7% by mass, the effect of improving toughness is not sufficient, and when it exceeds 40% by mass, the heat resistance tends to decrease.

  In addition, the laminated acrylic resin film of the present invention is within the range that does not impair the object of the present invention, such as polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, etc. Other thermoplastic resins, phenol-based, melamine-based, polyester-based, silicone-based, and epoxy-based thermosetting resins may be further contained. In addition, hindered phenol, benzotriazole, benzophenone, benzoate, and cyanoacrylate UV absorbers or antioxidants, higher fatty acids, acid esters and acid amides, and higher alcohol and other lubricants or plasticizers , Montanic acid, its salts, its esters, its half esters, release agents such as stearyl alcohol, stearamide and ethylene wax, anti-coloring agents such as phosphites and hypophosphites, halogen-based or phosphorus-based and silicone It may contain additives such as non-halogen flame retardants, nucleating agents, amine-based, sulfonic acid-based, polyether-based antistatic agents, pigments and other colorants. However, in light of the characteristics required by the application to be applied, it is preferable to add the additive within a range where the color of the additive does not adversely affect the thermoplastic polymer and the transparency is not lowered. Specifically, the total content of resins and additives other than the acrylic resin α and the acrylic elastic particles β with respect to the acrylic resin film is preferably 10% by mass or less.

  The laminated acrylic resin film of the present invention preferably has a breaking elongation of 15% or more, more preferably 20% or more. The elongation at break here is measured as the elongation at which the film breaks when a tensile test is performed at a speed of 300 m / min on a sample having an initial length of 50 mm and a width of 10 mm sampled in the longitudinal direction of the film. If the elongation at break is low, it means that the toughness is inferior, and if it is less than 15%, for example, a film breakage occurs in the film transport process, and a problem that slitting at high speed becomes difficult occurs. The upper limit of the elongation at break is not limited, but if it is 40%, it can be sufficiently put into practical use.

The acrylic resin film of the present invention preferably has a Charpy impact strength in the longitudinal direction of the film of 60 kJ / m ² · 100 μm or more, more preferably 90 kJ / m ² · 100 μm or more. By setting Charpy impact strength to 60 kJ / m ² · 100 μm or more, a film that can withstand slits at high speed can be obtained. In order to obtain an acrylic resin film having a large Charpy impact strength, it is effective to increase the average particle diameter of the acrylic elastic particles within a range that does not deteriorate the optical characteristics.

  The laminated acrylic resin film of the present invention preferably has a total light transmittance of 91% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve the excellent transparency expressed by the total light transmittance, it is necessary not to introduce an additive or a copolymer component that absorbs visible light, or to reduce the refractive index of the acrylic resin α. Is effective.

  In addition, the laminated acrylic resin film of the present invention preferably has a haze value (turbidity) that is one of the indices indicating transparency of 1.5% or less, more preferably 1.0% or less. is there. In order to achieve such a haze value, it is effective to reduce the refractive index difference between the acrylic resin α and the acrylic elastic particles β as described above.

  In addition, since the surface roughness also affects the haze value as surface haze, the particle diameter and addition amount of the acrylic elastic particles β are suppressed within the above range, or the cooling roll, calender roll, drum, belt, solution during film formation It is also effective to reduce the surface roughness of the coated substrate in film formation.

  The laminated acrylic resin film of the present invention utilizes its excellent transparency, heat resistance, light resistance, and toughness to make housings such as electric / electronic parts, optical filters, automobile parts, mechanical mechanism parts, OA equipment, home appliances, etc. It can be used for various applications such as those parts and general goods.

  Specific applications of the molded product include, for example, various covers, various terminal boards, printed wiring boards, speakers, microscopes, binoculars, cameras, optical instruments represented by watches, and excellent transparency and heat resistance. From the point of view, finder such as camera, VTR, projection TV, filter, prism, Fresnel lens, etc. as video equipment related parts, various optical disc (VD, CD, DVD, MD, LD, etc.) substrates as optical recording / optical communication related parts Information equipment related parts such as protective films, optical switches, optical connectors, etc., liquid crystal displays, flat panel displays, plasma display light guide plates, Fresnel lenses, polarizing plates, polarizer protective films, retardation films, light diffusion films, viewing angles Magnifying film, reflective film, antireflection film, antiglare film Brightness enhancement film, conductive films for touch panels, covers, etc., is very useful for these various applications.

  Next, a method for producing the laminated acrylic resin film of the present invention will be described.

  The acrylic resin α containing the glutaric anhydride unit represented by the structural formula (1) can basically be produced by the following method.

  An unsaturated carboxylic acid monomer represented by the following general formula (4), an unsaturated carboxylic acid alkyl ester monomer represented by the following general formula (5), and other vinyl monomer units: When it is contained, the vinyl monomer giving the unit is polymerized to obtain a copolymer (a).

However, ^{R 5} represents hydrogen or an alkyl group having 1 to 5 carbon atoms.

However, R ⁶ is hydrogen or an aliphatic or alicyclic hydrocarbon group having 1 to 5 carbon atoms, R ⁷ represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms.

  As a polymerization method for producing the copolymer (a), a known polymerization method such as bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization or the like basically by radical polymerization can be used, and there are fewer impurities. Particularly preferred are solution polymerization, bulk polymerization and suspension polymerization.

  The polymerization temperature for producing the copolymer (a) is preferably 95 ° C. or lower, more preferably 85 ° C. or lower, from the viewpoint of preventing the resin from being colored and having a good color tone. Preferably it is 75 degrees C or less. Further, the lower limit of the polymerization temperature is preferably 50 ° C. or higher, more preferably 60 ° C. or higher from the viewpoint of productivity in consideration of the polymerization rate. Further, for the purpose of improving the polymerization yield or the polymerization rate, the polymerization temperature may be raised according to the progress of the polymerization. In this case as well, the upper limit temperature is preferably controlled to 95 ° C. or lower throughout the process, and the polymerization initiation temperature is increased. Is preferably performed at a relatively low temperature of 75 ° C. or lower.

  Moreover, as polymerization time which produces | generates a copolymer (a), 60-360 minutes are preferable from the point of production efficiency, More preferably, it is 90-180 minutes.

  Since the molecular weight of the acrylic resin α is determined by the molecular weight of the copolymer (a), as described above, when the acrylic resin α is within the range of its preferred mass average molecular weight (80,000 to 150,000), the copolymer ( The molecular weight of a) is also preferably 80,000 to 150,000 in terms of mass average molecular weight.

  The molecular weight of the copolymer (a) is, for example, a radical polymerization initiator such as an azo compound or a peroxide, or a chain transfer agent such as an alkyl mercaptan, carbon tetrachloride, carbon tetrabromide, dimethylacetamide, dimethylformamide, triethylamine or the like. It can control by adjusting the addition amount. In particular, a method of adjusting the addition amount of alkyl mercaptan as a chain transfer agent can be preferably employed from the viewpoint of stability of polymerization, ease of handling, and the like.

  Examples of the alkyl mercaptan used here include n-octyl mercaptan, t-dodecyl mercaptan, n-dodecyl mercaptan, n-tetradecyl mercaptan, n-octadecyl mercaptan and the like, among which t-dodecyl mercaptan and n-dodecyl. Mercaptans are preferably used.

  When the copolymer (a) is heated in the presence or absence of a suitable catalyst, the copolymer (a) is dehydrated from adjacent carboxyl groups of two unsaturated carboxylic acid units or adjacent to each other. The alcohol is eliminated from the unsaturated carboxylic acid unit and the unsaturated carboxylic acid alkyl ester unit to produce one unit of the glutaric anhydride unit.

  Examples of the method for heating and dehydrating and / or dealcoholizing the copolymer (a), that is, performing an intramolecular cyclization reaction, include a method using a heated extruder having a vent, an inert gas atmosphere or A method using an apparatus capable of heating and devolatilizing under reduced pressure is preferable from the viewpoint of productivity.

  As a specific apparatus, for example, a single-screw extruder equipped with a “unimelt” type screw, a twin-screw extruder, a three-screw extruder, a continuous or batch kneader type kneader, and the like can be used. It is preferable to use a twin screw extruder in terms of continuous productivity, reaction temperature, time, and shear rate, and quality stability. The length / diameter ratio (L / D) of the screw of the extruder is preferably 40 or more. By setting the L / D to 40 or more, it is possible to secure a sufficient heating time for advancing the intramolecular cyclization reaction. The amount of saturated carboxylic acid units remaining can be reduced, and a polymer can be obtained with less generation of bubbles in the molded product due to re-advancement of the reaction during the heat molding process, and deterioration of the color tone at the time of molding residence can be suppressed.

  Moreover, it is more preferable that the apparatus has a structure capable of introducing an inert gas such as nitrogen into them. This is because when the intramolecular cyclization reaction by heating in the presence of oxygen tends to increase yellowness, it is preferable to sufficiently replace the system with an inert gas such as nitrogen. For example, as a method of introducing an inert gas such as nitrogen into a twin screw extruder, a method of flowing an inert gas of about 10 to 100 L / min by connecting piping from the upper part and / or the lower part of the hopper can be mentioned.

  The temperature for heating for the intramolecular cyclization reaction is preferably from 180 to 300 ° C, more preferably from 200 to 280 ° C, from the viewpoint that the reaction proceeds smoothly.

  The heating time for the intramolecular cyclization reaction may be appropriately set according to the desired copolymer composition, but is usually preferably 1 to 60 minutes, more preferably 2 to 30 minutes, and even more preferably 3 ~ 20 minutes.

  Moreover, when heating for the intramolecular cyclization reaction, it is also preferable to add one or more of an acidic catalyst, an alkaline catalyst, and a salt catalyst. Examples of the acidic catalyst include hydrochloric acid, sulfuric acid, p-toluenesulfonic acid, phosphoric acid, phosphorous acid, phenylphosphonic acid, methyl phosphate, and the like. Examples of the basic catalyst include metal hydroxides, amines, imines, alkali metal derivatives, alkoxides and the like. Examples of the salt-based catalyst include acetic acid metal salt, stearic acid metal salt, metal carbonate salt, ammonium hydroxide salt and the like. Among them, a basic catalyst or a salt-based catalyst containing an alkali metal can be preferably used because it exhibits an excellent reaction promoting effect with a relatively small addition amount. Specifically, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide, sodium methoxide, sodium ethoxide, sodium phenoxide, potassium methoxide, potassium ethoxide, alkoxide compounds such as potassium phenoxide, Examples thereof include organic carboxylates such as lithium acetate, sodium acetate, potassium acetate and sodium stearate. Among them, sodium hydroxide, sodium methoxide, lithium acetate and sodium acetate can be preferably used.

  The addition amount of these catalysts is preferably about 0.01 to 1 part by mass with respect to 100 parts by mass of the copolymer (a). By setting it as 0.01 mass part or more, the effect as the said catalyst can be acquired, and by setting it as 1 mass part or less, the color which the catalyst possesses has a bad influence on coloring of a thermoplastic polymer, or transparency. Can be prevented from decreasing.

  When the acrylic elastic particles β are contained and dispersed in the acrylic resin α or the precursor thereof, the acrylic elastic particles β are laminated with an acrylic resin having a glass transition temperature of 60 ° C. or higher on the surface layer, or vinyl-based. It is preferably carried out in a state where the monomer is graft copolymerized. By doing so, adhesion / aggregation of the acrylic elastic particles β made of a rubbery polymer is prevented, the handling property is improved, and the dispersibility in the acrylic resin α is also improved.

  “60 ° C.” constituting the shell portion of the acrylic elastic particles β in an aspect (hereinafter also referred to as “core-shell type”) in which an acrylic resin having a glass transition temperature of 60 ° C. or higher is laminated on the surface layer. As the “acrylic resin having the above glass transition temperature”, those containing an unsaturated carboxylic acid alkyl ester unit or an unsaturated carboxylic acid unit are preferable. When the core-shell type acrylic elastic particles β containing these in the shell portion are added to the copolymer (a) and heated, for example, the affinity with the matrix resin is good and the dispersibility is improved. Moreover, since the intramolecular cyclization reaction also proceeds in the shell portion by the heating, and the shell portion and the matrix resin are assimilated, it is possible to prevent the transparency of the acrylic resin film from being inhibited by the shell portion. . Further, since the acrylic elastic particles β are firmly held in the matrix resin, mechanical properties such as impact resistance are also improved.

  As a monomer used as a raw material of the unsaturated carboxylic acid alkyl ester unit, (meth) acrylic acid alkyl ester is preferable, and methyl (meth) acrylate is more preferably used.

  Moreover, as a monomer used as the raw material of an unsaturated carboxylic acid-type unit, (meth) acrylic acid is preferable and methacrylic acid is more preferably used.

  In the core / shell type acrylic elastic particles β, the mass ratio between the core and the shell is preferably 50 to 90% by mass, more preferably 50% to 90% by mass of the core (rubber polymer). Is 60-80 mass%.

  Examples of commercially available core-shell type acrylic elastic particles β include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., Ltd., “Kane Ace” manufactured by Kaneka Chemical Industry Co., Ltd., “Paraloid” manufactured by Kureha Chemical Industry Co., Ltd. Acryloid ", Ganz Kasei Kogyo Co., Ltd." Staffyroid ", Kuraray Co., Ltd." Parapet SA "and the like may be used, and these may be used alone or in combination of two or more.

  Further, in a mode in which a vinyl monomer is graft-copolymerized (hereinafter also referred to as “graft copolymer type”) in the acrylic elastic particle β, the vinyl monomer may be an unsaturated carboxylic acid having a vinyl group. An ester monomer, an unsaturated carboxylic acid monomer having a vinyl group, an aromatic vinyl monomer, or the like can be employed. Further, other vinyl monomers may be copolymerized in accordance with the compatibility with the rubbery polymer or matrix resin constituting the acrylic elastic particles β.

  The amount of the vinyl monomer to be imparted to the acrylic elastic particles β is preferably (10-80) :( 20-90), more preferably, by mass ratio of rubbery polymer: vinyl monomer. (20 to 70): (30 to 80), more preferably (30 to 60): (40 to 70). The effect of this aspect can be acquired by making a vinyl monomer into 20 mass% or more. On the other hand, it can suppress that impact strength falls by making a vinyl-type monomer 90 mass% or less.

  The graft copolymer type acrylic elastic particles β may contain a component derived from a vinyl monomer that is not graft copolymerized. From the viewpoint of impact strength, the graft ratio is 10 to 100%. Preferably there is. Here, the graft ratio is a mass ratio of a graft copolymerized vinyl monomer provided to the rubber polymer. In addition, the intrinsic viscosity measured at 30 ° C. of the methylethylketone solvent of the ungrafted copolymer is not particularly limited, but 0.1 to 0.6 dl / g is a balance between impact strength and moldability. From the viewpoint of, it is preferably used.

  Polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be employed as a method for making the acrylic elastic particles β into the graft copolymerization type.

  The particle diameter, content, and refractive index of the core-shell type or graft copolymer type acrylic elastic particles β are evaluated for rubbery polymers excluding the shell part and graft copolymer part. The particle diameter can be evaluated by excluding the shell portion and the graft copolymer portion from, for example, cross-sectional observation with a transmission electron microscope. Moreover, content can be evaluated from the insoluble component after making it melt | dissolve in solvents, such as acetone, which melt | dissolves an acrylic resin.

  As a method of blending acrylic elastic particles β and other additives into acrylic resin α or a precursor thereof, for example, after blending acrylic resin α and other additive components in advance, usually at 200 to 350 ° C., uniaxially or A method of uniformly kneading with a twin screw extruder can be employed.

  In addition, acrylic elastomer particles β and other additives are added to the copolymer (a) which is a precursor of acrylic resin α, and simultaneously with the intramolecular cyclization reaction by a twin screw extruder or the like, the acrylic elastomer Blending by melt kneading of the particles β and other additives can be performed.

  In the melt-kneading, a cyclization reaction of unsaturated carboxylic acid monomer units such as a shell portion imparted to the acrylic elastic particles β and unsaturated carboxylic acid alkyl ester monomer units can be simultaneously performed.

  In the case of solution casting described later, a method of removing the solvent after mixing the acrylic resin α and the acrylic elastic particles β in a solvent that dissolves or disperses can be used.

  Particularly in solution casting, the resin constituting the acrylic resin film of the present invention is preferably filtered for the purpose of removing foreign substances. By removing the foreign matter, the resin can be prevented from being colored and can be usefully used as an optical application film. Filters made of sintered metal, porous ceramics, sand, wire mesh, etc. at a temperature of 25 ° C. to 100 ° C. with a resin dissolved in a solvent such as tetrahydrofuran, acetone, methyl ethyl ketone, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone Can be filtered.

  The laminated acrylic resin film of the present invention can be formed by melt film formation. Examples of the melt film formation include an inflation method, a T-die method, a calendar method, a cutting method, and the T-die method can be particularly preferably employed. Examples of the solution casting include a casting method on a polymer film, a casting drum method, a casting method on a metal belt, and the casting method on a polymer film can be preferably used. Hereinafter, each manufacturing method will be described as an example.

For melt film formation, an extruder type melt extrusion apparatus equipped with a single screw or a twin screw can be used. The L / D of the screw is preferably 25 to 120 in order to prevent coloring. The melt extrusion temperature for producing the acrylic resin film of the present invention is preferably 150 to 350 ° C, more preferably 200 to 300 ° C. The melt shear rate, 1,000 s ^-1 or 5,000 S ^-1 or less. Moreover, when melt-kneading using a melt-extrusion apparatus, it is preferable to perform melt-kneading under a reduced pressure using a vent or nitrogen stream from a viewpoint of coloring suppression.

  An acrylic resin α constituting the A layer and an acrylic resin α containing the acrylic elastic particles β constituting the B layer are prepared in the form of pellets or the like. If necessary, the pellets are pre-dried in hot air or under reduced pressure and supplied to an extruder. In the extruder, the resin melted by heating to the melting point or higher is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or modified resin is filtered through a filter or the like. Further, the resin is formed into a desired shape with a die and then discharged.

  As a method for obtaining a multi-layer film of 4 layers or more, a multi-manifold die for laminating resin sent from different flow paths using two or more extruders inside the die and a field block for laminating before the die. Alternatively, a method of laminating in a multilayer using a static mixer or the like can be used. Moreover, you may combine these arbitrarily.

  In the T-die method, molten resin is measured by a gear pump and then discharged from a T-die die, and is adhered to a cooling medium such as a drum by an electrostatic application method, an air chamber method, an air knife method, a press roll method, or the like. The film can be obtained by cooling and solidifying. In particular, the press roll method is preferable for obtaining a film having little thickness unevenness and a small haze.

  Hereinafter, the configuration and effects of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

[Measuring method]
(1) Composition of each component Acetone was added to the acrylic resin film and refluxed for 4 hours, and this solution was centrifuged at 9,000 rpm for 30 minutes to separate into an acetone soluble component and an acetone insoluble component. The acetone-soluble component was dried under reduced pressure at 60 ° C. for 5 hours, and each component unit was quantified to obtain each component composition of the acrylic resin α.

In general, an infrared spectrophotometer or a proton nuclear magnetic resonance ( ¹ H-NMR) measuring instrument is used for quantification of each component unit, but here, it is determined by a proton nuclear magnetic resonance method. ^{In the 1} H-NMR method, for example, in the case of a copolymer consisting of a glutaric anhydride unit, methacrylic acid, and methyl methacrylate, the spectral assignment in a dimethyl sulfoxide heavy solvent is 0.5 to 1.5 ppm peak. Is hydrogen of α-methyl group of methacrylic acid, methyl methacrylate and glutaric anhydride ring compound, peak of 1.6 to 2.1 ppm is hydrogen of methylene group of polymer main chain, peak of 3.5 ppm is methyl methacrylate The carboxylic acid ester (—COOCH ₃ ) of hydrogen, the peak at 12.4 ppm can determine the copolymer composition from the carboxylic acid hydrogen of methacrylic acid and the integral ratio of the spectrum. In addition to the above, in the case of a copolymer containing styrene as another copolymer component, hydrogen of an aromatic ring of styrene is seen at 6.5 to 7.5 ppm, and the copolymer is similarly obtained from the spectral ratio. The composition can be determined.

(2) Mass average molecular weight (absolute molecular weight)
Gel permeation chromatograph (pump: model 515, manufactured by Waters, column: TSK-gel-GMH _XL , Tosoh) equipped with a DAWN-DSP type multi-angle light scattering photometer (manufactured by Wyatt Technology) using dimethylformamide as a solvent. The measurement was performed using

(3) Charpy impact strength According to JIS K7111 (2006). Using a test piece without notch sampled in the longitudinal direction of the film, the test was performed with a length of 50 mm and a width of 10 mm. The measurement was performed 10 times or more with respect to a separate sample, and the average value was used to convert per 100 μm thickness.

(4) Total light transmittance, haze The total light transmittance (%) and haze (haze) (%) at 589.3 nm and 23 ° C. were measured using a direct reading haze meter manufactured by Toyo Seiki Co., Ltd. The total light transmittance was in accordance with JIS-K7361 (1997), and haze was in accordance with JIS K7136 (2000).

  The measurement was performed 10 times or more on separate samples, and the average value was used.

(5) Bending resistance Sampling with a width of 10 mm and a length of 200 mm was performed in the longitudinal direction of the film, 10 mm at both ends were bonded with an adhesive tape to form a loop, and a laminator (Lami Packer LPD650 manufactured by NBS Ricoh Co., Ltd.) was used at 25 ° C. Each of the rubber rolls was passed once and bent 180 times, and the following determinations were made.

      A: No cracks and no creases.

      ○: A crease entered but did not break.

      X: A crack occurred in a part or the entire surface of the film.

(6) Slit property Using a 1,300 mm width biaxial slitter manufactured by Toray Engineering Co., Ltd., with an air cut with a single blade (FAS-10) manufactured by Feather Safety Razor Co., Ltd., a film having a length of 500 m has a tension of 15 kg. / M, 50 m / min were slit, and the end face after the slit was visually observed to make the following determination.

    A: The end face is a straight line, and end face disorder with a period of 0.5 mm or more is not observed by visual judgment.

    ○: Although slitting was possible, there was a portion where the end face was uneven, and end face disturbance with a period of 0.5 mm or more and an amplitude of 1 mm or more and less than 5 mm was visually observed.

    X: Even if the film was broken and could not be slit in the slit, or the slit was possible, there was a portion where the end face was uneven, and the end face disorder with a period of 0.5 mm or more and an amplitude of 5 mm or more was visually observed.

(7) Defect frequency / size
A defect in a 1 m ² film plane was detected using a transmission type defect detector. The detected defect was observed with a microscope to determine the diameter of the defect. Here, the diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter (diameter of circumscribed circle) is determined. The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope. When observing with reflected light, if the size of the defect is not clear, aluminum or platinum may be deposited on the surface for observation. Of the defects whose diameters have been determined as described above, the number of defects having a diameter of 5 μm or more is determined. The number of defects having a diameter of 5 μm or more per 1 m ² was divided by 100 to determine the number of defects having a diameter of 5 μm or more per 10 cm square, that is, the frequency of defects (pieces / 10 cm square).

A: Defect frequency is less than 0.1 / 10 cm square ○: Defect frequency is 0.1 / 10 cm square or more, less than 1/10 cm square X: Defect frequency is 1/10 cm square or more [Example]
(1) Preparation of acrylic resin First, a methyl methacrylate / acrylamide copolymer suspending agent was prepared as follows.

20 parts by weight of methyl methacrylate,
80 parts by mass of acrylamide,
0.3 parts by mass of potassium persulfate,
1,500 parts by mass of ion-exchanged water was charged into the reactor, and while the reactor was replaced with nitrogen gas, the reaction was allowed to proceed at 70 ° C. until the monomer was completely converted to a polymer. The obtained aqueous solution was used as a suspending agent. A solution in which 0.05 part by mass of the above suspending agent is dissolved in 165 parts by mass of ion-exchanged water is supplied to a stainless steel autoclave having a volume of 5 liters and equipped with a baffle and a foudra-type stirring blade, and the system is filled with nitrogen gas. It stirred at 400 rpm, replacing.

  Next, a mixed substance having the following charge composition was added while stirring the reaction system.

Methacrylic acid: 27 parts by weight Methyl methacrylate: 73 parts by weight t-dodecyl mercaptan: 1.2 parts by weight 2,2′-azobisisobutyronitrile: 0.4 parts by weight After the addition, the temperature was raised to 70 ° C., The time at which the internal temperature reached 70 ° C. was set as the polymerization start time, and the polymerization was continued for 180 minutes. Thereafter, the reaction system was cooled, the polymer was separated, washed and dried in accordance with a normal method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the mass average molecular weight was 130,000.

Add 0.2% by mass of additive (NaOCH ₃ ) to the above copolymer and use 10L of nitrogen from the hopper using a twin screw extruder (TEX30 (manufactured by Nippon Steel), L / D = 44.5). An intramolecular cyclization reaction was performed at a screw rotation speed of 100 rpm, a raw material supply rate of 5 kg / h, and a cylinder temperature of 290 ° C. while purging at an amount of / min. To obtain a pellet-like acrylic resin α.

(2) Preparation of acrylic elastic particles (core-shell type acrylic elastic particles) In a glass container with a cooler (capacity 5 liters), as an initial adjustment solution,
120 parts by weight of deionized water,
0.5 parts by weight of potassium carbonate,
0.5 parts by weight of dioctyl sulfosuccinate,
After charging 0.005 parts by mass of potassium persulfate and stirring under a nitrogen atmosphere,
53 parts by weight of butyl acrylate,
17 parts by mass of styrene,
1 part by weight of allyl methacrylate (crosslinking agent) was charged. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a rubbery polymer.

Then
21 parts by mass of methyl methacrylate,
9 parts by weight of methacrylic acid,
A mixture of 0.005 parts by mass of potassium persulfate was continuously added over 90 minutes at 70 ° C. and held for another 90 minutes to polymerize the shell layer.

  This polymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered and dried to obtain core / shell type acrylic elastic particles β. The average particle size of the rubbery polymer portion of the acrylic elastic particles measured with an electron microscope was 140 nm.

(3) Blending of acrylic resin α and acrylic elastic particle β β Acrylic resin α and acrylic elastic particle β are blended in combinations as shown in Table 1 in each of the examples and comparative examples. Using Nippon Steel Corporation TEX30, L / D = 44.5), the mixture was kneaded at a screw speed of 150 rpm and a cylinder temperature of 280 ° C. to obtain a pellet-shaped acrylic resin composition.

(4) Film Formation In each Example / Comparative Example, film formation was performed by melt film formation as shown in Table 1. Both film forming methods were performed as follows.

Example 1
Acrylic resin α forming the A layer (referred to as resin A), a mixed composition of acrylic resin α and acrylic elastic particles β forming the B layer (mixing ratio; 80 parts by mass: 20 parts by mass, referred to as resin B) Is dried under reduced pressure at 80 ° C. for 8 hours, discharged using two 65 mmφ single screw extruders with vents, and after passing through a gear pump and a filter, respectively, the resins A and B are merged in the first stage feed block. A laminated resin is formed, and a total of 9 layers as a structure in which the resin A is alternately laminated in the thickness direction of 5 layers and the resin B is 4 layers (hereinafter, the alternating layers are referred to as A layer and B layer, respectively). A feed block was used. The lamination thickness ratio was adjusted by the discharge amount so that A: B = 1: 3.

  The laminate consisting of a total of 9 layers thus obtained was supplied to a T die, formed into a sheet, and then extruded through a T die (set temperature 270 ° C.) with a slit gap of 0.5 mm, and the surface finished 1S stainless steel. An acrylic resin film having a film thickness of 40 μm was obtained by cooling so that both sides were completely adhered to a polishing roll (70 ° C.).

  Detailed production conditions and film characteristics for this film are shown in Tables 1 and 2.

(Examples 2 to 12, Comparative Examples 1 to 9)
In the same manner as in Example 1, as shown in Table 1, an acrylic resin film having a film thickness of 40 μm was obtained by changing the resin mixing ratio, the lamination ratio, the number of laminations, and the lamination method. The detailed production conditions and film characteristics of each are shown in Table 1.

  The laminated acrylic resin film of the present invention is suitably used as a protective film for polarizers used in polarizing plates by taking advantage of its excellent transparency, defect-free properties, heat resistance, and toughness, as well as electric / electronic parts, optical filters. It can be used for various purposes such as automobile parts, machine mechanism parts, OA equipment, home appliances and other housings and their parts, and general goods.

  Specific applications of the molded product include, for example, various covers, various terminal boards, printed wiring boards, speakers, microscopes, binoculars, cameras, optical instruments represented by watches, and excellent transparency and heat resistance. From the point of view, finder such as camera, VTR, projection TV, filter, prism, Fresnel lens, etc. as video equipment related parts, various optical disc (VD, CD, DVD, MD, LD, etc.) substrates as optical recording / optical communication related parts Information equipment related parts such as protective films, optical switches, optical connectors, etc., liquid crystal displays, flat panel displays, plasma display light guide plates, Fresnel lenses, polarizing plates, polarizer protective films, retardation films, light diffusion films, viewing angles Magnifying film, reflective film, antireflection film, antiglare film Brightness enhancement film, a prism sheet, conductive films for touch panels, covers, etc., is very useful for these various applications.

Claims (6)

A laminated acrylic resin film containing an acrylic resin α containing a glutaric anhydride unit represented by the following structural formula (1) and acrylic elastic particles β, and containing 5% by mass or less of acrylic elastic particles β When the layer to be made is the A layer and the layer containing 7 to 40% by mass of the acrylic elastic particles β is the B layer, the A layer and the B layer are alternately laminated in at least three layers in the thickness direction, A laminated acrylic resin film comprising an A layer having a thickness of at least 1 μm on any surface, and the total thickness of the A layer being 30% or less of the total film thickness.

In said formula, R < ¹ >, R < ² > represents the same or different hydrogen atom or a C1-C5 alkyl group. The laminated acrylic resin film according to claim 1, wherein five or more A layers and B layers are laminated. The laminated acrylic resin film according to claim 1 or 2, wherein the haze value is 1.5% or less. The polarizer protective film which uses the laminated acrylic resin film in any one of Claims 1-3. A polarizing plate comprising the polarizer protective film according to claim 4. A liquid crystal display using the polarizing plate according to claim 5.