JP5546235B2 - Optical film - Google Patents

Description

  The present invention relates to an optical film containing an acrylic polymer having a ring structure in the main chain and triacetyl cellulose.

  Cellulose-based resin is a film that protects photographic negative film supports and polarizers used in liquid crystal displays because of its high transparency, low birefringence, and easy adhesion to polarizers. Has been used.

  Acrylic resins, on the other hand, are not only transparent, but also have excellent surface gloss and weather resistance, and have a good balance of mechanical strength, moldability, and surface hardness. Widely used in Furthermore, in recent years, a resin containing an acrylic polymer having a ring structure in the main chain that has both transparency and heat resistance has been developed, and application to optical film applications and the like has been studied. A resin containing an acrylic polymer having a ring structure in the main chain has a glass transition temperature (Tg) higher than that of a general acrylic resin. For example, in an image display device, the resin is disposed close to a heat generating part such as a light source. It has various practical advantages such as being easy. For example, Patent Documents 1 and 2 disclose resins containing an acrylic polymer having a lactone ring structure in the main chain obtained by cyclization of a polymer having a hydroxyl group and an ester group in the molecular chain. ing. Patent Document 3 discloses a resin containing an acrylic polymer having a glutarimide structure in the main chain as a ring structure, and Patent Document 4 discloses an acrylic resin having a glutaric anhydride structure in the main chain as a ring structure. A resin containing a polymer is disclosed.

  Further, Patent Document 5 discloses that a resin containing an acrylic polymer having a ring structure in the main chain is useful as a modifier for a cellulose resin that has been used in optical films such as a polarizer protective film. It is known to suppress deformation failure of the original film such as horseback failure and convex failure of the cellulose resin film.

JP 2006-96960 A JP-A-2005-146084 WO05 / 108438 publication WO05 / 105918 JP 2009-1744 A

  However, it has been found that when an acrylic polymer is added to a cellulosic resin, the problem of the cellulosic resin can be improved, but the transparency of the film is lowered, making it difficult to apply to an optical film. The present invention is an optical film comprising an acrylic polymer having a ring structure in the main chain and a cellulose resin, and has excellent optical properties common to an acrylic polymer having a ring structure in the main chain and a cellulose resin. An object is to provide an optical film having heat resistance.

  The present invention is an optical film comprising an acrylic polymer having a ring structure in the main chain and triacetyl cellulose, and having a haze of 1 or less.

  The acrylic polymer having a ring structure in the main chain preferably has a glass transition temperature of 110 ° C. or higher.

  The acrylic polymer having a ring structure in the main chain preferably has a ring structure content of 10% by weight or more.

  The optical film preferably contains 5 to 50% by weight of an acrylic polymer having a ring structure in the main chain and 50 to 95% by weight of triacetyl cellulose.

  The optical film of the present invention is an optical film containing an acrylic polymer having a ring structure in the main chain and triacetyl cellulose, and can provide an optical film having high transparency.

In the following description, “%” means “% by weight” and “parts” means “parts by weight” unless otherwise specified. In addition, “A to B” indicating a range indicates that the range is A or more and B or less.
<< Acrylic polymer having a ring structure in the main chain >>
The acrylic polymer having a ring structure in the main chain in the present invention includes a structure derived from a (meth) acrylate monomer and a ring structure in the main chain. The total content of the structural units derived from the (meth) acrylate monomer and the content of the cyclic structural units is preferably 50% by weight or more, more preferably 70% by weight or more, and still more preferably 90% by weight in the main chain. %, Particularly preferably 95% by weight or more, most preferably 99% by weight or more. In particular, the content of the ring structure is preferably 25% by weight or more, more preferably 35% by weight or more, and most preferably 40% by weight or more.

  (Meth) acrylic acid ester units are, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t- (meth) acrylic acid t- Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acryl Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, (meth) acrylic acid 2, 3,4,5,6-pentahydroxyhexyl, 2,3,4,5-tetrahydro (meth) acrylic acid Shipenchiru is a structural unit derived from a monomer such as. You may have 2 or more types of these structural units. It is preferable to have a methyl methacrylate unit. In this case, the thermal stability of an acrylic polymer, a composition containing the acrylic polymer, and a molded article such as a film obtained by molding the composition is improved.

  The acrylic polymer having a ring structure in the main chain may have a structural unit other than the (meth) acrylic acid ester unit. In order to introduce a ring structure into the main chain by a cyclization reaction, the acrylic polymer is preferably copolymerized with a monomer having a hydroxyl group or a carboxylic acid group at the time of polymerization. Specifically, as a monomer having a hydroxyl group, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, methyl 2- (hydroxyethyl) acrylate, or a carboxylic acid group As the monomer, the (meth) acrylic acid unit is a structural unit derived from a monomer such as acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, and the like. Is mentioned. Two or more kinds of these monomers may be copolymerized. A monomer having a hydroxyl group or a carboxylic acid group changes to a ring structure by a cyclization reaction, but is derived from a monomer having an unreacted hydroxyl group or carboxylic acid group in an acrylic polymer having a ring structure in the main chain. A structural unit may be included.

  In addition, the acrylic polymer having a ring structure in the main chain may have other structural units, such as styrene, vinyl toluene, α-methylstyrene, α-hydroxymethylstyrene. , Α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, 4-methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N- It is a structural unit derived from monomers such as vinylpyrrolidone and N-vinylcarbazole. The acrylic polymer may have two or more of these structural units.

  An acrylic polymer having a ring structure in the main chain has a higher Tg than a normal acrylic polymer having no ring structure, and the heat resistance of the resulting film is improved. Thus, a film containing an acrylic polymer having a ring structure in the main chain is suitable for use as an optical film because it can be easily placed near a heat generating part such as a light source in an image display device.

  Although the kind of ring structure is not specifically limited, For example, it is at least 1 sort (s) chosen from lactone ring structure, glutaric anhydride structure, glutarimide structure, N-substituted maleimide structure, and maleic anhydride structure. Among these, a lactone ring structure is preferable from the viewpoint of compatibility with triacetyl cellulose.

  The lactone ring structure that the acrylic polymer may have in the main chain is not particularly limited, and may be, for example, a 4- to 8-membered ring. A 6-membered ring is preferable, and a 6-membered ring is more preferable. The lactone ring structure which is a 6-membered ring is, for example, the structure disclosed in Japanese Patent Application Laid-Open No. 2004-168882. However, a high lactone ring is produced due to the high polymerization yield of the precursor and the cyclization reaction of the precursor. The structure represented by the following general formula (1) is preferable because an acrylic polymer having a content rate can be obtained and a polymer having a methyl methacrylate unit as a constituent unit can be used as a precursor.

  In the above general formula (1), R1, R2 and R3 are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The organic residue in the general formula (1) is, for example, an alkyl group having 1 to 20 carbon atoms, such as a methyl group, an ethyl group, or a propyl group. An aromatic hydrocarbon group having 1 to 20 carbon atoms, such as a saturated aliphatic hydrocarbon group, a phenyl group, or a naphthyl group, and the alkyl group, the unsaturated aliphatic hydrocarbon group, and the aromatic hydrocarbon group are One or more hydrogen atoms may be substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group, and an ester group.

  The glass transition temperature (Tg) of the acrylic polymer having a ring structure in the main chain is not particularly limited, but is preferably 110 ° C. or higher. Since Tg as an acrylic polymer can be improved, the Tg of the acrylic polymer is more preferably 115 ° C. or higher, and further preferably 120 ° C. or higher. In addition, Tg of a general acrylic polymer is about 100 ° C.

  The content of the ring structure of the acrylic polymer having a ring structure in the main chain is not particularly limited, but is preferably 10% by weight or more, more preferably 15 to 95% by weight, and still more preferably from the viewpoint of compatibility with triacetyl cellulose. Is 20 to 90% by weight, particularly preferably 25 to 85% by weight, most preferably 35 to 80% by weight. When the content of the ring structure in the acrylic polymer is less than 10% by weight, the transparency and heat resistance of the optical film may be lowered. On the other hand, when the content rate is transiently increased, moldability at the time of molding an optical film may be deteriorated.

  The acrylic polymer having a ring structure in the main chain is not particularly limited, but is preferably thermoplastic. If it is thermoplastic, melt molding including pelletization is possible, and moldability is improved.

  The weight average molecular weight (Mw) of the acrylic polymer having a ring structure in the main chain is preferably 50,000 or more. More preferably, it is 50,000 or more and 1 million or less, More preferably, it is 80,000 or more and 500,000 or less. Further, the dispersity is preferably 3.5 or less, more preferably 3 or less. The weight average molecular weight and dispersity were determined by polystyrene conversion using GPC (gel permeation chromatograph). The dispersity is the weight average molecular weight / number average molecular weight, and is calculated from the measurement results of the weight average molecular weight and the number average molecular weight by GPC. By setting the weight average molecular weight of the acrylic polymer having a ring structure in the main chain to 50,000 or more, the thermal stability during processing and the strength when formed into a molded product are improved. Further, by setting the degree of dispersion to 3.5 or less, the branched structure of the resin is suppressed, and the heat stability during processing and the appearance when formed into a molded product are improved.

  An acrylic polymer having a ring structure in the main chain can be produced by a known method. An acrylic polymer whose ring structure is a glutaric anhydride structure or a glutarimide structure can be produced, for example, by the method described in WO2007 / 26659 or WO2005 / 108438. An acrylic polymer whose ring structure is a maleic anhydride structure or an N-substituted maleimide structure can be produced, for example, by the method described in JP-A-57-153008 and JP-A-2007-31537. An acrylic polymer whose ring structure is a lactone ring structure can be produced, for example, by the method described in JP-A-2006-96960, JP-A-2006-171464, or JP-A-2007-63541.

  As a method for producing an acrylic polymer having a ring structure in the main chain, it is preferable to carry out a cyclization reaction after the polymerization step for polymerizing the acrylic polymer to introduce the ring structure into the main chain.

  The content of (meth) acrylic acid ester in the monomer component to be subjected to the polymerization step is preferably 30 to 95% by weight, more preferably 50 to 90% by weight, still more preferably 60 to 90% by weight, particularly preferably. 65 to 85% by weight. When the content of the (meth) acrylic acid ester is less than 30% by weight, the optical properties of the obtained acrylic polymer may be inferior. On the contrary, when the content of (meth) acrylic acid ester exceeds 95% by weight, the heat resistance of the obtained acrylic polymer may be lowered.

  The content of (meth) acrylic acid in the monomer component used for the polymerization step is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, still more preferably 0 to 10% by weight, and particularly preferably. Is 0 to 5% by weight. When the content of (meth) acrylic acid exceeds 30% by weight, gelation may occur in the polymerization step.

  You may mix | blend monomers other than (meth) acrylic acid ester and (meth) acrylic acid in the monomer component with which it uses for a superposition | polymerization process. These monomers may be used alone or in combination of two or more.

  The polymerization temperature and the polymerization time vary depending on the type of monomer (monomer composition) used, the ratio of use, etc., but preferably the polymerization temperature is in the range of 0 to 150 ° C., and the polymerization time is 0.5 to The polymerization time is in the range of 20 hours, and more preferably, the polymerization temperature is in the range of 80 to 140 ° C., and the polymerization time is in the range of 1 to 10 hours. The polymerization solvent is preferably an organic solvent, and is not particularly limited. For example, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ethers such as tetrahydrofuran Solvents: Alcohol solvents such as methanol, ethanol, butanol and the like. These solvents may be used alone or in combination of two or more.

  The polymerization solvent preferably contains an alcohol-based solvent because a crosslinking reaction between main chains caused by a dealcoholization reaction such as a transesterification reaction can be suppressed. However, when the content of the alcohol solvent is high, the solubility of the acrylic polymer having a ring structure in the main chain becomes poor, so the content of the alcohol solvent in the organic solvent is preferably 0 to 90%, more Preferably it is 0 to 50%, more preferably 0 to 20%, particularly preferably 0 to 5%.

  Moreover, since the residual volatile matter of the acrylic polymer finally obtained will increase when the boiling point of a polymerization solvent is too high, the solvent whose boiling point is 40-200 degreeC is preferable, and when implementing solution casting It is also possible to mix with triacetyl cellulose as it is without devolatilization, but in this case, the boiling point of the polymerization solvent is preferably 40 to 100 ° C. When the boiling point of the polymerization solvent exceeds 100 ° C., a method of lowering the boiling point of the organic solvent by reducing the pressure in the polymerization tank, cooling the jacket part, or cooling by a coil introduced into the polymerization tank is performed. A form in which the temperature is controlled by the method is also a preferable polymerization form.

  During the polymerization reaction, a polymerization initiator may be added as necessary. The polymerization initiator is not particularly limited. For example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl Organic peroxides such as carbonate and t-amylperoxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2 ′ -Azobis (2,4-dimethylvaleronitrile), dimethyl 2,2'-azobisisobutyrate; and the like. These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator used is not particularly limited as long as it is appropriately set according to the combination of monomers and reaction conditions.

  When carrying out the polymerization, it is preferable to control the concentration of the acrylic polymer produced in the polymerization solution to be 60% by weight or less in order to suppress gelation of the polymerization solution. Specifically, when the concentration of the acrylic polymer produced in the polymerization solution exceeds 60% by weight, it is preferable to add a polymerization solvent to the polymerization solution and control it to be 60% by weight or less. The concentration of the acrylic polymer produced in the polymerization solution is more preferably 45% by weight or less, still more preferably 40% by weight or less. In addition, since productivity will fall when the density | concentration of the acrylic polymer produced | generated in the polymerization solution is too low, the density | concentration of the acrylic polymer produced | generated in the polymerization solution becomes like this. Preferably it is 10 weight% or more, More preferably, it is 20 % By weight or more.

  In order to control the viscosity of the polymerization solution and the polymerization temperature, adding an organic solvent during the polymerization is one of preferable modes. It does not specifically limit as a form to add, For example, a polymerization solvent may be added continuously to a polymerization solution, and a polymerization solvent may be added intermittently. In addition, the polymerization solvent to be added may be, for example, the same type of polymerization solvent as that used at the initial stage of the polymerization reaction or a different type of polymerization solvent. It is preferred to use the same type of solvent that is sometimes used. Moreover, the polymerization solvent to be added may be only one kind of single solvent or two or more kinds of mixed solvents. By adding a polymerization solvent during the polymerization of the resin, the viscosity of the polymerization solution in the polymerization tank can be controlled within a certain range, and sufficient stirring can be performed. Branching and crosslinking of the generated polymer chain can be suppressed. In addition, since a polymerization solvent having a temperature lower than the polymerization temperature is added, the polymerization temperature in the polymerization system that generates heat during the polymerization can be easily controlled.

  The polymerization solution obtained when the above polymerization process is completed usually contains an organic solvent in addition to the obtained acrylic polymer, but the solvent is completely removed to solidify the acrylic polymer. It is not necessary to take it out in a state, and it is preferable to introduce it into the subsequent cyclization reaction step in a state containing an organic solvent. Further, if necessary, a solvent suitable for the subsequent cyclization reaction may be added again after taking out in a solid state.

  The cyclization reaction is preferably performed after polymerization, and the cyclization reaction is accelerated by heating. In the case of an acrylic polymer having a lactone ring structure or a glutaric anhydride structure in the main chain, a hydroxy group or a carboxyl group present in the molecular chain of the acrylic polymer and an ester group undergo a cyclization reaction to form a lactone ring structure or This reaction produces a glutaric anhydride structure. Alcohol is generated by the cyclization reaction and dealcoholization is performed. In the case of an acrylic polymer having a glutarimide structure in the main chain, an amino group of the added amino group-containing compound, a carboxyl group present in the polymer chain, and an ester group cause a cyclization reaction, and the cyclization reaction causes water and Alcohol is generated and dehydration and dealcoholization are performed. By forming the ring structure in the molecular chain of the acrylic polymer (in the main skeleton of the acrylic polymer), high heat resistance is imparted.

  It is preferable to add a known cyclization catalyst when performing the cyclization reaction. By adding a cyclization catalyst after polymerization of the resin, side reaction of the monomer and catalyst and branching / crosslinking during the polymerization are suppressed, and the acrylic polymer has excellent thermal stability and mechanical strength. I can do it.

  As the cyclization catalyst, an esterification catalyst such as p-toluenesulfonic acid or a transesterification catalyst may be used, or an organic carboxylic acid such as acetic acid, propionic acid, benzoic acid, acrylic acid or methacrylic acid may be used as the catalyst. Good. Furthermore, as disclosed in, for example, JP-A-61-254608 and JP-A-61-261303, a basic compound, an organic carboxylate such as zinc acetate, a carbonate, or the like may be used. .

  Alternatively, an organic phosphorus compound may be used as a catalyst for the cyclization reaction. Examples of the organic phosphoric acid compounds that can be used include alkyl (aryl) phosphonous acids such as methyl phosphonous acid, ethyl phosphonous acid, and phenyl phosphonous acid (however, these are alkyl (aryl) which are tautomers. ) Which may be phosphinic acid) and their monoesters or diesters; dialkyl (aryl) phosphinic acids such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid and their Esters; alkyl (aryl) phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid and their monoesters or diesters; methylphosphinic acid, ethylphosphinic acid Alkyl (aryl) phosphinic acids such as phenylphosphinic acid and esters thereof; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite, phosphorus phosphite Phosphorous acid monoester, diester or triester such as trimethyl phosphate, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, isodecyl phosphate, lauryl phosphate, phosphoric acid Stearyl, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, octyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, diisostearyl phosphate, Diphenyl phosphate, trimethyl phosphate, triethyl phosphate Phosphoric acid monoesters, diesters or triesters such as triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine, diethylphosphine , Diphenylphosphine, trimethylphosphine, triethylphosphine, triphenylphosphine, etc. mono-, di- or tri-alkyl (aryl) phosphine; methyldichlorophosphine, ethyldichlorophosphine, phenyldichlorophosphine, dimethylchlorophosphine, diethylchlorophosphine, diphenyl Alkyl (aryl) halogen phosphines such as chlorophosphine; methylphosphine oxide, ethylphosphine oxide, oxide Mono-, di- or tri-alkyl (aryl) phosphines such as phenyl phosphine, dimethyl phosphine oxide, diethyl phosphine oxide, diphenyl phosphine oxide, trimethyl phosphine oxide, triethyl phosphine oxide, triphenyl phosphine oxide; tetramethylphosphonium chloride, chloride And halogenated tetraalkyl (aryl) phosphoniums such as tetraethylphosphonium and tetraphenylphosphonium chloride. These organic phosphorus compounds may be used alone or in combination of two or more. Among these organophosphorus compounds, since the catalytic activity is high and the colorability is low, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester, and alkyl (aryl) phosphonic acid Preferably, alkyl (aryl) phosphonous acid, phosphorous acid monoester or diester, phosphoric acid monoester or diester is more preferable, and alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester is particularly preferable.

  Further, a basic cyclization catalyst can be used, and a group 12 element compound described in JP-A-2009-144112, particularly a zinc compound is preferable. Specific types of the zinc compound are not particularly limited. For example, organic zinc compounds such as zinc acetate, zinc propionate, and zinc octylate; inorganic zinc compounds such as zinc oxide, zinc chloride, and zinc sulfate; zinc trifluoromethanesulfonate And an organic zinc compound containing fluorine.

  Although the usage-amount of the catalyst used in the case of a cyclization reaction is not specifically limited, For example, Preferably it is 0.001-5 weight% with respect to an acrylic polymer, More preferably, it is 0.01-2. 0.5 wt%, more preferably 0.01 to 1 wt%, particularly preferably 0.05 to 0.5 wt%. When the amount of the catalyst used is less than 0.001% by weight, the reaction rate of the cyclization reaction may not be sufficiently improved. Conversely, if the amount of the catalyst used exceeds 5% by weight, the resulting acrylic polymer may be colored, or the main chain of the acrylic polymer may be cross-linked, making melt molding difficult.

  The addition timing of the catalyst is not particularly limited. For example, the catalyst may be added during the polymerization process, may be added after the polymerization process, or may be added in both of them. The catalyst may be added while heating during the polymerization or after the polymerization, or may be heat-treated at a high temperature after the addition of the cyclization catalyst.

  The method for heating in the cyclization reaction is not particularly limited, and a conventionally known method may be used. For example, the polymerization solution containing the polymerization solvent obtained by the polymerization step may be heat-treated as it is, or the solvent may be heat-treated after devolatilization. In one preferred embodiment, the cyclization reaction is carried out at a temperature of 200 ° C. or higher in a pressure-resistant device such as an autoclave in a solution state to promote the cyclization reaction at a high temperature. Or a devolatilization process can also be performed using the heating furnace or reaction apparatus provided with the vacuum apparatus or devolatilization apparatus for removing a volatile component, the extruder provided with the devolatilization apparatus, etc. In the present invention, it is one of preferred embodiments to heat the polymerization solution containing the catalyst under pressure. After heating in a state containing a polymerization solvent and a cyclization catalyst to be described later, and further cyclizing by heating to 200 ° C. or higher under pressure in a pressure-resistant apparatus, without devolatilization and deterioration in the re-dissolution process, An acrylic polymer having a high degree of conversion and excellent heat resistance and having a ring structure in the main chain can be obtained in a solution state, and can be directly mixed with triacetyl cellulose to form a solution film.

  The reactor that can be employed in the cyclization reaction is not particularly limited, and examples thereof include an autoclave, a kettle reactor, a devolatilization apparatus composed of a heat exchanger and a devolatilization tank, and the like. A vented extruder suitable for the cyclization reaction using the devolatilization step at the same time can also be used. Among these reactors, a kettle reactor, an autoclave, and a heat exchanger are particularly preferable in the present invention. In one preferred embodiment, the cyclization catalyst is added and then heat-treated at normal pressure in a kettle reactor and then heat-treated at a high temperature of 200 ° C. or higher under pressure using a pressure-resistant device such as an autoclave or a heat exchanger. is there.

  In the cyclization reaction, for example, it is possible to heat-react the polymerization solution containing the acrylic polymer obtained in the polymerization step and the polymerization solvent without using a catalyst, but in the present invention, a cyclization catalyst is added. Then, a method of heating reaction is preferable. Although the heating time is not particularly limited, for example, the heating temperature is preferably 40 to 300 ° C., and the heating time is preferably 1 to 20 hours, more preferably 2 to 10 hours. If the heating temperature is less than 40 ° C. or the heating time is less than 1 hour, the cyclization reaction rate may decrease. Conversely, when the heating temperature exceeds 300 ° C. or the heating time exceeds 20 hours, the resin may be colored or decomposed.

  In the present invention, the devolatilization step described in JP-A-2000-230016, JP-A-2007-262396, JP-A-2007-262399, etc. can be used in combination with the cyclization reaction. The acrylic polymer having a ring structure in the devolatilized main chain is redissolved in the solvent used at the time of polymerization or a low boiling point solvent preferable for solution film formation, and used for solution film formation.

  It is preferable to perform the cyclization reaction in the presence of a solvent and to use a devolatilization step in combination with the cyclization reaction. In this case, a mode in which a devolatilization step is used throughout the cyclization reaction and a mode in which the devolatilization step is not used over the entire cyclization reaction but only in a part of the process are included. In the method using the devolatilization step in combination, the alcohol produced as a by-product in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous for the production side.

  The devolatilization step refers to a step of removing volatile components such as a solvent and residual monomers and alcohol produced as a by-product by a cyclization reaction leading to a lactone ring structure under reduced pressure heating conditions as necessary. If this removal treatment is insufficient, the residual volatile components in the produced resin increase, resulting in problems such as coloration due to alteration during molding, or molding defects such as bubbles or silver streaks.

  In the case of using the devolatilization step throughout the cyclization reaction, the apparatus to be used is not particularly limited, but in order to more effectively perform the present invention, a devolatilization apparatus comprising a heat exchanger and a devolatilization tank, It is preferable to use an extruder with a vent, and the devolatilizer and the extruder arranged in series, more preferably a devolatilizer comprising a heat exchanger and a devolatilizer or an extruder with a vent. .

  In the case of using a devolatilizer comprising the heat exchanger and the devolatilization tank, the reaction treatment temperature is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the reaction treatment temperature is lower than 150 ° C., the cyclization reaction may be insufficient and the residual volatile matter may increase, and if it is higher than 350 ° C., coloring or decomposition may occur.

  In the case of using a devolatilizer comprising the heat exchanger and the devolatilization tank, the pressure during the reaction treatment is preferably within a range of 931 to 1.33 hPa (700 to 1 mmHg), and 798 to 66.5 hPa (600 to 50 mmHg). ) Is more preferable. When the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol easily remain, and when the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  When using the extruder with a vent, one or a plurality of vents may be used, but it is preferable to have a plurality of vents.

  In the case of using the vented extruder, the reaction treatment temperature is preferably in the range of 150 to 350 ° C, more preferably in the range of 200 to 300 ° C. If the temperature is lower than 150 ° C, the cyclization reaction may be insufficient and the residual volatile matter may increase. If the temperature is higher than 350 ° C, coloring or decomposition may occur.

  In the case of using the extruder with a vent, the pressure during the reaction treatment is preferably within a range of 931 to 1.33 hPa (700 to 1 mmHg), and more preferably within a range of 798 to 13.3 hPa (600 to 10 mmHg). When the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol easily remain, and when the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  In addition, in the case of using the devolatilization step throughout the cyclization reaction, as described later, the physical properties of the acrylic polymer having a cyclic structure in the main chain obtained under severe heat treatment conditions may deteriorate, Preferably, the above-described dealcoholization reaction catalyst is used and it is preferably carried out using a vented extruder or the like under the mildest conditions possible.

  Further, in the case of a form in which a devolatilization step is used throughout the cyclization reaction, preferably, the polymer obtained in the polymerization step is introduced into the cyclization reactor system together with a solvent, but in this case, if necessary, It may be passed through the reactor system such as a vented extruder once again.

  You may perform the form which uses together a devolatilization process only in a part of process, without using together over the whole process of a cyclization reaction. For example, the apparatus for producing the polymer is further heated, and if necessary, a part of the devolatilization step is used together to advance the cyclization reaction to some extent in advance, and then the devolatilization step is used at the same time. In this form, a cyclization reaction is performed to complete the reaction.

  In the form of using the devolatilization step throughout the cyclization reaction described above, for example, when the polymer is heat-treated at a high temperature of about 250 ° C. or higher using a twin-screw extruder, Due to the difference, partial decomposition or the like may occur before the cyclization reaction occurs, and the physical properties of the acrylic polymer having a ring structure in the main chain may be deteriorated. Therefore, before the cyclization reaction using the devolatilization process at the same time, if the cyclization reaction is allowed to proceed to some extent, the reaction conditions in the latter half can be relaxed, and the resulting acrylic polymer having a ring structure in the main chain It is preferable because deterioration of physical properties can be suppressed. As a particularly preferred embodiment, the devolatilization step is started after a lapse of time from the start of the cyclization reaction, that is, the hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step are cyclized in advance. The cyclization reaction rate may be raised to some extent, and then the cyclization reaction using the devolatilization step at the same time is performed. Specifically, for example, a cyclization reaction is allowed to proceed to a certain reaction rate in the presence of a solvent in advance using a kettle-type reactor, and then a reactor equipped with a devolatilizer, for example, heat exchange Preferred is a mode in which the cyclization reaction is completed with a devolatilizer comprising a vessel and a devolatilization tank, an extruder with a vent, or the like. Particularly in this form, it is more preferable that a catalyst for the cyclization reaction is present.

  As described above, the cyclization reaction rate is raised to some extent by previously cyclizing the hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step, and then the devolatilization step is simultaneously used in combination. The method for carrying out the cyclization reaction is a preferred form for obtaining an acrylic polymer having a ring structure in the main chain. With this form, an acrylic polymer having a cyclic structure in the main chain having a higher cyclization reaction rate, a higher glass transition temperature and excellent heat resistance can be obtained. In this case, as a measure of the cyclization reaction rate, the weight loss rate between 150 and 300 ° C. in the dynamic TG measurement shown in the examples is preferably 2% or less, more preferably 1.5% or less. More preferably 1% or less.

  The reactor that can be employed in the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time is not particularly limited, but preferably from an autoclave, a kettle reactor, a heat exchanger, and a devolatilization tank. A vented extruder suitable for a cyclization reaction in which a devolatilization step is simultaneously used can also be used. More preferred are autoclaves and kettle reactors. However, even when using a reactor such as an extruder with a vent, by adjusting the temperature condition, barrel condition, screw shape, screw operating condition, etc. It is possible to carry out the cyclization reaction in the same state as the reaction state in the kettle reactor.

  In the cyclization reaction performed in advance before the cyclization reaction using the devolatilization step at the same time, preferably, a mixture containing the polymer and the solvent obtained in the polymerization step is added (i) by adding a catalyst. , A method of heating reaction, (ii) a method of heating reaction without a catalyst, and a method of performing the above (i) or (ii) under pressure.

  The “mixture containing a polymer and a solvent” to be introduced into the cyclization reaction in the cyclization step may be the polymerization reaction mixture obtained in the polymerization step as it is or after removing the solvent once. It means that a solvent suitable for the cyclization reaction may be added again.

  Solvents that can be re-added during the cyclization reaction performed in advance prior to the cyclization reaction using the devolatilization process at the same time are not particularly limited. For example, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; methyl ethyl ketone, Ketones such as methyl isobutyl ketone; chloroform, DMSO, tetrahydrofuran and the like may be used, but the same solvent as that used in the polymerization step is preferable.

  Examples of the catalyst added in the above method (i) include esterification catalysts such as p-toluenesulfonic acid or transesterification catalysts, basic compounds, organic carboxylates, carbonates and the like that are generally used. Is preferably the above-described organophosphorus compound.

  The addition timing of the catalyst is not particularly limited, and it may be added at the beginning of the reaction, during the reaction, or both. The amount of the catalyst to be added is not particularly limited, but is preferably in the range of 0.001 to 5% by weight, more preferably in the range of 0.01 to 2.5% by weight, still more preferably based on the weight of the polymer. It is in the range of 0.01 to 1% by weight, particularly preferably in the range of 0.05 to 0.5% by weight. The heating temperature and heating time in method (i) are not particularly limited, but the heating temperature is preferably room temperature or higher, more preferably 50 ° C. or higher, and the heating time is preferably in the range of 1 to 20 hours. More preferably, it is in the range of 2 to 10 hours. If the heating temperature is low, or if the heating time is short, the cyclization reaction rate decreases, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Examples of the method (ii) include a method of heating the polymerization reaction mixture obtained in the polymerization step as it is using a pressure-resistant kettle or the like. The heating temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher. The heating time is preferably in the range of 1 to 20 hours, more preferably in the range of 2 to 10 hours. If the heating temperature is low, or if the heating time is short, the cyclization reaction rate decreases, which is not preferable. Further, if the heating time is too long, the resin may be colored or decomposed, which is not preferable.

  Both the above methods (i) and (ii) have no problem even under pressure depending on conditions. Moreover, in the case of the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time, there is no problem even if a part of the solvent volatilizes spontaneously during the reaction.

  The weight loss rate between 150 and 300 ° C. in dynamic TG measurement at the end of the cyclization reaction performed in advance before the cyclization reaction using the devolatilization process at the same time, that is, immediately before the start of the devolatilization process is 2%. The following is preferable, more preferably 1.5% or less, and still more preferably 1% or less. When the weight reduction rate is higher than 2%, the cyclization reaction rate does not rise to a sufficiently high level even if the cyclization reaction is performed simultaneously with the devolatilization step, and the resulting main chain has a cyclic structure. There exists a possibility that the physical property of a polymer may fall. In addition, when performing said cyclization reaction, in addition to a polymer, you may coexist other acrylic polymer.

  The hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step are preliminarily cyclized to increase the cyclization reaction rate to some extent. In the case of the form to be performed, devolatilization is performed without separating the polymer obtained by the cyclization reaction performed in advance (a polymer in which at least a part of the hydroxyl groups and ester groups in the molecular chain are cyclized) and the solvent. You may perform the cyclization reaction which used the process together simultaneously. If necessary, the polymer (a polymer in which at least a part of the hydroxyl group and ester group present in the molecular chain is cyclized) is separated and then subjected to other treatments such as adding a solvent again. From the above, a cyclization reaction using a devolatilization step at the same time may be performed.

  The devolatilization step is not limited to being completed at the same time as the cyclization reaction, and may be completed after a lapse of time from the completion of the cyclization reaction.

  Even after a cyclization catalyst is added and the cyclization reaction is sufficiently performed, a trace amount of unreacted reactive groups may remain, and problems such as foaming and thickening due to cross-linking between polymers may occur during molding. It is preferable to add a catalyst deactivator. The addition of the deactivator is also effective for suppressing degradation of triacetyl cellulose during solution film formation by the remaining catalyst. In many cases, an acidic catalyst or a basic catalyst is used for the cyclization reaction, and in this case, the deactivator deactivates the catalyst by a neutralization reaction. Therefore, when the catalyst is an acidic substance, A basic substance may be used. Conversely, when the catalyst is a basic substance, an acidic substance may be used as the deactivator. The deactivator is not particularly limited as long as it does not generate a substance that inhibits the resin composition at the time of heat processing, but when a basic substance is used as the deactivator, for example, metal carboxylate, metal A complex, a metal oxide, etc. are mentioned, A metal carboxylate and a metal oxide are preferable, and a metal carboxylate is especially preferable. Here, the metal is not particularly limited as long as it does not inhibit the physical properties of the resin composition and does not cause environmental pollution at the time of disposal. For example, alkali metals such as lithium, sodium, and potassium; magnesium Alkaline earth metals such as calcium, strontium and barium; zinc; zirconium; and the like. The carboxylic acid constituting the metal carboxylate is not particularly limited. For example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, Lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, tridecanoic acid, pentadecanoic acid, heptadecanoic acid, lactic acid, malic acid, citric acid, oxalic acid, malonic acid, succinic acid, fumaric acid, maleic acid, adipic acid, etc. Is mentioned. The organic component in the metal complex is not particularly limited, and examples thereof include acetylacetone. Examples of the metal oxide include zinc oxide, calcium oxide, magnesium oxide and the like, and zinc oxide is preferable. On the other hand, when an acidic substance is used for the deactivator, for example, an organic phosphoric acid compound or a carboxylic acid can be used. A quencher may be used independently or may use 2 or more types together. The quenching agent may be added in any form such as a solid, powder, dispersion, suspension, aqueous solution, etc., and is not particularly limited.

  The blending amount of the deactivator may be appropriately adjusted according to the catalyst used in the cyclization reaction, and is not particularly limited, but is preferably 10 to 10,000 ppm, more preferably based on the acrylic polymer. Preferably it is 50-5,000 ppm, More preferably, it is 100-3,000 ppm. If the amount of the deactivator is less than 10 ppm, the action of the deactivator is insufficient, and foaming or thickening due to cross-linking between polymers may occur during molding. On the contrary, when the compounding amount of the deactivator exceeds 10,000, the deactivator is used more than necessary, and the physical properties of the resin composition may be inhibited such as a decrease in molecular weight.

  The timing of adding the deactivator is after the catalyst is added and the cyclization reaction is sufficiently performed in the production of the acrylic polymer, and before the obtained acrylic polymer is film-formed in solution. There is no particular limitation. For example, a deactivator is added at a predetermined stage during production of an acrylic polymer, or a cyclization catalyst is added to the acrylic polymer and heat treated to advance the cyclization reaction, and then the deactivator is added. Alternatively, after the acrylic polymer is produced, the acrylic polymer, the deactivator, and other components are simultaneously heated and melted and kneaded; after the acrylic polymer is produced, the acrylic polymer, A method of dissolving a deactivator and other components in a solvent; a method of adding a deactivator to a solution used in the solution casting method; an acrylic polymer, other components, etc. are heated and melted; Examples include a method of adding an activator and kneading; a method of heating and melting an acrylic polymer, and adding a deactivator, other components, and the like to knead.

The number of foreign substances contained in the acrylic polymer having a ring structure in the main chain obtained by cyclization reaction of the acrylic polymer is the number of foreign substances in the acrylic polymer production process and / or film formation process. The polymer solution or melt can be reduced by, for example, filtering with a filter having a filtration accuracy of 0.01 to 15 μm.

《Triacetylcellulose》
The triacetyl cellulose used in the present invention preferably has a number average molecular weight (Mn) of 50,000 to 150,000, more preferably a number average molecular weight of 55,000 to 120,000, and a number average molecular weight of 60000 to 100,000. Is most preferred. Further, it preferably has a weight average molecular weight (Mw) of 100,000 to 300,000, more preferably has a weight average molecular weight of 100,000 to 250,000, and most preferably has a weight average molecular weight of 120,000 to 200,000. Furthermore, those having a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 1.3 to 5.5 are preferably used, particularly preferably 1.5 to 5.0, and more preferably 1. It is 7-4.0, More preferably, 2.0-3.5 triacetyl cellulose is used preferably. Mn and Mw / Mn were calculated in terms of polystyrene by gel permeation chromatography (GPC) in the following manner.
The raw cellulose of triacetyl cellulose used in the present invention may be wood pulp or cotton linter, and the wood pulp may be softwood or hardwood, but softwood is more preferable. A cotton linter is preferably used from the viewpoint of peelability during film formation. Triacetyl cellulose made from these can be used as a mixture or used alone.
Triacetyl cellulose can be obtained, for example, by substituting the hydroxyl group of the raw material cellulose with an acetyl group by acetic anhydride using a conventional method. The method for synthesizing such triacetyl cellulose is not particularly limited, and for example, it can be synthesized with reference to the method described in JP-A-10-45804 or JP-A-6-501040.
Since triacetylcellulose is used in solution casting, it is preferable to dissolve triacetylcellulose in a solvent. It is conceivable that the dope is formed by dissolving the triacetyl cellulose or additive in an organic solvent in a kettle while stirring, or the polymer solution or additive solution is mixed with the triacetyl cellulose solution to form a dope. . It is also possible to use the triacetyl cellulose as it is dissolved in a solvent during the synthesis of triacetyl cellulose. For dissolution of triacetyl cellulose, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, 9-95557 or 9 Various melting methods such as a method of cooling and dissolving as described in JP-A-95538 and a method of performing at high pressure as described in JP-A No. 11-21379 can be used. The concentration of triacetyl cellulose in the dope is preferably 10 to 35% by weight. An additive excluding the matting agent is added to and dissolved in the dope during or after dissolution, and then filtered through a filter medium, defoamed, and sent to the next step with a liquid feed pump.
Filtration is carried out after foreign substances in triacetylcellulose are dissolved in a solvent, and additives such as UV absorbers, plasticizers, deterioration inhibitors, antioxidants and antiblocking agents are added and mixed as necessary. I can do it. As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. You may cool to -20 degrees C or less in the process of dissolution, or you may heat to 80 degrees C or more. Of course, the triacetyl cellulose may be dissolved in a solvent during synthesis of the triacetyl cellulose and reduced by filtration.
The filter medium for filtration preferably has an absolute filtration accuracy of 0.04 mm or less, and more preferably in the range of 0.01 to 0.02 mm. There is no particular limitation on the material of the filter medium, and a normal filter medium can be used. However, a filter medium made of plastic fibers such as polypropylene and Teflon and a metal filter medium such as stainless steel fibers are preferable because they do not drop off fibers.

<Optical film>
The optical film of the present invention contains an acrylic polymer having a ring structure in the main chain and triacetyl cellulose. The ratio of the acrylic polymer having a ring structure in the main chain and triacetyl cellulose is not particularly limited, but preferably 5 to 50% by weight of the acrylic polymer having a ring structure in the main chain and 50 to 95% by weight of triacetyl cellulose. And more preferably 5 to 45% by weight of an acrylic polymer having a ring structure in the main chain and 55 to 95% by weight of triacetyl cellulose, and more preferably an acrylic polymer 5 having a ring structure in the main chain. 30% by weight and 70 to 95% by weight of triacetyl cellulose, particularly preferably 5 to 20% by weight of an acrylic polymer having a ring structure in the main chain and 80 to 95% by weight of triacetyl cellulose. If the content of the acrylic polymer having a ring structure in the main chain is lower than 5% by weight, the moisture resistance is lowered, and if it is too high, the flexibility is lowered.

  The optical film of the present invention has a haze of 1% or less, more preferably 0.5% or less. If the haze exceeds 1%, the transmittance is lowered and it is not suitable for optical applications.

Although the thickness of the optical film of this invention is not specifically limited, For example, they are 10 micrometers-500 micrometers, 20 micrometers-300 micrometers are preferable, and 30 micrometers-100 micrometers are especially preferable.
The optical film of the present invention preferably has a total light transmittance of 85% or more. More preferably, it is 90% or more, More preferably, it is 91% or more. The total light transmittance is a measure of transparency, and if it is less than 85%, the transparency is lowered and it is not suitable as an optical film.

  The optical film of the present invention contains a component other than an acrylic polymer having a ring structure in the main chain and triacetyl cellulose in a proportion of less than 50% by weight, preferably less than 10% by weight in the film. May be.

  When other thermoplastic resins are included, the other thermoplastic resins are, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, poly (4-methyl-1-pentene); vinyl chloride, chlorinated vinyl Halogen-containing polymers such as resins; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc. Polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal: polycarbonate; polyphenylene oxide; polyphenylene sulfide: polyether ether Ton; polyether nitrile; polysulfone; polyether sulfone; polyoxyethylene Penji alkylene; polyamideimide; and the like.

  Among the above-exemplified thermoplastic resins, the cyanide is excellent in compatibility with an acrylic polymer having a ring structure in the main chain, and particularly in an compatibility with an acrylic polymer having a lactone ring structure in the main chain. A copolymer containing a structural unit derived from a vinyl monomer and a structural unit derived from an aromatic vinyl monomer is preferred. The copolymer is, for example, a styrene-acrylonitrile copolymer.

  The optical film of the present invention may contain an ultraviolet absorber. When an ultraviolet absorber is included, examples of the ultraviolet absorber include benzophenone compounds, salicinate compounds, benzoate compounds, triazole compounds, and triazine compounds. Examples of the benzophenone compounds include 2,4-dihydroxybenzophenone, 4-n-octyloxy-2-hydroxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2-hydroxy-4-n-octyl. Examples thereof include oxybenzophenone, bis (5-benzoyl-4-hydroxy-2-methoxyphenyl) methane, 1,4-bis (4-benzoyl-3-hydroxyphenone) -butane and the like. Examples of the silicate compound include pt-butylphenyl silicate. Examples of the benzoate compound include 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate. Examples of triazole compounds include 2,2′-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (3 , 5-Di-tert-butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzotriazole- 2-yl] -4-methyl-6- (tert-butyl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-tert-butyl Enol, 2- (2H-benzotriazol-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol, 2- (2H-benzotriazol-2-yl) -4-methyl-6 -(3,4,5,6-tetrahydrophthalimidylmethyl) phenol, methyl 3- (3- (2H-benzotriazol-2-yl) -5-tert-butyl-4-hydroxyphenyl) propionate / polyethylene glycol 300 reaction products, 2- (2H-benzotriazol-2-yl) -6- (linear and side chain dodecyl) -4-methylphenol, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-Hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 3- (2H-ben Triazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy -C7-9 side chain and straight chain alkyl esters. Further, triazine compounds include 2,4-diphenyl-6- (2-hydroxy-4-methoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-). Ethoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-propoxyphenyl) -1,3,5-triazine, 2,4-diphenyl- (2-hydroxy-4-) Butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2- Hydroxy-4-hexyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-octyloxyphenyl) -1,3,5-tria 2,4-diphenyl-6- (2-hydroxy-4-dodecyloxyphenyl) -1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-benzyloxyphenyl)- 1,3,5-triazine, 2,4-diphenyl-6- (2-hydroxy-4-butoxyethoxy) -1,3,5-triazine, 2,4-bis “2-hydroxy-4-butoxyphenyl” -6- (2,4-dibutoxyphenyl) -1,3-5-triazine, 2,4-bis (2,4-dimethylphenyl) -6- [2-hydroxy-4- (3-alkyloxy- 2-hydroxypropyloxy) -5-α-cumylphenyl] -s-triazine skeleton (alkyloxy; long-chain alkyloxy groups such as octyloxy, nonyloxy, decyloxy, etc.) A line absorber is mentioned. Commercially available products include, for example, “Tinuvin 1577”, “Tinuvin 460” and “Tinuvin 477” (manufactured by Ciba Specialty Chemicals) as triazine-based UV absorbers, and “Adeka Stub LA-31” (Asahi Denka Co., Ltd.) as triazole-based UV absorbers. Manufactured by Kogyo Co., Ltd.).

  These can be used alone or in combination of two or more. Although the compounding quantity of the said ultraviolet absorber is not specifically limited, It is preferable that it is 0.01-25 weight% in a film, More preferably, it is 0.05-10 weight%. If the amount added is too small, the contribution to improving the weather resistance is low, and if it is too large, the mechanical strength may be lowered or yellowing may be caused.

  The optical film of the present invention may contain an antioxidant. Although antioxidant is not specifically limited, For example, well-known antioxidants, such as a hindered phenol type, a phosphorus type, or a sulfur type, can be used by 1 type or in combination of 2 or more types.

  The antioxidant may be a phenolic antioxidant. Examples of the phenolic antioxidant include n-octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, n-octadecyl-3- (3,5-di-t-butyl- 4-hydroxyphenyl) acetate, n-octadecyl-3,5-di-t-butyl-4-hydroxybenzoate, n-hexyl-3,5-di-t-butyl-4-hydroxyphenylbenzoate, n-dodecyl- 3,5-di-t-butyl-4-hydroxyphenylbenzoate, neododecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, dodecyl-β- (3,5-di-t -Butyl-4-hydroxyphenyl) propionate, ethyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, Kutadecyl-α- (4-hydroxy-3,5-di-t-butylphenyl) isobutyrate, octadecyl-α- (4-hydroxy-3,5-di-t-butyl-4-hydroxyphenyl) propionate, 2- (N-octylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (n-octylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- ( n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxyphenyl acetate, 2- (n-octadecylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-hydroxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, diethyl glycol bis- (3,5-di- t-butyl-4-hydroxy-phenyl) propionate, 2- (n-octadecylthio) ethyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, stearamide-N, N-bis- [Ethylene-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], n-butylimino-N, N-bis- [ethylene-3- (3,5-di-t-butyl- 4-hydroxyphenyl) propionate], 2- (2-stearoyloxyethylthio) ethyl-3,5-di-t-butyl-4-hydroxybenzoate, 2- (2-stearoyloxyethylthio) ethyl-7- ( 3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,2-propylene glycol bis- [3- (3,5-di- -Butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], neopentyl glycol bis- [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate], ethylene glycol bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), glycerin-1-n-octadecanoate-2,3 -Bis- (3,5-di-t-butyl-4-hydroxyphenyl acetate), pentaerythritol tetrakis- [3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl) propionate], 1,1,1-trimethylolethanetris- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propyl Pionate], sorbitol hexa- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-hydroxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) ) Propionate, 2-stearoyloxyethyl-7- (3-methyl-5-tert-butyl-4-hydroxyphenyl) heptanoate, 1,6-n-hexanediol bis [(3 ′, 5′-di-t- Butyl-4-hydroxyphenyl) propionate], pentaerythritol tetrakis (3,5-di-t-butyl-4-hydroxyhydrocinnamate), 3,9-bis [1,1-dimethyl-2- [β- ( 3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] ethyl] -2,4,8,10-tetraoxaspir [5,5] - it is undecane.

  The phenolic antioxidant is preferably used in combination with a thioether antioxidant or a phosphoric acid antioxidant. The amount of antioxidant added in combination is 0.01% or more of each of the phenolic antioxidant and the thioether antioxidant relative to the acrylic polymer, or the phenolic antioxidant and the phosphoric acid antioxidant. Each of the agents is 0.025% or more.

  Examples of the thioether-based antioxidant include pentaerythrityl tetrakis (3-lauryl thiopropionate), dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl- 3,3′-thiodipropionate.

  Examples of the phosphoric acid antioxidant include tris (2,4-di-t-butylphenyl) phosphite, 2-[[2,4,8,10-tetrakis (1,1-dimethylethyl) dibenzo [d. , F] [1,3,2] dioxaphosphin-6-yl] oxy] -N, N-bis [2-[[2,4,8,10-tetrakis (1,1 dimethylethyl) dibenzo [D, f] [1,3,2] dioxaphosphin-6-yl] oxy] -ethyl] ethanamine, diphenyltridecyl phosphite, triphenyl phosphite, 2,2-methylenebis (4,6- Di-t-butylphenyl) octyl phosphite, bis (2,6-di-t-butyl-4-methylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite Cyclic neopentanetetraylbis is (2,6-di -t- butyl-4-methylphenyl) phosphite. The addition amount of the antioxidant in the optical film of the present invention is, for example, 0 to 10%, preferably 0 to 5%, more preferably 0.01 to 2%, and further preferably 0.05 to. 1%. When the amount of the antioxidant added is excessively large, the antioxidant bleed out or silver streaks may occur during molding.

  The optical film of the present invention may contain other additives. Other additives include, for example, a stabilizer such as a light stabilizer, a weather stabilizer, and a heat stabilizer; a reinforcing material such as a glass fiber and a carbon fiber; a near infrared absorber; a tris (dibromopropyl) phosphate, a triallyl phosphate, Flame retardants such as antimony oxide; antistatic agents typified by anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, dyes; organic fillers, inorganic fillers; resin modifiers; Antiblocking agent; matting agent; acid scavenger; metal deactivator; plasticizer; lubricant; flame retardant; rubber mass such as ASA and ABS. The addition amount of the said other additive in the optical film of this invention is 0 to 5%, for example, Preferably it is 0 to 2%, More preferably, it is 0 to 0.5%. The manufacturing method of the optical film of this invention is demonstrated. The manufacturing method of the optical film of this invention is not specifically limited, A well-known manufacturing method is possible. Examples of the film forming method include known film forming methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable.

  As a specific example of the melt extrusion method, the kneader used for extrusion kneading is not particularly limited. For example, a known kneader such as a single screw extruder, a twin screw extruder, or a pressure kneader is used. Can be used. Moreover, after adding resin and an additive as needed and pre-blending with mixers, such as an omni mixer, the obtained mixture may be extrusion-kneaded from a kneader.

  Examples of the melt extrusion method include a T-die method and an inflation method, and the molding temperature at that time is preferably 200 to 350 ° C., more preferably 250 to 300 ° C., still more preferably 255 to 300 ° C., and particularly preferably. Is 260-300 ° C.

  When the T-die method is used, a resin film wound into a roll can be obtained by attaching a T-die to the tip of the extruder and winding the film extruded from the T-die. At this time, it is also possible to control the temperature and speed of winding and to stretch (uniaxial stretching) in the extrusion direction of the film. Further, the film may be stretched in a direction perpendicular to the extrusion direction, and sequential biaxial stretching or simultaneous biaxial stretching may be performed.

  When an extruder is used for extrusion molding, the type is not particularly limited and may be uniaxial, biaxial, or multiaxial, but its L / D value is (L is the value of the extruder) In order to sufficiently plasticize the resin and obtain a good kneaded state, D is preferably from 10 to 100, more preferably from 15 to 80, and even more preferably 20 It is 60 or less. When the L / D value is less than 10, the resin cannot be sufficiently plasticized and a good kneaded state may not be obtained. On the other hand, when the L / D value exceeds 100, the resin in the composition may be thermally decomposed due to excessive shearing heat generation applied to the resin.

  In this case, the set temperature of the cylinder is preferably 200 to 350 ° C or less, more preferably 250 to 300 ° C or less. If setting temperature is less than 200 degreeC, the melt viscosity of resin will become high too much and productivity of a resin film will fall. On the other hand, if the set temperature exceeds 350 ° C., the resin may be thermally decomposed.

  When an extruder is used for extrusion molding, the shape is not particularly limited, but the extruder preferably has one or more open vent portions. By using such an extruder, the decomposition gas can be sucked from the open vent portion, and the amount of volatile components remaining in the obtained resin film can be reduced. In order to suck the decomposition gas from the open vent portion, for example, the open vent portion may be in a reduced pressure state, and the degree of pressure reduction is preferably in the range of 931 to 1.3 hPa as the pressure of the open vent portion, 798 A range of ˜13.3 hPa is more preferable. When the pressure in the open vent is higher than 931 hPa, volatile components or monomer components generated by the decomposition of the resin are likely to remain in the thermoplastic resin. On the other hand, it is industrially difficult to keep the pressure of the open vent part lower than 1.3 hPa.

  When producing the optical film of the present invention, it is preferable to incorporate a filtration step such as filtration with a polymer filter. By incorporating a filtration step, foreign substances present in the resin can be removed, so that defects in the appearance of the obtained film can be reduced. In addition, at the time of filtration with a polymer filter, the resin is in a high temperature molten state. For this reason, the resin deteriorates when passing through the polymer filter, and gas components and colored deterioration products formed by the deterioration flow into the composition, and the resulting film has holes, flow patterns, flow lines, etc. May be observed. This defect is particularly apt to be observed during the continuous forming of a film. For this reason, when the resin filtered with the polymer filter is molded, the molding temperature decreases the melt viscosity of the thermoplastic resin and shortens the residence time of the thermoplastic resin in the polymer filter, for example, 255 to 350. It is 260 degreeC and 260-320 degreeC is preferable.

  The configuration of the polymer filter is not particularly limited, but a polymer filter in which a large number of leaf disk filters are arranged in a housing can be suitably used. The filter material of the leaf disk type filter may be any of a type in which a metal fiber nonwoven fabric is sintered, a type in which metal powder is sintered, a type in which several metal meshes are laminated, or a hybrid type in which they are combined. The sintered type is most preferred.

  The filtration accuracy by the polymer filter is not particularly limited, but is usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. If the filtration accuracy is 1 μm or less, the residence time of the resin becomes longer, so that the thermal degradation of the composition increases, and the productivity of the resin film decreases. On the other hand, when the filtration accuracy exceeds 15 μm, it is difficult to remove foreign substances in the resin.

  The filtration area with respect to the resin composition throughput per hour in the polymer filter is not particularly limited, and can be appropriately set according to the resin throughput. The filtration area is, for example, 0.001 to 0.15 m2 / (kg / hour).

  The shape of the polymer filter is not particularly limited. For example, an inner flow type having a plurality of resin flow ports and a resin flow path in the center pole; the inner peripheral surface of the leaf disk filter at a plurality of vertices or faces And an external flow type having a resin flow path on the outer surface of the center pole. In particular, it is preferable to use an external flow type in which the resin stays are small.

  Although there is no restriction | limiting in particular in the residence time of the thermoplastic resin in a polymer filter, Preferably it is 20 minutes or less, More preferably, it is 10 minutes or less, More preferably, it is 5 minutes or less. Further, the filter inlet pressure and the filter outlet pressure during filtration are, for example, 3 to 15 MPa and 0.3 to 10 MPa, respectively, and the pressure loss (the pressure difference between the filter inlet pressure and the outlet pressure) is 1 MPa to 15 MPa. A range is preferred. When the pressure loss is 1 MPa or less, the flow path through which the thermoplastic resin passes through the filter tends to be biased, and the quality of the obtained resin film tends to deteriorate. On the other hand, when the pressure loss exceeds 15 MPa, the polymer filter is easily damaged.

  What is necessary is just to set suitably the temperature of resin introduce | transduced into a polymer filter according to the melt viscosity, for example, it is 250-300 degreeC, Preferably it is 255-300 degreeC, More preferably, it is 260-300 degreeC.

  The specific process of obtaining a resin film with few foreign substances and colored substances by filtration using a polymer filter is not particularly limited. For example, (1) a process in which a resin is formed and filtered in a clean environment, and then a thermoplastic resin is molded in a clean environment, and (2) a thermoplastic resin having foreign matter or colored substances is removed in a clean environment. (3) A process of molding a thermoplastic resin in a clean environment after filtration, and (3) A process of molding a thermoplastic resin having a foreign substance or a colored substance at the same time as filtering in a clean environment. Can be mentioned. You may perform the filtration process of resin by a polymer filter in multiple times for each process.

  When filtering the resin with the polymer filter, it is preferable to install a gear pump between the extruder and the polymer filter to stabilize the pressure of the resin in the filter.

  After the production of the resin, it is preferable to extrude it as it is to obtain a resin film. Since heat history can be reduced as compared with the case where an optical film is formed by remelting the obtained pellets after pelletizing the resin, thermal deterioration of the resin can be suppressed. Moreover, in this method, since mixing of the foreign material from an environment can be suppressed, it can suppress that a foreign material exists in the obtained optical film or coloring of the obtained optical resin film. A gear pump and a polymer filter are preferably arranged between the extruder and the T die.

  In the case of the solution casting method, the process includes (1) a dissolution process, (2) a casting process, and (3) a drying process.

(1) Dissolution process:
When the acrylic polymer having a ring structure in the main chain and triacetyl cellulose are dissolved in a solvent, the solutions may be mixed separately after dissolving in the solvent, or the acrylic polymer having a ring structure in the main chain may be mixed. A resin composition containing the coalescence and triacetyl cellulose may be dissolved in a solvent. The acrylic polymer having a ring structure in the main chain can be used in the dissolution step in the state of a polymerization solution containing a polymerization solvent without going through a devolatilization step, while stirring a separately prepared triacetyl cellulose solution. By adding the acrylic polymer solution little by little, a dope used for solution film formation can be prepared. Additives necessary for the dope during or after dissolution are added and dissolved, then filtered with a filter medium, defoamed, and sent to the next step with a liquid feed pump. The filter medium for filtration preferably has an absolute filtration accuracy of 0.04 mm or less, and more preferably in the range of 0.01 to 0.02 mm. There is no particular limitation on the material of the filter medium, and a normal filter medium can be used. However, a filter medium made of plastic fibers such as polypropylene and Teflon and a metal filter medium such as stainless steel fibers are preferable because they do not drop off fibers.

  As the solvent, a good solvent used in a solution casting method such as methylene chloride, methyl acetate or dioxolane can be used, and a poor solvent such as methanol, ethanol or butanol may be used at the same time. In the present invention, a polymerization solvent contained in a polymerization solution of an acrylic polymer having a ring structure in the main chain can also be used. Among these, a plurality of solvents may be included in the solution. You may cool to -20 degrees C or less in the process of dissolution, or you may heat to 80 degrees C or more.

  In order to prepare a solution of triacetyl cellulose, the triacetyl cellulose having a good solvent for triacetyl cellulose (in the form of flakes) is dissolved in an organic solvent in a kettle, an acrylic polymer having a ring structure in the main chain, It is conceivable to dissolve the additive while stirring to form a dope, or to mix a solution of an acrylic polymer having a ring structure in the main chain or an additive solution with the triacetyl cellulose solution to form a dope. For dissolution of triacetyl cellulose, a method carried out at normal pressure, a method carried out below the boiling point of the main solvent, a method carried out under pressure above the boiling point of the main solvent, JP-A-9-95544, 9-95557 or 9 Various dissolution methods such as a method performed by a cooling dissolution method as described in JP-A-95538 and a method performed at a high pressure as described in JP-A No. 11-21379 can be used, but the concentration of triacetyl cellulose in the dope Is preferably 10 to 35% by weight.

(2) Casting process:
This is a step of casting a dope on a support to obtain a uniform film.

Generally, if a deformation stress is applied in the film forming process, the orientation proceeds and the birefringence value of the film increases. As the birefringence value increases, it becomes difficult to maintain the uniformity of the film, and the variation in optical characteristics also increases. Therefore, it is desirable to form a film under a relatively low stress with a low viscosity. In addition, it is preferable that the dope has a low viscosity because the film thickness is uniformed by the leveling effect after coating. The preferred viscosity of the solution is from 10 poise to 100 poise, more preferably from 15 poise to 70 poise. In addition, since it will flow out from a support body when it is lower than 10 poise, measures, such as providing a partition plate suitably, are needed.
As a coating method, a die coater, a doctor blade coater, a roll coater, a comma coater, a lip coater, and the like are preferable, but various methods that are usually used are possible without being limited to these examples.

  As a preferable support, a metal support such as a stainless steel endless belt or a rotating metal drum, or a film such as a polyimide film or a biaxially stretched polyethylene terephthalate film can be used.

(3) Drying process:
This is a step of heating a dope film in which a dope is cast on a metal support and evaporating the solvent to obtain a dry film.

  Heat drying is performed in a state where the liquid film immediately after casting or coating is not dried, and if there is a rapid flow of air or heating, thickness unevenness is likely to occur. That is, there are also means for preventing direct wind from being applied to the film or heating by applying microwaves instead of wind. It is also important to prevent rapid heating and cooling. Furthermore, since the dope film is foamed by the humidity in the atmosphere, the humidity control is also important. Thereafter, it is preferably dried so as to reduce the residual solvent by blowing hot air after the semi-solidified state.

The drying after casting can be carried out while being supported on the support, but if necessary, the predried film can be peeled off from the support until it has self-supporting property, and further dried. In general, a float method, a tenter or a roll conveying method can be used for drying the film. In the case of the float process, the film itself is subjected to complicated stress, and optical characteristics are likely to be uneven. In the case of the tenter method, it is necessary to balance the film width shrinkage due to solvent drying and the tension to support its own weight depending on the distance between the pins or clips that support both ends of the film. There is a need. On the other hand, in the case of the roll conveyance method, since the tension for stable film conveyance is in principle applied to the film flow direction (MD direction), it has a characteristic that the direction of stress is easily made constant. Therefore, the film is most preferably dried by a roll conveyance method. Above all, in order to reduce the stress caused by gravity, the vertical path method (vertical suspension path method) that arranges multiple rolls on the top and bottom and passes the film up, down, up, down, etc. is a long drying path while omitting the oven installation space. Can be ensured.
Further, drying in an atmosphere kept at a low humidity so that the film does not absorb moisture when the solvent is dried is an effective method for obtaining a film having high mechanical strength and transparency.

  In addition to the steps (1) to (3) described above, the optical film production process of the present invention includes a saponification treatment, a corona treatment, a plasma treatment, and an application of an easy-adhesion layer, etc., in order to improve adhesion. You may have a process. Moreover, it is also possible to have the process of providing various functional coating layers, such as a glare-proof layer and a hard-coat layer, and an extending | stretching process.

  When stretching the optical film of the present invention, it may be uniaxial stretching or biaxial stretching. In the case of biaxial stretching, simultaneous biaxial stretching or sequential biaxial stretching may be used. When stretched, the mechanical strength is improved and the film performance is improved.

  The stretching temperature is preferably performed in the vicinity of the glass transition temperature of the optical film. Specifically, it is preferably performed at (glass transition temperature-30) ° C. to (glass transition temperature + 100) ° C., more preferably (glass The transition temperature is −20) ° C. to (glass transition temperature + 80) ° C. When it is lower than (glass transition temperature-30) ° C., a sufficient draw ratio cannot be obtained, which is not preferable. When the temperature is higher than (glass transition temperature + 100) ° C., resin flow occurs and stable stretching cannot be performed.

  The court stretch ratio defined by the area ratio is preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times. When it is less than 1.1 times, it is not preferable because it does not lead to improvement of toughness accompanying stretching. If it is larger than 25 times, the effect of increasing the draw ratio is not recognized.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost is increased, which is not preferable. If it is faster than 20000% / min, the optical film may be broken, which is not preferable.

  In order to stabilize the optical isotropy and mechanical properties of the film, a heat treatment (annealing) or the like can be performed after the solution film formation or after the stretching process.

  Various functional coating layers may be formed on the surface of the optical film of the present invention as necessary. Functional coating layers include, for example, antistatic layers, adhesive layers, adhesive layers, easy adhesion layers, antiglare (non-glare) layers, antifouling layers such as photocatalyst layers, antireflection layers, hard coat layers, and UV shielding layers. Layers, heat ray shielding layers, electromagnetic wave shielding layers, gas barrier layers, and the like.

Although the use of the optical film of the present invention is not particularly limited, it can be suitably used as an optical member due to its high transparency and heat resistance. The optical member is, for example, an optical protective film, specifically, a protective film for various optical disk (VD, CD, DVD, MD, LD, etc.) substrates, and a polarized light included in an image display device such as a liquid crystal display (LCD). It is a polarizer protective film used for a board. The optical film of the present invention may be used as an optical film such as a retardation film, a viewing angle compensation film, a light diffusion film, a reflection film, an antireflection film, an antiglare film, a brightness enhancement film, and a conductive film for a touch panel. In particular, it is suitably used as a polarizer protective film.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples. Hereinafter, for convenience, “part by weight” may be simply referred to as “part”, and “liter” may be simply referred to as “L”.
[Dynamic TG]
The polymer (or polymer solution or pellet) is once dissolved or diluted in tetrahydrofuran, poured into excess hexane or methanol for reprecipitation, and the taken out precipitate is vacuum dried (1 mmHg (1.33 hPa), 80 ° C. Volatile components and the like were removed by conducting the reaction for 3 hours or more, and the obtained white solid resin was analyzed by the following method (dynamic TG method).

Measuring device: ThermoPlus2TG-8120DynamicTG (manufactured by Rigaku Corporation)
Measurement conditions: Sample amount 5-10 mg
Temperature increase rate: 10 ° C / min
Atmosphere: Nitrogen flow 200ml / min
Method: Step-like isothermal control method (controlled at a weight reduction rate value of 0.005% / sec or less between 60 ° C and 500 ° C)
[Glass-transition temperature]
The glass transition temperature (Tg) of the polymer was determined according to JIS K7121. Specifically, a differential scanning calorimeter (manufactured by Rigaku Corporation, DSC-8230) is used to raise a temperature of about 10 mg from room temperature to 200 ° C. (temperature increase rate: 20 ° C./min) in a nitrogen gas atmosphere. From the obtained DSC curve, it was evaluated by the starting point method. Α-alumina was used as a reference.
[Melt flow rate]
The melt flow rate was measured based on JISK6874 at a test temperature of 240 ° C. and a load of 10 kg.
[Average molecular weight]
The number average weight average molecular weight (Mn) and the weight average weight average molecular weight (Mw) of the polymer were determined in terms of polystyrene using gel permeation chromatography (GPC). The apparatus and measurement conditions used for the measurement are as follows.

System: manufactured by Tosoh Column: TSK-GEL SuperHZM-M 6.0 × 150 2 in series Guard column: TSK-GEL SuperHZ-L 4.6 × 35 1 Reference column: TSK-GEL SuperH-RC 6.0 × 150 Two in series Eluent: Chloroform Flow rate 0.6 mL / min Column temperature: 40 ° C
[Content of ring structural unit]
First, based on the weight loss that occurs when all the hydroxyl groups are dealcoholated as methanol from the polymer composition obtained by polymerization, before the decomposition of the polymer starts from 150 ° C. before the weight reduction starts in dynamic TG measurement. From the weight loss due to the dealcoholization reaction up to 300 ° C., the dealcoholization reaction rate was determined.

That is, in the dynamic TG measurement of the polymer having a ring structure, the weight loss rate between 150 ° C. and 300 ° C. is measured, and the obtained actual weight loss rate is defined as (X). On the other hand, from the composition of the polymer, the theoretical weight loss rate when assuming that all the hydroxyl groups contained in the polymer composition are involved in ring formation and become alcohol is dealt with (i.e., 100% desorption in the composition). The weight reduction rate calculated on the assumption that an alcohol reaction has occurred is defined as (Y). The theoretical weight reduction rate (Y) is more specifically the molar ratio of raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material unit in the polymer composition. It can be calculated from the content of the monomer. These values (X, Y) are calculated from the dealcoholization formula:
1- (actual weight reduction rate (X) / theoretical weight reduction rate (Y))
Substituting into, the value is obtained and expressed in% to obtain the dealcoholization reaction rate.

  As an example, the proportion of the lactone ring structure in the pellets obtained in Production Example 1 described later is calculated. When the theoretical weight loss rate (Y) of this polymer was determined, the molecular weight of methanol was 32, the molecular weight of methyl 2- (hydroxymethyl) acrylate was 116, and methyl 2- (hydroxymethyl) acrylate. Since the content (weight ratio) in the polymer is 15% by weight in terms of composition, (32/116) × 15≈4.14% by weight. On the other hand, the actual weight loss rate (X) by dynamic TG measurement was 0.35% by weight. When these values are applied to the above-described dealcoholization calculation formula, 1− (0.35 / 4.14) ≈0.915, and the dealcoholization reaction rate is 91.5%.

  And the content rate (weight ratio) in the said copolymerization composition of the raw material monomer which has the structure (hydroxy group) which participates in lactone cyclization as what the predetermined | prescribed lactone cyclization was performed by this dealcoholization reaction rate ) Is multiplied by the dealcoholization reaction rate and converted to the content (weight ratio) of the structure of the lactone ring unit, the content of the lactone ring structure in the copolymer can be calculated. In the case of Example 1, the content of methyl 2- (hydroxymethyl) acrylate in the copolymer is 15.0% by weight, the calculated dealcoholization reaction rate is 91.5% by weight, and the molecular weight is 116- ( Since the formula amount of the lactone cyclized structural unit produced when methyl hydroxymethyl) is condensed with methyl methacrylate is 170, the content of the lactone ring in the copolymer is 20.1 (15. 0 × 0.915 × 170/116) wt%.

The content of the ring structure other than the lactone ring can also be calculated from the above devolatilization amount or calculated by a known method such as NMR.
[Haze]
The haze of the film was measured using a turbidimeter (Nippon Denshoku Industries Co., Ltd., NDH 5000).
[Flexibility]
The test was conducted according to JIS K5600-5-1. The method prescribed in the standard is a method for evaluating the bending resistance of the coating film formed on the substrate, and the bending resistance of the film itself was evaluated. That is, the diameter of the mandrel used for the test was reduced in order, and the diameter of the mandrel at which the film first broke was recorded. Similar to the evaluation of the coating film, it can be said that the smaller the value, the higher the flex resistance. For the test, a paint film bending tester manufactured by Yasuda Seiki Seisakusho was used.
[Production Example 1]
To a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe and nitrogen introduction pipe, 8500 g of methyl methacrylate (MMA), 1500 g of methyl 2- (hydroxymethyl) acrylate (MHMA), 10000 g of 4-methyl- 2-Pentanone (methyl isobutyl ketone, MIBK), 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. When refluxed, 10.0 g of tertiary butyl peroxyisopropyl as an initiator While adding carbonate (manufactured by Akzo Kayaku Co., Ltd., trade name: Kaya-Carbon Bic-75), while simultaneously adding dropwise a solution of 10.0 g of tertiary butyl peroxyisopropyl carbonate and 230 g of MIBK over 4 hours, Solution polymerization at about 105-120 ° C) The reaction mixture was then aged over further 4 hours. The polymerization reaction rate was 92.7%, and the MHMA content (weight ratio) in the polymerization pair was 14.6%.

  600 g of acetic acid was added to the obtained polymer solution, and a cyclization condensation reaction was performed under reflux (about 90 to 120 ° C.) for 5 hours. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (φ = 30 mm, L / D = 40) at a processing rate of 2.0 kg / hour in terms of the amount of resin, and the cyclization condensation reaction and devolatilization are carried out in the extruder. By taking out, a transparent pellet (A1) was obtained.

When the obtained resin pellet (A1) containing an acrylic polymer having a ring structure in the main chain was measured for dynamic TG, a weight loss of 0.35% by weight was detected. The lactone cyclization rate was 91.5%, the weight average molecular weight of the pellets was 166000, the melt flow rate was 3.9 g / 10 min, and the glass transition temperature was 127 ° C.
[Production Example 2]
In a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe, 8000 g of MMA, 2000 g of MHMA, and 10,000 g of toluene were charged, and the temperature was raised to 105 ° C. while refluxing nitrogen. At the same time, 10.0 g of tertiary amyl peroxyisononanoate was added as an initiator, and at the same time, 20.0 g of tertiary amyl peroxyisonononanoate (Lupelox 570, manufactured by Arkema Yoshitomi Co., Ltd.) and 100 g of toluene. While the solution was added dropwise over 2 hours, solution polymerization was performed under reflux (about 105 to 110 ° C.), followed by further aging for 4 hours. The polymerization reaction rate was 96.6%, and the content (weight ratio) of MHMA in the polymerization pair was 20.0%.

  To the obtained polymer solution, 10 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added, and cyclization condensation was performed under reflux (about 90 to 120 ° C.) for 5 hours. Reaction was performed. Next, the polymer solution obtained by the cyclization condensation reaction was subjected to cyclization condensation reaction and devolatilization in a vent type screw twin screw extruder in the same manner as in Production Example 1, and extruded to obtain transparent pellets (A2 )

When the obtained resin pellet (A2) containing an acrylic polymer having a ring structure in the main chain was subjected to dynamic TG measurement, a weight loss of 0.17% by weight was detected. The lactone cyclization rate was 96.9%, the weight average molecular weight of the pellets was 148,000, the melt flow rate was 11.0 g / 10 min, and the glass transition temperature was 130 ° C.
[Production Example 3]
A 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introduction pipe was charged with 667 g of MMA, 3000 g of MHMA, 6667 g of a mixed solvent consisting of MIBK and methyl ethyl ketone (MEK) (9: 1 by weight), and nitrogen was passed through it. While heating up to 105 ° C. and refluxing, 6.0 g of t-amylperoxyisonononanoate was added as an initiator, and at the same time, 12.0 g of t-amylperoxyisonononanoate, consisting of MIBK and MEK. While a solution consisting of 3315 g of a mixed solvent (weight ratio 9: 1) was added dropwise over 3 hours, solution polymerization was performed under reflux (about 95 to 110 ° C.), followed by further aging over 4 hours. The polymerization reaction rate was 94.5%, and the content (weight ratio) of MHMA in the polymerization pair was 29.7%.

  To the obtained polymer solution, 20 g of an octyl phosphate / dioctyl phosphate mixture was added, and a cyclization condensation reaction was performed under reflux (about 85 to 100 ° C.) for 2 hours, and further using a heating medium at 240 ° C. The cyclization condensation reaction was carried out in an autoclave under pressure (gauge pressure up to about 2 MPa) for 1.5 hours. Next, the polymer solution obtained by the cyclization condensation reaction was subjected to cyclization condensation reaction and devolatilization in a vent type screw twin screw extruder in the same manner as in Production Example 1, and extruded to obtain transparent pellets (A3 )

When the obtained resin pellet (A3) containing an acrylic polymer having a ring structure in the main chain was subjected to dynamic TG measurement, a weight loss of 0.25% by weight was detected. The lactone cyclization rate was 97.0%, the weight average molecular weight of the pellets was 127,000, the melt flow rate was 6.5 g / 10 min, and the glass transition temperature was 140 ° C.
[Production Example 4]
In a 30 L reaction kettle equipped with a stirrer, temperature sensor, cooling pipe and nitrogen introduction pipe, MMA 6000 g, MHMA 3000 g, n-butyl methacrylate (BMA) 1000 g, mixed solvent consisting of MIBK and MEK (weight ratio 9: 1) 6667 g The mixture was heated to 105 ° C. and refluxed while nitrogen was passed through it. At the same time, 6.0 g of t-amylperoxyisonononanoate was added as an initiator and at the same time 12.0 g of t-amylperoxyisonononanoate. , Solution polymerization was performed under reflux (about 95 to 110 ° C.) while dropping a solution consisting of 3315 g of a mixed solvent consisting of MIBK and MEK (weight ratio 9: 1) over 3 hours, and further aged over 4 hours Went. The polymerization reaction rate was 90.5%, and the MHMA content (weight ratio) in the polymerization pair was 29.7%.

  To the resulting polymer solution, 20 g of an octyl phosphate / dioctyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-8) was added, and the cyclization condensation reaction was performed under reflux (about 85 to 100 ° C.) for 2 hours. Furthermore, a cyclization condensation reaction was carried out for 1.5 hours under pressure in an autoclave using a heating medium at 240 ° C. (gauge pressure was about 2 MPa at maximum). Next, the polymer solution obtained by the cyclization condensation reaction was subjected to cyclization condensation reaction and devolatilization in a vent-type screw twin-screw extruder in the same manner as in Production Example 1, and extruded to obtain transparent pellets (A4 )

When the obtained resin pellet (A4) containing an acrylic polymer having a ring structure in the main chain was subjected to dynamic TG measurement, a weight loss of 0.25% by weight was detected. The lactone cyclization rate was 97.0%, the weight average molecular weight of the pellets was 134,000, the melt flow rate was 14.5 g / 10 min, and the glass transition temperature was 130 ° C.
[Production Example 5]
Transparent resin pellets (A5) containing an acrylic polymer were prepared in the same manner as in Production Example 2 except that the composition of the monomer charged in the reaction vessel was MMA 9,500 g and MA 500 g, and the cyclization condensation process was not performed. )
[Example 1]
<Preparation of optical film 1>
(Dope solution composition)
Resin A1 containing acrylic polymer 10 parts by weight cellulose triacetate (C1, acetyl group substitution degree 61.3-61.9%, number average molecular weight Mn = 64000, weight average molecular weight Mw = 171000)
90 parts by weight Methylene chloride 1900 parts by weight The above composition was sufficiently dissolved to prepare a dope solution.
<Formation of optical film 1>
The prepared dope solution was uniformly cast on a PET film support using an applicator. The solvent was evaporated on the PET film support until it became tack-free (a state where the dope film did not adhere when touched with a finger), and was peeled off from the PET film support. The peeled optical film was dried in an oven at 100 ° C. for 3 minutes. The film thickness after drying was 50 μm.
[Examples 2 to 4]
Optical film samples 2 to 4 were produced in the same manner as the optical film 1 except that the type of the resin (A) containing the acrylic polymer was changed as shown in Table 1.
[Comparative Example 1]
An optical film sample 5 containing no ring structure was produced in the same manner as the optical film 1 except that the resin A5 containing an acrylic polymer was used.
[Comparative Example 2]
A3 for resin containing acrylic polymer, cellulose acetate propionate for cellulose ester (C) (C2, acetyl group substitution degree 2.5%, hydroxyl group substitution degree 1.8%, propionyl group substitution degree 46%, number An optical film sample 6 was prepared in the same manner as the optical film 1 except that the weight ratio was changed as shown in Table 1 using the average molecular weight Mn = 63000 and the weight average molecular weight Mw = 175000.
[Comparative Example 3]
Optical film sample 5 was produced in the same manner as optical film 1 except that resin A3 containing an acrylic polymer was used and the weight ratio with cellulose triacetate was changed as shown in Table 1.

The evaluation results for the obtained optical films 1 to 7 are shown in Table 1.

Compared with the Example of Table 1, the haze of the film containing the acrylic polymer which does not have the ring structure of Comparative Example 1 at all and triacetyl cellulose was large, and was inappropriate as an optical film. Moreover, when Example 1 of Table 1 is compared with Example 2 and Example 3, the optical film sample which concerns on this invention is a film of a film as the content rate of the cyclic structure of the acrylic copolymer contained increases. It can be seen that haze decreases. Further, when Example 3 and Comparative Example 2 in Table 1 were compared, the haze of the film using cellulose acetate propionate as the cellulose ester was very large and was inappropriate as an optical film. Further, when Example 3 and Comparative Example 3 were compared, the film having a large weight ratio of the acrylic polymer having a ring structure in the main chain had a large haze and was inappropriate as an optical film.

  The optical film of the present invention, due to its high transparency and heat resistance, for example, a polarizer protective film used for a polarizing plate provided in an image display device such as a liquid crystal display device (LCD) and various optical disks (VD, CD, DVD, (MD, LD, etc.) For protective films for substrates such as protective films for substrates, retardation films, viewing angle compensation films, light diffusion films, reflective films, antireflection films, antiglare films, brightness enhancement films, conductive films for touch panels, etc. It is possible to use. In particular, it is suitably used as a polarizer protective film.

Claims (7)

The main chain includes a mixture of an acrylic polymer having at least one ring structure selected from a 6-membered lactone ring structure, a glutaric anhydride structure, and a glutarimide structure, and triacetyl cellulose , and has a haze of 1 or less. An optical film. The optical film according to claim 1, which is obtained by forming a solution or melt of the acrylic polymer and the triacetyl cellulose. The optical film according to claim 1 or 2, obtained by forming a dope solution in which the acrylic polymer and the triacetyl cellulose are dissolved. The optical film according to any one of claims 1 to 3 , wherein the acrylic polymer having a ring structure in the main chain has a glass transition temperature of 110 ° C or higher. The optical film according to any one of claims 1 to 4 the content of the ring structure of the acrylic polymer having a ring structure in its main chain is 10 wt% or more. The optical film according to any one of claims 1 to 5, comprising 5 to 50% by weight of an acrylic polymer having a ring structure in the main chain and 50 to 95% by weight of triacetyl cellulose. The optical film according to any one of claims 1 to 6, wherein the film forming method is a solution casting method or a melt extrusion method.