JP2014095926A - Optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical film with less film defect caused by thermal deterioration in molding processing and having excellent transparency.SOLUTION: An optical film comprises: an acrylic thermoplastic resin having glass transition temperature of 110°C or higher; and a triazine-based compound. The optical film contains 0.01 pt.wt. or more and 0.2 pt.wt or less of the triazine-based compound based on 100 pts.wt. of the acrylic thermoplastic resin so that the optical film having high thermal stability and less film defects in molding processing can be obtained.

Description

  The present invention relates to an optical film, and more particularly to an optical film having excellent transparency with few film defects caused by thermal deterioration during film formation.

  2. Description of the Related Art In recent years, electronic devices have become increasingly smaller, and liquid crystal display devices that take advantage of the features of light weight and compactness, such as notebook personal computers, mobile phones, and portable information terminals, have been increasingly used. These liquid crystal display devices start with a polarizing film, and various films are used to maintain the display quality. Also, a plastic liquid crystal display device using a resin film instead of a glass substrate has been put into practical use for the purpose of further reducing the weight of the liquid crystal display device for portable information terminals and mobile phones.

  When handling polarized light as in a liquid crystal display device, the resin film used is optically transparent, optically homogeneous, less colored or discolored, and appearance defects such as punctiform or streak-like It is required that there is little. Further, as in the case of a film substrate for a plastic liquid crystal display device in which the glass substrate is replaced with a resin film, it may be required that the phase difference represented by the product of birefringence and thickness is small. Furthermore, it may be required that the phase difference of the film hardly changes due to external stress or the like.

  Similarly to liquid crystal display devices, conventional glass used in various photographing devices such as cameras, film-integrated cameras, video cameras, optical pickup devices such as CDs and DVDs, OA equipment such as projectors, etc. has been used. Lenses are also being replaced with resin to reduce weight. Such plastic lenses are easily affected by phase difference due to focal length shift due to distortion due to temperature, humidity, and other usage environments, and stress during processing such as injection molding. It is demanded that it is difficult to change as well as film. As a resin composition that satisfies these requirements, the use of a (meth) acrylic resin having high transparency and high heat resistance in place of conventional triacetyl cellulose has been studied.

  Because optical films with few appearance defects are required, if a resin material mainly composed of (meth) acrylic resin is used as the optical film material, foreign substances in the resin material that cause appearance defects are removed. Therefore, when extruding and molding an optical film by molding a molding material containing the resin material, it is necessary to remove foreign substances through a polymer filter. However, there has been a problem that the (meth) acrylic resin is thermally deteriorated by heat applied during the filtering, and foaming due to decomposed monomers and optical defects occur in the film after molding. It is known to add an antioxidant such as a phosphorus compound, a hindered phenol compound, a lactone compound, a hindered amine compound, and a thioether compound in order to prevent such thermal deterioration of the (meth) acrylic resin. (Patent Document 1). On the other hand, in such an optical film, an ultraviolet absorber typified by a triazine-based compound may be added as necessary to impart an ultraviolet absorbing ability (Patent Document 2, Patent Document 3, and Patent Document 4).

WO 2006/054410 JP 2008-76764 A JP 2009-052021 A WO2005 / 109052 publication

  In the method of Patent Document 1, there is room for improvement with respect to film defects in long-time production.

  Further, as in Patent Documents 2, 3, and 4, triazine compounds have been conventionally used as ultraviolet absorbers, and about 1 to 5 parts by weight with respect to 100 parts by weight of resin in order to obtain sufficient ultraviolet absorbing ability. It was necessary to add a large amount of. As a result, new problems such as an increase in cost and bleeding out from the film have occurred. Moreover, there also existed a problem that the light transmittance in a short wavelength range (380-400 nm) fell and the transparency in a wide wavelength range deteriorated. In addition, since the triazine compound is only supposed to be used as an ultraviolet absorber, it has only been assumed to be added to a site where the amount exposed to ultraviolet rays is relatively large in the field of optical films. The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an optical film having excellent transparency with few film defects due to thermal deterioration during molding.

  As a result of intensive studies in view of the above problems, the present inventors have found that an optical film containing an acrylic thermoplastic resin and a compound having a triazine structure is excellent as an optical film. That is, the present invention relates to the following.

  (I) An optical film comprising an acrylic thermoplastic resin having a glass transition temperature of 110 ° C. or higher and a triazine compound, wherein 0.01 weight of triazine compound is added to 100 parts by weight of the acrylic thermoplastic resin. An optical film characterized by containing 0.2 part by weight or more and 0.2 part by weight or less.

  (Ii) The optical film as described in (i), wherein the 1% heat loss temperature of the triazine compound is 340 ° C. or higher.

  (Iii) The optical film as described in (i) or (ii), wherein the light transmittance at 380 nm at a film thickness of 40 μm is 30% or more.

  (Iv) The optical film according to any one of (i) to (iii), wherein the acrylic resin is a lactone resin, a glutaric acid anhydride resin, or a glutarimide resin.

  (V) The optical film as described in (iv), wherein the glutarimide resin includes a unit represented by the following general formula (1) and a unit represented by the following general formula (2): .

  (Vi) The optical film as described in (v), wherein the glutarimide resin further contains a unit represented by the following general formula (3).

  (Vii) The optical film as described in (v) or (vi), wherein the acrylate unit is less than 1% by weight.

  (Viii) The optical film as described in any one of (i) to (vii), which is a stretched film.

  (Ix) A polarizer protective film comprising the optical film described in (i) to (viii).

  (X) A polarizing plate comprising at least one polarizer protective film according to (ix).

  ADVANTAGE OF THE INVENTION According to this invention, there are few film defects resulting from the heat deterioration at the time of a shaping | molding process, and the optical film which has the outstanding transparency can be obtained.

  An embodiment of the present invention will be described below.

  The optical film of the present invention contains an acrylic resin and a triazine compound. (Acrylic resin) The acrylic resin contained in the optical film of the present invention has a glass transition temperature of 110 ° C or higher, preferably 115 ° C or higher, and more preferably 120 ° C or higher. Below this range, the heat resistance of the film is inferior, resulting in a large change in physical properties at high temperatures and a narrow application range. In particular, when used in optical applications, if the glass transition temperature is lower than the above range, the film tends to be distorted in a high temperature environment, and stable optical characteristics tend not to be obtained.

  The acrylic resin is not particularly limited as long as the glass transition temperature is 110 ° C. or higher, and specific examples include glutaric anhydride resin, resin having a lactone ring structure, and glutarimide resin. Can do. Although it does not restrict | limit especially as glutaric anhydride resin, It can manufacture according to the method of Unexamined-Japanese-Patent No. 2007-254703, etc. The resin having a lactone ring structure can be produced according to the method described in JP-A-2008-9378. (Glutarimide resin) The glutarimide resin will be described in detail below. Specific examples of the glutarimide resin include the following general formula (1).

(Wherein R1 and R2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or A unit containing a C 5-15 aromatic ring.) (Hereinafter also referred to as “glutarimide unit”), and the following general formula (2)

(Wherein R4 and R5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or A glutarimide resin containing a unit represented by a C 5-15 aromatic ring-containing unit (hereinafter also referred to as “(meth) acrylate unit”) can be suitably used.

  Moreover, the said glutarimide resin is the following general formula (3) as needed.

(Wherein R7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 is an aryl group having 6 to 10 carbon atoms) (hereinafter referred to as "aromatic vinyl unit"). May be further included.

  In the general formula (1), R1 and R2 are each independently hydrogen or a methyl group, R3 is preferably hydrogen, a methyl group, a butyl group, or a cyclohexyl group, and R1 is a methyl group R2 is more preferably hydrogen and R3 is more preferably a methyl group.

  The glutarimide resin may include only a single type as a glutarimide unit, or may include a plurality of types in which R1, R2, and R3 in the general formula (1) are different.

  The glutarimide unit can be formed by imidizing the (meth) acrylic acid ester unit represented by the general formula (2).

  In addition, acid anhydrides such as maleic anhydride, or half esters of such acid anhydrides and linear or branched alcohols having 1 to 20 carbon atoms; acrylic acid, methacrylic acid, maleic acid, maleic anhydride, The glutarimide unit can also be formed by imidizing an α, β-ethylenically unsaturated carboxylic acid such as itaconic acid, itaconic anhydride, crotonic acid, fumaric acid or citraconic acid.

  In the general formula (2), R4 and R5 are each independently hydrogen or a methyl group, R6 is preferably hydrogen or a methyl group, R4 is hydrogen, R5 is a methyl group, R6 is more preferably a methyl group.

  The glutarimide resin may contain only a single type as a (meth) acrylic acid ester unit, or a plurality of types in which R4, R5, and R6 in the general formula (2) are different. Also good. When the glutarimide resin contains an acrylate ester unit, the content is preferably less than 1% by weight, and more preferably less than 0.5% by weight. If the acrylate unit is within the above range, the glutarimide resin will be excellent in thermal stability, but if it exceeds the above range, the thermal stability will deteriorate, and the resin molecular weight and There is a tendency for the viscosity to decrease and the physical properties to deteriorate.

  In the glutarimide resin, the content of the glutarimide unit represented by the general formula (1) is not particularly limited, and is preferably changed depending on, for example, the structure of R3.

  Generally, the content of the glutarimide unit is preferably 1% by weight or more of the glutarimide resin, more preferably 2% by weight to 95% by weight, and 2% by weight to 90% by weight. More preferably, it is more preferably 2 to 80% by weight.

  If the content of the glutarimide unit is within the above range, the heat resistance and transparency of the resulting glutarimide resin may decrease, or the moldability and mechanical strength when processed into a film may decrease. There is no.

  On the other hand, when the content of the glutarimide unit is less than the above range, the resulting glutarimide resin tends to be insufficient in heat resistance or impaired in transparency. On the other hand, if the amount is larger than the above range, the heat resistance and melt viscosity are unnecessarily increased, the molding processability is deteriorated, the mechanical strength during film processing becomes extremely brittle, or the transparency is impaired. Tend.

  In the glutarimide resin, the content of the aromatic vinyl unit represented by the general formula (3) is not particularly limited, and can be appropriately set according to required physical properties. Depending on the application used, the content of the aromatic vinyl unit represented by the general formula (3) may be zero.

  The glutarimide resin may further be copolymerized with other units other than the glutarimide unit and the (meth) acrylic acid ester unit, if necessary.

  Other units include, for example, nitrile monomers such as styrene, acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide and N-cyclohexylmaleimide. Can be mentioned.

  These other units may be directly copolymerized or graft copolymerized in the glutarimide resin.

The weight average molecular weight of the glutarimide resin is not particularly limited, but is preferably 1 × 10 ^{4 to} 5 × 10 ⁵ , and more preferably 5 × 10 ^{4 to} 3 × 10 ⁵ . If it is in the said range, moldability will not fall or the mechanical strength at the time of film processing will not be insufficient.

  On the other hand, if the weight average molecular weight is smaller than the above range, the mechanical strength of the film tends to be insufficient. Moreover, when larger than the said range, the viscosity at the time of melt-extrusion is high, there exists a tendency for the moldability to fall and for the productivity of a molded article to fall.

  The acid value of the glutarimide resin is not particularly limited, but is preferably 0.5 mmol / g or less, and more preferably 0.35 mmol / g or less. If the acid value is within the above range, a glutarimide resin having an excellent balance of heat resistance, mechanical properties and molding processability can be obtained.

  On the other hand, for example, when the acid value is larger than the above range, foaming of the resin at the time of melt extrusion tends to occur, the moldability tends to be lowered, and the productivity of the molded product tends to be lowered.

  The acid value can be calculated by, for example, a titration method described in JP-A-2005-23272.

  In the glutarimide resin, the content (in other words, the ratio) of the units represented by the general formulas (1) to (3) is not particularly limited, and physical properties required for the glutarimide resin, What is necessary is just to determine according to the optical characteristic requested | required of the optical film concerning this invention. (Method for Producing Glutarimide Resin) Here, an embodiment of the method for producing the glutarimide resin will be described, but the present invention is not limited thereto.

  First, a (meth) acrylic acid ester polymer is produced by polymerizing a (meth) acrylic acid ester. The production method is not particularly limited, and known emulsion polymerization methods, emulsion-suspension polymerization methods, suspension polymerization methods, bulk polymerization methods, solution polymerization methods, and the like can be applied. From the viewpoint of being small, the bulk polymerization method and the solution polymerization method are particularly preferable. For example, it can be produced according to the methods described in JP-A-56-8404, JP-B-6-86492, JP-B-52-32665, and the like. The (meth) acrylic acid ester polymer is preferably polymethyl methacrylate. When the glutarimide resin of the present invention contains an aromatic vinyl unit, a (meth) acrylic acid ester and an aromatic vinyl are copolymerized to produce a (meth) acrylic acid ester-aromatic vinyl copolymer. The methyl methacrylate-styrene copolymer is produced according to the method described in, for example, JP-A-57-149111, JP-A-57-153010, JP-A-10-152505, JP-A-2001-31046, JP-A-2004-27191, etc. it can. When the glutarimide resin of the present invention contains an acrylate unit, the acrylate unit in the (meth) acrylate polymer used as a raw material is preferably less than 1% by weight, preferably 0.5% by weight. More preferably, it is less.

  In this step, examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, and (meth) acrylic acid t. -Butyl, benzyl (meth) acrylate, and cyclohexyl (meth) acrylate are preferably used, and methyl methacrylate is more preferably used.

  These (meth) acrylic acid esters may be used alone or in combination of two or more. By using multiple types of (meth) acrylic acid esters, it is possible to give multiple types of (meth) acrylic acid ester units to the finally obtained glutarimide resin.

  Moreover, when the said glutarimide resin contains an aromatic vinyl unit, the ratio of an aromatic vinyl unit can be adjusted by adjusting the polymerization rate of (meth) acrylic acid ester and aromatic vinyl.

  The structures of the (meth) acrylic acid ester-aromatic vinyl copolymer and the (meth) acrylic acid ester polymer are not particularly limited as long as the imidization reaction is possible. Specifically, any of a linear (linear) polymer, a block polymer, a core-shell polymer, a branched polymer, a ladder polymer, and a crosslinked polymer may be used.

  In the case of a block polymer, it may be any of AB type, ABC type, ABA type, and other types of block polymers. In the case of the core-shell polymer, it may be composed of only one core and only one shell, or each may be composed of multiple layers.

  Next, an imidizing agent is added to the (meth) acrylic acid ester polymer or (meth) acrylic acid ester-aromatic vinyl copolymer to perform imidization. Thereby, the said glutarimide resin can be manufactured.

  The imidizing agent is not particularly limited as long as it can generate the glutarimide unit represented by the general formula (1), and examples thereof include those described in WO2005 / 054311. Specifically, for example, an aliphatic hydrocarbon group-containing amine such as ammonia, methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, n-hexylamine, Mention may be made of aromatic hydrocarbon group-containing amines such as aniline, benzylamine, toluidine and trichloroaniline, and alicyclic hydrocarbon group-containing amines such as cyclohexylamine.

  In addition, urea-based compounds that generate amines exemplified above by heating, such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, can also be used.

  Of the imidizing agents exemplified above, methylamine, ammonia, and cyclohexylamine are preferably used from the viewpoint of cost and physical properties, and methylamine is particularly preferably used.

  Further, gaseous methylamine or the like at normal temperature may be used in a state dissolved in alcohols such as methanol.

  In this imidization step, a ring closure accelerator (catalyst) may be added as necessary in addition to the imidizing agent.

  In this imidization step, the ratio of glutarimide units and (meth) acrylate units in the resulting glutarimide resin can be adjusted by adjusting the ratio of the imidizing agent added.

  Moreover, by adjusting the degree of imidization, the physical properties of the obtained glutarimide resin, the optical characteristics of an optical film formed by molding the glutarimide resin according to the present invention, and the like can be adjusted.

  The method for imidizing the (meth) acrylic acid ester polymer or the (meth) acrylic acid ester-aromatic vinyl copolymer is not particularly limited, and any conventionally known method can be used. (1) Using an extruder or the like, the (meth) acrylic acid ester polymer or (meth) acrylic acid ester-aromatic vinyl copolymer in a molten state is reacted with an imidizing agent, or (2) imide It can be obtained by reacting (meth) acrylic acid ester polymer or (meth) acrylic acid ester-aromatic vinyl copolymer with an imidizing agent using a non-reactive solvent for the reaction. It is done.

  When manufacturing the said glutarimide resin using an extruder, the extruder to be used is not specifically limited, Various extruders can be used. Specifically, for example, a single screw extruder, a twin screw extruder, a multi-screw extruder, or the like can be used.

  Among these, it is preferable to use a twin screw extruder. According to the twin screw extruder, when using an imidizing agent (ring closure accelerator) for the raw material polymer (that is, (meth) acrylic acid ester-aromatic vinyl copolymer or (meth) acrylic acid ester polymer), Mixing of an imidizing agent and a ring closure accelerator) can be promoted.

  Examples of the twin-screw extruder include a non-meshing type same direction rotating type, a meshing type same direction rotating type, a non-meshing type different direction rotating type, and a meshing type different direction rotating type. Among them, it is preferable to use a meshing type co-rotating type. Since the meshing type co-rotating twin-screw extruder can rotate at a high speed, mixing of the imidizing agent (in the case of using a ring closure accelerator and an imidization agent and a ring closure accelerator) with the raw polymer is further improved. Can be promoted.

  The above-exemplified extruders may be used alone, or a plurality of the extruders may be connected in series. For example, a tandem reaction extruder described in JP-A-2008-273140 can be used. When imidization is performed in an extruder, for example, a raw material (meth) acrylic acid ester polymer or (meth) acrylic acid ester-aromatic vinyl copolymer is charged from a raw material charging portion of the extruder, After the resin is melted and the inside of the cylinder is filled, an imidizing agent is injected into the extruder using an addition pump, whereby the imidization reaction can proceed in the extruder.

  In this case, the reaction zone temperature (resin temperature) in the extruder is preferably 180 to 300 ° C, more preferably 200 to 290 ° C. When the temperature of the reaction zone (resin temperature) is less than 180 ° C., the imidization reaction hardly proceeds and the heat resistance tends to decrease. When the reaction zone temperature exceeds 300 ° C., the resin is significantly decomposed, so that the bending resistance of a film that can be formed from the resulting glutarimide resin tends to be lowered. Here, the reaction zone in the extruder refers to a region between the injection position of the imidizing agent and the resin discharge port (die part) in the cylinder of the extruder. By increasing the reaction time in the reaction zone of the extruder, imidization can be further advanced. The reaction time in the reaction zone of the extruder is preferably longer than 10 seconds, and more preferably longer than 30 seconds. In the reaction time of 10 seconds or less, imidation may hardly proceed. The resin pressure in the extruder is preferably in the range of atmospheric pressure to 50 MPa, and more preferably in the range of 1 MPa to 30 MPa. If it is less than 1 MPa, the solubility of the imidizing agent is low, and the progress of the reaction tends to be suppressed. On the other hand, if it is 50 MPa or more, the mechanical pressure limit of a normal extruder is exceeded, and a special apparatus is required, which is not preferable in terms of cost.

  The extruder is preferably equipped with a vent port that can be reduced to atmospheric pressure or lower. According to such a configuration, unreacted imidizing agent, or by-products such as methanol and monomers can be removed.

  For the production of the glutarimide resin, instead of an extruder, for example, a horizontal biaxial reactor such as a Violac manufactured by Sumitomo Heavy Industries, Ltd. or a vertical biaxial agitation tank such as Super Blend is used. Viscosity-compatible reactors can also be suitably used.

  When manufacturing the said glutarimide resin using a batch type reaction tank (pressure vessel), the structure of the batch type reaction vessel (pressure vessel) is not specifically limited.

  Specifically, it has a structure in which the raw material polymer can be melted by heating and stirred, and an imidizing agent (in the case of using a ring closure accelerator, an imidizing agent and a ring closure accelerator) can be added. However, it is preferable to have a structure with good stirring efficiency.

  According to such a batch-type reaction vessel (pressure vessel), it is possible to prevent the polymer viscosity from increasing due to the progress of the reaction and the stirring to be insufficient. As a batch type reaction tank (pressure vessel) having such a structure, for example, a stirred tank Max Blend manufactured by Sumitomo Heavy Industries, Ltd. can be exemplified. Specific examples of the imidization method include known methods such as those described in JP-A-2008-273140 and JP-A-2008-274187.

  According to the method as described above, a glutarimide resin in which the ratio of glutarimide units, (meth) acrylic acid ester units, and aromatic vinyl units is controlled as desired can be easily produced. (Triazine compound) The triazine compound contained in the optical film according to the present invention is not particularly limited as long as it has a triazine skeleton, but has a 2-hydroxyphenyl-1,3,5-triazine skeleton. Those are preferred. As long as it has the skeleton, it may be substituted with other substituents. Specific examples include the following compounds described in WO2001 / 047900.

(Wherein iC ₈ H ₁₇ is a mixture of C7-C9 alkyl isomers)

  In addition, the following compounds described in WO2005 / 109052 are exemplified.

  Further, the following compounds described in WO2007 / 114112 are also exemplified.

  Moreover, the following compounds described in JP-A-2007-217667 are also exemplified.

Moreover,

Etc. Commercially available products include trade names Tinuvin 400, Tinuvin 460, Tinuvin 477 and the like manufactured by Ciba Specialty Chemicals. These may be used alone or in combination of two or more.

  Among these, since it is assumed that the thermal stabilization effect is high, it is considered preferable to have two or more substituted or unsubstituted hydroxyphenyl groups. Even when the triazine compound is a mixture of two or more, it is considered preferable that the number of hydroxyphenyl groups per one is large.

  Moreover, since there are few side reactions at the time of shaping | molding at high temperature, it is thought that it is preferable that there are few reactive functional groups as a substituent of a hydroxyphenyl group.

  From the above, among the triazine compounds described above, the above formulas (7), (8), (11), (12), (13), (14), (15), and (17) are preferable. It is conceivable that those having the structures of the above formulas (7), (8), (11), (12), and (13) are considered particularly preferable.

  The triazine-based compound preferably has a 1% heat loss temperature of 340 ° C. or higher, more preferably 350 ° C. or higher, further preferably 360 ° C. or higher, and particularly preferably 380 ° C. or higher. preferable. When the temperature is lower than 340 ° C., it is close to the processing temperature, and therefore, volatilization is often not preferable. The upper limit is not particularly limited, but is preferably 500 ° C. or lower from the balance between handling and physical properties. Here, the 1% heat loss temperature is the temperature when the heat loss (% by weight) is 1% (when the original weight is 100% by weight, it is 99% by weight). Specifically, , 15 mg of the triazine compound was heated from room temperature at 10 ° C./min in a nitrogen atmosphere with a thermogravimetry apparatus (TGA, TGA-50 manufactured by Shimadzu Corporation), and the thermal loss (wt%) was 1. It is the temperature when it becomes%.

  The triazine compound of the present invention is preferably 0.01 to 0.20 part by weight, and 0.05 to 0.15 part by weight of (B) the triazine compound with respect to 100 parts by weight of the acrylic resin. Is more preferable.

  When the amount of the triazine-based compound is within the above range, defects due to thermal degradation of the optical film can be reduced, and transparency can be increased.

  On the other hand, if the triazine-based compound is less than 0.01 parts by weight, film defects due to thermal deterioration increase, and if it is more than 0.20 parts by weight, the light transmittance tends to decrease particularly in the short wavelength region (380 to 400 nm). is there.

  The triazine compound of the present invention can be used in combination with other general heat stabilizers as necessary. Although it does not specifically limit as a heat stabilizer to use together, A phosphorus compound, a hindered phenol compound, a lactone compound, a hindered amine compound, and a thioether compound can be used suitably in this especially a phosphorus heat stabilizer Can be suitably used.

  The phosphorous compound is not particularly limited as long as it is phosphoric acid and its alkyl esters. For example, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t -Butylphenyl) -4,4'-biphenylene phosphite, trisnonylphenyl phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite, distearyl pentaerythritol diphosphite, etc. Can do.

  The hindered phenol compound is not particularly limited as long as it is a compound containing a phenolic hydroxyl group. For example, triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) Propionate], pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) Propionate, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- {3- (3-t -Butyl-4-hydroxy-5-methylphenyl) propionyloxy} -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro [ 5] Undecane, 2-t-butyl-6- (3'-t-butyl-5'-methyl-2'-hydroxybenzyl) -4-methylphenyl acrylate, 2,4-di-t-amyl-6 -(3 ', 5'-di-t-amyl-2'-hydroxy-α-methylbenzyl) methylphenyl acrylate, 2-t-butyl-6- (3'-t-butyl-2'-hydroxy-5 '-Methyl-methylbenzyl) -4-methylphenyl acrylate, 2,5-di-t-butyl-6- (3', 5'-di-t-butyl-2'-hydroxy-α-methylbenzyl) methyl Examples thereof include phenyl acrylate.

  The lactone compound is not particularly limited as long as it is a compound containing a lactone ring. For example, 5,7-di-t-butyl-3- (3,4-dimethylphenyl) -3H-benzofuran-2- You can mention ON.

  The hindered amine compound is not particularly limited as long as it is a compound containing a 2,2,6,6, -tetramethyl-4-piperidyl group. For example, poly [{6- (1,1,3,3 -Tetramethylbutyl) amino} -1,3,5-triazine-2,4-diyl] {(2,2,6,6-tetramethyl-piperidyl) imino} hexamethylene {(2,2,6,6 -Tetramethyl-piperidyl) imino}] and the like.

  The thioether compound is not particularly limited as long as it is a compound containing a thioether group. For example, dilauryl 3,3′-thiodipropionate, dimyristyl 3,3′-thiodipropionate, distearyl 3,3 Examples include '-thiopropionate, pentaerythrityltetrakis (3-laurylthiopropionate), ditridecyl 3,3'-thiodipropionate. Even when other heat stabilizers as described above are included in the resin composition according to the present invention, the blending ratio of the thermoplastic resin and the triazine compound is within the above-described range. It is preferable. (Other Additives) Examples of other additives that can be contained in the optical film according to the present invention include conventionally known additives such as plasticizers, lubricants, and fillers. Resins other than the acrylic resins described above can also be contained as other additives. The other additives are optional components, and the resin composition according to the present invention may not contain these other additives.

  The plasticizer includes, in addition to a so-called plasticizer, a polymer having flexibility (flexible polymer). That is, in this specification, a plasticizer, a flexible polymer, and the like are collectively referred to as a plasticizer.

  The plasticizer is not particularly limited, and any conventionally known plasticizer can be used. Specific examples include aliphatic dibasic acid plasticizers such as di-n-decyl adipate and phosphate ester plasticizers such as tributyl phosphate.

  By including the plasticizer in the resin composition according to the present invention, the mechanical properties of the film formed by molding the resin composition can be improved.

  On the other hand, the addition of the plasticizer may cause a problem that the glass transition temperature of the resulting film is lowered and the heat resistance is impaired or the transparency is impaired.

  Therefore, when the thermoplastic resin composition according to the present invention contains the plasticizer, it is preferably added within a range in which the performance of the film is not hindered in the film formed by molding the thermoplastic resin composition.

  Specifically, the content of the plasticizer in the thermoplastic resin composition is preferably 20% by weight or less, preferably 10% by weight or less, and more preferably 5% by weight or less. .

  When a resin other than the acrylic resin described above is used as the other additive, the resin is not particularly limited. For example, a thermoplastic resin other than the acrylic resin described above may be used, or a thermosetting resin may be used. Among these, it is preferable to contain a thermoplastic resin other than the acrylic resin described above.

  In addition, resin contained as another additive may be used individually by 1 type, and may be used in combination of multiple types of resin.

  When the above resin is added as another additive, the content in the thermoplastic resin composition is preferably 1% by weight to 30% by weight, more preferably 2% by weight to 20% by weight, More preferably, it is 3 to 10% by weight.

  On the other hand, when there is more content of the said resin than the said range, there exists a tendency for the performance of the acrylic resin mentioned above and a triazine type compound to fully exhibit. On the other hand, if the content of the resin is less than the above range, the effect of adding the resin may be difficult to obtain.

  The filler is not particularly limited, and any conventionally known filler used for a film can be used. The filler may be inorganic fine particles or organic fine particles.

  Examples of fillers that are inorganic fine particles include metal oxide fine particles such as silicon dioxide, titanium dioxide, aluminum oxide, and zirconium oxide, and calcined calcium silicate, hydrated calcium silicate, aluminum silicate, and magnesium silicate. Examples include acid salt fine particles, calcium carbonate, talc, clay, calcined kaolin, and calcium phosphate.

  Examples of the filler that is an organic fine particle include resin fine particles such as a silicon resin, a fluorine resin, an acrylic resin, and a crosslinked styrene resin.

  By adding such a filler, the slipperiness of the film can be improved.

  The addition amount of the filler is not particularly limited, but when the acrylic resin composition according to the present invention is molded into an optical film, the optical properties of the resulting film may be in a range that is not significantly impaired. preferable.

  In general, in the thermoplastic resin composition according to the present invention, the content of the filler is preferably 10% by weight or less.

  Even when other additives as described above are included in the resin composition according to the present invention, the mixing ratio of the acrylic resin and the triazine compound should be within the above-described range. Is preferred.

(Optical film and manufacturing method thereof)
Examples of the optical film according to the present invention include a retardation film, a polarizer protective film, a polarizer protective film having a retardation development function, and a base film of a coating material imparting an optical compensation function. The optical film according to the present invention may be a film that satisfies the conditions described above, but is preferably a stretched film, that is, a stretched film. According to the stretched film, the mechanical properties can be improved.

  In addition, when the optical film concerning this invention is a stretched film, the uniaxially stretched film uniaxially stretched may be sufficient, and the biaxially stretched film obtained by combining a extending process may be sufficient.

  When the optical film according to the present invention is a stretched film, the thickness is not particularly limited, but is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and more preferably 30 μm to 100 μm. More preferably it is.

  When the thickness of the film is within the above range, an optical film having uniform optical characteristics and good haze can be obtained.

  On the other hand, if the thickness of the film exceeds the above range, the cooling of the film becomes non-uniform and the optical characteristics tend to be non-uniform. Moreover, when the thickness of the film is less than the above range, the draw ratio becomes excessive, and the haze tends to deteriorate.

  The optical film according to the present invention has a light transmittance of 380 nm at a film thickness of 40 μm of 30% or more, and more preferably 40% or more.

  The light transmittance at a wavelength of 400 nm at a film thickness of 40 μm is 80% or more, and more preferably 85% or more. 400 nm is a visible light region, and it is particularly preferable that the light transmittance at this wavelength is high.

  If the light transmittance at a wavelength of 380 nm and 400 nm at a film thickness of 40 μm is within the above range, the colorless transparency of the film can be made high. Therefore, the optical film according to the present invention can be suitably used for applications requiring colorless transparency.

  The optical film according to the present invention preferably has a haze of 1% or less, more preferably 0.7% or less, and even more preferably 0.5% or less.

  If the haze of the optical film according to the present invention is within the above range, the transparency of the film can be increased. Therefore, the optical film according to the present invention can be suitably used for applications requiring transparency.

  The optical film according to the present invention preferably has a total light transmittance of 85% or more, and more preferably 88% or more.

  If the total light transmittance is within the above range, the transparency of the film can be increased. Therefore, the optical film according to the present invention can be suitably used for applications requiring transparency.

  The optical film according to the present invention preferably has a small optical anisotropy when used as a polarizer protective film. In particular, it is preferable that not only the optical anisotropy in the in-plane direction (length direction, width direction) of the film but also the optical anisotropy in the thickness direction is small. In other words, it is preferable that both the in-plane retardation and the thickness direction retardation are small.

  More specifically, the in-plane retardation is preferably 10 nm or less, more preferably 5 nm or less, and further preferably 3 nm or less with respect to the raw material film. The in-plane retardation of the stretched film is preferably 10 nm or less, more preferably 6 nm or less, and further preferably 5 nm or less.

  The thickness direction retardation is preferably 50 nm or less, more preferably 10 nm or less, and further preferably 5 nm or less with respect to the raw material film. Moreover, regarding the stretched film, the thickness direction retardation is preferably 50 nm or less, more preferably 20 nm or less, and further preferably 10 nm or less.

  If it is set as the structure which has such an optical characteristic, the optical film concerning this invention can be used suitably as a polarizer protective film with which the polarizing plate of a liquid crystal display device is equipped.

  When the in-plane retardation of the film exceeds 10 nm or the thickness direction retardation exceeds 50 nm, the polarizer protective film using the optical film according to the present invention is used as a polarizing plate of a liquid crystal display device. Problems such as a decrease in contrast may occur in the display device.

  On the other hand, when the optical film according to the present invention is used for a retardation film or a polarizer protective film having a retardation development function, it is preferable that the optical anisotropy is large.

  Specifically, the in-plane retardation (Re) of the optical film is preferably 30 to 100 nm and the thickness direction retardation (Rth) is preferably 50 to 320 nm. The in-plane retardation of the optical film is more preferably 40 to 100 nm. The thickness direction retardation is more preferably 100 to 300 nm. When the in-plane retardation of the optical film is 30 nm or less, there may be a problem that the necessary retardation cannot be imparted.

  The in-plane retardation (Re) and the thickness direction retardation (Rth) can be calculated by the following equations, respectively.

  Re = (nx−ny) × d Rth = | (nx + ny) / 2−nz | × d In the above formula, nx, ny, and nz each indicate the direction in which the in-plane refractive index is maximum X The axis, the direction perpendicular to the X axis is the Y axis, and the thickness direction of the film is the Z axis. D represents the thickness of the film, and || represents an absolute value.

Moreover, when the optical film concerning this invention is used as a polarizer protective film, it is preferable that the value of orientation birefringence is 0-0.1 * 10 < ^-3 >, and 0-0.01 * 10 < ^-3 >. It is more preferable that

  If the orientation birefringence is within the above range, stable optical characteristics can be obtained without causing birefringence during molding even when the environment changes.

On the other hand, when the optical film according to the present invention is used for a retardation film or a polarizer protective film having a retardation development function, the value of orientation birefringence is 1.0 × 10 ⁻³ or more. It is preferable that it is 2.0 × 10 ⁻³ or more.

  In the present specification, unless otherwise specified, “orientation birefringence” is intended to mean birefringence that develops when stretched 100% at a temperature 5 ° C. higher than the glass transition temperature of a thermoplastic resin. The orientation birefringence (Δn) is defined by Δn = nx−ny = Re / d and can be measured by a phase difference meter, using nx and ny described above.

In the optical film according to the present invention, the absolute value of the photoelastic coefficient is preferably 20 × 10 ⁻¹² m ² / N or less, more preferably 10 × 10 ⁻¹² m ² / N or less, More preferably, it is 5 × 10 ⁻¹² m ² / N or less.

  If the photoelastic coefficient is within the above range, even if the optical film according to the present invention is used in a liquid crystal display device, phase difference unevenness occurs, contrast at the periphery of the display screen decreases, or light leakage occurs. There is nothing to do.

On the other hand, when the absolute value of the photoelastic coefficient is larger than 20 × 10 ⁻¹² m ² / N, when the optical film according to the present invention is used in a liquid crystal display device, unevenness in phase difference occurs, There is a tendency that the contrast of the light is reduced or light leakage is likely to occur. This tendency becomes particularly remarkable in a high temperature and high humidity environment.

  In addition, when an external force is applied to an isotropic solid to generate stress (ΔF), it temporarily exhibits optical anisotropy and exhibits birefringence (Δn). By “photoelastic coefficient” is intended the ratio of stress to birefringence. That is, the photoelastic coefficient (c) is calculated by the following equation.

  c = Δn / ΔF However, in the present invention, the photoelastic coefficient is a value measured at 23 ° C. and 50% RH at a wavelength of 515 nm by the Senarmon method.

  The optical film according to the present invention may be subjected to surface treatment as necessary. Specifically, for example, when the optical film according to the present invention is used by applying surface processing such as coating processing to the surface or laminating another film on the surface, the optical film according to the present invention is used. It is preferable to perform a surface treatment.

  By performing such a surface treatment, mutual adhesion between the optical film according to the present invention and another film to be coated or laminated can be improved.

  In addition, the objective of the surface treatment with respect to the optical film concerning this invention is not limited to what aims at an effect. That is, the optical film according to the present invention may be subjected to a surface treatment regardless of its use.

  The surface treatment is not particularly limited, and examples thereof include corona treatment, plasma treatment, ultraviolet irradiation, and alkali treatment. Among these, corona treatment is preferable.

  Since the optical film according to the present invention has the characteristics as described above, it can be used as it is as a final product for various applications. Moreover, the range of uses can be expanded by performing various processes as described above.

  Although the use of the optical film according to the present invention is not particularly limited, specifically, for example, imaging fields such as cameras, VTRs, projectors, viewfinders, filters, prisms, and Fresnel lenses, CDs, etc. Optical field for optical discs such as optical discs for CD players, DVD players, MD players, liquid crystal light guide plates, polarizer protective films, retardation films, etc. Information equipment field such as LCD display film and surface protection film, optical communication field such as optical fiber, optical switch and optical connector, automotive field such as automobile headlight, tail lamp lens, inner lens, instrument cover, sunroof, glasses and contact Len , Endoscopic lenses, medical devices such as medical supplies that require sterilization, road translucent plates, pair glass lenses, lighting windows and carports, lighting lenses and covers, and building material sizing It can be suitably used in the field of building materials, microwave cooking containers (tableware) and the like.

  As described above, the optical film according to the present invention is excellent in optical characteristics such as optical homogeneity and transparency. Therefore, it can use especially suitably for well-known optical uses, such as a liquid crystal display periphery, such as an optically isotropic film, a polarizer protective film, and a transparent conductive film, using these optical characteristics.

  The optical film of the present invention can be used as a polarizing plate by being attached to a polarizer. That is, the optical film according to the present invention can be used as a polarizer protective film for a polarizing plate. The polarizer is not particularly limited, and any conventionally known polarizer can be used. Specific examples include a polarizer obtained by containing iodine in stretched polyvinyl alcohol.

  The optical film of the present invention can be used as a polarizer protective film or a retardation film as described above. However, it is more effective to use it in a region where the exposure amount of ultraviolet rays is small due to its characteristics. Therefore, it is preferable. That is, when a liquid crystal display device including a liquid crystal and two polarizing plates is assumed, since the polarizer protective film used on the outermost surface has the largest amount of exposure to ultraviolet rays, it is preferably used on the surface other than the outermost surface. .

  Here, although one Embodiment of the method to manufacture the optical film concerning this invention is described, this invention is not limited to this. In other words, any conventionally known method can be used as long as it can produce the optical film according to the present invention.

  Specific examples include injection molding, melt extrusion film molding, inflation molding, blow molding, compression molding, spinning molding, solution casting molding, spin coating molding, and the like.

  Among them, it is preferable to use a melt extrusion method that does not use a solvent. According to the melt extrusion method, it is possible to reduce the burden on the global environment and the working environment due to manufacturing costs and solvents.

  Hereinafter, as an embodiment of the method for producing a film according to the present invention, a method for producing an optical film according to the present invention by a melt extrusion method will be described in detail. In the following description, a film formed by the melt extrusion method is distinguished from a film formed by another method such as a solution casting method and is referred to as a “melt extrusion film”.

  When the optical film according to the present invention is formed by a melt extrusion method, first, the above-mentioned acrylic resin composition is supplied to an extruder, and the resin composition is heated and melted.

  The resin composition is preferably pre-dried before being supplied to the extruder. By performing such preliminary drying, foaming of the resin extruded from the extruder can be prevented.

  Although the method of preliminary drying is not particularly limited, for example, the raw material (that is, the resin composition according to the present invention) can be formed into pellets or the like and can be performed using a hot air dryer or the like.

  Next, the resin composition heated and melted in the extruder is supplied to the T die through a gear pump and a filter. At this time, if a gear pump is used, the uniformity of the extrusion amount of the resin can be improved and thickness unevenness can be reduced. On the other hand, if a filter is used, the foreign material in a thermoplastic resin composition can be removed and the film excellent in the external appearance without a defect can be obtained.

  Next, the resin composition supplied to the T die is extruded from the T die as a sheet-like molten resin. Then, the sheet-like molten resin is sandwiched between two cooling rolls and cooled to form a film.

  One of the two cooling rolls sandwiching the sheet-like molten resin is a rigid metal roll having a smooth surface, and the other has a metal elastic outer cylinder having a smooth surface and capable of elastic deformation. A flexible roll is preferred.

  With such a rigid metal roll and a flexible roll having a metal elastic outer cylinder, the sheet-like molten resin is sandwiched and cooled to form a film, thereby correcting minute surface irregularities and die lines. Thus, a film having a smooth surface and thickness unevenness of 5 μm or less can be obtained.

  In this specification, “cooling roll” is used to mean “touch roll” and “cooling roll”.

  Even when the rigid metal roll and the flexible roll are used, since the surface of each cooling roll is metal, when the film to be formed is thin, the surfaces of the cooling roll come into contact with each other. The outer surface may be scratched, or the cooling roll itself may be damaged.

  Therefore, when forming a film by sandwiching the sheet-like molten resin between the two cooling rolls as described above, first, the sheet-like molten resin is sandwiched and cooled by the two cooling rolls, and the film is relatively thick. Obtain raw material film once. Thereafter, the raw film is preferably uniaxially or biaxially stretched to produce a film having a predetermined thickness.

  More specifically, when an optical film having a thickness of 40 μm is produced, the sheet-like molten resin is sandwiched and cooled by the two cooling rolls, and a raw material film having a thickness of 150 μm is once obtained. Thereafter, the raw material film may be stretched by biaxial stretching in the vertical and horizontal directions to produce a film having a thickness of 40 μm.

  Thus, when the optical film according to the present invention is a stretched film, the resin composition according to the present invention is once formed into an unstretched raw material film, and then subjected to uniaxial stretching or biaxial stretching. A stretched film can be produced.

  In the present specification, for convenience of explanation, a film before being stretched after the resin composition according to the present invention is formed into a film shape, that is, an unstretched film is referred to as a “raw film”. It should be noted that the raw film is also an embodiment of the optical film according to the present invention.

  When stretching the raw material film, the raw material film may be stretched immediately after the raw material film is formed, or after the raw material film is molded, the raw material film is temporarily stored or moved to stretch the raw material film. You may go.

  In addition, when the raw material film is stretched immediately after being formed into a raw material film, the state of the raw material film may exist only for a very short time (in some cases, instantaneously) in the film manufacturing process.

  Moreover, when the said raw material film is extended | stretched after that, what is necessary is just to maintain the film form of a grade sufficient to be extended | stretched, and does not need to be the state of a perfect film. Moreover, the said raw material film does not need to have the performance as an optical film which is a finished product.

  The method for stretching the raw material film is not particularly limited, and any conventionally known stretching method may be used. Specifically, for example, transverse stretching using a tenter, longitudinal stretching using a roll, sequential biaxial stretching in which these are sequentially combined, and the like can be used.

  Moreover, the simultaneous biaxial stretching method which extends | stretches the length and the width | variety simultaneously can be used, or the method of performing the horizontal extending | stretching by a tenter can be used after performing roll vertical stretching.

  When the raw material film is stretched, it is preferable that the raw material film is once preheated to a temperature 0.5 to 5 ° C., preferably 1 to 3 ° C. higher than the stretching temperature, and then cooled and stretched to the stretching temperature.

  By preheating within the above range, the thickness of the raw material film can be maintained with high accuracy, and the thickness accuracy of the stretched film does not decrease and thickness unevenness does not occur. Further, the raw material film does not stick to the roll and does not loosen due to its own weight.

  On the other hand, if the preheating temperature of the raw material film is too high, there is a tendency that the raw material film sticks to the roll or is loosened by its own weight. In addition, if the difference between the preheating temperature and the stretching temperature of the raw material film is small, it tends to be difficult to maintain the thickness accuracy of the raw material film before stretching, the thickness unevenness increases, or the thickness accuracy tends to decrease.

  In addition, when the resin composition according to the present invention is stretched after being formed into a raw material film, it is difficult to improve the thickness accuracy by utilizing a necking phenomenon. Therefore, in the present invention, it is important to manage the preheating temperature in order to maintain or improve the thickness accuracy of the obtained optical film.

  The stretching temperature when stretching the raw material film is not particularly limited, and may be changed according to the mechanical strength, surface property, thickness accuracy, and the like required for the stretched film to be produced.

  In general, when the glass transition temperature of the raw material film obtained by the DSC method is defined as Tg, the temperature range is preferably (Tg-30 ° C) to (Tg + 30 ° C), and (Tg-20 ° C) to ( Tg + 20 ° C. is more preferable, and a temperature range of (Tg) to (Tg + 20 ° C.) is more preferable.

  When the stretching temperature is within the above temperature range, thickness unevenness of the obtained stretched film can be reduced, and further, mechanical properties such as elongation, tear propagation strength, and fatigue resistance can be improved. Moreover, generation | occurrence | production of the trouble that a film adheres to a roll can be prevented.

  On the other hand, when the stretching temperature is higher than the above temperature range, the thickness unevenness of the stretched film obtained tends to be large, and the mechanical properties such as elongation, tear propagation strength, and fatigue resistance cannot be improved sufficiently. There is. Furthermore, there is a tendency that troubles such as the film sticking to the roll tend to occur.

  In addition, when the stretching temperature is lower than the above temperature range, the haze of the stretched film to be obtained becomes large, or in extreme cases, there is a tendency that process problems such as tearing or cracking of the film occur. is there.

  When the raw material film is stretched, the stretch ratio is not particularly limited, and may be determined according to the mechanical strength, surface properties, thickness accuracy, and the like of the stretched film to be produced. Although it depends on the stretching temperature, the stretching ratio is generally preferably selected in the range of 1.1 to 3 times, more preferably in the range of 1.3 to 2.5 times. Preferably, it is more preferable to select in the range of 1.5 times to 2.3 times.

  If the draw ratio is within the above range, the mechanical properties such as the elongation rate of the film, tear propagation strength, and fatigue resistance can be greatly improved. Therefore, a stretched film having a thickness unevenness of 5 μm or less and a haze of 1% or less can be produced.

  In addition, in the optical film according to the present invention, by adjusting the mixing ratio of the acrylic thermoplastic resin and the triazine compound within the above range and selecting appropriate stretching conditions, it is possible to substantially increase haze. Without accompanying, a film with small thickness unevenness can be easily manufactured.

  The optical film according to the present invention may be used by laminating another film with an adhesive or the like, or forming a hard coat layer or a coating layer of a compound having an optical compensation function on the surface, as necessary. Can do.

  When surface processing such as coating is applied to the surface of the optical film according to the present invention or when another film is laminated on the surface, the stretched film produced by the above method (the raw film is the optical film according to the present invention) In this case, it is preferable to subject the raw material film) to a surface treatment.

  The types of surface treatment are as described above. In the film according to the present invention, when the surface treatment is performed, the degree of the surface treatment is not particularly limited, but is preferably 50 dyn / cm or more, and is 50 dyn / cm to 80 dyn / cm or less. It is more preferable.

  With such a surface treatment, the surface treatment can be performed using a conventionally known surface treatment facility.

  The present invention is not limited to the configurations described above, and various modifications can be made within the scope of the claims, and the technical means disclosed in different embodiments are appropriately combined. The obtained embodiment is also included in the technical scope of the present invention.

  The present invention will be described more specifically based on examples and comparative examples, but the present invention is not limited to this. Those skilled in the art can make various changes, modifications, and alterations without departing from the scope of the present invention.

(Calculation of imidization rate)
¹ H-NMR ¹ H-NMR measurement of the resin was performed using BRUKER Avance III (400 MHz). From the area A of the peak derived from the O-CH ₃ proton of methyl methacrylate in the vicinity of 3.5 to 3.8 ppm and the area B of the peak derived from the N-CH ₃ proton of glutarimide in the vicinity of 3.0 to 3.3 ppm. Was obtained by the following equation.

  Im% = B / (A + B) × 100 Here, “imidation rate” refers to the ratio of imide carbonyl groups in all carbonyl groups.

〔Glass-transition temperature〕
Using an acrylic resin 10 mg, a differential scanning calorimeter (DSC, DSC-50 manufactured by Shimadzu Corporation) was used to measure under a nitrogen atmosphere at a heating rate of 20 ° C./min, and determined by the midpoint method. .

[Acid value]
Acrylic resin pellets (0.3 g) were dissolved in dichloromethane (37.5 ml), and methanol (37.5 ml) was added. To this solution, 2 drops of 1 wt% phenolphthalein ethanol solution was added, 5 ml of 0.1N sodium hydroxide aqueous solution was added, and the mixture was stirred for 1 hour. 0.1N hydrochloric acid was added dropwise to this solution, and the amount of 0.1N hydrochloric acid added (Aml) until the reddish purple color of the solution disappeared was measured. Next, 2 drops of 1 wt% phenolphthalein ethanol solution was added to a mixed solution of 37.5 ml of dichloromethane and 37.5 ml of methanol. To this, 5 ml of 0.1N sodium hydroxide aqueous solution was added and stirred for 1 hour. 0.1N hydrochloric acid was added dropwise to this solution, and the amount of 0.1N hydrochloric acid added (Bml) until the reddish purple color of the solution disappeared was measured. The ratio of the acid component (mono derived from a carboxyl group and an acid anhydride group) remaining in the resin was defined as the acid value Cmmol / g, and the following formula was used. C = 0.1 × ((5-A−B) /0.3) Further, the acid components remaining in the pellets sampled every 10 minutes during 1 hour after the reaction reached a steady state. The difference between the maximum value and the minimum value was defined as variation.

[Measurement of 1% heat loss temperature of triazine compounds]
Using 15 mg of the triazine compound, the temperature was increased from room temperature at 10 ° C./min in a nitrogen atmosphere with a thermogravimetric apparatus (TGA, TGA-50 manufactured by Shimadzu Corporation), and the thermal loss (wt%) was 1%. The temperature at which it becomes is measured.

[Measurement of heat loss]
At the time when 90 minutes passed after heating to 290 ° C. in an air atmosphere with a thermogravimetric apparatus (TGA, TGA-50 manufactured by Shimadzu Corporation) using 15 mg of a resin containing an acrylic resin and a triazine compound. The heat loss (weight%) of was measured.

(Light transmittance)
The light transmittance was evaluated by measuring the transmittance at 380 nm and 400 nm using an ultraviolet-visible spectrophotometer (JASCO, V-560).

[Film appearance evaluation]
A test piece of 210 mm length and 300 mm width was cut out from the obtained film, and the periphery of the film defect observed visually was irradiated with light from a desk stand (National SQ948H, fluorescent lamp 27W) in a dark room. I checked with a pen. Subsequently, the defects checked with a transmission optical microscope (digital microscope (VH-Z75), manufactured by Keyence Corporation) with a magnification of 50 times were observed. The above observations were made on both sides of the film, and the total number and type of defects were measured. In order to distinguish between defects derived from resin due to thermal degradation of resin, defects due to contamination of rolls by bleeding out of triazine compounds, and defects caused by general foreign matter, transmission type optics with a magnification of 50 times or more Judgment was made by the color of the defect when observed with a microscope. Defects resulting from thermal degradation are yellow and colorless and transparent. Resin-derived defects were counted. The number of defects derived from the contamination of the roll is indicated as “X” when the number of defects is very large, “◯” where several defects are observed, and “◎” where there are no defects.

[Production Example 1]
An imidized resin was produced using a methyl methacrylate polymer (Mw: 105,000) as a raw material resin and monomethylamine as an imidizing agent.

  The extruder used was a meshing type co-rotating twin screw extruder having a diameter of 15 mm. The set temperature of each temperature control zone of the extruder was 230 to 250 ° C., and the screw rotation speed was 150 rpm. The raw material resin was supplied at 2 kg / hr, and the resin was melted and filled with a kneading block, and then 2 parts by weight of monomethylamine (Mitsubishi Gas Chemical Co., Ltd.) was injected into the resin from the nozzle. A reverse flight was placed at the end of the reaction zone to fill the resin. By-products and excess methylamine after the reaction were removed by reducing the pressure at the vent port to -0.092 MPa. The resin that emerged as a strand from the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized resin (I).

  Next, in a meshing type co-rotating twin screw extruder with a diameter of 15 mm, the set temperature of each temperature control zone of the extruder was 230 ° C. and the screw rotation speed was 150 rpm. The imidized resin (I) obtained from the hopper was supplied at 1 kg / hr, and the resin was melted and filled with a kneading block, and then 0.8 parts by weight of dimethyl carbonate and 0.2 wt. A mixed solution of parts by weight of triethylamine was injected to reduce carboxyl groups in the resin. A reverse flight was placed at the end of the reaction zone to fill the resin. The by-product after reaction and excess dimethyl carbonate were removed by reducing the pressure at the vent port to -0.092 MPa. The resin that emerged as a strand from a die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized resin (II) with a reduced acid value.

  Further, the imidized resin (II) is applied to a meshing type co-rotating twin screw extruder having a diameter of 15 mm, the set temperature of each temperature control zone of the extruder is 230 ° C., the screw rotation speed is 150 rpm, and the supply amount is 1 kg / hr. It was put in condition. The vent port pressure was reduced to -0.095 MPa, and volatile components such as unreacted auxiliary materials were removed again. The devolatilized imide resin that emerged as a strand from the die provided at the outlet of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imidized resin (III).

  The imidized resin (III) includes a glutamylimide unit represented by the general formula (1) described in the above embodiment, a (meth) acrylic acid ester unit represented by the general formula (2), and It corresponds to a glutarimide resin copolymerized with an aromatic vinyl unit represented by the general formula (3).

  About imidized resin (III), the imidation ratio, the glass transition temperature, and the acid value were measured according to said method. As a result, the imidation ratio was 4 mol%, the glass transition temperature was 127 ° C., and the acid value was 0.28 mmol / g.

[Example 1]
100 parts by weight of the imidized resin (3) obtained in Production Example 1 and 0.12 part by weight of Tinuvin 477 (manufactured by Ciba Specialty Chemicals) having a 1% heat loss temperature of 350 ° C. as a triazine compound. The pellet was formed into a pellet using an axial extruder to obtain a pellet-shaped resin composition. The pellet was subjected to heat loss measurement.

  After drying this pellet-shaped resin composition at 100 ° C. for 5 hours, the sheet-shaped molten resin obtained by extruding at 270 ° C. using a 40 mmφ single screw extruder and a 400 mm wide T-die is cooled with a cooling roll. Upon cooling, a film having a width of 300 mm and a thickness of 130 μm was obtained. About this film, film external appearance evaluation was performed according to said method (Table 1).

  The film was subjected to simultaneous biaxial stretching (biaxial stretching device X4HD manufactured by Toyo Seiki Co., Ltd.) at a stretching ratio of 2 times (longitudinal and lateral) and a temperature 10 ° C. higher than the glass transition temperature to prepare a biaxially stretched film. About this biaxially stretched film, the light transmittance of wavelength 380nm was measured according to said method (Table 1).

[Example 2]
A film was prepared in the same manner as in Example 1 except that TINUVIN 460 (manufactured by Ciba Specialty Chemicals) was used at 0.10 parts by weight of the triazine compound. The results are shown in Table 1.

Example 3
A film was prepared in the same manner as in Example 1 except that the triazine compound was changed to 0.20 part by weight of TINUVIN400 (manufactured by Ciba Specialty Chemicals). The results are shown in Table 1.

Example 4
A film was prepared in the same manner as in Example 1 except that the triazine compound was 0.10 parts by weight of the compound represented by the general formula (11) (Compound No. 18 described in WO2005 / 109052). The results are shown in Table 1.

[Comparative Example 1]
A film was prepared in the same manner as in Example 1 except that the triazine compound was not added. The results are shown in Table 1.

[Comparative Example 2]
A film was prepared in the same manner as in Example 1 except that 1.20 parts by weight of TINUVIN477 was used as the triazine compound. The results are shown in Table 1.

[Comparative Example 3]
A film was prepared in the same manner as in Example 4 except that the amount of the triazine compound was changed to 1.00 parts by weight. The results are shown in Table 1.

[Comparative Example 4]
A film was prepared in the same manner as in Example 1 except that 0.10 parts by weight of AO330 (manufactured by ADEKA), which is a hindered phenol compound, was used instead of the triazine compound. The results are shown in Table 1.

Claims (9)

  A polarizer protective film comprising an acrylic thermoplastic resin having a glass transition temperature of 110 ° C. or higher and a triazine compound, wherein the triazine compound is 0.01 parts by weight or more per 100 parts by weight of the acrylic thermoplastic resin. And 0.2 parts by weight or less of a polarizer protective film.   The polarizer protective film according to claim 1, wherein a thickness of the polarizer protective film is 10 μm to 200 μm.   The polarizer protective film according to claim 1 or 2, wherein the triazine compound has a 1% heat loss temperature of 340 ° C or higher.   The polarizer protective film according to any one of claims 1 to 3, wherein the acrylic resin is a lactone resin, a glutaric anhydride resin, or a glutarimide resin. The polarizer protective film according to claim 4, wherein the glutarimide resin includes a unit represented by the following general formula (1) and a unit represented by the following general formula (2).

(Wherein R1 and R2 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R3 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.)

(Wherein R4 and R5 are each independently hydrogen or an alkyl group having 1 to 8 carbon atoms, and R6 is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or This is a substituent containing an aromatic ring having 5 to 15 carbon atoms.) The polarizer protective film according to claim 5, wherein the glutarimide resin further includes a unit represented by the following general formula (3).

(In the formula, R7 is hydrogen or an alkyl group having 1 to 8 carbon atoms, and R8 is an aryl group having 6 to 10 carbon atoms.)   The polarizer protective film according to claim 5 or 6, wherein the acrylic ester unit is less than 1% by weight.   The polarizer protective film according to claim 1, wherein the polarizer protective film is a stretched film.   A polarizing plate comprising at least one polarizer protective film according to claim 1.