JP5574787B2 - Resin composition and production method thereof, molded product, film, optical film, polarizer protective film, polarizing plate - Google Patents

Description

  The present invention relates to a film having excellent optical properties such as transparency and few appearance defects, a resin composition therefor, and a method for producing the same.

  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, for example, Patent Document 1 discloses a resin composition having a lactone ring structure. Patent Document 2 discloses a resin composition having a maleimide structure. However, even with these resin compositions, it has become difficult to meet the increasing market demand in recent years regarding optical properties and appearance defects. Patent Documents 3 and 4 disclose resins having a glutarimide structure that is different from the resin composition having the lactone ring structure and the resin composition having a maleimide structure.

JP 2006-96960 A JP 2007-31537 A WO2005 / 108438 WO2005 / 054311 Publication

  By the way, the resin composition obtained by patent document 1 and patent document 2 was difficult to respond to a market request | requirement about an optical characteristic and an external appearance defect from the property of the resin. Patent Document 3 discloses a film in which a commercially available polymethyl methacrylate is imidized and a phase difference close to 0 having a glutarimide structural unit and a methyl methacrylate structural unit. However, when a commercially available polymethyl methacrylate copolymerized with methyl acrylate is imidized, foreign matter may be observed during film formation. Therefore, there is room for improvement in order to use the obtained imide resin for optical applications. Patent Document 4 discloses a resin composition having a glutarimide structure containing styrene as an essential component. However, since it contains a large amount of styrene resin, there is room for improvement in terms of solvent resistance and cost. It was. The present invention has been made in view of the above problems, and an object thereof is to provide an optical molded article excellent in appearance and optical characteristics, particularly a film and a resin composition for producing such a film. And

  As a result of intensive studies in view of the above problems, the present inventors have found that according to a specific resin composition, it is possible to provide a molded body excellent in appearance suitable for a molded body and the like, in particular, a film. . That is, the present invention relates to the following.

  (I) A method for producing an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, wherein the polymethyl methacrylate resin has an acrylate unit content of less than 1% by weight. A method for producing an imide resin, comprising a step of heating and melting and treating with 100 to 10 parts by weight of a polymethyl methacrylate resin with 0.5 to 10 parts by weight of an imidizing agent.

(Wherein R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms; R3 represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or carbon; Represents an aryl group of formula 6-10.)
(Ii) The production method according to (i), wherein the imidizing agent is monomethylamine.

  (Iii) The method according to (i) or (ii), further comprising a step of treating with 0 to 12 parts by weight of an esterifying agent with respect to 100 parts by weight of the polymethyl methacrylate resin.

  (Iv) The production method according to (i) to (iii), wherein the esterifying agent contains dimethyl carbonate.

  (V) An imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, with an imidation ratio of 2.5 to 5.0% and an acid value of 0.1 to 0.1. A resin composition having a range of 0.6 mmol / g and an acrylic ester unit content of less than 1% by weight.

(Wherein R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms; R3 represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or carbon; Represents an aryl group of formula 6-10.)
(Vi) An optical film comprising the resin composition according to (v).

  (Vii) The optical film as described in (vi), which is a stretched film.

  (Viii) The optical film as described in (vi) or (vii), wherein an in-plane retardation at a wavelength of 589 nm per 40 μm thickness is 10 nm or less and a thickness direction retardation is 20 nm or less.

  (Ix) A polarizer protective film comprising the optical film according to any one of (vi) to (viii).

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

  INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide an optical molded body excellent in appearance and optical characteristics, particularly a film, which is extremely useful.

  An embodiment of the present invention will be described below, but the present invention is not limited to this.

  The production method of the present invention is a method for producing an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, wherein the polyacrylate is less than 1% by weight. It includes a step of heating and melting a methyl methacrylate resin and treating with 0.5 to 10 parts by weight of an imidizing agent with respect to 100 parts by weight of a polymethyl methacrylate resin.

 Here, R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, R3 represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or the number of carbon atoms 6-10 aryl groups are shown.

 R1 is preferably a methyl group, R2 is preferably hydrogen, and R3 is preferably a methyl group.

(Polymethyl methacrylate resin)
First, a polymethyl methacrylate resin is produced by polymerizing methyl methacrylate.

    In this step, in addition to methyl methacrylate, for example, methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, (meth) Benzyl acrylate, cyclohexyl (meth) acrylate and the like may be used in combination, but when these are used in combination, the acrylate unit is less than 1% by weight. The methyl acrylate unit is more preferably less than 0.5% by weight, and even more preferably less than 0.3% by weight.

  In addition to the above monomers, nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide can also be copolymerized. It is.

  The structure of the polymethyl methacrylate resin is not particularly limited, and may be any of linear (linear) polymer, block polymer, core-shell polymer, branched polymer, ladder polymer, and crosslinked polymer.

  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.

  The production method of the polymethyl methacrylate resin is not particularly limited, and a known emulsion polymerization method, emulsion-suspension polymerization method, suspension polymerization method, bulk polymerization method, solution polymerization method and the like can be applied. In the case of use in the bulk polymerization method, the bulk polymerization method and the solution polymerization method are particularly preferable from the viewpoint of few impurities. For example, it can be produced according to the method described in JP-A-56-8404, JP-B-6-86492, JP-B-7-37482, or JP-B-52-32665.

(Imidization process)
The manufacturing method of this invention includes the process (imidation process) which heat-melts the said polymethyl methacrylate resin, and processes it with an imidizing agent. Thereby, an imide resin can be produced.

  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, by adjusting the addition ratio of the imidizing agent, the ratio of glutarimide units and (meth) acrylic acid ester units in the resulting glutarimide resin can be adjusted.

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

  The imidizing agent is preferably 0.5 to 10 parts by weight, more preferably 0.5 to 6 parts by weight with respect to 100 parts by weight of the polymethyl methacrylate resin. When the addition amount of the imidizing agent exceeds the above range, the imidizing agent may remain in the resin and induce appearance defects and foaming after molding. Moreover, when the addition amount of the imidizing agent is less than the above range, the imidization rate of the finally obtained resin composition is lowered, so that the heat resistance is remarkably lowered, and an appearance defect after molding may be induced. .

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

  The method of melting by heating and treating with an imidizing agent is not particularly limited, and any conventionally known method can be used. For example, the polymethyl methacrylate resin can be imidized by a method using an extruder, a batch type reaction vessel (pressure vessel) or the like.

  When heat-melting using an extruder and processing with an imidizing agent, the extruder to be used is not particularly limited, and 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, it is possible to promote mixing of an imidizing agent (in the case where a ring closing accelerator is used) with respect to the polymethyl methacrylate resin.

  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, polymethyl methacrylate resin is charged from the raw material charging part of the extruder, the resin is melted, the inside of the cylinder is filled, and then imidized using an addition pump. By injecting the agent into the extruder, the imidization reaction can proceed in the extruder.

  In this case, the reaction zone temperature (resin temperature) in the extruder is preferably 180 ° C. to 270 ° C., more preferably 200 to 250 ° 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 270 ° C., the resin is significantly decomposed, so that the bending resistance of the film that can be formed from the obtained imidized 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.

  Moreover, when using an extruder, in order to remove an unreacted imidizing agent and a by-product, it is preferable to attach the vent hole which can be pressure-reduced below atmospheric pressure. According to such a configuration, unreacted imidizing agent, or by-products such as methanol and monomers can be removed.

  In addition, in the production of the imide resin, instead of an extruder, for example, a high viscosity such as a horizontal biaxial reactor such as Violac manufactured by Sumitomo Heavy Industries, Ltd. or a vertical biaxial agitation tank such as Super Blend. A corresponding reaction apparatus can also be suitably used.

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

  Specifically, the polymethyl methacrylate resin 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. (Esterification process)
In the manufacturing method of this invention, in addition to the said imidation process, the process processed with an esterifying agent can be included. By this esterification step, the acid value of the imidized resin obtained in the imidization step can be adjusted within a desired range.

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

    In this imidization step, the esterifying agent is preferably 0 to 12 parts by weight, and more preferably 0 to 8 parts by weight with respect to 100 parts by weight of the polymethyl methacrylate resin.

    If the esterifying agent is within the above range, the acid value can be adjusted to an appropriate range. On the other hand, if it is out of the above range, an unreacted esterifying agent may remain in the resin, which may cause foaming or odor generation when molding is performed using the resin.

    In addition to the esterifying agent, a catalyst may be used in combination. The type of the catalyst is not particularly limited, and examples thereof include aliphatic tertiary amines such as trimethylamine, triethylamine, and tributylamine. Among these, triethylamine is preferable from the viewpoint of cost and reactivity.

  In this esterification step, only heat treatment or the like can be performed without treatment with an esterifying agent. When only heat treatment (mixing / dispersion of molten resin in the extruder) is performed, dehydration reaction between carboxylic acids in the imide resin by-produced in the imidization step and / or dealcoholization of carboxylic acid and alkyl ester group A part or all of the carboxylic acid can be converted to an acid anhydride group by reaction or the like. At this time, it is also possible to use a ring closure accelerator (catalyst).

Even in the case of treatment with an esterifying agent, acid anhydride grouping by heat treatment can proceed.
(Devolatilization process, filtration process)
The imide resin that has undergone the imidization step and the esterification step contains an unreacted imidizing agent, an unreacted esterifying agent, a volatile component by-produced by the reaction, and a resin decomposition product. It is possible to attach a vent port that can be depressurized below.

  Moreover, when an imide resin is used for optical applications, it is also possible to install a filter at the end of the extruder for the purpose of reducing foreign substances in the resin. It is preferable to install a gear pump in front of the filter in order to pressurize the imide resin. As the type of filter, it is preferable to use a stainless steel leaf disc filter capable of removing foreign substances from the molten polymer, and it is preferable to use a fiber type, a powder type, or a composite type thereof as the filter element.

  (Imide resin) The imide resin of the present invention is an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, and has an imidization ratio of 2.5 to 5.0%. The acid value is in the range of 0.1 to 0.6 mmol / g, and the acrylate unit is less than 1% by weight.

(Wherein R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms; R3 represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or carbon; Represents an aryl group of formula 6-10.)
(Imidation rate)
It is essential that the imidization rate according to the present invention is in the range of 2.5 to 5.0%. The imidation rate indicates the ratio of glutarimide groups in the resin, and the larger the value, the more glutarimide groups in the molecule. Since the glutarimide group itself has a function of giving positive intrinsic birefringence, the birefringence of the resin composition and the molded product obtained by molding the composition can be set by setting the range. It can suppress, and the use use as an optical member of the resin molded product (for example, resin film) formed from the resin composition of this invention expands.

The imidation ratio (I%) according to the present invention is a value that can be measured by, for example, the following method. ¹ H-NMR The ¹ H-NMR measurement of the resin is 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. The following formula is used.

I% = B / (A + B) × 100
The imidation ratio is preferably 2.5 to 5.0%, more preferably 2.5% to 4.5%, and particularly preferably 3.0% to 4.5%. preferable.

  If the imidation ratio is within the above range, the heat resistance and transparency of the resulting imide resin will not decrease, and the moldability and mechanical strength when processed into a film will not decrease.

  On the other hand, when the imidation ratio is less than the above range, the resulting imide resin tends to have insufficient heat resistance or the transparency may be impaired. 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.

  (Acid Value) The acid value of the imide resin of the present invention represents the content of carboxylic acid units and acid anhydride units in the imide resin. The acid value can be calculated by, for example, a titration method described in WO2005-054311. The acid value of the resin composition according to the present invention is 0.10 to 0.60 mmol / g, and more preferably 0.15 to 0.50 mmol / g. If the acid value is within the above range, an imide resin having an excellent balance of heat resistance, mechanical properties and molding processability can be obtained. When the acid value is larger than the above range, when the obtained resin composition is molded, many appearance defects of foaming and gel-like materials may occur, which is not preferable. Foaming is considered to be the influence of water generated in the anhydride formation of carboxylic acids adjacent in the molecule. Moreover, it seems that a gel-like substance is formed by the pseudo bridge | crosslinking by the hydrogen bond between the carboxylic acids between molecules. When the acid value is smaller than the above range, it is necessary to spend more modifying agent to adjust to the acid value, which may increase the cost or induce the generation of a gel-like material due to the remaining of the modifying agent. This is not preferable.

  As described above, in particular, the presence of carboxylic acid among the acid components is not preferable because foaming occurs in the molded body or a gel-like material is formed. The carboxylic acid content is preferably 0.25 mmol / g or less, and more preferably 0.20 mmol / g or less. Even if the carboxylic acid content is 0.25 mmol / g or less, the acid value (carboxylic acid + acid anhydride) exceeds 0.60 mmol / g, that is, the amount of acid anhydride increases, so that the melt viscosity of the resin is increased. Since it becomes high and molding processability becomes disadvantageous, it is not preferable.

The measurement method of the amount of carboxylic acid can be calculated by using an acid value (DMSO acid value) obtained by changing the solvent of the titration method described in WO2005-054311 from methanol to dimethyl sulfoxide. Specifically, (carboxylic acid amount) = 2 × (acid value) − (DMSO acid value)
It is. While titration with methanol counts one molecule of acid anhydride, titration with dimethyl sulfoxide counts acid anhydride as two molecules, so the above formula can be applied.

(Acrylic acid ester unit)
The acrylic ester unit contained in the glutarimide resin of the present invention is less than 1% by weight. More preferably, it is less than 0.5% by weight, and particularly preferably less than 0.3% by weight. The lower limit is not particularly limited, and is preferably as small as possible, and more preferably not contained.

    If the acrylic ester unit is within the above range, the imide resin has excellent thermal stability. Tends to deteriorate and the physical properties tend to deteriorate.

The method for quantifying the acrylate unit in the resin composition containing the glutarimide unit and the methyl methacrylate unit of the present invention is not particularly limited, but the weight ratio of the acrylate unit in the polymethyl methacrylate as a raw material is It may be calculated from the imidization rate. That is, assuming that the imidization rate is I% and the amount of the acrylate unit in the raw material is m%, from the following formulas (1) to (3), the mol% (Amol) of the unit represented by the general formula (1) %), Methacrylic acid alkyl ester monomer units (B mol%), and mol% (C mol%) of acrylic ester units. When the molecular weight of the unit represented by the general formula (1) is ag / mol, the molecular weight of the methacrylic acid alkyl ester monomer unit is b g / mol, and the molecular weight of the acrylate ester unit is c g / mol, the following formula Calculate from (4).
A = I (1)
B = (100−I) × (100−m) / 100 (2)
C = 100−A−B (3)
(Acrylic ester content of product) = (100 × C × c) / (A × a + B × b + C × c) (4)
Needless to say, when the acrylate is 0% in the raw material, the acrylate content of the product is also 0.

  The content of acrylate units in polymethyl methacrylate can be quantified by gas chromatography or the like, but the quantification method is not particularly limited.

  Moreover, when manufacturing the imide resin containing the glutarimide unit and the methyl methacrylate unit of the present invention, for example, as disclosed in JP-A-2008-255175, the polymerized raw material resin is heated and cyclized by adjusting the monomer species and the monomer ratio. In this case, the weight ratio of methyl methacrylate and methyl acrylate at the time of charging the monomer may be substituted. Needless to say, when methyl acrylate is not used, the amount of methyl acrylate in the imide resin is 0%.

  If necessary, the imide resin may further be copolymerized with other units other than glutarimide units, methyl methacrylate units, carboxylic acid or carboxylic anhydride units, and acrylate units.

  As other units, structural units obtained by copolymerizing nitrile monomers such as 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 imide resin.

  The resin composition obtained in the present invention is required not to contain an aromatic vinyl monomer such as styrene from the viewpoint of solvent resistance.

The weight average molecular weight of the imide 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, when the weight average molecular weight is smaller than the above range, the mechanical strength when formed into a 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 glass transition temperature of the imide resin is not particularly limited, but is preferably 110 ° C. or higher, more preferably 115 ° C. or higher, and particularly preferably 120 ° C. or higher. Below this range, the heat resistance when formed into a molded body or film is inferior, so that the change in physical properties at high temperatures becomes large, and the application range becomes narrow. For example, when used in optical applications, if the glass transition temperature is lower than the above range, the molded product or film is likely to be distorted in a high temperature environment, and stable optical characteristics tend not to be obtained. It is not preferable.

  For the imide resin, weather resistance stabilizers such as generally used antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, radical scavengers, catalysts, plasticizers, lubricants, antistatic agents, as necessary. A coloring agent, a shrinkage inhibitor, an antibacterial / deodorizing agent, etc. may be used alone or in combination of two or more, so long as the object of the present invention is not impaired. These additives can also be added when molding an imide resin described later. Examples of the ultraviolet absorber include triazine compounds, benzotriazole compounds, benzophenone compounds, cyanoacrylate compounds, benzoxazine compounds, and oxadiazole compounds. Among these, a triazine compound is preferable from the viewpoint of ultraviolet absorption performance with respect to the added amount.

(the film)
One preferred embodiment of the resin composition of the present invention is a film-like molded body. Therefore, hereinafter, the film according to the present invention will be described as an embodiment of the present invention, but the present invention is not limited thereto.

  Although the film concerning this invention should just be formed by shape | molding the resin composition concerning this invention mentioned above, it is preferable that it is the stretched film, ie, a stretched film.

  According to the stretched film, the mechanical properties can be improved. Conventionally, in a stretched film, it has been difficult to avoid the occurrence of retardation. However, according to the resin composition of the present invention, even if a stretching treatment is performed, the retardation is not substantially generated and mechanically generated. A stretched film with improved properties can be produced.

  In addition, when the film which concerns on 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 film according to the present invention is a stretched film, the thickness thereof is not particularly limited, but is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and 30 μm to 100 μm. Is more preferable.

  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 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 film according to the present invention can be suitably used for applications requiring transparency.

  The 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 film according to the present invention can be suitably used for applications requiring transparency.

  The film according to the present invention preferably has a small optical anisotropy. 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 film concerning this invention can be used as a polarizer protective film with which the polarizing plate of a liquid crystal display device is equipped.

  On the other hand, 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 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.

  The in-plane retardation (Re) and the thickness direction retardation (Rth) can be calculated by the following equations, respectively. That is, in an ideal film that is completely optically isotropic in the three-dimensional direction, both the in-plane retardation Re and the thickness direction retardation Rth are zero.

  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, and represents the refractive index in each axial direction. D represents the thickness of the film, and || represents an absolute value.

In addition, the film according to the present invention preferably has an orientation birefringence value of 0 to 0.1 × 10 ⁻³ , and more preferably 0 to 0.01 × 10 ⁻³ .

  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.

  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 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, and 5 × More preferably, it is 10 ⁻¹² m ² / N or less.

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

On the other hand, if the absolute value of the photoelastic coefficient is larger than 20 × 10 ⁻¹² m ² / N, when the film according to the present invention is used for a liquid crystal display device, phase difference unevenness occurs or the contrast of the peripheral portion of the display screen is increased. Tends to decrease or light leakage tends 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 film according to the present invention may be subjected to a surface treatment as necessary. Specifically, for example, when the surface of the film according to the present invention is subjected to surface processing such as coating processing or another film is laminated on the surface, the film according to the present invention is subjected to surface treatment. It is preferable.

  By performing such a surface treatment, mutual adhesion between the 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 film which concerns on this invention is not limited to what aims at an effect. That is, the 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 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 film according to the present invention is not particularly limited, specifically, for example, imaging fields such as cameras, VTRs, projectors, viewfinders, filters, prisms, Fresnel lenses, CD players, Lens field such as optical disk pickup lens such as DVD player and MD player, optical recording field for optical disk such as CD player, DVD player and MD player, liquid crystal display such as light guide plate for liquid crystal, polarizer protective film and retardation film Film, surface protection film and other information equipment fields, optical fibers, optical switches, optical connectors and other optical communication fields, automotive headlights, tail lamp lenses, inner lenses, instrument covers, sunroofs and other vehicle fields, glasses and contact lenses, Insight Lenses, medical equipment such as medical supplies that require sterilization, road translucent plates, pair glass lenses, lighting windows and carports, lighting lenses and covers, and building materials sizing for building materials, electronics It can be suitably used for a range cooking container (tableware) or the like.

  As described above, the film according to the present invention is excellent in optical properties 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.

  In addition, the film of the present invention can be attached to a polarizer and used as a polarizing plate. That is, the 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.

  Here, although one Embodiment of the method to manufacture the film which concerns on this invention is described, this invention is not limited to this. That is, any conventionally known method can be used as long as it is a method capable of producing a film by molding the thermoplastic resin composition (imide resin) according to the present invention.

  Specific examples include injection molding, melt extrusion film molding, inflation molding, blow molding, compression molding, and spinning molding.

  In addition, the film according to the present invention can be produced by a solution casting method or a spin coating method in which the thermoplastic resin composition according to the present invention is dissolved in a soluble solvent and then molded.

  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.

  In addition, because the thermoplastic resin composition according to the present invention is used, even under molding conditions at high temperatures such as using T-die film formation, without causing contamination of the molding machine or film defects due to scattering of the UV absorber, A film can be produced.

  Hereinafter, as an embodiment of the method for producing a film according to the present invention, a method for producing a film by molding the thermoplastic resin composition 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 thermoplastic resin composition according to the present invention is formed into a film by a melt extrusion method, first, the thermoplastic resin composition according to the present invention is supplied to an extruder, and the thermoplastic resin composition is heated and melted.

  The thermoplastic 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 thermoplastic resin composition according to the present invention) can be formed into pellets and the like and can be performed using a hot air dryer or the like.

  Next, the thermoplastic 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 thermoplastic 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 a film having a thickness of 40 μm is manufactured, 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 film according to the present invention is a stretched film, the thermoplastic 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 thermoplastic 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 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 the raw material film, the state of the raw material film is very short (in some cases, instantaneous in some cases). In this case, it is only necessary to maintain a film shape sufficient to be stretched, and it is not necessary to be in a complete film state, and the raw material film has performance as a film as a finished product. It does not have to be.

  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 thermoplastic 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 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, a birefringence of substantially zero, and a haze of 1% or less can be produced.

  Further, in the resin composition according to the present invention, by selecting appropriate stretching conditions, a film with small thickness unevenness substantially without causing birefringence and without substantially increasing haze. Can be easily manufactured.

  The film according to the present invention can be used by laminating another film with an adhesive or the like, or by forming a coating layer such as a hard coat layer on the surface, if necessary.

  When the surface of the film according to the present invention is subjected to surface processing such as coating, or when another film is laminated on the surface, the stretched film produced by the above method (when the raw film is used as the film according to the present invention) Is preferably subjected to a surface treatment.

  The types of surface treatment are as described above. Further, 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 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 using a H-NMR BRUKER AvanceIII (400MHz) , result of ¹ H-NMR measurement of the resin. From the peak area A derived from the O—CH ₃ proton of methyl methacrylate in the vicinity of 3.5 to 3.8 ppm and the peak area B 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.

I% = B / (A + B) × 100
(In-plane retardation Re and thickness direction retardation Rth measurement)
A 40 mm × 40 mm test piece was cut out from the film. Using an automatic birefringence meter (KOBRA-WR manufactured by Oji Scientific Co., Ltd.), the in-plane retardation Re was measured at a temperature of 23 ± 2 ° C. and a humidity of 50 ± 5% at a wavelength of 590 nm and an incident angle of 0 °. It was measured.

  The thickness d of the test piece measured using a digimatic indicator (manufactured by Mitutoyo Corporation), the refractive index n measured by an Abbe refractometer (manufactured by Atago Co., Ltd. 3T), the wavelength 590 nm measured by an automatic birefringence meter, and the surface The three-dimensional refractive index nx, ny, nz is obtained from the internal phase difference Re and the phase difference value in the 40 ° tilt direction, and the thickness direction phase difference Rth = | (nx + ny) / 2−nz | × d (|| is the absolute value) Represents).

(Acid value measurement)
0.3 g of the resin was dissolved in 37.5 mL of methylene chloride, and 37.5 mL of methanol was further added. Next, 5 mL of 0.1 mmol% sodium hydroxide aqueous solution and several drops of ethanol solution of phenolphthalein were added. Next, back titration was performed using 0.1 mmol% hydrochloric acid, and the acid value was determined from the amount of hydrochloric acid required for neutralization.

(Measurement of carboxylic acid content)
0.3 g of the resin was dissolved in 37.5 mL of methylene chloride, and 37.5 mL of dimethyl sulfoxide was further added. Next, 5 mL of a 0.1 mmol% aqueous sodium hydroxide solution and several drops of a phenolphthalein dimethyl sulfoxide solution were added. Next, back titration was performed using 0.1 mmol% hydrochloric acid, and the DMSO acid value was determined from the amount of hydrochloric acid required for neutralization.

  Using the values of (acid value) and (DMSO acid value) measured by titration with methanol, the following formula was used.

(Amount of carboxylic acid) = 2 × (acid value) − (DMSO acid value)
(Foreign substance evaluation)
From the obtained stretched film, 1 m ² was cut out, and the number of foreign matters of 20 μm or more was counted by observation with a microscope or the like, and totaled to obtain the number of foreign matters.

(Quantification of acrylate units)
By using a pyrolysis gas chromatograph-mass spectrometer manufactured by Shimadzu Corporation as the raw material resin, the ratio of the area value of methyl methacrylate to the area value of the acrylate ester unit was maintained under the condition that the sample pyrolysis temperature was maintained at 590 ° C. for 5 seconds. The acrylate units were quantified.

  (Solvent resistance) A film having a thickness of 30 μm to 35 μm is cut out in a width direction of 20 mm × longitudinal direction of 50 mm, immersed in ethyl acetate in a state of a load of 15 g in the longitudinal direction of 30 mm, and the solvent resistance is determined according to the time until breaking. It was.

Example 1
A resin was produced using a tandem reaction extruder in which two extrusion reactors were arranged in series. As for the tandem type reactive extruder, the first extruder (1) and the second extruder (2) are both in the same direction meshing type with a diameter of 75 mm and L / D (ratio of the length L to the diameter D of the extruder) of 74. Using a twin-screw extruder, the raw material resin was supplied to the raw material supply port of the first extruder using a constant weight feeder (manufactured by Kubota Corporation). Moreover, the pressure reduction degree of each vent in the 1st extruder and the 2nd extruder was set to -0.095 MPa. Furthermore, the pressure control mechanism in the part connects the first extruder and the second extruder with a pipe having a diameter of 38 mm and a length of 2 m, and connects the resin discharge port of the first extruder and the raw material supply port of the second extruder. A constant flow pressure valve was used. The resin (strand) discharged from the second extruder was cooled by a cooling conveyor and then cut by a pelletizer to form pellets. Here, the outlet of the first extruder, the first extruder and the second extruder are used to adjust the pressure in the part connecting the resin discharge port of the first extruder and the raw material supply port of the second extruder, or to determine the fluctuation of the extrusion. A resin pressure gauge was provided at the center of the machine connecting part and at the outlet of the second extruder.

  Regarding the first extruder, a polymethyl methacrylate resin (Mw: 105,000) was used as a raw material resin, and monomethylamine was used as an imidizing agent to produce an imide resin intermediate 1. At this time, the maximum temperature of the extruder was 280 ° C., the screw rotation speed was 55 rpm, the raw material resin supply amount was 150 kg / hour, and the addition amount of monomethylamine was 2.0 parts with respect to 100 parts of the raw material resin. Moreover, the constant flow pressure valve was installed just before the 2nd extruder raw material supply port, and the 1st extruder monomethylamine press-fit part pressure was adjusted so that it might be set to 8 Mpa.

  Regarding the second extruder, after devolatilizing the imidization reaction reagent and by-products remaining in the rear vent and vacuum vent, a mixed solution of dimethyl carbonate and triethylamine is added as an esterifying agent to produce an imide resin intermediate 2 did. At this time, each barrel temperature of the extruder was 260 ° C., the screw rotation speed was 55 rpm, the addition amount of dimethyl carbonate was 3.2 parts with respect to 100 parts of the raw material resin, and the addition amount of triethylamine was 0.2 parts with respect to 100 parts of the raw material resin. 8 parts. Furthermore, after removing the esterifying agent with a vent, the resin composition was obtained by extruding from a strand die, cooling in a water tank, and pelletizing with a pelletizer.

  The imidation ratio of this resin composition was 3.7%, the acid value was 0.29 mmol / g, and the amount of carboxylic acid was 0.05 mmol / g.

  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.

  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.

This biaxially stretched film had an in-plane retardation of 0.1 nm, a thickness direction retardation of 3.4 nm, and a thickness of 34 μm. The number of foreign matters was 20 / m ² . When the obtained biaxially stretched film was immersed in ethyl acetate under a load of 15 g, the time until breaking was 440 seconds.

  A polyvinyl alcohol film was impregnated with iodine and stretched to prepare a polarizer. A cellulose acetate film (80 μm thick) having a degree of substitution with an acetyl group of 2.5 was bonded to one side of the polarizer using a polyacrylic adhesive. Furthermore, the stretched film produced on the opposite surface of the polarizer was bonded using a polyacrylic adhesive to produce a polarizing plate having an optical compensation layer.

  Prepare a liquid crystal display device equipped with an IPS liquid crystal cell, and remove the polarizing plate on the outgoing light side, and attach the above polarizing plate to the liquid crystal cell instead so that the stretched film is on the outgoing light side of the liquid crystal cell. A display device was manufactured. As a result of observing the display screen, a good image was obtained without changing the color display when viewed from the front or from an oblique direction.

(Example 2)
A resin composition was prepared in the same manner as in Example 1 except that the addition amount of dimethyl carbonate was 4.8 parts with respect to 100 parts of the raw material resin and the addition amount of triethylamine was 1.2 parts with respect to 100 parts of the raw material resin. A biaxially stretched film was produced.

  The imidation ratio of the obtained resin composition was 3.7%, the acid value was 0.19 mmol / g, and the amount of carboxylic acid was 0.04 mmol / g.

The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 3.4 nm. The number of foreign matters was 18 / m ² .

  Further, as a result of observing the display screen of the display device, a good image was obtained without changing the color display when viewed from the front or from an oblique direction.

(Example 3)
A resin composition was prepared in the same manner as in Example 1 except that the addition amount of dimethyl carbonate was 1.6 parts with respect to 100 parts of the raw material resin, and the addition amount of triethylamine was 0.4 parts with respect to 100 parts of the raw material resin. A biaxially stretched film was produced.

  The imidation ratio of the obtained resin composition was 3.7%, the acid value was 0.41 mmol / g, and the amount of carboxylic acid was 0.06 mmol / g.

The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 3.4 nm. The number of foreign matters was 34 / m ² .

  Further, as a result of observing the display screen of the display device, a good image was obtained without changing the color display when viewed from the front or from an oblique direction.

(Example 4)
A resin composition was prepared in the same manner as in Example 1 except that the amount of dimethyl carbonate added was 3.2 parts with respect to 100 parts of the raw resin, and a biaxially stretched film was prepared. The imidation ratio of the obtained resin composition was 3.7%, the acid value was 0.42 mmol / g, and the amount of carboxylic acid was 0.10 mmol / g. The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 3.4 nm. The number of foreign matters was 32 / m ² . Further, as a result of observing the display screen of the display device, a good image was obtained without changing the color display when viewed from the front or from an oblique direction.

(Example 5)
A resin composition was prepared in the same manner as in Example 1 except that the amount of monomethylamine added was 1.8 parts with respect to 100 parts of the raw resin, and a biaxially stretched film was prepared.

  The imidation ratio of the obtained resin composition was 3.4%, the acid value was 0.30 mmol / g, and the amount of carboxylic acid was 0.05 mmol / g.

The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 0.5 nm. The number of foreign matters was 18 / m ² .

  Further, as a result of observing the display screen of the display device, a good image was obtained without changing the color display when viewed from the front or from an oblique direction.

(Comparative Example 1)
A resin composition was prepared in the same manner as in Example 1 except that a methacrylic resin manufactured by Kuraray Co., Ltd. and HR-S (methyl acrylate unit: 1.1% by weight, Mw: 109000) were used as a raw material resin. A biaxially stretched film was produced.

  The imidation ratio of the obtained resin composition was 3.4%, the acid value was 0.29 mmol / g, and the amount of carboxylic acid was 0.05 mmol / g. Moreover, the acrylic ester unit was 1.2% as described above.

The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 3.4 nm. The number of foreign matters was 1900 / m ² .

  Further, as a result of observing the display screen of the display device, a large number of foreign matter-derived points were confirmed on the screen.

(Comparative Example 2)
A resin composition was prepared in the same manner as in Example 1 except that no monomethylamine was added, and a biaxially stretched film was prepared.

  The imidation ratio of the obtained resin composition was 0%, the acid value was 0.32 mmol / g, and the amount of carboxylic acid was 0.08 mmol / g.

The obtained biaxially stretched film had an in-plane retardation of -1.2 nm and a thickness direction retardation of -9.8 nm. The number of foreign matters was 5200 / m ² .

  Moreover, as a result of observing the display screen of the display device, in addition to the fact that many points derived from foreign matters were confirmed on the screen, when viewed from an oblique direction, the color when viewed from the front due to the birefringence of the liquid crystal display device constituent members The display was different.

(Comparative Example 3)
A resin composition was prepared in the same manner as in Example 1 except that the addition amount of dimethyl carbonate was 8 parts with respect to 100 parts of the raw material resin, and the addition amount of triethylamine was 4 parts with respect to 100 parts of the raw material resin. A film was prepared.

  The imidation ratio of the obtained resin composition was 3.6%, the acid value was 0.08 mmol / g, and the amount of carboxylic acid was 0.01 mmol / g.

The obtained biaxially stretched film had an in-plane retardation of 0.1 nm and a thickness direction retardation of 3.5 nm. The number of foreign matters was 952 / m ² .

  Further, as a result of observing the display screen of the display device, a large number of foreign matter-derived points were confirmed on the screen.

(Comparative Example 4)
The same operation as in Example 1 was performed except that a methyl methacrylate-styrene copolymer having a styrene amount of 11% by weight as a raw material resin and an injection amount of monomethylamine was set to 16 parts by weight. The biaxially stretched film was obtained.

  The obtained biaxially stretched film had an in-plane retardation of 0.7 nm, a thickness retardation of 18 nm, and a thickness of 35 μm. When the obtained biaxially stretched film was immersed in ethyl acetate in the same manner as in Example 1, the time until breaking was 120 seconds.

Claims (6)

It is an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit, the imidation ratio is 2.5 to 5.0%, and the acid value is 0.1 to 0.6 mmol. / g in the range of state, and are less than 1% by weight acrylic acid ester units, and, imide resin acid content, characterized in der Rukoto below 0.25 mmol / g.

(Wherein R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms; R3 represents hydrogen, an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or carbon; Represents an aryl group of formula 6-10.) An optical film comprising the imide resin according to claim 1 . The optical film according to claim 2 , wherein the optical film is a stretched film. Plane retardation at a wavelength of 589nm per thickness 40μm is not more 10nm or less, the optical film according to claim 2 or 3 the thickness direction retardation is equal to or is 20nm or less. A polarizer protective film comprising the optical film according to any one of claims 2 to 4 . A polarizing plate comprising at least one polarizer protective film according to claim 5 .