JP2011081124A - Optical compensation film and polarizing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical compensation film excellent in appearance and optical properties. <P>SOLUTION: The optical compensation film has a base film, an alignment film and an optically anisotropic layer formed of a liquid crystal composition in this order. A support is formed of an acrylic resin containing at least one of a lactone ring unit, a glutaric acid anhydride unit, a glutarimide unit and an N-substituted maleimide unit, and a methylmethacrylate unit. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a resin composition suitably used as a liquid crystal display device, particularly as a TN mode optical compensation film.

  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. However, in the TN mode, which is currently the mainstream of liquid crystal display devices, there has been a problem of so-called viewing angle characteristics such as a change in display color and contrast depending on the viewing direction in principle. In order to improve the viewing angle characteristics and realize a liquid crystal display device with high display quality, in Patent Document 1 and Patent Document 2, an optical compensation in which an optical anisotropic layer made of a discotic liquid crystal is coated on a transparent support is disclosed. It is described that the viewing angle characteristics can be suitably improved by using a polarizing plate in which the film is a protective film on one side of a polarizing film.

Japanese Patent Laid-Open No. 7-191217 JP 2009-69821 A

  However, even with the method of Patent Document 1 or 2, it has become difficult to meet the increasing market demand in recent years for optical characteristics and appearance defects.

  This invention is made | formed in view of said subject, Comprising: It aims at providing the optical compensation film excellent in the external appearance and the optical characteristic.

  As a result of intensive studies in view of the above problems, the present inventors have found that if a specific resin composition is used for the base film, it is possible to provide an optical compensation film having excellent appearance and optical characteristics, and the present invention has been achieved. It was. That is, the present invention relates to the following.

  (I) An optical compensation film having an optically anisotropic layer formed of a base film, an alignment film and a liquid crystal composition in this order, wherein the support is a lactone ring unit, a glutaric anhydride unit, a glutarimide unit An optical compensation film comprising an acrylic resin containing at least one N-substituted maleimide unit and a methyl methacrylate unit.

  (II) The optical compensation film according to (I), wherein the base film is an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit.

(In the formula, R 1 and R 2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or 6 carbon atoms. Represents 10 to 10 aryl groups.)
(III) The optical compensation film according to any one of (I) to (II), wherein the imidation ratio of the base film is 30 to 90%.

  (IV) The optical film according to claim 1, wherein the in-plane retardation (Re) of the base film is −20 to 20 nm and the thickness direction retardation (Rth) is 50 to 150 nm.

  (V) A polarizing plate comprising at least one optical compensation film according to (IV).

  According to the present invention, it is possible to provide an optical compensation film excellent in appearance and optical characteristics, which is extremely useful.

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

  An optical compensation film according to the present invention is an optical compensation film having an optically anisotropic layer formed of a base film, an alignment film and a liquid crystal composition in this order, wherein the support comprises a lactone ring unit, anhydrous glutar It consists of an acrylic resin containing at least one of an acid unit, a glutarimide unit, and an N-substituted maleimide unit and a methyl methacrylate unit.

(Manufacture of base film)
The base film according to the present invention is essentially an acrylic resin containing at least one of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, an N-substituted maleimide unit, and a methyl methacrylate unit. The resin having a ring structure is particularly preferable as an optical material because it has high heat resistance and low moisture permeability, and is particularly suitable as a base film of the present invention. Among them, it is an acrylic resin containing a glutarimide unit and a methyl methacrylate unit represented by the following general formula (1) because it has excellent heat resistance in terms of suitably controlling optical characteristics. Is preferred.

  In the formula, R1 and R2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, R3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or 6 to 6 carbon atoms. 10 aryl groups are shown. R1 is preferably a methyl group, R2 is preferably hydrogen, and R3 is preferably a methyl group.

  Hereinafter, it describes about the manufacturing method of the base film which consists of acrylic resin containing a glutarimide unit and a methyl methacrylate unit.

  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. More preferably, the methyl acrylate units are less than 0.5% by weight.

  In addition to the above monomers, copolymerize styrene, nitrile monomers such as acrylonitrile and methacrylonitrile, and maleimide monomers such as maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. Is also possible.

  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 methods described in JP-A-56-8404, JP-B-6-86492, JP-B-7-37482, JP-B-52-32665, JP-B-55-7845, and the like.

  Next, the polymethyl methacrylate resin is heated and melted and processed with an imidizing agent (imidation process) to produce an imide resin.

  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.

  Moreover, the optical characteristics etc. of the optical film formed by shape | molding the acrylic resin obtained by adjusting the degree of imidation can be adjusted.

  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 imidization is performed 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 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 the film that can be formed from the imidized resin obtained 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.

  In addition to the imidization step, a step of treating 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 esterifying agents 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 is preferable from the viewpoints of cost, reactivity, and the like.

  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.

  When employing an acrylic resin containing glutarimide, the imidation rate is preferably 30 to 90%, more preferably 40 to 80%. When the imidization rate is less than 30%, the retardation development property tends to be insufficient, and when the imidization rate exceeds 90%, the melt viscosity at the time of film formation becomes high and the workability tends to deteriorate. There is. The imidation rate in the imide resin described above can be appropriately set according to the required physical properties of the optical film.

  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 (Im%) 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.

  Im% = B / (A + B) × 100

(Acid value)
The acid value of the acrylic resin containing glutarimide represents the content of carboxylic acid units and carboxylic anhydride units in the imide resin. The acid value can be calculated by, for example, a titration method described in WO2005-054311.

  A preferable acid value when an acrylic resin containing glutarimide is employed is 0.001 to 0.30 mmol / g, and more preferably 0.005 to 0.20 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 an influence of water generated when the carboxyl groups adjacent in the molecule are anhydrated. 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. The acid value of the imide resin of the present invention represents the content of carboxylic acid units and carboxylic anhydride units in the imide resin. The acid value can be calculated by, for example, a titration method described in WO2005-054311.

  When an acrylic resin containing glutarimide is employed, a preferable ratio of the acrylate unit is less than 1% by weight. More preferably, it is less than 0.5% by weight.

  If the acrylate unit is within the above range, the imide resin will have excellent thermal stability, but if it exceeds the above range, the thermal stability will deteriorate, and the resin molecular weight and viscosity during resin production or molding will be reduced. There exists a tendency for a fall to fall and for a physical property to deteriorate.

  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.

  Examples of other units include aromatic vinyl monomers such as styrene, nitrile monomers such as acrylonitrile and methacrylonitrile, maleimide, N-methylmaleimide, N-phenylmaleimide, and N-cyclohexylmaleimide. A structural unit obtained by copolymerizing a maleimide monomer can be exemplified.

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

The weight average molecular weight of the 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 the productivity of a molded article to fall.

  The glass transition temperature of the imide resin is not particularly limited, but is preferably 120 ° C. or higher, more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. Below this range, the heat resistance when formed into a film is inferior, so the change in physical properties at high temperatures becomes large and the application range becomes narrow.

  The base film according to the present invention may be a uniaxially stretched film, or may be a biaxially stretched film obtained by combining stretching processes.

  The thickness of the base film according to the present invention is not particularly limited, but is preferably 10 μm to 200 μm, more preferably 20 μm to 150 μm, and further preferably 30 μm to 100 μm.

  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, when the thickness of the base 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 a base film is less than the said range, a draw ratio will become excessive and there exists a tendency for haze to deteriorate.

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

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

  In addition, the base film according to the present invention has an in-plane retardation Re (550) of 0 to 10 nm at a wavelength of 550 nm in view of the retardation of the optical compensation film finally obtained and the retardation of the optically anisotropic layer. The retardation Rth (550) in the thickness direction at a wavelength of 550 nm is preferably 30 to 150 nm.

  If it is set as the structure which has such an optical characteristic, the base film which concerns on this invention can be used as an optical compensation film with which the polarizing plate of a liquid crystal display device is equipped.

  On the other hand, if the Re and Rth of the base film exceed the above ranges, problems such as a decrease in contrast may occur in the liquid crystal display device when the obtained optical compensation film is incorporated in the liquid crystal 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 are respectively the direction in which the in-plane refractive index is the maximum as the X axis, the direction perpendicular to the X axis as the Y axis, and the thickness direction of the film as the Z axis. Represents the refractive index in each axial direction. D represents the thickness of the film, and || represents an absolute value.

In the base 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. It is more preferable that it is not more than × 10 ⁻¹² m ² / N.

  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 = △ n / △ F
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.

(Alignment film)
As the alignment film according to the present invention, a conventionally known inorganic or organic alignment film can be suitably used. Typical examples of inorganic alignment films are SiO oblique deposition films, and organic alignment films are rubbed polyimide films, but other glass substrates treated with rubbed modified poval or rubbed silylating agents. Alternatively, a rubbed gelatin film or the like may be used.

(Liquid crystal composition)
The liquid crystal composition according to the present invention can be selected from a wide range regardless of a low molecular liquid crystal material or a high molecular liquid crystal material. Furthermore, the molecular shape of the liquid crystal substance may be a rod shape or a disk shape. For example, a discotic liquid crystal compound exhibiting a discotic nematic liquid crystal property can also be used. In addition, the liquid crystal composition may be subjected to post-treatment such as polymerization by cross-linking.

  Examples of the liquid crystal phase of the liquid crystal composition according to the present invention include a nematic phase, a twisted nematic phase, a cholesteric phase, a smectic phase, and a discotic nematic phase. Examples of the alignment state include a homogeneous alignment that is horizontally aligned on the alignment substrate, a homeotropic alignment that is aligned vertically, and a tilt alignment and a hybrid alignment that are considered to be an intermediate state therebetween.

  Low molecular liquid crystal substances include saturated benzene carboxylic acids, unsaturated benzene carboxylic acids, biphenyl carboxylic acids, aromatic oxycarboxylic acids, Schiff base types, bisazomethine compounds, azo compounds, azoxy compounds, cyclohexane ester compounds Examples thereof include a compound exhibiting liquid crystallinity in which the reactive functional group is introduced at the terminal, such as sterol compounds, and a composition obtained by adding a crosslinkable compound to a compound exhibiting liquid crystallinity among the compounds.

  Examples of the discotic liquid crystal compound include triphenylene and torquesen.

  As the polymer liquid crystal substance, various main chain type polymer liquid crystal substances, side chain type polymer liquid crystal substances, or a mixture (composition) thereof can be used.

(Optical compensation film)
In the optical compensation film according to the present invention, it is essential that an optically anisotropic layer formed of a base film, an alignment film, and a liquid crystal composition is laminated in this order.

  Here, although one Embodiment of the method to manufacture the base 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 according to the present invention.

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

  Further, the base 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 base 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 equipped with 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. Then, the raw material film may be stretched by vertical and horizontal biaxial stretching 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 to the stretching temperature and stretched.

  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 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 film elongation, 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, the mixing ratio of the thermoplastic resin and the ultraviolet absorber is adjusted within the above-described range, and appropriate birefringence is generated by selecting appropriate stretching conditions. In addition, a film with small thickness unevenness can be easily manufactured without substantially increasing haze.

  Next, an alignment film is formed on the base film. Before the alignment film is formed, surface modification means such as primer treatment, saponification treatment, corona treatment, or plasma treatment may be used for the base film in order to improve the adhesion between the base film and the alignment film.

  A method for forming the alignment film can be selected according to the alignment film to be used, such as oblique vapor deposition, coating, and bonding. Further, after the alignment film is formed, a post-treatment such as heat treatment, light irradiation, or rubbing may be added.

  The optically anisotropic layer is formed by a method such as coating or vapor deposition after forming the alignment film. After the formation, addition of post-treatment such as alignment treatment with light or heat or polymerization treatment may be appropriately selected.

  The optical compensation film according to the present invention can be attached to a polarizer and used as 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 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 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, the “imidization rate” refers to the ratio of the imide carbonyl group in the total carbonyl group.

(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.

Example 1
An imide resin was produced using polymethyl methacrylate (molecular weight 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 280 ° C., and the screw rotation speed was 150 rpm. Polymethyl methacrylate (hereinafter also referred to as “methacrylic resin”) is supplied at 2 kg / hr, and the resin is melted and filled with a kneading block, and then 13.5 parts by weight of monomethylamine with respect to the resin from the nozzle (Mitsubishi Gas Chemical Co., Ltd.) was injected. 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. After cooling the resin which came out as a strand from the die | dye provided in the extruder exit with the water tank, the imide resin (I) was obtained by pelletizing with a pelletizer.

  Next, in 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 250 ° C. and the screw rotation speed was 150 rpm. The imide 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 8.0 parts by weight of dimethyl carbonate and 2.0 wt. Part of the mixed solution 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 the die provided at the exit of the extruder was cooled in a water tank and then pelletized with a pelletizer to obtain an imide resin (II) having a reduced acid value.

  Furthermore, the imide 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. I put it in. 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 imide resin (III).

  For the imide resin (III), the imidization ratio, glass transition temperature, and acid value were measured according to the above-described method. As a result, the imidation ratio was 50%, the glass transition temperature was 145 ° C., and the acid value was 0.01 mmol / g.

  The obtained imide resin was dried at 100 ° C. for 5 hours, and then the sheet-like molten resin obtained by extrusion at 240 ° C. using a 40 mmφ single-screw extruder and a 400 mm wide T-die was cooled with a cooling roll. An unstretched film having a width of 300 mm and a thickness of 130 μm was obtained.

  This film was successively biaxially stretched at a temperature 5 ° C. higher than the glass transition temperature at a draw ratio of 2.5 times in length and 2.0 times in width to produce a base film.

  This base film had an in-plane retardation of 0 nm and a thickness direction retardation of 100 nm.

After corona treatment on both sides of the base film with a discharge amount of 133 w · min / m ² , the modified polyvinyl alcohol is mainly contained in the film by the method described in Example 1-1 of JP-T-2008-533002. An alignment film was provided. Next, after the rubbing treatment is performed on the alignment film, the discotic liquid crystal composition is used as a main component by the method described in Example 1-1 Preparation of first optically anisotropic layer A in JP-T-2008-533502. An optical compensation film was prepared by providing an optically anisotropic layer.

  Next, iodine was adsorbed on the stretched polyvinyl alcohol film to prepare a polarizing film. The base film side of the optical compensation film prepared above was attached to one side of the polarizing film using a polyvinyl alcohol-based adhesive. Next, Z-TAC manufactured by FUJIFILM Corporation was attached to the opposite side of the polarizing film using a polyvinyl alcohol-based adhesive. A polarizing plate was produced by the above-described means.

  Prepare a liquid crystal display device equipped with a TN liquid crystal cell and remove the polarizing plate on the outgoing light side. Instead, attach the above polarizing plate to the liquid crystal cell 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 base film, a polarizing plate and a display device were produced in the same manner as in Example 1 except that the amount of monomethylamine added was 18 parts.

  The imidation ratio was 66%, the glass transition temperature was 153 ° C., and the acid value was 0.01 mmol / g.

  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 3)
A base film, a polarizing plate and a display device were produced in the same manner as in Example 1 except that the amount of monomethylamine added was 10 parts.

  The imidation ratio was 40%, the glass transition temperature was 140 ° C., and the acid value was 0.01 mmol / g.

  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.

(Comparative Example 1)
A display device in which the polarizing plate and the polarizing plate were bonded to a liquid crystal cell by the same means as in Example 1 except that Z-TAC manufactured by Fuji Film Co., Ltd. was used instead of the optical compensation film of Example was produced.

  As a result of observing the display screen of the display device, when viewed from an oblique direction, the color display was different from that when viewed from the front.

Claims (5)

An optical compensation film having an optically anisotropic layer formed of a base film, an alignment film and a liquid crystal composition in this order, wherein the support is a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, N- An optical compensation film comprising an acrylic resin containing at least one substituted maleimide unit and a methyl methacrylate unit. The optical compensation film according to claim 1, wherein the base film is an imide resin containing a glutarimide unit represented by the following general formula (1) and a methyl methacrylate unit.

(In the formula, R 1 and R 2 each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R 3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or 6 carbon atoms. Represents 10 to 10 aryl groups.) The optical compensation film according to claim 1, wherein the base film has an imidization ratio of 30 to 90%. The optical film according to claim 1, wherein the in-plane retardation (Re) of the base film is −20 to 20 nm and the thickness direction retardation (Rth) is 50 to 150 nm. A polarizing plate comprising at least one optical compensation film according to claim 4.