JP6092594B2 - Copolyester and polyester composition - Google Patents

Description

  The present invention is an optical film obtained by laminating a polyester having a high refractive index and a polyester having a low refractive index, and is suitable for use as a polyester having a low refractive index by collecting edge scraps generated in the film forming process. The present invention relates to a polymerized polyester and a polyester composition.

  A film in which low refractive index layers and high refractive index layers are alternately laminated can be an optical interference film that selectively reflects or transmits light of a specific wavelength by structural optical interference between the layers. In addition, such a multilayer film can obtain a high reflectance equivalent to that of a film using metal by gradually changing the film thickness or by bonding films having different reflection peaks. It can also be used as a film or a reflection mirror. Furthermore, by stretching such a multilayer film only in one direction, it can also be used as a polarization reflection film that reflects only a specific polarization component. It is known that these can be used as a brightness enhancement film for a liquid crystal display or the like by using the liquid crystal display or the like.

  For example, as shown in Patent Document 1, by using a resin having a positive stress optical coefficient in one layer, the refractive index of such a layer is birefringent by stretching in a uniaxial direction. By applying a method to increase the refractive index difference between layers in the stretching direction in the film plane, while reducing the refractive index difference between layers in the direction perpendicular to the stretching direction in the film plane, only a specific polarization component Can be reflected.

In Patent Document 2, polyethylene-2,6-naphthalenedicarboxylate (hereinafter sometimes referred to as 2,6-PEN) is used for a layer having a high refractive index, and thermoplasticity is used for a layer having a low refractive index. The multilayer film using the PEN which copolymerized 30 mol% of elastomers and terephthalic acid is illustrated. This is because a resin having a positive stress optical coefficient is used in one layer and a resin having a very low stress optical coefficient (extremely low birefringence due to stretching) is used in the other layer. The reflective polarizing film which reflects only polarized light is illustrated.
Patent Document 3 describes a multilayer laminated film containing polyethylene-2,6-naphthalenedicarboxylate as a high refractive index layer and containing inert particles.

  As described above, it is conventionally known that 2,6-PEN is used for a layer having a high refractive index. However, if it is attempted to reuse edge dust generated in the film forming process, the layer having a low refractive index is high. Due to the difference in the composition of the polyester used between the layers, there was a problem that it could not be uniformly mixed and whitened and reused.

JP-A-4-268505 Japanese National Patent Publication No. 9-506837 International Publication No. 01/47711 Pamphlet

  An object of the present invention is to provide a copolymerized polyester capable of resolving the above-mentioned problems of conventional multilayer films and reusing edge scraps and the like produced in the film forming process, and a polyester composition using the same.

Thus, according to the present invention, the following 1) to 3 ) copolymer polyester, 4 ) or 5 ) polyester composition is provided.
1) 50 to 70 mol% of the acid component is a 2,6-naphthalenedicarboxylic acid component, 30 to 50 mol% is a cyclohexanedicarboxylic acid component, 30 to 50 mol% of the glycol component is an ethylene glycol component, and 50 to 70 mole% is a copolyester which is a spiro glycol component, the average refractive index Ri range near the 1.540 to 1.560, a glass transition temperature (Tg) of 95 to 115 ° C. der Ru copolyesters.
2) The copolyester according to the above 1, which is used for melt kneading with an ethylene naphthalate resin having an average refractive index of 1.630 or more at a weight ratio of 35-50: 65-50.
3 ) The copolyester according to 1 above, wherein the copolyester contains 0.1 to 0.5% by weight of an antioxidant.
4 ) An average refractive index obtained by melt-kneading an ethylene naphthalate-based resin having an average refractive index of 1.630 or more and the copolymer polyester according to any one of the above 1 to 3 at a weight ratio of 35 to 50:65 to 50. A polyester composition in the range of 1.580 to 1.590.
5 ) The ethylene naphthalate resin is a 2,6-naphthalenedicarboxylic acid component with 60 to 95 mol% of the dicarboxylic acid component and 6,6 ′-(alkylenedioxy) with 5 to 40 mol% of the dicarboxylic acid component. The polyester composition as described in 4 ) above, which is a di-2-naphthoic acid component.

  According to the present invention, by using a copolymer polyester having a composition compatible with the ethylene naphthalate resin constituting the high refractive index layer as the polyester constituting the low refractive index layer, waste generated in the film forming process is used. Can be reusable.

<Copolymerized polyester>
In the copolymerized polyester of the present invention, 50-70 mol% of the acid component is a 2,6-naphthalenedicarboxylic acid component, 30-50 mol% is a cyclohexanedicarboxylic acid component, and 30-50 mol% of the glycol component is ethylene glycol. The component is a copolyester in which 50 to 70 mol% is a spiroglycol component.

  A high refractive index can be obtained by using a 2,6-naphthalenedicarboxylic acid component as the acid component of the copolyester in the present invention, and an ethylene naphthalate-based resin can be obtained by using a large amount of the 2,6-naphthalenedicarboxylic acid component. Compatibility is also improved and recoverability is improved. If the amount of 2,6-naphthalenedicarboxylic acid is less than 50 mol%, the compatibility with the ethylene naphthalate resin is deteriorated, and if it exceeds 70 mol%, the refractive index of the resulting polyester composition becomes too high.

  The copolymerized polyester of the present invention copolymerizes a cyclohexanedicarboxylic acid component in the range of 30 to 50 mol% as a copolymerization component of the acid component. In general, when a highly rigid component such as a 2,6-naphthalenedicarboxylic acid component is used, the glass transition point can be maintained high, but the refractive index is also increased. For this reason, if the copolymerization amount of the cyclohexanedicarboxylic acid component is too small, the refractive index becomes too high, and conversely if it is too much, the compatibility deteriorates. Therefore, in order to set the refractive index of the copolymer polyester to 1.540 to 1.560 and the refractive index of the polyester composition melt-kneaded with the ethylene naphthalate resin to 1.590 or less, the acid component in the copolymer polyester is The 2,6-naphthalenedicarboxylic acid component is 50 to 70 mol%, and the cyclohexanedicarboxylic acid component is 30 to 50 mol%. In addition, the copolymer polyester of this invention may copolymerize conventionally well-known things, such as a terephthalic acid component and an isophthalic acid component, in the range which does not impair the effect of this invention.

  As the glycol component of the copolymerized polyester of the present invention, it is difficult to control the compatibility and the refractive index only with the ethylene glycol component, so that spiroglycol is copolymerized. By copolymerizing spiroglycol, the refractive index can be significantly lowered while maintaining a high glass transition temperature (Tg). Therefore, it is preferable to increase the amount of spiroglycol as much as possible. However, when the spiroglycol component is large, the spiroglycol is decomposed to form a crosslinked structure, so that the polymer is easily gelled. Therefore, from the viewpoint of controlling the refractive index and polymerization, the glycol component contains 30 to 50 mol% ethylene glycol component and 50 to 70 mol% spiroglycol component. Here, spiroglycol refers to 3,9-bis (2-hydroxy-1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro [5,5] undecane. Moreover, the copolymer polyester of the present invention may be copolymerized with a conventionally known product such as cyclohexanedimethanol as long as the effects of the present invention are not impaired.

  The copolymerized polyester of the present invention can be polymerized by a method known per se. For example, a 2,6-naphthalenedicarboxylic acid component and a cyclohexanedicarboxylic acid component are used as an acid component, an ethylene glycol compound and a spiroglycol component are used as a glycol component, After the transesterification reaction, the phosphorous compound is added to complete the reaction, and then the ester reaction vessel can be transferred to the polycondensation reaction vessel to obtain the polycondensation reaction.

  At that time, the copolymerized polyester of the present invention preferably contains an antioxidant because it is copolymerized with spiroglycol which is easily decomposed when heated in an acidic or water-containing condition. By containing such an antioxidant, the formation of a crosslinked structure can be suppressed, and the adverse effect on discharge stability, polymer cutting, and the like can be suppressed because the polymer becomes rubbery. Such a copolyester that suppresses the formation of crosslinks has an antioxidant added before the esterification reaction or transesterification reaction to suppress the decomposition of spiroglycol and a relatively low polycondensation reaction temperature of about 260 ° C. Is effective.

  Examples of the antioxidant in the present invention include phenolic antioxidants, sulfur-based antioxidants, lactone-based antioxidants and aromatic amine-based antioxidants as non-phosphoric acid-based antioxidants. In the production of the polyester of the present invention, since the reaction system from the esterification reaction or transesterification reaction to the polycondensation reaction is adopted, the affinity with the polyester, and the properties, thermal stability, color tone, etc. of the resulting polyester are deteriorated. It is preferable to use a non-phosphorus antioxidant having a low content, and among them, a phenol-based antioxidant is preferable.

Examples of phenolic antioxidants include pentaerythritol lakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris (3 , 5-di-tert-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1, 1-dimethylethyl] -2,4,8,10-tetraoxaspiro- [5.5] undecane, triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ], 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2,4-bis- (n-octylthio) -6 (4-Hydroxy-3,5-di-t-butylanilino) -1,3,5-triazine, 2,2-thio-diethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate], octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate, N, N′-hexamethylenebis (3,5-di-tert-butyl-4-hydroxy-hydro) Cinnamamide), 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, bis (3,5-di-t-butyl-4-hydroxybenzylphosphonate ethyl) calcium, tris ( 3,5-di-tert-butyl-4-hydroxybenzyl) -isocyanurate, octylated diphenylamine, 2,4-bis [(octylthio) methyl] -o-crezo Le, isooctyl-3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate and the like, but not limited thereto. Two or more phenolic antioxidants may be used in combination. Among them, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl- from the viewpoint of affinity with polyester and the effect of suppressing oxidative degradation 2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3,9-bis [2- [3- (3-t-butyl-4-hydroxy-5-methyl Phenyl) -propionyloxy] -1,1-dimethylethyl] -2,4,8,10-tetraoxaspiro- [5.5] undecane is preferred.
Furthermore, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] is more preferable.

  The addition amount of the antioxidant in the present invention is preferably 0.5% by weight or less based on the weight of the copolyester. If the amount added exceeds 0.5% by weight, foaming may occur during the reaction, and foaming may cause a rise in liquid level or blockage of the vacuum circuit due to scattered matter. On the other hand, if the addition amount is less than 0.1% by weight, the function as an antioxidant may not sufficiently function. A preferable addition amount of the antioxidant is 0.1 to 0.3% by weight.

  The Tg of the copolymerized polyester of the present invention is preferably close to the Tg of the ethylene naphthalate resin laminated as the film layer A described later. If the Tg difference is large, the characteristics are likely to change with time, and the film forming stability is likely to be impaired. On the other hand, when the Tg of the copolyester is higher than the Tg of the ethylene naphthalate resin laminated as the film layer B described later, the refractive index difference between the film layers A and B described later becomes small and the reflection performance decreases. There are things to do. Therefore, the Tg of the copolyester is preferably 95 ° C to 115 ° C.

  The copolymer polyester of the present invention constitutes a laminated film with an ethylene naphthalate resin having a refractive index of 1.630 to 1.670, and has an average refractive index of 1.540 to 1. 560 is preferable. When this average refractive index is lower than the lower limit, when melt-kneaded with the ethylene naphthalate resin, a refractive index difference can be made in the direction in which the refractive index should be aligned with the film layer A, which will be described later, and the reflective polarization performance decreases. End up. On the other hand, if the average refractive index is larger than the upper limit, the difference in refractive index in the direction in which a difference in refractive index with a film layer A to be described later is desired is reduced and the reflectance is lowered. From such a viewpoint, the average refractive index of the copolyester is 1.540 to 1.560, preferably 1.545 to 1.555.

  Here, the average refractive index is a substitute for a uniaxially stretched film by melting the copolymer polyester constituting the film layer B alone, creating a balloon film by winding the melted polymer around a glass rod and blowing it out. The refractive index in each of the X direction, Y direction, and Z direction of the film is measured at a wavelength of 633 nm using a metricon prism coupler, and the average value thereof is defined as the average refractive index. Optical isotropy means that the refractive index difference between the two directions of the refractive index in the X direction, Y direction, and Z direction is 0.05 or less, preferably 0.03 or less.

<Ethylene naphthalate resin having a refractive index of 1.630 or more>
The ethylene naphthalate-based resin in the present invention can be produced by subjecting the main dicarboxylic acid component to a naphthalene dicarboxylic acid component and the main glycol component to an ethylene glycol component, which are subjected to a polycondensation reaction. In addition, main here means 60 mol% or more on the basis of the number-of-moles of all the acid components.

The ethylene naphthalate-based resin in the present invention contains, as a dicarboxylic acid component, a 2,6-naphthalenedicarboxylic acid component of 60 mol% or more and 95 mol% or less and a 6,6 ′-(5 mol% or more and 400 mol% or less of 6,6 ′-( It preferably comprises a component derived from (alkylenedioxy) di-2-naphthoic acid. By using such a resin, when the film layer A is used, the refractive index in the thickness direction of the film layer A and the refractive index of the film layer A in the direction desired to be aligned with the refractive index of the film layer B can be made closer. it can.
The 2,6-naphthalenedicarboxylic acid component in the present invention may be used as it is, or may be used, for example, in the form of a lower alkyl ester having 1 to 3 carbon atoms.

  As the 6,6 ′-(alkylenedioxy) di-2-naphthoic acid component, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid, 6,6 ′-(trimethylenedioxy) di- Examples include 2-naphthoic acid and 6,6 ′-(butyleneoxy) di-2-naphthoic acid, and these may be used in the form of derivatives such as the aforementioned 2,6-naphthalenedicarboxylic acid component. . Among these, considering the conjugated system, those having an even number of carbon atoms connecting the aromatic rings are preferable, and components derived from 6,6 '-(ethylenedioxy) di-2-naphthoic acid are particularly preferable.

  The diol component constituting the ethylene naphthalate resin of the present invention is an ethylene glycol component, and as described above, based on the number of moles of all glycol components, is 60 mol% or more, preferably 80 mol% or more, More preferably, it is 90 mol% or more, Most preferably, it is 95 mol% or more. Preferable examples of the copolymer component other than the ethylene glycol component include a trimethylene glycol component and a tetramethylene glycol component.

  Since the ethylene naphthalate resin in the present invention is configured as a copolymerized polyester and a laminated film of the present invention, the average refractive index is preferably in the range of 1.630 to 1.670. When the average refractive index is less than the lower limit, the refractive index of the polyester resin recovered as a laminated film is lowered, and when used again as a laminated film, there is no difference in refractive index from the copolymerized polyester and the polarizing performance is significantly lowered. End up. On the other hand, when the average refractive index exceeds the upper limit, it becomes difficult to match the refractive index in the thickness direction with the film layer B which is a low refractive index layer.

  In particular, the ethylene naphthalate resin in the present invention is excellent in having a low temperature expansion coefficient and a humidity expansion coefficient by copolymerizing a component derived from 6,6 ′-(alkylenedioxy) di-2-naphthoic acid. Dimensional stability and the like can be imparted, and the refractive index can be increased without changing the mechanical strength. Furthermore, since the refractive index increases in the stretching (X-axis) direction by performing uniaxial stretching, the polarization performance in the case of a laminated film can be made extremely excellent.

  As a method for producing an ethylene naphthalate resin in the present invention, first, as a first reaction step, a 2,6-naphthalenedicarboxylic acid component and 6,6 ′-(alkylenedioxy) di-2-naphthoic acid or its The ester-forming derivative and ethylene glycol are esterified or transesterified, and then, as a second reaction step, a polymerization catalyst such as a titanium catalyst is added to shift to a polycondensation reaction, and the polycondensation reaction is performed at 30 Pa. It is obtained through

<Polyester composition>
The polyester composition of the present invention is obtained by melt-kneading the ethylene naphthalate resin having an average refractive index of 1.630 to 1.670 and the copolymer polyester of the present invention in a weight ratio of 35 to 50:65 to 50. It is a thing.
And in order to be able to express when the above reflective characteristics are made into a laminated film, the average refractive index needs to exist in the range of 1.580-1.590.

  One of the major features of the polyester composition of the present invention is that it is made compatible by melting and kneading copolymer polyesters of different compositions and ethylene naphthalate resin at a specific ratio, and reused as a uniform polyester composition. It is in the point to make it possible. This polyester composition can improve compatibility by setting the weight ratio of the copolymer polyester to be equal to or greater than that of the ethylene naphthalate resin. When the weight ratio of the copolymerized polyester is less than 50%, the compatibility is deteriorated, and even when melt-kneading is performed, the polymer is not uniform and tends to be whitened. Further, when the copolymerized polyester component exceeds 65%, the heat resistant dimensional stability, which is an effect of the ethylene naphthalate resin, is deteriorated, and there is a high possibility that the polyester resin cannot endure reuse. For this reason, the optimal weight ratio of the ethylene naphthalate resin component and the copolymerized polyester component is preferably 35 to 50:65 to 50, and more preferably 40 to 50:60 to 50.

  In producing the polyester composition of the present invention, it is melt kneaded using a general twin-screw extruder, but it should be noted that the melting temperature should not be higher than 290 ° C. Is preferred. When melt-kneaded at a high temperature of 290 ° C. or higher, decomposition of the copolyester composition containing a large amount of the spiroglycol component due to heat is accelerated, and the quality of the extruded polymer may be significantly lowered. On the other hand, if the melting temperature is less than 260, the melting in the polymer state does not proceed and the mixture is not sufficiently kneaded to form a uniform polymer. Therefore, in order to obtain a polyester composition, it is preferable to melt knead at a temperature of 260 ° C. or higher and lower than 290 ° C.

<Laminated polyester film>
The copolymerized polyester and the polyester composition of the present invention can be suitably used as a raw material for a laminated polyester film. As a specific laminated polyester film, a film layer A on the high refractive index side and a film layer B on the low refractive index side are alternately laminated, and the film has 277 layers or more and is stretched in at least one axial direction. Preferably there is. And in the film layer A and the film layer B which comprise a laminated polyester film, it exists in using the above-mentioned polyester composition for the film layer B using the above-mentioned polyester with high refractive index for the film layer A.

  By performing uniaxial stretching using the ethylene naphthalate-based resin, the difference in refractive index between the X direction and the Y direction of the stretched film layer A can be increased, and interlayers in both the Y direction and the Z direction can be achieved. It is possible to reduce the refractive index difference. As a result, it is possible to improve both the polarization performance and to suppress the hue shift of the transmitted polarized light with respect to the incident light in the oblique direction.

Furthermore, in the present invention, the ethylene naphthalate resin used for the film layer A has excellent heat-resistant dimensional stability by bringing the glass transition temperature of the copolymer polyester used for the film layer B close to 95 ° C to 115 ° C. It can also have excellent haze resistance that does not cause whitening due to crystallization even for a long time.
Here, the refractive index in the stretching direction (X direction) is described as n _X , the refractive index in the direction orthogonal to the stretching direction (Y direction) is expressed as n _Y , and the refractive index in the film thickness direction (Z direction) is described as _NZ. There is.

When the ethylene naphthalate resin is uniaxially stretched, the refractive index n _{X in the X} direction is in a direction that increases by stretching, and the refractive index n _{Y in the Y} direction and the refractive index n _{Z in the} Z direction both decrease with stretching. In addition, the difference in refractive index between n _Y and n _Z is very small regardless of the draw ratio. Further, the film layer A has a high refractive index characteristic such that the refractive index n _{X in the} X direction is 1.80 to 1.90 by uniaxial stretching. Thereby, the difference in refractive index in the X direction between the film layer A and the film layer B is increased, and sufficient reflective polarization performance is exhibited.
Further, the difference in refractive index between the refractive index n _Y after uniaxial stretching in the Y direction and the refractive index n _Z after uniaxial stretching in the Z direction is preferably 0.05 or less, and can be made as small as possible. Even if the polarized light is incident at an oblique incident angle, there is an effect that no hue shift occurs.

In the present invention, the film layer B of the laminated film is preferably a copolyester having a glass transition temperature of 95 ° C. or higher and 115 ° C. or lower, and has an average refractive index of 1.540 to 1.560 and is optically isotropic. A layer is preferred.
The difference in refractive index in the X direction between the film layer A and the film layer B in the film plane is preferably 0.10 to 0.45, more preferably 0.20 to 0.40, and still more preferably 0.25 to 0.25. 0.30. When the refractive index difference in the X direction is within such a range, the reflection characteristics can be improved efficiently, and a high reflectance can be obtained with a smaller number of layers.

  Moreover, it is preferable that the refractive index difference of the Y direction of the film layer A and the film layer B and the refractive index difference of the Z direction are each 0.05 or less. Since the refractive index difference between the layers in the Y direction and the Z direction is both in the above-described range, a hue shift can be suppressed when polarized light is incident at an oblique incident angle.

The laminated film in the present invention is preferably one in which the above-mentioned film layer A and film layer B are alternately laminated in a total of 277 layers. By providing such a number of layers, it is possible to obtain a constant high average reflectance over a wavelength range of 400 to 800 nm with respect to the average reflectance characteristic of the polarization component parallel to the incident surface including the stretching direction.
The number of laminated films is not particularly limited, but as the number of laminated films increases, a higher reflectance is obtained for polarized light parallel to the reflection axis direction, preferably 601 layers or more, more preferably 701 layers or more, and even more preferably 801. More than layers.

Further, in order to obtain a laminated film having a number of laminated layers of 801 or more, a melt in an alternately laminated state is obtained in a range of 300 or less layers, and 1: 1 with respect to the lamination direction while maintaining such a layer configuration. It is possible to increase the number of layers by dividing the ratio so that the number of layers (doubling number) is 2 to 4 times.
In order that the film layer A and the film layer B selectively reflect light by optical interference between layers, the thickness of each layer is preferably 0.01 μm or more and 0.5 μm or less. When the layer thickness exceeds 0.5 μm, the reflection band becomes an infrared region, and usefulness as a reflective polarizing film may not be obtained. On the other hand, when the layer thickness is less than 0.01 μm, the polyester component may absorb light and the reflection performance may not be obtained.

  In the laminated film of the present invention, the ratio of the maximum layer thickness and the minimum layer thickness in each of the film layer A and the film layer B is preferably 2.0 or more and 5.0 or less. In the laminated film, the reflected wavelength is determined by the refractive index difference between layers, the number of layers, and the thickness of the layers. If each of the laminated layers has a constant thickness, the reflected wavelength is limited and uniform reflection characteristics are obtained. It may not be possible. In addition, when the ratio between the maximum layer thickness and the minimum layer thickness exceeds the upper limit value, the reflection band is excessively widened, and the reflectance of the polarization component parallel to the incident surface including the stretching direction (X direction) may decrease. is there. Here, by changing the thickness ratio of the film layer A and the film layer B, light in a wide wavelength range can be reflected.

  The method for laminating the laminated film in the present invention is not particularly limited. For example, the A and B layers obtained by branching the ethylene naphthalate resin of the film layer A into 138 layers and the copolymer polyester of the film layer B into 137 layers are alternately arranged. And a multi-layer feed block device in which the flow path is continuously changed by 2.0 to 5.0 times.

In the laminated film of the present invention, the ratio of the average layer thickness of the film layer B to the average layer thickness of the film layer A is preferably in the range of 1.5 to 5.0 times.
In order to make each layer thickness uniform in the laminated film in the present invention, in addition to the film layer A and the film layer B, a thickness adjusting layer having a layer thickness of 2 μm or more and not contributing to the reflection characteristics is formed between the film layer A and the film layer B. You may have in a part of alternate lamination structure.

The laminated film in the present invention is stretched at least in the uniaxial direction in order to satisfy the optical characteristics as the target reflective polarizing film. The uniaxial stretching in the present invention includes not only a film stretched only in a uniaxial direction but also a film stretched in a biaxial direction and further stretched in one direction. The uniaxial stretching direction (X direction) may be either the film longitudinal direction or the width direction. Further, in the case of a film stretched in a biaxial direction and stretched in one direction, the direction (X direction) that is more stretched may be either the film longitudinal direction or the width direction. In the direction where the draw ratio is low, it is preferable that the draw ratio is about 1.05 to 1.20 times from the viewpoint of improving the polarization performance.
Although it does not specifically limit as a extending | stretching method, You may use well-known extending | stretching methods, such as heating extending | stretching with a rod-shaped heater, roll heating extending | stretching, and tenter stretching.

The laminated film in the present invention preferably has a haze value of 1.0% or less in order to obtain a high degree of polarization. Furthermore, it is preferable that it is 0.5% or less. This property is achieved by keeping the copolymer polyester of film layer B high.
The stretching temperature of the laminated film is preferably in the range of ethylene naphthalate resin Tg to Tg + 50 ° C. of the film layer A. The draw ratio at this time is preferably 2 to 10 times, and more preferably 5 to 7 times. The greater the draw ratio, the more uniform each layer, the greater the difference in refractive index between the film layer A and the film layer B, and the higher the polarization performance.

  In the present invention, for example, as a more preferable method for obtaining a multilayer uniaxially stretched film having 801 layers or more, a melt in an alternately laminated state is obtained in a range of 300 layers or less, and while maintaining such a layer configuration, a direction perpendicular to the lamination direction The number of layers can be increased by a method of dividing the layers so as to have a ratio of 1: 1 and stacking again so that the number of layers (doubling number) is 2 to 4 times. When performing such doubling treatment, it can be performed by a known method, and after the obtained melt in the laminated state is cast on a cast drum to obtain a laminated unstretched film, the laminated film is subjected to the above-described stretching process. Can be obtained.

  Examples of the polyester composition recovered and reused in the present invention include film edges that are gripped by clips generated in the stretching process of unstretched film, and film scraps that are cut when the film-forming film is wound up. It is cut with a cutting machine, melt-kneaded and pelletized with a general twin-screw extruder, melt-kneaded with the above-mentioned copolymerized polyester of the present invention, and can be reused again as the polyester composition of the present invention.

  The invention is further described by way of examples. In addition, the physical property and characteristic in an Example were measured or evaluated by the following method.

(1) Intrinsic viscosity (IV)
The intrinsic viscosity of the obtained polyester was determined by dissolving the polymer using a mixed solvent of P-chlorophenol / 1,1,2,2-tetrachloroethane (40/60 weight ratio) and measuring at 35 ° C.

(2) Glass transition point (Tg) of polyester and film
10 mg of a polyester sample or a film sample was sampled, and a melting point and a glass transition point were measured using a DSC (trade name: DSC2920, manufactured by TA Instruments) at a heating rate of 20 ° C./min.

(3) Refractive index and average refractive index in each direction Each polymer constituting each layer was melted and blown from a glass rod to prepare a balloon film, which was prepared as an alternative to a stretched film. With respect to the obtained balloon film, the refractive index (respectively denoted as n _X , n _Y , and n _Z ) in the stretching direction (X direction), the orthogonal direction (Y direction), and the thickness direction (Z direction) is measured. The refractive index at a wavelength of 633 nm was measured by using a prism coupler manufactured, and the average value of n _X , n _Y , and n _Z was determined for the average refractive index.

(4) Compatibility 70 g of ethylene naphthalate resin of the film layer A on the high refractive index side and the polyester copolymer resin of the film layer B on the low refractive index side are collected at a weight ratio of 35-50: 65-50, and nitrogen Then melt at 310 ° C. After melting, the stirring blade was rotated at a stirring speed of 20 rpm under nitrogen, and the time from the start of stirring until the resin became transparent was measured and evaluated according to the following criteria.
◎: Less than 5 minutes from the start of stirring ○: More than 5 minutes and less than 8 minutes from the start of stirring △: More than 8 minutes and less than 12 minutes from the start of stirring ×: More than 12 minutes from the start of stirring

[Reference Example 1]
As ethylene naphthalate-based polyester for high refractive index layer, dimethyl 2,6-naphthalenedicarboxylate, 6,6 ′-(ethylenedioxy) di-2-naphthoic acid and ethylene glycol are used in the presence of titanium tetrabutoxide. An esterification reaction and a transesterification reaction were performed, followed by a polycondensation reaction to obtain an ethylene naphthalate resin. The obtained ethylene naphthalate resin had an intrinsic viscosity of 0.52 dl / g, an average refractive index of 1.650, and a glass transition temperature of 118 ° C.

[Example 1]
In a transesterification reaction vessel, dimethyl 2,6-naphthalenedicarboxylate, dimethyl cyclohexanedicarboxylate, ethylene glycol, spiroglycol, manganese acetate (30 mmol% based on the number of moles of acid component) as a transesterification reaction catalyst, tetratitanium butoxide (acid 20 mmol% based on the number of moles of the component), pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (manufactured by Ciba Japan Co., Ltd.) as a non-phosphorus antioxidant , IRGANOX 1010), heated to 150 ° C., melted and stirred. The reaction was advanced while the temperature inside the reaction vessel was slowly raised to 230 ° C., and the produced methanol was distilled out of the reaction vessel. When the distillation of methanol was completed, triethyl phosphonoacetate (30 mmol% based on the number of moles of the acid component) was added as a phosphorus compound to complete the transesterification reaction (hereinafter abbreviated as EI reaction). Subsequently, after heating to 245 ° C. to distill a part of ethylene glycol, the reaction product was transferred to a polycondensation apparatus having a stirring blade inside. The reaction temperature was allowed to reach 260 ° C. over 40 minutes while gradually increasing the degree of vacuum. While maintaining this temperature, the degree of vacuum was kept at 40 Pa, and a polycondensation reaction (hereinafter abbreviated as PN reaction) was performed. Thereafter, the PN reaction was terminated when the target stirring torque was reached. The obtained polymer had an intrinsic viscosity of 0.60. The polymer composition and physical properties of the obtained copolyester are shown in Table 1.
The prepared polyester copolymer for the low refractive index side film and the ethylene naphthalate polyester for the high refractive index side film prepared in Reference Example 1 were melt-kneaded at a weight ratio of 65:35 to obtain a polyester composition. The time to clear the polyester composition was 7 minutes. The properties of the obtained copolyester and polyester composition are shown in Table 1.

[Examples 2 to 7]
As shown in Table 1, a copolymerized polyester and a polyester composition were obtained in the same manner as in Example 1 except that the composition of the copolymerized polyester was changed. The properties of the obtained copolyester and polyester composition are shown in Table 1.

[Examples 8 to 9]
As shown in Table 1, a copolymerized polyester and a polyester composition were obtained in the same manner as in Example 1 except that the composition of the copolymerized polyester and the addition amount of the antioxidant were changed. The properties of the obtained copolyester and polyester composition are shown in Table 1.

[Example 10]
As shown in Table 1, a polyester composition was obtained in the same manner as in Example 1 except that the blend ratio in the polyester composition was changed. The properties of the obtained polyester composition are shown in Table 1.

[Comparative Examples 1-4]
As shown in Table 1, a copolymerized polyester and a polyester composition were obtained in the same manner as in Example 1 except that the composition of the copolymerized polyester was changed. The properties of the obtained copolyester and polyester composition are shown in Table 1.

[Comparative Example 5]
As shown in Table 1, a polyester composition was obtained in the same manner as in Example 1 except that the blend ratio in the polyester composition was changed. The properties of the obtained polyester composition are shown in Table 1.

[Comparative Examples 6 and 7]
As shown in Table 1, a copolymerized polyester and a polyester composition were obtained in the same manner as in Example 1 except that the composition of the copolymerized polyester was changed. The properties of the obtained copolyester and polyester composition are shown in Table 1.

  In Table 1, NDC is 2,6-naphthalenedicarboxylic acid component, CHDC is cyclohexanedicarboxylic acid component, EG is ethylene glycol component, SPG is spiroglycol component, TA is terephthalic acid component, CHDM is cyclohexanedimethanol component, blend ratio Is the ratio (weight ratio) of the copolyester in the polyester composition.

  The copolymerized polyester and the polyester composition of the present invention can be reused as a polymer for recovering film waste and constituting a laminated film.

Claims (5)

50 to 70 mol% of the acid component is a 2,6-naphthalenedicarboxylic acid component, 30 to 50 mol% is a cyclohexanedicarboxylic acid component, 30 to 50 mol% of the glycol component is an ethylene glycol component, and 50 to 70 mol% there a copolymerized polyester which is a spiro glycol component, the average refractive index Ri range near the 1.540 to 1.560, a glass transition temperature (Tg) of 95 to 115 ° C. der Ru copolyesters.   The copolymer polyester according to claim 1, which is used for melt-kneading an ethylene naphthalate resin having an average refractive index of 1.630 or more and a weight ratio (copolymer polyester: ethylene naphthalate resin) of 35-50: 65-50. .   The copolyester according to claim 1, wherein the copolyester contains 0.1 to 0.5% by weight of an antioxidant. An average refractive index of 1 obtained by melt-kneading an ethylene naphthalate-based resin having an average refractive index of 1.630 or more and the copolymer polyester according to any one of claims 1 to 3 at a weight ratio of 35 to 50:65 to 50. A polyester composition in the range of 580 to 1.590. In the ethylene naphthalate resin, 60 mol% or more and 95 mol% or less of the dicarboxylic acid component is 2,6-naphthalenedicarboxylic acid component, and 5 mol% or more and 40 mol% or less is 6,6 ′-(alkylenedioxy) di. The polyester composition according to claim 4, which is a 2-naphthoic acid component.