JP2008039829A - Retardation film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a retardation film having little changes in retardation by the use environment. <P>SOLUTION: The retardation film is manufactured by stretching a rolled film made of a polyester resin that contains dicarboxylic acid units and diol units, in which 1 to 80 mol% of the diol units are diol units having a cyclic acetal skeleton, and then heat treating the film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a retardation film mainly used in a liquid crystal display device.

  The retardation film is an important member that realizes an improvement in contrast and expansion of a viewing angle range in an image display device such as a liquid crystal display device by optical compensation. Examples of the resin forming the retardation film generally include engineering plastics such as polycarbonate (hereinafter PC) and cycloolefin polymer (hereinafter COP). Regarding the production of a retardation film, these resins are formed into a film by a casting method or a melt extrusion method, the film is stretched as a raw film, and controlled to a desired retardation to obtain a retardation film. However, although a melt extrusion method can be applied to COP, there is a problem that an unexpected retardation appears due to orientation or stress of a polymer bond chain during molding (see Patent Document 1).

One indicator of the retardation retention capability is the glass transition temperature (Tg). The phase difference holding power is an ability that the phase difference does not change in the use environment. The glass transition temperature of ZEONOR Film ZF14 from Nippon Zeon Co., Ltd. is 136 ° C (catalog value). The pure ace of Teijin Chemicals Limited is 160 ° C (catalog value). Kaneka's Elmec is 150 ° C (catalog value). The higher the glass transition temperature, the higher the retardation retention ability. However, Tg is only a guide. Therefore, each company conducts various reliability tests to confirm the durability of the stretched retardation film in-house. For example, the pure ace of Teijin Chemicals Co., Ltd. has a phase difference change within ± 4.0 nm at 90 ° C x 1000 hrs and a phase difference change within ± 4.0 nm at 80 ° C, 90% RH x 1000 hrs (all catalogs issued by the company) Is described). Kaneka's Elmec retardation film has a retardation change within ± 2.0 nm at 80 ° C x 1000 hrs, and within ± 2.0 nm at 60 ° C, 90% RH x 1000 hrs (both listed in the catalog issued by the company). Is described). If it is a reliability test result on said conditions, it can fully be used as a phase difference film of the liquid crystal panel in which reliability is calculated | required.
However, some resins have a low glass transition temperature and a film whose phase difference greatly varies in the reliability test. Even with such a resin, it is necessary that the retardation change due to the use environment is small.
JP 2004-109355 A

  An object of the present invention is to provide, at a low cost, a retardation film with little change in retardation due to the use environment even if the resin has a low glass transition temperature as described above.

  As a result of diligent research, the present inventors have found that the resin used for the retardation film is a polyester resin containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit is a diol unit having a cyclic acetal skeleton. It has been found that the manufacturing conditions for polyester films formed by the melt T-die extrusion method are relatively wide because of low costs and manufacturing costs. Furthermore, it has also been found that any retardation can be controlled by using the polyester film as a raw film and stretching it. Furthermore, the polyester film retardation film is low in retardation due to the use environment even if the glass transition temperature is relatively low by first relaxing the molecular group that is easy to relax orientation by heat treatment by heat treatment of the stretched film. Made it possible to provide

  That is, the present invention is a method in which a raw film obtained by melt-extruding a polyester resin containing a dicarboxylic acid unit and a diol unit and having a diol unit in which 1 to 80 mol% of the diol unit has a cyclic acetal skeleton is heat-treated after stretching. The present invention relates to a retardation film to be manufactured and a manufacturing method thereof.

  The retardation film of the present invention is produced by stretching the raw film and controlling the retardation, and then heat-treating the molecular groups that are easily moved by heat to relax the orientation in advance. Accordingly, there is an effect that the retardation film hardly changes in the use environment of the final product, and the retardation film is less changed by the use environment. A practical retardation film can be obtained with inexpensive raw materials and manufacturing methods, and the impact on the conventional retardation film market, which has high heat resistance but only expensive resin films, is great.

  The present invention stretches a polyester raw film made of a polyester resin containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit is a diol unit having a cyclic acetal skeleton, and the retardation is controlled. The present invention relates to a retardation film characterized by

  It is preferable that the ratio of the diol unit which has a cyclic acetal skeleton in the polyester resin used for this invention is 1-80 mol%. By including 1 mol% or more of diol units having a cyclic acetal skeleton, a decrease in crystallinity of the polyester resin and an increase in the glass transition temperature are achieved simultaneously, and the polyester film obtained from the resin has improved transparency and heat resistance. . In addition, the polyester film has improved processability such as the generation of whiskers during processing such as cutting and punching, and further reduced the retardation value, reduced unevenness of the retardation value, and unevenness in thickness during melt extrusion. The optical performance is improved such as reduction. On the other hand, when the ratio of the diol unit having a cyclic acetal skeleton in the polyester resin exceeds 80 mol%, the crystallinity of the polyester resin increases and the transparency of the resulting polyester film may decrease. Therefore, the ratio of the diol unit having a cyclic acetal skeleton is preferably 11 to 60 mol%, more preferably 20 to 55 mol% from the viewpoint of heat resistance, transparency, processability, and optical performance of the polyester film. 30-50 mol% is especially preferable.

または一般式（２）：

で表される化合物に由来する単位が好ましい。一般式（１）と（２）において、Ｒ^１およびＲ^２はそれぞれ独立して、炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^１およびＲ^２は、メチレン基、エチレン基、プロピレン基、ブチレン基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピレン基、イソブチレン基が例示される。Ｒ^３は炭素数が１〜１０の脂肪族炭化水素基、炭素数が３〜１０の脂環式炭化水素基、及び炭素数が６〜１０の芳香族炭化水素基からなる群から選ばれる炭化水素基を表す。Ｒ^３は、メチル基、エチル基、プロピル基、ブチル基、又はこれらの構造異性体が好ましい。これらの構造異性体としては、例えば、イソプロピル基、イソブチル基が例示される。一般式（１）及び（２）の化合物としては、３，９−ビス（１，１−ジメチル−２−ヒドロキシエチル）−２，４，８，１０−テトラオキサスピロ〔５．５〕ウンデカン、５−メチロール−５−エチル−２−（１，１−ジメチル−２−ヒドロキシエチル）−１，３−ジオキサン等が特に好ましい。 The diol unit having a cyclic acetal skeleton in the diol structural unit of the polyester resin used in the present invention is represented by the general formula (1):

Or general formula (2):

The unit derived from the compound represented by these is preferable. In the general formulas (1) and (2), R ¹ and R ² are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and This represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms. R ¹ and R ² are preferably a methylene group, an ethylene group, a propylene group, a butylene group, or a structural isomer thereof. Examples of these structural isomers include an isopropylene group and an isobutylene group. R ³ is a carbon selected from the group consisting of an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and an aromatic hydrocarbon group having 6 to 10 carbon atoms. Represents a hydrogen group. R ³ is preferably a methyl group, an ethyl group, a propyl group, a butyl group, or a structural isomer thereof. Examples of these structural isomers include isopropyl group and isobutyl group. Examples of the compounds of the general formulas (1) and (2) include 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, 5-methylol-5-ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane and the like are particularly preferable.

  In addition, the diol constituent unit other than the diol unit having a cyclic acetal skeleton is not particularly limited, but ethylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol. , Aliphatic diols such as diethylene glycol, propylene glycol and neopentyl glycol; 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,2-decahydronaphthalenediethanol, 1,3-decahydronaphthalene Methanol, 1,4-decahydronaphthalene diethanol, 1,5-decahydronaphthalene diethanol, 1,6-decahydronaphthalene diethanol, 2,7-decahydronaphthalene diethanol, tetralin dimethanol, norbornane Alicyclic diols such as methanol, tricyclodecane dimethanol and pentacyclododecane dimethanol; polyether compounds such as polyethylene glycol, polypropylene glycol and polybutylene glycol; 4,4 ′-(1-methylethylidene) bisphenol; Bisphenols such as methylene bisphenol (bisphenol F), 4,4′-cyclohexylidene bisphenol (bisphenol Z), 4,4′-sulfonylbisphenol (bisphenol S); alkylene oxide adducts of the bisphenols; hydroquinone, resorcin, Aromatic dihydroxy compounds such as 4,4′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenylbenzophenone; Alkylene oxide adducts of the diol units families dihydroxy compounds can be exemplified. Considering the mechanical strength, heat resistance, and availability of the diol of the polyester resin, diol units such as ethylene glycol, diethylene glycol, trimethylene glycol, 1,4-butanediol, and 1,4-cyclohexanedimethanol are preferable. Glycol units are particularly preferred.

  The dicarboxylic acid structural unit of the polyester resin used in the present invention is not particularly limited, but succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, cyclohexane Dicarboxylic acid, decalin dicarboxylic acid, norbornane dicarboxylic acid, tricyclodecane dicarboxylic acid, pentacyclododecanedicarboxylic acid, 3,9-bis (1,1-dimethyl-2-carboxyethyl) -2,4,8,10-tetra Aliphatic dicarboxylic acid units such as oxaspiro [5.5] undecane, 5-carboxy-5-ethyl-2- (1,1-dimethyl-2-carboxyethyl) -1,3-dioxane, dimer acid; terephthalic acid , Isophthalic acid, phthalic acid, 2-methylterephthalic acid, 1,3 For aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, biphenyldicarboxylic acid, tetralindicarboxylic acid, etc. Examples are derived units. Considering the mechanical strength and heat resistance of the polyester resin, a unit derived from an aromatic dicarboxylic acid is preferable, and considering the availability of the dicarboxylic acid, a unit derived from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid Is particularly preferred. In addition, the dicarboxylic acid structural unit of a polyester resin may be comprised from 1 type, or may be comprised from 2 or more types.

  The polyester resin has a monoalcohol unit such as butyl alcohol, hexyl alcohol, and octyl alcohol, trimethylolpropane, glycerin, 1, 3, and the like within the range not impairing the object of the present invention in order to adjust the melt viscoelasticity and molecular weight. Trihydric or higher polyhydric alcohol units such as 5-pentanetriol and pentaerythritol, monocarboxylic acid units such as benzoic acid, propionic acid and butyric acid, polycarboxylic acid units such as trimellitic acid and pyromellitic acid, glycolic acid and lactic acid Oxyacid units such as hydroxybutyric acid, 2-hydroxyisobutyric acid, and hydroxybenzoic acid may be included.

  In view of moldability, heat resistance, mechanical performance, etc., particularly in the polyester resin used in the present invention, the diol unit having a cyclic acetal skeleton is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4. , 8,10-tetraoxaspiro [5.5] undecane unit, the diol constituent unit other than the diol unit having a cyclic acetal skeleton is an ethylene glycol unit, the dicarboxylic acid constituent unit is a terephthalic acid unit, an isophthalic acid unit, And at least one dicarboxylic acid unit selected from 2,6-naphthalenedicarboxylic acid units.

  The intrinsic viscosity of the polyester resin used in the present invention can be appropriately selected according to the molding method and application. In the polyester resin used in the present invention, a range of 0.5 to 1.5 dl / g as measured at 25 ° C. using a mixed solvent of phenol and 1,1,2,2-tetrachloroethane in a mass ratio of 6: 4. More preferably, it is 0.5-1.2 dl / g, More preferably, it is 0.6-1.0 dl / g. When the intrinsic viscosity is within this range, the polyester resin used in the present invention has an excellent balance between moldability and mechanical performance.

  Although the glass transition temperature of the polyester resin used for this invention can be suitably selected according to a use, it is preferable that it is 85 degreeC or more, More preferably, it is 90 degreeC or more, Especially preferably, it is 94 degreeC or more. When the glass transition temperature is in the above range, the polyester film used in the present invention is excellent in heat resistance.

  There is no restriction | limiting in particular in the method to manufacture the polyester resin used for this invention, The conventionally well-known manufacturing method of polyester can be applied. Examples thereof include a melt polymerization method such as a transesterification method and a direct esterification method, or a solution polymerization method. In the direct esterification method, after dicarboxylic acid is esterified with a diol having no cyclic acetal skeleton, it may be necessary to react with a diol having a cyclic acetal skeleton after reducing the acid value. Various catalysts such as transesterification catalysts, esterification catalysts, polycondensation catalysts, etc., etherification inhibitors, heat stabilizers, light stabilizers, and other stabilizers, polymerization regulators, and the like that are conventionally used may be used. These can be appropriately selected according to the reaction rate, the color tone of the polyester resin, safety, thermal stability, weather resistance, self-elution properties, and the like.

  The polyester resins used in the present invention include antioxidants, light stabilizers, ultraviolet absorbers, plasticizers, extenders, matting agents, drying regulators, antistatic agents, antisettling agents, surfactants, flow improvers. Various additives such as drying oil, waxes, fillers, colorants, reinforcing agents, surface smoothing agents, leveling agents, curing reaction accelerators, thickeners, and molding aids can be added. Resin such as polyolefin resin, polyamide resin, acrylonitrile resin, vinyl chloride resin, vinyl acetate resin, acrylic resin, methacrylic resin, polystyrene, ABS resin, AS resin, polyimide resin, AS resin, polyester resin having no cyclic acetal skeleton Or these oligomers can also be added. These additives, resins, and oligomers may be added at the production stage of a polyester resin having a cyclic acetal skeleton or a polyester resin or polycarbonate resin not having a cyclic acetal skeleton to be blended, or may be added after the production. . Moreover, you may add at the time of shaping | molding.

  Next, the polyester raw film used in the present invention will be described. Examples of the method for forming the polyester resin into a film include a melt extrusion method and a casting method, but the melt extrusion method is preferable from the balance between economic efficiency and film performance.

  The melt extrusion method will be further described in detail. The polyester raw film used in the present invention can be formed using a conventionally known method. Examples of the melt extrusion method include a T-die extrusion method and an inflation method, but the T-die extrusion method is desirable from the viewpoint of obtaining an optically isotropic film. As an apparatus for melting the polyester resin, a generally used extruder may be used, and a single-screw extruder or a multi-screw extruder may be used. The extruder may have one or more vents, and may remove moisture, low-molecular substances, etc. from the molten resin by reducing the vents. Moreover, you may provide a metal-mesh filter, a sintered filter, and a gear pump as needed at the front-end | tip or downstream side of an extruder. As the die, a T die, a coat hanger die, a fish tail die, a stack plate die, or the like can be used.

  The extrusion temperature is preferably 200 to 300 ° C, more preferably 210 to 280 ° C, and particularly preferably 220 to 270 ° C. When the extrusion temperature is in the above range, the resulting polyester raw film is excellent in the balance of optical isotropy, smoothness, transparency, color tone, mechanical properties and the like.

  A conventionally known method can be used as a method for cooling the molten resin extruded from the die. In general, it can be cooled by a cooling drum. Since the polyester resin used in the present invention is a substantially amorphous resin, the temperature of the cooling drum can be set widely. In order to obtain an optically isotropic optical film, the temperature of the cooling drum is preferably 30 ° C. above and below the glass transition temperature of the polyester resin, more preferably 20 ° C. above and below the glass transition temperature of the polyester resin, particularly preferably. Is 10 ° C. above and below the glass transition temperature of the polyester resin. In order to obtain an optically isotropic optical film, it is preferable to control the discharge speed and the take-up speed according to the apparatus so that the film is not substantially stretched.

  The in-plane retardation at a wavelength of 550 nm of the polyester raw film used in the present invention is preferably 20 nm or less, more preferably 15 nm or less, still more preferably 10 nm or less, and particularly preferably 5 nm or less. When it is in the above range, it is possible to produce a retardation film in which the retardation is controlled in an arbitrary numerical range by applying the polyester raw film used in the present invention to the original film of the retardation film and applying stretching. Become.

  The thickness of the polyester raw film can be arbitrarily set according to the required specifications. The thinner the retardation film is, the better from the viewpoint of reducing the weight of the liquid crystal display device. However, the thickness of the polyester raw film is desirably 20 to 200 μm because of restrictions on the melt extruder.

  The total light transmittance of the polyester raw film used in the present invention is preferably 85% or more, more preferably 90% or more. Moreover, it is preferable that a haze is 3% or less, More preferably, it is 2% or less. When these values are in the above range, the film has sufficient performance as an original film of a retardation film used for a liquid crystal display device.

Next, the stretching method for the polyester raw film will be described in detail. The original film can be stretched by uniaxial stretching, sequential biaxial stretching, or simultaneous biaxial stretching. Stretching is performed at a temperature equal to or higher than the glass transition temperature of the resin at a stretch ratio of 2 times or less. The lower the stretching temperature, the greater the retardation, and the larger the stretching ratio, the greater the retardation. In actual stretching, the retardation is adjusted to a desired retardation by adjusting the stretching temperature and the magnification within the above range.
In the case of uniaxial stretching, the Nz coefficient (= (nx-nz) / (nx-ny), where nx and ny represent the main refractive index in the film plane, and nx> ny, nz is the normal of the film plane The retardation film is approximately 1 in size (representing the main refractive index in the direction). In the case of sequential and simultaneous biaxial stretching, the retardation film can be adjusted in the range of 1 to ∞ of the Nz coefficient. For example, in the case of a retardation film suitably used for STN mode liquid crystal, a retardation film having an Nz coefficient of about 1 and an in-plane retardation of 100 to 500 nm can be obtained by uniaxial stretching. In the case of a retardation film suitably used for a VA (Vertical Alignment) mode liquid crystal, the Nz coefficient is in the range of 1 to ∞ and the in-plane retardation is in the range of 0 to 200 nm by sequential or simultaneous biaxial stretching. It can be a phase difference film.

After stretching, heat treatment is performed. The heat treatment step may be performed continuously after stretching as a subsequent step of the stretching step, or may be performed after unfolding the stretched film that has been wound up and after a certain time after stretching. Since the heat treatment temperature and time vary depending on the stretching conditions (stretching temperature, stretching speed, etc.), it is desirable to match the actual machine. That is, in order to obtain a desired stretched film, the stretching conditions and the heat treatment conditions are changed, for example, a reliability test at 90 ° C. × 1000 hrs or 65 ° C. 95% RH × 1000 hrs is performed, and the change in retardation is within the specified range. Confirm that it is within the range, and set the conditions on the actual machine.
By carrying out what has been described above, it is possible to produce a retardation film with little retardation change due to the use environment in which the retardation is stable. The reduction rate of the in-plane retardation is preferably 3% or less under the conditions of 60 ° C., 95% RH and 1,000 hours, and 11% or less under the conditions of 90 ° C., 5% RH and 1,000 hours.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited by these examples.

<Evaluation method of polyester resin>
(1) Ratio of diol units having a cyclic acetal skeleton The ratio of diol units having a cyclic acetal skeleton in the polyester was calculated by ¹ H-NMR measurement. The measuring apparatus used JNM-AL400 by JEOL Co., Ltd., and measured it at 400 MHz. Deuterated chloroform was used as the solvent.
(2) Glass transition temperature As for the glass transition temperature of polyester, DSC / TA-50WS manufactured by Shimadzu Corporation is used, about 10 mg of polyester is put in an aluminum non-sealed container, and the temperature rising rate is 20 in a nitrogen gas (30 ml / min) stream. A sample heated and melted at 280 ° C./min to 280 ° C. was rapidly cooled to obtain a measurement sample. The sample was measured under the same conditions, and the temperature at which the difference between the baselines before and after the transition of the DSC curve changed by 1/2 was taken as the glass transition temperature.
(3) Intrinsic Viscosity For the intrinsic viscosity measurement sample, 0.5 g of polyester was dissolved in 120 g of a mixed solvent of phenol and 1,1,2,2-tetrachloroethane (mass ratio = 6: 4) by heating, filtered, and 25 ° C. Prepared by cooling to. The measurement was performed at a temperature of 25 ° C. using a capillary viscometer automatic measuring device SS-300-L1 manufactured by Shibayama Scientific Machinery Co., Ltd.
(4) Melt viscosity The melt viscosity was measured using Toyo Seiki Seisakusho, trade name: Capillograph 1C. The diameter of the capillary is 1 mm, the length is 10 mm, and the measurement conditions are a measurement temperature of 240 ° C., a preheating time of 3 minutes, and a shear rate of 100 sec ⁻¹ .

<Evaluation method of film>
(6) Thickness Measured using a digital micrometer M-30 manufactured by Sony Magnescale Co., Ltd.
(7) Retardation Incidence angle dependency of retardation was measured using a spectroscopic ellipsometer manufactured by JASCO Corporation, trade name: M-220. The value of in-plane retardation is the value at the time of normal incidence of this measurement result. The measurement wavelength was 400 nm.

Production Example 1
[Production of polyester]
The raw material monomers listed in Table 1 are charged into a 1.5 cubic meter polyester production apparatus equipped with a packed tower type rectification tower, a partial condenser, a full condenser, a cold trap, a stirrer, a heating device, and a nitrogen introduction pipe, In the presence of 0.03 mol% of manganese acetate tetrahydrate based on the acid component, the temperature was raised to 215 ° C. in a nitrogen atmosphere to conduct a transesterification reaction. After the reaction conversion rate of the dicarboxylic acid component is set to 90% or more, 0.02 mol% of antimony (III) oxide and 0.06 mol% of trimethyl phosphate are added to the dicarboxylic acid component, and the temperature and pressure are gradually increased. And finally polycondensation was performed at 270 ° C. and 0.1 kPa or less. The reaction was terminated when the melt viscosity reached an appropriate level, and polyester was produced. The evaluation results are shown in Table 1.
In addition, the meaning of the abbreviation in a table | surface is as follows.
DMT: dimethyl terephthalate EG: ethylene glycol SPG: 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane

[Manufacture of polyester film]
Using a single screw extruder (GT-32 manufactured by Plastic Engineering Laboratory Co., Ltd.) having a screw diameter of 32 mmφ with a 300 mm wide coat hanger die, the polyester of Production Example 1 has a cylinder temperature of 230 to 250 ° C., a die temperature of 250 ° C., Melt extrusion was performed at a discharge rate of 9 kg / h. The extruded molten resin was cooled with a first roll set at 90 ° C. and a second roll set at 70 ° C., and taken up at 4.5 m / min to produce a polyester raw film having a thickness of 100 μm and a width length of 270 mm.

Example 1
[Stretching of the raw film]
The polyester raw film was uniaxially stretched with a stretching machine. Drawing was carried out at a draw ratio of 1.5 times, a drawing speed of 30 mm / min, and a drawing temperature of 135 ° C. (Tg + 25 ° C.).
The number of stretched samples was 13. The evaluation results of in-plane retardation are shown in Table 3.
[Heat treatment of stretched film]
Samples (1) to (12) of the stretched film produced under the above stretching conditions were placed in a hot air dryer set at 102 ° C., heated for 120 seconds, and then taken out. Table 4 shows the evaluation results of the in-plane retardation after the heat treatment. The orientation is relaxed by heat, and the average is 0.8 times lower than the in-plane retardation after stretching.
[Reliability test of stretched heat-treated film 1]
The heat-treated films (1) to (6) were placed in an environment of 65 ° C. and 95% RH with a thermo-hygrostat, and changes in in-plane retardation were traced until 1,000 hours had passed.
The results are shown in FIG. Table 5 shows the evaluation results of in-plane retardation after 1,000 hours. The decrease in in-plane retardation was within 5 nm, and the decrease rate was within 3%.
[Reliability test of stretched heat-treated film 2]
The heat-treated films (7) to (12) were placed in an environment of 90 ° C. and 5% RH using a thermo-hygrostat, and the change in in-plane retardation was followed until 1,011 hours had passed.
The results are shown in FIG. Table 6 shows the evaluation results of the in-plane retardation after 1,011 hours. The reduction in in-plane retardation was within 15 nm, and the reduction rate was within 11%.

Comparative Example 1
As comparative examples, JSR Corporation's Arton Film (raw material is COP), ZEON Corporation's ZEONOR Film ZF14 (raw material is COP), and Teijin Chemicals' Pure Ace (raw material is PC) are stretched under the conditions shown in Table 7. did. The number of samples was 3 for each.
The stretched film was traced for in-plane retardation for 1,008 hours under the same conditions as [Reliability Test No. 1] and [Reliability Test No. 2]. The results are shown in Tables 8 and 9.
The decrease in in-plane retardation after 65 ° C. and 95% RH × 1,008 hours was within 5 nm of Arton, within 5 nm of Zeonore, and within 7 nm of Pure Ace.
The decrease in in-plane retardation after 90 ° C., 5% RH × 1,008 hours was within 9 nm of Arton, within 17 nm of Zeonore, and within 5 nm of Pure Ace. In addition, the film (sample 13) which only extended | stretched the polyester resin of the manufacture example 1 had a large fall of in-plane retardation.
Table 10 summarizes the results of the polyester film of the present invention and the comparative example. From Table 10, it can be seen that the polyester film of the present invention is equivalent to the ZEONOR film.

Table 1
Production example number Production example 1
Monomer charge amount Dicarboxylic acid component DMT (mole) 1780
Diol component SPG (mole) 818
EG (mole) 3629
Evaluation result of polyester Ratio of diol unit having cyclic acetal skeleton (mol%) 45
Glass transition temperature (° C) 110
Intrinsic viscosity (dl / g) 0.70
Melt viscosity (Pa · s) 2150

Table 2

Resin production example 1
Evaluation result of raw film Thickness (μm) 100
In-plane retardation Re (nm) 1.6

Table 3
In-plane retardation measurement after stretching

In-plane retardation Re
Sample (1) 182.34
Sample (2) 196.45
Sample (3) 182.61
Sample (4) 209.24
Sample (5) 194.64
Sample (6) 180.15
Sample (7) 157.64
Sample (8) 177.57
Sample (9) 195.91
Sample (10) 198.15
Sample (11) 183.81
Sample (12) 195.38
Sample (13) 154.19
The unit is (nm). The measurement wavelength is 400 nm.

Table 4
In-plane retardation measurement results after heat treatment

In-plane retardation Re
Sample (1) 149.12
Sample (2) 163.78
Sample (3) 150.67
Sample (4) 172.60
Sample (5) 161.94
Sample (6) 153.07
Sample (7) 125.59
Sample (8) 140.87
Sample (9) 157.06
Sample (10) 152.67
Sample (11) 152.70
Sample (12) 159.07
The unit is (nm). The measurement wavelength is 400 nm.

Table 5
In-plane retardation measurement results after reliability test (65 ° C., 95% RH × 1,000 hours)

In-plane retardation Re Difference from initial value ΔRe (decrease rate)
Sample (1) 145.98-3.14 (2.16%)
Sample (2) 160.23 -3.55 (2.22%)
Sample (3) 147.48-3.19 (2.17%)
Sample (4) 169.10-3.50 (2.07%)
Sample (5) 159.15 -2.79 (1.76%)
Sample (6) 149.86 -3.21 (2.15%)
The unit is (nm). The measurement wavelength is 400 nm.

Table 6
In-plane retardation measurement results after reliability test (90 ° C., 5% RH × 1,011 hours)

In-plane retardation Re Difference from initial value ΔRe (decrease rate)
Sample (7) 121.82 -3.77 (3.10%)
Sample (8) 132.92-7.95 (5.99%)
Sample (9) 146.06 -11.00 (7.54%)
Sample (10) 138.15-14.52 (10.52%)
Sample (11) 140.12-12.58 (8.99%)
Sample (12) 144.56-14.51 (10.04%)
The unit is (nm). The measurement wavelength is 400 nm.

Table 7
Comparative test

Stretch rate (mm / min) Stretch temperature (° C) Stretch ratio (times)
Arton 30.0 177.0 1.2
Zeonoa 30.0 142.0 1.2
Pure Ace 30.0 190.0 1.2

Table 8
Comparative test (65 ° C, 95% RH x 1,008 hours)

Initial value Re 1,008 hours later Re Difference from initial value ΔRe (Reduction rate)
Arton (1) 158.31 153.57 -4.74 (3.00%)
Arton (2) 147.50 145.06 -2.44 (1.66%)
Arton (3) 153.97 151.48 -2.49 (1.62%)
Zeonoa (1) 160.83 156.21 -4.62 (2.88%)
ZEONOR (2) 156.41 153.30-3.11 (1.99%)
ZEONOR (3) 133.01 130.53 -2.48 (1.87%)
Pure Ace (1) 161.99 158.46 -3.53 (2.18%)
Pure Ace (2) 155.61 149.11-6.50 (4.18%)
Pure Ace (3) 147.98 145.50 -2.48 (1.68%)
Production Example 1 Sample (13) 154.19 107.51 -46.68 (30.28%)
The unit is (nm). The measurement wavelength is 400 nm.

Table 9
Comparative test (90 ° C, 5% RH x 1,008 hours)

Initial value Re 1,008 hours later Re Difference from initial value ΔRe (Reduction rate)
Arton (4) 171.22 162.82 -8.40 (4.91%)
Arton (5) 171.84 165.54-6.30 (3.67%)
Arton (6) 168.56 161.13 -7.42 (4.41%)
ZEONOR (4) 187.13 171.16-15.98 (8.54%)
Zeonoa (5) 197.18 181.72-15.46 (7.85%)
ZEONOR (6) 187.83 171.10-16.73 (8.91%)
Pure Ace (4) 157.51 153.68 -3.83 (2.44%)
Pure Ace (5) 158.38 154.20 -4.18 (2.64%)
Pure Ace (6) 172.76 168.46 -4.30 (2.49%)
The unit is (nm). The measurement wavelength is 400 nm.

Table 10
Summary of differences from initial values of in-plane retardation after 1,000 hours of test

65 ° C, 95% RH 90 ° C, 5% RH
Polyester of the present invention -4-15
Arton -5 -9
Zeonore (4) -5 -17
Pure Ace (6) -7 -5
The unit is (nm). The measurement wavelength is 400 nm. Rounded down the value of the worst sample.

Change of in-plane retardation of retardation film (polyester stretch heat-treated film) according to an example of the present invention in an environment of 65 ° C. and 95% RH Change of in-plane retardation of retardation film (polyester stretched heat-treated film) according to an embodiment of the present invention in an environment of 90 ° C. and 5% RH

Claims (7)

A polyester raw film made of a polyester resin containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit is a diol unit having a cyclic acetal skeleton, is stretched, and is subjected to heat treatment after controlling the retardation. A retardation film. The diol unit having a cyclic acetal skeleton has the general formula (1):

(In the formula, R ¹ and R ² may be the same or different and are each independently an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, And a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms.)
Or general formula (2):

(In the formula, R ¹ is the same as above, R ³ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, an alicyclic hydrocarbon group having 3 to 10 carbon atoms, and 6 to 10 carbon atoms. Represents a hydrocarbon group selected from the group consisting of aromatic hydrocarbon groups of
The retardation film according to claim 1, which is a diol unit derived from a diol represented by: The diol unit having a cyclic acetal skeleton is 3,9-bis (1,1-dimethyl-2-hydroxyethyl) -2,4,8,10-tetraoxaspiro [5.5] undecane or 5-methylol-5. The retardation film according to claim 2, which is a diol unit derived from -ethyl-2- (1,1-dimethyl-2-hydroxyethyl) -1,3-dioxane. The diol unit other than the diol unit having a cyclic acetal skeleton is a diol unit derived from one or more diols selected from ethylene glycol, diethylene glycol, trimethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol. The retardation film according to claim 1. The retardation film according to claim 1, wherein the dicarboxylic acid unit is derived from one or more dicarboxylic acids selected from terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid. The reduction rate of in-plane retardation is 3% or less under the conditions of 60 ° C., 95% RH and 1,000 hours, and the reduction rate of in-plane retardation is 11 under the conditions of 90 ° C., 5% RH and 1,000 hours. The retardation film according to claim 1, which is% or less. A polyester raw film made of a polyester resin containing a dicarboxylic acid unit and a diol unit, wherein 1 to 80 mol% of the diol unit is a diol unit having a cyclic acetal skeleton is stretched, and the heat treatment is performed after controlling the retardation. A method for producing a retardation film.

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