JP2013234249A - Copolyester and optical sheet comprising the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a copolyester having excellent heat resistance, chemical resistance and further a high refractive index and low birefringence, and a sheet comprising the polyester.SOLUTION: A copolyester comprises an acid component comprising 65-75 mol% of a naphthalene dicarboxylic acid unit and 35-25 mol% of a terephthalic acid unit, and a diol component comprising an ethylene glycol unit, and further includes cobalt and manganese as elements derived from compounds used as a catalyst, phosphorus as an element derived from a compound used as a stabilizer, and germanium derived from a catalyst, where the contents satisfy specific four numerical expressions simultaneously.

Description

  The present invention relates to a transparent resin having low birefringence and excellent heat resistance and chemical resistance. The copolymer polyester obtained in the present invention can be suitably used for touch panel members such as smartphones.

  In recent years, research and development using a resin having excellent transparency such as acrylic and polycarbonate as a touch panel material typified by a smartphone has been vigorously conducted. In addition to heat resistance, transparency, and chemical resistance, low birefringence is also required for touch panel members of smartphones that have recently become widespread. However, acrylic and polycarbonate resins are excellent in transparency but low in chemical resistance, so touching them with a soiled hand with food oil may contaminate the touch panel part and impair the function as an optical member (for example, patent documents) 1-3.) In addition, in the case of a polycarbonate resin, birefringence increases due to molecular orientation that occurs during molding, so that the function as an optical component may be impaired. Furthermore, since the drive unit that generates heat is miniaturized as the electronic equipment is reduced in size and weight, optical parts are also required to have heat resistance, but acrylic resin is insufficient in heat resistance. On the other hand, although the polyester resin which has heat resistance and chemical resistance is manufactured, since compatibility is low, it is inferior in transparency (for example, refer patent documents 4-5), and the copolymerization ratio is not optimal. There exists a problem that birefringence becomes large (for example, refer patent documents 6-7).

JP 2008-152120 A JP 2010-230832 A JP 2008-163194 A Japanese Patent No. 3616522 Japanese Patent Laid-Open No. 08-309833 Japanese Patent No. 3267902 JP-A-10-245433

  The present invention has been achieved as a result of investigations to solve the above-mentioned problems of the prior art, and has excellent heat resistance, chemical resistance, and further, a copolyester having high refractive index and low birefringence, and It aims at providing the sheet | seat which consists of it.

The present inventor has intensively studied to solve such problems. As a result, the acid component is composed of 65 to 75 mol% naphthalenedicarboxylic acid units and 35 to 25 mol% terephthalic acid units, and the diol component is ethylene. A copolymer polyester comprising glycol units, comprising a cobalt element, a manganese element, a phosphorus element, and a germanium element, and a content of the copolymer polyester that simultaneously satisfies the following formulas (1) to (4) and a sheet comprising the same The present invention has been found.
2 ≦ Co ≦ 20 mmol% (1)
10 ≦ Mn ≦ 60 mmol% (2)
0.7 ≦ P / (Co + Mn) ≦ 1.5 (3)
30 ≦ Ge ≦ 50 mmol% (4)
[However, each element of Co, Mn, P and Ge in the above formula represents the content with respect to the acid component constituting the copolymer polyester. ]

  Since the copolymerized polyester of the present invention is excellent in heat resistance, transparency, chemical resistance, high refractive index and low birefringence, it can be suitably used for touch panel members such as smartphones.

  As polyester of this invention, an acid component contains 65-75 mol% of naphthalene dicarboxylic acid units, and 35-25 mol% of terephthalic acid units. When the terephthalic acid unit exceeds 35 mol%, the heat resistance is lowered, which is not preferable. Further, if the terephthalic acid unit is less than 25 mol%, the birefringence of the copolymer polyester of the present invention is increased, so that it cannot be used for an optical member. More preferably, the copolymerization rate ranges from 68 to 75 mol% for naphthalenedicarboxylic acid units and from 32 to 25 mol% for terephthalic acid units, and more preferably from 70 to 75 mol% for naphthalenedicarboxylic acid units and 30 for terephthalic acid units. ~ 25 mol%. The naphthalenedicarboxylic acid unit is preferably a 2,6-naphthalenedicarboxylic acid unit. In addition, the other dicarboxylic acid component may be copolymerized in the range which does not inhibit the effect which this invention show | plays. Examples of such dicarboxylic acid components include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, decalin dicarboxylic acid, isophthalic acid. Acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylthioetherdicarboxylic acid, benzophenonedicarboxylic acid And diphenylsulfone dicarboxylic acid, benzophenone dicarboxylic acid, diphenylmethane dicarboxylic acid, and diphenoxyethane dicarboxylic acid. In addition, the derivative | guide_body which has these ester formation property may be sufficient, Specifically, they are the C1-C6 dialkyl ester, diphenyl ester, and dicarboxylic acid halide (dicarboxylic acid halide) of dicarboxylic acid.

  In the present invention, an ethylene glycol unit is used as a glycol component, and a part of the ethylene glycol unit is, for example, 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, Triethylene glycol, 1,4-dihydroxycyclohexane, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, p- (2-hydroxyethoxy) benzene, 4,4 ′-(2-hydroxyethoxy) biphenyl, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis (4′-β-hydroxyethoxyphenyl) sulfonic acid, bis (4′-β-hydroxyethoxyethoxyphenyl) The two other in a range of less than 10% by weight substituted with one or more functional compounds may be a copolymer made to copolymers such as a sulfonic acid. Furthermore, compounds having three or more ester-forming functional groups such as trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, tricarballylic acid, pentaerythritol, tetrakis (hydroxymethyl) methane, or methanol, ethanol, hexanol, octanol , Decanol, dodecanol, phenol, naphthol, caproic acid, caprylic acid, caproic acid, lauric acid, myristic acid, palmitic acid, stearic acid, benzoic acid, naphthoic acid, biphenyl monocarboxylic acid, etc. A small amount of the compound may be copolymerized.

  When the copolymerized polyester of the present invention is polymerized by the transesterification method, it is preferable that the acid component is a lower dialkyl ester of naphthalenedicarboxylic acid (specifically, 2,6-naphthalenedicarboxylic acid dimethyl ester) and a lower dialkyl of terephthalic acid. The total amount of the acid component constituting the copolyester of the present invention, preferably the total amount of the dicarboxylic acid component constituting the copolyester of the present invention, in the ester (specifically dimethyl terephthalate) and the glycol component ethylene glycol It is necessary that the cobalt compound is contained so as to contain 2 to 20 mmol% of cobalt element and the manganese compound is contained so as to contain 10 to 60 mmol% of manganese element. The cobalt compound and the manganese compound are preferably added as a transesterification catalyst, but may be added as an antioxidant, a hue stabilizer or other stabilizer.

  Here, one of the purposes of adding the cobalt compound is to suppress yellowing of the copolyester, which is a cause of the deterioration of the hue, in addition to the effect of the transesterification reaction catalyst. If the addition amount is less than 2 mmol%, this effect is not exhibited, and if it exceeds 20 mmol%, the hue becomes gray and the hue deteriorates, which is not preferable. More preferably, the above content is added in the range of 2.5 to 15 mmol%. When the total amount of the manganese compound exceeds 60 mmol%, when the manganese compound is added as a transesterification catalyst, a whitening phenomenon is observed during molding due to the influence of the precipitated particles due to the catalyst residue, and transparency is impaired. . Conversely, if it is less than 10 mmol%, not only the transesterification reaction becomes insufficient, but also the subsequent polymerization reaction becomes slow, which is not preferable. More preferably, the above content is added in the range of 20 to 50 mmol%.

  Further, a phosphorus compound is added to deactivate the transesterification catalyst. It is necessary that the addition amount (molar ratio) of the phosphorus compound be in the range of 0.7 to 1.5 with respect to the total addition amount of the cobalt compound and the manganese compound. That is, it is necessary to satisfy 0.7 ≦ P / (Co + Mn) ≦ 1.5. If this molar ratio is less than 0.7, the transesterification catalyst is not completely deactivated, the thermal stability is poor, and the copolyester is colored due to the influence, and there is a disadvantage that brings about a decrease in physical properties at the time of molding. . Conversely, if it exceeds 1.5, the thermal stability of the copolyester may be inferior, which is not preferable. More preferably, it is adding so that said ratio may be set to 1.0-1.4.

  The manganese compound and cobalt compound used in the present invention can be used as, for example, halides such as oxides and chlorides, carbonates and carboxylates. Among these, it is preferable to add acetate, that is, a manganese compound as manganese acetate and a cobalt compound as cobalt acetate.

  Examples of the phosphorus compound include trimethyl phosphate, triethyl phosphate, tributyl phosphate (including all cases where the butyl group is n-butyl, sec-butyl or t-butyl group; the same shall apply hereinafter), trihexyl phosphate, tris (2 -Ethylhexyl) phosphate, triphenyl phosphate, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dihexyl phosphate, bis (2-ethylhexyl) phosphate, diphenyl phosphate, monomethyl phosphate, monoethyl phosphate, monobutyl phosphate, monohexyl phosphate, mono (2 -Ethylhexyl) phosphate, monophenyl phosphate, monomethyl phosphinic acid, monoethyl phosphinic acid, monobutyl phosphate Acid, monohexylphosphinic acid, mono (2-ethylhexyl) phosphinic acid, monophenylphosphinic acid, monomethylphosphonic acid, monoethylphosphonic acid, monobutylphosphonic acid, monohexylphosphonic acid, mono (2-ethylhexyl) phosphonic acid, Monophenylphosphonic acid, carbomethoxymethanephosphonic acid, carboethoxymethanephosphonic acid, carbopropoxymethanephosphonic acid, carboptoxymethanephosphonic acid, carbomethoxy-phosphono-phenylacetic acid, carboethoxy-phosphono-phenylacetic acid, carboprotoxy- Phosphono-phenylacetic acid and carbobutoxy-phosphono-phenylacetic acid, or dimethyl, diethyl, dipropyl and dibutyl esters of these carboalkoxyphosphonic acids Others can be given a positive phosphoric acid or phosphorous acid. Trimethyl phosphate is preferred.

  Furthermore, the copolymerized polyester of the present invention needs to contain a germanium compound so as to contain 30 to 50 mmol% of germanium element with respect to the acid component constituting the copolymerized polyester. This germanium compound is preferably added as a polymerization reaction catalyst for the copolyester. More preferably, the polymerization reaction catalyst is amorphous germanium dioxide from the viewpoint of hue. If the amount of germanium dioxide added is less than 30 mmol%, the polymerization reactivity is low and the productivity is poor. More preferably, the above content is added in the range of 32 to 40 mmol%. The germanium dioxide as described above is preferably added as a liquid dispersed or dissolved in ethylene glycol having a concentration of 0.5 to 5% by weight.

  As for the addition timing of the above-mentioned various catalysts and stabilizers, it is preferable to add all of the cobalt compound and manganese compound during the beginning of the transesterification reaction. On the other hand, a phosphorus compound can be added until the intrinsic viscosity reaches 0.3 dL / g after the transesterification reaction is substantially completed. The germanium compound is added more than 10 minutes before the phosphorus compound is added until the intrinsic viscosity reaches 0.2 dL / g.

  In the above, an example of producing a copolyester by a so-called transesterification method has been given, but by an esterification method using a corresponding dicarboxylic acid, that is, naphthalenedicarboxylic acid and terephthalic acid as a dicarboxylic acid component, and ethylene glycol as a diol component. Similarly, when the copolymerized polyester of the present invention is polymerized, if the content of each element described above satisfies a predetermined mathematical formula, it goes without saying that the present invention falls within the scope of the present invention.

In the copolymerized polyester of the present invention, the intrinsic viscosity [η] of the copolymerized polyester obtained by melt polymerization preferably satisfies the following formula (5) from the viewpoint of mechanical properties.
0.55 dL / g ≦ [η] ≦ 0.95 dL / g (5)
If the intrinsic viscosity is lower than 0.55 dL / g, the mechanical strength is inferior. If it is higher than 0.95 dL / g, it may not be able to be extruded from the polymerization kettle, and the molding fluidity is lowered and the molding processability is inferior. If it is strong, the hue will deteriorate. More preferably, the intrinsic viscosity [η] of the copolyester is 0.60 to 0.85 dL / g.

  The glass transition temperature of the copolyester obtained by the present invention is preferably 100 ° C. or higher from the viewpoint of the physical properties of the molded product. If the glass transition temperature is 100 ° C. or lower, the heat resistance of the molded product is inferior, which is not preferable. In order to make the glass transition temperature within the range of this value, the range of the glass transition temperature can be achieved by the copolymerization rate at the time of producing the copolyester. More preferably, the glass transition temperature of the copolyester is 103 ° C. or higher. The deflection temperature under a load of 1.80 MPa of the copolyester obtained by the present invention is preferably 80 ° C. or higher from the viewpoint of the physical properties of the molded product. If the deflection temperature under load is 80 ° C. or lower, the heat resistance of the molded product is inferior, which is not preferable. In order to make the deflection temperature under this range of values, this range of the deflection temperature under load can be achieved by the copolymerization rate when producing the copolyester. More preferably, the deflection temperature under a load of 1.80 MPa of the copolyester is 81 ° C. or higher.

  The sheet or film made of the copolymerized polyester in the present invention is formed by any method such as an injection molding method, a compression molding method, an injection compression molding method, or an extrusion molding method. The refractive index of light at 25 ° C. and a wavelength of 589 nm of the sheet or film formed from the copolymerized polyester in the present invention is preferably 1.625 to 1.635. This range of refractive index values can be achieved by the copolymerization rate of polyethylene naphthalate and polyethylene terephthalate described above. More preferably, the refractive index of light at 25 ° C. and a wavelength of 589 nm of the sheet or film made of the copolyester is 1.627 to 1.633. The sheet formed from the copolyester in the present invention preferably has a total light transmittance of 80% or more. Further, it is preferably 85% or more. If the total light transmittance is lower than 80%, it is difficult to use as a sheet. Depending on the copolymerization rate of polyethylene naphthalate and polyethylene terephthalate, this range of transmittance values can be achieved. More preferably, the total light transmittance of a sheet of 1 mm thickness made of copolymerized polyester is 85% or more. Moreover, it is preferable that the sheet | seat of this invention has a small optical distortion. A sheet made of general naphthalenedicarboxylic acid type polyester has a large optical distortion, and it may be possible to reduce the value depending on molding conditions. However, the range of conditions is usually very small, and therefore molding is very difficult. Have difficulty. On the other hand, the copolymerized polyester of the present invention has a small optical strain caused by the orientation of the resin and a small molding strain. Therefore, a good optical element can be obtained without setting molding conditions strictly.

  A coating layer such as an antireflection layer or a hard coating layer may be provided on the surface of the sheet formed from the copolyester according to the present invention, if necessary. The antireflection layer may be a single layer or a multilayer, and may be organic or inorganic, but is preferably inorganic. Specific examples include oxides or fluorides such as silicon oxide, aluminum oxide, zirconium oxide, titanium oxide, cerium oxide, magnesium oxide, and magnesium fluoride.

  The present invention will be described more specifically with reference to the following examples. Various physical properties of the copolyester were analyzed and evaluated by the following methods.

(A) Intrinsic viscosity ([η]):
The copolymer polyester sample was measured at 35 ° C. from a solution using a mixed solvent of tetrachloroethane: phenol = 4: 6.

(A) ¹ H-NMR spectrum measurement:
The copolymerization rate in the copolymerized polyester obtained by the present invention was calculated by measuring a ¹ H-NMR spectrum at 600 MHz using JEOLA-600 manufactured by JEOL.

(C) Glass transition temperature (Tg) measurement:
The copolymer polyester dried under reduced pressure at 25 ° C. for 24 hours was measured using a differential scanning calorimeter (DSC) while increasing the temperature at a temperature increase rate of 10 ° C./min. About 10 mg of a measurement sample was weighed in an aluminum pan (TA Instruments) and measured under a nitrogen atmosphere.

(D) Col-b (hue):
The copolymer polyester obtained according to the present invention was heat-treated in a nitrogen atmosphere at 170 ° C. for 3 hours, and then measured with a CM-7500 type color machine manufactured by Color Machine Co., Ltd.

(E) Content of each element in the copolyester:
It measured by the usual method from the molded article of copolyester by the fluorescent X ray (Rigaku make, Rataflex RU200).

(F) Deflection temperature under load:
The copolymer polyester obtained according to the present invention was measured according to the method of ISO 75.

(G) Refractive index:
The film formed from the copolymerized polyester was measured for refractive index in the thickness direction using an Abbe refractometer manufactured by ATAGO DR-M2.

(H) Total light transmittance:
Using a MDH-300A manufactured by Nippon Denshoku Co., Ltd., the total light transmittance in the thickness direction of the 1 mm thick molded piece was measured.

(K) Birefringence (optical distortion):
A lens molded from the copolyester was sandwiched between two polarizing plates and evaluated by visually observing light leakage from behind using a direct Nicol method. The evaluation was as follows: ○: almost no light leakage, x: light leakage was remarkable.

(K) Chemical resistance test:
The obtained copolyester chip was injection-molded to obtain a flat molded product having a thickness of 3 mm. When the molded product was immersed in acetone at 23 ° C. for 48 hours, it was confirmed whether or not the appearance of the molded product was changed. The case where no change in appearance (whitening, swelling, etc.) was observed was marked with ◯, and the case where it was not, was marked with ×.

[Example 1]
75 parts by weight of 2,6-naphthalenedicarboxylic acid dimethyl ester (hereinafter abbreviated as NDC), 25 parts by weight of dimethyl terephthalate (hereinafter abbreviated as DMT), ethylene glycol (hereinafter abbreviated as EG) 53 parts by weight of cobalt acetate tetrahydrate (hereinafter may be abbreviated as Co) in a total amount of 6 mmol% with respect to the number of moles of divalent dicarboxylic acid, manganese acetate tetrahydrate (hereinafter, , Mn may be abbreviated as amorphous germanium dioxide (hereinafter abbreviated as Ge) by transesterification using 30 mmol% as a transesterification catalyst as a total amount with respect to the number of moles of divalent dicarboxylic acid. After adding 35 mmol% of the 1% EG solution to the total number of moles of divalent dicarboxylic acid, 5 minutes later Sufeto was allowed terminated added transesterification 33 mmol% as the total amount with respect to the number of moles of divalent dicarboxylic acid (hereinafter, sometimes abbreviated as P). Next, a polycondensation reaction was subsequently performed under high temperature and high vacuum, and then a strand-type chip was formed by a chip cutter. The intrinsic viscosity of the obtained copolyester was 0.63 dL / g. In addition, Table 1 and Table 2 show the copolyester quality and the evaluation results obtained.

[Example 2, Comparative Examples 1 to 5]
Table 1 shows the amounts and ratios of 2,6-naphthalenedicarboxylic acid dimethyl ester, dimethyl terephthalate, cobalt acetate tetrahydrate, manganese acetate tetrahydrate, trimethyl phosphate, amorphous germanium dioxide, and antimony trioxide. The procedure was basically the same as in Example 1 except that the change was made. Moreover, these obtained copolyester quality and each evaluation result are also shown in Table 1 and Table 2.

  The copolymerized polyester obtained by the present invention is excellent in heat resistance, transparency, chemical resistance, and also has a high refractive index and low birefringence, and therefore is suitably used for touch panel members such as smartphones and tablets (computers). Can do. Therefore, it is a very significant invention in the entire industry related to the optical sheet, but it is very significant particularly in the business of personal computers and portable electronic terminals.

Claims (6)

A copolyester having an acid component of 65 to 75 mol% naphthalenedicarboxylic acid units and 35 to 25 mol% of terephthalic acid units, and a diol component of ethylene glycol units, cobalt element, manganese element, phosphorus element and germanium A copolyester containing an element, the content of which simultaneously satisfies the following formulas (1) to (4).
2 ≦ Co ≦ 20 mmol% (1)
10 ≦ Mn ≦ 60 mmol% (2)
0.7 ≦ P / (Co + Mn) ≦ 1.5 (3)
30 ≦ Ge ≦ 50 mmol% (4)
[However, each element of Co, Mn, P and Ge in the above formula represents the content with respect to the acid component constituting the copolymer polyester. ] The copolyester obtained by melt polymerization, wherein the intrinsic viscosity ([η]) satisfies the following formula (5) and the glass transition temperature is 100 to 110 ° C.
0.55 dL / g ≦ [η] ≦ 0.95 dL / g (5)   A sheet formed by molding the copolymerized polyester according to claim 1 or 2.   The sheet according to claim 3, wherein the refractive index of the copolyester is 1.625 to 1.635.   The sheet according to any one of claims 3 to 4, wherein the copolyester has a total light transmittance of 80% or more.   The sheet according to any one of claims 3 to 5, wherein the deflection temperature under load of the copolyester is 80 ° C or higher.