Polyethylene naphthalate resin composition for optical member and uniaxially stretched film

Abstract

The present invention provides a polyethylene naphthalate resin composition which can be used for an optical member such as an optical film. A polyethylene naphthalate resin composition for an optical member according to the present invention contains: (A) a polyethylene naphthalate; and (B) a phosphorus compound represented by formula (I) or (II), or a salt thereof (in the formula, R1 represents an alkyl group having 1-12 carbon atoms, an aryl group having 6-12 carbon atoms, or a benzyl group, R2 and R3 represent an alkyl group having 1-12 carbon atoms, an aryl group having 6-12 carbon atoms, a benzyl group, an ethylene glycol group, or a hydrogen atom, and R1 and R2 may be bonded to form a ring).

Description

Polyethylene naphthalate resin composition for optical components and uniaxially stretched film

[0001] The present invention relates to a polyethylene naphthalate resin composition for optical members that can exhibit a high refractive index in the stretching direction when stretched, and to a uniaxially stretched film made of this resin composition.

[0002] Polyethylene naphthalate resins are widely known to have great industrial value due to their excellent mechanical properties, such as strength, elongation, Young's modulus, or elastic recovery rate, their excellent physical properties, such as heat resistance or dimensional stability, and their excellent chemical properties, such as chemical resistance or water resistance, and their low cost. Polyethylene naphthalate resins are widely used, for example, in fibers, resin molded articles, films, and the like.

[0003] However, polyethylene naphthalate resin has a rigid molecular chain and therefore has lower crystallinity than polyethylene terephthalate resin (PET), resulting in poor moldability (particularly in the blow molding of PET bottles), which makes it difficult to mold into large bottles such as Fire Extinguisher Type 20. To improve this crystallinity, it has been proposed to add a specific phosphorus compound (see, for example, Patent Documents 1 and 2).

[0004] International Publication No. 2015 / 125846 (Patent No. 6181847) JP 2008-247932 A (Patent No. 5217052)

[0005] Patent Documents 1 and 2 state that polyethylene naphthalate resin compositions containing the above-mentioned phosphorus compounds have improved blow moldability and that the resulting molded articles have excellent physical properties such as weather resistance. However, Patent Documents 1 and 2 do not consider the optical properties such as refractive index of such resin compositions, and therefore it is unclear whether such resin compositions can be used for optical components.

[0006] In contrast, the inventors have found that a polyethylene naphthalate resin composition containing a specific phosphorus compound exhibits a high refractive index in the stretching direction when a film of the resin composition is stretched, and therefore can be used for optical members such as optical films. An object of the present invention is to provide a polyethylene naphthalate resin composition that can be used for optical members such as optical films.

[0007] The present inventors have found that the above-mentioned problems can be solved by the present invention having the following aspects: <Aspect 1> A polyethylene naphthalate resin composition for optical members, comprising: (A) polyethylene naphthalate, and (B) a phosphorus compound represented by the following formula (I) or (II) or a salt thereof: (In the formula, R １ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group; R ２ and R ３ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a benzyl group, an ethylene glycol group, or a hydrogen atom; R １ and R ２may be bonded to form a ring). Aspect 2: The resin composition according to Aspect 1, wherein the amount of the phosphorus compound or a salt thereof added is 0.1 to 10,000 ppm. Aspect 3: The resin composition according to Aspect 1, wherein the phosphorus compound or a salt thereof is phenylphosphonic acid or a salt thereof, or 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or a salt thereof. Aspect 4: The resin composition according to Aspect 1, wherein the salt is at least one selected from a manganese salt, a cobalt salt, and a zinc salt, and / or the resin composition contains at least one selected from a manganese ion, a cobalt ion, and a zinc ion. Aspect 5: The resin composition according to Aspect 1, wherein a sheet of the resin composition is uniaxially stretched at a maximum stretch ratio, and the refractive index in the stretching direction of the sheet is higher than the refractive index of a sheet of a resin composition not containing the phosphorus compound or a salt thereof, and the sheet is uniaxially stretched at a maximum stretch ratio under the same conditions. Aspect 6: A uniaxially stretched film made of the resin composition according to Aspect 1. Aspect 7: The uniaxially stretched film according to Aspect 5, having a refractive index in the stretching direction of 1.80 to 1.95. Aspect 8: The uniaxially stretched film according to Aspect 5, having a degree of orientation of 94.5% or more and a crystal size of 6 nm or less.

[0008] The polyethylene naphthalate resin composition of the present invention exhibits a high refractive index in the stretching direction when stretched, making it useful for optical applications such as optical films, etc. In addition, since the birefringence is also improved, it can be suitably used for applications such as reflective polarizers and polarizing films.

[0009] The polyethylene naphthalate resin composition of the present invention (hereinafter, sometimes referred to as a PEN composition) is a composition containing (A) polyethylene naphthalate and (B) a phosphorus compound having a specific chemical structural formula or a salt thereof.

[0010] (A) Polyethylene naphthalate The polyethylene naphthalate in the PEN composition of the present invention is represented by the following formula: As shown in the figure, this is a polymer using 2,6-naphthalenedicarboxylic acid as the dicarboxylic acid component and ethylene glycol as the diol component, but other dicarboxylic acids and other diol components may be copolymerized within the range that does not impair the effects of the present invention, and the PEN composition of the present invention may also contain small amounts of polyesters composed of other dicarboxylic acids and other diol components. The amounts of dicarboxylic acid components and diol components that may be copolymerized are each independently 10 mol % or less relative to the naphthalenedicarboxylic acid component. Furthermore, the amount of polyesters composed of the dicarboxylic acids and other diol components that may be contained is 20 wt % or less relative to the weight of the PEN composition of the present invention.

[0011] Examples of other dicarboxylic acid components include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and ester-forming derivatives thereof. Specific examples of aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 1,6-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylethanedicarboxylic acid, 4,4'-diphenylpropanedicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, diphenylthioether-4,4'-dicarboxylic acid, tetralindicarboxylic acid, and 6,6'-(alkylenedioxy)di-2-naphthoic acid. Alternatively, in the case of diphenyldicarboxylic acid and the like, the substituents are not limited to the 4,4'-positions, but may be aromatic dicarboxylic acids in which the substituents are located at the 2,4'-, 3,4'-, 2,5'-, 2,2'-, 3,3'-, etc. positions.

[0012] Furthermore, the ester-forming derivatives of aromatic dicarboxylic acids refer to lower dialkyl esters having 1 to 6 carbon atoms, lower diaryl esters having 6 to 10 carbon atoms, and diacid halides. More specific examples include dimethyl esters, diethyl esters, di-n-propyl esters, di-iso-propyl esters, di-n-butyl esters, di-sec-butyl esters, di-tert-butyl esters, dipentyl esters, dihexyl esters, dioctyl esters, dinonyl esters, didecyl esters, diphenyl esters, dibenzyl esters, dinaphthyl esters of the above-mentioned dicarboxylic acids, as well as aromatic dicarboxylic acid difluorides, aromatic dicarboxylic acid dichlorides, aromatic dicarboxylic acid dibromides, and aromatic dicarboxylic acid diiodides. The dialkyl ester having 1 to 6 carbon atoms and the diaryl ester having 6 to 10 carbon atoms may further have one or more hydrogen atoms substituted with a halogen atom, an alkyl ether group, an aryl ether group, an alkyl ester group, an aryl ester group, an alkylcarbonyl group such as an acetyl group, or an arylcarbonyl group such as a benzoyl group.

[0013] Specific examples of other aliphatic dicarboxylic acid components and alicyclic dicarboxylic acid components include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosane diacid, docosane diacid, fumaric acid, maleic acid, and itaconic acid; Examples of alicyclic dicarboxylic acids include carboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, perhydronaphthalenedicarboxylic acid (decalindicarboxylic acid), dimer acid (e.g., a reaction product obtained by Diels-Alder reaction of 9,11-conjugated linoleic acid and non-conjugated linoleic acid), cyclobutanedicarboxylic acid, tetramethylcyclobutanedicarboxylic acid, tricyclodecanedicarboxylic acid, norbornanedicarboxylic acid, and adamantanedicarboxylic acid.

[0014] The other dicarboxylic acid component may be an anhydride or an ester-forming derivative as described above. It is more preferable to use one or two of these dicarboxylic acid components. Preferably, the copolymerization rate of these dicarboxylic acid components relative to the 2,6-naphthalenedicarboxylic acid component is 0 to 10 mol %, more preferably 2 to 8 mol %. Furthermore, a compound having three or more carboxyl groups in the molecule, such as trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, or tricarballylic acid, may be copolymerized in a range of 1 to 5 mol %.

[0015] Furthermore, a diol component other than the ethylene glycol component may be copolymerized in part of the ethylene glycol component constituting the polyethylene naphthalate in the PEN composition of the present invention. Preferred examples include diol components having 2 to 20 carbon atoms, and specific examples thereof include 1,2-propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, decamethylene glycol, undecamethylene glycol, dodecamethylene glycol, tridecamethylene glycol, tetradecamethylene glycol, pentadecamethylene glycol, hexadecamethylene glycol, neopentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, tetrapentylene glycol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,1-dihydroxycyclohexane, 1,2-dihydroxycyclohexane, 1,3 ... Cyclohexane, 1,4-dihydroxycyclohexane, 1,1-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethylcyclobutane-1,3-diol, p-bis(2-hydroxyethoxy)benzene, p-bis(3-hydroxypropoxy)benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, 4,4'-bis(3-hydroxypropoxy) ) biphenyl, 2,2-bis(4-β-hydroxyethoxyphenyl)propane, 2,2-bis(4-γ-hydroxypropoxyphenyl)propane, 2,2-bis(4-ω-hydroxyethoxyethoxyphenyl)propane, bis(4-β-hydroxyethoxyphenyl)sulfone, bis(4-γ-hydroxypropoxyphenyl)sulfone, bis(4-ω-hydroxyethoxyethoxyphenyl)sulfone, 2,2-bis(4-β-hydroxyethoxycycloalkyl)propane, 2,2-bis(4-γ-hydroxypropoxycycloalkyl)propane, bis(4-β-hydroxyethoxycycloalkyl)sulfone, bis(4-γ-hydroxypropoxycycloalkyl)sulfone, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, adamantanediol, spiroglycol, tricyclo[5.2.1.0, ２，６ ] decanedimethanol. It is more preferable that the other diol component besides the above two be one or two of these compounds. Furthermore, a compound having three or more hydroxyl groups in the molecule, such as pentaerythritol or tetrakis(hydroxymethyl)methane, may be copolymerized in an amount of 1 to 3 mol % when the aromatic dicarboxylic acid component is taken as 100%.

[0016] Furthermore, in the present invention, compound components other than the above-mentioned dicarboxylic acid component, diol component, compound having three or more carboxyl groups in the molecule, and compound having three or more hydroxy groups in the molecule, i.e., hydroxycarboxylic acid, may be copolymerized as necessary. Examples of hydroxycarboxylic acids include glycolic acid, lactic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, 10-hydroxystearic acid, malic acid, alcoholic acid, citramalic acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinelaideic acid, cerebronic acid, quinic acid, shikimic acid, 4-(β-hydroxy)ethoxybenzoic acid, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone. When a hydroxycarboxylic acid is copolymerized, it is preferably used in an amount of 10 mol % or less relative to the 2,6-naphthalenedicarboxylic acid component. The PEN composition of the present invention may also contain small amounts of monocarboxylic acids and monoalcohols as copolymers.

[0017] The polyethylene naphthalate in the PEN composition of the present invention can be obtained preferably by a production method in which an ester-forming derivative of a dicarboxylic acid component as described above is subjected to an ester exchange reaction with a glycol such as ethylene glycol, followed by polycondensation, or by a production method in which a dicarboxylic acid is subjected to an esterification reaction with a glycol such as ethylene glycol, followed by polycondensation.

[0018] (B) Phosphorus Compound or Salt Thereof The PEN composition of the present invention also contains a phosphorus compound represented by the following formula (I) or (II) or a salt thereof. In the above general formula (I) or (II), R １ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group; R ２ and R ３ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a benzyl group, an ethylene glycol group, or a hydrogen atom; R １ and R ２ may be bonded to form a ring.

[0019] The amount of the phosphorus compound or salt thereof added is preferably 0.1 to 10,000 ppm. The amount of the phosphorus compound or salt thereof added may be 0.1 ppm or more, 1 ppm or more, 5 ppm or more, 10 ppm or more, 50 ppm or more, or 100 ppm or more, and may be 10,000 ppm or less, 8,000 ppm or less, 6,000 ppm or less, 4,000 ppm or less, 3,000 ppm or less, or 2,000 ppm or less.

[0020] This phosphorus compound or its salt acts as a crystallization nucleating agent in the PEN composition, and is preferably added during the transesterification reaction. Addition of this phosphorus compound or its salt not only deactivates the transesterification catalyst, but also improves the crystallinity of the PEN composition and the refractive index of a film formed from this composition when stretched. On the other hand, if the amount of this phosphorus compound added is too large, the phosphorus compound may aggregate in the PEN composition of the present invention. As a result, the transparency of the PEN composition is undesirably lost.

[0021] The compound represented by formula (I) or (II) above is an organic phosphonic acid or a phosphate ester thereof, more specifically, alkylphosphonic acid, arylphosphonic acid, or benzylphosphonic acid or a phosphate ester thereof. Specific examples of the alkylphosphonic acid include methylphosphonic acid, ethylphosphonic acid, n-propylphosphonic acid, tert-butylphosphonic acid, n-pentylphosphonic acid, iso-pentylphosphonic acid, n-hexylphosphonic acid, iso-hexylphosphonic acid, heptylphosphonic acid, octylphosphonic acid, nonylphosphonic acid, decylphosphonic acid, undecylphosphonic acid, dodecylphosphonic acid, cyclohexylphosphonic acid, cyclooctylphosphonic acid, and cyclodecanephosphonic acid. Specific examples of arylphosphonic acids include phenylphosphonic acid, methylphenylphosphonic acid, dimethylphenylphosphonic acid, trimethylphenylphosphonic acid, tetramethylphenylphosphonic acid, pentamethylphenylphosphonic acid, ethylphenylphosphonic acid, methylethylphenylphosphonic acid, diethylphenylphosphonic acid, monomethyldiethylphenylphosphonic acid, dimethyldiethylphenylphosphonic acid, triethylphenylphosphonic acid, propylphenylphosphonic acid, methylpropylphenylphosphonic acid, dimethylpropylphenylphosphonic acid, ethylpropylphenylphosphonic acid, dipropylphenylphosphonic acid, butylphenylphosphonic acid, methylbutylphenylphosphonic acid, ethylbutylphenylphosphonic acid, dimethylbutylphenylphosphonic acid, pentylphenylphosphonic acid, methylpentylphenylphosphonic acid, hexylphenylphosphonic acid, naphthylphosphonic acid, methylnaphthylphosphonic acid, dimethylnaphthylphosphonic acid, ethylnaphthylphosphonic acid, and further benzylphosphonic acid. Of these compounds, compounds in which multiple aliphatic groups are bonded to a phenyl group or naphthyl group fall within the phosphorus compounds represented by general formula (I) or (II) of the present invention, regardless of the substitution positions of the aliphatic groups on the phenyl group or naphthyl group.

[0022] Specific examples of the phosphate esters of alkylphosphonic acid, arylphosphonic acid, and benzylphosphonic acid include the dimethyl ester, diethyl ester, dipropyl ester, di-n-butyl ester, di-tert-butyl ester, di-n-pentyl ester, di-iso-pentyl ester, dihexyl ester, di-iso-hexyl ester, diheptyl ester, dioctyl ester, dinonyl ester, didecyl ester, diundecyl ester, and didodecyl ester of the above alkylphosphonic acid, arylphosphonic acid, and benzylphosphonic acid. ester, dicyclohexyl ester, dicyclooctyl ester, dicyclodecane ester, diethylene glycol ester, methyl ethyl ester, methyl propyl ester, methyl-n-butyl ester, methyl-tert-butyl ester, methyl-n-pentyl ester, methyl-iso-pentyl ester, methyl hexyl ester, methyl-iso-hexyl ester, methyl heptyl ester, methyl octyl ester, methyl nonyl ester, methyl decyl ester, methyl undecyl ester, methyl dodecyl ester, methyl cyclohexyl ester xyl ester, methyl cyclooctyl ester, methyl cyclodecane ester, ethyl propyl ester, ethyl-n-butyl ester, ethyl-tert-butyl ester, ethyl-n-pentyl ester, ethyl-iso-pentyl ester, ethylhexyl ester, ethyl-iso-hexyl ester, ethylheptyl ester, ethyl octyl ester, ethyl nonyl ester, ethyl decyl ester, ethyl undecyl ester, ethyl dodecyl ester, ethyl cyclohexyl ester, ethyl cyclooctyl ester, ethyl cyclodecane ester, propyl-n-butyl ester, propyl-tert-butyl ester, propyl-n-pentyl ester, propyl-iso-pentyl ester, propyl hexyl ester, propyl-iso-hexyl ester, propylheptyl ester, propyl octyl ester, propyl nonyl ester, propyl decyl ester, propyl undecyl ester, propyl dodecyl ester, propyl cyclohexyl ester, propyl cyclooctyl ester, propyl cyclodecane ester, n-butyl-tert-butyl ester,n-Butyl n-pentyl ester, n-butyl-iso-pentyl ester, n-butylhexyl ester, n-butyl-iso-hexyl ester, n-butylheptyl ester, n-butyloctyl ester, n-butylnonyl ester, n-butyldecyl ester, n-butylundecyl ester, n-butyldodecyl ester, n-butylcyclohexyl ester, n-butylcyclooctyl ester, n-butylcyclodecane ester, tert-butyl n-pentyl ester, tert-butyl-iso-pentyl ester, tert-butyl n-butylhexyl ester, tert-butyl-iso-hexyl ester, tert-butylheptyl ester, tert-butyloctyl ester, tert-butylnonyl ester, tert-butyldecyl ester, tert-butylundecyl ester, tert-butyldodecyl ester, tert-butylcyclohexyl ester, tert-butylcyclooctyl ester, tert-butylcyclodecane ester, n-pentyl-iso-pentyl ester, n-pentylhexyl ester, n-pentyl-iso-hexyl ester, n- Pentylheptyl ester, n-pentyloctyl ester, n-pentylnonyl ester, n-pentyldecyl ester, n-pentylundecyl ester, n-pentyldodecyl ester, n-pentylcyclohexyl ester, n-pentylcyclooctyl ester, n-pentylcyclodecane ester, iso-pentylhexyl ester, iso-pentyl-iso-hexyl ester, iso-pentylheptyl ester, iso-pentyloctyl ester, iso-pentylnonyl ester, iso-pentyldecyl ester, iso- Pentyl undecyl ester, iso-pentyl dodecyl ester, iso-pentyl cyclohexyl ester, iso-pentyl cyclooctyl ester, iso-pentyl cyclodecane ester, hexyl-iso-hexyl ester, hexyl heptyl ester, hexyl octyl ester, hexyl nonyl ester, hexyl decyl ester, hexyl undecyl ester, hexyl dodecyl ester, hexyl cyclohexyl ester, hexyl cyclooctyl ester, hexyl cyclodecane ester, iso-hexyl heptyl ester,iso-Hexyl octyl ester, iso-Hexyl nonyl ester, iso-Hexyl decyl ester, iso-Hexyl undecyl ester, iso-Hexyl dodecyl ester, iso-Hexyl cyclohexyl ester, iso-Hexyl cyclooctyl ester, iso-Hexyl cyclodecane ester, heptyl octyl ester, heptyl nonyl ester, heptyl decyl ester, heptyl undecyl ester, heptyl dodecyl ester, heptyl cyclohexyl ester, heptyl cyclooctyl ester, heptyl cyclodecane ester, octyl nonyl ester, octyl decyl ester, octyl undecyl ester, octyl dodecyl ester, octyl cyclohexyl ester, octyl cyclooctyl ester, octyl cyclodecane ester, nonyl decyl ester, nonyl undecyl ester Examples of such esters include esters, nonyl dodecyl esters, nonyl cyclohexyl esters, nonyl cyclooctyl esters, nonyl cyclodecane esters, decyl undecyl esters, decyl dodecyl esters, decyl cyclohexyl esters, decyl cyclooctyl esters, decyl cyclodecane esters, undecyl dodecyl esters, undecyl cyclohexyl esters, undecyl cyclooctyl esters, undecyl cyclodecane esters, dodecyl cyclohexyl esters, dodecyl cyclooctyl esters, dodecyl cyclodecane esters, cyclohexyl cyclooctyl esters, cyclohexyl cyclodecane esters, cyclooctyl cyclodecane esters, diphenyl esters, dinaphthyl esters, dibenzyl esters, phenyl naphthyl esters, phenyl benzyl esters, and naphthyl benzyl esters.

[0023] The compound represented by the formula (II) is an organic phosphinic acid or its phosphate ester, and more specifically, alkylphosphinic acid, arylphosphinic acid, or benzylphosphinic acid, or their phosphate esters. Examples of alkylphosphinic acid, arylphosphinic acid, and benzylphosphinic acid include compounds in which the phosphonic acid moiety of the phosphonic acid compounds listed above is replaced with phosphinic acid. Specific examples of the phosphate esters of alkylphosphinic acids, arylphosphinic acids, and benzylphosphinic acids include the methyl esters, ethyl esters, n-propyl esters, n-butyl esters, tert-butyl esters, n-pentyl esters, iso-pentyl esters, n-hexyl esters, iso-hexyl esters, heptyl esters, octyl esters, nonyl esters, decyl esters, undecyl esters, dodecyl esters, cyclohexyl esters, cyclooctyl esters, cyclodecane esters, ethylene glycol esters, phenyl esters, naphthyl esters, and benzyl esters of the above alkylphosphinic acids, arylphosphinic acids, and benzylphosphinic acids. Another example is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0024] The compound represented by formula (I) or (II) above may be a salt thereof, and the salt is preferably at least one selected from manganese salts, cobalt salts, and zinc salts.

[0025] The PEN composition of the present invention preferably contains at least one ion selected from manganese ions, cobalt ions, and zinc ions, which can be obtained by adding a compound containing such ions, such as manganese acetate tetrahydrate, cobalt acetate tetrahydrate, or zinc acetate dihydrate.

[0026] These manganese ions, cobalt ions, and zinc ions function as catalysts for the transesterification of polyethylene naphthalate. The content of at least one selected from manganese ions, cobalt ions, and zinc ions is preferably 10 to 50 mmol% per mole of the dicarboxylic acid component constituting the polyethylene naphthalate. If this content is less than 10 mmol%, the effect is not exhibited, while if it exceeds 50 mmol%, the hue may become grayish, resulting in deterioration of the hue. This content is more preferably 15 to 45 mmol%, even more preferably 18 to 40 mmol%, and particularly preferably 20 to 35 mmol%.

[0027] The sheet formed from the PEN composition of the present invention is characterized in that the refractive index in the stretching direction of the sheet stretched at the maximum uniaxial stretching ratio is higher than the refractive index of a sheet formed from a resin composition not containing the phosphorus compound or a salt thereof stretched at the maximum uniaxial stretching ratio under the same conditions. Here, the maximum uniaxial stretching ratio means the stretching ratio at which the sheet is uniaxially stretched immediately before it breaks.

[0028] Therefore, the present invention also relates to a uniaxially stretched film formed by uniaxially stretching the above-mentioned PEN composition. The uniaxially stretched film of the present invention preferably has a refractive index in the stretching direction of 1.80 to 1.95, more preferably 1.85 to 1.95.

[0029] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples as long as it does not depart from the gist of the invention. The film-forming conditions and stretching conditions of the obtained polyethylene naphthalate resin composition film, as well as the measurement of various physical properties, were carried out by the following methods. In the following, the term "parts" refers to "parts by weight" unless otherwise specified.

[0030] (a) Film-forming conditions: Chips of the PEN composition were dried at 160°C for 5 hours to remove moisture before film formation. Film formation was carried out at a film-forming temperature of 285 to 300°C, with the thickness of the resulting sheet adjusted to about 200 µm, to obtain an unstretched sheet.

[0031] (b) Stretching conditions Stretching was performed at a stretching temperature of 140° C. and a stretching speed of 2.1 m / min. The sheet was stretched until just before breaking, and the stretching ratio was calculated from the elongation of marks made at 1 cm intervals before stretching.

[0032] (c) Refractive Index The refractive index of the stretched film was measured using a Metricon Prism Coupler Model 2010 with a laser wavelength of 633 nm.

[0033] (d) Intrinsic Viscosity A PEN composition was dissolved in a mixed solvent of phenol / tetrachloroethane (60 / 40 weight ratio) to prepare a solution with a polymer concentration of 1.2 g / dL, and the intrinsic viscosity was determined by measuring at 35°C.

[0034] (e) Glass transition temperature (Tg) Tg was measured using a differential scanning calorimeter (DSC) while increasing the temperature at a rate of 20°C / min. Approximately 10 mg of the measurement sample was weighed into an aluminum pan (manufactured by TA Instruments) and the measurement was performed under a nitrogen atmosphere.

[0035] (f) Degree of Orientation After stretching, the film was subjected to WAXD (wide-angle X-ray diffraction) measurement, and the degree of orientation was calculated from the measurement results in through view using the half-width Wh of the orientation peak at a diffraction angle 2θ = 15.3° as follows: degree of orientation = (180 - Wh) / 180 × 100. An orientation degree of 94.5% or more is preferred from the viewpoint of improving the refractive index in the stretching direction, since it increases the crystallinity due to molecular orientation.

[0036] (g) Crystal size: WAXD (wide-angle X-ray diffraction) measurement was performed on the stretched film, and the crystal size was calculated from the peak at a diffraction angle 2θ = 15.3° from the measurement results in thru view using the following Schuller formula. A crystal size of 6 nm or less is preferable from the viewpoint of suppressing light scattering and uniformly improving the refractive index. Schuller formula: D = Kλ / BCosθ, where D: crystal size, K: Schuller constant (0.94), λ: wavelength of X-ray (154.2 nm), B: half-width of peak, θ: Bragg angle

[0037] Example 1 100 parts of 2,6-naphthalenedicarboxylic acid dimethyl ester (hereinafter sometimes abbreviated as NDC) and 51 parts of ethylene glycol (hereinafter sometimes abbreviated as EG) were charged into a reaction vessel, and a transesterification reaction was initiated using manganese acetate tetrahydrate as a transesterification catalyst in a total amount of 30 mmol% relative to the number of moles of NDC. 20 minutes after the start of the transesterification reaction and the distillation of methanol, a polymerization catalyst, antimony trioxide was added in a total amount of 20 mmol% relative to the number of moles of NDC, and the transesterification reaction was continued. Thereafter, approximately 1 hour later, phenylphosphonic acid was added in a total amount of 40 mmol% (260 ppm) relative to the number of moles of NDC to terminate the transesterification reaction. Subsequently, a polycondensation reaction was carried out at high temperature and under high vacuum, and the polymer was then withdrawn from the reaction vessel and chipped.

[0038] The resulting polyethylene-2,6-naphthalate composition was subjected to film formation to obtain an unstretched sheet. The intrinsic viscosity of the resulting unstretched sheet was 0.55 dL / g. Stretching was then carried out to obtain a stretched film. The refractive index of the resulting stretched film was measured, and the results are shown in Table 1.

[0039] Example 2 Chips were produced in the same manner as in Example 1, except that HCA (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide represented by the following chemical formula) was added in a total amount of 150 mmol% (1268 ppm) relative to the number of moles of NDC instead of phenylphosphonic acid, and an unstretched sheet was obtained by film formation. The intrinsic viscosity of the unstretched sheet obtained was 0.60 dL / g. Stretching was then carried out to obtain a stretched film. The refractive index of the stretched film obtained was measured, and the results are shown in Table 1.

[0040] [Comparative Example 1] Chips were produced in the same manner as in Example 1, except that 40 mmol% of phenylphosphonic acid was replaced with 50 mmol% (200 ppm) of orthophosphoric acid, and an unstretched sheet was obtained by film formation. The intrinsic viscosity of the unstretched sheet obtained was 0.51 dL / g. Stretching was then performed to obtain a stretched film. The refractive index of the stretched film obtained was measured, and the results are shown in Table 1.

[0041] [Comparative Example 2] Chips were produced in the same manner as in Comparative Example 1, except that TPP (triphenyl phosphate represented by the chemical formula below) was added in a total amount of 500 mmol% (4536 ppm) relative to the moles of NDC instead of orthophosphoric acid, and an unstretched sheet was obtained by film formation. The intrinsic viscosity of the obtained unstretched sheet was 0.58 dL / g. Then, stretching was performed to obtain a stretched film. The refractive index of the obtained stretched film was measured, and the results are shown in Table 1.

[0042]

Claims

1. A polyethylene naphthalate resin composition for an optical member, comprising: (A) polyethylene naphthalate, and (B) a phosphorus compound represented by the following formula (I) or (II) or a salt thereof: (In the formula, R １ represents an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a benzyl group, and R ２ and R ３ represent an alkyl group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a benzyl group, an ethylene glycol group, or a hydrogen atom, and R １ and R ２ may be bonded to form a ring).

2. The resin composition according to claim 1, wherein the addition amount of the phosphorus compound or a salt thereof is 0.1 to 10,000 ppm.

3. The resin composition according to claim 1, wherein the phosphorus compound or a salt thereof is phenylphosphonic acid or a salt thereof, or 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide or a salt thereof.

4. The resin composition according to claim 1, wherein the salt is at least one selected from manganese salts, cobalt salts, and zinc salts, and / or the resin composition contains at least one selected from manganese ions, cobalt ions, and zinc ions.

5. The resin composition according to claim 1, wherein the refractive index in the stretching direction of the sheet obtained by stretching the sheet of the resin composition at the maximum uniaxial stretching ratio is higher than the refractive index of the sheet obtained by stretching the sheet of the resin composition without adding the phosphorus compound or a salt thereof at the maximum uniaxial stretching ratio under the same conditions.

6. A uniaxially stretched film composed of the resin composition according to claim 1.

7. The uniaxially stretched film according to claim 5, wherein the refractive index in the stretching direction is 1.80 to 1.

95.

8. The uniaxially stretched film according to claim 5, wherein the degree of orientation is 94.5% or more and the crystal size is 6 nm or less.

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