JP2018063437A - White polyester film for liquid crystal display - Google Patents
White polyester film for liquid crystal display Download PDFInfo
- Publication number
- JP2018063437A JP2018063437A JP2017221636A JP2017221636A JP2018063437A JP 2018063437 A JP2018063437 A JP 2018063437A JP 2017221636 A JP2017221636 A JP 2017221636A JP 2017221636 A JP2017221636 A JP 2017221636A JP 2018063437 A JP2018063437 A JP 2018063437A
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- JP
- Japan
- Prior art keywords
- film
- layer
- polyester
- liquid crystal
- mass
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- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Links
- 229920006267 polyester film Polymers 0.000 title claims abstract description 53
- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 41
- -1 polyethylene terephthalate Polymers 0.000 claims abstract description 47
- 229920000728 polyester Polymers 0.000 claims abstract description 45
- 229920005989 resin Polymers 0.000 claims abstract description 33
- 239000011347 resin Substances 0.000 claims abstract description 33
- 229920000139 polyethylene terephthalate Polymers 0.000 claims abstract description 32
- 239000005020 polyethylene terephthalate Substances 0.000 claims abstract description 32
- 230000000930 thermomechanical effect Effects 0.000 claims abstract description 12
- 238000004458 analytical method Methods 0.000 claims abstract description 10
- 229920001634 Copolyester Polymers 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims description 28
- 229920001577 copolymer Polymers 0.000 claims description 27
- QQVIHTHCMHWDBS-UHFFFAOYSA-N isophthalic acid Chemical compound OC(=O)C1=CC=CC(C(O)=O)=C1 QQVIHTHCMHWDBS-UHFFFAOYSA-N 0.000 claims description 12
- 229920001707 polybutylene terephthalate Polymers 0.000 claims description 7
- ORLQHILJRHBSAY-UHFFFAOYSA-N [1-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1(CO)CCCCC1 ORLQHILJRHBSAY-UHFFFAOYSA-N 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 229920000874 polytetramethylene terephthalate Polymers 0.000 claims description 3
- 239000000203 mixture Substances 0.000 abstract description 8
- 239000010410 layer Substances 0.000 description 62
- 238000000034 method Methods 0.000 description 20
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 15
- 239000000523 sample Substances 0.000 description 13
- 239000002245 particle Substances 0.000 description 12
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 10
- 239000010954 inorganic particle Substances 0.000 description 10
- 238000005259 measurement Methods 0.000 description 10
- 230000009477 glass transition Effects 0.000 description 9
- 238000009998 heat setting Methods 0.000 description 9
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 8
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 8
- 230000005484 gravity Effects 0.000 description 8
- 238000011156 evaluation Methods 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
- 230000008859 change Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 229920005672 polyolefin resin Polymers 0.000 description 6
- YIMQCDZDWXUDCA-UHFFFAOYSA-N [4-(hydroxymethyl)cyclohexyl]methanol Chemical compound OCC1CCC(CO)CC1 YIMQCDZDWXUDCA-UHFFFAOYSA-N 0.000 description 5
- 238000007334 copolymerization reaction Methods 0.000 description 5
- 150000001925 cycloalkenes Chemical group 0.000 description 5
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 5
- 229920001225 polyester resin Polymers 0.000 description 5
- 239000004645 polyester resin Substances 0.000 description 5
- 238000002310 reflectometry Methods 0.000 description 5
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 239000000377 silicon dioxide Substances 0.000 description 4
- 235000012239 silicon dioxide Nutrition 0.000 description 4
- 239000004408 titanium dioxide Substances 0.000 description 4
- 239000011800 void material Substances 0.000 description 4
- BYEAHWXPCBROCE-UHFFFAOYSA-N 1,1,1,3,3,3-hexafluoropropan-2-ol Chemical compound FC(F)(F)C(O)C(F)(F)F BYEAHWXPCBROCE-UHFFFAOYSA-N 0.000 description 3
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 230000007774 longterm Effects 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 230000008018 melting Effects 0.000 description 3
- 230000000704 physical effect Effects 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 229920000642 polymer Polymers 0.000 description 3
- 230000008569 process Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- BJZYYSAMLOBSDY-QMMMGPOBSA-N (2s)-2-butoxybutan-1-ol Chemical compound CCCCO[C@@H](CC)CO BJZYYSAMLOBSDY-QMMMGPOBSA-N 0.000 description 2
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 description 2
- VGGSQFUCUMXWEO-UHFFFAOYSA-N Ethene Chemical compound C=C VGGSQFUCUMXWEO-UHFFFAOYSA-N 0.000 description 2
- 239000005977 Ethylene Substances 0.000 description 2
- OFOBLEOULBTSOW-UHFFFAOYSA-N Malonic acid Chemical compound OC(=O)CC(O)=O OFOBLEOULBTSOW-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000002202 Polyethylene glycol Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 description 2
- HEDRZPFGACZZDS-MICDWDOJSA-N Trichloro(2H)methane Chemical compound [2H]C(Cl)(Cl)Cl HEDRZPFGACZZDS-MICDWDOJSA-N 0.000 description 2
- 239000005083 Zinc sulfide Substances 0.000 description 2
- 150000001336 alkenes Chemical group 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 150000002009 diols Chemical class 0.000 description 2
- 239000002270 dispersing agent Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 2
- CKFGINPQOCXMAZ-UHFFFAOYSA-N methanediol Chemical compound OCO CKFGINPQOCXMAZ-UHFFFAOYSA-N 0.000 description 2
- 239000012046 mixed solvent Substances 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 229920001083 polybutene Polymers 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920000306 polymethylpentene Polymers 0.000 description 2
- 239000011116 polymethylpentene Substances 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 239000006228 supernatant Substances 0.000 description 2
- 239000011787 zinc oxide Substances 0.000 description 2
- 229910052984 zinc sulfide Inorganic materials 0.000 description 2
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 2
- WKBPZYKAUNRMKP-UHFFFAOYSA-N 1-[2-(2,4-dichlorophenyl)pentyl]1,2,4-triazole Chemical compound C=1C=C(Cl)C=C(Cl)C=1C(CCC)CN1C=NC=N1 WKBPZYKAUNRMKP-UHFFFAOYSA-N 0.000 description 1
- WSQZNZLOZXSBHA-UHFFFAOYSA-N 3,8-dioxabicyclo[8.2.2]tetradeca-1(12),10,13-triene-2,9-dione Chemical compound O=C1OCCCCOC(=O)C2=CC=C1C=C2 WSQZNZLOZXSBHA-UHFFFAOYSA-N 0.000 description 1
- RMDKEBZUCHXUER-UHFFFAOYSA-N 4-methylbicyclo[2.2.1]hept-2-ene Chemical group C1CC2C=CC1(C)C2 RMDKEBZUCHXUER-UHFFFAOYSA-N 0.000 description 1
- 239000004925 Acrylic resin Substances 0.000 description 1
- 229920000089 Cyclic olefin copolymer Polymers 0.000 description 1
- 239000004713 Cyclic olefin copolymer Substances 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- 238000005481 NMR spectroscopy Methods 0.000 description 1
- 239000004734 Polyphenylene sulfide Substances 0.000 description 1
- 229910000004 White lead Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 150000007933 aliphatic carboxylic acids Chemical class 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 239000002216 antistatic agent Substances 0.000 description 1
- 238000000149 argon plasma sintering Methods 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 238000004581 coalescence Methods 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000001938 differential scanning calorimetry curve Methods 0.000 description 1
- 230000008034 disappearance Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 239000000806 elastomer Substances 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 235000019256 formaldehyde Nutrition 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- RYZCLUQMCYZBJQ-UHFFFAOYSA-H lead(2+);dicarbonate;dihydroxide Chemical compound [OH-].[OH-].[Pb+2].[Pb+2].[Pb+2].[O-]C([O-])=O.[O-]C([O-])=O RYZCLUQMCYZBJQ-UHFFFAOYSA-H 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- KYTZHLUVELPASH-UHFFFAOYSA-N naphthalene-1,2-dicarboxylic acid Chemical compound C1=CC=CC2=C(C(O)=O)C(C(=O)O)=CC=C21 KYTZHLUVELPASH-UHFFFAOYSA-N 0.000 description 1
- 238000000655 nuclear magnetic resonance spectrum Methods 0.000 description 1
- JRZJOMJEPLMPRA-UHFFFAOYSA-N olefin Natural products CCCCCCCC=C JRZJOMJEPLMPRA-UHFFFAOYSA-N 0.000 description 1
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- XNGIFLGASWRNHJ-UHFFFAOYSA-L phthalate(2-) Chemical compound [O-]C(=O)C1=CC=CC=C1C([O-])=O XNGIFLGASWRNHJ-UHFFFAOYSA-L 0.000 description 1
- 229920003207 poly(ethylene-2,6-naphthalate) Polymers 0.000 description 1
- 229920006350 polyacrylonitrile resin Polymers 0.000 description 1
- 229920005668 polycarbonate resin Polymers 0.000 description 1
- 239000004431 polycarbonate resin Substances 0.000 description 1
- 239000011112 polyethylene naphthalate Substances 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920000069 polyphenylene sulfide Polymers 0.000 description 1
- 229920005990 polystyrene resin Polymers 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000013074 reference sample Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000002040 relaxant effect Effects 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 239000000454 talc Substances 0.000 description 1
- 229910052623 talc Inorganic materials 0.000 description 1
- KKEYFWRCBNTPAC-UHFFFAOYSA-L terephthalate(2-) Chemical compound [O-]C(=O)C1=CC=C(C([O-])=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-L 0.000 description 1
- 229920006346 thermoplastic polyester elastomer Polymers 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
- 229910001928 zirconium oxide Inorganic materials 0.000 description 1
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
- B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B27/00—Layered products comprising a layer of synthetic resin
- B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
- B32B27/20—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents
- B32B27/205—Layered products comprising a layer of synthetic resin characterised by the use of special additives using fillers, pigments, thixotroping agents the fillers creating voids or cavities, e.g. by stretching
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0205—Diffusing elements; Afocal elements characterised by the diffusing properties
- G02B5/0236—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element
- G02B5/0247—Diffusing elements; Afocal elements characterised by the diffusing properties the diffusion taking place within the volume of the element by means of voids or pores
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/02—Diffusing elements; Afocal elements
- G02B5/0273—Diffusing elements; Afocal elements characterized by the use
- G02B5/0284—Diffusing elements; Afocal elements characterized by the use used in reflection
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
- G02F1/1333—Constructional arrangements; Manufacturing methods
- G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
- G02F1/1336—Illuminating devices
- G02F1/133602—Direct backlight
- G02F1/133605—Direct backlight including specially adapted reflectors
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2250/00—Layers arrangement
- B32B2250/24—All layers being polymeric
- B32B2250/244—All polymers belonging to those covered by group B32B27/36
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/40—Properties of the layers or laminate having particular optical properties
- B32B2307/416—Reflective
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2307/00—Properties of the layers or laminate
- B32B2307/50—Properties of the layers or laminate having particular mechanical properties
- B32B2307/514—Oriented
- B32B2307/518—Oriented bi-axially
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2457/00—Electrical equipment
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B32—LAYERED PRODUCTS
- B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B32B2457/00—Electrical equipment
- B32B2457/20—Displays, e.g. liquid crystal displays, plasma displays
- B32B2457/202—LCD, i.e. liquid crystal displays
Landscapes
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- General Physics & Mathematics (AREA)
- Nonlinear Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Chemical & Material Sciences (AREA)
- Mathematical Physics (AREA)
- Laminated Bodies (AREA)
- Optical Elements Other Than Lenses (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
- Liquid Crystal (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Manufacture Of Macromolecular Shaped Articles (AREA)
Abstract
Description
本発明は、液晶ディスプレイ用としての使用に好適な白色ポリエステルフィルムに関する。画像表示用のバックライト装置およびランプリフレクターの反射シートに好適に使用され、特に画像表示用のバックライト装置の反射板に好適に使用することができる白色ポリエステルフィルムに関するものである。 The present invention relates to a white polyester film suitable for use as a liquid crystal display. The present invention relates to a white polyester film which can be suitably used for a backlight device for image display and a reflection sheet of a lamp reflector, and particularly suitable for a reflector of a backlight device for image display.
液晶ディスプレイ等に用いられる平面型画像表示方式における、面光源装置の反射板および反射シート、照明看板の背面反射シート、太陽電池の背面反射シートなどの用途に、白色ポリエステルフィルムが、均一で高い輝度、熱寸法安定性、安価である等の特性から広く用いられている。 A white polyester film has a uniform and high brightness for applications such as reflectors and reflectors for surface light source devices, back reflector sheets for lighting signs, and back reflector sheets for solar cells in flat image display systems used in liquid crystal displays, etc. It is widely used because of its characteristics such as thermal dimensional stability and low cost.
液晶テレビ、パソコン用の液晶ディスプレイ装置では、小型化や高性能化、液晶ディスプレイのバックライトに使用されている光源(例えば、LED)の発熱量の増大によって、装置内での発熱量が増加し、長時間バックライトを使用していると、白色フィルムが波打つように変形し、画面にムラが生じる現象が明らかになった。特に最近では液晶ディスプレイのサイズが大きくなり、波打ち現象や画面ムラが大きな問題になってきている。 In liquid crystal display devices for liquid crystal televisions and personal computers, the amount of heat generated in the device increases due to downsizing, high performance, and an increase in the amount of heat generated by the light source (for example, LED) used in the backlight of the liquid crystal display. When the backlight was used for a long time, the phenomenon that the white film was deformed to wave and the screen was uneven was clarified. In particular, recently, the size of liquid crystal displays has increased, and the wavy phenomenon and screen unevenness have become major problems.
高い輝度を発現する方法として、ポリエステルフィルム中に例えば硫酸バリウムなどの無機粒子を多数含有し、ポリエステル樹脂と粒子の界面および、粒子を核として生成する微細な空洞の空洞界面での光反射を利用する方法(特許文献1参照)、ポリエステルと非相溶な樹脂を混合することにより、非相溶な樹脂を核として生成する微細な空洞の空洞界面での光反射を利用する方法(特許文献2参照)、圧力容器中で不活性ガスをポリエステルフィルムに含浸させることで、内部に生成した空洞の界面での光反射を利用する方法(特許文献3参照)等、ポリエステルフィルム中に含有された無機粒子とポリエステル樹脂の屈折率差および微細な空洞とポリエステル樹脂の屈折率差を利用した方法が広く用いられている。 As a method to achieve high brightness, polyester film contains many inorganic particles such as barium sulfate, and uses light reflection at the interface between the polyester resin and the particles and the hollow interface of the fine cavities generated using the particles as nuclei. (Refer to Patent Document 1), a method of utilizing light reflection at the cavity interface of fine cavities generated by mixing an incompatible resin with polyester and using an incompatible resin as a nucleus (Patent Document 2) Inorganic contained in the polyester film, such as a method utilizing light reflection at the interface of the cavity formed inside by impregnating the polyester film with an inert gas in a pressure vessel (see Patent Document 3) A method using a difference in refractive index between particles and polyester resin and a difference in refractive index between fine voids and polyester resin is widely used.
また、大型TVでの初期の画面ムラを低減させる検討として、フィルムの長手方向、幅方向の光線透過率のバラつきを下げる方法(特許文献4参照)、表面に無機粒子を含有させ光沢度を下げる方法が検討されている(特許文献5参照)。 In addition, as a study to reduce initial screen unevenness in a large TV, a method of reducing the variation in light transmittance in the longitudinal direction and the width direction of the film (see Patent Document 4), and the surface contains inorganic particles to reduce the glossiness. A method has been studied (see Patent Document 5).
しかしながら、これらの方法では、見かけ比重が軽くなる傾向があり、クッション性や絶縁性などが高く、単位面積当たりのコスト面でも有利である反面、熱寸法安定性に劣ることが多く、特に内部が高温となりやすいLEDバックライトを用いた大型TVを長時間使用した場合、フィルムが波打ち、画面ムラとなる問題があるために薄型化には限界がある。 However, these methods tend to reduce the apparent specific gravity, have high cushioning properties and insulation properties, and are advantageous in terms of cost per unit area, but are often inferior in thermal dimensional stability. When a large TV using an LED backlight that tends to become high temperature is used for a long time, there is a limit to reducing the thickness because there is a problem that the film undulates and the screen becomes uneven.
本発明では、液晶ディスプレイ内部、特にLEDバックライトを用いた液晶ディスプレイ内部での使用によって生じるフィルムの波打ち現象や画面ムラを改善する。これによって長期の使用中、高い反射性能を維持することを目的とする。 In the present invention, the wavy phenomenon of the film and the screen unevenness caused by the use in the liquid crystal display, particularly in the liquid crystal display using the LED backlight are improved. This aims at maintaining high reflection performance during long-term use.
上記課題を解決する本発明の白色ポリエステルフィルムは、以下の構成を有する。すなわち、
(A)
実質的に空洞を含有しないA層と空洞を含有するB層との少なくとも2層を有する白色ポリエステルフィルムであって、該白色ポリエステルフィルムが、下記の(1)〜(4)の要件を満たす液晶ディスプレイ用白色ポリエステルフィルム、
(1)B層はポリエステルに非相溶樹脂を含有し気泡を有すること、
(2)B層がポリエチレンテレフタレートを基本構成とし、少なくとも1種類以上の共重合ポリエステルを含有し、共重合ポリエステルがB層質量に対して1.0質量%以上20.0質量%以下であること、
(3)フィルムの見かけ密度が0.5g/cm3以上1.1g/cm3以下であること、
(4)フィルムの長手方向、および幅方向の40℃から100℃での熱機械分析にて計測される熱収縮率が−0.5%以上0.0%以下であること、
(B)
ポリエステルB層のポリエステルに非相溶樹脂の含有量がB層質量に対して5質量%以上25質量%以下である、(A)に記載の液晶ディスプレイ用白色ポリエステルフィルム、
(C)
少なくとも一方の表面の波長560nmでの相対反射率が97.0%以上であることを特徴とする(A)または(B)に記載の液晶ディスプレイ用白色ポリエステルフィルム、
(D)
該白色ポリエステルフィルムの全厚みが50μm以上500μm以下であることを特徴とする(A)〜(C)のいずれかに記載の液晶ディスプレイ用白色ポリエステルフィルム、
(E)
B層を構成するポリエステルがポリエチレンテレフタレートを基本構成とし、ポリエチレンテレフタレートとイソフタル酸との共重合体、ポリエチレンテレフタレートとシクロヘキサンジメタノールとの共重合体、ポリブチレンテレフタレートとポリテトラメチレンテレフタレートとの共重合体から選ばれる、少なくとも2種類以上の共重合ポリエステルを含有することを特徴とする(A)〜(D)のいずれかに記載の液晶ディスプレイ用白色ポリエステルフィルム、
(F)
ポリエステルとポリエステルに非相溶な成分を含有するフィルムを二軸延伸し、フィルム内に空洞を発生せしめた後、100〜200℃で5〜50秒熱処理することにより得られる(A)〜(E)のいずれかに記載の液晶ディスプレイ用白色ポリエステルフィルム、
(G)
(A)〜(F)のいずれかに記載の液晶ディスプレイ用白色ポリエステルフィルムを光反射材として用いることを特徴とする液晶ディスプレイ用バックライト、
(H)
バックライトの光源がLED方式であることを特徴とする(G)に記載の液晶ディスプレイ用バックライト、
である。
The white polyester film of the present invention that solves the above problems has the following configuration. That is,
(A)
A white polyester film having at least two layers of an A layer substantially free of voids and a B layer containing voids, wherein the white polyester film satisfies the following requirements (1) to (4) White polyester film for display,
(1) Layer B contains incompatible resin in polyester and has bubbles,
(2) The B layer has polyethylene terephthalate as a basic structure, contains at least one copolymer polyester, and the copolymer polyester is 1.0% by mass or more and 20.0% by mass or less based on the mass of the B layer. ,
(3) The apparent density of the film is 0.5 g / cm 3 or more and 1.1 g / cm 3 or less,
(4) The thermal shrinkage rate measured by thermomechanical analysis at 40 ° C. to 100 ° C. in the longitudinal direction and the width direction of the film is −0.5% or more and 0.0% or less,
(B)
The white polyester film for liquid crystal display according to (A), wherein the content of the incompatible resin in the polyester of the polyester B layer is 5% by mass or more and 25% by mass or less with respect to the mass of the B layer,
(C)
The white polyester film for liquid crystal display according to (A) or (B), wherein the relative reflectance at a wavelength of 560 nm of at least one surface is 97.0% or more,
(D)
The white polyester film for liquid crystal display according to any one of (A) to (C), wherein the total thickness of the white polyester film is 50 μm or more and 500 μm or less,
(E)
The polyester constituting the B layer is based on polyethylene terephthalate, a copolymer of polyethylene terephthalate and isophthalic acid, a copolymer of polyethylene terephthalate and cyclohexanedimethanol, a copolymer of polybutylene terephthalate and polytetramethylene terephthalate A white polyester film for a liquid crystal display according to any one of (A) to (D), which contains at least two types of copolyesters selected from:
(F)
(A) to (E) obtained by biaxially stretching a polyester and a polyester-containing film containing a component incompatible with the polyester and generating a cavity in the film, followed by heat treatment at 100 to 200 ° C. for 5 to 50 seconds. ) White polyester film for liquid crystal display according to any one of
(G)
A backlight for a liquid crystal display, wherein the white polyester film for a liquid crystal display according to any one of (A) to (F) is used as a light reflecting material;
(H)
The backlight for the liquid crystal display according to (G), wherein the light source of the backlight is an LED system,
It is.
本発明によれば、液晶ディスプレイ内部、特にLEDバックライトを用いた液晶ディスプレイ内部での使用によって生じるフィルムの波打ち現象や画面ムラを改善することができる。これによって長期の使用中、高い反射性能を維持することができる。 ADVANTAGE OF THE INVENTION According to this invention, the wavy phenomenon and screen nonuniformity of a film which arise by use inside a liquid crystal display, especially the inside of a liquid crystal display using LED backlight can be improved. Accordingly, high reflection performance can be maintained during long-term use.
本発明の白色ポリエステルフィルムは、ポリエステルで構成された実質的に空洞を含有しないA層と空洞を含有するB層との少なくとも2層を有する白色ポリエステルフィルムである。 The white polyester film of the present invention is a white polyester film having at least two layers of an A layer made of polyester and substantially free of voids and a B layer containing voids.
[A層]
本発明において、A層は実質的に気泡を含有しない。実質的に気泡を含有しないとは、空隙率が10%未満である層の状態をいい、A層とB層の厚みは、断面を電子顕微鏡観察し、表面から実質的に気泡が含有されていない断面方向深さまでの厚みとして求まり、実質的に気泡が含有されていない層の厚みをA層厚みとし、気泡(空洞)を含有する層の厚みをB層厚みとする。
[A layer]
In the present invention, the A layer contains substantially no bubbles. The term “substantially containing no bubbles” means a state of a layer having a porosity of less than 10%, and the thicknesses of the A layer and the B layer are substantially free of bubbles from the surface by observing a cross section with an electron microscope. The thickness up to the depth in the cross-sectional direction is determined, and the thickness of the layer containing substantially no bubbles is defined as the A layer thickness, and the thickness of the layer containing bubbles (cavities) is defined as the B layer thickness.
A層はポリエステルに無機粒子を含有させることが好ましく、光を散乱させる役割がある。また、背面への光漏洩を防ぐ役割、製膜を安定化させる支持層の役割がある。 The A layer preferably contains polyester with inorganic particles and has a role of scattering light. In addition, it has a role of preventing light leakage to the back surface and a role of a support layer for stabilizing film formation.
A層の光散乱性は主に表面粗さを制御することにより調整することができ、他の方法としては、例えば、ポリエステル樹脂に屈折率の異なる粒子を添加する方法が挙げられる。 The light scattering property of the A layer can be adjusted mainly by controlling the surface roughness. As another method, for example, a method of adding particles having different refractive indexes to a polyester resin can be mentioned.
ここで、A層に含有させる無機微粒子の種類としては、特に限定されるものではないがモース硬度3.0以上であることが好ましく、例えば炭酸カルシウム、二酸化チタン、酸化亜鉛、二酸化珪素、硫化亜鉛、硫酸バリウム、アルミナ、タルクなどが挙げられる。これらの無機粒子は、光沢度調整や白色度調整、耐光性付与などといった表面機能の付与の必要性に応じて、単独で、あるいは組み合わせて使用することができる。 Here, the kind of inorganic fine particles to be contained in the A layer is not particularly limited, but preferably has a Mohs hardness of 3.0 or more, for example, calcium carbonate, titanium dioxide, zinc oxide, silicon dioxide, zinc sulfide. , Barium sulfate, alumina, talc and the like. These inorganic particles can be used alone or in combination depending on the necessity of imparting surface functions such as glossiness adjustment, whiteness adjustment, and light resistance.
本発明においてA層およびB層を構成する樹脂はポリエステルである。特に、ポリエチレンテレフタレート、ポリエチレンナフタレートが好ましい。 In the present invention, the resin constituting the A layer and the B layer is polyester. In particular, polyethylene terephthalate and polyethylene naphthalate are preferable.
また、このポリエステルの中には、公知の各種添加剤、例えば、酸化防止剤、帯電防止剤などが添加されていても良い。 In addition, various known additives such as an antioxidant and an antistatic agent may be added to the polyester.
[B層]
B層はフィルム内部に微細な気泡を含有することによって白色化されている。微細な気泡の形成は、フィルム母材、たとえばポリエステル中に、ポリエステルとは非相溶なポリマー(非相溶樹脂)を細かく分散させ、それを延伸(たとえば二軸延伸)することにより達成できる。
[B layer]
The B layer is whitened by containing fine bubbles inside the film. Formation of fine bubbles can be achieved by finely dispersing a polymer (incompatible resin) incompatible with polyester in a film base material, for example, polyester, and stretching (for example, biaxial stretching).
[非相溶樹脂]
本発明において、B層にはポリエステルに非相溶な樹脂を含有することが必要である。ポリエステルに非相溶な樹脂(以下、非相溶樹脂と略すことがある)としては、単独重合体であっても共重合体であってもよく、ポリエチレン、ポリプロピレン、ポリブテン、ポリメチルペンテンなどのポリオレフィン樹脂、環状ポリオレフィン樹脂、ポリスチレン樹脂、ポリアクリレート樹脂、ポリカーボネート樹脂、ポリアクリロニトリル樹脂、ポリフェニレンスルフィド樹脂、フッ素樹脂などが好適に用いられる。これらは2種以上を併用してもよい。特にポリエステルとの臨界表面張力差が大きく、延伸後の熱処理によって変形しにくい樹脂が好ましく、具体的には、ポリオレフィン系樹脂が好ましい。ポリオレフィン系樹脂としては、ポリエチレン、ポリプロピレン、ポリブテン、ポリメチルペンテンなどのポリオレフィン樹脂、環状ポリオレフィン樹脂、および、これらの共重合体を挙げることができる。これらの中でも特に環状オレフィン共重合体であるエチレンとビシクロアルケンの共重合体が好ましい。
また、非相溶樹脂のガラス転移温度は、180℃以上220℃以下が好ましく、更に好ましくは、190℃以上220℃以下である。ガラス転移温度については、ガラス転移温度が180℃よりも低い領域では、フィルム製造工程における熱処理工程において、延伸時に発現したボイドが変形し、潰れてしまうことがあるためである。特に、微分散し小径化したボイドでは小さな変形がボイド消失の原因となり、白色ポリエステルフィルムの反射率の低下、ひいては、輝度の低下に影響を与えることがある。また、220℃よりも高い領域では、B層を構成する樹脂と溶融混練する際、十分に非相溶樹脂が融解せずに微分散化が促進されないことがあるためである。
[Incompatible resin]
In the present invention, the B layer needs to contain a resin incompatible with the polyester. As a resin incompatible with polyester (hereinafter sometimes abbreviated as incompatible resin), it may be a homopolymer or a copolymer, such as polyethylene, polypropylene, polybutene, polymethylpentene, etc. A polyolefin resin, a cyclic polyolefin resin, a polystyrene resin, a polyacrylate resin, a polycarbonate resin, a polyacrylonitrile resin, a polyphenylene sulfide resin, a fluorine resin, or the like is preferably used. Two or more of these may be used in combination. In particular, a resin having a large difference in critical surface tension from polyester and being hardly deformed by heat treatment after stretching is preferable, and specifically, a polyolefin-based resin is preferable. Examples of the polyolefin resin include polyolefin resins such as polyethylene, polypropylene, polybutene, and polymethylpentene, cyclic polyolefin resins, and copolymers thereof. Among these, a copolymer of ethylene and bicycloalkene, which is a cyclic olefin copolymer, is particularly preferable.
The glass transition temperature of the incompatible resin is preferably 180 ° C. or higher and 220 ° C. or lower, and more preferably 190 ° C. or higher and 220 ° C. or lower. Regarding the glass transition temperature, in the region where the glass transition temperature is lower than 180 ° C., voids developed during stretching may be deformed and crushed in the heat treatment process in the film manufacturing process. In particular, in a finely dispersed void with a reduced diameter, small deformation causes void disappearance, which may affect a decrease in the reflectance of the white polyester film, and thus a decrease in luminance. Further, in the region higher than 220 ° C., when melt kneading with the resin constituting the B layer, the incompatible resin is not sufficiently melted and fine dispersion may not be promoted.
ガラス転移点は非晶質固体材料にガラス転移が起きる温度であり、Tgと略記する。本発明においてTgの測定は、DSC曲線におけるベースラインの接線及びガラス転移による吸熱領域の急峻な下降位置の接線との交点とを読みとる。 The glass transition point is a temperature at which glass transition occurs in an amorphous solid material, and is abbreviated as Tg. In the present invention, Tg is measured by reading the tangent of the base line in the DSC curve and the intersection of the tangent of the steeply descending position of the endothermic region due to glass transition.
Tgを制御する方法は、直鎖のオレフィン部(エチレン部)とシクロオレフィン部(メチルーノルボルネン部)の共重合比率を制御することによって、任意に変更することができ、Tgを上げるためには、シクロオレフィンの比率をあげることによって達成できる。直鎖オレフィン部:シクロオレフィン部=3:7よりもシクロオレフィン部の比率をさらに上げることで185℃以上とすることができる。 The method for controlling Tg can be arbitrarily changed by controlling the copolymerization ratio of the linear olefin part (ethylene part) and cycloolefin part (methyl-norbornene part). It can be achieved by increasing the ratio of cycloolefin. It can be set to 185 degreeC or more by further raising the ratio of a cycloolefin part rather than a linear olefin part: cycloolefin part = 3: 7.
Tgが上記の範囲にあると、熱処理時にボイドが消失しにくくなる効果がある他、延伸時にボイドを発現させる際に核となるシクロオレフィンの剛性が高く、ボイド生成率が格段に上がるため良好である。ボイドを微細に多重に積層することができることによって反射率の向上ひいては、輝度向上に有効である。 If Tg is in the above range, voids are less likely to disappear during heat treatment, and the rigidity of cycloolefin, which is a nucleus when expressing voids during stretching, is high, and the void generation rate is significantly increased. is there. Since voids can be finely stacked in multiple layers, it is effective in improving reflectivity and thus in luminance.
非相溶樹脂を含有することにより、延伸時に非相溶樹脂を核とした空洞が生まれ、この空洞界面により光反射が起きる。 By containing the incompatible resin, a cavity having the incompatible resin as a nucleus is formed at the time of stretching, and light reflection occurs at the cavity interface.
本発明において、B層中に含有させる非相溶樹脂の好ましい含有量は5質量%以上25質量%以下である。これは、非相溶樹脂の含有量を増やすことで空洞数が増えるため、比重は低下する。見かけ比重が0.5g/cm3以上1.1g/cm3以下とする上で好ましい。 In this invention, preferable content of the incompatible resin contained in B layer is 5 mass% or more and 25 mass% or less. Since the number of cavities increases by increasing the content of the incompatible resin, the specific gravity decreases. It is preferable when the apparent specific gravity is 0.5 g / cm 3 or more and 1.1 g / cm 3 or less.
本発明において、B層中に含有させる非相溶樹脂は、ポリエステル樹脂からなるマトリックス中に数平均粒径が0.4μm以上3.0μm以下で分散していることが、適切な反射界面数、フィルム強度を得る上で好ましく、さらに好ましくは0.5μm以上1.5μm以下の範囲である。ここでいう数平均粒径とは、フィルムの幅方向(TD)の断面を切り出し、その断面のB層部分を日立製作所製走査型電子顕微鏡(FE−SEM)S−2100A形を用いて観測される粒子100個の面積を求め、真円に換算した際の直径の平均値である。 In the present invention, the incompatible resin to be contained in the B layer is dispersed in a matrix composed of a polyester resin with a number average particle size of 0.4 μm or more and 3.0 μm or less. It is preferable for obtaining film strength, and more preferably in the range of 0.5 μm or more and 1.5 μm or less. The number average particle size referred to here is a cross section of the film in the width direction (TD), and the B layer portion of the cross section is observed using a scanning electron microscope (FE-SEM) S-2100A manufactured by Hitachi, Ltd. It is the average value of the diameter when the area of 100 particles is calculated and converted into a perfect circle.
本発明において、B層中に無機粒子を含有させてもよく、例えば炭酸カルシウム、二酸化チタン、酸化亜鉛、酸化ジルコニウム、硫化亜鉛、塩基性炭酸鉛(鉛白)、硫酸バリウムなどが挙げられるが、これらの中で、400〜700nmの可視光域において吸収の少ない炭酸カルシウム、硫酸バリウム、二酸化チタンなどが反射特性や隠蔽性、製造コスト等の観点で好ましい。本発明において、フィルムの巻取り性、長時間の製膜安定性、反射特性向上の観点から、硫酸バリウム、二酸化チタンが最も好ましい。無機粒子の粒径としては、数平均粒径で0.1μm以上3.0μm以下のものを使用することが優れた反射性、隠蔽性を実現する上で好適である。 In the present invention, inorganic particles may be contained in the B layer, and examples thereof include calcium carbonate, titanium dioxide, zinc oxide, zirconium oxide, zinc sulfide, basic lead carbonate (lead white), and barium sulfate. Among these, calcium carbonate, barium sulfate, titanium dioxide, and the like that absorb less in the visible light region of 400 to 700 nm are preferable from the viewpoints of reflection characteristics, concealability, manufacturing cost, and the like. In the present invention, barium sulfate and titanium dioxide are the most preferable from the viewpoints of rollability of the film, long-term film-forming stability, and improved reflection characteristics. As the particle size of the inorganic particles, it is preferable to use particles having a number average particle size of 0.1 μm or more and 3.0 μm or less in order to realize excellent reflectivity and concealability.
[共重合ポリエステル]
本発明において、B層に共重合ポリエステルを用いることが好ましい。B層に高濃度に無機物を含有する組成物であっても安定して製膜することが出来、また、B層中の非相溶樹脂の分散剤として役割を有する。
[Copolyester]
In the present invention, it is preferable to use a copolyester for the B layer. Even a composition containing an inorganic substance at a high concentration in the B layer can be stably formed, and has a role as a dispersant for the incompatible resin in the B layer.
共重合ポリエステルは、主たるジカルボン酸成分がテレフタル酸であり、主たるグリコール成分がエチレングリコールであって、共重合成分が、イソフタル酸、ナフタレンジカルボン酸等の芳香族カルボン酸または脂肪族カルボン酸、およびテトラメチレングリコール、シクロヘキサンジメタノール、ポリエチレングリコール、ポリテトラメチレングリコール等の脂肪族ジオール、よりなる群から選ばれる少なくとも1種であるものを含有するポリエステルである。用いられる共重合ポリエステルとしては、ポリエチレンテレフタレートを基本構成とし、ポリエチレンテレフタレートとイソフタル酸との共重合体、ポリエチレンテレフタレートとシクロヘキサンジメタノールとの共重合体、ポリブチレンテレフタレートとポリテトラメチレンテレフタレートとの共重合体から選ばれる、少なくとも2種類以上の共重合ポリエステルを含有することが好ましい。 The copolymer polyester has a main dicarboxylic acid component of terephthalic acid, a main glycol component of ethylene glycol, and a copolymer component of aromatic carboxylic acid or aliphatic carboxylic acid such as isophthalic acid or naphthalene dicarboxylic acid, and tetra A polyester containing at least one selected from the group consisting of aliphatic diols such as methylene glycol, cyclohexanedimethanol, polyethylene glycol, and polytetramethylene glycol. The copolymer polyester used is based on polyethylene terephthalate, a copolymer of polyethylene terephthalate and isophthalic acid, a copolymer of polyethylene terephthalate and cyclohexanedimethanol, and a copolymer of polybutylene terephthalate and polytetramethylene terephthalate. It is preferable to contain at least two or more types of copolyesters selected from the coalescence.
B層中に含有させる共重合ポリエステルの含有量はB層質量を基準として1質量%以上20質量%以下であり、好ましくは、2質量%以上15質量%以下である。1質量%未満であると、温度変化に対する収縮応力の変化が小さく、熱寸法安定性に優れているが、非相溶樹脂の分散性が低下し反射性能が落ち、無機粒子を含有させた場合の延伸応力が高くなり製膜できないことがある。また、共重合ポリエステルを多く含有する場合、熱収縮率が高くなる傾向がある。そのため、20質量%を超えると温度変化に対する収縮応力の変化が大きく、熱寸法安定性が劣る。この場合、40℃から100℃での熱機械分析にて計測される熱収縮率が−0.5%以上0.0%以下を満たさないため、バックライト内部で、フィルムの波打ちが発生し、画面ムラとなる。また、製膜が困難になることがある。 The content of the copolymerized polyester contained in the B layer is 1% by mass or more and 20% by mass or less, preferably 2% by mass or more and 15% by mass or less based on the mass of the B layer. When the amount is less than 1% by mass, the change in shrinkage stress with respect to the temperature change is small and the thermal dimensional stability is excellent, but the dispersibility of the incompatible resin is lowered and the reflection performance is lowered, and inorganic particles are contained. The stretching stress of the film becomes so high that film formation may not be possible. Moreover, when it contains many copolymer polyesters, there exists a tendency for a thermal contraction rate to become high. Therefore, when it exceeds 20 mass%, the change of the shrinkage stress with respect to the temperature change is large, and the thermal dimensional stability is inferior. In this case, since the thermal shrinkage rate measured by thermomechanical analysis at 40 ° C. to 100 ° C. does not satisfy −0.5% or more and 0.0% or less, the wave of the film occurs inside the backlight, The screen becomes uneven. In addition, film formation may be difficult.
共重合ポリエステル中の共重合成分の割合は全ジカルボン酸成分または全ジオール成分あたり、好ましくは1〜30mol%、さらに好ましくは3〜25mol%である。1mol%未満であると、非相溶樹脂の分散性が低下し反射性能が落ち、また無機粒子を含有させた場合の延伸応力が高くなり製膜できないことがある。一方、30mol%を超えると熱寸法安定性に欠けたり、製膜が困難になることがある。 The ratio of the copolymerization component in the copolymerized polyester is preferably 1 to 30 mol%, more preferably 3 to 25 mol% per total dicarboxylic acid component or total diol component. If it is less than 1 mol%, the dispersibility of the incompatible resin is lowered, the reflection performance is lowered, and the stretching stress is increased when inorganic particles are contained, so that film formation may not be possible. On the other hand, if it exceeds 30 mol%, thermal dimensional stability may be lacking or film formation may be difficult.
本発明で使用される共重合ポリエステルは、融点170℃以上230℃以下の範囲にあることが好ましい。さらに好ましくは180℃以上220℃以下の範囲である。熱可塑性ポリエステルエラストマーの融点が170℃未満の場合、均一な分散が得られにくくなることがあり、反射板として使用した際、輝度が下がってしまうことがある。また230℃より高い場合には分散効果が認められないことがあるため、好ましくない。 The copolymer polyester used in the present invention is preferably in the range of melting point 170 ° C. or higher and 230 ° C. or lower. More preferably, it is the range of 180 degreeC or more and 220 degrees C or less. When the melting point of the thermoplastic polyester elastomer is less than 170 ° C., uniform dispersion may be difficult to obtain, and when used as a reflector, the luminance may decrease. On the other hand, when the temperature is higher than 230 ° C., the dispersion effect may not be recognized, which is not preferable.
[比重(見かけ密度)]
本発明において、白色ポリエステルフィルムの比重は0.5(g/cm3)以上1.1(g/cm3)以下、好ましくは0.55(g/cm3)以上1.05(g/cm3)以下、より好ましくは0.6(g/cm3)以上1.0(g/cm3)以下であることが、より高反射率を得るために好ましい。また、比重が0.5(g/cm3)未満であると、製膜安定性が劣る。また、非相溶成分の周りに空洞を形成しているため、従来のポリエステルフィルムと比較して、熱収縮率が大きい傾向がある。一方、1.1(g/cm3)を超える場合は、微細気泡の発生が不十分な場合がある。
[Specific gravity (apparent density)]
In the present invention, the specific gravity of the white polyester film is 0.5 (g / cm 3 ) or more and 1.1 (g / cm 3 ) or less, preferably 0.55 (g / cm 3 ) or more and 1.05 (g / cm). 3 ) or less, more preferably 0.6 (g / cm 3 ) or more and 1.0 (g / cm 3 ) or less, in order to obtain a higher reflectance. Further, when the specific gravity is less than 0.5 (g / cm 3 ), the film-forming stability is inferior. Moreover, since the cavity is formed around the incompatible component, the thermal shrinkage tends to be larger than that of the conventional polyester film. On the other hand, when it exceeds 1.1 (g / cm 3 ), the generation of fine bubbles may be insufficient.
[総厚み]
本発明において、白色ポリエステルフィルムの総厚みは50μm以上500μm以下が好ましく、より好ましくは150μm以上350μm以下である。白色ポリエステルフィルムの全厚みが50μm以上とすることは反射率の点で好ましく、また厚みが厚いほど剛性が高くなり筐体内での撓みが発生しにくいため輝度ムラの点からも好ましい。また、上限は特に制限する必要はないが、反射率、作業性、コストの点から500μm以下、より好ましくは350μm以下とすることが好ましい。500μmを超えるとこれ以上厚くしても反射率の上昇が望めず、またバックライトに組み込むために枚葉にして作業する際に高質量化により作業性(ハンドリング性)が悪化する。
[Total thickness]
In the present invention, the total thickness of the white polyester film is preferably from 50 μm to 500 μm, more preferably from 150 μm to 350 μm. The total thickness of the white polyester film is preferably 50 μm or more from the viewpoint of reflectivity, and the thicker the thickness, the higher the rigidity and the less likely to bend in the housing. The upper limit is not particularly limited, but is preferably 500 μm or less, more preferably 350 μm or less from the viewpoint of reflectance, workability, and cost. If the thickness exceeds 500 μm, an increase in reflectivity cannot be expected even if the thickness is greater than this, and workability (handling properties) deteriorates due to the increase in mass when working as a single wafer for incorporation into a backlight.
[反射率]
本発明の白色ポリエステルフィルムの少なくとも一方の表面の波長560nmでの相対反射率が97.0%以上であることが、反射板として使用する上で好ましい。なお相対反射率は98.5%以上がより好ましく、さらに好ましくは99.0%以上、最も好ましくは99.5%以上である。本発明において、相対反射率とは日立ハイテクノロジーズ製分光光度計(U―3310)に積分球を取り付け、この分光光度計に付属の標準白色板(酸化アルミニウム)をリファレンスとしてこの反射率を100%としたときの反射率である。
[Reflectance]
The relative reflectance at a wavelength of 560 nm of at least one surface of the white polyester film of the present invention is preferably 97.0% or more when used as a reflector. The relative reflectance is more preferably 98.5% or more, further preferably 99.0% or more, and most preferably 99.5% or more. In the present invention, the relative reflectance means that an integrating sphere is attached to a spectrophotometer (U-3310) manufactured by Hitachi High-Technologies, and the reflectance is 100% with reference to a standard white plate (aluminum oxide) attached to the spectrophotometer. It is a reflectance at that time.
[熱機械分析(TMA)]
本発明において、フィルムの長手方向、および幅方向の40℃から100℃での熱機械分析にて計測される熱収縮率が−0.5%以上0.0%以下であることが必要である。
[Thermomechanical analysis (TMA)]
In the present invention, the thermal shrinkage measured by thermomechanical analysis at 40 ° C. to 100 ° C. in the longitudinal direction and the width direction of the film needs to be −0.5% or more and 0.0% or less. .
本発明における熱機械分析(TMA)とは、セイコーインスツルメンツ社製の熱機械分析装置(TMA/SS6000)を用いて後述の条件で測定した値をいう。各データは少なくとも1℃につき1つのデータが得られるようにして、各温度における熱収縮率を下記式を用いて算出する。熱機械分析は、物質の温度を調節されたプログラムに従って変化させながら、非振動的な荷重を加えてその物質の変形を温度の関数として測定する方法であり、温度変化に対する収縮応力の変化を示すものである。測定条件は以下の通りである。
試料サイズ:幅4mm、長さ20mm
測定温度範囲:25℃〜160℃
昇温速度:10℃/分
測定荷重:19.6mN
測定室環境:温度23℃、相対湿度65%、大気中
熱収縮率(T℃)=(L(25℃)―L(T℃))/L(25℃)×100
L(T℃):T℃におけるサンプル長、熱収縮率(T℃):T℃における熱収縮率(%)。
The thermomechanical analysis (TMA) in the present invention refers to a value measured under the conditions described later using a thermomechanical analyzer (TMA / SS6000) manufactured by Seiko Instruments Inc. As for each data, at least one data per 1 ° C. is obtained, and the thermal shrinkage rate at each temperature is calculated using the following formula. Thermomechanical analysis is a method of measuring the deformation of a substance as a function of temperature by applying a non-vibrating load while changing the temperature of the substance according to a regulated program, and shows the change of shrinkage stress with respect to temperature change. Is. The measurement conditions are as follows.
Sample size: width 4mm, length 20mm
Measurement temperature range: 25 ° C to 160 ° C
Temperature increase rate: 10 ° C./min Measurement load: 19.6 mN
Measurement chamber environment: temperature 23 ° C., relative humidity 65%, atmospheric thermal shrinkage (T ° C.) = (L (25 ° C.) − L (T ° C.)) / L (25 ° C.) × 100
L (T ° C.): sample length at T ° C., heat shrinkage (T ° C.): heat shrinkage (%) at T ° C.
近年、液晶ディスプレイの光源として、消費電力量が小さく高出力化が可能なLED光源を側面に配置させる薄型化に有利な方式が採用されており、LED光源に近い部分のバックライト内部温度は100℃付近まで達し、離れている部分でも60℃付近まで達する。このように、バックライト内部で温度勾配があるため、上記範囲から外れると、バックライト用反射板として使用している際にバックライト内部で、フィルムの波打ちが発生し、画面ムラとなる。TMAで測定される熱収縮率を上記の範囲とすることでフィルムの波打ちを抑制することができ、画面ムラを抑えることができる。この熱収縮率の値は、−0.5%以上0.0%以下、より好ましくは−0.4%以上0.0%以下である。 In recent years, as a light source for a liquid crystal display, an LED light source that is low in power consumption and capable of high output is arranged on the side, which is advantageous for thinning. The backlight internal temperature near the LED light source is 100 It reaches around ℃, and even at a distant part, it reaches around 60 ℃. As described above, since there is a temperature gradient inside the backlight, if it is out of the above range, the film is undulated inside the backlight when used as a reflector for backlight, resulting in unevenness of the screen. By setting the heat shrinkage rate measured by TMA within the above range, the waviness of the film can be suppressed, and screen unevenness can be suppressed. The value of this heat shrinkage rate is -0.5% or more and 0.0% or less, more preferably -0.4% or more and 0.0% or less.
さらにまた、中型または小型エッジライトタイプのディスプレイに組み込まれる場合でも端部に反射板が把持されるような場合には、熱寸法安定性のよい反射板が求められるため本発明はこのような使用の場合にも好適である。 Furthermore, when the reflector is gripped at the end even when incorporated in a medium-sized or small edge light type display, a reflector having good thermal dimensional stability is required. This is also preferable.
[製造方法]
次に、本発明の白色ポリエステルフィルムの製造方法について説明するが、この例に限定されるものではない。非相溶樹脂として環状オレフィンを、分散剤(共重合ポリエステル)として1,4−シクロヘキサンジメタノールとポリエチレンテレフタレートとの共重合物、ポリブチレンテレフタレートとポリテトラメチレングリコールとの共重合物を、ポリエチレンテレフタレートに混合し、それを充分混合・乾燥させて270〜300℃の温度に加熱された押出機Bに供給する。二酸化珪素の無機粒子を含んだポリエチレンテレフタレートを常法により押出機Aに供給して、Tダイ3層口金内で押出機A層のポリマーが両表層となるようA層/B層/A層なる3層構成を得た。
[Production method]
Next, although the manufacturing method of the white polyester film of this invention is demonstrated, it is not limited to this example. Cyclic olefin as incompatible resin, copolymer of 1,4-cyclohexanedimethanol and polyethylene terephthalate as dispersant (copolyester), copolymer of polybutylene terephthalate and polytetramethylene glycol as polyethylene terephthalate The mixture is sufficiently mixed and dried, and then supplied to the extruder B heated to a temperature of 270 to 300 ° C. Polyethylene terephthalate containing inorganic particles of silicon dioxide is supplied to Extruder A by a conventional method, and A layer / B layer / A layer is formed so that the polymer of Extruder A layer becomes both surface layers in the T die 3 layer die. A three-layer configuration was obtained.
この溶融されたシートを、ドラム表面温度10〜60℃に冷却されたドラム上で静電気力にて密着冷却固化し、該未延伸フィルムを80〜120℃に加熱したロール群に導き、長手方向に2.8〜4.0倍延伸する。 This melted sheet is closely cooled and solidified by electrostatic force on a drum cooled to a drum surface temperature of 10 to 60 ° C., and the unstretched film is led to a group of rolls heated to 80 to 120 ° C. in the longitudinal direction. 2.8-4.0 times stretching.
より好ましくは3.1〜3.4倍である。3.1倍未満とすると反射特性に劣ったり、フィルムの厚み斑が悪くなり良好なフィルムが得られず、3.4倍を超えると製膜中に破断が発生し易くまた、長手方向の熱収縮率が高くなるため好ましくない。縦延伸後のフィルムは、続いて、縦方向と直交する方向(以降、横方向と呼ぶ)の延伸、熱固定、熱弛緩の処理を順次施して二軸配向フィルムとするが、これら処理はフィルムを走行させながら行う。横延伸の処理はポリエステルのガラス転移温度(Tg)より高い温度から始める。そしてTgより(5〜70)℃高い温度まで昇温しながら行う。横延伸過程での昇温は連続的でも段階的(逐次的)でもよいが通常逐次的に昇温することが好ましい。例えばテンターの横延伸ゾーンをフィルム走行方向に沿って複数に分け、ゾーン毎に所定温度の加熱媒体を流すことで昇温する。横延伸の倍率は、用途の要求特性にもよるが、好ましくは2.5〜4.5倍、より好ましくは2.8〜3.9倍である。2.5倍未満であるとフィルムの厚み斑が悪くなり良好なフィルムが得られず、4.5倍を超えると製膜中に破断が発生し易くなる。 More preferably, it is 3.1 to 3.4 times. If it is less than 3.1 times, the reflective properties are inferior, the film thickness unevenness is deteriorated and a good film cannot be obtained, and if it exceeds 3.4 times, breakage is likely to occur during film formation, and the heat in the longitudinal direction This is not preferable because the shrinkage rate is increased. The film after longitudinal stretching is subsequently subjected to stretching in the direction orthogonal to the longitudinal direction (hereinafter referred to as the transverse direction), heat setting, and thermal relaxation to form a biaxially oriented film. While running. The transverse stretching process starts from a temperature higher than the glass transition temperature (Tg) of the polyester. And it is performed while raising the temperature to (5 to 70) ° C. higher than Tg. The temperature increase in the transverse stretching process may be continuous or stepwise (sequential), but it is usually preferable to increase the temperature sequentially. For example, the transverse stretching zone of the tenter is divided into a plurality along the film running direction, and the temperature is raised by flowing a heating medium having a predetermined temperature for each zone. The transverse stretching ratio is preferably 2.5 to 4.5 times, more preferably 2.8 to 3.9 times, although it depends on the required characteristics of the application. If it is less than 2.5 times, the thickness unevenness of the film is deteriorated and a good film cannot be obtained, and if it exceeds 4.5 times, breakage tends to occur during film formation.
このようにして、得られた未延伸フィルムを少なくとも一方向に延伸することで、ポリエステルと非相溶な樹脂または気泡形成性の無機粒子を核として空洞を発現することができる。ここでは、逐次二軸延伸法によって延伸する場合を例に詳細に説明したが、本発明の白色ポリエステルフィルムは逐次二軸延伸法、同時二軸延伸法のいずれの方法で延伸してもよい。 In this way, by stretching the obtained unstretched film in at least one direction, it is possible to develop a cavity with a resin or an air-forming inorganic particle incompatible with polyester as a nucleus. Here, the case of stretching by the sequential biaxial stretching method has been described in detail as an example, but the white polyester film of the present invention may be stretched by either the sequential biaxial stretching method or the simultaneous biaxial stretching method.
得られた二軸延伸フィルムの結晶配向を完了させて、平面性と熱寸法安定性を付与するために、引き続きテンター内にて180〜220℃の温度で1〜30秒間の熱固定を行い、均一に徐冷後、室温まで冷却し、巻き取る。その後、得られたフィルムに熱処理を加える。熱処理工程中では、必要に応じて横方向あるいは縦方向に0.5〜10%の弛緩処理を施してもよい。熱固定、熱処理工程は本発明の液晶ディスプレイ用白色ポリエステルフィルムを得るために重要な工程であるために以下、詳述する。 In order to complete the crystal orientation of the obtained biaxially stretched film and to impart flatness and thermal dimensional stability, it is subsequently heat-set at a temperature of 180 to 220 ° C. for 1 to 30 seconds in a tenter, After gradually cooling uniformly, cool to room temperature and wind up. Thereafter, heat treatment is applied to the obtained film. In the heat treatment step, a relaxation treatment of 0.5 to 10% may be performed in the horizontal direction or the vertical direction as necessary. The heat setting and heat treatment steps are important steps for obtaining the white polyester film for liquid crystal display of the present invention, and will be described in detail below.
[熱固定]
本発明の液晶ディスプレイ用白色ポリエステルフィルムは、非相溶成分の周りに空洞を形成しており、これにより従来のポリエステルフィルムよりも見かけ密度が低下している。この空洞含有ポリエステルフィルムは、従来のポリエステルフィルムと比較して、熱収縮率が大きい傾向がある。熱収縮率を小さくするためには、横延伸後の熱固定の温度を高くすることが有効である。そのため、熱固定の温度は180〜220℃で行うことが好ましい。より好ましくは、190〜210℃である。熱固定処理を180℃より低い温度で行うと、熱固定ゾーンでの結晶化緩和が不十分で、均一な低い縦方向熱収縮率が得られないことがある。一方、220℃より高い温度で行うとポリエステルおよび非相溶樹脂が軟化してしまい、空洞がつぶれてしまったり、あるいは消滅してしまうため、見かけ比重が大きくなったり、本来の目的が果たせなくなってしまう。ポリエステルフィルムは空気透過性が低いため、横延伸により空洞が発生した直後は空洞内に空気が十分に充填されていない(つまり、真空状態に近い)場合がある。この状態で、高温での熱固定により、ポリエステルおよび非相溶樹脂が軟化すると、空洞が真空状態であるがゆえに、空洞がつぶれてしまうのである。空洞がつぶれてしまうと、反射率が低下してしまう。
[Heat setting]
The white polyester film for liquid crystal display of the present invention forms cavities around the incompatible component, and thus the apparent density is lower than that of the conventional polyester film. This void-containing polyester film tends to have a higher thermal shrinkage rate than conventional polyester films. In order to reduce the heat shrinkage rate, it is effective to increase the temperature of heat setting after transverse stretching. Therefore, it is preferable to perform the heat setting at 180 to 220 ° C. More preferably, it is 190-210 degreeC. When the heat setting treatment is performed at a temperature lower than 180 ° C., crystallization relaxation in the heat setting zone is insufficient, and a uniform low longitudinal heat shrinkage rate may not be obtained. On the other hand, if it is performed at a temperature higher than 220 ° C., the polyester and the incompatible resin are softened, and the cavity is crushed or disappears, so that the apparent specific gravity is increased and the original purpose cannot be achieved. End up. Since the polyester film has low air permeability, there are cases where the cavity is not sufficiently filled with air (that is, close to a vacuum state) immediately after the cavity is generated by transverse stretching. In this state, when the polyester and the incompatible resin are softened by heat fixation at a high temperature, the cavity is crushed because the cavity is in a vacuum state. If the cavity is collapsed, the reflectivity will decrease.
熱処理工程については、二軸延伸ポリエステルフィルムの製造中に行う方法(熱処理A:インライン処理)が製造コストの観点で好ましいが、一度製膜したフィルムを再びオーブン中に通し、緩和処理を行う方法(熱処理B:オフライン処理)を行っても良い。 Regarding the heat treatment step, a method (heat treatment A: in-line treatment) performed during the production of the biaxially stretched polyester film is preferable from the viewpoint of production cost, but the film once formed is again passed through an oven and subjected to a relaxation treatment ( Heat treatment B: off-line treatment) may be performed.
[熱処理A:インライン処理]
テンター出口にて端縁部がクリップから開放される近傍に切断刃を設置し、フィルム端縁部を切断除去し、フィルムを一旦常温まで冷却する。次に、横延伸、熱固定とは別のインラインのオーブン内にて、フィルムの引取速度を減じることで、クリップから外れた状態のフィルム全幅を長手方向に熱処理、弛緩する。弛緩させる手段としては巻き取り側のロール群の速度を調整する。特に、TMAで測定される熱収縮率を−0.5%以上0.0%以下とするため、上記熱処理は特に好ましい。
[Heat treatment A: In-line treatment]
A cutting blade is installed in the vicinity where the edge is opened from the clip at the tenter outlet, the film edge is cut and removed, and the film is once cooled to room temperature. Next, in the in-line oven different from transverse stretching and heat setting, the film take-off speed is reduced to heat-treat and relax the entire width of the film removed from the clip in the longitudinal direction. As a means for relaxing, the speed of the roll group on the winding side is adjusted. In particular, the heat treatment is particularly preferable because the heat shrinkage measured by TMA is set to -0.5% or more and 0.0% or less.
弛緩させる割合として、テンターのフィルムライン速度に対してロール群の速度ダウンを行い、好ましくは0.1〜1.5%、さらに好ましくは0.2〜1.2%、特に好ましくは0.3〜1.0%の速度ダウンを実施してフィルムを弛緩して縦方向の熱収縮率を調整する。 As the rate of relaxation, the speed of the roll group is reduced with respect to the film line speed of the tenter, preferably 0.1 to 1.5%, more preferably 0.2 to 1.2%, particularly preferably 0.3. The film is relaxed by performing a speed reduction of ˜1.0% to adjust the heat shrinkage in the machine direction.
[熱処理B:オフライン処理]
空洞内に空気を充填するために、二軸延伸の完了したフィルムを一定時間大気圧(90000Pa)以上の圧力条件下にて空気中に据え置くことが好ましい。据え置きする環境の温度は、ポリエステルのガラス転移点(Tg)以下の温度であることが好ましく、具体的には、70℃以下が好ましく、より好ましくは55℃以下、さらに好ましくは40℃以下である。温度が70℃を超えると、ポリエステルおよび/または非相溶樹脂が軟化する可能性があり、この後の熱処理の効果が薄れ、また、コスト面でも好ましくない。温度の下限は特に限定されるものではないが、コストの観点から−5℃以上が好ましい。また、静置する時間は、空洞に空気を十分に充填させるために、24時間以上が好ましい。
[Heat treatment B: Offline treatment]
In order to fill the air in the cavity, it is preferable to leave the biaxially stretched film in the air under a pressure condition of atmospheric pressure (90000 Pa) or higher for a certain time. The temperature of the environment for deferment is preferably a temperature not higher than the glass transition point (Tg) of the polyester, specifically 70 ° C. or lower, more preferably 55 ° C. or lower, and further preferably 40 ° C. or lower. . If the temperature exceeds 70 ° C., the polyester and / or the incompatible resin may be softened, the effect of the subsequent heat treatment is reduced, and the cost is not preferable. Although the minimum of temperature is not specifically limited, -5 degreeC or more is preferable from a viewpoint of cost. In addition, the standing time is preferably 24 hours or more in order to sufficiently fill the cavity with air.
上記のようにフィルムを据え置いて、空洞に空気を充填させた後、オーブンなどで熱処理行う。この熱処理により、熱収縮率を小さくすることができるだけでなく、空洞内に充填された空気が膨張し、空洞を拡張させることにより、見かけ密度を低下させることができる。特に、TMAで測定される熱収縮率を−0.5%以上0.0%以下とするため、熱処理は特に好ましい。 After leaving the film as described above and filling the cavity with air, heat treatment is performed in an oven or the like. By this heat treatment, not only the thermal shrinkage rate can be reduced, but also the air filled in the cavity expands and the cavity is expanded, whereby the apparent density can be lowered. In particular, the heat treatment is particularly preferable because the heat shrinkage measured by TMA is set to -0.5% or more and 0.0% or less.
熱処理A,Bの温度は、ポリエステルの融点(Tm)以下であることが好ましく、具体的には、100〜200℃が好ましく、より好ましくは120〜180℃である。熱処理の温度が100℃よりも低いと熱収縮率が十分に小さくならず、200℃よりも高いと見かけ密度が十分に低下せず、またフィルムの平面性が悪化するため、好ましくない。また、熱処理の時間は、5〜50秒間が好ましく、より好ましくは10〜40秒間である。熱処理の時間が5秒間よりも短いと熱収縮率が十分に小さくならず、50秒間よりも長いと比重が十分に低下しないため、好ましくない。このような熱処理により、従来の手法では成し得なかった高い反射性能と熱寸法安定性の両立を達成することができる。 It is preferable that the temperature of heat processing A and B is below melting | fusing point (Tm) of polyester, specifically, 100-200 degreeC is preferable, More preferably, it is 120-180 degreeC. If the temperature of the heat treatment is lower than 100 ° C., the thermal shrinkage rate is not sufficiently reduced, and if it is higher than 200 ° C., the apparent density is not sufficiently lowered and the flatness of the film is deteriorated. Further, the heat treatment time is preferably 5 to 50 seconds, more preferably 10 to 40 seconds. If the heat treatment time is shorter than 5 seconds, the thermal shrinkage rate is not sufficiently reduced, and if it is longer than 50 seconds, the specific gravity is not sufficiently lowered, which is not preferable. By such heat treatment, it is possible to achieve both high reflection performance and thermal dimensional stability, which could not be achieved by conventional methods.
このようにして得られる本発明の白色ポリエステルフィルムは、液晶バックライトの輝度向上を図ることができ、長時間使用しても反射板の浪打が無く、反射率の低下が少ないので、液晶画面用のエッジライトおよび直下型ライトの面光源の反射板、およびリフレクターとして好都合に使用することができる。得られた本発明の液晶ディスプレイ反射用白色ポリエステルフィルムは、特にLEDを用いたサイドライトタイプ及び直下型ライトタイプの液晶ディスプレイの反射板として使用された場合に高い輝度を維持することができる。 The white polyester film of the present invention thus obtained can improve the brightness of the liquid crystal backlight, and even when used for a long time, there is no splatter of the reflector, and the decrease in reflectance is small. It can be conveniently used as a reflector for surface light sources and reflectors of edge lights and direct type lights. The obtained white polyester film for reflecting a liquid crystal display of the present invention can maintain high luminance particularly when used as a reflector of a side light type and direct light type liquid crystal display using LEDs.
〔物性の測定ならびに効果の評価方法〕
本発明の物性値の評価方法ならびに効果の評価方法は次の通りである。
[Measurement of physical properties and evaluation method of effects]
The physical property value evaluation method and the effect evaluation method of the present invention are as follows.
(1)フィルム厚み・層厚み、空隙率
フィルムの厚みは、JIS C2151−2006に準じて測定した。
フィルムをミクロトームを用いて厚み方向に潰すことなく、幅方向(TD)に切断し、切片サンプルを得た。
該切片サンプルの断面を日立製作所製走査型電子顕微鏡(FE−SEM)S−2100A形を用いて、3000倍の倍率で撮像し、撮像から積層厚みを採寸し各層厚みと厚み比を算出した。また、同時に空隙(気泡)を観察し気泡と観察される部分の面積を観察されている層の面積で割って100をかけたものを空隙率とした。
(1) Film thickness / layer thickness, porosity The thickness of the film was measured according to JIS C2151-2006.
The film was cut in the width direction (TD) without crushing in the thickness direction using a microtome to obtain a slice sample.
The cross section of the section sample was imaged at a magnification of 3000 times using a scanning electron microscope (FE-SEM) S-2100A manufactured by Hitachi, Ltd., and the thickness of each layer was measured and the thickness ratio was calculated. At the same time, voids (bubbles) were observed and the area of the portion observed as bubbles was divided by the area of the observed layer and multiplied by 100 to obtain the porosity.
(2)熱機械分析(TMA)
セイコーインスツルメンツ社製の熱機械分析装置(TMA/SS6000)を用いて以下の条件で測定した。各データは少なくとも1℃につき1つ以上のデータが得られるようにして、各温度における熱収縮率を下記式を用いて算出した。
試料サイズ:幅4mm、長さ20mm
測定温度範囲:25℃〜160℃
昇温速度:10℃/分
測定荷重:19.6mN
測定室環境:温度23℃、相対湿度65%、大気中
熱収縮率(T℃)=(L(25℃)―L(T℃))/L(25℃)×100
L(T℃):T℃におけるサンプル長、熱収縮率(T℃):T℃における熱収縮率(%)。
(2) Thermomechanical analysis (TMA)
Measurement was performed under the following conditions using a thermomechanical analyzer (TMA / SS6000) manufactured by Seiko Instruments Inc. Each data was such that at least one data per 1 ° C. was obtained, and the thermal shrinkage at each temperature was calculated using the following formula.
Sample size: width 4mm, length 20mm
Measurement temperature range: 25 ° C to 160 ° C
Temperature increase rate: 10 ° C./min Measurement load: 19.6 mN
Measurement chamber environment: temperature 23 ° C., relative humidity 65%, atmospheric thermal shrinkage (T ° C.) = (L (25 ° C.) − L (T ° C.)) / L (25 ° C.) × 100
L (T ° C.): sample length at T ° C., heat shrinkage (T ° C.): heat shrinkage (%) at T ° C.
(3)見かけ密度
フィルムを100×100mm角に切取り、ダイアルゲージ(三豊製作所製No.2109−10)に、直径10mmの測定子(No.7002)を取り付けたものにて10点の厚みを測定し、厚みの平均値d(μm)を計算する。また、このフィルムを直示天秤にて秤量し、重さw(g)を10−4gの単位まで読み取る。下記の式で計算される値を見かけ密度とする。
見かけ密度=w/d×100 (g/cm3)。
(3) Apparent density The film was cut into a 100 × 100 mm square, and a thickness of 10 points was measured with a dial gauge (No. 2109-10, manufactured by Mitoyo Seisakusho) attached with a 10 mm diameter probe (No. 7002). Then, the average thickness d (μm) is calculated. Further, this film is weighed with a direct balance, and the weight w (g) is read up to a unit of 10 −4 g. The value calculated by the following formula is the apparent density.
Apparent density = w / d × 100 (g / cm 3 ).
(4)白色フィルム端部の形状
ハイセンスジャパン株式会社製32型液晶TV LHD32K15JPバックライト内に張り合わせてある反射フィルムを所定のフィルムサンプルに変更し、温度60℃、相対湿度80%条件下、4時間点灯させた。その後、液晶TVからバックライトユニットを外し反射板の白色フィルムを平面に置いた。このとき、フィルム端部の浮き上がりを測定した。
下記の通りの評価結果とした。
A:変形なし(0mm以上1mm未満)
B:かすかに波うちがある。(1mm以上4mm未満)
C:大きな波うちがある。(4mm以上)
上記のAおよびBを合格とした。
(4) Shape of the edge of the white film The 32-inch liquid crystal TV LHD32K15JP manufactured by Hisense Japan Co., Ltd. The reflective film laminated in the backlight is changed to a predetermined film sample, and the temperature is 60 ° C. and the relative humidity is 80% for 4 hours. Lighted up. Thereafter, the backlight unit was removed from the liquid crystal TV, and the white film of the reflector was placed on a flat surface. At this time, the lifting of the film edge was measured.
The evaluation results were as follows.
A: No deformation (0 mm or more and less than 1 mm)
B: There is a faint wave. (1mm and less than 4mm)
C: There is a big wave. (4mm or more)
Said A and B were set as the pass.
(5)輝度ムラ(画面ムラ)および輝度
新品のハイセンスジャパン株式会社製32型液晶TV LHD32K15JPバックライト内に張り合わせてある反射フィルムを上記(4)で取り出した反射板に変更し点灯させた。その状態で1時間待機して光源を安定化させた後、液晶画面部をCCDカメラ(SONY製DXC−390)にて撮影し、画像解析装置アイシステム製アイスケールで画像を取り込んだ。その後、撮影した画像の輝度レベルを3万ステップに制御し自動検出させ、輝度に変換した。
輝度ムラ(%)=(輝度最大値−輝度最小値)/輝度平均値×100
S:優良 (2%未満)
A:良好 (2%以上5%未満)
B:劣る (5%以上10%未満)
C:非常に劣る (10%以上)
上記のSおよびAを合格とした。
また、輝度評価として、東レ株式会社製ルミラー(登録商標)#250E6SLを基準サンプル(100%)とし、下記の通りの評価結果とした。
S:優良 (103%以上)
A:良好 (102%以上103%未満)
B:劣る (101%以上102%未満)
C:非常に劣る (101%未満)
上記のSおよびAを合格とした。
(5) Luminance unevenness (screen unevenness) and new brightness product Hisense Japan Co., Ltd. 32 type liquid crystal TV LHD32K15JP The reflective film pasted in the backlight was changed to the reflective plate taken out in the above (4) and turned on. In this state, after waiting for 1 hour to stabilize the light source, the liquid crystal screen was photographed with a CCD camera (DXC-390, manufactured by SONY), and the image was captured with an eye scale manufactured by an image analyzer, Eye System. Thereafter, the brightness level of the photographed image was controlled to 30,000 steps to be automatically detected and converted to brightness.
Unevenness of luminance (%) = (maximum luminance value−minimum luminance value) / average luminance value × 100
S: Excellent (less than 2%)
A: Good (2% or more and less than 5%)
B: Inferior (5% or more and less than 10%)
C: Very poor (10% or more)
Said S and A were set as the pass.
In addition, as a luminance evaluation, Lumirror (registered trademark) # 250E6SL manufactured by Toray Industries, Inc. was used as a reference sample (100%), and the following evaluation results were obtained.
S: Excellent (over 103%)
A: Good (102% or more and less than 103%)
B: Inferior (101% or more and less than 102%)
C: Very poor (less than 101%)
Said S and A were set as the pass.
(6)製膜安定性
安定に製膜できるか、下記基準で評価した。
A:24時間以上安定に製膜できる。
B:12時間以上24時間未満安定に製膜できる。
C:12時間以内に破断が発生し、安定な製膜ができない。
上記のAおよびBを合格とした。
(6) Film-forming stability It was evaluated according to the following criteria whether the film could be stably formed.
A: The film can be stably formed for 24 hours or more.
B: The film can be stably formed for 12 hours or more and less than 24 hours.
C: Breakage occurs within 12 hours, and stable film formation is not possible.
Said A and B were set as the pass.
(7)相対反射率
日立ハイテクノロジーズ製分光光度計(U―3310)に積分球を取り付け、この分光光度計に付属の標準白色板(酸化アルミニウム)を100%とした時の反射率を波長560nmにおける相対反射率を測定した。
97%以上を合格とした。
(7) Relative reflectance The reflectance when the integrating sphere is attached to the spectrophotometer (U-3310) manufactured by Hitachi High-Technologies and the standard white plate (aluminum oxide) attached to this spectrophotometer is 100% is 560 nm. The relative reflectance at was measured.
More than 97% was accepted.
(8)フィルム中の樹脂の含有量の測定
フィルムを秤量後、ヘキサフルオロイソプロパノール(HFIP)/クロロホルム(質量比50/50)の混合溶媒に溶解する。不溶な成分がある場合は、この不溶成分を遠心分離で分取した後、質量を測定し、元素分析、FT−IR、NMR法により該成分の構造と質量分率を測定する。上澄み成分についても同様に分析すれば、ポリエステル成分および他成分の質量分率と構造が特定される。上澄み成分から溶媒を留去した後にHFIP/重クロロホルム(質量比50/50)混合溶媒に溶解した後、1H核のNMRスペクトルを測定する。
(8) Measurement of resin content in film After weighing the film, it is dissolved in a mixed solvent of hexafluoroisopropanol (HFIP) / chloroform (
得られたスペクトルで、各成分に特有の吸収のピーク面積強度を求め、その比率とプロトン数よりブレンドのモル比を算出する。さらにポリマーの単位ユニットに相当する式量より質量比を算出する。このようにして各成分の質量分率と構造を特定した。 From the obtained spectrum, the peak area intensity of absorption peculiar to each component is obtained, and the molar ratio of the blend is calculated from the ratio and the number of protons. Further, the mass ratio is calculated from the formula amount corresponding to the unit unit of the polymer. Thus, the mass fraction and structure of each component were specified.
(9)白色フィルム中央部の形状
ハイセンスジャパン株式会社製32型液晶TV LHD32K15JPバックライト内に張り合わせてある反射フィルムを所定のフィルムサンプルに変更し、温度60℃、相対湿度80%条件下、4時間点灯させたものを、2サンプル準備した。
その後、液晶TVからバックライトユニットを外し反射フィルムを取り出して、1サンプルは長辺方向に3cm間隔で全幅分切り出した。他の1サンプルは、短辺方向に3cm間隔で全幅を切り出した。切り出したサンプルを、平板上に置き、平板から反射フィルム端部の浮き上がり高さの最大値を全数測定し、切り出したサンプル中の最大値をその水準の結果とした。
平板上に置くときに上面とする面に指定はなく、両面を確認した。
下記の通りの評価結果とした。
A:変形なし(0mm以上1mm未満)
B:かすかに波うちがある。(1mm以上4mm未満)
C:大きな波うちがある。(4mm以上)
上記のAおよびBを合格とした。
(9) Shape of white film center part 32 inch liquid crystal TV LHD32K15JP manufactured by Hisense Japan Co., Ltd. The reflective film pasted in the backlight is changed to a predetermined film sample, and the temperature is 60 ° C. and the relative humidity is 80% for 4 hours. Two samples were lit up.
Thereafter, the backlight unit was removed from the liquid crystal TV, the reflective film was taken out, and one sample was cut out in the long side direction at an interval of 3 cm for the entire width. Another sample cut out the full width at intervals of 3 cm in the short side direction. The cut sample was placed on a flat plate, and the maximum value of the floating height from the flat plate to the edge of the reflective film was measured in total. The maximum value in the cut sample was taken as the result of that level.
There was no designation as the upper surface when placing on a flat plate, and both sides were confirmed.
The evaluation results were as follows.
A: No deformation (0 mm or more and less than 1 mm)
B: There is a faint wave. (1mm and less than 4mm)
C: There is a big wave. (4mm or more)
Said A and B were set as the pass.
本発明を実施例に基づいて説明する。 The present invention will be described based on examples.
[実施例1]
重合後のポリエチレンテレフタレートの色調(JIS K7105−1981、刺激値直読方法で測定)がL値62.8、b値0.5、ヘイズ0.2%であるポリエチレンテレフタレートを使用し、ポリエチレンテレフタレート94質量部、ポリブチレンテレフタレートとポリテトラメチレングリコールの(PBT/PTMG)共重合物を0.5質量部(商品名:東レデュポン社製ハイトレル)、ジオール成分に対し1,4−シクロヘキサンジメタノールが33mol%共重合された共重合ポリエチレンテレフタレート(33mol%CHDM共重合PET)0.5質量部、ガラス転移温度が210℃であるシクロオレフィン系コポリマー(商品名:ポリプラスチックス社製TOPAS)5質量部を調整混合し、180℃で3時間乾燥させた後、270〜300℃に加熱された押出機Bに供給(B層)した。
[Example 1]
Using polyethylene terephthalate having a color tone of polyethylene terephthalate after polymerization (measured by JIS K7105-1981, stimulus value direct reading method) of L value 62.8, b value 0.5, haze 0.2%, polyethylene terephthalate 94 mass Part, 0.5 part by mass of (PBT / PTMG) copolymer of polybutylene terephthalate and polytetramethylene glycol (trade name: Hytrel manufactured by Toray DuPont), 33 mol% of 1,4-cyclohexanedimethanol with respect to the diol component 0.5 parts by mass of copolymerized polyethylene terephthalate (33 mol% CHDM copolymerized PET) and 5 parts by mass of cycloolefin copolymer (trade name: TOPAS manufactured by Polyplastics Co., Ltd.) having a glass transition temperature of 210 ° C. are prepared. After mixing and drying at 180 ° C for 3 hours , And supplied to Extruder B heated to 270 to 300 ° C. (B layer).
一方、ポリエチレンテレフタレート63質量部、数平均粒径3.5μmの二酸化珪素粒子ポリエチレンテレフタレートマスター17質量部(マスターチップ総量に対して二酸化珪素6質量%含有)と、ポリエチレンテレフタレートにイソフタル酸を18mol%共重合したもの(PET/I)を20質量部とを180℃で3時間真空乾燥した後、280℃に加熱された押出機Aに供給し(A層)、これらポリマーをA層/B層/A層となるように積層装置を通して積層し、Tダイよりシート状に成形した。さらにこのフィルムを表面温度25℃の冷却ドラムで冷却固化した未延伸フィルムを85〜98℃に加熱したロール群に導き、長手方向に3.4倍縦延伸し、21℃のロール群で冷却した。続いて、縦延伸したフィルムの両端をクリップで把持しながらテンターに導き120℃に加熱された雰囲気中で長手に垂直な方向に3.6倍横延伸した。その後テンター内で190℃の熱固定を行い、続いて同温度にて幅方向に6%の弛緩処理を施し、その後均一に徐冷後、室温まで冷却し二軸延伸された積層フィルムを得た。その後、25℃にて24時間据置処理した後、オーブンにて200℃、5秒の条件で熱処理を加えた。光反射用基材としての物性は表1の通りである。 On the other hand, 63 parts by mass of polyethylene terephthalate, 17 parts by mass of silicon dioxide particles polyethylene terephthalate master having a number average particle size of 3.5 μm (containing 6% by mass of silicon dioxide based on the total amount of the master chip), 18 mol% of isophthalic acid in polyethylene terephthalate. 20 parts by mass of the polymerized material (PET / I) was vacuum-dried at 180 ° C. for 3 hours, and then supplied to Extruder A heated to 280 ° C. (A layer). It laminated | stacked through the lamination apparatus so that it might become A layer, and it shape | molded in the sheet form from T-die. Further, the unstretched film obtained by cooling and solidifying this film with a cooling drum having a surface temperature of 25 ° C. was led to a roll group heated to 85 to 98 ° C., longitudinally stretched 3.4 times in the longitudinal direction, and cooled with a roll group at 21 ° C. . Subsequently, the film was stretched by 3.6 times in a direction perpendicular to the longitudinal direction in an atmosphere heated to 120 ° C. while being guided to a tenter while holding both ends of the longitudinally stretched film with clips. Thereafter, heat setting at 190 ° C. was performed in a tenter, followed by a relaxation treatment of 6% in the width direction at the same temperature, and then uniformly cooled, then cooled to room temperature and a biaxially stretched laminated film was obtained. . Then, after a stationary treatment at 25 ° C. for 24 hours, heat treatment was performed in an oven at 200 ° C. for 5 seconds. The physical properties of the light reflecting substrate are shown in Table 1.
[実施例2〜20]
A層、B層の原料組成、製膜条件、熱処理条件を表1、2に記載したとおりに変更した以外は、実施例1と同様の方法で白色ポリエステルフィルムを得た。いずれの実施例もフィルムの形状、輝度ムラおよび輝度は良好であった。
[Examples 2 to 20]
A white polyester film was obtained in the same manner as in Example 1 except that the raw material composition of the A layer and B layer, the film forming conditions, and the heat treatment conditions were changed as described in Tables 1 and 2. In all examples, the film shape, luminance unevenness, and luminance were good.
[比較例1〜2]
A層、B層の原料組成、製膜条件を表3に記載したとおりに変更した以外は、実施例1と同様の方法で厚み225μmのフィルムを得た。B層の共重合成分の含有量が多く、熱処理を行っていないので、フィルムの形状、輝度ムラが不十分であった。
[Comparative Examples 1-2]
A film having a thickness of 225 μm was obtained in the same manner as in Example 1 except that the raw material composition of the A layer and the B layer and the film forming conditions were changed as described in Table 3. Since the content of the copolymerization component of the B layer was large and heat treatment was not performed, the film shape and luminance unevenness were insufficient.
[比較例3〜6]
A層、B層の原料組成、製膜条件を表3に記載したとおりに変更した以外は、実施例1と同様の方法で白色ポリエステルフィルムを得た。B層の共重合成分の含有量が少ないが、熱処理を行っていないのでフィルムの形状、輝度ムラ、製膜安定性が不十分であった。
[Comparative Examples 3 to 6]
A white polyester film was obtained in the same manner as in Example 1 except that the raw material composition of the A layer and the B layer and the film forming conditions were changed as described in Table 3. Although the content of the copolymerization component in the B layer is small, since the heat treatment was not performed, the film shape, luminance unevenness, and film formation stability were insufficient.
[比較例7]
A層、B層の原料組成、製膜条件を表3に記載したとおりに変更した以外は、実施例1と同様の方法で白色ポリエステルフィルムを得た。B層の共重合成分の含有量が多いので、熱処理を行ったが、フィルムの形状、輝度ムラが不十分であった。
[Comparative Example 7]
A white polyester film was obtained in the same manner as in Example 1 except that the raw material composition of the A layer and the B layer and the film forming conditions were changed as described in Table 3. Since the content of the copolymerization component in the B layer was large, heat treatment was performed, but the film shape and luminance unevenness were insufficient.
ここで、表1〜表3中の略号は次の内容を表す。すなわち、
PET:ポリエチレンテレフタレート、
PET/I:ポリエチレンテレフタレートにイソフタル酸を18mol%共重合したもの、
PET/CHDM:ポリエチレン−1,4−シクロヘキシレンジメチレンテレフタレート(エチレングリコールに対し1,4−シクロヘキサンジメタノールが33mol%共重合されたポリエチレンテレフタレート共重合体)、
PBT/PTMG:ポリエステルエーテルエラストマブチレン/ポリ(アルキレンエーテル)フタレート(ブチレンテレフタレートに対し、アルキレングリコールが30mol%の共重合体)(商品名:東レデュポン社製ハイトレル)、
である。
PET/I/PEG:ポリエチレンテレフタレートイソフタル酸10mol%とポリエチレングリコールを5mol%共重合させた共重合体(商品名:東レ製T794M)
Here, the abbreviations in Tables 1 to 3 represent the following contents. That is,
PET: Polyethylene terephthalate,
PET / I: Polyethylene terephthalate copolymerized with 18 mol% isophthalic acid,
PET / CHDM: polyethylene-1,4-cyclohexylenedimethylene terephthalate (polyethylene terephthalate copolymer obtained by copolymerizing 33 mol% of 1,4-cyclohexanedimethanol with respect to ethylene glycol),
PBT / PTMG: Polyester ether elastomer mabutylene / poly (alkylene ether) phthalate (copolymer having 30 mol% of alkylene glycol with respect to butylene terephthalate) (trade name: Hytrel manufactured by Toray DuPont)
It is.
PET / I / PEG: a copolymer obtained by copolymerizing 10 mol% of polyethylene terephthalate isophthalic acid and 5 mol% of polyethylene glycol (trade name: T794M manufactured by Toray)
本発明の液晶ディスプレイ用白色ポリエステルフィルムは、バックライトに好適に用いることが出来る。
The white polyester film for liquid crystal displays of the present invention can be suitably used for a backlight.
Claims (8)
(1)B層はポリエステルに非相溶樹脂を含有し気泡を有すること、
(2)B層がポリエチレンテレフタレートを基本構成とし、少なくとも1種類以上の共重合ポリエステルを含有し、共重合ポリエステルがB層質量に対して1.0質量%以上20.0質量%以下であること、
(3)フィルムの見かけ密度が0.5g/cm3以上1.1g/cm3以下であること、
(4)フィルムの長手方向、および幅方向の40℃から100℃での熱機械分析にて計測される熱収縮率が−0.5%以上0.0%以下であること。 A white polyester film having at least two layers of an A layer substantially free of voids and a B layer containing voids, wherein the white polyester film satisfies the following requirements (1) to (4) White polyester film for display.
(1) Layer B contains incompatible resin in polyester and has bubbles,
(2) The B layer has polyethylene terephthalate as a basic structure, contains at least one copolymer polyester, and the copolymer polyester is 1.0% by mass or more and 20.0% by mass or less based on the mass of the B layer. ,
(3) The apparent density of the film is 0.5 g / cm 3 or more and 1.1 g / cm 3 or less,
(4) The thermal shrinkage measured by thermomechanical analysis at 40 ° C. to 100 ° C. in the longitudinal direction and the width direction of the film is −0.5% or more and 0.0% or less.
8. The backlight for a liquid crystal display according to claim 7, wherein a light source of the backlight is an LED system.
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