GB2394718A - Polymerised liquid crystal film with retardation pattern and method of making - Google Patents
Polymerised liquid crystal film with retardation pattern and method of making Download PDFInfo
- Publication number
- GB2394718A GB2394718A GB0320342A GB0320342A GB2394718A GB 2394718 A GB2394718 A GB 2394718A GB 0320342 A GB0320342 A GB 0320342A GB 0320342 A GB0320342 A GB 0320342A GB 2394718 A GB2394718 A GB 2394718A
- Authority
- GB
- United Kingdom
- Prior art keywords
- film
- retardation
- polymerisable
- liquid crystal
- different
- Prior art date
- 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.)
- Granted
Links
- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 258
- 238000004519 manufacturing process Methods 0.000 title description 4
- 239000000463 material Substances 0.000 claims abstract description 119
- 239000000203 mixture Substances 0.000 claims abstract description 60
- 238000000034 method Methods 0.000 claims abstract description 56
- 230000003287 optical effect Effects 0.000 claims abstract description 50
- 239000000758 substrate Substances 0.000 claims description 78
- 150000001875 compounds Chemical class 0.000 claims description 58
- 238000006116 polymerization reaction Methods 0.000 claims description 28
- 210000004027 cell Anatomy 0.000 claims description 21
- 239000012298 atmosphere Substances 0.000 claims description 13
- 230000005855 radiation Effects 0.000 claims description 13
- 210000002858 crystal cell Anatomy 0.000 claims description 12
- 229910052751 metal Inorganic materials 0.000 claims description 11
- 239000002184 metal Substances 0.000 claims description 11
- 239000011261 inert gas Substances 0.000 claims description 9
- 239000007787 solid Substances 0.000 claims description 5
- 230000005684 electric field Effects 0.000 claims description 4
- 229920006255 plastic film Polymers 0.000 claims description 3
- 239000002985 plastic film Substances 0.000 claims description 3
- 239000010408 film Substances 0.000 description 198
- 230000000694 effects Effects 0.000 description 23
- 238000002360 preparation method Methods 0.000 description 19
- 239000012299 nitrogen atmosphere Substances 0.000 description 18
- 229920006254 polymer film Polymers 0.000 description 16
- 238000001723 curing Methods 0.000 description 14
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 13
- 229910052753 mercury Inorganic materials 0.000 description 13
- -1 acryl Chemical group 0.000 description 12
- 239000000049 pigment Substances 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 10
- 125000000217 alkyl group Chemical group 0.000 description 8
- 239000011230 binding agent Substances 0.000 description 7
- 125000004432 carbon atom Chemical group C* 0.000 description 7
- 238000004132 cross linking Methods 0.000 description 7
- 239000004094 surface-active agent Substances 0.000 description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 6
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 6
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 238000009472 formulation Methods 0.000 description 6
- 229920000139 polyethylene terephthalate Polymers 0.000 description 6
- 239000005020 polyethylene terephthalate Substances 0.000 description 6
- 229920000642 polymer Polymers 0.000 description 6
- 239000004411 aluminium Substances 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 239000002019 doping agent Substances 0.000 description 5
- 239000011888 foil Substances 0.000 description 5
- 229910052757 nitrogen Inorganic materials 0.000 description 5
- 230000010287 polarization Effects 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 229920002284 Cellulose triacetate Polymers 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 4
- NNLVGZFZQQXQNW-ADJNRHBOSA-N [(2r,3r,4s,5r,6s)-4,5-diacetyloxy-3-[(2s,3r,4s,5r,6r)-3,4,5-triacetyloxy-6-(acetyloxymethyl)oxan-2-yl]oxy-6-[(2r,3r,4s,5r,6s)-4,5,6-triacetyloxy-2-(acetyloxymethyl)oxan-3-yl]oxyoxan-2-yl]methyl acetate Chemical compound O([C@@H]1O[C@@H]([C@H]([C@H](OC(C)=O)[C@H]1OC(C)=O)O[C@H]1[C@@H]([C@@H](OC(C)=O)[C@H](OC(C)=O)[C@@H](COC(C)=O)O1)OC(C)=O)COC(=O)C)[C@@H]1[C@@H](COC(C)=O)O[C@@H](OC(C)=O)[C@H](OC(C)=O)[C@H]1OC(C)=O NNLVGZFZQQXQNW-ADJNRHBOSA-N 0.000 description 4
- 125000003545 alkoxy group Chemical group 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 230000003098 cholesteric effect Effects 0.000 description 4
- WCLNGBQPTVENHV-MKQVXYPISA-N cholesteryl nonanoate Chemical compound C([C@@H]12)C[C@]3(C)[C@@H]([C@H](C)CCCC(C)C)CC[C@H]3[C@@H]1CC=C1[C@]2(C)CC[C@H](OC(=O)CCCCCCCC)C1 WCLNGBQPTVENHV-MKQVXYPISA-N 0.000 description 4
- 125000004386 diacrylate group Chemical group 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 4
- 239000011521 glass Substances 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- 239000000178 monomer Substances 0.000 description 4
- 239000004033 plastic Substances 0.000 description 4
- 229920003023 plastic Polymers 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
- 238000000576 coating method Methods 0.000 description 3
- 239000003086 colorant Substances 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- NBVXSUQYWXRMNV-UHFFFAOYSA-N fluoromethane Chemical compound FC NBVXSUQYWXRMNV-UHFFFAOYSA-N 0.000 description 3
- 239000012788 optical film Substances 0.000 description 3
- 230000000379 polymerizing effect Effects 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical class OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- JRXXLCKWQFKACW-UHFFFAOYSA-N biphenylacetylene Chemical group C1=CC=CC=C1C#CC1=CC=CC=C1 JRXXLCKWQFKACW-UHFFFAOYSA-N 0.000 description 2
- 239000012986 chain transfer agent Substances 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 239000003085 diluting agent Substances 0.000 description 2
- HNRMPXKDFBEGFZ-UHFFFAOYSA-N ethyl trimethyl methane Natural products CCC(C)(C)C HNRMPXKDFBEGFZ-UHFFFAOYSA-N 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 238000007429 general method Methods 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910044991 metal oxide Inorganic materials 0.000 description 2
- 150000004706 metal oxides Chemical class 0.000 description 2
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000000059 patterning Methods 0.000 description 2
- 125000006850 spacer group Chemical group 0.000 description 2
- 238000010561 standard procedure Methods 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- MYWOJODOMFBVCB-UHFFFAOYSA-N 1,2,6-trimethylphenanthrene Chemical compound CC1=CC=C2C3=CC(C)=CC=C3C=CC2=C1C MYWOJODOMFBVCB-UHFFFAOYSA-N 0.000 description 1
- 125000004955 1,4-cyclohexylene group Chemical group [H]C1([H])C([H])([H])C([H])([*:1])C([H])([H])C([H])([H])C1([H])[*:2] 0.000 description 1
- WZZBNLYBHUDSHF-DHLKQENFSA-N 1-[(3s,4s)-4-[8-(2-chloro-4-pyrimidin-2-yloxyphenyl)-7-fluoro-2-methylimidazo[4,5-c]quinolin-1-yl]-3-fluoropiperidin-1-yl]-2-hydroxyethanone Chemical compound CC1=NC2=CN=C3C=C(F)C(C=4C(=CC(OC=5N=CC=CN=5)=CC=4)Cl)=CC3=C2N1[C@H]1CCN(C(=O)CO)C[C@@H]1F WZZBNLYBHUDSHF-DHLKQENFSA-N 0.000 description 1
- GDOBGDUGIFUCJV-UHFFFAOYSA-N 2,2-dimethylbutane;2-methylprop-2-enoic acid Chemical compound CCC(C)(C)C.CC(=C)C(O)=O.CC(=C)C(O)=O.CC(=C)C(O)=O GDOBGDUGIFUCJV-UHFFFAOYSA-N 0.000 description 1
- LWRBVKNFOYUCNP-UHFFFAOYSA-N 2-methyl-1-(4-methylsulfanylphenyl)-2-morpholin-4-ylpropan-1-one Chemical compound C1=CC(SC)=CC=C1C(=O)C(C)(C)N1CCOCC1 LWRBVKNFOYUCNP-UHFFFAOYSA-N 0.000 description 1
- PMNLUUOXGOOLSP-UHFFFAOYSA-M 2-sulfanylpropanoate Chemical compound CC(S)C([O-])=O PMNLUUOXGOOLSP-UHFFFAOYSA-M 0.000 description 1
- JPEVEWTZGBSVHD-UHFFFAOYSA-N 3-ethenoxy-1-(3-ethenoxyprop-1-enoxy)prop-1-ene Chemical compound C(=C)OCC=COC=CCOC=C JPEVEWTZGBSVHD-UHFFFAOYSA-N 0.000 description 1
- FBPFZTCFMRRESA-KVTDHHQDSA-N D-Mannitol Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-KVTDHHQDSA-N 0.000 description 1
- FBPFZTCFMRRESA-ZXXMMSQZSA-N D-iditol Chemical compound OC[C@@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-ZXXMMSQZSA-N 0.000 description 1
- 241000854350 Enicospilus group Species 0.000 description 1
- 239000004593 Epoxy Substances 0.000 description 1
- 239000004890 Hydrophobing Agent Substances 0.000 description 1
- 229930195725 Mannitol Natural products 0.000 description 1
- 229910018487 Ni—Cr Inorganic materials 0.000 description 1
- 229910018967 Pt—Rh Inorganic materials 0.000 description 1
- 239000004990 Smectic liquid crystal Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- OWVIRVJQDVCGQX-VSGBNLITSA-N [(4r,5r)-5-[hydroxy(diphenyl)methyl]-2,2-dimethyl-1,3-dioxolan-4-yl]-diphenylmethanol Chemical class C=1C=CC=CC=1C(O)([C@H]1[C@@H](OC(O1)(C)C)C(O)(C=1C=CC=CC=1)C=1C=CC=CC=1)C1=CC=CC=C1 OWVIRVJQDVCGQX-VSGBNLITSA-N 0.000 description 1
- DHKHKXVYLBGOIT-UHFFFAOYSA-N acetaldehyde Diethyl Acetal Natural products CCOC(C)OCC DHKHKXVYLBGOIT-UHFFFAOYSA-N 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 125000004453 alkoxycarbonyl group Chemical group 0.000 description 1
- 125000005194 alkoxycarbonyloxy group Chemical group 0.000 description 1
- 125000005250 alkyl acrylate group Chemical group 0.000 description 1
- 125000004448 alkyl carbonyl group Chemical group 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 description 1
- 239000005030 aluminium foil Substances 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
- 239000002518 antifoaming agent Substances 0.000 description 1
- ZDZHCHYQNPQSGG-UHFFFAOYSA-N binaphthyl group Chemical group C1(=CC=CC2=CC=CC=C12)C1=CC=CC2=CC=CC=C12 ZDZHCHYQNPQSGG-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 125000002091 cationic group Chemical group 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- HVYWMOMLDIMFJA-DPAQBDIFSA-N cholesterol group Chemical group [C@@H]1(CC[C@H]2[C@@H]3CC=C4C[C@@H](O)CC[C@]4(C)[C@H]3CC[C@]12C)[C@H](C)CCCC(C)C HVYWMOMLDIMFJA-DPAQBDIFSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 229910052681 coesite Inorganic materials 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 229910052906 cristobalite Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- WNAHIZMDSQCWRP-UHFFFAOYSA-N dodecane-1-thiol Chemical compound CCCCCCCCCCCCS WNAHIZMDSQCWRP-UHFFFAOYSA-N 0.000 description 1
- 239000000975 dye Substances 0.000 description 1
- 238000004049 embossing Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- IHPDTPWNFBQHEB-UHFFFAOYSA-N hydrobenzoin Chemical group C=1C=CC=CC=1C(O)C(O)C1=CC=CC=C1 IHPDTPWNFBQHEB-UHFFFAOYSA-N 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000003999 initiator Substances 0.000 description 1
- KEHCHOCBAJSEKS-UHFFFAOYSA-N iron(2+);oxygen(2-);titanium(4+) Chemical compound [O-2].[O-2].[O-2].[Ti+4].[Fe+2] KEHCHOCBAJSEKS-UHFFFAOYSA-N 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- 239000010985 leather Substances 0.000 description 1
- 238000001459 lithography Methods 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000000594 mannitol Substances 0.000 description 1
- 235000010355 mannitol Nutrition 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 125000005641 methacryl group Chemical group 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 125000000843 phenylene group Chemical group C1(=C(C=CC=C1)*)* 0.000 description 1
- 238000000016 photochemical curing Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920000515 polycarbonate Polymers 0.000 description 1
- 239000004417 polycarbonate Substances 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 239000011112 polyethylene naphthalate Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000010526 radical polymerization reaction Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 238000004528 spin coating Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 229910052682 stishovite Inorganic materials 0.000 description 1
- 125000003011 styrenyl group Chemical group [H]\C(*)=C(/[H])C1=C([H])C([H])=C([H])C([H])=C1[H] 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 239000004753 textile Substances 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- 229910052905 tridymite Inorganic materials 0.000 description 1
- 238000009281 ultraviolet germicidal irradiation Methods 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 239000000080 wetting agent Substances 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B42—BOOKBINDING; ALBUMS; FILES; SPECIAL PRINTED MATTER
- B42D—BOOKS; BOOK COVERS; LOOSE LEAVES; PRINTED MATTER CHARACTERISED BY IDENTIFICATION OR SECURITY FEATURES; PRINTED MATTER OF SPECIAL FORMAT OR STYLE NOT OTHERWISE PROVIDED FOR; DEVICES FOR USE THEREWITH AND NOT OTHERWISE PROVIDED FOR; MOVABLE-STRIP WRITING OR READING APPARATUS
- B42D25/00—Information-bearing cards or sheet-like structures characterised by identification or security features; Manufacture thereof
- B42D25/30—Identification or security features, e.g. for preventing forgery
- B42D25/36—Identification or security features, e.g. for preventing forgery comprising special materials
- B42D25/364—Liquid crystals
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/38—Polymers
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K19/00—Liquid crystal materials
- C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
- C09K19/38—Polymers
- C09K19/3833—Polymers with mesogenic groups in the side chain
- C09K19/3842—Polyvinyl derivatives
- C09K19/3852—Poly(meth)acrylate derivatives
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3016—Polarising elements involving passive liquid crystal elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B5/00—Optical elements other than lenses
- G02B5/30—Polarising elements
- G02B5/3083—Birefringent or phase retarding elements
-
- 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
- G02F1/13363—Birefringent elements, e.g. for optical compensation
- G02F1/133631—Birefringent elements, e.g. for optical compensation with a spatial distribution of the retardation value
Landscapes
- Chemical & Material Sciences (AREA)
- Physics & Mathematics (AREA)
- Crystallography & Structural Chemistry (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Nonlinear Science (AREA)
- Polarising Elements (AREA)
- Liquid Crystal (AREA)
Abstract
A method of controlling the retardation in a film comprising polymerised liquid crystal material, obtained by polymerisation of polymerised liquid crystal material, by varying the composition of the polymerised liquid crystal material and/or varying the polymerisation conditions during polymerisation of the polymerised liquid crystal material. The film may comprise a monoreactive polymerisable group and a multireactive polymerisable group. Also shown is a film with planar orientation having at least two regions or a pattern of regions with different retardation and an LCD comprising the film. The film may be used in optical, electrooptical, decorative and security applications.
Description
23947 1 8
- 1 Polymerised Liquid Crystal Film with Retardation Pattern Field of the Invention
5 The invention relates to a method of controlling the retardation in a film comprising polymerised liquid crystal material with uniform orientation, to a film comprising a retardation pattern prepared by said method and its use for optical, electrooptical, decorative and security applications.
Backoround and Prior Art
Anisotropic films comprising polymerised liquid crystal (LC) material with uniform orientation are known in prior art. They are typically
15 used as retardation, compensation or polarization films for LC displays or other optical or electrooptical applications. The films can be prepared e.g. from a mixture comprising polymerisable LC compounds, also known as reactive mesogens (RM). These compounds typically comprise a mesogenic group that is linked to a 20 polymerisable group, optionally by a spacer group. The preparation of planar polymerised LC films is described for example in WO 98/04651. Usually a mixture of polymerisable LC compounds is coated onto a substrate, aligned into the desired orientation and polymerised to fix the alignment of the LC molecules.
For many applications, e.g. for use as optical components for example in liquid crystal displays, projection systems, decorative or security uses it would be advantageous to have LC films that exhibit a pattern of regions with different optical properties, like for example 30 a retardation pattern.
In prior art it is suggested to prepare patterned LC films comprising
regions with a different orientation direction of the LC material, for example by using patterned substrates that induce different 35 alignment directions in the polymerisable LC material, or photoalignment and photocuring with polarised light in combination
-2 with photomasking or photolitographic techniques, as described for example in US 6,144,428 and US 6,160,597. However, these methods require the use or the preparation of additional alignment layers and are material- and time consuming.
There is a still demand for an improved film comprising a retardation pattern. There is also a demand for a process friendly method of controlling the retardation and thereby the birefringence of a polymerised and/or polymerisable LC film. In particular there is a 10 demand for a simple process for modifying the retardation of a polymerised liquid crystal film that is intended to be included inside a LC display.
The aim of the present invention is to provide a method for 15 controlling the retardation of polymerized LC films, in particular planar aligned LC films.
Another aim of the present invention is to provide patterned or pixellated polymerised LC films having a retardation pattern, in 20 particular films with planar orientation, that do not have the drawbacks of films known from prior art and allow easy and
economic fabrication even at large scales.
Another aspect of the invention relates to the use of a polymerized 25 LC film with patterned retardation for decorative or security uses.
In prior art it is known that polymerized LC films can be used as
security markings for the authentification and prevention of counterfeiting of documents of value, like banknotes, tickets, credit or 30 ID cards. The LC films provide non reproduceable effects, such as thermochromaticity and optically variable effects. Other features may be hidden such as the reflection of light with a certain polarization state, infra-red reflecting or UV reflecting materials. These effects can only be seen with the use of viewing devices such as polarising 35 films or specrophotometers.
- 3 Much work has focussed on the use of cholesteric LC (CLC) materials. These materials exhibit specific optical properties, such as angular colour dependence and reflection of circular polarised light, due to their chirality which induces a helically twisted molecular 5 structure in the cholesteric phase. Suitable CLC materials and their use in security applications are described for example in GB 2 330 360 A, EP 0 601 483 A, and WO 97/30136. However, CLC materials have several drawbacks, e.g. they are difficult to prepare and expensive, especially if both chiral forms are required. Furthermore, 10 for cholesteric materials an absorbing or black background is
required to give best effects.
The use of nematic LC films for security devices has also been reported in prior art. GB 2 357 061 describes a hot stamping foil for
15 security applications, comprising a layer of polymerized or crosslinked nematic LC material with uniform orientation applied onto a reflective layer. The birefringent nematic LC layer provides a hidden optical effect, as it is invisible when viewed under unpolarised light, and produces a bright birefringence colour when viewed at 20 between linear polarisers. The colour changes if the LC layer is rotated relatively to the polarization direction of the polarizers.
However, the use of nematic materials as described in GB 2 357 061 has several drawbacks, as they need to be applied to a reflective background and subsequently cured using actinic radiation or
25 transferred after polymerization from a carrier film to a reflective film.
Also, the formation of images or patterns would require specific materials or additional techniques such as photomasking or photoorientation. 30 Therefore, another aim of the present invention is to provide a polymerized LC film that is suitable as birefringent marking, in particular for decorative, security, authentification or identification applications, does not have the drawbacks of the prior art devices,
exhibits effects difficult to counterfeit and allows an economic 35 fabrication even at large scales.
- 4 Other aims of the present invention are immediately evident to the person skilled in the art from the following detailed description.
The above aims can be achieved by providing methods and films 5 according to the present invention.
The retardation of an LC film is given by the product of its thickness and its birefringence. The birefringence of a polymerized planar aligned LC film is dependent on various parameters, like the quality 10 of alignment of the LC material, the birefringence of the uncured LC molecules, the length of the spacer between the polymerisable group and the core group of the LC molecules, and the polymerization conditions. In prior art it is described for example how to control the
birefringence of a planar polymerized LC film by temperature, as 15 disclosed in Dirk J Broer, Rifat A. M. Hikmet, Ger Challa, Makromol.
Chem., 190, 3201 (1989), by careful molecular design of the reactive mesogens, as disclosed in Dirk J Broer, Jan Boven, Grietje N. Mol and Gere Challa; Makromol. Chem., 190, 2255 (1989) describe, or by applying a field to a cell containing a polymerisable LC mixture, as
20 disclosed in Hiroshi Hasebe, Kiyofumi Takeuchi and Haruyoshi Takatsu. DIC Technical Review, 3, 199 (1998).
It is known in prior art that the birefringence of a layer of
polymerisable LC material that is planar aligned in its nematic phase 25 often changes, and typically decreases, during polymerization. It is desired to minimise this change in birefringence so that the desired retardation values can be obtained in a preferably thin film.
In this invention, a method of controlling the change in birefringence 30 by controlling the polymerization conditions of polymerisable LC formulations is described. This invention also defines LC mixture parameters within which this effect is particularly enhanced. For example, the inventors of the present invention have found that it is possible to increase the effective birefringence of a polymerized LC 35 film by approximately 50% by using a combination of a suitable polymerisable LC formulation and process conditions. This method
- a - can also be used to form a patterned retardation film, which is useful for e.g. pixellation or subpixellation of retardation films.
Furthermore, the inventors of the present invention have found that a 5 polymerised LC film with patterned retardation that is prepared according to the inventive method on a reflective substrate like e.g. an aluminised plastic film such as Al-coated PET, can be used as security marking. The retardation pattern is not visible under normal conditions, but becomes visible when viewed under polarised light.
Summary of the Invention
The invention relates to an optical retardation film, characterized in that it comprises at least two regions having different retardation, 15 preferably a film that comprises polymerised or crosslinked liquid crystal material.
The invention further relates to a method of controlling the retardation in a film comprising polymerized liquid crystal (LC) 20 material and being prepared by polymerization of a polymerisable LC material, by varying the composition of the polymerisable LC material and/or by varying the polymerization conditions during polymerization of the LC material.
25 The invention further relates to a method of preparing a film comprising polymerized liquid crystal (LC) material and having at least two regions or a pattern of regions with different retardation, comprising the steps of providing a polymerisable LC material on a substrate and photopolymerising different selected areas of the 30 polymerisable LC material under different polymerization conditions, in particular wherein different selected areas are photopolymerised with or without an inert gas atmosphere and/or different selected areas are photopolymerised using different intensity of photoradiation and/or different selected areas are photopolymerised at different 35 temperature.
- 6 The invention further relates to a film obtained by the method as described above and below.
The invention further relates to a film having at least two regions or a 5 pattern of regions with different retardation, which can be obtained by the methods as described above and below.
The invention further relates to a polymerised LC film having a pattern of at least two regions with different retardation as described 10 above and below, said film being provided on a reflective substrate.
The invention further relates to the use of the films as described above and below in optical or electrooptical devices, for decorative or security applications.
The invention further relates to an LC display comprising a film as described above and below.
The invention further relates to a security marking comprising a 20 patterned film as described above and below.
The invention further relates to an object or document of value comprising a security marking as described above and below.
25 The invention further relates to the use of a film as described above and below, in particular a film having at least two regions or a pattern of regions with different retardation, as optical retardation film in an LC display. 30 The invention further relates to the use of a film as described above and below, in particular a film having at least two regions or a pattern of regions with different retardation, as optical retardation film in an LCD, characterized in that the film is positioned between the substrates of the switchable LC cell.
The invention further relates to a liquid crystal display (LCD) comprising at least one polariser and a switchable LC cell comprising a layer of an LC medium between two plane parallel substrates at least one of which is transparent to incident light, characterized in that 5 the LCD comprises at least one film comprising polymerised LC material as described above and below that is positioned between the substrates of the LC cell.
The invention further relates to an LCD as described above and 10 below, characterized in that it comprises - a liquid crystal cell formed by two plane parallel substrates at least one of which is transparent to incident light, an electrode layer provided on the inside of at least one of said two transparent substrates and optionally superposed with an alignment layer, 15 and a liquid crystal medium which is present between the two substrates and is switchable between at least two different states by application of an electric field,
- a first linear polariser on one side of the liquid crystal cell, 20 optionally a second linear polariser on the side of the liquid crystal cell opposite to that of the first linear polariser, characterized in that it comprises at least one film comprising polymerized LC material as described above and below that is positioned between the two plane parallel substrates forming the 25 liquid crystal cell.
Definition of Terms In connection with polarization, compensation and retardation layers, 30 films or plates as described in the present application, the following definitions of terms as used throughout this application are given.
The term'film'as used in this application includes self-supporting, i.e. free-standing, films that show more or less pronounced mechanical 35 stability and flexibility, as well as coatings or layers on a supporting substrate or between two substrates.
- 8 The term 'liquid crystal or mesogenic material'or 'liquid crystal or mesogenic compound' should denote materials or compounds comprising one or more rod-shaped, board-shaped or disk-shaped 5 mesogenic groups, i.e. groups with the ability to induce liquid crystal phase behaviour. Liquid crystal (LC) compounds with rod-shaped or board-shaped groups are also known in the art as'calamitic' liquid crystals. Liquid crystal compounds with a disk-shaped group are also known in the art as'discotict liquid crystals. The compounds or 10 materials comprising mesogenic groups do not necessarily have to exhibit a liquid crystal phase themselves. It is also possible that they show liquid crystal phase behaviour only in mixtures with other compounds, or when the mesogenic compounds or materials, or the mixtures thereof, are polymerized.
For the sake of simplicity, the term 'liquid crystal material' is used hereinafter for both liquid crystal materials and mesogenic materials.
The term 'reactive mesogen' (RM) means a polymerisable mesogenic 20 compound. The term 'director' is known in prior art and means the preferred
orientation direction of the long molecular axes (in case of calamitic compounds) or short molecular axis (in case of discotic compounds) 25 of the mesogens in a liquid crystal material.
The term 'planar structure' or 'planer orientation' refers to a film wherein the optical axis is substantially parallel to the film plane.
30 The term 'homeotropic structure' or'homeotropic orientation' refers to a film wherein the optical axis is substantially perpendicular to the film plane, i.e. substantially parallel to the film normal.
The terms 'tilted structure' or 'tilted orientation' refers to a film 35 wherein the optical axis is tilted at an angle between 0 and 90 degrees relative to the film plane.
JO - 9 - The term 'splayed structure' or 'sprayed orientation' means a tilted orientation as defined above, wherein the tilt angle additionally varies monotonuously in the range from O to 90 , preferably from a minimum 5 to a maximum value, in a direction perpendicular to the film plane.
The tilt angle of a splayed film hereinafter is given as the average tilt angle Gavel unless stated otherwise.
10 The average tilt angle Dave iS defined as follows d B'(d) _ d'=0 Haved 15 wherein O'(d') is the local tilt angle at the thickness d' within the film, and d is the total thickness of the film.
In planar, homeotropic and tilted optical films comprising uniaxially positive birefringent liquid crystal material with uniform orientation, 20 the optical axis of the film is given by the director of the liquid crystal material. The term 'helically twisted structure' relates to a film comprising one or more layers of liquid crystal material wherein the mesogens are 25 oriented with their main molecular axis in a preferred direction within molecular sublayers, said preferred orientation direction in different sublayers being twisted at an angle around a helix axis. The term helically twisted structure with planar orientation' means a film with helically twisted structure as described above, wherein the helix axis 30 is substantially perpendicular to the film plane, i.e. substantially parallel to the film normal.
The term 'A plate' refers to an optical retarder utilizing a layer of uniaxially birefringent material with its extraordinary axis oriented 35 parallel to the plane of the layer.
- 10 The term 'C plate' refers to an optical retarder utilizing a layer of uniaxially birefringent material with its extraordinary axis perpendicular to the plane of the layer.
5 The term 'O plate' refers to an optical retarder utilizing a layer of a uniaxially birefringent material with its extraordinary axis oriented at an oblique angle with respect to the plane of the layer.
In A-, C- and O-plates comprising optically uniaxial birefringent liquid 10 crystal material with uniform orientation, the optical axis of the film is given by the direction of the extraordinary axis.
An A-, C- or O plate comprising optically uniaxial birefringent material with positive birefringence is also referred to as'+ AIC/O plate' or 15 'positive AIC/O plate'. An A-, C- or O plate comprising a film of optically uniaxial birefringent material with negative birefringence is also referred to as '- AIC/O plate' or 'negative AIC/O plate'.
A retardation film with positive or negative birefringence is also shortly 20 referred to as 'positive' or 'negative' retardation film, respectively.
A transmissive or transflective LCD according to the present invention preferably contains a polariser and an analyser, which are arranged on opposite sides of the arrangement of LC layer and 25 birefringent layer.
Polariser and Analyser are jointly referred to as "polarizers" in this application. In a linear absorption polariser, unless stated otherwise, the term "polarization axis" refers to the transmission direction of the 30 polariser, which is at 90 degrees to the absorption direction of the polariser. Detailed Descriotion of the Invention 35 In the method according to the present invention a polymerized LC film, preferably a planar aligned calamitic LC film, is prepared by
- 11 photopolymerisation of a polymerisable LC material such that the birefringence of the resulting film and thereby its retardation is controlled and preferably maximised. Several ways are described of increasing the birefringence of the above film. Especially effective 5 and therefore preferred is a method to polymerise a low-crosslinked polymerisable nematic LC mixture with a low amount of photoinitiator and/or with an actinic lamp with low power and/or under an inert atmosphere. A mixture which is highly cross-linked, comprising an amount of di- or higher reactive compounds of greater than 70%, 10 does not show the effect in the same extent and is less preferred.
Also described is a method of using a pixellated mask to form areas on the same planar aligned LC film with different retardation values.
Unless stated otherwise, the general preparation of polymerized LC 15 films in this invention is carried out according to standard methods known from the literature. Typically a polymerisable LC material is coated or otherwise applied onto a substrate where it aligns into uniform orientation, and polymerised in situ in its LC phase e.g. by exposure to heat or actinic radiation, preferably by photo 20 polymerization, very preferably by UV-photopolymerisation, thereby fixing the alignment of the LC molecules. Uniform alignment can also be induced or enhanced by additional means like shearing, surface treatment of the substrate, or addition of surfactants to the LC material.
25 The preparation of planar LC films according to this procedure is described e.g. in WO 98/04651, the preparation of homeotropic LC films is described e.g. in WO 98/00475, the preparation of tilted or splayed LC films is described e.g. in US 5,619,352, WO 97/44702 and WO 98/12584, the preparation of a helically twisted LC films with 30 planar orientation is described for example in GB 2,315,072 and WO 01/20394, with the entire disclosure of all these documents being
incorporated into this application by reference.
The method according to this invention has the following advantages:
- 12 - it defines polymerization process conditions which enhance the birefringence of an in-situ photopolymerised planar aligned LC film and so allows to reduce the film thickness necessary to give a certain retardation.
5 - it defines a polymerisable LC mixture formulation that demonstrate this effect.
- it describes a method of pixellating or patterning a polymerised LC film with areas of different retardation.
10 The film according to the present invention can have planar homeotropic, tilted, splayed or helically twisted orientation. Especially preferred are planar, homeotropic, tilted and splayed films. Most preferred are planar films.
15 A first preferred embodiment of the present invention relates to a method of controlling the retardation in a film comprising polymerised LC material with uniform orientation by varying the composition of the polymerisable LC material and/or the polymerization conditions during polymerization of the LC material.
The plarar LC film is prepared preferably by providing a polymerisable LC material onto a substrate, aligning it into the desired orientation and polymerizing it by exposure to photoradiation, preferably UV radiation, according to standard procedures that are 25 known to the expert and are described in the literature.
The polymerisable LC material is preferably a nematic LC material. It preferably comprises a photoinitiator to start the polymerization reaction. The film is preferably provided on a plastic substrate for 30 manufacturing on a roll to roll coating machine.
According to this first preferred embodiment, the birefringence of a uniformly aligned LC film, preferably a planar film, very preferably a calamitic LC film, prepared on a substrate can be maximised by 35 controlling the polymerization conditions during polymerization of the LC material. It is further possible to maximise the birefringence of the
- 13 LC film by controlling the composition of the polymerisable LC mixture used for preparation of the film. As the retardation of the LC film is given by the product of its thickness and its birefringence, an increase of the birefringence of the film will also lead to an increase 5 of its retardation if the thickness is not changed.
In this first preferred embodiment of the present invention, the effect of the following mixture and process variables on the optical properties of a polymerized LC film are investigated: a) Effect of intensity of photoradiation. This can be controlled for example by using a UV lamp for photopolymerisation and varying the lamp power.
15 It was found that polymerisable LC mixtures that were polymerized by UV photopolymerisation with low intensity of UV radiation gave films with higher birefringence than mixtures that were polymerised with higher radiation intensity. This effect is especially significant when polymerizing under an inert gas atmosphere, e.g. under 20 nitrogen. Thus, a first preferred method according to this first preferred embodiment is to increase the birefringence and/or retardation of an aligned polymerised LC film prepared by photopolymerisation, in 25 particular by UV photopolymerisation, by reducing the intensity of radiation used for polymerization.
However, there is a minimum amount of UV exposure required below which polymerization of the film is insufficient. Thus, the intensity of 30 photoradiation is preferably varied between a minimum and a maximum value. In this way, it is possible to maximise the birefringence of the polymerized LC film without significantly reducing its mechanical and optical performance.
35 The minimum amount of light intensity needed depends on the polymerisable mixture used, and also on the atmosphere. For the
- 14 preferred mixtures shown below, the radation intensity when curing under nitrogen is preferably from 0.1 to 1 mW/cm2, in particular from 0.2 to 0.5 mW/cm2, and when curing in air preferably from 5 mW/cm2 to 20 mW/cm2, very preferably from 7 to 15 mW/cm2, however, the 5 invention is not limited to these values.
b) Effect of polymerising in different atmospheres, for example in air and in an inert gas atmosphere, preferably in nitrogen.
10 It was found that polymerisable LC mixtures that were polymerized under an inert gas atmosphere gave films with higher birefringence than mixtures that were polymerised in air.
Thus, a second preferred method according to this first preferred 15 embodiment is to increase the birefringence and/or retardation of an aligned polymerised LC film by polymerising in an inert gas atmosphere, preferably in nitrogen.
c) Effect of cross-linking density. This can be controlled for example 20 by using a polymerisable LC material comprising at least one polymerisable compound having one polymerisable group (monoreactive) and at least one polymerisable compound having two or more polymerisable groups (di- or multireactive), and varying the ratio of monoreactive and multireactive compounds.
It was found that the birefringence of the polymerised LC film increases with decreasing degree of crosslinking, achieved by reducing the amount of multireactive compounds.
30 Thus, a third preferred method according to this first preferred embodiment is to increase the birefringence and/or retardation of an aligned polymerised LC film by reducing the amount of multireactive compounds in the polymerisable LC material.
35 However, the polymerisable LC mixture should preferably comprise a certain amount of multireactive compounds. Due to the presence of
- 15 multireactive compounds a 3-dimensional polymer network is formed and the orientation of the LC material is permanently fixed.
This yields a stable, self-supporting film with a high mechanical and thermal stability and a low temperature dependence of the physical 5 and optical properties.
The amount of multireactive compounds in the polymerisable LC material is preferably varied between a minimum and a maximum value. In this way, it is possible to maximise the birefringence of the 10 polymerised LC film without significantly reducing its mechanical and optial performance.
Preferably the polymerisable LC material comprises one or more multireactive compounds, in particular multireactive mesogenic 15 compounds, in an amount of from 5 to 70 %, preferably from 10 to 60 % by weight of the total amount of solid components in the material.
d) Effect of concentration of the photoinitiator (Pl).
20 It was found that the birefringence of the polymerized LC film increases when the amount of photoinitiator in the polymerisable mixture is reduced.
Thus, a fourth preferred method according to this first preferred 25 embodiment is to increase the birefringence and/or retardation of an aligned polymerised LC film by reducing the amount of photoinitiator in the polymerisable LC material.
Preferably the polymerisable LC material comprises one or more 30 photoinitiators in an amount of from 0.5 to 10 %, preferably from 2 to 8 % by weight of the total amount of solid components in the material. e) Effect of polymerising at different temperatures.
Rae - - 16 The birefringence of a polymerisable LC mixture usually decreases with increasing temperature. Thus, a polymerisable LC mixture that is polymerized at a lower temperature gives a film with higher birefringence than a mixture that is polymerised at a higher 5 temperature. Thus, a fifth preferred method according to this first preferred embodiment is to increase the birefringence and/or retardation of an aligned polymerised LC film by polymerising at a low temperature 10within the LC phase of the polymerisable LC material.
A second preferred embodiment of the invention relates to a method of preparing a film comprising polymerised liquid crystal (LC) material with uniform orientation and having at least two regions or a pattern 15 of two or more regions with different retardation.
The film is preferably prepared from a layer of polymerisable LC material, in partiuclar a nematic LC material, that is provided on a substrate using the general conditions as described above. Different 20 areas of the LC layer are then photopolymerised under different conditions, for example with or without an inert gas atmosphere or using different lamp power as described above.
For example, certain areas of the layer of polymerisable LC material 25 are covered with a mask, and the layer is exposed to low power UV light under a nitrogen atmosphere. A previously masked part of the layer is then uncovered and exposed to an UV light of intermediate intensity. The final mask is then removed and exposed to high intensity UV light.
As a result, the different areas of the film polymerised under different conditions show different birefringence and thus different retardation.
The method according to this second preferred embodiment 35 preferably comprises the steps of providing a polymerisable LC material on a substrate and photopolymerising different selected
- 17 areas of the polymerisable LC material under different polymerization conditions, in particular by polymerising different selected areas with or without an inert gas atmosphere and/or polymerising different selected areas using different intensity of photoradiation.
A third preferred embodiment of the present invention relates to a polymerised LC film, preferably a planar film, comprising at least two regions or a pattern of regions with different retardation prepared by a method as described above, which is used for decorative or 10 security applications.
Especially preferred is a patterned film that is provided on a reflective substrate. The film can be prepared from a polymerisable LC material, preferably a nematic LC material, as described above and 15 then be laminated to a reflective substrate. Alternatively the film is directly prepared on a reflective substrate.
The film is preferably prepared from a layer of polymerisable LC material using the preferred methods as described above, especially 20 preferably using a reflective substrate. Selected regions of the layer of polymerisable LC material are aligned, preferably into planar orientation, and cured in several steps under different conditions as described above. For example, a black mask is applied to the layer to create a pattern and the layer exposed to a high radiation intensity 25 at ambient temperature and in air. The mask is then removed and the layer exposed to low radiation intensity under a nitrogen atmosphere. As a result the area of the film cured under in the second step has higher retardation than the area cured in the first step. In this way an image is fabricated in the film, which is not visible under normal conditions, but becomes visible when viewed at an angle between two linear polariser or using a circular polariser. For example, if such a planar patterned film on a reflective substrate is 35 provided between two polarizers, polarised light travels towards the film and is retarded by the LC material, reflected off the reflective
- 18 surface and retarded again as it travels towards the analyser which is crossed with reference to the polariser. Where there is no LC material, the film appears black, but where there is some LC material film, the film appears coloured, with the actual colour depending on 5 the thickness of the film and the angle of viewing. By changing the birefringence of the LC layer, the optical path length can be changed.
A film that contains a pattern with high and low birefringent area will retard light to different extent and so will be viewed as different colours by the viewer when using polarised light, but will appear 10 colourless when viewed with unpolarised light. The effect can also be viewed using a single circular polariser.
The optical properties of this film have advantageous security applications. Preferred reflective substrates are metallic or metallised substrates, i.e. substrates comprising or incorporating or being covered by one or more metal layers. In addition these substrates may also be part of a hot stamping foil or of a holographic image. Further preferred are 20 substrates incorporating or being covered by one or more layers of reflective pigments, like metal flakes, pearlescent or interference pigments or liquid crystal pigments, or mixtures thereof.
Metal substrates or metallised layers can be selected e.g of Al, Cu.
25 Ni, Ag, Or or alloys like e.g. Pt-Rh or Ni-Cr, or layers comprising one or more metal flakes dispersed in a light transmissive binder.
Suitable metal flakes are e.g. flakes aluminium, gold or titan, or metal oxide flakes of e.g. Fe2O3 and/or TiO2.
30 Suitable pearlescent or interference pigments are e.g. mica, SiO2, Al2O3, TiO2 or glass flakes that are coated with one or more layers of e. g. titanium dioxide, iron oxide, titanium iron oxide or chrome oxide or combinations thereof, flakes comprising combinations of metal and metal oxide, metal flakes of e.g. aluminium coated with layers of 35 iron oxide layers and/or silicium dioxide. These pigments are known to the expert and are commercially available in a wide variety.
- 19 Preferred pigments are for example the commercially available Iriodin6), Colourstream() or XirallicG) (from Merck KGaA, Darmstadt, Germany), or Paliochrome) (from BASE AG, Ludwigshafen, Germany), or optically variable pigments e.g. from Flex Corp It is also possible to use LC pigments or coatings comprising a polymerized or crosslinked CLC material, e.g. CLC pigments dispersed in a transparent binder. Suitable LC pigments and binder systems are known to the expert and are described for example in 10 US 5,364,557, US 5,834,072, EP 0 601 483, WO 94/22976, WO
97/27251, WO 97t27252, WO 97/30136 and WO 99/02340.
Preferably the substrate comprises a surface of metal, in particular of aluminium, at the substrate - liquid crystal layer interface. Especially 15 preferred are aluminised plastic substrates such as Al-coated PET.
A fourth preferred embodiment of the invention relates to the use of a film comprising polymerised liquid crystal (LC) material with uniform orientation as optical retardation film in an LC display, wherein said 20 polymerised LC film is positioned between the substrates of the switchable LC cell (incell application). Especially preferred is a film prepared by the methods as described above and below. Further preferred is a film having at least two regions or a pattern of regions with different retardation.
For some applications it is desirable to place the optical retardation film not outside the switchable LC cell of a display, but between the substrates, usually glass substrates, forming the switchable LC cell and containing the switchable LC medium (incell application).
30 Compared to conventional displays where optical retarders are usually placed between the LC cell and the polarisers, incell application of an optical retardation film has several advantages. For example, a display where the optical film is attached outside of the glass substrates forming the LC cell usually suffers from parallax problems, 35 which can severely impair viewing angle properties. If the retardation
- 20 fiims is prepared inside the LC display cell, these parallax problems can be reduced or even avoided.
Furthermore, incell application of the optical retardation film allows to 5 reduce the total thickness of the LCD device, which is an important advantage for flat panel displays. Also, the displays become more robust. Especially advantageous for incell aspplication is a film comprising polymerised LC material according to the present invention, as it can be made thinner due to the higher birefringence of 10 the LC material compared e.g. to stretched plastic films. Thus, a film with a thickness of 2 microns or less can be used, which is especially suitable for incell applications.
Also, patterned or pixelated films according to the present invention 15 are especially useful for incell use in pixelated or matrix LCDs, for example in multiplexed TN- or STN-LCDs or in an active matrix driven (AMD) LCDs. In these displays it is possible to form the patterned optical retardation film such that the optical properties in the different regions of the film, like e.g. the retardation, are adjusted to the pattern 20 of individual pixels in the LCD. For example, a pixelated quarter wave retardation layer can be constructed having three types of pixels with a retardation of approximately 1 12 nm, 1 37nm and 150 nm, which correspond to approximately a quarter of the wavelength of the blue pixel at 450 nm, green pixel at 550 nm and red pixel at 600 nm of the 25 colour filter, respectively. In contrast, conventional optical films will only provide an average uniform property for all areas of the display.
Thus, the invention further relates to an LCD comprising - a liquid crystal cell formed by two plane parallel substrates at 30 least one of which is transparent to incident light, an electrode layer provided on the inside of at least one of said two transparent substrates and optionally superposed with an alignment layer, and a liquid crystal medium which is present between the two substrates and is switchable between at least two different states 35 by application of an electric field,
- 21 - a first linear polariser on one side of the liquid crystal cell, optionally a second linear polariser on the side of the liquid crystal cell opposite to that of said first linear polariser, 5 characterized in that it comprises at least one film comprising polymerised LC material as described above and below that is positioned between the two plane parallel substrates of said liquid crystal cell.
10 An preferred LCD according to this embodiment comprises 1) a liquid crystal (LC) cell comprising the following elements, starting from the edges to the centre of the cell in the sequence listed below 15 1 1) a first and a second substrate plane parallel to each other, at least one of which is transparent to incident light, 12) an array of nonlinear electric elements on one of said substrates which can be used to individually switch individual pixels of said LC cell, said elements being preferably active 20 elements like transistors, very preferably TFTs, 13) a colour filter array provided on one of said substrates, preferably on the substrate opposite to that carrying the array of nonlinear elements, said colour filter optionally being covered by a planarisation layer, 25 14) a first electrode layer provided on the inside of said first substrate, 15) optionally a second electrode layer provided on the inside of said second substrate, 30 16) optionally first and second alignment layers provided on said first and second electrodes, 17) an LC medium that is switchable between at least two different states by application of an electric field,
35 2) a first linear polariser on one side of the LC cell,
- 22 3) optionally a second linear polariser on the side of the LC cell opposite to that of the first linear polariser, and 4) at least one patterned optical retardation film, 5 characterized in that said patterned optical retardation films 4) is situated between the first and second substrate of the LC cell, preferably between the colour filter and the liquid crystal medium, very preferably between the colour filter and one of said electrode layers, or if a planarisation layer is present, between the planarising 1 layer and one of said electrode layers.
An LCD according to this preferred embodiment is exemplarily depicted in Figure 3, comprising two substrates (11a, 11b), a TFT array (12), a colour filter array (1 3a), a planarisation layer (1 3b), 15 electrode layers ((14) and optionally (15)), optionally two alignment layers (16a, 16b), an LC medium (17), and an optical retardation film (4) that is positioned between the planarisation layer and LC medium and optionally provided on another alignment layer (1 6c). Depending on the display mode, the alignment layer (16a) and/or (16b), and one 20 of the electrode layers (14) and (15) may also be omitted. Preferably, an alignment layer (16c) is present between the optical retardation film (4) and the planarisation layer (13b).
The optical retardation film (4) can also be positioned directly (i.e. 25 without the presence of an intermediate layer) on the colour filter array (1 3a) without the presence of a planarisation layer (1 3b), so that the optical retardation film serves as planarisation layer. It is also possible that the optical retardation film (4) is positioned between the colour filter array (1 3a) and the planarisation layer (1 3b). Preferably, an 30 alignment layer (1 6c) is present between the optical retardation film (4) and the colour filter (1 3a).
Especially preferably, the optical retardation film (4) is prepared directly on top of the colour filter (1 3a) or the planarisation layer (1 3b) 35 inside the display cell, i.e. the colour filter or planarisation layer,
- 23 optionally covered by an alignment layer, serve as substrate for the LC film preparation.
As colour filter (1 3a) any standard colour filter known in prior art for
5 use in flat panel displays can be used. Such a colour filter typically has a pattern of different pixels transmitting one of the primary colours red, green and blue (R. G. B). The optical retardation film (4) preferably exhibits a pattern of pixels with three different retardations, each of which is adjusted such that its efficiency of converting 10 linearly polarised light into circularly polarised light is optimised for one of the colours R. G and B. and is preferably positioned on the colour filter such that each R-, G- or B-pixel of the colour filter is covered by a corresponding pixel of the optical retardation film having a retardation optimised for this colour.
Especially preferred are multiplexed or matrix displays, very preferably active matrix displays.
The on-axis retardation (i.e. at 0 viewing angle) of an LC film 20 according to the present invention is preferably from 60 nm to 400 nm, especially preferably from 100 nm to 350 nm.
The thickness of an LC film according to the present invention is preferably from 0.5 to 2.5 microns, very preferably from 0.6 to 2 25 microns, most preferably from 0.7 to 1.5 microns.
The polymerisable LC material is preferably a nematic or smectic LC material, in particular a nematic material, and preferably comprises at least one mono reactive achi ral polymerisable mesogenic compound 30 and at least one di- or multireactive achiral polymerisable mesogenic compound. Polymerisable mesogenic mono-, di- and multireactive compounds used for the instant invention can be prepared by methods which are 35 known per se and which are described, for example, in standard works of organic chemistry such as, for example, Houben-Weyl,
- 24 Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.
Typical examples are described for example in WO 93/22397; EP O 261 712; DE 19504224; DE 4408171 and DE 4405316. The compounds disclosed in these documents, however, are to be 5 regarded merely as examples that do not limit the scope of this invention. Examples representing especially useful mono- and direactive polymerisable mesogenic compounds are shown in the following list 10 of compounds, which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention: 15 P-(cH2)xo COO Y (la) P-(cH2)xO 3 coo BY (lb) P(CH2)x COO OCO Y (Ic) P-(CH2)xO COO R (Id) P-(cH2)xo COO T: R (le) P-(CH2)xO Zz R (Ifl
- 25 P(CH2)X-O ≤L R
v (19) P-(CH2)xO CH=CH-COO R (I h) P(CH2)xO /3 (COO)v R (1i) P-(CH2)XO COO CH2CH(CH3)C2H5
(Ik) 15 it\ P-(CH2)XO COO COO CH2CH(CH3)c2Hs 20 P-(CH2)XO COO-Ter (In) P(CH2)xO COO-Chol (lo) P-(CH2)x W3 COO -
(Ip) L1 L2 P(CH2)x COO OCO O(CH2)yP (1 la) 35 P(CH2)xo CH2CH2 CH2CH2 o(CH2)yP
on - 26 L1 L2 POCO2602CO̳ (IIC) P-(CH2)XO CH=CHCO o - OOCCH=CH o(CH2) yP (I Id) P-{CHz10 O(C-P 15 (lie) In the above formulae, P is a polymerisable group, preferably an acryl, methacryl, vinyl, vinyloxy, propenyl ether, epoxy or styrene group, x and y are each independently 1 to 12, A and D are 1,4 20 phenylene that is optionally mono- di or trisubstituted by L' or 1,4 cyclohexylene, u and v are 0 or 1, Z is -COO, -OCO-, -CH2CH2- or a single bond, Y is a polar group, R is an unpolar alkyl or alkoxy group, Ter is a terpenoid radical like e.g. menthyl, Chol is a cholesteryl group, and L' and L2 are each independently H. F. Cl, CN 25 or an optionally halogenated alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkoxycarbonyloxy group with 1 to 7 C atoms.
The term 'polar group' in this connection means a group selected from F. Cl, CN, NO2, OH, OCH3, OCN, SCN, an optionally fluorinated 30 carbonyl or carboxyl group with up to 4 C atoms or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. The term unpolar group' means an alkyl group with 1 or more, preferably 1 to 12 C atoms or an alkoxy group with 2 or more, preferably 2 to 12 C atoms.
- 27 The polymerisable LC material preferably comprises one or more monoreactive polymerisable mesogenic compounds and one or more di- or multireactive polymerisable mesogenic compounds.
5 A preferred polymerisable liquid crystal material comprises - 5 - 70 %, preferably 5 - 50 %, very preferably 5 - 40 % by weight of one or more direactive achiral mesogenic compounds, - 30 - 95 % preferably 50 - 75 % by weight of one or more 10 monoreactive achiral mesogenic compounds.
The monoreactive achiral compounds are preferably selected from above formulae la-lg and li, in particular la, le and 19, wherein v is 1.
The direactive achiral compounds are preferably selected from 15 above formulae Ha and lib, in particular lla.
Especially preferred are mixtures comprising one or more polymerisable compounds comprising an acetylene or tolane group with high birefringence, like e.g. compounds of formula 19 above.
20 Suitable polymerisable tolanes are described for example in GB 2,351, 734.
For the preparation of planar films with helically twisted structure, the polymerisable LC material preferably comprises one or more achiral 25 polymerisable mesogenic compounds and at least one chiral compound. The chiral compound can be selected from non polymerisable chiral compounds, like e.g. conventional chiral dopants, polymerisable chiral non-mesogenic or polymerisable chiral mesogenic compounds.
Suitable chiral dopants can be selected e.g. from the commercially available cholesterol nonanoate (CN), CB15, R/S-81 1, R/S-101 1, R/S-2011, R/S-3011 or R/S-4011 (Merck KGaA, Darmstadt).
Particularly suitable are dopants with high twisting power comprising 35 a chiral sugar group, in particular dianhydrohexitol derivatives like for example derivatives of sorbitol, mannitol or iditol, very preferably
So - 28 sorbitol derivatives as disclosed in WO 98/00428. Further preferred are dopants comprising a hydrobenzoin group as described in GB 2,328,207, chiral binaphthyl derivatives as described in WO 02/94805, chiral binaphthol acetal derivatives as described in WO 5 02/34739, chiral TADDOL derivatives as described in WO 02/06265, and chiral dopants with at least one fluorinated linkage group and a terminal or central chiral group as described in WO 02/06196 and WO 02/06195.
10 The polymerisable material is preferably dissolved or dispersed in a solvent, preferably in an organic solvent. The solution or dispersion is then coated onto the substrate, for example by spin-coating or other known techniques, and the solvent is evaporated off before polymerization. In most cases it is suitable to heat the mixture in 15 order to facilitate the evaporation of the solvent.
The polymerisable LC material may additionally comprise a polymeric binder or one or more monomers capable of forming a polymeric binder and/or one or more dispersion auxiliaries. Suitable 20 binders and dispersion auxiliaries are disclosed for example in WO 96/02597. Especially preferred, however, are LC materials not containing a binder or dispersion auxiliary.
In another preferred embodiment the polymerisable LC material 25 comprises an additive that induces or enhances planar alignment of the liquid crystal material on the substrate. Preferably the additive comprises one or more surfactants. Suitable surfactants are described for example in J. Cognard, Mol.Cryst.Liq.Cryst. 78, Supplement 1,1-77 (1981). Particularly preferred are non-ionic 30 surfactants, very fluorocarbon surfactants, like for example the commercially available fluorocarbon surfactants Fluorad FC-171<g) (from 3M Co.), or Zonyl FSN O (from DuPont).
Polymerisation of the LC material is preferably achieved by exposing 35 it to actinic radiation. Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays
To - 29 or irradiation with high energy particles, such as ions or electrons.
Preferably polymerization is carried out by photoirradiation, in particular with UV light. As a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a 5 high lamp power the curing time can be reduced. Another possible source for photoradiation is a laser, like e.g. a UV laser, an IR laser or a visible laser.
Polymerisation is carried out in the presence of an initiator absorbing 10 at the wavelength of the actinic radiation. For example, when polymerizing by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or ions that start the polymerization reaction. UV photoinitiators are preferred, in particular radicalic UV photoinitiators. As standard 15 photoinitiator for radical polymerization for example the commercially available IrgacureO 907,1rgacure) 651, Irgacure() 184, DarocuretE) 1173 or Darocure@) 4205 (all from Ciba Geigy AG) can be used, whereas in case of cationic photopolymerisation the commercially available UVI 6974 (Union Carbide) can be used.
The polymerisable LC material can additionally comprise one or more other suitable components such as, for example, catalysts, sensitizers, stabilizers, chain-transfer agents, inhibitors, co-reacting monomers, surface-active compounds, lubricating agents, wetting agents, dispersing 25 agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes or pigments.
In another preferred embodiment the mixture of polymerisable 30 material comprises up to 70%, preferably 1 to 50 % of a monoreactive non-mesogenic compound with one polymerisable functional group. Typical examples are alkyl acrylates or alkyl methacrylates with alkyl groups of 1 to 20 C atoms.
35 It is also possible, in order to increase crosslinking of the polymers, to add up to 20% of a non-mesogenic compound with two or more
To - 30 polymerisable functional groups to the polymerisable LC material alternatively or in addition to the di- or multireactive polymerisable mesogenic compounds to increase crosslinking of the polymer.
Typical examples for direactive non-mesogenic monomers are alkyl 5 diacrylates or alkyl dimethacrylates with alkyl groups of 1 to 20 C atoms. Typical examples for multireactive non-mesogenic monomers are trimethylpropane trimethacrylate or pentaerythritol tetraacrylate. 10 It is also possible to add one or more chain transfer agents to the polymerisable material in order to modify the physical properties of the polymer film. Especially preferred are thiol compounds, such as monofunctional thiol compounds like e.g. dodecane thiol or multifunctional thiol compounds like e.g. trimethylpropane tri(3 15 mercaptopropionate), very preferably mesogenic or liquid crystalline thiol compounds. When adding a chain transfer agent, the length of the free polymer chains and/or the length of the polymer chains between two crosslinks in the inventive polymer film can be controlled.
When the amount of the chain transfer agent is increased, the 20 polymer chain length in the obtained polymer film is decreasing.
Suitable substrates include films, paper, board, leather, cellulose sheeting, textiles, plastics, glass, ceramics and metals. Suitable polymer films are for example polyester such as 25 polyethyleneterephthalate (PET) or polyethylenenaphthalate (PEN), polyvinyla lcohol (PVA), polycarbon ate (PC) or triacetylcell u lose (TAC) , especially preferably PET or TAC. Especially preferred are substrates metallised with aluminium, or aluminium foils.
30 The substrate or at least the surface of the substrate covered with the LC material is preferably flat, like e.g. a foil, film or sheet, and has preferably a thickness smaller than 200 um, in particular smaller than 60,um, most preferably smaller than 20,um.
35 The substrate surface is preferably planar. The substrate may also be structured, patterned and/or have a relief. The use of structured
To - 31 substrates is especially suitable when preparing patterned films for use as security markings. The shape, structure, pattern andlor relief of the substrate is preferably adapted to the desired application of the inventive security marking. Suitable structuring and patterning 5 techniques are well known to the one skilled in the art, in particular in the fields of precision engineering and microtechnology, and include
but are not limited to lithography, etching, cutting, stamping, punching, embossing, molding and electron discharge machining techniques. In particular for the preparation of patterned films for use as security markings it is also possible to use a reflective substrate comprising a hologram or kinegram or common holographic optical element (HOE), a holographic layer with an embossed, patterned or 15 structured surface, or a layer of reflective holographic pigments. Light reflected by higher regions of the structured surface will interfer with light reflected by lower regions of the structured surface, thereby forming a holographic image. The preparation of holographic layers is described for example in US 4,588,664, the entire disclosure of
20 which is incorporated into this application by reference.
Thus, for example a substrate like e.g. a banknote, or selected regions thereof, can be printed or coated with a hologram or reflective metal layer, onto which the LC material is applied.
25 Alternatively the marking may be prepared separately on a reflective substrate which is then applied to the document of value for example as security thread or as another form of a security marking.
This embodiment is particularly suitable for use as false-proof 30 security threads or holograms on banknotes or documents of value, providing a security marking by which the banknote is easy to authenticate when viewed through a polariser.
The films according to the present invention can be used as 35 retardation or compensation films in conventional LCDs, in particular those of the DAP (deformation of aligned phases) or VA (vertically
A:-) - 32 aligned) mode, like e.g. ECB (electrically controlled birefringence), CSH (colour super homeotropic), VAN or VAC (vertically aligned nematic or cholesteric) displays, MVA (multi-domain vertically aligned) or PVA (patterned vertically aligned) displays, in displays of the bend 5 mode or hybrid type displays, like e.g. OCB (optically compensated bend cell or optically compensated birefringence), R-OCB (reflective OCB),HAN (hybrid aligned nematic) or pi-cell (rc-cell) displays, furthermore in displays of the TN (twisted nematic), HTN (highly twisted nematic) or STN (super twisted nematic) mode, in AMD-TN 10 (activematrix driven TN) displays, or in displays of the IPS (in plane switching) mode which are also known as 'super TFT' displays.
Especially preferred are VA, MVA, PVA, OCB and pi-cell displays.
15 The birefringent marking according to this invention can be used in decorative, security, authentification or identification applications, as security, authentification or identification marking, or in a thread or device comprising the security marking.
20 The security marking can be used for direct application e.g. onto an article, device or document, or as threads, holograms or hot stamping foils for decorative or security applications, to authenticate and prevent counterfeiting of documents of value, for identification of hidden images, informations or patterns. It can be applied to 25 consumer products or household objects, car bodies, foils, packing materials, clothes or woven fabric, incorporated into plastic, or applied as security markings or threads on documents of value like banknotes, credit cards or ID cards, national ID documents, licenses or any propduct with money value, like stamps, tickets, shares, cheques etc The examples below serve to illustrate the invention without limiting it. In the foregoing and the following, all temperatures are given in degrees Celsius, and all percentages are by weight, unless stated otherwise. An is the birefringence at 20 C and 550 nm. Unless stated 35 otherwise, the polymer films in the following examples were made using the following general method: The polymerisable compounds
on - 33 were dissolved in a mixture of organic solvents such as toluene and isopropanol solutions (wow 8:2) and coated on a triacetylcellulose (TAC) substrate using a No. O wire wound bar at room temperature.
The solvent was allowed to evaporate and the film was cured under 5 different conditions, but always at ambient temperature unless stated otherwise. Example 1
10 Preparation of planar aliened LC polymer films The following polymerisable LC mixtures were formulated Compound (in % by weight) 15 Mixture M1 M2 MaM4 M5 FC171 Irg907 1 42.25 18.78 0.48 5.63
2 34.40 5.00 14.0040.00 0.60 6.00
3 6.00 43.50 33.5017.00 0.50 4.00
20 66.50 7.00 21.00 0.50 5.00
5_ 93.40 =-- 0.606.00
70.00 23.40 0.606.00
7 46.70 -46.70 0.606.00
258 34.40 5.00 14.00 44.00 0.602.00
CH3 CH2=CHCO2(CH2)3o COO OCO <3 O(CH2)302CCH=CH2 30 (M1)
CH2=CHCOO(CH2)6O /3 COO IN
(M2)
on - 34 CH2=CHCOO(CH2)6O COO OCH3
(M3) CH2=CHCOO(CH2)6O COO C3H7
(M4) CH2=CHCoo(CH2)3O <3 H3 c2H5 (M5) 15 The direactive compound (M1) can be prepared as described in WO 93/22397. The monoreactive compounds (M2) and (M3) can be prepared according to or in analogy to the methods described in D.J.Broer et al., Makromol.Chem. 190, 3201-3215 (1989). The monoreactive compound (M4) iS described in GB 2,280,445. The 20 monoreactive compound (M5) is described in GB 2,351,734. Irgacure 907 iS a commercially available photoinitiator (from Ciba AG, Basel, Switzerland). Fluorad FC 171 is a commercially available non-ionic fluorocarbon surfactant (from 3M).
25 Planar aligned LC polymer films were prepared from these mixtures using different curing conditions and their retardation was measured.
The results are discussed in the following examples.
ExamPIe 2 Preparation of olanar aliened LC nolvmer films using different UV lamn oower and qas atmosoheres Planar aligned LC polymer films were prepared from mixture 2 of 35 example 1 with different UV lamp power and under different
o - 35 atmosphere, and their retardation was measured. The results are shown in Table 2.
Table 2
5 Mix. No. Curing Atmo- Retardation Thickness An Lamp* sphere (nary) (em) 2 A air 163.4 0.846 0.193 2 B air 119.3 0.846 0.141 10 H N2 142.2 0.890 0. 160
C air 143.2 0.913 0.157 2 K N2 146.2 0.840 0.174
G air 125.5 0.854 0.147 15 2 H N2 139.4 0.860 0.162
2 N2 152.5 0.792 0.193
*Conditions A. Uncured film (thickness in first approximation same as cured film) 20 B.4 passes under minicure lamp at 15m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2) C.1 pass under minicure lamp at 15m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2) G. Dr Honle mercury lamp with dichroic mirror, not focused, 16mW, 30sec 25 H.4 passes under minicure lamp at 15m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2), nitrogen atmosphere I. Or Honle mercury lamp with dichroic mirror, not focused, nitrogen atmosphere, 16mW,30 see J Fluorescent lamp TL05 (Philips Lighting), 0.6mW/cm2,2 min. nitrogen atmosphere K.1 pass under minicure lamp at 15m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2), nitrogen atmosphere It can be seen that curing the LC mixtures under a nitrogen atmosphere generally gives films with higher birefringence than
o - 36 those cured in air. This is especially apparent in films cured under a low lamp power and under a nitrogen atmosphere.
Example 3
Preparation of planar aliened LC polymer films with different decree of crosslinkinu Planar aligned LC polymer films were prepared from mixtures 1-7 of 10 example 1 using different curing conditions and their retardation was measured. The results are shown in Table 3 and 4.
Table 3
15Mix. No. Curing Retardation Thickness fin Lamp* (nary) (pm) A - 141.4 0.8036 0.176
H 132.7 0.889 0.149
20 1 J 137.7 0.941 0.146
H 181.2 1.082 0.167
J 156.6 0.823 0.190
4 H 116.5 0.843 0.138
4 J 112.3 0.822 0.137
Table 4
30 7 J 128.5 0.972 0.132
J 156.9 0.819 0.192
J 151.1 0.703 0.215
5 H 113.9 0.815 0.140
6 H 137.1 0.955 0.144
35 7 H 121.0 0.798 0.152
To - 37 *Conditions A. Uncured film (thickness in first approximation same as cured film) H. 4 passes under minicure lamp at 1 5m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2), nitrogen 5 atmosphere J. Fluorescent lamp TL05 (Philips Lighting), 0. 6mW/cm2, 2 min. nitrogen atmosphere Table 3 shows the effect of changing the cross-linking density on the 10 final optical properties of the film. A highly crosslinked mixture is more stable to curing conditions than a low crosslinked mixture. This effect can be further magnified if the film is also cured under a fluorescent lamp and under a nitrogen atmosphere (condition J), this agrees with the effects shown in example 1 and 2. This effect can be 15 seen even more clearly from the data presented in Table 4, where mixtures with compound M5, a higher birefringence monoacrylate comprising a tolane group, is combined with the mesogenic diacrylate M1 in three different ratios. From Table 4 it is apparent that polymerisable LC formulations with a high crosslinking density do not 20 show this effect, whilst formulations with lower amount of crosslinking give an enhanced effect.
Example 4
25 Preparation of planar aliened LC noivmer films using different amounts of ohotoinitiator Planar aligned LC polymer films were prepared from mixtures 2 and 8 of example 1 using different curing conditions and their retardation 30 was measured. The results are shown in Table 5.
*Table 6
Mix. No. Curing Atmo- Retardation Thickness An 35 Lamp* sphere (nary) m) 2 A air 163.4 0.846 0.193
To - 38 2 B 1 air 1 119.3 0.846 1 0.141 1 1 H N2 136.8 0.818 0.167
2 I N2 1 152.5 1 0.848 1 0.180 l j 2 J N2 167.5 1 0.819 1 0.204 8 1 A air 1 196.6 1.015 0.192 8 1 B air 1 133.9 1.015 1 0.132 l 8 H N2 1 153.7 1 0.836 1 0.184
10 8 N2 161.1 | 0.805 0.200
8 J N2 1 174.5 1 0.821 0.212
*Conditions 15 A. Uncured film (thickness in first approximation same as cured film) B.4 passes under minicure lamp (high power focused medium pressure mercury lamp, lamp power 65mW/cm2) H. 4 passes under minicure lamp (high power focused medium pressure mercury lamp, lamp power 65mW/cm2), nitrogen atmosphere 20 I. Dr Honle mercury lamp with dichroic mirror, not focused, 16mW, 30 see, nitrogen atmosphere J. Fluorescent lamp TL05 (Philips Lighting), 0.6mW/cm2, 2 min. nitrogen atmosphere 25 Table 5 shows the effect of changing the photoinitiator concentration on the optical properties of the planar films. A significant increase in birefringence can be obtained if the photoinitiator concentration is lowered and the films are cured under a nitrogen atmosphere.
30 Example 5
Preparation of a planar aliened LC polymer film with patterned retardation Mixture 7 of example 1 containing the high birefringent monoacrylate 35 M5 and the diacrylate M1 was coated using the general conditions described above. Certain parts of the film were covered with a mask,
o - 39 and the film exposed to low power UV light under a nitrogen atmosphere. A previously masked part of the film was then uncovered and exposed to an UV light of intermediate intensity. The final mask was then removed and exposed to high intensity UV light.
5 The retardation values in different part of the film were measured and the results are shown in Table 6.
Table 6
10 Mix. No. Curing Atmo- Retardation Lamp* sphere (nary) B air 129.5 7 N2 141.8
15 7 J N2 153.8
*Conditions B. 4 passes under minicure lamp at 1 5m/min (high power focused medium pressure mercury lamp, lamp power 65mW/cm2) 20 I. Or Honle mercury lamp with dichroic mirror, not focused, 16mW, 30 see, nitrogen atmosphere J. Fluorescent lamp TL05 (Philips Lighting), 0.6mW/cm2, 2 min. nitrogen atmosphere 25 A picture of the planar film taken through crossed polarisers with the optic axis at 45 to the absorption axis of the polarisers shows areas of different retardation which have been cured under different conditions. The difference in retardation between the lowest and maximum area is 23nm, however with further optimization of the 30 polymerisable mixture formulation and curing conditions, this difference can be further increased.
Example 6
35 Preparation of a planar aligned LC polymer film with patterned retardation on a reflective substrate for use as security marking
To - 40 Mixture 7 of example 1 containing the high birefringent monoacrylate M5 and the diacrylate M1 was dissolved in toluene/isopropanol (8:2 w/w) solution as a 30% (w/w) solids solution This solution was 5 coated on rubbed aluminium PET using a No O wire wound bar (RK).
The thickness of the film was approximately 1,um. The solvent was allowed to evaporate and the mixture allowed some time to align.
The coated mixture was covered with a black mask to create a pattern and exposed to a high power focused medium pressure 10 mercury lamp (lamp power 65mW/cm2, total does 520 mJ/cm2). The mask was removed and the film exposed to a low power Fluorescent lamp TL05 (Philips Lighting, lamp power 0.6mW/cm2, total dose 72 mJ/cm2) under a nitrogen atmosphere.
15 The resulting polymer film exhibits a pattern in the shape of the black mask, wherein areas that were cured in the first step under the high power lamp have lower retardation and areas that were cured in the second step under the low power lamp have higher retardation. The pattern is invisible to the naked eye, but becomes visible when 20 viewed using polarised light, e.g. between two linear polarisers or using a circular polariser. the patterned film can be used as security marking e.g. for authentification of objects or documents of value.
Example 7
Preparation of Patterned planar aliened LC nolvmer film bv curing at different temperatures The following polymerisable mixture (8) was prepared (M1)39.4%
(M2)24.6%
(M3)24.6%
(M6)9.8%
35 Irgacure6511.0% Fluorad FC1710.6%
\: - 41 CH3 CH2=CHCO2(CH2)6o COO OCO O(CH2)6o2CCH=CH2 5 (M6)
Various samples of the mixture were planar aligned and cured by the general method as described above, but at different polymerization temperatures, to give polymer films with different birefringence. The 10 birefringence of the resulting polymer films decreases with increasing polymerization temperature as shown in Figure 1.
A patterned film is prepared as follows: A photomask was used to cover selected areas of the polymerisable LC mixture, and the 15 unmasked regions are cured at a first temperature. The previously masked regions were then cured at a second temperature. One of the first and second temperatures was in the nematic phase and the other was in the isotropic of the polymerisable LO mixture. A planar film with a striped pattern of regions with different retardation was 20 obtained as shown in Figure 2. The film thickness is 2 microns. The region cured in the nematic phase (light) has a retardation of 340 nm, the region cured in the isotropic phase (dark) is not birefringent and has no retardation.
Claims (28)
1. A method of controlling the retardation in a film comprising polymerised liquid crystal (LC) material and being obtained by 5 polymerization of a polymerisable LC material, by varying the composition of the polymerisable LC material and/or varying the polymerization conditions during polymerization of the LC material.
2. A method as claimed in claim 1, wherein the polymerised LC to material has planar orientation.
3. A method as claimed in claim 1 or 2, wherein the polymerized LC film is prepared by photopolymerisation and the retardation of the film is increased by reducing the intensity of radiation used for polymerisation.
4. A method as claimed in any of the preceding claims, wherein the retardation of the polymerized LC film is increased by polymerization in an inert gas atmosphere.
2U
5. A method as claimed in any of the preceding claims, wherein the polymerisable LC material comprises at least one polymerisable compound having one polymerisable group (mono reactive) and at least one polymerisable compound having two or more as polymerisable groups (di- or multireactive).
6. A method as claimed in claim 5, wherein the retardation of the polymerized LC film is increased by reducing the amount of multireactive compounds.
7. A method as claimed in claim 5 or 6, wherein the polymerisable LC material comprises one or more multireactive compounds,
<) 43
preferably multireactive mesogenic compounds, in an amount from 5 to 70 %, preferably from 10 to 60% by weight of the total amount of solid components in the material.
5
8. A method as claimed in any of the preceding claims, wherein the polymerisable LC material comprises at least one photoinitiator, and wherein the retardation of the polymerised LC film is increased by reducing the amount of photoinitiator.
to
9. A method as claimed in claim 8, wherein the polymerisable LC material comprises one or more photoinitiators in an amount from 0.5 to
10 %, preferably from 2 to 8 % by weight of the total amount of solid components in the material.
I5 10. A method as claimed in any of claims 1 to 7, wherein the retardation of the film is increased by reducing the temperature at which the film is polymerized.
11. A method of controlling the retardation in a film, substantially as so hereinbefore described with reference to the Examples.
-
12. A method of preparing a film comprising polymerised liquid crystal (LC) material with planar orientation and having at least two regions or a pattern of regions with different retardation, comprising the 25 steps of providing a polymerisable LC material on a substrate and photopolymerising different selected areas of the polymerisable LC material under different polymerization conditions, characterized in that different selected areas are polymerized with or without an inert gas atmosphere and/or different selected areas are polymerized do using different intensity of photoradiation and/or different areas are polymerized at different temperatures.
rid 44
13. A method of preparing a film comprising polymerised LC material with planar orientation and having at least two regions or a pattern of regions with different retardation, substantially as hereinbefore 5 described with reference to the Examples.
14. A film comprising polymerised liquid crystal (LC) material obtained by a method as claimed in any of the preceding claims.
to
15. A film as claimed in claim 14, which has at least two regions or a pattern of resigns with different retardation.
16. A film as claimed in claim 14 or 15, which is provided on a reflective substrate.
17. A film as claimed in claim 16, wherein the reflective substrate comprises one or more metal or metallised layers.
18. A film as claimed in claim 17, wherein the reflective substrate is an 20 aluminised plastic film.
19. A-film as claimed in any of claims 14 to 18, which has a retardation of from 60 to 4000 nm and a thickness of from 0.5 to 2.5 microns.
25
20. Use of a film as claimed in any of claims 14 to 19 in optical or electrooptical devices, for decorative or security applications.
21. A liquid crystal display comprising a film as claimed in any of claims 14 to 19.
22. A security marking comprising a film as claimed in any of claims 14 to 19.
<3 45
23. An object or document of value comprising a security marking as claimed in claim 22.
s
24. Use of a film as claimed in any of claims 14 to 19 as an optical retardation film in an LC display.
25. Use as claimed in claim 24, wherein the film is positioned between the substrates of the switchable LC cell.
26. A liquid crystal display (LCD) comprising at least one polariser and a switchable LC cell comprising a layer of an LC medium between two plane parallel substrates at leastone of which is transparent to incident light, wherein the LCD comprises at least one optical Is retardation film that is positioned between the substrates of the LC cell.
27. An LCD comprising a liquid crystal cell formed by two plane parallel substrates at to least one of which is transparent to incident light, an electrode layer provided on the inside of at least one of said two transparent substrates and optionally superposed with an alignment layer, and a liquid crystal medium which is present between the two substrates and is switchable between at 25 least two different states by application of an electric field,
- a first linear polariser on one side of the liquid crystal cell, optionally a second linear polariser on the side of the liquid crystal cell opposite to that of the first linear polariser, characterized in that it further comprises at least one optical do retardation film that is positioned between the two plane parallel substrates forming the liquid crystal cell.
) 46
28. An LCD as claimed in claim 26 or 27, wherein the optical retardation film is a film as claimed in any of claims 14 to 19.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP02019792 | 2002-09-05 |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB0320342D0 GB0320342D0 (en) | 2003-10-01 |
| GB2394718A true GB2394718A (en) | 2004-05-05 |
| GB2394718B GB2394718B (en) | 2007-03-07 |
Family
ID=28685920
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB0320342A Expired - Fee Related GB2394718B (en) | 2002-09-05 | 2003-08-29 | Polymerised liquid crystal film with retardation pattern |
Country Status (2)
| Country | Link |
|---|---|
| KR (1) | KR20040022179A (en) |
| GB (1) | GB2394718B (en) |
Cited By (24)
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| GB2398077A (en) * | 2003-01-31 | 2004-08-11 | Merck Patent Gmbh | Polymerised liquid crystal film with improved adhesion |
| WO2004104656A1 (en) * | 2003-05-16 | 2004-12-02 | Kent State University | A method of making optical compensation film using polymer stabilization technique |
| WO2006025023A1 (en) * | 2004-09-03 | 2006-03-09 | Koninklijke Philips Electronics N.V. | A collimator for use in a backlight liquid crystal display system |
| GB2425774A (en) * | 2005-01-11 | 2006-11-08 | Merck Patent Gmbh | Polymerized liquid crystal film with low retardation |
| WO2008052376A1 (en) * | 2006-11-03 | 2008-05-08 | Rolic Ag | Birefringent layer of c-plate and o-plate type |
| EP1925954A2 (en) | 2006-11-21 | 2008-05-28 | FUJIFILM Corporation | Process of producing patterned birefringent product |
| WO2008067932A2 (en) | 2006-12-04 | 2008-06-12 | Giesecke & Devrient Gmbh | Security element having a motif-producing liquid crystal layer |
| WO2008077261A1 (en) * | 2006-12-22 | 2008-07-03 | Rolic Ag | Patternable liquid crystal polymer comprising thio-ether units |
| WO2009062853A1 (en) * | 2007-11-12 | 2009-05-22 | Bundesdruckerei Gmbh | Document having an integrated display device |
| WO2009093718A2 (en) | 2008-01-22 | 2009-07-30 | Fujifilm Corporation | Method of producing a patterned birefringent product and birefringent product |
| EP2113807A2 (en) | 2008-04-30 | 2009-11-04 | Fujifilm Corporation | Optical material having a colored optically anisotropic layer |
| EP2124076A1 (en) | 2008-05-21 | 2009-11-25 | Fujifilm Corporation | Birefringent pattern builder and laminated structure material for preventing forgery |
| EP2093609A3 (en) * | 2008-02-19 | 2010-10-20 | FUJIFILM Corporation | Substrate for liquid crystal display device and liquid crystal display device |
| US7879634B2 (en) | 2005-09-16 | 2011-02-01 | Fujifilm Corporation | Process for producing a liquid crystal cell substrate having a TFT driver element, a liquid crystal cell substrate, and liquid crystal display device |
| US7920232B2 (en) | 2006-01-19 | 2011-04-05 | Fujifilm Corporation | Method of producing liquid crystal cell substrate, liquid crystal cell substrate, and liquid crystal display device |
| US7919153B2 (en) | 2006-03-03 | 2011-04-05 | Fujifilm Corporation | Laminated structure, process of producing a liquid crystal cell substrate using the same, liquid crystal cell substrate, and liquid crystal display device |
| US20110104445A1 (en) * | 2008-04-07 | 2011-05-05 | Ko Hermans | Process for preparing a polymeric relief structure |
| US8094271B2 (en) | 2006-02-03 | 2012-01-10 | Fujifilm Corporation | Liquid crystal display device and color film plate, and processes for producing the same |
| US8189138B2 (en) | 2005-09-08 | 2012-05-29 | Fujifilm Corporation | Transfer material, process for producing a color filter using the same, a color filter and liquid crystal display device |
| US8253898B2 (en) | 2005-03-29 | 2012-08-28 | Fujifilm Corporation | Transfer material, and process for producing liquid crystal cell substrate and liquid crystal display device using the same |
| US8304017B2 (en) | 2008-03-18 | 2012-11-06 | Fujifilm Corporation | Method of producing a patterned birefringent product |
| US20130094084A1 (en) * | 2010-06-30 | 2013-04-18 | 3M Innovative Properties Company | Mask processing using films with spatially selective birefringence reduction |
| US8451420B2 (en) | 2005-11-14 | 2013-05-28 | Fujifilm Corporation | Process of producing substrate for liquid crystal display device, substrate for liquid crystal display device, and liquid crystal display device |
| EP2605061A1 (en) * | 2011-10-20 | 2013-06-19 | Boe Technology Group Co. Ltd. | Liquid crystal display |
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| GB2398077B (en) * | 2003-01-31 | 2006-12-06 | Merck Patent Gmbh | Polymerised liquid crystal film with improved adhesion |
| GB2398077A (en) * | 2003-01-31 | 2004-08-11 | Merck Patent Gmbh | Polymerised liquid crystal film with improved adhesion |
| WO2004104656A1 (en) * | 2003-05-16 | 2004-12-02 | Kent State University | A method of making optical compensation film using polymer stabilization technique |
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| WO2006025023A1 (en) * | 2004-09-03 | 2006-03-09 | Koninklijke Philips Electronics N.V. | A collimator for use in a backlight liquid crystal display system |
| GB2425774B (en) * | 2005-01-11 | 2010-05-19 | Merck Patent Gmbh | Polymerized liquid crystal film with low retardation |
| GB2425774A (en) * | 2005-01-11 | 2006-11-08 | Merck Patent Gmbh | Polymerized liquid crystal film with low retardation |
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| EP1925954A2 (en) | 2006-11-21 | 2008-05-28 | FUJIFILM Corporation | Process of producing patterned birefringent product |
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| JP2009069793A (en) * | 2006-11-21 | 2009-04-02 | Fujifilm Corp | Process of producing patterned birefringent product |
| WO2008067932A3 (en) * | 2006-12-04 | 2008-09-25 | Giesecke & Devrient Gmbh | Security element having a motif-producing liquid crystal layer |
| EP2261053A1 (en) * | 2006-12-04 | 2010-12-15 | Giesecke & Devrient GmbH | Security element having a motif producing liquid crystal layer |
| WO2008067932A2 (en) | 2006-12-04 | 2008-06-12 | Giesecke & Devrient Gmbh | Security element having a motif-producing liquid crystal layer |
| US8574454B2 (en) | 2006-12-22 | 2013-11-05 | Rolic Ag | Patternable liquid crystal polymer comprising thio-ether units |
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| EP2605061A4 (en) * | 2011-10-20 | 2014-07-23 | Boe Technology Group Co Ltd | Liquid crystal display |
| JP2014531050A (en) * | 2011-10-20 | 2014-11-20 | 京東方科技集團股▲ふん▼有限公司 | LCD display |
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Also Published As
| Publication number | Publication date |
|---|---|
| KR20040022179A (en) | 2004-03-11 |
| GB2394718B (en) | 2007-03-07 |
| GB0320342D0 (en) | 2003-10-01 |
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Legal Events
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| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20120829 |