United States Patent
`[19]
`[11] Patent Number:
`5,828,488
`
`Ouderkirk et al.
`[45] Date of Patent:
`Oct. 27, 1998
`
`U8005828488A
`
`[75]
`
`[54] REFLECTIVE POLARIZER DISPLAY
`.
`-
`.
`Inventors 11:21:13: ir (Ligfirggvkoggfler
`.
`’
`"
`,y’
`SanfordCobb, Jr., St Mary S P01m>
`a110f Mlm; {311195 M- J0nla> Round
`Rock, TeX; Mlchael F. Weber,
`ShoreVieW, Minn.; David L. Wortman;
`Carl A. Stover, both of St. Paul, Minn.
`
`[73] ASSIgIlCCI Minnesota Mining and
`Manufacturing C0., St. Paul, Minn.
`
`[21] App1~ N0~I 402,349
`.
`.
`Flled‘
`
`[22]
`
`Ma“ 10’ 1995
`
`FOREIGN PATENT DOCUMENTS
`1327286
`3/1994 Canada ............................ G02B 6/00
`12/1993 China ....................
`G02F 1/1335
`218041
`
`056843
`8/1982 European Pat. Off.
`G02F 1/33
`062751
`10/1982 European Pat. Off.
`602B 1/08
`
`.. 602B 27/28
`0 460 241 A1
`12/1991
`European Pat. Off.
`
`0 469 732A3
`2/1992 European Pat. Off.
`602B 1/04
`
`0 488 544 A1
`6/1992 European Pat. Off.
`GOZB 5/30
`......... H04N 9/31
`0 492 636 A1
`7/1992 European Pat. Off.
`.......... G02B 5/08
`0 514 223
`11/1992 European Pat. Off.
`
`.. 60213 27/28
`0 552 725 A1
`7/1993 European Pat. Off.
`0 573 905 A1
`12/1993 European Pat. Off.
`........ 602B 27/28
`0 597 261 A1
`5/1994 European Pat. Off.
`...... G02F 1/1335
`0 606 939
`7/1994 European Pat. Off.
`...... G02F 1/1335
`.......... 602B 5/30
`0 606 940
`7/1994 European Pat. Off.
`
`41 21 861 A1
`1/1992 Germany ...............
`G02B 5/30
`181201
`7/1988
`Japan ................................ F21V 5/02
`
`Related US. Application Data
`
`(List continued on next page.)
`
`[63]
`
`Continuation—in—part of Ser. No. 171,239, Dec. 21, 1993,
`abandoned, Ser. No. 172,593, Dec. 21, 1993, abandoned,
`Ser. No. 359,436, Dec. 20, 1994, abandoned, and a continu—
`ation—in—part of Ser. No. 360,204, Dec. 20, 1994, abandoned.
`Int. CIF .............................. G02B 5/30; G02B 27/28
`[51]
`[52] US. Cl.
`.......................... 359/487; 359/495; 359/497;
`
`“
`
`OTHER PUBLICATIONS
`.
`,,
`.
`.
`.
`nght Duffusmg Film > .Optical SYStemS’ 3M 1993'
`IIIl Ct al, “COCXtruded Mlcrolayer Film and Sheet”, Journal
`$813?” F‘l’" “mi Sheenng’ V01‘ 4’ pp‘ 104—115 (Apr"
`MacLeOd, H.A. Thin Film Optical Filters, Adam Hilger,
`
`[58] Field Of Search ..................................... 359/485, 486,
`359/487, 488, 490, 491, 492, 493, 494,
`495, 496, 497, 498, 837; 362/19; 349/62,
`96
`
`[56]
`
`References CitEd
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`/
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`.
`(L1st confirmed on next Page)
`.
`.
`.
`.
`Pr‘mary Exammer—Rld‘y D: Shafer
`Attorney, Agent, or Firm—William D. Miller
`
`ABSTRACT
`[57]
`Abrightness enhanced reflective polarizer includes a reflec-
`tive polarizer and a structured surface material.
`
`(List continued on next page.)
`
`92 Claims, 32 Drawing Sheets
`
`149
`
`146
`
`K/
`
`|\
`
`
`
`
`
`
`LGE_001197
`
`LG Electronics Ex. 1018
`
`LGE_001197
`
`LG Electronics Ex. 1018
`
`

`

`5,828,488
`
`Page 2
`
`US. PATENT DOCUMENTS
`
`
`
`5,166,817
`11/1992 Ota et al.
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`
`5,194,975
`3/1993 Akatsuka et al.
`......................... 359/73
`5,200,843
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`5,221,982
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`
`5,233,465
`8/1993 Wheatley 6t a1~
`~~ 359/359
`5234729
`8/1993 Wheatley etal
`428/3O
`
`5,237,446
`.. 350/359
`......
`8/1993 Takahashi
`
`572389738
`-~ 428/333
`8/1993 M1116? ~;
`
`572457456
`9/1993 Y05h1m16ta~
`359/73
`
`572559029
`~~ 353/122
`“”1993 Vogeley 6t a1~
`592629894 “/1993 Wheatley 6t a1~
`~~ 359586
`
`572697995 ””993 Ramanathan 6t a1~
`~~ 264““
`“1994 Kama“ etal'
`592789680
`359/40
`
`572787694
`“1994 Wheatley et al-
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`2/1994 Nakamura et a1~
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`592869418
`3/1994 Konuma 6t a1~ ~~
`~~ 359/487
`592959018
`5,303,083
`4/1994 Blanchard et al.
`.. 359/495
`5309422
`5/1994 Kurd“ 6t a1~
`~~ 369/110
`5316703
`5/1994 Schrenk ~~~~~
`~~ 26443
`593259218
`“994 W916“ 6t a1~
`359/53
`573337072
`7/1994 Wllle“ ~~~~~~~~
`~ 359/41
`593377174
`8/1994 wad.a.etal‘
`359/73
`
`5,339,179
`8/1994 Rudisill et al.
`359/49
`573397198
`8/1994 Wheatley et al-
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`5,345,146
`9/1994 Koenck et al.
`315/1693
`5,359,691
`10/1994 Taietal.
`.. 385/146
`573609659
`“/1994 “ends a a1~
`~~ 428/216
`593819309
`“1995 B°r9hardt
`362/31
`5,389,324
`2/1995 LeWis et al.
`.. 264/171
`574229756
`“995 Weber ~~~~~~~~~~~~
`~~ 359/487
`~~ 359584
`5448404
`9/1995 SChrenk etal-
`
`~~ 428495
`5451449
`9/1995 Shetty 6t a1~
`~~ 359/498
`5486949
`“1996 SChrenk etal-
`
`7/1996 SChrenk ~~~~~~~~~~~~
`~~ 428/212
`595409978
`595529927
`9/1996 Wheatley 6t a1~
`~~ 35%”
`575597634
`9/1996 Weber ~~~~~~~~~~~~~~~
`~~ 359/638
`575689316
`“”1996 SChrenk 6t a1~
`~~ 359584
`B1 4,660,936
`1/1990 Nosker ................................ 350/339 D
`FOREIGN PATENT DOCUMENTS
`
`
`
`
`
`
`Japan ............................... B02B 5/30
`5/1992
`4—141603
`Japan .
`. G03B 21/14
`7/1992
`4—184429
`
`Japan .
`G02B 5/18
`5288910 11/1993
`Japan .
`G02B 5/18
`6—11607
`1/1994
`Japan ...........
`G02B 5/02
`6222207
`8/1994
`2 052 779
`1/1981 United Kingdom
`.. G02F 1/133
`W0 91/09719
`7/1991 WIPO ..............
`. B29C 43/20
`W0 94/11776
`5/1994 WIPO
`G02F 1/1335
`W0 94/29765
`12/1994 WIPO
`.. G02F 1/1335
`W0 95/17303
`6/1995 WIPO
`B32B 7/02
`W0 95/17691
`6/1995 WIPO
`G02B 5/30
`W0 95/17692
`6/1995 WIPO
`G02B 5/30
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`6/1995 WIPO ........................... G02F 1/1335
`
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`.
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`3,610,729
`
`3/1972 Schrenk et al.
`.. 161/165
`3,647,612
`1/1973 Alfrey, Jr. et al.
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`3,711,176
`
`7/1973 Schrenk .................................. 425/131
`3,746,485
`9/1973 Schrenk etal.
`......................... 425/131
`3,759,647
`
`.. 264/171
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`3,773,882
`
`.. 161/181
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`3,801,429
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`3,847,585
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`4,446,305
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`
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`4,521,588
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`4,525,413
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`
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`4,586,790
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`4,590,119
`
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`4,659,523
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`
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`4,791,540 12/1988 Dreyer, Jr. et al.
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`
`.. 350/337
`4,796,978
`1/1989 Tanaka etal.
`1/1989 van Raalte .............................. 350/345
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`4,799,772
`1/1989 Utsumi ................................ 350/339 R
`
`.. 350/96.28
`4,805,984
`2/1989 Cobb, Jr.
`........
`4/1989 Nakamura etal.
`....................... 524/89
`4,824,882
`4,840,463
`6/1989 Clark etal.
`.......................... 350/350 8
`
`11/1989 Whitehead .....
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`........................... 350/336
`
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`......................... 428/213
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`
`12/1990 Solomon ................................. 350/399
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`4,989,076
`1/1991 Owada et al.
`............................ 358/61
`5,009,472
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`
`................................. 359/40
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`5,056,888 10/1991 Messerly etal.
`....................... 385/123
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`...........
`.. 359/831
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`5,061,050 10/1991 0gura .............
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`..
`5,093,739
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`
`.. 250/339
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`6/1992 Wheatley .......
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`5,132,880
`3133;
`3111511111-----------l
`-- gig/:2;
`5,134,516
`7/1992 Lehiilte: :tt :1.
`.. 350/301
`’
`’
`’
`"
`5,138,474
`8/1992 Arakawa
`350/73
`5,139,340
`8/1992 Okumura .......
`359/63
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`5,149,578
`
`5,157,526
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`359/63
`5,159,478 10/1992 Akiyama etal.
`......................... 359/69
`
`
`
`
`’
`
`
`
`
`LGE_001198
`
`LGE_001198
`
`

`

`5,828,488
`Page 3
`
`Derwent Abstract, JP 63017023.
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`Instruction Sheet
`
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`
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`
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`
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`
`LGE_001199
`
`LGE_001199
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 1 0f 32
`
`5,828,488
`
`
`
`15
`
`18 20
`
`= 23
`E 42
`11—h»
`
`44
`
`12
`
`38
`
`40
`
`32 (all We
`
`__
`
`__
`
`30 ‘- __ _\_
`34
`
`63
`
`24
`
`->
`
`46
`
`__
`
`39
`
`Fig. 2
`
`LGE_001200
`
`LGE_001200
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 2 0f 32
`
`5,828,488
`
`17
`
`18
`
`20
`
`—_
`
`
`
`LGE_001201
`
`LGE_001201
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 3 0f 32
`
`5,828,488
`
`31
`
`1 00
`
`80
`
`60
`
`40
`
`20
`
`%T
`
`33
`
`0
`
`400
`
`500
`
`600
`
`700
`
`7k (nm)
`Flg. 5
`
`LGE_001202
`
`LGE_001202
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 4 0f 32
`
`5,828,488
`
`K146
`/|\
`
`
`
`242
`Fig. 7
`
`LGE_001203
`
`LGE_001203
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 5 0f 32
`
`5,828,488
`
`226
`
`
`9.4°
`
`TRANSMITTED
`
`//7_g
`
`Fig. 8
`
`REFLECTED
`
`gag
`
`00
`
`
`9.4°
`
`146
`
`TRANSMITTED
`
`2—35\\
`
`140
`
`156 (b,c,d)
`
`157 (a,b,c,d) Fig. 9
`
`LGE_001204
`
`LGE_001204
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 6 0f 32
`
`5,828,488
`
`
`
`LGE_001205
`
`LGE_001205
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 7 0f 32
`
`5,828,488
`
`164
`
`162
`
`0 5101520 25 30 354045 5055 6065 70
`Degrees off normal
`Fig. 12
`
`149
`
`146
`
`K /
`
`|\
`
`
`
`
`
`RelativeBrightness
`
`160
`
`140
`
`_L N O
`
`_L OO
`
`0')oo0O
`
`N-hOO
`
`O
`
`LGE_001206
`
`LGE_001206
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 8 0f 32
`
`5,828,488
`
`
`
`LGE_001207
`
`LGE_001207
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 9 0f 32
`
`5,828,488
`
`/100
`
`102
`
`104
`
`LGE_001208
`
`LGE_001208
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 10 0f 32
`
`5,828,488
`
`0.05
`
`REFLECTIVITY
`
`REFLECTIVITY
`
`0.04
`
`0.03
`
`0.01
`
`0.02
`
`010 20 30 40 50 60 70 80 90
`
`ANGLE OF INCIDENCE IN 1.60 MEDIUM
`
`Fig. 16
`
`0.05
`
`0.04
`
`0.03
`
`0.02
`
`0.01
`
`0
`
`10
`
`20 30 40 50 60 70 80 90
`
`ANGLE OF INCIDENCE IN 1.60 MEDIUM
`
`Fig. 17
`
`LGE_001209
`
`LGE_001209
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 11 0132
`
`5,828,488
`
`0.012
`
`0.01
`
`9 oo oo
`
`REFLECTIVITY 0.004
`
`0.006
`
`0.002
`
`0
`
`010 20 3O 40 50 60 70 80 90
`
`ANGLE OF INCIDENCE IN 1.00 MEDIUM
`
`Fig. 18
`
`INDEX
`
`IN-PLANE
`
`INDEX 1
`
`
`
`I INCREASING '
`lN-PLANE
`NO BREWSTER ANGLE,
`I BREWSTER .
`INDEX 2
`|SOTROP|C :
`ANGLE
`: R INCREASES WITH ANGLE
`CASE
`T
`
`Fig 19
`
`NO BREWSTER ANGLE,
`R CONSTANT
`
`LGE_001210
`
`LGE_001210
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 12 0f 32
`
`5,828,488
`
`INDEX
`
`
`
`lN-PLANE
`
`INDEX 1
`
`
`
`ISOTFIOPIC
`CASE
`
`
`
`
`DECREASING
`BREWSTER
`ANGLE
`
`lN-PLANE
`
`INDEX 2
`
`
`
`Fig. 20
`
`INDEX
`
`
` IN-PLANE
`INDEX 1
`
`
`
`
`lN—PLANE
`INDEX 2
`
`l
`I
`n22
`
`.
`'
`l
`|
`
`Isegagfmz
`I
`INCREAQNG
`I R'NCREASES
`
`
`
`
`
`NO BREWSTER
`ANGLE
`’
`
`ANGLE
`
`Fig. 21
`
`LGE_001211
`
`LGE_001211
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 13 0f 32
`
`5,828,488
`
`1 .0
`
`0.8
`
`.0 on
`
`
`
`—LOG[1-R] .0 .b
`
`0
`
`.A.--‘.....AA____“.4
`
`
`
`LA“---
`
`400
`
`450
`
`500
`
`550
`
`600
`
`650
`
`700
`
`WAVELENGTH (nm)
`
`Fig. 22
`
`0.0001
`
`REFLECTIVITY
`
`0.00008
`
`0.00006
`
`0.00002
`
`0.00004
`
`0
`
`10 20 30 40 50
`
`60 70 80 90
`
`ANGLE OF INCIDENCE IN 1.00 MEDIUM
`
`Fig. 23
`
`LGE_001212
`
`LGE_001212
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 14 0f 32
`
`5,828,488
`
`REFLECTIVITY
`
`0.0001
`
`0.00008
`
`0.00006
`
`0.00004
`
`0.00002
`
`0
`
`LGE_001213
`
`0
`
`0
`
`10
`
`20 30 40
`
`50
`
`60 70 80 90
`
`ANGLE OF INCIDENCE IN 1.00 MEDIUM
`
`Fig. 24
`
`LGE_001213
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 15 0f 32
`
`5,828,488
`
`0.02
`
`0.01
`
`Any
`
`-0.01
`
`-0.02
`-0.075
`
`-0.05
`
`-0.025
`
`0
`
`0.025
`
`0.05
`
`0.075
`
`a
`
`Anz
`
`Fig. 25
`
`LGE_001214
`
`LGE_001214
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 16 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`40%Transmission
`
`20
`
`0
`400
`
`450
`
`500
`
`550
`
`600
`
`650
`
`700
`
`Wave Length (nm)
`
`Fig. 26
`
`LGE_001215
`
`LGE_001215
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 17 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`40%Transmission
`
`20
`
`O
`400
`
`450
`
`600
`550
`500
`Wave Length (nm)
`
`650
`
`700
`
`Fig. 27
`
`LGE_001216
`
`LGE_001216
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 18 0f 32
`
`5,828,488
`
`100
`
`80 W
`
`°/oTransmission
`
`60
`
`40
`
`20
`
`400
`
`450
`
`500
`
`550
`
`600
`
`650
`
`700
`
`Wave Length (nm)
`Fig. 28
`
`LGE_001217
`
`LGE_001217
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 19 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`4o
`
`20
`
`%Transmission
`
`U
`
`400
`
`500
`
`600
`
`700
`
`800
`
`900
`
`1000
`
`1100
`
`Wave Length (nm)
`
`Fig. 29
`
`LGE_001218
`
`LGE_001218
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 20 0f 32
`
`5,828,488
`
`100
`
`O)O%Transmission #-O
`
`20
`
`400
`
`450
`
`500
`
`550
`
`600
`
`650
`
`700
`
`Wave Length (nm)
`
`Fig. 30
`
`LGE_001219
`
`LGE_001219
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 21 0f 32
`
`5,828,488
`
`b
`
`a
`
`400
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`
`Fig. 31
`
`10
`
`8
`
`C
`
`.9
`.3 6
`
`E 2 E
`
`+— 4
`
`°\0
`
`2
`
`LGE_001220
`
`LGE_001220
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 22 0f 32
`
`5,828,488
`
`100
`
`80
`
`a
`
`60
`
`4O%Transmission
`
`20
`
`400
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`Fig. 32
`
`LGE_001221
`
`LGE_001221
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 23 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`%Transmission 40
`
`20
`
`400
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`
`Fig. 33
`
`LGE_001222
`
`LGE_001222
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 24 0f 32
`
`5,828,488
`
`b
`
`100
`
`80
`
`60
`
`40%Transmission
`
`20
`
`400
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`
`Fig. 34
`
`LGE_001223
`
`LGE_001223
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 25 0f 32
`
`5,828,488
`
`100
`
`°/oTransmission
`
`60
`
`80
`
`20
`
`0
`
`400
`
`500
`
`-3
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`
`Fig. 35
`
`LG E_001 224
`
`LGE_001224
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 26 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`4O%TRANSMISSION
`
`20
`
`400
`
`500
`
`600
`
`700
`
`800
`
`WAVE LENGTH (nm)
`
`Fig. 36
`
`LGE_001225
`
`LGE_001225
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 27 0f 32
`
`5,828,488
`
`700800
`
`500
`
`600
`
`
`
`
`
`WAVELENGTH(nm) Fig.37
`
`000000
`OQOVN
`
`400
`
`% TRANSMISSION
`
`LGE_001226
`
`LGE_001226
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 28 0f 32
`
`5,828,488
`
`100
`
`90
`
`a
`
`°/oTRANSMISSION
`
`0
`
`400
`
`500
`
`600
`
`700
`
`300
`
`,._\
`
`WAVE LENGTH (nm)
`
`Fig. 38
`
`LGE_001227
`
`LGE_001227
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 29 0f 32
`
`5,828,488
`
`100
`
`80
`
`60
`
`40%TRANSMISSION
`
`20
`
`400
`
`500
`
`600
`
`700
`
`800
`
`WAVE LENGTH (nm)
`
`Fig. 39
`
`LGE_001228
`
`LGE_001228
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 30 0f 32
`
`5,828,488
`
`100
`
`80
`
`b
`
`a
`
`C
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`
`Fig. 40A
`
`S
`"a 60
`.9
`E(I)
`
`C E
`
`l—
`o\° 4o
`
`20
`
`0
`400
`
`LGE_001229
`
`LGE_001229
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 31 0f 32
`
`5,828,488
`
`100
`
`°/oTransmission
`
`80
`
`O)O
`
`.bO
`
`20
`
`O
`
`0
`400
`
`500
`
`600
`
`700
`
`800
`
`Wave Length (nm)
`Fig. 403
`
`LGE_001230
`
`LGE_001230
`
`

`

`US. Patent
`
`Oct. 27, 1998
`
`Sheet 32 0f 32
`
`5,828,488
`
`100
`
`80
`
`4‘
`
`b
`
`a
`
`S
`'7) 60
`.1)
`EU)
`
`C E
`
`I...
`
`c
`
`500
`
`600
`Wave Length (nm)
`
`700
`
`800
`
`Fig. 400
`
`o\° 40
`
`20
`
`0
`400
`
`LGE_001231
`
`LGE_001231
`
`

`

`1
`REFLECTIVE POLARIZER DISPLAY
`
`2
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`5,828,488
`
`CROSS-REFERENCE TO RELATED
`APPLICATIONS
`
`This is a continuation in part of US. patent application
`Ser. Nos. 08/171,239 and 08/172,593, which were filed Dec.
`21, 1993, now abandoned and is a continuation in part of
`US. patent application Ser. Nos. 08/359,436 and 08/360,
`204, which were filed Dec. 20, 1994, now abandoned all of
`which are incorporated herein by reference.
`
`TECHNICAL FIELD
`
`The invention is an improved optical display.
`
`BACKGROUND
`
`Optical displays are widely used for lap-top computers,
`hand-held calculators, digital watches and the like. The
`familiar liquid crystal (LC) display is a common example of
`such an optical display. The conventional LC display locates
`a liquid crystal and an electrode matrix between a pair of
`absorptive polarizers. In the LC display, portions of the
`liquid crystal have their optical state altered by the applica-
`tion of an electric field. This process generates the contrast
`necessary to display “pixels” of information in polarized
`light.
`For this reason the traditional LC display includes a front
`polarizer and a rear polarizer. Typically, these polarizers use
`dichroic dyes which absorb light of one polarization orien-
`tation more strongly than the orthogonal polarization orien-
`tation. In general, the transmission axis of the front polarizer
`is “crossed” with the transmission axis of the rear polarizer.
`The crossing angle can vary from zero degrees to ninety
`degrees. The liquid crystal,
`the front polarizer and rear
`polarizer together make up an LCD assembly.
`LC displays can be classified based upon the source of
`illumination. “Reflective” displays are illuminated by ambi-
`ent light that enters the display from the “front.” Typically
`a brushed aluminum reflector is placed “behind” the LCD
`assembly. This reflective surface returns light to the LCD
`assembly while preserving the polarization orientation of the
`light incident on the reflective surface.
`It is common to substitute a “backlight” assembly for the
`reflective brushed aluminum surface in applications where
`the intensity of the ambient light is insufficient for viewing.
`The typical backlight assembly includes an optical cavity
`and a lamp or other structure that generates light. Displays
`intended to be viewed under both ambient light and backlit
`conditions are called “transflective.” One problem with
`transflective displays is that the typical backlight is not as
`efficient a reflector as the traditional brushed aluminum
`
`surface. Also the backlight randomizes the polarization of
`the light and further reduces the amount of light available to
`illuminate the LC display. Consequently, the addition of the
`backlight to the LC display makes the display less bright
`when viewed under ambient light.
`Therefore, there is a need for a display which can develop
`adequate brightness and contrast under both ambient and
`backlight illumination.
`
`SUMMARY
`
`The optical display of the present invention comprises
`three basic elements. The first element is a reflective polar-
`izer. This reflective polarizer is located between a liquid
`crystal display (LCD) assembly and an optical cavity, which
`comprise the second and third elements respectively.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`The drawings depict representative and illustrative imple-
`mentations of the invention. Identical reference numerals
`
`refer to identical structure throughout the several figures,
`wherein:
`
`FIG. 1 is a schematic cross section of an optical display
`according to the invention;
`FIG. 2 is a schematic cross section of an illustrative
`
`optical display according to the invention;
`FIG. 3 is a schematic cross section of an illustrative
`
`optical display according to the invention;
`FIG. 4 is an exaggerated cross sectional view of the
`reflective polarizer of the invention;
`FIG. 5 shows the optical performance of the multilayer
`reflective polarizer of Example 2;
`FIG. 6 is a schematic diagram of an optical display
`according to the invention with brightness enhancement;
`FIG. 7 is a diagram illustrating the operation of a bright-
`ness enhancer;
`FIG. 8 is a graph illustrating the operation of a brightness
`enhancer;
`FIG. 9 is a schematic cross section of an illustrative
`
`optical display;
`FIG. 10 is a schematic cross section of an illustrative
`
`optical display;
`FIG. 11 is a schematic cross section of an illustrative
`
`optical display;
`FIG. 12 is a graph of test results;
`FIG. 13 is a schematic cross section of an illustrative
`
`optical display;
`FIG. 14 is a schematic cross section of a brightness
`enhanced reflective polarizer;
`FIG. 15 shows a two layer stack of films forming a single
`interface.
`
`FIGS. 16 and 17 show reflectivity versus angle curves for
`a uniaxial birefringent system in a medium of index 1.60.
`FIG. 18 shows reflectivity versus angle curves for a
`uniaxial birefringent system in a medium of index 1.0.
`FIGS. 19, 20 and 21 show various relationships between
`in-plane indices and z-index for a uniaxial birefringent
`system.
`FIG. 22 shows off axis reflectivity versus wavelength for
`two different biaxial birefringent systems.
`FIG. 23 shows the effect of introducing a y-index differ-
`ence in a biaxial birefringent film with a large z-index
`difference.
`
`FIG. 24 shows the effect of introducing a y-index differ-
`ence in a biaxial birefringent film with a small z-index
`difference.
`
`FIG. 25 shows a contour plot summarizing the informa-
`tion from FIGS. 18 and 19;
`FIGS. 26—31 show optical performance of multilayer
`mirrors given in Examples 3—6;
`FIGS. 32—36 show optical performance of multilayer
`polarizers given in Examples 7—11;
`FIG. 37 shows optical performance of the multilayer
`mirror given in Example 12;
`FIG. 38 shows optical performance of the AR coated
`polarizer given in Example 13;
`FIG. 39 shows optical performance of the polarizer given
`in Example 14; and
`
`LGE_001232
`
`LGE_001232
`
`

`

`5,828,488
`
`3
`FIGS. 40A—40C show optical performance of multilayer
`polarizers given in Example 15 .
`
`DETAILED DESCRIPTION
`
`FIG. 1 is a schematic diagram of an illustrative optical
`display 10 that includes three principle components. These
`include the polarizing display module shown as LCD assem-
`bly 16, a reflective polarizer 12, and an optical cavity 24.
`The LCD assembly 16 shown in this figure is illuminated
`by polarized light provided by the reflective polarizer 12 and
`the optical cavity 24.
`Ambient light incident on the display 10, depicted by ray
`60 traverses the LCD module 16, the reflective polarizer 12
`and strikes the diffuse reflective surface 37 of the optical
`cavity 24. Ray 62 depicts this light as it is reflected by the
`diffusely reflective surface 37 toward the reflective polarizer
`12.
`
`Light originating from within the optical cavity 24 is
`depicted by ray 64. This light is also directed toward the
`reflective polarizer 12 and passes through the diffusely
`reflective surface 37. Both ray 62 and ray 64 have light
`exhibiting both polarization states (a,b).
`FIG. 2 shows a schematic optical display 11 illustrated
`with a three layer LCD assembly 15 that includes a front
`polarizer 18, a liquid crystal 20 and a rear polarizer 23. In
`this embodiment the optical cavity 24 is an edge lit backlight
`which includes a lamp 30 in a reflective lamp housing 32.
`Light from the lamp 30 is coupled to the light guide 34
`where it propagates until it encounters a diffuse reflective
`structure such as spot 36. This discontinuous array of spots
`is arranged to extract lamp light and direct it toward the LCD
`module 15. Ambient light entering the optical cavity 24 may
`strike a spot or it may escape from the light guide through
`the interstitial areas between spots. The diffusely reflective
`layer 39 is positioned below the light guide 34 to intercept
`and reflect such rays. In general, all the rays that emerge
`from the optical cavity 24 are illustrated by ray bundle 38.
`This ray bundle is incident on the reflective polarizer 12
`which transmits light having a first polarization orientation
`referred to as “(a)” and effectively reflects light having the
`orthogonal polarization orientation (b). Consequently, a cer-
`tain amount of light, depicted by ray bundle 42, will be
`transmitted by the reflective polarizer 12 while a substantial
`amount of the remaining light will be reflected as indicated
`by ray bundle 40. The preferred reflective polarizer material
`is highly efficient and the total losses due to absorption
`within the reflective polarizer 12 are very low (on the order
`of 1 percent). This lost light is depicted by ray bundle 44.
`The light having polarization state (b) reflected by the
`reflective polarizer 12 reenters the optical cavity 24 where it
`strikes the diffusely reflective structures such as spot 36 or
`the diffusely reflective layer 39. The diffusely reflective
`surfaces serve to randomize the polarization state of the light
`reflected by the optical cavity 24. This recirculation and
`randomization process is depicted as path 48. The optical
`cavity 24 is not a perfect reflector and the light losses in the
`cavity due to scattering and absorption are depicted by ray
`bundle 46. These losses are also low (on the order of 20
`percent). The multiple recirculations effected by the combi-
`nation of the optical cavity 24 and the reflective polarizer 12
`form an efficient mechanism for converting light from state
`(b) to state (a) for ultimate transmission to the viewer.
`The effectiveness of this process relies on the low absorp-
`tion exhibited by the reflective polarizer disclosed herein
`and the high reflectivity and randomizing properties exhib-
`ited by many diffusely reflective surfaces. In FIG. 2 both the
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`discontinuous layer depicted by spot 36 and the diffusely
`reflective continuous layer 39 may be formed of a titanium
`oxide pigmented material. It should be appreciated that a
`diffuse reflective surface 37 (shown in FIG. 1) can be formed
`of transparent surface textured polycarbonate. This material
`could be placed above the light guide 34 to randomize
`incident light in the configuration shown in FIG. 2. The
`specific and optimal configuration will depend on the par-
`ticular application for the completed optical display.
`In general, the gain of the system is dependent on the
`efficiency of both the reflective polarizer body 12 and the
`optical cavity 24. Performance is maximized with a highly
`reflective optical cavity 24 consistent with the requirement
`of randomization of the polarization of incident light, and a
`very low loss reflective polarizer 12.
`FIG. 3 shows a schematic optical display 14 illustrated
`with a two layer LCD assembly 17 that includes a front
`polarizer 18 and a liquid crystal 20. In this embodiment the
`optical cavity 24 includes an electroluminescent panel 21.
`The traditional electroluminescent panel 21 is coated with a
`phosphor material 19 that generates light when struck by
`electrons and that is also diffusely reflective when struck by
`incident
`light. Usually, electroluminescent displays are
`“grainy” because of the variations in efficiencies associated
`with the phosphor coating. However, light returned by the
`reflective polarizer 12 has a tendency to “homogenize” the
`light emissions and improve overall uniformity of illumina-
`tion exhibited by the optical display 14. In the illustrative
`optical display 14 the LCD assembly 17 lacks a rear polar-
`izer. In this optical display 14 the reflective polarizer 12
`performs the function normally associated with the rear
`polarizer 23 shown in optical display 11 in FIG. 2.
`FIG. 4 is a schematic perspective diagram of a segment of
`the reflective polarizer 12. The figure includes a coordinate
`system 13 that defines X, Y and Z directions that are referred
`to in the description of the reflective polarizer 12.
`The illustrative reflective polarizer 12 is made of alter-
`nating layers (ABABA .
`.
`. ) of two different polymeric
`materials. These are referred to as material “(A)” and
`material “(B)” throughout the drawings and description. The
`two materials are extruded together and the resulting mul-
`tiple layer (ABABA. .
`. ) material is stretched (5:1) along
`one axis (X), and is not stretched appreciably (1:1) along the
`other axis (Y). The X axis is referred to as the “stretched”
`direction while the Y axis is referred to as the “transverse”
`direction.
`
`index of refraction
`The (B) material has a nominal
`(n=1.64 for example) which is not substantially altered by
`the stretching process.
`The (A) material has the property of having the index of
`refraction altered by the stretching process. For example, a
`uniaxially stretched sheet of the (A) material will have one
`index of refraction (n=1.88 for example) associated with the
`stretched direction and a different
`index of refraction
`
`(n=1.64 for example) associated with the transverse direc-
`tion. By way of definition, the index of refraction associated
`with an in-plane axis (an axis parallel to the surface of the
`film) is the effective index of refraction for plane-polarized
`incident light whose plane of polarization is parallel to that
`ax1s.
`
`Thus, after stretching the multiple layer stack
`(ABABA .
`.
`. ) of material shows a large refractive index
`difference between layers (delta n=1.88—1.64=0.24) associ-
`ated with the stretched direction. While in the transverse
`
`direction, the associated indices of refraction between layers
`are essentially the same (delta n=1.64—1.64=0.0). These
`
`LGE_001233
`
`LGE_001233
`
`

`

`5,828,488
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`5
`optical characteristics cause the multiple layer laminate to
`act as a reflecting polarizer that will transmit the polarization
`component of the incident light that is correctly oriented
`with respect to the axis 22. This axis is defined as the
`transmission axis 22 and is shown in FIG. 4. The light which
`emerges from the reflective polarizer 12 is referred to as
`having a first polarization orientation (a).
`The light that does not pass through the reflective polar-
`izer 12 has a polarization orientation (b) that differs from the
`first orientation (a). Light exhibiting this polarization orien-
`tation (b) will encounter the index differences which result
`in reflection of this light. This defines a so-called “extinc-
`tion” axis shown as axis 25 in FIG. 4. In this fashion the
`
`reflective polarizer 12 transmits light having a selected
`polarization (a) and reflects light having the polarization (b).
`Although the reflective polarizer 12 has been discussed
`with an exemplary multiple layer construction which
`includes alternating layers of only two materials it should be
`understood that
`the reflective polarizer 12 may take a
`number of forms. For examp