EP0840160A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Reflective liquid crystal device
Assignee: Sharp Corp
•
Filing: 1997-10-30
•
Granted: —
•
Expires: 2017-10-30
Abstract
Abstract A reflective liquid crystal device comprises a polariser 1 and a mirror 2 between which are disposed several retarders 3, 4, 5. At least one of the retarders 4 is a variable liquid crystal element whose optic axis is switchable so as to switch the device between a reflective state and a non-reflective state. In the non-reflective state, the total retardance of the retarders 3, 4, 5 between the polariser 1 and the mirror 2 is equal to an odd number of quarter wavelengths for a wavelength at or adjacent the middle of the visible spectrum.
Inventors
- 👤 Martin David Tillin
- 👤 Michael John Towler
- 👤 Kirstin Ann Saynor
- 👤 Sandra Gilmour
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 13:43
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/137; G02F1/139; G02F1/1393; G02F1/133; G02F1/1333; G02F1/1335; G02F1/13363; G02F1/13356; G02F1/133565; G02F1/133638; G02F1/1396; G02F1/1398; G02F2202/00; G02F2202/40; G02F2203/00; G02F2203/02; G02F2413/00; G02F2413/02; G02F2413/08; G02F2413/15
Claims Analysis
Total Claims: 51
Claim 1
Independent Claim
134 words
A reflective liquid crystal device comprising a linear
polariser (1), a polarisation preserving reflector (2), and a retarder
arrangement characterised in that the retarder arrangement comprises at
least three retarders, a first (3) of which is disposed between the polariser
(1) and the reflector(2), a second (4) of which is disposed between the first
retarder (1) and the reflector (2), and a third (5) of which is disposed
between the second retarder (4) and the reflector (2), at least one (4) of the
first, second and third retarders (3, 4, 5) comprising a liquid crystal layer
which is switchable between a non-reflective device state, in which the
retardation of the retarder arrangement is equal to (2n+1)λ/4 where n is
an integer and λ is a wavelength of visible light, and a reflective device
state.
Claim 2
Dependent Claim
45 words
A device as claimed in Claim 1, characterised in that, in
the non-reflective device state, the first retarder (3) has a retardation of
substantially λ/2, the second retarder (4) has a retardation of substantially
λ/2, and the third retarder has a retardation of substantially λ/4.
Claim 3
Dependent Claim
121 words
A device as claimed in Claim 2, characterised in that, in
the non-reflective device state, the optic axis (7) of the first retarder (3) is
substantially at an angle (α + B.180 0 ) to the polarisation or absorption
axis (6) of the polariser (1), the optic axis (8) of the second retarder (4) is
substantially at an angle of (x.α + C.180 0 ) to the polarisation or
absorption axis (6), and the optic axis (9) of the third retarder (5) is
substantially at an angle of (2(β-α)+ sign (α).45° + D.180°) to the
polarisation or absorption axis (6), where x is a positive real number, B, C
and D are integers and sign (α) is the sign of α.
Claim 4
Dependent Claim
16 words
A device as claimed in Claim 3, characterised in that α is
substantially equal to 6.9°.
Claim 5
Dependent Claim
18 words
A device as claimed in Claim 3 or 4, characterised in that x
is substantially equal to 5.
Claim 6
Independent Claim
47 words
A device as claimed in any one of Claims 2 to 5,
characterised in that the first or second retarder comprises the liquid
crystal layer (4) whose optic axis (8) rotates during switching by an angle
substantially equal to 22.5° about the normal direction of light passage.
Claim 7
Independent Claim
51 words
A device as claimed in any one of Claims 2 to 5,
characterised in that the second retarder comprises the liquid crystal layer
(4) and has a retardation which is switchable between substantially (pλ/2
+ δ) and substantially ((p+1)λ/2 + δ), where p is an integer and 0≤ δ <
λ/2.
Claim 8
Dependent Claim
17 words
A device as claimed in Claim 7, characterised in that p is
equal to zero or one.
Claim 9
Independent Claim
49 words
A device as claimed in any one of Claims 2 to 5,
characterised in that the third retarder comprises the liquid crystal layer (4)
and has a retardation which is switchable between substantially (qλ/4 + δ)
and substantially ((q +1)λ/4 + δ), where q is an integer and 0≤δ<λ/4.
Claim 10
Dependent Claim
17 words
A device as claimed in Claim 9, characterised in that q is
equal to zero or one.
Claim 11
Independent Claim
27 words
A device as claimed in any one of Claims 7 to 10,
characterised in that the liquid crystal layer (4) is an out-of-plane switching
nematic liquid crystal.
Claim 12
Dependent Claim
43 words
A device as claimed in Claim 1, characterised in that, in
the non-reflective device state, the first retarder (3) has a retardation of
23λ/72, the second retarder (4) has a retardation of λ/2, and the third
retarder (5) has a retardation of 23λ/72.
Claim 13
Dependent Claim
89 words
A device as claimed in Claim 12, characterised in that, in
the non-reflective device state, the optic axis (7) of the first retarder (3) is at
an angle of substantially 14.25° to the polarisation or absorption axis (6) of
the polariser (1), the optic axis (8) of the second retarder (4) is at an angle
of substantially 84.5° to the polarisation or absorption axis (6), and the
optic axis (9) of the third retarder (5) is at an angle of substantially 14.25°
to the polarisation or absorption axis (6).
Claim 14
Dependent Claim
41 words
A device as claimed in Claim 12 or 13, characterised in
that the second retarder comprises the liquid crystal layer (4) whose optic
axis rotates during switching by an angle substantially equal to 22.5° about
the normal direction of light passage.
Claim 15
Dependent Claim
47 words
A device as claimed in Claim 12 or 13, characterised in
that the second retarder comprises the liquid crystal layer (4) and has a
retardation which is switchable between substantially (rλ/2 + δ) and
substantially ((r + 1)λ/2 + δ), where r is an integer and 0≤δ<λ/2.
Claim 16
Dependent Claim
17 words
A device as claimed in Claim 15, characterised in that r is
equal to zero or one.
Claim 17
Dependent Claim
37 words
A device as claimed in Claim 12 or 13, characterised in
that the third retarder comprises the liquid crystal layer (4) and has a
retardation which is switchable between substantially 23λ/72 and
substantially 23λ/324 or substantially 46λ/81.
Claim 18
Independent Claim
27 words
A device as claimed in any one of Claims 15 to 17,
characterised in that the liquid crystal layer (4) is an out-of-plane switching
nematic liquid crystal.
Claim 19
Dependent Claim
138 words
A reflective liquid crystal device comprising a linear
polariser (1), a polarisation preserving reflector (2), and a retarder
arrangement comprising a first retarder (4) disposed between the polariser
(1) and the reflector (2) and a second retarder (5) disposed between the
first retarder (1) and the reflector (2), at least one of the first and second
retarders (4, 5) comprising an untwisted liquid crystal layer which is
switchable between a non-reflective device state, in which the retardation
of the retarder arrangement is equal to (2n + 1)λ/4 where n is an integer
and λ is a wavelength of visible light, and a reflective device state,
characterised in that the first retarder (4) comprises the liquid crystal layer
and has an optic axis (8) which rotates during switching by a
predetermined angle about the normal direction of light passage.
Claim 20
Dependent Claim
36 words
A device as claimed in Claim 19, characterised in that, in
the non-reflective device state, the first retarder (4) has a retardation of
substantially λ/2 and the second retarder (5) has a retardation of
substantially λ/4.
Claim 21
Dependent Claim
85 words
A device as claimed in Claim 20, characterised in that, in
the non-reflective device state, the optic axis (8) of the first retarder (4) is
substantially at an angle (α+E.180 0 ) to the polarisation or absorption axis
(6) of the polariser (1) and the optic axis (9) of the second retarder (5) is
substantially at an angle of (2α + sign(α).45° + F.180°) to the polarisation or
absorption axis (6), where E and F are integers and sign (α) is the sign of α.
Claim 22
Dependent Claim
16 words
A device as claimed in Claim 21, characterised in that a is
substantially equal to 15°.
Claim 23
Dependent Claim
26 words
A device as claimed in Claim 21, characterised in that a is
substantially equal to 22.5° and the predetermined angle is substantially
equal to 22.5 0.
Claim 24
Independent Claim
26 words
A device as claimed in any one of Claims 6, 14 and 23,
characterised in that the liquid crystal layer (4) is a ferroelectric liquid
crystal.
Claim 25
Independent Claim
26 words
A device as claimed in any one of Claims 6, 14 and 23,
characterised in that the liquid crystal layer (4) is an antiferroelectric liquid
crystal.
Claim 26
Independent Claim
26 words
A device as claimed in any one of Claims 6, 14 and 23,
characterised in that the liquid crystal layer (4) is an electroclinic liquid
crystal.
Claim 27
Independent Claim
28 words
A device as claimed in any one of Claims 6, 14 and 23,
characterised in that the liquid crystal layer (4) is an in-plane switching
nematic liquid crystal.
Claim 28
Dependent Claim
117 words
A reflective liquid crystal device comprising a linear
polariser (1), a polarisation preserving reflector (2), and a retarder
arrangement comprising a first retarder (4) disposed between the polariser
(1) and the reflector (2) and a second retarder (5) disposed between the
first retarder (4) and the reflector (2), at least one of the first and second
retarders (4, 5) comprising an untwisted liquid crystal layer which is
switchable between a non-reflective device state, in which the retardation
of the retarder arrangement is equal to (2n+1)λ/4, where n is an integer
and λ is a wavelength of visible light, and a reflective device state,
characterised in that the liquid crystal layer (4) is an out-of-plane switching
liquid crystal.
Claim 29
Dependent Claim
36 words
A device as claimed in Claim 28, characterised in that, in
the non-reflective device state, the first retarder (4) has a retardation of
substantially λ/2 and the second retarder (5) has a retardation of
substantially λ/4.
Claim 30
Dependent Claim
88 words
A device as claimed in Claim 29, characterised in that, in
the non-reflective device state, the optic axis (8) of the first retarder (4) is
substantially at an angle of (α+E.180 0 ) to the polarisation or absorption
axis (6) of the polariser (1) and the optic axis (9) of the second retarder (5)
is substantially at an angle of (2α+sign(α).45 0 + F.180 0 ) to the polarisation
or absorption axis (6), where E and F are integers and sign (α ) is the sign
of α.
Claim 31
Dependent Claim
18 words
A device as claimed in Claim 30, characterised in that α is
substantially equal to 15 0 .
Claim 32
Independent Claim
46 words
A device as claimed in any one of Claims 28 to 31,
characterised in that the first retarder comprises the liquid crystal layer (4)
having a retardation which is switchable between substantially (pλ/2+δ)
and substantially ((p +1)λ/2 + δ) where p is an integer, and 0≤δ<λ/2.
Claim 33
Dependent Claim
17 words
A device as claimed in Claim 32, characterised in that p is
equal to zero or one.
Claim 34
Independent Claim
44 words
A device as claimed in any one of claims 28 to 31,
characterised in that the second retarder comprises the liquid crystal layer
(4) and has a retardation which is switchable between substantially
(qλ/4+δ) and substantially ((q+1)λ/4+δ), where q is an integer, and
0≤δ<λ/4.
Claim 35
Dependent Claim
17 words
A device as claimed in Claim 34, characterised in that q is
equal to zero or one.
Claim 36
Independent Claim
27 words
A device as claimed in any one of Claims 28 to 35,
characterised in that the liquid crystal layer (4) is an out-of-plane switching
nematic liquid crystal.
Claim 37
Dependent Claim
116 words
A reflective liquid crystal device comprising a linear
polariser (1), a polarisation preserving reflector (2) and a retarder
arrangement (4, 5) comprising a first retarder disposed between the
polariser (1) and the reflector (2) and a second retarder disposed between
the first retarder and the reflector (2), at least one of the first and second
retarders comprising a liquid crystal layer (4) which is switchable between
a non-reflective device state, in which the retardation of the retarder
arrangement is equal to (2n+1)λ/4, where n is an integer and λ is a
wavelength of visible light, and a reflective device state, characterised in
that at least one of the first and second retarders comprises a twisted
retarder.
Claim 38
Independent Claim
29 words
A device as claimed in any one of Claims 11, 18, 36 and
37, characterised in that the liquid crystal layer (4) comprises a
homogeneously aligned nematic liquid crystal.
Claim 39
Independent Claim
29 words
A device as claimed in any one of Claims 11, 18, 36 and
37, characterised in that the liquid crystal layer (4) comprises a
homeotropically aligned nematic liquid crystal.
Claim 40
Independent Claim
36 words
A device as claimed in any one of claims 11, 18, 36 and
37, characterised in that the liquid crystal layer (4) is homogeneously
aligned at a first surface and homeotropically aligned at a second surface.
Claim 41
Independent Claim
20 words
A device as claimed in any one of the preceding claims,
characterised in that the liquid crystal layer is parallel-aligned.
Claim 42
Independent Claim
21 words
A device as claimed in any one of claims 1 to 40,
characterised in that the liquid crystal layer is antiparallel-aligned.
Claim 43
Independent Claim
59 words
A device as claimed in any one of Claims 7 to 11, 15 to 18
and 28 to 40, characterised in that the retarder arrangement comprises a
further retarder (30) whose optic axis (31) is substantially perpendicular to
the optic axis (8) of the liquid crystal layer (4) and which is disposed
optically adjacent the liquid crystal layer (4).
Claim 44
Dependent Claim
37 words
A device as claimed in Claim 43 when dependent on any
one of Claims 7 to 11, 15, 16 and 32 to 35, characterised in that the
further retarder (30) has a retardation substantially equal to δ.
Claim 45
Dependent Claim
57 words
A device as claimed in Claim 43 when dependent on any
one of Claims 7 to 11, 15, 16 and 32 to 35, characterised in that the
further retarder (30) has a retardation substantially equal to the retardation of the liquid crystal layer (4) in the absence of an applied field across the liquid crystal layer (4).
Claim 46
Independent Claim
15 words
A device as claimed in any one of the preceding Claims, characterised in that n=0.
Claim 47
Independent Claim
23 words
A device as claimed in any one of the preceding claims, characterised in that λ is between substantially 500 and substantially 570 nanometres.
Claim 48
Dependent Claim
19 words
A device as claimed in Claim 47, characterised in that λ is between substantially 510 and substantially 550 nanometres.
Claim 49
Dependent Claim
19 words
A device as claimed in Claim 48, characterised in that λ is between substantially 525 and substantially 530 nanometres.
Claim 50
Independent Claim
34 words
A device as claimed in any one of the preceding claims, characterised in that the retarder arrangement has a retardation substantially equal to mλ/2 in the reflective device state, where m is an integer.
Claim 51
Independent Claim
32 words
A device as claimed in any one of Claims 1 to 18, characterised in that at least one of the first, second and third retarders (3, 4, 5) is a twisted retarder.
References Cited (Backward Citations)
No citation records indexed.
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