Reflection-type liquid crystal device with polarization of output light perpendicular to that of input light
First Claim
1. A reflection-type liquid crystal device comprising:
- a liquid crystal cell including a pair of spaced apart opposed transparent substrates,a polarizing means disposed at a first side said liquid crystal cell,a reflecting means disposed at a second side of said liquid crystal cell,said liquid crystal cell comprising a twisted nematic liquid crystal layer having a twist angle and having a birefringence property, Δ
n, and having a thickness, d, for transforming the character of first linearly polarized light or first circularly polarized light propagating therethrough, respectively, into substantially circularly polarized light or substantially linearly polarized light incident at said reflecting means and transforming said substantially circularly polarized light or substantially linearly polarized light reflected from said reflecting means, respectively, into substantially second linearly polarized light or substantially second circularly polarized light having a polarization direction orthogonal with respect to a polarization direction of said first linearly polarized light or first circularly polarized light, respectively,said polarizing means characterized by having a polarization angle greater than zero wherein said polarization angle is an angle formed between a polarization axis of said polarizer and liquid crystal molecular director of said liquid crystal layer at a surface of said liquid crystal cell at said first side, andfirst and second optimized conditions for said twist angle relative to a given polarization angle and a product of Δ
nd, the first optimized condition comprising a twist angle range between about 0° and
65°
with a Δ
nd in a range between about 0.13 and 0.40, the second optimized condition comprising a twist angle range between about 0° and
200°
with Δ
nd in a range between about 0.53 and 0.97,said optimized conditions applicable for said given polarization angle plus or minus multiplies of approximately 90°
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Abstract
A reflection-type liquid crystal (LC) device having a twisted nematic (TN) LC layer that lets linearly-polarized incident light enter and become circularly-polarized at a reflecting surface, and then linearly polarizes it, after reflecting, with a plane of polarization that has been rotated 90° from the incident light at an light output surface. The TN LC layer allows linearly-polarized incident light to enter at an angle to the molecular plane of light input of the twisted nematic LC, and to linearly polarize the light after reflection. The plane of polarization is rotated 90° from the incident light at the light output surface. The TN LC layer also allows circularly-polarized incident light to enter and become linearly-polarized light at the reflecting surface. Circularly-polarized light after reflection may be rotated opposite the incident circularly-polarized light at the light output surface to provide for reverse on/off states.
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Citations
15 Claims
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1. A reflection-type liquid crystal device comprising:
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a liquid crystal cell including a pair of spaced apart opposed transparent substrates, a polarizing means disposed at a first side said liquid crystal cell, a reflecting means disposed at a second side of said liquid crystal cell, said liquid crystal cell comprising a twisted nematic liquid crystal layer having a twist angle and having a birefringence property, Δ
n, and having a thickness, d, for transforming the character of first linearly polarized light or first circularly polarized light propagating therethrough, respectively, into substantially circularly polarized light or substantially linearly polarized light incident at said reflecting means and transforming said substantially circularly polarized light or substantially linearly polarized light reflected from said reflecting means, respectively, into substantially second linearly polarized light or substantially second circularly polarized light having a polarization direction orthogonal with respect to a polarization direction of said first linearly polarized light or first circularly polarized light, respectively,said polarizing means characterized by having a polarization angle greater than zero wherein said polarization angle is an angle formed between a polarization axis of said polarizer and liquid crystal molecular director of said liquid crystal layer at a surface of said liquid crystal cell at said first side, and first and second optimized conditions for said twist angle relative to a given polarization angle and a product of Δ
nd, the first optimized condition comprising a twist angle range between about 0° and
65°
with a Δ
nd in a range between about 0.13 and 0.40, the second optimized condition comprising a twist angle range between about 0° and
200°
with Δ
nd in a range between about 0.53 and 0.97,said optimized conditions applicable for said given polarization angle plus or minus multiplies of approximately 90°
. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification