Liquid crystal display

• US 6,362,862 B1
• Filed: 04/25/1997
• Issued: 03/26/2002
• Est. Priority Date: 04/26/1996
• Status: Expired due to Term

• Current Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Hitachi, Ltd.
• Inventors: Hirota, Shoichi, Komura, Shinichi, Adachi, Masaya, Hiyama, Ikuo, Itoh, Osamu
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGUYEN, DUNG T
• Application Number:
  US08/840,622
• Time in Patent Office: 1,796 Days
• Field of Search: 349/119, 349/117, 349/118, 349/5
• US Class Current: 349/119
• CPC Class Codes: G02F 1/133553 Reflecting elements associated to illuminating devices G02F1/133605
• CPC Class Codes: G02F 1/13363 Birefringent elements, e.g. for optical compensation
• CPC Class Codes: G02F 1/133637 characterised by the wavelength dispersion
• CPC Class Codes: G02F 1/133638 Waveplates, i.e. plates with a retardation value of lambda/n
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2413/02 Number of plates being 2
• CPC Class Codes: H04N 5/7441 the modulator being an array of liquid crystal cells
• CPC Class Codes: H04N 9/3105 for displaying all colours simultaneously, e.g. by using two or more electronic spatial light modulators simultaneous projection in colour photography G03B33/10; beam splitting or combining systems per se G02B27/10
• CPC Class Codes: H04N 9/3158 for controlling the spectrum

Abstract

A liquid crystal display featuring excellent visibility with both good brightness and a high contrast ratio uses a projection optical system in which a polarizing plate, a first phase plate and a second phase plate in which the retardation of each of the phase plates and a gradient of wavelength dispersion of the retardation can be freely set, a liquid crystal layer, and a reflection plate are arranged in parallel and a transmitted light is reflected by the reflection plate. A gradient of one of the phase plates is set to an extremely steep gradient, a gradient of the other phase plate is set to an extremely flat gradient, and the wavelength dispersion of a retardation composite value obtained from the liquid crystal layer and the two phase plates is approximated to a retardation curve expressed by a relational expression of (0.25+0.5n)λ, where (n) is an integer and λ is a wavelength (nm) of the transmitted light.

Claims

1. A liquid crystal display in which a polarizing plate, first and second phase plates, an upper substrate, a liquid crystal layer, a drive device, and a lower substrate also serving as a reflection plate are sequentially laminated in a travelling direction of transmitted light, and an absorption axis direction of the polarizing plate and an alignment direction of the liquid crystal layer, which is on the side adjacent to the polarizing plate have a non-parallel relation, wherein each of the first and second phase plates has a wavelength dispersion of a retardation such that a wavelength dispersion of a retardation composite value of the first and second phase plates and the liquid crystal layer is substantially approximated to a retardation curve expressed by a relational expression of one of (0.25+0.5n)λ

and (0.5n)λ

in a range of wavelengths from 400 nm to 700 nm of said transmitted light,

where n is an integer and λ

is a wavelength (nm) of the transmitted light.

5. A liquid crystal display according to claim 1 or 2, characterized in that n is less than 0, and wherein:

a gradient of the wavelength dispersion of the retardation of the first phase plate is steeper than that of the liquid crystal layer and a gradient of the wavelength dispersion of the retardation of the second phase plate is flatter than that of the liquid crystal layer,

the first phase plate is arranged so that the delay axis of the first phase plate is in parallel with an alignment direction of the liquid crystal layer and the second phase plate is arranged so that the delay axis of the second phase plate perpendicularly crosses the alignment direction of the liquid crystal layer, and

a retardation at the wavelength 550 (nm) of the second phase plate is larger than a retardation at the wavelength 550 (nm) of the first phase plate.

6. A liquid crystal display according to claim 1, characterized in that the relational expression (0.25+0.5n)λ

is utilized.

7. A liquid crystal display according to claim 6, characterized in that n is 0 or larger, and wherein:

a gradient of the wavelength dispersion of the retardation of the first phase plate is steeper than that of the liquid crystal layer and a gradient of the wavelength dispersion of the retardation of the second phase plate is flatter than that of the liquid crystal layer,

the first phase plate is arranged so that a delay axis of the first phase plate perpendicularly crosses the alignment direction of the liquid crystal layer, and the second phase plate is arranged so that a delay axis of second the phase plate is in parallel with the alignment direction of the liquid crystal layer, and

a retardation at the wavelength 550 (nm) of the second phase plate is larger than a retardation at the wavelength 550 (nm) of the first phase plate.

2. A liquid crystal display in which a polarizing means, first and second phase plates, an upper substrate, a liquid crystal layer, a drive device, and a lower substrate also serving as a reflection plate are sequentially laminated in a travelling direction of transmitted light, and an absorption axis direction of the polarizing means and an alignment direction of the liquid crystal layer, which is on the side adjacent to the polarizing means, have a non-parallel relation, wherein the polarizing means is a polarizing plate of a type in which a vibration direction of a transmission polarization component of the polarizing means rotates by 90°

when a passing direction of the transmission light is changed, and

each of the first and second phase plates has a wavelength dispersion of a retardation, such that a wavelength dispersion of a retardation composite value of the first and second phase plates and the liquid crystal layer is set so as to be substantially approximated to a retardation curve expressed by a relational expression of (0.5n)λ

in a range of wavelengths from 400 nm to 700 nm of said transmitted light,

where n is an integer and λ

is a wavelength (nm) of the transmitted light.

3. A liquid crystal display according to claim 2, characterized in that n is 1 or larger, and wherein:

a gradient of the wavelength dispersion of the retardation of the first phase plate is steeper than that of the liquid crystal layer and a gradient of the wavelength dispersion of the retardation of the second phase plate is flatter than that of the liquid crystal layer,

the first phase plate is arranged so that a delay axis of the first phase plate perpendicularly crosses the alignment direction of the liquid crystal layer, and the second phase plate is arranged so that a delay axis of the second phase plate is in parallel with the alignment direction of the liquid crystal layer, and

retardation at the wavelength 550 (nm) of the second phase plate is larger than a retardation at the wavelength 550 (nm) of the first phase plate.

4. A liquid crystal display according to claim 2, characterized in that n is equal to 0, and wherein:

a gradient of the wavelength dispersion of the retardation of the first phase plate is steeper than that of the liquid crystal layer and a gradient of the wavelength dispersion of the retardation of the second phase plate is flatter than that of the liquid crystal layer, and

the first phase plate and the second phase plate are arranged so that a respective delay axis of each of the first and second phase plates perpendicularly crosses an alignment direction of the liquid crystal layer.

8. A liquid crystal display having a projection optical system in which a polarizing plate, a phase plate arrangement, a liquid crystal layer, and a reflection plate are arranged in parallel and transmitted light is reflected by the reflection plate, wherein the phase plate arrangement comprises first and second phase plates in which a retardation of each of the first and second phase plates and a gradient of wavelength dispersion of the retardation can be freely set, and

the gradient of the first phase plate is set so as to be larger than the gradient of the liquid crystal layer and the gradient of the second phase plate is set so as to be smaller than the gradient of the liquid crystal layer, and wavelength dispersion of a retardation composite value in the projection optical system which is provided by a combination of the liquid crystal layer and the first and second phase plates is brought substantially close to a retardation curve expressed by a relational expression of (0.25+0.5n)λ

where n is an integer and λ

is a wavelength (nm) of the transmitted light.

9. A projection-type liquid crystal display comprising a drive device, a light source, an optical system, and a plurality of liquid crystal display elements, characterized in that each of the plurality of liquid crystal display elements includes a liquid crystal layer, two substrates, and at least one phase plate, and retardations of the phase plates of the plurality of liquid crystal display elements are different from each other, wherein the two substrates forming each of the plurality of liquid crystal display elements have a display electrode and an alignment layer, the display electrode which is provided on a lower substrate of the two substrates also serving as a reflection plate, the display electrode on the lower substrate being connected to an active element, the two substrates being arranged so as to face each other with the liquid crystal layer sandwiched therebetween, and a delay axis of the phase plate is in parallel with or perpendicularly crosses an adjacent alignment direction of the liquid crystal layer,

wherein a composite value of a retardation of the phase plate and a retardation of the liquid crystal layer which form each of the plurality of liquid crystal display elements substantially satisfies the relationship 0.5nλ

(where n is an integer) at least in a range of 100 nm in a visible wavelength range of λ

=400 nm to 700 nm when an arbitrary voltage VB is applied to the liquid crystal layer.

10. A projection-type liquid crystal display according to claim 9, wherein n is positive, two phase plates are provided in a liquid crystal display element, wavelength dispersion of retardation of one phase plate is steeper than that of the liquid crystal layer and a delay axis of the one phase plate is set so as to be in parallel with an adjacent alignment direction of the liquid crystal layer, and the wavelength dispersion of retardation of the other phase plate is flatter than that of the liquid crystal layer and a delay axis of the other phase plate is set so as to perpendicularly cross an adjacent alignment direction of the liquid crystal.

11. A projection-type liquid crystal display according to claim 9, wherein (n) is a negative integer, two phase plates are provided in a liquid crystal display element, the wavelength dispersion of retardation of one of the phase plates is steeper than that of the liquid crystal layer and a delay axis of the one phase plate is set so as to perpendicularly cross an adjacent alignment direction of the liquid crystal, and the wavelength dispersion of retardation of the other phase plate is flatter than that of the liquid crystal layer and a delay axis of the other phase plate is set so as to be in parallel with an adjacent alignment direction of the liquid crystal.