Elliptically polarizing plate comprising discotic liquid crystal and in which 30≦[(NX+NY)/2--NZ]×D≦150

Claim 2

An elliptically polarizing plate comprising a polarizing film and an optical compensatory sheet provided thereon, wherein said sheet has an optically negative monoaxial property and a direction of a minimum retardation inclined at 5 to 50 degrees from the normal of the sheet, the sheet comprising a transparent film and an oriented layer of a discotic liquid crystal provided thereon, said transparent film having a light transmittance of not less than 80%, showing optical isotropy on the plane of the transparent film, and satisfying the condition of: 30≦{(nx+ny)/2-nz}×d≦150 in which nx and ny are main refractive indices on the plane of the transparent film, nz is a main refractive index in the thickness direction of the transparent film, and d is the thickness of the transparent film, wherein the unit for d is nm.

Claim 3

The elliptically polarizing plate as defined in claim 1, wherein the optical compensatory sheet is disposed on one side of the polarizing film and a second transparent film is disposed on the other side of the film.

Claim 4

The elliptically polarizing plate as defined in claim 1, wherein an orientation layer is provided between the transparent film and the oriented layer of a discotic liquid crystal.

Claim 5

The elliptically polarizing plate as defined in claim 3, wherein the orientation layer is a polymer layer which has been subjected to rubbing treatment.

Claim 6

The elliptically polarizing plate as defined in claim 3, wherein the orientation layer is prepared by obliquely depositing an inorganic compound on the transparent film.

Claim 7

A liquid crystal display comprising a liquid crystal cell which comprises a pair of substrates provided with a transparent electrode and twist-oriented nematic liquid crystal sealed therebetween, and the elliptically polarizing plate defined in claim 1 which is arranged on at least one side of the cell.

Claim 8

A liquid crystal display as defined in claim 6, wherein two elliptically polarizing plates defined in claim 1 are arranged on both sides of the cell.

Claim 9

The elliptically polarizing plate as defined in claim 1, wherein the transparent film is a triacetyl cellulose film.

Claim 10

A process for preparation of an elliptically polarizing plate which comprises sandwiching a polarizing film with an optical compensatory sheet and a transparent film by passing the optical compensatory sheet, the polarizing film, and the transparent film simultaneously between a pair of rollers, wherein said sheet has an optically negative monoaxial property and a direction of a minimum retardation inclined at 5 to 50 degrees from the normal of the sheet, the sheet comprising a transparent film and an oriented layer of a discotic liquid crystal provided thereon, said transparent film having a light transmittance of not less than 80%, showing optical isotropy on the plane of the transparent film, and satisfying the condition of: 30≦{(nx+ny)/2-nz}×d≦150 in which nx and ny are main refractive indices on the plane of the transparent film, nz is a main refractive index in the thickness direction of the transparent film, and d is the thickness of the transparent film, wherein the unit for d is nm.

Claim 11

A process for preparation of an elliptically polarizing plate which comprises sandwiching a polarizing film with an optical compensatory sheet and a transparent film by passing the optical compensatory sheet, the polarizing film, and the transparent film simultaneously between a pair of rollers, wherein said sheet has an optically negative monoaxial property and a direction of a minimum retardation inclined at 5 to 50 degrees from the normal of the sheet, the sheet comprising a transparent film and an oriented layer of a discotic liquid crystal provided thereon, said transparent film having a light transmittance of not less than 80%, showing optical isotropy on the plane of the transparent film, and satisfying the condition of: 30≦{(nx+ny)/2-nz}×d≦150 in which nx and ny are main refractive indices on the plane of the transparent film, nz is a main refractive index in the thickness direction of the transparent film, and d is the thickness of the transparent film, wherein the unit for d is nm.