Process of producing circularly-polarized-light-extracting optical element, circularly-polarized-light-extracting optical element, polarized-light-emitting device including the optical element, and liquid crystal display including the optical element

• US 20020176167A1
• Filed: 04/04/2002
• Published: 11/28/2002
• Est. Priority Date: 04/04/2001
• Status: Active Grant

• Current Assignee: Dai Nippon Printing Company Limited
• Original Assignee: Dai Nippon Printing Company Limited
• Inventors: Kashima, Keiji
• Granted Patent: US 6,891,585 B2
• Time in Patent Office: Days
• US Class Current: 359/500
• CPC Class Codes: G02B 5/3033 in the form of a thin sheet or foil, e.g. Polaroid

Abstract

Disclosed herein is a process of producing a circularly-polarized-light-extracting optical element adapted to effectively prevent the appearance of bright and dark stripes on the screen of a display to avoid lowering of the displaying quality of the display. The circularly-polarized-light-extracting optical element includes a glass substrate 11, an alignment layer 12 laminated to the glass substrate 11, and a cholesteric layer 13 formed on the alignment layer 12, in which molecules are aligned in the sate of planar alignment due to the alignment-regulating action of the surface of the alignment layer 12. The cholesteric layer 13 has a first surface 13a on its glass substrate 11 side, and a second surface 13b opposite to the first surface 13a. Director directions of molecules on the first surface 13a of the cholesteric layer 13 are aligned in substantially one direction owing to the alignment-regulating action of the surface of the alignment layer 12. Further, the chiral pitch in the cholesteric layer 13 varies so that the chiral pitch p₂ on the second surface 13b side is longer than the chiral pitch p₁ on the first surface 13a side.

Claims

1. A process of producing a circularly-polarized-light-extracting optical element, comprising the steps of:

coating a substrate with a polymerizable material, and orienting the polymerizable material by an alignment-regulating action of a surface of the substrate, which acts in substantially one direction; and

three-dimensionally cross-linking the polymerizable material oriented, while causing a cholesteric structure formed by the polymerizable material to have a chiral pitch varying in a direction of thickness of the substrate, thereby forming a cholesteric layer in which the chiral pitch on its first surface side, which is on the substrate side, is shorter than that on its second surface side opposite to the first surface side.

2. A process of producing a circularly-polarized-light-extracting optical element, comprising the steps of:

coating a substrate with a polymerizable material, thereby orienting the polymerizable material by an alignment-regulating action of a surface of the substrate, which acts in substantially one direction;

three-dimensionally cross-linking the polymerizable material oriented, thereby forming a first coating cholesteric film with a predetermined chiral pitch;

directly applying a laminating polymerizable material to the first coating cholesteric film, and orienting the laminating polymerizable material by an alignment-regulating action of a surface of the first coating cholesteric film; and

three-dimensionally cross-linking the laminating polymerizable material, thereby forming, on the first coating cholesteric film, a second coating cholesteric film with a chiral pitch longer than that in the first coating cholesteric film.

3. A process of producing a circularly-polarized-light-extracting optical element, comprising the steps of:

coating a substrate with a liquid crystalline polymer, and orienting the liquid crystalline polymer by an alignment-regulating action of a surface of the substrate, which acts in substantially one direction; and

transforming the oriented liquid crystalline polymer into a glassy state by cooling, while cousing a cholesteric structure formed by the liquid crystalline polymer to have a chiral pitch varying in a direction of thickness of the substrate, thereby forming a cholesteric layer in which the chiral pitch on its first surface side, which is on the substrate side, is shorter than that on its second surface side opposite to the first surface side.

4. A process of producing a circularly-polarized-light-extracting optical element, comprising the steps of:

coating a substrate with a liquid crystalline polymer, and orienting the liquid crystalline polymer by an alignment-regulating action of a surface of the substrate, which acts in substantially one direction;

transforming the oriented liquid crystalline polymer into a glassy state by cooling, thereby forming a first coating cholesteric film with a predetermined chiral pitch;

directly applying a laminating liquid crystalline polymer to the first coating cholesteric film, and orienting the laminating liquid crystalline polymer by an alignment-regulating action of a surface of the first coating cholesteric film; and

transforming the oriented laminating liquid crystalline polymer into a glassy sate by cooling, thereby forming, on the first coating cholesteric film, a second coating cholesteric film with a chiral pitch longer than that in the first coating cholesteric film.

5. A circularly-polarized-light-extracting optical element comprising:

a substrate; and

a cholesteric layer formed on the substrate, the cholesteric layer being oriented by an alignment-regulating action of a surface of the substrate,

wherein the cholesteric layer has a first surface and a second surface opposite to the first surface, director directions of molecules on the first surface of the cholesteric layer are aligned in substantially one direction owing to the alignment-regulating action of the surface of the substrate, and a chiral pitch on the second surface side of the cholesteric layer is longer than that on the first surface side.

6. The circularly-polarized-light-extracting optical element according to claim 5, wherein the chiral pitch in the cholesteric layer gradually varies from the first surface side to the second surface side.

7. The circularly-polarized-light-extracting optical element according to claim 5, wherein the cholesteric layer is composed of a laminate of a plurality of coating cholesteric films.

8. The circularly-polarized-light-extracting optical element according to claim 5, wherein the cholesteric layer partially transmits either right- or left-handed circularly polarized component of incident light, having wavelength in a selective reflection wave range.

9. The circularly-polarized-light-extracting optical element according to claim 5, wherein the chiral pitch in the cholesteric layer on its second surface side is chosen so that a selective reflection wavelength on the second surface side will be 687 nm or more.

10. A polarized-light-emitting device comprising:

a circularly-polarized-light-extracting optical element according to claim 5;

a light guide that causes light entering from its side to emerge from either its top or bottom, thereby projecting this emergent light on the circularly-polarized-light-extracting optical element; and

a light source that emits light towards the side of the light guide.

11. A liquid crystal display comprising:

a polarized-light-emitting device according to claim 10; and

a liquid crystal cell that receives polarized light emitted from the polarized-light-emitting device and transmits the polarized light while varying polarized light transmittance.