Liquid crystal display device with directional backlight and image production capability in the light scattering mode

• US 5,570,210 A
• Filed: 01/31/1994
• Issued: 10/29/1996
• Est. Priority Date: 05/06/1993
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Fujitsu Limited
• Inventors: Yamada, Fumiaki, Tsuda, Hideaki, Hanaoka, Kazutaka, Yoshida, Hidefumi, Nakamura, Kimiaki
• Primary Examiner(s): Gross, Anita Pellman
• Assistant Examiner(s): NGUYEN, TIEP HUU
• Application Number:
  US08/188,901
• Time in Patent Office: 1,002 Days
• Field of Search: 359/51, 359/52, 359/99, 359/49, 359/65
• US Class Current: 349/86
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133543 Cholesteric polarisers
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 1/13756 the liquid crystal selectively assuming a light-scattering state G02F1/1334, G02F1/13718 take precedence

Abstract

A liquid crystal device including a liquid crystal layer comprising a liquid crystal of a dispersed type in which liquid crystal molecules are randomly distributed so that an incident light impinging against the liquid crystal molecules scatters to produce a white display spot. A polarizer and an analyzer are arranged on either side of the first and second transparent plates. A directional backlight is arranged on the outside of the polarizer for supplying light having a directivity in the direction perpendicular to the first and second transparent plates toward the polarizer.

Claims

1. A direct viewing type liquid crystal display device, comprising:

a first transparent plate having inside and outside parallel main surfaces and a first transparent electrode formed on the inside main surface thereof;

a second transparent plate having inside and outside parallel main surfaces and a second transparent electrode formed on the inside main surface thereof, the second transparent plate being positioned in spaced, parallel relationship to the first transparent plate with a gap between the respective inside main surfaces thereof;

a liquid crystal layer having, selectively, a light scattering mode and a light transmitting mode and being disposed in the gap between the first and second transparent plates;

a polarizer arranged on the outside main surface of the first transparent plate;

an analyzer arranged on the outside main surface of the second transparent plate; and

a directional backlight unit supplying a backlight to the direct viewing type liquid crystal display device, the backlight having a directivity substantially in a normal direction relatively to the respective main surfaces of the first and second transparent plates and a large proportion of the backlight, supplied from the backlight unit to the polarizer, having a directivity within an angular range of up to an angle of 10 degrees relative to the normal direction, the backlight being transmitted through the liquid crystal device in the light scattering mode of the liquid crystal layer for image production and being blocked by the analyzer after transmission through the liquid crystal layer in the light transmitting mode of the liquid crystal layer.

2. A direct viewing type liquid crystal display device according to claim 1, wherein the backlight unit comprises:

a lamp which emits divergent light beams; and

a lens which converts the divergent light beams emitted by the lamp into generally parallel light beams extending substantially in the normal direction and within the angular range relative thereto, as supplied to the polarizer.

3. A direct viewing type liquid crystal display device according to claim 2, wherein the backlight unit further comprises means for inducing polarized light.

4. A direct viewing type liquid crystal display device according to claim 1, wherein the backlight unit further comprises:

a lamp which emits divergent light beams;

a lens which bends the divergent light beams emitted by the lamp into generally parallel light beams;

a reflector arranged on a side of the lamp remote from the lens; and

means, arranged between the lens and the polarizer, for receiving the generally parallel light beams and emitting the received light beams as polarized light beams.

5. A direct viewing type liquid crystal display device according to claim 1, wherein the liquid crystal layer includes randomly distributed liquid crystal molecules, incident light from the backlight unit impinging on the liquid crystal molecules being scattered thereby.

6. A direct viewing type liquid crystal display device according to claim 5, wherein the liquid crystal layer comprises a dispersed-type liquid crystal material in which liquid crystal molecules are randomly distributed so that incident light, impinging on the liquid crystal molecules, is scattered thereby in the absence of a voltage being applied to the liquid crystal layer and the liquid crystal molecules uniformly rise relative to the first and second transparent plates, when a voltage is applied to the liquid crystal, so that the incident light from the directional backlight unit and having a directivity substantially in the normal direction passes through the liquid crystal layer without being scattered by the liquid crystal molecules.

7. A direct viewing type liquid crystal display device according to claim 6, wherein the liquid crystal layer comprises liquid crystal capsules dispersed in a transparent material.

8. A direct viewing type liquid crystal display device according to claim 5, wherein the liquid crystal layer comprises:

a first liquid crystal material in the gap between the first and second transparent plates; and

liquid crystal capsules dispersed in the first liquid crystal material, each capsule including therein a second liquid crystal material.

9. A direct viewing type liquid crystal display device according to claim 5, wherein the liquid crystal layer comprises a polymer network type liquid crystal material.

10. A direct viewing type liquid crystal display device according to claim 5, wherein the liquid crystal layer comprises a macromolecular liquid crystal material.

11. A direct viewing type liquid crystal display device according to claim 1, wherein the liquid crystal layer has a scattering value greater than 5, the scattering value being defined by a reciprocal (L/T) of a ratio of an intensity of light (T) transmitting through the liquid crystal layer, measured by arranging the liquid crystal layer between a source of the laser beam and a light detector arranged so as to receive divergent light beams from the liquid crystal panel within the angular range of approximately 6 degrees, to an intensity of light (L) of the source of the laser beam, measured in the same arrangement of the source of the laser beam and the light detector but without any liquid crystal therebetween.

12. A direct viewing type liquid crystal display device according to claim 1, wherein the polarizer and the analyzer have respective transmitting axes which are perpendicular to each other, the backlight being transmitted through the liquid crystal display device in the light scattering mode of the liquid crystal layer and being blocked from transmission through the liquid crystal display device in the light non-scattering mode of the liquid crystal layer.