Reflective type liquid crystal display device

• US 6,351,298 B1
• Filed: 09/08/2000
• Issued: 02/26/2002
• Est. Priority Date: 02/10/1997
• Status: Expired due to Term

• Current Assignee: Sharp Electronics Corporation (Hon Hai Precision Industry Co., Ltd.), Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Ueki, Shun, Okamoto, Masayuki, Mitsui, Seiichi
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US09/658,552
• Time in Patent Office: 536 Days
• Field of Search: 349/113, 349/117, 349/86, 349/88, 349/112
• US Class Current: 349/113
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal
• CPC Class Codes: C09K 2019/546 creating a polymeric network
• CPC Class Codes: G02F 1/133504 Diffusing, scattering, diffracting elements associated to illuminating devices G02F1/133606
• CPC Class Codes: G02F 1/133528 Polarisers
• CPC Class Codes: G02F 1/133626 providing two modes of illumination, e.g. day-night
• CPC Class Codes: G02F 2203/02 reflective

Abstract

A reflective type liquid crystal display device in accordance with the present invention includes a reflector film having excellent polarization preservation properties and an anisotropic diffusing film for diffusing only the light polarized in a particular direction. The anisotropic diffusing film is composed of a complex of liquid crystal and a polymer and selectively diffuses incident light. If a liquid crystal layer composed of dichroic dye and liquid crystal is employed, it becomes possible to carry out high contrast display with the anisotropic diffusing film and the reflector film and to prevent reflections of nearby objects appearing on the screen. Similarly, if a liquid crystal layer composed of liquid crystal and a polymer and having a twist angle of orientation of the liquid crystal specified to be in a range of 40° to 50° between an insulating substrate and a reflector member is employed, and the reflector film possesses excellent polarization preservation properties, similarly to the above case a reflective type liquid crystal display device can be obtained which reflects no nearby objects on the screen and can carry out high contrast display.

Claims

1. A reflective type liquid crystal display device, having a liquid crystal display element provided with:

a quarter-wavelength plate; and

a pair of substrates, each substrate being provided with a transparent electrode,

the reflective type liquid crystal display device carrying out display by using ambient light,

said element, comprising;

a reflector member, possessing an excellent polarization preservation property, for reflecting incident light; and

a complex member, composed of a complex of liquid crystal and a polymer that are phase separated, for selectively diffusing incident light while transmitting the incident light,

wherein the complex member is a liquid crystal layer disposed between the substrate and the reflector member, the liquid crystal being oriented with a twist angle in the range of 40°

to 50°

, and

the quarter-wavelength plate is disposed between the reflector member and the liquid crystal layer, and

a polarizer plate is provided on a side where the incident light enters.

2. The reflective type liquid crystal display device as defined in claim 1,

wherein the polymer composing the liquid crystal layer is composed of a material exhibiting birefringence, and the liquid crystal layer exhibits a diffusion state when voltage is applied and does not exhibit a diffusion state when no voltage is applied.

3. The reflective type liquid crystal display device as defined in claim 1,

wherein the reflector member has mirror finished surface.

4. The reflective type liquid crystal display device as defined in claim 1,

wherein the reflector member is a diffusing mirror having smooth convexities and concavities.

5. The reflective type liquid crystal display device as defined in claim 1,

wherein the quarter-wavelength plate is composed of a liquid crystalline polymer.

6. The reflective type liquid crystal display device as defined in claim 1,

wherein the quarter-wavelength plate is composed of a polymer obtained from a low molecule having liquid crystallinity by stabilizing the orientation of the liquid crystal.

7. The reflective type liquid crystal display device as defined in claim 1, further comprising

a color filter.

8. A reflective type liquid crystal display device, comprising a polarizer plate on a side of a liquid crystal element, through which side light enters the liquid crystal element,

the liquid crystal element includes:

an insulating substrate at least provided with a transparent electrode;

a light reflector member provided with an opposite electrode for driving display in collaboration with the transparent electrode and a light reflector film formed on one of the surfaces of the insulating substrate;

a polymer-dispersed liquid crystal layer that is a complex layer composed of an aligned liquid crystal phase and polymer resin phase provided between the insulating substrate and the light reflector member, twist angle of orientation of the liquid crystal being specified to be in the range of 40°

to 50°

between the insulating substrate and the reflector member, wherein the complex layer diffuses polarized light only in a specific direction without changing the plane of the polarized light while transmitting the polarized light; and

a quarter-wavelength plate formed between the light reflector member and the polymer-dispersed liquid crystal layer.

9. The reflective type liquid crystal display device as defined in claim 8,

wherein the polarizer plate has a transparent axis placed so as to coincide with either of directions of twisted orientation of the polymer-dispersed liquid crystal.

10. The reflective type liquid crystal display device as defined in claim 8,

wherein the polymer-dispersed liquid crystal layer is composed of a polymer material exhibiting birefringence, and the polymer-dispersed liquid crystal layer exhibits a diffusion state when voltage is applied and does not exhibit a diffusion state when no voltage is applied.

11. The reflective type liquid crystal display device as defined in claim 8,

wherein the light reflector film forming a light reflector surface of the light reflector member is disposed on a side of the light reflector member, the side facing the polymer-dispersed liquid crystal layer.

12. The reflective type liquid crystal display device as defined in claim 8,

wherein the light reflector surface is either flat mirror finished surface or a diffusing mirror having smooth convexities and concavities.

13. The reflective type liquid crystal display device as defined in claim 8,

wherein the quarter-wavelength plate is composed of either a liquid crystalline polymer or a polymer obtained from a low molecule having liquid crystallinity by stabilizing the orientation of the liquid crystal.

14. The reflective type liquid crystal display device as defined in claim 8,

wherein the quarter-wavelength plate is disposed on the light reflector film of the light reflector member and is provided with a transparent electrode formed thereon, the transparent electrode being specified to oppose the transparent electrode formed on the insulating substrate.

15. The reflective type liquid crystal display device as defined in claim 8,

wherein a color filter layer is provided either on the insulating substrate or on the transparent electrode on the insulating substrate.

16. The reflective type liquid crystal display device as defined in claim 8,

wherein the quarter-wavelength plate is composed at least of a first layer and a second layer, the first layer has a retardation of 120 nm to 150 nm with respect to incident light entering at a right angle, the second layer is disposed so that the second layer and a reflector surface flank the first layer therebetween, the second layer has approximately double the retardation of the first layer, and the direction of a slow axis in a layer plane of the first layer is displaced from the direction of a slow axis in a layer plane of the second layer by 60°

to 120°

.

17. The reflective type liquid crystal display device as defined in claim 8,

wherein the polymer-dispersed liquid crystal layer contains the liquid crystal in a rang of 50 weight % to 98 weight %.