Polymer-wall LCD having liquid crystal molecules having a plane-symmetrical bend orientation

• US 5,668,651 A
• Filed: 02/27/1995
• Issued: 09/16/1997
• Est. Priority Date: 03/18/1994
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Yamada, Nobuaki, Kozaki, Shuichi, Hirai, Toshiyuki, Horie, Wataru
• Primary Examiner(s): Gross, Anita Pellman
• Assistant Examiner(s): TON, MINH TOAN T
• Application Number:
  US08/394,472
• Time in Patent Office: 932 Days
• Field of Search: 359/81, 359/63, 359/73, 359/62, 359/51
• US Class Current: 349/156
• CPC Class Codes: G02F 1/133377 Cells with plural compartments or having plurality of liquid crystal microcells partitioned by walls, e.g. one microcell per pixel
• CPC Class Codes: G02F 1/1395 Optically compensated birefringence [OCB]- cells or PI- cells

Abstract

A liquid crystal display device according to the present invention includes: a pair of electrode substrates including a plurality of pixels arranged in a matrix shape and an electrode formed on a surface of each electrode substrate, at least one of the surfaces being subjected to a rubbing treatment; a wall-like structure formed between the pair of electrode substrates, the wall-like structure including unit walls, and each unit wall corresponding to one of the plurality of pixels; and a liquid crystal layer at least partially partitioned by the wall-like structure and including liquid crystal regions between the pair of electrode substrates, each liquid crystal region corresponding to one of the plurality of pixels, wherein liquid crystal molecules in the liquid crystal regions have a plane-symmetrical orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates, the liquid crystal molecules having a bend orientation.

Claims

1. A liquid crystal display device comprising:

a pair of electrode substrates including a plurality of pixels arranged in a matrix shape and an electrode formed on a surface of each electrode substrate, at least one of the surfaces being subjected to a rubbing treatment;

a wall-like structure formed between the pair of electrode substrates, the wall-like structure including unit walls, and each unit wall corresponding to one of the plurality of pixels; and

a liquid crystal layer at least partially partitioned by the wall-like structure and including liquid crystal regions between the pair of electrode substrates, each liquid crystal region corresponding to one of the plurality of pixels, wherein liquid crystal molecules in the liquid crystal regions have a plane-symmetrical bend orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates.

2. A liquid crystal display device according to claim 1, wherein the pair of electrode substrates are in close contact with the wall-like structure.

3. A liquid crystal according to claim 1, wherein a liquid crystalline polymer material is included in a material constituting the wall-like structure.

4. A liquid crystal display device according to claim 1 further comprising a pair of polarizers, each polarizer being formed on the surface of one of the pair of electrode substrates, and respective polarizing axes of the polarizers being perpendicular to each other,

wherein the polarizing axis of one of the pair of polarizers is at 45°

with respect to a direction in which the rubbing treatment is conducted for the electrode substrates.

5. A liquid crystal display device according to claim 4 further comprising a mono-axial optical compensated film between the liquid crystal layer and one of the pair of polarizers, a main axis of the mono-axial optical compensated film being perpendicular to a longitudinal axis direction of the liquid crystal molecules, and the mono-axial optical compensated film having a retardation equal to d•

Δ

n, wherein d represents a thickness of the liquid crystal layer and Δ

n represents an effective anisotropy of refractive index of the liquid crystal layer.

6. A liquid crystal display device according to claim 4 further comprising a bi-axial optical compensated film between the liquid crystal layer and one of the pair of polarizers, a main axis of the bi-axial optical compensated film being perpendicular to a longitudinal axis direction of the liquid crystal molecules, and the bi-axial optical compensated film having a retardation equal to d•

Δ

n, wherein d represents a thickness of the liquid crystal layer and Δ

n represents an effective anisotropy of refractive index of the liquid crystal layer.

7. A liquid crystal display device according to claim 1, wherein a material for at least one of the pair of electrode substrates is a polymer material capable of transmitting visible light at least in some wavelengths.

8. A liquid crystal display device according to claim 1, wherein an ordinary refractive index n_o and an extraordinary refractive index n_e of a liquid crystal material constituting the liquid crystal layer, and a refractive index n_p of the material constituting the wall-like structure satisfies the following relationship:

space="preserve" listing-type="equation">|((n.sub.e or n.sub.o)-n.sub.p)|≦

0.1.

9.

9. A method for producing a liquid crystal display device comprising:

a pair of electrode substrates including a plurality of pixels arranged in a matrix shape, at least one of the electrode substrates being transparent;

a polymer wall including unit walls, each unit wall corresponding to one of the plurality of pixels; and

a liquid crystal layer at least partially partitioned by the polymer wall and including liquid crystal regions between the pair of electrode substrates, each liquid crystal region corresponding to one of the plurality of pixels, liquid crystal molecules in the liquid crystal regions having a plane-symmetrical bend orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates

wherein the method comprises the steps of;

injecting a mixture of a liquid crystal material, a liquid crystalline compound having a polymerizable functional group within molecules thereof, a polymerizable compound, and a photopolymerization initiator between the pair of electrode substrates, at least one of surfaces of the electrode substrates being subjected to a rubbing treatment; and

irradiating a liquid crystal cell including the pair of electrode substrates and the mixture with light having a regular spatial distribution of intensities of high and low so as to correspond to the plurality of pixels, while applying at least one of an electric field and a magnetic field, whereby liquid crystal and a polymer material are phase-separated through a photopolymerization reaction so as to form the liquid crystal layer and the polymer wall, respectively.

10. A method according to claim 9, wherein the light having a regular spatial distribution of intensities of high and low is generated by means of a photomask.

11. A method according to claim 9, wherein the mixture present in the liquid crystal cell including the pair of electrode substrates and the mixture is subjected to a photopolymerization by using the light having a regular spatial distribution of intensities of high and low at a temperature equal to or greater than a homogenization temperature of the liquid crystal material, and thereafter is cooled while applying at least one of an electric field and a magnetic field.

12. A method according to claim 11, wherein the liquid crystal cell is irradiated with light again after the cooling.

13. A liquid crystal display device comprising a display medium including a pair of opposing electrode substrates, a liquid crystal layer interposed between the pair of electrode substrates, and a polymer layer,

wherein liquid crystal molecules in the liquid crystal layer have a bend orientation so as to be plane-symmetrical with respect to a plane taken in the middle of and in parallel to the electrode substrates, the polymer layer including a cross-linked polymer in an amount of 0.1% to 5%, by weight, based on the display medium.

14. A liquid crystal display device according to claim 13, wherein the cross-linked polymer includes a liquid crystalline compound having a polymerizable functional group within molecules thereof.

15. A liquid crystal display device according to claim 13 further comprising:

a pair of polarizers, each polarizer being formed on a surface of one of the pair of electrode substrates, and respective polarizing axes of the polarizers being perpendicular to each other; and

a mono-axial optical compensated film provided between the liquid crystal layer and one of the pair of polarizers, a main axis of the mono-axial optical compensated film being perpendicular to a longitudinal axis direction of the liquid crystal molecules,

wherein the polarizing axis of one of the pair of polarizers is at 45°

with respect to a direction in which the rubbing treatment is conducted for the electrode substrates.

16. A liquid crystal display device according to claim 13 further comprising:

a pair of polarizers, each polarizer being formed on a surface of one of the pair of electrode substrates, and respective polarizing axes of the polarizers being perpendicular to each other; and

a bi-axial optical compensated film provided between the liquid crystal layer and one of the pair of polarizers, a main axis of the bi-axial optical compensated film being perpendicular to a longitudinal axis direction of the liquid crystal molecules,

wherein the polarizing axis of one of the pair of polarizers is at 45°

with respect to a direction in which the rubbing treatment is conducted for the electrode substrates.

17. A method for producing a liquid crystal display device comprising a display medium including a pair of opposing electrode substrates, a liquid crystal layer interposed between the pair of electrode substrates, and a polymer layer,

wherein liquid crystal molecules in the liquid crystal layer have a bend orientation so as to be plane-symmetrical with respect to a plane taken in the middle of and in parallel to the electrode substrates,

wherein the method comprises the steps of:

injecting a mixture of 0.1% to 5% by weight of a polymer cross-linkable material including a liquid crystalline polymerizable compound having a functional group in molecules thereof and a liquid crystal material between the pair of electrode substrates, at least one of the electrode substrates being transparent; and

phase-separating the liquid crystal layer and the polymer layer by applying at least one of light energy and heat energy to the mixture while stabilizing the bend orientation of the liquid crystal molecules by applying at least one of an electric field and a magnetic field.

18. A method for producing a liquid crystal display device comprising a display medium including a pair of opposing electrode substrates, a liquid crystal layer interposed between the pair of electrode substrates, at least one of the electrode substrates being transparent, and a polymer layer, where liquid crystal molecules in the liquid crystal layer have an initially unstable orientation, comprising the steps of:

injecting a mixture of a polymer cross-linkable material including a liquid crystalline polymerizable compound and a liquid crystal material between the pair of electrode substrates;

phase-separating the liquid crystal layer and the polymer layer by applying at least one of light energy and heat energy to the mixture while initially applying at least one of an electric field and a magnetic field to stabilize the initial unstable orientation of liquid crystal molecules using the polymer layer formed as a result of the phase separation process;

removing application of the at least one of the electric and magnetic fields; and

maintaining the stabilized orientation of the liquid crystal molecules after the at least one of the electric and magnetic fields is removed.

19. The method in claim 18, wherein during the phase separating step, the polymer layer formed on a surface of one of the electrode substrates includes liquid crystal molecules having a tilt angle with respect to the substrate surface.

20. The method in claim 18, wherein when the at least one of the electric and magnetic fields is removed, the tilted liquid crystal molecules are fixed by the polymer layer such that the polymer layer including the fixed tilted liquid crystal molecules functions as an alignment layer to stabilize the bend orientation.

21. The method in claim 18, wherein the liquid crystal molecules have a plane-symmetrical bend orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates.

22. The method in claim 19, wherein the liquid crystal molecules have a plane-symmetrical bend orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates.

23. The method in claim 20, wherein the liquid crystal molecules have a plane-symmetrical bend orientation with respect to a plane taken in the middle of and in parallel to the electrode substrates.