Method for aligning liquid crystals, alignment device and liquid crystal display element

• US 6,295,112 B1
• Filed: 04/23/1997
• Issued: 09/25/2001
• Est. Priority Date: 07/10/1996
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.), The secretary of state for defence in her Britannic Majesty's Government of the United Kingdom of Great Britain And Northern Ireland
• Inventors: Kaneko, Takashi, Shigeta, Mitsuhiro, Kabe, Masaaki, Itoh, Nobuyuki, Koden, Mitsuhiro
• Primary Examiner(s): Sikes, William L.
• Assistant Examiner(s): NGUYEN, DUNG T
• Application Number:
  US08/842,245
• Time in Patent Office: 1,616 Days
• Field of Search: 349/133, 349/134, 349/126
• US Class Current: 349/126
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/1416 Details of the smectic layer structure, e.g. bookshelf, chevron, C1 and C2

Abstract

A method of aligning a liquid crystal includes a step of fixing on a hot plate and heating a liquid crystal cell in which a liquid crystal composed of a ferroelectric liquid crystal material sealed between electrode substrates respectively having alignment films having applied thereto a uniaxial alignment by rubbing. According to the described method, a pressure is applied to the liquid crystal cell by a roller, and a portion subjected to an application of pressure is moved by moving the roller. Further, the liquid crystal is heated within a temperature range between a phase transition temperature of SmA phase SmC* phase and a temperature 10° C. below the phase transition temperature, and the portion subjected to an application of pressure is moved in the same direction as the rubbing direction, thereby achieving the C2 orientation at higher yield. Within the described temperature range, by moving the portion in an opposite direction to the rubbing direction, a C2 orientation can be always achieved at high yield (almost 100%). As a result, the C2 orientation can be surely achieved in the liquid crystal display element with ease.

Claims

1. A method of aligning liquid crystals, designed for aligning a liquid crystal material of a liquid crystal display element, said liquid crystal material sealed between a pair of planar light-transmissive substrates respectively having alignment films formed on surfaces thereof which face each other, comprising the step of:

locally applying a pressure to said liquid crystal material under an applied heat in order to align the liquid crystal material, said locally applied pressure being applied to the planar light-transmissive substrates,

wherein a portion subjected to an application of pressure in said liquid crystal material is moved in an opposite direction to a direction of an alignment treatment applied to said alignment films.

2. The method for aligning liquid crystals as set forth in claim 1, wherein:

said liquid crystal material is a ferroelectric liquid crystal material.

3. The method for aligning liquid crystals as set forth in claim 1, wherein:

said liquid crystal material is a ferroelectric liquid crystal material.

4. The method for aligning liquid crystals as set forth in claim 3, wherein:

said liquid crystal material is a SmC* phase liquid crystal material having a SmC* phase, and

said SmC* phase liquid crystal material is heated at temperature ranging from a temperature 10°

C. below a phase transition temperature, at which a transition in phase occurs from a SmA phase to a SmC* phase, to the phase transition temperature.

5. A liquid crystal alignment device for aligning a liquid crystal material of a liquid crystal display element, said liquid crystal material being sealed between a pair of planar light-transmissive substrates respectively having alignment films formed on surfaces thereof which face each other, comprising:

heat application means for heating said liquid crystal material;

pressure application means for locally applying a pressure onto said liquid crystal material under an applied heat by said heat application means in order to align the liquid crystal material, said locally applied pressure being applied to the planar light-transmissive substrates; and

moving means for moving a portion subjected to an application of pressure of said liquid crystal material in an opposite direction to a direction of an alignment treatment applied to said alignment films.

6. The liquid crystal alignment device as set forth in claim 5, wherein:

said liquid crystal material is a SmC* phase liquid crystal material,

said heating means is permitted to set a heating temperature such that said SmC* phase liquid crystal material is heated within a temperature range of from a temperature 10°

C. below a phase transition temperature at which a transition in phase occurs from a SmA phase to a SmC* phase, to the phase transition temperature.

7. The liquid crystal alignment device as set forth in claim 5, wherein:

said pressure application means is at least one roller provided at a fixed position; and

said moving means is a stage for placing thereon said liquid crystal display element, and moving said liquid crystal display element in the same direction as a direction of an alignment treatment applied to said alignment films.

8. The liquid crystal alignment device as set forth in claim 7, wherein:

said roller is freely rotatable.

9. The liquid crystal alignment device as set forth in claim 7, wherein:

said roller is fixed.

10. The liquid crystal alignment device as set forth in claim 9, further comprising:

cooling means for cooling off said roller that is heat treated by said heat application means.

11. The liquid crystal alignment device as set forth in claim 10, wherein:

said cooling means supplies a cooling water to a hollow space which penetrates both ends of said roller.

12. The liquid crystal alignment device as set forth in claim 7, wherein:

said roller is made of stainless steel, and is covered with a protective film.

13. The liquid crystal alignment device as set forth in claim 7, wherein:

said roller has a length which is longer than a length between both ends of a display area in said liquid crystal display element in a lengthwise direction of said roller and is shorter than a length between both ends of said liquid crystal display element.

14. The liquid crystal alignment device as set forth in claim 5, wherein:

said pressure application means and said moving means are rollers which move in an opposite direction to a direction of an alignment treatment applied to said alignment films.

15. The liquid crystal alignment device as set forth in claim 14, wherein:

said roller is freely rotatable.

16. The liquid crystal alignment device as set forth in claim 14, wherein:

said roller is fixed.

17. The liquid crystal alignment device as set forth in claim 14, wherein:

said roller is made of stainless steel, and is covered with a protective film.

18. The liquid crystal alignment device as set forth in claim 14, wherein:

said roller has a length which is longer than a length between both ends of a display area in said liquid crystal display element in a lengthwise direction of the roller and is shorter than a length between both ends of said liquid crystal display element.

19. The liquid crystal alignment device as set forth in claim 14, further comprising:

cooling means for cooling off said roller that is heat treated by said heat application means.

20. The liquid crystal alignment device as set forth in claim 19, wherein:

said cooling means supplies a cooling water to a hollow space which penetrates both ends of said roller.

21. A liquid crystal alignment device for aligning a liquid crystal material of a liquid crystal display element, said liquid crystal material being sealed between a pair of planar light-transmissive substrates respectively having alignment films formed on surfaces thereof which face each other, comprising:

a heater for heating said liquid crystal material;

a pressurizer for locally applying a pressure onto said liquid crystal material under an applied heat by said heater in order to align the liquid crystal material, said locally applied pressure being applied to the planar light-transmissive substrates; and

a moving mechanism for moving a portion subjected to an application of pressure of said liquid crystal material in an opposite direction to a direction of an alignment treatment applied to said alignment films.

22. A liquid crystal alignment device for aligning a liquid crystal material of a liquid crystal display element, said liquid crystal material being sealed between a pair of planar light-transmissive substrates respectively having alignment films formed on surfaces thereof which face each other, comprising:

a heater for heating said liquid crystal material; and

a pressurizer for locally applying a pressure onto said liquid crystal material under an applied heat by said heater in order to align the liquid crystal material, said locally applied pressure being applied to the planar light-transmissive substrates,

wherein said liquid crystal material is a SmC* phase liquid crystal material, and

said heater is permitted to set a heating temperature such that said SmC* phase liquid crystal material is heated within a temperature range of from a temperature 10°

C. below a phase transition temperature at which a transition in phase occurs from a SmA phase to a SmC* phase, to the phase transition temperature.

23. A liquid crystal display element including a liquid crystal material sealed between a pair of planar light-transmissive substrates respectively having alignment films formed on surfaces thereof which face each other, wherein:

said liquid crystal material is locally subjected to an application of pressure under an applied heat in order to align the liquid crystal material, said locally applied pressure being applied to the planar light-transmissive substrates, and

in a process of locally applying a pressure to said liquid crystal material, the portion subjected to an application of pressure of said liquid crystal material is moved in an opposite direction to a direction of an alignment treatment applied to said alignment films.

24. The liquid crystal display element as set forth in claim 23, wherein:

said liquid crystal material shows ferroelectricity.

25. The liquid crystal display element as set forth in claim 23, wherein:

said liquid crystal material shows ferroelectricity.

26. The liquid crystal display element as set forth in claim 23, wherein:

said liquid crystal material shows ferroelectricity.

27. The liquid crystal display element as set forth in claim 26, wherein:

said liquid crystal material shows a SmC* phase, and

a heating temperature is set within a range of from a temperature 10°

C. below a phase transition temperature at which a transition in phase occurs from a SmA phase to a SmC* phase, to the phase transition temperature.