Liquid crystal display device and its driving method

• US 6,525,707 B1
• Filed: 07/26/1999
• Issued: 02/25/2003
• Est. Priority Date: 11/28/1997
• Status: Expired due to Fees

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Inventors: Yoshikawa, Kazuhiko, Kaneko, Yasushi
• Primary Examiner(s): Hjerpe; Richard
• Assistant Examiner(s): ZAMANI, ALI A
• Application Number:
  US09/355,201
• Time in Patent Office: 1,310 Days
• Field of Search: 345/50,88,102,150,87,96 349/19,29,68,118,119,102,151,77-81 348/742,19,29,30,61,68 368/84-71
• US Class Current: 345/88
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/1347 Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
• CPC Class Codes: G02F 1/13471 in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells G02F1/13475 takes precedence
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: G09G 5/02 characterised by the way in which colour is displayed details of colour display specific for CRTs G09G1/28; specific for flat matrix panels other than liquid crystal displays G09G3/2003; specific for liquid crystal displays G09G3/3607

Abstract

A liquid crystal display device capable of displaying in multiple colors, and a method for driving the liquid crystal display device using a typical monochrome liquid crystal driving IC. A display portion of a birefringence color liquid crystal display device has a usual letter display portion (41) for displaying letters in a single color and a mark display portion (42) for displaying a variety of colors. A liquid crystal cell is driven by supplying scanning signals to scanning electrodes for the letter display portion (41) and data signals to scanning electrodes for the mark display portion (42).

Claims

1. A liquid crystal display device, consisting of a liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrodes and a transparent second substrate having second electrodes and a liquid crystal driving circuit which outputs scanning signals and data signals for driving said liquid crystal display cell,

wherein a display portion has a letter display portion and a mark display portion, and

said liquid crystal driving circuit supplies scanning signals to said first electrodes while supplying data signals to said second electrodes in said letter display portion, and data signals to both said first electrodes and second electrodes in said mark display portion.

2. The liquid crystal display device according to claim 1,

further comprising a reflector which is a transflective reflector is arranged on the outside of said liquid crystal cell, and

a backlight unit arranged on the opposite side of said transflective reflector from said liquid

crystal cell to illuminate said liquid crystal cell through said transflective reflector.

3. The liquid crystal display device according to claim 1,

further comprising a pair of polarizing films arranged on and under the liquid crystal cell, and

a retardation film arranged between said liquid crystal cell and said polarizing film positioned on the visible side.

4. The liquid crystal display device according to claim 2,

further comprising a pair of polarizing films arranged on and under the liquid crystal cell, and

a retardation film arranged between said liquid crystal cell and said polarizing film positioned on the visible side.

5. The liquid crystal display device according to claim 1,

further comprising a pair of polarizing films arranged on and under the liquid crystal cell, and

a twisted retardation film arranged between said liquid crystal cell and said polarizing film positioned on the visible side.

6. The liquid crystal display device according to claim 2,

further comprising a pair of polarizing films arranged on and under the liquid crystal cell, and

a twisted retardation film arranged between said liquid crystal cell and said polarizing film positioned on the visible side.

7. The liquid crystal display device according to claim 1,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1300 nm to 1600 nm.

8. The liquid crystal display device according to claim 2,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1300 nm to 1600 nm.

9. The liquid crystal display device according to claim 3,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1500 nm to 1800 nm, and a retardation value of said retardation film ranges from 1600 nm to 1900 nm.

10. The liquid crystal display device according to claim 4,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1500 nm to 1800 nm, and a retardation value of said retardation film ranges from 1600 nm to 1900 nm.

11. The liquid crystal display device according to claim 3,

wherein said retardation film is a retardation film forming relations of nx>

nz>

ny, where nx is the refractive index of a phase delay axis, ny is the refractive index in a direction orthogonal to the phase delay axis, and nz is the refractive index in a thickness direction.

12. The liquid crystal display device according to claim 4,

wherein said retardation film is a retardation film forming relations of nx>

nz>

ny, where nx is the refractive index of a phase delay axis, ny is the refractive index in a direction orthogonal to the phase delay axis, and nz is the refractive index in a thickness direction.

13. The liquid crystal display device according to claim 5,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1500 nm to 1800 nm, and a Δ

nd value of said twisted retardation film ranges from 1400 nm to 1800 nm.

14. The liquid crystal display device according to claim 6,

wherein said liquid crystal cell is an STN liquid crystal cell in which said nematic liquid crystal is aligned at a twist angle in the range from 180 degrees to 270 degrees, and a Δ

nd value which is the product of a value Δ

n in the birefringence of the liquid crystal and a gap d of the liquid crystal cell, ranges from 1500 nm to 1800 nm, and a Δ

nd value of said twisted retardation film ranges from 1400 nm to 1800 nm.

19. The liquid crystal display device according to claim 1, wherein said letter display portion is a display portion displaying in a single color, and said mark display portion is a display portion displaying in a plurality of colors.

20. The liquid crystal display device according to claim 2, wherein said letter display portion is a display portion displaying in a single color, and said mark display portion is a display portion displaying in a plurality of colors.

15. A liquid crystal display device, comprising:

a first liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrodes and a transparent second substrate having second electrodes;

a second liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having a first electrode and a transparent second substrate having a second electrode, arranged on a visible side to the first liquid crystal cell; and

a liquid crystal driving circuit which outputs scanning signals and data signals for driving said first and second liquid crystal display cells,

wherein a liquid crystal driving circuit is a circuit for supplying said scanning signals to said first electrodes of said first liquid crystal cell, said data signals to said second electrodes of said first liquid crystal cell, and said data signals to both said first electrode and said second electrode of said second crystal liquid cell.

16. A liquid crystal display device comprising:

a first liquid crystal display device consisting of a first liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrodes and a transparent second substrate having second electrodes, a pair of polarizing films respectively arranged on and under the first liquid crystal cell, and a reflector arranged on a face of one of the polarizing films, the face being on the opposite side to said liquid crystal cell;

a second liquid crystal display device arranged on the visible side of said first liquid crystal display device, and consisting of a second liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrode and a transparent second substrate having a second electrode, a third polarizing film arranged on a face of the second liquid crystal cell on the visible side, and a reflection-type polarizing film arranged on the opposite side of said second liquid crystal cell from the visible side; and

a liquid crystal driving circuit for driving said first and second liquid crystal cells to supply scanning signals to said first electrodes of said first liquid crystal cell, data signals to said second electrodes of said first liquid crystal cell, and data signals to said first electrode and said second electrode of said second crystal liquid cell.

17. A method for driving a liquid crystal display device, comprising a liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrodes and a transparent second substrate having second electrodes, a liquid crystal driving circuit which outputs scanning signals and data signals for driving said crystal display cell,

wherein a display portion of said liquid crystal display device has a letter display portion and a mark display portion, said method comprising steps of:

supplying scanning signals to said first electrodes while supplying data signals to said second electrodes in said mark display portion for displaying a single color; and

supplying data signals to both said first electrode and second electrode in said mark display portion for displaying in a plurality of colors.

18. A method for driving a liquid crystal display device, comprising

a first liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having first electrodes and a transparent second substrate having second electrodes,;

a second liquid crystal cell in which nematic liquid crystal is sandwiched and filled in a gap between a transparent first substrate having a first electrode and a transparent second substrate having a second electrode, arranged on a visible side of the first liquid crystal, and

a liquid crystal driving circuit which outputs scanning signals and data signals for driving said first and second crystal display cells, said method comprising steps of;

supplying scanning signals to said first electrodes of said first liquid crystal cell while supplying data signals to said second electrodes thereof;

for displaying a single color; and

supplying data signals to both said first electrode and said second electrode of said second liquid crystal cell for displaying in a plurality of colors.