Liquid Crystal Display Apparatus

• US 20070206131A1
• Filed: 01/18/2006
• Published: 09/06/2007
• Est. Priority Date: 01/18/2005
• Status: Active Grant

• Current Assignee: Citizen Watch Co Limited (Citizen Electronics Company Limited)
• Original Assignee: Citizen Holdings Co., Ltd. (Citizen Electronics Company Limited)
• Inventors: Kondoh, Shinya, Ohara, Mie
• Granted Patent: US 7,787,077 B2
• Time in Patent Office: Days
• US Class Current: 349/96
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/1393 the birefringence of the liquid crystal being electrically controlled, e.g. ECB-, DAP-, HAN-, PI-LC cells G02F1/1396, G02F1/141 take precedence
• CPC Class Codes: G02F 2203/02 reflective
• CPC Class Codes: G02F 2203/64 Normally black display, i.e. the off state being black
• CPC Class Codes: G02F 2203/66 Normally white display, i.e. the off state being white
• CPC Class Codes: G09G 2300/0491 Use of a bi-refringent liquid crystal, optically controlled bi-refringence [OCB] with bend and splay states, or electrically controlled bi-refringence [ECB] for controlling the color
• CPC Class Codes: G09G 3/36 using liquid crystals

Abstract

The present invention is directed to the provision of a liquid crystal display apparatus that can produce a bright display state without utilizing birefringence. The liquid crystal display apparatus according to the present invention includes a first substrate, a second substrate, a reflective polarizer, mounted on the first substrate and having a first transmission axis and a first reflection axis at right angles to each other, for transmitting linearly polarized light vibrating in a plane parallel to the first transmission axis and for reflecting linearly polarized light vibrating in a plane parallel to the first reflection axis, a polarizer, mounted on the second substrate and having a second transmission axis, for transmitting linearly polarized light vibrating in a plane parallel to the second transmission axis, and a liquid crystal layer, provided between the first and second substrates, having a first mode which causes the direction of polarization of incident light to change by utilizing birefringence and a second mode which does not utilize birefringence and therefore does not cause the direction of polarization of incident light to change, wherein a display state is switched between a bright display state and a dark display state by applying a voltage to the liquid crystal layer, and the bright display state is produced by driving the liquid crystal layer in the second mode.

Claims

1. A liquid crystal display apparatus comprising:

a first substrate;

a second substrate;

a reflective polarizer, mounted on said first substrate and having a first transmission axis and a first reflection axis at right angles to each other, for transmitting linearly polarized light vibrating in a plane parallel to said first transmission axis and for reflecting linearly polarized light vibrating in a plane parallel to said first reflection axis;

a polarizer, mounted on said second substrate and having a second transmission axis, for transmitting linearly polarized light vibrating in a plane parallel to said second transmission axis; and

a liquid crystal layer provided between said first and second substrates, and having a first mode which causes the direction of polarization of incident light to change by utilizing birefringence and a second mode which does not utilize birefringence and therefore does not cause the direction of polarization of incident light to change, wherein

a display state is switched between a bright display state and a dark display state by applying a voltage to said liquid crystal layer, and

said bright display state is produced by driving said liquid crystal layer in said second mode.

2. The liquid crystal display apparatus according to claim 1, wherein said bright display state is produced by causing ambient light entering said liquid crystal layer through said second transmission axis of said polarizer to be reflected at said reflective polarizer and by allowing said reflected light to return through said liquid crystal layer and emerge from said polarizer.

3. The liquid crystal display apparatus according to claim 2, wherein said first transmission axis and said second transmission axis are arranged substantially at right angles to each other.

4. The liquid crystal display apparatus according to claim 1, wherein said liquid crystal layer maintains one or the other of first and second stable states in the absence of an applied voltage, and one or the other of said first and second stable states is set as said second mode.

5. The liquid crystal display apparatus according to claim 4 wherein, in said second stable state, liquid crystal molecules are aligned in a direction substantially parallel to said second transmission axis.

6. The liquid crystal display apparatus according to claim 4 wherein, in said first stable state, liquid crystal molecules are aligned in a direction tilted at approximately 45 degrees from the direction in which said liquid crystal molecules are aligned in said second stable state.

7. The liquid crystal display apparatus according to claim 1, wherein said liquid crystal layer is a vertically aligned liquid crystal layer, and has a first state in which liquid crystal molecules are aligned substantially vertically between said first and second substrates and a second state in which said liquid crystal molecules are tilted at a prescribed angle with respect to said second transmission axis, and wherein said first state is set as said second mode.

8. The liquid crystal display apparatus according to claim 1, further comprising an auxiliary light source mounted outside said reflective polarizer, and

said liquid crystal layer is driven in said second mode with said auxiliary light source turned off.

9. The liquid crystal display apparatus according to claim 1, further comprising an auxiliary light source mounted outside said reflective polarizer, and

said liquid crystal layer is driven in said second mode with said auxiliary light source turned on.

10. The liquid crystal display apparatus according to claim 9, wherein said bright display state is produced by allowing light emitted from said auxiliary light source and entering said liquid crystal layer through said first transmission axis of said reflective polarizer to pass through said second transmission axis of said polarizer and emerge on a viewer side thereof.

11. The liquid crystal display apparatus according to claim 10, wherein said first transmission axis and said second transmission axis are arranged substantially parallel to each other.

12. The liquid crystal display apparatus according to claim 1, further comprising:

an auxiliary light source mounted outside said reflective polarizer; and

a light absorbing layer, disposed between said reflective polarizer and said auxiliary light source, for absorbing light in a certain spectral region.

13. The liquid crystal display apparatus according to claim 1, further comprising:

an auxiliary light source mounted outside said reflective polarizer; and

a light absorbing layer, disposed between said reflective polarizer and said auxiliary light source, for absorbing a portion of light in a visible region.

14. The liquid crystal display apparatus according to claim 1, further comprising an auxiliary light source mounted outside said reflective polarizer, wherein

said auxiliary light source is provided with a reflective layer for reflecting a portion of light in a visible region.