Liquid crystal display

• US 20060290847A1
• Filed: 06/26/2006
• Published: 12/28/2006
• Est. Priority Date: 06/24/2005
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Kim, Jae-Hyun
• Application Number:
  US11/474,785
• Publication Number:
  US 20060290847A1
• Time in Patent Office: Days
• US Class Current: 349/113
• CPC Class Codes: G02F 1/133541 Circular polarisers
• CPC Class Codes: G02F 1/133545 Dielectric stack polarisers
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one
• CPC Class Codes: G02F 2203/01 transmissive
• CPC Class Codes: G02F 2203/09 transflective

Abstract

A liquid crystal display is provided with a reflective polarizer and an optical retarder between an absorbing polarizer and a backlight unit. This structure recycles light that would ordinarily be removed by absorption in conventional LCDs to be used for the display, so that light efficiency and display luminance of the LCD are improved.

Claims

1. A liquid crystal display comprising:

a display panel;

a reflective polarizer that is provided under the display panel to transmit light linearly polarized in a first direction and to reflect light linearly polarized in a second direction perpendicular to the first direction;

an optical retarder that is provided under the reflective polarizer; and

a backlight unit that is provided under the optical retarder and includes a light source for supplying light to the display panel,

wherein the reflective polarizer is made of alternating layers of two media have same index of refraction in the first direction and the different indices of refraction in the second direction.

2. The liquid crystal display of claim 1, further comprising a first absorbing polarizer that is provided between the display panel and the reflective polarizer.

3. The liquid crystal display of claim 2, wherein a transmission axis of the first absorbing polarizer is in the first direction.

4. The liquid crystal display of claim 3, further comprising a second absorbing polarizer that is attached to an upper surface of the display panel.

5. The liquid crystal display of claim 4, wherein a transmission axis of the second absorbing polarizer is in the second direction.

6. The liquid crystal display of claim 1, wherein the optical retarder has a slow axis and a fast axis, and a phase difference between the two axes is a quarter-wave to convert circularly polarized light into linearly polarized light or linearly polarized light into circularly polarized light.

7. The liquid crystal display of claim 6, wherein the fast axis or the slow axis of the optical retarder is formed at ±

45°

to the first direction or the second direction.

8. The liquid crystal display of claim 1, wherein the backlight unit includes a reflective plate for reflecting light toward the display panel that is provided above the backlight unit.

9. A liquid crystal display comprising:

a display panel;

a reflective polarizer that is provided under the display panel and includes a selective reflection film that transmits light linearly polarized in a first direction and reflects light linearly polarized in a second direction perpendicular to the first direction and an optical retardation film that is coated on a lower surface of the selective reflection film; and

a backlight unit that is provided under the reflective polarizer and includes a light source for supplying light to the display panel,

wherein the reflective polarizer is made of alternating layers of two media have same index of refraction in the first direction and the different indices of refraction in the second direction.

10. The liquid crystal display of claim 9, further comprising a first absorbing polarizer that is provided between the display panel and the reflective polarizer.

11. The liquid crystal display of claim 10, wherein a transmission axis of the first absorbing polarizer is in the first direction.

12. The liquid crystal display of claim 11, further comprising a second absorbing polarizer that is attached to an upper surface of the display panel.

13. The liquid crystal display of claim 12, wherein a transmission axis of the second absorbing polarizer is in the second direction.

14. The liquid crystal display of claim 9, wherein the optical retardation film has a slow axis and a fast axis, and a phase difference between the two axes is a quarter-wave to convert circularly polarized light into linearly polarized light or linearly polarized light into circularly polarized light.

15. The liquid crystal display of claim 16, wherein either of the fast axis or the slow axis of the optical retardation film is formed at ±

45°

to the first direction or the second direction.

16. The liquid crystal display of claim 9, wherein the optical retardation film is obtained by curing liquid crystal.

17. The liquid crystal display of claim 9, wherein the backlight unit further includes a reflective plate for reflecting light toward the display panel that is provided above the backlight unit.

18. A liquid crystal display comprising:

a display panel;

a reflective polarizer that is provided under the display panel to transmit light linearly polarized in a first direction and to reflect light linearly polarized in a second direction perpendicular to the first direction;

a first absorbing polarizer having a transmission axis in the first direction that is provided between the display panel and the reflective polarizer;

a second absorbing polarizer having a transmission axis in the second direction that is attached to an upper surface of the display panel; and

a backlight unit that is provided under the optical retarder and includes a light source for supplying light to the display panel,

wherein the reflective polarizer is made of alternating layers of two media have same index of refraction in the first direction and the different indices of refraction in the second direction.

19. The liquid crystal display of claim 18, further comprising an optical retarder that is provided under the reflective polarizer.

20. The liquid crystal display of claim 18, wherein said reflective polarizer comprises a selective reflection film that transmits light linearly polarized in a first direction and reflects light linearly polarized in a second direction perpendicular to the first direction and an optical retardation film that is coated on a lower surface of the selective reflection film.