Display unit and electronic apparatus

• US 20050041179A1
• Filed: 10/06/2003
• Published: 02/24/2005
• Est. Priority Date: 10/24/2002
• Status: Active Grant

• Current Assignee: BOE Technology Group Co., Ltd.
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Suzuki, Nobutaka
• Granted Patent: US 7,106,396 B2
• Time in Patent Office: Days
• US Class Current: 349/74
• CPC Class Codes: G02F 1/133342 for double-sided displays
• CPC Class Codes: G02F 1/133536 Reflective polarizers G02F1/13362 takes precedence
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/13362 providing polarized light, e.g. by converting a polarisation component into another one

Abstract

The invention provides a display unit that displays images on both the front and the rear surfaces and that displays images brightly without increasing the electrical power consumption. A liquid crystal display unit includes two liquid crystal cells, a backlight, which is interposed between the two liquid crystal cells and which emits light to the liquid crystal cells, and two reflective polarizers interposed between the backlight and each of the liquid crystal cells, respectively.

Claims

1. A display unit, comprising:

two transmissive polarization axis rotating devices to vary the polarization axis of transmitted light;

an illumination device disposed between the two transmissive polarization axis rotating devices to emit light to the two transmissive polarization axis rotating devices; and

two reflective polarized light selecting devices, each disposed between the illumination device and each of the two transmissive polarization axis rotating devices, the illumination device transmitting the reflected light from the two reflective polarized light selecting devices.

2. The display unit according to claim 1, the two reflective polarized light selecting devices reflecting light linearly polarized in a predetermined direction while transmitting light linearly polarized in a direction intersecting the reflected polarized light, and the reflective polarization axes of the two reflective polarized light selecting devices intersecting each other.

3. The display unit according to claim 2, further including two absorptive polarized light selecting devices, to absorb light linearly polarized in a predetermined direction while transmitting light linearly polarized in a direction intersecting the absorbed polarized light, interposed between the respective reflective polarized light selecting devices and the respective transmissive polarization axis rotating devices, and each of the reflective polarization axis of the reflective polarized light selecting devices and each of the transmissive polarization axes of the absorptive polarized light selecting devices intersecting each other.

4. The display unit according to claim 1, each of the reflective polarized light selecting devices including a cholesteric liquid crystal and reflecting circularly polarized light with a predetermined rotative direction while transmitting circularly polarized light with the opposite rotative direction, and each of the two reflective polarized light selecting devices reflecting circularly polarized light with the same rotative direction.

5. The display unit according to claim 4, further including a λ

/4 retardation film interposed between each of the two reflective polarized light selecting devices and each of the two transmissive polarization axis rotating devices to vary the polarization axis of the transmitted light.

6. The display unit according to claim 1, further including scatterers disposed between each of the two reflective polarized light selecting devices and each of the two absorptive polarized light selecting devices.

7. The display unit according to claim 1, the illumination device having a light source and a light guiding plate to guide light from the light source and emitting the light from both sides of the light guiding plate to the transmissive polarization axis rotating devices.

8. The display unit according to claim 1, the illumination device including a transparent planar light source.

9. The display unit according to claim 7, the light guiding plate having a birefringence of about zero.

10. The display unit according to claim 7, the birefringence of the light guiding plate being λ

/2, and the angle formed by the slow axis of the light guiding plate and the reflective polarization axis of each reflective polarized light selecting devices being about 45°

.

13. An electronic device, comprising:

the display unit according to claim 1.

11. A display unit, comprising:

two liquid crystal panels;

a lighting unit interposed between the liquid crystal panels to emit light to each liquid crystal panel; and

two reflective polarizers interposed between the lighting unit and each of the liquid crystal panels.

12. The display unit according to claim 11, each of the two reflective polarizers reflecting light linearly polarized in a predetermined direction while transmitting light linearly polarized in the direction intersecting the reflected polarized light, and the polarization axes of the two reflective polarizers intersecting each other.