Display unit and electronic apparatus including a backlight disposed between two display surfaces

• US 7,106,396 B2
• Filed: 10/06/2003
• Issued: 09/12/2006
• 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
• Primary Examiner(s): CHOWDHURY, TARIFUR RASHID
• Application Number:
  US10/678,185
• Publication Number:
  US 20050041179A1
• Time in Patent Office: 1,072 Days
• Field of Search: 349/74, 349/61, 349/62, 349/96, 349/98, 349/113, 349/115
• 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

To provide a display device that can display images on both the front and the rear surfaces and that can display images brightly without increasing the electrical power consumption.

A liquid crystal device 100 includes two liquid crystal cells 10 and 20, a backlight 40, which is interposed between the two liquid crystal cells 10 and 20 and which can emit light to the liquid crystal cells 10 and 20, and two reflective polarizers 31 and 32 interposed between the backlight 40 and each of the liquid crystal cells 10 and 20, 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;

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, 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; and

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.

2. 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.

3. The display unit according to claim 2, 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.

4. 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.

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

6. The display unit according to claim 1, the light guiding plate having a birefringence of about zero.

7. An electronic device, comprising:

the display unit according to claim 1.

8. 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,

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, and

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 polarized light selecting devices being about 45°

.

9. 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;

a first reflective polarizer interposed between the lighting unit and one of the liquid crystal panels;

a second reflective polarizer interposed between the lighting unit and another of the liquid crystal panels;

a first absorptive polarizer interposed between the one of the liquid crystal panels and the first reflective polarizer; and

a second absorptive polarizer interposed between the other of the liquid crystal panels and the second reflective polarizer.

10. The display unit according to claim 9, 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.