Planar light source, display device, portable terminal device, and ray direction switching element

• US 20080137000A1
• Filed: 10/31/2007
• Published: 06/12/2008
• Est. Priority Date: 05/24/2004
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd. (Tianma Microelectronics Company Limited)
• Original Assignee: NEC Corporation
• Inventors: Okumura, Fujio, Sumiyoshi, Ken, Uehara, Shinichi, Suzuki, Teruaki
• Granted Patent: US 7,499,123 B2
• Time in Patent Office: Days
• US Class Current: 349/62
• CPC Class Codes: G02F 1/1323 Arrangements for providing a switchable viewing angle
• CPC Class Codes: G02F 1/133524 Light-guides, e.g. fibre-optic bundles, louvered or jalousie light-guides
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/13476 in which at least one liquid crystal cell or layer assumes a scattering state

Abstract

A planar light source includes a large variable width of an irradiation angle of illumination light, a display device having a large variable width of an angle of field that uses the planar light source, a portable terminal device that uses the display device, and a ray direction switching element that is incorporated in the planar light source. A beam direction regulating element (a louver), which controls a direction of light, and a transparent and scattering switching element, which can switch the transparent state and the scattering state according to ON and OFF of an applied voltage, are provided between a backlight and a liquid crystal panel, whereby it is possible to increase a variable width of an irradiation angle of light in the planar light source and increase a variable width of an angle of field of the liquid crystal display device that uses the planar light source.

Claims

1. A planar light source comprising:

a backlight that emits light in a planar shape;

a ray direction regulating element that regulates a direction of light made incident from the backlight and emits the light and in which a transparent area for transmitting light and an absorption area for absorbing light are formed alternately in a direction perpendicular to a light regulating direction thereof; and

a transparent and scattering switching element that is capable of switching a state in which light made incident from the ray direction regulating element is transmitted and a state in which the light is scattered,

wherein, in the ray direction regulating element, the transparent area is provided in the absorption area in a matrix shape when the ray direction regulating element is viewed from the light regulating direction.

2. The planar light source according to claim 1, wherein an amount of light of the backlight and the transparent and scattering states of the transparent and scattering switching element can be set independently.

7. The display device that has the planar light source according to claim 1.

11. A portable terminal device that has the planar light source according to claim 1.

12. The portable terminal device according to claim 11, wherein the portable terminal device is a cellular phone, a personal digital assistant, a game machine, a digital camera, or a digital video camera.

13. The portable terminal device according to claim 11, further comprising adjusting means that can change an amount of the backlight and the transparent and scattering states of the transparent and scattering switching element independently from each other.

14. The portable terminal device according to claim 13, further comprising:

electric power accumulating means;

residual amount detecting means for electric power accumulated in the electric power accumulating means; and

control means that automatically changes an amount of light of the backlight and the transparent and scattering states of the transparent and scattering switching element on the basis of detected residual amount information.

3. A display device comprising:

a backlight that emits light in a planar shape;

a ray direction regulating element that regulates a direction of light made incident from the backlight and emits the light and in which a transparent area for transmitting light and an absorption area for absorbing light are formed alternately in a direction perpendicular to a light regulating direction thereof;

a transparent and scattering switching element that is capable of switching a state in which light made incident from the ray direction regulating element is transmitted and a state in which the light is scattered; and

a liquid crystal panel that displays an image with light made incident from the transparent and scattering switching element, wherein, in the ray direction regulating element, the transparent area is provided in the absorption area in a matrix shape when the ray direction regulating element is viewed from the light regulating direction.

4. The display device according to claim 3, wherein, when the transparent and scattering switching element is in the scattering state, the display device adjusts brightness of an image displayed on the display panel by setting an amount of light of the backlight larger than that in the case in which the transparent and scattering switching element is in the transparent state.

5. The display device according to claim 4, wherein the backlight is a white light source.

6. The display device according to claim 4, wherein

the backlight includes a red light source, a green light source, and a blue light source and

the red light source, the green light source, and the blue light source are adjusted independently from each other.

8. The display device according to claim 3, wherein

flat electrodes of the transparent and scattering switching element are formed in a line shape or a block shape and perform switching of transparent and scattering of the transparent and scattering switching element partially on the basis of image information displayed on the display panel.

9. The display device according to claim 5, wherein the white light source includes a blue LED and a yellow phosphor to adjust an amount of light with pulse modulation.

10. The display device according to claim 3, wherein the display panel is a liquid crystal panel and

the liquid crystal display panel is a panel of a lateral electric field mode, a multi-domain vertical orientation mode, or a film compensation TN mode.

15. A light regulator for a planar light source having a backlight that emits light in a planar shape, said regulator comprising:

a ray direction regulating element that regulates a direction of light made incident from the backlight and emits the light and in which a transparent area for transmitting light and an absorption area for absorbing light are formed alternately in a direction perpendicular to a light regulating direction thereof; and

a transparent and scattering switching element that is switchable between a state in which light which is transmitted by the ray direction regulating element and made incident on said switching element is transmitted and a state in which the light is scattered,

wherein, in the ray direction regulating element, the transparent area is provided in the absorption area in a matrix shape when the ray direction regulating element is viewed from the light regulating direction.

16. The light regulator of claim 15, wherein an amount of light emitted by the backlight and an amount of light transmitted by the light regulator are independently settable.

17. The light regulator of claim 16, further comprising:

a substrate, said ray direction regulating element being formed on said substrate and said transparent and scattering switching element being formed on said ray direction regulating element.