Light source, display device, portable terminal device, and ray direction switching element

• US 7,728,925 B2
• Filed: 01/15/2009
• Issued: 06/01/2010
• Est. Priority Date: 05/24/2004
• Status: Active Grant

• Current Assignee: NLT Technologies, Ltd.
• Original Assignee: NEC Corporation
• Inventors: Okumura, Fujio, Sumiyoshi, Ken, Uehara, Shinichi, Suzuki, Teruaki
• Primary Examiner(s): QI, ZHI QIANG
• Application Number:
  US12/320,052
• Publication Number:
  US 20090135336A1
• Time in Patent Office: 502 Days
• Field of Search: 349/66, 349/61, 349/62
• US Class Current: 349/66
• 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 light source comprising:

a backlight;

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 switches the light made incident from the ray direction regulating element so as to transmit source light and the light so as to be scattered,

wherein in the transparent and scattering switching element, a polymer/liquid crystal composite layer, which included liquid crystal molecules and polymer, is sandwiched between a pair of flat electrodes,

wherein the polymer/liquid crystal composite layer includes a high density portion where a density of the liquid crystal molecules is high and a low density portion where a density of the liquid crystal molecules is low, and

wherein the high density portion and the low density portion are formed alternately in a direction perpendicular to the light regulating direction.

2. The light source of claim 1, wherein the density of the liquid crystal molecules in the high density portion is greater than the density of the liquid crystal molecules in the low density portion.

3. The light source of claim 1, wherein the polymer/liquid crystal composite layer comprises a modulated polymer/liquid crystal composite layer in which a distribution of the liquid crystal molecules is cyclically uneven.

4. The light source of claim 3, wherein the modulated polymer/liquid crystal composite layer scatters incident light intensely in the direction in which the high density and low density portions are repeated cyclically.

5. A light source comprising:

a backlight;

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 switches the light made incident from the ray direction regulating element so as to transmit source light and the light so as to be scattered,

wherein in the transparent and scattering switching element, a polymer/liquid crystal composite layer, which included liquid crystal molecules and polymer, is sandwiched between a pair of flat electrodes, and

wherein the polymer/liquid crystal composite layer is in a state in which the polymer/liquid crystal composite layer transmits incident light when a voltage is not applied between the flat electrodes and in a state in which the polymer/liquid crystal composite layer scatters incident light when a voltage is applied between the flat electrodes.

6. The light source according to claim 5, wherein an orientation state of the liquid crystal molecules at the time when a voltage is applied thereto is held after the application of the voltage is stopped.

7. A light source comprising:

a backlight;

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 switches the light made incident from the ray direction regulating element so as to transmit source light and the light so as to be scattered,

wherein in the transparent and scattering switching element, a polymer/liquid crystal composite layer, which included liquid crystal molecules and polymer, is sandwiched between a pair of flat electrodes, and

wherein the polymer/liquid crystal composite layer is in a state in which the polymer/liquid crystal composite layer transmits incident light when a voltage is applied between the flat electrodes and in a state in which the polymer/liquid crystal composite layer scatters incident light when a voltage is not applied between the flat electrodes.

8. The light source according to claim 7, wherein an orientation state of the liquid crystal molecules at the time when a voltage is applied thereto is held after the application of the voltage is stopped.

9. The light source of claim 7, wherein the backlight comprises a two-dimensional directivity.

10. The light source of claim 7, wherein the voltage applied between the flat electrodes comprises a slight voltage.

11. The light source of claim 10, wherein the slight voltage is less than a voltage for bringing the transparent and scattering switching element into a transparent state.

12. The light source of claim 10, wherein if the slight voltage is applied at the time of scattering of the transparent and scattering switching element, a scattering property of the transparent and scattering switching element is slightly decreased.

13. 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 switches the light made incident from the ray direction regulating element so as to transmit the light and the light so as to be scattered; and

a liquid crystal panel that displays an image with light made incident from the transparent and scattering switching element,

wherein in the transparent and scattering switching element, a polymer/liquid crystal composite layer, which included liquid crystal molecules and polymer, is sandwiched between a pair of flat electrodes,

wherein the polymer/liquid crystal composite layer has a high density portion where a density of the liquid crystal molecules is high and a low density portion where a density of the liquid crystal molecules is low, and

wherein the high density portion and the low density portion are formed alternately in a direction perpendicular to the light regulating direction.

14. 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 switches the light made incident from the ray direction regulating element so as to transmit the light and the light so as to be scattered; and

a liquid crystal panel that displays an image with light made incident from the transparent and scattering switching element,

wherein in the transparent and scattering switching element, a polymer/liquid crystal composite layer, which included liquid crystal molecules and polymer, is sandwiched between a pair of flat electrodes, and

wherein the polymer/liquid crystal composite layer is in a state in which the polymer/liquid crystal composite layer transmits incident light when a voltage is not applied between the flat electrodes and in a state in which the polymer/liquid crystal composite layer scatters incident light when a voltage is applied between the flat electrodes.

15. The display device according to claim 14, wherein an orientation state of the liquid crystal molecules at a time when a voltage is applied thereto is held after application of the voltage is stopped.