BACKLIGHT UNIT AND IMAGE DISPLAY DEVICE

• US 20170365225A1
• Filed: 09/05/2017
• Published: 12/21/2017
• Est. Priority Date: 03/06/2015
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: YONEYAMA, Hiroyuki
• Granted Patent: US 10,443,817 B2
• Time in Patent Office: Days
• CPC Class Codes: F21V 9/30 Elements containing photoluminescent material distinct from or spaced from the light source shades F21V1/17; globes, bowls or cover glasses F21V3/08, F21V3/12; refractors F21V5/10; reflectors F21V7/26, F21V7/30; elements with provision for controlling the spectral properties or intensity F21V9/40
• CPC Class Codes: G02F 1/133601 for spatial active dimming
• CPC Class Codes: G02F 1/133603 with LEDs
• CPC Class Codes: G02F 1/133605 including specially adapted reflectors
• CPC Class Codes: G02F 1/133606 including a specially adapted diffusing, scattering or light controlling members
• CPC Class Codes: G02F 1/133607 the light controlling member including light directing or refracting elements, e.g. prisms or lenses
• CPC Class Codes: G02F 1/133611 including means for improving the brightness uniformity
• CPC Class Codes: G02F 1/133614 using photoluminescence, e.g. phosphors illuminated by UV or blue light
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0238 Improving the black level
• CPC Class Codes: G09G 2320/0242 Compensation of deficiencies in the appearance of colours
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0686 with two or more screen areas displaying information with different brightness or colours
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources

Abstract

The backlight unit includes a light source unit, and a wavelength conversion member disposed on an optical path of light emitted from the light source unit. The light source unit includes a light source allocated to each of the areas, a control of the backlight brightness for each area is performed by controlling a light emission intensity of each light source allocated to each area independently of a light emission intensity of a light source allocated to a different area, and a light source allocated to at least one area includes a light source group including two or more kinds of light sources having different light emission maximum wavelengths, and a light emission intensity of at least one kind of light source included in the light source group is capable of being controlled independently of a light emission intensity of a different light source included in the light source group.

Claims

1. A backlight unit capable of controlling a backlight brightness for each of areas, comprising:

a light source unit; and

a wavelength conversion member that is disposed on an optical path of light emitted from the light source unit,

wherein the wavelength conversion member includes a wavelength conversion layer including at least a fluorescent body that is excited by excitation light and emits green light and a fluorescent body that is excited by excitation light and emits red light,

wherein the light source unit includes a light source allocated to each of the areas,

wherein a control of the backlight brightness for each area is performed by controlling a light emission intensity of each light source allocated to each area independently of a light emission intensity of a light source allocated to a different area, and

wherein a light source allocated to at least one area includes a light source group including two or more kinds of light sources having different light emission maximum wavelengths, and a light emission intensity of at least one kind of light source included in the light source group is capable of being controlled independently of a light emission intensity of a different light source included in the light source group.

2. The backlight unit according to claim 1,

wherein each light source allocated to each area includes a light source group including two or more kinds of light sources having different light emission maximum wavelengths, and a light emission intensity of at least one kind of light source included in the light source group is capable of being controlled independently of a light emission intensity of a different light source included in the light source group.

3. The backlight unit according to claim 1,

wherein the light emission maximum wavelengths of the light sources included in the light source group are in a range from a blue light wavelength band to an ultraviolet light wavelength band.

4. The backlight unit according to claim 2,

wherein the light emission maximum wavelengths of the light sources included in the light source group are in a range from a blue light wavelength band to an ultraviolet light wavelength band.

5. The backlight unit according to claim 1,

wherein the light source is a light emitting diode, and the wavelength conversion member is a sheet shaped member.

6. The backlight unit according to claim 2,

wherein the light source is a light emitting diode, and the wavelength conversion member is a sheet shaped member.

7. The backlight unit according to claim 3,

wherein the light source is a light emitting diode, and the wavelength conversion member is a sheet shaped member.

8. The backlight unit according to claim 4,

wherein the light source is a light emitting diode, and the wavelength conversion member is a sheet shaped member.

9. The backlight unit according to claim 1, further comprising:

at least one member having a reflective characteristic on at least one of an emission side of the wavelength conversion member or a light source unit side thereof.

10. The backlight unit according to claim 9,

wherein the member having the reflective characteristic includes at least one sheet shaped member.

11. An image display device comprising:

the backlight unit according to claim 1;

an image display unit; and

a local dimming control unit.

12. The image display device according to claim 11,

wherein the local dimming control unit creates light source light emission intensity information for each area of the backlight unit on the basis of display brightness information for each area of an image to be displayed on a display surface of the image display unit, and determines a light emission intensity of each light source included in a light source group including two or more kinds of light sources having different light emission maximum wavelengths on the basis of the created light source light emission intensity information, or on the basis of corrected light source light emission intensity information obtained by performing a correction process based on the influence of leaked light that is generated from a light source allocated to a different area of the backlight unit with respect to the created light source light emission intensity information, and

wherein each light source included in the light source group emits light having the determined light emission intensity.

13. The image display device according to claim 12,

wherein the correction process based on the influence of the leaked light that is generated from the light source allocated to the different area of the backlight unit includes, as the influence of the leaked light becomes larger, among two or more kinds of light sources included in the light source group, a process of increasing an absolute value or a relative value of a light emission intensity of a light source of which a light emission maximum wavelength is positioned on a long wavelength side, a process of decreasing an absolute value or a relative value of a light emission intensity of a light source of which a light emission maximum wavelength is positioned on a short wavelength side, or a process of increasing the absolute value or the relative value of the light emission intensity of the light source of which the light emission maximum wavelength is positioned on the long wavelength side and decreasing the absolute value or the relative value of the light emission intensity of the light source of which the light emission maximum wavelength is positioned on the short wavelength side.

14. The image display device according to claim 12,

wherein the image display unit includes a pair of electrodes and a liquid crystal cell disposed between the electrodes,

wherein the local dimming control unit creates liquid crystal control information for each area of the liquid crystal cell on the basis of the display brightness information for each area of the image to be displayed on the display surface of the image display unit, and determines a voltage application condition for each area of the liquid crystal cell on the basis of the created liquid crystal control information or on the basis of corrected liquid crystal control information obtained by performing a correction process based on the corrected light source light emission intensity information with respect to the created liquid crystal control information, and

wherein the pair of electrodes applies a voltage to the liquid crystal cell under the determined voltage application condition.

15. The image display device according to claim 12,

wherein the correction process based on the influence of the leaked light that is generated from the light source allocated to the different area of the backlight unit includes a process of setting a light emission intensity of at least one of a light source allocated to a portion that is greatly affected by leaked light or a light source allocated to a different portion in the same area to be different from a value determined by the light source light emission intensity information.