Display device

• US 10,497,322 B2
• Filed: 12/19/2017
• Issued: 12/03/2019
• Est. Priority Date: 01/23/2017
• Status: Active Grant

• Current Assignee: Japan Display Incorporated
• Original Assignee: Japan Display Incorporated
• Inventors: Kato, Hirofumi
• Primary Examiner(s): Pham, Viet D
• Application Number:
  US15/847,114
• Publication Number:
  US 20180211611A1
• Time in Patent Office: 714 Days
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/13347 working in reverse mode, i.e. clear in the off-state and scattering in the on-state
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence
• CPC Class Codes: G02F 1/133622 Colour sequential illumination
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 1/137 characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
• CPC Class Codes: G02F 2201/121 common or background
• CPC Class Codes: G02F 2201/123 pixel
• CPC Class Codes: G09G 2300/0478 related to liquid crystal pixels
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/062 Adjustment of illumination source parameters
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0666 for control of colour parameters, e.g. colour temperature
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 : using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3655 : Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors

Abstract

In an embodiment, a display device comprises a display panel, a light source and a controller. The display panel including pixels, a common electrode, pixel electrodes and a liquid crystal layer containing a polymer dispersed liquid crystal. The light source emits light to the display panel. The liquid crystal layer scatters light when scattering voltage is applied between the common electrode and the pixel electrodes, and transmits light when transparent voltage is applied between the common electrode and the pixel electrodes. The controller applies the transparent voltage in a first period, and applies voltage in accordance with image data in a second period.

Claims

1. A display device comprising:

a display panel including a plurality of pixels, a common electrode, a plurality of pixel electrodes provided for the pixels, respectively, and a liquid crystal layer containing a polymer dispersed liquid crystal, wherein the display panel has a first edge and a second edge that is opposite the first edge;

a light source which emits light to the display panel from the first edge into the liquid crystal layer towards the second edge; and

a controller which controls voltage between the common electrode and the pixel electrodes, wherein

the liquid crystal layer scatters light from the light source when a scattering voltage is applied between the common electrode and the pixel electrodes, and transmits light from the light source from the first edge across the liquid crystal layer to the second edge when a transparent voltage less than the scattering voltage is applied between the common electrode and the pixel electrodes such that the common electrode and the pixel electrode are at a substantially same potential with the transparent voltage applied, and

the controller applies the transparent voltage between the common electrode and the pixel electrodes in a first period, and applies the scattering voltage between the common electrode and the pixel electrodes in accordance with image data in a second period.

2. The display device of claim 1, wherein

the controller turns off the light source in the first period and lights up the light source in the second period.

3. The display device of claim 1, wherein

a frame period in which an image is displayed in accordance with image data includes at least one first period.

4. The display device of claim 3, wherein

the light source includes a first light-emitting element which emits light in a first color, and a second light-emitting element which emits light in a second color,

the image data includes first sub-frame data indicating an image in the first color, and second sub-frame data indicating an image in the second color,

the second period includes a first sub-frame period and a second sub-frame period, and

the controller

in the first sub-frame period, lights up the first light-emitting element, and applies voltage between the common electrode and the pixel electrodes in accordance with the first sub-frame data, and

in the second sub-frame period, lights up the second light-emitting element, and applies voltage between the common electrode and the pixel electrodes in accordance with the second sub-frame data.

5. The display device of claim 4, wherein

in the frame period, the first sub-frame period and the second sub-frame period follow the first period.

6. The display device of claim 4, wherein

in the frame period, the first period is provided between the first sub-frame period and the second sub-frame period.

7. The display device of claim 3, wherein

the first period is less than or equal to half the frame period.

8. The display device of claim 1, wherein

the controller is capable of applying a positive voltage higher than a reference voltage and a negative voltage lower than the reference voltage to the common electrode and the pixel electrodes, and

a voltage of each of the pixel electrodes in the second period has a polarity different from a polarity of a voltage of the common electrode, or is the reference voltage.

9. The display device of claim 8, wherein

the voltage of each of the pixel electrodes in the first period has a same polarity as the voltage of the common electrode.

10. The display device of claim 8, wherein

both the voltage of the common electrode and the voltage of each of the pixel electrodes in the first period are the reference voltage.

11. The display device of claim 8, wherein

the display panel includes a plurality of switching elements provided in the pixels, respectively, a plurality of scanning lines which scan the switching elements, and a plurality of signal lines which intersect the scanning lines and are connected to the pixel electrodes via the switching elements, and

the controller supplies a scanning signal to the scanning lines in series in the second period, and inverts the polarity of the voltage of the common electrode and a polarity of voltage applied to the signal lines every time a scanning signal is supplied to at least one of the scanning lines.

12. The display device of claim 1, wherein

luminance of light scattered by the liquid crystal layer to which the transparent voltage is applied is less than 10% of luminance of light scattered by the liquid crystal layer to which an upper limit of the scattering voltage is applied.

13. The display device of claim 1, wherein

the first period is shorter than the second period.

14. The display device of claim 1, wherein

the light source faces an end portion of the display panel, and

in the first period, a background of the display panel is viewable.

15. The display device of claim 1, wherein

the transparent voltage is substantially 0 V.