Liquid crystal display device

• US 8,102,359 B2
• Filed: 11/20/2006
• Issued: 01/24/2012
• Est. Priority Date: 03/07/2006
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Shiomi, Makoto
• Primary Examiner(s): DINH, DUC Q
• Application Number:
  US12/087,382
• Publication Number:
  US 20090135126A1
• Time in Patent Office: 1,891 Days
• Field of Search: 345/204, 345/690, 345/98, 345/99, 345/100, 345/102
• US Class Current: 345/102
• CPC Class Codes: G02F 1/133604 with lamps
• CPC Class Codes: G02F 1/133613 characterized by the sequence of light sources
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• 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 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

Provided are data lines, scanning lines crossing the data lines, and a switching element in vicinity of each intersection of the data lines and the scanning lines, the data lines being connected via the switching elements with pixel electrodes arranged in matrix. Direct-type backlights arranged in parallel with the scanning lines are provided, and a backlight turning-ON drive circuit for turning the direct-type backlights in order at a predetermined frequency in sync with a scanning signal is provided. In at least one embodiment, the backlight turning-ON drive circuit includes a controller for controlling the direct-type backlights to turn ON in order in sync with the scanning signal in such a manner that the direct-type backlights are turned ON discretely over frames being continuous based on a vertical sync signal. In at least one embodiment, this provides a liquid crystal display device, which adopts scanning-type backlights and in which the pseudo contour and the flickering can be prevented with a driving clock of 60 Hz, which is generally adopted in liquid crystal display devices.

Claims

1. A liquid crystal display device including data lines, scanning lines crossing the data lines, and a switching element in vicinity of each intersection of the data lines and the scanning lines, the data lines being connected via the switching elements with pixel electrodes arranged in matrix, the liquid crystal display device comprising:

direct-type backlights arranged in parallel with the scanning lines; and

a backlight turning-ON drive circuit configured to turn ON the direct-type backlights in order at a predetermined frequency in sync with a scanning signal,

the backlight turning-ON drive circuit including a controller configured to control the direct-type backlights to turn ON in order in sync with the scanning signal in such a manner that the direct-type backlights are turned ON discretely over frames being continuous based on a vertical sync signal, and

the backlight turning-ON drive being configured to provide different turn ON timings for the direct-type backlights for different frames, regardless of whether displayed images are changed or not.

2. The liquid crystal display device as set forth in claim 1, wherein

the controller included in the backlight turning-ON drive circuit is configured to control the direct-type backlights to turn ON in such a manner that, among frames being continuous based on the vertical sync signal, the direct-type backlights turn ON in order at a first timing in some frames, while the direct-type backlights turn ON in order at a second timing in other frames.

3. The liquid crystal display device as set forth in claim 1, wherein the controller is configured such that in every other frame among the frames being continuous based on the vertical sync signal, the controller turns ON the direct-type backlights in order in sync with the scanning signal.

4. A liquid crystal display device as set forth in claim 3, wherein the predetermined frequency for turning ON the direct-type backlights is 2/(2n+1) of a refresh period of the scanning lines (where n is an integer greater than or equal to 1), and scanning is repeated in two frame periods that are designated as frames in which the synchronization is carried out.

5. The liquid crystal display device as set forth in claim 1, wherein the backlight turning-ON drive circuit is configured to drives the direct-type backlights in such a manner that the direct-type backlights repeat a turning-ON period and a turning-OFF period, which periods are identical in length.

6. The liquid crystal display device as set forth in claim 1, wherein:

the liquid crystal display device is configured such that scanning lines are scanned at 60 Hz, and

the backlight turning-ON drive circuit is configured to drives the direct-type backlights at 90 Hz.

7. The liquid crystal display device as set forth in claim 1, wherein the direct-type backlights are cold cathode fluorescent tubes.

8. The liquid crystal display device as set forth in claim 2, wherein the controller is configured such that in every other frame among the frames being continuous based on the vertical sync signal, the controller turns ON the direct-type backlights in order in sync with the scanning signal.

9. A liquid crystal display device as set forth in claim 8, wherein the predetermined frequency for turning ON the direct-type backlights is 2/(2n+1) of a refresh period of the scanning lines (where n is an integer greater than or equal to 1), and scanning is repeated in two frame periods that are designated as frames in which the synchronization is carried out.

10. The liquid crystal display device as set forth in claim 2, wherein the backlight turning-ON drive circuit is configured to drive the direct-type backlights in such a manner that the direct-type backlights repeat a turning-ON period and a turning-OFF period, which periods are identical in length.

11. The liquid crystal display device as set forth in claim 2, wherein:

the liquid crystal display device is configured such that the scanning lines are scanned at 60 Hz, and

the backlight turning-ON drive circuit is configured to drives the direct-type backlights at 90 Hz.

12. The liquid crystal display device as set forth in claim 2, wherein the direct-type backlights are cold cathode fluorescent tubes.