Display device

• US 10,650,762 B2
• Filed: 04/03/2019
• Issued: 05/12/2020
• Est. Priority Date: 04/05/2018
• 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: Kitagawa, Makoto, Fujimoto, Hideki, Nishihara, Yusuke
• Primary Examiner(s): Cheng, Joe H
• Application Number:
  US16/373,670
• Publication Number:
  US 20190311688A1
• Time in Patent Office: 405 Days
• CPC Class Codes: G02F 1/13606 having means for reducing parasitic capacitance
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 3/3622 using a passive matrix G09G3/3674 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence

Abstract

During a drive period, luminance momentarily decreases when the value β(A−B) is positive and momentarily increases when the value β(A−B) is negative. When the luminance increases during a pause period in accordance with the balance in time constant between an alignment film and a liquid crystal material that are included in a pixel forming portion, primary and secondary parasitic capacitances are adjusted so as to set the value β(A−B) to be negative.

Claims

1. A liquid crystal display device performing pause drive by alternating between a drive period and a pause period with predetermined frequency, the drive period being a period during which an image is displayed based on externally inputted image data, the pause period being a period during which the image is displayed based on the image data written during the drive period, the device comprising:

a display portion including a plurality of pixel forming portions;

a drive portion configured to drive the pixel forming portions; and

a display control portion configured to control the drive portion based on the externally inputted image data, wherein,

the pixel forming portion includes a liquid crystal material and alignment films between which the liquid crystal material is situated, the alignment films controlling orientation of liquid crystal molecules in the liquid crystal material, and

the display control portion cancels out a luminance change in the image displayed by the pixel forming portions during the pause period, by changing luminance of the image during the drive period.

2. The display device according to claim 1, wherein the luminance change in the image during the pause period is determined by a magnitude relationship between the liquid crystal material and the alignment film in terms of time constant.

3. The display device according to claim 2, wherein,

the luminance change during the drive period is determined by value β

(A−

B), as represented by the following equation (A);

β

(A−

B)={C_sd(A)−

C_sd(B)}/C_pi 

 

(A)

where C_pi denotes a liquid crystal capacitance formed by a pixel electrode and a common electrode, C_sd(A) denotes a primary parasitic capacitance formed by a data signal line for a pixel and a drain electrode of the pixel, and C_sd(B) denotes a secondary parasitic capacitance formed by the drain electrode and another data signal line for an adjacent pixel, and

the luminance during the drive period momentarily decreases when the value β

(A−

B) is positive and momentarily increases when the value β

(A−

B) is negative.

4. The display device according to claim 3, wherein, when the alignment film has a lower time constant than the liquid crystal material, the luminance during the pause period increases.

5. The display device according to claim 4, wherein, when the luminance during the pause period increases, the primary parasitic capacitance C_sd(A) is rendered higher than the secondary parasitic capacitance C_sd(B) in order to set the value β

(A−

B) to be positive.

6. The display device according to claim 4, wherein,

a luminance change rate during the drive period is represented by multiplying the value β

(A−

B) by a negative constant, and

the constant varies from one structure to another of the pixel forming portion.

7. The display device according to claim 4, wherein a sum of the luminance change rate during the drive period and a luminance change rate during the pause period falls within a range satisfying the following relation (B):

−

1.8%≤

Δ

L_drive≤

Δ

L_pause+1.8% 

 

(B),

where Δ

L_drive denotes the luminance change rate during the drive period, and Δ

L_pause denotes the luminance change rate during the pause period.

8. The display device according to claim 7, wherein flicker value is minimized when the value β

(A−

B) is represented by the following equation (C);

β

(A−

B)=−

Δ

L_pause/k 

 

(C).

9. The display device according to claim 3, wherein, when the alignment film has a higher time constant than the liquid crystal material, the luminance during the pause period decreases.

10. The display device according to claim 9, wherein, when the luminance during the pause period decreases, the primary parasitic capacitance C_sd(A) is rendered lower than the secondary parasitic capacitance C_sd(B) in order to set the value β

(A−

B) to be negative.