WO2017036063A1

WO2017036063A1 - Quick response method for multistage gray scale electrophoresis electronic paper

Info

Publication number: WO2017036063A1
Application number: PCT/CN2016/070367
Authority: WO
Inventors: 周国富; 王利; 易子川
Original assignee: 深圳市国华光电科技有限公司; 深圳市国华光电研究院; 华南师范大学
Priority date: 2015-08-31
Filing date: 2016-01-07
Publication date: 2017-03-09
Also published as: CN105070254A

Abstract

A quick response method for multistage gray scale electrophoresis electronic paper, for use in driving multistage gray scale electrophoresis electronic paper. The method comprises the steps of: A, increasing the absolute value of a drive voltage to be greater than 15V; B, applying a voltage waveform that is opposite to the electric property of an original image to erase the original image; C, applying a square wave voltage waveform having a duty cycle of 50% to activate electrophoresis particles; and D, applying a voltage waveform having a proper length to flash a new gray scale. Quick response of multistage gray scale electrophoresis electronic paper is achieved by properly increasing the drive voltage and changing different drive voltage waveform lengths. Specifically, in step D, quick response of four-stage gray scale electrophoresis electronic paper is achieved by applying a positive voltage, and quick response of electrophoresis electronic paper having a gray scale greater than a four stage gray scale is achieved by applying both a positive voltage and a negative voltage.

Description

Fast response method of multi-level gray scale electrophoresis electronic paper

Technical field

The invention relates to the field of electrophoretic display technology, in particular to a rapid response method of multi-level gray scale electrophoresis electronic paper.

Background technique

Electronic paper using electrophoretic display (EPD) technology has become a very important information display carrier, and has been widely used in e-book readers, electronic tags, electronic billboards, and the like. It has good bistable characteristics and consumes almost no power during static display. It is a display technology with energy saving and environmental protection features. However, electrophoretic electronic paper also has a number of disadvantages, such as slow response. These shortcomings have seriously affected the display effect of electrophoretic electronic paper and restricted the scope of application in the market. The gray scale display of the electrophoretic electronic paper is mainly driven by a voltage sequence applied to the pixel electrode, and this voltage sequence is called a driving waveform. The shortcomings exhibited by electrophoretic electronic paper display are caused by poor design of the driving waveform.

In the electrophoretic display, the display of a specific gray scale has no fixed threshold voltage, so it is necessary to drive the pixel display gray scale by using the driving waveform. This grayscale display process is also the process by which the electric field force drives the particle electrophoresis motion. Electrophoretic particles are an important component of electrophoretic displays. During electrophoretic display, charged black and white particles undergo electrophoretic effects when voltage is applied, but this electrophoretic effect is non-linear for the length of applied voltage. Therefore, in order to achieve the correct display of the gray scale, an appropriate drive waveform must be selected to drive the electrophoretic particles. A typical drive waveform consists of three phases: erasing the original image, activating the electrophoretic particle, and flashing the new grayscale. At the end of the second phase, a white gray scale with a relatively stable reflectance value is generated, and is used as a reference gray scale to further drive the particles to form a target gray scale. In any case, this driving process drives the particles to change the direction of electrophoresis in the microcapsules due to the voltage change, and causes the high and low transition of the screen reflectivity. This phenomenon is reflected in the human eye, which is flicker, and the visual comfort. Has had a bad effect.

In the electronic paper microcapsule particle system, since the amount of charge carried by the particles is fixed, when the voltage applied to the pixel is larger, the electric field force of the particle is larger, and the particle electrophoresis speed is faster. However, when the particles are in the process of accelerating electrophoresis, the viscous drag of the charge control agent of the particles is also increased, and the collision resistance generated between the particles is also increasing. When the particle resistance is gradually increased, the consumed electric energy is also increasing. Therefore, finding a suitable driving voltage is very important for the application of electrophoretic electronic paper.

Summary of the invention

The object of the present invention is to overcome the shortcomings of the prior art, and provide a rapid response method for multi-level gray scale electrophoresis electronic paper for driving multi-level gray scale electrophoretic electronic paper, comprising the steps of:

A: increase the absolute value of the driving voltage to greater than 15V;

B: applying a voltage waveform opposite to the original image to erase the original image;

C: applying a square wave voltage waveform with a duty ratio of 50% to activate the electrophoretic particles;

D: Apply a voltage waveform of appropriate length to write a new gray scale.

Preferably, the absolute value of the driving voltage is configured by the following steps:

A1: Obtain a graph of voltage versus reflectivity under a positive or negative voltage driving waveform of different lengths;

A2: Determine the absolute 驱动 of the driving voltage capable of forming a uniform multi-level gray scale display in the range of 20-25V.

Preferably, the drive voltage is set to 21V to form a uniform four-level gray scale display.

Preferably, the driving voltage waveform lengths corresponding to the uniform four-level gray scale display are respectively set to 0 ms, 20 ms, 40 ms, and 100 ms.

Preferably, the length of the voltage waveform applied in the step B is equal to the length of the driving voltage waveform corresponding to the original image to achieve DC balance compensation.

Preferably, the square wave voltage of the step C is set to be turned from a positive voltage to a negative voltage to ensure a white state as a reference gray scale.

Preferably, the step D uses a positive voltage to flash a new gray scale.

Preferably, the D step is combined using positive and negative voltages to form a gray scale display greater than four levels.

The beneficial effects of the invention are:

At present, the mainstream driving voltage is plus or minus 15V. In this case, the charged particles move at a slower speed under the action of the electric field. However, its gray-scale resolution is better, which is convenient for forming multi-level gray scales. In the present invention, focusing on the display of the four-level gray scale image, appropriately increasing the driving voltage is advantageous for improving the response speed of the electrophoretic electronic paper. In addition, it is also possible to form a gray scale display larger than four levels by a combination of positive and negative voltages to improve image display quality.

DRAWINGS

The invention will now be further described with reference to the accompanying drawings and examples.

1a-1b are graphs showing the relationship between driving voltage intensity and reflectance at different driving voltages obtained by the multi-step gray scale electrophoretic electronic paper rapid response method of the present invention.

2 is a driving voltage waveform used in the four-step gray scale electrophoresis electronic paper quick response method of the present invention.

3a-3b are driving effect diagrams of the four-step gray-scale electrophoresis electronic paper rapid response method of the present invention, and reflectance diagrams corresponding to gray levels of each level.

detailed description

According to the first embodiment of the present invention, first, A: the absolute value of the driving voltage is raised to be greater than 15V, and the absolute value of the driving voltage is specifically configured by the following steps: 1. Acquiring the voltage under the driving waveform of the positive or negative voltage of different lengths Graph of reflectance; 2. Determine the absolute 驱动 of the driving voltage capable of forming a uniform multi-level gray scale display in the range of 20-25V. Specifically, a series of driving voltage waveforms of different lengths are first designed, in which only positive voltages or only negative voltages are downloaded, and then these driving voltage waveforms are downloaded into a waveform lookup table and passed through a reflectance measuring device. Make observations. The TFT scanning frequency used in the experiment is 50HZ. Therefore, in the process of designing the driving waveform, the length of time in any stage must be an integral multiple of 20ms. In the present invention, the length of the driving waveform is set to 20ms, 40ms, 60ms. ..., 260ms. The absolute value of the voltage is gradually increased from 10V to 25V, and the same driving waveform is used to drive the electronic paper, and the camera is used to record the change of the reflectance of the electronic paper, and the frame rate of the camera is set to 100 frames/second. The voltage versus reflectance curves are driven by drive waveforms of different lengths as shown in Figure 1. As can be seen from FIG. 1, the electronic paper of the prior art with a positive and negative 15V driving voltage has a slow response speed, and is convenient to form a multi-level gray scale. The present embodiment focuses on the fast response of the four-level gray scale.

From Fig. 1, we can see that when the absolute value of the driving voltage is increased, the low-order gray-scale resolution is lowered. In addition, since the number of black carbon particles having a small particle size is large, in an EPD system, the screen is relatively easy to change from white to black, and when converting from black to white, it takes a long time. For example, when the absolute value of the driving voltage is 20V, the electronic paper display screen must take 160ms to convert from black to white, but it takes only 100ms to switch from the white state to the all black state. Therefore, in the design of the driving waveform, the white state is often used as the reference grayscale to reduce the time required to write the new grayscale, so we use a positive voltage to write a new grayscale. In Fig. 1(b), when the driving voltage is 21V, the electronic paper forms a uniform four-level gray scale, and the corresponding driving waveform lengths are positive voltages of 0ms, 20ms, 40ms and 100ms, respectively, wherein the driving voltage waveform length The voltage and reflectance curves for 20ms, 40ms, and 100ms correspond to curves 1, 2, and 3 in Figure 1(b), respectively. At this time, the driving waveforms of the above four different lengths correspond to the states of white (W), light gray (LG), dark gray (DG), and black (B) of the electronic paper, respectively.

Then, the design of the voltage driving waveform is performed, including the following steps: B: applying a voltage waveform opposite to the original image to erase the original image; C: applying a square wave voltage waveform with a duty ratio of 50% to activate the electrophoretic particle; : Apply a voltage waveform of the appropriate length to write a new grayscale.

2 is a driving voltage waveform used in the fast response method of the fourth-level gray-scale electrophoresis electronic paper according to the embodiment, and the three voltage values of the driving waveform are set to 21V, - 21V or 0V. The distance between the two dashed lines is a minimum time unit, and the length of time is 1 / 50 = 20ms, where the frame rate is 50 frames/second, the driving waveforms in Figure 2 can only be set to an integer multiple of 20 milliseconds. The first phase of the drive waveform in Figure 2 is set to the negative voltage compensation phase, and the latter two phases are to activate the electrophoretic particle phase and to write a new grayscale. In the first phase of the drive waveform, a negative voltage is applied to achieve DC balance. For example, when the time for writing a new gray scale is 40 ms, the drive waveform must be designed with a negative voltage for 40 ms to achieve DC balance compensation. The square wave designed in the second stage has a duty cycle of 50%, and the pulse lengths of the positive and negative voltages are equal, so this stage has no effect on the DC balance. In the example of the driving waveform of Fig. 2, the white gray scale is used as the reference gray scale, so the square wave of the second stage must be turned from the positive voltage to the negative voltage to ensure that the white gray scale brush is written. In the third phase, the forward voltage is flushed to the new gray scale with the appropriate length.

According to the above analysis, the voltage value in the drive waveform is set to 21V, - At 21V or 0V, the response time of a set of four-stage gray-scale electrophoresis electronic paper can be shortened to 400ms. By downloading the designed driving voltage waveform data to the electronic paper controller driving waveform lookup table, uniform display of four levels of gray scale can be realized. FIG. 3 is a driving effect diagram obtained in the present embodiment and a reflectance corresponding to each gray scale. It has higher response speed than the driving waveform of the traditional EPD.

According to the second embodiment of the present invention, it is basically the same as the first embodiment. The difference is that, referring to FIG. 1 again, the combination of positive and negative voltages is used in the third stage of the driving waveform to facilitate formation of a gray scale display greater than four levels. Improve image display quality.

The above is a detailed description of the preferred embodiments of the present invention, but the present invention is not limited to the embodiments, and various equivalent modifications or substitutions can be made by those skilled in the art without departing from the spirit of the invention. These equivalent variations or alternatives are intended to be included within the scope of the claims.

The specific order of the steps described herein is for illustrative purposes only and not limitation, unless a required step requires an input resulting from the preceding steps.

Claims

A fast response method for multi-level gray scale electrophoresis electronic paper for driving multi-level gray scale electrophoretic electronic paper, comprising the steps of:

A: increase the absolute value of the driving voltage to greater than 15V;

B: applying a voltage waveform opposite to the original image to erase the original image;

C: applying a square wave voltage waveform with a duty ratio of 50% to activate the electrophoretic particles;

D: Apply a voltage waveform of appropriate length to write a new gray scale.
The method of claim 1, wherein the absolute value of the driving voltage is configured by:

A1: Obtain a graph of voltage versus reflectivity under a positive or negative voltage driving waveform of different lengths;

A2: Determine the absolute 驱动 of the driving voltage capable of forming a uniform multi-level gray scale display in the range of 20-25V.
The method of claim 2, wherein the driving voltage is set to 21 V to form a uniform four-level gray scale display.
The method of claim 3, wherein the length of the driving voltage waveform corresponding to the uniform four-level gray scale display is set to 0 ms, 20 ms, 40 ms, respectively. And 100ms.
The method of claim 1, wherein the length of the voltage waveform applied in the step B is equal to the length of the driving voltage waveform corresponding to the original image to achieve DC balance compensation. .
The method of claim 1, wherein the square wave voltage of the step C is set to be a positive voltage to a negative voltage to ensure a white state as a reference gray scale .
The method of claim 3, wherein the step D uses a positive voltage to write a new gray scale.
The method of claim 1, wherein the step D is combined with positive and negative voltages to form a gray scale display greater than four levels.