Driving method of low-power-consumption multi-gray-scale electrowetting display
Technical Field
The invention relates to the technical field of displays, in particular to a driving method of a low-power-consumption multi-gray-scale electrowetting display.
Background
In recent years, electronic paper display devices have attracted attention because of their advantages of paper-like appearance, low power consumption, environmental protection, and the like. Compared with electrophoretic electronic paper, the electrowetting electronic paper can also realize high brightness, high contrast and low energy consumption, has a response speed higher than that of electrophoretic electronic paper, and can be used for video display. Therefore, it is becoming an important research direction for new generation of electronic paper display.
There is a hysteresis in the electrowetting contact angle, i.e. there are four stages in the change of the contact angle. The first stage is that when the pixel voltage is applied, the electrowetting contact angle is not changed greatly, and the optical change of the display, namely the threshold voltage of the contact angle, cannot be observed visually by human eyes; in the second stage, along with the increase of voltage, the electrowetting contact angle changes obviously, and obvious optical change can be observed; in the third stage, the voltage is continuously increased, and the change of the electrowetting contact angle is obviously slowed down compared with the second stage; the fourth phase is that as the voltage continues to increase, the electrowetting contact angle is substantially unchanged, in a saturated state, with no significant optical change being observed as well. And due to the electrowetting display, there are phenomena of ink backflow, charge trapping, etc., so that the optical state of the display, i.e., the contrast or gray scale of the display, is reduced.
Since the substrate captures different charges in different gray states and the electrowetting contact angle needs different time for resetting, the reset pulse generally uses a sub-frame pulse time to release the charges.
Disclosure of Invention
In view of the above, the present invention provides a driving method of a multi-gray electrowetting display with low power consumption, which improves the display quality of the electrowetting e-paper display and reduces the power consumption of the electrowetting display.
In order to achieve the purpose, the invention adopts the following technical scheme:
a method of driving a low power consumption multi-gray electro-wetting display, comprising the steps of:
step S1: the method comprises the steps of (1) acquiring a change curve of electrowetting gray scale, namely a gray scale-voltage curve, of the electrowetting electronic paper display along with the increase of voltage;
step S2: determining the threshold voltage V of the electrowetting contact angle according to the gray-voltage curveth;
Step S3 threshold voltage V according to gray-scale voltage curve and electrowetting contact anglethCalculating the duration Tp of the preset pulse P applied to the electrowetting display;
step S4: dividing the preset pulse P into a plurality of short subframes according to the duration Tp;
step S5, dividing the gray scale-voltage curve into a, b, c and d stages;
step S6, dividing the pulse of stage b into four short subframes, the pulse of stage c into four short subframes, the pulse of stage d is composed of one subframe;
in step S7, a reset pulse is applied after the display pulse to obtain a final waveform consisting of the preset pulse, the display pulse and the reset pulse.
Further, the multi-gray-scale electrowetting display pixel unit comprises a polar fluid, a non-polar fluid, a hydrophobic insulating medium layer, a transparent conductive electrode and a white substrate which are arranged from top to bottom; and pixel walls are arranged on two sides of the nonpolar fluid.
Furthermore, the four stages a, b, c and d correspond to voltage values of 0-10V, 10-15V, 15-25V and 25-30V respectively.
Further, the preset pulse P is divided into three short subframes of equal width by stepwise increasing.
Compared with the prior art, the invention has the following beneficial effects:
the invention can effectively improve the display quality of the electrowetting electronic paper display and reduce the power consumption of the electrowetting display.
Drawings
FIG. 1 is a block diagram of an electrowetting electronic paper display pixel cell of the present invention;
FIG. 2 is a voltage-gray curve according to an embodiment of the present invention;
FIG. 3 is a preset frame drive waveform in one embodiment of the present invention;
FIG. 4 is a conventional 9-gray electrowetting electronic paper drive waveform in an embodiment of the present invention;
FIG. 5 illustrates a conventional 16 gray scale non-equidistant gray scale modulation driving waveform in accordance with an embodiment of the present invention;
fig. 6 is an electrowetting e-paper drive waveform with adjusted gray scale 16 in accordance with an embodiment of the present invention.
Detailed Description
The invention is further explained below with reference to the drawings and the embodiments.
Referring to fig. 1, in the present embodiment, the multi-gray electrowetting display pixel unit includes a polar fluid 1, a non-polar fluid 2, a hydrophobic insulating medium layer 4, a transparent conductive electrode 5, and a white substrate 6 disposed from top to bottom; pixel walls 3 are arranged on both sides of the non-polar fluid 5. The polar fluid 1 is an aqueous solution and the non-polar fluid 2 is an ink. When no voltage is applied, the non-polar fluid is laid down on the hydrophobic insulating dielectric layer 4, as shown in the left figure of fig. 1. When a voltage is applied, the contact angle between the polar fluid 1 and the non-polar fluid 2 changes, the hydrophobic insulating medium layer 4 changes into a hydrophilic medium layer, and the polar fluid 1 "pushes" the non-polar fluid 2 into the corner, as shown in the right diagram of fig. 1. Thereby enabling a switching state of the electrowetting e-paper display.
The invention provides a driving method of a low-power consumption multi-gray-scale electrowetting display, which comprises the following steps of:
step S1: the method comprises the steps of (1) acquiring a change curve of electrowetting gray scale, namely a gray scale-voltage curve, of the electrowetting electronic paper display along with the increase of voltage;
step S2: determining the threshold voltage V of the electrowetting contact angle according to the gray-voltage curveth;
Step S3 threshold voltage V according to gray-scale voltage curve and electrowetting contact anglethCalculating the duration Tp of the preset pulse P applied to the electrowetting display;
step S4: dividing the preset pulse P into a plurality of short subframes according to the duration Tp;
step S5, dividing the gray scale-voltage curve into a, b, c and d stages;
step S6, dividing the pulse of stage b into four short subframes, the pulse of stage c into four short subframes, the pulse of stage d is composed of one subframe;
in step S7, a reset pulse is applied after the display pulse to obtain a final waveform consisting of the preset pulse, the display pulse and the reset pulse.
Referring to fig. 2, in the present embodiment, the gray scale variation of the electrowetting display can be roughly divided into four stages a, b, c, and d, where the ink in the first stage a is in the state to be activated and the gray scale is almost unchanged; immediately after the preset pulse in the second phase b, the gray scale changes fastest; the third stage c is connected after the first stage b, and the gray change speed of the third stage c is slower than that of the stage a; the fourth stage d is followed by the second stage c, and the gray scale change speed is slowest. The third gray phase c is longest in duration compared to the other three phases. The final gray level of the second gray level phase d may be up to half the total gray level. The four stages a, b, c and d correspond to voltage values of 0-10V, 10-15V, 15-25V and 25-30V respectively.
The conventional driving waveform of fig. 4 can modulate 9 gray scales by each sub-frame combination.
In fig. 6, subframe 1 corresponds to phase b in fig. 2, 4 short subframes of subframe 1 are similar to the conventional 9-gray electrowetting drive waveform combination, and 9 gray scales can be modulated, and different from the conventional drive waveform, the duration of 4 short subframes in subframe 1 is much shorter than the duration of 4 subframes in the conventional waveform, that is, when driving a low-gray-scale pixel, the low-gray-scale pixel has lower power consumption, so that a better power consumption limiting effect can be achieved, and meanwhile, in order to improve the ink backflow phenomenon, the situation that all 4 consecutive short subframes are in an on state is eliminated, that is, subframe 1 can modulate 8 gray scales; the modulation of the sub-frames 2 and 3 needs to ensure that the sub-frame 1 is at the highest gray scale level, and 8 gray scale levels can be modulated by 4 short sub-frames, but the state that the 4 short sub-frames are all closed needs to be omitted to avoid the repetition with the highest gray scale level modulated by the sub-frame 1, so that 7 gray scale levels can be modulated by the sub-frames 2 and 3; the single subframe duration of the subframe 4 is the longest compared with the previous subframe, so that the condition of the maximum voltage difference is abandoned, and the subframe 4 can modulate 1 gray level, in order to avoid the condition that the same pressure difference duration is too long and the ink backflow phenomenon is caused because the same pressure difference is formed with the highest gray level pressure difference combined by the subframes 2 and 3. In conclusion, the low-power-consumption multi-gray-scale driving waveform provided by the invention can finally modulate 8+7+1=16 gray scales, improves the phenomena of ink splitting, ink backflow and the like, and has lower power consumption than the traditional driving waveform.
In this embodiment, a preset frame with step size increasing is adopted as the waveform 1, a plurality of short sub-frames with equal width are divided in the preset frame, and the driving voltage is gradually increased to reduce the instantaneous electrostatic force required for stabilizing the ink movement, so that the effect between the ink and the water is moderate, and compared with a fixed driving waveform 2, the ink has more time to combine with each other, thereby effectively inhibiting the ink from splitting and improving the pixel aperture ratio.
In this embodiment, each two identical pulses are followed by a different pulse to further improve the ink reflow and charge trapping phenomena.
The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.