This Non-provisional application claims priority under 35 U.S.C. §119(a) on Patent Application No(s). 100136813 filed in Taiwan, Republic of China on Oct. 11, 2011, the entire contents of which are hereby incorporated by reference.
1. Field of Invention
The invention relates to a driving method of a display apparatus and, in particular, to a driving method of a blue phase liquid crystal display apparatus.
2. Related Art
The blue phase liquid crystal (BPLC) is a self-assembly three-dimensional photonic crystal structure, existing between the isotropic phase and the cholesteric phase. The BPLC is featured by a 3D crystalline characteristic while showing a liquid property, and besides, the lattice parameter of the BPLC is easily changeable, so that it becomes an excellent tunable photonic crystal providing various optical-electronic properties. Therefore, the BPLC can be applied to a stereoscopic display apparatus. Furthermore, compared with the conventional liquid crystal display technology, the BPLC display apparatus is capable of high LC response time with a wide viewing angle and needn't be configured with alignment layers. Hence, it has been more focused on and researched by the industry recently. However, the blue phase liquid crystals with different crystalline orientations have different optical-electronic properties under the application of an electric field, and the BPLC is submitted to the hysteresis effect, both of which cause the BPLC display apparatus image retention (IR).
In the present research of the LCD apparatus, the hysteresis effect of the BPLC apparatus is becoming a big subject for the optical performance. Although the conventional dark-state black frame insertion can solve the hysteresis problem of the BPLC to enhance the contrast and light transmittance of the display apparatus, it can not diminish the dark-state leakage of the BPLC display apparatus so that the dark-state transmittance of the BPLC display apparatus is unstable, affecting the contrast seriously.
Therefore, it is an important subject to provide a driving method that can diminish the dark-state leakage of the BPLC display apparatus.
In view of the foregoing subject, an objective of the invention is to provide a driving method that can diminish the dark-state leakage of the BPLC display apparatus.
To achieve the above objective, according to the invention, a driving method of a blue phase liquid crystal (BPLC) display apparatus cooperated with a BPLC display apparatus having at least one data line, at least one scan line and at least one pixel comprises the steps of transmitting a first gray level voltage to the pixel through the data line; transmitting a first recovery voltage to the pixel through the data line; and transmitting a first black frame insertion voltage to the pixel through the data line, wherein the absolute value of the first recovery voltage is higher than those of the first gray level voltage and the first black frame insertion voltage.
In one embodiment, when the transmission of the first recovery voltage follows the transmission of the first gray level voltage, the first gray level voltage and the first recovery voltage have opposite polarities.
In one embodiment, the first gray level voltage, the first recovery voltage, and the first black frame insertion voltage are transmitted in sequence during a frame time.
In one embodiment, the ratio of the duty time of the first gray level voltage to the duty time of the first recovery voltage is between 1:1˜1:0.025 during a frame time.
In one embodiment, the ratio of the duty time of the first recovery voltage to the duty time of the first black frame insertion voltage is between 1:1˜1:0.025 during a frame time.
In one embodiment, the driving method further comprises: transmitting a second gray level voltage to the pixel through the data line.
In one embodiment, the driving method further comprises: transmitting a second gray level voltage and a second recovery voltage to the pixel through the data line.
In one embodiment, the driving method further comprises: transmitting a second gray level voltage and a second black frame insertion voltage to the pixel through the data line.
In one embodiment, the driving method further comprises: transmitting a second gray level voltage, a second recovery voltage, and a second black frame insertion voltage to the pixel through the data line.
In one embodiment, the first gray level voltage and the second gray level voltage have opposite polarities.
In one embodiment, the first recovery voltage and the second recovery voltage have opposite polarities.
In one embodiment, the first black frame insertion voltage and the second black frame insertion voltage have opposite polarities.
In one embodiment, the first gray level voltage, the second gray level voltage, the first recovery voltage, the second recovery voltage, the first black frame insertion voltage, and the second black frame insertion voltage are transmitted in sequence during the two consecutive frame times.
In one embodiment, the first gray level voltage, the second gray level voltage, the first recovery voltage, the first black frame insertion voltage, and the second black frame insertion voltage are transmitted in sequence during the two consecutive frame times.
In one embodiment, the first gray level voltage, the second gray level voltage, the second recovery voltage, the first black frame insertion voltage, and the second black frame insertion voltage are transmitted in sequence during the two consecutive frame times.
In one embodiment, the first gray level voltage, the second gray level voltage, the first recovery voltage, and the first black frame insertion voltage are transmitted in sequence during the two consecutive frame times.
In one embodiment, the first gray level voltage, the second gray level voltage, the second recovery voltage, and the second black frame insertion voltage are transmitted in sequence during the two consecutive frame times.
In one embodiment, the first recovery voltage or the, second recovery voltage is between 15V and 60V.
In one embodiment, the absolute value of the first recovery voltage is between 1.2 times and 4 times of the absolute value of the first gray level voltage or the first black frame insertion voltage.
As mentioned above, according to the driving method of the BPLC display apparatus of the invention, the first gray level voltage is transmitted to the pixel through the data line, the first recovery voltage is transmitted to the pixel through the data line, and the first black frame insertion voltage is transmitted to the pixel through the data line. Besides, the absolute value of the first recovery voltage is higher than those of the first gray level voltage and the first black frame insertion voltage. Thereby, following the first gray level voltage, the first recovery voltage with higher level is transmitted so that the BPLC can be furnished with larger recovery force to more easily return to the optically isotropic sphere state, diminishing the dark-state leakage of the LCD apparatus and also enhancing the stability of the dark-state transmittance.
The invention will become more fully understood from the detailed description and accompanying drawings, which are given for illustration only, and thus are not limitative of the present invention, and wherein:
The present invention will be apparent from the following detailed description, which proceeds with reference to the accompanying drawings, wherein the same references relate to the same elements.
The driving method of the BPLC display apparatus is cooperated with the BPLC display apparatus 1. As shown in
As shown in
The BPLC display panel 2 includes a first substrate 21, a second substrate 22, and a BPLC layer 23 (the BPLC molecules are not shown in the figure). The first substrate 21 can be a color filter substrate or a transparent glass substrate, and the second substrate 22 is an active matrix substrate, such as a thin film transistor (TFT) substrate, which is disposed opposite to the first substrate 21. The BPLC layer 23 is sandwiched in between the first and second substrates 21 and 22, and includes a liquid crystal material having blue phase, a polymer and a chiral dopant, wherein monomers are polymerized to become the polymer by the illumination of the ultraviolet, thereby stabilizing the BPLC's structure to increase the temperature range for the existence of the BPLC as well as the operational temperature range of the BPLC. The polymer can include, for example, acrylate, methacrylate, or epoxy, or their combinations. In the embodiment, the polymer's material is not limited.
The second substrate 22 includes a pixel electrode 221, an electrode layer 222, and a transparent substrate 223. The pixel electrode 221 and the electrode layer 222 are disposed on the transparent substrate 223. Herein, the electrode layer 222 is a common electrode layer. The second substrate 22 can further include an insulating layer 224, which is disposed between the pixel electrode 221 and the electrode layer 222 to insulate them from each other for preventing the short circuit. When the TFT is turned on, the gray level voltage can be transmitted to the pixel electrode 221 so that an electric field substantially in parallel with the transparent substrate 223 is formed between the pixel electrode 221 and the electrode layer 222 (common electrode layer), thereby driving the molecules of the PBLC layer 23 to rotate for modulating the light. To be note, in the embodiment, the pixel electrode 221 is disposed on the insulating layer 224 while the electrode layer 222 (common electrode layer) is disposed below the insulating layer 224. However, in other embodiments, the electrode layer 222 (common electrode layer) can be disposed on the insulating layer 224 while the pixel electrode 221 is disposed below the insulating layer 224.
Besides, the BPLC display panel 2 can further include two polarizing plates 241 and 242, which are disposed at the respective outsides of the first and second substrates 21 and 22. As shown in
As shown in
As below, refer the relative figures to further illustrate the driving method of the invention.
In the step P02, the first recovery voltage V1 is transmitted to the pixel through the data line. Herein, when the scan lines S11˜S1n are enabled at the same time, the first recovery voltages V1 are transmitted to the all pixels simultaneously. The first recovery voltages V1 have negative polarity. The first recovery voltage V1 can make the BPLC display apparatus 1 display white images.
In the step P03, the first black frame insertion voltage B1 is transmitted to the pixel through the data line. Herein, when the scan lines S11˜S1n are enabled at the same time, the first black frame insertion voltages B1 are transmitted to the all pixels simultaneously. The first black frame insertion voltage B1 is related to the conventional black frame insertion technology, making the BPLC display apparatus 1 display black images to resist the hysteresis effect of the BPLC. The first black frame insertion voltage B1 substantially can be zero or other preset voltages.
The absolute value of the first recovery voltage V1 is higher than those of the first gray level voltage G1 and the first black frame insertion voltage B1, and preferably between 1.2 times and 4 times of the absolute value of the first gray level voltage G1 or the first black frame insertion voltage B1. In other words, the first recovery voltage V1 has higher voltage. With respective driving characteristics possessed by BPLC display apparatuses, the first recovery voltage V1 can be set between 15V and 60V for example. Anyhow, the first recovery voltage V1 is preferably between 1.2 times and 4 times of the absolute value of the first gray level voltage G1 or the first black frame insertion voltage B1. The first recovery voltage V1 can make the BPLC display apparatus 1 display white images, thereby diminishing the dark-state leakage of the BPLC of the BPLC display apparatus 1.
The possible reason that the first recovery voltage V1 can diminish the dark-state leakage of the BPLC is described as below. The image can not be driven to a complete dark-state due to the hysteresis effect of the BPLC, but however, when a higher driving voltage (the first recovery voltage V1) is applied, the lattice sphere with an optical isotropy of the BPLC is drawn out to become an ellipsoid that is featured by birefringence and constrained by the polymer. Then, when the driving voltage is done, the ellipsoid can be deformed back to the sphere by the elastic recovery force. In other words, by the driving of the first recovery voltage V1, the ellipsoid can have higher recovery force. Therefore, after the driving of the first recovery voltage V1 finishes, the ellipsoid is easier to return to the optically isotropic sphere, which makes the following black image displayed by the black frame insertion voltage darker so that the dark-state leakage of the BPLC can be diminished. Besides, the driving of the first recovery voltage V1 may transform the lattice structure of the BPLC into the nematic phase, so once the driving of the first recovery voltage V1 finishes, the lattice structure returns, without the hysteresis effect, to the optically isotropic sphere state that is constrained by the polymer, thereby also diminishing the dark-state leakage of the BPLC.
As shown in
Besides, during a frame time T, the ratio of the duty time of the first gray level voltage G1 to the duty time of the first recovery voltage V1 can be set between 1:1 and 1:0.025. During a frame time T, the ratio of the duty time of the first recovery voltage V1 to the duty time of the first black frame insertion voltage B1 can be set between 1:1 and 1:0.025. The duty times of the first gray level voltage G1, the first recovery voltage V1 and the first black frame insertion voltage B1 can be varied according to different BPLC display apparatus.
In the embodiment, during the two consecutive frame times T, the first and second gray level voltages G1 and G2, the first and second recovery voltages V1 and V2, and the first and second black frame insertion voltages B1 and B2 are transmitted in sequence. The ratio of the duty times of the second gray level voltage G2, the second recovery voltage V2 and the second black frame voltage B2 can be set differently in response to different BPLC display apparatuses. The duty times of the first recovery voltage V1 and the second recovery voltage V2 can be the same or different, and they are the same in the embodiment for example. The first gray level voltage G1 and the second gray level voltage G2 have opposite polarities. The duty times of the first gray level voltage G1 and the second gray level voltage G2 can be arranged adjacent to each other or separated by an interval, and herein they are adjacent to each other for example. The first recovery voltage V1 and the second recovery voltage V2 have opposite polarities, the first black frame insertion voltage B1 and the second black frame insertion voltage B2 have opposite polarities, and the second gray level voltage G2 and the first recovery voltage V1 have opposite polarities.
The conventional black frame insertion technology has no first recovery voltage, wherein the black frame insertion voltage just follows the first gray level voltage. In the driving method of the invention, however, after inputting the first gray level voltage, the first recovery voltage and the black frame voltage are inputted in sequence, and the level of the first recovery voltage is higher than those of the black frame insertion voltage and the gray level voltage. In
As shown in
In summary, according to the driving method of the BPLC display apparatus of the invention, the first gray level voltage is transmitted to the pixel through the data line, the first recovery voltage is transmitted to the pixel through the data line, and the first black frame insertion voltage is transmitted to the pixel through the data line. Besides, the absolute value of the first recovery voltage is higher than those of the first gray level voltage and the first black frame insertion voltage. Thereby, following the first gray level voltage, the first recovery voltage with higher level is transmitted so that the BPLC can be furnished with larger recovery force to more easily return to the optically isotropic sphere state, diminishing the dark-state leakage of the LCD apparatus and also enhancing the stability of the dark-state transmittance.
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments, will be apparent to persons skilled in the art. It is, therefore, contemplated that the appended claims will cover all modifications that fall within the true scope of the invention.
Number | Date | Country | Kind |
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100136813 | Oct 2011 | TW | national |