CN203673178U - Cholesteric liquid crystal display device and its driving circuit - Google Patents

Abstract

The utility model provides a cholesterol liquid crystal display device and a driving circuit thereof. The utility model transmits a non-selection signal to all common electrodes corresponding to the image screen area after writing the image screen to the display panel, so as to solve the color difference problem between the non-selection area and the selection area caused by the crosstalk phenomenon generated in the non-selection area.

Description

Cholesteric liquid crystal display device and its driving circuit

technical field

The utility model relates to the field of liquid crystal display, in particular to a cholesterol liquid crystal display device and a driving circuit thereof.

Background technique

Cholesteric liquid crystal display (Cholesteric liquid crystal display) is a new display technology with the advantages of high brightness, high contrast, power saving, memory, wide viewing angle, and no flicker. Its biggest advantage is energy saving, the average power consumption is only 1/50 of the transmissive LCD panel, and it has been successfully applied to e-book products. At the same time, cholesteric liquid crystal also has a bistable memory function, even if the power is turned off after the image is fully displayed, it can still continue to display images, which is very suitable for outdoor billboards and portable products.

Cholesteric liquid crystals undergo phase transitions depending on the applied electric field. The most common arrangement is the planar state and the vertical spiral (focal conic) state. As shown in Fig. 1A, it is the schematic diagram of the planar state of the prior art, if we change the applied electric field, the helical axis of the cholesteric liquid crystal molecules will fall down and arrange, and the direction of the helical axis at this time is parallel to the surface of the liquid crystal cell. It is called planar arrangement. As shown in FIG. 1B , the vertical helical state (focal conic) schematic diagram of the prior art is called vertical helical state arrangement.

Generally speaking, the planar state is a bright state (Bright state), that is, the liquid crystal cells 15 are arranged in a regular planar state between the transparent substrates 11 and 13 (as shown in FIG. 1A ), so that external light can pass through the transparent The substrate 11 and the liquid crystal cell 15 are reflected. Therefore, cholesteric liquid crystal display devices are usually used in e-books, etc., which can use external light to display images without frequent screen switching and without external voltage, so as to save energy. The vertical spiral state is a dark state, the liquid crystal cells 15 are arranged irregularly (as shown in FIG. 1B ), and the external light is scattered into the transparent substrate 13 . As for when there is no external voltage, when the stable state of the cholesteric liquid crystal display is a planar state or a vertical helical state, it is determined by the signal of the previously applied voltage.

However, since the R-V (Reflectance-voltage, reflectivity and applied voltage) characteristic curve of cholesteric liquid crystals shifts over time, the rated output voltage of the drive circuit is higher (or lower) than the original voltage characteristics of the liquid crystal, making the non-selection of the partial area of the display panel Areas form crosstalk (Cross talk) phenomenon, resulting in chromatic aberration or poor quality of the display screen.

Therefore, the utility model provides a cholesteric liquid crystal display device and its driving circuit to solve the above problems.

Utility model content

One purpose of the present utility model is to provide a cholesteric liquid crystal display device and its drive circuit, which can solve the problem by sending non-selection signals to all the common electrodes corresponding to the area of the image screen after writing the image screen on the display panel. The non-selected area produces a crosstalk phenomenon, resulting in a problem of color difference between the non-selected area and the selected area.

Another purpose of the present utility model is to provide a cholesteric liquid crystal display device and its drive circuit. After the display panel writes the video picture, it transmits the selection signal to the last common electrode corresponding to the area of the video picture, and transmits the non- The selection signal is sent to the remaining common electrodes to solve the problem of color difference between the non-selection area and the selection area due to the crosstalk phenomenon generated by the non-selection area.

In order to achieve the above purpose and effect, the utility model provides a cholesteric liquid crystal display device, which includes: a display panel with a plurality of common electrodes and a plurality of segment electrodes, and according to the common electrode and the segment electrodes A potential difference between them to display an image frame; a common driver, coupled to the display panel, and respectively transmit a selection signal or a non-selection signal to the common electrode; a segment driver, coupled to the display panel , and corresponding to the selection signal or the non-selection signal output by the common driver, respectively transmit a display signal to the segment electrodes, for writing an image picture on the display panel, and for the display panel to display the image picture; and a controller, after writing the image frame to the display panel, the controller controls the segment drivers to respectively transmit display signals to the segment electrodes, and then controls the common driver to respectively and simultaneously transmit non-selection signals to the common electrodes , or control the common driver to respectively transmit the selection signal and the non-selection signal to the last common electrode and the rest of the common electrodes corresponding to the area of the image frame.

The utility model also provides a driving circuit for a cholesteric liquid crystal display device, which includes: a common driver, coupled to a display panel, and respectively transmitting a selection signal or a non-selection signal to a plurality of common electrodes of the display panel; and A segment driver, coupled to the display panel, and corresponding to the selection signal or non-selection signal output by the common driver, respectively transmits a display signal to the plurality of segment electrodes of the display panel, for write an image frame on it, and provide the display panel to display the image frame; wherein, after writing the image frame to the display panel for display, the segment drivers respectively transmit display signals to the segment electrodes, and the common drivers respectively And transmit the non-selection signal to the common electrode at the same time, or the common driver transmits the selection signal and the non-selection signal to the last common electrode and the rest of the common electrodes corresponding to the area of the image frame respectively.

Description of drawings

Figure 1A is a schematic plan view of the prior art;

Figure 1B is a schematic diagram of a vertical spiral state in the prior art;

Fig. 2 is the schematic diagram of the cholesteric liquid crystal display device of a preferred embodiment of the present invention;

3 is a schematic diagram of the R-V characteristic curve of cholesteric liquid crystal;

Fig. 4 is a signal waveform diagram of a preferred embodiment of the present utility model;

FIG. 5 is a schematic diagram of a phenomenon of crosstalk generated in an image frame;

6 is a schematic diagram of a display image screen of the first embodiment of the present invention;

7 is a schematic diagram of a display image screen of a second embodiment of the present invention;

8 is a schematic diagram of a display image screen of a third embodiment of the present invention;

FIG. 9 is a schematic diagram of a display image screen of a fourth embodiment of the present invention.

Explanation of reference signs: 11, 13-transparent substrate; 15-liquid crystal unit; 2-cholesteric liquid crystal display device; 20-display panel; 202-common electrode; 204-segment electrode; 206, 207, 208-display area; -common driver; 24-section driver; 26-controller; A, B, C, D-waveform; a, b-characteristic curve; DI1, DI2, DI3, DI4, DI5, DI6-image screen; SS-selection Signal; NSS-non-selection signal; PS-plane state signal; FCS-vertical spiral state signal; V1, V2, V3, V4, V5, V6-voltage.

Detailed ways

The utility model uses name vocabulary in the specification and claims to represent specific components. Those of ordinary skill in the art should understand that hardware manufacturers may refer to the same component by different names. The description and claims of the utility model do not use the difference in name as the way to distinguish components, but use the difference in function of the components as the criterion for distinguishing. Furthermore, the term "coupled" herein includes any direct and/or indirect means of electrical connection. Therefore, in this case, it is described that a first device is coupled to a second device, including that the first device is directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means. .

The technical solutions in the preferred embodiments of the utility model are clearly and completely described below in conjunction with the accompanying drawings. Apparently, the described embodiments are only some of the embodiments of the utility model, not all of them. Based on the embodiments of the present utility model, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of the present utility model.

Please refer to FIG. 2 . FIG. 2 is a schematic diagram of a cholesteric liquid crystal display device according to a preferred embodiment of the present invention. As shown in FIG. 2 , the cholesteric liquid crystal display device 2 of the present invention includes a display panel 20 and a driving circuit, and the driving circuit includes a common driver 22 and a segment driver 24 . The display panel 20 has a plurality of common electrodes 202 and a plurality of segment electrodes 204 , and the display panel 20 displays an image frame according to the potential difference between the common electrodes 202 and the segment electrodes 204 . The common driver 22 is coupled to the display panel 20 and used for transmitting a selection signal SS or a non-selection signal NSS to the common electrode 202 respectively. The segment driver 24 is coupled to the display panel 20, and transmits a display signal DS to the segment electrode 204 corresponding to the selection signal SS or the non-selection signal NSS output by the common driver 22, for writing an image frame into the display panel. 20, and display the image on the display panel 20.

Wherein, the common electrode 202 and the segment electrodes 204 are alternately arranged with each other, and a liquid crystal layer of cholesteric liquid crystal is provided between the common electrode 202 and the segment electrodes 204, and between the common electrode 202 and the Pixels are arranged at the intersections of the segment electrodes 204, which are used to base on the potential difference between the common electrode 202 and the segment electrodes 204 (that is, the potential difference between the selection signal SS or the non-selection signal NSS and the display signal DS). ), to determine the rotation direction of the liquid crystal at the pixel.

In addition, the cholesteric liquid crystal display device 2 of the present invention may further include a controller 26 for controlling the common driver 22 to transmit the selection signal SS or the non-selection signal NSS to the common electrode 202 and the segment driver 24 to transmit the display signal DS to the common electrode 202. Timing of the segment electrodes 204 .

Please refer to FIG. 3 and FIG. 4 , FIG. 3 is a schematic diagram of the R-V characteristic curve of cholesteric liquid crystal, and FIG. 4 is a signal waveform diagram of a preferred embodiment of the present invention. As shown in Figure 3, when the initial state of the cholesteric liquid crystal is a bright state, it is represented by a characteristic curve a (voltage V1, V2, V3 to V5), and when the initial state of the cholesteric liquid crystal is a dark state, it is represented by a characteristic curve b (voltage V2, V3, V4 to V6) said.

As shown in FIG. 4, when the common driver 22 transmits the selection signal SS to a certain common electrode 202, the segment driver 24 transmits a planar signal (Planar signal, PS) or a vertical spiral signal (Focal conic) of the display signal DS. signal, FCS) to the section electrode 204, the potential difference at the intersection of the common electrode 202 and the section electrode 204 is equal to the level of the selection signal SS minus the level of the planar state signal PS or the vertical spiral state signal FCS , as shown in waveforms A and B respectively. When the common driver 22 transmits the non-selection signal NSS to a certain common electrode 202, and the segment driver 24 transmits the planar state signal PS or the vertical spiral state signal FCS to the segment electrode 204, as shown in waveforms C and D respectively. Show.

When the pixel corresponding to a certain common electrode 202 is to display a bright state or a dark state, a selection signal SS is transmitted to the common electrode 202, and a planar state signal PS or a vertical spiral state signal FCS is transmitted, so that the The pixels corresponding to the common electrode 202 are displayed in a bright state or a dark state according to the planar state signal PS or the vertical spiral state signal FCS, and the other common electrodes 202 that have been scanned receive the non-selection signal NSS.

Please continue to refer to Figure 3 and Figure 4, taking the characteristic curve a as an example, because the R-V characteristic curve of cholesteric liquid crystal may shift over time, resulting in the rated output voltage of the drive circuit being higher or lower (that is, the amplitude is greater than) the original voltage characteristic of the liquid crystal, Taking the pixel receiving the non-selection signal NSS as an example, as shown in Figure 3, it will shift from the voltage V1 to the voltage V2 (the dotted line part of the waveform C in Figure 4, (V5-V3)/2= V1), therefore, the reflectivity of the pixels receiving the non-selection signal NSS will be reduced (shifted from the voltage V1 to the voltage V2), thereby generating crosstalk.

Wherein, the waveforms of the selection signal SS, the non-selection signal NSS, the planar state signal PS and the vertical spiral state signal FCS shown in this embodiment are only a preferred embodiment and are not intended to limit the present invention.

Please refer to FIG. 5 at the same time. FIG. 5 is a schematic diagram of the phenomenon of crosstalk in video frames. As shown in FIG. 5 , when the general display panel 20 writes the image frame DI1, it transmits the selection signal SS to the position of the bright state font cholesteric liquid crystal (Cholesteric liquid crystal) in the image frame DI1 through the common driver 22, and the rest parts transmit the non-selection signal SS. The signal NSS is selected, so the potential difference of the selected area (the area receiving the selection signal SS) is as shown in the waveforms A and B of Figure 4, while the potential difference of the non-selected area (the area receiving the non-selection signal NSS) is as shown in the waveform C, As shown in D, crosstalk will occur in the non-selected area, and the problem of color difference between the selected area and the non-selected area will occur, as shown in the color difference CD1 and CD2.

Please continue to refer to FIG. 6 . FIG. 6 is a schematic diagram of a display image screen according to the first embodiment of the present invention. As shown in FIG. 6 , in this embodiment, the image frame DI1 written on the display panel 20 is a bright state of Cholesteric liquid crystal, while the rest of the background color is in a dark state. When it is necessary to write the image frame DI1 to the display panel 20, a preferred embodiment is that the common driver 22 sequentially transmits the selection signal SS or the non-selection signal NSS to the common electrode 202 of the display panel 20, and the segment driver 24 Then, corresponding to the selection signal SS, the non-selection signal NSS and the image frame DI1 to be written, the planar state signal PS or the vertical spiral state signal FCS is respectively transmitted to the segment electrodes 204 of the display panel 20 . Wherein, how to write the image frame DI1 to the display panel 20 is well known to those skilled in the art, and it is not intended to limit the present invention, so details are not repeated here.

The key point of this embodiment is that after the image frame DI1 is written into the display panel 20, the common driver 22 respectively and simultaneously transmits the non-selection signal NSS to all the common electrodes 202, so that each common electrode 202 can feel the non-selection signal at the same time. The signal NSS is selected, and the segment driver 24 respectively transmits the planar state signal PS or the vertical spiral state signal FCS to the segment electrode 204. At this time, the potential difference at the intersection of the common electrode 202 and the segment electrode 204 is A waveform as shown in waveform C or D as shown in FIG. 4 is formed, that is, the potential differences at the intersections of all the common electrodes 202 and the segment electrodes 204 of the display panel 20 are the same.

As mentioned above, when the image frame DI1 is written, the potential difference of the pixel on the common electrode 202 receiving the selection signal SS can be changed from waveform A or B in FIG. 3 to waveform C or D, that is, All the selected areas of the display panel 20 that originally received the selection signal SS are transformed into non-selected areas by receiving the non-selection signal NSS, which means that all areas of the display panel 20 generate crosstalk, so there will be no crosstalk caused by the non-selected areas. This results in a color difference problem between the non-selected area and the selected area.

Please refer to FIG. 7 . FIG. 7 is a schematic diagram of an image display screen according to a second embodiment of the present invention. The image frame DI2 written in the display panel 20 of this embodiment is the same as the image frame DI1 of the first embodiment, the difference lies in the method of this embodiment to solve the color difference problem caused by the crosstalk phenomenon.

As shown in FIG. 7 , when the common driver 22 of this embodiment writes the image frame DI2 to the display panel 20, it transmits the selection signal SS or The non-selection signal NSS, and when writing the last common electrode 202, transmit the selection signal SS to the last common electrode 202, that is, when writing the image frame DI2 is completed, the common driver 22 transmits the selection signal SS to the last common electrode 202. And when transmitting the selection signal SS to the last common electrode 202, the common driver 22 simultaneously transmits the non-selection signal NSS to the remaining common electrodes 202, and the segment driver 24 transmits the planar state signal PS according to the pattern of the image frame DI2 Or the vertical spiral state signal FCS is sent to the segment electrodes 204 of the display panel 20 .

Since the image frame DI2 written in this embodiment is a bright font, the segment driver 24 transmits the planar state signal PS to all the segment electrodes 204 to make a display area corresponding to the last common electrode 202 206 is displayed in a bright state, and since the rest of the common electrodes 202 receive the non-selection signal NSS, the rest of the display areas except the display area 206 maintain displaying the previously written image frame DI2.

The concept and principle of this embodiment are the same as those of the first embodiment. By making all the common electrodes 202 receive the non-selection signal NSS, the problem of color difference caused by the crosstalk phenomenon is solved. The difference is that the last common The electrodes 202 transmit the selection signal SS, so that the display area 206 corresponding to the last common electrode 202 is displayed in a bright state or a dark state according to the font of the image frame DI2 .

Please refer to FIG. 8 . FIG. 8 is a schematic diagram of an image display screen according to a third embodiment of the present invention. The difference between this embodiment and the second embodiment is that the video frame displayed on the display panel 20 is divided into two parts DI3 and DI4, and when only the part of the video frame DI4 is updated (that is, written into the video frame DI4), the present embodiment only It is necessary to display the last common electrode 202 in the area corresponding to the image frame DI4 as a bright state, that is, after writing the image frame DI4, the common driver 22 only transmits the selection signal SS to the last electrode in the area corresponding to the image frame DI4 common electrode 202, and transmit the non-selection signal NSS to the remaining common electrodes 202, and the segment driver 24 then transmits the planar state signal PS to all said segment electrodes 204 according to the font of the image picture DI4 being in a bright state, so that the display area 207 is displayed as a bright state. Wherein, the principle of solving the chromatic aberration problem caused by the crosstalk phenomenon in this embodiment is the same as that in the second embodiment, and will not be repeated here.

Please refer to FIG. 9 . FIG. 9 is a schematic diagram of an image display screen according to a fourth embodiment of the present invention. As shown in Figure 9, the difference between this embodiment and the third embodiment is that the image frames DI5 and DI6 of this embodiment are dark fonts and bright background colors, so when it is necessary to update the part of the image frame DI6, this embodiment An example is to display the last common electrode 202 in the area corresponding to the image frame DI6 as a dark state, that is, after writing the image frame DI6 is completed, the common driver 22 transmits the selection signal SS to the last electrode in the area corresponding to the image frame DI6 common electrode 202, and transmit the non-selection signal NSS to the remaining common electrodes 202, and the segment driver 24 then transmits the vertical spiral state signal FCS to all said segment electrodes 204 according to the font of the image frame DI6 being in a dark state, so that the display Region 208 is shown in a dark state. Wherein, the principle of solving the chromatic aberration problem caused by the crosstalk phenomenon in this embodiment is the same as that of the third embodiment, and will not be repeated here.

Wherein, although the second to fourth embodiments of the present utility model are based on whether the font of the image screen is bright or dark, it is determined that the last common electrode 202 is displayed as bright or dark, for example, the font in Figure 8 is bright Then the last common electrode 202 is displayed in a bright state, and the font in FIG. 9 is in a dark state, then the last common electrode 202 is displayed in a dark state. But the utility model is not limited thereto, it can also be determined according to the part of the video image that will produce crosstalk. The electrode 202 is displayed in a bright state, and if the dark state area in the image frame is affected by the crosstalk phenomenon to increase the brightness, the last common electrode 202 can be designed to be displayed in a dark state.

To sum up, the cholesteric liquid crystal display device and its drive circuit of the present invention solve the problem of non-selection by transmitting the non-selection signal to all the common electrodes corresponding to the area of the image frame after writing the image frame to the display panel. Crosstalk occurs in the area, resulting in a color difference problem between the non-selected area and the selected area.

The above-mentioned embodiments are only preferred embodiments of the present utility model, and are not used to limit the scope of implementation of the present utility model. Equivalent changes and modifications made according to the shape, structure, characteristics and spirit of the present utility model, All are included in the protection scope of the present utility model.

Claims (10)

1. A cholesteric liquid crystal display device, characterized in that, comprising: A display panel has multiple common electrodes and multiple segment electrodes, and displays an image frame according to the potential difference between the common electrodes and the segment electrodes; a common driver, coupled to the display panel, and respectively transmits a selection signal or a non-selection signal to the common electrode; and A segment driver, coupled to the display panel, and corresponding to the selection signal or the non-selection signal output by the common driver, respectively transmits a display signal to the segment electrodes for the image frame write to the display panel, and allow the display panel to display the image; A controller, coupled to the common driver and the segment driver, after the display panel displays the image frame, the controller controls the common driver to transmit the non-selection signal to the common electrode separately and simultaneously , or control the common driver to respectively transmit the selection signal and the non-selection signal to the last common electrode and the remaining common electrodes of the common electrodes corresponding to the area of the image frame. 2. The cholesteric liquid crystal display device according to claim 1, wherein the controller controls the segment driver to transmit a planar state signal or a vertical spiral state signal of the display signal according to the image frame signal to the segment electrodes. 3. The cholesteric liquid crystal display device according to claim 1, wherein after the display panel displays the video image, the controller controls the segment drivers to transmit the display signals to the regions respectively. segment electrodes. 4. The cholesteric liquid crystal display device as claimed in claim 3, wherein after the display panel displays the image frame, the controller controls the segment drivers to transmit the A planar state signal of the display signal is sent to the segment electrodes. 5. The cholesteric liquid crystal display device as claimed in claim 3, wherein after the display panel displays the image frame, the controller controls the segment drivers to transmit the A vertical spiral signal of the display signal to the segment electrodes. 6. A drive circuit for a cholesteric liquid crystal display device, characterized in that it comprises: a common driver, coupled to a display panel, and respectively transmitting a selection signal or a non-selection signal to a plurality of common electrodes of the display panel; and A segment driver, coupled to the display panel, and corresponding to the selection signal or the non-selection signal output by the common driver, respectively transmits a display signal to a plurality of segment electrodes of the display panel to write Inputting an image frame into the display panel, and allowing the display panel to display the image frame; Wherein, after the display panel displays the image picture, the common driver respectively and simultaneously transmits the non-selection signal to the common electrode, or the common driver transmits the selection signal and the non-selection signal respectively to the last common electrode of the common electrodes corresponding to the area of the image frame and the rest of the common electrodes. 7. The drive circuit according to claim 6, wherein the segment driver transmits a planar signal or a vertical spiral signal of the display signal to the segment electrodes according to the image frame . 8 . The driving circuit according to claim 6 , wherein after the display panel displays the image frame, the segment drivers respectively transmit the display signals to the segment electrodes. 9. The drive circuit according to claim 8, wherein after the display panel displays the image frame, the segment driver transmits a planar state of the display signal according to the pattern of the image frame signal to the segment electrodes. 10. The driving circuit according to claim 8, wherein after the display panel displays the image frame, the segment driver respectively transmits a vertical spiral of the display signal according to the pattern of the image frame status signal to the segment electrodes.

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