TWI395186B - Display and driving apparatus and method thereof - Google Patents

Description

Display and its driving device and method

The present invention relates to a flat display technology, and more particularly to a color sequential liquid crystal display having colorlessness and high display brightness, and a driving apparatus and method thereof.

In general, color filter type liquid crystal displays (CF-type LCDs) are often subject to their own structural characteristics such that their color gamut is low. In addition, the color filter type liquid crystal display is affected by the inherent time dependent effect of the LC capacitance, resulting in dynamic blur of the image image it presents.

Therefore, in order to effectively solve the numerous defects derived from the conventional color filter type liquid crystal display, a color sequential type LCD has emerged. However, although the color sequential liquid crystal display can effectively solve the problem of dynamic image sticking and greatly improve the color gamut, the color sequential liquid crystal display is still affected by the time-varying effect of the liquid crystal capacitor in essence, and the dissimilar gray is made. The brightness of the order transition to the same gray level will be inconsistent. As a result, the image frame presented by the color sequential liquid crystal display will produce a color shift.

In addition, the traditional color sequential liquid crystal display is driven during each sub-picture period (ie, during the red, green or blue sub-picture period), and all the scan lines are written and wait for a reaction time (ie, After the reaction time for the liquid crystal molecules is turned on, the light-emitting diode backlight mode is turned on. A sub-light source (ie, a red, green, or blue sub-light source) of the LED backlight module, and such a driving method will cause insufficient light on time of the LED backlight module during each sub-picture period. This also causes the brightness of the overall display of the color sequential liquid crystal display to be dark.

In view of the above, an object of the present invention is to provide a driving device and method for a display, which can effectively solve the problem of color shift of a color sequential liquid crystal display, and can further improve the brightness of the overall display of the color sequential liquid crystal display.

Another object of the present invention is to provide a color sequential liquid crystal display having colorlessness and high display brightness.

Based on the above and other objects, the present invention provides a driving method for a display, comprising the steps of: first, during the writing of data of a scan line during at least one of the picture frames during a picture period of the display; Perform a black screen technology. Then, after the data writing of the partial scan lines is performed during the sub-picture period and waiting for a reaction time, a sub-light source of the backlight module is turned on.

According to an embodiment of the invention, during the process of writing the data of the scan line during the sub-picture, the method further includes performing an over-driving technique to match the black-frame technology.

According to an embodiment of the invention, the black screen technology is to simultaneously write black data to the partial scan lines, or sequentially write black data to the partial scan lines.

According to an embodiment of the invention, the display of the present invention is driven The method is suitable for driving a color sequential liquid crystal display.

According to an embodiment of the invention, the sub-picture period includes a red sub-picture period, a green sub-picture period, or a blue sub-picture period, or a combination of the three.

According to an embodiment of the invention, the backlight module is a light-emitting diode backlight module, and the sub-light source comprises a red light source, a green light source or a blue sub-light source.

From another point of view, the present invention provides a display driving device including a timing controller, a gate driver, a source driver, and a backlight module driving unit. The gate driver is coupled to the display panel and controlled by the timing controller for sequentially turning on the scan lines in the display panel. The source driver is coupled to the display panel and controlled by the timing controller for writing the corresponding data to the scan line opened by the gate driver in conjunction with the gate driver. The backlight module driving unit is coupled to the backlight module and controlled by the timing controller for driving the backlight module.

The timing controller is matched with the gate driver, the source driver and the backlight module driving unit to perform a black screen technology during the writing of the scan line data during at least one sub-picture period of one screen period of the display And after the data writing of the partial scan lines is completed during the sub-picture period and waiting for a reaction time, a sub-light source of the backlight module is turned on.

According to an embodiment of the invention, the timing controller is further configured with a gate driver, a source driver and a backlight module driving unit to perform an overdrive technique during data writing of the scan line during the sub-picture. To match the black screen technology.

According to an embodiment of the invention, the black screen technology is to simultaneously write black data to the partial scan lines, or sequentially write black data to the partial scan lines.

According to an embodiment of the invention, the driving device of the display of the present invention is adapted to drive a color sequential liquid crystal display.

According to an embodiment of the invention, the sub-picture period includes a red sub-picture period, a green sub-picture period, or a blue sub-picture period, or a combination of the three.

According to an embodiment of the invention, the backlight module is a light-emitting diode backlight module, and the sub-light source comprises a red light source, a green light source or a blue sub-light source.

According to an embodiment of the invention, the display panel is a liquid crystal display panel.

From another point of view, the present invention provides a display comprising a display panel, a backlight module, and the driving device of the display provided by the present invention.

The driving device and method for displaying a display of the present invention are suitable for driving a color sequential liquid crystal display, which mainly performs a process of writing data of a scan line during at least one sub-picture of one picture period of a color sequential liquid crystal display. A black screen technology and/or an overdrive technology is performed, and then a sub-light source of the backlight module is turned on after the data writing of the partial scan lines is performed during the sub-picture period and waits for a reaction time. In this way, not only can the problem of color shift of the color sequential liquid crystal display be effectively solved, but also the brightness of the overall display of the color sequential liquid crystal display can be improved.

The above and other objects, features and advantages of the present invention will become more <

The object of the present invention is to solve the problem of color shift of a color sequential liquid crystal display and to improve the brightness of the overall display of a color sequential liquid crystal display. The following description of the technical features and functions of the present invention will be described in detail for those skilled in the art.

FIG. 1 is a system block diagram of a display 100 according to an embodiment of the invention. Referring to FIG. 1 , the display 100 of the present embodiment will be described by taking a color sequential type LCD as an example, and includes a liquid crystal display panel (LCD panel) 101 and a light-emitting diode backlight module ( LED backlight module 103, and the invention comprising a timing controller (T-con) 107, a gate driver 109, a source driver 111 and a backlight module driving unit 113 Drive device 105.

In this embodiment, the liquid crystal display panel 101 has a plurality of pixels (pixels, not shown) arranged in an array for displaying the image images for viewing by the user. The LED backlight module 103 is used to sequentially supply three (three) sub-sources of red (R), green (G), and blue (B) to the liquid crystal display panel 101. However, since the configuration of the liquid crystal display panel 101 and the light-emitting diode backlight module 103 and the effects thereof are well known to those skilled in the art, in order not to confuse the spirit of the present invention, this is no longer the case. Describe it.

In general, the color sequential liquid crystal display 100 has three sub-picture periods (ie, red, green, and blue sub-picture periods) in one frame period, and is an example of displaying 60 pictures per second of a moving image. The frame rate of the color sequential liquid crystal display 100 can be as high as 180 Hz (that is, 5.56 ms per sub-picture period). For this reason, the liquid crystal molecules of the pixels in the liquid crystal display panel 101 usually adopt fast liquid crystal molecules (for example, OCB liquid crystal molecules, but are not limited thereto), and the driving method of the color sequential liquid crystal display 100 is adopted.

As can be seen from the above, the drive device 105 is mainly composed of the timing controller 107, the gate driver 109, the source driver 111, and the backlight module driving unit 113. The gate driver 109 is coupled to the liquid crystal display panel 101 and controlled by the timing controller 107, which is mainly used to sequentially turn on scan lines (not shown) in the liquid crystal display panel 101. The source driver 111 is coupled to the liquid crystal display panel 101 and controlled by the timing controller 107. The main purpose is to cooperate with the gate driver 109 to write corresponding data (eg, pixel data) to the gate driver 109. The scan line that is turned on.

The backlight module driving unit 113 is coupled to the LED backlight module 103 and controlled by the timing controller 107 for driving the LED backlight module 103. The timing controller 107 is matched with the gate driver 109, the source driver 111 and the backlight module driving unit 113 for at least one sub-picture period of one of the picture periods of the color sequential liquid crystal display 100 (this embodiment will first be green) The screen period is taken as an example for explanation, but the spirit of the present invention is not limited thereto) in the process of writing data of the scan line. The green (G) sub-light source of the LED backlight module 103 is turned on after the black screen technology is inserted and the data of the partial scan lines is written during the green sub-picture and waits for a reaction time.

For example, FIG. 2 is a schematic diagram of a black screen technology according to an embodiment of the present invention. Referring to FIG. 1 and FIG. 2 together, it can be easily seen from FIG. 2 that the present embodiment is exemplified by a liquid crystal display panel 101 having a resolution of 320*240 as an image pattern array (VGA), but is not limited thereto. And the mark Tf in FIG. 2 is represented as one picture period (ie, 16.67 ms) of the color sequential type liquid crystal display 100; the marks Tr, Tg, and Tb are respectively indicated as red, green, and blue sub-pictures of the color sequential type liquid crystal display 100. During the period (all are 5.56ms); the marks G1 to G320 are shown as the scanning lines of the liquid crystal display panel 101; the marks R, G, and B are respectively indicated by the red (R) and green (G) of the light-emitting diode backlight module 103. The lighting time with the blue (B) sub-light source; and the mark BFI is indicated as the black data.

In this embodiment, the timing controller 107 is matched with the gate driver 109, the source driver 111, and the backlight module driving unit 113, and only during the green sub-picture period Tg in the picture period Tf of the color sequential liquid crystal display 100 is The black screen technology is executed during the data writing of the scanning lines G1 G G320, and the data of some scanning lines (for example, 160 scanning lines) is written during the green sub-picture period Tg and waits for a reaction time. The green (G) sub-light source of the LED backlight module 103 is turned on.

More specifically, the timing controller 107 is matched with the gate driver 109, the source driver 111, and the backlight module driving unit 113, so that the green sub-picture period Tg in the picture period Tf of the color sequential type liquid crystal display 100 is Before the data of the scanning lines G1 to G160 is written, black data is simultaneously written to the scanning lines G1 to G160 to compensate for the degree to which the color sequential liquid crystal display 100 is affected by the time-varying effect of the liquid crystal capacitance. Then, after the data of the scan lines G1 G G160 is written and waits for a reaction time during the green screen, the timing controller 107 controls the LED backlight module 103 to turn on the LED backlight module. The green (G) sub-light source of 103.

Thereafter, the timing controller 107 is further configured with the gate driver 109, the source driver 111, and the backlight module driving unit 113 so that the green sub-picture period Tg in the picture period Tf of the color sequential liquid crystal display 100 is on the scanning line G161. Before the data of the ~G320 is written, the black data is simultaneously written to the scanning lines G161 to G320 to compensate for the degree to which the color sequential liquid crystal display 100 is affected by the time-varying effect of the liquid crystal capacitor. Finally, after the data of the scan lines G161~G320 is written and waits for a reaction time during the green screen, the timing controller 107 controls the LED backlight module 103 again to turn on the LED backlight module. The green (G) sub-light source of 103.

In this way, since the driving device 105 of the embodiment separately writes the black data at the same time before the data writing is performed on the scanning lines G1 G G160 and G 161 G G320, the color sequence liquid crystal display 100 is compensated by the liquid crystal capacitor. In essence, the time-varying effect affects the degree, so the color-sequence type liquid crystal display 100 of the present embodiment is less affected by the time-varying effect of the liquid crystal capacitance (LC capacitance) to cause a color shift phenomenon. .

It should be noted that, in another embodiment of the present invention, the driving device 105 may also separately write the black data before the data writing in the scan lines G1 G G160 and G161 G G320, and thus A method different from the black screen technology of the previous embodiment (that is, simultaneous writing of black data) can also compensate for the extent to which the color sequential liquid crystal display 100 is affected by the time-varying effect of the liquid crystal capacitor in nature, and can also cause The color sequential liquid crystal display 100 is less susceptible to color shift due to the inherent time-varying effect of the liquid crystal capacitor.

However, the driving device 105 of the present embodiment causes the addressing time allocated to the scanning lines G1 to G320 to be written in the Tg during the period of occupying too many green sub-pictures in order to avoid being affected by the black-screening technique. Therefore, the timing controller 107 of the present embodiment is further matched with the gate driver 109, the source driver 111, and the backlight module driving unit 113, and the green sub-picture period Tg in the picture period Tf of the color sequential type liquid crystal display 100 is In the process of writing data of the scanning lines G1 to G320, over driving technology (OD technology) is executed to match the black screen technology.

In this way, the user can adjust the amplitude of the black data written to the scan lines G1 G G320 according to the actual design requirements, so as to reduce the Tg of the green sub-picture period occupied by the driving device 105. The time allocated to the scan lines G1 to G320 for data writing. In addition, since the red (R), green (G), and blue (B) sub-light sources of the LED backlight module 103 are illuminated twice during the red, green, and blue sub-picture periods Tr, Tg, and Tb, Its individual lighting time R, G, B will pull Therefore, the brightness displayed by the color sequential liquid crystal display 100 as a whole is also greatly improved.

In addition, the driving device 105 of the present embodiment performs scanning during at least one sub-picture period (ie, red, green or blue sub-picture period Tr, Tg or Tb) in one picture period Tf of the color sequential liquid crystal display 100. The mechanism for performing the black screen technology in the process of writing the data of the lines G1 to G320 can also be associated with the critical voltage (Vcr) of the fast liquid crystal molecules (ie, OCB liquid crystal molecules) of the pixels in the liquid crystal display panel 101. It becomes smaller, so that the OCB liquid crystal molecules in the Bend state are not easily turned back to the Splay state, and are continuously maintained in a displayable state.

However, the spirit of the present invention is not limited to the embodiments of the above embodiments. FIG. 3 is a schematic diagram of a black screen technology according to another embodiment of the present invention. Referring to FIG. 1 to FIG. 3, it can be easily seen from FIG. 3 that the driving device 205 of the present embodiment performs the scanning line G1 in the green sub-picture period Tg in the picture period Tf of the color sequential liquid crystal display 100. In the process of writing the data of the G320, the black screen technology is executed, and the red picture period Tr in the picture period Tf of the color sequence type liquid crystal display 100 is also in the process of writing the data of the scanning lines G1 to G320. Perform black screen technology. As a result, the numerous advantages described in the above embodiments can be further improved.

It is further worth mentioning that the driving device 205 of the present invention is not limited to the data recording of the scanning lines G1 G G320 during the green sub-picture period Tg in the picture period Tf of the color sequential liquid crystal display 100. In the process The black screen technology is executed, or the red and green sub-picture periods Tr and Tg in the picture period Tf of the color sequence type liquid crystal display 100 are executed in the process of writing data of the scan lines G1 to G320. .

In other words, in another embodiment of the present invention, the driving device 205 of the present invention can perform the scanning line G1 according to any combination of the red, green, and blue sub-picture periods Tr, Tg, and Tb in the picture period Tf. The black screen technology is executed during the writing of the G320 data, and many of the various modified embodiments are one of the categories to be protected by the present invention.

To this end, in order to make the technical knowledge of the driving device 205 of the present invention known to those skilled in the art, the technical effects are obtained. The measurement results of several experiments will be listed below for reference to those of ordinary skill in the art.

4 is a schematic diagram showing the effect of a time-varying effect of a liquid crystal capacitor in a conventional color sequential liquid crystal display, wherein the horizontal axis represents time (ms) and the vertical axis represents luminance (nits). FIG. 5 is a schematic diagram showing the influence of the time-varying effect of the liquid crystal capacitor on the color sequence type liquid crystal display 100 of the present invention, wherein the horizontal axis represents time (ms) and the vertical axis represents brightness (nits). Please refer to FIG. 4 and FIG. 5 together. It can be easily seen from the circled area A of FIG. 4 that the brightness of the different gray levels (ie, L0 and L63) converted to the same gray level (ie, L127) may be inconsistent. Therefore, the image displayed by the conventional color sequential liquid crystal display will have a color shift.

However, it can be easily seen from the circled area B of FIG. 5 that the different gray levels (ie, L0, L31, L63, L95, L127, L159, L191, L223) are converted to the same gray level (ie, L255). The brightness of the liquid crystal display 100 of the present invention is not affected by the liquid crystal capacitance. The effect of the time-varying effect causes the color shift of the image image it presents.

It is believed that the technical features, functions, and spirits of the present invention should be understood by those of ordinary skill in the art of the present invention. Therefore, in the following, the driving method of at least one display will be summarized according to the content disclosed in the above embodiments to those skilled in the art.

6 is a flow chart of a driving method of a display according to an embodiment of the invention. Referring to FIG. 6, the driving method of the display of the embodiment includes the following steps. First, as described in step S601, during the at least one sub-picture period of one of the screen periods of the display, the data writing process of the scan line is performed. A black screen technology is inserted. It is worth mentioning that the driving method of the display of the embodiment is suitable for driving a color sequential liquid crystal display, and the sub-picture period includes a red sub-picture period, a green sub-picture period or a blue sub-picture period, or the three The combination between the two.

Then, as described in step S603, after the data writing of the partial scan lines is performed during the sub-picture period and waiting for a reaction time, a sub-light source of the backlight module is turned on. In the embodiment, during the process of writing the data of the scan line during the sub-picture, the method further includes performing an over-driving technique to match the black-frame technology, and the black-screen technology may be simultaneous or The black data is sequentially written to the partial scan lines. In addition, the backlight module is a light-emitting diode backlight module, and the sub-light source includes a red sub-light source, a green sub-light source or a blue sub-light source.

Therefore, according to the driving method of the display provided by the present invention, it is known that any of the sub-picture periods of the color sequential liquid crystal display (that is, during the red, green or blue sub-picture period) before the data writing of the scan lines is performed, It is within the scope of the present invention to perform any type of black insertion technique in a state in which the sub-light source corresponding thereto is not illuminated.

In summary, the driving device and method for displaying a display of the present invention are suitable for driving a color sequential liquid crystal display, which mainly performs scanning lines during at least one sub-picture period of one picture period of the color sequential liquid crystal display. During the data writing process, a black screen technology and/or an overdrive technology is executed, and then the data writing of the partial scan lines is performed during the sub-picture period and waits for a reaction time before the backlight module is turned on. A sub-light source. In this way, not only can the problem of color shift of the color sequential liquid crystal display be effectively solved, but also the brightness of the overall display of the color sequential liquid crystal display can be improved, and the OCB liquid crystal molecules in the curved state can not be easily turned back. A number of advantages of the state of the curved state.

While the invention has been described above in terms of a plurality of embodiments, which are not intended to limit the scope of the invention, the invention may be modified and modified without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

100‧‧‧Color sequence LCD

101‧‧‧LCD panel

103‧‧‧Lighting diode backlight module

105‧‧‧ drive

107‧‧‧Timing controller

109‧‧‧gate driver

111‧‧‧Source Driver

113‧‧‧Backlight module drive unit

One screen period of Tf‧‧‧ color sequential LCD

Red, green, and blue sub-picture periods of Tr, Tg, Tb‧‧‧ color sequential liquid crystal displays

G1~G320‧‧‧ scanning line of LCD panel

Lighting time of red (R), green (G) and blue (B) sub-light sources for R, G, B‧‧ ‧ LED backlight modules

BFI‧‧‧Writing black material

A, B‧‧‧ circled area

S601~S603‧‧‧ respective steps of the driving method of the display of the present invention

FIG. 1 is a system block diagram of a display 100 according to an embodiment of the invention.

FIG. 2 is a schematic diagram of a black screen technology according to an embodiment of the invention.

FIG. 3 is a schematic diagram of a black screen technology according to another embodiment of the present invention.

FIG. 4 is a schematic diagram showing the effect of a time-varying effect of a liquid crystal capacitor on a conventional color sequential liquid crystal display.

FIG. 5 is a schematic diagram showing the effect of the time-varying effect of the liquid crystal capacitor on the color sequence type liquid crystal display 100 of the present invention.

6 is a flow chart of a driving method of a display according to an embodiment of the invention.

S601~S603‧‧‧ respective steps of the driving method of the display of the present invention

Claims (28)

A method for driving a display, comprising the steps of: performing a black-black screen technique during data writing of a scan line during at least one of the picture periods of one of the screens of the display; and performing during the sub-picture period After a part of the scan line is written and waits for a reaction time, a sub-light source of a backlight module is turned on, wherein during the sub-picture, the over-driving technology is further included in the process of writing the data of the scan line. With the black screen technology, the time that the black screen technology is executed during the sub-picture period is reduced. The driving method of the display of claim 1, wherein the black screen technology simultaneously writes a black material to the partial scan line, and the overdrive technology is to adjust the write to the partial scan line. The amplitude of the black data. The method for driving a display according to claim 1, wherein the black screen technology sequentially writes a black data to the partial scan line, and the overdrive technology adjusts the write to the partial scan. The amplitude of the black data of the line. The driving method of the display of claim 1, wherein the driving method is adapted to drive a color sequential liquid crystal display. The method for driving a display according to claim 4, wherein the sub-picture period includes a red sub-picture period, a green sub-picture period, or a blue sub-picture period. The driving method of the display of claim 4, wherein the sub-picture period includes a red picture period, a green picture period And a combination of the three during a blue screen. The driving method of the display device of claim 4, wherein the backlight module is a light-emitting diode backlight module. The driving method of the display of claim 7, wherein the sub-light source comprises a red light source, a green light source or a blue light source. A display driving device includes: a timing controller; a gate driver coupled to a display panel and controlled by the timing controller for sequentially turning on a scan line in the display panel; a source driver, The display panel is coupled to the timing controller for writing the corresponding data to the scan line opened by the gate driver in cooperation with the gate driver; and a backlight module driving unit coupled to the The backlight module is controlled by the timing controller for driving the backlight module; wherein the timing controller matches the gate driver, the source driver and the backlight module driving unit for the display Performing a black screen technique during the writing of the data of the scan line during at least one sub-picture period of a picture period, and performing data writing of a part of the scan lines during the sub-picture period and waiting for a reaction time, Turning on a sub-light source of the backlight module, wherein the timing controller is further matched with the gate driver, the source driver, and the backlight module driving unit for the sub-picture Between the scanning lines during the data writing process is performed in a period of overdrive technique to match the picture screen black insertion technique, thereby reducing the black insertion in the sub-picture in the art The time of execution. The driving device of the display of claim 9, wherein the black screen technology is to simultaneously write a black material to the partial scan line, and the overdrive technology is to adjust the write to the partial scan line. The amplitude of the black data. The driving device of the color sequential liquid crystal display device of claim 9, wherein the black screen technology sequentially writes a black material to the partial scan line, and the overdrive technology is to adjust the write to The amplitude of the black data of the partial scan line. The driving device of the display of claim 9, wherein the driving device is adapted to drive a color sequential liquid crystal display. The driving device of the display of claim 12, wherein the sub-picture period comprises a red picture period, a green sub-picture period or a blue sub-picture period. The driving device of the display of claim 12, wherein the sub-picture period comprises a combination of a red picture period, a green picture period, and a blue screen period. The driving device of the display device of claim 12, wherein the backlight module is a light emitting diode backlight module. The driving device of the display of claim 15, wherein the sub-light source comprises a red light source, a green light source or a blue light source. The driving device of the display of claim 12, wherein the display panel is a liquid crystal display panel. A display device includes: a display panel; a backlight module; and a driving device coupled to the display panel and the backlight module for performing scanning lines during at least one of the screen periods of one of the screens of the display During the process of writing data, a black screen technology is executed, and after a part of the scanning line data is written and waits for a reaction time, a sub-light source of the backlight module is turned on, wherein the driving During the sub-picture period, the device further performs an overdrive technology to match the black screen technology during the data writing of the scan line, thereby reducing the time that the black screen technology is executed during the sub-picture period. The display device of claim 18, wherein the driving device comprises: a timing controller; a gate driver coupled to the display panel and controlled by the timing controller for sequentially turning on the liquid crystal display a scan line in the panel; a source driver coupled to the display panel and controlled by the timing controller for cooperating with the gate driver to write corresponding data to the scan line turned on by the gate driver; And a backlight module driving unit coupled to the backlight module and controlled by the timing controller for driving the backlight module; wherein the timing controller matches the gate driver, the source driver, and the The backlight module driving unit performs the black insertion screen technology. The display device of claim 19, wherein the timing controller further matches the gate driver, the source driver and the backlight module driving unit to perform data writing on the scan line during the sub-picture. The overdrive technology is executed during the process to match the black screen technology. The display of claim 20, wherein the black screen technology simultaneously writes a black material to the partial scan line, and the overdrive technique is to adjust the write to the partial scan line. The amplitude of the black data. The display device of claim 20, wherein the black screen technology sequentially writes a black material to the partial scan line, and the overdrive technology adjusts the write to the partial scan line. The amplitude of the black data. The display of claim 18, wherein the display comprises at least one color sequential liquid crystal display. The display of claim 23, wherein the sub-picture period comprises a red picture period, a green sub-picture period or a blue sub-picture period. The display of claim 23, wherein the sub-picture period comprises a combination of a red picture period, a green picture period, and a blue screen period. The display device of claim 23, wherein the backlight module is a light-emitting diode backlight module. The display of claim 26, wherein the sub-light source comprises a red light source, a green light source or a blue light source. The display of claim 23, wherein the display panel is a liquid crystal display panel.