Method for driving liquid crystal display panel and liquid crystal display device

#The present invention relates to a multi-line selection (MLS) drive method in which a plurality of scanning electrodes are simultaneously selected mainly in a simple matrix liquid crystal display panel and mainly has for its object to provide a flickerless gradation display method.

#In the simple matrix liquid crystal display panel, a liquid crystal material having a high response speed of not more than 100 msec. is desirably employed so as to deal with display of moving pictures. However, if response speed of liquid crystal is raised, a so-called frame response phenomenon occurs and thus, such problems as flicker and drop of contrast arise. In order to solve such problems, a prior art technique called a “multi-line selection (MLS) drive method” in which a plurality of L scanning electrodes are simultaneously selected is known. A summary of a MLS drive method for selecting four scanning electrodes simultaneously, which is abbreviated as “MLS4”, hereinafter, is given as follows.

#In MLS drive, an orthogonal function 215 expanded by an orthogonal function generator 213 performs an H×S matrix operation by an input signal 211 and an arithmetic unit 212 and outputs to the result to a segment signal line 214 as shown in FIG. 10. In the case of simultaneous selection of four rows, the orthogonal function 215 expands a four-row and four-column seed function into the number of scanning electrodes, 168 in this example as shown in FIG. 11. Therefore, the number of the columns is the number of the scanning electrodes and has a value of “1” or “−1” at the time of selection of the scanning electrodes and a value of “0” at the time of the nonselection. Drive waveforms of the scanning electrodes at this time are shown in FIG. 12. As shown in FIG. 12, since four scanning electrodes are selected simultaneously, one frame of the 168 scanning electrodes is constituted by first to fourth sub-frames. Supposing that the input signal 211 does not change among the first to fourth sub-frames, the matrix operation of the orthogonal function 215 is performed. Hereinafter, a principle of the MLS drive method is described and on-state and off-state effective voltages are obtained.

#FIG. 1 is a functional block diagram of a first embodiment of the present invention.

#FIG. 2 is a view explanatory of shift of one example (117 gradation pattern of MLS4 drive) of a gradation pattern in the first embodiment of the present invention.

#FIGS. 3A and 3B are views explanatory of shift of a 1/7 gradation pattern and a 2/7 gradation pattern of MLS drive in a second embodiment of the present invention, respectively.

#Hereinafter, embodiments of the present invention are described with reference to the drawings.

#(First Embodiment)

#A first embodiment of the present invention relates to a drive method of mainly driving, by a multi-lie selection (MLS) drive method for simultaneously driving a plurality of L scanning lines, a simple matrix liquid crystal display panel in which one frame is constituted by L sub-frames and more particularly, to a drive method in which control is performed by a frame rate control (FRC) method as a gradation display method. A gradation register for storing a gradation pattern for displaying an ON state and an OFF state at each gradation level, a gradation control circuit for performing a shift arithmetic operation of the gradation pattern of the gradation register and a gradation selecting circuit provided on each signal electrode are employed. The present invention is characterized in that by the gradation control circuit, the gradation pattern of the gradation register is subjected to a shift arithmetic operation for each frame synchronously with a vertical synchronous signal, a shift arithmetic operation for each line synchronously with a horizontal synchronous signal and a shift arithmetic operation for each sub-frame such that gradation display is performed.