JPS61121086A - Driving of phase shift type liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a display device composed of a cholesteric-nematic phase change type liquid crystal, which has a display memory function and is called a storage type liquid crystal.

[Conventional technology]

FIG. 5 is a flow chart for explaining the process of displaying using a phase change type liquid crystal.

As is clear from the figure, (1) Initialization (2) Writing (3) Memory display This is done in the following order.

FIG. 6 is a diagram illustrating the relationship between the light transmittance of the liquid crystal cell and the voltage applied to the liquid crystal cell when performing the above display.

In the figure, the vertical axis represents transmittance, and the horizontal axis represents cell applied voltage.

First, when initializing, set 2■ to all cells. A voltage of s (H) is applied to make the entire structure transparent.

Next, when writing is performed, a voltage O is applied to the cell to be clouded, that is, a cell to be written, and a voltage 2vo is applied to the cell to be kept transparent.

Next, when performing memory display, a memory voltage vo is applied to all cells.

In Figure 6, the black circle (・) indicates a transparent cell, and the inner circle (0)
represent cloudy cells.

Incidentally, the relationship between . and O is the same in the following description.

FIG. 7 is a diagram illustrating the main parts of four cells extracted from a liquid crystal panel in which cells are arranged in a matrix.

In the figure, Y+ and Y2 indicate row lines (represented by Y), and X+ and X2 indicate column lines (represented by X), respectively.

FIG. 8 is a timing chart of pulses applied to each cell when displaying as shown in FIG. 7.

Here again, the flow of (1) initialization, (2) writing, and (3) memory display remains unchanged, and the relationship between the voltages applied to each cell is also as described above. In addition, in Figure 8,
Cells related to column line XI and row line Y, and cells related to column line Xz and row line Y1 are displayed as representing transparent and cloudy operations, respectively.

As is clear from the figure, during writing, voltage 2v0 continues to be applied to cells associated with column line X and row line Y after initialization, and thereafter voltage 2v0 is applied. is applied to move to memory display, and
A voltage of 0 is once applied to the cells related to the column line Xz and the row line Y, and the cells become cloudy, and then the voltage is applied to the cell. It can be recognized that is applied and the display shifts to memory display.

[Problem that the invention seeks to solve]

By the way, to write on the liquid crystal, it takes several [m seconds] to several tens [m seconds] per line, for example, 4
On an LCD panel with 50 [lines] of scanning lines, it takes a long time ranging from 1 [second] to several [seconds] to rewrite one screen, and it takes a long time to rewrite a part of the displayed screen. Even if there is, it requires rewriting the entire screen.

Therefore, when it becomes necessary to rewrite a part of the displayed screen, if the entire screen is rewritten by following steps (1) to (3) above, for example, in the case of keyboard input, it is difficult to A problem arises in that it cannot be followed.

Therefore, the inventors of the present invention previously provided a technology in which when rewriting a display using a phase change type liquid crystal, rewriting is performed line by line by selectively scanning only the squares that require rewriting. However, sufficient rewriting speed has not yet been obtained.

The reason for this will be explained with reference to FIGS. 9 and 10, which are similar to FIG. 6.

That is, as shown in FIG. 9, when a transparent cell is made cloudy, the operation is completed in several milliseconds as described above;
As shown in Figure 10, it takes several tens of milliseconds to make a cloudy cell transparent, so if there are 10 lines to rewrite, it will take several hundred milliseconds in total. However, even though it is rewriting line by line, it is difficult to follow the key manually when writing. It is also possible to initialize the entire line to be rewritten, but if you do this, the entire line becomes transparent for a moment, and this can be seen clearly, so it may be a problem in terms of display quality. Undesirable.

In the present invention, when rewriting a part of the display screen of a phase change type liquid crystal panel, it is possible to perform high-speed processing by using both initialization and writing for the block that requires rewriting (for example, one character). rewriting and displaying with good quality.

[Means for solving problems]

In the method for driving a phase change type liquid crystal display device according to the present invention, when rewriting a display using a phase change type liquid crystal, only a block that requires rewriting, for example, one character, is initialized, and then, Writing is performed by selectively scanning only the rows that include the block.

[Effect]

In this way, it is possible to perform rewriting at a much higher speed than a conventional driving method, for example, a driving method in which rewriting is performed row by row.

〔Example〕

FIGS. 1A to 1C are explanatory plan views of essential parts of a matrix liquid crystal panel for explaining one embodiment of the present invention.

In the figure, LP indicates a liquid crystal panel, b, . . . bz□ indicate blocks, and 'II+C2□ indicates a row.

Now, as shown in FIG. 1(a), alphabets are displayed on the liquid crystal panel LP, and the case where N, which is surrounded by a broken line, is to be rewritten to M will be described.

As shown in FIG. 1 (bl), a common initialization is performed on the cells included in the block bll to be rewritten and all are made transparent.

As shown in FIG. 1 (C1), the process ends by writing the row C11 that includes the block bl+ to be rewritten.

The series of operations described above can be better understood by referring to the following description of FIG.

In the phase change type liquid crystal panel consisting of 4x4 matrix cells shown in Fig. 2, all blocks surrounded by broken lines
The case where the display of block a is rewritten to the display shown in block a is also shown in the timing chart of FIG.
This will be explained with reference to a diagram showing the relationship between transmittance and cell applied voltage.

In FIGS. 2 and 3, the same parts as those explained with respect to FIGS. 5 to 10 are indicated by the same symbols, and Y3 and Y4 are row lines, and X3 and X4 are Needless to say, it is a column line.

In this case as well, as in the conventional example described above, after the process of (11 initialization = (2) writing - (3) memory display), voltage ■ is currently applied to all cells to perform static display. shall be taken as a thing.

Now, in order to rewrite, (4) block initialization =
The process of (5) partial writing and (6) memory display will be performed, but here we will consider the case where only the display of block all is rewritten so that it appears in block azz.

In this case, in addition to FIGS. 1 to 3, it will be easier to understand by referring to FIG. 4, which shows the principle of partial rewriting using waveforms.

First, (0, 3
By applying a voltage of (v, ) or (3V,,O), a voltage of ±3Vo is commonly applied to the group of cells to be rewritten to perform initialization.

At this time, the other row lines and column lines have a voltage of 2■ as shown in FIG. Or ■. By applying
As shown in FIG. 3, a voltage of ±vO is applied to the cell itself to maintain the display.

Next, (5) Since the block all to be rewritten by partial writing exists on row lines Y and Y2, selective scanning is performed only on these two scan lines, and column lines X1 and X2, etc. Predetermined signals are applied to all data lines and all cells on row lines Y1 and Y2 are written to the state of block a2□ as seen in FIG.

At this time, since the cells on rows Y and Y4 are not rewritten, the voltage v0 is continued to be applied as in the step (3) of memory display.

In the case of the above embodiment, the cell operation as shown in FIG. 9, that is, the time required to change from a transparent state to a cloudy state is T, and the cell operation as shown in FIG. In other words, the time required to change from a cloudy state to a transparent state is l0
TI and the number of lines to be rewritten is 10, then 10TI + (TI XIO line) = 20TI
By the way, according to the conventional technology, 10T,
Xl0-100T.

becomes. In addition, when rewriting, the address operation is only visible in a limited area of the screen, unlike the conventional method.
There are no phenomena such as white lines running across the entire screen, and the display quality is good.

Now, next, a case in which the driving method of the present invention is implemented will be explained specifically and in detail.

In order to realize the driving method explained in the above embodiment, CMO5 (comp 1 emmen t a r
y metal oxide semiconductor
Although it is also possible to output a voltage of 0 to 3 vo to the column electrodes and row electrodes using an analog switch consisting of a The drive circuit configuration for realizing the above-described drive waveform will be described with reference to a 4×4 matrix.

FIG. 11 shows a timing chart of a liquid crystal panel and a specific voltage waveform for driving it.

FIG. 12 is a circuit diagram showing a drive circuit configuration for realizing the voltage waveform shown in FIG. 11.

FIG. 13 is a waveform diagram showing one cycle of the drive voltage waveform,
This indicates that the one cycle consists of a first half cycle and a second half cycle for driving the liquid crystal panel.

In Fig. 12, b=J (1rJ-1 to 4) is a liquid crystal cell, X and -X4 are column electrodes, Y4 is a row electrode, and QxiJ (r, J = 1 to 4) is A switching element that applies voltage to the column electrode, Qy=j (i, j=1
~4) is a switching element that applies voltage to the row electrode, V,
is the power supply of the column drive circuit, V7 is the power supply of the row drive circuit, and XB and Ym are the reference voltage pulsers, respectively.

In this circuit, the voltage applied to the column electrode Xl-X4 is the switching element Q = j (i + J = 1 to 4)
The voltage applied to the row electrodes Y, ~Y4 is switched by the switching element Qy=j (1゜j-1
~4).

The switching elements QX, , (r = l to 4) and the switching elements Qyi+ (i -1 to 4) are connected between the power supplies VX and Vv of the column and row drive circuits, respectively, and a reference potential, and the reference potential is the reference potential. Voltage pulser X,
and Y are generated, and the reference voltage pulsers X++ and YB output a pulse Vo periodically or non-periodically. Note that the power supply VV also serves as a voltage selection circuit for switching the power supply of the row drive circuit group between VO and 2VO.

Now, FIG. 11 is a timing chart showing a drive voltage waveform similar to that in FIG. 2, and is for explaining the method of outputting voltage from the drive circuit.

In the figure, the hatched parts and black parts indicate the voltage components output from the reference voltage pulsers X3 and Yll.

That is, in this specific example, by superimposing a predetermined voltage on the reference voltage, a binary output switching element is used to generate a voltage of 0 to 3.

It has a configuration that can output four types of voltage, and as shown in Figure 13, one of the ground or pulsed reference potentials can be output.
Selection and non-selection signals can be distributed to each electrode depending on whether the voltage from the switching element is superimposed in the first half cycle (la, 2a, 3a) or in the second half cycle.

Here, block initialization will be explained with reference to FIG.

The illustrated pulse v0 is output from the column and row reference voltage pulsers vX and VV. Here, the switching element QX of the column and row drive circuit including the block a33 to be rewritten is
=+ (i=1-2) and switching element Q□,
(i = 1 to 2) is turned on when the reference voltage pulse is Q. 3). is output, and in the remaining ° half cycle, when the reference voltage pulse is zero (V), the switching elements Q, 1. (i
= l~2) and switching element Q□2 (i=
1 to 2) are turned on and 3V and zero [■] are applied to the column and row electrodes as shown.

For other column and row electrodes, the reference voltage pulse is zero (V
), the switching element QX,, (i !3゛～
4) and switching element Qy++ (i = 3~
4) is turned on, and the reference voltage pulse is ■. At the time of , switching element Q-tz (i = 3 to 4) and switching element Q-iz (j = 3 to 4) are turned on, as shown in the figure. and 2■. It is possible to output a voltage of .

In addition, in this block initialization, the voltage selection circuit which is the power supply
It is switched to the VV□ side so as to give .

In the subsequent partial writing, the reference voltage pulser Xi of the column drive circuit is always set to zero (V), and the reference voltage pulser YB of the row drive circuit is set to vo and v (V) as in the block initialization.
outputs a pulse of In this case, it is assumed that the voltage selection circuit, which is the power source 7, is switched to the VVI side.

Of the row electrodes Y1 and Y2 that perform selective scanning, first, when scanning the row electrode Y, the switching elements Q are turned on at the same timing as the reference voltage pulser YB outputs the pulse v0 only to the row electrode Y1. For the other row electrodes Y2 and Y3, the switching element Qyiz (i=
2 to 3) are turned on.

At the timing when the reference voltage pulser Yll becomes zero (V), the above procedure is performed in the opposite manner. At this time, the column electrodes are exposed to 2 cm from the switching element at a predetermined timing as shown in FIG. 11 depending on whether the column electrodes are transparent or cloudy. It is good to output .

Partial writing can be performed in the same manner as described above also when scanning the row electrode Y2.

In addition, "initialization" and "writing" shown in Fig. 11
, "Memory display" can also output a predetermined voltage to each electrode in the same process as described above.

〔Effect of the invention〕

In the method for driving a phase change type liquid crystal display device according to the present invention,
When rewriting the display, first, only the blocks that need to be rewritten are initialized, and then only the rows that include the blocks are selectively scanned to perform row-by-row rewriting.

Therefore, when rewriting a part of the display, the entire screen is rewritten, or compared to conventional drive methods that simply rewrite line by line, extremely high-speed rewriting is possible, and the display at the time of rewriting is The quality is also good.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the main parts of a liquid crystal panel for explaining the outline of rewriting by implementing the present invention, and Fig. 2 is a diagram showing a liquid crystal panel and driving it for explaining an embodiment of the present invention. Timing chart of voltage waveform, Figure 3 is a diagram showing the relationship between transmittance and cell applied voltage, Figure 4 is a diagram to explain partial rewriting using the applied voltage waveform, and Figure 5 is a diagram showing the relationship between transmittance and cell applied voltage. A flow chart of the display process, Figure 6 is a diagram showing the relationship between liquid crystal transmittance and cell applied voltage, Figure 7 is an explanatory diagram of the main parts of the liquid crystal panel, and Figure 8 can be seen in Figure 7. A timing chart of the voltage waveform that drives the liquid crystal panel, FIGS. 9 and 10 are diagrams showing the relationship between liquid crystal transmittance and cell applied voltage, and FIG. 11 is for explaining a specific example of the present invention. 12 is a circuit diagram showing a specific drive circuit configuration, and FIG. 13 is a waveform diagram showing one cycle of the drive voltage waveform. . In the figure, LP is a liquid crystal panel, X+, and Xz. X3. X4 is the column line, Yl, Yz, '
Y:l and Y4 indicate row lines, respectively. Patent Applicant Fujitsu Co., Ltd. Representative Patent Attorney Shoji Aitani Representative Patent Attorney Hiroshi Watanabe - Figure 5 Figure 7 Figure 6 vo2i/. Voltage applied Fig. 8 Fig. 12 Fig. 13 Fig. 2a 2b

Claims (1)

[Claims] When rewriting the display using phase-change liquid crystal, first initialize only the blocks that require rewriting.
Next, a method for driving a phase change type liquid crystal display device, characterized in that writing is performed by selectively scanning only the row including the block.