JPS61245139A - Scanning system for optical modulating element - Google Patents

Abstract

PURPOSE:To decrease the number of lead-out wires and to realize a scanning system which suits to a large screen and high density by providing a gate circuit between a scanning electrode and a source line for supplying a scanning signal thereto and controlling the gate circuit by a shift register. CONSTITUTION:Display signal electrodes 6 and scanning signal electrodes 7 are arranged in a matrix and transistors (TR) TR1-TR6 are arranged at input terminals of scanning lines S1-S6 and controlled with signals Q0-Q6 of the shift register 9. When an on signal is outputted is outputted to the Q0-Q5 successively,the TRs TR1-TR6 also turn on successively and a signal from a terminal Vs is read in and a scanning signal is applied to a liquid crystal layer. Thus, a gate 8 is provided to the scanning line, so time-division driving becomes possible and the driving is performed only during this period, so only one common signal input line is required. Consequently, the number of lead-out lines is decreased and the scanning system which suits to a large screen and high density is realized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a scanning method for an optical modulation element, and more particularly to a scanning method in which ferroelectric liquid crystal elements having memory properties are driven by a circuit configured in a matrix. .

[Prior Art] Conventionally, multi-plex drive such as the TN system has been the mainstream for liquid crystal display elements, but there has been a limit to increasing the screen size and density due to the number of time-division drives. On the contrary,
What has been attracting attention recently?

This is a display element that uses so-called ferroelectric liquid crystal and has the ability to memorize orientation states, so there is no limit to the division of scanning lines, and high-definition displays can be expected.

[Problem to be solved by the invention J However, in display elements using ferroelectric liquid crystal elements,
It is necessary to wire the matrix electrodes at a high density, and the lead lines tend to be complex and diverse.The number of lead lines becomes a non-negligible problem, including crosstalk and manufacturing costs.Also, the output stage of the scanning circuit It is also desired to reduce the number of elements constituting the device. Furthermore, when performing matrix driving, there is a phenomenon in which the driving waveform becomes dull due to the resistance of the transparent electrode part and the capacitance of the liquid crystal layer.
The problem tended to become more pronounced as the panel size and capacity increased.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a scanning method for a matrix drive circuit suitable for an optical modulation element having memory properties such as a ferroelectric liquid crystal.

[Means for Solving the Problems] In the present invention, a means for solving the above problems is to drive an optical modulation element having a memory property with a matrix configuration of display signal electrodes and scanning signal electrodes. In a circuit scanning method, a source line that applies a scanning signal to a scanning signal electrode, a gate circuit interposed between the source line and the scanning signal electrode, and a shift register circuit that periodically drives the gate circuit are used. This is a scanning method for an optical modulation element, which is characterized in that it is configured in a drive circuit.

The present invention also increases the effects of the above-mentioned scanning method by forming these circuits with TFTs or by connecting the output ends of the drive circuit to both ends or multiple locations of the electrodes. In addition, ferroelectric liquid crystals, particularly smectic C", I', F. Note that an FET is usually used as the gate circuit.

The ferroelectric substance used in the present invention is a substance that takes either a first optically stable state or a second optically stable state depending on an applied electric field, that is, a bistable state with respect to an electric field. In particular, liquid crystals having such properties are used.

As the ferroelectric liquid crystal having bistability that can be used in the present invention, chiral smectic liquid crystal having ferroelectricity is most preferable, and among these, chiral smectic C phase (S■C'') and H phase (SsH'') are most preferable. LCD is suitable. Regarding this ferroelectric liquid crystal, “Le Journal de Physique Rutile” (“LE J
OURNAL DE PHYSIOUELETTERS
”) In 1975, “Ferroelectric Liquid Crystals” (rF) published in issue 3B (L-89)
error electric liquid crystal
``Applied Physics Letters''
) 1380, ``Submicro Second Bisteple Electro-Optic Switching in Liquid Crystals J'' published in Issue 3B (11)
(rsubmicro 5econdBistab
le Electrooptic Switch
ng in Liquid CrystalsJ);
It is described in "Liquid Crystal" published in "Solid State Physics", 1981, No. 1 (141), and the ferroelectric liquid crystal disclosed in these can be used in the present invention.

More specifically, an example of a ferroelectric liquid crystal compound used in the method of the present invention is decyloxybenzylidene-P'-amino-2-methylbutylcinnamate (DOBAMBC).
), hexyloxybenzylidene-p'-amino-2
-Chloropropyl cinnamate (HOBACPC) and 4-o-(2-methyl)-butylresorsilitin-4
'-octylaniline (MBRA6) and the like.

When constructing an element using these materials, in order to maintain the temperature state such that the liquid crystal compound becomes the S-C" phase or the SmH- phase, the element may be placed in a copper block with a heater embedded, etc., as necessary. It can be supported by

Note that FIG. 5 schematically depicts an example of a ferroelectric liquid crystal cell. 1 and 1' are In2O3, 5n02 and ITO (
A transparent electrode such as Indium-Tin-Oxide (Indium-Tin-Oxide) is formed on a curved substrate (glass plate), and a Sac'' phase liquid crystal in which the liquid crystal molecular layer 2 is oriented perpendicular to the glass surface is sealed between them. A thick line 3 represents a liquid crystal molecule, and this liquid crystal molecule 3 has a dipole moment (P) 4 in a direction perpendicular to the molecule.

When a voltage higher than a certain threshold is applied between the constant electrodes on the substrates l and 1', the helical structure of the liquid crystal molecules 3 is unraveled, and the liquid crystal molecules 3 are twisted so that all the dipole moments (P↓) 4 are directed in the direction of the electric field. change the orientation direction. Liquid crystal molecules 3
has an elongated shape and exhibits refractive index anisotropy in its long axis direction and short axis direction. Therefore, for example, if polarizers are placed above and below the glass surface in a crossed nicol positional relationship, the optical It is easily understood that this becomes a liquid crystal optical modulation element whose characteristics change. Furthermore, when the thickness of the liquid crystal cell is made sufficiently thin (for example, 1jL), the helical structure of the liquid crystal molecules unravels (non-helical structure) even when no electric field is applied, as shown in Figure 6. The dipole moment P or P' is directed upward (4a) or downward (4b
). In such a cell, as shown in FIG. 6, an electric field E or E' of different polarity above a certain threshold value is applied.
is applied for a predetermined period of time, the dipole moment changes its direction upward (4a) or downward (4b) in response to the electric field vector of the electric field E or E', and in response to this, the liquid crystal molecules
orientation state 5 or second orientation state 5'.

The advantages of using such a ferroelectric liquid crystal as an optical modulation element are that the response speed is extremely fast and that the orientation of the liquid crystal molecules has a bistable state.
In the figure, when an electric field E is applied, the liquid crystal molecules are aligned in a first alignment state 5, but this state remains stable even when the electric field is turned off. Further, when an electric field E' in the opposite direction is applied, the liquid crystal molecules are aligned to a second alignment state 5' and the orientation of the molecules is changed, but this state remains even after the electric field is cut off. Also,
As long as the applied electric field E does not exceed a certain threshold value, each orientation state is still maintained. In order to effectively realize such fast response speed and bistability, it is preferable for the cell to be as thin as possible, and generally, the thickness is 0.5
%~20 end, especially IIL~5 river is suitable. A liquid crystal-electro-optical device having a matrix electrode structure using ferroelectric liquid crystals of this kind has been proposed, for example, by Clark and Ragabal in US Pat. No. 4,367,924.

[Function] By providing a gate in the scanning line, time-division driving becomes possible. Therefore, since it is only necessary to drive each scanning line during the period when each gate is on, the signal input line for the scanning line can be a single common signal input line, and it can be connected in parallel to that one line. Become. F as a gate circuit
If ET is used, it will mechanically serve as the connection point, which is even more logical. Then, in order to control the synchronization between the time division drive and the scanning signal input, a shift register or an equivalent circuit may be connected and the timing by a clock may be adjusted.

[Example 1] Hereinafter, the present invention will be described in detail with reference to examples and drawings thereof.

FIG. 1 is a circuit configuration diagram showing an example of a drive circuit for an optical modulation element embodying the present invention. In FIG. 1, the drive circuit of the optical modulation element includes the signal lines ■1 to I of the display signal electrode 6.
n and the signal lines S1 to S6 of the scanning signal electrode 7 are arranged in a matrix, and the scanning signal lines
A transistor trl"tr6 serving as a gate 8 is disposed at the input end of -s6, and this transistor trl"tr6 is disposed as a gate 8.
~tr6 is turned on and off in a time-divided manner by the pulse group of the scanning signal train VS for driving the liquid crystal, and the scanning signal line Sl-3
A scanning signal is supplied to 6. This transistor trl~t
r6 is a FET that connects the power supply to the scanning electrode of the liquid crystal panel
and the signal Qo sent from the shift register 9
” Controlled by Qs.

FIG. 2 is a circuit configuration diagram showing an example of a shift register used in the above-mentioned drive circuit embodying the present invention. Second
In the figure, Vdd is a high level voltage (5v),
vbb is a voltage (e.g. 2V) that keeps the gate on all the time; a synchronous clock signal is input to φt and φ2;
The 00M terminal is grounded. IIVIN is an information input terminal of the shift register, and an ON signal is input once when scanning 1 frame.

FIG. 3 is a time chart showing an example of the operation of the above drive circuit. In FIG. 3, the first stage Vs is given the pulse train before dividing the pulses to each scanning signal line, where T corresponds to the selection signal time, and T
2 is the interval, and the scanning frequency is 1/(TFT2
).

As for the operation of the shift register, when H is input at the beginning of scanning one frame with VIN, the H signal will be φ1, φ2.
The bits are sequentially transferred according to the clock of φ2, and the H level is outputted to the output terminal Qo''Qs of the shift register only for the time according to the clock of φ2.

When ON signals are sequentially output to Qo''Qs, the transistors Tr1 to Trb are also turned on at the same time, reading the signal from VS and applying a scanning signal to the liquid crystal layer.

Note that the pulse widths of φ1 and φ21VIN mentioned above are
It is sufficient that the charging time of the capacitor existing in parallel with the transistor Tr2 disposed closest to the input end in the figure is exceeded.

The above circuit is constructed by forming a TFT (thin film transistor) on a liquid crystal substrate, and connecting it to a transparent electrode on the substrate.
In this case, there is an advantage that only a small number of lead lines are required in the scanning signal system.

FIG. 4 is a circuit configuration diagram showing another example of a matrix drive circuit embodying the present invention. As shown in FIG. 4, shift registers 9a and 9b are provided on both sides of the stripe electrodes constituting the matrix panel 10, and selection signals are input from both ends of the stripe electrodes.
The phenomenon of waveform blunting can be improved by the resistance of the stripe electrodes and the capacitance in the liquid crystal layer. In addition,
In this case, it is possible to share the two shift registers 9a and 9b and to share the power supply. The output ends are not limited to both sides, and can be multiple.

According to the method of the above embodiment, the scanning output stage of the liquid crystal panel is set to one line, and the subsequent stages are divided by FETs, so that the number of elements constituting one circuit can be reduced, and the construction itself can be simplified. Furthermore, if the above circuit is formed on a liquid crystal substrate using TFTs, the number of drawers will increase compared to the number of scanning lines of the panel.
! For example, in this embodiment, there are six lines in total, five from the shift register and one from the power supply, and any number of scanning lines can be driven.

Furthermore, as shown in the application example, by applying voltage pulses of the same waveform to terminals on both sides of the stripe electrode on one side of the substrate of the matrix panel, the rounding of the waveform due to the resistance and capacitance of one circuit can be reduced. In this case as well, if TFTs are formed on the substrate, driving can be achieved with a significantly smaller number of lead lines than the lead lines of conventional drive circuits.

[Effects of the Invention] As explained above, according to the present invention, the number of lead lines and the number of elements of a display panel can be dramatically reduced, driving waveforms can be prevented from slowing down, and the strength suitable for large screens and high density can be achieved. It is possible to provide a scanning method for a matrix drive circuit of an optically modulated display element having memory properties such as a dielectric liquid crystal.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of a shift register, FIG. 3 is a time chart according to the present invention, and FIG. 4 is a circuit configuration diagram of another embodiment of the present invention. figure,
FIGS. 5 and 6 are explanatory diagrams of a ferroelectric liquid crystal element. DESCRIPTION OF SYMBOLS 1...Substrate, 3...Liquid crystal molecule, 6...Display signal electrode, 7...Scanning signal electrode, 8...Gate, 9...
Shift register, 10...matrix panel.

Claims (6)

[Claims] (1) In a scanning method of a drive circuit that drives an optical modulation element having a memory property with a matrix configuration of display signal electrodes and scanning signal electrodes, a source line that supplies a scanning signal to the scanning signal electrode, and a source line and scanning 1. A scanning method for an optical modulation element, characterized in that a drive circuit includes a gate circuit interposed between a signal electrode and a shift register circuit that periodically drives the gate circuit. (2) A scanning method for an optical modulation element according to claim 1, characterized in that a driving circuit is formed using a TFT (thin film transistor) on the same substrate as the scanning signal electrode substrate of the matrix panel. (3) A scanning method for an optical modulation element according to claim 1 or 2, characterized in that an output end of a drive circuit is connected to a plurality of locations of the scanning signal electrodes of the matrix panel. (4) A scanning method for an optical modulation element according to claim 1 or 2, wherein output ends of a drive circuit are connected to both ends of the signal line of the striped scanning signal electrode. (5) A scanning method for an optical modulation element according to any one of claims 1 to 4, wherein the optical modulation element having memory properties is a ferroelectric liquid crystal. (6) Ferroelectric liquid crystal is smectic C^*, I^*, F^*
, J^*, G^*, and H^* liquid crystal phases according to claim 5.