DE3613446A1 - METHOD AND DEVICE FOR DRIVING A LIGHT MODULATION DEVICE - Google Patents

Description

Method and device for controlling a light module

lation device

The invention relates to a method and a device for controlling a light modulator device having a memory property, and particularly one for a display device, an image forming device and the like suitable light modulation device with memory property.

Flat panel displays have been and are avidly around the world developed. Of these, observing the restriction to small-sized devices The liquid crystal display devices were totally adopted for commercial use. · It was, however extremely difficult to use a conventional liquid crystal system (such as a system operating in polarization rotation mode or TN mode (twisted nematic mode) or the light scattering control mode or DS mode (dynamic scattering mode) is used) to develop a display device,

A / 25

which has such a high resolution and such has a large image area that it can replace a cathode ray tube.

To eliminate the shortage of these liquid crystal devices the prior art was disclosed by Clark and Lagerwall (for example in JP-OS 56-107216, US-PS 4367924 etc.) the use of a liquid crystal

■ j ^ q direction with bistability suggested. In this case Generally, as liquid crystals with bistability, ferroelectric liquid crystals with chiral smectic are used C-phase (SmC *) or Η-phase (SmH *) used. These liquid crystals have about one erected on it electric field bistability, namely a first and a second stable state. Accordingly, they will be different from the optical or light modulating devices using the aforementioned TN liquid crystals be used, the bistable liquid crystal mo-

_o _ leküle aligned in a first and second optically stable state in accordance with one and another electric field vector. The liquid crystals of this kind have the characteristics of being converted into either of the two at an extremely high speed

__ stable states are aligned and that they are their Maintain states when no electric field is applied. By taking advantage of these properties you can with these liquid crystals with the chiral smectic phase, a large number of the

guided tours of the devices according to the state of Tech-30

nik problems are essentially solved.

In these devices with the bistable liquid crystals, however, there is still a problem when the number

of picture elements is extremely large and an An-35

high speed control is required.

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Specifically, for a ferroelectric liquid crystal cell having bistability, if a threshold voltage required to bring about a first stable state for a predetermined voltage application time is given by -Vth1 and a threshold voltage required to bring about a second stable state is given by Vth2, a in can The display state (for example, "white") written in the picture element can be reversed to the other display state IQ (for example, "black") when a voltage is continuously applied to the picture element for a long period of time.

Fig. 1 illustrates the threshold characteristic of a bistable ferroelectric liquid crystal cell. In detail, FIG. 1 shows the dependency of a threshold voltage required for changing the display states (Vth) of the voltage application time in the cases that HOBACPC as ferroelektriscb.es liquid crystal (Characteristic curve 11) or DOBAMBC (characteristic curve 12) is used.

It can be seen from FIG. 1 that the threshold voltage Vth is dependent on the application time, the dependence The shorter the mooring time, the more pronounced it becomes. From this fact it can be seen that in the Use of the ferroelectric liquid crystal cell in a device having a large number of scanning lines and which is controlled at high speed, there is a possibility that even then, if a picture element is in a display state (e.g., the bright state) is set, the display state before the completion of scanning of the entire image area is reversed to the other display state (e.g. the dark state) when the Picture element during scanning of subsequent lines

an information signal continued below Vth is created.

The invention is based on the object of solving the problem in the conventional liquid crystal display devices or -light shutters occurring problems a method for driving a light modulation device with a high response speed and to provide an apparatus for carrying out this method.

Another object of the invention is to provide a method for driving a light modulation device with a high pixel density be created.

To solve the problem, the invention creates a method for controlling a light modulator device, which has a plurality of picture elements arranged in N lines, each of which is a pair of each other has spaced apart electrodes between which a light modulating material is inserted, which with respect to of an electric field shows at least two stable states. According to the invention, a write process each for one of a variety of blocks

2g, each containing a large number η of lines, wherein the writing operation has a first step in which the picture elements arranged on the η lines Such a voltage signal is applied that a first, stable state of the Light modulation material corresponding display state is caused, and comprises a second step at to the selected picture elements on the η lines line by line such a voltage signal is applied that to the selected picture elements a display state corresponding to a second stable state of the light modulating material is caused, where N and η are integers

which satisfy the condition N> η.

JC, The invention is explained in more detail below on the basis of exemplary embodiments with reference to the drawing.

Fig. 1 shows threshold characteristics of ferroelectric liquid crystals.

Figs. 2 and 3 are schematic perspective views

which is the principle of operation of the one according to the invention Illustrate the method and the device according to the invention used ferroelectric liquid sigkristallvorrichtung.

4A and 4B show the design of the device according to the invention according to an example in connection with display states before or after a new label.

Fig. 5 is a partial circuit diagram of an output stage of a driver circuit of the device according to the invention.

Fig. 6 is a signal timing diagram therefor.

7 and 8 are each a partial circuit diagram of the invention Apparatus according to a further example.

Fig. 9 is a plan view of a picture element matrix arrangement; which is used in the method or the device according to the invention.

Fig. 10 shows waveforms of to respective electrodes

applied signal voltages.

Fig. 11 shows waveforms of signal voltages applied to picture elements.

Fig. 12 shows the structure of the device according to the invention according to a further example in connection with a display state.

Fig. 13 shows a scan line driver circuit.

Fig. 14 is a signal timing diagram therefor,
jp- Fig. 15 shows a signal line driving circuit.
Fig. 16 is a signal timing chart therefor.

Fig. 17 shows a curve shape in the omission of a signal _on additive.

In a control method according to the invention can can be used as an optical or light modulation material, a material depending on it

_nt - established electric field shows at least two stable states and in particular either a first optically stable state or a second optically stable state, namely multiple stability or bistability with respect to the applied electric field, namely

_on in particular a liquid crystal with this property.

Liquid crystals with bistability, which are preferably used in the control method according to the invention are smectic, especially chiral smectic

Liquid crystals with ferroelectricity. Of these, 35 are

Liquid crystals in chiral smectic C phase (SmC *)

or H phase (SmH *) are particularly suitable. This ferroelectric Liquid crystals are for example in "Le Journal de Physique Letters" 36 (L-69), 1975, "Ferroelectrie Liquid Crystals ";" Applied Physics Letters ", 36 (11) 1980," Submicro Second Bistable Electrooptic Switching in Liquid Crystals "," Kotai Butsuri (Solid State Physics) "16 (141), 1981," Liquid Crystal ", etc. The ferroelectric 2Q described in these publications See liquid crystals can be used in the method and the device according to the invention.

Examples of those which can be used in the method according to the invention Ferroelectric liquid crystal compounds are the individual decycloxybenzylidene-p'-amino-2-methylbutylcinnamate (DOBAMBC), hexyloxy-benzylidene-p'-amino-2-chloropropyl cinnamate (HOBACPC), 4-o- (2-methyl) -butylresorcylidene-4'-octylaniline (MBRA8), etc.

When making a device using these materials is constructed, it can be supported with a copper block or the like in which a heating element is embedded is to bring about a temperature state in which the liquid crystal compounds the SmC * -

_{Accept the oc} phase or the SmH * phase.

Furthermore, in the method according to the invention in addition to the liquid crystals in the SmC * or SmH * .- phase, a ferroelectric liquid crystal in the chiral smectic F-phase, I-phase, J-phase or K-phase be used.

An example of a ferroelectric liquid crystal cell is shown schematically in FIG. With 21a and 21b base plates or glass plates are referred to, on each of which transparent electrodes are made, for example

-12- - - --- "- 'DE 5778 * ---

In ₂ O ,, SnO ₂ , indium tin oxide (ITO) or the like are attached. Liquid crystal in SmC * phase is hermetically enclosed between the base plates, in which liquid crystal molecular layers 22 are aligned perpendicular to the surface of the glass plates. Liquid crystal molecules are shown with solid lines 23. Each liquid crystal molecule 23 has a dipole moment (PX) 24 in a direction perpendicular to its axis

IQ direction. When a voltage above a certain threshold value is applied between the electrodes formed on the base plates 21a and 21b, the helical structure of the liquid crystal molecules 23 is dissolved and the orientation direction of the respective liquid crystal molecules 23 is changed so that the dipole moments (PX) 24 are all in the direction of the electrical Are aligned. The liquid crystal molecules 23 are elongated in shape and show refractive anisotropy between their long and short axes. It is therefore easy to see that, for example, when polarizers are arranged with Nikolscher crossover, namely with the crossover of their polarization directions above or below the glass plates, the liquid crystal cell acts as an optical or light modulation device

_.- optical properties depend on the polarity of an applied voltage. Further, when the liquid crystal cell is sufficiently thin (such as 1μΐη thick), the helical structure of the liquid crystal molecules becomes even without establishing an "electric field

resolved, whereby according to FIG. 3 the dipole moment is one of 30

two states, namely Pa in an upward direction 34a or assumes Pb in a downward direction 34b. If on a cell with these properties according to FIG electric field Ea or Eb, the stronger

than a certain threshold value, the fields 35

have different polarity from each other, is dependent on

ability of the vector of the electric field Ea or Eb das Dipole moment aligned in either the upward direction 34a or in the downward direction 34b. Accordingly the liquid crystal molecules become either in a first stable state 33a or in a second stable state Aligned state 33b.

If the ferroelectric flux described above

- ^ q sigkristallzelle as an optical or light modulation element is used, two advantages can be achieved. The first is that the speed of response is quite high. The second is that the orientation of the liquid crystal shows bistability. Of the

The second advantage is illustrated, for example, on the basis of FIG explained in more detail. When the electric field Ea is established on the liquid crystal molecules, they become in the first stable state 33a aligned. This state remains stable even if the electric field disappears. On the other hand, when the electric field Eb is opposite to the direction of the electric field Ea Direction is established, the liquid crystal molecules are aligned in the second stable state 33b, so that thereby the directions of the molecules are changed.

“Ρ- This state is also maintained in a stable manner even when the electric field disappears. As long as further the strength of the established electric field Ea or Eb does not exceed a certain threshold value, the liquid crystal molecules remain in their jeweili _n s alignment states. In order to effectively bring about a high response speed and bistability, it is advantageous if the cell is as thin as possible, namely usually 0.5 to 20 μm and most preferably 1 to 5 μm thick.

FIGS. 4A and 4B schematically show an example of

-14- -: - -: - 'DE 5778 ^; - ""

a picture element matrix structure which is suitable for the method according to the invention. Fig. 4A shows one Display state before re-inscription, while FIG. 4B shows a display state after re-inscription shows. According to these figures, a cell 46 has a picture element matrix structure with signal electrodes 47 leading signal lines 11 to IN, to scanning electrodes 48 leading scan lines S1 to SN and one between

■ j ^ Q inserted the signal lines and the scan lines bistable optical or light modulation material. The number N of electrodes of each group is one positive integer, which is "16" in this example for ease of explanation. The scan lines are

- ^ f- controlled with a driver circuit 40, while the signal lines are controlled with a driver circuit 49. To simplify the explanation, a case is used as an example in which the binary states “white” and “black” are displayed. In Figs. 4A and 4B is at

_"N a picture element by the representation in black and a black state and shown by the display in white, a white state. It is assumed here that 8x8 picture elements are used to represent a single character, so that four characters can be represented with the cell 46. 4A, "A" is displayed in a character area A11, "B" in a character area A12, "C" in a character area A21, and "d" in a character area A22. Thereafter, according to FIG. 4B, only the character area A22 is converted to a capital letter "D".

_. wrote. This process is explained below.
30th

Fig. 5 is a partial circuit diagram showing an example of the output stage of the aforesaid scan line driver circuit shows. According to Fig. 5 includes a

Buffer level 51 Buffer B1 to BN (with this at -35

game N is 16), the output level of which is

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connections 5 2 can be controlled via connections Q1 and Q2, whereby when the connection Q2 is selected the buffer B1 to B8 simultaneously for the unchanged transmission of the levels at connections R1 to R8 to connections S1 to S8 are turned on, while if the terminal Q2 is not selected, the terminals or scanning lines SI to S8 at a prescribed constant level for maintaining the unselected state of the ^ q cell to be held. Terminal Q1 is for the buffers B9 to B16 have the same function as terminal Q2.

Figure 6 is a timing diagram for the output stage described above. According to Fig. 6, the threshold

, p · value by a pulse with a height of 2Vo for the duration £ t formed, the letter being formed by creating a Pulse over 2Vö, namely, for example, 3Vo takes place. It will now start the rewriting process for the drawing area A22 explained, the explanation of the rewriting of the scanning lines S1 to S16 and the signal lines 11 to 18 omitted certain areas is. First, the terminal Q2 is selected, at a point in time a to the scanning lines S1 to S8 and the signal lines 11 to 116 apply erase signals

_{Become OR} to write "white" in the character areas A11 and A12, respectively. Thereafter, a selection signal is successively applied to the scanning lines S1 to S8 to successively display the information signals on the signal lines Π to 116, displaying "A" in the area A11 and "B" in the area A12. Thereafter, the terminal Q1 is selected, at a point in time b, erasing signals are applied to the scanning lines S9 to S16 and the signal lines 11 to 116 in order to write "white" in the two character areas A21 and A22. After a dial pulse is successively applied to the scanning lines S9 to S16,

-16- -: - -: - '-DE 5778' - "■ .."

then the information on the signal lines 11 to 116, thereby displaying "C" in the area A21 and "d" in the area A22. To rewrite the Character area A22 on "D" is selected as the next step at a point in time c, the connection Q1, where to the scan lines S9 to S16 and the signal lines 19 to 116 erase signals are applied. At this point in time, signal lines 11 to 18 are connected

, λ no erase signal applied, so only in the character area A22 the "white" state is created. Thereafter, a dial pulse is applied successively to the scan lines S9 to S16 are applied, whereby successively the information signals on signal lines 19 to 116

are ever displayed. Through the above-described During operation, the characters in the character areas A11, A12 and A21 are retained, whereas only the character is rewritten in the character area A22, such as "D".

In the example given above, a binary signal display of "white" and "black" was described, however, it is of course also possible to partially rewrite any multilevel display, one _, - analog display, a monochrome display, a color display, of a still picture or a moving picture.

Fig. 7 is a partial circuit diagram showing another

Example of an output stage of a driver circuit for ovj

shows the implementation of the method according to the invention. Fig. 7 shows a scanning signal output stage in which the scanning lines are not divided into blocks. To 7 includes a buffer stage 73, buffers B1 to B16.

Scanning lines on which a paraphrase is desired 35

are, by means of a row addressing circuit 74

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selected, after which scanning lines S1 to S16 are activated for partial writing.

8 shows a further example of the structure for carrying out the method according to the invention. 8, display information signals are generated by means of a common display signal generator 85, while a scanning line driver circuit 86 is divided into units # 1 -J ₀ to # 3 for driving display areas A, B and C, respectively. The scan line driver circuits # 1 to # 3 are each constituted by separate logic circuit units with which the necessary scan lines are first selected and then separately written into the areas A, B and C, thereby enabling a large amount of information to be written at high speed and in high density can be brought about.

According to the invention, either the scanning lines or the signal lines or both controlled by division into a plurality of blocks, with for writing only controls the signal lines for a block in which a picture element is currently being written is. Further, the signal lines or the scanning lines and the signal lines may be in a plurality divided by blocks required to display characters including letters and symbols, which for writing a letter or symbol

bols as an information bit separately by activating it 30th

only the signal lines for a block can be controlled.

If in another embodiment of the method

or the device according to the invention of the previous 35

including said first and second step

-18- ---- -'- "DE S778 '■

Writing operation is carried out for the respective blocks, the picture elements can be sequentially changing or alternating voltage are applied after for an m-th block of M blocks (where m and M whole Are numbers that satisfy the condition m <M) the second step is completed, each having a plurality η of Contain lines, and before the second step for an (m + 1) th block is started. In particular, the IQ a control method described below alternating voltage is applied to the picture elements in the unselected blocks, so that thereby the occurrence crosstalk can be prevented. This control method will now be described.

FIG. 9 shows schematically, as an example, a cell 91 with a matrix electrode arrangement in which between Pairs in groups of spaced apart electrodes form a ferroelectric (not shown) Liquid crystal material is inserted. With 92 and 93 are each a group of scanning electrodes S, to the scanning signals are applied, or a group of signal electrodes I denotes to which information signals are applied will. To simplify the explanation, a case is taken as an example in which binary signals for "White" and "Black" are displayed. In Fig. 9, broken lines correspond to picture elements shown "Black" based on the second stable state of the ferroelectric liquid crystal, while the

the first stable state of the other picture elements 30th

ferroelectric liquid crystal correspond.

Figs. 10 (a) to (c) show the scanning electrodes, respectively Scanning signals applied to S1 to S3. The Fig. 10 (d)

through (f) point to the signal electrodes 11 through 13, respectively 35

applied information signals. These signals correspond

-19- - - ^: - DB 5/78 '- "* - ■

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the display state shown in FIG. Figure 11 (a) to Cf) indicate the chronological sequence of voltages applied to respective picture elements A to F of Fig. 9. The one shown in Figs Writing operation is one for writing in picture elements of a block with a prescribed Number η of scanning lines and is carried out successively for a plurality M of blocks in order to produce a inscribe a single image.

In the driving method shown in FIGS. 10 and 11, all picture elements can be on a plurality of Scan lines in a block simultaneously in the first

stable state (white state), after which 15

then, for writing, the scanning lines successively can be selected in order to bring desired picture elements into the second stable state (black state).

FIGS. 10 and 11 illustrate one type of control method described above. In a period ti for the application of a cancellation signal, positive pulse voltage 2Vo is applied to all scanning lines, while in phase with this, a negative pulse voltage -Vo is applied to all signal lines, whereby all Image elements in a block can be deleted on "white". Then successively to the scanning lines of the Blocks a scan selection signal is applied, which consists of a positive Voltage pulse 2Vo and a negative voltage pulse -2Vo exists, which alternate in periods t2 and t3 for the application of the write signal. . In phase with the scan selection signal are applied to the picture elements where the white state is maintained

should, a white signal from a positive pulse Vo and 35

a negative impulse -Vo alternately during the period-

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the t2 and t3 are applied and to the picture elements at which the display state is reversed to the black state should, a black signal composed of a negative pulse Vo and a positive pulse Vo alternately during the Periods are created, whereby the labeling of a block is completed.

In the method according to the invention, before the application , Q of the write signals to the signal lines 11, 12, ... in Phase with the sample select signal during periods t2 and t3 for the picture elements in the (m + 1) -th block and after the writing of the picture elements on the m-th block a voltage signal which, with respect to a reference potential, corresponds to that during the erasing signal application period ti voltage signal applied to the scanning lines opposite The polarity has been applied to the scanning lines as an additional signal during an additional signal application period to, whereby a voltage below the threshold voltage is applied to the relevant picture elements. Consequently becomes the length of time during which the picture elements in the unselected blocks are continued Voltage of one polarity is applied, to a maximum of twice the write pulse duration (assuming the Relationship ti = t2 = t3 = to), thereby reducing the aforementioned problem of the occurrence of crosstalk can be solved.

In the process described above, each

certain voltage values are set in such a way that the following 30

Conditions are met:
2Vo <Vth2 <3Vo and
-3Vo <-Vth1 <-2Vo

where Vth2 is a threshold voltage for the second stable state ("black") of the ferroelectric liquid crystal 35

stalls, -Vth1 is a threshold voltage for the first

-21- —- - ^: - CH 5778 "-""■ - '

χ 36134A6

stable state ("white") of the ferroelectric liquid crystal and essentially the relationship j-Vth1 | ξ iVth2 (can be brought about.

The above-described process is explained in more detail below.

Fig. 12 shows a liquid crystal device for carrying out the driving method of the present invention. Referring to Fig. 12, a liquid crystal panel or ferroelectric liquid crystal cell has 125 scanning lines 123 which are driven by means of a scanning line driver circuit 121, and signal lines 124 which

by means of a signal line driver circuit 122

be controlled. In this example, binary signals for "white" and "black" are displayed. It is believed that 16 scanning lines and signal lines are provided in each case. As in Figures 4A and 4B, one is black

displayed picture element in the black state and one white 20th

displayed picture element in the white state. Cell 125 displays four characters if a single Characters with 8x8 picture elements. According to FIG. 12, the letters "A" are in an m-th block A1

and "B" are displayed, while in an (m + 1) -th block A2 25

the letters "C" and "D" are displayed.

FIG. 13 is a partial circuit diagram showing an example of the output stage of the scan line driver circuit 121

shows. According to FIG. 13, switching elements 30 are common with 131

denotes g1 to gN (where in this example N equals

16), the output levels of which are controlled via dial-up lines 132. If a connection Q2 is selected, the switching elements g1 to g8 are switched on at the same time in order to keep the level at the connections R1 to R8 unchanged

changes to transmit while when the terminal Q2

-22- DE 5778 "

is not selected, the outgoing scanning lines S1 to S8 are held at a prescribed constant level at which the cell 125 is in the unselected State is maintained. For the switching elements g9 to g16, a terminal Q1 has the same function as that Connection Q2.

Figure 14 is a timing diagram for this output stage. In the example shown in Fig. 14, the picture elements in a block are consecutively Erase signal, an additional signal and a write signal during periods ti, to and t2 + t3 for the respective signals applied, whereby in a write period T1 in an internal block and in a write period T2 in a (m + 1) th block is written (where, for example, T1 = T2).

FIG. 15 is a partial circuit diagram showing an example of the output stage of the signal line driver circuit 122 Fig. 16 is a timing chart therefor. Fig. 15 shows an input terminal D for serial input of data (such as image signals corresponding to those shown at D in Fig. 16)

and an input terminal CLK for shift clock pulses. 25th

When all the data have been collected in a shift register 151, the potential at a terminal L rises from "0" to "1" so that the data are held by means of a buffer 152. Until then, it differs

the function does not differ from that of an ordinary 30th

Information driver circuit.

A property of the control system according to this Example is that the intermediate memory is followed by OR gates 153 output signals through the OR

Linking the output signals of the buffer with

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Signals. Submit CLR. The CLR signals are normally "0" so that the latch output signals to exclusive-OR gates or antivalence elements 154 are transmitted. Signals S consist of a simple repetition of pulses "1" and "0" which are unchanged on positive logic output terminals and unchanged on negative logic output terminals are output inverted when the buffer output signals, namely the image signals Are "0" (for "black"). On the other hand, when the latch outputs are "1" (for "white"), the inverted pulses of the signals S are applied to the positive logic output connections and to the negative logic output connections the pulses of the signals S emitted unchanged. These signal pulses are in an arrangement

input by switching elements 155, which are controlled via a terminal G and their output signals to Level shifters 156 are transmitted. The level converters provide input signals to connections A or B according to the following table 1 three types of voltage

values, namely GND (ground potential), -Vo and + Vo.

Table 1

^{A B In}

L L GND

L. H -Vo

H L + Vo

As can be seen from the circuit according to FIG. 15,

the following output signals are achieved:
for G = 1 (switching elements connected):
+ Vo - »-Vo if the image signal is the black signal

is and
if

-Vo -> + Vo if the image signal is the white signal

-24- - DE 5778

! 3 R 1 3 /.

is,

and for G = O (switching elements blocked):
GND independent of the image signal.

The case CLR = 0 was explained above. In the initial period (to and ti) of a block scan however, the case CLR = 1 occurs. In this case, all output signals of the OR gates are "1" and all output

jQ output signals of the level converter "-Vo * ■ * + Vo". Consequently a voltage signal "-Vo - * · + Vo" is applied to all signal lines prior to the block scanning process, whereby the desired control is brought about. Is due to the picture elements in the relevant sample block however, a voltage signal "-3Vo -> - + Vo" is on.

For comparison, FIG. 17 shows an example in which the period to provided in the above-described example for the application of the additional signal is omitted ^.

17 shows an example of waveforms of pulses applied to a signal electrode or signal line. At a time point Xm, the scanning of the m-th block is finished, while at a time point Xm + 1 the scanning of the (m + 1) -th block starts. The negative pulse between Xm and Xm + 1 corresponds to the negative pulse applied during the aforementioned period ti of the application of the erase signal and is used for _n simultaneous writing of "white" in the (m + 1) th block. In this example, the last signal for writing in the m-th block is a white signal consisting of a positive pulse and a negative pulse in this sequence during periods t2 and t3, while the first signal for writing in the (m + 1) - th block a black signal from a negative

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Pulse and a positive pulse in this sequence during periods t2 and t3. If those Signals applied are sequential as shown in Fig. 17 around the period ti, three negative pulses are applied, which remain unchanged on the picture elements on the lines not selected are created. This means that the period of time during which a voltage is below the threshold voltage with a certain polarity is continuously applied to unselected picture elements, can be three times the write pulse duration in the case of an activation with block division, while in an activation without block division, the duration is a maximum of twice the write pulse duration. This causes

sometimes as a problem inherent in the imaging process 15

a reversal of an unselected picture element, namely the so-called crosstalk. With the invention this problem is solved by a driving method in which the occurrence of crosstalk is prevented.

According to the above statements, the invention results in a control method for an optical or light modulation device, which can be used as a visual display device with a large image area, wherein

The process provides a high level of reliability

visibly the control with high density and at high speed, a shortening of the writing time, one Reduction in drive power consumption and a results in extended life of the light modulating device.

If, furthermore, according to the method according to the invention or with the device according to the invention has a display panel with a ferroelectric liquid crystal device is driven at high speed is both for a picture element in an unselected block and

-26- - ^; · '- ■ DE 577S "..

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for a picture element to which no scan selection signal is applied, the maximum pulse duration of one continues the voltage applied to the picture element is limited to twice a write pulse duration AT. As a result, can can effectively prevent the phenomenon from occurring during the course of scanning for writing a one display state is reversed into the other state for each image.

A method and a device for controlling a light modulator device are also provided. a multitude indicated by picture elements arranged in N lines / each of which is a pair of spaced apart opposite one another Has electrodes between which a light module

tion material is inserted, which shows at least two stable states with respect to an electric field. For a plurality of blocks, each of which contains a plurality η of lines, one write operation is carried out at a time executed in which in a first step

the picture elements arranged on the η lines produce a voltage signal which puts the picture elements in a display state corresponding to a first stable state of the light modulating material, and in

a second step to selected picture elements on the η 25

Lines a voltage signal is applied that the selected Picture elements in a display state corresponding to a second stable state of the light modulating material offset, where N and η are integers that satisfy the condition N > η suffice.

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Claims (17)

T 'r% .. \ £ / ■ * patent attorneys and IEDTKE - ÖUHLING - IVlNNE "UIRUPE representative at the EPO ff * f ^. ^> ... Dipl 11 te) H Ticdtko ΓΈΙ-LMANN" IJIRAMS - OTRUIF:; ": Dipi-Cten aßühling -: ...;. ■ .. - ϋίΐΐΓ-lng __ R Kinne Dipl Ing P Grupu Dipl Ing B Pellmann 3613446 Dipl.-Ing K. Grams Dipl. Chfiii Dr. B. Struif Bavariaring 4, P.O. Box 20 24Oi 8000 Munich 2 Tel 089-539653 lelux b? A 845 tipal ΤοΙο · «: ορΐι. · Ι. 0 89 537377 cabl <; Cicrmaniapcitenl Munich April 21, 1986 DE 5778 patent claims 1st A method of driving a light modulation device comprising a plurality of picture elements arranged in N lines, each of which has a pair of spaced apart electrodes between which a light modulation material is inserted which exhibits at least two stable states with respect to an electric field, characterized in that, that for a plurality of blocks, each of which contains a plurality of η of lines, a write operation is carried out in which, in a first step, a voltage signal is applied to the picture elements arranged on the η lines, which the picture elements in a first stable State of the light modulation material corresponding ^ display state, and in a second step a voltage signal is applied line by line to selected picture elements on the η lines, which the selected picture elements in a second stable state of the light modulation material corresponding display state offset, where N and η are integers which - satisfy the condition N> η. 2. The method according to claim 1, characterized in that a voltage signal is applied in the first step, A? 25th with which the picture elements on the n lines are simultaneously in the display state corresponding to the first stable state be moved. 3. The method according to claim 1 or 2, characterized in that the picture elements in a not selected Block of the plurality of blocks, a successively changing voltage is applied. 4. The method according to claim 3, characterized in that as the successively changing voltage, an alternating voltage is created. 5. The method according to any one of claims 1 to 4, characterized in that the light modulation material is a ferroelectric liquid crystal. 6. The method according to claim 5, characterized in that _n the ferroelectric liquid crystal ^ is a liquid crystal in a chiral smectic phase. 7. A method for driving a light modulation device which has a plurality of arranged in N lines _{rt (} _ has picture elements, each of which is a pair of each other Zo has spaced electrodes between which is inserted a light modulating material which is stable at least two in terms of an electric field Shows states, characterized in that for a Multiplicity M of blocks, each of which has a multiplicity η 30 of lines, a write operation is carried out in each case, in which, in a first step, the on the η Lines arranged picture elements a voltage signal is applied, which the picture elements in a first Stable state of the light modulation material corresponding display state, and in a second Step a voltage signal is applied line by line to selected picture elements on the η lines, which voltage signal puts the selected picture elements in a display state corresponding to a second stable state of the light modulation material, the picture elements being sent to the picture elements in a period after the completion of the second step for an mth block and before At the beginning of the second step for an (m + 1) th block an alternating voltage is applied IQ and where N, n, M and m are integers which satisfy the conditions N> η and M> m. 8. The method according to claim 7, characterized in that a voltage signal is applied in the first step, ■ each with which the picture elements on the η lines simultaneously in the display state corresponding to the first stable state can be set. 9. The method according to claim 7 or 8, characterized in that the picture elements in a not selected Block of the plurality of blocks, a successively changing voltage is applied. 10. The method according to claim 9, characterized in that that an alternating voltage is applied as a successively changing voltage. · 11. The method according to any one of claims 7 to 10, characterized in that the picture elements in a period after the completion of the second step for the mth block and before the beginning of the first step for the (m + 1) -th block an alternating voltage is applied. 12. The method according to any one of claims 7 to 11, characterized in that the light modulation material is a ferroelectric liquid crystal. 13. The method according to claim 12, characterized in that that the ferroelectric liquid crystal is a liquid crystal in a chiral smectic phase. 14. Device for controlling a light modulator direction which is provided with a light modulation material »which shows at least two stable states with one to the light modulator device via a multi- 2Q number of scan lines connected scan line driver circuit and one connected to the light modulating device through a plurality of signal lines Signal line driver circuit, characterized by a plurality of switching elements (51; 131), ^ g each connected to one of the scanning lines (S) are a plurality of control lines (52; 132) each connected to a prescribed number of the switching elements are connected, and a device for successively applying a switching signal to the control lines. 15. The device according to claim 14, characterized in that that the signal line driver circuit (122) has a latch device (152) and an OR device (153), which is a by ORing the output signal of the intermediate storage device with an applied clock pulse signal formed OR output signal gives away. 16. The method as claimed in claim 14 or 15, characterized in that it is 30 draws that the light modulating material is a ferroelectric liquid crystal. ·. 17. The method according to claim 16, characterized in that __ that the ferroelectric liquid crystal is a liquid crystal stall is in a chiral smectic phase.