JPH01500149A - Electronic addressing methods for ferroelectric and flexoelectric liquid crystal devices - Google Patents

Abstract

PCT No. PCT/SE86/00476 Sec. 371 Date Jun. 15, 1987 Sec. 102(e) Date Jun. 15, 1987 PCT Filed Oct. 14, 1986 PCT Pub. No. WO87/02495 PCT Pub. Date Apr. 23, 1987.A driving method is provided for arrays of liquid crystal elements having a linear response to an applied electric field, and specifically ferroelectric liquid crystals capable of two surface-stabilized states. The presented schemes write simultaneously both states in one scan of the array, recognizing both the threshold as a critical voltage-time area and keeping this integrated averaged area equal to zero for symmetrically responding pixels. The voltage pulse trains are optimized to intrinsically assure stabilizing rms torques without applying separate holding voltages. Improvements in contrast and frame writing speed are achieved by optimizing driving parameters and scan procedures, such as scanning in loops, in combination with impedance switching.

Description

[Detailed description of the invention] of ferroelectric and flexoelectric liquid crystal devices.

1, 8 The present invention relates to an electronic driving method technology for a liquid crystal device, and more specifically, to a method for electronically driving a liquid crystal device, and more specifically, to a method for electronically driving a liquid crystal device. driving a device containing a liquid-crystalline medium exhibiting at least partially linear response; Regarding the method. Examples of such liquid crystal media include ferroelectric and flexoelectronic media. It has a metric liquid crystal structure. All chirally graded smectic liquid crystals are ferroelectric The ability to exhibit plexoelectric responsiveness in some deformation states have power. The nematic liquid crystal is flexoelectric in some deformed states At present, many expectations are placed on ferroelectric liquid crystals (FLCs).

The reason for this is that it has excellent properties that are difficult to find in other types of liquid crystals. This is because FLC has this.

Regarding this point, there is a particular problem with so-called surface stabilized ferroelectric liquid crystals (SSFLC). In the 5SFLC cell, polarization is possible due to surface interference, and bulk As a result of surface interference, an essential helix (helical structure, threaded structure) The reason for this is that ``(re)'' never appears. 5SFLC is easy to polarize and has high speed Can perform qualitative gray scale and color functions. However, they are It is related to rows and structures and is very sensitive to them, and is also sensitive to electrical pulse drive circuits. It is also relevant to the design of the required addressing method. A small number of ferroelectric actuators are already available. However, no driving method that is practically satisfactory has been proposed to date. The reason is that FLC and Important differences with nematic drive properties are only partially recognized and therefore , address requirements have not been fully analyzed. proposed to date The driving method is disclosed in European Patent Application No. 0092181 (Hitachi Systems, Ltd.). (Application date: April 14, 1983), West German patent application DE341470 4A1 (Canon Co., Ltd., filing date: April 18, 1984), West German Special *DE3443011A1 (Canon Co., Ltd., filing date: January 1984) January 26th), European Patent Application No. 01498995 (Seiko Electronic Industries Ltd. Shikisha, filing date: December 7, 1984).

Conventional devices and methods may operate to varying degrees under certain conditions. However, according to our analysis under all conditions, especially 5SFLC equipment Well then.

Problems with electrical addressing in conventionally proposed techniques.

In particular, it is impossible to solve the problem of obtaining excellent optical contrast. 5 SF In an LC, the liquid crystal is confined in a very narrow space between two plates; These problems become more pronounced due to the physical dimensions and characteristics of the 5SFLC device. In other words, The volume of charge on the surface creates a substantial electric field, which This is particularly problematic in several ways.

An object of the present invention is to provide an electrical addressing method (addressing operation method) for a liquid crystal device. , More specifically, considering the above problems, especially in FLC devices, bistability and To provide an addressing method that takes full advantage of the essential advantages of high speed. It is in.

FLC addressing is quite difficult with conventional LCD addressing methods; In explaining the address behavior of To.

An example of a multi-addressing method that works well will now be described.

Next, the present invention will be explained based on the drawings.

Brief description of the drawing Figure 1 is a schematic cross-sectional view of a ferroelectric liquid crystal end structure, and Figure 2 is a module diagram corresponding to Figure 1. A perspective view of orientation, Figure 3 is a typical example of switching in ferroelectric liquid crystals. A diagram showing the time-voltage relationship, Figure 4 shows electrical pulses of different durations. Schematic diagrams illustrating optical responsivity, Figures 5 and 6, for a 1-pixel or linear array device. A diagram showing the basic polarity drive characteristics, Figure 7 shows some DC compensation switching waveforms. 8 is a schematic diagram showing an example of direct current compensation drive in a linear arrangement. To explain the DC and AC stabilization of bistable or first-order monostable liquid crystal cell structures. The schematic diagrams, Fig. 10, Fig. 11, Fig. 12, and Fig. 13 are different ways of multiplex drive. Figure 14 is a schematic diagram for explaining an example of the AC stabilization drive method. Schematic diagram, Figure 15 illustrates pulse width and pulse height modulation for gray scale driving FIG. 16 is a schematic diagram for explaining the selective column scanning and selective row driving method. Schematic diagram.

FIG. 17 shows additional information about the method of FIG. 12 used in the selective row drive method. Schematic diagram of a “non-modified” pulse train, Figure 18 illustrates the high impedance switching concept. A schematic diagram of FIG. Schematic diagrams of the driving method with increasing selection ratio, Figures 20 and 21 are first-order asymmetrical switches. 2 is a schematic diagram illustrating an example of a driving method for compensating for dynamic characteristics.

2.L Mokugyo 11 Gradient smectic liquid crystals composed of chiral molecules are Journal de Ph. ysique 1975. Volume 3G, page L69 article It is a ferroelectric property as first described by R, B, Meyer et al. these FLC has an external electric current based on the secondary dielectric effect that always appears in liquid crystals due to its anisotropy. In most cases, the coupling property is stronger than that with the field, and the coupling property is linear. As shown, the simplest, and therefore most common, ferroelectric smectic is the chirastic smectic. Cuteic C phase, which generally in practice consists of different chiral and non-chiral Balanced polymorphism of mesogenic molecules with chiral polarity and viscosity-suppressing dopants It is a mixture of components. In this medium, it is displayed as C*, and the molecular direction is 8 (this direction is approximately (equal to the two optical axes, or more precisely, equal to the average direction of the two optical axes) The tick phase is tilted by an angle θ from the vertical and is perpendicular to the director at any location. . A similar and higher order strongly galvanic phase results in a lower temperature in the same conbound. It exists in degrees etc. Among these, the most important are II, J*, Q*, H *It is called.

In the normal crystalline state, the CI phase exhibits a non-ferroelectric region, and the dipole moment is As in the case of magnetization of a helimagnet, P (and n ) is continuously canceled by spiralization. In the 5SFLC device, the helix (this The common C* phase structure with a being pushed out of the ruque state. Applicable structure (“bookshelf structure” Smectic The phase is approximately perpendicular to the boundary glass plate separated by a few microns), the formation of helices and any other heterogeneous (“splayed”) conditions; Instead, there are two Either surface stabilization direction is chosen.

These “spin-up” and r-spin-down directions are respectively between the rates is conserved roughly throughout the layer and naturally, i.e., due to the action of an external electric field. It corresponds to a ferroelectric domain that occurs in an idle state. These domains, and is described in U.S. Patent No. 4,563,059 (filing date: July 7, 1983). Several similar more complex domains are characteristic of the SS FLC structure. Bo Larization P follows the direction of the DC electric field applied to the sample and has a high cost. between intersecting polarizers of contrast and high speed (k)lz”MHz range). leading to electro-optic birefringence effects. By performing appropriate surface treatment.

Switching is bistable and can be achieved by short pulses of 3-30v (volt) amplitude. Can be done. This effect involves some kind of threading that is strongly dependent on cell thickness and boundary conditions. There is a shoulder.

Because the physical effects in ferroelectric and non-ferroelectric liquid crystals are of very different nature, For this purpose, a method similar to that done for some of the other liquid crystal electro-optic effects. In particular, thin film transistors (TPTs) and similar high cost and large 5SFLC instrument matrices without using any active devices such as restricted elements. Issues include address behavior and whether multiplexing is possible. come. However, there are many problems with such addressing methods, especially regarding optical contrast ratio. Until now, no thorough analysis has been carried out regarding the basic physical requirements for stomach.

For a preferred addressing method, the most unique and useful It is necessary to consider the characteristics, that is, bistability (excluding speed) when using it. child Its properties depend very sensitively on the material chosen and the surface treatment.

C1ark et al, Mo1. Cryst, Liq, Crystal, 19 83. Volume 94゜page 213. Largerwall a tal, Mo1. Cryst, Llq, Cryst.

1984, Volume 114. page 151. )(andsch y at al, Farrpe Hectrics 1984. Volume 59. Page 69. Wahl at al, Ferroelect rlcs 1984. Volume 59. Some of Page 161 etc. As stated in the article. Good and especially symmetrical bistability shows that 5SF It is clear that this has significant positive consequences for the multiplexability of LC devices. It is.

In reality, there may be a slight asymmetry, and it is more effective to switch around 0. Asymmetry in the timing can be revealed by appropriate drive techniques as described below.

Figure 1 shows the homogeneous state (a) with increased volatility (“spin”) and The corresponding state (b) of rationing down is shown schematically. (C) is non-uniform This is an example of quality status. The smecti layer is parallel to the plane of the figure.

The molecular axis is horizontal in (a) and (b), and for convenience, point toward the front from the page of the figure. A hat is attached to the end of the molecular rod. For the up and down states in Figure 1 The corresponding molecular positions (10 and -0) are shown in Figure 2, where the top plate The plate and bottom plate are shown in perspective view.

Switching between up and down states has some very distinctive characteristics However, very few statistical studies have been conducted so far, and DOBAMBC and In addition to substances such as HOBACPC, only a small number of materials have been investigated. . The switching time τ for the latter is shown in FIG. The pulse amplitude is shown schematically as a function of the voltage V applied to the sample. below In the description, the voltage V (at a certain cell thickness) as well as the corresponding electric field E (electro-optical The mechanical response is basically an electric field effect). Two areas are immediately identified . In the W1 pressure drop region (II), the nucleation phenomenon is dominated by domain wall motion as an important factor. become a force. As the electric field increases, more nucleation regions are activated, so that The domain wall does not move to the connected up state, and the inn moves faster and the entire As a whole, it generally contributes to the E-2 dependency relationship. Once the nucleation regions come together, the reverse process The nucleation threshold for That will happen. However, the actual bistability depends significantly on the size of the threshold. Ru. In addition, in the high electric field region (I), the collective bulk spin-flip operation is caused by surface-influenced prisms. It becomes dominant from the process, resulting in a simple linear electric field behavior state. In that state, γ is If the effective rotational viscosity is taken as P and the volarization is taken as τ~γ/PE. ■− The crossover voltage vO in the region between 2 and V −1 is typically 1 to It will be several volts. In any case, as the density of nucleation centers increases, vO We can expect it to decrease. The quantity τ in Figure 3 is important for the switching time. However, traditional methods used for electro-optic responsivity of nematic liquid crystals However, in the present case, when a voltage V is applied to the sample, bistable τ is utilized for the pulse duration required to achieve latching. Professional The mechanical state of the The increase in optical transmission from the polarzar annihilation state is greater than the non-annihilation state. is depicted in response to three different length pulses achieving . about 70 of τ and For the first two pulses of 85% length, the optical responsivity is increases, then decreases.

The latched state occurs after a pulse of duration ±τ. As the amplitude decreases, so does the response. However, at a sufficiently low voltage VDC, the optical responsivity remains until it completely disappears ( Region III in Figure 3) Becomes gradual.

The switching operating characteristics are summarized as follows.

i.e. even if the cell is activated for infinitely long.

Ensure that no switching occurs even in the presence of an absolute low threshold It is always possible to choose the pulse height sufficiently low. About HOBACPC For example.

The absolute voltage threshold IVDcI is approximately 0.0 for the C* phase. IV (cell thickness is approx. 2 μm), increasing this threshold by a factor of 10 results in the results discussed in Chapter 13. As we will see, the most accommodating matrix addressing method for 5SFLC devices is It becomes possible to predict easily. Such a high value of IVDcl indicates a higher Column phase I*, J*.

0 seen in Flll, G* For example, in the C* phase of HOBACPC.

Applicants have discovered that IVDcI is approximately 1v.

When increasing the applied electric field, the area where there is no practical voltage threshold , there is a threshold value for the multiplier of the pulse height and width, in other words, it is not a critical VC. Then, the state shifts to a state where a critical (V·τ)C region exists. The threshold characteristic is (as is valid for all field effects) depending on the liquid crystal material, temperature, surface condition, and cell thickness. and change significantly.

The existence of a threshold region is the most unexpected fundamental property, 5 It is of significant importance regarding the addressing operation of SFLC devices. Another important thing? One obvious characteristic is the horizontal nature of switching; It is possible that a pulse is always a DC signal. However, such temporary direct current The signal must be compensated with pulses of opposite voltage sign, usually 1 When averaged over time 1 >> τ, the effective DC voltage for any element is This DC compensation does not appear at all and otherwise harmful electrolytic effects are not avoided. Preferably done without backswitching caused by compensation pulses. In addition, in some cases, DC drive may cause the liquid crystal matrix (particularly highly conductive materials) to may cause field separation, such that a sufficiently long pulse of one polarity is When removed, the active electric field may be reversed. In this case, another kind of harmful Backswitching may occur. Furthermore, bistability is not necessarily It does not have to be totally symmetrical (symmetry is sensitive to surface alignment on the two surfaces). ).

In that case, asymmetric drive conditions (e.g. certain precautions and DC offsets in the cell structure) It can be modified by adjusting the cut voltage). In short, you need to pay attention to the following characteristics: There is a point.

(a) Switching back and forth between states is performed with DC pulses of opposite sign.

That is, the switching pulse activation is polar.

(b) Sensitivity to the addition of subcritical pulses, where the pulse amplitude is V and the corresponding pulse When the pulse width is τ, a threshold pulse region (V·τ)C exists.

(c) Switching time and voltage characteristics are different from normal ones.

It can be roughly indicated by τc"IVIC-.

At high voltages (for example, voltages greater than 5V for HIBACPC) a = 1. Therefore, at low voltage, a≧2.

(d) Desirability of zero DC voltage for all picture elements.

i.e., zero time averaging on sufficiently long time scales to prevent field effects. Voltage.

(e) Prevention of electric field reversal from ion conduction effects.

(f) Threshold symmetry by asymmetric surface treatment or DC offset voltage.

It is inevitable that some of the above items (e.g. d and f) may contradict each other. It is always obvious and requires particularly careful consideration. A perfectly symmetrical threshold Whether this is achievable depends on several factors, especially the surface arrangement.

The threshold is usually higher than Prime Minister C.

This can be easily achieved in low temperature phases such as Il, J*, p's, Q*. In the CI phase , characterized by fast and weakest threshold conditions, where the symmetric threshold The jord is particularly sensitive and most easily accessed by shear.

It is also possible to use several array techniques suitable for mass production; This is more favorable for low placement height arrays, which often result in asymmetric thresholds. However, in the case of the FLC phase, it is more gradual. Simplify a wide variety of situations For convenience, symmetric and asymmetric threshold conditions are discussed separately (Section 5).

4.1 Ba, Yu・ The harmful effects of intrinsic electric field reversal can be seen in liquid crystal devices (especially the so-called dynamic scattering effect). It has already been recognized in very early research (direct current addressing research) on

When DC activation is performed, relatively high ionic conduction occurs even when the Wl field is removed. The liquid crystal material characterized by this property is a zero ferroelectric liquid crystal that remains in an active state for only a certain period of time. A similar effect was observed in some experiments when pulses of excessively long duration were exerted. A partial or complete switchback to the original state occurs instantaneously in a mixture of In some cases, this means that the cell does not switch at all. This phenomenon is What Applicant calls the "reverse switching effect" This can sometimes be suppressed by opening the drive circuit at about the same time (analog switch or is a tri-state driver), this technology allows some cells to drive standard Switching can be performed with a pulse duration approximately two to three times longer than in the case of a circuit.

(This point will be explained again in Chapter 12C), pack switching is The long pulse separates the space charge, thereby causing devolization (depolization). arization) A reverse electric field is generated which becomes the electric field ED (especially compensates for the applied electric field E). It means to be. The external charge forming E is (relatively low driver impedance) and flows away in a very short time. In that case , EDs are formed over particularly long pulse times, resulting in the application of significantly excessive critical conditions. Survives when combined with voltage. In that case, critical or supercritical application of opposite sign appears as a voltage, causing the molecule to at least partially switch back to its original state of opposite polarity. state, ED increases with increasing pulse duration and space charge density (conductivity). Therefore, reverse switching can be avoided by using short pulses. and in any case it is desirable to use only high resistance materials with it. Delicious.

5. Pare Gu-・1, (a) Symmetric threshold case Ferroelectric liquid crystals can be electrically addressed in various ways and why As such, we can list the basic properties of those materials, and more specifically, we can list the basic properties of those materials. Regarding the addressing method of surface-stable ferroelectric liquid crystal, there is no method that does not satisfy the following conditions. Either they are insufficient in some sense, or they result in contrast effective in that it does not take advantage of inherent speed or bistability, with reduced overall performance including This is because it is not very effective.

The first essential characteristic needed for two-state switching (up and down states) is: It is as follows.

1. The switching pulse applied to the image stop is polar and therefore direct current , and they are characterized by the voltage-time product (Vτ) in the area AX.

2. The switching pulse must be AX > AC, and in that sense, There is a threshold AC in area rather than voltage. If AX<AC, partial switching generally occurs, but latching to a new state does not occur; vice versa. A picture element that is switched into a state is called a selection element.

Note: In the above explanation, image blocking is in the initial state during the time T >> τ (τ is the pulse time). It is necessary that the If the state of image blocking is complete or partial in the nearer time , the threshold depends to some extent on the preceding pulse and will be discussed in later chapters. As I explain, I have to slightly change the description.

3. The time-integrated voltage must be alternating current, i.e. The amplitude and pulse length and polarity are selected to cancel any DC bias. It is necessary to perform built-in DC compensation with new pulses in the area AY.

4. The DC compensation pulse is preferably less than critical, that is, AY<AC, Otherwise, redundant pack switching will occur. Similarly, below criticality Adding a full pulse to the critical pulse value, e.g. by reaching close in time Σadj　(A　yl)＜　A　c. be.

5.For all pulses, follow JK characteristics other than those listed above (however, L, usually more gradual limit) is required due to the inherent tendency for reverse switching. In fact, San With weak forcing leading to a limiting condition on the pulse length, which is influenced by the resistance of the pull. be. Therefore, using long unipolar pulses requires high resistance and Even in the case of deviation, it is a desirable property in liquid crystal materials applied in practical devices.

These requirements are sufficient if they are met simultaneously; , direct drive to all image elements on a macroscopic time scale at any time. and matrix addressing, which cannot be satisfied dependently. There are some desirable characteristics that must therefore be taken into account in the individual application conditions. It is necessary to search for optimal conditions. The most important of these requirements is It is as follows.

6. It is desirable that AX in item 1 above be as high as possible with respect to AC, and any The sum of adjacent subcritical pulses ΣadJ (Ayl) is kept as low as possible to achieve high selection. A selection ratio must be formed, where a selection ratio of 1 means that all subcritical nonselectivity The ratio of any overcritical switching pulse area to the switching pulse area be. 1 Both have either a positive or negative sign, and the switching pulse region The switching or non-switching DC compensated pulse region immediately before is excluded. Ru.

7. The requirements for items 1 to 6 above are 1. For example, superimposing pulse height or pulse width modulation. This must be done without reducing the selectivity. It is impossible.

8. Requirement 3 above is very basic, but it is more effective if it is not strictly satisfied. In some cases, it may be necessary to operate with a slight DC offset and to Try to compensate for any symmetry in the switching state.

However, any DC offset requires special care as described below. It is.

(b) Case of asymmetric threshold 5SFLC cells often exhibit asymmetric switching behavior characteristics in different aspects. In this case, it is usually possible to adjust the addressing method without changing the general principles. 0 required e.g. pulse range for latching to up and down states (Vτ)C characteristics are different or in one state, similar to monostable devices. There will be no threshold. As I have repeatedly pointed out, this It depends very sensitively on the appropriate choice of surface treatment for the ferroelectric liquid crystal. asymmetrical One of the main reasons for the There is a polar bond of the LC molecule, in which case a localized volarization occurs on the bottom surface. and into the liquid crystal, and towards the boundary at the top surface. This asymmetry is caused by surface treatment. It can be made smaller by compensating for the asymmetry (see Figure 2).

Other parts (or even entire parts) can be compensated for by asymmetrical drive. fruit In some cases, the relaxation time is long enough, e.g. Monostable devices can also work very well if they are sufficiently long than . In this regard, Chapters 11 and 13 contain some corresponding examples. Explained in chapter.

６　・　-　-　-こ　　' “Static” drive mode supports single pixel and simple linear arrays and individually It can be conveniently used for matrices of pixels to be dressed. like that The matrix is small and has low resolution or, more specifically, In other extreme cases (e.g., on significantly larger resolution display boards, a single pixel is sufficiently large that there are mechanical and mechanical problems with individual address operations. In such a mode, the device elements generally Switch between two stable states by applying short positive or negative voltage pulses to the electrodes. and thereby the voltage appearing during the pulse duration τ for the electrode overlap region. The pressure difference V satisfies the condition Vτ>(Vτ)C, where (Vτ)C is, as mentioned above, is the minimum pulse region for latching to one side of the bistable state. In particular, one Ground the electrode and apply positive and negative pulses to the other electrode, thereby It is also possible to carry out switching, or to perform monopolar pulses in which both electrodes are shifted in time. For convenience, the (data) signal can be applied to one electrode (e.g. rows of a plane or matrix) and a “common” signal to the other electrodes (e.g. rows of a matrix). In the following description, the voltage difference between the electrodes is V (common) - ■ (data).

In static drive, the 1 selection ratio is virtually infinite, so the address operation There are no severe problems; in principle, Bixel should not change its state to the contrary. Addressed only when not available. In up and down state in all pixels DC compensation for static changes and screens with quasi-static information. is not required, but if necessary, repeating addresses with the same data signal (pulse) operation, thereby requiring some additional electronic circuits as described below. Integration of unipolar pulses can be achieved by utilizing the

As a first example of the 5SFLC drive technology of this invention, as shown in FIG. static electrodes) and m>1 row (data electrodes). Apply static method. In this case, the column is grounded (connected to ground) and , each row connects an electronic circuit consisting of several different functional parts as shown in the block diagram. It continues. FIG. 5 shows an example of a waveform appearing for a pixel.

The actual data signals for up and down states, respectively, are always stored. , when a new data signal arrives, it is compared with the previous signal. two signals are the same , the row driver emits no pulses (ground voltage level); Otherwise, it can be positive or negative depending on the desired change state of the associated vixel state. A pulse is applied to the row. Therefore, in this example, there are three internal Different data signals are used, one of which is switching up and the other One is for switching down and the other one is for no change.

In Figure 6, the time sequence of an actual pulse applied to several rows of a linear array is shown. This is an indication. In this case, only unipolar (positive) pulses are associated with used in conjunction with pulse sequences that occur on a regular basis. To simplify the explanation, In this and the following descriptions, up and down switches are used with positive or negative pulses, respectively. arbitrarily identify the patching. In this driving method, the total address time of a pixel τ C is twice the time τ required for latching into a new bistable state at an applied voltage V. be. This is twice the time required in the previous example, but in that case the positive and negative In other words, it is necessary to apply twice the voltage V.

To prevent the accumulation of switching pulses of the same polarity (DC bias), The use of electronic memories and comparators is often unnecessary or undesirable; Such an integration has an integral area (Vτ) equal to that of the switching pulse and an inverse Combine all switching bars and systems with one or more appropriately selected compensation pulses of polarity. This can be prevented by matching. As a result of this compensation, first, the total time of address operation The interval τe becomes longer. Generally, τe is chosen as a multiple of τ, such that τe=nτ1 However, this is not necessary; Figure 7 shows some examples of this type of DC compensation. Certain 0 portions (a) and (b) are of opposite polarity located just before the switching pulse. Compensation with only one pulse is shown. This bipolar pulse shape of duration 2τ ( ±V), the last (shaded) pulse determines the final state of the device elements; The first pulse depends on the previous state.

The address vixel can be adjusted to the opposite state intermediately. This allows the same - If the repetition rate of the addressing operation of the electro-optic element is too high, the contrast may decrease. That will happen. However, in cases such as matrices with a large number of scanning lines (columns), the Non-determined intermediate switching does not have a significant effect on contrast.

Intermediate switching can be reversed by applying an equal number of small subcritical compensation pulses. However, the effective address time increases as described above. (c in Figure 7) ) and (d) show the appropriate waveforms for the pixels in the case of down-switching. Two examples are illustrative. As shown in Figure 7(c), continuous (subcritical) compensation pulses the ferroelectric elements are separated from each other by a sufficiently long time interval to avoid critical activation of the ferroelectric element. It is very important that

Figure 8 shows an example of a simple method for static drive; In this case, one pulsed DC compensation and just a single polarity (positive) electrode signal are used. Ru.

The minimum address time for this method is τC=3τ. Such a method can be easily applied to linear array devices.

7.11th I As is quite clear to those skilled in the art, currently available twisted nematic devices ferroelectric liquid crystal devices cannot be multiplexed by the same principle as is well known. It is Noh. For at least one of every vixel, a transistor or diode Is it possible to multiplex 5SFLCIIllZ without using active devices such as cards? Questions have been raised about this in the past. Active matrix addressing method For example, European Patent Application No. 0146231 (Applicant: Inter national 5 standard Electric Corporation on, filing date: October 18, 1984). Previously proposed techniques In the technique, the 5SF is Multiplexing the LC matrix results in significant crosstalk between adjacent pixels. is supposed to occur. However, the applicant's analysis and According to the test of the driving method of the applicant, the above matters are not applicable at all. It became clear that something was wrong. Contrary to the above, the release of crosstalk became significant.

To clarify the reason for this, the above method was carried out with extremely high selectivity and Figure 3 points out that τ is the general response time, not the latching time. For a pulse of constant width τl, there is a voltage threshold v1. , this threshold is very sharp.

The actual multiple drive method will be explained in Chapter 11. The principles listed in Chapter 5 generally 1 For example, global DC compensation is always included and precautions against reverse switching are taken into account. However, without following such principles, the following three goals are should be considered as having the highest priority level for practical device circuits. No.

In other words, the degree to which these are satisfied is the performance and quality standard (i) low effective line (and (11) For display devices, large viewing angles and high High selection of switching and non-switching pulse regions for contrast ratio (ili) Regarding the switching itself, the RC value needs to be as small as possible. However, the external drive circuit impedance is changed almost at the same time as switching takes place. as high as possible to prevent electrical discharge and provide the highest possible optical contrast on the device. Maintain it well.

8, :5SFLC and TN The biggest advantage of SSFLC cells is that they have sharp thresholds and very fast response times. It is bistable. Especially in the case of static drive and low data conversion rates. Therefore, the power consumption is lower than that of ordinary TN cells, which need to be permanently activated with alternating voltage. For example, the operation of the time and date numbers on a clock display is very low compared to the case of 0. That's all I can think of.

Contrary to the (passive) TN device, the number of scan electrode lines in multiple drive is 5SFLC device. In the case of 1 selection ratio is almost constant, there is almost no limit (this ratio is 2:1 and 3 :1, and the corresponding ratio for TN devices decreases with the multiplexing factor. , for example, is only 1, and for a multiplex ratio of 100, it is 11:1. ) 6 layers or more voltage levels typically applied for high multiplexing ratio TN addressing operations.

Furthermore, in TN cells, the multiplexing ratio (at a constant threshold voltage) can be increased to It is necessary to increase the battery voltage. The 5SFLC cell is, for example, 5~ Can be easily operated at constant voltage in the normal CMO5 range of 15V. Ru. Overall, the 5SFLC multiplexing technique of the present invention consumes less drive electronics. This reduces equipment costs.

9ei　r　・ Apart from the ferroelectric torque, there is always a dielectric torque acting on the molecule. Those are If it has a negative ΔE value, a planar arrangement is favored and the threshold becomes more mature. At the same time, effects such as increased bistability occur. Additional (stabilizing) By applying a flowing electric field to a glass plate.

You can take advantage of this. However, this type of stabilization with subcritical pulses has already been achieved. This is an essential feature of all DC compensation drive methods, and all addresses discussed here Stabilizing effects on off and on states for materials with negative mode dielectric anisotropy It can be easily confirmed that it has.

Unavoidable “crosstalk” and subcritical (see Chapter 11) pulses are a matrix of the sign of the dielectric torque (rms operating characteristic) when applied to all vixels of For example, AC stabilization, which helps stabilize the two switching characteristics, Can be easily made stronger by increasing the pulse frequency in the selected column . This will be explained in a later chapter.

In 5SFLC cells with asymmetric or monostable switching characteristics, 'flow stabilization' can be very different, and in most cases very good stabilization. will be held. Such situations can be solved by applying a small DC bias of appropriate polarity. In this case, bistability can be increased with only a slight loss of contrast. Nothing In theory, this contradicts the above requirement of zero DC voltage to prevent electrolytic effects. It is something that However, in the case where the applicant conducted long-term experiments, If a suitable insulating layer is provided at the cell boundary, a DC level of knee-immersion is permissible. I know that. Currently, generally accepted long-term DC values are for commercial TN display devices. That's 0. up to IV, and in many cases, DC stabilization conditions are satisfied at this level. can be done. AC and DC stabilization are as compared in Figure 9. 9th The diagram schematically shows a monostable switching state S (real M) and a symmetric bistable state (dashed line ) with either a suitably treated boundary or a bias electric field. ghee is shown. AC stabilization consists of the essentially symmetrical superposition of dielectric torques. DC stabilization essentially refers to the superposition of asymmetric ferroelectric torques. I'm tasting it. This technology will be explained again in Chapter 11.

10, Shi - Rerebere - Su - 1g The previous chapters describe the basic optical and electrical characteristics of 5SFLC cells. Finally, some people want to display different gray levels and colors. The method will be explained, and then a specific driving example will be explained.

(a) Raster technology (spatial integration) For example, similar to general newspaper printing First, additive mixing of the optical states of adjacent vixels can be used.

In very thin cells with negligible intrinsic color.

As currently used for the TPT addressed TN matrix, red/green ・A blue filter can also be integrated. Particularly useful for high-intensity reflectors By using a specific double refraction color obtained by creating a cell with a stepwise change in phase thickness, You can also Because of the electric field threshold, then for different colors Vτ Repeating three-color patterns that require different values and are controlled by selective addressing can be placed in the zone. Below is a simple matrix addressing method: This will be explained in section (Q).

A drawback of raster technology is that it requires increasing pixel density. can be mentioned. here.

Resolution gain affects appropriate digital data processing, e.g. Theoretically, , one pixel is required to display different gray levels or colors. . To a more limited extent, this can be done in any of the following ways.

(b) Switching of duty ratio of J% (time integration) Due to the fast response of FLC, adjustable on/off time ratio allows the display element to remain permanently In that case, the frequency should be set high enough to avoid flickering. This method is easily applied in the case of “static” drive. data processing and recording, especially for video rate high resolution matrices. A large amount of extra electronic circuitry is required for storage. This time accumulation (11 minutes) type speed A common problem with switching is power consumption.

This means that it will increase.

(c) Multi-state switching It has already been described in detail in U.S. Patent No. 4,563,059 (filed on July 8, 1983). As has been shown, especially in the higher order states of the ferroelectric smectic phase, Under certain conditions, more than two switching conditions can be obtained. additional form The state is a partially stable state with no holding field and no threshold switching characteristics. Therefore, by applying pulses at different Vτ, different optical shapes can be obtained. The display element can be switched between the states.

With one pixel and linear alignment device, driving is simple. In the case of multiple drives, It is necessary to keep the different thresholds close enough to each other for the overall selection ratio. Ru. In the simplest case, use one of the matrix addressing methods described below. You can also switch in either width or amplitude as described below. Modulation of the switching and compensation pulses can be performed. In this method, the effective selection ratio It is important to note that this decreases.

(c) Partial spatial switching (spatial integration) Although some cell manufacturing conditions (see below) exhibit an optically uniform appearance macroscopically, , when viewed under magnification, a multi-domain ultrafine grain structure can be obtained.

Such structures are dominant with very strong remanent magnetism due to defects and domain walls. The zero-particle structure exhibiting bistability is

To some extent, it reduces the overall maximum achievable contrast, but some gray It has the advantage of displaying the level and generally being more stable even in the absence of an electric field. Ru. For an ideal 5SFLC structure, let the pulse region Vτ around the threshold value be Modulation allows switching of small or large numbers of domains within a single pixel Sometimes.

Spatial integration as in method (a) results in different levels of play. However, the zero-grain structure, which has the advantage of high resolution, can be obtained with thin cells; , a polyimide surface coating was constructed microscopically by photolithography. The boundary surface itself may become rough, and the VC may be partially changed. becomes a large number of nucleation sites.

11. Two ゛ Based on the response characteristics described above, for both up and down state time address operation. Several embodiments of driving methods for one row in the data will be described below. which fruit The example also satisfies the above-mentioned requirements, but different It has characteristics.

10, 11, 12, and 13 show column and row voltage waveforms and intersection points ( The difference between them that appears in the image elements (or pixels) is indicative. Matrix traversal The continuous waveform at one pixel while performing is illustrated in the example of FIG. can be easily obtained by concatenating the display selection and non-selection pulse sequences as described above. It will be done.

With multiple drives, every element receives a changing voltage signal, and the signal is is the difference between the signal applied to the corresponding column and the signal simultaneously applied to the corresponding row. be.

The column and row signals are each one of two waveforms of duration τe, and the column signal is Indicated by "0" and "1" ("non-selected" and "selected"), and the row signal is "10" and r -" (r up" and "down"); in that case, (0) - (+) and (0)-(-) combinations do not cause a change in the state of the pixel. , (1)-(+) and (1)-(-) are up and down respectively. Causes switching to a state.

Continuously scanning the matrix means that signal (1) (write or common signal) (also referred to as \) is applied to all rows in turn. Other parts of frame time In minutes, (i.e. Nτe for a matrix of N scan rows), the row is (0 ) Connected to the signal is called non-select.

All non-selected pixels receive a data signal ((+) or (-) which is placed on the corresponding column. )). In that case the waveform switches pixels from one state to another. must not contain pulses with enough force to change the Due to the potential negative impact on the contrast of the Also crosses the 0 selection vixel which must consist only of called pulses. Assume that there is a talk pulse, that is, in the writing process of one line, there is a switching pulse. All single pulses (part of a pulse train) that are too small to induce crosstalk Think of it as Kupals. In the latching time unit, the address operation time τe is τe= It is a multiplier of nτ, and in the simplest case, τ1, τ2 . ...Uniform length expressed by τn It consists of discrete voltage phase pulses. In general, address operations (and The pulse train (for writing or scanning) consists of a switching pulse X and an associated compensation pulse X. ', one or more crosstalk pulses YJ and associated compensation pulses Yi'; Consisting of one or more zero phases O1 (see Figure 10), in general, Yi' and Yj The identification between is not relevant.

(a) Driving method with 1 pulse compensation FIG. 10 shows a main example of the driving method according to the present invention. top column selected The pixel is moved during phases τ5 and τ2 by voltage pulses of amplitude V>VC, respectively. Re.

Switches between "up" and "down" states. Corresponding compensation for x, x’ The pulses are in phase τ4 as well as τl. This method uses one pass for switching. Ruth DC compensation is used to keep the overall column address operation time τe short. Crosstalk pulses are used.

Thermal theory, as shown in Figures 7c and d, and further described below, and some subcritical compensations. A similar method can also be easily set up with pulses. bipolar switching cycle is a low crosstalk pulse (Yj, Yj’) vibration for the non-selected rows of pixels. shifted in time to lower the width and thereby obtain a higher effective selectivity.

Also, due to this shift, crosstalk pulses are also generated in the pulse train for the selected pixel. arise. As a result, the minimum duration of the pulse train for one row in a certain time address operation is The duration time is τe=4τ.

This drive method also includes an appropriately set zero-volt phase Oj, which is It can be used to most effectively set the switching operating characteristics. its main purpose completely (or partially) prevents undesired switching and In particular, cells that are not very uniformly aligned (threshold pulse regions) ), a preceding subcritical (crosstalk) pulse of the same polarity The purpose is to prevent problems arising from the accumulation of Yj and Yjo. Such separation function is represented by τ6 in the addressing method of FIG. According to it, the analogy For example, when passing from the selected pulse train to the non-selected pulse train in the down state, two positive clocks Prevent loss talk pulses from accumulating. This separation method is clearly shown in Figure 11. The zero phase shown is not absolutely necessary for that reason.

One example is that the composite crosstalk pulse is in a subcritical state. Also, depending on that This improves the selectivity. In other cases, it may be convenient to impose two or more separate zero phases. often.

In fact, it may be necessary in some cases.

In another embodiment, the zero phase τ3 in FIG. 10 could be removed, in which case the down The overall non-interspaced (spatial residual) pattern for switching to The advantage is that the loss region is larger, making it favorable for downswitching. This property of the subject method is particularly helpful in avoiding the asymmetric switch often seen in 5SFLC cells. It can be used to compensate to some extent for operating characteristics. In a similar method, “A It is a hot theory that "top" switching is also effective.

In a fixed pulse width unit, the selection ratio is defined as the selection and non-selection pulse amplitude (Vs/ It is defined as the ratio of Vns). The best overall voltage selection ratio is 3:1. , the unavoidable crosstalk pulse is generated with an amplitude as large as the battery voltage VB. A high switching pulse of 173 can be maintained.

For the best effective switching selection ratio, subcritical crosstalk pulses are The switching pulse amplitude should be lower than the crossover voltage, and the switching pulse amplitude should be lower than the crossover voltage. - It is necessary to select a voltage that is larger than the voltage (VO>VC). This is generally The 6 selection ratio achieved by appropriately adjusting the pulse width is (in a general sense) ) is effectively set between 2:1 and 3:1.

The waveform for a pixel is generated as a voltage difference between the appropriate column and row waveforms, as usual. , thereby allowing different waveform pairs to lead to identical results as seen in the vixels. can be set.

FIG. 11 shows in detail a typical example of another driving method according to the invention. child In this example, a sequence of pulse trains is depicted to illustrate the relationship between selected and non-selected waveforms. It's clear. This method uses a "down" switching pulse and an "up" switching pulse. The compensation pulses for the switching pulses are the compensation pulses with respect to their position (τ3) in the pulse train. Match. When compared with the driving method shown in Fig. 10, for non-selected image elements (cross There are only two talk pulses (instead of four). This is especially true for matric This is effective in minimizing power consumption when the space is large.

In the modified example of the driving method shown in FIG. 11, the address operation time (n = 4) can also be decreased. In this way, only the circular time period At this point, two small crosstalk pulses will be integrated.

However, the combination region remains subcritical, especially when the amplitude is low in vO. Temporarily group Even if the mating region causes some partial switching, the scan line When the number is large, it approaches and precedes the switching pulse, resulting in poor contrast. No significant effect is exerted (frame time is long compared to τe), Conversely, in yet another example of this addressing method, one or more Insert a zero voltage sum Oi, followed by a "down" switching pulse of opposite polarity It can also be separated from crosstalk pulses. This means that reverse switching It is preferred in the case of ferroelectric mixtures of relatively high conductivity to reduce the tendency There are cases.

In addition, a suitable reverse switching tendency can promote desirable switching. In the drive method, this is achieved by a large compensation pulse before the switching pulse. done automatically. Insert zero voltage sum between thermal theory, compensation and switching pulses By doing so, such effects can be attenuated.

(b) Driving method with subcritical compensation pulses Figures 12 and 13 show the subcritical compensation pulse. An example of driving with compensation pulses (1/3V and 2/3V, respectively) is shown. this According to This will slightly increase the physical contrast. Also, during whole row address operation The interval τe increases.

In the method shown in FIG. 12, compensation pulses of V/3 and 2v/3 are used.

In this case, τe is equal to 6τ, and using a suitably inserted zero phase The accumulation of consecutive pulses can be prevented. In another embodiment of FIG. 12, the zero phase τ3 is It can also be removed. In this case, V/3 before the "down" switching pulse and 2V/3 pulses may be added to result in one partial switching.

Similarly, in the method shown in Figure 13, only the V/3 compensation (and crosstalk) pulse is used with τ8=8τ.

(Q) Drive with AC stabilization The driving methods shown in FIGS. 10 and 11 differ in the points described later. effective pa The pulse frequency and the resulting rmS voltage (within pulse sequence time τθ) are different. There is.

If power requirements are not relevant, select the drive method as shown in Figure 10 and leave the unselected motor By increasing the effective (rms) voltage and frequency in the cell, alternating current due to dielectric torque In another embodiment of the present drive method, which can enhance stabilization, the above frequency and voltage The pressure can be further increased in a very simple way, specifically with constant positive and In the negative region sum, each voltage pulse (and zero phase) of the non-selected column waveform is symmetrically divided. It can be increased by dividing. This method maintains overall DC compensation. , the present invention is applicable to all driving methods. About the driving method in Figure 1O An example of this is shown in FIG. In Figure 14, the new time unit for unselected rows is Similarly, τ/4. You can also use τ/6... can. Furthermore, the "modulation" amplitude (here v/3) is It can be selected depending on the main drive characteristics. Here, for example, twice the original amplitude The crosstalk pulse appears on the pixel, but since the pulse width is small, it It is not critical for switching.

(d) Drive with DC stabilization The stabilizing overall DC bias is determined by the drive method, e.g., row waveforms and column voltage levels. can be easily obtained by biasing at least one of the More specifically, for non-selected vixels, the sum of positive and negative compensation or crosstalk pulses does not disappear within the address operation period τθ. If the unselected pixels are small If a DC bias is required, select ``up'' and ``down'' pulse sequences. By immediately preceding one or several large pulses of opposite polarity and equal region, Overall DC compensation can be maintained within the frame address operation time.

(e) Gray scale drive Another example of the subject driving method is to combine the appropriate cell states and conditions described in Chapter 10 above. It is also possible to display different colors or a certain gray level. for this purpose In order to and modulate symmetrically. These methods, when applied to the driving method shown in Figure 10, Two examples are shown in FIGS. 15a and 15b. For ease of explanation, it Only two stages of modulation are shown for each case. The modulation of the pulse width (τ′) is , the zero selection can be done at different voltage levels using the switch, as shown in Figure 15b. In principle, the ratio of selected and non-selected pulse areas is All symmetrical modulations are allowed as long as it remains sufficiently greater than 1. As a general rule Therefore, strictly speaking, the switching pulse corresponds to the transition region of the corresponding critical curve (see Figure 3). It is necessary to modulate around the VC in the range. The slope of this curve is Processing can already reduce some gray levels to display As stated. If the number of scan lines is small enough, the previously mentioned (time integration), r up” and “down” status display time By scanning at a very high speed with a suitable duty ratio of It can also be generated.

12. Drive method and examples of selective switching Power saving and address operation or effectiveness Reduced frame time.

Useful Techniques for Improving the Contrast of Liquid Crystal Devices with Inherently Memory Capabilities Let me explain some of them. The technique is particularly applicable to 5SFLC devices and is described below. Examples relate to their specific drive characteristics. Another type of bistable fluid Crystal devices can also be driven in the same way.

(a) Selective scanning The usual procedure when driving a matrix device is to remove one set of electrodes (e.g. a column). After removal, one electrode row is scanned or selected sequentially, while a second set of electrodes is scanned or selected. Appropriate data signals for each electrode row at the contralateral electrode (eg column).

It is designed to have a big impact. This method is illustrated in FIG.

In many cases, it appears that only a small portion of the matrix has changed data. In some cases, it is generally necessary to scan the entire matrix at all times. An example of this is the display of a typewriter or word processor. , where one character is written after another in a line of text, and all In other words, (normally) there is data change only in the 7th to 12th column electrodes. Ru. By applying predictive memory capabilities and some extra electronics, the The rows are scanned repeatedly through only those columns until the next row of text is written. At the same time, keep other columns unselected and repeat this operation. This scanning method can be used for any of the matrix drive methods in question. It is clear that it can be applied. An example of such selective scanning is It is shown in the figure as method r■.

Particularly when applying this method with single-pulse compensation, it is important to consider multiple drives in such embodiments. It should be reiterated that the overall contrast can be improved.

(b) Selective driving (row) When trying to change state, switching pulses are applied only to those pixels. can improve the overall (frame) contrast. Linear array (5th We have already explained the underlying principle for the case of selective switching of pixels in Figure). Explaining. Therefore, the third "neutral" data pulse train for the row "unchanged" is Matrix can be easily manipulated by adding generation electronics and memory. can. FIG. 17 shows an example of an additional "unmodified" data pulse train. Yes, in which case using the different column and row pulse trains of the addressing method of Figure 12 , the resulting pulse train for the pixels for the selected and unselected columns is 0 The column address operation time is τe=6 in this case.

Another embodiment of the subject selective drive technique combines selective column and selective row drives, Maximizes contrast while minimizing effective frame address operation time. can be done. An embodiment of this kind is shown schematically in FIG. 16 as Method III. It is.

(c) High impedance switching Applicants have found that the pulse for latching into a bistable state The path width τ as well as the contrast and bistability are determined at the final end of the switching pulse. open-circuit the SSL FC device elements (for example, analog This can be improved by using a power switch or a 3-state driver). . In some cases, the pulse width for latching is It is known that this is about 2 to 3 times lower than when there is no tinging. This results in The overall frame address operation time will also be significantly reduced.

The principle of low/high impedance driving of matrix (and linear array) is shown in Figure 18. , where the column is continuously taken from an open circuit condition to voltage ground level. (or some other constant voltage level) and back to high impedance. This makes column scanning easier. During the contact time τe to the ground, The switching pulse is applied to one row as shown. This method allows non- The problem of crosstalk for selected rows has been resolved, and therefore Chapter 6 (Fig. The addressing method for static drive described in FIGS.

In the first embodiment of high impedance multiplex driving, columns are scanned as shown in Fig. 18. , applying positive and negative switching pulses to the rows under the conditions of FIG. , that is, continuous addressing of the same pixel with switching of the same polarity. It is proposed to prevent In a second embodiment of this kind, the selection column is low impedance. - connected to the dance, and the death pulse train shown in Figure 6c is applied. related during that time row pulse is applied, in which case the row goes high at the final end of the switching pulse. impedance, thereby converting the (relatively) low ohm driver output to Similarly, in the third embodiment, it is preferable to prevent rapid discharge through the eighth The method with bipolar (DC compensated) switching pulses shown in the figure can be applied. child In a further variation of the embodiment, another compensation step may be used, for example as in the example shown in FIG. It is also possible to use switching pulses.

Finally, yet another embodiment will be described. All of those embodiments are shown in Figures 10 to 15. Either of the low impedance addressing methods already explained in Figure 17 or (Fig. 19.20.21). these example, all columns are scanned one or more times during each frame time. (e.g. by exerting a column driver with an “inhibition function”) and at the same time a high switch to pedance. In that case, at the final end of the frame address operation time, This address pause is preferably switched to high impedance. The length of time that can be spent for thermal analysis (stopping) depends on the desired rate of change of information above. There is. Furthermore, the latching time of the FLC needs to be sufficiently fast. Similar implementation In the example, all columns and all rows can be similarly switched to high impedance at the same time. Some of the contrast of the matrix device in question can also be achieved with this intermediate high It can also be shown to increase by affecting the impedance time interval.

13.　　　　Level　 Regarding the response characteristics shown in Figure 3, the SS FLC device was operated in different electric field regions. You can also For static drive, to obtain the fastest switching time Alternatively, a high voltage (in the E-1 region) can always be selected.

In that case, in multiple drives, switching and non-switching pulse regions or pulse It is very important to choose the voltage properly to minimize crosstalk. So requires non-fast switching times and non-fast frame times. If required, select (switch) larger than the crossover voltage VO (equal to τ). Select the pulse amplitude (selected) and the smaller non-selected pulse amplitude Vns. I will do it. As already explained, the best overall ratio (Vs/Vns) is 3. child The ratio can be improved to some extent, but only partially, for example, as explained below. , only for unselected rows.

For crosstalk, select Vns and Vs in the deeper region E-2 in Figure 3. It can be further reduced by doing this. Furthermore, improvements in liquid crystal materials and cell technology have led to If the DC threshold VDC can be increased to a few volts, Vns It will be selected to be less than teVDC. In this case, some of the amplitudes are less than vDC The accumulation of pulses is not a problem, and therefore, the zero voltage sum The address operation time τe can be reduced by excluding everything related to . One such embodiment is the driving method of FIG. ) zero voltage sums τ2, τ4, τ6, τ8 are excluded. (corresponding to that (The column and row waveforms will be collapsed).

Such embodiments are difficult to use due to high VDC, such as I*, F*, J*, G*, H cars. In a favorable state when operating a 5SFLC device in a highly oriented smectic phase, Applicable.

Even in the two cases mentioned above, the zero voltage sum can also be excluded as a result, in which case V If ns < VO, it will depend on the FLC and cell technology, but the matrix Any accumulation of subcritical pulses during a scan will significantly reduce contrast. I would like to emphasize again that there is a possibility that

If the FLC is not very well aligned but fast enough, a small critical It may have a slight effect on sub-field pulses (see the case in Figure 4), thereby The maximum achieved contrast is reduced to some extent. In the matrix, the switching It is possible to further reduce the voltage of non-switching pulses while maintaining the pulse voltage. If you can.

Under such circumstances, the overall contrast can be improved.

This is generally not possible due to the combination of multiple single pixels in the matrix. It is Noh. However, if you reduce the pulse amplitude in all non-selected rows to some extent, e.g. and.

The amplitude of non-switching pulses at the selected row increases. A large number of unselected rows are dominant. Therefore, only the increased pulse amplitude in the selected row is made sufficiently low to prevent FLC latching ( If it is possible to prevent this (full switching), the overall contrast can be emphasized. Ru.

Such effective driving will require higher voltage levels than previously available. . In one embodiment shown in FIG. 19, the amplitude of the non-switching pulse at the selected pixel is The ratio of switching pulse amplitude to The ratio of required to non-switching amplitude is 3.33. The voltage level used is shown in Figure 19. As shown.

Other ratios that can actually be used are 1.5 or more and 6 or less, and such ratios are easy to create. can be obtained. An example of a ratio of 2 to 4 is shown in FIG. 20A. In that case , the area for down-switching (for example) has increased by 50%, and that This results in asymmetric switching behavior, as already explained in Chapters 9 and 11. Another example of a ratio of 1.5 to 6, useful in the case of characteristics, is shown in Figure 20B. .

Another embodiment shown in FIG. 21 shows the asymmetric switching operating characteristics of a 5SFLC device. Can be used in cases. In this example, the pulse height of the non-switching pulse is in the switching direction or downswitching direction, the pulse height V of the switching pulse 0. In the positive voltage direction, the selective non-switching pulse height is only twice It is 0.4v. Full global DC compensation is maintained. to down-switching pulse It is also noteworthy that the height of the DC compensation pulse is only 0.8V. . Another asymmetrical pulse amplitude ratio can be obtained by appropriately selecting one row and the striking force level. Obtainable. ``Up'' and ``down'' switches if actually required. In Figure 1, the positive (“up”) switch also gets different amplitudes. Increase the height of the switching pulse by 0.2V and add another pulse with an amplitude of 0.2V in the negative voltage direction. Additional pulses can also be applied for DC compensation.

14,・　-.

14.1 Optical memory Two-dimensional arrays have improved bistability and a high identification rate in the addressing method. Due to the characteristics.

An optical processor with memory can be configured compactly. the Large and subcritical (non-latching) When a pulse is applied to each element, the element either responds for a short time or does not respond at all. Then, the information is maintained by returning to the initial state (see FIG. 4). twin Stable and inexpensive drive sequencers are essential for high performance linear array storage and output. In the optical field, where force devices have binary characteristics, large amounts of information can be handled. Wear. Ideally, the addressing principle described above should be combined with a bistable linear arrangement. Examples that are suitable for this purpose are described below.

14.2 Halftone image formation in an addressed linear array As we all know, high-quality halftone images such as photographs encode the video content in binary form. It can be caused by Grayscale is traditional raster It is not based on size like in printing, but by evenly positioning the dots. . There are many different encoding systems available, of which ray diffusion linearization method and some related algorithms algorithm is the most suitable for our purposes.

This method is based on rFloyd et al, Proc, SID 19F, Volume 17, page 78J (Bryndabl, Op, Soc, Am, 1978. Volume 68, page 416. Bill lBllottet-Hoff et al, Proc, SID 1983, Volume 24. page 253, Hauck at al, J, O pt, Soc, Am, A., 1984. Volume l, page 5 (see also). In the application example described there, when there is a photographic image In between, the digitized content is optically scanned in rows into a linear array of elements. is stored in association with a fixed periodic raster consisting of . The situation that occurred in that way The information shall be printed in a general electrophotographic manner with a general outline of 0 or more. The described driving method combines a bistable linear array with a simple microprocessor. In combination, an extremely compact electronically controlled printing device can be realized. such a device With this, it is possible to form black and white halftone images, and it is also possible to print entire pages and illustrations of magazines, etc. It allows you to process text and images in the same way and scan them in the same scan. can be formed. Color images use birefringent colors or Three linear arrays or three consecutive scans using filters are required. Dressed like this Due to its small size, it can actually form the heart of a small non-impact printing press. similar When one synthetic hologram is made by computer control using the method described above, or when one skilled in the art It can also be used for many similar tasks that are self-evident.

7fufu・tau〉su7ley FIG. 5 FIG.6 FIG.7 ・Pifcell ha ■Pik4shi Daeun FIG.8 FIG.9 (Rito Axel 'Taraseei' 0hi'kuse J and tJg on '1.

FIG. 10 Snake? Nita Town child town Tail 1 gun He°sis Takano Xasis Nobumugi style FIG. 15 Direction of writing text FIG. 16 FIG. 1B Take　9〉〉 international search report 1mlIMj1^-both@-ceramic,p(=,Sε86100476

Claims (10)

[Claims] 1. Address for driving an array of electro-optic elements with a linear electrical response column Preferably, the element is ferroelectric or flexoelectric. with up and down polarization. A helix with at least two states. Free polymer or non-polymer - Consists of liquid crystals, and horizontally (for example, N≧1) on opposite sides. interposed between a pair of substrates comprising a set of electrodes (in parallel rows) and a set of vertical electrodes with M≧1. In a method described above, the method is applied simultaneously to N and M sets of electrodes for a duration τ a train of voltage pulses with e=nτ, thereby causing A pulse train whose duration τ and amplitude V is greater than or equal to a critical value (VτC) positive or negative to force latched into the desired up and down states, respectively. voltage pulses, and the pulse train at all non-selected pixels is a subcritical pulse. only, so that the above method can be Allows simultaneous switching of up and down states, and also allows n to be the address of many columns. In order to maintain a low enough time for operation, it is preferably 8 or less. An addressing method characterized by: 2. When integrated over the entire duration τe, everything that appears in every pixel The time integral of the pulse train is 0 (∫Vdt=0), so the above method The pulses include one or more DC compensated pulses of opposite polarity, and the switching pulses A pulse compensation of one of the pulses is preceded immediately before said pulse, and the method is particularly advantageous in that Two adjacent pulse trains or consecutive subcritical pulses of the same polarity belonging to the same pulse train When used to space pulses, one or more of the durations τ within the pulse train It also has a zero voltage phase for switching and thereby Prevention of unwanted switching and contrast-reduced partial switching In order to prevent the addition of the relevant pulse region to the continuous region approaching the critical value, the above The zero voltage phase can also be used to separate switching pulses from continuous pulses of opposite polarity. , thereby reducing the tendency for back-switching due to reverse field effects. A method according to claim 1, characterized in that: 3. For a time unit τ, the amplitude of the switching pulse V=Vs is preferably 1. All non-switching voltages that range from 2VC to 1.5VC and appear at any time The maximum amplitude Vns of the programming pulse is preferably VC/2 or more, and the non-selected pin The pulse at the selected pixel is preferably smaller than the non-switching pulse at the selected pixel. The values of the amplitudes Vs and Vns are determined by the V-τ response of a particular electro-optical element. Select according to the characteristics to satisfy the necessary conditions, and select the switch according to the necessary conditions. For maximum speed, both Vs and Vns must be equal to or higher than the crossover voltage VO. The crosstalk is also large, and in order to reduce crosstalk, both Vns and Vs must be is less than VO, or Vns is less than VO and Vs is greater than VO. , in order for it to be possible to eliminate the zero voltage phase, Vns must be less than VDC, Claim 1 or 2, characterized in that the addressing method can be simplified. How to put it on. 4. The asymmetric up/down switching operating characteristics are compensated by different means, The means may be applied alone or in combination with each other, wherein the method first applies to a pixel. a pulse train in which a positive or negative switching pulse is immediately followed by a is followed by a subcritical pulse of the same polarity in one of the two switching directions. The second method is to increase the switching power of the (unselected and/or or selection) where the pulses have different amplitudes in the positive and negative voltage directions and are preferred Specifically, in the non-selected pulse train, Vns≦0.4Vs in one direction and Vn in the other direction. s<0.25, and the above method is smaller by one or more time units (within τe) DC offset in combination with a sufficiently thick insulation layer for the electrodes, each The above DC offset within a time unit is the bias of the column and/or row pulse train. Preferably, the pulse train is a non-selected pulse train, and Note that the DC offset is finally the reverse polarity of the selection up and down sequence just before And by using 1 or decimal large pulses of uniform area, one frame time Claims 1 to 3 are characterized in that the direct current is partially or completely compensated within a range of The method according to any of paragraph 3. 5. The rms voltage and the number m of polarity reversals in the non-selected pulse train of length τe need to be different. First, the column and row pulse trains should be selected appropriately. Incorporating several zero voltage layers instead of pulses reduces overall power consumption. and secondly, any small amplitude vibrations of molecules caused by subcritical pulses. and increase the intrinsic stability of the bistable state with rms voltage. , for negative dielectric anisotrophies, m and rms values increase and extend to non-selected columns. is most easily achieved by dividing each voltage pulse symmetrically in a pulse train Claims 1 to 4, characterized in that: Any method described. 6. With appropriate defect-inducing surface treatments, the threshold VC can be locally reduced within each image element. , thereby setting the corresponding partial switch of a domain to ing, giving the pixel elements a microscopic grainy appearance in the optical state, and Macroscopically merges with the partially switched gray state, whose level increases with the pulse height The statement changes the applied switch by modulating the pulse width to be greater than a certain voltage level. controlled by varying the voltage-time domain of the pulse Application of associated pulses in the row (data) pulse train while maintaining full DC compensation Claim 1, characterized in that it can be easily achieved by appropriate modulation. ~The method according to any one of paragraphs 4 to 4. 7. Take full advantage of the bistability of electro-optic elements to eliminate unnecessary switching and control. Avoiding last reduction switching by different means, and using the above means alone Or use them in combination with each other, and as a means to do so, first, change the state. Scan only the column on the pixel that you want to scan, and then apply an appropriate pulse train to the row It not only performs switching up and switching down, but also ” so that only the pixels that actually need to change state are switched. In this way, for example, in the case of a linear arrangement, the switching pulse Due to the The method according to any one of claims 1 to 6, characterized in that: 8. N or M sets of electrodes, or both electrodes, are switched to high impedance. This increases the overall contrast and reduces the latching time τ. The method comprises a scanning step in which one column next to another column is scanned for a period τe. is a constant voltage level (e.g. ground) from high impedance to low impedance. rows are switched up and down or "unchanged". receiving a data pulse for the purpose, the method further comprising a scanning step; During the switching time τe of the selected column to low impedance, the column and row patterns are russ train in accordance with the claims above, in which case maintaining full DC compensation. state, at the end of each switching pulse the row is already switched to high impedance. If the method further comprises a general scanning step, then , a low impedance is connected to each column and row driver, and a pulse train is connected to the above claims. corresponds to all columns or all columns and all columns for a certain time interval τp>τe. all rows switch to high impedance at the same time, and this "high" period τp lasts once or multiple times during the entire scan time (frame time), preferably Claims 1 to 3 are applied at the final end of each scan of the trix. The method according to any one of paragraphs 4, 6, and 7. 9. High speed electronic printing, preferably in combination with an array of 1 to 3 linear light shutters now applies to color printing and binary gray scale printing. 9. A method according to any one of claims 1 to 8, characterized in that: 10. combined with optical SSFLC memory, in which case the stored information is critical is searched by scanning with pulses less than The feature is that it generates a response that can be viewed without changing the state of the object. The method according to any one of claims 1 to 9.