RU2206914C2 - Passive-matrix liquid-crystal screen and procedure of control over given screen - Google Patents

Abstract

FIELD: playback of images. SUBSTANCE: application of procedure makes it feasible to obtain technical result in the form of improved contrast and time characteristics of screen with simultaneous enlargement of angle of aspect. This result is achieved thanks to manufacture of liquid-crystal layer in proposed screen with potential for dynamic self-compensating configuration and thanks to arrangement of optical axes of polaroid films along bisectors of angles between orientation vectors of surface molecules. EFFECT: improved contrast and time characteristics of screen. 10 cl, 4 dwg, 1 tbl

Description

 The invention relates to indicator technology and can be used in flat screens of televisions, computers, game consoles, fax machines, mobile phones, etc.

 Known active-matrix screen [1], containing a liquid crystal (LC) layer located between two transparent dielectric plates, on the external surfaces of which are polaroid films, on the inner surface of one of the dielectric plates a thin-film integrated circuit (including MxN thin-film field-effect transistors is made ) and two groups of transparent input electrodes, the first of which forms N rows, and the second group of M matrix columns, with the input of each thin-film field tra the resistor is connected to the electrodes of the corresponding row and column, and its output is connected to the corresponding element of the output transparent electrode, consisting of MxN elements and in contact through the polymer layer with the LC layer, while the polymer layers provide the initial orientation of the adjacent LC molecules and their spiral twist in the volume of the LCD layer.

 The color version of such a screen contains a triple number of columns, under the electrodes of which there are light filters of three primary colors.

The active-matrix screen is controlled by matrix addressing of the inputs (gates) of thin-film transistors, therefore, the threshold characteristic of the active-matrix screen is determined by the threshold for switching on the thin-film transistor. If the threshold voltage level is exceeded (at the input of the selected thin-film transistor), the capacitor (which is an integral part of the thin-film integrated circuit) is rapidly charged, connected at the output of the thin-film transistor in parallel with the electrodes of the region of the LCD layer that corresponds to the screen element to be switched on. The charge on the capacitor provides a memory effect for a given element of the screen, providing a supporting voltage on the corresponding region of the LCD layer during the frame scan time T _F. On the contrary, when the voltage at the input of the selected thin-film transistor is lower than the threshold level, the capacitor charge circuit will remain open, and the corresponding region of the LCD layer will be under zero voltage for the whole scan time T _F , i.e. the screen element in question will be turned off in this case.

 The high threshold characteristics of the active-matrix screen, combined with the presence of electronic memory in it, ensure the implementation of large drops in the control voltage on the switched regions of the LCD layer, and, as a result, high (up to 500: 1) contrast and good speed (total time) are realized in such screens reaction and relaxation of the screen element up to 25 ms).

 The main disadvantage of the active matrix screen is its complexity (high cost), due to the technological complexity of manufacturing a defect-free thin-film electronic circuit, especially in the case of a large aperture of the screen. For this reason, mainly active-matrix screens with a diagonal of no more than 15 inches and a resolution of no more than 1024x768 color triads (not exceeding the XGA format) are mainly produced.

Known passive-matrix LCD screen on super twisted nematics (super twist nematics) or briefly - STN screen [2], containing an LCD layer consisting of nematic LC molecules with positive dielectric anisotropy and located between two transparent dielectric plates, on the outer surfaces of which are respectively the first and second polaroid films, and on the inner surfaces, respectively, the first and second groups of transparent electrodes with the first and second polymer layers deposited on them, the first group of transparent electrodes forms N rows of the matrix, and the second group M columns, the first and second polymer layers provide the initial orientation of adjacent LC molecules, respectively, at angles α ₁ and α ₂ to the surfaces of the corresponding plates, and a rotational additive is present in the LC layer, specifying the initial spiral twist of the molecules in the volume of the layer at an angle β ₀ within 180-270 ^o . The orientation of nematic LC molecules is understood as the orientation of their long axes.

 Technologically, such a screen is much simpler than the active matrix due to the lack of a complex thin-film electronic circuit.

The control of this screen is carried out in accordance with the known method [2], namely, that the frame is scanned in N consecutive cycles, supplying control signals in each cycle to the electrodes of M columns and N lines of the screen and acting by their resulting electromagnetic field on those areas of the LCD a layer consisting of nematic liquid crystal molecules with positive dielectric anisotropy, which correspond to the MxN elements of the screen, while in the ith step, where i = 1, 2, ... N, only the i-th page is selected ok, changing the physical properties of the corresponding regions of the LC layer by exceeding in these areas a certain value of the amplitude of the resulting electromagnetic field, while during the whole time T _F scan frame creates a supporting voltage on each element of the i-th line.

Direct matrix addressing of the LCD layer in the passive matrix (STN) screen leads to problems with the implementation of high contrast and time characteristics. To obtain high contrast, it is necessary to create a large voltage drop between the on and off states of each screen element, and with a characteristic absence of memory in the addressable elements for this screen, the specified voltage drop must be maintained throughout the frame scan time T _F , which with direct matrix addressing of LCD areas layer leads to the inability to use the entire dynamic range of its volt-contrast characteristic (WCC) for information modulation (in contrast to active -matrix display), as a passive-matrix display a substantial portion of the dynamic range by FCC occupy support voltage drops. Work on a very limited section of the WSS with insufficient steepness (for real-life LCD materials) makes it impossible to realize maximum contrast and speed for elements of a passive-matrix screen; according to these parameters, the latter is inferior to the active matrix screen by approximately an order of magnitude. In addition, in passive-matrix screens, the real value of the control voltage that actually acts on the LCD layer always decreases due to the resistance of the electrode strips and interelectrode capacitances of the screen, which in the known screen due to the lack of reserve in the dynamic range of the control voltage additionally limits the limiting level of multiplexing ( the maximum number of elements involved in the formation of each image frame) and the maximum size of the screen diagonal. Even special corrective control algorithms cannot solve these problems, therefore, passive-matrix screens are inferior to active-matrix ones not only in terms of contrast and speed, but also in information content (1.5-2 times).

 The technical result achieved using the present invention in a passive matrix LCD screen is to improve its contrast, time characteristics, increase information content, improve the viewing angle of the image.

The specified technical result is achieved by the fact that in the passive-matrix LCD screen containing the LCD layer, consisting of nematic LC molecules with positive dielectric anisotropy, the first and second transparent dielectric plates, on the outer surfaces of which are the first and second polaroid films, respectively, and on the inner surfaces - respectively, the first and second group of transparent electrodes, which form respectively N rows and M columns of the matrix, on which the first and second polymer layers are applied defining the orientation of the molecules adjacent to them in the first and second directions, respectively, with the angles of inclination α ₁ and α ₂ to the surfaces of the corresponding dielectric plates, and in the LC layer there is a rotational additive that sets the initial spiral orientation of the molecules at an angle β ₀ in the volume of the LC layer, optical the axes of the first and second polaroid films coincide with the bisectors of adjacent angles between the projections of the orientation vectors of the molecules adjacent to the first and second dielectric plates, on the plane of these plates, the LC layer is made with the possibility of the existence of a dynamic self-compensating configuration, a structure which is characterized by a gradual change in the angle of inclination of the molecules along the thickness of the LC layer from α ₁ to α ₂ with a transition through α _c = 90 ^° for molecules in the central part of the LC layer, with the sign of the angle of rotation of the molecules at the transition from the angle α ₁ to the angle α _c = 90 ^{° is} opposite to the sign of the angle of rotation of the molecules during the transition from the angle α _c = 90 ^° to the angle α ₂ , and the threshold characteristic of the screen is determined by the energy barrier between the initial state of the LC layer and its condition with the presence of a self-compensating configuration.

The achievement of the specified technical result is primarily associated with the presence in the LC layer of a dynamic self-compensating configuration that occurs only after the procedure of applying and removing a high-level control voltage, the value of which is sufficient to overcome the energy barrier of the formation of this configuration. Obtaining high contrast and increasing the viewing angle is due to the mutual optical compensation (self-compensation) of two symmetric (relative to the central part of the LC layer) parts of the configuration due to the mutual opposite signs of the angle α of rotation of the molecules. At the same time, the ability to obtain a sufficiently long (not less than the time T _F scan frame) time τ _{memory of the} existence of a self-compensating configuration allows you to implement optical memory, which is a physical analogue of the electronic memory of the active matrix screen. The high threshold characteristics of the proposed device (achieved by the physical properties of the energy barrier, which must be overcome to form a self-compensating configuration) lead to the possibility of increasing the maximum possible number of addressable screen elements (increasing its information content), since the old (typical for a known screen) significant restrictions on the length of the electrodes are removed matrices, since in the proposed device there is a margin in the level of control voltage, and therefore are not significantly impact resistance and capacitance of the electrode array to reduce the actual current (LCD layer) control voltage value.

The speed of the screen is improved due to both reducing the on-time of the elements of the screen (due to the use of large voltage drops of the control voltage) and by reducing the relaxation time of the elements (to the value of the lifetime of the dynamic self-compensating configuration, chosen not exceeding T _F frame scan).

In a first particular embodiment of the device, the optical axes of the first and second polaroid films are mutually orthogonal, while the optical axis of at least one of the polaroid films is parallel to the projection on its surface of the orientation vector of the molecules located at the surface of the LC layer closest to the polaroid film, the angle of inclination of the molecules meet the condition α ₁ = α ₂ , the twist angle β ₀ is 180 ^o , and the product of the optical anisotropy Δn and the thickness of the LC layer is within 0.4 μm≤Δnd≤0.7 μm.

 In such a particular embodiment of the device, the maximum contrast of the formed image can approach in the limit the magnitude of the contrast of the polaroid films themselves with a certain decrease in the transmittance (optical efficiency) of the screen in the initial state compared to the general case.

 In a second particular embodiment, a film compensator is additionally introduced into the device between at least one of the dielectric plates and the adjacent polaroid film, which makes it possible to increase the viewing angle of the image.

 In a third particular embodiment of the device, the transparent electrode of each column of the matrix is divided into three longitudinal segments, filters are additionally introduced into the screen, each of which is located between the surface of one of the dielectric plates and the corresponding segment of the transparent electrode, with each triple column of the screen having a triad of filters of three primary colors. This screen option allows you to get a full color image.

 The technical result achieved using the proposed method is to improve the contrast and dynamic characteristics of the generated image.

The indicated technical result is achieved by the fact that the frame is scanned in N consecutive clock cycles, supplying control signals in each cycle to the electrodes of M columns and N lines of the screen, acting by the resulting electromagnetic field on those areas of the LC layer consisting of nematic LC molecules with positive dielectric anisotropy which correspond to M x N display elements, while in the i-th clock cycle, where i = 1, 2, ... N, only elements selected i-th row selecting period of recording time t _W, during which act electron omagnitnym field recording signals with amplitude U _1> U ₀ (t _W) to the areas of the LC layer, which correspond to include elements of row i-th, where U ₀ (t _W) is the threshold voltage of formation of self-compensating configuration LC layer, in the same clock cycle during the same recording period of duration t _{W, the} areas of the LC layer corresponding to the nonincluded elements of the i-th row either do not supply the electromagnetic field of the control signals or act on these areas with the electromagnetic field of the recording signals with the amplitude U ₂ <U ₀ (t _W ), leaving those m the indicated regions of the LC layer in the initial state or by transferring them to a weakly excited state, and the remaining 1, ... i-1, i + 1, ... N clock cycles of this frame during all the corresponding recording periods on the region of the LCD layer corresponding to the i-th line, they act by the electromagnetic field of the recording signals with an amplitude of U ₂ <U ₀ (t _W ) or they remove the electromagnetic field from these areas.

In this case, the time T _{F of the} scan frame is selected not exceeding the time τ _{memory of the} existence of a self-compensating configuration.

The improvement of the contrast and dynamic characteristics of the formed image is due to the fact that, while maintaining the simplicity of direct matrix control of the areas of the LCD layer (typical for passive-matrix screens), the self-compensating configuration is excited in the latter, which leads not only to the appearance of optical memory in the screen elements, but also to the appearance of a steep dynamic VHC of the screen due to the inertia of the response of LC molecules to a rapid increase in the level of an exciting electromagnetic field (during the duration t _{W of} recording periods ) The shorter the control voltage pulse, the higher the threshold for the formation of a self-compensating configuration. It is significant that in this case the same LCD material is used, which is characterized by a low slope of the water supply system with conventional matrix control (characteristic of the known passive-matrix screen).

In the first particular embodiment of the method, during the i-th recording period of duration t _{W, a} recording signal in the form of a voltage of U _{S is} supplied to the electrode of the i-th row, recording signals in the form of a voltage of U _D are supplied to the column electrodes of the included elements of the i-th row, and zero voltage is applied to the electrodes of the remaining columns and rows, while the duration t _{W of the} i-th recording period is selected in accordance with the conditions T _W > T _{D + S} , T _W <T _D , T _W <T _S , where T _{D + S} , T _D and T _S - time of formation of a dynamic self-compensating configuration of the LC layer by d by the action of voltage, respectively, with the values of U _s + U _D , U _D and U _S , and the rest of the i-th cycle, zero voltage is applied to all electrodes of the screen, and the duration of the remaining cycle time is selected sufficient to return non-switched elements 1, 2, .. .i-th lines and all elements (i + 1), (i + 2), ... N-th lines of the screen from an intermediate state to the initial state.

In the second particular variant of the method, the i-th recording period is divided into two adjacent time intervals t _WS and t _WD , during the interval t _WS, voltage U _{S is} applied only to the electrodes of the i-th row, and zero voltage is applied to the electrodes of the remaining rows and all columns voltage, and during the interval t _WD, voltage U _{D is} applied only to the electrodes of those columns that correspond to the included elements of the i-th row, and zero voltage is applied to the electrodes of all other rows and columns, and the values of the time intervals are selected in accordance with conditions t _WS + t _WD > T _S , t _WS + t _WD > T _D , t _WS <T _S , t _WD <T _D , where T _D and T _S are the times of formation of a dynamic self-compensating configuration of the LC layer under the action of voltage, respectively, by the values U _D and U _S , and the rest of the time of the i-th cycle, all the electrodes of the screen are supplied with zero voltage, and the duration of the remaining cycle time is selected sufficient to return the non-switched elements 1, 2,. . . i-th lines and all elements (i + 1), (i + 2), ... N-th lines of the screen from a slightly excited state to the initial state.

 The second particular variant of the method allows the use of extremely short control voltage pulses at the maximum values of the amplitude of the latter, which leads to the realization of an extremely short addressing time for each line, and, as a result, to the achievement of the maximum multiplexing value N (to the possibility of controlling the screen with the maximum number of N lines) .

In the third particular embodiment of the method, the i-th beat is divided into successive i-th erase cycles and i-th recording cycle, during the first of which an erasing signal with an amplitude U _E whose frequency f is greater than the critical frequency is fed to the i-th line f ₀ changes the sign of the dielectric anisotropy of the nematic liquid crystal, and the magnitude of the amplitude U _{E0 of the} erasing signal during the duration Δt _E0 of the erase period ensures the complete elimination of the self-compensating configuration in all areas of the LC layer corresponding to the ith row.

In this case, the speed of information reproduction by the screen remains equal to the rate of change of frames even if τ _memory corresponding to the natural relaxation conditions of the self-compensating configuration is selected for more than the frame scan time T _f .

In the fourth particular embodiment of the method, the ith step is divided into successive recording and erasing cycles, and during the last, an erasing signal with a frequency f that is higher than the critical frequency f _{0 of} changing the sign of the dielectric anisotropy of the liquid crystal is fed to the i-th line This is varied by the amplitude U _{E of the} erasing signal and the duration Δt _E of the erasure period, thereby controlling the speed and degree of elimination of the self-compensating configuration in the corresponding regions of the LC layer.

 The specified private variant of the method allows the formation of a multi-gradation (grayscale) image due to the partial elimination of the self-consistent configuration of the LCD layer by varying the parameters of the erasing signal that follows the time immediately after the recording signal.

In the fifth particular embodiment of the method, the erasing signal in the form of an alternating meander with a variable amplitude U _E and a frequency f> f _{0 is} formed only on switched off elements of the i-th row, for which a signal is applied to the electrode of the latter in the form of an alternating meander with a frequency f ₁ equal to f / 3 <f ₀ , and the signal in the form of a sequence of groups of alternating pulses of amplitude U _{E is} applied to the electrodes of the columns corresponding to the elements of the i-th row being turned off, while the period T _{1 of the} sequence is 1 / f ₁ , the duration of each pulse is T ₁ / 3k where k is the number of pulses in the group, and the sign of each current pulse coincides with the sign of the current amplitude of the meander. In this particular embodiment of the method, selective erasing of the erasing signal is achieved only on switched off elements by obtaining a high frequency f (higher than f ₀ ) for the erasing signal by adding signals with frequencies lower than f ₀ .

 The invention is illustrated by drawings, in the figures of which the following is presented.

 Figure 1 is a cross section of a passive matrix LCD screen.

 Figure 2 - curves of the coefficient K of the optical transmission element of the LCD screen when applying a control voltage.

 FIG. 3 is a diagram of a change in the state of an LC layer upon application and removal of an electric field (control voltage).

 FIG. 4 - formation of an erasing signal with a Raman carrier frequency.

A passive-matrix LCD screen having MxN elements contains (Fig. 1) an LC layer 1 consisting of nematic LC molecules with positive dielectric anisotropy, two dielectric plates 2, 3, on the outer surfaces of which there are polaroid films 4, 5, on the inner the surface of the dielectric plate 2 there is one group of transparent electrodes parallel to each other (a longitudinal section of the i-th electrode 6 _{i is} shown, directed along the plane of the drawing, where i = 1, 2, ... N), on the inner surface of the dielectric plate 3 another group of transparent electrodes parallel to each other is laid (a cross section of the jth electrode 7 _{j is} shown, directed orthogonally to the plane of the drawing, where j = 1, 2, ... M), polymer layers 8 and 9 are applied to the transparent electrodes, which provide the initial the orientation of the molecules of the LC layer 1. The direction (vector) of the orientation of the nematic LC molecules is determined by the direction of their long axes. The surface molecules (located directly on both surfaces of the LC layer 1) are inclined, respectively, at angles α ₁ and α ₂ to the inner surfaces of the corresponding dielectric plates 2 and 3. In the LC layer 1, there is a rotational additive that sets the initial spiral twist of the molecules at an angle β ₀ in the volume LCD layer. The optical axis OO 'of the first 4 and O ₁ -O ₁ ' of the second 5 polaroid films (Fig. 1, bottom) coincide with the bisectors of adjacent angles between the projections P ₁ and P ₂ of the orientation vectors of the molecules adjacent to the first 2 and second 3 dielectric plates, on the plane of these plates. The LC layer 1 is configured to have a dynamic self-compensating configuration in it, which is characterized by a gradual change in the angle of inclination of the molecules along the thickness of the LC layer from α ₁ to α ₂ with a transition through α _c = 90 ^° for molecules in the central part of the LC layer, the sign of the angle of rotation of the molecules when moving from the angle α ₁ to the angle α _c = 90 ^{° is} opposite to the sign of the angle of rotation of the molecules when moving from the angle α _c = 90 ^° to the angle α ₂ . The threshold characteristic of the screen is determined by the energy barrier between the initial state of the LC layer 1 and its state with the presence of a self-compensating configuration. The formation time of the latter does not exceed the scan time of one line of the screen, and the lifetime does not exceed the time T _F frame scan of the screen.

 The indicated mutual arrangement of the axes of the polaroid films 4 and 5 and the orientation vectors of the surface molecules corresponds to minimizing the effect of self-compensating configurations on the optical characteristics of polarized light passing through the LC layer 1. Deviation from this arrangement leads to a decrease in contrast due to an increase in the ellipticity of the light passing through the LC layer.

 The possibility of the existence of a dynamic self-compensating configuration in the LC layer 1 is determined by the choice of the corresponding composition of the LC layer 1, by specifying the nature of the connection of its surface molecules with polymer layers 8, 9.

In the first particular embodiment of the device, the optical axes of the first 4 and second 5 polaroid films are mutually orthogonal, while the optical axis of at least one of the polaroid films is parallel to the projection onto its surface of the orientation vector of the molecules located at the surface of the liquid crystal layer closest to the polaroid film, tilt angles molecules meet the condition α ₁ = -α ₂ the twist angle β ₀ is 180 ^o , and the product of the optical anisotropy Δn and the thickness of the LC layer is in the range of 0.4 μm≤Δnd≤0.7 μm. In this embodiment, the influence of inhomogeneities in the initial orientation of the molecules (for the initial state of the LC layer) on the uniformity of the image background is minimized due to the minimal effect of the corresponding deviations in the optical anisotropy Δn on the optical properties of transmitted polarized light.

 In a second particular embodiment of the device, a film compensator is additionally introduced between at least one of the dielectric plates (for example, 2) and the adjacent polaroid film 4, which makes it possible to obtain an expanded viewing angle of the image due to the mutual compensation of the optical anisotropy of the LC layer and the film compensator.

 In the third particular embodiment of the screen, the transparent electrode of each column is divided into three longitudinal segments, filters are additionally introduced into the screen, each of which is located between the surface of one of the dielectric plates and the corresponding segment of the transparent electrode, with each triad of the screen corresponding to a triad of filters of three primary colors. This particular version of the screen is designed to produce a color image.

 The device operates as follows.

First, consider the operation of one screen element (located at the intersection of the i-th row of the j-th column). In the absence of an electric (electromagnetic) field in the initial state of the LC layer, the optical transmission of the screen element is a function of the interference of two elementary light waves with mutually orthogonal polarization directions (into which you can decompose an arbitrary input polarized light wave), between which a phase delay occurs after they pass through the LCD layer (along the axis of a spirally twisted molecular configuration). When a voltage is applied (to the i-th row and j-th column) above a certain threshold value U _{1, the} molecules reorient along the lines of force of the electric field arising in the LC layer, i.e., they tend to orthogonal (relative to the surfaces of the dielectric plates 2, 3) orientation , which is characterized by an angle of rotation of the molecules α _c = 90 ^° , while the effective value of the phase delay created by the LC layer decreases (tends to zero with increasing voltage). After stress release, the molecules tend to return to their original state. In this case, the torque acting on the molecules located between the first dielectric plate 2 and the central part of the LC layer 1 is opposite to the torque acting on the molecules between the central part of the LC layer 1 and the second dielectric plate 3. Since the molecules of the central part of the LC layer 1 at this operating force equal in magnitude but opposite in sign, and after the termination of the field the molecules remain in a state with α _c = 90 ^° for a time τ _memory (related to time Este Twain relaxation τ _relax). During the time τ _memory, there is a self-compensating configuration characterized by a gradual change in the angle of inclination of the molecules along the layer thickness from α ₁ in the first plate to α ₂ in the second plate with a transition through α _c = 90 ^° (perpendicular to the dielectric plates) for the molecules in the central part of the LC layer (at least one molecular layer in said central portion), and the sign of the rotation angle of molecules in the transition from the angle α ₁ to an angle α _c = 90 ^° opposite to the rotation angle of molecules in the transition from the angle _c = 90 ^° to the angle α _2.

 The dynamic self-compensating configuration is characterized by relaxation in the form of a continuous process of the return of the edge symmetrically located (relative to the central part of the LC layer) molecules to the initial state. A characteristic property of such relaxation is the practical absence of changes in the effect of the LC layer on transmitted polarized light during the entire relaxation process, which is due to the mutual compensation (self-compensation) of optical activity of a different sign resulting from a different sign of rotation of the molecules relative to the central part of the LC layer.

Finding the LCD layer in a dynamic self-compensating configuration during the time τ _memory in the absence of external voltage is equivalent to the presence of an energy-independent optical memory for each screen element (the time τ _memory is chosen not exceeding the frame time T _F to obtain maximum screen speed).

где η - вязкость жидкого кристалла,
ε₀ - диэлектрическая проницаемость вакуума,
Δε - анизотропия диэлектрической проницаемости жидкого кристалла,
U_n - пороговое напряжение,
d - толщина ЖК слоя.The formation time of a self-compensating configuration is selected no more than the scan time of one line of the screen. The magnitude of the time of occurrence of a self-compensating configuration depends on the magnitude of the control voltage; the larger the value of the latter, the shorter the required time for applying voltage, which is associated with a decrease in the inertia of the response of the molecules. The inertia of the response of molecules to an increase in the applied electric field voltage is described by the delay time τ _delay , which is part of the reaction time τ _react [3]

where η is the viscosity of the liquid crystal,
ε ₀ - dielectric constant of vacuum,
Δε is the anisotropy of the dielectric constant of the liquid crystal,
U _n is the threshold voltage,
d is the thickness of the LC layer.

для данного экрана, при этом ρ для последнего превышает 1 (как и для активно-матричного экрана), в то время как в известных пассивно-матричных экранах, как правило, ρ<<1).Physically, the presence of the indicated inertia is due to the need to overcome the moment of friction between the stationary and rotating layers of molecules in the volume of the liquid crystal layer. It follows from (1) that, theoretically, for any given duration τ of the action of an external electric field on the LC layer, there always exists a voltage U _on at which the molecules are reoriented along the electric field lines at least in the central part of the LC layer (the molecules of the latter in contact with orienting polymer coating of the electrodes, do not change their position at any voltage), and there is also such a voltage U _off at which all molecules of the LC layer remain motionless. The greater the difference in the voltages U _on and U _off , the shorter duration τ of the action of the electric field is necessary and sufficient to separate the screen elements on and off. Such a physical mechanism leads to a high slope of the volt-contrast characteristic

for this screen, while ρ for the latter exceeds 1 (as for the active-matrix screen), while in the known passive-matrix screens, as a rule, ρ << 1).

 Consider the dynamics of switching the screen element in various states (figure 2 and figure 3).

When a voltage is applied to an element with a value of U ₁ (curve 1 in FIG. 2) that exceeds the threshold value U ₀ for the recording time of τ _write (U ₁ ), the state of the LC layer changes from the initial swirling structure A (FIG. 3) to the vertical oriented structure B. The reaction time of molecules τ _react (U ₁ ) consists of the delay time τ _delay (U ₁ ) and the time interval for the formation of a vertically oriented structure. During the last interval corresponding to the leading edge of curve 7, there is a sharp change in the transmission K of the screen element from the initial value to the value corresponding to a vertically oriented structure. After removing the voltage, the LC layer goes into a self-compensating configuration (in state C in Fig. 3), and continues to be in it for a time τ _memory (U ₁ ). If no supporting external electrical signal is received during τ _memory (U ₁ ), then the LC layer passes from state C first to state C * (in which the self-compensating configuration ceases to exist), and then returns to the initial state A. The transition from state C * to state A is accompanied by a sharp change in the optical transmission of the element (which is described by the trailing edge of curve 1 in figure 2).

As a result, the total relaxation time τ _{relax of the} self-compensating configuration (corresponding to the complete transition of the LC layer from state C to the initial state A) is the sum of the time τ _{memory of the} self-compensating configuration (state C) exists and the time of a fast transmission change (transition
between states C * and A). It is significant that the total time τ _relax does not depend on the magnitude of the applied voltage U ₁ , although each of the two indicated terms of this time depends on U ₁ . Curve 2 in figure 2 describes the change in the optical response of the screen element when applying a control voltage U ₂ half the voltage U ₁ .

It can be seen that the delay time τ _delay (U ₂ ) corresponding to the reduced voltage U _{2 is} much longer than τ _delay (U ₁ ). Therefore, if you apply a reduced voltage U ₂ for a shorter time (for example, not exceeding τ _react (U ₁ )), the molecules do not have time to react, and the screen element does not turn on (curve 3 in figure 2). However, the element can go into the weakly excited state A * (Fig. 3), which practically does not differ in optical transmission K from the initial state A.

In order to prevent false excitation of this element due to the accumulation of repeated weak influences during subsequent recording cycles, it is necessary that each cycle also contains a damping time interval sufficient for the natural relaxation of the weakly excited state. During the damping interval, the screen element should not be supplied with voltage, and the duration τ _{decay of} the damping interval should be sufficient to return the molecules on the unincorporated element from the intermediate state A * to the initial state A, i.e. τ _decay must be at least the decay time of the weakly excited state A *. The value of τ _decay can be estimated from the following. Since the LC layer does not undergo structural rearrangement upon its transition from the initial state A to the weakly excited state A * (the moment of friction in the LC layer exceeds the momentum of external forces), the damping interval equal to the minimum recording time is enough to return the molecules from the weakly excited state A * to the initial state A. With very weak or short effects on the screen elements, the damping interval can be selected less than the write time τ _write . In other words, the tact time τ _cycle (the cycle time of the repetition of actions on a given element) should include the subsequent _write period τ _write and the decay period corresponding to τ _decay , and, as a rule, τ _write > τ _decay .

Obviously, the greater the voltage U applied to the element, the greater the number of layers of molecules in the state B of the LC layer (Fig. 3), which is rearranged perpendicular to the dielectric plates and, therefore, the longer the self-compensating configuration will exist, the lifetime τ _memory of which sets the pause duration in changing the optical transmittance of the screen element after removing the voltage. Since the number of layers of liquid crystal molecules is limited, there is also a limit value τ _memory .

Since the transition of the element to its initial state begins after the expiration of the τ _memory interval, for the constant stay of the element in the on state, the supply of control signals should be repeated with a period T _{F of} no more than τ _react + τ _memory .

The way to control this screen is that the frame is scanned in N consecutive cycles, supplying control signals in each cycle to the electrodes of M columns and N lines of the screen, acting by their resulting electromagnetic field on those areas of the LC layer, consisting of nematic LC molecules with positive dielectric anisotropy, which correspond to the MxN elements of the screen, while in the i-th cycle, where i = 1, 2, ... N, include the specified elements of only the i-th row, changing the physical properties of the corresponding region elements In this case, exceeding a certain value of the amplitude of the resulting electromagnetic field in these regions, characterized in that at the beginning of each i-th clock cycle of the frame, a recording period of duration t _{W is} allocated, during which the electromagnetic field of recording signals with an amplitude of U ₁ > U ₀ (f _W ) to those regions of the LC layer that correspond to the included elements of the i-th row, where U ₀ (t _W ) is the threshold voltage for the formation of a dynamic self-compensating configuration of the LCD layer for a time duration t _W , in the same during the same recording period of duration t _{W, the} regions of the LC layer corresponding to the non-inclusive elements of the i-th row either do not supply an electromagnetic field of control signals, or act on these areas with an electromagnetic field of recording signals with an amplitude of U ₂ <U ₀ (t _W ), thereby leaving the indicated regions of the LC layer in the initial state or translating them into a weakly excited state, and into the remaining 1, .., i-1, i + 1, ... N scan cycles of this frame during all the corresponding recording periods on the LCD region layers corresponding to i troc, either act on the electromagnetic field of the recording signals with an amplitude of U ₂ <U ₀ (t _W ) or remove the electromagnetic field from these areas.

In this case, the time T _{F of the} frame sweep does not exceed the time τ _{memory of the} existence of a self-compensating configuration.

In the first particular embodiment of the method, during the i-th recording period of duration t _{W, a} recording signal in the form of a voltage of U _{S is} supplied to the electrode of the i-th row, recording signals in the form of a voltage of U _D are supplied to the column electrodes of the included elements of the i-th row, and zero voltage is applied to the electrodes of the remaining columns and rows, while the duration t _{W of the} i-th recording period is selected in accordance with the conditions t _W > T _{D + S} , t _W <T _D , t _W <T _S , where T _{D + S,} T _D and T _S - formation times self-compensating configuration of the LC layer under the effect of voltage values, respectively U _S + U _D, U _D and U _S, and the remainder of the stroke of the i-screen all electrodes serves zero voltage, and the duration of the rest cycle time is chosen sufficient to return nevklyuchaemyh elements 1, 2, ... i -th lines and all elements (i + 1), (i + 2), ... N - th lines of the screen from an intermediate state to the initial state.

The included screen elements are selected not only by exceeding the total amplitude U _S + U _D over the amplitudes U _D or U _S separately, but also due to the faster response of the optical response of LC molecules to the total voltage U _S + U _D (compared to U _S or U _D ). For this, the duration t _{W of the} i-th recording period is selected to be longer than T _{D + S} , but shorter than each of the times T _D and T _S.

If we divide the total frame time T _F (selected taking into account T _F ≤τ _react + τ _memory ) into cycles of duration T _F / N, in each of which there is both an exciting voltage with an amplitude of U _S + U _D and insufficient line-by-line U _S and columnar U _D voltages are applied, for example, during a half- _cycle (τ _cycle / 2), and the rest of the time the voltage at the electrodes is 0, then multiplex control with duty cycle N (i.e., the ability to control a screen consisting of N lines ) To increase the duty cycle, it is sufficient to increase the amplitudes U _S and U _D , thereby reducing - proportionally (U _S + U _D ) ² - the duration of the T / N cycle. The maximum possible value of U _S + U _{D is} limited only by the breakdown voltage of the screen element; the last parameter is determined by the dielectric properties of not only the liquid crystal layer, but also the orienting and insulating layers. With this in mind, the maximum voltage U _S + U _{D is} very large, and therefore, the restrictions on the multiplexing level (number of lines) N of this screen are significantly reduced.

Another important feature of this control method is the independence of the instantaneous optical transmittance of the newly emerged dynamic self-compensating configuration from the voltage value U _S + U _D : in state C (Fig. 3), mutual compensation of both symmetric parts of the LC layer is carried out as if there is only one vertically oriented (c α _c = 90 ^° ) layer of molecules, and in the presence of many such layers of vertically oriented molecules with a narrow transition region from α ₁ to α _c and from α _c to α ₂ . This allows you to increase the value of the applied voltage to compensate for the voltage drop across the electrodes with a slight change in the electrical and optical parameters of the screen.

The dependence of the duration τ _memory on the magnitude of the applied voltage allows for grayscale modulation. If the amplitude U _D (m) and the duration τ of the signal applied to the mth column of the ith row to be recorded are sufficient to reorient the maximum possible number of layers of molecules in the region of the LC layer corresponding to the imth element, then the time value τ _{memory is} maximum. As the voltage U _S + U _D (m) decreases, the number of formed layers of molecules with an angle of inclination α _c = 90 ^° decreases, and, consequently, the time τ _{memory of the} existence of a self-compensating configuration decreases. With a further decrease in the indicated voltage, the process with a sharp change in the optical transmittance begins immediately after the termination of the voltage supply, and the optical transmittance and relaxation time will be proportional to (U _S + U _D (m) -U ₀ ) ² . Similarly, the reduction of the time τ _{memory is} affected by the reduction of the time τ of the voltage supply U _D (m) in the range 0 <τ≤t _W.

Equating the residence time of the LC structure in a self-compensating configuration to the frame time T _F allows you to get a short screen relaxation time to its original state, which in this case is equal to the time of a sharp change in the optical transmission of one screen element. The effective speed of the LCD material in this mode of operation is significantly higher compared to its speed, characteristic of the mode of operation in the known passive-matrix screens. Since the memory assumes the main load for the implementation of matrix addressing, and the requirements for the slope of the liquid-crystal complex of liquid-crystal materials are significantly reduced, a larger variety of liquid-crystal materials can be used in the proposed device. For a fixed external voltage, the elastic constants of the LC material and the dielectric anisotropy Δε do not significantly affect the value of τ _memory . According to this property, the proposed device is significantly different from the known passive-matrix displays, in which, to increase the steepness of the WCC, the constant K ₃₃ should be the largest relative to the transverse bending constant K ₁₁ .

The time τ _{memory of the} existence of a self-compensating configuration is noticeably affected by the step P of the spiral twist of the molecules, which is specified by the rotational additive in the LC layer. As in all passive-matrix screens, in order to avoid the formation of defects in the LCD structures, the pitch P of the spiral twist should satisfy the relation
β ₀ / 360-0,25 <d / P <β _0/360 + 0.25 (2)
Within this ratio, an increase in d / P leads to a decrease in the value of the natural relaxation time τ _{relax by} 1.5–2 times, and in the time τ _memory , by 2–3 times. Thus, the time τ _memory will be the largest at the maximum allowable pitch P of the spiral twist.

In the second particular embodiment of the method, the i-th recording period is divided into two adjacent time intervals t _WS and t _WD , during the interval t _{WS, a} voltage of U _{S is} applied only to the electrode of the i-th row, and zero voltage is applied to the electrodes of the remaining rows and all columns voltage, and during the interval t _WD supplied voltage U _D to the electrodes only those columns that correspond to elements consisting of i-th row, and the electrodes of all other rows and columns fed zero voltage, the magnitude of the time intervals is selected in accordance with Word _{t WS + t WD> T D} , t WS + t WD> T S, t WS <T S, t WD <T D, where T _D and T _S - formation times self-compensating configuration of the LC layer under the effect of the voltage, respectively the values U _D and U _S , and the rest of the time of the i-th cycle, all the electrodes of the screen are supplied with zero voltage, and the duration of the remaining time of the cycle is selected sufficient to return the non-included elements of the previous (1, 2, ... i-th) lines and all elements of the subsequent (i + 1, i + 2, ... N) lines of the screen from a slightly excited state to the initial state.

A feature of the second private variant of the method is that the selection of the included screen elements is carried out by summing the durations t _WS and t _{WD of the} intervals of the action of the control signal supplied first to the row electrode and then to the column electrode (at the intersection of which there is an addressable element). This allows you to use the maximum possible amplitudes of the control voltage (by minimizing the duration of the influence of the latter) and shorten the cycle time, since here the damping period of the slightly excited state of the switched off elements of the selected row overlaps with the selection period of the included elements of the same row. This leads to the realization of an extremely short addressing time for each line (therefore, to the possibility of controlling the maximum number of N lines for a given duration t _{memory of the} existence of a self-compensating configuration).

In the third particular embodiment of the method, the i-th beat is divided into successive i-th erase cycles and i-th recording cycle, during the first of which an erasing signal with an amplitude U _E whose frequency f is greater than the critical frequency is fed to the i-th line f ₀ changes the sign of the dielectric anisotropy of the nematic liquid crystal, and the magnitude of the amplitude U _{E0 of the} erasing signal during the duration Δt _E0 of the erase period ensures the complete elimination of the self-compensating configuration in all areas of the LC layer corresponding to the ith row.

The specified private variant of the method allows forcibly reducing the time of a sharp change in the optical transmission of the screen τ ′ = τ _relax- τ _memory to values comparable with the response time of the screen element to a sharp increase in voltage. For this purpose, the property of LC substances with positive dielectric anisotropy (Δε> 0) is used to change its sign to the opposite (Δε <0) when a high-frequency voltage is applied, the frequency f of which is higher than a certain critical frequency f ₀ (typical for this LC substance). When applying voltage, LC molecules with Δε <0 tend to orient themselves orthogonally to the field lines of force (parallel to the dielectric plates); therefore, vertically or obliquely oriented molecules of the self-compensating configuration C (Fig. 3) are forcibly rearranged under the influence of external voltage into the initial, parallel (or almost parallel) , since α ₁ and α ₂ are small) the position of the dielectric plates, i.e., the LC layer is forced to return to its original state A. The time of such forced relaxation is determined by Δε and the voltage amplitude U _E according to formula (1), and can be reduced to fractions of a millisecond.

According to a third particular variant of the method, a high-frequency signal with an amplitude U _E0 and a frequency f> f ₀ is supplied during the erasure time Δt _E0 sequentially to all lines at the end of the frame time. The duration Δt _E0 and the amplitude U _E0 must be such that by the beginning of the recording part of the measure of the i-th line, all the elements of this line return to their original state. (Recording signals in the second particular embodiment of the method are supplied in the same way as in its first particular embodiment). By performing forced relaxation in this way at a predetermined time, it is possible to ensure a stable duration of "flashing" of the screen elements, which does not depend on fluctuations in the magnitude of the applied voltage, the resistance of the electrodes, changes in the ambient temperature, etc.

When implementing this method without sacrificing screen performance, the time τ _memory (corresponding to the conditions of natural relaxation of this configuration) can be selected more than T _F frame scan, because due to the forced erasure, the real time of existence of the configuration in question will not exceed the frame scan time T _F .

In the fourth particular embodiment of the method, the ith step is divided into successive recording and erasing cycles, and during the last, an erasing signal with a frequency f that is higher than the critical frequency f _{0 of} changing the sign of the dielectric anisotropy of the liquid crystal is fed to the i-th line this is varied by the amplitude U _{E of the} erasing signal and the duration Δt _E of the erasure period, thereby controlling the speed and degree of elimination of the self-compensating configuration in the corresponding regions of the LC layer; This ensures the implementation of multi-gradation (grayscale) image. The frame duration can be divided into subframes according to the number of halftones, and the formation of a gray scale is provided by a corresponding change in the duty cycle of the erasing signal.

In the fifth particular embodiment of the method, the erasing signal in the form of an alternating meander with a variable amplitude U _E and a frequency f> f _{0 is} formed only on switched off elements of the i-th row, for which a signal is applied to the electrode of the latter in the form of an alternating meander with a frequency f ₁ equal to f / 3 <f ₀ , and the signal in the form of a sequence of groups of alternating pulses of amplitude U _{E is} applied to the electrodes of the columns corresponding to the elements of the i-th row being turned off, while the period T _{1 of the} sequence is 1 / f ₁ , the duration of each pulse is T ₁ / 3k where k is the number of pulses in the group, and the sign of each current pulse coincides with the sign of the current amplitude of the meander.

Consider the implementation of the fifth particular variant of the method for the case when k = 1. In this case, to obtain a high-frequency (f ₁ > f ₀ ) alternating meander, a combination of two low-frequency (f ₁ <f ₀ ) alternating meanders is used. Namely, an alternating square wave of amplitude U _E and frequency f ₁ is supplied to the column electrode, and a sequence of alternating pulses of the same amplitude with the same frequency f ₁ , but with a duty cycle of 3, is visible to the row electrode. It is seen (Fig. 4) that the resulting (combinational) erasing signal has an amplitude U _E and a frequency of 3f> f ₀ , while each of the original signals had a frequency less than f ₀ . This ensures selective supply of high-frequency voltage only to switch-off elements for the forced return of the latter to its original state.

 Specific implementation examples and specific values of the screen parameters and how to control them.

As the dielectric plates 2 and 3, glass plates with indium oxide electrodes 6.7 are used, coated with 8.9 polymer layers of AD9103 material, which provides an angle of inclination of the surface molecules (angle of pretilt) of α ₁ = -α ₂ = 2 ÷ 3 ^° ; The LC layer 1 with a thickness of d = 6.3 μm is made of a material of the type ZhKM3064 (manufactured by MNPO NIIOPiK, Russia) with Δn = 0.1 and an optically active additive HDN-1, which provides a spiral twist of the molecules through an angle β ₀ = 180 ^° at the equilibrium pitch of the spiral is P = 20 μm. Polaroid films 5 and 6 are of type NPF G1229DU from Nitto (Japan), the optical axis of the polaroid film 5 is parallel to the projection of the direction vector of the surface molecules located on the dielectric glass plate 2, and the optical axis of the polaroid film 6 is perpendicular to the projection of the direction vector of the orientation of surface molecules in the dielectric glass plate 3. The product Δn by d is 0.63 μm.

The table shows the specific time parameters for an example of a specific implementation of the screen, corresponding to various values of the total amplitude U _{Σ of the} control voltage. The voltage amplitude is in volts, the time parameters are in milliseconds.

The value ϒ _Σ is equal to the sum of the amplitudes of the control voltages U _S + U _D supplied respectively to the row and column of the selected screen element.

For example, for the first example, U _S = U _D = 20 V, i.e. the amplitude U _{Σ of the} selection pulse is 40 V. From the table it can be seen that at this voltage, τ _react = 0.1 ms is required to complete the formation of the self- _compensating configuration. The duration of memory τ _memory after stress relief is 20 ms. And just as much is the time τ ′ of a sharp change in transmittance (τ ′ = τ _relax- τ _memory ). For U = 20 V (applied to an unselected screen element), the delay time τ _{delay of the} optical response is 0.21 ms, i.e. if an electric signal with an amplitude of U = 20 V is supplied for only 0.1 ms, there will be no excitation of unselected screen elements. The decay interval τ _decay (in the cycle τ _cycle ) should be 50-100% of the time of weak excitation of the LC layer, which is equal to the time τ _react = 0.1 ms, i.e. τ _decay = 0.05-0.1 ms. Then the cycle time τ _cycle = τ _react + τ _decay = 0.15-0.2 ms, the frame time T _F = τ _memory = 20 ms. Achievable multiplexing level (number of rows) N = T _F / τ _cycle = 133 rows (266 rows for a double matrix).

For another example, at U _S = U _D = 80 V (see table), the time τ _delay = 0.01 ms. Let the voltage U _{D be} applied to the columns of the selected elements of the i-th row during the i-th cycle τ _cycle to the first half of τ _WD of the recording period, and the voltage U _S to the i-th row to the second half of τ _WS of the recording period. Then the duration of the signal with an amplitude of 80 V on the selectable elements is 0.02 ms, which is sufficient for switching on (since τ _react = 0.02 ms). The decay interval τ _decay for unselected elements of all other rows takes the second half of a measure, and for unselected elements of the ith row, it takes the first half of the next measure. Therefore, the tact time τ _{cycle is} reduced to the value τ _react = 0.02 ms, which at T _F = τ _memory = 20 ms gives N = T _F / τ _cycle = 1000 (in the double matrix N = 2000).

For all the modes indicated in the table, the maximum screen transmittance was 15%, the screen contrast without a film compensator was about 500: 1, and the viewing angle, within which the contrast was higher than 20: 1, was ± 45 ^o in a plane perpendicular to the direction of the initial orientation of the molecules ( in the horizontal plane), and ± 70 ^o - in the vertical plane (corresponding to the direction of the initial orientation of the molecules). The coefficient K _{0 of the} initial light transmission (luminous efficiency) of the screen can be 10-30% (depending on the value of the angle β _{0 of the} spiral twist, optical anisotropy Δn and the thickness d of the LC layer). For many LC materials, the optimal mode of operation in the mode with a self-compensating configuration can be selected based on the spiral twist angle β ₀ , the product of the optical anisotropy Δn and the thickness d of the LC layer, as well as the values τ _relax , τ _memory, and τ _react . For example, for ZhKM1391 (produced by MNPO NIIOPiK, Russia) at β ₀ = 180 ^° , α ₁ = -α ₂ = 2 ^° and at Δn = 0.13, the maximum initial transmittance K ₀ is observed at Δn d = 0.55 μm (at d = 4 microns) and is 17%. In this case, τ _memory = 10 ms. At a swirl angle β ₀ = 210 ^{°, the} maximum transmittance K ₀ is observed at Δn d = 0.65 μm (at d = 4.6 μm) and is 25%, at a voltage of 13 V the contrast is 250: 1, τ _react = 0, 8 ms, τ _memory = 8 ms, τ _relax = 45 ms.

A specific example of using the change in the dielectric anisotropy sign of the LC layer to accelerate the return of the latter to its original state: when using LC material ZhKM1862 (manufactured by MNPO NIIOPiK, Russia), a voltage of amplitude U _E0 = 20 V (or 60 V) with a frequency of 15 kHz (f ₀ = 9 kHz) for Δt _E0 = 1 ms (or 0.1 ms, respectively) forcibly returns the LC layer from the state with a self-compensating configuration to the initial state.

 A passive-matrix screen based on a dynamic self-compensating configuration of the LCD layer and a control method for such a screen can be used to create flat high-contrast television displays that allow you to play back quickly changing (including color) images without delay with a wide viewing angle and the number of N lines of about 1000 -2000 when using standard LC materials and with reduced technological requirements for maintaining uniformity of the thickness of the LC layer, the quality of the initial orientation of the LC molecules and other

Literature
1. US patent 6040813, MKI G 09 G 3/36, NCI 345/92, publ. 03/21/00.

 2. US patent 5977943, MKI G 09 G 3/36, NCI 345/98, publ. 10/02/99.

 3. A. S. Sukharier. LCD indicators. M .: Radio and communications, 1991, pp. 7-10.1

Claims (10)

1. A passive-matrix liquid crystal screen containing a liquid crystal layer consisting of nematic liquid crystal molecules with positive dielectric anisotropy and located between the first and second transparent dielectric plates, on the outer surfaces of which are the first and second polaroid films, respectively, and on the inner surfaces, respectively the first and second groups of transparent electrodes, which form respectively N rows and M columns of the matrix, on which p the first and second polymer layers, which determine the orientation of the molecules adjacent to them in the first and second directions, respectively, with the angles of inclination α ₁ and α ₂ to the surfaces of the corresponding dielectric plates, and in the liquid crystal layer there is a rotational additive that sets the initial spiral orientation of the molecules at an angle β ₀ in the volume of the liquid crystal layer, characterized in that the optical axes of the first and second polaroid films coincide with the bisectors of adjacent angles between the projections of the orientation vectors of the molecules adjacent boiling for the first and second dielectric plates, in the plane of these plates, liquid crystal layer is arranged to the existence therein of the dynamic self-compensating configuration, the formation of which does not exceed the sweep time one line of the screen, the existence of which does not exceed the time T _F HR screen scanning, and the structure which is characterized by a gradual change in the angle of inclination of the molecules along the thickness of the liquid crystal layer from α ₁ to α ₂ with a transition through α _c = 90 ^° for molecules in the central part of the liquid crystal layer, and the sign of the angle of rotation of the molecules when passing from the angle α ₁ to the angle α _c = 90 ^{° is} opposite to the sign of the angle of rotation of the molecules when moving from the angle α _c = 90 ^° to the angle α ₂ , and the threshold characteristic The screen is determined by the energy barrier between the initial state of the liquid crystal layer and its state with the presence of a dynamic self-compensating configuration. 2. The passive-matrix liquid crystal screen according to claim 1, characterized in that the twist angle β ₀ is 180 ^° , the molecular tilt angles correspond to the condition α ₁ = -α ₂ , the optical axes of the first and second polaroid films are mutually orthogonal, and the optical axis at least one of them is parallel to the projection onto its surface of the orientation vector of molecules located at the surface of the liquid crystal layer closest to the polaroid film, while the product of the optical anisotropy Δn by the thickness d of the liquid crystal layer is in affairs 0.4 micron ≤ Δnd ≤ 0,7 mm.  3. The passive-matrix liquid crystal screen according to claim 1 or 2, characterized in that an additional film compensator is introduced between at least one of the dielectric plates and the adjacent polaroid film.  4. The passive-matrix liquid crystal screen according to claim 1, or 2, or 3, characterized in that the transparent electrode of each column is divided into three longitudinal segments, light filters are additionally introduced into the screen, each of which is located between the surface of one of the dielectric plates and the corresponding a segment of the transparent electrode, with each column of the screen corresponds to a triad of filters of three primary colors. 5. A method for controlling a passive matrix liquid crystal screen, which consists in the fact that the frame is scanned in N consecutive clock cycles, supplying control signals in each cycle to the electrodes of M columns and N lines of the screen, acting by their resulting electromagnetic field on those areas of the liquid crystal layer consisting of of nematic liquid crystal molecules with positive dielectric anisotropy, which correspond to M • N elements of the screen, while in the i-th cycle, where i = 1, 2, ... N, include the given elements then only the ith row, changing the physical properties of the regions of the liquid crystal layer corresponding to these elements by exceeding in these regions a certain value of the amplitude of the resulting electromagnetic field, characterized in that at the beginning of each ith clock cycle of the frame, a recording period of duration t _{W is} allocated during which apply the electromagnetic field to the amplitude of recording signals U _1> U ₀ (t _W) to the areas of the liquid crystal layer includes elements that correspond to i-th row, where U ₀ (t _W) - are threshold voltage of the dynamic self-compensating configuration of the liquid crystal layer corresponding to the duration time t _W recording period, the same i-th measure over the same period of recording time t _W at respective nevklyuchaemym elements of the i-th row of the area of the liquid crystal layer either not supplied electromagnetic field control signals or act on these areas with an electromagnetic field of recording signals with an amplitude of U ₂ <U ₀ (t _W ), thereby leaving the indicated areas of the liquid crystal layer in initial state or by translating them into a slightly excited state, and into the rest 1,. .., i-1, i + 1, ..., N scanning cycles of a given frame during all periods corresponding to the recording area of the liquid crystal layer corresponding to the i-th row, operate the electromagnetic field of the recording signal with amplitude U ₂ <U ₀ ( t _W ) either remove the electromagnetic field from these areas. 6. The control method of the passive-matrix liquid crystal screen according to claim 5, characterized in that during the i-th recording period of duration t _{W the} recording signal in the form of a voltage of value U _{S is} applied to the electrode of the i-th row, to the column electrodes of the included elements i -th row supply recording signals in the form of a voltage of value U _D , and zero voltage is applied to the electrodes of the remaining columns and rows, and the duration t _{W of the} i-th recording period is selected in accordance with the conditions t _W > T _{D + S} , t _W < T _D, t _W <T _S, where T _{D + S,} T _D and T _S - times formirova Ia dynamic self-compensating configuration of the liquid crystal layer under the action of the voltage, respectively the values U _S + U _D, U _D and U _S, and the rest of the i-th clock cycle for all screen electrodes serves zero voltage, and the duration of the rest cycle time is chosen sufficient to return nevklyuchaemyh elements 1, 2, ..., i-th lines and all elements i + 1, i + 2, ..., N-th lines of the screen from a slightly excited state to the initial state. 7. The method of controlling the passive matrix liquid crystal screen according to claim 5, characterized in that the i-th recording period is divided into two adjacent time intervals t _WS and t _WD , during the interval t _WS voltage is applied with the value U _S only to the electrodes i- of the ith row, and zero voltage is applied to the electrodes of the remaining rows and all columns, and during the interval t _{WD, the} voltage U _{D is} applied only to the electrodes of those columns that correspond to the included elements of the ith row, and zero is applied to the electrodes of all other rows and columns voltage, while elichiny time intervals selected in accordance with the terms _{t WS + t WD> T D} , t WS + t WD> T S, t WS <T S, t WD <T D, where T _D and T _S - formation times dynamic self-compensating configuration the liquid crystal layer under the action of voltage, respectively, by the values of U _D and U _S , and the rest of the time of the i-th cycle, zero voltage is applied to all electrodes of the screen, and the duration of the remaining cycle time is selected sufficient to return the non-switching elements 1, 2, ..., i- th lines and all elements i + 1, i + 2, ..., N-th lines of the screen from a slightly excited state ence to its original state. 8. A method for controlling a passive matrix liquid crystal screen according to claim 5, 6, or 7, characterized in that the i-th beat is divided into i-th beat of erasing and the i-th beat of recording, successive during the first of of which the erasing line is supplied with an erasing signal with an amplitude U _E , the frequency f of which is greater than the critical frequency f _{0 of} changing the sign of the dielectric anisotropy of the nematic liquid crystal, and the amplitude U _{EO of the} erasing signal over the duration Δt _EO of the erasure period completely eliminates the dynamic self-compensating the existing configuration in all areas of the liquid crystal layer corresponding to the ith row. 9. A method for controlling a passive matrix liquid crystal screen according to claim 5, 6, or 7, characterized in that the i-th clock is divided into successive recording and erasing clocks, and during the last, the erasing line is fed to the i-th line signal with a frequency f, which is higher than the critical frequency f ₀ changing sign of dielectric anisotropy nematic liquid crystal, the amplitude can vary from U _E and the duration of the erase signal erase period Δt _E, thereby controlling the rate and degree of removal of self-compensating dynamic con iguratsii in the respective areas of the liquid crystal layer. 10. A method for controlling a passive matrix liquid crystal screen according to claim 8 or 9, characterized in that the erasing signal in the form of an alternating meander with a variable amplitude U _E and a frequency f> f _{0 is} formed only on switched off elements of the i-th line, for which purpose a signal in the form of an alternating meander with a frequency f ₁ equal to f / 3 <f _{0 is} applied to the electrode of the latter, and a signal in the form of a sequence of groups of alternating pulses of amplitude U _{E is} applied to the electrodes of the columns corresponding to the switched off elements of the i-th row, while the period T ₁ placentas telnosti equal to 1 / f _1, the duration of each pulse is equal to T ₁ / 3k, where k - number of pulses in the group, and the sign of each current pulse coincides with the sign of the current square wave amplitude.

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