RU2340923C1 - Liquid crystal spatial light modulator (versions) - Google Patents

Abstract

FIELD: physics; measurements.

SUBSTANCE: present invention pertains to measurement techniques. The liquid crystalline substance used in the modulator, which fills the space between current conducting coatings, is a smectic C*-type composition with ferroelectric properties, capable of forming in its layer, spatially inhomogeneous structures, with high speed modulating phase of the transmitted light, under the effect of pulsed alternating electrical voltage. The light is modulated using one spatially inhomogeneous modulating element, whose surface area is equal to the aperture of the whole modulator, with solid current conducting coatings on the whole aperture. The pulsed control alternating electrical voltage is applied to the single pair of current conducting coatings. In the second version, one of the current conducting coatings is reflective.

EFFECT: faster operation with simplification of the structure of the device and manufacturing process.

4 cl, 8 dwg

Description

The invention relates to the field of optoelectronics and can be used in devices and systems for the visualization and display of information using lasers, in particular in projection displays, including television, in spatial light modulators, in devices for storage, conversion and image processing, etc. .

Currently, devices and systems using coherent or partially coherent light emitted primarily by various types of lasers are becoming increasingly widespread in the technique of visualizing and displaying information. When randomly inhomogeneous objects are illuminated by it, such as, for example, a rough screen surface or a transparent medium with a refractive index fluctuating in space, a spotted pattern or speckle structure is formed due to interference of scattered waves. In fact, it is noise, and this speckle noise significantly reduces the quality of images (see [1], [2]).

An enlarged fragment of the speckle pattern in the field of diffraction of a laser beam on a rough surface is shown in Figure 1 (view 1.1). In the diagram shown in FIG. 1 (view 1.2), the speckle structure is formed in free space and is called the objective speckle pattern. Such patterns are easy to observe using laser radiation. Subjective speckle patterns are observed in imaging optical systems in which the conditions of coherent illumination of an object are substantially less demanding. Therefore, subjective speckles can be observed with the naked eye even in the polychromatic light of extended sources. In the circuit shown in FIG. 1 (view 1.3), light passes through a scattering medium, and speckles are observed in the image plane of the illuminating source. Subjective speckle patterns formed according to the scheme of Figure 1 (view 1.3) are clearly visible even when observing streetlights through a foggy or frozen vehicle window (see [2]). 1 shows a light source 101, a randomly inhomogeneous object 102 (or medium), a schematic view 103 of a longitudinal section of a speckle layer, a randomly distorted wavefront 104, depicting an optical system 105.

Devices and systems for visualization and display of information, as a rule, provide for the display of images on the screen for visual perception. Therefore, the urgent task is to eliminate the speckle structure that creates noise in the image (speckle modulation) of a relatively low frequency, because the sizes of individual speckles are determined by the resolution of the eye (see [1]). The problem is solved in different ways based on the following two approaches, namely:

- the destruction of the speckle structure directly on the screen and

- the destruction of phase relations leading to the creation of a speckle structure in a beam of light before its projection onto the screen.

In both cases, the speckle destruction rate should be substantially greater than the reaction of the eye.

In the first approach, it is necessary to take into account the limiting angular resolution of the eye. It is taken equal to one minute, or 20-30 lines / mm, but this value can vary depending on the lighting conditions, screen structure, image color. The speckle structure is eliminated by averaging it when using a matte diffuser screen in the process of observing an image on it (see [3, 4]). Obviously, the movement of the matte diffuser should be fast enough so that the eyes do not have time to track the displacement of the speckle structure relative to the image.

In [5], a method was proposed for eliminating the speckle structure using two matte diffusers, one of which moves non-stop relative to the other. In this case, there is no dependence on the transfer function of the optical system, since the magnitude of the correlation function of the scatterer is usually much less than the pulse response of the output optical system. The elimination of the speckle structure using two opaque diffusers has been successfully implemented (see [6]).

Figure 2 shows the design of the matte screen 201 with two diffusers (see [6]), which is made in the form of a decorative supporting frame. A fixed matte diffuser 202 and a moving mechanism of the movable diffuser are fixed on it. The movement mechanism (in this case, rotation), shown in FIG. 2, includes a DSM-60-220 low-speed engine with a two-arm symmetrical gear reducer, which shows: engine 203, pinion gear 204, intermediate gears 205 and 206, leading output gears 207 and 208, eccentric axes 209 and 210, which are the leading link in the movable frame 211 with frosted glass 212. When moving, the movable frame 211 rests on the hardened clearance-adjusting screws 213. The springs 214 squeeze the frame 211 when it rotates. The parameters of motion are as follows: angular velocity - 1 rpm, radius of circular motion - 1 mm, rotation speed of the movable plate - 38 rpm. The screen has a size of 230 × 330 mm ² and a resolution of 25 lines / mm. This design provided reliable suppression of speckle noise in images reconstructed from holograms.

An obvious drawback of the considered solution for eliminating speckle noise directly on the screen is the use of a complex and cumbersome mechanical device for moving the screen, all the more complex and cumbersome, the larger the aperture of the screen. Although this approach was proposed and implemented over 20 years ago, the technical implementation over the years has remained virtually unchanged.

The second approach to the elimination of speckle noise associated with the destruction of temporal and spatial coherence of radiation is implemented using more compact technical means, but requires a much higher spatial resolution, which is due to the subsequent expansion of the beam aperture to the screen size. Another important condition is the preservation of the directivity of the light beam, which does not allow the use of light-scattering media.

It is known to solve this problem using controlled spatial phase masks (filters). An example of such a mask (see [1]) is a holographic plate illuminated with a diffuser and then bleached with interference suppression depth π of the phase delay distributed randomly over the beam aperture (that is, over the area of the plate). Obviously, such a plate, as in the case of scattering screens considered above, must be quickly moved in the direction transverse to the beam, which is a significant drawback of this solution.

As a phase mask, a liquid crystal phase spatial light modulator can be used that generates Walsh functions or other orthogonal functions when controlling voltage or light according to a specially developed computer program (see [7]). Such a spatial light modulator is selected as a prototype for its purpose, control principle and technical implementation.

The scheme and principle of operation of a liquid crystal (LCD) electrically controlled spatial light modulator according to [7] are explained in FIG. 3. The basis of the design of such a modulator and similar devices is a liquid crystal cell, which, as a rule, contains two parallel-mounted transparent dielectric plates 301, on the outer sides of which are coated antireflection coatings 302, and on the inside - transparent conductive coatings 303 (usually with antireflection layers), one of which or both are coated with a layer of a transparent anisotropic dielectric substance (orientant) 304. The space between the plates is filled with a liquid crystal substance 305, to Thoroe can change its optical anisotropy depending on the amplitude and / or duration of pulses of alternating electric voltage applied to the conductive coating. The initial orientation of the liquid crystal molecules in the absence of an external electric field is determined by the anisotropic coating. The image is observed either when light passes through the layer in one direction, if both conductive coatings are made transparent (view 3.1), or when light passes twice if the second conductive coating 306 is made reflective (view 3.2).

In practice, phase modulation of laser radiation used spatial light modulators based on the S effect in a nematic type liquid crystal with a limited number of elements (maximum 256 × 256) in the matrix, which is applicable for suppressing speckle noise only when observing simple images. In the case of displaying highly informative images, the spatial resolution of such a spatial modulator should be hundreds of inverse mm. In fact, this is a liquid crystal active-matrix microdisplay, working on the transmission of light. Light losses in such a device are quite large due to a decrease in the working aperture due to the presence of control electronic elements (usually thin-film transistors) and gaps between the matrix elements. Moreover, the periodic structure of the matrix introduces distortions of the wavefront of coherent light, leading to distortion of the image on the screen. Controlling a spatial light modulator is a separate complex task.

In liquid-crystal spatial modulators and displays, liquid-crystalline substances of a nematic type are most widely used (see [8]). As is known, the optical response (reaction) of a liquid crystal to an electric field is the result of a change in the anisotropy of the optical properties due to the general orientation of the long axes of the molecules in the bulk of the layer. The physical reason for the orientation (reorientation) of the nematic liquid crystal molecules (NLC, or nematic) by the electric field is the dielectric constant anisotropy due to their anisotropic (elongated) shape.

For example, molecules with a positive value of dielectric anisotropy (ε _1l > ε _⊥ ), tending to the state with the lowest energy, upon reaching a certain threshold value U _n ^s necessary to overcome elastic forces, are oriented with their long axes (director) along the field and direction lines light propagation (Figure 4). In the general case, as a result of the reorientation of the molecules, the NLC layer undergoes Splay deformation, and its birefringent properties change (electro-optical S effect). Such a display cell can modulate both the phase of the transmitted light and its intensity (using polarizers). Moreover, more often than others, it is the S effect that is used for phase modulation of light. Figure 4 shows the reorientation of NLC molecules during splay-deformation of the layer (S-effect), where n ₀ is the refractive index for an ordinary ray, n _e is the refractive index for an extraordinary ray. Δn - refractive index difference (birefringence), U ^S _n - reorientation threshold voltage, D - the polarization direction of the incident light wave. The direction of the light beam and the electric field (E) coincide.

Nematics have a number of advantages, but do not provide sufficient speed, because the time of their electro-optical response lies in the range of units and tens of milliseconds and, in principle, cannot be reduced without a sharp increase in the control voltage. The main reason for this is the quadratic mechanism of interaction of the nematic with the electric field and the deformation of the nematic layer as a continuous elastic medium.

электрического поля, расположенный в плоскости смектического слоя; вектор

, показывающий направление ориентации длинных осей молекул в смектических слоях сегнетоэлектрического жидкого кристалла; вектор

спонтанной поляризации; шаг р₀ геликоида; нормаль L к смектическим слоям; координатная ось х, перпендикулярная пластинам 1; координатная ось y, параллельная пластинам 1; координатная ось z, совпадающая по направлению с вектором

; угол Θ наклона длинных осей молекул по отношению к вектору

(угол между векторами

и

); угол (в плоскости XY между нормалью к пластинам и вектором

; направления Р и А осей пропускания поляризатора и анализатора; интенсивность I₀ падающего на ячейку света; интенсивность I промодулированного ячейкой света; диаметр D падающего светового пучка; угол β между поляризатором и осью геликоида (вид 5.1), между R и А (вид 5.2).On the other hand, it is known that liquid crystals of the smectic type with ferroelectric properties (smectics C ^* or C ^* LC) have significantly greater electro-optical switching speeds — tens or hundreds of microseconds than nematics [9]. In them, the direction of the preferred orientation of the long axes of the molecules is determined by the polar angle на at which they are inclined relative to the normal to the smectic layers, and the azimuthal angle (in the plane of the smectic layer (Figure 5). Due to the special stoichiometry of the molecules in the absence of external influences, each layer of molecules has a spontaneous polarization (P _s ), and the polar axes of the various smectic layers are rotated relative to each other so that an equilibrium helically twisted structure (helicoid) is formed. cell, however, is absent, because the angle φ in the smectic layers varies from 0 to π at a distance equal to the helix pitch p _0. It is due to the indicated polarization of the layers that the smectics C ^* LC have much greater sensitivity to the action of the electric field than nematics and provide a 100-1000 times higher frequency of light modulation. Fig. 5 shows a physical model of a display cell with a ferroelectric smectic LC with a helix pitch larger (view 5.1) and smaller (view 5.2) of the layer thickness, which shows: planes of 508 smectic layers of liquid crystal la, perpendicular to the surface of the plates 501; vector

an electric field located in the plane of the smectic layer; vector

showing the direction of orientation of the long axes of the molecules in the smectic layers of a ferroelectric liquid crystal; vector

spontaneous polarization; ₀ helix pitch p; normal L to smectic layers; x coordinate axis perpendicular to the plates 1; y coordinate axis parallel to plates 1; coordinate axis z, coinciding in direction with the vector

; angle Θ of the slope of the long axes of the molecules with respect to the vector

(angle between vectors

and

); angle (in the XY plane between the normal to the plates and the vector

; directions of P and A axes of transmission of the polarizer and analyzer; intensity I _{0 of the} light incident on the cell; intensity I of the cell modulated light; diameter D of the incident light beam; the angle β between the polarizer and the axis of the helicoid (view 5.1), between R and A (view 5.2).

Liquid crystalline ferroelectric compositions were created from a non-chiral smectic C liquid crystal mixture of substituted phenylpyrimidines and phenylbenzates in the amount of 60-90% of the total weight of the liquid crystal composition and a chiral additive from optically active derivatives of terphenyl dicarboxylic acid in the amount of 10-40% of the total weight of the liquid crystal composition (see [ 10]). These compositions provide an indication of the helicoid with a helix pitch of more than 1 μm, spontaneous polarization of more than 50 nC / cm ² and a smectic tilt angle of more than 10 °. Such a cell has the property of bistability (called “bulk bistability”), which is caused not so much due to the interaction of the C ^* LC layer with its bounding surfaces, but due to stoichiometry of the liquid crystal composition itself, and therefore appears even with a layer thickness of more than 10 μm.

In addition to bistability, this C ^* LCD cell has the property of multistability, which makes it possible to obtain a gray scale in information displays. The gray scale can be implemented physically, i.e. not by electronic tricks and excessive requirements for resolution or speed of the display cell, but directly during electro-optical switching of a liquid crystal substance. It is reproduced in the form of an almost continuous sequence of stable optical states ranging from a state with zero intensity to a maximum (Fig.6), and therefore the above conditions are essentially conditions for the manifestation of multistability. Both extreme and all intermediate states are set by an inverting pulse of the corresponding amplitude and duration for tens or hundreds of microseconds. Figure 6 shows the time variation of the electro-optical response C ^{* of the} LCD cells (upper lines) to control electric pulses (lower lines) for three types of response: monostable (without storing the optical state on the left), bistable (with two stable optical states on the right , marked in bold) and multistable (with gray levels remembered after switching off the pulse - on the right, all lines). Multistability is clearly manifested as a change in the ratio between the width of the light and dark bands observed behind the analyzer (Fig. 7, view 7.3), due to spatially periodic modulation of the direction of orientation of the polarization vector (Fig. 8) above a certain threshold voltage. Figure 8 shows the orientation of the polarization vector and the azimuth angle distribution of the director along the normal (z) to the smectic layers at different values of voltage (U ₁ <U ₂ <U _3).

The period of the bands (units to tens of micrometers) is determined by the value of the spontaneous polarization of the liquid crystal substance (Fig. 7, view 7.1). When the threshold is exceeded, at first those regions of the cell for which φ are maximal and other regions do not switch are switched. As a result, the initial domains are broken, and a change in the field polarity does not allow the establishment of a regular domain lattice. Moreover, the phase modulation of the transmitted light reaches π or more depending on the thickness of the C ^* LC layer (usually from 5 to 30 μm) and the applied voltage (from units to tens of volts). The presence of domains, periodic modulation of the angle (along the z coordinate, and storing of the variable periodic lattice at any point of the hysteresis loop are caused only by the material parameters of the liquid crystal substance.

Compositions of C ^* LC with bulk bistability, under a certain regime of electric excitation, allow intensively scattering light (see [11]).

The properties of forming spatially inhomogeneous domain structures in a C ^* LC layer and controlling them with high speed is of interest from the point of view of their use as the basis for creating a spatial speckle-suppressing modulator. However, there is no information on such an application of C ^* LCD cells, and the constructions used, suitable C ^* LCD compositions, electro-optical effects and control modes of any C ^* LCD modulator with this purpose are unknown.

The technical problem solved by the proposed variants of the invention, forming a single inventive concept, is the creation of a liquid crystal device for suppressing speckle noise in images, which, in comparison with the analogue, has a significantly simpler design and manufacturing technology, higher spatial resolution, higher transmittance and higher speed.

The solution to this problem is provided by the fact that in the known liquid crystal spatial light modulator, containing two parallel arranged transparent dielectric plates, the outer sides of which are coated with antireflection coatings, and the inner sides are transparent conductive coatings, and a liquid crystal substance that fills the space between the conductive coatings and changes its optical anisotropy under the influence of an electric field, such a liquid crystal substance is used on which is a composition of the smectic C ^* -type ferroelectric properties having the ability to generate a spatially inhomogeneous layer structure, a high speed by modulating a pulsed alternating voltage phase of the transmitted light; at the same time, one spatially inhomogeneous modulating element with an area equal to the aperture of the entire modulator, with conductive coatings continuous throughout the aperture and an alternating pulse alternating voltage is applied to one single pair of conductive coatings for light modulation.

In the first embodiment of the technical solution, a spatial modulator is proposed that suppresses speckle noise when a laser beam passes through it in one direction (according to the scheme shown in Figure 3, view 3.1). The C ^* LC layer enclosed in the modulator, due to its properties when controlling electric voltage, destroys the phase relationships in the beam, leading to the creation of a speckle structure in the images. The applied liquid crystalline substance based on the composition of the smectic C ^* type with ferroelectric properties has no chevron defects and allows one to achieve high stability when switching light transmission states, which ensures high quality of the image passing through the cell.

In the second embodiment, instead of a cell operating in light, it is proposed to use a liquid crystal cell of the reflective type, for which it is enough to make one of the conductive coatings reflective (see Figure 3, view 3.2). Such a cell with an aperture equal to the size of the screen onto which the image is projected can serve to suppress speckles when installed directly in front of the screen or instead of it. In the latter case, the composition C ^* LCD is used, which intensively scatters light when an alternating voltage is applied.

In addition, in both embodiments, the liquid crystal substance is a smectic type composition with ferroelectric properties, in which the non-chiral smectic C liquid crystal mixture contains substituted phenylpyrimidines and phenylbenzoates in a weight ratio of 3: 1 to 2: 1, while substituted phenylpyrimidines include at least one organic a compound selected from group (I, II) consisting of:

(I)

(I)

where n≥8, m≤10

(II)

(Ii)

where n≥6, m≤10

phenylbenzoates include at least one organic compound selected from the group (III, IV) consisting of:

(III)

(III)

where n≥8, m≤10

(IV)

(Iv)

where n≥6, m≤10

and the chiral additive includes organic compounds (V, VI), consisting of:

(V)

(V)

n≥4, m≤6

where n = 0.1; m≥2

(VI)

(Vi)

where n≥3, m≤6

in a mass ratio of from 1: 1 to 2: 1 and organic compound (VII):

the mass of which is 15-30% of the total mass of the chiral additive.

The advantages of the claimed speckle-suppressing C ^* LCD spatial modulator are provided due to the proposed:

- C ^* LCD cell designs,

- the composition of the liquid crystal substance and

- cell control mode.

Replacing an NLC with a C ^* LCD can significantly (more than 100 times) increase the speed. The composition of C ^* LC provides the conditions for the creation of controlled spatially inhomogeneous structures in the layer. The rejection of the matrix of modulating elements and the use of a single uniform C ^* aperture LCD cell as a flat single-channel wide-aperture modulator makes it possible to ensure spatially inhomogeneous phase modulation of laser radiation continuously in aperture and to exclude multiplex or active-matrix addressing of matrix elements. The control mode of pulsed alternating voltage provides the necessary speed and depth of phase modulation in the absence of light scattering and image distortion. The modulator can be manufactured with a working aperture size suitable for the used power and the laser beam cross section, in order to prevent the temperature regime from escaping or to provide the most favorable conditions for the modulation of the light phase.

In this prior art is not obvious that suppress speckle of laser radiation can be achieved by applying the fast C ^LC having bistable and multistable properties without impairing its stability or disorder mentioned properties caused by the influence of the bounding C ^LC layers mode of the electrical pulse control or passing laser radiation.

To improve the characteristics of speckle-suppressing C ^* LC modulators, it is advisable to use individually or in the aggregate various directions for their improvement, such as: changing the type and composition of liquid crystal substances, changing the control mode of the cell, modifying the design of the modulator, etc. For example, to enhance the effect of suppressing speckle noise, it is proposed to provide two sequentially located C ^* LCD cells in the design of the modulator. In the modulator it is also advisable to use polymer-liquid crystal layers, antiferroelectric compositions LC, flexoelectric effect, etc.

Thus, the use of the proposed modulator design, liquid crystal composition, and control mode of alternating pulsed alternating voltage makes it possible to obtain a laser speckle suppression device that has high speed (tens of microseconds), high resolution (up to several micrometers) and stability of light transmission parameters without image distortion, which makes it possible to use the modulator for its intended purpose and to create on the basis of such modulo s and laser imaging devices and video display, including projection differing high resolution and good image quality and meet the requirements of modern and advanced storage, conversion, image processing and displaying information using a laser beam, while simplifying their design and manufacturing technology.

The inventive modulator as a device for suppressing speckle noise in images can be widely used in the development of displays and other optoelectronic display devices using laser radiation to visualize information.

Information sources

1. Collier R., Berhard K., Lin L. Optical holography. Moscow: World, p. 390 (1973).

2. Ryabuho V.P. // Coolant, N 5, pp. 102-109 (2001).

3. Lohmann A.V., J. Opt. Soc. Am., V. 55, 1030 (1965).

4. Arsenault H., Lowenthal S. Opt. Commun., V. 57, 493 1970).

5. Lowenthal S., Joyeux D., J. Opt. Soc. Am., V. 61, 7, 847 (1971).

6. Turukhano B.G. Disk system of holographic memory. In the collection “Optical holography. Practical Applications ”, Leningrad: Science, pp. 75-95 (1985).

7. Vasiliev A.A., Casasent D., Kompanets I.N., Parfenov A.V. Spatial Light Modulators / Ed. I.N. Kompanza /, Moscow: Radio and Communications (1987).

8. L. M. Blinov, Electro and magneto-optics of liquid crystals, Moscow: Nauka (1978).

9. V. G. Chigrinov, Liquid crystal devices: physics and applications, Artech House, Boston, London, UK (1999).

10. Andreev A.L., Kompanets I.N., Pozhidaev E.P. Liquid crystal ferroelectric display cell. Russian patent No. 2092883 dated 10/10/1997 (according to the application No. 95109563 with priority dated 07/07/1995).

11. Andreev A.L., Bobylev Yu.P., Gubasaryan N.A., Kompanets I.N., Pozhidaev E.P., Fedosenkova TB, Shoshin V.M., Shumkina Yu.P. Electric field controlled light scattering in ferroelectric liquid crystals. Optical Journal, vol. 79, No. 9, 58-65 (2005).

Claims (4)

1. A liquid crystal spatial light modulator containing two parallel-mounted transparent dielectric plates with antireflection coatings on the outside and transparent conductive coatings on the inside, and a liquid crystal substance filling the space between the conductive coatings and changing its optical anisotropy under the influence of an electric field characterized in that a liquid crystalline substance is used, which is a smectic composition whom C ^* -type with ferroelectric properties, with the ability to form spatially inhomogeneous structures in the layer, which at high speed modulate the phase of transmitted light under the influence of a pulsed alternating electric voltage; in this case, the light is modulated by one spatially inhomogeneous modulating element, whose area is equal to the aperture of the entire modulator, with conductive coatings continuous over the entire aperture, and a control pulse alternating electric voltage is applied to a single pair of conductive coatings. 2. The liquid crystal spatial light modulator according to claim 1, characterized in that the liquid crystal substance is a composition of a smectic C ^* type with ferroelectric properties, in which the non-chiral smectic C liquid crystal mixture contains substituted phenylpyrimidines and phenylbenzoates in a mass ratio of from 3: 1 to 2: 1, wherein substituted phenylpyrimidines include at least one organic compound selected from group (I, II) consisting of:

where n≥8, m≤10

where n≥6, m≤10, phenylbenzoates include at least one organic compound selected from the group (III, IV) consisting of:

where n≥8, m≤10

where n≥6, m≤10, and the chiral additive includes organic compounds (V, VI), consisting of:

(V)

n≥4, m≤6

where n = 0.1; m≥2

(Vi)

where n≥3, m≤6 in a mass ratio of from 1: 1 to 2: 1 and organic compound (VII): where n≥3

(Vii) where n≥3 the mass of which is 15-30% of the total mass of the chiral additive. 3. A liquid crystal spatial light modulator, containing two parallel arranged transparent dielectric plates, at least one of which is transparent and provided with an antireflection coating applied to its external side, conductive coatings applied to the internal side of the plates, one of which is applied to a plate with an antireflection coating, made transparent, and another reflective, and a liquid crystal substance filling the space between the conductive coatings and which exhibits its optical anisotropy under the influence of an electric field, characterized in that a liquid crystalline substance is used, which is a composition of a smectic C * type with ferroelectric properties, which is capable of forming spatially inhomogeneous structures in the layer, which at high speed modulate the phase of transmitted light under the influence of pulsed alternating voltage ; in this case, the light is modulated by one spatially inhomogeneous modulating element, whose area is equal to the aperture of the entire modulator, with conductive coatings continuous over the entire aperture, and a control pulse alternating voltage applied to a single pair of conductive coatings. 4. The liquid crystal spatial light modulator according to claim 3, characterized in that the liquid crystalline substance is a composition of a smectic C * type with ferroelectric properties, in which the non-chiral smectic C liquid crystal mixture contains substituted phenylpyrimidines and phenyl benzoates in a mass ratio of from 3: 1 to 2: 1, wherein substituted phenylpyrimidines include at least one organic compound selected from group (I, II) consisting of:

where n≥8, m≤10

where n≥6, m≤10, phenylbenzoates include at least one organic compound selected from the group (III, IV) consisting of:

where n≥8, m≤10

where n≥6, m≤10, and the chiral additive includes organic compounds (V, VI), consisting of:

(V)

n≥4, m≤6

where n = 0.1; m≥2

(Vi)

where n≥3, m≤6 in a mass ratio of from 1: 1 to 2: 1 and organic compound (VII):

where n≥3, the mass of which is 15-30% of the total mass of the chiral additive.

Images