RU2707990C2 - Polarization-sensitive material based on photochemically stable organic substances - Google Patents

Abstract

FIELD: optics.

SUBSTANCE: invention relates to technical means of applied physical optics, specifically to polarization-sensitive materials. Material exhibiting in solid-state effect of photoinduced guidance or change in it of long-term optical anisotropy during absorption of polarized or non-polarized, but directed radiation of a polarization sensitive component in form of a photochemically stable, non-luminescent or weakly luminescent substance with formation in its volume or on the surface of an anisotropic spatially modulated ordered molecular structure, optical properties - dichroism of absorption and birefringence, orientation direction of optical axis and orientation molecular order, in which directly correlate with spatial distribution of polarization state and energy characteristics and direction of propagation of activating radiation absorbed in polarization-sensitive material, wherein said material contains photochemically stable, anisotropically absorbing dichroic and non-luminescent or weakly luminescent substance and low-molecular weight additives regulating film-forming and viscous properties.

EFFECT: invention enables to obtain a photochemically stable material which exhibits the effect of photoinduced optical anisotropy.

18 cl, 3 dwg, 1 tbl, 6 ex

Description

FIELD OF TECHNOLOGY

The present invention relates to technical means of applied physical optics, in particular to polarization-sensitive materials (FFM), in which long-lived optical anisotropy (absorption dichroism and birefringence) is formed under the influence of polarized light absorbed by them.

FHM layers based on non-luminescent or weakly luminescent, photochemically stable, anisotropic absorbing (dichroic) substances can be used in technical tools of applied anisotropic optics, including as photo-orienting layers for thermotropic and lyotropic liquid crystal devices (LCs).

BACKGROUND

Significant progress in the development of IFMs has come with the discovery of lasers that generate polarized radiation and holography and optical memory based on their use. Currently, only one type of polarization-sensitive material is known, adopted as a prototype based on the use of photochemically sensitive substances in it.

It is described in a huge number of patents in which many compositions were used based on various photochemical reactions of destruction or structuring, including under the action of polarized radiation.

einen neuen effekt der strahlung in lichtempfindlichen schichten. Verhandl. Deutsch. Physik. Ges., 21, 479-491, 615, 623 (1919)].This method of photochemical selection is based on the Weigert effect), first discovered in 1919 [F. Weigert

einen neuen effekt der strahlung in lichtempfindlichen schichten. Verhandl. Deutsch. Physik. Ges., 21, 479-491, 615, 623 (1919)].

The essence of this method of photochemical selection is that the absorption of optical radiation by a photochemically active molecule occurs with maximum probability if the direction of the long axis of its dipole moment of transition at the wavelength of the activating radiation coincides with the direction of the electric vector of the light wave and is close to zero with a perpendicular mutual direction these vectors.

Light-induced orientational ordering and anisotropy in such MFMs, like liquid crystals [V.G. Chigrinov, Liquid Crystal Devices. Physics an Applications, Artech House Boston - London, 1999], I am defined as:

- order parameter S:

- dichroic ratio d:

- birefringence Δn:

и

- показатели преломления п и оптические плотности А, измеряемые для компонент, ориентированных параллельно и перпендикулярно вектору поляризации активирующего света, соответственно.Where,

and

- refractive indices n and optical densities A, measured for components oriented parallel and perpendicular to the polarization vector of the activating light, respectively.

In this case, the value of the order parameter S can vary from 0 (completely disordered structure) to 1 (fully ordered structure).

The magnitude of the phase delay δ is determined by the expression:

where: Δn and d are the birefringence and the thickness of the optically transparent film, respectively; λ is the wavelength of the measuring light.

The anisotropy induced by light in such materials decreases or completely disappears at a sufficiently high exposure energy and is not thermally stable, quickly disappearing when heated.

The disadvantages of IFMs formed using photosensitive substances based on passive photochemical selection are their extremely limited reversibility, the low value of the optically formed orientational order (S <0.1-0.3), the change in the shape of the absorption spectra during the formation of photoinduced anisotropy, and the absence of a threshold power density effect activating radiation and the presence of only one (disordered isotropic) thermodynamically stable state.

Disclosure of invention

The objective of the present invention is to develop new polarization-sensitive materials (hereinafter referred to as FFM) based on photochemically stable, anisotropically absorbing (dichroic) substances (PCFS), exhibiting the previously unknown photo-induced optical anisotropy effect (dichroism of absorption and birefringence) under the action of polarized or non-polarized but directional radiation absorbed by them.

The problem is solved due to the fact that, in contrast to PCMs based on photochemically sensitive substances, PCMs must be able to form polarization-optical elements in the volume state in the solid state in the form of spatially modulated ordered anisotropic molecular structures by irradiation with polarized or polarized directional radiation of the indicated IFM absorbed by the polarization-sensitive component that is part of this material.

A polarization-sensitive material has been created that exhibits in the solid state the effect of photo-induced guidance or a change in its long-term optical anisotropy (dichroism of absorption and / or birefringence) upon absorption of a polarized or non-polarized, but directed radiation by its constituent polarized-sensitive component in the form of a photochemically stable , non-luminescent or weakly luminescent substances with the formation in its volume or on the surface of the anisotropic space a substantially modulated ordered molecular structure, optical properties (absorption dichroism and birefringence), the direction of orientation of the optical axis and the orientational molecular order in which are directly correlated with the spatial distribution of the polarization state and energy characteristics and the direction of propagation of the activating radiation absorbed in the polarization-sensitive material, The material contains the following components:

- as a polarization sensitive component, at least one photochemically stable, anisotropically absorbing (dichroic) and not luminescent or weakly luminescent substance and

- special low molecular weight additives that regulate film-forming, viscous and other physicochemical properties.

The formation in the bulk and on the surface of spatially modulated orientations of ordered molecular structures occurs as a result of one- or two-photon (through the real or virtual intermediate level) absorption of spatially modulated by this polarization and intensity linear, elliptically or circularly polarized radiation or not polarized, but directed radiation.

The spatial distribution of the degree of ordering and its direction of spatially modulated and orientationally ordered molecular structures formed in the bulk and on the surface are in direct correlation with the local spatial distribution of activating radiation during one- or two-photon absorption by the material.

In the material, the properties of orientationally ordered molecular structures in its solid state are manifested in the anisotropy of the optical properties (absorption dichroism and birefringence) and the angular dependences of any other physicochemical properties, for example, the EPR signal shape.

Moreover, the manifestation of the anisotropy of the optical properties of photochemically stable substances in the material under the influence of absorbed radiation is not accompanied by a change in the shape of its absorption spectra, accompanied only by “clarification” of the polarized parallel component material in the spectral region of the activating radiation and “dimming” for the orthogonal component.

Moreover, photochemically stable substances are selected from the groups exhibiting absorption bands in the UV, visible and / or IR spectral regions between 150 nm and 2000 nm.

As photochemically stable substances use low molecular weight organic substances selected from the classes: L-Type Azo Dyes: monoazodyes, disazodyes, tris-and polyazodyes, metal-complexing azodyes; T-type azo dyes and L, T-type azo dyes quinone dyes; anthraquinone dyes: mono- and polyoxyanthraquinines, s-substituted hydroxythioanthraquinones, aminoanthraquinones, aminohydroxyanthraquinones, S-acrylaminoohydroxythioanthraquinones, T-type anthraquinones dyes, anthrapirimidinesin, d W-type azo dyes; benzo- and naphthoquinones, anthraquinone dyes, azomethines dyes, tolanes n-nitroaniline, biphenyls, aromatic nitro and nitroso compounds, 2'-n-nitrosodimethylaniline, dimethylaminostyrene and others, mono-, bis-, tris- and poly-azoyes -complex azo dyes; quinone dyes; mono-and poly-oxyanthraquinone dyes, sulphur-substituted hydroxythio-anthraquinone dyes, aminohydroxy-anthraquinone dyes; anthrapyrimidinone dyes; merocyane dyes; azomethine dyes; polycyclic compounds; benzoquinones, naphthoquinones; tolanes; diphenyls; p-nitroanilines, p-nitrosodialkylanilines; dialkylaminostyroles etc.

In this case, photochemically stable substances are introduced directly into the composition of the liquid crystal polymer, as the chromophores covalently linked to it in the side chain.

Photochemically stable substances in the form of dichroic chromophores are introduced directly into the main chain of the macromolecule or as covalently linked chromophores in the side chain.

Photochemically stable substances are presented in the form of covalently bound bi- or multifunctional molecules, which, in addition to the dichroic chromophore, also include, for example, luminescent or photochromic fragments, or one or more photosensitive fragments, which contribute to the photochemical formation of the spatial network during irradiation.

Moreover, special low molecular weight additives have close (resonant) vibrational absorption bands in the ground electronic state with vibrational absorption spectra of photochemically stable substances (or chromophores).

As special low molecular weight additives, active additives are used that exhibit high selectivity and efficiency of the thermo-photographic or just chemical processes that occur in them, depending on the degree of their ordering in the highly oriented matrix.

Photochemically stable substances (or chromophores) comprise at least two OH, COOH, NYR and other substituents capable of forming at least two specific intermolecular donor-acceptor or hydrogen bonds between the dichroic substance and the macromolecule of the polymer matrix or between the dichroic molecules themselves with the formation of a spatial orientationally ordered network.

Material from photochemically stable substances is prepared by thermal vacuum spraying, solution irrigation, or the Langmuir-Blodgett method.

In this case, the material is used as a chemical and / or structural material in phototechnology for the production of various picture two- and three-dimensional polarization-optical elements and devices of nano-, micro- and macroelectronic equipment, in instrumentation using polarization-optical elements, in optical anisotropic fiber products and integrated optics such as anisotropic photonic crystals, bulk diffraction gratings, radiation input-output devices, lenses, selective light beam dividers in, etc.

The material according to the invention can have three thermodynamically stable states, of which one isotropic initial state with an arbitrary (random) orientation of molecules in space and two photoinduced ones produced either by polarized or not polarized but directed radiation absorbed by a photostable substance, and in the first case anisotropically the absorbed molecules are oriented in a plane perpendicular to the polarization vector of the activating radiation, and in the second, in the direction of its propagation.

In this case, the orientational order parameter of photochemically stable molecules in the material reaches values of more than 0.8, and photoinduced birefringence of more than 0.4. A photoinduced anisotropy can be enhanced by additional heating at a temperature lower than the melting point of photochemically stable molecules.

Moreover, the irradiation energy necessary to achieve the limiting value of photoinduced anisotropy decreases several times when using a single pulse of activating irradiation with a duration of several nanoseconds with a power density of the order of MW / cm ² . And photoinduced anisotropy reaches its maximum photostationary value asymptotically. In this case, photoinduced anisotropy reaches its maximum value by additional heating at a temperature below the melting point of a photochemically stable substance.

Brief Description of the Drawings

The essence of the invention, is illustrated by specific examples of the invention with reference to the accompanying drawings, in which:

In FIG. one

The absorption spectra of the amorphous dye layer KD-2 are presented (in the table) before and after irradiation with polarized radiation.

In FIG. 2

A typical view of the kinetic curves of guidance, erasure, and dark relaxation of optical anisotropy (birefringence) in an amorphous KD-2 dye layer is shown.

In FIG. 3

The absorption spectra of the amorphous layer of the PCH dye (in the table) are presented before and after irradiation with polarized radiation.

SUMMARY OF THE INVENTION

The table shows the structural formulas of photochemically stable azobenzene-containing low molecular weight substances and a liquid crystal polymer with azo dyes in the side chain, in which the effect of photoinduced optical anisotropy was detected.

Further, as examples, the options for the formation, irradiation, and application of the proposed PMFs based on FHSW are given.

EXAMPLE 1

A KD-2 (4-94-nitrophenyl) -4 '- (4-N, N-dioctylaminophenylazole) benzene bisazo dye film was used as a PMR)

For this, in a vacuum ~ 2 10 ^-5 mm Hg. At the VUP-4 installation, the amorphous layer of KD-2 bisazo dye with a melting point Tm = 164С and a maximum absorption band in the visible spectral region λ = 500 nm was deposited on a glass substrate with a temperature of ~ 20 ° C by sublimation. The spraying rate was 15.1 A / min. The total spraying time was 2.54 minutes. In this case, the final thickness of the obtained film was 0.23 μm. Further, the sample was exposed to the polarized light of a DRSh-250 lamp with OS-11-PS-7-SZS-21 filters, emitting radiation with λ = 546 nm. Glan prism was used as a polarizer. The power density Ract in the plane of the sample was 22.3 mW / cm ² .

In FIG. Figure 1 shows the initial (before irradiation with polarized radiation with a wavelength of λ = 546 nm) absorption spectrum of this film (curve 1) and after its irradiation with linearly polarized radiation for components that coincide (curve 2) and orthogonal (curve 3) with orientation polarization vector of the activating radiation. As can be seen from fig. 1, the orientational order parameter exceeds 0.83.

In FIG. Figure 2 shows a typical view of the kinetic curves of guidance, erasure, and dark relaxation of optical anisotropy (birefringence) in the amorphous KD-2 layer. The arrows ↑ (up) and ↓ (down) denote the moments of on and off of photoactivating radiation with the corresponding state of polarization.

At short irradiation times (low doses of absorbed energy), switching off the activating radiation leads to a rapid decrease in the induced anisotropy due to Brownian rotational diffusion of azo dye molecules. This process of dark relaxation has almost only one fast dynamic component. With an increase in the dose of absorbed energy, along with the dynamic component, a quasistatic component appears, the proportion of which increases until the relaxation process stops completely. Moreover, with a certain excess of this critical dose of absorbed radiation, we observed an anomalous dark “relaxation up”, i.e. after switching off the activating radiation, a further dark self-ordering of the molecules takes place. In this case, the dark amplification of the anisotropy induced by the light can be multiple. The rate of dark “relaxation upward” increases significantly upon heating up to the melting point of KD-2 dye (~ 164 ° С).

Example 2

A MEL-5 surfactant film 100-200 nm thick obtained by the Langmuir-Blodgett method by sequential transfer of monolayers of organic molecules from the surface of the water onto fused silica wafers was used as a PMM.

The source of polarized activating radiation was a DRSh-250 mercury lamp with glass filters and a Glan prism.

The orientational order and birefringence monotonically increased during irradiation and reached photostationary values of 0.7 (in the absorption band 400–520 nm) and 0.23 (at a wavelength of λ = 633 nm).

Example 3

The photodichroic absorption spectrum of the azo dye of a pure yellow dye (PCF) is shown in Fig. 3. The film was obtained by watering a 1% solution of PCH in dimethylformamide

The source of polarized activating radiation was a DRSh-250 mercury lamp with glass filters and a Glan prism.

In fig. Figure 3 shows the initial (before irradiation with polarized radiation with a wavelength of 365 nm) absorption spectrum of this film (cr. 1) and after its irradiation with linearly polarized radiation for components that coincide (cr. 2) and orthogonal (cr. 3) with the orientation of the polarization vector activating radiation. As can be seen from fig. 1, the orientational order parameter is about 0.8.

The value of the orientational order, as for all PCFs based on PCF, monotonically increased during irradiation and reached a photostationary value of 0.8 (in the absorption band of 330–460 nm)

The monomolecular layer of a pure yellow etching dye (ПЖЖ), obtained by drawing a glass substrate from a 1% aqueous dye solution, was used as a photo-orientation of a thermotropic LC from Merck according to the method described in [V.G. Chigrinov, V.M. Kozenkov, H.S. Kwok, Photoalignment of Liquid Crystalline Materials: Physics and Applications, 232 pp., Wiley, August 2008].

Example 4

A liquid crystal polymer with an azo dye in the side chain, the structural formula of which is given in the table, was used as a photochemically stable dichroic substance.

A 1.5 μm thick sample was obtained by centrifugation of a 3% solution of an LC polymer in toluene at a rotation speed of 5000 rpm.

Example 5

A thin (about 0.3 μm) layer of KD-2 dye, obtained as in Example 1 by thermal evaporation in vacuum, was used as a photo-orientant of lyotropic LC firms NIOPiK (Russia) and Corning (USA) also according to the method described in [V.G. Chigrinov, V.M. Kozenkov, H.S. Kwok, Photoalignment of Liquid Crystalline Materials: Physics and Applications, 232 pp., Wiley, August 2008].

Example 6

As an FCM based on PCF, layers of azo dye (1V) were used,

obtained by watering from a solution of an organic solvent of dimethylformamide. An FHM solid film was used in experiments on reverse recording of images in a medium.

The given examples confirm the fulfillment of the task.

INDUSTRIAL APPLICABILITY

The material proposed in the claimed invention can be used as a chemical and / or structural material in phototechnology for the production of a variety of pictorial two - and / or three-dimensional polarization-optical elements and devices of nano-, micro- and macro-optoelectronic devices, in instrumentation using such polarization-optical elements.

It can be used in the manufacture of optical anisotropic products such as anisotropic photonic crystals, bulk diffraction gratings, radiation input-output devices, lenses, polarization-selective light beam dividers, etc., as well as photo-orientants of liquid crystals.

The material can be used in phototechnology for the production of photothermally stable adaptive internal thin-film phase plates and polaroids, as well as photo-orientants of liquid crystals.

The material can also be used as a polarization-sensitive photoanisotropic medium in the technical means of recording, storing, processing and displaying information, including in systems of two - (2D) and / or three - (3D) dimensional optical memory WORM and VR - type, in polarized computer and conoscopic holography, in means of protection against counterfeiting and identification of securities and other products for household and technical purposes, when creating new instruments and devices of measuring equipment for studying mechanically stresses in various products photoelasticity method.

Claims (20)

1. Polarization-sensitive material exhibiting in the solid state the effect of photoinduced guidance or a change in it of long-term optical anisotropy, dichroism of absorption and / or birefringence, upon absorption of polarized or non-polarized, but directed radiation, a polarizing-sensitive component in its composition in the form of a photochemically stable, non-luminescent or weakly luminescent substances with the formation in its volume or on the surface of anisotropic spatial on modulated ordered molecular structure, optical properties, absorption dichroism and birefringence, the direction of orientation of the optical axis and the orientational molecular order, in which they directly correlate with the spatial distribution of the polarization state and energy characteristics and the direction of propagation of the activating radiation absorbed in the polarization-sensitive material, The material contains the following components: - as a polarization-sensitive component, at least one photochemically stable, anisotropically absorbing dichroic and non-luminescent or weakly luminescent substance and - low molecular weight additives that regulate film-forming, viscous properties and have close resonant vibrational absorption bands in the ground electronic state with vibrational absorption spectra of photochemically stable substances or chromophores. 2. The material according to claim 1, in which the formation in the volume and on the surface of spatially modulated orientationally ordered molecular structures occurs as a result of the absorption by this material of spatially modulated by polarization and intensity of linear, elliptically or circularly polarized radiation or not polarized, but directed radiation. 3. The material according to paragraphs. 1 and 2, in which the spatial distribution of the degree of ordering and its direction of spatially modulated and orientationally ordered molecular structures formed in the volume and on the surface are in direct accordance with the local spatial distribution of the activating radiation during one- or two-photon absorption by the material. 4. The material according to paragraphs. 1 and 2, in which the properties of orientationally ordered molecular structures in its solid state are manifested in the anisotropy of optical properties - dichroism of absorption and birefringence. 5. The material according to paragraphs. 1 and 4, in which the manifestation of the anisotropy of the optical properties of photochemically stable substances under the action of absorbed radiation is not accompanied by a change in the shape of its absorption spectra, accompanied only by the clarification of the material of the polarized parallel component in the spectral region of the activating radiation and dimming for the orthogonal component. 6. The material of claim 1, wherein the photochemically stable substances are selected from groups exhibiting absorption bands in the UV, visible and / or IR spectral region between 150 nm and 2000 nm. 7. The material according to paragraphs. 1 and 6, where low molecular weight organic substances selected from the classes are used as photochemically stable substances: L-type azo dyes (mono-, dis-, tri- and polyazo dyes, azo dyes with metal complexes), T-type azo dyes, L- quinone dyes and T-type, anthraquinone dyes (mono- and polyoxyanthraquinones, s-substituted hydroxythioanthraquinones, s-acrylaminohydroxythioanthraquinones, T-type anthraquinones, anthrapyrimidinone dyes, merocyanine dyes, I-type azo dyes, benzene, and naphthamines trachinone dyes, azomethine dyes, tolans, biphenyls, aromatic nitro and nitroso compounds, 2'-n-nitrozodimethylaniline, dimethylaminostirol, polycyclic compounds, nitroanilines, sodium nitronylanilines, dialkylaminostyrenes. 8. The material according to paragraphs. 1 and 6, where photochemically stable substances are directly introduced into the composition of the liquid crystal polymer as chromophores covalently linked to it in the side chain. 9. The material according to paragraphs. 1 and 6, where photochemically stable substances in the form of dichroic chromophores are introduced directly into the main chain of the macromolecule or as covalently linked chromophores in the side chain. 10. The material according to paragraphs. 1 and 6, where photochemically stable substances are represented as covalently bound bi- or multifunctional molecules, which, in addition to the dichroic chromophore, also include, for example, luminescent or photochromic fragments, or one or more photosensitive fragments that contribute to the photochemical formation of the spatial network upon irradiation . 11. The material according to paragraphs. 1 and 6, in which photochemically stable substances have at least two substituents of the type OH, COOH, NHR, capable of forming at least two intermolecular donor-acceptor or hydrogen bonds between the dichroic substance and the macromolecule of the polymer matrix or between the dichroic molecules themselves with the formation of a spatial orientationally ordered grid. 12. The material according to claim 1, in which the material from photochemically stable substances is prepared by thermal vacuum spraying, irrigation from a solution, or the Langmuir-Blodgett method. 13. The material according to claim 1, which has three thermodynamically stable states, one of which is the initial isotropic state with an arbitrary orientation of the molecules in space and two photoinduced ones produced either by polarized or not polarized, but directed radiation absorbed by a photostable substance, and in the first In the case of anisotropically absorbed molecules, they are oriented in the plane perpendicular to the polarization vector of the activating radiation, and in the second, in the direction of its propagation. 14. The material according to claim 1, in which the orientational order parameter of the photochemically stable molecules reaches values of more than 0.8, and the photoinduced birefringence of more than 0.4. 15. The material according to claim 1, in which the photoinduced anisotropy is enhanced one- or two-photon through a real or virtual intermediate level by its additional heating at a temperature lower than the melting point of photochemically stable molecules. 16. The material according to claim 1, in which the irradiation energy necessary to achieve the limiting value of photoinduced anisotropy is reduced when using a single pulse of activating radiation. 17. The material according to claim 1, in which the photoinduced anisotropy reaches its maximum photostationary value asymptotically. 18. The material according to paragraphs. 1 and 17, in which photoinduced anisotropy reaches its maximum value by additional heating at a temperature below the melting point of a photochemically stable substance.

Images