Patent Application
20250164838
Part of the present invention was disclosed in a paper published in Xinyi Yu, et al. P-92: Photo-sensitive Vertical Alignment Material with Room Temperature Dip-coating Technique, Society for Information Display, Digest of Technical Papers, Volume 55, Issue 1, 1743-1746, 2024. This paper is a grace period inventor-originated disclosure disclosed within one year before the filing date of this application and falls within the exceptions defined under 35 USC § 102(b)(1). This paper is hereby incorporated by reference in its entirety.
The present disclosure relates to precursor compounds useful for preparing photoalignment layers and methods of use and products thereof.
The alignment of liquid crystals can be performed by various methods known in the art. In one example, a rubbing method can be used wherein a polymer film, such as a polyimide, is rubbed in a predetermined direction by fibers or a cloth material. However, this method suffers from several disadvantages, such as for example, practical difficulties, including particles left by fibers or cloth material on the substrate surface, which can lead to defects as well as static charge buildup, which can attract particles leading to further defects. The rubbing methods can also lead to uneven surface, which can result in uneven gaps between the liquid crystal and substrate.
Photoalignment layers have been developed to address some of the problems associated with rubbing methods. Notably, photoalignment methods can avoid particles left behind the surface as well as any static buildup resulting from rubbing methods. Further, photoalignment methods can avoid deformation of the substrate mentioned above. However, photoalignment methods can suffer from poor voltage holding ratio (VHR).
Typically, photoalignment layers are prepared by depositing a photoactive polymer on a substrate, which then irradiated inducing the polymeric material to align itself such that the liquid crystal disposed thereon is properly aligned, anchored and can be oriented at a certain angle. Photoactive polymers used in this approach can include photoisomerizable polymers, such as, e.g., polymers having azo groups, photodimerizable polymers, such as polymers having coumarins or cinnamate groups, photocrosslikable polymers, photodecomposable polymers such as polyimides, and the like. Photoalignment can be achieved by exposing the polymer layer to linearly polarized light.
As shown above there still exists a need for improved photoalignment materials with high alignment quality, controllable pretilt, high transmittance and good value of VHR.
The present disclosure provides a precursor compound useful in fabricating a photoalignment layer that can be used in liquid crystal devices. The precursor compound can comprise at least one anchoring group (e.g., a phosphonic acid) and at least one double C═C bond conjugated with at least one electron-withdrawing group, such as a carbonyl group, a carboxylic acid, a carboxamide, a nitrile or a ketone. The precursor compound can be coated, e.g., by dip-washing procedure, on at least one surface of a substrate [e.g., an indium tin oxide (ITO) layer] thereby forming a self-assembled layer due to anchoring via the anchoring group to the substrate surface. The self-assembled layer after irradiation, e.g., with linearly polarized UV light (in the wavelength range 250-400 nm), induces alignment of a liquid crystal in a certain direction and with variable pretilt angle, e.g., in the range from vertical alignment) (˜90° to almost planar alignment) (˜1-5°. The desired value of pretilt angle can be achieved either by varying the chemical structure of the precursor compound, or by using a mixture thereof, or by varying the dosage of UV irradiation. UV irradiation can be applied either directly on the coated substrate with self-assembled layer or onto an assembled cell, which is either empty or already charged with a liquid crystal. Using known technology for irradiation with UV light, the alignment on the substrate surface can be achieved either uniform unidirectional or patterned.
The precursor compounds described herein distinguish from cinnamate polymers known in the art by two features: (i) the precursor compounds described herein are not polymers and (ii) the precursor compounds described herein contain an anchoring group that provides reliable linking with a substrate. The anchoring described herein comprises a phosphonic acid moiety. Advantageously, the chemical structure of the precursor compounds described herein, the number of aromatic rings can be reduced to one ring (see
In a first aspect, provided herein is a photoalignment layer comprising at least one precursor compound selected from the group consisting of a compound of Formula I, II, III, IV, and V:
wherein:
In certain embodiments, the at least one precursor compound is conjugated to a surface of a substrate.
In certain embodiments, the substrate comprises a metal oxide.
In certain embodiments, the substrate is selected from the group consisting of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), indium-doped cadmium oxide (ICO), indium zinc oxide (IZO), alumina, silica, and combinations thereof.
In certain embodiments, each of i and p is 1.
In certain embodiments, R1 is benzene-1,4-diyl optionally substituted with one or more moieties selected from the group consisting of fluorine, chlorine, cyano, —C1-C10 alkyl, or —O—C1-C10 alkyl.
In certain embodiments, each of R2 and R3 is independently selected from the group consisting of benzene-1,4-diyl optionally substituted with one or more moieties selected from the group consisting of fluorine, chlorine, cyano, —C1-C10 alkyl, or —O—C1-C10 alkyl.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
wherein:
In certain embodiments, each of A2 and A3 is independently —O— or —O(C═O)—; each of L1 and L2 is independently —(CH2)6-14—; and each of R4, R5, and R6 is independently hydrogen or —OMe.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
wherein:
In certain embodiments, each of R4 and R5 is —OMe.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
In certain embodiments, the at least one precursor compound is conjugated to a surface of a substrate, wherein the substrate is indium tin oxide (ITO) or alumina.
In certain embodiments, the at least one precursor compound is two precursor compounds selected from the group consisting of a compound of Formula I, II, III, IV, and V.
In a second aspect, provided herein is a method of preparing a photoalignment layer comprising a dimerized or polymerized compound, the method comprising: providing a substrate with the photoalignment layer described herein coated on a surface of the substrate and exposing the photoalignment layer to a polarized electromagnetic radiation thereby inducing dimerizing or polymerizing the at least one precursor compound and forming the photoalignment layer comprising the dimerized or polymerized compound.
In certain embodiments, the polarized electromagnetic radiation has a wavelength of 280-400 nm.
In certain embodiments, the method further comprises depositing a composition comprising a liquid crystal on a surface of the photoalignment layer before the step of exposing the photoalignment layer to a polarized electromagnetic radiation or after the step of exposing the photoalignment layer to a polarized electromagnetic radiation.
In a third aspect, provided herein is a photoalignment layer comprising the dimerized or polymerized compound prepared according to the method described herein.
In a fourth aspect, provided herein is a photoalignment layer comprising the dimerized or polymerized compound described herein, wherein the photoalignment layer has a pretilt angle of 0-10 degrees or 80-90 degrees.
In a fifth aspect, provided herein is a liquid crystal device comprising the photoalignment layer comprising the dimerized or polymerized compound described herein and a liquid crystal layer.
Advantageously, the photoalignment layer described herein can be about 5-20 times thinner than commonly used polyimide (PI) photoalignment layers or with other photoalignment polymers. Additionally, the process of coating a substrate with the precursor compound is simpler than that of commonly used photoalignment polymers and can include dip-washing-drying process and does not require hard-baking and/or rubbing. The photoalignment layer described herein is not sensitive to overshining with UV light thereby providing a wide and reliable processing window. Starting materials used to synthesize the precursor compound are inexpensive and readily available and involve common synthetic protocols.
The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated and understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings.
Throughout the present disclosure, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. It is also noted that in this disclosure and particularly in the claims and/or paragraphs, terms such as “comprises”, “comprised”, “comprising” and the like can have the meaning attributed to it in U.S. Patent law; e.g., they can mean “includes”, “included”, “including”, and the like; and that terms such as “consisting essentially of” and “consists essentially of” have the meaning ascribed to them in U.S. Patent law, e.g., they allow for elements not explicitly recited, but exclude elements that are found in the prior art or that affect a basic or novel characteristic of the present invention.
Furthermore, throughout the present disclosure and claims, unless the context requires otherwise, the words “include”, “comprise” or variations such as “includes”, “including” “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.
The use of the singular herein includes the plural (and vice versa) unless specifically stated otherwise. In addition, where the use of the term “about” is before a quantitative value, the present teachings also include the specific quantitative value itself, unless specifically stated otherwise. As used herein, the term “about” refers to a ±10%, ±7%, ±5%, ±3%, ±1%, or ±0% variation from the nominal value unless otherwise indicated or inferred.
As used herein, unless otherwise indicated, the term “halo” or “halide” includes fluoro, chloro, bromo or iodo.
As used herein, “alkyl” refers to a straight-chain or branched saturated hydrocarbon group. Examples of alkyl groups include methyl-, ethyl-, propyl (e.g., n-propyl and isopropyl), butyl (e.g., n-butyl, iso-butyl, sec-butyl, tert-butyl), pentyl groups (e.g., 1-methylbutyl, 2-methylbutyl, iso-pentyl, tert-pentyl, 1,2-dimethylpropyl, neopentyl, and 1-ethylpropyl), hexyl groups, and the like. In various embodiments, an alkyl group can have 1 to 40 carbon atoms (i.e., C1-C40 alkyl group), for example, 1-30 carbon atoms (i.e., C1-C30 alkyl group). In certain embodiments, an alkyl group can have 1 to 6 carbon atoms, and can be referred to as a “lower alkyl group.” Examples of lower alkyl groups include methyl, ethyl, propyl (e.g., n-propyl and isopropyl), and butyl groups (e.g., n-butyl, isobutyl, sec-butyl, tert-butyl). In certain embodiments, alkyl groups can be optionally substituted as described herein. An alkyl group is generally not substituted with another alkyl group, an alkenyl group, or an alkynyl group.
As used herein, “cycloalkyl” by itself or as part of another substituent means, unless otherwise stated, a monocyclic hydrocarbon having between 3-12 carbon atoms in the ring system and includes hydrogen, straight chain, branched chain, and/or cyclic substituents. Exemplary cycloalkyls include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and the like.
The term “optionally substituted” refers to a chemical group, such as alkyl, cycloalkyl aryl, and the like, wherein one or more hydrogen may be replaced with a substituent as described herein, for example, halogen, azide, alkyl, aralkyl, alkenyl, alkynyl, cycloalkyl, hydroxyl, alkoxyl, amino, nitro, sulfhydryl, imino, amido, phosphonate, phosphinate, carbonyl, carboxyl, silyl, ether, alkylthio, sulfonyl, sulfonamido, ketone, aldehyde, ester, heterocyclyl, aromatic or heteroaromatic moieties, —CF3, —CN, or the like
The term “nitro” is art-recognized and refers to —NO2; the term “halogen” is art-recognized and refers to —F, —Cl, —Br or —I; the term “sulfhydryl” is art-recognized and refers to —SH; the term “hydroxyl” means-OH; and the term “sulfonyl” and “sulfone” is art-recognized and refers to —SO2—. “Halide” designates the corresponding anion of the halogens.
The symbol “” or“
” or “
” or “
” in a chemical structure represents a position from where the specified chemical structure is bonded to another chemical structure.
In order to provide excellent photoalignment for liquid crystal applications with controlled pretilt angle, lowers layer thickness and easy route of fabrication we propose new compounds, exemplified by derivatives of (E)-3-(4-hydroxy-3-methoxyphenyl) acrylic acid (ferulic acid or cinnamate acid derivative) with general structure shown at
The present disclosure provides a photoalignment layer comprising at least one precursor compound selected from the group consisting of a compound of Formula I, II, III, IV, and V:
wherein:
In certain embodiments, R1 is represented by a moiety selected from the group consisting of:
wherein m is 1, 2, or 3; and R6 for each instance is independently fluorine, chlorine, cyano, —C1-C10 alkyl, —O—C1-C10 alkyl, —O—C1-C8 alkyl, —O—C1-C6 alkyl, —O—C1-C4 alkyl, —O—C1-C2 alkyl, or —OMe.
In certain embodiments, R2 is selected from the group consisting of:
wherein n is 1, 2, or 3; and R4 for each instance is independently is fluorine, chlorine, cyano, —C1-C10 alkyl, —O—C1-C10 alkyl, —O—C1-C8 alkyl, —O—C1-C6 alkyl, —O—C1-C4 alkyl, —O—C1-C2 alkyl, or —OMe.
In certain embodiments, R2 is
wherein n is 1 and R4 is —C1-C10 alkyl, —O—C1-C10 alkyl, —O—C1-C8 alkyl, —O—C1-C6 alkyl, —O—C1-C4 alkyl, —O—C1-C2 alkyl, or —OMe.
In certain embodiments, R3 is selected from the group consisting of:
wherein q is 1, 2, or 3; and R5 for each instance is independently fluorine, chlorine, cyano, —C1-C10 alkyl, —O—C1-C10 alkyl, —O—C1-C8 alkyl, —O—C1-C6 alkyl, —O—C1-C4 alkyl, —O—C1-C2 alkyl, or —OMe.
In certain embodiments, R3 is
wherein q is 1 and R5 is —C1-C10 alkyl, —O—C1-C10 alkyl, —O—C1-C8 alkyl, —O—C1-C6 alkyl, —O—C1-C4 alkyl, —O—C1-C2 alkyl, or —OMe.
Each of L1 and L2 can independently be —(CH2)t—, wherein t is a whole numbers selected from 1-20, 1-18, 1-16, 1-14, 1-12, 1-10, 1-8, 1-6, 1-4, 1-2, 2-20, 4-20, 6-20, 8-20, 10-20, 12-20, 14-20, 16-20, 18-20, or 6-18 wherein —(CH2)t— is optionally substituted with one or more F; furthermore; and one or more —CH2— is optionally independently replaced with —CF2—, —O—, or —(C═O)— moieties provided that two O atoms are not linked together forming a peroxide moiety (—O—O—). In certain embodiments each of L1 and L2 is independent 6-8 or 12-20.
In certain embodiments, each of A1, A2, and A3 is independently a covalent bond, —O—, —S—, —(C═O)O—, or —O(C═O)—. In certain embodiments, A2 is —O— or —O(C═O)—; and A3 is —O—. In the interest of clarity, when A1, A2, and A3 is a covalent in, for example, the precursor compound of Formula III can be represented by the structure:
Each of Z1 and Z2 is independently selected from the group consisting of a carboxylic acid, a carboxylic ester (such as a carboxylic-C1-C10 alkyl ester), cyano, a phosphine oxide P═O (such as a C1-C10 dialkyl phosphine oxide) a sulfoxide S═O (such as a —C1-C10 alkyl sulfoxide), a sulfonic SO2 (such as a carboxylic C1-C10 sulfonic ester), a carbonyl (such as a —C1-C10 alkyl carbonyl), a pyridine (such as pyridin-2-yl or pyridin-4-yl), a pyrimidine (such as pyrimidin-2-yl or pyrimidin-4-yl), a quinoline (such as quinolin-2-yl), and a quinazoline (quinazolin-2-yl). In certain embodiments, each of Z1 and Z2 is independently selected from the group consisting —CO2H, —CO2 (C1-C20 alkyl), —CO2 (C1-C18 alkyl), —CO2 (C1-C16 alkyl), —CO2 (C1-C14 alkyl), —CO2 (C1-C12 alkyl), —CO2 (C1-C10 alkyl), —CO2 (C1-C8 alkyl), —CO2 (C1-C6 alkyl), —CO2 (C1-C4 alkyl), —CO2 (C1-C1 alkyl), or —CN.
In certain embodiments, B1 is —O—, —NH—, —N(C1-C12 alkyl)-, —N(C1-C10 alkyl)-, —N(C1-C8 alkyl)-, —N(C1-C6 alkyl)-, —N(C1-C4 alkyl)-, or —N(C1-C2 alkyl)-. In certain embodiments, B1 is —O—.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
wherein each of A2, A3, L1, L2, R4, R5, and R6 is independently as defined in any embodiment or combination of embodiments described herein.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
wherein each of L1, L2, R4, R5, and R6 is independently as defined in any embodiment or combination of embodiments described herein.
In certain embodiments, the at least one precursor compound is selected from the group consisting of:
In certain embodiments, the at least one precursor compound is conjugated to a surface of a substrate. In certain embodiments, the substrate comprises a metal or conductive metal oxide. Exemplary metals and conductive metal oxides include, but are not limited to aluminum, gold, silver, and indium-tin oxide (ITO), aluminum-doped zinc oxide (AZO), indium-doped cadmium oxide (ICO), indium zinc oxide (IZO), alumina, silica, and combinations thereof. In certain embodiments, the substrate is ITO.
The at least one precursor compound can be conjugated to the surface of a substrate via one or more of a covalent bond, a hydrogen bond, a dative bond, an ionic bond, or combination thereof between the phosphonic acid moiety and the substrate surface. In certain embodiments, the conjugation of the phosphonic acid moiety and the substrate surface can be represented by any one or more of the following chemical structures:
wherein R* is L1 or L2.
The precursor compounds described herein have notable advantages comparing to polymers described before:
An exemplary scheme of synthesizing a precursor compound comprising a phosphonic acid functional group with several benzene rings (see
The scheme of synthesis of simplified structure of new alignment materials bearing single benzene ring (see
The scheme of synthesis of “reverse” cinnamate phosphonic acid derivatives where activated C═C bond and phosphonic acid group are on the same site of benzene ring (see
Advantageously, the impurities that form during the synthetic steps have different enough solubilities than the at least one precursor compound allowing for convenient purification of the desired compound. Therefore, to obtain the intermediate products and final phosphonic acids in high purity, two simple steps are enough: flash-chromatography of the crude half products on short plug of silica gel and by re-crystallization from an appropriate solvent, which is exemplified in Examples 1-15.
The present disclosure also provides a method of preparing a photoalignment layer comprising a dimerized or polymerized compound, the method comprising: providing a substrate with the photoalignment layer described herein coated on a surface of the substrate and exposing the photoalignment layer to a polarized electromagnetic radiation thereby inducing dimerizing or polymerizing the at least one precursor compound and forming the photoalignment layer comprising the dimerized or polymerized compound.
Irradiating the photoalignment layer comprising the at least precursor compound with polarized electromagnetic radiation induces [2+2] cycloaddition dimerization reactions of the at least one precursor compounds comprising a single olefin moiety. In instances in which the at least one precursor compounds comprise more than one olefin moiety, irradiating photoalignment layer induces [2+2] cycloaddition polymerization reactions.
Advantageously, adjusting the intensity and duration of the polarized electromagnetic radiation of the photoalignment layer can modify the pretilt angle of the resulting photoalignment layer comprising the dimerized or polymerized compound.
The polarized electromagnetic radiation can have a wavelength of 280-400 nm.
In certain embodiments, the method further comprises depositing a composition comprising the at least one precursor compound described herein and a solvent on a surface of a substrate thereby forming the photoalignment layer coated on the surface of the substrate; and optionally removing the solvent.
The solvent is not particularly limited and can be any solvent in which the at least one precursor compound described herein is at least partially soluble. In certain embodiments, the solvent is an amide, formamide, a phosphoramide, haloalkane, ether, an aromatic solvent, an ester, an alcohol, dialkyl sulfoxide, or a combination thereof. Exemplary solvents include, but are not limited to, N-methyl-2-pyrrolidone (NMP), ethanol, ethyl acetate, tetrahydrofuran, toluene, and combinations thereof.
The solvent can be removed using any method known in the art, such as the application of heat, vacuum, or a combination thereof.
The substrate can comprise a conductive metal oxide, such as ITO, AZO, ICO, IZO, alumina, silica, and combinations thereof. In certain embodiments, the substrate comprises ITO.
Also provided herein is the photoalignment layer comprising the at least one precursor disposed on at least one surface of a substrate.
In certain embodiments, the method further comprises depositing a composition comprising a liquid crystal on a surface of the photoalignment layer before the step of exposing the photoalignment layer to a polarized electromagnetic radiation or after the step of exposing the photoalignment layer to a polarized electromagnetic radiation.
Also provided herein is a photoalignment layer comprising the dimerized or polymerized compound prepared according to the methods described herein.
In certain embodiments, the photoalignment layer comprising the dimerized or polymerized compound has a pretilt angle of 0-10 degrees or 80-90 degrees. In certain embodiments, the photoalignment layer comprising the dimerized or polymerized compound has a pretilt angle of about 0-2 degrees and about 86 degrees.
The proposed new way of modifying surface allows to achieve monomolecular alignment layer with excellent alignment.
To a cooled (ice-water), stirred solution of 3.50 g (15.8 mmol) of 4-((tetrahydro-2H-pyran-2-yl)oxy)benzoic acid, 3.64 g (17.5 mmol) of methyl (E)-3-(4-hydroxy-3-methoxyphenyl) acrylate and 5 mg of 4-N,N-dimethylaminopyridine in 30 ml of dichloromethane (DCM) was added dropwise solution of 3.60 g (17.5 mmol) of dicyclohexyl-carbodiimide (DCC) in 20 ml of dry DCM. After finishing addition, the mixture was stirred while reaction is completed (monitoring by TLC), then precipitation was filtered off and washed additionally with 100 ml of DCM. Combined solutions in DCM were evaporated to dryness, dissolved in toluene, and purified by flash chromatography on SiO2 using toluene as an eluent top yield a colorless oil. The colorless oil was crystallized from isopropyl alcohol (IPA) in fridge. Yield 78% (5.1 g) of a white amorphous powder.
To a hot, stirred solution (60° C.) of 4.50 g (10.9 mmol) (E)-2-methoxy-4-(3-methoxy-3-oxoprop-1-en-1-yl)phenyl 4-((tetrahydro-2H-pyran-2-yl)oxy)benzoate in 100 ml ethanol and 5 ml H2O was added 0.55 g (2.2 mmol) of pyridinium salt of toluene sulfonic acid. Solution was stirred at 60° C. while reaction is completed (monitoring by TLC). After ¾ of solvent was evaporated and rest of the solution was poured on ice to yield a white gum-like precipitate. The white gum-like precipitate was washed by 100 ml cold water. Yield 98% (3.54 g).
A mixture of 2.50 g (7.6 mmol) (E)-2-methoxy-4-(3-methoxy-3-oxoprop-1-en-1-yl)phenyl 4-hydroxybenzoate, 14.50 g (53.4 mmol) 1,8-dibromooctane and 4.20 g (30.4 mmol) potassium carbonate in 75 ml acetonitrile was refluxed for 3 hours. After cooling the inorganic part was filtered off and washed by an additional 50 ml of acetonitrile. The combined solutions were evaporated and recrystallized twice from IPA and hexane. Yield 86% (3.39 g) of white powder.
A solution of 2 g (3.9 mmol) (E)-2-methoxy-4-(3-methoxy-3-oxoprop-1-en-1-yl)phenyl 4-((8-bromooctyl)oxy)benzoate in 25 ml of triethyl phosphite was degassed and refluxed in azote atmosphere for 8 h. After excess triethyl phosphite was removed under vacuum to yield a colorless oil, which was solidified after cooling to room temperature with quantitative yield.
To a cooled by ice stirred solution of 2.2 g (3.8 mmol) of (E)-2-methoxy-4-(3-methoxy-3-oxoprop-1-en-1-yl)phenyl 4-((8-(diethoxyphosphoryl) octyl)oxy) benzoate in 30 ml of DCM 0.87 g (5.7 mmol) of trimethylsilyl bromide was added dropwise. Solution was stirred 8 hours. After DCM was evaporated to dryness and 30 ml of methanol was added. Solution was kept under stirring 8 hours more. After methanol was removed on rotary evaporator and product recrystallized from IPA in fridge as white powder. Yield 90% (1.79 g).
The synthesis of Compound 7a was carried out essentially following to the protocol described in Example 3. Excess alkylating agent was removed by flash chromatography using hexane as eluent. Product was eluted by toluene and recrystallized from IPA in fridge. Yield 64% (3.66 g).
The synthesis of compound 8a was carried out essentially following the protocol described in Example 4 with quantitative yield.
The synthesis of Compound 9a was carried out essentially following the protocol described in Example 5 with 81% yield.
The synthesis of Compound 7b was carried out essentially following the protocol described in Example 3 with 58% yield.
The synthesis of Compound 8b was carried out essentially following the protocol described in Example 4 with quantitative yield.
The synthesis of Compound 9b was carried out essentially following the protocol described in Example 5. Product was recrystallized from hexane with 77% yield.
The synthesis of Compound 10 was carried out essentially following the protocol described in Example 3, recrystallized from acetonitrile with 95% yield.
A solution of 1.5 g Methyl (E)-3-(3-methoxy-4-(3.3 mmol) (octadecyloxy)phenyl) acrylate, 1.8 g (9.9 mmol) 6-bromo-1-hexanol and catalytic amount of toluene sulfonic acid (˜50 mg) were refluxed 48 hours. After reaction complete solution were filtered through silica gel with toluene as eluent. After toluene was evaporated on rotary evaporator and product was recrystallized from 50 ml of acetonitrile with 83% yield (1.65 g).
The synthesis of Compound 12 was carried out essentially following the protocol described in Example 4 with quantitative yield.
The synthesis of Compound 13 was carried out essentially following the protocol described in Example 5. Product was recrystallized from isopropyl alcohol with 78% yield.
Preparation of a solution The concentration of the precursor compound varied from 0.1˜0.5 wt/wt %. The precursor compound or mixture thereof were dissolved in an appropriate solvent by adding the solvent to a sample of the precursor compound and stirring for at least 10 min to complete dissolution. The appropriate solvents preferably provide enough solubility at the desired concentration, do not chemically react with the precursor compound and can be selected but not limited from the following list: N-methyl-2-pyrrolidone (NMP), ethanol, ethyl acetate, tetrahydrofuran, toluene, and mixtures thereof.
Treatment of the substrate Substrates coated with ITO or alumina (Al2O3) were cleaned in the usual manner typically used for substrate cleaning for LC cells, and then treated with ozone. Then, the substrates were dipped into the solution prepared described above for several seconds, typically for 5-10 seconds. Then, the dipped substrate was twice washed in the same solvent that was used for dissolving the precursor compound (each time is approx. for 10 min), optionally assisted with sonicating washing bath at ambient temperature. Finally, the residual solvent after washing was removed by soft baking the substrate at 100° C. for 20 min, optionally, in the vacuum chamber at pressure of 100 mbar or lower.
Thereafter, the prepared substrate was treated with UV light to provide alignment. Three kinds of treatments were applied: The substrates are tilted by angle θ within the range of 10 to 80 degree along the polarization direction, preferably within 40-50 degree, most preferably at 45° along the direction of polarized light, see
The cell was injected with a nematic liquid crystal containing 3 wt % of dichroic dye (N-methyl-4-((2-methyl-4-((3′-methyl-4′-((4-(butyloxy)phenyl)diazenyl)-[1,1′-biphenyl]-4-yl)diazenyl)phenyl)diazenyl)-N-octyl-aniline). The dichroic ratio of the LC cell is measured by spectrometer equipped with a linear polarizer. The cell was then placed onto a rotational holder and the position of rotation was found when absorbance at 490 is minimal (Dmin) and maximal (Dmax). Then the dichroic ratio was calculated as DR=Dmax/Dmin. The order parameter(S) was calculated accordingly to the following equation S═(DR−1)/(DR+2). The S is within the range 0.6-0.7.
VHR was measured by an electro-optical setup at 60° C., by applying a 5V pulse following to the method described in [Tseng M. C., Yaroshchuk O., Bidna T., Srivastava A. K., Chigrinov V., Kwok H. S. Strengthening of liquid crystal photoalignment on azo dye films: Passivation by reactive mesogens. RSC Advances. 2016, 6, 48181-48188]. Then, the VHR value was calculated as a relative decreasing the voltage measured after 16.7 ms to that after 5 ms of pulse applying. The measured VHR values was not lower than 98%.
For measuring RDC voltage, a 10 V DC signal was applied to the LC cell for 1 hour at 60° C. Then the cell was disconnected and short-circuited for 1 s to discharge the LC capacitor, following the standard definition stated in [Guo Q., Srivastava A. K., Chigrinov V. G., Kwok H. S. Polymer and azo-dye composite: A photoalignment layer for liquid crystals. Liquid Crystals. 2014, 41, 1465-1472]. Thereafter, the residual voltage was measured after 10 min. The value was ˜6 mV.
The LC cell was set as a twist nematic cell for measuring AAE. The AAE was obtained by measuring the twist angle of the cell, referring to [Ichimura Y., Kobayashi N. K. N., Kobayashi S. K. S. A new method for measuring the azimuthal anchoring energy of a nematic liquid crystal. Japanese journal of applied physics, 1994, 33 (3B): L434.]. The value reached 1.14×10−4 J/m2.
In order to check the stability of alignment provided with new compounds, the transmittance versus voltage curve (TVC) of LC cells are measured before and after shining with light: (i) stability to visible light: the cell is put at 3 cm under a 450 lm lamp (67.4 mW/cm2 at 555 nm) for 24 h, approximately 5.8 KJ/cm2 (ii) UV stability: the cell is exposed with 365 nm UV light for dosage of 2 J/cm2. The resulted TVC's are given in
The present application claims priority from U.S. Provisional Patent Application No. 63/599,572, filed on Nov. 16, 2023, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63599572 | Nov 2023 | US |
