WO2010099214A1 - Lyotropic chromophoric compounds, liquid crystal systems and optically anisotropic films - Google Patents

Abstract

Lyotropic chromophoric compounds formed by reaction of a precursor comprising an anhydride with an amino acid are described. The compounds can be used to form lyotropic liquid crystal systems possessing high quality optical properties. The resulting liquid crystal systems are readily applied onto a substrate to obtain optically isotropic or anisotropic, at least partially crystalline films applicable in various fields.

Description

LYOTROPIC CHROMOPHORIC COMPOUNDS, LIQUID CRYSTAL SYSTEMS AND OPTICALLY ANISOTROPIC FILMS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 61/155,978, which was filed on February 27, 2009, and is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

[0002] The present invention relates generally to the fields of organic chemistry and optically anisotropic coatings. More specifically, the present invention relates to lyotropic chromophoric compounds, lyotropic liquid crystal systems comprising one or more lyotropic chromophoric compounds, and optically isotropic or anisotropic films.

Description of the Related Art

[0003] Optical elements are increasingly based on new materials possessing specific, precisely controllable properties. An important element in modern visual display systems is an optically anisotropic film having a combination of optical and other characteristics that can be optimized to suit the requirements of a particular device, since each device often has its own set of requirements.

[0004] Various polymeric materials have been used in the manufacture of optically anisotropic films. Films based on such materials may acquire anisotropic optical properties through uniaxial extension and modification with organic dyes or iodine. In many applications, the base polymer is polyvinyl alcohol (PVA). Such films are described in greater detail in the monograph Liquid Crystals: Applications and Uses, B. Bahadur (ed.), World Scientific, Singapore-N.Y. (1990), Vol. 1 , p. 101. However, the low thermal stability of PVA-based films can limit their application. Development of new materials and methods for the synthesis of optically anisotropic films possessing improved characteristics is therefore quite advantageous. Particularly, films having properties such as higher heat resistance, convenient synthesis, and uniformity are highly desirable.

[0005] Organic dichroic dyes have gained prominence in the manufacture of optically anisotropic films with improved optical and working characteristics. Films based on these compounds may be obtained by applying a layer of a liquid crystal (LC) aqueous dye solution containing dye supramolecules onto a substrate surface followed by evaporation of the solvent. The resulting LC films acquire can anisotropic properties in several ways. For example, the anisotropic properties can be acquired by preliminary mechanical ordering of the underlying substrate surface as described, for example, in U.S. Pat. No. 2,553,961. Or, the anisotropic properties can be acquired by subsequent application of external mechanical, electromagnetic, or other orienting forces to the LC coating on the substrate as described, for example, in PCT Publication No. WO 94/28073.

(0006] Investigations into the application of LC dyes, as well as the properties of related systems have become more extensive in the past fifteen years. Recent studies into these phenomena have been motivated largely by industrial applications in liquid crystal displays (LCD's) and glazing. The dye supramolecules may form lyotropic liquid crystal (LLC) phases in which the dye molecules pack into supramolecular complexes that are generally shaped like columns, which are the basic structural units of a mesophase. A high degree of ordering of dye molecules in the columns allows such mesophases to be used for obtaining oriented films characterized by a strong dichroism.

[0007] Dye molecules that form supramolecular LC mesophases typically include peripheral groups that render the dyes water soluble. The mesophases of organic dyes are characterized by specific structures, phase diagrams, optical properties, and dissolving capabilities, as described for example in J. Lydon, Chromonics, Handbook of Liquid Crystals (Wiley-VCH, Weinheim, 1998), Vol. 2B, pp. 981 to 1007.

[0008] Previous research has also focused on thermotropic LC compounds. While thermotropic LC compounds may be oriented into anisotropic films by mechanical forces, such orientation may disappear when the mechanical forces are discontinued. In contrast, LLC phases often retain their dichroic orientation even when a mechanical force is applied and then removed.

[0009] Such properties of LLC phases account for the growing interest in LLC materials, prompting the development of methods for preparing films based on organic dyes. Recent improvements have involved both film application conditions and identification of new LLC systems. In particular, new LLC compositions for the synthesis of optically anisotropic films may be obtained by introducing modifiers, stabilizers, surfactants, and other additives to known dyes as described in, for example, published PCT Publication No. WO 94/28073.

[0010] Recently, there has been increasing demand for films possessing high optical anisotropy that are also characterized by improved selectivity in various wavelength ranges. Films whose absorption maxima occur at different locations in the wide spectral range from the infrared (IR) to the ultraviolet (UV) are very desirable. Several compounds have been developed that are capable of forming LLC films possessing these characteristics. However, the number of dyes known to form stable lyotropic mesophases remains relatively small.

[0011] Disulfoderivative organic dyes, including perylenetetracarboxylic acid (PTCA) based compounds, are important water-soluble dichroic dyes capable of forming stable LLC phases. PCTA species applicable in the manufacturing of optically anisotropic films are described in PCT Publication No. WO 94/28073 and U.S. Pat. Nos. 7,025,900 and 7,160,485. In general, PTCA derivatives are characterized by excellent chemical, thermal, and photochemical stability.

[0012] To improve the solubility of the perylene dyes in organic solvents, various substituents have been introduced into the molecules. Examples of such substituents include oxy ethyl groups as described in Cormier et al., Phys. Chem. 101 (51), 1 1004 to 1 1006 (1997) and phenoxy groups as described in Quante et al, Chem. Mater. 6(2), 495 to 500 (1997). Solubility of perylene dyes may also be increased by substitution with amino groups, as described in Iverson, et al, Langmuir 18(9), 3510 to 5316 (2002), and by substitution with sulfonic groups, as described in PCT Publication No. WO 94/28073 and U.S. Pat. No. 7,025,900. Increased solubility may also be obtained through the substitution of carboxylic groups. Various dye compositions (also referred to as "inks") used in the manufacture of polarizer films based on other PTCA sulfoderivatives have been disclosed in U.S. Pat. No. 5,739,296, U.S. Pat. No. 7,160,485, Japanese Pat. App. 2006-098927, and U.S. Pat. App. Pub. No. 2006/0272546

[0013] Optically anisotropic films may be formed on glass, plastic, or other substrate materials. Films which exhibit high quality optical characteristics may be used as polarizers, which are described in Bobrov, et al. , Environmental and Optical Testing of Optiva Thin Crystal Film® Polarizers, Proceedings of the 10th SID Symposium "Advanced display technologies," (Minsk, Republic of Belarus, Sep. 18-21 , 2001), p. 23 to 30. Methods for the preparation of such films, including those with a high degree of crystallinity, are described in PCT Publication No. WO 02/063,660. The aforementioned PTCA derivatives are capable of forming LLC phases, and anisotropic films obtained using the LLC system possess excellent optical characteristics and exhibit good performance as polarizers.

[0014] One disadvantage of manufacturing anisotropic films is that obtaining reproducible samples can be difficult. Currently, film application technologies generally require that the process parameters, such as concentration of the reactants, temperature for the film formation, etc., be carefully selected and strictly maintained. However, even if all of the processing conditions used in film formation are precisely followed, random local variation of the coating regime can still occur. This may cause the formation of misorientation zones and microdefects as a result of non-uniform micro- and macro- crystallization processes in the course of solvent removal. In addition, the manufacture of LLC systems carries the risk of non-uniform thickness of the applied coating, which also decreases reproducibility of the film parameters.

[0015] Accordingly, it is desirable to develop different compounds and/or different methods of film application/formation that can provide reproducible LLC films and systems having good optical characteristics. Each of the references cited above is hereby incorporated by reference in their entirety, particularly for the purpose of describing manufacturing methods of the optical compounds, LLC systems, and device applications.

SUMMARY OF THE INVENTION

[0016] An embodiment provides a lyotropic chromophoric compound. The compound can be formed by reaction of a precursor comprising an anhydride with an amino acid. In an embodiment, the lyotropic chromophoric compound comprises a naphthalimide derivative. In an embodiment, the lyotropic chromophoric compound comprises a perylene-3,4-dicarboxylic imide derivative. In an embodiment, the lyotropic chromophoric compound comprises a perylenetetracarboxylic diimide derivative. In an embodiment, the lyotropic chromophoric compound is a compound having the general structural formula (I), a compound having the general structural formula (II), or a compound having the general structural formula (III):

wherein =N-M| and =N-M₂ each independently represent a reaction product of an amino acid and an anhydride, or salt thereof; Xi, X₂, X₃ and X₄ are each independently selected from -H, -NHCH₃, a pyrrolidinyl group, or a halogen; and y is an integer in the range from 0 to about 4.

[0017] The lyotropic chromophoric compounds described herein can be used in optical devices and systems used to manufacture such devices. An embodiment provides a lyotropic liquid crystal system comprising at least one lyotropic chromophoric compound as described above. In an embodiment, the lyotropic liquid crystal system comprises a solvent, such as water or water intermixed with an organic solvent. The compounds described herein can be used in the manufacture of anisotropic or isotropic optical films. Another embodiment provides an optically anisotropic film comprising at least one lyotropic chromophoric compound as described herein. The film can be formed by applying a lyotropic liquid crystal system described herein onto a substrate. The films described herein can be used in the manufacture of liquid crystal display devices.

[0018] These and other embodiments are described in greater detail below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Described herein are lyotropic chromophoric compounds that are capable of forming stable liquid crystals, and methods of synthesizing such compounds. The lyotropic chromophoric compounds described herein may generally be referred to as chromophores. Also provided are LLC systems, comprising a solvent and one or more lyotropic chromophoric compounds as described herein. Also provided are isotropic, anisotropic, or at least partially crystalline films based on these systems and compounds, and methods for manufacturing such films. Embodiments of the films described herein possess excellent optical properties and working characteristics.

[0020] These and other advantages of the embodiments described herein can be achieved with a lyotropic chromophoric compound comprising a naphthalimide derivative having the general structural formula (I), a perylene-3,4-dicarboxylic imide derivative having the general structural formula (II), or a perylenetetracarboxylic diimide derivative having the general structural formula (III), described above.

[0021] Each =N-M, and =N-M₂ in formulae (I), (II), and (III) can independently represent a reaction product of an amino acid and an anhydride. The anhydride. precursor preferably further comprises an aromatic group. One example of a reactant anhydride for synthesizing a compound of formula (I) includes naphthalene dicarboxylic anhydride such that X] and X₂ of formula (I) are both hydrogen. However, other substituted variations of naphthalene dicarboxylic anhydride can be used when X| and/or X₂ in formula (I) are not hydrogen. Other examples of reactant anhydrides for synthesizing a compound of formula (II) or (III) include perylene dicarboxylic anhydride and perylene tetracarboxylic dianhydride, respectively. It is also contemplated that the reactant anhydride further comprise larger aromatic groups, e.g. such that y in formula (III) is greater than 0.

[0022] Various types of amino acids can be used for the reaction with the anhydride. In an embodiment, the amino acid is selected from isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, alanine, asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, serine, tyrosine, arginine, or histidine. Prefereably, the amino acid is glycine, alanine, glutamine, glutamate, or serine. The amino acid can have the D- or L- configuration, or be a mixture of stereoisomers. Additionally, non-naturally occurring amino acids can also be used. Mi and M₂ in formulae (I), (II), and (III) are discussed in greater detail below, particularity with respect to formula (IV), below.

[0023] Xi, X₂, X₃ and X₄ in formulae (I), (II), and (III) are each independently selected from -H, -NHCH₃, a pyrrolidinyl group, or a halogen. In an embodiment, the halogen can be selected from fluorine, chlorine, iodine, or bromine. In an embodiment, Xi, X₂, X₃ and X₄ are each selected to be hydrogen. In an embodiment, Xi and X₂ in formulae (I) and (II) are selected to be different substituents. In an embodiment, at least one of Xi, X₂, X₃ and X₄ in formulae (I), (II), and (III) is selected to be different from the other substituents.

[0024] In an embodiment, y in formula (III) is selected to be an integer in the range of 0 to 4. As y is increased, the aromatic nature of the compound is also increased. Increasing aromaticity can decrease the solubility of the compound. The peak at which absorbance occurs in the UV-Vis spectrum can be adjusted by increasing or decreasing y. Higher aromatic behavior generally causes peak absorption at higher wavelengths, whereas less aromaticity generally causes peak absorption at lower wavelengths. In an embodiment, y is selected to be an integer in the range of 0 to about 2.

[0025] Preferably, after reaction of the amino acid with the aromatic anhydride, Mi and M₂ in formulae (I), (II), or (III) are each independently represented by the general formula (IV):

(IV) wherein Ri, R₂, R₃ and R₄ are independently selected from hydrogen, an optionally substituted Ci to C₆ alkyl group, an optionally substituted C₂ to C₆ alkenyl group, an optionally substituted C₂ to C₆ alkynyl group, an optionally substituted C₃ to C₆ cycloalkyl group, an optionally substituted C₆ to Cio aryl group, an optionally substituted C₆ to C]₀ aralkyl group, an optionally hydroxy 1 containing Ci to C₆ alkyl group, an optionally carboxylic acid containing Ci to C₆ alkyl group; M is selected from hydrogen or a cation; and n is an integer from 0 to about 5. In an embodiment, n is an integer from 0 to about 3. M] and M₂ in formula (III) can be the same or different. [0026] An alkyl group may be linear alkyl or branched alkyl and includes methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hydroxyl methyl, carboxylic methyl, and carboxylic ethyl etc.

[0027] Each of the alkyl, alkenyl, alkynyl, cycloalkyl or aryl groups in Rj, R₂, R₃ and R₄ as described above can be "optionally substituted" with one or more substituent group(s). When substituted, the substituent group(s) is(are) one or more group(s) individually and independently selected from alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, heteroaryl, heteroalicyclyl, aralkyl, heteroaralkyl, (heteroalicyclyl)alkyl, hydroxy, protected hydroxyl, alkoxy, aryloxy, acyl, ester, mercapto, alkylthio, arylthio, cyano, halogen, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amido, N-amido, S-sulfonamido, N-sulfonamido, C-carboxy, protected C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, nitro, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkyl, haloalkoxy, trihalomethanesulfonyl, trihalomethanesulfonamido, and amino, including mono- and di-substituted amino groups, and the protected derivatives thereof. Non-limiting examples of the substituent group(s) include methyl, ethyl, propyl, butyl, pentyl, isopropyl, methoxide, ethoxide, propoxide, isopropoxide, butoxide, pentoxide and phenyl.

[0028] The alkyl, alkenyl, and alkynyl groups in Ri, R₂, R₃, and R₄ can be linear or branched groups. Some examples of Ri, R₂, R₃, and R₄ as alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, and tert-butyl. Additionally, Ri, R₂, R₃, and R₄ can be various cycloalkyl groups. For example, the cycloalkyl group can include cyclopentyl, cyclohexyl, or cyloheptyl. Some examples of useful aryl groups include phenyl, tolyl, naphthyl, phenanthryl, and anthracenyl. Some examples of useful aralkyl groups include benzyl, phenethyl, naphthylmethyl, phenanthylmethyl, and anthranylmethyl. Preferably, Rj, R₂, R₃, and R₄ are independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, butyl, t-butyl, and cyclohexyl.

[0029] The reaction product of an amino acid and an anhydride, as represented by =N-M] and =N-M₂, can further be modified into a salt. In embodiments where Mi and/or M₂ of the chromophoric compound comprise an amino acidic group, e.g. where M is hydrogen, the amino acidic group can be converted to a salt by intermixing the chromophoric compound with a suitable base. For example, where M in formula (IV) is hydrogen, the terminal -COOH group of formula (IV) can be converted to a salt having a -COO^" anion and a positive counter ion. Selection of the counter ion, e.g. formed from the reaction with the acid or base, can be determined by those having ordinary skill in the art, guided by the disclosure herein. Each M| and M₂ can be selected to be salts that configure the compound to be soluble in water or water intermixed with another organic solvent. For example, conversion of the acidic or basic groups into salts can increase the solubility of the compound. Thus solubility of the compound can be controlled by selection of the salt group of Mi and/or M₂. Preferably, the amino acid and the anhydride with which it is reacted are selected such that the resulting compound is at least partially water soluble. In an embodiment, the compound is at least partially soluble in water. In an embodiment, the compound is soluble in water. In an embodiment, the compound is soluble in water intermixed with another organic solvent.

[0030] In an embodiment, one or both of Mi and M₂ further comprises one or more counter ion. In an embodiment, M in formula (IV) is a counter ion. In an embodiment, the counter ion is independently selected from H⁺, NH₄ ¹, K.^1", Li⁺, Na⁺, Cs⁺,

/ C-!a ++ , CSr++ , n M /ig ++ , rB>a ++ , /C-1o ++ , Λ M *n ++ , Z r?n ++ , C /-<u ++ , rP>ib++ , x

Nri⁺⁺ , A Λ Il3+ , /C-Ie 3+ , TLa 3+ , or a protonated organic amine, or similar counter ions. Examples of suitable protonated organic amines include NH(Et)₃ ⁺, NH₂(Et)₂ ⁺, NH₃(Et)⁺, NH(Me)₃ ⁺, NH₂(Me)₂ ⁺, NH₃(Me)⁺, H₃NCH₂CH₂OH⁺, and H₂NCH₂(CH₂OCH₂CH₂OH)⁺. In an embodiment, the counter ion is independently selected from NH₄ ⁺ and NH(Et)₃ ⁺. In an embodiment, the counter ion is Na⁺. The number of counter ions can vary and may be fractional if the counter ion or ions are associated with more than one molecule. In an embodiment, one or more counter ions are shared by at least two molecules.

[0031] An "LLC system" as described herein is a solution comprising a solvent and one or more lyotropic chromophoric compounds as described herein. In an embodiment, the LLC system comprises an LLC mesophase. An LLC mesophase is formed when the concentration of lyotropic chromophoric compound in an LLC system is at or above the critical concentration for the formation of a liquid crystal within the system. The compounds described herein can be configured to absorb light in the visible spectrum range and also can be configured to form LLC systems with increased stability over thermotropic liquid crystals. These stable LLC systems may be used in the formation of anisotropic, isotropic, and/or at least partially crystalline films with highly reproducible, optimal optical characteristics. Film formation with greater uniformity and fewer microdefects upon solvent removal can be accomplished using embodiments of the LLC systems comprising the lyotropic chromophoric compounds described herein. [0032] Embodiments of the LLC systems formed with the compounds described herein further possess increased stability over a broad range of concentrations, temperatures, and pH ranges. Thus, the systems and compounds simplify the process of anisotropic film formation and permit the use of a variety of techniques for creation of film layers. The production of films is facilitated with highly reproducible parameters. Embodiments of the organic compounds described herein exhibit improved aqueous solubility. The increased optical anisotropy demonstrated by embodiments of the films comprising the chromophoric compounds is highly desirable. Without being bound by theory, the inventors believe that the high degree of optical anisotropy exhibited by certain embodiments is derived through non-covalent bonding, such as hydrogen bonding and cation-anion interactions, between two or more molecules.

[0033] The LLC systems can be formed over a broad range of pH. For example, by selection of various hydrophilic amino acids used in the reaction with the anhydride, Mi and M₂ can be adjusted by one of ordinary skill in the art to affect the solubility in various pH solutions. In an embodiment, the compound of formulae (I), (II), and/or (III) has a pH in the range of about 1 to about 6. in solution, depending on the concentration of the compound.

[0034] The compounds described herein can be synthesized by one having ordinary skill in the art, guided by the disclosure herein, by way of commonly used techniques used to synthesize similar lyotropic organic structures. The compounds having the general structural formulas (I), (II), or (III) can form stable LLC phases both individually and in mixtures. Various combination of compounds of formulas (I), (II), and (III) can be used in the manufacture of LLC systems and films. Furthermore, each of these compounds can be mixed with other known lyotropic compounds. In an embodiment, the compounds having the general structural formulas (I), (II), and/or (III) are combined with other dichroic dyes capable of forming LLC phases to form LLC systems. In an embodiment, the compounds having the general structural formulas (I), (II), and/or (III) are combined with other substances that are generally non-absorbing (colorless) or weakly absorbing in the visible range and capable of forming LLC systems. The LLC systems can be formed, for example, by intermixing the compounds with a solvent, such as water. After removal of the solvent, this LLC system can form an anisotropic, isotropic and/or at least partially crystalline film with reproducibly high optical characteristics. Methods and systems for forming stable LLC systems and resultant anisotropic, isotropic and/or at least partially crystalline optical films are described in greater detail in U.S. Pat. No. 6,563,640, the disclosure of which is incorporated by reference, particularly for the purpose of describing optical films and methods for making them.

[0035] Lyotropic chromophoric compounds in aqueous solutions as described herein typically exhibit a maximum optical absorption in the wavelength interval between about 400 nm to about 780 nm. In an embodiment, the chromophoric compounds in aqueous solutions exhibit a maximum optical absorption in the wavelength interval between about 450 nm to about 700 nm. The hydrophilic-hydrophobic balance of the molecular aggregates formed in LLC systems can be controlled when using the compounds described herein. For example, the chromophoric perylene core structure in formula (III) can be adjusted by varying y (e.g., to produce tetra perylene or higher orders) to increase hydrophobicity. Additionally, the amino acid to be reacted with the anhydride may be selected to provide any desired degree of hydrophiϋcity. By varying either or both of these parameters, one of ordinary skill can change the solubility of the compound and the solution viscosity when mixed with a solvent. Additionally, one of ordinary skill can also adjust the absorption wavelengths and produce chromophoric compounds that cover all or part of the full color wavelength spectrum. Embodiments of the lyotropic chromophoric compounds described herein can be used to form stable lyotropic liquid crystal systems. LLC systems of individual compounds having the general structural formulae (I), (II), or (III), as well as mixtures of such compounds, can be prepared by one of ordinary skill in the art, guided by the disclosure herein.

[0036] One or more of the compounds described herein can be intermixed with a solvent to form an LLC system, which can then be applied onto a substrate surface and oriented by any known method such as, for example, those described in PCT Publication Nos. WO 94/28073 and WO 00/25155, the disclosures of which are incorporated by reference. The types of substrate suitable for making optically anisotropic films may include transparent/translucent substrates, such as glass, plastic, color filter, and transparent/translucent polymer sheet, and semiconductors. In some embodiments, the LLC system is applied onto a substrate by means of spraying, pouring, printing, coating, dipping or transferring by a spoon, a spatula, a rod or any object capable of transferring a liquid crystal system. The desired orientation of the liquid crystals may be provided, for example, by applying shear stress, gravitational force, or an electromagnetic field. In some embodiments, an applicator rod or suitable tools may be used to apply pressure on the surface to orient or arrange the LLC system. A linear velocity in the range of about 25 mm/s to about 1 m/s can be applied on the film surface to orient the liquid crystal mesophases. The film forming process may be carried out at room temperature. In some embodiments, the relative humidity during orientation may be in the range of from about 55% to about 85%. In some embodiments, diimides described herein provide one of the simple ways to line up the molecules by requiring only a minimal mechanical "spreading" with a glass rod onto the substrate to orient the LLC systems. In an embodiment, the LLC system comprises an LLC mesophase. In one embodiment, the LLC systems are oriented by spreading the LLC system in one direction.

[0037] Subsequent removal of the solvent from the oriented liquid crystal solution can be carried out to form an optically anisotropic film with a thickness in the range of about 0.1 μm to about 2 μm. In an embodiment, the film has a thickness in the range of about 0.2 μm to about 1 μm. In an embodiment, the film has a thickness in the range of about 0.3 μm to about 0.5 μm. In some embodiments, the anisotropic film may also be a polycrystalline film.

[0038] To improve substrate wetting and optimization of the rheological properties of a liquid crystal system, the solution can be modified, for example, by adding plasticizing water-soluble polymers and/or anionic or non-ionic surfactants. The LLC system may further comprise one or more water-soluble, low-molecular-weight additives. Each of the additives can be advantageously selected so as not to destroy the alignment properties of the liquid crystal system. Examples of water-soluble, low-molecular-weight additives include, but are not limited to, plasticizing polymer, such as PVA and polyethylene glycol, and anionic or non-ionic surfactants such as those available under the tradename TRITON, which is a nonionic surfactant having hydrophilic polyethylene oxide groups and a hydrocarbon lipophilic or hydrophobic group. These additives may improve substrate wetting and optimize the rheological properties of an LLC system. All additives are preferably selected so as not to destroy the alignment properties of the LLC system.

[0039] Embodiments of the films formed from the LLC systems described herein can be generally characterized by an approximately 10% or greater performance advantage, e.g., increase in reproducibility of one or more performance parameters from batch to batch, between different films in the same batch, and over the surface of one film as compared to the other films.

[0040] The compounds described herein may be also used to obtain isotropic films. For example, the LLC system comprising a compound having the general structural formula (I), (II), or (III) and a solvent may be applied onto a substrate and not be subjected to any external orienting action. This can be achieved through application of the LLC system by methods such as spraying, offset printing, and silk screening. Removal of the solvent leaves the substrate covered with a polycrystalline film with an overall domain structure that possesses isotropic optical properties.

[0041] The lyotropic chromophoric compounds can be used to form at least partially crystalline films and/or polarizing films and/or birefringent films. These lyotropic chromophoric compounds may be used in the production of optically isotropic or anisotropic, polarizing films and/or phase-retarding films and/or birefringent films. In an embodiment, the LLC system used to form an optically isotropic or anisotropic film comprises at least two compounds selected from the general structural formulas (I), (II), and (III). In another embodiment, the LLC system used to form an optically isotropic or anisotropic film comprises at least two specific compounds of at least one of formulas (I), (II), and (III), wherein the two specific compounds comprise at least two different substituents for Xi₁ X₂, X₃, or X₄. In some embodiments, the LLC system may encompass an aqueous liquid crystal solution that may be referred to as a "water-based ink composition."

[0042] In an embodiment, the LLC system is water-based. For example, the LLC system can comprise one or more compounds of the disclosed lyotropic chromophores having the general structural formulas (I), (II), and/or (III) and water. Other solvents can also be used.

[0043] In an embodiment, the LLC system comprises a mixture of water and an organic solvent miscible with water. In an embodiment, the LLC system comprises a mixture of water and an organic solvent, which is alternatively miscible with water in any proportion or characterized by limited miscibility with water. Useful organic solvents include polar solvents, such as dimehtyl sulfoxide (DMSO), dimethylformamide (DMF), alcohol (e.g., methanol or ethanol) and N-Methyl-2-pyrrolidone (NMP).

[0044] Other materials known to those having ordinary skill in the art may also be included. In an embodiment, the LLC system further comprises one or more surfactants. In an embodiment, the surfactant is present in an amount of up to about 5% by weight of the LLC system. In an embodiment, the surfactant is present in an amount in the range of about 0.1% to about 1% by weight of the LLC system. In an embodiment, the LLC system further comprises one or more plasticizers. In an embodiment, the plasticizer is present in an amount of up to about 5% by weight of the LLC system. In an embodiment, the plasticizer is present in an amount in the range of about 0.1% to about 1% by weight of the LLC system.

[0045] The concentration of the lyotropic chromophoric compound or mixture of lyotropic chromophoric compounds in the LLC systems described herein can vary. In an embodiment, the concentration of the lyotropic chromophoric compound in the LLC system is in the range of about 5% to about 50 % by weight of the LLC system. In an embodiment, the concentration of the lyotropic chromophoric compound in the LLC system is in the range of about 8% to about 40 % by weight of the LLC system. In an embodiment, the concentration of the lyotropic chromophoric compound in the LLC system is in the range of about 10% to about 30% by weight of the LLC system.

[0046] The concentration of individual lyotropic chromophoric compounds in the LLC system can also vary, depending on the required properties of the film, as described below. In an embodiment, the LLC system comprises a combination of two or more compounds of the general structural formulae (I), (II), and/or (III), wherein the amount of compound according to formula (I) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds, the amount of compound according to formula (II) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds, and the amount of compound according to formula (III) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds. Optionally, the total amount of compounds according formulae (I), (II), and/or (III) can account for at least 50% of the total weight of chromophoric compounds. Optionally, the total amount of compounds according formulae (I), (II), and/or (III) can account for at least 75% of the total weight of chromophoric compounds. Optionally, the total amount of compounds according formulae (I), (II), and/or (III) can account for at least 90% of the total weight of chromophoric compounds. Optionally, the total amount of compounds according formulae (I), (II), and/or (III) can account for about 100% of the total weight of chromophoric compounds. [0047] In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 1% to about 100% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 5% to about 95% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 10% to about 90% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 20% to about 80% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 1% to about 50% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (I) in the LLC system is in the range of about 50% to about 99% by weight, based on the total amount of chromophoric compounds.

[0048J In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 1% to about 100% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 5% to about 95% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 10% to about 90% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 20% to about 80% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 1% to about 50% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (II) in the LLC system is in the range of about 50% to about 99% by weight, based on the total amount of chromophoric compounds.

[0049] In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 1% to about 100% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 5% to about 95% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 10% to about 90% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 20% to about 80% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 1% to about 50% by weight, based on the total amount of chromophoric compounds. In an embodiment, the amount of compound according to formula (III) in the LLC system is in the range of about 50% to about 99% by weight, based on the total amount of chromophoric compounds.

[0050] In an embodiment, a lyotropic liquid crystal system comprises a first compound according to formula (I), (II), or (III), wherein the first compound has a concentration of about 0% to about 50% by mass, and a second compound according to formula (I), (II), or (III) that is different from the first compound, wherein the second compound has a concentration of about 0% to about 50% by mass, wherein the total amount of the first compound and the second compound is up to about 50% by mass, based on the total mass of the LLC system.

[0051] In an embodiment, the LLC system further comprises at least one water-soluble organic dye or at least one substantially colorless organic compound. In an embodiment, the organic dye or substantially colorless organic compound is configured to participate in the formation of a liquid crystal. The resulting films can also comprise organic dyes or other organic compounds.

[0052] Optically anisotropic films of the present invention may be obtained by applying an LLC system described herein onto a substrate, optionally followed by orienting action, and then drying. Illustrative examples describing the synthesis of lyotropic chromophoric compounds, forming LLC system comprising the compounds, and then forming organic films using the LLC system are described in detail below.

[0053] In an embodiment, the optically anisotropic film is formed by depositing an LLC system comprising at least one lyotropic chromophoric compound onto a substrate. In an embodiment, the film is at least partially crystalline. In an embodiment, the film further comprises at least one water soluble organic dye. In an embodiment, the film is a polarizing film. In an embodiment, the film is a phase-retarding film.

[0054] Another embodiment provides a liquid crystal display comprising at least one E-type polarizer. In an embodiment, the at least one E-type polarizer comprises at least one optically anisotropic film as described herein and a substrate. An embodiment provides a dichroic light-polarizing element comprising a substrate and at least one LLC film as described herein. In some embodiments, the dichroic light-polarizing element is an E-type polarizer. One embodiment provides a liquid crystal active display comprising at least one E-type polarizer film, wherein the E-type polarizer film comprises at least one LLC film as described herein. Conventional LC displays often use O-type films, and the contrast ratio can drop off drastically when the LC display is viewed from an angle off the normal directly. Conversely, a LC display comprising at least one E-type polarizer film may provide wide viewing angles without a substantial drop in contrast ratio. Furthermore, in preferred embodiments the process of making an E-type polarizer comprising an LLC film as described herein can be conducted more easily compared to the conventional process for making O-type polarizers. This also can lead to simplified and lower cost LC devices. The designs and components of a LC display comprising an E-type polarizer are described in more detail in US Pat. No. 7,015,990, which is also incorporated by reference in its entirety, and particularly for the purpose of describing such designs and components.

[0055] Another embodiment provides a method of forming an optically anisotropic film. In an embodiment, the method of forming an optically anisotropic film comprises applying an LLC system as described herein onto a substrate, wherein the LLC system comprises a plurality of LLC mesophases, and orienting the plurality of LLC mesophases. In an embodiment, the method further comprises forming the LLC system by mixing at least one chromophoric compound described herein with water or a mixture of water and an organic solvent. In an embodiment, the method comprises drying the LLC system on the substrate. In an embodiment, the orienting of the plurality of LLC mesophases comprises spreading the LLC mesophases in one direction.

EXAMPLES Example 1

[0056] Perylenetetracarboxylic dianhydride (1.96 g, 5 mmol)) and alanine (0.98g, 11 mmol) were intermixed in 20 mL of anhydrous dimethyl sulfoxide (DMSO). The mixture was sonicated for 10 minutes, and then irradiated at 160 ⁰C for 40 minutes using a microwave reactor. Then the mixture was cooled to room temperature. The solvent was removed by distillation under vacuum. The residue was purified by recrystallization with CHCl₃/hexane solvent. The product was further purified by silica gel chromatography eluted by CHCl₃/Me0H (4: l/v:v) (1.5g). The acidic product was reacted with a Na base to form a salt, represented below in Table 1. Examples 2-5

[0057] Using a similar procedure described above in Example 1, glycine, L- alanine, glutamic acid, and serine were used instead of alanine. After the reactions, perylene derivatives were converted to sodium salts, the structures of which are illustrated in Table 1. The optical performance of each of these compounds was determined by measuring the dichroic ratio (DR).

TABLE 1

[0058] The above description discloses several methods and materials of the preferred embodiments. This invention is susceptible to modifications in the methods and materials, as well as alterations in the fabrication methods and equipment. Such modifications will become apparent to those skilled in the art from a consideration of this disclosure or practice of the invention disclosed herein. Consequently, it is not intended that this invention be limited to the specific embodiments disclosed herein, but that it cover all modifications and alternatives coming within the true scope and spirit of the invention as embodied in the attached claims.

Claims

WHAT IS CLAIMED IS:

1. A lyotropic chromophoric compound having the general structural formula (I), the general structural formula (II), or the general structural formula (III):

wherein =N-Mi and =N-M₂ each independently represent a reaction product of an amino acid and an anhydride, or salt thereof; Xi, X₂, X₃ and X₄ are each independently selected from -H, -NHCH₃, a pyrrolidinyl group, or a halogen; and y is an integer in the range from 0 to about 4.

2. The compound of Claim 1, wherein M| and M₂ are each independently represented by the general formula (IV):

wherein Ri, R₂, R₃ and R₄ are each independently selected from hydrogen, an optionally substituted Ci to C₆ alkyl group, an optionally substituted C₂ to C₆ alkenyl group, an optionally substituted C₂ to C₆ alkynyl group, an optionally substituted C₃ to C₆ cycloalkyl group, an optionally substituted C₆ to C]₀ aryl group, an optionally substituted C₆ to Cio aralkyl group, an optionally hydroxy 1 containing C i to C₆ alkyl group, or an optionally carboxylic acid containing Ci to C₆ alkyl group; M is selected from hydrogen or a counter ion; and n is an integer in the range of from 0 to about 3.

3. The compound of Claim 2, wherein R], R₂, R₃ and R₄ are each independently selected from hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, hydroxylmethyl, carboxylic methyl, and carboxylic ethyl.

4. The compound of any of Claims 1 to 3, wherein Xi, X₂, X₃ and X₄ are hydrogen.

5. The compound of any of Claims 1 to 4, wherein Mi and M₂ each independently comprise a counter ion selected from the group consisting of NH₄ ⁺, NH(Et)₃ ⁺, K⁺, Li⁺, Na⁺, Cs⁺, Ca⁺⁺, Sr⁺⁺, Mg⁺⁺, Ba⁺⁺, Co⁺⁺, Mn⁺⁺, Zn⁺⁺, Cu⁺⁺, Pb⁺⁺, Fe⁺ \ Ni⁺⁺, Al³⁺, Ce³⁺, and La³⁺.

6. The compound of Claim 5, wherein one or more counter ions are shared by at least two molecules.

7. A lyotropic liquid crystal system comprising at least one lyotropic chromophoric compound of any of Claims 1 to 6.

8. The lyotropic liquid crystal system of Claim 7, wherein the lyotropic liquid crystal system is water-based.

9. The lyotropic liquid crystal system of Claim 7, wherein the lyotropic liquid crystal system comprises a mixture of water and an organic solvent miscible with water.

10. The lyotropic liquid crystal system of any of Claims 7 to 9, wherein the concentration of the lyotropic chromophoric compound in the lyotropic liquid crystal system is in the range of about 5% to about 50 % by weight of the liquid crystal system.

1 1. The lyotropic liquid crystal system of any of Claims 7 to 10, further comprising one or more surfactants in an amount of up to about 5% by weight of the liquid crystal system.

12. The lyotropic liquid crystal system of any of Claims 7 to 11, further comprising one or more plasticizers in an amount of up to about 5% by weight of the liquid crystal system.

13. The lyotropic liquid crystal system of any of Claims 7 to 12, comprising a combination of two or more lyotropic chromophoric compounds of the general structural formulae (1), (II), and/or (III), wherein the amount of compound according to formula (I) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds, the amount of compound according to formula (II) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds, and the amount of compound according to formula (III) is in the range of about 0% to about 99% by weight, based on the total amount of chromophoric compounds, provided that the total amount of compounds according to formulae (I), (II), and/or (III) accounts for at least 50% of the total weight of all the chromophoric compounds in the lyotropic liquid crystal system.

14. The lyotropic liquid crystal system of any of Claims 7 to 13, further comprising at least one water-soluble organic dye or an organic compound, the organic dye or organic compound being configured to participate in the formation of a liquid crystal.

15. An optically anisotropic film comprising at least one lyotropic chromophoric compound of any of Claims 1 to 7.

16. The optically anisotropic film of Claim 15, wherein the film is formed by depositing a lyotropic liquid crystal system comprising at least one lyotropic chromophoric compound onto a substrate.

17. The optically anisotropic film of any of Claims 15 to 16, wherein the film is at least partially crystalline.

18. The optically anisotropic film of any of Claims 15 to 17, further comprising at least one water soluble organic dye.

19. The optically anisotropic film of any of Claims 15 to 18, wherein the film is a polarizing film.

20. The optically anisotropic film of any of Claims 15 to 19, wherein the film is a phase-retarding film.