TWI498416B - Polymerisable liquid crystal mixture - Google Patents

Description

Polymerizable liquid crystal mixture

The present invention relates to a polymerizable mixture, a use thereof for preparing a polymer film having improved adhesion to a substrate, a method of preparing the polymer film, a multilayer film comprising the polymer film, and for use in a mixture and a film. For optical, electro-optical, decorative or safety devices and coating applications.

Polymerizable liquid crystal (LC) materials are commonly used in the preparation of optical films in liquid crystal display devices. Such materials typically comprise a specific amount of a compound having two or more polymerizable groups (di- or polyfunctional) which are crosslinked to give a hard film. However, such hard films are generally not easily adhered to the surface of a plastic substrate that is shared by the manufacturing process because the film is shrunk due to polymerization and crosslinking processes. Therefore, the film made of the LC material is usually delaminated and attached to another substrate such as glass or plastic for a polarizer of a liquid crystal display device. However, the process of delamination and coating to another substrate takes time and materials. Two potential points are also provided, and loss of film can occur during delamination or re-lamination, resulting in a lower overall product yield.

In the prior art, adhesion and alignment layers were also recorded to bond the LC polymer layer to the plastic substrate. For example, US 5,631,051 discloses a method of first providing an adhesive layer of gelatin on a TAC film to prepare an optical compensation sheet on a transparent substrate of triacetyl cellulose (TAC). The alignment layer is then formed from a solution of coated denatured polyvinyl alcohol (PVA) which is chemically modified on the gelatin layer by the addition of a polymerizable group, evaporating the solvent and unidirectionally rubbing the surface of the PVA layer. Finally, an optically anisotropic layer comprising a disc-shaped LC material is coated on the friction surface of the PVA and polymerized.

US 5,747,121 discloses a method for preparing an optical compensation sheet by coating a solution of denatured polyvinyl alcohol (PVA) by chemically modifying a transparent substrate by adding a polymerizable group, evaporating the solvent and unidirectional rubbing polymerization. The surface of the PVA layer. Then, an optically anisotropic layer containing a disk-shaped LC material was coated on the friction surface of the PVA and polymerized. Thereafter, the film is subjected to heat treatment, whereby it is reported that the PVA layer and the disk-shaped LC material are chemically bonded to each other via the free crosslinkable group.

However, the above method requires many separate coating steps. In addition, the use of several intermediate layers such as adhesion or alignment layers comprising isotropic materials such as gelatin or PVA can adversely affect the optical properties of the optical film.

GB 2 398 077 discloses a crosslinked LC film which provides good adhesion using a polymerisable LC material comprising not more than 7% by weight of a crosslinkable compound having two or more polymerizable groups. The film provides better adhesion to plastic substrates commonly used in the optical film industry. However, since the low crosslinked LC film is soft and allergic to mechanical stress, it is preferably covered by a hard film or another polymeric film comprising a highly crosslinked polymer.

Accordingly, there is a need for an advantageous method of providing a film of a crosslinked LC material that adheres well to a plastic substrate while saving time and allowing for loss in processing loss of the LC film, and wherein the film has a harder resistance to mechanical stress or loss. High stability.

It is an object of the present invention to provide a crosslinked LC film which does not have the above disadvantages, and a preparation method and material thereof. Other objects of the invention will become apparent from the following description.

The above objects are accomplished by providing the films, methods and materials described below in accordance with the present invention.

The term "film" includes rigid or flexible, self-supporting or free standing films with mechanical stability, and coating films or layers between the support substrate or between the two substrates, the term "liquid crystal or liquid crystal raw material" or "liquid crystal" Or a liquid crystal raw compound "means a material or compound comprising one or more rod-like, plate-like or dish-shaped liquid crystal primaries, ie, a group having the ability to induce a liquid crystal (LC) phase. LC compounds having a rod or plate base are known in the art as "album" liquid crystals. LC compounds having a dish base are also known in the art as "disc" liquid crystals. The compound or material comprising the liquid crystal primordium does not have to show the LC phase itself. It is shown that the LC phase can also be used only in a mixture with other compounds, or when a liquid crystal original compound or material or a mixture thereof is polymerized.

For the sake of simplicity, the term "liquid crystal material" is used below for the liquid crystal source and the LC material.

A polymerizable compound having one polymerizable group is also referred to as a "single-reactive" compound, a compound having two polymerizable groups is referred to as a "di-reactive" compound, and a compound having more than two polymerizable groups is referred to as "multiple Reactive "compound. Compounds without polymerizable groups are also referred to as "non-reactive" compounds. Polyreactive compounds are also known as "crosslinkable" compounds.

The term "reactive mesogen" (RM) means a polymerizable liquid crystal or a liquid crystal compound.

Unless otherwise indicated, the weight % of each of the following solid or liquid crystal compounds in the polymerizable liquid crystal material is the total amount of the solid or liquid crystal compound in the material.

The term "derivation" means that the liquid crystal is based on the preferred orientation of the long molecular axis (in the case of a rosewood compound) or the short molecular axis (in the case of a dished compound) within the LC material.

In a film comprising a uniaxial positive birefringence LC material, the optical axis is provided by a derivation.

The term "cholesteric structure" or "helical torsion structure" means a film comprising LC molecules in which the director is helically twisted parallel to the plane of the film and about an axis perpendicular to the plane of the film.

The term "vertical structure" or "vertical orientation" means a film in which the optical axis is substantially perpendicular to the plane of the film.

The term "planar structure" or "planar orientation" means a film in which the optical axis is substantially parallel to the plane of the film.

The term "inclined structure" or "tilted orientation" means a film in which the optical axis is inclined at an angle θ between 0 and 90° with respect to the plane of the film.

The term "beveled structure" or "beveled orientation" means an oblique orientation as defined above, wherein the angle of inclination varies in a direction perpendicular to the plane of the film, preferably from lowest to highest values.

The present invention relates to a mixture comprising a) > 0 to 12% of one or more crosslinkable compounds, preferably a crosslinkable liquid crystal precursor compound, and b) 50% of one or more compounds of formula I Wherein P is a crosslinkable group, Sp is a spacer or a single bond, A is an aromatic or aliphatic 5- or 6-ring, or contains two or three fused aromatic or aliphatic 5- or 6-rings. The cyclonics need to contain one or more heteroatoms selected from N, O and S, optionally substituted by one or more identical or different radicals L ¹ , and Z is independently -O- in the case of multiple occurrences. ,-S-,-CO-,-COO-,-OCO-,-S-CO-,-CO-S-,-O-CO-O-,-CO-NR ⁰ -,-NR ⁰ -CO- , -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF ₂ -, -CH ₂ CH _{2 -, - CF 2 CH 2 -} , - CH 2 CF 2 -, - CF 2 CF 2 -, - CH = CR 0 -, - CH = CH -, - CH = CF -, - CY 1 = CY 1 -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, Z ¹ has one of the meanings of Z, and R ⁰ is H or an alkyl group having 1 to 12 carbon atoms, Y ¹ is H, F, Cl or CN, m is 0 or 1, and L ¹ and L ^{2 are} independently of each other, F, Cl, Br, I, CN, NO ₂ , P-Sp- or have 1 to 12 carbon atoms. Alkyl, alkoxy, alkylcarbonyl, alkoxy Carbonyl, alkylcarbonyloxy or alkoxycarbonyloxy, in which one or more H atoms optionally substituted with F or Cl, r1, r2 each independently 0,1,2,3 or 4.

The invention further relates to a polymer film obtainable by crosslinking a mixture according to the invention.

The invention further relates to the use of a mixture or film according to the invention for optical, electrooptical, information storage, decorative and security coating.

The invention further relates to an optical component or device comprising a mixture or film according to the invention.

The invention further relates to a liquid crystal display device comprising a mixture or film according to the invention.

The invention further relates to an identification, identification or security mark or coloured image comprising a mixture or film according to the invention.

The invention further relates to an object or document comprising the values of the above identified and identified identification, identification or security signs or images.

In the above and the following formulae, A is preferably selected from the group consisting of 1,4-phenylene groups, which are optionally substituted with 1 to 4 of the above-defined groups L ¹ or trans-1,4-cyclohexene.

Z ^{1 is} preferably selected from -COO-, -OCO-, -CH ₂ CH ₂ -, CH=CH- or a single bond, and particularly preferably -COO- or -OCO-.

Z is preferably selected from the group consisting of -COO-, -OCO-, -CH ₂ CH ₂ -, CH=CH- or a single bond.

L ¹ and L ^{2 are} preferably selected from the group consisting of F, Cl, CN, NO ₂ , CH ₃ , C ₂ H ₅ , OCH ₃ , OC ₂ H ₅ , COCH ₃ , COC ₂ H ₅ , COOCH ₃ , COOC ₂ H ₅ , CF ₃ , OCF ₃ , OCHF ₂ or OC ₂ F ₅ , especially F, Cl, CN, CH ₃ , C ₂ H ₅ , OCH ₃ , COCH ₃ or OCF ₃ , most preferably F, Cl, CH ₃ , OCH ₃ or COCH ₂ .

R1 and r2 are preferably 0, 1, or 2.

Substituted phenylene is preferably selected from , ,or , in addition Where L has ^one of the meanings of L ¹ of formula I.

The halogen is preferably F or Cl.

Y ^{1 is} preferably H or F.

The reactive or polymerizable group P is a group which may participate in a polymerization reaction such as free or ionic chain polymerization, polyaddition or polycondensation, or may be grafted or added to the polymer backbone, for example, in a polymer analog reaction. Particularly preferred are polymerizable groups for chain polymerization such as free, anionic or cationic polymerization. Particularly preferred are polymerizable groups containing a C-C double or triple bond, and polymerizable groups such as oxetane or epoxide which can be polymerized by the ring opening reaction.

The polymerizable or reactive group P is most preferably selected from the group consisting of CH ₂ =CW ¹ -COO-, , , CH ₂ =CW ² -(O) _{k 1} -,CH ₃ -CH=CH-O-,(CH ₂ =CH) ₂ CH-OCO-,(CH ₂ =CH-CH ₂ ) ₂ CH-OCO- , (CH ₂ =CH) ₂ CH-O-, (CH ₂ =CH-CH ₂ ) ₂ N-, (CH ₂ =CH-CH ₂ ) ₂ N-CO-, HO-CW ² W ³ -, HS -CW ² W ³ -,HW ² N-,HO-CW ² W ³ -NH-,CH ₂ =CW ¹ -CO-NH-,CH ₂ =CH-(COO) _{k 1} -Phe-(O) _{k 2-} , Phe-CH=CH-, HOOC-, OCN- and W ⁴ W ⁵ W ⁶ Si-, W ¹ is H, Cl, CN, phenyl or an alkyl group having 1 to 5 carbon atoms, especially H, Cl or CH ₃ , W ² and W ^{3 are} each independently H or an alkyl group having 1 to 5 carbon atoms, particularly methyl, ethyl or n-propyl, and W ⁴ , W ⁵ and W ^{6 are} independent of each other. Is Cl, oxaalkyl or oxacarbonylalkyl having 1 to 5 carbon atoms, Phe is 1,4-phenylene, which is optionally substituted by one or more of the above defined radicals, k ₁ and k _{2 is} independent of each other by 0 or 1.

P is preferably a vinyl group, an acrylate group, a methacrylate group, an oxetanyl group or an epoxy group, and is preferably an acrylate group or a methacrylate group.

With regard to the spacer Sp, all of the groups known to those skilled in the art can be used. The spacer Sp is preferably of the formula Sp'-X such that P-Sp- is P-Sp'-X-, wherein Sp' is an alkylene having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. a group which is mono- or polysubstituted by F, Cl, Br, I or CN, and one or more of which are non-contiguous CH ₂ groups, in each case, independently of each other -O-, -S- , -NH-, -NR ⁰ -, -SiR ⁰ R ^{0 0} -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -NR ^0- CO-O-, -O-CO-NR ⁰ -, -NR ⁰ -CO-NR ⁰ -, -CH=CH- or -C≡C-substitution, in that the O and/or S atoms are not mutually Directly connected, X is -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR ⁰ -, -NR ⁰ -CO-, -NR ⁰ -CO -NR ⁰ -, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF ₂ -,- CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH=N-, -N=CH-, -N=N-, -CH=CR ⁰ -, -CY ¹ =CY ^{2 -, - C≡C -, -} CH = CH-COO -, - OCO-CH = CH- single bond, R ⁰ and R ^{0 0} Is independently H or an alkyl group having 1 to 12 carbon atoms, and Y ¹ and Y ² each independently is H, F, Cl or CN.

X is preferably -O-, -S-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S- , -SCF ₂ -, -CH ₂ CH ₂ -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH=N-, -N=CH-, -N=N -, -CH=CR ⁰ -, -CY ¹ = CY ² -, -C≡C- or a single bond, especially -O-, -S-, -C≡C-, -CY ¹ =CY ² - or A single bond, preferably a group that forms a conjugated system, such as -C≡C- or -CY ¹ =CY ² - or a single bond.

The typical group Sp' is, for example, -(CH ₂ ) _p -, -(CH ₂ CH ₂ O) _q -CH ₂ CH ₂ -, -CH ₂ CH ₂ -S-CH ₂ CH ₂ - or -CH ₂ CH ₂ -NH-CH ₂ CH ₂ - or -(SiR ⁰ R ^{0 0} -O) _p -, p is an integer from 2 to 12, q is an integer from 1 to 3, and R ⁰ and R ^{0 0} have the above meanings.

Preferred groups Sp' are, for example, an exoethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, a octyl group, a stilbene group, a stilbene group, an eleventh group, and a thirteenth. Base, octadecyl, ethyl ethoxyethyl, methyl oxybutyl, ethyl thioethyl, ethyl ethyl N-methylimine, 1-methylalkylene, Stretching vinyl, propylene and butyl groups.

Further preferred are compounds wherein Sp is a single bond.

Preferred mixtures comprise - one or more compounds of formula Ia Wherein P, Sp, L ¹ , L ² , r 1 and r 2 have the meaning of formula I, one or more compounds of formula I or Ia, wherein r 1 and r 2 are 0, one or more compounds of formula I or Ia, wherein R1 and r2 are 1, one or more compounds of formula I or Ia, wherein one of r1 and r2 is 0 and the other is 1, one or more crosslinkable liquid crystal compounds of formula II, Wherein P, Sp, L ¹ , L ² , r1 and r2 are defined as Formula I, L ³ has one of the meanings of L ¹ in Formula I, r ³ is 0, ¹ , ² , 3 or 4 and Z ¹ and Z ² have Z is one of the meanings of Formula I.

- one or more compounds of Formula II, wherein r2 and r3 is 0, r1 is 0, 1 or 2, - one or more compounds of the formula II, wherein Z ¹ and Z ² is selected from -COO -, - OCO- , -CH ₂ CH ₂ - and a single bond, - one or more crosslinkable liquid crystal compounds of the formula IIa, Wherein P, Sp, L ¹ and r1 are as defined in formula II, r1 is preferably 0 or 1, and L ^{1 is} preferably Cl, CH ₃ or OCH ₃ .

- an additional component c) comprising one or more compounds of the formula III Wherein P and Sp are as defined in formula I and R are alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 carbon atoms, one of which Or a plurality of H atoms may be substituted by F or Cl, -5 to 12% of one or more crosslinkable compounds, -> 7 to 12% of one or more crosslinkable compounds, from -50 to 80%, preferably 55. Up to 75% of one or more compounds of formula I or Ia, from 5 to 50%, preferably from 10 to 40%, of one or more compounds of formula III, -a) > 0 to 12% of one or more crosslinkable compounds, b) >50% of one or more compounds of formula I or Ia, c) one or more compounds of formula III, d) one or more photoinitiators, preferably from 0.5 to 8%, e) as needed Or a plurality of surfactants, preferably at a concentration of from 0.1 to 2%, f) one or more stabilizers as needed.

The clear point of the polymerizable LC mixture is preferably at least 50 ° C, more preferably at least 60 ° C.

The invention also relates to a method of preparing a polymer film by - providing a mixture layer according to the invention on a substrate, - aligning the mixture as needed, such that the liquid crystal or LC compound is uniformly oriented, - crosslinking the mixture to form The polymer film, and - the polymer film is removed from the substrate as needed.

The thickness of the polymer film according to the present invention is preferably from 0.5 to 5 μm, more preferably from 1 to 2 μm.

The LC molecules within the polymer preferably have a planar orientation.

The polymer film according to the present invention has a limited crosslink density due to a low amount of crosslinkable compound and exhibits particularly good adhesion to a plastic substrate. Therefore, it can be used as an adhesive or a base coating for a subsequent LC layer which would otherwise not adhere well to the substrate. At the same time, the polymer film has a harder surface, which is less viscous and exhibits improved durability compared to prior art low crosslinked films.

The polymer film according to the invention can also promote alignment within the LC layer coated on top of it. Therefore, it can be used as an alignment layer of LC material. By varying the thickness of the polymer film, the orientation can be affected, particularly the tilt angle of the subsequent LC layer. For example, a polymer film having a planar orientation in accordance with the present invention can be used to induce planar orientation of subsequent LC layers. Polymer films having a sloped or beveled orientation in accordance with the present invention can be used to induce tilting or bevel orientation of subsequent LC layers.

Accordingly, another preferred embodiment of the present invention is directed to a multilayer comprising a low crosslinked polymer film according to the present invention as a base layer, and further comprising one or more additional polymerized or crosslinked LC films. A base polymer film or an additional LC polymer film or both can be used, for example, as an optical layer.

The invention also relates to a method of preparing a multilayer by providing a polymerizable LC mixture layer according to the invention on a substrate, optionally aligning the mixture such that the liquid crystal or LC compound is uniformly oriented, the LC mixture Polymerizing to form a polymer film, providing a second layer of polymerizable LC material on the free surface of the polymer film, - aligning the second LC material as needed, such that the liquid crystal or LC compound is uniformly oriented, and - the first The two LC materials are polymerized to form a second polymer film.

The second polymeric film has, for example, a planar, inclined or beveled orientation.

The polymerizable LC mixture according to the invention comprises at least one polymerizable compound having one polymerizable group (single reactivity) and at least one polymerizable compound having two or more polymerizable groups (two or more reactivity).

The polymerizable LC mixture may also comprise one or more pairs of palms which may also be polymerizable and/or liquid crystal or liquid crystal.

The polymerizable LC mixture preferably has a nematic or smectic phase or a cholesteric phase, more preferably a nematic phase.

The polymerizable liquid crystal or LC compound is preferably a monomer, more preferably a rosewood monomer. These materials generally have good optical properties, such as reduced chroma and can be easily aligned to the desired orientation, which is especially important for industrial manufacturing of large scale polymer films.

Polymerizable liquid crystal monomers, di- and polyreactive compounds suitable for the present invention can be prepared by methods known per se and are described in standard procedures for organic chemistry, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgaer.

The polymerizable LC mixture according to the present invention may further comprise a palmitic or non-palphagic polymerizable liquid crystal precursor or LC compound. Suitable such compounds are disclosed, for example, in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586, WO 97/00600, US 5,518,652, US 5,750,051, US 5,770,107 and US 6,514,578.

Examples of particularly useful and preferably polymerizable liquid crystal precursors or LC compounds are shown below.

Wherein P is a polymerizable group, preferably a propenyl group, a methacryl group, a vinyl group, a vinyloxy group, a propylene ether, an epoxy group or a styryl group, and x and y are the same or different integers from 1 to 12, A And D is a 1,4-phenylene group which is mono-, di- or tri-substituted by L ¹ or 1,4-cyclohexenyl as desired, and u and v are independently 0 or 1 and Z ⁰ is -COO-, -OCO-, -CH ₂ CH ₂ - or a single bond, Y is F, Cl, CN, NO ₂ , OCH ₃ , OCN, SCN, if desired, a fluorinated alkylcarbonyl group having 1 to 4 carbon atoms, an alkoxy group a carbonyl group, an alkylcarbonyloxy group or an alkoxycarbonyloxy group, or a mono-, oligo or polyfluorinated alkyl or alkoxy group having 1 to 4 carbon atoms, R ⁰ having 1 fluorinated as needed Or a plurality, preferably an alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group or an alkoxycarbonyloxy group of 1 to 12 carbon atoms, and Ter is a decene free radical such as Menthol, Chol is a cholesteryl group, and L ¹ and L ^{2 are} independently H, F, Cl, CN or, if desired, halogenated alkyl, alkoxy, alkylcarbonyl, alkane having 1 to 5 carbon atoms Oxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy

Suitable palm compoundes are those shown in the above table, in addition to commercially available palmitic dopants such as R- or S-811, R- or S-1011, R- or S-2011, R- or S-3011, R- or S-4011, R- or S-5011, or CB 15 (all from Merck KGaA, Darmstadt, Germany). More preferably, it is a palm-like compound having a helical twisting force (HTP), particularly a compound containing a sorbitol group, as described in WO 98/00428, a compound containing hydrogen benzoin, as described in GB 2,328,207, a bis-naphthyl derivative, as described in WO 02/94805, for a palmitic bis-naphthol acetal derivative, as described in WO 02/34739, for a palmitic TADDOL derivative, as described in WO 02/06265, And having at least one fluorinated linking group and terminal or central pair of palmitic groups as described in WO 02/06196 and WO 02/06195.

Unless otherwise indicated, the general preparation of polymer LC films in accordance with the present invention can be carried out according to standard methods known in the literature. Typically, the polymerisable LC material is coated or coated onto a substrate wherein it is aligned to a uniform orientation and polymerized in situ with its LC phase, for example, by exposure to heat or actinic radiation, preferably by photopolymerization, More preferably by UV photopolymerization, the alignment of the LC molecules is fixed. If necessary, uniform alignment may be by additional means such as shearing the LC material, surface treatment of the substrate, or adding a surfactant to the LC material.

As the substrate, for example, a glass or quartz plate or a plastic film can be used. The second substrate can also be placed on top of the coated material before and/or during and/or after polymerization. The substrate can be removed after polymerization or not after polymerization. When two substrates are used by actinic radiation under curing, at least one of the substrates must transport actinic radiation for polymerization. An isotropic or birefringent substrate can be used. If the substrate is not removed from the polymeric film after polymerization, it is preferred to use an isotropic substrate.

Suitable and preferred plastic substrates are, for example, polyester films such as polyethylene terephthalate (PET) or polyethyl naphthalate (PEN), polyvinyl alcohol (PVA), polycarbonate (PC) or Ethylene cellulose (TAC), more preferably PET or TAC film. As the birefringent substrate, for example, a uniaxially stretched plastic film can be used. PET is available, for example, from DuPont Teijin Films under the trade name Melinex .

The polymerizable material can be applied to the substrate by conventional coating techniques such as spin coating or knife coating. It can also be screen printing, offset printing, reel-to-reel printing, embossed letter printing, gravure printing, gravure printing, rubber printing, intaglio printing, pad printing, heat sealing printing, spraying by traditional printing techniques known to experts. Ink printing or printing onto a substrate using printing of a stamp or printing plate.

The polymerizable material can also be dissolved in a suitable solvent. This solution is then applied or printed onto the substrate, such as by spin coating or printing or other known techniques, and the solvent evaporates prior to polymerization. In most cases, it is preferred to heat the mixture for evaporation of the solvent. As the solvent, for example, an organic solvent can be used. For example, the solvent may be selected from ketones such as acetone, methyl ethyl ketone, methyl ketone or cyclohexanone; acetates such as methyl acetate, ethyl or butyl or methyl acetoxyacetate; alcohols such as methanol, Ethanol or isopropanol; aromatic solvents such as toluene or xylene; halogenated hydrocarbons such as di or trichloromethane; ethylene glycols or esters thereof such as PGMEA (propylene glycol monomethyl ether acetate), □-butyrolactone, and the like. It is also possible to use a binary, ternary or higher mixture of the above solvents.

Initial alignment of the polymerisable LC material (eg, planar alignment), for example, by rubbing of the substrate, shearing of the material during or after coating, coating of the alignment layer, application of a magnetic or electric field to the coating Material or addition of surface active compounds to the material is achieved. A discussion of alignment techniques is disclosed, for example, in I. Sage "Thermotropic Liquid Crystals", GWGray, John Wiley & Sons, 1987, ed., pp. 75-77; and T. Uchida and H. Seki in "Liquid Crystals - Liquid Crystals-Applications and Uses Vol. 3", B. Bahadur, World Scientific Publishing, Singapore 1992, 1-63. A discussion of alignment materials and techniques is disclosed in J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 1-77.

Particularly preferred are polymeric materials comprising one or more surfactants that promote specific surface alignment of the LC molecules. Suitable surfactants are described, for example, in J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 1-77. Preferred alignment agents for planar alignment are, for example, nonionic surfactants, preferably fluorocarbon surfactants such as the commercially available Fluorad FC-171. (3M company) or Zonyl FSN (DuPont), a surfactant as described in GB 2 383 040 or a polymerizable surfactant as described in EP 1 256 617.

An alignment layer can also be applied over the substrate and a polymerizable material can be provided on the alignment layer. Suitable alignment layers are known in the art, for example, by rubbing polyimide or alignment layers prepared by light alignment, as described in US 5,602,661, US 5,389,698 or US 6,717,644.

For example, the polymerization is achieved by exposing the polymerizable material to thermal or actinic radiation. Actinic radiation means irradiation with light such as UV light, IR light or visible light, irradiation with X-rays or gamma rays or irradiation of high-energy particles such as ions or electrons. The polymerization is preferably carried out by UV irradiation. Regarding the source of actinic radiation, for example, a single UV lamp or a UV lamp set can be used. When high lamp power is used, the curing time can be reduced. Another source of possible actinic radiation is a laser such as UV, IR or visible laser.

The polymerization is preferably carried out in the presence of an initiator which absorbs at the wavelength of actinic radiation. For example, when polymerizing with UV light, a photoinitiator can be used which can decompose under UV irradiation to produce radicals or ions that initiate polymerization. As the polymeric acrylate or methacrylate group, a free radical photoinitiator is preferably used. As the polymerization of ethylene, epoxide or oxetane, a cationic photoinitiator is preferably used. It is also possible to use a thermal polymerization initiator which decomposes upon heating to produce radicals or ions which initiate polymerization. Typical free photoinitiators are, for example, Irgacure 907, Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (Ciba Geigy AG), and typical cationic photoinitiators are, for example, UVI 6974 (Union Carbide).

The curing time depends on the reactivity of the polymerizable material, the thickness of the coated layer, the type of polymerization initiator, and the power of the UV lamp. The curing time is preferably ≦5 minutes, more preferably 3 minutes, the best is 1 minute. For mass production, the preferred short cure time is 30 seconds.

The polymerizable material may also comprise one or more dyes having a maximum absorption value adjusted to the wavelength of the radiation used for the polymerization, in particular a UV dye such as 4,4"-oxidized azoanisole or Tinuvin. Dye (Ciba AG, Basel, Switzerland).

In another preferred embodiment, the polymerizable material comprises one or more monoreactive, polymerizable non-liquid crystalline precursor compounds, preferably in an amount of from 0 to 50%, more preferably from 0 to 20%. Typical examples are alkyl acrylates or alkyl methacrylates.

One or more chain transfer agents may also be added to the polymerizable material to improve the physical properties of the polymer film. More preferably, it is a thiol compound, for example, a monofunctional thiol such as dodecyl mercaptan or a polyfunctional thiol such as trimethylpropane tris(3-thiol propionate). More preferred are liquid crystal precursors or LC thiols, for example, as disclosed in WO 96/12209, WO 96/25470 or US 6,420,001. Using a chain transfer agent, the length of the free polymer chain and/or the length of the polymer chain can be controlled between the two crosslinks within the polymer film. When the amount of chain transfer agent is increased, the length of the polymer chain within the polymer film is reduced.

The polymerizable material may additionally comprise one or more additional ingredients such as a catalyst, a sensor, a stabilizer, an inhibitor, a chain transfer agent, a co-reactive monomer, a surface active compound, a lubricant, a wetting agent, a dispersing agent, a hydrophobic agent, and an adhesive. Agents, flow improvers, defoamers, deaerators, diluents, reactive diluents, adjuvants, colorants, dyes or pigments.

The polymer film of the present invention can be used as an alignment layer, retardation or compensation film in a conventional LC display device, for example, having vertical alignment such as DAP (Alignment Phase Deformation), ECB (Electrically Controlled Birefringence), CSH (Colored) Display device with super verticality, VA (vertical alignment), VAN or VAC (vertically aligned nematic or cholesteric), MVA (multi-domain vertically aligned) or PVA (formed vertical alignment) mode; with curved or mixed alignment Such as OCB (bending battery as needed or birefringence as needed), R-OCB (reflective OCB), HAN (hybrid aligned nematic) or pi-battery (π-battery) mode; with twist alignment Display devices such as TN (twisted nematic), HTN (high twisted nematic), STN (super twisted nematic), AMD-TN (active matrix driven TN) mode display devices; IPS (plane conversion) mode display A device, or a display device that is optically phase-converted, as described in WO 02/93244.

In the foregoing and the following, all temperatures are provided in Celsius, and all percentages are by weight unless otherwise indicated. The following abbreviations are used to illustrate the effects of LC phase: C, K = crystallization; N = nematic; S = smectic; N ^* , Ch = palmitic nematic or cholesteric; I = isotropic. The number between these symbols indicates the phase transition temperature (°C). Further, mp is the melting point and cp is the clearing point (°C).

The following examples illustrate the invention but are limited thereto.

Example 1

The polymerizable LC mixture was formulated from compounds (1) to (8) at various concentrations as seen in Table 1.

(1) = crosslinkable (reactive) liquid crystal original compound (2), (4) = monoreactive liquid crystal original compound (3), (5) = monoreactive liquid crystal original compound of formula (I) (6) =Irgacure 907 (Photoinitiator, Ciba AG) (7) = Irganox 1076 (Stabilizer, Ciba AG) (8) = Fluorad FC171 (interface live, sex agent, 3M company)

The LC polymer film with planar alignment is prepared by dissolving in a mixture of xylene or toluene at a concentration of 30% or 50%. This solution was applied to the substrate by bar coating using a wire rod to deposit a wet film thickness of about 4 microns (rod #0, RK Coating, UK). The sample was annealed at 60 ° C for 30 seconds immediately after coating, and polymerized in an air atmosphere at a power of 20 mW/cm 2 for 60 seconds using a medium pressure mercury lamp. The substrate was triethyl cellulose (TAC) available from LoFo, Germany. Prior to coating, the TAC film was rubbed with a velvet cloth to provide planar alignment of the polymerizable LC mixture.

The pencil hardness of the surface of the polymer film was measured in accordance with ASTM D3363-00. The degree of cure (the EoC) is defined as the percentage of acrylate groups, and which reaction system has been adopted by the FTIR before and after the polymerization of the acrylate peak (at 810 cm ^{- 1)} Determination of the ratio of the area. The adhesion of the polymer film to the TAC substrate is determined using a hatching method (25 squares) with Scotch 610 (3M) ("Tape 1") and Sekisui no. 252 tape ("Tape 2"), at least 3 The average of the subtests. The hatching method involves scoring the film (i.e., cutting the substrate) with a device that produces 25 square grids, then applying a tape to it and pressing it before removal. The number of squares left for each grid is then determined and then generally quoted to the total percentage of the specified film. This method is detailed in British Standard IS 2409: 1992 (E).

The compositions and clearing points of the polymerizable LC mixture, and the EoC, pencil hardness and adhesion of the polymer films P1-P12 prepared therein are shown in Table 1 below.

Mixtures 1-5 contain low amounts of cross-linking compounds of formula I and mono-reactive compounds. The resulting polymer films P1-P5 have a locally good adhesion to TAC, but still have a viscous surface after polymerization. The film tends to stick to itself, for example, when wound on a roll, for example, when an optical film or multilayer assembly is produced, which occurs during the manufacturing process, thus causing film damage.

Mixture 6 comprises a relatively high amount of a monoreactive compound of formula I and more than 12% of a crosslinkable compound. The resulting polymer film P6 has a hard surface but low adhesion to TAC.

The mixture 7-12 according to the invention comprises up to 12% of a crosslinking compound and a high amount of a monoreactive compound of the formula I. The resulting polymer film P7-P12 has good or sufficient adhesion to TAC while having a hard surface which is less viscous and more stable to mechanical stress, for example, when further processed or used to prepare optical multilayers.

Claims (15)

A polymerizable liquid crystal mixture comprising a) > 7 to 12% by weight of one or more crosslinkable compounds, and b) 50 to 80% by weight of one or more compounds of formula I Wherein P is a polymerizable group, Sp is a spacer or a single bond, A is an aromatic or aliphatic 5- or 6-ring, or contains two or three fused aromatic or aliphatic 5- or 6-rings. a group, such rings do not contain or contain one or more heteroatoms selected from N, O and S, and are unsubstituted or substituted by one or more identical or different L ¹ groups, Z being in the case of multiple occurrences Independent of each other -O-, -S-, -CO-, -COO-, -OCO-, -S-CO-, -CO-S-, -O-CO-O-, -CO-NR ⁰ -, -NR ⁰ -CO-, -OCH ₂ -, -CH ₂ O-, -SCH ₂ -, -CH ₂ S-, -CF ₂ O-, -OCF ₂ -, -CF ₂ S-, -SCF ₂ - _, -CH ₂ CH ₂ -, -CF ₂ CH ₂ -, -CH ₂ CF ₂ -, -CF ₂ CF ₂ -, -CH=CR ⁰ -, -CH=CH-, -CH=CF-, -CY ¹ = CY ¹ -, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond, Z ¹ has one of the meanings of Z, R ⁰ is H or has 1 to 12 carbons An alkyl group of atoms, Y ¹ is H, F, Cl or CN, m is 0 or 1, and L ¹ and L ^{2 are} independently of each other, F, Cl, Br, I, CN, NO ₂ , P-Sp- or have 1 An alkyl group, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group or an alkoxycarbonyloxy group to 12 carbon atoms in which one or more H atoms are unsubstituted or substituted by F or Cl , r1, r2 are independent of each other 3 or 4. A mixture according to claim 1, characterized in that it comprises one or more compounds of the formula Ia Wherein P, Sp, L ¹ , L ² , r1 and r2 have the meanings given in formula I. A mixture of claim 1 or 2, characterized by comprising one or more crosslinkable liquid crystal precursor compounds of formula II, Wherein P and Sp, L ¹ , L ² , r1 and r2 are as defined in formula I, L ³ has one of the meanings of L ¹ in formula I, r3 is 0, ¹ , 2, 3 or 4, and Z ¹ And Z ² has one of the meanings of Z in the formula I. A mixture of claim 1 or 2, characterized by comprising one or more crosslinkable liquid crystal precursor compounds of formula IIa, Wherein P, Sp, L ¹ and r1 are defined as Formula II. A mixture of claim 1 or 2 characterized by comprising one or more compounds of formula III Wherein P and Sp are as defined in formula I, and R is an alkyl group having 1 to 12 carbon atoms, an alkoxy group, an alkylcarbonyl group, an alkoxycarbonyl group, an alkylcarbonyloxy group or an alkoxycarbonyloxy group, wherein One or more H atoms are unsubstituted or substituted by F or Cl. A mixture according to claim 5, characterized in that it comprises from 50 to 80% of one or more compounds of the formula I or Ia and from 5 to 40% of one or more compounds of the formula III. A mixture of claim 1 or 2 additionally comprising d) one or more photoinitiators. A mixture of claim 7 additionally comprising e) one or more surfactants, and/or f) one or more stabilizers. A mixture of claim 1 or 2 wherein each of L ¹ and L ² is F, Cl, CH ₃ , OCH ₃ or COCH ₃ . A polymer film obtainable by crosslinking a mixture of any one of claims 1 to 9. A use of a mixture according to any one of claims 1 to 9 or a polymeric film according to claim 10 for optical, electrooptical, information storage, decorative and safe coating. An optical component comprising the mixture of any one of claims 1 to 9 Or the polymeric film of claim 10. A liquid crystal display device comprising the mixture of any one of claims 1 to 9 or the polymer film of claim 10. A use of a mixture according to any one of claims 1 to 9 or a polymeric film according to claim 10 for identification, identification or safety marking or coloring of images. The use of claim 14, wherein the authentication, authentication or security mark or image is for a value object or document.