Photocrosslinkable naphthyl derivatives

The present invention relates to photocrosslinkable naphthyl derivatives, mixtures containing such compounds and their use in the crosslinked state for optical components.

Liquid crystals with at least two photochemically oligomerizable or polymerizable groups can be oriented on a substrate or in a cell, for example by means of orientation layers or in a field. These oriented liquid crystals, provided with a suitable amount of a photoinitiator, are polymerized by irradiation with light of a suitable wavelength. The cross-linked structure thus created is retained even at high temperatures. Such layers can be parts of hybrid layers, for example, as are described in Swiss patent applications CH 2016/94 and CH 2017/94. In this way, optical components such as retarders, waveguides, optical gratings and filters, integrated color filters, or cells with piezoelectric and those with non-linear optical (NLO) properties, etc., can be produced. Such optical components are used, for example, in projection systems.

Other properties, such as birefringence, the refractive index, transparency, etc., must meet different requirements depending on the area of ​​application. For example, materials for optical retarders should have a high birefringence so that the layer thickness of the integrated optical components can be kept to a minimum.

In addition to the general interest in photo-crosslinkable liquid crystals for optical components, such liquid-crystalline materials are suitable as cladding of glass fibers for optical data transmission. The use of such materials increases the elastic modulus in the longitudinal axis of the fiber, reduces the thermal expansion coefficient and reduces microbending losses. This leads to increased mechanical stability.

The photocrosslinkable liquid crystals must have good chemical and thermal stability, good solubility in common solvents and good stability against electric fields and electromagnetic radiation. Furthermore, they should have a suitable mesophase from about 25 ° C. to about 80 ° C., if possible from about 25 ° C. to about 100 ° C., for example a broad smectic or nematic mesophase or chiral smectic or cholesteric mesophase.

Since liquid crystals are generally used as mixtures of several components, it is important that the components are readily miscible with one another. Conventional photochemically oligomerizable or polymerizable liquid crystals generally have a high melting and clearing point. This has the disadvantage that spontaneous, thermal polymerization can occur prematurely during processing, which is carried out at temperatures just below the clearing point, because at this temperature the viscosity in the liquid-crystalline state is the lowest and therefore favorable for good orientation. This spontaneous polymerization leads to the formation of domains, which significantly affects the optical and thermal properties in the crosslinked layers produced. The melting point can be lowered by the production of complex mixtures with several components, which allows processing at lower temperatures, but entails the risk of crystallization of the conventional polymerizable liquid crystals. Compounds which can be photochemically oligomerized or polymerized are described, for example, in EP-A-0 331 233.

It was therefore the task, particularly for use in optical filters, to produce photochemically oligomerizable or polymerizable compounds which are distinguished by a particularly high optical anisotropy Δn and at the same time have lower melting and clearing points, so that they are in the liquid-crystalline state at temperatures above room temperature and can also be processed very well in solution. Furthermore, they should be orientable and structurable as domain-free as possible and also have excellent thermal stability and long-term stability in the cross-linked state.

The present invention now provides compounds which are outstandingly suitable as individual components or as components of liquid crystal mixtures for such optical components, namely compounds of the general formula<chemistry id="chem0001" num="0001"><img file="EP0731084A2_D0001.tif" /></chemistry>    wherein<dl id="dl0001" compact="compact"><dt>R¹ and R²</dt><dd>independently of one another a crosslinkable group such as ethylene, acrylate, methacrylate, 2-chloroacrylate, 2-phenyl acrylate, acryloylphenylene, acrylamide, methacrylamide, 2-chloroacrylamide, 2-phenylacrylamide, epoxy, itaconic acid ester, vinyloxy, vinyl ester, styrene derivatives, siloxanes, ethyleneimine Derivatives, maleic acid derivatives, fumaric acid derivatives or a cinnamic acid derivative optionally substituted with methyl, methoxy, cyano and / or halogen;</dd><dt>S¹ and S²</dt><dd>- (CY₂)_m-, -O (CY₂)_m-, - (CY₂)_mO-, - (CY₂)_mCOO-, - (CY₂)_mOOC-, - (Si [(CH₃)₂]O)_m-, -OCH₂(Themselves₃)₂]O)_mThemselves₃)₂] CH₂O-, or -NHCH₂(Themselves₃)₂]O)_mThemselves₃)₂] CH₂NH-;</dd><dt>Y</dt><dd>Hydrogen, fluorine or methyl;</dd><dt>a</dt><dd>0 or 1;</dd><dt>b</dt><dd>1 or 2, with the proviso that <maths id="math0001" num=""><math display="inline"><mrow><mtext>a + b = 2</mtext></mrow></math><img file="EP0731084A2_D0002.tif" /></maths> is;</dd><dt>m</dt><dd>an integer from 1 to 16;</dd><dt>A¹ and A²</dt><dd>independently of one another optionally with halogen, cyano, methyl, methoxy and / or acetyl mono- or polysubstituted 1,4-phenylene, pyridine-2, 5-diyl, pynmidin-2, 5-diyl, trans-1,4-cyclohexylene or trans -1,3-dioxane-2,5-diyl; and</dd><dt>Z.¹ and Z²</dt><dd>independently of each other a single bond, -CH₂CH₂-, -OCH₂-, -CH₂O-, -COO-, -OOC-, - (CH₂)₄-, -O (CH₂)₃- or - (CH₂)₃O- mean.</dd></dl>

The compounds of the general formula I are distinguished by their relatively low viscosity. They can therefore be easily applied to a suitable surface. This is usually done by spin coating. Since the compounds according to the invention also have a liquid-crystalline phase, they can be aligned by applying an electrical field before crosslinking.

The expression “1,4-phenylene which is mono- or polysubstituted or substituted by halogen, cyano, methyl, methoxy and / or acetyl” in the context of the present invention includes 1,4-phenylene, by fluorine, bromine, chlorine, cyano, methyl, methoxy or acetyl substituted 1,4-phenylene, such as 2- or 3-fluoro-1,4-phenylene, 2,3-, 2,6- or 3,5-difluoro-1,4-phenylene, 2- or 3-chloro-1,4-phenylene, 2,3-, 2,6- or 3,5-dichloro-1,4-phenylene, 2- or 3-bromo-1,4-phenylene, 2nd - or. 3-cyano-1,4-phenylene, 2,3-dicyano-1,4-phenylene, 2- or 3-acetyl-1,4-phenylene, 2- or 3-methyl-1,4-phenylene, 2- or 3-methoxy-1,4-phenylene, and the like. Particularly preferred compounds of the formula I are those in which the rings A¹ and A² are the same and mean 1,4-phenylene or 2- or 3-fluoro-1,4-phenylene.

The spacer groups S¹ and S² can optionally also be chiral. Preferred compounds of formula I are those in which S¹ and S² have the same meaning. Preferred spacer groups are those in which Y is hydrogen and m is an integer from 4 to 12.

Preferred radicals R¹ and R² are acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate, acryloylphenylene, acrylamide, methacrylamide, 2-phenylacrylamide, epoxy, vinyloxy, vinyl ester, styrene derivatives, maleic acid derivatives, fumaric acid derivatives and the like. These are residues which can be photochemically crosslinked after coating the suitable support with compounds of the formula I. In particular, those compounds of formula I are preferred in which the radicals R¹ and R² have the same meaning. They preferably mean acrylate, methacrylate, 2-chloroacrylate, 2-phenyl acrylate, vinyloxy or epoxy.

Particularly preferred compounds of formula I are those in which the naphthyl ring in positions 1 and 5, or 1 and 4 with Z¹ and Z² is linked, especially those in which Z¹ and Z² are the same and -OCH₂-, -CH₂O-, -COO- or -OOC- mean.

Compounds which are particularly preferred are those of the formulas<chemistry id="chem0002" num="0002"><img file="EP0731084A2_D0003.tif" /></chemistry>    wherein<dl id="dl0002" compact="compact"><dt>R</dt><dd>Acrylate, methacrylate, 2-chloroacrylate, 2-phenyl acrylate, vinyloxy or epoxy;</dd><dt>S</dt><dd>- (CH2)_{m '}-, -O (CH₂)_{m '}- or - (CH₂)_{m '}Mean O-;</dd><dt>m '</dt><dd>is an integer from 4 to 12;</dd><dt>A</dt><dd>1,4-phenylene or 2- or 3-fluoro-1,4-phenylene; and</dd><dt>Z.</dt><dd>-Oh₂- or -OOC- mean.</dd></dl>

The compounds of the formula I are very easily accessible synthetically. For example, compounds in which Z represents a group -OOC- can be prepared from 4- [ω-acryloxyalkyloxy] benzoic acids and the corresponding naphthoquinone (see schemes 1 and 2). The esterification can be carried out in a manner known per se. A preferred method is the reaction of the naphthohydroquinone with the carboxylic acid in a polar but inert organic solvent (e.g. in dimethylformamide (DMF) or a halogenated hydrocarbon such as dichloromethane) in the presence of 4- (dimethylamino) pyridine (DMAP) and N, N'-dicyclohexylcarbodimide (DCC). The 4- [ω-acryloxyalkyloxy] benzoic acids are known per se and can be prepared by alkylating 4-hydroxybenzoic acid in the presence of a strong base and an ω-halogenated alcohol and potassium iodide and then esterifying the 4- [ω-hydroxyalkyloxy] benzoic acids with acrylic acid in the presence of p-toluenesulfonic acid (PTS).

The symbols used in the schemes have the meanings given above.<chemistry id="chem0003" num="0003"><img file="EP0731084A2_D0004.tif" /></chemistry><chemistry id="chem0004" num="0004"><img file="EP0731084A2_D0005.tif" /></chemistry>

A small amount of BHT (2,6-di-tert-butyl-4-methylphenol / "butylhydroxytoluene") is added to each stage to avoid undesired thermal crosslinking.

1,4-bis (4- [ω-acryloyloxyalkyloxy] phenylmethyleneoxy) naphthalene derivatives, ie. Compounds of formula I, wherein Z is the group -OCH₂- Means can be prepared in a manner known per se by etherification of the corresponding naphthohydroquinone with 4- [ω-acryloyloxyalkyloxy)] benzyl alcohols. The reaction can be carried out, for example, in the presence of dialkyl azodicarboxylic acid and triphenylphosphine. The 4- [ω-acryloyloxyalkyloxy)] benzyl alcohols used as starting material can be prepared by reducing the reaction product of acrylic acid with 4- [ω-hydroxyalkyloxy)] benzyl aldehydes. The 4- [ω-hydroxyalkyloxy)] benzyl aldehydes can be prepared by etherification of 4-hydroxybenzaldehyde with ω-hydroxyalkyl halides in the presence of conventional bases.

The compounds of formula I can be used as pure compounds or in the form of mixtures with one another and / or with other liquid crystal components.

The liquid-crystalline mixtures according to the invention contain at least 2 components, of which at least one component is a compound of the formula I. A second and optionally further components can be further compounds of the formula I or other known liquid-crystalline compounds with or without photocrosslinkable groups. One or more chiral components can also be contained in the mixture.

Because of the good solubility of the compounds of the formula I and because of their good miscibility with one another, the proportion of different compounds of the formula I in the mixtures according to the invention can be high and can be up to 100% by weight.

In addition to one or more compounds of the formula I, the mixtures according to the invention preferably contain one or more compounds from the group of the compounds of the general formulas<chemistry id="chem0005" num="0005"><img file="EP0731084A2_D0006.tif" /></chemistry><chemistry id="chem0006" num="0006"><img file="EP0731084A2_D0007.tif" /></chemistry><chemistry id="chem0007" num="0007"><img file="EP0731084A2_D0008.tif" /></chemistry><chemistry id="chem0008" num="0008"><img file="EP0731084A2_D0009.tif" /></chemistry>    wherein<dl id="dl0003" compact="compact"><dt>p</dt><dd>an integer from 2 to 12;</dd><dt>R³ and R⁴</dt><dd>independently of one another alkyl or alkenyl having 2 to 12 carbon atoms;</dd><dt>X</dt><dd>Hydrogen, lower alkyl, fluorine, bromine, chlorine or cyano;</dd><dt>m '</dt><dd>an integer from 4 to 12; and</dd><dt>*</dt><dd>mean a center of chirality.</dd></dl>

"Lower alkyl" in connection with the compound of formula II includes methyl, ethyl, propyl, i-propyl, butyl, i-butyl and tert-butyl.

The following examples further illustrate the preparation of the compounds of the formula I and liquid-crystalline mixtures comprising these compounds. C means a crystalline phase, S a smectic phase, N a nematic phase and I the isotropic phase.

example 1

To a solution of 1.25 g of 4- [8-acryloyloxyoctyloxy)] benzoic acid and 0.25 g of 1,4-naphthohydroquinone, 0.2 g of 4-dimethylaminopyridine (DMAP) in 20 ml of dichloromethane was 0.8 while stirring at room temperature g of N, N'-dicyclohexyldicarbodiimide (DCC). The reaction mixture was stirred at room temperature overnight, poured onto 100 ml of water and then extracted three times with 50 ml of dichloromethane each time. The organic phases were combined, washed twice with 100 ml of water each time, dried over magnesium sulfate, filtered and the filtrate was then concentrated. Chromatographic purification of the residue on silica gel with cyclohexane / ethyl acetate (vol. 8: 2) and recrystallization of the fractions according to thin layer chromatography from ethyl alcohol gave 0.2 g of 1,4-bis (4- [8-acryloyloxyoctyloxy] phenylcarbonyloxy) naphthatin; M.p. (CN) 94^OC, Klp. (NI) 104^OC.

The following connections can be made in an analogous manner: 1,4-bis (4- [3-acryloyloxypropyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [4-acryloyloxybutyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [5-acryloyloxypentyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [6-acryloyloxyhexyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [7-acryloyloxyheptyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [9-acryloyloxynonyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [10-acryloyloxydecyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [11-acryloyloxyundecyloxy] phenylcarbonyloxy) naphthalene; M.p. (CI) 106^OC, Klp. (NI) 98^OC. 1,4-bis (4- [12-acryloyloxydodecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [3-acryloyloxypropyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [4-acryloyloxybutyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [5-acryloyloxypentyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [6-acryloyloxyhexyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [7-acryloyloxyheptyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [8-acryloyloxyoctyloxy] phenylcarbonyloxy) naphthalene; M.p. (CI) 130^OC, Klp. (NI) 108^OC. 1,5-bis (4- [9-acryloyloxynonyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [10-acryloyloxydecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [11-acryloyloxyundecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [12-acryloyloxydodecyloxy] phenylcarbonyloxy) naphthalene.

Example 2

To a solution of 1.25 g of 4- [8-vinyloxyoctyloxy)] benzoic acid and 0.25 g of 1,4-naphthohydroquinone, 0.2 g of 4-dimethylaminopyridine in 20 ml of dichloromethane is mixed with 0.8 g of N at room temperature. Given N'-dicyclohexyldicarbodiimide. The reaction mixture is stirred at room temperature overnight, poured onto 100 ml of water and then extracted three times with 50 ml of dichloromethane each time. The organic phases are combined, washed twice with 100 ml of water each time, dried over magnesium sulfate, filtered and the filtrate is then concentrated. Chromatographic purification of the residue on silica gel with cyclohexane / ethyl acetate (vol. 8: 2) and recrystallization twice from ethyl alcohol to give pure fractions according to thin-layer chromatography gives 0.5 g of 1,4-bis (4- [8-vinyloxyoctyloxy] phenylcarbonyloxy) naphthalene.

The following connections can be made in an analogous manner: 1,4-bis (4- [3-vinyloxypropyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [4-vinyloxybutyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [5-vinyloxypentyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [6-vinyloxyhexyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [7-vinyloxyheptyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [9-vinyloxynonyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [10-vinyloxydecyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [11-vinyloxyundecyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [12-vinyloxydodecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [3-vinyloxypropyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [4-vinyloxybutyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [5-vinyloxypentyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [6-vinyloxyhexyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [7-vinyloxyheptyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [8-vinyloxyoctyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [9-vinyloxynonyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [10-vinyloxydecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [11-vinyloxyundecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [12-vinyloxydodecyloxy] phenylcarbonyloxy) naphthalene.

Example 3

To a solution of 1.25 g of 4- [7, 8-oxiranoctyloxy)] benzoic acid and 0.25 g of 1,4-naphthohydroquinone, 0.2 g of 4-dimethylaminopyridine in 20 ml of dichloromethane is added to 0.8 g with stirring at room temperature N, N'-dicyclohexyldicarbodiimide given. The reaction mixture is stirred at room temperature overnight, poured onto 100 ml of water and then extracted three times with 50 ml of dichloromethane each time. The combined organic phases are washed twice with 100 ml of water each time, dried over magnesium sulfate, filtered and the filtrate is then concentrated. Chromatographic purification of the residue on silica gel with cyclohexane / ethyl acetate (vol. 8: 2) and recrystallization twice from ethyl alcohol to give pure fractions according to thin-layer chromatography gives 0.5 g of 1,4-bis (4- [7,8-oxiranoctyloxy] phenylcarbonyloxy) naphthalene .

The following connections can be made in an analogous manner: 1,4-bis (4- [2,3-oxiranopropyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [3,4-oxiranbutyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [4,5-oxiranpentyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [5, 6-oxiranhexyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [6, 7-oxiranheptyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [8, 9-oxirannonyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [9, 10-oxirane decyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [10, 11-oxiranundecyloxy] phenylcarbonyloxy) naphthalene; 1,4-bis (4- [11,12-oxirandodecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [2,3-oxiranopropyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [3,4-oxiranbutyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [4,5-oxiranpentyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [5, 6-oxiranhexyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [6, 7-oxiraneheptyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [7, 8-oxiranoctyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [8, 9-oxirannonyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [9, 10-oxirane decyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [10, 11-oxiranundecyloxy] phenylcarbonyloxy) naphthalene; 1,5-bis (4- [11,12-oxirandodecyloxy] phenylcarbonyloxy) naphthalene.

Example 4

A mixture (CN, &lt;20^OC, NI, 105^OC) from 80% by weight of 1,4-bis (4- [8-acryloyloxyoctyloxy] phenylcarbonyloxy) naphthalene and 20% by weight of 1-chloro-2,5-bis (4- [6-acryloyloxyhexyloxy)] phenylcarbonyloxy) benzene presented with 1 wt.% Of a photoinitiator (IRGACURE, Ciba Geigy), dissolved in anisole (40 wt.%) and then spun at 2000 revolutions per minute on a glass plate. The glass plate was previously coated with poly [methacryloyloxyethyl-3- (E) - [4-cyano-4'-biphenyl] acrylate] as described in Swiss patent application CH 2016/94 and then irradiated with linearly polarized light. A predetermined structure was inscribed photolithographically in the (PPN) layer using a mask. The new layer (on the PPN layer) was at 90^OC dried on a warm bench, then in a vacuum cabinet under vacuum at 90^OC exposed to xenon light. The original structure registered was preserved and was faithfully adopted by the new network. A clear birefringence (Δn) was evident. This layer can be used as a structured optical retarder.