GB2396154A - 4,5-Dicyanoimidazole derivatives and their use in liquid crystal media and liquid crystal devices - Google Patents

Abstract

The use of 4,5-dicyanoimidazole derivatives in liquid crystal media, liquid crystal devices, anisotropic polymers and various applications such as semiconductor, optical recording and electroluminescent applications and liquid media, polymers and display comprising 4,5-dicyanoimidazole derivatives. In particular, the derivatives used are of formula I in which A<1> and A<2> are each independently optionally substituted, aromatic or alicyclic, carbocyclic or heterocyclic groups and, where Z<1> is a single bond, A<1> may form a zwitterion with the 4,5-dicyanoimidazole group, Z<1> and Z<2> are independently various residues or a single bond, R is H or one of various substituent groups, including a group P-Sp-X wherein P is a polymerisable or reactive group, Sp is a spacer group or a single bond and X is a linkage group or a single bond, U<1> has one of the meanings of R or -N(U<1>)- is -N<->-and m is 0, 1 or 2. Subject to certain provisos, compounds of formula I are disclosed per se. In preferred compounds, U<1> is a methyl group, Z<1> is an ethynyl group, A<1> is a 1,4-phenylene group, m is 0 and R is an alkyl group. <EMI ID=1.1 HE=46 WI=70 LX=257 LY=1331 TI=CF>

Description

- 1 4,5-Dicyanoimidazole Derivatives and their Use in Liquid Crystal Media

and Liquid Crystal Devices Field of the Invention

The invention relates to the use of 4,5-dicyanoimidazole derivatives in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical 10 recording, electroluminescent, photoconductor and electrophotographic applications. The invention further relates to liquid crystal media, polymers and displays comprising 4,5 dicyanoimidazole derivatives. The invention further relates to novel 4,5-dicyanoimidazole derivatives.

Backoround and Prior Art

For use in liquid crystal display (LCD) applications it is often required to have available liquid crystal (LC) compounds and media with a 20 high positive value of the dielectric anisotropy As, which in turn requires that the material has a large molecular dipole. Until now, materials with terminal cyano groups have been used extensively for this purpose, as the cyano group is of high polarisability.

25 Thus, LC compounds with a Ac of + 20 or more and having a terminal cyano group are widely known in prior art. For many

applications, however, LC compounds and media with still higher Ac are needed. Furthermore, the compounds known from prior art do

often have unfavourable properties, like high melting points, smectic 30 phases or unfavourable vaues of the birefringence.

Consequently, there is still a need for materials with high polarity and positive As that can be used in LC media to increase the value of As, without negatively affecting the other properties of the media, such 35 as the LC phase range.

- 2 The inventors of the present invention have found that the above mentioned drawbacks can be overcome by using 4,5 dicyanoimidazole derivatives in LC media and LCDs. Furthermore, novel 4,5-dicyanoimidazole derivatives have been prepared, 5 especially mesogenic or liquid crystalline 4,5-dicyanoimidazoles with a rod-shaped molecular structure and polymerisable 4,5 dicyanoimidazoles, which have advantageous properties and are suitable for use in optical, electrooptical, security, electronic, charge transport, semiconductor, optical recording, electroluminescent, 10 photovoltaic or electrophotographic applications, in particular in LC media and LC devices.

4,5-Dicyanoimidazole derivatives have been described in prior art,

for example in EP-A-0 269 238, EP-A-0 283 173, WO 92/13451, WO 15 94/01432, WO 94/05652, WO 95/18122, WO 01/40195, US

3,793,339, US 4,220,466, JP-A-49-134676 and JP 50-069080, for use as insecticides, pesticides, parasiticides, acaricides, anthelminthics and for plant growth regulation. However, the use of 4,5-dicyano-imidazole derivatives in LC media, LC devices, optical, 20 electrooptical, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor or electrophoto graphic applications has neither been disclosed nor suggested in prior art.

25 One aim of the present invention is to provide improved LC media with high polarity and high positive values of the dielectric anisotropy that do not have the drawbacks of LC media known from prior art.

Another aim of the invention is to provide novel 4,5-dicyanoimidazole 30 derivatives with improved properties, especially mesogenic or liquid crystalline 4,5-dicyanoimidazoles with a rod-shaped molecular structure and polymerisable 4,5-dicyanoimidazoles.

Another aim is to provide advantageous uses for the 4,5 35 dicyanoimidazoles, such as liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative,

- security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor and electrophotographic applications.

Other aims of the present invention are immediately evident to the 5 person skilled in the art from the following detailed description.

Summary of the Invention

The invention relates to the use of compounds comprising at least 10 one 4,5-dicyanoimidazole group as mesogenic or liquid crystalline material in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor and 15 electrophotographic applications.

The invention further relates to the use of compounds comprising at least one 4,5-dicyanoimidazole group as mesogenic or liquid crystalline material for the applications described above, wherein the 20 4,5- dicyanoimidazole group is selected of formula (1) NO C\ N / I (1)

25 TIC IN

NO U wherein U is H or an optionally substituted aliphatic, cycloaliphatic or aromatic group with up to 20 C atoms that optionally comprises one 30 or more hetero atoms and optionally comprises fused rings, or -N(U) is -N-- (negatively charged N atom).

The invention further relates to the uses as described above, wherein the 4,5-dicyanoimidazole derivatives are selected of formula I

- 4 N rat \iZ1-A1-(Z2-A2) -R I N N-,,C U

wherein A1 and A2 are independently of each other an aromatic or alicyclic 10 ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms selected from N. O and S. and are optionally mono- or polysubstituted by L, and, If z1 is a single bond, A, may also form a zwitterion with the 4,5 15 dicyanoimidazole group, L is F. Cl, Br, I, CN, NO2 or alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonlyoxy with 1 to 7 C atoms, wherein one or more H atoms are optionally substituted 20 by F or Cl, Z. and Z2 are independently of each other -O-, -S-, -CO-, -COO-, OCO-, -S-CO-, -CO-S-, -O-COO-, -CO-N R -, -N R -CO-,

OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-,

25 -SCF2- -CH2CH2-, -CF2CH2-, -CH2CF2-, -CF2CF2-,

CH=N-, -N=CH-, -N=N-, -CH=CR -, -CY'=CY2-, -C_C-,

CH=CH-COO-, -OCO-CH=CH- or a single bond, Y' and y2 are independently of each other H. F. Cl or CN, R is H. F. Cl, Br, I, CN, NO2, NCS, SF5 or alkyl which is straight chain or branched, has 1 to 20 C-atoms, is unsubstituted, mono- or poly-substituted by F. Cl, Br, I or CN, and in which one or more non-adjacent CH2 groups 35 are optionally replaced, in each case independently from one another, by-O-, -S-, -NH-, -NR -, SiR R -, -CO-,

- 5 COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -CY4=CY2- or -C_C- in such a manner that O and/or S atoms are not linked directly to one another, or R denotes P-Sp-X, 5 R and R are independently of each other H or alkyl with 1 to 12 C-atoms, has one of the meanings of R. or-N(U4)- is -N -, 10 P is a polymerisable or reactive group, Sp is a spacer group or a single bond, X is a linkage group or a single bond, and m isO, 1 or2.

The invention further relates to novel 4,5-dicyanoimidazole derivatives of formula 1, in particular to 4,5-dicyanoimidazole 20 derivatives of formula I wherein A', A2, z,, Z2, R. U' and m have the meanings given above, with the provisos that, a) if m is 0, U' is H or alkyl, Z' is a single bond and A' is phenyl, then R is P-Sp-X or alkyl as defined in formula I with more than 2 C atoms, 25 b) if m is 0, R is not P-Sp-X and Z'-A' is phenylene, then U' is H or unsubstituted alkyl or-N(U')- is -N, c) if m is O or 1, U' is H or alkyl and R is not P-Sp-X, then -Z,-A4-(Z2 A2)m-R is not biphenyl, phenethyl, styryl, phenoxyphenyl, 30 benzyloxyphenyl, substituted or unsubstituted furyl or pyrrolyl or unsubstituted pyridinyl, e) if m is 1, U' is H or alkyl, R is not P-Sp-X, Z' is a single bond, Z2 iS O or S and A' is phenylene, then A2 is not benzthiazole, pyridine or pyrimidine,

- 6 f) if m is 1, U' is H or alkyl, Z' is a O. S or a single bond, Z2 iS a single bond, A' is a nitrogen containing heteroaromatic group and A2 is substituted phenylene or pyridine, then R is P-Sp-X or alkyl as defined in formula I with more than 2 C-atoms, The invention further relates to an LC medium comprising at least one 4,5-dicyanoimidazole derivative which preferably comprises a group of formula (1) and very preferably is selected of formula 1.

10 The invention further relates to a polymerisable LC medium comprising at least one 4,5-dicyanoimidazole derivative, which preferably comprises a group of formula (1) and very preferably is selected of formula 1, and comprising at least one polymerisable compound, wherein said polymerisable compound may be said 4,5 15 dicyanoimidazole derivative or an additional compound.

The invention further relates to a polymer obtained by polymerising a 4,5dicyanoimidazole derivative or a polymerisable LC medium as described above and below.

The invention further relates to an anisotropic polymer obtained by polymerizing a 4,5-dicyanoimidazole derivative or a polymerisable LC medium as described above and below in its oriented state, preferably in form of a film.

The invention further relates to the use of a 4,5-dicyanoimidazole derivative, a polymer or a polymer film as described above and below in electrooptical displays, liquid crystal displays, optical films, polarisers, compensators, beam splitters, reflective films, alignment 30 layers, colour filters, holographic elements, hot stamping foils, coloured images, decorative or security markings e.g. for consumer objects or documents of value, LC pigments, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, nonlinear optics, optical information storage, as chiral 35 dopants, in electronic devices like for example field effect transistors

(PET) as components of integrated circuitry, as thin film transistors in

flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications, electroluminescent displays or backlights of LCDs, for photovoltaic or sensor devices, as electrode 5 materials in batteries, as photoconductors, or for electrophotographic applications or electrophotographic recording.

The invention further relates to an LC device comprising a 4,5 dicyanoimidazole derivative or an LC medium, polymer or polymer 10 film as described above and below.

Definition of Terms The terms'liquid crystalline or mesogenic materiel' or'liquid 15 crystalline or mesogenic compound' means materials or compounds comprising one or more rod-shaped, lath-shaped or disk-shaped mesogenic groups, i.e., groups with the ability to induce LC phase behaviour. The compounds or materials comprising mesogenic groups do not necessarily have to exhibit an LC phase themselves. It 20 is also possible that they show LC phase behaviour only in mixtures with other compounds, or when the mesogenic compounds or materials, or the mixtures thereof, are polymerized.

The terms 'polymerisable' end 'reactive' include compounds or 25 groups that are capable of participating in a polymerization reaction, like radicalic or ionic chain polymerization, polyeddition or polycondensation, and reactive compounds or reactive groups that are capable of being grafted for example by condensation or addition to a polymer backbone in a polymeranaloguous reaction.

The term 'film' includes self-supporting, i.e., free-standing, films that show more or less pronounced mechanical stability and flexibility, as well as coatings or layers on a supporting substrate or between two substrates. Detailed Description of the Invention

- 8 The LC media and LC devices according to the present invention comprising one or more 4,5-dicyanoimidazole derivatives are advantageous as they exhibit an increased dielectric anisotropy Ac.

In particular the novel compounds of formula I are advantageous as they exhibit a very high value of As the dielectric anisotropy.

Therefore, it is possible to considerably increase the value of Ac in LC media by using the inventive compounds even in only small amounts.

The 4,5-dicyanoimidazole derivatives, in particular the compounds of formula 1, are especially useful for a display using liquid crystals in the isotropic state, hereinafter shortly referred to as "isotropic mode display", as described for example in DE 102 172 73 and WO 15 02/93244 A1. Thus, another object of the present invention is a display of the isotropic mode comprising at least one 4,5 dicyanoimidazole derivative, which is preferably a compound of formula I or of the preferred compounds shown above and below, or comprising an LC medium comprising such a 4,5dicyanoimidazole 20 derivative. Another aspect of the invention relates to polymerisable compounds of formula 1, also known as reactive mesogens, and to LC polymers obtained from these compounds or mixtures comprising them.

Another aspect of the invention relates to highly ordered anisotropic LC polymer films that are obtained from polymerisable compounds or reactive mesogens of formula 1, or mixtures comprising them, by aligning them in their LC phase into uniform orientation and 30 polymerising them in situ, e.g. by thermal or photopolymerisation.

The novel compounds of formula I have the following advantages - they are easy to prepare in excellent yield from cheap, commercially available starting materials.

- 9 - - they are highly polar and, when appropriately substituted, show increased dielectric anisotropy Ac = all- cl due to increased c,'.

- they are rod shaped and are suitable as components of LC mixtures in LCDs. The molecules themselves do not necessarily 5 have to exhibit an LC phase, but by being rod shaped they do not diminish the electro-optical properties of the LC host in to which they are dissolved.

- their high polarity is due to the dicyano groups on a conjugated 10 system and gives the compounds high dielectric anisotropy As.

- they can also be designed to have high birefringence An. High Ac and high An are desirable properties in LCD applications.

- they can be used to reduce the operating voltage in LCDs, and to 15 modify physical properties of a mixture used for LCDs such as birefringence, viscosity leading to improvements in optical performance of a display device.

- the presence of an alkyl group U' on the imidazole ring, like for example methyl, increases overall polarity of the system by 20 pushing electrons in to the ring towards the electron withdrawing cyano constituents. The lateral substituent U' also gives rise to smectic phase suppression and also lower melting points. Low melting points are particularly important for compounds in LC mixtures which operate at ambient temperatures.

25 - they can be polymerized if appropriately substituted.

- their polarity can be massively increased by preparing a stable zwitterion which gives the molecule a permanent polarity across the length of the molecule. High polarity is particularly desirable in isotropic mode displays.

The compounds of formula I are especially suitable for use in mixtures for LCD applications, in particular for applications using LC mixtures in the nematic or isotropic phase where high birefringence, high polarity and high dielectric anisotropy are required.

- 10 Furthermore, the compounds of formula I can be used as reactive mesogens and can be used to make polymers or polymer films for use as optical films, in particular optical retardation or compensation films, alignment layers, colour filters or polarisers in an LCD.

Another field of use of polymerisable compounds of formula I is as

semiconductors or charge transport materials. These materials can be used in electronic devices like for example field effect transistors

(FET) as components of integrated circuitry, as thin film transistors in 10 flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting components for organic light emitting diode (OLED) applications, electroluminescent displays or backlights of LCDs, for photovoltaic or sensor devices.

15 It is also possible to co-polymerise compounds of formula I via group P with other polymerisable mesogenic monomers, as well as with other compounds of formula 1, in order to induce or enhance LC phase behaviour.

20 The LCDs according to the present invention are for example conventional LCDs, in particular those of the DAP (deformation of aligned phases) or VA (vertically aligned) mode, like e.g. ECB (electrically controlled birefringence), CSH (colour super homeotropic), VAN or VAC (vertically aligned nematic or cholesteric) 25 displays, MVA (multidomain vertically aligned) or PVA (patterned vertically aligned) displays, in displays of the bend mode or hybrid type displays, like e.g. OCB (optically compensated bend cell or optically compensated birefringence), R-OCB (reflective OCB), HAN (hybrid aligned nematic) or pi-cell (-cell) displays, furthermore in 30 displays of the TN (twisted nematic), HTN (highly twisted nematic) or STN (super twisted nematic), in AMD-TN (active matrix driven TN) displays, in displays of the IPS (in plane switching) mode which are also known as 'super TFT' displays, or in isotropic mode displays.

35 Especially preferred are TN, STN and isotropic mode displays.

r Particularly preferred are compounds of formula 1, wherein - Z' is a single bond and A' is an unsaturated heterocyclic group, especially preferably pyridine or pyrimidine, that is linked via an N atom to the 4, 5-dicyanoimidazole group to form a zwitterion, - Z. is -C-C- or a single bond, Z2 iS -COO-, -OCO-, -C-C- or a single bond, - R is P-Sp-X, 10 - R is straight chain alkyl or alkoxy with 1 to 12, preferably 1 to 8 C atoms or alkenyl with 2 to 12, preferably 2 to 7 C-atoms, - U' is H. alkyl with 1 to 8 C-atoms or alkenyl with 2 to 7 C-atoms, very preferably H or methyl, 15 - -N(U')- is -N -, - Sp is alkylene with 1 to 12 C atoms which is optionally mono- or polysubstituted by F and wherein one or more nonadjacent CH2 may be replaced, in each case independently from one another, by -O-, -CH=CH- or-C_C-, 20 - X is -O-, -COO-, -OCO-, -OCOO- or a single bond.

- Sp and X are a single bond, - Sp-X is different from a single bond, - m is 1 ore, U in formula (1) has preferably one of the meanings of U. of formula I or one of the preferred meanings of U. given above and below.

L is preferably F. Cl, CN, OH, NO2, CH3, C2H5, OCH3, OC2H5, 30 COCH3, COC2H5, COOCH3, COOC2H5, CF3, OCF3, OCHF2 or OC2F5, in particular F. Cl, CN, CH3, C2H5, OCH3, COCH3 or OCF3, most preferably F. Cl, CH3, OCH3 or COCH3.

A' and A2 are independently of each other an aromatic or alicyclic 35 ring, preferably a 5-, 6- or 7-membered ring, or a group comprising two or more, preferably two or three, fused aromatic or alicyclic rings,

- 12 wherein these rings optionally contain one or more hetero atoms selected from N. O and S. and are optionally mono- or polysubstituted by L as defined as described above and below.

5 Preferred groups A' and A2 are for example furan, pyrrol, thiophene, oxazole, thiazole, thiadiazole, imidazole, phenylene, cyclohexylene, cyclohexenylene, pyridine, pyrimidine, pyrazine, azulene, indane, naphthalene, tetrahydronaphthalene, anthracene and phenanthrene.

10 Particularly preferably A' and A2 are selected from furane-2,5-diyl, thiophene-2,5-diyl, thienothiophene-2,5-diyl, dithienothiophene-2,6 dlyl, pyrrol-2,5-diyl, 1,4-phenylene, azulene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-dlyl, naphthalene-2,6-dlyl, 1,2,3,4-tetrahydro naphthalene2,6-dlyl, indane-2,5-diyl, or 1,4-cyclohexylene wherein 15 one or two nonadjacent CH2 groups are optionally replaced by O and/or S. wherein these groups are unsubstituted, mono- or polysubstituted by L as defined in formula 1.

Preferably the group -A'-(Z2-A2)m- contains only monocyclic groups 20 A' and A2. Very preferably the group -A'-(Z2-A2)m- is a group with one or two 5- or 6-membered rings.

Preferred subformulae for -A,-(Z2-A2)m- are listed below. For reasons of simplicity, Phe in these groups is 1,4-phenylene, PheL is a 1,4 25 phenylene group which is substituted by 1 to 4 groups L as defined above, Pyd is pyridine-2,5-diyl and Pyr is pyrimidine-2,5-diyl. The following list of preferred groups -A4-(Z2-A2)m- is comprising the subformulae 11-1 to 11-16 as well as their mirror images, 30 -Phe- 11-1 - Pyd- 11-2 -Pyr11-3 -PheL- I 1-4 -Cyc- 1 1-5 35 -Phe-Z-Cyc- 11-6 -Cyc-Z- Cyc- 1 1-7

- 13 -PheL-Cyc- 11-8 -Phe-Z-Phe- I 1-9 -Phe-Z-Pyd- 11-1 0 -Pyd-Z-Phe- 111 1 5 -Phe-Z-Pyr- 11-12 -Pyr-Z-Phe- 11-1 3 -PheL-Z-Phe- 11-1 4 -PheL-ZPyd- 11-1 5 -PheL-Z-Pyr- 11-16 10 -Pyr-Z-Pyd- 11-17 -Pyd-Z-Pyd- 11-1 8 Pyr-Z-Pyr- 11-1 9 -PheL-Z-PheL- 11-20 15 In these preferred groups Z has the meaning of Z' as given in formula 1. Preferably Z is -COO-, -OCO-, CH2CH2 -C_C- or a single bond.

Very preferably -A'-(Z-A2)m- is selected from the following formulae 20 and their mirror images (L)r +h: -Nor llb 30 (L)r (L), He

J - 14 (L)r (L)r SCOOT lid 5 (L)r Or He 10 I If \/ 119

wherein L has the meaning given above and r is 0, 1, 2, 3 or 4, preferably 0, 1 or 2.

(L)r The group in these preferred formulae is very preferably L L L L L

25 denoting or furthermore with L having each independently one of the meanings given above.

Especially preferred compounds of formula I comprise at least 30 (L)r one group wherein r is 1.

Further preferred compounds of formula I comprise at least

! - 15 (L), two groups wherein r is 1 and/or at least one group (L)r 5 wherein ris2.

If R is an alkyl or alkoxy radical, i.e. where the terminal CH2 group is replaced by-O-, this may be straight-chain or branched. It is 10 preferably straight-chain, has 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore methyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, 15 tridecoxy or tetradecoxy, for example.

Oxaalkyl, i.e. where one CH2 group is replaced by-O-, is preferably straight-chain 2-oxapropyl (=methoxymethyl), 2- (=ethoxymethyl) or 3oxabutyl (=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or 5 20 oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7oxaoctyl, 2-,3-,4-,5-,6-,7-or8-oxanonylor2-,3-,4-,5-,6-,7-,8-or9 oxadecyl, for example.

If R is an alkyl group wherein one or more CH2 groups are replaced 25 byCH=CH-, this may be straight-chain or branched. It is preferably straightchain, has 2 to 10 C atoms and accordingly is preferably vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3 or pent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, inept-1-, 2-, 3-, 4-, 5 or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4 30 5-, 6-, 7or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.

Especially preferred alkenyl groups are C2 C7-1 E-alkenyl, C4-C7-3E-

alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl and C7-6-alkenyl, in particular C2-C7-1 E-alkenyl, C4-C7-3E-alkenyl and C5-C7-4-alkenyl.

Examples for particularly preferred alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl,

- 16 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups having up to 5 C atoms are generally preferred.

If R is an alkyl group, wherein one CH2 group is replaced by -O- and 5 one by-CO-, these radicals are preferably neighboured. Accordingly these radicals together form a carbonyloxy group -CO-O- or an oxycarbonyl group -O-CO-. Preferably this group R is straight-chain and has 2 to 6 C atoms.

10 It is accordingly preferably acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2propionyloxyethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, 15 ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy carbonyl) ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl, 20 4(methoxycarbonyl)-butyl. If R is an alkyl group, wherein two or more CH2 groups are replaced by-O- and/or-COO-, it can be straight-chain or branched. It is preferably straight-chain and has 3 to 12 C atoms. Accordingly it is 25 preferably bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6, 6-bis-carboxy hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9bis-carboxy nonyl, 10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl, 2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl, 30 4,4bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl, 6,6-bis(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl, 8,8-bis(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl, 2,2-bis (ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl, 4,4-bis (ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.

- 17 lf R is an alkyl or alkenyl group that is monosubstituted by CN or CF3, it is preferably straight-chain. The substitution by CN or CF3 can be in any desired position.

5 If R is an alkyl or alkenyl group that is at least monosubstituted by halogen, it is preferably straight-chain. Halogen is preferably F or Cl, in case of multiple substitution preferably F. The resulting groups include also perfluorinated groups. In case of monosubstitution the F or Cl substituent can be in any desired position, but is preferably in to 10 -position. Examples for especially preferred straight-chain groups with a terminal F substituent are fluormethyl, 2-fluorethyl, 3- fluorpropyl, 4-fluorbutyl, 5-fluorpentyl, 6-fluorhexyl and 7-fluorheptyl. Other positions of F are, however, not excluded.

15 Halogen is preferably F or Cl.

R can be a polar or a non-polar group. In case of a polar group, it is selected from CN, SFs, halogen, OCH3, SON, CoR5, CoOR5 or a mono- oligoor polyfluorinated alkyl or alkoxy group with 1 to 4 C 20 atoms. R5 is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3 C atoms. Especially preferred polar groups are selected of F. Cl, CN, OCH3, COCH3, COC2Hs, COOCH3, COOC2H5, CF3, CHF2, CH2F, OCF3, OCHF2, OCH2F, C2F5 and OC2F5, in particular F. Cl, CN, CF3, OCHF2 and OCF3. In case of a nonpolar group, it is preferably alkyl 25 with up to 15 C atoms or alkoxy with 2 to 15 C atoms.

R can be an achiral or a chiral group. In case of a chiral group it is preferably selected of formula lil: 30 Q' CH Q2

Q lil wherein

- 18 Q' is an alkylene or alkylene-oxy group with 1 to 9 C atoms or a single bond, Q2 is an alkyl or alkoxy group with 1 to 10 C atoms which may be 5 unsubstituted, mono- or polysubstituted by F. Cl, Br or ON, it being also possible for one or more non-adjacent CH2 groups to be replaced, in each case independently from one another, by -C-C-, -O-, -S-, -N H-, -N (C H3)-, -CO-, -COO-, -OCO-, -OCO-O-,

-S-CO- or -CO-S- in such a manner that oxygen atoms are not 10 linked directly to one another, Q3 is F. Cl, Br, ON or an alkyl or alkoxy group as defined for Q2 but being different from Q2.

15 In case Q' in formula lil is an alkylene-oxy group, the O atom is preferably adjacent to the chiral C atom.

Preferred chiral groups of formula lil are 2-alkyl, 2-alkoxy, 2methylalkyl, 2-methylalkoxy, 2-fluoroalkyl, 2-fluoroalkoxy, 2-(2-ethin)alkyl, 2-(2 20 ethin)-alkoxy, 1,1,1-trifluoro-2-alkyl and 1,1,1-trifluoro2-alkoxy.

Particularly preferred chiral groups are 2-butyl (=1-methylpropyl), 2 methylbutyl, 2-methylpentyl, 3-methylpentyl, 2-ethylhexyl, 2 propylpentyl, in particular 2-methylbutyl, 2-methylbutoxy, 2 25 methylpentoxy, 3methylpentoxy, 2-ethylhexoxy, 1-methylhexoxy, 2 octyloxy, 2-oxa-3methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-hexyl, 2-octyl, 2nonyl, 2-decyl, 2-dodecyl, 6-methoxyoctoxy, 6 methyloctoxy, 6-methyloctanoyloxy, 5-methylheptyloxycarbonyl, 2 methylbutyryloxy, 3-m ethylva le royl oxy, 4- methyl hexanoyloxy, 2 30 chlorpropionyloxy, 2chloro-3-methylbutyryloxy, 2-chloro-4 methylvaleryloxy, 2-chloro-3methylvaleryloxy, 2-methyl-3-oxapentyl, 2-methyl-3-oxahexyl, 1methoxypropyl-2-oxy, 1-ethoxypropyl-2-oxy, 1-propoxypropyl-2-oxy, 1butoxypropyl-2-oxy, 2-fluorooctyloxy, 2 fluorodecyloxy, 1,1,1-trifluoro-2octyloxy, 1,1,1-trifluoro-2-octyl, 2 35 fluoromethyloctyloxy for example. Very preferred are 2-hexyl, 2-octyl,

- 19 2-octyloxy, 1,1,1-trifluoro-2-hexyl, 1,1,1-trifluoro-2-octyl and 1,1, 1 trifluoro-2-octyloxy. In addition, compounds containing an achiral branched group R may 5 occasionally be of importance, for example, due to a reduction in the tendency towards crystallization. Branched groups of this type generally do not contain more than one chain branch. Preferred achiral branched groups are isopropyl, isobutyl (=methylpropyl), isopentyl (=3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3 1 0 methylbutoxy.

The polymerisable or reactive group P is preferably selected from o 15 CH2=CW1-cOo, W HO-CH- W242(CH2)k,-O CH2=CW2 ( )k1-, CH3-CH=CH-O-, (CH2=CH)2CH-OCO-, (CH2=CH-CH2)2CH OCO-, (CH2=CH)2CH-O-, (CH2=CH-CH2)2N-, Ho-CW2W3-, HS CW2W3-, HW2N-, Ho-CW2W3-NH-, CH2=CW1-CO-NH-, CH2=CH (COO)k,Phe-(O)k2-, Phe-CH =C H-, HOOC-, OCN-, and W4W5W6Si-, 20 with W1 being H. Cl, ON, phenyl or alkyl with 1 to 5 C-atoms, in particular H. Cl or CH3, w2 and W3 being independently of each other H or alkyl with 1 to 5 Catoms, in particular methyl, ethyl or n propyl, W4, Ws and w6 being independently of each other Cl, oxaalkyl or oxacarbonylalkyl with 1 to 5 C-atoms, Phe being 1,4 25 phenylene and k1 and k2 being independently of each other 0 or 1.

Especially preferably P is a vinyl group, an acrylate group, a methacrylate group, an oxetane group or an epoxy group, especially preferably an acrylate or methacrylate group.

For the spacer Sp all groups can be used that are known for this purpose to those skilled in the art. The spacer group Sp is preferably a linear or branched alkylene group having 1 to 20 C atoms, in particular 1 to 12 C atoms, in which, in addition, one or more non 35 adjacent CH2 groups may be replaced by -O-, -S-, -NH-, -N(CH3)-,

- 20 CO-, -O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-, -CH(halogen)-, C(halogen)2, -CH(CN)-, -CH=CH- or-C_C-,or a siloxane group.

Typical spacer groups are for example -(CH2)p-, -(CH2CH2O)r-CH2CH2-, 5 CH2CH2-S-CH2CH2- or-CH2CH2-NH-CH2CH2- or -(SiR R -O)p-, with p being an integer from 2 to 12, r being an integer from 1 to 3 and R and R having the meanings given in formula 1.

Preferred spacer groups are ethylene, propylene, butylene, 10 pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyl iminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene for example.

Further preferred are compounds with one or two groups P-Sp wherein Sp is a single bond. In case of compounds with two or more groups P-Sp, each of the polymerisable groups P and the spacer groups Sp can be identical or different.

In another preferred embodiment the spacer group Sp is a chiral group of formula IV: -Q'-CH-Q4

25 1 Q3 IV wherein 30 O' and Q3 have the meanings given in formula lil, and Q4 is an alkylene or alkylene-oxy group with 1 to 10 C atoms or a single bond, being different from Q, 35 with Q' being linked to the polymerizable group P.

- 21 Particularly preferred compounds of formula I are those of the following formulae \NR la N/ \U R lb Nit \U R lo 20 IN - +N) ' k I Id /N le N U' 30 N FIR If 35:+Nalkyl 19

- 22 N \O-alkyl Ih (CH2)n-P i; 15 (CH2)n-P I k Nit U OOC (CH2)nP Im ION S IS ( )m(cH2)nP I n N U' /N\53 (o)m-(cH2)n-p lo \>) O(CH2)n-p I P

e - 23 \ N>O-alkyl Iq ú \ = OR I r N\ \ =\ r CO R ts NO wherein R has one of the meanings of formula I and is preferably straight chain alkyl or alkoxy with 1 to 8 C-atoms or alkenyl with 2 to 7 C-atoms, U' has one of the meanings of U' in formula I and is preferably H or alkyl with 1, 2 or 3 C-atoms, very preferably methyl, 20 'alkyl' is a straight chain alkyl group with 1 to 12 C-atoms, wherein in formula Id compounds wherein both alkyl denote methyl are excluded, P has one of the meanings given above and below, L', L2 and L3 are H or F. m is O or 1, and n is an integer from 1 to 12. The aromatic rings in 25 formula la to Ip are optionally substituted with 1, 2 or 3 groups L as defined above.

The compounds of formula I can be synthesized according to or in analogy to methods which are known per se and which are described in standard works of organic chemistry such as, for example, 30 Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart. Some specific and preferred methods are described in the reaction schemes below. Further methods can be taken from the examples.

35 Scheme 1:

- 24 N-Nxs Br2 IN1. NEt3 IN | A)' | \Br | \> Br Nit-N an NaOH // 2N2. Me2SO4 At-N\ 3 5 E= C5H

10 -IN≥

Scheme 2: \ Br + N N \ N N NO \ NO

3 5 6

Scheme 3: N Br HO IN= | Suzuki 30 < F

NN\- Scheme 4:

- 25 N, F 5 NBr HO Suzuki N g F 10 In=-it' Scheme 5: 1' 5 N Net- + O-(CH2) 6 OF l Sonogashira Ned, O NS=O-(CH2)6 out For the applications described above the LC media preferably contain at least one compound of formula 1, and a nematic host mixture comprising one or more nematic or nematogenic 30 compounds. Preferably the LC media consist of 2 to 25, preferably 3 to 15 compounds, at least one of which is a compound of formula I or 11.

The other compounds, forming the nematic host mixture, are 35 preferably low molecular weight liquid crystal compounds selected from nematic or nematogenic substances, for example from the known classes of the azoxybenzenes, benzylidene-anilines,

- 26 biphenyls, terphenyls, phenyl or cyclohexyl benzoates, phenyl or cyclohexyl esters of cyclohehexanecarboxylic acid, phenyl or cyclohexyl esters of cyclohexylbenzoic acid, phenyl or cyclohexyl esters of cyclohexylcyclohexanecarboxylic acid, cyclohexylphenyl 5 esters of benzoic acid, of cyclohexanecarboxylic acid and of cyclo hexylcyclohexanecarboxylic acid, phenylcyclohexanes, cyclohexyl biphenyls, phenylcyclohexylcyclohexanes, cyclohexylcyclohexanes, cyclohexylcyclohexenes, cyclohexylcyclohexylcyclohexenes, 1,4-bis cyclohexylbenzenes, 4,4'-bis-cyclohexylbiphenyls, phenyl- or cyclo 10 hexylpyrimidines, phenyl- or cyclohexylpyridines, phenyl- or cyclo hexylpyridazines, phenyl- or cyclohexyidioxanes, phenyl- or cyclo hexyl-1, 3-dithianes, 1,2-diphenyl-ethanes, 1,2-dicyclohexylethanes, 1-phenyl-2cyclohexylethanes, 1-cyclohexyl-2-(4-phenylcyclohexyl) ethanes, 1cyclohexyl-2-biphenyl-ethanes, 1-phenyl2-cyclohexyl 15 phenylethanes, optionally halogenated stilbenes, benzyl phenyl ether, tolanes, substituted cinnamic acids and further classes of nematic or nematogenic substances. The 1,4-phenylene groups in these compounds may also be laterally mono- or difluorinated.

20 The most important compounds that are possible as components of these LC mixtures can be characterized by the following formula R'-L'-G'-E-R"

25 wherein L' and E, which may be identical or different, are in each case, independently from one another, a bivalent radical from the group formed by -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -BPhe- and -B-Cyc- and their mirror images, where Phe is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans 30 1,4-cyclohexylene or 1,4-cyclohexenylene, Pyr is pyrimidine-2,5-dlyl or pyridine-2,5-dlyl, Dio is 1,3-dioxane-2,5-dlyl abd B is 2-(trans-1,4 cyclohexyl)ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 1,3-dioxane 2,5-dlyl. 35 G' in these compounds is selected from the following bivalent groups -CH=CH-, N(0)N-, -CH=CY-, -CH=N(0)-, -C-C-, -CH2-CH2-,

- 27 -CO-O-, -CH2-O-, -CO-S-, -CH2-S-, -CH=N-, -COO-Phe-COO- or a single bond, with Y being halogen, preferably chlorine, or -CN.

R' and R" are, in each case, independently of one another, alkyl, 5 alkenyl, alkoxy, alkenyloxy, alkanoyloxy, alkoxycarbonyl or alkoxycarbonyloxy with 1 to 18, preferably 3 to 12 C atoms, or alternatively one of R' and R" is F. CF3, OCF3, Cl, NCS or ON.

In most of these compounds R' and R" are, in each case, 10 independently of each another, alkyl, alkenyl or alkoxy with different chain length, wherein the sum of C atoms in nematic media generally is between 2 and 9, preferably between 2 and 7.

Many of these compounds or mixtures thereof are commercially 15 available. All of these compounds are either known or can be prepared by methods which are known per se, as described in the literature (for example in the standard works such as Houben-Weyl, Methoden der Organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction 20 conditions which are known and suitable for said reactions. Use may also be made here of variants which are known per se, but are not mentioned here.

Examples of suitable polymerisable mesogenic compounds that can 25 be used as comonomers together with the compounds of formula I in a polymerisable LC mixture, are disclosed for example in WO 93/22397, EP 0 261 712, DE 195 04 224, WO 95/22586, WO

97/00600 and GB 2 351 734. The compounds disclosed in these documents, however, are to be regarded merely as examples that 30 shall not limit the scope of this invention.

Preferably the polymerizable LC mixture comprises at least one polymerisable mesogenic compound having one polymerisable functional group and at least one polymerisable mesogenic 35 compound having two or more polymerisable functional groups.

- 28 Examples of especially useful chiral and achiral polymerisable mesogenic comonomers are shown in the following lists which should, however, be taken only as illustrative and is in no way intended to restrict, but instead to explain the present invention: P-(CH2)xO COO Y (Va) 10 P-(CH2)xO COO By (Vb) P-(CH2)XO COO By} R (Vc) P-(CH2)xO COO R (Vd) P-(CH2)XO CH=CH-COO R (Ve) 25 P(CH2)x-O = vR (Vf) P(CH2)xOz = (Vg) P-(CH2)XO R

(F) (F) (F) (Vh) 35 P-(CH2)X03Coo{], CH2CH(CH3)C2H5 (Vi)

- 29 P-(CH2)x 3 COO COO CH2CH(CH3)C2H5 (Vk) P-(CH2)xo 3 COO-Ter (Vm) P(CH2)x \3 COO-Chol 10 (Vn) P-(CH2)xo 3 COO I! (Vo) 15 L' L;

P(CH2)x coo oco o(cH2)yP (Via) L' L2 P(CH2)XO 3 CH2CH2 CH2CH2 O(CH2)yP L1 L2 25 I/\/\: oóCo26O2c43o - (Vlc) P(CH2)x CH=CHCOO9, O 30 OOCCH=CH (> O(CH2)yP

- 30 P(CHz)xO '3 O(CHz)yP wherein P has one of the meanings of formula I and its preferred meanings as mentioned above, x and y are identical or different 10 integers from 1 to 12, A and D are 1,4-phenylene or 1,4 cyclohexylene, v is 0 or 1, Y is a polar group, R is a non-polar alkyl or alkoxy group, Ter is a terpenoid radical like e.g. menthyl, Chol is a cholesterol group, the phenylene rings in formulae Va to Vlc may also be substituted by 1, 2, 3 or 4 groups L4, in particular mono- or 15 difluorinated, and L' and L2 are each independently H. F. Cl, OH, CN, NO2 or optionally alkyl, alkoxy, alkylcarbonyl or alkoxycarbonyl with 1 to 7 C atoms.

The term 'polar group' in this connection means a group selected from 20 F. Cl, CN, NO2, OH, OCH3, OCN, SON, an optionally fluorinated carbonyl or carboxyl group with up to 4 C atoms or a mono- oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4 C atoms. The term 'non polar group' means an alkyl group with 1 or more, preferably 1 to 12 C atoms or an alkoxy group with 2 or more, preferably 2 to 12 C atoms.

The polymerisable LC mixtures according to the present invention may also comprise one or more non-reactive chiral dopants in addition or alternatively to chiral polymerisable mesogenic compounds. Typically used chiral dopants are e.g. the commercially 30 available R or S 811, R or S 1011, R or S 2011 or CB 15 (from Merck KGaA, Darmstadt, Germany). Very preferred are chiral dopants with a high helical twisting power (HTP), in particular dopants comprising a sorbitol group as described in WO 98/00428, dopants comprising a hydrobenzoin group as described in GB 2, 328,207, chiral binaphthyl 35 derivatives as described in WO 02/94805, chiral binaphthol acetal derivatives as described in WO 02/34739, chiral TADDOL derivatives

- 31 as described in WO 02/06265, and chiral dopants with at least one fluorinated linkage group and a terminal or central chiral group as described in WO 02/06196 and WO 02/06195.

5 To prepare anisotropic polymer films, the polymerisable LC mixture is preferably coated onto a substrate, aligned and polymerised in situ, for example by exposure to heat or actinic radiation, to fix the orientation of the LC molecules. Alignment and curing are carried out in the LC phase of the mixture. This technique is well-known in the 10 art and is generally described for example in D.J. Broer, et al., Angew. Makromol. Chem.183, (1990),45-66.

Alignment of the LC material can be achieved for example by treatment of the substrate onto which the material is coated, by 15 shearing the material during or after coating, by application of a magnetic or electric field to the coated material, or by the addition of

surface-active compounds to the LC material. Reviews of alignment techniques are given for example by 1. Sage in "Thermotropic Liquid Crystals", edited by G. W. Gray, John Wiley & Sons, 1987, pages 75 20 77, and by T. Uchida and H. Seki in "Liquid Crystals - Applications and Uses Vol. 3", edited by B. Bahadur, World Scientific Publishing, Singapore 1992, pages 1-63. A review of alignment materials and techniques is given by J. Cognard, Mol. Cryst. Liq. Cryst. 78, Supplement 1 (1981), pages 177.

Polymerisation takes place by exposure to heat or actinic radiation.

Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays or irradiation with high energy particles, such as ions or electrons. Preferably 30 polymerization is carried out by UV irradiation at a non-absorbing wavelength. As a source for actinic radiation for example a single UV lamp or a set of UV lamps can be used. When using a high lamp power the curing time can be reduced. Another possible source for actinic radiation is a laser, like e.g. a UV laser, an IR laser or a visible 35 laser.

- 32 Polymerisation is preferably carried out in the presence of an initiator absorbing at the wavelength of the actinic radiation. For example, when polymerizing by means of UV light, a photoinitiator can be used that decomposes under UV irradiation to produce free radicals or 5 ions that start the polymerization reaction. When curing polymerisable materials with acrylate or methacrylate groups, preferably a radical photoinitiator is used, when curing polymerisable materials with vinyl, epoxide and oxetane groups, preferably a cationic photoinitiator is used. It is also possible to use a 10 polymerization initiator that decomposes when heated to produce free radicals or ions that start the polymerization. As a photoinitiator for radical polymerization for example the commercially available Irgacure 651, Irgacure 184, Darocure 1173 or Darocure 4205 (all from Ciba Geigy AG) can be used, whereas in case of cationic 15 photopolymerisation the commercially available UVI 6974 (Union Carbide) can be used.

The polymerisable material can additionally comprise one or more other suitable components such as, for example, catalysts, sensitizers, 20 stabilizers, inhibitors, chain-transfer agents, co-reacting monomers, surface-active compounds, lubricating agents, wetting agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes or pigments.

The examples below serve to illustrate the invention without limiting it. In the foregoing and the following, all temperatures are given in degrees Celsius, and all percentages are by weight, unless stated otherwise. Example 1

1-Methyl-2-(4-pentylphenylethynyl)-4,5-dicyanoimidazole (4) is prepared by the method described by Paul G. Apen and Paul G. 35 Rasmussen in Heterocycles, 29, 1989, according to reaction scheme 1 above.

- 33 \ 2-Bromo-4,5-dicvanoimidazole (2): 4,5-Dicyanoimidazole (25.0 9,0. 212 mol) and sodium hydroxide solution (2.0 g in 500 ml water) were stirred at room temperature.

10 Bromine (38 ml, 0.74 mol) was dripped in over 1 hour, the mixture was left to stir over night at room temperature, then acidified with dilute hydrochloric acid. The off-white solid was filtered, rinsed with water and then recrystallized from boiling water to give yellow needles (40.9 g, 98%) GCMS: Purity = 100%, M+ = 196,198 (M, M+2),171,169.

1-methyl-2-bromo-4 5,-dicyanoimidazole (3): 20 Triethylamine (14.2 ml,0. 102 mol) was added to a flask containing the bromo compound (20.0 g, 0. 102 mol) in THF (120 ml). After stirring for 1 h at room temperature, the mixture was cooled to 0 C, and dimethyl sulphate (9.7 ml, 0.102 mol) was added dropwise over 1 hour. The reaction mixture was stirred over night. THF was 25 removed on a rotary evaporator to leave a yellow oil. Water was added to the oil, a whitish solid precipitate was formed, which was removed by filtration and dried in a vacuum oven. The solid was recrystallized from ethanol to give white needles (19.2 g, 89%) 30 1 methvl-2-(4-pentylohenvlethynvl)-4,5-dicvanoimiazole (4): 4Pentylphenylacetylene (4.1 g, 0.024 mol), copper (1) iodide (0.1g), palladium bis(triphenylphoshine) dichloride (0.3 g),1-methyl-2 bromo-4,5,dicyanoimidazole (5.0 g, 0.024 mol), triethylamine (10 ml) 35 and THF (30 ml)were stirred under nitrogen at 40 C.

- 34 After 16 h, the mixture was cooled to room temperature, and poured in to dilute hydrochloric acid. The solution was extracted with DCM.

The DCM layer was removed, washed with water and dried over sodium sulphate. The dry solution was evaporated to dryness on a 5 rotary evaporator to leave a residual brown solid.

Purification was achieved by flash column chromatography using petrol:DCM (1:1) as eluant. Evaporation of the appropriate fractions gave the desired product as a white solid (5.1 9,70%). 'H and '3C 10 NMR gave expected signals.

Example 2

1-Methyl-2-(4-propylphenyl)-4,5-dicyanoimiazole (7) is prepared by 15 Suzuki coupling (see reaction scheme 3) as shown below.

o 20 NBr \/ 3 Ethylphenylboronic acid (0.914 9,6.092 mmol),1-methyl-2bromo 4,5-dicyanoimidazole (1.286 9, 6.092 mmol), water (3 ml), sodium 25 metaborate octahydrate (1.287 9, 6.092 mmol), Pd(PPh3)2CI2 (0.025 9) and hydrazine hydrate(O.001 9) were stirred in tetrahydrofuran (5 ml) under reflux for 16 hours. After 16 h, the mixture was cooled to room temperature, and poured in to brine.

The solution was extracted with DCM. The DCM layer was removed, 30 washed with water and dried over sodium sulphate. The dry solution was evaporated to dryness on a rotary evaporator. Purification was achieved by flash column chromatography to give upon evaporation of the appropriate fractions a white solid. GCMS showed the mass ion of 236. NMR spectroscopy showed expected signals.

Claims (18)

in - 35 Claims

1. Use of a compound comprising at least one 4,5 dicyanoimidazole group as a mesogenic or liquid crystalline 5 material in liquid crystal media, liquid crystal devices, anisotropic polymers, optical, electrooptical, decorative, security, cosmetic, diagnostic, electric, electronic, charge transport, semiconductor, optical recording, electroluminescent, photoconductor or electrophotographic applications.

2. Use according to claim 1, characterized in that the 4,5 dicyanoimidazole group is selected from groups of formula (1) Nay 15 C N\ (1)

N''kC U 20 wherein U is H or an optionally substituted aliphatic, cycloaliphatic or aromatic group with up to 20 C atoms that optionally comprises one or more hetero atoms and optionally comprises fused rings, or -N(U)- is -N -.

25

3. Use according to claim 1, characterized in that the compounds comprising at least one 4,5-dicyanoimidazole group are selected from compounds of formula I N<c 30 i:Z'-A'-(Z2-A2)m R 1 N''C 35 wherein

- 36 A' and A2 are independently of each other an aromatic or alicyclic ring, or a group comprising two or more fused aromatic or alicyclic rings, wherein these rings optionally contain one or more hetero atoms 5 selected from N. O and S. and are optionally mono or polysubstituted by L, and, if Z' is a single bond, A' may also form a zwitterion with the 4, 5 dicyanoimidazole group, 10 L is F. Cl, Br, I, CN, NO2 or alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl or alkylcarbonlyoxy with 1 to 7 C atoms, wherein one or more H atoms are optionally substituted by F or Cl, 15 Z' and Z2 are independently of each other -O-, -S-, -CO-, COO-, -OCO-, -S-CO, -CO-S-, -O-COO-, -CO

NR -, -NR -CO-, -OCH2-, -CH2O-, -SCH2-, -CH2S-,

CF2O-, -oCF2-, -CF2S-, -SCF2-' -CH2CH2-, CF2CH2-, -CH2CF2-, -CF2CF2-, CH=N-, -N=CH-,

20 N=N-,-CH=CR0-,-CY4=CY2-,-C_C-,-CH=CH

COO-, -OCO-CH=CH- or a single bond, Y' and y2 are independently of each other H. F. Cl or CN, 25 R is H. F. Cl, Br, I, CN, NO2, NCS, SF5 or straight chain or branched alkyl with 1 to 20 C-atoms, which is unsubstituted, mono- or poly-substituted by F. Cl, Br, I or CN, and wherein one or more non-adjacent CH2 groups are optionally replaced, in each case 30 independently from one another, by -O-, -S-, -NH-, N R -, Si R R -, -CO-, -COO-, -OCO-, -OCO-O-, S-CO-, -CO-S-, -CY'=CY2- or-C_Cin such a manner that O and/or S atoms are not linked directly to one another, or denotes P-Sp-X,

e - 37 R and R are independently of each other H or alkyl with 1 to 1 2 C-atoms, U' has one of the meanings of R. or -N(U')- is -N -, P is a polymerisable or reactive group, Sp is a spacer group or a single bond, 10 X is a linkage group or a single bond, and m is 0, 1 or 2.

4. A 4,5-dicyanoimidazole derivative of formula I NO ó \> Z1 A1-(Z2-A2)mR I N 20 N''kC u1 wherein A,, A2, z', Z2, R. U. and m have the meanings given in claim 3, with the provisos that 25 a) if m is 0, U' is H or alkyl, Z1 is a single bond and A1 is phenyl, then R is P-Sp-X or alkyl as defined in formula I with more than 2 C-atoms, b) if m is 0, R is not PSp-X and Z1-A1 is phenylene, then U1 is H or unsubstituted alkyl or-N(U')is -N--, 30 c) if m is 0 or 1, U' is H or alkyl and R is not P-Sp-X, then -Z' A'-(Z2-A2)m-R is not biphenyl, phenethyl, styryl, phenoxyphenyl, benzyloxyphenyl, substituted or unsubstituted furyl or pyrrolyl or unsubstituted pyridinyl, e) if m is 1, U' is H or alkyl, R is not P-Sp-X, Z1 is a single bond, Z2 iS O or S and A, is phenylene, then A2 is not benzthiazole, pyridine or pyrimidine,

pt - 38 fl if m is 1, U1 is H or alkyl, Z' is a O. S or a single bond, Z2 iS a single bond, A1 is a nitrogen containing heteroaromatic group and A2 is substituted phenylene or pyridine, then R is P-Sp-X or alkyl as defined in formula I with more than 2 C-atoms,

5 A 4,5-dicyanoimidazole derivative according to claim 4, characterized in that A1 and A2 are selected from furane-2,5 dlyl, thiophene-2,5-dlyl, thienothiophene-2,5- dlyl, dithienothiophene-2,6-dlyl, pyrrol-2,5-diyl, 1,4-phenylene, 10 azulene-2,6-diyl, pyridine-2,5-diyl, pyrimidine-2,5-diyl, naphthalene2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-dlyl, indane-2,5-dlyl, or 1,4cyclohexylene wherein one or two non adjacent CH2 groups are optionally replaced by O and/or S. wherein these groups are unsubstituted, mono- or 15 polysubstituted by L as defined in claim 3.

6. A 4,s-dicyanoimidazole derivative according to claim 4 or 5, characterized in that Z' is a single bond and A1 is an unsaturated heterocyclic group comprising at least one N atom, 20 which is linked via an N atom to the 4,5-dicyanoimidazole group to form a zwitterion.

7. A 4,5-dicyanoimidazole derivative according to at least one of claims 4 to 6, characterized in that -A1-(Z2-A2)m- is selected from 25 the following formulae and their mirror images (L)r -N I lb

- 39 (L)r (L)r no 5 (L)r (L)r SCOOT lid 1 0 (L)r (L)r He 15 llf 20 kg wherein L has the meaning of formula I and r is 0, 1, 2, 3 or 4.

25 A 4,5-dicyanoimidazole derivative according to at least one of claims 4 to 7, characterized in that R is P-Sp-X.

9 A 4,5-dicyanoimidazole derivative according to at least one of claims 4 to 7, characterized in that R is straight chain alkyl, alkenyl 30 or al koxy with u p to 1 2 C atoms.

10. A 4,5-dicyanoimidazole derivative according to at least one of claims 4 to 9, characterized in that it is selected from the following formulae

po - 40 :N>R la MEN\ MAR lb [:N>_ = OR ic MEN N\alikkyl Id 20 Nat >R le Ut 25 N; ó N)R If U' 30 Nit ó \ - N>alkyl 19

-41 óN: Ih N// \ \O-alkyl IN= > (CH2)nP

li DIN = 0(CH2)nP Ik ≥OOCóO(CH2) n-p Im 20 KIN >( )m(CH2)nP In N U' 25 N)S ( )m-(CH2)n-P lo N U' /ó O(CH2) nP Ip N U'

- 42 O-alkyl Iq N\ I r No wherein R has one of the meanings of formula 1, U' has one of the meanings of U. in formula 1, 'alkyl' is a straight chain alkyl group with 1 to

12 C-atoms, wherein in formula Id compounds wherein both alkyl denote methyl are excluded, P has one of the 20 meanings given in formula 1, L', L2 and L3 are H or F. m is O or 1, n is an integer from 1 to 12, and the aromatic rings in formula la to Ip are optionally substituted with 1, 2 or 3 groups L as defined in formula 1.

25 11. A liquid crystal medium, characterized in that it comprises at least one compound comprising at least one 4,5-dicyanoimidazole group or at least one compound according to at least one of claims 2 to 10.

30 12. A liquid crystal medium according to claim 11, characterized in that comprises at least one polymerisable compound.

13. A polymer obtained by polymerising a 4,5-dicyanoimidazole derivative according to at least one of claims 2 to 10 compnsng 35 at least one polymerisable group, or a liquid crystal medium according to claim 12.

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14 An anisotropic polymer obtained by polymerising a 4,5 dicyanoimidazole derivative according to at least one of claims 2 to 10 comprising at least one polymerisable group, or a liquid 5 crystal medium according to claim 12, in its oriented state.

15. Use of a 4,5-dicyanoimidazole derivative, a polymer or a polymer film according to at least one of claims 1 to 14 in electrooptical displays, liquid crystal displays, optical films, 10 polarisers, compensators, beam splitters, reflective films, alignment layers, colour filters, holographic elements, hot stamping foils, coloured images, decorative or security markings, liquid crystal pigments, adhesives, synthetic resins with anisotropic mechanical properties, cosmetics, diagnostics, 15 nonlinear optics, optical information storage, as chiral dopants, in electronic devices like for example field effect transistors

(FET) as components of integrated circuitry, as thin film transistors in flat panel display applications or for Radio Frequency Identification (RFID) tags, or in semiconducting 20 components for organic light emitting diode (OLED) applications, electroluminescent displays or backlights of liquid crystal displays, for photovoltaic or sensor devices, as electrode materials in batteries, as photoconductors, or for electrophotographic applications or electrophotographic 25 recording.

16. A liquid crystal device, characterized in that it comprises a 4,5-

dicyanoimidazole derivative, liquid crystal medium, polymer or polymer film according to at least one of claims 1 to 14.

17. A liquid crystal device according to claim 16, characterized in that it is a display of the TN, STN or isotropic mode.

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18. A 4,5-dicyanoimidazole derivative substantially as hereinbefore described with reference to Examples 1 and 2.