Liquid crystal compounds

Abstract

Compound of formula I, wherein group R 1 and R 2 It has the meaning indicated in claim 1. It includes the preparation method thereof, a liquid crystal medium comprising at least one compound of formula I, and an energy-saving electro-optical display containing such a liquid crystal medium.

Description

[0001] This invention relates to compounds of formula I.

[0002]

[0003] Wherein group R 1 and R 2 It is as defined below and in the claims (acyclic groups, such as alkyl groups). Furthermore, the invention includes methods for preparing compounds of formula I, liquid crystal media comprising at least one compound of formula I, and their use as one or more components in a liquid crystal medium. Furthermore, the invention relates to liquid crystal and electro-optic display elements containing liquid crystal media according to the invention.

[0004] In recent years, the application fields of liquid crystal compounds have significantly expanded to various types of display devices, electro-optical devices, electronic components, sensors, etc. For this reason, a large number of different structures have been proposed, especially in the field of nematic liquid crystals. To date, nematic liquid crystal mixtures have been found to have the widest range of applications in flat panel display devices. They have been particularly used in passive TN or STN matrix displays or in systems with TFT active matrices.

[0005] The liquid crystal compounds according to the present invention can be used as one or more components of a liquid crystal medium, particularly for displays based on the torsional liquid crystal cell principle, guest-subject effect, deformation effect of alignment phase DAP or ECB (electrically controlled birefringence), IPS (in-plane conversion) effect or dynamic scattering effect.

[0006] Liquid crystal compounds used in electro-optic applications typically possess a certain polarity, particularly dielectric anisotropy (Δε), so that they can be oriented by an electric field. Furthermore, various nonpolar liquid crystal compounds exist to be mixed with the liquid crystal phase to improve other properties. Commonly used typical nonpolar compounds have, for example, structures selected from bicyclohexane or biphenyl:

[0007]

[0008] The following partially hydrogenated indacene derivative is described in specification DE3908269A1.

[0009]

[0010] The object of this invention is to find new, stable compounds suitable as one or more components of a liquid crystal medium. In particular, the compound should simultaneously possess relatively low viscosity and sufficient solubility. For many current mixture concepts in the field of liquid crystals, it is advantageous to use a combination of compounds with strong positive dielectric anisotropy Δε and compounds with particularly low viscosity, because it is almost impossible to find a compound with an ideal combination of all the desired properties.

[0011] Given the very wide range of applications for this type of compound with low viscosity, it is desirable to provide other compounds that have properties precisely tailored to their respective applications.

[0012] Therefore, the object of this invention is to find new stable compounds suitable as one or more components of liquid crystal media, particularly for liquid crystal media used in, for example, VA, PS-VA, IPS, FFS, TN, STN and TN-TFT displays.

[0013] Furthermore, under the dominant conditions in the application field, the compounds according to the invention should be thermally and photochemically stable. As mesogens, they should contribute to a broad nematic phase in mixtures formed with liquid crystal co-components and exhibit excellent miscibility with nematic base mixtures, especially at low temperatures. For most applications, preferred compounds are those that facilitate the formation of nematic liquid crystal phases at different temperatures. Substances with low melting points and low enthalpy of fusion are also preferred, as these parameters are indicators of the desired properties mentioned above, such as high solubility in combination with other liquid crystal components, a broad liquid crystal phase in the mixture, and a low tendency for spontaneous crystallization in the mixture at low temperatures. In particular, solubility at low temperatures while avoiding any crystallization is important for the safe operation and transportation of displays in motor vehicles and aircraft, as well as outdoors.

[0014] Surprisingly, the compounds according to the invention have been found to be extremely suitable as components of liquid crystal media. They can be used to obtain liquid crystal media for displays that have low viscosity and therefore short response times. The compounds according to the invention possess sufficient stability and are colorless. Furthermore, they exhibit high elastic constant values ​​(K0). 11 / K 22 / K 33 This is particularly important in terms of lower power consumption in displays. This results in media with short response times and high contrast, and displays with low energy consumption—the energy-saving applications of the compound. Additionally, the compound has a lower vapor pressure compared to bicyclohexane, which has a considerably clearer point, improving the suitability of the mixture for operation under reduced pressure. This includes, for example, the use of the compound in avionics, such as cockpit displays.

[0015] By providing the compounds according to the invention, the range of liquid crystal materials suitable for preparing liquid crystal mixtures from a variety of application perspectives is significantly expanded in a very general way.

[0016] Compounds of Formula I have a wide range of applications. Generally, liquid crystal base materials from other compound classes are added to the compounds according to the invention to, for example, influence the dielectric anisotropy and / or optical anisotropy of this type of dielectric and / or optimize its threshold voltage and / or viscosity.

[0017] This invention therefore relates to compounds of formula I.

[0018]

[0019] in

[0020] R 1 This indicates an alkyl group having 1 to 15 carbon atoms, wherein one or more CH2 groups in the group, including the terminal carbon atom, may in each case be independently converted to -C≡C-, -CH=CH-, -O-, -S-, -CO-O-, or -O-CO- are substituted in a manner in which the O / S atoms are not directly connected to each other, and one or more H atoms may also be substituted with halogens.

[0021] R 2 Represents H or an alkyl group having 1 to 15 carbon atoms, wherein one or more CH2 groups in the group, including the terminal carbon atom, may in each case be independently converted to -C≡C-, -CH=CH-, -O-, -S-, -CO-O-, or -O-CO- are substituted in a manner in which the O / S atoms are not directly connected to each other, and one or more of the H atoms may also be substituted with halogens.

[0022] Preferably,

[0023] R 2 This indicates an alkyl group having 1 to 15 carbon atoms, wherein one or more CH2 groups in the group, including the terminal carbon atom, may in each case be independently modified by -C≡C-, -CH=CH-, -O-, -S-, -CO-O-, or -O-CO- are replaced by O / S atoms that are not directly connected to each other, and one or more H atoms may also be replaced by halogens.

[0024] The present invention further relates to the use of compounds of formula I in liquid crystal media.

[0025] The present invention also relates to a liquid crystal medium having at least two liquid crystal components, wherein the liquid crystal components comprise at least one compound of formula I.

[0026] Compound I contains a perhydro-s-indidazolium as a structural element. In its pure state, compound I is colorless and, advantageously within a temperature range suitable for electro-optic applications, forms a liquid crystal mesocrystalline phase, either directly or in a mixture. The compounds according to the invention enable a wide range of nematic phases. In liquid crystal mixtures, the substances according to the invention significantly reduce rotational viscosity. Furthermore, the compounds are characterized by good UV stability.

[0027] In a preferred embodiment of the present invention, the end base R 1 and R 2 In each case, it independently represents an alkyl group having up to 8 carbon atoms, wherein one or more CH2 groups in the group, including the terminal carbon atom, may also be independently represented by -CH=CH- in each case. Substitution, and one or more of the H atoms can also be substituted by halogens.

[0028] Group R in Formula I and its sub-formulas 1 Preferably, it represents an alkyl or alkenyl group having up to 8 carbon atoms. R 1 Particularly preferred are straight-chain alkyl groups having 1 to 7 carbon atoms or unbranched alkenyl groups having 2 to 8 carbon atoms, especially unbranched alkyl groups having 2 to 7 carbon atoms.

[0029] For ease of synthesis, it is preferred that the group R 1 and R 2 They are the same. In applications such as low melting point performance, it is preferred that the two groups R... 1 and R 2 They are different. For example, they can be composed of straight-chain alkyl groups with different numbers of carbon atoms.

[0030] Contains branched or substituted flanking groups R 1 Compounds of formula I are sometimes important due to their better solubility in commonly used liquid crystal base materials. Group R 1 The preferred option is a linear chain.

[0031] Group R 1 The following structural parts are particularly preferred:

[0032] -CH3

[0033] -C2H5

[0034] -C3H7

[0035] -C4H9

[0036] -C5H 11

[0037] -C6H 13

[0038] -CH=CH2

[0039] -CH=CH2-CH3

[0040] -CH2-CH=CH2

[0041] -CH2-CH=CH-CH3

[0042] -CH2-CH2-CH=CH2

[0043] -CH2-CH2-CH=CH-CH3

[0044] The alkyl chain is preferably unbranched (n-alkyl).

[0045] Optional group R 1 It is selected from cyclopentyl, 2-fluoroethyl, cyclopropylmethyl, cyclopentylmethyl, cyclopentylmethoxy, cyclobutylmethyl, 2-methylcyclopropyl, 2-methylcyclobutyl and 2-alkoxyethoxy.

[0046] The end group R 1 Particularly preferred are methyl, ethyl, n-propyl, n-butyl, or n-pentyl. Independently, the terminal group R... 2 Especially preferred are ethyl, n-propyl, n-butyl, or n-pentyl.

[0047] The selected compounds of formula I are those of formulas I-1 to I-43:

[0048]

[0049]

[0050]

[0051]

[0052]

[0053] Among the compounds of formulas I-1 to I-43, compounds of formulas I-1 to I-13 are preferred, and in particular compounds of formulas I-4, I-5, I-6, I-7 and I-9.

[0054] The preferred stereochemical configuration of the compound is as follows:

[0055]

[0056] The cyclohexane ring is in a boat-shaped conformation, and

[0057]

[0058] The cyclohexane ring is in a chair conformation. Group R 1 and R 2 They have the meaning indicated by Formula I, or a narrower meaning, or they are selected from groups such as those in Formulas I-1 to I-43.

[0059] Compounds of Formula I are prepared by methods known per se, as described in the literature (e.g., in standard works such as Houben-Weyl, Methoden der Organischen Chemie, Georg-Thieme-Verlag, Stuttgart), more precisely under reaction conditions known and suitable for the stated reactions. Variations known per se, not mentioned in more detail here, may also be used.

[0060] Compounds of Formula I can be advantageously prepared as illustrated in the synthesis and examples (Schemes 1 to 3) described below:

[0061]

[0062] Scheme 1. A general synthetic scheme for preparing compounds of formula I. The group -CH2R corresponds to the group R in formula I. 1 and R 2 Reaction conditions: a) base; b) 1. NaOH, 2. Δ, -CO2, 3. Wolff-Kishner; c) H2 / PtO2, AcOH.

[0063] Isomer 5 (Scheme 2) was obtained by changing the hydrogenation of the benzene ring in two selective hydrogenations.

[0064]

[0065] Option 2. An alternative synthetic route for preparing compound I. Reaction conditions: a) Birch reduction; b) H2 (trans-hydrogenation).

[0066] Compound 2 is first reduced to form cyclohexadiene by Birch reduction, followed by selective trans-hydrogenation. Homogeneous transition metal catalysts (Wilkinson catalysts and the like) are suitable for this purpose.

[0067] Alternatively, by modifying the side group synthesis in Scheme 1, Scheme 3 can be generated, which is used to prepare the corresponding alkoxy compounds.

[0068]

[0069] Scheme 3. A general synthetic scheme for preparing compounds of formula I, wherein R 1 and R 2 This represents an alkoxy group. The group -OR corresponds to the group R in formula I. 1 and R 2 Reaction conditions: a) 1. NaOH, 2. Δ, -CO2; b) 1. Baeyer-Villiger, 2. H2; c) ROH.

[0070] The corresponding starting materials can usually be readily prepared by those skilled in the art using synthetic methods known from the literature, or they are commercially available.

[0071] Instead of the heterogeneous platinum catalyst shown, a trans-selective hydrogenation catalyst may be used to obtain other isomers of Formula I.

[0072] The present invention also relates to a method for preparing a compound of formula I, wherein a compound of formula II is converted into a compound of formula I by hydrogenation of the double bond of the six-membered ring in the ring system of formula II over a metal catalyst.

[0073]

[0074] Where R 1 and R 2 As defined for equation I,

[0075]

[0076] Formula II represents compounds of formula IIa or IIb:

[0077]

[0078] To enable compound II to undergo a catalytic reaction to produce the product of formula I, it is preferable to dissolve compound II in a liquid phase and react it with hydrogen in the presence of a catalyst. Such hydrogenation of the C-C double bond on a heterogeneous or homogeneous dissolved catalyst is well known to those skilled in the art. Suitable catalysts are, in particular, platinum, rhodium, and palladium, and compounds thereof. It is preferable to hydrogenate the aromatic compound of formula IIa on a suitable platinum catalyst on a support material. Alternatively, the compound of formula IIa may also first undergo a Birch reduction on sodium or lithium to form a diene compound of formula IIb. The compound of formula IIb can be hydrogenated relatively readily, for example, at atmospheric pressure on a Wilkinson catalyst. Alternatively, the reduction can be carried out by protonation (e.g., using trifluoroacetic acid) in the presence of a hydride source (e.g., trialkylsilane).

[0079] The reaction methods and reagents used are, in principle, known from the literature. Additional reaction conditions can be obtained from examples.

[0080] Other preferred method variations not mentioned above are disclosed in the embodiments or claims.

[0081] The method and subsequent post-treatment of the reaction mixture can be carried out substantially as a batch reaction or in a continuous reaction process. The continuous reaction process includes, for example, reactions in a continuous stirred tank reactor, a cascade of stirred tank reactors, a circulating or cross-flow reactor, a flow tube, or a microreactor. The reaction mixture may optionally be post-treated as needed by: filtration through a solid phase, chromatography, separation between immiscible phases (e.g., extraction), adsorption onto a solid support, distillation to remove solvent and / or azeotropic mixtures, selective distillation, sublimation, crystallization, co-crystallization, or nanofiltration over a membrane.

[0082] The present invention also relates to a liquid crystal medium comprising one or more compounds of formula I according to the invention. The liquid crystal medium comprises at least two components. These are preferably obtained by mixing the components with each other. The method for preparing a liquid crystal medium according to the invention is therefore characterized by mixing at least one compound of formula I with at least one additional mesocrystalline compound, and optionally adding additives.

[0083] The achievable combination of clearing point, viscosity at low temperature, thermal / UV stability, dielectric anisotropy, response time, and contrast is far superior to previous materials from existing technologies.

[0084] The liquid crystal medium according to the invention preferably contains, in addition to one or more compounds according to the invention, 2 to 40, particularly preferably 4 to 30, components as additional ingredients. Specifically, these media contain, in addition to one or more compounds according to the invention, 7 to 25 components. These additional ingredients are preferably selected from nematogenic (univariant or isotropic) substances, particularly from substances of the following categories: azobenzene, benzyl aniline, biphenyl, terphenyl, phenyl benzoate or cyclohexyl benzoate, phenyl cyclohexanecarboxylate or cyclohexanecarboxylate, phenyl cyclohexylbenzoate or cyclohexyl benzoate, phenyl cyclohexanecarboxylate or cyclohexyl cyclohexanecarboxylate, cyclohexyl benzoate, cyclohexanecarboxylate or cyclohexyl cyclohexanecarboxylate, phenylcyclohexane, cyclohexylbiphenyl, phenylcyclohexylcyclohexane, cyclohexyl... Cyclohexane, cyclohexylcyclohexylcyclohexane, 1,4-bicyclohexylbenzene, 4,4'-bicyclohexylbiphenyl, phenylpyrimidine or cyclohexylpyrimidine, phenylpyridine or cyclohexylpyridine, phenyldioxane or cyclohexyldioxane, phenyl-1,3-dithiane or cyclohexyl-1,3-dithiane, 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2-(4-phenylcyclohexyl)ethane, 1-cyclohexyl-2-biphenylethane, 1-phenyl-2-cyclohexylphenylethane, optionally halogenated diphenylethylene, benzylphenyl ether, diphenylacetylene, and substituted cinnamic acid. In these compounds, the 1,4-phenylene group may also be fluorinated.

[0085] The most important compounds suitable as additional components of the medium according to the invention can be characterized by formulas 1, 2, 3, 4 and 5:

[0086] R'-LER" 1

[0087] R'-L-COO-ER" 2

[0088] R'-L-CF2O-ER" 3

[0089] R'-L-CH2CH2-ER" 4

[0090] R'-LC≡CER" 5

[0091] In formulas 1, 2, 3, 4, and 5, L and E, which may be the same or different, independently represent divalent groups selected from the group consisting of the following structural elements: -Phe-, -Cyc-, -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -Py-, -G-Phe-, -G-Cyc-, and their mirror images, wherein Phe represents unsubstituted or fluorinated 1,4-phenylene, Cyc represents trans-1,4-cyclohexylene, Pyr represents pyrimidin-2,5-diyl or pyridine-2,5-diyl, Dio represents 1,3-dioxane-2,5-diyl, Py represents tetrahydropyran-2,5-diyl, and G represents 2-(trans-1,4-cyclohexyl)ethyl.

[0092] Preferably, one of the groups L and E is Cyc, Phe, or Pyr. E is preferably Cyc, Phe, or Phe-Cyc. The medium according to the invention preferably comprises one or more components selected from compounds of formula 1, 2, 3, 4, and 5 in which L and E are selected from Cyc, Phe, and Pyr, and simultaneously comprises one or more components selected from compounds of formula 1, 2, 3, 4, and 5 in which one of the groups L and E is selected from Cyc, Phe, Py, and Pyr and another group is selected from -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe-, and -G-Cyc-, and optionally comprises one or more components selected from compounds of formula 1, 2, 3, 4, and 5 in which the groups L and E are selected from -Phe-Cyc-, -Cyc-Cyc-, -G-Phe-, and -G-Cyc-.

[0093] R' and / or R" each independently represent an alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy, or alkanoyloxy group having up to 8 carbon atoms, or -F, -Cl, -CN, -NCS, or -(O). i CH 3-k F k , where i is 0 or 1 and k is 1, 2 or 3.

[0094] In the smaller subgroups of compounds of formulas 1, 2, 3, 4, and 5, R' and / or R" each independently represent an alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy, or alkanoyloxy group having up to eight carbon atoms. This smaller subgroup is referred to as Group A below, and the compounds are designated as subformulas 1a, 2a, 3a, 4a, and 5a. In most of these compounds, R' and R" are distinct from each other, wherein one of these groups is typically an alkyl, alkenyl, alkoxy, or alkoxyalkyl group.

[0095] In another smaller subgroup of compounds of formulas (II), (III), (IV), (V), and (VI) (which is referred to as group B), E represents...

[0096]

[0097] In the compounds of group B designated with formulas (IIb), (IIIb), (IVb), (Vb) and (VIb), R' and R" have the meanings indicated in the case of compounds with formulas (IIa) to (VIa), and are preferably alkyl, alkenyl, alkoxy or alkoxyalkyl (oxaalkyl).

[0098] In compounds of formulas 1b, 2b, 3b, 4b and 5b, R' has the meaning indicated in the case of compounds of formulas 1a to 5a, and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.

[0099] In another smaller subgroup of compounds of formulas 1, 2, 3, 4, and 5, R" represents -F, -Cl, -NCS, or -(O). i CH 3- k F k Where i is 0 or 1 and k is 1, 2 or 3. This subgroup is referred to as group C below. Compounds in which R" has this meaning are designated as formulas 1c, 2c, 3c, 4c and 5c. Particularly preferred are compounds in formulas 1c, 2c, 3c, 4c and 5c in which R" has the meaning of -F, -Cl, -NCS, -CF3, -OCHF2 or -OCF3. In compounds of formulas 1c, 2c, 3c, 4c and 5c, R' has the meaning indicated in the case of compounds of formulas 1a to 5a, and is preferably alkyl, alkoxy or alkenyl.

[0100] In addition to the preferred compounds of groups A, B, and C, other compounds of formulas 1, 2, 3, 4, and 5 with other variations having the proposed substituents are also commonly used. All of these substances can be obtained by methods known from the literature or similar methods.

[0101] In addition to the compound of formula I according to the invention, the medium according to the invention preferably also contains one or more compounds selected from groups A, B, and / or C. The weight ratio of compounds selected from these groups in the medium according to the invention is preferably:

[0102] Group A: 0 to 90%, preferably 20 to 90%, particularly preferably 30 to 90%;

[0103] Group B: 0 to 80%, preferably 10 to 80%, particularly preferably 10 to 65%;

[0104] Group C: 0 to 80%, preferably 0 to 60%, particularly preferably 0 to 50%;

[0105] In each case, the total weight ratio of the compounds of group A, B and / or C present in the medium according to the invention is preferably 5 to 90%, and particularly preferably 10 to 90%.

[0106] The medium according to the invention preferably contains 1 to 40%, particularly preferably 3 to 30%, of the compound according to the invention.

[0107] The liquid crystal mixtures according to the invention are prepared in their own conventional manner. Typically, the desired amount of the component used in a small quantity is dissolved in the component constituting the main component, preferably at an elevated temperature. The components can also be mixed in an organic solvent, such as a solution in acetone, chloroform, or methanol, and the solvent is removed again, for example, by distillation, after thorough mixing. Alternatively, the mixtures can be prepared in other conventional ways, such as by using premixes, such as homologue mixtures, or using a so-called "multi-bottle" system.

[0108] The dielectric may also contain other additives known to those skilled in the art and described in the literature. For example, 0 to 15%, preferably 0 to 10%, of pleochroic dyes, chiral dopants, stabilizers, or nanoparticles may be added. The individual compounds added are used at a concentration of 0.01 to 6%, preferably 0.1 to 3%. However, the concentrations indicated herein for the remaining components of the liquid crystal mixture (i.e., the liquid crystal or mesocrystalline compound) are given without regard to the concentrations of these additives.

[0109] The liquid crystal mixture according to the invention enables a significant expansion of the range of available parameters.

[0110] The present invention also relates to electro-optic displays containing this type of medium (particularly TFT displays having two plane-parallel outer plates forming a liquid crystal cell together with a frame, integrated nonlinear elements for switching individual pixels on the outer plates, and a nematic liquid crystal mixture having positive dielectric anisotropy and high specific resistance located within the liquid crystal cell), and to the use of these media for electro-optic purposes.

[0111] The term "alkyl" encompasses both unbranched and branched alkyl groups having 1-15 carbon atoms, particularly unbranched groups such as methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, and n-heptyl. Groups having 2-5 carbon atoms are generally preferred.

[0112] The term "alkenyl" encompasses both unbranched and branched alkenyl groups having up to 15 carbon atoms, particularly the unbranched groups. Particularly preferred alkenyl groups are C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, C5-C7-4-alkenyl, C6-C7-5-alkenyl, and C7-6-alkenyl, especially C2-C7-1E-alkenyl, C4-C7-3E-alkenyl, and C5-C7-4-alkenyl. Examples of 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, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl, and similar groups. Groups having up to 5 carbon atoms are generally preferred.

[0113] In this disclosure, the term "halogen" is preferably used to refer to fluorine or chlorine, and particularly preferably to fluorine.

[0114] The matrix display according to the invention, formed by a polarizer, an electrode substrate, and surface-treated electrodes, corresponds to a conventional design for this type of display. The term "conventional design" is interpreted broadly herein and includes all derivatives and variations of the matrix display, particularly matrix display elements based on poly-Si TFTs.

[0115] However, the main difference between the display according to the present invention and conventional displays based on twisted nematic liquid crystal cells to date lies in the selection of liquid crystal parameters of the liquid crystal layer.

[0116] The following embodiments illustrate the invention but are not intended to limit it. Those skilled in the art will be able to extract details not given in detail in the general description from the embodiments, generalize them based on common knowledge in the art, and apply them to specific problems.

[0117] In the preceding and following text, percentage data are expressed as weight percentages. All temperatures are indicated in degrees Celsius. Additionally, C = crystalline state, N = nematic phase, Sm = smectic phase (more specifically, SmA, SmB, etc.), Tg = glass transition temperature, and I = isotropic phase. Data between these symbols represent transition temperatures. Δn indicates optical anisotropy (589 nm, 20 °C), Δε indicates dielectric anisotropy (1 kHz, 20 °C), and γ1 indicates rotational viscosity (20 °C; in mPa·s).

[0118] Physical, physicochemical, and electro-optical parameters are determined using commonly known methods, such as those described in the brochure "MerckLiquid Crystals". As described in "Physical Properties of Liquid Crystals - Description of the Measurements Methods", Merck KGaA, 1998, Darmstadt.

[0119] The dielectric anisotropy Δε of individual substances was determined at 20 °C and 1 kHz. For this purpose, 5–10 wt% of the substance under study was measured in a dielectric positive mixture ZLI-4792 (Merck KGaA), and the measurements were extrapolated to a 100% concentration. The optical anisotropy Δn was determined at 20 °C and a wavelength of 589.3 nm, and the rotational viscosity γ1 was determined at 20 °C; both were also determined by linear extrapolation.

[0120] In this application, unless otherwise expressly stated, the plural form of a term refers to both the singular and plural forms, and vice versa. Further combinations of embodiments and variations of the invention can be derived from the appended claims or from a combination of several of these claims, according to the specification. Example

[0121] The invention is described in detail below with reference to the following non-limiting embodiments.

[0122] Example 1: 2,6-Dipropylperhydro-s-indalene (1)

[0123]

[0124] 2 g of 2,6-dipropyl-1,2,3,5,6,7-hexahydro-s-indazate was dissolved in 20 ml of glacial acetic acid, and 0.8 g of platinum(IV) oxide hydrate was added. The mixture was stirred overnight in a hydrogen atmosphere at room temperature and atmospheric pressure. Conventional post-treatment yielded 500 mg of 1.

[0125] analyze: 13 C NMR (101MHz, chloroform-d) δ 14.47 (CH3), 21.92 (CH2-CH3), 34.31 (cyclohexyl-CH2), 37.89 (cyclohexyl-CH,CH3CH2CH2), 40.19 (cyclopentyl-CH2), 41.10 (cyclopentyl-CH).

[0126] Single-crystal X-ray structural analysis:

[0127] Triclinic crystal system, space group P-1; a=110.420(18)°, b=102.127(15)°, g=102.387(14)°

[0128] The obtained compound is stereochemically homogeneous and is an extended isomer in which the cyclohexane ring adopts a boat shape.

[0129] The compound exhibits the following phase behavior:

[0130] C 51SmB 55I.

[0131] Δε: -2.0

[0132] Δn: 0.019

[0133] γ1: 21 mPa s

[0134] Similarly, the following compounds were prepared:

Claims

1. Compound of Formula I, in R 1 and R 2 In each case, it independently represents an alkyl group having up to 8 carbon atoms, wherein one or more CH2 groups in these groups, including the terminal carbon atom, may also be independently represented by -CH=CH- in each case. The H atoms can be replaced, and one or more of them can be replaced by halogens.

2. The compound according to claim 1, characterized in that... R 1 It indicates an alkyl or alkenyl group having up to 8 carbon atoms.

3. The compound according to claim 1 or 2, characterized in that... R 1 and R 2 They are the same.

4. The compound according to claim 1 or 2, characterized in that... R 1 and R 2 They are different.

5. The compound according to claim 1 or 2, characterized in that... R 1 It represents methyl, ethyl, n-propyl, n-butyl, or n-pentyl.

6. The compound according to claim 1 or 2, characterized in that... R 2 It represents ethyl, n-propyl, n-butyl, or n-pentyl.

7. The compound according to claim 1 or 2, wherein the compound is selected from the following formula:

8. A method for preparing a compound of formula I according to any one of claims 1 to 7, wherein a compound of formula II is converted into a compound of formula I by hydrogenation of the double bond of the six-membered ring in the ring system of formula II over a metal catalyst. Where R 1 and R 2 It is as defined for formula I in claim 1.

9. Use of one or more compounds of Formula I according to any one of claims 1 to 7 as components in a liquid crystal medium.

10. A liquid crystal medium comprising at least two mesocrystalline compounds, characterized in that... It comprises at least one compound of formula I according to any one of claims 1 to 7.

11. Use of the liquid crystal medium according to claim 10 in an electro-optic liquid crystal display.

12. An electro-optic liquid crystal display comprising the liquid crystal medium according to claim 10.

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