JP5225531B2 - Negative DC anisotropic tetracyclic compound and liquid crystal medium - Google Patents

Description

  The present invention relates to tetracyclic compounds with negative dielectric anisotropy (DC anisotropy), their use as components of liquid crystal media, and to liquid crystals and electro-optical display elements comprising the liquid crystal media according to the invention.

  The compounds according to the invention can be used as components of liquid crystal media, in particular as twisted cells, guest-host effect, DAP (deformation of oriented phases), ECB (electrically controlled birefringence), CSH (color super homeotropic), It can be used for displays based on the principle of VA (vertical alignment) or IPS (in-plane switching) effect or dynamic scattering effect.

  The principle of electrically controlled birefringence, ECB effect or DAP (orientated phase deformation) effect was first described in 1971 (MFSchieckel and K. Fahrenschon, "Deformation of nematic liquid crystals with vertical orientation in electrical fields ", Appl. Phys. Lett. 19 (1971), 3912). This was followed by a paper by J. F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).

By J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), J. Duchene (Displays 7 (1986), 3) and H. Schad (SID 82 Digest Techn. Papers (1982), 244) The paper shows that the liquid crystal phase has a high value for the ratio of elastic constants K ₃₃ / K ₁₁ , a high value for the optical anisotropy Δn and about −0. It is noted that it must have a value for a dielectric (DC) anisotropy Δε of 5 to about −5. An electro-optic display element based on the ECB effect has a homeotropic or vertical edge orientation, ie an orientation substantially perpendicular to the electrode surface, in the switched off state.

  More recent types of ECB displays with homeotropic edge alignment are based on CSH, VAN (vertical alignment nematic) or VAC (vertical alignment cholesteric) effects. CSH displays are known in particular from H. Hirai, Japan Displays 89 Digest, 184 (1989), J. F. Clerc et al., Japan Displays 89 Digest, 188 (1989) and J. F. Clerc, SID 91 Digest, 758 (1991). VAN displays are described in particular in S. Yamauchi et al., SID Digest of Technical Papers, pages 378 et seq. (1989), and VAC displays are described in KA Crabdall et al., Appl. Phys. Lett. 65, 4 (1994).

  Similar to previously disclosed ECB displays, more recent VAN and VAC displays include a layer of liquid crystal media between two transparent electrodes, which are negative for DC anisotropy Δε. Has a value. The molecules of the liquid crystal layer have a homeotropic or tilt homeotropic alignment in the switched off state. Due to the negative DC anisotropy, realignment of the liquid crystal molecules parallel to the electrode surface occurs in the switched-on state.

  In contrast to conventional ECB displays, where liquid crystal molecules have a uniform selective direction and parallel orientation across the entire liquid crystal cell in the switched-on state, this uniform parallel orientation is typically Limited to small domains in the cell. Tilting exists between these domains, also known as tilt domains.

  As a result, VAN and VAC displays have greater viewing angle independence of contrast and gray tones compared to conventional ECB displays. Furthermore, this type of display is easier to manufacture. The reason is that an additional treatment of the electrode surface, for example by rubbing for the uniform orientation of the molecules in the switched-on state, is no longer necessary.

  In contrast to VAN displays, liquid crystal media in VAC displays can also be one or more chiral compounds, for example, a helical twist of liquid molecules in the liquid crystal layer at an angle of 0-360 ° in the switched-on state. A chiral dopant that induces The twist angle in the preferred case is about 90 °.

For displays with vertical edge orientation, the use of compensators, such as optically coaxial negative compensation films, has been proposed to compensate for unwanted light transmission of the display in the switched off state at an inclined viewing angle.
Furthermore, the specific design of the electrode makes it possible to control the selective direction of the tilt angle without the need for additional surface treatment of the electrode, for example with an alignment layer. This type of CSH display is described, for example, in Yamamoto et al., SID 91 Digest, 762 (1991).

In an IPS display, an electrical signal is generated such that the electric field has a significant component parallel to the liquid crystal layer (in-plane switching). International patent application WO 91/10936 discloses a liquid crystal display of this type. The principle of operating this type of display is described, for example, by RASoref in Journal of Applied Physics, Vol. 45, No. 12, pp. 5466-5468 (1974). EP
0 588 568 discloses various addressing methods for handling this type of display.

  These IPS displays can be operated with liquid crystal materials having positive or negative dielectric anisotropy (Δε ≠ 0). However, for previously known materials, relatively high threshold voltages and long response times have been achieved in IPS displays. Furthermore, the problem of crystallization of liquid crystal media at low temperatures can occur in IPS displays containing conventionally known materials.

  The display described above can be of active matrix or passive matrix (multiplex) type. Thus, for example, ECB and VA displays that operate as active matrix or multiplex displays have been described, while CSH displays typically operate as multiplex displays.

This type of matrix liquid crystal display is known. Non-linear elements that can be used for individual switching of individual pixels are, for example, active elements (ie transistors). The term “active matrix” is then used when a distinction can be made between the two types:
1. MOS (metal oxide semiconductor) or other diode on a silicon wafer as substrate.
2. A thin film transistor (TFT) on a glass plate as a substrate.

The use of single crystal silicon as the substrate material limits the size of the display. The reason is that even if the various partial displays are modularly assembled, a problem occurs in the joint portion.
For the more promising type 2, which is preferred, the electro-optical effect used is usually the TN effect. A distinction is made between two technologies: TFTs comprising compound semiconductors, such as CdSe, or TFTs based on polycrystalline or amorphous silicon. Special research efforts are being made around the world for the latter technique.

  The TFT matrix is applied to the inside of one glass plate of the display, and the inside of the other glass plate has a transparent counter electrode. Compared with the size of the pixel electrode, the TFT is very small and has virtually no detrimental effect on the image. This technology can also be developed into a full color capable display in which mosaic red, green and blue filters are generally arranged so that the filter elements are located opposite each switchable pixel. it can.

  In this specification, the term MLC display encompasses any matrix display with integrated nonlinear elements. That is, in addition to the active matrix, also included are displays with passive elements such as varistors or diodes (MIM = metal-insulator-metal).

This type of MLC display is particularly suitable for TV applications (eg pocket television receivers) or computer applications (laptop type) and advanced information displays for automobile or aircraft construction. In addition to problems related to the angular dependence of contrast and response time, MLC displays have problems due to inappropriately high resistivity values of liquid crystal mixtures [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO, E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc. Eurodisplay 84, September 1984: A210-288 Matrix LCD Controlled by Double Stage Diode Rings, p. 141 et seq. STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, 145 et seq., Paris].
As the resistance value decreases, the contrast of the MLC display decreases and the afterimage erasure problem may occur. The specific resistance value of the liquid crystal mixture generally decreases over the life of the MLC display due to its interaction with the inner surface of the MLC display, so it is high for displays that must have an acceptable resistance value over a long period of operation ( The initial resistance is very important.

Furthermore, it is important that the resistivity exhibits the smallest possible decrease with increasing temperature and after heating and / or UV exposure. The low temperature properties of the mixtures from the prior art are also particularly disadvantageous. Crystallization and / or smectic phases do not occur even at low temperatures, and the temperature dependence of viscosity is required to be as low as possible.
Therefore, MLC displays from the prior art do not meet today's requirements.

Industrial use in electro-optic display elements of the above-described effect requires an LC phase that has to fulfill several requirements. Of particular importance here are chemical resistance to moisture, air and physical effects such as heat, infrared, visible and ultraviolet radiation and direct and alternating electric fields.
LC phases that can be used in industry are further required to have a liquid crystal mesophase in a suitable temperature range and low viscosity.

  None of the series of compounds having a liquid-crystalline mesophase previously disclosed includes individual compounds that meet all these requirements. Therefore, in general, a mixture of 2 to 25, preferably 3 to 18 compounds is prepared to obtain a material that can be used as the LC phase. However, it was not possible to easily prepare the optimal phase in this way. This is because liquid crystal materials with significantly negative dielectric anisotropy have not been available to date to an appropriate extent.

  EP 0 474 062 discloses an MLC display based on the ECB effect. The LC mixtures disclosed herein are based on 2,3-difluorophenyl derivatives that contain ester, ether or ethyl bridges but have a low value for voltage holding ratio (HR) after exposure to UV. Therefore, they are not suitable for use in the aforementioned display.

  Therefore, it has a very high specific resistance, at the same time a wide operating temperature range, a short response time even at low temperatures, and a low threshold voltage that promotes many gray shades, high contrast and a wide viewing angle, and exhibits the aforementioned drawbacks. There continues to be a great demand, especially for ECB, VA and CSH type MLC displays, which are only shown to the extent of low or low.

Problems to be solved by the invention

The present invention was aimed at providing an MLC display which does not have the disadvantages indicated above or only has to a small extent, preferably at the same time having a very high resistivity value and a low threshold voltage.
Another object was to provide novel stable liquid crystals or negative DC anisotropy mesophase forming compounds which are particularly suitable as components of liquid crystal media for ECB, VA, CSH, DAP and IPS displays described above. It was.
All materials previously used for this purpose have certain disadvantages, such as inadequate stability to heat, light or electric fields or undesirable mesophase, elastic and / or dielectric properties.

Means for solving the problem

It has now been found that this object can be achieved when the compounds and media of the invention are used in LC displays.
Thus, in particular, the compounds of the present invention have been found to be significantly suitable as components of liquid crystal media. By using these, a stable liquid crystal medium particularly suitable for the LC display described above can be obtained. The novel compounds are distinguished by a high thermal stability, which is particularly advantageous for high retention ratios and exhibits significant negative DC anisotropy and favorable clearing points and birefringence values.

By providing the tetracyclic compounds of the present invention, the range of suitable liquid crystal materials from the perspective of various applications for the preparation of liquid crystal mixtures is very generally significantly increased.
In the pure state, the compounds according to the invention are colorless and form a liquid-crystalline mesophase in the temperature range which is preferably arranged for electro-optical use. They are stable to chemical, thermal and light.

式中、
Ｒ^１およびＲ^２は、互いに独立して、非置換であるか、ハロゲン、ＣＮまたはＣＦ_３で一置換または多置換されている１〜１２個の炭素原子を有するアルキルであり、ここでさらに、１つまたは２つ以上のＣＨ_２基が、各々互いに独立して、−Ｏ−、−Ｓ−、−ＣＯ−、−ＣＯ−Ｏ−、−Ｏ−ＣＯ−、−Ｏ−ＣＯ−Ｏ−、−ＣＨ＝ＣＨ−、−ＣＨ＝ＣＦ−、−ＣＦ＝ＣＦ−、−Ｃ≡Ｃ−または１，３−シクロブチレンで、Ｓおよび／またはＯ原子が互いに直接結合しないように置換されていてもよく、
Ａ^１、Ａ^２、Ａ^３およびＡ４は、互いに独立して、非置換であるか、ＣＮ、Ｆ、Ｃｌ、ＣＦ_３またはＯＣＦ_３により一置換または二置換されている１，４−フェニレンであり、さらに、１つまたは２つのＣＨ基は、Ｎにより置換されていてもよく、基Ａ^１およびＡ^４の１つまたは２つは、二者択一的にトランス−１，４−シクロヘキシレンであり、ここでさらに、１つまたは２つ以上の隣接していないＣＨ_２基は、−Ｏ−および／または−Ｓ−または１，４−シクロヘキセニレンにより置換されていてもよく、
Ｚ^１、Ｚ^２およびＺ^３は、各々−ＣＨ_２Ｏ−、−ＯＣＨ_２−、−ＣＦ_２Ｏ−、−ＯＣＦ_２−、−ＣＯＯ−、−ＯＣＯ−、−ＣＦ_２ＣＦ_２−、−ＣＨ_２ＣＨ_２−、−（ＣＨ_２）_４−、−（ＣＨ_２）_３Ｏ−、−Ｏ（ＣＨ_２）_３−、−ＣＦ_２ＣＨ_２−、−ＣＨ＝ＣＨ−、−ＣＨ＝ＣＦ−、−ＣＦ＝ＣＦ−、−Ｃ≡Ｃ−または単結合であり、
ただし、
ａ）化合物は、２位または３位において置換されている少なくとも２つの１，４−フェニレン基または２位および３位においてＣＮ、Ｆ、Ｃｌ、ＣＦ_３またはＯＣＦ_３により置換されている少なくとも１つの１，４−フェニレン基を含み、
ｂ）Ｚ^１、Ｚ^２およびＺ^３が単結合である場合には、基Ｒ^１およびＲ^２の一方がアルキルまたはオキサアルキルであり、他方がアルキル、オキサアルキルまたはアルケニルであり、２つの環Ａ^１およびＡ^４またはＡ^２およびＡ^３がトランス−１，４−シクロヘキシレンであり、他の２つの環が同時には２，３−ジフルオロ−１，４−フェニレンではない、
で表される負のＤＣ異方性の四環式化合物に関する。Accordingly, the present invention provides compounds of formula I

Where
R ¹ and R ² are, independently of one another, alkyl having 1 to 12 carbon atoms which are unsubstituted or mono- or polysubstituted by halogen, CN or CF ₃ , where One or more CH ₂ groups are each independently of each other —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, -CH = CH-, -CH = CF-, -CF = CF-, -C≡C- or 1,3-cyclobutylene, substituted so that S and / or O atoms are not directly bonded to each other Often,
A ¹ , A ² , A ³ and A4 are independently of each other 1,4-phenylene which is unsubstituted or mono- or disubstituted by CN, F, Cl, CF ₃ or OCF ₃ Furthermore, one or two CH groups may be substituted by N, and one or two of the groups A ¹ and A ⁴ may alternatively be trans-1,4-cyclohexylene. Yes, further wherein one or more non-adjacent CH ₂ groups may be substituted by —O— and / or —S— or 1,4-cyclohexenylene,
Z ¹ , Z ² and Z ³ are —CH ₂ O—, —OCH ₂ —, —CF ₂ O—, —OCF ₂ —, —COO—, —OCO—, —CF ₂ CF ₂ —, —CH, respectively. ₂ CH ₂ —, — (CH ₂ ) ₄ —, — (CH ₂ ) ₃ O—, —O (CH ₂ ) ₃ —, —CF ₂ CH ₂ —, —CH═CH—, —CH═CF—, -CF = CF-, -C≡C- or a single bond,
However,
a) the compound is at least one 1,4-phenylene group substituted at the 2 or 3 position or at least one substituted by CN, F, Cl, CF ₃ or OCF ₃ at the 2 and 3 positions Contains a 1,4-phenylene group,
b) when Z ¹ , Z ² and Z ³ are single bonds, one of the radicals R ¹ and R ² is alkyl or oxaalkyl and the other is alkyl, oxaalkyl or alkenyl, ¹ and A ⁴ or A ² and A ³ are trans-1,4-cyclohexylene and the other two rings are not simultaneously 2,3-difluoro-1,4-phenylene,
It is related with the tetracyclic compound of negative DC anisotropy represented by these.

The invention further relates to the use of a compound of formula I as a component of a liquid crystal medium.
The invention further relates to a liquid crystal medium having at least two liquid crystal components comprising at least one compound of the formula I.
The invention further relates to a liquid crystal display element, in particular an electro-optical display element, comprising as a dielectric a liquid crystal medium according to the invention.

Particularly preferred are liquid crystal display elements having homeotropic edge alignment in the switched off state, in particular ECB, VA, CSH and DAP displays. Further preferred is an IPS display.
The meaning of Formula I includes all isotopes of chemical elements attached in the compounds of Formula I. In enantiomerically pure or rich form, the compounds of formula I are also suitable as chiral dopants and to achieve generally chiral mesophases.

を包含する。In the present specification, R ¹ , R ² , A ¹ , A ² , A ³ , A ⁴ , Z ¹ , Z ² and Z ³ are as defined above unless otherwise specified. If more than one group is present, this may adopt the same or different meanings.
Disubstituted 1,4-phenylene means substitution at the 2 and 3 positions unless stated otherwise.
The term 1,3-dioxane-2,5-diyl means in each case two regioisomers

Is included.

を有する。
式Ｉ中のＺ^１、Ｚ^２およびＺ^３が単結合である場合には、Ａ^４は２，３−ジフルオロ−１，４−フェニレンであり、Ｒ^２はアルキルまたはオキサアルキルであり、Ｒ^１は好ましくはアルケニル基ではない。
特に好ましいのは、Ｒ^１およびＲ^２が、１〜１２個の炭素原子を有するアルキルまたはオキサアルキルあるいは２〜１０個の炭素原子を有するアルケニルまたはオキサアルケニルである、式Ｉで表される化合物である。The cyclohexylene-1,4-diyl group preferably has the following structure:

Have
When Z ¹ , Z ² and Z ^{3 in} Formula I are single bonds, A ⁴ is 2,3-difluoro-1,4-phenylene, R ² is alkyl or oxaalkyl, R ¹ Is preferably not an alkenyl group.
Particularly preferred are compounds of formula I, wherein R ¹ and R ² are alkyl or oxaalkyl having 1 to 12 carbon atoms or alkenyl or oxaalkenyl having 2 to 10 carbon atoms. is there.

Particularly preferred is
-A ¹ , A ² , A ³ and A ⁴ are 1,4-phenylene which is unsubstituted or mono- or disubstituted by CN, F, Cl or CF ₃ ;
One, two or three of the groups A ^{1 to} A ⁴ are trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl, preferably trans-1,4-cyclohexylene ,
- at least one of the groups ^Z 1, ^{Z 2} and ^{Z 3,} preferably not more than one or two single bonds, preferably _{-CF 2 O -, - OCF 2} -, - CH 2 CH 2 -, - CH ═CH—, —C≡C— or —CF ₂ CF ₂ —.
-Z ^{1, Z 2} and ^{Z 3} are each, independently of one _{another, -CH 2 CH 2 -, -} CH = CH -, - C≡C -, - CF 2 CF 2 -, - CF 2 O-, it is or a single bond, - -OCF ₂
-R ¹ and R ² are linear alkyl or oxaalkyl having 1 to 10 carbon atoms or alkenyl or oxaalkenyl having 2 to 10 carbon atoms,
At least one of the radicals R ¹ and R ² is alkenyl or oxaalkenyl having 2 to 7 carbon atoms,
The at least two groups A ¹ , A ² , A ³ and A ⁴ are 2,3-difluoro-1,4-phenylene or 2,3-dicyano-1,4-phenylene, preferably at least one other Is a group of 2- or 3-fluorophenylene or 2- or 3-cyanophenylene,
At least one, preferably one, two or three of the groups A ¹ , A ² , A ³ and A ⁴ is 1,4-phenylene which is mono- or disubstituted by CN or CF ₃ ,
-A ¹ , A ² , A ³ and A ⁴ are unsubstituted or mono- or disubstituted by CN, F, Cl or CF ₃ , and at least one of the groups Z ¹ , Z ² and Z ³ Are —CF ₂ O—, —OCF ₂ —, —CH═CH—, —C≡C—, —CF ₂ CF ₂ —, —CF═CF— or —CH═CF—,
One, two or three of the groups A ^{1 to} A ⁴ are trans-1,4-cyclohexylene or 1,3-dioxane-2,5-diyl, preferably trans-1,4-cyclohexylene , R ¹ and / or R ² is alkenyl or oxaalkenyl having ² to 7 carbon atoms, and at least one, preferably one or two of Z ¹ , Z ² and Z ³ is other than a single bond And is preferably —CF ₂ O—, —OCF ₂ —, —CH ₂ CH ₂ —, —CH═CH—, —C≡C— or —CF ₂ CF ₂ —.
A compound represented by Formula I.

The compounds of the following subordinate formula are particularly preferred. In these formulas, Cyc represents a 1,4-cyclohexylene group, Phe represents a 1,4-phenylene group, and PheL represents a 1,4-phenylene group substituted at the 2-position or 3-position. , PheLL represents a 1,4-phenylene group substituted at the 2-position and 3-position with L, and L is CN, F, Cl or CF ₃ . Z is as defined for Z ¹ under Formula I. R ¹ and R ² are as defined under formula I.

L in the dependent formulas I1 to I76 is preferably F, CN or CF ₃ .
Z in the subordinate formulas I1 to I76 is preferably CF ₂ O, OCF ₂ , CH ₂ O, OCH ₂ , CH═CH, CH ₂ CH ₂ or a single bond.
R ¹ and R ² in the dependent formulas I1 to I76 are particularly preferably straight-chain alkyl or oxaalkyl having 1 to 8 carbon atoms or alkenyl or oxaalkenyl having 2 to 10 carbon atoms.
Particularly preferred compounds of the dependent formulas I1 to I76 are those in which L is F, R ¹ or R ² is alkenyl or oxaalkenyl having ² to 7 carbon atoms and Z is a single bond .

Preferred is further
The compounds of the dependent formulas I17 to I42, I54 to I64 and I72 to I75, wherein L in the group PheLL is F and L in the group PheL is F, CN or CF ₃ ;
The compounds represented by the dependent formulas I10 to I42 and I45 to I64 and I70 to I74, wherein L in at least one of the groups PheL is CN or CF ₃ , -R ¹ and / or R ² is ² to 7 A compound of the dependent formulas I1 to I76, which is alkenyl or oxaalkenyl having 1 carbon atom,
- at least one group Z _{is, CF 2 O, OCF 2,} CF 2 CF 2, CH = CH, a CF = CF or _CH 2 CH _2, the compound represented by the subformulae I1～I76, - the sub-formulas I43 Compounds represented by ˜I76, in particular compounds of the dependent formulas I43 to I67 and I70 to I76, very particularly preferably compounds of the dependent formulas I75 and I76.

特に、Ｌ^１およびＬ^２がＦである化合物、並びにＲ^１およびＲ^２が、１〜８個の炭素原子を有するアルキルまたは２〜７個の炭素原子を有するアルケニルである化合物である。Very particular preference is given to the following compounds:

In particular, compounds in which L ¹ and L ² are F, and compounds in which R ¹ and R ² are alkyl having 1 to 8 carbon atoms or alkenyl having 2 to 7 carbon atoms.

When R ¹ and / or R ² in the formulas herein are alkyl groups, this can be straight-chain or branched. It is preferably straight-chain and has 2, 3, 4, 5, 6 or 7 carbon atoms and is therefore preferably ethyl, propyl, butyl, pentyl, hexyl or heptyl, furthermore methyl, octyl, Nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl or pentadecyl.

If R ¹ and / or R ² is an alkyl group in which one CH ₂ group is substituted by —O—, this can be linear or branched. This is preferably straight-chain and has 1 to 10 carbon atoms. The first CH ₂ group in this alkyl group is preferably substituted by —O—, so that the group R ¹ has the meaning of alkoxy, preferably methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyl. Oxy, heptyloxy, octyloxy or nonyloxy.

Furthermore, it is also possible for the CH ₂ group elsewhere to be substituted by —O—, so that the radicals R ¹ and / or R ² are preferably linear 2-oxapropyl (= methoxymethyl) ), 2-(= ethoxymethyl) or 3-oxabutyl (= 2-methoxyethyl), 2-, 3- or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-3 -, 4-, 5- or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- Or 8-oxanonyl, or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl.

If R ¹ and / or R ² is an alkyl group in which one CH ₂ group is substituted by —CH═CH—, this can be straight-chain or branched. This is preferably straight-chain and has 2 to 10 carbon atoms. This is therefore especially the case for vinyl, prop-1- or 2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl. Hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct -1-, -2-, -3-, -4-, -5, -6, or -7-enyl, non-1-, -2-, -3-, mono-4-, -5, -6, -7- or -8-enyl, or dec-1-, -2-, -3-, -4-, -5, -6, -7-, -8- or -9- Enil.

Preferred alkenyl _groups, C ₂ -C 7 -1E- _alkenyl, C ₄ -C 7 -3E- _alkenyl, C ₅ -C 7 -4- _alkenyl, C ₆ -C 7 -5- alkenyl and _C 7-6- alkenyl, in particular _C 2 _-C 7 -1E- _alkenyl, C ₄ -C 7 -3E-alkenyl and _C 5 _-C 7 -4- alkenyl.

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

When R ¹ and / or R ² are alkyl groups in which one CH ₂ group is substituted by —O— and one is substituted by —CO—, they are preferably adjacent. They therefore contain an acyloxy group —CO—O— or an oxycarbonyl group —O—CO—. These are preferably straight-chain and have 2 to 6 carbon atoms.

  Thus, these are in particular acetoxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetoxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetoxyethyl, 2-propionyloxyethyl, 2-butyryloxyethyl, 3-acetoxypropyl, 3-propionyloxypropyl, 4-acetoxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxycarbonylmethyl, propoxycarbonylmethyl , Butoxycarbonylmethyl, 2- (methoxycarbonyl) ethyl, 2- (ethoxycarbonyl) ethyl, 2- (propoxycarbonyl) Chill, 3- (methoxycarbonyl) propyl, 3- (ethoxycarbonyl) propyl or 4- (methoxycarbonyl) butyl.

R ¹ and / or R ² is such that one CH ₂ group is unsubstituted or substituted with —CH═CH— and the adjacent CH ₂ group is substituted with CO or CO—O or O—CO—. If it is an alkyl group, it can be linear or branched. This is preferably straight-chain and has 4 to 13 carbon atoms. Thus, this is especially true for acryloyloxymethyl, 2-acryloyloxyethyl, 3-acryloyloxypropyl, 4-acryloyloxybutyl, 5-acryloyloxypentyl, 6-acryloyloxyhexyl, 7-acryloyloxyheptyl, 8-acryloyl. Oxyoctyl, 9-acryloyloxynonyl, 10-acryloyloxydecyl, 1-methacryloyloxymethyl, 2-methacryloyloxyethyl, 3-methacryloyloxypropyl, 4-methacryloyloxybutyl, 5-methacryloyloxypentyl, 6-methacryloyloxyhexyl 7-methacryloyloxyheptyl, 8-methacryloyloxyoctyl or 9-methacryloyloxynonyl.

When R ¹ and / or R ² is an alkyl or alkenyl group monosubstituted by CN or CF ₃ , this group is preferably straight-chain and substitution by CN or CF ₃ is ω-position At.
When R ¹ and / or R ² is an alkyl group at least monosubstituted by halogen, this group is preferably straight-chain. Halogen is preferably F or Cl. In the case of polysubstitution, the halogen is preferably F. The resulting group also contains a perfluorinated group. In the case of monosubstitution, the fluorine or chlorine substituent can be in any desired position, but is preferably in the ω position.

Compounds of formula I having branched wing groups R ¹ and / or R ² may sometimes be important due to the better solubility of conventional liquid crystal substrates, especially when they are optically active As a chiral dopant. This type of smectic compound is suitable as a component of a ferroelectric material.
This type of branching group generally contains only one chain branch. Preferred branching groups R ¹ and / or R ² are isopropyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methylpropyl), 2-methylbutyl, isopentyl (= 3-methylbutyl), 2-methyl Pentyl, 3-methylpentyl, 2-ethylhexyl, 2-propylpentyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentyloxy, 3-methylpentyloxy, 2-ethylhexyloxy 1-methylhexyloxy or 1-methylheptyloxy.

Formula I includes both racemic and optical antipodes of these compounds and mixtures thereof.
Among these compounds of formula I and subordinate formulas, preference is given to those in which at least one group present therein has one of the preferred meanings indicated.
Compounds of formula I are known per se as described in the literature (eg standard academic books such as Houben-Weyl, Methodender Organischen Chemie, Gerog-Thieme-Verlag, Stuttgart) According to the method, it can be accurately produced under known reaction conditions suitable for the reaction. Also here, variants which are known per se but are not described in more detail in the present description can be used.

Ｒ、Ｒ’＝Ｃ_１−１２アルキル、アルケニル、オキサアルキル、オキサアルケニルThe compounds of formula I can be prepared, for example, according to or analogously to the following reaction scheme. Other synthetic methods are found in the examples.
Scheme 1

R, R ′ = C _1-12 alkyl, alkenyl, oxaalkyl, oxaalkenyl

Ｒ、Ｒ’＝Ｃ_１−１２アルキル、アルケニル、オキサアルキル、オキサアルケニル Scheme 2

R, R ′ = C _1-12 alkyl, alkenyl, oxaalkyl, oxaalkenyl

If desired, the starting materials can also be formed in situ by not isolating them from the reaction mixture, but instead immediately converting them to compounds of formula I.
Alternatively, the ester of formula I can be obtained by esterification of the corresponding carboxylic acid (or reactive derivative thereof) using alcohol or phenol (or reactive derivative thereof) or by the DCC method (DCC = dicyclohexylcarbodiimide). Can do.

Corresponding carboxylic acids and alcohols are known or can be prepared analogously to known methods.
Suitable reactive derivatives of the aforementioned carboxylic acids are in particular acid halides, in particular chlorides and bromides, furthermore anhydrides, azides or esters, in particular alkyl esters having 1 to 4 carbon atoms in the alkyl group. is there.
Suitable reactive derivatives of the aforementioned alcohols are particularly preferably the corresponding metal alkoxides of alkali metals, such as Na or K.

  The esterification is advantageously carried out in the presence of an inert solvent. Highly suitable solvents are in particular ethers such as diethyl ether, di-n-butyl ether, THF, dioxane and anisole, ketones such as acetone, butanone or cyclohexanone, amides such as DMF or hexamethylphosphate triamide, hydrocarbons, Examples are benzene, toluene or xylene, halogenated hydrocarbons such as tetrachloromethane or tetrachloroethylene and sulfoxides such as dimethyl sulfoxide or sulfolane. Water-immiscible solvents can be advantageously used at the same time for the azeotropic removal of the water formed during esterification by distillation. Excess organic bases such as pyridine, quinoline or triethylamine can also sometimes be used as solvents for esterification. Esterification can also be carried out in the absence of a solvent, for example by simply heating the components in the presence of sodium acetate. The reaction temperature is generally −50 ° C. to + 250 ° C., preferably −20 ° C. to + 80 ° C. At these temperatures, the esterification reaction is generally complete after 15 minutes to 48 hours.

  In particular, the reaction conditions for the esterification depend substantially on the nature of the starting materials used. Accordingly, free carboxylic acids are generally reacted with free alcohols in the presence of strong acids such as mineral acids such as hydrochloric acid or sulfuric acid. A preferred reaction procedure is the reaction of an acid anhydride or in particular an acid chloride with an alcohol, preferably in a basic medium, the important base being in particular an alkali metal hydroxide such as sodium hydroxide or water. Potassium oxide, alkali metal carbonates or bicarbonates such as sodium carbonate, sodium bicarbonate, potassium carbonate or potassium bicarbonate, alkali metal acetates such as sodium acetate or potassium acetate, alkaline earth metal hydroxides such as hydroxide Calcium or an organic base such as triethylamine, pyridine, lutidine, collidine or quinoline. In another preferred embodiment of the esterification, the alcohol is first converted into sodium alkoxide or potassium alkoxide, for example by treatment with ethanolic sodium hydroxide solution or potassium hydroxide solution, and the alkoxide is isolated, which is converted to an acid anhydride or In particular, reacting with an acid chloride.

  Nitriles can be obtained by halogen exchange using copper cyanide or alkali metal cyanide.

In another method for the preparation of compounds of formula I wherein Z ¹ , Z ² or Z ³ is —CH═CH—, the aryl halide is in the presence of an olefin, a tertiary amine, and the presence of a palladium catalyst. The reaction is performed under (see RF Heck, Acc. Chem. Res. 12 (1979) 146). Examples of suitable aryl halides are chloride, bromide and iodide, especially bromide and iodide. Tertiary amines required for successful coupling reactions, such as triethylamine, are also suitable as solvents. Examples of suitable palladium catalysts are the salts, in particular Pd (II) acetate, and organophosphorus (III) compounds such as triarylphosphine. This process can be carried out in the presence or absence of an inert solvent at a temperature of about 0 ° C. to 150 ° C., preferably 20 to 100 ° C .; suitable solvents are for example nitriles such as acetonitrile, or Hydrocarbons such as benzene or toluene. The aryl halides and olefins used as starting materials are in many cases commercially available or known from the literature, for example by halogenation of the corresponding parent compound or elimination reaction to the corresponding alcohol or halide. Can be prepared.

  In this way, for example, a stilbene derivative can be prepared. Stilbenes can be further prepared by reaction of 4-substituted benzaldehydes with the corresponding phosphorus ylides by the Wittig method. However, tolanes of formula I can also be prepared by using monosubstituted acetylenes instead of olefins (Synthesis 627 (1980) or Tetrahedron Lett. 27, 1171 (1986)).

For the coupling of aromatic compounds, an aryl halide and an aryl tin compound can be further reacted. These reactions are preferably carried out under a protective gas, in the presence of a catalyst, for example a palladium (0) complex, in an inert catalyst, for example a hydrocarbon, at an elevated temperature, for example in boiling xylene.
The coupling reaction of an alkynyl compound with an aryl halide is carried out in a manner similar to that described by AOKing, E. Negishi, FJ Villiani and A. Silveira in J. Org. Chem 43, 358 (1978). Can do.

Tolanes of formula I, wherein Z ¹ , Z ² or Z ³ is —C≡C— can also be prepared by the Fritsch-Buttenberg-Wiechell rearrangement (Ann. 279, 319, 1984), where 1, 1-Diaryl-2-haloethylene is rearranged in the presence of a strong base to give diarylacetylene.
Tolanes of formula I can also be prepared by bromination of the corresponding stilbene followed by dehydrohalogenation. Here, it is possible to use variants of this reaction which are known per se but which are not described in more detail here.

The ethers of the formula I are obtained by etherification of the corresponding hydroxyl compounds, preferably the corresponding phenols, wherein the hydroxyl compounds are advantageously first of all the corresponding metal derivatives, such as the corresponding alkali metal alkoxides or alkali metal phenoxides. _, the conversion NaH, NaNH 2, NaOH, KOH, by treatment with _Na 2 CO ₃ or _K 2 CO _3. The metal derivative is then combined with a suitable alkyl halide, alkyl sulfonate or dialkyl sulfate, preferably in an inert solvent such as acetone, 1,2-dimethoxyethane, DMF or dimethyl sulfoxide, or alternatively. It can also be reacted with excess aqueous or hydroalcoholic NaOH or KOH at a temperature of about 20 ° C to 100 ° C.

To prepare the laterally substituted fluorine or chlorine compound of formula I, the corresponding aniline derivative is combined with sodium nitrite and tetrafluoroboric acid (to introduce F atoms) or copper chloride (I ) (To introduce Cl atoms) to give a diazonium salt, which can then be thermally decomposed at temperatures of 100-140 ° C.
Bonds of aromatic rings to non-aromatic rings or bonds of two non-aromatic rings, preferably organolithium or organomagnesium compounds and ketones when the aliphatic group Z ¹ is intended to be between the rings Obtained by condensation with.

Organometallic compounds are, for example, metal-halogen exchanges between the corresponding halogenated compounds and organolithium compounds, preferably tert-butyllithium or lithium naphthalenide (eg Org. React. 6, 339-366 (1951 ))) Or by reaction with magnesium turnings.
The coupling of the two aromatic rings to the aromatic ring is preferably effected by Friedel-Crafts alkylation or acylation by reaction of the corresponding aromatic compound with a Lewis acid catalyst. Suitable Lewis acids are, for example, SnCl ₄ , ZnCl ₂ , AlCl ₃ and TiCl ₄ .

In addition, the bonding of the two aromatic rings can be accomplished by the Ullmann reaction (eg Synthesis 1974,9) between aryl iodide and copper iodide, but preferably between aryl copper compounds and aryl iodide, or aryl. It can be carried out by the rubber Berg-Bachmann reaction (eg Org. React. 2, 224 (1944)) between a diazonium salt and the corresponding aromatic compound.
Tolanes of formula I can be prepared, for example, by reaction of the corresponding aryl halide with acetylide in a basic solvent with a transition metal catalyst; here, preferably a palladium catalyst, in particular bis ( A mixture of triphenylphosphine) palladium (II) and copper iodide can be used in piperidine as a solvent.

Furthermore, by reducing a compound of formula I which is compatible with formula I but which contains one or more reducible groups and / or C—C bonds instead of H atoms, Can be prepared.
Suitable reducible groups are preferably carbonyl groups, in particular keto groups, furthermore, for example, free or esterified hydroxyl groups or aromatically bonded halogen atoms. Preferred starting materials for the reduction are compatible with Formula I but contain a cyclohexene ring or a cyclohexanone ring instead of a cyclohexane ring and / or a —CH ₂ CH ₂ — group instead of a —CH═CH— group. And / or containing —CO— groups in place of —CH ₂ — groups and / or free or functionally modified (eg in the form of this p-toluenesulfonate) instead of H atoms A compound containing an OH group.

The reduction is carried out, for example, at a temperature of about 0 ° C. to about 200 ° C. and a pressure of about 1 to 200 bar, such as inert solvents such as alcohols such as methanol, ethanol or isopropanol and ethers such as tetrahydrofuran (THF) or dioxane, For example, it can be carried out by catalytic hydrogenation in ethyl acetate, carboxylic acids such as acetic acid or hydrocarbons such as cyclohexane. Suitable catalysts are advantageously noble metals, such as Pt or Pd, which are in the form of oxides (for example PtO ₂ or PdO) on a support (for example Pd on carbon, calcium carbonate or strontium carbonate). Or in finely divided form.

Ketones can also be converted to the corresponding compounds of formula I containing alkyl groups and / or —CH ₂ CH ₂ — bridges using the method of Clementen (zinc, zinc amalgam or tin and hydrochloric acid, preferably in aqueous alcoholic solution. Or in a heterogeneous phase comprising water / toluene at a temperature of about 80-120 ° C., or the Wolff-Kishner method (using hydrazine, preferably in the presence of alkali, for example KOH or NaOH) Can be reduced in high boiling solvents such as diethylene glycol or triethylene glycol at temperatures of about 100-200 ° C.

Furthermore, reduction with complex hydrides is possible. For example, arylsulfonyloxy groups can be reductively removed using LiAlH ₄ , in particular p-toluenesulfonyloxymethyl groups are advantageously about 0, in an inert solvent such as diethyl ether or THF. It can be reduced to a methyl group at a temperature of ~ 100 ° C. Double bonds can be hydrogenated using NaBH ₄ or tributyltin hydride in methanol.
Starting materials are known or can be prepared analogously to known compounds.

  The liquid crystal medium of the present invention preferably contains 2 to 40, particularly 4 to 30, components as components other than the one or more compounds of the present invention. These media very particularly preferably contain 7 to 25 components in addition to one or more compounds according to the invention. These other components are preferably nematic or nematogenic (monotropic or isotropic) substances, in particular azoxybenzene, benzylideneaniline, biphenyl, terphenyl, phenyl benzoate or cyclohexyl benzoate, cyclohexanecarboxylic acid Phenyl or cyclohexyl ester of cyclohexyl, phenyl or cyclohexyl ester of cyclohexyl benzoic acid, phenyl or cyclohexyl ester of cyclohexyl cyclohexane carboxylic acid, cyclohexyl phenyl ester of benzoic acid, cyclohexyl phenyl ester of cyclohexane carboxylic acid or cyclohexyl cyclohexane carboxylic acid, phenyl cyclohexane, cyclohexyl biphenyl , Phenylcyclohexylcyclohexane Xane, cyclohexylcyclohexane, cyclohexylcyclohexylcyclohexene, 1,4-biscyclohexylbenzene, 4,4'-biscyclohexylbiphenyl, phenyl or cyclohexylpyrimidine, phenyl or cyclohexylpyridine, phenyl or cyclohexyldioxane, phenyl or cyclohexyl-1,3-dithiane 1,2-diphenylethane, 1,2-dicyclohexylethane, 1-phenyl-2-cyclohexylethane, 1-cyclohexyl-2- (4-phenylcyclohexyl) ethane, 1-cyclohexyl-2-biphenylylethane, 1- Phenyl-2-cyclohexylphenylethane, optionally halogenated stilbene, benzylphenyl ether, tolans and substituted cinnamic acids Infested a selected substance. The 1,4-phenylene group in these compounds may also be fluorinated.

The most important compounds suitable as other components of the media of the invention can be characterized by the formulas 1, 2, 3, 4 and 5:

  In formulas 1, 2, 3, 4 and 5, L and E, which may be the same or different, are each independently of each other -Phe-, -Cyc-, -Phe-Phe-, -Phe- A divalent group from the group formed from Cyc-, -Cyc-Cyc-, -Pyr-, -Dio-, -G-Phe- and -G-Cyc- and their mirror images, where Phe Is unsubstituted or fluorine-substituted 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexylene, and Pyr is pyrimidine-2,5-diyl or pyridine-2. , 5-diyl, Dio is 1,3-dioxane-2,5-diyl, G is 2- (trans-1,4-cyclohexyl) ethyl, pyrimidine-2,5-diyl, pyridi 2,5-diyl or 1,3-dioxane-2,5-diyl.

  One of the groups L and E is preferably Cyc, Phe or Pyr. E is preferably Cyc, Phe or Phe-Cyc. The medium of the invention is preferably one selected from compounds of formula 1, 2, 3, 4 and 5 where L and E are selected from the group consisting of Cyc, Phe or Pyr. Or two or more components and simultaneously formulas 1, 2, 3, 4 and 5 wherein one of the groups L and E is selected from the group consisting of Cyc, Phe or Pyr, One or more selected from the group consisting of: -Phe-Phe-, -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc-) And optionally formulas 1, 2, 3, 4 and 5 (wherein the radical and E consist of -Phe-Cyc-, -Cyc-Cyc-, -G-Phe- and -G-Cyc- Selected from the group) It comprises one or more components which.

R ′ and / or R ″, independently of one another, are alkyl, alkenyl, alkoxy, alkoxyalkyl, alkenyloxy or alkanoyloxy, —F, —Cl, —CN, —NCS having up to 8 carbon atoms. Or-(O) _i CH _{3- (k + 1)} F _k Cl _l , wherein i is 0 or 1, and k and l are 1, 2 or 3.

  In a smaller subordinate group of compounds of formula 1, 2, 3, 4 and 5, R ′ and R ″ are each independently of one another alkyl, alkenyl, alkoxy, alkoxyalkyl having up to 8 carbon atoms, Alkenyloxy or alkanoyloxy. This smaller subordinate group will be referred to hereinafter as group A, and the compounds will be represented by subordinate formulas 1a, 2a, 3a, 4a and 5a. In most of these compounds, R ′ and R ″ Are different from each other and one of these groups is usually alkyl, alkenyl, alkoxy or alkoxyalkyl.

In another smaller subordinate group of compounds of formula 1, 2, 3, 4 and 5, known as Group B, R ″ is —F, —Cl, —NCS or — (O) _i CH _{3- (k + 1). )} F _k Cl _l (wherein i is 0 or 1, k and l are 1, 2 or 3); compounds with R ″ having this meaning are represented by the subordinate formulas 1b, 2b, 3b, Indicated by 4b and 5b. Particularly preferred are compounds of the dependent formulas 1b, 2b, 3b, 4b and 5b, wherein R ″ is —F, —Cl, —NCS, —CF ₃ , —OCHF ₂ or one OCF _3. .

In the compounds of the dependent formulas 1b, 2b, 3b, 4b and 5b, R ′ is as defined for the compounds of the dependent formulas la to 5a and is preferably alkyl, alkenyl, alkoxy or alkoxyalkyl.
In other smaller subordinate formulas of the compounds of formulas 1, 2, 3, 4 and 5, R ″ is —CN; this subordinate group will be referred to below as group C, and the subordinate compounds of the corresponding group Dependent formulas 1c, 2c, 3c, 4c and 5c, wherein in the compounds of the dependent formulas 1c, 2c, 3c, 4c and 5c, R ′ is as defined for the compounds of the dependent formulas 1a to 5a, preferably Is alkyl, alkoxy or alkenyl.

  In addition to the preferred compounds of groups A, B and C, other compounds of formulas 1, 2, 3, 4 and 5 having other variants of the proposed substituents are also common. All these substances are obtained by methods analogous to or known from the literature.

In addition to the compounds of the formula I according to the invention, the medium according to the invention preferably comprises one or more compounds selected from group A and / or group B and / or group C. The proportion by weight of these groups of compounds in the medium of the invention is preferably
Group A: 0 to 90%, preferably 20 to 90%, especially 30 to 90%
Group B: 0-80%, preferably 10-80%, especially 10-65%
Group C: 0-80%, preferably 5-80%, especially 5-50%
And the sum of the weight proportions of the compounds of group A and / or group B and / or group C present in each medium of the invention is preferably 5% to 90% and in particular 10% to 90% .

  The medium of the invention preferably contains 1-40%, particularly preferably 5-30%, of a compound of the invention. Preference is furthermore given to media containing more than 40%, in particular 45-90%, of the compounds according to the invention. The medium preferably contains 3, 4 or 5 compounds of the invention.

式中、
Ｒ^４およびＲ^５は、互いに独立して、１２個までの炭素原子を有するアルキルまたはアルケニル基であり、ここで、さらに、１つまたは２つ以上の非隣接ＣＨ_２基は、−Ｏ-、−Ｓ−および／または−≡Ｃ−により置換されていてもよく、Ｂは、トランス−１，４−シクロヘキシレシまたは１，４−フェニレンであり、ｍは０または１である、
で表される１種または２種以上の化合物を含み；Particular preference is given to compounds of the formula I
a) Further formula II:

Where
R ⁴ and R ⁵ are, independently of one another, an alkyl or alkenyl group having up to 12 carbon atoms, wherein one or more non-adjacent CH ₂ groups are —O—, Optionally substituted by -S- and / or -≡C-, B is trans-1,4-cyclohexylene or 1,4-phenylene, m is 0 or 1;
Including one or more compounds represented by:

式中、
Ｒ^４およびＲ^５は、互いに独立して、式ＩＩの下に定義した通りであり、Ｃは、１，４−トランス−シクロヘキシレンまたは随意に２位または３位においてフッ素化されている１，４−フェニレンであり、および
ｋは１または２である、
で表される１種または２種以上の化合物を含み；b) Further formula III:

Where
R ⁴ and R ⁵ , independently of one another, are as defined under formula II and C is 1,4-trans-cyclohexylene or optionally fluorinated in the 2 or 3 position 4-phenylene, and k is 1 or 2.
Including one or more compounds represented by:

式中、
アルキルは、各々の場合において、互いに独立して、１〜６個の炭素原子を有する直鎖状アルキル基である、
から選択された１種または２種以上の化合物を含み；c) Formulas IIa-IIe:

Where
Alkyl in each case, independently of one another, is a linear alkyl group having 1 to 6 carbon atoms.
One or more compounds selected from:

式中、
アルキルは、各々の場合において、互いに独立して、１〜６個の炭素原子を有する直鎖状アルキル基であり、アルケニルは、２〜７個の炭素原子を有する直鎖状アルケニル基であり、ｎは０または１であり、ＬはＨまたはＦである、
から選択された１種または２種以上の化合物を含む
液晶媒体である。d) Formulas IIIa-IIIg:

Where
Alkyl in each case, independently of one another, is a linear alkyl group having 1 to 6 carbon atoms, alkenyl is a linear alkenyl group having 2 to 7 carbon atoms, n is 0 or 1, L is H or F,
A liquid crystal medium comprising one or more compounds selected from the group consisting of:

Particularly preferred are furthermore the following media:
e) A medium comprising a compound of formula I selected from one or more, preferably 2-5, preferably selected from formulas Ia and Ib.
f) A medium comprising at least one compound of formula IIa, at least one compound of formula IIb and optionally at least one compound of formula IIc and / or IIIa.
g) A medium comprising at least one compound of formula IIIa and / or IIIb and / or IIIe.
h) A medium comprising at least one compound of formula IIIc and / or IIId and / or IIIg.
i) Medium in which the proportion of compounds of the formula I in the mixture as a whole is at least 5% by weight, preferably 8-35% by weight, particularly preferably 10-25% by weight.
k) A medium in which the proportion of compounds of the formula II in the mixture as a whole is at least 30% by weight, preferably 30 to 95% by weight, particularly preferably 45 to 85% by weight.
l) Medium in which the proportion of compounds of the formula III in the mixture is at least 2% by weight, preferably 3 to 35% by weight, particularly preferably 5 to 30% by weight.

  The liquid crystal mixture which can be used in the present invention is itself prepared by a usual method. In general, the desired amount of the components used in relatively small amounts is dissolved in the components that constitute the important constituents, preferably at elevated temperatures. Alternatively, the solution of the components can be removed by mixing in an organic solvent, such as acetone, chloroform or methanol, and again distilling the solvent, for example after thorough mixing. Furthermore, the mixture can also be prepared by other conventional methods, for example using a premix, for example the equivalent mixture or using a so-called “multi-bottle” system.

  The dielectric is also known to those skilled in the art and can include other additives described in the literature. For example, 0-15%, preferably 0-10% of polychromatic dyes and / or chiral dopants can be added. The individual compounds added are used at a concentration of 0.01-6%, preferably 0.1-3%. However, the concentration numbers for the liquid crystal mixture, i.e. the liquid crystal or other constituents of the mesophase-forming compound, are indicated without considering the concentration of these additives.

In this application and in the following examples, the structure of the liquid crystal compound is indicated by an acronym and the conversion to chemical formula is obtained according to the following Tables A and B All groups C _n H _{2n + 1} and C _m H _{2m + 1} are linear alkyl groups having n and m carbon atoms, respectively. n and m are integers, preferably 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12, where n = m or n ≠ m is there. . The encoding of Table B is self-explanatory. In Table A, only the initials for the basic structure are shown. In each case, the acronym for this basic structure is followed by a dash and the codes for the substituents R ^{1 *} , R ^{2 *} , L ^{1 *} and L ^{2 *} are shown.

Preferred mixture components are found in Tables A and B.
Table A:

Table B:

Table C:
Table C shows possible dopants that are typically added to the mixtures of the present invention.

  Particularly preferred are mixtures according to the invention comprising, in addition to one or more compounds of the formula I, two, three or four or more compounds selected from Table B.

  The following examples are intended to illustrate the present invention without limiting it. In the present specification, the percentage is% by weight. All temperatures are given in degrees Celsius. m. p. Indicates melting point, cl. p. = Clearing point. Furthermore, C = crystalline state, N = nematic phase, Sm = smectic phase and I = isotropic phase. The number between these symbols is the transition temperature. Δn represents optical anisotropy (589 nm, 20 ° C.), and Δε is dielectric anisotropy (1 kHz, 20 ° C.).

  The Δn and Δε values of the compounds of the invention were obtained by extrapolation from a liquid crystal mixture consisting of 10% of each compound of the invention and 90% of the commercially available liquid crystal mixture ZLI-4792 (Merck, Darmstadt).

  "Conventional work-up" involves adding water if desired, extracting the mixture with methylene chloride, diethyl ether or toluene, separating the phases, drying the organic phase, evaporating, and reducing the product under reduced pressure. Meaning purification by distillation or crystallization and / or chromatography under. RT indicates room temperature.

１−１）タ一シクロヘキサノン（１ａ）の調製
１１３．７ｇ（０．５ｍｏｌ）のＺｎＢｒ_２および１４ｇ（２ｍｏｌ）のＬｉを、２ｌのＴＨＦ中の３４５．８ｇ（ｌｍｏｌ）の４’−プロモ−４−ペンチルビシクロヘキシルに同時に加え、混合物を０〜１０℃で４時間超音波で処理した。冷却を除去した後、２６３．７ｇ′（１ｍｏｌ）の４−ブロモフェノールベンジルエーテルおよび１４．６ｇのＰｄＣｌ２−ｄｐｐｆを加え、混合物をＲＴで７２時間かきまぜた。混合物にその後、従来の作業を施した。得られた生成物４’−（４−ベンジルオキシフェニル）−４−ペンチルビシクロヘキシルを、ＴＨＦ中のＰｄ／Ｃ（５％）を用いて水素化した。得られた４−（４’−ペンチルビシクロヘキシル−４−イル）フェノール（収率８３．１％）をその後、ＴＨＦ中のＲｈ／Ｃ（５％）を用いて水添してケトンとした。従来の作業により、４−ペンチル［１，１’；４’，１”］ターシクロヘキサン−４”−オン（１ａ）が得られた（収率６６．８％）。 Example 1
Compound 1 was prepared as follows according to Scheme 1 above.

1-1) Preparation of tert- cyclohexanone (1a) 113.7 g (0.5 mol) ZnBr ₂ and 14 g (2 mol) Li were converted to 345.8 g (lmol) 4′-promo-4 in 2 l THF. -Simultaneously added to pentylbicyclohexyl and the mixture was sonicated for 4 hours at 0-10 <0> C. After removing the cooling, 263.7 g '(1 mol) of 4-bromophenol benzyl ether and 14.6 g of PdCl2-dppf were added and the mixture was stirred at RT for 72 hours. The mixture was then subjected to conventional work. The resulting product 4 ′-(4-benzyloxyphenyl) -4-pentylbicyclohexyl was hydrogenated with Pd / C (5%) in THF. The resulting 4- (4′-pentylbicyclohexyl-4-yl) phenol (yield 83.1%) was then hydrogenated to the ketone using Rh / C (5%) in THF. Conventional work yielded 4-pentyl [1,1 ′; 4 ′, 1 ″] tercyclohexane-4 ″ -one (1a) (yield 66.8%).

1-2) (1) Preparation 15 ml (0.025 mol) BuLi (15% in n-hexane) at −70 ° C. 3.2 g (0.025 mol) 2,3-difluorotoluene in 70 ml THF It was dripped at the solution melt | dissolved in. After stirring the mixture for 30 minutes, a solution of 8.1 g (0.025 mol) of (la) dissolved in 30 ml of THF was added dropwise, and the mixture was further stirred for 1 hour. The mixture was warmed to RT, hydrolyzed and subjected to conventional work. The obtained 4 "-(2,3-difluoro-4-methylphenyl) -4-engineeryl- [1,1 ';4',1"] tercyclohexane-4 "-ol (yield 93.2%) ) Was boiled on a water separator with 300 mg of p-toluenesulfonic acid in toluene for removal of water and the batch was subjected to conventional work. The resulting 4 "-(2,3- Difluoro-4-methylphenyl) -4-ethyl- [1,1 ′; 4 ′, 1 ″] tercyclohexane-3 ″ -ene (yield 69.8%) Hydrogenated at 50 ° C. and 5.8 bar using a Ni / ion exchanger. The compound (1) was obtained by conventional work (HPLC: 98.9%).
C 62 SmB 286 N 317.3 I: Δε = −2.8; Δn = 0.1254

The following compounds were prepared similarly:

２−１）１，２−ジフルオロ−３−（４−プロピルシクロヘキシル）ベンゼン（２ａ）の調製
３４４ｍｌ（０．５５ｍｏｌ）のＢｕＬｉ（ｎ−ヘキサン中１５％）を、−７０℃で、５７ｇ（０．５ｍｏｌ）の２，３−ジフルオロベンゼンを７５０ｍｌのＴＨＦに溶解した溶液に滴下した。混合物を３０分間かきまぜた後に、８４．２ｇ（０．６ｍｏｌ）の４−プロピルシクロヘキサノンを２５０ｍｌのＴＨＦに溶解した溶液を滴下した。混合物をＲＴに加温し、加水分解し、半濃ＨＣｌを用いて酸性化し、従来の作業を施した。得られた１−（２，３−ジフルオロ−４−メチルフェニル）−４−プロピルシクロヘキサノール（粗製の収率１００％）を、水の除去のために、トルエン中の１０ｇのｐ−トルエンスルホン酸と共に４時間水分離装置上で沸騰させ、バッチに、従来の作業を施し、２，３−ジフルオロー１−メチル−４−（４−プロピルシクロヘクス−１−エニル）ベンゼン（収率９７．３％）を得た。ＴＨＦ中のＰｄ／Ｃ（５％）を用いた水素化により、１，２−ジフルオロ−３−（４−プロピルシクロヘキシル）ベンゼンが得られた。異性化のために、生成物を、５００ｍｌの１−メチル−２−ピロリドン中の等モル量のカリウムｔｅｒｔ−ブトキシドと共に５℃で一夜かきまぜ、従来の作業を施した（収率６５．２％）。 Example 2
Compound 2 was prepared as follows according to Scheme 2 above.

2-1) Preparation of 1,2-difluoro-3- (4-propylcyclohexyl) benzene ( 2a) 344 ml (0.55 mol) of BuLi (15% in n-hexane) were added at 57 g (0 0.5 mol) of 2,3-difluorobenzene was added dropwise to a solution of 750 ml of THF. After the mixture was stirred for 30 minutes, a solution of 84.2 g (0.6 mol) of 4-propylcyclohexanone dissolved in 250 ml of THF was added dropwise. The mixture was warmed to RT, hydrolyzed, acidified with semi-concentrated HCl and subjected to conventional work. The resulting 1- (2,3-difluoro-4-methylphenyl) -4-propylcyclohexanol (crude yield 100%) was converted to 10 g of p-toluenesulfonic acid in toluene for removal of water. And boil on a water separator for 4 hours and subject the batch to conventional work up to give 2,3-difluoro-1-methyl-4- (4-propylcyclohex-1-enyl) benzene (97.3% yield). ) Hydrogenation with Pd / C (5%) in THF gave 1,2-difluoro-3- (4-propylcyclohexyl) benzene. For isomerization, the product was stirred overnight at 5 ° C. with an equimolar amount of potassium tert-butoxide in 500 ml of 1-methyl-2-pyrrolidone and subjected to the conventional work (yield 65.2%). .

Preparation of 2-2 (2) 68.8 ml (0.11 mol) of BuLi (15% in n-hexane) was added to 23.8 g (0.1 mol) of 1,2 in 250 ml of THF at -70 ° C. “Difluoro-3- (4-propylcyclohexyl) benzene (2a) was added dropwise and the mixture was stirred for 30 minutes. 24.5 g (0.11 mol) of 4′-propylbicyclohexyl-4-one was added to 100 ml of THF. The dissolved solution was then added dropwise, the mixture was warmed to RT, hydrolyzed, acidified with semi-concentrated HCl and subjected to conventional work (crude yield), then 2-1) Similarly, the obtained cyclohexanol derivative (2b) was converted to a cyclohexene derivative by removing water, followed by catalytic hydrogenation to obtain compound (2) (yield after hydrogenation) 98.9%) .
C 85 SmB 188 N297.1 I; Δε = −2.7: Δn = 0.0936

The following compounds were prepared similarly:

Comparative examples Liquid crystal mixtures containing:

は、透明点、ＤＣ異方性および回転粘度の匹敵する値を有する比較例と比較して、顕著に低下した複屈折を有する。 Example 3
Liquid crystal mixture containing:

Has significantly reduced birefringence compared to comparative examples having comparable values of clearing point, DC anisotropy and rotational viscosity.

は、透明点および回転粘度について匹敵する値を有する比較例と比較して、顕著に低下した複屈折および一層強く負のＤＣ異方性を有する。 Example 4
Liquid crystal mixture containing:

Has significantly reduced birefringence and stronger and more negative DC anisotropy compared to comparative examples having comparable values for clearing point and rotational viscosity.

Claims (7)

Formula I
[Chemical 1]

Where
R ¹ and R ² are, independently of one another, an alkyl group having 1 to 12 carbon atoms that are unsubstituted,
A ¹ , A ² , A ³ and A ⁴ are independently of each other 1,4-phenylene substituted in the 2 and 3 positions by CN, F, Cl, CF ₃ or OCF ₃ or trans -1,4-cyclohexylene,
Z ¹ , Z ² and Z ³ are each a single bond,
However,
a) one of the radicals ^A 1 to A ⁴ but, CN at 2 and 3 positions, F, Cl, that is substituted by CF ₃ or OCF ₃ 1, a 4-phenylene group,
b) Three of the groups A ^{1 to} A ⁴ are trans-1,4-cyclohexylene,
A compound represented by
Compound, 2-position and 3 that have been substituted by F at position 1, 4-phenylene containing group, compounds of the formula I according to claim 1.
Use of a compound of formula I according to claim 1 or 2 as a component of a liquid crystal medium.
Liquid crystal medium having at least two liquid crystal components, characterized in that it comprises at least one compound according to claim 1 or 2 .
Liquid crystal display element, characterized in that it comprises a liquid crystal medium according to claim 4 .
6. The liquid crystal display element according to claim 5 , wherein the liquid crystal display element is an ECB, VA, CSH, DAP or IPS display element.
Electro-optical display element, characterized in that it comprises as a dielectric the liquid-crystal medium according to claim 4 .