DE19511632A1 - Alkenyl-cyclohexane(s) for liquid crystal mixt. for super-twist LCD with high contrast and short switching time - Google Patents

Abstract

Alkenyl-cyclohexane cpds. (IA-J) of formula R<1>-(A*)-(CH=CH)r-Cyc-CH=CH-(Cyc)s-R<2> (A), having substits. as follows, are new. (IA) : A* = Cyc; p, s = 1; r = 0; (IB) : A* = Cyc; p, r, s = 1; R<2> = alkyl; (IC) : p, r = 0; s = 1; R<1> = R<b>-CH=CH-(CH2)n-; (ID) : p, r = 0; s = 1 or 2; R<1> = Rb-CH=CH-(CH2)n-; R<2> = (CH2)o-CH=CH-Rb; (IE) : p, r = 0; s = 2; R<1> = Rb-CH=CH-(CH2)n-; (IF) : p, s = 1; r = 0; R<1> = Rb-CH=CH-(CH2)n; (IG) : p, r = 0; s = 1; R<1> = Rb-CH=CH-(CH2)n-; R<2> = Phe'-R<1>; (IH) : p, r = 0; s = 1 or 2; R<1> = Rb-CH=CH-(CH2)n-; R<2> = -(CH2)o-CH=CH-Rb'; (IJ) : p, s = 1; r = 0; Cyc = trans-1,4-cyclohexylene; Phe' = 1,4-phenylene (Phe), 3-fluoro-1,4-phenylene (Phe-F) or 3,5-difluoro-1,4-phenylene (Phe-2F) (end gp. in 4-position); in general, when not specified: A* = Cyc, Phe' or 2-fluoro-1,4-phenylene; R<1> = 1-10C alk(en)yl or alkoxy, opt. mono-substd. by CN or CF3 or at least mono-substd. by halogen, in which 1 or more CH2 gps. may be replaced by -O-; R<2> = (CH2)n-CH=CH-Ra, (CH2)n-CH=CH2 and, if r = 1, also Ra; Ra = 1-6C linear alkyl; Rb,Rb' = H or 1-6C alkyl; n, o = 0-6; r = 0, 1 or 2; s = 1 or 2. Also claimed are (i) a supertwist LCD contg. a nematic liquid crystal (LC) mixt. comprising LC components A, B and opt. D and an optically active component C, in which component B contains cpd(s). (I) of formula (A) with the general range of substits.; (ii) the LC mixt. per se; and (iii) new intermediates (II) of formula (I; p, r = 0; s = 1; R<1> = 1-6C alkyl-OOC-; R<2> = Rb).

Description

The invention relates to supertwist liquid crystal displays (SFA) with very short switching times and good slopes and angle dependencies as well as the novel nematic liquid crystal used therein mixtures.

SFA according to the preamble are known, for. From EP 0 131 216 B1 DE 34 23 993 A1 EP 0 098 070 A2; M. Schadt and F. Leenhouts, 17. Freiburg Workshop on Liquid Crystals (8.-10.04.87); K. Kawasaki et al. SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katoh et al., Japanese Journal of Applied Physics, Vol. 26, No. 11, L 1 784-L 1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 50 (21), 1468 (1987); HA. van Sprang and H.G. Koopman, J. Appl. Phys. 62 (5), 1734 (1987); T.J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987) and E.P. Raynes, Mol. Cryst. Liq. Cryst. Letters Vol. 4 (1), pp. 1-8 (1986). The term SFA here includes any higher twist display element with a twist angle of between 160 ° and 360 °, such as the display elements according to Waters et al. (C.M. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Internal Display Confe rence, Kobe, Japan), the STN-LCD's (DE OS 3503259), SBE-LCD's (T.J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021), OMI-LCD's (M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCD's (EP OS 0 246842) or BW-STN-LCDs (K.Kawasaki et al., SID 87 Digest 391 (20.6)).

Such SFAs are distinguished by comparison with standard TN displays significantly better slopes of the electro-optical characteristic and thus associated better contrast levels as well as a significant clause gere angle dependence of the contrast. Of special interest are SFA with very short switching times especially at lower Temperatures. To achieve short switching times were previously in the special the viscosities of the liquid crystal mixtures optimized under  Use of mostly monotropic additives with relatively high vapor print. However, the switching times achieved were not for every application sufficient.

To achieve a steep electro-optical characteristic, the liquid crystal _{mixtures should} have relatively large values for K₃ / K₁ and relatively small values for Δε / ε _⟂ .

Beyond the optimization of contrast and switching times placed on such mixtures further important requirements:

• 1. Wide d / p window
• 2. High chemical stability
• 3. High electrical resistance
• 4. Low frequency dependence of the threshold voltage.

The obtained parameter combinations are far from exhaustive especially for high-multiplex STN (1/400). Partly this is due to the fact that the various requirements are Material parameters are influenced in opposite directions.

There is thus still a great need for SFA with very short ones Switching times with simultaneous high operating temperature range, high Slope slope, good angle dependence of contrast and low ger threshold voltage, the above requirements satisfy.

In DE 35 09 170 compounds of the formula

called.

In Chemiker Zeitung 104 (1980), 269-271 compounds of the Formula I with long-chain alkyl radicals (m + n <9) described. Latter Representatives, however, have only those for use in nemati liquid crystal mixtures unfavorable, smectic phases. Surprisingly, by shortening the chain length a nematic phase range with simultaneous suppression of the smek table phase.

The invention has for its object to provide SFA, the Above mentioned disadvantages not or only to a lesser extent and at the same time have short switching times and very good slopes.

It has now been found that this problem can be solved if one uses nematic liquid crystal mixtures, the 1,2-dicyclo hexylethylene derivatives of the formula IA or IB

contain,
wherein
Ra and R ^{b are} each independently H or alkyl of 1 to 6 C atoms,
Ra in the case of the formula IB and r = 0 also alkoxy having 1 to 6 carbon atoms or fluorine, and
r 0 or 1
mean,
wherein the phenyl ring in formula IB may optionally be substituted by one or more fluorine atoms.

The compounds of formula I significantly shorten the switching times of STN blends without degrading the slopes.

The invention is thus an SFA with

• - Two plane-parallel carrier plates, with a border a Form cell,
• a nematic liquid crystal mixture in the cell with positive dielectric anisotropy,
• - Electrode layers with overlying alignment layers on the insides of the carrier plates,
• an angle of attack between the longitudinal axis of the molecules at the Surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, and
• a twist angle of the liquid crystal mixture in the cell of Orientation layer to orientation layer in the amount between 100 and 600 °,
• - A nematic liquid crystal mixture consisting of
  • a) 20-90 wt .-% of a liquid-crystalline component A, best starting from one or more compounds having a dielectric anisotropy rule over +1.5;
  • b) 10-65% by weight of a liquid-crystalline component B, consisting of one or more compounds having a dielectric anisotropy between -1.5 and +1.5;
  • c) 0-20 wt .-% of a liquid-crystalline component D, consisting of one or more compounds having a dielectric anisotropy of less than -1.5 and
  • d) an optically active component C in an amount such that the ratio between layer thickness (spacing of the plane-parallel support plates) and natural pitch of the chiral nematic liquid-crystal mixture is about 0.2 to 1.3,

characterized in that component B at least one Compound of the formula IA or IB

contains
wherein
Ra and ^{Rb are} each independently H or alkyl of 1 to 6 carbon atoms
Ra in the case of the formula IB and r = 0 is also alkoxy having 1 to 6 C atoms or fluorine, and
r 0 or 1
mean,
wherein the phenyl ring in formula IB may optionally be substituted by one or more fluorine atoms.

The invention also relates to corresponding liquid crystal mixtures for use in SFA.

Preferred compounds of the formula IA are in particular compounds the sub-formulas IA1 to IA2.

The invention also relates to compounds of the formula IA1 and IA2.

Preferred compounds of the formula IB are in particular compounds the sub-formulas IB1 to IB3

Ra is preferably straight-chain H or alkyl.
R ^b is preferably H.

The preparation of the compounds of the invention takes place for. B. as in DE 35 09 170 A1 describes:

Scheme 1

Scheme 2

The invention also relates to a process for the preparation of Compounds of formulas IA1 and IA2 and the new intermediate the formula A,

wherein R ^{b has} the meaning given and alkyl C₁-C₆-alkyl.

Component A preferably contains compounds of the formulas II and / or III,

wherein
R is an alkyl group having 1 to 12 carbon atoms, wherein one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -OCO- or -COO-, in particular a trans-alkenyl group having 2 to 7 carbon atoms,

each independently

L ^{1-6 are} each independently H or F
Z¹ is -COO-, -CH₂CH₂- or a single bond,
Z 2 is -CH₂CH₂-, -COO-, -C =C- or a single bond,
Q -CF₂-, -CHF-, -OCF₂-, -OCHF- or a single bond
YF or Cl
a 1 or 2, and
b 0 or 1
mean.

Preferred compounds of the formula II correspond to the sub-formulas IIa to IId:

wherein R, L¹ and L⁵ have the meaning given above.  

Preferred compounds of the formula III correspond to the sub-formulas IIIa-IIIt:

Preferred mixtures contain, in addition to one or more Verbindun gene of formula I one, two, three or more compounds of the formulas IIa, IIb, IIc, IId, IIId, IIIh, IIIi, IIIl, IIIm or IIIs, preferably one or several compounds of the formula IIId or IIIh and one to four compounds compounds of the formula I and one to three compounds of the formulas IIb and IIc.

The individual connections z. As the formulas II and III or their sub formulas or other compounds used in the invention SFA can be used, are either known or they can be prepared analogously to the known compounds.

In a particularly preferred embodiment, component A contains in addition compounds of the formulas AI to AV:

wherein
R is an alkyl group having 1 to 12 carbon atoms, wherein also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -OCO- or -COO-.

or a single bond

mean.

Preferably, the mixtures contain 5 to 50% of compounds of Formula AI. Preference is given to those compounds of the formula AI where Z¹ is -CH₂CH₂-, -COO- or a single bond, in particular compounds of the formulas IIa1, IIb1, IIc1, IId1, IIa2, IIb2 and IIc2:

Component A preferably contains one or more compounds of the Formulas IIb1 and optionally one or more compounds of Formulas IIc2.

Preferably, the mixtures according to the invention contain one or several polar compounds with a high clearing point selected from the group consisting of the compounds IIe to IIj:

In the compounds IIe to IIj, the 1,4-phenylene rings can also be lateral be substituted by one or two fluorine atoms. Preferred compound of this type are the compounds of the formulas IIf1 to IIj1:

In the mixtures according to the invention, the proportion of the compounds IIe to IIj preferably at about 2 to 25%. Preferred liquid crystal mixtures contain one or more compounds of group B. preferably 10 to 40%. The compounds of group B are distinguished both by their low values for the rotational viscosity (γ₁) <150 mPa · s and by their high clearing point (<120 ° C).

Component B contains one or more compounds selected from the group consisting of the compounds of formulas IV1 to IV9:

wherein R¹ and R² have the meaning given for R.

In a particularly preferred embodiment, the mixture according to the invention comprises at least one compound of the formula IB and at least one compound of the formula IV6 in which one of the radicals R 1 and R 2 is C _2-10 -alkenyl, in particular alk-1-enyl or alk-3. enyl means.

Component B additionally contains one or more compounds selected from the group consisting of the compounds of Formulas IV10 to IV24,

wherein R¹ and R² have the meaning given for R and the 1,4-Phe nylene groups in IV10 to IV9, IV23 and IV24 each independently others may also be mono- or polysubstituted by fluorine.

In a particularly preferred embodiment, the inventions contain According to the invention media at least one compound of the formula IA and at least one compound of formulas IV12 and / or IV16, wherein R¹ trans-alkenyl having 2 to 10 carbon atoms, in particular alk-1-enyl or Alk-3-enyl means.

Component B additionally contains one or more compounds selected from the group consisting of the compounds of For my name is IV25 to IV30,

wherein R¹ and R² have the meaning given for R and the 1,4-phenylene groups in IV25 to IV30 each independently may also be mono- or polysubstituted by fluorine.

Component B contains one or more compounds selected from the group consisting of IV31 and IV32:

wherein C _r H _{2r + 1 is} a straight-chain alkyl group having up to 9 C atoms.

The liquid-crystal mixture contains components A, B and C in addition to the components additionally one or more compounds selected from the group consisting of III and IV wherein R¹ and R² are the meaning given for R. have.

Preferred liquid-crystal mixtures contain at least one compo component selected from the group of the following compounds:

where Hal is F or Cl and L is H or F and R is the one given above Has meaning.

The liquid-crystalline mixtures also contain an optically active Component C in an amount such that the ratio between layer thickness (Distance between the plane-parallel support plates) and natural pitch of the chiral nematic liquid-crystal mixture is greater than 0.2. For the comm Components are available to the person skilled in the art, in part commercially available  Licher chiral dopants available for. As cholesteryl nonanoate, S811 from E. Merck, Darmstadt, Germany and CB15 (BDH, Poole, UK). The choice of dopants is not critical per se.

The liquid-crystal mixture of the invention preferably contains a or several compounds selected from the group B1 from compounds of the formulas B1I to B1IV:

wherein
R¹ and R² each independently have the meaning of R,
Z is -CH₂CH₂, -CO-O-, -O-CO- or a single bond, and

mean,
and / or at least one compound selected from the group B2 consisting of compounds of the formulas B1V to B1VII:

wherein
R has the meaning given above,
Z ° -CH₂CH₂- or a single bond,

where r 1-9,
X CN or F,
L 1 H or F
mean,
and / or at least one compound selected from the group B3 consisting of compounds of the formulas B1VIII, B1IX and B1X:

wherein
R¹ and R² independently of one another have the meaning of R,
YF or Cl, and

mean.

In a particularly preferred embodiment, the inventions contain Mixtures according to the invention about 5 to 35%, in particular 10 to 20% liquid-crystalline tolane compounds. This can at lower Layer thicknesses (about 5-6 microns) are worked, whereby the switching times be significantly shorter. Particularly preferred are mixtures containing one or more compounds selected from the group T consisting from the compounds of the formulas T1 to T3:

wherein

t 0 or 1,
L ^{1-6 are} each independently H or F,
Q is -CF₂-, -CHF-, -OCF₂-, -OCHF- or a single bond,
YF or Cl,
Z ° is -CO-O-, -CH₂CH₂- or a single bond, and
R¹ and R² each independently represent the meaning given for R
have.

The proportion of the compounds from the group T is preferably 5 to 30%, especially 5 to 20%.

Preferably component B contains one or more compounds of Formulas X to XIII:

wherein
R¹ and R² each independently of one another have the meaning given for R and R¹ preferably alkyl having 1 to 4 C-atoms, in particular 1 to 2 C-atoms and R² before preferably alkoxy having 1 to 4 C-atoms, in particular 1 to 2 C-atoms atoms,
mean.

The proportion of compounds from group B1 is preferably 10 up to 50%, in particular 15 to 40%. Compounds of the formula B1III and B1IV are preferred.

Particularly preferred compounds of formula B1III are those of following sub-formulas B1IIIa and B1IIIb,

wherein
R³ 'CH₃- (CH₂) _o -, CH₃- (CH₂) _o -O-, CH₃- (CH₂) _p -, trans -H- (CH₂) _q -CH = CH- (CH₂CH₂) _b -CH₂O or trans- H- (CH₂) _q -CH = CH- (CH₂CH₂) _b -, CH₃- (CH₂) _o -O-CH₂-,
R⁴'CH₃- (CH₂) _p -,
0, 1, 2, 3 or 4
q is 0, 1, 2 or 3
b 0 or 1, and
p is 1, 2, 3 or 4
is.

Particular preference is given to compounds of the formula B1IIIa in which R³ 'is trans-H- (CH₂) _q -CH = CH-, and of the formula B1III in which one of the radicals R³ or R⁴ is O- (CH₂) _o -CH₃ or CH₂-O - (CH₂) _o -CH₂- means.

Further preferred are those partial formulas

wherein R⁴ and R⁴ are each independently the above Have meaning.

The proportion of the compounds of formula B1III of the above Partial formulas is preferably about 5 to 45%, particularly preferably about 10% to 35%. Particularly preferred compounds of the formula B1IV are those of the following subformula,

wherein
R * CH₃- (CH₂) _o -O- or trans -H- (CH₂) _q -CH = CH- (CH₂CH₂) _b - CH₂O- and
R² 'is CH₃- (CH₂) _p -, where
o 1, 2, 3 or 4,
q 0, 1, 2 or 3,
b 0 or 1, and
p is 1, 2, 3 or 4
is.

The proportion of these compounds, or of the compounds of the formula BIV, is preferably about 5 to 40%, more preferably about 10 to 35%.

Preferably, the mixtures contain compounds of the formula B1III, in particular those of the sub-formula

in particular wherein R¹ and R² are each independently alkyl 1 to 7 carbon atoms, or wherein one of R¹ and R² Akyl with 1 to 7 carbon atoms and the other alk-1-enyl or alk-3-enyl with 2 to 7 carbon atoms means.  

In a particularly preferred embodiment, the Mischun at the same time compounds of the formulas B1III and B1IV, wherein the Total share for components of group B1.

If compounds of the formulas B1I and / or B1III are present, be Preferably, R² and R³ are each independently n-alkyl with 1 to 7 C atoms or (trans) -n-alkenyl with 3 to 7 C atoms. Z is preferably a single bond.

Further preferred are mixtures according to the invention, one or contain a plurality of compounds of formula B1IV, wherein

R¹ and R² is one of the above given preferred meanings, especially preferred n-alkyl having 1 to 7 carbon atoms.

In any case, the total amount remains for components of group B1 maintained.

The proportion of the compounds of group B2 is preferably about 5 up to 45%, in particular 5 to 20%. The proportion (preferred ranges) for B1V to B1VII is as follows:

B1V: approx. 5 to 30%, preferably approx. 5 to 15%
Sum B1VI and B1VII: about 5 to 25%, preferably about 10 to 20%.

Preferred compounds of group B2 are given below:

R is preferably n-alkyl having 1 to 7 carbon atoms or (trans) n-alkenyl with 3 to 7 carbon atoms. Z ° is preferably a single bond. R¹ has in front preferably the preferred meaning given above for R or be indicates fluorine. L 1 is preferably fluorine. x is 1-15.

Preferably, the mixtures according to the invention contain one or several compounds selected from the group consisting of B1V3, B1VI1 and B1VII1 in a total proportion of about 5 to 35%.

In a particularly preferred embodiment, the inventions contain Mixtures according to the invention in addition to B1V3, B1VI1, B1VII1 (R = F) further terminal fluorinated compounds, for example, selected from the group consisting of

and / or polar heterocycles selected from the group consisting of

wherein R¹ is preferably n-alkyl having 1 to 7 carbon atoms or (trans) n-alkenyl with 3 to 7 carbon atoms, a is 1 or 2, b is 0 or 1, X is F, Cl, CF₃, -OCF₃ or -OCHF₃, and L is H or F means.

The total amount of all terminal fluorinated compounds is preferred example, about 5 to 65%, in particular about 15 to 40%.

The proportion of compounds from group B3 is preferably about 5 to 30%, more preferably about 10 to 20%. R² is preferably n-alkyl or n-alkoxy each having 1 to 9 carbon atoms.  

However, analogous compounds with alkenyl or alkenyl can also be used oxy groups are used. Compounds of formula B1VIII are prefers.

The mixtures according to the invention preferably contain Verbindun of the formula I and compounds of at least one of the groups B1, B2 and B3. Preferably, they contain one or more verbs from group B1 and one or more compounds Group B2 and / or B3.

The proportion of the compounds of component C is preferably 0 up to 20%, in particular 0 to 10%.

In a particularly preferred embodiment, the inventions contain Mixtures according to the invention preferably about 5 to 20% of one or several compounds with a dielectric anisotropy of less than -2 (Component C). Such compounds are known, for. B. derivatives of 2,3-Dicyanhydroquinones or cyclohexane derivatives with the structural element

according to DE-OS 32 32 707 and DE-OS 34 07 013.

Preferably, however, compounds with the structural element 2,3-difluoro-1,4-phenylene selected, for. B. compounds according to DE-OS 38 07 801, 38 07 861, 38 07 883, 38 07 864 or 38 07 908. Particularly preferred are tolans with this structural element according to the International Patent Application PCTIDE 88/00133, especially those the formulas

wherein R⁵ and R⁶ are each independently preferably n-alkyl having 1 to 7 carbon atoms or n-alkenyl having 3 to 7 carbon atoms, and
Z ° is -COO-CH₂H₂- or a single bond.

Particularly preferred are phenylcyclohexylcarboxylates of the formulas

Component C contains one or more compounds selected from the group consisting of V to IX:

wherein R¹ and R² have the meaning given for R and b is 0 or 1 is.

In particular, component C leads to an increased steepness of Curve.

Component B contains one or more compounds selected from the group consisting of Xa to XIIa,

wherein alkyl and alkoxy an alkyl or alkoxy radical having 1 to 7 carbon atoms mean.

In a particularly preferred embodiment, the Mischun about 5 to 35%, more preferably about 10 to 20% of liquid crystalline tolan compounds. This can be at lower layer  thick (about 5-6 microns) are worked, whereby the switching times significantly get shorter. Particularly preferred tolans are listed below give:

R 1 is preferably n-alkyl or n-alkoxy having 1 to 7 C atoms,
Z ° is -CO-O-, -CH₂CH₂- or a single bond,

Q³ is

in which
X ° is F, Cl or OCF₃, where
R² is n-alkyl or n-alkoxy each having 1 to 7 carbon atoms or n-alkenyl or n-alkenyloxy each having 3 to 7 carbon atoms.

Preferably, component A contains one or more compounds of Formula T3a

wherein

x an integer from 1-15,
L ^{3-6 are} each independently H or F, and
X 'is F, Cl or OCF₃
mean.

In the following further particularly preferred embodiments:

• Component C contains one or more compounds with one 1-cyano-trans-1,4-cyclohexyl group or a 2,3-difluoro- 1,4-phenylene
• at least two compounds of the formulas AIII or AV
• Compounds of formulas AIII and AV
• - at least one compound from the group: wherein alkyl is a straight-chain alkyl or alkenyl radical having 2 to 7 C atoms and LH or F;
• one or more compounds wherein R is a trans-alkenyl group or a trans-alkenyloxy group;
• - one or more compounds selected from the following group: wherein R¹ and R² have the preferred meanings mentioned under compounds of component B. The 1,4-phenylene group in the above-mentioned compounds may also be substituted by fluorine. The proportion of these compounds in the liquid crystal mixtures is 0 to 25%, preferably 5 to 15%.

In a further preferred embodiment, the mixtures contain

• - One or more, in particular 1, 2, 3 or 4 compounds out selects from the compounds of formulas IIId, IIIb, IIIi and IIIp;
• at least two compounds selected from the compounds of the formulas IIa1, IIa2, IIb1, IIc1 and IIc2;
• one or more compounds of formula B1IV;
• one or more compounds of formula T1 or T2;
• one or more compounds of the formulas wherein R has the meaning given in formula III.

In a preferred embodiment, the inventive liquid-crystalline media 3, 4, 5 or 5 compounds of the formulas Ia and / or Ib; the content of these compounds is usually 10  to 60 wt .-%, preferably 15 to 50 wt .-% based on the total mixture.

Media comprising compounds of the formula Ia and of the formula Ib are particularly preferred, in particular these media comprise at least one compound of the formulas Ia and / or Ib, wherein R ^{b is} hydrogen be.

The mixtures according to the invention are characterized in particular when used in SFAs with high layer thicknesses by very low sum switching times (= t _on + t _off ).

Low sum switching times are an important criterion in particular for SFAs when used as laptops, cursor movements to represent trouble-free.

The liquid crystal mixtures used in the SFAs of the present invention are dielectrically positive with Δε 1. Particularly preferred are liquid crystal mixtures with Δε 3 and especially those with Δε 5.

The liquid-crystal _{mixtures according} to the invention have favorable values for the threshold voltage V _10/0/20 and for the flow viscosity η. If the value for the optical path difference d · Δn is predetermined, the value for the layer thickness d is determined by the optical anisotropy Δn. In particular, especially at relatively high values for Δn, the use of liquid crystal mixtures according to the invention having a relatively high optical anisotropy value is preferred, since then the value for d can be chosen to be relatively small, which leads to more favorable values for the switching times. However, liquid crystal displays according to the invention which contain liquid crystal mixtures according to the invention with smaller values for Δn are also characterized by advantageous values for the switching times. The liquid-crystal mixtures according to the invention are further characterized by advantageous values for the steepness of the electro-optical characteristic and can be operated at high multiplex rates. In addition, the liquid-crystal mixtures according to the invention have a high stability and favorable values for the electrical resistance and the frequency dependence of the threshold voltage. The fiction, contemporary liquid crystal displays have a large operating temperature range and a good angular dependence of the contrast.

The structure of the liquid crystal display elements according to the invention Polarizers, electrode base plates and electrodes with such Surface treatment that the preference orientation (director) of the ever because of adjacent liquid crystal molecules from one to other electrode usually by amount 160 ° to 720 ° against is twisted each other, corresponds to that for such display elements usual construction. The term of the usual construction is here far also includes all modifications and modifications of the super twist cell, in particular matrix display elements and the additional Liche magnets containing display elements. The surface angle on the two support plates may be the same or different. Same Tilt angles are preferred.

A significant difference of the display elements of the invention to the usual on the basis of the twisted nematic cell However, there is the choice of liquid crystal components of the liquid crystal layer.

The preparation of the liquid crystal which can be used according to the invention Mixtures takes place in a conventional manner. In general, the ge desired amount of components used in lesser amount the components constituting the main component are solved, purpose moderately at elevated temperature. It is also possible solutions of Components in an organic solvent, eg. In acetone, Chloroform or methanol, and the solvent after Remove again mixing, for example by distillation.

The dielectrics may also other, known in the art and in the Literature described additives contain. For example, 0-15% pleochroic dyes are added.  

The following examples are intended to illustrate the invention without going to limit.

It means:

SN phase transition temperature smectic-nematic,
Nl phase transition temperature nematic-isotropic,
Klp. clearing point,
Visc. Viscosity (m Pa · s),
t _on from switching on until reaching 90% of maximum contrast,
t _off time from switching off to reaching 10% of the maximum contrast,
V₉₀ / V₁₀ steepness,

The SFA is controlled in multiplex mode (multiplex ratio) 1: 240, bias 1:16, operating voltage 10 volts, so that t _on = t _off ).

Above and below, all temperatures are given in ° C. The Pro Numbers are weight percentages. The values for the switching times and Viscosities refer to 20 ° C.

In the present application and in the following examples, the structures of the liquid crystal compounds are indicated by acronyms, wherein the transformation into chemical formulas according to the following Tabel len A and B takes place. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m C atoms. The alkenyl radicals have the trans configuration. The coding according to Table B is self-evident. In Table A, only the acronym for the main body is given. In individual cases, a code for the substituents R 1, R 2, L 2 and L 2 follows separately from the acronym for the main body with a dash:

Table A

Table B

The following examples are intended to illustrate the invention without being limits. Above and below are percentages by weight percent. All temperatures are in degrees Celsius. Mp means Melting point, bp. = Clearing point. Furthermore, K = crystalline state, N = nematic phase, S = smectic phase and I = isotropic phase. The Indications between these symbols represent the transition temperatures Δn means optical anisotropy (589 nm, 20 ° C) and viscosity (mm² / sec) was determined at 20 ° C.

"Usual workup" means: if necessary, add water, extracted with dichloromethane, diethyl ether, methyl tert. Butyl ether or Toluene, separated, the organic phase is dried, evaporated and purified the product by distillation under reduced pressure or crystallization and / or chromatography. The following abbreviations are used:

DAST: diethylaminosulfur trifluoride
DMEU: 1,3-dimethyl-2-imidazolidinone
KOT: Potassium tertiary butoxide
THF: tetrahydrofuran
pTsOH: p-toluenesulfonic acid.

example 1

In a nitrogen atmosphere 2.93 ml Methoxymethyltrimethyltri phenylphosphonium chloride and 2.93 moles of 4-cyclohexanonecarboxylic acid  dissolved in 4 l of THF and at room temperature with stirring with 2.93 mol Kaliumtert.butylat added. It is stirred for 2 h, mixed with water and verd. Hydrochloric acid and works up as usual.

50.4 mmol II, 1.0 g 10% HCl, 20 ml THF and 50.4 mmol acetaldehyde are stirred for 0.75 h at room temperature. It is mixed with water and Methyl tert-butyl ether and works up as usual.

In a nitrogen atmosphere, 46.1 mmol of potassium tert.butylate in 20 ml of THF to 46.1 mmol of ethyltriphenylphosphonium bromide dissolved in 50 ml THF is added dropwise at 0 ° C. After stirring for 10 minutes, 46.1 mmol III are dissolved in 20 ml of THF was added dropwise to the solution. It is allowed to reach room temperature heat, mixed with water and dilute HCL and methyl tert-butyl ether and works up as usual.

65.8 mmol of Vitride be presented at 0 ° C in 35 ml of toluene and dissolved under stirring with 72.3 mmol of morpholine in 20 ml of toluene. The Solution is added dropwise at -40 ° C to 32.9 mmol IV dissolved in 30 ml of toluene and stirred at -40 to -50 ° for 70 min. It is mixed at -40 ° C with water and at -10 ° C with 10% HCl. Subsequently, as usual is working.

0.04 mol of V, 0.04 mol of 4- (trans-4-ethylcyclohexyl) methyltriphenylphosphonium iodide and 1140 ml of THF are introduced and treated in portions with 0.40 mol of potassium tert.butylat, wherein the reaction temperature should not exceed 35 ° C. , It is stirred overnight at room temperature, hydrolyzed, treated with dil. HCl and worked up as usual. K 33 S _B (20) N 45.5 l

Analogously, the following compounds of the formula

manufactured:

applications Example A

An STN ad with the following parameters:

Twist | 240 ° MuX 1: 240 d · Δn [μm] 0.85

contains a nematic mixture with the following properties:

Clearing point | 90.1 ° C Δn [589 nm] .1421 d / p 0.53

consisting of:

ME2N.F | 2.0% ME3N.F 3.0% PCH-3 20.0% PCH-5 6.0% PTP 201 5.0% BCH-32 8.0% BCH-52 8.0% CPTP-301 5.0% CPTP-302 5.0% CPTP-303 4.0% PCH-302 6.0% CCH-34 5.0% CCH-35 5.0% CVC-2-V1 6.0% CVC-3-V1 6.0% CVC-4-V1 6.0%

has the following switching behavior:

V₁₀ | 2.39 V V₉₀ / V₁₀ 1,051 t _ave 217 ms

Example B

An STN display as described in Example A contains a nematic Mixture with the following properties:

Clearing point | 93.1 ° C Δn [589 nm] .1408 d / p 0.53

consisting of:

ME-2N.F | 2.0% K6 6.0% K9 6.0% PCH-3 18.0% BCH-32 7.0% BCH-52 7.0% CPTP-301 5.0% CPTP-302 4.0% CPTP-303 4.0% CCH-34 5.0% CCH-35 4.0% CVC-2-V1 10.0% CVC-3-V1 10.0% CVC-4-V1 10.0% CBC 33 2.0%

has the following switching behavior:

V₁₀ | 2.496 V V₉₀ / V₁₀ 1,048 t _ave 213 ms

Example C

An STN display as described in Example A contains a nematic Mixture with the following properties:

Clearing point | 87.6 ° C .DELTA.n 0.1397 d / p 0.52

consisting of:

ME-2N.F | 2.0% K6 4.0% K9 5.0% PCH-3 22.0% PTP 201 2.0% BCH-32 5.0% BCH-52 5.0% CPTP-301 5.0% CPTP-302 5.0% CPTP-303 5.0% CCH-34 5.0% CCH-35 5.0% CVC-2-V1 10.0% CVC-3-V1 10.0% CVC-4-V1 10.0%

has the following switching behavior:

V₁₀ | 2,435 V V₉₀ / V₁₀ 1,039 t _ave 223 ms

Example D

An STN display as described in Example A contains a nematic Mixture with the following properties:

Clearing point | 86.4 ° C .DELTA.n 0.1395 d / p 0.52

consisting of:

ME-2N.F | 2.0% K6 4.0% K9 5.0% PCH-3 22.0% PTP 201 2.0% BCH-32 5.0% BCH-52 5.0% CPTP-301 5.0% CPTP-302 5.0% CPTP-303 5.0% CCH-34 5.0% CCH-35 5.0% CVC-2-V1 10.0% CVC-3-V1 10.0% CVC 3-V0 10.0%

has the following switching behavior:

V₁₀ | 2.432V V₉₀ / V₁₀ 1,042 t _ave 215 ms

Example E

An STN display as described in Example A contains a nematic Mixture with the following properties:

Clearing point | 85.9 ° C .DELTA.n 0.1395 d / p 0.52

consisting of:

ME-2N.F | 2.0% K6 4.0% K9 5.0% PCH-3 22.0% PTP 201 2.0% BCH-32 5.0% BCH-52 5.0% CPTP-301 5.0% CPTP-302 5.0% CPTP-303 5.0% CCH-34 5.0% CCH-35 5.0% CVC-2-V1 10.0% CVC-3-V1 10.0% CVC-1V-V0 10.0%

has the following switching behavior:

V₁₀ | 2.4V V₉₀ / V₁₀ 1,039 t _ave 209 ms

Example F-K

The compositions of the liquid crystalline media and the self of STN displays produced with their help (Twist = 2400) can be found in the following tables:

Table I

Table II

Example L-O

The compositions of the liquid crystalline media and the self of STN displays produced with their help (Twist = 2400) can be found in the following tables.

Table III

Table IV

Example P-U

The compositions of the liquid crystalline media and the self of STN displays produced with their help (Twist = 2400) can be found in the following tables.  

Table V

Table VI

Example V

A liquid-crystalline medium is prepared consisting of:

ME2N.F | 2.0% K6 6.0% K9 5.0% PCH-3 18.0% PTP 102 4.0% PTP 201 4.0% BCH-32 7.0% BCH-52 7.0% CPTP-301 3.0% CCH-34 8.0% CCH-35 7.0% CVCP V F. F 4.0% CVCP-V-1 7.0% CVCP V 01 5.0% CVC-V-3 8.0% CVC-V-4 5.0%

.DELTA.n | 0.1390 clearing point 84.6 ° C V₁₀ 2,265V V₉₀ / V₁₀ 1,045 t _ave [ms] 200

Comparative Example 1

An STN display as described in Example A:

PCH-3 | 21.0% PCH-5 15.0% PCH-302 23.0% K6 4.0% BCH-32 7.0% CCP 2OCF₃ 4.0% CCP 3OCF₃ 2.0% ECCP 31 5.0% ECCP 32 5.0% CPTP-301 5.0% CPTP-302 5.0% CPTP-303 4.0%

Clearing point [° C] +85.4 Δn [589 nm] +0.1415 STN 240 ° @ d · Δn [μm] 0.85 d / p 0.54 V _(10,0,20) [V] 2.36 V₉₀ / V₁₀ 1,043 t _ave [ms] 245

Comparative Example 2

An STN ad as described in Example R:

ME2N.F | 4.0% ME3N.F 3.0% PTP-20F 4.0% BCH-32 6.0% CCH-34 3.0% CCH 3-2V 29.0% PCH-1V-N 25.0% PCH 3V-N 5.0% BCH 3V 2 21.0%

Clearing point [° C] | +87,2 Δn [589 nm] .1365 STN 240 ° @ d.Δn [μm] 0.85 V₁₀ [V] 2.26 V₉₀ / V₁₀ 1,038 t _ave [ms] 208 ns

Claims (14)

1. Supertwist liquid crystal display with

• two plane-parallel carrier plates, which form a cell with a border,
• a nematic liquid crystal mixture in the cell having positive dielectric anisotropy,
• Electrode layers with overlying orientation layers on the insides of the carrier plates,
• an angle of attack between the longitudinal axis of the molecules on the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, and
• a twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer in the amount between 100 and 600 °,
• - A nematic liquid crystal mixture consisting of
  • a) 20-90 wt .-% of a liquid-crystalline component A, consisting of one or more compounds having a dielectric anisotropy of over +1.5;
  • b) 10-65 wt .-% of a liquid-crystalline component B, consisting of one or more compounds having a dielectric anisotropy between -1.5 and +1.5;
  • c) 0-20 wt .-% of a liquid-crystalline component D, consisting of one or more compounds having a dielectric anisotropy of less than -1.5 and
  • d) an optically active component C in an amount such that the ratio between layer thickness (distance between the plane-parallel support plates) and natural pitch of the chiral nematic liquid-crystal mixture is about 0.2 to 1.3,

characterized in that component B comprises at least one compound of the formula IA and / or of the formula IB contains
wherein
Ra and R ^{b are} each independently H or alkyl of 1 to 6 C atoms,
Ra in the case of the formula IB and r = 0 also alkoxy having 1 to 6 carbon atoms or F, and
r 0 or 1
mean,
wherein the phenyl ring in formula IB may optionally be substituted by one or more fluorine atoms 2. Display according to claim 1, characterized in that compo nent A compounds of the formulas II and / or III wherein
R is an alkyl group having 1 to 12 carbon atoms, wherein also one or two non-adjacent CH₂ groups may be replaced by -O-, -CH = CH-, -CO-, -OCO- or -COO-, each independently L ^{1-6 are} each independently H or F,
Z¹ is -COO-, -CH₂CH₂- or a single bond,
Z 2 is -CH₂CH₂-, -COO-, -C =C- or a single bond,
Q is -CF₂-, -CHF-, -OCF₂-, -OCFH- or a single bond,
YF or Cl
a 1 or 2, and
b 0 or 1
mean,
contains. 3. Display according to claim 1 or 2, characterized in that component A at least one compound of the formulas IIa to IId, wherein
R, L¹ and L⁵ have the meaning given in claim 2,
contains. 4. Display according to one of claims 1 to 3, characterized in that component B one or more compounds of the formulas wherein
R¹ and R² are each independently alkyl, alkoxy, alkenyl, alkenyloxy of 1-12 C atoms, and and Z 2 have the meaning given in claim 2,
contain. 5. Display according to at least one of claims 1 to 4, characterized in that the liquid-crystal mixture contains one or more compounds of formula B1IIIa. wherein
R³ 'CH₃- (CH₂) _o -, CH₃- (CH₂) _o -O-, CH₃- (CH₂) _p -, trans -H- (CH₂) _q -CH = CH- (CH₂CH₂) _b -CH₂O- or trans -H- (CH₂) _q -CH = CH- (CH₂CH₂) _b -, CH₃- (CH₂) _o -O-CH₂-,
R⁴'CH₃- (CH₂) _p -,
0, 1, 2, 3 or 4
q is 0, 1, 2 or 3
b 0 or 1, and
p is 1, 2, 3 or 4
is. 6. Display according to claim 5, characterized in that the liquid crystal mixture contains one or more compounds of the formula IA and one or more compounds of the formula B1III ent holds, wherein R³ 'for trans-H- (CH₂) _q -CH = CH- or trans -H- (CH₂) _q -CH = CH-CH₂CH₂-, and q is 0, 1, 2 or 3. 7. Display according to at least one of claims 1 to 6, characterized in that component C contains one or more compounds Ver selected from the group consisting of V to IX, wherein R¹ and R² are as defined for R and b is 0 or 1. 8. A display according to at least one of claims 1 to 7, characterized in that component B contains one or more connec tions selected from the group consisting of XA to XIIIa, wherein the alkyl and alkoxy radical contains up to 7 carbon atoms. 9. Display according to at least one of claims 1 to 8, characterized in that component A contains one or more connec tions of the formula T3a, wherein x an integer from 1-15,
L ^{3-6 are} each independently H or F, and
X 'is F, Cl or OCF₃
mean. 10. Liquid crystal mixture of defined in any of claims 1 to 9 composition. 11. Compounds of the formula IA1, wherein
Ra and R ^{b have} the meaning given in claim 1. 12. Compounds of the formula IA2, wherein
Ra and R ^{b have} the meaning given in claim 1. 13. Compound of formula A wherein
R ^{b has} the meaning given in claim 1 and
alkyl is C₁-C₆-alkyl.