DE4441469B4 - New nematic liquid crystal mixtures and their use in STN liquid crystal displays - Google Patents

Abstract

worin
R Alkyl, Alkoxy, Alkenyl oder Alkenyloxy mit bis zu 12 C-Atomen,

L³ bis L⁸ jeweils unabhängig voneinander H oder F;
Z¹ -COO-, -CH₂CH₂- oder eine Einfachbindung,
Z² -COO-, -CH₂CH₂- oder eine Einfachbindung,
Q CF₂, OCF₂, CFH, OCFH oder eine Einfachbindung,
Y F oder Cl,
m 1 oder 2 und
n 0 oder 1 bedeuten,
b) 55–80 Gew.-% einer flüssigkristallinen Komponente T bestehend aus drei oder mehr Verbindungen der Formel I

besteht,
worin
R¹ Alkyl, Alkoxy, Alkenyl oder Alkenyloxy mit 1 bis 8 C-Atomen,
L¹ und L² jeweils unabhängig voneinander H oder F,
R² F, OCF₃, Alkyl oder Alkoxy mit 1 bis 8...Nematic liquid-crystal mixture essentially
a) 15-50 wt .-% of a liquid-crystalline component A consisting of one or more di- or trinuclear compounds having a dielectric anisotropy of more than +1.5 of the formulas II and / or III

wherein
R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 C atoms,

L ³ to L ^{8 are} each independently H or F;
Z ^{1 is} -COO-, -CH ₂ CH ₂ - or a single bond,
Z ^{2 is} -COO-, -CH ₂ CH ₂ - or a single bond,
Q CF ₂ , OCF ₂ , CFH, OCFH or a single bond,
YF or Cl,
m 1 or 2 and
n is 0 or 1,
b) 55-80 wt .-% of a liquid-crystalline component T consisting of three or more compounds of formula I.

consists,
wherein
R ^{1 is} alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 C atoms,
L ¹ and L ^{2 are} each independently H or F,
R ² F, OCF ₃ , alkyl or alkoxy with 1 to 8 ...

Description

The The invention relates to novel nematic liquid-crystal mixtures, and their use in STN liquid crystal displays.

SFA are out for example EP 0 131 216 B1 ; DE 34 23 993 A1 ; EP 0 098 070 A2 ; M. Schadt and F. Leenhouts, 17th Freiburg Liquid Crystal Conference (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, L1784-L1786 (1987); F. Leenhouts et al., Appl. Phys. Lett. 50 (21), 1468 (1987); HA van Sprang and NG Koopman, J. Appl. Phys. 62 (5), 1734 (1987); TJ Scheffer and J. Nehring, Appl. Phys. Lett. 45 (10), 1021 (1984); M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987); and EP Raynes, Mol. Cryst. Liq. Cryst. Letters, Vol. 4 (1), pages 1-8 (1986). The term SFA here includes all relatively high-twist display elements with a twist angle between 160o and 720o, such as the display elements according to Waters et al. (CM Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd International Advertising Conference, Kobe, Japan), STN liquid crystal displays (DE-OS 35 03 259), SBE liquid crystal displays (TJ Physics Lett 45 (1984) 1021), OMI liquid crystal displays (M. Schadt and F. Leenhouts, Appl. Phys. Lett 50 (1987), 236, DST liquid crystal displays (EPG), Scheffer and J. Nehring. OS 0 246 842) or BW-STN liquid crystal displays (K.Kawasaki et al., SID 87 Digest 391 (20.6)).

Compared to standard TN displays are such SFAs by significantly better slopes the electro-optical characteristic and associated better contrast values and characterized by a significantly lower angle dependence of the contrast. Of particular interest are SFAs with extremely short switching times, especially at relatively low temperatures. To achieve short switching times have been the viscosities of liquid crystal mixtures in particular with the help of usually optimized combinations of liquid crystal components and optionally also monotropic additives with relatively high Optimized steam pressure.

The However, achieved switching times were not satisfactory for all applications.

In front Briefly (T. J. Scheffer et al., Displays, vol. 14 (2) 1993, pages 74-85) is a method of electronic addressing highly twisted Advertisements have become known with very short response times. At this technology known as active addressing is in contrast to the conventional one line by line addressing each line of the display during one longer Time period of the frame time addressed, whereby each line only once during of each frame addressed with orthogonal waveforms becomes. Will the latter become conventional Technique in a supertwist liquid crystal display used with very low response times, so does the general Directive that the Picture change time (usually 1.6 ms for a VGA display for a PC) should be 10% of the response time, not met, causing it due to the relaxation of the liquid crystal from the "ON" state to a Lowering the contrast ratio comes. Active addressing opened the possibility, Super twisted liquid crystal displays to address, which makes this simple technique possibly a Challenge to the high-cost, high-performance level, that of the currently active matrix addressed liquid crystal displays goes out, can represent.

Shorter switching times can also be reduced by reducing the FK layer thickness of the SFA and by using it of liquid crystal mixtures with higher Birefringence Δn to reach.

Alles these approaches to achieve shorter However, switching times still do not always work for every application suitable mixtures.

Farther will be higher by SFA Multiplexibility (which leads to a lower number of electronic Drivers - ICs (integrated circuits), lower threshold voltages and a steep characteristic required.

Because of the opposite influence of different material sizes However, no optimal sizes at the same time for all the above mentioned Achieve properties.

Consequently there is still a high need for improved SFA with short ones Switching times with a simultaneously wide operating temperature range, low values for the steepness, good angle dependence of contrast and low threshold voltage.

The object of the invention is to provide SFA having the above-mentioned disadvantages not or only to a small extent and at the same time have very useful overall properties.

It was found now that this Task by using nematic liquid crystal mixtures according to Claim 1 with 55-80 Wt .-% of three or more compounds with a tolan-4,4'-diyl structural element can be solved can.

simultaneously owns the nematic liquid crystal mixture a nematic phase range of at least 60 ° C, a viscosity of not more than 25 mPa · s, a birefringence of at least 0.220 and a dielectric Anisotropy of at least +1, with the dielectric anisotropies the compounds and those associated with the nematic liquid crystal mixture Sizes up a temperature of 20 ° C are related.

• – zwei planparallelen Trägerplatten, die zusammen mit einer Umrandung eine Zelle bilden,
• – einer in der Zelle befindlichen nematischen Flüssigkristallmischung mit positiver dielektrischer Anisotropie,
• – Elektrodenschichten mit darüberliegenden, auf der Innenseite der Trägerplatten befindlichen Orientierungsschichten, die jedes Pixel mittels einer orthogonalen Zeilenwellenform adressieren,
• – einem Voranstellwinkel zwischen der Moleküllängsachse an der Oberfläche der Trägerplatten und den Trägerplatten von etwa 1 Grad bis 30 Grad, sowie
• – einem Wert zwischen 100 und 600° für den Verdrillungswinkel der Flüssigkristallmischung in der Zelle von Orientierungsschicht zu Orientierungsschicht, worin die nematische Flüssigkristallmischung im wesentlichen aus a) 15–50, vorzugsweise 25–50 Gew.-% einer flüssigkristallinen Komponente A aus einer oder mehreren zwei- oder dreikernigen Verbindungen mit einer dielektrischen Anisotropie von mehr als +1,5 der Formeln II und/oder III wie unten definiert; b) 0–40 Gew.-% einer flüssigkristallinen Komponente B aus einer oder mehreren zwei- oder dreikernigen Verbindungen mit einer dielektrischen Anisotropie von –1,5 bis +1,5; c) 55–80 Gew.-% einer flüssigkristallinen Komponente T aus drei oder mehr Verbindungen mit einem Tolan-4,4'-diyl-Strukturelement, sowie d) einer optisch aktiven Komponente D in solch einer Menge, daß das Verhältnis zwischen Schichtdicke (Abstand der planparallelen Trägerplatten) und der natürlichen Ganghöhe der chiralen nematischen Flüssigkristallmischung etwa 0,2 bis 1,3 beträgt

und die nematische Flüssigkristallmischung einen nematischen Phasenbereich von mindestens 60°C, eine Viskosität von nicht mehr als 25 mPa·s, eine Doppelbrechung von mindestens 0,220 und eine dielektrische Anisotropie von mindestens +1 besitzt, wobei die dielektrischen Anisotropien der Verbindungen und die mit der nematischen Flüssigkristallmischung verbundenen Größen auf eine Temperatur von 20°C bezogen sind, besteht dadurch gekennzeichnet, daß die Komponente T aus mindestens drei Verbindungen der Formel I

besteht,
worin
R¹ Alkyl, Alkoxy, Alkenyl oder Alkenyloxy mit 1 bis 8 C-Atomen,
L¹ und
L² jeweils unabhängig voneinander Hoder F,
R² F, OCF₃, Alkyl oder Alkoxy mit 1 bis 8 C-Atomen,
Z -COO- oder eine Einfachbindung und
p 0 oder 1 bedeuten.The invention thus relates to the liquid-crystal mixture and its use for a highly multiplexed SFA

• Two plane-parallel carrier plates, which together with a border form a cell,
• An in-cell nematic liquid-crystal mixture having positive dielectric anisotropy,
• Electrode layers with overlying orientation layers located on the inside of the carrier plates, which address each pixel by means of an orthogonal line waveform,
• - An advance angle between the molecule longitudinal axis at the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, and
• A value between 100 and 600 ° for the twist angle of the liquid-crystal mixture in the cell from orientation layer to orientation layer, wherein the nematic liquid-crystal mixture consists essentially of a) 15-50, preferably 25-50% by weight of a liquid-crystalline component A of one or more bi- or trinuclear compounds having a dielectric anisotropy greater than +1.5 of Formulas II and / or III as defined below; b) 0-40 wt .-% of a liquid-crystalline component B of one or more di- or trinuclear compounds having a dielectric anisotropy of -1.5 to +1.5; c) 55-80 wt .-% of a liquid-crystalline component T of three or more compounds with a tolan-4,4'-diyl structural element, and d) an optically active component D in such an amount that the ratio between layer thickness ( Pitch of the plane-parallel support plates) and the natural pitch of the chiral nematic liquid-crystal mixture is about 0.2 to 1.3

and the nematic liquid crystal mixture has a nematic phase range of at least 60 ° C, a viscosity of not more than 25 mPa · s, a birefringence of at least 0.220, and a dielectric anisotropy of at least +1, wherein the dielectric anisotropies of the compounds and nematic Liquid crystal mixture associated sizes are related to a temperature of 20 ° C, characterized in that the component T from at least three compounds of the formula I.

consists,
wherein
R ^{1 is} alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 C atoms,
L ¹ and
Each L ² is independently H or F,
R ² F, OCF ₃ , alkyl or alkoxy having 1 to 8 C atoms,
Z is -COO- or a single bond and
p is 0 or 1.

worin
R Alkyl, Alkoxy, Alkenyl oder Alkenyloxy mit bis zu 12 C-Atomen,

L³ bis
L⁸ jeweils unabhängig voneinander Hoder F,
Z¹ -COO-, -CH₂CH₂- oder eine Einfachbindung,
Z² -COO-, -CH₂CH₂- oder eine Einfachbindung,
Q CF₂, OCF₂, CFH, OCFH oder eine Einfachbindung,
Y F oder Cl,
m 1 oder 2 und
n 0 oder 1 bedeuten, insbesondere solche ausgewählt aus den Formeln IIa bis IId:

worin R und L¹, L³ und L⁷ die angegebene Bedeutung besitzen.Component A preferably contains compounds of the formulas II and III,

wherein
R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 C atoms,

L ³ to
L ^{8 are} each independently H or F,
Z ^{1 is} -COO-, -CH ₂ CH ₂ - or a single bond,
Z ^{2 is} -COO-, -CH ₂ CH ₂ - or a single bond,
Q CF ₂ , OCF ₂ , CFH, OCFH or a single bond,
YF or Cl,
m 1 or 2 and
n is 0 or 1, in particular those selected from the formulas IIa to IId:

wherein R and L ¹ , L ³ and L ^{7 have} the meaning given.

worin n und m die angegebene Bedeutung besitzen, zur Verbesserung der Schaltzeiten und der Steilheit von STN-Anzeigen, deren Pixel jeweils durch eine orthogonale Zeilenwellenform adressiert werden.Another object of the disclosure is the use of compounds of the formula Ia1

wherein n and m have the meaning given to improve the switching times and the steepness of STN displays whose pixels are each addressed by an orthogonal line waveform.

The Individual compounds of the formulas I, II and III and also others in Compounds useful in the disclosed SFA are either known or can be prepared analogously to known compounds.

The compounds of formula I are made US 3,925,482 and WO 88/07514, but there is no suggestion that the switching times of highly multiplexed SFA can be improved with their help.

Out GB-A-2 255 465 are mixtures of dinuclear or trinuclear Tolan and a liquid crystal of the type of component (A), wherein liquid crystals of the component type (B) can be added. However, it is possible reach an n value of only 0.133.

A liquid crystal composition aimed at increasing the n value by means of a high n-value tolan-containing liquid crystal compound is disclosed in Japanese Patent Laid-Open Nos. 61-97383 and 61-97384, and Japanese Patent Laid-Open Nos EP 178937 known. These liquid crystal compositions mainly contain a high n-type tolan-containing liquid crystal compound, an ester bond liquid crystal compound, and a cyano-group-high-component-type component (A) liquid crystal compound.

Since such a conventional liquid crystal composition contains a high Δn value tolan-containing liquid crystal compound, the optical anisotropy of the resulting composition is relatively high. Since a compound having an ester bond is contained in the composition, no smectic phase is usually observed in a cryogenic atmosphere. An ester bond-having cyclohexanecarboxylic acid phenyl liquid crystal compound has a low Δn value, therefore the optical anisotropy of the composition is not so high (at most about 0.175). Among the low-viscosity liquid crystal compounds, the liquid crystal compound having the ester bond has a relatively high viscosity. The ester-bond-having liquid crystal compound has, for example, a viscosity of about 20 cp. For this reason, the viscosity of the liquid crystal composition having such a liquid crystal compound has a high value of, for example, 28 cp or more.

From the EP 0 268 226 For example, mixtures of binuclear and trinuclear tolan containing greater than 20% of component (B) type binuclear liquid crystals are known for low and intermediate multiplexing TN applications, as can be seen from the low clearing points of about 55 ° C to 65 ° C. These are usually used in calculators and video games. These mixtures are characterized by very low slopes in the devices of usually 85%.

From the pamphlets DE 3923064 A1 . US 5,021,189 and EP 0481293 A2 For example, supertwist liquid crystal displays are disclosed which disclose one or more of the compounds or classes of compounds used herein in mixtures.

With On the other hand, the mixtures of this invention can be highly multiplexed SFA with very high multiplexing ratios, wide working temperature range, low threshold voltages (below 3 volts, preferably between 1.25 and 2.80, especially between 1.60 and 2.20 volts) and steep Characteristic curves as well as high clearing points of more than 75 ° C, preferably 76 to 110 ° C, especially 90 ° C up to 100 ° C, will be realized.

The compounds of the formulas I, II and III have low viscosities, in particular low rotational viscosities, and low values for the ratio of the elastic constants (K ₃ / K ₁ ) and therefore give short switching times.

The Mixtures according to the present Invention have an optical anisotropy (n) of more than 0.220, in particular from 0.220 to 0.250, on.

worin R, L³ und L⁷ die angegebene Bedeutung besitzen.The mixtures according to the invention preferably contain one or more compounds of the formula II and / or of the formula III selected from the following group:

wherein R, L ³ and L ^{7 have} the meaning given.

preferred Mixtures contain two or more compounds of formulas IIa, IIb, IIc, IId, IIIh, in particular one or more compounds of the formula IIa or IIb and three to six compounds of the formula I.

preferred Liquid crystal mixtures according to the invention contain one or more compounds from group A preferably in a proportion of 20% to 50%, preferably 22% to 40%. These Compound or these compounds from group A have a dielectric Anisotropy of more than +3 (preferably more than +8, in particular more than +12) and form the component A of the FK mixtures of these Invention.

Preferably, the mixtures contain one or more compounds of formula II from 22% to 40%. Preferred are those compounds in which Z ^{1 is} a single bond, -CH ₂ CH ₂ - or -CO-O-, and particularly preferred are the following compounds:

Also preferred are the following compounds:

group A preferably consists of one or more compounds selected from the formulas IIb1 to IIc1 and optionally one or more Compounds of formula IIc2.

Preferably, the mixtures furthermore contain one or more polar compounds having a higher clearing point, which are selected, for example, from the following compounds:

In the above four formulas can the 1,4-phenylene rings are substituted by a fluorine atom side by side be, e.g.

These polar compounds with a higher clearing point are preferably used to 2 to 25%.

In another preferred embodiment the mixtures contain one or more compounds with very high dielectric anisotropy. Such compounds are preferred used at 2 to 15%. Preferred compounds of this type are those of the formulas I, IIc2 and IIj1.

preferred liquid crystal mixtures contain one or more compounds from group B, preferably in a proportion of 0 to 25%. This compound or these compounds from group B have either low values for the rotational viscosity (γ1) <150 mPa · s or a clearing point of more than 120 ° C and are dielectrically neutral ((Δε) <2, in particular 0 to 10) and form component B of the FK blends of this invention.

bei denen R³ und R⁴ die für R angegebene Bedeutung besitzen, und/oder eine oder mehrere Verbindungen ausgewählt aus der Gruppe bestehend aus IV8 bis IV21 mit drei Ringen:

worin R³ und R⁴ die angegebene Bedeutung besitzen und die 1,4-Phenylengruppen IV7 bis IV17 und IV21 jeweils unabhängig voneinander auch durch Fluor einfach oder mehrfach substituiert sein können. Enthält die Komponente B mehr als 10 % an einer oder mehreren zweikernigen Verbindungen, so enthält die nematische Mischung zusätzlich eine oder mehrere, vorzugsweise nur eine Verbindung ausgewählt aus der Gruppe bestehend aus IV22 bis IV27:

worin R³ und R⁴ die angegebene Bedeutung besitzen und die 1,4-Phenylengruppen in IV22 bis IV27 jeweils unabhängig voneinander auch durch Fluor einfach oder mehrfach substituiert sein können.Component B preferably contains one or more compounds selected from the group consisting of IV1 to IV7 with two rings:

in which R ³ and R ^{4 have} the meaning given for R, and / or one or more compounds selected from the group consisting of IV 8 to IV 21 having three rings:

wherein R ³ and R ^{4 have} the meaning given and the 1,4-phenylene groups IV7 to IV17 and IV21 each independently of one another may also be monosubstituted or polysubstituted by fluorine. If component B contains more than 10% of one or more binuclear compounds, the nematic mixture additionally contains one or more, preferably only one compound selected from the group consisting of IV22 to IV27:

wherein R ³ and R ⁴ have the meaning indicated and the 1,4-phenylene groups in IV22 to IV27 may be substituted one or more times independently by fluorine.

On contains every case the nematic mixture only up to 5 wt .-%, preferably 0 to 4% by weight of one or more compounds of the formulas IV22 to IV27.

worin R¹ und R² die angegebene Bedeutung besitzen, und G für N oder CH steht.In a preferred embodiment, the nematic mixtures contain at least one heterocyclic compound of the formula V.

wherein R ¹ and R ^{2 have} the meaning given, and G is N or CH.

The LC mixtures also contain an optically active component C in such a quantity that the relationship between the layer thickness (distance of the two plane-parallel carrier plates) and the natural pitch of the chiral liquid crystal mixture is more than 0.2 and to the desired Twist angle adapted is. Suitable dopants can be made of the most diverse select known chiral materials and commercially available dopants, such as e.g. Nonanoic-cholesteryl S 811 (E. Merck, Darmstadt, FRG) and CB 15 (Merck Ltd., formerly BDH, Poole, GB). Their selection is not critical in itself.

worin R¹ die angegebene Bedeutung besitzt und Alkyl n-Alkyl mit 1 bis 8 C-Atomen bedeutet.In a further preferred embodiment, the LC mixtures contain five or more compounds selected from the group consisting of Ia to Ie:

wherein R ^{1 has} the meaning given and alkyl n-alkyl having 1 to 8 carbon atoms.

Of the Proportion of the component or components from group T is preferably 55% to 80%, especially 55% to 65%.

Of the Proportion of binuclear tolans of the formulas Ia and Ib is preferably 16 to 60% and the proportion of trinuclear tolans of the formulas Ic to Ie preferably 18 to 35%.

Of the Total content of all endfluorinated compounds of the non-tolan type is preferably about 5% to 25%, especially about 10% to 20%.

Of the Proportion of compounds of an additional Component C consisting of one or more compounds with a dielectric anisotropy of <-1.5 is preferably about 0% to 20%, especially about 0% to 10%. To achieve the desired Threshold voltage, the skilled artisan can easily correct this proportion, where it is possible in principle is, all conventional liquid crystal compounds with <-1.5.

In a particularly preferred embodiment, the mixtures according to the invention preferably contain about 0% to 10% of one or more compounds having a dielectric anisotropy of less than -2 (component C). Such compounds are known, for example derivatives of 2,3-Dicyanhydrochinons or cyclohexane derivatives with the structural element

Preferably However, compounds with the structural element 2,3-difluoro-1,4-phenylene selected e.g. Compounds as described in DE-OS 38 07 801, 38 07 861, 38 07 863, 38 07 864 or 38 07 908.

worin R² und R³ jeweils unabhängig voneinander vorzugsweise n-Alkyl mit 1 bis 7 C-Atomen oder n-Alkenyl mit 3 bis 7 C-Atomen und Z⁰ -CH₂CH₂- oder eine Einfachbindung bedeuten.Particularly preferred are these structural elements having tolans as in International Patent Application PCT / DE 88/00133, in particular those of the formulas

wherein R ² and R ^{3 are} each independently preferably n-alkyl having 1 to 7 carbon atoms or n-alkenyl having 3 to 7 carbon atoms and Z ^{0 is} -CH ₂ CH ₂ - or a single bond.

wobei
R³ n-Alkyl oder n-Alkoxy mit jeweils 1 bis 7 C-Atomen oder n-Alkenyl oder n-Alkenyloxy mit jeweils 3 bis 7 C-Atomen bedeutet.Particular preference is furthermore given to cyclohexanecarboxylic acid phenyl esters of the formulas

in which
R ³ 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.

worin

n eine ganze Zahl von 1 bis 15,
L¹ und
L² jeweils unabhängig voneinander Hoder F und
X F, Cl oder OCF₃ bedeuten.The component T preferably contains one or more compounds of the formula T3

wherein

n is an integer from 1 to 15,
L ¹ and
L ² each independently Hoder F and
XF, Cl or OCF ₃ mean.

• – 15–60 Gew.-% an zwei oder mehr Verbindungen der Formel I mit p gleich 0, vorzugsweise mindestens zwei Verbindungen der Formeln Ia und/oder Ib, insbesondere eine bis fünf Verbindungen der Formel Ia1
  
  worin m 1 oder 2 ist, und n für eine ganze, zwischen 1 und 7 steht
• – 10–40 Gew.-% an zwei oder mehr Verbindungen der Formel I mit p gleich 1, vorzugsweise mindestens zwei Verbindungen der Formel Id und/oder Ie
• – eine Komponente C, die eine oder mehrere Verbindungen mit einer trans-1-Cyan-1,4-cyclohexylengruppe oder einer 2,3-Difluor-1,4-phenylengruppe enthält,
• – mindestens eine Verbindung aus folgender Gruppe:
  
  worin Alkyl eine geradkettige Alkylgruppe mit 2–7 C-Atomen und X H oder F bedeuten,
• – eine oder mehrere Verbindungen, worin R eine trans-Alkenylgruppe oder eine trans-Alkenyloxygruppe bedeutet,
• – eine oder mehrere Verbindungen ausgewählt aus folgender Gruppe:
  
  worin R² und R³ die bei Komponente B angegebenen bevorzugten Bedeutungen besitzen und eine der zwei 1,4-Phenylengruppen auch durch Fluor substituiert sein kann; der Anteil dieser Verbindungen beträgt 0 % bis 25 %, vorzugsweise etwa 5 % bis 15 %.

In further, particularly preferred embodiments, the mixtures contain

• 15-60% by weight of two or more compounds of the formula I where p is 0, preferably at least two compounds of the formulas Ia and / or Ib, in particular one to five compounds of the formula Ia1
  
  wherein m is 1 or 2, and n is a whole, between 1 and 7
• 10-40% by weight of two or more compounds of the formula I where p is 1, preferably at least two compounds of the formula Id and / or Ie
• A component C containing one or more compounds having a trans-1-cyano-1,4-cyclohexylene group or a 2,3-difluoro-1,4-phenylene group,
• - at least one compound from the following group:
  
  where alkyl is a straight-chain alkyl group having 2-7 C atoms and X is H or F,
• One or more compounds in which R represents a trans-alkenyl group or a trans-alkenyloxy group,
• One or more compounds selected from the following group:
  
  wherein R ² and R ^{3 have} the preferred meanings given for component B and one of the two 1,4-phenylene groups may also be substituted by fluorine; the proportion of these compounds is 0% to 25%, preferably about 5% to 15%.

• – mindestens zwei Verbindungen ausgewählt aus den Formeln IIb1, IIc1 oder IIc2,
• – zwei oder mehr Verbindungen der Formeln Ia oder Ib oder
• – eine oder mehrere Verbindungen ausgewählt aus folgender Gruppe:
  
  worin R² und R³ die für die Verbindungen der Formel III angegebene Bedeutung besitzen.

In a further particularly preferred embodiment, the mixtures contain

• At least two compounds selected from the formulas IIb1, IIc1 or IIc2,
• Two or more compounds of the formulas Ia or Ib or
• One or more compounds selected from the following group:
  
  wherein R ² and R ^{3 have} the meaning given for the compounds of formula III.

In a further preferred embodiment, the mixtures contain
15-50 wt .-% of a consisting essentially of compounds of formula III, liquid crystalline component A, and at least
30-50 wt .-% of at least one compound of formula I, wherein R ^{2 is} F or OCF ₃ .

In another preferred embodiment, the mixtures contain:
0 or 5 to 35 wt .-%, in particular 10 to 20 wt .-% of a liquid-crystalline component B, which consists essentially of compounds selected from the formulas IV2, IV6, IV10, IV12 and V.

The structure of the liquid crystal display elements of polarizers, electrode base plates and electrodes with such surface treatment that the preferred orientation (director) of each adjacent liquid crystal molecules is generally twisted from one electrode to the next by an angle of 160 ° to 720 ° corresponds to that for Such display elements conventional construction. Here, the term of the usual construction is very broad and includes all modifications and modifications of Supertwist cells, in particular matrix display elements. The angle of attack on the two Trägerplat may be the same or different. Same angles of attack are preferred.

The Display is made by orthogonal waveforms, such as from T.J. Scheffer et al., Vol. 14 (2), 1993, pages 74-85.

One significant difference of the display elements to the usual however, based on the twisted nematic cell, there exists the choice of liquid crystal components in the liquid crystal layer.

The Production of the Liquid-Crystal Mixtures According to the Invention takes place in per se usual Wise. In general, the desired Amount of components used in a relatively small amount solved the components constituting the main component, useful in increased Temperature. However, it is also possible solutions of the components in one suitable organic solvent, e.g. in acetone, chloroform or methanol, and to mix the solvent after mixing again, e.g. by distillation.

The Dielectrics can also further, known in the art and described in the literature additions contain. For example, you can 0-15% pleochroic dyes are added.

The following examples serve to illustrate the invention, without representing a limit.

T_on Zeit vom Einschalten bis zum Erreichen von 90 % des maximalen Konstrasts,
T_off Zeit vom Ausschalten bis zum Erreichen von 10 % des maximalen Kontrasts,
V₁₀ Schwellenspannung (Volt),
V₉₀ Sättigungsspannung,
V₉₀/N₁₀ Steilheit
γ_rot Rotationsviskosität.The abbreviations have the following meanings:
SN smectic-nematic phase transition temperature,
NI nematic-isotropic phase transition temperature,
Kp clearing point,
Visc. Viscosity (mPa.s),

T _on time from switching on until reaching 90% of the maximum constrast,
T _off time from switching off to reaching 10% of the maximum contrast,
V ₁₀ threshold voltage (volts),
V ₉₀ saturation voltage,
V ₉₀ / N ₁₀ slope
γ _red rotational viscosity.

The SFA is generated with an orthonormal waveform (multiplexing ratio 1: 256, Bias 1:16, operating voltage 7.2 volts) addressed.

In front- and below, all temperatures are degrees Celsius. percentages mean weight percent. Get the values for the switching times and viscosity to 20 ° C.

Tabelle A:

Tabelle B:

In the present patent application and in the following examples, all chemical structures of the FK compounds are indicated by acronyms, wherein the transformation into chemical formulas is carried out as shown below. All radicals C _n H _{2n + 1} and C _m H _{2m + 1} are straight-chain alkyl radicals with n or m carbon atoms. The coding according to Table B is self-evident. In Table A, only the acronym for the main body is given. In the individual case, a code for the substituents R ¹ , R ² , L ¹ and L ² follows separately from the acronym for the main body with a dash as follows:
The compounds listed in Tables A and B are particularly preferred components of the present invention.

Table A:

Table B:

Example 1 (Only for comparison / as Reference for Episode examples)

An STN ad with the following sizes: twist 240 ° preload 1:16 multiplexing rate 1: 256 Bildfolgefrequent 80 Hz angle of attack 5 ° d 4.2 μm contains a liquid crystal medium, which has the following properties: SN <-30 ° C NI 95 ° C .DELTA.n .2024 γ _red 75 mPa · s and from an achiral base mixture: PCH-3 13.0 K6 10.0 PCH-301 18.0 PCH-302 7.0 CPTP-301 6.0 CPTP-302 6.0 CPTP-303 6.0 CPTP-30CF3 6.0 CPTP-50CF3 6.0 PTP 102 6.0 PTP 201 6.0 PTP-20F 6.0 CBC 33 4.0 exists and
doped with 1.07% S-811 and
is addressed with orthogonal line waveforms, and
shows the following switching variables: T _mtl 140 ms V ₁₀ 2,33 v V ₉₀ / V ₁₀ 1.056.

Example 2

An STN display with d = 3.5 μm as described in Example 1, which is a liquid-crystalline medium having the following sizes: SN <-30 ° C NI + 96 ° C .DELTA.n .2444 γ _red 95 mPa · s contains and from an achiral base mixture: PCH-3 18.0 K6 9.0 K 9.0 PTP-20F 8.0 PTP-40F 7.0 PTP-302FF 8.0 PTP-502FF 8.0 CPTP-302FF 9.0 CPTP-502FF 9.0 CPTP-301 5.0 CPTP-302 5.0 CPTP-303 5.0 exists and is doped with 1.30% S-811, the following switching variables are shown: T _mtl 140 ms V ₁₀ 2.09 V V ₉₀ / V ₁₀ 1.028.

Example 3

An STN display with d = 3.75 μm as described in Example 1, which is a liquid-crystalline medium with the following properties: SN <0 ° C NI + 78 ° C .DELTA.n .2267 γ _red 70 mPa · s contains and from an achiral base mixture: K6 8.00 K9 8.00 PYP-5F 10.00 PCH-3 13,00 PCH 30 6.00 PTP-20F 8.00 PTP-40F 7.00 PTP 102 5.00 PTP 201 6.00 CPTP-302FF 5.00 CPTP-502FF 5.00 CPTP-301 5.00 CPTP-302 5.00 CPTP-303 5.00 CPTP-30CF3 4.00 exists and is doped with 1.43% S-811, the following switching variables are shown: T _mtl 102 ms V ₁₀ 1.92 v V ₉₀ / V ₁₀ 1.068.

Example 4

An STN display as described in Example 1, containing a liquid-crystalline medium, having the following properties: SN <0 ° C NI + 85 ° C .DELTA.n 0.2416 and from an achiral base mixture: PTP 501 12.0 PTP 502 11.0 PTP 504 6.0 PTP 102 5.0 PTP 201 6.0 PTP-20F 6.0 PTP-40F 5.0 PTP-60F 5.0 PCH-3 12.0 PCH-4 12.0 CPTP-302FF 5.0 CPTP-502FF 5.0 CPTP-301 5.0 CPTP-302 5.0 and doped with 1.46% S-811 shows very fast switching times and high multiplexibility.

example

An STN display as described in Example 1, containing a liquid-crystalline medium, having the following properties: SN <0 ° C NI 85 ° C .DELTA.n .2398 and from an achiral base mixture: PTP 501 22.0 PTP 502 11.0 PTP 504 6.0 PTP 201 6.0 PTP-20F 6.0 PTP-40F 5.0 PCH-3 12.0 PCH-4 12.0 CPTP-302FF 5.0 CPTP-502FF 5.0 CPTP-301 5.0 CPTP-302 5.0 and doped with 1.55% S-811 shows very fast switching times and high multiplexibility.

Comparative Example 1

An STN display as described in Example 1 contains a medium having the following properties: SN -30 ° C NI + 91 ° C .DELTA.n 0.2077 γ _red 116 mPa · s has, from: PCH-3 10.0 PCH-5 8.0 ME2N.F 2.0 ME3N.F 2.0 ME5N.F 4.0 PTP-20F 9.0 PTP-40F 9.0 PTP-60F 6.0 PTP 102 5.0 PTP 201 6.0 CPTP-301 6.0 CPTP-302 4.0 CPTP-303 6.0 PCH-301 11.0 CBC-33F 4.0 CBC-53F 4.0 CBC-55F 4.0 and doped with 1.27% S-811, the following switching sizes are shown: T _mtl 168 ms V ₁₀ 2,12 v V ₉₀ / V ₁₀ 1.058.

Out This comparison clearly shows that large quantities of binuclear FK of type B component (PCH-301) in combination with more than 5 % tetranuclear FK (CBC-nmF) give slow switching times.

Example 6

An STN display as described in Example 1, containing a liquid-crystalline medium, having the following properties: NI 91 ° C .DELTA.n .2305 has, from an achiral base mixture: PTP-20F 13.0 PTP-40F 13.0 PTP-60F 13.0 PCH-302 18.0 PTP 102 5.0 PTP 201 5.0 CPTP-301 5.0 CPTP-302 4.0 CPTP-303 5.0 BCH 3F.F 8.0 BCH 5F.F 8.0 CBC-53F 8.0 and doped with S-811 shows very fast switching times and V ₁₀ 3.28 v V ₉₀ / V ₁₀ 1.326.

Examples 7 to 11

An STN display as described in Example 1, which contains a liquid-crystalline medium whose properties and compositions are listed in the following table, shows very fast switching times and high multiplexability. Table I

Claims (10)

Nematic liquid-crystal mixture which comprises a) 15-50 wt .-% of a liquid-crystalline component A consisting of one or more di- or trinuclear compounds having a dielectric anisotropy of more than +1.5 of the formulas II and / or III

wherein R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 C atoms,

L ³ to L ⁸ are each independently H or F; Z ¹ -COO-, -CH ₂ CH ₂ - or a single bond, Z ² -COO-, -CH ₂ CH ₂ - or a single bond, Q CF ₂ , OCF ₂ , CFH, OCFH or a single bond, YF or Cl, m is 1 or 2 and n is 0 or 1, b) 55-80% by weight of a liquid-crystalline component T consisting of three or more compounds of the formula I.

in which R ^{1 is} alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 C atoms, L ¹ and L ^{2 are} each independently H or F, R ² F, OCF ₃ , alkyl or alkoxy having 1 to 8 C atoms, Z is -COO- or a single bond and p is 0 or 1, and c) contains an optically active component D and which has a nematic phase range of at least 60 ° C, a viscosity of not more than 25 mP · a, a birefringence of at least 0.220 and has a dielectric anisotropy of at least +1, wherein the dielectric anisotropies of the compounds and the sizes associated with the nematic liquid crystal mixture are at a temperature of 20 ° C. A liquid-crystal mixture according to claim 1, characterized in that the component A contains compounds of the formulas II and III,

wherein R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 C atoms,

L ³ to L ^{8 are} each independently H or F, Z ^{1 is} -COO-, -CH ₂ CH ₂ - or a single bond, Z ^{2 is} -COO-, -CH ₂ CH ₂ - or a single bond, Q is CF ₂ , OCF ₂ , CFH, OCFH or a single bond, YF or Cl, m is 1 or 2 and n is 0 or 1. A liquid-crystal mixture according to claim 1 or 2, characterized in that the component A contains at least one compound selected from the formulas IIa to IId:

wherein R and L ¹ , L3 ³ and L ^{7 have} the meaning given in claim 1. A liquid-crystal mixture according to at least one of claims 1 to 3, characterized in that component B contains one or more compounds selected from the group consisting of IV1 to IV7:

wherein R ³ and R ^{4 have} the meaning given in claim 1 for R. A liquid-crystal mixture according to at least one of claims 1 to 4, characterized in that component B contains one or more compounds selected from the group consisting of IV8 to IV21:

wherein R ³ and R ^{4 have} the meaning given and the 1,4-phenylene groups IV7 to IV17 and IV21 each independently of one another may also be monosubstituted or polysubstituted by fluorine. A liquid-crystal mixture according to at least one of claims 1 to 5, characterized in that the component T contains five or more compounds selected from the group consisting of Ia to Ie:

wherein R ^{1 has} the meaning given and alkyl n-alkyl having 1 to 8 carbon atoms. Liquid-crystal mixture according to at least one of Claims 1 to 6, characterized in that component T contains one to five compounds of the formula Ia1:

m is 1 or 2, and n is an even number between 1 and 9, preferably 1, 2, 3 or 5. liquid crystal mixture according to at least one of the claims 1 to 7, characterized in that the nematic liquid crystal mixture 30-60 Wt .-% of at least one compound of formula Ia. A liquid-crystal mixture as claimed in any of claims 1, 2 and 4 to 8, characterized in that the nematic liquid-crystal mixture comprises 10-50% by weight of the liquid-crystalline component A consisting essentially of compounds of the formula III and at least 30-50% by weight of at least one Compound of formula I with R ² is F or OCF ₃ contains. Use of a liquid-crystal mixture after at least one of the claims 1 to 9 in a STN liquid crystal display.