DE4441469A1 - Highly multiplexed supertwist liq. crystal (LC) display - Google Patents

Abstract

Highly-multiplexed supertwist liq. crystal (SLC) displays comprise two plane-parallel base plates which, together with an edge form a cell, a nematic LC mixt. with positive dielectric anisotropy (d.an.) in the cell, and electrode layers with orientation layers on the inside of the base plates, which address each pixel with orthogonal line waveforms; the angle of incidence between the long axis of the mol. and the surface of the plate is 1-30 deg. and the angle of twist in the LC mixt. from orientation layer to orientation layer is 100-600 deg. The LC mixt. contains (a) 15-50 wt.% LC component (A) comprising bi- or tri-nuclear cpd(s). with a d.an. of more than +1.5, (b) 0-40 wt.% LC component (B) with bi- or tri-nuclear cpd(s). with a d.an. of -1.5 to +1.5, (c) 40-80 wt.% LC component (T) contg. 3 or more tolan-4,4'-diyl cpds. of formula (I), and (d) an optically active component (D) in amts. such that the ratio between layer thickness (distance between plates) and the natural pitch of the chiral nematic LC mixt. is ca. 0.2-1.4. This LC mixt. has a nematic phase range of at least 60 deg. C, a viscosity of not more than 25 mPa.s, a birefringence of at least 0.1950 and a d.an. of at least +1 (at 20 deg. C). In the formula, R<1> = 1-8C alkyl, alkoxy, alkenyl or alkenyloxy; L<1>, L<2> = H or F; R<2> = F, OCF3 or 1-8C alkyl or alkoxy; Z = -COO-, -CH2CH2- or a single bond; p = 0 or 1. Also claimed are LC mixts. with the above compsn.

Description

The invention relates to highly multiplexed supertwist liquid crystal displays (SFA) with extremely short switching times and good slopes and angles and the new nematic liquid used for this purpose crystal mixtures.

SFA as in the title are z. From EP 0 131 216 B1; DE 34 23 993 A1; ER 0 098 070 A2; M. Schadt and F. Leenhouts, 17th Freiburger liquid crystal conference (8-10.04.87); 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 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, May. Cryst. Liq. Cryst. Letters, Vol. 4 (1), pp. 1-8 (1986) known. The term SFA here includes all relatively high-twisted display elements with a twist angle between 160 ° and 720 °, such. B. the display elements according to Waters et al. (C.M. 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 (T.J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984). 1021), OMI liquid crystal displays (M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST liquid crystal displays (EP-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 SFA by significantly better slopes of the electro-optical characteristic and thus associated better contrast levels as well as through a clear lower angle dependence of the contrast characterized. From Of particular interest are SFA with extremely short switching times, esp especially at relatively low temperatures. To achieve a short  Switching times have been the viscosities of liquid in particular crystal mixtures with the help of usually optimized combinations of liquid crystal components and optionally also monotropic Additives with relatively high vapor pressure optimized.

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

Recently (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 known as active addressing technique is in contrast to her conventional line by line addressing format each line of the display addressed during a longer period of frame time, with each line only once during each frame with orthogonal waveforms is addressed. Will the latter be conventional A very low technology supertwist liquid crystal display Used response times, then the general rule is that the picture change time (usually 1.6 ms for a VGA display for a PC) 10% of the response time should be, not met, which causes it the relaxation of the liquid crystal from the "ON" state to an Er Low contrast ratio comes. Active addressing opened the possibility to address Supertwist liquid crystal displays where possibly a challenge through this simple technique the highly cost-intensive high-performance level of the currently with an active matrix addressed liquid crystal displays emanates can make.

Shorter switching times can also be achieved by reducing the FK Layer thickness of the SFA and by using Flüssigkristallmischun reach with higher birefringence Δn.

However, all these approaches to achieve shorter switching times result in the end still not suitable for every application Mixtures.  

Furthermore, from SFA a higher multiplexability (the one to smaller number of electronic drivers - ICs (integrated circuits) leads), lower threshold voltages and a steep characteristic required.

Because of the opposite influence of different material sizes, however, can not be optimal sizes for all at the same time reach the above-mentioned properties.

Thus, there is still a great need for improved SFA short switching times with a simultaneously wide operating temperature range, low values for the steepness, good angular dependence of the Kon trasts and low threshold voltage.

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

It has now been found that this object is achieved by using nematic liquid-crystal mixtures with 40-80 wt .-% of three or solved more compounds with a tolan-4,4'-diyl structural element can be.

Preferably, the nematic liquid-crystal mixture has a nema phase range of at least 60 ° C, a viscosity of not more than 25 mPa · s, a birefringence of at least 0.195, and a dielectric anisotropy of at least +1, wherein the dielectric Anisotropies of the compounds and those with the nematic liquid crystal mixture connected sizes to a temperature of 20 ° C. are related.

The invention thus provides a highly multiplexed SFA with

• - Two plane-parallel support plates, which together with a Umran form a cell,  
• a nematic liquid crystal mixture in the cell with positive dielectric anisotropy,
• - Electrode layers with overlying, on the inside of the Carrier plates located orientation layers, each pixel address by means of an orthogonal line waveform,
• an advance angle between the longitudinal molecular axis at the Surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees, as well
• 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 wt .-% of a liquid-crystalline component A of one or more di- or trinuclear compounds having a dielectric anisotropy of more than +1.5;
  • 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) 40-80 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 the layer thickness (distance of the plane-parallel support plates) and the natural pitch of the chiral nema tables 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 0.195 and a dielectric anisotropy of at least +1, wherein the dielectric anisotropies of the compounds and those with nematic Liquid crystal mixture associated sizes are related to a temperature of 20 ° C, characterized in net that the component T from at least three compounds of formula I. exists 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-, -CH₂CH₂- or a single bond and
    p is 0 or 1.

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,

and

each independently

L³ to L⁶ are each independently H or F,
Z¹ is -COO-, -CH₂CH₂- or a single bond,
Z² is -COO-, -CH₂CH₂-, -CC or a single bond,
Q is CF₂, OCF₂, 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 L¹ have the meaning given.

Another object of the invention is the use of verbin 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 each be addressed by an orthogonal line waveform.

The individual compounds of the formulas I, II and III and also others in the compounds of the invention are either known or can be prepared analogously to known compounds become.  

The compounds of the formula I are known from US 3,925,482 and WO 88/07514 known, but there is no indication that the switch improve the times of highly multiplexed SFAs with their help.

From GB-A-2 255 465 are mixtures of dinuclear or three Rustic tolan and a component type (A) type liquid crystal known, wherein liquid crystals of the type of component (B) was added can be. However, an n value of only 0.133 can be achieved chen.

A liquid crystal composition with an increase in n value with the aid of a high n-value tolan-containing liquid crystal compound is desired, is from Japanese Patent Disclosures no. 61-97383 and 61-97384 and EP 178 937 known. This liquid Crystal compositions mainly contain a tolan-containing High-n-liquid crystal compound, a liquid crystal compound with an ester bond and a liquid crystal compound of the type the cyano group-terminated component (A) having a high Δn value.

Since such a conventional liquid crystal composition is a tolan containing high-value liquid-crystal compound containing nn, is the opti The anisotropy of the resulting composition is relatively high. Because in the composition contain a compound with an ester bond is usually no smectic phase in a low temperature observed. An ester bond-containing liquid crystal Compound of cyclohexanecarboxylic acid phenyl ester has a niedi gen Δn value, which is why the optical anisotropy of the composition not so high (at most about 0.175). Among the low-viscosity Liquid crystal compounds has the ester bond Liquid crystal compound has a relatively high viscosity. The the esters Bonding liquid crystal compound has z. As a viscosity from about 20 cp. For this reason, the viscosity has such a Liquid crystal compound having liquid crystal composition a high value of z. B. 28 cp or more.

From EP 0 268 226 are mixtures of binuclear and dreikerni Tolan with more than 20% of binuclear liquid crystals of the type component (B) for TN applications with low or medium Multiplexing is known, as from the low clear points of about 55 ° C to 65 ° C is visible. These are usually at bags computers and video games. These mixtures are distinguished by very small slopes in the devices of usually 85% off.

By contrast, the mixtures of this invention are highly multiplexed tre SFA with very high multiplexing ratios, wide working temp range, low threshold voltages (below 3 volts, before preferably between 1.25 and 2.80, in particular between 1.60 and 2.20 volts) and steep characteristics and high clearing points of more as 75 ° C, preferably 76 to 110 ° C, in particular 90 ° C to 100 ° C, will be realized.

The compounds of the formulas I, II and III have low viscosities, especially low rotational viscosities, and low values for the Ratio of elastic constants (K₃ / K₁) and therefore give short Switching times.

The mixtures according to the present invention have an optical Anisotropy (n) of more than 0.200, preferably 0.201-0.270, esp especially from 0.220-0.250, up.

Preferably, the mixtures according to the invention contain one or several compounds of formula II and / or of formula III selected from the following group:

wherein R, L³ and L⁷ have the meaning given.

Preferred mixtures contain two or more compounds of Formulas IIa, IIb, IIc, IId, IIIh, in particular one or more verbin of the formula IIa or IIb and three to six compounds of Formula I.

Preferred liquid crystal mixtures usable according to the invention are ent preferably contain one or more compounds from group A in a proportion of 20% to 50%, preferably 22% to 40%. These Compound or these compounds from group A have a dielek trical anisotropy of more than +3 (preferably more than +8, esp more than +12) and form component A of the LC mixtures this invention.

Preferably, the mixtures contain one or more compounds of formula II to 22% to 40%. Preferred are those compounds in where Z¹ is a single bond, -CH₂CH₂- or -CO-O-, and be the following compounds are particularly preferred:

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 several compounds of formula IIc2.

Preferably, the mixtures further contain one or more polar compounds with a higher clearing point, the z. B. from the following Compounds are selected:

In the above four formulas, the 1,4-phenylene rings can also be replaced by a Fluorine atom be substituted laterally, for. B.

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

In another preferred embodiment, the mixtures contain one or more compounds with very high dielectric anisotropy pie. Such compounds are preferably 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 Ver Group B compounds, preferably in a proportion of 0 to 25%. This compound or these compounds from group B ent neither 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 the component B of the FK Mixtures of this invention.

Component B preferably contains one or more compounds selected from the group consisting of IV1 to IV7 with two rings:

in which R³ and R⁴ have the meaning given for R, and / or one or more compounds selected from the group consisting from IV8 to IV21 with three rings:

wherein R³ and R⁴ have the meaning given and the 1,4-pheny Groups IV7 to IV17 and IV21 each independently may be mono- or polysubstituted by fluorine. Contains the Component B more than 10% of one or more binuclear Compounds, the nematic mixture additionally contains one or a plurality, preferably only one compound selected from the group consisting of IV22 to IV27:

wherein R³ and R⁴ have the meaning given and the 1,4-pheny in each of IV22 to IV27 each independently by Fluorine can be monosubstituted or polysubstituted.

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

In a preferred embodiment, the nematic Mixtures at least one heterocyclic compound of Formula V

wherein R¹ and R² are as defined, and G is N or CH stands.

The LC mixtures also contain an optically active component C in such an amount that the ratio between the layer thickness (Distance between the two plane-parallel support plates) and the natural Pitch of the chiral liquid crystal mixture is more than 0.2 and adapted to the desired twist angle. Suitable dopants Fabrics can be made from a wide variety of known chiral materials and select commercially available dopants, such as. Nonane acid cholesteryl ester S 811 (E. Merck, Darmstadt, Germany) and CB 15 (Merck Ltd., formerly BDH, Poole, UK). Their selection is not in itself critical.

In a further preferred embodiment, the FK Mixtures five or more compounds selected from the Group consisting of Ia to Ie:

wherein R¹ has the meaning given and alkyl n-alkyl with 1 to 8 carbon atoms means.

The proportion of the component or components from group T is preferably 40% to 80%, in particular 42% to 65%.

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

The total amount of all end-fluorinated compounds of the non-tolan type is preferably about 5% to 25%, especially about 10% to 20%.

The proportion of compounds of an additional component C consisting from one or more compounds with a dielectric anisotropic pie of <-1.5 is preferably about 0% to 20%, in particular about 0% to 10%. To achieve the desired threshold voltage The skilled person can easily correct this proportion, and it is in principle possible, all conventional liquid crystal compounds with <-1.5 use.

In a particularly preferred embodiment, the inventions contain Mixtures according to the invention preferably about 0% to 10% of one or several compounds with a dielectric anisotropy of less as -2 (component C). Such compounds are known, for. B. Deri vate of 2,3-Dicyanhydrochinons or Cyclohexanderivate with the structural element

from DE-OS 32 31 707 or DE-OS 34 07 013.

Preferably, however, compounds with the structural element 2,3-difluoro-1,4-phenylene selected, for. B. compounds as in the DE-OS 38 07 801, 38 07 861, 38 07 863, 38 07 864 or 38 07 908.  

Particularly preferred are these structural elements having tolans as in International Patent Application PCT / DE 88/00133, in special ones of the formulas

wherein R² and R³ are each independently preferably n-alkyl 1 to 7 C atoms or n-alkenyl having 3 to 7 C atoms and Z ° -CH₂CH₂- or mean a single bond.

Particular preference is furthermore given to cyclohexanecarboxylic acid phenyl esters the formulas

in which
R³ 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, the component T contains one or more Compounds of the formula T3

wherein

n is an integer from 1 to 15,
L 1 and L 2 are each independently H or F and
XF, Cl or OCF₃ mean.

In further, particularly preferred embodiments, the mixtures

• 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 with p equal to 1, preferably at least two compounds of the formula Id and / or Ie  
• a component C containing one or more compounds with a trans-1-cyano-1,4-cyclohexylene group or a 2,3-difluoro-1,4- contains 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 wherein R is a trans-alkenyl group or a trans-alkenyloxy group,
• one or more compounds selected from the following group: wherein R² and R³ 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%.

In a further particularly preferred embodiment, the mixtures

• 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 R² and R³ have the meaning given for the compounds of formula III.

In a further preferred embodiment, the mixtures contain
15-50 wt .-% of a substantially of compounds of formula III, in particular compounds of formula IIIs, consist of the liquid-crystalline component A, and at least
30-50 wt .-% of at least one compound of formula I, wherein R² is F or OCF₃.

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 according to the invention Polarizers, electrode base plates and electrodes with such Surface treatment that the preferential orientation (director) of the in each case adjacent liquid crystal molecules in general of one electrode to the next mutually by an angle of 160 ° 720 ° twisted, corresponds to the usual for such display elements Construction. The term of the usual construction is here very far  and includes all modifications and modifications of Supertwist cells, in particular also matrix display elements. The Anstellwinkel on the two carrier plates may be the same or different his. Same angles of attack are preferred.

The display according to the invention is characterized by orthogonal waveforms, such as From T.J. Scheffer et al., Vol. 14 (2), 1993, pages 74-85 described, addressed.

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 in 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 desired amount of Kompo used in relatively small amount in the components making up the main component, expedient at elevated temperature. However, it is also possible Solutions of the components in a suitable organic solution medium, z. In acetone, chloroform or methanol and to mix Solvent after mixing to remove again, z. B. 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 serve to illustrate the inventions without limiting it.

The abbreviations have the following meanings:

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

Above and below, all temperatures are degrees Celsius. Percentages mean weight percent. The values for the switching Times and viscosity refer to 20 ° C.

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 individual cases, separated from the acronym for the main body followed by a dash, a code for the substituents R¹, R², L¹ and L² as follows:
The compounds listed in Tables A and B are particularly preferred components of the present invention.

Table A

Table B

example 1

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:

S-N | <-30 ° C N-I 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 V₁₀ 2,33 v V₉₀ / V₁₀ 1.056.

Example 2

An STN display with d = 3.5 μm as described in Example 1, the one liquid crystalline medium with the following sizes:

S-N | <-30 ° C N-I + 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 V₁₀ 2.09 V V₉₀ / V₁₀ 1.028.

Example 3

An STN display as described in Example 1 with d = 3.75 μm, the one liquid crystalline medium having the following properties:

S-N | <0 ° C N-I + 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 V₁₀ 1.92 v V₉₀ / V₁₀ 1.068.

Example 4

An STN display as described in Example 1, which is a liquid contains crystalline medium, the following properties:

S-N | <0 ° C N-I + 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 is doped with 1.46% S-811 shows very fast switching times and high multiplexability.

Example 5

An STN display as described in Example 1, which is a liquid contains crystalline medium, the following properties:

S-N | <0 ° C N-I 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 multiplexability.  

Comparative Example 1

An STN display as described in Example 1 contains a medium the following properties:

S-N | -30 ° C N-I + 91 ° C .DELTA.n 0.2077 γc _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

exists and is doped with 1.27% S-811, the following switching variables are shown:

T _mtl | 168 ms V₁₀ 2,12 v V₉₀ / V₁₀ 1.058.

It is clear from this comparison that large quantities of two nucleated type B component (PCH-301) in combination with more than 5% tetranuclear FK (CBC-nmF) slow switching times result.

Example 6

An STN display as described in Example 1, which is a liquid contains crystalline medium, the following properties:

N-I | 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

V₁₀ | 3,28 V V₉₀ / V₁₀ 1.326.

Examples 7 to 11

An STN display as described in Example 1, which is a liquid contains crystalline medium whose properties and composition tongues listed in the following table shows very fast Switching times and high multiplexability.

Table I

Examples 12-18

An STN display as described in Example 1, which is an LC medium whose properties and compositions are shown in Table II can be taken, shows very fast switching times.  

Table II

Claims (11)

1. Highly multiplexed supertwist liquid crystal display with

• two plane-parallel carrier plates, which together with a border form a cell,
• a nematic liquid crystal mixture in the cell 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 orthogonal line waveforms,
• - 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 of orientation layer to orientation layer, wherein the nematic liquid crystal mixture substantially
  • a) 15-50 wt .-% of a liquid-crystalline component A best starting from one or more two- or dreikernigen connec tions with a dielectric anisotropy of more than +1.5;
  • b) 0-40 wt .-% of a liquid-crystalline component B consisting of one or more di- or trinuclear Verbindun conditions having a dielectric anisotropy of -1.5 to +1.5;
  • c) 40-80 wt .-% of a liquid-crystalline component T best starting from three or more compounds with a tolan-4,4'-diyl structural element, and
  • d) an optically active component D ent in such an amount keeps ent, that the ratio between the layer thickness (distance 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 0.1950 and a dielectric anisotropy of at least +1, wherein the dielectric anisotropies of the compounds and those with the nematic liquid-crystal mixture ver related sizes are based on a temperature of 20 ° C, characterized in that the component T from at least three compounds of the formula I. exists 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-, -CH₂CH₂- or a single bond and
    p is 0 or 1.

2. Display according to claim 1, characterized in that component A contains compounds of the formulas II and / or III, wherein
R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 C atoms, and each independently L³ to L⁶ are each independently H or F,
Z¹ is -COO-, -CH₂CH₂- or a single bond,
Z² is -COO-, -CH₂CH₂-, -CC or a single bond,
Q is CF₂, OCF₂, 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. 3. A display according to claim 1 or 2, characterized in that component A contains at least one compound selected from the formulas IIa to IId: wherein R and L¹ have the meaning given. 4. A display according to at least one of claims 1 to 3, characterized in that component B compounds one or more Ver selected from the group consisting of IV1 to IV7 contains: wherein R³ and R⁴ have the meaning given in claim 1 for R. 5. A display according to at least one of claims 1 to 4, characterized in that component B compounds one or more Ver selected from the group consisting of IV8 to IV21 contains: wherein R³ and R⁴ have the meaning given and the 1,4-phenylene IV7 to IV17 and IV21 each independently of one another by fluorine may be monosubstituted or polysubstituted. 6. A display according to at least one of claims 1 to 5, characterized in that the component T five or more connec tions selected from the group consisting of Ia to Ie contains: wherein R¹ has the meaning given and alkyl n-alkyl having 1 to 8 carbon atoms. 7. A display according to at least one of claims 1 to 6, characterized in that the component T contains one to five compounds of formula Ia1: m is 1 or 2, and
n is an even number between 1 and 9, preferably 1, 2, 3 or 5. 8. Display according to at least one of claims 1 to 7, characterized characterized in that the nematic liquid crystal mixture 30-60 Wt .-% of at least one compound of formula Ia. 9. Display according to one of claims 1, 2 and 4 to 8, characterized in that the nematic liquid-crystal mixture
10-50 wt .-% of the consisting essentially of compounds of formula III, in particular compounds of formula IIIs, liquid crystalline component A and at least
30-50 wt .-% of at least one compound of formula I with R² equal to F or OCF₃. 10. A liquid-crystal mixture as claimed in any one of claims 1 to 9 defined composition.   11. Use of the compounds of the formula Ia1 wherein n and m have the meaning given to improve tion of the switching times and slopes of STN displays whose pixels are each addressed by an orthogonal line waveform.