JP2001294862A - Supertwist nematic liquid crystal display - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a supertwist nematic liquid crystal display (STN-LCD) having improved temperature-dependency of working voltage by a short switching time, high steepness and improved frequency dependency of dielectric constant especially at a low temperature. SOLUTION: The new nematic liquid crystal mixture contains one or more kinds of the compound of general formula I and one or more kinds of the alkenyl compound of general formula II (R1 and R2 are each a fluorinated 1-12C alkyl, alkoxy, alkenyl or alkenyloxy; one CH2 group or two non-adjacent CH2 groups may be replaced with O, CH=CH, CO, OCO or COO wherein O atoms are not adjacent to each other; R3 is a 2-7C alkenyl; and L1 and L2 are each H or F). The STN-LCD is produced by using the liquid crystal mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a super-twisted nematic liquid crystal display (ST) having a very short switching time and good steepness and angle dependence.
N-LCD), and also to novel nematic liquid crystal mixtures used in such displays.

[0002]

2. Description of the Related Art STN-LCDs in the title are, for example, EP 0,131,216 B1; DE 3,423,993 A1; EP 0,098,070 A
2; 17th Freiburg c by M. Schadt and F. Leenhouts
onferenceon liquid crystals (April 8-10, 1987);
SID87 Digest391 (20.6) by K. Kawasaki et al .; M. Schadt
And SID87 Digest372 (20.1) by F. Leenhouts;
Katoh et al., Japanese Journal of Applied Physics,
Vol. 26, No. 11, L1784-L1786 (1987); Appl. Phys. Lett. 50 (21), 1468 (1987) by F. Leenhouts et al .; HAvan Spr.
J. Appl. Phys. 62 (5), 1734 by ang and HG Koopman.
(1987); Appl. Ph. By TJ Scheffer and J. Nehring
ys. Lett. 45 (10), 1021 (1984); M. Schadt and F. Leenho.
Appl.Phys.Lett. 50 (5), 236 (1987) and E.
Mol.Cryst.Liq.Cryst.Letters, Vol.4 by P.Raynes
(1), pages 1-8 (1986).

[0003] In this specification, the term STN-LCD is intended to encompass all display elements having a relatively large twist, having a numerical twist angle between 160 ° and 720 °, and Display elements include, for example,
Display elements such as Waters (Proc.Soc.In by CMWaters etc.)
f.Disp. (New York) (1985) (3rd Intern.Display Confere
nce, Kobe, Japan), STN-LCD (DE OS 3,503,259),
SBE-LCD (by TJ Scheffer and J. Nehring
Appl. Phys. Lett. 45 (1984) 1021), OMI-LCD (M. Sch.
Appl.Phys.Lett. 50 by Adt and F. Leenhouts (198
7), 236, DST-LCD (EP OS 0,246,842) or BW
-STN-LCD (SID87 Digest391 by K. Kawasaki et al.
(20.6)).

Compared to a standard TN display, this type of STN-LCD has a particularly good steepness of the electro-optical characteristic curve (hereinafter simply referred to as 'steepness') and, for example, from 1/32 to 1 / At 64 and higher medium and high time division drive ratios, the associated good contrast values stand out. On the other hand, TN displays
It typically exhibits high contrast due to good dark color, and has less angular dependence of contrast than STN displays at low time division drive ratios, eg, less than 32. S with very short switching times, especially at relatively low temperatures
TN-LCD is particularly important. Heretofore, in order to obtain short switching times, in particular the rotational viscosity of the liquid-crystal mixture has been optimized, in particular by using an optimal combination of monotropic additives which optionally have a relatively high vapor pressure in the liquid-crystal components. However, the switching times achieved were not suitable for every application.

[0005] Shorter switching times are required for STN-LCDs.
Reducing the thickness of the liquid crystal layer and increasing the birefringence Δ
This is achieved by using a liquid crystal mixture having n. However, all approaches to such short switching times result in mixtures that are not suitable for any application. Further demands on STN-LCDs are higher split driving forces (and consequently fewer drive ICs), lower threshold voltages and higher steepness.
In order to obtain a high steepness in STN-LCD, the liquid crystal mixture must exhibit a relatively large value of the elastic constant K ₃₃ / K ₁₁ ratio and a relatively small {ε / ε _} value, where △ ε is the dielectric anisotropy, and _⊥ is the dielectric constant in the direction perpendicular to the long molecule axis.

Apart from optimizing the contrast and the switching time, this type of mixture has further important requirements: 1. A wide d / p window defined by the range between the lower and upper d / p values of the cell gap d and pitch p. 2. High chemical stability 3. High electrical resistance Small Temperature and Frequency Dependence of Threshold Voltage However, the optimal parameters cannot simultaneously achieve all of the above properties due to the opposing effects of different parameters depending on the materials such as dielectric and elastic. Thus, hitherto achieved combinations of these parameters are particularly high time division drive STN-LCD
(Time-division drive ratio 1/400) as well as medium and low time-division drive STN-LCDs (1/64 and 1/16 time-division drive ratios, respectively) are still not satisfactory.

[0007] Thus, while having a short switching time which satisfies the above requirements, a wide operating temperature range, high steepness (ie low steepness value), good angle dependence of contrast and low threshold voltage are achieved. There continues to be a great demand for improved STN-LCDs having.

[0008]

SUMMARY OF THE INVENTION The object of the invention is to have only a small extent or none of the disadvantages mentioned above, while at the same time having very effective overall properties, in particular short switching times at low temperatures and high switching times. An object of the present invention is to provide an STN-LCD having an improved temperature dependence of an operating voltage due to an improved frequency dependence of the steepness and the dielectric constant.

[0009]

According to the invention, one or more compounds of the formula I

Embedded image And one or more compounds of formula II

Embedded image Wherein R ¹ and R ² are, independently of one another, an optionally fluorinated alkyl, alkoxy, alkenyl or alkenyloxy group having 1 to 12 carbon atoms, wherein one CH ₂ group or Two non-adjacent CH ₂
The groups are-assuming that the O atoms are not directly adjacent to each other-
O-, -CH = CH-, -CO-, -OCO- or-
A nematic liquid crystal mixture comprising: R ³ is an alkenyl group having 2 to 7 carbon atoms, and L ¹ and L ² are each independently H or F. It has been found that the above problem can be achieved by using.

By using the compounds of the formulas I and II in the liquid-crystal mixtures for STN-LCDs according to the invention,
In particular, high steepness, small threshold voltage with small temperature dependence, and short switching times, especially at low temperatures, are obtained.
Furthermore, the liquid-crystal mixtures according to the invention exhibit the following advantages: low viscosity, low temperature dependence of the threshold voltage and operating voltage, improved stability of the mixture of the display at low temperatures.

Accordingly, the present invention provides: two plane-parallel outer substrates forming a cell together with a frame; a nematic liquid crystal mixture having a positive dielectric anisotropy present in the cell; an inner surface of the outer substrate. An electrode layer having an overlying alignment film, a pretilt angle between the long axis of the molecules on the surface of the outer substrate and the surface of the outer substrate is about 1 degree to 30 degrees, and The twist angle of the liquid crystal mixture in the cell up to ま で has a value of 22.5 ° to 600 °, and the nematic liquid crystal mixture always has a) one or two types having a dielectric anisotropy greater than +1.5. 15-80% by weight of liquid crystal component A containing the above compound; b) 20-85% by weight of liquid crystal component B containing one or more compounds having a dielectric anisotropy of -1.5 to +1.5. %; C) having a dielectric anisotropy smaller than -1.5 0-20% by weight of the liquid crystal component D comprising one or more compounds that,
And d) optionally, an amount of optically active component C 2 , such that the ratio of layer thickness (plane-parallel outer substrate separation) to natural pitch of the chiral nematic liquid crystal mixture is about 0.2-1.3.
A super twisted liquid crystal display comprising

The liquid-crystal mixture comprises at least one compound of the formula I

Embedded image And at least one compound of formula II

Embedded image Wherein R ¹ and R ² are, independently of one another, an optionally fluorinated alkyl, alkoxy, alkenyl or alkenyloxy group having 1 to 12 carbon atoms, wherein one CH ₂ group or Two non-adjacent CH ₂
The groups are-assuming that the O atoms are not directly adjacent to each other-
O-, -CH = CH-, -CO-, -OCO- or-
COO- may also be replaced by, R ³ is an alkenyl group having 2 to 7 carbon atoms, and L ¹ and L ² are independently of one another H or F, including alkenyl Compound STN-LCD characterized by the following:
It is about.

An object of the present invention is also the liquid crystal mixtures according to the invention described above and below for use in STN-LCDs. It is especially preferred that the compounds of formula I have L ¹ and L ² are F. It is further preferred that the compounds of the formula I are those in which R ¹ is a straight-chain alkyl having 1 to 8 carbon atoms, in particular 1 to 5 carbon atoms. Compounds of formula II, ^{R 3} is, it is, particularly preferably 1E- alkenyl or 3E- alkenyl having 2-7 carbon atoms. Compounds of formula II is more preferably R ² is alkyl or alkoxy, especially alkoxy of 1-8 carbon atoms. Particularly preferred compounds of formula II are
Appendix IIa

[0014]

Embedded image Wherein k is 1, 2, 3, 4, or 5, and m and n are, independently of each other, m + n ≦ 5 and 0, 1,
Is 2, or 3, and o is 0 or 1,
Is a compound of

More preferably, component A is one or more of the following formulas

Embedded image

[0016]

Embedded image Wherein R has ^one of the meanings of R ¹ in formula I, and L ¹ , L ² and L ³ independently of one another are H or F. Formula IIIb, III
Compounds of c and IIIf are particularly preferred, especially L ¹ and / or L ² are F. More preferably, L
Preference is given to compounds of the formula IIIh in which ² is H and L ¹ is H or F, in particular F.

In another preferred embodiment, component A has the formula:

Embedded image One or more 3,4,5-trifluorophenyl compounds selected from the group consisting of

[0018]

Embedded image

[0019]

Embedded image

[0020]

Embedded image Wherein R has ^one of the meanings of R ¹ in formula I and L ³ and L ⁴ are, independently of one another, H or F. Includes compounds with polar end groups.

In particular, among these compounds, R is preferably alkyl or alkoxy having 1 to 8 carbon atoms. In particular, the formulas IVa, IVb, IVc, IVd,
Compounds of the formulas IVh and Vi, in particular compounds of the formulas IVa, IVh and Vi, are preferred. Suitable liquid-crystal mixtures which can be used in the invention comprise one or more compounds from component A , preferably in a proportion of 15% to 80%,
Particularly preferably, it is contained at a ratio of 20% to 70%. These compounds or this compound are preferably Δε ≧ + 3, preferably ΔΔ
It has a dielectric anisotropy of ε ≧ + 8, particularly Δε ≧ + 12.

Suitable liquid-crystal mixtures containing one or more compounds from component B are preferably from 20% to 85%
, Particularly preferably 30% to 80%. The compounds of component B, have a particularly low rotational viscosity values gamma _1. Component B preferably has two rings, IV1 to IV1.
IV9

Embedded image One or more compounds selected from the group comprising and / or IV10 to IV24 having three rings

[0023]

Embedded image

[0024]

Embedded image One or more compounds selected from the group comprising and / or IV25 to IV31 having four rings

[0025]

Embedded image Wherein R ¹ and R ² are each independently of the formulas I and I
1,4-phenylene groups of formulas IV10 to IV19 and IV23 to IV31, which also have one of the meanings of I, may also be mono- or polysubstituted by F, independently of one another Contains one or more compounds selected.

Particularly preferably, each of carbon atoms 1 to 7
Have R¹Is alkyl and R ²Is alkyl or
A compound of formulas IV25-IV31, which is alkoxy
You. More preferably, formulas IV25-I, wherein L is F
It is a compound of V31. Particular preference is given to formula IV25
To IV31. Compounds of Formulas IV1-IV30
R in things¹And R²Is particularly preferably a carbon source
Linear alkyl or alkoxy having 1 to 12 atoms
It is.

In another preferred embodiment, the liquid crystal mixture has the formula VI

Embedded image Wherein R ³ is an alkenyl group having 2 to 7 carbon atoms, R ⁴ has ^one of the meanings of R ¹ in formula I, or when m is 1, Q- Y may mean Y, and Q is —CF ₂ —, —OCF ₂ —, —CFH
-, - OCFH- or a single bond, Y is F or Cl, m is 0 or 1, and ^{L 1} and ^{L 2} are independently of one another H or F, alkenyl It contains one or more compounds.

Equation VI is the following equation:

Embedded image including.

The STN-LCD is particularly preferably of the formula V
It comprises at least one compound selected from I-1 and VI-2, in particular at least one compound of each of the formulas VI-1 and VI-2. R ³ in formulas VI-1, VI-2 and VI- ³ is particularly preferably carbon atom 2
1E-alkenyl or 3E-alkenyl having up to 7 Particularly preferred compounds of the formula VI-1 are those wherein R ⁴ is alkenyl having 2 to 7 carbon atoms, in particular of the formula VI-
1a to VI-1e

Embedded image Wherein R ^3a and R ^4a are independently of each other H, CH
_3, a _C 2 _{H 5} or _n-C 3 _{H 7,,} and "al
kyl "is a compound of the formula, which is an alkyl group having 1 to 7 carbon atoms.

The STN-LCD according to the present invention has the formula VI-
Particularly preferred is a liquid crystal mixture containing at least one compound selected from 1d and VI-1e. R
^3a and R ^4a are each of the formula VI-
STN-LCDs containing at least one compound selected from 1a and VI-1c are more preferred.

Compounds of the formula VI-2 are particularly preferably those in which L ¹ and L ² represent H. Compounds of formula VI-2 are those in which R ⁴ has 1 to 8 carbon atoms, in particular 1, 2 or 3
Even more preferred are alkyls having 2 carbon atoms, wherein R ³ is 1E-alkenyl or 3E-alkenyl having 2 to 7, especially 2, 3 or 4 carbon atoms. The compound of formula VI-2 has the formula:

Embedded image In the formula, R ^3a , R ^4a and “alkyl” have the above-mentioned meaning, and in particular, a compound selected from R ^3a being H is particularly preferable.

The compounds of Formula VI-3, in particular, one or both of ^{L 1} and ^{L 2} are F, Q-Y is a compound of F or OCF ₂ is preferred. The compound of formula VI-3 is
R ³ is 2 to 7 carbon atoms, those more preferably a particularly 1E- alkenyl or 3E- alkenyl that chromatic 2, 3 and 4 carbon atoms. Compounds of formulas VI-1 and VI-2 having a dielectric anisotropy of -1.5 to +1.5,
Included in Component B as defined above. Polar compounds of the formula VI-2 and especially of the formula VI-3 having a dielectric anisotropy of more than +1.5 are included in component A as defined above.

By using the compounds of the formula VI, it is possible to obtain mixtures according to the invention with particularly low rotational viscosity values and STN-LCDs with a high steepness of the electro-optical curve and especially with a fast switching time at low temperatures. In a further preferred embodiment, the liquid crystal mixture is one or two
Contains more than one liquid crystal tolan compound. The high birefringence of the tolane compound allows the cell thickness of the STN-LCD to be reduced, resulting in significantly shorter switching times.
Tolan compounds are preferably Ta-Th

Embedded image Wherein R ¹ and R ² are each independently of the formulas I and I
Has one of the meanings of I, Z is, -COO -, - _CH 2 C
A compound selected from the group T comprising H ₂ -or a single bond, and L ^{1 to} L ⁶ , independently of one another, are H or F. Particularly preferred are compounds of the formula Th.

Compounds of formula T2e are those wherein one, two or three of the radicals L ^{1 to} L ⁶ are F and the others are H;
Particularly preferred are those in which ¹ and L ² , L ³ and L ⁴ , L ⁵ and L ⁶ are not both F at the same time. The proportion of compounds from group T is preferably between 2% and 55%, in particular 5%.
% To 35%.

The liquid crystal mixture optionally contains an optically active component C , the content of which is determined by the ratio of the layer thickness (the distance between the plane-parallel carrier substrates) and the natural pitch of the chiral nematic liquid crystal mixture to the desired twist angle. The amount is greater than 0.2 so as to be suitable for Suitable dopants can be selected from a wide range of known chiral materials and commercially available dopants, such as cholesteryl nonanoate, S811 (Merck, KGaA Darmstadt, FRG) and CB15 (Merck Ltd., former, BDH, Poole). , United Kingdom). There is no limit on the choice itself.

The proportion of the compound of component C is preferably from 0 to
It is 10%, especially 0-5%, particularly preferably 0-3%. The liquid crystal mixture may contain up to 20% of one or more compounds having a dielectric anisotropy of −2 or less ( component D 2 ). Component D is preferably a compound comprising the structural unit 2,3-difluoro-1,4-phenylene, for example DE-O
It includes one or more compounds described in S 38 07 801, 38 07 861, 38 07 863, 38 07 864 or 38 07 908. Particularly preferred compounds are tolan compounds having this structural unit, as described in PCT / DE88 / 00133.

Furthermore, the known compounds of the component D also include, for example, the following structural units as described in DE-OS 32 31 707 or DE-OS 3407 013, respectively.

Embedded image 2,3-dicyanohydroquinone derivatives or cyclohexane derivatives having the formula: The proportion of the compound of component D containing one or more compounds having a dielectric anisotropy of <-1.5 is preferably about 0% to 10%, particularly about 0% to 5%. . One skilled in the art can easily adjust this ratio to achieve the desired threshold voltage, and can use any conventional liquid crystal compound with Δε <−1.5 in principle. Particularly preferably, the displays according to the invention are free of compounds of component D.

Formulas I, II, III, IV, V, VI, T
Each of the above compounds and other compounds that can be used in the STN-LCD of the present invention are known, and can be produced by a method similar to the known compounds. In particular, the compounds of the formula II have a low viscosity, in particular a low rotational viscosity, a low elastic constant (K ₃ / K ₁ ) value, so that a short switching time is obtained, while the compounds of the formula II having a high dielectric anisotropy
Reduce the threshold voltage, especially when present in high amounts, such as in the displays of the present invention.

R and R¹~ R⁴In the sense of
The term alkenyl is, for R, from 2 to 7 carbon atoms;
R¹, R², R³And R⁴In the case of 2 to 12
Linear and branched alkenyl groups having carbon atoms
Including. Linear alkenyl groups are preferred. More preferred
An alkenyl group is a C_Two~ C₄-1E-alkenyl, C _Four
~ C₇-3E-alkenyl, C_Five~ C₇-4-alkenyl
Le, C₆~ C₇-5-alkenyl and C₇-6-Al
Kenyl, especially C_Two~ C₇-1E-alkenyl, C_Four~ C
₇-3E-alkenyl and C_Five~ C₇-4-alkenyl
It is. Examples of suitable alkenyl include vinyl, 1E-p
Lopenyl, 1E-butenyl, 1E-pentenyl, 1E-
Hexenyl, 1E-heptenyl, 3-butenyl, 3E-
Pentenyl, 3E-hexenyl, 3E-heptenyl, 4
-Pentenyl, 4Z-hexenyl, 4E-hexenyl,
4Z-heptenyl, 5-hexenyl, 6-heptenyl
There is. Alkenyl groups having up to 5 carbon atoms are particularly preferred.
Good. Particularly preferred are vinyl, 1E-propeni
1E-butenyl, 3E-butenyl and 3E-pen
Thenyl, especially vinyl and 3E-butenyl.
You.

In a further particularly preferred embodiment, the liquid-crystal mixtures according to the invention comprise: -1 or more, preferably 2 to 4, compounds of the formula II
a compound-1 to 2 or more, especially 1 to 3 compounds of the formula I, 3 to 35% by weight, preferably 5 to 25% by weight-1 or 2 or more, especially 2 to 5 From 8 to 45% by weight, preferably from 10 to 30% by weight, of one or more, especially from 2 to 6, cyano compounds of the formula III, particularly preferably of the formulas IIIb and IIIc
10 to 45% by weight, preferably 15 to 35% by weight of a compound selected from the group consisting of 10 to 60% by weight, preferably 25 to 60% by weight of one or more, especially 2 to 6, alkenyl compounds of the formula VI 5
0% by weight -1 5 or 25% by weight, preferably 8 to 20% by weight, of one or more, in particular one to three, tolan compounds of group T, particularly preferably compounds selected from the formula Th More preferred embodiments of the liquid-crystal mixture, which comprise more than 50% by weight of alkenyl compounds, include:-without the compounds of component B of formulas IV-1 to IV-31 and / or without the compounds of component D- It always consists of compounds of the formulas I, II, III, VI and of group T.

The mixture according to the invention is characterized in that it has a very short overall switching time (t _tot = t _on + t _off ), especially when used in STN-LCDs with thick cell spacing. A short switching time is a particularly important requirement for STN-LCDs, for example, to improve the display of cursor movements when used in laptop displays. Particularly preferably, 300 msec or less,
In particular, a display having a switching time of 250 msec or less is preferable.

The STN-LCD of the present invention is characterized by a low threshold voltage. Preferably, the threshold voltage is 1.5V or less. The liquid crystal mixture in the STN-LCD of the present invention has a positive dielectric property of Δε ≧ 1.5. Particular preference is given to liquid-crystal mixtures with Δε ≧ 3, very particularly Δε ≧ 5.
Is a liquid crystal mixture.

The threshold voltage V of the liquid crystal mixture of the present invention
_10/0/20 and rotational viscosity value gamma ₁ shows a preferred value. When the optical path difference d · Δn value is fixed, the numerical value of the cell interval d is determined by the optical anisotropy Δn. In particular, when the value of d · Δn is large, it is generally preferred to use the liquid crystal mixture according to the invention having a large Δn value.
In this case, a relatively small d value can be selected, and as a result, an improved switching time value can be obtained. However, the liquid crystal displays of the present invention comprising the liquid crystal mixtures of the present invention with small Δn values are also characterized by having advantageous switching time values.

The liquid-crystal mixtures according to the invention are furthermore characterized in that the steepness has an advantageous value, so that they can be operated with a high time-sharing drive ratio, especially at temperatures above 20 ° C. Furthermore, the mixture has a high degree of stability and exhibits a high electrical resistance and a low frequency dependence of the threshold voltage. The liquid crystal display according to the invention has a wide operating temperature range and good viewing angle dependence of the contrast. The preferred orientation (director) of the polarizing plate, the electrode substrate and each of the liquid crystal molecules respectively adjacent thereto is usually one between the electrode and the other electrode.
The structure of a liquid crystal display according to the invention from an electrode having a surface that is surface-treated so as to be mutually twisted by a value between 60 ° and 720 ° corresponds to a structure customary for a display of this type. As used herein, the term conventional structure is used in a broad sense, and includes any derived and modified forms of supertwisted cells, especially matrix display elements. The surface tilt angles of the two support substrates may be the same or different. The same tilt angle is preferred.

In the TN display of the present invention, the tilt angle between the major axis of the molecule on the surface of the basic substrate and the basic substrate is preferably 0 ° to 7 °, particularly 0.01 ° to 5 °, particularly preferably 0.1 ° to 5 °. 1% to 2%. In the STN display according to the invention, this tilt angle is preferably between 1 ° and 30 °,
In particular, it is 1 ° to 12 °, particularly preferably 3 ° to 10 °. The twist angle of the liquid crystal mixture between the alignment films of the two basic substrates in the cell is 2 for the TN-display of the present invention.
It has a numerical value between 2.5 ° and 170 °, in particular between 45 ° and 130 °, particularly preferably between 80 ° and 115 °. The twist angle in STN displays is between 100 ° and 600 °, especially between 170 ° and 300 °, particularly preferably between 180 ° and 27 °.
0 °.

The liquid-crystal mixtures which can be used according to the invention are prepared in a manner customary per se. Generally, the desired amount of the components used in relatively small amounts is dissolved in the components making up the base component at elevated temperatures for convenience.
It is also possible to mix the solutions of the components in an organic solvent, for example acetone, chloroform or methanol, and then to remove the solvent after mixing, for example by distillation. The dielectric may also further comprise additives known to those skilled in the art and described in the publication. For example, 0-1
5% of polychromatic dyes can be added.

In the present patent application and the following examples, the chemical structures of liquid crystal compounds are all indicated by initials, and conversion into chemical formulas is performed as shown below. Any group C _n
H _{2n +1} and the group C _m H _{2m + 1} are all straight-chain alkyl groups having n or m carbon atoms, respectively. The codes in Table B need not be further described. In Table A, only the initials for the basic structure are shown. In specific compounds, this acronym indicates-and the codes for the following substituents R ¹ , R ² , L ¹ and L ² :

The compounds shown in Tables A and B are particularly preferred components of the present invention.

[Table 1]

Table A : (L ¹ , L ² and L ³ = H or F)

Embedded image

Table B :

Embedded image

The following examples are intended to illustrate but not limit the invention.

The abbreviations have the following meanings: Δn 589 nm, birefringence at 20 ° C. n ₀ ordinary light refractive index (589 nm, 20 ° C.) Δε dielectric anisotropy (1 kHz, 20 ° C.) ε _{の 長} molecular length Dielectric constant perpendicular to the axis (1 kHz
z, 20 ° C.) T _ave average switching time = 0.5 (T _on + T
_off ) Time from turning _{on the} T _on switch until 90% of the maximum contrast is achieved. Time from turning _{off the} switch off to achieving 10% of the maximum contrast. V ₁₀ Threshold voltage (volt) V ₉₀ saturation voltage V ₉₀ / V ₁₀ steepness γ ^rot rotational viscosity (mPa.s)

In the above and below, unless otherwise indicated, all temperatures are degrees Celsius and percentages are percentages by weight. The values of the switching time and the viscosity are numerical values at 20 ° C. The switching time is the average value t _ave defined as described above. STN-LCD is 1/6
Addressing is performed by a division drive ratio of 4 and a division drive of 1/7 bias.

Example 1 STN display containing a liquid crystal mixture having the following properties: Clearing point + 95 ° C. Δn 0.1443 V ₁₀ 1.45V V ₉₀ / V ₁₀ 1.054 T _ave 149 msec

[Table 2]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/13 500 G02F 1/13 500 1/133 500 1/133 500 (71) Applicant 591032596 Frankfighter Str. 250, D-64293 Darmstadt, Federal Republic of Germany (72) Inventor Akihiro Kojima Germany Day-64293 Darmstadt Frankfurter Straße 250 (72) Inventor Kazuo Toya Day-64293 Darmstadt Germany Fulter Strasse 250

Claims (10)

[Claims] 1. forming a cell together with a frame;
A plane-parallel outer substrate,-a nematic liquid crystal mixture with positive dielectric anisotropy present in the cell,-each pixel having an alignment film overlying the inner surface of the outer substrate, which is addressed with a waveform aligned in a straight line. An electrode layer having: a pretilt angle between the long axis of the molecules on the surface of the outer substrate and the outer substrate being about 1 degree to 30 degrees; and a twist of the liquid crystal mixture in the cell from alignment layer to alignment layer. The angle has a numerical value of 22.5 ° to 600 °, and the nematic liquid crystal mixture necessarily includes a) 15) of the liquid crystal component A containing one or more compounds having a dielectric anisotropy greater than +1.5. B) 20 to 85% by weight of the liquid crystal component B containing one or more compounds having a dielectric anisotropy of -1.5 to +1.5; c) less than -1.5 One or more compounds having dielectric anisotropy 0-20% by weight of the liquid crystal component D containing an object,
And d) the ratio of the layer thickness (the distance between the plane-parallel outer substrates) to the natural pitch of the chiral nematic liquid crystal mixture is about 0.5.
A super-twisted liquid crystal display, comprising an amount of optically active component C 2 , such as from 2 to 1.3, wherein the liquid crystal mixture comprises at least one compound of the formula I And at least one compound of formula II Wherein R ¹ and R ² are, independently of one another, an optionally fluorinated alkyl, alkoxy, alkenyl or alkenyloxy group having 1 to 12 carbon atoms, wherein one CH ₂ group or Two non-adjacent CH ₂
The groups are-assuming that the O atoms are not directly adjacent to each other-
O-, -CH = CH-, -CO-, -OCO- or-
COO- may also be replaced by, R ³ is an alkenyl group having 2 to 7 carbon atoms, and L ¹ and L ² are independently of one another H or F, including alkenyl Compound The liquid crystal display as described above. 2. One or more of the formulas IIa Wherein k is 1, 2, 3, 4, or 5, and m and n are, independently of each other, m + n ≦ 5 and 0, 1,
Is 2, or 3, and o is 0 or 1,
The display according to claim 1, characterized in that the display comprises: 3. Component A is represented by the following formula: Wherein R has ^one of the meanings of R ¹ in formula I and L ¹ , L ² and L ³ are, independently of one another, H or F. 3. The display according to claim 1, comprising at least one cyano compound. 4. One or more compounds of the formula VI Wherein R ³ is an alkenyl group having 2 to 7 carbon atoms, R ⁴ has ^one of the meanings of R ¹ in formula I or, when m is 1, also Q- may also mean Y, Q _{is, -CF 2 -, - OCF 2} -, - CFH-,
-OCFH- or a single bond, Y is F or Cl
And m is 0 or 1, and L ¹ and L
^2. The display according to claim 1, comprising alkenyl compounds of ² independently being H or F. 5. 5. Formulas VI-1a to VI-1e At least one compound selected from and / or of formulas VI-2a and VI-2b Wherein R ^3a and R ^4a are independently of each other H, CH
₃ , C ₂ H ₅ , or nC ₃ H ₇ and Alkyl are at least one compound selected from the group consisting of alkyl groups having 1 to 7 carbon atoms. 5. The display according to any one of the above items 4. 6. The following formula: Wherein R ¹ and R ² are each independently of the formulas I and I
2. The composition according to claim 1, which comprises one or more trans compounds selected from those having one of the meanings of I.
6. The display according to any one of claims 5 to 5. 7. The method of claim 1, wherein one or more compounds of the formula I
A liquid crystal mixture containing about 35% by weight.
The display according to any one of claims 1 to 6. 8. The display according to claim 1, wherein the display is a liquid-crystal mixture containing 8 to 45% by weight of one or more compounds of the formula II. 9. A liquid crystal mixture containing more than 50% by weight of an alkenyl compound.
A display according to any one of the preceding claims. 10. A liquid crystal mixture or composition according to claim 1.