JPH11158468A - Liquid crystal mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high-multiplex super twist liq. crystal display which has a short switching time and good steepness and angle dependence by using a liq. crystal mixture having a specified dielectric anisotropy. SOLUTION: A nematic liq. crystal mixture is used which essentially comprises 20-90 wt.% liq. crystal component contg. at least one compd. of formula I and at least one compd. having a dielectric anisotropy higher than +1.5, 10-80 wt.% liq. crystal component contg. at least one compd. having a dielectric anisotropy of from -1.5 to +1.5, 2-20 wt.% liq. crystal component contg. at least one compd. of formula II and at least one compd. having a dielectric anisotropy lower than -1.5, and an optically active component having a ratio of the thickness of a layer (the distance between a plane and a parallel outer plate) to the natural pitch of a chiral nematic liq. crystal mixture of about 0.2-1.3. In the formulas, R<1> to R<3> are each a 1-8C alkyl, alkoxy, alkenyl, or alkenyloxy; and L is H or F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to supertwisted liquid crystal displays (SFAs) having short switching times and good sharpness and angle dependence, and to novel nematic liquid crystal mixtures used in such displays.

[0002]

2. Description of the Related Art A super twisted liquid crystal display as described above is disclosed in, for example, EP 0,131,216B1; DE 3,423,993A1;
P 0,098,070A2; M. Schadt and F. Leenhouts, 17th Fr
eiburg conference on liquid crystals (8-10.04.87);
K. Kawasaki et al., SID 87 Digest 391 (20.6); M. Sch
adt and F. Leenhouts, SID 87 Digest 372 (20.6);
Schadt and F. Leenhouts, SID 87 Digest 372 (20.1);
K. Katoh et al., Japanese Journal of Applied Physi
cs, Vol. 26, No. 11, L 1784-L1786 (1987); F. Leenhou
ts et al., Appl. Phys. Lett. 50 (21), 1468 (1987);
HA van Sprang and HGKoopman, J. Appl. Phys.
62 (5), 1734 (1987); TJ Scheffer and J. Nehrin
g, Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schad
t and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236,
(1987) and EP Raynes, Mol. Cryst. Liq. Cryst.
Letters, Vol. 4 (1), pp. 1-8 (1986). Here, the term SFA is used, for example, in Waters et al. (C.
M. Waters et al., Proc. Soc. Inf. Disp. (New York)
(1985) (3rd Intern.Display Conference, Kobe, Japa
n), the STN-LCDs (DE OS 3,503,259), SBE-LCDs (T.
J. Scheffer and J. Nehring, Appl. Phys. Lett. 45
(1984) 1021), OMI-LCDs (M. Schadt and F. Leenhouts,
Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP OS
0,246,842) or BW-STN-LCDs (K. Kawasaki et al., SID
87 Digest 391 (20.6)), including any relatively high twist display element having a twist angle between 160 ° and 720 °.

Compared to a standard TN display, this type of super-twisted liquid crystal display has a significantly better steepness of the electro-optical properties and, consequently, a good contrast value and a significantly lower angle dependence of the contrast. Characterized by gender. Of particular interest are super-twisted liquid crystal displays that have fairly short switching times, especially at relatively low temperatures. To achieve short switching times, the rotational viscosity, especially the rotational viscosity of the liquid crystal mixture, has hitherto usually been optimized by optimally combining the liquid crystal components, including the use of any relatively high vapor pressure monotropic additive. It has become.

However, the switching time obtained is
It was not suitable for all applications. Shorter switching times can also be achieved by reducing the thickness of the liquid crystal layer of the super twisted liquid crystal display and using a mixture having a higher birefringence n. However,
All of these approaches to shorter switching times result in mixtures that are not suitable for all applications. Further demands on super twisted liquid crystal displays are greater multiplexing capability (resulting in fewer ICs), lower threshold voltages and steep characteristic curves.

[0005] However, the optimum parameters cannot simultaneously achieve all of the above physical properties due to the reaction of different material parameters such as, for example, dielectric properties and elasticity. Accordingly, there remains a great need for improved super-twisted liquid crystal displays having short switching times and, at the same time, wide operating temperature ranges, good sharpness values of contrast and low angle dependence and low threshold voltage.

[0006]

It is an object of the present invention to provide a supertwisted liquid crystal display which has little or no of the disadvantages mentioned above and at the same time has particularly useful physical properties as a whole.

[0007]

The object of the present invention is to provide a compound of the formula IA:

Embedded image With a compound of formula IB;

Embedded image Wherein R ¹ to R ³ are each, independently of one another, alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 carbon atoms, and L ¹ is H or F. It has been found that using a liquid crystal mixture can be achieved.

The nematic liquid crystal mixture preferably has a nematic phase width of at least 60 ° C., a rotational viscosity of less than 180 mPa.s, a birefringence of at least 0.1200 and at least +1.
Wherein the parameters for the dielectric anisotropy of the compound and the nematic liquid crystal mixture are based on a temperature of 20 ° C.

Accordingly, the present invention provides: two planes which together with a frame form a cell;
A parallel skin,-a nematic liquid crystal mixture in the cell, having a positive dielectric anisotropy,-an electrode layer with an alignment film on the surface, inside the skin, addressing each pixel with an orthogonal column waveform. -A pretilt angle of about 1 ° to 30 ° between the long axis of the molecules on the skin surface and the skin, and a twist angle from 100 ° to 600 ° between the alignment films of the liquid crystal mixture in the cell. Wherein the nematic liquid crystal mixture essentially comprises: a) 20% to 90% by weight of a liquid crystal component A containing one or more compounds having a dielectric anisotropy greater than +1.5; b) -1.5 to +1 Liquid crystal component B containing one or more compounds having a dielectric anisotropy of 0.5 to 80% by weight; c) containing one or more compounds having a dielectric anisotropy of less than -1.5 Ca and spacing of parallel outer plates) - thickness of and d) layer (plane; 20 wt% of the liquid crystal component D from 2 wt% to A high multiplex super twisted liquid crystal display ratio of the natural pitch consisting of component C, optically active in amounts such that about 0.2 to 1.3 Lal nematic liquid crystal mixture, component A has the formula IA;

Embedded image Compound contains at least one, and component D is of the formula IB;

Embedded image Wherein R ¹ to R ³ are each, independently of one another, alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 carbon atoms and L ¹ is H or F. It relates to a high multiplex super twist liquid crystal display characterized by containing at least one.

A preferred embodiment of the present invention is a compound of formula IC together with a compound of formula IA and IB;

Embedded image (Wherein formula R ³ has the meaning of formula IB, k is 0 or 1 and
R ^* is an alkenyl having 2 to 8 carbon atoms). Formula IC
The use of the compounds of the formula (1) leads to mixtures according to the invention having especially low rotational viscosity values and supertwisted liquid crystal displays having a high steepness of the electro-optical gradient and a fast switching time at exceptionally low temperatures.

Suitable components A are, in addition to the compounds of the formula IA, compounds of the formulas II and III;

Embedded image Wherein R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 carbon atoms,

Embedded image But each independently,

Embedded image And L ³ to L ⁸ are each independently H or F, Z ¹ is —COO—, —CH ₂ CH ₂ — or a single bond, and Z
_{^2, -COO -, - CH 2 CH} 2 -, - C≡C- or a single bond, Q _{is, CF 2, OCF 2, CFH} , a OCFH or a single bond, Y
Is F or Cl, m is 1 or 2, and n is 0 or 1.
Is contained.

The individual compounds of the formulas IA, IB, IC, II and III and the other mixtures which can be used in the supertwist display according to the invention are each known or known compounds It can be prepared similarly. The compounds of the formulas IA, IB, IC, II and III have low viscosities, in particular low rotational viscosities and low values of the modulus of elasticity (K ₃ / K ₁ ), so that short switching times are obtained.
The mixture according to the invention has an optical anisotropy of greater than 0.1200
(Δn).

A preferred mixture according to the invention comprises at least one compound of the formulas IA-1 and IA-2;

Embedded image Wherein the alkyl is a straight chain alkyl having 1 to 5 carbon atoms.

The mixtures according to the invention preferably have the formula II and / or the formula II selected from one or more of the following groups:
A compound of I;

Embedded image

[0015]

Embedded image

[0016]

Embedded image (Wherein, R, L ³ , L ⁴ , L ⁶ and L ⁷ are as described above)
It contains.

Preferred compounds are those of the formula IIa, IIb, IIc, I
One or more compounds of the formulas Id, IIf, IIId and IIIj,
In particular, it contains one or more compounds of the formula IIa, IIb and / or IIc, one or more compounds of the formula IA and at least one compound of the formula IB. Suitable liquid-crystal mixtures which can be used according to the invention comprise one or more compounds from group A , preferably from 20% to 70%, preferably from 20% to 50%.
%. These compounds from group A or this compound have a dielectric anisotropy of more than +3 (preferably greater than +8, especially greater than +12) and component A of the liquid-crystal mixtures according to the invention To form

Preferably, the mixture contains one or more compounds of the formula II in the range from 10% to 40%. The compounds are preferably those wherein Z ¹ is a single bond, —CH ₂ CH ₂ — or —CO—
O-. Particularly preferred are the compounds of formula IIa and the following compounds:

Embedded image It is.

Group A preferably comprises the compounds of the formulas IIa and IIb1
From one or more of the compounds selected from Formula IIc2 from:
In particular it contains from 1 to 4 compounds of the formulas IIa and IIc2. Suitable liquid-crystal mixtures contain one or more compounds from group B , preferably in a proportion of from 20% to 70%. group
These compounds from B or this compound are <150 mPa · s
Having a low value of rotational viscosity (γ ₁ ) or a clearing point higher than 120 ° and a dielectric neutrality ((Δε) <2, in particular from 0 to 10), of component B of the liquid-crystal mixtures according to the invention. To form

Suitable components B include compounds of formula IC from IV1 to IV7 having at least one and two rings;

Embedded image (Wherein R ³ and R ⁴ have the meaning of R) from one or more and / or IV8 to IV22 having three rings;

[0021]

Embedded image

[0022]

Embedded image (Wherein R ³ and R ⁴ are as described above, and the 1,4-phenylene groups IV7 to IV17 and IV21 each independently of one another,
(Which may be mono- or polysubstituted by fluorine). 10% of the compound in which the component B has one or more two rings
If higher, the nematic mixture comprises one or more, preferably IV23 to IV29;

[0023]

Embedded image Wherein R ³ and R ⁴ are as described above, and the 1,4-phenylene groups of formulas IV23 to IV27 are each independently of one another and may be mono- or polysubstituted by fluorine. And further contains only compounds selected from: Particularly preferably, the nematic liquid crystal mixture has the formula IV
23 or more compounds in one or more, up to 20% by weight, preferably
Contains from 5% to 15% by weight.

The liquid crystal mixture also has an optically active component C in which the ratio between the phase thickness (plane-parallel carrier plate spacing) and the natural pitch of the chiral nematic liquid crystal mixture is greater than 0.2, which is suitable for the desired twist angle. It is contained in such an amount. Suitable dopants include various known chiral materials and cholesteryl nonanoate, S811 (Merck KGaA, D
armstadt, FRG) and CB 15 (Merck Ltd., formerly BDH, Poole,
UK)). The choices themselves are not important.

In a further preferred embodiment, the liquid crystal mixture comprises:
The liquid crystalline trans compound is contained in an amount of 2% by weight to 45% by weight, preferably 5% by weight to 30% by weight. Thereby, the cell thickness and switching time of the super twisted liquid crystal display can be reduced.

In a particularly preferred embodiment, the liquid crystal mixture is TI
a to Tie;

Embedded image Wherein R ¹ is as defined above and alkyl is n-alkyl having 1 to 8 carbon atoms.
1 or 2 or more tolans selected from The proportion of components from group T is preferably between 2% and 45%, especially
5% to 30%.

Particularly preferred are the formulas TIa and TId 3
Mixtures containing preferably 3% to 10% tolanes having two rings. Compounds with dielectric anisotropy <-1.5
Alternatively, the proportion of compound of component D containing two or more is preferably about 2% to 20%, especially about 2% to 10%. Those skilled in the art
This ratio can be easily adjusted to obtain the desired threshold voltage, and in principle all conventional liquid crystal compounds with Δε <−1.5 can be used.

In a particularly preferred embodiment, in addition to the compound of the formula IB, the mixtures according to the invention preferably contain one or more compounds having a dielectric anisotropy of less than −2 (component D) by at least about 0
% To 10%. Compounds of this type are, for example, 2,3-
Derivatives of dicyanohydroquinone or structural elements in DE-OS 3,231,707 or DE-OS 3,407,031;

Embedded image Cyclohexane derivatives containing are known.

The term alkenyl, meaning R, R ^* and R ¹ to R ⁴ , refers to R ^* , R ¹ and R 2 having 2 to 8 carbon atoms.
In the case of R ² , R, R ³ and R ⁴ having 2 to 12 carbon atoms include straight-chain and branched alkenyl groups. Linear alkyl groups are preferred. Further suitable alkenyl groups, C ₂ -C ₄ -1E- alkenyl, C ₄ -C ₇ -3E- alkenyl, C ₅ -C ₇ -4- alkenyl, C ₆ -C ₇ -5- alkenyl and C ₇ - 6 alkenyl, in particular C ₂ -C ₇ -1E- alkenyl, C ₄ -C ₇ -3E-alkenyl and C ₅ -C ₇ -4- alkenyl. Examples of suitable alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3E-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl and 6-heptenyl. Carbon atom
Alkyl groups having up to 5 are particularly preferred. Particularly preferred are vinyl, 1E-propenyl, 1E-butenyl, 3E-butenyl and 3E-pentenyl, especially vinyl and
3E-butenyl.

In a further particularly preferred embodiment, the mixture comprises: 5% to 30% by weight of one or more compounds of the formula IA-1 and IA-2, at least one compound of the formula IA and at least one 1
7 to 50% by weight of one compound of formula IB, preferably 1
0% to 35% by weight, at least one compound of the formula IC from 10% to 60% by weight
2% to 10% by weight of one or more compounds of the formula IC-1;

Embedded image 15% to 50% by weight of one or more, preferably 2 or 3, compounds of the formula IC-2;

Embedded image From 2% to 10% by weight of one or more compounds of formula IB-1;

Embedded image Wherein alkyl is straight-chain alkyl having 1 to 5 carbon atoms, t is 0, 1 or 2, preferably 0, and s is 0, 1 or 2, preferably 0. Is included).

Usually, from one electrode to the other electrode
The structure of the liquid crystal display element according to the invention, consisting of electrodes, electrode substrates and polarizers, having a surface treatment, such as twisting at an angle of 160 ° to 720 °, in each case the main orientation of the adjacent liquid crystal molecules ( The director corresponds to the usual structure of this type of display element. The term ordinary structure here is used in a broad sense and encompasses all super twisted cell variants and variants, especially matrix liquid crystal elements. The surface tilt angles of the two support plates may be the same or different. The same tilt angle is preferred.

However, the essential difference between the display element according to the invention and the conventional twisted nematic cell based display element lies in the choice of the liquid crystal components in the liquid crystal layer. Liquid crystal mixtures that can be used according to the invention are:
It is prepared in its usual manner. Generally, the desired amount of the components used in relatively small amounts is preferably warmed,
Dissolves in the components that make up the main components. It is also possible to mix the solution of the components in an organic solvent such as, for example, acetone, chloroform or methanol, and after mixing the solvent is again removed, for example by distillation. The dielectric may also contain further additives known by those skilled in the art and described in the literature. For example, from 0% to 15
% Can also be added.

Examples of the present invention are shown below, but the present invention is not limited thereto. Abbreviations have the following meanings. SN smectic-nematic phase transition temperature, NI nematic-isotropic phase transition temperature, cp clearing point, Time from T _on switch on to 90% of maximum contrast, Time off from T _off switch off to 10% of maximum contrast, V ₁₀ Threshold voltage (volts) V ₉₀ Saturation voltage V ₉₀ / V ₁₀ Steepness γ ^rot rotational viscosity (mPa · s) Super twisted liquid crystal displays are addressed by multiplex operation (multiplex ratio 1:24
0, bias 1:15).

In this specification, all temperatures are in ° C. Percentages are weight percentages. The switching time and viscosity values are at 20 ° C. In the present specification and examples, the chemical structures of all liquid crystal compounds are represented by abbreviations, and the chemical formulas are changed as shown below. All C _n H _{2n + 1} residues and C _m H
_{The 2m + 1} residue is a straight-chain alkyl group having n and m carbon atoms, respectively. The code in Table B is self-explanatory. In Table A,
Only the abbreviations of the basic structure are shown. In specific compounds, this abbreviation is represented by a dash and the substituents R ¹ , R ² , L ¹ and L ² as follows. The compounds shown in Tables A and B are particularly preferred components of the invention.

[0035]

Embedded image

Table A:

Embedded image

Table B:

Embedded image

[0038]

【Example】Example 1  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0039]Example 2  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0040]Example 3  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0041]Example 4  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0042]Example 5  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0043]Example 6  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

[0044]Example 7  STN displays include liquid crystal media with the following physical properties:
Have:

Embedded image

 ──────────────────────────────────────────────────続 き Continuation of front page (71) Applicant 591032596 Frankfurter Str. 250, D-64293 Darmstadt, Federal Republic of Germany (72) Inventor Yukiko Fujii, Germany D-64293 Darmstadt Frankfurter Strasse 250 (72) Inventor Akihiro Kojima D-Day D-64293 Darmstadt Fulter Straße 250 (72) Inventor Fumio Shimano Federal Republic of Germany D-64293 Darmstadt Frankfurter Straße 250 (72) Inventor Kazuo Toya D-64293 Darm Stadt Frankfurter Straße 250

Claims (11)

[Claims] Claims:-two planes forming a cell together with a frame-a parallel skin-a nematic liquid crystal mixture having a positive dielectric anisotropy in the cell-an orthogonal column waveform for each pixel An electrode layer with an alignment film on the surface, inside the skin to be addressed;-a long axis of molecules on the skin surface and a pretilt angle between the skins of about 1 ° to 30 °; and-a liquid crystal mixture in the cell. The nematic liquid crystal mixture contains one or more compounds having a dielectric anisotropy greater than a) +1.5, including values between 100 ° and 600 ° of twist angle from alignment film to alignment film 20% to 90% by weight of liquid crystal component A ; b) 10% to 80% by weight of liquid crystal component B containing one or more compounds having a dielectric anisotropy of -1.5 to +1.5; c) the liquid crystal component D containing one or more compounds having a smaller dielectric anisotropy than -1.5 2 wt% Et 20 wt%; and d) layer thickness (plane - parallel skin distance) and chiral nematic optically active component ratio of amounts such that about 0.2 to 1.3 with the natural pitch of the liquid crystal mixture C, A high multiplex super twisted liquid crystal display comprising: wherein component A is of the formula IA; Compound contains at least one of, and component D is of the formula IB; embedded image Wherein R ¹ to R ³ are each, independently of one another, alkyl, alkoxy, alkenyl or alkenyloxy having 1 to 8 carbon atoms and L ¹ is H or F. The display, comprising at least one. 2. The composition according to claim 1, wherein the component B is of the formula IC: (Wherein formula R ³ has the meaning of formula IB, k is 0 or 1 and
The display according to claim 1, characterized in that it comprises at least one compound wherein R ^* is alkenyl having 2 to 8 carbon atoms. 3. Component A is a compound of formula II and / or III. Wherein R is alkyl, alkoxy, alkenyl or alkenyloxy having up to 12 carbon atoms, But each independently: And L ³ to L ⁸ are each independently H or F, Z ¹ is —COO—, —CH ₂ CH ₂ — or a single bond, and Z
_{^2, -COO -, - CH 2 CH} 2 -, - C≡C- or a single bond, Q _{is, CF 2, OCF 2, CFH} , a OCFH or a single bond, Y
Is F or Cl, m is 1 or 2, and n is 0 or 1.
The display according to claim 1, wherein the display comprises: 4. Component A comprises at least one compound of formula IIa to formula I
Id and Formula IIf; Wherein R, L ³ , L ⁴ and L ⁷ are as defined in claim 3, characterized in that they contain at least one compound selected from the group consisting of: 3. The display according to 3. The display, comprising: 5. The composition of claim 4, wherein component B is a compound of formula IV to formula IV7; (Wherein R ³ and R ⁴ are as defined as R in claim 3), characterized in that they contain one or more compounds selected from the group comprising The display according to one. 6. Component B is a compound of the formula IV8 to the formula IV22; [Formula 10] (Wherein R ³ and R ⁴ are 1,4-phenylene groups IV7 to IV17 and I
V21 each independently of one another may be monosubstituted or polysubstituted by fluorine), or contains one or more compounds selected from the group comprising:
6. The display according to at least one of the claims 1 to 5. 7. The formula TIa to the formula TIe; (Wherein R ¹ represents one of the aforementioned as and alkyl have an n- alkyl eight from 1 carbon atoms) that contain components T that contains a compound selected from the group 1 or 2 or more comprising A display according to at least one of the claims 1 to 6, characterized in that: 8. Component B comprises at least one compound of formula IC-1
And / or at least one of the compounds of the formula IC-2; Wherein alkyl is a linear alkyl group having 1 to 5 carbon atoms and t is each independently 0, 1 or 2. A display according to at least one of claims 7 to 7. 9. Component A is a compound of formula IA-1 and / or IA-2; Display according to at least one of claims 1 to 8, characterized in that it contains at least one compound wherein the alkyl is a straight-chain alkyl having 1 to 5 carbon atoms. 10. The at least one of claims 1 to 9, characterized in that the nematic liquid-crystal mixture contains from 10% to 50% by weight of at least one compound of the formula IA and at least one of the compounds of the formula IB. Display according to one. 11. Liquid crystal mixture of the composition defined in one of claims 1 to 10.