DD226004A1 - NEMATIC LIQUID CRYSTALLINE MIXTURES - Google Patents

Abstract

Due to their dielectric and optical anisotropy, nematic liquid-crystalline mixtures are used in optoelectronic components for the modulation of the continuous or reflected light as well as for the colored or black-and-white reproduction of numbers, characters and images. The object of the invention is the use of new liquid crystal mixtures having low relaxation frequencies in electro-optical arrangements. According to the invention, liquid-crystalline mixtures are used which contain from 0.1 to 60 mol% of 4- (4 (4-Substituted benzoyloxy) benzoyloxy) benzylidene malonic acid diesters. Non-liquid-crystalline substances, in particular dyes, can also be added to the mixtures according to the invention.

Description

Nematic liquid-crystalline mixtures Field of application of the invention

The invention relates to nematic liquid-crystalline mixtures for electro-optical arrangements for the modulation of the transmitted or reflected light and to the colored or black-and-white display of "numerals, characters and" moving or still images.

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Characteristic of the known technical solutions

It is known that liquid-crystalline substances can be used for the modulation of light and for the display of measured values or the reproduction of information. These methods are based on the fact that the preferred orientation can be changed in thin layers of the liquid-crystalline substance by applying an electric field. This change in orientation involves a change in the optical behavior (birefringence, rotation, light absorption). Depending on the initial orientation, the dielectric anisotropy, the conductivity, the dichroism and the strength, frequency and direction of the applied electric field achieved by a special pretreatment of the enclosing electrodes or by addition of suitable substances, various electro-optical effects are observed and used technically / M , Tobias: International Handbook of Liquid Crystal Displays 1975-1976, Ovum Ltd., London 1976; G. Meier, E. Sac-kmann, J.C. Graomaier: Application of Liquid Crystals, Springer-Verlag, Berlin-Heidelberg-New York 1975 /.

Thus, a "known" method is based on the fact that by applying an electric field, the optical rotation of a layer with twisted structure repealed and thus between parallel (crossed) polarizers permeability (extinction) for incident light is found / M. Schadt, W. Helfrich: Applied Physics letters _18, 127 (1971) /. In another, "known" method, the frequency dependence of the dielectric anisotropy of a nematic substance is exploited in order to shorten the switching times considerably. HK Bücher, RT Klingbiel, JP van Meter: Appl. Phys. Lett. 25,186 (1974) /.- At frequencies f «f _p (f ^ relaxation frequency), the dielectric anisotropy ASq, positive, while at f» f _R, the negative-dielectric anisotropy AOq _{2 is} measured. To avoid high capacitive currents, f _R must be as low as possible. The deepest so far. Relaxation frequencies of a nematic mixture are at 22 ⁰ C: 1.2 kHz and at 35 ⁰ C. 7 kHz / (M Schadt, Mol Cryst Liqu Cryst 89, 77 (1982) /....

 Depending on the underlying electro-optical effect, the substances used must have certain requirements with regard to their melting and clearing point, their viscosity, chemical and thermal stability, conductivity, dielectric anisotropy and dielectric relaxation frequencies. Pure substances that fulfill all these requirements at the same time are not available. Therefore mixtures of different substances are used. However, due to limited miscibility, it is not possible to combine any substances.

Object of the invention

The aim of the invention are liquid-crystal mixtures for optoelectronic components, in particular with dual-frequency control, which have low relaxation frequencies.

Explanation of the essence of the invention

The object of the invention is to provide suitable substances which have the relaxation frequencies of crystalline liquid nematic

Humiliate mixtures to find.

It has been found that nematic crystalline liquid mixtures containing one or more representatives of the class of 4j_4 (4-Subst.-benzoylox ^ -bensoyloxyj-benzjliden-malonic acid di-ester having the general formula

COOR ² R ¹ Q) OOS) (S)

COOP.

° - 'V _{2n +} I ⁰⁰⁰ ^ ^C n ^H 2n-H ^C ° -'" ^CN >

^C n ^H 2n ₊ r ^IH ' ^C n ^H 2n ₊ -1 ^NC m ^H 2m ₊ 1 ^{SO as r2 and} ^ same or different alkyl groups C Sp, - or CO-Cyanoalkylgruppeη C Hp CN with n, m = 1 to 12 denote contained in amounts of 0.1 'up to 60 moliö, are very well suited for optoelectronic devices, especially those with two-frequency control. The 4- (4- (4-substituted-benzoyloxy) -benzoyloxy-benzylidene-malonic acid di-esters are colorless substances with high chemical and thermal stability. In the pure state, they have smectic phases (see Table 1), which, however, are suppressed by the appropriate mixing partners.

Depending on the intended use, these mixtures can not be mixed with liquid-crystalline substances, in particular with dyes.

Table 1

Transformationalities of the compounds

: Ooh "

00 - <(3> -C0 0 - << 3) -CH = C

R, K S, N is

J Λ

"1 7 ^ CH ₃ CH ₃ , 102 , 127 , 162 H ₁ 7 ° C ₂ H ₅ C ₂ H ₅ , 105 , 112 , 146 H ₁ 7 ° C ₃ H ₇ , 68 , 101 , 131 , -7 W / ' "4-" 9 C ₄ H ₉ , 69 S4 , 117

_ 4 Forts. Tab. 1

C ₈ H _{1 7} 0 R ₂ 1 p TT 1 K 54 ³ A N is ^C 8 ^H 1 7 ° C ₅ H ₁₁ ch from ^C 6 ^H 1 3 52 , 88 , 110 p T_J Pj ^C 6 ^H 13 [4 (4-n-0ct.y ρ TT 5 • 61 , 86 , 102 • C ₈ H ₁₇ 0 P ρ ^C 8 ^H 1 7 • 60 , 85 , 99 • C ₈ H _{1 7} 0 ^C 8 ^H 1 7 p TT 9 • 59 , 85 • C ₈ H _{1 7} 0 CgH ₁₉ C ₁₀ H 21 • 63 , 87. • C ₈ H ₁₇ O C ₁₀ H ₂₁ C ₁₁ H 23 * 60 , 84 , 91 • ρ TT f ~ \ \ ^ JTIL ji r ~} \ - s ^C 11 ^H 23 P U 25 • 67 , 84 , 90 • 10 CgH ₁₉ O η Tj C ₅ H ₁ 1 • 70 , 84 , 89 • S ^H 11 * , 88 , 107 • Au 3fuh.run.esbe! Play example A Gemis ! oxy 15 40 mo IS 4 nzo ₇ ) -benzoylo xy] -ben: Sy II

malonic acid-di-n-decyl ester and 60 molvö 2n-heptyl-1, 4-bis- (4-n-octyloxybenzo, ylox, y) -berLzen aat a melting point of 47 C and a clearing point of 78 ⁰ C. At 47 ⁰ C is the dielectric relaxation frequency fp = 7 kHz and Δδ * = +0.60. The dielectric anisotropy after passing through the low-frequency absorption region is ^ f ₀₂ = -1 j40. At 57 ⁰ C, 4 (S ₀₁ = +0.55, ^ Cq2 ⁼ +1.35 and fp = 23 kHz.) The relaxation frequency extrapolated to 22 ⁰ C is f -, = 250 Hz.

Example 2

A mixture of the following composition is prepared:

1 7.5 rnoliä 4 [4 (4-n-octyloxybenzo.ylox7) -benzoylox.y] -benzylidenemalonic acid di-n-deoester,

32.5 moles of 4,4- (4-n-octyloxybenzoyloxy) -benzo.yloxy '] - "-benzylidenemalonic acid di-n-hexyl ester

20 raol # 2-n-heptyl-1,4-bis- (4-n-octyloxybenzoyloxy) -benzenes 30 moles of 2-n-octyl-1,4-bis- (4-n-heptyloxybenzoyloxy) -benzene.

This nematic mixture has the following characteristics: Melting point: 32 ⁰ C (unterkühlbar to 15 ⁰ C) clearing point: 80 ⁰ C

₀₁ = +0.7, Λ £ ₀₂ = -1.4, f _R = 1.5 kHz (32 ^° C)

Extrapolated to 22 ⁰ C: f _R = 400 Hz

At a temperature of 37.5 C, the following ap-

Kling times 10 f / Hz with pleasure SEN: hinted t ₉₀ / 50 (NF) t ₁₀ / ms 2100 1200 5000 (NF) 1 U / V 600 400 3400 0 -> 15NF 15NF 1400th 1300 5HF- * 15nF 640 20HF - 20nF

subside t ₉₀ / , _n / ras 6600 300 6900 200 230 70 120 40

Claims (2)

) r , Nematic crystalline liquid mixtures for electro-optical arrangements, in particular for two-frequency activation with low relaxation frequencies, characterized in that the mixtures clay 0.1 to 60 mol #> one or more representatives of the substance class of 4- £ 4- (4-Subst. -benzoyloxy) -benzoyloxyj-benzylidene-malic acid diester having the general formula -cöo- <0) -coo " where R ^1. = C ₁ H _{2n + 1} -, C _n -CN, C _n H _{2n + 1} IHi, C _n H _{2n + 1} NC _m H _{2m + 1,} and R ² and R ³ identical or different Alkylgruppeη CE _{2n + 1} - or ω -Cyanoalkylgruppen - C _n H _2n CN with n, m = Λ to 10 mean. 2. nematic mixtures according to item 1, characterized in that these mixtures are not liquid-crystalline substances, in particular dyes, mixed.