DE2026280A1 - Electro-optical connections and devices - Google Patents

Description

2026280 Dipl.-Ing. H. Sauerland · Dr.-lng. R. King

Patent Attorneys ■ 4ODO Düsseldorf - Cecilienallee 7B - Telephone 43S7 32

Our file: 25 812 May 26, 1970

RCA Corporation, New York, NY (V _e St _e A.)

"Electro-optical connections and devices"

The invention relates to new liquid crystal compounds as well as improved electro-optical devices utilizing these novel interconnections.

The liquid crystal compounds described here, are so-called "Schiff bases" of the general formula

wherein OR and OM are either normal alkoxy groups or normal acyloxy radicals, but alternately, ie in the event that OR is an alkoxy group, an acyloxy radical takes the place of OM, and vice versa. Thin layers of such nematic liquid crystals are relatively translucent in the unexcited state, ie when no electrical current flows through them. However, if they are in the excited state, i.e. under the influence of electrical current, they refract the light. The flow of current is brought about by applying a voltage across the liquid crystal, which zvf un - '. Hen. two conductive elements is »Dwr I.ichtbr» tiGhimgseffekt, which both with the above

Γ; Π S Bf) O /? ! 7 2 ORIGINAL BATHROOM

named, known liquid-crystal compounds as well as in the compounds according to the invention occurs, is the consequence of the turbulence effect of liquid crystal areas. This effect is also called dynamic Refraction called.

The refraction created by liquid crystals can be reflective, absorbent and translucent flat display panels as well as in light shutters and other electro-optical devices.

An important consideration for any commercial device is its lifespan. The life of liquid crystal devices is essentially determined by the rate of disintegration of the crystal compounds in the devices certainly. The object of the present invention is to reduce the comparatively short service life of known devices to lengthen and in particular to significantly reduce the rate of disintegration of the crystal compounds.

This is done according to the invention with compounds of the general formula

=! L /> > -OM

achieved, where OR is an alkoxy radical with 1 to 8 carbon atoms and OM represents a branched, chain-like acyloxy radical with 4 to 10 carbon atoms «

An electro-optical Ge = proposed according to the invention advises consists of a layer of a nematic liquid-crystal mixture, the at least one compound from the defined by the general formula given above Group, as well as suitable & n furnishing

0/2

_ßAD ORIGINAL

for the application of an electric field.

A liquid crystal composition according to the invention has mixtures which have the behavior of liquid crystals show, although individual components of the mixture do not themselves have a liquid crystal state to need. It has been found in the context of the invention that when branched, chain-like acyloxy radicals are used the service life of the device can be increased by at least one order of magnitude.

The invention is explained in more detail with the aid of the attached drawing explained. In the drawing show:

Fig. 1 is a side view of a simple, inventive, electro-optic light tube, and

FIG. 2 shows the front view of the object shown in FIG.

The object shown is a simple number display device 10, which consists of a rear cover plate 11, which is on one surface with a continuous, mirror-like reflective, conductive layer 12 is provided, and from a front cover plate 13, which is on one surface with a transparent, conductive Layer 14 is provided. A liquid is located between the conductive layers or electrodes 12 and 14 Crystal composition 15. The transparent, conductive Electrode 14 on the front cover plate 13 is made in the shape of the pattern provided by the device is to be reproduced, e.g. in the form of the number 1. The mirror-like reflective electrode 12 can e.g. made of aluminum vapor-deposited in a vacuum and the transparent, conductive electrode 14 made of a tin oxide

0098SC / 217.2

pass a layer. The thickness of the liquid crystal layer is preferably about 1/160 to
1/80 mm ₀ The edges of the device are best covered with a thermoplastic sealant 16.

During operation, the transparent and reflective electrodes are connected to a voltage source 21. This can supply either AC or DC voltage. With regard to the longest service life of the AC voltage is preferred for the device. If ambient light falls on the device when it is switched off, a Observer who looks at the front of the device, no pattern can be perceived. With the help of the voltage source 21 voltage is applied to the crystalline liquid 15 via a switch 22, so that when the switch 22 is closed, the liquid crystals are generated to refract the light between the electrodes 12 and 14. As a result, the observer sees a glowing one Pattern corresponding to that of the transparent electrode 14.

The system described above is just one of the many ways in which the invention can be carried out, for example, "It is not It is necessary that one electrode is reflective, rather both electrodes can be transparent. In such In cases, the device works in a translucent manner, i.e. with a light source on top of the observer opposite side of the device. It is also possible to have row and column guiding elements without excitation to incorporate selected sections of the liquid crystal element.

The liquid crystal composition of the present invention The device is described in more detail below.

009850/2172

In general, there is the main characteristic of electro-optic vision Medium according to the invention in that it contains a composition of nematic ^, liquid crystals in which at least one by the formula

defined connection is included. In it, OR is a normal alkoxy radical with 1 to 8 carbon atoms and OM is a branched, chain-like acyloxy radical having 4 to 10 carbon atoms.

It can be assumed that the service life of known devices is influenced by the responsiveness of the normally unstable Oxygen of the unbranched, chain-shaped acyloxy group of previously used compositions is limited this labile oxygen reacted with hydroxyl groups and thereby the disintegration of the liquid-crystal compound caused.

In the compounds according to the invention is of the Assumed the reactivity of the labile oxygen, that it is reduced by steric hindrance caused by the branched structure according to the invention. In order to achieve the greatest steric hindrance, it is advantageous to when the branched chains extend from the carbon atoms that are close to the unstable oxygen-containing carbon atoms are located, e.g. the alpha and beta carbon atoms of the acyloxy group,

In operation, the system is heated to a temperature at which the crystal composition of the device their mesomorphic or liquid. crystalline state

00 98 5 0/2172

is enough, "It is therefore beneficial" such liquid-crystal compounds to use ^ which show mesomorplies behavior as close as possible at room temperature, in principle Of the compositions according to the invention, those have the lowest transition temperature to the nematic crystal state in which the alkoxy group is a methoxy group.

Examples of several compounds according to the invention with their transition temperatures from crystalline to nematic State (C-N) and from nematic to isotropic, liquid state (N-L) are given in Table I. These compounds are mesomorphic or liquid crystalline in the temperature range between these two transition temperatures » It must be noted that these compounds are below the transition temperature can be mesomorphic to the nematic state. if they be hypothermic «,

In the table also mean;

LN = transition liquid - nematic CS = transition crystalline solid - amorphous solid SL = transition amorphous solid - liquid SN = amorphous solid - nematic «

009850/2172

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009850/2172

ORIGINAL INSPECTED

Table I (continued)

OR
OM • Methoxy
-OCH ₃ Ethoxy
-OC ₂ H ₅ . Propoxy
-OC ₃ H ₇ ι
ω
ι Remainder of the 2-methyi-valerian
acid
-0-C-CHCH ₂ CH ₂ CH ₃ M.p. 32-33 ° C M.p. 58-59 ° C Mp 59-60 ⁰ C Remainder of the 5-methyl-capron-
acid
Q 9H3
-0-C-CH ₂ CH ₂ CH ₂ CHCH ₃ CN 61 ° C
NL 76 ° C CN 79-80 ⁰ C
NL 103 ⁰ C CN 70-71 ⁰ C
NL 88 ⁰ C 2026280 Remainder of the 3-methyl-capron-
acid
Ο. CHj
-0-C-CH ₂ CHCH ₂ -CH ₂ CH ₃ CN 48-49 ⁰ C
NL 78 ⁰ C * Remainder d @ r 2-methyl-capron-
acid Mp 42-43 ⁰ C Remainder of the d- »5 ~ Aeetd5sy-4-
methyliralerian acid
-O-ÖCCH) CT-H 0-8 CH M.p. 35 ° C

Table I (continued)

OR
OM Methoxy
-OCH ₃ Ethoxy
-OC ₂ H ₅ Propoxy
-OC ₃ H ₇ 1
I. 2026280 Remainder of the 3-trifluoromethyl
. butyric acid
0 ^CF 3
-0-C-CH ₂ CHCH ₃ Mp 187-189 ⁰ C. ο
ο
co Remainder of the 3 »5,5-trimethyl-
Caproic acid
Q 9 ^H 3 9H ₃
-0-C-CH ₂ CHCH ₂ CCH ₃ CH ₃ Mp 75 ⁰ C 850/217 Remainder of the 3,7-dimethyl
Caprylic acid
9 QH ₃ QH ₃
^ "\ j" * ^ V _L / * "* \ yJjj, ^ i ^ rX t ν / .Πίι *% /" ^ \ ^ Alw · Xl ^ T Mp 55-56 ⁰ C
LN 55 ⁰ C Remainder of the 3,7-dimethyl
6-octenoic acid '
Q 9 ^H 3. 9H3
-0-C-CH ₂ CH (CH ₂ ) ₂ CH = CCH ₃ CN 48 ⁰ C
NL 51 ⁰ C

Table I (continued)

O
©
>
-ο
R. rest of
Propionsl
Q 5H3. OR
OM Butoxy
-OC ₄ H ₉ ⁰ C Pentoxy Hexoxy Heptoxy Octoxy
-OC ₈ H ₁₇ I.
O
I. 202628 3 '.
JTJ rest of
Butter sauce
-OC-CHOl 2-methyl
iure 79-80 ⁰ C O Heat the 2-methyl
Irishman 79-80 m
W,
Q R @ g * t είθΣ ³
■ 9 P3 3-S5ethyl- CH 75 ° C
HL 94 ° C ■ ^c CH 75 ⁰ C
NL 85.5 ⁰ C CN 75-76 ⁰ C
NL 90 ° C CN 77-78 ° C
NL 87 ⁰ C CS 77 ⁰ C
SN 82 ⁰ C
BaL 91 ⁰ C - »α o "8 '-" 2 »Metliyl» M.p. 61-63
LN 53 ⁰ C ⁰ C M.p. 59-60 ° C Mp 57-58 ⁰ C Eat the
Qp * onoaj CN 74-75
NL 98 ⁰ C CN 75 »77 ° C
NL 88 ⁰ C , CS 76-77 ⁰ C CS 74 ⁰ C
SN 82 ⁰ C
NL 88 ⁰ C CS 69-70 ⁰ C
CT OO ^ f ¹ 3-Metfeyl-
L22 ³ ® CN 62 ⁰ C
NL 90 ⁰ C

Those of the compounds belonging to this series which branch on the alpha carbon atom of the acyl radical show no liquid crystal behavior. These Compounds are nonetheless useful in liquid crystal compositions within the scope of the invention when used as Part of a mixture with another compound of the Series showing liquid crystal behavior are used.

Compounds in Table I for which the melting points instead of the transition temperatures to the nematic state are not liquid crystal compounds. Table II gives various compositions consisting of mixtures of compounds, including mixtures of a liquid crystal compound of the series with a non-liquid crystal compound of the series. These mixtures show liquid-crystal behavior.

Table II

Liquid crystal mixtures of compounds according to the formula

-OM _n

= -C-CH ₉ -QH-CHp-CH _x , 3

= -C-CH ₀ -CH-CH ₀ -CH ₀ -CH _x , ^ CH _x ^ ^{2 3}

9 ⁵

M _x * —C — CHp-CHp-CH _x ,

β -C-CH ₂ -CH ₂ -CH ₂ -CH-CH ₃ , and

CH-z

-C-CH-CH ₂ -CH ₂ -CH ₃

CH,

009850/217 2

Table II (continued)

MoI-Ji 9 0 ^Μ 4 - ⁰ C ■ C-N N-L M ₂ 0 35-36 78 100 0 100 48-49 78 0 100 0 52 108 0 0 50 29-30 77 50 50 50 10 36 94-95 0 50 33 20th 43 94-95 50 0 75 30th 35 * 5 90 33 33 10 40 41-42 103-104 10 15th 15th 50 44 82 15th 75 20th 60 40 84 75 10 40 36.5 85 40 40 40 38 91.5 40 20th 25th 35 92 20th 40 50 36 87 50 25th 25th 34.5 94.5 Ζϊ 25th 33.5 87 25th 50 10 35 76 90 20th 35 75 * 5 80 30th 35 74-76 70 40 36.5 74-76 60 100 61 76 0 "36 67-70 90 29-30 58-59 80 28 "5 49-51 70 25th 29 60 23 27.5-30.5 50 4ß ■ 17--1Β.5 40

009 8 5 0/2172

The service life of liquid crystal light tubes was tested in a nitrogen atmosphere with a direct voltage of 30 volts applied to the crystal layer. The light tubes were operated at a temperature of 80 ⁰ C, "One of the cells tested consisted of a 1/80 mm thick layer of p-methoxybenzylidene-p'-aminophenyl-3-methylvalerate. Another cell consisted of a 1/80 mm thick layer of p-methoxybenzylidene p ^l -amino-5-methylhexanoate. After 3600 hours of uninterrupted operation, the refractive capabilities of these cells were reduced by 50% and 75%, respectively. These percentages were estimated by qualitative visual observation of the cells.

The compounds of the invention can by reaction of p-alkoxybenzylidene-p'-aminophenol with branched Acyloxy anhydride can be made in pyridine.

Example I.

A solution of 54.5 g p-aminophenol, 68.0 g anisaldehyde and 0.1 g of benzenesulfonic acid in 200 milliliters of benzene was refluxed for 4 hours, approximately 9.0 milliliters of water were deposited in a Dean-Stark trap. The product p-methoxybenzylidene p'-aminophenol was collected and recrystallized from an ethanol-benzene solution (ratio 50:50) to obtain colorless crystals. A mixture of 2.1 g these crystals, 50 milliliters of pyrids and 1.9 g of 3-methylvalerian anhydride were stirred for about 1 hour. The mixture was poured over crushed ice, stirred and filtered with suction. Of the resulting filtrate cake was made from isopropyl alcohol

009850/2172

recrystallized. This results in colorless crystals of p-methoxybenzylidene-p'Aminophenol-3-methylvalerianate.

Example II

p-methoxybenzylidene-p'-aminophenyl-3-methylhexanoate was prepared according to Example I. * Only instead of 3-methylvalerian anhydride was the anhydride the 3-methylcaproic acid used.

Example III

p-Ethoxybenzylidene-p'-aminophenyl-5-methylhexanoate is by reaction of p-ethoxybenzylidene-p'-aminophenol prepared with 5-methylcaproic anhydride

p-propoxybenzylidene-p ^! -Aminophenyl-3-methylvalerianate is formed by the reaction of p ~ propoxybenzylidene-p ^t ~ .Ajnino ™ phenol with 3-methylvalerian anhydride /

Example ¥

p-Anisylidene-p'-aminophenol methylbutanoate is made by Reaction of p-anisylidene-p'-alainophenol with 3-methyl butyric anhydride formed.

009850/217

Claims (5)

Claims; 1J Compound of a chemical composition, characterized by the formula where OR is an alkoxy radical with 1 to 8 carbon atoms and OM is a branched, chain-like acyloxy radical with Is 4 to 10 carbon atoms. 2. Chemical composition according to claim 1, characterized in that OM is a branched, chain-like acyloxy radical with 5 to 10 carbon atoms, which is a branch on the beta carbon atom having, 3. Composition according to claim 1 or 2, characterized characterized in that OR is a methoxy radical 4. Liquid crystal substance, marked by a mixture of compounds according to claim 1. 5. Use of the compositions according to one or more of claims 1 to 3 as a layer of liquid crystals between electrical conductors in an electro-optical Device. , 009850/2172 Blank page