Organosilicon compounds

Details Organosilicon compounds Organosilicon compounds

2001-05-02

2003-01-28

Moore, Margaret G. (Department: 1712)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

Alignment layer of specified composition

C556S479000, C428S447000, C427S387000

Reexamination Certificate

active

06511720

ABSTRACT:

The invention relates to novel organosilicon compounds of the formula I
R
1
—(A
1
)
m
—Z
1
—A
2
—(Z
2
—A
3
)
n
—W—SiX
a
Y
b
Z
c
  I
in which
R
1
is a chiral or achiral alkyl group having up to 10 carbon atoms, in which, in addition, one or two non-adjacent CH
2
groups may be replaced by —O— atoms, or is F, Cl or a halogenated alkyl, alkoxy, alkenyl or alkenyloxy radical having 1 to 3 carbon atoms
A
1
, A
2
, and A
3
are each, independently of one another,
a) a 1,4-cyclohexylene radical, in which, in addition, one or two non-adjacent CH
2
groups may be replaced by —O— and/or —S—,
b) a 1,4-cyclohexenylene radical, or
c) a 1,4-phenylene radical, in which, in addition, one or more CH groups may be replaced by N atoms,
where the radicals a), b) and c) may be substituted by one or two fluorine atoms,
Z
1
and Z
2
are each —CH
2
CH
2
—, —CO—O—, —C
2
H
4
—, —(CH
2
)
4
—, —CH
2
CHCH═CH
2
—, —CH
2
—O—, —O—CH
2
—, —O—CF
2
—, —CF
2
—O—, —CH═CH—, —C≡C— or a single bond,
m is 0 or 1,
n is 0, 1 or 2 where m+n is ≧1,
W is a straight-chain or branched alkylene group having up to 10 carbon atoms, in which, in addition, one or two non-adjacent CH
2
groups may be replaced by —CHF— and/or —CH(CF
3
)—,
X, Y and Z are each, independently of one another, OCN, CN, R′, OR′, H or Cl, where at least one of the substituents X, Y and Z is not H,
R′ is an alkyl group having 1 to 15 carbon atoms, in which, in addition, one or more non-adjacent CH
2
groups may be replaced by —O—, —CO— and/or —CH═CH—, and
a, b and c are 0, 1, 2 or 3, where a+b+c=3.
The compounds of the formula I are excellently suitable for the homeotropic alignment of liquid-crystalline phases on surfaces, for example glass plates, which may also be coated, as used in the production of electro-optical display elements. The alignment of liquid-crystalline phases oriented in this way can be modified by an external electric field owing to their negative dielectric anisotropy. They are suitable for use in displays operated on the principle of deformation of aligned phases (Appl. Phys. Lett. 19, 391 (1971)), the principle of dynamic scattering (Proc. IEE 56, 1162 (1968)) or the guest-host principle (Mol. Cryst. Liq. Cryst. 63, 19 (1981)).
It was hitherto technically quite difficult to produce a uniform and stable homeotropic alignment of liquid-crystalline phases. For example, the liquid-crystalline phase used has been doped with surface-active substances, such as lecithins, long-chain aliphatic amines, quaternary ammonium or phosphonium salts or carboxylatochromium complexes (Appl. Phys. Lett., 268 (1975)). Also common was coating of glass surfaces with said substances before introduction of the liquid-crystalline phase. However, the uniformity and stability of the resultant homeotropic alignment of liquid-crystalline phases are unsatisfactory.
German Patent Applications P 33 31 515 and P 36 01 742 disclose trialkanoyloxysilanes for producing a homeotropic alignment of liquid-crystalline phases on surfaces. However, these compounds have a number of disadvantages. For example, their preparation from acid anhydrides and trichlorosilanes is frequently accompanied by the formation of dark-brown byproducts, which can be separated from the desired trialkanoyloxysilane only with difficulty. Products contaminated in this way are not suitable for surface treatment, since they reduce the optical transparency of the substrate material. Furthermore, hydrolysis of the trialkanoyloxy compounds on the substrate surface by the process indicated in P 33 31 515, frequently results only in low-molecular-weight hydrolysis products, which are volatile with the steam used and thus do not contribute to the modification of the treated surface, which results in complete or only partial surface alignment of liquid-crystalline phases applied. Furthermore, it has been found in practice that the known alignment materials very frequently do not exhibit uniform perpendicular alignment, which means that complex processes, such as inclined vapour deposition, are still—as also in most known organosilicon compounds—necessary in addition to the alignment material.
There is, therefore, a demand for stable, novel organosilicon compounds which can be used to achieve uniform tilt without additional process steps having to be carried out.
The invention therefore had the object of enabling better, in particular more uniform and more stable homeotropic alignment of liquid-crystalline phases on surfaces. This object has been achieved by the provision of the compounds of the formula I.
The invention thus relates to the compounds of the formula I and to a process for their preparation, characterized in that an unsaturated compound of the formula II
R
1
—(A
1
)
m
—Z
1
—A
2
—(Z
2
—A
3
)
n
—W—CH═CH
2
  II
is reacted with a silane H—SiX
a
Y
b
Z
c
, in which R
1
, A
1
, A
2
, A
3
, Z
1
, Z
2
, m, n, X, Y, Z, W, a, b and c are as defined above, or in that a halide of the formula III
R
1
—(A
1
)
m
—Z
1
—A
2
—(Z
2
—A
3
)
n
—W—Hal  (III)
is reacted with a silane H—SiX
a
Y
b
Z
c
, in which R
1
, A
1
, A
2
, A
3
, Z
1
, Z
2
, m, n, X, Y, Z. W, a, b and c are as defined above, and Hal is Cl, Br or I.
The invention furthermore relates to the use of the compounds of the formula I as components of liquid-crystalline dielectrics for electro-optical display elements, and to their use for producing homeotropic alignment of liquid-crystalline phases on surfaces. The compounds of the formula I also enable the surface tension to be matched to the liquid-crystalline mixture in the display. Furthermore, the compounds according to the invention have an antistatic action and are therefore highly suitable as adhesion promoters to the polymer films in the display. The silicon compounds may additionally be used to build up an ion-barrier layer.
The invention also relates to the use of compounds of the formula I in printing processes for producing homeotropic alignment of liquid-crystalline phases on surfaces.
The invention furthermore relates to liquid-crystalline dielectrics containing at least one compound of the formula I, and to electro-optical display elements containing dielectrics of this type and/or containing surfaces which have been treated with a compound of the formula I.
Above and below, R
1
, A
1
, A
2
, A
3
, Z
1
, Z
2
, n, X, Y, Z, W, R′, a, b and c are as defined above, unless expressly stated otherwise.
According to the definitions of the various groups, the compounds of the formula I embrace those of the subformulae Ia to If:
R
1
—A
1
—A
2
—W—SiX
a
Y
b
Z
c
la
R
1
—A
1
—Z
1
—A
2
—W—SiX
a
Y
b
Z
c
lb
R
1
—A
1
—A
2
—A
3
—W—SiX
a
Y
b
Z
c
lc
R
1
—A
1
—Z
1
—A
2
—A
3
—W—SiX
a
Y
b
Z
c
ld
R
1
—A
1
—A
2
—Z
2
—A
3
—W—SiX
a
Y
b
Z
c
le
R
1
—A
1
—Z
1
—A
2
—Z
2
—A
3
—W—SiX
a
Y
b
Z
c
lf
Compounds of the formulae Ia, Ic and Ie are particularly preferred.
Above and below, PheF is 1,4-phenylene which is substituted by fluorine in the ortho-position to R
1
, and PheFF is 1,4-phenylene which is disubstituted by 15 fluorine in each ortho-position to R
1
. Cy denotes a 1,4-cyclohexylene group.
The compounds of the subformula Ia embrace the preferred compounds of the subformulae Iaa and Iai:
R
1
—PheF—Phe—W—SiX
a
Y
b
Z
c
laa
R
1
—PheF—Cy—W—SiX
a
Y
b
Z
c
lab
R
1
—PheFF—Phe—W—SiX
a
Y
b
Z
c
lac
R
1
—PheFF—Cy—W—SiX
a
Y
b
Z
c
lad
F—PheF—Phe—W—SiX
a
Y
b
Z
c
lae
F—PheF—Cy—W—SiX
a
Y
b
Z
c
laf
R
1
—Phe—Phe—W—SiX
a
Y
b
Z
c
lag
R
1
—Phe—Cy—W—SiX
a
Y
b
Z
c
lah
R
1
—Cy—Cy—W—SiX
a
Y
b
Z
c
lai
Particular preference is given to the compounds of the formulae Iaa, Iab, Iae, Iaf, Iag and Iai.
The compounds of the subformula Ib embrace the preferred compounds of the subformulae Iba to Ibh:
R
1
—PheF—Z
1
—Phe—W—SiX
a
Y
b
Z
c
lba
R
1
—PheF—Z
1
—Cy—W—SiX
a
Y
b
Z
c
lbb
R
1
—PheFF—Z
1
—Phe—W—SiX
a
Y
b
Z
c
lbc
R
1
—PheFF—Z
1
—Cy—W—SiX
a
Y
b
Z
c
lbd
F—PheF—Z
1
—Phe—W—SiX
a
Y
b
Z
c
lbe
F—PheF—Z
1
—Cy—W—SiX
a
Y
b
Z
c
lbf
R
1
—Phe—Z
1
—Phe—W—SiX
a
Y
b
Z
c
lbg
R
1
—Phe—Z
1
Cy—W—SiX
a
Y
b
Z
c
lbh
The compounds of the subformula Ic embrace the pr

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