Photoactive polymers

Details Photoactive polymers Photoactive polymers

2001-10-03

2003-11-18

Berman, Susan W. (Department: 1711)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

Alignment layer of specified composition

C428S001230, C428S001250, C428S001260, C428S001270, C430S020000, C522S148000, C522S150000, C522S153000, C522S162000, C522S164000, C526S242000, C526S279000, C526S328000, C528S025000, C528S026000, C528S065000, C528S306000, C528S322000, C349S127000

Reexamination Certificate

active

06649230

ABSTRACT:

This application is a national stage filing under 35 U.S.C. §371 of international application no. PCT/IB00/00349, filed on Mar. 27, 2000, which published in the English language.
The present invention relates to new photoactive polymers, and their use as orientation layers for liquid crystals and in the construction of unstructured and structured optical elements and multi-layer systems.
Different electro-optical effects used for liquid crystal displays (LCD) require alignment layers with very high pretilt angles. Vertically aligned nematic (VAN). LCDs for instance require pretilt angles between 85° and 90°, measured from the surface plane. In the case of hybrid aligned nematic (HAN)-LCDs, the pretilt angle at one of the substrates has to be in the above range, whereas the tilt angle at the other substrate is low (typically 0-10°). Brushed polyimides which are capable of inducing high pretilt angles suffer from the known drawbacks of the brushing technique. In the case of VAN-LCDs especially scratches caused by brushing and insufficient pretilt angle uniformity are well known problems of the brushing technique. On the other hand, stable photoalignable materials for high pretilt angles, which would solve the above problems, are not known so far.
Most of the known electro-optic LCD-modes suffer from residual birefringence of the liquid crystal layer which results in reduced contrast, intrinsic colours and/or restricted viewing angles. Optical retarders are applied to the LCD to compensate for the residual birefringence. Tilted LC-configurations which are formed upon applying a voltage to the LCD are used in most of the commercialised LCDs to adjust grey scale. The very asymmetric viewing angle dependence of such tilted LC-configurations is optimally compensated if the optical axis of the compensating retarder is tilted as well. Liquid crystal polymers (LCP) which were photoaligned by LPP-materials prior to polymerisation are ideally suited to such an application, as the tilt of the optical axis can principally be adjusted to any value between 0° and 90° by the adjacent alignment layer. A drawback of known alignment materials inducing very high pretilt angles is their high surface tension which causes wetting problems. Consequently, it is not possible to coat a uniform layer of LCP-prepolymers on top of such alignment layers.
EP-A-0 611 786 (F. Hoffinann-La Roche AG) discloses polymers having isomerisation/dimerisation units of the general formula:
wherein:
M
a
, M
b
, M
c
signify monomer units for homo- or copolymers;
x, y, z indicate mole fractions of the copolymers, whereby in each case 0<x≦1; 0≦y≦1 and 0≦z≦1;
Sa, Sb represent spacer units;
Za, Zb represent molecule units which can undergo photochemical isomerisation/dimerisation;
n is from 4-100 000; and
m is 0 or 1.
These linear and cyclic polymers or oligomers have a photoreactive ethene group for use as orientating layers for liquid crystals.
WO-A-96/10049 (F. Hoffinann-La Roche AG) discloses polymers of the general formula:
wherein:
M
1
and M
2
signify monomer units for homo- or copolymers; x and yindicate mole fractions of the comonomers, with in each case 0<x≦1 and 0≦y<1 and x+y=1;
p signifies 4 to 30 000;
S
1
and S
2
signify spacer units;
Q
1
signifies a structural unit of the formula:
—A—(Z
1
—B)
z
—Z
2
—  IIa;
Q
2
signifies a structural unit of the formula:
—A—(Z
1
—B)
z
—R
1
—  IIb;
A and B each independently signify pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or optionally substituted 1,4-phenylene;,
Z
1
and Z
2
each independently signify a single covalent bond, —CH
2
—CH
2
—, —CH
2
O—, —OCH
2
—, —CONR—, —RNCO—, —COO— or —OOC—;
R signifies hydrogen or lower alkyl;
R
1
signifies hydrogen, optionally substituted alkyl or alkoxy with in each case 1 to 12 carbon atoms, cyano, nitro or halogen;
z signifies 0 or 1;
C signifies a photochemically dimerisable coumarin or quinolinone derivative; and
m and n each independently signify 0 or 1.
These linear and cyclic polymers or oligomers of coumarin and quinolinone derivatives have a photoreactive ethene group and may be used as orienting layers for liquid crystals.
EP-A-0 763 552 (Rolic AG) discloses polymer compositions in which repeating units of general formula I are present:
wherein
M
1
signifies a repeating monomer unit from the group; acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate; optionally N-lower alkyl substituted acrylamide, methacrylamide, 2-chloroacrylamide and 2-phenylacrylamide; vinyl ether, vinyl ester, styrene derivative, siloxane;
S
1
signifies spacer units such as, for example, a single covalent bond, a straight-chain or branched alkylene grouping represented hereinafter by —(CH
2
)
r
—, as well as —(CH
2
)
r
—O—, —(CH
2
)
r
—O—(CH
2
)
s
—, —(CH
2
)
r
—O—(CH
2
)
s
—O—, —(CH
2
)
r
—CO—, —(CH
2
)
r
—CO—O—, —(CH
2
)
r
—O—CO—, —(CH
2
)
r
—NR
2
—, —(CH
2
)
r
—CO—NR
2
—, —(CH
2
)
r
—NR
2
—CO—, —(CH
2
)
r
—NR
2
—CO—O— or —(CH
2
)
r
—NR
2
—CO—NR
3
—, which is optionally mono- or multiply-substituted with fluorine, chlorine or cyano and in which r and s are each a whole number of 1 to 20, with the proviso that r+s≦20, and R
2
and R
3
each independently signify hydrogen or lower alkyl;
ring A signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl, cyclohexane-1,4-diyl, piperidine-1,4-diyl, piperazine-1,4-diyl;
ring B signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4- or 2,6-naphthylene, 1,3-dioxane-2,5-diyl, cyclohexane-1,4-diyl;
Y
1
, Y
2
each independently signify a single covalent bond, —(CH
2
)
t
—, —O—, —CO—, —CO—O—, —O—OC—, —NR
4
—, —CO—NR
4
—, —R
4
N—CO—, —(CH
2
)
u
—O—, —O—(CB
2
)
u
—, —(CH
2
)
u
—NR
4
— or —NR
4
—(CH
2
)
u
—, in which
R
4
signifies hydrogen or lower alkyl;
t signifies a whole number of 1 to 4;
u signifies a whole number of 1 to 3;
m, n each independently signify 0 or 1;
ring C signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, or pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene;
Z signifies —O— or —NR
5
—, in which R
5
signifies hydrogen or lower alkyl, or a second group of formula D, in which
D signifies a straight-chain or branched alkylene group with 1 to 20 carbon atoms which is optionally substituted with fluorine or chlorine, a cycloalkyl residue with 3 to 8 ring atoms which is optionally substituted with fluorine, chlorine alkyl or alkoxy.
These cross-linkable, photoactive polymer materials with 3-arylacrylic acid esters and amides may be used as orienting layers for liquid crystals and for the production of non-structured and structured optical elements and multi-layer systems.
EP-A-0860455 (Rolic AG) discloses polymers of the general formula I:
wherein:
M
1
, M
1
′ denote a recurring monomer unit form the group: acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate; optionally by lower alkyl N-substituted acrylamide, methacrylamide, 2-chloroacrylamide and 2-phenylacrylamide; vinyl ethers, vinyl esters, styrene derivatives, siloxanes;
M
2
denotes a recurring monomer unit from the group: acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate, optionally by lower alkyl N-substituted acrylamide, methacrylamide, 2-chloroacrylamide and 2-phenylacrylamide; vinyl ether, vinyl ester; straight-chain or branched alkyl esters of acrylic or methacrylic acid, allyl esters of acrylic or methacrylic acid, alkyl vinyl ethers or ester, phenoxyalkyl acrylates or phenoxyalkyl methacrylates or hydroxyalkyl acrylates or hydroxyalkyl methacrylates, phenylalkyl acrylates or phenylalkyl methacrylates, in which the alkyl groups have 1 to 20, preferably 5 to 20, but in particular 5 to 18 carbon atoms; acrylonitrile, methacrylonitrile, styrene, 4-methylstyrene

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