| Title of Invention | PHOTOACTIVE POLYIMIDES POLYAMIDE ACIDS OR ESTERS THEREOF WITH SPECIFIC SIDE CHAIN PHOTOCROSSLINABLE GROUPS AS ORIENTATION LAYERS FOR LIQUID CRYSTALS |
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| Abstract | A photoactive polymer from the class of polyimides, poiyamide acids and esters thereof, characterised in that it comprises as a side-chain a photocrosslinkable group of the general formula I: Qv Y wherein the broken line indicates the point of linkage to the polyimide main chain and wherein: A represents pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene, or phenylene; optionally substituted by a group selected from fluorine, chlorine, cyano or by a Ci-18 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl -CHr- groups are optionally replaced by a group Q; B is a straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more non-adjacent CB.2 groups may independently be replaced by a group Q; C1 and C2 each independently of the other represents an aromatic or alicyclic group which is unsubstituted or substituted by fluorine, chlorine, cyano, or by a cyclic, straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 18 carbon atoms and wherein one or more non-adjacent CH? groups may independently be replaced by a group Q; 5 D represents an oxygen atom or -NR1- wherein R1 represents a hydrogen atom or lower alkyl; S1 and S2 each independently of the other represent a single covalent bond or a spacer unit; S3 represents a spacer unit: Q represents a group selected from -0-, -CO-, -CO-0-, -0-CO-, -Si(CH3)2-0-Si(CH3)2- -NR1-, -NR'-CO-, -CO-NR1--N^-CO-O-, -O-CO-NR1-, -NR'-CO-NR1-, -CH=CH-, -C=C-and -0-CO-O-, wherein R1 represents a hydrogen atom or lower alkyl; n1 and n2 are each independently 0 or 1; and X, Y each independently of the other represents hydrogen, fluorine, chlorine, cyano, alkyl optionally substituted by fluorine having from 1 to 12 carbon atoms in which optionally one or more non-adjacent CEb groups are replaced by -0-, -CO-0-, -O-CO- and/or -CH=CH- |
| Full Text | FORM 2 COMPLETE SPECIFICATION [See section 10; Rule 13] PHOTOACTIVE POLYIMIDES, POLYAMIDE ACIDS OR ESTERS THEREOF WITH SPECIFIC SIDE CHAIN PHOTOCROSSLINABLE GROUPS AS ORIENTATION LAYERS FOR LIQUID CRYSTALS; ROLIC AG, A CORPORATION ORGANIZED AND EXISTING UNDER THE LAWS OF SWITZERLAND, WHOSE ADDRESS IS CHAMERSTRASSE 50, 6301 ZUG SWITZERLAND. THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE 0|F THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED. The present invention relates to new photoactive polymers based on polyimides, polyamic acids and esters thereof and their use as orientation layers for liquid crystals and in the construction of unstructured and structured optical elements and multi-layer systems. The successful functioning of a Liquid Crystal Device relies upon the ability of the LC molecules within that device to adopt and maintain an alignment imposed upon them. Alignment of the LC molecules is achieved by use of an orientation layer which defines a direction of orientation for the LC molecules of the device with the result that the longitudinal axes of the molecules become aligned with the direction of orientation defined by the orientation layer. In addition to this directional alignment, the orientation layer is also able to impart to the LC molecules an angle of tilt so that the molecules align themselves at an angle to the surface of the orientation layer rather than lying parallel hereto. Tilt angles of between 1° and 15° are usual for Nematic LCDs. Some electro-optical effects used for liquid crystal displays (LCD) however 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°). Methods of preparing structured and unstructured orientation layers are well known to a skilled person. Customarily used uniaxially rubbed polymer orientation layers such as, for example, polyimides however impact a series of disadvantages like dust generation during rubbing process, destruction of thin film transistors and lack of structuring. The rubbing process consequently does not allow the production of structured layers. Orientation layers in which the direction of orientation can be predetermined by irradiation with polarized light have been known for some time. It is by that means possible to avoid the problems inherent in the rubbing process. In addition, it is possible to provide areas having different orientation and thus to structure the orientation layer as described for example in Jpn. J. Appl. Phys.. 31 (1992), 2155-64 (Schadt et al.), in that process the dimerisation of polymer-bonded photoreactive cinnamic acid groups induced by irradiation with linearly polarized light is employed leading to an ansiotropic polymer network. Those photo-oriented polymer networks can be used wherever structured or unstructured liquid crystal orientation layers are required. In addition to their use in LCDs, such orientation layers can also be used, for example , in the production of so-called hybrid layers as exemplified in European Patent Applications EP-A -0611981, EP -A-0689084 and EP -A-0753785 (all F. Hoffmann-La Roche AG). EP-A -0611981 describes An optical component includes an anisotropic layer of cross-linked liquid crystal monomers with varying local orientation of the liquid crystal molecules. The liquid crystal layer is in contact with an orientation layer comprising a photo-orientable polymer network (PPN). A method of making includes orienting the liquid crystal monomers by the interaction with the PPN layer and subsequently fixing the molecules by cross-linking. EP 689084 An optical component having a hybrid layer structure includes an orienting layer, a further layer in contact with the orienting layer and incorporating a cross-linked liquid crystalline monomer and at least one additional orienting layer on top of the liquid crystalline layer, and preferably includes one additional cross-linked liquid crystalline monomer. The layers have different functions, such as orienting or retarding. At least one of the orienting layers should be a photo-orientating polymer network layer, or have locally varying orienting pattern. These optical components are useful in transmittance and reflective liquid crystal displays, such as rotation cells, STN cells, ferroelectric cells, and cells having an addressable active matrix. Such cells are useful in optical and integrated optical devices, and may be used for safeguarding against counterfeiting and copying in transmission. EP 689084 describes an optical component having a hybrid layer structure includes an orienting layer, a further layer in contact with the orienting layer and incorporating a cross-linked liquid crystalline monomer and at least one additional orienting layer on top of the liquid crystalline layer, and preferably includes one additional cross-linked liquid crystalline monomer. The layers have different functions, such as orienting or retarding. At least one of the orienting layers should be a photo-orientating polymer network layer, or have locally varying orienting pattern. These optical components are useful in transmittance and reflective liquid crystal displays, such as rotation cells, STN cells, ferroelectric cells, and cells having an addressable active matrix. Such cells are useful in optical and integrated optical devices, and may be used for safeguarding against counterfeiting and copying in transmission. EP 753785 describes a polarization mask for producing light of locally different polarization from unpolarized or uniformly polarized light. On the light output side, discrete areas with different polarization directions are present, which are either static or switchable. The mask is useful for, among other things, the transfer of polarization pattern onto a PPN layer. Using those hybrid layers of photostructured polymers and crosslinkable low molecular weight liquid crystals it is possible to realize optical elements such as, for example, non-absorptive colour filters, linear and circular polarisers, optical delay layers and so on. EP-A-0611786 and WO-A-96/10049 (both Hoffmann-La Roche AG), as well as EP-A-0763552 (Rolic AG), describe cinnamic acid polymers that are suitable in principle for the synthesis of such anisotropically crosslinked, photostructured orientation layers for liquid crystals. EP-A-0611786 relates to novel linear and cyclic polymers or oligomers containing a photoreactive ethene group for use as alignment (orientation) layer for liquid crystals of the formula in which Ma, Mb and Mc are monomer units for homopolymers or copolymers; x, y and z represent molar fractions of the copolymers, where in each case 0 number from 4 to 100,000; and m is 0 or 1, and to their use as alignment layers for liquid crystals.. WO 9610049 describes a polymer having the formula ##STR1## wherein M.sup.1 and M.sup.2 signify monomer units for homo- or copolymers, "x" and "y" indicate the mole fractions of the comonomers, with in each case 0 In case of compounds described in EP-A-0763552 and WO-A-96/10049 on irradiation with linearly polarized light it is possible, in addition to inducing the desired orientation, simulataneously to induce an angle of tilt. It is thus possible to produce layers having structuring in respect of surface orientation and angle of tilt. The above photostructured orientation layers have the disadvantage, however that for certain applications, especially for use in TFT displays, they result in adjacent liquid crystal mixture having an insufficient electrical resistance values. In TFT displays, too low a resistance value of the liquid crystal medium leads to an inadequate "holding ratio", which is a measure of the voltage drop in the display after the voltage has been switched off. Low holding ratio values, however, bring about undesirable changes in brighness and contrast over time and thus result in unstable graduations of the grey tones. Recently photoreactive materials for orientation layers with improved holding rations were described in WO-A-99/49360 (Rolic AG), JP-A-10-195296, JP-A-10-232400 (both Samsung Electron Devices Co., Ltd.), WO-A-99/15576 (Rolic AG) and WO-A-99/51662(Kanegafuchi Kagaku Kogyo KK). WO-A-99/49360 describes a linearly photopolymerised (LLP) orientation layers for liquid crystals, that is to say liquid crystal orientation layers, are oriented and crosslinked by means of linearly polarized light. The properties of an LPP orientation layer, such as the angle of tilt, surface wetting, voltage holding ratio and anchoring energy, can be adjusted and/or improved by mixing further substances into the starting material for the preparation of the orientation layer. JP-A-10-195296 describes The light-orientating composition comprises (A) a cinnamate or coumarin polymer and (B) a polymer comprising (B1 ) a polyimide having alkyl groups at both the ends or (B2 ) a polyamide having a structure of the formula R1 is a 3-10C cycloalkyl [substituted by a group (G) such as a 1-10C alkyl, an aromatic group or a (substituted) amino], a (G-substituted) 3-10C cycloalkenyl, etc.; R2 is R1 , a (G-substituted) aromatic ring; X1 is COO, O, OCO; R3 is a 3-20C alkyl; (ml )>=0; (n1 )>=1; (ml ):(n1 ) is 1:99 to 20:80} in an A:B weight ratio of e.g. 99:1to80:20. JP-A-10-232400 describes a composition containing a vinyl cinnamate deriv. Polymer and a polyimide by 98:2 to 2:98 weight ratio. The vinyl cinnamate deriv. Polymer is preferably is poly (vinyl cinnamate) or poly (vinyl methoxycinnamate), and its weight averabge mol.wt ranges 5000 to 30000. the polyimide is preferably a side-chain polyimide having 5000 to 20000 weight average mol.wet or a straight- chain polyimide having 5000 to 30000 weight average mol.wt. when the two kinds of polymers are mixed in cinnate deriv, polymer has an effect to induce optical alighment while the polyimide has an effect to improve thermal stability and to produce the pretilt angle of aliquid crystal. WO-A-99/15576 relates to novel crosslinkable photoactive polymers from the class of polyimides, polyimide acids, and esters thereof and to their use as orientation layers for liquid crystals and in the construction of unstructured and structured optical elements and multi-layer systems. The polymers contain as side-chain photocrossslinkable groups of formula (1). The broken line indicates the point of linkage ot the polymer main chain. In addition, A,B each independently of the other represents unsubstituted or optionally fluoro-, chloro-, cyano-, alkyl-, alkoxy-, fluoralkyl-, or fluoroalkoxy-substituted phenylene, pyridine-2-5-diyl, pyrimidine - 2,5,-diyl cyclohexane-1,4-diyl piperidine-1,4-diyl piperazine-1,4 diyl; C represents unsubstituted or optionally fluoro-, chlor-, alkyl-, alkoxy-, fluroalkyl- or fluroalkoxy-substituted phenylene or pyrimidine-2,5 diyl pyridine-2,5-diyl, 2,5-thiophenylene, 2,5 furanylene, 1,4-or 2,6-naphtylene. WO-A-99/51662 discloses novel polyimide compositions having a cinnamic acid or cinnamic acid derivative skeleton and possessing both the photoreactivity and heat reactivity characteristics to the cinnamic acid skeleton. Novel diamines and acid dianydrides, which are usable mainly in producing the above novel polyimide compositions having the cinnamic acid skeleton having the cinnamic acid skeleton or the cinnamic acid derivative skeleton in the main chain or in the side chain. In WO-A-99/49360 (Rolic AG), JP-A-10-195296 and JP-A-10-232400 blends of polymeric compounds containing photoreactive polymers on the one hand and polyimides on the other hand are proposed. A disadvantage of such blends is their limited miscibility. Low contents of photoreactive polymers however lead to a loss of orienting properties and consequently to a reduced contrast ratio of liquid crystal layers to be oriented whereas a reduced polyimide content results in insufficient holding ratios. In WO-A-99/15576 and WO-A-99/511662 polyimides incorporating photoreactive cinnamate groups in their side chains are described. WO-A-99/15576 discloses photoactive polymers which contain as side-chains photocrosslinkable groups of the following formula: A typical monomer unit is 3,5 diaminobenzoic acid 6-[2-methoxy-4-(2methoxycarbonylvinyl)phenoxy] hexyl ester. The cinnamic acid derivatives disclosed in WO-A-99/15576 are linked to the polyimide backbone such that the phoioreactive groups are pointing away from the backbone. WO-A-99/51662 discloses photoactive polymers having a cinnamic skeletal structure. Atypical monomer disclosed is of the following formula: The polyimide compositions are said to combine the photoreactivity and thermal reactivity characteristic of the cinnamic acid skeletal structure. There is no teaching of the improvement of the orientation of liquid crystals. Consequently stable photoalignable materials for high pretilt angles with sufficiently high holding ratios are not known so far. The problem underlying the invention was, therefore, to find photoreactive polymers that, when irradiated with polarised light, result in the production of stable, high-resolution orientation patterns having very high angle of tilt and at the same time result in sufficiently high holding ratios in the adjacent liquid crystal medium. Surprisingly, it has now been found that polyimides, incorporating cinnamic acid derivatives in their side chains in such a way, that the cinnamic acid groups are linked to the polyimide backbone via the carboxylic group by means of a flexible spacer, perfectly fulfil the above requirements. The illumination of those compounds, using linearly polarised light, results in excellent orientation of the liquid crystals, in a 25 sufficiently high holding ratio of the liquid crystal medium and simultaneously in an appreciable increase of the tilt angle up to 90°. A first aspect of the present invention therefore provides photoactive polymers from the class of polyimides. polyamide acids and esters thereof, characterised in that they comprise as side-chains photocrosslinkable groups of the general formula I: —- S^ Xf y—{ A V+S1 CH-f S2 C2]—B h11 n2 wherein the broken line indicates the point of linkage to the polyimide main chain and wherein: A represents pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene, or phenylene; which is optionally substituted by a group selected from fluorine, chlorine, cyano or by a Ci-u cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl -CH2- groups are optionally replaced by a group Q; B is a straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q; C1 and C2 each independently of the other represents an aromatic or alicyclic group which is unsubstituted or substituted by fluorine, chlorine, cyano, or by a cyclic, straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 18 carbon atoms and wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q; D represents an oxygen atom or -NR1- wherein R1 represents a hydrogen atom or lower alkyl; S1 and S" each independently of the other represent a single covalent bond or a spacer unit, such as a straight-chain or branched alkylene residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q; S3 represents a spacer unit, such as a straight-chain or branched alkylene residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 2 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by an aromatic, an alicyclic group or a group Q; Q represents a group selected from -0-, -CO-, -CO-0-, -O-CO-, -Si(CH3)2-0-Si(CH3)2- -NR1-, -NR'-CO- -CO-NR1--NR'-CO-O-, -O-CO-NR1- -NR'-CO-NR1- -CH=CH- -OC-and -O-CO-O-, wherein R1 represents a hydrogen atom or lower alkyl; n1 and n2 are each independently 0 or 1; and X, Y each independently of the other represents hydrogen, fluorine, chlorine, cyano, alkyl optionally substituted by fluorine having from 1 to 12 carbon atoms in which optionally one or more non-adjacent CH2 groups are replaced by -0- -CO-0-, -0-CO- and/or -CH=CH- f \ - ■ ; n -; By the term "aromatic" it should be understood to include optionally-substituted carbocylic and heterocyclic groups incorporating five, six or ten ring atoms like furan, phenyl, pyridine, pyrimidine, naphthalene, or tetraline units. By the term "cyclic, straight-chain or branched alkyl group, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent -CH?- groups are optionally replaced by a group Q" it should be understood to include groups selected from the group comprising methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-buty\, pentyl, isopentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, 3-methylpentyl, allyl, but-3-en-l-yl, pent-4-en-l-yl, hex-5-en-l-yl, propynyl, butynyl, pentynyl, methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, sec-butoxy, rer/-butoxy, pentyloxy, isopentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, 3-methylpentyloxy, allyloxy, but-3-enyloxy, pent-4-enyloxy, cylohexylmethoxy, cyclopentylmethoxy, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, te/*r-butoxycarbonyl, pentyloxycarbonyl, isopentyloxycarbonyl, cyclopentyloxy- carbonyl, hexyloxycarbonyl, cyclohexyloxycarbonyl, octyloxycarbonyl, nonyloxy- carbonyl, decyloxycarbonyl, undecyloxycarbonyl, dodecyloxycarbonyl, 3-methylpentyloxycarbonyl, allyloxycarbonyl, but-3-enyloxycarbonyl, pent-4-enyl- oxycarbonyl, cylohexylmethoxycarbonyl, cyclopentylmethoxycarbonyl, acetoxy, ethylcarbonyloxy, propylcarbonyloxy, isopropylcarbonyloxy, butylcarbonyloxy, isobutylcarbonyloxy, sec-butylcarbonyloxy, rer/-butylcarbonyloxy, pentyl- carbonyloxy, isopentylcarbonyloxy, cyclopentylcarbonyloxy, hexylcarbonyloxy, cyclohexylcarbonyloxy, octylcarbonyloxy, nonylcarbonyloxy, decylcarbonyloxy, undecylcarbonyloxy, dodecylcarbonyloxy, 3-methylpentylcarbonyloxy, but-3-enyloxy, pent-4-enyloxy, acetyl, ethylcarbonyl, propylcarbonyl, isopropyl-carbonyl, butylcarbonyl, isobutylcarbonyl, sec-butylcarbonyl, pentylcarbonyl, isopentylcarbonyl, cyclohexylcarbonyl, octylcarbonyl, nonylcarbonyl, decylcarbonyl, undecylcarbonyl, dodecylcarbonyL methoxyacetoxy, 1 -methoxy-2-propoxy, 3-methoxy-l-propoxy, 2-methoxyethoxy, 2-isopropoxyethoxy, ]-ethoxy-3-pentyloxy, 3-butynyloxy, 4-pentynyloxy, 5-chloropentynyl, 4-pentynecarbonyloxy, 6-propyloxy-hexyl, 6-propyloxyhexyloxy, 2-fluoroethyl, trifluoromethyl, 2,2,2-trifluoroethyl, IN, l/T-pentadecafluorooctyl, IN, IN, 7//-dodecafluoroheptyl, 2-(perfluorooctyl)ethyl, 2-(perfluorobutyl)ethyl, 2-(perfluorohexyl)ethyl, 2-(perfluorodecyl)ethyl, perfluoro-propyl, perfluorobutyl, perfluoroheptyl, peffluorooctyl, perfluorononyl. 1-fluoropropoxy, 1-fluoropentyloxy, 2-fluoropropoxy, 2,2-difluoropropoxy, 3-fluoropropoxy, 3,3-difluoropropoxy, 3,3,3-trifluoropropoxy, trifluoromethoxy and the like. By the term "lower alkyl" it should be understood to include straight chain and branched hydrocarbon radicals having from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. Methyl, ethyl, propyl and isopropyl groups are especially preferred. By the term "alicyclic" it should be understood to include non-aromatic carbocyclic or heterocyclic ring systems with 3 to 10 carbon atoms like cyclopropane, cyclobutane, cyclopentane, cyclopentene, cyclohexane, cyclohexene, cyclohexadiene and decaline. It is also preferred that the group A is selected from pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene and a phenylene group, which is optionally substituted by a C1-12 cyclic, straight-chain or branched alkyl residue, which alkyl group is optionally substituted by one or more halogen atoms and in which one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO-, -CH=CH- and -Cs£- It is especially preferred that A is selected from phenylene, which is optionally substituted by a C1-12 straight-chain or branched alkyl residue, which alkyl group is substituted by one or more fluorine atoms, and wherein one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO- and -CH=CH- By the term "phenylene" it should be understood to include 1,2-, 1.3- or 1,4-phenylene, which is optionally substituted. It is preferred that the phenylene group is either a 1,3- or a 1,4-phenylene. Preferred groups B are selected from straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more CH2 groups may independently be replaced by -0-, -CO-, -CO-O-, -O-CO-, -CH=CH- -C=C-, with the proviso that oxygen atoms are not directly attached to each other. It is especially preferred that B is selected from straight-chain or branched alkyl residue which is unsubstituted, mono-substituted or poly-substituted by halogeno, having 3 to 12 carbon atoms, wherein one or more CH2 groups may independently be replaced by -0-, -CO-, -CO-O-, -O-CO-, with the proviso that oxygen atoms are not directly attached to each other. It is preferred that each of the groups C1 and C2 are selected from cyclohexane-l,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1,4- or 2,6-naphthylene and phenylene, which is optionally substituted by one or more groups selected from fluorine, chlorine, cyano and a C1-12 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl -CH2- groups are optionally independently replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO-, -CH=CH- -CsC- and -O-CO-O-. It is especially preferred that the groups C1 and C2 are selected from cyclohexane-l,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyI, 2,6-naphthyiene and phenylene, which is optionally substituted by one or more fluorine atoms or a Ci_g straight-chain or branched alkyl residue, which is optionally substituted by one or more fluorine atoms, and in which one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO- and -CH=CH- Preferred groups D are oxygen atom or -NH-. It is especially preferred that D is an oxygen atom. It is preferred that the groups S1 and S2 are selected from a single covalent bond, -0-, -CO-O-, -O-CO- -NR1- -NR'-CO-, -CO-NR1-, -NR'-CO-O-, -O-CO-NR1-, -NR'-CO-NR1-, -CH=CH-, -C=C-7 -O-CO-O-and a straight-chain or branched alkylene group, in which two or three non-adjacent alkylene -CH2- group are independently optionally replaced by a group Q with the proviso the total number of chain carbon atoms in the alkylene group does not exceed 24, wherein R1 represents a hydrogen atom or lower alkyl. It is more preferred that S1 and S2 are selected from a single covalent bond, -CO-O-, -O-CO- -(CH2)r- -(CH2)-0- -(CH2)-CO- -(CH2)-CO-0~ -(CH2)r-0-CO- -(CH^-CO-NR1- -(CH2)r-NR]-CO- -(CH2)r-NR1-, -0-(CH2)r-, -CO-0-(CH2)r- -0-CO-(CH2)r-, -NR^CO-fCH^- -CO-NR'-CCHzX-, -NR1-(CH2)t-, -0-(CH2)-CO-0- ~0-(CH2)-0-CO-, -0-(CH2)r-CO-NR'~, -O-CCH.^-NR1-, -0-(CH2)r~0- -0-(CH2)-NR'-CO-, -NR'-(CH2)r-CO-0-, -NR'-fCH^-O- -NR'-CCH^-NR1-, -NR^CH^-O-CO-, -CO-NR1-(CH2X-0-, -CO-NR1-(CH2)r-NR1- -C0-NR]-(CH2)r-0-CO-, -0-CO-(CH2)r-CO- -0-CO-(CH2)r-0- -0~CO-(CH2)-NR2- -0-CO-(CH2)-CO-0-, -0-CO-(CH2)r-CO-NR'-. -0-CO-(CH2)-NR]-CO-, -(CH2)r-0-(CH2)s-, -(CH2}r-CO-0-(CH2)^, -(CH2)-0-CO-(CH2)s- -(CH2)r-NR'-CO-(CH2)s-, -(CH2)-NR1CO-0-(CH2)s-, -(CH2)r-0-(CH2)s-0-, -(CH2X-CO-0-(CH2)s-0- -(CH2)-0-CO-(CH2)s-0- -(CH2)-NR'-CO-(CH2)s-0-, ~{CH2)T-m}-CO~0-(CU2)-0^ -0-(CH2X-0-(CH2)s-,-0-(CH2)-CO-0-(CH2)s-,-O-CCHzJ-NR^CO-CC^),-, -O-fCHs^-NR'-CO-O-fCHo),-, ~0-(CH2),-CO-0-(CH2)s-0- -0-(CH2)-CHCH2)s-0- -0-(CH2)T-NR,-CO-(CH2)s-0-, -0-(CH2)-NR1-CO-0-(CH2)5-0-. -CO-0-(CH2)r-0-(CH2)s- and _CO-0-(CH2y-0-(CH2)s-0-, wherein R1 is as defined above, r and s each represent an integer from 1 to 20, preferably from 1 to 12, and r + s By the terms -(CH2)r-and -(CH2)5- it should be understood to include straight-chain or branched alkylene groupings containing r or s carbon atoms respectively. It is especially preferred that S1 and S2 are selected from a single covalent bond, -(CH2)-, -(CH2)r-CK -(CH2)r-CO-0- -(CH2)r-0-CO- -(CH2y-CO-NH- -(CH2)-NH-CO-. -0-(CH2)r- -CO-0-(CH2)r- -CO-NH-(CH2)r- -NH-CO~(CH2)r- -0-CO-(CH2)-, -0-CO-(CH2)-CO~0- -0-(CH2)r-0-CO-, -0(CH2)-CO-NH- -0-(CH2)r-NH-CO-, -CO-0-(CH2)r-0-, -CO-NH-(CH2)-0- -0-(CH2)-0- -(CH^-NH-CCMCH^-, -(CH2)r-NH-CO-0-(CH2)-, -(CH2)r-0-(CH2)-0- -(CH^-^-CO^CH^-O- -(CH2)r-NHCO-0-(CH2)-0- -0-(CH2)r-Mi-CO-(CH2)s-, -0-(CH2V-0-(CH2)s-O, -0-CO-(CH2)-0-(CH2)s~0-, -CO-0-(CH2)r-0-(CH2)-0- -0-(CH2)r-NH-CO-(CH2)s-0- and -0-CO-(CH2)-NH-CO-(CH2)i-0-, wherein r and s each represent an integer from 1 to 12 and T + s Examples of preferred groups S1 and S2 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl- 1,4-butylene, methyleneoxy, 2-ethyleneoxy, 3-propyleneoxy, 3-propyleneoxycarbonyl, 2-ethylene- carbonyloxy, 4-butyleneoxy, 4-butyleneoxycarbonyl, 3-propylenecarbonyloxy, 5-pentyleneoxy, 5-pentyleneoxycarbonyl, 4-butylenecarbonyloxy, 6-hexyleneoxy, 6-hexyleneoxycarbonyl, 5-pentylenecarbonyloxy, 7-heptyleneoxy, 7-heptyleneoxy- carbonyl, 6-hexylenecarbonyloxy, 8-octyleneoxy, 8-octyleneoxycarbonyl, 7-heptylenecarbonyloxy, 9-nonyleneoxy, 9-nonyleneoxycarbonyl, 8-octylene- carbonyloxy, 10-decyleneoxy, 10-decyleneoxycarbonyl, 9-nonylenecarbonyloxy, 11 -undecyleneoxy, 11 -undecy leneoxycarbonyl, 10-decylenecarbony loxy, 12-dodecyleneoxy, 12-dodecyleneoxycarbonyl, 11-undecy lenecarbony loxy, 3-propyleneiminocarbonyl, 4-butyleneiminocarbonyl, 5-pentyleneiminocarbonyl, 6-hexyleneiminocarbonyl, 7-heptyleneiminocarbonyl, 8-octyleneiminocarbonyl, 9-nonyleneiminocarbonyl, 10-decyleneiminocarbonyl, 11-undecyleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethylenecarbonylimino, 3-propylenecarbonylimino, 4-butylenecarbonylimino, 5-pentylenecarbonylimino, 6-hexylenecarbonylimino, 7-heptylenecarbonyIimino, 8-octylenecarbonyIimino, 9-nonylenecarbonyIimino, 10-decylenecarbonylimino, 11-undecylenecarbonylimino, 6-(3-propyleneimino-carbonyloxy)hexylene, 6-(3-propyleneoxy)hexylene, 6-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneiminocarbonyloxy)hexyleneoxy, 6-(3-propyleneiminocarbonyl)hexyl, 6-(3-propyleneiminocarbonyl)hexyloxy, 1,2-ethylenedioxy, 1,3-propylenedioxy, 1,4-butylenedioxy, 1,5-pentylenedioxy, 1,6-hexylenedioxy, 1,7-heptylenedioxy, 1,8-octylenedioxy, 1,9-nonylenedioxy, 1,10-decylenedioxy, 1,11-undecylenedioxy, 1,12-dodecylenedioxy and the like. It is preferred that the group S3 is selected from a spacer unit, such as a straight-chain or branched alkylene residue having 5 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q. More preferably the group S3 has 6 to 24 carbon atoms, and especially 7 to 20 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by a group Q. Note that, when the polyimide main chain includes an aromatic ring linking the polymerisable groups, the ring is to be regarded as part of the main chain and not to be regarded as part of the spacer. It is more preferred that S3 is selected from -(CH2)r-i-, -0-(CH2X-, -CO-CMCHiX-, -0-CO-(CH2)r- -NR'-CO-OCHaV-, -CO-NR^CJ^)-, -NR,- -iCH2)r-sNR}-CO-0-(CH2%-, -0-{CH2)r-0-(CH2)s- -0-(CH2)r-CO-0-(CH2)s- -0-(CH2)r-^NRI-CO-(CH2)s-, -O-fCHj^-N^-CO-CMCH^- and -C0-0-(CH2)r-O-(CH2)s- , wherein R1 is as defined above, r and s each represent an integer from 1 to 20, preferably from 2 to 12, and r + s Examples of preferred group S3 are 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 2-oxy- ethylene, 3-oxypropylene, 4-oxybutylene, 5-oxypentylene, 6-oxyhexylene, 7-oxy- heptylene, 8-oxyoctylene, 9-oxynonylene, 10-oxydecylene, 11-oxyundecylene, 12-oxydodecylene, 2-(oxycarbonyl)ethylene, 3-(oxycarbonyl)propylene, 4-(oxy- carbonyl)butylene, 5-(oxycarbonyl)pentylene, 6-(oxycarbonyl)hexylene, 7-(oxycarbonyl)heptylene, 8-(oxycarbonyl)octylene, 9-(oxycarbonyl)nonylene, 10-(oxycarbonyl)decylene, 1 l-(oxycarbonyl)undecylene, 12-(oxycarbonyl)- dodecyiene, 2-(carbonyloxy)ethyIene, 3-(carbonyloxy)propylene, 4-(carbonyloxy)-butylene, 5-(carbonyloxy)pentylene, 6-(carbonyloxy)hexylene, 7-(carbonyloxy)- heptylene, 8-(carbonyloxy)octylene, 9-(carbonyloxy)nonylene, lO-(carbonyloxy)- decylene, ll-(carbonyloxy)undecylene, 12-(carbonyloxy)dodecylene, 2-(carbonvl- imino)ethylene, 3-(carbonyIimino)propylene, 4-(carbonylimino)butylene, 5-(carbonyliminojpentylene, 6-(carbonylimino)hexylene, 7-(carbonylimino)- heptylene, 8-(carbonylimino)octyIene, 9-(carbonylimino)nonylene, 10-(carbonyl- imino)decylene, 1 l-(carbonylimino)undecylene, 12-(carbonylimino)dodecylene, 2-iminoethylene, 3-iminopropylene, 4-iminobutylene, 5-iminopentylene, 6-imino- hexylene, 7-iminoheptylene, 8-iminooctylene, 9-iminononylene, 10-iminodecylene, 11-irainoundecylene, 12-iminododecylene, 2-iminocarbonylethylene, 3-imino- carbonylpropylene, 4-iminocarbonylbutylene, 5-iminocarbonylpentylene, 6-imino- carbonylhexylene, 7-iminocarbonylheptylene, 8-iminocarbonyloctylene, 9-imino- carbonylnonylene, 10-iminocarbonyldecylene, 11-iminocarbonylundecylene, 12-iminocarbonyldodecylene, 2-(2-ethyleneoxy)ethylene, 2-(3-propyleneoxy>- ethylene, 6-(4-butyleneoxy)hexylene, 2-(2-ethyleneiminocarbonyl)ethylene, 2-(3-propyleneiminocarbonyl)ethylene, 6-(4-butyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneiminocarbonyl)hexylene and the like. It is preferred that the groups X and Y represent hydrogen. It is preferred that n1 + n2 = 0 or 1, and especially preferred that n1 = n2 = 0. Preferred monomer units from which the main chains of the side-chain polymers according to the invention are built up, are the imide groups of the general formulae II, IV and VI and/or the analogous amic acid groups and amic acid ester groups of the general formulae III, V and VII; especially preferred are the groups of the formulae II, JR, VI and VII: 0 G -4-E S8—N [f ; O vn wherein: the broken line symbolises the linkage to S3 T1 represents a tetravalent organic radical; T2, T3 each independently represent a trivalent aromatic or alicyclic group which is optionally substituted by a group selected from fluorine, chlorine, cyano and a Ci_i8 cyclic, straight-chain or branched .alkyl residue, which is optionally substituted by one or more halogen groups and in which one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -O-, -CO-, -CO-O-, -0-CO-, -CH=CH-and-C=:-; S4to S8 are each independently seleaed from a single covalent bond and a C-24 straight-chain or branched alkylene residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjaceru alkylene -CH2- groups are, independently, optionally replaced by a group Q; E is selected from the group comprising a nitrogen atom, a group -CR - and an aromatic or alicvclic divalent, trivalent or tetravalent group, which is 2A optionally substituted by one or more groups selected from fluoro, chloro, cyano and a Ci_is cvclic, straight-chain or branched alkyl residue which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent -CHi- groups are, independently, optionally, replaced by a group selected from -O-, -CO-, -CO-0-, -O-CCK -CH=CH- and -C=C- wherein R1 is as defined above; F .represents an aliphatic, alicyclic or aromatic divalent radical; and G represents a hydrogen atom or a monovalent organic group. By the term "aliphatic" it should be understood to include saturated and unsiaturated, straight-chain and branched alkyl groups, which may be optionally substituted and in which one cr more non-adjacent -CH2- groups are replaced by one or more heteroatoms. Optional substituents include alkyl, aryl, cycloalkyl, amino, cyano, epoxy, halogen, hydroxy, nitro and oxo. Examples of heteroatoms that can replace the one or more -CH2- groups include nitrogen, oxygen and sulfur. Replacement nitrogen atoms may be further substituted with groups such as alkyl, aryl and cycloalkyl. The tetravalent organic radical T1 is preferably derived from an aliphatic, alicyclic or aromatic tetracarboxylic acid dianhydride. Alicyclic or aliphatic tetracarboxylic acid anhydrides are preferably selected from 1,1,4,4-butane- tetracarboxylic acid dianhydride, ethylenemaleic acid dianhydride, 1,2,3,4-cyclo- butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 3,5,6-tricarboxy- norbomylacetic acid diannydride, 2,3,4,5-tetrahydrofurantetracarboxylic acid dianhydride, 4-(2,5-aioxotetrahydrofuran-3-yl)tetrahydronaphthalene-1,2-di- carboxylic acid dianhydride. 5-(2,5-dioxotetrahydrofuran-3-yl)-3-methyl-3-cyclo- hexene-l,2-dicarboxylic acic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetra-carboxylic acid dianhydriLe, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride and l,8-dimethylbicyclo[2.2.2]oct-7-ene-2,3,5,6~tetracarboxyIic acid dianhydride. Aromatic tetracarbox\ iic acid dianhydrides are preferably selected from pyromellitic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 4,4'-oxydiphtha:ic acid dianhydride, 3,3',4,4'-diphenylsulfoneteTra-carboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 3,3',4,4'-dimethyldiphenylsilane-tetracarboxylic acid dianhydride, 3,3',4,4'-tetraphenylsilanetetracarboxylic acid dianhydride, 1,2,3,4-furantetracarboxylic acid dianhydride, 4,4'-bis(3,4-dicarboxy-phenoxy)diphenyl sulfide dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenyl sulfone dianhydride, 4,4'-bis(3,4-dicarboxyphenoxy)diphenylpropane dianhydride, 3,3',4,4'-biphenyltetracarboxylJc acid dianhydride, ethylene glycol bis(trimellitic acid) dianhydride, 4,4'-(l,4-phenylene)bis(phthalic acid) dianhydride, 4,4'-(l,3-phenylene)-bis(phthalic acid) dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride, 4,4'-oxydi(l,4-phenylene)bis(phthalic acid) dianhydride and 4,4'-methylenedi(l,4-phenylene)bis(phthalic acid) dianhydride. It is especially preferred that the tetracarboxylic acid dianhydrides used to form the tetravalent organic radical T1 are selected from 1,2,3,4-cyclobutanetetra-carboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 2,3,5-tricarboxycyclopentylacetic acid dianhydride, 5-(2,5-dioxotetrahydrofuran--3-yl)-3-methyl-3-cyclohexene-l,2-dicarboxylic acid dianhydride, 4-(2,5-dioxotetra-hydrofuran-3-yl)tetrahydronaphthalene-l,2-dicarboxylic acid dianhydride, 4,4'-(hexa-fluoroisbpropylidene)diphthalic acid dianhydride and bicyclo[2.2.2]oct-7-ene-2,3,5,6--tetracarboxylic acid dianhydride. Each of the groups T and T can be derived from an aliphatic, alicyclic or aromatic dicarboxylic acid anhydride. The groups T" and T^ are preferably trivalent aromatic or alicyclic groups, the :hree valencies of which are distributed between three different carbon atoms, with :he proviso that two of the valencies are located at adjacent carbon atoms. Ii is especially preferred that the groups T2 and T3 are trivalent benzene derivatives. The group S4 is preferably selected from a single covalent bond, - -(CH2)r-CO-0-(CH2)s-, - CH2)r-0-CO-(CH2)s- -(CJfcWW.'-CCHCHjV-, -{CH2)r-NR1-CO-0-(CH2)s-> -(CH2)r-0-(CH2)s-0-, -(CH2)r-CO-0-(CH2)s-0-, -(CH2)r-0-CO-(CH2)s-0-, -(CHj^-NR'-CO-fCHs),-^, -(CH2)r-NR,-CO-O-(CH2V0-, -(CH2)r-0- oxycarbonyl, 10-decylenecarbonyloxy, 12-dodecyleneoxy, 12-dodecylene- oxycarbonyl, 11 -undecylenecarbonyloxy, 3-propyleneiminocarbonyl, 4-butylent- iminocarbonyl, 5-pentyleneiminocarbonyl, 6-hexyleneiminocarbonyl, 7-heptylene- iminocarbonyl, 8-octyleneim nocarbonyl, 9-nonyleneiminocarbonyl, 10-decylene- iminocarbonyl, 1 1-undecvleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethyIenecarbonyIimino, 3 -propylenecarbonylimino, 4-butyIenecarbonyIimino, 5-pentylenecarbonylimino, o-hexylenecarbonylimino, 7-heptylenecarbonylimino, 8-octylenecarbonylimino, &-nonylenecarbonylimino, 10-decylenecarbonylimino, 11 -undecylenecarbonylimino. 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneoxy)hexylene, 5-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneimino-carbonyloxy)hexyleneoxy, 6- 3-propyleneiminocarbonyl)hexylene, 6-(3-propylene-iminocarbonyl)hexyleneoxy and the like. The groups S5 and S8 are preferably selected from a single bond, -(CH2)r-, -0-(CH2)r- -CO-(CH2)r-, -CO-0-(CH2)r- -0-CO-(CH2)r- -NR'-CCHCHJX- -NR1-ICH2)r-, -CO-NR'-CCHaJr- -NR1-CO-(CH2)r-, -(CH2)r-0- -0-(CH2)r-CO-CHCH2)s-, -CKCH2)r-0-CO-(CH2)s-, -0-(CH2)r-NRJ-CO- heptylene, 8-oxyoctylene. 9-oxynonylene, 10'Oxydecylene, 11-oxyundecylene, 12-oxydodecylene, 2-(oxycarbonyl)ethylene, 3-(oxycarbonyl)propylene, 4-(oxy- carbonyl)butylene, 5-(oxycarbonyl)pentylene, 6-(oxycarbonyl)hexylene, 7-(oxycarbonyl)heptylene, 8-(oxycarbonyI)octylene, 9-(oxycarbonyl)nonylene, 10-(oxycarbonyl)decylene, 1 l-(oxycarbonyl)undecylene, 12-(oxycarbonyl)- dodecylene, 2-(carbonyloxy)ethylene, 3-(carbonyloxy)propylene, 4-(caibonyloxy)- butylene, 5-(carbonyloxy)pentylene, 6-(carbonyloxy)hexylene, 7-(carbonyloxy)- heptylene, 8-(carbonyloxy)octylene, 9-(carbonyloxy)nonylene, lO-(carbonyloxy)- decylene, ll-(carbonyloxy)undecylene, 12-(carbonyloxy)dodecylene, 2-(carbonyl- imino)ethylene, 3-(carbonylimino)propylene, 4-(carbonylimino)butylene, 5-(carbonylimino)pentylene, 6-(carbonylimino)hexylene, 7-(carbonylimino)- heptylene, 8-(carbonylimino)octylene, 9-(carbonylimino)nonylene, 10-(carbonyl- imino)decylene, 1 l-(carbonylimino)undecylene, 12-(carbonylimino)dodecylene, 2-iminoethylene, 3-iminopropylene, 4-iminobutylene, 5-iminopentylene, 6-imino- hexylene, 7-iminoheptylene, 8-iminooctylene, 9-iminononylene, 10-iminodecylene, 11-iminoundecylene, 12-iminododecylene, 2-iminocarbonylethylene, 3-imino- carbonylpropylene, 4-iminocarbonylbutylene, 5-iminocarbonylpentylene, 6-imino- carbonylhexylene, 7-iminocarbonylheptylene, 8-iminocarbonyloctylene, 9-imino- carbonylnonylene, 10-iminocarbonyldecylene, 11-iminocarbonylundecylene, 12-iminocarbonyldodecylene, 2~(2-ethyleneoxy)ethylene, 2-(3-propyleneoxy)- ethylene, 6-(4-butyleneoxy)hexylene, 2-(2-ethyleneiminocarbonyl)ethylene, 2-(3-propyleneiminocarbonyl)ethylene, 6-(4-butyleneiminocarbonyl)hexylene, 6-(3-pTopyleiidn\mocarbonyloxy)hexylene, 6-(3-propyleneimmocarbotiyl)hexylene and the like. The groups S6 and S7 are preferably selected from a single bond, - -(CH^-CO-NR1-, -(CH2)-NR1-CO-, -(CH^-NR1-, -0- -0-(CH2)r-NR1-, -0-(CH2)r-0- -0-(CH2)r-NR1-CO-, -NR^CH^-CO-O, -NR'-(CH2)r-0-, -NR'-fCHaJr-NR1-, -NR'-(CH2)r-0-CO-, -CO-NR1-(CH2)r-0-, -CO-NR,-(CH2)r-NR1-, -CO-NR'-(CH2)r-0-CCK -0-CO(CH2)r-CO- -O-CCHCH2V-O-, -0-CO-(CH2)r-NR'- -0-CO-(CH2)r-CO-0-, -0-CO-(CH2)r-CO-NR1-, -O-CCHCHJV-NR'-CO- -(CH2)-0-(CH2)s-, -(CH2)-CO-0-(CH2)s-, -(CH2)r-0-CO-(CH2 ),-, -(CH^-NR'-CCHCH^s- -(CH^-NR'-CO-O-fCHz),-, -(CH2)r-0-(CH2)s-0-, -idi2)r-C0-0-(C}i2)s-O~, -(CH2X-0-CO-(CH2)s-0-, -icn2)r-m}~ccHCH2)s~o~. -(CH^-NR'CO-CMCH^S-O-, -0-(CH2)r-0-(CH2)s- -O-(0H2)r-CO-O-(CH2)i-, -0-(CH2)r-NR1-CO-(CH2 )S- -CHC^X-NR'-CO-CKCH; )s-, -CHC^Jr-CO-O-fCHj^-O-, -0-(CH2)r-0-(CH2)s-0-, -0-iCH2)-mLl-CO-(CH2)s-0-, -0-(CH2)r-NR1-C0-0-(CH2)s-O-, -CO-0-(CH2)-0-(CH2)s- -CO-0-(CH2)r-0-(CH2)s-0-, wherein R1 is defined as herein above; r and s each represent an integer from 1 to 20; and r + s Examples of preferred groups S6 and S7 include 1,2-ethylene, 1,3-propylene, 1,4-butylene, 1,5-pentylene, 1,6-hexylene, 1,7-heptylene, 1,8-octylene, 1,9-nonylene, 1,10-decylene, 1,11-undecylene, 1,12-dodecylene, 3-methyl-1,4-butylene, 3-propyleneoxy, 3-propyleneoxycarbonyl, 2-ethylenecarbonyloxy, 4-butyleneoxy, 4-butyleneoxycarbonyl, 3-pj opylenecarbonyloxy, 5-pentyleneoxy, 5-pentylene-oxycarbonyl, 4-butyIenecarbonyloxy, 6-hexyleneoxy, 6-hexyleneoxycarbonyl, 5-pentylenecarbonyloxy, 7-heptyleneoxy, 7-heptyleneoxycarbonyl, 6-hexylene-carbonyloxy, 8-octyleneoxy 8-octyleneoxycarbonyl, 7-heptylenecarbonyloxy, 9-nonyleneoxy, 9-nonyleneo:;ycarbonyl, 8-octylenecarbonyloxy, 10-decyleneoxy, 10-decyleneoxycarbonyl, 9-nonylenecarbonyloxy, 11-undecyleneoxy, 11-undecylene-oxycarbonyl, 10-decylenecarbonyloxy, 12-dodecyleneoxy, 12-dodecyleneoxy-carbonyL, 11-undecylenecarbonyloxy, 3-propyleneiminocarbonyl, 4-butyleneimino- carbonyl, 5-pentyleneiminocarbonyl, 6-hexyleneiminocarbonyl, 7-heptyleneimino-carbonyl, 8-octyleneiminocarbonyl, 9-nonyleneiminocarbonyl, 10-decyleneimino-carbonyl, 11-undecyleneiminocarbonyl, 12-dodecyleneiminocarbonyl, 2-ethylene-carbonylimino, 3-propylenecarbonylimino, 4-butylenecarbonylimino, 5-pentylene-carbonylimino, 6-hexylenecarbonylimino, 7-heptylenecarbonylimino, 8-octylene-carbonylimino, 9-nonylenecarbonylimino, 10-decylenecarbonylimino, 11-undecylene-carbonylimino, 6-(3-propyleneiminocarbonyloxy)hexylene, 6-(3-propyleneoxy)-hexylene, 6-(3-propyleneoxy)hexyleneoxy, 6-(3-propyleneiminocarbonyloxy)-hexyleneoxy, 6-(3-propyleneiminocarbonyl)hexylene, 6-(3-propyleneiminocarbonyl)-hexyleneoxy, 1,2-ethylenedioxy, 1,3-propylenedioxy, 1,4-butylenedioxy, 1,5-pentylenedioxy, 1,6-hexylenedioxy, 1,7-heptylenedioxy, 1,8-octylenedioxy, 1,9-nonylenedioxy, 1,10-decylenedioxy, 1,11-undecylenedioxy, 1,12-dodecylene-dioxy and the like. The aliphatic, alicyclic or aromatic divalent radical F is derivable from aliphatic, alicyclic or aromatic diamines by formal removal of the amino groups. Examples of aliphatic or alicyclic diamines from which the radical F can be derived include ethylenediamine, 1,3-propylenediamine, 1,4-butylenediamine, 1,5-pentylene-diamine, 1,6-hexylenediamine, 1,7-heptylenediamine, 1,8-octylenediamine, 1,9-nonylenediamine, 1,10-decylenediamine, 1,11-undecylenediamine, 1,12-dodecyl-enediamine, a,a'-diamino-w-xylene, a,a'-diamino-/?-xylene, (5-amino2,2,4-trimethyl-cyclopentyl)methylamine, 1,2-diaminocyclohexane, 4,4'-diaminodicyclohexyl-methane, l,3-bis(methylamino;cyclohexane and 4,9-dioxadodecane-l,12-diamine. Examples of aromatic diamines from which the radical F can be derived include 3,5-diaminobenzoic acid methyl ester, 3,5-diaminobenzoic acid hexyl ester, 3,5-diaminobenzoic acid dodecyl ester, 3,5-diaminobenzoic acid isopropyl ester, 4,4'-methylenedianiline, 4}4'-ethylenedianiline, 4,4'-diamino-3,3'-dimethyldipheny 1-methane, S^'^S'-tetramethylbenzidine, 4,4'-diaminodiphenyl sulfone, 4,4'-diammo-diphenyl ether, 1,5-diaminonaphthalene, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,4'-diaminodiphenyl ether, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 4,4,-diamino-2,2'-dimethylbibenzyl, bis[4-(4-aminophenoxy)phenyl] sulfone, l,4-bis(4-aminophenoxy)benzene, l,3-bis(4-aminophenoxy)benzene, l,3-bis(3- aminophenoxy)benzene, 2,7-diaminofluorene, 9,9-bis(4-aminophenyI)fluorene, 4,4'-methylenebis(2-chloroaniline), 4,4'-bis(4-aminophenoxy)biphenyl, 2,2',5,5-tetra- chloro-4,4'-diaminobiphenyl, 2,2,-dichloro-4,4'-diamino-5,5'-dimethoxybiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 4,4'-(l,4-phenyleneisopropylidene)bisaniline, 4,4'-( 1,3-phenyleneisopropylidene)bisaniline, 2,2-bis[4-(4-aminophenoxy)phenyl]- propane, 2,2-bis[3-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[3-amino- -4-methylphenyl]hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2'-bis[4-(4-amino-2-trifluoromethylphenoxy)phenyl]hexafluoropropane, 4,4'-di-amino-2,2'-bis(trifiuoromethyl)biphenyl, and 4,4'-bis[(4-amino-2-trifluoromethyl)-phenoxy]-2,3,5,6,2^5\6'-octafluorobiphenyl. The group E may be divalent, tnvalent or tetravalent. When E is divalent, it serves to link the groups S4 and S5, S6 and S7 or S8 and N respectively of the groups IE to VII. It will be appreciated that when E is a divalent group, the monomer unit of which it forms a part is not linked to a side chain group of formula (I). When E is a tnvalent or a tetravalent group, it serves to link the monomer unit, of which it forms a part, to one or two side chain groups of formula (I) respectively. It is preferred that the photoactive polymer comprises less than 75 % of monomer units including a divalent group E, preferably less than 50 % and especially less than 30 %. Monomer units comprising a tnvalent group E are preferred. The building blocks of the formulae HI, V and VTI are amic acid groupings or amic acid ester groupings (i.e. carboxamide-carboxylic acid groupings or carboxamide-carboxylic acid ester groupings) which on the one hand may occur as a result of incomplete imidisation in the polyimide chain. On the other hand, polymers that consist only of building blocks of formulae HI, V or VII, that is to say polyamic acids or polyamic acid esters, are important precursors for the preparation of the polyimides according to the invention and are also included in the present invention. Of those polymers which contain groups of formulae III, V or VII, preference is given to those in which G is hydrogen, that is to say those which consist exclusively of, or contain some, polyamic acid groups. The polymers of the invention may be prepared using methods that are known to a person skilled in the art ana a second aspect of the invention provides a method of ^ ■ ~ -^ ' ——— ———.—„ preparing a compound of formula (I) as defined above. ) Polyamic acids and polyimides of the present invention may be prepared in accordance with known methods, such as those described in Plast. Eng. 36 (1996) (Polyimides, fundamentals and applications). For example, the polycondensation reaction for the preparation of the polyamic acids is carried out in solution in a polar aprotic organic solvent, such as ■y-butyrolactone, 7/^-dimethylacetamide, JV-methylpyrrolidone or AVV-dimethyl-formamide. In most cases equimolar amounts of the dianhydride and the diamine are used, that is to say one amino group per anhydride group. If it is desired to stabilise the molecular weight of the polymer, it is possible for that purpose to add an excess or a less-than-stoichiometric amount of one of the two components or to add a monofunctional compound in the form of a dicarboxylic acid monoanhydride or in the form of a monoamine. Examples of such monofunctional compounds are maleic acid anhydride, phthalic acid anhydride, aniline and so on. The reaction is carried out preferably at a temperature of less than 100 °C. The cyclisation of the polyamic acids to form the polyimides can be carried out by heating, that is to say by condensation with removal of water or by other imidisation reactions with reagents. When carried out purely thermally, the imidisation of the polyamic acids is not always complete, that is to say the resulting polyimides may still contain proportions of polyamic acid. The imidisation reactions are generally carried out at a temperature of from 60 to 250 °C, but preferably at less than 200 °C. In order to achieve imidisation at rather lower temperatures there are additionally mixed into the reaction mixture reagents that facilitate the removal of water. Such reagents are, for example, mixtures consisting of acid anhydrides, sucn as acetic acid anhydride, propionic acid anhydride, phthalic acid anhydride, trifluoroacetic acid anhydride, and tertiary amines, such as triethylamine, trimethylamine, tributylamine, pyridine, MJV-dimethylaniline, lutidine, collidine etc. The amount of reagents used in that case is preferably at least two equivalents of amine and four equivalents of acid anhydride per equivalent of polyamic acid to be condensed. The imidisation reaction can be carried out before or alternatively only after application to a support. The latter variant is preferred especially when the polyimide in question has poor solubility in the customary solvents. The polyamic acids and the polyimides of the present invention have an intrinsic viscosity preferably in range of 0.05 to 10 dL/g, more preferably 0.05 to 5 dL/g. Herein, the intrinsic viscosity (riinh = In iWC) is determined by measuring a solution containing a polymer in a concentration of 0.5 g/100 ml for its viscosity at 30 °C using Af-methyl-2-pyrrolidone as solvent. The polyamic acid chains or polyimide chains of the present invention preferably contain from 2 to 2000 monomer units, especially from 3 to 200. Additives such as silane-containing compounds and epoxy-containing cross-linking agents may be added to the polymers of the invention in order to improve the adhesion of the polymer to a substrate. Suitable silane-containing compounds are described in Plast Eng. 36 (1996) (Polyimides, fundamentals and applications). Suitable epoxy-containing crosslinking agents include 4,4-methylenebis-(TV^-diglycidylaniline), trimethylolpropane triglycidyl ether, benzene-l,2,4,5-tetra- carboxylic acid l,2:4,5-N,Af'-diglycidyldiimide, polyethylene glycol diglycidyl ether, 7V,Af-diglycidylcyclohexylamine and the like. Further additives such as a photosensitiser, a photoradical generator and/or a cationic photoinitiator may also be added to the polymers of the invention. Suitable photoactive additives include 2,2-dirnethoxypheny\ethanone, a mixture of diphenyl-methanone and A^A'-dimethylbenzenamine or ethyl 4-(dimethylamino)benzoate, xanthone, thioxanthone, IRGACURE™ 184, 369, 500, 651 and 907 (Ciba), Michler's ketone, triaryl sulfonium salt and the like. 1 I The polymers according to the invention may be used alone pr in combination with other polymers, oligomers, monomers, photoactive polymers, photoactive oligomers and/or photoactive monomers, depending up on the application to which the polymer layer is to be put. It will therefore be appreciated that by varying the composition of the polymer layer it is possible to control properties such as an induced pretilt angle, good surface wetting, high voltage holding ratio, a specific anchoring energy etc. Polymer layers may be readily prepared from the polymers of the present invention and a third^aspectjjf theJnyention provides ajx^rngr layer comprising a polymer according to the present invention in a crosslinked form. The polymer layer is preferably prepared by applying one or more polymers according to the invention to a support and, after any imidisation step which may be necessary, crosslinking the polymer or polymer mixture by irradiation with linearly polarised light. It is possible to vary the direction of orientation and the tilt angle within the polymer layer by controlling the direction of irradiation of the linearly polarised light. It will be appreciated that by selectively irradiating specific regions of the polymer layer it is possible to align very specific regions of the layer and provide layers with a defined angle of tilt. This orientation and tilt is retained in the polymer layer by the process of crosslinking. It will be appreciated that the polymer layers of the present invention can also be used as orientation layers for liquid crystals and a preferred embodiment of the third aspect of the invention provides an orientation layer comprising one or more polymers according to the invention in a crosslinked form. Such orientation layers can be used in the manufacture of optical constructional elements, preferably in the production of hybrid layer elements. The orientation layers are suitably prepared from a solution of the polymer material. The polymer solution is applied to a support optionally provided with an electrode (for example a glass plate coated with indium-tin oxide (ITO)) by a spin coating process, to produce homogeneous layers of 0.05 to 50 urn thickness. For applying the polymer material, generally different coating techniques may be used like spincoating, miniscuscoating, wirecoating, slotcoating, offsetprinting, flexoprinting, and gravurprinting. The resulting layer is imidised, if required, and may then be selectively orientated by irradiation with a high-pressure mercury vapour lamp, a xenon lamp or a pulsed UV laser, using a polariser and optionally a mask for creating images of structures. The irradiation time is dependent upon the output of the individual lamps and can vary from a few seconds to several hours. The crosslinking reaction can also be carried out by irradiation using filters that, for example, only allow the radiation suitable for the crosslinking reaction to pass through. It will be appreciated that the polymer layers of the invention may be used in the production of optical or electro-optical devices having at least one orientation layer as well as unstructured and structured optical elements and multi-layer systems; especially for use in vertical aligned nematic (VAN) LCDs and hybrid aligned nematic (HAN) LCDs. ^. A further embodiment of the third aspect of the invention provides an optical or electro-optica! device comprising one or more polymers according to the first aspect of the invention in crosslinked form. The electro-optical devices may comprise more than one layer. The or each of the orientation layers may contain one or more regions of different spatial orientation. The polymers in accordance with the invention are illustrated in more detail by the following Examples. Example 1 182.5 mg (0.9306 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydridewas^|ddje4_to a solution of 0.501 g (1.0339 mmol) 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-butoxyphenyl)acryloyloxy]hexyl ester in 3.5 ml of tetrahydrofuran. Stirring was then carried out at 0 °C for 2 hours. Then another 20.3 mg (0.1035 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride were added. The mixture was subsequently allowed to^jsact__f^r.^44Jiours at room temperature. The polymer mixture was diluted with 3.5 ml THF, precipitated into 200 ml diethyl ether and collected by filtration. The polymer was reprecipitated form THF (10 ml) into 600 ml water to yield, after drying at room temperature under vacuum, 0.61 g of polyamic acid 1 in the from of a beige powder; [r\] = 0.52 dL/g. The 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-butyloxyphenyl)acryloyl-oxy]hexyl ester used as starting material was prepared in accordance with the following procedure Preparation of fEM-butvloxy-S-methoxvcinnamic acid methyl ester 4.16 g (20.0 mmol) ferulic acid methyl ester was dissolved in 115 mi 2-butanone. 2.09 ml (22.0 mmol) w-butyl bromide and 11.06g (80 mmol) potassium carbonate were added. The reaction suspension was then heated at reflux temperature for 20 hours. The reaction mixture was filtered. The filtrate was concentrated by evaporation. The crude product was recrystallised from 42 ml isopropyl alcohol and yielded 4.85 g (92 %) (£^-butyloxy-3-methoxycinnamic acid methyl ester as white crystals. Preparation of ffi)-4-butvloxy-3-methoxvcinnamic acid 10 g (0.15 mol) potassium hydroxide weTe dissolved in a mixture of 200 ml methyl alcohol and 5 ml water. 4.85 g (18.35 mmol) /E^-^butyloxy-B-methoxycinnamic acid methyl ester was added. The reaction mixture was subsequently heated to 60 °C. After 2.5 h - the mixture was concentrated by evaporation. The residue was dissolved in 100 ml cold water and acidified to pH=l with 13.5 ml hydrochloric acid 37 wt. %. The product was filtered off, washed with water and dried at 50 °C under vacuum to give 4.24 g (92 %) f£>-4-butyloxy-3-methoxycinnamic acid as white crystals. Preparation of ^-4-butvloxy-3-methoxycinnamic acid 6-hvdroxvhexvl ester 1.38 g (5.50 mmol) (E)-4-butyloxy-3-methoxycinnamic acid was suspended in 3 ml acetonitrile. A mixture of 0.84 g (5.50 mmol) l,8-diazabicyclo[5.4.0]undec--7-ene( 1,5-5) (DBU) and 3 ml acetonitrile was added dropwise over a period of 5 minutes. 0.46 g (1.25 mmol) tetrabutylammonium iodide and 0.68 g (5.00 mmol) 6-chlorohexanol was added and the resulting mixture was then refiuxed for 6 hours. The reaction mixture was cooled and then extracted using ethyl acetate and water. The ethyl acetate phase was washed with water, dried over sodium sulfate, filtered and concentrated by rotary evaporation. The residue was purified by chromatography using a silica gel column (120 g) and toluene:ethyl acetate (1:1) as eluant to give 1.39 g (79%) (£J^butyloxy-3-methoxycinnamic acid 6-hydroxyhexyl ester as colourless oil. 3.5-Dinitrobenzoic acid 6-p-(3-rnethoxv-4-butvloxvphenyl)acrvlovloxy"lhexyl ester / o o N-0 fi = 0 o" 3.00 g (8.56 mmol) ^-4-butyloxy-3-methoxycinnamic acid 6-hydroxyhexyl ester 2.07 g (8.98 mmol) 3,5-dinitrobenzoyl chloride and lOmg 4-dimethyl-aminopyridine were dissolved in 30 ml dichloromethane. The solution was subsequently cooled to 0 °C and then 3.5 ml (43.36 mmol) pyridine was added dropwise, in the course of 20 minutes. After 2.5 hours at 0 °C the reaction mixture was partitioned between dichloromethane and water. The organic phase was washed repeatedly with water, dried over sodium sulfate, filtered and concentrated by rotary evaporation. Chromatography of the residue on 50 g silica gel using toluene: ethyl acetate (9:1) yielded 3.80 g (81 %) 3,5-dinitrobenzoic acid 6-[3-(3-methoxy-4-butyl-oxyphenyl)acryloyloxy]hexyl ester as yellow oil. 3.80 g (6.98 mmol) 3,5-dinitrobenzoic acid 6-[3-(3-methoxy-4-butyloxy-phenyl)acryloyloxy]hexyl ester and 1.47 g (27.48 mmol) of ammonium chloride were *37 3.5-Diaminobenzoic acid 6-[3-(3-methoxv-4-butvloxvphenvl)acrvlov)oxvlhexvl ester suspended in 75 ml of a mixture consisting of methanol : water 9.1. 9.07 g (0.139 mol) of zinc powder was then added in one portions. The reaction temperature rose to 36 °C. The suspension was then heated at 40 °C for 1.5 hours. The reaction suspension was partitioned between dichloromethane and water. The resulting suspension was filtered, the organic phase was washed with a saturated sodium bicarbonate solution and repeatedly with water. The organic phase was then dried over sodium sulfate, filtered and concentrated by evaporation to yielded 3.47 g (99 %) 3,5'diaminobenzoic acid 6-[3-(3-methoxy-4-butylo^yphenyl)acryloyloxy]hexyl ester as yellow oil Example 2 177.0 mg (0.9025 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid diaflhydride was added to a solution of 0.500 g (1.0028 mmol) 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-pentyloxyphenyl)acryloyloxy]hexyI ester in 3.1 ml of tetrahydroftiran. Stirring was then carried out at 0 °C for 2 hours. Then another 19.7 mg (0.1003 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride were added. The mixture was subsequently allowed to react for 21 hours at room temperature. The polymer mixture was diluted with 3.5 ml THF, precipitated into 200 ml diethyl ether and collected. The polymer was repreciphated form THF (10 ml) into 600 ml water to yield, after drying at room temperature under vacuum, 0.59 g of polyamic acid 2 in the form of a beige powder; [t|] * 0.52 dL/g. The 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-pentyloxyphenyl)acryloyl-oxy]hexyl ester used as starting material was prepared using the procedure according to Example 1. Example 3 182.1 mg (0.9285 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride was added to a solution of 0.2572 g (0.5158 mmol) 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-pentyloxyphenyl)acryloyloxy]hexyI ester and 0.250G g (0.5159 mmol) 3,5-diaminobenzoic acid 6-[3-(3-methoxy-4-butyloxyphenyl)acryloyl-oxyjhexyl ester in 3.5 ml of tetrahydrofuran. Stirring was then carried out at 0 °C for 2 hours. Then another 20.2 mg (0.1030 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride were added. The mixture was subsequently allowed to react for 22 hours at room temperature. The polymer mixture was diluted with 3.5 ml THF, precipitated into 200 ml diethyl ether and collected. The polymer was reprecipitated form THF (10 ml) into 600 ml water to yield, after drying at room temperature under vacuum, 0.65 g of polyamic acid 3 in the form of a beige powder; [y\] = 0.52 dL/g. Example 4 148.4 mg (0.7567 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride was added to a solution of 500.0 g (0.8406 mmol) 3,5-diaminobenzoic acid ll-[3-(3-methoxy-4-cyclohexylmethoxyphenyl)acryloyloxy]undecyl ester in 3.5 ml of tetrahydrofuran. Stirring was then carried out at 0 °C for 2 hours. 16.5 mg (0.0841 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride were added. The mixture was subsequently allowed to react for 21 hours at room temperature. The polymer mixture was diluted with 3.5 ml THF, precipitated into 200 ml diethyl ether and collected. The polymer was reprecipitated form THF (10 ml) into 600 ml water to yield, after drying at room temperature under vacuum, 0.55 g of polyamic acid 4 in the form of a beige powder; [r\] = 0.31 dL/g. Example 5 Preparation was carried out analogously to Example 1 using 208.3 mg (0.1.062 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride and 480.7 g (1.062 mmol) 3,5-diaminobenzoic acid 6-[3-(4-pentylphenyl)acryloyloxy]hexyl ester to give 0.60 g of polyamic acid 5 in the form of a beige powder; [r\] = 0.94 dL/g . Example 6 Preparation was carried out analogously to Example 1 using 215.7mg (0.1.100 mmol) of 1,2,3,4-cyclobutantetracarboxylic acid dianhydride and 480.7 g (1.100 mmol) 3,5-diaminobenzoic acid 6-[3-(4-butyloxyphenyl)acryloyloxy]hexyl ester to give 0.67 g of polyamic acid 6 in the form of a beige powder; [r|] = 0.86 dL/g . Example 7: Production of an orientation layer A 2 % solution of polyamic acid 1 in cyclopentanone was filtered over a 0.2 u.m Teflon filter and applied to a glass plate, which had been coated with indium-tin oxide (ITO), in a spin-coating apparatus at 3000 rev./min. in the course of 60 seconds. The resulting film was then predried for 15 minutes at 130 °C and then imidised for 1 hour at 180 °C to form the polyimide. The glass plate so coated was then irradiated for 4 minutes with the linearly polarised UV light of a 350 W high-pressure mercury vapour lamp. A liquid-crystalline mixture of diacrylates was then applied by spin-coating to the irradiated layer and subsequently crosslinked by isotropic UV light for 30 minutes. Under a polarisation microscope, a uniaxially double-refractive layer of oriented liquid crystal molecules was observed. Using a tilt compensator it was ascertained that the direction of orientation agreed with the direction of polarisation of the UV light used for the polyimide layer irradiation. 4o Example 8: Production of an orientation layer having a defined angle of til: Two glass plates coated with polyamic acid 1 as in Example 7 were irradiated for 4 minutes with linearly polarised UV light, the direction of incidence of the light being inclined by 40° relative to the plate normal. The direction of polarisation of the light was kept in the plane defined by the direction of incidence of the light and the plate normal. From both plates a cell of 20 u,m spacing was built such that the illuminated surfaces were facing each other and the previous polarisation directions of illumination were parallel. The cell was then filled with liquid crystal mixture MLC6610 from Merck in the isotropic phase at 105 °C. The cell was then gradually cooled to room temperature at a rate ranging from 0.1 °C/min to 2 °C/min. Between crossed polarisers a uniformly oriented liquid crystal layer was observed. The tilt angle of this parallel cell, by crystal rotation method, was 86°. Example 9: Determination of the holding ratio (HR) Two glass plates coated in accordance with Example 7 were irradiated perpendicularly during 4 minutes with linearly polarised UV light. From both plates a cell of 4 urn spacing was built such that the illuminated surfaces were facing each other and the previous polarisation directions of illumination were parallel. This cell was then maintained at 120 °C under high vacuum for 14 hours and thereafter filled with TFT liquid crystal mixture MLC6610 from Merck in vacuo at room temperature. Between crossed polarisers a uniformly oriented liquid crystal layer was observed. Prior to testing the holding ratio (HR) the cell was first subjected to ageing for 50 hours at 120 °C. The voltage decay V (at T = 20 ms) of a voltage surge of 64 us with Vo (V at t = 0) = 0.2 V was then measured over a period of T = 20 ms. The holding ratio then determined, given by HR = V™ (t = T)/V0, was 98 % at room temperature and 91 % at 80 °C. WE CLAIM 1. A photoactive polymer from the class of polyimides, poiyamide acids and esters thereof, characterised in that it comprises as a side-chain a photocrosslinkable group of the general formula I: Qv Y wherein the broken line indicates the point of linkage to the polyimide main chain and wherein: A represents pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene, or phenylene; optionally substituted by a group selected from fluorine, chlorine, cyano or by a Ci-18 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl -CHr- groups are optionally replaced by a group Q; B is a straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more non-adjacent CB.2 groups may independently be replaced by a group Q; C1 and C2 each independently of the other represents an aromatic or alicyclic group which is unsubstituted or substituted by fluorine, chlorine, cyano, or by a cyclic, straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 1 to 18 carbon atoms and wherein one or more non-adjacent CH? groups may independently be replaced by a group Q; 5 D represents an oxygen atom or -NR1- wherein R1 represents a hydrogen atom or lower alkyl; S1 and S2 each independently of the other represent a single covalent bond or a spacer unit; S3 represents a spacer unit: Q represents a group selected from -0-, -CO-, -CO-0-, -0-CO-, -Si(CH3)2-0-Si(CH3)2- -NR1-, -NR'-CO-, -CO-NR1--N^-CO-O-, -O-CO-NR1-, -NR'-CO-NR1-, -CH=CH-, -C=C-and -0-CO-O-, wherein R1 represents a hydrogen atom or lower alkyl; n1 and n2 are each independently 0 or 1; and X, Y each independently of the other represents hydrogen, fluorine, chlorine, cyano, alkyl optionally substituted by fluorine having from 1 to 12 carbon atoms in which optionally one or more non-adjacent CEb groups are replaced by -0-, -CO-0-, -O-CO- and/or -CH=CH- 2. A polymer as claimed in claim 1 wherein the group A is optionally substituted by a Ci_i2 cyclic, straight-chain or branched alkyl residue, which alkyl group is optionally substituted by one or more halogen atoms and in which one or more non-adjacent alky) -CBz- groups are independently optionally replaced by a group selected from -O- -CO-, -CO-0-, -O-CO-, -CH=CH- and -C=C-. 3. A polymer as claimed in claim 2 wherein the group A comprises phenylene, optionally substituted by a C1-12 straight-chain or branched alkyl residue, which alkyl group is substituted by one or more fluorine atoms, and wherein one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-, -CO-0-, -O-CO- and -CH=CH-. 4. A polymer as claimed in claim 3 wherein the phenylene group comprises a 1.3- or 1,4-phenylene. 5. A polymer as claimed in any preceding claim wherein the group B comprises a straight-chain or branched alkyl residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 3 to 18 carbon atoms, wherein one or more CH2 groups may independently be replaced by -O-, -CO-, -CO-O-, -O-CO-, -CH^CH-, -CsC-, with the proviso that oxygen atoms are not directly attached to each other. 6. A polymer as claimed in claim 5 wherein the alkyl residue of group B has 3 to 12 carbon atoms, wherein one or more CH2 groups may independently be replaced by -0-, -CO-, -CO-O-, -O-CO-, with the proviso that oxygen atoms are not directly attached to each other. 7. A polymer as claimed in any preceding claim wherein each of the groups C1 and C2 is selected from cyclohexane-l,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1.4- or 2,6-naphthylene and phenylene; optionally substituted by one or more groups selected from fluorine, chlorine, cyano and a C1-12 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkyl -CH2- groups are optionally independently replaced by a group selected from -0~, -CO-. -CO-0-, -0-CO-, -CH=CH-, -C=C~ and -0-CO-0-. 8. A polymer as claimed in claim 7 wherein the groups C1 and C2 are selected from cyclohexane-l,4-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,6-naphthylene and phenylene; optionally substituted by one or more fluorine atoms or a Ci_s straight-chain or branched alkyl residue, which is optionally substituted by one or more fluorine atoms, and in which one or more non-adjacent alkyl -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-. -CO-0-, -O-CO- and -CH=CH-. 9. A polymer as claimed in any preceding claim wherein D is an oxygen atom or -NH-. 10. A polymer as claimed in any preceding claim wherein the groups S' and S~ are selected from a single covalent bond, -0-, -CO-0-, -O-CO-, -NR1-, -NR'-CO-, -CO-NR1-, -NR^-CO-O-, -O-CO-NR1-, -NR'-CO-NR1-, -CH=CH-, -C=C-, -O-CO-O- and a straight-chain or branched alkylene group, in which two or three non-adjacent alkylene -CH2> group are independently optionally replaced by a group Q with the proviso the total number of chain carbon atoms in the alkylene group does not exceed 24, wherein R1 represents a hydrogen atom or lower alkyl. 11. A polymer as claimed in claim 10 wherein S1 and S2 are selected from a single covalent bond, -C0-O-, -O-CO-, -(CH2)r- -(CH2)r-0- -(CH2)r-CO-, -(CH2)r-CO-0-, -(CH2)r-0-CO- -(CH2)r-CO-NR1-, -(CHzV-NR'-CO--(CR^-NR1-, -0-(CH2)r~, -CO-0-(CH2)r-, -0-CO-(CH2)r--MRI~CO-(CH2)r- -CO-NR]-(CH2)r- -NR'-fCHaV-, -0-(CH2)-CO-0--O-fCH^-O-CO- -O-CCH^-CO-NR1-, -C-(CH2)-NR1-, -0-(CH2X-0-, -0~iCB2)r-m}-CO~, -NR1-(CH2)r-CO-0-) -NR'-fCHzX-O- -KR'-CCHJX-NR1-, _NR1-(CH2)-0-CO~, -CO-NR'-CCHJX-O-. -CO~NR]-(CH2)r-NR'-, -CONR'-(CH:),-0-CO-, -0-CO-(CH2)r-CO-. -0-CO-(CH2)-0- -0-CO-(CH2)r-NR2- -0-CO-(CH2)-CO-0 . -O-CCHCHJX-CONR1- -0-CO-(CH2)r-NR'-CO-, -(CH2)r-0-(CH2)s- -(CH2)r-CO-0-(CH2)s- -(CH2)r-0-CO-(CH2)s- -(CH2)r-NR'-CO-(CH2)s-. -(CH^-NR'CO-CMOtys- -(CH2)r-0-(CH2)5-0-, -(CH2)r-CO-0-(CH2)s-0-, -(CH2)r-0-CO-(CH2)s-0- -(CH2)r-NR1-CO-(CH2)s-0-, -(CH2X-NRI-CO-0-(CH2)s-0-, -0-(CH2X-0-(CH2)s-, -CKCH2)-CO-0-(CH2)s- -O-fCH.X-NR'-CO-CCH,),-, -0-(CH2)-NR,-CO-0-(CH2)s-, -O-(CH2)r-C0-0-(CH2)s-0- -0-(CH2X-O-(CH2)s-0-, -0-(CH2)r-NR1-CO-(CH2)s-0-, -O-CCHZX-NR'-CO-O^CHJX-O- -CO-0-(CH2)r-0-(CH2)s- and -CO-0-(CH2)r-0-(CH2)s-0-, wherein R1 is as defined in claim 10, r and s each represent an integer from 1 to 20. 12. A polymer as claimed in claim 11 wherein S1 and S are selected from a single covalent bond, -{CH2X- -(CH2)r-0- -(CH2)r-CO-0- _(CH2)-0-CO- -(CH2X-CO-NH-, -(CHiX-NH-CO-, -0-(CH2)r-, -COCHCH2)-, -CO-NH-(CH2)r- -NH-CO-(CH2)-, -0-CO-(CH2)r-, -0-CO-(CH2)-CO-0- -CKCH2X-O-CO-, -0(CH2)r-CO-NH-, -0-(CH2)-NH-CO-, -CO-O-CCHJX-O-, -CO-NH-(CH2)T-0-, -0-(CH2>-0-, -(CH2X-NH-CO-(CH2)s-, -(CHaX-NH-CO-O-fCHzX-, -(CH2)r-0-(CH2)s-0-, -(CHzX-NH-CO-fCHj^-O, -(CH2)-NHCO-0-(CH2)s-CK -0-{CH2)-NH-CO-(CH2)s-, -O-(CH2)r-O-(CH2)s-0-, -0-CO-(CH2)r-0-(CH2)s-0-, -CO-0-(CH2X-0-(CH2)s-0-, -0-(CH2X-NH-CO-(CH2)s-0- and -0-CO-(CH2)r-NH-CO-(CH2)s-0-, wherein r and s each represent an integer from 1 to 12 and r + s 13 A polymer as claimed in any preceding claim wherein the group S"' comprises a straight-chain or branched alkylene residue which is unsubstituted, mono-substituted by cyano or halogeno, or poly-substituted by halogeno, having 6 to 24 carbon atoms, wherein one or more non-adjacent CH2 groups may independently be replaced by an aromatic, an alicyclic group or a group Q, wherein Q is as defined in claim 1. 14. A polymer as claimed in any claim 13 wherein S3 is selected from -(CH2)r-i-, -0-(CH2)r- -CO-0-(CH2)r- -0-CO-(CH2)r- -NE^-CCHCHiJr--CO-NR'-(CH2)r- -NR]-(CH2)r- -(CH2)-0-(CH2)s-, -(CH2)r-CO-0-(CH:).-, -(CH2)r-0-CO-(CH2)s- -(CH2)-NR1-CO-(CH2)s-, -(CH^-NR'-CO-CMCH;.)*- -O-(CH2)r-0-(CH2)s- -0-(CH2)r-CO-0-(CH:)s--0-(CH2)r-NR'-CO-(CH2)s-, -0-(CH2)-NR1-C0-O-(CH2)s- and -CO-0-(CH2)r-0-(CH2)s- , wherein R1 represents a hydrogen atom or lower alkyl, r and s each represent an integer from 1 to 20, and r + s 15. A polymer as claimed in any preceding claim wherein the groups X and Y represent hydrogen. 16. A polymer as claimed in any preceding claim wherein 17. A polymer as claimed in any preceding claim wherein the monomer units from which the main chain comprises imide groups of the general formulae II, IV and VI and/or the analogous amic acid groups and amic acid ester groups of the general formulae m, V and VII: wherein: the broken line symbolises the linkage to S3 T represents a tetravalent organic radical; T , T each independently represent a trivalent aromatic or alicyclic group which is optionally substituted by a group sei acted from fluorine, chlorine, cyano and a Ci_i8 cyclic, straight-chain or branched alkyl residue, which is optionally substituted by one or more halogen groups and in which one or more non-adjacent alky] -CH2- groups are independently optionally replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO-, -CH=CH- and -OC-; S to S8 are each independently selected from a single covalent bond and a C1-24 straight-chain or branched alkylene residue, which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent alkylene -CH2- groups are, independently, optionally replaced by a group Q; E is selected from the group comprising a nitrogen atom, a group -CR1- and an aromatic or alicyclic divalent, trivalent or tetravalent group, which is optionally substituted by one or more groups selected from fluoro, chloro, cyano and a Ci_ig cyclic, straight-chain or branched alkyl residue which is optionally substituted by a single cyano group or by one or more halogen atoms and in which one or more non-adjacent -CH2- groups are, independently, optionally, replaced by a group selected from -0-, -CO-, -CO-O-, -O-CO, -CH=CH- and -C=C-, wherein R1 represents a hydrogen atom or lower alkyl; F represents an aliphatic, alicyclic or aromatic divalent radical; and G represents a hydrogen atom or a monovalent organic group. 18. A polymer as claimed in claim 17 wherein the tetravalent organic radical T1 is derived from an aliphatic, alicyclic or aromatic tetracarboxylic acid dianhydride. 19. A polymer as claimed in claim 17 or 18 wherein one or more of the groups T2 and T3 is derived from an aliphatic, alicyclic or aromatic dicarboxylic acid anhydride. 20. A polymer as claimed in any one of claims 17 to 19 wherein the group S4 is selected from a single covalent bond, -(CH2)r-, -(CH2)r-0-, -(CH2)r-CO-, -(CH2)r-CO-0- _(CH2)r-0-CO- -(CH2X-CO-NR1-, ^CHzV-NR'-CCK -(CFtX-NR1- -(CH2)r-0-(CH2)s- -(CH2y-CO-0-(CH2)s--(CH^-O-CCMCH^-, -(CH^-r^-CCHCH^-, -(CHzV-N^-CO-CHCH,),-, -(CH^-O-CCH^-O- -(CH2X-CO-0-(CH2)5-0--(CH2)r-0-CO-(CH2)s-0-, -(CH2)r-NR1-CO-(CH2)-0-, -(CH2)-NR1-CO-0-(CH2)s-0-, -(CH2X-0-(CH2)s-CO-0- and -(CH2)r-0-{CH2)5-0-CO-, wherein R1 represents a hydrogen atom or lower alkyl; r and s each represents an integer from 1 to 20; and r + s 21 A polymer as claimed in any one of claims 17 to 20 wherein the groups S" and S8 are selected from a single bond, -(CH2)r-, -0-(CH2)r-, -CO-(CH:)r-, -COO-(CH2)r~ -0-CO-(CH2)r-, -NR!-CO-(CH2)r- -NR1~(CH2)r-, -CO-NR1-(CH2)r-, -NR'-CO-(CH2)-, -(CH2)-0-(CH2)S- -(CH2)r-CO-0-(CH2)s- -(CH2)r-0-CO-(CH2)s-, -(CH2)r-NR1-CCKCH2)s-, -(CH2)-NR1CO-0-(CH2)s-, -0-(CH2)r-0-(CH2)s- -0-(CH2)r-C0-0-(CH2)s- -0-(CH2)r-OCO-(CH2)s-, -0-(CH2)r-NR'-CO-(CH2)s-, -0-(CH2)r-NR1-CO-0-(CH2)s-, -0-CCHCH2)r-0-(CH2)s- and -CO-0-(CH2)r-0-(CH2)s-, wherein R1 represents a hydrogen atom or lower alkyl; r and s each represent an integer from 1 to 20; and r + s 22. A polymer as claimed in any one of claims 17 to 21 wherein the groups S6 and S7 are selected from a single bond, -(CH2)r-, -(CH2)r~0-, -(CH2)r-CO-, -(CH2)r-CO-CK -(CH2y-0-CO- -(CHJX-CO-NR1-, -(CH^-NJ^-CO-, -(CH^-NR1- -0-(CH2)r- -CO-0-(CH2)r- -0-CO-(CH2)r-, -NT^-CCHCHJX- -CO-NKl-(CH2)-, -NR'-CCH^- -CMCI^-CO-O- -0-(CH2X-0-CO-, -CHCJkX-CO-NR1-, -CHCH^r-NR1- -0-(CH2)r-0- -O-CC^X-NR'-CO- -NR'-CCHaV-CO-O-, -NR'-CCHZ^-CK -NR'-CCHay-NR1-, -NR'-tCH^-O-CO-, -CO-NR'-CCH^-O- -CO-NR'-CCHzX-NR1-, -CO-NR1-(CH2)r-0-CO-, -O-CCKCHj^-CO- -O-CCHCH^-O- -0-CO-(CH2)-NR'-, -O-CCHCH^-CO-O- -O-CCHCH^-CO-NR1- -0-CO-(CH2)T-m}-CO-, -(CHA-CKCH,)*- -(CH2)r-CO-0-(CH2)s-, -(CH2)r-0-CO-(CH2)s-, -(CHjJr-NR^CHCHa),- -(CHJX-NR'-CO-O-CCHJJS-,-(CH2)r-0-(CH2)s-0- -(CH2)-CO-0-(CH2)s-0- -(CH2)r-0-CO(CH2)s-0-, -(CH2)r-NR1-CO-(CH2)s-0- -(CH2)r-NR'- CO-0-(CH2)s-0-, -0-(CH2)-0-(CH2)s- -0-(CH2)r-CO-0-(CH2)s- -0-{CH2)r-NRl-CO-(CH2)s-, -O-CCHJV-^-CO-CHCHIV, -O-(CH2)r-C0-0-(CH2X-0- -a-(CH2)-0-(CH2)5-0-, 0-(CH2)rNR'-CO-(CH2)s,-0-, 0-(CH2)rNR,-CO-0-(CH2)s-0-CO-0-(CH2)r-0-(CH2)S -, -CO-0-(CH2)rO-(CH2)s -O- wherein R' represents a hydrogen atom or lower alkyl; r and s each represent an integer from I to 20, and r + s 23. A polymer as claimed in any preceding claim having an intrinsic viscosity in the range of 0.05 to 10 dl_/g, the intrinsic viscosity (rn„h = In WC) being determined by measuring a solution containing a polymer in a concentration of 0.5 g/100 ml for its viscosity at 30°C using N-methyl-2-pyrrolidone as solvent. 24. A polymer as claimed in any preceding claim containing from 2 to 2000 monomer units. 25. A polymer as claimed in any preceding claim further including an additive comprising a silane-containing compound, an epoxy-containing crosslinking agent, a photosensitiser, a photoradical generator and/or a cationic photoinitiator. 26. A polymer layer comprising a polymer as claimed in any preceding claim in a crosslinked form. 27. A process for preparing a polymer layer as claimed in claim 26 comprising applying one or more polymers to a support and crosslinking the one or more polymers by irradiation with linearly polarized light. 28. A process for preparing a polymer layer as claimed in claim 27, comprising an imidisation step after applying the one or more polymers to a support and prior to crosslinking of the one or more polymers. 29. An orientation layer for liquid crystals comprising one or more polymers as claimed in any one of claims 1 to 25 in a crosslinked form. 30. An optical constructional element comprising an orientation layer as claimed in claim 29. 31. An optical or electro-optical device comprising one or more polymers as claimed in any one of claims 1 to 25 in crosslinked form. 32. Method for making an orientation layer for liquid crystals, wherein a polymer as claimed in any one of claims 1 to 25 is formed to a layer, preferably in that a solution of the polymer is applied to a support by spincoating, meniscus coating, wire coating, slot coating, offset printing or gravure printing, the layer is imidised if required and subsequently cross-linked. 33. Method for constructing an unstructured and / or structured optical element with at least one orientation layer, wherein polymer as claimed in any one of claims 1 to 25 is formed to a layer, preferably in that a solution of the polymer is applied to a support by spin coating, meniscus coating, wire coating, slot coating, offset printing, or gravure printing, the layer is imidised if required and subsequently oriented and cross-linked. 34. Method for constructing a multi-layer system, wherein a polymer as claimed in any one of claims 1 to 25 is formed to at least one layer, preferably in that a solution of the polymer is applied to a support by spin coating, meniscus coating, wire coating, slot coating, offset printing, or gravure printing, the layer is imidised if required and subsequently oriented and cross-linked. Dated this 18th day of June, 2002. FOR ROLIC AG By their Agent (UMA BAsKARAN) KRISHNA & SAURASTRI |
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in-pct-2002-00827-mum-cancelled pages(13-12-2005).pdf
in-pct-2002-00827-mum-claims(granted)-(18-06-2002).doc
in-pct-2002-00827-mum-claims(granted)-(18-06-2002).pdf
in-pct-2002-00827-mum-correspondence(13-12-2005).pdf
in-pct-2002-00827-mum-correspondence(ipo)-(12-10-2006).pdf
in-pct-2002-00827-mum-form 19(24-11-2004).pdf
in-pct-2002-00827-mum-form 1a(18-06-2002).pdf
in-pct-2002-00827-mum-form 2(granted)-(18-06-2002).doc
in-pct-2002-00827-mum-form 2(granted)-(18-06-2002).pdf
in-pct-2002-00827-mum-form 3(15-04-2005).pdf
in-pct-2002-00827-mum-form 3(18-06-2002).pdf
in-pct-2002-00827-mum-form 5(18-06-2002).pdf
in-pct-2002-00827-mum-form-pct-ipea-409(13-12-2005).pdf
in-pct-2002-00827-mum-form-pct-isa-210(13-12-2005).pdf
in-pct-2002-00827-mum-power of authority(22-11-2000).pdf
| Patent Number | 204713 | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Indian Patent Application Number | IN/PCT/2002/00827/MUM | ||||||||||||
| PG Journal Number | 24/2007 | ||||||||||||
| Publication Date | 15-Jun-2007 | ||||||||||||
| Grant Date | 02-Mar-2007 | ||||||||||||
| Date of Filing | 18-Jun-2002 | ||||||||||||
| Name of Patentee | ROLIC AG | ||||||||||||
| Applicant Address | CHAMERSTRASSE 50, 6301 ZUG, SWITZERLAND. | ||||||||||||
Inventors:
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| PCT International Classification Number | G 02 F 1/337 | ||||||||||||
| PCT International Application Number | PCT/CH01/00044 | ||||||||||||
| PCT International Filing date | 2005-04-15 | ||||||||||||
PCT Conventions:
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