Liquid crystal alignment composition, liquid crystal alignment film and liquid crystal display element

Abstract

The present invention relates to a photo-alignment composition for the alignment of liquid crystals. Further the present invention relates to the liquid crystal alignment film and coating layer prepared from the said composition and the use to fabricate optical and electrooptical elements and devices.

Claims

1. A liquid crystal photoalignment composition comprising: a) at least one polyimide and/or polyamic acid compound (I) represented by the general Formula 1, comprising repeating structural units (1) and/or (2): ##STR00038## and/or a repeating structural unit represented by the general Formula 2, comprising repeating structural units (3) and/or (4): ##STR00039## where A is a tetravalent organic residue of a tetracarboxylic dianhydride, B is the divalent residue of a substituted or unsubstituted non-aromatic or aromatic diamine NH.sub.2BNH.sub.2 without phenolic OH-groups, M is the divalent residue of a substituted or unsubstituted aromatic diamine NH.sub.2-M-NH.sub.2 carrying at least two phenolic OH-groups, n and m are integers and the sum n+m has a value from 10 to 200, where m is greater than 0 and n is equal to 0 or greater than 0, and under the proviso that at least 5 weight % of the aromatic diamine carrying phenolic OH groups NH.sub.2-M-NH.sub.2 are present in 100 weight % of compound (I), b) at least one photoactive compound (II) comprising photoalignment groups, c) a solvent or solvent mixture, d) optionally at least one additive, and the amount of compound (I) is 50%-99.5% by weight of the sum of weights of compound (I) and compound (II); wherein the substituted or unsubstituted aromatic diamine carrying at least two phenolic OH groups NH.sub.2-M-NH.sub.2 is a bis-o-aminophenol carrying at least 2 phenolic OH groups and comprising 2 or 3 benzene rings in the molecular structure, where the phenolic OH groups are in para-position relative to the bridging group X and the amino groups are in ortho-position relative to the phenolic OH groups, as depicted in the following formulae: ##STR00040## and wherein Y represents a hydrogen atom, C.sub.1-C.sub.4 alkyl group, C.sub.1-C.sub.4 alkoxy group, Cl, F, Br or I, and p represents an integer from 1-3.

2. The liquid crystal photoalignment composition according to claim 1, where the aromatic diamine carrying at least two phenolic OH groups NH.sub.2-M-NH.sub.2 is selected from the bis-o-aminophenol compounds selected from the group consisting of: ##STR00041##

3. The liquid crystal photoalignment composition according to claim 1, where the polyimide and/or polyamic acid compound (I) is a copolymer comprising at least one molecular type of dianhydride and at least two molecular types of diamines, one being of the type NH.sub.2BNH.sub.2 without phenolic OH groups and one being NH.sub.2-M-NH.sub.2 carrying at least two phenolic OH groups, under the proviso that the amount of diamine NH.sub.2-M-NH.sub.2 is 10% by weight relative to the total amount of diamines.

4. The liquid crystal photoalignment composition according to claim 1, where the polyimide and/or polyamic acid compound (I) comprises at least one molecular type of dianhydride and one molecular type of diamine NH.sub.2-M-NH.sub.2 containing phenolic OH groups.

5. The liquid crystal photoalignment composition according to claim 1, where the compound (I) is a block copolymer comprising recurring block units . . . [Block].sub.b . . . [Block C].sub.c . . . where Block B comprises prepolymerized recurring structural units from at least one molecular type of dianhydride and at least one molecular type of diamine NH.sub.2BNH.sub.2 without phenolic OH-groups, according to Formula 3: ##STR00042## and Block C comprises prepolymerized recurring structural units from at least one molecular type of dianhydride and at least one molecular type of diamine NH.sub.2-M-NH.sub.2 containing phenolic OH-groups, according to Formula 4: ##STR00043## where A, B and M have the same meaning as given in claim 1 and s, t, are integers indicating the number of recurring units in Block B and Block C, such that b*s+c*t is a value of 10 to 1000, under the proviso that at least 10 weight % of the recurring units of the Block C are present in 100 weight % of compound (I).

6. The liquid crystal photoalignment composition according to claim 1, where the photoactive compound (II) comprising photoalignment groups is a monomer, oligomer, dendrimer, prepolymer or copolymer, where the photoalignment groups comprise functional groups selected from the group consisting of: cinnamates, chalcones, coumarines, quinolones, and stilbenes, where these functional groups can be unsubstituted or comprise substituents selected from the group consisting of: fluorine, chlorine, bromine, cyano, C.sub.1-C.sub.4-alkoxy, carboxylic acid, ester groups with linear or branched C.sub.1-C.sub.12 alkyl, optionally substituted with fluorine or cyano groups, linear or branched alkyl and cycloalkyl groups with 1-12 C atoms, optionally substituted with fluorine or cyano groups, and aromatic groups with 6-18 C atoms optionally substituted with fluorine or cyano groups.

7. The liquid crystal photoalignment composition according to claim 1, where the photoactive compound (II) comprising photoalignment groups is an oligomer, polymer or copolymer.

8. The liquid crystal photoalignment composition according to claim 1, where the photoactive compound (II) comprising photoalignment groups is a polyimide and/or polyamic acid oligomer or polymer.

9. A method of preparation of the liquid crystal photoalignment composition according to claim 1, comprising mixing and/or blending together the components a) to d), providing the composition according to claim 1 for using it as a photoalignment film or coating material to align liquid crystalline compounds to fabricate structured or unstructured optical and electro-optical elements and devices.

10. A photoalignment film or coating layer prepared by the processes of a) applying the composition according to claim 1 on a substrate to form a liquid crystal alignment film or coating layer, b) optionally drying, c) optionally heating the coated layer at 80 C. to 230 C., d) photoirradiating the photoalignment film or coating layer prepared via steps a) to c) with aligning light of a suitable wavelength to induce the anisotropy in the film or coating layer.

11. A photoalignment film or coating layer comprising a composition according to claim 1.

12. A method of using the photoalignment film or coating layer according to claim 11, comprising aligning liquid crystalline compounds with said photoalignment film or coating layer to fabricate structured or unstructured optical and electro-optical elements and devices.

13. Structured or unstructured optical and electro-optical elements and devices comprising the photoalignment film or coating layer according to claim 11.

Description

EXAMPLES

Definitions

(1) BC=Butyl cellosolve (2-butoxy ethanol)

(2) Butylal=Formaldehyde di-n-butylacetal

(3) DEE=Diethylene glycol diethylether

(4) DMSO=Dimethylsulfoxide

(5) EEP=Ethyl 3-ethoxypropionate

(6) GBL=gamma-Butyrolactone

(7) MIAK=Methyl isoamyl ketone (2-Methyl-5-hexanone)

(8) MLC-6610 (Merck KGA)=Licristal MLC-6610 (Merck KGA), nematic liquid crystal

(9) NMP=N-methyl-pyrrolidone

(10) o.th.=of theory

(11) Pd/C=Palladium on carbon (catalyst)

(12) THF=Tetrahydrofurane

(13) Availability of Materials and Components

(14) The polyimide or polyamic acid compounds (I) are prepared from dianhydrides and diamines NH.sub.2BNH.sub.2 and NH.sub.2-M-NH.sub.2, as described in Polymer Examples.

(15) The dianhydrides (A-dianhydride) are commercial materials or can be prepared by known methods.

(16) The diamines NH.sub.2BNH.sub.2 without additional phenolic OH-groups are generally available from commercial sources.

(17) The diamines NH.sub.2-M-NH.sub.2 with additional phenolic OH-groups are either commercially available or can be synthesized by known methods, e.g. by nitration of the corresponding bisphenols with nitric acid, followed by reduction of the dinitrocompounds using e.g. hydrazine hydrate and a catalyst such as Pd/C (Examples 1-3 below).

(18) Non-limiting examples of the preparation of the photoactive compounds (II) with photoalignment groups is given in Photopolymer examples PP1 to PP7. Other photoactive compounds (II) are either commercially available or can be prepared according to the state of the art.

(19) Preparation of Diaminophenol Compounds

Example 1: Preparation of 2-amino-4-[1-[3-[1-(3-amino-4-hydroxy-phenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]phenol

(20) ##STR00019##

(21) Nitration: A 350 ml 4-neck reactor is charged with 17.30 g (0.050 Mole) 4,4-(1,3-phenylenediisopropylidene)bisphenol (Bisphenol M) [13595-25-0] and 130 ml of dichloromethane. The suspension is stirred and cooled to 0 C. with an ice-bath and 11.30 g of an aqueous 65%-nitric acid solution are slowly (dropwise) added over 1 hour, keeping the temperature between 0 C.-5 C. The brownish reaction mixture is stirred and kept at this temperature for additional 4 hours.

(22) 120 ml of water are added and the mixture stirred vigorously to extract the excess of nitric acid into the aqueous phase. The water phase is separated and the organic dichloromethane phase extracted once with 150 ml of an aqueous 10%-solution of sodium hydrogen carbonate, followed by 150 ml pure water. The dichloromethane phase is dried with little sodium sulphate, filtered and the filtrate concentrated on a rotary evaporator to yield 43 g of a yellow-brown oil. Crystallization is effected by adding isopropyl alcohol (100 ml) and cooling with an ice bath. After several hours a brownish suspension has formed, which is filtered and the residue washed with cold isopropyl alcohol. The solid product is dried in vacuo at 40 C. to afford 15 g (68% o.th.) of yellow-brown, crystalline 2,2-Dinitro-bisphenol M. HPLC purity (254 nm, area %): 88%.

(23) Reduction: 14.00 g (0.0321 Mole) of 2,2-Dinitro-bisphenol M are dissolved in 80 ml of N-methyl-pyrrolidone (NMP). 1.925 g of the catalyst Palladium on carbon E1002 U/W (from Degussa) are added, followed by 30 ml of methanol. The black suspension is heated to 45 C. 8 ml (0.168 Mole NH.sub.2NH.sub.2) of hydrazine monohydrate 98% (65% NH.sub.2NH.sub.2) are drop wise added within 30 minutes. The temperature rapidly rises to the reflux temperature of methanol (76-80 C.), and the reaction is accompanied by the evolution of nitrogen gas. The black reaction mixture is refluxed for 2 hours with an oil bath of 90 C. After cooling to 40 C. internal temperature the catalyst is filtered off. The yellowish, clear filtrate is again heated to 90 C. and 180 ml of water are added. The product starts to crystallize. After cooling to 0 C. the crystals are filtered, washed with water and dried in vacuo at 50 C. to constant weight. 10.45 g (86.6% o.th.) slightly beige, crystalline 2-amino-4-[1-[3-[1-(3-amino-4-hydroxy-phenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]phenol are obtained, HPLC purity (230 nm, area %): 96%.

(24) .sup.1H-NMR 300 MHz, DMSO-d6, ppm:

(25) 8.72 (s, 2H), 7.17-6.24 (m, 10H), 4.35 (s, 4H), 1.49 (s, 12H)

Example 2: Preparation of 2-amino-4-[1-[4-[1-(3-amino-4-hydroxy-phenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]phenol

(26) ##STR00020##

(27) Nitration: 17.32 g (0.05 Mole) of 4-[1-[4-[1-(4-hydroxyphenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]phenol (Bisphenol P) [2167-51-3] in 140 ml dichloromethane are treated with 11.30 g aqueous 65%-nitric acid solution according to the procedure described in example 1. 16.18 g (74% o.th.) of greenish-yellow, crystalline 4-[1-[4-[1-(4-hydroxy-3-nitro-phenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]-2-nitro-phenol are obtained. HPLC purity (254 nm, area %): 95.2%.

(28) Reduction: 16.00 g (0.0366 Mole) of dinitro compound in 90 ml NMP and 35 ml methanol are treated with 2.20 g Palladium on carbon catalyst and 9.5 ml hydrazine monohydrate according to the procedure described in example 1. 13.24 g (96% o.th.) slightly beige, crystalline 2-amino-4-[1-[4-[1-(3-amino-4-hydroxy-phenyl)-1-methyl-ethyl]phenyl]-1-methyl-ethyl]phenol are obtained, HPLC purity (230 nm, area %): 97%.

(29) .sup.1H-NMR 300 MHz, DMSO-d6, ppm:

(30) 8.72 (s, 2H), 7.06 (s, 4H), 6.54-6.43 (m, 6H), 4.35 (s, 4H), 1.51 (s, 12H)

Example 3: Preparation of 2-amino-4-[1-(3-amino-4-hydroxy-phenyl)cyclohexyl]phenol

(31) ##STR00021##

(32) Nitration: 18.78 g (0.07 Mole) of 4-[1-(4-hydroxyphenyl)cyclohexyl]phenol [843-55-0] in 140 ml dichloromethane are treated with 15.61 g aqueous 65%-nitric acid solution according to the procedure described in example 1. 15.84 g (63% o.th.) of yellow, crystalline 4-[1-(4-hydroxy-3-nitro-phenyl)cyclohexyl]-2-nitro-phenol are obtained. HPLC purity (254 nm, area %): 97.3%.

(33) Reduction: 20.00 g (0.056 Mole) of dinitro compound in 110 ml NMP and 55 ml methanol, are treated with 3.35 g Palladium on carbon catalyst and 14 ml hydrazine monohydrate according to the procedure described in example 1. The crystalline raw product (20.54 g) was recrystallized from 100 ml of ethanol to yield 16.3 g (98% o.th.) of slightly beige product, HPLC purity (254 nm, area %): 98.8%.

(34) .sup.1H-NMR 300 MHz, DMSO-d6, ppm:

(35) The NMR analysis revealed that the product forms a mixture with the solvent NMP 8.63 (s, 2H), 6.51-6.48 (m, 4H), 6.31-6.28 (m, 2H), 4.29 (s, 4H), 2.02 (s broad, 4H), 1.43 (s broad, 6H).

(36) Preparation of Homopolymeric or Copolymeric Polyimide and Polyamic Acid Compounds (I)

(37) List of Diamines Used or the Polymer Preparation

(38) TABLE-US-00001 Structure Designation Diamine 1 Diamine 2 Diamine 3 Diamine 4 (Preparation Example 1) Diamine 5 Diamine 6 (Preparation Example 3) Diamine 7 Diamine 8 0 Diamine 9 (Preparation Example 2) Diamine 10

(39) List of Dianhydrides Used for the Polymer Preparation

(40) TABLE-US-00002 Structure Designation CBDA TCA

Polymer Example P1: Preparation of Polyamic Acid from Diamine 1 (2,2-Bis(3-amino-4-hydroxyphenyl)propane) and Dianhydride (CBDA)

(41) A solution is prepared from 10.00 g (38 mMol) 2,2-Bis(3-amino-4-hydroxyphenyl)propane in 40.70 g NMP at room temperature. 7.59 g (38 mMol) CBDA are added and the reaction mixture is stirred for 24 hours at room temperature. Thereafter, the reaction mixture is diluted with 30 g of THF and is poured into an excessive amount of water to precipitate the polymer. The precipitated product is dried at 40 C. under vacuum for 24 hours to yield 16.5 g of polyamic acid (Designation PAA-1) as an off-white solid. Intrinsic viscosity []=0.40 dl/g.

(42) .sup.1H-NMR 300 MHz, DMSO-d6, ppm:

(43) 12.32 (s broad, approx. 2H), 9.55-9.49 (m, 4H), 7.65 (s, 2H), 6.74 (s, 4H), 3.98-3.28 (m, 4H), 1.52 (s, 6H)

(44) Analogous to the procedure described in Polymer example P1 the following polymers are prepared from the diamines and dianhydrides indicated in the following table:

(45) TABLE-US-00003 Intrinsic viscosity [] .sup.1H-NMR 300 MHz, Polymer example Diamine Dianhydride dl/g DMSO-d6, ppm P2 (comparative Diamine 2 CBDA 0.69 12.32 (s broad, 2H), example, without 10.15 (s, 2H), phenolic OH), 7.60-7.56 (m, 4H), (PAA-2) 6.96-6.93 (m, 4H), 3.88-3.53 (m, 4H). P3 (PAA-3) Diamine 3 CBDA 0.45 P4 (PAA-4) Diamine 4 CBDA 0.42 P5 (PAA-5) Diamine 5 CBDA 0.48 12.7 (s broad, 2H), 10.30 (s, 2H), 9.52 (s, 2H), 8.22-8.17 (d, 2H), 6.90-6.81 (m, 4H), 3.99-3.50 (m, 4H). P6 (PAA-6) Diamine 1 + CBDA 0.53 Diamine 2 1/1 (molar) P7 (PAA-7) Diamine 1 + CBDA 0.50 Diamine 2 2/8 (molar) P8(PAA-8) Diamine 6 CBDA 0.44 12.49 (s broad, 2H), 9.56 (s, 2H), 9.47 (s, 2H), 7.71 (s, 2H), 6.74-6.71 (m, 4H), 4.00-3.51 (m, 4H), 2.28-2.09 (m, 4H), 1.45 (s broad, 6H) P9 (PAA-9) Diamine 7 CBDA 0.34 P10 (PAA-10) Diamine 8 CBDA 0.99 P11 (PAA-11) Diamine 9 CBDA 0.54 12.48 (s broad, 2H), 9.51-9.58 (m, 4H), 7.70 (s, 2H), 7.08 (s, 4H), 6.74 (s, 4H), 3.99-3.45 (m, 4H), 1.55 (s, 12H) P12 (PAA-12) Diamine 1 TCA 0.49 P14 (PAA-14) Diamine 10 CBDA 0.50

Polymer Example P13: Preparation of Block Type Copolymeric Polyamic Acid from Diamine 1

(46) (2,2-Bis(3-amino-4-hydroxyphenyl)propane) and CBDA (Block 1) and Diamine 2 (4,4-oxydianiline) and CBDA (Block 2); ratio of Block 1:Block 2=54:46 (weight %).

(47) 1.8086 g 2,2-Bis(3-amino-4-hydroxyphenyl)propane are dissolved in 25.11 g N-methyl-pyrrolidone and cooled to 0 C. 1.569 g of CBDA are added and the mixture stirred for 2 hours at room temperature.

(48) 1.6022 g of 4,4-oxydianiline are added and stirred until completely dissolved. 0.0754 g of succinic anhydride are added and the mixture cooled to 0 C. 1.226 g of CBDA are added and the mixture stirred at room temperature for 18 hours. Thereafter, the reaction mixture is diluted with 30 g of THF and is poured into an excessive amount of water to precipitate the polymer. The precipitated product is dried at 40 C. under vacuum for 24 hours to yield the polyamic acid (PAA-13) as an off-white solid. Intrinsic viscosity []=0.58 dl/g.

Polymer Example P15: Preparation of Block Type Copolymeric Polyamic Acid from Diamine 1

(49) (2,2-Bis(3-amino-4-hydroxyphenyl)propane) and CBDA (Block 1) and Diamine 2 (4,4-oxydianiline) and CBDA (Block 2); ratio of Block 1:Block 2=11:89 (weight %).

(50) Analogous to the preparation of PAA-13 in Polymer Example P13, the polyamic acid PAA-15 is prepared by using 0.1295 g 2,2-Bis(3-amino-4-hydroxyphenyl)propane, 11.8821 g N-methyl-pyrrolidone, 0.1948 g CBDA and 1.4018 g 4,4-oxydianiline, 0.0371 g succinic anhydride, 1.2014 g CBDA. After 18 hours at room temperature a clear, viscous solution is obtained with an intrinsic viscosity []=0.5016 dl/g. This solution can be directly used to prepare a composition according to the present invention.

Formation of Polyimide from Polyamic Acid

Polymer Example PI 1

(51) 1.45 g of polyamic acid from Polymer Example 4 is dissolved in 3.5 ml of NMP. Thereto are added 0.165 ml of pyridine and 0.195 ml of acetic anhydride. The dehydration and ring closure is carried out at 80 C. for 2 hours. The reaction mixture is diluted with 10 ml of NMP, precipitated by pouring into 100 ml diethyl ether and collected by filtration. The polymer is reprecipitated from 10 ml THF by pouring into 200 ml water and collected by filtration. The reprecipitated product is dried at room temperature under vacuum to yield 1.10 g of polyimide (PI-1) as an off-white solid. Intrinsic viscosity []=0.40 dL/g; Imidization degree 42%.

Polymer Example PI 2

(52) Analogous to the preparation of Polymer Example 18, the polyamic acid of Polymer Example 5 is used to yield the corresponding polyimide (PI-2) as an off-white solid. Intrinsic viscosity []=0.65 dL/g.

(53) Preparation of Photoactive Compounds (II) Comprising Photoalignment Groups

(54) List of Diamines NH.sub.2PD-NH.sub.2 Used or the Polymer Preparation

(55) TABLE-US-00004 Structure Designation PD1 PD2 PD3 PD4

Photopolymer Example PP1: Preparation of Polyamic Acid from Diamine PD1 and Dianhydride TCA

(56) A solution is prepared from 2.117 g (3.66 mMol) diamine PD1 in 6.56 ml NMP at room temperature. The solution is cooled to 0 C. and 0.820 g (3.66 mMol) 2,3,5-tricarboxy-cyclopentylacetic-1,2:3,4-dianhydride (TCA) are added. The reaction mixture is stirred for 2 hours at 0 C. and then for 21 hours at room temperature. Thereafter, the reaction mixture is diluted with 18 ml of THF and is slowly poured into 800 ml of water to precipitate the polymer. The precipitated product is dried at 40 C. under vacuum for 24 hours to yield 2.76 g of polyamic acid (Designation PP-1) as a white solid. Intrinsic viscosity []=0.33 dL/g. Analogous to the procedure described in Photopolymer example PP1 the following polymers are prepared from the diamines and dianhydrides indicated in the following table:

(57) TABLE-US-00005 Photopolymer example Diamine Dianhydride Intrinsic viscosity [] PP2 PD2 TCA 0.50 dl/g PP3 PD2 + PD4 TCA 0.48 dl/g Mass ratio 95:5 PP4 PD2 + PD4 TCA 0.48 dl/g Mass ratio 90:10 PP5 PD2 + PD4 TCA 0.33 dl/g Mass ratio 80:20 PP6 PD2 + PD3 TCA 0.39 dl/g Mass ratio 90:10 PP7 PD2 + PD3 TCA 0.31 dl/g Mass ratio 80:20

(58) Preparation of the Inventive Photoalignment Composition

(59) The homopolymeric or copolymeric polyimide and polyamic acid compounds (I) are prepared as described above.

(60) The photoactive compounds (II) comprising photoalignment groups may be prepared as described above.

(61) General procedure: A solution of the required concentration is prepared by mixing the compounds (I) and (II) with the solvent or solvent mixture in the required weight ratios and stirring thoroughly until complete dissolution is attained. If required additives are added and the formulation according to the present invention is then filtered (Sartorius PTFE 0.2 m) and used as described in the application examples.

(62) Results (% concentrations are by weight):

(63) TABLE-US-00006 Compound (I) Solvent 1 (%) (%) Solvent 2 (%) Polymer Compound (II) Solvent 3 (%) concentration Solution Example (%) Solvent 4 (%) (%) quality F1. PAA-1 97 NMP 60 4.5 PP2 3 BC 40 F2.(comp.) PAA-2 97 NMP 60 4.5 PP2 3 BC 40 F3. PAA-1 90 NMP 60 4.5 PP2 10 BC 40 F4.(comp.) PAA-2 90 NMP 60 4.5 PP2 10 BC 40 F5. PAA-1 95 NMP 60 7.5 PP2 5 BC 40 F6. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 MIAK 10 F7.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 MIAK 10 F8. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 2-Heptanone 10 F9.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 2-Heptanone 10 F10. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 3-Heptanone 10 F11.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 3-Heptanone 10 F12. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 4-Heptanone 10 F13.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 4-Heptanone 10 F14. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 5-Methyl- 10 3-Heptanone F15.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 5-Methyl- 10 3-Heptanone F16. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 EEP 10 F17.(comp.) PAA-2 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 EEP 10 F18. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 Isoamylbutyrate 10 F19.(comp.) PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 Isoamylbutyrate 10 F20. PAA-1 95 NMP 25 4 PP2 5 GBL 25 DEE 40 Isoamylbutyrate 10 F21. PAA-1 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 Butylal 10 F22. PAA-1 95 NMP 25 4 PP2 5 GBL 25 DEE 40 Butylal 10 F23. PAA-1 95 NMP 25 4 PP2 5 GBL 25 DEE 40 MIAK 10 F24. PAA-1 95 NMP 25 4 PP2 5 GBL 25 DEE 40 Propylal 10 F25. PAA-1 95 NMP 25 4 PP2 5 GBL 25 DEE 40 Diethylcarbonate 10 F26. PAA-1 95 NMP 50 7.5 PP2 5 BC 30 EEP 20 F27. PAA-1 95 NMP 50 7.5 PP2 5 BC 30 Butylal 20 F28. PAA-1 95 NMP 50 7.5 PP2 5 BC 30 Propylal 20 F29. PAA-1 95 NMP 50 7.5 PP2 5 BC 30 Isoamylbutyrate 20 F30. PAA-1 95 NMP 50 7.5 PP2 5 BC 30 MIAK 20 F31. PAA-13 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 EEP 10 F32. PAA-15 97 NMP 25 4.5 PP2 3 GBL 25 DEE 40 EEP 10

Symbol and Abbreviation List

(64) : Solution homogenous, clear and perfectly soluble

(65) : Solution turbid, not clear

(66) X: Precipitation of the polymer

(67) N-methyl-2-pyrrolidone (NMP), (gamma)-butyrolactone (GBL or BL), ethylene glycol mono butyl ether or butyl glycol or butyl cellosolve (BC), diethylene glycol diethyl ether (DEE or DEDG), 3-ethoxyethyl propionate (EEP), methyl isoamyl ketone (MIAK).

Application Examples

(68) Cell Preparation and Evaluation.

(69) A liquid crystal cell wherein the liquid crystals are aligned by the photoalignment coating layer of the present invention is prepared in the following manner:

(70) A 4.5 weight % solution of compounds (I) and (II) is spin-coated onto two ITO coated glass substrates at a spin speed of 1600-2100 rpm for 30 seconds. After spin-coating, the substrates are subjected to a baking procedure consisting of pre-baking for 1.5 minutes at 80 C. and post-baking for 40 minutes at a temperature of 200 C. The resulting layer thickness is around 100 nm. The substrates with the coated polymer layer on top are exposed to linearly polarized UV light (LPUV) at an incidence angle of 40 relative to the normal of the substrate surface. The plane of polarization is within the plane spanned by the substrate normal and the propagation direction of the light. The applied exposure dose is 20 mJ/cm.sup.2 at a wavelength of 280-330 nm. After LPUV exposure, a cell is assembled with the 2 substrates, the exposed polymer layers facing the inside of the cell. The substrates are adjusted relative to each other such that the induced alignment directions are parallel to each other (corresponds to the anti-parallel rubbed configuration in case of alignment by rubbing procedure). The cell is capillary filled with liquid crystal MLC-6610 (Merck KGA), which had a negative dielectric anisotropy. The filled cell is further subjected to a thermal annealing at 130 C. for 30 minutes, thereby completing the cell process.

(71) Voltage holding ratio of this cell is measured at 60 C. The voltage decay V (at T=16.67 ms and T=1667 ms) of a voltage surge of 64 s with V.sub.0 (V at t=0)=1 V is then measured over a period of T=16.67 ms and T=1667 ms. The voltage holding ratio (VHR) is then determined, given by VHR (%)=V.sub.rms (t=T)/V.sub.0*100.

(72) Tilt angle is measured using the crystal rotation method. The liquid crystal orientation is determined by polarization microscopy.

(73) Results:

(74) TABLE-US-00007 Solvent 1 (%) Compound (I) (%) Solvent 2 (%) VHR (%) Compound (II) Solvent 3 (%) 16.67 ms/ Tilt Example (%) Solvent 4 (%) 1667 ms angle Orientation A1 PAA-1 97 NMP 60 99.50/95.20 88.62 Homeotropic PP2 3 BC 40 A2 PAA-2 97 NMP 60 99.20/91.30 88.50 Homeotropic (comp.) PP2 3 BC 40 A3 PAA-1 90 NMP 60 99.45/94.50 86.67 Homeotropic PP1 10 BC 40 A4 PAA-2 90 NMP 60 99.20/91.52 87.60 Homeotropic (comp.) PP1 10 BC 40 A5 PAA-1 97 NMP 25 99.35/93.48 88.54 Homeotropic PP2 3 GBL 25 DEE 40 MIAK 10 A6 PAA-2 97 NMP 25 99.00/93.43 88.58 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 MIAK 10 A7 PAA-1 97 NMP 25 99.35/94.19 88.59 Homeotropic PP2 3 GBL 25 DEE 40 2-Heptanone 10 A8 PAA-2 97 NMP 25 99.07/93.58 88.57 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 2-Heptanone 10 A9 PAA-1 97 NMP 25 99.30/93.65 88.56 Homeotropic PP2 3 GBL 25 DEE 40 3-Heptanone 10 A10 PAA-2 97 NMP 25 99.02/93.50 88.60 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 3-Heptanone 10 A11 PAA-1 97 NMP 25 99.35/94.19 88.60 Homeotropic PP2 3 GBL 25 DEE 40 4-Heptanone 10 A12 PAA-2 97 NMP 25 99.07/93.14 88.62 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 4-Heptanone 10 A13 PAA-1 97 NMP 25 99.30/94.45 88.64 Homeotropic PP2 3 GBL 25 DEE 40 5-Methyl3- 10 Heptanone A14 PAA-2 97 NMP 25 99.10/93.27 88.62 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 5-Methyl3- 10 Heptanone A15 PAA-1 97 NMP 25 99.37/93.76 88.58 Homeotropic PP2 3 GBL 25 DEE 40 EEP 10 A16 PAA-2 97 NMP 25 99.10/91.10 88.53 Homeotropic (comp.) PP2 3 GBL 25 DEE 40 EEP 10 A17 PAA-1 97 NMP 25 99.27/93.96 88.55 Homeotropic PP2 3 GBL 25 DEE 40 Isoamylbutyrate 10 A18 PAA-1 97 NMP 25 99.35/94.32 88.52 Homeotropic PP2 3 GBL 25 DEE 40 Butylal 10

(75) With reference to the results in the table above, compound PAA-1 (Polymer example P1), which comprises repeating structural units from Diamine 1 carrying phenolic OH-groups, shows excellent voltage holding ratio performance in comparison to the compound PAA-2 (Polymer example 2), which comprises repeating structural units from Diamine 2 carrying no phenolic OH-groups. When compound PAA-1 is used in the composition together with a photopolymer compound (II), it doesn't disturb alignment of liquid crystals and maintains good homeotropic orientation.