METHOD FOR THE PREPARATION OF PHOTOALIGNING POLYMER MATERIALS AND COMPOSITIONS

Abstract

The present invention relates to a novel method for the preparation of photoaligning polymer materials comprising aryl acrylic acid ester groups, to photoalignment compositions obtained by this process, to the use of the composition as orienting layer for liquid crystals and to non-structured and structured optical elements, electro-optical elements, multi-layer systems or in nanoelectronics comprising the compositions.

Claims

1. A process for the preparation of a photoaligning polymer material comprising aryl acrylic acid ester groups comprising the steps of: a. reacting a compound of formula (II) ##STR00017## wherein ring C is phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 2,5-thiophenylene, 2,5-furanylene, 1,4- or 2,6-naphthylene, Y is either CR′ or O; and if Y is CR′ then q=1 and R═COOR″ wherein R′ and R″ are independently from each other hydrogen or a straight-chain or branched alkylene group with 1 to 20 carbon atoms which is optionally at least once substituted with halogen or with at least one siloxane moieties, or a cycloalkyl residue with 3 to 8 ring atoms which is optionally substituted with at least one halogen, alkyl or alkoxy; or if Y is O, then q=0; with a compound of formula (III) ##STR00018## M.sup.1 signifies a repeating monomer unit from the group consisting of acrylate, methacrylate, 2-chloroacrylate, 2-phenylacrylate, acrylamide, methacrylamide, 2-chloroacrylamide, 2-phenylacrylamide, N-lower alkyl substituted acrylamide, N-lower alkyl substituted methacrylamide, N-lower alkyl substituted 2-chloroacrylamide, N-lower alkyl substituted 2-phenylacrylamide, vinyl ether, vinyl ester, styrene, diamine, amide, imide, siloxane, amic ester, and amic acid; S.sup.1 is a spacer unit; ring A signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3-dioxane-2,5-diyl, cyclohexane-1,4-diyl, piperidine-1,4-diyl or piperazine-1,4-diyl; ring B signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,4- or 2,6-naphthylene, 1,3-dioxane-2,5-diyl or cyclohexane-1,4-diyl; Y.sup.1, Y.sup.2 each independently signify a single covalent bond, —(CH.sub.2).sub.t—, —O—, —CO—, —CO—O—, —O—OC—, —CF.sub.2O—, —OCF.sub.2—, —NR.sup.4—, —CO—NR.sup.4—, —R.sup.4N—CO—, —(CH.sub.2).sub.u—O—, —O—(CH.sub.2).sub.u—, —(CH.sub.2).sub.u, —NR.sup.4— or —NR.sup.4—(CH.sub.2).sub.u—, in which R.sup.4 signifies hydrogen or lower alkyl; t signifies a whole number of 1 to 4; u signifies a whole number of 1 to 3; and m, n signifies a whole number of 0 to 4; and optionally with a compound of formula (IV) or (IV′) ##STR00019## and b. optionally reacting the compound obtained under step a. with a compound of formula (V) ##STR00020## wherein X is OH, F, Cl or I; Z and Z′ are independently from each other either H or halogen; q and q′ are independently from each other an integer between 0 and 2; p is an integer between 0 and 10 r and r′ are independently from each other an integer between 0 and 3; c. polymerizing the compound obtained under step a. or b. with an organic or inorganic peroxide; d. stopping the reaction by heating; e.

2. A process according to claim 1, wherein the spacer unit is S.sup.2 if m and n are 0 and wherein the spacer unit is S.sup.3 if at least one m or n is 1, and wherein S.sup.2 and S.sup.3 are unsubstituted or unsubstituted, straight-chain or branched, —(CH.sub.2).sub.r—, as well as —(CH.sub.2).sub.r—O—, —(CH.sub.2).sub.r—O—(CH.sub.2).sub.s—, —(CH.sub.2).sub.r—O—(CH.sub.2).sub.s—O—, —(CH.sub.2).sub.r—CO—, —(CH.sub.2).sub.r—CO—O—, —(CH.sub.2).sub.r—O—CO—, —(CH.sub.2).sub.r—NR.sup.2—, —(CH.sub.2).sub.r—CO—NR.sup.2—, —(CH.sub.2).sub.r—NR.sup.2—CO—, —(CH.sub.2).sub.r—NR.sup.2—CO—O— or —(CH.sub.2).sub.r—NR.sup.2—CO—NR.sup.3—, which is optionally mono- or poly-substituted with C.sub.1-C.sub.24-alkyl, hydroxy, fluorine, chlorine, cyano, ether, ester, amino, amido; wherein one or more —CH.sub.2— group may be replaced by a linking group, alicyclic or aromatic group; and, in which r and s are each a whole number of 1 to 20, with the proviso that 3≤r+s≤24 for S.sup.2; and 8≤r+s≤24 for S.sup.3; and R.sup.2 and R.sup.3 each independently signify hydrogen or lower alkyl.

3. A process according to claim 1, wherein M.sup.1 is a monomer unit selected from the group consisting of acrylate and methacrylate; ring A is unsubstituted phenylene or phenylene which is substituted with alkyl or alkoxy; ring B is unsubstituted phenylene or phenylene which is substituted with fluorine, alkyl or alkoxy; Y.sup.1, Y.sup.2 each independently is a single covalent bond, —CO—O—, —O—OC—; m, n each independently is 0 or 1; ring C is unsubstituted phenylene or phenylene which is substituted with alkyl or alkoxy; S.sup.1 is a spacer unit, wherein, if m and n are 0 then the spacer unit is S.sup.2 and if at least one m or n is 1, then the spacer unit is S.sup.3; wherein S.sup.2 is C.sub.4-C.sub.24alkylene; and wherein S.sup.3 is C.sub.8-C.sub.24alkylene; and wherein alkylene is unsubstituted or substituted, straight-chain or branched alkylene, in which one or more —CH.sub.2— groups may be replaced by at least one linking group, alicyclic or/and aromatic group; Z is —O—;

4. A process according to claim 3 wherein n=0 and m=1 and wherein S.sup.3 is a straight-chain alkylene grouping represented by —(CH.sub.2).sub.r—, wherein r is 8, 9, 10, 11, 12, as well as —(CH.sub.2).sub.r—O—, —(CH.sub.2).sub.r—CO—O— and —(CH.sub.2).sub.r—O—CO—.

5. A process according to claim 1 wherein n=0 and m=1 and wherein: M.sup.1 is acrylate, methacrylate and styrene derivatives; ring B signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, alkyl or alkoxy, pyridine-2,5-diyl, pyrimidine-2,5-diyl, cyclohexane-1,4-diyl; Y.sup.2 signifies a single covalent bond, —CO—O— or —O—OC—; S.sup.3 is substituted or unsubstituted, straight-chain or branched, —(CH.sub.2).sub.r—, as well as —(CH.sub.2).sub.r—O—, —(CH.sub.2).sub.r—O—(CH.sub.2).sub.s—, —(CH.sub.2).sub.r—O—(CH.sub.2).sub.s—O—, —(CH.sub.2).sub.r—CO—, —(CH.sub.2).sub.r—CO—O—, —(CH.sub.2).sub.r—O—CO—, —(CH.sub.2).sub.r—NR.sup.2—, —(CH.sub.2).sub.r—CO—NR.sup.2—, —(CH.sub.2).sub.r—NR.sup.2—CO—, —(CH.sub.2).sub.r—NR.sup.2—CO—O— or —(CH.sub.2).sub.r—NR.sup.2—CO—NR.sup.3—, wherein the suffix “r” is a whole number between 8 and 24, preferably between 8 and 12 and especially 8, 9, 10, 11 or 12; and ring C signifies phenylene which is unsubstituted or optionally substituted with fluorine, chlorine, cyano, methyl, ethyl, propyl, methoxy, ethoxy or propoxy or 1,4- or 2,6-naphthylene; Z signifies —O— and D is a C.sub.1-C.sub.3 straight-chain or branched alkylene chain which is optionally halogenated at least once or contains one or more siloxane moieties.

6. Compounds obtained by the process according to claim 1.

7. A composition comprising the compounds according to claim 6.

8. A composition comprising: a homopolymer comprising monomers of formula (I): ##STR00021## and at least one monomer of formula (I); wherein M.sup.1, S.sup.1, ring A, Y.sup.1, ring B, Y.sup.2, n, m, ring C, Z and D have the same meaning as described above.

9. Composition according to claim 7 further comprising a solvent and optionally at least an additive.

10. Composition according to claim 9, wherein the at least one additive is selected from the group consisting of polymerizable liquid crystal, UV curable compounds, crosslinking agents, silane-containing compounds, photo-active additives, photo-initiators, surfactants, emulsifiers, antioxidant, levelling agent, dyes, epoxy-containing crosslinking agents and curable compounds.

11. Use of the composition according to claim 7 as orienting layer for liquid crystals.

12. A method for the preparation of an orientation layer for liquid crystals comprising irradiating the composition according to claim 7 with aligning light.

13. Orientation layers comprising a composition according to claim 7.

14. Optical, electro-optical or nanoelectronic elements comprising a composition according to claim 7.

15. Optical, electro-optical or nanoelectronic elements comprising an orientation layer according to claim 13.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0147] The invention is further illustrated by the accompanying drawing figures. It is emphasized that the various features are not necessarily drawn to scale.

[0148] FIG. 1 depicts an example of the characteristics of the liquid crystals orientation at the two interfaces (the interface of the liquid crystal polymer layer to air and the interface of the liquid crystal to the orientation layer) for different exposure energies of the orientation layer, where the tilt angle corresponds to the angle between the main axis of the liquid crystal molecules and the substrate surface.

[0149] The continuous lines represent the tilt angles at the interface of the liquid crystal to the orientation layer. The dotted lines represent the tilt angles at the interface of the liquid crystal polymer layer to air. The different symbols correspond to different ratios of polymer 1 and its monomeric compound 2.

[0150] The polymers in accordance with the invention are illustrated in more detail by the following Examples.

EXAMPLES

Example 1

Preparation of [2-methoxy-4-[(E)-3-methoxy-3-oxo-prop-1-enyl]phenyl] 4-[8-(2-methylprop-2-enoyloxy)octoxy]benzoate Compound 2

[0151] ##STR00012##

[0152] 10.0 g of 4-((8-hydroxyoctyl)oxy)-benzoic acid (from Angene), 1.20 g of hydroquinone, 1.30 g of p-toluenesulfonic acid monohydrate and 30.0 g of methacrylic acid are suspended in 100.0 g of toluene. The resulting mixture is heated under reflux while removing the formed water via a Dean Stark separator, under Nitrogen atmosphere. After 4 hours of reflux, 2/3 of toluene is distilled off under vacuum. 100 mL of ethanol are added to the reaction mixture which is then cooled down to room temperature. 100 g of water are added slowly to form a “white precipitate”. The solid is filtered off and washed 3 times with water to obtain 6.35 g of compound 1 as a white solid with an HPLC purity of >93%. This compound 1 is 4-[8-(2-methylprop-2-enoyloxy)octoxy]benzoic acid.

[0153] 1H NMR (300 MHz) in DMSO-d.sup.6 of compound 1: 12.59 (s, 1H), 7.87 (d, 2H), 6.98 (d, 2H), 6.01 (s, 1H), 5.65 (s, 1H), 4.08 (m, 4H), 1.86 (s, 3H), 1.71 (m, 4H), 1.32 (m, 8H).

[0154] 4.5 g of compound 1 and 0.03 g of butylated hydroxyl toluene (BHT) are dissolved in 100 g of toluene. The reaction mixture is heated up to 70° C. and 1.22 mL of thionyl chloride are added dropwise to the reaction mixture. After the addition the mixture is stirred at 70° C. for 4 hours. The excess of thionyl chloride is distilled off from the reaction mixture under vacuum. The reaction mixture is cooled down to 10° C. and a solution of 2.8 g of methyl (E)-3-(4-hydroxy-3-methoxy-phenyl)prop-2-enoate, 0.16 g of dimethyl amino pyridine (DMAP) and 2.2 mL of trimethylamine in 40 g of toluene are added dropwise to form a white turbid solution. The reaction mixture is stirred at room temperature for 30 minutes. 100 g of methanol are added to the reaction mixture at 10° C. to form a white precipitate which is filtered off, washed with methanol and water to obtain 3.1 g of compound 2 as a white solid with an HPLC purity of >95%.

[0155] 1H NMR (300 MHz) in DMSO-d.sup.6 of compound 2: 8.05 (d, 2H), 7.68 (d, 1H), 7.57 (s, 1H), 7.37 (d, 1H), 7.25 (d, 1H), 7.11 (d, 2H), 6.98 (d, 1H), 6.01 (s, 1H), 5.66 (s, 1H), 4.09 (m, 4H), 3.81 (m, 6H), 1.88 (s, 3H), 1.72 (m, 4H), 1.34 (m, 8H).

Example 2

Polymerization Process—Preparation of Poly [2-methoxy-4-[(E)-3-methoxy-3-oxo-prop-1-enyl]phenyl] 4-[8-(2-methylprop-2-enoyloxy)octoxy]benzoate (Polymer 1)

[0156] 14 g of the compound 2 are mixed together with 52.50 g of cyclohexanone (CHN) and stirred under nitrogen until complete dissolution. The reaction mixture is heated up to 75° C. under nitrogen. 0.22 g of Luperox® LP (dilauryl peroxide from Sigma) are added in one portion. The reaction mixture is maintained at 75° C. for 5 hours and then the temperature is increased to 100° C. After 1 hour at 100° C. the reaction mixture is cooled down to RT and filtered to obtain the polymer in CHN solution. The resulting polymer solution obtained is called Photoalignment Composition 1.

##STR00013##

[0157] Photoalignment Composition 1 contains Polymer 1 (Mw=264690 and Mn=60031) and its monomeric compound 2 in a ratio 90:10 (measured by GPC).

Example 3

[0158] The crosslinkable liquid crystal compound 1 (LCC1) is pentyl 2,5-bis[[4-(6-prop-2-enoyloxyhexoxy)benzoyl]oxy]benzoate and has the following molecular structure.

##STR00014##

[0159] The crosslinkable liquid crystal compound 2 (LCC2) is 3-cyanopropyl 2,5-bis[[4-(6-prop-2-enoyloxyhexoxy)benzoyl]oxy]benzoate and has the following molecular structure.

##STR00015##

[0160] The crosslinkable monomeric compound 3 is (4-cyanophenyl) 4-(6-prop-2-enoyloxyhexoxy)benzoate and has the following molecular structure.

##STR00016##

[0161] The solution S-LCP1 is prepared by dissolving 35 wt % of

TABLE-US-00006 98.525% LCC1 1.00% Irgacure 907 (BASF) 0.20% Tinuvin 123 (BASF) 0.25 Tegoflow 300 (Evonik) 0.025% BHT (Sigma Aldrich)
in 65 wt % of a solvent mixture of 80% n-butylacetate and 20% CNH and stirring the mixture for 30 minutes at room temperature.

[0162] The solution S-LCP2 is prepared by dissolving 25 wt % of

TABLE-US-00007 48.45% LCC2 48.45% Compound 3 3.0% Irgacure 369 (IGM Resins) 0.1% BHT (Sigma Aldrich)
in 75 wt % of a solvent mixture of 80% methylethylketone (MEK) and 20% cyclohexanone (CHN) and stirring the mixture for 30 minutes at room temperature.

[0163] The solution S-LCP3 is prepared by dissolving 35 wt % of

TABLE-US-00008 49.45% LCC1 49.45% LCC2 1.0% Irgacure 907 (BASF) 0.1% BHT (Sigma Aldrich)
in 65 wt % of a solvent mixture of 60% of butyl acetate (BA) and 40% cyclohexanone CHN and stirring the mixture for 30 minutes at room temperature.

Example 4: Preparation of Photoalignment Solution (PAS1)

[0164] The solution PAS1 is prepared by adding 15 wt % of the Photoalignment Composition 1 in 85 wt % of cyclopentanone (CP) and stirring the mixture for 30 minutes at room temperature.

APPLICATION EXAMPLES

Example 1: Preparation of a Primer Coated Substrate

[0165] A triacetate cellulose (TAC) foil was coated by means of Kbar coater (bar size 1) with a primer solution (DYMAX OC-4021 20 w % solid content in 80% Butyl acetate). The wet film was dried at 80° C. for 30 s; the thickness of the resulting dry film was about 2 μm. Then the dry film was exposed to UV light (1500 mJ, under nitrogen atmosphere).

Example 2: Preparation of an Orientation Layer Using PAS1

[0166] A primer coated TAC substrate of example 1 was Kbar coated (bar size 0) with PAS1. The wet film was dried at 80° C. for 30 s; the dry film thickness was about 100 nm. Then the dry film was exposed to aligning light, which was collimated and linearly polarized UV (LPUV) light (280-320 nm) with various exposure energy from 10 to 100 mJ/cm2. The plane of polarization was 0° with regard to a reference edge on the TAC substrate.

Example 3: Preparation of an LCP1 Layer Aligned by the Orientation Layer

[0167] An LCP1 layer is prepared on top of the orientation layer of example 2 by Kbar coating (bar size 1) solution S-LCP1. The wet layer was dried at 50° C. for 60 s and subsequently the liquid crystals are cross-linked at room temperature under nitrogen atmosphere by UV-A light exposure of 30 mW/cm2 for 50 seconds.

Example 4: Evaluation of Orientation

[0168] For an efficient manufacturing process it is of interest to know how much exposure energy does a photo-alignment layer require to achieve a good visible and homogeneous (without any visible defect) contrast in a LCP layer aligned by the orientation layer. The films produced have been analysed between crossed polarizers.

[0169] The alignment quality has been ranked as the following: [0170] .box-tangle-solidup..box-tangle-solidup. very good alignment homogeneous orientation [0171] .box-tangle-solidup. good orientation (disclination lines (DL's) area <1% of coating area) [0172] ◯ few DL's (1«5% of coating area) [0173] x DL's visible (>5% of coating area) [0174] xx inhomogeneous orientation or no orientation

[0175] Optical devices have been produced by the following sequence, a primer coated substrate (as produced in Application Example 1) has been coated by an orientation layer using PAS1 (as described in Application Example 2) and aligning an LCP layer (as shown in Application Example 3). Various exposure energies have been used to orient the photoalignment material.

[0176] Summary of the results are shown in the Table below:

TABLE-US-00009 LPUV dosage (mJ/cm.sup.2) 10 20 30 40 50 60 70 80 90 100 PAS1 xx x .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup. .box-tangle-solidup.

[0177] PAS1 requires only very low LPUV dosage to obtain a very good alignment quality without any visible defects.

Example 5: Preparation of an Orientation Layer Using PAS1

[0178] A COP substrate was pre-treated with Corona (0.75 kW, 20 rpm, 2 times). The pre-treated substrate was Kbar coated (bar size 0) with PAS1. The wet film was dried at 80° C. for 30 s. The dry film thickness was about 100 nm. The dry film was exposed to non-polarized UV light (broadband Fusion H-bulb type) with an exposure energy of 120 mJ/cm.sup.2.

Example 6: Preparation of an LCP2 Layer Aligned by the Orientation Layer

[0179] An LCP2 layer is prepared on top of the orientation layer of example 5 by Kbar coating (bar size 2) solution S-LCP2. The wet layer was dried at 50° C. for 120 s and subsequently the liquid crystals are cross-linked at room temperature under nitrogen atmosphere by UV-A light exposure of 30 mW/cm.sup.2 for 50 seconds, to form a cured layer of a liquid crystal composition. The liquid crystals were aligned homeotropically. Characteristics of the retardation layer are shown in FIG. 1.

[0180] The dotted line represents the variation of the retardation of the COP substrate at different viewing angles.

[0181] The continuous line represents the retardation measurement of the LCP2 layer of example 6 at different viewing angle. The liquid crystal layer behaves as a positive C-plate. The homeotropic orientation is induced by the photoalignment solution PAS 1 oriented without polarized light.

Example 7: Preparation of a Photoalignment Solution PAS2

[0182] The Photoalignment Solution PAS2 is prepared by adding 3 wt % of a mixture of polymer 1 and its monomeric compound 2 in a ratio 97:3, 90:10, 85:15, 80:20 and 50:50 in 97 wt % of cyclopentanone (CP) or a mixture of 50% cyclopentanone (CP) and 50% of cyclohexanone (CHN) and stirring the mixture for 30 minutes at room temperature.

Example 8: Preparation of an Orientation Layer Using PAS2

[0183] A D263 glass (a borosilicate glass) substrate was cleaned and spin coated at 1′700 rpm for 30 s with the variations of PAS2, comprising different ratios of polymer 1 and its monomeric compound 2. The wet films were dried at 180° C. for 10 min. The dry films thickness was about 100 nm. The dry films were exposed to polarized UV light (high pressure mercury lamp) with an exposure energy of 10, 20, 30, 40, 50, 60, 70, 80 and 90 mJ/cm.sup.2, at an oblique incidence angle of 50° to the normal of the surface. The plane of polarization was 0° with regards to a reference edge on the D263 glass substrate.

Example 9: Preparation of an LCP3 Layer Aligned by the Orientation Layer PAS2

[0184] An LCP3 layer is prepared on top of the orientation layers of example 8 by spin coating solution S-LCP3 at 2′500 rpm for 40 s. The wet layer was dried at 60.5° C. for 60 s and subsequently the liquid crystals are cross-linked at room temperature under nitrogen atmosphere by UV-A light exposure of 30 mW/cm.sup.2 for 50 seconds, to form a cured layer of a liquid crystal composition. The liquid crystals exhibited hybrid alignment, were the tilt angle of the liquid crystals at the interface PAS2-LCP3 is in general different than the tilt angle of the liquid crystals at the interface LCP3-air. In the bulk of the film, the tilt angle is considered to vary linearly between the tilt angles at the interfaces. Characteristics of the liquid crystals orientation at the interfaces are shown in FIG. 1 for different exposure energies of PAS2, where the tilt angle corresponds to the angle between the main axis of the liquid crystal molecules and the substrate surface.

[0185] The continuous lines represent the tilt angles at the PAS2-LCP3 interface. The dotted lines represent the tilt angles at the LCP3-air interface. The different symbols correspond to different ratios of polymer 1 and its monomeric compound 2.