WO2008052376A1

WO2008052376A1 - Birefringent layer of c-plate and o-plate type

Info

Publication number: WO2008052376A1
Application number: PCT/CH2007/000533
Authority: WO
Inventors: Thomas Bachels; Mario Schwab; Guy Marck
Original assignee: Rolic Ag
Priority date: 2006-11-03
Filing date: 2007-10-29
Publication date: 2008-05-08

Abstract

The present invention relates to a method for the preparation of a birefringent layer of C-plate and O-plate type comprising polymerizing a composition comprising one or more liquid crystal of formula (I) wherein A1 and A2 denote independently from each other a polymerisable organic residue, Z1 and Z2 are independently from each other -CH(OH)-, -CO-, -O-, -CH2(CO)-, -SO-, -CH2(SO)-, -SO2-, -CH2(SO2)-, -COO-, -OCO-, -OCOO-, -COCF2-, -CF2CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH2-CH2-, -OCH2-, -CH2O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH3)=N, -N=N- or a single covalent bond; preferably, -COO-, -OCO-, -OCOO-, more preferably -COO- and -OCO-, R1, R2, R3, R4, R5 and R6 are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -C1-C40aIkyl, -NO2, -CN or halogen; preferably R1, R2, R3, R4, R5 and R6 are hydrogen, R7 is C1-C20alkyl or C1-C20alkenyl, wherein any -CH2-group of C1-C20alkyl or C1-C20alkenyl may be replaced independently from each other by -O-, -COO- or -CO-, with the proviso that -O-, -COO- and/or -CO- are not linked together, and at least one organic compound, having a terminal polar group. Further, the present invention relates to birefringent layers of O-plate and C-plate types prepared according to the method of the invention, and to optical and electrooptical components, and devices comprising the birefringent layers according to the invention.

Description

Birefringent layer of C-plate and O-plate type

The present invention relates to a method for the preparation of a birefringent layer of C-plate and O-plate type comprising polymerizing a composition comprising one or more liquid crystal of formula (I)

wherein

Ai and A₂ denote independently from each other a polymerisable organic residue, Zi and Z₂ are independently from each other -CH(OH)-, -CO-, -0-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-, -N=N- or a single covalent bond; preferably, -COO-, -OCO-, -OCOO-, more preferably -COO- and -OCO-, Ri, R₂, R₃, R₄, R₅ and R₆ are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -CrC^alkyl, -NO2, -CN or halogen; preferably R₁, R₂, R₃, R₄, R5 and R₆ are hydrogen,

R₇ is Ci-C₂₀alkyl or Ci-C₂₀alkenyl, wherein any -CH₂-group of C^C^alkyl or Ci-C_2Oalkenyl may be replaced independently from each other by -0-, -COO- or -CO-, with the proviso that -0-, -COO- and/or -CO- are not linked together, and at least one organic compound, having a terminal polar group.

Birefringent layer with tilted optical axis are customarily used as retarders or compensation films. Conventionally uniaxial or biaxial retarders are usually prepared through uniaxial or biaxial stretching of polymer films (for example, polycarbonate or polyvinylalcohol). Liquid crystalline monomers and polymers can also be used for the preparation of birefringent films as described by D. J. Broer, J. Boven, G. N. MoI and G. Challa: makromol.Chem. 1990 (1989) 2255. Differences found in the tilt angles are related to the chemical structures of the compounds. There is still always a demand for the provision of new birefringent layer with specific large or low tilted optical axis depending on their envisaged use.

In the present invention a method for the preparation of a birefringent layer of C-plate and O-plate type, preferably positive C-plate and O-plate type, comprising polymerizing a composition, comprising one or more liquid crystal of formula (I)

wherein A₁ and A₂ denote independently from each other a polymerisable organic residue, Z₁ and Z₂ are independently from each other -CH(OH)-, -CO-, -0-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-, -N=N- or a single covalent bond; preferably, -COO-, -OCO-, -OCOO-, more preferably -COO- and -OCO-,

R₁, R₂, R₃, R₄, R₅ and R₆ are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -d-doalkyl, -NO2, -CN or halogen; preferably R₁, R₂, R₃, R₄, R₅ and R₆ are hydrogen, R₇ IS CrC₂oalkyl or d-C₂oalkenyl, wherein any -CH₂-group of d-C₂₀alkyl or CrC₂₀alkenyl may be replaced independently from each other by -0-, -COO- or -CO-, with the proviso that -O-, -COO- and/or -CO- are not linked together, preferably d-C₂oalkyl is CrC^alkyl, more preferably d-C₆alkyl and most preferably methyl, ethyl or propyl, and especially most preferred is methyl; preferably d-C₂₀alkenyl is d-C₁₂alkylen, more preferably d-C₆alkylen; and at least one organic compound, having a terminal polar group, was found. In the context of the present invention 'O plate' refers to an optical retarder utilizing a layer of birefringent material with its optical axis oriented at an oblique angle with respect to the plane of the layer.

In the context of the present invention 'C plate' refers to an optical retarder utilizing a layer of birefringent material with its optical axis perpendicular to the plane of the layer. 'Positive c-plate' refers to positively birefringent c-plates, i.e. c-plates with a positive An, where Δn is defined as the difference between the extraordinary and the ordinary index of refraction, i.e. An=n_e-n₀ . The organic compound, having a terminal polar group, may be a liquid crystal. In the context of the present invention the terms 'alkyl' and 'alkylen' and 'alkenyl' comprise branched or straight chain alkyl, respectively alkylen groups and are unsubstituted, mono- or polysubstituted by alkyl, aryl, cycloalkyl, amino, cyano, epoxy, halogen, hydroxyl, nitro, especially by F, Cl, Br, I or CN. Alternatively or in addition one or more of CH₂ groups present in the hydrocarbon chain may be replaced, independently, by one or more groups selected from -O-, -S-, -NH-, N(CH₃)-,

-CH(OH)-, -CO-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -C≡C-, -(CF₂)_r1-, -(CH₂)_S1- or C(W₁J=C(W₂)-, with the proviso that two oxygen atoms are not directly linked to each other. W₁ and W₂ each represent, independently, H, H-(CH₂)_q2- or Cl. The integer r1 , s2 and q2 each independently represent a number of between 1 and 15.

In the context of the present invention CrC₄₀alkyl denotes especially Ci-C₃₀alkyl, preferably Ci-C₂oalkyl, more preferably d-Ci₆alkyl, most preferably CrC^alkyl and especially most preferably C_rC₆alkyl. Accordingly alkylen is for example Ci-C₄₀alkylen, especially Ci-C₃₀alkylen, preferably C_rC₂oalkylen, more preferably C_rC₁₆alkylen, most preferably Ci-Cioalkylen and especially most preferably Ci-C₆alkylen. Accordingly alkenyl is for example Ci-C₄oalkenyl, especially Ci-C₃₀alkenyl, preferably CrC₂oalkenyl, more preferably C_rC₁₆alkenyl, most preferably Ci-C₁₀alkenyl and especially most preferably Ci-C₆alkenyl. In the context of the present invention the aromatic, carbocyclic or heterocyclic group is for example unsubstituted or mono- or poly-substituted. Preferred substitutents of carbocyclic or heterocyclic aromatic groups are at least one halogen, hydroxyl, a polar group, acryloyloxy, alkylacryloyloxy, alkoxy, alkylcarbonyloxy, alkyloxycarbonyloxy, alkyloxocarbonyloxy, methacryloyloxy, vinyl, vinyloxy and/or allyloxy group, wherein the alkyl residue has preferably from 1 to 20 carbon atoms, and more preferably having from 1 to 10 carbon atoms. Preferred polar groups are nitro, cyano or a carboxy group, and/or a cyclic, straight-chain or branched Ci-C₃₀alkyl, which is unsubstituted, mono- or poly-substituted. Preferred substitutents of C^Csoalkyl are methyl, fluorine and/or chlorine, wherein one or more, preferably non-adjacent, -CH₂- group may independently of each other be replaced by a linking group. Preferably, the linking group is selected from -O-, -CO-, -COO- and/or -OCO-.

A monocyclic ring of five or six atoms is for example furan, benzene, preferably phenylene, pyridine, pyrimidine. A bicyclic ring system of eight, nine or ten atoms is for example naphthalene, biphenylene or tetraline.

A tricyclic ring system of thirteen or fourteen atoms is for example phenanthrene.

In the context of the present invention the term "phenylene", preferably denotes a 1 ,2-,

1 ,3- or 1 ,4-phenylene group, which is optionally substituted. It is preferred that the phenylene group is either a 1 ,3- or a 1 ,4-phenylene group. 1 ,4-phenylene groups are especially preferred.

Preferably, a polymerisable organic residue is of formula (III)

P-(Sp)_k-(X)_t - (III)

wherein:

P is a polymerizable functional group having an unsaturated carbon-carbon bond selected from groups comprising norbornene, vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, allyl triazine, allyl isocyanurate, alkene, alkyne, acrylate, unsaturated ester, imides, maleimide, methacrylate, acrylonitrile, styrene, diene, vinyl amide and allylamide; preferably P is acrylate or methacrylate, Sp is an unsubstituted or substituted straight chain or branched C_{1 30}alkylene group, in which one or more -CH- groups may be replaced by a heteroatom and/or one or more carbon-carbon single bond(s) is/are replaced by a carbon- carbon double or a triple bond, and/or is replaced by at least a substituted or unsubstituted aromatic, carbocyclic or heterocyclic group, k is an integer having a value of from O to 1 , X is -O-, -S-, -NH-, -N(CH₃)-, -CH(OH)-, -CO-, -CH₂(CO)-, -SO-, -CH₂(SO)-,

-SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH2O-, -CH=CH-, -C≡C-, or a single bond, preferably X is -0-, -COO-, -OCO- or -OCO-O-, t is an integer having a value of O or 1.

Preferably, alkylene denotes the correspondent definitions as given for alkyl above.

In the context of the present invention the term 'heteroatom' denotes for example to nitrogen, oxygen or sulfur atom.

In the context of the present invention the term "halogen" denotes a chloro, fluoro, bromo or iodo substituent, preferably a chloro or fluoro substituent.

More preferably, a polymerisable organic residue is of formula (III) wherein:

P is a polymerizable functional group having an unsaturated carbon-carbon bond selected from groups comprising vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, alkene, alkyne, acrylate and methacrylate; preferably,

P is acrylate and methacrylate; Sp is an unsubstituted or substituted straight chain or branched C_{1 20}alkylene group, in which one or more -CH- groups may be replaced by a heteroatom, such as -0-, preferably, Sp is an unsubstituted straight chain C^alkylene group, more preferably, Sp is an unsubstituted straight chain C^^alkylene group, k is 1 ,

X is -0-, -COO-, -OCO-, -OCO-O-, or a single bond; preferably X is -OCO-O-, t is 1.

More preferably, the present invention relates to method for the preparation of a birefringent layer of C-plate and O-plate type by polymerising a liquid crystal of formula (Ia)

(Ia), wherein

R⁸ is Ci-C₆alkyl, wherein any -CH₂-group of Ci-C₆alkyl may be replaced independently from each other by -O-, -COO-, -OCO- or -CO-; preferably by -COO-, -OCO-; with the proviso that -0-, -COO-.-OCO-; and/or -CO- are not linked together, preferably Ci-

C₆alkyl is methyl, ethyl or propyl, more preferably methyl or ethyl or propyl.

R⁹ is methyl or hydrogen, and n is an integer from 2 to 12, preferably an integer 4, 5, 6, 7 or 8.

Most preferably, the present invention relates to method for the preparation of a birefringent layer of C-plate and O-plate type by polymerising a liquid crystal of formula (Ib)

(Ib). Preferably, the organic compound, having a terminal polar group is of formula (II)

(P¹WC⁴-Z⁴) a4 -Sp¹- (Z¹-C¹)_aT- (Z²-C²) a2 -(Z³-C³) a3 polar group

(M) wherein the polar group is nitro, cyano, halogen, -OCOOR or -OCOR¹⁰, -COOR¹⁰, -OR¹⁰ and preferably cyano, wherein

R¹⁰ is hydrogen or CrC_∑oalkyl, which is unsubstituted or substituted with halogen, preferably Br, Cl or F and more preferably with F; preferably, R¹⁰ is hydrogen or

Ci-Ci₂alkyl, which is unsubstituted or substituted with halogen, preferably Br, Cl or F and more preferably with F; more preferably R¹⁰ is hydrogen or d-C₆alkyl , which is unsubstituted or substituted with halogen, preferably Br, Cl or F and more preferably with F; and most preferably R¹⁰ is methyl or OCF₃;

C to C⁴are independently from each other substituted or unsubstituted non-aromatic, aromatic, carbocyclic or heterocyclic groups, Z¹ to Z⁴ are independently from each other -CH(OH)-, -CO-, -CH₂(CO)-, -SO-,

-CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -0-, -OCOO-, -COCF₂-,

-CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-,

-N=N- or a single covalent bond, preferably, Z¹ to Z⁴ are independently from each other -COO-, -OCO-, -0-, -OCOO-, or a single covalent bond,

P¹ is a polymerizable functional group having an unsaturated carbon- carbon bond selected from groups comprising vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, alkene, alkyne, acrylate and methacrylate; preferably,

P¹ is acrylate and methacrylate; x of (P)_x is an integer from O to 4, preferably O to 3 and more preferably 1 or 2,

Sp^{1 is} an unsubstituted or substituted straight chain or branched C^alkylene group, in which one or more -CH- groups may be replaced by a heteroatom, such as -0-; preferably, Sp¹ is an unsubstituted or substituted straight chain or branched

C^alkylene group, more preferably, Sp¹ represents a C_4-11 unsubstituted or substituted straight chain or branched alkylene group, especially ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene or undecylene a_r a_2i a₃and a₄ are independently from each other integers from O to 3, such that 1 ≤

4.

The term "polar group", preferably denotes -NO₂₁-CN, -F, -Br, Cl, -I, -OCOO-, -OOCO-, -OCO-, -COO-, -CO-; OCrCealkyl, more preferably, -OCH₃, OCF₃.

Preferably, C¹ to C⁴ are selected from:

wherein:

L is -CH3, -COCH3, -NO2, -CN or halogen, u1 is 0, 1, 2 u2 is 0, 1, 2 u3 is 0, 1 or 2,

P is 0, 1 or 2.

More preferably, C to C⁴ are selected from:

wherein L, u1 , u2, u3 or p have the same meaning as given above.

Most preferably C¹ to C⁴ are selected from: .

wherein L, u1 or p have the same meaning as given above.

Preferably, Z¹ , Z², Z³ and Z⁴ represent independently from each other -O-, -COO-, -OCOO-, -OCO-, -CH2-CH2-, -OCH2-, -CH2O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single covalent bond.

More preferably, Z¹ , Z², Z³ and Z⁴ represent independently from each other -O-, -COO-, -OCO-, -OCOO-, -CH=CH-COO-, -OCO-CH=CH- or a single covalent bond.

Most preferably, Z¹ , Z², Z³ and Z⁴ represent independently from each other -O-, -COO-, -OCO-, a single covalent bond -or OCOO-.

Preferably, the organic compound, having a terminal polar group is of formula (Ma)

wherein P¹ , C⁴, x, Z¹ to Z⁴ and polar group have the same meanings and preferences as given above, and a2, a3 and a4 are independently from each other O or 1.

More preferably, the organic compound denotes formula (Mb)

(lib) wherein P¹ , C⁴, x, Z² to Z⁴ and polar group have the same meanings and preferences as given above, and a4 and a3 are independently from each other 0 or 1 , or the organic compound , having a terminal polar group is of formula (lie)

wherein P¹, C⁴, x, Z² to Z⁴ and polar group have the same meanings and preferences as given above, and a4 is 0 or 1.

Especially, most preferably, the organic compound, having a terminal polar group is of formula (Md)

(lid) wherein P¹, C⁴, x, Z³ and Z⁴ and polar group have the same meanings and preferences as given above, and a4 is 0 or 1 , preferably Z³ is -O- or -OCOO-, or the organic compound, having a terminal polar group is of formula (lie)

wherein P¹ , C⁴, x, Z³ and Z⁴ and polar group have the same meanings and preferences as given above, and a4 is O or 1 , preferably Z³ is -O- or -OCOO-, or the organic compound, having a terminal polar group is of formula (lid)

wherein P¹ , C⁴, x, Z³ and Z⁴ and polar group have the same meanings and preferences as given above, and a4 is 0 or 1 , preferably Z³ is -O- or -OCOO-

More especially most preferably, the organic compound denotes formula (Hg)

(iig) wherein R^{1 1} is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or

-OCOO-, and Z⁴ is -O- or -COO- or -OCO-, preferably Z⁴ is-COO-; or the organic compound, having a terminal polar group is of formula (Hh)

wherein R¹² is methyl or hydrogen and Z³ is -O- or -OCOO-, or the organic compound, having a terminal polar group is of formula (Mi)

(Hi) wherein R¹³ is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or

-OCOO-, and Z⁴ is -O- or -COO- or -OCO-, preferably Z⁴ is -COO-; or the organic compound, having a terminal polar group is of formula (Mj)

wherein R¹⁴ is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or

-OCOO-, or the organic compound, having a terminal polar group is of formula (Ilk)

wherein R¹⁵ is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or -OCOO-, or the organic compound, having a terminal polar group is of formula (Mm)

wherein R¹⁶ is methyl or hydrogen, Z³ is -O- or -OCOO-. A preferred embodiment of the invention relates to a method for the preparation of a birefringent layer of C-plate and O-plate type comprising polymerizing a composition comprising one or more liquid crystal of formula (Ia)

(Ia), wherein

R⁸ is Ci-C_βalkyl, wherein any -CH₂-group of Ci-C₆alkyl may be replaced independently from each other by -O-, -COO- or -CO-, with the proviso that -O-, -COO- and/or -CO- are not linked together, preferably d-Cealkyl is methyl, ethyl or propyl, more preferably methyl,

R⁹ is methyl or hydrogen, and n is an integer from 2 to 12, preferably an integer 4, 5, 6,

7 or 8, and at least one organic compound, which denotes to any of formulae (Mg) to (Mm).

More preferred the present invention relates to a method for the preparation of a birefringent layer of C-plate and O-plate type comprising polymerizing a composition comprising a liquid crystal of formula (Ib)

(Ib) at least one organic compound, having a terminal polar group, which denotes to any of formulae (Hn), (Mo), (Mp) or (Mq)

(Hn), wherein n is an integer from 1 to 11 , preferably an integer from 4 to 11 and R >17 is methyl or hydrogen, or

wherein n is an integer from 1 to 10, preferably an integer from 3 to 10 and more preferably n is 4, and R¹⁸ is methyl or hydrogen, or

wherein n is an integer from 1 to 10, preferably an integer from 3 to 10 and more preferably n is 4, and R¹⁹ is methyl or hydrogen, or

wherein n is an integer from 1 to 10, preferably an integer from 3 to 10 and more preferably n is 4, and R²⁰ is methyl or hydrogen,

or

wherein n is an integer from 1 to 10, preferably an integer from 3 to 10 and more preferably n is 4, and R²¹ is methyl or hydrogen, or

wherein n is an integer from 1 to 10, preferably an integer from 3 to 10 and more preferably n is 4, and R 22 is methyl or hydrogen.

In a preferred embodiment of the invention the method comprises photo-polymerizing of the composition according to the invention.

Optionally, the photo-polymerization may be conducted without a photoinitiator in a manner analogous to that described by Bowman where special UV light sources with strong emissions ( Bowman et. at. Macromolecules 2002, 35, 5361-5365) and with use of maleimides as described in EP0618237.

Conventionally, a lamp is used for photo-polymerization. The intensity of the lamp used for the irradiation should be preferably higher than 5 mW/cm2, most preferably higher than 50 mW/cm². Most likely the polymerization may be initiated by most any actinic light source. Conventionally, polymerization is accomplished at ordinary room temperature conditions. A class of actinic light useful herein is ultraviolet light and other forms of actinic radiation which are normally found in radiation emitted from the sun or from artificial sources such as Type RS Sunlamps, carbon arc lamps, xenon arc lamps, mercury vapor lamps, tungsten halide lamps and the like.

Usually, the light used for photo-polymerization is at least partially linearly polarized, elliptically polarized, such as for example circulary polarized, or non-polarized, most preferably circulary polarized, or non-polarized light exposed obliquely, or at least partially linearly polarized light, especially most preferred is the use of non-polarized light. The liquid crystal polymer can also be polymerized by electron beam (EB).

Customary, the method of the invention is conducted by applying the liquid crystal (I) and an organic compound, having a terminal polar group on a substrate and then polymerizing, preferably crosslinking, by using UV light to give a cross-linked liquid crystalline polymer (LCP) layer, respectively birefringent layer according to the invention.

The liquid crystal (I) and the organic compound may be applied together as a composition or seperately.

The both components, the liquid crystal (I) and the organic compound, can be stored together as a mixture or stored in separately, for example in two bottles. This storage may be of advantage if the ratio of liquid crystal (I) to the organic compound has to be adjusted according to manufacturing conditions.

In general, transparent substrates such as glass or plastic substrates, optionally coated with indium tin oxide (ITO) are used. For the preparation of birefringent layers, it is particularly important to avoid the formation of defects or inhomogeneties. Thus preferred substrates include glass or plastic, especially those including a layer of rubbed polyimide or polyamide or a layer of photo-oriented photopolymers (LPP). Said layers are used to allow uniform orientation of the liquid crystalline mixture. Uniform orientation can also be achieved by other methods known in the art. The present invention also relates to the composition used in the method of the invention: A composition comprising a liquid crystal of formula (I)

wherein

Ai and A₂ denote independently from each other a polymerisable organic residue, Z₁ and Z₂ are independently from each other -CH(OH)-, -CO-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-,

-CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-, -N=N- or a single covalent bond; preferably, -COO-, -OCO-, -OCOO-, more preferably -COO- and -OCO-, Ri, R2, R3, R₄, R5 and R₆ are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -Ci-C_4Oalkyl, -NO2, -CN or halogen; preferably Ri, R₂, R₃, R₄, R5 and R₆ are hydrogen,

R₇ is Ci-C₂oalkyl or Ci-C₂₀alkenyl, wherein any -CH₂-group of C^C^alkyl or CrC^alkenyl may be replaced independently from each other by -0-, -COO- or -CO-, with the proviso that -0-, -COO- and/or -CO- are not linked together, preferably Ci-C₂₀alkyl is Ci-Ci₂alkyl, more preferably Ci-C₆alkyl and most preferably methyl, ethyl or propyl, and especially most preferred is methyl; preferably

and at least one organic compound, having a terminal polar group.

The liquid crystal (I) and the organic compound used in the composition denotes the same meaning and preferences as described above in the method according to the invention.

Especially most preferred composition comprising a liquid crystal of formula (I)

and at least one organic compound, having a terminal polar group of the below given formula

The compounds of the invention may be readily prepared using methods that are well known to the person skilled in the art, such as those documented in Houben-Weyl, Methoden der Organischen Chemie, Thieme-Verlag, Stuttgart.

The composition may comprise further components, such as a reactive or non-reactive additives, and/or a solvents.

The term "reactive additive" as used in the context of the present invention denotes a polymerizable reactive additive, with at least a single polymerizable group.

The term "non-reactive additive" as used in the context of the present invention denotes an additive, which does not have a polymerizable group.

Preferably, the polymerizable functional group comprises an unsaturated carbon- carbon bond, which is preferably selected from the group of compound residues comprising norbomene, alkyne, vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, allyl triazine, ally isocyanurate, alkene, acrylate, unsaturated ester, imides, maleimide, methacrylate, acrylonitrile, styrene, diene and vinyl amide; and more preferably, the polymerizable functional group having an unsaturated carbon-carbon bond is selected from the group of compound residues comprising alkyne, alkene, vinyl ether, vinyl ester, allyl ether, allyl ester, acrylate and methacrylate, and most preferably, the polymerizable functional group having an unsaturated carbon-carbon bond is selected from the group of compound residues comprising acrylate and methacrylate.

For example reactive additive is a cross-linker, a reactive diluent, a mono-reactive liquid crystal.

Further, reactive and non-reactive additives are for example selected from the below listed group of additives, which carry at least one polymerizable group: antioxidants, accelerators, dyes, inhibitors, activators, fillers, chain transfer inhibitor, pigments, antistatic agents, flame-retardant agents, initiator, thickeners, thixotropic agents, nonvolatile surface-active agents, viscosity modifiers, extending oils, plasticizers, tackifiers, catalysts, sensitizers, stabilizers, lubricating agents; dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, auxiliaries, colorants, dyes and pigments.

The term "mono-reactive liquid crystal" as used in the context of the present invention denotes a liquid crystal having a single polymerizable functional group, preferably an unsaturated carbon-carbon bond. The unsaturated carbon-carbon bond preferably comprises double and/or triple bonds, and more preferably double bonds. Preferably, the reactive additive has at least a single, preferably two polymerizable functional groups. Preferred are polymerizable functional groups having an unsaturated carbon-carbon bond, especially acrylate or methacrylate groups. Cross-linkers are well known to the skilled person. Suitable compounds are described e.g. in patent publications EP 0 331 233, WO 95/24454, US 5,567,349, US 5,650,534, WO 00/04110, WO 00/07975, WO 00/48985, WO 00/55110 and WO 00/63154.

The composition is solid, or diluted in a solvent, which is an organic solvent and/or water, as a solution, gel, dispersion or emulsion.

Examples of solvents (depending on the solubility of the liquid crystal) are cyclopentanone (CP), anisole (AN), cyclohexanone (CH), 2-butanoe, methyl isobutyl ketone (MIBK), 1-methoxy-2-propanol acetate (MPA), N,N-dimethylformamide (DMF), dichloromethane, gamma-butyrolactone, 2,6-Di-t-butyl-4-kresol, Butyl-hydroxy-toluol, BHT) or mixtures thereof.

The amount of the reactive or non reactive additives in the composition is limited by the liquid crystal phase of the composition, which has to be preserved. Conventionally, the reactive or non reactive additives have an amount of 0.1 to 50% by weight of the composition, preferably an amount of 1 to 30% by weight, even more preferably an amount of 1 to 10 % by weight.

In case the compositions of the invention comprise a stabilizer, the latter is generally present in an amount of 0.01 to 5% by weight of the composition, preferably in an amount of 0.1 to 1% by weight. The compositions according to the invention can be used to form birefringent layers, preferably birefringent films or networks.

In addition, the present invention relates to a birefringent layer, preferably of C-plate or O-plate type, comprising a compound of formula (I), as described above within all preferences given, and at least one organic compound, having a terminal polar group, as described above within all preferences given.

Further, the present invention relates to birefringent layer of O-plate and C-plate type, preferably of positive C-plate type, prepared by the methods according to the invention.

In addition, the present invention relates to the use of an O-plate and C-plate retarder according to the present invention for the manufacture of optical or electro-optical components.

In addition, the present invention concerns optical or electro-optical components comprising birefringent layers of O-plate and/or C-plate types according to the invention.

A further embodiment of the present invention relates to the use of an optical or electro-optical component according to the invention. Preferably optical or electro-optical components are compensation and retardation films (for viewing angle, color shift, contrast, gray level stability, brightness) for twisted nematic liquid crystal displays, hybrid aligned nematic liquid crystal displays, parallel cell liquid crystal displays, known as electrically controlled birefringence (ECB) liquid crystal displays, STN LCDs (supertwisted nematic liquid crystal displays), OCB LCDs (optically compensated birefringence liquid crystal displays), also known as pi-cell liquid crystal displays, IPS LCDs (in-plane switching liquid crystal displays), FFS LCD (fringe field switching liquid crystal display) MVA LCD (multidomain vertically aligned liquid crystal display), reflective LCD, transflective LCD (liquid crystal display comprising transmissive and reflective picture elements) and all further types of projection and direct view applications. The birefringent layer according to the invention can be used in the manufacture of devices such as waveguides, optical gratings, filters, retarders, polarizers, piezoelectric cells or thin films exhibiting non-linear optical properties. The present invention concerns devices comprising optical or electrooptical components according to the present invention or comprising a birefringent layer according to the present invention.

A further embodiment of the present invention relates to devices comprising an optical or electro-optical component, preferably compensation and retardation films according to the invention for: multi-domain (e.g. transflective liquid crystal displays) compensation: birefringent compensation film optionally with patterned properties according to the laterally varying properties of the device to be compensated, component of multiview liquid crystal displays: compensation or retardation film as a component of a display providing different images for different viewing angles, component of three-dimensional liquid crystal displays: compensation or retardation film used as a component of a liquid crystal display providing three-dimensional image information, achromatic retarder: retarder film which in contrast to a simple chromatic retarder provides for a similar change in polarization state for a broader wavelength band, in particular the whole visible wavelength spectrum, polarization state correction / adjustment films: birefringent films which are used to correct or adjust the polarization state with the goal to enable the function or improve the performance of an optical device, component of polarization sensitive/selective sensors, component of brightness enhancement film, security devices or decorative optical devices.

A further embodiment of the present invention relates to devices comprising a polarizer with an anisotropic absorber, which comprises an optical or electro-optical component, preferably compensation and retardation films.

Preferably the polarizer with an anisotropic absorber is a thin film polarizer, in-cell polarizer, a security device or a decorative optical device.

A further embodiment of the present invention relates to devices comprising a reflective circular polarizer, which comprises an optical or electro-optical component, preferably compensation and retardation films .

Preferably the reflective circular polarizer is a brightness enhancement film, a security device or a decorative optical device.

A further embodiment of the present invention relates to devices comprising a reflective linear polarizer, which comprises an optical or electro-optical component, preferably compensation and retardation films.

Preferably the reflective linear polarizer is a brightness enhancement film, a security device or a decorative optical device. A further embodiment of the present invention relates to a beam steering device, which comprises an optical or electro-optical component, preferably compensation and retardation films for wavefront adjustment devices.

More preferably, the present invention relates to a method for the preparation of a birefringent layer of C-plate or O-plate type with highly tilted optical axis, preferably in the range of 20 to 90°tilt average.

A further embodiment of the present invention relates to a method of adjusting, preferably gradually adjusting, the average tilt of a liquid crystal, preferably a liquid crystal of formula (I), as described above and within all preferences given above, by bringing the liquid crystals into contact with organic compound having a terminal polar group, as described above and within all preferences given above. In addition, the present invention relates to a method for the manufacturing of a birefringent layer, preferably of C-plate or O-plate type, comprising adjusting the tilt of a liquid crystal of formula (I), as described above and within all preferences given above, by bringing the liquid crystal into contact with an organic compound having a terminal polar group, as described above and within all preferences given above. The average tilt angle θ_ave is defined as follows d θ_ave = ∑ θ^' (d') ^^ ' d wherein θ^' (d¹) is the local tilt angle at the thickness d' within the film, and d is the total thickness of the film.

Preferably, the average tilt of a liquid crystal is gradually adjusted by bringing into contact the liquid crystal with proportions of the organic compound having a terminal polar group.

The liquid crystal and the organic compound are mixed together and then formulated for the preparation of a birefringent layer, or they are formulated seperatly and then these both formulations are mixed together in a certain ratio to end up at a final formulation which is used to prepare the birefringent film. The ratio of the two - formulations enables to adjust the average tilt of the optical axis within birefringent layer. The formulations usally comprise solvents, such as and additives, such as reactive and non-reactive additives especially photoinitiators and surface active additives. The term "formulation" denotes the same meaning and preferences as given for the term "composition" above. The advantage of the invention is based on the adjustability of the average tilt for a given basic liquid crystal formulation. This is favorable if the tilt profiles have to be adaptable for the desired application or if there are restrictions in the manufacturing conditions. The proportion of the additional organic compound having a terminal polar group according to the invention allows to gradually adjust the tilt angle of the LC molecules at both the interface to the alignment layer and the opposite interface.

EXAMPLES

Preparation of 4'-cyano-1 ,1 '-biphenyl-4-yl 4-({[4-(acryloyloxy)butoxy]carbonyl}oxy) benzoate

13,0 g (42.0 mmol) of 4-({[4-(acryloyloxy)butoxy]carbonyl}oxy)benzoic acid, 10 drops of DMF, 6.0 ml ( 63.0 mmol) of thionylchloride are suspended in 50 ml Toluene After 1.5h at reflux temperature, toluene and the excess of thionylchloride is remove by rotary evaporation. The brownish oil residue is dissolved in 50 ml of THF, tetrahydrofuran, and is added dropwise to a solution of 7.38 g (37.8 mmol) 4'-hydroxy- 1-1 '-biphenyl-4-carbonitrile, 11 ,7 ml (84.0 mmol) triethylamine, 260 mg (2.1 mmol) 4- Dimethylaminopyridine in 50 ml THF at 0°C.The reaction mixture was stirred at 60 ⁰C for 18h. After cooling at room temperature the reaction mixture is filtered over Celite. The Celite cake is washed with 200 ml Ethyl acetate. 200 ppm inhibitor 2,6-di-tert.- butyl-4-methylphenol (BHT) is added and the filtrate is concentrated by rotary evaporation. Chromatography of the residue on 1 kg silica gel using toluene:ethyl acetate 9:1 as eluant and crystallization from ethyl acetate and hexane 1 :1 yield 4.6 g as off-white crystals. Crystalline 91.4^oC N >200^oC N (nematic).

Example 1 / Film preparation

The commercially available photo-alignment material (Rolic® ROP-103 is a linearly photopolymerisable polymer (LPP) commercially available from Rolic Technologies Ltd, Switzerland) was used for the preparation of the photo-alignment layer. This photo-alignment polymer is based on cinnamate as photo-reactive groups. The polymer backbone of the photo-alignment material is of acrylate type. For the spin- coating of the alignment layer onto the substrate the ROP-103 was dissolved in 2- butanone at a solid concentration of 2 weight percent. The solution is stirred for 30 minutes at room temperature.

Then a LCP mixture A is prepared of the following components in anisole 70 Wt % Of

is accessible in analogy with the general procedure described in Hikmet RAM.; Zwerver B.H.; Lub J. Macromolecules, 1994, 27, 6722 and 1995, 28, 3313; 30 wt % of

Further, 2000 ppm inhibitor 2,6-di-tert.-butyl-4-methylphenol (BHT) is added to prevent premature polymerisation. For the radical photo-polymerisation 10000 ppm of a photoinitiator is added (Irgacure™ 819, commercially available from Ciba Geigy, Basle, Switzerland). The mixture is stirred at room temperature for 30 minutes.

Then the above prepared mixture is spin-coated at 2000 rpm onto a clean glass plate, which were then dried for 30 minutes at 130^cC.

Subsequently, the substrate is exposed (30 mJ/cm²) to the linearly polarized ultraviolet light of a 200W high pressure mercury lamp at an inclination of 45° from the substrate normal to obtain a photo-aligned orientation layer. For the exposure, the polarization axis of the uv-light is within the plane defined by the direction of incidence and the substrate normal.

Subsequently, the LCP solution is spincoated at 1200 rpm for 60 s on top of the substrate with the orientation layer to form a layer of about 1000 nm. This film is dried at 80⁰C for 2 minutes and photo-polymerised by irradiation with UV light using a Mercury lamp (1 J/cm²) at room temperature under N₂ atmosphere. When the resulting film is arranged between crossed polarizers it appeared dark for any angle of orientation as long as it is observed from the vertical. However, when looked at large polar angles and at 45° azimuth the film appeared grey. This observation indicates that the molecules in the film were aligned homeotropic.

From ellipsometric evaluation of the film the above conclusion is confirmed. The tilt angle at the substrate-film interface is determined to 88° relative to the plane of the substrate and the tilt angle at the film-air interface is 89°. Example 2

A second LCP mixture B of the following components in anisole was prepared

70 wt % of

30 wt % of

prepared according to WO 00/63154

Further 2000 ppm inhibitor BHT and 10000 ppm Irgacure™ 819 is added. The mixture is stirred at room temperature for 30 minutes and then spincoated on a substrate with an orientation layer prepared as in example 1 , to form a layer of ca. 1000 nm. This film is dried at 8O⁰C for 2 minutes and photo-polymerised by irradiation with UV light using a Mercury lamp (5OmW/"¹² and 1 J/cm²) at room temperature under N₂ atmosphere. Again the visual inspection between crossed polarizers indicated homeotropic orientation which is further confirmed by ellipsometric evaluation.

As a result, the tilt angle at the substrate-film interface is determined to 88° relative to the plane of the substrate and the tilt angle at the film-air interface is 89°.

Example 3/ Gradually adjustable tilt

A 50% by weight LCP mixture (I) in anisol, which contains: a) 78.4% by weight of component A

A in and b) 18.6 % by weight of component B

B is accessible in analogy with the general procedure described in Hikmet RAM.; Zwerver B.H.; Lub J. Macromolecules, 1994, 27, 6722 and 1995, 28, 3313; and c) 0.98% by weight of Tinuvin^® 123 (commercially available from Ciba Specialty Chemicals) d) 0.98% by weight of Irgacure^® 369 (commercially available from Ciba Specialty Chemicals) e) 0.98% by weight of BHT( 2,6-Di-t-butyl-4-kresol;Butyl-hydroxy-toluol, commercially available from Fluka) and

is stirred at room temperature for 30 minutes and then spincoated on a substrate with an orientation layer prepared as in example 1 , to form a layer of ca. 1000 nm. This film is dried at 8O⁰C for 2 minutes and photo-polymerised by irradiation with UV light using a Mercury lamp (50mW/^m2 and 1 J/cm²) at room temperature under N₂ atmosphere. As a result, the tilt angle is 63°. The following 7 LCP mixtures were prepared with the same procedure and the same components as described above for the LCP mixture (I) with the proviso that the proportions of components A and B are varied. The resulted average tilt angles are shown in the below given table.:

It is shown in the table that in dependence from the concentration of the organic compound A having a terminal polar group the tilt angle is adjustable.

Claims

1.) Method for the preparation of a birefringent layer of C-plate and O-plate type comprising polymerizing a composition, comprising one or more liquid crystal of formula (I)

wherein

Ai and A₂ denote independently from each other a polymerisable organic residue, Z₁ and Z₂ are independently from each other -CH(OH)-, -CO-, -0-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-, -N=N- or a single covalent bond; R₁, R_2> R_3> R₄, R5 and R₆ are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -CrC₄oalkyl, -NO2, -CN or halogen;

R₇ is C₁-C_2OaIKyI or d-C^alkenyl, wherein any -CH₂-group of C_rC₂oalkyl or C₁-C₂oalkenyl may be replaced independently from each other by -O-, -COO- or -CO-, with the proviso that -O-, -COO- and/or -CO- are not linked together, and at least one organic compound, having a terminal polar group.

2.) Method according to claim 1 , wherein the polymerisable organic residue is of formula (III)

P-(Sp)_k-(X)_t - (III)

wherein:

P is a polymerizable functional group having an unsaturated carbon-carbon bond selected from groups comprising norbomene, vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, allyl triazine, allyl isocyanurate, alkene, alkyne, acrylate, unsaturated ester, imides, maleimide, methacrylate, acrylonitrile, styrene, diene, vinyl amide and allylamide;

Sp is an unsubstituted or substituted straight chain or branched C_{1 30}alkylene group, in which one or more -CH- groups may be replaced by a heteroatom and/or one or more carbon-carbon single bond(s) is/are replaced by a carbon- carbon double or a triple bond, and/or is replaced by at least a substituted or unsubstituted aromatic, carbocyclic or heterocyclic group, k is an integer having a value of from 0 to 1 , X is -O-, -S-, -NH-, -N(CH₃)-, -CH(OH)-, -CO-, -CH₂(CO)-, -SO-, -CH₂(SO)-,

-SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, or a single bond, t is an integer having a value of O or 1.

3.) Method according to any of the preceeding claims, wherein the liquid crystal is of formula (Ia)

(Ia), wherein R⁸ is Ci-C₆alkyl, wherein any -CH₂-group of C_rC₆alkyl may be replaced independently from each other by -O-, -COO-, -OCO- or -CO-, with the proviso that -0-, -COO-, -

OCO- and/or -CO- are not linked together,

R⁹ is methyl or hydrogen, and n is an integer from 2 to 12.

4.) Method according to any of the preceeding claims, wherein the organic compound, having a terminal polar group, denotes formula

(P¹)_x-(C⁴-Z⁴)_a4 -Sp¹-(Z¹-C¹)_a— (Z²-C²)_a— (Z³-C³)_aTfpolar group

(H) wherein the polar group is nitro, cyano, halogen, -OCOOR¹⁰ or -OCOR¹⁰, -COOR¹⁰, -OR¹⁰ and, wherein

R¹⁰ is hydrogen or CrC₂oalkyl, which is unsubstituted or substituted with halogen,

C¹ to C⁴are independently from each other substituted or unsubstituted non-aromatic, aromatic, carbocyclic or heterocyclic groups,

Z¹ to Z⁴ are independently from each other -CH(OH)-, -CO-, -CH₂(CO)-, -SO-,

-CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -O-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃J=N-, -N=N- or a single covalent bond,

P¹ is a polymerizable functional group having an unsaturated carbon- carbon bond selected from groups comprising vinyl ether, vinyl ester, allyl ether, allyl ester, propenyl ether, alkene, alkyne, acrylate and methacrylate; x of (P)_x is an integer from O to 4, preferably O to 3 and more preferably from 1 and 2, and most preferably 2, Sp¹ is an unsubstituted or substituted straight chain or branched C_{1 20}alkylene group, in which one or more -CH- groups may be replaced by a heteroatom, a_r a_2i a₃and a₄ are independently from each other integers from O to 3, such that 1 ≤ a^ + a₂ + a₃ + a₄ ≤ 4.

5.) Method according to any of the preceeding claims, wherein C¹ to C⁴ are selected from:

wherein:

L is -CH₃, -COCH3, -NO2, -CN or halogen, u1 is 0, 1 , 2 u2 is 0, 1 , 2 u3 is 0, 1 or 2,

P is 0, 1 or 2. fO

6.) Method according to any of the preceeding claims, wherein the organic compound denotes formula (Ma)

(Ha)

wherein P¹ , C⁴, x, Z¹ to Z⁴ and polar group have the same meaning as described in claim 4, and a2, a3 and a4 are independently from each other 0 or 1 and n is an integer from 1 to 10.

7.) Method according to any of the preceeding claims, wherein the organic compound denotes formula (Hg)

(Hg) wherein R^{1 1} is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or -OCOO-, and Z⁴ is -O- or -COO- or -OCO-, or the organic compound denotes formula (Nh)

wherein R¹² is methyl or hydrogen and Z³ is -O- or -OCOO-, or the organic compound denotes formula (IN)

-OCOO-, and Z⁴ is -O- or -COO- or -OCO-, or the organic compound denotes formula (Mj)

wherein R¹⁴ is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or -OCOO-, or the organic compound denotes formula (Ilk)

wherein R¹⁵ is methyl or hydrogen, x is 1 or 2 and preferably 2, and Z³ is -O- or -OCOO-, or the organic compound denotes formula (Hm)

wherein R¹⁶ is methyl or hydrogen, Z³ is -O- or -OCOO-.

8.) A composition comprising a liquid crystal of formula (I)

wherein Ai and A₂ denote independently from each other a polymerisable organic residue,

Z₁ and Z₂ are independently from each other -CH(OH)-, -CO-, -0-, -CH₂(CO)-, -SO-, -CH₂(SO)-, -SO₂-, -CH₂(SO₂)-, -COO-, -OCO-, -OCOO-, -COCF₂-, -CF₂CO-, -S-CO-, -CO-S-, -SOO-, -OSO-, -SOS-, -CH₂-CH₂-, -OCH₂-, -CH₂O-, -CH=CH-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH-, -CH=N-, -CH(CH₃)=N-, -N=N- or a single covalent bond;

R₁, R₂, R₃, R₄, R5 and R₆ are independently from each other hydrogen, an aromatic, carbocyclic or heterocyclic group, -CrC^alkyl, -NO2, -CN or halogen; R₇ is Ci-C₂₀alkyl or Ci-C₂₀alkenyl, wherein any -CH₂-group of Ci-C₂oalkyl or CrC₂₀alkenyl may be replaced independently from each other by -O-, -COO- or -CO-, with the proviso that -0-, -COO- and/or -CO- are not linked together, and at least one organic compound, having a terminal polar group.

9.) Birefringent layers of O-plate and C-plate types comprising a liquid crystal of formula (I) and an organic compound having a terminal polar group according to claim 1 , or a birefringent layer prepared by the methods according to the claims 1 to 7.

10.) Use of birefringent layer of O-plate and C-plate types prepared according to claims 1 to 7 for the manufacture of optical or electro-optical components and devices.

11.) Optical or electro-optical components comprising birefringent layer of O-plate and C-plate types according to claim 10.

12.) Devices comprising a birefringent layer according to claim 9 or an optical or electro-optical component according to claim 10.

13.) Method of adjusting the average tilt of a liquid crystal by bringing a liquid crystal of formula (I) according to claim 1 into contact with an organic compound having a terminal polar group according to claim 1.

14.) Method for the manufacturing of a birefringent layer having an adjusted tilt, comprising adjusting the tilt of a liquid crystal of formula (I) according to claim 1 , by bringing the liquid crystal into contact with organic compound having a terminal polar group according to claim 1.