WO2021151846A1

WO2021151846A1 - Method for adjustment of alignment of liquid crystals

Info

Publication number: WO2021151846A1
Application number: PCT/EP2021/051650
Authority: WO
Inventors: Simon SIEMIANOWSKI; Izumi Saito; Martin STEINZER
Original assignee: Merck Patent Gmbh
Priority date: 2020-01-29
Filing date: 2021-01-26
Publication date: 2021-08-05
Also published as: TW202141147A

Abstract

A process for adjustment of the alignment director of a liquid-crystalline layer between a pair of substrates using UV radiation from an oblique angle. The process makes use of additives based on cinnamate structures and others. Suitable vertically aligning LC mixtures are disclosed.

Description

Method for adjustment of alignment of liquid crystals

The invention relates to a process for adjustment of the alignment director of a liquid-crystalline layer between a pair of substrates using UV radiation from an oblique angle. The process makes use of additives based on cinnamate structures. Suitable vertically aligning LC mixtures are disclosed.

Oblique UV radiation was used previously for the preparation of alignment layer materials on a substrate as in US 5,889,571 or US 2019/0129256 A1. US 2019/0113812 A1 reports the use of a mixture comprising cinnamate compounds for a photo-alignment process in combination with oblique and polarized UV irradiation. These methods were not applied to LC mixtures inside a liquid crystal cell. Further they did not intend to adjust the tilt of the liquid-crystalline phase.

Cinnamate based additives were previously also used for processes involving polarized UV irradiation for effecting a unidirectional planar alignment. WO 2017/102068 A1 discloses cinnamates as additives for the purpose of a polyimide-free homogeneous photoalignment method in combination with another polymerizable compound in a liquid-crystalline host mixture.

In contrast to the prior art, the current process does not need polarized UV, nor is it limited to planar alignment.

A number of display modes rely on surface pre-tilt in order to give a director geometry that can switch without generating defects. For example, conventional vertical alignment (VA) display, PS-VA displays and also STN displays. For a number of applications, and also from a general process point of view, it would be advantageous if pre-tilt could be generated without the need of applied electric fields. The viewing characteristics and the switching of commercial LC displays has been greatly improved by defining the pre-tilt of the liquid-crystalline layer. Tilt-generation is often desirable in aligned liquid-crystalline phases since a small pre-tilt can enhance the induced twisting of the director into the direction of the pre-tilt. In such situations the switching of an aligned liquid-crystalline phase by an external electrical field can be considerably faster than without any pretilt. Further, the change of director is much more uniform into one desired direction once a pre-tilt is introduced.

It is not trivial to generate pre-tilt. Currently the introduction of a pretilt requires a process using a combination of electrical field and induced polymerization, which requires at the same time suitable technical equipment and time for polymerization. This causes high cost in production lines. For example, in the case of the VA mode, usually an electrically induced tilt is used, whereby an electric field is applied to the cell electrodes during a concurrent polymerisation process to give a specified persistent level of pre-tilt. The same principle can be applied for planar alignment.

A more simple process is therefore desirable. For a number of applications, and also from a general process point of view, it would be advantageous if pre-tilt could be generated without the need of applied electric fields. Currently pretilt is often introduced by tilting the LC layer by the help of an electric field (e.g. on the existing electrodes) and simultaneously cross-linking a polymerizable additive (polymer supported alignment). The invention relates to a process for adjustment of the alignment director of a liquid-crystalline layer between a pair of substrates using UV radiation, wherein the liquid-crystalline layer comprises a liquid-crystalline mixture comprising component A) comprising one or more photoreactive mesogens of formula I,

^11 -CY¹²=CY¹²-C0-0-, -CY¹²=CY¹²- or -CY¹²=CY¹²-CO-,

A¹¹ denotes a group selected from the following: a) a group consisting of 1 ,4-phenylene and 1 ,3- phenylene, wherein, in addition, one or two CH groups may be replaced by N and wherein, in addition, one or more H atoms may be replaced by L, b) a group selected from the group consisting of

where, in addition, one or more H atoms in these radicals may be replaced by L, and/or one or more double bonds may be replaced by single bonds, and/or one or more CH groups may be replaced by N,

A have each, independently of one another, in each occurrence one of the meanings for A¹¹ or a) group consisting of trans-1 ,4-cyclohexylene, 1 ,4- cyclohexenylene, wherein, in addition, one or more non-adjacent CH₂ groups may be replaced by -0- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F, or b) a group consisting of tetrahydropyran-2,5-diyl,

1 ,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1 ,3-diyl, piperidine-1 ,4-diyl, thiophene-2, 5- diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L,

L on each occurrence, identically or differently, denotes -OH, -F, -Cl, -Br, -I, -CN, -N0₂, -SCN, -C(=0)N(R^z)₂, -C(=0)R^z, -N(R^z)₂, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight- chain or branched or cyclic alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, or X²¹-Sp²¹-R²¹,

M denotes -0-, -S-, -CH2-, -CHR^Z- or -CR^yR^z-,

R^y and R^z each, independently of one another, denote H, CN, F or alkyl having 1 -12 C atoms, wherein one or more H atoms may be replaced by F,

Y¹¹ and Y¹² each, independently of one another, denote FI, F, phenyl or optionally fluorinated alkyl having 1 -12 C atoms,

Z denotes, independently of each other, in each occurrence, a single bond, -COO-, -OCO-, -O-CO-O-, -OCH2-, -CH2O-, -OCF2-, -CF2O-, -(CH₂)n-,

-CF₂CF₂-, -CH=CH-, -CF=CF-, -CH=CH-COO-, -OCO- CH=CH-, -CO-S-, -S-CO-, -CS-S-, -S-CS-,

-S-CSS- or -CºC-, n denotes an integer between 2 and 8, o and p denote each and independently 0, 1 or 2,

X¹¹ and X²¹ denote independently from one another, in each occurrence a single bond, -CO-O-, -O-CO-, -O-COO-, -0-, -CH=CH-, -CºC-, -CF2-O-, -O-CF2-, -CF2-CF2-, -CH2-O-, -O-CH2-, -CO-S-, -S-CO-, -CS-S-, -S-CS-, -S-CSS- or -S-, Sp¹¹ and Sp²¹ denote each and independently, in each occurrence a single bond or a spacer group comprising 1 to 20 C atoms, wherein one or more non-adjacent and non- terminal Chh groups may also be replaced by -0-, -S-,

-NH-, -N(CH₃)-, -CO-, -0-C0-, -S-CO-, -0-C00-, -CO-S-, -C0-0-, -CF₂- -CF2O-, -OCF2- -C(OH)-, -CH(alkyl)-, -CH(alkenyl)-,-CH(alkoxyl)-, -CH(oxaalkyl)-, -CH=CH- or -CºC-, however in such a way that no two O-atoms are adjacent to one another and no two groups selected from -O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O- and -CH=CH- are adjacent to each other,

R¹¹ denotes P,

R²¹ denotes P, halogen, CN, optionally fluorinated alkyl or alkenyl with up to 15 C atoms in which one or more non- adjacent Chh-groups may be replaced by -0-, -S-, -CO-, -0(0)0-, -O-C(O)-, 0-C(0)-0-

P each and independently from another in each occurrence a polymerizable group, and a liquid-crystalline component B), comprising one or more nematogenic compounds, characterised in that the UV radiation is applied from an oblique angle. A further object of the invention are LC layers and display devices made by the process. One embodiment of the invention is a LC layer between two substrates with a nematic alignment, wherein the LC layer is aligned with a pre-tilt to the vertical or a tilt to the planar adjacent to both surfaces of the two substrates, characterized in that the pre-tilt to the vertical or tilt angle to the planar on the surface of a first substrate is greater than the pre-tilt or tilt angle respectively on the surface of the second substrate.

The current invention proposes as one element of the invention to use certain LC mixtures with self-aligning properties. Furthermore, a source of UV radiation which is optionally polarized is used. For the case of vertical initial alignment the use of polarized UV radiation can have influence on the generation of a pre-tilt angle. Preferably polarized UV radiation with polarization perpendicular to the azimuthal plane of the angle of oblique irradiation is employed for obtaining higher degrees of pre-tilt.

The current process can optionally be combined with photoalignment, which is a technology for achieving a unidirectional liquid crystal (LC) alignment. Photoalignment intends to replace the conventional rubbing of the substrate surface with a fibrous material and effect similarly a light- induced orientational ordering of the alignment of the liquid crystals on the substrate surface. This can be achieved through the mechanisms of photodecomposition, photodimerization, and photoisomerization (N.A. Clark et al. Langmuir 2010, 26(22), 17482-17488, and literature cited therein) by means of suitable polarised light. Frequently polarized UV irradiation is used. One functional group known to enable photoalignment is the phenylethenylcarbonyloxy group (cinnamate), which is also contained in compounds of formula (I). In one embodiment of the current invention polarized UV is used in combination with oblique irradiation. The orientation of alignment can be either parallel or orthogonal to the direction of the polarized light. For example, three ring cinnamates and biscinnamates of the structures shown above will usually induce a planar alignment perpendicular to the direction of polarised UV. Other two ring cinnamtes may induce a planar alignment parallel to the direction of polarised UV. A further improvement is to avoid the use of polyimide and other alignment layers at all. For different kinds of nematic LC mixtures this was achieved by adding a self-alignment agent for vertical alignment to the mixture that induces homeotropic alignment in situ by a self-assembling mechanism as disclosed in US 2015-0252265 and WO 2012/038026.

Further details according to each embodiment of the invention are disclosed in the dependent claims, in combinations of two or more of the claims, and in this specification including the examples. Terms and Definitions

The terms "liquid-crystalline" and "liquid crystal" both refer to a liquid- crystalline mesogenic state. It may be abbreviated as "LC". A photoreactive group according to the present invention is a functional group of a molecule that causes a change of the geometry of the molecule either by bond rotation, skeletal rearrangement or atom- or group- transfer, or by dimerization, upon irradiation with light of a suitable wavelength that can be absorbed by the molecule.

The term "mesogenic group" as used herein is known to the person skilled in the art and described in the literature, and means a group which, due to the anisotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystalline (LC) phase in low-molecular- weight or polymeric substances. Compounds containing mesogenic groups (mesogenic compounds) do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerisation. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units. An overview of the terms and definitions used in connection with mesogenic or LC compounds is given in Pure Appl. Chem. 2001, 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.

The term nematogenic compound in a narrower sense refers to compounds which have in their pure state a nematic phase between their melting point and isotropic liquid phase.

The term ‘oblique irradiation’ here means that a surface, mostly a LC layer, is irradiated with a source of (UV) light from an angle other than vertical to the plane. The angle of irradiation is measured here in degrees deviation from the orthogonal direction. Oblique preferably refers to an angle of at least 10° from the direction vertical to the substrate(s). A preferred range is from 20° or more to 70° or less, more preferably from 30° or more to 60° or less. According to the present application, the term "linearly polarised light" means light, which is at least partially linearly polarized. Preferably, the polarized light is linearly polarized with a degree of polarization of more than 5:1. Wavelengths, intensity and energy of the linearly polarised light are chosen depending on the photosensitivity of the photo-alignable material. Typically, the wavelengths are in the UV-A, UV-B and/or UV-C range. Preferably, the linearly polarised light comprises light of wavelengths less than 450 nm, more preferably less than 420 nm at the same time the linearly polarised light preferably comprises light of wavelengths longer than 280 nm, preferably more than 320 nm, more preferably over 350 nm. - IQ -

The term "director" is known in prior art and means the preferred orientation direction of the long molecular axes (in case of calamitic compounds) or short molecular axes (in case of discotic compounds) of the liquid-crystalline molecules. In case of uniaxial ordering of such anisotropic molecules, the director is the axis of anisotropy.

The term “alignment” or “orientation” relates to alignment (orientation ordering) of anisotropic units of material such as small molecules or fragments of big molecules in a common direction named “alignment direction”. In an aligned layer of liquid-crystalline material, the liquid- crystalline director coincides with the alignment direction so that the alignment direction corresponds to the direction of the anisotropy axis of the material. The term "planar orientation/alignment", for example in a layer of an liquid-crystalline material, means that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of a proportion of the liquid-crystalline molecules are oriented substantially parallel (about 180°) to the plane of the layer.

The term "vertical orientation/alignment" or, for example in a layer of a liquid-crystalline material, means that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of a proportion of the liquid-crystalline molecules are oriented at an angle Q ("tilt angle") between about 80° to 90° relative to the plane of the layer. It also know as “homeotropic alignment”.

The terms "uniform orientation" or "uniform alignment" of an liquid- crystalline material, for example in a layer of the material, mean that the long molecular axes (in case of calamitic compounds) or the short molecular axes (in case of discotic compounds) of the liquid-crystalline molecules are oriented substantially in the same direction. In other words, the lines of liquid-crystalline director are parallel to each other.

The wavelength of light generally referred to in this application is 550 nm, unless explicitly specified otherwise.

The birefringence Dh herein is defined by the following equation

Dh = n_e - n₀ wherein n_e is the extraordinary refractive index and n₀ is the ordinary refractive index and the effective average refractive index n_av. is given by the following equation n_av. = [(2 n₀ ² + n_e ²)/3]^1/2

The extraordinary refractive index n_e and the ordinary refractive index n₀ can be measured using an Abbe refractometer.

In the present application the term “dielectrically positive” is used for compounds or components with De > 3.0, “dielectrically neutral” with -1 .5 < De < 3.0 and “dielectrically negative” with De < -1 .5. De is determined at a frequency of 1 kHz and at 20°C. The dielectric anisotropy of the respective compound is determined from the results of a solution of 10 % of the respective individual compound in a nematic host mixture. In case the solubility of the respective compound in the host mixture is less than 10 % its concentration is reduced by a factor of 2 until the resultant mixture is stable enough at least to allow the determination of its properties. Preferably, the concentration is kept at least at 5 %, however, to keep the significance of the results as high as possible. The capacitance of the test mixtures are determined both in a cell with homeo- tropic and with homogeneous alignment. The cell gap of both types of cells is approximately 20 pm. The voltage applied is a rectangular wave with a frequency of 1 kHz and a root mean square value typically of 0.5 V to 1.0 V; however, it is always selected to be below the capacitive threshold of the respective test mixture.

De is defined as (e| | - e_±), whereas e_9n. is (e 11 + 2 e_±) / 3. The dielectric permittivity of the compounds is determined from the change of the respective values of a host mixture upon addition of the compounds of interest. The values are extrapolated to a concentration of the compounds of interest of 100 %. A typical host mixture is ZLI-4792 or ZLI-2857, both commercially available from Merck, Darmstadt.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s-pentyl, cyclopentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, trifluoromethyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl and perfluorohexyl.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl and cyclooctenyl.

Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl and octynyl.

Preferred alkoxy groups are, for example, methoxy, ethoxy, 2-methoxy- ethoxy, n-propoxy, i-propoxy, n-butoxy, i-butoxy, s-butoxy, t-butoxy, 2-methylbutoxy, n-pentoxy, n-hexoxy, n-heptoxy, n-octoxy, n-nonoxy, n-decoxy, n-undecoxy and n-dodecoxy.

Aryl and heteroaryl groups can be monocyclic or polycyclic, i.e. they can contain one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently bonded (such as, for example, biphenyl), or contain a combination of fused and linked rings. Heteroaryl groups contain one or more heteroatoms, preferably selected from 0, N, S and Se. A ring system of this type may also contain individual non-conjugated units, as is the case, for example, in the fluorene basic structure.

Particularly preferred substituents L are, for example, F, Cl, CN, CH3, C2H5, -CH(CH₃)2, OCHS, OC2H5, CFs, OCFs, OCHF2, OC2F5, furthermore phenyl.

Above and below "halogen" denotes F, Cl, Br or I.

For the present invention, the groups

denote trans-1 ,4-cyclohexylene, and the groups

For the present invention the groups -CO-O-, -COO- -C(=0)0- or -CO2-

X O denote an ester group of formula , and the groups -O-CO- -OCO-,

-OC(=0)-, -O2C- or -OOC- denote an ester group of formula

Furthermore, the definitions as given in C. Tschierske, G. Pelzl and S. Diele, Angew. Chem. 2004, 116, 6340-6368 shall apply to non-defined terms related to liquid crystal materials in the instant application. Detailed description

The invention relates to a process for adjustment of the alignment director of a liquid-crystalline layer between a pair of substrates using UV radiation from an oblique angle, the liquid-crystalline layer (“LC layer”) comprising a polymerizable or polymerized compound of the structural formula I,

as defined above.

For formula I independently the following preferred embodiments are provided: Z¹¹ preferably denotes -CY¹²=CY¹²-C0-0- or -CF=CF-, more preferably -CY¹²=CY¹²-C0-0-,

A¹¹ preferably denotes a radical selected from the following groups: a) a group consisting of 1 ,4-phenylene and 1 ,3- phenylene, wherein one or more FI atoms may be replaced by L, b) a group selected from the group consisting of

where, in addition, one or more FI atoms in these radicals may be replaced by L, A have each, independently of one another, in each occurrence one of the meanings for A¹¹ or a) group consisting of trans-1 ,4-cyclohexylene, 1 ,4- cyclohexenylene, b) a group consisting of tetrahydropyran-2,5-diyl,

1 ,3-dioxane-2,5-diyl,

L on each occurrence, identically or differently, preferably denotes -OH, -F, -Cl, -CN, -NO2, -C(=0)N(R^z)₂, -C(=0)R^z, or straight-chain or branched or cyclic alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, preferably 1 to 6 C atoms , in which, in addition, one or more H atoms may be replaced by F or Cl, or X²¹-Sp²¹- R²¹,

R^y and R^z each, independently of one another, denote H, CN, F or alkyl having 1 -12 C atoms, wherein one or more H atoms may be replaced by F, preferably H, methyl, ethyl, propyl, butyl, more preferably FI or methyl, in particular FI,

Y¹¹ and Y¹² each, independently of one another, denote preferably H, methyl, ethyl, propyl, butyl, more preferably H or methyl, in particular H,

Z denotes, independently of each other, in each occurrence, preferably a single bond, -COO-,-OCO-,

-OCF2-, -CF2O-, or -(CH₂)n- more preferably a single bond, -COO-, or -OCO-, n denotes preferably 2, o and p denote each and independently preferably 0 or 1 , X¹¹ and X²¹ denote independently from one another, in each occurrence preferably a single bond -C0-0-,

-0-C0-, -O-COO- or -0-, more preferably a single bond or -0-,

Sp¹¹ and Sp²¹ denote each and independently, in each occurrence preferably alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, more preferably straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene,

R²¹ denotes preferably P.

In the instant application, polymerizable groups (P) are groups that are suitable for a polymerisation reaction, such as, for example, free-radical or ionic chain polymerisation, polyaddition or polycondensation, or for a polymer-analogous reaction, for example addition or condensation onto a main polymer chain. Particular preference is given to groups for chain polymerisation, in particular those containing a C=C double bond or -CºC- triple bond, and groups which are suitable for polymerisation with ring opening, such as, for example, oxetane or epoxide groups. Preferred groups P are selected from the group consisting of

CH₃-CH=CH-0-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-, (CH₂=CH)₂CH-0-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, CH₂=CW¹- CO-NH-, CH₂=CH-(C00)ki-Phe-(0)k2-, CH₂=CH-(C0)_ki-Phe-(0)_k2- and Phe-CH=CH-, wherein W¹ denotes H, F, Cl, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, Cl or CH₃, W² and W³ each, independently of one another, denote FI or alkyl having 1 to 5 C atoms, in particular FI, methyl, ethyl or n-propyl, W⁷ and W⁸ each, independently of one another, denote FI, Cl or alkyl having 1 to 5 C atoms, Phe denotes 1 ,4-phenylene, which is optionally substituted by one or more radicals L as defined above, ki, k₂ and k₃ each, independently of one another, denote 0 or 1 , k₃ preferably denotes 1 , and W denotes an integer from 1 to 10.

Further preferred, P denotes a group

preferably a group

Y denotes H, F, phenyl or optionally fluorinated alkyl having 1-12 C atoms, preferably FI, methyl, ethyl, propyl, butyl, more preferably FI or methyl, in particular FI.

Particularly preferred groups P are selected from the group consisting of CH₂=CW¹-C0-0-, in particular CH₂=CH-C0-0-, CH₂=C(CH₃)-C0-0- and CH₂=CF-C0-0-, furthermore CH₂=CH-0-, (CH₂=CH)₂CH-0-C0-,

wherein

Y denotes FI or methyl, in particular FI.

Very particularly preferred groups P, especially for formula I, are selected from the group consisting of acrylate, methacrylate, fluoroacrylate, furthermore vinyloxy, chloroacrylate, oxetane, epoxide groups and a group,

Y denotes H or methyl, in particular H, and of these preferably an acrylate or methacrylate group or a group,

wherein Y denotes H or methyl. Most preferred is an acrylate group.

The compounds of formula I are preferably selected from compounds of the sub-formulae 1-1 to 1-18,

1-1

Y

' °

R¹¹-Sp¹¹ -X¹¹-A¹²-Z¹¹ -A¹¹ O— A²¹— X²¹-Sp²¹-R²¹

Y¹² I -2 Y 11

,o

R 1¹1 — _Spii— X yi'i — -A D¹'¹ { O A²¹— Z²¹— A²²— X²¹-Sp²¹-R 21

_T ² I -3

Y 11

,o

R 1¹1 — _Spii - Xyi'i — -A' '/ ^Xo_ A²¹ -Z²¹ - A²² -Z²² - A²³-X²¹ -Sp²¹-R²¹

Y¹² I -8

^Y\ ,o

11_ I -9

R Sp '^ΐΐ-c^ΐΐ— A¹³— Z¹²— A¹²— Z¹¹— A¹¹ — ft O — A²¹— Z²¹— A²²— Z²²— A²³— X²¹-Sp²¹ — I R 21

Y¹²

wherein R¹¹, R²¹, A¹¹, X¹¹, X²¹, Y¹¹, Y¹², Sp¹¹, and Sp²¹ have one of the meanings as given above in formula I, A¹² to A²³ have one of the meanings for A in formula I, A¹¹ has one of the meanings as given above under formula I, and Z¹¹ to Z²² have one of the meanings for Z as given above under formula I. Y¹¹, Y¹² are preferably both F.

Further preferred compounds of formula 1-1 are selected from the compounds of formulae 1-1-1 to 1-1-3,

wherein R¹¹, R²¹, A¹¹, X¹¹, X²¹, Sp¹¹, and Sp²¹ have one of the meanings as given above in formula I, A²¹ has one of the meanings for A in formula I, preferably A²¹ denotes a group consisting of 1 ,4-phenylene , wherein, in addition, one or two CH groups may be replaced by N and wherein, in addition, one or more FI atoms may be replaced by L as given above under formula I, or a group consisting of trans-1 ,4-cyclohexylene, 1 ,4- cyclohexenylene, wherein, in addition, one or more non-adjacent CFh groups may be replaced by -0- and/or -S- and wherein, in addition, one or more FI atoms may be replaced by F. Preferred compounds of formula 1-2 are selected from the following sub formula 1-2-1 to I-2-3:

1-2-3 wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and Z¹¹ has one of the meanings for Z as given above under formula I, A¹², A²¹ have one of the meanings for A given above under formula I, preferably A¹², A²¹ denote each and independently a group consisting of 1 ,4-phenylene , wherein, in addition, one or two CH groups may be replaced by N and wherein, in addition, one or more H atoms may be replaced by L as given above under formula I, or a group consisting of trans-1 ,4-cyclohexylene, 1 ,4-cyclohexenylene, wherein, in addition, one or more non-adjacent CFh groups may be replaced by -0- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F.

Preferred compounds of formula I-3 are selected from the following subformulae 1-3-1 to I-3-3,

1-3-1

I -3-4 wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, Z²¹ has one of the meanings for Z as given above under formula I, A²¹ and A²² have one of the meanings for A as given above under formula I. Preferably A²¹ and A²² denote each and independently a group consisting of 1 ,4-phenylene, wherein, in addition, one or two CH groups may be replaced by N and wherein, in addition, one or more H atoms may be replaced by L as given above under formula I, or a group consisting of trans-1 ,4-cyclohexylene, 1 ,4-cyclohexenylene, wherein, in addition, one or more non-adjacent CFh groups may be replaced by -O- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F.

Preferred compounds of formula I-4 are selected from the following subformulae,

wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, A¹², A²¹ and A²² have one of the meanings for A as given above under formula I, Z¹¹, and Z²¹ have one of the meanings for Z as given above under formula I, r and q denote 1 , 2 or 3, s denotes an integer from 1 to 6, and A¹², A²¹ and A²² have one of the meanings for A s given above under formula I. Preferably A¹², A²¹ and A²² denote each and independently a group consisting of 1 ,4-phenylene, wherein one or two CH groups may be replaced by N and wherein, in addition, one or more H atoms may be replaced by L as given above under formula I, or a group consisting of trans-1 ,4-cyclohexylene, 1 ,4-cyclohexenylene, wherein, in addition, one or more non-adjacent Chh groups may be replaced by -0- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F.

Preferred compounds of formula I-5 are selected from the following sub formula,

wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, Z¹¹, Z¹² and Z²¹ have one of the meanings for Z as given above under formula I, and A¹², A¹³, A²¹ and A²² have one of the meanings for A as given above under formula I. Preferably, A¹², A¹³, A²¹ and A²² denote each and independently a group consisting of 1 ,4- phenylene, wherein one or two CH groups may be replaced by N and wherein, in addition, one or more H atoms may be replaced by L as given above under formula I, or a group consisting of trans-1 ,4-cyclohexylene,

1 ,4-cyclohexenylene, wherein, in addition, one or more non-adjacent CH2 groups may be replaced by -0- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F.

Preferred compounds of formula 1-2-1 are compounds of the following sub-formula,

wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I , Z¹¹ has one of the meanings for Z as given above under formula I, and

wherein L have one of the meanings as given above in formula I, and preferably denotes F, Cl, OCH3, COCH3 or alkyl having 1 to 6 C Atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

Preferred compounds of formulae 1-3-1 to I-3-3 are compounds of the following sub-formulae:

1-3-1 c wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I , Z²¹ has one of the meanings for Z as given above under formula I, and

wherein L have one of the meanings as given above in formula I, and preferably is F, Cl, OCH3, COCH3 or alkyl having 1 to 6 C Atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclo pentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

Preferred compounds of formulae 1-4-1 are compounds of the following sub-formula:

1-4-1 a wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I , Z¹¹ and Z²¹ has one of the meanings for Z as given above under formula I, r and q denote 1 , 2 or 3 and s denotes an integer from 1 to 6, and

wherein L have one of the meanings as given above in formula I, and preferably F, Cl, OCFI3, COCFI3 or alkyl having 1 to 6 C Atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclo pentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

Preferred compounds of formulae 1-5-1 are compounds of the following sub-formula:

wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, Z¹¹, Z¹² and Z²¹ has each and independently one of the meanings for Z as given above under formula I, r and q denote 1 , 2 or 3 and s denotes an integer from 1 to 6, and

wherein L have one of the meanings as given above in formula I, and preferably is F, Cl, OCFI3, COCFI3 or alkyl having 1 to 6 C Atoms, such as, methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

Further preferred compounds of formula 1-2-1 a are compounds of the following sub-formula:

wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and L denotes F, Cl, OCFI3, COCFI3 or alkyl having 1 to 6 C Atoms, such as, methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

Further preferred compounds of formulae 1-3-1 a to 1-3-1 c are compounds of the following sub-formulae:

Further preferred compounds of formulae 1-4-1 are compounds of the following sub-formulae:

1-4-1 a-1

Further preferred compounds of formulae 1-5-1 are compounds of the following sub-formulae:

1-5-1 a-7 wherein R¹¹, R²¹, X¹¹ , X²¹, Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and L denotes F, Cl, OCH3, COCH3 or alkyl having 1 to 6 C Atoms, such as, methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, cyclohexyl, or X²¹-Sp²¹-R²¹ _.

wherein

X denotes each and idependently methyl or H, preferably methyl

Y denotes methyl or H,

Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and preferably denote each and idependently preferably alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, more preferably straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, and

L denotes F, Cl, OCFI3 and COCFI3 or alkylene having 1 to 6 C Atoms, preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, or cyclohexyl. Further preferred compounds of formula 1-3-1 a to 1-3-1 c are compounds of the following sub-formula:

30

30

wherein

X denotes each and idependently methyl or H, preferably methyl

Y denotes methyl or H,

Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and preferably denote each and idependently preferably alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, more preferably straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, and L denotes F, Cl, OCFI3 and COCFI3 or alkylene having 1 to 6 C Atoms, preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, or cyclohexyl.

30

30 wherein

X denotes each and idependently methyl or H, preferably methyl

Y denotes methyl or H,

Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and preferably denote each and idependently alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, more preferably straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, and

L denotes F, Cl, OCFI3 and COCFI3 or alkylene having 1 to 6 C Atoms, preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, or cyclohexyl.

30

wherein

X denotes each and idependently methyl or H, preferably methyl

Y denotes methyl or H,

Sp¹¹ and Sp²¹ have one of the meanings as given above in formula I, and preferably denote each and idependently, alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN, more preferably straight-chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, and L denotes F, Cl, OCH3 and COCH3 or alkylene having 1 to 6 C Atoms, preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, cyclopropyl, cylobutyl, cyclopentyl, or cyclohexyl.

The compounds of formula I and subformulae thereof are preferably synthesised according to or in analogy to the procedures described in WO 2017/102068 and JP 2006-6232809.

The mixtures used according to the invention preferably comprise from 0.01 to 10%, particularly preferably from 0.05 to 5% and most preferably from 0.1 to 3% of compounds of formula I according to the invention.

The mixtures preferably comprise one, two or three, more preferably one or two and most preferably one compound of the formula I according to the invention.

In another preferred embodiment the liquid crystal layer comprises an alignment aid comprising a compound of formula I as described above and below, and additionally a vertical self-alignment additive of formula II, MES-R^a II in which

MES is a calamitic mesogenic group comprising two or more rings, which are connected directly or indirectly to each other or which are condensed to each other, which are optionally substituted and which mesogenic group is optionally substituted additionally by one or more polymerizable groups P, which are connected to MES directly or via a spacer, and R^ais a polar anchor group, residing in a terminal position of the calamitic mesogenic group MES which comprises at least one carbon atom and at least one group selected from -OH, -SH, -COOH, -CHO or primary or secondary amine function and which optionally comprises one or two polymerizable groups P, and P a polymerisable group.

The resulting LC layer has an directors of the alignment, which is vertical to the substrate plane.

The invention further relates to the liquid-crystalline mixture comprising a component A) comprising one or more polymerizable or polymerized compounds of the structural formula I, as defined above and below, a liquid-crystalline component B), comprising one or more nematogenic compounds, and additionally a vertical self-alignment additive of formula II,

MES-R^a II in which

MES is a calamitic mesogenic group comprising two or more rings, which are connected directly or indirectly to each other or which are condensed to each other, which are optionally substituted and which mesogenic group is optionally substituted additionally by one or more polymerizable groups P, which are connected to MES directly or via a spacer, and R^a is a polar anchor group, residing in a terminal position of the calamitic mesogenic group MES which comprises at least one carbon atom and at least one group selected from -OH, -SH, -COOH, -CHO or primary or secondary amine function and which optionally comprises one or two polymerizable groups P, and

P is a polymerisable group.

Preferred embodiments of the liquid-crystalline mixture are defined by the closer defined embodiments of the components and combinations thereof.

The term "polymerized molecular compound" refers to a polymer made by polymerizing the polymerizable groups P in the current formulae. The group P typically is a methacrylate or an acrylate group.

Self-alignment additives with polymerizable groups can be polymerised in the LC mixture under the same or similar conditions as applied for the compounds of formula (I). Preferably they are polymerized simultaneously.

In formula II the group MES preferably contains rings, which are selected from aromatic, alicyclic and heterocyclic groups, as defined above, including their preferred meanings. Most preferred rings are 1 ,4- phenylene, which may be substituted by L¹ and -Sp-P as defined below, or 1 ,4-cyclohexylene.

In formula II the group MES preferably is a group selected from the following structures, which may be mono- or polysubstituted by any of the substituents L¹ and -Sp-P:

wherein

L¹ in each case, independently of one another, denotes F, Cl, Br, I, -CN, - NO2, -NCS, -C(=0)N(R°)₂, -C(=0)R°, optionally substituted silyl, optionally substituted aryl or cycloalkyl having 3 to 20 C atoms, or straight-chain or branched alkyl, alkenyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkyl- carbonyloxy or alkoxycarbonyloxy having up to 25 C atoms, in which, in addition, one or more H atoms may each be replaced by F or Cl, P denotes a polymerizable group, and

Sp denotes a spacer group or a single bond, and the dotted line indicates the attachment point of the polar anchor group R^a.

Preferably the self-alignment additive for vertical alignment of formula II is selected of formula lla Rⁱ-[A²-Z²]_m-A¹-R^a lla in which

A¹, A² each, independently of one another, denote an aromatic, hetero aromatic, alicyclic or heterocyclic group, which may also contain fused rings, and which may also be mono- or polysubstituted by a group L¹ or -Sp-P, preferably an aromatic group,

L¹ in each case, independently of one another, denotes F, Cl, Br,

I, -CN, -NO2, -NCS, -C(=0)N(R°)₂, -C(=0)R°, optionally substituted silyl, optionally substituted aryl or cycloalkyl having 3 to 20 C atoms, or straight- chain or branched alkyl, alkenyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having up to 25 C atoms, in which, in addition, one or more FI atoms may each be replaced by F or Cl, p denotes a polymerizable group,

Sp denotes a spacer group or a single bond, Z² in each case, independently of one another, denotes a single bond, -0-, -S-, -CO-, -C0-0-, -OCO-, -0-C0-0-, -0CH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -0CF2-, -CF2S-, -SCF2-, -(CH₂)m-, -CF2CH2-, -CH2CF2-, -(CF₂)ni-, -CH=CH-, -CF=CF-, -CºC-, -CH=CH-COO-, -OCO-CH=CH-,

-(CR°R⁰⁰)ni-, -CH(-Sp-P)-, -CH₂CH(-Sp-P)-, or -CH(-Sp-P)CH(-Sp-P)-, preferably a single bond, -CH=CH-, -CF=CF- or -CºC-, n1 denotes 1 , 2, 3 or 4, m denotes 1 , 2, 3, 4, 5 or 6, preferably 1 , 2, 3 or 4,

R° in each case, independently of one another, denotes alkyl having

1 to 12 C atoms,

R⁰⁰ in each case, independently of one another, denotes FI or alkyl having 1 to 12 C atoms,

R¹ independently of one another, denotes FI, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CFI2 groups may each be replaced by -0-, -S-, -CO-, -CO-O-, -O-CO-, or -O-CO-O- in such a way that 0 and/or S atoms are not linked directly to one another and in which, in addition, one or more FI atoms may each be replaced by F or Cl, or a group -Sp-P, and

R^ais defined as above, preferably denotes a polar anchor group further defined by having at least one group selected from -OH, -NH2, NHR¹¹,

C(0)0H and -CHO, where R¹¹ denotes alkyl having 1 to 12 C atoms. In a preferred embodiment, the LC-host mixture (component B) according to the present invention comprises one or more, preferably two or more, non-polymerizable compounds, and which are no polymers. The latter are stable or unreactive with respect to a polymerisation reaction or photoalignment under the conditions used for the polymerisation of the polymerizable compounds or photoalignment of the photoreactive mesogen of formula I.

In principle, a suitable host mixture is any dielectrically negative or positive LC mixture. Typical examples include mixtures, which are suitable for use in conventional VA, IPS or FFS displays. Mixtures suitable for other uses may be equally employed.

Suitable LC mixtures are known to the person skilled in the art and are described in the literature. LC mixtures for VA displays having negative dielectric anisotropy are described in for example EP 1 378557 A1.

Suitable LC mixtures having positive dielectric anisotropy which are suitable for LCDs and especially for IPS displays are known, for example, from JP 07-181 439 (A), EP 0667555, EP 0673986, DE 19509410,

DE 19528 106, DE 19528 107, WO 96/23851, WO 96/28521 and WO 2012/079676.

Preferred embodiments of the liquid-crystalline mixture having negative or positive dielectric anisotropy according to the invention are indicated below and explained in more detail by means of the working examples.

The LC host mixture is preferably a nematic LC mixture, and preferably does not have a chiral LC phase. The liquid-crystalline layer preferably is one having an optical anisotropy of 0.10 or more, more preferably 0.13 or more and most preferable 0.16 or more. The invention allows to design switchable lenses and liquid-crystalline layers with gratings and/or structured surfaces more easily.

In a preferred embodiment of the present invention the LC mixture contains an LC host mixture with negative dielectric anisotropy. Preferred embodiments of such an LC mixture, and the corresponding LC host mixture, are those of sections a)-d) below: a) LC mixture which comprises one or more compounds of the formu- lae CY and/or PY:

wherein a denotes 1 or 2, b denotes 0 or 1 ,

R¹ and R² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adja- cent Chh groups may be replaced — — ’ / ’ -0-CO- or -CO-O- in such a way that 0 atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms,

Z^x and Z^y each, independently of one another, denote -CH₂CH₂-, -CH=CH-, -CF₂O-, -OCF₂-, -CH₂O-, -OCH₂-, -C0-0-, -0-C0-, -C₂F₄-, -CF=CF-, -CH=CH- CFI₂O- or a single bond, preferably a single bond,

L^1-4 each, independently of one another, denote F, Cl, OCF₃, CFs, CHs, CH2F, CHF2.

Preferably, both L¹ and L² denote F or one of L¹ and L² denotes F and the other denotes Cl, or both L³ and L⁴ denote F or one of L³ and L⁴ denotes F and the other denotes Cl.

The compounds of the formula CY are preferably selected from the group consisting of the following sub-formulae:

wherein a denotes 1 or 2, alkyl and alkyl* each, independently of one another, denote a linear or cyclic alkyl radical having 1-6 C atoms, and alkenyl denotes a linear alkenyl radical having 2-6 C atoms, and (0) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂- CH=CH-, CH₃-(CH₂)₂-CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃- CH=CH-(CH₂)₂-.

The compounds of the formula PY are preferably selected from the group consisting of the following sub-formulae:

wherein alkyl and alkyl^* each, independently of one another, denote a linear alkyl radical having 1-6 C atoms, and alkenyl denotes a linear alkenyl radical having 2-6 C atoms, and (0) denotes an oxygen atom or a single bond. Alkenyl preferably denotes CH2=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃-CH₂-CH=CH-, CH₃-(CH₂)₂- CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃-CH=CH-(CH₂)₂-. b) LC mixture which additionally comprises one or more compounds of the following formula:

in which the individual radicals have the following meanings:

R³ and R⁴ each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adja- cent CFI2 groups may be replaced by -0-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that 0 atoms are not linked directly to one another,

denotes -CH2CH2-, -CH=CH- -CF2O-, -OCF2-, -CH2O-, -OCH2- -CO-O-, -O-CO-, -C2F4-, -CF=CF- -CH=CH- CFI₂O- or a single bond, preferably a single bond.

The compounds of the formula ZK are preferably selected from the group consisting of the following sub-formulae:

in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and alkenyl denotes a straight-chain alkenyl radical having 2-6 C atoms. Alkenyl preferably denotes CH₂=CH-, CH₂=CHCH₂CH₂-, CH₃-CH=CH-, CH₃- CH₂-CH=CH-, CH₃-(CH₂)₂-CH=CH-, CH₃-(CH₂)₃-CH=CH- or CH₃- CH=CH-(CH₂)₂-.

Especially preferred are compounds of formula ZK1 and ZK3. Particularly preferred compounds of formula ZK are selected from the following sub-formulae:

wherein the propyl, butyl and pentyl groups are straight-chain groups.

Most preferred are compounds of formula ZK1 a and ZK3a. c) LC mixture which additionally comprises one or more compounds of the following tolane compounds of the formulae

in which

R¹¹ and R¹² identically or differently, denote H, alkyl or alkoxy having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in which one or more CH2-

which one or more H atoms may be replaced by fluorine,

L¹¹, |_12 |_¹³ independently of one another, denote H, methyl, Cl or

F,

The compounds of formula TO are preferably selected from the group of compounds of formulae TO-1 to TO-3, particularly preferably from formula TO-3

in which the occurring groups have the respective meanings given above under formula TO, and in formulae TO-1 and TO-2 preferably

R¹¹ is n-alkyl or alkenyl having up to 7 C atoms, most preferably n-alkyl having 1 to 5 C atoms, and

R¹² is n-alkoxy or alkenyloxy having 1 to 6 C atoms, most preferably n-alkoxy having 1 to 4 C atoms, and in formula TO-3 preferably

R¹¹ is n-alkyl or alkenyl having up to 7 C atoms, most preferably n-alkyl having 1 to 5 C atoms, and R¹² is n-alkyl or alkenyl having up to 7 C atoms, most preferably n-alkyl having up to 5 C atoms.

The liquid crystal media according to the present invention preferably comprise one or more compounds of formula TO-1 , preferably selected from the group of compounds of formulae TO-1 a to TO-1d, preferably of formulae TO-1 a and/or TO-1 d, most preferably of formula TO-1 a,

wherein the occurring groups have the meanings given above for TO.

The liquid-crystalline media according to the present invention preferably comprise one or more compounds of formula TO-2, preferably selected from the group of compounds of formulae TO-2a to TO-2f, preferably of formulae TO-2a and/or TO-2d, most preferably of formula TO-2d,

wherein the occurring groups have the respective meanings given above for TO.

The liquid crystal media according to the present invention preferably comprise one or more compounds of formula TO-3, preferably selected from the group of compounds of formulae TO-3a to TO-3d, preferably of formulae TO-3c and/or TO-3c and/or TO-3d, most preferably of formula TO-3d,

TO-3a

wherein the occurring groups have the respective meanings given above for TO.

Very preferably, the medium comprises one or more compounds of formula TO-3d. d) LC mixture which additionally comprises one or more compounds selected from dibenzofurans and dibenzothiophens of the following formulae:

in which R¹⁰ and R¹¹ each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non-adjacent CH2 (including any terminal carbon -CH2-H) groups may be replaced

0 and H atoms are not linked directly to one another, preferably alkyl or alkoxy having 1 to 6 C atoms, and R¹⁰ and R¹¹ preferably denote straight-chain alkyl or alkoxy having 1 to 6 C atoms or straight-chain alkenyl having 2 to 6 C atoms, and b denotes 0 or 1 , L denotes F, and r denotes 1 , 2 or 3.

Particularly preferred compounds of the formulae PH, BF and BS are selected from the group consisting of the following sub-formulae:

in which R and R¹ each, independently of one another, denote a straight-chain alkyl, cyclopentyl, cyclopentylmethoxy, cyclopropyl, cyclopropylmethoxy or an alkoxy radical having 1-7 C atoms.

Particularly preferred are compounds of formula DBF and DBT are selected from the formulae:

wherein R and R' are independently straight-chain alkyl having 1 to 8 C atoms, cyclopentyl, cyclopentylmethyl, cyclopropyl or cyclopropylmethyl.

In a preferred embodiment, the liquid crystal mixture according to the present invention further comprises one or more further polymerizable compounds other than component A), preferably in an amount of 0.1 to 10 % by weight. The further polymerizable compounds can be selected from isotropic or mesogenic polymerizable compounds known to the skilled person in the art and preferably chosen from one or more polymerizable compounds of formula P,

P^a-Sp^a-(AP)n₂-Sp^b-P^b P wherein the individual radicals have the following meanings:

P^a, P^b each, independently of one another, denote a polymerizable group, preferably each and independently selected from the group consisting of acrylate, methacrylate, ethacrylate, fluoroacrylate, vinyloxy, chlorcmacrylate, oxetane, or epoxide groups Sp^a, Sp^b on each occurrence, identically or differently, denote a spacer group or a single bond,

A^p each and independently from another, in each occurrence, a group selected from 5, 6 or 7-membered alicyclic groups wherein, in addition, one or more non-adjacent CFh groups may be replaced by -NH-, -0- and/or -S-, wherein one or more non-adjacent -CH2-CH2- groups may be replaced by -CH=CH-, and wherein one or more H atoms may be replaced by F, preferably 5-membered groups such as cyclopentane, cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrroli dine, or6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1,3-dioxane, 1 ,3-dithiane, piperidine, or 7-membered groups, such as cycloheptane, trans-1 ,4- cyclohexylene, more preferably 1 ,4-cyclohexylene or 1 ,4-cyclo- hexenylene, and n2 denotes 0, 1 , 2 or 3, preferably 1 or 2. Preferred spacer groups Sp^{a b} are selected from the formula Sp"-X", so that the radicals P-Sp- and p^a/b-Sp^a/b- conforms to the formulae P-Sp"-X"- and P^a/b-Sp"-X"-, respectively, wherein

Sp" denotes alkylene having 1 to 20, preferably 1 to 12, C atoms, which is optionally mono- or polysubstituted by F, Cl, Br, I or CN and wherein, in addition, one or more non- adjacent CFh groups may each be replaced, independently of one another, by -0-, -S-, -NH-,

-N(R⁰)-, -Si(R⁰⁰R⁰⁰⁰)-, -CO-, -C0-0-, -0-C0-, -0-C0-0-, -S-CO-, -CO-S-, -N(R⁰⁰)-CO-O-, -0-C0-N(R⁰⁰)-, -N(R⁰⁰)-CO-N(R⁰⁰)-, -CH=CH- or -CºC- in such a way that 0 and/or S atoms are not linked directly to one another, or a single bond,

X" denotes -0-, -S-, -CO-, -C0-0-, -0-C0-,

-0-C0-0-, -CO-N(R⁰⁰)-, -N(R⁰⁰)-CO-, -N(R⁰⁰)-CO-N(R⁰⁰)-, -OCH2-, -CH2O-, -SCH2-, -CH2S-, -CF2O-, -OCF2-, -CF2S-, -SCF2-, -CF2CH2-, -CH2CF2-, -CF2CF2-, -CH=N-, -N=CH-, -N=N-, -CH=CR⁰-, -CY³=CY⁴-, -CºC-, -CH=CH-C0-0-, -0-C0-CFI=CFI- or a single bond, preferably a single bond

R°, R°° and R⁰⁰⁰ each, independently of one another, denote H or alkyl having 1 to 12 C atoms, and

Y³ and Y⁴ each, identically or differently, denote FI, F, Cl or CN.

X” is preferably -0-, -S-, -CO-, -C(0)0-, -OC(O)-, -0-C(0)0-, -CO- NR⁰-, -NR°-CO-, -NR°-CO-NR°- or a single bond. Typical spacer groups Sp” are, for example, a single bon, -(CH₂)_PI-, -(CH₂CH20)_qi-CH₂CH2-, -CH₂CH₂-S-CH₂CH₂-, -CH₂CH₂- NH-CH₂CH₂- or -(SiR⁰⁰R⁰⁰⁰-O)pi-, wherein p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R⁰⁰ and R⁰⁰⁰ have the meanings indicated above.

Particularly preferred groups -Sp”-X”- are a single bond, -(CH₂)_PI-, -(CH₂)pi-0-, -(CH₂)pi-0-C0-, -(CH₂)pi-0-C0-0-, wherein p1 and q1 have the meanings indicated above.

Particularly preferred groups Sp” are, for example, in each case straight- chain methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.

Particularly preferred monomers of formula P are the following:

The amount of the polymerizable component in the LC mixture as a whole is preferably ranging from 0.1 to 10 %, more preferably ranging from 0.3 to 5 %, especially ranging from 0.5 to 2 %.

The amount of one or more compounds of formula P in the mixtures as a whole is preferably ranging from 0.05 to 10%, more preferably ranging from 0.1 to 5%, especially ranging from 0.2 to 2%. The polymerizable compounds of formulae I and P are also suitable for polymerisation without an initiator, which is associated with considerable advantages, such as, for example, lower material costs and, in particular, reduced contamination of the LC mixture by possible residual amounts of the initiator or degradation products thereof. The polymerisation can thus also be carried out without addition of an initiator. The LC mixture thus, in a preferred embodiment, comprises no polymerisation initiator. The LC mixture of the layers may also comprise one or more stabilisers in order to prevent undesired spontaneous polymerisation of the RMs, for example during storage or transport. Suitable types and amounts of stabilisers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, the commercially available stabilisers from the Irganox® series (BASF SE), such as, for example, Irganox® 1076. If stabilisers are employed, their proportion, based on the total amount of the RMs or the polymerizable component, is preferably 10 - 10,000 ppm, particularly preferably 50 - 1000 ppm. The mixtures according to the invention preferably comprise from 0.01 to 10%, particularly preferably from 0.05 to 7.5% and most preferably from 0.1 to 5% of the compounds of formula P. The mixtures preferably comprise one, two or three, more preferably one or two and most preferably one compound of the formula P.

By means of suitable additives, the liquid-crystalline phases of the present invention can be modified in such a way that they can be used in all types of liquid crystal display elements that have been disclosed hitherto. Additives of this type are known to the person skilled in the art and are described in detail in the literature (H. Kelker/ R. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980). For example, pleochroic dyes can be added for the production of coloured guest-host systems or substances can be added in order to modify the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases.

The mixtures used according to the invention are prepared in a manner conventional per se. In general, the components are dissolved in one another, preferably at elevated temperature.

The invention preferably relates to a device produced by the process according to the invention in which none or only one of the top and bottom substrates contains a polyimide layer.

In one embodiment of the present invention the liquid crystal composition is injected between the first and second substrate or it is filled into the cell by capillary force after combining the first and second substrate. In an alternative embodiment, the liquid crystal composition may be interposed between the first and second substrates by combining the second substrate to the first substrate after loading the liquid crystal composition on the first substrate. Preferably, the liquid crystal is dispensed dropwise onto a first substrate in a process known as “one drop filling” (ODF) process, as disclosed in for example JPS63-179323 and JPH10-239694, or using the Ink Jet Printing (UP) method.

In a preferred embodiment, the process according to the invention contains a process step where the liquid crystal inside the device is allowed to rest for a period of time in order to evenly redistribute the liquid crystal mixture inside the panel (herein referred to as “annealing”).

However it is likewise preferred that the annealing step is combined with a previous step, such as edge sealant pre-curing. In which case a ‘separate’ annealing step may not be necessary at all. For the production of the device according to the present invention, the photoreactive mesogen of formula I is preferably allowed to redistribute in the panel. After filling and assembly, the display panel is annealed for a time between 1 min and 3h, preferably between 2 min and 1 h and most preferably between 5 min and 30 min. The annealing is preferably performed at room temperature.

In an alternative embodiment, the annealing is performed at elevated temperature, preferably at above 20°C and below 140°C, more preferably above 40°C and below 100°C and most preferably above 50°C and below 80°C.

In a preferred embodiment, one or more of the process steps of filling the display, annealing, photoalignment and curing of the polymerizable compound is performed at a temperature above the clearing point of the liquid crystal host mixture.

In a preferred embodiment of the present invention the photoreactive component comprising one or more compounds of formula I, is photoaligned in a first step using linearly polarised UV light and in a second step further cured using linearly polarized or unpolarised UV light. In one or both of these steps irradiation is from an oblique angle. In the second step any other polymerizable compounds are also further cured. In another preferred embodiment, the linearly polarised light applied according to the inventive process is ultraviolet light from an oblique angle which enables simultaneous photoalignment and photocuring of the photoreactive component comprising one or more compounds of formula I, and, if present, photocuring of the other polymerizable components.

Photoalignment of the photoreactive compounds of formula I and curing of the polymerizable groups of compounds of formula I and the curing of the optional polymerizable compounds of formula P can be performed simultaneously or stepwise. In case the process is split into different steps, the individual steps can be performed at the same temperature or at different temperatures.

Suitable and preferred polymerisation methods for the polymerizable component are, for example, thermal or photopolymerization, preferably photopolymerization, in particular UV photopolymerization. One or more initiators can optionally also be added here. Suitable conditions for the polymerisation and suitable types and amounts of initiators are known to the person skilled in the art and are described in the literature. Suitable for free-radical polymerisation are, for example, the commercially available photoinitiators Irgacure651®, Irgacure184®, Irgacure907®, Irgacure369® or Darocurel 173® (BASF SE). If an initiator is employed, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.

Further combinations of the embodiments and variants of the invention in accordance with the description arise from the claims.

The invention is explained in greater detail below with reference to work ing examples, but without intending to be restricted thereby. The person skilled in the art will be able to glean from the examples working details that are not given in detail in the general description, generalise them in accordance with general expert knowledge and apply them to a specific problem.

All percentages of compositions throughout this disclosure are "% by weight". The sum of all percentages in a composition should give 100 %. Besides the usual and well-known abbreviations, the following abbrevia tions are used:

C: crystalline phase; N: nematic phase; Sm: smectic phase; I: isotropic phase. The numbers between these symbols show the transition temperatures of the substance concerned.

Temperature data are in °C, unless indicated otherwise.

Physical, physicochemical or electro-optical parameters are determined by generally known methods, as described, inter alia, in the brochure "Merck Liquid Crystals - Licristal® - Physical Properties of Liquid Crystals - Description of the Measurement Methods", 1998, Merck KGaA, Darmstadt.

Above and below, Dh denotes the optical anisotropy (589 nm, 20°C) and Le denotes the dielectric anisotropy (1 kHz, 20°C). The dielectric anisot ropy De is determined at 20°C and 1 kHz. The optical anisotropy Dh is determined at 20°C and a wavelength of 589.3 nm.

The De and Dh values and the rotational viscosity (gi) of the compounds according to the invention are obtained by linear extrapolation from liquid- crystalline mixtures consisting of 5 to 10% of the respective compound according to the invention and 90-95% of the commercially available liquid crystal mixture ZLI-2857 (for De) or ZLI-4792 (for Dh, gi) (mixtures, Merck

KGaA, Darmstadt).

The compounds used in the present invention are prepared by methods known per se, as described in the literature (for example in the standard works, such as Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Georg-Thieme-Verlag, Stuttgart), to be precise under reaction conditions which are known and suitable for the said reactions. Use can also be made here of variants known per se, which are not mentioned here in greater detail.

In the present invention and especially in the following examples, the structures of the mesogenic compounds are indicated by means of abbreviations, also called acronyms. In these acronyms, the chemical formulae are abbreviated as follows using Tables A to C below. All groups C_nH_2n+i, C_mH_2m+i and C1H21₊₁ or C_nH_2n.i, C_mH_2m.-i and C1H21-1 denote straight-chain alkyl or alkenyl, preferably 1 E-alkenyl, each having n, m and I C atoms respectively. Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B shows the linking groups. Table C gives the meanings of the codes for the left- hand or right-hand end groups. The acronyms are composed of the codes for the ring elements with optional linking groups, followed by a first hyphen and the codes for the left-hand end group, and a second hyphen and the codes for the right-hand end group. Table D shows illustrative structures of compounds together with their respective abbreviations.

Table A: Ring elements

Table B: Linking groups

E -CH2CH2- z -co-o-

V -CH=CH- Zl -o-co-

X -CF=CH- O -CH₂-0-

XI -CH=CF- 01 -0-CH2- B -CF=CF- Q -CF₂-0- T -CºC- Ql -0-CF2- w -CF2CF2- T -cºc-

Table C: End groups

Left-hand side Right-hand side Use alone

-n- CnFl2n+1- -n — CnFl2n+1 -nO- C_nFl_2n+i-0- -On -0-CnFl2n+1 -V- CH₂=CH- -V -CH=CH₂ -nV- C_nH_2n+i-CH=CH- -nV -C_nH2n-CH=CH₂ -Vn- CH₂=CH- C_nH_2n+i- -Vn -CH=CH-C_nH_2n+i -nVm- CnFl2n+i-CFI=CFI-CmFl2m- -nVm -CnFl2n-CFI ⁼ CFI-CmFl2m+1 -N- NºC- -N -CºN -S- S=C=N- -s -N=C=S -F- F- -F -F -CL- Cl- -CL -Cl -M- CFH₂- -M -CFH₂ -D- CF₂H- -D -CF₂H -T- CF₃- -T -CF₃ -MO- CFH₂O - -OM -OCFH2 -DO- CF₂HO - -OD -OCF₂H -TO- CF3O - -OT -OCF₃ -FXO- CF₂=CH-0- -OXF -O-CH=CF₂ -A- H-CºC- -A -CºC-H

Use together with one another and with others -...A...- -CºC- -...A... -CºC-

-...V...- CH=CH- -...V... -CH=CH-

-...Z...- -CO-O- -...Z... -CO-O-

-...Zl...- -O-CO- -...Zl... -O-CO-

-...K...- -CO- -...K... -co- -...W...- -CF=CF- -...W... -CF=CF- wherein n and m each denote integers, and the three dots are place holders for other abbreviations from this table.

The following table shows illustrative structures together with their respective abbreviations. These are shown in order to illustrate the meaning of the rules for the abbreviations. They furthermore represent compounds which are preferably used.

Table D: Illustrative structures

CC-n-mV

CC-n-mVI

^H2C=CH0 0 ^CH=CH* cc-v-v

CC-nV-Vm

CP-V-V PP-n-Om

CCP-n-Om

CCP-nVm-l

CPP-nV-m PGP-n-mVI

CCZPC-n-m

GP-n-F

CCG-V-F

CGU-n-F

CCPU-n-F CCZU-n-F

PGQU-n-F CPUQU-n-F APUQU-n-F

CCY-V-m CCY-Vn-m LYLI-n-m LY-n-(0)m

CCYY-n-m CPYG-n-(0)m

DFDBC-n(0)-(0)m C-DFDBF-n-(0)m wherein n, m and I preferably, independently of one another, denote 1 to 7.

The following table, Table E, shows illustrative compounds which can be used as stabilisers in the mesogenic mixtures according to the present invention.

Table E Table E shows possible stabilisers which can be added to the LC mixtures according to the invention.

(n here denotes an integer from 1 to 12, preferably 1, 2, 3, 4, 5, 6, 7 or 8, terminal methyl groups are not shown).

30

25

30

The LC mixtures preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight, particularly preferably 1 ppm to 1% by weight, of stabilisers.

Table F below shows illustrative compounds which can preferably be used as chiral dopants in the mesogenic mixtures according to the present invention.

Table F

CB 15

CN

R/S-4011 In a preferred embodiment of the present invention, the mesogenic mixtures comprise one or more compounds selected from the group of the compounds from Table F.

The mesogenic mixtures according to the present application preferably comprise two or more, preferably four or more, compounds selected from the group consisting of the compounds from the above tables. The liquid-crystalline mixtures according to the present invention preferably comprise

- seven or more, preferably eight or more, individual compounds, preferably of three or more, particularly preferably of four or more, dif- ferent formulae, selected from the group of the compounds from

Table D.

Hereinafter, the present invention is described in more detail and specifically with reference to the Examples, which however are not intended to limit the present invention.

Examples

Utilized photoreactive compounds of formula I:

Ċ Optionally added self-alignment additives for vertical alignment:

Optionally added polymerizable compounds of formula P (reactive mesoqens without photoalignment):

Nematic host mixtures

The nematic LC host mixtures are prepared as indicated in the following tables:

H1: Nematic host mixture (De < 0)

CP P-3-2 6.5% Clearing point [°C]: 74.7

CC-3-V1 8.0% Dh (589 nm, 20°C): 0.104

CC-2-3 17.0% De (1 kHz, 20°C): -3.0

CC-3-4 6.5%

CCY-3-01 3.5%

CCY-3-02 12.5%

CPY-2-02 5.5%

CPY-3-02 10.0% CY-3-02 15.5%

CP-3-01 4.5%

PP-1-2V1 5.0%

H2: Nematic host mixture (De < 0)

CC-3-V1 37.0% Clearing point [°C]: 73.5 CCY-3-01 5.0% Dh (589 nm, 20°C): 0.1005 CCY-3-02 9.5% De (1 kHz, 20°C): -3.7 CCY-4-02 5.0% CPY-2-02 10.0% C PY-3-02 10.0% CY-3-02 11.5%

H3: Nematic host mixture (De > 0)

GGP-3-CL 10.5% Clearing point [°C]: 103.5

GGP-5-CL 27.0% Dh (589 nm, 20°C): 0.232

CPGP-4-3 3.0% De (1 kHz, 20°C): 21.1 CPGP-5-2 3.0%

CPGP-5-3 3.0%

CCGU-3-F 9.0%

PUQU-2-F 7.0%

PUQU-3-F 8.0%

PGU-2-F 8.0% PGU-3-F 8.0%

PGU-5-F 8.0%

H4: Nematic host mixture (De > 0)

CC-3-V 36.0% Clearing point [°C]: 78

CC-3-V1 5.0% Dh (589 nm, 20°C): 0.110 CCP-V-1 8.0% De (1 kHz, 20°C): 12.9

PGP-2-2V 3.0%

H5: Nematic host mixture (De < 0)

CY-3-04 24.0% Clearing point [°C]: 87

CCY-3-03 7.0% Dh (589 nm, 20°C): 0.168

CPY-2-02 12.0% De (1 kHz, 20°C): -3.8

CPY-3-02 12.0%

PYP-2-3 18.0%

PGP-2-3 10.0%

PGP-2-4 10.0%

CCH-301 7.00%

H7: Nematic host mixture (De < 0)

H9: Nematic host mixture (De 0)

CY-3-04 4.0% cl.p. [°C]: 123

PYP-2-3 7.0% Dh [589 nm, 20°C]:

PTP-1-02 4.0% n_e [589 nm, 20°C]:

PTP-3-01 4.0% n₀ [589 nm, 20°C]: 1.5063 PPTUI-3-2 16.0% De [1 kHz, 20°C]: -3.3

PPTUI-3-4 16.0% e,_| [1 kHz, 20°C]: 4.3

PTY-3-02 13.0% e± [1 kHz, 20°C]: 7.6 Example 1: Dependency of irradiation angle

A liquid-crystalline mixture for a LC layer is prepared by adding to the nematic host mixture H4 1 % by weight of the cinnamate compound 1-1 and homogenizing the mixture.

The mixture is filled into a cell made of a pair of glass substrates covered with transparent indium-tin oxide (ITO) electrodes (without polyimide coating, cell gap 4 pm). This mixture usually aligns almost parallel (homogeneous) relative to the substrate plane.

The LC layer inside the cell is then irradiated with UV light in a two-step procedure at certain temperatures indicated in the table below. The equipment is Omnicure 2000. The first step is made with polarized UV light. The second UV step is made with non-polarized UV light from an oblique angle or from a vertical direction (comparison). The angle is measured from the vertical direction (vertical = 0°)

Table 1. Conditions for UV irradiation two-step procedure. Lamp: Hg lamp, OmniCure® S2000, igb-tech GmbH). Step 1: with wire grid polarizer (UVD260A/UB), step2: no wire grid polarizer

After each irradiation step the resulting director of alignment on the substrate surfaces of the cell is measured (AxoScan™, Axometrics Inc.). The tilt indicated below provides the angle between the director of alignment and the substrate plane. The tilt is evaluated for the two substrates separately, resulting in a front value for the substrate adjacent to the UV source, and a back tilt for the more distant substrate. The average tilt value is calculated for the coupled tilt, which is the representative value for the whole LC layer.

Table 2. Results for various times of UV irradiation (0 /40 )

Oblique irradiation can be varied between 20 to 60°, however in this set of data the relative highest tilt is observed for 40° angle of irradiation (no.

1.3.2). This angle of 40° is used for the further examples.

Example 2: Dependency of irradiation time

In this experiment the time of irradiation is varied. A LC layer between substrates in a cell is prepared as in Example 1. The cell is irradiated according to the protocol of Example 1 with oblique UV from 40°. The results for different times of oblique irradiation are presented in the following table. Table 3. Results for various angles of UV irradiation (300 s)

The result of the table show that the amount of tilt generation can be advantageously controlled by varying the time period of the oblique angle UV step 2. This method can be exploited to obtain the preferred value of tilt/pre-tilt for a given system.

Example 3: Generation of pre-tilt angle in VA cell

A liquid-crystalline mixture for a LC layer is prepared by adding to the nematic host mixture H1 1 % by weight of the cinnamate compound 1-1 (or others according to table below) and 0.6 % by weight of an additive for vertical self-alignment SA-3 and then homogenizing the mixture.

The mixture is filled into a cell made of a pair of glass substrates covered with transparent indium-tin oxide (ITO) electrodes (without polyimide coating, cell gap 4 pm). This mixture usually aligns spontaneously almost vertical (homeotropic) relative to the substrate plane.

The LC layer inside the cell is then irradiated with oblique UV light in a one-step procedure at room temperature as indicated in the table below. The equipment is Omnicure® 2000. Table 4. Conditions for UV irradiation one-step procedure for pre-tilt generation in vertical alignment cell. Lamp: Hg lamp, OmniCure® S2000, igb-tech GmbH), without wire grid polarizer.

The results of tilt angle measurement for different additives are presented in the following table.

Table 5. Results for various photoalignment additives (two independent results for each mixture)

The table shows that additives 1-1 to I-4 induce a significant change in the pre-tilt angle after oblique UV irradiation. In the comparative group of photoreactive additives RM-1 and RM-2 without cinnamate structure the change of pre-tilt angle after UV irradiation is about zero.

Example 4: Influence of polarized irradiation

The setup of Example 3.1 is repeated, but the UV conditions are changed in that a polarization filter is placed between the UV source and the sample (wire grid polarizer). For compensation of the loss of intensity in the polarization filter the power is raised to 55 mw/cm²

Table 6. Polarization dependent tests. The direction of polarization is indicated relative to the azimuthal plane of the oblique angle.

The results of the table show that polarization has a significant influence on the amount of induced pre-tilt. UV light polarized perpendicular (here horizontally to the substrate) is particularly effective.

Example 5: Generation of pre-tilt angle in VA cell A liquid-crystalline mixture for a LC layer is prepared by adding to the nematic host mixture H5 1 % by weight of the cinnamate compound 1-11 and 0.6 % by weight of an additive for vertical alignment SA-3 and homogenizing the mixture. The mixture is filled into a cell made of a pair of glass substrates covered with transparent indium-tin oxide (ITO) electrodes (without polyimide coating, cell gap 4 pm). This mixture usually aligns almost vertical (homeotropic) relative to the substrate plane. The LC layer inside the cell is then irradiated with UV light in a one-step procedure at room temperature according to Example 3 with an irradiation time of 600 s.

Table 6. Results for photoalignment additive 1-11 in host H-5

Example 6: Preparation of a Fresnel lens structure with tilted vertical alignment

A test cell comprising a Fresnel lens structure substrate that is fabricated in accordance with the procedure given in GB 201810565, paragraph [0171] to [0181] and a plain glass substrate is prepared. 10pm spacers, in UV curable sealant, are used to separate the two substrates. The sealant containing glass spacers is applied to the edges of the cell, and the cell is then illuminated with UV light to cure the glue. The cell is capillary filled with mixture consisting of 98.4 % by weight of host H-6, 0.6% by weight of SA-1 and 1.0% by weight of 1-1.

This mixture aligns vertical (homeotropic) relative to the substrate plane. The mixture inside the cell is then irradiated with UV light of Omnicure® 2000 (55 mW/cm² for 900 s) without wire grid polarizer at an oblique angle of 40° with respect to the substrate plane. The cell gives uniform vertical alignment when observed under the microscope. The process avoids the formation of domains with different alignment. The embossed Fresnel lens is clearly visible in the bright state. Self-alignment is achieved over the entire region of the embossed surface feature. The vertical alignment is preserved at any angle with respect to the orientation of the surface features.

In the same manner lenses comprising the following formulations are produced:

The lenses show very good vertical alignment when observed under the microscope and showed an improvement of the electrooptical characteristics, such as improved switching speed.

Claims

Patent Claims

1. A process for adjustment of the alignment director of a liquid- crystalline layer between a pair of substrates using UV radiation, wherein the liquid-crystalline layer comprises a liquid-crystalline (LC) mixture comprising a component A) comprising one or more polymerizable or polymerized compounds of the structural formula I,

wherein

Z¹¹ -CY¹²=CY¹²-C0-0-, -CY¹²=CY¹²- or -CY¹²=CY¹²-CO-,

A have each, independently of one another, in each occurrence one of the meanings for A¹¹ or a) group consisting of trans-1 ,4-cyclohexylene, 1 ,4- cyclohexenylene, wherein, in addition, one or more non-adjacent CFh groups may be replaced by -0- and/or -S- and wherein, in addition, one or more H atoms may be replaced by F, or b) a group consisting of tetrahydropyran-2,5-diyl,

1 ,3-dioxane-2,5-diyl, tetrahydrofuran-2,5-diyl, cyclobutane-1 ,3-diyl, piperidine-1 ,4-diyl, thiophene-2, 5- diyl and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by

L,

L on each occurrence, identically or differently, denotes

-OH, -F, -Cl, -Br, -I, -CN, -N0₂, -SCN, -C(=0)N(R^z)₂, -C(=0)R^z, -N(R^z)₂, optionally substituted silyl, optionally substituted aryl having 6 to 20 C atoms, or straight- chain or branched or cyclic alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, or X²¹-Sp²¹-R²¹,

M denotes -0-, -S-, -CH₂-, -CHR^Z- or -CR^yR^z-,

R^y and R^z each, independently of one another, denote H, CN, F or alkyl having 1-12 C atoms, wherein one or more H atoms may be replaced by F,

Y¹¹ and Y¹² each, independently of one another, denote H, F, phenyl or optionally fluorinated alkyl having 1-12 C atoms,

Z denotes, independently of each other, in each occurrence, a single bond, -COO-, -OCO-, -0-C0-0-,

-OCH₂-, -CH₂0-, -OCF₂-, -CF₂0-, -(CH₂)_n-,

-S-CSS- or -CºC-, denotes an integer between 2 and 8, o and p denote each and independently 0, 1 or 2,

X¹¹ and X²¹ denote independently from one another, in each occurrence a single bond, -CO-0-, -0-CO-, -0-COO-, -0-, -CH=CH-, -CºC-, -CF2-O-, -O-CF2-, -CF2-CF2-,

-CH2-O-, -O-CH2-, -CO-S-, -S-CO-, -CS-S-, -S-CS-, -S-CSS- or -S-,

Sp¹¹ and Sp²¹ denote each and independently, in each occurrence a single bond or a spacer group comprising 1 to 20 C atoms, wherein one or more non-adjacent and non terminal CFI2 groups may also be replaced by -0-, -S-, -NH-, -N(CH₃)-, -CO-, -O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O-, -CF2-, -CF2O-, -OCF2- -C(OH)-, -CH(alkyl)-, -CH(alkenyl)-,-CH(alkoxyl)-, -CH(oxaalkyl)-, -CH=CH- or -CºC-, however in such a way that no two O-atoms are adjacent to one another and no two groups selected from -O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O- and -CH=CH- are adjacent to each other,

R¹¹ denotes P,

R²¹ denotes P, halogen, CN, optionally fluorinated alkyl or alkenyl with up to 15 C atoms in which one or more non- adjacent CFh-groups may be replaced by -0-, -S-, -CO-, -0(0)0-, -O-C(O)-, 0-C(0)-0-

P each and independently from another in each occurrence a polymerizable group, and a liquid-crystalline component B), comprising one or more nematogenic compounds, characterised in that the UV radiation is applied from an oblique angle oblique to the normal to the substrate surface of at least 20° from the direction vertical to the substrates.

2. A process according to claim 1 characterised in that the total concentration of compounds of formula I in the mixture is in the range of from 0.01 to 10% by weight.

3. Process according to claim 1 or 2, characterised in that the liquid- crystalline layer comprises a further polymerizable or polymerized compound other than the component A), preferably in an amount of 0.1 to 10 % by weight.

4. Process according to claim 1 or 2, characterised in that the liquid- crystalline layer is irradiated with UV radiation at an angle between 20° or more and 70° or less measured from the vertical direction.

5. Process according to claim 1 or 2, characterized in that the LC mixture has negative dielectric anisotropy.

6. Process according to claim 1 or 2, wherein the liquid-crystalline layer has vertical alignment, and it comprises one or more self-alignment additives for vertical alignment of formula II

MES-R^a II in which

MES is a calamitic mesogenic group comprising two or more rings, which are connected directly or indirectly to each other or which are condensed to each other, which are optionally substituted and which mesogenic group is optionally substituted additionally by one or more polymerizable groups P, which are connected to MES directly or via a spacer, and

R^a is a polar anchor group, residing in a terminal position of the calamitic mesogenic group MES which comprises at least one carbon atom and at least one group selected from -OH, -SH, -COOH, -CHO or primary or secondary amine function and which optionally comprises one or two polymerizable groups P, and

P is a polymerisable group.

7. Process according to one or more of claims 1 to 5, characterised in that the liquid-crystalline layer has positive dielectric anisotropy.

8. Process according to one or more of claims 1 to 8, wherein the LC layer comprises one or more compounds selected from the following formulae:

wherein a is 1 or 2, b is 0 or 1, R¹ and R² each, independently of one another, denote alkyl having 1 to 12 C atoms, where, in addition, one or two non- adjacent CH2 groups may be replaced

such a way that 0 atoms are not linked directly to one another,

Z^x and Z^y each, independently of one another, denotes -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH- CH₂O- or a single bond,

9. Process according to one or more of claims 1 to 8, wherein the LC mixture comprises one or more compounds of the following formula:

in which the individual radicals have the following meanings: R³ and R⁴ each, independently of one another, denote alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent Chh groups may be replaced by -0-, -CH=CH-, -CO-, -O-CO- or -CO-O- in such a way that 0 atoms are not linked directly to one another,

denotes -CH2CH2-, -CH=CH-, -CF2O-, -OCF2-, -CH2O-, -OCH2-, -CO-O-, -O-CO-, -C2F4-, -CF=CF-, -CH=CH- CH2O- or a single bond.

10. A process according to any of claims 1 to 9, wherein the induced pre-tilt angle on the surface of the first substrate adjacent to the source of UV radiation is greater than the induced pre-tilt angle on the surface of the second substrate distant to the UV source.

11. Liquid-crystalline mixture comprising a component A) comprising one or more polymerizable or polymerized compounds of the structural formula I, wherein

Z¹¹ -CY¹²=CY¹²-C0-0-, -CY¹²=CY¹²- or -CY¹²=CY¹²-CO-,

M denotes -0-, -S-, -CH2-, -CHR^Z- or -CR^yR^z-,

Y¹¹ and Y¹² each, independently of one another, denote FI, F, phenyl or optionally fluorinated alkyl having 1-12 C atoms,

-CF2CF2-, -CH=CH-, -CF=CF-, -CH=CH-COO-, -OCO- CH=CH-, -CO-S-, -S-CO-, -CS-S-, -S-CS-,

X¹¹ and X²¹ denote independently from one another, in each occurrence a single bond, -CO-O-, -O-CO-, -O-COO-, -0-, -CH=CH-, -CºC-, -CF2-O-, -O-CF2-, -CF2-CF2-, -CH2-O-, -O-CH2-, -CO-S-, -S-CO-, -CS-S-, -S-CS-, -S-CSS- or -S-,

Sp¹¹ and Sp²¹ denote each and independently, in each occurrence a single bond or a spacer group comprising 1 to 20 C atoms, wherein one or more non-adjacent and non terminal Chh groups may also be replaced by -0-, -S-, -NH-, -N(CH₃)-, -CO-, -0-C0-, -S-CO-, -0-C00-, -CO-S-, -C0-0-, -CF₂-, -CF2O-, -OCF2- -C(OH)-, -CH(alkyl)-, -CH(alkenyl)-,-CH(alkoxyl)-, -CH(oxaalkyl)-, -CH=CH- or -CºC-, however in such a way that no two O-atoms are adjacent to one another and no two groups selected from -O-CO-, -S-CO-, -O-COO-, -CO-S-, -CO-O- and -CH=CH- are adjacent to each other,

R¹¹ denotes P,

P each and independently from another in each occurrence a polymerizable group, a liquid-crystalline component B), comprising one or more nematogenic compounds, and additionally a vertical self-alignment additive of formula II,

MES-R^a II in which MES is a calamitic mesogenic group comprising two or more rings, which are connected directly or indirectly to each other or which are condensed to each other, which are optionally substituted and which mesogenic group is optionally substituted additionally by one or more polymerizable groups

P, which are connected to MES directly or via a spacer, and

P is a polymerisable group.

12. Liquid-crystalline mixture according to claim 11 wherein the component B) comprises one or more compounds selected from the formulae CY and PY defined in claim 8.

13. Liquid-crystalline mixture according to claim 11 or 12 which further comprises one or more polymerizable compounds of formula P

P^a-Sp^a-(A^P)_n2-Sp^b-P^b P wherein the individual radicals have the following meanings:

P^a, P^b each, independently of one another, denote a polymerizable group, Sp^a, Sp^b on each occurrence, identically or differently, denote a spacer group or a single bond, A^p each and independently from another, in each occurrence, a group selected from 5, 6 or 7-membered alicyclic groups wherein, in addition, one or more non-adjacent CFh groups may be replaced by -NH-, -0- and/or -S-, wherein one or more non-adjacent -CH2-CH2- groups may be replaced by -CH=CH-, and wherein one or more H atoms may be replaced by F, and n2 denotes 0, 1 , 2 or 3, preferably 1 or 2.