EP3630921A1

EP3630921A1 - Liquid-crystal media and pnlc light modulation element

Info

Publication number: EP3630921A1
Application number: EP18724577.4A
Authority: EP
Inventors: Benjamin Snow; Rachel TUFFIN
Original assignee: Merck Patent GmbH
Current assignee: Merck Patent GmbH
Priority date: 2017-05-24
Filing date: 2018-05-22
Publication date: 2020-04-08
Also published as: WO2018215393A1; TW201903133A; CN110651020A

Abstract

The present invention relates to liquid crystalline (LC) medium, to a method of its production and to the use of such LC media in polymer network liquid crystalline (PNLC) light modulation elements, preferably operated in the ECB mode. Furthermore, the present invention relates to such light modulation elements, as such, to the use of such light modulation elements in electro-optic devices, in particular in LC displays, and to a method of production of such light modulation.

Description

Liquid-crystal media and PNLC light modulation element

Technical Field

The present invention relates to liquid crystalline (LC) medium, to a method of its production and to the use of such LC media in polymer network liquid crystalline (PNLC) light modulation elements, preferably operated in the ECB mode. Furthermore, the present invention relates to such light modulation elements, as such, to the use of such light modulation elements in electro optic devices, in particular in LC displays, and to a method of production of such light modulation elements according to the present invention.

BACKGROUND OF THE INVENTION

Liquid crystal spatial light modulators (LC SLMs) have been widely used in

· digital hologram generation [O. Matoba, T. J. Naughton, Y. Frauel, N.

Bertaux, and B. Javidi, Appl. Opt. 41 , 6187 (2002); or P. Clemente, V. Duran, E. Tajahuerce, P. Andres, V. Climent, and J. Lancis, Opt. Lett. 38, 2524 (2013)],.

· adaptive optics [G. D. Love, Appl. Opt. 36, 1517 (1997).or S. Quirin, D. S. Peterka, and R. Yuste, Opt. Express 21 , 16007 (2013)],

• adaptive lens [H. Ren and S. T. Wu, Introduction to Adaptive Lenses (Wiley, 2012)], .and

· laser beam steering [P. F. McManamon, T. A. Dorschner, D. L.

Corkum, L. J. Friedman, D. S. Hobbs, M. Holz, S. Liberman, H. Q. Nguyen, D. P. Resler, R. C. Sharp, and E. A. Watson, Proc. IEEE 84, 268 (1996); or S. Serati and J. Stockley, Proc. SPIE 5894, 58940K (2005); or F. Feng, I. H. White, and T. D. Wilkinson, J. Lightwave Technol. 31 , 2001 (2013)]. For these applications, fast response times, 2π phase changes, and low operation voltages are some basic requirements. In this regard, various LC technologies and modes have been explored, such as, for example:

• ferroelectric LC [J. Fuenfschilling and M. Schadt, Jpn. J. Appl. Phys.,

Part 1 30, 741 (1991 )],

• dual frequency liquid crystal (DFLC) [W. J. De Jeu, C. J. Gerritsma, P. Van Zanten, and W. J. A. Goossens, Phys. Lett. A 39, 355 (1972)].

• stressed LC [L. West, G. Zhang, A. Glushchenko, and Y. Reznikov, Appl. Phys. Lett. 86, 031 1 1 1 (2005); or Y.-H. Wu, Y.-H. Lin, H. Ren,

X. Nie, J.-H. Lee, and S.-T. Wu, Opt. Express 13, 4638 (2005)], and

• polymer network liquid crystal (PNLC) [Y.-H. Fan, Y.-H. Lin, H. Ren, S. Gauza, and S.-T. Wu, Appl. Phys. Lett. 84, 1233 (2004); or J. Sun and S.-T. Wu, J. Polym. Sci., Part B: Polym. Phys. 52, 183 (2014)].

Each of the above mentioned approaches have its own advantages and disadvantages, which will be explained below in more detail.

Ferroelectric LC, e.g., shows microsecond response time, but it is a bistable device and is difficult to obtain continuous phase-only

modulation.

DFLC offers fast rise time and decay time, but its mandatory crossover frequency is quite sensitive to the temperature.

Stressed LC does not require an alignment layer, but needs a delicate mechanical shearing process, which is not compatible to modern mass production processes.

PNLCs have been developed for wavelength of 1 .55 μιτι and 1 .06 μιτι [J. Sun, H. Xianyu, Y. Chen, and S.-T. Wu, Appl. Phys. Lett. 99, 021 106 (201 1 )]. However, these PNLCs scatter light strongly in the visible region because of voltage-induced micron-sized multi-domain structures [J. Sun, Y. Chen, and S.-T. Wu, Opt. Express 20, 20124 (2012)].

To suppress scattering in the visible region, one approach is to reduce the domain size to approximately 100 nm [J. Sun, S. Xu, H. Ren, and S.- T. Wu, Appl . Phys. Lett. 102, 161 106 (2013)]. In this regard, the major challenge is that the operation voltage increases dramatically due to strong anchoring from these fine polymer network structures and a corresponding PNLC requires a ν_2π of about 50 V to obtain 2% phase change in reflective mode at a wavelength of around 514 nm, while the commonly used high resolution liquid-crystal-on-silicon (LCoS) has a maximum voltage of 24 V [S. A. Serati, X. Xia, O. Mughal, and A.

Linnenberger, Proc. SPIE 5106, 138 (2003)].

To integrate a sub millisecond-response PNLC with LCoS for

widespread applications, J. Sun, S.-T. Wu and Y. Haseba in Appl. Phys. Lett. 104, 023305 (2014) suggest a low voltage polymer network liquid crystal (PNLC) with sub millisecond response time by employing a PNLC mixture with 92.3 wt.% LC host (JC-BP07N, JNC) with 7.2% monomer (RM257, Merck) and 0.5% photo-initiator (BAPO, Genocure). As a result, the ν_2π voltage could be lowered to 23V at a wavelength of 514 nm with compromises concerning unfavourable scattering and slower response time.

In view of the above mentioned problems, the invention is based on the object of providing novel suitable materials, in particular LC media for use in PNLC light modulation elements preferably operated in the TN, STN, VA or ECB mode, which do not have the disadvantages indicated above or do so to a reduced extent. Especially, the invention is based on the object of providing LC media for PNLC light modulation elements based on the ECB mode and PNLC light modulation elements operated in the ECB mode, as such, preferably exhibiting one or more advantages mentioned above and below.

In particular, the invention is based on the object of providing improved LC media for use in PNLC light modulation elements operated in the

ECB mode, which enable fast switching times (3 ms off-time or faster), and which produce a retardation change of 2π at an V_2jt of 9 V or less.

Other aims of the present invention are immediately evident to the person skilled in the art from the following description.

Surprisingly, the inventors have found out that one or more of the above and below defined objects can be achieved by the present invention according to claim 1 .

Brief Description Thus, the invention relates to a medium for a PNLC light modulation element comprising

- a polymerisable component A) in an amount of > 2% to < 10%

comprising, preferably consisting of, one or more polymerisable compounds, at least one of which is a compound of formula I,

P¹¹-Sp¹¹-Ar-Sp¹²-P¹² I wherein

Ar is a group selected from the following formulae -5-

which is optionally substituted by one or more groups L,

L is on each occurrence identically or differently F, CI, -CN,

P-Sp-, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH₂- groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and/or S- atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or CI, p¹¹ and P¹² denote each and independently from another a

polymerisable group,

Sp¹¹ and Sp¹² denote each and independently from another a spacer group that is optionally substituted by one or more groups P¹¹ or P¹², or a single bond, preferably a spacer group or a single bond, more preferably a single bond, and

- a liquid-crystalline component B), hereinafter also referred to as "LC host mixture", exhibiting dielectrically positive anisotropy, which comprises, preferably consists of, one or more non-polymerisable mesogenic or liquid-crystalline compounds.

The liquid-crystalline component B) of an LC medium according to the present invention is hereinafter also referred to as "LC host mixture", and preferably comprises one or more, preferably at least two

mesogenic or LC compounds selected from low-molecular-weight compounds, which are unpolymerisable. The invention furthermore relates to an LC medium or a PNLC light modulation element as described above and below, wherein the compounds of formula I, or the polymerisable compounds of component

A), are polymerised.

The invention furthermore relates to a process for preparing an LC medium as described above and below, comprising the steps of mixing one or more mesogenic or LC compounds, or an LC host mixture or LC component B) as described above and below, with a polymerisable component A) in an amount of > 2% to < 10% comprising, preferably consisting of, one or more polymerisable compounds, at least one of which is a compound of formula I, and optionally with further LC compounds and/or additives.

The invention furthermore relates to the use of an LC medium as described above and below in a light modulation element based on the normally transparent PNLC mode.

The invention furthermore relates to a PNLC light modulation element comprising a LC cell comprising two opposing substrates, an electrode structure and a layer of an LC medium as described above and below located between the substrates, characterized in that the polymerisable compounds of the LC medium are polymerized.

The invention furthermore relates to PNLC light modulation element comprising a polymer network obtainable by polymerisation of one or more compounds of formula I or of a polymerisable component A) as described above and below. The invention furthermore relates to the use a PNLC light modulation element as described above and below, in an electro-optical device.

Thus, the invention also relates to electro-optical devices comprising the PNLC light modulation elements as described above and below as such.

The invention furthermore relates to a process for the production of the PNLC light modulation element as described above and below in which an LC medium as described above and below, is introduced into an LC cell having two substrates and an electrode structure as described above and below, and the polymerisable LC compounds of the LC medium are polymerised.

Especially, by utilizing the LC media according to the present invention in PNLC light modulation elements, the above and below mentioned requirements, amongst others, can be fulfilled, preferably at the same time.

In particular, the PNLC light modulation elements exhibit, preferably at the same time,

- favourable fast response times, in particular favourable fast

switching off times (t₀ff), and

- favourable low voltages required for addressing,

and are therefore especially useful for devices utilizing a field sequential colour switching.

In addition, the PNLC light modulation elements can be produced by compatible, commonly known methods for the mass production.

Terms and Definition Unless explicitly stated otherwise, the following meanings apply above and below:

The term "liquid crystal", "mesomorphic compound", or "mesogenic compound" (also shortly referred to as "mesogen") means a compound that under suitable conditions of temperature, pressure and

concentration can exist as a mesophase (nematic, smectic, etc.) or in particular as a LC phase. Non-amphiphilic mesogenic compounds comprise for example one or more calamitic, banana-shaped or discotic mesogenic groups.

The term "mesogenic group" means a group with the ability to induce liquid-crystalline phase (or mesophase) behaviour. The compounds comprising mesogenic groups do not necessarily have to exhibit a liquid- crystalline mesophase themselves. It is also possible that they show liquid-crystalline mesophases only in mixtures with other compounds, or when the mesogenic compounds or materials, or the mixtures thereof, are polymerised. This includes low-molecular-weight non-reactive liquid- crystalline compounds, reactive or polymerisable liquid-crystalline compounds, and liquid-crystalline polymers. For the sake of simplicity, the term "liquid crystal" is used hereinafter for both mesogenic and LC materials.

A calamitic mesogenic group is usually comprising a mesogenic core consisting of one or more aromatic or non-aromatic cyclic groups connected to each other directly or via linkage groups, optionally comprising terminal groups attached to the ends of the mesogenic core, and optionally comprising one or more lateral groups attached to the long side of the mesogenic core, wherein these terminal and lateral groups are usually selected e.g. from carbyl or hydrocarbyl groups, polar groups like halogen, nitro, hydroxy, etc., or polymerisable groups. The term "reactive mesogen" or "polymerisable LC compounds" means a polymerisable mesogenic or liquid crystal compound, preferably a monomeric compound. These compounds can be used as pure compounds or as mixtures of reactive mesogens with other compounds functioning as photoinitiators, inhibitors, surfactants, stabilizers, chain transfer agents, non-polymerisable compounds, etc.

Polymerisable compounds with one polymerisable group are also referred to as "monoreactive" compounds, compounds with two polymerisable groups as "direactive" compounds, and compounds with more than two polymerisable groups, i.e. three, four, five or more as "multireactive" compounds. Compounds without a polymerisable group are also referred to as "non-reactive or non-polymerisable "compounds.

The term "non-mesogenic compound or material" means a compound or material that does not contain a mesogenic group as defined above.

As used herein, the term "unpolymerisable compound" will be

understood to mean a compound that does not contain a functional group that is suitable for polymerisation under the conditions usually applied for the polymerisation of the RMs.

The terms, LC material, LC medium or LC formulation, each non- polymerisable or polymerisable, or mixtures thereof, mean a material, which comprises of more than 80% by weight, preferably more than 90% by weight, more preferably more than 95% by weight of mesogenic compounds, as described above and below.

"Polymerisable groups" (P) are preferably selected from groups containing a C=C double bond or C≡C triple bond, and groups which are suitable for polymerisation with ring opening, such as, for example, oxetane or epoxide groups.

Preferably, polymerisable groups (P) are selected from the group

O

consisting of CH₂=CW¹-COO-, CH₂=CW¹-CO-, W²HC— CH - ,

CH=CH-O-, (CH₂=CH)₂CH-OCO-, (CH₂=CH-CH₂)₂CH-OCO-,

(CH₂=CH)₂CH-O-, (CH₂=CH-CH₂)₂N-, (CH₂=CH-CH₂)₂N-CO-, CH₂

CH=CH-,

in which

W¹ denotes H, F, CI, CN, CF₃, phenyl or alkyl having 1 to 5 C atoms, in particular H, F, CI or CH₃,

W² denotes H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl,

W³ and W⁴ each, independently of one another, denote H, CI or alkyl having 1 to 5 C atoms, Phe denotes 1 ,4-phenylene, which is optionally substituted by one or more radicals L as being defined above but being different from P-Sp, preferably preferred substituents L are F, CI, CN, NO₂, CH₃, C₂H₅, OCH₃, OC2H5, COCH₃, COC2H5, COOCH₃, COOC2H5, CF₃, OCF₃, OCHF2, OC2F5, furthermore phenyl, and ki, k₂ and k₃ each, independently of one another, denote 0 or 1 , k₃ preferably denotes 1 , and k₄ is an integer from 1 to 10.

Particularly preferred polymerizable groups P are CH₂=CH-COO-, CH₂=C(CH₃)-COO-, CH₂=CF-COO-, CH₂=CH-, CH₂=CH-O-,

O

2 ^X

=CH)₂CH-OCO-, (CH₂=CH)₂CH-O-, HC CH - and (^{C H}2)kr°- , in which W² denotes H or alkyl having 1 to 5 C atoms, in particular H, methyl, ethyl or n-propyl and ki denotes 0 or 1 .

Further preferred polymerizable groups (P) are, vinyl, vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane and epoxide, most preferably acrylate or methacrylate, in particular acrylate.

Preferably, all multireactive polymerisable compounds and sub-formulae thereof contain instead of one or more radicals P-Sp-, one or more branched radicals containing two or more polymerisable groups P (multireactive polymerisable radicals).

Suitable radicals of this type, and polymerisable compounds containing them, are described, for example, in US 7,060,200 B1 or

US 2006/0172090 A1 .

Particular preference is given to multireactive polymerisable radicals selected from the following formulae:

-X-alkyl-CHP^x-CH₂-CH₂P^y l*a -X-alkyl-C(CH₂P^x)(CH₂P^y)-CH₂P^z l*b -X-alkyl-CHP^xCHP^y-CH₂P^z

-X-alkyl-C(CH₂P^x)(CH₂P^y)-CaaH2aa₊i

-X-alkyl-CHP^x-CH₂P^y

-X-alkyl-CHP^xP^y

-X-alkyl-CP^xP^y-CaaH_2aa₊i

-X-alkyl-C(CH₂P^v)(CH₂P^w)-CH₂OCH₂-C(CH₂P^x)(CH₂Py)CH₂P^z -X-alkyl-CH((CH₂)aaP^x)((CH₂)_bbP^y) -X-alkyl-CHP^xCHP^y-CaaH_2aa+i in which denotes a single bond or straight-chain or branched alkylene having 1 to 12 C atoms, in which one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by -C(R^X)=C(R^X)-, -C≡C-, -N(R^X)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, CI or CN, where R^x has one the above-mentioned meaning, aa each, independently of one another, denote 0, 1 , 2, 3, 4, 5 or 6

X has one of the meanings indicated for X', and P^vto P^z each, independently of one another, have one of the meanings indicated above for P.

The term "spacer group", hereinafter also referred to as "Sp", as used herein is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 2001 , 73(5), 888 and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 1 16, 6340-6368. As used herein, the terms "spacer group" or "spacer" mean a flexible group, for example an alkylene group, which connects the mesogenic group and the polymerisable group(s) in a polymerisable mesogenic

compound.

If the spacer group Sp is different from a single bond, it is preferably of the formula Sp'-X', so that the respective radical P-Sp- conforms to the formula P-Sp'-X', wherein

Sp' denotes alkylene having 1 to 20, preferably 1 to 12 C

atoms, which is optionally mono- or polysubstituted by F, CI, Br, I or CN and in which, in addition, one or more non- adjacent CH₂ groups may each be replaced, independently of one another,

by -O-, -S-, -NH-, -NR**-, -SiFTR^-, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-, -NFT-CO-O-, -O-CO-NR**-, -NFT-CO-NR^W-, -CH=CH- or -C≡C- in such a way that O and/or S atoms are not linked directly to one another,

X' denotes -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR**-,

-NFT-CO-, -NFT-CO-NR^W-, -OCH₂-, -CH₂O-, -SCH₂-, -CH₂S-, -CF₂O-, -OCF₂-, -CF₂S-, -SCF₂-, -CF₂CH₂-,

-CH₂CF₂-, -CF₂CF₂-, -CH=N-, -N=CH-, -N=N-, -CH=CR^XX-, -CY^CY**-, -C≡C-, -CH=CH-COO-, -OCO-CH=CH- or a single bond,

preferably -O-, -S- -CO-, -COO-, -OCO-, -O-COO-,

-CO-NR**-, -NR^-CO-, -NR^-CO-NR^- or a single bond.

R™ and R^yy each, independently of one another, denote H or alkyl

having 1 to 12 C atoms, and

Y** and Y^yy each, independently of one another, denote H, F, CI or CN.

Typical spacer groups Sp' are, for example, -(CH₂) i-, -(CH₂CH₂O)_qi- CH₂CH₂-, -CH₂CH₂-S-CH₂CH₂-, -CH₂CH₂-NH-CH₂CH₂- or -(SiR^R^-O)^-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R^x and R^yy have independently from another one the above-mentioned meanings. Particularly preferred groups -X'-Sp'- are -(CH₂)_pi-, -O-(CH₂)_pi-, -OCO- (CH₂)_pi-, -OCOO-(CH₂)_pi-, in which p1 is an integer from 1 to 12.

Particularly preferred groups Sp' are, for example, methylene, ethylene or a straight alkyl chain, such as, for example, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, or ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethylene-N- methyliminoethylene, 1 -methylalkylene, ethenylene, propenylene and butenylene.

As used herein, the term "polymer" will be understood to mean a molecule that encompasses a backbone of one or more distinct types of repeating units (the smallest constitutional unit of the molecule) and is inclusive of the commonly known terms "oligomer", "copolymer", "home-polymer" and the like. Further, it will be understood that the term polymer is inclusive of, in addition to the polymer itself, residues from initiators, catalysts, and other elements attendant to the synthesis of such a polymer, where such residues are understood as not being covalently incorporated thereto. Further, such residues and other elements, while normally removed during post polymerisation purification processes, are typically mixed or co-mingled with the polymer such that they generally remain with the polymer when it is transferred between vessels or between solvents or dispersion media.

The term "(meth)acrylic polymer" as used in the present invention includes a polymer obtained from (meth)acrylic monomers, a polymer obtainable from (meth)acrylic monomers, and a corresponding copolymer obtainable from mixtures of methacrylic monomers and acrylic monomers.

A "polymer network" is a network in which all polymer chains are interconnected to form a single macroscopic entity by many crosslinks, preferably which extends through the whole cell if utilized in an PNLC device. The polymer network can occur in the following types:

1 . A graft polymer molecule is a branched polymer molecule in which one or more the side chains are different, structurally or

configurationally, from the main chain.

2. A star polymer molecule is a branched polymer molecule in which a single branch point gives rise to multiple linear chains or arms. If the arms are identical, the star polymer molecule is said to be regular. If adjacent arms are composed of different repeating subunits, the star polymer molecule is said to be variegated.

3. A comb polymer molecule consists of a main chain with two or more three-way branch points and linear side chains. If the arms are identical, the comb polymer molecule is said to be regular. 4. A brush polymer molecule consists of a main chain with linear, unbranched side chains and where one or more of the branch points has four-way functionality or larger.

The term "polymerisation" means the chemical process to form a polymer by bonding together multiple polymerisable groups or polymer precursors (polymerisable compounds) containing such polymerisable groups.

The definitions as given in C. Tschierske, G. Pelzl and S. Diele, Angew. Chem. 2004, 1 16, 6340-6368 shall apply additionally to the before given definitions and in particular to non-defined terms related to liquid crystal materials in the instant application.

The birefringence Δη herein is defined by the following equation Δη = 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

The extraordinary refractive index n_e and the ordinary refractive index n₀ can be measured e.g. using a modified Abbe refractometer in

accordance to "Merck Liquid Crystals, Physical Properties of Liquid Crystals", Status Nov. 1997, Merck KGaA, Germany.

Visible light is electromagnetic radiation that has wavelength in a range from about 400 nm to about 800 nm. Unless stated otherwise, ultraviolet (UV) light is electromagnetic radiation with a wavelength in a range from about 200 nm to about 400 nm.

The term "transparent" in the context of this application is taken to mean that the transmission of light through the PNLC light modulation element is at least 65 % of the incident light, more preferably at least 80 %, even more preferably at least 90 %.

The radiation dose (E_e) is defined as the power of electromagnetic radiation (d9) per unit area (dA) incident on a surface:

E_e = d0/dA.

The radiation intensity (H_e), is defined as the radiation dose (E_e) per time (t):

The term "clearing point" means the temperature at which the transition between the mesophase with the highest temperature range and the isotropic phase occurs.

Throughout the application and unless explicitly stated otherwise, all concentrations are quoted in percent by weight and relate to the respective mixture as a whole, all temperatures are quoted in degrees Celsius and all temperature differences are quoted in differential degrees.

In the present application the term "dielectrically positive" is used for compounds or components with Δε > 3.0, "dielectrically neutral" with -1 .5 ≤ Δε≤ 3.0 and "dielectrically negative" with Δε < -1 .5. Δε 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 medium is less than 10 % its concentration is reduced by a factor of 2 until the resultant medium is stable enough at least to allow the determination of its properties. In a preferred embodiment, the

concentration is kept at least at 5 %, however, in order to keep the significance of the results a high as possible. The capacitance of the test mixtures are determined both in a cell with homeotropic and with homogeneous alignment. The cell gap of both types of cells is

approximately 20 μιτι. 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.

Δε is defined as (ε - ε±), whereas ε_3ν. is (ε + 2 ε±) / 3. The dielectric permittivity of the compounds is determined from the change of the respective values of a host medium upon addition of the compounds of interest. The values are extrapolated to a concentration of the

compounds of interest of 100 %. A typical host medium is ZLI-4792 or BL-087 both commercially available from Merck, Darmstadt.

Unless the context clearly indicates otherwise, as used herein plural forms of the terms herein are to be construed as including the singular form and vice versa.

For the present invention, denote 1 ,4-cyclohexylene, preferably

and denote trans-1 ,4-cylohexylene.

For the resent invention, and

denote 1 ,4-phenylene.

For the present invention the groups -COO- -C(=O)O- or -CO2- denote o an ester group of formula ⁰ , and the groups -OCO-, -OC(=0)-

O

-O2C- or -OOC- denote an ester group of formula ⁰

In a group , the single bond shown between the two ring atoms can be attached to any free position of the benzene ring.

Above and below, "carbyl group" denotes a mono- or polyvalent organic group containing at least one carbon atom which either contains no further atoms (such as, for example, C≡C ) or optionally contains one or more further atoms, such as, for example, N, O, S, P, Si, Se, As, Te or Ge (for example carbonyl, etc.). "Hydrocarbyl group" denotes a carbyl group, which additionally contains one or more H atoms and optionally one or more heteroatoms, such as, for example, N, O, S, P, Si, Se, As, Te or Ge. A carbyl or hydrocarbyl group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl, or alkinyl groups. A carbyl or hydrocarbyl group having more than 3 C atoms can be straight chain, branched and/or cyclic and may contain spiro links or condensed rings.

Throughout the application, unless stated explicitly otherwise, the term "aryl and heteroaryl groups" encompass groups, which can be

monocyclic or polycyclic, i.e. they can have one ring (such as, for example, phenyl) or two or more rings, which may also be fused (such as, for example, naphthyl) or covalently linked (such as, for example, biphenyl), or contain a combination of fused and linked rings.

Heteroaryl groups contain one or more heteroatoms, preferably selected from O, N, S and Se. Particular preference is given to mono-, bi- or tricyclic aryl groups having 6 to 25 C atoms and mono-, bi- or tricyclic heteroaryl groups having 2 to 25 C atoms, which optionally contain fused rings, and which are optionally substituted. Preference is furthermore given to 5 , 6 or 7-membered aryl and heteroaryl groups, in which, in addition, one or more CH groups may be replaced by N, S or O in such a way that O atoms and/or S atoms are not linked directly to one another. Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl, [1 ,1 ':3',1 "]terphenyl-2'-yl, naphthyl, anthracene, binaphthyl,

phenanthrene, pyrene, dihydropyrene, chrysene, perylene, tetracene, pentacene, benzopyrene, fluorene, indene, indenofluorene,

spirobifluorene, more preferably 1 ,4- phenylene, 4,4'-biphenylene, 1 , 4- tephenylene.

Preferred heteroaryl groups are, for example, 5 membered rings, such as pyrrole, pyrazole, imidazole, 1 ,2,3-triazole, 1 ,2,4-triazole, tetrazole, furan, thiophene, selenophene, oxazole, isoxazole, 1 ,2 thiazole, 1 ,3- thiazole, 1 ,2,3-oxadiazole, 1 ,2,4 oxadiazole, 1 ,2,5-oxadiazole, 1 ,3,4- oxadiazole, 1 ,2,3-thiadiazole, 1 ,2,4-thiadiazole, 1 ,2,5-thiadiazole, 1 ,3,4- thiadiazole, 6 membered rings, such as pyridine, pyridazine, pyrimidine, pyrazine, 1 ,3,5-triazine, 1 ,2,4-triazine, 1 ,2,3-triazine, 1 ,2,4,5-tetrazine, 1 ,2,3,4-tetrazine, 1 ,2,3,5-tetrazine, or condensed groups, such as indole, iso-indole, indolizine, indazole, benzimidazole, benzotriazole, purine,

5

naphth-imidazole, phenanthrimidazole, pyridimidazole, pyrazinimidazole, quinoxalinimidazole, benzoxazole, naphthoxazole, anthroxazole, phen- anthroxazole, isoxazole, benzothiazole, benzofuran, isobenzofuran, dibenzofuran, quinoline, isoquinoline, pteridine, benzo-5,6-quinoline,

10

benzo-6,7-quinoline, benzo-7,8-quinoline, benzoisoquinoline, acridine, phenothiazine, phenoxazine, benzopyridazine, benzopyrimidine, quinoxaline, phenazine, naphthyridine, azacarbazole, benzocarboline, phenanthridine, phenanthroline, thieno[2,3b]thiophene, thieno[3,2b]- 15 thiophene, dithienothiophene, isobenzothiophene, dibenzothiophene, benzothiadiazothiophene, or combinations of these groups. The heteroaryl groups may also be substituted by alkyl, alkoxy, thioalkyl, fluorine, fluoroalkyl or further aryl or heteroaryl groups.

20

In the context of this application, the term "(non-aromatic) alicyclic and heterocyclic groups" encompass both saturated rings, i.e. those that contain exclusively single bonds, and partially unsaturated rings, i.e. 2^ those that may also contain multiple bonds. Heterocyclic rings contain one or more heteroatoms, preferably selected from Si, O, N, S and Se. The (non-aromatic) alicyclic and heterocyclic groups can be monocyclic, i.e. contain only one ring (such as, for example, cyclohexane), or polycyclic, i.e. contain a plurality of rings (such as, for example,

30

decahydro-naphthalene or bicyclooctane). Particular preference is given to saturated groups. Preference is furthermore given to mono-, bi- or tricyclic groups having 3 to 25 C atoms, which optionally contain fused rings and that are optionally substituted. Preference is furthermore given ^ to 5-, 6-, 7- or 8-membered carbocyclic groups in which, in addition, one or more C atoms may be replaced by Si and/or one or more CH groups may be replaced by N and/or one or more non-adjacent CH₂ groups may be replaced by -O- and/or -S-. Preferred alicyclic and heterocyclic groups are, for example, 5-membered groups, such as cyclopentane, tetrahydrofuran, tetrahydrothiofuran, pyrrolidine, 6-membered groups, such as cyclohexane, silinane, cyclohexene, tetrahydropyran, tetrahydrothiopyran, 1 ,3-dioxane, 1 ,3-dithiane, piperidine, 7-membered groups, such as cycloheptane, and fused groups, such as

tetrahydronaphthalene, decahydronaphthalene, indane,

bicyclo[1 .1 .1 ]pentane-1 ,3-diyl, bicyclo[2.2.2]octane-1 ,4-diyl,

spiro[3.3]heptane-2,6-diyl, octahydro-4,7-methanoindane-2,5-diyl, more preferably 1 ,4-cyclohexylene 4,4'- bicyclohexylene, 3,17- hexadecahydro-cyclopenta[a]phenanthrene, optionally being substituted by one or more identical or different groups L. Especially preferred aryl-, heteroaryl-, alicyclic- and heterocyclic groups are 1 ,4-phenylene, 4,4'- biphenylene, 1 , 4-terphenylene, 1 ,4-cyclohexylene, 4,4'- bicyclohexylene, and 3,17-hexadecahydro-cyclopenta[a]-phenanthrene, optionally being substituted by one or more identical or different groups L.

Preferred substituents (L) of the above-mentioned aryl-, heteroaryl-, alicyclic- and heterocyclic groups are, for example, solubility-promoting groups, such as alkyl or alkoxy and electron-withdrawing groups, such as fluorine, nitro or nitrile.

Preferred substituents, also referred to as "L" below, are,

for example, F, CI, Br, I, -OH, -CN, -NO₂, -NCO, -NCS, -OCN, -SCN, -C(=O)N(R^x)₂, -C(=O)Y^x, -C(=O)R^x, -C(=O)OR^x, -N(R^X)₂, in which R^x has the above-mentioned meaning, and above Y^x denotes halogen, optionally substituted silyl, optionally substituted aryl or heteroaryl having 4 to 40, preferably 4 to 20 ring atoms, and straight-chain or branched alkyl, alkenyl, alkinyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 25 C atoms, in which one or more H atoms may optionally be replaced by F or CI.

"Substituted silyl or aryl" preferably means silyl or aryl substituted by halogen, -CN, R^y, -OR^y, -CO-R^y, -CO-O-R^y, -O-CO-R^y or -O-CO-O-R^y, in which R^y denotes H, a straight-chain, branched or cyclic alkyl chain having 1 to 12 C atoms.

In the formulae shown above and below, a substituted phenylene ring

in which L has, on each occurrence identically or differently, one of the meanings given above and below, and is preferably F, CI, CN, ΝΟ₂, CH₃, C2H5, C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH3)C₂H5, OCH₃, OC₂H₅, COCH₃, COC2H5, COOCH3, COOC2H5, CF₃, OCF3, OCHF₂, OC2F5 or P-Sp-, very preferably F, CI, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, most preferably F, CI, CH₃, OCH₃, COCH₃ or OCF₃.

"Halogen" denotes F, CI, Br or I, preferably F or CI, more preferably F.

Above and below, the terms "alkyl", "aryl", "heteroaryl", etc., also encompass polyvalent groups, for example alkylene, arylene,

heteroarylene, etc. The term "aryl" denotes an aromatic carbon group or a group derived there from.

The term "heteroaryl" denotes "aryl" in accordance with the above definition containing one or more heteroatoms.

Preferred alkyl groups are, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, 2-methylbutyl, n-pentyl, s- pentyl, cyclo-pentyl, n-hexyl, cyclohexyl, 2-ethylhexyl, n-heptyl, cydoheptyl, n-octyl, cydooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoro-methyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluoro-hexyl, etc.

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, n-dodecoxy.

Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cydopentenyl, hexenyl, cydohexenyl, heptenyl, cydoheptenyl, octenyl, cyclooctenyl.

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

Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to (and do not) exclude other components. On the other hand, the word "comprise" also encompasses the term "consisting of but is not limited to it.

Throughout the description and claims of this specification, the words "obtainable" and "obtained" and variations of the words, mean "including but not limited to", and are not intended to (and do not) exclude other components. On the other hand, the word "obtainable" also

encompasses the term "obtained" but is not limited to it.

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 "homeotropic orientation/alignment", 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 Θ ("tilt angle") between about 80° to 90° relative to the plane of the layer. Detailed Description

Preferably in the compounds of formula I and its subformulae as described above and below all polymerisable groups P that are present in the compound have the same meaning, and more preferably denote acrylate or methacrylate, most preferably methacrylate.

Further preferred are compounds of formula I and its subformulae wherein the group Ar is selected from formulae Ar5, Ar 6 and Ar7, and the groups P present in the compound are identical or different.

In the compounds of formula I and its subformulae as described above and below, Ar is preferably selected from formulae Ar1 , Ar2 and Ar5.

Preferred compounds of formula I are selected from the following subformulae

I3

wherein P, Sp, and L have one of the meanings given in formula I, r1 , r3, r7 are independently of each other 0, 1 , 2 or 3,

r2 is 0, 1 , 2, 3 or 4,

r4, r5, r6 are independently of each other 0, 1 or 2. Very preferred are compounds of formula 11 , I2 and I5.

Further preferred compounds of formula I are selected from the following subformulae

15-1

wherein P, Sp, L, -r7 have the meanings given in formula I or one of the preferred meanings as given above and below.

Very preferred compounds of formula I are selected from the following subformulae:

11 -1 -1

35 wherein P, Sp, have the meanings given above or below, and

La and L have each and independently from another one of the meanings given for L above or below.

Very preferred compounds of subformulae 11 -1 -1 to 12-1 -18 are those wherein all groups P are identical and denote either an acrylate or methacrylate group, furthermore those wherein Sp is, -(CH₂) i-, -(CH₂) i- O-, -(CH₂)_pi-O-CO- or -(CH₂)_pi-CO-O-, in which p1 is an integer from 1 to 12, preferably 1 to 6, and the O- or CO-group is connected to the benzene ring, furthermore those wherein L^a and L denotes F, CH₃, CH₂CH₃, OCH₃, OC₂H₅, O(CH₂)₂CH₃, OC(CH₃)₃ or OCF₃.

Further preferred compounds of formula I and its subformulae are selected from the following preferred embodiments, including any combination thereof:

All groups P in the compound have the same meaning,

Ar is selected from formulae Ar1 , Ar2, Ar3 and Ar4, and all groups P present in the compound have the same meaning,

Ar is selected from formulae Ar1 , Ar2, Ar3, Ar4 and Ar5, and all groups P present in the compound have the same meaning,

Ar is selected from formulae Ar1 , Ar2, Ar3, Ar4 and Ar6, and all groups P present in the compound have the same meaning,

Ar is selected from formulae Ar1 , Ar2, Ar3, Ar4 and Ar7, and all groups P present in the compound have the same meaning,

Ar is selected from formulae Ar1 , Ar2, Ar3, Ar4, A5 and Ar7, and all groups P present in the compound have the same meaning, Ar is selected from formulae Ar1 , Ar2, Ar3, Ar4, A6 and Ar7, and all groups P present in the compound have the same meaning,

Ar is selected of formula Ar5, and the groups P present in the compound can have the same or different meanings,

Ar is selected of formula Ar6, and the groups P present in the compound can have the same or different meanings,

Ar is selected of formula Ar7, and the groups P present in the compound can have the same or different meanings, the compounds contain exactly two polymerisable groups

(represented by the groups P),

P is selected from the group consisting of acrylate, methacrylate and oxetane,

Sp, when being different from a single bond, is -(CH₂) 2-, -(CH₂)_p2- O-, -(CH₂)_P2-CO-O-, -(CH₂)_P2-O-CO-, wherein p2 is 2, 3, 4, 5 or 6, and the O-atom or the CO-group, respectively, is connected to the benzene ring,

L , when being different from L^a, denotes F, CI or CN,

L^a is F, CH₃, CH₂CH₃, OCH₃, OC₂H₅, O(CH₂)₂CH₃, OC(CH₃)₃ or OCF₃. r1 , r2 and r3 denote 0 or 1 , r1 , r2, r3, r4, r5 and r6 denote 0 or 1 , one of r1 and r7 is 0 and the other is 1 , r1 is 1 , and r2 and r3 are 0, r3 is 1 and r1 and r2 are 0, one of r4 and r5 is 0 and the other is 1 , r4 and r6 are 0 and r5 is 1 , r1 and r4 are 0 and r3 is 1 , r1 and r3 are 0 and r4 is 1 , r3 and r4 are 0 and r1 is 1 .

Further preferred compounds of formula I and its subformulae are selected from compounds of formula 11 -1 -1 , 11 -1 -3, 11 -2-2 and 12-1 -1 to 12-1 -6 wherein P is selected from the group consisting of acrylate, methacrylate and oxetane, L^a and L is each and independently from another F, CH₃, CH₂CH₃, OCH₃, OC₂H₅, O(CH₂)₂CH₃, OC(CH₃)₃ or OCF₃.

The compounds and intermediates of the formula I and sub-formulae thereof can be prepared analogously to processes known to the person skilled in the art and described in standard works of organic chemistry, such as, for example, in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart.

For example, acrylic or methacrylic esters can be prepared by

esterification of the corresponding alcohols with acid derivatives like, for example, (meth)acryloyl chloride or (meth)acrylic anhydride in the presence of a base like pyridine or triethyl amine, and 4-(N,N- dimethylamino)pyridine (DMAP). Alternatively the esters can be prepared by esterification of the alcohols with (meth)acrylic acid in the presence of a dehydrating reagent, for example according to Steglich with

dicyclohexylcarbodiimide (DCC), A/-(3-dimethylaminopropyl)-/V - ethylcarbodiimide (EDC) or A/-(3-dimethylaminopropyl)-/V - ethylcarbodiimide hydrochloride and DMAP.

Particular preference is given to LC media in which the polymerisable component A) comprises one, two or three polymerisable compounds of formula I. Preference is furthermore given to LC media in which the polymerisable component A) comprises exclusively polymerisable compounds of formula I.

Optionally one or more polymerisation initiators are added to the LC medium. 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® (Ciba AG). If a polymerisation initiator is employed, its proportion is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1 % by weight.

The polymerisable compounds according to the invention are also suitable for polymerisation without an initiator, which is accompanied by considerable advantages, such, for example, lower material costs and in particular less contamination of the LC medium by possible residual amounts of the initiator or degradation products thereof. The

polymerisation can thus also be carried out without the addition of an initiator. In a preferred embodiment, the LC medium thus does not contain a polymerisation initiator.

The LC medium may also comprise one or more stabilisers in order to prevent undesired spontaneous polymerisation of the RMs, for exampl 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 (Ciba AG), such as, for example, Irganox® 1076. If stabilisers are employed, their proportion, based on the total amount of RMs or the polymerisable component (component A), is preferably 10-500,000 ppm, particularly preferably 50- 50,000 ppm.

Preferably, the LC medium according to the present invention does essentially consist of a polymerisable component A), or one or more polymerisable compounds of formula I, and an LC component B), or LC host mixture, as described above and below.

However, the LC medium may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to co-monomers, chiral dopants, polymerisation initiators, inhibitors, stabilizers, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.

Corresponding to the above-said, a certain additive can therefore be classified in a number of the groups c1 ) to c3) described below.

The antifoams in group c1 ) include silicon-free and silicon-containing polymers. The silicon-containing polymers are, for example, unmodified or modified polydialkylsiloxanes or branched copolymers, comb or block copolymers comprising polydialkylsiloxane and polyether units, the latter being obtainable from ethylene oxide or propylene oxide.

The deaerators in group c1 ) include, for example, organic polymers, for example polyethers and polyacrylates, dialkylpolysiloxanes, in particular dimethylpolysiloxanes, organically modified polysiloxanes, for example arylalkyl-modified polysiloxanes, and fluorosilicones. The action of the antifoams is essentially based on preventing foam formation or destroying foam that has already formed. Antifoams essentially work by promoting coalescence of finely divided gas or air bubbles to give larger bubbles in the medium to be deaerated, for example the compositions according to the invention, and thus accelerate escape of the gas (of the air). Since antifoams can frequently also be employed as deaerators and vice versa, these additives have been included together under group c1 ).

Such auxiliaries are, for example, commercially available from Tego as TEGO® Foamex 800, TEGO® Foamex 805, TEGO® Foamex 810, TEGO® Foamex 815, TEGO® Foamex 825, TEGO® Foamex 835, TEGO® Foamex 840, TEGO® Foamex 842, TEGO® Foamex 1435,

TEGO® Foamex 1488, TEGO® Foamex 1495, TEGO® Foamex 3062, TEGO® Foamex 7447, TEGO® Foamex 8020, Tego® Foamex N, TEGO® Foamex K 3, TEGO® Antifoam 2-18,TEGO® Antifoam 2-18, TEGO® Antifoam 2-57, TEGO® Antifoam 2-80, TEGO® Antifoam 2-82, TEGO® Antifoam 2-89, TEGO® Antifoam 2-92, TEGO® Antifoam 14, TEGO® Antifoam 28, TEGO® Antifoam 81 , TEGO® Antifoam D 90, TEGO® Antifoam 93, TEGO® Antifoam 200, TEGO® Antifoam 201 , TEGO® Antifoam 202, TEGO® Antifoam 793, TEGO® Antifoam 1488, TEGO® Antifoam 3062, TEGOPREN® 5803, TEGOPREN® 5852, TEGOPREN® 5863, TEGOPREN® 7008, TEGO® Antifoam 1 -60, TEGO® Antifoam 1 - 62, TEGO® Antifoam 1 -85, TEGO® Antifoam 2-67, TEGO® Antifoam WM 20, TEGO® Antifoam 50, TEGO® Antifoam 105, TEGO® Antifoam 730,

TEGO® Antifoam MR 1015, TEGO® Antifoam MR 1016, TEGO®

Antifoam 1435, TEGO® Antifoam N, TEGO® Antifoam KS 6, TEGO® Antifoam KS 10, TEGO® Antifoam KS 53, TEGO® Antifoam KS 95, TEGO® Antifoam KS 100, TEGO® Antifoam KE 600, TEGO® Antifoam KS 91 1 , TEGO® Antifoam MR 1000, TEGO® Antifoam KS 1 100, Tego® Airex 900, Tego® Airex 910, Tego® Airex 931 , Tego® Airex 935, Tego® Airex 936, Tego® Airex 960, Tego® Airex 970, Tego® Airex 980 and Tego® Airex 985 and from BYK as BYK®-01 1 , BYK®-019, BYK®-020, BYK®-021 , BYK®-022, BYK®-023, BYK®-024, BYK®-025, BYK®-027, BYK®-031 , BYK®-032, BYK®-033, BYK®-034, BYK®-035, BYK®-036,

BYK®-037, BYK®-045, BYK®-051 , BYK®-052, BYK®-053, BYK®-055, BYK®-057, BYK®-065, BYK®-066, BYK®-070, BYK®-080, BYK®-088, BYK®-141 and BYK®-A 530.

The auxiliaries in group c1 ) are optionally employed in a proportion from about 0.01 to 10.0% by weight, preferably from about 0.1 to 5% by weight, more preferably from about 1 .0 to 4% by weight based on the total weight of the LC medium.

In group c2), the lubricants and flow auxiliaries typically include silicon- free, but also silicon-containing polymers, for example polyacrylates or modifiers, low-molecular-weight polydialkylsiloxanes. The modification consists in some of the alkyl groups having been replaced by a wide variety of organic radicals. These organic radicals are, for example, polyethers, polyesters or even long-chain alkyl radicals, the former being used the most frequently.

The polyether radicals in the correspondingly modified polysiloxanes are usually built up from ethylene oxide and/or propylene oxide units.

Generally, the higher the proportion of these alkylene oxide units in the modified polysiloxane, the more hydrophilic is the resultant product.

Such auxiliaries are, for example, commercially available from Tego as TEGO® Glide 100, TEGO® Glide ZG 400, TEGO® Glide 406, TEGO® Glide 410, TEGO® Glide 41 1 , TEGO® Glide 415, TEGO® Glide 420, TEGO® Glide 435, TEGO® Glide 440, TEGO® Glide 450, TEGO® Glide A 1 15, TEGO® Glide B 1484 (can also be used as antifoam and deaerator), TEGO® Flow ATF, TEGO® Flow 300, TEGO® Flow 460, TEGO® Flow 425 and TEGO® Flow ZFS 460. Suitable radiation-curable lubricants and flow auxiliaries, which can also be used to improve the scratch resistance, are the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700, which are likewise obtainable from TEGO.

Such-auxiliaries are also available, for example, from BYK as BYK®-300 ^{1 0} BYK®-306, BYK®-307, BYK®-310, BYK®-320, BYK®-333, BYK®-341 , BYK® 354, Byk®361 , Byk®361 N, BYK®388.

Such-auxiliaries are also available, for example, from Merck KGaA as 15 Tivida® FL 2300 and Tivida® FL 2500

The auxiliaries in group c2) are optionally employed in a proportion from about 0.01 to 10.0% by weight, preferably from about 0.1 to 5% by weight, 20 more preferably from about 1 .0 to 4% by weight based on the total weight of the LC medium.

In group c3), the radiation-curing auxiliaries include, in particular,

2^ polysiloxanes having terminal double bonds which are, for example, a constituent of an acrylate group. Such auxiliaries can be crosslinked by actinic or, for example, electron radiation. These auxiliaries generally combine a number of properties together. In the uncrosslinked state, they can act as antifoams, deaerators, lubricants and flow auxiliaries and/or

30

substrate wetting auxiliaries, while, in the crosslinked state, they increase, in particular, the scratch resistance, for example of coatings or films which can be produced using the compositions according to the invention. The improvement in the gloss properties, for example of precisely those ^ coatings or films, is regarded essentially as a consequence of the action of these auxiliaries as antifoams, deaerators and/or lubricants and flow auxiliaries (in the uncrosslinked state).

Examples of suitable radiation-curing auxiliaries are the products TEGO® Rad 2100, TEGO® Rad 2200, TEGO® Rad 2500, TEGO® Rad 2600 and TEGO® Rad 2700 available from TEGO and the product BYK®-371 available from BYK.

Thermally curing auxiliaries in group c3) contain, for example, primary OH groups, which are able to react with isocyanate groups, for example of the binder. Examples of thermally curing auxiliaries, which can be used, are the products BYK®-370, BYK®-373 and BYK®-375 available from BYK.

The auxiliaries in group c2) are optionally employed in a proportion from about 0.01 to 10.0% by weight, preferably from about 0.1 to 5% by weight, more preferably from about 1 .0 to 4% by weight based on the total weight of the LC medium. Preferably, the proportion of compounds of formula I in the LC medium is from > 2 to < 10%, preferably from > 4 to < 10%, more preferably from > 5 to < 10%, even more preferably > 5 to < 10%.

In another preferred embodiment the polymerisable component A) comprises, in addition to the compounds of formula I, one or more further polymerisable compounds ("co-monomers"), preferably selected from RMs.

Suitable and preferred mesogenic co-monomers are selected from the following formulae: ĭ44

35 in which the individual radicals have the following meanings:

P¹, P² and P³ each, independently of one another, denote an acrylate or methacrylate group,

Sp¹, Sp² and Sp³ each, independently of one another, denote a single bond or a spacer group having one of the meanings indi- cated above and below for Sp, and particularly preferably denote -(CH₂) i-,

-(CH₂)_Pi-O-, -(CH₂)_pi-CO-O-, -(CH₂)_pi-O-CO- or -(CH₂)_pi-O- CO-O-, in which p1 is an integer from 1 to 12, where, in addition, one or more of the radicals P¹-Sp¹-, P¹-Sp²- and P³-Sp³- may denote R^aa, with the proviso that at least one of the radicals

P¹-Sp¹-, P²-Sp² and P³-Sp³- present is different from R^aa,

R^aa denotes H, F, CI, CN or straight-chain or branched alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH₂ groups may each be replaced, independently of one another, by

C(R°)=C(R⁰⁰)-, -C≡C-, -N(R⁰)-, -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a way that O and/or S atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by F, CI, CN or P¹-Sp¹-, particularly preferably straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms (where the alkenyl and alkynyl radicals have at least two C atoms and the branched radicals have at least three C atoms),

R°, R⁰⁰ each, independently of one another and identically or

differently on each occurrence, denote H or alkyl having 1 to 12 C atoms,

R^y and R^z each, independently of one another, denote H, F, CH₃ or

CF₃, X¹, X² and X³ each, independently of one another, denote -CO-O-, -O- CO- or a single bond,

Z¹ denotes -O-, -CO-, -C(R^yR^z)- or -CF₂CF₂-, Z² and Z³ each, independently of one another, denote -CO-O-,

-O-CO-, -CH₂O-, -OCH₂-, -CF₂O-, -OCF₂- or -(CH₂)_n-, where n is 2, 3 or 4,

L on each occurrence, identically or differently, denotes F,

CI, CN or straight-chain or branched, optionally mono- or polyfluorinated alkyl, alkoxy, alkenyl, alkynyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms, preferably F, L' and L" each, independently of one another, denote H, F or CI, r denotes 0, 1 , 2, 3 or 4, s denotes 0, 1 , 2 or 3, t denotes 0, 1 or 2, x denotes 0 or 1 .

Especially preferred are compounds of formulae M2, M13, M17, M22, M23, M24 and M30.

Further preferred are trireactive compounds M15 to M30, in particular M17, M18, M19, M22, M23, M24, M25, M26, M30 and M31 .

In the compounds of formulae M1 to M31 the group

wherein L on each occurrence, identically or differently, has one of the meanings given above or below, and is preferably F, CI, CN, NO2, CH₃, C2H5, C(CH₃)₃, CH(CH₃)₂, CH₂CH(CH3)C₂H5, OCH₃, OC₂H₅, COCH₃, COC2H5, COOCH3, COOC2H5, CF₃, OCF3, OCHF₂, OC2F5 or P-Sp-, very preferably F, CI, CN, CH₃, C₂H₅, OCH₃, COCH₃, OCF₃ or P-Sp-, more preferably F, CI, CH₃, OCH₃, COCH₃ or OCF₃ , especially F or CH₃.

Besides the polymerisable compounds described above, the LC media for use in the LC displays according to the invention comprise an liquid- crystalline component B) or LC host mixture exhibiting dielectrically positive anisotropy, which preferably comprises one or more, more preferably two or more LC compounds, which are selected from low-mole- cular-weight compounds that are unpolymerisable. These LC compounds are selected such that they stable and/or unreactive to a polymerisation reaction under the conditions applied to the polymerisation of the polymerisable compounds.

Preferred LC compounds, which can be employed in the liquid-crystalline component B) according to the invention, are indicated below:

31

in which the individual radicals have, independently of each other and on each occurrence identically or differently, the following meanings: each, independently

of one another and on each occurrence, identically or differently

each, independently of one another, alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated,

X° F, CI, CN, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, Z³¹ -CH₂CH₂-, -CF₂CF₂-, -COO-, frans-CH=CH-, trans-

CF=CF-, -CH2O- or a single bond, preferably -

-COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, trans-CH=CH- or a single bond, L²¹, L ²², L³¹, L ³² each, independently of one another, H or F, g 0, 1 , 2 or 3.

In the compounds of formula A and B, X° is preferably F, CI, CF₃, CHF₂, OCF3, OCHF₂, OCFHCF3, OCFHCHF₂, OCFHCHF₂, OCF₂CH₃,

OCF₂CHF₂, OCF₂CHF₂, OCF₂CF₂CHF₂, OCF₂CF₂CHF₂, OCFHCF₂CF₃, OCFHCF₂CHF₂, OCF₂CF₂CF₃, OCF₂CF₂CCIF₂, OCCIFCF₂CF₃ or CH=CF₂, very preferably F or OCF₃, most preferably F. In the compounds of formula A and B, R²¹ and R³¹ are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight-chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms. In the compounds of formula A and B, g is preferably 1 or 2.

In the compounds of formula B, Z³¹ is preferably COO, trans-CH=CH or a single bond, very preferably COO or a single bond.

Preferably, component B) of the LC medium comprises one or more compounds of formula A selected from the group consisting of the following formulae:

in which A²¹, R²¹, X°, L²¹ and L²² have the meanings given in formula A, L²³ and L²⁴ each, independently of one another, are H or F, and X° is preferably F. Particularly preferred are compounds of formulae A1 and A2.

Particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae: in which R²¹, X°, L²¹ and L²² have the meaning given in formula A1 , L²³, L²⁴, L²⁵ and L²⁶ are each, independently of one another, H or F, and X° is preferably F.

Very particularly preferred compounds of formula A1 are selected from the group consisting of the following subformulae:

A1 b1

In which R is as defined in formula A1.

Particularly preferred compounds of formula A2 are selected from the group consisting of the following subformulae:



in which R²¹, X°, L²¹ and L²² have the meaning given in formula A2, L²³, L²⁴, L²⁵ and L²⁶ each, independently of one another, are H or F, and X° is preferably F. -60-

in which R²¹ and X° are as defined in formula A2.

Particularly preferred compounds of formula A3 are selected from the group consisting of the following subformulae:

in which R²¹, X°, L²¹ and L²² have the meaning given in formula A3, and X° is preferably F.

Particularly preferred compounds of formula A4 are selected from the group consisting of the following subformulae: in which R is as defined in formula A4.

Preferably, component B) of the LC medium comprises one or more compounds of formula B selected from the group consisting of the following formulae:

in which g, A³¹, A³², R³¹, X°, L³¹ and L³² have the meanings given in formula B, and X° is preferably F or CN. Particularly preferred are compounds of formulae B1 and B2. Particularly preferred compounds of formula B1 are selected from the group consisting of the following subformulae:

in which R³¹, X°, L³¹ and L³² have the meaning given in formula B1 , and X° is preferably F.

Very particularly preferred compounds of formula B1 a are selected from the group consisting of the following subformulae:

in which R is as defined in formula B1 .

Very particularly preferred compounds of formula B1 b are selected from the group consisting of the following subformulae:

in which R³¹ is as defined in formula B1 .

Particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae:

B2d



in which R³¹, X°, L³¹ and L³² have the meaning given in formula B2, L³³, L³⁴, L³⁵ and L³⁶ are each, independently of one another, H or F, and X° is preferably F or CN.

Very particularly preferred compounds of formula B2 are selected from the group consisting of the following subformulae:

B2a3

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2b are selected from the group consisting of the following subformulae

in which R³¹ is as defined in formula B2. Very particularly preferred compounds of formula B2c are selected from the group consisting of the following subformulae:

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2d and B2e are selected from the group consisting of the following subformulae: in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2f are selected from the group consisting of the following subformulae:

B2f3

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2g are selected from the group consisting of the following subformulae:

B2g3

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2h are selected from the group consisting of the following subformulae:

in which R is as defined in formula B2. Very particularly preferred compounds of formula B2i are selected from the group consisting of the following subformulae:

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2k are selected from the group consisting of the following subformulae:

in which R is as defined in formula B2.

Very particularly preferred compounds of formula B2I are selected from the group consisting of the following subformulae: in which R is as defined in formula B2.

Alternatively to, or in addition to, the compounds of formula B1 and/or B2 component B) of the LC medium may also comprise one or more compounds of formula B3 as defined above.

Particularly preferred compounds of formula B3 are selected from the group consisting of the following subformulae:

in which R is as defined in formula B3. Preferably, component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula C

in which the individual radicals have the following meanings: each, independently of one another, and

on each occurrence, identically or differently

each, independently of one another, alkyl, alkoxy, oxaalkyl or alkoxyalkyl having 1 to 9 C atoms or alkenyl or alkenyloxy having 2 to 9 C atoms, all of which are optionally fluorinated, each, independently of one another, -CH₂CH₂-, -COO- frans-CH=CH-, frans-CF=CF-, -CH₂O-, -CF₂O-, -C≡C- a single bond, preferably a single bond, h 0, 1 , 2 or 3. In the compounds of formula C, R and R are preferably selected from straight-chain alkyl or alkoxy with 1 , 2, 3, 4, 5 or 6 C atoms, and straight- chain alkenyl with 2, 3, 4, 5, 6 or 7 C atoms.

In the compounds of formula C, h is preferably 0, 1 or 2.

In the compounds of formula C, Z⁴¹ and Z⁴² are preferably selected from COO, trans-CH=CH and a single bond, very preferably from COO and a single bond.

Preferred compounds of formula C are selected from the group consisting of the following subformulae:

C5

wherein R⁴¹ and R⁴² have the meanings given in formula C, and preferably denote each, independently of one another, alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy with 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl with 2 to 7 C atoms.

Preferably, the component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula D

in which A , A , Z , Z , R , R and h have the meanings given formula C or one of the preferred meanings given above.

Preferred compounds of formula D are selected from the group consisting of the following subformulae:

D2 in which R and R have the meanings given in formula D and R preferably denotes alkyl, and in formula D1 R⁴² preferably denotes alkenyl, particularly preferably -(CH₂)2-CH=CH-CH3, and in formula D2 R⁴² preferably denotes alkyl, -(CH₂)2-CH=CH₂ or -(CH₂)₂-CH=CH-CH₃.

Preferably, the component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula E containing an alkenyl group in which the individual radicals, on each occurrence identically or differently, each, independently of one another, have the following meaning:

R A1 alkenyl having 2 to 9 C atoms or, if at least one of the rings X,

Y and Z denotes cyclohexenyl, also one of the meanings of nA2 R alkyi having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH₂ groups may be replaced by -O- , -CH=CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another, x 1 or 2.

R^A2 is preferably straight-chain alkyi or alkoxy having 1 to 8 C atoms or straight-chain alkenyl having 2 to 7 C atoms.

Preferred compounds of formula E are selected from the following sub- formulae:

alkenyl— < H — ( H — ( O >— alkyl

alken

in which alkyl and alkyl^* each, independently of one another, denote a straight-chain alkyl radical having 1 -6 C atoms, and alkenyl and alkenyl^* each, independently of one another, denote a straight-chain alkenyl radical having 2-7 C atoms. Alkenyl and alkenyl^* preferably denote 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-. Very preferred compounds of the formula E are selected from the following sub-formulae:

in which m denotes 1 , 2, 3, 4, 5 or 6, i denotes 0, 1 , 2 or 3, and R denotes H, CH₃ or C2H5.

Very particularly preferred compounds of the formula E are selected from the following sub-formulae:

E1 a3

Most preferred are compounds of formula E1 a2, E1 a5, E3a1 and E6a1 .

Preferably, the component B) of the LC medium comprises, in addition to the compounds of formula A and/or B, one or more compounds of formula F

in which the individual radicals have, independently of each other and on each occurrence identically or differently, the following meanings: denote

F, CI, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms,

721 -CH2CH2-, -CF2CF2-, -COO-, frans-CH=CH-, trans- CF=CF-, -CH2O- or a single bond, preferably -

-COO-, trans-CH=CH- or a single bond, particularly preferably -COO-, frans-CH=CH- or a single bond, each, independently of one another, H or F,

0, 1 , 2 or 3. Particularly preferred compounds of formula F are selected from the group consisting of the following formulae:

in which R²¹, X°, L²¹ and L²² have the meaning given in formula F, L²⁵ and L²⁶ are each, independently of one another, H or F, and X° is preferably F.

Very particularly preferred compounds of formula F1 -F3 are selected from the group consisting of the following subformulae:

In which R²¹ is as defined in formula F1 The medium preferably comprises one or more neutral compounds of the general formula N, in which

R and R each, independently of one another, denote an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH₂ groups in these radicals may each be replaced, independently of one another, by -C≡C-, -CF₂O-, - - · "^X^" - -°'·

-CO-O-, -O-CO- in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, rings A^N1, A^N2 and A^N3 each, independently of one another, denote 1 ,4- phenylene, 2-fluoro-1 ,4-phenylene, 3-fluoro-1 ,4-phenylene, 2,6-difluoro- 1 ,4-phenylene, 3, 5-difluoro-1 ,4-phenylene trans-1 ,4-cyclohexylene, in which, in addition, one or two CH₂ groups may be replaced by -O-, or 1 ,4-cyclohexenylene,

Z^N1 and Z^N2 each, independently of one another, denote a single bond or -C≡C-,whereby at least one of Z^N1 and Z^N2 denotes -C≡C-, n denotes 0, 1 or 2.

Preferred compounds of the formula N are shown below:

in which alkyl and alkyl^* each, independently of one another, denote a straight- chain alkyl radical having 1 to 9 C atoms, preferably 2 to 6 C atoms, and alkenyl and alkenyl^* each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms.

The concentration of the compounds of formula A and B in the LC host mixture is preferably from 2 to 60%, very preferably from 3 to 55%, most preferably from 4 to 50%.

The concentration of the compounds of formula C and D in the LC host mixture is preferably from 5 to 75%, very preferably from 10 to 70%, most preferably from 15 to 60%.

The concentration of the compounds of formula E in the LC host mixture is preferably from 5 to 30%, very preferably from 10 to 25%. The concentration of the compounds of formula F in the LC host mixture is preferably from 2 to 30%, very preferably from 5 to 20%.

Further preferred embodiments of the present invention are listed below, including any combination thereof. The LC host mixture comprises one or more compounds of formula A and/or B with high positive dielectric anisotropy, preferably with Δε > 15.

The LC host mixture comprises one or more compounds selected from the group consisting of formulae A1 a2, A1 b1 , A1d1 , A1f1 , A2a1 , A2h1 , A2I2, A2k1 , B2g3, and/or B2F. The proportion of these compounds in the LC host mixture is preferably from 5 to 50.

2c) The LC host mixture comprises one or more compounds selected from the group consisting of formulae C3, C4, C5, C9 and D2. The proportion of these compounds in the LC host mixture is preferably from 8 to 75%, very preferably from 10 to 70%.

2d) The LC host mixture comprises one or more compounds selected from the group consisting of formulae E1 , E3 and E6, preferably E1 a, E3a and E6a, very preferably E1 a2, E1 a5, E3a1 and E6a1 . The proportion of these compounds in the LC host mixture is preferably from 5 to 40%, very preferably from 10 to 25%.

The optimum mixing ratio of the compounds of the above-mentioned formulae in the liquid-crystalline component B) depends substantially on the desired properties, on the choice of the components of the above- mentioned formulae and on the choice of any further components that may be present. Preferred physical properties are given in the following.

In a preferred embodiment, the liquid-crystalline component B) according to the invention are characterised by optical anisotropy values as high as possible. Preferably, the liquid-crystalline component B) exhibits an optical anisotropy (Δη) in the range from 0.05 or more to 0.500 or less, more preferably in the range from 0.100 or more to 0.300 or less, especially in the range from 0.150 or more to 0.250 or less.

Preferably, the liquid-crystalline component B) according to the invention is characterised by relatively high positive values of the dielectric anisotropy (Δε), preferably as high as possible. In a preferred

embodiment, the liquid-crystalline component B) exhibits a dielectrically positive anisotropy in the range from 3 to 50, preferably from 4 or more to 25 or less, particularly preferably from 5 or more to 20 or less.

The nematic phase of the liquid-crystalline component B) according to the invention preferably extends at least from 0°C or below to 70°C or above, more preferably at least from -20°C or below to 75°C or above, very preferably at least from -30°C or below to 75°C or above and in particular at least from -40°C or below to 80°C or above. The clearing point of the liquid-crystalline component B) according to the invention is preferably in the range from 10°C to 120°C, particularly preferably in the range from 40°C to 1 10°C and very particularly preferably in the range from 60°C to 100°C.

The rotational viscosity of the liquid-crystalline component B) is preferably as low as possible. Preferably, the liquid-crystalline

component B) exhibits a rotational viscosity of approximately 500 mPas or less, preferably in the range from 1 mPas or more to 500 mPas or less, more preferably in the range from 10 mPas or more to 300 mPas or less, especially in the range from 50 mPas to 200 mPas.

The LC media according to the present invention are prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned polymerisable compounds with one or more non polymerisable compounds as defined above, and optionally with further liquid-crystalline compounds and/or additives. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. Accordingly, the invention also relates to the process for the preparation of the LC media according to the invention.

The LC media according to the present invention are very suitable for the use in different types of light modulation elements. Therefore, the present invention also relates to the use of an LC medium as described and below, especially in a PNLC light modulation element.

Typically such PNLC light modulation element comprises a LC cell having two opposing substrates and an electrode structure and a layer of the LC medium as described above and below located between the substrates of the LC cell. Therefore, the present invention also relates to the PNLC light modulation element comprising a pair of opposing substrates, an electrode structure and a LC medium located in the interspace of said substrates, characterized in that the PNLC light modulation element comprises a polymer network obtainable from the LC medium according as described above by exposing said LC medium to actinic radiation that induces photopolymerisation of the

polymerisable compounds in the LC medium.

The invention furthermore relates to a process for the production of a PNLC light modulation element according to one or more of claims 10 to 13 comprising at least the steps of

- cutting and cleaning of the substrates, - providing an electrode structure on each of the substrates,

- optionally providing an alignment layer on the electrode structure,

- assembling the cell,

- filling the cell with the LC medium according to the present invention, and

- exposing said LC medium to actinic radiation that induces

photopolymerisation of the polymerisable compounds in the LC medium.

In one embodiment of the present invention, the liquid crystal composition is injected between the first and second substrates or is filled into the assembled cell by capillary force after combining the first and second substrates.

However, it is likewise preferable that 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. In a preferred embodiment, 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 the irradiation step, the cell is exposed to actinic radiation that causes photopolymerisation of the polymerisable functional groups of the polymerisable compounds contained in the cholesteric liquid crystal medium. Polymerisation is achieved for example by exposing the polymerisable material to heat or actinic radiation. Actinic radiation means irradiation with light, like UV light, IR light or visible light, irradiation with X-rays or gamma rays or irradiation with high-energy particles, such as ions or electrons. Preferably, polymerisation is carried out by UV irradiation. As a source for actinic radiation, for example a single UV lamp or a set of UV lamps can be used. Another possible source for actinic radiation is a laser, like for example a UV, IR or visible laser.

Because of the irradiation, the polymerisable compounds are

substantially crosslinked in situ within the liquid crystal medium between the substrates forming the PNLC light modulation element whereby the polymer network preferably extends through the whole switching layer.

The utilized wavelength of the actinic radiation should not be too low, in order to avoid damage to the LC molecules of the medium, and should preferably be different from, very preferably higher than, the UV absorption maximum of the LC host mixture. On the other hand, the wavelength of the photo radiation should not be too high, to allow quick and complete UV photopolymerisation of the polymerisable compounds, and should be not higher than, preferably the same as or lower than the UV absorption maximum of the polymerisable component.

Suitable wavelengths are preferably selected from wavelengths in the range from 250 to 450 nm, for example 400 nm or less, preferably 350 nm or less, more preferably 300 nm or less.

The irradiation or exposure time should be selected such that

polymerisation is as complete as possible, but still not be too high to allow a smooth production process. In addition, the radiation intensity should be high enough to allow quick and complete polymerisation as possible, but should not be too high to avoid damage to the cholesteric liquid crystal medium. The curing time depends, inter alia, on the reactivity of the polymerisable material, the thickness of the coated layer, the type of polymerisation initiator and the power of the UV lamp. The curing time is preferably≤ 10 minute, very preferably≤ 5 minutes, and most preferably≤ 1 minutes. In general, for mass production shorter curing times are preferred, such as approximately 60 seconds to 1 second.

A suitable UV radiation power is preferably in the range from 5 to 150 mWcm^"2' more preferably in the range from 10 to 75 mWcm^"2, especially in the range from 25 to 60 mWcm^"2, and in particular 45 to 55 mWcm^"2.

Polymerisation is preferably performed under an inert gas atmosphere, preferably in under a nitrogen atmosphere, but also polymerisation in air is possible.

Polymerisation is preferably performed at a temperature in the range from -10°C to +70°C, more preferably 0°C to +50°C, even more preferably +15°C to +40°C.

In an preferred embodiment, the PNLC light modulation element can additionally be annealed after the polymerisation, preferably at a temperature above 20°C and below 140°C, more preferably above 40°C and below 130°C and most preferably above 70°C and below 120°C, in order to reach full conversion of the monomers and in order to achieve an optimum stability

Typically, the structure of the PNLC light modulation element according to the invention corresponds to the conventional structure for displays, which is known to the person skilled in the art. As substrate, for example, glass or quartz sheets or plastic films can be used. When using two substrates in case of curing by actinic radiation, at least one substrate has to be transmissive for the actinic radiation used for the polymerisation.

Suitable and preferred plastic substrates are for example films of polyester such as polyethyleneterephthalate (PET) or polyethylene- naphthalate (PEN), polyvinylalcohol (PVA), polycarbonate (PC) or triacetylcellulose (TAC), very preferably PET or TAC films. As

birefringent substrates for example uniaxially stretched plastic films can be used. PET films are commercially available for example from DuPont Teijin Films under the trade name Melinex ®.

In a preferred embodiment, the substrates are arranged with a

separation in the range from approximately 1 μιτι to approximately 20 μιτι from one another, preferably in the range from approximately 3 μιτι to approximately 10 μιτι from one another, and more preferably in the range from approximately 3 μιτι to approximately 6 μιτι from one another. The layer of the liquid-crystalline medium is thereby located in the

interspace.

The substrate layers can be kept at a defined separation from one another, for example, by spacers, or projecting structures in the layer. Typical spacer materials are commonly known to the expert, as for example spacers made of plastic, silica, epoxy resins, or the like.

In a further preferred embodiment of the invention, the layer of the liquid- crystalline medium is located between two flexible layers, for example flexible polymer films. The PNLC light modulation element according to the invention is consequently flexible and bendable and can be rolled up, for example. The flexible layers can represent the substrate layer, the alignment layer, and/or polarisers. Further layers, which are preferable flexible, may also, be present. For a more detailed disclosure of the preferred embodiments, in which the layer of the liquid-crystalline medium is located between flexible layers, reference is given to the application US 2010/0045924 A1 .

Furthermore, an electrode arrangement and optionally further electrical components and connections are be present in the PNLC light modulation element according to the invention in order to facilitate electrical switching of the PNLC light modulation element, comparable to the switching of an LC display. Preferably, the PNLC light modulation element comprises an electrode arrangement, which is capable to allow the application of an electric field, which is substantially perpendicular to the substrate main plane or the liquid-crystalline medium layer. Suitable electrode arrangements fulfilling this requirement are commonly known to the expert.

Preferably, the PNLC light modulation element comprises an electrode arrangement comprising at least two electrode structures provided on opposing sides of the substrates. Preferred electrodes structures are provided as an electrode layer on the entire opposing surface of each substrate and/or the pixel area.

Suitable electrode materials are commonly known to the expert, as for example electrode structures made of metal or metal oxides, such as, for example indium tin oxide (ITO), which is preferred according to the present invention. Thin films of ITO, for example, are preferably deposited on substrates by physical vapour deposition, electron beam evaporation, or sputter deposition techniques.

Preferably, the electrodes of the PNLC light modulation element are associated with a switching element, such as a thin film transistor (TFT) or thin film diode (TFD).

In a preferred embodiment, the PNLC light modulation element comprises at least one dielectric layer, which is preferably on the electrode structure. Typical dielectric layer materials are commonly known to the expert, such as, for example, SiOx, SiNx, Cytop, Teflon, and PMMA.

The dielectric layer materials can be applied onto the substrate or electrode layer by conventional coating techniques like spin coating, roll coating, blade coating, or vacuum deposition such as PVD or CVD. It can also be applied to the substrate or electrode layer by conventional printing techniques, which are known to the expert, like for example screen printing, offset printing, reel-to-reel printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat-seal printing, ink-jet printing or printing by means of a stamp or printing plate.

In a further preferred embodiment, the PNLC light modulation element comprises at least one alignment layer, which is preferably provided on the electrode structure.

The PNLC light modulation element may have further alignment layers, which are in direct contact with the layer of the liquid-crystalline medium. The alignnnent layers may also serve as substrate layers, so that substrate layers are not necessary in the PNLC light modulation element. If substrate layers are additionally present, the alignment layers are in each case arranged between the substrate layer and the layer of the liquid-crystalline medium.

Preferably, the alignment layer(s) induce(s) planar alignment, preferably throughout the entire liquid-crystalline medium.

Suitable planar alignment layer materials are commonly known to the expert, such as, for example, AL-3046 or AL-1254 both commercially available from JSR.

The alignment layer materials can be applied onto the substrate array or electrode structure by conventional coating techniques like spin coating, roll coating, dip coating or blade coating. It can also be applied by vapour deposition or conventional printing techniques, which are known to the expert, like for example screen printing, offset printing, reel-to-reel printing, letterpress printing, gravure printing, rotogravure printing, flexographic printing, intaglio printing, pad printing, heat-seal printing, ink-jet printing or printing by means of a stamp or printing plate.

In a preferred embodiment, the planar alignment layer is processed by rubbing or photo-alignment techniques known to the skilled person, preferably by rubbing techniques. Accordingly, a uniform preferred direction of the director can be achieved without any physical treatment of the cell like shearing of the cell (mechanical treatment in one direction), etc. The rubbing direction is uncritical and mainly influences only the orientation in which the polarizers have to be applied. Typically the rubbing direction is in the range of +/- 45°, more preferably in the range of +/- 20°, even more preferably, in the range of +/-10, and in particular, in the range of the direction +/- 5° with respect to the substrates largest extension.

In a further preferred embodiment of the invention, the PNLC light modulation element optionally comprises two or more polarisers, at least one of which is arranged on one side of the layer of the liquid-crystalline medium and at least one of which is arranged on the opposite side of the layer of the liquid-crystalline medium. The layer of the liquid-crystalline medium and the polarisers here are preferably arranged parallel to one another. The polarisers can be linear polarisers. Preferably, precisely two polarisers are present in the PNLC light modulation element. In this case, it is furthermore preferred for the polarisers either both to be linear polarisers. If two linear polarisers are present in the PNLC light modulation element, it is preferred in accordance with the invention for the polarisation directions of the two polarisers to be crossed.

It is furthermore preferred in the case where two circular polarisers are present in the PNLC light modulation element for these to have the same polarisation direction, i.e. either both are right-hand circular-polarised or both are left-hand circular-polarised.

The polarisers can be reflective or absorptive polarisers. A reflective polariser in the sense of the present application reflects light having one polarisation direction or one type of circular-polarised light, while being transparent to light having the other polarisation direction or the other type of circular-polarised light. Correspondingly, an absorptive polariser absorbs light having one polarisation direction or one type of circular- polarised light, while being transparent to light having the other polarisation direction or the other type of circular-polarised light. The reflection or absorption is usually not quantitative; meaning that complete polarisation of the light passing through the polariser does not take place.

For the purposes of the present invention, both absorptive and reflective polarisers can be employed. Preference is given to the use of polarisers, which are in the form of thin optical films. Examples of reflective polarisers which can be used in the PNLC light modulation element according to the invention are DRPF (diffusive reflective polariser film, 3M), DBEF (dual brightness enhanced film, 3M), DBR (layered-polymer distributed Bragg reflectors, as described in US 7,038,745 and US 6,099,758) and APF (advanced polariser film, 3M).

Examples of absorptive polarisers, which can be employed in the PNLC light modulation elements according to the invention, are the Itos XP38 polariser film and the Nitto Denko GU-1220DUN polariser film. An example of a circular polariser, which can be used in accordance with the invention, is the APNCP37-035-STD polariser (American Polarizers). A further example is the CP42 polariser (ITOS).The PNLC light modulation element may furthermore comprise filters which block light of certain wavelengths, for example, UV filters. In accordance with the invention, further functional layers, such as, for example, protective films, heat-insulation films or metal-oxide layers, may also be present.

The functional principle of the PNLC light modulation element according to the invention will be explained in detail below. It is noted that no restriction of the scope of the claimed invention, which is not present in the claims, is to be derived from the comments on the assumed way of functioning. In a first preferred embodiment, the retardation or phase change of the PNLC light modulation element according to the invention is dependent on the applied electric field. Preferably, the retardation gradually increases while applying an electric field with gradually increasing voltage.

In this preferred embodiment, the components A and B are selected dependently from one another in that way that birefringence of the polymerisable component A matches the birefringence of the component B. Preferably, the difference between values for the birefringence is below 10%, more preferably below 5% and more preferably below 3%. The required applied electric field strength is mainly dependent on the electrode gap and the modulus of Δε of the LC mixture. The applied electric field strengths are typically lower than approximately 50 V/μηη^"1, preferably lower than approximately 30 V/μηη^"1 and more preferably lower than approximately 25 V/μηη^"1. In particular, the applied electric field strengths is in the range from 1 V/μηη^"1 to 20ν/μηη^"1.

Preferably, the applied driving voltage in order to switch the PNLC light modulation element should be as low as possible. Typically, the applied driving voltage is in the range from 2 V to approximately 20 V, more preferably in the range from approximately 5 V to approximately 10 V.

In this first preferred embodiment, the retardation change or phase chan e (Γ) is given in accordance with the following equation

wherein d is the layer thickness of the applied liquid crystalline medium, λ is the wavelength of the incident light and n_etf is the effective

birefringence induced by the reorientation of the LC in the applied field. In a second preferred embodiment, the PNLC light modulation element according to the invention has a boundary state A and a boundary state B.

The PNLC light modulation element preferably has the boundary state A with a transmission T_A when no electrical field is applied, the so called "off state" or transparent state.

The PNLC light modulation element preferably has another boundary state B when an electric field is applied, the so called "on state" or opaque state, whereby

T_A > T_B.

In this second preferred embodiment, the components A and B are selected dependently from one another in that way that birefringence of the polymerisable component A differs from the birefringence of the component B. Preferably, the difference between values for the birefringence is more than 3%, more preferably more than 5% and more preferably more than 10%.

The required applied electric field strength is mainly dependent on the electrode gap and the modulus of Δε of the LC mixture. The applied electric field strengths are typically lower than approximately 50 V/μηη^"1, preferably lower than approximately 30 V/μηη and more preferably lower than approximately 25 V/μηη^"1. In particular, the applied electric field strengths is in the range from 1 V/μηη^"1 to 20ν/μηη^"1.

Preferably, the applied driving voltage in order to switch the PNLC light modulation element should be as low as possible. Typically, the applied driving voltage is in the range from 2 V to approximately 200 V, more preferably in the range from approximately 3 V to approximately 100 V, and even more preferably in the range from approximately 5 V to approximately 50 V.

The transmission change is governed by the strength of the applied field. With more field applied to the system, the degree of scatter increases, which causes a reduction in the intensity of forward propagating light, and an increase in light emitted in other directions. Hence for side- illuminated devices, the amount of light visible orthogonal to the illumination direction increases with increasing applied field strength. As described above, the PNLC light modulation element of the present invention can be used in various types of optical and electro-optical devices. Accordingly, the present invention is also directed to the use of the PNLC light modulation element as described above in an optical or electro-optical device and to an optical or electro-optical device comprising the PNLC light modulation element according to the present invention.

Said optical and electro optical devices include, without limitation electro-optical displays, liquid crystal displays (LCDs), non-linear optic (NLO) devices, optical information storage devices, light shutters and Smart Windows, privacy windows, virtual reality devices and augmented reality devices.

It will be appreciated that many of the features described above, particularly of the preferred embodiments, are inventive in their own right and not just as part of an embodiment of the present invention.

Independent protection may be sought for these features in addition to, or alternative to any invention presently claimed. It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Alternative features serving the same, equivalent or similar purpose may replace each feature disclosed in this specification, unless stated otherwise. Thus, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

All of the features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Likewise, features described in non-essential combinations may be used separately (not in

combination).

Without further elaboration, it is believed that one skilled in the art can, using the preceding description, utilize the present invention to its fullest extent. The following examples are, therefore, to be construed as merely illustrative and not limitative of the remainder of the disclosure in any way whatsoever.

The parameter ranges indicated in this application all include the limit values including the maximum permissible errors as known by the expert. The different upper and lower limit values indicated for various ranges of properties in combination with one another give rise to additional preferred ranges.

In the present application and especially in the following examples, the structures of the liquid crystal compounds are represented by

abbreviations, which are also called "acronyms". The transformation of the abbreviations into the corresponding structures is straightforward according to the following three tables A to C. Table A lists the symbols used for the ring elements, table B those for the linking groups and table C those for the symbols for the left hand and the right hand end groups of the molecules.

All groups C_nH_2n+-i, C_mH_2m+i, and GH2i₊iare preferably straight chain alkyl groups with n, m and I C-atoms, respectively, all groups C_nH_2n, C_mH_2m and C1H21 are preferably (CH₂)_n, (CH₂)_m and (CH₂)i, respectively and - CH=CH- preferably is trans- respectively E vinylene.

Table B: Linking Groups

-O-CO-

-CH=CF

Table C: End Groups

-C≡C-H

-C=C-C_nH2n+1

-C≡C-C≡N

Left hand side, used in combination Right hand side, used in with others only combination with others only

-...n...- -C_nH2n- -...n... -C_nH2n-

-...M...- -CFH- -...M... -CFH-

-...D...- -CF₂- -...D... -CF₂-

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

-...∑...- -CO-O- -...Z... -CO-O-

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

-...K...- -CO- -...K... -CO-

-...W...- -CF=CF- -...W... -CF=CF- wherein n und m each are integers and three points indicate a space for other symbols of this table.

Examples

Utilized polymerisable liquid crystalline compounds

Methods

Switching speed measurement:

Switching times are recorded either using a microscope or with a HeNe laser operating at 632.8nm, with the sample placed between crossed polarizers in both cases. Transmitted light is received by a photodiode, which is connected to an oscilloscope in the microscope case, or connected to a data acquisition board in the laser case. The switching times are acquired from the oscilloscope or from analyzing the data acquired from the data acquisition board.

Retardation measurements

Retardation measurements taken using an Axometrics AxoStep Muller Matrix polarimeter.

Haze

The haze level is determined in accordance to the ASTM D1003 standard definition of haze.

Four different transmission measurements (T1 to T4) are performed, which are commonly known by the skilled person:

T1 : Transmission without sample and white reflection standard

T2 : Transmission with sample and white reflection standard

T3: Transmission without sample with light trap

T4: Transmission with sample and with light trap As commonly known by the skilled person, the total transmittance (T2) is thereby defined as the sum of the parallel transmittance and the diffusion transmittance (T4).

The Haze is thereby defined as follows: Haze = [(T4/T2) - (T3/T1 )] x

The haze data is taken from the active area of the cell only. The glue is masked off from the measurement system to avoid inconsistencies Example 1

The following comparative mixture CM-1 is prepared

1 .1 Comparative Example I:

On each of two ITO coated glass substrates, a polyimide (AL60702, JSR) layer is provided, and the polyimide layers are rubbed,

respectively. The test cell is assembled utilizing Norland spacer beads and a pressure sensitive adhesive, whereby the above-described substrates are oriented anti-parallel to each other with respect to the rubbing direction of the polyimide layers. The resulting cell has a cell gap of 3.5 μιτι. The cell is capillary filled with mixture CM-1 at 40°C. An electric field as given in the following table 1 .1 is applied to the test cell at room temperature (approx. 21 °C) in order to switch from the "off state" to the "on state" and the switching times are determined. Table 1.1 : Switch on and switch off times of comparative mixture CM-1 , taken at room temperature, as a function of applied voltage.

1 .2 Comparative example II:

Three test cells are prepared in analogy to comparative example 1 .1 . The cells are capillary filled at 40°C with mixture CM-1 , and comparative mixtures CM-1 containing additionally 2.5% or 5 % of RM-1

(commercially available from Merck, Darmstadt, Germany) and 5% of the RM-1 weight of Irgacure 651 as photoinitiator (commercially available from CIBA, Switzerland), respectively, resulting in comparative mixtures CM-1 .2.1 and CM-1 .2.2. The cells are cured at 50mW/cm² for 60 seconds using Omnicure 250-450 nm broadband exposure. An electric field of 9 V as is applied to the test cells in order to switch from the "off state" to the "on state" and the switching times are determined.

Table 1.2: Switch on and switch off times of comparative mixture CM- 1 .2.1 and CM-1 .2.2, taken at room temperature and at an applied electric field of 9 V.

Mixture RM 1 (%-w/w) ton (ms) toff (ms)

CM-1 0 0.5 4.0

CM-1 .2.1 2.5 0.9 4.5

CM-1 .2.2 5.0 0.4 2.3

1 .3 Working Example I

Three test cells are prepared in analogy to comparative example 1 .1 .

The cells are capillary filled at 40°C with mixtures corresponding to mixture CM-1 additionally containing 2.5%, 5%, or 7.5 % of RM-2 and 5% of the RM-2 weight of Irgacure 651 , respectively, resulting in

mixtures M-1 .3.1 , M-1 .3.2 and M-1 .3.3 according to the present

invention. The cells are cured at 50mW/cm² for 60 seconds using

Omnicure 250-450 nm broadband exposure. An electric field as given in the following table 1 .3 is applied to the test cell at room temperature (approx. 21 °C) in order to switch from the "off state" to the "on state" and the switching times are determined.

Table 1.3: Switch on and switch off times of mixtures M-1 .3.1 , M-1 .3.2 and M-1 .3.3 taken at room temperature, as a function of applied voltage.

Mixture M-1.3.1 M-1.3.2 M-1.3.3

V (V) toff (ms) ton (ms) toff (ms) ton (ms) toff (ms) ton (ms)

3 2.6 7.70 1 .4 2.8

4 1 .60 2.80

5 3.40 2.00 1 .50 2.60

9 3.60 0.80 1 .70 0.44 0.63 1 .30

12 1 .80 0.28

15 3.90 0.24 1 .95 0.29 0.63 0.30

20 1 .80 0.16

25 0.60 0.10

30 0.58 0.08

1 .4 Summary

In all cases, the switch-on times decrease monotonically with increasing voltage as expected for a voltage driven process. The switch-off times are fairly stable with respect to voltage as expected for a surface anchoring induced effect. The switch-off times do vary considerably with the concentration of RM dopant, and are significantly faster than an equivalent sample without polymer network.

The data shows that the switching off times for RM-2 are significantly lower than those of RM-1 , for the same concentration and curing conditions. We attribute this to the much more rigid network formed by RM-2, due to the lack of spacers in the molecule.

Example 2

Four test cells are prepared in analogy to comparative example 1 .1 . The cells are capillary filled at 40°C with the following mixtures:

• Comparative mixture CM-1 ,

• Comparative mixture CM-1 additionally containing 3.8% of RM-2, 5.0 % of the RM-2 weight of Irgacure 651 , and 3.2 % of HDDA (hexanediol diacrylate), resulting in mixture M-2.1 according to the present invention,

• Comparative mixture CM-1 additionally containing 5.0 % of RM-2, 5.0% of the RM-2 weight of Irgacure 651 , and 3.2 % of HDDA (hexanediol diacrylate), resulting in mixture M-2.2 according to the present invention,

• Comparative mixture CM-1 additionally containing 7.5 % of RM-2 and 5.0 % of the RM-2 weight of Irgacure 651 , resulting in mixture M-2.3 according to the present invention.

The cells are cured at 50 mW/cm² for 60 seconds using Omnicure 250- 450 nm broadband exposure. An electric of 9 V is applied to the test cell at room temperature (approx. 21 °C) in order to switch from the "off state" to the "on state" and the switching off times as well as the retardation is determined.

Table 2.1 : Switch off times and retardation of comparative mixture CM-1 and example mixtures M-2.1 to M-2.3 taken at room temperature and at an applied electric field of 9 V.

The data shows that HDDA can be used as an additional polymerizable additive, which provides similar benefits in switching off times to a system using only RM-2, but can allow for slightly improved retardation change for similar total polymer concentration.

Example 3:

Ten test cells are prepared in analogy to comparative example 1 .1 . Five test cells are capillary filled at 40°C with comparative mixture CM-1 additionally containing 5.0 % of RM-1 and 3.0 % of the RM-1 weight of Irgacure 651 , resulting in comparative mixture CM-3.

The remaining five test cells are capillary filled at 40°C with comparative mixture CM-1 additionally containing 5.0 % of RM-3 and 3.0 % of the RM-3 weight of Irgacure 651 , resulting in mixture M-3 according to the present invention.

A pair of test cells (containing mixture CM-3 or M-3) is cured with broadband UV light (Omnicure 250-450nm) for 2, 4, 6, 8 or 10 seconds at 50 mW/cm², respectively. Each test cell is annealed after curing on a hotplate at 50°C for 60 minutes. An electric of 10 V or 16 V is applied to each test cells at a temperature of 20°C in order to switch from the "off state" to the "on state" and the switching off times and the switching off times are determined. Table 3.1 summarizes the results.

Table 3.1 : Switch off times of comparative mixture CM-3 and example mixture M-3 taken at 20°C and at an applied electric field of 10 V or 16

Curing time (s) -> 2 4 6 8 10

Mixture V (V) toff (ms

CM-3 10 4.2 3.9 3.6 3.4 3.2

M-3 10 1 .7 1 .7 1 .5 1 .4 1 .6

CM-3 16 4.5 3.9 3.6 3.4 3.1

M-3 16 2 1 .6 1 .4 1 .4 1 .5 Example 4:

Ten test cells are prepared in analogy to comparative example 1 .1 . Five test cells are capillary filled at 40°C with comparative mixture CM-1 additionally containing 5.0 % of RM-1 and 3.0 % of the RM-1 weight of Irgacure 651 , resulting in comparative mixture CM-4.

The remaining five test cells are capillary filled at 40°C with comparative mixture CM-1 additionally containing 5.0 % of RM-3 and 3.0 % of the RM-3 weight of Irgacure, resulting in mixture M-4 according to the present invention.

A pair of test cells (containing mixture CM-4 or M-4) is cured with broadband UV light (Omnicure 250-450nm) for 2, 4, 6, 8 or 10 seconds at 50 mW/cm², respectively. Each test cell is annealed after curing on a hotplate at 50°C for 60 minutes. An electric of 10 V or 16 V is applied to each test cell at a temperature of 35°C in order to switch from the "off state" to the "on state" and the switching off times and the switching off times are determined. Table 4.1 summarizes the results.

Table 4.1 : Switch off times of comparative mixture CM-3 and example mixture M-3 taken at 35°C and at an applied electric field of 10 V or 16

Curing time (s) -> 2 4 6 8 10

Mixture V (V) toff (ms

CM-4 10 3.3 2.8 2.6 2.4 2.5

M-4 10 2 0.85 0.82 0.88 1

CM-4 16 3.6 3.1 3.4 2.3 2.5

M-4 16 2.2 0.88 0.72 0.7 0.9 Example 4

The following comparative mixture CM-2 is prepared

Three test cells are prepared in analogy to comparative example 1 .1 . Each test cell is capillary filled at 40°C with mixture M-5, containing additionally to comparative mixture CM-2, 6.0 % of RM-3 and 3.0 % of the RM-3 weight of Irgacure 651 .

The test cells are cured with broadband UV light (Omnicure 250-450nm) for 4, 6, or 8 seconds at 50 mW/cm², respectively.

Each test cell is annealed after curing on a hotplate at 50°C for 60 minutes. An electric of 10 V or 16 V is applied to each test cell at a temperature of 20°C in order to switch from the "off state" to the "on state" and the switching off times and the switching off times are determined. Table 5.1 summarizes the results.

Table 5.1 : Switch off times of example mixture M-5 taken at 20°C and at an applied electric field of 10 V or 16 V.

Curing time (s) -> 4 6 8

Mixture V (V) toff (ms)

M-5 10 1 .41 0.97 2

M-5 16 1 .8 1 .2 0.9

Example 6

Three test cells are prepared in analogy to comparative example 1 .1 . Each test cell is capillary filled at 40°C with mixture M-6, which additionally contains to comparative mixture CM-2, 6.0 % of RM-3 and 3.0 % of the RM-3 weight of Irgacure 651 .

The test cells are cured with broadband UV light (Omnicure 250-450nm) for 4, 6, or 8 seconds at 50 mW/cm , respectively.

Each test cell is annealed after curing on a hotplate at 50°C for 60 minutes.

An electric of 10 V or 16 V is applied to each test cell at a temperature of 35°C in order to switch from the "off state" to the "on state" and the switching off times are determined. Table 6.1 summarizes the results.

Table 6.1 : Switch off times of example mixture M-6 taken at 35°C and at an applied electric field of 10 V or 16 V.

Curing time (s) -> 4 6 8

Mixture V (V) toff (ms)

M-6 10 1 .3 1 .2 0.6

M-6 16 1 .2 1 .3 0.75

Example 7

Five test cells are prepared in analogy to comparative example 1 .1 , with the exception that a cell gap of approximately 5.3 μιτι is chosen.

The test cells are capillary filled at 40°C with the following mixtures, respectively:

• CM-2,

• M-7.1 , which in addition to comparative mixture CM-2 contains 6.0

% of RM-3, 3.0 % of the RM-3 weight of Irgacure 651 and 1 % Tego Airex 931 (commercially available from Evonik, Germany),

• M-7.2, which additionally contains to comparative mixture CM-2, 6.0 % of RM-3, 3.0 % of the RM-3 weight of Irgacure 651 and 2 % Tego Airex 931 ,

• M-7.3 which additionally contains to comparative mixture CM-2, 6.0 % of RM-3, 3.0 % of the RM-3 weight of Irgacure 651 and 3 % Tego Airex 931 , and

· M-7.4 which additionally contains to comparative mixture CM-2,

6.0 % of RM-3, 3.0 % of the RM-3 weight of Irgacure 651 and 4 % Tego Airex 931 . The test cells are cured at with broadband UV light (Omnicure 250- 450nm) for 8 seconds at 50 mW/cm². Each test cell is annealed after curing on a hotplate at 50°C for 60 minutes.

An electric field as given in the following table 7.1 is applied to the test cell at a temperature of 20°C and the corresponding retardation as a function of the applied voltage. Table 7.1 : Retardation-voltage data as a function of the concentration of

Tego Airex 931 .

The total retardation change is significantly better with respect to mixture M-7.3 and mixture M-7.4 when compared with the comparative mixture CM-2.

An electric of 10 V is applied to each test cell at room temperature (approx. 21 °C) in order to switch from the "off state" to the "on state" and the switching off times are determined. Table 7.2 summarizes the Switching speeds as a function of surfactant concentration.

Table 7.2: Switching speeds as a function of the concentration of Tego Airex 931 .

Mixture ton (ms) toff (ms)

CM-2 0.84 1 .70

M-7.1 0.96 1 .92

M-7.2 1 .90 2.28

M-7.3 1 .94 2.86

M-7.4 0.68 1 .60 Example 8

The following comparative mixture CM-3 is prepared Three test cells are prepared in analogy to comparative example 1 .1 .

The test cells are capillary filled at 40°C with the mixture M-8, which in addition to comparative mixture CM-3 contains 6.0 % of RM-3.

The test cells are cured at with broadband UV light (Omnicure 250- 450nm) for 1 , 3 and 5 minutes at 50 mW/cm²

An electric of V is applied to each test cell at room temperature in order to switch from the "off state" to the "on state" and the switching off times are determined. Table 8.1 summarizes the results. Table 8.1 : Switch off times of mixture M-8 as a function of curing time taken at 20°C and at an applied electric field of 10 V or 16 V.

For all systems, especially those cured for 5 minutes or longer, the switching off times are significantly lower than those of the undoped system.

Example 9

The following comparative mixture CM-4 is prepared

Four test cells are prepared in analogy to comparative example 1 .1 .

The test cells are capillary filled at 40°C with the mixture M-9, which in addition to comparative mixture CM-4 contains 6.0 % of RM-3.

The test cells are cured at with broadband UV light (Omnicure 250- 450nm) for 1 , 3, 5 and 10 minutes at 50 mW/cm²

An electric is applied to each test cell at room temperature in order to switch from the "off state" to the "on state" and the switching off times are determined. Table 8.1 summarizes the results. Table 9.1 : Switch off times of mixture M-9 as a function of curing time taken at 20°C and at an applied electric field of 10 V or 16 V.

Example 10

Five test cells are prepared in analogy to comparative example 1 .1 . The test cells are capillary filled at 40°C with the following mixtures:

• M-10.1 , containing comparative mixture CM-3 and 6.0 % RM-3,

• M-10.2, containing comparative mixture CM-3 and 6.0 % RM-4,

• M-10.3, containing comparative mixture CM-3 and 6.0 % RM-4 as well as 2% Tego Airex 931 ,

• M-10.4, containing comparative mixture CM-3 and 6.0 % RM-5,

• M-10.5, containing comparative mixture CM-3 and 3.0 % RM-5, respectively.

The test cells are cured at with broadband UV light (Omnicure 250- 450nm) for 10 minutes at 50 mW/cm²

An electric field as given in the following table 10.1 is applied to the test cell at a temperature of 20°C and the corresponding retardation as a function of the applied voltage is determined.

Table 10.1 : Retardation-voltage data of mixtures M-10.1 to M-10.5.

Mixtures M-10.1 M-10.2 M-10.3 M-10.4 M-10.5

Voltage (V)

0 0.0 0.0 0.0 0.0 0.0

2 2.2 1 .8 1 .3 0.0 0.9

4 3.5 31 .1 30.0 1 .2 5.7

6 30.1 133.0 168.1 0.9 23.1

8 1 16.4 261 .6 310.9 1 .5 64.4

10 209.6 378.5 425.5 2.0 127.3

12 300.4 473.1 505.8 2.6 208.2

14 385.3 538.9 560.2 3.5 293.1

16 453.5 587.2 602.0 5.5 367.9

18 510.4 622.7 631 .8 8.5 431 .2

20 558.3 649.2 655.6 14.0 480.8

22 594.0 671 .2 675.3 23.6 523.9

24 623.2 688.3 690.8 36.3 558.0

26 647.7 702.5 704.1 52.7 587.3

28 668.5 714.8 715.0 72.4 61 1 .2

30 686.9 727.8 725.3 94.5 635.1

32 701 .6 736.9 733.5 120.7 651 .8

34 714.5 743.7 741 .6 150.0 667.4

36 726.3 750.5 748.5 181 .4 681 .2

38 736.9 756.4 755.2 214.9 694.2

40 746.8 762.6 760.3 247.5 705.1

42 767.0 279.7

44 771 .9 313.9

46 775.7 341 .4

48 779.6 368.0

50 783.1 392.8 An electric field is applied to the test cells containing the mixtures M- 10.2 to M-10.5 at room temperature (approx. 21 °C) in order to switch from the "off state" to the "on state" and the switching off times are determined as a function of the applied voltage. Table 10.2 summarizes the results.

Table 10.2: Switching off times as a function of the applied voltage with respect to of mixtures M-10.2 to M-10.5.

Mixtures M-10.2 M-10.3 M-10.4 M-10.5

Voltage (V)

9 1 .92 2.82 1 .86

10 2.02 2.86 1 .9

15 2.44 2.98 3.98

20 2.5 3.12 0.24 6.92

25 2.6 3.26 0.36 9.12

30 2.72 3.4 0.3 16.02

35 2.78 0.34

40 2.88 0.44

45 0.7

50 1 .18

Example 11

Five test cells are prepared in analogy to comparative example 1 .1 .

Each test cell is capillary filled at 40°C with a mixture CM-3 additionally containing 3% of RM-3 and 3% of RM 4.

The test cells are cured at with broadband UV light (Omnicure 250- 450nm) for 20 minutes at 25 mW/cm², 10 minutes at 50 mW/cm², 5 minutes at 100 mW/cm², 3 minutes 20 seconds at 150 mW/cm², and 10 minutes at 25 mW/cm² (half dose).

The haze level as a function of the wavelength of each test cell is determined at 0 V and room temperature (approx. 21 °C). In comparison to that, a test cell is filled with mixture E7 (commercially available from Merck, Germany) and the haze level is determined in the same manner. The results are summarized in table 1 1 .1 .

Table 11.1 : Haze level of the test cells as a function of the wavelength determined at 0 V.

As can be seen from the data in table 1 1 .1 by applying distinct curing conditions, it is possible to achieve an off-state haze level with a PNLC according to the present invention, which is similar to that of a pure LC system (E7) throughout the whole visible spectrum. Furthermore, the haze level as a function of the wavelength of each test cell is determined at 20 V and room temperature (approx. 21 °C). In comparison to that, a test cell is filled with mixture E7 (commercially available from Merck, Germany) and the haze level is determined in the same manner. The results are summarized in table 1 1 .2.

Table 11.2: Haze level of the test cells as a function of the wavelength determined at 20 V.

As can be seen from the data in table 1 1 .2, even at moderate voltages, it is possible to achieve a moderately efficient scattering system, with haze values approaching 20%. Furthermore, the switching off speed and the haze level of each test cell at an applied voltage of 30 V is determined. The results are summarized in table 1 1 .3

Table 11.3: Haze level at an applied voltage of 30 V and switching off times at an applied voltage of 20V of the test cells.

As can be seen from table 1 1 .3 the switching off times for examples according to the present invention exhibit all sub-millisecond switching off times, which is significantly faster than a non-polymerized system e.g. a comparable cell filled with E7 of similar thickness has an off time of approximately 15ms.

Moreover the haze level a function of applied voltage of the test cell that is cured with broadband UV light (Omnicure 250-450nm) for 20 minutes at 25 mW/cm² is determined. The results are summarized in table 1 1 .4.

Table 11.4: Haze level as a function of applied voltage of the test cell that is cured with broadband UV light (Omnicure 250-450nm) for 20 minutes at 25 mW/cm²

As can be seen from the data in table 1 1 .4, the cell switches from a very low scatter off state, to a moderately high scatter on state. This effect is in particular useful for applications in the field of transparent displays.

Example 12

The following comparative mixture CM-5 is prepared:

On each of two ITO coated glass substrates, a polyimide (AL3046, JSR) layer is provided, and the polyimide layers are rubbed, respectively. The test cell is assembled utilizing Norland spacer beads and a pressure sensitive adhesive, whereby the above-described substrates are oriented anti-parallel to each other with respect to the rubbing direction of the polyimide layers. The resulting cell has a cell gap of approximately 5 μιτι. Two test cells are prepared in the same manner. The cells are each capillary filled at room temperature with the LC mixture CM-5 additionally containing 2% by weight of RM-3 and 4% by weight of RM-4. The cells are cured at 50 mW/cm² for 600 seconds using Omnicure 250- 450 nm broadband exposure. An electric field as given in the following tables is applied to the test cells at room temperature (approx. 21 °C) in order to to measure the haze as well as measure the switching speed.

Table 12.1 : Haze measurements as a function of applied voltage for a PN-LC cell filled with mixture CM-5 and also containing 2% by weight of RM-3 and 4% by weight of RM-4.

Applied voltage (V) Haze (%) Haze (%)

0 0.37 0.00

2 0.43 0.00

4 0.37 0.00

6 0.33 0.00

8 0.70 0.00

10 2.74 0.37

12 8.25 2.89

14 16.93 8.19

16 23.78 15.19

18 28.59 21 .38

20 30.21 25.85

22 30.60 27.77

24 30.69 28.65

26 30.48 28.99

28 29.99 28.99

30 29.42 28.65

32 28.99 28.41

34 28.62 28.08

36 28.05 27.59

38 27.65 27.19 40 27.34 26.80

The haze data in Table 12.1 shows that the systems are highly suitable for a dynamic scattering device (e.g. for transparent display

applications). The zero-voltage (off-state) haze is very low (below the measurement threshold of the equipment). Peak on-state haze of approximately 30% is achieved at approximately 24V.

Table 12.2: Switching on and off times as a function of applied voltage for a PN-LC cell filled with mixture CM-5 containing 2% by weight of RM- 3 and 4% by weight of RM-4.

At 20V or above, the system exhibits fast switching on times, together with sub-millisecond switching off-times.

With a combination of very low off-state haze, high on-state haze, low switching voltage requirement and fast switching speeds, such systems are highly suitable for dynamic scattering or transparent display devices.

Example 13

Two test cells are prepared in the same manner as given in example 12. The cells are each capillary filled at 40°C with the LC mixture CM-5 additionally containing 6% by weight of RM-6 . The cells are cured at 50 mW/cm² for 600 seconds using Omnicure 250-450 nm broadband exposure. An electric field as given in the following tables is applied to the test cells at room temperature (approx. 21 °C) in order to measure the haze as well as measure the switching speed. Table 13.1 : Haze measurements as a function of applied voltage for a PN-LC cell filled with mixture CM-5 and also containing 6% by weight of RM-6.

The zero-voltage (off-state) haze is again very low. Peak on-state haze of approximately 47% is achieved at approximately 8V. This system exhibits both higher peak haze and lower required voltage than the previous example 12. Table 13.2: Switching on and off times as a function of applied voltage for a PN-LC cell filled with mixture CM-5 and also containing 6% by weight of RM-6.

At 20V or above, this system exhibits sub-millisecond switching on times. The switching off-times are consistent around 5-6ms, which is more than an order of magnitude faster than the pure LC system CM-5. In this case, the switching off times are approximately 75 milliseconds.

While this system has a moderately slower switching off time than the system in example 1 , its haze characteristics are improved, with higher peak haze values obtained at lower switching voltages.

Example 14

The following comparative mixture is prepared, CM-6.

Two test cells are prepared in the same manner as given in example 12. The cells are each capillary filled at 40°C with the LC mixture CM-6 additionally containing 6% by weight of RM-6 . The cells are cured at 50 mW/cm² for 600 seconds using Omnicure 250-450 nm broadband exposure. An electric field as given in the following tables is applied to the test cells at room temperature (approx. 21 °C) in order to measure the haze as well as measure the switching speed.

Table 14.1 : Haze measurements as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 6% by weight of

RM-6.

In this system, the zero-voltage (off-state) haze is very low, in all samples below the measurement threshold of the equipment. Peak state haze of approximately 44% is achieved at approximately 10V. Table 14.2: Switching on and off times as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 6% by weight of RM-6.

At 10V or above, this system exhibits fast switching on times. The switching off-times are consistent around 4-5ms, which is more than an order of magnitude faster than the pure LC system CM-5. In this case, the switching off times are approximately 75 milliseconds.

This system exhibits faster switching off times than example 12, and comparable switching on times, while still maintaining excellent haze characteristics.

Example 15

Two test cells are prepared in the same manner as given in example 12. The cells are each capillary filled at 40°C with the LC mixture CM-6 additionally containing 3% by weight of RM-3 and 3% by weight of RM-4. The cells are cured at 50 mW/cm² for 600 seconds using Omnicure 250- 450 nm broadband exposure. An electric field as given in the following tables is applied to the test cells at room temperature (approx. 21 °C) in order to measure the haze as well as measure the switching speed. Table 15.1 : Haze measurements as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 3% by weight of RM-3 and 3% by weight of RM-4.

In this system, the zero-voltage (off-state) haze is low. Peak on-state haze of approximately 40% is achieved at approximately 16V. Table 15.2: Switching on and off times as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 3% by weight of RM-3 and 3% by weight of RM-4.

At 15V or above, this system exhibits fast switching on times. The switching off-times are consistent around 2.5ms.

This system exhibits significantly faster switching off times than examples 2 and 3, and comparable switching on times, while still maintaining excellent haze characteristics.

Example 16

Two test cells are prepared in the same manner as given in example 12. The cells are each capillary filled at 40°C with the LC mixture CM-6 additionally containing 4% by weight of RM-3 and 2% by weight of RM-4. The cells are cured at 50 mW/cm² for 600 seconds using Omnicure 250- 450 nm broadband exposure. An electric field as given in the following tables is applied to the test cells at room temperature (approx. 21 °C) in order to measure the haze as well as measure the switching speed. Table 16.1 : Haze measurements as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 4% by weight of RM-3 and 2% by weight of RM-4.

This system again exhibits extremely low off-state haze. Peak on-state haze of approximately 30% is achieved at approximately 28V. Table 16.2: Switching on and off times as a function of applied voltage for a PN-LC cell filled with mixture CM-6 and also containing 4% by weight of RM-3 and 2% by weight of RM-4.

At 20V or above, this system exhibits fast switching on times. The switching off-times are faster than previous examples, at approximately 1 ms.

This system exhibits significantly faster switching off times than examples 13, 14 and 15, and comparable switching on times, while still maintaining excellent haze characteristics.

The peak haze is lower than examples 14 and 15.

Claims

Patent Claims m for a PNLC light modulation element comprising

a polymerisable component A) in an amount of > 2% to < 10% comprising, one or more polymerisable compounds, at least one of which is a compound of formula I,

P¹¹-Sp¹¹-Ar-Sp¹²-P¹² I wherein

Ar is a group selected from the following formulae

which is optionally substituted by one or more groups L,

L is on each occurrence identically or differently F,

CI, CN, P-Sp-, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH₂-groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O- CO-O- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F or CI,

P¹¹ and P¹² denote each and independently from another a polymerisable group, Sp¹¹ and Sp¹² denote each and independently from another a spacer group that is optionally substituted by one or more groups P¹¹ or P¹², or a single bond and a liquid-crystalline component B) exhibiting dielectrically positive anisotropy, which comprises one or more non- polymerisable mesogenic or liquid-crystalline compounds.

2. Medium according to claim 1 , wherein the liquid-crystalline

component B) exhibits an optical anisotropy (Δη) in the range from 0.05 or more to 0.500 or less.

3. Medium according to claim 1 or 2, wherein the liquid-crystalline component B) exhibits a dielectrically positive anisotropy in the range from 3 to 50.

4. Medium according to claim 1 or 3, wherein the liquid-crystalline component B) exhibits a rotational viscosity in the range from 1 to 500 mPas.

5. Medium according to one or more of claims 1 to 4, wherein the liquid-crystalline component B) comprises one or more

compounds of formula A and/or B,

A 31

in which the individual radicals have, independently of each other and on each occurrence identically or differently, the following

meanings: each, independently

of one another and on each occurrence, identically or differently

X° F, CI, halogenated alkyl or alkoxy having 1 to 6 C atoms or halogenated alkenyl or alkenyloxy having 2 to 6 C atoms, Z³¹ -CH₂CH₂-, -CF₂CF₂-, -COO-, trans-CH=CH-, trans-

CF=CF-, -CH2O- or a single bond,

_L21 _L 22

L³¹ and L ³² each, independently of one another, H or F, g 0, 1 , 2 or 3.

6. Mediunn according to one or more of claims 1 to 5, comprising additionally a surfactant.

7. Medium according to one or more of claims 1 to 6, comprising a photoinitiator.

8. Process for the production of a medium according to one or more of claims 1 to 7 comprising at least the step of mixing the non- polymerisable LC component B) with > 2% to < 10% of the polymerisable LC component A).

9. Use of the medium according to one or more of claims 1 to 7, in a

PNLC light modulation element.

y

10. PNLC light modulation element comprising a pair of opposing substrates, an electrode structure and a LC medium located in the interspace of said substrates, characterized in that the light modulation element comprises a polymer network obtainable from the LC medium according to one or more of claims 1 to 7 by exposing said LC medium to actinic radiation that induces photopolymerisation of the polymerisable compounds in the LC medium.

1 1 . PNLC light modulation element according to claim 10, comprising additionally a planar alignment layer.

12. PNLC light modulation element according to claim 10 or 1 1 ,

comprising an electrode structure, which is capable of providing an electric field perpendicular to the substrates main plane.

13. PNLC light modulation element according to one or more of

claims 10 to 12, wherein the interspace between the two opposing substrates is in the range from 1 to 20 μιτι.

14. Process for the production of a PNLC light modulation element according to one or more of claims 10 to 13 comprising at least the steps of

cutting and cleaning of the substrates,

providing an electrode structure on each of the substrates, - optionally providing an alignment layer on the electrode

structure,

assembling the cell,

filling the cell with the LC medium according to one or more of claims 1 to 7, and

exposing said LC medium to actinic radiation that induces photopolymensation of the polymerisable compounds in the LC medium.

15. Process according to claim 14, wherein photopolymensation

is performed at a temperature between -10°C to +70°C.

16. Process according to claim 14 or 15, wherein photopolymensation step is performed with light having a wavelength in the range from 250 to 450 nm.

17. Process according to one or more of claims 14 to 16, wherein photopolymensation step is performed with an irradiation intensity in the range from 5 to 150 mW/cm².

18. Use of the PNLC light modulation element according to one or more of claims 10 to 13, in an optical or electro-optical device.

19. Optical or electro-optical device comprising the PNLC light

modulation element according to one or more of claims 10 to 13.