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WO2012055473A1 - Milieu à cristaux liquides, et procédé d'élaboration de dispositif à cristaux liquides - Google Patents

Milieu à cristaux liquides, et procédé d'élaboration de dispositif à cristaux liquides Download PDF

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WO2012055473A1
WO2012055473A1 PCT/EP2011/004851 EP2011004851W WO2012055473A1 WO 2012055473 A1 WO2012055473 A1 WO 2012055473A1 EP 2011004851 W EP2011004851 W EP 2011004851W WO 2012055473 A1 WO2012055473 A1 WO 2012055473A1
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atoms
compounds
alkenyl
groups
independently
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Ming-Chou Wu
Achim Goetz
Andreas Taugerbeck
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Merck Patent GmbH
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Merck Patent GmbH
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    • C09K19/10—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing at least two benzene rings
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    • C09K2019/0466—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit characterized by a linking chain between rings or ring systems, a bridging chain between extensive mesogenic moieties or an end chain group the linking chain being a -CF2O- chain
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    • C09K19/3001—Cyclohexane rings
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    • C09K19/3001—Cyclohexane rings
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    • C09K19/3001—Cyclohexane rings
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    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
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    • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
    • C09K19/3001—Cyclohexane rings
    • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
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    • C09K19/3402—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom
    • C09K19/3405—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom the heterocyclic ring being a five-membered ring
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    • C09K2019/3422—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom the heterocyclic ring being a six-membered ring
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    • C09K19/542—Macromolecular compounds
    • C09K2019/548—Macromolecular compounds stabilizing the alignment; Polymer stabilized alignment

Definitions

  • Liquid-crystal medium and process for preparing a liquid-crystal device Liquid-crystal medium and process for preparing a liquid-crystal device
  • the present invention relates to a liquid-crystal (LC) medium comprising a photosensitive compound and a compound having an alkenyl group, to a process of preparing an LC display of the PS (polymer stabilised) or PSA (polymer sustained alignment) type, and to PS or PSA type LC displays obtained by such a process and containing such an LC medium.
  • LC liquid-crystal
  • the LC displays used at present are mostly those of the TN (twisted nematic) type. However, these have the disadvantage of a strong viewing- angle dependence of the contrast.
  • VA vertical alignment
  • the LC cell of a VA display contains a layer of an LC medium between two transparent electrodes, where the LC medium usually has a negative value of the dielectric anisotropy.
  • the molecules of the LC layer are aligned perpendicular to the electrode surfaces (homeotropically) or have a tilted homeotropic alignment.
  • an electrical voltage to the electrodes a realignment of the LC molecules parallel to the electrode surfaces takes place.
  • OCB optical compensated bend
  • OCB displays which are based on a birefringence effect and have an LC layer with a so- called "bend" alignment and usually positive dielectric anisotropy. On application of an electrical voltage, a realignment of the LC molecules perpendicular to the electrode surfaces takes place.
  • OCB displays normally contain one or more birefringent optical retardation films in order to prevent undesired transparency to light of the bend cell in the dark state.
  • OCB displays have a broader viewing angle and shorter response times compared with TN displays.
  • IPS in-plane switching
  • FFS far field switching
  • VA displays of the more recent type uniform alignment of the LC molecules is restricted to a plurality of relatively small domains within the LC cell. Disclinations can exist between these domains, also known as tilt domains.
  • VA displays having tilt domains have, compared with conventional VA displays, a greater viewing-angle independence of the contrast and the grey shades.
  • displays of this type are simpler to produce since additional treatment of the electrode surface for uniform align- ment of the molecules in the switched-on state, such as, for example, by rubbing, is no longer necessary. Instead, the preferential direction of the tilt or pretilt angle is controlled by a special design of the electrodes.
  • MVA multidomain vertical alignment
  • the slitted electrodes generate an inhomogeneous electric field in the LC cell on application of a voltage, meaning that controlled switching is still achieved.
  • the separations between the slits and protrusions can be increased, but this in turn results in a lengthening of the response times.
  • protrusions are rendered completely superfluous in that both electrodes are structured by means of slits on the opposite sides, which results in increased contrast and improved transparency to light, but is technologically difficult and makes the display more sensitive to mechanical influences (tapping, etc.).
  • a shortening of the response times and an improvement in the contrast and luminance (transmission) of the display are desired.
  • PS polymer sustained
  • PSA polymer sustained alignment
  • a small amount for example 0.3% by weight, typically ⁇ 1% by weight
  • a polymerisable compound is added to the LC medium and, after introduction into the LC cell, is polymerised or crosslinked in situ, usually by UV photopolymerisation, optionally with an electrical voltage applied between the electrodes.
  • RMs reactive mesogens
  • PSA-VA, PSA-OCB, PS-IPS and PSTN displays are known.
  • PSA-VA and PSA-OCB displays polymerisation is usually carried out while a voltage is applied to the electrodes
  • PSA-IPS displays polymerisation it is carried out with or without, preferably without application of a voltage.
  • the PSA method results in a pretilt in the cell.
  • PSA- OCB displays it is therefore possible for the bend structure to be stabilised so that an offset voltage is unnecessary or can be reduced.
  • this pretilt has a positive effect on response times.
  • a standard MVA or PVA pixel and electrode layout can be used.
  • posi-VA displays (“positive VA") have proven to be a particularly suitable mode.
  • the initial orientation of the LC molecules in posi-VA displays is homeotropic, i.e. substantially perpendicular to the substrates, in the initial state when no voltage is applied.
  • posi- VA displays LC media with positive dielectric anisotropy are used.
  • the two electrodes in posi-VA displays are arranged on only one of the two substrates, and preferably exhibit intermeshed and comb-shaped (interdigital) structures.
  • the interdigital electrodes By application of a voltage to the interdigital electrodes, which create an electrical field that is substantially parallel to the layer of the LC medium, the LC molecules are transferred into an orientation that is substantially parallel to the
  • PSA polymer stabilisation
  • PSA-VA displays are described, for example, in JP 10-036847 A,
  • PSA-OCB displays are described, for example, in T.-J- Chen et al., Jpn. J. Appl. Phys. 45, 2006, 2702-2704 and S. H. Kim, L.-C- Chien, Jpn. J. Appl. Phys. 43, 2004, 7643-7647.
  • PSA-IPS displays are described, for example, in
  • PSA-TN displays are described, for example, in Optics Express 2004, 12(7), 1221.
  • PSA displays like the conventional displays described above, can be operated either as active matrix or passive matrix displays.
  • active matrix type displays the individual pixels are usually addressed by integrated, non-linear active elements like for example thin film transistors (TFT), in passive matrix type displays by multiplexing, with both methods being well-known from prior art.
  • TFT thin film transistors
  • the selected material system of LC mixture (also referred to as "LC host mixture”) and polymerisable component should have the best possible electrical properties, in particular a high "voltage holding ratio" (HR or VHR).
  • HR voltage holding ratio
  • a high HR after irradiation with UV light is especially important for use in a PSA display, because UV irradiation is an indis- pensible part of the display manufacturing process, although it can also occur as "normal" stress in the finished display.
  • HR voltage holding ratio
  • PSA displays of prior art often show the undesired "image sticking” or “image burn” effect, wherein the image generated in the display by addressing selected pixels remains visible, even when the voltage for this pixel has been switched off, or when other pixels have been addressed.
  • Image sticking can occur for example when using LC host mixtures with a low HR, wherein the UV component of ambient light or emitted by the display backlight can induce undesired cleavage reactions in the LC molecules. This can lead to ionic impurities which are enriched at the electrodes or alignment layers, where they cause a reduction of the effective voltage applied to the display. This effect is also known for conventional displays not containing a polymeric component. ln PSA displays an additional image sticking effect can be observed which is caused by the presence of residual unpolymerised RMs. In such displays the UV component of ambient light or emitted by the backlight causes undesired spontaneous polymerisation of the unreacted RMs. In the addressed pixels this can change the tilt angle after several addressing cycles, thereby causing a change of the transmission, whereas in the unaddressed pixels the tilt angle and transmission remain unaffected.
  • RMs and LC host mixtures are desired which enable a complete and effective polymerisation reaction. In addition it is desired to achieve a controlled polymerisation of any residual amounts of unreacted RMs that are still present in the display. Also, RMs and LC host mixtures are desired that enable a faster and more effective polymerisation than the materials currently known.
  • LC media known in prior art for use in LC displays including but not limited to those of the PSA type, do often exhibit high viscosities and, as a consequence, high switching times.
  • LC compounds with an alkenyl group In order to reduce the viscosity and switching time of the LC medium, it has been suggested in prior art to add LC compounds with an alkenyl group.
  • LC media containing alkenyl compounds often show a decrease of the reliability and stability, and a decrease of the VHR especially after exposure to UV radiation.
  • VHR drop was observed in LC media with alkenyl-containing compounds even after UV exposure at higher wavelengths of 300nm or more. This is a considerable disadvantage when using LC media with alkenyl-containing compounds in PSA displays, because the photo- polymerisation of the RMs in the PSA display is usually carried out by exposure to UV radiation with a wavelength around 300nm, which will then cause a VHR drop in the LC medium.
  • the VHR drop in alkenyl-containing LC media at high UV wavelengths cannot simply be explained by a higher UV absorption of the alkenyl groups compared to e.g. alkyl groups, because the alkenyl groups do not show significant UV absorption at wavelengths around 300nm, which are normally used for photopolymerisation of the RMs. Instead, the alkenyl groups contained in conventional LC compounds do usually show signifcant UV absorption only at very short wavelengths below 200nm. This is, however, far below the wavelength of UV lamps that are commonly used for photopolymerisation in a standard PSA display production process.
  • the improved LC media for use in PSA displays should have a high specific resistance, a large working-temperature range, short response times even at low temperatures, and a low threshold voltage, which enable a large number of grey shades, high contrast and a wide viewing angle, and have high values for the HR after UV exposure.
  • the LC media should show low threshold voltage and high birefringence. Also, the LC media should have high reliability and do not cause unwanted image sticking. They should enable the fast generation of a hight pretilt and allow quick and complete polymerisation of the RMs, with low amounts, or preferably no amounts at all, of unpolymerised RM remaining in the LC medium.
  • the improved processes for manufacturing PSA displays should enable to avoid the above-mentioned negative effects of the alignment layer material on the LC medium, should also enable fast and complete polymerisation of the RMs contained in the LC medium by photopolymerisation inside the display cell, and should also avoid a decrease of the reliability, stability and VHR of the LC medium in the display.
  • the inventors of the present invention have found that it is possible to provide a process for preparing a PSA display from a polymerisable LC medium containing LC compounds with an alkenyl group, which allows to avoid a decrease of the reliability and VHR of the LC medium during UV photopolymerisation of the polymerisable
  • an LC medium for PSA use which contains alkenyl compounds, does not show a significant decrease of the VHR after exposure to UV wavelengths at the upper end of the range from 300 to 400nm, e.g. from 360 to 400nm, whereas, after exposure to UV wavelengths at the lower end of the range from 300 to 400nm, e.g. from 300 to 340nm, the LC medium shows a significant decrease of the VHR.
  • PSA displays could negatively affect the reliability and VHR of an LC medium that contains compounds with alkenyl groups.
  • PSA displays do usually contain alignment layers provided on the surfaces of the electrodes contacting the LC layer, in order to create the initial vertical alignment of the LC molecules.
  • the alignment layers usually consist of polyimide which is prepared from commercially available precursor materials that are coated on the electrodes and e.g. thermally cured.
  • the commonly used polyimide materials often show significant absorption of UV light in the range from 300 to 340nm. Therefore, during photopolymerisation of the RMs in the LC medium when manufacturing the PSA display, the polyimide can absorb UV light that generates undesired radicals, which can interact especially with the alkenyl compounds in the LC medium and cause decomposition reactions that lead to a decrease of the reliability and VHR.
  • the inventors have found that, by using UV radiation of higher
  • the RMs that have been suggested in prior art for use in PSA displays do often show maximum UV absorption at short wavelengths, for example around 300nm.
  • this drawback is overcome by using RMs which show sufficient absorption at the higher UV wavelengths applied in the photopolymerisation step, in particular in the range between 340nm and 400nm.
  • the use of these RMs enables quick and complete photopolymerisation and reduces the amount of unreacted RMs.
  • the inventors have found an effective way of selecting RMs that are suitable for the process of the present invention. This is achieved by selecting the RMs according to their total absorption over a broader UV waveband. Accordingly, for the purposes of this invention the UV absorption of a given RM is defined by its integral of the molar extinction coefficient over a desired wavelength range. Thus, by using higher UV wavelengths for photopolymerisation of the
  • the invention relates to a liquid crystal (LC) medium, characterized in that said LC medium comprises one or more mesogenic compounds or liquid crystal compounds that contain an alkenyl group, and in that said LC medium further comprises one or more photosensitive compounds which are polymerisable by photopolymerisation and which have an integral molar extinction coefficient E ⁇ C M OO ⁇ 1000 L nm cm '1 mol "1 in the wavelength range from 340nm to 400nm.
  • the invention further relates to the use of an LC medium
  • PS polymer sustained
  • PSA polymer sustained alignment
  • an LC medium comprising
  • a polymerisable component A comprising one or more photosensitive compounds as described above and below, and - an LC component B), preferably having a nematic phase, comprising one or more mesogenic or LC compounds containing an alkenyl group.
  • the invention further relates to a method of preparing an LC medium as described above and below, by mixing one or more photosensitive compound with one or more mesogenic or LC compounds and optionally with one or more further liquid-crystalline compounds and/or additives.
  • the invention further relates to an LC display comprising an LC medium as described above and below, which is preferably a PS or PSA display.
  • PS and PSA displays are PSA-VA, PSA-OCB, PSA- IPS, PS-FFS, PSA-posi-VA or PSA-TN displays, very preferred PSA-VA and PSA-IPS displays.
  • the invention further relates to an LC medium, its use in PS and PSA displays, and to PS and PSA displays comprising it as described above and below, wherein the photosensitive compounds, or the polymerisable component, respectively, are polymerised.
  • the invention further relates to the use of an LC medium comprising a polymerisable component and an LC component as described above and below, for the generation of a pretilt angle in a layer of said LC medium when being provided in a display comprising two substrates and two electrodes, by in situ polymerisation of the polymerisable component while applying a voltage to the electrodes.
  • the invention further relates to a process of manufacturing a PS or PSA display as described above and below, comprising the steps of
  • the invention further relates to a PS or PSA display obtained by a process as described above and below.
  • the PS or PSA display comprises two substrates and two electrodes, wherein at least one substrate comprises one or two
  • the unpolymerised LC component comprises one or more mesogenic or LC compounds that contain an alkenyl group
  • the polymerised component is obtained by photopolymerisation of a polymerisable component in the LC medium between the substrates, and
  • said polymerisable component comprises one or more
  • photopolymerisation of said polymerisable component is carried out by exposing it to UV radiation with a wavelength > 340nm, preferably > 340nm,
  • the PS and PSA displays of the present invention preferably comprise two electrodes, preferably in form of transparent layers, which are applied onto one or both of the two substrates which form the display.
  • two electrodes are provided on each of the two substrates, as for example in PSA-VA, PSA-OCB or PSA-TN displays.
  • two electrodes are provided on one of the two substrates and no electrode is provided on the other substrate, as for example in PSA-posi-VA, PSA-IPS or PSA-FFS displays.
  • at least one substrate, very preferably both substrates are transparent to visible light.
  • PSA PSA
  • tilt angle refers to a tilted or inclined orientation of the LC molecules in an LC mixture or LC medium relative to the surface of the cell walls in an LC display.
  • the tilt angle herein means the average angle ( ⁇ 90°) between the molecular long axes of the LC molecules (LC director) and the surface of the plane parallel substrates forming the LC cell.
  • a low value of the tilt angle i.e. a large deviation from the 90° angle
  • a suitable method for measuring the tilt angle is described in the example section. Unless stated otherwise, the tilt angle values as given above and below refer to this measurement method.
  • photosensitive compound means a compound that contains one or more functional groups that undergo a polymerisation reaction when exposed to photoradiation, for example UV radiation.
  • the photosensitive compounds are selected from reactive mesogens which are photopolymerisable (i.e. polymerisable by photopolymerisation, i.e. by polymerisation caused by exposure to photoradiation).
  • reactive mesogen denotes a compound containing a mesogenic group and one or more functional polymerisable groups.
  • the UV absorption of a photosensitive polymerisable compound as used in an LC medium or a process according to the present invention is defined by the integral of the molar absorption (extinction) coefficient of the compound within a given wavelength range (in L nm cm '1 mol " ).
  • this refers to the absorption spectrum of a solution of the compound in dichloromethane (DCM), which is measured using a UV/VIS/NIR-spectrometer Varian Cary 500 (from Varian Inc.).
  • DCM dichloromethane
  • the molar extinction coefficient of a chemical compound which is also known as “molar absorption coefficient” or “molar absorptivity”, is known to the skilled person as an intrinsic compound property, and is a measure of the absorption of the compound at a given wavelength. It is defined by equation (1)
  • ⁇ is the molar decadic extinction coefficient
  • E is the extinction (or absorption) at the given wavelength of the compound sample (as used in the measurement of the absorption spectrum)
  • c is the concentration of the compound in the sample (which is usually a solution)
  • d is the distance the light travels through the sample, i.e. the path length of the light, which is given by the layer thickness of the sample.
  • the integral molar extinction coefficient ⁇ ⁇ ⁇ - ⁇ 2 as used in the present invention is given by equation (2) as the integral of the molar extinction coefficient ⁇ in the range from wavelength ⁇ 1 to wavelength ⁇ 2 (in L nm cm “1 mol “1 ).
  • the integral molar extinction coefficient E 32 o-4oo refers to the wavelength range from 320nm to 400nm
  • the integral molar extinction coefficient E340-400 refers to the wavelength range from 340nm to 400nm.
  • LC mixture or LC component B which contains mesogenic or LC compounds with an alkenyl group and optionally further LC or mesogenic compounds, but does not contain the polymerisable or polymerised photosensitive compounds, is hereinafter also referred to as "(LC) host mixture or "(LC) low-molecular-weight component".
  • (LC) host mixture or "(LC) low-molecular-weight component”.
  • the LC compounds containing an alkenyl group comprised in the LC media of the present invention do not photopolymerise, at least not to a significant extent, under the conditions used for the UV photopolymerisa- tion of the photosensitive compounds.
  • "Significant extent” as used herein means that more than 5 mol% of the compounds will polymerise.
  • nematic component and nematic LC mixture as used hereinafter mean an LC mixture which has a nematic LC phase, but may in addition have other LC phases (like e.g. a smectic phase), but very preferably means an an LC mixture that has only a nematic LC phase and no other LC phases.
  • meogenic group is known to the person skilled in the art and is described in the literature, and denotes a group which, due to the ani- sotropy of its attracting and repelling interactions, essentially contributes to causing a liquid-crystal (LC) phase in low-molecular-weight or polymeric substances.
  • mesogenic com- pounds do not necessarily have to have an LC phase themselves. It is also possible for mesogenic compounds to exhibit LC phase behaviour only after mixing with other compounds and/or after polymerisation. Typical mesogenic groups are, for example, rigid rod- or disc-shaped units.
  • spacer group also referred to as “Sp”
  • spacer group is known to the person skilled in the art and is described in the literature, see, for example, Pure Appl. Chem. 73(5), 888 (2001) and C. Tschierske, G. Pelzl, S. Diele, Angew. Chem. 2004, 116, 6340-6368.
  • spacer group or “spacer” above and below denotes a flexible group which connects the mesogenic group and the polymerisable group(s) to one another in a polymerisable mesogenic compound or RM.
  • conjugated means a compound or moiety containing mainly C atoms with sp 2 -hybridisation (or optionally also sp-hybridisation), which may also be replaced by hetero atoms, or hetero atoms with lone pairs (of electrons). In the simplest case this is for example a compound with alternating C-C single and double (or triple) bonds, but does also include compounds with aromatic units like 1 ,4-phenylene, or compounds with lone paris like N, O or S.
  • Containing mainly C atoms with sp 2 -hybridisation means in this connection that a compound with naturally (spontaneously) occurring defects, which may lead to interruption of the conjugation, is still regarded as a conjugated compound, and that the compound or moiety may in addition also contain C atoms with sp 3 -hybridisation that do not interrupt the conjugation, e.g. in side chains or substitutents attached to the conjugated C atoms or hetero atoms.
  • the LC medium for use in the PSA displays according to the present invention contains one or more photosensitive compounds which are polymerisable by exposure to UV radiation.
  • the LC medium contains an LC host mixture comprising one or more compounds selected from mesogenic or LC compounds, preferably selected from nematic or nematogenic compounds, wherein one or more of these compounds contain at least one alkenyl group that does not polymerise or otherwise react under the condition used for UV photopolymerisation of the
  • the LC host mixture preferably consists only of low-molecular-weight (i.e. monomeric or unpolymerised) compounds, which are stable or unreactive to a polymerisation reaction under the conditions used for the UV photopolymerisation of the photosensitive compounds.
  • the LC medium may contain further additives like for example polymerisation initiators, inhibitors, surfactants, wetting agents, defoamers etc.
  • the LC compounds containing an alkenyl group preferably do not photopolymerise, at least not to a significant extent, under the conditions used for the UV photopolymerisation of the photosensitive compounds.
  • the process for the preparation of PSA displays and the LC media according to the present invention provide one or more of the following advantages:
  • - PSA displays can be manufactured by using longer UV wavelengths of
  • the VHR of the LC medium can be increased, so that it can even show a similar VHR level as an LC medium that does not contain a
  • the polymerisation of the RMs can be carried out fast and effectively, and the extent of polymerisation of the RMs can be increased, thereby also reducing the amount of residual unpolymerised RMs in the display,
  • the LC media and LC mixtures of the present invention have high specific resistance values and a good low temperature stability (LTS) against undesired spontaneous crystallization, and when used in PSA displays, exhibit adequate tilt angles, even without the use of a
  • the invention also relates to a process of manufacturing a PS or PSA display as described above and below, which comprises the steps of providing an LC medium, which comprises one or more photosensitive compounds and one or more mesogenic or LC compounds that contain an alkenyl group as described above and below, in a display or display cell comprising two substrates and two electrodes, wherein at least one substrate is transparent to light and at least one substrate has one or two electrodes provided thereon, and polymerising the photosensitive compounds by exposing them to UV radiation, preferably with a wavelength > 340nm, further preferably while applying a voltage to the electrodes.
  • an LC medium which comprises one or more photosensitive compounds and one or more mesogenic or LC compounds that contain an alkenyl group as described above and below
  • a display or display cell comprising two substrates and two electrodes, wherein at least one substrate is transparent to light and at least one substrate has one or two electrodes provided thereon, and polymerising the photosensitive compounds by exposing them to UV radiation, preferably with a wavelength
  • the polymerisable compounds are polymerised or crosslinked (if a com- pound contains two or more polymerisable groups) by in-situ UV
  • photosensitive compounds to UV radiation, preferably while a voltage is applied to the electrodes that are provided on the substrates.
  • the conditions are selected such that all photosensitive compounds present in the LC medium are polymerised as completely as possible.
  • the wavelength of the UV radiation used for photopolymerisation can be controlled for example by using a conventional UV lamp together with one or more optical filters that do only transmit the desired wavelengths, for example conventional interference or absorption filters, which are known to the skilled person and are commercially available.
  • LP longpass
  • SP shortpass
  • BP bandpass
  • LP and SP filters can be characterized by their cut-off wavelength (also known as cut-on or center wavelength), which corresponds to the wavelength at 50% of their peak (i.e. maximum) transmission.
  • cut-off wavelength also known as cut-on or center wavelength
  • a 340nm LP filter has a cut-off wavelength of 340nm, below which it transmits ⁇ 50% of the maximum transmission.
  • Suitable LP, SP and BP filters for use in the process according to the present invention are known to the skilled person, like for example the optical filters from the Schott WG® or Schott GG® series, which are commercially available from Schott AG
  • UV light when photopolymerisation by irradiation with UV light of wavelengths from 300 to 400nm is desired, this can be achieved by using a UV lamp emitting in this range and and a BP filter being substantially transmissive for wavelengths between 300nm and 400nm.
  • a LP filter that transmits UV light above 300nm wavelength and also visible light, since the latter will usually not negatively affect the polymerisation reaction.
  • the cut-off wavelength is the wavelength above which the LP filter (or below which an SP filter) transmits 50% or more of its maximum transmission. Therefore, if it is desired to completely exclude a certain part of wavelengths, the filter has to be chosen accordingly.
  • filters with a steep slope of the wavelength/transmission curve are used, so that the total transmission of light below the cut-off wavelength (in case of LP filters) or outside the desired waveband (in case of BP filters) is as small as possible.
  • Figure 1 shows the transmission spectra of several longpass filters of the Schott WG® or Schott GG® series, which are suitable for use in a process according to the present invention.
  • the individual graphs show (a) a WG320 filter, (b) a WG335 filter, (c) a
  • WG345 filter and (d) a GG375 filter (the numbers indicating the cut-off wavelength).
  • Graph (e) shows a calculated combination of a WG335 and WG345 filter, having a cut-off wavelength of ca. 340nm. It can be seen that for example the 320nm LP filter has at least 50% transmission at wavelengths above 320nm, but no substantial transmission at wavelengths below 300nm. Likewise, the 340nm LP filter has no substantial transmission at wavelengths below 320nm, and the 375nm LP filter has no substantial transmission at wavelengths below 355 nm and even below 360nm. "No substantial transmission” as used herein means less than 5%, preferably less than 1% of the maximum
  • irradiation with UV light having a wavelength ⁇ > 320nm and excluding UV light having a wavelength ⁇ 320nm is preferably achieved by using a 340nm LP filter.
  • wavelength ⁇ 340nm is preferably achieved by using a 360nm LP filter, and irradiation with UV light having a wavelength ⁇ > 360nm and excluding UV light having a wavelength ⁇ 360nm is preferably achieved by using a 360nm or 375nm LP filter.
  • the skilled person can select further suitable filters for achieving the desired wavelengths.
  • the photosensitive polymerisable compounds are polymerised by exposure to UV radiation having a wavelength of 340nm or higher than 340nm, preferably 350nm or higher than 350nm, very preferably 360nm or higher than 360nm, most preferably 375nm or higher than 375nm.
  • Exposure to UV radiation having a wavelength of XXX nm or higher means that the UV radiation spectrum, to which the
  • Substantial intensity at a given wavelength as used herein means at least 5% of the maximum intensity observed within the entire radiation spectrum to which the compound is exposed.
  • the UV radiation used in the process according to the present invention does not contain radiation of substantial intensity at wavelengths ⁇ 340nm, preferably ⁇ 340nm.
  • the photopolymerisation of the photosensitive compounds is carried out in-situ in the LC medium, which is confined between the two substrates of the display or display cell.
  • the display further comprises two electrodes, wherein only one electrode is provided on each of the two substrates, or both electrodes are provided on only one of the substrates.
  • a voltage is applied to the electrodes during UV exposure of the LC medium containing the photosensitive compound(s), to cause a reorientation of the LC molecules.
  • the voltage can be applied during the entire UV exposure step, or for a given time period that may be shorter or longer than the time period of UV exposure.
  • the UV absorption of a photosensitive compound at a given wavelength is usually defined by its molar extinction coefficient or molar absorptivity, which is an intrinsic material property and can be determined by measurement and calculation methods known to the skilled person and described in the "Definitions" section.
  • the UV lamps conventionally used for photopolymerisation of the polymerisable compounds in the PSA display manufacturing process do not emit a single wavelength but a wavelength band. Also, different
  • photosensitive polymerisable compounds usually have a different shape of their absorption spectrum over a broad waveband. Therefore, for the purposes of the present invention the effective UV absorption of a photosensitive compound is defined by its integral of the extinction coefficient over a given UV wavelength range. This was found to be a better way for evaluating the total UV absorption of the
  • photosensitive compound when being photopolymerised in the PSA display manufacturing process, and thus a better way for selecting photosensitive compounds that are best suitable for this process.
  • the integral molar extinction coefficient (from 340 to 400nm) of the compound is ⁇ 1000 L nm cm “1 mol "1 , it was observed that the polymerisation is slow and incomplete, and the compound is not suitable for the PSA display process. If the integral molar extinction coefficient of the compound is in the range from 1000 to 10000 L nm cm '1 mol "1 , it was observed that the speed and completeness of the polymerisation are already acceptable. If the integral molar extinction coefficient of the compound is > 10000 L nm cm '1 mol "1 , it was observed that the speed and completeness of the polymerisation are especially good, and these compounds are especially preferred for use in an LC medium and a process according to the present invention.
  • the photosensitive compounds are selected such that they are especially adopted to the longer wavelengths used for photopolymerisation in the process according to the present invention.
  • the photosensitive compounds used in the LC medium and the process according to the present invention have an integral molar extinction coefficient E340- 00 ⁇ 1000 L nm cm “1 mol "1 in the range from 340nm to 400nm, wherein E340-400 ' s as defined above.
  • E340- 00 ⁇ 1000 L nm cm “1 mol "1 in the range from 340nm to 400nm, wherein E340-400 ' s as defined above.
  • photosensitive compounds have a value of E340- 400 ⁇ 2000 L nm cm “1 mol "1 , most preferably a value of E340- 400 ⁇ 3000 L nm cm '1 mol “1 .
  • photosensitive compounds are selected such that they have an integral molar extinction coefficient E 32 o oo ⁇ 5000 L nm cm “1 mol "1 in the range from 320nm to 400nm, wherein E 32C OO is the as defined above.
  • the photosensitive compounds of this preferred embodiment have a value of E320-4 00 ⁇ 10000 L nm cm “1 mol “1 .
  • photosensitive compounds are selected such that they have an integral molar extinction coefficient E 30 o- oo ⁇ 20000 L nm cm '1 mol '1 in the range from 300nm to 400nm, wherein E300- 400 is the as defined above.
  • the photosensitive compounds of this preferred embodiment have a value of E 30 o-4oo ⁇ 30000 L nm cm '1 mol "1 .
  • the photosensitive compounds are selected such that they have an E340- 400 ⁇ 1000 L nm cm “1 mol “1 , very preferably an E 3 0- 4oo ⁇ 3000 L nm cm “1 mol “1 , and at the same time have an E320- 00 ⁇ 5000 L nm cm “1 mol “1 , very preferably an E 32 o-4oo ⁇ 10000 L nm cm “1 mol '1 .
  • the photosensitive compounds are selected such that they have an E 3 4o-4oo ⁇ 1000 L nm cm “1 mol “1 , very preferably an E34o- oo ⁇ 3000 L nm cm '1 mol “1 , and at the same time have an E320-400 ⁇ 5000 L nm cm “1 mol “1 , very preferably an E 32 o-4oo ⁇ 10000 L nm cm “1 mol "1 , and at the same time have an E 3 oo-4oo ⁇ 20000 L nm cm “1 mol “1 , very preferably an E 30 o- oo ⁇ 20000 L nm cm “1 mol “1 .
  • the photosensitive compounds are selected from compounds containing a conjugated moiety and one or more photopolymerisable functional groups, which are attached to the conjugated moiety either directly or via spacer groups.
  • said conjugated moiety contains five or more than five, preferably more than six electron pairs that are
  • the conjugated moiety is preferably a ring system comprising one or more aromatic or partially unsaturated rings. If the conjugated system comprises two or more rings, these rings can be linked directly to each other via single or double bonds, or can be linked to each other via linear or branched conjugated groups, or can be fused with each other.
  • said conjugated moiety contains six or more than six, preferably six, electron pairs that are delocalized (as defined above), and wherein the conjugated moiety is a ring system comprising two or more rings, wherein each ring is linked to at least one adjacent ring via at least two ring atoms such that conjugation is maintained and such that the entire ring system has a planar structure.
  • two adjacent rings are linked to each other at a first position via a first carbon or hydrocarbon bridging group that is saturated or unsaturated, and at a second position via a single bond or via a second carbon or hydrocarbon bridging group that is saturated or unsaturated.
  • Suitable and preferred bridging groups are for example saturated alkylene or alkyleneoxy groups.
  • the photosensitive compounds are selected from the group consisting of the following formulae:
  • alkylcarbonyloxy or alkoxycarbonyloxy having 2 to 25 C atoms wherein in all of these groups, in addition, one or more H atoms may be replaced by F, CI or P-Sp-, is halogen, is P, P-Sp-, H, halogen, straight-chain, branched or cyclic alkyl having 1 to 25 C atoms, in which, in addition, one or more non-adjacent CH 2 groups may be replaced by -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 P-Sp-, independently of each other -O-, -S-, -CO-, -CO-O-, -OCO-, - O-CO-O-, -OCH
  • the compounds of formula A-F are preferably selected from the group consisting of the following subformulae:
  • R e has one of the meanings of R a as given in formula A that is different from P-Sp-, s+t > 1 , s+r > 1 , in formulae H3 and H4 at least one s is > 1 , r1 is 0, 1 or 2, r2 is 0, 1 or 2, with r1+r2 > 1 , and r3 is 1 or 2.
  • L denotes, F, CI, straight-chain or branched alkyl or alkoxy having 1 to 12 C atoms, or straight-chain or branched alkenyl, alkinyl, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 2 to 12 C atoms, wherein in all of these groups, in addition, one or more H atoms may be replaced by F or CI, very preferably F, CI, or alkyl, alkoxy or carbonyl with 1 to 4 C atoms that is optionally fluorinated.
  • the compounds contain two groups P-Sp, wherein of the two groups Sp one is a single bond and the other of the two groups Sp is not a single bond,
  • the compounds contain two groups P-Sp, wherein both groups Sp are a single bond,
  • R a , R b , R c , R d or R e that is different from P-Sp- denotes alkyl or alkoxy having from 1 to 12 C atoms wherein one or more H atoms are optionally replaced by F,
  • P is acrylate, methacrylate or oxetane, preferably acrylate or methacrylate,
  • the groups Sp that are not a single bond denote -(CH 2 ) p1 -, -(CH 2 ) p i- O-, -(CH 2 ) P i-O-CO-, -(CH 2 ) p i-O-CO-O-, very preferably -(CH 2 ) p1 - or -
  • a 1 and A 2 denote 1 ,4-phenylene that it optionally substituted by one or more groups L,
  • L denotes, F, CI, straight-chain or branched alkyl or alkoxy having 1 to 12 C atoms, or straight-chain or branched alkenyl, alkinyl, alkyl- carbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 2 to 12 C atoms, wherein in all of these groups, in addition, one or more H atoms may be replaced by F or CI,
  • R a -(A 1 -Z 1 ) p - and -(Z 2 -A 2 ) q -R b are not halogen.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula A and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula B and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula C and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula D and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula E and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula F and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula G and its preferred subformulae.
  • Another preferred embodiment of the present invention relates to a process and an LC medium as described above and below, wherein the photosensitive compounds are selected from formula H and its preferred subformulae.
  • “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.
  • “Halogen” denotes F, CI, Br or I.
  • a carbyl or hydrocarbyl group can be a saturated or unsaturated group. Unsaturated groups are, for example, aryl, alkenyl or alkynyl groups.
  • a carbyl or hydrocarbyl group having more than 3 C atoms can be straight- chain, branched and/or cyclic and may also contain spiro links or condensed rings.
  • alkyl also encompass polyvalent groups, for example alkylene, arylene,
  • heteroarylene etc.
  • aryl denotes an aromatic carbon group or a group derived therefrom.
  • heteroaryl denotes "aryl” in
  • Preferred carbyl and hydrocarbyl groups are optionally substituted alkyl, alkenyl, alkynyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy and alkoxycarbonyloxy having 1 to 40, preferably 1 to 25, particularly preferably 1 to 18 C atoms, optionally substituted aryl or aryloxy having 6 to 40, preferably 6 to 25 C atoms, or optionally substituted alkylaryl, arylalkyi, alkylaryloxy, arylalkyloxy, arylcarbonyl, aryloxycarbonyl, arylcarbonyloxy and aryloxycarbonyloxy having 6 to 40, preferably 6 to 25 C atoms.
  • carbyl and hydrocarbyl groups are C1-C40 alkyl, C2-C40 alkenyl, C2-C40 alkynyl, C3-C40 allyl, C4-C40 alkyldienyl, C4-C40 polyenyl, C&- C40 aryl, C6-C40 alkylaryl, C 6 -C 4 o arylalkyi, C 6 -C 4 o alkylaryloxy, C6-C40 aryl- alkyloxy, C2-C40 heteroaryl, C4-C40 cycloalkyl, C4-C40 cycloalkenyl, etc.
  • C1-C22 alkyl Particular preference is given to C1-C22 alkyl, C2-C22 alkenyl, C2-C22 alkynyl, C3-C22 allyl, C4-C22 alkyldienyl, C 6 -Ci2 aryl, C6-C20 arylalkyi and C2-C20 heteroaryl.
  • R x preferably denotes H, halogen, a straight-chain, branched or cyclic alkyl chain having 1 to 25 C atoms, in which, in addition, one or more non- adjacent C atoms may be replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, and in which one or more H atoms may be replaced by fluo- rine, an optionally substituted aryl or aryloxy group having 6 to 40 C atoms or an optionally substituted heteroaryl or heteroaryloxy group having 2 to 40 C atoms.
  • 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, cycloheptyl, n-octyl, cyclooctyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, dodecanyl, trifluoro- methyl, perfluoro-n-butyl, 2,2,2-trifluoroethyl, perfluorooctyl, perfluoro- hexyl, etc.
  • Preferred alkenyl groups are, for example, ethenyl, propenyl, butenyl, pentenyl, cyclopentenyl, hexenyl, cyclohexenyl, heptenyl, cycloheptenyl, octenyl, cyclooctenyl, etc.
  • Preferred alkynyl groups are, for example, ethynyl, propynyl, butynyl, pentynyl, hexynyl, octynyl, 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-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-undecyloxy, n-dodecyloxy, etc.
  • Preferred amino groups are, for example, dimethylamino, methylamino, methylphenylamino, phenylamino, etc.
  • Aryl and heteroaryl groups 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.
  • Preferred aryl groups are, for example, phenyl, biphenyl, terphenyl,
  • 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, ,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,
  • the (non-aromatic) alicyclic and heterocyclic groups encompass both saturated rings, i.e. those which contain exclusively single bonds, and also partially unsaturated rings, i.e. those which 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 poly- cyclic, i.e. contain a plurality of rings (such as, for example, 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 are optionally substituted.
  • 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-
  • the aryl, heteroaryl, carbyl and hydrocarbyl radicals optionally have one or more substituents, which are preferably selected from the group comprising silyl, sulfo, sulfonyl, formyl, amine, imine, nitrile, mercapto, nitro, halogen, Ci-12 alkyl, Ce-12 aryl, C 1- 2 alkoxy, hydroxyl, or combinations of these groups.
  • Preferred substituents are, for example, solubility-promoting groups, such as alkyl or alkoxy, electron-withdrawing groups, such as fluorine, nitro or nitrile, or substituents for increasing the glass transition temperature (Tg) in the polymer, in particular bulky groups, such as, for example, t-butyl or optionally substituted aryl groups.
  • R x has the above- mentioned meaning
  • Y 1 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, alkynyl, 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 substituted by halogen, -CN, R°, -OR 0 , -CO-R 0 , -CO-O-R 0 , -O-CO-R 0 or -O-CO-O-R 0 , in which R° has the above-mentioned meaning.
  • substituents L are, for example, F, CI, CN, NO 2 , CH 3 , C 2 H 5 , OCH 3 , OC 2 H5, COCH3, COC 2 H5, COOCH 3 , COOC 2 H 5 , CF 3 , OCF 3 , OCHF 2) OC 2 F 5 , furthermore phenyl.
  • L has, on each ocurrence identically or differently, one of the meanings given abvoe and below, and is preferably F, CI, CN, NO 2 , CH 3 , C 2 H 5 , C(CH 3 ) 3 , CH(CH 3 ) 2 , CH 2 CH(CH 3 )C 2 H 5 , OCH 3) OC 2 H 5 , COCH 3 , COC 2 H 5 , COOCH3, COOC 2 H 5 , CF 3 , OCF 3 , OCHF 2 , OC 2 F 5 or P-Sp-, very preferably F, CI, CN, CH 3 , C 2 H 5 , OCH 3 , COCH 3 , OCF 3 or P-Sp-, most preferably F, CI, CH 3 , OCH 3 , COCH 3 or OCF 3 .
  • the polymerisable compounds of the formulae and II * and sub-formulae thereof contain, instead of one or more radicals ⁇ -Sp-, one or more branched radicals containing two or more polymerisable groups P (multifunctional
  • 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 multifunctional polymerisable radicals selected from the following formulae:
  • P 1"5 each, independently of one another, have one of the meanings indicated above for P.
  • Preferred spacer groups Sp are selected from the formula Sp'-X', so that the radical "P-Sp-" conforms to the formula "P-Sp'-X'-", where 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 CH 2 groups may each be replaced, independently of one another, by -O-, -S-, -NH-, -NR 0 -, -SiR°R 00 -, -CO-, -COO-, -OCO-, -OCO-O-, -S-CO-, -CO-S-,
  • X' denotes -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -,
  • R° and R 00 each, independently of one another, denote H or alkyl having 1 to 12 C atoms, and
  • Y 2 and Y 3 each, independently of one another, denote H, F, CI or CN.
  • X' is preferably -O-, -S-, -CO-, -COO-, -OCO-, -O-COO-, -CO-NR 0 -, -NR°-CO-, -NR°-CO-NR°- or a single bond.
  • Typical spacer groups Sp' are, for example, -(CH 2 ) p i-, -(CH 2 CH 2 O) q i- CH 2 CH 2 -, -CH 2 CH 2 -S-CH 2 CH 2 -, -CH 2 CH 2 -NH-CH 2 CH 2 - or -(SiR°R 00 -O) p i-, in which p1 is an integer from 1 to 12, q1 is an integer from 1 to 3, and R° and R 00 have the above-mentioned meanings.
  • Particularly preferred groups -X'-Sp - are -(CH 2 ) p i-, -0-(CH 2 ) p i-, -OCO- (CH 2 ) p i-, -OCOO-(CH 2 ) p1 -.
  • Particularly preferred groups Sp' are, for example, in each case straight- chain ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, undecylene, dodecylene, octadecylene, ethyleneoxyethylene, methyleneoxybutylene, ethylenethioethylene, ethyl- ene-N-methyliminoethylene, 1-methylalkylene, ethenylene, propenylene and butenylene.
  • polymerisable compounds are 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.
  • the synthesis of polymerisable acrylates and methacrylates of the formula I can be carried out analogously to the methods described in US 5,723,066. Further, particularly preferred methods are given in the examples.
  • the synthesis is carried out by esterification or etheri- fication of commercially available diols of the general formula HO-A 1 -(Z 1 - A 2 )mi-OH, in which A 1 , A 2 , Z 1 and ml have the above-mentioned
  • the photosensitive compounds are preferably selected from compounds that contain only one photopolymerisable group and compounds that contain only two photopolymerisable groups. It is, however, also possible to use photosensitive compounds that contain more than two, for example three, four, five or six, photopolymerisable groups. In another preferred embodiment of the present invention, the
  • polymerisable component of the LC medium comprises one or more polymerisable compounds containing only one polymerisable group
  • polymerisable compounds containing two or more, preferably only two, polymerisable groups (di- or multireactive).
  • polymerisable component of the LC medium consists of polymerisable compounds containing only two polymerisable groups (direactive).
  • the proportion of the photosensitive, polymerisable compounds in the LC medium is preferably >0 and ⁇ 5%, especially >0 and ⁇ 1%, very
  • the LC medium preferably contains one, two or three, most preferably only one, photosensitive compound(s).
  • the proportion of the LC host mixture in the LC medium is preferably > 95%, very preferably > 99%.
  • the LC medium according to the present invention does essentially consist of one or more photosensitive compounds and an LC host mixture as described above and below.
  • the LC medium or LC host mixture may additionally comprise one or more further components or additives, preferably selected from the list including but not limited to chiral dopants, polymerisation initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments and nanoparticles.
  • photoinitiators may also be 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 photoinitiators for free-radical polymerisation are, for example, the commercially available photoinitiators Irgacure651 ® , Irgacure184 ® , Irgacure907®, Irgacure369 ® or Darocurel 173 ® (Ciba AG). If an initiator is employed, its proportion in the mixture as a whole is preferably 0.001 to 5% by weight, particularly preferably 0.001 to 1% by weight.
  • the LC medium does not comprise a polymerisation initiator.
  • the polymerisable component or the LC medium may also comprise one or more stabilisers in order to prevent undesired spontaneous polymerisation of the RMs, for example during storage or transport.
  • Suitable types and amounts of stabilisers are known to the person skilled in the art and are described in the literature. Particularly suitable are, for example, the commercially available stabilisers of the Irganox ® series (Ciba AG).
  • stabilisers are employed, their proportion, based on the total amount of RMs or polymerisable component A), is preferably 10 - 5000ppm, particularly preferably 50 - 500ppm.
  • the polymerisable compounds according to the invention are also suitable for polymerisation without initiator, which is associated with considerable advantages, such as, 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 polymerisable compounds according to the invention can be added individually to the LC media, but it is also possible to use mixtures comprising two or more polymerisable compounds. On polymerisation of mixtures of this type, copolymers are formed.
  • the invention furthermore relates to the polymerisable mixtures mentioned above and below.
  • the LC medium according to the invention comprises a low- molecular-weight component.
  • the low-molecular-weight component is preferably an LC mixture ("LC host mixture") comprising one or more, preferably two or more, low-molecular-weight (i.e. monomeric or unpolymerised) compounds, where at least one of these compounds is a mesogenic or liquid-crystalline compound containing one or more alkenyl groups (“alkenyl compound”), where these alkenyl groups are stable to a polymerisation reaction under the conditions used for the polymerisation of the methacrylate groups.
  • LC host mixture comprising one or more, preferably two or more, low-molecular-weight (i.e. monomeric or unpolymerised) compounds, where at least one of these compounds is a mesogenic or liquid-crystalline compound containing one or more alkenyl groups (“alkenyl compound”), where these alkenyl groups are stable to a polymerisation reaction under the conditions used for the polymerisation of the methacryl
  • the LC host mixture is preferably a nematic LC mixture.
  • the alkenyl groups are preferably straight-chain, branched or cyclic alkenyl, in particular having 2 to 25 C atoms, particularly preferably having 2 to 12 C atoms, in which, in addition, one or more non-adjacent CH 2 groups may be replaced by -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 and/or CI.
  • Preferred alkenyl groups are straight-chain alkenyl having 2 to 7 C atoms and cyclohexenyl, in particular ethenyl, propenyl, butenyl, pentenyl, hex- enyl, heptenyl, 1 ,4-cyclohexen-1-yl and 1 ,4-cyclohexen-3-yl.
  • concentration of compounds containing an alkenyl group in the LC host mixture is preferably from 5% to 100%, very preferably from 20% to 60%.
  • LC mixtures containing 1 to 5, preferably 1 , 2 or 3 compounds having an alkenyl group are especially preferred.
  • the compounds containing an alkenyl group are preferably selected from the following formulae:
  • 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 R d , alkyl having 1 to 12 C atoms, in which, in addition, one or two non-adjacent CH 2 groups may be replaced by -0-, -CH CH-, -CO-, -OCO- or -COO- in such a way that O atoms are not linked directly to one another,
  • R 22 is preferably straight-chain alkyl or alkoxy having 1 to 8 C atoms or straight-chain alkenyl having 2 to 7 C atoms.
  • L 1 and L 2 denote F, or one of L 1 and L 2 denotes F and the other denotes CI, and L 3 and L 4 denote F, or one of L 3 and L 4 denotes F and the other denotes CI.
  • the compounds of the formula AN are preferably selected from the following sub-formulae:
  • the compounds of the formula AY are preferably selected from the following sub-formulae:
  • alkyi denotes a straight-chain alkyi radical having 1-6 C atoms
  • LC host mixture comprising one or more compounds selected from the following formulae:
  • both L 1 and L 2 denote F, or one of L 1 and L 2 denote F and the other denotes CI.
  • the compounds of formula CY are preferably selected from the following sub-formulae:
  • alkyl and alkyl * each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms, and (O) denotes an O atom or a single bond.
  • the compounds of formula PY are preferably selected from the following sub-formulae:
  • LC host mixture which comprises one or more compounds of the following formula: in which the individual radicals have the following meanings:
  • the compounds of the formula ZK are preferably selected from the following sub-formulae:
  • alkyl and alkyl * each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms.
  • LC host mixture which additionally comprises one or more compounds of the following formula: in which the individual radicals have on each occurrence, identically or differently, the following meanings: R 5 and R 6 each, independently of one another, have one of the meanings indicated above for R 1 ,
  • LC host mixture which additionally comprises one or more
  • L 5 and L 6 each, independently of one another, denote F, CI, OCF 3 ,
  • both radicals L 5 and L 6 denote F or one of the radicals L 5 and L 6 denotes F and the other denotes CI.
  • the compounds of the formula TY are preferably selected from the following sub-formulae:
  • R 1 has the above-mentioned meaning, (O) denotes an O atom or a single bond, alkyl denotes a straight-chain alkyl radical having 1-6 C atoms, and v denotes an integer from 1 to 6.
  • R 1 preferably denotes straight-chain alkyl having 1-6 C atoms.
  • the LC medium according to the invention preferably comprises one or more compounds of the above-mentioned formulae in amounts of > 0 to ⁇ 10% by weight.
  • LC host mixture which additionally comprises one or more
  • alkyl denotes d-6-alkyl
  • L x denotes H or F
  • Particular preference is given to compounds of the formula G1 in which X denotes F.
  • LC medium preferably comprises one or more compounds of the above-mentioned formulae in amounts of > 0 to ⁇ 10% by weight.
  • LC host mixture which additionally comprises one or more biphenyl compounds of the following formula:
  • alkyl and alkyl * each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms,.
  • the proportion of the biphenyls of formula BP in the LC mixture is preferably at least 3% by weight, in particular > 5% by weight.
  • the compounds of the formula BP are preferably selected from the following sub-formula: B1a in which alkyl* denotes an alkyl radical having 1-6 C atoms.
  • LC host mixture which additionally comprises one or more compounds of the following formulae:
  • R and R 2 have the above-mentioned meanings and preferably each, independently of one another, denote straight-chain alkyl or alkenyl.
  • Preferred mixtures comprise one or more compounds selected from the formulae O1 , 03 and 04.
  • LC host mixture which additionally comprises one or more compounds of the following formula:
  • R 9 denotes H, CH 3 , C 2 H 5 or n-C 3 H 7
  • (F) denotes an optional fluoro substituent
  • q denotes 1 , 2 or 3
  • R 7 has one of the meanings indicated for R 1 , preferably in amounts of > 3% by weight, in particular > 5% by weight and very particularly preferably 5-30% by weight.
  • Particularly preferred compounds of the formula Fl are selected from the following sub-formulae:
  • R 7 preferably denotes straight-chain alkyl having 1-6 C atoms
  • R 9 denotes CH 3l C2H5 or n-C3H 7 .
  • LC host mixture which additionally comprises one or more compounds of the following formulae:
  • LC host mixture which additionally comprises one or more compounds which contain a tetrahydronaphthyl or naphthyl unit, such as, for example, the compounds selected from the following formulae:
  • R 10 and R 1 each, independently of one another, have one of the meanings indicated for R 1 , preferably denote straight-chain alkyl or straight-chain alkoxy having 1-6 C atoms or straight-chain alkenyl having 2-6 C atoms
  • LC host mixture which additionally comprises one or more difluoro- dibenzochromans and/or chromans of the following formulae: in which R 11 and R 12 each, independently of one another, have the above-mentioned meaning, and c denotes 0 or 1 , preferably in amounts of 3 to 20% by weight, in particular in amounts of 3 to 15% by weight.
  • alkyl and alkyl* each, independently of one another, denote a straight-chain alkyl radical having 1-6 C atoms
  • alkenyl and alkenyl * each, independently of one another, denote a straight-chain alkenyl radical having 2-6 C atoms.
  • mixtures comprising one, two or three compounds of the formula BC-2.
  • LC host mixture which additionally comprises one or more fluorinated phenanthrenes or dibenzofurans of the following formulae:
  • R 11 and R 12 each, independently of one another, have the above-mentioned meanings
  • b denotes 0 or 1
  • L denotes F
  • r denotes 1 , 2 or 3.
  • Particularly preferred compounds of the formulae PH and BF are selected from the following sub-formulae: in which R and R' each, independently of one another, denote a straight-chain alkyl or alkoxy radical having 1-7 C atoms.
  • LC host mixture which comprises one or more, preferably from 3 to 20 compounds of the formulae CY, PY and/or TY.
  • the proportion of these compounds in the host mixture as a whole is preferably from 10 to 80 % very preferably from 20 to 70 %.
  • the content of these individual compounds is preferably in each case from 2 to 25 % by weight.
  • LC host mixture or nematic component wherein the compounds of formulae CY, PY and TY are selected from the group consisting of formulae CY1 , CY2, CY9, CY10, PY1 , PY2, PY9 and PY10.
  • LC host mixture which comprises one or more, preferably from 3 to 20 compounds of the formulae ZK and DK.
  • the proportion of these compounds in the host mixture as a whole is preferably from 5 to 50% very preferably from 10 to 40%.
  • the content of these individual compounds is preferably in each case from 2 to 20 % by weight.
  • LC host mixture or nematic component wherein the compounds of formulae ZK and DK are selected from the group consisting of formulae ZK1 , ZK2, ZK5, ZK6, DK1 and DK2.
  • LC medium which comprises 1 to 5, preferably 1 , 2 or 3 polymerisable compounds.
  • LC medium in which the proportion of polymerisable compounds in the medium as a whole is 0.05 to 5 %, preferably 0.1 to 1 %.
  • LC medium which comprises in addition one or more, preferably low- molecular-weight and/or unpolymerisable, chiral dopants, very preferably selected from Table B, preferably in the concentration ranges given for Table B.
  • the combination of compounds of the preferred embodiments mentioned above with the polymerised compounds described above and below effects low threshold voltages and very good low-temperature stabilities with maintenance of high clearing points and high HR values in the LC media according to the invention and allows a pretilt angle to be set in PSA displays.
  • the LC media exhibit significantly shortened response times, in particular also the grey-shade response times, in PSA displays compared with the media from the prior art.
  • the LC host mixture preferably has a nematic phase range of at least 80 K, particularly preferably at least 100 K, and a rotational viscosity of not greater than 450 mPa-s, preferably not greater than 350 mPa-s, at 20°C.
  • the LC host mixture preferably has a negative dielectric anisotropy ⁇ , preferably of about -0.5 to -7.5, in particular of about -2.5 to -6.0, at 20°C and 1 kHz.
  • the LC host mixture preferably has a birefringence ⁇ > 0.06, very preferably > 0.09, most preferably > 0.12, and preferably has a
  • birefringence ⁇ ⁇ 0.20 very preferably ⁇ 0.18, most preferably ⁇ 0.16.
  • the LC media may also comprise further additives known to the person skilled in the art and described in the literature, like for example chiral dopants, polymerisation initiators, inhibitors, stabilizers, surfactants, wetting agents, lubricating agents, dispersing agents, hydrophobing agents, adhesive agents, flow improvers, defoaming agents, deaerators, diluents, reactive diluents, auxiliaries, colourants, dyes, pigments or nanoparticles.
  • additives can be polymerisable or unpolymerisable. Accordingly, polymerisable additives will belong to the polymerisable component, and unpolymerisable additives will belong to the nematic component of the LC media.
  • the LC media can for example contain one or more chiral dopants, which are preferably selected from the group consisting of compounds from Table B below.
  • pleochroic dyes For example, 0 to 15% by weight of pleochroic dyes may be added.
  • nanoparticles preferably ethyldimethyldo- decylammonium 4-hexoxybenzoate, tetrabutylammonium tetraphenyl- borate or complex salts of crown ethers (see e.g. Haller et al., Mol. Cryst.
  • Liq. Cryst. 24, 249-258 (1973) may be added to improve the conductivity.
  • substances may be added to modify the dielectric anisotropy, the viscosity and/or the alignment of the nematic phases. Substances of this type are described, for example, in DE-A 22 09 27, 22 40 864,
  • Preference is furthermore given to LC media comprising one, two or three polymerisable compounds as described above and below. Preference is furthermore given to achiral polymerisable compounds and LC media comprising, preferably consisting exclusively of, achiral compounds.
  • the LC media which can be used in accordance with the invention are prepared in a manner conventional per se, for example by mixing one or more of the above-mentioned compounds with one or more polymerisable compounds as defined above and optionally with further liquid-crystalline compounds and/or additives.
  • 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.
  • the invention furthermore relates to the process for the preparation of the LC media according to the invention.
  • the LC media according to the invention may also comprise compounds in which, for example, H, N, O, CI, F have been replaced by the corresponding isotopes.
  • the construction of the LC displays according to the invention corresponds to the conventional geometry for PSA displays, as described in the prior art cited at the outset. Geometries without protrusions are preferred, in particular those in which, in addition, the electrode on the colour filter side is unstructured and only the electrode on the TFT side has slits. Par- ticularly suitable and preferred electrode structures for PSA-VA displays are described, for example, in US 2006/0066793 A1.
  • the LC media according to the invention comprise one or more compounds selected from the group consisting of compounds from Table A.
  • Table B indicates possible dopants which can be added to the LC media according to the invention.
  • the LC media preferably comprise 0 to 10% by weight, in particular 0.01 to 5% by weight and particularly preferably 0.1 to 3% by weight, of dopants.
  • the LC media preferably comprise one or more dopants selected from the group consisting of compounds from Table B.
  • Table C indicates possible stabilisers which can be added to the LC media according to the invention (n here denotes an integer from 1 to 12, terminal methyl groups ar not shown)
  • the LC media preferably comprise 0 to 10% by weight, in particular 1 ppm to 5% by weight and particularly preferably 1ppm to 3% by weight, of stabilisers.
  • the LC media preferably comprise one or more stabilisers selected from the group consisting of compounds from Table C.
  • the following abbreviations and symbols are used:
  • V 0 denotes threshold voltage, capacitive [V] at 20°C,
  • Vpp denotes applied voltage peak-to-peak
  • n e denotes extraordinary refractive index at 20°C and 589 nm
  • n 0 denotes ordinary refractive index at 20°C and 589 nm
  • ⁇ denotes optical anisotropy at 20°C and 589 nm
  • ⁇ denotes the dielectric permittivity perpendicular to the
  • ⁇ denotes dielectric anisotropy at 20°C and 1 kHz
  • T(N,I) denotes clearing point [°C]
  • ⁇ - denotes rotational viscosity at 20°C [mPa-s]
  • Ki denotes elastic constant, "splay" deformation at 20°C [pN],
  • K 2 denotes elastic constant, "twist" deformation at 20°C [pN],
  • K 3 denotes elastic constant, "bend" deformation at 20°C [pN],
  • LTS denotes low-temperature stability, determined in test cells
  • HR / VHR denotes voltage holding ratio at 100°C [%].
  • the term "threshold voltage” relates to the capa- citive threshold (V 0 ), also known as the Freedericksz threshold, unless explicitly indicated otherwise.
  • V 0 capa- citive threshold
  • the optical threshold for 10% relative contrast (Vi 0 ) may also be indicated.
  • the display test cells used for the measurements described in the examples contain two plane-parallel outer plates at a separation of 4 ⁇ and electrode layers with overlying alignment layers of rubbed polyimide on the insides of the outer plates, which cause a homeotropic edge alignment of the liquid-crystal molecules.
  • pp peak-to-peak
  • polymerisation was carried out at 40°C using a 100 mW/cm 2 metal halide lamp, the intensity was measured using a standard UV meter (model Ushio UNI meter). In this case the lamp intensity itself was measured, not UV after specific filters.
  • the tilt angle is determined by a rotational crystal experiment (Autronic- Melchers TBA-105). A small value (i.e. a large deviation from a 90° angle) corresponds to a large tilt here.
  • the VHR is measured as follows: To the LC host mixture a defined amount (e.g. 0.3%) of the RM are added, and the resulting mixture is filed into VA-VHR test cells (no rubbing, alignment layer VA polyimide, cell gap 6 pm). The test cells are exposed to UV radiation using a 100 mW/cm 2 metal halide lamp at 40°C, and the VHR value is measured after certain time intervals at 1V, 60Hz, 64ps pulse, 100°C (Autronic-Melchers VHRM- 105). The UV absorption of the photosensitive compounds is determined as follows: The compound is dissolved in a solvent, unless stated otherwise in dichloromethane (DCM). The UV/VIS spectrum of the sample is then measured using a UV/VIS/NIR-spectrometer Varian Cary 500 with the following parameters:
  • the integral of the extinction (y-axis of the spectrum) over a given wavelength range (x-axis of the spectrum) is calculated for each compound and multiplied with its mass and divided by its concentration in the measurement sample and by the sample thickness, in accordance with equations (1) and (2) above, to give the integral molar extinction coefficient ⁇ ⁇ ⁇ - ⁇ 2 for the wavelength range from ⁇ 1 to ⁇ 2.
  • the value of ⁇ ⁇ ⁇ - ⁇ 2 for a given compound is in theory independent from the concentration, sample thickness and molar mass, and is an intrinsic compound property. Nevertheless, in order to reduce measurement errors, it is preferable to prepare multiple samples with similar and/or varying concentration, and to use the average of the ⁇ ⁇ ⁇ - ⁇ 2 values obtained from individual measurements. In addition the same solvent should be used (e.g. DCM) if different samples are compared due to the fact that the molar extinction coefficient depend on the solvent used for the experiments.
  • DCM solvent
  • the extinction values described above and below are given for a temperature of 20°C.
  • the process of polymerizing the photosensitive compounds in the PSA displays as described above and below is carried out at a temperature where the LC medium exhibits a liquid crystal phase, preferably a nematic phase, and most preferably is carried out at room temperature.
  • the UV/VIS absorption spectra of various photosensitive polymerisable compounds were measured in DCM as described above, and the integral extinction coefficient was calculated.
  • Table 1 shows for each compound the chemical structure, the wavelength X max of the absorption maximum, the molar extinction coefficient ⁇ at the maximum wavelength X max , and the integral molar extinction coefficient ⁇ ⁇ in the range from 340 to 400nm.
  • compounds RM1-RM6 have a value of E340-400 ⁇ 1000 in the desired wavelength range, and therefore represent photosensitive compounds in the sense of the present invention
  • compound RM7 has a value of E 3 0- 4oo ⁇ 1000 and does not represent a photosensitive compound in the sense of the present invention.
  • a high value of the wavelength at the absorption maximum ⁇ [ ⁇ 3 ⁇ , and/or a high value of the extinction coefficient ⁇ at does not necessarily mean that the compound also has a high value of ⁇ 340-400 ⁇ in the desired wavelength range from 340-400nm.
  • RM5 and RM6 have an absorption maximum at a lower wavelength than RM7, but do still have a higher overall extinction at higher wavelengths, as indicated by their higher values of E 3 4 0- 4oo- R 2 has a lower value of the extinction coefficient ⁇ at max than RM1 , but does still have a higher overall extinction at higher wavelengths, as indicated by its value of £40-400 ⁇ RM4 and RM5 have similar values of and ⁇ at X max , nevertheless RM5 has a significantly higher value of E340-400 than RM4.
  • nematic LC host mixture C1 is formulated:
  • the mixture C1 does not contain a compound with an alkenyl group.
  • nematic LC host mixture M1 is formulated: CY-3-02 18.00 % Cl.p +74.5
  • the mixture M1 contains 40% of a compound with an alkenyl group selected of formula A1 , and shows a significantly reduced viscosity compared to LC host mixture C1.
  • the polymerisable LC media PC1-PC3 are prepared by adding 0.4% of one of RM1 , RM2 and RM3, respectively, to the alkenyl-free host mixture C1 of Comparison Example 1.
  • the polymerisable LC media PC4 and PC5 are prepared by adding 0.3% of RM7 (see Table 1) to the alkenyl-containing host mixture M1 of Example 1 , and to the alkenyl-free host mixture C1 of Comparison Example 1 , respectively.
  • RM7 see Table 1
  • the polymerisable LC media PM1-PM3 are prepared by adding 0.4% of one of RM1 , RM2 and RM3 (see Table 1), respectively, to the alkenyl- containing host mixture M1 of Example 1.
  • compositions of the individual mixtures are shown in Table 2 below.
  • PM1-PM3 represent polymerisable LC media according to the invention, whereas PC1-PC5 do not represent polymerisable LC media according to the invention.
  • the VHR is measured for mixtures M1 , C1 , PC4 and PC5 by the general method as described above, after exposure to UV light for different time periods using a UV lamp and a 320nm cut-off filter. As shown in Figure 1, this results in exposure to UV light that does not contain radiation of substantial intensity below 300nm. The results are shown in Table 3.
  • the alkenyl-free host mixture C1 shows a decrease of the VHR after UV exposure.
  • the resulting polymerisable mixture PC4 does only show a slight decrease of the VHR, so that by addition of RM7 the VHR drop is suppressed.
  • the alkenyl-containing host mixture M1 shows a stronger decrease of the VHR than the alkenyl-free host mixture C1.
  • the VHR decrease in the resulting polymerisable mixture PC5 is even stronger.
  • the VHR drop after UV exposure in the alkenyl-containing host M1 is much stronger, and is not suppressed, but to the contrary even enhanced, by addition of RM 7.
  • the VHR is measured for the polymerisable LC media PM1-PM3 and PC1-PC3 by the general method as described above, after exposure for different time periods to UV radiation having either a shorter wavelength or a longer wavelength, by using a UV lamp with a 340nm cut-off filter or a 375nm cut-off filter, respectively.
  • the use of a 340nm cut-off filter results in exposure to UV light that does not contain radiation of substantial intensity below 320nm
  • the use of a 375nm cut-off filter results in exposure to UV light that does not contain radiation of substantial intensity below 340nm.
  • the polymerisable mixture PM1 with the alkenyl-containing host and RM1 shows a larger drop of the VHR than the polymerisable mixture PC1 with the alkenyl-free host and RM1 , wherein almost no drop of the VHR is observed.
  • UV-A ultraviolet
  • polymerisable mixture PM1 with the alkenyl-containing host shows almost no drop of the VHR, just like polymerisable mixture PC1 with the alkenyl-free host. The same result is obtained for the
  • VHR is measured for polymerisable mixture PM1 by the general method as described above, but wherein the mixture is either exposed to two different UV wavelengths in two steps, either first to UV light having a shorter wavelength and then to UV light having a longer wavelength, or vice versa, by using either a 340nm or 375nm cut-off filter as described above.
  • Table 5 The results are shown in Table 5.
  • VHR values after exposure to either a longer or a shorter wavelength in a single step are also shown.
  • the polymerisable LC media PM1 and PM2 are filled into a test cell and the RM is polymerised while applying a voltage to the cell, following the general method as described above, wherein the test cells are exposed to UV radiation of shorter or longer wavelength by using a 340nm or 375nm cut-off filter as described above.
  • the pretilt angle generated in an individual mixture after polymerisation of the RM is determined by the general method as described above. The results are shown in Table 6.
  • the amount of unpolymerised RM in a test cell is measured for mixtures PM1-PM3 and PC5 after different time periods of UV exposure.
  • each mixture is polymerised in the test cell following the general method as described above, wherein the test cells are exposed to UV radiation of shorter or longer wavelength by using a 340nm or 375nm cutoff filter as described above.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Liquid Crystal (AREA)
  • Liquid Crystal Substances (AREA)

Abstract

La présente invention concerne un milieu à cristaux liquides comprenant un composé photosensible et un composé comprenant un groupe alcényle. L'invention concerne également un afficheur à cristaux liquides de type PS, c'est-à-dire stabilisé par polymères (Polymer Stabilized), ou de type PSA, c'est-à-dire à alignement aidé par les polymères (Polymer Sustained Alignment). L'invention concerne enfin des afficheurs à cristaux liquides de type PS ou PSA obtenus par un tel procédé et contenant un tel milieu à cristaux liquides.
PCT/EP2011/004851 2010-10-26 2011-09-28 Milieu à cristaux liquides, et procédé d'élaboration de dispositif à cristaux liquides Ceased WO2012055473A1 (fr)

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JP2015205879A (ja) * 2014-04-22 2015-11-19 メルク パテント ゲゼルシャフト ミット ベシュレンクテル ハフツングＭｅｒｃｋ Ｐａｔｅｎｔ Ｇｅｓｅｌｌｓｃｈａｆｔ ｍｉｔ ｂｅｓｃｈｒａｅｎｋｔｅｒ Ｈａｆｔｕｎｇ ４，６−ジフルオロジベンゾチオフェン誘導体
CN105778927A (zh) * 2015-01-12 2016-07-20 三星显示有限公司 液晶组合物和包括其的液晶显示器
CN108949191A (zh) * 2017-05-27 2018-12-07 北京八亿时空液晶科技股份有限公司 一种含有联苯戊烯基化合物的液晶组合物及其应用
CN109960066A (zh) * 2017-12-22 2019-07-02 Dic株式会社 液晶显示元件的制造方法
CN110358547A (zh) * 2018-04-10 2019-10-22 北京八亿时空液晶科技股份有限公司 一种新型可聚合性化合物及其应用
CN110484281A (zh) * 2019-07-31 2019-11-22 北京八亿时空液晶科技股份有限公司 一种负性液晶组合物及其应用
CN110527521A (zh) * 2018-05-23 2019-12-03 北京八亿时空液晶科技股份有限公司 一种含有茚满结构的可聚合性化合物及其制备方法与应用
CN111592891A (zh) * 2020-06-12 2020-08-28 江苏三月科技股份有限公司 一种液晶取向剂及其制备的液晶取向膜、液晶显示元件
CN115368241A (zh) * 2022-08-26 2022-11-22 河南省科学院化学研究所有限公司 一种基于2，7-二溴-9-芴酮-4-甲酸的衍生物及其合成方法

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EP3048159B1 (fr) * 2015-01-22 2019-08-07 Merck Patent GmbH Support à cristaux liquides

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JP2015205879A (ja) * 2014-04-22 2015-11-19 メルク パテント ゲゼルシャフト ミット ベシュレンクテル ハフツングＭｅｒｃｋ Ｐａｔｅｎｔ Ｇｅｓｅｌｌｓｃｈａｆｔ ｍｉｔ ｂｅｓｃｈｒａｅｎｋｔｅｒ Ｈａｆｔｕｎｇ ４，６−ジフルオロジベンゾチオフェン誘導体
CN105778927A (zh) * 2015-01-12 2016-07-20 三星显示有限公司 液晶组合物和包括其的液晶显示器
CN108949191A (zh) * 2017-05-27 2018-12-07 北京八亿时空液晶科技股份有限公司 一种含有联苯戊烯基化合物的液晶组合物及其应用
CN109960066A (zh) * 2017-12-22 2019-07-02 Dic株式会社 液晶显示元件的制造方法
JP2019113675A (ja) * 2017-12-22 2019-07-11 Dic株式会社 液晶表示素子の製造方法
JP7091652B2 (ja) 2017-12-22 2022-06-28 Dic株式会社 液晶表示素子の製造方法
CN109960066B (zh) * 2017-12-22 2023-04-14 Dic株式会社 液晶显示元件的制造方法
CN110358547A (zh) * 2018-04-10 2019-10-22 北京八亿时空液晶科技股份有限公司 一种新型可聚合性化合物及其应用
CN110527521A (zh) * 2018-05-23 2019-12-03 北京八亿时空液晶科技股份有限公司 一种含有茚满结构的可聚合性化合物及其制备方法与应用
CN110484281A (zh) * 2019-07-31 2019-11-22 北京八亿时空液晶科技股份有限公司 一种负性液晶组合物及其应用
CN111592891A (zh) * 2020-06-12 2020-08-28 江苏三月科技股份有限公司 一种液晶取向剂及其制备的液晶取向膜、液晶显示元件
CN115368241A (zh) * 2022-08-26 2022-11-22 河南省科学院化学研究所有限公司 一种基于2，7-二溴-9-芴酮-4-甲酸的衍生物及其合成方法

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