EP0500832A1 - Supertwist liquid crystal display - Google Patents

Supertwist liquid crystal display

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Publication number
EP0500832A1
EP0500832A1 EP19910914327 EP91914327A EP0500832A1 EP 0500832 A1 EP0500832 A1 EP 0500832A1 EP 19910914327 EP19910914327 EP 19910914327 EP 91914327 A EP91914327 A EP 91914327A EP 0500832 A1 EP0500832 A1 EP 0500832A1
Authority
EP
European Patent Office
Prior art keywords
liquid crystal
compounds
crystal mixture
pdx
ccp
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19910914327
Other languages
German (de)
French (fr)
Inventor
Georg Weber
Reinhard Hittich
Volker Reiffenrath
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Merck Patent GmbH
Original Assignee
Merck Patent GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Merck Patent GmbH filed Critical Merck Patent GmbH
Publication of EP0500832A1 publication Critical patent/EP0500832A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/42—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
    • C09K19/3402—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K19/00—Liquid crystal materials
    • C09K19/04—Liquid crystal materials characterised by the chemical structure of the liquid crystal components, e.g. by a specific unit
    • C09K19/06—Non-steroidal liquid crystal compounds
    • C09K19/34—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring
    • C09K19/3402—Non-steroidal liquid crystal compounds containing at least one heterocyclic ring having oxygen as hetero atom
    • 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

Definitions

  • the invention relates to supertwist liquid crystal displays
  • the invention further relates to the novel nematic liquid crystalline mixtures used therein which exhibit a low viscosity, a high stability versus chemicals, heat and radiation, a high electrical resistivity and a low value for the ratio of the dielectrical anisotropy ⁇ and the dielectrical constant ⁇ ⁇ measured perpendicular with respect to the nematic director.
  • STN-LCDs as characterized in the preamble of claim 1 are known, for example from EP 0,131,216 BI; DE 3,423,993
  • SFA includes any relatively highly twisted display element having a twist angle with a value between 160° and 720°, such as, for example, the display elements of Waters et al. (CM. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display
  • STN-LCDs of this type are distinguished by a significantly better steepness of the electrooptical characteristic line and, associated therewith, better contrast values, and by a significantly lower angle dependence of the contrast.
  • STN-LCDs with high information content exhibiting a high multiplexing ratio.
  • the selection ratio S i.e. the ratio of the rms voltage across a selected element to the voltage across a nonselected element, is decreasing with the number of multiplexed lines because of crosstalk.
  • the STN-LCD in order to obtain a sufficient contrast ratio between the selected and nonselected state it is necessary for the STN-LCD to exhibit a high or even very high steepness of the electrooptical characteristic line.
  • the steepness of the electrooptical characteristic line is mainly influenced by elastic and dielectric constants of the liquid crystalline medium and it has been shown quite generally that the steepness improves with decreasing ⁇ / ⁇ ⁇ (see for example Raynes, E.P. et al., Proc. Eurodisplay, London 1987, 100). Since ⁇ must not be chosen too low in order to realize an acceptable threshold voltage the value of ⁇ ⁇ should be as large as possible.
  • the liquid crystal media used in such STN-LCDs have to exhibit a high stability and a high electrical resistance which ideally should not deteriorate under various influences such as heat or radiation because for a fixed driving frequency the refreshing frequency at each pixel is decreasing with increasing driving duty ratio.
  • the voltage across a pixel drops with a certain decay time which is decisively influenced by the resistance of the liquid crystal layer; therefore, STN-LCDs operated with a high multiplex ratio usually require liquid crystalline media which exhibit a high stability and a high electrical resistivity.
  • the STN-LCDs should furthermore exhibit short switching times, in particular also at relatively low temperatures, which generally require optimization of the viscosity of the liquid crystalline medium used. It is also possible, however, to reduce the thickness of the LC layer of the STN-LCD and to use liquid crystalline media with a higher optical anisotropy ⁇ n.
  • the invention has the object of providing STN-LCDs exhibiting a good overall combination of the properties mentioned above and especially a high multiplexability, short switching times and a high stability and resistivity of the liquid crystalline medium used.
  • R 1 is alkyl having 1-12 C atoms, wherein one or two non-adjacent CH 2 groups can also be replaced by -O-,
  • -CH CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1
  • ring A is trans-1,4-cyclohexylene or 1,4-phenylene
  • X is F, Cl, CF 3 ,
  • OCF 3 or OCHF 2 and Y and Z each independently of one another denotes H or F.
  • the nematic liquid-crystal mixture preferably has a nematic phase range of at least 60 °C, a viscosity of not more than 30 mPa.s and a dielectric anisotropy of at least +5, the dielectric anisotropies of the compounds and the parameters related to the nematic liquid-crystal mixture being based on a temperature of 20 °C.
  • the invention thus relates to an SFA having
  • the nematic liquid crystal mixture contains one or more compounds of the formula I
  • R 1 is alkyl having 1-12 C atoms, wherein one or two non-adjacent CH 2 groups can also be replaced by -O-,
  • -CH CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1
  • ring A is trans-1,4-cyclohexylene or 1,4-phenylene
  • X is F, Cl, CF 3 ,
  • OCF 3 or OCHF 2 and Y and Z each independently of one another denotes H or F.
  • the invention also relates to correponding liquid crystalline media.
  • the construction of the liquid-crystal display elements according to the invention from polarizers, electrode base plates and electrodes having a surface treatment such that the preferential orientation (director) of the liquid- crystal molecules in each case adjacent thereto is usually mutually twisted from one electrode to the other by a value of 100° to 720°, corresponds to the customary construction for display elements of this type.
  • customary construction here is used in broad terms and also includes all derivatives and modifications of supertwist cells, in particular also matrix display elements.
  • the surface tilt angle at the two support plates may be identical or different. Identical tilt angles are preferred.
  • mixtures according to the invention preferably contain one or more compounds of part formulae l1-l3
  • R 1 preferably is alkyl, alkoxy, oxaalkyl or alkenyl and can exhibit a straight-chain or branched structure.
  • Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms.
  • they are preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.
  • Oxaalkyl is preferably straight-chain 2-oxapropyl
  • Alkenyl is preferably straight-chain and has 2 to 10 C atoms.
  • Branched groups of this type as a rule contain not more than one chain branching.
  • 2-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 2-methyl- hexoxy, 1-methylhexoxy, 1-methylheptoxy ( 2-octyloxy), 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxcy, oxy, 2-me- thyl-3-oxapentyl and 2-,ethyl-3-oxahexyl.
  • the terminal group can be laterally unsubstituted or
  • Liquid crystalline compounds according to part formulae l1-l3 are generally characterized by advantageous values of ⁇ ⁇ and ⁇ / ⁇ ⁇ . Furthermore, they exhibit a high resistivity and a high stability versus heat and radiation, especially UV-light. Compounds according to part formulae l1-l3 with a terminal group according to formulae (1)-(3) are generally preferred.
  • Compounds of part formulae l1-l3 with a terminal group (1) generally exhibit a somewhat lower value of ⁇ than the coresponding compounds with a terminal group (2) or (3) while the value of ⁇ ⁇ is more or less the same.
  • Compounds of part formulae l1-l3 with a terminal group (1) consequently exhibit a lower value of the quotient ⁇ / ⁇ ⁇ which is favourable in view of a steep electrooptical characteristic line; on the other hand a relatively high or high value of ⁇ results in a relatively low or low value of the threshold voltage which is often desired.
  • X preferably is F, Cl, CF 3 , OCF 3 and OCHF 2 and especially F, Cl, CF 3 and OCF 3 .
  • Preferred liquid-crystalline media which can be used according to the invention contain one or more compounds from group A preferably in a proportion of 5 % to 60 % and especially of 10 % to 40 %. These compounds or this compound from group A have a dielectric anisotropy of more than +8 (preferably of more than +12) and form the component A of the LC mixtures of this invention.
  • group A comprises compounds selected from the following group:
  • R is alkyl having 1-12 C atoms, wherein one or two non- adjacent CH 2 groups can also be replaced by -O-,
  • Z 1 is CH 2 CH2-, a single bond, -CH 2 CH 2 -, -CO-O-
  • the mixtures comprise one ore more compounds of the formula Al in the range of 5 to 50 %.
  • Preferred are those compounds wherein Zi denotes a single bond, -CH 2 CH 2 - or -CO-O- and especially preferred are the following compoundd:
  • Group A preferably comprises one ore more compounds selected from the formulae All to AI3 and optionally also one or more compounds of the formula AI4.
  • the mixtures further contain one or more polar compounds with a higher clearing point, e.g. selected from the following compounds:
  • 1,4-phenylene rings can also be laterally substituted by one fluorine atom, e.g.
  • polar compounds with a higher clearing point are preferably used in the range of 2 to 15 %.
  • the mixtures comprise one or more compounds with a very high dielectric anisotropy. Such compounds are preferably used in the range of 2 to 50 %.
  • Preferred compounds of this type are those of the formulae All, AIII and AV, wherein Q denotes 1,4-phenylene or 3- fluoro-1,4-phenylene or compounds of the formula AI7:
  • Preferred liquid-crystal mixtures contain one or more compounds from group B, preferably in a proportion of 5 % to 40 % and especially of 5 % to 30 %. These compounds or this compound from group B have a clearing point of more than 120° and are dielectrically neutral (( ⁇ ) ⁇ 2) or medium polar ( ⁇ in the range of +2 to +10, preferably +4 to +8) and form component B of the LC mixtures of this invention.
  • group B comprises compounds selected from the following group: ( ) ( ) ⁇ H ) ⁇ ) i y
  • R 1 and R 2 each independently of one another are R as defined in claim 3, Z 0 is -CO-O-, -O-CO- or -CH 2 CH 2 -, Q is as defined in claim 3 and the 1,4-phenylene ring in BI to BVII may also be substituted in 2- or 3-position by fluorine.
  • the mixtures comprise one or more compounds with four rings of the formulae BI to BIV in order to achieve a high clearing point.
  • These compounds are preferably selected from the group of the following four-ring compounds:
  • mixtures comprise also one or more compounds selected from the following group of three-ring compounds:
  • the liquid crystalline media according to the invention can contain dielectrically neutral compounds with -1.5 ⁇ ⁇ ⁇ +1.5 the proportion of which generally depends on the ratio between compounds of formula I and carbonitriles of, for example, formulae AI-AIV. If the proportion of carbonitriles exceeds the proportion of the compounds of formula I by more than a factor of 1.5 and especially 2.5 the proportion of dielectrically neutral compounds preferably is not too small and especially more than 10 % and in particular more than 20 %.
  • the proportion of the carbonitriles and the compounds of formula is less than 1.5 or especially if the proportion of the compounds of formula I is equal or greater than the proportion of carbonitriles the proportion of dielectrically neutral compounds can be smaller and is preferably smaller than 25 % and especially not larger than 15 %. In case the proportion of compounds of formula I distinctively exceeds the proportion of carbonitriles the proportion of dielectrically compounds can be smaller than 10 % and preferably smaller than 5 %.
  • Hal is F or Cl and L and R are as defined above.
  • the LC media according to the invention also preferably comprise an optically active component C, in an amount such that the ratio between the layer thickness (separation of the plane-parallel carrier plates) and the natural pitch of the chiral nematic liquid crystal mixture is more than 0.2 suitable to the desired twist angle.
  • Suitable dopants can be selected from a wide variety of known chiral materials and commercially available dopants such as cholesteryl nonanoate, S 811 (E. Merck, Darmstadt, FRG) and CB 15 (BDH, Poole, UK). The choice thereof is not crucial per se.
  • the liquid crystalline media according to the invention are especially suited for STN-LCDs exhibiting a high twisting angle.
  • mixtures also contain one or more compounds from group B1 comprising the compounds of the formulae B1I to B1IV:
  • R 1 and R 2 in each case independently of one another, are as defined for R, Z2 is -CH 2 CH 2 -, -CO-O-, -O-CO- or a single bond, and
  • R 1 is as defined for R
  • Z 0 is -CH 2 CH 2 - or a single bond
  • n 1 to 9
  • X is CN or F and Y is H or F; and/or at least one component selected from group B3 comprising the compounds of the formulae BVIII and BIX:
  • R 1 and R 2 in each case independently of one another, are as defined for R, and
  • component (s) from group B1 is preferably 5 % to 45 %, in particular preferably about 10 % to 40 %.
  • Components of the formulae B1III and B1IV are preferred.
  • Particularly preferred compounds of the formula B1lII are those of the following sub-formulae:
  • R 2 is CH 3 -(CH 2 ) t -, n is 1, 2, 3 or 4, r is 0, 1, 2 or 3,
  • s is 0 or 1
  • t 1, 2, 3 or 4.
  • R 1 and R 2 are as defined above.
  • the proportion of the compounds of the formula B1III of the abovementioned sub-formulae is preferably about 5 % to 45 %, in particular preferably about 10 % to 35 %.
  • Particularly preferred compounds of the formula B1IV are those of the following sub-formula:
  • the proportion of these compounds or of the compounds of the formula B1IV is preferably about 5 % to 40 %, in particular preferably about 10 % to 35 %.
  • the mixtures preferably contain compounds of the formula III, in particular those of the sub-formula
  • the mixtures simultaneously contain compounds of the formulae B1III and B1IV, the total proportion for components of group B1 being observed.
  • R 1 and R 2 are preferably, in each case independently of one another, n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms.
  • Z 2 is preferably a single bond. BI is particularly preferred.
  • preferred mixtures according to the invention are those which contain one or more compounds of the formula B1IV in which and R 1 and R 2 have
  • the proportion of the compounds of group B2 is preferably about 5 % to 45 %, in particular preferably 5 % to 20 %.
  • the proportion (preferred ranges) for B1V to BIVII is as follows:
  • B1V about 5 % to 30 %, preferably about 5 % to 15 %
  • B1VII about 5 % to 25 %, preferably about 10 % to 20 %.
  • R 1 is preferably n-alkyl having 1 to 7 C atoms or (trans)-n- alkenyl having 3 to 7 C atoms.
  • Z 0 is preferably a single bond.
  • R preferably has the preferred meaning mentioned above for R 1 or is fluorine.
  • Y is preferably fluorine.
  • mixtures according to the invention preferably contain one or more compounds selected from the group comprising
  • B1V3, BIVII and B1VII1 in a total proportion of about 5 to
  • R 1 is preferably n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms, X is 1 or 2, y is 0 or 1 and Y is H or F.
  • the total proportion of all terminally fluorinated compounds is preferably about 5 % to 65 %, in particular about 15 % to 40 %.
  • the proportion of the compounds from group B3 is preferably about 5 % to 30 %, in particular preferably about 10 % to 20 %.
  • R 1 is preferably n-alkyl or n-alkoxy, each having 1 to 9 C atoms.
  • Compounds of the formula BVIII are preferred. is preferably 1,4-phenylene.
  • the mixtures according to the invention contain compounds from at least one of groups B1, B2 and B3. They preferably contain one or more compounds from BI and one or more compounds from group B2 and/or B3.
  • the proportion of compounds of component C is preferably about 5 % to 60 %, in particular about 20 % to 50 %. Those skilled in the art can easily adjust this proportion to produce the threshold voltage desired, it being possible to use, in principle, all customary liquid-crystal compounds where ⁇ > +2. If predominantly less-positive terminally fluorinated compounds are used, the total proportion can be above the upper range (about 35 % to 80 %), while the proportion may be lower (about 10 % to 35 %) if terminally cyano-substituted compounds are used.
  • the mixtures according to the invention preferably contain about 5 % to 20 % of one or more compounds having a dielectric anisotropy of less than -2 (component D).
  • component D Component D
  • compounds of this type are known, for example derivatives of 2,3-dicyanohydroquinone or cyclohexane derivatives containing the structural element in DE-OS 3,231,707 or DE-OS 3,407,013.
  • compounds containing the structural element 2,3- difluoro-1,4-phenylene are preferably chosen, for example compounds as in DE-OS 3,807,801, 3,807,861, 3,807,863, 3,807,864 or 3,807,908.
  • Particularly preferred are tolans containing these structural elements, as in International Patent Application PCE/DE 88/00133, in particular those of the formulae
  • R 1 and R 2 in each case independently of one another, are preferably n-alkyl having 1 to 7 C atoms or n-alkenyl having 3 to 7 C atoms, and Z 0 is -CH 2 CH 2 - or a single bond.
  • Component D causes, in particular, an improvement in the steepness of the characteristic line.
  • the mixtures contain about 5 % to 35 %, in particular preferably about 10 % to 20 %, of liquid-crystalline tolan compounds. These make it possible to work with smaller cell thicknesses (about
  • R 1 is preferably n-alkyl having 1 to 7 C atoms, Z 0 is -CH 2 CH 2 - or a single bond, Q
  • R 2 is n-alkyl or n-alkoxy, each having 1 to 7 C atoms, or n-alkenyl or n-alkenyloxy, each having 3 to 7 C atoms.
  • the mixtures contain
  • component D which contains one or more compounds having a 1-cyano-trans-1,4-cyclohexylene group or a
  • alkyl is a straight-chain alkyl group having 2-7 C atoms, and X is H or F,
  • R is a trans-alkenyl group or a trans-alkenyloxy group.
  • R is a trans-alkenyl group or a trans-alkenyloxy group.
  • R 1 and R 2 have the preferred meanings indicated in the case of component B, and one of the two 1,4-phenylene groups may also be substituted by fluorine; the proportion of these compounds is 0 % to 25 %, preferably about 5 % to 15 %.
  • the liquid-crystal mixtures which can be used according to the invention are prepared in a manner customary per se.
  • the desired amount of the components used in a relatively small amount is dissolved in the components making up the principal constituent, expediently at elevated temperature.
  • the dielectrics may also contain further additives known to those skilled in the art and described in the literature. For example, 0-15 % of pleochroic dyes may be added.
  • the mixtures of this invention are very stable and have a high resistivity. They allow the realization of STN-LCDs with a steep characteristic electrooptical line, a high multiplex ratio, a broad temperature range of operation, a low threshold voltage and a short switching time. The mixtures of this invention thus are of considerable economic importance.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • Example 3 A STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds PDX-3Cl.F 16.0
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds PDX-3CF 3 8.0
  • BCH-5F.F 14.0 is characterized by advantageous properties.
  • a STN display containing a liquid crystal medium which comprises the following compounds PCH-5F 8.0
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • CBC-55F 3.0 is characterized by advantageous properties.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • CBC-55F 2.0 is characterized by advantageous proprrties.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • ⁇ n 0.0840 (20 °C, 589 nm)
  • a STN display containing a liquid crystal medium which comprises the following compounds PCH-32 17.6
  • Example 12 A STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds PCH-32 17.6
  • PDX-50CF 3 10.0 is characterized by advantageous properties.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • Example 21 A STN display containing a liquid crystal medium which comprises the following compounds
  • ⁇ n 0.1250 (20 °C, 589 nm)
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds ME3N.F 9.00
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • Example 29 A STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds PCH-5F 8.0
  • ⁇ n 0.086 (20 °C, 589 nm)
  • a STN display containing a liquid crystal medium which comprises the following compounds ECCP-32 12.000
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • CBC-55F 2.0 is characterized by advantageous properties.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • CBC-55F 5.0 is characterized by advantageous properties.
  • a STN display containing a liquid crystal medium which comprises the following compounds
  • a STN display containing a liquid crystal medium which comprises the following compounds PDX-5F.F 10.0
  • CBC-55F 2.0 is characterized by advantageous properties.

Abstract

L'invention se rapporte à des systèmes d'affichage à cristaux liquides à supertorsion (STN-LCD) comportant deux plaques-support à plans parallèles qui, avec un rebord, forment une cellule; un mélange de cristal liquide nématique présentant une anisotropie diélectrique positive, se trouvant dans la cellule; des couches d'électrodes comportant des couches à orientation superposée, situées à l'intérieur des plaques-support; un angle d'incidence situé entre l'axe longitudinal des molécules de la surface des plaques-support et les plaques-support, d'environ 1 degré à 30 degrés et, un angle de torsion du mélange de cristal liquide se trouvant dans la cellule d'une couche d'orientation à l'autre, en fonction de la quantité, situé entre 160 et 720 °C. Le mélange de cristal liquide nématique contient un ou plusieurs composés de la formule (I), dans laquelle R1 représente alkyle possédant de 1 à 12 atomes C, dans laquelle un ou deux groupes CH2 non contigus peuvent également se remplacer par -O-, -CH=CH-, -CO-, -O-CO- ou -CO-O-, r est 0 ou 1, le composé cyclique A représente trans-1,4-cyclohexylène ou 1,4-phénylène, X est F, Cl, CF3, OCF3 ou OCHF2 et Y et Z, chacun indépendemment l'un de l'autre, représentent H ou F.The invention relates to super-twisted liquid crystal display systems (STN-LCD) comprising two support plates with parallel planes which, with a flange, form a cell; a nematic liquid crystal mixture having a positive dielectric anisotropy, located in the cell; electrode layers comprising layers with superimposed orientation, situated inside the support plates; an angle of incidence located between the longitudinal axis of the molecules of the surface of the support plates and the support plates, from about 1 degree to 30 degrees and, an angle of twist of the liquid crystal mixture found in the cell from one orientation layer to another, depending on the quantity, located between 160 and 720 ° C. The nematic liquid crystal mixture contains one or more compounds of formula (I), in which R1 represents alkyl having from 1 to 12 C atoms, in which one or two non-contiguous CH2 groups can also be replaced by -O-, - CH = CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1, the cyclic compound A represents trans-1,4-cyclohexylene or 1,4-phenylene, X is F, Cl, CF3, OCF3 or OCHF2 and Y and Z, each independently of the other, represent H or F.

Description

Supertwist Liquid Crystal Display
The invention relates to supertwist liquid crystal displays
(STN-LCD) which exhibit short switching times and a good steepness of the electrooptical characteristic line and which can be driven at high duty ratios. The invention further relates to the novel nematic liquid crystalline mixtures used therein which exhibit a low viscosity, a high stability versus chemicals, heat and radiation, a high electrical resistivity and a low value for the ratio of the dielectrical anisotropy Δε and the dielectrical constant ε⊥ measured perpendicular with respect to the nematic director.
STN-LCDs as characterized in the preamble of claim 1 are known, for example from EP 0,131,216 BI; DE 3,423,993
Al; EP 0,098,070 A2; M. Schadt and F. Leenhouts, 17th
Freiburg conference on liquid crystals (8-10.04.87); K.
Kawasaki et al., SID 87 Digest 391 (20.6); M. Schadt and F. Leenhouts, SID 87 Digest 372 (20.1); K. Katoh et al.,
Japanese Journal of Applied Physics, Vol. 26, No. 11,
L 1784-L1786 (1987); F. Leenhouts et al., Appl. Phys. Lett.50 (21), 1468 (1987); H.A. van Sprang and H.G. Koopman, J. Appl. Phys. 62 (5), 1734 (1987); T.J. Scheffer and J.
Nehring, Appl. Phys. Lett. 45 (10), 1021 (1984), M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (5), 236 (1987) and E.P. Raynes, Mol. Cryst. Liq. Cryst. Letters, Vol. 4 (1), pp. 1-8 (1986). The term SFA here includes any relatively highly twisted display element having a twist angle with a value between 160° and 720°, such as, for example, the display elements of Waters et al. (CM. Waters et al., Proc. Soc. Inf. Disp. (New York) (1985) (3rd Intern. Display
Conference, Kobe, Japan), the STN-LCDs (DE OS 3,503,259),
SBE-LCDs (T.J. Scheffer and J. Nehring, Appl. Phys. Lett. 45 (1984) 1021), OMI-LCDs (M. Schadt and F. Leenhouts, Appl. Phys. Lett. 50 (1987), 236, DST-LCDs (EP OS 0,246,842) or BW-STN-LCDs (K. Kawasaki et al., SID 87 Digest 391 (20.6)).
Compared with standard TN displays with a twist angle of about 90° STN-LCDs of this type are distinguished by a significantly better steepness of the electrooptical characteristic line and, associated therewith, better contrast values, and by a significantly lower angle dependence of the contrast. Of particular interest are STN-LCDs with high information content exhibiting a high multiplexing ratio. According to the "iron law of multiplexing" first formulated by Alt and Pleshko (P.M. Alt and P. Pleshko, IEEE Trans Electron Devices, ED-21, 1974, 146) the selection ratio S, i.e. the ratio of the rms voltage across a selected element to the voltage across a nonselected element, is decreasing with the number of multiplexed lines because of crosstalk. Therefore, in order to obtain a sufficient contrast ratio between the selected and nonselected state it is necessary for the STN-LCD to exhibit a high or even very high steepness of the electrooptical characteristic line. The steepness of the electrooptical characteristic line is mainly influenced by elastic and dielectric constants of the liquid crystalline medium and it has been shown quite generally that the steepness improves with decreasing Δε/ε⊥ (see for example Raynes, E.P. et al., Proc. Eurodisplay, London 1987, 100). Since Δε must not be chosen too low in order to realize an acceptable threshold voltage the value of ε⊥ should be as large as possible.
Furthermore, the liquid crystal media used in such STN-LCDs have to exhibit a high stability and a high electrical resistance which ideally should not deteriorate under various influences such as heat or radiation because for a fixed driving frequency the refreshing frequency at each pixel is decreasing with increasing driving duty ratio. The voltage across a pixel, however, drops with a certain decay time which is decisively influenced by the resistance of the liquid crystal layer; therefore, STN-LCDs operated with a high multiplex ratio usually require liquid crystalline media which exhibit a high stability and a high electrical resistivity. The STN-LCDs should furthermore exhibit short switching times, in particular also at relatively low temperatures, which generally require optimization of the viscosity of the liquid crystalline medium used. It is also possible, however, to reduce the thickness of the LC layer of the STN-LCD and to use liquid crystalline media with a higher optical anisotropy Δn.
Further demands for STN-LCDs are low threshold voltages, a broad temperature range of operation, an advantageous temperature dependence of the electrooptical properties, a good contrast and a good angle dependence of contrast. The liquid crystalline media developed so far do not fulfill these requirements to a desirable extent. Furthermore, optimal parameters cannot be achieved simultaneously for all the properties mentioned above because of the opposite influence of different material parameters such as, for example, dielectric and elastic properties.
Therefore, there continues to be a great demand for improved STN-LCDs having a steep electrooptical characteristic line and hence a high multiplexibility and, at the same time, short switching times, a great temperature range of operation, a good contrast, a good viewing angle dependence of contrast and a high stability and electrical resistivity of the liquid crystal medium used therein.
The invention has the object of providing STN-LCDs exhibiting a good overall combination of the properties mentioned above and especially a high multiplexability, short switching times and a high stability and resistivity of the liquid crystalline medium used.
Still other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from reading of the following detailed description.
It has been found that these and other advantages can be achieved if the nematic liquid crystalline mixture used contains one or more compounds of the formula I
wherein R1 is alkyl having 1-12 C atoms, wherein one or two non-adjacent CH2 groups can also be replaced by -O-,
-CH=CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1, ring A is trans-1,4-cyclohexylene or 1,4-phenylene, X is F, Cl, CF3,
OCF3 or OCHF2 and Y and Z each independently of one another denotes H or F.
The nematic liquid-crystal mixture preferably has a nematic phase range of at least 60 °C, a viscosity of not more than 30 mPa.s and a dielectric anisotropy of at least +5, the dielectric anisotropies of the compounds and the parameters related to the nematic liquid-crystal mixture being based on a temperature of 20 °C.
The invention thus relates to an SFA having
- two plane-parallel carrier plates which, with an
edging, form a cell,
- a nematic liquid crystal mixture of positive dielectric anisotropy in the cell,
- electrode layers with superimposed orientation layers on the inside of the carrier plates,
- an angle of incidence between the longitudinal axis of the molecules on the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees and - a twisting angle of the liquid crystal mixture in the cell from orientation layer to orientation layer, according to the amount, of between 100 and 720 °C, characterized in that the nematic liquid crystal mixture contains one or more compounds of the formula I
wherein R1 is alkyl having 1-12 C atoms, wherein one or two non-adjacent CH2 groups can also be replaced by -O-,
-CH=CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1, ring A is trans-1,4-cyclohexylene or 1,4-phenylene, X is F, Cl, CF3,
OCF3 or OCHF2 and Y and Z each independently of one another denotes H or F.
The invention also relates to correponding liquid crystalline media.
The construction of the liquid-crystal display elements according to the invention from polarizers, electrode base plates and electrodes having a surface treatment such that the preferential orientation (director) of the liquid- crystal molecules in each case adjacent thereto is usually mutually twisted from one electrode to the other by a value of 100° to 720°, corresponds to the customary construction for display elements of this type. The term customary construction here is used in broad terms and also includes all derivatives and modifications of supertwist cells, in particular also matrix display elements. The surface tilt angle at the two support plates may be identical or different. Identical tilt angles are preferred.
An essential difference between the display elements according to the invention and the display elements customary hitherto based on the twisted nematic cell is, however, the choice of liquid-crystal components in the liquid-crystal layer.
The mixtures according to the invention preferably contain one or more compounds of part formulae l1-l3
In the compounds of part formulae l1-l3 R1 preferably is alkyl, alkoxy, oxaalkyl or alkenyl and can exhibit a straight-chain or branched structure. Alkyl or alkoxy preferably are straight-chain and have 2, 3, 4, 5, 6 or 7 C atoms. Accordingly they are preferably ethyl, propyl, butyl, pentyl, hexyl, heptyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy or heptoxy, also methyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, methoxy, octoxy, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy.
Oxaalkyl is preferably straight-chain 2-oxapropyl
(= methoxymethyl), 2- (= ethoxymethyl) or 3-oxybutyl
(= 2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4- or 5-oxahexyl, 2-, 3-, 4-, 5- or 6-oxaheptyl, 2-, 3-, A-, 5-, 6- or 7-oxaoctyl, 2-, 3-, A-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8-, or 9 oxadecyl. Alkenyl is preferably straight-chain and has 2 to 10 C atoms. It is accordingly, in particular, vinyl, prop-1- or prop-2-enyl, but-1-, -2- or -3-enyl, pent-1-, -2-, -3- or -4-enyl, hex-1-, -2-, -3-, -4- or -5-enyl, hept-1-, -2-, -3-, -4-, -5- or -6-enyl, oct-1-, -2-, -3-, -4-, -5-, -6- or -7-enyl, non-1-, -2-, -3-, -4-, -5-, -6-, -7- or -8-enyl or dec-1-, -2-, -3-, -4-, -5-, -6-, -7-, -8- or -9-enyl. Compounds of the formula I containing a branched terminal group can occasionally be of importance because of an improved solubility in the customary liquid crystal base materials, but in particular as chiral doping substances if they are optically active.
Branched groups of this type as a rule contain not more than one chain branching. Preferred branched radicals are iso- propyl, 2-butyl (= 1-methylpropyl), isobutyl (= 2-methyl- propyl), 2-methylbutyl, isopentyl, (= 3-methylbutyl),
2-methylpentyl, 2-ethylhexyl, 2-propylpentyl, 2-octyl, isopropoxy, 2-methylpropoxy, 2-methylbutoxy, 3-methylbutoxy, 2-methylpentoxy, 3-methylpentoxy, 2-ethylhexoxy, 2-methyl- hexoxy, 1-methylhexoxy, 1-methylheptoxy (= 2-octyloxy), 2-oxa-3-methylbutyl, 3-oxa-4-methylpentyl, 4-methylhexyl, 2-nonyl, 2-decyl, 2-dodecyl, 6-methyloctoxcy, oxy, 2-me- thyl-3-oxapentyl and 2-,ethyl-3-oxahexyl.
The terminal group can be laterally unsubstituted or
laterally mono- or difluorinated:
Liquid crystalline compounds according to part formulae l1-l3 are generally characterized by advantageous values of ε⊥ and Δε/ε⊥. Furthermore, they exhibit a high resistivity and a high stability versus heat and radiation, especially UV-light. Compounds according to part formulae l1-l3 with a terminal group according to formulae (1)-(3) are generally preferred.
Compounds of part formulae l1-l3 with a terminal group (1) generally exhibit a somewhat lower value of Δε than the coresponding compounds with a terminal group (2) or (3) while the value of ε⊥ is more or less the same. Compounds of part formulae l1-l3 with a terminal group (1) consequently exhibit a lower value of the quotient Δε/ε⊥ which is favourable in view of a steep electrooptical characteristic line; on the other hand a relatively high or high value of Δε results in a relatively low or low value of the threshold voltage which is often desired.
In the compounds according to part formulae l1-l3 X preferably is F, Cl, CF3, OCF3 and OCHF2 and especially F, Cl, CF3 and OCF3. By varying the percentage of the compounds of part formulae 11-13 with the terminal groups (1)-(4) the expert can easily accentuate and optimize certain properties with respect to the intended application. At any rate the liquid crystalline media of this invention are very stable and have a high resistivity. They allow the realization of SFAs with a steep characteristic electrooptical line, a multiplex ratio, a broad temperature range of operation, a low threshold voltage and a short switching time.
The following smaller groups of compounds according to part formulae l1-l3 are especially preferred.
Compounds according to part formula I1:
l
l
0
Preferred liquid-crystalline media which can be used according to the invention contain one or more compounds from group A preferably in a proportion of 5 % to 60 % and especially of 10 % to 40 %. These compounds or this compound from group A have a dielectric anisotropy of more than +8 (preferably of more than +12) and form the component A of the LC mixtures of this invention.
Preferably group A comprises compounds selected from the following group:
wherein
R is alkyl having 1-12 C atoms, wherein one or two non- adjacent CH2 groups can also be replaced by -O-,
-CH=CH-, -CO-, -O-CO- or -CO-O-, F
Q is the formula
Z1 is CH2CH2-, a single bond, -CH2CH2-, -CO-O-
or -O-CO- and
Preferably the mixtures comprise one ore more compounds of the formula Al in the range of 5 to 50 %. Preferred are those compounds wherein Zi denotes a single bond, -CH2CH2- or -CO-O- and especially preferred are the following compoundd:
)
Also preferred are the following compounds: ( ( )
Group A preferably comprises one ore more compounds selected from the formulae All to AI3 and optionally also one or more compounds of the formula AI4.
Preferably the mixtures further contain one or more polar compounds with a higher clearing point, e.g. selected from the following compounds:
In the above four formulae the 1,4-phenylene rings can also be laterally substituted by one fluorine atom, e.g.
These polar compounds with a higher clearing point are preferably used in the range of 2 to 15 %. In another preferred embodiment the mixtures comprise one or more compounds with a very high dielectric anisotropy. Such compounds are preferably used in the range of 2 to 50 %. Preferred compounds of this type are those of the formulae All, AIII and AV, wherein Q denotes 1,4-phenylene or 3- fluoro-1,4-phenylene or compounds of the formula AI7:
Preferred liquid-crystal mixtures contain one or more compounds from group B, preferably in a proportion of 5 % to 40 % and especially of 5 % to 30 %. These compounds or this compound from group B have a clearing point of more than 120° and are dielectrically neutral ((Δε) < 2) or medium polar (Δε in the range of +2 to +10, preferably +4 to +8) and form component B of the LC mixtures of this invention.
Preferably group B comprises compounds selected from the following group: ( ) ( ) } H ) { ) i y
wherein R1 and R2 each independently of one another are R as defined in claim 3, Z0 is -CO-O-, -O-CO- or -CH2CH2-, Q is as defined in claim 3 and the 1,4-phenylene ring in BI to BVII may also be substituted in 2- or 3-position by fluorine.
Preferably the mixtures comprise one or more compounds with four rings of the formulae BI to BIV in order to achieve a high clearing point. These compounds are preferably selected from the group of the following four-ring compounds:
Preferably the mixtures comprise also one or more compounds selected from the following group of three-ring compounds:
- The liquid crystalline media according to the invention can contain dielectrically neutral compounds with -1.5 ≤ Δε ≤ +1.5 the proportion of which generally depends on the ratio between compounds of formula I and carbonitriles of, for example, formulae AI-AIV. If the proportion of carbonitriles exceeds the proportion of the compounds of formula I by more than a factor of 1.5 and especially 2.5 the proportion of dielectrically neutral compounds preferably is not too small and especially more than 10 % and in particular more than 20 %. If, however, the ratio between the proportion of the carbonitriles and the compounds of formula is less than 1.5 or especially if the proportion of the compounds of formula I is equal or greater than the proportion of carbonitriles the proportion of dielectrically neutral compounds can be smaller and is preferably smaller than 25 % and especially not larger than 15 %. In case the proportion of compounds of formula I distinctively exceeds the proportion of carbonitriles the proportion of dielectrically compounds can be smaller than 10 % and preferably smaller than 5 %.
In another preferred embodiment the LC mixtures also contain one or more compounds from the following group:
wherein Hal is F or Cl and L and R are as defined above.
The LC media according to the invention also preferably comprise an optically active component C, in an amount such that the ratio between the layer thickness (separation of the plane-parallel carrier plates) and the natural pitch of the chiral nematic liquid crystal mixture is more than 0.2 suitable to the desired twist angle. Suitable dopants can be selected from a wide variety of known chiral materials and commercially available dopants such as cholesteryl nonanoate, S 811 (E. Merck, Darmstadt, FRG) and CB 15 (BDH, Poole, UK). The choice thereof is not crucial per se. The liquid crystalline media according to the invention are especially suited for STN-LCDs exhibiting a high twisting angle.
Preferably the mixtures also contain one or more compounds from group B1 comprising the compounds of the formulae B1I to B1IV:
in which R1 and R2, in each case independently of one another, are as defined for R, Z2 is -CH2CH2-, -CO-O-, -O-CO- or a single bond, and
and/or at least one component selected from group B2 comprising the compounds of the formulae B1V to B1VII:
in which R1 is as defined for R,
Z0 is -CH2CH2- or a single bond, and
Q is -CnH2n+1,
where n is 1 to 9, X is CN or F and Y is H or F; and/or at least one component selected from group B3 comprising the compounds of the formulae BVIII and BIX:
in which R1 and R2, in each case independently of one another, are as defined for R, and
The proportion of component (s) from group B1 is preferably 5 % to 45 %, in particular preferably about 10 % to 40 %. Components of the formulae B1III and B1IV are preferred. Particularly preferred compounds of the formula B1lII are those of the following sub-formulae:
in which
R1 is CH3-(CH2)n-O-, -CH3-(CH2)t-, trans-H-(CH2)r- CH=CH-(CH2CH2)s-CH2O- or trans-H-(CH2)r-CH=CH-(CH2CH2)s-,
R2 is CH3-(CH2)t-, n is 1, 2, 3 or 4, r is 0, 1, 2 or 3,
s is 0 or 1 , and
t is 1, 2, 3 or 4.
Furthermore preferred compounds are those of the sub-formula (
in which R1 and R2 are as defined above.
The proportion of the compounds of the formula B1III of the abovementioned sub-formulae is preferably about 5 % to 45 %, in particular preferably about 10 % to 35 %. Particularly preferred compounds of the formula B1IV are those of the following sub-formula:
in which
R1 is CH3-(CH2)n-O- or trans-H-(CH2)r-CH=CH-(CH2CH2)s-CH2O- and R2 is CH3-(CH2)t-, where n is 1, 2, 3 or 4, r is 0, 1, 2 or 3, s is 0 or 1, and t is 1, 2, 3 or 4 . The proportion of these compounds or of the compounds of the formula B1IV is preferably about 5 % to 40 %, in particular preferably about 10 % to 35 %.
The mixtures preferably contain compounds of the formula III, in particular those of the sub-formula
In a particularly preferred embodiment, the mixtures simultaneously contain compounds of the formulae B1III and B1IV, the total proportion for components of group B1 being observed.
If compounds of the formulae B1I and B1III are present, R1 and R2 are preferably, in each case independently of one another, n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms. Z2 is preferably a single bond. BI is particularly preferred. Furthermore preferred mixtures according to the invention are those which contain one or more compounds of the formula B1IV in which and R1 and R2 have
one of the abovementioned preferred meanings, in particular preferably n-alkyl having 1 to 7 C atoms In all cases, the total proportion for components of group B1 is observed.
The proportion of the compounds of group B2 is preferably about 5 % to 45 %, in particular preferably 5 % to 20 %. The proportion (preferred ranges) for B1V to BIVII is as follows:
B1V about 5 % to 30 %, preferably about 5 % to 15 %
Total of B1VI
and B1VII: about 5 % to 25 %, preferably about 10 % to 20 %.
Preferred compounds of group B2 are indicated below:
R1 is preferably n-alkyl having 1 to 7 C atoms or (trans)-n- alkenyl having 3 to 7 C atoms. Z0 is preferably a single bond. R preferably has the preferred meaning mentioned above for R1 or is fluorine. Y is preferably fluorine.
The mixtures according to the invention preferably contain one or more compounds selected from the group comprising
B1V3, BIVII and B1VII1 in a total proportion of about 5 to
35 %.
In a particularly preferred embodiment, the mixtures according to the invention contain, besides B1V3, BIVII, B1VII1 and B1V2 (R = F), further terminally fluorinated compounds, for example selected from the group comprising:
l / k
in which R1 is preferably n-alkyl having 1 to 7 C atoms or (trans)-n-alkenyl having 3 to 7 C atoms, X is 1 or 2, y is 0 or 1 and Y is H or F.
The total proportion of all terminally fluorinated compounds is preferably about 5 % to 65 %, in particular about 15 % to 40 %.
The proportion of the compounds from group B3 is preferably about 5 % to 30 %, in particular preferably about 10 % to 20 %. R1 is preferably n-alkyl or n-alkoxy, each having 1 to 9 C atoms. However, it is also possible to employ analogous compounds containing alkenyl or alkenyloxy groups. Compounds of the formula BVIII are preferred. is preferably 1,4-phenylene.
The mixtures according to the invention contain compounds from at least one of groups B1, B2 and B3. They preferably contain one or more compounds from BI and one or more compounds from group B2 and/or B3.
The proportion of compounds of component C is preferably about 5 % to 60 %, in particular about 20 % to 50 %. Those skilled in the art can easily adjust this proportion to produce the threshold voltage desired, it being possible to use, in principle, all customary liquid-crystal compounds where Δε > +2. If predominantly less-positive terminally fluorinated compounds are used, the total proportion can be above the upper range (about 35 % to 80 %), while the proportion may be lower (about 10 % to 35 %) if terminally cyano-substituted compounds are used.
In a particularly preferred embodiment, the mixtures according to the invention preferably contain about 5 % to 20 % of one or more compounds having a dielectric anisotropy of less than -2 (component D). Compounds of this type are known, for example derivatives of 2,3-dicyanohydroquinone or cyclohexane derivatives containing the structural element in DE-OS 3,231,707 or DE-OS 3,407,013.
However, compounds containing the structural element 2,3- difluoro-1,4-phenylene are preferably chosen, for example compounds as in DE-OS 3,807,801, 3,807,861, 3,807,863, 3,807,864 or 3,807,908. Particularly preferred are tolans containing these structural elements, as in International Patent Application PCE/DE 88/00133, in particular those of the formulae
in which R1 and R2 , in each case independently of one another, are preferably n-alkyl having 1 to 7 C atoms or n-alkenyl having 3 to 7 C atoms, and Z0 is -CH2CH2- or a single bond.
Component D causes, in particular, an improvement in the steepness of the characteristic line.
In a particularly preferred embodiment, the mixtures contain about 5 % to 35 %, in particular preferably about 10 % to 20 %, of liquid-crystalline tolan compounds. These make it possible to work with smaller cell thicknesses (about
5-6 μm), which significantly shorten the switching times. Particularly preferred tolans are indicated below:
R1 is preferably n-alkyl having 1 to 7 C atoms, Z0 is -CH2CH2- or a single bond, Q
where
R2 is n-alkyl or n-alkoxy, each having 1 to 7 C atoms, or n-alkenyl or n-alkenyloxy, each having 3 to 7 C atoms. In further particularly preferred embodiments, the mixtures contain
- a component D which contains one or more compounds having a 1-cyano-trans-1,4-cyclohexylene group or a
2, 3-difluoro-1, 4-phenylene group,
- at least two compounds of the formulae AllI or AV, - compounds of the formulae AllI and AV,
- at least one compound from the following group: [
in which alkyl is a straight-chain alkyl group having 2-7 C atoms, and X is H or F,
- one or more compounds in which R is a trans-alkenyl group or a trans-alkenyloxy group. - one or more compounds selected from the following group
in which R1 and R2 have the preferred meanings indicated in the case of component B, and one of the two 1,4-phenylene groups may also be substituted by fluorine; the proportion of these compounds is 0 % to 25 %, preferably about 5 % to 15 %.
The liquid-crystal mixtures which can be used according to the invention are prepared in a manner customary per se. In general, the desired amount of the components used in a relatively small amount is dissolved in the components making up the principal constituent, expediently 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, after mixing, for example by distillation. The dielectrics may also contain further additives known to those skilled in the art and described in the literature. For example, 0-15 % of pleochroic dyes may be added. The mixtures of this invention are very stable and have a high resistivity. They allow the realization of STN-LCDs with a steep characteristic electrooptical line, a high multiplex ratio, a broad temperature range of operation, a low threshold voltage and a short switching time. The mixtures of this invention thus are of considerable economic importance.
The examples below are intended to illustrate the invention without representing a limitation. Above and below all temperatures are given in °C. The percentages are percent by weight. The STN displays given in the examples below exhibit advantageous properties. The liquid-crystal compounds which are comprised by the liquid crystalline media are indicated to acronyms, with the transformation into chemical formulae taking place in accordance with Tables A and B below. All radicals CnH2n+1 are straight-chain alkyl radicals containing n or m carbon atoms. The coding in Table B is self-evident. In Table A, only the acronym for the base structure is given. In individual cases, the acronym for the base structure is followed, separated by a hyphen, by a code for the substituents R1, R2, L1, L2 and L3: able
Example 1
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F.F 12.0
PDX-5F.F 10.0
PDX-7F.F 10.0
CCP-20CF3 10.0
CCP-30CF3 12.0
CCP-40CF3 10.0
CCP-50CF3 12.0
BCH-3F.F 12.0
BCH-5F.F 12.0 and exhibits the following physical parameter
Δn = 0.0808 (589 nm, 20 °C)
is characterized by advantageous properties.
Example 2
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 12.0
PDX-5F 10.0
PDX-7F 10.0
CCP-20CF3 10.0
CCP-30CF3 12.0
CCP-40CF3 10.0
C CCP-50CF3 12.0 BCH-3F .F 12 . 0
BCH-5F .F 12 .0 and exhibits the following physical parameter
Δn = 0.08.66 (589 nm, 20 °C)
is characterized by advantageous properties.
Example 3 A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F.F 16.0
PDX-5F 12.0
CCP-20CF3 8.0
CCP-30CF3 13.0
CCP-40CF3 5.0
CCP-50CF3 12.0
BCH-3F.F 12.0
BCH-5F.F 14.0
ECCP-2F.F 8.0 and exhibits the following physical parameter
Δn = 0.0874 (589 nm, 20 °C)
is characterized by advantageous properties.
Example 4
A STN display containing a liquid crystal medium which comprises the following compounds PDX-3Cl.F 16.0
PCH-5F 12.0
PCH-6F 0.0
PCH-7F 0.0
CCP-20CF3 8.0
CCP-30CF3 13.0
CCP-40CF3 5.0
CCP-50CF3 12.0
BCH-3F.F 12.0
BCH-5F.F 14.0
ECCP-2F.F 8.0 and exhibits the following physical parameter
Δn = 0.0934 (589 nm, 20 °C) N 66.6 I
is characterized by advantageous properties.
Example 5
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F 15.5
PCH-5F 14.6
CCP-20CF3 7.8
CCP-30CF3 12.6
CCP-40CF3 4.9
CCP-50CF3 11.6
BCH-3F.F 11.6
BCH-5F.F 13.6
ECCP-2F.F 7.8 and exhibits the following physical parameter
Δn = 0.0868 (589 nm, 20 °C) N 65.5 I
is characterized by advantageous properties. Example 6
A STN display containing a liquid crystal medium which comprises the following compounds PDX-3CF3 8.0
PDX-5CF3 6.0
PDX-3CF3 0.0
PCH-5F 12.0
PCH-6F 8.0
PCH-7F 0.0
CCP-20CF3 8.0
CCP-30CF3 13.0
CCP-40CF3 5.0
CCP-50CF3 12.0
BCH-3F.F 14.0
BCH-5F.F 14.0 is characterized by advantageous properties.
Example 7
A STN display containing a liquid crystal medium which comprises the following compounds PCH-5F 8.0
PCH-6F 0.0
PCH-7F 0.0
PDX-7F 8.0
PDX-3F 10.0
CCP-20CF3 10.0
CCP-30CF3 14.0
CCP-40CF3 10.0
CCP-50CF3 12.0
BCH-3F.F 8.0
BCH-5F.F 8.0
ECCP-3F.F 12.0 and exhibits the following physical parameter
Δn = 0.0857 (589 nm, 20 °C) N 75 I
is characterized by advantageous properties.
Example 8
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 10.0
PDX-5F 8.0
PDX-7F 6.0
CCP-20CF3 8.0
CCP-30CF3 10.0
CCP-40CF3 7.0
CCP-C0CF3 10.0
BCH-3F.F.F 12.0
BCH-5F.F.F 10.0 ECCP-30CF3 5.0
ECCP-50CF3 5.0
CBC-33F 3.0
CBC-53F 3.0
CBC-55F 3.0 is characterized by advantageous properties.
Example 9
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 10.0
PDX-5F 8.0
PDX-7F 6.0
CCP-30CF3 11.0
CCP-40CF3 6.0
CCP-50CF3 10.0
CCP-3F.F.F 10.0
BCH-3F.F 12.0
BCH-5F.F 10.0
ECCP-30CF3 5.0
ECCP-50CF3 5.0
CBC-33F 3.0
CBC-53F 2.0
CBC-55F 2.0 is characterized by advantageous proprrties. Example 10
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F.F 10.0
PDX-5F 10.0
PDX-7F 10.0
CCP-30CF3 13.0
CCP-50CF3 12.0
ECCP-30CF3 10.0
ECCP-3F.F 13.0
ECCP-5F.F 10.0
CBC-33 4.0
CBC-53F 4.0
CBC-55F 4.0 and exhibits the following physical parameters
N 91.3 I
η = 16.8 mm2 s-1 (20 °C)
Δn = 0.0840 (20 °C, 589 nm)
Δε = 5.6 (20 °C, 1 kHz)
is characterized by advantageous properties. Example 11
A STN display containing a liquid crystal medium which comprises the following compounds PCH-32 17.6
PCH-301 16.0
PCH-302 12.0
BCH-32 15.2
BCH-52 11.2
CBC-33 4.0
CBC-53 4.0
PDX-3CF3 10.0
PDX-5CF3 10.0 is characterized by advantageous properties. Example 12 A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F.F 16.3
PDX-5F 10.2
CCP-20CF3 8.2
CCP-30CF3 13.3
CCP-40CF3 5.1
CCP-50CF3 12.2
BCH-3F.F 12.2
BCH-5F.F 14.3
ECFP-2F.F 8.2 and exhibits the following physical parameter
Δn = 0.0886 (20 °C, 589 nm)
is characterized by advantageous properties. Example 13
A STN display containing a liquid crystal medium which comprises the following compounds PCH-32 17.6
PCH-301 16.0
PCH-302 12.0
BCH-32 15.2
BCH-52 11.2
CBC-33 4.0
CBC-53 4.0
PDX-30CF3 10.0
PDX-50CF3 10.0 is characterized by advantageous properties.
Example 14
A STN display containing a liquid crystal medium which comprises the following compounds
IS-3968 12.0
PDX-7F 10.0
PCH-7F 10.0
CCP-30CF3 13.0 CCP-50CF3 12.0
ECCP-30CF3 20.0
ECCP-3F.F 13.0
CBC-33F 3.0
CBC-53F 4.0
CBC-55F 3.0 and exhibits the following physical parameter
Δn = 0.0844 (20 °C, 589 nm)
is characterized by advantageous properties.
Example 15
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 12.0
IS-3968 10.0
PDX-7F 10.0
CCP-30CF3 13.0
CCP-50CF3 12.0
ECCP-30CF3 20.0
ECCP-3F.F 13.0
CBC-33F 3.0
CBC-53F 4.0
CBC-55F 3.0 and exhibits the following physical parameters
N 89 I
Δn = 0.0835 (20 °C, 589 nm)
is characterized by advantageous properties. Example 16
A STN display containing a liquid crystal medium which comprises the following compounds
IS-3968 12.0
PDX-7F 10.0
PCH-7F 4.0
CCP-30CF3 11.0
CCP-50CF3 11.0
ECCP-30CF3 11.0
ECCP-3F.F 11.0
BCH-3F.F 11.0
BCH-5F.F 10.0
CBC-33F 3.0
CBC-53F 3.0
CBC-55F 3.0 and exhibits the following physical parameters
N 93 I
Δn = 0.0992 (20 °C, 589 nm)
is characterized by advantageous properties.
Example 17
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 12.0
IS-3968 10.0
PDX-7F 8.0
CCP-30CF3 13.0 CCP-50CF3 12.0
ECCP-30CF3 10.0
ECCP-3F.F 13.0
BCH-3F.F 11.0
CBC-33F 4.0
CBC-53F 4.0
CBC-55F 3.0 and exhibits the following physical parameters
N 86 I
Δn = 0.0924
is characterized by advantageous properties.
Example 18
A STN display containing a liquid crystal medium which comprises the following compounds
IS-3968 12.0
PDX-7F 10.0
PCH-7F 5.0
CCP-30CF3 11.0
CCP-50CF3 11.0
ECCP-30CF3 11.0
ECCP-3F.F 12.0
BCH-3F.F 10.0
BCH-5F.F 9.0
CBC-33F 3.0
CBC-53F 3.0
CBC-55F 3.0 and exhibits the following physical parameters
N 91 I
Δn = 0.0964 (20 °C, 589 nm)
is characterized by advantageous properties.
Example 19
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3F 12.0
IS-3968 10.0
PDX-7F 7.0
CCP-30CF3 13.0
CCP-50CF3 12.0
ECCP-30CF3 10.0
ECCP-3F.F 13.0
BCH-3F.F 11.0
CBC-33F 4.0
CBC-53F 4.0
CBC-55F 4.0 and exhibits the following physical parameters
N 90 I
Δn = 0.0935 (20 °C, 589 nm)
is characterized by advantageous properties. Example 20
A STN display containing a liquid crystal medium which comprises the following compounds
ECCP-3Cl 12.00
ECCP-5Cl 17.00
ECCP-3Cl.F 6.00
ECCP-5Cl.F 13.00
G9 14.00
CCPC-33 6.00
PTP-102 7.00
PTP-35 10.00
PDX-3Cl 10.00
PDX-2Cl 5.00 and exhibits the following physical parameters
N 94 I
Δn = 0.1393 (20 °C, 589 nm)
η = 19.7 mm2s-1 (20 °C)
is characterized by advantageous properties.
Example 21 A STN display containing a liquid crystal medium which comprises the following compounds
ECCP-3Cl 8.32
ECCP-5Cl 12.5
ECCP-3Cl.F 4.25
ECCP-5Cl.F 9.806
K6 6.9 G9 11.82
PCH-3 6.82
PCH-5F 8.34
PCH-7F 4.17
PTP-102 4.19
PTP-35 5.95
CCPC-33 4.21
CCPC-35 2.92
PDX-3C1 9.81 and exhibits the following physical parameters
N 75 I
Δn = 0.1250 (20 °C, 589 nm)
η = 17.0 mm2s-1 (20 °C)
is characterized by advantageous properties.
Example 22
A STN display containing a liquid crystal medium which comprises the following compounds
ECCP-3Cl 8.49
ECCP-5Cl 12.69
ECCP-5Cl.F 8.46
K6 10.19
G9 11.87
PCH-3 6.96
PCH-5F 8.52
PCH-7F 4.24
PTP-102 6.18
CCPC-33 6.46
CCPC-35 5.98
PDX-3Cl 9.96 and exhibits the following physical parameters
N 82 I
Δn = 0.1292 (20 °C, 589 nm)
η = 18.2 mm2s-1 (20 °C)
is characterized by advantageous properties.
Example 23
A STN display containing a liquid crystal medium which comprises the following compounds
ECCP-3Cl 8.44
ECCP-5Cl 12.71
ECCP-5Cl.F 8.49
K6 10.08
G9 11.90
PCH-3 6.77
PCH-5F 5.64
PCH-7F 4.24
PTP-102 6.15
CCPC-33 6.48
CCPC-35 5.98
PDX-3Cl 10.00
ME2N.F 3.12 and exhibits the following physical parameters
N 83 I
Δn = 0.1331 (20 °C, 589 nm)
η = 19.5 mm2s-1 (20 °C)
is characterized by advantageous properties. Example 24
A STN display containing a liquid crystal medium which comprises the following compounds
ECCP-3Cl 15.73
ECCP-5Cl 20.23
ECCP-5ClF 17.16
PDX-3Cl 11.15
PDX-5Cl 12.48
EPCH-3Cl 16.49
CCH303 6.76 and exhibits the following physical parameters
N 76.7 I
Δn = 0.0967 (20 °C, 589 nm)
η = 16.02 mm2s-1 (20 °C)
is characterized by advantageous properties. Example 25
A STN display containing a liquid crystal medium which comprises the following compounds ME3N.F 9.00
D-33 6.24
D-35 7.62
D-37 5.94
CHE 15.30
CP-55F 9.00
PCH-3 8.10
K6 3.60 PDX-3 12.60
PDX-5 12.60
PDX-3Cl 10.00 and exhibits the following physical parameter
Δn = 0.1246 (20 °C, 589 nm)
is characterized by advantageous properties.
Example 26
A STN display containing a liquid crystal medium which comprises the following compounds
ME3N.F 8.50
D-33 5.89
D-35 7.20
D-37 5.61
CHE 14.44
CP-55F 8.50
PCH-3 7.65
K6 3.40
PDX-3 11.89
PDX-5 11.89
PDX-3Cl 10.02
CCPC-33 5.01 and exhibits the following physical parameters
N 71 I
Δn = 0.1257 (20 °C, 589 nm)
is characterized by advantageous properties. Example 27
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3Cl 9.97
ME3N.F 4.96
D-33 13.17
D-35 16.09
D-37 12.54
CHE 10.18
CP-55F 9.96
PCH-3 10.00
K6 5.13
PDX-3 8.00 and exhibits the following physical parameters
η = 27 mm2s-1 (20 °C)
Δn = 0.1063 (20 °C, 588 nm)
is characterized by advantageous properties.
Example 28
A STN display containing a liquid crystal medium which comprises the following compounds
132 11.33
135 11.34
152 11.33
K6 6.80
K9 5.95
K15 8.5 PCH-3 21.25
CBC-33 4.25
CBC-53 4.25
PDX-3Cl 10.00
CCPC-33 5.00 and exhibits the following physical parameters
N 85.3 I
η = 24 mm2s-1 (20 °C)
Δn = 0.1554 (20 °C, 589 nm)
is characterized by advantageous properties.
Example 29 A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3Cl 10
D-33 14.17
D-35 17.33
D-37 13.5
K6 15
K12 15
CHE 10
CBC-53 5 and exhibits the following physical parameters
Δn = 0.1314 (20 °C, 589 nm)
η = 28 mm2s-1 (20 °C)
is characterized by advantageous properties. Example 30
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-3Cl 10
ME15 14.48
ME35 17
ME55 8.52
K6 15
K12 15
CHE 10
CBC-53 5
CBC-55F 5 and exhibits the following physical parameters
Δn = 0.1566 (20 °C, 589 nm)
is characterized by advantageous properties. Example 31
A STN display containing a liquid crystal medium which comprises the following compounds PCH-5F 8.0
PDX-7F 8.0
PDX-3F 10.0
CCP-2OCF3 10.0
CCP-3OCF3 14.0
CCP-4OCF3 10.0
CCP-5OCF3 12.0 BCH-3F .F 8 . 0
BCH-5F .F 8. 0
ECCP-3F .F 12 . 0 and exhibits the following physical parameters
N 75 I
Δn = 0.086 (20 °C, 589 nm)
is characterized by advantageous properties. Example 32
A STN display containing a liquid crystal medium which comprises the following compounds ECCP-32 12.000
ECCP-35 12.000
PCH-3 12.000
G9 10.000
PDX-3Cl 8.000
FET-5C1 10.000
BECH-3Cl.F 10.000
CCPC-33 7.000
K6 10.000
PYP-3N.F 4.000
PYP-5N.F 5.000
is characterized by advantageous properties. Example 33
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F 10.0
PDX-7F 8.0
PDX-3F 6.0
CCP-20CF3 8.0
CCP-30CF3 12.0
CCP-40CF3 7.0
CCP-50CF3 11.0
BCH-3F.F 12.0
BCH-5F.F 10.0
ECCP-30CF3 5.0
ECCP-50CF3 5.0
CBC-33F 2.0
CBC-53F 2.0
CBC-55F 2.0 is characterized by advantageous properties.
Example 34
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F.F 24.0
PDX-7F.F 23.0
PDX-3F.F 23.0
CBC-33 5.0 CBC-53 5.0
CBC-55 5.0
CBC-33F 5.0
CBC-53F 5.0
CBC-55F 5.0 is characterized by advantageous properties.
Example 35
A STN display containing a liquid crystal medium which comprises the following compounds
PDX-5F 24.0
PDX-7F 23.0
PDX-3F 23.0
CBC-33 5.0
CBC-53 5.0
CBC-55 5.0
CBC-33F 5.0
CBC-53F 5.0
CBC-55F 5.0 is characterized by advantageous properties. Example 36
A STN display containing a liquid crystal medium which comprises the following compounds PDX-5F.F 10.0
PDX-7F.F 8.0
PDX-3F.F 6.0
CCP-20CF3 8.0
CCP-30CF3 12.0
CCP-40CF3 7.0
CCP-50CF3 11.0
BCH-3F.F 12.0
BCH-5F.F 10.0
ECCP-30CF3 5.0
ECCP-50CF3 5.0
CBC-33F 2.0
CBC-53F 2.0
CBC-55F 2.0 is characterized by advantageous properties.

Claims

Patent Claims 1. Supertwist liquid crystal display having
- two plane-parallel carrier plates which, with an
edging, form a cell,
- a nematic liquid crystal mixture of positive dielectric anisotropy in the cell,
- electrode layers with superimposed orientation layers on the inside of the carrier plates,
- an angle of incidence between the longitudinal axis of the molecules on the surface of the carrier plates and the carrier plates of about 1 degree to 30 degrees and
- a twisting angle of the liquid crystal mixture in the cell from orientation layer to orientation layer, according to the amount, of between 160 and 720 °C, characterized in that the nematic liquid crystal mixture contains one or more compounds of the formula I
wherein R1 is alkyl having 1-12 C atoms, wherein one or two non-adjacent CH2 groups can also be replaced by
-O-, -CH=CH-, -CO-, -O-CO- or -CO-O-, r is 0 or 1, ring A is trans-1,4-cyclohexylene or 1,4-phenylene, X is F, Cl, CF3, OCF3 or OCHF2 and Y and Z each independently of one another denotes H or F.
2. Display according to claim 1, characterized in that the nematic liquid crystal mixture further comprises a) 5-60 % by weight of a liquid crystalline component A consisting of one or more compounds having a dielectric anisotropy of more than +8, b) 10-40 % by weight of a liquid crystalline component B consisting of one or more compounds having a clearing point of more than 120 °C, and c) an optically active component C, in an amount such that the ratio between the layer thickness (separation of the plane-parallel carrier plates) and the natural pitch of the chiral nematic liquid crystal mixture is more than 0.2 suitable to the desired twist angle, and in that the nematic liquid crystal mixture has a nematic phase range of at least 60 °C, a viscosity of not more than 30 mPa.s and a dielectric anisotropy of at least +5, the dielectric anisotropies of the compounds and the parameters relating to the nematic liquid crystal mixture being based on a temperature of 20 °C.
3. Display according to claim 2, characterized in that component A comprises compounds selected from the following group: wherein
R is alkyl having 1-12 C atoms, wherein one or two non- adjacent CH2 groups can also be replaced by -O-,
-CH=CH-, -CO-, -O-CO- or -CO-O-,
Q is the formula
Z1 is CH2CH2-, a single bond, -CH2CH2-, -CO-O-
or -O-CO- and
4. Display according to one of claims 1 to 3, characterized in that component B comprises compounds selected from the following group:
wherein R1 and R2 each independently of one another are R as defined in claim 3, Z0 is -CO-O-, -O-CO- or -CH2CH2-, Q is as defined in claim 3 and the 1,4-phenylene ring in BI to BVII may also be substituted in 2- or 3-position by fluorine.
5. Display according to one of claims 1 to 4, characterized in that the liquid crystal mixture contains at least one compound from the following group:
wherein Hal is F or Cl and L and R are as defined above.
6. Display according to at least one of claims 1 to 5, characterized in that the liquid crystal mixture contains one or more compounds wherein R is a trans-alkenyl group or a trans-alkenyloxy group.
7. Liquid crystal mixture of the composition defined in at least one of Claims 1 to 6.
EP19910914327 1990-08-31 1991-08-14 Supertwist liquid crystal display Withdrawn EP0500832A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP90116733 1990-08-31
EP90116733 1990-08-31

Publications (1)

Publication Number Publication Date
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WO (1) WO1992004422A1 (en)

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GB9220189D0 (en) * 1992-09-24 1992-11-04 Central Research Lab Ltd Dioxane derivatives
JPH08199168A (en) * 1995-01-19 1996-08-06 Chisso Corp Liquid crystal composition and liquid crystal display element
DE19528107B4 (en) * 1995-03-17 2010-01-21 Merck Patent Gmbh Liquid-crystalline medium and its use in an electro-optical liquid crystal display
DE19528665A1 (en) * 1995-08-04 1997-02-06 Merck Patent Gmbh Liquid crystalline medium
DE19532292A1 (en) * 1995-09-01 1997-03-06 Merck Patent Gmbh Liquid crystalline medium

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Publication number Priority date Publication date Assignee Title
DE3807958B4 (en) * 1988-03-10 2004-03-18 Merck Patent Gmbh Super twisted liquid crystal display element
DE3835804B4 (en) * 1988-10-20 2006-12-28 Merck Patent Gmbh Nematic liquid-crystal mixture
KR920701195A (en) * 1989-12-08 1992-08-11 위르겐 호이만·라인하르트 슈틀러 Phenyldioxane
JP3043065B2 (en) * 1990-03-09 2000-05-22 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 ハフトング Liquid crystal medium

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Title
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