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.

Landscapes

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=8204403

Family Applications (1)

Country Status (2)

Families Citing this family (5)

Family Cites Families (4)

• 1991
  • 1991-08-14 WO PCT/EP1991/001540 patent/WO1992004422A1/en not_active Application Discontinuation
  • 1991-08-14 EP EP19910914327 patent/EP0500832A1/de not_active Withdrawn

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events