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
  • C09K19/06—Non-steroidal liquid crystal compounds
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
• • 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
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3028—Cyclohexane rings in which at least two rings are linked by a carbon chain containing carbon to carbon single bonds
• • 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
  • C09K19/44—Mixtures of liquid crystal compounds covered by two or more of the preceding groups C09K19/06 - C09K19/40 containing compounds with benzene rings directly linked
• • 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
  • C09K19/08—Non-steroidal liquid crystal compounds containing at least two non-condensed rings
  • C09K19/30—Non-steroidal liquid crystal compounds containing at least two non-condensed rings containing saturated or unsaturated non-aromatic rings, e.g. cyclohexane rings
  • C09K19/3001—Cyclohexane rings
  • C09K19/3003—Compounds containing at least two rings in which the different rings are directly linked (covalent bond)
  • C09K2019/3021—Cy-Ph-Ph-Cy

Definitions

• the present invention relates to a liquid-crystalline medium, its use for electro-optical purposes and displays containing this medium.
• Liquid crystals are mainly used as dielectrics in display devices, since the optical properties of such substances can be influenced by an applied voltage.
• Electro-optical devices based on liquid crystals are well known to the person skilled in the art and can be based on various effects. Such devices are, for example, cells with dynamic scattering, DAP cells (deformation of aligned phases), guest / host cells, TN cells with a twisted nematic structure, STN cells (super-twisted nematiic), SBE cells ("super birefringence effect”) and OMI cells ("optical mode interference").
• DAP cells deformation of aligned phases
• guest / host cells guest / host cells
• TN cells with a twisted nematic structure STN cells (super-twisted nematiic)
• SBE cells super birefringence effect
• OMI cells optical mode interference
• the liquid crystal materials must have good chemical and thermal stability and good stability against electric fields and electromagnetic radiation. Furthermore, the liquid crystal materials should have a low viscosity and result in short response times, low threshold voltages and a high contrast in the cells. Furthermore, they should have a suitable mesophase at the usual operating temperatures, ie in the widest possible range below and above room temperature, for example a nematic or cholesteric mesophase for the above-mentioned cells. Since liquid crystals are generally used as mixtures of several components, it is important that the components are readily miscible with one another. Other properties, such as electrical conductivity, dielectric anisotropy and optical anisotropy, must meet different requirements depending on the cell type and area of application. For example, materials for cells with a twisted nematic structure should have positive dielectric anisotropy and low electrical conductivity.
• matrix liquid crystal displays with integrated non-linear elements for switching individual pixels (MLC displays)
• MLC displays matrix liquid crystal displays with integrated non-linear elements for switching individual pixels
• Such matrix liquid crystal displays are known.
• active elements ie transistors
• MOS Metal Oxide Semiconductor
• TFT Thin film transistors
• the TN effect is usually used as the electro-optical effect.
• TFTs made of compound semiconductors such as CdSe or TFT's based on polycrystalline or amorphous silicon The latter technology is being worked on with great intensity worldwide.
• the TFT matrix is applied to the inside of one glass plate of the display, while the other glass plate carries the transparent counter electrode on the inside. Compared to the size of the pixel electrode, the TFT is very small and practically does not disturb the image.
• This technology can also be used for full color images be expanded, a mosaic of red, green and blue filters being arranged in such a way that one filter element each is opposite a switchable picture element.
• the TFT displays usually work as TN cells with crossed polarizers in transmission and are illuminated from behind.
• Such MFK displays are particularly suitable for TV applications (e.g. pocket TVs) or for high-information
• the invention has for its object to provide media in particular for such MFK, TN or STN displays, which do not have the disadvantages indicated above or only to a lesser extent, and preferably at the same time have very high resistivities and low threshold voltages.
• the invention thus relates to a liquid-crystalline medium based on a mixture of polar compounds with positive dielectric anisotropy, characterized in that it contains one or more compounds of the general formula I.
• a 1 and A 2 each independently of one another trans-1, 4-cyclohexylene, 1,4-phenylene or 3-fluoro-l, 4-phenylene, Z -CH 2 CH 2 - or a single bond, LH or F, YH or F, XF, Cl, CF 3 , OCF 3 or OCHF 2 and R is alkyl, oxaalkyl, fluoroalkyl or alkenyl, each having up to 7 carbon atoms.
• the invention also relates to electro-optical displays (in particular STN or MFK displays with two plane-parallel carrier plates which form a cell with a border, integrated non-linear elements for switching individual pixels on the carrier plates and a nematic liquid crystal mixture in the cell with a positive one dielectric anisotropy and high resistivity) containing such media and the use of these media for electro-optical purposes.
• electro-optical displays in particular STN or MFK displays with two plane-parallel carrier plates which form a cell with a border, integrated non-linear elements for switching individual pixels on the carrier plates and a nematic liquid crystal mixture in the cell with a positive one dielectric anisotropy and high resistivity
• liquid crystal mixtures according to the invention enable a significant expansion of what is available
• the liquid-crystal mixtures according to the invention enable dielectric anisotropy values ⁇ > 3.5 at the same time at low viscosities at low temperatures (at -30 ° C ⁇ 600, preferably ⁇ 550 mPa.S; at -40 ° C ⁇ 1800, preferably ⁇ 1700 mPa.s) , preferably> 4.0, clearing points above 65 °, preferably above 70 ° and to achieve a high value for the specific resistance, as a result of which excellent STN and MKF displays can be achieved.
• the MFK displays according to the invention preferably operate in the first transmission minimum according to Gooch and Tarry [CH Gooch and HA Tarry, Electron. Lett. 10, 2-4, 1974; CH Gooch and HA Tarry, Appl. Phys., Vol.
• the first minimum can be clearly seen using the mixtures according to the invention Realize higher resistivities than with mixtures with cyan compounds.
• the person skilled in the art can set the birefringence required for a given layer thickness of the MLC display by means of suitable routine selection of the individual components and their proportions by weight.
• the viscosity at 20 ° C is preferably ⁇ 25 mPa.s.
• the nematic phase range is preferably at least 70 °, in particular at least 80 °. This range preferably extends at least from -30 ° to + 70 °.
• the UV stability of the mixtures according to the invention is also considerably better, ie they show a significantly smaller decrease in HR under UV exposure.
• the threshold voltages (V Lh ) achieved are generally ⁇ 1.8 volts, preferably in the range 1.4 to 1.7 volts.
• the media according to the invention are also distinguished by extraordinarily high elastic constants with very favorable viscosity values, which results in distinct advantages over media from the prior art, particularly when used in STN displays.
• the media according to the invention are preferably based on several (preferably two or more) compounds of the formula I, i.e. the proportion of these compounds is> 25%, preferably> 40%.
• - Medium additionally contains one or more compounds selected from the group consisting of the general formulas II, III and IV:
• R alkyl, oxaalkyl, fluoroalkyl or alkenyl
• - Medium additionally contains one or more compounds selected from the group consisting of the general formulas V to VIII:
• Total mixture is 30 to 70% by weight -
• the medium contains compounds of the formulas II and
• the medium contains further compounds, preferably selected from the following group: -
• the weight ratio I: (II + III - IV) is preferably 1: 4 to 1: 1.
• alkyl includes straight chain and branched
• Alkyl groups with 1-7 carbon atoms especially the straight-chain groups methyl, ethyl, propyl, butyl, pentyl, hexyl and heptyl. Groups with 2-5 carbon atoms are generally preferred.
• alkenyl encompasses straight-chain and branched alkenyl groups having 2-7 carbon atoms, in particular the straight-chain groups. Alkenyl groups in particular are C 2 -C 7 -1E-
• alkenyl groups are vinyl, 1E-propenyl, 1E-butenyl, 1E-pentenyl, 1E-hexenyl, 1E-heptenyl, 3-butenyl, 3E-pentenyl, 3E-hexenyl, 3E-heptenyl, 4-pentenyl, 4Z-hexenyl, 4E-hexenyl, 4Z-heptenyl, 5-hexenyl, 6-heptenyl and the like. Groups of up to 5 carbon atoms are generally preferred.
• fluoroalkyl preferably encompasses straight chain groups with terminal fluorine, i.e. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorhexyl and 7-fluorohexyl.
• fluorine i.e. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorhexyl and 7-fluorohexyl.
• fluorine i.e. Fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorhexyl and 7-fluorohexyl.
• other positions of the fluorine are not excluded.
• the response times, the threshold voltage, the steepness of the transmission characteristics, etc. can be modified in a desired manner by a suitable choice of the meanings of R, X and Y.
• R, X and Y For example, lE-alkenyl residues, 3E-alkenyl residues, 2E-alkenyloxy residues and the like generally lead to shorter response times, improved nematic tendencies and a higher ratio of the elastic constants k 33
• k 33 / k 11 compared to alkyl or alkoxy residues.
• 4-alkenyl residues, 3-alkenyl residues and the like generally give lower threshold voltages and smaller values of k 33 / k 11 compared to alkyl and alkoxy residues.
• a group -CH 2 CH 2 -in Z 1 or Z 2 generally leads to higher values of k 33 / k 11 compared to a simple covalent bond. Higher values of k 33 / k 11 enable, for example, flatter transmission characteristics in TN cells with 90 ° twist (to achieve gray tones) and steeper transmission characteristics in STN, SBE and OMI cells (higher multiplexability) and vice versa.
• the optimal quantitative ratio of the compounds of the formulas I and II + III + IV largely depends on the desired properties, on the choice of the components of the formulas I, II, III and / or IV and on the choice of further components which may be present. Suitable proportions within the range given above can easily be determined from case to case.
• the total amount of compounds of the formulas I to XII in the mixtures according to the invention is not critical.
• the mixtures can therefore contain one or more further components in order to optimize various properties.
• the observed effect on the response times and the threshold voltage is generally greater the higher the total concentration of compounds of the formulas I to XII.
• the media according to the invention contain compounds of the formula II, III, V and / or VII (preferably II and / or III), in which X is CF 3 , OCF 3 or X means OCHF 2 .
• X is CF 3 , OCF 3 or X means OCHF 2 .
• the media according to the invention preferably contain compounds of the formulas II to VII mentioned above in which X, L and Y simultaneously mean F.
• the media preferably contain compounds selected from the group consisting of the formulas V to VIII, where X is preferably OCHF 2 .
• the media according to the invention can also contain a component A consisting of one or more compounds having a dielectric anisotropy of -1.5 to +1.5 of the general formula I '
• R 1 and R 2 each independently of one another n-alkyl, n-alkoxy, ⁇ -fluoroalkyl or n-alkenyl with up to 9 carbon atoms, the rings A 1 , A 2 and A 3
• Z 1 and Z 2 each independently of one another -CH 2 CH 2 -, C ⁇ E-, -CO-O-, -O-CO-, or a single bond, and m denotes 0, 1 or 2.
• Component A preferably contains one or more compounds selected from the group consisting of III to 117: II1 II II II6 II
• Component A preferably additionally contains one or more compounds selected from the group consisting of 118 to II20: II II II II11 II I1 II II1 II
• Component A also preferably contains one or more compounds selected from the group consisting of II21 to II25 and contains: II21 II II
• R 1 and R 2 have the meaning given in formula V and the 1,4-phenylene groups in II21 to II25 each
• mixtures of this type are preferred, whose component A is one or more compounds.
• selected from the group consisting of II26, II27 and II28 contains: II26 II27 II28 wherein C r H 2r + 1 is a straight-chain alkyl group with up to 7
• R 1 and R 2 have the meaning given for formula I 'and
• liquid crystal mixtures which contain one or more compounds selected from the group consisting of III 'and IV:
• the type and amount of polar compounds with positive dielectric anisotropy is not critical. The person skilled in the art can select suitable materials in simple routine tests from a wide range of known and in many cases also commercially available components and base mixtures.
• the media according to the invention preferably contain one or more compounds of the formula I "
• Z 1 , Z 2 and m have the meaning given for formula I ', Q 1 and Q 2 each independently of one another 1,4-phenylene, trans-1,4-cyclohexylene or 3-fluoro-1,4-phenylene or one of the radicals Q 1 and Q 2 also denotes trans-1,3-dioxane-2, 5-diyl, pyrimidine-2, 5-diyl, pyridine-2, 5-diyl or 1,4-cyclohexenylene, R ° n-alkyl, n-alkenyl, n-alkoxy or n-oxaalkyl, each with up to 9 carbon atoms, LH or F, YH or F and X 'is CN, halogen, CF 3 , OCF 3 or OCHF 2 .
• the media according to the invention for STN or TN applications are based on compounds of the formula I "in which X 'is CN. It is understood that smaller or larger proportions of other compounds of the formula I"(X' ⁇ CN) come into question.
• the structure of the STN or MFK display according to the invention from polarizers, electrode base plates and electrodes with surface treatment corresponds to the design customary for such displays.
• the term conventional construction is broadly encompassed here and also includes all modifications and modifications of the MLC display, in particular also matrix display elements based on poly-Si TFT or MIM.
• liquid crystal parameters of the liquid crystal layer A significant difference between the displays according to the invention and those previously used on the basis of the twisted nematic cell, however, is the choice of the liquid crystal parameters of the liquid crystal layer.
• the liquid crystal mixtures which can be used according to the invention are prepared in a manner which is conventional per se. As a rule, the desired amount of the components used in smaller amounts is dissolved in the components which make up the main constituent, advantageously at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent after thorough mixing, for example by distillation.
• the dielectrics can also contain further additives known to the person skilled in the art and described in the literature. For example, 0-15% pleochroic dyes or chiral dopants can be added.
• C means a crystalline, S a smectic, S B a smectic B, N a nematic and I the isotropic phase.
• V 10 denotes the voltage for 10% transmission (viewing direction perpendicular to the plate surface).
• t on denotes the switch-on time and t off the switch-off time at an operating voltage corresponding to 2.5 times the value of V 10 •
• ⁇ n denotes the optical anisotropy and n o the refractive index.
• the electro-optical data were recorded in a TN cell at the 1st minimum (ie at ad • ⁇ n value of 0.5) measured at 20 ° C, unless expressly stated otherwise.
• the optical data were measured at 20 ° C, unless expressly stated otherwise.
• Table A shows only the acronym for the base body.
• a code for the substituents R 1 , R 2 , L 1 , L 2 and L 3 follows with a dash, separately from the acronym for the base body:

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=6404400

Family Applications (1)

Country Status (3)

Families Citing this family (8)

Family Cites Families (19)

• 1991
  • 1991-04-05 EP EP19910907534 patent/EP0481032A1/de not_active Withdrawn
  • 1991-04-05 JP JP3506844A patent/JP2795325B2/ja not_active Expired - Lifetime
  • 1991-04-05 WO PCT/EP1991/000646 patent/WO1991016394A1/de not_active Application Discontinuation
• 1998
  • 1998-02-25 JP JP4382198A patent/JPH10324873A/ja active Pending
• 1999
  • 1999-07-08 JP JP11194667A patent/JP2000026860A/ja active Pending

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events