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
  • C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
• • 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
  • C09K19/02—Liquid crystal materials characterised by optical, electrical or physical properties of the components, in general
  • C09K19/0208—Twisted Nematic (T.N.); Super Twisted Nematic (S.T.N.); Optical Mode Interference (O.M.I.)

Definitions

• the invention relates to the improvement of a twisted nematic liquid crystal display device operating in the high multiplex mode with a very high contrast and with a particularly steep electro-optical characteristic.
• the device is operating in the first Gooch and Tarry transmission minimum.
• the invention furthermore relates to new liquid crystal dielectrics which have a ratio of the elastic constants K 3 /K 1 as small as possible but not more than 0.9 and a ratio of ⁇ / ⁇ of at most 0.3. Such, dielectrics are used in the matrix. type liquid crystal display devices driven by time sharing according to the invention.
• nematic or nematic-cholesteric liquidcrystalline materials are utilized for liquid-crystal display elements in order to effect significant changes in their optical properties, such as light transmission, light scattering, birefringence, reflectance or color, under the influence of electric fields.
• the functioning of display elements of this type is based here, for example, on the phenomena of dynamic scattering, the deformation of aligned phases or the Schadt-Helfrich effect in the twisted cell.
• liquid-crystal display elements especially those based on the twisted nematic cell (TN cell) have gained particular importance recently, because they can be operated with relatively low control voltages which can be readily made available even by small batteries.
• these display elements have hitherto been the best which can be constructed as matrix display elements, which allow the presentation of a high information density without an intolerably large number of control lines, lead-ins and lead-outs.
• the TN cell in particular in the form of matrix display elements, still raises considerable difficulties. These include above all the more or less pronounced dependence of the contrast on the angle of observation and the restricted multiplexing capacity.
• a subject of the invention is the improvement of a twisted nematic liquid crystal display device operating in the high multiplex mode and having a high contrast, wherein the liquid crystal dielectric has a ratio of the elastic constants K 3 /K 1 as small as possible but not more than 0.9 and a ratio of ⁇ / ⁇ of at most +0.3 and comprises at least three liquid crystal materials:
• A is 1,4-phenylene or trans-1,4-cyclo- hexylene
• Z 1 is -CO-O-, -O-CO-, -CH 2 -O-, -OCH,-, -CH--CH ⁇ --or a single bond
• Q 1 is 1,4-phenylene or trans-1,4-cyclohexylene
• m. is 0, 1 or 2
• the first liquid crystal material comprises at least one of liquid crystal compounds represented by general formulae lb to Ii:
• the third liquid crystal material comprises at least one liquid crystal compound represented by the general formulae Illd to Illh, III6 to III15 and/or III16 and III17:
• R 11 , R 13 , R 15 and R 18 each independently represent R
• R 9 , R 10 , R 12 , R 14 , R 16 and R 17 each independently represent R or OR
• a 4 is 1,4-cyclohexenylen
• R 29 , R 31 , R 33 , R 35 , R 37 , R 39 , R 40 , R 41 R 43 , R 45 , R 46 , R 47 , and R 48 each independently represent R, R 30 , R 32 , R 34 , R 36 , R 38 , R 42 and R 44 each independently represent R or OR,
• a 4 is 1,4-cyclohexenylen
• R 49 , R 50 , R 51 and R 52 each represent R
• R being in each case independently a straight chain alkyl group having up to 12 carbon atoms wherein one or two non-adjacent CH 2 groups may be replaced by
• a further subject of the invention is a method of simultaneously minimizing the dependence of contrast on the angle of observation of an electro-optical display element based on a liquid crystal dielectric and of maximizing its multiplexing capacity by maximizing its steepness of its characteristic curve, comprising operating the element in the first Gooch and Tarry transmission minimum, selecting a dielectric as outlined above.
• the construction of the liquid crystal display element according to the invention from polarizers, electrode base plates and electrodes with such a surface treatment that the preferential orientation of the particular adjoining liquid crystal molecules is usually twisted by 90° from one electrode to the other, corresponds to the type of construction conventional for such display elements.
• the concept of the conventional type of construction is here taken in a very wide sense and also comprises all the variations and modifications, known from the literature, of the twisted nematic cell, and in particular also matrix display elements.
• An essential difference between the display elements according to the invention and those hitherto conventional and based on the twisted nematic cell is, however, the choice of the liquid crystal parameters in the liquid crystal layer.
• the K 3 /K 1 ratio in the conventional liquid-crystalline phases for display elements of this type is at least > 0.8 and the ⁇ / ⁇ ratio is normally between 1.2 and 1.7
• the K 3 /K 1 ratio in the display elements according to the invention is ⁇ 0.9 and ⁇ / ⁇ is ⁇ 0.3
• the K 3 /K 1 ratio in the display ele ments according to the invention preferably is 0.4 to 0.9 and ⁇ / ⁇ preferably is 0.4 to 0.3.
• Particularlypreferred dielectrics are those, wherein K 3 /K 1 is 0.2 to 0.75 and ⁇ / ⁇ is 0.1 to 0.3.
• the parameters used to define the invention are fully known to skilled workers. The contemplated definitions are to be found in many publications, e.g. W.H. De Jeu, Physical Properties of Liquid Crystal Materials, Gordon and Breach 1980 and the brochure "Liquid Crystals, Measurement of the Physical Properties" of E. Merck, whose disclosures are incorporated by reference herein.
• the thickness of a liquid crystal layer of the display element according to the invention and/or the optical anisotropy ⁇ n of the liquid crystal material are chosen such that
• the layer thicknesses of the display elements according to the invention can, for example, be within the range from 2 to 10 ⁇ m.
• the smallest possible layer thicknesses are chosen, the lower limit of d being determined by the quality standards rrquired for mass production.
• a particularly preferred range of d is thus 3 to 8 ⁇ m, in particular 4 to 7 ⁇ m.
• Liquid-crystalline dielectrics the material parameters of which are within the ranges according to the invention, can be prepared from conventional liquid-crystalline base materials. Numerous such materials are known from the literature.
• the dielectrics used for the display elements according to the invention comprise (a) at least 10 wt% of a first liquid crystal material comprising at least one of liquid crystal compounds represented by general formula:
• A is 1 ,4-phenylene or trans-1,4-cyclohexylene
• Z 1 is -CO-O-, -O-CO-, -CH 2 -O-, -OCH 2 -, -CH 2 CH 2 - or a single bond
• Q is 1,4-phenylen or trans-1,4-cyclohexylene
• m is 0, 1 or 2
• the first liquid crystal material comprises at least one of liquid crystal compounds represented by general formulae lb to li:
• the third liquid crystal material comprises at least one liquid crystal compound represented by the general formulae Illd to Illh, III6 to III15 and/or III16 and III17:
• R 11 , R 13 , R 15 and R 18 each independently represent R
• R 9 , R 10 , R 12 , R 14 , R 16 and R 17 each independently represent R or OR
• R 29 , R 31 , R 33 , R 35 , R 37 , R 39 , R 40 , R 41 R 43 , R 45 , R 46 , R 47 , and R 48 each independently represent R, R 30 , R 32 , R 34 , R 36 , R 38 , R 42 and R 44 each independently represent R or OR,
• a 4 is 1,4-cyclohexenylen
• R 49 , R 50 , R 51 and R 52 each represent
• R being in each case independently a straight chain alkyl group having up to 12 carbon atoms wherein one or two non-adjacent
• the dielectric comprises at least one liquid crystal compound represented by the general formula la
• the second liquid crystal material comprises at least one of liquid crystal compounds represented by the general formulae Ila to lId:
• X being hydrogen or fluorine
• Y being cyano, trifluoromethoxy or fluorine
• r being 0 or 1
• the third liquid crystal material comprises preferably liquid crystal compounds having a dielectric anisotropy of -1 to +1.
• the third liquid crystal material comprises at least one of liquid crystal compounds represented by the general formulae IlIa to IIIc; wherein R 3 represents R; and R 4 represents R or OR
• R 5 represents R; and R 6 represents R or OR
• R 7 represents R; and R 8 represents R or OR;
• liquid crystal material further comprises at least one of liquid crystal compounds represented by general formulae:
• R 19 and R 20 represent independently from one another R
• R 21 and R 22 represent mdenpendehtly from one another R;
• R 23 and R 24 represent independently from one another R
• R 25 and R 26 represent independently from one another R
• liquid crystal compounds are shown with their physical properties. These compounds can be used for example for the display elements according to the invention.
• R 1 preferably is n-alkyl having
• R 2 preferably is ethyl, n-propyl or n-alkoxy having 5 to 9 carbon atoms.
• liquid crystal compound having a negative or substantially 0 ⁇ value there can be used liquid crystal compounds of phenylcyclohexane type represented by general formula IlIa (German Patent 26 36 684), phenyl cyclohexane carboxylates represented by general formula nib (German Patent 24 29 093), cyclohexyl cyclohexanes (USP 4,622,164) represented by general formula IIIc, biphenylcyclohexanes - formula Illl - (Japanese Patent 1,311,608), phenyl cyclohexylcyclohexane carboxy- lates - formula Ill2 - (Japanese Patent 1,297,121),
• liquid crystal compounds are low viscosity liquid crystal compounds for controlling viscosity, high temperature liquid crystal for raising N-I point and liquid crystals for suppressing smectic phases.
• low viscosity liquid crystal compounds there can be used liquid crystal compounds shown in Table 3 which show ⁇ of approximately 6 to 20 mPa.s.
• liquid crystal compounds shown in Table 4 having N-I point of approximately 130 to 330 °C. ⁇ is approximately 13 to 65 mPa.s.
• R is preferable alkyl of 1 to 10 carbon atoms.
• a particularly preferred range is 1 to 5 carbon atoms.
• At least one of the liquid crystal compounds shown in these Tables 3 and 4 or at least one of the compounds of general formulae Illd to Illh and III6 to III17 may be used for said third liquid crystal material.
• Preferred devices according to the invention are those, wherein the liquid crystal dielectric comprises at least five components.
• Preferred embodiments are those, wherein
• the liquid crystal mixture is adjusted for a device, operating in the first Gooch and Tarry transmission minimum.
• the liquid crystal mixture is adjusted for a device, wherein the electro-optical characteristic curve is at least as steep as that curve in the second such transmission minimum.
• the liquid crystal mixture is adjusted for a device, wherein the steepness of the characteristic curve in the first minimum is greater than that in the second minimum.
• the liquid crystal mixture shows K 3 /K 1 of 0.4 to 0.9 and ⁇ / ⁇ is 0.4 to -0.3.
• the liquid crystal mixture shows K 3 /K 1 of 0.2 to 0.75 and ⁇ / ⁇ is 0.1 to 0.3.
• the liquid crystal mixture comprises at least five components.
• the first liquid crystal material comprises at least one of liquid crystal compounds represented by the general formula la
• the second liquid crystal material comprises at least one of liquid crystal compounds represented by the general formulae Ila to lId:
• X being hydrogen or fluorine
• Y being cyano, trifluoromethoxy or fluorine
• the third liquid crystal material comprises liquid crystal compounds having a dielectric anisotropy of -1 to +1.
• the third liquid crystal material comprises at least one of liquid crystal compounds represented by the general formulae IlIa to IIIc;
• R 3 represents R; and R 4 represents R or OR
• R 5 represents R; and R 6 represents R or OR
• R 7 represents R; and R 8 represents R or OR;
• the third liquid crystal material further comprises at least one of liquid crystal compounds represented by general formulae:
• R 19 and R 20 represent independently from one another R
• R 21 and R 22 represent indenpendently from one another R;
• R 23 and R 24 represent independently from one another R
• R 25 and R 26 represent independently from one another R
• the formulation ratios of said first liquid crystal material, said second liquid crystal material and said third liquid crystal material are at least 30 wt%, less than 10 wt% and less than 70 wt%, respectively.
• the formulation ratios of said first liquid crystal material, said second liquid crystal material and said third liquid crystal material are 30 to 65 wt%, less than 5 wt% and 35 to 70 wt%, respec- tively.
• Preferred dielectrics are those, wherein the formulation ratios of said first liquid crystal material, said second liquid crystal material and said third liquid crystal material are at least 30 wt%, less than 10 wt% and less than 70 wt%, respectively.
• Particularly preferred dielectrics are those, wherein the formulation ratios of said first liquid crystal material, said second liquid crystal material and said third liquid crystal material are 30 to 65 wt%, less than 5 wt% and 35 to 70 wt%, respectively.
• Such dielectrics can additionally contain dyes and/or doping substances in the usual quantities, unless the liquid crystal parameters are thus taken out of the ranges according to the invention. Mixing of the liquid crystalline components to achieve the parameters discussed above can be routinely accomplished by the usual preliminary orientation experiments taking into account the usual considerations.
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of
• a liquid crystalline phase consisting of

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• 1989
  • 1989-01-04 WO PCT/EP1989/000003 patent/WO1989006677A1/en not_active Application Discontinuation
  • 1989-01-04 EP EP89901058A patent/EP0354940A1/de not_active Withdrawn
  • 1989-01-04 JP JP1500752A patent/JPH02502921A/ja active Pending
  • 1989-01-04 KR KR1019890701684A patent/KR900700564A/ko not_active Application Discontinuation

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