Electro-rheological fluid and haptic device

Abstract

The present invention relates to an electro-rheological fluid comprising particles of at least one inorganic or organic material suspended in a polar liquid crystalline medium, the use of such electro-rheological fluid in an haptic device, an haptic device itself, a method of the production of such haptic device and the use of such haptic device in electro-optical devices.

Claims

1. An electro-rheological fluid comprising particles of at least one inorganic or organic material suspended in a polar liquid crystalline medium exhibiting a dielectrically anisotropy of 5, wherein said liquid-crystalline medium comprises one or more mesogenic compounds selected formulae I and/or I*: ##STR00130## wherein L.sup.11 to L.sup.16 are independently of each other H or F, ##STR00131## are independently of each other, ##STR00132## R.sup.11 is alkyl group, which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are each optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl, or CN, and alternatively one of Y.sup.01 and Y.sup.02 can be H, R.sup.01 and R.sup.02 are, independently of each other, H, or alkyl with 1 to 12 C-atoms, and X.sup.11 halogen, CN, a mono-, di- or polyhalogenated alkyl-, or alkoxy group having 1 to 6 C-atoms or a mono-, di- or polyhalogenated alkenyl group having 2 to 6 C-atoms.

2. The electro-rheological fluid according to claim 1, wherein the amount of particles of the inorganic or organic material in the electro-rheological fluid as a whole is in the range from 5 to 70% wt.

3. The electro-rheological fluid according to claim 1, wherein the size of the particles of the inorganic or organic material is in the range from 1 nm to 1000 nm.

4. The electro-rheological fluid according to claim 1, wherein said particles are of at least one inorganic material selected from amorphous silicon and TiO.sub.2.

5. The electro-rheological fluid according to claim 1, wherein said particles are of at least one organic material selected from porous poly(methyl methacrylate, lithium polymethacrylate and styrene.

6. The electro-rheological fluid according to claim 1, wherein said fluid comprises particles of at least one inorganic material suspended in said polar liquid crystalline medium.

7. The electro-rheological fluid according to claim 1, wherein said fluid comprises particles of at least one organic material suspended in said polar liquid crystalline medium.

8. The electro-rheological fluid according to claim 1, wherein the amount of said particles in the electro-rheological fluid as a whole is in the range from 5 to 70% wt.

9. The electro-rheological fluid according to claim 1, wherein the amount of said liquid-crystalline medium in the electro-rheological fluid as a whole is in the range from 2 to 95% wt.

10. The electro-rheological fluid according to claim 1, wherein said one or more mesogenic compounds of formula I and/or I* are selected from compounds of its sub-formulae I-1 and I-2: ##STR00133##

11. The electro-rheological fluid according to claim 10, wherein said liquid-crystalline medium further comprises one or more mesogenic compounds of formula III: ##STR00134## wherein L.sup.31 to L.sup.33 are independently of one another H or F, Z.sup.31 is COO or CF.sub.2O, R.sup.31 is an alkyl group, which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are each optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl or CN, and alternatively one of Y.sup.01 and Y.sup.02 can be H, R.sup.01 and R.sup.02 are, independently of each other, H or alkyl with 1 to 12 C-atoms, and X.sup.31 denotes halogen, CN, a mono- or polyhalogenated alkyl-, or alkoxy group having 1 to 6 C-atoms or a mono- or polyhalogenated alkenyl group having 2 to 6 C-atoms.

12. The electro-rheological fluid according to claim 11, wherein said one or more mesogenic compounds of formula III are selected from compounds of formulae III-1 and/or III-2 ##STR00135## wherein R.sup.31, L.sup.31 to L.sup.33 and X.sup.31 have the meanings given in claim 11.

13. The electro-rheological fluid according to claim 10, wherein R.sup.H is n-alkyl.

14. The electro-rheological fluid according to claim 10, wherein the concentration of the compounds of formulae I-1 and/or I-2 is in the range from 0.5% or more to 90% or less.

15. The electro-rheological fluid according to claim 10, wherein the concentration of the compounds of formulae I-1 and/or I-2 is in the range from 1% or more to 80 or less.

16. The electro-rheological fluid according to claim 1, wherein said liquid crystal medium comprises one or more mesogenic compounds selected formula I.

17. The electro-rheological fluid according to claim 1, wherein said liquid crystal medium comprises one or more mesogenic compounds selected formula I*.

18. The electro-rheological fluid according to claim 17, wherein ##STR00136## are independently of each other, ##STR00137##

19. The electro-rheological fluid according to claim 17, wherein said one or more mesogenic compounds of formula I are selected from sub-formulae I*-1 to I*-8: ##STR00138## wherein R.sup.11 and X.sup.11 are as defined in claim 17.

20. The electro-rheological fluid according to claim 19, wherein the concentration of the compounds of formulae I*-5 and/or I*-6 and/or I*-8 is in the range from 0.5% or more to 90% or less.

21. The electro-rheological fluid according to claim 19, wherein the concentration of the compounds of formulae I*-5 and/or I*-6 and/or I*-8 is in the range from 1% or more to 80 or less.

22. The electro-rheological fluid according to claim 1, wherein X.sup.11 is F, Cl, CN, CF.sub.3, CHF.sub.2, OCF.sub.3, OCFHCF.sub.3, OCFHCHF.sub.2, OCF.sub.2CH.sub.3, OCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CHF.sub.2, OCFHCF.sub.2CF.sub.3, OCFHCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CF.sub.3, OCF.sub.2CF.sub.2CClF.sub.2, OCClFCF.sub.2CF.sub.3 or CHCF.sub.2.

23. The electro-rheological fluid according to claim 1, wherein the concentration of the compounds of formulae I and/or I* is in the range from 0.5% or more to 90% or less.

24. The electro-rheological fluid according to claim 1, wherein the concentration of the compounds of formulae I and/or I* is in the range from 1% or more to 80% or less.

25. The electro-rheological fluid according to claim 1, wherein said liquid-crystalline medium further comprises one or more mesogenic compounds of formula II ##STR00139## L.sup.21 to L.sup.24 are independently of each other H or F, R.sup.21 is alkyl group, which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are each optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, ##STR00140## denotes a diradical group selected from: a) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene and 1,4-bicyclohexylene, in which, in addition, one or more non-adjacent CH.sub.2 groups may each be replaced by O or S and in which, in addition, one or more H atoms may each be replaced by F, and b) the group consisting of 1,4-phenylene and 1,3-phenylene, in which, in addition, one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by F, Z.sup.21 is COO, OCO or CF.sub.2O, and X.sup.21 denotes halogen, CN, a mono- or polyhalogenated alkyl-, or alkoxy group having 1 to 6 C-atoms or a mono- or polyhalogenated alkenyl group having 2 to 6 C-atoms.

Description

DETAILED DESCRIPTION

(1) In a preferred embodiment, the electrode structure adjacent to the electro-rheological fluid and having a significant component of the electrical field parallel with respect to the substrate main plane corresponds to an in-plane electrode structure. The in-plane electrode structure is so constituted that the electric field is applied to the adjacent electro-rheological fluid layer substantially in parallel with respect to the substrate main plain.

(2) In a further preferred embodiment, the in-plane electrode structure is selected from interdigitated electrodes, IPS electrodes, FFS electrodes or comb like electrodes, preferably interdigitated electrodes or comb like electrodes. In this connection, document WO 2008/104533 A1 describes arrangements where the electrodes are arranged as an IPS electrode and arrangements where an additional base electrode is disposed on the same substrate, as a fringe-field switching (FFS) electrode.

(3) Suitable electrode materials are commonly known to the expert, as for example electrodes made of metal or metal oxides, such as, for example transparent indium tin oxide (ITO), which is preferred according to the present invention.

(4) The spacing between the electrodes is preferably in the range from approximately 1 m to approximately 1000 m, more preferably in the range from approximately 10 m to approximately 500 m, and even more preferably in the range from approximately 10 m to approximately 100 m, in particular in the range from approximately 10 m to approximately 50 m.

(5) Preferably, the electrodes of the device are associated with a switching element, such as a thin film transistor (TFT) or thin film diode (TFD).

(6) Preferably, the driving voltage is in the range from 100 to 800 V, more preferably in the range from 150 to 600 V, even more in the range from 200 to 400 V.

(7) The applied electric field strengths are typically higher than approximately 1 V/m.sup.1, preferably higher than approximately 2 V/m.sup.1 and more preferably higher than approximately 3 V/m.sup.1.

(8) In a preferred embodiment, the electrode structure is preferably placed on the lower substrate and is therefore protected from mechanical damage. Unless the entire display assembly is intended to be flexible, preferably the electrodes may be formed on a low cost rigid substrate, which will further increase the durability of the device. In accordance with the invention, such substrate may consist of a polymeric material, of metal oxide, for example ITO and of glass, preferably glass or ITO, and in particular glass.

(9) The upper polymer cover sheet may comprise a robust but highly flexible polymer such as poly(ethylene terephthalate) (PET), polyolefin, polyester or other low cost polymers. This sheet may also carry additional functional layers such as anti-reflection coatings, self-cleaning or dirt-shedding layers, printed legends and the like. Preferably for use in a haptic display, at least some areas of the polymer sheet are, suitable thin to experience an haptic effect and highly transparent, while coloured or scattering films may also be used provided they allow some light through make the underlying display visible.

(10) In a preferred embodiment, the substrates are initially arranged with a separation in the range from approximately 10 m to approximately 1000 m from one another, preferably in the range from approximately 20 m to approximately 800 m from one another, and more preferably in the range from approximately 30 m to approximately 500 m from one another. The layer of the ER fluid is thereby located in the interspace.

(11) The substrate layers can be kept at a defined separation from one another, for example, by spacers or electrodes, which extend through the full cell thickness or projecting structures in the layer. Typical spacer materials are commonly known to the expert, as for example spacers made of plastic, silica, epoxy resins, etc.

(12) The simplicity of the device allows fabrication at low cost, and allows a wide choice of ER fluids to be used without any compatibility problems between this fluid and the other components of the display.

(13) A typical process for the production of a device according to the invention comprises i.a. the following steps: cutting and cleaning the lower substrate, on which the electrodes are arranged, providing a layer of the ER fluid onto the substrate, providing the upper, flexible substrate onto it, and assembling the cell using a UV curable adhesive.

(14) The device of the present invention can be used as a standalone unit or used in various types of optical and electro-optical devices.

(15) Said optical and electro optical devices include, without limitation electro-optical displays, liquid crystal displays (LCDs), non-linear optic (NLO) devices, and optical information storage devices.

(16) However, in a preferred embodiment the device according to the present invention comprises an electro-rheological fluid, which is selected from a binary solid-liquid phase mixture, preferably, a mixture comprising particles of at least one inorganic or organic material corresponding to the solid phase and at least one liquid-crystalline compound, which corresponds to the liquid phase.

(17) Suitable particle sizes are in the range from 1 nm to 1000 nm, more preferably in the range from 1 nm to 500 nm, even more preferably in the range from 1 nm to 250 nm.

(18) Such ER fluid may comprise a wide variety of particulate dispersions in liquid crystalline fluids or in isotropic dielectric liquids. A suitable and preferred electro-rheological fluid comprises particles of at least one inorganic or organic material suspended in a polar liquid crystalline medium.

(19) Suitable materials utilized for the particles in the ER fluid are selected from materials exhibiting a permittivity of at least 1 more preferably of at least 2 and even more preferably of at least 3.

(20) The permittivity of a material describes how much electric flux is generated per unit charge in that material. More electric flux exists in a material with a high permittivity (per unit charge) because of polarization effects. Permittivity is directly related to electric susceptibility, which is a measure of how easily a dielectric polarizes in response to an electric field. Thus, permittivity relates to a material's ability to transmit (or permit) an electric field. In SI units, permittivity is measured in farads per meter (F/m); electric susceptibility is dimensionless. They are related to each other through
=.sub.r.sub.0=(1+).sub.0
where .sub.r is the relative permittivity of the material, and .sub.0=8.8541878176.10.sup.12 F/m is the vacuum permittivity.

(21) In a preferred embodiment suitable particles are selected from particles of an inorganic material such as for example amorphous silicon and TiO.sub.2. In a likewise preferred embodiment suitable particles are selected from particles of an organic material such as PMMA, LiPMAC and styrene.

(22) In a preferred embodiment of the present invention, the amount of particles in the electro-rheological fluid as a whole is in the range from 5 to 70% wt, more preferably in the range from 8 to 60% wt, even more preferably in the range from 10 to 40% wt.

(23) A suitable ER fluid in accordance with the present invention comprises 2 or more, preferably at least 3, particularly preferably at least 4 and very particularly preferably at least 5, different liquid-crystalline compounds, which form the liquid crystalline component of the ER fluid.

(24) In a preferred embodiment of the present invention, the ER fluid comprises an amount of the liquid-crystalline component, with respect to the electro-rheological fluid as a whole, in the range from 2 to 95% wt, more preferably in the range from 5 to 90% wt, even more preferably in the range from 10 to 80% wt.

(25) In the following conditions for the liquid-crystalline component according to preferred embodiments of the present invention are given. These preferred conditions may be fulfilled individually or, preferably in combinations with each other. Binary combinations thereof are preferred, whereas ternary or higher combinations thereof are particularly preferred.

(26) In accordance with the invention, the liquid-crystalline component preferably exhibits positive values for the dielectric anisotropy . In this case, preferably has a value of 5, more preferably 10, even more preferably 25, especially 100, and in particular of 200.

(27) The liquid-crystal component in accordance with the present invention preferably have a clearing point of approximately 55 C. or more, more preferably approximately 60 C. or more, still more preferably 65 C. or more, particularly preferably approximately 70 C. or more and very particularly preferably approximately 75 C. or more.

(28) The liquid-crystal component in accordance with the present invention preferably exhibits a nematic phase. The nematic phase preferably extends at least from approximately 0 C. or less to approximately 65 C. or more, more preferably at least from approximately 20 C. or less to approximately 70 C. or more, very preferably at least from approximately 30 C. or less to approximately 70 C. or more and in particular at least from approximately 40 C. or less to approximately 90 C. or more. In individual preferred embodiments, it may be necessary for the nematic phase of the media according to the invention to extend to a temperature of approximately 100 C. or more and even to approximately 110 C. or more.

(29) In a preferred embodiment of the present invention, the liquid-crystalline component comprises one or more mesogenic compounds, which are selected from the group of compounds of formula I and/or I*,

(30) ##STR00001##
wherein L.sup.11 to L.sup.16 are independently of each other H or F,

(31) ##STR00002##
are independently of each other,

(32) ##STR00003##
preferably

(33) ##STR00004## R.sup.11 is alkyl group, which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl, or CN, and alternatively one of them may be H, R.sup.01 and R.sup.02 are, independently of each other, H, or alkyl with 1 to 12C-atoms, X.sup.11 halogen, CN, a mono-, di- or polyhalogenated alkyl-, or alkoxy group having 1 to 6C-atoms or a mono-, di- or polyhalogenated alkenyl group having 2 to 6C-atoms, preferably F, Cl, CN, CF.sub.3, CHF.sub.2, OCF.sub.3, OCFHCF.sub.3, OCFHCHF.sub.2, OCF.sub.2CH.sub.3, OCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CHF.sub.2, OCFHCF.sub.2CF.sub.3, OCFHCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CF.sub.3, OCF.sub.2CF.sub.2CClF.sub.2, OCClFCF.sub.2CF.sub.3 or CHCF.sub.2.

(34) In a preferred embodiment of the present invention the liquid-crystalline component of the ER fluid comprises one more compounds of formula I, preferably selected from the group of compounds of its sub-formulae I-1 and I-2, preferably of formula I-2,

(35) ##STR00005##
wherein R.sup.11 has the meaning given under formula I above and preferably is n-alkyl, most preferably ethyl, n-propyl, n-butyl, n-pentyl, or n-hexyl.

(36) In a preferred embodiment of the present invention the liquid-crystalline component of the ER fluid comprises one more compounds of formula I*, preferably selected from the group of compounds of its sub-formulae I*-1 to I*-8,

(37) ##STR00006##
wherein R.sup.11 has one of the meanings given above under formula I and preferably is n-alkyl, most preferably ethyl, n-propyl, n-butyl, n-pentyl, or n-hexyl, and X.sup.11 has one of the meanings given above under formula I and preferably is F, CN, CF.sub.3 OCHF.sub.2 or OCF.sub.3.

(38) In a preferred embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one or more compounds of formula II

(39) ##STR00007## L.sup.21 to L.sup.24 are independently of each other H or F, R.sup.21 has one of the meanings as indicated above for R.sup.11 in formula I,

(40) ##STR00008##
denotes a diradical group selected from the following groups: a) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene and 1,4-bicyclohexylene, in which, in addition, one or more non-adjacent CH.sub.2 groups may be replaced by O and/or S and in which, in addition, one or more H atoms may be replaced by F, b) the group consisting of 1,4-phenylene and 1,3-phenylene, in which, in addition, one or two CH groups may be replaced by N and in which, in addition, one or more H atoms may be replaced by F, Z.sup.21 is COO, OCO or CF.sub.2O, and X.sup.21 denotes halogen, CN, a mono- or polyhalogenated alkyl-, or alkoxy group having 1 to 6C-atoms or a mono- or polyhalogenated alkenyl group having 2 to 6 C-atoms, preferably F, Cl, CN, CF.sub.3, CHF.sub.2, OCF.sub.3, OCFHCF.sub.3, OCFHCHF.sub.2, OCF.sub.2CH.sub.3, OCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CHF.sub.2, OCFHCF.sub.2CF.sub.3, OCFHCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CF.sub.3, OCF.sub.2CF.sub.2CClF.sub.2, OCClFCF.sub.2CF.sub.3 or CHCF.sub.2, particular preferably F, CN or CF.sub.3.

(41) In a preferred embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one more compounds of formula II selected from the group of compounds of formulae II-1 to II-5

(42) ##STR00009##
wherein the parameters have one of the meanings as indicated under formula II.

(43) In a preferred embodiment of the present invention the liquid-crystalline component of the ER fluid the compounds of formula II-1 to II-5 are preferably selected from the group of compounds of the sub-formulae II-1a to II-5f, more preferably from the group of compounds of formula II-3-c and/or II-2f,

(44) ##STR00010## ##STR00011## ##STR00012##
wherein R.sup.21 has one of the meanings as indicated above in formula II and preferably is n-alkyl, most preferably ethyl, n-propyl, n-butyl, n-pentyl or n-hexyl.

(45) In a another embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one or more compounds of formula III,

(46) ##STR00013##
wherein L.sup.31 to L.sup.33 are independently of one another H or F, Z.sup.31 is COO or CF.sub.2O, R.sup.31 is an alkyl group, which is straight chain or branched, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl or CN, and alternatively one of them may be H, and R.sup.01 and R.sup.02 are, independently of each other, H or alkyl with 1 to 12 C-atoms, and X.sup.31 denotes halogen, CN, a mono- or polyhalogenated alkyl-, or alkoxy group having 1 to 6C-atoms or a mono- or polyhalogenated alkenyl group having 2 to 6 C-atoms, preferably F, Cl, CN, CF.sub.3, CHF.sub.2, OCF.sub.3, OCFHCF.sub.3, OCFHCHF.sub.2, OCF.sub.2CH.sub.3, OCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CHF.sub.2, OCFHCF.sub.2CF.sub.3, OCFHCF.sub.2CHF.sub.2, OCF.sub.2CF.sub.2CF.sub.3, OCF.sub.2CF.sub.2CClF.sub.2, OCClFCF.sub.2CF.sub.3 or CHCF.sub.2, particular preferably F, CN or CF.sub.3.

(47) In a further preferred embodiment the compounds of formula III are preferably selected from compounds of formulae III-1 and/or III-2

(48) ##STR00014##
wherein the parameters R.sup.31, L.sup.31 to L.sup.33 and X.sup.31 have one of corresponding meanings given above in formula III.

(49) In another preferred embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one or more compounds of formula III-1 selected from the group of compounds of its sub-formulae III-1 a to III-1d, more preferably of the compounds of formula III-1a

(50) ##STR00015##
wherein R.sup.31 and X.sup.31 have one of the meanings given under formula III above.

(51) In an especially preferred embodiment of the present invention the liquid-crystalline component of the ER fluid medium comprises one more compounds of formula III-1a to III-1d, which are preferably selected from the group of compounds of the following sub-formulae

(52) ##STR00016## ##STR00017##
wherein R.sup.31 has the meaning given under formula III above and preferably is n-alkyl, most preferably ethyl, n-propyl, n-butyl, n-pentyl or n-hexyl.

(53) In another preferred embodiment of the present invention the liquid-crystalline component of the ER fluid comprises one or more compounds of formula III-2 selected from the group of compounds of its sub-formulae III-2a to III-2d,

(54) ##STR00018##
wherein R.sup.31 and X.sup.31 have one of the meanings given under formula III above.

(55) In an especially preferred embodiment of the present the liquid-crystalline component of the ER fluid comprises one more compounds of formula III-2a to III-2d, which are preferably selected from the group of compounds of the following sub-formulae

(56) ##STR00019## ##STR00020##
wherein R.sup.31 has the meaning given under formula III above and preferably is n-alkyl, most preferably ethyl, n-propyl, n-butyl, n-pentyl or n-hexyl.

(57) In a preferred embodiment, the liquid-crystalline component of the ER fluid according to the present invention comprises one more compounds of formula IV

(58) ##STR00021##
wherein R.sup.41 has one of the meanings given for R.sup.11 under formula I above,

(59) ##STR00022##
are independently of each other

(60) ##STR00023##
preferably

(61) ##STR00024## X.sup.41 denotes F or CF.sub.3, preferably F.

(62) In a preferred embodiment of the present invention the liquid-crystalline component of the ER fluid comprises one more compounds of formula IV, preferably selected from the group of compounds of its sub-formulae IV-1 to IV-4,

(63) ##STR00025## R.sup.41 has one of the meanings given for R.sup.11 under formula I above, X.sup.41 denotes F or CF.sub.3, and in IV-1, IV-3 and IV-4 preferably F.

(64) In a preferred embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one more compounds of formula V,

(65) ##STR00026##
wherein L.sup.51 to L.sup.53 are, independently of each other, H or F R.sup.51 is an alkyl group, which is straight chain or branched, preferably has 1 to 20C-atoms, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, preferably n-alkyl, n-alkoxy with 1 to 9C-atoms, preferably 2 to 5C-atoms, alkenyl, alkenyloxy or alkoxyalkyl with 2 to 9C-atoms, preferably with 2 to 5C-atoms or halogenated alkyl, halogenated alkenyl or halogenated alkoxy, preferably mono fluorinated, di-fluorinated or oligofluorinated alkyl, alkenyl or alkoxy, most preferably n-alkyl, n-alkoxy, alkenyl, alkenyloxy or alkoxyalkyl, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl, or CN, and alternatively one of them may be H, R.sup.01 and R.sup.02 are, independently of each other, H or alkyl with 1 to 12 C-atoms, and X.sup.51 denotes F or CF.sub.3, or R.sup.51

(66) In a preferred embodiment of the present invention the liquid-crystalline component of the ER fluid comprises one more compounds of formula V, preferably selected from the group of compounds of its sub-formulae V-1 to V-8,

(67) ##STR00027## ##STR00028##
wherein R.sup.51 has the meaning given under formula II above.

(68) Preferably, the liquid-crystalline component of the ER fluid according to the present invention comprises one more compounds formula VI

(69) ##STR00029##
wherein R.sup.61 is alkyl, which is straight chain or branched, preferably has 1 to 20C-atoms, is unsubstituted, mono- or poly-substituted by F, Cl or CN, preferably by F, and in which one or more CH.sub.2 groups are optionally replaced, in each case independently from one another, by O, S, NR.sup.01, SiR.sup.01R.sup.02, CO, COO, OCO, OCOO, SCO, COS, CY.sup.01CY.sup.02 or CC in such a manner that O and/or S atoms are not linked directly to one another, preferably n-alkyl or n-alkoxy with 1 to 9C-atoms, preferably with 2 to 5C-atoms, alkenyl, alkenyloxy or alkoxyalkyl with 2 to 9C-atoms, preferably with 2 to 5C-atoms or halogenated alkyl, halogenated alkenyl or halogenated alkoxy with preferably up to 9C-atoms, preferably mono fluorinated, di-fluorinated or oligofluorinated alkyl, alkenyl or alkoxy with preferably up to 9C-atoms, most preferably n-alkyl, n-alkoxy, alkenyl, alkenyloxy or alkoxyalkyl with preferably up to 9C-atoms, L.sup.61 and L.sup.62 are, independently of each other, H or F, preferably one is F sand the other H or F and most preferably both are F, Y.sup.01 and Y.sup.02 are, independently of each other, F, Cl or CN, and alternatively one of them may be H, and R.sup.01 and R.sup.02 are, independently of each other, H or alkyl with 1 to 12 C-atoms.

(70) Preferably, the compounds of formula VI are selected from the compounds of formula VI-1 and VI-2, preferably from formula VI-2

(71) ##STR00030##
wherein R.sup.61 has the meaning given under formula VI above.

(72) An alkyl group or an alkoxy group, i.e. an alkyl group where the terminal CH.sub.2 group is replaced by O, in this application may be straight chain or branched. It is preferably straight-chain, has 1, 2, 3, 4, 5, 6, 7 or 8 carbon atoms and accordingly is preferably methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, or octoxy, furthermore nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, nonoxy, decoxy, undecoxy, dodecoxy, tridecoxy or tetradecoxy, for example.

(73) Oxaalkyl, i.e. an alkyl group in which one non-terminal CH.sub.2 group is replaced by O, is preferably straight-chain 2-oxapropyl(=methoxy-methyl), 2-(=ethoxymethyl) or 3-oxabutyl(=2-methoxyethyl), 2-, 3-, or 4-oxapentyl, 2-, 3-, 4-, or 5-oxahexyl, 2-, 3-, 4-, 5-, or 6-oxaheptyl, 2-, 3-, 4-, 5-, 6- or 7-oxaoctyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-oxanonyl or 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-oxadecyl, for example.

(74) An alkenyl group, i.e. an alkyl group wherein one or more CH.sub.2 groups are replaced by CHCH, may be straight chain or branched. It is preferably straight-chain, has 2 to 10C atoms and accordingly is preferably vinyl, prop-1-, or prop-2-enyl, but-1-, 2- or but-3-enyl, pent-1-, 2-, 3- or pent-4-enyl, hex-1-, 2-, 3-, 4- or hex-5-enyl, hept-1-, 2-, 3-, 4-, 5- or hept-6-enyl, oct-1-, 2-, 3-, 4-, 5-, 6- or oct-7-enyl, non-1-, 2-, 3-, 4-, 5-, 6-, 7- or non-8-enyl, dec-1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or dec-9-enyl.

(75) Especially preferred alkenyl groups are C.sub.2-C.sub.7-1E-alkenyl, C.sub.4-C.sub.7-3E-alkenyl, C.sub.5-C.sub.7-4-alkenyl, C.sub.6-C.sub.7-5-alkenyl and C.sub.7-6-alkenyl, in particular C.sub.2-C.sub.7-1E-alkenyl, C.sub.4-C.sub.7-3E-alkenyl and C.sub.5-C.sub.7-4-alkenyl. Examples for particularly preferred 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 having up to 5C-atoms are generally preferred.

(76) In an alkyl group, wherein one CH.sub.2 group is replaced by O and one by CO, these radicals are preferably neighboured. Accordingly, these radicals together form a carbonyloxy group COO or an oxycarbonyl group OCO. Preferably, such an alkyl group is straight chain and has 2 to 6C atoms.

(77) It is accordingly preferably acetyloxy, propionyloxy, butyryloxy, pentanoyloxy, hexanoyloxy, acetyloxymethyl, propionyloxymethyl, butyryloxymethyl, pentanoyloxymethyl, 2-acetyloxyethyl, 2-propionyloxy-ethyl, 2-butyryloxyethyl, 3-acetyloxypropyl, 3-propionyloxypropyl, 4-acetyloxybutyl, methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, butoxycarbonyl, pentoxycarbonyl, methoxycarbonylmethyl, ethoxy-carbonylmethyl, propoxycarbonylmethyl, butoxycarbonylmethyl, 2-(methoxycarbonyl)ethyl, 2-(ethoxycarbonyl)ethyl, 2-(propoxy-carbonyl)ethyl, 3-(methoxycarbonyl)propyl, 3-(ethoxycarbonyl)propyl, 4-(methoxycarbonyl)-butyl.

(78) An alkyl group wherein two or more CH.sub.2 groups are replaced by O and/or COO, it can be straight chain or branched. It is preferably straight chain and has 3 to 12C atoms. Accordingly it is preferably bis-carboxy-methyl, 2,2-bis-carboxy-ethyl, 3,3-bis-carboxy-propyl, 4,4-bis-carboxy-butyl, 5,5-bis-carboxy-pentyl, 6,6-bis-carboxy-hexyl, 7,7-bis-carboxy-heptyl, 8,8-bis-carboxy-octyl, 9,9-bis-carboxy-nonyl, 10,10-bis-carboxy-decyl, bis-(methoxycarbonyl)-methyl, 2,2-bis-(methoxycarbonyl)-ethyl, 3,3-bis-(methoxycarbonyl)-propyl, 4,4-bis-(methoxycarbonyl)-butyl, 5,5-bis-(methoxycarbonyl)-pentyl, 6,6-bis-(methoxycarbonyl)-hexyl, 7,7-bis-(methoxycarbonyl)-heptyl, 8,8-bis-(methoxycarbonyl)-octyl, bis-(ethoxycarbonyl)-methyl, 2,2-bis-(ethoxycarbonyl)-ethyl, 3,3-bis-(ethoxycarbonyl)-propyl, 4,4-bis-(ethoxycarbonyl)-butyl, 5,5-bis-(ethoxycarbonyl)-hexyl.

(79) An alkyl or alkenyl group that is monosubstituted by CN or CF.sub.3 is preferably straight chain. The substitution by CN or CF.sub.3 can be in any desired position.

(80) An alkyl or alkenyl group that is at least monosubstituted by halogen, it is preferably straight chain. Halogen is preferably F or Cl, in case of multiple substitutions preferably F. The resulting groups include also perfluorinated groups. In case of monosubstitution, the F or Cl substituent can be in any desired position, but is preferably in co-position. Examples for especially preferred straight-chain groups with a terminal F substituent are fluoromethyl, 2-fluoroethyl, 3-fluoropropyl, 4-fluorobutyl, 5-fluoropentyl, 6-fluorohexyl, and 7-fluoroheptyl. Other positions of F are not excluded.

(81) Halogen means F, Cl, Br and I and is preferably F or Cl, most preferably F.

(82) Each of R may be a polar or a non-polar group. In case of a polar group, it is preferably selected from CN, SF.sub.5, halogen, OCH.sub.3, SCN, COR.sup.5, COOR.sup.5 or a mono-oligo- or polyfluorinated alkyl or alkoxy group with 1 to 4C atoms. R.sup.5 is optionally fluorinated alkyl with 1 to 4, preferably 1 to 3C atoms. Especially preferred polar groups are selected of F, Cl, CN, OCH.sub.3, COCH.sub.3, COC.sub.2H.sub.5, COOCH.sub.3, COOC.sub.2H.sub.5, CF.sub.3, CHF.sub.2, CH.sub.2F, OCF.sub.3, OCHF.sub.2, OCH.sub.2F, C.sub.2F.sub.5 and OC.sub.2F.sub.5, in particular F, Cl, CN, CF.sub.3, OCHF.sub.2 and OCF.sub.3. In case of a non-polar group, it is preferably alkyl with up to 15C atoms or alkoxy with 2 to 15C atoms.

(83) In addition, compounds containing an achiral-branched alkyl group may occasionally be of importance, for example, due to a reduction in the tendency towards crystallization. Branched groups of this type generally do not contain more than one chain branch. Preferred achiral branched groups are isopropyl, isobutyl(=methylpropyl), isopentyl(=3-methylbutyl), isopropoxy, 2-methyl-propoxy and 3-methylbutoxy.

(84) All herein mentioned compounds are accessible by the usual methods known to the expert. Starting materials are either commercially available or accessible by published methods such as, for example, in Houben-Weyl, Methoden der organischen Chemie [Methods of Organic Chemistry], Thieme-Verlag, Stuttgart.

(85) Comprising in this application means in the context of compositions that the entity referred to, e.g. the medium or the component, contains the compound or compounds in question, preferably in a total concentration of 10% or more and most preferably of 20% or more.

(86) Predominantly consisting, in this context, means that the entity referred to contains 80% or more, preferably 90% or more and most preferably 95% or more of the compound or compounds in question.

(87) Entirely consisting, in this context, means that the entity referred to contains 98% or more, preferably 99% or more and most preferably 100.0% of the compound or compounds in question.

(88) The concentration of the compounds of formula I and/or I*, preferably selected from the compounds of formulae I-1 and/or I-2 and/or I*-2 and/or I*-5 and/or I*-6 and/or I*-8 are contained in the liquid-crystalline component of the ER fluid according to the present application preferably is in the range from 0.5% or more to 90% or less, more preferably in the range from 1% or more to 80% or less and most preferably in the range from 10% or more to 75% or less.

(89) In a preferred embodiment the liquid-crystalline component of the ER fluid according to the instant invention, comprise one compound or more compounds selected from the group of compounds of formula II, preferably in a total concentration of 1% to 40% by weight, more preferably in a concentration of 1% to 35% by weight, and most preferably in a concentration of case of 1% to 10% by weight for each single compound present, or one compound or more compounds of formula III-1, preferably in a total concentration of 1% to 40% by weight, more preferably in a concentration of 1% to 30% by weight, and most preferably in a concentration of case of 1% to 20% by weight for each single compound present, and/or one compound or more compounds of formula III-2, preferably in a total concentration of 1% to 25% by weight, more preferably in a concentration of 1% to 10% by weight, and most preferably in a concentration of case of 1% to 15% by weight for each single compound present. one compound or more compounds selected from the group of compounds of formula IV, preferably in a concentration of 1% to 25% by weight, and/or optionally, preferably obligatorily, one or more compounds selected from the group of compounds of formulae V preferably in a concentration of 1% to 25% by weight, and/or optionally, preferably obligatorily, one or more compounds selected from the group of compounds of formula VI preferably in a concentration of 1% to 25% by weight.

(90) In another embodiment of the present invention, the liquid-crystalline component of the ER fluid according to the instant invention, comprise

(91) Suitable the liquid-crystalline components of the ER fluid preferably comprises one or more compounds selected from the group of compounds of formulae I and/or I* and II and optionally III, preferably in a total concentration in the range from 5% or more to 99% or less, preferably from 10% or more to 95% or less and most preferably from 12% or more to 90% or less.

(92) In particular, the liquid-crystalline component of the ER fluid preferably comprises one or more compounds of formula I and or I* in a total concentration in the range from 40% or more to 80% or less, preferably from 45% or more to 75% or less and most preferably from 50% or more to 70% or less.

(93) In case the liquid-crystalline component of the ER fluid comprises one or more compounds formula II, the total concentration of these compounds preferably is in the range from 1% or more to 35% or less, preferably from 2% or more to 20% or less and most preferably from 4% or more to 17% or less.

(94) In case the liquid-crystalline component of the ER fluid comprises one or more compounds formula III, the total concentration of these compounds preferably is in the range from 1% or more to 75% or less, preferably from 2% or more to 50% or less and most preferably from 3% or more to 30% or less.

(95) In case the liquid-crystalline component of the ER fluid comprises one or more compounds formula IV the total concentration of these compounds preferably is in the range from 1% or more to 20% or less, preferably from 2% or more to 15% or less and, most preferably, from 5% or more to 10% or less.

(96) In case the liquid-crystalline component of the ER fluid comprises one or more compounds formula V the total concentration of these compounds preferably is in the range from 3% or more to 45% or less, preferably from 5% or more to 40% or less and most preferably from 7% or more to 35% or less.

(97) In case the liquid-crystalline component of the ER fluid comprises one or more compounds formula VII the total concentration of these compounds preferably is in the range from 1% or more to 15% or less, preferably from 3% or more to 12% or less and most preferably from 5% or more to 10% or less.

(98) Preferred embodiments are indicated below: The medium comprises one, two, three, four or more compounds of formula I and/or 1*, preferably selected from the group of compounds of formulae I-1, I-2, and/or I*-2, I*-5, I*-6, I*-8 the medium comprises one, two or more compounds of formula II, preferably of formulae II-3 and II-4, more preferably of formulae II-3a, II-3c and II-4d, and/or the medium comprises one or more compounds of formula III preferably of formulae III-1 and III-2, more preferably of formulae III-1b and III-2a and/or the medium comprises one, two or more compounds of formula IV, and/or the medium comprises optionally one, two, three or more compounds of formula V, and/or the medium comprises optionally one, two, three or more compounds of formula VI, preferably of formula VI-2 and/or

(99) Preference is given, in particular, to a liquid-crystalline component of the ER fluid, which, besides one or more compounds of the formula I and/or I*, comprise one or more compounds of the formula III.

(100) The compounds of the formulae I to VI are colourless, stable, and readily miscible with one another and with other liquid-crystalline materials.

(101) The optimum mixing ratio of the compounds of the formulae I and/or I* and II and III depends substantially on the desired properties, on the choice of the components of the formulae I and/or I*, II and/or III, and on the choice of any other components that may be present. Suitable mixing ratios within the range given above can easily be determined from case to case.

(102) The total amount of compounds of the formulae I and II and optionally III in the liquid-crystalline component of the ER fluid in accordance with the present invention is in many cases not crucial. The mixtures can therefore comprise one or more further components for the purposes of optimisation of various properties. However, the observed effect on the operating voltage and the operating temperature range is generally greater, the higher the total concentration of compounds of the formulae I and II and optionally III.

(103) In a particularly preferred embodiment, the liquid-crystalline component of the ER fluid in accordance with the present invention comprises one or more compounds each of the formulae I and II and optionally III. A favourable synergistic effect with the compounds of the formula I results in particularly advantageous properties.

(104) The individual compounds of the formulae I, I*, II to VI, which can be used in the liquid-crystalline component of the ER fluid according to the invention, either are known or can be prepared analogously to the known compounds.

(105) Other mesogenic compounds, which are not explicitly mentioned above, can optionally and advantageously also be used in an amount 60%, preferably 55%, even more preferably 55%, in the media in accordance with the present invention. Such compounds are known to the person skilled in the art and are, for example, selected from the group of compounds characterized by the formulae A, B, C, D, E, and F:
R-L-E-R(A)
R-L-CF.sub.2O-E-R(B)
R-L-COO-E-R(C)
R-L-CH.sub.2CH.sub.2-E-R(D)
R-L-CHCH-E-R(E)
R-L-CC-E-R(F)
wherein

(106) L, E are each independently selected from the group consisting of -Phe-, -Cyc-, -Phe-Phe-, -Cyc-Phe-, -Cyc-Cyc-, -Dio-, -G-Phe-, and -G-Cyc-; as well as the mirror images of the groups mentioned before, wherein Phe is unsubstitued 1,4-phenylene, Cyc is trans-1,4-cyclohexylene or 1,4-cyclohexenylene, Dio is 1,3-dioxane-2,5-diyl, and G is 2-(trans-1,4-cyclohexyl)-ethyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, or 1,3-dioxane-2,5-diyl;

(107) preferably at least one of the groups L and E is Cyc, Phe; more preferably E is Cyc, Phe or Phe-Cyc.

(108) In a preferred embodiment of the present invention the liquid crystal compositions of the present invention contain one or more components selected from the group consisting of formulae A, B, C, D, E, and F, wherein L and E are selected from the group consisting of Cyc, Phe, and at the same time one or more components selected from compounds of formulae A, B, C, D, and E, wherein one of the groups L and E is selected from the group consisting of Cyc, Phe, and the other group is selected from the group consisting of -Phe-Phe, -Cyc-Phe-, -Cyc-Cyc-, -G-Phe-, and -G-Cyc, and optionally one or more components selected from the group consisting of the compounds of formulae A, B, C, D, E, and F, wherein the groups L and E are selected from the group consisting of -Cyc-Phe-, -Cyc-Cyc-, -G-Phe-, and -G-Cyc.

(109) R and R each are independently of each other alkyl, alkenyl, alkoxy, alkenyloxy or alkanoyloxy having from 1 to 8 carbon atoms, preferably R and R are different and at least one of R and R is alkyl or alkenyl.

(110) In a further embodiment R is alkyl, alkenyl, alkoxy, alkenyloxy, or alkanoyloxy having from 1 to 8 carbon atoms, preferably alkyl or alkenyl, and

(111) The compounds of the present invention are either commercially available or can be synthesized according to or in analogy to methods which are known per se and which are described in standard works of organic chemistry such as, for example, Houben-Weyl, Methoden der organischen Chemie, Thieme-Verlag, Stuttgart.

(112) Throughout the description and claims of this specification, the words comprise and contain and variations of the words, for example comprising and comprises, mean including but not limited to, and are not intended to (and do not) exclude other components. On the other hand, the word comprise also encompasses the term consisting of but is not limited to it.

(113) The liquid-crystal component of the ER fluid according to the present invention is prepared in a manner conventional per se. In general, the desired amount of the components used in lesser amount is dissolved in the components making up the principal constituent, preferably at elevated temperature. It is also possible to mix solutions of the components in an organic solvent, for example in acetone, chloroform or methanol, and to remove the solvent again, for example by distillation, after thorough mixing. It is furthermore possible to prepare the mixtures in other conventional manners, for example through the use of pre-mixes, for example homologue mixtures, or using so-called multibottle systems.

(114) The electro-rheological fluid as described above and below is especially suitable for the use in a device according to the present invention as described above and below.

(115) The functional principle of the device according to the invention will be explained in detail below. It is noted that no restriction of the scope of the claimed invention, which is not present in the claims, is to be derived from the comments on the assumed way of functioning.

(116) In operation, the user is expected to touch the flexible cover substrate of the device. Hereby, a direct finger touch is preferred but indirect touch with a pencil or stylus is also possible. As the point of touch is moved across the device, activation of electrodes in certain areas leads to the spontaneous solidification of the ER fluids, or at least to the dramatically increase of its viscosity, in response to an electric field, due to the formation of particle chains that bridge the electrodes. Therefore, a detectable change in resistance to movement, apparent surface relief, or surface texture is provided. No other means for displacing the ER fluid is required.

(117) It will be appreciated that variations to the foregoing embodiments of the invention can be made while still falling within the scope of the invention. Alternative features serving the same, equivalent, or similar purpose may replace each feature disclosed in this specification, unless stated otherwise. Thus, unless stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

(118) All of the features disclosed in this specification may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. In particular, the preferred features of the invention are applicable to all aspects of the invention and may be used in any combination. Likewise, features described in non-essential combinations may be used separately (not in combination).

(119) It will be appreciated that many of the features described above, particularly of the preferred embodiments, are inventive in their own right and not just as part of an embodiment of the present invention. Independent protection may be sought for these features in addition to or alternative to any invention presently claimed.

(120) The parameter ranges indicated in this application all include the limit values, unless expressly stated otherwise.

(121) The different upper and lower limit values indicated for various ranges of properties in combination with one another give rise to additional preferred ranges.

(122) Compounds containing a vinyl end group and compounds containing a methyl end group have low rotational viscosity.

(123) In the present invention and especially in the following examples, the structures of the mesogenic compounds are indicated by means of abbreviations also referred to as acronyms. In these acronyms, the chemical formulae are abbreviated as follows using Tables A to C below. All groups C.sub.nH.sub.2n+1, C.sub.mH.sub.2m+1 and C.sub.lH.sub.2l+1 or C.sub.nH.sub.2n1, C.sub.mH.sub.2m1 and C.sub.lH.sub.2l1 denote straight-chain alkyl or alkenyl, preferably 1-E-alkenyl, respectively, in each case having n, m or l C atoms. Table A lists the codes used for the ring elements of the core structures of the compounds, while Table B shows the linking groups. Table C gives the meanings of the codes for the left-hand or right-hand end groups. Table D shows illustrative structures of compounds with their respective abbreviations. Table E shows illustrative structures of stabilizers.

(124) TABLE-US-00001 TABLE A Ring elements C P D DI A AI G GI U UI 0 Y M MI N NI Np dH N3f N3fI tH 0 tHI tH2f tH2fI K KI L LI F FI

(125) TABLE-US-00002 TABLE B Linking groups E CH.sub.2CH.sub.2 Z COO V CHCH ZI OCO X CFCH O CH.sub.2O XI CHCF OI OCH.sub.2 B CFCF Q CF.sub.2O T CC QI OCF.sub.2 W CF.sub.2CF.sub.2 T CC

(126) TABLE-US-00003 TABLE C End groups Left-hand side Right-hand side Use alone -n- C.sub.nH.sub.2n+1 -n C.sub.nH.sub.2n+1 -nO C.sub.nH.sub.2n+1O -nO OC.sub.nH.sub.2n+1 V CH.sub.2CH V CHCH.sub.2 -nV C.sub.nH.sub.2n+1CHCH -nV C.sub.nH.sub.2nCHCH.sub.2 Vn- CH.sub.2CHC.sub.nH.sub.2n+1 Vn CHCHC.sub.nH.sub.2n+1 -nVm- C.sub.nH.sub.2n+1CHCHC.sub.mH.sub.2m -nVm C.sub.nH.sub.2nCHCHC.sub.mH.sub.2m+1 N NC N CN S SCN S NCS F F F F CL Cl CL Cl M CFH.sub.2 M CFH.sub.2 D CF.sub.2H D CF.sub.2H T CF.sub.3 T CF.sub.3 MO CFH.sub.2O OM OCFH.sub.2 DO CF.sub.2HO OD OCF.sub.2H TO CF.sub.3O OT OCF.sub.3 OXF CF.sub.2CHO OXF OCHCF.sub.2 A HCC A CCH -nA CnH.sub.2n+1CC An CCC.sub.nH.sub.2n+1 NA NCCC AN CCCN Use together with one another and/or with others - . . . A . . . - CC - . . . A . . . CC - . . . V . . . - CHCH - . . . V . . . CHCH - . . . Z . . . - COO - . . . Z . . . COO - . . . ZI . . . - OCO - . . . ZI . . . OCO - . . . K . . . - CO - . . . K . . . CO - . . . W . . . - CFCF - . . . W . . . CFCF in which n and m each denote integers, and the three dots . . . are place-holders for other abbreviations from this table.

(127) The following table shows illustrative structures together with their respective abbreviations. These are shown in order to illustrate the meaning of the rules for the abbreviations. They furthermore represent compounds, which are preferably used.

(128) TABLE-US-00004 TABLE D Illustrative structures 0 0 0 0 00 01 02 03 04 in which n (m and l) preferably, independently of one another, denote(s) an integer from 1 to 7, preferably from 2 to 6.

(129) The following table, Table E, shows illustrative compounds that can be used as stabiliser in the mesogenic media according to the present invention.

(130) TABLE-US-00005 TABLE E 05 06 07 08 09 0 0

(131) In a preferred embodiment of the present invention, the liquid-crystalline component of the ER fluid comprises one or more compounds selected from the group of the compounds from Table E.

(132) The media according to the present application preferably comprise two or more, preferably four or more, compounds selected from the group consisting of the compounds from the above tables.

Examples

(133) The invention will now be described in more detail by reference to the following working examples, which are illustrative only and do not limit the scope of the invention.

Mixture Examples

(134) The following mixtures are prepared.

(135) TABLE-US-00006 Composition and properties liquid crystal mixture M-1 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 PGU-3-F 4.0 T(N,I) = 80 C. 2 PUQU-3-F 10.0 n.sub.o(20 C., 589 nm) = 1.4898 3 CCQU-3-F 8.0 n.sub.e(20 C., 589 nm) = 1.6218 4 CPGU-3-OT 4.0 n(20 C., 589 nm) = 0.1320 5 APUQU-2-F 6.0 .sub.(20, 1 kHz) = 3.7 6 APUQU-3-F 4.0 (20, 1 kHz) = 11.5 7 CCGU-3-F 8.0 8 PGUQU-3-F 4.0 9 PCH-301 8.0 10 CC-3-V 19.0 11 CC-3-V 4.0 12 CC-%-V 4.0 13 PP-1-2V1 4.0 14 CCP-V-1 2.0 15 PGP-2-3 2.0 16 PGP-2-2V 9.0 100.0

(136) TABLE-US-00007 Composition and properties liquid crystal mixture M-2 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 ME2N.F 14.0 T(N,I) = 70 C. 2 ME3N.F 14.0 n.sub.o(20 C., 589 nm) = 1.5028 3 ME4N.F 13.0 n.sub.e(20 C., 589 nm) = 1.6565 4 ME5N.F 13.0 n(20 C., 589 nm) = 0.1537 5 PYP-4 11.0 .sub.(20, 1 kHz) = 55.0 6 CPZG-3-N 4.0 (20, 1 kHz) = 11.8 7 CPZG-4-N 4.0 8 CCZU-2-F 8.0 9 CCZU-3-F 11.0 10 CCPC-3-3 4.0 11 CCPC-3-3 4.0 100.0

(137) TABLE-US-00008 Composition and properties liquid crystal mixture M-3 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 GUQGU-3-F 8.0 T(N,I) = 72.5 C. 2 GUQGU-4-F 6.0 n.sub.o(20 C., 589 nm) = 1.4882 3 GUQGU-5-F 4.0 n.sub.e(20 C., 589 nm) = 1.6811 4 GUUGU-3-N 6.0 n(20 C., 589 nm) = 0.1929 5 GUQU-3-F 7.0 .sub.(20, 1 kHz) = 11.5 6 GUQU-4-F 6.0 (20, 1 kHz) = 202.1 7 GUQGU-2-T 12.0 8 GUQGU-3-T 12.0 9 GUQGU-4-T 12.0 10 GUQGU-5-T 12.0 11 DPGU-4-F 8.0 12 PGU-5-T 3.0 13 PGU-4-T 4.0 100.0

(138) TABLE-US-00009 Composition and properties liquid crystal mixture M-4 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 GUQU-3-N 8.0 T(N,I) = 70 C. 2 GUQU-4-N 8.0 n.sub.o(20 C., 589 nm) = 1.4937 3 GUUQU-3-N 10.0 n.sub.e(20 C., 589 nm) = 1.6838 4 ME2N.F 10.0 n(20 C., 589 nm) = 0.1901 5 ME3N.F 10.0 .sub.(20, 1 kHz) = 152.8 6 PUQGU-3-T 7.0 (20, 1 kHz) = 236.3 7 PUQGU-4-T 8.0 8 PUQGU-5-T 7.0 9 DUUQU-3-F 7.0 10 DUUQU-4-F 8.0 11 DUUQU-5-F 8.0 12 DPGU-4-F 5.0 13 PPGU-3-F 4.0 100.00

(139) TABLE-US-00010 Composition and properties liquid crystal mixture M-5 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 DPGU-4-F 8.00 T(N,I) = 76 C. 2 DUUQU-3-F 3.00 n.sub.o(20 C., 589 nm) = 3 DUUQU-4-F 10.00 n.sub.e(20 C., 589 nm) = 4 DUUQU-5-F 7.00 n(20 C., 589 nm) = 5 GUQGU-2-T 7.00 .sub.(20, 1 kHz) = 6 GUQGU-3-T 8.00 (20, 1 kHz) = 7 GUQU-2-N 13.00 8 GUQU-3-N 12.00 9 GUUQU-3-N 10.00 10 GUUQU-4-N 10.00 11 ME2N.F 12.00 100.00

(140) TABLE-US-00011 Composition and properties liquid crystal mixture M-6 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 PGU-3-F 4.0 T(N,I) = 80 C. 2 PUQU-3-F 10.0 n.sub.o(20 C., 589 nm) = 1.4945 3 CPGU-3-OT 4.0 n.sub.e(20 C., 589 nm) = 1.6265 4 APUQU-2-F 4.0 n(20 C., 589 nm) = 0.1320 5 APUQU-3-F 4.0 .sub.(20, 1 kHz) = 3.5 6 CCGU-3-F 4.0 (20, 1 kHz) = 8.3 7 PGUQU-3-F 4.0 8 PCH-301 12.0 9 CC-3-V 20.0 10 CC-3-V1 4.0 11 CC-5-V 4.0 12 PP-1-2V1 2.0 13 CCP-V-1 4.0 14 CCP-V2-1 4.0 15 PGP-2-3 2.0 16 PGP-2-2V 10.0 17 BCH-32 2.0 18 BCH-52 2.0 100.0

(141) TABLE-US-00012 Composition and properties liquid crystal mixture M-7 Composition Compound Conc./ No. Abbreviation mass-% Physical Properties 1 GUQGU-3-T 10.0 T(N,I) = C. 2 GUQGU-4-T 10.0 n.sub.o(20 C., 589 nm) = 3 GUQGU-5-T 10.0 n.sub.e(20 C., 589 nm) = 4 GUUGU-3-N 10.0 n(20 C., 589 nm) = 5 GUQU-2-N 11.0 .sub.(20, 1 kHz) = 6 GUQU-3-N 11.0 (20, 1 kHz) = 7 GUQU-5-N 11.0 8 DPGU-4-F 5.0 9 PUQGU-3-T 11.0 10 PUQGU-5-T 11.0 100.0
Formulation

(142) In all the examples reported here the following procedure for formulation is followed.

(143) The solid materials are weighed out. After all components have been added a magnetic stirring flea is placed into the sample vial. The sample is then mixed for 12 hour to ensure full dispersion of the particles in the liquid crystalline component. The formulation is then placed in a vacuum oven to degas fully before testing.

EXAMPLES

Example 1

(144) A commercially available porous PMMA particles (0.1494 g, =3.0) is dispersed in M1 (0.3633 g, =11.5) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 2

(145) A commercially available porous PMMA particles (0.1456 g, =3.0) is dispersed in M2 (0.3543 g, =55) following the method described above.

(146) Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 3

(147) A commercially available porous PMMA particles (0.1462 g, =3.0) is dispersed in M3 (0.3541 g, =200) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 4

(148) A commercially available porous PMMA particles (0.1480 g, =3.0) is dispersed in M4 (0.3579 g, =360) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 5

(149) A commercially available porous PMMA particles (0.1444 g, =3.0) is dispersed in M5 (0.3641 g, =500) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 6

(150) A commercially available Lithium polymethacrylate (LiPMAC, 0.1490 g) is dispersed in M6 (0.3529 g, =400) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 7

(151) A commercially available porous Lithium polymethacrylate (LiPMAC, 0.0846 g) is dispersed in M7 (0.2017 g, =400) with the dispersant Tegorad 2800 (0.0014 g) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 8

(152) A commercially available Styrene particles (0.0353 g, =2.5) is dispersed M4 (0.2258 g, =360) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 9

(153) A commercially available Amorphous Si particles (0.0371 g, =3.9) is dispersed in M4 (0.2198 g, =360) following the method above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

Example 10

(154) A commercially available titanium dioxide particles (0.0362 g, =110) is dispersed in M4 (0.2258 g, =360) following the method described above. Once formulated this sample is then tested following the method described in Force Gauge Measurements.

(155) Force Gauge Measurements

(156) The force gauge measurements were taken using a Sauter FH-2 force gauge mounted on its commercially available test stand. This allowed the force gauge to be lowered into a purpose built high voltage sample chamber. The sample chamber is mounted onto a motorized labjack (L490MZ/M) which provided a means to translate the sample at micrometer precision.

(157) The sample to be tested is placed onto a glass substrate (held in the high voltage sample chamber) with inter-digitated ITO electrodes. Once the sample is deposited a thin plastic substrate is placed onto to prevent contamination of the force gauge probe.

(158) The process to collect the data is as follows; 1. The probe is lower such that it is in contact with the plastic substrate. 2. An in-house program is initiated to log the data given by the force gauge. 3. The motorized labjack is raised a total of 100 microns in 10 micron steps where there is a 10 s delay between each step. 4. After the 10th step the force gauge is left in place for 100 s to record the equilibrium behaviour. 5. The data logging is stopped 6. The force gauge is raised 7. Using an insulated blunt rod the sample is probe in order to ensure that it returns to an equilibrium disordered state.

(159) This process is repeated in total 6 times; 3 times where no voltage is applied to the sample and 3 time where a high voltage is applied.

(160) When the voltage is applied the formulation experiences an electric field of 3.75 V m.sup.1.

(161) Force Gauge Data

(162) The following table shows the collected data of the force gauge measurements.

(163) TABLE-US-00013 Particle Ave ER Conc. response No. Type [% wt] Mixture [N] 1 Porous 30 3 M1 11.5 0.086 PMMA 2 Porous 30 3 M2 55 0.060 PMMA 3 Porous 30 3 M3 200 0.028 PMMA 4 Porous 30 3 M4 360 0.035 PMMA 5 Porous 30 3 M5 500 0.053 PMMA 6 LiPMAC 30 M6 8.3 0.033 7 LiPMAC 30 M7 400 0.064 8 Styrene 15 2.5 M4 360 0.054 9 Amorph. 15 3.9 M4 360 0.261 Si 10 TiO.sub.2 15 110 M4 360 0.282