WO2009037506A1

WO2009037506A1 - Display devices

Info

Publication number: WO2009037506A1
Application number: PCT/GB2008/050839
Authority: WO
Inventors: Martyn Earle
Original assignee: The Queen's University Of Belfast
Priority date: 2007-09-19
Filing date: 2008-09-18
Publication date: 2009-03-26
Also published as: GB0718283D0

Abstract

Disclosed are display devices comprising ionic liquids and more specifically devices comprising ionic liquids and at least one other substance, wherein the at least one other substance is a solid or a liquid and is generally immiscible with, or 5 insoluble in, the ionic liquid. The display devices use convection and/or mechanically formed currents to create interesting visual effects, particularly when the container is illuminated and the ionic liquid and the at least one other substance are coloured.

Description

Display Devices

The present invention relates to a display devices comprising ionic liquids and more specifically to devices comprising ionic liquids and at least one other substance, wherein the at least one other substance is a solid or a liquid and is generally immiscible with, or insoluble in, the ionic liquid. The display devices preferably use convection currents to create interesting visual effects, particularly when the container is illuminated and the ionic liquid and the at least one other substance are coloured.

Ionic liquids are a novel class of compounds which have been developed over the last few years. The term "ionic liquid" as used herein refers to a liquid that is capable of being produced by melting a solid, and when so produced consists solely of ions. Ionic liquids may be derived from organic salts.

An ionic liquid may be formed from a homogeneous substance comprising one species of cation and one species of anion, or it can be composed of more than one species of cation and/or anion. Thus, an ionic liquid may be composed of more than one species of cation and one species of anion. An ionic liquid may further be composed of one species of cation, and one or more species of anion.

Still further, an ionic liquid may be composed of more than one species of cation and more than one species of anion.

The term "ionic liquid" includes compounds having both high melting temperature and compounds having low melting points, e.g. at or below room temperature (i.e.

15 to 30°C). The latter are often referred to as "room temperature ionic liquids" and often derived from organic salts having pyridinium and imidazolium based cations. A feature of ionic liquids is that they have particularly low (essentially zero) vapour pressures. Many organic ionic liquids have low melting points, for example, less than 100°C, particularly less than 60°C, and around room temperature, e.g. 15 to 30°C, and some have melting points well below 0°C. In one aspect of the present invention, the ionic liquid has a melting-point above ambient temperature, for example 40°C or higher, or 25⁰C or higher. Alternatively the ionic liquid may have a melting point below room temperature, for example 2O⁰C or lower, 10⁰C or lower, or O⁰C or lower.

The inventors of the present invention have surprisingly found that the use of ionic liquids in the display devices of the present invention provides a number of advantages over display devices known in the art. A wide range of ionic liquids may be used, and the skilled person is able to select ionic liquids having precisely defined physical properties, for example, properties such as the density, viscosity, immiscibility, and thermal expansion coefficient. The properties of the ionic liquid may readily be selected/adjusted by a person skilled in the art so as to give rise to unique visual effects in comparison with prior art display devices. Advantageously, ionic liquids are also stable to heat, ultraviolet and visible light, water and organic solvents. Thus ionic liquids can be exposed to any of these in the display device of the present invention without significant degradation. Ionic liquids are preferably useful for the present invention as they additionally possess negligible vapour pressure, temperature stability, low flammability and are recyclable thereby making them environmentally friendly.

According to the present invention there is provided a display device having a container which comprises:

(a) an ionic liquid; and

(b) at least one other solid or liquid substance which is generally immiscible with the ionic liquid.

According to a further aspect of the present invention there is provided a display device having a container which comprises:

(a) an ionic liquid;

(b) at least one other solid or liquid substance which is generally immiscible with the ionic liquid; and

(c) one or more heating means. According to yet a further aspect of the present invention there is provided a display device having a container which comprises:

(a) an ionic liquid;

(c) one or more mechanical means for creating visual patterns.

The ionic liquid may be defined by the formula:

[Cat⁺] [X ],

wherein [Cat⁺] is a cationic species and [X ] is an anionic species.

In accordance with the present invention, [Cat⁺] may be a cationic species selected from ammonium, phosphonium, imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolium, azathiazolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrrolium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, /so-oxazolium, iso- triazolium, tetrazolium, benzofuranium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annulenium, phthalazinium, quinazolinium, quinoxalinium, quinolinium, isoquinolinium, thiazinium, azaannulenium, ammonium, pyrrolidinium, diazabicycloundecenium, diazabicyclononenium, diazabicyclodecenium, phosphonium or triazadecenium.

Preferably, [Cat⁺] is a heterocyclic species selected from:-

and

wherein: R^a, R^b, R^c, R^d, R^e, R^f, R⁹ and R^h can be the same or different, and are each independently selected from hydrogen, a Ci to C₁₅, straight chain or branched alkyl group, a C3 to Cs cycloalkyl group, or a Ce to do aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to Ce alkoxy, Ce to do ^aryl_> CN, OH, NO₂, C₇ to do aralkyl and C₇ to do alkaryl, or any two of R^b, R^c, R^d, R^e and R^f attached to adjacent carbon atoms form a methylene chain -(CH₂)_q- wherein q is from 3 to 6.

Preferably, R^a and R⁹ may be each independently selected from Ci to do, linear or branched, alkyl, and one of R^a and R⁹ may also be hydrogen. More preferably, R^a and R⁹ may be selected from Ci to Cs linear or branched alkyl, and most preferably Ci to Ce linear or branched alkyl.

Further examples include wherein one of R^a and R⁹ is selected from ethyl, butyl, hexyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl and octadecyl.

In a further embodiment, [Cat]⁺ may be a cationic species selected from:

and

wherein: R^a, R^b, R^c, R^d, and R^e are as defined above.

In a further preferred embodiment, [Cat⁺] may be an acrylic species selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺ and [P(R^a)(R^b)(R^c)(R^d)]⁺

wherein R^a, R^b, R^c, and R^d are each independently selected from hydrogen, a Ci to Ci5, straight chain or branched alkyl group, a C₃ to C₈ cycloalkyl group, or a C₆ to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C₆ alkoxy, C₆ to C₁₀ aryl, CN, OH, NO₂, C₇ to C₁₀ aralkyl and C₇ to C₁₀ alkaryl.

More preferably, R^a, R^b, R^c, and R^d are each independently selected from hydrogen, a d to Ci₀, straight chain or branched alkyl group, a C₃ to C₆ cycloalkyl group, or a C₆ to C₈ aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C₆ alkoxy, C₆ to Ci₀ aryl, CN, OH, NO₂, C₇ to C₃₀ aralkyl and C₇ to C₃₀ alkaryl. More preferably Cat⁺ is selected from:

[(CH₃)₃N(R^a)]⁺

wherein: R^a is selected from hydrogen, a Ci to do, straight chain or branched alkyl group, a C₃ to C₆ cycloalkyl group, or a C₆ to C₈ aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C₆ alkoxy, C₆ to do aryl, CN, OH, NO₂, C₇ to C₃₀ aralkyl and C₇ to C₃₀ alkaryl.

Most preferably Cat⁺ is:

[(CH₃)₃N(CH₂CH₂OH)]⁺.

In accordance with the present invention X^" may be selected from: [BF₄]^", [PF₆]^", [F]^", [Cl]^", [Br]^", [I]^", [NO₃]^", [NO₂]^", [H₂PO₄]^", [BBDB]^", [BOB]^", [(CF₃SOz)₃C]-,

[Co(CO₄)]^", [(CN)₂N]^", [(CFs)₂N]^", [(CF₃SOz)₂N]-, [(C₂Fs)₃PF₃]^", [(C₃F_T)₃PF₃]-, [(C₂Fs)₂P(O)O]^", [SbF₆]^", [SCN]^", [HSO₄]^", [CH₃OSO₃]^", [C₂H₅OSO₃]^", [C₈H₁₇OSO₃]^", [CH₃SO₃]^", [CH₃(C₆H₄)SO₃]^", [CF₃SO₃]^", [TO]₅ ^", [H₃CO(CHz)₂O(CH₂)OSO₃]-, and [H₃C(OCH₂CH₂)_nOSO₃]^".

More preferably, X^" may be selected from: [F]^", [Cl]^", [Br]^", [I]^", [NO₃]^", [NO₂]^", [H₂PO₄]^", [CH₃SO₃]^", [CH₃(C₆H₄)SO₃]^", [CF₃SO₃]^", and [(CF₃SO₂)₂N]\ Most preferably X^" is [Cl]^".

In one embodiment of the present invention the at least one solid substance is particles suspended in the ionic liquid.

Solid substances for use in the display device of the present invention may include decorative materials which can circulate in the ionic liquid, thereby giving rise to an interesting visual effect. Suitable substances may include light reflecting particles, fluorescent particles or phosphorescent particles or a combination of these. The solid particles used in the present invention are preferably of an appropriate size to be discernable by the naked eye. Preferably the particles are from 0.1 to 50 mm in diameter, more preferably 0.5 to 20 mm in diameter and most preferably 1.0 to 10 mm in diameter.

In order to obtain a preferred desired optical effect, it is preferable to match the density of the ionic liquid and the density of the solid substance such that the particles are suspended in the ionic liquid. If the particles are too dense they will remain at the bottom of the container and will not be suitably dispersed. Conversely, if the particles are not dense enough they will float on the surface of the ionic liquid and again will not be suitably dispersed. Ideally the density of the ionic liquid and the solid particles will be selected such that the solid particles are of equal density to the ionic liquid, or are marginally more dense than the ionic liquid. Particles with a high-surface area to volume ratio are preferred as these are more easily circulated, especially by convection currents (see below) in the ionic liquid.

Reflective particles for use in the present invention may include metallic foil particles, for example noble metals such as gold, silver and platinum or an alloy such as bronze or brass. Alternatively the reflective particles may be selected from glass particles, semi-precious stones or gem stones. The reflective particles may also be selected from reflective plastic particles, such as glitter.

The display devices of the present invention preferably also comprise one or more heating means. The heating means create a temperature differential between different parts of the container, thereby promoting convection currents, which in turn produce desirable visual patterns. Preferably the heating means is positioned at the base of the container so as to cause a temperature differential between the lower portion of the container and the upper portion of the container. Further heating means may be positioned elsewhere in the container if desired so as to achieve other visual effects. Suitable heating means include incandescent light bulbs, fluorescent light bulbs, rope heaters, mica strips, coil heaters, and combinations thereof.

In addition, or alternatively, the display devices may comprise one or more (for example 1 , 2 or even 3) mechanical means to achieve desirable visual patterns. Such means may include, but are not limited to, pumps, fans, stirrers and other suitable devices. In some embodiments, the means may be retained within the display device.

By way of example, the mechanical means may be used to create a vortex or fountain effect within the display device. In addition, the mechanical means may be used to create different current flows within the display device.

In addition, or in the alternative, the mechanical means may create visual effects by manipulation of the display device (such as the container), for example, by rotation, tilting, oscillation and/or vibration.

It will be understood that suitable mechanical devices can be selected by a person of suitable skill in the art in order to obtain the results detailed above, and thus further disclosure of such mechanisms is unnecessary.

The display devices of the present invention may also comprise a light source. Suitable light sources may include one or more incandescent light bulbs, fluorescent light bulbs, ultraviolet lamps, neon lamps, light emitting diodes (LEDs), or a combination thereof.

An incandescent or fluorescent light bulb may serve as both a heating means and an illuminating means for the display devices.

Where a UV light source is used, the particles may be fluorescent particles which emit bright and distinctive colours when stimulated by the short wavelength light.

This property improves their contrast and visibility relative to background materials, thereby adding to the visual effect. Suitable fluorescent materials for use in the present invention may comprise a fluorescent compound contained in a polymer material such as a polystyrene resin. Suitable fluorescent compounds include acridine dyes, cyanine dyes, fluorescein derivatives, fluorone dyes and stilbene derivatives. A wide variety of fluorescent particles can be prepared ranging in size, type of fluorophore, colour or fluorescence, and fluorescence intensity.

As will be well known by persons skilled in the art, phosphorescent materials, or phosphors, contain molecules that can store light energy in the form of a metastable excited electronic state. Phosphors slowly emit light over a period of time. Phosphorescent particles for use according to the present invention preferably comprise phosphors having half-lives of from 1 second to 12 hours, preferably 30 seconds to 6 hours and most preferably 5 minutes to 2 hours. Suitable phosphors may include zinc sulphide activated by copper or silver (green afterglow), mixed calcium-strontium sulfides activated by bismuth (blue afterglow), mixed zinc and cadmium sulfides and strontium aluminate activated by europium.

Phosphorescent particles for use in the present invention may prepared by mixing a phosphorescent compound with a polymer material, such as a polystyrene resin.

According to a further aspect of the present invention there is provided a display device wherein the at least one other substance is a liquid which is immiscible with the ionic liquid.

The second liquid substance may be an aqueous liquid or a non-aqueous liquid.

Suitable non-aqueous liquids include liquid hydrocarbons, such as pentane, hexane, cyclohexane, toluene, light petroleum, mineral oil, and molten paraffin wax; alcohols, such as methanol, ethanol, propanol, butanol and isomers thereof; polyhydroxy compounds, such as glycerol, ethylene glycol and propylene glycol; halogen containing solvents, such as dichloromethane, chloroform and carbon tetrachloride; silicone oils; and mixtures thereof. It will be appreciated that the second liquid substance may also be a solid at room temperature, but liquid under the display device operating conditions.

In one embodiment the second liquid substance may be more dense than the ionic liquid and thus forms a liquid layer below the ionic liquid. Alternatively, the second liquid substance may be more dense than the ionic liquid substance and thus forms a liquid layer below the ionic liquid.

Thus, the present invention provides a display device wherein the ionic liquid and the second liquid substance form a biphasic system having a lower liquid layer and an upper liquid layer. When heat is applied to the system (using methods such as those described above), convection currents in the ionic liquid and/or the second liquid substance cause irregular and unpredictable turbulence at the phase boundary between the ionic liquid layers and the second liquid substance layer, thereby giving rise to interesting visual effects. Alternatively (or in addition), a mechanical device, such as those discussed above, may be used to create interesting visual effects.

In a further embodiment the ionic liquid and the second liquid substance is selected such that one of the liquids is slightly more dense than the other liquid at room temperature, but has a higher thermal expansion coefficient than the other liquid such that it becomes slightly less dense than the other liquid when heated. Thus, the ionic liquid may be more dense than the second liquid substance at room temperature, but less dense than the second liquid substance at higher temperatures. The ionic liquid therefore initially forms a liquid layer below the second liquid substance, but upon the application of heat to the display device, the ionic liquid becomes less dense than the second liquid substance. Globules of the heated ionic liquid may then ascend and circulate in the second liquid substance thereby producing a desirable visual effect. As the globules of ionic liquid cool they become more dense and descend back to the base of the container. The cycle of rising and falling globules of the ionic liquid continues as long as a suitable temperature differential is maintained between the lower portion and the upper portion of the container. A mechanical device may also be used to enhance the visual effect.

Alternatively the second liquid substance may be more dense than the ionic liquid at room temperature, but less dense than the ionic liquid at higher temperatures. Thus, the second liquid substance initially forms a liquid layer below the ionic liquid, but upon the application of heat to the display device, the second liquid substance becomes less dense than the ionic liquid. Globules of the heated second liquid substance may then ascend and circulate in the ionic liquid so as to produce a desirable visual effect. As the globules of second liquid substance cool they become more dense and descend back to the base of the container. The cycle of rising and falling globules of the second liquid substance continues as long as a suitable temperature differential is maintained between the lower portion and the upper portion of the container. Again, a mechanical device may additionally be used to enhance the visual effect.

In a further embodiment the ionic liquid and/or the second liquid substance may additionally contain suspended light reflecting particles, fluorescent particles or phosphorescent particles as described above. Such particles may also be suspended in the ionic liquid layer alone, or in the second liquid substance alone. Alternatively, such particles may be suspended in both the ionic liquid and the second liquid substance. The particles suspended in the ionic liquid and the second liquid substance may be the same or different.

According to yet a further aspect of the present invention the display device additionally comprise a third substance which is liquid at the operating temperature of the display device and which is generally immiscible with the ionic liquid and with the second liquid substance.

Third liquid substance may be an aqueous liquid or a non-aqueous liquid as described above and which is generally immiscible with the second liquid substance and/or the ionic liquid. Both the second liquid substance and the third liquid substance are preferably immiscible with the ionic liquid. In one embodiment the ionic liquid is more dense than the second liquid substance and the third liquid substance, and thus forms a liquid layer below the second and third liquid substances. The more dense of the second and third liquid substances forms an intermediate liquid layer above the ionic liquid layer and below an upper liquid layer formed by the less dense of the second and third liquid substances, i.e. a triphasic system.

Alternatively, the ionic liquid has a density that is intermediate the densities of the second and third liquid substances. In this embodiment the ionic liquid forms an intermediate liquid layer above a lower liquid layer formed by the more dense of the second and third liquid substances, and below an upper liquid layer formed by the less dense of the second and third liquid substances.

As a further alternative, the ionic liquid is less dense than both the second and third liquid substances, and thus forms an upper liquid layer above the second and third liquid substances. The less dense of the second and third liquid substances thus forms an intermediate liquid layer below the ionic liquid and above the lower liquid layer formed by the more dense of the second and third liquid substances.

In the above described embodiments, a mechanical device may be used to provide, or enhance, the visual effect.

Thus, the use of three different liquids provides a display device wherein the ionic liquid and the second and third liquid substances form a triphasic system having a lower liquid layer, an intermediate liquid layer and an upper liquid layer. By selecting the liquids according to their densities, the ionic liquid can occupy any of the lower, intermediate an upper layers. When heat is applied to this system, convection currents in the ionic liquid and in the second and third liquid substances cause irregular and unpredictable turbulence at the phase boundary between the lower liquid layer and the intermediate liquid layer, and the phase boundary between the intermediate liquid layer and the upper liquid layer, thereby giving rise to desirable visual effects.

In another embodiment, the lower liquid is chosen such that it has a higher thermal expansion coefficient than the intermediate liquid, such that it becomes slightly less dense than the intermediate liquid when heated. Globules of the heated lower liquid may then ascend and circulate in the intermediate liquid so as to produce an interesting visual effect. As the globules of the lower liquid cool they become more dense and descend back into the lower liquid layer.

In a further embodiment, the intermediate liquid is chosen such that it has a higher thermal expansion coefficient than the upper liquid, such that it becomes slightly less dense than the upper liquid when heated. Globules of the heated intermediate liquid may then ascend and circulate in the upper liquid so as to produce an interesting visual effect. As the globules of the intermediate liquid cool they become more dense and descend back into the intermediate liquid layer.

In yet a further embodiment, the lower liquid is chosen such that it has a higher thermal expansion coefficient than the intermediate liquid, such that it becomes slightly less dense than the intermediate liquid when heated. The intermediate liquid is also chosen such that it has a higher thermal expansion coefficient than the upper liquid, such that it becomes slightly less dense than the upper liquid when heated. Globules of the heated lower liquid may then ascend and circulate in the intermediate liquid, and globules of the heated intermediate liquid may also ascend and circulate in the upper liquid so as to produce a desirable visual effect.

As the globules of the lower and intermediate liquids cool, they become more dense and descend back into the lower and intermediate liquid layers respectively.

In still yet another embodiment, the lower liquid is chosen such that it has a higher thermal expansion coefficient than the intermediate liquid and the upper liquid, such that it becomes slightly less dense than the intermediate liquid and the upper liquid when heated. Globules of the heated lower liquid may then ascend and circulate in the intermediate liquid and in the upper liquid so as to produce a different desirable visual effect. As the globules of the lower liquid cool, they become more dense and descend back into the lower liquid layer.

In another embodiment, the lower liquid is chosen such that it has a higher thermal expansion coefficient than the intermediate liquid and the upper liquid, such that it becomes slightly less dense than the intermediate liquid and the upper liquid when heated. The intermediate liquid is also chosen such that it has a higher thermal expansion coefficient than the upper liquid, such that it becomes slightly less dense than the upper liquid when heated. Globules of the heated lower liquid may then ascend and circulate in the intermediate liquid and in the upper liquid, and globules of the heated intermediate liquid may also ascend and circulate in the upper liquid so as to produce yet another desirable visual effect.

In one preferred embodiment, the triphasic display device of the present invention comprises a heat source positioned at the base of the container. In a further preferred embodiment, the triphasic display device of the present invention comprises a heat source positioned at the base of the container, and a further heat source, or heat sources, positioned so as to heat a different portion of the container. For instance, a second heat source may be positioned so as to provide additional heating to the intermediate liquid layer, or to the upper liquid layer.

For the triphasic display devices, the ionic liquid and/or the second liquid substance and/or the third liquid substance may contain suspended light reflecting particles, fluorescent particles or phosphorescent particles as described above. Such particles may be suspended in the ionic liquid layer alone, in the second liquid substance alone, or in the third liquid substance alone. Alternatively, such particles may be suspended in two or more of the ionic liquid and in the second and third liquid substances. The particles suspended in the ionic liquid and in the second and third liquid substances can be the same or different.

In all of the display devices of the present invention, the ionic liquid and/or the other liquid substance(s) that may be present may be coloured so as to enhance the visual effect obtainable. Where the display device contains second and third liquid substances in addition to the ionic liquid, it is preferred that each liquid substance is a different colour, such that the different liquid phases can be easily discerned.

It will be understood that all of the triphasic display devices may also comprise a mechanical device, as described above, to improve the visual effect (the mechanical device may, in some embodiments, be used instead of a heating means).

Where the display devices comprise an ionic liquid and a second liquid substance, the ionic liquid may be coloured and the second liquid substance may be colourless. Alternatively, the ionic liquid may be colourless and the second liquid substance may be coloured. Preferably the ionic liquid and the second liquid substance are not both colourless. Most preferably, both the ionic liquid and the second liquid substance are both coloured.

In the triphasic system described above, which comprises an ionic liquid, a second liquid substance and a third liquid substance, one or more of the ionic liquid, the second liquid substance and a third liquid substance may be coloured. Preferably, each liquid layer of the triphasic system should be adjacent to a liquid layer of a contrasting colour. Thus, a colourless liquid layer is preferably not adjacent to another colourless liquid layer, and a coloured layer is preferably not adjacent to another coloured layer that is the same colour. Preferably the colours of the different liquid layers are chosen so as to be visually complementary to each other. For instance, a blue liquid layer adjacent to a red liquid layer would produce a purple colour at the turbulent phase boundary between the two liquids, or when globules of the lower liquid layer ascend and circulate in the upper liquid as described above.

Colourants may be used to colour the ionic liquid and/or any further liquid substances (if present), and preferably have a suitable partition coefficient that leaching of the colourant across the phase boundary between one liquid phase and another liquid phase does not occur, or occurs only to a minor extent.

Colourants for aqueous and hydrophobic liquids are well known in the art, and the skilled person can readily select appropriate colourants or mixtures thereof, at appropriate concentrations so as to obtain a wide range of shades at different depths of colour. Suitable colourants may include transition metal salts, such as copper (II) sulphate, nickel (II) chloride, cobalt (II) chloride, cobalt (II) aluminate, and cobalt (II) sulphate; organic dyes, such as acridine yellow, acridine orange, azo dyes, aniline dyes, phthalocyanine blue, and phthalocyanine green; and natural dyes, such as carmine and indigo. In a preferred embodiment the ionic liquid may comprise an organic dye molecule covalently bound to an anionic or cationic moiety of the ionic liquid, thereby immobilising the dye molecule in the ionic liquid layer.

The ionic liquid layer and/or any further liquid substances (if present) may also comprise a solution or a suspension of one or more phosphorescent compounds or fluorescent compounds as described above.

In a further preferred embodiment, the ionic liquid of the display devices may comprise or consist of a fluorescent, phosphorescent or electroluminescent complex salt formed between a complexed metal anion and a selected organic cation. Suitable light emitting complex salts have the formula: ([Cat]ⁿ⁺)_m . ([M(Lg)_p]^m- )„

wherein m = 1 , 2, 3 or 4; n = 1 or 2; p = 3, 4, 5 or 6;

M is a metal; each Lg, which may be the same or different, represents a ligand; and

[Cat]ⁿ⁺ represents a cationic species as defined above.

For a given anion, ([M(l_g)_p]^m~ )_n, complex salts according to the invention can be produced with a range of selected physical properties, such as melting point and solubility in organic solvents. Thus, complex salts according to the invention may have melting points below, below 125°C, and below 100⁰C.

Examples of metals "M" include Group VII or VIII metals, e.g. manganese or ruthenium and examples of ligand Lg (each Lg may be the same or different) are halogen, especially chlorine or bromine.

The values of m, n and p will depend upon the valence state and coordination number of metal M. Typically, for a four-coordinated metal ion in the +2 oxidation state, such as manganese (II), m will be 2, n will be 1 and p will be 4. With other metal ions, p may have other values, e.g. 5 or 6.

Typical formulae for the anion ([M(Lg)_p]^m") include ([M(CI)_p]^m") or ([M(BrVT), especially ([M(CI)₄]^2") or ([M(Br)₄]^2"). E.g. where the metal is manganese, the anions may, for example, be of formulae ([Mn(CI)₄]^2") or ([Mn(Br)₄]^2").

Other examples of metals, include lanthanides such as cerium or europium. In these cases the anion ([M(Lg)_p]^m") may have the formula ([M(Lg)₆]^3"). E.g

([M(Lg)_p]^m") may have the formula ([M(CI)₆]^3") or ([M(Br)₆]^3"). More specifically in the case of cerium, the anion ([M(Lg)_p]^m") could have the formula ([Ce(CI)₆]^3") or ([Ce(Br)₆ i]3-^"). In the case of europium the anion ([M(Lg)_p] ^") could have the formula

Examples of light emitting organic salts include:

(intense green phosphorescence);

(intense yellow-green phosphorescence);

(intense green phosphorescence);

(intense yellow-green luminescence);

(intense green luminescence up to 100 °C);

3 -

[ (hexyl)₃P(C₁₀H₂₁)] [CeCl₍

(strong blue luminescence in liquid phase); and

3 -

[ (hexyl)₃P(C₁₀H₂₁)] [EUC1₍

(red luminescence in liquid phase).

The ionic liquid and/or any further liquid substances (if present) may also include one or more additives selected from density controlling agents, thermal expansion coefficient controlling agents, pH modifiers, opacifiers, defoaming agents, antioxidants and UV stabilisers. Preferably the additives used in the ionic liquid and/or any further liquid substances (if present) have a suitable partition coefficient that leaching of the additive across the phase boundary between one liquid phase and another liquid phase does not occur, or occurs only to a minor extent.

It will be appreciated that the container for use in the present invention should preferably have at least one wall that is translucent or transparent in order that the visual effect can be observed. Preferably the at least one wall should have a light transmittance of at least 10%, more preferably at least 25% and most preferably at least 50%. Suitable materials for the at least one translucent or transparent wall include glass, an acrylic polymer material such as polymethyl methacrylate

(Perspex), or a polycarbonate polymer material such as those sold under the tradename LEXAN (General Electric).

The display device of the present invention may be used in a number of different forms. For instance, it may be used in the form of a freestanding decorative display device. Alternatively it may be used in the form of a light filter which produces interesting effects when a light source is projected through the device.

The present invention will now be described by way of example and with reference to the accompanying drawing in which:

Figure 1 is a diagrammatic view of a triphasic lava lamp.

Example 1

A triphasic display device according to the present invention, as shown in Fig. 1 , is prepared by adding water, cyclohexane, carbon tetrachloride and the ionic liquid [Bu₃P(Ci6H33)]⁺[CH3(C₆H₄)SO3]^" to a transparent container 1. The cyclohexane and carbon tetrachloride combine to form a lower hydrophobic layer 2. Sufficient carbon tetrachloride is added to adjust the density of this layer such that it is slightly more dense than the water layer which forms the intermediate layer 3. The ionic liquid forms an upper layer 4.

Cobalt sulphate is added as a colorant and is partitioned between the intermediate water layer 3 and the upper ionic liquid layer 4 such that the water is coloured deep red, and the ionic liquid is coloured pale pink.

A heat source 5 is provided at the base of the container such that when heat is applied, a convection current is established in the lower layer 2 causing irregular and unpredictable turbulence at the phase boundary 6 between the lower hydrophobic layer and the intermediate aqueous layer. A second convection current in the intermediate aqueous layer 3 is also established, thereby causing unpredictable turbulence at the phase boundary 7 between the intermediate aqueous layer and the upper ionic liquid layer. This turbulence gives an interesting visual effect especially when the container is illuminated by a light source.

Heat dissipation to the surroundings is sufficient to maintain a suitable temperature differential between the upper portion and the lower portion of the container, such that the convection currents could be maintained indefinitely.

Claims

CLAIMS:

1. A display device having a container and comprising:

(a) an ionic liquid; (b) at least one other solid or liquid substance which is generally immiscible with the ionic liquid; and (c) one or more heating means.

2. A display device having a container and comprising: (a) an ionic liquid;

(c) one or more mechanical means for creating visual patterns.

3. A display device according to Claim 1 or Claim 2 wherein the ionic liquid has the formula:

[CaI⁺][X ];

wherein: [Cat⁺] is a cationic species; and [X ] is an anionic species.

4. A display device according to Claim 3 wherein [Cat⁺] is a cationic species selected from ammonium, phosphonium, imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolium, azathiazolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiazolium, triazolium, selenozolium, oxaphospholium, pyrrolium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, /so-oxazolium, iso- triazolium, tetrazolium, benzofuranium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholinium, pyranium, annulenium, phthalazinium, quinazolinium, quinoxalinium, quinolinium, isoquinolinium, thiazinium, azaannulenium, ammonium, pyrrolidinium, diazabicycloundecenium, diazabicyclononenium, diazabicyclodecenium, phosphonium or triazadecenium.

5. A display device according to Claim 4 wherein [Cat⁺] is a cationic species selected from:

and

wherein: R^a, R^b, R^c, R^d, R^e, R^f, R⁹ and R^h can be the same or different, and are each independently selected from hydrogen, a Ci to C₁₅, straight chain or branched alkyl group, a C3 to Cs cycloalkyl group, or a Ce to C₁0 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to Ce alkoxy, Ce to do aryl, CN, OH, NO₂, C₇ to do aralkyl and C₇ to do alkaryl, or any two of R^b, R^c, R^d, R^e and R^f attached to adjacent carbon atoms form a methylene chain -(CH₂)_q- wherein q is from 3 to 6.

6. A display device according to Claim 4 wherein [Cat]⁺ is a cationic species selected from:

+

and

RS

\

N N

R^b' \ / ^R^c

N

wherein: R^a, R^b, R^c, R^d, R^e, R^f, R⁹ and R^h are each independently selected from hydrogen, a Ci to C₁₅ straight chain or branched alkyl group, a C3 to Cs cycloalkyl group, or a Ce to do aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to Ce alkoxy, C₂ to C₁₂ alkoxyalkoxy, Ce to C10 aryl, -CN, -OH, -NO₂, C₇ to C10 aralkyl and C₇ to C10 alkaryl, -CO₂(Ci to C₆)alkyl, -OC(O)(Ci to C₆)alkyl, or any two of R^b, R^c, R^d, R^e and R^f attached to adjacent carbon atoms may form a methylene chain -(CH₂)_q- wherein q is from 3 to 6.

A display device according to Claim 5 or Claim 6 wherein R^a and R⁹ are selected from Ci to C₁0, linear or branched, alkyl, and one of R^a and R⁹ may also be hydrogen.

A display device according to Claim 7 wherein R^a and R⁹ are selected from Ci to Cs, linear or branched alkyl.

9. A display device according to Claim 8 wherein R^a and R⁹ are selected from Ci to C₆, linear or branched alkyl.

10. A display device according to Claim 4 wherein [Cat⁺] is a cationic species selected from:

[N(R^a)(R^b)(R^c)(R^d)]⁺ and [P(R^a)(R^b)(R^c)(R^d)]⁺

wherein R^a, R^b, R^c, and R^d are each independently selected from hydrogen, a Ci to Ci₅, straight chain or branched alkyl group, a C₃ to C₈ cycloalkyl group, or a C₆ to Cio aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C₆ alkoxy, C₆ to Cio aryl, CN, OH, NO₂, C₇ to C₁₀ aralkyl and C₇ to C₁₀ alkaryl.

11. A display device according to Claim 10 wherein R^a, R^b, R^c, and R^d are each independently selected from hydrogen or a Ci to Ci₀, straight chain or branched alkyl group.

12. A display device according to Claim 10 or Claim 11 wherein [Cat⁺] is a cationic species selected from:

wherein R^a is selected from hydrogen, a Ci to Ci₀, straight chain or branched alkyl group, a C₃ to C₆ cycloalkyl group, or a C₆ to C₈ aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: Ci to C₆ alkoxy, C₆ to Cio aryl, CN, OH, NO₂, C₇ to C₃₀ aralkyl and C₇ to C₃₀ alkaryl.

13. A display device according to Claim 12 wherein [Cat⁺] is:

[(CHs)₃N(CH₂CH₂O!-!)]'.

14. A display device according to any one of Claims 3 to 13 wherein [X ] is selected from: [BF₄]^", [PF₆]^", [F]^", [Cl]^", [Br]^", [I]^", [NO₃]^", [NO₂]^", [H₂PO₄]^"

, [BBDB]^", [BOB]^", [(CF₃SO₂)₃C]^", [Co(CO₄)]^", [(CN)₂N]^", [(CFs)₂N]^", [(CFsSO₂)₂N]^", [(C₂F₅)SPF₃]^", [(C₃F₇)₃PF₃]^", [(C₂Fs)₂P(O)O]^", [SbF₆]^", [SCN]^", [HSO₄]^", [CHsOSOs]^", [C₂H₅OSOs]^", [C₈H₁₇OSOs]^", [CH₃SO₃]^", [CHs(C₆H₄)SOs]^", [CFsSOs]^", [TO]₅ ^", [H₃CO(CH₂)₂O(CH₂)OSO₃]^", and

[H₃C(OCH₂CH₂)_nOSOs]^".

15. A display device according to Claim 14 wherein [X ] is selected from: [F]^", [Cl]^", [Br]^", [I]^", [NO₃]^", [NO₂]^", [H₂PO₄]^", [CH₃SO₃]^", [CHs(C₆H₄)SOs]^", [CFsSOs]^", and [(CF₃SO₂)₂N]^".

16. A display device according to Claim 15 wherein [X ] is [Cl]^".

17. A display device according to any of the preceding claims, wherein the second substance is a solid at temperatures below 150°C.

18. A display device according to Claim 17 wherein the second substance comprises a solid suspended in the ionic liquid in the form of particles.

19. A display device according to Claim 18 wherein the second substance is selected from metallic foil particles, glass particles, semi-precious stones, gem stones, glitter or plastic particles.

20. A display device according to Claim 18 or Claim 19 wherein the second substance is light reflective, fluorescent or phosphorescent.

21. A display device according to any one of the Claims 2 to 20 wherein the device further comprises one or more heating means.

22. A display device according to any one of Claims 1 to 21 , wherein the heating means is selected from the group consisting of a light bulb, a rope heater, a mica strip, a coil heater.

23. A display device according to any one of Claims 1 to 16, wherein the second substance is a liquid substance selected from oil-based liquids or water-based liquids that form with the ionic liquid a biphasic system having a lower liquid layer and an upper liquid layer.

24. A display device according to Claim 23, wherein the second liquid substance is an oil-based substance selected from liquid hydrocarbons, such as pentane, hexane, cyclohexane, toluene, light petroleum, mineral oil, and molten paraffin wax; alcohols, such as methanol, ethanol, propanol, butanol and isomers thereof; polyhydroxy compounds, such as glycerol, ethylene glycol and propylene glycol; halogen containing solvents, such as dichloromethane, chloroform and carbon tetrachloride; silicone- based oils; and mixtures thereof.

25. A display device according to Claim 24, wherein the oil based substance is a molten paraffin wax.

26. A display device according to Claim 24, wherein the oil based substance is a silicone-based oil.

27. A display device according to any one of Claims 23 to 26 wherein the lower liquid layer becomes less dense than the upper liquid layer as the temperature of the lower liquid layer is increased from room temperature.

28. A display device according to any one of Claims 23 to 26 additionally comprising a third liquid substance wherein the third liquid substance is an oil-based liquid or a water-based liquid that is generally immiscible with the ionic liquid and the second substance wherein the ionic liquid, the second substance and the third substance form a triphasic system having a lower liquid layer, an intermediate liquid layer and an upper liquid layer.

29. A display device according to Claim 28 wherein the lower liquid layer becomes less dense than the intermediate liquid layer as the temperature of the lower liquid layer is increased from room temperature.

30. A display device according to Claim 28 or Claim 29 wherein the intermediate liquid layer becomes less dense than the upper liquid layer as the temperature of the intermediate liquid layer is increased from room temperature.

31. A display device according to any one of Claim 29 or Claim 30 wherein the lower liquid layer becomes less dense than the intermediate liquid layer and the upper liquid layer as the temperature of the lower liquid layer is increased from room temperature.

32. A display device according to any one of Claims 23 to 31 wherein one or more of the ionic liquid, the second liquid substance and the third liquid substance comprises a solid suspended therein in the form of particles as described in Claims 19 and 20.

33. A display device according to any one of the preceding claims wherein at least one of the ionic liquid, the second liquid substance and the third liquid substance comprises a colorant.

34. A display device according to Claim 33 wherein the colorant is selected from transition metal salts, synthetic dyes; and natural dyes.

35. A display device according to Claim 34 wherein the colorant is selected from copper (II) sulphate, nickel (II) chloride, cobalt (II) chloride, cobalt (II) aluminate, cobalt (II) sulphate, acridine yellow, acridine orange, azo dyes, aniline dyes, phthalocyanine blue, and phthalocyanine green, carmine and indigo.

36. A display device according to Claim 33 wherein the colorant is selected from fluorescent dyes and phosphorescent compounds.

37. A display device according to any one of the preceding claims wherein at least one of the ionic liquid, the second liquid substance and the third liquid substance comprises an additive selected from density controlling agents, thermal expansion coefficient controlling agents, pH modifiers, opacifiers, defoaming agents, antioxidants and UV stabilisers.

38. A display device according to any one of Claims 23 to 37 further comprising one or more heating means.

39. A display device according to Claim 38, wherein the heating means is selected from the group consisting of light bulbs, rope heater, mica strips and/or coil heaters.

40. A display device according to any one of the preceding claims in the form of a decorative lamp.

41. A display device according to any one of the preceding claims in the form of a light filter.