Compound for Use in Colour Change Compositions

Abstract

Novel reaction media for electron donating and electron accepting components in colour-change compositions are described. The compound is of formula (I):

##STR00001## wherein R.sub.1, and R.sub.2 are selected from a linear or branched alkyl group, alkenyl group, alkoxy group, aryl group and an alkylene aryl group having from 6 to 22 carbon atoms; X.sub.1 and X.sub.2 are selected from —OC(O)-, —CO.sub.2- and O; R.sub.3, R.sub.4 and R.sub.5 are selected from hydrogen and an linear or branched alkyl group, cycloalkyl group, alkenyl group, alkoxy group, aryl and alkylene aryl group; R.sub.6 is selected from hydrogen, R.sub.3, —X.sub.1R.sub.1 and aryl and halogen; Y.sub.1 Y.sub.2 Y.sub.3 and Y.sub.4 are selected from hydrogen, R.sub.3, —OR.sub.3 and halogen; a is 0 to 4; b is 0 or 1; x and y are independently is 0 or 1 provided that where x and y are 0, a is 0 and b is 1 and R.sub.6 is —CO.sub.2R.sub.1; and wherein when a is 0 and b is 1 and R.sub.5 or R.sub.6 is phenyl, R.sub.6 and R.sub.5 respectively are not hydrogen or C.sub.1-7 alkyl. The compounds are useful in ink compositions, writing implements containing the compound and medical and industrial applications in which temperature sensitive colour change may be required.

Claims

1. A compound of formula (I): ##STR00025## wherein: R.sub.1, and R.sub.2 are independently selected from an optionally substituted linear or branched alkyl group, alkenyl group, alkoxy group, aryl group and an alkylene aryl group; X.sub.1 and X.sub.2 are independently selected from —OC(O)—, —CO.sub.2- and O; R.sub.3, R.sub.4 and R.sub.5 are independently selected from hydrogen and an optionally substituted linear or branched hydrocarbyl group; R.sub.6 is selected from hydrogen, halogen, R.sub.3 and —X.sub.1R.sub.1 and phenyl; Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are independently selected from hydrogen, halogen, R.sub.3, —OR.sub.3 and halogen provided that —OR.sub.3 is not —O-alkenyl; and a is 0 to 4; b is 0 or 1; x and y are independently 0 or 1.

2. The compound according to claim 1 wherein R.sub.1, and R.sub.2 are the same or different alkyl groups.

3. The compound according to claim 2 wherein R.sub.1, and R.sub.2 are the same or different unsubstituted alkyl groups.

4. The compound according to claim 2 wherein R.sub.1 and R.sub.2 are independently selected from methyl, ethyl, isopropyl, n-propyl, butyl, tert-butyl, n-hexyl, n-decyl, n-dodecyl, cyclohexyl, octyl, iso-octyl, hexadecyl, octadecyl, iso-octadecyl and docosyl.

5. The compound according to claim 4 wherein R.sub.1 and R.sub.2 are independently selected from n-propyl and butyl.

6. The compound according to claim 1 wherein Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are independently selected from hydrogen and C.sub.1-4 alkyl.

7. The compound according to claim 1 wherein a is 0.

8. The compound according to claim 1 wherein b is 0.

9. The compound according to claim 1 wherein R.sub.1X.sub.1- is in a para position and/or R.sub.2X.sub.2- is in a para position.

10. The compound according to claim 1 wherein X.sub.1 and X.sub.2 are independently selected from —CO.sub.2- wherein the carbon atom is bonded to the phenyl ring, and O.

11. The compound according to claim 10 wherein at least one of X.sub.1 and X.sub.2 is —CO.sub.2- wherein the carbon atom is bonded to the phenyl ring.

12. The compound according to claim 10 wherein one of X.sub.1 and X.sub.2 is —CO.sub.2- wherein the carbon atom is bonded to the phenyl ring, and the other of X.sub.1 and X.sub.2 is O.

13. The compound according to claim 1 in which a is 0, b is 0, R.sub.1 and R.sub.2 are butyl, X.sub.1 is —CO.sub.2- wherein the carbon atom is bonded to the phenyl ring, and X.sub.2 is O and Y.sub.1, Y.sub.2, Y.sub.3 and Y.sub.4 are hydrogen.

14. A method of making a colour-change composition, said method comprising: utilizing a compound of formula (I) as defined in claim 1.

15. A colour-change composition comprising: A) an electron donating organic colouring compound, B) an electron accepting compound and C) a compound as defined in claim 1.

16. The colour-change composition according to claim 15 having a fully coloured temperature T4 higher than ambient temperature and a fully decolorized temperature T1 lower than 20° C.

17. The colour-change composition according to claim 15 wherein the colour-change composition is in the form of a microencapsulated composition.

18. The colour-change composition according to claim 15 wherein component C) is such that the said composition temperature has a T2 temperature at 0° C. and a T3 temperature above 50° C.

19. The colour-change composition according to claim 17 wherein component C) is such that the said composition temperature has a T2 temperature at 0° C. and a T3 temperature above 50° C.

20. The colour-change composition according to claim 17 wherein said microencapsulated composition is in the form of an ink composition for a writing implement.

Description

[0091] By way of illustration, in the initial state at ambient temperature above T2 and below T3 is represented in FIG. 2a. As the temperature drops below the temperature T2, and is kept below T4 at all times, the state of the indicator changes to that shown in FIG. 2b. By raising the temperature to greater than T3 the indicator provides two colourless compositions as shown in FIG. 2c).

[0092] The indicator may also be configured so it may not be reset and provides a single use indicator.

[0093] The invention provides for a single use indicator comprising a first portion of a colour-change composition in its coloured state and a second portion of the same colour-change composition in its discoloured state wherein the composition is according to the present invention.

[0094] Suitably, the indicator has a thermochromic composition or pigment according to the invention suitably in the form of a printable ink applied to it and heated to a temperature exceeding T4 prior to application to the indicator, for example in a printing process. An ink showing permanent colour change at a desired temperature, for example 50° C. is applied to the indicator, for example printed next to the memory composition pigment converted into printed ink. Any known permanent colour change ink may be employed and a preferred example is available from TMC Hallcrest, under the brand name Kromagen. The printed label is allowed to dry at temperature not exceeding T3 or 50° C. and preferably not below T2. The combination on the label is now suitable for indication of temperature below zero, of what can be cold a “freeze indicator”. The indicator used a single time.

[0095] By way of illustration, FIGS. 3a, 3b and 3c illustrate the various forms of the indicator where the indicator comprises a composition according to the invention comprising Kromagen ink. FIG. 3a shows the initial state at ambient temperature above T2 and below the temperature of colour transition of Kromagen. FIG. 3b shows the indicator as the temperature drops below T2 and below the temperature at which Kromagen changes colour and FIG. 3c shows the indicator as it appears after heating above T4.

[0096] The invention is now illustrated by the following non-limiting examples in which parts are by weight unless otherwise stated.

EXAMPLE 1

[0097] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

4 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A)) available from Yamada Chemicals and 6 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 6 parts of 1,1-bis(4′-hydroxyphenyl)-2-methylpropane (both components B)) available from Sigma Aldrich and 84 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00011##

[0098] Component IVa is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,4-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of decanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0099] The resulting memory composition changed colour from blue to colourless.

[0100] The thermochromic colour memory composition was heated above T4. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10 solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above T4 and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0101] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 2

[0102] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0103] 4 parts of 3,3-bis(1-n-butyl-2-methylindol-3-yl)phthalide (Component A)) available from Yamamoto Chemicals and 6 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 6 parts of 1,1-bis(4′-hydroxyphenyl)-2-methylpropane (both Component B)) available from Sigma Aldrich and 84 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldodecanoate) (Component C) specifically component IVb) as shown below):

##STR00012##

[0104] Component IVb was prepared using the same procedure as described in Example 1 for Component IVa save that dodecanoyl chloride was employed rather than decanoyl chloride.

[0105] The resulting memory composition changed colour from magenta to colourless. The thermochromic colour memory composition was heated above T4. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10 solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above T4 and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0106] The resulting dispersion was then drum dried and the pigment was isolated in encapsulated form, the thermochromic colour memory pigment having a particle size of 2.5 microns changed colour from magenta to colourless.

EXAMPLE 3

[0107] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0108] 4 parts of 2-(2-chloroanilino)-6-di-n-butylaminofluoran (Component A)) available from Hodogaya Chemical Co. Ltd. and 6 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 6 parts of 1,1-bis(4′-hydroxyphenyl)-2-methylpropane (Component B)) available from Sigma Aldrich and 84 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenylhexadecanoate) (Component C) specifically component IVc) as shown below). The resulting memory composition changed colour from black to colourless.

##STR00013##

[0109] Component IVc was prepared using the same procedure as described in Example 1 for Component IVa save that hexadecanoyl chloride was employed rather than decanoyl chloride.

[0110] The thermochromic colour memory composition was heated above T4. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10 solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above T4 and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0111] The resulting dispersion was then air dried and the pigment was isolated in encapsulated form, the thermochromic colour memory pigment having a particle size of 4 microns changed colour from black to colourless.

EXAMPLE 4

[0112] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0113] 4.1 parts of 3-Diethylamino-6-methyl-7-(2,4-xylidino)fluoran (component A) available from Yamamoto Chemicals and 4.75 parts 4,4′-Cyclohexylidenebisphenol and 4.75 parts of 4-Hydroxyphenyl-4′-isopropoxyphenyl sulfone (both components B) available from Sigma Aldrich and 86.4 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00014##

[0114] Component IVa is synthesised as per example 1

[0115] The resulting memory composition changed colour from black to colourless.

[0116] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

EXAMPLE 5

[0117] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0118] 4.1 parts of 3,3-Bis(1-butyl-2-methylindol-3-yl)phthalide (component A) available from Yamamoto Chemicals and 5.3 parts 4,4′-Cyclohexylidenebisphenol and 4.1 parts of 4,4′-(1-Phenylethylidene)bisphenol (both components B)) available from Sigma Aldrich and 86.5 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00015##

[0119] Component IVa is synthesised as per example 1

[0120] The resulting memory composition changed colour from magenta to colourless.

[0121] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

EXAMPLE 6

[0122] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0123] 4.1 parts of 3,3-bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide (component A) available from Yamamoto Chemicals and 3 parts 4,4′-Cyclohexylidenebisphenol, 6.5 parts of 4,4′-(1-Phenylethylidene)bisphenol, 2 parts of 4,4′-Thiodiphenol and 2 parts of 2-hydroxy-4-methoxy benzophenone (all components B)) available from Sigma Aldrich and 82.4 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00016##

[0124] Component IVa is synthesised as per example 1

[0125] The resulting memory composition changed colour from turquoise to colourless.

[0126] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

EXAMPLE 7

[0127] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0128] 7 parts 2′-chloro-6′-diethylaminofluoran (component A) available from Yamamoto Chemicals and 6 parts 4,4′-Cyclohexylidenebisphenol, 6 parts of 4,4′-(1-Phenylethylidene)bisphenol, 4 parts of 4,4′-Thiodiphenol and 2 parts of 2-hydroxy-4-methoxy benzophenone (all components B)) available from Sigma Aldrich and 75 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00017##

[0129] Component IVa is synthesised as per example 1

[0130] The resulting memory composition changed colour from red to colourless.

[0131] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

EXAMPLE 8

[0132] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0133] 3.1 parts of 6′-(diethylamino)-2′-(phenylamino)-3H-spiro[2-benzofuran-1,9′-xanthen]-3-one (component A) and 5.1 parts 4,4′-Cyclohexylidenebisphenol, 5.1 parts of 4,4′-(1-Phenylethylidene)bisphenol and 1.9 parts of 2-hydroxy-4-methoxy benzophenone (all components B) available from Sigma Aldrich and 84.8 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) (Component C, specifically component IVa) as shown below):

##STR00018##

[0134] Component IVa is synthesised as per example 1

[0135] The resulting memory composition changed colour from green to colourless.

[0136] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

EXAMPLE 9

[0137] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0138] parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A) available from Yamada Chemicals and 12.6 parts 4,4′-Isopropylidenedi-o-cresol available from Sigma Aldrich (components B) and 84.4 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenylundecanoate) (Component C, specifically component IVd) as shown below):

##STR00019##

[0139] Component IVd is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,4-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of undecanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0140] The resulting memory composition changed colour from blue to colourless.

[0141] The thermochromic colour memory composition was heated above 100° C. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0142] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 10

[0143] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0144] parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A)) available from Yamada Chemicals, 6.4 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 6.4 parts of butyl 4-hydroxybenzoate available from Sigma Aldrich (both components B) and 83.2 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyltetradecanoate) (Component C, specifically component IVe) as shown below):

##STR00020##

[0145] Component IVe is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,4-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of tetradecanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0146] The resulting memory composition changed colour from blue to colourless.

[0147] The thermochromic colour memory composition was heated above 100° C. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0148] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 11

[0149] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0150] 4.1 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A) available from Yamada Chemicals, 4.85 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane, 4.85 parts 4,4′-(1-Phenylethylidene)bisphenol and 8.6 parts of lauric acid (all components B) available from Sigma Aldrich and 77.6 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenylhexanoate) (Component C, specifically component IVf) as shown below):

##STR00021##

[0151] Component IVf is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,4-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of hexanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0152] The resulting memory composition changed colour from blue to colourless.

[0153] The thermochromic colour memory composition was heated above 100° C. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0154] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 12

[0155] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0156] 4.15 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A)) available from Yamada Chemicals and 4.85 parts 2,2-bis(4′-hydroxyphenyl)hexafluoropropane and 4.85 parts of 1,1-bis(4′-hydroxyphenyl)-2-methylpropane (both components B)) available from Sigma Aldrich and and 86.15 parts of 4,4′-[1,3-Phenylenebis(1-methylethylydene)]bis(4-phenylhexadecanoate) (Component C, specifically component Va) as shown below):

##STR00022##

[0157] Component Va is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,3-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of hexadecanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0158] The resulting memory composition changed colour from blue to colourless.

[0159] The thermochromic colour memory composition was heated above 100° C. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0160] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 13

[0161] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0162] 4.1 parts of 3-(4-diethylamino-2-hexyloxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide (component A) available from Yamada Chemicals, 4.85 parts 4,4′-(1-Phenylethylidene)bisphenol and 4.85 parts 4,4′-lsopropylidenedi-o-cresol available from Sigma Aldrich (both components B) and 86.2 parts of 4,4′-[1,3-Phenylenebis(1-methylethylydene)]bis(4-phenyltetradecanoateanoate) (Component C, specifically component Vb) as shown below):

##STR00023##

[0163] Component Va is suitably synthesised by stirring a mixture of 1 mole of 4,4′-(1,3-Phenylenediisopropylidene)bisphenol, commercially available from Mitsui Chemicals, and 2.5 moles of triethyl amine in acetone and cooling to 5° C. 2.2 moles of tetradecanoyl chloride is added gradually so that temperature does not rise above 35° C. during the addition. After the addition is complete the reaction is brought to room temperature and stirred for 24-48 hours. The resulting reaction medium is then poured into 7% aqueous ice cold HCl. The precipitate is filtered off and washed with water and saturated sodium bicarbonate solution. The solid precipitate is crystallised from isopropanol. The relative quantities of bisphenol/acid chloride/triethylamine are 1/2.2/2.5 moles.

[0164] The resulting memory composition changed colour from blue to colourless.

[0165] The thermochromic colour memory composition was heated above 100° C. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

[0166] Some of the resulting dispersion was then drum dried and the pigment in encapsulated form was isolated, the thermochromic colour memory pigment having a particle size of 2 microns changed colour from blue to colourless.

EXAMPLE 14

[0167] A thermochromic colour memory composition was obtained by homogeneously compatibilizing:

[0168] 3.1 parts of 6′-(diethylamino)-2′-(phenylamino)-3H-spiro[2-benzofuran-1,9′-xanthen]-3-one (component A) and 5.1 parts 4,4′-Cyclohexylidenebisphenol, 5.1 parts of 4,4′-(1-Phenylethylidene)bisphenol and 1.9 parts of 2-hydroxy-4-methoxy benzophenone (all components B) available from Sigma Aldrich and 70 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyldecanoate) and 14.8 parts of 4,4′-[1,4-Phenylenebis(1-methylethylydene)]bis(4-phenyloctanoate) (Components C, respectively component IVa and IVg as shown below):

##STR00024##

[0169] The resulting memory composition changed colour from green to colourless.

[0170] The thermochromic colour memory composition was heated above 100 degrees. 100 parts of the hot thermochromic colour memory composition was then dispersed into 100 parts of a 10% solution of methyl vinyl ether—maleic anhydride copolymerized resin neutralised with sodium hydroxide to pH 4 by means of a high speed homogeniser. The resulting emulsion was maintained at temperature above 80° C. and slowly added 25 parts of a solution of melamine formaldehyde resin. The resulting emulsion was stirred and heated to a temperature of 80° C. for 6 hours.

Preparation of the Measuring Samples

[0171] 10 parts of the thermochromic colour memory composition of the water dispersion obtained in Example 1 in encapsulated form were dispersed in 10 parts of a polyvinyl alcohol solution was screen printed onto sheet of copy paper, thereby obtaining a test sample.

[0172] The same method has been carried out in order to obtain a test sample for the thermochromic colour memory composition of Examples 2 to 13 in encapsulated form. Each of the test samples was heated and cooled by the below described method, The measuring sample thus prepared was set on a predetermined position of a Linkam (manufactured by linkam, UK) and the colour density at each temperature was measured by heating and cooling at a rate of 5° C./min with a temperature width of 100° C.

[0173] For example, in the case of Example 1, the sample was heated up to 100° C. at a rate of 5° C./min from a measurement starting temperature of 0° C., and then cooled to −20° C. at a rate of 5° C./min. The brightness of the colour displayed at each temperature was plotted on a graph to prepare the colour density-temperature curve as illustrated in FIG. 1, and each of T.sub.1, T2, T3, T.sub.4, and ΔH was obtained.

[0174] The results of the temperature analysis in ° C. of the microcapsules is reported below as per their temperature of full clearing (T4) and temperature of full colour return (T1) as well as practical hysteresis ΔH. The results are reported below for the Components C) with different R.sub.1 groups as shown in the formula below.

TABLE-US-00001 Example T1 T2 T3 T4 ΔH Example 1 −20 −5 55 71 60 Example 2 4 18 60 78 42 Example 3 30 40 75 87 35 Example 4 −20 −15 55 71 70 Example 5 −25 −10 43 70 53 Example 6 −18 −10 45 70 55 Example 7 −20 −10 40 67 50 Example 8 −15 −10 55 73 65 Example 9 2 19 45 72 26 Example 10 20 27 55 82 28 Example 11 −20 −15 35 60 50 Example 12 18 21 55 65 34 Example 13 −3 2 45 60 43 Example 14 −20 −16 45 65 61