Irreversible heat-sensitive composition

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a heat-sensitive ink comprising a heat-sensitive composition, which can undergo an irreversible color tone change at a predetermined temperature to thus permit the recording of whether a specific substance is exposed to a temperature higher than a predetermined level or not, as well as a heat-sensitive indicator using the same.

[0002] There have been known products, for instance, processed food products, which should be heat-treated at a temperature higher than a specific level during the manufacture of the same. There have also been known some products or articles such as products for medical use and food products, which are deteriorated, decomposed and/or putrefied, if they are exposed to a temperature higher than a specific one. In addition, there have likewise been known such products as electric equipments and electric parts, which get out of order, are broken and/or possibly cause a fire due to overheat in case of, for instance, a motor.

[0003] As a means for detecting whether a particular product experiences or is exposed to a temperature exceeding a predetermined level or not, there have conventionally been used, for instance, temperature-indicating materials capable of changing their color tone upon exposure thereof to such a predetermined temperature.

[0004] As such temperature-indicating materials, there have been known those comprising heat-fusible substances and acid-base indicators, specific examples of which are disclosed in, for instance, Japanese Patent Provisional Publication No. Sho 61-12783 and Japanese Patent Provisional Publication No. Sho 61-14284. The temperature-indicating materials of this type are reversible temperature indicators since they undergo color change upon heating and the color tone thereof is returned back to the original one when they are cooled. If a temperature-indication material of this type is used, whether a product is exposed to a temperature exceeding a predetermined level or not can be confirmed by monitoring the color tone change of the material during heating. However, if the color tone change of such a material is not monitored, it is impossible to confirm if a product experiences a temperature exceeding a predetermined level once the time elapses and the temperature of the product is reduced. Moreover, it is also impossible to record and preserve such a temperature history of the product.

[0005] In addition, Japanese Patent Provisional Publication No. Hei 10-239172 discloses a device for monitoring the upper temperature limit, which comprises a thin film of pigmented solid paraffin and a thin solid paraffin film having the same quality and deposited on the former. This device is one prepared by forming a thin film of paraffin previously pigmented and then depositing a thin film of non-pigmented paraffin on the surface of the former and should have a predetermined shape. This device is designed in such a manner that, when the device is exposed to a temperature exceeding a predetermined one, the fused upper layer or non-pigmented paraffin thin film is admixed with the lower layer or the pigmented paraffin thin film likewise in the fused state to thus develop a color tone apparently different from that observed prior to the fusion.

[0006] Moreover, Japanese Utility Model Application Publication No. Sho 46-28235 discloses an irreversible label. This label should be produced as a three-dimensional structure and therefore, the application thereof is quite limited.

SUMMARY OF THE INVENTION

[0007] Accordingly, it is a first object of the present invention to provide a heat-sensitive composition, which undergoes an irreversible color change responding to a temperature change, which permits the use of a wide variety of dyestuffs, which can be used in printing irrespective of the shape of a target to be printed, which can be mass-produced and permits the reduction of the production cost thereof and which allows the systematization of temperatures for indication or detection.

[0008] The irreversible heat-sensitive composition according to the present invention developed to achieve the first object of the present invention comprises a mixture of a granular (or granular) or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution.

[0009] It is a second object of the present invention to provide a heat-sensitive ink, which can indicate, with high precision, whether it is exposed to a temperature exceeding a predetermined level or it has a desired temperature history or not, through a clear color tone change.

[0010] The heat-sensitive ink according to the present invention developed to accomplish the second object of the present invention comprises the foregoing irreversible heat-sensitive composition and an ink vehicle capable of diffusing the fused heat-fusible substance therein.

[0011] According to another embodiment of the heat-sensitive ink of the present invention comprises microcapsules in which the foregoing irreversible heat-sensitive composition is enclosed or encapsulated.

[0012] It is a third object of the present invention to provide a heat-sensitive indicator, which can indicate, with high precision, whether it is exposed to a temperature exceeding a predetermined level or it has a desired temperature history or not, through a clear color tone change which the color change itself could be preserved, and could easily be mass-produced.

[0013] The heat-sensitive indicator according to the present invention developed to achieve the third object of the invention comprises a substrate, which the foregoing heat-sensitive ink is printed on.

DETAILED EXPLANATION OF THE INVENTION

[0014] The irreversible heat-sensitive composition according to the present invention comprises a mixture of a granular or powdery heat-fusible substance with a granular or powdery dyestuff.

[0015] The irreversible heat-sensitive composition preferably comprises 0.001 to 100 parts by weight of the granular or powdery dyestuff per 100 parts by weight of the granular or powdery heat-fusible substance.

[0016] The heat-fusible substance is a component, which determines the color change-temperature of the irreversible heat-sensitive composition and a substance, which has, under ordinary pressure, a melting point corresponding to the temperature to be recorded and which can be fused when heated to a temperature higher than the melting point and undergo a change in state from a granular or powdery state to a liquid state. The heat-fusible substance suitably used herein is at least one member selected from the group consisting of fatty acid derivatives, alcohol derivatives, ether derivatives, aldehyde derivatives, ketone derivatives, amine derivatives, amide derivatives, nitrile derivatives, hydrocarbon derivatives, thiol derivatives and sulfide derivatives.

[0017] Specific examples of fatty acid derivatives are myristic acid, palmitic acid, adipic acid, octanoic acid, tricosanoic acid, tetratriacontanoic acid, 2,3dimethyl nonanoic acid, 23methyl tetracosanoic acid, 2-hexenoic acid, brassidic acid, 2-methyl-2-dodecenoic acid, β-eleostearic acid, behenolic acid, cis-9,10-methylene octadecanoic acid, chaulmoogric acid, n-dodecyl 3,3′-thiodipropionate, trilaurin, palmitic acid anilide, stearic acid amide, zinc stearate, salicylic acid anilide, N-acetyl-L-glutamic acid, caproic acid-β-naphthylamide, enanthic acid phenylhydrazide, p-chlorophenacyl arachionate, cholesteryll formate, 1-aceto-2,3distearin, pentadecyl thiolaurate, stearic acid chloride, palmitic acid anhydride, stearic acid-acetic acid anhydride, succinic acid, sebacic acid benzyl ammonium salt, 2-bromovaleric acid, methyl α-sulfostearic acid sodium salt, and 2-fluoroarachic acid.

[0018] Specific examples of alcohol derivatives are octadecyl alcohol, cholesterin, D-mannitol, galactitol, hepta-triacontanol, hexadecan-2-ol, 1-trans-2-octadecenol, β-eleostearyl alcohol, cycloeicosanol, d(+)cellobiose, p,p′-biphenol, riboflavin, 4-chloro-2-methylphenol and 2-bromo-1-indanol.

[0019] Specific examples of ether derivatives include dihexadecyl ether, dioctadecyl ether, cytidine, adenosine, sodium phenoxyacetate, 1,3-bis (4-hydroxyphenoxy)-benzene and aluminium triethoxide.

[0020] Specific examples of aldehyde derivatives are stearin aldehyde, paralauryl aldehyde, parastearin aldehyde, naphthoaldehyde, p-chlorobenzaldehyde, phthalaldehyde and 4-nitrobenzaldehyde.

[0021] Specific examples of ketone derivatives are stearone, docoson-2-one, phenyl heptadecyl ketone, cyclononadecane, vinyl heptadecyl ketone, 4,4-bisdimethyl aminobenzophenone, bis (2,4-pentanedionite) calcium and 1-chloroanthraquinone.

[0022] Specific examples of amine derivatives include tricosylamine, dioctadecylamine, N,N-dimethyl octylamine, heptadecamethyleneimine, naphthylamine, ethyl p-aminobenzoate, o-trithiourea, sulfamethazine, guanidine nitrate, p-chloroaniline and propylamine hydrochloride.

[0023] Specific examples of amide derivatives are hexylamide, octacosylamide, N-methyl dodecylamide, N-methyl heptacosylamide, α-cyanoacetamide, salicylamide, dicyandiamide, 2-nitrobenzamide and N-bromoacetamide.

[0024] Specific examples of nitrile derivatives include pentadecane nitrile, margaronitrile, 2-naphthonitrile, o-nitrophenoxy acetic acid, 3bromobenzonitrile, 3cyanopyridine and 4-cyanophenol.

[0025] Specific examples of hydrocarbon derivatives are hexadecane, 1-nonatriacontene, trans-n-2-octadecene, hexatriacontyl benzene, 2-methylnaphthalene, picene, cyanuric chloride, 1-fluorononadecane, 1-chloroeicosane, 1-iodopentadecane, 1-bromoheptadecane and 1,2,4,5-tetrakis (bromomethyl) benzene.

[0026] Specific examples of thiol derivatives are pentadecane thiol, eicosane thiol, 2-naphthalene thiol, 2-mercaptoethyl ether and 2-nitrobenzene sulfenyl chloride.

[0027] Specific examples of sulfide derivatives are 1,3-diatine, 2,11-dithia [3,3] paracyclophane, bis (4-hydroxy-3-methylphenyl) sulfide, 4,4-dipyridyl sulfide and 4-methyl mercaptophenol.

[0028] This heat-fusible substance preferably has a particle size ranging from 0.01 μm to 5 mm.

[0029] The dyestuff is included in the irreversible heat-sensitive composition in the form of granules or powder and can diffuse into the fused heat-fusible substance through dispersion or dissolution. Alternatively, the dyestuff may likewise be one such that the surface of the dyestuff granule or powder is wetted with the fused heat-fusible substance and changed to a wet color. The dyestuff may be selected from wide variety of dyestuffs, for instance, dyes such as direct dyes, acid dyes, basic dyes, disperse dyes, reactive dyestuffs, oil-soluble dyes, vat dyes, mordant dyes, azo dyes and sulfide dyes; pigments such as organic pigments and inorganic pigments; and pigmented substances. These dyestuffs may be used alone or in any combination of at least two of them.

[0030] Specific examples of dyes include C.I. Direct Orange 39, C.I. Direct Brown 2, C.I. Acid Yellow 73, C.I. Acid Red 52, C.I. Acid Violet 49, C.I. Basic Yellow 11, C.I. Basic Red 38, Cathilon Red GTLH, Cathilon Red 4GH, Cathilon Red 7BN11 and Cathilon Red SGLH (available from Hodogaya Chemical Co., Ltd.); C.I. Mordant Red 7, C.I. Mordant Black 38, C.I. Azoic Blue 9, C.I. Azoic Diazo Component 11, C.I. Sulfur Black 1, C.I. Sulfur Red 5, C.I. Vat Green 9, C.I. Vat Violet 2, C.I. Disperse Blue 3 and Discharge Red BB (available from Mitsui Toatsu Dyes Co., Ltd.); C.I. Reactive Blue 19, C.I. Reactive Blue 15 and Remazol Br Blue R-KN (available from Mitsubishi Chemical Industries, Ltd.); C.I. Solvent Orange 2, C.I. Solvent Blue 25, C.I. Acid Green 1, Flavianic Acid Disodium Salt and Primuline Sulfonic Acid.

[0031] Specific examples of organic pigments are 4,10-dibromoanthanthrone, dibenzoanthrone, cochineal lake, C.I. Pigment Yellow 1, C.I. Pigment Red 38, C.I. Pigment Blue 15, C.I. Pigment Red 209, C.I. Pigment Yellow 109, C.I. Pigment Green 10, C.I. Basic Red 1-Lake, C.I. Acid Red 87-Lake, C.I. Pigment Blue 6, C.I. Pigment Red 179, C.I. Pigment Red 88, Alizarin Lake, C.I. Pigment Violet 23, C.I. Pigment Green 8, C.I. Pigment Red 53, C.I. Pigment Yellow 23-Lake, tannic acid-gallic acid-iron lake, C.I. Pigment Yellow 34 and C.I. Pigment Yellow 35. In this connection, the foregoing term “C.I.” is an abbreviation of “color index”.

[0032] Specific examples of inorganic pigments are kaolin, Prussian blue, strontium sulfate, titanium dioxide, aluminum hydroxide, calcium silicate and carbon black.

[0033] The dyestuff preferably has a particle size ranging from 0.001 μm to 5 mm.

[0034] In the irreversible heat-sensitive composition, the granular or powdery heat-fusible substance and the granular or powdery dyestuff are in a mixed state, the dyestuff is covered up with the heat-fusible substance and the granular or powdery heat-fusible substance is fused, while the granular or powdery dyestuff is dispersed or dissolved in or wetted with the fused heat-fusible substance to thus cause a color tone change when the temperature reaches or exceeds a desired level. After the color tone change, it is never returned back to the original color tone even if the composition is cooled and the heat-fusible substance is solidified.

[0035] To obtain this irreversible heat-sensitive composition, a heat-fusible substance and a dyestuff are mixed together in a desired mixing ratio, followed by pulverization of the resulting mixture to a desired particle size; or the foregoing two components are separately pulverized to a desired particle size and then the pulverized components are mixed together in a desired mixing ratio.

[0036] The heat-sensitive ink according to the present invention comprises the foregoing irreversible heat-sensitive composition comprising a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution; and an ink vehicle capable of diffusing the fused heat-fusible substance therein.

[0037] The ink vehicle does not permit any dissolution or diffusion of the heat-fusible substance and the dyestuff at ordinary temperature, but permits the diffusion of the fused substance in which the dyestuff is dispersed or dissolved. The ink vehicle may be, for instance, acrylic resins, phenol resins, nylon, ethyl cellulose, hydroxymethyl cellulose, polyvinyl alcohol and carboxymethyl cellulose. The ink vehicle may likewise be any commercially available ink vehicles such as PAS800 Medium (the trade name of a product available from Jujo Chemical Industry Co., Ltd.) and High Set Mat Medium (the trade name of a product available from Mino Group K.K.).

[0038] It is preferred that the heat-fusible substance be included in the heat-sensitive ink in an amount ranging from 10 to 70% by weight. This is because if the amount thereof is less than 10% by weight, the resulting color tone change is insufficient or indistinct, while if it exceeds 70% by weight, the adhesive force of the resulting ink is too low to coat or print a substrate with the ink.

[0039] This heat-sensitive ink may comprise a solvent, which does not dissolve the heat-fusible substance and the dyestuff, but can dissolve the ink vehicle. Such a solvent may be, for instance, water, ethanol, butanol, ethyl acetate, isoamyl acetate, methyl ethyl ketone, methyl isobutyl ketone, xylene, diethyl benzene, toluene, butyl cellosolve, ethyl cellosolve and mineral spirit.

[0040] This heat-sensitive ink can be prepared by uniformly kneading, in a kneader, the foregoing heat-fusible substance and dyestuff, which are pulverized to a desired particle size, an ink vehicle and a solvent.

[0041] According to another embodiment of the heat-sensitive ink of the present invention may comprise microcapsules each of which encloses the foregoing irreversible heat-sensitive composition comprising a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution. The microcapsules are unevenly distributed in the resulting ink.

[0042] The microcapsule is, for instance, a minute particle having a uniform outer wall and having a size ranging from about 0.01 μm to about 10 mm, which encloses the granular or powdery dyestuff and heat-fusible substance.

[0043] In the present invention, it is preferred that the outer wall of the microcapsule be formed from a polymer compound selected from the group consisting of polyvinyl alcohol, polystyrene, silicone resins, epoxy resins, acrylic resins, urea resins, gelatin, methyl cellulose, polyurethane, waxes, gum arabic, dextrin, and nylon.

[0044] Such microcapsules are, for instance, prepared by an interfacial polymerization method, an in-situ production method, a phase separation method, a suspension-in air method, an electrostatic coalescence method, a spray coagulation method and a drying-in liquid method.

[0045] The microcapsules are preferably contained in the heat-sensitive ink in an amount ranging from 10 to 70% by weight. This is because if the amount thereof is less than 10% by weight, the color tone change of the resulting ink is insufficient or indistinct, while if it exceeds 70% by weight, the adhesive force of the resulting ink is too low to coat or print a substrate with the ink.

[0046] The use of the microcapsules permits the improvement of not only the stability of the heat-fusible substance and the dyestuff present in the ink, but also the environmental resistance of the ink. Moreover, in the preparation of the ink, vehicles and solvents to be incorporated into the ink are not restricted to those, which do not dissolve the heat-fusible substance and the dyestuff and the resulting ink is excellent in the printability and the storage stability after printing.

[0047] The heat-sensitive ink preferably comprises an ink vehicle identical to those described above. The ink vehicle may be commercially available ones other than those listed above such as Aqua Set Ink (the trade name of a product available from Jujo Chemical industry Co., Ltd.), VAR-000 Medium (the trade name of a product available from Teikoku Ink K.K.) and Ramistar R Medium (the trade name of a product available from Toyo Ink Mfg. Co., Ltd.).

[0048] This heat-sensitive ink may comprise a solvent capable of dissolving the ink vehicle. This solvent may be isopropyl alcohol in addition to those listed above.

[0049] This heat-sensitive ink can preferably be prepared as follows: First, microcapsules are prepared according to the interfacial polymerization method. More specifically, a heat-fusible substance and a dyestuff are dispersed or emulsified in a solvent which does not dissolve the heat-fusible substance and the dyestuff, but can dissolve a polymeric compound for forming the outer wall of the microcapsules using a device such as a stirring machine, a disperser, a homogenizer or a mixer. Then an emulsifying-hardening agent is added to the resulting dispersion to thus form the outer wall of the microcapsules and thereafter the resulting microcapsules are separated from the solvent by, for instance, filtration to thus give desired microcapsules in which the heat-fusible substance and the dyestuff are enclosed. Finally, an ink vehicle, a solvent for ink vehicle and the resulting microcapsules are kneaded in a kneader to give a heat-sensitive ink.

[0050] In this respect, the heat-sensitive ink may further comprise a dispersant for improving the dispersibility of the dyestuff and for making the color tone change of the ink more distinct, such as talc, magnesium carbonate and silica. In order to make the color tone change more distinct, the heat-sensitive ink may optionally comprise at least one member selected from the group consisting of dyes such as direct dyes, acid dyes, basic dyes, disperse dyes, reactive dyestuffs, oil-soluble dyes, vat dyes, mordant dyes, azo dyes and sulfide dyes; pigments such as organic pigments and inorganic pigments, which are auxiliary coloring agents showing colors contrast to the color tone of the dyestuff. Moreover, the heat-sensitive ink may likewise comprise a wax and/or a surfactant for controlling the flowability and the drying characteristics of the ink.

[0051] The heat-sensitive indicator according to the present invention comprises a substrate and a printed layer of the foregoing heat-sensitive ink, which is applied onto the surface of the substrate and comprises an irreversible heat-sensitive composition, which is a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution, and an ink vehicle capable of diffusing the fused heat-fusible substance therein.

[0052] According to another embodiment of the present invention, the heat-sensitive indicator comprises a substrate and a printed layer of the foregoing heat-sensitive ink, which is applied onto the surface of the substrate and comprises microcapsules each of which encloses the irreversible heat-sensitive composition comprising a mixture of a granular or powdery heat-fusible substance having a melting point corresponding to a temperature to be recorded and a granular or powdery dyestuff diffusible into the fused heat-fusible substance through dispersion or dissolution.

[0053] Examples of such substrates are paper such as plain paper, Japan art paper and Kent paper; synthetic paper; wood such as sun tree timber; and plastic substrates such as polypropylene, polyethylene terephthalate, acrylonitrile-butadiene-styrene resin, polycarbonate and acrylic resin substrates.

[0054] These heat-sensitive indicators may be in the form of a card-like, sheet-like or rod-like shape. Alternatively, they may be labels, which carry an adhesive layer on the back face.

[0055] The printing of the substrate with the heat-sensitive ink is performed by, for instance, screen-printing, offset printing, gravure printing and brush coating techniques.

[0056] The ink layers formed on the substrate by printing with these heat-sensitive inks may be covered up with a transparent or translucent laminate material made of a resin. Examples of such laminate materials are plastic films such as polypropylene, polyethylene terephthalate, acrylonitrile-butadiene-styrene resin, polycarbonate and acrylic resin films; and printing mediums for laminate such as acrylic resins, nylon and phenol resin.

[0057] In these heat-sensitive indicators, the heat-fusible substance and the dyestuff are in a mixed state, prior to heating. If the indicator is heated to a temperature higher than the melting point of the heat-fusible substance, however, the dyestuff diffuses into the fused heat-fusible substance through dispersion or dissolution or the surface of the granular or powdery dyestuff is wetted with the fused heat-fusible substance so that the indicator undergoes a desired color tone change. Alternatively, in case of the indicator, which makes use of microcapsules, the heat-fusible substance and the dyestuff enclosed in the microcapsules may be permeated through the outer wall of the microcapsules and diffuse into the ink vehicle, after the fusion of the heat-fusible substance by heating.

[0058] This diffusion of the foregoing components is irreversible. Therefore, once the indicator undergoes a desired color tone change, the color tone thereof is never returned back to the original one even if the heat-fusible substance is cooled, after the color tone change, and solidified.

[0059] When practically using these heat-sensitive indicators, they are arranged near the product of which temperature history is to be detected or they are adhered to such a product. Alternatively, it is also possible to directly print such a product with the heat-sensitive ink.

EXAMPLES

[0060] The irreversible heat-sensitive composition, the heat-sensitive ink containing the composition and the heat-sensitive indicator using the ink thereof according to the present invention will hereunder be described in more detail with reference to the following Examples.

[0061] In the following Examples 1 to 121, there are embodied the preparation of the irreversible heat-sensitive compositions according to the present invention, while in the following Comparative Examples 1 to 6, there are embodied compositions, which are beyond the scope of the present invention.

Examples 1 to 121

[0062] A heat-fusible substance was blended with 0.001 to 100 parts by weight of a dyestuff, which underwent a color tone change when it is dissolved or dispersed in or wetted with the heat-fusible substance after the fusion thereof, per 100 parts by weight of the former and then the resulting blend was pulverized, using a mortar and a pestle, to such an extent that the particle size of the heat-fusible substance fell within the range of 0.01 μm to 5 mm and that the particle size of the dyestuff fell within the range of 0.001 μm to 5 mm to thus give each corresponding composition. Each prepared composition was heated till it was fused and then the fused composition was cooled till re-solidified to thus confirm any color tone change of the composition. The kinds and amounts of part by weight, color tone before and after the color change and the melting temperature of the heat-fusible substances and dyestuffs are summarized in the following Tables 1 to 4.

1TABLE 1(Examples 1 to 30)AfterIndicatingHeat-fusibleBeforere-solid-PointEx.SubstanceAmountDyestuffAmountheatingification(° C.) 1Myristic acid100Acid Yellow0.1WhiteYellow 5073 2Palmitic acid100Basic Yellow0.1WhiteYellow 6011 3Adipic acid100Basic Red 381WhiteRed150 4Octanoic acid100Pigment100WhiteYellow 17Yellow23-Lake 5Tricosanoic100Pigment Blue50WhiteBlue 79acid15 6Tetratriaconta-100Pigment50WhiteYellow 98noic acidYellow 34 72,3-Dimethyl-100Carbon Black10WhiteBlack122nonanoic acid 823-Methyl-100Direct0.001WhiteOrange 83tetracosanoicOrange 39acid 92-Hexenoic100Mordant Red1WhiteRed 32acid710Brassidic acid100Azoic Blue 91WhiteBlue 62112-Methyl-2-100Vat Green 90.1WhiteGreen 33dodecenoicacid12β-Eleostearic100Mordant1WhiteBlack 72acidBlack 3813Behenolic acid100Sulfur Black 10.01WhiteBlack 5814cis-9,10-100Solvent Blue1WhiteBlue 87Methylene-25octadecanoicacid15Chaulmoogric100Cathilon Red0.01WhiteRed 69acidSGLH16n-Dodecyl 3,3′-100Direct Brown1WhiteBrown 40thiodipropionate217Trilaurin100Sulfur Red 50.1WhiteRed 4518Palmitic acid100Reactive Blue1WhiteBlue 85anilide1919Stearic acid100Basic Red 381WhiteRed 90amide20Zinc stearate100Acid Yellow0.1WhiteYellow1107321Salicylic acid100Disperse Blue1WhiteBlue130anilide322N-Acetyl-L-100Vat Violet 20.1WhitePurple190glutamic acid23Caproic acid-100Reactive Blue1WhiteBlue107β-naphthyl15amide24Enanthic acid100Solvent0.001WhiteOrange103phenylhydrazideOrange 225p-Chlorophenacyl100Azoic Diazo0.1WhiteRed 86arachionateComponent1126Cholesteryl100Remazol0.1WhiteBlue 96formateBrilliant BlueR-KN271-Aceto-2,3-1004,10-Dibromo-1WhiteRed 57distearinanthanthrone28Pentadecyl100Dibenzo-10WhiteBlack 52thiolaurateanthrone29Stearic acid100Cochineal10WhiteRed 23chloridelake30Palmitic acid100Pigment100WhiteYellow 64anhydrideYellow 1

[0063]

2

TABLE 2

(Examples 31 to 60)

After
Indicating

Heat-fusible

Before
re-solid-
Point

Ex.
Substance
Amount
Dyestuff
Amount
heating
ification
(° C.)

31
Stearic acid-
100
Mordant Red
1
White
Red
54

acetic acid

7

anhyride

32
Succinic acid
100
Direct Orange
0.1
White
Orange
185

39

33
Sebacic
100
Acid Red 52
0.01
White
Red
122

acid benzyl

ammonium salt

34
2-Bromovaleric
100
Pigment Red
50
White
Red
67

acid

209

35
Methyl α-
100
Basic Yellow
0.1
White
Yellow
180

sulfostearic

11

acid sodium

salt

36
2-Fluoroarachic
100
Azoic Blue 9
1
White
Blue
90

acid

37
Octadecyl
100
Primuline
1
White
Yellow
55

alcohol

Sulfonic Acid

38
Cholesterin
100
Pigment Red
50
White
Red
140

38

39
D-mannitol
100
Basic Red
50
White
Red
165

1-Lake

40
Galactitol
100
Reactive Blue
1
White
Blue
185

15

41
Hepta-
100
Disperse Blue 3
1
White
Blue
91

triacontanol

42
Hexadecan-
100
Basic Yellow
0.1
White
Yellow
44

2-ol

11

43
1-trans-2-
100
Pigment
100
White
Yellow
48

Octadecenol

Yellow 109

44
β-Eleostearyl
100
Cathilon Red
0.01
White
Red
59

alcohol

SGLH

45
Cycloeicosanol
100
Azoic Diazo
0.1
White
Red
69

Component 11

46
d(+)Cellobiose
100
Pigment Blue
50
White
Blue
180

15

47
p,p′-Biphenol
100
Basic Yellow
0.1
White
Yellow
280

11

48
Riboflavin
100
Solvent Blue
1
White
Blue
320

25

49
4-Chloro-2-
100
Acid Red
10
White
Red
47

methylphenol

87-Lake

50
2-Bromo-1-
100
Acid Red 52
0.01
White
Red
131

indanol

51
Dihexadecyl
100
Pigment Blue 6
50
White
Blue
54

ether

52
Dioctadecyl
100
Dibenzo-
10
White
Black
59

ether

anthrone

53
Cytidine
100
Solvent
0.01
White
Orange
210

Orange 2

54
Adenosine
100
Sulfur Black 1
0.01
White
Black
220

55
Sodium
100
Pigment
50
White
Green
240

phenoxy-

Green 10

Acetate

56
1,3-Bis(4-hydroxy-
100
Acid Yellow 73
0.1
White
Yellow
130

phenoxy)-

benzene

57
Aluminium
100
Pigment Red
50
White
Red
159

triethoxide

88

58
Stearin
100
Sulfur Red 5
0.1
White
Red
38

aldehyde

59
Paralauryl-
100
Pigment Red
50
White
Red
57

aldehyde

179

60
Parastearin-
100
Mordant Red
1
White
Red
78

aldehyde

7

[0064]

3

TABLE 3

(Examples 61 to 90)

After
Indicating

Heat-fusible

Before
re-solid-
Point

Ex.
Substance
Amount
Dyestuff
Amount
heating
ification
(° C.)

61
Naphtho-
100
Sulfur Black 1
0.01
White
Black
61

aldehyde

62
p-Chlorobenz-
100
Vat Violet 2
0.1
White
Purple
48

aldehyde

63
Phthalaldehyde
100
Acid Green 1
0.1
White
Green
99

64
4-Nitrobenz-
100
4,10-Dibromo-
1
White
Red
105

aldehyde

anthanthrone

65
Stearone
100
Sulfur Black 1
0.01
White
Black
89

66
Docosan-
100
Basic Red 38
1
White
Red
64

2-one

67
Phenyl
100
Pigment
50
White
Green
59

heptadecyl

Green 8

ketone

68
Cyclonona-
100
Azoic Blue 9
1
White
Blue
72

decane

69
Vinyl
100
Reactive Blue
1
White
Blue
41

heptadecyl

15

ketone

70
4,4-Bisdimethyl-
100
Pigment Red
50
White
Red
170

aminobenzo-

209

phenone

71
Bis(2,4-pentane-
100
Cochineal
10
White
Red
290

dionite)

lake

calcium

72
1-Chloro-
100
Sulfur Black 1
0.01
White
Black
210

anthraquinone

73
Tricosylamine
100
Acid Yellow
0.001
White
Yellow
63

73

74
Dioctadecyl-
100
Pigment Red
50
White
Red
72

amine

88

75
N,N-Dimethyl-
100
Direct
0.1
White
Orange
191

octylamine

Orange 39

76
Heptadeca-
100
Pigment
50
White
Yellow
65

methyleneimine

Yellow

23-Lake

77
Naphthyl-
100
Pigment
10
White
Purple
113

Amine

Violet 23

78
Ethyl p-amino-
100
Tannic
1
White
Black
90

Benzoate

acid-Gallic

acid-Iron lake

79
o-Trithiourea
100
Pigment Blue
50
White
Blue
160

15

80
Sulfamethazine
100
Pigment Red
50
White
Red
195

53

81
Guanidine
100
Solvent
0.01
White
Orange
200

nitrate

Orange 2

82
p-Chloroaniline
100
Flavianic
100
White
Yellow
71

Acid

Disodium Salt

83
Propylamine
100
Acid Yellow
0.01
White
Yellow
161

hydrochloride

73

84
Hexylamide
100
Acid Red 52
0.01
White
Red
101

85
Octacosyl-
100
Acid Yellow
0.01
White
Yellow
119

Amide

73

86
N-Methyl
100
Acid Violet 49
0.1
White
Purple
56

dodecylamide

87
N-Methyl
100
Basic Yellow
0.1
White
Yellow
98

heptacosyl-

11

Amide

88
α-Cyanoacet-
100
Discharge
0.01
White
Red
120

amide

Red BB

89
Salicylamide
100
Carbon Black
10
White
Black
140

90
Dicyandiamide
100
Pigment
50
White
Yellow
200

Yellow

23-Lake

[0065]

4

TABLE 4

(Examples 91 to 121)

After
Indicating

Heat-fusible

Before
re-solid-
Point

Ex.
Substance
Amount
Dyestuff
Amount
heating
ification
(° C.)

91
2-Nitrobenz-
100
Pigment Blue
50
White
Blue
175

amide

15

92
N-Bromo-
100
Pigment
50
White
Yellow
105

acetamide

Yellow 34

93
Pentadecane-
100
Azoic Diazo
0.1
White
Red
23

nitrile

Compon-ent

11

94
Margaronitrile
100
Sulfur Black 1
0.01
White
Black
34

95
2-Naphtho-
100
Pigment
10
White
Purple
63

nitrile

Violet 23

96
o-Nitrophenoxy-
100
Reactive Blue
1
White
Blue
155

acetic acid

19

97
3-Bromo-
100
Aluminum
10
Yellow
White
39

benzonitrile

hydroxide

98
3-Cyanopyridine
100
Acid Green 1
0.1
White
Green
83

99
4-Cyano-
100
Vat Green 9
0.1
White
Green
112

phenol

100
Hexadecane
100
Basic Red 38
1
White
Red
18

101
1-Nonatri-
100
Disperse Blue
1
White
Blue
78

acontene

3

102
trans-n-2-
100
Vat Green 9
0.1
White
Green
13

Octadecene

103
Hexatriaconlyl-
100
Pigment Red
50
White
Red
80

benzene

38

104
2-Methyl-
100
Alizarin Lake
10
White
Red
35

naphthalene

105
Picene
100
Solvent Blue
1
White
Blue
368

25

106
Cyanuric
100
Pigment
50
White
Yellow
147

chloride

Yellow 35

107
1-Fluoro-
100
4,10-Dibromo-
1
White
Red
39

nonadecane

anthanthrone

108
1-Chloro-
100
Remazol
0.1
White
Blue
38

eicosane

Brilliant Blue

R-KN

109
1-lodo-
100
Strontium
10
Yellow
White
24

pentadecane

sulfate

110
1-Bromo-
100
Direct
0.1
White
Orange
30

heptadecane

Orange 39

111
1,2,4,5-Tetrakis-
100
Solvent
0.01
White
Orange
160

(bromomethyl)-

Orange 2

benzene

112
Pentadecane
100
Primuline
1
White
Yellow
18

thiol

Sulfonic Acid

113
Eicosane thiol
100
Kaolin
10
Yellow
White
37

114
2-Naphthalene
100
Disperse Blue
1
White
Blue
80

thiol

3

115
2-Mercapto-
100
Vat Green 9
0.1
White
Green
80

ethyl ether

116
2-Nitrobenzene
100
Prussian Blue
1
White
Blue
75

sulfenyl

chloride

117
1,3-Diatine
100
Pigment
100
White
Yellow
53

Yellow 1

118
2,11-Dithia-
100
Titanium
50
Yellow
White
222

[3,3] para-

dioxide

cyclophane

119
Bis-(4-hydroxy-3-
100
Disperse Blue
1
White
Blue
123

methylphenyl)

3

sulfide

120
4,4-Dipyridyl
100
Calcium
10
Yellow
White
65

sulfide

silicate

121
4-Methyl-
100
Remazol
0.1
White
Blue
84

mercapto-

Brilliant Blue

phenol

R-KN

[0066] The results of the foregoing Examples clearly indicate that the granular or powdery dyestuff is covered with the granular or powdery heat-fusible substance in the irreversible heat-sensitive composition of the present invention and that the composition undergoes a color tone change when heated and the color tone is never returned back to the original one even if the composition is again solidified with cooling. The results shown in Tables 1 to 4 also indicate that a wide variety of irreversible heat-sensitive compositions whose indicating point ranges from 13 to 368° C. can be prepared by variously combining heat-fusible substances and dyestuffs. This clearly indicates that the temperature at which the composition undergoes a color tone change may arbitrarily be selected over a wide range extending from a low temperature to a high temperature, or the color tone change-temperature can be well systematized.

Comparative Examples 1 to 6

[0067] In these Comparative Examples 1 to 6, irreversible heat-sensitive compositions were prepared by repeating the same procedures used in Example 1 except for the following points. The heat-fusible substance of each composition thus prepared was heated till it was fused and thereafter the fused composition was cooled till it was re-solidified to thus confirm the color tone of the composition. The kinds and amounts (part by weight), color tone before and after the color change and the indicating temperature of the heat-fusible substances and dyestuffs are summarized in the following Table 5.

[0068] Comparative Ex. 1: The amount of the dyestuff was changed to 0.0001 part by weight.

[0069] Comparative Ex. 2: The amount of the dyestuff was changed to 200 parts by weight.

[0070] Comparative Ex. 3: The heat-fusible substance was pulverized by a mortar and a pestle to such an extent that the particle size thereof was less than 0.01 μm.

[0071] Comparative Ex. 4: The heat-fusible substance was pulverized by a mortar and a pestle to such an extent that the particle size thereof was greater than 5 mm.

[0072] Comparative Ex. 5: The dyestuff was pulverized by a mortar and a pestle to such an extent that the particle size thereof was less than 0.001 μm.

[0073] Comparative Ex. 6: The dyestuff was pulverized by a mortar and a pestle to such an extent that the particle size thereof was greater than 5 mm.

5TABLE 5(Comparative Examples 1 to 6)AfterIndicatingComp.Heat-fusibleBeforere-solid-PointEx.SubstanceAmountDyestuffAmountheatingification(° C.)1Myristic acid100Acid Yellow0.0001WhiteWhite50732Myristic acid100Acid Yellow200YellowYellow50733Myristic acid100Acid Yellow0.1WhiteWhite50734Myristic acid100Acid Yellow0.1YellowYellow50735Myristic acid100Acid Yellow0.1WhiteWhite50736Myristic acid100Acid Yellow0.1YellowYellow5073

[0074] The results of the foregoing Comparative Examples 1 to 6 clearly indicate that the achievement of an intended object of the present invention or the preparation of the irreversible heat-sensitive composition can simply be attained if the following requirements are satisfied: the amount of the dyestuff should fall within the range of from 0.001 to 100 parts by weight per 100 parts by weight of the heat-fusible substance; the particle size of the heat-fusible substance should be limited to the range of from 0.01 μm to 5 mm; and that of the dyestuff should be limited to the range of from 0.001 μm to 5 mm. In other words, a particular heat-sensitive composition never undergoes any color tone change at around the melting point of the heat-fusible substance, if either of the foregoing requirements is beyond the scope defined above.

[0075] Then heat-sensitive indicators were manufactured by way of trial using the heat-sensitive ink according to the present invention in the following Examples 122 to 127, and heat-sensitive indicators were likewise manufactured by way of trial using heat-sensitive inks, which were beyond the scope of the present invention, in Comparative Examples 7 to 9.

Example 122

[0076] A heat-fusible substance, a dyestuff, an ink vehicle and a solvent were admixed together in the amounts specified in the following Table 6, followed by uniformly kneading the resulting mixture to give a heat-sensitive ink. The resulting ink was printed on the surface of synthetic paper of a plastic, which is a substrate, by the screen-printing technique to give a heat-sensitive indicator.

Examples 123 to 127 and Comparative Examples 7 to 9

[0077] The same procedures used in Example 122 were repeated except that the heat-fusible substance, dyestuff, ink vehicle and solvent were used in the amounts specified in Table 6 to give each corresponding heat-sensitive indicator.

[0078] The indicators manufactured in Examples 122 to 127 and Comparative Examples 7 to 9 by way of trial were heated in a thermostatic chamber to thus determine the temperature at which each indicator underwent a color tone change. The results thus obtained are listed in Table 6.

6TABLE 6Heat-Color tonefusibleDye-BeforeAfterTemp.*SubstancestuffInk vehicleSolventheatingheating(° C.)Examples122MyristicAcidEthylDiethylWhiteYellow50acid (100)Yellowcellulosebenzene73 (0.1)(8)(200)123Stearic acidBasicAcrylicIsoamylWhiteRed90amide (100)Red 38resins (7)acetate(1)(200)124β-EleostearylCathilonPAS800ButylWhiteRed59alcohol (100)RedmediumcellosolveSGLH(50)(50)(0.01)125SalicylamideCarbonHigh Set MatMineralWhiteBlack140 (100)BlackMedium (60)spirit (50)(10)126Cyclo-AzoicEthylDiethylWhiteBlue72nonadecaneBlue 9 (1)cellulose (8)benzene(100)(200)1271,2,4,5-TetrakisSolventHydroxy-mWaterWhiteOrange160 (bromomethyl)Orangeethyl(150)benzene2 (0.01)cellulose(100)(8)ComparativeExamples 7MyristicAcidHigh Set MatMineralYellowYellow—acid (100)YellowMedium (60)spirit (50)73 (0.1) 8Stearic acidBasicHydroxy-mWaterRedRed—amide (100)Red 38ethyl(150)(1)cellulose (8) 9MyristicAcidHigh Set MatMineralWhiteWhite—acid (10)YellowMedium (60)spirit (50)73 (0.1)Parts by weight shown in brackets ( ) *: Color changing temperature

[0079] As will be seen from the data shown in Table 6, the indicators of Examples 122 to 127 cause distinct color changes at predetermined temperatures and can indicate that they experience desired temperature histories. Moreover, if the indicators were preserved after the color tone changes, the color tones observed after the color changes were certainly maintained. On the other hand, the indicators of Comparative Examples 7 and 8 were already pigmented at the time of the manufacture of the same by way of trial since the heat-fusible substance and the dyestuff had been dissolved in the solvent when kneaded and therefore, the color tone of the indicators observed when they were manufactured by way of trial was maintained even after the fusion of the heat-fusible substance. Further, the indicator of Comparative Example 9 never underwent any color change and thus the original color tone thereof was maintained even after the fusion of the heat-fusible substance, because the amount of the heat-fusible substance incorporated into the indicator was too small.

[0080] Moreover, in the following Examples 128 to 133, heat-sensitive indicators were prepared using heat-sensitive inks according to other embodiments of the present invention, while in the following Comparative Examples 10 to 11, indicators were prepared using inks, which were beyond the scope of the present invention.

Example 128

[0081] Microcapsules used in these Examples were prepared according to the interfacial polymerization technique.

[0082] First, there were mixed 7 parts by weight of a mixture containing 99.9% of myristic acid as a heat-fusible substance and 0.1% of Acid Yellow 73 as a dyestuff with 30 parts by weight of Epicoat 828 (the trade name of a product available from Yuka Shell Epoxy K.K.) as an epoxy resin for forming the outer walls of the microcapsules. The resulting mixture was dispersed in a dispersion medium obtained by admixing 500 parts by weight of a 2% aqueous solution of sodium alginate and 3 parts by weight of Uramine P-1500 (the trade name of a product available from Mitsui Toatsu Chemicals, Inc.) as a urea resin, followed by stirring the mixture over 20 minutes to give an emulsion.

[0083] Thereafter, 30 parts by weight of Epicure (the trade name of a product available from Yuka Shell Epoxy K.K.) as a curing agent was added to the resulting emulsion, followed by stirring the mixture for 8 hours to thus form the walls of the microcapsules.

[0084] The resulting liquid was filtered to give microcapsules each of which enclosed the heat-fusible substance and the dyestuff therein.

[0085] Then there were kneaded, in a kneader, 100 parts by weight of the resulting microcapsules, 50 parts by weight of PAS800 Medium as an ink vehicle and 50 parts by weight of butyl cellosolve as a solvent for the ink vehicle to give a heat-sensitive ink. The surface of synthetic paper of a plastic, which is a substrate, was printed with this ink by the screen-printing technique to give a heat-sensitive indicator.

Examples 129 to 133 and Comparative Example 10

[0086] Microcapsules were prepared using polymeric compounds, heat-fusible substances and dyestuffs in amounts specified in the following Table 7 according to various preparation methods. In this respect, the following methods were substituted for the interfacial polymerization method used in Example 128: the phase separation method in Examples 129 and 131 to 133; the drying-in liquid method in Example 130; and the interfacial polymerization method in Comparative Example 10 as in Example 128. Thereafter, the same procedures used in Example 128 were repeated to prepare inks and to manufacture indicators.

Comparative Example 11

[0087] There were kneaded, in a kneader, 100 parts by weight of myristic acid, 0.1 part by weight of Acid Yellow 73, 50 parts by weight of PAS800 Medium, and 50 parts by weight of butyl cellulose to give an ink without enclosing the mixture in microcapsules. An indicator was prepared by printing a substrate with the resulting ink according to the same manner used in Example 128.

7Blending of heat-sensitive inkMicrocapsuleHeat-sensitivePolymericSolvent for inkindicatorcompoundsInk vehiclevehicleColor toneformingComprised heat-fusibleMixingMixingMixingBeforeAfterTemp.*outer wallsubstanceamountamountamountheatingheating(° C.)Examples128EpoxyMyristic acid:Acid Yellow73100PAS80050Butyl50WhiteYellow50resins(99.9%:0.1%)mediumcellosolve129PolystyreneStearic acid amide:100High Set60Mineral50WhiteRed90Basic Red38Matspirit(99%:1%)Medium130Siliconeβ-Eleostearyl alcohol:100Aqua100 Water20WhiteRed59resinsCathilon Red SGLHSet Ink(99.99%:0.01%)131PolystyreneSalicylamide Carbon Black100VAR-00070Ethanol30WhiteBlack140 (89.9%:10.1%)Medium132PolyvinylCyclononadecane:100Ramistar100 Isopropyl50WhiteBlue72acetateAzoic Blue 9Ralcohol(99%:1%)Medium133Gelatin1,2,4,5-Tetrakis (bromomethyl)100Ethyl 8Diethyl200WhiteOrange160 benzene:cellulosebenzeneSolvent Orange 2(99.99%:0.01%)ComparativeExamples 10EpoxyMyristic acid:Acid Yellow 7310PAS80050Butyl30WhiteWhite—resins(99.9%:0.1%)mediumcellosolve 11NoneMyristic acid:Acid Yellow 73100.1PAS80050Butyl50YellowYellow—(100:0.1 parts by weight)mediumcellosolve*: Color changing temperature

[0088] The indicators prepared in Examples 128 to 133 and Comparative Examples 10 to 11 were heated in a thermostatic chamber to thus determine the temperature at which each indicator underwent a color tone change. The results thus obtained are summarized in Table 7.

[0089] As will be seen from the data listed in Table 7, the heat-sensitive indicators of Examples 128 to 133 undergo distinct color changes at desired temperatures and could indicate that they experienced the desired temperature histories. Moreover, the heat-sensitive indicators were preserved after the color tone changes, but maintained the color tones observed after the color changes and there was not observed any color tone change. On the other hand, the indicator of Comparative Example 10 maintained its original color tone even after the heat-fusible substance was fused with heating since the amount of the microcapsules incorporated is too small. Further, in case of the indicator of Comparative Example 11, the heat-fusible substance and the dyestuff were dissolved in the solvent when they were kneaded together with the latter and the resulting ink was pigmented at this stage. For this reason, the indicator maintained the color tone observed after the pigmentation even when heating the same.

[0090] Regarding all of the dyestuffs listed in Table 7, “C.I.” of each dyestuff is omitted.

[0091] As has been discussed above in detail, the irreversible heat-sensitive composition according to the present invention can be used in printing operations irrespective of the shape thereof. For instance, a printing ink can be prepared using an appropriate vehicle prior to practical use thereof in printing. In addition, the composition of the present invention permits the use of a wide variety of dyestuffs unlike those, which make use of chemical decomposition or chemical reactions of dyestuffs. This composition also permits the establishment of a variety of color change temperatures extending from a low temperature to a high temperature, by variously combining different heat-fusible substances and dyestuffs. This accordingly permits the systematization of the color change temperatures of such irreversible heat-sensitive compositions.

[0092] Heat-sensitive indicator can be mass-produced by the printing operations if using the heat-sensitive ink according to the present invention and this accordingly leads to the substantial reduction of the cost required for the production of such indicators.

[0093] The heat-sensitive indicator prepared by printing operations using this heat-sensitive ink undergoes an irreversible color tone change and can be preserved while maintaining the color tone observed after the color change.

[0094] Moreover, if microcapsules are used in the heat-sensitive ink, the heat-fusible substance and the dyestuff encapsulated in the microcapsules show excellent stability and resistance to environment in the ink. In addition, when preparing an ink, vehicles or solvents for the vehicles to be incorporated into the ink must not be limited to those in which the heat-fusible substance and dyestuff are insoluble and the resulting ink is excellent in the printing characteristics and the preservation stability after printing.

[0095] The heat-sensitive indicator of the invention can favorably be used for the confirmation of whether a product such as a processed food product requiring desired temperature control is certainly heated to a temperature of not less than a predetermined level in the heating step of the product; and of whether a product, which must not be heated to a predetermined temperature level, such as a medical product including a drug, a food product or an electric part is not heated to such a temperature level or not during distribution, storage and/or use thereof.

Number	Date	Country
2000-124431	Apr 2000	JP
2001-020557	Jan 2001	JP
2001-020558	Jan 2001	JP

Irreversible heat-sensitive composition

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