Heating and cooking packaging

Abstract

The present invention provides a packaging for food that can be heated to reveal a design, and the revealed state is maintained for a period of time, thereby informing a third party other than the cook that the food is being cooked or has finished cooking. [Solution] A package for cooking food that can be contained in a package, wherein the packaging base material is provided with a heat-colored image made of a heat-color-developing reversible thermochromic material that develops color when heated from a decolorized state and decolorizes when cooled from a colored state, wherein the heat-color-developing reversible thermochromic material is in a decolorized state, and the heat-color-developing reversible thermochromic material has a color development start temperature T3 of 50°C or higher with respect to a color density-temperature curve, a complete decolorization temperature T1 of 5 to 40°C, and a decolorization start temperature T2 of less than the color development start temperature T3, in a package for cooking food.

Description

Technical Field

[0001] The present invention relates to a package for cooking by heating.

Background Art

[0002] Conventionally, ready-to-cook foods such as retort foods, instant foods, and frozen foods are known. These foods are housed inside a package, and can be eaten by pouring hot water inside the package or heating the food by means such as a microwave oven or a kettle to perform cooking. After cooking by heating, the food and the package housing the food are in a hot state. Therefore, a cooking package film in which a thermochromic region is formed in a part of the film body has been disclosed so that it can be notified that the temperature has dropped to a temperature that can be held by hand (see, for example, Cited Reference 1). The above-mentioned cooking package film is such that the thermochromic region of the film body changes color at a predetermined temperature. However, when the temperature becomes lower than the predetermined temperature and the thermochromic region returns to the initial state before discoloration, the person cooking can grasp that the food housed in the cooking package film is during or after cooking, but a third party other than the person cooking cannot grasp the cooking status of the food from the appearance of the cooking package film, and there is a risk of burns. Also, there is a possibility of accidentally reheating it again.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made based on the background art as described above, and aims to provide a package for cooking by heating in which a design appears by cooking by heating and the state in which the design appears is maintained for a while. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides the following embodiments. [1] A packaging for cooking food that can contain cooked food, The packaging material is provided with a heat-activated color image comprising a heat-activated reversible thermochromic material that develops color upon heating from a decolorized state and decolorizes upon cooling from a colored state, wherein the heat-activated reversible thermochromic material is in a decolorized state. The aforementioned heat-activated reversible thermochromic material is a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color reaction of components (a) and (b). It exhibits hysteresis characteristics with respect to the color density-temperature curve, showing tautomorphism between a colored state and a decolorized state, and in the process of the temperature rising from the decolorized state, the color development start temperature T3 A packaging material for cooking, in which color development begins when a certain temperature is reached, and the color is fully developed in the temperature range above the complete color development temperature T4, which is higher than temperature T3. In the process of the temperature decreasing from the colored state, color decolorization begins when the decolorization start temperature T2 is reached, and the color is completely decolorized in the temperature range below the complete decolorization temperature T1, which is lower than temperature T2, exhibiting hysteresis characteristics. The color development start temperature T3 is 50°C or higher, the complete decolorization temperature T1 is 5 to 40°C, and the decolorization start temperature T2 is less than the color development start temperature T3. [2] The heat-cooking packaging according to [1] above, wherein with respect to the decolorization start temperature T2 and the color development start temperature T3, T2 < (T3 - 10). [3] A heat-cooking packaging according to [1] or [2] above, wherein an irreversible heat-change layer is provided between the packaging substrate and the heat-activated color image. [4] The heat-decolorized image is further provided, comprising a heat-decolorizing reversible thermochromic material that decolorizes upon heating from a colored state and develops color upon cooling from a decolorized state, wherein the heat-decolorizing reversible thermochromic material is in a colored state. The heat-developing and decolorizing type reversible thermochromic material is a reversible thermochromic microcapsule pigment containing at least a reversible thermochromic composition composed of (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color reaction of the components (a) and (b). It exhibits hysteresis characteristics with respect to the color density-temperature curve and shows the mutability between the colored state and the decolored state. In the process of temperature rising from the colored state, it starts to decolorize when reaching the decolorization start temperature t3, and becomes completely decolorized in the temperature range of the complete decolorization temperature t4 or higher than the temperature t3. In the process of temperature dropping from the decolorized state, it starts to develop color when reaching the color development start temperature t2, and becomes completely colored in the temperature range of the complete color development temperature t1 or lower than the temperature t2, showing the hysteresis characteristics. The packaging body for heat cooking according to any one of [1] to [3] above. [5] Regarding the color development start temperature T3 of the heat-developing type reversible thermochromic material and the complete decolorization temperature t4 of the heat-developing and decolorizing type reversible thermochromic material, satisfying t4 < T3, the packaging body for heat cooking according to [4] above. [6] The heat-developing image and the heat-decolorizing image are in a laminated state with each other. The packaging body for heat cooking according to [4] or [5] above. [7] The heat-developing image and the heat-decolorizing image are arranged side by side with each other. The packaging body for heat cooking according to [4] or [5] above. [8] A plurality of the heat-developing images and the heat-decolorizing images are provided, and it includes a region where the heat-developing image and the heat-decolorizing image are in a laminated state with each other and a region where the heat-developing image and the heat-decolorizing image are arranged side by side with each other. The packaging body for heat cooking according to [4] or [5] above. [9] The packaging body substrate is in a bag shape. The packaging body for heat cooking according to any one of [1] to [8] above.

[10] The packaging body substrate is a container, and the container is composed of a bottomed cylindrical container body having an opening at the upper part and a lid material for closing the opening of the container body. The packaging body for heat cooking according to any one of [1] to [8] above.

[11] The heat-developing image is provided on the lid material. The packaging body for heat cooking according to

[10] above.

Advantages of the Invention

[0006] The present invention can provide a packaging body for heat cooking, in which the design appears by heat cooking and the state where the design appears is maintained for a while, so that a third party other than the cook can be informed that the food is during or after cooking.

Brief Description of the Drawings

[0007] [Figure 1] It is a graph explaining the hysteresis characteristics in the color density-temperature curve of a heat-developing reversible thermochromic composition. [Figure 2] It is a graph explaining the hysteresis characteristics in the color density-temperature curve of a heat-fading reversible thermochromic composition. [Figure 3] It is a graph explaining the hysteresis characteristics in the color density-temperature curve of a heat-fading reversible thermochromic composition having color memory. [Figure 4] It is a longitudinal sectional explanatory view of an example of a laminate constituting the packaging body for heat cooking according to the present invention. [Figure 5] It is an example of the packaging body for heat cooking according to the present invention. [Figure 6] It is a longitudinal sectional explanatory view of another example of a laminate constituting the packaging body for heat cooking according to the present invention. [Figure 7] It is another example of the packaging body for heat cooking according to the present invention. [Figure 8] It is a longitudinal sectional explanatory view of another example of a laminate constituting the packaging body for heat cooking according to the present invention. [Figure 9] It is an explanatory view of a lid material constituting the packaging body for heat cooking according to the present invention. [Figure 10] It is a longitudinal sectional explanatory view of another example of a laminate constituting the packaging body for heat cooking according to the present invention. [Figure 11] It is another example of the packaging body for heat cooking according to the present invention.

Modes for Carrying Out the Invention

[0008] The packaging body for cooking by heating according to the present invention (hereinafter sometimes referred to as "packaging body") is provided with a heat-developing image on a packaging body base material, and the heat-developing image contains a heat-developing type reversible thermochromic material. The heat-developing image is held in a decolorized state in the normal temperature range and in the temperature range near the upper limit of the normal temperature range. That is, the heat-developing image of the packaging body is in a decolorized state in the initial state. In the present invention, "normal temperature" is based on 20°C ± 15°C defined in JIS Z 8703, and the "normal temperature range" is a temperature range of 5 to 35°C. The "temperature range near the upper limit of the normal temperature range" is a temperature range exceeding 35°C and not exceeding 40°C.

[0009] (Heat-developing type reversible thermochromic material) The heat-developing type reversible thermochromic material changes from a decolorized state to a colored state by heating, and changes from a colored state to a decolorized state by cooling. That is, the color changes from colorless to colored by heating, and from colored to colorless by cooling. <00001​​​​​​​​The discoloration temperature range is the temperature range between the complete decolorization temperature T1 and the complete color development temperature T4, and can exhibit either a colored state or a decolorized state. The temperature range between the decolorization start temperature T2 and the color development start temperature T3, which is the region with a large difference in color density, is essentially the two-phase retention temperature range. Furthermore, the length of line segment EF is a measure of the contrast of the discoloration, and the length of line segment HG passing through the midpoint of line segment EF is the temperature range indicating the degree of hysteresis. This temperature range is the hysteresis range (ΔH). If the ΔH value is small, only one of the two states before and after discoloration can exist in the room temperature range. Conversely, if the ΔH value is large, it becomes easier to maintain both the before and after discoloration states.

[0011] The components (a), (b), and (c) of the heat-activated reversible thermochromic composition applied to the present invention will be described in detail below.

[0012] (i) Components (a) Component, i.e., the electron-donating chromogenic organic compound, is the component that determines the color, and is a compound that produces color by donating electrons to component (b), which is a color developer.

[0013] Examples of electron-donating colorimetric organic compounds include phthalide compounds, fluorane compounds, styrinoquinoline compounds, diazalodamine lactone compounds, pyridine compounds, quinazoline compounds, and bisquinazoline compounds. Examples of phthalide compounds include diphenylmethane phthalide compounds, phenylindolyl phthalide compounds, indolyl phthalide compounds, diphenylmethane azaphthalide compounds, phenylindolyl azaphthalide compounds, and their derivatives. Among these, phenylindolyl azaphthalide compounds and their derivatives are preferred. Examples of fluorane compounds include aminofluorane compounds, alkoxyfluorane compounds, and their derivatives.

[0014] The following are examples of compounds that can be used in component (a). 3,3-bis(4-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)phthalide, 3,3-Bis(1-n-butyl-2-methylindole-3-yl)phthalide, 3,3-Bis(2-ethoxy-4-diethylaminophenyl)-4-azaphthalide, 3-(2-ethoxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(2-n-hexyloxy-4-diethylaminophenyl)-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, 3-(2-acetamido-4-diethylaminophenyl)-3-(1-propyl-2-methylindole-3-yl)-4-azaphthalide, 3,6-bis(diphenylamino)fluorane, 3,6-Bis(N-phenyl-Nm-tolylamino)fluorane, 3,6-Dimethoxyfluorane, 3,6-di-n-butoxyfluorane, 2-methyl-6-(N-ethyl-Np-tolylamino)fluorane, 3-Chloro-6-cyclohexylaminofluorane, 2-methyl-6-cyclohexylaminofluorane, 2-chloroamino-6-di-n-butylaminofluorane, 2-(2-chloroanilino)-6-di-n-butylaminofluorane, 2-(3-trifluoromethylanilino)-6-diethylaminofluorane, 2-(3-trifluoromethylanilino)-6-di-n-pentylaminofluorane, 2-Dibenzylamino-6-diethylaminofluorane, 2-N-methylanilino-6-(N-ethyl-Np-tolylamino)fluorane, 1,3-dimethyl-6-diethylaminofluorane, 2-Chloro-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methoxy-6-diethylaminofluorane, 2-anilino-3-methyl-6-di-n-butylaminofluorane, 2-anilino-3-methoxy-6-di-n-butylaminofluorane, 2-Xylidino-3-methyl-6-diethylaminofluorane, 2-anilino-3-methyl-6-(N-ethyl-Np-tolylamino)fluorane, 6-Diethylamino-1,2-benzofluorane, 6-(N-ethyl-N-isobutylamino)-1,2-benzofluorane, 6-(N-ethyl-N-isopentylamino)-1,2-benzofluorane, 2-(3-methoxy-4-dodecoxystyryl)quinoline, 2-Diethylamino-8-diethylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidine-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-di-n-butylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidine-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-diethylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidine-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-(N-ethyl-N-isoamylamino)-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidine-5,1′(3′H)-isobenzofuran]-3′-one, 2-di-n-butylamino-8-di-n-pentylamino-4-methylspiro[5H-[1]benzopyrano[2,3-d]pyrimidine-5,1′(3′H)-isobenzofuran]-3′-one, 4,5,6,7-Tetrachloro-3-(4-dimethylamino-2-methoxyphenyl)-3-(1-n-butyl-2-methylindole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-(4-diethylamino-2-ethoxyphenyl)-3-(1-n-pentyl-2-methylindole-3-yl)-1(3H)-isobenzofuranone, 4,5,6,7-Tetrachloro-3-(4-diethylamino-2-methylphenyl)-3-(1-ethyl-2-methylindole-3-yl)-1(3H)-isobenzofuranone, 3′,6′-bis[phenyl(2-methylphenyl)amino]spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 3′,6′-bis[phenyl(3-methylphenyl)amino]spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 3′,6′-bis[phenyl(3-ethylphenyl)amino]spiro[isobenzofuran-1(3H),9′-[9H]xanthene]-3-one, 2,6-bis(2′-ethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-Bis(2′,4′-diethyloxyphenyl)-4-(4′-dimethylaminophenyl)pyridine, 2,6-bis(2,4-diethyloxyphenyl)-4-[4-bis(4-methyloxyphenyl)aminophenyl]pyridine, 2-(4′-dimethylaminophenyl)-4-methoxyquinazoline, 4,4′-Ethylenedioxy-bis[2-(4-diethylaminophenyl)quinazoline]

[0015] Furthermore, fluoranes may include not only compounds having substituents on the phenyl group forming the xanthene ring, but also compounds that exhibit a blue or black color, having substituents on the phenyl group forming the xanthene ring and also on the phenyl group forming the lactone ring (for example, alkyl groups such as methyl groups, halogen atoms such as chlorine atoms).

[0016] (b) component (b) Component, i.e., the electron-accepting compound, is a compound that accepts electrons from component (a) and functions as a color developer for component (a).

[0017] (b) Examples of components include alkoxyphenol compounds represented by the following formula (1). [ka] (In the formula, R represents an alkyl group.) Examples of compounds represented by formula (1) include pn-propyloxyphenol, pn-butyloxyphenol, pn-pentyloxyphenol, pn-hexyloxyphenol, pn-heptyloxyphenol, pn-octyloxyphenol, pn-nonyloxyphenol, pn-decyloxyphenol, pn-undecyloxyphenol, pn-dodecyloxyphenol, pn-tridecyloxyphenol, pn-tetradecyloxyphenol, pn-pentyldecyloxyphenol, pn-hexyldecyloxyphenol, pn-heptyldecyloxyphenol, and pn-octyldecyloxyphenol.

[0018] (b) Examples of components include hydroxybenzoic acid ester compounds represented by the following formula (2). [ka] (In the formula, R represents a linear or branched alkyl group having 13 to 22 carbon atoms, one or two of X, Y, or Z represent hydroxyl groups, and the remainder represent hydrogen atoms.) Compounds represented by formula (2) include tridecyl 3-hydroxybenzoate, tetradecyl 3-hydroxybenzoate, pentadecyl 3-hydroxybenzoate, hexadecyl 3-hydroxybenzoate, heptadecyl 3-hydroxybenzoate, octadecyl 3-hydroxybenzoate, nonadecyl 3-hydroxybenzoate, eicosyl 3-hydroxybenzoate, heneicosyl 3-hydroxybenzoate, docosyl 3-hydroxybenzoate, and 4-hydroxybenzoate. Tridecyl hydroxybenzoate, tetradecyl 4-hydroxybenzoate, pentadecyl 4-hydroxybenzoate, hexadecyl 4-hydroxybenzoate, heptadecyl 4-hydroxybenzoate, octadecyl 4-hydroxybenzoate, nonadecyl 4-hydroxybenzoate, eicosyl 4-hydroxybenzoate, heneicosyl 4-hydroxybenzoate, docosyl 4-hydroxybenzoate, tridecyl 3,4-dihydroxybenzoate, 3 ,4-Dihydroxybenzoate tetradecyl ester, 3,4-Dihydroxybenzoate pentadecyl ester, 3,4-Dihydroxybenzoate hexadecyl ester, 3,4-Dihydroxybenzoate heptadecyl ester, 3,4-Dihydroxybenzoate octadecyl ester, 3,4-Dihydroxybenzoate nonadecyl ester, 3,4-Dihydroxybenzoate eicosyl ester, 3,4-Dihydroxybenzoate heneicosyl ester, 3,4-Dihydroxybenzoate docosyl ester, 3,5-Dihydroxybenzoate tri Examples include decyl esters, tetradecyl 3,5-dihydroxybenzoate, pentadecyl 3,5-dihydroxybenzoate, hexadecyl 3,5-dihydroxybenzoate, heptadecyl 3,5-dihydroxybenzoate, octadecyl 3,5-dihydroxybenzoate, nonadecyl 3,5-dihydroxybenzoate, eicosyl 3,5-dihydroxybenzoate, heneicosyl 3,5-dihydroxybenzoate, and docosyl 3,5-dihydroxybenzoate.

[0019] (b) Examples of components include gallic acid ester compounds. Examples include dodecyl gallate, tridecyl gallate, tetradecyl gallate, pentadecyl gallate, hexadecyl gallate, octadecyl gallate, eicosyl gallate, and behenyl gallate.

[0020] (H) component We will now explain component (c), which is the reaction medium that determines the temperature at which the color reaction of components (a) and (b) occurs. (h) Examples of components include hydrocarbons, halogenated hydrocarbons, sulfides, ethers, ketones, esters, alcohols, acid amides, waxes, etc. Semi-liquid substances such as medium molecular weight polymers may also be used. These can be used individually or in combination of two or more.

[0021] Examples of hydrocarbons include saturated-chain hydrocarbons, unsaturated-chain hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. Examples of saturated chain hydrocarbons include pentadecane, hexadecane, heptadecane, octadecane, nonadecane, eicosane, heneicosane, docosane, tricosane, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, and triacontane. Examples of unsaturated chain hydrocarbons include 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 1-heneicosene, 1-docosene, 1-tricosene, 1-tetracosene, 1-pentacosene, 1-hexacosene, 1-heptacosene, 1-octacosene, 1-nonacosene, and 1-triaconthene. Examples of alicyclic hydrocarbons include cyclooctane, cyclododecane, n-pentadecylcyclohexane, n-octadecylcyclohexane, n-nonadecylcyclohexane, and decahydronaphthalene. Examples of aromatic hydrocarbons include dodecylbenzene, biphenyl, ethylbiphenyl, 4-benzylbenzene, phenyltolylmethane, diphenylethane, 1,3-diphenylbenzene, dibenzyltoluene, methylnaphthalene, 2,7-diisopropylnaphthalene, methyltetraline, naphthylphenylmethane, and the like.

[0022] Examples of halogenated hydrocarbons include 1-bromodecane, 1-bromoundecane, 1-bromododecane, 1-bromotridecane, 1-bromotetradecane, 1-chlorotetradecane, 1-bromopentadecane, 1-bromohexadecane, 1-chlorohexadecane, 1-iodohexadecane, 1-bromoheptadecane, 1-bromooctadecane, 1-chlorooctadecane, 1-iodooctadecane, 1-bromoeicosane, 1-chloroeicosane, 1-bromodocosane, and 1-chlorodocosane.

[0023] Examples of sulfides include di-n-octyl sulfide, di-n-nonyl sulfide, di-n-decyl sulfide, di-n-dodecyl sulfide, di-n-tetradecyl sulfide, di-n-hexadecyl sulfide, di-n-octadecyl sulfide, octyldodecyl sulfide, diphenyl sulfide, dibenzyl sulfide, dityl sulfide, diethylphenyl sulfide, dinaphthyl sulfide, 4,4′-dichloro-diphenyl sulfide, and 2,4,5,4′-tetrachloro-diphenyl sulfide.

[0024] Examples of ethers include aliphatic ethers, alicyclic ethers, and aromatic ethers, which have a total of 10 or more carbon atoms. Examples of aliphatic ethers with a total of 10 or more carbon atoms include dipentyl ether, dihexyl ether, diheptyl ether, dioctyl ether, dinonyl ether, didecyl ether, diundecyl ether, didodecyl ether, ditridecyl ether, ditetradecyl ether, dipentadecyl ether, dihexadecyl ether, dioctadecyl ether, decanediol dimethyl ether, undecanediol dimethyl ether, dodecanediol dimethyl ether, tridecanediol dimethyl ether, decanediol diethyl ether, and undecanediol diethyl ether. Examples of alicyclic ethers include s-trioxane. Examples of aromatic ethers include phenyl ether, benzylphenyl ether, dibenzyl ether, di-p-tolyl ether, 1-methoxynaphthalene, and 3,4,5-trimethoxytoluene.

[0025] Examples of ketones include aliphatic ketones with 10 or more total carbon atoms, arylalkyl ketones, arylaryl ketones, and alicyclic ketones with 12 to 24 total carbon atoms. Examples of aliphatic ketones with a total of 10 or more carbon atoms include 2-decanone, 3-decanone, 4-decanone, 2-undecanone, 3-undecanone, 4-undecanone, 5-undecanone, 6-undecanone, 2-dodecanone, 3-dodecanone, 4-dodecanone, 5-dodecanone, 2-tridecanone, 3-tridecanone, 2-tetradecanone, 2-pentadecanone, 8-pentadecanone, 2-hexadecanone, 3-hexadecanone, 9-heptadecanone, 2-octadecanone, 2-nonadecanone, 10-nonadecanone, 2-eicosanone, 11-eicosanone, 2-heneicosanone, 2-docosanone, laurone, stearone, and the like. Examples of arylalkyl ketones with a total carbon number of 12 to 24 include n-octadecanophenone, n-heptadecanophenone, n-hexadecanophenone, n-pentadecanophenone, n-tetradecanophenone, 4-n-dodecacetophenone, n-tridecanophenone, 4-n-undecanoacetophenone, n-laurophenone, 4-n-decanoacetophenone, n-undecanophenone, 4-n-nonylacetophenone, n-decanophenone, 4-n-octylacetophenone, and n-nonano. Examples include phenone, 4-n-heptylacetophenone, n-octanophenone, 4-n-hexylacetophenone, 4-n-cyclohexylacetophenone, 4-tert-butylpropiophenone, n-heptaphenone, 4-n-pentylacetophenone, cyclohexylphenyl ketone, benzyl-n-butyl ketone, 4-n-butylacetophenone, n-hexanophenone, 4-isobutylacetophenone, 1-acetonaphthone, 2-acetonaphthone, and cyclopentylphenyl ketone. Examples of arylarylketones include benzophenone, benzylphenyl ketone, and dibenzyl ketone. Examples of alicyclic ketones include cyclooctanone, cyclododecanone, cyclopentadecanone, and 4-tert-butylcyclohexanone.

[0026] Effective esters include those having 10 or more carbon atoms, such as ester compounds obtained from any combination of a monohydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring; ester compounds obtained from any combination of a polyhydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring; and ester compounds obtained from any combination of a monohydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring. For example, ethyl caprylate, octyl caprylate, stearyl caprylate, myristyl caprate, docosyl caprate, 2-ethylhexyl laurate, n-decyl laurate, 3-methylbutyl myristate, cetyl myristate, isopropyl palmitate, neopentyl palmitate, nonyl palmitate, cyclohexyl palmitate, n-butyl stearate, 2-methylbutyl stearate, 3,5,5-trimethylhexyl stearate, n-undecyl stearate, pentadecyl stearate, stearyl stearate, cyclohexylmethyl stearate, isopropyl behenate, hexyl behenate, lauryl behenate, behenyl behenate, cetyl benzoate, p-tert-butyl stearyl benzoate, dimethyl phthalate Examples include ristil, distearyl phthalate, dimyristyl oxalate, dicetyl oxalate, dicetyl malonate, dilauryl succinate, dilauryl glutarate, diundecyl adipate, dilauryl azelaate, di-(n-nonyl) sebacate, 1,18-octadecylmethylenedicarboxylic acid dineopentyl, ethylene glycol dimyristate, propylene glycol dilaurate, propylene glycol distearate, hexylene glycol dipalmitate, 1,5-pentanediol distearate, 1,2,6-hexanetriol trimyristate, 1,4-cyclohexanediol didecyl, 1,4-cyclohexanedimethanol dimyristate, xylene glycol dicaprinate, xylene glycol distearate, etc.

[0027] The esters may be ester compounds obtained from a combination of a saturated fatty acid and a branched aliphatic alcohol; ester compounds obtained from a combination of an unsaturated fatty acid or a branched or substituted saturated fatty acid and a branched or carbon-16 or more aliphatic alcohol; or ester compounds selected from cetyl butyrate, stearyl butyrate, and behenyl butyrate. For example, 2-ethylhexyl butyrate, 2-ethylhexyl behenate, 2-ethylhexyl myristate, 2-ethylhexyl caprate, 3,5,5-trimethylhexyl laurate, 3,5,5-trimethylhexyl palmitate, 3,5,5-trimethylhexyl stearate, 3,5,5-trimethylhexyl behenate, 2-methylbutyl caproate, 2-methylbutyl caprylate, 2-methylbutyl caprate, 1-ethylpropyl palmitate, 1-ethylpropyl stearate, 1-ethylpropyl behenate 1-ethylhexyl laurate, 1-ethylhexyl myristate, 1-ethylhexyl palmitate, 2-methylpentyl caproate, 2-methylpentyl caprylate, 2-methylpentyl caprate, 2-methylpentyl laurate, 2-methylbutyl stearate, 2-methylbutyl stearate, 3-methylbutyl stearate, 1-methylheptyl stearate, 2-methylbutyl behenate, 3-methylbutyl behenate, 1-methylheptyl stearate, 1-methylheptyl behenate, 1-methylheptyl caproate -Ethylpentyl, 1-ethylpentyl palmitate, 1-methylpropyl stearate, 1-methyloctyl stearate, 1-methylhexyl stearate, 1,1-dimethylpropyl laurate, 1-methylpentyl caprate, 2-methylhexyl palmitate, 2-methylhexyl stearate, 2-methylhexyl behenate, 3,7-dimethyloctyl laurate, 3,7-dimethyloctyl myristate, 3,7-dimethyloctyl palmitate, 3,7-dimethyloctyl stearate, 3 behenate Examples include 7-dimethyloctyl oleate, stearyl oleate, behenyl oleate, stearyl linoleate, behenyl linoleate, 3,7-dimethyloctyl erucate, stearyl erucate, isostearyl erucate, cetyl isostearate, stearyl isostearate, 2-methylpentyl 12-hydroxystearate, 2-ethylhexyl 18-bromostearate, isostearyl 2-ketomyristate, 2-ethylhexyl 2-fluoromyristate, cetyl butyrate, stearyl butyrate, behenyl butyrate, etc.

[0028] The esters may be carboxylic acid ester compounds containing a substituted aromatic ring in the molecule; carboxylic acid ester compounds obtained from a combination of a carboxylic acid containing an unsubstituted aromatic ring and an aliphatic alcohol having 10 or more carbon atoms; carboxylic acid ester compounds containing a cyclohexyl group in the molecule; carboxylic acid ester compounds obtained from a combination of a fatty acid having 6 or more carbon atoms and an unsubstituted aromatic alcohol or phenol; carboxylic acid ester compounds obtained from a combination of a fatty acid having 8 or more carbon atoms and a branched aliphatic alcohol; carboxylic acid ester compounds obtained from a combination of a dicarboxylic acid and an aromatic alcohol or a branched aliphatic alcohol; or carboxylic acid ester compounds selected from dibenzyl cinnamate, heptyl stearate, didecyl adipate, dilauryl adipate, dimyristyl adipate, dicetyl adipate, distearyl adipate, trilaurin, trimiristine, tristearin, dimyristine, and distearin.

[0029] The esters may be fatty acid ester compounds obtained from a combination of an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid; or fatty acid ester compounds with a total of 17 to 23 carbon atoms obtained from a combination of n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid having 10 to 16 carbon atoms. For example, n-pentadecyl acetate, n-tridecyl butyrate, n-pentadecyl butyrate, n-undecyl caproate, n-tridecyl caproate, n-pentadecyl caproate, n-nonyl caprylate, n-undecyl caprylate, n-tridecyl caprylate, n-pentadecyl caprate, n-heptyl caprate, n-nonyl caprate, n-undecyl caprate, n-tridecyl caprate, n-pentadecyl caprate, n-pentyl laurate, n-heptyl laurate, n-nonyl laurate, n-undecyl laurate, n-tridecyl laurate, n-pentadecyl laurate, n-pentyl myristate, n-heptyl myristate, myristi Examples include n-nonyl palmitate, n-undecyl myristate, n-tridecyl myristate, n-pentadecyl myristate, n-pentyl palmitate, n-heptyl palmitate, n-nonyl palmitate, n-undecyl palmitate, n-tridecyl palmitate, n-pentadecyl palmitate, n-nonyl stearate, n-undecyl stearate, n-tridecyl stearate, n-pentadecyl stearate, n-nonyl eicosanoate, n-undersi eicosanoate, n-tridecyl eicosanoate, n-pentadecyl eicosanoate, n-nonyl behenate, n-undecyl behenate, n-tridecyl behenate, and n-pentadecyl behenate.

[0030] Examples of alcohols include aliphatic monohydric saturated alcohols, aliphatic unsaturated alcohols, alicyclic alcohols, aromatic alcohols, and polyhydric alcohols. Examples of monohydric aliphatic saturated alcohols include decyl alcohol, undecyl alcohol, dodecyl alcohol, tridecyl alcohol, tetradecyl alcohol, pentadecyl alcohol, hexadecyl alcohol, heptadecyl alcohol, octadecyl alcohol, eicosyl alcohol, and docosyl alcohol. Examples of aliphatic unsaturated alcohols include allyl alcohol and oleyl alcohol. Examples of alicyclic alcohols include cyclopentanol, cyclohexanol, cyclooctanol, cyclododecanol, and 4-tert-butylcyclohexanol. Examples of aromatic alcohols include 4-methylbenzyl alcohol and benzhydrol. Examples of polyhydric alcohols include polyethylene glycol.

[0031] Examples of acid amides include acetamide, propionic acid amide, butyrate amide, caproic acid amide, caprylic acid amide, capric acid amide, lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, benzamide, caproic acid anilide, caprylic acid anilide, capric acid anilide, lauric acid anilide, myristic acid anilide, palmitic acid anilide, stearic acid anilide, behenic acid anilide, oleic acid anilide, erucic acid anilide, and N-methyl caproic acid anilide. N-methylamide caprylic acid, N-methylamide capric acid, N-methylamide laurate, N-methylamide myristate, N-methylamide palmitate, N-methylamide stearate, N-methylamide behenate, N-methylamide oleate, N-methylamide erucate, N-ethylamide laurate, N-ethylamide myristate, N-ethylamide palmitate, N-ethylamide stearate, N-ethylamide oleate, N-butylamide laurate, N-butylamide myristate, N-butylamide palmitate, stear N-butylamide phosphate, N-butylamide oleate, N-octylamide laurate, N-octylamide myristate, N-octylamide palmitate, N-octylamide stearate, N-octylamide oleate, N-dodecylamide laurate, N-dodecylamide myristate, N-dodecylamide palmitate, N-dodecylamide stearate, N-dodecylamide oleate, dilaurate, dimyristateamide, dipalmitamide, distearate, dioleamide, trilaurate, tri Myristic acid amide, tripalmitic acid amide, tristearic acid amide, trioleic acid amide, succinic acid amide, adipic acid amide, glutaric acid amide, malonic acid amide, azelaic acid amide, maleic acid amide, succinic acid N-methylamide, adipic acid N-methylamide, glutaric acid N-methylamide, malonic acid N-methylamide, azelaic acid N-methylamide, succinic acid N-ethylamide, adipic acid N-ethylamide, glutaric acid N-ethylamide, malonic acid N-ethylamide, azelaic acid N-ethylamide, succinic acid N-butylamide,Examples include N-butylamide adipic acid, N-butylamide glutarate, N-butylamide malonate, N-octylamide adipic acid, and N-dodecylamide adipic acid.

[0032] Examples of waxes or medium molecular weight polymers include paraffin wax, microcrystalline wax, petrolactam, oxidized paraffin wax, oxidized petrolactam, shellac, sugarcane wax, carnauba wax, candelilla wax, castor wax, hydrogenated beef tallow oil, hydrogenated fish oil, hydrogenated rapeseed oil, montan wax, palm wax, babassu wax, molasses wax, wolf's wool fat, oxidized polyethylene wax, montanic acid wax, ethylene vinyl acetate copolymer wax, ethylene acrylic copolymer wax, vinyl ether wax, palm oil, babassu oil, liquid paraffin, polybutene, polybutadiene, polystyrene oligomers, etc., all with a melting point of 50 to 120°C.

[0033] (h) The component may be an aliphatic hydrocarbon having 17 or more carbon atoms. Furthermore, additional components may be used in combination with component (c). For example, hydrocarbons selected from the group consisting of (c) chain hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, and halogenated hydrocarbons may be used in combination with (d) compounds selected from the group consisting of alcohols, esters, ethers, ketones, and acid amides, having a melting point of 50°C or higher. Alternatively, hydrocarbons may be used in combination with (d) styrene compounds having a softening point of 5°C or higher and a mass-average molecular weight of 200 to 100,000. Alternatively, hydrocarbons may be used in combination with (d) styrene polymers having a softening point of 5°C or higher and a mass-average molecular weight of 200 to 100,000, and (e) alkoxyphenyl compounds. Furthermore, (c) hydrocarbons, (d) linear dibasic acid compounds having 3 to 22 carbon atoms, and (e) compounds selected from the group consisting of alcohols, esters, ethers, ketones, acid amides, and aromatic hydrocarbons, with a melting point of 50°C or higher, may be used in combination.Optionally, (f) oligomers selected from the group consisting of styrene oligomers with a mass average molecular weight of 200 to 6000, terpene oligomers with a mass average molecular weight of 250 to 4000, or terpene phenol oligomers with a mass average molecular weight of 200 to 2000 may be used in combination.

[0034] A heat-activated, reversible thermochromic composition is a compatible mixture comprising the above-mentioned components (a), (b), and (c) as essential components. The proportion of each component depends on the concentration, color change temperature, color change form, or type of component. Generally, the component ratio that yields the desired properties is in the range of 0.1 to 50 parts by mass, preferably 0.5 to 20 parts by mass, of component (b) per 1 part by mass of component (a), and in the range of 1 to 200 parts by mass, preferably 5 to 100 parts by mass, of component (c).

[0035] ·others Heat-activated, reversible thermochromic compositions may contain various light stabilizers as needed. Light stabilizers are included to prevent photodegradation of the reversible thermochromic composition, which consists of at least components (a), (b), and (c). The component ratio for obtaining the desired properties is in the range of 0.3 to 24 parts by mass, preferably 0.3 to 16 parts by mass, of the light stabilizer per 1 part by mass of component (a). Among the light stabilizers, ultraviolet absorbers effectively cut ultraviolet rays contained in sunlight, etc., and prevent photodegradation caused by the excitation state due to the photoreaction of component (a). In addition, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, etc., suppress oxidation reactions caused by light. Light stabilizers are used individually or in combination of two or more types.

[0036] The heat-activated, reversible thermochromic composition may contain non-thermochromic colorants such as general dyes and / or pigments. By containing non-thermochromic colorants, the heat-activated, reversible thermochromic composition undergoes an alternating color change from a first color to a second color.

[0037] • Microencapsulated pigments The heat-activated reversible thermochromic material according to the present invention is a heat-activated reversible thermochromic microcapsule pigment (hereinafter sometimes referred to as "microcapsule pigment") in which the aforementioned heat-activated reversible thermochromic composition (encapsulated) is encapsulated in a wall film. By encapsulating the reversible thermochromic composition in microcapsules, a chemically or physically stable pigment can be constructed, and furthermore, the reversible thermochromic composition can maintain the same composition and exert the same effects under various usage conditions.

[0038] The wall film forms an internal space that encloses the reversible thermochromic composition, and this internal space is separated from the outside. As a result, the microcapsule pigment is less susceptible to external influences, protecting the reversible thermochromic composition from various degradation factors and allowing it to exhibit its reversible thermochromic function over a long period of time. The reversible thermochromic function of a heat-developing type reversible thermochromic composition refers to the function of becoming decolorized in the temperature range below the low-temperature color change point (complete decolorization temperature) and becoming colored in the temperature range above the high-temperature color change point (complete color development temperature).

[0039] The material of the wall film is not particularly limited. Examples include polyurea, polyamide, polyurethane, epoxy resin, melamine resin, urea resin, urea urethane resin, isocyanate resin, vinyl resin, gelatin, ethylcellulose, polyvinyl alcohol, carboxymethylcellulose, etc. These can be used individually or in combination of two or more.

[0040] Microencapsulated pigments are obtained by known microencapsulation methods. Examples of microencapsulation methods include interfacial polymerization, in situ polymerization, liquid curing and coating, phase separation from aqueous solutions, phase separation from organic solvents, melt-dispersion-cooling, air suspension and coating, and spray drying, and are selected as appropriate depending on the application.

[0041] Depending on the purpose, a resin coating or the like may be applied to the surface of the microcapsules to provide durability or modify the surface properties.

[0042] Microcapsule pigments consist of a microcapsule wall (wall material) and an encapsulated substance (including a reversible thermochromic composition), with a preferred mass ratio of encapsulated substance to wall film of 7:1 to 1:1. Having the mass ratio of encapsulated substance to wall film within this range prevents a decrease in color density and vividness during color development. More preferably, the mass ratio of encapsulated substance to wall film is 6:1 to 1:1.

[0043] The average particle size of the microcapsule pigment is preferably in the range of 0.1 to 20 μm, more preferably 0.5 to 15 μm, even more preferably 1 to 10 μm, and particularly preferably 2 to 7 μm. If the average particle size exceeds 20 μm, the dispersion stability and processability will be poor when blended into inks, paints, or resins. On the other hand, if the average particle size is less than 0.1 μm, it will be difficult to exhibit high-concentration color development.

[0044] The average particle diameter is the equivalent diameter of an isovolume sphere measured using a laser diffraction / scattering particle size distribution analyzer that has undergone a predetermined calibration [for example, Horiba, Ltd., product name: LA-960V2]. The average particle size is the average value of the equivalent diameter of an equal-volume sphere (the particle size D50, i.e., the median diameter, which corresponds to a frequency of 50% when the particle size distribution is determined based on volume).

[0045] The prescribed calibration will be explained. If the particle size of all microcapsules exceeds 0.20 μm, the average value of the equivalent diameter of equivolute spheres is measured using the Coulter method with a particle size distribution analyzer (e.g., Multisizer 4e, manufactured by Beckman Coulter, Inc.), and calibration is performed based on that value.

[0046] In cases other than those described above, the microcapsule region is determined using image analysis-based particle size distribution measurement software (for example, MacView, manufactured by Mountec Co., Ltd.), the projected area equivalent diameter (Heywood diameter) is calculated from the area of ​​the microcapsule region, and calibration is performed based on the average value of these equivalent diameters of equivolute spheres.

[0047] The heat-activated reversible thermochromic material according to the present invention has a color-development initiation temperature T3 of 50°C or higher, a complete decolorization temperature T1 of 5 to 40°C, and a decolorization initiation temperature T2 that is less than the color-development initiation temperature T3. Because the color development start temperature T3 is 50°C or higher, the heated colored image remains colorless in the normal living environment, including at room temperature and near the upper limit of room temperature, and only appears rapidly upon cooking. Therefore, it is possible to reliably inform consumers that the food contained in the packaging according to this invention has been cooked. Furthermore, the unexpected appearance of the design on the packaging after cooking can attract the interest of cooks. Regarding the full color development temperature T4 and the color development start temperature T3, it is preferable that T4 ≥ (T3 + 10). This allows the gradual appearance of the heat-induced coloration during cooking to be visually observed, further attracting the interest of the cook. It is also preferable that the full color development temperature T4 is 55°C or higher. It is said that the growth of food poisoning bacteria can be suppressed at temperatures of 55°C or higher, and it is possible to determine from the color development state of the heat-induced coloration on the packaging that the food has reached a temperature at which it is sufficiently heated. Since the complete decolorization temperature T1 is 5-40°C and the decolorization start temperature T2 is less than the color development start temperature T3, the heated color image is maintained in a colored state for a certain period after cooking, and then the heated color image gradually decolorizes until the food temperature gradually decreases to the room temperature range or near the upper limit of the room temperature range. In other words, since the heated color image does not become decolorized immediately after cooking, a third party other than the cook can understand that the food is being cooked or has been cooked, and can prevent burns from touching the food or accidentally reheating it. It is preferable that the decolorization start temperature T2 and the color development start temperature T3 satisfy T2 < (T3 - 10) as it is easier to maintain the heated color image in a colored state. The complete decolorization temperature T1 is preferably 20 to 35°C. This allows the packaging according to the present invention to be easily returned to its initial state where the heat-activated color image is decolorized, even if it is accidentally exposed to a high-temperature environment during the manufacturing process, causing the heat-activated color image to become colored.

[0048] The hysteresis width (ΔH) of the heat-activated reversible thermochromic material is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. This makes it easier for the heat-activated reversible thermochromic material to selectively maintain either a colored state or a decolorized state, making it easier for a third party other than the cook to understand the cooking status of the food from the appearance of the packaging.

[0049] [Composition of packaging for cooking] The heat-curing packaging according to the present invention has a heat-curing image provided on the packaging substrate, which is a dried ink composition containing a heat-curing reversible thermochromic material.

[0050] <Package base material> The material of the packaging substrate is not particularly limited. Examples include paper, synthetic paper, fibers, fabrics, synthetic leather, genuine leather, plastics, foams, glass, ceramics, wood, stone, and metals. Preferably, it is paper, synthetic paper, plastic, foam, or metal. The packaging substrate may also have gas barrier properties.

[0051] The shape of the packaging material is not particularly limited, as long as it is a shape that can contain and allow for the removal of cooked food. Examples include bags, boxes, containers, etc. The bag-shaped packaging material (hereinafter sometimes referred to as "bag") may be sealed by heat sealing or the like from the viewpoint of preserving the food contained inside. A notch may be provided to facilitate opening the bag. Furthermore, a packaging material with one side open may be provided with a zipper on or near the edge of the open side (opening) to easily switch between open and closed states. This allows food to be stored in a sealed state inside the bag, and the bag can be opened as needed to remove the stored food. In other words, food can be stored and removed repeatedly, making it highly practical. The zipper consists of a convex portion on one side of the packaging material in the open state and a concave portion on the other side, with the convex portion and concave portion facing each other. By pressing the convex portion and concave portion together by hand, they fit together to close the bag, and by pulling them apart by hand, the bag opens. There may be multiple convex portions and concave portions, and multiple zippers may be provided on the bag. A fitting device (slider member) for fitting the zipper may be provided on the edge of the opening, and the opening can be opened and closed by moving the fitting device laterally (perpendicular to the opening direction of the opening). Alternatively, the opening with the zipper may be sealed by heat welding (heat sealing). This not only improves the shelf life of the food until it is opened, but also allows any remaining food to be stored in an airtight state for a period of time after opening.

[0052] The packaging material may be a container. The container has a shape that allows food to be contained inside and removed. The container is composed of, for example, a bottomed cylindrical container body with an opening at the top, and a lid that closes the opening of the container body. The heat-activated color image is formed on the outer surface of the container, for example, on the outer surface of the container body or on the lid material. From the viewpoint of visibility of the heat-activated color image, it is preferable to provide the heat-activated color image on the lid material.

[0053] The packaging material contains cooked food. The cooked food is not particularly limited. Examples include retort foods such as curry, pasta sauce, and stew; instant foods such as dried noodles and dried powders; rapidly frozen meat and vegetables; and frozen foods such as pasta dishes.

[0054] <Image showing color development after heating> The heat-induced color image is the dried and solidified ink composition, as described later. The heat-induced color image is formed when the ink composition dries and solidifies. Solidification refers to the change of the ink composition from liquid to solid. The solidified ink composition is the dried and solidified material, which in this invention corresponds to the heat-induced color image. The heat-induced color image may contain components other than the volatile components contained in the ink composition, or their reaction products.

[0055] The heat-activated color image is formed by directly printing or coating the ink composition onto the packaging substrate or the underlayer described later. One method for providing a heat-activated color image on the packaging substrate is to attach a label or seal with the heat-activated color image to the packaging substrate via an adhesive layer. However, when cooking by pouring hot water into the packaging (container) or by using a microwave oven, the packaging according to the present invention allows heat from inside the packaging substrate to be directly transferred to the heat-activated color image, compared to packaging using a label or seal with a heat-activated color image. Therefore, the heat-activated color image can change color rapidly due to cooking. Furthermore, when cooking by using a water bath, packaging using a label or seal with a heat-activated color image may experience a decrease in adhesive strength due to the hot water, causing the label or seal to peel off. On the other hand, with the packaging according to the present invention, since the heat-activated color image is directly attached to the packaging substrate, there is no risk of the heat-activated color image peeling off. Examples of printing methods include screen printing, offset printing, gravure printing, coater printing, pad printing, and transfer printing. Examples of coating methods include brush painting, spray painting, electrostatic painting, electrodeposition painting, pouring, roller painting, and dipping.

[0056] Hereafter, "drying solidification" will refer to the process of solidifying after printing or coating without any chemical change. Furthermore, "curing drying" will refer to the process of solidifying after printing or coating by chemical hardening (polymerization) of the polymerizable vehicle, as described later.

[0057] The heat-activated color image may be formed on the entire packaging substrate or on only a part of it. The heat-activated color image may be formed to represent, for example, shapes such as circles, ovals, squares, and rectangles; pictures of people, animals, plants, fruits, food products, tableware, vehicles, buildings, celestial bodies, etc.; various letters or sentences; product names of cooked foods; cooking instructions for cooked foods; various symbols; or geometric patterns. These may be used individually or in combination of two or more. It is also preferable that the image be of a word that serves as a warning to inform the consumer that the food contained inside the packaging is being cooked or has been cooked and that there is a risk of burns (for example, "Hot," "Caution," "Burn Warning," etc.). The packaging according to the present invention may have multiple heat-induced color-developed images.

[0058] The thickness of the heated color image is not particularly limited and is set appropriately so that reversible thermal color change is achieved. The thickness of the heated color image is preferably in the range of 1 to 20 μm, and more preferably in the range of 5 to 15 μm.

[0059] The packaging according to the present invention has a design that is invisible when heated and colored at room temperature and near the upper limit of room temperature, and the design appears when heated and cooked. Humans tend to be highly perceptive of new changes, such as images appearing from nothing, and the transformation of the invisible, colored image into a colored state can attract the interest of both the cook and third parties. In other words, the packaging according to the present invention allows the cook to enjoy the appearance of the design as it emerges, and informs third parties of the cooking status of the food, preventing burns or accidental reheating.

[0060] (Ink composition) The ink composition according to the present invention comprises a heat-activated reversible thermochromic material and a vehicle. The ink composition is prepared by mixing and stirring each component. Specifically, it is prepared by stirring a mixture of the required amounts of each component using various stirrers such as propeller stirrers, homodispersers, or homomixers, or by dispersing it using various dispersers such as bead mills.

[0061] The content of the heat-colorable, reversible thermochromic material is preferably in the range of 25 to 65% by mass of the mass of the ink composition, more preferably in the range of 30 to 60% by mass of the mass of the ink composition, and even more preferably in the range of 35 to 55% by mass of the mass of the ink composition.

[0062] • Vehicle The vehicle includes, for example, a binder, a solvent, and various additives as needed. The vehicle may be curable (polymerizable). The curable (polymerizable) vehicle may be oxidatively polymerizable, thermosetting (including room temperature curing), ultraviolet curable, or electron beam curable.

[0063] ·binder The binder is an organic compound. The binder comprises at least one of a polymerizable monomer, a polymerizable oligomer, and a polymer. The polymer may be polymerizable (prepolymer) or nonpolymerizable.

[0064] Examples of polymerizable monomers include epoxy (meth)acrylates, urethane (meth)acrylates, oligoester (meth)acrylates, polyester (meth)acrylates, and (meth)acrylate compounds with a mass-average molecular weight (Mw) of 100 to 800. Examples of (meth)acrylate compounds include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate; cyclic (meth)acrylates such as tetrahydrofurfuryl (meth)acrylate, isoboronyl (meth)acrylate, and cyclohexyl (meth)acrylate; aromatic acrylates such as benzyl (meth)acrylate; di(meth)acrylates such as butanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and neopentyl glycol di(meth)acrylate; and trimethylol Examples include tri(meth)acrylates such as lupropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; tetra(meth)acrylates such as pentaerythritol tetra(meth)acrylate; hexa(meth)acrylates such as dipentaerythritol hexa(meth)acrylate; neopentyl glycol acrylate benzoate; phosphate-containing (meth)acrylates such as 2-acryloyloxyethyl acid phosphate; hydroxyl-containing (meth)acrylates such as 2-hydroxyethyl acrylate, N-vinylpyrrolidone; (meth)acrylamide; N-methylolacrylamide; acryloylmorpholine; glycidyl(meth)acrylate-(meth)acrylic acid adducts; methylenebis(meth)acrylamide, etc. These can be used individually or in combination of two or more. Note that "(meth)acrylate compound" refers to a compound containing an acryloyl group (CH2=CH-COO-) or a methacryloyl group (CH2=C(-CH3)-COO-).

[0065] Examples of polymerizable oligomers include urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, oligoester (meth)acrylate, unsaturated polyester, butadiene (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, etc. Alternatively, dimers, trimers, tetramers, or low molecular weight polymers with a mass-average molecular weight (Mw) of 100 to 10,000 of one or more of the above polymerizable monomers may be used. These can be used individually or in combination of two or more.

[0066] Examples of polymers include non-drying oil alkyd resins, semi-drying oil alkyd resins, drying oil alkyd resins, urethane-modified alkyd resins, styrene-modified alkyd resins, (meth)acrylic-modified alkyd resins, epoxy-modified alkyd resins, phenol-modified alkyd resins, oil-free alkyd resins, acid-curable amino alkyd resins, rosin-modified alkyd resins, silicone-modified alkyd resins, rosin-modified phenol resins, rosin-modified maleic acid resins, (meth)acrylic resins, styrene-(meth)acrylic copolymer resins, silicone-modified (meth)acrylic resins, alkyd-modified (meth)acrylic resins, and cellulose acetate butyrate (CAB)-modified resins. Examples include (meth)acrylic resins, (meth)acrylic polyols, epoxy resins, (meth)acrylic-modified epoxy resins, amine-modified epoxy resins, fluororesins, polycarbonates, amino resins, melamine resins, benzoguanamine resins, urea resins, isocyanate resins, chlorinated polyolefin resins, vinyl chloride resins, vinyl chloride-vinyl acetate copolymer resins, ethylene-vinyl chloride copolymer resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl chloride-vinyl acetate copolymer resins, acrylic-vinylidene chloride resins, amide resins, petroleum resins, cellulose derivatives, rosin derivatives, chlorinated rubber, cyclized rubber, and chlorinated polyolefins. These can be used individually or in combination of two or more.

[0067] The solid content of the binder is preferably in the range of 15 to 50% by mass of the mass of the vehicle, more preferably in the range of 20 to 45% by mass, and even more preferably in the range of 25 to 40% by mass.

[0068] ·solvent Examples of solvents include water or organic solvents. There are no particular restrictions on the type of water used. Examples include tap water, deionized water, ultrafiltered water, and distilled water. The organic solvents are not particularly limited. Examples include aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, alcohol solvents, ester solvents, and ketone solvents. Specifically, examples include industrial solvents, kerosene, Sorbesso 100, Sorbesso 150, xylene, mineral spirits, n-butanol, anone, isophorone, cellosolve, and cellosolve acetate. These can be used individually or in combination of two or more. Alternatively, a mixture of water and a water-compatible organic solvent (water-soluble organic solvent) may be used. Examples of water-soluble organic solvents include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulforane, 2-pyrrolidone, N-methyl-2-pyrrolidone, and the like.

[0069] The solvent content is preferably in the range of 50 to 80% by mass of the vehicle's mass, more preferably in the range of 55 to 75% by mass, and even more preferably in the range of 60 to 70% by mass.

[0070] • Additives Various additives may be added to the vehicle as needed. Examples of additives include surfactants, dispersants, plasticizers, waxes, thixotropy-imparting agents, wetting agents, coupling agents, curing agents, viscosity modifiers, crosslinking agents, antioxidants, UV absorbers, light stabilizers, chelating agents, polymerization inhibitors for dark-temperature stabilization, leveling agents, defoamers, adhesion-imparting agents, antistatic agents, preservatives and antifungal agents, flame retardants, rust inhibitors, extender pigments, and the like.

[0071] A polymerization initiator and a polymerization initiator may be added to a vehicle containing a polymerizable binder. It is desirable that polymerization inhibitors and polymerization initiators are not present together.

[0072] <Other layers> The packaging may include a base layer interposed between the packaging substrate and the heat-activated color image. The base layer may be a layer that does not exhibit reversible thermal discoloration (an irreversible thermal discoloration layer). Examples of the base layer include a white ink layer and a sealing layer. These layers can enhance the color development of the heat-activated color image or the heat-decolorized image described later. The thickness of the underlayer is not particularly limited and can be set as appropriate depending on the purpose, etc. The base layer is formed, for example, by the printing or coating method, lamination method, or heat-pressing method described above.

[0073] The packaging may have a transparent protective layer over the heat-activated color image. The transparent protective layer protects the heat-activated reversible thermochromic material from physical impact. Transparency means that the total light transmittance is 70% or higher. The total light transmittance can be measured by a method in accordance with JIS K 7361-1. The transparent protective layer may contain a light stabilizer or a transparent metallic luster pigment from the viewpoint of lightfastness. Examples of light stabilizers include ultraviolet absorbers, antioxidants, anti-aging agents, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, visible light absorbers, infrared absorbers, etc. Examples of transparent metallic luster pigments include those in which the surface of a base material such as natural mica, synthetic mica, glass fragments, alumina, or transparent film fragments is coated with a metal oxide such as titanium dioxide. The thickness of the transparent protective layer is not particularly limited and can be set as appropriate depending on the purpose, etc. The transparent protective layer is formed, for example, by the printing or coating method, lamination method, or heat-pressing method described above.

[0074] The packaging may include an anchor coat layer. The anchor coat layer enhances the adhesion of layers provided above and below it. The anchor coat layer may contain a light stabilizer or a transparent metallic luster pigment from the viewpoint of lightfastness. The light stabilizer or transparent metallic luster pigment can be the same as those described above. The thickness of the anchor coat layer is not particularly limited and can be set as appropriate depending on the purpose, etc. The anchor coat is formed, for example, by the printing or coating method, lamination method, or heat-pressing method described above.

[0075] The packaging may include a layer that does not exhibit reversible thermochromicity (an irreversible thermochromic layer). The irreversible thermochromic layer may be positioned adjacent to the heating-developed image below (between the packaging substrate and the heating-developed image), adjacent to the heating-developed image above, or on the same plane as the heating-developed image. Due to the irreversible thermochromic layer, the packaging undergoes an alternating color change from a first color to a second color.

[0076] The irreversible thermochromic layer may be formed by solid printing and may be formed as an image (irreversible thermochromic image) to represent shapes such as circles, ellipses, squares, and rectangles; pictures of people, animals, plants, fruits, food products, tableware, vehicles, buildings, celestial bodies, etc.; various letters or sentences; product names of cooked foods; cooking instructions for cooked foods; various symbols; and geometric patterns. The thickness of the irreversible thermal discoloration layer is not particularly limited and can be set as appropriate depending on the purpose. The irreversible thermal discoloration layer can be formed, for example, by the printing method or coating method described above.

[0077] The packaging may include a gas barrier layer. The gas barrier layer may be made of, for example, a resin film made of ethylene-vinyl alcohol copolymer resin, polyvinylidene chloride, etc., or a metal foil such as aluminum foil. Alternatively, a vapor-deposited film may be used, such as a synthetic resin film made of polyethylene terephthalate (PET) with metal vapor deposition of aluminum, etc., or with an inorganic compound vapor deposition, or with an inorganic compound coating layer on top of a vapor-deposited inorganic compound layer.

[0078] The packaging may include a heat-decolorizing image comprising a heat-decolorizing type reversible thermochromic material, as described later.

[0079] (Reversible thermochromic material that decolorizes when heated) Heat-decolorizing reversible thermochromic materials change from a colored state to a decolorized state upon heating, and from a decolorized state to a colored state upon cooling. In other words, they change color from colored to colorless upon heating, and from colorless to colored upon cooling. The heat-decolorizing reversible thermochromic material is a heat-decolorizing reversible thermochromic microcapsule pigment in which a heat-decolorizing reversible thermochromic composition containing at least three essential components—(a) an electron-donating coloring organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of components (a) and (b) occurs—is encapsulated in a microcapsule.

[0080] As a heat-decolorizing type reversible thermochromic composition, a heat-decolorizing type reversible thermochromic composition having a relatively small hysteresis width (ΔH) (ΔH = 1 to 7°C), as described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc., can be used. This reversible thermochromic composition changes color before and after a predetermined temperature (color change point), exhibiting a decolorized state in the temperature range above the high-temperature color change point and a colored state in the temperature range below the low-temperature color change point. Of the two states, only one specific state exists in the room temperature range, and the other state is maintained as long as the heat or cold required to bring about that state is applied, but returns to the state exhibited in the room temperature range when the application of heat or cold is stopped (see Figure 2).

[0081] As a heat-decolorizing type reversible thermochromic composition, a heat-decolorizing type reversible thermochromic composition having a large hysteresis width (ΔH = 8 to 80°C) as described in Japanese Patent Publication No. 4-17154, Japanese Patent Application Publication No. 7-179777, Japanese Patent Application Publication No. 7-33997, Japanese Patent Application Publication No. 8-39936, Japanese Patent Application Publication No. 2005-1369 can also be used. This reversible thermochromic composition exhibits color memory properties in a specific temperature range (between the color-development start temperature t2 and the color-deactivation start temperature t3 (essentially a two-phase retention temperature range)). The shape of the curve plotting the change in color intensity due to temperature changes follows a significantly different path depending on whether the temperature is raised from a temperature below the color-development temperature range or from a temperature above the color-development temperature range t4. The colored state at temperatures below the complete color-development temperature t1, or the decolorized state at temperatures above the complete decolorization temperature t4, is distinct from the color-deactivation state at temperatures above t3 (essentially a two-phase retention temperature range) (see Figure 3).

[0082] This paper describes the hysteresis characteristics in the color density-temperature curve of a heat-decolorizing, reversible thermochromic material. In Figures 2 and 3, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to temperature changes progresses along the arrows. Here, A represents the density at the temperature t4 (hereinafter referred to as the complete decolorization temperature) where complete decolorization is reached, B represents the density at the temperature t3 (hereinafter referred to as the decolorization start temperature) where decolorization begins, C represents the density at the temperature t2 (hereinafter referred to as the color development start temperature) where color development begins, and D represents the density at the temperature t1 (hereinafter referred to as the complete color development temperature) where complete color development is reached. The discoloration temperature range is the temperature range between the complete decolorization temperature t4 and the complete color development temperature t1, and can exhibit either a colored state or a decolorized state. The temperature range between the decolorization start temperature t3 and the color development start temperature t2, which is the region with a large difference in color density, is essentially the two-phase retention temperature range. Furthermore, the length of line segment EF is a measure of the contrast of the discoloration, and the length of line segment HG passing through the midpoint of line segment EF is the temperature range indicating the degree of hysteresis. This temperature range is the hysteresis range (ΔH). If the ΔH value is small, only one of the two states before and after discoloration can exist in the room temperature range. Conversely, if the ΔH value is large, it becomes easier to maintain both the before and after discoloration states.

[0083] The components (a), (b), and (c) of the heat-decolorizing, reversible thermochromic composition applied to the present invention will be described in detail below.

[0084] (i) Components (i) The component may be the same as the electron-donating color-developing organic compound used in a heat-activated reversible thermochromic composition.

[0085] (b) component (b) The component can be selected from the group of compounds having active protons, the group of pseudoacidic compounds (compounds that are not acids but act as acids in reversible thermochromic products to cause the component in (a) to develop color), and the group of compounds having electron vacancies. Among these, compounds selected from the group of compounds having active protons are preferred.

[0086] Examples of compounds having active protons include compounds having a phenolic hydroxyl group and their derivatives, carboxylic acids and their derivatives, acidic phosphate esters and their derivatives, azole compounds and their derivatives, 1,2,3-triazoles and their derivatives, cyclic carbosulfimides, C2-C5 halohydrins, sulfonic acids and their derivatives, and inorganic acids. Preferred carboxylic acids and their derivatives are aromatic carboxylic acids and their derivatives, or C2-C5 aliphatic carboxylic acids and their derivatives. Examples of pseudoacidic compounds include metal salts of compounds having a phenolic hydroxyl group, metal salts of carboxylic acids, metal salts of acidic phosphate esters, metal salts of sulfonic acids, aromatic carboxylic acid anhydrides, aliphatic carboxylic acid anhydrides, mixed anhydrides of aromatic carboxylic acids and sulfonic acids, cycloolefin dicarboxylic acid anhydrides, urea and its derivatives, thiourea and its derivatives, guanidine and its derivatives, and halogenated alcohols. Compounds containing electron vacancies include borates, borate esters, and inorganic salts.

[0087] Among the components of (b) above, compounds having a phenolic hydroxyl group are preferred because they can more effectively exhibit thermal discoloration properties. Compounds having a phenolic hydroxyl group broadly include monophenol compounds to polyphenol compounds, and further include bisphenol compounds, trisphenol compounds, phenol-aldehyde condensation resins, etc. It is preferable that compounds having a phenolic hydroxyl group have at least two benzene rings. Furthermore, compounds having a phenolic hydroxyl group may have substituents such as alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxyl groups and their esters or amide groups, halogen atoms, etc.

[0088] Examples of metals contained in metal salts of compounds having a phenolic hydroxyl group include sodium, potassium, calcium, zinc, zirconium, aluminum, magnesium, nickel, cobalt, tin, copper, iron, vanadium, titanium, lead, and molybdenum.

[0089] The following are examples of compounds that can be used in component (b). Phenol, o-cresol, 4-np-nonylphenol, 4-n-octylphenol, 4-n-dodecylphenol, 4-n-stearylphenol, 4-chlorophenol, 4-bromophenol, 2-phenylphenol, 4-hydroxybenzoate n-butyl, 4-hydroxybenzoate n-octyl, resorcinol, 4-tert-butylcatechol, 2,4-dihydroxy-4′-tert-butylbenzophenone, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)propane, 1,1-bis( 4-hydroxyphenyl)n-butane, 1,1-bis(4-hydroxyphenyl)n-pentane, 1,1-bis(4-hydroxyphenyl)n-hexane, 1,1-bis(4-hydroxyphenyl)n-heptane, 1,1-bis(4-hydroxyphenyl)n-octane, 1,1-bis(4-hydroxyphenyl)n-nonane, 1,1-bis(4-hydroxyphenyl)n-decane, 1,1-bis(4-hydroxyphenyl)n-dodecane, 1,1-bis(4-hydroxyphenyl)-2-methylpropane, 1,1-bis(4-hydroxyphenyl )-3-methylbutane, 1,1-bis(4-hydroxyphenyl)-3-methylpentane, 1,1-bis(4-hydroxyphenyl)-2,3-dimethylpentane, 1,1-bis(4-hydroxyphenyl)-2-ethylbutane, 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, 1,1-bis(4-hydroxyphenyl)-3,7-dimethyloctane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1-phenyl-1,1-bis( 4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)n-butane, 2,2-bis(4-hydroxyphenyl)n-pentane, 2,2-bis(4-hydroxyphenyl)n-hexane, 2,2-bis(4-hydroxyphenyl)n-heptane, 2,2-bis(4-hydroxyphenyl)n-octane, 2,2-bis(4-hydroxyphenyl)n-nonane, 2,2-bis(4-hydroxyphenyl)n-decane, 2,2-bis(4-hydroxyphenyl)n-dodecane, 2,2-Bis(4-hydroxyphenyl)ethylpropionate, 2,2-Bis(4-hydroxyphenyl)-4-methylpentane, 2,2-Bis(4-hydroxyphenyl)-4-methylhexane, 2,2-Bis(4-hydroxyphenyl)hexafluoropropane, 2,2-Bis(4-hydroxy-3-methylphenyl)propane, 2,2-Bis(4-hydroxy-3-methylphenyl)butane, 9,9-Bis(4-hydroxy-3-methylphenyl)fluorene, 1,3-Bis[2-(4-hydroxyphenyl) -2-propyl]benzene, bis(2-hydroxyphenyl)methane, 4,4′-dihydroxydiphenylsulfone, 4-isopropoxy-4′-hydroxydiphenylsulfone, bis(4-hydroxyphenyl)sulfide, 1,1,1-tris(4-hydroxyphenyl)ethane, 4,4′-[1-{4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl}ethylidene]bisphenol, 4,4′-[4-(4-hydroxyphenyl)-sec-butylidene]bis(2-methylphenol),

[0090] (H) component (h) Examples of components include alcohols, esters, ketones, ethers, and acid amides. When applying the heat-decolorizing, reversible thermochromic composition according to the present invention to microencapsulation and secondary processing, low molecular weight compounds evaporate outside the capsule when subjected to high heat treatment. Therefore, compounds with 10 or more carbon atoms are preferably used to stably retain them inside the capsule.

[0091] As for alcohols, monohydric aliphatic saturated alcohols with 10 or more carbon atoms are effective.

[0092] Effective esters include those having 10 or more carbon atoms, such as ester compounds obtained from any combination of a monohydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring; ester compounds obtained from any combination of a polyhydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a monohydric alcohol having an aliphatic and alicyclic or aromatic ring; and ester compounds obtained from any combination of a monohydric carboxylic acid having an aliphatic and alicyclic or aromatic ring and a polyhydric alcohol having an aliphatic and alicyclic or aromatic ring.

[0093] The esters may be ester compounds obtained from a combination of a saturated fatty acid and a branched aliphatic alcohol; ester compounds obtained from a combination of an unsaturated fatty acid or a branched or substituted saturated fatty acid and a branched or carbon-16 or more aliphatic alcohol; or ester compounds selected from cetyl butyrate, stearyl butyrate, and behenyl butyrate.

[0094] The esters may be carboxylic acid ester compounds exhibiting a ΔT value (melting point-cloud point) of 5°C or higher and less than 50°C as described in Japanese Patent Publication No. 4-17154. By using these ester compounds, it is possible to impart color memory properties that depend on temperature changes by exhibiting large hysteresis characteristics with respect to the color density-temperature curve.

[0095] The esters may be fatty acid ester compounds obtained from a combination of an odd-numbered aliphatic monohydric alcohol having 9 or more carbon atoms and an even-numbered aliphatic carboxylic acid; or fatty acid ester compounds with a total of 17 to 23 carbon atoms obtained from a combination of n-pentyl alcohol or n-heptyl alcohol and an even-numbered aliphatic carboxylic acid having 10 to 16 carbon atoms.

[0096] Effective ketones include aliphatic ketones with a total of 10 or more carbon atoms, as well as arylalkyl ketones with a total of 12 to 24 carbon atoms.

[0097] As for ethers, aliphatic ethers with a total of 10 or more carbon atoms are effective.

[0098] Examples of the alcohols, esters, ketones, ethers, and acid amides mentioned above include the compounds described in Japanese Patent Publication No. 2020-100710.

[0099] (h) The component may be a compound represented by the following formula (3). [ka] (In the formula, R1 represents a hydrogen atom or a methyl group, m represents an integer from 0 to 2, and either X1 or X2 is -(CH2) n OCOR2 or -(CH2) n COOR2, where the other element represents a hydrogen atom, n is an integer from 0 to 2, R2 represents an alkyl or alkenyl group with 4 or more carbon atoms, Y1 and Y2 independently represent a hydrogen atom, an alkyl group with 1 to 4 carbon atoms, a methoxy group, or a halogen atom, and r and p independently represent integers from 1 to 3. Among the compounds represented by formula (3), when R1 is a hydrogen atom, a reversible thermochromic composition with a wider hysteresis width is obtained, which is preferable, and it is even more preferable when R1 is a hydrogen atom and m is 0. Furthermore, among the compounds represented by formula (3), the compounds represented by the following formula (4) are more preferable. [ka] (In the formula, R represents an alkyl or alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, and more preferably an alkyl group having 12 to 22 carbon atoms.)

[0100] (h) The component may be a compound represented by the following formula (5). [ka] (In the formula, R represents an alkyl or alkenyl group having 8 or more carbon atoms, m and n each independently represent an integer from 1 to 3, and X and Y each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom.)

[0101] (h) The component may be a compound represented by the following formula (6). [ka] (In the formula, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen atom; m represents an integer from 1 to 3; and n represents an integer from 1 to 20.)

[0102] (h) The component may be a compound represented by the following formula (7). [ka] (In the formula, R represents an alkyl or alkenyl group having 1 to 21 carbon atoms, and n represents an integer from 1 to 3.)

[0103] (h) The component may be a compound represented by the following formula (8). [ka] (In the formula, X represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; m represents an integer from 1 to 3; and n represents an integer from 1 to 20.)

[0104] (h) The component may be a compound represented by the following formula (9). [ka] (In the formula, R represents any of the following: an alkyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, a cycloalkyl group, or an alkenyl group having 4 to 22 carbon atoms; X represents any of the following: a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom; and n represents 0 or 1.)

[0105] (h) The component may be a compound represented by the following formula (10). [ka] (In the formula, R represents an alkyl group having 3 to 18 carbon atoms or an aliphatic acyl group having 3 to 18 carbon atoms; X represents a hydrogen atom, an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom; Y represents a hydrogen atom or a methyl group; and Z represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom.)

[0106] (h) The component may be a compound represented by the following formula (11). [ka] (In the formula, R represents any of the following: an alkyl group having 4 to 22 carbon atoms, an alkenyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, or a cycloalkyl group; X represents any of the following: a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; Y represents any of the following: a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom; and n represents 0 or 1.)

[0107] (h) The component may be a compound represented by the following formula (12). [ka] (In the formula, R represents any of the following: an alkyl group having 3 to 18 carbon atoms, a cycloalkylalkyl group having 6 to 11 carbon atoms, a cycloalkyl group having 5 to 7 carbon atoms, or an alkenyl group having 3 to 18 carbon atoms; X represents any of the following: a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, or a halogen atom; and Y represents any of the following: a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, an ethoxy group, or a halogen atom.)

[0108] (h) The component may be a compound represented by the following formula (13). [ka] (In the formula, R represents a cycloalkyl group having 3 to 8 carbon atoms or a cycloalkylalkyl group having 4 to 9 carbon atoms, and n represents an integer from 1 to 3.)

[0109] (h) The component may be a compound represented by the following formula (14). [ka] (In the formula, R represents one of the alkyl groups having 3 to 17 carbon atoms, cycloalkyl groups having 3 to 8 carbon atoms, or cycloalkylalkyl groups having 5 to 8 carbon atoms; X represents one of the hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a methoxy group, an ethoxy group, or a halogen atom; and n represents an integer from 1 to 3.)

[0110] Examples of compounds represented by formulas (4) to (14) include those described in Japanese Patent Publication No. 2020-100710.

[0111] The heat-decolorizing reversible thermochromic composition is a compatible mixture comprising the above-mentioned components (a), (b), and (c) as essential components. The proportion of each component depends on the concentration, discoloration temperature, discoloration form, or type of each component. Generally, the component ratio that yields the desired properties is in the range of 0.1 to 100 parts by mass, preferably 0.1 to 50 parts by mass, more preferably 0.5 to 20 parts by mass, of component (b) per 1 part by mass of component (a), and in the range of 1 to 800 parts by mass, preferably 5 to 200 parts by mass, more preferably 10 to 100 parts by mass, of component (c).

[0112] ·others Heat-decolorizing reversible thermochromic compositions may contain various light stabilizers as needed. Light stabilizers are included to prevent photodegradation of the reversible thermochromic composition, which consists of at least components (a), (b), and (c). The component ratio for obtaining the desired properties is in the range of 0.3 to 24 parts by mass, preferably 0.3 to 16 parts by mass, of the light stabilizer per 1 part by mass of component (a). Among the light stabilizers, ultraviolet absorbers effectively cut ultraviolet rays contained in sunlight, etc., and prevent photodegradation caused by the excitation state due to the photoreaction of component (a). In addition, antioxidants, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, etc., suppress oxidation reactions caused by light. Light stabilizers are used individually or in combination of two or more types.

[0113] The heat-decolorizing, reversible thermochromic composition may contain non-coloring agents such as general dyes and / or pigments. By containing non-coloring agents, the heat-decolorizing, reversible thermochromic composition undergoes an alternating color change from a first color to a second color.

[0114] The heat-decolorizing, reversible thermochromic composition is encapsulated in microcapsules and used as a heat-developing, reversible thermochromic microcapsule pigment (hereinafter sometimes referred to as "microcapsule pigment"). The "heat-decolorizing type reversible thermochromic microcapsule pigment" according to the present invention can take the same form as the "heat-color-developing type reversible thermochromic microcapsule pigment" described above, and the explanation that overlaps with that of the heat-color-developing type reversible thermochromic microcapsule pigment will be omitted.

[0115] <Heat-decolorized image> The decolorized image produced by heating may take the same form as the "color-developed image produced by heating" described above, and any explanation that overlaps with that of the color-developed image produced by heating will be omitted. The heat-induced color change pattern is maintained in the colored state at room temperature. In other words, the heat-induced color change pattern of the packaging is in the colored state in its initial state. The heat-activated color image and the heat-decolorized image may be stacked on top of each other. That is, the heat-decolorized image may be positioned adjacent to the heat-activated color image below (between the packaging substrate and the heat-activated color image), or adjacent to the heat-activated color image above. The heated color-developing image and the heated color-decolorizing image may be placed side by side. That is, the heated color-decolorizing image and the heated color-developing image may be arranged on the same plane.

[0116] The thickness of the heat-decolorized image is not particularly limited and is set appropriately so that reversible thermal discoloration is achieved. The thickness of the heat-decolorized image is preferably in the range of 1 to 20 μm, and more preferably in the range of 5 to 15 μm.

[0117] In the packaging according to the present invention, by using both a heat-activated color-developing image and a heat-activated color-decolorizing image, the design changes during cooking can be made more diverse and surprising. Specifically, by using both a heat-activated color-decolorizing image that is color-developed at room temperature and a heat-activated color-developing image that is color-decolorized at room temperature and has a different design from the heat-activated color-decolorizing image, only the heat-activated color-decolorizing image is visible at room temperature. However, as the temperature rises due to cooking, the heat-activated color-decolorizing image disappears, and at the same time, the heat-activated color-developing image in a color-decolorized state appears, and the heat-activated color-decolorizing image with a different design from the heat-activated color-developing image becomes visible. For example, it is preferable to use both a heat-activated color-decolorizing image that evokes the state before cooking and a heat-activated color-developing image that evokes the state after cooking. Specifically, one example is a configuration in which the heat-activated color-decolorizing image is an image that mimics the ingredients, and the heat-activated color-developing image is an image that mimics the dish made using those ingredients. Another example is a configuration in which the heat-activated color-decolorizing image is an image of the words "Let's cooking!" and the heat-activated color-developing image is an image of the words "Enjoy!". This configuration allows the image to change in conjunction with the actual cooking process, making the cooking experience more enjoyable for the cook. Alternatively, the image that changes color upon heating could be the image of the cooking instructions, and the image that changes color upon heating could be the image of the warning text. The cooking instructions can be viewed before cooking, and the warning text can be viewed after cooking. This configuration allows only one of the images to be viewed at a time, thus attracting the attention of both the cook and third parties. The decolorization start temperature t3 of the heat-decolorizing reversible thermochromic material is preferably above 35°C and below 40°C. This prevents the decolorizing pattern from disappearing at room temperature, making it easy to maintain the decolorized pattern in its colored state in the initial state of the packaging.

[0118] Regarding the complete decolorization temperature t4 of the heat-decolorizable reversible thermochromic material and the color development start temperature T3 of the heat-color-developable reversible thermochromic material, it is preferable that t4 < T3, more preferably that (t4 - 5) < T3, and even more preferably that (t4 - 10) < T; Regarding the color development start temperature t2 of the heat-decolorizable reversible thermochromic material and the complete decolorization temperature T1 of the heat-color-developable reversible thermochromic material, it is preferable that t2 < T1, more preferably that (t2 - 5) < T1, and even more preferably that (t2 - 10) < T1. Thus, when the heat-color-developed image and the heat-decolorized image are laminated and used together, when either the heat-color-developed image or the heat-decolorized image is in the colored state, the other is in the decolorized state, preventing the heat-color-developed image and the heat-decolorized image from overlapping and being visually recognized. Therefore, only one of the heat-color-developed image and the heat-decolorized image can be visually recognized, and each image can be clearly visually recognized. Further, since only one of the heat-color-developed image and the heat-decolorized image is visually recognized, a color change not based on subtractive color mixing can be imparted, enabling a package with excellent variability even when the heat-color-developed image and the heat-decolorized image have the same design. For example, a configuration in which a pink heat-decolorized image and a blue heat-color-developed image are laminated and used together can be cited. In the initial state, the pink heat-decolorized image is visually recognized, but as the temperature rises, the blue heat-color-developed image is visually recognized. [[ID=__]] [[ID=__]]

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[0121] ​​​ The number of prints is not particularly limited and can be set appropriately according to the desired color density. The number of prints may be one, two, or more.

[0122] After printing, volatile components (typically solvents) contained in the vehicle are removed to solidify the ink composition. The drying and solidification method is not particularly limited. Examples of drying and solidification methods include natural drying, heat drying, and hot air drying. The curing and drying method is appropriately selected according to the properties of the vehicle. Examples of curing and drying methods include the addition of an oxidizing agent, heating, ultraviolet irradiation, and electron beam irradiation. Curing and drying may be carried out by heating. The heating temperature for curing and drying may be 40 to 100°C.

[0123] When forming a heat-colored or heat-decolorized image by heating using a polymerizable vehicle, the heating temperature may be between 150°C and 250°C. The heating process may be performed multiple times. For example, the first heating step (primary drying) removes the solvent contained in the ink composition to obtain a touch-dry or semi-dried heat-colored or heat-decolorized image. Primary drying suppresses color transfer of the ink composition and improves the handling properties of the printed material. Subsequently, the vehicle in the heat-colored or heat-decolorized image is chemically cured in the second heating step (secondary drying).

[0124] The primary drying temperature and the secondary drying temperature may be the same or different. The secondary drying temperature may be higher than the primary drying temperature. This facilitates the curing of the vehicle and improves the durability of the heat-colored or heat-decolorized image.

[0125] The heat-activated color-developed or heat-decolorized image may be formed by gravure printing. Gravure printing has the following characteristics: (1) The plates have high durability and can be used for mass production. (2) It can be printed on various substrates (e.g., paper, plastic, metal, etc.). (3) Designs with vibrant colors can be printed. Therefore, gravure printing is used for packaging materials that contain food products, which require a wide variety of base materials, high quality, and the ability to mass-produce.

[0126] The packaging according to the present invention may be in the form of a bag. A bag-shaped packaging can be manufactured by providing each image (each layer) containing a heat-activated color-developing image or a heat-decolorizing image on a packaging substrate such as a film made of synthetic resin, as described later, and then providing a heat-seal layer on the top surface of the laminate (the side of each image (each layer) opposite to the side on which the substrate is provided), and then heat-welding (heat-sealing process) the three sides of the laminate with the heat-seal layer facing each other. Here, the packaging substrate is located on the outermost layer of the packaging and constitutes the surface of the packaging. The bag-shaped packaging may be formed from the laminate as described above and may be a single layer.

[0127] Examples of packaging substrates include films made from synthetic resins such as polyolefin, nylon, and polyethylene terephthalate (PET). From the viewpoint of heat resistance during cooking, synthetic resin films made of polypropylene or polyethylene terephthalate are preferred. From the viewpoint of durability and gloss of the packaging, synthetic resin films made of polyethylene terephthalate are preferred. The synthetic resin film used as the packaging base material may be unstretched or biaxially oriented. From the viewpoint of heat resistance, a biaxially oriented synthetic resin film is preferred.

[0128] Examples of materials used for the heat seal layer include synthetic resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, and polypropylene. Unstretched polypropylene is preferred from the viewpoint of heat resistance during cooking. The heat-seal layer may be formed by various lamination methods. For example, it may be formed by providing a film made of the above-mentioned synthetic resin on the uppermost surface of the laminate using a dry lamination method with an adhesive. Alternatively, it may be formed by coating the uppermost surface of the laminate with the molten synthetic resin using an extrusion lamination method. Furthermore, by using a thermal lamination method in which heat is applied to the synthetic resin film and pressed together, the heat-seal layer can be provided without using an adhesive.

[0129] In the dry lamination method using adhesives, an adhesive layer is applied to the top surface of the laminate, which is made by providing each layer (each image) on the packaging substrate (the side of each layer opposite to the side where the substrate is provided), and then a heat-seal layer is applied. The adhesive layer plays a role in improving the adhesion between each layer (each image) and the heat-seal layer. The adhesive layer can be made from materials such as epoxy, acid anhydride, polyester, or urethane resins. The adhesive may be an organic solvent type diluted with an organic solvent, a solvent-free type that does not use an organic solvent, an emulsion type in which the adhesive component is dispersed in water, or a hot-melt type using a thermoplastic resin.

[0130] The bag-shaped packaging manufactured as described above has an open side. Cooked food is placed inside through the open side (opening). From the standpoint of preserving food, the opening of the packaging may be sealed by heat sealing (heat welding) or similar methods after the food has been placed inside. Furthermore, from the viewpoint of preserving the food contained inside and reusing the bag, a zipper may be provided on or near the edge of the opening to allow the opening to be opened and closed. The zipper consists of a protrusion on one side of the opening and a recess on the other side, with the protrusion and recess facing each other. As a result, pressing the protrusion and recess together by hand engages them to close the opening, and pulling them apart by hand opens the opening. There may be multiple protrusions and recesses, and multiple zippers may be provided on the bag. A fitting device (slider member) for fitting the zipper may be provided on the edge of the opening, and the opening can be opened and closed by moving the fitting device laterally (perpendicular to the opening direction of the opening). By providing a fitting device, the open and closed states of the opening can be easily switched. Furthermore, from the standpoint of preserving the food until it is opened and the remaining food after opening, the opening with the zipper may be sealed by heat sealing (heat welding) or similar methods.

[0131] The packaging according to the present invention may be a container. The container has a shape that allows it to contain and remove cooked food inside, and for example, it is composed of a container body in the shape of a bottomed cylindrical body with an opening at the top, and a lid material that closes the opening of the container body. The heat-induced color image is formed on the outer surface of the container, for example, on the outer surface of the container body or on the lid material.

[0132] Examples of materials used for the container body include plastic, paper, and foam. The container body may have a single (single-layer) structure, or it may have a double-layer or triple-layer structure.

[0133] The lid material is constructed by providing each image (each layer) including a heat-activated color-developing image or a heat-decolorizing image on the outer surface of the lid material base material, and a sealing layer on the inner surface of the container (the side where heated food is contained). Examples of materials used for the lid base material include coated paper, polypropylene, and synthetic resins such as polyethylene terephthalate (PET).

[0134] A sealing layer is provided to heat-seal the opening of the container body to the lid material. Examples of materials used for the sealing layer include synthetic resins such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, and polypropylene. The sealing layer may be provided by various lamination methods. For example, it may be formed by providing a film made of the above-mentioned synthetic resin to the inner surface of the lid material base material using a dry lamination method with an adhesive. Alternatively, it may be formed by coating the inner surface of the lid material base material with molten synthetic resin using an extrusion lamination method. [Examples]

[0135] Examples are shown below, but the present invention is not limited thereto. In the examples, "parts" refers to parts by mass.

[0136] Preparation of heat-activated reversible thermochromic material A (heat-activated reversible thermochromic microcapsule pigment A) A reversible thermochromic composition consisting of (a) 1 part of 3-[2-ethoxy-4-(N-ethylanilino)phenyl]-3-(1-ethyl-2-methylindole-3-yl)-4-azaphthalide, (b) 8 parts of hexadecyl 3,5-dihydroxybenzoate, (c) 20 parts of octadecane, and (d) 1 part of distearyl ketone was uniformly heated and dissolved, and encapsulated in microcapsules by interfacial polymerization to prepare a microcapsule dispersion. Heat-developing reversible thermochromic microcapsule pigment A was obtained from the above microcapsule dispersion by centrifugation. Microcapsule pigment A had a complete decolorization temperature T1: 15°C, a decolorization onset temperature T2: 30°C, a color development onset temperature T3: 52°C, a complete color development temperature T4: 63°C, and a hysteresis width ΔH: 35°C. It reversibly changed from colorless to blue with temperature changes.

[0137] Preparation of heat-activated reversible thermochromic material B (heat-activated reversible thermochromic microcapsule pigment B) A reversible thermochromic composition consisting of (a) 3 parts of 3,6-bis(N-phenyl-Nm-tolylamino)fluorane, (b) 15 parts of 4-hydroxybenzoate behenyl, (c) 30 parts of pentadecane, (d) 2 parts of eicosanedioic acid, (e) 1 part of p-terphenyl, and (f) 20 parts of a styrene oligomer (styrene-α-methylstyrene copolymer) [manufactured by Eastman Chemical Company, product name: Picolastic A-75 (weight average molecular weight: 917)] was uniformly heated and dissolved, and encapsulated in microcapsules by interfacial polymerization to prepare a microcapsule dispersion. Heat-developing reversible thermochromic microcapsule pigment B was obtained from the above microcapsule dispersion by centrifugation. Microcapsule pigment B had a complete decolorization temperature T1: 35°C, a decolorization onset temperature T2: 39°C, a color development onset temperature T3: 54°C, a complete color development temperature T4: 62°C, and a hysteresis width ΔH: 21°C. It reversibly changed from colorless to blue with temperature changes.

[0138] Preparation of heat-decolorizing reversible thermochromic material a (heat-decolorizing reversible thermochromic microcapsule pigment a) A reversible thermochromic composition consisting of (a) 1.5 parts of 6-(N-ethyl-N-isobutylamino)-1,2-benzofluorane, (b) 2 parts of 1-phenyl-1,1-bis(4-hydroxyphenyl)ethane and 5 parts of 1,1-bis(4-hydroxyphenyl)-2-ethylhexane, and (c) 50 parts of nonyl stearate was uniformly heated and dissolved, and encapsulated in microcapsules by interfacial polymerization to prepare a microcapsule dispersion. Heat-decolorizing reversible thermochromic microcapsule pigment a was obtained from the above microcapsule dispersion by centrifugation. Microcapsule pigment a had a complete color development temperature t1: 27°C, a color development start temperature t2: 30°C, a decolorization start temperature t3: 36°C, a complete decolorization temperature t4: 39°C, and a hysteresis width ΔH: 9°C. It reversibly changed from pink to colorless with temperature changes.

[0139] Preparation of heat-decolorizing reversible thermochromic material b (heat-decolorizing reversible thermochromic microcapsule pigment b) A reversible thermochromic composition consisting of (a) 2 parts of 6-(N-ethyl-N-isobutylamino)-1,2-benzofluorane, (b) 5 parts of 2,2-bis(4-hydroxyphenyl)hexafluoropropane, and (c) 50 parts of 4-biphenyldecyl acetate was uniformly heated and dissolved, and encapsulated in microcapsules by interfacial polymerization to prepare a microcapsule dispersion. Heat-decolorizing reversible thermochromic microcapsule pigment b was obtained from the above microcapsule dispersion by centrifugation. Microcapsule pigment b had a complete color development temperature t1: -9°C, a color development start temperature t2: -3°C, a decolorization start temperature t3: 37°C, a complete decolorization temperature t4: 49°C, and a hysteresis width ΔH of 49°C, and reversibly changed from pink to colorless with temperature changes.

[0140] Example 1 Preparation of packaging for cooking (see Figures 4 and 5) A heat-activated, reversible thermochromic microcapsule pigment A was prepared by stirring and mixing 65 parts of a heat-activated, reversible thermochromic ink A for gravure printing, 24 parts of an acrylic resin emulsion (50% solids), 56 parts of a styrene-acrylic copolymer resin aqueous solution (30% solids), 2 parts of an antifoaming agent, and 3 parts of water. As a packaging substrate (21), a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film was used to print the words "Hot, Caution!" onto a predetermined area (30 mm vertically x 60 mm horizontally) using a heat-reactive, reversible thermochromic ink A via gravure printing. The print was then heated to 60°C and dried to form a heat-reactive image (22). Next, a white, irreversible thermochromic ink for gravure printing was used to print gravure on the entire area where the heat-reactive image was formed. The print was then heated to 60°C and dried to form a white ink layer (23). Subsequently, a polyurethane adhesive was applied to the entire surface of the PET film on the side where the heat-reactive image and the white ink layer were located. A 7 μm thick aluminum foil (Al) was then applied by dry lamination to form a gas barrier layer (24). Furthermore, a polyurethane adhesive was applied to the gas barrier layer, and a 50 μm thick unstretched polypropylene (CPP) film was prepared by dry lamination to form a heat-seal layer (25). This resulted in a laminate (20) with a layer structure of PET film / heat-activated color image / white ink layer / Al / CPP film. Furthermore, a polyurethane adhesive was applied to a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film as the packaging base material (31), and a 7 μm thick aluminum foil (Al) was provided by dry lamination to form a gas barrier layer (34). In addition, a polyurethane adhesive was applied to the gas barrier layer, and a 50 μm thick unstretched polypropylene (CPP) film was provided by dry lamination to form a heat seal layer (35). This resulted in a laminate (30) with a layer structure of PET film / Al / CPP film. The laminate (20) described above was cut to a size of 170 mm in length and 130 mm in width so as to encompass the predetermined range, and a wall film (11) was obtained. The laminate (30) was also cut to a size of 170 mm in length and 130 mm in width, and a wall film (12) was obtained. With the wall film (11) on the front side and the wall film (12) on the back side, the heat-seal layers (CPP film) of the two wall films were placed on the inside, and the three sides, two long sides and one short side, were heat-sealed to obtain a cooking packaging body (retort pouch) (10) having an opening. Next, curry was filled into a cooking container as a cooking food, the opening was heat-sealed to enclose the food in the cooking container, and then retort sterilization was performed in a steam-type retort kettle.

[0141] During the manufacturing process, the packaging for cooking is heated to a temperature T3 or higher, causing the heated color image to become visible. However, the complete decolorization temperature T1 is within the room temperature range, and the heated color image naturally decolorizes and becomes invisible. In other words, in the initial state before cooking, the heated color image of the packaging remains in a decolorized state, so nothing is visible on the packaging. When the package was placed in boiling water, the heating-induced color image on the front side became colored, and a blue text image ("Hot, Caution!") appeared. After a predetermined time had elapsed, when the package was removed from the water, the heating-induced color image remained colored in the temperature range above the decolorization start temperature T2. Because the heating-induced color image did not disappear immediately after being removed from the water, and remained visible as long as the temperature was above the decolorization start temperature T2, a third party other than the cook could understand the cooking status of the food, preventing them from being burned by touching it or accidentally reheating it.

[0142] Example 2 Preparation of packaging for cooking (see Figures 6 and 7) A heat-activated, reversible thermochromic microcapsule pigment B was prepared by stirring and mixing 65 parts of a heat-activated, reversible thermochromic ink B for gravure printing. This mixture consisted of 24 parts of an acrylic resin emulsion (50% solids), 56 parts of a styrene-acrylic copolymer resin aqueous solution (30% solids), 2 parts of an antifoaming agent, and 3 parts of water. As a packaging substrate (41), a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film was used to print images of pasta dishes at predetermined positions using gravure printing with irreversible thermochromic inks of cyan, magenta, yellow, and black, thereby forming irreversible thermochromic images (46). Next, an image of the product name was printed at predetermined positions on the PET film using gravure printing with heat-developing reversible thermochromic ink B, and the film was heated and dried at 60°C to form a heat-developed image (42). Then, gravure printing was performed on the entire surface of the PET film on the side where the irreversible thermochromic images and heat-developed images were provided, using white irreversible thermochromic ink for gravure printing, and the film was heated and dried at 60°C to form a white ink layer (43). Next, a polyurethane adhesive was applied to the white ink layer, and a 50 μm thick unstretched polypropylene (CPP) film was laid by dry lamination to form a heat-seal layer (45). This resulted in a laminate (40) with a layer structure of PET film / irreversible thermal color change image / heat-developed color image / white ink layer / CPP film. The irreversible thermal color change image and the heat-developed color image are arranged side by side. Furthermore, a heat-decolorizing, reversible thermochromic ink a for gravure printing was prepared by stirring and mixing 65 parts of heat-decolorizing, reversible thermochromic ink a, 24 parts of acrylic resin emulsion (solids content 50%), 56 parts of styrene-acrylic acid copolymer resin aqueous solution (solids content 30%), 2 parts of defoaming agent, and 3 parts of water. As a packaging substrate (51), a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film was used to print an image of cooking instructions at a predetermined position using gravure printing with a heat-decolorizing reversible thermochromic ink a. The image was then heated at 60°C and dried to form a heat-decolorizing image (57). Next, an image of the white text "Caution: High Temperature" was printed on the heat-decolorizing image using gravure printing with a heat-developing reversible thermochromic ink B. The image was then heated at 60°C and dried to form a heat-developed image (52). Subsequently, gravure printing was performed on the entire surface of the PET film on the side where the heat-developed image and the heat-decolorizing image were provided, using a white gravure printing irreversible thermochromic ink. The image was then heated at 60°C and dried to form a white ink layer (53). Next, a polyurethane adhesive was applied to the white ink layer, and a 50 μm thick unstretched polypropylene (CPP) film was laid by dry lamination to form a heat-seal layer (55). This resulted in a laminate (50) with a layer structure of PET film / heat-decolorized image / heat-developed image / white ink layer / CPP film. The heat-decolorized image and the heat-developed image are laminated to each other. Furthermore, a polyurethane adhesive was applied to a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film as a packaging substrate (61), and a 50 μm thick unoriented polypropylene (CPP) film was formed by dry lamination to create a heat-seal layer (65). This resulted in a laminate (60) with a layer structure of PET film / CPP film. The laminates (40) and (50) described above were each cut to a size of 170 mm in length and 130 mm in width so as to enclose the printed area, thereby obtaining two wall films (11, 12). Furthermore, the laminate (60) was cut to a size of 50 mm in length and 130 mm in width to obtain a bottom film (13). With the wall film (11) facing the front and the wall film (12) facing the rear, the two wall films and the bottom film were heat-sealed at predetermined locations with the heat-seal layer (CPP film) facing inward to obtain a stand-up type retort pouch (10) for cooking with an opening. Furthermore, notches (14) were formed on the two long sides at a position 10 mm vertically from the opening. Next, pasta sauce was filled into a cooking container as a food item to be cooked, and the opening was heat-sealed. The food was then sealed inside the cooking container and sterilized using a steam retort kettle.

[0143] During the manufacturing process, the packaging for cooking is heated to a temperature above the color-development start temperature T3, and the color-developed image becomes visible in its colored state. However, the complete decolorization temperature T1 is in the room temperature range, so the color-developed image naturally decolorizes and becomes invisible. Furthermore, since the complete color-development temperature t1 is in the room temperature range and the decolorization start temperature t3 is in a temperature range above room temperature, the packaging for cooking retains the color-developed image in a decolorized state and the decolorized image in a colored state in its initial state before cooking. Therefore, on the front of the packaging, an image of a pasta dish is visible due to irreversible thermal color change, and on the back, an image of the pink cooking instructions is visible due to the decolorization of the heating process. When the package was placed upright in a microwave oven and heated, and then removed after a predetermined time, the heating-induced color image (42) on the front side became colored, revealing a blue image of the product name. Furthermore, on the back side, the heating-induced color-decolorizing image (57) became colorless, and the heating-induced color image (52) became colored, revealing an image of white text on a blue background ("Caution: High Temperature"). In other words, heating caused the image of the pink cooking instructions to change to an image of white text on a blue background. The heating-induced color image did not disappear immediately after being removed from the microwave oven, and remained visible as long as the temperature exceeded the color-decolorization start temperature T2. Therefore, a third party other than the cook could understand the cooking status of the food on the back side, preventing them from being burned by touching it or accidentally reheating it. In addition, the image of the product name remained visible on the front side, resulting in a package with excellent design.

[0144] Example 3 Preparation of packaging for cooking (see Figures 8 and 9) A 20 μm thick coated paper was used as the packaging base material (71), and a 7 μm thick aluminum foil (Al) was used as the gas barrier layer (74) and laminated by extrusion lamination. Next, a polyurethane adhesive was applied to the aluminum foil, and a 50 μm thick linear low-density polyethylene (LLDPE) film was applied by dry lamination to form a heat seal layer (75). A white ink layer (73) was formed by gravure printing on the entire surface of the coated paper side (the side without the gas barrier layer and heat seal layer) using a white irreversible thermochromic ink for gravure printing, and then heating and drying at 60°C. Next, an image of a flower petal was printed on a predetermined position on the white ink layer by gravure printing using a heat-developing reversible thermochromic ink A, and then heating and drying at 60°C to form a heat-developed image (72). Next, an image of a flower petal was printed on or adjacent to the heat-developed image by gravure printing using a heat-decolorizing reversible thermochromic ink a, and then heating and drying at 60°C to form a heat-decolorizing image (77). In addition, an image of the word "Caution!" was printed by gravure printing using a heat-developing reversible thermochromic ink A, and then heating and drying at 60°C to form a heat-developed image (72'). Next, the outline of the petal image was printed using a black irreversible thermochromic ink for gravure printing, creating a heat-activated color image and a heat-decolorized image. This was then heated at 60°C to form an irreversible thermochromic image (76). Subsequently, a polyurethane adhesive was applied to the entire surface of the coated paper where the heat-activated color image, heat-decolorized image, and irreversible thermochromic image were located. A 12 μm thick biaxially oriented polyethylene terephthalate (PET) film was then applied by dry lamination to form a transparent protective layer (78). This resulted in a laminate (70) with a layer structure of heat-seal layer / Al / coated paper / white ink layer / heat-activated color image, heat-decolorized image / irreversible thermochromic layer / PET film. The laminate comprises regions where the heat-activated color image and the heat-decolorized image are stacked on top of each other, and regions where they are arranged side by side. This laminate was punched out to obtain a lid material (15). Next, dried noodles were filled into a bottomed cylindrical container body (16) made of expanded polystyrene as a food to be heated, and the opening of the container body and the heat seal layer of the lid material were heat-sealed to obtain a package (container) (10) for heated food.

[0145] During the manufacturing process, the packaging for cooking is heated to a temperature above the color-development start temperature T3, and the heat-developed color image becomes visible in its colored state. However, the complete decolorization temperature T1 is in the room temperature range, so the heat-developed color image naturally decolorizes and becomes invisible. Furthermore, since the complete color development temperature t1 is in the room temperature range and the decolorization start temperature t3 is in a temperature range above room temperature, the heat-developed color image is maintained in a decolorized state and the heat-decolorized image is maintained in a colored state in the initial state before cooking. Therefore, a floral pattern is visible on the packaging, consisting of pink petals from the heat-decolorized image and white petals from the irreversible thermal color change image. When the lid of the packaging was partially opened, boiling water was poured in, and the lid was closed, the heat-decolorizing image (77) disappeared, and the heat-developing image (72) became colored. In areas where the heat-developing image and the heat-decolorizing image were stacked on top of each other, the pink petals changed to blue. In areas where the heat-developing image and the heat-decolorizing image were side by side, the pink petals changed to white, and the white petals changed to blue. In other words, the flower pattern changed due to heating, demonstrating superior changeability. At the same time, the heat-developing image (72') became colored, and a blue image of letters ("Caution!") appeared. The heat-developing image of the packaging did not disappear, and as long as the temperature was above the decolorization start temperature T2, the heat-developing image remained visible. This allowed a third party other than the cook to understand the cooking status of the food, preventing them from being burned by touching it or accidentally reheating it. Furthermore, the appearance of the product in its initial state was completely different from its appearance after cooking, and the unexpected change in the packaging design strongly attracted the interest of cooks.

[0146] Example 4 Preparation of packaging for cooking (see Figures 10 and 11) A biaxially oriented polyethylene terephthalate (PET) film with a thickness of 12 μm was used as the packaging substrate (81). Gravure printing was performed on the entire surface using an anchor coating agent made of synthetic resin and containing a light stabilizer, and the surface was heated and dried at 60°C to form an anchor coating layer (89). Next, an image of food selected from the group consisting of vegetables, fish, and meat was printed by gravure printing using a heat-decolorizing reversible thermochromic ink b, and the surface was heated and dried at 60°C to form a heat-decolorizing image (87). Next, an image of a dish was printed on the side where the heat-decolorizing image was to be provided using a heat-developing reversible thermochromic ink B, and the surface was heated and dried at 60°C to form a heat-developed image (82). Finally, gravure printing was performed on the entire surface of the side of the PET film where the heat-developed image and the heat-decolorizing image were to be provided using a white irreversible thermochromic ink for gravure printing, and the surface was heated and dried at 60°C to form a white ink layer (83). Next, a polyurethane adhesive was applied to the white ink layer, and a 50 μm thick unstretched polypropylene (CPP) film was laid by dry lamination to form a heat-seal layer (85). This resulted in a laminate (80) with a layer structure of PET film / anchor coat layer / heat-decolorized image / heat-colored image / white ink layer / CPP film. The heat-decolorized image and the heat-colored image are laminated to each other. The anchor coat layer also contains a light stabilizer, which improves the lightfastness of the heat-decolorized image and the heat-colored image. Furthermore, a polyurethane adhesive was applied to a 12 μm thick biaxially oriented polyethylene terephthalate (PET) film as a packaging substrate (91), and a 50 μm thick unstretched polypropylene (CPP) film was formed by dry lamination to create a heat-seal layer (95). This resulted in a laminate (90) with a layer structure of PET film / CPP film. The laminate (80) described above was cut to a size of 170 mm vertically x 130 mm horizontally so as to encompass the printed areas for the heat-activated color image and the heat-decolorized image, thereby obtaining a wall film (11). The laminate (90) was also cut to a size of 170 mm vertically x 130 mm horizontally to obtain a wall film (12). A protrusion (17) for forming a chuck (19) was formed on one of the wall films (11) at a position 20 mm vertically from one of its short sides, parallel to the short side. Similarly, a recess (18) for forming a chuck was formed on one of the short sides of the other wall film (12). With wall film (11) on the front side and wall film (12) on the back side, and with the heat-seal layers (CPP film) of the two wall films facing inward, the two long sides were heat-sealed together so that the protrusion and recess faced each other. The convex and concave portions were fitted together, and the short sides near the convex and concave portions (the upper parts of the convex and concave portions) were heat-sealed to obtain a heat-cooking packaging body (zippered bag) (10) having an opening. Furthermore, notches (14) were formed on the two long sides at positions 10 mm vertically from the short sides near the convex and concave portions. Next, the frozen food was placed inside a cooking-ready package, and the opening was heat-sealed to seal the food inside the cooking-ready package. This package was then stored in a general-purpose freezer.

[0147] During the manufacturing process, the packaging for cooking is heated to a temperature T3 or higher, causing the heat-induced colored image to become visible. However, the complete decolorization temperature T1 is within the room temperature range, causing the heat-induced colored image to naturally decolorize and become invisible. Furthermore, storing the packaging in a freezer causes the heat-induced decolorized image to become colored and visible. Additionally, since the decolorization onset temperature t3 is above room temperature, when the packaging is removed from the freezer, the heat-induced colored image remains in a decolorized state, and the heat-induced decolorized image remains in a colored state in its initial state before cooking. Therefore, on the front of the packaging, a pink image of the food is visible due to the heat-induced decolorization. When the package was placed in a microwave oven and heated for a predetermined time, it was removed, and the heating-induced color image on the front of the package became colored, revealing a blue image of food. In other words, heating changed the image from a pink food image to a blue food image. The heating-induced color image did not disappear immediately after being removed from the microwave oven, and remained visible as long as the temperature exceeded the discoloration start temperature T2. This allowed a third party other than the cook to understand the cooking status of the food, preventing them from being burned by touching it or accidentally reheating it. Furthermore, the image visible in the initial state and the image visible after heating were completely different, and the unexpected change in the package design strongly attracted the interest of cooks. The packaging had a zipper, and even after opening, the protruding and recessed parts could be pressed together by hand to re-engage and close the package, allowing for the preservation of cooked food. Furthermore, the package could be easily opened by pulling the protruding and recessed parts apart by hand, allowing the food to be consumed at the desired time. The ability to repeatedly switch between open and closed states thanks to the zipper made it highly practical. [Explanation of Symbols]

[0148] 10 Packaging for heating and cooking 11, 12 Wall film 13 Bottom film 14 Notches 15 Lid material 16 Container body 17 Convex part 18 recesses 19 Chuck 20, 30, 40, 50, 60, 70, 80, 90 laminated bodies 21, 31, 41, 51, 61, 71, 81, 91 Packaging base material 22, 42, 52, 72, 72′, 82 Heat-activated color images 23, 43, 53, 73, 83 White ink layer 24, 34, 74 Gas barrier layer 25, 35, 45, 55, 65, 75, 85, 95 Heat seal layer 46, 76 Irreversible thermal discoloration layer 57, 77, 87 Heat decolorized image 78 Transparent protective layer 89 Anchor Coat Layer

Claims

1. A packaging for cooking food that can contain cooked food, The packaging material is provided with a heat-activated color image comprising a heat-activated reversible thermochromic material that develops color upon heating from a decolorized state and decolorizes upon cooling from a colored state, wherein the heat-activated reversible thermochromic material is in a decolorized state. The heat-developing reversible thermochromic material is a reversible thermochromic microcapsule pigment containing at least a reversible thermochromic composition composed of (a) an electron-donating color-forming organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color-forming reaction of the components (a) and (b). It exhibits hysteresis characteristics with respect to the color density-temperature curve and shows the mutuality between the coloring state and the decoloring state. In the process of temperature rising from the decoloring state, when the temperature reaches the color-developing start temperature T １ , ４ , it begins to develop color. When the temperature is higher than the complete color-developing temperature T ３ , it completely enters the coloring state in the temperature range above that. In the process of temperature dropping from the coloring state, when the temperature reaches the decoloring start temperature T ２ , it begins to decolor. When the temperature is lower than the complete decoloring temperature T ２ , it completely enters the decoloring state in the temperature range below that, showing hysteresis characteristics. The color-developing start temperature T ３ is 50°C or higher, the complete decoloring temperature T １ is 5 - 40°C, and the decoloring start temperature T ２ is lower than the color-developing start temperature T ３ . A package for heat cooking.​​​​

2. The decolorization start temperature T ２ and the temperature at which color development begins T ３ Regarding T ２ <(T ３ A heat-cooking packaging body according to claim 1, satisfying -10).

3. The heat-cooking packaging according to claim 1 or 2, wherein an irreversible heat-discoloring layer is provided between the packaging substrate and the heat-colored image.

4. The heat-decolorized image is further provided, comprising a heat-decolorizing reversible thermochromic material that decolorizes upon heating from a colored state and develops color upon cooling from a decolorized state, wherein the heat-decolorizing reversible thermochromic material is in a colored state. The aforementioned heat-decolorizing reversible thermochromic material is a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition comprising at least (a) an electron-donating color-developing organic compound, (b) an electron-accepting compound, and (c) a reaction medium that controls the color reaction of components (a) and (b). It exhibits hysteresis characteristics with respect to the color density-temperature curve, showing tautomorphism between a colored state and a decolorized state, and in the process of the temperature rising from the colored state, the decolorization onset temperature t ３ When it reaches a certain temperature, it begins to lose its color, ３ Higher complete decolorization temperature t ４ At the above temperature range, the color completely disappears, and during the process of the temperature decreasing from the colorless state, the color development start temperature t ２ When it reaches a certain temperature, it begins to develop color, ２ Lower full color temperature t １ The heat-cooking packaging according to claim 1, which exhibits hysteresis characteristics that result in complete color development within the following temperature range.

5. The color change onset temperature T of the heat-activated, reversible thermochromic material. ３ The complete decolorization temperature t of the heat-decolorizing type reversible thermochromic material. ４ Regarding t ４ <T ３ A heat-cooking packaging body according to claim 4, satisfying the requirements.

6. The heating-colored image and the heating-decolorized image are stacked on top of each other, according to claim 4 or 5.

7. The heating-colored image and the heating-decolorized image are arranged side by side, according to claim 4 or 5, for use as a heating-cooking package.

8. A heating-cooking packaging body according to claim 4 or 5, comprising a plurality of heating-color-developing images and heating-decolor-removing images, wherein the heating-color-developing images and heating-decolor-removing images are stacked on top of each other, and the heating-color-developing images and heating-decolor-removing images are arranged side by side.

9. The heat-cooking packaging according to claim 1 or 4, wherein the packaging material is in the shape of a bag.

10. The packaging material is a container, and the container comprises a bottomed cylindrical container body with an opening at the top, and a lid material that closes the opening of the container body, according to claim 1 or 4.

11. The heating-colored image is provided on the lid material, as described in claim 10.

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