JP2017115136A - Ink composition for reversible thermochromic stamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink composition for reversible thermochromic stamp high in fixability of images to seal surface, having no detachment even when imaged is scratched by a friction member and excellent in scratch resistance.SOLUTION: There is provided an ink composition for reversible thermochromic stamp containing a reversible thermochromic micro capsule pigment including a reversible thermochromic composition, water, a moisturizing agent and a resin emulsion, wherein a resin in the resin emulsion has specific solid component acid value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a reversible thermochromic stamp ink composition. More specifically, the present invention relates to a reversible thermochromic stamp ink excellent in fixability and scratch resistance of a printed image imprinted on a imprinting surface.

  Conventionally, water-based ink compositions for stamps using dyes, pigments, and the like as colorants are known. In order to improve the fixability of the image formed using these water-based ink compositions for stamps on the stamped surface, it has been studied to use a binder resin (for example, Patent Document 1).

  On the other hand, as a colorant, a reversible thermochromic stamp ink using a reversible thermochromic microcapsule pigment that can be discolored and discolored by heat is known (Patent Document 2). The printed image formed using the ink composition can be discolored or decolored by heat, and when stamped on a notebook or notebook, the location where the printed image is formed or the printed image itself can be easily changed. Or changing the color of the printed image and enjoying the change.

  The ink compositions for stamps described in Patent Documents 1 and 2 are printed on the stamping surface in order to improve the fixability of the printed image. It has been found that there is room for improvement such as peeling of the printed image depending on the binder resin and the stamping surface used, without rubbing the printed image with a member or the like.

JP-A-63-86769 JP 2002-121427 A

  The present invention provides a reversible thermochromic stamp ink composition having excellent fusing resistance, having high fixability of a printed image on a stamped surface, and preventing the printed image from peeling off even when the printed image is rubbed with a friction member. Is to provide.

The present invention has solved the above-mentioned problems by using a resin emulsion in which the resin in the resin emulsion has a specific solid acid value in the ink composition.
That is, the present invention
“1. (a) a component comprising an electron-donating color-forming organic compound;
(B) a component comprising an electron-accepting compound;
(C) a reaction medium for reversibly causing an electron transfer reaction by the component (a) and the component (b) in a specific temperature range;
A reversible thermochromic microcapsule pigment encapsulating a reversible thermochromic composition comprising water, a moisturizing agent, and a resin emulsion, the ink composition for a reversible thermochromic stamp comprising the resin in the resin emulsion A reversible thermochromic stamp ink composition having a solid acid value of 1 or more and 100 or less.
2. 2. The ink composition for reversible thermochromic stamp according to item 1, wherein the resin emulsion is an acrylic resin emulsion or a urethane resin emulsion.
3. The mixing ratio of water and the humectant contained in the ink composition is such that water / humectant is 1 / 3.3 to 1 / 1.8 as a mass ratio. The ink composition for reversible thermochromic stamps according to Item. ".

  According to the present invention, the resin in the resin emulsion uses a resin emulsion having a specific solid content acid value, so that the fixability of the printed image is improved even when smooth paper is used as the stamping surface. In order to decolorize or discolor, the printed image is not peeled off from the imprinting surface even when it is rubbed with a friction member, and an excellent image such as being able to obtain a printed image having excellent scratch resistance is obtained. .

It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment which included the heat decoloring type reversible thermochromic composition. It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment which included the heat decoloring type reversible thermochromic composition which has color memory property. It is explanatory drawing which shows the discoloration behavior of the microcapsule pigment which included the heating coloring type reversible thermochromic composition. It is a longitudinal cross-sectional explanatory drawing of an example of the reversible thermochromic stamp which mounts the ink composition for reversible thermochromic stamps of this invention. It is a longitudinal cross-sectional explanatory drawing of the other example of the reversible thermochromic stamp which mounts the ink composition for reversible thermochromic stamps of this invention.

  The reversible thermochromic stamp ink composition according to the present invention includes a reversible thermochromic microcapsule pigment, water, a humectant, and a resin emulsion, and the resin emulsion has a solid content acid value of 100 or less. It is one of the characteristics.

  The resin emulsion used in the present invention is one in which the resin does not dissolve in water but exists in the form of particles, and the water evaporates to form particles by binding the particles together.

  The resin emulsion used in the present invention has a solid acid value of the resin in the resin emulsion of 1 or more and 100 or less. If it is larger than this range, when the print image is formed, the film of the print image becomes fragile or cannot be formed, and the print image cannot be fixed or fixed on the pressing surface. When it is scraped off, the printed image is peeled off. Preferably, the solid content acid value is 5 or more, and 60 or less is preferable. More preferably, it is 55 or less. By setting this range, the print image film is firmly formed, so that the fixability of the print image is improved, and even when the print image is rubbed with a friction member, the print image is peeled off from the imprinted surface. There is no.

The solid content acid value in the present invention is the acid value of the resin itself in the emulsion, and is a value obtained from the following formula by the indicator titration method described in JISK2501.
AN = 56.1 × cKOH × (V1-V0) / m
AN: Acid value (mgKOH / g)
V1: Amount of 0.1 mol / l potassium hydroxide 2-propanol solution required for titration of sample (ml)
V0: Amount of 0.1 mol / l potassium hydroxide 2-propanol solution required for titration in blank test (ml)
cKOH: Molar concentration (mol / l) of a 2-propanol solution of 0.1 mol / l potassium hydroxide
m: Amount of sample taken (g)
56.1: Formula weight of potassium hydroxide

  The mixing ratio of the resin in the resin emulsion used in the present invention is 1% or more and preferably 15% by mass or less with respect to the total mass of the ink composition. More preferably, it is 3 mass% or more and 10 mass% or less. If it is larger than this range, the viscosity of the ink composition increases, the fluidity of the ink composition tends to deteriorate, and a clear print image may not be obtained. In addition, the stability over time of the ink composition tends to be inferior. If the thickness is smaller than this range, the film of the print image is not formed or there is a tendency that it takes time to form the film, and the fixability of the print image may be deteriorated. Within this range, the ink composition has good fluidity and a clear print image can be obtained, and when the print image is formed, the film of the print image can be firmly formed, thereby improving the fixability of the print image. . Further, even when the print image is rubbed with a friction member or the like, the print image is firmly fixed to the stamp surface, and therefore, the print image is not peeled off.

  As the resin emulsion used in the present invention, an acrylic resin emulsion, a urethane resin emulsion, and the like can be used. More specifically, examples of the acrylic emulsion include acrylic acid, methacrylic acid, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer ester, alkali metal salt, ammonium salt, and amine salt. Examples of the urethane emulsion include polyether polyol copolymer type, polyester polyol copolymer type, and polycarbonate polyol copolymer type urethane emulsion.

  The reversible thermochromic stamp ink composition according to the present invention includes a reversible thermochromic microcapsule pigment, water, a humectant, and a resin emulsion. The amount of the humectant is based on the total mass of the ink composition. It is preferable that it is 30-60 mass%. When the amount is less than this range, the printed surface is dried, and the printed image cannot be obtained. On the other hand, if the amount is larger than this range, the hygroscopicity becomes high, and the printed image is blurred or spotted, so that a clear printed image cannot be obtained. More preferably, it is 30-55 mass%, More preferably, it is 40-50 mass%. When the ink injection amount and the amount of the humectant are within the above ranges, the ink is not dried and does not absorb moisture, and an impression is clearly obtained.

  The humectant used in the present invention is not particularly limited as long as it can be generally used as a humectant, but a water-soluble organic solvent is preferable. Examples of the water-soluble organic solvent include glycols such as glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, 1,3-butylene glycol, ethylene glycol monomethyl ether, and their lower alkyl ethers, 2-pyrrolidone, N- Vinyl pyrrolidone, etc., and (b) an electron-donating color-forming organic compound, (b) an electron-accepting compound, (c) an electron-receiving reaction by the components (a) and (b) in a specific temperature range In the case of using a reversible thermochromic microcapsule pigment encapsulating a reversible thermochromic composition comprising a reaction medium reversibly generated in glycerol, glycerin and propylene glycol are preferably used as the water-soluble organic solvent.

  The compounding ratio of the resin and the humectant in the resin emulsion is preferably 1/3 to 1/100 of the resin / humectant in the resin emulsion as a mass ratio. More preferably, it is 1/5 to 1/20. If the blending ratio of the resin emulsion is less than this range, the fixability of the printed image tends to be inferior. If it is more than this range, the storage stability of the ink composition is increased. There is a tendency to be inferior. When it is in the above range, the fixing property of the printed image is sufficient, and the storage stability of the ink composition is also good.

In addition, the ink composition of the present invention can be used as a penetrable stamp ink composition having a marking surface, but the mixing ratio of water and humectant contained in the ink composition is water / humidity retention as a mass ratio. The agent is preferably 1 / 3.3 to 1 / 1.8. More preferably, it is 1/3 to 1 / 1.9. If the mixing ratio of water is less than this range, the ink absorbs moisture at the time of cap-off when the stamp is formed, and the moisture on the printing surface increases. There is a tendency for the printed image to bleed, and if the amount of water is larger than this range, the amount of moisture in the moisturizing agent is large, so that the water in the ink evaporates, and thus the printed image tends to be blurred when stamped. Within the above range, it is possible to suppress ink moisture absorption and moisture evaporation at the time of cap-off, and a good printed image can be obtained at the time of stamping. In particular, when the mixing ratio of water and the humectant is within the above range, and the mixing ratio of the humectant is within the preferable range, which is 30 to 60% by mass with respect to the total mass of the ink composition, the effect becomes remarkable. .
Furthermore, a clear image can be obtained by making the blending ratio of the resin in the resin emulsion contained in the ink composition of the present invention 1% or more and 15% by mass or less with respect to the total mass of the ink composition. While maintaining the good fixability and scratch resistance of the printed image, the performance at the time of imprinting when the cap was turned off as a stamp, the fixability of the image formed by imprinting, It is possible to further improve the performance as a stamp, for example, it is possible to maintain good scratching properties.

  In addition to the water, an organic solvent usually used for stamping inks may be used as a medium. Specifically, castor oil fatty acid alkyl esters, cellosolve solvents such as methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, ethylene glycol acetate, ethylene glycol diethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, pro Alkylene glycol solvents such as lenglycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol diethyl ether, dipropylene glycol monomethyl ether acetate, tripropylene glycol monomethyl ether, ethyl Formate, amyl formate, ethyl acetate, ethyl acetoacetate, propyl acetate, butyl acetate, 3-methyl-3-methoxybutyl acetate, amyl acetate, methyl-3-methoxypropionate, ethyl-3-methoxypropionate Ethyl-3-ethoxypropionate, propyl-3-methoxypropionate, Ester solvents such as til-3-methoxypropionate, methyl lactate, ethyl lactate, ethyl-2-hydroxybutyrate, butyl butyrate, butyl stearate, ethyl caprate, diethyl oxalate, ethyl pyruvate, ethyl benzoate , N-pentane, n-hexane, n-octane, n-dodecane, diisobutylene, dipentene, hexene, methylcyclohexene, bicyclohexyl, hydrocarbon solvents such as mineral spirits, halogenated hydrocarbons such as amyl chloride and butyl chloride Solvents, alcohol solvents such as 3-methoxy-3-methylbutanol and 3-methoxy-3-methylpentanol, diethyl ether, dipropyl ether, ethyl isobutyl ether, dibutyl ether, diisopropyl ether Ether solvents such as ether, diamyl ether, dihexyl ether, acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl butyl ketone, methyl isobutyl ketone, methyl isoamyl ketone, ethyl amyl ketone, methyl hexyl ketone, methyl nonyl ketone, diisopropyl ketone, diisobutyl Ketone solvents such as ketone, methoxymethylpentanone, cyclohexanone, propionic acid solvents such as 3-methoxypropionic acid, 3-ethoxypropionic acid, dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone, benzonitrile, etc. A highly polar solvent or a mixed solvent thereof may be used.

  The reversible thermochromic ink composition used in the present invention contains a reversible thermochromic microcapsule pigment, but the (a) electron donating color-forming organic compound, (b) electron accepting compound, (c) the above ( (B) A reversible thermochromic microcapsule pigment in which a microcapsule encapsulates a reversible thermochromic composition comprising at least a reaction medium that reversibly causes an electron transfer reaction in a specific temperature range. explain.

  Examples of the reversible thermochromic microcapsule pigment include a predetermined temperature (discoloration point) described in JP-B-51-44706, JP-B-51-44707, JP-B-1-29398, and the like. Before and after the color change, the color disappears in the temperature range above the high temperature side discoloration point, and the color develops in the temperature range below the low temperature side discoloration point. The other state is maintained while the heat or cold required to develop the state is applied, but when the heat or cold is no longer applied, the hysteresis width returns to the state exhibited in the normal temperature range. Applying a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition that has a relatively small characteristic (ΔH = 1 to 7 ° C.) (decolored by heating and develops color by cooling) (Fig. 1 Irradiation).

In addition, large hysteresis characteristics (ΔH _B = 8 to 50 ° C.) described in JP- _B -4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, and the like. ), That is, when the shape of the curve plotting the change in the color density due to the temperature change is lowering the temperature from the lower temperature side than the color changing temperature range, as opposed to increasing the temperature from the lower temperature side. In the specific temperature range, the color changes in a low temperature range below the complete color development temperature (t ₁ ) or the color erase state in the high temperature range above the complete color erase temperature (t ₄ ). A reversible thermochromic composition having a color memory property in a temperature range between t _{2 and} t ₃ (substantially two-phase holding temperature range) (decolored by heating and developed by cooling). Reversible thermochromic micro Capsule pigments can also be applied (see FIG. 2).

  The hysteresis characteristics in the color density-temperature curve of the microcapsule pigment encapsulating the reversible thermochromic composition will be described below with reference to the graph of FIG.

In FIG. 2, the vertical axis represents color density and the horizontal axis represents temperature. The change in color density due to the temperature change proceeds along the arrow. Here, A is a point indicating a density at a temperature t ₄ (hereinafter referred to as a complete decoloring temperature) reaching a completely decolored state, and B is a temperature t ₃ (hereinafter referred to as a decoloring start temperature) at which decoloring starts. C is a point indicating a density at a temperature t ₂ at which color development starts (hereinafter referred to as a color development start temperature), and D is a temperature t ₁ at which a fully colored state is reached (hereinafter referred to as a color development start temperature). , Referred to as a complete color development temperature).

  The length of the line segment EF is a scale indicating the discoloration contrast, and the length of the line segment HG is a temperature width indicating the degree of hysteresis (hereinafter referred to as hysteresis width ΔH). It is easy to maintain each state before and after the color change.

Here, the difference between t ₄ and t ₃ , or the difference between t ₂ and t ₁ (Δt) is a scale indicating the sensitivity of discoloration.

Further, only one specific state (coloring state) exists in the normal temperature range among the color development / decoloration states of the reversible thermochromic composition, and the image formed by the reversible thermochromic composition is easily generated by frictional heat generated by friction. In order to change color (discolor), the complete color erasing temperature (t ₄ ) is preferably 50 to 95 ° C., and the color development start temperature (t ₂ ) is preferably −50 to 10 ° C.

Here, the color development state can be maintained in the normal temperature range, and in order to facilitate discoloration due to the friction of the print image, the complete color erasing temperature (t ₄ ) is 50 to 95 ° C., and the color development start temperature (t _2). ) is to explain whether the -50~10 ℃, when stopping the heating in a state that does not reach from the colored state to the through decoloring starting temperature (t ₃₎ complete decoloring temperature (t _4), the first re The phenomenon of returning to the state occurs, and even if the cooling is stopped in the state where the color development start temperature (t ₂ ) has not reached the complete color development temperature (t ₁ ) from the decolored state, the color developed state is maintained. Therefore, if the complete decoloring temperature (t ₄ ) is 50 ° C. or more exceeding the normal temperature range, the color development state is maintained in the normal use state, and the color development start temperature (t ₂ ) is within the normal temperature range. If the temperature is lower than −50 to 10 ° C., the decolored state is maintained in normal use. Is done.

Further, when the print image is erased by friction, if the complete color erasing temperature (t ₄ ) is 95 ° C. or less, the print image formed on the surface to be printed is subjected to frictional heat caused by friction several times by the friction member. Can change color sufficiently.

When the complete decolorization temperature (t ₄ ) exceeds 95 ° C., the frictional heat obtained by friction with the friction member is difficult to reach the complete decolorization temperature, so that it is difficult to discolor easily and the number of friction increases. Or, since the load tends to be excessively rubbed, there is a risk of damaging the paper surface when the image surface is paper.

  Therefore, the temperature setting is an important requirement in order to select and visually recognize a discolored image on the stamping surface, and can satisfy convenience and practicality.

In the temperature setting of the complete color erasing temperature (t ₄ ), a higher temperature is preferable in order to maintain the color development state in a normal use state, and the frictional heat due to friction is a complete color erasure temperature ( In order to exceed t ₄ ), a low temperature is preferred. Therefore, the complete decoloring temperature (t ₄ ) is preferably 50 to 90 ° C., more preferably 60 to 80 ° C. Further, in the temperature setting of the color development start temperature (t ₂ ) described above, it is preferably a lower temperature in order to maintain the decolored state in a normal use state, and −50 to 5 ° C. is preferable. -50-0 degreeC is more suitable. In the present invention, the hysteresis width (ΔH) is in the range of 50 ° C. to 100 ° C., preferably 55 to 90 ° C., more preferably 60 to 80 ° C.

As the microcapsule pigment used for the reversible thermochromic stamp according to the present invention, a reversible thermochromic composition having a complete decoloring temperature (t ₄ ) on the higher temperature side than the above-mentioned color change temperature range can also be used.

Among the color development and decoloring states of the reversible thermochromic composition, only one specific state (coloring state) is present in the normal temperature range, and heat obtained from a heat erasing tool or the like by printing an image of the reversible thermochromic composition In order to erase the color, the complete color erasing temperature (t ₄ ) is 80 ° C. or higher, and the color development start temperature (t ₂ ) is 15 ° C. or lower. Here, the color development state can be maintained in a normal temperature range, and the color erasure state is maintained in normal use. Therefore, the complete color erasure temperature (t ₄ ) is 80 ° C. or more and the color development start temperature (t ₂ ). If the heating is stopped in a state where the color disappearance temperature does not reach the complete color erasing temperature (t ₄ ) from the color developing state through the color erasing start temperature (t ₃ ), the state returns to the first state again. And the state in which color development is maintained even if the cooling is stopped in a state where the color development start temperature (t ₂ ) has not reached the complete color development temperature (t ₁ ) from the decolored state. When the complete color erasing temperature (t ₄ ) is 80 ° C. or more exceeding the normal temperature range, the color development state is maintained in a high temperature environment such as a car in summer and the color development start temperature (t ₂ ) is 15 ° C. below the normal temperature range. The decolored state is maintained in normal use at the following temperatures. Further, if the complete color erasing temperature (t ₄ ) is 90 ° C. or higher, the color development state is more maintained in a high temperature environment, and if the color development start temperature (t ₂ ) is 10 ° C. or lower, the color erasure state is normal. More maintained in use. Therefore, the temperature setting is an important requirement for selectively displaying a color-changed image on the stamping surface, and the image can achieve the intended purpose. In the above-described temperature setting of the complete color erasing temperature (t ₄ ), it is preferable that the color development state be higher in order to be maintained in a high temperature environment, and the complete color erasing temperature (t ₄ ) is preferably 90 °. More than 100 degreeC, More preferably, it is 100 degreeC or more. Furthermore, in the temperature setting of the color development start temperature (t ₂ ) described above, it is preferably a lower temperature in order to maintain the decolored state in a normal use state, and −50 to 10 ° C. is preferable. -50-5 degreeC is more suitable. In order to bring the reversible thermochromic composition into a colored state in advance, it is preferable to cool in a general-purpose freezer as a cooling means, but considering the cooling capacity of the freezer, the limit is up to −50 ° C., Therefore, the complete color development temperature (t ₁ ) is preferably −50 ° C. or higher. In the present invention, the hysteresis width (ΔH) is in the range of 70 ° C to 150 ° C.

  By using the reversible thermochromic composition, a printed image formed on an important document or the like is not erased even when left in a high temperature environment such as a car in summer, and the application range as a stamp can be expanded. it can. Furthermore, since it becomes difficult to erase by rubbing with the friction member, it can be used to determine the authenticity of the document. At that time, the use of the reversible thermochromic stamp ink composition according to the present invention is particularly useful because the printed image is not peeled off.

  Hereinafter, the components (a), (b) and (c) constituting the reversible thermochromic composition will be described.

  In the present invention, the component (a) donates an electron to the component (b), which is a developer, and a ring structure such as a lactone ring of the component (a) is opened, thereby taking a resonance structure with the component (b). It consists of an electron-donating color-forming organic compound that develops color. Examples of such electron-donating color-forming organic compounds include diphenylmethane phthalides, phenyl indolyl phthalides, indolyl phthalides, diphenyl methane azaphthalides, phenyl indolyl azaphthalides, fluorans, styrinoquinolines. , Diazarhodamine lactones, pyridines, quinazolines, bisquinazolines and the like.

  As the electron-accepting compound of component (b), a group of compounds having active protons, a group of pseudo-acidic compounds (a group of compounds that are not acids but act as an acid in the composition and cause component (a) to develop color), electrons There is a group of compounds having pores.

  Examples of compounds having active protons include monophenols to polyphenols as compounds having phenolic hydroxyl groups, and alkyl groups, aryl groups, acyl groups, alkoxycarbonyl groups, carboxy groups and esters thereof as substituents. Alternatively, those having an amide group, a halogen group, etc., and bis-type and tris-type phenols, phenol-aldehyde condensation resins and the like can be mentioned. Moreover, the metal salt of the compound which has the said phenolic hydroxyl group may be sufficient.

  Examples of the (c) component of the reaction medium that causes the electron transfer reaction by the (a) component and the (b) component to occur reversibly in a specific temperature range include alcohols, esters, ketones, and ethers. .

  The component (c) is preferably a large hysteresis characteristic regarding the color density-temperature curve (a curve plotting a change in color density due to a temperature change changes the temperature from the low temperature side to the high temperature side and the high temperature side to the low temperature side). A carboxylic acid ester compound having a ΔT value (melting point-cloud point) of 5 ° C. or more and less than 50 ° C., which can form a reversible thermochromic composition exhibiting color memory properties, which changes color when changing to the side) Used. As such a compound, various compounds have been proposed and can be arbitrarily selected and used. Specific examples thereof include the following.

（式中、Ｒ１は水素原子又はメチル基を示し、ｍは０〜２の整数を示し、Ｘ１、Ｘ２のいずれか一方は−（ＣＨ２）ｎＯＣＯＲ２又は−（ＣＨ２）ｎＣＯＯＲ２、他方は水素原子を示し、ｎは０〜２の整数を示し、Ｒ２は炭素数４以上のアルキル基又はアルケニル基を示し、Ｙ１及びＹ２は水素原子、炭素数１〜４のアルキル基、メトキシ基、又は、ハロゲンを示し、ｒ及びｐは１〜３の整数を示す。） First, as the component (c), a compound represented by the following general formula (1) described in JP-A No. 2006-137886 is suitably used.

(In the formula, R1 represents a hydrogen atom or a methyl group, m represents an integer of 0 to 2, one of X1 and X2 represents — (CH2) nOCOR2 or — (CH2) nCOOR2, and the other represents a hydrogen atom. , N represents an integer of 0 to 2, R2 represents an alkyl group or alkenyl group having 4 or more carbon atoms, Y1 and Y2 represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a methoxy group, or a halogen. , R and p represent an integer of 1 to 3)

Among the compounds represented by the formula (1), when R ₁ is a hydrogen atom, it is preferable because a reversible thermochromic composition having a wider hysteresis width can be obtained, and R ₁ is a hydrogen atom, and , M is more preferably 0.

（式中のＲは炭素数８以上のアルキル基又はアルケニル基を示すが、好ましくは炭素数１０〜２４のアルキル基、更に好ましくは炭素数１２〜２２のアルキル基である。） Of the compounds represented by the formula (1), a compound represented by the following general formula (2) is more preferably used.

(In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, preferably an alkyl group having 10 to 24 carbon atoms, more preferably an alkyl group having 12 to 22 carbon atoms.)

（式中、Ｒは炭素数８以上のアルキル基又はアルケニル基を示し、ｍ及びｎはそれぞれ１〜３の整数を示し、Ｘ及びＹはそれぞれ水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲンを示す。） Furthermore, a compound represented by the following general formula (3) can also be used as the component (c).

(In the formula, R represents an alkyl group or alkenyl group having 8 or more carbon atoms, m and n each represents an integer of 1 to 3, X and Y represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, carbon, respectively. (The alkoxy group of Formula 1-4 is shown, and a halogen.)

  Furthermore, a compound represented by the following general formula (4) can also be used as the component (c).

（式中、Ｘは水素原子、炭素数１〜４のアルキル基、メトキシ基、ハロゲン原子のいずれかを示し、ｍは１乃至３の整数を示し、ｎは１〜２０の整数を示す。） (I) an electron donating color-forming organic compound, (b) an electron accepting compound, (c) a reaction medium that reversibly causes an electron transfer reaction by the components (a) and (b) in a specific temperature range; A reversible thermochromic microcapsule pigment in which a reversible thermochromic composition comprising at least the above is encapsulated in microcapsules will be described below.

(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 of 1 to 3, and n represents an integer of 1 to 20).

（式中、Ｒは炭素数１乃至２１のアルキル基又はアルケニル基を示し、ｎは１〜３の整数を示す。） Furthermore, a compound represented by the following general formula (5) can also be used as the component (c).

(In the formula, R represents an alkyl group or alkenyl group having 1 to 21 carbon atoms, and n represents an integer of 1 to 3).

（式中、Ｘは水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲン原子のいずれかを示し、ｍは１〜３の整数を示し、ｎは１〜２０の整数を示す。） Furthermore, a compound represented by the following general formula (6) can also be used as the component (c).

(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 of 1 to 3, and n represents 1 to 20) Indicates an integer.)

（式中、Ｒは炭素数４〜２２のアルキル基、シクロアルキルアルキル基、シクロアルキル基、炭素数４〜２２のアルケニル基のいずれかを示し、Ｘは水素原子、炭素数１〜４のアルキル基、炭素数１〜４のアルコキシ基、ハロゲン原子のいずれかを示し、ｎは０又は１を示す。） Furthermore, a compound represented by the following general formula (7) can also be used as the component (c).

(In the formula, R represents any of an alkyl group having 4 to 22 carbon atoms, a cycloalkylalkyl group, a cycloalkyl group, and an alkenyl group having 4 to 22 carbon atoms, and X represents a hydrogen atom and an alkyl having 1 to 4 carbon atoms. A group, an alkoxy group having 1 to 4 carbon atoms, or a halogen atom, and n represents 0 or 1.)

  Examples of the compound include decyl 4-phenylbenzoate, lauryl 4-phenylbenzoate, myristyl 4-phenylbenzoate, cyclohexylethyl 4-phenylbenzoate, octyl 4-biphenylacetate, nonyl 4-biphenylacetate, 4-biphenylacetic acid Decyl, 4-biphenyl lauryl acetate, 4-biphenyl acetate myristyl, 4-biphenyl acetate tridecyl, 4-biphenyl acetate pentadecyl, 4-biphenyl acetate cetyl, 4-biphenyl acetate cyclopentyl, 4-biphenyl acetate cyclohexyl methyl, 4-biphenyl acetate hexyl And cyclohexylmethyl 4-biphenylacetate.

（式中、Ｒは炭素数３〜７のアルキル基を示し、Ｘは水素原子、メチル基、ハロゲン原子のいずれかを示し、Ｙは水素原子、メチル基のいずれかを示し、Ｚは水素原子、炭素数１〜４のアルキル基、炭素数１又は２のアルコキシ基、ハロゲン原子のいずれかを示す。） Furthermore, a compound represented by the following general formula (8) can also be used as the component (c).

(In the formula, R represents an alkyl group having 3 to 7 carbon atoms, X represents a hydrogen atom, a methyl group or a halogen atom, Y represents a hydrogen atom or a methyl group, and Z represents a hydrogen atom. Or an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 or 2 carbon atoms, or a halogen atom.)

  Examples of the compound include phenylethyl 4-butoxybenzoate, phenoxyethyl 4-butoxybenzoate, phenoxyethyl 4-pentyloxybenzoate, and the like.

  Further, as the electron-accepting compound, a specific alkoxyphenol compound having a linear or side chain alkyl group having 3 to 18 carbon atoms can be used (Japanese Patent Laid-Open Nos. 11-129623 and 11-5973), Hydroxybenzoic acid esters (Japanese Patent Laid-Open No. 2001-105732), gallic acid esters and the like (Japanese Patent Publication No. 51-44706, Japanese Patent Laid-Open No. 2003-253149) are used. A microcapsule pigment containing a reversible thermochromic composition that is decolored by cooling) can also be applied (see FIG. 3).

  The proportions of the components (a), (b), and (c) depend on the concentration, color change temperature, color change form, and type of each component, but generally desired color change characteristics can be obtained. The component ratio is in the range of (b) component 1 to (b) component 0.1 to 50, preferably 0.5 to 20, (c) component 1 to 800, preferably 5 to 200 (see above). All percentages are based on mass). Moreover, you may use each component in mixture of 2 or more types, respectively.

  The reversible thermochromic composition is encapsulated in microcapsules and used as a reversible thermochromic microcapsule pigment. This is because the reversible thermochromic composition can be kept in the same composition under the various use conditions and can exhibit the same effects.

  Methods for microencapsulating the reversible thermochromic composition include interfacial polymerization, interfacial polycondensation, in situ polymerization, in-liquid curing coating, phase separation from aqueous solution, and phase separation from organic solvent. There are a melt dispersion cooling method, an air suspension coating method, a spray drying method, and the like, which are appropriately selected according to use. Furthermore, a secondary resin film may be provided on the surface of the microcapsule according to the purpose to impart durability, or the surface characteristics may be modified for practical use.

  Here, the mass ratio of the reversible thermochromic composition to the microcapsule wall membrane satisfies the range of 7: 1 to 1: 1, preferably 6: 1 to 1: 1.

  When the ratio of the reversible thermochromic composition to the wall film is larger than the above range, the thickness of the wall film becomes too thin, and the resistance to pressure and heat tends to decrease, and the ratio of the wall film to the reversible thermochromic composition When the value is larger than the above range, color density and sharpness during color development tend to be reduced.

  The reversible thermochromic microcapsule pigment includes antioxidants, ultraviolet absorbers, infrared absorbers, dissolution aids, antiseptic / antifungal agents, non-thermochromic dyes and pigments as long as they do not affect their functions. Various additives such as can be added.

  The microcapsule pigment of the reversible thermochromic stamp ink composition used for the reversible thermochromic stamp according to the present invention is preferably 0.1 to 10 μm. If it is smaller than this range, the obtained printed image tends to show through from the paper surface, and the color density as a colorant decreases, so that the printed image is not clear. Furthermore, it may be difficult to maintain a stable state in the ink, the microcapsule pigment is likely to aggregate, the ink is less likely to flow through the continuous pores, and as a result, the print image may be faded, Continuous imprinting may not be possible. On the other hand, if it is larger than this range, the ink discharge tends to be poor or the print image will not be sharp. Preferably, it is 0.1-7 micrometers, More preferably, it is 0.3-5 micrometers. Within this range, the printed image is clear and sharp, and a high-quality printed image can be obtained even when continuously stamped. The average particle diameter of the microcapsule pigment is calculated on a volume basis.

  The reversible thermochromic stamp ink used in the present invention may use a thickener, but as a thickener, xanthan gum, welan gum, or a saccharine whose constituent monosaccharide is an organic acid-modified heteropolysaccharide of glucose and galactose. Synoglycan (average molecular weight of about 1 to 8 million), guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alginic acid alkyl esters, polymers having a molecular weight of 100,000 to 150,000 based on alkyl esters of methacrylic acid, glyco Mannan, polysaccharide thickener with gelling ability extracted from seaweed such as agar and carrageenin, benzylidene sorbitol and benzylidene xylitol or their derivatives, crosslinkable acrylic acid polymer, inorganic fine particles, polyglycerin fatty acid ester, polyoxyethylene Sorbitan fat HLB values of esters, polyethylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene lanolin, lanolin alcohol, beeswax derivatives, polyoxyethylene alkyl ether / polyoxypropylene alkyl ether, polyoxyethylene alkyl phenyl ether, fatty acid amide, etc. Examples of the nonionic surfactant of 8 to 12 and salts of dialkyl or dialkenylsulfosuccinic acid may be used alone or in combination.

  In addition, additives such as pH adjusters, preservatives, and antifungal agents can be added as necessary.

  Examples of the pH adjuster include inorganic basic salts such as ammonia, sodium carbonate, sodium phosphate, sodium hydroxide and sodium acetate, and organic basic compounds such as water-soluble amine compounds such as triethanolamine and diethanolamine.

  Examples of the preservative or antifungal agent include carboxylic acid, sodium salt of 1,2-benzisothiazolin-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl paraoxybenzoate, 2, 3, 5, 6 -Tetrachloro-4- (methylsulfonyl) pyridine and the like.

  In addition, an antifoaming agent such as a fluorine-based surfactant that improves the permeability of the solvent, a nonion, an anion, a cationic surfactant, or dimethylpolysiloxane may be added.

  It should be noted that a non-thermochromic dye or pigment is blended in the ink composition so that a thermochromic image exhibiting tautomerism from colored (1) to colored (2) can be formed by temperature change. Can do.

  The ink composition has an ink viscosity of 3000 to 10000 mPa · s, preferably 3500 to 7000 mPa · s, more preferably 4000 to 6000 mPa · s, measured at 6 ° C. using a BL type viscometer at 25 ° C. Degree (ink viscosity measured at 6 rpm / ink viscosity measured at 60 rpm) is 1.1 to 2.5, preferably 1.2 to 2.0.

  When the ink viscosity is less than 3000 mPa · s, the printed image formed on the paper surface using the ink composition tends to spread. If it exceeds 10,000 mPa · s, the fluidity of the microcapsule pigment is insufficient in the continuous pores, and the smooth flow of the ink composition to the printing surface cannot be ensured, and an unclear image is formed by continuous printing operation. .

  If the degree of change is less than 1.1, the printed image formed on the paper surface using the ink composition tends to bleed, and if it exceeds 2.5, the microcapsule pigment has insufficient fluidity in the continuous pores. A smooth flow of the ink composition to the ink cannot be ensured, and an unclear image is formed by a continuous printing operation.

  The blending ratio of the reversible thermochromic microcapsule pigment is preferably 5% by mass to 50% by mass, more preferably 10% by mass to 35% by mass, and still more preferably 10% by mass to 30% by mass with respect to the total mass of the ink composition. If the amount is less than this range, the color density tends to decrease. If the amount is more than this range, the dispersion stability tends to be slightly deteriorated in the ink composition.

  The compounding ratio of the resin in the resin emulsion to the reversible thermochromic microcapsule pigment is preferably 3/1 to 1/25 as a mass ratio of resin / reversible thermochromic microcapsule pigment in the resin emulsion. More preferably, the ratio is 1/1 to 1/5. If the blending ratio of the resin emulsion is less than this range, the fixability of the printed image tends to be inferior. If it exceeds this range, the storage stability of the ink composition is increased. There is a tendency to be inferior. When it is in the above range, the fixing property of the printed image is sufficient, and the storage stability of the ink composition is also good.

  The ink composition for a reversible thermochromic stamp according to the present invention can be used for a reversible thermochromic stamp in which a printing material is impregnated with an ink composition. When the reversible thermochromic stamp is used and pressed against the imprinting surface, the ink composition moves from the ink penetrating surface to the imprinting surface, and a printed image is formed. The reversible thermochromic stamp is placed on the stamp base so that the marking surface is exposed, and the exposed surface is provided with a cap to prevent contamination of the ink composition when it is not used and drying. preferable. In addition, the structure which increases the frequency | count of stamping by providing the ink storage part which supplies an ink composition to a printing material in the rear part of the printing material which has a continuous pore may be sufficient.

  The reversible thermochromic stamp can form printed images on various stamped surfaces. Further, the printed image can be discolored or decolored by rubbing with a friction member or application of a heating tool or a cooling tool. However, even when rubbing with a friction member, the reversible thermochromic stamp ink according to the present invention is used. By using it, the printed image can be discolored and decolored without peeling off.

  As the heating tool, a thermal head equipped with a resistance heating element such as a PTC element, a heating roller, an electric heating color changing tool using a hot stamp, a heating color changing tool filled with a medium such as hot water, steam or laser light is used. Application of heating discoloring tools and hair dryers. Preferably, a friction member is used as means capable of changing color by a simple method.

  As the friction member, an elastic body such as an elastomer or a plastic foam which is rich in elasticity and can generate frictional heat by rubbing at the time of rubbing is suitable. As the material of the friction member, silicone resin, SEBS resin (styrene ethylene butylene styrene block copolymer), polyester resin, polyester elastomer and the like are used. The friction member can be obtained by combining a stamp and a friction body, which is a separate member having an arbitrary shape, to obtain a stamp set. However, by providing the stamp with a friction member, it becomes excellent in portability.

As a heat discoloring tool for a reversible thermochromic stamp using the reversible thermochromic composition having a complete color erasing temperature (t ₄ ) on the high temperature side where the complete color erasing temperature (t ₄ ) is 80 ° C. or higher, PTC Thermal head, heat roller, energization heating color changer using hot stamp, heating color changer filled with medium such as hot water, heating color changer using steam or laser light, hair dryer Is preferably used.

  Examples of the cooling / heating tool include a cooling / heating discoloration tool using a Peltier element, a cooling / heating discoloration tool filled with a refrigerant such as cold water and ice pieces, a cold insulation agent, and application of a refrigerator and a freezer.

  The reversible thermochromic stamp (1) is obtained by impregnating a reversible thermochromic stamp ink composition into a printing material having continuous pores, and is fixed to the stamp substrate (3) so that the marking surface is exposed. 4) and a cap (5) can be fitted. In addition, the friction member as a tail plug (4) can also be provided in the rear-end part of a stamp base material (3).

  As another method for producing the reversible thermochromic stamp (1), the printing material (2) having continuous pores is fixed to the stamp base (3) so that the printing surface is exposed, and then the reversible thermochromic stamp is used. It can be prepared by impregnating the ink composition and fitting the tail plug (4) and the cap (5). As in the production method, a friction member as a tail plug (4) can be provided at the rear end of the stamp base material (3). Furthermore, when the printing material is impregnated with ink, it may be injected from the side opposite to the printing surface to impregnate the printing material.

  Although the reversible thermochromic stamp (1) according to the present invention can be used alone, it can also be used as a stamp set in which a plurality of the reversible thermochromic stamps (1) are combined depending on the difference in ink color or the difference in print image.

(Example 1)
(Manufacture of microcapsule pigments)
As component (a), 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide (1 part), 2 parts of 2-bis (4-hydroxyphenyl) hexafluoropropane, (c) reversible color memory comprising 50.0 parts of cyclohexylmethyl 4-biphenylacetate and 5.0 parts of p-methylbenzyl stearate A thermochromic composition is heated and dissolved, and a solution prepared by mixing 30.0 parts of an aromatic isocyanate prepolymer and 40.0 parts of a co-solvent as a wall film material is emulsified and dispersed in an aqueous 8% polyvinyl alcohol solution, followed by heating. While continuing stirring, 2.5 parts of a water-soluble aliphatic modified amine was added, and stirring was further continued to obtain a reversible thermochromic microcapsule pigment suspension. The suspension was filtered with a filter to isolate a reversible thermochromic microcapsule pigment.
The average particle diameter D of the microcapsule pigment is 2.0 μm, t ₁ : −18 ° C., t ₂ : −12 ° C., t ₃ : 42 ° C., t ₄ : 66 ° C., temperature-sensitive color change color memory. Composition: wall film = 2.6: 1.0 The film showed a behavior having hysteresis characteristics and reversibly changed from blue to colorless and from colorless to blue.

(Preparation of reversible thermochromic stamp ink)
Microcapsule pigment 17.5 parts by weight Water-soluble organic solvent (glycerin) 50 parts by weight Resin emulsion A 13.2 parts by weight (urethane resin emulsion solid content acid value 5.6
NeoRezR-650 (Brand name Enomoto Kasei Co., Ltd. solid content 38%))
pH adjuster (triethanolamine) 0.5 parts by weight Thickener 4 parts by weight (Primal TT935 (trade name, manufactured by Rohm & Haas Japan))
Penetrant 0.5 parts by weight Preservative 0.2 parts by weight Water 14.1 parts by weight The above mixture was mixed to obtain a reversible thermochromic stamp ink.
(Production of reversible thermochromic stamp)
The reversible thermochromic stamp ink is injected into a printing material (ethylene vinyl acetate copolymer) having continuous pores, fixed to the stamp base material (3) so that the printing surface is exposed, and a cap (5) is fitted. Got a stamp. In addition, a friction member made of SEBS resin was provided as a tail plug (4) at the rear end of the stamp base material (3).

(Examples 2 to 8)
A reversible thermochromic stamp ink composition was obtained in the same manner as in Example 1 except that the formulation shown in Table 1 was used. Further, a reversible thermochromic stamp was obtained in the same manner as in Example 1.

(Examples 9 to 15)
A reversible thermochromic stamp ink composition was obtained in the same manner as in Example 1 except that the formulation shown in Table 2 was used. Further, a reversible thermochromic stamp was obtained in the same manner as in Example 1.

(Comparative Examples 1-6)
A reversible thermochromic stamp ink composition was obtained in the same manner as in Example 1 except that the formulation shown in Table 3 was used. Further, a reversible thermochromic stamp was obtained in the same manner as in Example 1.

  Using the reversible thermochromic stamps obtained in Examples 1 to 15 and Comparative Examples 1 to 6, the coated paper (Esprit Coat W (manufactured by Nippon Paper Industries Co., Ltd.)) was stamped to form an image. The imprinting property, the fixing property, the scratch resistance and the cap-off property were evaluated by the following methods, and the results are shown in (Table 1) to (Table 3).

樹脂エマルションＡ：ウレタン系樹脂エマルション 固形分酸価 ５．６ ＮｅｏＲｅｚＲ−６５０ 楠本化成（株）製 固形分３８％
樹脂エマルションＢ：スチレン−アクリル系樹脂エマルション 固形分酸価 ５１ ジョンクリル７１００（商品名 ＢＡＳＦジャパン（株）製 固形分４８％）
樹脂エマルションＣ：アクリル系樹脂エマルション 固形分酸価 ５５ ジョンクリル７７５（商品名 ＢＡＳＦジャパン（株）製 固形分４５％）
樹脂エマルションＤ：アクリル系樹脂エマルション 固形分酸価 ６０ ジョンクリル７６００（商品名 ＢＡＳＦジャパン（株）製 固形分４７％）
樹脂エマルションＥ：アクリル系樹脂エマルション 固形分酸価 ８７ ジョンクリルＰＤＸ−７３７０（商品名 ＢＡＳＦジャパン（株）製 固形分４２％）
樹脂エマルションＦ：アクリル系樹脂エマルション 固形分酸価 ２００ ジョンクリルＰＤＸ−７６３０Ａ（商品名 ＢＡＳＦジャパン（株）製 固形分３２％）
水溶性樹脂Ａ：アルカリ可溶型アクリル樹脂 固形分酸価 ２１５ ジョンクリル５７Ｊ（商品名 ＢＡＳＦジャパン（株）製 固形分３７％）
水溶性樹脂Ｂ：ポリビニルアルコール ゴーセノールＧＬ０３（商品名 日本合成化学工業（株）製）

押印性：コート紙に押印して印像を形成し、その際の印像について、目視により評価した。
◎：鮮やかな印像が得られている。
○：印像がわずかに滲んでいるか、わずかな掠れがあるが印像として視認可能。
△：印像が滲んでいるか、掠れがあるが印像としては視認可能。
×：印像が滲みがひどいか、掠れがひどく、印像として視認できない。

定着性：コート紙に押印後、所定の時間経過した後に印像を手で擦り、そのときの印像の状態を目視により確認した。
○：印像が流れずに押印面に定着しており、鮮明な印像が確認できる。
△：印像の一部が流れるが印像が確認できる。
×：印像が流れていしまい、印像を確認できない。

耐擦過性：コート紙に押印後、３０分経過した後に印像をＳＥＢＳ樹脂製の摩擦部材で、印像を擦過し、印像を消色した状態を目視により確認した。さらに、印像が消色した状態のコート紙を−２０℃に冷却し、そのときの印像の状態を確認した。
○：印像が剥がれることなく、そのままの状態で消色しており、冷却後、印像が押印した状態で発色する。
△：印像の一部が剥がれた状態で消色しており、冷却後、印像の一部が流れた状態で発色する。
×：印像が完全に剥がれた状態で消色しており、冷却後、印像が得られない。

キャップオフ性：キャップ（５）を外した後、２０℃、６５％ＲＨの雰囲気下で２４時間放置した後、コート紙に押印し、そのときの印像の状態を確認した。
◎：初期と同等の印像が得られており、良好なキャップオフ性能が得られている。
○：初期と比較して、印像がわずかに滲んでいるか、わずかな掠れがあるが十分なキャップオフ性能が得られている。
△：初期と比較して、印像が滲んでいるか、掠れがあるが印像としては視認可能であるが、キャップオフ性能は若干劣っている。
×：初期と比較して、印像の滲みがひどいか、掠れがひどく、印像として視認できず、キャップオフ性能を有していない。

Resin Emulsion A: Urethane Resin Emulsion Solid Content Acid Value 5.6 NeoRezR-650 Enomoto Kasei Co., Ltd. Solid Content 38%
Resin Emulsion B: Styrene-acrylic resin emulsion Solid acid value 51
Resin Emulsion C: Acrylic Resin Emulsion Solid Content Acid Value 55 Jonkrill 775 (trade name: BASF Japan Ltd. Solid Content 45%)
Resin Emulsion D: Acrylic Resin Emulsion Solid Content Acid Value 60 Jonkrill 7600 (Brand Name: BASF Japan Co., Ltd. Solid Content 47%)
Resin Emulsion E: Acrylic Resin Emulsion Solid Content Acid Value 87 Joncrill PDX-7370 (Trade Name: BASF Japan Ltd. Solid Content 42%)
Resin Emulsion F: Acrylic Resin Emulsion Solid Content Acid Value 200 Joncrill PDX-7630A (Brand Name BASF Japan Co., Ltd. Solid Content 32%)
Water-soluble resin A: Alkali-soluble acrylic resin Solid content acid value 215 Jonkrill 57J (trade name BASF Japan KK solid content 37%)
Water-soluble resin B: Polyvinyl alcohol Gohsenol GL03 (trade name, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.)

Imprintability: Imprinted on a coated paper to form a printed image, and the printed image at that time was visually evaluated.
A: A vivid image is obtained.
○: The printed image is slightly blurred or slightly blurred but visible as a printed image.
Δ: The printed image is blurred or blurred, but the printed image is visible.
X: The printed image is severely blurred or drowned and cannot be visually recognized as a printed image.

Fixability: After imprinting on the coated paper, the print image was rubbed by hand after a predetermined time had elapsed, and the state of the print image at that time was visually confirmed.
○: The printed image is fixed on the stamped surface without flowing, and a clear printed image can be confirmed.
Δ: A part of the print image flows, but the print image can be confirmed.
X: The printed image flows and the printed image cannot be confirmed.

Scratch resistance: 30 minutes after imprinting on the coated paper, the printed image was scratched with a friction member made of SEBS resin, and the state where the printed image was decolored was visually confirmed. Further, the coated paper in a state in which the printed image was erased was cooled to −20 ° C., and the state of the printed image at that time was confirmed.
○: The printed image is erased as it is without being peeled off, and after cooling, the printed image is colored in a pressed state.
Δ: Color is erased in a state where a part of the print image is peeled off, and color develops in a state where a part of the print image flows after cooling.
X: Decolored in a state where the printed image is completely peeled off, and the printed image cannot be obtained after cooling.

Cap-off property: After removing the cap (5), it was allowed to stand in an atmosphere of 20 ° C. and 65% RH for 24 hours, and then stamped on the coated paper, and the state of the printed image at that time was confirmed.
(Double-circle): The image equivalent to the initial stage is obtained, and favorable cap-off performance is obtained.
○: Compared with the initial stage, the print image is slightly blurred or slightly blurred, but sufficient cap-off performance is obtained.
(Triangle | delta): Compared with the initial stage, although a print image is blurring or blurring, it can be visually recognized as a print image, but the cap-off performance is slightly inferior.
X: Compared with the initial stage, the blur of the printed image is severe, the blurring is severe, it cannot be visually recognized as a printed image, and it does not have cap-off performance.

  As is clear from the results shown in (Table 1) to (Table 3), the reversible thermochromic stamp ink composition according to the present invention is compared with the reversible thermochromic stamp ink composition of the comparative example. It was revealed that the fixing property and scratch resistance were improved, and the ink composition was excellent as a reversible thermochromic stamp ink composition.

  Furthermore, as is clear from the results shown in (Table 1) and (Table 2), the reversible thermochromic stamp ink composition according to the present invention was excellent in cap-off performance. In particular, Examples 1, 3 to 6, 9, 10, and 12 showed good performance with the same sealability as the initial one. Further, Examples 1, 3, 4, and 9 are also excellent in fixability and scratch resistance of a printed image when imprinted, and are clearly excellent as reversible thermochromic stamp ink compositions. became. From these results, the application range as a stamp can be expanded, for example, it can be used for a stamp that does not have an airtight cap, which is represented by a type in which the stamp surface appears and disappears.

t ₁ Full color development temperature of microcapsule pigment encapsulating reversible thermochromic composition of heat decoloring type t ₂ Color development start temperature of microcapsule pigment encapsulating reversible thermochromic composition of heat decoloring type t ₃ Heat decoloration Decoloration start temperature of microcapsule pigment encapsulating reversible thermochromic composition of color type t ₄ Complete decolorization temperature of microcapsule pigment encapsulating reversible thermochromic composition of heat decoloring type T ₁ complete decoloring temperature T ₂ heat-coloring type of decoloring starting temperature T ₃ heating color development type reversible thermal discoloration microcapsule pigment enclosing a reversible thermochromic composition of the microcapsule pigment enclosing a reversible thermochromic composition Color development start temperature of microcapsule pigment encapsulating composition T ₄ Complete color development temperature of microcapsule pigment encapsulating reversible thermochromic composition of heating color development type ΔH Hysteresis width 1 Stamp 2 Stamping material 3 Stamp material 4 Tail plug 5 Cap 6 Ink reservoir

Claims (3)

(A) a component comprising an electron-donating color-forming organic compound;
(B) a component comprising an electron-accepting compound;
(C) a reaction medium for reversibly causing an electron transfer reaction by the component (a) and the component (b) in a specific temperature range;
A reversible thermochromic microcapsule pigment encapsulating a reversible thermochromic composition comprising water, a moisturizing agent, and a resin emulsion, the ink composition for a reversible thermochromic stamp comprising the resin in the resin emulsion A reversible thermochromic stamp ink composition having a solid acid value of 1 or more and 100 or less. The reversible thermochromic stamp ink composition according to claim 1, wherein the resin emulsion is an acrylic resin emulsion or a urethane resin emulsion. 3. The mixing ratio of water and the humectant contained in the ink composition is such that water / humectant is 1 / 3.3 to 1 / 1.8 as a mass ratio. The ink composition for reversible thermochromic stamps as described.

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