JP5634225B2 - Discoloring ink composition and writing instrument - Google Patents

Description

  The present invention relates to a color-changing ink composition capable of discoloring characters and coatings, etc. written or printed on paper by heating, and in which discolored characters are difficult to return to the original color, and the same It is related with the writing instrument using.

  Various color-changing ink compositions have been proposed so far, which can decolorize the handwriting or coating film written or printed on paper by heating or using an organic solvent. The color-changing ink composition is useful as one that contributes to the reuse of paper or one that can easily correct writing errors.

  For example, in Patent Document 1 (Japanese Patent Application Laid-Open No. 9-165537), a heat erasable ink composition obtained by dispersing a colorant formed by reacting a leuco dye with a developer and a color erasing agent in water. Has been proposed. In Patent Document 2 (Japanese Patent Application Laid-Open No. 2001-123084), there is a decolorizable dye composition comprising a developer, a color developing compound, and an erasing agent. The main component exists in the form of fine particles or microphase separation having an average diameter of 1 nm to 100 μm when the shape is approximated by a sphere, and the main component of the decolorant exists in a decolored composition in a molecularly dispersed state. A erasable dye composition has been proposed.

  Patent Document 3 (Japanese Patent Publication No. 5-87105) discloses a resin composition containing at least a heat-meltable water-insoluble resin having a melting point or softening point of 60 to 180 ° C., a color former, and a volatile developer, and a melting point or Heat decoloring property in which a non-volatile decoloring agent having a softening point of 60 to 180 ° C. or a resin composition containing the non-volatile decoloring agent is mixed and dispersed in a medium mainly composed of water as separate fine particles Ink jet ink compositions have been proposed. Patent Document 4 (Japanese Patent Application Laid-Open No. 2005-89548) describes (a) an electron donating color-forming organic compound, (b) an electron-accepting compound, and (c) controlling the color reaction of (a) and (b). Proposing a temperature-sensitive color-changing color memory liquid composition comprising a microcapsule pigment encapsulating a temperature-sensitive color-changing color memory composition composed of a homogeneous solution of a specific ester compound and a vehicle containing a resin. doing.

  Patent Document 5 discloses a wax containing 1) an electron-donating color-forming organic compound and an electron-accepting compound in order to eliminate or alleviate the inconveniences described later, which are found in the compositions described in Patent Documents 1 to 4 described above. A color-changing ink composition comprising particles, a color erasing agent and water, and 2) wax particles comprising an electron donating color-forming organic compound and an electron accepting compound, wax particles comprising a color erasing agent, and water. A discolorable ink composition is proposed. Patent Document 5 proposes to use a fatty acid, a fatty acid ester, a fatty acid anhydride, an acyl glycerin, a fatty acid amide, or the like having a melting point within the range of 40 ° C. to 120 ° C. as the wax.

JP-A-9-165537 JP 2001-123084 A Japanese Patent Publication No. 5-87105 JP 2005-89548 A International Publication WO / 2009/060972 Pamphlet

  Any of the compositions described in the above-mentioned patent documents still has room for improvement in order to be used as a decolorizable ink composition. For example, in the heat erasable ink composition described in Patent Document 1, since the colorant and the color erasing agent are combined and dispersed in water, there is a high probability that the colorant is in contact with the color erasing agent, and heat is not applied. However, decolorization may occur. In order to reduce such possibilities and increase the stability of the colorant, the decolorizer must be selected to work at higher temperatures. This increases the amount of heat required for erasing, increases the cost of erasing work, and / or requires a heating device for erasing, making it difficult for anyone to easily perform erasing work. .

  The erasable dye composition described in Patent Document 2 needs to control the size of the color erasing agent itself in a colored state, which makes the preparation of the composition difficult. Further, in Patent Document 2, it is exemplified that the temperature is set to 190 ° C. and 200 ° C. in order to achieve a decolored state. To achieve such a high temperature, a large amount of heat is required. Any heating device must be used for the decoloring work.

  The ink composition described in Patent Document 3 is used for giving information such as position information, member names, and used parts for cutting and sewing to fabrics, and is used for writing or printing on paper. It is not an ink composition. In addition, the decoloring temperatures employed in the examples of the document are as high as 160 ° C. and 150 ° C., and the ink composition described in the document is similar to the problem pointed out in relation to Patent Documents 1 and 2. Have a problem.

  As shown in FIGS. 1 and 2 of the document, the temperature-sensitive color-changing color memory composition described in Patent Document 4 decreases in color density (that is, decolored) at a high temperature, and then cooled. When done, the color density remains low, but when cooled to a certain temperature, the color density becomes high again. Therefore, even if characters written or printed with this composition are erased, the erased characters may “return” depending on the temperature. Such “return” needs to be avoided, for example, when the paper from which the characters are erased is used again, or when more characters are written in the erased portion.

  The color-changing ink composition described in Patent Document 5 is stable in color development such as written or printed characters, and can be decolored by applying heat of about the frictional heat generated when rubbing the paper surface. In addition, the stability of decolorization is good. However, it has been found that the composition using the aliphatic compound or derivative thereof described in the same document as a wax may cause slight discoloration when stored at a high temperature (for example, about 50 to 55 ° C.). It was. In addition, it has also been found that some of the compositions using the aliphatic compound or derivative thereof described in the same document as a wax have a relatively wide temperature range from the start to the end of decoloring. Here, the temperature range from the end of decoloring to the start is the temperature range from the temperature at which the color starts to fade until the color becomes as thin as desired. Can be determined by, for example, a color difference (ΔE *) measured by a color difference meter described later. Such a color-changing ink composition requires a long time or a high heating rate before it changes color as desired.

  As described above, the conventional decolorizable ink composition has the temperature required for decoloring, the stability of color development, the ease of production, the stability of decoloring, the high temperature storage property, and the decolorization start temperature to the end temperature. There was still room for improvement depending on the application in terms of range. The present invention stably maintains color development of written or printed characters, etc., and can be erased by applying heat of about the frictional heat generated when rubbing the paper surface. An object is to provide a color-changing ink composition that is good and excellent in storage at high temperatures. Furthermore, an object of the present invention is to provide a color-changing ink composition having, in addition to the above-described properties, the property that decoloring ends within a narrow temperature range.

  The color-changing ink composition of the present invention comprises a group of an electron-donating colorable organic compound and an electron-accepting compound in a state where the electron-donating colorable organic compound is colored by the electron-accepting compound, and has a melting point. The above-mentioned problem was solved by separating from a decolorant using an aromatic compound having a temperature of 40 ° C. to 120 ° C., preferably an aromatic compound having two or more benzene rings in one molecule.

  In the first aspect, the present invention includes a colored particle containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 40 ° C to 120 ° C, a color erasing agent, and water. Discolorable ink compositions are provided.

  In the second aspect, the present invention provides a colored particle containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 40 ° C to 120 ° C, a decolorizer and a melting point of 40 ° C to 40 ° C. There is provided a color-changing ink composition comprising decolorizing particles containing an aromatic compound at 120 ° C. and water.

  Here, the term “discoloration” means that at least one of hue, saturation and lightness of a color changes, and the color changes to colorless (that is, “decoloring” and “erasing”). ) Concept. The terms “decoloring” and “erasing” not only make the color completely unrecognizable (ie make it colorless), but also make the color lighter (make it more colorless). Used to mean including

  The color-changing ink composition of the present invention comprises at least an electron-donating colorable organic compound and an electron-accepting compound before heating, that is, in a state where the electron-donating colorable organic compound is colored by the electron-accepting compound. By forming a particulate material together with the aromatic compound having the specific melting point, many groups of electron donating color-forming organic compounds (specifically, electron donating presents that do not exist on the surface of the particles). The contact between the color organic compound) and the color erasing agent is prevented, thereby maintaining good color development of the electron donating color developing organic compound. The color change is performed by liquefying the aromatic compound, bringing the decoloring agent closer to the electron-donating color-developing organic compound, and causing the electron-accepting compound and the decoloring agent to interact with each other. When the color-changing ink composition of the present invention contains only an electron-donating color-forming organic compound as a color forming component, the color-changing ink composition is decolored by heating.

  The aromatic compound constituting the colored particle constitutes the particle as a medium for dispersing the electron-donating color-forming organic compound and the electron-accepting compound, and has a melting point in the range of 40 ° C to 120 ° C. The temperature within this temperature range is, for example, a temperature obtained by frictional heat generated when a letter or a film written or printed on paper and a coating film are rubbed with an elastic body. Therefore, if an aromatic compound having a melting point within this temperature range is used, it is possible to change the color of written or printed characters by rubbing with an elastic body.

  Further, the color-changing ink composition of the present invention maintains its color development until reaching a predetermined temperature according to the melting point of the aromatic compound. In other words, until the predetermined temperature is reached, the color development does not change or the color development level changes slightly. This improves the stability of color development and stores the color-changing ink composition at a high temperature by selecting the melting point of the aromatic compound so that the predetermined temperature is about 55 ° C., for example. Is possible.

  Furthermore, the color-changeable ink composition of the present invention tends to have a narrower temperature range from the start to the end of decoloring and / or a greater degree of color change. This imparts a quick and / or clear color change to the color change ink composition.

The decolorizer is preferably a basic compound in any of the color-changing ink compositions. Here, the basic compound refers to a compound having a property of donating an electron pair. Specifically, the basic compound is
Aliphatic amines,
Aliphatic diamines,
Amino alcohol,
An aromatic compound having one or more amino groups in the molecule and an alkylene group between the amino group and the aromatic ring,
A compound represented by the general formula NH ₂ —C ₂ H ₄ — (NH—C ₂ H ₄ ) _n —NH ₂ (n ≧ 0) and a derivative thereof;
Imidazole and its derivatives,
And a compound generally called a hindered amine and having a piperidyl group and its derivative in the molecule. These compounds easily react with the electron-accepting compound and impart good discoloration to the ink composition.

  The color-changeable ink composition of the present invention may further contain a colorant that does not change color by heating. In that case, when the electron-donating color-forming organic compound becomes decolored by the action of the decoloring agent, the color of the colorant appears.

  The color-changing ink composition of the present invention can be used as ink for writing instruments. The handwriting or the like written with a writing instrument using the color-changing ink composition of the present invention as ink is changed in color by, for example, rubbing with an elastic body such as an eraser or a soft elastic resin (for example, decoloring). can do. Alternatively, the color-changing ink composition of the present invention can be used as an ink for an inkjet printer. Alternatively, the color-changing ink composition of the present invention can be used as a temperature indicator.

  The color-changing ink composition of the present invention is a colored particle comprising an electron-donating color-forming organic compound colored by an electron-accepting compound, an electron-accepting compound, and an aromatic compound having a melting point of 40 ° C to 120 ° C. In some cases, the color erasing agent and the aromatic compound having a melting point of 40 ° C. to 120 ° C. form separate particles and develop color, and when heated, the aromatic compound (the color erasing agent is aromatic) In the case of forming particles with the compound, in addition, when the aromatic compound is liquefied, the electron-donating color-forming organic compound is decolored. That is, the color-changing ink composition of the present invention is prevented from fading by being separated from the decolorant by the aromatic compound having a melting point of 40 ° C. to 120 ° C. at the room temperature. When heated, the liquefied aromatic compound becomes a medium, and the decolorization of the electron donating color-forming organic compound is promoted.

  Therefore, when the ink composition of the present invention contains only the electron-donating color-forming organic compound as the color forming component, both good color maintenance and reliable decolorization can be achieved. When the ink composition of the present invention contains a colorant that is not discolored by heating, the color of the colorant is increased by heating from the color mixture of the color of the electron-accepting compound in a colored state and the color of the colorant. The color changes to a strongly appearing color, and different colors are excellent before and after heating.

  The ink composition of the present invention can be decolored with a small amount of heat by forming colored particles using an aromatic compound having a melting point in the range of 40 ° C. to 120 ° C., and the melting point of the aromatic compound. By appropriately selecting, decoloring does not start until a predetermined temperature. Therefore, for example, it is possible to change the color of the character or the coating film by a relatively simple operation such as rubbing the written character or the coating film, and it is possible to better maintain the colored state up to a predetermined temperature. It becomes. Furthermore, by using the aromatic compound having the predetermined melting point, an ink composition having a narrow temperature range from the start to the end of decoloring may be obtained. It is possible to shorten the time to color or to reduce the labor required for decoloring.

3 is a graph showing a color change temperature curve of an ink composition produced in Example 2. FIG. 4 is a graph showing a color change temperature curve of an ink composition produced in Example 3. FIG. 3 is a graph showing a discoloration temperature curve of an ink composition produced in Comparative Example 1. 6 is a graph showing a discoloration temperature curve of an ink composition produced in Comparative Example 2.

  The color-changing ink composition of the present invention includes an electron-donating color-forming organic compound, an electron-accepting compound, a decoloring agent, and water. 1) An electron-donating color-forming organic compound and an electron-accepting compound The combination forms a colored particle with an aromatic compound having a melting point of 40 ° C. to 120 ° C., and 2) the combination of the electron donating color-forming organic compound and the electron accepting compound has a melting point of 40 ° C. to 120 ° C. The colored particles are formed together with the aromatic compound, and the decoloring agent takes any of the forms forming the decoloring particles together with the aromatic compound having a melting point of 40 ° C to 120 ° C. A stable colored state can be obtained by forming particles together with the aromatic compound having the predetermined melting point by the electron-donating color-forming organic compound and the electron-accepting compound. Furthermore, when the decoloring agent forms particles together with the aromatic compound, the decoloring agent can be prevented from reacting with the additive in the ink composition and inhibiting its decoloring function. Hereinafter, components contained in the color-changing ink composition of the present invention (sometimes simply referred to as “ink composition”) will be described.

(Electron donating colorable organic compound)
The color-changing ink composition of the present invention contains an electron-donating color-forming organic compound. An electron-donating color-forming organic compound is a compound that develops color with an electron-accepting compound, and can be said to be a color-forming component. The electron-donating color-forming organic compound is not particularly limited, and a known electron-donating color-forming organic compound (for example, a leuco dye) can be arbitrarily used. Specifically, for example, the following compounds can be used as the electron-donating color-forming organic compound.

Fluoranes such as 1,2-benzo-6- (N-ethyl-N-isoamylamino) fluorane, 2-anilino-3-methyl-5- (N-ethyl-Nn-propylamino) fluorane, 2- Chloro-3-methyl-6- (4-di-n-butylaminoanilino) fluorane, 3-diethylamino-6-benzyloxyfluorane, 3,6-diphenylaminofluorane, 3,6-diphenylaminofluorane, 2 '-[(2-chlorophenyl) amino] -6'-(dibutylamino) spiro [isobenzofluoran-1 (3H), 9 '-(9H) xanthen] -3-one, 6'-[ethyl ( 4-methylphenyl) amino] -2'-methyl-spiro [isobenzofluorane-1 (3H), 9 '-(9H) xanthen] -3-one, and 6- (dimethylaminoamino) -3,3 -Bis [4- (dimethylamino) phenyl] -1 (3H) -isobenzofluorane phenothiazines such as benzoylleucomethylene blue, ethylleucome Renburu,
Indolines such as 2- (phenyliminoethylidene) -3,3-dimethylindoline

Spiropyrans such as 1,3,3-trimethyl-indolino-7-chloro-β-naphthospiropyran, N-3,3-trimethylindolinobenzospiropyran;
Leucooramines such as N-acetyloramine, N-phenyloramine;
Rhodamine lactams, such as rhodamine B lactams;
-Polyaryl carbinols, such as crystal violet carbinol, malachite green carbinol;

Diphenylmethane phthalides, such as 3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide, 3,3-bis (p-dimethylaminophenyl) phthalide;
-Triphenylmethanephthalides, such as crystal violet lactone, malachite green lactone;
Phenylindolylphthalides, such as 3- (4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (2-methyl-4-diethylamino) phenyl- 3- (1- (2-methoxyethyl) -2-methylindol-3-yl) phthalide;

Diphenylmethane azaphthalides, such as 3,3-bis- (2-ethoxy-4-diethylaminophenyl) -4-azaphthalide;
Phenylindolyl azaphthalides, such as 3- (2-ethoxy-4-diethylaminophenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4- Diethylamino-2-methylphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide;
Styrylquinolines, such as 2- (3-methoxy-4-dodecoxystyryl) quinoline;

Pyridines, such as 2,6-bis (6-n-butoxyphenyl) -4- (4-dimethylaminophenyl) pyridine;
Quinazolines, such as 2- (4-dimethylaminophenyl) -4-methoxyquinazoline, 2- (4-dimethylaminophenyl) -4- (1-chlorophenyloxy) quinazoline;
Bisquinazolines, such as 4,4 '-(ethylenedioxy) -bis [2- (4-diethylaminophenyl) quinazoline], 4,4'-(ethylenedioxy) -bis [2- (4-pi Peridinophenyl) quinazoline];

Ethylene phthalides, such as 3,3-bis [1,1-bis- (p-dimethylaminophenyl) ethyleno-2] phthalide, 3,3-bis [1,1-bis- (2-methyl-4- Dimethylaminophenyl) ethyleno-2] phthalide;
Ethylene azaphthalides, such as 3,3-bis [1,1-bis- (p-dimethylaminophenyl) ethyleno-2] -4-azaphthalide, 3,3-bis [1,1-bis- (p-dimethylaminophenyl) ethyleno-2] -4,7-diazaphthalide;
Fluorenes such as 3,6-bis (dimethylamino) fluorene spiro (9.3 ')-4'-azaphthalide, 3,6-bis (dimethylamino) fluorene spiro (9.3')-7'-azaphthalide.

  Preferably, as the electron-donating color-forming organic compound, fluorans, 2 ′-[(2-chlorophenyl) amino] -6 ′-(dibutylamino) spiro [isobenzofluorane-1 (3H), 9 '-(9H) xanthen] -3-one, 3,6-diphenylaminofluorane, 6'-[ethyl (4-methylphenyl) amino] -2'-methyl-spiro [isobenzofluorane-1 (3H ), 9 '-(9H) xanthen] -3-one and 6- (dimethylaminoamino) -3,3-bis [4- (dimethylamino) phenyl] -1 (3H) -isobenzofluorane It is done. As the electron donating color-forming organic compound, only one compound may be used, or a plurality of compounds may be used.

  The electron donating color-forming organic compound is preferably contained in the whole ink composition in an amount of 0.01 to 40% by weight, and preferably in an amount of 0.1 to 20% by weight. More preferred. When the amount of the electron donating color-forming organic compound is too small, the color density is lowered. When there are too many electron donating colorable organic compounds, an electron donating colorable organic compound may precipitate. The deposited electron-donating color-forming organic compound may not be colored by the electron-accepting compound in the colored particles, or may cause clogging in an ink discharge portion of a writing instrument or a printing machine (for example, an ink jet printer).

  The electron donating color-forming organic compound is preferably contained in the colored particles in an amount of 0.01 to 40% by weight, and more preferably 0.1 to 20% by weight. When an electron donating color-forming organic compound is contained in one colored particle in an amount of less than 0.01% by weight, the color density decreases, and when it is contained in an amount of more than 40% by weight, an electron donating color forming is included. Since the organic organic compound precipitates, it becomes difficult to form particles.

(Electron-accepting compound)
The electron-accepting compound acts on the electron-donating color-forming organic compound to cause the electron-donating color-forming organic compound to develop a color. The electron-accepting compound is a compound having an active proton, a pseudo-acidic compound, or a compound having an electron vacancy.

  The electron accepting compound is not particularly limited. For example, a compound having a phenolic hydroxyl group (for example, phenol, o-cresol, m-octylphenol, n-dodecylphenol, n-stearylphenol, carboxylic acids and metal salts thereof (for example, zinc salicylate, 3,5-di (α -Methylbenzyl) zinc salicylate), acidic phosphates and their metal salts, urea-thiourea compounds, and 1,2,3-triazole and its derivatives can be used as electron-accepting compounds.

  The electron-accepting compound is preferably nonvolatile and does not have sublimability. When the electron-accepting compound is volatile or sublimable, the color density of written or printed characters or coatings may change over time.

  Preferably, zinc salicylate and zinc 3,5-di (α-methylbenzyl) salicylate are used as the electron-accepting compound. As the electron-accepting compound, only one kind of compound may be used, or a plurality of compounds may be used.

  The electron-accepting compound is preferably contained in the ink composition in an amount of 0.01 to 50% by weight, more preferably in an amount of 0.1 to 20% by weight. When the amount of the electron accepting compound is too small, the color density is lowered. When there are too many electron-accepting compounds, an electron-accepting compound may precipitate. When the electron-accepting compound is deposited, clogging occurs in the discharge part of a writing instrument or a printing machine (for example, an ink jet printer).

  The electron-accepting compound is preferably contained in the colored particles in an amount of 0.1 wt% to 60 wt%, and more preferably 1 wt% to 40 wt%. In one colored particle, when the electron-accepting compound is contained in an amount of less than 0.1% by weight, the coloring density is lowered, and when it is contained in an amount of more than 60% by weight, the electron-accepting compound is precipitated. Particleization becomes difficult.

(Decolorizer)
The color erasing agent inhibits the color developing action by the electron accepting compound. Therefore, the color erasing agent serves to eliminate or weaken the color development of the electron donating color-forming organic compound when performing an erasing operation. The decolorizer is preferably a basic compound. The color change of the ink composition is considered to be related to the basic strength of the color erasing agent. The stronger the color erasing agent, the better the color-developing state of the electron-donating color-forming organic compound. And the discoloration by heating of the ink composition is improved. In the present invention, it is preferable to use a compound selected from the following compounds as the color erasing agent.
Aliphatic amines,
Aliphatic diamines,
Amino alcohol,
An aromatic compound having one or more amino groups in the molecule and an alkylene group between the amino group and the aromatic ring,
Formula _NH 2 _-C 2 _H 4 _- compounds and their derivatives represented by _{(NH-C 2 H 4)} n -NH 2 (n ≧ 0), imidazole and derivatives thereof, and generally referred to as hindered amines, piperidyl A compound having a group and its derivative in the molecule.

  The aliphatic amine is a primary amine, secondary amine or tertiary amine. The aliphatic amine is preferably a secondary amine or a tertiary amine. Aliphatic amines are specifically octylamine, decylamine, dioctylamine, didecylamine, didodecylamine, trioctylamine, stearylamine, behenylamine, dimethyllaurylamine, dimethylpalmitylamine, dimethylstearylamine, distearylamine And bis (2-hydroxyethyl) oleylamine.

  An aliphatic diamine is a compound in which hydrogen of an aliphatic compound is substituted with two amino groups. An aliphatic diamine tends to exhibit higher decoloring performance as a decoloring agent as the number of carbon atoms increases. However, when the carbon number exceeds a certain level, the decoloring performance does not change so much. Accordingly, the aliphatic diamine is preferably a compound having 3 to 30 carbon atoms, and more preferably a compound having 6 to 22 carbon atoms. Specific examples of the aliphatic diamine include diaminodecane, diaminooctane, hexamethylenediamine, diaminobutane, cured beef tallow diamine, and cured beef tallow propylene diamine.

  An amino alcohol is a compound having a hydroxyl group and an amino group. The amino alcohol is preferably a secondary alcohol or a tertiary alcohol from the viewpoint of the color erasing performance of the color erasing agent. Specific examples of the amino alcohol include isopropanolamine, diisopropanolamine, benzylethanolamine, and triisopropanolamine.

  Aromatic compounds containing one or more amino groups in the molecule and having an alkylene group between the amino group and the aromatic ring are specifically xylylenediamine, benzylethanolamine, metaxylylenediamine and styrene. Polymer and the like. Benzylethanolamine may be classified as an amino alcohol as described above.

The compounds represented by the general formula NH ₂ —C ₂ H ₄ — (NH—C ₂ H ₄ ) _n —NH ₂ (n ≧ 0) and their derivatives have better decoloring properties as the molecular weight increases. Indicates color performance. This compound may have a molecular weight in the range of 100 to 100,000, for example. Formula _NH 2 _-C 2 _H 4 _- compounds and their derivatives represented by _{(NH-C 2 H 4)} n -NH 2 (n ≧ 0) , specifically, diethylenetriamine, triethylenetetramine, tetraethylene Examples thereof include pentamine, pentaethylenehexamine, diethylenetriamine ethylene oxide adduct, diethylenetriamine propylene oxide adduct, and diethylenetriaminebutylene oxide adduct.

  Specific examples of imidazole and derivatives thereof include imidazole and 2-phenylimidazole.

  As a compound generally called a hindered amine and having a piperidyl group and its derivative in its molecule, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) = 1,2,3,4-butanetetracarboxyl , Tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl) = 1,2,3,4-butanetetracarboxylate, N, N′-bis (2,2,6,6-tetra Methyl-4-piperidyl) -1,6-hexamethylenediamine and 2,4-dichloro-6- (4-morpholinyl) -1,3,5-triazine copolymer, N, N′-bis (1, 2,2,6,6-pentamethyl-4-piperidyl) -1,6-hexamethylenediamine and 2,4-dichloro-6- (4-morpholinyl) -1,3,5-triazine copolymer, 2 , 2,4,4-Tetramethyl-7-oxa-3,20-diazadispiro- [5.1.11.2] -heneicosan-21-one, poly [{6- (1,1,3,3-tetramethylbutyl) A -1,3,5-triazine-2,4-diyl} {2,2,6,6-tetramethyl-4-piperidyl) imino} hexamethylene {(2,2,6,6-tetramethyl-4 -Piperidyl) imino}].

Among these compounds, dioctylamine, diaminodecane, pentaethylenehexamine, hexamethylenediamine, behenylamine, distearylamine, cured beef tallow propylenediamine, diethylenetriaminebutylene oxide adduct, a copolymer of metaxylylenediamine and styrene, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) = 1,2,3,4-butanetetracarboxylate is preferably used.
Two or more different compounds may be used as the color erasing agent.

  The decolorizer is preferably contained in the ink composition in an amount of 0.01 to 50% by weight, and more preferably in an amount of 0.1 to 20% by weight. When there are too few decoloring agents, the electron donating color-forming organic compound cannot be sufficiently decolored, and the discoloring effect of the ink becomes insufficient. When there are too many decoloring agents, the storage stability of an ink composition will deteriorate. The amount of the color erasing agent is preferably selected in consideration of the amount of the electron accepting compound. In the whole ink composition, the color erasing agent: electron accepting compound = 1: 10 to 10: 1 (weight ratio). ) Is preferably selected.

When the color erasing agent forms particles for color erasing together with an aromatic compound having a melting point of 40 to 120 ° C., it is preferably contained in the particles in an amount of 1% by weight to 80% by weight. More preferably. When the color erasing agent is contained in one color erasing particle in an amount of less than 1% by weight, a sufficient color change effect may not be obtained when the ink composition is discolored by heating.
In addition, when the decolorizer itself has a property like wax, that is, it is solid at normal temperature and has a property of becoming a liquid upon heating, it can be used as it is and used as an erasable particle. It may be dispersed in the composition.

(Aromatic compounds)
The ink composition of the present invention includes colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 40 to 120 ° C. Decolorizing particles containing an aromatic compound at 0 ° C. Here, the “aromatic compound” refers to a compound having one or more aromatic rings in the molecule. Aromatic compounds are specifically benzene, naphthalene and anthracene, and derivatives thereof.

  Aromatic compounds with a melting point in the range of 40 ° C. to 120 ° C. have a narrower temperature range from the temperature at which liquefaction starts to the temperature at which liquefaction ends, compared to resin, making it easier to control the discoloration temperature. Has the advantage of Furthermore, when an aromatic compound having a melting point within this range is used, it becomes easy to obtain an ink composition in which decoloring does not start until a predetermined temperature (particularly high temperature (for example, 55 ° C.)). Furthermore, the aromatic compound generally provides an ink composition having a relatively narrow temperature range from the start to the end of decoloring. Furthermore, aromatic compounds generally provide ink compositions with a high degree of discoloration. The aromatic compound preferably has a melting point (more precisely, a temperature at which liquefaction starts) in the range of 60 ° C to 120 ° C, more preferably in the range of 60 ° C to 100 ° C, and 65 ° C. Even more preferably, it is in the range of ˜85 ° C.

  An aromatic compound having a melting point within this range is liquefied by frictional heat, for example, when a handwriting or coating film written on paper is rubbed with an eraser or a soft elastic resin. Therefore, an ink composition containing particles in which such an aromatic compound is present as a solid is an ink composition that can discolor (for example, erase) the handwriting with the sensation of erasing the handwriting by rubbing with an eraser. give. If the melting point is less than 40 ° C., the aromatic compound may not be granular, so that the color development stability may be reduced, and a sufficient color density may not be obtained, or the color will fade over time. Sometimes. When the melting point exceeds 120 ° C., the aromatic compound is not liquefied even when rubbed with an eraser or a soft resin, and it is difficult to discolor the ink composition with a simple operation.

  The aromatic compound having a melting point in the range of 40 ° C. to 120 ° C. is preferably a compound containing two or more benzene rings in one molecule. Here, in addition to a compound in which two or more benzene rings are connected to a compound containing two or more benzene rings, a compound containing a polycyclic aromatic ring in which two or more benzene rings are condensed, such as naphthalene and anthracene And compounds in which such a polycyclic aromatic ring and a benzene ring are linked. More specifically, for example, the following compounds may be used in the present invention. The melting point is shown in parentheses.

1) Compounds in which at least two benzene rings are linked by a substituent containing a carboxyl group: benzophenone (50 ° C.), benzyl (96 ° C.), benzyl phenyl ketone (57 ° C.), benzoin methyl ether (49 ° C.), benzoin Isopropyl ether (81 ° C), methyl 2-benzoylbenzoate (54 ° C), 2,2-dimethoxy-2-phenylacetophenone (68 ° C), 4-methoxybenzophenone (63 ° C), 4-methylbenzophenone (58 ° C) 4-methylbenzyl phenyl ketone (97 ° C), 1,3-diphenyl-1,3-propanedione (79 ° C).

2) Compounds in which at least two benzene rings are linked by a substituent containing an ester bond: p-tolyl benzoate (72 ° C), phenyl benzoate (70 ° C), p-tolyl phenylacetate (76 ° C), benzoic acid Acid-2-naphthyl (107 ° C), diphenyl carbonate (79 ° C), diphenyl phthalate (74 ° C), salicylic acid-4-octylphenyl (74 ° C).

3) Compounds in which at least two benzene rings are linked by a substituent containing an ether bond: 4-benzyloxyphenylacetic acid methyl ester (61 ° C), benzylphenyl ether (40 ° C), 3,5-dibenzyloxybenzoic acid Methyl acid (72 ° C), 1,3-diphenoxybenzene (61 ° C), 1,4-diphenoxybenzene (77 ° C), di-p-tolyl ether (49 ° C).

4) Compound in which at least two benzene rings are linked by a substituent containing an amide bond: N, N-diphenylacetamide (102 ° C.)
5) Biphenyl compounds: biphenyl (71 ° C), 4,4'-bismethoxymethylbiphenyl (54.5 ° C), 4-acetoxybiphenyl (80 ° C), 4-butyrylbiphenyl (95 ° C)
6) Compound containing naphthalene ring: methyl 3-hydroxy-2-naphthoate (71 ° C)

  Two or more of these compounds may be used in combination. Of these, in the present invention, 1,3-diphenyl-1,3-propanedione (79 ° C.), phenyl benzoate (70 ° C.) and 4-acetoxybiphenyl (80 ° C.) are particularly preferably used. These aromatic compounds do not substantially start to discolor up to at least 55 ° C., or discolor in the direction of increasing color density, and start discoloration by reaction with a decolorant at a temperature higher than 55 ° C. An ink composition is provided. Therefore, when these aromatic compounds are used, even when stored at a high temperature of about 55 ° C., discoloration does not start, and the color changes with heat of about the frictional heat generated when rubbing on the paper surface with an eraser or the like. An ink composition having good storage properties and capable of changing color by an easy operation is obtained. Moreover, these aromatic compounds give an ink composition having a relatively narrow temperature range from decoloring to discoloration. Furthermore, these aromatic compounds give ink compositions with a high degree of discoloration.

  When the ink composition of the present invention includes both colored particles and decoloring particles, the aromatic compound constituting the colored particles and the aromatic compound constituting the decoloring particles are preferably close in melting point. . In the two types of particles, when the melting points of the compounds to be liquefied are close to each other, the compounds liquefy at the same temperature, and the decoloring agent can act on the electron accepting compound, so that the color change can be carried out smoothly. Alternatively, the colored particles and the decoloring particles may contain the same compound (ie, the same aromatic compound) or different compounds from each other (for example, the decoloring particles have different fragrances from the aromatic compounds constituting the colored particles. Group compounds). Alternatively, among the colored particles, the aromatic compound of some particles and the aromatic compound of other particles may be different. The same applies to decolorizing particles.

  In the colored particles, the aromatic compound preferably constitutes 30% to 99% by weight of the particle, and more preferably constitutes 50% to 95% by weight. In the colored particles, if the amount of the aromatic compound is small, when heated, the liquefied medium that links the colored particle and the decoloring particle is insufficient, the decoloring property is lowered, and the amount of the aromatic compound is large. The color density decreases.

  In the decolorizing particles, the aromatic compound preferably constitutes 20% to 99% by weight of the particle, and more preferably constitutes 40% to 95% by weight. In the color erasing particles, if the amount of the aromatic compound is small, the solid content becomes small and it becomes difficult to form particles. If the amount of the aromatic compound is large, the amount of the color erasing agent decreases, and the ink composition The discoloration effect may be insufficient.

  The aromatic compound is preferably contained in an amount of 1 to 70% by weight, more preferably 5 to 50% by weight, based on the entire ink composition. In the ink composition of the present invention, if the amount of the aromatic compound is small, the decoloring performance is deteriorated. Further, in the ink composition of the present invention, considering that the electron donating color-forming organic compound is always contained in the colored particles, if the amount of the aromatic compound is too large, the color density may be lowered. . In the ink composition of the present invention, when the color erasing particles are included, the total amount of the aromatic compound contained in the color developing particles and the aromatic compound contained in the color erasing particles is within the above range. It is preferable.

(water)
The ink composition of the present invention contains water that functions as a dispersion medium. As water, normally used water, for example, ion-exchanged water and distilled water can be used. The water content in the ink composition is not particularly limited, and is appropriately selected according to the content of the color forming particles and / or the color erasing particles and the viscosity to be obtained. For example, the water content may be in the range of 95% to 40% by weight, and preferably about 90% to 50% by weight.

(Non-thermochromic colorant)
In addition to the above components, the ink composition of the present invention may further contain a colorant whose hue does not change by heating, that is, a non-thermochromic colorant. The non-thermochromic colorant is preferably one that is not affected by the electron-accepting compound and the decoloring agent and does not change color. When the ink composition of the present invention contains a non-thermochromic colorant, the ink composition of the present invention has a color exhibited by a colored electron-donating colorable organic compound and a color exhibited by the colorant before heating. Are mixed, and after heating, the color exhibited by the electron-donating color-forming organic compound is colorless, resulting in an ink composition in which the color of the colorant strongly appears. Therefore, an ink composition containing such a colorant is, for example, a color-changing ink composition that changes from one hue to another.

  Non-thermochromic colorants include, for example, water-soluble dyes such as acid dyes, direct dyes, basic dyes, inorganic pigments such as carbon black, titanium oxide, alumina silica, and talc; azo pigments and naphthol pigments Phthalocyanine pigments, selenium pigments, quinacridone pigments, anthraquinone pigments, dioxane pigments, dioxazine pigments, indigo pigments, thioindigo pigments, perinone pigments, perylene pigments, indolenone pigments, and azomethine pigments Organic pigments such as pigments; metal powder pigments such as aluminum powder and bronze powder; fluorescent pigments; pearl pigments; These colorants can also be used as pigment dispersions. In the ink composition of the present invention, these colorants may be used alone or in combination of two or more.

  Alternatively, plastic pigments (synthetic resin particle pigments) having various shapes such as a spherical shape, a flat shape, and a hollow shape can be used as the non-thermochromic colorant. For example, in the present invention, a resin powder of 100 μm or less can be used, or a resin powder of 100 μm or less dispersed in water can be used. The resin powder can be colored with a pigment or dye and used as a colored resin emulsion.

  The amount of the non-thermochromic colorant in the ink composition is not particularly limited, and is appropriately selected so that a desired color can be obtained when the electron donating color-forming organic compound stops coloring. . The amount of the non-thermochromic colorant is preferably 0.001% to 30% by weight of the ink composition, and more preferably 0.01% to 15% by weight of the ink composition.

  The ink composition of the present invention may contain commonly used components in addition to the components described above. Hereinafter, the commonly used components will be described.

  The ink composition of the present invention may contain an emulsifier when producing colored particles by emulsification. An emulsifier is used to disperse the colored particles. Emulsifiers are, for example, polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, sorbitan monostearate, sorbitan monostearate polyoxyethylene derivatives, and polyoxyethylene stearyl ether.

  The ink composition of the present invention may contain components other than those described above as necessary. Specifically, lubricants, wetting agents, rust preventives, antiseptics, antifungal agents, antifoaming agents, leveling agents, anti-aggregation agents, pH adjusters, water-soluble organic solvents, surfactants, and the like are added. Good.

  Next, the manufacturing method of the ink composition of this invention is demonstrated. In the production of the ink composition of the present invention, a dispersion (emulsion) in which colored particles are dispersed, and a dispersion (emulsion) in which decolorizing particles are dispersed as required are prepared. The dispersion can be prepared using a known emulsification method or pulverization method. An example of a method for preparing a dispersion in which colored particles or decoloring particles are dispersed by emulsification is shown below.

  A dispersion in which colored particles are dispersed is prepared by the following procedure. First, an electron-donating color-forming organic compound and an electron-accepting compound are dissolved in an aromatic compound heated to 120 to 160 ° C. This is cooled and solidified to obtain a powder (solid matter). Separately, an aqueous emulsifier solution in which an emulsifier (eg, polyvinyl alcohol) is dissolved in water is prepared, and the powder is added to the aqueous solution while the aqueous emulsifier solution is subjected to medium shear stirring. The powder is preferably added so that the weight ratio of the powder: aqueous solution is 1:99 to 90:10. Next, stirring is performed using a bead mill or the like to disperse the powder, thereby obtaining a dispersion of colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound.

  A dispersion in which decolorizing particles are dispersed is prepared by the following procedure. First, the decolorizer is dissolved in an aromatic compound heated to 120 to 160 ° C. This is cooled and solidified to obtain a powder (solid matter). Separately, an aqueous emulsifier solution in which an emulsifier (eg, polyvinyl alcohol) is dissolved in water is prepared, and the powder is added to the aqueous solution while the aqueous emulsifier solution is subjected to medium shear stirring. The powder is preferably added so that the weight ratio of powder: aqueous solution is 1:99 to 90:10. Next, stirring is performed using a bead mill or the like to disperse the powder, thereby obtaining a dispersion of decolorizing particles containing a decoloring agent.

  When only a dispersion in which colored particles are dispersed is prepared, this dispersion is mixed with a decoloring agent. In that case, an aqueous solution in which the color erasing agent is dissolved or a dispersion in which the color erasing agent is dispersed using an emulsifier (for example, polyvinyl alcohol) may be mixed with a dispersion containing colored particles. When a dispersion in which colored particles are dispersed and a dispersion in which decolorizing particles are dispersed are prepared, both are mixed. Mixing is performed by a known method, for example, with stirring. In any case, the mixing is performed by mixing the dispersion and the aqueous solution so that the electron-donating color-forming organic compound, the electron-accepting compound, the color erasing agent, and water are included in the above-described ratio, The mixing ratio of the dispersion is selected as appropriate.

  The ink composition of the present invention is preferably used as ink for various writing instruments. The writing instrument is preferably in the form of, for example, a core-type writing instrument such as a marker and a sign pen, or a ballpoint pen that allows ink to ooze from the pen tip. A ballpoint pen is a writing instrument in which an ink storage tube loaded with ink is provided in a shaft, and ink is drawn out from a pen tip on which a small sphere is attached. The center-type writing instrument has a center core in which the fiber bundle is converged as an ink containing portion, and a pen tip (tip) for discharging the ink stored in the center core. As the tip, for example, a ball, fiber, plastic It is a writing instrument provided with a lead, a brush-like object, or a brush-like object.

  The writing instrument can be assembled using known members. For example, a ballpoint pen can be manufactured by loading ink into an ink containing tube formed of a known material and having a known size and assembling it with a known structure of a ballpoint pen tip of a known structure made of a known material. The ink storage tube is, for example, a synthetic resin pipe such as polyethylene and polypropylene, or a metal pipe. The ballpoint pen tip may be a normal one, and a difference between the ball diameter and the ball house inner diameter of, for example, 0.01 mm or more can be used.

  Alternatively, the ink composition of the present invention can also be used as printing ink (particularly ink for inkjet printers), paint, or paint.

  The medium for forming the handwriting or the coating film using the ink composition of the present invention is preferably paper. Alternatively, the media may be synthetic paper, cloth, plastic film, sheet or plate, metal sheet or plate, or glass sheet or plate. The handwriting or coating film on which the ink composition of the present invention is formed on these media is a temperature indicator (indicating that the atmosphere has reached a predetermined temperature by discoloration) in a predetermined atmosphere (for example, in a gas or liquid). ) May be used.

  When the ink composition of the present invention contains only the electron-donating color-forming organic compound as the color forming component, the handwriting or the coating film of the ink composition, when the aromatic compound is heated to a temperature equal to or higher than the melting point, Discolored. More specifically, due to the liquefaction of the aromatic compound, the electron-accepting compound and the decoloring agent inside the colored particles separated by the aromatic compound approach, and the decoloring agent is brought into the electron-accepting compound. In operation, the ink composition is decolored. When the melting point of the aromatic compound is 40 ° C to 120 ° C, the heating temperature is preferably equal to or higher than the melting point of the aromatic compound, more preferably about 1 ° C to 5 ° C. When the temperature is within this range, for example, heating can be performed by rubbing the handwriting or the coating film with rubber or elastic resin. The erasing rubber or resin may be previously attached to the end of the writing instrument opposite to the writing tip. Thereby, for example, it becomes easy to erase and correct a written character or to erase a marked part later. The erasing resin is preferably a resin (for example, a styrene-butylene-styrene copolymer or a styrene-ethylene / butylene-styrene copolymer) having a high frictional resistance against the paper surface.

  Alternatively, the heating may be performed by a method such as passing over a heated roll or blowing hot air. When a roll or hot air is used, handwriting written in a relatively large area or a coating film having a relatively large area can be erased at a time. Therefore, by using the ink composition of the present invention in combination with a heating device, it is possible to construct a recycling system for repeatedly using written or printed paper.

  As described above, “erasing” and “erasing” include making the color light, and can be practically used as a color-changing ink composition even if it is not completely colorless depending on the application. For example, if it is a written letter, it will not be completely colorless, and even if some of the color remains, if the handwriting after heating is illegible, the written contents will be deleted for confidentiality reasons. It is enough to use. When the ink composition of the present invention is used for the purpose of decoloring, the electron-donating color-forming organic compound is black, and the color difference (ΔE *) measured with a colorimeter before heating is ΔE * ′, When the color difference (ΔE *) measured with a color difference meter after heating is ΔE * ″, the color may be reduced by heating to such an extent that ΔE * ′ − ΔE * ″ is 5 or more. preferable.

  Further, in the ink composition of the present invention, when the electron donating color-forming organic compound is black, the color difference (ΔE * (55) measured at 55 ° C. when the temperature is raised at about 10 ° C./min. C) and a color difference (ΔE * (30 ° C.)) measured at 30 ° C. is preferably high temperature resistance such that ΔE * (30 ° C.) − ΔE * (55 ° C. ) Is 1 or more, for example, discoloration may occur in the ink composition during storage in a warehouse in summer, and it may not be provided as a product.

  In the case where the ink composition of the present invention contains a non-thermochromic colorant as described above and is used for the purpose of causing the color of the non-thermochromic colorant to appear strongly by heating, as described above, The handwriting or coating film is discolored by rubbing with an elastic resin to liquefy the aromatic compound. Alternatively, the ink composition of the present invention includes a plurality of types of colored particles using a plurality of types of electron-donating color-forming organic compounds, aromatic compounds having different melting points, and electron-accepting compounds. It may be. Such an ink composition exhibits multistage discoloration in which different colors appear when the heating temperature is changed stepwise.

(Preparation of dispersions 1-6)
2 '-[(2-Chlorophenyl) amino] -6'-(dibutylamino) spiro [isobenzofluorane-1 (3H), 9 '-(9H) xanthene] -3 as an electron-donating color-forming organic compound -ON is prepared, the following five kinds of compounds are prepared as an aromatic compound and an aliphatic compound, 3,5-di (α-methylbenzyl) salicylic acid zinc salt is prepared as an electron accepting compound, and an emulsifier As a preparation, polyvinyl alcohol was prepared.

Aromatic compound 1: 4-acetoxybiphenyl (melting point 80 ° C.)
Aromatic compound 3: phenyl benzoate (melting point 70 ° C)
Aromatic compound 3: 1,3-diphenyl-1,3-propanedione (melting point 79 ° C.)
Aliphatic compound 1: glycerin mono-12 hydroxystearate (melting point 74 ° C.)
Aliphatic compound 2: sorbitan tribehenate (melting point 68 ° C)
Aliphatic compound 3: Glycerol ditristearate (melting point 60 ° C)

  The electron donating color-forming organic compound and the electron accepting compound were dissolved in an aromatic compound or an aliphatic compound heated to 160 ° C. This was cooled and solidified to obtain a powder. Separately, an aqueous emulsifier solution in which an emulsifier (eg, polyvinyl alcohol) was dissolved in water was prepared, and the powder was added to the aqueous solution. Next, stirring was performed using a bead mill to disperse the powder, thereby obtaining a dispersion of colored particles. Further, while stirring, the mixture is cooled to room temperature, and dispersions 1 to 6 of colored particles containing an electron-donating color-forming organic compound and an electron-accepting compound and in which an aromatic compound or an aliphatic compound is solid. Got. The colored particles and the aqueous emulsifier solution were prepared and mixed so that the finally obtained dispersion had the composition described in Table 1 below. In the dispersion after cooling, the colored particles had a particle diameter of about 5 to 50 μm.

(Discolorant dispersions 1-3)
As the decolorizer, the following three types of compounds are prepared, each of which is dispersed in ion-exchanged water using polyvinyl alcohol, and the decolorizer, polyvinyl alcohol and ion-exchanged water are contained in the proportions shown in Table 2 below. Decolorant dispersions 1 to 3 were obtained.
Decolorizer A: 2,2,4,4, -Tetramethyl-7-6oxa-3,20-diazadispiro- [5,1,11,2] -heneicosan-21-one decolorizer B: Poly [ {6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {2,2,6,6-tetramethyl-4-piperidyl) imino} Hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}]
Eraser C: N, N'-bis (2,2,6,6-tetramethyl-4-piperidylnyl) -1,3-benzenedicarboxamide

Example 1
Colored particle dispersion 1 and decolorant dispersion 1 were mixed at a weight ratio of 70:30 to prepare a color-changing ink composition. The obtained color-changing ink composition was applied to Kent paper using a 20 μm bar coater to form a coating film, and dried at room temperature. After drying, the Kent paper was placed on a temperature control plate, the plate temperature was changed from 30 ° C. to 90 ° C. at a rate of 10 ° C./min, and the color was measured every 2 ° C.

  The colorimetry was carried out by obtaining the color difference (ΔE *) between the handwriting and the paper using a color difference meter CR-300 manufactured by the former Minolta Co., Ltd. As this difference becomes smaller, the handwriting is more erased. The color difference is expressed by the following formula. In the formula, L * indicates a lightness index, and a * and b * indicate a chromaticness index.

  From the obtained discoloration temperature curve, the color stability up to 55 ° C. was evaluated by (color difference with Kent paper at 30 ° C.) − (Color difference with Kent paper at 55 ° C.). In Example 1, (color difference with Kent paper at 30 ° C.) − (Color difference with Kent paper at 55 ° C.) is −0.4 as shown in Table 3, and excellent color stability up to 55 ° C. Indicated. Moreover, the Kent paper after heating to 90 degreeC was cooled to -25 degreeC. By cooling, the color density of the coating film formed on the Kent paper increased, that is, the color did not develop again. This has shown that the decoloring of the color-change ink composition of this invention is irreversible.

(Examples 2 and 3)
One dispersion selected from colored particle dispersions 2 to 3 is mixed with one dispersion selected from decolorant dispersions 1 to 3 at a ratio shown in Table 3 to obtain a color-changing ink composition. A product was prepared. The obtained color-changing ink composition was applied to Kent paper in the same manner as in Example 1 to form a coating film. Using the coating film formed on the Kent paper, a discoloration temperature curve was obtained, and (color difference with Kent paper at 30 ° C.) − (Color difference with Kent paper at 55 ° C.) was obtained. The evaluation results are shown in Table 3. Moreover, about these Examples, a discoloration temperature curve is shown in FIG. 1 and FIG. In Examples 2 to 3, even when the Kent paper heated to 90 ° C. was cooled to −25 ° C., the color density (ΔE) did not increase.

(Comparative Examples 1-3)
One dispersion selected from colored particle dispersions 4 to 6 and one dispersion selected from decolorant dispersions 1 to 3 were mixed at a ratio shown in Table 3 to obtain a color-changing ink composition. A product was prepared. The obtained discolorable ink composition was applied to Kent paper in the same manner as in Example 1 to form a coating film to obtain a discoloration temperature curve (color difference from Kent paper at 30 ° C.) − (55 ° C. Color difference with Kent paper). The results are shown in Table 3. Furthermore, the discoloration temperature curves of Comparative Examples 1 and 2 are shown in FIGS. All ink compositions showed discoloration by heating. However, (color difference with Kent paper at 30 ° C.) − (Color difference with Kent paper at 55 ° C.) is all greater than 3, and color stability up to 55 ° C. is inferior to Examples 1-3. It was. Further, as is clear from the graphs showing the discoloration temperature curves of Comparative Examples 1 and 2 (FIGS. 3 and 4), the erasing is finished after the erasing is started (specifically, the color difference from the Kent paper is The temperature range up to 5 times smaller than that at the time when decolorization started was wider than that in Examples 2 and 3.

  Although the melting point (74 ° C.) of the aliphatic compound used in Comparative Example 1 is higher than the melting point (70 ° C.) of the aromatic compound used in Example 2, the ink composition of Comparative Example 1 has 55 The degree of discoloration at 0 ° C. was greater than that of Example 2. Further, the difference between the melting point (70 ° C.) of the aliphatic compound used in Comparative Example 2 (68 ° C.) and the aromatic compound used in Example 2 and the implementation with the aliphatic compound used in Comparative Example 1 (74 ° C.). Although the difference in the aromatic compounds used in Example 3 (79 ° C.) was not so large, the degree of discoloration at 55 ° C. was higher in the comparative example.

  The discolorable ink composition of the present invention does not change color up to a predetermined temperature (particularly about 55 ° C.) and can be changed to colorless or other colors substantially irreversibly by heating. Or as a printing ink such as an ink for an ink jet printer.

Claims (13)

See containing colored particles electron-donating coloring organic compound and an electron-accepting compound and melting point containing an aromatic compound of 60 ° C. to 120 ° C., decolorizer, and water,
Aromatic compounds
Two benzene rings, or a compound in which a polycyclic aromatic ring and a benzene ring are linked by a substituent containing a carboxyl group,
A compound in which two benzene rings, or a polycyclic aromatic ring and a benzene ring are linked by a substituent containing an ester bond,
Two benzene rings, or a compound in which a polycyclic aromatic ring and a benzene ring are connected by a substituent containing an ether bond,
Two benzene rings, or a compound in which a polycyclic aromatic ring and a benzene ring are connected by a substituent containing an amide bond,
Biphenyl compounds, and
Compound containing naphthalene ring
One or more compounds selected from
Discoloring ink composition. Including colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 60 ° C to 120 ° C, a color erasing agent, and water,
Aromatic compounds
Two benzene rings, or a compound in which a polycyclic aromatic ring and a benzene ring are linked by a substituent containing a carboxyl group,
Two benzene rings, or a compound in which a polycyclic aromatic ring and a benzene ring are linked by a substituent containing an ester bond, and
Biphenyl compounds
One or more compounds selected from
Discoloring ink composition. Including colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 60 ° C to 120 ° C, a color erasing agent, and water,
The aromatic compound is a compound in which two benzene rings, or a polycyclic aromatic ring and a benzene ring are connected by a substituent containing an ester bond.
Discoloring ink composition. Including colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 60 ° C to 120 ° C, a color erasing agent, and water,
Aromatic compounds
Benzophenone, benzyl, benzyl phenyl ketone, benzoin methyl ether, benzoin isopropyl ether, methyl 2-benzoylbenzoate, 2,2-dimethoxy-2-phenylacetophenone, 4-methoxybenzophenone, 4-methylbenzophenone, 4-methylbenzyl phenyl ketone , 1,3-diphenyl-1,3-propanedione, p-tolyl benzoate, phenyl benzoate, p-tolyl phenylacetate, 2-naphthyl benzoate, diphenyl carbonate, diphenyl phthalate, 4-octylphenyl salicylate 4-benzyloxyphenyl acetic acid methyl ester, benzyl phenyl ether, methyl 3,5-dibenzyloxybenzoate, 1,3-diphenoxybenzene, 1,4-diphenoxybenzene, di-p-tolyl ether, N, N-diphenylacetamide, biphenyl, 4,4'-bismethoxymethyl bif Sulfonyl, 4-acetoxy-biphenyl, 4-butyryl-biphenyl, and 3-hydroxy-2-naphthoic acid methyl
One or more compounds selected from
Discoloring ink composition. Including colored particles containing an electron-donating color-forming organic compound, an electron-accepting compound, and an aromatic compound having a melting point of 60 ° C to 120 ° C, a color erasing agent, and water,
Aromatic compounds
4-acetoxybiphenyl, phenyl benzoate, 1,3-diphenyl-1,3-propanedione, diphenyl carbonate, 4-butyryl biphenyl, 2-naphthyl benzoate, methyl 3-hydroxy-2-naphthoate, and salicylic acid -4-octylphenyl
One or more compounds selected from
Discoloring ink composition .   The discolorable ink composition according to any one of claims 1 to 3, wherein the aromatic compound has a melting point of 65C to 85C. 1 wherein the aromatic compound is selected from benzoin isopropyl ether, 1,3-diphenyl-1,3-propanedione, phenyl benzoate, p-tolyl phenylacetate, 1,4-diphenoxybenzene, and 4-acetoxybiphenyl Or the discolorable ink composition of Claim 6 which is a some compound. The color-changing ink composition according to any one of claims 1 to 5 , wherein the decolorizer is a basic compound. The decolorizer
Aliphatic amines,
Aliphatic diamines,
Amino alcohol,
An aromatic compound having one or more amino groups in the molecule and an alkylene group between the amino group and the aromatic ring,
A compound represented by the general formula NH ₂ —C ₂ H ₄ — (NH—C ₂ H ₄ ) _n —NH ₂ (n ≧ 0) and a derivative thereof;
Imidazole and its derivatives, and at least one compound selected from compounds having a piperidyl group and its derivatives in the molecule, generally called hindered amines,
The discolorable ink composition according to claim 8 . The discolorable ink composition according to any one of claims 1 to 5 , wherein the electron-accepting compound is non-volatile. The color-changing ink composition according to any one of claims 1 to 5 , further comprising a colorant that does not change color by heating. A writing instrument using the discolorable ink composition according to any one of claims 1 to 5 as ink. The ink for inkjet printers which consists of a color-change ink composition of any one of Claims 1-5.

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