Ink composition for color-changeable writing utensil, and writing utensil and writing utensil set accommodating the same

Abstract

To provide an ink composition for a color-changeable writing utensil capable of forming handwriting while visually observing the handwriting, exhibiting a color-changeable behavior in which the handwriting becomes invisible with time, and visually observing the faded handwriting upon light irradiation, and to provide a writing utensil and a writing utensil set containing the ink composition.SOLUTION: There are provided an ink composition 2 for a color-changeable writing utensil having a pH in the range of 8 to 12, comprising: water; a reversible photochromic microcapsule pigment in which a photochromic compound is encapsulated within microcapsules, or a reversible photochromic resin particle in which a photochromic compound is dispersed in a thermoplastic or thermosetting resin; a pH indicator that develops color in an alkaline range and fades in a neutral to acidic range; and an alkaline substance, as well as a writing utensil 1 and a writing utensil set accommodating the ink composition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a color-changing ink composition for a writing instrument, and a writing instrument and a writing instrument set containing the same. More specifically, the present invention relates to a color-changing ink composition for a writing instrument that allows the writing history to be confirmed, and a writing instrument and a writing instrument set containing the same. [Background technology]

[0002] Conventionally, a decolorizable ink composition containing a pH indicator and a basic substance has been disclosed (see, for example, Patent Document 1). The ink composition is an ink in which a pH indicator is colored with a basic substance, and handwriting can be neutralized or acidified over time by absorbing acidic components such as carbon dioxide in the air, causing it to fade. However, it has been difficult to confirm the history of handwriting from faded marks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 54-131428 Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to provide a color-changing ink composition for a writing instrument, which allows handwriting to be visually observed under normal use conditions, so that handwriting can be formed while being confirmed, and which also allows the history of handwriting to be confirmed by irradiating the handwriting with light after the handwriting has faded over time, as well as a writing instrument and writing instrument set containing the same. [Means for solving the problem]

[0005] The present invention provides a color-changing ink composition for a writing instrument, which contains water, a reversible photochromic microcapsule pigment in which a photochromic compound is encapsulated in microcapsules, or reversible photochromic resin particles in which a photochromic compound is dispersed in a thermoplastic or thermosetting resin, a pH indicator that develops color in the alkaline range and loses color in the neutral to acidic range, and an alkaline substance, and which has a pH in the range of 8 to 12. Furthermore, the present invention also provides a writing instrument containing the color-changing ink composition for a writing instrument, and the writing instrument equipped with a light irradiation device. Furthermore, the present invention is also concerned with a writing instrument set comprising a writing instrument containing the color-changing ink composition for a writing instrument and a light irradiation device. [Effects of the Invention]

[0006] The present invention provides a highly convenient color-changing ink composition for a writing instrument, which allows handwriting to be formed while being visually observed, exhibits color change behavior such that the handwriting becomes invisible over time, and the handwriting that has been erased by irradiation with light can be visually recognized, and can be used for security purposes such as counterfeit prevention and passwords, as well as for memorization and games, as well as a writing instrument and a writing instrument set containing the same. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is an explanatory diagram of an embodiment of a writing instrument containing the color-changing ink composition for a writing instrument of the present invention. [Figure 2] FIG. 2 is an explanatory diagram of another embodiment of a writing instrument containing the color-changing ink composition for a writing instrument of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0008] As the photochromic compound, spirooxazine derivatives, spiropyran derivatives, naphthopyran derivatives, etc. can also be used. The spirooxazine derivatives are shown below, but the present invention is not limited thereto. Examples of indolinospirobenzoxazine compounds include: 1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 6′-chloro-5-fluoro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 3,3-dimethyl-1-ethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5,7-difluoro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-cyano-3,3-dimethyl-1-(methoxycarbonyl)methylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 1'-methyldispiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[4,3-f][1,4]benzoxazine], 1'-methyl-5'-nitrodispiro[cyclopentane-1,3'-[3H]-indole-2'(1'H),3"-[3H]pyrido[4,3-f][1,4]benzoxazine], 1,3,3,5′-tetramethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 6'-fluoro-1'-methyldispiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[4,3-f][1,4]benzoxazine], 1-benzyl-6'-chloro-3,3-dimethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 6'-Methoxy-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-chloro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-bromo-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-iodo-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-trifluoromethyl-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 3,3-diethyl-1-methylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 1,3,3,6′-tetramethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 6-chloro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5'-fluoro-1'-methyldispiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-cyano-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-ethoxycarbonyl-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 4',6'-difluoro-1'-methyldispiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[4,3-f][1,4]benzoxazine], 3,3-dimethyl-1-(methoxycarbonyl)methylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 3,3-dimethyl-1-phenylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 5-Methoxy-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 1,3,3,5-tetramethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 7'-chloro-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 1,3,3,7′-tetramethylspiro[2H-indole-2,3′-[3H]pyrido[4,3-f][1,4]benzoxazine], 7'-Methoxy-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[4,3-f][1,4]benzoxazine], 1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 6′-chloro-5-fluoro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[2,3-f][1,4]benzoxazine], 5-chloro-1,3-dimethyl-3-ethyl-5'-methoxyspiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 3,3-diethyl-1-methyl-5-nitrospiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 1',6'-dimethylspiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 9"-Bromo-1'-methoxycarbonylmethyl-5'-trifluoromethyldispiro[cyclopentane-1,3'-[3H]-indole-2'[1'H],3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 1-benzyl-3,3-di-n-butyl-7′-ethyl-5-methoxyspiro[2H-indole-1,3′-[3H]pyrido[2,3-f][1,4]benzoxazine], 1'-n-butyl-6'-iododispiro[cycloheptane-1,3'-[3H]-indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 3,3-dimethyl-9'-iodo-1-naphthylspiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 4'-cyano-1'-(2-(methoxycarbonyl)ethyl)dispiro[cyclohexane-1,3'-[3H]indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 7-Methoxycarbonyl-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 4-bromo-3,3-diethyl-9′-ethoxy-1-(2-phenyl)ethyl spiro[2H-indole-2,3′-[2,3-f][1,4]benzoxazine], 1'-methyldispiro[cyclohexane-1,3'-[3H]-indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 6-fluoro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[2,3-f][1,4]benzoxazine], 5-ethyl-9-fluoro-1,3,3-trimethylspiro[2H-indole-2,3′-[3H]pyrido[2,3-f][1,4]benzoxazine], 1'-benzyl-6"-iododispiro[cyclopentane-1,3'-[3H]-indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 5-ethoxy-1,3,3-trimethylspiro[2H-indole-2,3'-[3H]pyrido[2,3-f][1,4]benzoxazine], 1'-methyl-5'-trichloromethyldispiro[cyclohexane-1,3'-[3H]-indole-2'(1'H),3"-[3H]pyrido[2,3-f][1,4]benzoxazine], 1,3-diethyl-3-methylspiro[2H-indole-2,3′-[3H]pyrido[2,3-f][1,4]benzoxazine], Examples include 1'-methoxycarbonylmethyldispiro[cyclohexane-1,3'-[3H]-indole-2'(1'H)-[3H]pyrido[2,3-f][1,4]benzoxazine] and other indolinospirobenzoxazines substituted with halogen, methyl, ethyl, methylene, ethylene, hydroxyl, or the like on the indole and benzene rings.

[0009] Examples of indolinospironaphthoxazine compounds include: 1,3,3-trimethyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-chloro-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-bromo-spiroindoline naphthoxazine, 1,3,3,5-tetramethyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-n-propyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-iso-butyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-methoxy-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-n-propoxy-spiroindoline naphthoxazine, 1,3,3-trimethyl-5-cyano-spiroindoline naphthoxazine, 1-n-propyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-iso-butyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-n-octyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-n-octadecyl-3,3-dimethyl-spiroindoline naphthoxazine, Sodium 1,3,3-trimethyl-8′-sulfonate-spiroindoline naphthoxazine, 1,3,3-trimethyl-9′-methoxyspiroindoline naphthoxazine, 1,3,3-trimethyl-8′-cyano-spirobenzoindoline naphthoxazine, 1,3,3-trimethyl-5-trifluoro-spiroindoline naphthoxazine, 1-(4′-methylphenyl)-3,3-dimethyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-6′-(2,3-dihydro-1-indolino)-spiroindoline naphthoxazine, 1,3,3-trimethyl-6′-(1-piperidinyl)-spiroindoline naphthoxazine, 1,3,3-trimethyl-6′-(1-morpholino)-spiroindoline naphthoxazine, 1-ethyl-3,3-dimethyl-6-trifluoromethyl-6′-(1-morpholino)-spiroindoline naphthoxazine, 1,3,3-trimethyl-6-trifluoromethyl-6′-(1-piperidinyl)-spiroindoline naphthoxazine, 1-benzyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-(4-methoxybenzyl)-3,3-dimethyl-spiroindoline naphthoxazine, 1-(4-chlorobenzyl)-3,3-dimethyl-spiroindoline naphthoxazine, 1-ethyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-isopropyl-3,3-dimethyl-spiroindoline naphthoxazine, 1-(2-phenoxyethyl)-3,3-dimethyl-spiroindoline naphthoxazine, 1,3-dimethyl-3-ethyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-9′-hydroxy-spiroindoline naphthoxazine, 1,3-dimethyl-3-ethyl-8′-hydroxy-spiroindoline naphthoxazine, 1,3,3,5-tetramethyl-9′-methoxy-spiroindoline naphthoxazine, 1,3,3,5,6-pentamethyl-9′-methoxy-spiroindoline naphthoxazine, 1,3,3-trimethyl-4-trifluoromethyl-5′-methoxy-spiroindoline naphthoxazine, 1,3,3-trimethyl-5′-methoxy-6′-trifluoromethyl-spiroindoline naphthoxazine, 1,3,3-trimethyl-4-trifluoromethyl-9′-methoxy-spiroindoline naphthoxazine, 1,3,5,6-tetramethyl-3-ethyl-spiroindoline naphthoxazine, 1,3,3,5,6-pentamethyl-spiroindoline naphthoxazine, 1-methyl-3,3-diphenyl-spiroindoline naphthoxazine, 1-(4-methoxybenzyl)-3,3-dimethyl-spiroindoline naphthoxazine, 1-(3,5-dimethylbenzyl)-3,3-dimethyl-spiroindoline naphthoxazine, Examples include 1-(2-fluorobenzyl)-3,3-dimethyl-spiroindolinenaphthoxazine and other indolinospironaphthoxazines substituted with halogen, methyl, ethyl, methylene, ethylene, hydroxyl, and the like on the indole ring and benzene ring.

[0010] Examples of indolinospirophenanthrooxazine compounds include: Examples include 1,3,3-trimethyl-spiroindolinephenanthrooxazine, 1,3,3-trimethyl-5-chloro-spiroindolinephenanthrooxazine, and the like, and examples of indolinospirophenanthrooxazines having substitutions such as halogen, methyl, ethyl, methylene, ethylene, and hydroxyl groups on the indole ring and benzene ring.

[0011] Examples of indolinospiroquinolinoxazine compounds include: Examples include 1,3,3-trimethyl-spiroindolinequinolinoxazine and other indolinospiroquinolinoxazines substituted with halogen, methyl, ethyl, methylene, ethylene, hydroxyl, and the like on the indole ring and benzene ring.

[0012] The spiropyran derivatives include Examples include 1,3,3-trimethylindolinobenzopyrilospiran, 1,3,3-trimethylindolino-6'-bromobenzopyrilospiran, 1,3,3-trimethylindolino-8'-methoxybenzopyrilospiran, 1,3,3-trimethylindolino-β-naphthopyrilospiran, and 1,3,3-trimethylindolino-6'-nitrobenzopyrilospiran.

[0013] Examples of the naphthopyran derivatives include: 3,3,9,9-tetraphenyl-3H,9H-naphtho[2,1-b:6,5-b′]-dipyrane, 3,3,10,10-tetraphenyl-3H,10H-naphtho[2,1-b:7,8-b′]dipyrane, 3,3,9,9-tetraphenyl-3H,10H-naphtho[4,3-b:8,7-b]-dipyrane, 3,3-diphenyl-9-methoxy-3H-naphtho[4,3-b]pyran, 3,3-diphenyl-10-methyl-3H-naphtho[2,1-b:5,6-b]dipyran-8-one, 3,3,9,9-tetra(4′-methoxy-phenyl)-3H,9H-naphtho[2,1-b:6,5-b′]-dipyrane, 3,3-diphenyl-8-(2-(4-dimethylamino)phenyl)ethene-3H-naphtho[4,3-b]pyran, 3,3-diphenyl-5-acetoxy-3H-naphtho[4,3-b]pyran, Examples include 3,3-diphenyl-8-(1H-benzotriazol-1-yl)carbonyl-3H-naphtho[4,3-b]pyran.

[0014] Furthermore, by using the photochromic compound as a photochromic material comprising a styrene oligomer, it is possible to improve light resistance, color density, and water resistance. The styrene oligomer has a weight average molecular weight of 200 to 6,000, preferably 200 to 4,000. If the weight average molecular weight of the styrene oligomer is less than 200, the amount of the contained monomer will be large, and the composition will lack stability, making it difficult to achieve the effect of improving light resistance. If the weight average molecular weight exceeds 6,000, color retention occurs upon light irradiation, the color density decreases, and the color change sensitivity decreases. The weight average molecular weight is measured by the GPC method (gel permeation chromatography method). Examples of the styrene oligomer include low molecular weight polystyrene, styrene-α-methylstyrene copolymer, α-methylstyrene polymer, copolymer of α-methylstyrene and vinyltoluene, α-pinene polymer, β-pinene polymer, d-limonene polymer, etc. Examples of the low molecular weight polystyrene include those manufactured by Sanyo Chemical Industries, Ltd., under the trade names of Hymer SB-75 (weight average molecular weight 2000) and Hymer ST-95 (weight average molecular weight 4000). As the styrene-α-methylstyrene copolymer, products such as Picolastic A5 (weight average molecular weight 317) and Picolastic A75 (weight average molecular weight 917), manufactured by Rika Hercules Co., Ltd., can be used. Examples of α-methylstyrene polymers that can be used include those manufactured by Rika Hercules Co., Ltd. under the trade names Crystallex 3085 (weight average molecular weight 664), Crystallex 3100 (weight average molecular weight 1020), and Crystallex 1120 (weight average molecular weight 2420). As the copolymer of α-methylstyrene and vinyltoluene, products such as Picotex LC (weight average molecular weight 950) and Picotex 100 (weight average molecular weight 1740), manufactured by Rika Hercules Co., Ltd., can be used. As the α-pinene polymer, a product manufactured by Rika Hercules Co., Ltd., trade name: Piccolite A115 (weight average molecular weight 833) is used. As the β-pinene polymer, a product name: Piccolite S115 (weight average molecular weight 1710) manufactured by Rika Hercules Co., Ltd. is used. As the d-limonene polymer, a product name: Piccolite C115 (weight average molecular weight 902) manufactured by Rika Hercules Co., Ltd. is used. The polystyrene oligomers may be used alone or in combination of two or more kinds.

[0015] Furthermore, the photochromic compound can be configured to exhibit high decolorization sensitivity by using it as a photochromic material comprising an acrylic oligomer having a weight-average molecular weight of 12,000 or less. The photochromic compound is dissolved in an acrylic oligomer having a weight-average molecular weight of 12,000 or less for practical use, and has high color development sensitivity and can adjust the color change function by increasing the decolorization sensitivity.

[0016] As the acrylic oligomer having a weight-average molecular weight of 12,000 or less, an acrylic acid ester copolymer is preferably used, and examples thereof include those manufactured by Toa Gosei Co., Ltd., trade names: ARUFON UP-1170 (weight-average molecular weight 8,000, glass transition point -51°C), ARUFON UP-1080 (weight-average molecular weight 6,000, glass transition point -61°C), ARUFON UP-1000 (weight-average molecular weight 3,000, glass transition point -77°C), ARUFON UP-1020 (weight-average molecular weight 2,000, glass transition point -80°C), ARUFON UP-1010 (weight-average molecular weight 1,700, glass transition point -31°C), ARUFON UH-2000 (weight-average molecular weight 11,000, glass transition point -55°C), ARUFON US-6100 (weight-average molecular weight 2,500, glass transition point -58°C), and ARUFON UC-3510 (weight-average molecular weight 2,000, glass transition point -50°C).

[0017] The acrylic oligomer has a weight average molecular weight of 12,000 or less, preferably 1,000 to 8,000, and more preferably 1,500 to 6,000. If the weight average molecular weight of the acrylic oligomer exceeds 12,000, it becomes difficult to adjust the decolorization sensitivity, so it is desirable that it be within the above range. Furthermore, if the weight average molecular weight is less than 1000, the amount of contained monomers will be large, and the color density will be low and light resistance will be easily impaired due to lack of stability. The acrylic oligomers may be used alone or in combination of two or more kinds. The weight average molecular weight is measured by the GPC method (gel permeation chromatography method). Furthermore, the acrylic oligomer has a glass transition point (Tg) of −30° C. or lower, preferably −50° C. or lower, and therefore exhibits good decolorization sensitivity. If the glass transition point (Tg) exceeds −30° C., the color development sensitivity tends to decrease, which makes the material less practical. The glass transition point is the midpoint obtained by measuring at a heating rate of 10 K / min using a Mettler-Toledo FP900 Thermosystem (FP90 and FP85HT).

[0018] The weight ratio of the photochromic compound to the acrylic oligomer is preferably 1:1 to 1:10000, more preferably 1:5 to 1:500, and even more preferably 1:10 to 1:100. By satisfying the above weight ratio, the photochromic compound satisfies the color-developing and color-discharging functions and also tends to exhibit a sufficient color density. If the weight ratio of the acrylic oligomer to the photochromic compound is less than 1, the photochromic compound is difficult to dissolve in the acrylic oligomer, making it difficult to exhibit the desired function. On the other hand, if the weight ratio of the acrylic oligomer to the photochromic compound is more than 10,000, the color density becomes poor.

[0019] Furthermore, the photochromic compound may be configured to exhibit insensitive decolorization sensitivity by using a photochromic material composed of a plurality of oligomers having different glass transition points, or a combination of an oligomer and a polymer having different glass transition points, in which one of the oligomers has a glass transition point of −30° C. or lower and the other oligomer or polymer has a glass transition point of 40° C. or higher. The photochromic compound is dissolved in a plurality of oligomers having different glass transition temperatures, or in a combination of oligomers and polymers having different glass transition temperatures, and is put to practical use. When the glass transition point of one of the oligomers in the medium for dissolving the photochromic compound is -30°C or lower and the glass transition point of the other oligomer or polymer is 40°C or higher, it is possible to adjust the color change function by increasing the color development sensitivity and decreasing the decolorization sensitivity.

[0020] Examples of the oligomer include styrene-based oligomers and acrylic-based oligomers. As the styrene-based oligomer, the same styrene-based oligomer as described above can be used. Examples of the polymer include styrene-based resins, acrylic-based resins, and ester-based resins. Examples of the styrene-based resin include homopolymers of styrene derivatives such as styrene, α-methylstyrene, chlorostyrene, dichlorostyrene, bromostyrene, dimethylstyrene, and t-butylstyrene, and copolymers of combinations thereof; and copolymers of styrene derivatives with divinylbenzene, methyl methacrylate acrylonitrile, butadiene, isoprene, and the like. The acrylic resin may be a homopolymer or copolymer containing, as a constituent monomer, an acrylic monomer, for example, at least one monomer selected from (meth)acrylic acid and (meth)acrylic acid esters.

[0021] Examples of the oligomer having a glass transition temperature of −30° C. or less are given below. Examples of oligomers having a glass transition point of −30° C. or less include Eastman Kodak Company's Picolastic A5 (glass transition point −42° C., styrene-α-methylstyrene copolymer, weight-average molecular weight 317), and Toa Gosei Co., Ltd.'s ARUFON UP-1010 (glass transition point −31° C., acrylic oligomer, weight-average molecular weight 1700), ARUFON UP-1170 (glass transition point −51° C., acrylic ester copolymer, weight-average molecular weight 8000), ARUFON UP-2000 (glass transition point −55° C., acrylic ester copolymer, weight-average molecular weight 11000), ARUFON UP-1080 (glass transition point −61° C., acrylic ester copolymer, weight-average molecular weight 6000), and ARUFON UP-1000 (glass transition point −77° C., acrylic ester copolymer, weight-average molecular weight 3000). The oligomers may be used alone or in combination of two or more kinds. Furthermore, the oligomer has a glass transition point (Tg) of preferably −40° C. or lower, more preferably −50° C. or lower, and therefore exhibits good decolorization sensitivity. If the glass transition point (Tg) exceeds −30° C., the color development sensitivity tends to decrease, which makes the material less practical.

[0022] Examples of the oligomer or polymer having a glass transition temperature of 40° C. or higher are given below. Examples of the oligomer having a glass transition point of 40°C or higher include ARUFON UP-1150 (trade name, glass transition point 68°C, acrylic oligomer, weight average molecular weight 67,000) manufactured by Toa Gosei Co., Ltd., Hymer ST-95 (trade name, glass transition point 42°C, low molecular weight polystyrene, weight average molecular weight 4,000) manufactured by Sanyo Chemical Industries, Ltd., Picotex LC (trade name, glass transition point 40°C, copolymer of α-methylstyrene and vinyltoluene, weight average molecular weight 950) and Crystallex 5140 (trade name, glass transition point 85°C, α-methylstyrene polymer, weight average molecular weight 3,950) manufactured by Eastman Kodak Company. Examples of the polymer having a glass transition point of 40°C or higher include Hymer SB-150 (trade name, glass transition point 62°C, polystyrene resin, weight average molecular weight 67,000) manufactured by Sanyo Chemical Industries, Ltd., Picolastic D125 (trade name, glass transition point 53°C, styrene resin, weight average molecular weight 53,200) manufactured by Eastman Kodak Company, and Polyester TP217 (trade name, glass transition point 40°C, saturated polyester resin, weight average molecular weight 16,000) manufactured by Nippon Synthetic Chemical Industry Co., Ltd. The oligomers or polymers having a glass transition temperature of 40° C. or less may be used alone or in combination of two or more kinds. Furthermore, the oligomer or polymer preferably has a glass transition point (Tg) of 50 or more, and therefore exhibits good decolorization sensitivity. The weight average molecular weight is measured by GPC (gel permeation chromatography). Examples of the combination of the oligomer and polymer include a combination of a styrene oligomer having a weight average molecular weight of 5,000 or less or an acrylic oligomer having a weight average molecular weight of 12,000 or less and a polymer having a weight average molecular weight of 10,000 to 100,000.

[0023] The weight ratio of the photochromic compound to the oligomers having different glass transition points, or the oligomers and polymers having different glass transition points, is in the range of 1:1 to 1:10000, preferably in the range of 1:5 to 1:500, and more preferably in the range of 1:10 to 1:100. By satisfying the above weight ratio, the photochromic compound tends to exhibit a sufficient color density.

[0024] The weight ratio of the oligomer having a glass transition point of -30°C or lower to the oligomer or polymer having a glass transition point of 40°C or higher is in the range of 1:1 to 1:9, preferably in the range of 1:2 to 1:7, and more preferably in the range of 1:3 to 1:5. By satisfying the above weight ratio, it is possible to increase the color development sensitivity while further decreasing the decolorization sensitivity.

[0025] The photochromic compound or photochromic material is used as a reversible photochromic microcapsule pigment encapsulated in a microcapsule, or as a reversible photochromic resin particle in which the photochromic compound is dispersed in a thermoplastic or thermosetting resin. Microencapsulation can be performed by known methods such as isocyanate-based interfacial polymerization, in situ polymerization such as melamine-formalin polymerization, in-liquid curing coating, phase separation from an aqueous solution, phase separation from an organic solvent, melt-dispersion cooling, air suspension coating, and spray drying, and can be selected appropriately depending on the application. Furthermore, a secondary resin film may be provided on the surface of the microcapsule pigment depending on the purpose to impart durability or to modify the surface properties for practical use. Examples of resins constituting the microcapsules include urea resins, urethane resins, urea-urethane resins, epoxy resins, melamine resins, benzoguanamine resins, and isocyanate resins. The microcapsule pigment preferably has a mass ratio of inclusions / wall film of 7 / 1 to 1 / 1, and by having the wall film ratio within this range, it is possible to prevent a decrease in color density and clarity during color development, and more preferably, the mass ratio of inclusions / wall film is 6 / 1 to 1 / 1. By encapsulating the pigment in the microcapsules, a chemically and physically stable pigment can be obtained.

[0026] Reversible photochromic microcapsule pigment. The average particle size of the reversible photochromic resin particles is not particularly limited, but is preferably in the range of 0.1 to 5 μm, more preferably 0.3 to 5 μm, even more preferably 0.3 to 4 μm, and particularly preferably 0.5 to 3 μm. The average particle diameter was measured by determining the particle region using image analysis particle size distribution measurement software (manufactured by Mountec Co., Ltd., product name: MacView), calculating the diameter equivalent to a circle with a projected area (Heywood diameter) from the area of ​​the particle region, and measuring the average particle diameter of particles equivalent to a sphere with the same volume using this value. Furthermore, if the particle size of all or the majority of particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to an equal-volume sphere by the Coulter method using a particle size distribution analyzer (product name: Multisizer 4e, manufactured by Beckman Coulter, Inc.). Furthermore, the volumetric particle size and average particle size may be measured using a calibrated laser diffraction / scattering particle size distribution analyzer (manufactured by HORIBA, Ltd., product name: LA-960V2) based on values ​​measured using the above-mentioned software or a measuring device using the Coulter method.

[0027] The medium may be water, or a combination of water and a water-soluble organic solvent, and various additives may also be added. Examples of the water-soluble organic solvent include ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, sec-butyl alcohol, tert-butyl alcohol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulfolane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0028] Examples of pH indicators that develop color in the alkaline region and lose color in the neutral to acidic region include phenolphthalein, thymolphthalein, cresolphthalein, α-naphtholphthalein, nitrophenolphthalein, bromocarboxythymolphthalein, cyanine, xylenol orange, and xylenol blue.

[0029] The alkaline substance is used to adjust the pH of the ink to 8 to 12 and cause the pH indicator to develop color, and examples of such alkaline substances include phosphates such as disodium hydrogen phosphate and trisodium phosphate, carbonates such as sodium carbonate and sodium hydrogen carbonate, sulfites such as sodium sulfite and potassium sulfite, ammonia, alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, amines such as dipropylamine, amylamine, triethylamine and 2-amino-2-methylpropanol, and hydroxides such as sodium hydroxide and potassium hydroxide. The alkaline substance can also be used in combination with an organic amine. Examples of the organic amine include monoethanolamine, diethylamine, dipropylamine, triethanolamine, and triethylamine.

[0030] Examples of color-changing ink compositions for writing instruments that contain at least the reversibly photochromic microcapsule pigment or reversibly photochromic resin particles, a pH indicator that develops color in the alkaline range and loses color in the neutral to acidic range, an alkaline substance, and water include shear-thinning inks that contain a shear-thinning agent, and aggregating inks that contain a water-soluble polymer aggregating agent and suspend the microcapsule pigment in a loosely aggregated state.

[0031] By adding the shear thinning agent, aggregation and sedimentation of the reversible photochromic microcapsule pigment or reversible photochromic resin particles can be suppressed, and bleeding of handwriting can be suppressed, thereby forming good handwriting. Furthermore, when the writing implement to be filled with the ink is in the form of a ballpoint pen, it is possible to prevent ink leakage from the gap between the ball and the tip when not in use, and to prevent ink from flowing back when the writing tip is left facing upward (upright state). Examples of the shear thinning agent include xanthan gum, welan gum, succinoglycan (average molecular weight of approximately 1,000,000 to 8,000,000), which is an organic acid-modified heteropolysaccharide whose constituent monosaccharides are glucose and galactose, 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 and whose main component is an alkyl ester of methacrylic acid, glucomannan, thickening polysaccharides with gelling ability extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene xylitol or derivatives thereof, crosslinkable acrylic acid polymers, inorganic fine particles, polyglycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, nonionic surfactants with an HLB value of 8 to 12 such as fatty acid amides, and salts of dialkyl or dialkenyl sulfosuccinic acid. Examples include a mixture of N-alkyl-2-pyrrolidone and an anionic surfactant, and a mixture of polyvinyl alcohol and an acrylic resin.

[0032] Examples of the water-soluble polymer flocculant include polyvinylpyrrolidone, polyethylene oxide, and water-soluble polysaccharides. Examples of the water-soluble polysaccharides include tragacanth gum, guar gum, pullulan, cyclodextrin, and water-soluble cellulose derivatives. Specific examples of the water-soluble cellulose derivatives include methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose. In the ink composition of the present invention, any water-soluble polymer that exhibits a loose bridging action between microcapsulated pigment particles can be used, but among these, water-soluble cellulose derivatives function effectively.

[0033] Furthermore, the addition of a water-soluble resin can provide adhesion and viscosity to the paper surface. Examples of the water-soluble resin include alkyd resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, and dextrin, with polyvinyl alcohol being preferred. Furthermore, as the polyvinyl alcohol, a partially saponified polyvinyl alcohol having a saponification degree of 70 to 89 mol % is more preferably used because it is highly soluble in ink even in the acidic range. The amount of the water-soluble resin added to the ink is in the range of 0.3 to 3.0% by mass, preferably 0.5 to 1.5% by mass.

[0034] Furthermore, when the ink composition of the present invention is used by filling it into a ballpoint pen, it is preferable to add a lubricant such as a higher fatty acid such as oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, a thiophosphite triester such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester), a phosphate monoester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, a phosphate diester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, or a metal salt, ammonium salt, amine salt or alkanolamine salt thereof to prevent wear of the ball seat. Other additives that may be added include inorganic salts such as sodium carbonate, sodium phosphate, and sodium acetate; pH adjusters such as water-soluble amine compounds and other organic basic compounds; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitrite, diisopropylammonium nitrite, and saponin; preservatives or antifungal agents such as carbolic acid, 1,2-benzthiazolin-3-one sodium salt, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine; wetting agents such as urea, nonionic surfactants, reduced or non-reduced starch hydrolysates, oligosaccharides such as trehalose, sucrose, cyclodextrin, glucose, dextrin, sorbitol, mannitol, and sodium pyrophosphate; antifoaming agents; dispersants; and fluorine-based surfactants and nonionic surfactants that improve the penetration of the ink.

[0035] The ink composition is used in practice by being filled into a writing instrument such as a ballpoint pen or a marking pen having a ballpoint pen tip or a marking pen tip attached to the writing tip.

[0036] When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited, and an example is a ballpoint pen that has an ink reservoir tube filled with shear-thinning ink inside the barrel, the ink reservoir tube communicating with a tip having a ball attached to the tip, and further having a liquid plug tightly attached to the end face of the ink to prevent backflow.

[0037] To explain the ballpoint pen tip in more detail, it is possible to use a tip in which the ball is held in a ball holding portion formed by pressing inward from the outer surface near the tip of a metal pipe, or a tip in which the ball is held in a ball holding portion formed by cutting a metal material with a drill or the like, a tip in which a resin ball receiving seat is provided inside a metal or plastic tip, or a tip in which the ball held in the tip is urged forward by a spring body, etc. The balls may be made of cemented carbide, stainless steel, ruby, ceramic, resin, rubber, etc. and have a diameter of about 0.3 to 3.0 mm, preferably 0.3 to 1.5 mm, and more preferably 0.4 to 1.0 mm.

[0038] The ink reservoir tube for containing the ink is made of a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon. The ink reservoir may be directly connected to the tip, or may be connected to the tip via a connecting member. Furthermore, the ink reservoir tube may be in the form of a refill, with the refill stored within the barrel, or the barrel itself with a tip attached to the tip may serve as the ink reservoir, with ink being filled directly into the barrel. The ballpoint pen obtained as described above may be a ballpoint pen with a cap or a retractable ballpoint pen, and its shape is not particularly limited. Any retractable ballpoint pen can be used as long as the writing tip provided on the ballpoint pen refill is stored inside the barrel and exposed to the outside air, and the writing tip protrudes from the barrel opening when the retractable mechanism is activated. Examples of the method of operating the retractable mechanism include a knock type, a rotation type, and a slide type. The knock type has a knock portion at the rear end of the barrel or on the side of the barrel, and by pressing the knock portion, the ballpoint pen tip is caused to protrude and retract from the opening at the front end of the barrel, or by pressing a clip portion provided on the barrel, the ballpoint pen tip is caused to protrude and retract from the opening at the front end of the barrel. The rotating type can be exemplified by a configuration having a rotating part at the rear of the barrel, and by rotating the rotating part, the ballpoint pen tip can be made to appear and disappear from the opening at the front end of the barrel. The sliding type can be exemplified by a configuration in which a sliding portion is provided on the side of the barrel, and the ballpoint pen tip is made to protrude and retract from the opening at the front end of the barrel by operating the sliding portion, or a configuration in which the ballpoint pen tip is made to protrude and retract from the opening at the front end of the barrel by sliding a clip portion provided on the barrel.

[0039] The rear end of the ink contained in the ink reservoir tube can be filled with an ink backflow preventive material. The ink backflow preventive composition comprises a non-volatile liquid or a hardly volatile liquid. Specific examples include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, and the like, and one or more of these can be used in combination.

[0040] The non-volatile liquid and / or the hardly-volatile liquid is preferably thickened to a suitable viscosity by adding a thickener. Examples of the thickener include clay-based thickeners such as silica whose surface has been hydrophobically treated, fine particle silica whose surface has been methylated, aluminum silicate, swellable mica, and hydrophobically treated bentonite or montmorillonite; fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate; dextrin-based compounds such as tribenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, and fatty acid dextrins; and cellulose-based compounds. Furthermore, the liquid ink backflow preventive material can be used in combination with a solid ink backflow preventive material.

[0041] Furthermore, when filling a marking pen with an ink composition, the structure and shape of the marking pen itself are not particularly limited, and examples include a marking pen in which an ink occlusion body made of a fiber bundle is built into the barrel, and a pen tip made of a fiber processed body with capillary gaps formed therein is attached to the barrel directly or via an intermediate member, and the ink occlusion body and the pen tip are connected, and the ink occlusion body is impregnated with cohesive ink, and a marking pen in which the pen tip and an ink reservoir tube are arranged via a valve body that opens when the pen tip is pressed, and ink is directly stored in the ink reservoir tube.

[0042] The pen tip is a porous material with interconnected pores, such as a resin-processed fiber body, a fused heat-melting fiber body, or a felt body, with a porosity selected from a range of approximately 30 to 70%, and one end is processed into a shape suitable for the purpose, such as a bullet shape, a rectangle, or a chisel shape, for practical use. The ink occlusion body is made by bundling crimped fibers in the longitudinal direction, and is contained within a covering such as a plastic cylinder or film, with the porosity adjusted to a range of approximately 40 to 90%. The valve body may be of a pumping type, but it is preferable that the valve body be set to a spring pressure that can be pressed and released by the pressure of the writing pen. The marking pen obtained as described above may be a marking pen with a cap or a retractable marking pen, and its shape is not particularly limited.

[0043] Furthermore, the shape of the ballpoint pen or marking pen is not limited to those described above, but may be a composite writing instrument (double-headed, retractable, etc.) equipped with pen tips of different shapes or pen tips that dispense ink of different colors.

[0044] In the initial writing formed by a writing instrument containing the ink composition, the color of the pH indicator is visible, but as the pH of the writing decreases due to carbon dioxide in the air, the pH indicator fades, and over time the writing becomes colorless and no longer visible. When the handwriting is not visible, light irradiation is performed using sunlight or a light irradiation device, causing the photochromic compound in the handwriting to develop color and making the handwriting visible again, and when the light irradiation is stopped, the photochromic compound loses color and the handwriting becomes invisible. The light source used in the light irradiation device is not particularly limited as long as it can change the color of a photochromic compound. However, by using one that has a peak emission wavelength in the range of 400 to 495 nm and that mainly emits blue light, unlike conventional light sources that emit ultraviolet light with a peak wavelength around 350 to 390 nm, which effectively changes the color of photochromic compounds, the light emitted is purple to blue light, which has less impact on the human body and is highly safe.

[0045] The light source can be any light source having the peak emission wavelength, but a blue light emitting diode is preferably used. Examples of the light-emitting diode include a blue LED manufactured by Nichia Corporation, product number NSPB636CS (peak wavelength 465 nm), a blue LED manufactured by Kyosemi Corporation, product number KED471M31 (peak wavelength 470 nm), a blue LED manufactured by Seiwa Electric Co., Ltd., product number SEDB16001A1 (peak wavelength 460 nm), a purple LED manufactured by Kyosemi Corporation, product number KED405UH3 (peak wavelength 405 nm), a purple LED manufactured by OPTOSUPPLY, product number OSSV5111A (peak wavelength 430 nm), and a purple LED manufactured by OPTOSUPPLY, product number OSSV9131A (peak wavelength 430 nm). As the power source for the light irradiation device, a solar cell or a dry battery is preferably used, and the dry battery may be either a primary battery or a secondary battery. The light irradiation device can be provided on a writing instrument, and the location where it is provided is not particularly limited, but it can be provided at the rear end of the writing instrument (the side where the writing tip is not provided) or at the top of the cap (the side where the opening is not provided). Furthermore, a writing set can be obtained by combining the writing implement and a light irradiation device. [Example]

[0046] The color-changing ink composition for a writing instrument of the present invention, and the writing instrument and writing instrument set containing the same will be described below. In the examples, the formulations are in parts by mass. Example 1 Preparation of reversibly photochromic microencapsulated pigments A compatible solution of 1 part of 1,3,3-trimethyl-6-trifluoromethyl-indolino-6'-(1-piperidinyl)-naphthoxazine as a photochromic compound and 15 parts of styrene-α-methylstyrene copolymer (manufactured by Eastman Kodak Company, trade name: Picolastic A-5) was encapsulated in urethane resin microcapsules to obtain a reversible photochromic microcapsule pigment with an average particle size of 2 μm.

[0047] Preparation of color-changing ink composition for writing implements A color-changing ink composition for a writing instrument (pH of the ink was 11.0) was prepared by mixing 25 parts of the reversible photochromic microcapsule pigment, 0.5 parts of o-cresolphthalein, 0.3 parts of succinoglycan, 13 parts of urea, 10 parts of glycerin, 0.5 parts of lubricant, 0.6 parts of a nonionic penetrant, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of a preservative, 3.0 parts of triethanolamine, and 46.9 parts of water.

[0048] Creation of writing implements (see Figure 1) The color-changing ink composition 2 for a writing instrument was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a ball at its tip via a resin relay member 4 (holder). Next, an ink backflow preventive body 6 (liquid stopper) was filled into the rear end of the polypropylene pipe, and a tail plug 7 was fitted to the rear of the pipe to form a refill 8. The refill was then placed in a barrel 9 (consisting of a front barrel and a rear barrel), and a cap 10 was attached, followed by degassing by centrifugation to obtain a writing instrument 1 (ballpoint pen). The ballpoint pen tip is made by deforming a metal pipe by pressing the tip near the tip inward from the outer surface, and holding a stainless steel ball with a diameter of 0.5 mm at the tip, and the ball is biased forward by a spring. The writing implement was used to write on writing paper to form the blue-purple letters (handwriting) of "ABC." The handwriting becomes invisible over time as the pH indicator gradually changes from blue-purple to colorless. If you want to know what it is, use a light irradiation device that uses an LED (peak wavelength 430 nm) as a light source to shine light on it, and the red letters "ABC" will become visible. When the light irradiation is stopped and the surface is left as it is, the red writing becomes invisible, but when the light is irradiated again, it becomes visible. The light source of the light irradiation device irradiates blue light with a peak emission wavelength of 430 nm, so it has little effect on the human body and is a highly safe device.

[0049] Example 2 Preparation of reversibly photochromic microencapsulated pigments A reversible photochromic microencapsulated pigment (average particle size 1.5 μm) was obtained by encapsulating 2 parts of 1,3,3-trimethyl-8′-cyano-spiro[benzo[e]indoline-2,3′-[3H]naphtho[2,1-b][1,4]oxazine] as a photochromic compound, 15 parts of styrene-α-methylstyrene copolymer (manufactured by Eastman Kodak Company, trade name: Picolastic A-75), and 0.5 parts of 2-[5-chloro(2H)-benzotriazol-2-yl]-4-methyl-6-(tert-butyl)phenol in microcapsules made of urethane resin.

[0050] Preparation of color-changing ink composition for writing implements A color-changing ink composition for a writing instrument was prepared by mixing 25 parts of the reversible photochromic microcapsule pigment, 1.0 part of α-naphtholphthalein, 0.3 parts of succinoglycan, 13 parts of urea, 10 parts of glycerin, 0.5 parts of lubricant, 0.6 parts of a nonionic penetrant, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of a preservative, 0.5 parts of triethanolamine, 0.3 parts of potassium hydroxide, and 48.6 parts of water (pH of the ink was 10.0).

[0051] Creation of writing implements (see Figure 1) The color-changing ink composition 2 for a writing instrument was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a ball at its tip via a resin relay member 4 (holder). Next, an ink backflow preventive body 6 (liquid stopper) was filled into the rear end of the polypropylene pipe, and a tail plug 7 was fitted to the rear of the pipe to form a refill 8. The refill was then placed in a barrel 9 (consisting of a front barrel and a rear barrel), and a cap 10 was attached, followed by degassing by centrifugation to obtain a writing instrument 1 (ballpoint pen). The ballpoint pen tip is made by deforming a metal pipe by pressing the tip near the tip inward from the outer surface, and a stainless steel ball with a diameter of 0.7 mm is held at the tip, and the ball is biased forward by a spring. The writing implement was used to write on writing paper at room temperature (25°C) to form the blue-purple letters (handwriting) of "aiueo." The handwriting becomes invisible over time as the pH indicator gradually changes from blue-purple to colorless. If you want to know what it is, you can shine light on it using a light irradiation device that uses an LED (peak wavelength 430 nm) as a light source, and the blue letters "aiueo" will become visible. When the light irradiation is stopped and the surface is left as it is, the blue writing becomes invisible, but when the light is irradiated again, it becomes visible. The light source of the light irradiation device irradiates blue light with a peak emission wavelength of 430 nm, so it has little effect on the human body and is a highly safe device. It was.

[0052] Example 3 Preparation of reversibly photochromic microencapsulated pigments A reversible photochromic microcapsule pigment (average particle size 2 μm) was obtained by encapsulating 1 part of 1-ethyl-3,3-dimethyl-6-trifluoromethyl-indolino-6′-(1-morpholino)-naphthoxazine as a photochromic compound, 15 parts of styrene-α-methylstyrene copolymer (manufactured by Eastman Kodak Company, trade name: Picolastic A-5), 1 part of light stabilizer, and 5 parts of 2,4-bis(2-hydroxy-4-butyloxyphenyl)-6-(2,4-bis-butyloxyphenyl)-1,3,5-triazine in microcapsules made of urethane resin.

[0053] Preparation of color-changing ink composition for writing implements A color-changing ink composition for a writing instrument was prepared by mixing 25 parts of the microcapsule pigment, 0.5 parts of phenolphthalein, 0.3 parts of succinoglycan, 13 parts of urea, 10 parts of glycerin, 0.5 parts of lubricant, 0.6 parts of a nonionic penetrant, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of a preservative, 0.5 parts of triethanolamine, 0.3 parts of potassium hydroxide, and 49.1 parts of water. The composition (ink pH 11.0) was prepared.

[0054] Making ballpoint pen refills The color-changing ink composition 2 for writing instruments was suction-filled into a pipe (ink reservoir 3) made of polypropylene resin, and connected to a ballpoint pen tip 5 holding a 0.5 mm stainless steel ball at the tip via a resin relay member 4 (holder). Next, an ink backflow preventive (liquid plug) was filled into the rear end of the polypropylene pipe, and a tail plug was fitted onto the rear of the pipe to form a refill. The refill was incorporated into a barrel 9 to obtain a writing instrument 1 (retractable ballpoint pen) (see FIG. 2). The retractable ballpoint pen has a structure in which the writing tip provided on the ballpoint pen refill is stored inside the barrel while being exposed to the outside air, and the writing tip protrudes from the opening at the front end of the barrel by activation of a retraction mechanism (knock mechanism) provided at the rear end of the barrel. The retractable mechanism of the writing implement was activated to project the ballpoint pen tip from the front end opening of the barrel, and the characters "AIUEO" were written in red (handwritten) on the writing paper. The handwriting becomes invisible over time as the pH indicator gradually turns from red to colorless. If you want to know what it is, you can use a light irradiation device that uses an LED (peak wavelength 430 nm) as a light source to shine light on it, and the red letters "AIUEO" will become visible. When the light irradiation is stopped and the surface is left as it is, the red writing becomes invisible, but when the light is irradiated again, it becomes visible. The light source of the light irradiation device irradiates blue light with a peak emission wavelength of 430 nm, so it has little effect on the human body and is a highly safe device. It was.

[0055] Example 4 Preparation of reversibly photochromic microencapsulated pigments A compatible solution of 1 part of 1,3,3-trimethyl-6-trifluoromethyl-indolino-6'-(1-piperidinyl)-naphthoxazine as a photochromic compound and 15 parts of styrene-α-methylstyrene copolymer (manufactured by Eastman Kodak Company, trade name: Picolastic A-5) was encapsulated in urethane resin microcapsules to obtain a reversible photochromic microcapsule pigment with an average particle size of 2 μm.

[0056] Preparation of color-changing ink composition for writing implements A color-changing ink composition for a writing instrument (pH of the ink is 11.0) is prepared by mixing 25 parts of the reversible photochromic microcapsule pigment, 0.5 parts of thymolphthalein, 0.3 parts of succinoglycan, 13 parts of urea, 10 parts of glycerin, 0.5 parts of a lubricant, 0.6 parts of a nonionic penetrant, 0.1 parts of a modified silicone antifoaming agent, 0.1 parts of a preservative, 0.5 parts of triethanolamine, 0.3 parts of sodium hydroxide, and 49.1 parts of water. was prepared.

[0057] Making writing implements The color-changing ink composition for writing instruments was suction-filled into a pipe (ink reservoir) made of polypropylene resin, and connected to a ballpoint pen tip having a 0.7 mm stainless steel ball at the tip via a resin relay member (holder). Next, an ink backflow preventer (liquid stopper) was inserted into the rear end of the polypropylene pipe, and a tail plug was fitted to the rear of the pipe to form a refill. The refill was then placed in a barrel (consisting of a front barrel and a rear barrel), a cap was attached, and the contents were degassed by centrifugation to obtain a writing instrument (ballpoint pen). The top of the cap is provided with a light irradiation device using an LED (peak wavelength 430 nm) as a light source. The writing implement was used to write on writing paper to form the blue letters (handwriting) of "ABC." The handwriting becomes invisible over time as the pH indicator gradually turns from blue to colorless. If you want to know what it says, you can shine a light on it using the light irradiation device attached to the cap, and the red letters "ABC" will become visible. When the light irradiation is stopped and the surface is left as it is, the red writing becomes invisible, but when the light is irradiated again, it becomes visible. The light source of the light irradiation device irradiates blue light with a peak emission wavelength of 430 nm, so it has little effect on the human body and is a highly safe device.

[0058] Example 5 A writing implement set was obtained by combining the writing implement obtained in Example 2 with a light irradiation device using an LED (peak wavelength 430 nm) as a light source. The writing implement was used to write on writing paper at room temperature (25°C) to form the blue-purple letters (handwriting) of "aiueo." The handwriting becomes invisible over time as the pH indicator gradually changes from blue-purple to colorless. If you want to know what it is, you can shine light on it using a light irradiation device that uses an LED (peak wavelength 430 nm) as a light source, and the blue letters "aiueo" will become visible. When the light irradiation is stopped and the surface is left as it is, the blue writing becomes invisible, but when the light is irradiated again, it becomes visible.

[0059] Example 6 A writing implement set was obtained by combining the writing implement obtained in Example 3 with a light irradiation device using an LED (peak wavelength 430 nm) as a light source. The retractable mechanism of the writing implement was activated to project the ballpoint pen tip from the front end opening of the barrel, and the characters "AIUEO" were written on the writing paper in a bluish-purple color (handwriting). The handwriting becomes invisible over time as the pH indicator gradually changes from blue-purple to colorless. If you want to know the contents, you can use a light irradiation device that uses an LED (peak wavelength 430 nm) as a light source to shine light on it, and the red letters "AIUEO" will become visible. When the light irradiation is stopped and the surface is left as it is, the red writing becomes invisible, but when the light is irradiated again, it becomes visible. [Explanation of symbols]

[0060] 1 writing implements 2. Color-changing ink composition for writing instruments 3 Ink reservoir 4 Relay parts 5 chips 6 Ink backflow prevention body 7 tail plug 8 Refills 9 Shaft tube 10 Caps

Claims

1. The color-changing ink composition for a writing instrument contains water, a reversible photochromic microcapsule pigment in which a photochromic compound is encapsulated in microcapsules, or reversible photochromic resin particles in which a photochromic compound is dispersed in a thermoplastic or thermosetting resin, a pH indicator that develops color in the alkaline range and loses color in the neutral to acidic range, and an alkaline substance, and has a pH in the range of 8 to 12.

2. A writing instrument containing the color-changing ink composition for a writing instrument according to claim 1.

3. 3. The writing implement according to claim 2, further comprising a light irradiation device.

4. A writing instrument set comprising the writing instrument according to claim 2 and a light irradiation device.

Images