Ink composition for pen and pen containing same

Abstract

An ink composition for a pen, the ink composition comprising at least a pigment and a solvent, the pigment comprising a guanine pigment, and the guanine pigment having an average particle diameter of 0.2-0.95 [mu] m.

Description

Technical Field

[0001] The present invention relates to a writing ink composition and a writing instrument containing the writing ink composition. In more detail, the present invention relates to a writing ink composition and a writing instrument containing the writing ink composition, wherein the pigment in the writing ink composition has excellent dispersion stability and can form clear handwriting with high concealability. Background Art

[0002] In the past, in order to obtain handwriting with concealability, a writing ink composition using a white pigment such as titanium oxide is known. In addition, it is also preferred to use a writing ink composition that can form handwriting with a pastel color by mixing a colorant of another color with such a highly concealable ink composition.

[0003] However, titanium oxide is a pigment with a high specific gravity, so there is a problem that the pigment is easy to settle over time, and if a hard lump is formed, the pigment is difficult to redisperse. In addition, when a writing instrument using an ink composition containing titanium oxide is stored with the writing tip facing upward, the concentration of the handwriting is easy to decrease, and when the writing tip is stored with the writing tip facing downward, the ink discharge is easy to decrease. Therefore, research has been conducted to use a thickener or the like to make the ink have a high viscosity and inhibit the sedimentation of titanium oxide. However, there are limits to the pens that can be used with such a high-viscosity ink composition. In addition, in an ink composition that uses titanium oxide and a colorant of another color, the ink sometimes undergoes color separation due to the difference in specific gravity between titanium oxide and the colorant. Therefore, research has been conducted to inhibit the sedimentation of titanium oxide or inhibit the formation of hard lumps (for example, refer to patent documents 1 to 4).

[0004] Patent Document 1 discloses an aqueous pigment composition comprising titanium oxide, an aluminum silicate-based pigment, and a specific resin.

[0005] Furthermore, Patent Document 2 discloses an aqueous ink composition comprising at least titanium oxide, succinoglycan, and water.

[0006] Furthermore, Patent Document 3 discloses an aqueous ballpoint pen ink composed of titanium oxide and oleic acid.

[0007] Patent Document 4 discloses an aqueous pigment ink for writing instruments comprising titanium oxide, color pigment, silicon dioxide powder and / or aluminosilicate, a water-soluble resin, a specific dispersant, a surfactant, and water.

[0008] Although the above composition (ink composition) can slow down the sedimentation rate of titanium oxide by using a specific compound, titanium oxide will settle over time to form lumps or easily cause color separation in the ink, making it difficult to stably disperse titanium oxide in the ink composition.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: Japanese Patent Application Laid-Open No. 59-217776

[0012] Patent Document 2: Japanese Patent Application Laid-Open No. 8-113752

[0013] Patent Document 3: Japanese Patent Application Laid-Open No. 10-251588

[0014] Patent Document 4: Japanese Patent Application Laid-Open No. 11-217532 Summary of the invention

[0015] Problems to be solved by the invention

[0016] The present disclosure intends to provide a writing ink composition having excellent dispersion stability of a pigment and capable of forming clear handwriting with high concealability, and a writing instrument containing the writing ink composition.

[0017] Solutions for solving problems

[0018] A first aspect of the present invention is a writing ink composition comprising at least a pigment and a solvent, wherein the pigment comprises a guanine pigment, and the average particle size of the guanine pigment is 0.2 to 0.95 μm.

[0019] Aspect 2 of the present invention is the ink composition according to aspect 1, further comprising a dispersant.

[0020] A third aspect of the present invention is the ink composition according to the second aspect, wherein the dispersant has an acidic group and / or a salt of an acidic group.

[0021] A fourth aspect of the present invention is the ink composition according to any one of aspects 1 to 3, wherein the content of the guanine pigment is 1 to 50% by mass based on the total mass of the ink composition.

[0022] A fifth aspect of the present invention is the ink composition according to any one of aspects 1 to 4, further comprising a colorant.

[0023] A sixth aspect of the present invention is a writing instrument containing the ink composition according to any one of aspects 1 to 5.

[0024] Effects of the Invention

[0025] According to an embodiment of the present invention, there can be provided a writing ink composition and a writing instrument containing the writing ink composition, wherein the writing ink composition uses a pigment containing a guanine pigment, the pigment of the writing ink composition is not easy to settle over time, the pigment has excellent dispersion stability, and can form clear handwriting with high concealment. DETAILED DESCRIPTION

[0026] The writing ink composition according to the embodiment of the present invention (hereinafter sometimes referred to as "ink composition" or "ink") contains at least a pigment and a solvent, wherein the pigment contains a guanine pigment. Hereinafter, each component constituting the ink composition according to the embodiment of the present invention will be described.

[0027] The ink composition according to the embodiment of the present invention contains a guanine pigment. The guanine pigment is a pigment formed of guanine.

[0028] Guanine is one of the main bases that make up nucleic acids. It is an organic substance derived from living things. For example, it exists in a crystalline state on the surface of fish such as hairtail, herring, and sardines. The crystallized guanine (guanine crystals) forms a layered structure on the surface of these fish, which reflects or refracts light, so the surface of fish such as hairtail, herring, and sardines has a glossy (pearl glossy) appearance.

[0029] In addition, fish scale foil obtained from guanine crystals as a raw material is used as a pigment that exhibits pearlescent luster in cosmetics and food additives. Therefore, guanine is a compound itself with high safety and little impact on the human body and the environment.

[0030] Guanine can be obtained from commercial products, or natural guanine crystals collected from fish such as hairtail, herring, and sardines. In addition, artificial guanine crystals obtained by dissolving commercial products or natural guanine crystals in a solvent and recrystallizing them can also be used.

[0031] The guanine pigment used in the embodiment of the present invention has a high refractive index (n = 1.8 ~ 2.0) and is therefore white, which exerts the effect of giving concealment to handwriting. The titanium oxide used as a white pigment in the past has a large specific gravity, so it is easy to settle in the ink composition, and it is easy to form a lump when it settles, so it is sometimes difficult to redisperse. In contrast, the guanine pigment has a small specific gravity compared to titanium oxide, so it is not easy to settle over time, and the formation of a lump is suppressed. In addition, the average particle size of the guanine pigment is 0.2 ~ 0.95 μm, which exerts an excellent effect of dispersion stability.

[0032] By using a pigment containing a guanine pigment having a specific average particle size in the ink composition of an embodiment of the present invention, the pigment is not easy to settle over time and has excellent dispersion stability. Therefore, the ink composition of an embodiment of the present invention can form a clear handwriting with rich concealment at a uniform concentration. In addition, even when the ink composition of the present invention contains a colorant described later, the separation of the guanine pigment and the colorant in the ink composition is suppressed. Therefore, the ink composition of an embodiment of the present invention can form a colored handwriting with concealment at a uniform concentration.

[0033] The average particle size of the guanine pigment used in the embodiment of the present invention is 0.2 to 0.95 μm, preferably 0.25 to 0.65 μm, and more preferably 0.25 to 0.4 μm. When the average particle size is within the above range, the concealment property of the ink composition and the dispersion stability of the guanine pigment can be highly balanced.

[0034] The average particle size is a value of the average particle size (median particle size) based on a volume basis measured using a dynamic light scattering particle size distribution measuring device [manufactured by Microtrac BEL Co., Ltd., product name: NANOTRAC FLEX], and the dynamic light scattering particle size distribution measuring device is calibrated based on a standard sample or a value measured using other measuring methods.

[0035] Even when the ink composition according to an embodiment of the present invention contains pigments other than guanine pigment, guanine can be separated from other pigments by density gradient centrifugation using a specific gravity difference, thereby measuring the average particle size of guanine alone in the same manner as described above.

[0036] The content of guanine pigment relative to the total mass of the ink composition is not particularly limited, and is preferably in the range of 1 to 50% by mass, and more preferably in the range of 5 to 30% by mass. If the content of guanine pigment is greater than 50% by mass, the ink discharge stability of the writing instrument containing the ink composition is easily reduced, and poor writing such as flying white and flying lines is easily generated. On the other hand, when the content of guanine pigment is less than 1% by mass, it is difficult to obtain an appropriate handwriting concentration as a writing instrument, and the concealment of the handwriting is easily impaired.

[0037] As guanine pigment, there is no particular limitation as long as it can be dispersed in the ink composition. Guanine pigment can be manufactured by, for example, mechanically crushing commercially available products or natural or artificial guanine crystals using various dispersion machines such as jet mills, vertical ball mills, and bead mills to form granules. Alternatively, guanine pigment can also be manufactured by dissolving commercially available products or natural guanine crystals in a solvent and recrystallizing them into granules. As guanine pigment, pigments colored by guanine pigment itself can also be used.

[0038] A dispersant may be further added to the ink composition of the embodiment of the present invention. For example, when the solvent used in the present invention is water, the dispersant can be adsorbed on the surface of the guanine pigment, so that the guanine pigments are separated from each other, and the distance between the guanine pigments is kept at a certain level or more to prevent agglomeration, thereby improving the dispersibility of the guanine pigment in the ink. In addition, even when the guanine pigments agglomerate with each other to form an agglomerate, an agglomerate with low density is formed, so it is easy to suppress the hardening of the guanine pigment after sedimentation.

[0039] Examples of the dispersant include surfactants, polymer dispersants, and inorganic compounds.

[0040] Examples of the surfactant used as the dispersant include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants.

[0041] Examples of polymer dispersants used as dispersants include polyvinyl butyral; polyvinyl ether; ketone resins; carboxyl group-containing resins such as styrene-maleic acid copolymers, styrene-acrylic acid copolymers, and acrylic acid-sulfonic acid copolymers; hydroxyethyl cellulose and its derivatives; acrylic acid-based polymers; PO·EO adducts; and amine-based oligomers of polyesters.

[0042] Examples of the inorganic compound used as the dispersant include pyrophosphate and hexametaphosphate.

[0043] According to one embodiment of the present invention, the dispersant preferably has an acidic group and / or a salt of an acidic group. The acidic group and / or the salt of the acidic group easily reacts with guanine (e.g., -NH 2 The dispersant is easily concentrated around guanine due to the bonding of the dispersant with the guanine group (such as a phospho group, a carboxyl group, a sulfonic acid group, a phosphate group, a sulfate group, a nitrate group, a phosphite group, a phosphonic acid group, a sulfinic acid group, etc. The salt of the acidic group includes the metal salts such as potassium salt and sodium salt of the above acidic groups; or 2-amino-2-methyl-1-propanol salt, etc. They can contain one kind in one molecule, or a combination of two or more kinds.

[0044] Commercially available dispersants having an acidic group and / or a salt of an acidic group can be obtained, for example, from the DISPER BYK series of BYK JAPAN, the FLOWLEN series of Kyoeisha Chemical, the ARON series of Toagosei, the JONCRYL series of BASF JAPAN, the Solsperse series of Nippon Lubrizol, etc. It should be noted that the dispersant having an acidic group and / or a salt of an acidic group can also function as a surfactant and / or a lubricant, etc., like a phosphate-based surfactant, etc., but is treated as a dispersant in the embodiment of the present invention.

[0045] According to one embodiment of the present invention, the molecular weight (mass average molecular weight) may be 300 or more and 200,000 or less, or 300 or more and 50,000 or less.

[0046] According to one embodiment of the present invention, the dispersant preferably has an acid value, so that the dispersant can more easily bond with guanine.

[0047] According to one embodiment of the present invention, it is preferred that at least one of the following group consisting of (a) to (e) is satisfied. This makes it easier for the dispersant to bond to guanine.

[0048] (a): The acid value of the dispersant is 100 mgKOH / g or more.

[0049] (b): The acid value is 5 to 15 mgKOH / g and has a comb-type structure (ie, a structure in which a branch polymer portion is graft-bonded to a trunk polymer portion).

[0050] (c): Contains a styrene-acrylic acid copolymer containing a carboxyl group.

[0051] (d): Contains an acrylic acid-sulfonic acid copolymer.

[0052] (e): The acid value and the amine value are both 15 or more and less than 30.

[0053] Examples of commercially available dispersants having an acidic group and / or a salt of an acidic group and satisfying the above condition (a) include DISPER BYK-102 [manufactured by BYK Japan Co., Ltd.], JONCRYL 57J [manufactured by BASF Japan Co., Ltd.], JONCRYL 63J [manufactured by BASF Japan Co., Ltd.], and JONCRYL 70J [manufactured by BASF Japan Co., Ltd.].

[0054] Examples of commercially available dispersants having an acidic group and / or a salt of an acidic group and satisfying the above condition (b) include Solsperse 46000 (manufactured by Nippon Lubrizol Co., Ltd.) and Solsperse 47000 (manufactured by Nippon Lubrizol Co., Ltd.).

[0055] Examples of commercially available dispersants having an acidic group and / or a salt of an acidic group and satisfying the above condition (c) include JONCRYL 57J [manufactured by BASF Japan Co., Ltd.], JONCRYL 63J [manufactured by BASF Japan Co., Ltd.], and JONCRYL 70J [manufactured by BASF Japan Co., Ltd.].

[0056] Examples of commercially available dispersants having an acidic group and / or a salt of an acidic group and satisfying the above condition (d) include ARON A-12SL [manufactured by Toagosei Co., Ltd.], ARON A-6016A [manufactured by Toagosei Co., Ltd.], ARON A-6017 [manufactured by Toagosei Co., Ltd.], ARON A-6020 [manufactured by Toagosei Co., Ltd.], and ARON A-6031 [manufactured by Toagosei Co., Ltd.]. The acrylic acid-sulfonic acid copolymer may be a metal salt (preferably a sodium salt) or an unneutralized type, preferably an unneutralized type.

[0057] Examples of commercially available dispersants having an acidic group and / or a salt of an acidic group and satisfying the above condition (e) include DISPER BYK-2010 (manufactured by BYK JAPAN Co., Ltd.) and FLOWLEN G-700AMP (manufactured by Kyoeisha Chemical Co., Ltd.).

[0058] When the ink composition of the embodiment of the present invention contains a dispersant, the content of the dispersant relative to the guanine pigment is not particularly limited, and is preferably in the range of 0.1 to 100% by mass, more preferably 1 to 50% by mass, and further preferably 5 to 30% by mass. When the content of the dispersant is within the above range, the dispersibility of the guanine pigment in the ink composition can be more stably maintained.

[0059] The ink composition according to the embodiment of the present invention contains a solvent. Examples of the solvent include water and organic solvents.

[0060] The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltered water, and distilled water.

[0061] The organic solvent is not particularly limited, and examples thereof include glycol ether solvents, glycol solvents, alcohol solvents, ketone solvents, ester solvents, and hydrocarbon solvents.

[0062] Examples of the glycol ether solvent include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol.

[0063] Examples of the glycol-based solvent include diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol.

[0064] Examples of the alcohol solvent include benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, isobutanol, 2-butanol, tert-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols.

[0065] Examples of the ketone solvent include acetone, dimethyl ketone, diethyl ketone, methyl ethyl ketone, and methyl isobutyl ketone.

[0066] Examples of the ester solvent include n-butyl formate, isobutyl formate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, ethyl propionate, n-butyl propionate, methyl butyrate, ethyl butyrate, methyl lactate, and ethyl lactate.

[0067] Examples of the hydrocarbon solvent include n-hexane, n-heptane, n-octane, isooctane, cyclohexane, methylcyclohexane, ethylcyclohexane, toluene, xylene, and ethylbenzene.

[0068] The solvent may be used alone or in combination of two or more.

[0069] The content of the solvent relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 10 to 90 mass %, and more preferably in the range of 30 to 80 mass %.

[0070] The ink composition according to the embodiment of the present invention may further contain a colorant.

[0071] By using the guanine pigment and the colorant in combination, a colored (half-tone color) ink composition having hiding properties can be obtained.

[0072] The colorant is not particularly limited as long as it is a dye or pigment that can be dissolved or dispersed in a solvent.

[0073] Examples of the dye include acid dyes, basic dyes, direct dyes, oil-soluble dyes, and disperse dyes.

[0074] Examples of acid dyes include new carmine (CI16255), tartrazine (CI19140), acid blue black 10B (CI20470), Gini green (CI42085), brilliant blue FCF (CI42090), acid violet 6B (CI42640), soluble blue (CI42755), naphthalene green (CI44025), eosin (CI45380), fluorescent pink (CI45410), erythrosine (CI45430), nigrosine (CI50420), and acid flavin (CI56205).

[0075] Examples of basic dyes include basic orange (CI11270), methyl violet FN (CI42535), crystal violet (CI42555), malachite green (CI42000), Victoria blue FB (CI44045), rhodamine B (CI45170), acridine orange NS (CI46005), and methylene blue B (CI52015).

[0076] Examples of direct dyes include Congo Red (CI22120), Direct Lake Blue 5B (CI24400), Purple BB (CI27905), Direct Deep Black EX (CI30235), Kayalus Black G conc (CI35225), Direct Fast Black G (CI35255), and Phthalocyanine Blue (CI74180).

[0077] Examples of the oil-soluble dye include CISolvent Black 7, CISolvent Black 123, CISolvent Blue 2, CISolvent Blue 25, CISolvent Blue 55, CISolvent Blue 70, CISolvent Red 8, CISolvent Red 49, CISolvent Red 100, CISolvent Violet 8, CISolvent Violet 21, CISolvent Green 3, CISolvent Yellow 21, CISolvent Yellow 44, CISolvent Yellow 61, and CISolvent Orange 37.

[0078] Examples of the disperse dye include CI Disperse Yellow 82, CI Disperse Yellow 3, CI Disperse Yellow 54, CI Disperse Red 191, CI Disperse Red 60, and CI Disperse Violet 57.

[0079] Examples of the pigment include inorganic pigments, organic pigments, bright pigments, fluorescent pigments, and light-storing pigments.

[0080] Examples of the inorganic pigment include carbon black, iron black, yellow iron oxide, red iron oxide, and ultramarine blue.

[0081] Examples of organic pigments include azo pigments, phthalocyanine pigments, quinacridone pigments, perylene pigments, perylone pigments, isoindolinone pigments, isoindolinone pigments, dioxazine pigments, thioindigo pigments, anthraquinone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, reducing pigments, indigo pigments, phthalone pigments, methine / azomethine pigments, and metal complex pigments.

[0082] As the pigment, a water-dispersible pigment or the like which is obtained by finely and stably dispersing the pigment in an aqueous medium using a surfactant and / or a resin in advance may be used.

[0083] Examples of the resin in which the pigment is dispersed include polyamide, urethane resin, polyester, epoxy resin, melamine resin, phenolic resin, silicone resin, polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, polystyrene, acrylic resin, maleic acid resin, gum arabic, cellulose, dextran, casein and derivatives thereof, copolymers of the above resins, and the like.

[0084] Examples of bright pigments include metallic luster pigments obtained by coating the surface of a core material such as a glass sheet with gold, silver, or the like, natural mica, synthetic mica, pearlescent pigments obtained by coating the surface of a core material such as flaky aluminum oxide with a metal oxide such as titanium oxide, cholesteric liquid crystal type pigments, metal powder pigments, metallic pigments obtained by peeling off a metal vapor-deposited film of aluminum or the like formed on a substrate such as a film, metallic pigments obtained by forming a metal vapor-deposited film of aluminum or the like on a colorless transparent film or a colored transparent film and subjecting the resulting film to powder treatment, and the like.

[0085] Examples of the fluorescent pigment include fluorescent pigments in the form of synthetic resin fine particles obtained by solid-solutionizing various fluorescent dyes in a resin matrix.

[0086] As a luminescent pigment, any general luminescent pigment can be used as long as it has the property of absorbing and storing light from the sun and / or electric lights, and slowly releasing the light in the dark to emit light (this is called afterglow), and examples thereof include luminescent pigments of CaS / Bi series, CaSrS / Bi series, ZnS / Cu series, ZnCdS / Cu series, SrAl2O4 / rare earth metal series, etc.

[0087] The coloring agent may be used alone or in combination of two or more.

[0088] When the above-mentioned pigment is used as a colorant, a pigment dispersant may be used as needed. Examples of the pigment dispersant include anionic and nonionic surfactants, anionic polymers such as polyacrylic acid and styrene-acrylic acid, and nonionic polymers such as PVP and PVA.

[0089] The dye or pigment mentioned above can be used as it is, or microcapsule pigments formed by encapsulating the dye or pigment in microcapsules and / or resin particles containing the dye or pigment can be used as colorants. In particular, the dye or pigment is isolated and protected from the external environment by being encapsulated in the microcapsules, which can improve the water resistance and light resistance of the encapsulated material.

[0090] The microencapsulated pigment can be formed by encapsulating a coloring body obtained by dissolving or dispersing the above-mentioned dye or pigment in an oil medium in microcapsules.

[0091] Examples of the oily medium include esters such as monobasic acid esters, dibasic acid monoesters, dibasic acid diesters, partial esters or full esters of polyols, aromatic hydrocarbons such as alkylbenzenes and alkylnaphthalenes, higher alcohols, ketones, and ethers.

[0092] The oily medium may be used alone or in combination of two or more.

[0093] The microencapsulation of microcapsule pigments includes conventionally known isocyanate-based interfacial polymerization methods, melamine-formaldehyde-based in-situ polymerization methods, liquid solidification coating methods, phase separation methods from aqueous solutions, phase separation methods from organic solvents, melt dispersion cooling methods, air suspension coating methods, spray drying methods, etc., which are appropriately selected according to the application. As the material of the capsule, for example, epoxy resin, urea resin, urethane resin, isocyanate resin, etc. can be exemplified.

[0094] Depending on the purpose, a secondary resin film may be further provided on the surface of the microcapsule to impart durability or to modify the surface properties for practical use.

[0095] Examples of the resin particles containing a dye include resin particles in which the above-mentioned dye is uniformly dissolved or dispersed in the resin particles, and resin particles in which the dye is dyed and attached to the resin particles.

[0096] The resin constituting the resin particles is not particularly limited, but a thermosetting resin is preferred.

[0097] Thermosetting resins are preferred because they are superior in solvent resistance and heat resistance compared to thermoplastic resins, and also have superior resistance to migration of dyes contained therein, thereby suppressing elution of dyes from the resin.

[0098] Among thermosetting resins, guanamine resins or melamine resins are preferred because they can further suppress the elution of the dye.

[0099] Examples of the pigment-containing resin particles include resin particles in which the above-mentioned pigment is uniformly dispersed in resin particles and resin particles in which the surfaces of the resin particles are coated with the pigment.

[0100] The resin constituting the resin particles is not particularly limited, and general-purpose resins can be used.

[0101] The resin particles can be produced by a pulverization method, a spray drying method, or a polymerization method in which polymerization is performed in an aqueous or oily medium in the presence of a dye or a pigment. Examples of the polymerization method include suspension polymerization, suspension polycondensation, dispersion polymerization, and emulsion polymerization.

[0102] The shape of the resin particles is not particularly limited, and spherical shapes such as true spheres, ellipsoids, and substantially spheres, polygonal shapes, and flat shapes can be used. Among them, spherical resin particles are preferably used.

[0103] In the case where the colorant is a dye or pigment, or the above-mentioned microcapsule pigment or resin particles, the content of the colorant relative to the total mass of the ink composition is not particularly limited, preferably 0.01 to 50% by mass, more preferably in the range of 0.1 to 30% by mass. If the content of the colorant is greater than 50% by mass, the ink discharge property of the writing instrument containing the ink composition is easily reduced, and poor writing such as flying white and flying lines is easily produced. On the other hand, when the content of the colorant is less than 0.01% by mass, it is difficult to obtain an appropriate handwriting concentration as a writing instrument.

[0104] As coloring agents, color-changing materials such as thermochromic materials that change color due to temperature changes and / or photochromic materials that change color due to light irradiation can also be used. These color changes can be reversible or irreversible. From the perspective of being able to repeatedly reflect color changes due to temperature changes or light irradiation, reversible thermochromic materials and / or reversible photochromic materials are preferred.

[0105] Examples of reversible thermochromic materials include reversible thermochromic compositions comprising (i) an electron donating color-forming organic compound, (ii) an electron accepting compound, and (iii) a reaction medium that determines the temperature at which the color-forming reaction of the components (i) and (ii) occurs.

[0106] As a reversible thermochromic composition, a heat-decolorizable composition having a small hysteresis width (ΔH) characteristic (ΔH=1-7°C) as described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc. can be used. The heat-decolorizable composition means that the color is removed by heating and the color is developed by cooling. The reversible thermochromic composition changes color around a specified temperature (color change point) as a boundary, and is in a decolorized state in a temperature range above the color change point on the high temperature side, and in a color development state in a temperature range below the color change point on the low temperature side. Only a specific one of the two states exists in the normal temperature range, and the other state is maintained during the application of heat or cold heat required to embody the state, but if heat or cold heat is no longer applied, it returns to the state presented in the normal temperature range.

[0107] As the reversible thermochromic composition, a heat-decolorizing type reversible thermochromic composition having a large hysteresis width (ΔH=8 to 80° C.) described in Japanese Patent Publication No. 4-17154, Japanese Patent Application Laid-Open No. 7-179777, Japanese Patent Application Laid-Open No. 7-33997, Japanese Patent Application Laid-Open No. 8-39936, Japanese Patent Application Laid-Open No. 2005-1369, etc. can also be used. The heat-decolorizing type means that the color is removed by heating and the color is developed by cooling. The reversible thermochromic composition changes color along a path whose shape is greatly different in the following cases, where the temperature is increased from the lower temperature side of the color change temperature range and conversely decreased from the higher temperature side of the color change temperature range. The color development state in the temperature range below the complete color development temperature t1 or the color removal state in the high temperature range above the complete color removal temperature t4 has color memory in a specific temperature range [the temperature range between the color development start temperature t2 and the color removal start temperature t3 (the actual two-phase maintenance temperature range)].

[0108] It should be noted that, when the above-mentioned reversible thermochromic composition with color memory is applied in the embodiment of the present invention, as a reversible thermochromic composition, specifically, by specifying the complete color development temperature t1 to a temperature that can only be obtained in a freezer, a cold place, etc., and specifying the complete decolorization temperature t4 to a range of temperatures obtained by friction heat generated by a friction body and a temperature obtained by a close-fitting heating body such as a hair dryer, and specifying the ΔH value to 40 to 100°C, the function of maintaining the color presented in normal conditions (daily life temperature range) can be effectively exerted.

[0109] The temperature that can be obtained only in a freezer room, a cold place, etc. is in the range of -50 to 0°C, preferably -40 to -5°C, and more preferably -30 to -10°C.

[0110] The temperature obtained by a close-fitting heating body such as a hair dryer is in the range of 50 to 95°C, preferably 50 to 90°C, and more preferably 60 to 80°C.

[0111] As the reversible thermochromic composition, a heat-developing type reversible thermochromic composition using gallic acid esters described in Japanese Patent Publication No. 51-44706 and Japanese Patent Application Laid-Open No. 2003-253149 can be used. The heat-developing type is a composition that develops color by heating and loses color by cooling.

[0112] The reversible thermochromic composition is a phase-soluble body with the above-mentioned (one), (two), and (three) components as essential components, and the ratio of each component is affected by the concentration, color change temperature, color change form and the type of each component. The component ratio for obtaining the desired characteristics is usually in the following range: relative to the (one) component 1, the (two) component is 0.1 to 100, preferably 0.1 to 50, more preferably 0.5 to 20, and the (three) component is 1 to 800, preferably 5 to 200, and more preferably 10 to 100 (the above ratios are all parts by mass).

[0113] Examples of reversible photochromic materials include conventionally known photochromic compounds such as spirooxazine derivatives, spiropyran derivatives, and naphthopyran derivatives, which develop color when irradiated with sunlight, ultraviolet light, or blue light with a peak emission wavelength in the range of 400 to 495 nm and lose color when the irradiation is stopped.

[0114] Examples of the spirooxazine derivatives include conventionally known indolespirobenzoxazine compounds, indolespironaphthooxazine compounds, indolespirophenanthrooxazine compounds, indolespiroquinooxazine compounds, and the like.

[0115] Examples of photochromic compounds having light memory properties (color memory photochromic properties) include conventionally known fulgide derivatives and diarylethene derivatives.

[0116] Furthermore, as the reversible photochromic material, a reversible photochromic composition obtained by dissolving the above-mentioned photochromic compound in various oligomers may be used.

[0117] Examples of the oligomer include styrene-based oligomers, acrylic-based oligomers, terpene-based oligomers, and terpene-phenolic-based oligomers.

[0118] Examples of the styrene-based oligomer include low molecular weight polystyrene, styrene-α-methylstyrene copolymers, α-methylstyrene polymers, and α-methylstyrene-vinyltoluene copolymers.

[0119] Examples of the acrylic oligomer include acrylic acid ester copolymers and the like.

[0120] Examples of the terpene-based oligomers include α-pinene polymers, β-pinene polymers, and d-limonene polymers.

[0121] Examples of the terpene phenolic oligomer include α-pinene-phenol copolymers and the like.

[0122] By dissolving the photochromic compound in various oligomers, the light resistance of the photochromic compound can be improved, the color development concentration can be increased, and the color change sensitivity can be adjusted.

[0123] The oligomers may be used alone or in combination of two or more.

[0124] The above-mentioned reversible thermochromic composition or reversible photochromic composition can be effectively used as it is, or it can be encapsulated in microcapsules to form reversible thermochromic microcapsule pigments or reversible photochromic microcapsule pigments, or dispersed in thermoplastic resins or thermosetting resins to form reversible thermochromic resin particles or reversible photochromic resin particles, to be used as a colorant used in the embodiments of the present invention.

[0125] In addition, below, the reversible thermochromic microcapsule pigment and the reversible photochromic microcapsule pigment may be expressed as "microcapsule pigment", and the reversible thermochromic resin particles and the reversible photochromic resin particles may be expressed as "resin particles".

[0126] The reversible thermochromic composition or the reversible photochromic composition is preferably encapsulated in microcapsules to form a reversible thermochromic microcapsule pigment or a reversible photochromic microcapsule pigment. This is because the microcapsules can form chemically and physically stable microcapsule pigments, and the reversible thermochromic composition or the reversible photochromic composition can maintain the same composition and exert the same effect under various use conditions.

[0127] Microencapsulation includes conventionally known isocyanate-based interfacial polymerization methods, melamine-formaldehyde-based in-situ polymerization methods, liquid solidification coating methods, phase separation methods from aqueous solutions, phase separation methods from organic solvents, melt dispersion cooling methods, gas suspension coating methods, spray drying methods, etc., which can be appropriately selected according to the application. As the material of the capsule, for example, epoxy resin, urea resin, urethane resin, isocyanate resin, etc. can be exemplified.

[0128] Depending on the purpose, a secondary resin film may be further provided on the surface of the microcapsule to impart durability or to modify the surface properties for practical use.

[0129] The microcapsule pigment preferably has a mass ratio of inner substance to wall membrane of 7:1 to 1:1. When the mass ratio of inner substance to wall membrane is within the above range, the color concentration and brightness during color development can be prevented from decreasing. More preferably, the mass ratio of inner substance to wall membrane is 6:1 to 1:1.

[0130] A microcapsule pigment that exhibits a color change behavior from colored (1) to colored (2) can also be prepared by mixing a non-color-changing colorant such as a common dye or pigment into the microcapsule pigment.

[0131] In the case where the colorant is the above-mentioned color-changing material, the content of the colorant relative to the total mass of the ink composition is not particularly limited, and is preferably 5 to 40% by mass, more preferably 10 to 40% by mass, and further preferably in the range of 15 to 35% by mass. If the content of the colorant is greater than 40% by mass, the ink discharge property of the writing instrument containing the ink composition is reduced, and poor writing such as flying white and flying lines is likely to occur. On the other hand, when the content of the colorant is less than 5% by mass, it is difficult to obtain the appropriate color change and handwriting concentration as a writing instrument, and it is difficult to fully meet the color change function.

[0132] The average particle size of the reversible thermochromic microcapsule pigment or resin particles, or the reversible photochromic microcapsule pigment or resin particles is preferably 0.01 to 5 μm, more preferably 0.1 to 3 μm, and further preferably 0.5 to 3 μm. If the average particle size of the above-mentioned microcapsule pigment or resin particles is greater than 5 μm, it is difficult to obtain good ink discharge properties when used in writing instruments. On the other hand, when the average particle size of the above-mentioned microcapsule pigment or resin particles is less than 0.01 μm, it is difficult to show high-concentration color development.

[0133] It should be noted that the average particle size is measured by using image analysis particle size distribution measurement software [Mountech Co., Ltd., product name: Mac-View] to determine the area of ​​the particles, and calculate the projected area equivalent circle diameter (Heywood diameter) based on the area of ​​the particle area, and the value measured is the average particle size of the particles equivalent to a sphere of equal volume based on this value.

[0134] When the particle size of all or most particles is larger than 0.2 μm, the particle size distribution can be measured as the average particle size of particles equivalent to a sphere of equal volume by the Coulter method using a particle size distribution analyzer [Beckman Coulter Co., Ltd., product name: Multisizer 4e].

[0135] Furthermore, the volume-based particle size and average particle size may be measured using a calibrated laser diffraction / scattering particle size distribution measuring apparatus [manufactured by Horiba, Ltd., product name: LA-300] based on the values ​​measured using the above-mentioned software or a measuring apparatus utilizing the Coulter method.

[0136] The ink composition according to the embodiment of the present invention may contain, in addition to the above-mentioned essential components, any components within a range that does not impair the effects of the embodiment of the present invention.

[0137] A thickener may be added to the ink composition according to the embodiment of the present invention to suppress aggregation and sedimentation of the pigment, thereby making the ink composition have good stability over time.

[0138] As the thickener, a conventionally known substance can be used, and it is preferable to use a substance that can impart shear-thinning properties to the ink composition (shear-thinning property-imparting agent).

[0139] The ink composition using the shear-thinning agent does not flow easily due to its high viscosity when it is in a static state or when the stress is low, but it easily becomes less viscous when stress is applied from the outside. Therefore, when not writing, it is possible to prevent the ink from leaking out or preventing the ink from separating and flowing back, and when writing, it is easy to make the ink discharge from the pen tip stable.

[0140] In particular, when such an ink composition is used in a writing instrument (ballpoint pen) having a ballpoint pen tip as a pen tip, the ink composition is stably held in the ballpoint pen because it has a high viscosity when it is left at rest without applying shear stress. Therefore, when writing, a strong shear stress is applied to the ink composition by the rotation of the ball, and the ink composition near the ball is more likely to have a low viscosity, thereby achieving good ink discharge stability.

[0141] When the ink composition according to the embodiment of the present invention contains a thickener, the content of the thickener relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.1 to 20% by mass.

[0142] Examples of shear-thinning agents include water-soluble polysaccharides, polymers having a molecular weight of 100,000 to 150,000 and containing alkyl esters of methacrylic acid as a main component, crosslinked poly-N-vinylcarboxylic acid amides, benzylidene sorbitol and its derivatives, benzylidene xylitol and its derivatives, alkali thickening type acrylic resins, crosslinked acrylic polymers, inorganic fine particles, nonionic surfactants having an HLB value of 8 to 12, metal salts or amine salts of dialkyl sulfosuccinic acid, and the like.

[0143] The shear-thinning agent may be used alone or in combination of two or more.

[0144] Examples of water-soluble polysaccharides include xanthan gum, welan gum, zetashi gum, diutan gum, Macrophomopsis gum, succinoglycan (average molecular weight of about 1 million to 8 million) which is an organic acid-modified heteropolysaccharide whose structural monosaccharides are glucose and galactose, guar gum, locust bean gum and its derivatives, hydroxyethyl cellulose, alginic acid alkyl esters, glucomannan, agar, carrageenan and other carbohydrates having gelling ability extracted from seaweed.

[0145] The ink composition of the embodiment of the present invention may be mixed with a polymer coagulant. The polymer coagulant produces a slow cross-linking effect between pigments, and the pigments form loose aggregates through the polymer coagulant, thereby inhibiting direct aggregation of pigments and improving the dispersion stability of the pigments.

[0146] The polymer coagulant has an effect of suppressing the precipitation of the pigment in the ink composition in the capillary gaps of the ink storage body provided in the marking pen described below. Therefore, the ink composition containing the polymer coagulant is preferably used in the marking pen provided with the ink storage body.

[0147] The polymer coagulant may be used together with the above-mentioned dispersant. When both the polymer coagulant and the dispersant are used together, the dispersibility of the loose aggregates formed by the polymer coagulant can be improved.

[0148] When the ink composition according to the embodiment of the present invention contains a polymer flocculant, the content of the polymer flocculant relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.05 to 1% by mass.

[0149] Examples of the polymer coagulant include polyvinyl pyrrolidone, polyethylene oxide, and water-soluble polysaccharides.

[0150] Examples of the water-soluble polysaccharides include tragacanth gum, guar gum, pullulan, cyclodextrin, and water-soluble cellulose derivatives.

[0151] Examples of the water-soluble cellulose derivative include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose.

[0152] A surfactant may be added to the ink composition according to the embodiment of the present invention to adjust the surface tension of the ink composition to an appropriate range.

[0153] Surfactants for adjusting the surface tension include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants and the like, and any of them can be preferably used.

[0154] Examples of the surfactant for adjusting the surface tension include silicone-based surfactants, surfactants having an acetylene bond in the structure, and fluorine-based surfactants. These surfactants are appropriately selected depending on the components and application of the ink composition.

[0155] When the ink composition according to an embodiment of the present invention contains a surfactant for adjusting surface tension, the content of the surfactant for adjusting surface tension relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.01 to 2 mass %, and more preferably in the range of 0.05 to 1 mass %.

[0156] The ink composition according to the embodiment of the present invention may be blended with a pH adjuster to adjust the pH of the ink composition to an appropriate range. As the pH adjuster, various acidic substances or alkaline substances may be used.

[0157] Examples of the acidic substance include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, lactic acid, citric acid, tartaric acid, and malic acid.

[0158] Examples of the alkaline substance include ammonia, sodium carbonate, sodium hydrogen phosphate, potassium hydrogen phosphate, sodium hydroxide, potassium hydroxide, sodium acetate, and the like. In addition, alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine can also be used.

[0159] When the ink composition according to the embodiment of the present invention contains a pH adjuster, the content of the pH adjuster relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 0.1 to 5 mass %, more preferably 0.5 to 2 mass %.

[0160] When the solvent used in the embodiment of the present invention is water, a water-soluble organic solvent having compatibility with water may be added to suppress evaporation of water from the pen tip of the writing instrument.

[0161] Examples of the water-soluble organic solvent include ethanol, propanol, butanol, glycerol, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thioethylene 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.

[0162] The water-soluble organic solvent may be used alone or in combination of two or more.

[0163] In the case where the ink composition of an embodiment of the present invention includes a water-soluble organic solvent, the content of the water-soluble organic solvent relative to the total mass of the ink composition is not particularly limited, preferably 1 to 40% by mass, more preferably 5 to 30% by mass, and further preferably in the range of 10 to 25% by mass. If the content of the water-soluble organic solvent is greater than 40% by mass, the ink viscosity tends to increase, and the ink discharge of the writing instrument containing the ink composition is reduced, and poor writing such as flying white and flying lines is likely to occur. On the other hand, when the content of the water-soluble organic solvent is less than 1% by mass, there is a lack of the effect of suppressing water evaporation.

[0164] The ink composition of the embodiment of the present invention may be formulated with a water-soluble resin such as alkyd resin, acrylic resin, styrene-maleic acid copolymer, cellulose derivative, polyvinyl pyrrolidone, polyvinyl alcohol, dextrin, etc., to impart adhesion and tackiness to the paper surface.

[0165] The water-soluble resins may be used alone or in combination of two or more.

[0166] When the ink composition according to the embodiment of the present invention contains a water-soluble resin, the content of the water-soluble resin relative to the total mass of the ink composition is not particularly limited, but is preferably in the range of 1 to 30 mass %, more preferably 1 to 10 mass %.

[0167] The ink composition according to the embodiment of the present invention may further contain various additives as needed.

[0168] Examples of the additive include rust preventives, corrosion inhibitors or mildew preventives, bubble absorbers, wetting agents, defoamers, and specific gravity adjusters.

[0169] Examples of the rust inhibitor include dicyclohexylamine nitrite, diisopropylamine nitrite, and saponin.

[0170] Examples of the preservative or antifungal agent include carbolic acid, sodium salt of 1,2-benzothiazoline-3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl p-hydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine.

[0171] Examples of the bubble absorbent include ascorbic acids, erythorbic acids, α-tocopherol, catechins, synthetic polyphenols, kojic acid, alkylhydroxylamines, oxime derivatives, α-glucosylrutin, α-lipoic acid, phosphonates, phosphinates, sulfites, sulfoxylates, dithionites, thiosulfates, and thiourea dioxide.

[0172] Examples of the wetting agent include reduced or non-reduced starch hydrolyzates, disaccharides such as trehalose, oligosaccharides, sucrose, cyclodextrin, glucose, dextrin, sorbitol, mannitol, sodium pyrophosphate, and the like.

[0173] When the ink composition according to the embodiment of the present invention is contained in a writing instrument (ballpoint pen) having a ballpoint pen tip, a lubricant may be blended in the ink composition.

[0174] The lubricant can improve the lubricity of the ball holder provided inside the nib body and the ball provided at the front end of the nib body, thereby easily preventing the wear of the ball holder and improving the writing feel.

[0175] Examples of the lubricant include higher fatty acids such as oleic acid, nonionic surfactants having a long-chain alkyl group, and polyether-modified silicone oil.

[0176] The method for producing the ink composition according to the embodiment of the present invention is not particularly limited, and any conventionally known method may be used.

[0177] Specifically, the ink composition can be produced by stirring a mixture containing the above-mentioned components with various stirrers such as a propeller stirrer, a homodisperser, or a homomixer, or by dispersing the mixture with various dispersers such as a bead mill.

[0178] In the ink composition of the embodiment of the present invention, the viscosity characteristics are not particularly limited. For example, an ink composition with high shear thinning properties (gel ink), an ink composition with low viscosity and low shear thinning properties, an ink composition with low viscosity and non-shear thinning properties (Newtonian fluid ink) and the like can be used. The guanine pigment used in the embodiment of the present invention has excellent dispersion stability, and even if the ink composition is low viscosity, the pigment is not easy to settle, so as the ink composition of the embodiment of the present invention, a low viscosity ink composition is preferably used.

[0179] When the ink composition of the embodiment of the present invention is used in a ballpoint pen, the ink composition is subjected to rotation at a speed of 1 rpm (shear rate of 3.84 sec －1 ), the viscosity of the ink composition is preferably in the following range from the perspective of making the dispersion stability of the pigment more stable. Specifically, the viscosity of the ink composition in this case is preferably in the range of 1 to 2000 mPa·s, more preferably in the range of 10 to 1500 mPa·s, and even more preferably in the range of 100 to 1000 mPa·s.

[0180] In addition, at 20°C, the rotation speed was 100 rpm (shear speed 384 sec －1), the viscosity is preferably in the following range from the aspect of enabling good ink discharge from the tip of a ballpoint pen. Specifically, the viscosity of the ink composition in this case is preferably in the range of 1 to 200 mPa·s, more preferably in the range of 10 to 100 mPa·s, and even more preferably in the range of 20 to 50 mPa·s.

[0181] When the viscosity of the ink composition is within the above range, the dispersion stability of the pigment and the fluidity of the ink in the mechanism of the ballpoint pen can be maintained at a high level.

[0182] The viscosity of the ink composition was measured using a rheometer [manufactured by TA Instruments, product name: Discovery HR-2, cone and plate (diameter 40 mm, angle 1°)], in which the ink was placed in an environment of 20°C and rotated at a speed of 1 rpm (shear rate 3.84 sec －1 ) or rotation speed 100rpm (shear speed 384sec －1 ) under the conditions of

[0183] When the ink composition of the embodiment of the present invention is used for a marker pen, the viscosity of the ink composition is preferably in the following range from the perspective of maintaining the fluidity of the ink and the dispersion stability of the pigment at a high level when measured under an environment of 20°C and a rotation speed of 50 rpm. Specifically, the viscosity of the ink composition in this case is preferably in the range of 1 to 30 mPa·s, more preferably 1 to 20 mPa·s, and even more preferably 1 to 10 mPa·s.

[0184] The viscosity of the ink composition is a value measured by placing the ink composition in an environment of 20° C. using an E-type rotational viscometer [manufactured by Toki Sangyo Co., Ltd., product name: RE-85L, cone rotor: standard type (1°34′×R24)].

[0185] When the ink composition according to the embodiment of the present invention is used in a ballpoint pen or a marker pen, the pH thereof is preferably in the range of 6 to 10, more preferably 7 to 9. When the pH is in the above range, excessive increase in viscosity and deterioration of the ink composition can be suppressed.

[0186] The pH of the ink composition is a value measured by placing the ink in an environment of 20° C. using a pH meter [manufactured by DKK-TOA Co., Ltd., product name: IM-40S].

[0187] When the ink composition of the embodiment of the present invention is used in a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited, and the ink composition can be used by filling a ballpoint pen refill or a ballpoint pen having a ballpoint pen tip and an ink filling mechanism.

[0188] The ballpoint pen tip includes a pen tip body and a ball at the front end of the pen tip body. Examples of the ballpoint pen tip include a pen tip having a ball held in a ball holding portion formed by pressing and deforming the pen tip body formed of a metal tube from the outer surface to the inner side, a pen tip having a ball held in a ball holding portion formed by cutting a pen tip body formed of a metal material using a drill, a pen tip having a resin ball holder provided inside a metal or plastic pen tip body, or a pen tip having a ball held by the above pen tip urged forward by a spring.

[0189] The material of the nib body and the ball is not particularly limited, and examples thereof include cemented carbide (superhard), stainless steel, ruby, ceramic, resin, rubber, etc. Furthermore, the ball may be subjected to surface treatment such as DLC coating.

[0190] The diameter of the beads is usually in the range of 0.2 to 3 mm, preferably 0.2 to 2 mm, more preferably 0.2 to 1.5 mm, and even more preferably 0.2 to 1 mm.

[0191] As the ink filling mechanism, for example, an ink container that can be directly filled with ink can be exemplified.

[0192] As the ink container, for example, a molded body formed of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a metal tubular body is used.

[0193] By connecting the ballpoint pen tip directly or via a connecting member to the ink container and directly filling the ink container with ink, a ballpoint pen refill (hereinafter sometimes referred to as "refill") can be formed. By accommodating the refill in the pen barrel, a ballpoint pen can be formed.

[0194] The ink repellent reverse fluid is filled at the rear end of the ink filled in the ink container. As the ink repellent reverse fluid, a liquid plug or a solid plug can be cited.

[0195] The liquid plug is formed of a non-volatile liquid and / or a hardly volatile liquid, for example, vaseline, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, oligomers or co-oligomers of α-olefin, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, etc.

[0196] The nonvolatile liquid and / or the low-volatile liquid may be used alone or in combination of two or more.

[0197] It is preferred to add a thickener to the nonvolatile liquid and / or the low-volatile liquid to increase the viscosity to an appropriate level.

[0198] Examples of thickeners include: clay-based thickeners such as silica with a hydrophobic surface treatment, microparticle silica with a methylated surface treatment, aluminum silicate, expanded mica, hydrophobic bentonite and 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 amide, amide-modified polyethylene wax, hydrogenated castor oil, and fatty acid dextrin; cellulose-based compounds, etc.

[0199] Examples of the solid plug include a solid plug made of polyethylene, polypropylene, polymethylpentene, and the like.

[0200] As the ink repellent backflow fluid, the above-mentioned liquid plug and solid plug may be used in combination.

[0201] In addition, the pen barrel itself can also be used as the ink filling mechanism, ink can be directly filled into the pen barrel, and a ballpoint pen tip can be attached to the front end of the pen barrel, thereby forming a ballpoint pen with a ballpoint pen tip and an ink filling mechanism.

[0202] When the ink filled in the ink filling mechanism has a low viscosity, the ballpoint pen including the ballpoint pen tip and the ink filling mechanism may further include an ink supply mechanism for supplying the ink filled in the ink filling mechanism to the pen tip.

[0203] The ink supply mechanism is not particularly limited, and examples thereof include the following mechanisms: (1) a mechanism having an ink guide core formed of a fiber bundle as an ink flow regulator, and supplying ink to the pen tip in a manner of sandwiching the ink flow regulator; (2) a mechanism having a comb-groove-shaped ink flow regulator, and supplying ink to the pen tip in a manner of sandwiching the ink flow regulator; (3) a mechanism in which a plurality of disk bodies are arranged side by side with comb-groove-shaped intervals, a slit-shaped ink guide groove that runs longitudinally through the disk body in the axial direction and a ventilation groove that is larger than the width of the groove, an ink guide core for guiding ink from the ink filling mechanism to the pen tip is arranged at the axis center to form a pen core, and ink is supplied to the pen tip via the pen core.

[0204] The material of the pen core is not particularly limited as long as it is a synthetic resin that can be injection molded into a comb-shaped structure with multiple disc bodies. Examples of synthetic resins include general-purpose polycarbonate, polypropylene, polyethylene, acrylonitrile-butadiene-styrene copolymer (ABS resin), etc. In particular, acrylonitrile-butadiene-styrene copolymer (ABS resin) is preferably used because of its high moldability and ease of obtaining pen core performance.

[0205] When the ballpoint pen is provided with the above-mentioned ink supply mechanism, an ink storage body that can be filled with ink may be used as the ink filling mechanism in addition to the above-mentioned ink container and pen body.

[0206] The ink storage body is a fiber bundle formed by bundling crimped fibers in the longitudinal direction, and is configured to be built in a covering body such as a plastic rod or a film, and the porosity is adjusted to a range of approximately 40 to 90%.

[0207] In addition, an ink occlusion body impregnated with ink may be accommodated in an ink container, an ink supply mechanism may be provided at the front end of the ink container in a manner connected to the ink occlusion body, and a ballpoint pen tip may be directly connected to the ink supply mechanism or via a connecting member in a manner connected to the ink supply mechanism, thereby forming a ballpoint pen refill including a ballpoint pen tip, an ink filling mechanism, and an ink supply mechanism. Alternatively, an ink occlusion body impregnated with ink may be accommodated in an ink container, an ink supply mechanism may be provided inside the ink container in a manner connected to the ink occlusion body, and a ballpoint pen tip may be directly connected to the ink container in a manner connected to the ink supply mechanism or via a connecting member, thereby forming a ballpoint pen refill.

[0208] As the structure of a ballpoint pen that contains the ink composition of an embodiment of the present invention, specifically, the following ballpoint pens can be exemplified: (1) a ballpoint pen having an ink container filled with ink in a pen body, a ballpoint pen tip connected to the ink container directly or via a connecting member, and an ink backflow-proof fluid filled on the end surface of the ink; (2) a ballpoint pen having a mechanism in which the pen body is directly filled with ink, a comb-groove-shaped ink flow regulator or an ink guide core composed of a fiber bundle or the like is sandwiched as an ink flow regulator to supply ink to the pen tip; (3) a ballpoint pen having a mechanism in which the pen body is directly filled with ink, and ink is supplied to the pen tip via the above-mentioned pen core; (4) a ballpoint pen having a mechanism in which an ink storage body composed of a fiber bundle impregnated with ink is accommodated in the pen body, and an ink guide core composed of a fiber bundle or the like is sandwiched as an ink flow regulator to supply ink to the pen tip.

[0209] When the ink composition according to the embodiment of the present invention is used in a marking pen, the structure and shape of the marking pen itself are not particularly limited, and the composition may be used by filling a marking pen refill or a marking pen having a marking pen tip and an ink filling mechanism.

[0210] As the marking pen tip, for example, there can be shown: a porous member with interconnected pores in the porosity range of about 30 to 70% selected from resin processed bodies of fibers, fusion processed bodies of heat-soluble fibers, felt bodies, etc. that have been commonly used; or an extruded body of a synthetic resin having a plurality of ink outlet holes extending in the axial direction, etc., one end of which is processed into a shape corresponding to the purpose, such as a shell shape, a rectangular shape, a chisel shape, etc. for practical use.

[0211] As the ink filling mechanism, for example, an ink storage body that can be filled with ink can be exemplified.

[0212] The ink storage body is a fiber bundle formed by bundling crimped fibers in the longitudinal direction, and is configured to be built in a covering body such as a plastic rod or a film, and the porosity is adjusted to a range of approximately 40 to 90%.

[0213] The marking pen can be formed by accommodating an ink storage body impregnated with ink in a pen body, and connecting the marking pen tip to the pen body directly or via a connecting member so as to be connected to the ink storage body.

[0214] In addition, by accommodating an ink occlusion body impregnated with ink in the ink container, and connecting the marker pen tip to the ink container directly or via a connecting member in a manner connected to the ink occlusion body, a marker pen refill (hereinafter sometimes referred to as a "refill") can be formed. By accommodating the refill in the pen holder, a marker pen can be formed.

[0215] As the ink container, for example, a molded body formed of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a metal tubular body is used.

[0216] The marking pen including the marking pen tip and the ink filling mechanism may further include an ink supply mechanism for supplying the ink composition filled in the ink filling mechanism to the pen tip.

[0217] The ink supply mechanism is not particularly limited, and for example, in addition to the ink supply mechanism of the above-mentioned ballpoint pen, there can be listed: (4) an ink flow regulator based on a valve mechanism, which supplies ink to the pen tip by opening the valve, etc.

[0218] The valve mechanism may use a conventionally used pump-type valve mechanism that is opened by pressing the pen tip, and is preferably set to a spring pressure that can be pressed open by writing pressure.

[0219] When the marking pen has an ink supply mechanism, in addition to using the above-mentioned ink occlusion body, an ink container that can be directly filled with ink can be used as the ink filling mechanism. In addition, the pen itself can be used as the ink filling mechanism to directly fill the ink.

[0220] In addition, an ink occlusion body impregnated with ink may be contained in an ink container, an ink supply mechanism may be provided at the front end of the ink container in a manner connected to the ink occlusion body, and a marker pen tip may be connected to the ink supply mechanism directly or via a connecting member in a manner connected to the ink supply mechanism, thereby forming a marker pen refill having a marker pen tip, an ink filling mechanism, and an ink supply mechanism. Alternatively, an ink occlusion body impregnated with ink may be contained in an ink container, an ink supply mechanism may be provided inside the ink container in a manner connected to the ink occlusion body, and a marker pen tip may be connected to the ink container directly or via a connecting member in a manner connected to the ink supply mechanism, thereby forming a marker pen refill.

[0221] As the structure of the marking pen that accommodates the ink composition of the embodiment of the present invention, specifically, the following marking pens can be exemplified: (1) a marking pen in which an ink occluding body composed of a fiber bundle impregnated with ink is accommodated in a pen body, and a marking pen head composed of a fiber processed body or a resin molded body with a capillary gap is connected to the pen body directly or via a connecting member in such a way that the ink occluding body and the pen head are connected; (2) a marking pen having the following mechanism: the pen body is directly filled with ink, a comb-shaped ink flow regulating body or an ink guide core composed of a fiber bundle or the like is sandwiched as an ink flow regulating body to supply ink to the pen body; (3) A marking pen having the following mechanisms: a pen barrel is directly filled with ink, and the ink is supplied to the pen tip via the above-mentioned pen core; (4) A marking pen having a pen tip and an ink container via a valve mechanism that opens the valve by pressing the pen tip, and the ink container is directly filled with ink; (5) A marking pen having an ink container that contains an ink occlusion body composed of a fiber bundle and impregnated with ink in the pen barrel, and a marking pen tip composed of a fiber processed body or a resin molded body with a capillary gap formed, which is connected to the ink container directly or via a connecting member in a manner that the ink occlusion body is connected to the pen tip.

[0222] In the case where the ballpoint pen or marker of the embodiment of the present invention is directly filled with ink, in order to facilitate the redispersion of the pigment, a stirring body such as a stirring ball for stirring the ink may be built into the ink container or the pen holder for filling the ink. The shape of the stirring body may be a spherical body, a rod-shaped body, etc. The material of the stirring body is not particularly limited, and examples thereof include metal, ceramic, resin, glass, etc.

[0223] The writing tools such as the ballpoint pen or the marking pen of the embodiment of the present invention can also adopt the ink cartridge form as a detachable structure. In this case, by replacing with a new ink cartridge after exhausting the ink contained in the ink cartridge of the writing tool, the writing tool can be used again.

[0224] As the ink cartridge, an ink cartridge that is connected to the pen body and serves as the pen holder of the pen, or an ink cartridge that covers and protects the pen holder (rear holder) after being connected to the pen body can be used. It should be noted that in the latter, in addition to using the ink cartridge alone, the ink cartridge can be connected to the pen body before use, or the ink cartridge can be stored in the pen holder in a non-connected state, such as when the user of the pen uses the pen, the ink cartridge in the pen holder is connected and used.

[0225] In a writing instrument such as a ballpoint pen or a marker pen according to an embodiment of the present invention, a cap-type writing instrument is made by providing a pen cap attached in a manner covering the pen tip (writing front end), which can prevent the pen tip from drying out and becoming incapable of writing and prevent the writing front end from being contaminated / damaged.

[0226] In addition, in writing instruments such as ballpoint pens or marker pens that accommodate refills in the pen barrel, a telescopic mechanism that allows the writing tip to be retracted from the pen barrel can be set inside the pen barrel to make a telescopic writing instrument, which can prevent the writing tip from being contaminated / damaged.

[0227] Any retractable writing instrument can be used as long as the writing tip is housed in the pen body in a state exposed to the outside air, and the writing tip protrudes from the pen body opening by the operation of the retractable mechanism.

[0228] In addition, a composite telescopic writing instrument can be made in which a plurality of refills are housed in the pen body, and the writing tip of any refill can be extended and retracted from the opening of the pen body by the operation of the telescopic mechanism.

[0229] As examples of telescopic mechanisms, the following telescopic mechanisms can be exemplified: (1) a side-sliding telescopic mechanism in which an operating portion (pen clip) is provided protruding radially outward and movable along the rear side wall of the pen barrel in the front-to-rear direction, and the operating portion is slid forward to allow the writing tip portion to be telescoped from the front end opening of the pen barrel; (2) a rear-end push-type telescopic mechanism in which an operating portion provided at the rear end of the pen barrel is pressed forward to allow the writing tip portion to be telescoped from the front end opening of the pen barrel; (3) a side-push-type telescopic mechanism in which an operating portion protruding from the outer surface of the side wall of the pen barrel is pressed radially inward to allow the writing tip portion to be telescoped from the front end opening of the pen barrel; (4) a rotating telescopic mechanism in which an operating portion at the rear of the pen barrel is rotated to allow the writing tip portion to be telescoped from the front end opening of the pen barrel.

[0230] The shape of ballpoint pens and marker pens is not limited to the above-mentioned structure. In addition to pen tips of different shapes being attached or pen tips being attached that output ink of different tones or hues, it can also be a composite pen (double-headed or nib-dispensing type, etc.) that has pen tips of different shapes attached and the tones or hues of the ink output from each pen tip are different.

[0231] When a reversible thermochromic composition, a reversible thermochromic microcapsule pigment or a reversible thermochromic resin particle is used as a colorant, the handwriting formed on the writing surface using a writing instrument containing the ink composition of an embodiment of the present invention can change color by rubbing with a finger, heating a tool or cooling a tool.

[0232] As heating tools, there are: electric heating color-changing tools equipped with resistance heating elements such as PTC elements, heating color-changing tools filled with media such as warm water, heating color-changing tools using steam or laser, the use of hair dryers, etc. From the perspective of being able to change color by a simple method, friction components and friction bodies are preferred.

[0233] Examples of the cooling tool include an electrically conductive thermochromic tool using a Peltier element, a thermochromic tool filled with a refrigerant such as cold water and / or ice flakes, and applications of a refrigerant, a refrigerator, and a freezer.

[0234] As the friction member and the friction body, preferably an elastic body such as an elastomer or a plastic foam body that has a high elasticity and can generate friction heat by moderate friction when rubbing, but a plastic molded body, stone, wood, metal, cloth, etc. can also be used.

[0235] It should be noted that a normal eraser for erasing pencil marks may be used to erase the marks, but eraser scraps are generated during erasing, and therefore it is preferable to use the above-mentioned friction member and friction body which hardly generate eraser scraps.

[0236] Examples of materials for the friction member and the friction body include silicone resin, styrene-ethylene-butadiene-styrene block copolymer (SEBS resin), etc. Since silicone resin easily adheres to the portion removed by rubbing, and the handwriting is repelled when writing repeatedly, SEBS resin is more preferably used.

[0237] The friction member or friction body can be a member of any shape that is separate from the writing tool, and can be made into an object with excellent portability by being arranged on the writing tool. In addition, the writing tool and the friction member or friction body of any shape that is separate from the writing tool can also be combined to obtain a writing tool kit.

[0238] In the case of a writing instrument with a pen cap, the location where the friction component or friction body is provided is not particularly limited. For example, the pen cap itself can be formed by the friction component, or the pen body itself can be formed by the friction component, or when a pen clip is provided, the pen clip itself can be formed by the friction component, or the friction component or friction body can be provided at the front end (top) of the pen cap or the rear end of the pen body (the part where the writing front end is not provided).

[0239] In the case of a writing instrument with a telescopic mechanism, the location where the friction component or friction body is provided is not particularly limited. For example, the pen body itself may be formed by the friction component, or the pen clip itself may be formed by the friction component when a pen clip is further provided, or the friction component or friction body may be provided near the opening of the pen body, at the rear end of the pen body (the part where the writing front end is not provided), or at the pressing part.

[0240] The ink composition of the embodiment of the present invention can also be used for purposes other than writing tools. For example, it can be used as: printing ink for screen printing, offset printing, process printing, gravure printing, coater, pad printing (tampo printing), etc.; coating for brushing, spraying, electrostatic coating, electrophoretic coating, flow coating, roller coating, dip coating, etc.; ink for inkjet; ultraviolet curing ink; ink for coating tools; ink for seals; painting tools; cosmetics; coloring liquid for fibers.

[0241] Example

[0242] Examples are shown below, but the embodiments of the present invention are not limited thereto. It should be noted that, unless otherwise specified, "parts" and "%" in the examples represent "parts by mass" and "mass %", respectively.

[0243] Example 1

[0244] Preparation of pigment dispersions

[0245] 10 parts of guanine (manufactured by Tokyo Chemical Industry Co., Ltd.), 5 parts of dispersant (manufactured by Toagosei Co., Ltd., product name: ARONA-12SL (solid content: 40%)) and 85 parts of water were mixed. Then, 200 parts of zirconium oxide beads with a diameter of 1.4 to 1.6 mm were added as a medium, and a pulverization and dispersion treatment was performed using a bead mill for 1 hour to prepare a pigment dispersion (guanine pigment dispersion liquid). It should be noted that the content of the dispersant relative to the total mass of the pigment dispersion is 2%, and the content of the dispersant relative to the guanine pigment is 20%. In addition, the average particle size of the guanine pigment dispersed in the pigment dispersion was measured by the above method and the result was 0.63 μm.

[0246] Examples 2 to 7 and Comparative Examples 1 and 2

[0247] Preparation of pigment dispersions

[0248] The pigment dispersions of Examples 2 to 7 and Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the duration of the pulverization and dispersion treatment was set to the durations shown in Table 1 below. The average particle size of the guanine pigment dispersed in the pigment dispersion is shown in Table 1 below.

[0249] [Dispersion stability evaluation]

[0250] 40 g of each pigment dispersion of Examples 1 to 7 and Comparative Examples 1 and 2 was placed in a screw-capped tube bottle (No. 7) and left to stand at room temperature (25°C) for 7 days. After 7 days, each pigment dispersion was visually confirmed and the dispersion stability was evaluated according to the following criteria. The evaluation results are shown in Table 1 below. It should be noted that evaluations "A" to "C" were considered qualified.

[0251] A: The pigment remains dispersed and the pigment dispersion is uniform white.

[0252] B: The pigment slightly precipitated, and a thick white layer was slightly visually confirmed at the lower part of the pigment dispersion.

[0253] C: The pigment slightly precipitated, and a light white layer was visually confirmed on the upper part of the pigment dispersion (white shading occurred in the pigment dispersion).

[0254] D: A large amount of pigment precipitated, and a supernatant (aqueous layer) was visually confirmed in the pigment dispersion, which was completely separated into two layers.

[0255] [Concealment Test]

[0256] The pigment dispersions of Examples 1 to 7 and Comparative Examples 1 and 2 were uniformly applied to black paper (medium-thick, manufactured by Kawaei Co., Ltd.) using a bar coater (#2), and dried to obtain a test sample. The concentration of the coated portion of the test sample was visually confirmed, and the concealment was evaluated based on the following criteria. The evaluation results are shown in Table 1 below. It should be noted that evaluations "A" to "C" were considered qualified.

[0257] A: The applied area is clear white and fully concealed.

[0258] B: The applied area is slightly lighter white and has concealed properties.

[0259] C: The applied portion is slightly lighter white, and the black color of the paper can be visually recognized sporadically through the applied portion, but the concealment is at a level that does not cause any practical problems.

[0260] D: The applied portion was a noticeably light white color, and the black color of the paper was clearly visually recognized through the applied portion, indicating insufficient concealment.

[0261] [Table 1]

[0262]

[0263] Example 8

[0264] Preparation of ink composition for writing instruments

[0265] 20 parts of guanine (manufactured by Tokyo Chemical Industry Co., Ltd.), 7.5 parts of dispersant (manufactured by Toagosei Co., Ltd., product name: ARONA-12SL (solid content: 40%)) and 72.5 parts of water were mixed. Then, 200 parts of zirconium oxide beads with a diameter of 1.4 to 1.6 mm were added as a medium, and a grinding and dispersion treatment was performed for 5 hours using a bead mill to prepare a writing ink composition. It should be noted that the content of the dispersant relative to the total mass of the ink composition was 3%, and the content of the dispersant relative to the guanine pigment was 15%.

[0266] Production of pens

[0267] The above-mentioned ink composition for writing instruments is impregnated in an ink storage body formed by covering a polyester strip with a synthetic resin film, contained in a pen body formed of polypropylene resin, assembled into a resin-processed pen body (shell type) in which polyester fiber is connected to the front end of the pen body via a resin frame, and a pen cap is attached to produce a center-fill pen (marker pen).

[0268] Comparative Example 3

[0269] Preparation of ink composition for writing instruments

[0270] The writing ink composition of Comparative Example 3 was prepared in the same manner as in Example 8 except that the duration of the pulverization and dispersion treatment was changed to 96 hours. The content of the dispersant relative to the total mass of the ink composition was 3%, and the content of the dispersant relative to the guanine pigment was 15%.

[0271] Production of pens

[0272] The writing instrument (marking pen) of Comparative Example 3 was produced in the same manner as in Example 8.

[0273] Comparative Example 4

[0274] Preparation of ink composition for writing instruments

[0275] 20 parts of titanium oxide [Tayca Co., Ltd., product name: JR-707], 7.5 parts of dispersant [Byk Japan Co., Ltd., product name: DISPER BYK-190 (solid content: 40%)] and 72.5 parts of water were mixed. Then, 100 parts of glass beads with a diameter of 2.0 mm were added as a medium, and a bead mill was used to perform a pulverization and dispersion treatment for 1 hour to prepare a writing ink composition. It should be noted that the content of the dispersant relative to the total mass of the ink composition was 3%, and the content of the dispersant relative to the titanium oxide was 15%.

[0276] Production of pens

[0277] The writing instrument (marking pen) of Comparative Example 4 was produced in the same manner as in Example 8.

[0278] [Writing test]

[0279] Using each pen made in Example 8 and Comparative Examples 3 and 4, at room temperature (20 °C), write the character "Yong" by hand on high-quality black paper [medium thickness, manufactured by Wakabayashi Co., Ltd.]. Visually confirm the state of the handwriting, and evaluate the concealment of the handwriting according to the following criteria. The evaluation results are shown in Table 2 below. Note that evaluation "A" is considered qualified.

[0280] A: The handwriting is white and has concealment.

[0281] B: The handwriting is significantly light white, and the black color of the paper can be clearly visually confirmed through the handwriting, and the concealment is insufficient.

[0282] [Table 2]

[0283]

[0284] [Writing test over time]

[0285] Place each pen that has undergone the writing test above upright (tip up) at room temperature (20 °C) for 3 days. After 3 days, at room temperature (20 °C), write the character "Yong" by hand on high-quality black paper [medium thickness, manufactured by Wakabayashi Co., Ltd.]. Visually confirm the state of the handwriting, and evaluate the concealment of the handwriting over time according to the following criteria. The evaluation results are shown in Table 3 below. Note that evaluations "A" and "B" are considered qualified.

[0286] A: The whiteness of the handwriting is the same as or at the same level as the initial stage, and it has concealment.

[0287] B: The whiteness of the handwriting is slightly lighter than the initial handwriting, but it has a level of concealment that is not a problem in practice.

[0288] C: The color of the handwriting is lighter than the initial handwriting, and the concealment is insufficient. Or it is impossible to write.

[0289] [Table 3]

[0290]

[0291] Example 9

[0292] Preparation of the ink composition for the pen

[0293] 20 parts of guanine (manufactured by Tokyo Chemical Industry Co., Ltd.), 7.5 parts of a dispersant (manufactured by BYK JAPAN Co., Ltd., product name: DISPER BYK-2010 (solid content: 40%)) and 72.5 parts of water were mixed. Then, 200 parts of zirconium oxide beads with a diameter of 1.4 to 1.6 mm were added as a medium, and a pulverization and dispersion treatment was performed for 5 hours using a bead mill to prepare a pigment dispersion (guanine pigment dispersion).

[0294] 88 parts of the above pigment dispersion, 0.2 parts of a shear thinning agent (succinoglycan) [Rheozan manufactured by Sanjing Co., Ltd.], 1 part of a phosphate surfactant [PLYSURF AL manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], 1 part of a pH adjuster (triethanolamine), 0.1 parts of a preservative [Proxel XL-2(S) manufactured by Lonza Japan Co., Ltd.] and 9.7 parts of water were mixed to prepare a writing ink composition. The content of the dispersant (i.e., the total of DISPERBYK-2010 and PLYSURF AL) relative to the total mass of the ink composition was 3.6%, and the content of the dispersant (i.e., the total of DISPERBYK-2010 and PLYSURF AL) relative to the guanine pigment was 21%.

[0295] Production of pens

[0296] The above-mentioned writing ink composition was sucked and filled into an ink container made of a polypropylene tube, and then connected to a ballpoint pen tip having a superhard ball with a diameter of 0.5 mm at the top through a resin frame. Next, a viscoelastic ink backflow-proof fluid (liquid plug) mainly composed of polybutene was filled from the rear end of the ink container, and a tail plug was further fitted into the rear part of the tube, and deaeration treatment was performed by centrifugation to obtain a ballpoint pen refill.

[0297] Next, the refill is installed in the pen holder to produce a writing tool (retractable ballpoint pen).

[0298] The above-mentioned ballpoint pen is provided with the following rear end push-type telescopic structure: the pen tip provided on the ballpoint pen refill is stored in the pen body in a state exposed to the outside air, and by pressing the operating part provided on the rear end of the pen body forward, the pen tip protrudes from the front end opening of the pen body.

[0299] Using the ballpoint pen of Example 9, under room temperature (20°C), when writing by hand on black high-grade paper (medium thick, (strain) Huo Ying Co., Ltd. system), there is no poor writing such as flying white and flying lines, and white handwriting is formed. In addition, this handwriting conceals the writing surface and is a good handwriting rich in concealment.

[0300] Example 10

[0301] Preparation of pigment dispersions

[0302] 10 parts of guanine (manufactured by Tokyo Chemical Industry Co., Ltd.), 2.5 parts of dispersant (manufactured by Toagosei Co., Ltd., product name: ARONA-12SL (solid content: 40%)) and 87.5 parts of water were mixed. Then, 200 parts of zirconium oxide beads with a diameter of 1.4 to 1.6 mm were added as a medium, and a pulverization and dispersion treatment was performed using a bead mill for 6 hours to prepare a pigment dispersion (guanine pigment dispersion liquid). It should be noted that the content of the dispersant relative to the total mass of the pigment dispersion is 1%, and the content of the dispersant relative to the guanine pigment is 10%. In addition, the average particle size of the guanine pigment dispersed in the pigment dispersion was measured by the above method and the result was 0.35 μm.

[0303] Examples 11 to 16

[0304] Preparation of pigment dispersions

[0305] Each pigment dispersion of Examples 11 to 16 was prepared in the same manner as in Example 10 except that the types and amounts of the blended materials were changed to the contents described in the following Table 4. The content of the dispersant relative to the total mass of the pigment dispersion, the content of the dispersant relative to the guanine pigment, and the average particle size of the guanine pigment dispersed in the pigment dispersion are shown in the following Table 4.

[0306] [Table 4]

[0307]

[0308] The contents of the materials in Table 4 are explained according to the marked numbers.

[0309] (1) Manufactured by Tokyo Chemical Industry Co., Ltd.

[0310] (2) Unneutralized acrylic acid-sulfonic acid copolymer [manufactured by Toagosei Co., Ltd., product name: ARON A-12SL (solid content: 40%)].

[0311] (3) 2-Amino-2-methyl-1-propanol salt of a modified carboxyl group-containing polymer [manufactured by Kyoeisha Chemical Co., Ltd., product name: FLOWLEN G-700AMP (solid content: 45%), acid value: 25 mgKOH / g, amine value: 25 mgKOH / g].

[0312] (4) Controllable polymerization acrylic copolymer [manufactured by BYK JAPAN Co., Ltd., product name: DISPER BYK-2010 (solid content: 40%), acid value: 20 mgKOH / g, amine value: 20 mgKOH / g].

[0313] (5) A copolymer having an acidic group [manufactured by BYK JAPAN Co., Ltd., product name: DISPER BYK-102 (solid content: 99%), acid value: 101 mgKOH / g].

[0314] (6) Carboxyl group-containing styrene-acrylic acid copolymer [manufactured by BASF Japan Co., Ltd., product name: JONCRYL 57J (solid content: 37%), acid value: 215 mgKOH / g].

[0315] (7) Comb-type polymer dispersant containing an acidic group [manufactured by Japan Lubrizol Co., Ltd., product name: Solsperse 46000 (solid content: 50%), acid value: 12±2 mgKOH / g].

[0316] (8) Comb-type polymer dispersant containing an acidic group [manufactured by Japan Lubrizol Co., Ltd., product name: Solsperse 47000 (solid content: 40%), acid value: 8±1.5 mgKOH / g].

[0317] [Dispersion stability evaluation]

[0318] The dispersion stability of each pigment dispersion of Examples 10 to 16 was evaluated by the same method as in Examples 1 to 7 and Comparative Examples 1 and 2. The evaluation results are shown in Table 5 below.

[0319] [Table 5]

[0320]

[0321] Application Example 1

[0322] Preparation of liquid composition

[0323] 20 parts of guanine (manufactured by Tokyo Chemical Industry Co., Ltd.), 7.5 parts of a dispersant (manufactured by Toagosei Co., Ltd., product name: ARONA-12SL (solid content: 40%)) and 72.5 parts of water were mixed. Then, 200 parts of zirconium oxide beads with a diameter of 1.4 to 1.6 mm were added as a medium, and a pulverization and dispersion treatment was performed using a bead mill for 5 hours to prepare a liquid composition as a printing ink for screen printing.

[0324] Fabrication of laminated bodies

[0325] A solid pattern was printed on the surface of black high-quality paper (medium-thick, manufactured by Kawaei Co., Ltd.) by screen printing using the above-mentioned printing ink, and the printed paper was dried and cured to form a colored layer, thereby obtaining a laminate.

[0326] The colored layer of the laminate of Application Example 1 was clear white and had good hiding power, and the black color of the underlying paper was not visually recognized through the colored layer. In addition, the guanine pigment in the liquid composition had excellent dispersibility, so the colored layer had a uniform concentration and good appearance.

[0327] This application claims priority based on Japanese Patent Application No. 2022-105064, filed on June 29, 2022. Japanese Patent Application No. 2022-105064 is incorporated herein by reference.

Claims

1. A writing ink composition, wherein: The invention at least comprises a pigment and a solvent, wherein the pigment comprises a guanine pigment, and the average particle size of the guanine pigment is 0.2 to 0.95 μm.

2. The ink composition according to claim 1, wherein A dispersant is also included.

3. The ink composition according to claim 2, wherein The dispersant has an acidic group and / or a salt of an acidic group.

4. The ink composition according to any one of claims 1 to 3, wherein The content of the guanine pigment relative to the total mass of the ink composition is 1 to 50% by mass.

5. The ink composition according to any one of claims 1 to 4, wherein Also contains colorant.

6. A writing instrument, wherein: The ink composition according to any one of claims 1 to 5 is contained.

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