Oil-based ink for ballpoint pens

Abstract

PURPOSE: To provide an oil-based ink for ballpoints with reduced ink leakage from a pen tip even under a low humidity environment.CONSTITUTION: An oil-based ink for ballpoints comprises at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to oil-based ink for ballpoint pens.

Background Art

[0002] As a technique for suppressing ink leakage from the pen tip of oil-based ink for ballpoint pens, Patent Document 1 discloses a ballpoint pen ink containing spherical silicone resin fine particles. Patent Document 2 discloses an oil-based ballpoint pen ink composition comprising a salt-forming dye having a specific structure and polyvinyl butyral resin in an amount of 70% or more based on the total content of all resins in the ink composition.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0004] In the invention described in Patent Document 1, the silicone particles are damaged by the impact of being sandwiched between the ball and the base during writing, resulting in an uneven particle shape. This reduces the sealing effect due to density in areas where the ink flow path narrows, and in dry environments with low humidity, the pen tip cannot receive the support of reduced fluidity due to the precipitation of solid components in the ink due to moisture in the air, thus preventing ink leakage. In the invention described in Patent Document 2, in high-humidity environments, the solid components in the ink that appear on the surface of the pen tip precipitate due to the influence of moisture in the air, or the ink on the surface of the pen tip forms a protective layer, creating a seal on the pen tip surface, thus preventing ink leakage. However, in dry environments with low humidity, the precipitation rate of solid components in the ink is slow, and the ink on the surface of the pen tip does not easily form a protective layer, so the ink leakage prevention effect is not achieved, and ink leaks from the pen tip. Furthermore, when the pen tip is not retracted and is pressed against a display or other surface, the ball at the tip is pressed against the ball seat, which opens the ink flow path and prevents ink leakage from the pen tip.

[0005] The present invention aims to provide an oil-based ink for ballpoint pens that can suppress ink leakage from the pen tip even in low-humidity environments. [Means for solving the problem]

[0006] In other words, the present invention has as its first feature an oil-based ballpoint pen ink characterized by containing at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin; as its second feature an oil-based ballpoint pen ink according to the first feature in which the average particle diameter of the silicone composite particles is 0.1 μm or more and less than 1.0 μm; and as its third feature an oil-based ballpoint pen ink according to the first or second feature characterized by containing hydroxypropyl cellulose. [Effects of the Invention]

[0007] The silicone composite particles contained in the oil-based ballpoint pen ink of the present invention have a structure in which silicone rubber particles are coated with silicone resin. Therefore, due to the synergistic effect of the low intermolecular forces and low tackiness resulting from the silicone resin coating the silicone composite particles, and the elasticity of the silicone rubber inside the silicone composite particles, the particles can densely pack together without forming an aggregate structure in areas where the ink flow path narrows, without being damaged by the impact of being sandwiched between the ball and the pen seat during writing. This is thought to provide an excellent sealing effect and suppress ink leakage. [Modes for carrying out the invention]

[0008] The present invention will be described in detail below.

[0009] The silicone composite particles of the present invention, which have a structure in which silicone rubber particles are coated with silicone resin, are composite particles having an elastic silicone rubber with an internal silicone skeleton structure of M units and D units and a linear polymer structure, and a silicone resin with an external silicone skeleton structure of T units and Q units and a branched structure that is crosslinked in a three-dimensional network. The M, D, T, and Q units of silicone refer to the number of organic substituents attached to the silicon in the silicone. M units represent silicon with 3 organic substituents, D units represent silicon with 2 organic substituents, T units represent silicon with 1 organic substituent, and Q units represent silicon with no organic substituents. The rubber hardness can be appropriately adjusted by changing the proportion of each unit in the silicone skeleton of the silicone rubber part. The rubber hardness is preferably 25 to 80 on a durometer type A, and more preferably 50 to 80, so that the silicone composite particles deform when sandwiched between the ball and the ball seat, and immediately return to their original state when the gap between the seat and the ball widens after writing, and disperse into the ink flow path. The particle size of the silicone composite particles is appropriately selected to be able to be dispensed from the ballpoint pen tip, with particles between 0.1 μm and 12 μm being preferable. In particular, using silicone composite particles smaller than 1.0 μm is even preferable because it further increases the density during sealing, thereby further improving the effect of suppressing ink leakage from the pen tip. Furthermore, the particle diameter of the silicone composite particles represents the average particle diameter. The average particle diameter is measured using a laser diffraction / scattering particle size distribution analyzer (for example, Shimadzu Corporation's SALD-7100), and the volume-based average particle diameter is calculated based on that value. To obtain the silicone composite particles with the desired particle size, it is also possible to adjust the particle size distribution by sieving, centrifugation, or filtration.

[0010] In the oil-based ballpoint pen ink used in the present invention, specific examples of the silicone composite particles include KMP-600 (average particle diameter 5 μm, rubber hardness 30 durometer A, true specific gravity 0.99 g / cm3), KMP-601 (average particle diameter 12 μm, rubber hardness 30 durometer A, true specific gravity 0.98 g / cm3), KMP-602 (average particle diameter 30 μm, rubber hardness 30 durometer A, true specific gravity 0.98 g / cm3), KMP-605 (average particle diameter 2 μm, rubber hardness 75 durometer A, true specific gravity 0.99 g / cm3), and X-52-7030 (average particle diameter 0.8 μm, rubber hardness 75 durometer A, true specific gravity 1.01 g / cm3) (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0011] The silicone composite particles can be used alone or in combination, and the amount used is preferably 0.01% by weight or more and 10.0% by weight or less, and more preferably 0.05% by weight or more and 3.0% by weight or less, taking into consideration the performance of ink leakage at the pen tip and writing performance.

[0012] When adding the silicone composite particles to the ink, they may be added directly or as a pre-dispersed form. As the dispersion medium, organic solvents used in oil-based inks for ballpoint pens can be used, and alcohols, glycols, and glycol ethers are particularly preferred due to safety and odor issues.Examples of organic solvents include ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol dibutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, and triethylene glycol monomethyl ether. Glycol ethers such as triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butyl acetate, etc., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, octylene glycol,Examples include glycerin, polyethylene glycol, glycols such as 3-methyl-1,3-butanediol, 1,3-propanediol, 1,3-butanediol, and 1,5-pentanediol; benzyl alcohol, β-phenylethyl alcohol, α-methylbenzyl alcohol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, 3-methyl-3-methoxypentanol, lauryl alcohol, tridecyl alcohol, isodecyl alcohol, and isotridecyl alcohol; ethers such as methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether; and esters such as 2-ethylhexyl acetate, isobutyl isobutyrate, ethyl lactate, and butyl lactate.

[0013] Furthermore, surfactants and dispersion resins can be used as dispersants, including nonionic surfactants, acrylic copolymers, polyvinyl butyral resins, phosphate polyesters, phosphate polymers, copolymers having acidic groups, alkylol ammonium salts of copolymers containing acidic groups, and hydroxyl group-containing carboxylic acid esters.

[0014] Polyvinyl butyral is preferably used as the dispersant, and it is even more preferable to use a dispersant with an acid value of 100 mg KOH / g or higher in combination, as this improves the dispersion stability of the silicone composite particles and provides long-term storage stability. Specific examples of polyvinyl butyral include S-Lec BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-S, BX-L, BM-1, BM-2, BM-5, BM-S, BH-3, BH-6, BH-S, BX-1, BX-5, KS-10, KS-1, KS-3, KS-5 (all manufactured by Sekisui Chemical Co., Ltd.), Mowiital B 14 S, B 16 H, B 20 H, B 30 T, B 30 H, B 30 HH, B 45 H, B 60 T, B 60 H, B 60 HH, B 75 H (The above are manufactured by Kuraray Co., Ltd.) Examples of dispersants with an acid value of 100 mg KOH / g or higher include DISPERBYK-102 (acid value 129 mg KOH / g), DISPERBYK-106 (acid value 132 mg KOH / g, amine value 74 mg KOH / g), DISPERBYK-111 (acid value 129 mg KOH / g), BYK-P104 (acid value 180 mg KOH / g), BYK-P104S (acid value 150 mg KOH / g), BYK-P105 (acid value 365 mg KOH / g), and BYK-P220S (acid value 100 mg KOH / g) (all manufactured by BIC Chemie Japan Co., Ltd.). The amine value expressed here is the number of milligrams (mg) of potassium hydroxide (KOH) equivalent to hydrochloric acid required to neutralize the primary, secondary, and tertiary amines contained in 1 g of the sample.

[0015] Furthermore, the dispersant can be used alone or in combination, and it is preferable to use it in an amount of 10% to 200% by weight relative to the silicone composite particles.

[0016] In the present invention, the silicone composite particles can be dispersed by a generally accepted method. For example, the silicone composite particles, a solvent, and a dispersant are mixed, uniformly stirred with a propeller agitator or the like, and then dispersed using a disperser. Dispersers such as kneaders, roll mills, ball mills, sand mills, bead mills, Henschel mixers, homogenizers, high-pressure homogenizers, and thin-film swirling high-speed mixers are appropriately selected depending on the amount of solvent in the ink and the pigment concentration. Among these, dispersion using a high-pressure homogenizer or a thin-film swirling high-speed mixer is preferably used also from the viewpoint of improving the storage stability of the dispersion.

[0017] In order to improve the dispersion stability of the silicone composite particles, an aging step may be performed in advance, or in order to prevent aggregation due to solvent shock with components in the ink, the components in the ink may be added in advance when dispersing the silicone composite particles.

[0018] As the organic solvent used in the present invention, any organic solvent conventionally used for oil-based inks for ballpoint pens can be used without particular limitation, and alcohols, glycols and glycol ethers are particularly preferred from the viewpoints of safety and odor.

[0019] Specific examples of organic solvents include ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol dibutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, and triethylene glycol monomethyl ether. Glycol ethers such as triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butyl acetate, etc., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, octylene glycol,Glycols such as glycerin, polyethylene glycol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,3-butanediol, and 1,5-pentanediol; alcohols such as benzyl alcohol, β-phenylethyl alcohol, α-methylbenzyl alcohol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, 3-methyl-3-methoxypentanol, lauryl alcohol, tridecyl alcohol, isodecyl alcohol, and isotridecyl alcohol; ethers such as methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether; and esters such as 2-ethylhexyl acetate, isobutyl isobutyrate, ethyl lactate, and butyl lactate can be mentioned. Partial use of a low-boiling-point organic solvent easily reduces the viscosity of the ink and is suitable for improving writing feel. Low-boiling-point organic solvents that can be suitably used are organic solvents selected from glycols and glycol ethers having a boiling point of 140°C or higher and 200°C or lower, and specific examples include hexylene glycol, 3-methoxy-1-butanol, 3-methoxy-3-methyl-1-butanol, diethylene glycol monomethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and ethylene glycol monoisobutyl ether. In consideration of improving writing feel through viscosity reduction and drying resistance at the pen tip, it is preferable to use a combination of a low-boiling-point organic solvent selected from alcohols, glycols, and glycol ethers having a boiling point of 80°C or higher and 200°C or lower, and a high-boiling-point organic solvent having a boiling point exceeding 200°C. The weight ratio of the low-boiling-point organic solvent to the high-boiling-point organic solvent is preferably 1.0 or more and 30.0 or less, and more preferably 1.3 or more and 6.0 or less.

[0020] These organic solvents can be used alone or in combination, and the amount thereof used is preferably 10.0% by weight or more and 90.0% by weight or less based on the total amount of the oil-based ink for ballpoint pens.

[0021] In the present invention, the coloring agent is not particularly limited and can be an aqueous dye, an oil-soluble dye, or a pigment. Specifically, any of the following can be used as water-soluble dyes: direct dyes, acid dyes, and basic dyes. Specific examples of direct dyes include: Japanol Fast Black D Concentrate (CI Direct Black 17), Water Black 100L (CI Direct Black 19), Water Black L-200 (CI Direct Black 19), Direct Fast Black B (CI Direct Black 22), Direct Fast Black AB (CI Direct Black 32), Direct Deep Black EX (CI Direct Black 38), Direct Fast Black Concentrate (CI Direct Black 51), Kayaras Spray VGN (CI Direct Black 71), Kayaras Direct Brilliant Yellow G (CI Direct Yellow 4), Direct Fast Yellow 5GL (CI Direct Black 26), Eisen Primula Yellow GCLH (CI Direct Black 44), Direct Fast Yellow R (CI Direct Black 50), Eisen Direct Fast Red FH (CI Direct Red 1), Nippon Fast Scarlet GSX (CI Direct Red 4), Direct Fast Scarlet 4BS (CI Direct Red 23), Eisen Direct Rhodulin BH (31), Direct Scarlet B (37), Kayak Direct Scarlet 3B (39), Eisen Primula Pink 2BLH (75), Sumilight Red F3B (80), Eisen Primula Red 4BH (81), Kayaras Spurarbin BL (83), Kayaras Light Red F5G (225), Kayaras Light Red F5B (226), Kayaras Light Rose FR (2 27) Examples include Direct Sky Blue 6B (CI Direct Blue 1), Direct Sky Blue 5B (CI Direct Blue 15), Sumilight Supra Blue BRR Concentrate (CI Direct Blue 71), Daibogen Turquoise Blue S (CI Direct Blue 86), Water Blue #3 (CI Direct Blue 86), Kayaras Turquoise Blue GL (CI Direct Blue 86), Kayaras Supra Blue FF2GL (CI Direct Blue 106), and Kayaras Supra Turquoise Blue FBL (CI Direct Blue 199). Specific examples of acid dyes include Acid Blue Black 10B (CI Acid Black 1), Nigrosine (CI Acid Black 2), Suminol Milling Black 8BX (CI Acid Black 24), Kayanol Milling Black VLG (CI Acid Black 26), Suminol Fast Black BR ​​Concentrate (CI Acid Black 31), Mitsui Nylon Black GL (CI Acid Black 52), Eisen Opal Black WH Extra Concentrate (CI Acid Black 52), Sumilan Black WA (CI Acid Black 52), Ranil Black BG Extra Concentrate (CI Acid Black 107), Kayanol Milling Black TLB (CI Acid Black 109), Suminol Milling Black B (CI Acid Black 109), Kayanol Milling Black TLR (CI Acid Black 110), Eisen Opal Black New Concentrate (CI Acid Black 119), Water Black 187-L (CI Acid Black 154), Kayak Acid Brilliant Flavin FF (CI Acid Yellow 7:1), and Kayak Acid Yellow GG (CI Acid Yellow 17). Xylene Light Yellow 2G 140% (17), Suminol Leveling Yellow NR (19), Daiwa Turtrazine (23), Kayactrazine (23), Suminol Fast Yellow R (25), Diacid Light Yellow 2GP (29), Suminol Milling Yellow O (38), Suminol Milling Yellow MR (42), Water Yellow #6 (42), Kayano Yellow NFG (4 9) Suminol Milling Yellow 3G (72%), Suminol Fast Yellow G (61%), Suminol Milling Yellow G (78%), Kayanol Yellow N5G (110%), Suminol Milling Yellow 4G200% (141%), Kayanol Yellow NG (135%), Kayanol Milling Yellow 5GW (127%), Kayanol Milling Yellow 6GW (142%), Sumitomo Fast Scarlet A (CIAcid Red (8), Kayak Silk Scarlet (9), Solar Rubin Extra (14), Daiwa New Coccine (18), Eisen Bonso RH (26), Daiwa Red No. 2 (27), Suminol Leveling Brilliant Red S3B (35), Kayak Silk Rubinol 3GS (37), Eisen Erythrosine (51), Kayak Acid Rhodamine FB (52), Suminol Leveling Rubinol 3GP (57), Diacid Alizarin Rubinol F3G 200% (82), Eisen Eosin GH (87), Water Pink #2 (92), Eisen Acid Phloxin PB (92), Rose Bengal (94), Kayanol Mi Ring Scarlet FGW (111), Kayanol Milling Ruby 3BW (129), Suminol Milling Brilliant Red 3BN Concentrate (131), Suminol Milling Brilliant Red BS (138), Eisen Opal Pink BH (186), Suminol Milling Brilliant Red B Concentrate (249), Kayaku Acid Brilliant Red 3BL (254), Kayaku Acid Brilid Brilliant Red BL (265), Kayanol Milling Red GW (276), Mitsui Acid Violet 6BN (CI Acid Violet 15), Mitsui Acid Violet BN (17), Sumitomo Patent Pure Blue VX (CIAcid Blue 1), Water Blue #106 (same 1), Patent Blue AF (same 7), Water Blue #9 (same 9), Daiwa Blue No. 1 (same 9), Suprano Blue B (same 15), Orient Solubble Blue OBC (same 22), Suminol Leveling Blue 4GL (same 23), Mitsui Nylon Fast Blue G (same 25), Kayashil Blue AGG (same 40), Kayashil Blue BR (same 41), Mitsui Alizarin Saphirol SE (same 43), Suminol Leveling Sky Blue R Extra Concentrate (same 62), Mitsui Nylon Fast Sky Blue B (same 78), Sumitomo Brilliant Indocyanine 6Bh Examples include / c (83%), Sandran Cyanine N-6B 350% (90%), Water Blue #115 (90%), Orient Solubble Blue OBB (93%), Sumitomo Brilliant Blue 5G (103%), Kayanol Milling Ultra Sky SE (112%), Kayanol Milling Cyanine 5R (113%), Eisen Opal Blue 2GLH (158%), Daiwa Guinea Green B (CI Acid Green 3), Acid Brilliant Milling Green B (9%), Daiwa Green #70 (16%), Kayanol Cyanine Green G (25%), and Suminol Milling Green G (27%). Specific examples of basic dyes include Eisen Katiron Yellow 3GLH (CI Basic Yellow 11), Eisen Katiron Brilliant Yellow 5GLH (CI Basic Yellow 13), Sumiacrylic Yellow E-3RD (CI Basic Yellow 15), Maxilon Yellow 2RL (CI Basic Yellow 19), Astrazon Yellow 7GLL (CI Basic Yellow 21), Kayakuril Golden Yellow GL-ED (CI Basic Yellow 28), Astrazon Yellow 5GL (CI Basic Yellow 51), Eisen Katiron Orange GLH (CI Basic Orange 21), Eisen Katiron Brown 3GLH (CI Basic Yellow 30), Rhodamine 6GCP (CI Basic Red 1), Eisen Astrafloxine (CI Basic Yellow 12), Sumiacrylic Brilliant Red E-2B (CI Basic Yellow 15), and Examples include Strazon Red GTL (18), Eisen Katiron Brilliant Pink BGH (27), Maxilon Red GRL (46), Eisen Methyl Violet (CI Basic Violet 1), Eisen Crystal Violet (3), Eisen Rhodamine B (10), Astrazon Blue G (CI Basic Blue 1), Astrazon Blue BG (3), Methylene Blue (9), Maxilon Blue GRL (41), Eisen Katiron Blue BRLH (54), Eisen Diamond Green GH (CI Basic Green 1), Eisen Malachite Green (4), and Bismarck Brown G (CI Basic Brown 1). These can be used individually or in combination.

[0022] Specifically, oil-soluble dyes that can be used include acid dyes, basic dyes, metal complex dyes, salt-forming dyes, azine dyes, anthraquinone dyes, phthalocyanine dyes, and triphenylmethane dyes. Examples include: Negrocin Base EE, EEL, EX, EXBP, EB; Oil Yellow 101, 107; Oil Pink 312; Oil Brown BB, GR; Oil Green BG; Oil Blue 613; Oil Scarlet 308, BOS; Oil Black HBB, 860, BS; Varifast Yellow 1101, 1105, 1109, 1120, 3104, 3105, 3108, 4120, AUM; Varifast Orange 2210, 3209, 3210; Varifast Red 1306, 1308, 1320, 1355. , 1360, 2303, 2320, 3304, 3306, 3320, Varifast Pink 2310N, Varifast Brown 2402, 3405, Varifast Green 1501, Varifast Blue 1603, 1605, 1607, 1631, 2606, 2610, 2620, Varifast Violet 1701, 1702, Varifast Blue Rack 1802, 1805, 1807, 3804, 3806, 3808, 3810, 3820, 3830, Spirit Red 102, Spirit Black AB, Osprey Yellow RY, ROB-B, MVB3, SP Blue 105 (all manufactured by Orient Chemical Industry Co., Ltd.), Eisenspiron Yellow 3RH, GRLH Special, C-2GH, C-GNH New, Eisenspiron Orange 2RH, Eisenspiron GRH Conc Special, Eisenspiron Red GEH, Eisenspiron BEH, Eisenspiron GRLH Special, Eisenspiron C-GH, Eisenspiron C-BH, Eisenspiron Violet RH, Eisenspiron C-RH, Eisenspiron Brown BH Conc, Eisenspiron RH, Eisenspiron Mahogany RH, Eisenspiron Blue GNH, Eisenspiron Blue 2BNH, Eisenspiron C-RH, Eisenspiron BPNH, Eisenspiron Green C-GH, Eisenspiron 3GNH Special, Eisenspiron Black BNH, Eisenspiron MH, Eisenspiron RLH, Eisenspiron GMH Special, Eisenspiron BH Special, SBN Orange 703, SBN Violet 510, Eisenspiron Violet 521, SPT Orange 6, SPTBlue 111, SOT Pink 1, SOT Blue 4, SOT Black 1, SOT Black 6, SOT Black 10, SOT Black 12, SOT Black 13 Liquid, Eisen Rhodamine B Base, Eisen Methyl Violet Base, Eisen Victoria Blue B Base (all manufactured by Hodogaya Chemical Co., Ltd.), Oil Yellow CH, Oil Pink 330, Oil Blue 8B, Oil Black S, Oil Black FS Special A, Oil Black 2020, Oil Black 109, Oil Black 215, AL Yellow 1106D, Oil Black 31 01, AL Red 2308, Neo Super Yellow C-131, C-132, C-134, Neo Super Orange C-233, Neo Super Red C-431, Neo Super Blue C-555, Neo Super Brown C-732, C-733 (all manufactured by Chuo Synthetic Chemical Co., Ltd.), Oleozol Fast Yellow 2G, GCN, Oleozol Fast Orange GL, Oleozol Fast Red BL, RL (all manufactured by Taoka Chemical Co., Ltd.) Examples include: SAVINY 2GLS, SAVINY 2RLS, SAVINY 2RLS, SAVINY 2RLS, SAVINY 2GLS, SAVINY 2GLS, SAVINY 2GLS, SAVINY 2GLS, SAVINY 2GLS, SAVINY 2GLS, SAVINY 2GLS (all manufactured by Sandø, Switzerland), Magenta SP 247%, Crystal Violet 10B 250%, Malachite Green Crystal Conc, Brilliant Green Crystal H 90%, Spirit Solubble Red 64843 (all manufactured by Holiday, UK), Neptune Red Base 543, Neptune Blue Base 634, Neptune Violet Base 604, Basinyl Red 540, Basinyl Violet 600, Victoria Blue F4R, Nigrosine Base LK (all manufactured by BASF, Germany), Methyl Violet 2B Base (all manufactured by National Anilne Div., USA). These can be used individually or in combination.

[0023] Specifically, the pigments include carbon blacks such as Farnest Black, Contact Black, Thermal Black, and Acetylene Black, black iron oxide, yellow iron oxide, red iron oxide, ultramarine, Prussian blue, cobalt blue, titanium yellow, turquoise, molybdate orange, titanium dioxide, gold powder, silver powder, copper powder, aluminum powder, brass powder, tin powder, mica-based pigments, and CIPIGMENT RED. 2, 3, 5, 17, 22, 38, 41, 48:2, 48:3, 49, 50:1, 53:1, 57:1, 58:2, 60, 63:1, 63:2, 64:1, 88, 112, 122, 123 , 144, 146, 149, 166, 168, 170, 176, 177, 178, 179, 180, 185, 190, 194, 206, 207, 209, 216, 245, CIPIGMENT ORANGE 5, 10, 13, 16, 36, 40, 43, CIPIGMENT VIOLET Examples include 19, 23, 31, 33, 36, 38, 50, CIPIGMENT BLUE 2, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 16, 17, 22, 25, 60, 66, CIPIGMENT BROWN 25, 26, CIPIGMENT YELLOW 1, 3, 12, 13, 24, 93, 94, 95, 97, 99, 108, 109, 110, 117, 120, 139, 153, 166, 167, 173, CIPIGMENT GREEN 7, 10, 36, etc. These can be used individually or in combination of two or more. In addition to these pigments, processed pigments can also be used. Some examples include Renol Yellow GG-HW30, HR-HW30, Orange RL-HW30, Red HF2B-HW30, FGR-HW30, F5RK-HW30, Carmine FBB-HW30, Violet RL-HW30, Blue B2G-HW30, CF-HW30, Green GG-HW30, Brown HFR-HW30, Black R-HW30 (all manufactured by Clariant Japan Co., Ltd.), UTCO-001 Yellow, 012 Yellow, 021 Orange, 031 Red, 032 Red, 042 Violet, 051 Blue, 052 Blue, 061 Green, 591 Black, 592 Black (all manufactured by Dainichi Seika Kogyo Co., Ltd.), and MICROLITH Yellow. Examples include 4G-A, MX-A, 2R-A, Brown 5R-A, Scarlet RA, Red 2C-A, 3R-A, Magenta 2B-A, Violet BA, Blue 4G-A, and Green GA (all manufactured by Ciba Specialty Chemicals Co., Ltd.).

[0024] To improve the dispersibility of pigments, anionic, cationic, nonionic, and amphoteric surfactants, as well as polymer resins, can be used as auxiliary agents. Specifically, examples include anionic, nonionic, and cationic surfactants such as higher fatty acids, higher alcohol sulfates, fatty acid sulfates, alkylallyl sulfonic acids, phosphate esters, polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, and sorbitan fatty acid esters, as well as pigment dispersion resins and oligomers such as polyvinyl butyral resin, polyvinylpyrrolidone resin, polyacrylic acid ester resin, polymethacrylate ester resin, styrene-acrylic acid resin, and styrene-maleic acid resin. These can be used individually or in combination of two or more types.

[0025] Resin can be added to the ink in appropriate amounts to adjust its viscosity and improve the fixation of handwriting. Specific examples include polyvinylpyrrolidone resin, polyvinyl alcohol resin, polyvinyl butyral resin, ketone resin, acrylic acid-acrylic acid ester resin, acrylic acid-methacrylic acid ester resin, methacrylic acid-acrylic acid ester resin, methacrylic acid-methacrylic acid ester resin, styrene-acrylic acid resin, styrene-maleic acid resin, phenolic resin, rosin, rosin ester, modified rosin, modified rosin ester, maleated rosin, maleated rosin ester, fumarated rosin, fumarated rosin ester, celluloses such as carboxymethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, hydroxypropyl cellulose, synthetic polymers such as N-vinylacetamide polymerized crosslinked products, and inorganic clay minerals. These can be used individually or in combination of two or more types.

[0026] In this invention, by using a resin having an acidic group among the above resins, the apparent bulkiness increases due to electrostatic adsorption to the silicone composite particles, thereby preventing collisions between the silicone composite particles and improving dispersion stability. Furthermore, when writing again after writing, the silicone composite particles that acted as a sealant are quickly loosened, reducing streaking at the start of writing (hereinafter referred to as initial streaking). The degree of acidity of the resin is expressed by the acid value, which is the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize all acidic components contained in 1 g of the sample. A value of 50 mg KOH / g or more and 600 mg KOH / g or less is preferred, and a value of 150 mg KOH / g or more and 550 mg KOH / g or less is more preferred. Furthermore, if the resin contains OH groups, the interaction with acidic groups improves its adsorption to the silicone composite particles, thus improving lubricity and thus the writing experience. The amount of OH groups is expressed by the OH value, which is the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize the total acidic components contained in 1 g of sample after acetylation with acetic anhydride and quantification of the free acetic acid with potassium hydroxide. Specific examples include, as rosins, KR-612 (acid value 167 mg KOH / g) and KR-614 (acid value 175 mg KOH / g) (both manufactured by Arakawa Chemical Industries, Ltd.), as maleic acid rosins, Marquid No. 31 (acid value 188 mg KOH / g), Marquid No. 32 (acid value 130 mg KOH / g), Marquid No. 33 (acid value 305 mg KOH / g), and Marquid No. 3002 (acid value 100 mg KOH / g) (all manufactured by Arakawa Chemical Industries, Ltd.), and Harimac T-80 (acid value 185 mg KOH / g) (both manufactured by Harima Chemicals, Inc.), and as maleated rosin esters, Hariester MSR-4 ( Examples include Harima Chemicals Ltd. (acid value 135 mgKOH / g), KE-604 (acid value 238 mgKOH / g) and KR-120 (acid value 325 mgKOH / g) (both manufactured by Arakawa Chemical Industries, Ltd.) as acid-modified rosins, Haritack F-75 (acid value 145 mgKOH / g) and FG-90 (acid value 150 mgKOH / g) (both manufactured by Harima Chemicals Ltd.) as special modified rosins, and Joncryl 611 (acid value 53 mgKOH / g) and Joncryl 586 (acid value 108 mgKOH / g) (both manufactured by BASF Japan Ltd.) as styrene-acrylic acid resins.

[0027] In this invention, it is preferable to use hydroxypropyl cellulose among the above resins. It is considered that the coexistence of the silicone composite particles within the molecular network of hydroxypropyl cellulose not only provides a sealing effect in the ink channel, but also suppresses the spreading of ink leakage even if ink leaks onto a display when the pen tip is pressed against a display or the like without being retracted, as the hydroxypropyl cellulose and the silicone composite particles immediately orient themselves onto the ink surface. Specific examples include NISSO HPC-VH, H, M, L, SL, and SSL (all manufactured by Nippon Soda Co., Ltd.), and Klucel-H, M, G, J, L, and E (all manufactured by Ashland Japan Co., Ltd.).

[0028] As a lubricant for preventing ball bearing wear and improving writing performance, by using higher fatty acids such as oleic acid, nonionic surfactants having long-chain alkyl groups, polyether-modified silicone oil, monoalkyl phosphate, polyoxyethylene monoalkyl ether phosphate, dialkyl phosphate, polyoxyethylene dialkyl ether phosphate, trialkyl phosphate, polyoxyethylene trialkyl ether phosphate, polyoxyethylene monostyrene-modified phenyl ether phosphate ester, polyoxyethylene disstyrene-modified phenyl ether phosphate ester, perfluoroalkyl group-phosphate group-containing phosphate ester, or their metal salts, ammonium salts, amine salts, alkanolamine salts, etc., in combination with the silicone composite particles, lubricant molecules are adsorbed onto the surface of the silicone composite particles, forming lubricating particles covered with a lubricant molecular film, thereby providing even greater prevention of ball bearing wear and improvement of writing performance. Commercially available products include Phosphanol BH-650, SM-172, ED-200, GF-339, RA-600, GF-199, ML-200, ML-220, ML-240, RD-510Y, GF-185, RS-410, RS-610, RS-710, RL-210, RL-310, RB-410, and RP-71. 0, AK-25, GF702, RS-610NA, SC-6103, RD-720, LP-700, LS-500, LB400 (all manufactured by Toho Chemical Industry Co., Ltd.), and Prysurf A207H, A208B, A219B, A208S, A212S, A215C, AL, AL12 (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), NIKKOL Examples include DLP-10, DOP-8NV, DDP-2, DDP-4, DDP-6, DDP-8, DDP-10, TLP-4, TCP-5, TOP-0V, TDP-2, TDP-6, and TDP-8 (all manufactured by Nikko Chemicals Co., Ltd.), and Megafac F-510 (all manufactured by DIC Corporation). In particular, monoalkyl phosphate, polyoxyethylene monoalkyl ether phosphate, dialkyl phosphate, polyoxyethylene dialkyl ether phosphate, trialkyl phosphate, polyoxyethylene trialkyl ether phosphate, polyoxyethylene monostyrene-derived phenyl ether phosphate ester, and polyoxyethylene disstyrene-derived phenyl ether phosphate ester have strong adsorption forces to the surface of the silicone composite particles, and it is considered that the strength of the lubricant molecular film becomes even stronger, thus improving the effect of preventing ball seat wear and improving writing performance. Furthermore, if the alkyl group in the phosphate ester has 10 to 20 carbon atoms, wear between the ball and the ball seat is reduced even during heavy writing, which is preferable. Furthermore, to improve wear prevention between the ball and the ball seat, it is preferable to use a phosphate ester into which ethylene oxide groups have been introduced. It is preferable that the phosphate ester structure contains 1 mole to 20 moles of ethylene oxide groups. By appropriately adjusting the Hydrodrophile-Lipophile Balance (HLB) of the phosphate ester used in oil-based inks for ballpoint pens, the phosphate ester does not separate in the ink, thus maintaining good wear resistance between the ball and the ball seat over a long period of time. The preferred HLB range is between 5 and 12.

[0029] The amount of phosphate ester used is preferably 0.05% to 20.0% by weight of the total amount of oil-based ink for ballpoint pens, more preferably 0.1% to 10.0% by weight, and most preferably 0.3% to 2.0% by weight. This optimizes the adsorption state to the ballpoint pen tip and the silicone composite particles, significantly improving the lubricating components. If the amount used is less than 0.05% by weight, the improvement in writing quality is insufficient, and if it exceeds 20.0% by weight, the content of organic solvents in the ink decreases, which may lead to insufficient solubility of solid components in the ink such as dyes and resins, potentially causing ink to skip or fade.

[0030] In this invention, by maintaining the pH of the ink within an appropriate range, the adsorption capacity of acidic substances to the metal ballpoint pen tip and the silicone composite particles can be increased, thereby ensuring the suppression of dotted lines in handwriting and improving writing quality. The appropriate range is 2.5 to 7.0, and more preferably 4.0 to 6.0.

[0031] Furthermore, water can also be added to the oil-based ink for ballpoint pens of the present invention. The water can be selected from mineral water, tap water, deionized water, purified water, distilled water, pure water, etc. Among these, deionized water, purified water, distilled water, and pure water are preferred because they prevent the concentration of calcium and magnesium in the ink from reacting with the components in the ink to form insoluble precipitates such as calcium chloride, magnesium chloride, calcium-acid compounds, and magnesium-acid compounds. The addition of water increases conductivity and the adsorption force of acidic substances to the surface of the silicone composite particles due to pH is further increased, thus further improving the suppression of dotted lines in writing and the writing feel. The amount of water used can be added within a range that does not cause the ink to become unstable over time, and is preferably 0.1% to 15.0% by weight of the total amount of oil-based ink for ballpoint pens. More preferably, it is 0.5% to 10.0% by weight. Furthermore, there are no particular limitations on the method of adding water. Water can be added directly to an ink that has been appropriately mixed with other components, or the components used in oil-based ballpoint pen ink, such as colorants and resins, may be pre-moistened to absorb moisture.

[0032] The viscosity of the oil-based ink for ballpoint pens of the present invention is not particularly limited, but is calculated based on a shear rate of 100 sec in 25°C, assuming writing conditions. -1 The ink viscosity is preferably between 30 mPa·s and 3000 mPa·s. If it is less than 30 mPa·s, the lubricating film strength of the oil-based ink will be low, which may reduce the writing feel and the wear resistance of the ball bearing. If it exceeds 3000 mPa·s, the ink may skip when writing again, i.e., the initial skipping may worsen. By setting the ink viscosity between 50 mPa·s and 500 mPa·s, the ink film strength will be such that the elastic effect of the silicone composite particles can be exerted, resulting in a unique writing feel. Setting it between 60 mPa·s and 200 mPa·s will make the unique writing feel even more pronounced.

[0033] The vertical axial movement of the ball in the ballpoint pen tip used in this invention is preferably greater than 3 μm and 60 μm or less. This is because if it is 3 μm or less, it becomes difficult to obtain dark lines and a good writing feel, and if it exceeds 60 μm, the amount of ink dispensed becomes too large, resulting in severe ink bleeding. By setting it greater than 20 μm and 55 μm or less, a large amount of oily ink containing the silicone composite particles acts as a lubricant between the ball and the ball seat, which significantly improves the writing feel compared to conventional ballpoint pens.

[0034] The ballpoint pen refill consists of a ball tip that is directly housed in an ink reservoir tube, a ball as a writing element, and a ball holder that holds the ball with a portion protruding from the tip opening of the ink passage hole, the tip opening of the ink passage hole being smaller in diameter than the ball, and multiple inward protrusions formed in the middle of the inner wall of the ink passage hole to define the range of forward and backward movement of the ball, and is attached either directly to the tip of the ink reservoir tube or via a tip holder. The ball holder of the ballpoint pen tip is mainly made by forming a through hole that serves as the ink passage hole and inward protrusions in a cylindrical metal member such as stainless steel using a cutting blade such as a drill or broach, but it is also possible to use a pipe material with a pre-formed through hole. When using a pipe material, a recess is formed on the outer wall of the pipe material by pressing and deforming it with a pin, thereby forming a convex part on the inner wall corresponding to that part, and that convex part becomes the inward protrusion.

[0035] The balls that can be used with the aforementioned ballpoint pen tip have the following composition: tungsten (element symbol: W) 75.0% to 85.0% by weight, cobalt (element symbol: Co) 9.0% to 14.0% by weight, chromium (element symbol: Cr) 0.0% to 3.0% by weight, carbon (element symbol: C) 0.0% to 6.0% by weight, and Cr3C3 0.0% to 5.0% by weight. The surface roughness of the ball should be Ra 1.0 to 20.0. The Vickers hardness (HV) of the ball should be 1000 to 2000. In addition to the cemented carbide alloys mentioned above, other examples include those with a composition of silicon carbide (molecular formula: SiC) 0.0% to 95.0% by weight and yttrium oxide-aluminum oxide (molecular formula: Y2O3-Al2O3) 0.0% to 5.0% by weight, with a ball surface roughness of Ra 0.5nm to 10.0nm; those with a composition of zirconium dioxide (molecular formula: ZrO2) 0.0% to 95.0% by weight and yttrium oxide (molecular formula: Y2O3) 0.0% to 5.0% by weight, with a ball surface roughness of 0.5nm to 10.0nm; and those with a composition of aluminum oxide (molecular formula: Al2O3) 0.0% to 99.9% by weight and chromium (element symbol: Cr) 0.0% to 0.1% by weight, with a ball surface roughness of 0.5nm to 10.0nm. The ball diameter can be any of the conventionally known sizes between 0.1 mm and 30.0 mm. For fine lines, it is preferable to use a ball diameter of 0.5 mm or less, and for bold lines, it is preferable to use a ball diameter of 1.0 mm or more.

[0036] If the material of the ball holder that can be used with the aforementioned ballpoint pen tip is stainless steel, The following components may be used: chromium (element symbol: Cr) 18.0% to 22.0% by weight, molybdenum (element symbol: Mo) 0.5% to 3.0% by weight, manganese (element symbol: Mn) 0.0% to 2.0% by weight, silicon (element symbol: Si) 0.0% to 1.0% by weight, sulfur (element symbol: S) 0.0% to 0.2% by weight, phosphorus (element symbol: P) 0.0% to 0.1% by weight, carbon (element symbol: C) 0.0% to 0.1% by weight, lead (element symbol: Pb) 0.0% to 0.5% by weight, tellurium (element symbol: Te) 0.0% to 0.1% by weight, and iron (element symbol: Fe) 0.0% to 80.0% by weight. The ball holder must have a Vickers hardness (HV) of 150 to 300. If the ball holder is made of a copper alloy, it can be used if its composition is: carbon (C) 55.0% to 65.0% by weight, nickel (Ni) 12.0% to 18.0% by weight, manganese (Mn) 0.0% to 1.0% by weight, iron (Fe) 0.0% to 0.5% by weight, lead (Pb) 0.0% to 4.0% by weight, and zinc (Zn) 0.0% to 30.0% by weight. The ball holder can be used with a Vickers hardness (HV) of 150 to 300. In addition, the ball holder can be made of conventionally known materials such as resin or brass.

[0037] Furthermore, to improve the airtightness of the ball holder by pressing the ball against the inner edge of the tip opening of the ball holder and to prevent ink from seeping out from the tip of the ball pen, the ball holder may be equipped with a coil spring that pushes the ball forward from the back through a central hole formed in the center of multiple inward protrusions inside the ball pen tip. The coil spring is mainly made of stainless steel wire such as SUS304, but hard steel wire and piano wire can also be used. Resins such as polycarbonate and polyetheretherketone can also be used. Stainless steel wire and hard steel wire with nickel (element symbol: Ni) plating on the surface can also be used. The pressing load on the ball when the coil spring is installed inside the ball holder can be 0.01N or more and 1.50N or less.

[0038] The present invention will be described in more detail by the following examples, but the present invention is not limited to these examples.

[0039] The viscosity used in the examples was measured using MCR302 (manufactured by Anton Paar) at 25°C and a shear rate of 100 s⁻¹ using a rotor CP50-1. (Unit: mPa·s)

[0040] The pH in the examples was measured at 25°C using PICCOLO plus (manufactured by Hanna Instruments Japan Co., Ltd.). [Examples]

[0041] As shown in Table 1, oil-based inks were prepared as described in Examples 1-9 and Comparative Examples 1-6. The materials used are as follows. Pigment (1): Printex 35 (carbon black, manufactured by Orion Engineered Carbons Co., Ltd.) Pigment (2): FUJI FAST RED 8800 (CIPigment Red 254, manufactured by Fuji Pigment Co., Ltd.) Pigment (3): CROMOPHTAL Blue A3R (CIPigment Blue 60, manufactured by BASF Japan Ltd.) Dye (1): SPILON RED C-GH (Salt-forming dye made from xanthene-based basic dye and alkyl diphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Co., Ltd.) Dye (2): VALIFAST RED 1364 (a salt-forming dye made from CIBasic Red 1:1, alkylbenzene sulfonic acid, and alkyl diphenyl ether disulfonic acid, manufactured by Orient Chemical Industries, Ltd.) Dye (3): VALIFAST YELLOW 1120 (Onium salt of basic dye and colorless organic acid, manufactured by Orient Chemical Industries, Ltd.) Dye (4): SPILON YELLOW C-GNH new (Salt-forming dye made from indolinone-based basic dye and alkyl diphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Co., Ltd.) Dye (5): OIL BLUE 613 (a mixture of CISolvent Blue 5 and rosin-modified resin, manufactured by Orient Chemical Industries, Ltd.) Dye (6): VALIFAST BLUE 1631 (a salt-forming dye made from CIBasic Blue 7 and a colorless organic acid, manufactured by Orient Chemical Industries, Ltd.) Dye (7): VALIFAST VIOLET 1731 (a salt-forming dye made from CIAcid Violet 17 and methine-based dyes, manufactured by Orient Chemical Industries, Ltd.) Dye (8): Salt-forming dye of Acid Yellow 42 and benzoxonium chloride Organic solvent (1): n-propanol Organic solvent (2): Ethylene glycol monoisopropyl ether Organic solvent (3): Ethylene glycol monophenyl ether Organic solvent (4): Benzyl alcohol Phosphate ester (1): Phosphanol LB-400 (a mixture of phosphate monoesters, diesters, and triesters of polyoxyethylene (4) oleyl ether, HLB 8.6, manufactured by Toho Chemical Industry Co., Ltd.) Phosphate ester (2): Phosphanol GF-199 (a mixture of phosphate monoesters, diesters, and triesters of lauryl ether, HLB 5.5, manufactured by Toho Chemical Industry Co., Ltd.) Phosphate ester (3): Phosphanol LS-500 (a mixture of phosphate monoesters, diesters, and triesters of polyoxyethylene (4) tridecyl ether, HLB 9.0, manufactured by Toho Chemical Industry Co., Ltd.) Phosphate ester (4): Phosphanol RP-710 (a mixture of phosphate monoesters, diesters, and triesters of polyoxyethylene (6) phenyl ether, HLB 11.9, manufactured by Toho Chemical Industry Co., Ltd.) Phosphate ester (5): NIKKOL DDP-2 (di(C12-15)pareth-2 phosphate, HLB 6.5, manufactured by Nikko Chemicals Co., Ltd.) Organic amine (1): Triisopropanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.) Organic amine (2): Naymine L201 (polyethylene glycol-1 laurylamine, NOF Corporation) Organic amine (3): Triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.) Activating agent (1): Solgen 30 (sorbitan sesquiolate, HLB 3.7, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) Activating agent (2): Pegnol ST-7 (polyoxyethylene (7) alkyl (C12~14) ether, HLB 12.8, manufactured by Toho Chemical Industry Co., Ltd.) Activating agent (3): NIKKOL HCO-10 (polyoxyethylene hydrogenated castor oil, HLB 6.5, manufactured by Nikko Chemicals Co., Ltd.) Activating agent (4): NIKKOL Decaglyn 1-ISV (decaglyceryl monoisostearate, HLB 12.0, manufactured by Nikko Chemicals Co., Ltd.) Activating agent (5): NIKKOL BO-10V (polyoxyethylene oleyl ether, HLB 14.5, manufactured by Nikko Chemicals Co., Ltd.) Silicone composite particles (1): KMP-600 (silicone composite particles, average particle size 5 μm, rubber hardness 30 durometer A, true specific gravity 0.99 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Silicone composite particles (2): KMP-605 (silicone composite particles, average particle size 2 μm, rubber hardness 75 durometer A, true specific gravity 0.99 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Silicone composite particles (3): X-52-7030 (silicone composite particles, average particle size 0.8 μm, rubber hardness 75 durometer A, true specific gravity 1.01 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Silicone rubber particles: KMP-597 (silicone rubber particles, average particle size 5 μm, rubber hardness 30 durometer A, manufactured by Shin-Etsu Chemical Co., Ltd.) Silicone resin particles: Tospearl 120FL Silicone Beads (Silicone resin particles, average particle size 2μm, manufactured by Momentive Performance Materials Japan LLC) Titanium dioxide particles: JR-800 (Titanium dioxide particles, average particle size 0.27 μm, true specific gravity 3.9 g / cm³, manufactured by Teika Co., Ltd.) Silica particles: QSG-170 (hydrophobic silica spherical particles, average particle size 0.17 μm, true specific gravity 1.8 g / cm³, manufactured by Shin-Etsu Chemical Co., Ltd.) Resin (1): Esrec BL-1 (polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd.) Resin (2): Esrec BH-3 (polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd.) Resin (3): PVPK-90 (Polyvinylpyrrolidone, manufactured by Ashland Japan Co., Ltd.) Resin (4): TEGO Variplus SK (polyol resin, OH value 325 mg KOH / g, Tg 90℃, manufactured by Evonik Japan Co., Ltd.) Resin (5): TEGO Variplus CA (ketone aldehyde condensation resin, OH value 200 mg KOH / g, Tg 75℃, manufactured by Evonik Japan Co., Ltd.) Resin (6): Marquis 3002 (rosin maleate, acid value 100 mg KOH / g, Tg 175℃, manufactured by Arakawa Chemical Industries, Ltd.) Resin (7): Harimac T-80 (maleinated rosin, acid value 185 mg KOH / g, Tg 85℃, manufactured by Harima Chemicals Co., Ltd.) Resin (8): 42% acrylic acid-acrylic methacrylate copolymer in ethylene glycol monophenyl ether solution (solid equivalent: acid value 510 mg KOH / g, OH value 130 mg KOH / g, Tg 80℃) Resin (9): 42% acrylic acid-styrene-methacrylic acid copolymer in ethylene glycol monophenyl ether solution (solid equivalent: acid value 300 mg KOH / g, OH value 80 mg KOH / g, Tg 30℃) Resin (10): NISSO HPC-H (Hydroxypropylcellulose, manufactured by Nippon Soda Co., Ltd.) Dispersant (1): DISPERBYK-102 (a copolymer with acidic groups, acid value 101 mg KOH / g, manufactured by BIC Chemie Japan Co., Ltd.) Dispersant (2): DISPERBYK-111 (a copolymer containing an acid group, acid value 129 mg KOH / g, manufactured by BIC Chemie Japan Co., Ltd.) Dispersant (3): BYK-P105 (polymer of low molecular weight unsaturated carboxylic acid, acid value 365 mg KOH / g, manufactured by BYChemie Japan Co., Ltd.) Dispersant (4): DISPERBYK-180 (alkylol ammonium salt of an acid group copolymer, acid value 94 mg KOH / g, amine value 94 mg KOH / g, manufactured by BIC Chemie Japan Co., Ltd.) Dispersant (5): DISPERBYK-108 (hydroxyl group-containing carboxylic acid ester, amine value 71 mg KOH / g, manufactured by BIC Chemie Japan Co., Ltd.) Rust inhibitor: Benzotriazole (manufactured by E-CHEM ENTERPRISE CORPORATION) The manufacturing procedure involved stirring an organic solvent with the silicone composite particles, silicone rubber particles, silicone resin particles, titanium dioxide particles, or silica particles, along with the dispersion resin Esrec BL-1, a dispersant, and optionally a pigment, at 60°C. This was then processed for 2 minutes at a peripheral speed of 30 m / s using a thin-film swirling high-speed mixer. Other additives were then added, and the mixture was stirred with a propeller for 2 hours to obtain an oil-based ink. For commercially unavailable acrylic acid copolymer solutions, an arbitrary monomer and azobisisobutyronitrile, a polymerization initiator, were dissolved in phenyl glycol by propeller stirring, and then heated and polymerized to obtain the acrylic acid copolymer solution.

[0042] Making a ballpoint pen for testing The oil-based inks of Examples 1-9 and Comparative Examples 1-6 were filled in 1.0 mL each into a refill with the same structure as a water-based ballpoint pen equipped with a ballpoint pen tip (Retractable EnerGel, product code BLN75, manufactured by Pentel Co., Ltd., tip material: stainless steel, ball material: carbide, ball diameter: φ0.5 mm, vertical axis movement of the ball of the ballpoint pen tip: 30 μm). The pen tip was attached, the pen tip was sealed with a packing (HM200, ethylene-vinyl acetate copolymer resin-based hot melt adhesive), and the mixture was centrifuged.

[0043] Pen tip ink leakage confirmation test 1 Three of the above test ballpoint pens were prepared for each example and comparative example. After removing the gaskets, the "Diet Day" was handwritten in an environment of 25°C and 30% humidity. The pens were then attached to a backing sheet and left upside down for three days. The amount of ink leakage from the pen tip was then checked using a digital microscope (Keyence Corporation, VHX-7000) at 50x magnification, the diameter was recorded, and the average value was calculated (unit: mm).

[0044] Pen tip ink leakage confirmation test 2 Three test ballpoint pens, each with a 50g weight attached, were prepared for each example and comparative example. After removing the gasket, the "Diet Day" was handwritten in an environment of 25°C and 30% humidity. The pens were then placed vertically against an acrylic resin plate and left undisturbed for three days. The size of the ink that leaked from the pen tip onto the acrylic resin plate was measured using a digital microscope at 20x magnification, the diameter was recorded, and the average value was calculated (unit: mm).

[0045] Dispersion stability confirmation test of silicone composite particles One test ballpoint pen was prepared for each example and comparative example, and after being left undisturbed for 3 days in an environment with a temperature of 70°C and uncontrolled humidity, its appearance was examined. ○...There were no issues with the appearance, and the writing was fine. △...The silicone composite particles can be seen in small amounts at the grease interface or at the stepped portion that occurs between the pipe and the crimped part of the ballpoint pen tip component. ×...The silicone composite particles are heavily visible at the grease interface or at the stepped portion that occurs between the pipe and the crimped part of the ballpoint pen tip component.

[0046] Initial brushstroke smudging confirmation test Three ballpoint pens were prepared for each example and comparative example described above. After removing the gaskets, the "Diet Day" was handwritten in an environment of 25°C and 30% humidity. After leaving the pens to stand horizontally for one week, the "Diet Day" was written again by hand, and the distance of smudging was measured. The average value was taken as the initial smudging value. (Unit: mm)

[0047] The results are shown in Tables 1 to 3.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3]

[0051] The ballpoint pens of Examples 1 to 9 contain silicone composite particles in the ink, which have a structure in which silicone rubber particles are coated with silicone resin. Therefore, they do not break when the ball is pinched between the ball and the base during writing, and the particles can densely concentrate without forming an aggregate structure in areas where the ink flow path narrows. As a result, it is considered that they exhibit an excellent sealing effect even in low humidity environments, and ink leakage can be suppressed. Furthermore, since the ballpoint pens of Examples 4 to 7 contain silicone composite particles smaller than 1 μm in their ink, it is considered that the ink sealing effect was further improved, and the effectiveness of the pen tip ink leakage confirmation test 1 was enhanced. Furthermore, since the ballpoint pens of Example 2, Examples 4, 5, and Examples 7-9 contain hydroxypropyl cellulose, it is possible to suppress the spread of ink that leaks onto the acrylic plate, and it is considered that the effectiveness of the pen tip ink leakage confirmation test 2 was improved. In addition to the ink leakage suppression effect, the ballpoint pens of Examples 1 to 8 use both silicone composite particles and phosphate esters, resulting in a unique writing experience without causing fatigue during writing. Furthermore, the ballpoint pens of Example 2, Examples 4-6, and Examples 8 and 9, which use the silicone composite particles in combination with a resin having an acidic group, showed improved distance of initial ink skipping. Furthermore, in the ballpoint pens of Examples 4 to 6, the dispersion stability of the silicone composite particles was improved by using a dispersant with an acid value of 100 mg KOH / g or higher, and no bias of the composite particles was observed in the refill after the dispersion stability confirmation test. The ballpoint pen in Comparative Example 1 does not contain the silicone composite particles in its ink, so the sealing effect is not achieved and the ink leaks out. The ballpoint pen in Comparative Example 2 contains silicone rubber particles, and due to the surface deformation of the rubber powder, the contact area increases, making aggregation more likely. As a result, the sealing effect of the ink flow path within the ballpoint pen tip is weak and the ink leaks out. The ballpoint pen in Comparative Example 3 contains silicone resin particles, and when the ball is squeezed between the ball and the base during writing, the silicone resin particles are damaged, and the shape of the particles becomes uneven. This disrupts the structure when the particles are densely packed in areas where the ink flow path narrows, so the sealing effect is not sufficiently achieved and the ink leaks out. The ballpoint pens in Comparative Examples 4 and 5 contain particles other than silicone, so the particles aggregate or break in the ink flow path, and the shape of the particles becomes uneven, so the sealing effect is not sufficiently achieved and the ink leaks out. The ballpoint pen in Comparative Example 6 has an ink containing a dye with a specific structure and butyral resin above a certain level, but in a low humidity environment, the sealing effect is not sufficiently achieved and the ink leaks out.

[0052] In this specification, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equivalent state shall not only describe a state of being strictly equal, but also describe a state in which tolerances or differences exist to the extent that the same function can be obtained. Furthermore, in this specification, the expressions “equipment,” “includes,” or “possess” of a component are not exclusive expressions that exclude the existence of other components.

Claims

1. An oil-based ink for ballpoint pens, characterized by comprising at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin, and a dispersant.

2. The oil-based ink for ballpoint pens according to claim 1, wherein the acid value of the dispersant is 100 mg KOH / g or more.

3. It contains at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin, and is subjected to a shear rate of 100 sec at 25°C. ―１ An oil-based ink for ballpoint pens characterized by having a viscosity of 30 mPa·s or more and 3000 mPa·s or less.

4. It contains at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin, and is subjected to a shear rate of 100 sec at 25°C. ―１ An oil-based ink for ballpoint pens characterized by having a viscosity of 50 mPa·s or more and 500 mPa·s or less.

5. It contains at least silicone composite particles having a structure in which silicone rubber particles are coated with silicone resin, and is subjected to a shear rate of 100 sec at 25°C. ―１ An oil-based ink for ballpoint pens characterized by having a viscosity of 60 mPa·s or more and 200 mPa·s or less.

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