JP2024146874A - Oil-based ink composition for ballpoint pen and ballpoint pen - Google Patents

Abstract

To provide an oily ink composition for ballpoint pen and a ballpoint pen which are capable of obtaining satisfactory handwriting in satisfactory writing feel even when writing at high speed or high writing pressure while capable of effectively suppressing ink leakage.SOLUTION: An oily ink composition for ballpoint pen contains first phosphate ester which is polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 4 or more and 17 or less, second phosphate ester which is polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 18 or more and 24 or less, water and nonionic surfactant.SELECTED DRAWING: Figure 1

Description

This disclosure relates to an oil-based ink composition for a ballpoint pen and a ballpoint pen.

An oil-based ink for ballpoint pens that writes well and leaves good marks has been proposed.

Patent Document 1 discloses a ballpoint pen ink that is resistant to smudging even when left to stand for long periods of time, and contains a colorant, an organic solvent, a triester of oleyl alcohol and phosphoric acid, and water.

Patent Document 2 discloses an ink composition for oil-based ballpoint pens that improves the writing experience, prevents smearing or bleeding, and has good writing properties, and contains a colorant, an amide solvent, and a polyacrylic acid resin.

JP 2010-106187 A JP 2022-184953 A

However, with the oil-based inks for ballpoint pens in Patent Documents 1 and 2, when writing at high speed (when writing quickly) or with high writing pressure, there are cases where the handwriting is not good, such as when the ink smudges or ink blobs occur. In addition, it is desirable to be able to suppress ink leakage while obtaining a good writing feel and handwriting when writing at high speed or with high writing pressure.

In view of the above circumstances, at least one embodiment of the present invention aims to provide an oil-based ink composition for a ballpoint pen and a ballpoint pen that can effectively suppress ink leakage while providing a good writing feel and good handwriting even when writing at high speed or with high writing pressure.

The oil-based ink composition for ballpoint pens according to at least one embodiment of the present invention comprises:
a first phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having 4 to 17 carbon atoms;
a second phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having from 18 to 24 carbon atoms;
Water,
A nonionic surfactant;
Includes.

In addition, at least one embodiment of the ballpoint pen of the present invention is
Writing department and
An ink reservoir that contains the oil-based ink,
The oil-based ink is supplied from the ink reservoir to the writing section.

At least one embodiment of the present invention provides an oil-based ink composition for a ballpoint pen and a ballpoint pen that can effectively prevent ink leakage while providing a good writing feel and good handwriting even when writing at high speed or with high writing pressure.

1 is a vertical cross-sectional view showing a ballpoint pen according to an embodiment. 2 is a vertical cross-sectional view showing a refill used in the ballpoint pen shown in FIG. 1. FIG. 3 is an enlarged vertical cross-sectional view showing a portion I in FIG. 2 . FIG. 4 is an enlarged vertical cross-sectional view of a test ballpoint pen tip showing part II in FIG. 3 . FIG. 4 is a vertical cross-sectional view showing dimension measurement points. This is a cross-sectional view taken along line III-III' in Figure 5. This is a diagram showing the character strings written in pen tip ink leakage confirmation tests 1 to 3.

Below, several embodiments of the present invention will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described as the embodiments or shown in the drawings are not intended to limit the scope of the present invention and are merely illustrative examples.

(Ink composition)
An oil-based ink composition for a ballpoint pen according to some embodiments comprises a first phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 4 or more and 17 or less, a second phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 18 or more and 24 or less, water, and a nonionic surfactant.

According to the oil-based ink composition of the above-described embodiment, when writing with a ballpoint pen, a thick, water-containing, multi-layered film (hereinafter, "multi-layered film") that includes a layer of phosphate ester and a layer of nonionic surfactant is likely to be formed between the ball at the tip of the pen and the metal surface of the receiving seat of the ball holder.
That is, since the above-mentioned oil-based ink composition contains a first phosphate ester having a relatively small number of carbon atoms in the hydrocarbon group and a second phosphate ester having a relatively large number of carbon atoms in the hydrocarbon group, the phosphate groups of these phosphate esters are adsorbed to the metal surfaces of the ball and the receiving seat, forming a layer of phosphate ester on the metal surfaces of the ball and the receiving seat. Here, since the second phosphate ester has a relatively long hydrocarbon group, a relatively thick layer of phosphate ester is formed on the metal surface, and since the first phosphate ester has a relatively short hydrocarbon group, the second phosphate ester penetrates between the first phosphate esters, and a layer of phosphate ester having a dense structure is quickly formed on the metal surface.
The oil-based ink composition described above contains water and a nonionic surfactant. Therefore, when writing with a ballpoint pen, the hydrophobic group of the nonionic surfactant interacts with the hydrocarbon group of the phosphate ester, and a layer of the nonionic surfactant is formed between the layers of the phosphate ester formed on the surfaces of the ball and the receiving seat, respectively, so that a thick multilayer film is easily obtained, and the hydrophilic group of the nonionic surfactant interacts with water, and water with high surface tension is taken in by the layer of the nonionic surfactant, so that the cushioning property of the multilayer film is enhanced.
Thus, according to the above-mentioned embodiment, when writing with a ballpoint pen, a multilayer film with a large thickness and high cushioning properties is easily formed between the ball and the metal surface of the receiving seat, so that the multilayer film can be maintained between the ball and the receiving seat even when writing at high speed or with high writing pressure, and the lubrication during writing is good. Therefore, even when writing at high speed or with high writing pressure, the writing feel is good and smearing, skipped lines, or blobs can be suppressed.
In the above embodiment, the nonionic surfactant does not wet and spread in areas where there is no metal, so that the phosphate ester interacting with the nonionic surfactant is prevented from excessively spreading, and thus leakage of the ink composition from the pen tip can be effectively prevented.
Therefore, according to the above-described embodiment, it is possible to effectively prevent ink leakage, while still obtaining good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

In this specification, smearing refers to a state in which the ball of a ballpoint pen does not rotate and ink is not transferred. It also includes a state in which the ink becomes thicker over time and is no longer ejected. In addition, in this specification, skipped lines (dotted lines) refer to a state in which there is poor lubrication between the ball of a ballpoint pen and the receiving seat of the ball holder, causing the ball to rotate intermittently and resulting in intermittent transfer of ink.

The first phosphate ester and the second phosphate ester, which are polyoxyethylene hydrocarbon phosphate esters having a hydrocarbon group, may be monoesters, diesters or triesters, or may be mixtures thereof. When the polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group is a monoester, it is represented by the following formula (A).
RO-( _CH2CH2O ) _n -PO(OH) _{2 ...} (A)

The first phosphate ester has a hydrocarbon group (R in the above formula (A)) having 4 or more and 17 or less carbon atoms.
The second phosphate ester has a hydrocarbon group (R in the above formula (A)) having 18 or more and 24 or less carbon atoms.

The hydrocarbon group of the above-mentioned phosphate ester may include a straight chain hydrocarbon group, a branched chain hydrocarbon group, or a cyclic hydrocarbon group. The above-mentioned chain hydrocarbon group or cyclic hydrocarbon group may be an unsaturated hydrocarbon group (such as an alkyl group) or an unsaturated hydrocarbon group (such as an alkenyl group, an alkynyl group, or a phenyl group).

The average number of moles of ethylene oxide added to the polyoxyethylene groups of the above-mentioned phosphate ester (the average value of n in the above formula (A)) is not particularly limited, but may be 2 or more and 10 or less, or 2 or more and 6 or less.

Specific examples of the first phosphate ester include, for example, a phosphate ester of polyoxyethylene tridecyl ether (hydrocarbon group: alkyl group having 13 carbon atoms), a phosphate ester of polyoxyethylene lauryl ether (hydrocarbon group: alkyl group having 12 carbon atoms), a phosphate ester of polyoxyethylene phenyl ether (hydrocarbon group: unsaturated hydrocarbon group having 13 carbon atoms), and a phosphate ester of polyoxyethylene lauryl ether (hydrocarbon group: alkyl group having 12 carbon atoms).
Examples of commercially available products include Phosphanol BH-650, SM-172, ED-200, GF-339, RA-600, GF199, ML-200, ML-220, ML-240, RD-510Y, GF-185, RS-610, RS-710, RP-710, AK-25, GF702, RS-610NA, SC-6103, LP-700, and LS-500 (all manufactured by Toho Chemical Industry Co., Ltd.); and Plysurf A207H, A208B, A219B, A208S, A212S, and A215C (all manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).

The content of the first phosphate ester in the ink composition may be 0.2% by weight or more and 1.2% by weight or less, 0.3% by weight or more and 1.0% by weight or less, or 0.35% by weight or more and 0.6% by weight or less.

Specific examples of the second phosphate ester include, for example, polyoxyethylene oleyl ether phosphate ester (hydrocarbon group: unsaturated hydrocarbon group having 18 carbon atoms) and polyoxyethylene stearyl ether phosphate ester (hydrocarbon group: alkyl group having 18 carbon atoms).
Commercially available products include Phosphanol RL-210, RL-310, RB-410, RD-720, and LB-400 (all manufactured by Toho Chemical Industry Co., Ltd.).

The content of the second phosphate ester in the ink composition may be 0.05% by weight or more and 2.0% by weight or less, 0.1% by weight or more and 0.6% by weight or less, or 0.1% by weight or more and 0.3% by weight or less.

The difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the hydrocarbon group of the first phosphate ester may be 4 or more.

In this case, the difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the first phosphate ester is 4 or more, so the length of the carbon chains in the hydrocarbon groups of both differs to some extent. Therefore, in the layer of phosphate ester formed on the metal surface of the ball and the receiving seat, the second phosphate ester is more likely to penetrate between the first phosphate ester, and a layer of phosphate ester with a dense structure is more likely to form on the metal surface. Therefore, when writing with a ballpoint pen, a thick multilayer film containing a layer of phosphate ester and a layer of nonionic surfactant is more likely to form between the ball at the tip of the pen and the metal surface of the receiving seat. Therefore, a good handwriting with a good writing feel can be obtained even when writing at high speed or with high writing pressure.

In some embodiments, the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 12 or more and 14 or less, and the number of carbon atoms in the hydrocarbon group of the second phosphate ester is 18 or more and 20 or less.

In the above embodiment, the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 12 to 14, and the number of carbon atoms in the hydrocarbon group of the second phosphate ester is 18 to 20, so that the lengths of the carbon chains of the two hydrocarbon groups differ to some extent. Therefore, in the layer of phosphate ester formed on the metal surface of the ball and the receiving seat, the second phosphate ester is more likely to penetrate between the first phosphate ester, and a layer of phosphate ester with a dense structure is more likely to be formed on the metal surface. Therefore, when writing with a ballpoint pen, a thick multilayer film including a layer of phosphate ester and a layer of nonionic surfactant is more likely to be formed between the ball at the tip of the pen and the metal surface of the receiving seat. Therefore, it is possible to obtain good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

In some embodiments, the HLB value of the first phosphate ester and the HLB value of the second phosphate ester may be 4 or more and 14 or less, or 7 or more and 12 or less.

In this specification, the HLB (hydrophilic-lipophilic balance) value refers to the HLB value calculated by the Davis method. The HLB value is a value that indicates affinity with water and oil, and the higher the value, the greater the affinity with water.

In the above embodiment, the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 4 or more or 7 or more, so that the multilayer film has a moderate hydrophilicity and is unlikely to inhibit the incorporation of water. In addition, in the above embodiment, the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 14 or less or 12 or less, so that the hydrocarbon group of the first/second phosphate ester is likely to interact with the hydrophobic group of the nonionic surfactant. As a result, the hydrophilic group of the nonionic surfactant is likely to interact with water, and water is likely to be incorporated into the layer of the nonionic surfactant. Therefore, according to the above embodiment, water is likely to be held in the layer of the nonionic surfactant, so that the cushioning property of the multilayer film formed between the ball and the metal surface of the receiving seat is increased. Therefore, even when writing at high speed or with high writing pressure, the multilayer film is likely to be held between the ball and the receiving seat, and the lubrication during writing is likely to be good. Therefore, even when writing at high speed or with high writing pressure, a good writing feel and handwriting are likely to be obtained.

In some embodiments, the total content of the first phosphate ester and the second phosphate ester in the ink composition is 0.4% by weight or more and 3.0% by weight or less.

According to the above-mentioned embodiment, the total content of the first phosphate ester and the second phosphate ester is 0.4% by weight or more and 3.0% by weight or less, so that the density of the phosphate ester layer formed on the metal surface of the ball and the receiving seat is moderate, and therefore a multilayer film of moderate density is formed between the ball at the pen tip and the metal surface of the receiving seat. Therefore, while ink leakage can be effectively suppressed, it is easy to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

In some embodiments, the weight ratio of the content of the first phosphate ester to the content of the second phosphate ester (content of the first phosphate ester [wt %]/content of the second phosphate ester [wt %]) may be 0.2 or more and 8.0 or less, or may be 0.25 or more and 4.0 or less.

According to the above-mentioned embodiment, since the weight-based ratio of the content of the first phosphate ester to the content of the second phosphate ester is 0.2 to 8.0 or 0.25 to 4.0, the layer of phosphate ester formed on the metal surface is likely to have a dense structure. As a result, a multilayer film of appropriate density is formed between the ball of the pen tip and the metal surface of the receiving seat. Therefore, while ink leakage can be effectively suppressed, it is easy to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

As the nonionic surfactant, any well-known nonionic surfactant can be used without any particular limitation. As the nonionic surfactant, an ester type nonionic surfactant such as an ester of a polyhydric alcohol and a fatty acid, an ether type nonionic surfactant such as a polyoxyethylene hydrocarbon ether or a polyoxyethylene hydrocarbon phenyl ether, or an ester-ether type nonionic surfactant having both an ester bond and an ether bond in the molecule can be used.

The content of the nonionic surfactant in the ink composition may be 0.25% by weight or more and 2.0% by weight or less, or 0.5% by weight or more and 1.0% by weight or less.

In some embodiments, the HLB value of the nonionic surfactant is 4 or more and 15 or less.

In the above-mentioned embodiment, the nonionic surfactant has an HLB value of 4 or more, and therefore has a certain degree of hydrophilicity, so that water is easily taken up into the layer of the nonionic surfactant by interaction with water. Also, in the above-mentioned embodiment, the nonionic surfactant has an HLB value of 15 or less, so that the hydrophilicity is not excessive and it easily interacts with the hydrocarbon groups of the first and second phosphate esters, so that the above-mentioned multilayer film is easily formed between the ball and the metal surface of the receiving seat. Therefore, according to the above-mentioned embodiment, it is possible to effectively suppress ink leakage, while making it easier to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

Specific examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyoleyl ether, polyoxyethylene hydrogenated castor oil, sorbitan sesquioleate, polyoxyethylene sorbitan monooleate, and polyglycerin fatty acid decaglyceryl.
Commercially available products include NIKKOL BL-2, BL-4.2, BL-9EX, BC-2, BC-5.5, BC-7, BC-10, BS-2, BS-4, BO-2V, BO-7V, BO-10V, BB-5, BB-10, BD-4, BT-3, BT-5, BT-7, BT-9, BT-12, PBC-31, PBC-33, PBC-41, PBC-44, PEN-4612, PEN-4620, PEN-4630, and BPS-5. , BPS-10, HCO-5, HCO-10, HCO-20, HCO-30, HCO-40, HCO-50, HCO-60, HCO-80, TS-10V, TS-10MV, TS-106V, TS-30V, TI-10V, TO-10V , TO-10MV, TO-106V, TO-30V, GS-460, GO-4V, GO-430NV, GO-440V, GO-460V, Tetraglyn 1-SV, Tetraglyn 1-OV, Hexaglyn 1-L, Hexaglyn 1-M, Hexaglyn 1-SV, Hexaglyn 1-OV, Decaglyn 1-M, Decaglyn 1-SV, Decaglyn 1-50SV, Decaglyn 1-ISV, Decaglyn 1-OV, Decaglyn 1-LN, Decaglyn 2-SV, Decaglyn 2-ISV, Decaglyn 3-SV, Decaglyn 3-OV, TMGS-5V, TMGS-15V, TMGO-5, TMGO-15 (manufactured by Nikko Chemicals Co., Ltd.), Pegnol L-4, TH-8, L-9A, L-12S, T-6, TE-10A, ST-7, ST-9, ST-12, O-6S, O-1 6A, S-4DV (manufactured by Toho Chemical Co., Ltd.), Neugen Examples of such compounds include XL-40, XL-100, TDS-30, LF-60X, TDX-50, TDX-80, SD-30, SD-60, SD-70, SD-80, EA-87, Solgen 90, 110, and TW-60 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

The water in the ink composition may be mineral water, tap water, ion-exchanged water, purified water, distilled water, or pure water.

In some embodiments, the water content in the ink composition may be 1.0% by weight or more and 10.0% by weight or less, or 4.0% by weight or more and 8.0% by weight or less.

In the above-mentioned embodiment, the water content in the ink composition is 1.0% by weight or more or 4.0% by weight or more, so that a certain amount of water is incorporated into the above-mentioned multilayer film, and the cushioning properties of the multilayer film are enhanced. In addition, in the above-mentioned embodiment, the water content in the ink composition is 10.0% by weight or less or 8.0% by weight or less, so that the water content in the oil-based ink composition is not too high, and water can be stably dissolved in the oil-based ink. There is no particular limitation regarding the method of adding water, but water may be added directly to an ink in which components other than water are appropriately mixed, or water may be added to components used in the oil-based ink for ballpoint pens, such as colorants and resins, in a state in which the components have absorbed moisture or water in advance.

In some embodiments of the oil-based ink for ballpoint pens, the colorant can be any water-based dye, oil-soluble dye, or pigment, without any particular restrictions.

As the water-soluble dye, any of direct dyes, acid dyes, and basic dyes can be used. Specific examples of direct dyes include Japanol Fast Black D Concentrate (C.I. Direct Black 17), Water Black 100L (same 19), Water Black L-200 (same 19), Direct Fast Black B (same 22), Direct Fast Black AB (same 32), Direct Deep Black EX (same 38), Direct Fast Black Concentrate (same 51), Kayalas Spragray VGN (same 71), Kayalas Direct Brilliant Yellow G (C.I. Direct Yellow 4), Direct Fast Yellow 5GL (same 26), Aizen Primula Yellow GCLH (same 44), Direct Fast Yellow R (same 50), Aizen Direct Fast Red FH (C.I. Direct Red 1), Nippon Fast Scarlet GSX (same 4), Direct Fast Scarlet 4BS (same 23), Aizen Direct Trodurin BH (same 31), Direct Scarlet B (same 37), Kayak Direct Scarlet 3B (same 39), Aizen Primula Pink 2BLH (same 75), Sumi Light Red F3B (same 80), Aizen Primula Red 4BH (same 81), Kayalas Spralubin BL (same 83), Kayalas Light Red F5G (same 225), Kayalas Light Red F5B (same 226), Kayalas Light Rose FR (same 22 7), Direct Sky Blue 6B (C.I. Direct Blue 1), Direct Sky Blue 5B (same 15), Sumilite Splat Blue BRR Concentrate (same 71), Daibogen Turquoise Blue S (same 86), Water Blue #3 (same 86), Kayaru Turquoise Blue GL (same 86), Kayaru Splat Blue FF2GL (same 106), Kayaru Splat Turquoise Blue FBL (same 199), etc.

Specific examples of acid dyes include Acid Blue Black 10B (C.I. Acid Black 1), Nigrosine (C.I. Acid Black 2), Suminol Milling Black 8BX (C.I. Acid Black 24), Kayanol Milling Black VLG (C.I. Acid Black 26), Suminol Fast Black BR Concentrate (C.I. Acid Black 31), Mitsui Nylon Black GL (C.I. Acid Black 32), Aizen Opal Black WH Extra Concentrate (C.I. Acid Black 32), Sumiran Black WA (C.I. Acid Black 32), Ranil Black BG Extra Concentrate (C.I. Acid Black 32), Kayanol Milling Black TLB (C.I. Acid Black 32), Suminol Milling Black B (C.I. Acid Black 32), Kayanol Milling Black TLR (C.I. Acid Black 32), Kayanol Milling Black TLB (C.I. Acid Black 32), Kayanol Milling Black TLR ... Kayaku Acid Brilliant Flavin FF (C.I. Acid Yellow 7:1), Kayasil Yellow GG (same 17), Xylene Light Yellow 2G 140% (same 17), Suminol Leveling Yellow NR (same 19), Daiwa Tartrazine (same 23), Kayaku Tartrazine (same 23), Suminol Fast Yellow R (same 25), Diacid Light Yellow 2GP (same 29), Suminol Milling Yellow O (same 38), Suminol Milling Yellow MR (same 42), Water Yellow #6 (same 42), Kayanol Yellow NFG (same 49), Suminol Milling Yellow 3G (same 72), Suminol Fast Yellow G (same 61), Suminol Milling Yellow G (same 78), Kayanol Yellow N5G (same 110), Suminol Milling Guelo 4G 200% (same 141), Kayanol Yellow NG (same 135), Kayanol Milling Yellow 5GW (same 127), Kayanol Milling Yellow 6GW (same 142), Sumitomo Fast Scarlet A (C.I. Acid Red 8), Kayaku Silk Scarlet (same 9), Solar Rubin Extra (same 14), Daiwa New Kokushin (same 18), Aizen Bonsaw RH (same 26), Daiwa Red No. 2 (same 27), Suminol Leveling Brilliant Red S3B (same 35), Kayasil Rubinol 3GS (same 37), Aizen Erythrosine (same 51), Kayaku Acid Rhodamine FB (same 52), Suminol Leveling Rubinol 3GP (same 57), Diacid Alizarin Rubinol F3G 200% (same 82), Aizen Eosin GH (same 87), Water Pink #2 (same 92), Aizen Acid Phloxine PB (same 92), Rose Bengal (same 94), Kayanol Milling Scarlet FGW (same 111), Kayanol Milling Rubin 3 BW (same 129), Suminoall Milling Brilliant Red 3 BN Concentrate (same 131), Suminoall Milling Brilliant Red BS (same 138), Aizen Opal Pink BH (same 186), Suminoall Milling Brilliant Red B Concentrate (same 249), Kayaku Acid Brilliant Red 3 BL (same 254), Kayaku Acid Brilliant Brilliant Red BL (same 265), Kayanol Milling Red GW (same 276), Mitsui Acid Violet 6 BN (C.I. Acid Violet 15), Mitsui Acid Violet BN (same 17), Sumitomo Patent Pure Blue VX (C.I. Acid Blue 1), Water Blue #106 (same 1), Patent Blue AF (same 7), Water Blue #9 (same 9), Daiwa Blue No. 1 (same 9), Spranor Blue B (same 15), Orient Soluble Blue OBC (same 22), Suminol Leveling Blue 4GL (same 23), Mitsui Nylon Fast Blue G (same 25), Kayasil Blue AGG (same 40), Kayasil Blue BR (same 41), Mitsui Alizarin Sapphirol SE (same 43), Suminol Leveling Sky Blue R Extra Conc (same 62), Mitsui Nylon Fast Sky Blue -B (same 78), Sumitomo Brilliant Indocyanine 6Bh/c (same 83), Sandran Cyanine N-6B 350% (same 90), Water Blue #115 (same 90), Orient Soluble Blue OBB (same 93), Sumitomo Brilliant Blue 5G (same 103), Kayanol Milling Ultra Sky SE (same 112), Kayanol Milling Cyanine 5R (same 113), Aizen Opal Blue 2GLH (same 158), Daiwa Guinea Green B (C.I. Acid Green 3), Acid Brilliant Milling Green B (same 9), Daiwa Green #70 (same 16), Kayanol Cyanine Green G (same 25), Suminol Milling Green G (same 27), etc.

Specific examples of basic dyes include Aizenkachiron Yellow 3GLH (C.I. Basic Yellow 11), Aizenkachiron Brilliant Yellow 5GLH (C.I. Basic Yellow 13), Sumiacrylic Yellow E-3RD (C.I. Basic Yellow 15), Maxillon Yellow 2RL (C.I. Basic Yellow 19), Astrazon Yellow 7GLL (C.I. Basic Yellow 21), Kayakryl Golden Yellow GL-ED (C.I. Basic Yellow 28), Astrazon Yellow 5GL (C.I. Basic Yellow 51), Aizenkachiron Orange GLH (C.I. Basic Orange 21), Aizenkachiron Brown 3GLH (C.I. Basic Red 30), Rhodamine 6GCP (C.I. Basic Red 1), Aizen Astraphloxine (C.I. Basic Red 12), Sumiacrylic Brilliant Red E-2B (C.I. Basic Red 15), Astrazon Yellow 5GL (C.I. Basic Yellow 51), Astrazon Yellow 5GL (C.I. Basic Orange 2 ... Examples include Trazon Red GTL (C.I. 18), Aizen Catilon Brilliant Pink BGH (C.I. 27), Maxillon Red GRL (C.I. 46), Aizen Methyl Violet (C.I. Basic Violet 1), Aizen Crystal Violet (C.I. 3), Aizen Rhodamine B (C.I. 10), Astrazon Blue G (C.I. Basic Blue 1), Astrazon Blue BG (C.I. 3), Methylene Blue (C.I. 9), Maxillon Blue GRL (C.I. 41), Aizen Catilon Blue BRLH (C.I. 54), Aizen Diamond Green GH (C.I. Basic Green 1), Aizen Malachite Green (C.I. 4), Bismarck Brown G (C.I. Basic Brown 1), etc. These may be used alone or in combination.

Specific examples of 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. Specific examples include Nigrosine Base EE, Nigrosine Base EEL, Nigrosine Base EX, Nigrosine Base EXBP, Nigrosine Base EB, Oil Yellow 101, Nigrosine Base 107, Oil Pink 314, Oil Brown BB, Nigrosine Base GR, Oil Green BG, and Il Blue 613, Oil Scarlet 308, BOS, Oil Black HBB, 860, BS, Varifast Yellow 1101, 1105, 1109, 3104, 3105, 3108, 4120, AUM, Varifast Orange 2210, 3209, 3210, Varifast Red 1306, 1308, 1320, 1364, 1355, 1 360, 2303, 2320, 3304, 3306, 3320, Balifast Pink 2310N, Balifast Brown 2402, 3405, Balifast Green 1501, Balifast Blue 1603, 1605, 1607, 1631, 2606, 2610, 2620, Balifast Violet 1701, 1702, 1731, Balifast Black 1802, 1805, 1807, 3804, 3806, 3808, 3810, 3820, 3830, Spirit Red 102, Spirit Black AB, Ospi Yellow RY, ROB-B, MVB3, SP Blue 105 (all manufactured by Orient Chemical Industry Co., Ltd.), Aizen Spiron Yellow 3RH, GRLH Special, C-2GH, C-GNH new, Aizen Spiron Orange 2RH, Aizen Spiron GRH Concentrate Special, Aizen Spiron Red GEH, BEH, GRLH Special, C-GH, C-BH, Aizen Spiron Violet RH, C-RH, Aizen Spiron Brown BH Concentrate, RH, Aizen Spiron Mahogany RH, Aizen Spiron Blue GNH, 2BNH, C-RH, BPNH, Aizen Spiron Green C-GH, 3GNH Special, Aizen Spiron Black BNH, MH, RLH, GMH Special, BH Special, S.B.N. Orange 703, S.B.N. Violet 510, 521, S.P.T. Orange 6, S.P.T. Blue 111, SOT Pink 1, SOT Blue 4, SOT Black 1, SOT 6, SOT 10, SOT 12, SOT 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, Eisen FS Special A, Eisen 2020, Eisen 109, Eisen 215, AL Yellow 1106D, Eisen 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 Industry Co., Ltd.), Oleosol Fast Yellow 2G, Oleosol Fast Orange GL, Oleosol Fast Red BL, Oleosol Fast Red RL (all manufactured by Taoka Chemical Industry Co., Ltd.) Sanovinyl Yellow 2GLS, Sanovinyl RLS, Sanovinyl 2RLS, Sanovinyl Orange RLS, Sanovinyl Fire Red GLS, Sanovinyl Red 3BLS, Sanovinyl Pink 6BLS, Sanovinyl Blue RN, Sanovinyl GLS, Sanovinyl Green 2GLS, Sanovinyl Brown GLS (all manufactured by Sandoz, Switzerland), Magenta SP 247%, Crystal Violet 10B 250%, Malachite Green Crystal Conc, Brilliant Green Crystal H 90%, Spirit Soluble Red 64843 (all manufactured by Holliday, UK), Neptune Red Base 543, Neptune Blue Base 634, Neptune Violet Base 604, Bassonyl Red 540, Bassonyl 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 may be used alone or in combination.

Specific examples of pigments include carbon blacks such as furnace 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 oxide, gold powder, silver powder, copper powder, aluminum powder, brass powder, tin powder, mica pigments, C.I. PIGMENT 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, 14 4, 146, 149, 166, 168, 170, 176, 177, 178, 179, 180, 185, 190, 194, 206, 207, 209, 216, 245, 254, C. I. PIGMENT ORANGE 5, 10, 13, 16, 36, 40, 43, C. I. PIGMENT VIOLET 19, 23, 31, 33, 36, 38, 50, C. I. PIGMENT BLUE 2, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 16, 17, 22, 25, 60, 66, C. I. PIGMENT BROWN 25, 26, C. I. Examples of the pigments include C.I. Pigment Yellow 1, 3, 12, 13, 24, 93, 94, 95, 97, 99, 108, 109, 110, 117, 120, 139, 153, 166, 167, 173, C.I. Pigment Green 7, 10, and 36. These can be used alone or in combination of two or more.

In addition to these pigments, processed pigments can also be used. 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, and 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 Color & Chemicals Co., Ltd.), MICROLITH Yellow 4G-A, MX-A, 2R-A, Brown 5R-A, Scarlet R-A, Red 2C-A, 3R-A, Magenta 2B-A, Violet B-A, Blue 4G-A, Green G-A (all manufactured by Chiba Specialty Chemicals Co., Ltd.), etc.

In order to improve the dispersibility of the pigment, anionic, cationic, nonionic, or amphoteric surfactants or polymer resins can be used as auxiliary agents. Specific examples include anionic, nonionic, or cationic surfactants such as higher fatty acids, higher alcohol sulfates, fatty acid sulfates, alkylarylsulfonic acids, phosphates, polyoxyalkylene alkyl ethers, polyoxyalkylene alkylphenyl ethers, and sorbitan fatty acid esters, as well as resins and oligomers for dispersing pigments, such as polyvinyl butyral resins, polyvinylpyrrolidone resins, polyacrylic acid ester resins, polymethacrylic acid ester resins, styrene-acrylic acid resins, and styrene-maleic acid resins.
These may be used alone or in combination of two or more.

In some embodiments, the dispersion medium may be an organic solvent used in oil-based ballpoint pen inks. In view of safety and odor concerns, alcohol, glycol, and glycol ether are preferred organic solvents.

Examples of the organic solvent 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, triethylene glycol monomethyl ether, 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 monophen glycol ethers such as 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, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, octylene glycol, glycerin, polyethylene glycol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,3-butanediol, 1 , 5-pentanediol, and other glycols; 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, and other alcohols; methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether, and other esters; 2-ethylhexyl acetate, isobutyl isobutyrate, ethyl lactate, butyl lactate, and other esters.
Considering the improvement in writing feel due to the lower viscosity and the drying resistance of the pen tip, it is preferable to use a low-boiling organic solvent selected from alcohols, glycols, and glycol ethers having a boiling point of 80° C. to 200° C. inclusive, in combination with a high-boiling organic solvent having a boiling point of over 200° C. The weight ratio of low-boiling organic solvent/high-boiling organic solvent is preferably 1.0 to 30.0, and more preferably 1.3 to 6.0.

The ink composition according to some embodiments may optionally contain anti-leakage particles to prevent leakage of the ink.
Specific examples of the leakage prevention particles include silica particles, titanium oxide, silicone resin particles, silicone rubber particles, and silicone composite particles.

In particular, silicone composite particles have a structure in which silicone rubber particles are coated with silicone resin, and the low cohesion due to the low intermolecular forces and low adhesion of the silicone resin, combined with the elasticity of the silicone rubber within the silicone composite particles, results in a synergistic effect that allows them to function without breaking when writing and without forming an aggregated structure even in places where the ink flow path narrows, and is thought to be able to suppress ink leakage even in dry environments with low humidity.

When adding leakage prevention particles to the ink, they may be added directly or in the form of a pre-dispersed solution.

The ink composition according to some embodiments may include a dispersant for dispersing particles such as the leakage prevention particles described above. Examples of the dispersant include a dispersing resin and an activator, such as polybutyral resin, a polymer having an acidic group, an acrylic copolymer, a phosphoric acid copolymer, a phosphoric acid polyester, an alkylol ammonium salt of a copolymer containing an acidic group, a carboxylate ester having a hydroxyl group, and a nonionic activator.

As the dispersant, polyvinyl butyral is preferably used, and the use of a dispersant having an acid value of 60 mgKOH/g or more in combination is even more preferable, since 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 and KS-5 (all manufactured by Sekisui Chemical Co., Ltd.), Mowital 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 and B 60 Specific examples of dispersants having an acid value of 100 mgKOH/g or more include DISPERBYK-102 (acid value 101 mgKOH/g), DISPERBYK-106 (acid value 132 mgKOH/g, amine value 74 mgKOH/g), DISPERBYK-111 (acid value 129 mgKOH/g), DISPERBYK-140 (acid value 73 mgKOH/g, amine value 76 mgKOH/g), DISPERBYK-145 (acid value 76 mgKOH/g), DISPERBYK-150 (acid value 75 mgKOH/g, amine value 77 mgKOH/g), DISPERBYK-160 (acid value 75 mgKOH/g, amine value 78 mgKOH/g), DISPERBYK-170 (acid value 77 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-180 (acid value 78 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-190 (acid value 78 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-200 (acid value 78 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-210 (acid value 78 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-220 (acid value 78 mgKOH/g, amine value 79 mgKOH/g), DISPERBYK-230 (acid value 78 mgKOH/g, g, amine value 71 mg KOH/g), BYK-180 (acid value 94 mg KOH/g, amine value 94 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), BYK-220S (acid value 100 mg KOH/g), W9011 (acid value 65 mg KOH/g), and more, all manufactured by BYK Japan Co., Ltd., can be mentioned.
The amine value referred to here is expressed as the number of milligrams (mg) of potassium hydroxide (KOH) equivalent to the amount of hydrochloric acid required to neutralize the primary, secondary and tertiary amines contained in 1 g of sample.

Dispersants can be used alone or in combination, and are preferably used in an amount of 5% by weight to 200% by weight relative to the leak prevention particles (e.g., silicone composite particles).

The leakage prevention particles (silicone composite particles, etc.) can be dispersed in the ink composition by a general method. For example, the leakage prevention particles (silicone composite particles, etc.) are mixed with a solvent and a dispersant, and after uniformly stirring with a propeller stirrer, the leakage prevention particles (silicone composite particles, etc.) are dispersed with a dispersing machine. The dispersing machine is appropriately selected from a kneader, a roll mill, a ball mill, a sand mill, a bead mill, a Henschel mixer, a homogenizer, a high-pressure homogenizer, a thin film swirling type high-speed mixer, etc., depending on the amount of solvent in the ink and the pigment concentration.
In particular, dispersion using a thin film rotary high speed mixer, Filmix (manufactured by Primix Corporation), is preferred from the viewpoint of enhancing the storage stability of the dispersion.

In some embodiments, the ink composition may contain a resin to adjust the ink viscosity and improve the adhesion of the ink.

Specific examples of the above-mentioned resins 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, phenol resin, rosin, rosin ester, modified rosin, modified rosin ester, maleic rosin, maleic rosin ester, fumarated rosin, fumarated rosin ester, cellulose derivatives such as carboxymethyl cellulose, carboxyethyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, and hydroxypropyl cellulose, synthetic polymers such as N-vinylacetamide polymer crosslinked products, and inorganic clay minerals.
These may be used alone or in combination of two or more.

In some embodiments, a resin having an acidic group may be used as the resin described above. By using a resin having an acidic group as the resin described above, the apparent bulkiness increases due to electrostatic adsorption to the leakage prevention particles (such as silicone composite particles), preventing collisions between the leakage prevention particles (such as silicone composite particles), improving dispersion stability, and the silicone composite particles that acted as a sealant when rewriting after writing are quickly loosened, reducing smearing at the start of writing (hereinafter referred to as initial writing smearing).

The degree of acidity of a resin is expressed by its acid value, which is expressed as the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize all the acidic components contained in 1 g of sample, and is preferably 50 mg KOH/g or more and 600 mg KOH/g or less, and more preferably 150 mg KOH/g or more and 550 mg KOH/g or less.

Furthermore, if the resin contains OH groups, the interactions with the acidic groups will improve the adsorptivity to the silicone composite particles, improving the lubricity and the writing feel.
The amount of OH groups is expressed as the OH value, which is determined by acetylating with acetic anhydride, quantifying the free acetic acid with potassium hydroxide, and expressing it as the number of milligrams (mg) of potassium hydroxide (KOH) required to neutralize all the acidic components contained in 1 g of sample.

Specific examples of resins include rosin such as KR-612 (acid value 167 mg KOH/g) and KR-614 (acid value 175 mg KOH/g) (both manufactured by Arakawa Chemical Industries, Ltd.), and maleic acid rosin such as Malkid No. 31 (acid value 188 mg KOH/g), No. 32 (acid value 130 mg KOH/g), and No. Examples of the maleic rosin ester include Hariestar MSR-4 (acid value 135 mg KOH/g) (both manufactured by Harima Chemical Industries, Ltd.), and examples of the acid-modified rosin include KE-604 (acid value 238 mg KOH/g), KR-120 (acid value 240 mg KOH/g), and examples of the acid-modified rosin include KE-204 ... (acid value 325 mg KOH/g) (both manufactured by Arakawa Chemical Industries, Ltd.), special modified rosins include Haritac F-75 (acid value 145 mg KOH/g) and FG-90 (acid value 150 mg KOH/g) (both manufactured by Harima Chemical Industries, Ltd.), and styrene-acrylic acid resins include Joncryl 611 (acid value 53 mg KOH/g) and Joncryl 586 (acid value 108 mg KOH/g) (both manufactured by BASF Japan, Ltd.).

In some embodiments, it is preferable to use a cellulose derivative, particularly hydroxypropyl cellulose, as the resin. It is believed that the coexistence of silicone composite particles in the molecular network of hydroxypropyl cellulose not only provides a sealing effect in the ink flow path, but also prevents the ink from spreading when the pen tip is not retracted and is struck against a display, as the hydroxypropyl cellulose and silicone composite particles are immediately oriented on 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.).

The ink composition according to some embodiments may contain an amine as a pH adjuster. By maintaining the pH of the ink in an appropriate range, the adsorption of acidic substances to the metal ballpoint pen tip can be increased, suppressing dotted lines in handwriting and improving the writing feel. The pH range in the ink composition is preferably 2.5 or more and 7.0 or less, and more preferably 4.0 or more and 6.0 or less.

The ink composition according to some embodiments may contain a rust inhibitor. Benzotriazole or the like can be used as the rust inhibitor.

The viscosity of the oil-based ink for ballpoint pens of the present invention is not particularly limited, but it is preferable that the ink viscosity at 25°C and a shear rate of 100 sec ^-1 assuming writing is 30 mPa·s or more and 3000 mPa·s or less. If it is less than 30 mPa·s, the lubricating film strength of the oil-based ink may be low, and the writing feel and the wear resistance of the ball seat may be reduced. If it exceeds 3000 mPa·s, there is a risk that the handwriting smearing when rewriting, i.e., the initial handwriting smearing, may be deteriorated. More preferably, it is 50 mPa·s or more and 500 mPa·s or less, and more preferably 60 mPa·s or more and 200 mPa·s or less.

(Structure of Ballpoint Pen)
Next, a ballpoint pen according to some embodiments will be described. The ballpoint pen according to some embodiments includes a writing part including a ballpoint pen tip, and an ink reservoir tube (ink reservoir) that contains the above-mentioned oil-based ink, and is configured so that the oil-based ink from the ink reservoir tube is supplied to the writing part.

Figure 1 is a vertical cross-sectional view showing a ballpoint pen according to one embodiment. Figure 2 is a vertical cross-sectional view showing a refill portion of the ballpoint pen shown in Figure 1. In the exemplary embodiment shown in Figures 1 and 2, the ballpoint pen 100 includes a refill 200 and an exterior body 300.

In the embodiment shown in FIG. 1, the exterior body 300 is composed of a barrel 1, and the front barrel 2 and the rear barrel 3 are fixed to the barrel 1 by screwing so as to be freely attached and detached. The surface of the front barrel 2, which is made of a relatively hard resin material, is covered with a relatively soft resin material (soft member) as the grip portion 4. Examples of the relatively hard resin material forming the front barrel 2 and the rear barrel 3 include polycarbonate, polyethylene terephthalate, acrylic, acrylonitrile butadiene styrene copolymer (ABS), acrylonitrile styrene copolymer (AS), polypropylene, etc., and a transparent material or an opaque material may be used. In addition, examples of the relatively soft resin material (soft member) forming the grip portion 4 include thermoplastic elastomer, soft acrylic, etc., and a transparent material or an opaque material may be used. The grip portion 4 is preferably a grip that is not slippery when held, such as a grip with an uneven surface, a triangular grip, a grip with a polygonal outer surface, or a grip shaped to resemble a fingerprint. Crown 5 is attached and fixed to the rear of rear barrel 3 by being inserted into the inner hole of rear barrel 3 and threadedly engaged with the rear end of rear barrel 3, and the portion exposed from the rear end of rear barrel 3 is disposed so as to cover the base surface of clip 6 attached to the outer surface of rear barrel 3. Crown 5 is also cylindrical, and a groove formed therein serves as a cam groove for the debit cam mechanism, regulating the sliding position of rotor 7 housed therein and defining the forward and backward movement position of ballpoint pen refill 200 connected thereto as rotor 7 rotates due to the pushing operation of knock 8.
A ballpoint pen refill 200 is disposed in the barrel 1 so as to be movable back and forth. A resilient member 9 made of a coil spring or the like is disposed in front of the ballpoint pen refill 200, and biases the ballpoint pen refill 200 rearward. The rear end of the ballpoint pen refill 200 abuts on the tip of the rotor 7. In other words, the ballpoint pen refill 200 is a retractable ballpoint pen that retracts from the tip opening of the barrel 1 by pressing the knock 8.

As shown in FIG. 2, the refill 200 includes a ballpoint pen tip 10 as a writing part, and an ink reservoir 12 connected to the ballpoint pen tip 10 via a tip holder 11 having a through hole. The ballpoint pen tip 10 has a ball 13 as a writing member and a ball holder 14 that rotatably holds the ball 13. In addition, an ink composition 15 is contained in the ink reservoir 12 and is supplied to the ballpoint pen tip 10 (writing part). An ink backflow preventer 16 that is incompatible with the ink composition 15 is disposed in contact with the rear end interface of the ink composition 15, and a float 17 is disposed in contact with the ink backflow preventer 16. In addition, a tail plug or the like that prevents the ink composition 15 from leaking out can be disposed at the rear end of the ink reservoir 12 of the refill 200 to form a ballpoint pen body that does not use an outer body 300. The inner diameter of the ink reservoir 12 may be 1.0 mm or more and 5.0 mm or less. In particular, it is preferable that the inner diameter of the ink reservoir 12 is 1.0 mm or more and 3.1 mm or less, because the ink backflow preventer 16 has good shape retention and does not flow out, or the ink backflow preventer 16 does not flow out even if a float 17 in contact with the ink backflow preventer 16 is not used. The thickness of the ink reservoir 12 can be calculated by subtracting the inner diameter from the outer diameter, and the thickness of the ink reservoir 12 may be 0.5 mm or more and 10.0 mm or less. If the thickness of the ink reservoir 12 is 1.0 mm or more and 10.0 mm or less, the gas barrier properties are high and the evaporation of the ink solvent can be prevented, and further, if the thickness is 2.8 mm or more and 10.0 mm or less, the gas barrier properties are particularly high, making it even more preferable.

Fig. 3 is a diagram showing the configuration of the ballpoint pen tip 10 of the ballpoint pen refill 200 according to one embodiment, and is an enlarged vertical cross-sectional view of part I in Fig. 2. The ballpoint pen tip 10 shown in Fig. 3 rotatably holds the ball 13 as a writing member in the ball holder 14 with a part of the ball 13 protruding from the tip of the ink passage hole, which is a through hole, and a coil spring 18 as a resilient member is arranged behind the ball 13. The coil spring 18 is inserted from the rear of the ball holder 14 and pressed in so as to compress its entire length to prevent it from falling out, and the restoring force caused by the compression urges the ball 13 forward. The coil spring 18 is prevented from falling out by abutting the rear end of the coil spring 18 against the tip holder 11. As other methods for preventing the ball spring 18 from falling out, the rear inner wall surface of the ball holder 14 may be carved out by broaching to form a cutting piece, the rear end opening of the ball holder 14 may be reduced in diameter, or the side wall portion of the ball holder 14 may be recessed by punching or the like to form a convex portion on the inner wall surface, and the method and shape for preventing the coil spring 18 from falling out may be selected as appropriate.
Furthermore, in the case of a ballpoint pen in which the ballpoint pen tip 10 is protected by a cap when not in use, i.e., a so-called capped ballpoint pen, problems such as ink seeping out from the tip of the ballpoint pen tip 10 and writing smearing due to drying of the ink are unlikely to occur, so there is no need to bias the ball 13 forward to ensure airtightness, and a configuration without the coil spring 18 is also acceptable.

When the ball 13 is pressed against the writing surface such as paper, it moves backward, and ink flows out from the gap formed between the ball 13 and the ball holder 14 described later, or is conveyed outward as the ball 13 rotates and transfers it. The size of the ball 13 can be a diameter of 0.18 (mm) or more and 2.0 (mm) or less, which is the same as that used in general ballpoint pens. If the arithmetic mean height (Sa) of the surface of the ball 13 is large, localized contact between the metals of the ball 13 and the ball holder 14 is likely to occur, and the thick multilayer film including the phosphate ester layer and the nonionic surfactant layer cannot be maintained at the contact area where localized high pressure is applied. Considering that the lubrication of the multilayer film is more easily exhibited, the arithmetic mean height (Sa) of the surface of the ball 13 is preferably 1 (nm) or more and 20 (nm) or less. The ball 13 can be made of a variety of materials, including cemented carbide made primarily of tungsten carbide, metals such as stainless steel, aluminum, and iron, ceramics such as silicon carbide, silicon nitride, titanium nitride, chromium carbide, alumina, and zirconia, resin materials such as polyethylene, polypropylene, polyacetal, and polyamide, and glass, but cemented carbide and ceramics are preferred in terms of corrosion resistance to ink.

Next, the details of the ballpoint pen tip 10 will be described with reference to FIG. 4, which is an enlarged view of part II in FIG. 3. The ball holder 14 has an ink passage hole, which is a through hole, and the ink passage hole has a tip opening 19, which is crimped from the tip side to a small diameter, a ball holding part 21, which is partitioned by an inner protruding part 20 and in which the ball 13 is placed with a part protruding from the tip opening 19, a center hole 22 formed in the center part of the inner protruding part 20, and a rear hole 23. The outer edge of the tip opening 19 may be curved to prevent it from getting caught on the paper. The inner edge of the tip opening 19 is pressed against the ball 13 during crimping to improve the airtightness when the ball 13 is pressed and contacted by the coil spring 18, and is made mirror-finished while transferring the curved surface of the ball 13. In addition, a plurality of ink passage grooves 24 are formed radially at equal intervals in the inward protruding part 20 by cutting. The ink passage groove 24 penetrates the rear hole 23 to ensure ink supply to the ball holding part 21, but it may stop halfway in the center hole 22 without penetrating the rear hole 23. The concave ball receiving seat 25 is formed by pressing the ball 13 against the inward protrusion 20. The ball receiving seat 25 stabilizes the position of the ball 13 when it comes into contact with the paper surface or the like during writing and retracts, ensuring smooth rotation with little unnecessary vibration, and is shaped so that the ball 13 and the ball receiving seat 25 come into contact in a roughly planar manner. The ink passage groove 24 also has an opening outside the ball receiving seat 25 formed in the inward protrusion 20, ensuring ink supply to the ball holding part 21.

The diameter A of the ball 13 of the ballpoint pen tip 10 is preferably 0.18 mm or more and 2.0 mm or less. The dimensional values of the ballpoint pen tip 10 are as follows: the inner diameter B of the tip opening 19 is 80% or more and 98% or less of the diameter of the ball 13, the forward/backward movement distance C of the ball 13 is 2% or more and 10% or less of the diameter A of the ball 13, the ball protruding length D is 20% or more and 35% or less of the diameter A of the ball 13, the inner diameter E of the ball holding portion 21 is 90% or more and 130% or less of the diameter A of the ball 13, the number of ink passage grooves 24 is 2 or more and 6 or less, and the width F of the ink passage groove 24 is 0.05 mm. Preferably, the ink passage groove 24 has a depth G of 0.10 mm or more or may be passed through from the ball holding portion 21 to the rear hole 23, the ball receiving seat diameter H is 75% to 90% of the diameter A of the ball 13, the central hole diameter I is 40% to 70% of the diameter A of the ball 13, the seat angle α of the ball holding portion 21 is 90 degrees to 160 degrees, the crimping angle β is 50 degrees to 90 degrees, the chamfer angle γ is 20 degrees to 60 degrees, and the taper angle δ is 150 degrees or less. In order to maintain the ink in the ball receiving seat and to further exert the lubricity of the thick multilayer film including the phosphate ester layer and the nonionic surfactant layer, it is more preferable that the ball receiving seat diameter H is 80% to 90% of the diameter A of the ball 13, taking into consideration the dispersion of the force per unit area applied to the ball receiving seat when writing with high writing pressure. In addition, it is preferable to perform a hydrophilic or hydrophobic treatment on the surface of the ballpoint pen tip 10 depending on the ink used, as this can prevent ink from adhering to the ballpoint pen tip 10. The dimensions of each part are shown in Figures 4, 5, and 6 (ball 13 and coil spring 18 are not shown).

The present invention will be explained in more detail below with reference to the following examples, but the present invention is not limited to these examples.

The viscosity in the examples was measured using an MCR302 (manufactured by Anton Paar) with a rotor CP50-1 at 25°C and a shear rate of 100 s ^-1 (unit: mPa s).

The pH in the examples was measured at 25°C using a Piccolo Plus (Hanna Instruments Japan, Ltd.).

As shown in Tables 1 to 12, oil-based ink compositions were prepared for Examples 1 to 32 and Comparative Examples 1 to 6. The materials used are as follows. Tables 1 to 12 also show the content (weight %) of each material in the ink composition.

Phosphate ester (1) (first phosphate ester): Phosphanol LS-500 (phosphate ester, mixture of mono-, di- and triesters of polyoxyethylene (4) tridecyl ether phosphate, HLB 9.0, manufactured by Toho Chemical Industry Co., Ltd.)
Phosphate ester (2) (first phosphate ester): Phosphanol GF-199 (phosphate ester, mixture of mono-, di- and triesters of polyoxyethylene lauryl ether phosphate, HLB 5.5, manufactured by Toho Chemical Industry Co., Ltd.)
Phosphate ester (3) (first phosphate ester): Phosphanol RP-710 (phosphate ester, mixture of mono-, di- and triesters of polyoxyethylene (6) phenyl ether phosphate, HLB 11.9, manufactured by Toho Chemical Industry Co., Ltd.)
Phosphate ester (4) (first phosphate ester): Plysurf A219B (phosphate ester, phosphate ester of polyoxyethylene lauryl ether, HLB 16.2, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Phosphate ester (5) (second phosphate ester): Phosphanol LB-400 (phosphate ester, mixture of mono-, di- and triesters of polyoxyethylene (4) oleyl ether, HLB 8.6, manufactured by Toho Chemical Industry Co., Ltd.)
Phosphate ester (6) (second phosphate ester): Phosphanol RL-210 (phosphate ester, mixture of mono-, di- and triesters of polyoxyethylene (2) stearyl ether phosphate, HLB 5.4, manufactured by Toho Chemical Industry Co., Ltd.)
Phosphate ester (7): (NIKKOL TOP-0V (trioleyl phosphate, manufactured by Nikko Chemicals Co., Ltd.)

Ion exchange water

Surfactant (1) (nonionic surfactant): Pegnol ST-7 (polyoxyethylene (7) alkyl (C12-14) ether, HLB 12.8, manufactured by Toho Chemical Industry Co., Ltd.)
Surfactant (2) (nonionic surfactant): NIKKOL BT-5 (polyoxyethylene alkyl (C12-14) ether, HLB 10.5, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (3) (nonionic surfactant): NIKKOL BT-12 (polyoxyethylene alkyl (C12-14) ether, HLB 14.5, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (4) (nonionic surfactant): NIKKOL BO-10V (polyoxyethylene oleyl ether, HLB 14.5, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (5) (nonionic surfactant): NIKKOL BO-50V (polyoxyethylene oleyl ether, HLB 18.0, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (6) (nonionic surfactant): NIKKOL BB-5 (polyoxyethylene behenyl ether, HLB 7.0, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (7) (Nonionic Surfactant) NIKKOL HCO-20 (Polyoxyethylene hydrogenated castor oil, HLB 10.5, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (8) (nonionic surfactant): Sorgen 30V (sorbitan sesquioleate, HLB 3.7, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.)
Surfactant (9) (nonionic surfactant): NIKKOL TO-10V (polyoxyethylene sorbitan monooleate, HLB 15.0, manufactured by Nikko Chemicals Co., Ltd.)
Surfactant (10) (nonionic surfactant): NIKKOL Decaglyn 1-1SV (polyglyceryl monoisostearate, HLB 12.0, manufactured by Nikko Chemicals Co., Ltd.)

Organic amine (1): Nymeen O-205 (polyoxyethylene oleylamine, NOF Corp.)
Organic amine (2): Triisopropanolamine (Tokyo Chemical Industry Co., Ltd.)
Organic amine (3): Triethanolamine (Tokyo Chemical Industry Co., Ltd.)

Pigment (1): Printex 35 (colorant, carbon black, manufactured by Orion Engineered Carbons Co., Ltd.)
Pigment (2): FUJI FAST RED 8800 (colorant, C.I. Pigment Red 254, manufactured by Fuji Color Co., Ltd.)
Pigment (3): CROMOPHTAL Blue A3R (colorant, C.I. Pigment Blue 60, manufactured by BASF Japan Ltd.)

Dye (1): SPILON RED C-GH (a salt-forming dye of a xanthene-based basic dye and an alkyldiphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Industry Co., Ltd.)
Dye (2): VALIFAST RED 1364 (a salt-forming dye of C.I. Basic Red 1:1, alkylbenzenesulfonic acid, and alkyldiphenyletherdisulfonic acid, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (3): SPILON YELLOW C-GNH new (a salt-forming dye of an indolinone-based basic dye and an alkyldiphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Industry Co., Ltd.)
Dye (4): OIL BLUE 613 (a mixture of C.I. Solvent Blue 5 and rosin-modified resin, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (5): VALIFAST BLUE 1631 (a salt-forming dye made from C.I. Basic Blue 7 and a colorless organic acid, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (6): VALIFAST VIOLET 1731 (a salt-forming dye of C.I. Acid Violet 17 and a methine dye, manufactured by Orient Chemical Industries Co., Ltd.)

Organic solvent (1): n-propanol Organic solvent (2): ethylene glycol monoisopropyl ether Organic solvent (3): ethylene glycol monophenyl ether Organic solvent (4): benzyl alcohol

Resin (1): S-LEC BL-1 (polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd.)
Resin (2): S-LEC 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° C., manufactured by Evonik Japan Co., Ltd.)
Resin (5): TEGO Variplus CA (ketone aldehyde condensation resin, OH value 200 mg KOH/g, Tg 75° C., manufactured by Evonik Japan Co., Ltd.)
Resin (6): Malkied 3002 (maleic acid rosin, acid value 100 mg KOH/g, Tg 175° C., manufactured by Arakawa Chemical Industries, Ltd.)
Resin (7): Harimaq T-80 (maleic rosin, acid value 185 mg KOH/g, Tg 85°C, manufactured by Harima Chemicals Co., Ltd.)
Resin (8): 42% acrylic acid-acrylic/methacrylic acid ester copolymer in ethylene glycol monophenyl ether (acid value 510 mg KOH/g, OH value 130 mg KOH/g, Tg 80° C. in terms of solid)
Resin (9): 42% acrylic acid-styrene-methacrylic acid ester copolymer in ethylene glycol monophenyl ether (acid value 300 mg KOH/g, OH value 80 mg KOH/g, Tg 30° C. in terms of solid)
Resin (10): NISSO HPC-H (hydroxypropyl cellulose, weight average molecular weight: 1,000,000, manufactured by Nippon Soda Co., Ltd.)
Resin (11): NISSO HPC-M (hydroxypropyl cellulose, weight average molecular weight: 700,000, manufactured by Nippon Soda Co., Ltd.)
Resin (12): Metrose 65SH-1500 (weight average molecular weight: 216,600, hydroxypropyl methylcellulose, manufactured by Shin-Etsu Chemical Co., Ltd.)

Particles (1) (silicone composite particles): KMP-605 (silicone composite particles, average particle size 2 μm, rubber hardness 75 durometer A, true specific gravity 0.99 g/cm ³ , manufactured by Shin-Etsu Chemical Co., Ltd.)
Particles (2) (silicone composite particles): X-52-7030 (silicone composite particles, average particle size 0.8 μm, rubber hardness 75 durometer A, true specific gravity 1.01 g/cm ³ , manufactured by Shin-Etsu Chemical Co., Ltd.)

Dispersant (1): DISPERBYK-102 (a copolymer having an acidic group, acid value 101 mgKOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (2): BYK-W9011 (copolymer having an acidic group, acid value 65 mgKOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (3): DISPERBYK-111 (a copolymer containing an acid group, acid value 129 mg KOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (4): DISPERBYK-106 (polymer salt having an acid group, acid value 132 mg KOH/g, amine value 74 mg KOH/g, manufactured by BYK Japan Co., Ltd.)

Benzotriazole: Benzotriazole (manufactured by E-CHEM ENTERPRISE CORPORATION)

The procedure for making oil-based ink is as follows: organic solvent or ion-exchanged water, phosphate ester, surfactant, colorant, and resin are stirred at 60°C with a propeller stirrer, and then other additives and appropriate cellulose derivatives are added directly or after being uniformly dissolved or dispersed in a solvent with a propeller stirrer, etc., and the mixture is stirred with a propeller for 2 hours to obtain the oil-based ink.

(Creating test ballpoint pens)

Based on the ballpoint pen tip 10 shown in the figure, the first and second ballpoint pen tips used in the test were made with the dimensions shown below. The value in parentheses for each dimension is the ratio of each dimension value to the diameter A of the ball 13 of the ballpoint pen tip 10. Each dimension is shown in Figures 4, 5, and 6 (ball 13 and coil spring 18 are not shown). In Figure 5, the broken line shows the state in which the ball 13 is in contact with the ball transfer portion on the tip opening 19 side of the ball holder 14.

(First Ballpoint Pen Tip)
Diameter A of ball 13 = 0.5 mm
Inner diameter B of tip opening 19 = 0.48 mm (96% of diameter A of ball 13)
The distance C of the ball 13 moving in the forward and backward direction is 0.03 mm (6% of the diameter A of the ball 13).
Ball protrusion length D = 0.15 mm (30% of the diameter A of the ball 13)
Inner diameter E of ball holding portion 21 = 0.53 mm (106% of diameter A of ball 13)
Number of ink passage grooves 24 = 5 Width F of ink passage groove 24 = 0.09 mm
Depth G of ink passage groove 24 = 0.15 mm
Ball seat diameter H = 0.44 mm (88% of diameter A of ball 13)
Center hole diameter I=0.28 mm (56% of diameter A of ball 13)
Seat angle α of ball holding portion 21: 100 degrees Crimping angle β = 80 degrees
Chamfer angle γ=56°
Taper angle δ=30°
The wire diameter of the coil spring 18 was 0.14 mm, and the pressing load on the ball 13 with the coil spring 18 disposed in the ball holder 14 was 0.15 N.
The ball 13 used was a carbide ball PB-11 manufactured by Tsubaki Nakashima Co., Ltd., and had a surface roughness, arithmetic mean height (Sa: ISO 25178), of 4.0 nm.

(Second ballpoint pen tip)
Diameter A of ball 13 = 0.3 mm
Inner diameter B of tip opening 19 = 0.28 mm (93% of diameter A of ball 13)
The distance C of the ball 13 moving in the forward and backward direction is 0.02 mm (7% of the diameter A of the ball 13).
Ball protrusion length D=0.08 mm (27% of diameter A of ball 13)
Inner diameter E of ball holding portion 21 = 0.34 mm (113% of diameter A of ball 13)
Number of ink passage grooves 24 = 3 Width F of ink passage groove 24 = 0.06 mm
Depth G of ink passage groove 24 = Ink passage groove 24 penetrates from ball holding portion 21 to rear hole 23 Ball seat diameter H = 0.24 mm (80% of diameter A of ball 13)
Center hole diameter I = 0.18 mm (60% of diameter A of ball 13)
Seat angle α of ball holding portion 21: 150 degrees Crimping angle β = 80 degrees
Chamfer angle γ=56°
Taper angle δ=30°
The wire diameter of the coil spring 18 was 0.12 mm, and the pressing load on the ball 13 with the coil spring 18 disposed in the ball holder 14 was 0.15 N.
The ball 13 used was a carbide ball PB-11 manufactured by Tsubaki Nakashima Co., Ltd., and had a surface roughness, arithmetic mean height (Sa: ISO 25178), of 1.8 nm.

(Third Ballpoint Pen Tip)
Diameter A of ball 13 = 0.4 mm
Inner diameter B of tip opening 19 = 0.38 mm (95% of diameter A of ball 13)
The distance C of the ball 13 moving in the forward and backward direction is 0.03 mm (8% of the diameter A of the ball 13)
Ball protrusion length D = 0.12 mm (30% of the diameter A of the ball 13)
Inner diameter E of ball holding portion 21 = 0.45 mm (113% of diameter A of ball 13)
Number of ink passage grooves 24 = 3 Width F of ink passage groove 24 = 0.08 mm
Depth G of ink passage groove 24 = Ink passage groove 24 penetrates from ball holding portion 21 to rear hole 23 Ball seat diameter H = 0.33 mm (83% of diameter A of ball 13)
Center hole diameter I = 0.23 mm (58% of diameter A of ball 13)
Seat angle α of ball holding portion 21: 130 degrees Crimping angle β = 80 degrees
Chamfer angle γ=56°
Taper angle δ=30°
The wire diameter of the coil spring 18 was 0.12 mm, and the pressing load on the ball 13 with the coil spring 18 disposed in the ball holder 14 was 0.15 N.
The ball 13 used was a carbide ball PB-11 manufactured by Tsubaki Nakashima Co., Ltd., and had a surface roughness, arithmetic mean height (Sa: ISO 25178), of 1.8 nm.

The arithmetic mean height, which is the surface roughness of ball 13 in the examples, was calculated from the average value by measuring three arbitrary points in an area of 20 (μm) × 20 (μm) using a scanning probe microscope (AFM5100N; manufactured by Hitachi High-Tech Science Corporation).

The ink compositions of Examples 1 to 32 and Comparative Examples 1 to 6 were filled into refills 200 based on the example shown in Figure 2 and housed in exterior bodies 300 based on the example shown in Figure 1 to obtain test sample ballpoint pens with the first ballpoint pen tip, the second ballpoint pen tip, and the third ballpoint pen tip. The pen tips of the obtained ballpoint pens were sealed with a packing (HM200, ethylene-vinyl acetate copolymer resin-based hotmelt adhesive), and centrifugal force was applied to remove excess air bubbles so that the ink composition was distributed to the pen tip.

The following tests and evaluations were carried out on the ink compositions of each Example and Comparative Example. The evaluation results are shown in Tables 1 to 12.

(Writing feel)
Three test ballpoint pens having the above-mentioned first ballpoint pen tip were prepared for each Example and Comparative Example, and after removing the packing, handwriting was carried out in an environment of a temperature of 25° C. and a relative humidity of 65%. The evaluation criteria are as follows.
A: Very good writing feel B: Good writing feel C: Slightly poor writing feel D: Poor writing feel

(Follow-up test)
Three test ballpoint pens having the first and second ballpoint pen tips were prepared for each Example and Comparative Example, and the packing was removed. After that, the pen was visually inspected for 100 m of writing by a spiral pen at a writing angle of 70°, a writing load of 100 gf, a writing speed of 7 cm/sec (normal writing speed) and a writing speed of 10 cm/sec (fast writing speed) in an environment of 25°C and 65% relative humidity. The evaluation criteria are as follows.
A: There is no smearing on either the first or second ballpoint pen tip.
B: No smearing was observed with the first ballpoint pen tip, but some smearing was observed with the second ballpoint pen tip at a writing speed of 10 cm/sec (fast writing).
C: With both the first ballpoint pen tip and the second ballpoint pen tip, no smearing was observed at a writing speed of 7 cm/sec, but smearing was observed at a writing speed of 10 cm/sec (fast writing).
D: Blurring is observed even at 7 cm/sec.

(Bote confirmation test)
Three test ballpoint pens having the first ballpoint pen tip were prepared for each Example and Comparative Example, and the packing was removed. After that, 100 m of handwriting was visually confirmed by spiral writing at a writing angle of 70°, a writing load of 100 gf, a writing speed of 7 cm/sec (normal writing pressure), a writing load of 200 gf, and a writing speed of 7 cm/sec (strong writing pressure) in an environment of 25°C and 65% relative humidity. The evaluation criteria are as follows.
A: There is absolutely no bulge.
B: Blurring is observed under strong writing pressure conditions, but not under normal writing pressure.
C: Bote is visible.
D: Bote is commonly seen.
A blob is a phenomenon in which, when writing with a ballpoint pen, some ink does not transfer completely to the surface being written on, adheres to the outer surface of the ballpoint pen holder, accumulates, and grows into a large lump of ink that then adheres to the surface being written on.

(Pen tip ink leakage confirmation test 1 (Leakage confirmation test 1))
Three test ballpoint pens having the above-mentioned first ballpoint pen tip and a 50 g weight attached were prepared for each Example and Comparative Example, and after removing the packing, the "Date of the National Diet" (character string shown in FIG. 7) was written by hand in an environment of 25° C. temperature and 30% relative humidity, and the size of the ink leaked onto the acrylic resin plate was confirmed at 50 times using a digital microscope (Keyence Corporation, VHX-7000), the diameter was recorded, and the average value was calculated. The evaluation criteria are as follows.
A: No leakage to 0.30 mm or less B: 0.31 mm or more to 0.50 mm or less C: 0.51 mm or more to 1.00 mm or less D: 1.1 mm or more

(Pen tip ink leakage confirmation test 2 (Leakage confirmation test 2))
Three test ballpoint pens having the above-mentioned first ballpoint pen tip were prepared for each Example and Comparative Example, and after removing the packing, "Date of the National Diet" (character string shown in FIG. 7) was written by hand in an environment of 25°C temperature and 65% relative humidity, and then the pen was attached to a mount and left face down for three days. The size of ink leakage from the pen tip was then confirmed at 50x magnification using a digital microscope (Keyence Corporation, VHX-7000), the diameter was recorded, and the average value was calculated. The evaluation criteria are as follows.
A: No leakage to 0.30 mm or less B: 0.31 mm or more to 0.50 mm or less C: 0.51 mm or more to 1.00 mm or less D: 1.1 mm or more

(Pen tip ink leakage confirmation test 3 (Leakage confirmation test 3))
Three test ballpoint pens having the above-mentioned first ballpoint pen tip were prepared for each Example and Comparative Example, and after removing the packing, the "Date of the National Diet" (character string shown in FIG. 7) was written by hand in an environment of 25° C. temperature and 30% relative humidity, and then the pen was attached to a mount and left face down for three days. The size of ink leakage from the pen tip was then confirmed at 50x magnification using a digital microscope (Keyence Corporation, VHX-7000), the diameter was recorded, and the average value was calculated. The evaluation criteria are as follows.
A: No leakage to 0.30 mm or less B: 0.31 mm or more to 0.50 mm or less C: 0.51 mm or more to 1.00 mm or less D: 1.1 mm or more

The ink compositions of Examples 1 to 32 contain a first phosphate ester that is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 4 to 17, a second phosphate ester that is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 18 to 24, water, and a nonionic surfactant.

Therefore, when writing with a ballpoint pen, a thick, cushioned multilayer film containing a layer of phosphate ester and a layer of nonionic surfactant is formed between the ball at the tip of the pen and the metal surface of the receiving seat, so that the multilayer film can be maintained between the ball and the receiving seat even when writing at high speed (following ability test) or when writing with high writing pressure (blotting confirmation test), resulting in good lubrication during writing, a good writing feel, and suppression of smearing, skipped lines, or blotting. In addition, since nonionic surfactants do not wet and spread in areas where there is no metal, excessive wetting and spreading of the phosphate ester that interacts with the nonionic surfactant is suppressed, which is thought to have effectively suppressed leakage of the ink composition from the pen tip (pen tip ink leakage confirmation tests 1-3).

Therefore, it is believed that the ink compositions of Examples 1 to 32 were able to effectively prevent ink leakage while still providing a good writing feel and good handwriting even when writing at high speed or with high writing pressure.

In addition, in the ink compositions of Examples 1 to 32, the difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 4 or more. Therefore, when writing with a ballpoint pen, a thick multilayer film containing a layer of phosphate ester and a layer of nonionic surfactant is more likely to be formed between the ball at the pen tip and the metal surface of the receiving seat, and it is believed that this is why good handwriting with a good writing feel can be obtained even when writing at high speed (following ability test) or when writing with high writing pressure (blotting confirmation test).

In addition, in the ink compositions of Examples 1 to 32, the hydrocarbon group of the first phosphate ester has a carbon number of 12 or more and 14 or less, and the hydrocarbon group of the second phosphate ester has a carbon number of 18 or more and 20 or less. Therefore, when writing with a ballpoint pen, a thick multilayer film containing a layer of phosphate ester and a layer of nonionic surfactant is more likely to be formed between the ball at the pen tip and the metal surface of the receiving seat, and it is believed that this is why good handwriting with a good writing feel can be obtained even when writing at high speed (following ability test) or when writing with high writing pressure (blot confirmation test).

In addition, the ink compositions of Examples 1 to 31 have an HLB value of the first phosphate ester and an HLB value of the second phosphate ester of 4 or more and 14 or less. This makes it easier for water to be retained in the nonionic surfactant layer, increasing the cushioning properties of the multilayer film formed between the ball and the metal surface of the receiving seat, which is thought to have resulted in a good writing feel and good handwriting even when writing at high speed (following test) or when writing with high writing pressure (blob confirmation test).

In addition, the ink compositions of Examples 1 to 12, 14, and 17 to 31 have an HLB value of the first phosphate ester and an HLB value of the second phosphate ester of 7 or more and 12 or less. This makes it easier for water to be retained in the nonionic surfactant layer, which enhances the cushioning properties of the multilayer film formed between the ball and the metal surface of the receiving seat. This is thought to have resulted in a good writing feel and good handwriting even when writing at high speed (following test) or when writing with high writing pressure (blot confirmation test).

In addition, the ink compositions of Examples 1 to 32 have a total content of the first phosphate ester and the second phosphate ester of 0.4% by weight or more and 3.0% by weight or less. As a result, the density of the phosphate ester layer formed on the metal surface of the ball and the receiving seat is moderate, and a multilayer film of moderate density is formed between the ball at the pen tip and the metal surface of the receiving seat. This makes it possible to effectively suppress ink leakage (pen tip ink leakage confirmation tests 1 to 3), while providing a good writing feel and handwriting even when writing at high speed (following ability test) or when writing with high writing pressure (blob confirmation test).

In addition, the ink compositions of Examples 1 to 32 have a weight ratio of the content of the first phosphate ester to the content of the second phosphate ester of 0.2 or more and 8.0 or less. Therefore, the layer of phosphate ester formed on the metal surface of the ball and the receiving seat is likely to have a dense structure, and a multilayer film of appropriate density is formed between the ball at the pen tip and the metal surface of the receiving seat. This makes it possible to effectively suppress ink leakage (pen tip ink leakage confirmation tests 1 to 3), while still providing a good writing feel and handwriting even when writing at high speed (following ability test) or with high writing pressure (blob confirmation test).

In addition, the ink compositions of Examples 1 to 14 and 17 to 32 have a weight ratio of the content of the first phosphate ester to the content of the second phosphate ester of 0.25 or more and 4.0 or less. As a result, the layer of phosphate ester formed on the metal surface of the ball and the receiving seat is likely to have a denser structure, and a multilayer film of appropriate density is formed between the ball at the pen tip and the metal surface of the receiving seat. This makes it possible to effectively suppress ink leakage (pen tip ink leakage confirmation tests 1 to 3), while still providing a good writing feel and handwriting even when writing at high speed (following ability test) or when writing with high writing pressure (blob confirmation test).

In addition, the ink compositions of Examples 1 to 25, 27 to 28, and 30 to 32 have a nonionic surfactant HLB value of 4 or more and 15 or less. Therefore, since these ink compositions have a certain degree of hydrophilicity, water is easily taken up into the layer of the nonionic surfactant by interaction with water, and since the hydrophilicity is not excessive and it is easy to interact with the hydrocarbon groups of the first and second phosphate esters, it is thought that the above-mentioned multilayer film is easily formed between the ball and the metal surface of the receiving seat. Therefore, it is thought that while ink leakage can be effectively suppressed (pen tip ink leakage confirmation tests 1 to 3), a good writing feel and handwriting were obtained even when writing at high speed (following ability test) or when writing with high writing pressure (blot confirmation test).

The ink compositions of Comparative Examples 3 to 6 do not contain either or both of the first phosphate ester and the second phosphate ester. Therefore, it is difficult to form a multilayer film having a thickness and a dense structure between the ball of the pen tip and the metal surface of the receiving seat, and it is believed that this is why good writing feel and handwriting were not obtained when writing at high speed (following ability test) or when writing with high writing pressure (blot confirmation test).

In addition, the ink compositions of Comparative Examples 1 and 6 do not contain a nonionic surfactant. Therefore, it is believed that the ink composition was not suppressed from spreading onto areas without metal, causing leakage of the ink composition from the pen tip (pen tip ink leakage confirmation tests 1 to 3).

In addition, the ink compositions of Comparative Examples 2 and 5 do not contain water. Therefore, a layer of nonionic surfactant incorporating water is not formed, and the cushioning properties of the multilayer film are poor, so that when writing with a ballpoint pen, a multilayer film is difficult to form between the ball at the pen tip and the metal surface of the receiving seat, or the multilayer film is difficult to maintain. Therefore, when writing at high speed (following ability test) or when writing with high writing pressure (blot confirmation test), it is believed that a good writing feel and handwriting cannot be obtained, or leakage of the ink composition from the pen tip occurs (pen tip ink leakage confirmation tests 1 to 3).

The contents described in each of the above embodiments can be understood, for example, as follows:

[1] At least one embodiment of the oil-based ink composition for ballpoint pens according to the present invention comprises
a first phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having 4 to 17 carbon atoms;
a second phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having from 18 to 24 carbon atoms;
Water,
A nonionic surfactant;
Includes.

According to the above configuration [1], when writing with a ballpoint pen, a thick multilayer film (hereinafter, referred to as a multilayer film) containing a layer of phosphate ester and a layer of nonionic surfactant is likely to be formed between the ball at the pen tip and the metal surface of the receiving seat.
That is, the oil-based ink composition of [1] above contains a first phosphate ester having a relatively small number of carbon atoms in the hydrocarbon group and a second phosphate ester having a relatively large number of carbon atoms in the hydrocarbon group, and the phosphate groups of these phosphate esters are adsorbed to the metal surfaces of the ball and the receiving seat, forming a layer of phosphate ester on the metal surfaces of the ball and the receiving seat. Here, since the second phosphate ester has a relatively long hydrocarbon group, a relatively thick layer of phosphate ester is formed on the metal surface, and since the first phosphate ester has a relatively short hydrocarbon group, the second phosphate ester penetrates between the first phosphate esters, and a layer of phosphate ester having a dense structure is quickly formed on the metal surface.
The oil-based ink composition of [1] above contains water and a nonionic surfactant. Therefore, when writing with a ballpoint pen, the hydrophobic group of the nonionic surfactant interacts with the hydrocarbon group of the phosphate ester, and a layer of the nonionic surfactant is formed between the layers of the phosphate ester formed on the surfaces of the ball and the receiving seat, respectively, so that a thick multilayer film is easily obtained, and the hydrophilic group of the nonionic surfactant interacts with water, and water with high surface tension is taken in by the layer of the nonionic surfactant, so that the cushioning property of the multilayer film is enhanced.
Thus, according to the configuration of [1] above, when writing with a ballpoint pen, a multilayer film with a large thickness and high cushioning properties is easily formed between the ball and the metal surface of the receiving seat, so that the multilayer film can be maintained between the ball and the receiving seat even when writing at high speed or with high writing pressure, and the lubrication during writing is good. Therefore, even when writing at high speed or with high writing pressure, the writing feel is good and smearing, skipped lines, or blobs can be suppressed.
In the above-mentioned configuration [1], the nonionic surfactant does not wet and spread on areas where there is no metal, so that the phosphate ester interacting with the nonionic surfactant is prevented from excessively spreading, and thus leakage of the ink composition from the pen tip can be effectively prevented.
Therefore, according to the configuration [1] above, it is possible to effectively prevent ink leakage, while still obtaining good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

[2] In some embodiments, in the configuration of [1] above,
The difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 4 or more.

According to the configuration of [2] above, the difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the first phosphate ester is 4 or more, so the lengths of the carbon chains in the hydrocarbon groups of both differ to some extent. Therefore, in the layer of phosphate ester formed on the metal surface of the ball and the receiving seat, the second phosphate ester is more likely to penetrate between the first phosphate ester, and a layer of phosphate ester with a dense structure is more likely to be formed on the metal surface. Therefore, when writing with a ballpoint pen, a thick multilayer film containing a layer of phosphate ester and a layer of nonionic surfactant is more likely to be formed between the ball at the tip of the pen and the metal surface of the receiving seat. Therefore, it is possible to obtain good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

[3] In some embodiments, in the configuration of [2] above,
the hydrocarbon group of the first phosphate ester has 12 or more and 14 or less carbon atoms;
The hydrocarbon group of the second phosphate ester has 18 or more and 20 or less carbon atoms.

According to the above configuration [3], the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 12 to 14, and the number of carbon atoms in the hydrocarbon group of the second phosphate ester is 18 to 20, so that the lengths of the carbon chains of the two hydrocarbon groups differ to some extent. Therefore, in the layer of phosphate ester formed on the metal surface of the ball and the receiving seat, the second phosphate ester is more likely to penetrate between the first phosphate ester, and a layer of phosphate ester with a dense structure is more likely to be formed on the metal surface. Therefore, when writing with a ballpoint pen, a thick multilayer film including a layer of phosphate ester and a layer of nonionic surfactant is more likely to be formed between the ball at the pen tip and the metal surface of the receiving seat. Therefore, it is possible to obtain good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

[4] In some embodiments, in any one of the configurations [1] to [3] above,
The HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 4 or more and 14 or less.

In the above configuration [4], the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 4 or more, and therefore the multilayer film is moderately hydrophilic, and therefore the incorporation of water into the multilayer film is not easily hindered. In addition, in the above configuration [4], the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 14 or less, and therefore the hydrocarbon group of the first/second phosphate ester is likely to interact with the hydrophobic group of the nonionic surfactant. As a result, the hydrophilic group of the nonionic surfactant is likely to interact with water, and water is likely to be incorporated into the nonionic surfactant layer. Therefore, according to the above configuration [4], water is likely to be retained in the nonionic surfactant layer, and the cushioning properties of the multilayer film formed between the ball and the metal surface of the receiving seat are enhanced. Therefore, even when writing at high speed or with high writing pressure, the multilayer film is likely to be retained between the ball and the receiving seat, and the lubrication during writing is likely to be good. Therefore, even when writing at high speed or with high writing pressure, a good writing feel and handwriting are likely to be obtained.

[5] In some embodiments, in the configuration of [4] above,
The HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 7 or more and 12 or less.

In the above-mentioned configuration [5], the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 7 or more, and therefore the multilayer film is moderately hydrophilic, and therefore the incorporation of water into the multilayer film is not easily hindered. In addition, in the above-mentioned configuration [5], the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 12 or less, and therefore the hydrocarbon group of the first/second phosphate ester is easily interacted with the hydrophobic group of the nonionic surfactant. As a result, the hydrophilic group of the nonionic surfactant is easily interacted with water, and water is easily incorporated into the nonionic surfactant layer. Therefore, according to the above-mentioned configuration [5], water is easily retained in the nonionic surfactant layer, and the cushioning property of the multilayer film formed between the ball and the metal surface of the receiving seat is enhanced. Therefore, even when writing at high speed or with high writing pressure, the multilayer film is easily retained between the ball and the receiving seat, and the lubrication during writing is easily improved. Therefore, even when writing at high speed or with high writing pressure, a good writing feel and handwriting are easily obtained.

[6] In some embodiments, in any one of the configurations [1] to [5] above,
The total content of the first phosphate ester and the second phosphate ester is 0.4% by weight or more and 3.0% by weight or less.

According to the above configuration [6], since the total content of the first phosphate ester and the second phosphate ester is 0.4% by weight or more and 3.0% by weight or less, the density of the phosphate ester layer formed on the metal surface of the ball and the receiving seat is moderate, and therefore a multilayer film of moderate density is formed between the ball at the pen tip and the metal surface of the receiving seat. Therefore, while ink leakage can be effectively suppressed, it is easy to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

[7] In some embodiments, in any one of the configurations [1] to [6] above,
The ratio of the content of the first phosphate ester to the content of the second phosphate ester on a weight basis is 0.2 or more and 8.0 or less.

According to the configuration of [7] above, since the weight ratio of the content of the first phosphate ester to the content of the second phosphate ester is 0.2 or more and 8.0 or less, the layer of phosphate ester formed on the metal surface is likely to have a dense structure. As a result, a multilayer film of appropriate density is formed between the ball of the pen tip and the metal surface of the receiving seat. Therefore, while ink leakage can be effectively suppressed, it is easy to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

[8] In some embodiments, in the configuration of [7] above,
The ratio of the content of the first phosphate ester to the content of the second phosphate ester on a mass basis is 0.25 or more and 4.0 or less.

According to the configuration of [8] above, since the ratio of the content of the first phosphate ester to the content of the second phosphate ester on a weight basis is 0.25 or more and 4.0 or less, the layer of phosphate ester formed on the metal surface is likely to have a dense structure. As a result, a multilayer film of appropriate density is formed between the ball of the pen tip and the metal surface of the receiving seat. Therefore, while ink leakage can be effectively suppressed, it is easy to obtain a good writing feel and handwriting even when writing at high speed or with high writing pressure.

[9] In some embodiments, in any one of the configurations [1] to [8] above,
The HLB value of the nonionic surfactant is 4 or more and 15 or less.

In the above-mentioned [9] configuration, since the nonionic surfactant has an HLB value of 4 or more, it has a certain degree of hydrophilicity, and therefore water is easily taken up into the layer of the nonionic surfactant by interaction with water. In addition, in the above-mentioned [9] configuration, since the nonionic surfactant has an HLB value of 15 or less, it is not excessively hydrophilic and easily interacts with the hydrocarbon groups of the first and second phosphate esters, and therefore it is easy to form the above-mentioned multilayer film between the ball and the metal surface of the receiving seat. Therefore, according to the above-mentioned [9] configuration, it is possible to effectively suppress ink leakage, while easily obtaining a good writing feel and handwriting even when writing at high speed or with high writing pressure.

[10] At least one embodiment of the ballpoint pen of the present invention comprises:
Writing department and
An ink reservoir (e.g., the ink reservoir 12) for accommodating the oil-based ink according to any one of the above items [1] to [9];
The oil-based ink is supplied from the ink reservoir to the writing portion (for example, the ballpoint pen tip 10 described above).

According to the above configuration [10], when writing with a ballpoint pen, a thick multilayer film (hereinafter, multilayer film) containing a layer of phosphate ester and a layer of nonionic surfactant is likely to be formed between the ball at the pen tip and the metal surface of the receiving seat.
That is, the oil-based ink composition of [10] contains a first phosphate ester having a relatively small number of carbon atoms in the hydrocarbon group and a second phosphate ester having a relatively large number of carbon atoms in the hydrocarbon group, and the phosphate groups of these phosphate esters are adsorbed to the metal surfaces of the ball and the receiving seat, forming a phosphate ester layer on the metal surfaces of the ball and the receiving seat. Since the second phosphate ester has a relatively long hydrocarbon group, a relatively thick phosphate ester layer is formed on the metal surface, and since the first phosphate ester has a relatively short hydrocarbon group, the second phosphate ester penetrates between the first phosphate esters, and a phosphate layer having a dense structure is quickly formed on the metal surface.
The oil-based ink composition of [10] above contains water and a nonionic surfactant. Therefore, when writing with a ballpoint pen, the hydrophobic group of the nonionic surfactant interacts with the hydrocarbon group of the phosphate ester, and a layer of the nonionic surfactant is formed between the layers of the phosphate ester formed on the surfaces of the ball and the receiving seat, respectively, making it easy to obtain a thick multilayer film, and the hydrophilic group of the nonionic surfactant interacts with water, and water with high surface tension is taken in by the layer of the nonionic surfactant, increasing the cushioning properties of the multilayer film.
Thus, according to the configuration of [10] above, when writing with a ballpoint pen, a multilayer film with a large thickness and high cushioning properties is easily formed between the ball and the metal surface of the receiving seat, so that the multilayer film can be maintained between the ball and the receiving seat even when writing at high speed or with high writing pressure, and the lubrication during writing is good. Therefore, even when writing at high speed or with high writing pressure, the writing feel is good and smearing, skipped lines, or blobs can be suppressed.
In the above-mentioned configuration [10], the nonionic surfactant does not wet and spread on areas where there is no metal, so that the phosphate ester interacting with the nonionic surfactant is prevented from excessively spreading, and thus leakage of the ink composition from the pen tip can be effectively prevented.
Therefore, according to the configuration [10] above, it is possible to effectively prevent ink leakage, while still obtaining good handwriting with a good writing feel even when writing at high speed or with high writing pressure.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and also includes variations on the above-described embodiments and appropriate combinations of these embodiments.

In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial," do not only strictly represent such a configuration, but also represent a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained.
For example, expressions indicating that things are in an equal state, such as "identical,""equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained.
In addition, in this specification, the expressions "comprise,""include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements.

LIST OF SYMBOLS 1 Barrel 2 Front barrel 3 Rear barrel 4 Grip portion 5 Crown 6 Clip 7 Rotor 8 Knock 9 Elastic member 10 Ballpoint pen tip 11 Tip holder 12 Ink reservoir 13 Ball 14 Ball holder 15 Ink composition 16 Ink backflow prevention body 17 Float 18 Coil spring 19 Tip opening 20 Containing protruding portion 21 Ball holding portion 22 Central hole 23 Rear hole 24 Ink passage groove 25 Ball receiving seat 100 Ballpoint pen 200 Refill 300 Exterior body A Diameter of ball 13 B Inner diameter of tip opening 19 C Distance of movement of ball 13 in the front-to-rear direction D Ball protruding length E Inner diameter of ball holding portion 21 F Width of ink passage groove 24 G Depth of ink passage groove 24 H Diameter of ball receiving seat I Center hole diameter α Seat angle of ball holding portion 21 β Crimping angle γ Chamfer angle δ Taper angle

Claims (10)

a first phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having 4 to 17 carbon atoms;
a second phosphate ester which is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having from 18 to 24 carbon atoms;
Water,
A nonionic surfactant;
An oil-based ink composition for a ballpoint pen comprising the above. 2. The oil-based ink composition for ballpoint pens according to claim 1, wherein the difference between the number of carbon atoms in the hydrocarbon group of the second phosphate ester and the number of carbon atoms in the hydrocarbon group of the first phosphate ester is 4 or more. the hydrocarbon group of the first phosphate ester has 12 or more and 14 or less carbon atoms;
3. The oil-based ink composition for ballpoint pens according to claim 2, wherein the number of carbon atoms in the hydrocarbon group of the second phosphate ester is 18 or more and 20 or less. 4. The oil-based ink composition for ballpoint pens according to claim 1, wherein the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 4 or more and 14 or less. 5. The oil-based ink composition for ballpoint pens according to claim 4, wherein the HLB value of the first phosphate ester and the HLB value of the second phosphate ester are 7 or more and 12 or less. 4. The oil-based ink composition for ballpoint pens according to claim 1, wherein the total content of the first phosphate ester and the second phosphate ester is 0.4% by weight or more and 3.0% by weight or less. 4. The oil-based ink composition for ballpoint pens according to claim 1, wherein a ratio of a content of the first phosphate ester to a content of the second phosphate ester on a weight basis is 0.2 or more and 8.0 or less. 8. The oil-based ink composition for ballpoint pens according to claim 7, wherein a ratio of a content of the first phosphate ester to a content of the second phosphate ester on a mass basis is 0.25 or more and 4.0 or less. 4. The oil-based ink composition for ballpoint pens according to claim 1, wherein the HLB value of the nonionic surfactant is 4 or more and 15 or less. Writing department and
and an ink reservoir that contains the oil-based ink according to any one of claims 1 to 3;
A ballpoint pen characterized in that the oil-based ink is supplied from the ink reservoir to the writing portion.

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