Ballpoint pen refill and ballpoint pen

Abstract

This ballpoint pen refill comprises: an ink accommodation tube; an oil-based ink composition which is filled into the ink accommodation tube; and a ballpoint pen tip that is mounted at a front end part of the ink accommodation tube and that is configured such that the oil-based ink composition is supplied thereto, wherein: the ballpoint pen tip includes a ball, a ball holder that is for holding the ball such that the ball is positioned at the front end of the ballpoint pen tip and is capable of rotation, and a coil spring that is for biasing the ball forward; the coil spring includes a stainless steel bare wire; and the oil-based ink composition contains at least one type of phosphoric acid ester and elastic rubber particles.

Description

Ballpoint pen refills and ballpoint pens

[0001] The present disclosure relates to a ballpoint pen refill and a ballpoint pen.

[0002] Ballpoint pen inks have been proposed to improve the writing experience with ballpoint pens.

[0003] For example, Patent Document 1 discloses an oil-based ink composition for a ballpoint pen that provides a good writing feel even in cold climates and produces handwriting that is free of smearing, the oil-based ink composition containing an organic solvent, water, a colorant, a resin, a phosphate ester compound, a silicone activator, and castor oil.

[0004] Furthermore, Patent Document 2 discloses an ink composition for an oil-based ballpoint pen, which has little resistance and a good writing feel when written at a low load and low speed, and which contains an amidoamine compound containing a C11-23 hydrocarbon group, an organic amine selected from one or more of 2-amino-2-methyl-1,3-propanediol and 2-amino-2-methyl-1-propanol, a phosphate ester compound having an unsaturated hydrocarbon group in the molecule, an organic solvent, and a colorant.

[0005] JP 2018-035334 A JP 2016-194032 A

[0006] When writing with a ballpoint pen under an average load, the friction occurring between the ball provided on the ballpoint pen tip and the ball holder significantly affects the writing feel. On the other hand, when writing with a low load, the friction occurring between the ball provided on the ballpoint pen tip and the coil spring that presses the ball significantly affects the writing feel. The inventors' studies have revealed that ballpoint pens using conventional ink compositions may not be able to maintain a good writing feel over a long period of time when writing with a low load.

[0007] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a ballpoint pen refill and a ballpoint pen that provide a good writing feel when writing with a low load even after long-term use.

[0008] A ballpoint pen refill according to at least one embodiment of the present invention comprises: an ink reservoir; an oil-based ink composition filled in the ink reservoir; and a ballpoint pen tip attached to the front end of the ink reservoir so that the oil-based ink composition is supplied, wherein the ballpoint pen tip comprises: a ball; a ball holder for holding the ball so that the ball is rotatable at the front end of the ballpoint pen tip; and a coil spring for urging the ball forward, wherein the coil spring comprises bare stainless steel wire; and the oil-based ink composition contains at least one type of phosphate ester and rubber elastic particles.

[0009] A ballpoint pen according to at least one embodiment of the present invention includes the ballpoint pen refill described above, and a barrel in which the ballpoint pen refill is housed.

[0010] According to at least one embodiment of the present invention, a ballpoint pen refill and a ballpoint pen are provided that provide a good writing feel when writing with a low load even after long-term use.

[0011] Fig. 5 is a longitudinal sectional view showing a ballpoint pen according to one embodiment. Fig. 6 is a longitudinal sectional view showing a refill used in the ballpoint pen shown in Fig. 1. Fig. 7 is an enlarged longitudinal sectional view showing part I in Fig. 2. Fig. 8 is an enlarged longitudinal sectional view showing part II in Fig. 3. Fig. 9 is a longitudinal sectional view showing a dimension measurement point. Fig. 10 is a cross-sectional view taken along the line III-III' in Fig. 5.

[0012] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0013] (Configuration of Ballpoint Pen Refill and Ballpoint Pen) First, a ballpoint pen to which the ballpoint pen refill according to some embodiments is applied will be described. The ballpoint pen according to some embodiments includes a ballpoint pen refill including a ballpoint pen tip and an ink reservoir tube that contains an oil-based ink composition described below, and is configured so that the oil-based ink composition is supplied from the ink reservoir tube to the ballpoint pen tip.

[0014] Fig. 1 is a longitudinal cross-sectional view showing a ballpoint pen according to one embodiment. Fig. 2 is a longitudinal cross-sectional view showing a refill portion of the ballpoint pen shown in Fig. 1. In the exemplary embodiment shown in Figs. 1 and 2, the ballpoint pen 100 includes a ballpoint pen refill 200 and an exterior body 300.

[0015] In the embodiment shown in FIG. 1 , the exterior body 300 includes a barrel tube 1, to which a front axle 2 and a rear axle 3 are detachably fastened by threading. The surface of the front axle 2, which is formed from a relatively hard material (e.g., resin), is coated with a relatively soft material (a soft member such as a softer resin) to form the grip portion 4. Examples of relatively hard resin materials that form the front axle 2 and rear axle 3 include polycarbonate, polyethylene terephthalate, acrylic, acrylonitrile butadiene styrene copolymer (ABS), acrylonitrile styrene copolymer (AS), polypropylene, etc., and either a transparent or opaque material may be used. Furthermore, examples of relatively soft resin materials (soft members) that form the grip portion 4 include thermoplastic elastomers and soft acrylics, and either a transparent or opaque material may be used. The grip portion 4 is preferably a grip that is non-slip when held, such as a grip with an uneven surface, a triangular grip, a grip with a polygonal outer surface, or a grip shaped like a fingerprint. A crown 5 is inserted into the bore of the rear barrel 3 and attached and secured by a concave-convex threaded engagement at the rear of the rear barrel 3, with the portion exposed from the rear end of the rear barrel 3 covering the base surface of a clip 6 attached to the outer surface of the rear barrel 3. The crown 5 is cylindrical, and a groove formed therein serves as a cam groove for a debit cam mechanism, regulating the sliding position of the rotor 7 housed therein and determining the forward-backward movement position of the ballpoint pen refill 200 connected thereto as the rotor 7 rotates when the knock 8 is pressed in. The ballpoint pen refill 200 is housed within the barrel tube 1 so as to be movable forward and backward. A resilient member 9, such as a coil spring, is disposed in front of the ballpoint pen refill 200, biasing the ballpoint pen refill 200 rearward. The rear end of the ballpoint pen refill 200 abuts against the tip of the rotor 7. In other words, the ballpoint pen refill 200 is a retractable ballpoint pen in which the ballpoint pen refill 200 protrudes from and retracts from the tip opening of the barrel 1 by pressing the knock 8 .

[0016] As shown in FIG. 2 , the ballpoint pen 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 is attached to the front end of the ink reservoir 12. The ballpoint pen tip 10 has a ball 13 as a writing member and a ball holder 14 that rotatably holds the ball 13. The ink reservoir 12 is filled with an ink composition 15, and the ink composition 15 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. It is possible to provide a ballpoint pen body that does not use an outer case 300 by disposing a tail plug or the like at the rear end of the ink reservoir 12 of the ballpoint pen refill 200 to prevent leakage of the ink composition 15. The inner diameter of the ink reservoir 12 may be 1.00 mm or more and 5.00 mm or less. An inner diameter of 1.00 mm or more and 3.10 mm or less is particularly preferred, as this provides good shape retention for the ink backflow preventer 16, preventing the ink backflow preventer 16 from flowing out, and preventing the ink backflow preventer 16 from flowing out even without the float 17 in contact with the ink backflow preventer 16. The thickness of the ink reservoir 12 can be calculated by subtracting the outer diameter from the inner diameter, and may be 0.50 mm or more and 10.0 mm or less. A thickness of 1.00 mm or more and 10.0 mm or less provides high gas barrier properties and can prevent evaporation of the ink solvent, and a thickness of 2.80 mm or more and 10.0 mm or less is even more preferred, as it provides particularly high gas barrier properties.

[0017] Fig. 3 is a diagram showing the configuration of the ballpoint pen tip 10 of a ballpoint pen refill 200 according to one embodiment, and is an enlarged longitudinal cross-sectional view of part I in Fig. 2. The ballpoint pen tip 10 shown in Fig. 3 rotatably holds a ball 13 (writing element) within a ball holder 14 with the ball 13 partially protruding from the tip of the ink passage hole, which is a through-hole. A coil spring 18, which serves as a resilient member, is disposed 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, preventing it from coming out. The restoring force resulting from this compression urges the ball 13 forward. The coil spring 18 is prevented from coming out by abutting its rear end against the tip holder 11. Other methods of preventing the ball holder 14 from coming loose include forming a cut piece by broaching the rear inner wall surface of the ball holder 14, reducing the diameter of the rear end opening of the ball holder 14, or forming a convex portion on the inner wall surface by punching the side wall portion of the ball holder 14, and the method and shape of preventing the coil spring 18 from coming loose can be selected as appropriate.

[0018] When pressed against a writing surface such as paper, the ball 13 moves backward, causing ink to flow out from a gap formed between the ball 13 and the ball holder 14 (described later) or to be transported outward and transferred as the ball 13 rotates. The size of the ball 13 that can be used is a diameter of 0.18 mm or more and 2.00 mm or less, which is the size used in ordinary ballpoint pens. If the arithmetic mean height (Sa) of the surface of the ball 13 is large, localized metal-to-metal contact between the ball 13 and the ball holder 14 is likely to occur, and a thick lubricating film containing phosphate ester and rubber elastic particles cannot be maintained at the contact area where localized high pressure occurs. Therefore, considering that the lubricating properties of the lubricating film can be more easily exhibited, the arithmetic mean height (Sa) of the surface of the ball 13 is preferably 1.00 nm or more and 20.0 nm or less. The material of the ball 13 may be a cemented carbide alloy mainly composed of tungsten carbide, a metal such as stainless steel, aluminum, or iron, a ceramic such as silicon carbide, silicon nitride, titanium nitride, chromium carbide, alumina, or zirconia, a resin material such as polyethylene, polypropylene, polyacetal, or polyamide, or glass, but cemented carbide or ceramics are preferred in consideration of corrosion resistance by ink.

[0019] Next, details of the ballpoint pen tip 10 will be described in FIG. 4, an enlarged view of portion II in FIG. 3. The ball holder 14 has an ink passage hole, which is a through-hole. This ink passage hole includes a tip opening 19, which is crimped from the tip side to a smaller diameter, a ball holding portion 21 defined by an internal protrusion 20 and in which the ball 13 is positioned with a portion protruding from the tip opening 19, a central hole 22 formed in the center of the internal protrusion 20, and a rear hole 23. The outer edge of the tip opening 19 may be curved to prevent it from getting caught on paper. The inner edge of the tip opening 19 is pressed against the ball 13 during crimping, transferring the curved surface of the ball 13 and polishing it to a mirror finish, in order to improve sealing when the ball 13 is pressed against the ball 13 and comes into circumferential contact with the coil spring 18. Additionally, multiple ink passage grooves 24 are formed radially and equidistantly spaced by cutting into the inward protrusion 20. This ink passage groove 24 passes through to the rear hole 23 to ensure ink supply to the ball holding portion 21, but it may also stop halfway through the center hole 22 without passing through the rear hole 23. A concave ball receiving seat 25 is formed by pressing the ball 13 against the inward protruding portion 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 and retracts during writing, ensuring smooth rotation with little unnecessary vibration, and is shaped so that the ball 13 and ball receiving seat 25 come into approximate planar contact. The ink passage groove 24 also has an opening outside the ball receiving seat 25 formed in the inward protruding portion 20, ensuring ink supply to the ball holding portion 21.

[0020] The diameter A of the ball 13 of the ballpoint pen tip 10 is preferably 0.18 mm or more and 2.00 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% to 98% of the diameter of the ball 13; the forward / backward movement distance C of the ball 13 is 2% to 10% of the diameter A of the ball 13; the ball protrusion length D is 20% to 35% of the diameter A of the ball 13; the inner diameter E of the ball holding portion 21 is 90% to 130% of the diameter A of the ball 13; the number of ink channels 24 is 2 to 6; and the width F of the ink channels 24 is 0.05 mm. Preferably, the ink passage groove 24 has a depth G of 0.10 mm or more or may extend 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 ink retention in the ball receiving seat and to better utilize the lubrication provided by the lubricating film formed by the components of the ink composition (phosphate ester, etc.), it is necessary to distribute the force per unit area applied to the ball receiving seat when writing with high writing pressure, and therefore the ball receiving seat diameter H is more preferably 80% to 90% of the diameter A of the ball 13. Furthermore, 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 will prevent ink from adhering to the ballpoint pen tip 10. The dimensions of each part are shown in Figures 4, 5, and 6 (the ball 13 and coil spring 18 are not shown).

[0021] In some embodiments, the coil spring 18 is formed from bare stainless steel wire (i.e., stainless steel wire with no surface plating). Examples of bare stainless steel wire that can be used include stainless steels such as US303, SUS304, and SUS316, as well as bare wires with no surface plating, such as hard steel wire or piano wire. Similar effects can also be achieved by using bare wire springs made from wire with a plated surface, such as stainless steel, hard steel wire, or piano wire, in which the plating is removed by chemical treatment after the spring is formed.

[0022] 3 to 5, the straight portion of the coil spring 18 (the front end portion near the ball 13) is slightly inclined from the axial direction of the ballpoint pen. Since the coil spring 18 is compressed between the ball 13 and the tip holder 11, in actual ballpoint pens, the straight portion of the coil spring 18 is often inclined in this manner.

[0023] (Oil-Based Ink Composition) The ink composition 15 filled in the ink reservoir 12 of the ballpoint pen refill 200 according to some embodiments is an oil-based ink composition described below.

[0024] The oil-based ink composition according to some embodiments contains at least one phosphoric acid ester and rubber elastic particles.

[0025] The oil-based ink composition described above contains phosphate ester, which is easily chemically adsorbed to metal, and elastic rubber particles, so that a highly cushioning lubricating film containing phosphate ester and rubber elastic particles is formed on the surface of the ball 13 and the coil spring 18.

[0026] The phosphate ester has a phosphate group and a carbon chain-containing moiety connected to the phosphate group via an ester bond. In the oil-based ink composition (ink composition 15), the phosphate group of the phosphate ester is likely to adsorb to the metal (ball 13 and coil spring 18) and the rubber elastic particles by chemical adsorption. Therefore, a lubricating film with high cushioning properties is formed on the surface of the metal (coil spring 18) by the phosphate ester having a phosphate group and a relatively long carbon chain-containing moiety and the rubber elastic particles.

[0027] When writing with the ballpoint pen 100, the coil spring 18 is compressed, so that the tip surface of the coil spring 18 does not face the ball 13 directly, and the tip portion of the coil spring 18 is likely to be bent. Even in such a case, the lubricating film described above is formed not only on the tip surface of the coil spring 18 but also on the surface of the side facing the ball 13.

[0028] As a result, when writing with the ballpoint pen 100 under low load, the friction between the ball 13 and the coil spring 18 (including the tip end surface and side surface) is reduced, so the user of the ballpoint pen 100 is less likely to feel resistance due to friction when writing, resulting in a good writing feel.

[0029] Furthermore, in the ballpoint pen refill 200 filled with the oil-based ink composition, the coil spring 18 is formed from bare stainless steel wire, and therefore an oxide film with relatively high corrosion resistance and low reactivity is formed on the surface of the coil spring 18. This prevents the surface portion of the coil spring 18 from being separated as a precipitate due to reaction with the phosphate ester in the oil-based ink composition, and thus facilitates the stable formation of a lubricating film containing the phosphate ester and rubber elastic particles on the surface of the coil spring 18. Furthermore, as described above, the oxide film on the surface of the bare stainless steel wire is relatively corrosion-resistant, and therefore is less susceptible to changes in the moisture content and pH of the oil-based ink composition over time, and therefore the elastic lubricating film can be stably formed on the surface of the coil spring 18 for a long period of time.

[0030] As described above, according to the above-described embodiment, the lubricating film described above can maintain low friction between the ball 13 and the coil spring 18 even after long-term use of the ballpoint pen 100. Therefore, it is possible to obtain a ballpoint pen 100 that has a good writing feel when writing with a low load even after long-term use.

[0031] In some embodiments, the spring load of the coil spring 18 when the ballpoint pen 100 is not writing is 0.10 N or more and 0.60 N or less.

[0032] In the above-described embodiment, the spring load of the coil spring is 0.10 N or more, so that the ball 13 can be appropriately pressed toward the ball holder 14. This makes it possible to suppress seepage of the oil-based ink composition during writing and leakage of the oil-based ink composition when the ballpoint pen 100 is left stationary. Furthermore, in the above-described embodiment, the spring load of the coil spring 18 is 0.60 N or less, so that the pressure from the coil spring 18 on the ball 13 is not too great. This makes it difficult for the lubricating films formed on the surfaces of the ball 13 and the coil spring 18 to break, and tends to reduce friction between the ball 13 and the coil spring 18 when writing with a low load using the ballpoint pen 100. A good writing feel can be maintained over a long period of time when writing with a low load while suppressing seepage and leakage of the oil-based ink composition.

[0033] In some embodiments, the wire diameter of the coil spring 18 is equal to or greater than 0.05 mm and equal to or less than 0.20 mm.

[0034] In the above-described embodiment, the wire diameter of the coil spring 18 is 0.05 mm or more, which prevents localized pressure buildup between the ball 13 and the coil spring 18, making the lubricating film less likely to break down. Furthermore, in the above-described embodiment, the wire diameter of the coil spring 18 is 0.2 mm or less, which prevents the spring constant from being too large and the spring load from becoming too large, making the lubricating film less likely to break down. Therefore, according to the above-described embodiment, the lubricating film is stably formed on the surfaces of the ball 13 and the coil spring 18 for a long period of time, making it easier to maintain a good writing feel even when writing with a low load for a long period of time.

[0035] The spring constant k (N / mm) of the coil spring, the spring load P (N), the displacement δ (mm), and the modulus of transverse elasticity G (M / mm) of the spring material are ２ ), the wire diameter d (mm) of the spring, the number of effective turns Na (-), and the average coil diameter D (mm) have a relationship represented by the following formula (A).

[0036] In some embodiments, the effective number of turns of the coil spring 18 is greater than or equal to 10 and less than or equal to 40.

[0037] In the above-described embodiment, the effective number of turns of the coil spring 18 is between 10 and 40, both inclusive, so that the pressure between the coil spring 18 and the ball 13 tends to be within an appropriate range. This makes it difficult for the lubricating film to break down, and the lubricating film is stably formed on the surfaces of the ball 13 and the coil spring 18 for a long period of time, making it easier to maintain a good writing feel when writing with a low load for a long period of time.

[0038] In some embodiments, the phosphate ester contained in the oil-based ink composition is not particularly limited, and may be, for example, a phosphate ester having a hydrocarbon group, or a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group. The phosphate ester may be a monoester, diester, or triester, or a mixture thereof. The polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group, when it is a monoester, is represented by the following formula (B): RO—(CH ２ CH ２ O) ｎ -PO(OH) ２ …(B)

[0039] Specific examples of phosphate esters include phosphate esters of polyoxyethylene tridecyl ether (hydrocarbon group: saturated hydrocarbon group having 13 carbon atoms), phosphate esters of polyoxyethylene lauryl ether (hydrocarbon group: saturated hydrocarbon group having 12 carbon atoms), phosphate esters of polyoxyethylene phenyl ether (hydrocarbon group: unsaturated hydrocarbon group having 13 carbon atoms), phosphate esters of polyoxyethylene lauryl ether (hydrocarbon group: saturated hydrocarbon group having 12 carbon atoms), phosphate esters of polyoxyethylene oleyl ether (hydrocarbon group: unsaturated hydrocarbon group having 18 carbon atoms), and phosphate esters of polyoxyethylene stearyl ether (hydrocarbon group: saturated hydrocarbon group having 18 carbon atoms).

[0040] Examples of commercially available phosphate esters include Phosphanol BH-650, Phosphanol SM-172, Phosphanol ED-200, Phosphanol GF-339, Phosphanol RA-600, Phosphanol GF-199, Phosphanol ML-200, Phosphanol ML-220, Phosphanol ML-240, Phosphanol RD-510Y, Phosphanol GF-185, Phosphanol RS-610, Phosphanol RS-710, Phosphanol RP-710, Phosphanol AK-25, Phosphanol GF-702, and Phosphanol RS-6. Examples of suitable surfactants include 10NA, SC-6103, LP-700, LS-500, RL-210, RL-310, RB-410, RD-720, and LB-400 (all manufactured by Toho Chemical Industry Co., Ltd.), Plysurf A207H, A208B, A219B, A208S, A212S, A215C, and AL (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and NIKKOL DDP-2 (Zipalace-2 phosphate, manufactured by Nikko Chemicals Co., Ltd.).

[0041] The content of the phosphate ester in the oil-based ink composition may be 0.10% by weight or more and 20.0% by weight or less. If the content of the phosphate ester is 0.10% by weight, a highly cushioning lubricating film containing the phosphate ester and rubber elastic particles is easily formed on the surfaces of the ball 13 and the coil spring 18. If the content of the phosphate ester is 20.0% by weight or less, the content of the organic solvent in the oil-based ink composition can be ensured, so that solid components in the ink, such as dyes and resins, can be sufficiently dissolved, and the writing is less likely to be blurred.

[0042] In some embodiments, the oil-based ink composition comprises a first phosphate ester and a second phosphate ester, each having a hydrocarbon group and differing in the number of carbon atoms in the hydrocarbon group, wherein the number of carbon atoms in the hydrocarbon group of the second phosphate ester is greater than the number of carbon atoms in the hydrocarbon group of the first phosphate ester.

[0043] The first phosphate ester may be a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 4 to 17. The second phosphate ester may be a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with a carbon number of 18 to 30.

[0044] In this way, the 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, so that the second phosphate ester penetrates between the first phosphate esters, forming a densely structured lubricating film of phosphate ester on the metal surface. This makes the lubricating film more stable, and the lubricating film tends to reduce friction between the ball 13 and the coil spring 18. This tends to result in a good writing feel even when writing with a low load.

[0045] In this specification, rubber-elastic particles refer to polymer particles that have a crosslinked structure in which the molecules constituting the rubber-elastic particles are covalently bonded to each other, and thus have the property of returning to their original state from a deformed state (rubber elasticity). The elastic modulus and hardness can be adjusted by changing the molecules that form the crosslinked structure. Rubber-elastic particles are characterized by being resistant to pressure and impact, yet easily deformable. Therefore, they can reduce the impact of friction between the oil-based ink composition and the components (such as the ball) that constitute the ballpoint pen tip during writing, improving lubricity and improving the writing feel.

[0046] In some embodiments, the rubber-elastic particles are particles formed from at least one of a urethane resin, an acrylic resin, a styrene resin, and a silicone resin, and may be a mixture of particles of one or more of these resins. Furthermore, the rubber-elastic particles may be composite particles having rubber elasticity at the center and coated with a resin or the like to improve dispersibility. The rubber-elastic particles may be silicone composite particles having a structure in which silicone rubber particles are coated with a silicone resin.

[0047] In some embodiments, the rubber elastic particles may be particles made of silicone, and the silicone particles may be silicone composite particles having a structure in which silicone rubber particles are coated with a silicone resin.

[0048] When the oil-based ink composition contains rubber elastic particles made of silicone, it is easy to increase the elasticity of the lubricating film formed on the surfaces of the ball 13 and the coil spring 18. Therefore, when writing with the ballpoint pen 100 at a low load, the friction between the ball 13 and the coil spring 18 tends to be small, and as a result, the user of the ballpoint pen 100 is less likely to feel resistance due to friction when writing, which tends to improve the writing feel.

[0049] In some embodiments, the elastomeric particles may be acrylic particles, styrene particles, or urethane particles.

[0050] When the oil-based ink composition contains acrylic particles, styrene particles, or urethane particles, a highly cushioning lubricating film containing phosphate ester and rubber elastic particles can be formed on the surfaces of the ball 13 and the coil spring 18. As a result, when writing with the ballpoint pen 100 under low load, friction between the ball 13 and the coil spring 18 is reduced, so that the user of the ballpoint pen 100 is less likely to feel resistance due to friction when writing, resulting in a smooth writing experience.

[0051] The rubber elastic particles have a true specific gravity of 1.20 g / cm ３ or the true specific gravity may be less than 1.05 g / cm ３ The true specific gravity of the rubber elastic particles may be less than 1.20 g / cm ３ If the true specific gravity of the rubber elastic particles is less than 1.05 g / cm, the dispersibility of the rubber elastic particles in the oil-based ink composition is likely to be good. ３ If it is less than this, the dispersibility of the rubber elastic particles in the oil-based ink composition tends to be good for a long period of time.

[0052] The particle size of the rubber elastic particles can be appropriately selected so that they can be ejected from the ballpoint pen tip used. The average particle size of the rubber elastic particles may be 2.00 μm or more and 10.0 μm or less. The average particle size of the rubber elastic particles may be less than 1.00 μm. In this case, the oil-based ink composition tends to be easily ejected from the ballpoint pen tip. In addition, the particle size distribution can be adjusted by sieving, centrifugation, or filtration to obtain rubber elastic particles of the desired particle size.

[0053] In this specification, the particle size of the rubber elastic particles refers to the average particle size, which is calculated as the volume-based average particle size based on measurements taken using a laser diffraction / scattering particle size distribution analyzer (e.g., SALD-7100, manufactured by Shimadzu Corporation).

[0054] The content of the rubber elastic particles in the oil-based ink composition may be 0.10% by weight or more, or 1.00% by weight or more.

[0055] When adding the rubber elastic particles to the oil-based ink composition, the rubber elastic particles may be added directly to the oil-based ink composition, or the rubber elastic particles may be dispersed in a dispersion medium in advance to form a dispersion, which is then added to the oil-based ink composition.

[0056] The elasticity (hardness) of the rubber elastic particles is preferably 25 to 90, more preferably 50 to 80, in Type A durometer according to JIS K 6253. If the elasticity of the rubber elastic particles is within the above range, the rubber elastic particles are easily deformed when sandwiched between the coil spring and the ball, and when the gap between the coil spring and the ball widens during low-load writing, the rubber elastic particles immediately restore their original shape and are easily dispersed into the ink flow path.

[0057] As the nonionic surfactant, well-known nonionic surfactants can be used without any particular limitation. Examples of the nonionic surfactant that can be used include ester-type nonionic surfactants such as esters of polyhydric alcohols and fatty acids, ether-type nonionic surfactants such as polyoxyethylene hydrocarbon ethers or polyoxyethylene hydrocarbon phenyl ethers, and ester-ether-type nonionic surfactants having both ester bonds and ether bonds in the molecule.

[0058] 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: としては, NIKKOL BL-2, same as BL-4.2, same as BL-9EX, same as BC-2, same as BC-5.5, same as BC-7, same as BC-10, same as B S-2, same as BS-4, same as BO-2V, same as BO-7V, same as BO-10V, same as BB-5, same as BB-10, same as BD-4 , Same as BT-3, Same as BT-5, Same as BT-7, Same as BT-9, Same as BT-12, Same as PBC-31, Same as PBC-33, Same as P BC-41, same as PBC-44, same as PEN-4612, same as PEN-4620, same as PEN-4630, same as BPS-5 , same as BPS-10, same as HCO-5, same as HCO-10, same as HCO-20, same as HCO-30, same as HCO-40, same as HCO-50, same as HCO-60, same as HCO-80, same as TS-10V, same as TS-10MV, same as TS-106V, same as TS-30V, same as TI-10V, same as TO-10V, same as TO-10MV, same as TO-106V, same as TO-30V, same as GS-460, same as GO-4V, same as GO-430NV, same as GO-440V, same as GO-460V, same as Tetraglyn 1-SV, same as Tetraglyn 1-OV, same as Hexaglyn 1-L, same as Hexaglyn 1-M, same as Hexaglyn 1-SV, same as Hexaglyn 1-OV, same as Decaglyn 1-M, same as Decaglyn 1-SV, same as Decaglyn 1-50SV, same as Decaglyn 1-ISV, same as Decaglyn 1-OV, same as Decaglyn 1-LN, same as Decaglyn 2-SV, same as Decaglyn 2-ISV, same as Decaglyn 3-SV, same as Decaglyn 3-OV, same as TMGS-5V, same as TMGS-15V, same as TMGO-5, same as TMGO-15 (all made by Nikko Chemicals Co., Ltd.), Pegnor L-4, same as TH-8, same as L-9A, same as L-12S, same as T-6, same as TE-10A, same as ST-7, same as ST-9, same as ST-12, same as O-6S, same as O-16A, same as S-4DV (with Above, manufactured by Toho Chemical Industry Co., Ltd.), ノイゲンXL-40, same as XL-100, same as TDS -30, LF-60X, same as TDX-50, same as TDX-80, same as SD-30, same as S D-60, same as SD-70, same as SD-80, same as EA-87, ソルゲン30, 90, Same as 110, same as TW-60 (above, manufactured by Daiichi Industrial Co., Ltd.) をげることができる.

[0059] The water in the oil-based ink composition may be mineral water, tap water, ion-exchanged water, purified water, distilled water, or pure water.

[0060] In some embodiments, the water content in the oil-based ink composition may be 1.00% by weight or more and 10.0% by weight or less, or 4.00% by weight or more and 8.00% by weight or less.

[0061] In the above-mentioned embodiment, since the water content in the oil-based ink composition is 1.00% by weight or more or 4.00% by weight or more, a certain amount of water is taken up in the lubricating film, thereby enhancing the cushioning properties of the lubricating film. Also, in the above-mentioned embodiment, since the water content in the oil-based ink composition is 10.0% by weight or less or 8.00% by weight or less, the water content in the oil-based ink composition is not too high, and water can be stably dissolved in the oil-based ink composition.

[0062] In the oil-based ink for ballpoint pens according to some embodiments, the colorant is not particularly limited and may be a water-based dye, an oil-soluble dye, or a pigment.

[0063] Specific examples of the water-soluble dye include direct dyes, acid dyes, and basic dyes. Specific examples of direct dyes include Japanol Fast Black D Concentrate (C.I. Direct Black 17), Water Black 100L (C.I. Direct Black 19), Water Black L-200 (C.I. Direct Black 19), Direct Fast Black B (C.I. Direct Black 22), Direct Fast Black AB (C.I. Direct Black 32), Direct Deep Black EX (C.I. Direct Black 38), Direct Fast Black Concentrate (C.I. Direct Black 51), Kayalas Spragray VGN (C.I. Direct Black 71), Kayalas Direct Brilliant Yellow G (C.I. Direct Yellow 4), Direct Fast Yellow 5GL (C.I. Direct Black 26), Aizen Primula Yellow GCLH (C.I. Direct Black 44), Direct Fast Yellow R (C.I. Direct Black 50), Aizen Direct Fast Red FH (C.I. Direct Red 1), Nippon Fast Scarlet GSX (C.I. Direct Black 4), Direct Fast Scarlet 4BS (C.I. Direct Black 23), Aizen Direct Red Ctrodurin BH (same 31), Direct Scarlet B (same 37), Kayaku Direct Scarlet 3B (same 39), Aizen Primula Pink 2BLH (same 75), Sumi Light Red F3B (same 80), Aizen Primula Red 4BH (same 81), Kayalas Sprat Vin BL (same 83), Kayalas Light Red F5G (same 225), Kayalas Light Red F5B (same 226), Kayalas Light Rose FR (same 2 27), 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), Kayalas Turquoise Blue GL (same 86), Kayalas Splat Blue FF2 GL (same 106), Kayalas Splat Turquoise Blue FBL (same 199), etc.

[0064] 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 52), Eisen Opal Black WH Extra Concentrate (C.I. Acid Black 52), Sumiran Black WA (C.I. Acid Black 52), Ranil Black BG Extra Concentrate (C.I. Acid Black 107), Kayanol Milling Black TLB (C.I. Acid Black 109), Suminol Milling Black B (C.I. Acid Black 109), ), Kayanol Milling Black TLR (same 110), Aizen Opal Black New Conch (same 119), Water Black 187-L (same 154), 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 ( Suminol Milling Yellow MR (same 38), 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 N 5G (same 110), Suminol Milling Yellow 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 Cocchin (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),Eisen Acid Phloxine PB (same 92), Rose Bengal (same 94), Kayanol Milling Scarlet FGW (same 111), Kayanol Milling Rubin 3BW (same 129), Sumino All Milling Brilliant Red 3BN Concentrate (same 131), Sumino All Milling Brilliant Red BS (same 138), Eisen Opal Pink BH (same 186), Sumino All Milling Brilliant Red B Concentrate (same 249), Kayaku Acid Brilliant Red 3BL (same 254), Kayaku Acid Black Lilid Brilliant Red BL (same 265), Kayanol Milling Red GW (same 276), Mitsui Acid Violet 6BN (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 as 23), Mitsui Nylon Fast Blue G (same as 25), Kayasil Blue AGG (same as 40), Kayasil Blue BR (same as 41), Mitsui Alizarin Sapphirol SE (same as 43), Suminol Leveling Sky Blue R Extra Concentrate (same as 62), Mitsui Nylon Fast Sky Blue B (same as 78), Sumitomo Brilliant Indocyanine 6Bh / c (same as 83), Sandran Cyanine N-6B 350% (same as 90), Water Blue #115 (same as 90), Olie Examples include Int Soluble Blue OBB (same as above 93), Sumitomo Brilliant Blue 5G (same as above 103), Kayanol Milling Ultra Sky SE (same as above 112), Kayanol Milling Cyanine 5R (same as above 113), Eisen Opal Blue 2 GLH (same as above 158), Daiwa Guinea Green B (C.I. Acid Green 3), Acid Brilliant Milling Green B (same as above 9), Daiwa Green #70 (same as above 16), Kayanol Cyanine Green G (same as above 25), and Suminol Milling Green G (same as above 27).

[0065] Specific examples of basic dyes include Eisenkathiron Yellow 3GLH (C.I. Basic Yellow 11), Eisenkathiron Brilliant Yellow 5GLH (same 13), Sumiacrylic Yellow E-3RD (same 15), Maxiron Yellow 2RL (same 19), Astrazon Yellow 7GLL (same 21), Kayakryl Golden Yellow GL-ED (same 28), Astrazon Yellow 5GL (same 51), Eisenkathiron Orange GLH (C.I. Basic Orange 21), Eisenkathiron Brown 3GLH (same 30), Rhodamine 6GCP (C.I. Basic Red 1), Eisen Astraphloxine (same 12), Sumiacrylic Brilliant Red E-2B (same 15), Astrazon Yellow 5GL (same 51), Examples include Trazone Red GTL (C.I. 18), Eisen Katilon Brilliant Pink BGH (C.I. 27), Maxilon Red GRL (C.I. 46), Eisen Methyl Violet (C.I. Basic Violet 1), Eisen Crystal Violet (C.I. 3), Eisen Rhodamine B (C.I. 10), Astrazon Blue G (C.I. Basic Blue 1), Astrazon Blue BG (C.I. 3), Methylene Blue (C.I. 9), Maxilon Blue GRL (C.I. 41), Eisen Katilon Blue BRLH (C.I. 54), Eisen Diamond Green GH (C.I. Basic Green 1), Eisen Malachite Green (C.I. 4), Bismarck Brown G (C.I. Basic Brown 1), etc. These may be used alone or in combination.

[0066] 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 Nigrosine Base EB. Le Blue 613, Oil Scarlet 308, BOS, Oil Black HBB, 860, BS, Varifast Yellow 1101, 1105, 1108, 1109, 3104, 3105, 3108, 4120, AUM, Varifast Orange 2210, 3209, 3210, Varifast Red 1306, 1308, 1320, 1364, 1355 , 1360, 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 Sto 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, Aizen Spiron GRLH Special, Aizen C-2GH, Aizen 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, S.O.T. 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 3101, AL Red 230 8, 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 Yellow GCN, Oleosol Fast Orange GL, Oleosol Fast Red BL, Oleosol Fast Red RL (all manufactured by Taoka Chemical Co., Ltd.), Savvinyl Yellow 2GLS, Savvinyl RLS, Savvinyl 2RLS, Savvinyl Orange RLS, Savvinyl Fire Red GLS, Savvinyl Red 3BLS, Savvinyl Pink 6BLS, Savvinyl Blue RN, Savvinyl GLS, Savvinyl Green 2GLS, Savvinyl 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, Bassonil Red 540, Bassonil Violet 600, Victoria Blue F4R, Nigrosine Base LK (all manufactured by BASF, Germany), Methyl Violet 2B Base (all manufactured by National These may be used alone or in combination.

[0067] Specific examples of pigments include carbon black 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, 12 3, 144, 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 suitable 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, 36, etc. These can be used alone or in combination of two or more.

[0068] In addition to these pigments, processed pigments can also be used, such as 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, and 592 Black (all manufactured by Dainichiseika Color & Chemicals Mfg. 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, and Green G-A (all manufactured by Chiba Specialty Chemicals Co., Ltd.).

[0069] 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, and cationic surfactants such as higher fatty acids, higher alcohol sulfate ester salts, fatty acid sulfate ester salts, alkylarylsulfonic acids, phosphate esters, 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 surfactants may be used alone or in combination of two or more.

[0070] In some embodiments, the dispersion medium may be an organic solvent used in oil-based ballpoint pen inks. From the viewpoints of safety and odor, the organic solvent is preferably alcohol, glycol, or glycol ether.

[0071] Examples of organic solvents include ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoisobutyl ether, ethylene glycol dibutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, diethylene glycol dibutyl ether, diethylene glycol monohexyl ether, diethylene glycol mono-2-ethylhexyl ether, and triethylene glycol monomethyl ether. glycol ethers such as ethylene glycol, 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 tertiary butyl ether, propylene glycol monophenyl ether, dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butyl acetate, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, octylene glycol,Examples of the glycols include glycerin, polyethylene glycol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,3-butanediol, and 1,5-pentanediol; alcohols such as benzyl alcohol, β-phenylethyl alcohol, α-methylbenzyl alcohol, ethanol, n-propanol, 2-propanol, 1-butanol, 2-butanol, 3-methoxy-1-butanol, 3-methyl-3-methoxy-1-butanol, 3-methyl-3-methoxypentanol, lauryl alcohol, tridecyl alcohol, isodecyl alcohol, and isotridecyl alcohol; ethers such as methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether; and esters such as 2-ethylhexyl acetate, isobutyl isobutyrate, ethyl lactate, and butyl lactate. 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 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 1.00 to 30.0, and more preferably 1.30 to 6.00.

[0072] The ink composition according to some embodiments may contain a dispersant for dispersing particles such as the rubber elastic particles. Examples of the dispersant include a dispersing resin and an activator, such as a 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 carboxylic acid ester having a hydroxyl group, and a nonionic activator.

[0073] The dispersant used is preferably polyvinyl butyral, and it is even more preferable to use a dispersant with an acid value of 60 mgKOH / g or more in combination, as this improves the dispersion stability of the silicone composite particles and provides long-term storage stability. Specific examples of polyvinyl butyral include S-LEC BL-1, BL-1H, BL-2, BL-2H, BL-5, BL-10, BL-S, BX-L, BM-1, BM-2, BM-5, BM-S, BH-3, BH-6, BH-S, BX-1, BX-5, KS-10, KS-1, KS-3, 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 76 mgKOH / g), DISPERBYK-160 (acid value 76 mgKOH / g), DISPERBYK-170 (acid value 76 mgKOH / g), DISPERBYK-180 (acid value 76 mgKOH / g), DISPERBYK-190 (acid value 76 mgKOH / g), DISPERBYK-200 (acid value 76 mgKOH / g), DISPERBYK-210 (acid value 76 mgKOH / g), DISPERBYK-220 (acid value 76 mgKOH / g), DISPERBYK-230 (acid value 76 mgKOH / g), DISPERBYK-240 (acid value 76 mgKOH / g), DISPERBYK-250 (acid value 76 mgKOH / g), DISPERBYK-260 (acid value 76 mgKOH / g), DISPERBYK-270 (acid value 76 mgKOH / g), DISPERBYK-280 (acid value 76 mgKOH / g), DISPERBYK-290 (acid value 76 mgKOH / g), DISPERBYK-300 (acid value 76 mgKOH / Examples of suitable BYK-P104 (acid value 180 mg KOH / g, amine value 71 mg KOH / g), BYK-P180 (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), and W9011 (acid value 65 mg KOH / g) or higher are all manufactured by BYK Japan Co., Ltd. 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.

[0074] The dispersants can be used alone or in combination, and are preferably used in an amount of 5.00% by weight to 200% by weight based on the rubber elastic particles.

[0075] In some embodiments, a resin may be contained in the oil-based ink composition for the purposes of adjusting the viscosity of the ink and improving the fixation of handwriting.

[0076] Specific examples of the resin include polyvinylpyrrolidone resin, polyvinyl alcohol resin, polyvinyl butyral resin, ketone resin, acrylic acid-acrylic acid ester resin, acrylic acid-methacrylic acid ester resin, methacrylic acid-acrylic acid ester resin, methacrylic acid-methacrylic acid ester resin, styrene-acrylic acid resin, styrene-maleic acid resin, phenolic resin, rosin, rosin ester, modified rosin, modified rosin ester, maleated rosin, maleated rosin ester, fumarated rosin, fumarated rosin ester, 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.Specific examples of resins that can be used 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 HH. , and B 75 H (all manufactured by Kuraray Co., Ltd.), polyvinylpyrrolidone K-30, K-85, and K-90 (all manufactured by Nippon Shokubai Co., Ltd.), PVP K-15, K-30, K-60, K-90, and K-120 (all manufactured by ISP Japan Co., Ltd.), GE191-000, GE191-053, GE191-103, GE191-104, GE191-107, and GE191-405 (manufactured by Resonac Co., Ltd.), Tamanol 100S and Tamanol 510 (all manufactured by Arakawa Chemical Industries, Ltd.), Co., Ltd.), Hitanol 1501, Hitanol 2501 (all manufactured by NOF Corporation), YP-90, YP-90L, YS Polystar S145, YS Polystar #2100, #2115, #2130, YS Polystar T80, YS Polystar T100, YS Polystar T115, YS Polystar T130, YS Polystar T145, Mighty Ace G125, Mighty Ace 150 (all manufactured by Yasuhara Chemical Co., Ltd.), TEGO Variplus SK, TEGO EP-1201 TF, TEGO TC, TEGO CA, TEGO AP, TEGO EP-UC, TEGO DS 50, TEGO UC W 40, TEGO 3350 UV (manufactured by Evonik Japan Co., Ltd.). These may be used alone or in combination of two or more.

[0077] In some embodiments, a resin having an acidic group may be used as the resin. By using a resin having an acidic group as the resin, 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 also quickly loosening the silicone composite particles that act as a sealant when rewriting after writing, reducing smearing at the start of writing (hereinafter referred to as "initial stroke smearing").

[0078] 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 acidic components contained in 1 g of sample. The acid value 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.

[0079] Furthermore, if the resin contains OH groups, the interaction with the acidic groups improves the adsorption to the silicone composite particles, improving lubricity and the writing feel. The amount of OH groups is expressed as the OH value, which is calculated 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.

[0080] Specific examples of resins having an acidic group include rosins 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 examples of maleic acid rosins include Marquid No. 31 (acid value 188 mg KOH / g), Marquid No. 32 (acid value 130 mg KOH / g), and Marquid No. 33 (acid value 140 mg KOH / g). Examples of suitable rosin esters include PE-33 (acid value 305 mg KOH / g), PE-3002 (acid value 100 mg KOH / g) (both manufactured by Arakawa Chemical Industries, Ltd.), and Harimac T-80 (acid value 185 mg KOH / g) (both manufactured by Harima Chemicals Co., Ltd.). Examples of suitable rosin esters include Hariestar MSR-4 (acid value 135 mg KOH / g) (both manufactured by Harima Chemicals Co., Ltd.). Examples of suitable rosin esters include KE-604 (acid value 238 mg KOH / g), KR-12 Examples of special modified rosins include Haritac F-75 (acid value 145 mg KOH / g) and Haritac FG-90 (acid value 150 mg KOH / g) (both manufactured by Harima Chemical Co., Ltd.), and examples of 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.).

[0081] In some embodiments, it is preferable to use a cellulose derivative, particularly hydroxypropyl cellulose, as the resin. 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 is also thought to be able to prevent the ink from spreading even when the pen tip is not retracted and is struck against a display, etc., as the hydroxypropyl cellulose and silicone composite particles are immediately oriented on the ink surface.

[0082] 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.).

[0083] The oil-based ink composition according to some embodiments may contain an amine as a pH adjuster. Specific examples include polyoxyethylene alkylamines such as AMIT 102, AMIT 105, AMIT 302, AMIT 308, and AMIT 320, fatty amines such as Farmin CS, Farmin 08D, Farmin 20D, Farmin 80, Farmin 86T, Farmin O, Farmin T, and Farmin (all manufactured by Kao Corporation), and Nymeen L-201, Nymeen L-202, Nymeen L207, Nymeen F-215, Nymeen S-202, Nymeen S-204, Nymeen S-210, Nymeen S-215, Nymeen S-220, Nymeen T2-206, and Nymeen T2-210. Examples of suitable inks include alkyl polyetheramines such as Nymeen T2-230, Nymeen T2-260, Nymeen DT-203, and Nymeen DT-208 (all manufactured by Nippon Oil & Fats Co., Ltd.), as well as diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, triethylamine, dimethylaminoethanol, diethylaminoethanol, methyldiethanolamine, butyldiethanolamine, dibutylethanolamine, diethylisopropanolamine, butylisopropylamine, butylbenzylamine, and butoxypropylamine (all manufactured by Kanto Chemical Co., Ltd.). Maintaining the pH of the ink within an appropriate range can increase the adsorption of acidic substances to the metal ballpoint pen tip, thereby preventing dotted lines in handwriting and improving the writing feel. The pH of the ink composition is preferably in the range of 2.5 to 7.5, more preferably 3.5 to 6.0.

[0084] The oil-based ink composition according to some embodiments may contain a rust inhibitor, such as benzotriazole.

[0085] The viscosity of the oil-based ink composition 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 1.00 / s be 30 mPa·s or more and 3000 mPa·s or less. If it is less than 30 mPa·s, there is a risk of the ink bleeding from the pen tip. If it exceeds 3000 mPa·s, there is a risk of the ink following property being poor, resulting in poor handwriting smearing when writing, i.e., initial smearing. Furthermore, the viscosity of the oil-based ink composition for ballpoint pens is preferably 30 mPa·s or more and 3000 mPa·s or less at 25°C and a shear rate of 100 / s, which is the simulated time of writing. If it is less than 30 mPa·s, the lubricating film strength of the oil-based ink composition may be low, which may reduce the writing feel and the wear resistance of the ball seat. If the viscosity exceeds 3000 mPa·s, there is a risk that the handwriting will become smudged when rewriting, i.e., the initial smudged handwriting will become worse. The viscosity of the oil-based ink composition is preferably 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.

[0086] In some embodiments, an ink backflow preventer is disposed at the ink interface within the ink reservoir tube, thereby preventing unintended ink movement away from the pen tip and preventing ink leakage from the rear opening of the ink reservoir tube due to such movement. When the ink backflow preventer is a liquid composition, a non-volatile and / or low-volatile liquid can be used. Specific examples include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or cooligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, and fatty acid-modified silicone oil. These non-volatile and / or low-volatile liquids may be used alone or in combination. The non-volatile and / or hardly-volatile liquid is preferably thickened to a suitable viscosity by adding a gelling agent. Examples of such gelling agents include clay-based thickeners such as hydrophobically treated silica, methylated silica, aluminum silicate, swellable mica, and hydrophobically treated bentonite or montmorillonite; fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate; tribenzylidene sorbitol; fatty acid amides; amide-modified polyethylene wax; hydrogenated castor oil; dextrin-based compounds such as fatty acid dextrin; and cellulose-based compounds. Among these, fatty acid metal soaps, fatty acid dextrins, and amide-modified polyethylene wax are preferred due to their excellent solvent resistance. Additionally, fine particles of alcohol-based solvents, glycol-based solvents, surfactants, resins, metal oxides, etc., can be added to adjust gel strength and viscosity, prevent coloration of the backflow prevention body, and provide backflow prevention function. In addition, solids such as synthetic resin pillars called floats may be placed in the ink backflow prevention composition to narrow the apparent space in which the backflow prevention composition is placed, making it less likely to move due to external forces and improving impact resistance.

[0087] According to some embodiments, the ink ejection port, which is the tip opening of a ballpoint pen tip, is covered with a packing to protect the tip of the ballpoint pen tip and prevent ink leakage from the ink ejection port. Thermoplastic resins are generally used as the packing. Examples of thermoplastic resin materials include polyethylene, polypropylene, polyamide, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, polyolefin, polyester, polyurethane, polyvinyl chloride, polyester, silicone, styrene copolymer, polybutylene terephthalate, polycarbonate, polyethylene terephthalate, polyisobutylene, acrylic, polyacetal, vinyl chloride, polyurethane, polyvinyl ether, polyvinyl alcohol, polyvinyl acetate and copolymers, polyvinyl butyral, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, cellulose derivatives, polyolefin-based resins, synthetic rubber-based resins, styrene-isoprene-styrene block copolymers, and styrene-butadiene-styrene block copolymers. These resins may be used alone or in combination. The use of polyethylene, polypropylene, polyamide, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate, polyester, polyurethane, styrene-isoprene-styrene block copolymer, and styrene-butadiene-styrene block copolymer as such thermoplastic resins is particularly preferred because they can impart appropriate softness even in a cooled state, are less likely to come off or break when the pen tip is impacted, have low viscosity in a molten state, and have high wettability with the tip of the ballpoint pen tip they cover, thereby increasing adhesive strength.Furthermore, their low melting temperature makes them easy to work with and safe to use. Specific commercial products include polyamide resins such as HM360 (manufactured by Cemedine Co., Ltd.), EC-3779, EC-7375 (all manufactured by Sumitomo 3M Limited), and VESTAMELT 722 (manufactured by Polypla-Evonik Co., Ltd.), and ethylene vinyl acetate copolymers such as HM200, HM207, HM208S, HM214, HM223, HM224, HM232, HM244, HM2611 (all manufactured by Cemedine Co., Ltd.), and HIBORN 9800, HIBORN 9822, HIBORN 9876, HIBORN 9877, and HIBORN 9888 (all manufactured by Resonac Corporation).These may be used alone or in combination.

[0088] A specific method for adhering a thermoplastic resin to the ink discharge port, which is the opening at the tip of a ballpoint pen tip, and solidifying it to act as a packing to close the ink discharge port is, for example, as follows: An appropriate amount of thermoplastic resin is placed in a heat-resistant container placed on a heating device such as a hot plate with a temperature regulator, and melted at a specified temperature. The ballpoint pen tip is turned downward, and the molten thermoplastic resin is adhered to the ink discharge port, which is the opening at the tip of the ballpoint pen tip. After about one second, it is pulled up and left at room temperature for five seconds or more to solidify the thermoplastic resin, which then acts as a packing to close the ink discharge port.

[0089] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples.

[0090] The viscosity in the examples was measured using an MCR302 (manufactured by Anton Paar) with a rotor CP50-1 at 25°C at a shear rate of 1.00 / s and at a shear rate of 100 / s (unit: mPa s).

[0091] The pH values ​​in the examples were measured at 25°C using a Halo 2 (manufactured by Hanna Instruments Japan).

[0092] As shown in Tables 1 to 15, ballpoint pens containing the oil-based ink compositions of Examples 1 to 24 and Comparative Examples 1 to 7 were prepared. The materials used are as follows. Tables 1 to 15 also show the content (wt%) of each material in the oil-based ink composition.

[0093] <Ballpoint pen materials> Coil spring (1): SUS304 (unplated bare wire) Coil spring (2): Ni-plated SUS304 (plated wire)

[0094] <Materials of Ink Composition> Phosphate ester (1): Phosphanol GF-199 (a mixture of phosphoric acid monoester, diester, and triester of lauryl ether, HLB 5.5, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 12. Phosphate ester (2): Phosphanol LS-500 (a mixture of phosphoric acid monoester, diester, and triester of polyoxyethylene (4) tridecyl ether, HLB 9.0, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 13. Phosphate ester (3): Phosphanol LB-400 (a mixture of phosphoric acid monoester, diester, and triester of polyoxyethylene (4) oleyl ether, HLB 8.6, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 18. Phosphate ester (4): Phosphanol RP-710 (phosphate ester, mixture of phosphate monoester, diester, and triester of polyoxyethylene (6) phenyl ether, HLB 11.9, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 13. Phosphate ester (5): NIKKOL DDP-2 (Zipalace-2 phosphate, HLB 6.5, manufactured by Nikko Chemicals Co., Ltd.), number of carbon atoms in hydrocarbon group: 12-15. Phosphate ester (6): Plysurf A219B (phosphate ester, phosphate ester of polyoxyethylene lauryl ether, HLB 16.2, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), number of carbon atoms in hydrocarbon group: 12. Phosphate ester (7): Phosphanol RL-210 (phosphate ester, mixture of phosphate ester, diester, and triester of polyoxyethylene (2) stearyl ether, HLB 5.4, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 18. Phosphate ester (8): Phosphate ester of polyoxyethylene styrenated phenyl ether tristyrenated product Number of carbon atoms in hydrocarbon group: 30

[0095] Water: Ion-exchanged water

[0096] Surfactant (1): Sorgen 30 (sorbitan sesquioleate, HLB 3.7, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) Surfactant (2): Pegnol ST-7 (polyoxyethylene (7) alkyl (C12-14) ether, HLB 12.8, manufactured by Toho Chemical Industry Co., Ltd.) Surfactant (3): NIKKOL HCO-10 (polyoxyethylene hydrogenated castor oil, HLB 6.5, manufactured by Nikko Chemicals Co., Ltd.) Surfactant (4): NIKKOL Decaglyn 1-ISV (decaglyceryl monoisostearate, HLB 12.0, manufactured by Nikko Chemicals Co., Ltd.) Surfactant (5): NIKKOL BO-10V (polyoxyethylene oleyl ether, HLB 14.5, manufactured by Nikko Chemicals Co., Ltd.)

[0097] Organic amine (1): triisopropanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.) Organic amine (2): Nymeen L201 (polyethylene glycol-1 laurylamine, NOF Corporation) Organic amine (3): triethanolamine (manufactured by Tokyo Chemical Industry Co., Ltd.)

[0098] Pigment (1): Printex 35 (carbon black, manufactured by Orion Engineered Carbons Co., Ltd.) Pigment (2): FUJI FAST RED 8800 (C.I. Pigment Red 254, manufactured by Fuji Pigment Co., Ltd.) Pigment (3): CROMOPHTAL Blue A3R (C.I. Pigment Blue 60, manufactured by BASF Japan Ltd.)

[0099] Dye (1): SPILON RED C-GH (a dye formed by salt formation of a xanthene-based basic dye and alkyldiphenyletherdisulfonic acid, manufactured by Hodogaya Chemical Industry Co., Ltd.) Dye (2): SPILON YELLOW C-GNH new (a dye formed by salt formation of an indolinone-based basic dye and alkyldiphenyletherdisulfonic acid, manufactured by Hodogaya Chemical Industry Co., Ltd.) Dye (3): VALIFAST RED 1364 (a dye formed by salt formation of C.I. Basic Red 1:1, alkylbenzenesulfonic acid, and alkyldiphenyletherdisulfonic acid, manufactured by Orient Chemical Industry Co., Ltd.) Dye (4): VALIFAST YELLOW 1108 (colorant, disazo dye, manufactured by Orient Chemical Industry Co., Ltd.) Dye (5): OIL BLUE 613 (colorant, mixture of C.I. Solvent Blue 5 and rosin-modified resin, manufactured by Orient Chemical Industries Co., Ltd.) Dye (6): VALIFAST BLUE 1631 (salt-forming dye of C.I. Basic Blue 7 and colorless organic acid, manufactured by Orient Chemical Industries Co., Ltd.) Dye (7): VALIFAST BLUE 1605 (metal complex salt dye of C.I. Solvent Blue 38, manufactured by Orient Chemical Industries Co., Ltd.) Dye (8): VALIFAST BLUE 2680 (phthalocyanine dye of C.I. Basic Blue 70, manufactured by Orient Chemical Industries Co., Ltd.) Dye (9): OIL PINK 314 (C.I. Dye (10): SPILON RED C-BH (a salt-forming dye of C.I. Basic Violet 10 and an acidic substance, manufactured by Hodogaya Chemical Industry Co., Ltd.) Dye (11): VALIFAST VIOLET 1731 (a salt-forming dye of C.I. Acid Violet 17 and a methine dye, manufactured by Orient Chemical Industry Co., Ltd.)

[0100] Organic solvent (1): n-propanol (organic solvent) Organic solvent (2): ethylene glycol monoisopropyl ether (organic solvent) Organic solvent (3): benzyl alcohol (organic solvent) Organic solvent (4): ethylene glycol monophenyl ether (organic solvent)

[0101] 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): Marquid 3002 (maleic acid rosin, acid value 100 mg KOH / g, Tg 175°C, manufactured by Arakawa Chemical Industries, Ltd.) Resin (7): Harimac 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 solution (acid value 510 mg KOH / g, OH value 130 mg KOH / g, Tg 80°C, calculated as solid) Resin (9): 42% acrylic acid-styrene-methacrylic acid ester copolymer in ethylene glycol monophenyl ether solution (acid value 300 mg KOH / g, OH value 80 mg KOH / g, Tg 30°C, calculated as solid) Resin (10): NISSO HPC-H (hydroxypropyl cellulose, manufactured by Nippon Soda Co., Ltd.) Resin (11): NISSO HPC-M (hydroxypropyl cellulose, manufactured by Nippon Soda Co., Ltd.)

[0102] Rubber elastic particles (1): KMP-597 (crosslinked silicone rubber particles, average particle diameter 5 μm, rubber hardness 30 durometer A, manufactured by Shin-Etsu Chemical Co., Ltd.) Rubber elastic particles (2): KMP-605 (crosslinked silicone composite particles, average particle diameter 2 μm, rubber hardness 75 durometer A, true specific gravity 0.99 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Rubber elastic particles (3): KMP-600 (crosslinked silicone composite particles, average particle diameter 5 μm, rubber hardness 30 durometer A, true specific gravity 0.99 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Rubber elastic particles (4): X-52-7030 (crosslinked silicone composite particles, average particle diameter 0.8 μm, rubber hardness 75 durometer A, true specific gravity 1.01 g / cm3, manufactured by Shin-Etsu Chemical Co., Ltd.) Rubber elastic particles (5): Techpolymer ABX-8 (crosslinked polybutyl acrylate particles, average particle diameter Rubber elastic particles (6): MX-500 (crosslinked acrylic particles, average particle size 5 μm, true specific gravity 1.19, manufactured by Soken Chemical & Engineering Co., Ltd.) Rubber elastic particles (7): MX-40H3wT (crosslinked acrylic particles, average particle size 0.8 μm, true specific gravity 1.19, manufactured by Soken Chemical & Engineering Co., Ltd.) Rubber elastic particles (8): SX-500H (crosslinked styrene particles, average particle size 5 μm, true specific gravity 1.05, manufactured by Soken Chemical & Engineering Co., Ltd.) Rubber elastic particles (9): SX-130H (crosslinked styrene particles, average particle size 1.3 μm, true specific gravity 1.05, manufactured by Soken Chemical & Engineering Co., Ltd.) Rubber elastic particles (10): Art Pearl JC-800TR (crosslinked urethane particles, average particle diameter 6 μm, true specific gravity 1.21, manufactured by Negami Chemical Industries, Ltd.) Rubber elastic particles (11): Matsumoto Microsphere S-100 (crosslinked alkyl polyacrylate particles, average particle diameter 5 μm, manufactured by Matsumoto Yushi Pharmaceutical Co., Ltd.)

[0103] Non-rubber elastic particles (for comparison) (1): AKP-20 (alumina particles, average particle diameter 0.5 μm, manufactured by Sumitomo Chemical Co., Ltd.) Non-rubber elastic particles (for comparison) (2): JR-800 (titanium oxide particles, average particle diameter 0.27 μm, true specific gravity 3.9 g / cm ３ , manufactured by Teika Co., Ltd.) Non-rubber elastic particles (for comparison) (3): Seahoster KE-S250 (silica particles, average particle size 2.5 μm, true specific gravity 2.20, manufactured by Nippon Shokubai Co., Ltd.)

[0104] Dispersant (1): DISPERBYK-111 (copolymer containing acid groups, acid value 129 mg KOH / g, manufactured by BYK Japan Co., Ltd.) Dispersant (2): DISPERBYK-102 (copolymer having acid groups, acid value 101 mg KOH / g, manufactured by BYK Japan Co., Ltd.) Dispersant (3): BYK-P105 (polymer of low molecular weight unsaturated carboxylic acid, acid value 365 mg KOH / g, manufactured by BYK Japan Co., Ltd.) Dispersant (4): DISPERBYK-180 (alkylol ammonium salt of copolymer containing acid groups, acid value 94 mg KOH / g, amine value 94 mg KOH / g, manufactured by BYK Japan Co., Ltd.) Dispersant (5): DISPERBYK-108 (hydroxyl group-containing carboxylic acid ester, amine value 71 mg KOH / g, manufactured by BYK Japan Co., Ltd.)

[0105] Rust inhibitor: benzotriazole (manufactured by E-CHEM ENTERPRISE CORPORATION)

[0106] The procedure for preparing the oil-based ink composition was as follows: an organic solvent or ion-exchanged water, a phosphate ester, a surfactant, a colorant, and a resin were stirred at 60°C with a propeller stirrer, and then other additives and rubber-elastic particles or non-rubber-elastic particles were added, either directly or after being uniformly dissolved or dispersed in a solvent with a propeller stirrer, and the mixture was stirred with a propeller for 2 hours to obtain an oil-based ink composition.

[0107] The ink backflow preventer 16 was prepared as follows: 50.0 wt. % Spectrasyn 100 (α-olefin oligomer, base material, manufactured by ExxonMobil Corporation, USA), 45.3 wt. % Lucant HC-100 (ethylene-α-olefin oligomer, base material, manufactured by Mitsui Petrochemical Co., Ltd.), 3.50 wt. % Aerosil R972 (fine particle silica, gelling agent, manufactured by Nippon Aerosil Co., Ltd.), and 1.20 wt. % Leopearl KL (dextrin fatty acid ester, manufactured by Chiba Flour Milling Co., Ltd.) were mixed and stirred with a hot stirrer at 150°C for 2 hours to obtain a backflow preventer composition. The viscosity of this backflow preventer was 11,000 mPa·s at a temperature of 25°C and a shear rate of 1.00 / s, and 5,000 mPa·s at a temperature of 25°C and a shear rate of 100 / s.

[0108] (Preparation of Test Ballpoint Pens) Based on the ballpoint pen tip 10 shown in the figure, ballpoint pen tips used in the tests were prepared with the following dimensions. The parenthesized values ​​for each dimension indicate the ratio of each dimension to the diameter A of the ball 13 of the ballpoint pen tip 10. Each dimension is shown in Figures 4, 5, and 6 (the 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.

[0109] Diameter A of ball 13 = 0.50 mm Inner diameter B of tip opening 19 = 0.48 mm Back-and-forth movement distance C of ball 13 = 0.03 mm Ball protrusion length D = 0.15 mm Inner diameter E of ball holding portion 21 = 0.53 mm 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 Diameter H of ball receiving seat = 0.44 mm Diameter I of central hole = 0.28 mm Seat angle α of ball holding portion 21: 100 degrees Crimping angle β = 80 degrees Chamfer angle γ = 56 degrees Taper angle δ = 30 degrees

[0110] The pressing load on the ball 13 with the coil spring 18 disposed in the ball holder 14 was set to 0.15N.

[0111] The ball 13 used was a carbide ball PB-11 manufactured by Tsubaki Nakashima Co., Ltd., with a surface roughness, arithmetic mean height (Sa: ISO 25178), of 4.0 nm.

[0112] The arithmetic mean height, which is the surface roughness of the ball 13 in the examples, was calculated from the average value of measurements taken at three arbitrary 20 μm × 20 μm areas using a scanning probe microscope (AFM5100N; manufactured by Hitachi High-Tech Science Corporation).

[0113] The oil-based ink compositions of Examples 1 to 24 and Comparative Examples 1 to 7 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 above-mentioned ballpoint pen tips. The pen tips of the obtained ballpoint pens were sealed with packing, and centrifugal force was applied to remove excess air bubbles so that the ink composition was distributed all the way to the pen tip. HM200 was used as the thermoplastic resin for the packing in Examples 1 to 14 and Comparative Examples 1 to 7, and Hibon 9888 was used in Examples 15 to 24.

[0114] The ink compositions of the examples and comparative examples were subjected to the following tests and evaluations. The evaluation results and measurement results are shown in Tables 1 to 15.

[0115] (Writing Resistance Values ​​with Low Load Writing) Three test ballpoint pens having the above-mentioned ballpoint pen tips were prepared for each Example and Comparative Example, and after removing the packing, the writing resistance values ​​were measured in an environment of a temperature of 25°C and a relative humidity of 65%. The writing resistance values ​​were measured at 25°C using a static friction measuring instrument TL201Sa (manufactured by Trinity Lab Co., Ltd.). (Unit: N). The evaluation criteria are as follows: A: The average writing resistance value is 0.15 or less B: The average writing resistance value is greater than 0.15 and less than 0.20 C: The average writing resistance value is greater than 0.20 and less than 0.30 D: The average writing resistance value is greater than 0.30

[0116] (Low Load Writing Test) Three test ballpoint pens with the above-mentioned ballpoint pen tip were prepared for each Example and Comparative Example, and after removing the packing, a spiral writing test was carried out in an environment of 25°C temperature and 65% relative humidity, with a writing load of 0.50N, an inclination angle of the ballpoint pen axis to the writing surface of 70°, and a writing speed of 7 cm / sec (low load writing). The evaluation criteria are as follows: A: Writing can be completed without smearing with low load writing B: Writing can be completed with low load writing, but there is smearing C: Writing cannot be completed with low load writing, there is smearing

[0117] (Low Load Writing Test (Aging)) Three test ballpoint pens with the above-mentioned ballpoint pen tip were prepared for each Example and Comparative Example, and after removing the packing, they were left to stand for three months in an environment of 25°C temperature and 65% relative humidity. After that, the aged products were subjected to a spiral writing test at a writing load of 0.50 N, an inclination angle of the ballpoint pen axis to the writing surface of 70°, and a writing speed of 7 cm / sec (low load writing). The evaluation criteria were as follows: A: Writing can be completed without smearing with low load B: Writing can be completed with low load, but there is smearing C: Writing cannot be completed with low load, there is smearing

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[0119]

[0120]

[0121]

[0122]

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[0124]

[0125]

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[0130]

[0131]

[0132]

[0133] In the ballpoint pens of Examples 1 to 24, the coil spring is formed from unplated SUS304 (bare stainless steel wire), and the oil-based ink composition contains phosphate ester and rubber elastic particles. From this, it is believed that a stable phosphate ester lubricating film is formed on the surface of the ball and coil spring, and the rubber elastic particles penetrate into this lubricating film, maintaining a highly cushioning lubricating film, which makes it possible to suppress friction between the coil spring and ball even when writing with a low load, and to suppress friction between the coil spring and ball for a long period of time.

[0134] Furthermore, in the ballpoint pens of Examples 1 to 8 and 15 to 19, the oil-based ink composition contains rubber elastic particles made of silicone, which is thought to further improve the effect of the lubricating film described above and further reduce the writing resistance value when writing with a low load.

[0135] Furthermore, since the ballpoint pens of Examples 1 to 10 and Examples 15 to 21 contain two or more types of phosphate esters with different numbers of carbon atoms in the hydrocarbon chain, the lubricating film formed has a denser structure, which is thought to be why a stable lubricating film can be formed and the writing resistance value during low-load writing is reduced.

[0136] In contrast, the ballpoint pens of Comparative Examples 1, 3, and 4 did not contain rubber elastic particles in the oil-based ink composition, which is thought to have caused wear between the coil spring and the ball when writing with a low load, resulting in a poor writing feel and an increase in the writing resistance when writing with a low load.

[0137] Furthermore, in the ballpoint pens of Comparative Examples 2 and 4, the coil springs were plated, and therefore the film formed between the phosphate ester and the rubber elastic particles was not stable over time, which is thought to have resulted in smearing when writing with low load, making it impossible to finish writing, and also causing an increase in writing resistance.

[0138] Furthermore, since the oil-based ink composition of the ballpoint pen of Comparative Example 3 does not contain a phosphate ester, a lubricating film is not formed on the surface of the ball or coil spring, causing smearing and increasing the writing resistance value when writing with a low load.

[0139] Furthermore, since the ballpoint pens of Comparative Examples 5 to 7 contain particles with low rubber elasticity (non-rubber elastic particles), the cushioning properties of the lubricating film formed on the surface of the ball or coil spring are low, causing severe wear between the coil spring and the ball, resulting in smearing, making it impossible to finish writing, and also resulting in an increased writing resistance value when writing with a low load.

[0140] The contents described in each of the above embodiments can be understood, for example, as follows.

[0141] [1] A ballpoint pen refill (200) according to at least one embodiment of the present invention comprises: an ink reservoir (12); an oil-based ink composition filled in the ink reservoir; and a ballpoint pen tip (10) attached to the front end of the ink reservoir so that the oil-based ink composition is supplied, wherein the ballpoint pen tip comprises: a ball (13); a ball holder (14) for holding the ball so that the ball is rotatable at the front end of the ballpoint pen tip; and a coil spring (18) for urging the ball forward, wherein the coil spring comprises bare stainless steel wire; and the oil-based ink composition contains at least one type of phosphate ester and rubber elastic particles.

[0142] In the configuration [1], the oil-based ink composition contains a phosphate ester that is easily chemically adsorbed to metals and elastic rubber particles, so that a highly cushioning lubricating film containing the phosphate ester and the elastic rubber particles is formed on the surface of the ball and the coil spring. As a result, when writing with a low load using the ballpoint pen, friction between the ball and the coil spring is reduced, so that the user of the ballpoint pen feels less resistance due to friction when writing, resulting in a good writing experience.

[0143] In addition, in the above-mentioned configuration [1], since the coil spring is formed from a bare stainless steel wire (i.e., a stainless steel wire that is not plated), an oxide film with relatively high corrosion resistance and low reactivity is formed on the surface of the coil spring (bare stainless steel wire). This prevents the surface of the coil spring from reacting with the phosphate ester in the oil-based ink composition and becoming detached as a precipitate, making it easier for a lubricating film containing the phosphate ester and rubber elastic particles to be stably formed on the surface of the coil spring. Furthermore, as mentioned above, since the oxide film on the surface of the bare stainless steel wire is relatively corrosion-resistant, it is less susceptible to changes in the moisture content and pH of the oil-based ink composition over time. Therefore, the above-mentioned elastic lubricating film can be stably formed on the surface of the coil spring for a long period of time.

[0144] As described above, according to the configuration [1], the lubricating film can maintain low friction between the ball and the coil spring even after prolonged use of the ballpoint pen, resulting in a ballpoint pen that writes well even when writing with a low load, even after prolonged use.

[0145] [2] In some embodiments, in the configuration of [1] above, the at least one phosphate ester includes a first phosphate ester having a hydrocarbon group, and a second phosphate ester having a hydrocarbon group with a carbon number greater than that of the hydrocarbon group of the first phosphate ester.

[0146] According to the configuration [2] above, the 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. Therefore, the second phosphate ester penetrates between the first phosphate esters, forming a dense phosphate ester lubricating film on the metal surface. This makes the lubricating film more stable, which helps reduce friction between the ball and the coil spring. This tends to result in a good writing feel even when writing with a low load.

[0147] [3] In some embodiments, in the configuration of [2] above, the first phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 4 to 17 carbon atoms, and the second phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 18 to 30 carbon atoms.

[0148] According to the above-mentioned configuration [3], the hydrocarbon group of the first phosphate ester has a carbon number of 4 to 17, and the hydrocarbon group of the second phosphate ester has a carbon number of 18 to 30, so the carbon chain lengths of the hydrocarbon groups of the two phosphate esters differ to some extent. Therefore, in the lubricating film formed on the surfaces of the ball and the coil spring, the second phosphate ester easily penetrates between the first phosphate esters, making it easier to form a dense lubricating film on the metal surface. This makes the lubricating film more stable, and the lubricating film more likely to reduce friction between the ball and the coil spring. This tends to result in a good writing feel even when writing with a low load.

[0149] [4] In some embodiments, in any one of the above [1] to [3], the rubber elastic particles are made of silicone.

[0150] According to the above-mentioned configuration [4], since the oil-based ink composition contains rubber elastic particles made of silicone, it is easy to increase the elasticity of the lubricating film formed on the surface of the ball and the coil spring. Therefore, when writing with a ballpoint pen at a low load, the friction between the ball and the coil spring tends to be small, and therefore the user of the ballpoint pen feels less resistance due to friction when writing, which tends to improve the writing feel.

[0151] [5] In some embodiments, in any one of the configurations [1] to [3] above, the rubber elastic particles include acrylic particles, styrene particles, or urethane particles.

[0152] According to the above-mentioned feature [5], by using rubber elastic particles including acrylic particles, styrene particles, or urethane particles, it is possible to form a highly cushioning lubricating film containing phosphate ester and rubber elastic particles on the surfaces of the ball and the coil spring. As a result, when writing with a ballpoint pen at a low load, friction between the ball and the coil spring is reduced, so that the user of the ballpoint pen feels less resistance due to friction when writing, resulting in a good writing experience.

[0153] [6] In some embodiments, in the configuration of any one of [1] to [5] above, the spring load of the coil spring when the ballpoint pen is not writing is 0.10 N or more and 0.60 N or less.

[0154] In the configuration [6] above, the spring load of the coil spring is 0.10 N or more, so the ball can be appropriately pressed toward the ball holder. This makes it possible to suppress seepage of the ink composition during writing and leakage of the ink composition when the ballpoint pen is left stationary. Furthermore, in the configuration [6] above, the spring load of the coil spring is 0.60 N or less, so the pressure from the coil spring on the ball is not too great. This makes it difficult for the lubricating film formed on the surfaces of the ball and the coil spring to break, and tends to reduce friction between the ball and the coil spring when writing with a low load using the ballpoint pen. Therefore, the configuration [6] above makes it possible to maintain a good writing feel when writing with a low load for a long period of time while suppressing seepage and leakage of the ink composition.

[0155] [7] In some embodiments, in the configuration of any one of [1] to [6] above, the wire diameter of the coil spring is 0.05 mm or more and 0.20 mm or less.

[0156] In the configuration [7] above, the wire diameter of the coil spring is 0.05 mm or more, which prevents localized pressure buildup between the ball and the coil spring, making the lubricating film less likely to break down. Furthermore, in the configuration [7] above, the wire diameter of the coil spring is 0.20 mm or less, which prevents the spring constant from being too large and the spring load from becoming too large, making the lubricating film less likely to break down. Therefore, with the configuration [7] above, the lubricating film is stably formed on the surfaces of the ball and the coil spring for a long period of time, making it easier to maintain a good writing feel even when writing with a low load for a long period of time.

[0157] [8] In some embodiments, in the configuration of any one of [1] to [7] above, the effective number of turns of the coil spring is 10 or more and 40 or less.

[0158] In the configuration [8] above, the effective number of turns of the coil spring is between 10 and 40, so the pressure between the coil spring and the ball tends to be within an appropriate range. Therefore, in the configuration [7] above, the lubricating film is less likely to break down and is stably formed on the surfaces of the ball and the coil spring for a long period of time, making it easier to maintain a good writing feel when writing with a low load for a long period of time.

[0159] [9] A ballpoint pen (100) according to at least one embodiment of the present invention comprises: a ballpoint pen refill (200) according to any one of the above [1] to [8]; and a barrel (1) in which the ballpoint pen refill is housed.

[0160] In the above-mentioned configuration [9], the oil-based ink composition contains a phosphate ester that easily chemically adsorbs to metals and elastic rubber particles, so that a highly cushioning lubricating film containing the phosphate ester and the elastic rubber particles is formed on the surface of the ball and the coil spring. As a result, when writing with a low load using the ballpoint pen, friction between the ball and the coil spring is reduced, so that the user of the ballpoint pen feels less resistance due to friction when writing, resulting in a good writing experience.

[0161] In addition, in the above-mentioned configuration [9], since the coil spring is formed from a bare stainless steel wire (i.e., a stainless steel wire that is not plated), an oxide film with relatively high corrosion resistance and low reactivity is formed on the surface of the coil spring (bare stainless steel wire). This prevents the surface of the coil spring from being separated as a precipitate due to a reaction with the phosphate ester in the oil-based ink composition, and thus facilitates the stable formation of a lubricating film containing the phosphate ester and rubber elastic particles on the surface of the coil spring. Furthermore, as described above, since the oxide film on the surface of the bare stainless steel wire is relatively corrosion-resistant, it is less susceptible to changes in the moisture content and pH of the oil-based ink composition over time. Therefore, the above-mentioned elastic lubricating film can be stably formed on the surface of the coil spring for a long period of time.

[0162] As a result, with the configuration of [9] above, the lubricating film can maintain low friction between the ball and the coil spring even after prolonged use of the ballpoint pen, resulting in a ballpoint pen that writes well even when writing with a low load, even after prolonged use.

[0163] The above describes an embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and also includes forms in which the above-described embodiment is modified, or forms in which these forms are appropriately combined.

[0164] In this specification, expressions expressing relative or absolute arrangements, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," not only strictly express such arrangements, but also express 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 expressing that things are in an equal state, such as "identical," "equal," and "homogeneous," not only express a state in which there is a strict equivalence, but also express 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 expressing shapes such as a rectangular shape or a cylindrical shape not only express shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also express shapes including concave and convex portions, chamfered portions, etc., to the extent that the same effect is obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0165] REFERENCE SIGNS LIST 1 barrel 2 front barrel 3 rear barrel 4 grip portion 5 crown 6 clip 7 rotor 8 knock 9 resilient member 10 ballpoint pen tip 11 tip holder 12 ink reservoir tube 13 ball 14 ball holder 15 ink composition 16 ink backflow prevention body 17 float 18 coil spring 18a tip surface 18b side surface 19 tip opening 20 inner protrusion 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 protrusion 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 Diameter of center hole α Seat angle of ball holding portion 21 β Crimping angle γ Chamfering angle δ Taper angle

Claims

1. A ballpoint pen refill comprising: an ink reservoir; an oil-based ink composition filled into said ink reservoir; and a ballpoint pen tip attached to the front end of said ink reservoir so that said oil-based ink composition is supplied, said ballpoint pen tip comprising: a ball; a ball holder for holding said ball so that said ball is rotatable at the front end of said ballpoint pen tip; and a coil spring for urging said ball forward, said coil spring comprising bare stainless steel wire, and said oil-based ink composition comprising: at least one type of phosphate ester; and rubber elastic particles.

2. The ballpoint pen refill according to claim 1, wherein the at least one phosphate ester comprises: a first phosphate ester having a hydrocarbon group; and a second phosphate ester having a hydrocarbon group with a larger number of carbon atoms than the hydrocarbon group of the first phosphate ester.

3. The ballpoint pen refill according to claim 2, wherein the first phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 4 to 17 carbon atoms, and the second phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 18 to 30 carbon atoms.

4. A ballpoint pen refill according to any one of claims 1 to 3, wherein the rubber elastic particles are made of silicone.

5. The ballpoint pen refill according to any one of claims 1 to 3, wherein the rubber elastic particles include acrylic particles, styrene particles, or urethane particles.

6. A ballpoint pen refill according to any one of claims 1 to 3, wherein the spring load of the coil spring when the ballpoint pen is not writing is 0.10 N or more and 0.60 N or less.

7. A ballpoint pen refill according to any one of claims 1 to 3, wherein the wire diameter of the coil spring is 0.05 mm or more and 0.2 mm or less.

8. The ballpoint pen refill according to any one of claims 1 to 3, wherein the effective number of turns of the coil spring is 10 or more and 40 or less.

9. A ballpoint pen comprising: a ballpoint pen refill according to any one of claims 1 to 3; and a barrel in which the ballpoint pen refill is housed.

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