WO2025182424A1 - Ballpoint pen refill and ballpoint pen - Google Patents

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

This disclosure relates to ballpoint pen refills and ballpoint pens.

Ballpoint pen ink has been proposed to improve the writing experience with ballpoint pens.

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

Furthermore, Patent Document 2 discloses an ink composition for oil-based ballpoint pens that has a low resistance and a good writing feel when writing at low load and low speed. The ink composition 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.

JP 2018-035334 A Japanese Patent Application Laid-Open No. 2016-194032

When writing with a ballpoint pen at an average load, the friction that occurs between the ball attached to the ballpoint pen tip and the ball holder has a significant impact on the writing feel. On the other hand, when writing with a low load, the friction that occurs between the ball attached to the ballpoint pen tip and the coil spring that presses against the ball has a significant impact on the writing feel. Through research by the inventors, we have found that ballpoint pens using conventional ink compositions may not be able to maintain a good writing feel over an extended period of time when writing with a low load.

In light of the above circumstances, at least one embodiment of the present invention aims to provide a ballpoint pen refill and ballpoint pen that provide a good writing feel when writing with a low load, even when used for a long period of time.

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;
a ballpoint pen tip attached to the front end of the ink reservoir tube so as to supply the oil-based ink composition;
Equipped with
The ballpoint pen tip is
The ball and
a ball holder for holding the ball so that the ball is located at the front end of the ballpoint pen tip and can rotate;
a coil spring for biasing the ball forward;
Including,
the coil spring includes bare stainless steel wire;
The oil-based ink composition comprises
at least one phosphate ester;
Rubber elastic particles;
Contains:

In addition, the ballpoint pen according to at least one embodiment of the present invention comprises:
The ballpoint pen refill described above;
a barrel in which the ballpoint pen refill is housed;
Equipped with.

At least one embodiment of the present invention provides 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.

1 is a vertical cross-sectional view showing a ballpoint pen according to an embodiment. FIG. 2 is a vertical cross-sectional view showing a refill used in the ballpoint pen shown in FIG. 1 . FIG. 3 is an enlarged vertical cross-sectional view showing a portion I in FIG. 2 . FIG. 4 is an enlarged vertical cross-sectional view of the test ballpoint pen tip showing part II in FIG. 3. FIG. 2 is a vertical cross-sectional view showing dimension measurement points. FIG. 6 is a cross-sectional view taken along line III-III' in FIG. 5 .

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

(Configuration of ballpoint pen refill and ballpoint pen)
First, a ballpoint pen to which a 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, and is configured so that the oil-based ink composition is supplied from the ink reservoir tube to the ballpoint pen tip.

FIG. 1 is a vertical cross-sectional view showing a ballpoint pen according to one embodiment. FIG. 2 is a vertical cross-sectional view showing the 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.

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. Crown 5 is attached and fixed to the rear of rear barrel 3 by being inserted into the inner hole of rear barrel 3 and threadedly engaging with the recessed and projecting portions, and the portion exposed from the rear end of rear barrel 3 is disposed so as to cover the base surface of clip 6 attached to the outer surface of rear barrel 3. Crown 5 is also cylindrical, and a groove formed inside it serves as a cam groove for the debit cam mechanism, regulating the sliding position of rotor 7 housed therein, and determining the forward and backward movement position of ballpoint pen refill 200 connected thereto as rotor 7 rotates when knock 8 is pressed in.
A ballpoint pen refill 200 is housed in the barrel 1 so as to be movable back and forth. A resilient member 9 made of a coil spring or the like is disposed in front of the ballpoint pen refill 200, and urges 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 that protrudes and retracts from the tip opening of the barrel 1 when the knock 8 is pressed.

As shown in FIG. 2, the ballpoint pen refill 200 comprises 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. Note that a tail plug or the like that prevents leakage of the ink composition 15 can be disposed at the rear end of the ink reservoir 12 of the ballpoint pen refill 200 to create a ballpoint pen body that does not use an outer casing 300. 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 prevents evaporation of the ink solvent, and is even more preferred, as it provides particularly high gas barrier properties.

Figure 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 vertical cross-sectional view of part I in Figure 2. The ballpoint pen tip 10 shown in Figure 3 rotatably holds the ball 13, which serves as a writing member, within the 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 arranged behind the ball 13. The coil spring 18 is inserted from the rear of the ball holder 14 and pressed in so as to compress its entire length, 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 the rear end of the coil spring 18 against the tip holder 11. Other methods of preventing the ball holder 14 from falling out include forming a gouged cutting on the rear inner wall surface of the ball holder 14 using broaching, reducing the diameter of the rear end opening of the ball holder 14, or forming a protrusion on the inner wall surface by recessing the side wall of the ball holder 14 using punching or the like. The method and shape of preventing the coil spring 18 from falling out can be selected as appropriate.

When pressed against the writing surface, such as paper, the ball 13 moves backward, causing ink to flow out through the gap formed between it and the ball holder 14 (described below), or to be transported outward as the ball 13 rotates and transfer. The size of the ball 13 can be any diameter between 0.18 mm and 2.00 mm (used in general 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, making it impossible to maintain a thick lubricating film containing phosphate ester and rubber elastic particles at the contact area where localized high pressure occurs. Therefore, considering that the lubricating properties of the lubricating film can be more easily achieved, the arithmetic mean height (Sa) of the surface of the ball 13 is preferably between 1.00 nm and 20.0 nm. Possible materials for the ball 13 include cemented carbide primarily composed of tungsten carbide, metals such as stainless steel, aluminum, and iron, ceramics such as silicon carbide, silicon nitride, titanium nitride, chromium carbide, alumina, and zirconia, resin materials such as polyethylene, polypropylene, polyacetal, and polyamide, and glass, but cemented carbide and ceramics are preferred in terms of corrosion resistance to ink.

Next, details of the ballpoint pen tip 10 will be explained in Figure 4, which is an enlarged view of part II in Figure 3. The ball holder 14 has an ink passage hole, which is a through-hole. This ink passage hole has a tip opening 19, which is crimped from the tip side to a smaller diameter, a ball holding section 21 defined by an inner 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 inner 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 the paper. The inner edge of the tip opening 19 is pressed against the ball 13 during the crimping process, and is given a mirror finish while transferring the curved surface of the ball 13, in order to improve sealing when the ball 13 is pressed against the ball 13 by the coil spring 18 and comes into circumferential contact. In addition, multiple ink passage grooves 24 are formed radially and at equal intervals by cutting into the inward protrusion 20. This ink channel 24 passes through 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 protrusion 20. This ball receiving seat 25 stabilizes the position of the ball 13 when it comes into contact with the paper surface or the like during writing and retracts, ensuring smooth rotation with minimal unnecessary vibration. The shape of the ink channel 24 allows for approximately planar contact between the ball 13 and the ball receiving seat 25. The ink channel 24 also has an opening outside the ball receiving seat 25 formed in the inward protrusion 20, ensuring ink supply to the ball holding portion 21.

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 dimensions of the ballpoint pen tip 10 are as follows: the inner diameter B of the tip opening 19 is 80% or more and 98% or less of the diameter of the ball 13; the forward/backward movement distance C of the ball 13 is 2% or more and 10% or less of the diameter A of the ball 13; the ball protrusion length D is 20% or more and 35% or less of the diameter A of the ball 13; the inner diameter E of the ball holding portion 21 is 90% or more and 130% or less of the diameter A of the ball 13; the number of ink channels 24 is 2 or more and 6 or less; 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. Additionally, it is preferable to treat the surface of the ballpoint pen tip 10 with either a hydrophilic or hydrophobic treatment depending on the ink used, as this will prevent ink from adhering to the ballpoint pen tip 10. Dimensions of each part are shown in Figures 4, 5, and 6 (the ball 13 and coil spring 18 are not shown).

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, or 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 plating treatment on the surface, such as stainless steel, hard steel wire, or piano wire, which has been formed into a spring and then the plating removed by chemical treatment.

In Figures 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 way.

(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.

In some embodiments, the oil-based ink composition contains at least one phosphate ester and rubber elastic particles.

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

The phosphate ester has a phosphate group and a carbon chain-containing portion 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 rubber elastic particles through chemical adsorption. Therefore, a highly cushioning lubricating film is formed on the surface of the metal (coil spring 18) by the phosphate ester, which has a phosphate group and a relatively long carbon chain-containing portion, and the rubber elastic particles.

When writing with the ballpoint pen 100, the coil spring 18 is compressed, so 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 become 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.

As a result, when writing with the ballpoint pen 100 at a low load, friction between the ball 13 and the coil spring 18 (including the tip end surface and side surfaces) is reduced, meaning that the user of the ballpoint pen 100 feels less resistance due to friction when writing, resulting in a smooth writing experience.

Furthermore, in the above-mentioned ballpoint pen refill 200 filled with the above-mentioned 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 detached as a precipitate due to reaction with the phosphate ester in the oil-based ink composition, making it easier for a lubricating film containing phosphate ester and rubber elastic particles to be stably formed on the surface of the coil spring 18. Furthermore, as mentioned above, the oxide film on the surface of the bare stainless steel wire is relatively corrosion-resistant, and is therefore less susceptible to changes in the moisture content and pH of the oil-based ink composition over time. As a result, the above-mentioned elastic lubricating film can be stably formed on the surface of the coil spring 18 for an extended period of time.

As described above, according to the above-described embodiment, the lubricating film described above allows the friction between the ball 13 and the coil spring 18 to remain low even after the ballpoint pen 100 has been used for an extended period of time. Therefore, it is possible to obtain a ballpoint pen 100 that provides a good writing feel when writing with a low load, even after extended use.

In some embodiments, the spring load of the coil spring 18 when the ballpoint pen 100 is not writing is greater than or equal to 0.10 N and less than or equal to 0.60 N.

In the above-described embodiment, the spring load of the coil spring is 0.10 N or more, so the ball 13 can be appropriately pressed toward the ball holder 14. This prevents the oil-based ink composition from seeping out during writing and from leaking 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 the pressure from the coil spring 18 on the ball 13 is not too great. This makes it difficult for the lubricating film formed on the surfaces of the ball 13 and coil spring 18 to break down, and reduces friction between the ball 13 and 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 preventing the oil-based ink composition from seeping out or leaking.

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

In the above-described embodiment, the wire diameter of the coil spring 18 is 0.05 mm or more, which prevents localized pressure increases in the ball 13 and 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 means the spring constant is not too large and the spring load is not too large, making the lubricating film less likely to break down. Therefore, according to the above-described embodiment, a lubricating film is stably formed on the surfaces of the ball 13 and coil spring 18 over a long period of time, making it easier to maintain a good writing feel when writing with a low load over a long period of time.

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

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.

In the above-described embodiment, the effective number of turns of the coil spring 18 is between 10 and 40, so the pressure between the coil spring 18 and the ball 13 tends to be within an appropriate range. This makes the lubricating film less likely to break down, and the lubricating film remains stable on the surfaces of the ball 13 and coil spring 18 for a long period of time, making it easier to maintain a good writing feel over a long period of time when writing with a low load.

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. When the polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group is a monoester, it is represented by the following formula (B):
RO-( _CH2CH2O ) _n -PO(OH) ₂ ...(B ₎

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

Examples of commercially available phosphate esters include Phosphanol BH-650, SM-172, ED-200, GF-339, RA-600, GF-199, ML-200, ML-220, ML-240, RD-510Y, GF-185, RS-610, RS-710, RP-710, AK-25, GF-702, RS-610NA, SC-6103, and LP-70. Examples of suitable surfactants include Plysurf 0, Plysurf LS-500, Plysurf RL-210, Plysurf RL-310, Plysurf RB-410, Plysurf RD-720, and Plysurf LB-400 (all manufactured by Toho Chemical Industry Co., Ltd.), Plysurf A207H, Plysurf A208B, Plysurf A219B, Plysurf A208S, Plysurf A212S, Plysurf A215C, and Plysurf AL (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and NIKKOL DDP-2 (Zipalace-2 phosphate, manufactured by Nikko Chemicals Co., Ltd.).

The content of 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 phosphate ester is 0.10% by weight, it is easier to properly form a highly cushioned lubricating film containing phosphate ester and rubber elastic particles on the surfaces of the ball 13 and coil spring 18. If the content of phosphate ester is 20.0% by weight or less, the content of organic solvent in the oil-based ink composition can be ensured, allowing solid components in the ink, such as dyes and resins, to dissolve sufficiently, making it less likely for handwriting to smudge.

In some embodiments, the oil-based ink composition comprises a first phosphate ester and a second phosphate ester, each of which has a hydrocarbon group and the number of carbon atoms in the hydrocarbon group is different from each other. Here, 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.

The first phosphate ester may be a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 4 to 17 carbon atoms. The second phosphate ester may be a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group with 18 to 30 carbon atoms.

In this way, because the oil-based ink composition contains a first phosphate ester with a relatively small number of carbon atoms in the hydrocarbon group and a second phosphate ester with a relatively large number of carbon atoms in the hydrocarbon group, the second phosphate ester penetrates between the first phosphate esters, forming a lubricating film of phosphate ester with a dense structure on the metal surface. This makes the lubricating film more stable, and this lubricating film makes it easier to reduce friction between the ball 13 and the coil spring 18. This tends to result in a good writing feel when writing with a low load.

In this specification, rubber elastic particles refer to polymer particles that have a cross-linked structure in which the molecules that make up the rubber elastic particles are covalently bonded together, giving them the ability to return to their original shape (rubber elasticity) after being deformed. The elastic modulus and hardness can be adjusted by changing the molecules that form the cross-linked structure. Rubber elastic particles are characterized by being resistant to pressure and impact, and being easily deformed. As a result, they can reduce the impact of friction between the oil-based ink composition and the components that make up the ballpoint pen tip (such as the ball) when writing with a ballpoint pen, improve lubricity, and have the effect of improving the writing feel.

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

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

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 coil spring 18. As a result, when writing with the ballpoint pen 100 at a low load, friction between the ball 13 and coil spring 18 tends to be small, so the user of the ballpoint pen 100 is less likely to feel resistance due to friction when writing, which tends to result in a good writing feel.

In some embodiments, the rubber-elastic particles may be acrylic particles, styrene particles, or urethane particles.

When the oil-based ink composition contains acrylic particles, styrene particles, or urethane particles, a highly cushioned lubricating film containing phosphate ester and rubber elastic particles can be formed on the surfaces of the ball 13 and coil spring 18. As a result, when writing with the ballpoint pen 100 at a low load, friction between the ball 13 and coil spring 18 is reduced, meaning that the user of the ballpoint pen 100 feels less frictional resistance when writing, resulting in a smooth writing experience.

The rubber elastic particles may have a true specific gravity of less than 1.20 g/cm ³ or may have a true specific gravity of less than 1.05 g/cm ^3. If the rubber elastic particles have a true specific gravity of less than 1.20 g/cm ³ , the dispersibility of the rubber elastic particles in the oil-based ink composition tends to be good. If the rubber elastic particles have a true specific gravity of less than 1.05 g/cm ³ , the dispersibility of the rubber elastic particles in the oil-based ink composition tends to be good over the long term.

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 also be less than 1.00 μm. In this case, the oil-based ink composition is more likely to be ejected well from the ballpoint pen tip. Note that the particle size distribution can also be adjusted by sieving, centrifugation, or filtration to obtain rubber elastic particles of the desired particle size.

In this specification, the particle size of rubber elastic particles refers to the average particle size. This average particle size 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).

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.

When adding rubber elastic particles to an 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.

The elasticity (hardness) of the rubber elastic particles is preferably 25 to 90 inclusive, and more preferably 50 to 80 inclusive, on a Type A durometer in accordance with 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 return to their original shape and are easily dispersed into the ink flow path.

As the nonionic surfactant, well-known nonionic surfactants can be used without any particular limitation. Examples of nonionic surfactants 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 that have both ester bonds and ether bonds in the molecule.

Specific examples of nonionic surfactants include polyoxyethylene alkyl ether, polyoxyoleyl ether, polyoxyethylene hydrogenated castor oil, sorbitan sesquioleate, polyoxyethylene sorbitan monooleate, and polyglycerin fatty acid decaglyceryl.
Commercially available products include NIKKOL BL-2, BL-4.2, BL-9EX, BC-2, BC-5.5, BC-7, BC-10, BS-2, BS-4, BO-2V, BO-7V, BO-10V, BB-5, BB-10, BD-4, BT-3, BT-5, BT-7, BT-9, BT-12, PBC-31, PBC-33, PBC-41, PBC-44, PEN-4612, PEN-4620, PEN-4630, and BPS-5. , BPS-10, HCO-5, HCO-10, HCO-20, HCO-30, HCO-40, HCO-50, HCO-60, HCO-80, TS-10V, TS-10MV, TS-106V, T S-30V, TI-10V, TO-10V, TO-10MV, TO-106V, TO-30V, GS-460, GO-4V, GO-430NV, GO-440V, GO-460V, Tetraglyn 1-SV, Tetraglyn 1-OV, Hexaglyn 1-L, Hexaglyn 1-M, Hexaglyn 1-SV, Hexaglyn 1-OV, Decaglyn 1-M, Decaglyn 1-SV, Decaglyn 1-50SV, Decaglyn 1-ISV, Decaglyn 1-OV, Decaglyn 1-LN, Decaglyn 2-SV, Decaglyn 2-ISV, Decaglyn 3-SV, Decaglyn 3-OV, TMGS-5V, TMGS-15V, TMGO-5, TMGO-15 (manufactured by Nikko Chemicals Co., Ltd.), Pegnol L-4, TH-8, L-9A, L-12S, T-6, TE-10A, ST-7, ST-9, ST-12, O-6S, O-16A, S-4DV (manufactured by Toho Chemical Co., Ltd.), Neugen Examples of suitable steroids include XL-40, XL-100, TDS-30, LF-60X, TDX-50, TDX-80, SD-30, SD-60, SD-70, SD-80, EA-87, SOLGEN 30, 90, 110, and TW-60 (all manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.).

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

In some embodiments, the water content in the 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.

In the above-mentioned embodiment, the water content in the oil-based ink composition is 1.00% by weight or more or 4.00% by weight or more, so a certain amount of water is incorporated into the above-mentioned lubricating film, thereby increasing the cushioning properties of the lubricating film. Furthermore, in the above-mentioned embodiment, the water content in the oil-based ink composition is 10.0% by weight or less or 8.00% by weight or less, so the water content in the oil-based ink composition is not too high, allowing water to dissolve stably in the oil-based ink composition.

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

Specific examples of water-soluble dyes that can be used 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 Fast Black AB (C.I. Direct Deep Black EX (C.I. Direct Fast Black Concentrate) (C.I. Direct Black 51), Kayalas Spragray VGN (C.I. Direct Yellow 71), Kayalas Direct Brilliant Yellow G (C.I. Direct Yellow 4), Direct Fast Yellow 5GL (C.I. Direct Yellow 26), Eisen Primula Yellow GCLH (C.I. Direct Yellow 44), Direct Fast Yellow R (C.I. Direct Yellow 50), Eisen Direct Fast Red FH (C.I. Direct Red 1), Nippon Fast Scarlet GSX (C.I. Direct Fast Scarlet 4BS (C.I. Direct Yellow 23), and Eisen 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 as 15), Sumilite Splat Blue BRR Concentrate (same as 71), Daibogen Turquoise Blue S (same as 86), Water Blue #3 (same as 86), Kayalas Turquoise Blue GL (same as 86), Kayalas Splat Blue FF2 GL (same as 106), Kayalas Splat Turquoise Blue FBL (same as 199), etc.

Specific examples of acid dyes include Acid Blue Black 10B (C.I. Acid Black 1), Nigrosine (C.I. Acid Black 2), Suminol Milling Black 8BX (C.I. Acid Black 24), Kayanol Milling Black VLG (C.I. Acid Black 26), Suminol Fast Black BR Concentrate (C.I. Acid Black 31), Mitsui Nylon Black GL (C.I. Acid Black 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 M Ring Black B (same as 109), Kayanol Milling Black TLR (same as 110), Aizen Opal Black New Conch (same as 119), Water Black 187-L (same as 154), Kayaku Acid Brilliant Flavin FF (C.I. Acid Yellow 7:1), Kayasil Yellow GG (same as 17), Xylene Light Yellow 2G 140% (same as 17), Suminol Leveling Yellow NR (same as 19), Daiwa Tartrazine (same as 23), Kayaku Tartrazine (same as 23), Suminol Fast Yellow R (same as 25), Diacid Light Yellow 2GP (same as 29), Suminol Milling Yellow O (same as 38), Suminol Milling Yellow MR (same as 42), Water Yellow #6 (same as 42), Kayanol Yellow NFG (same as 49), Suminol Milling Yellow 3G (same as 72), Suminol Fast Yellow G (same as 61), Suminol Milling Yellow G (same as 78), Kayanol Yellow N 5G (same as 110), Suminol Milling Yellow 4G 200% (same as 141), Kayanol Yellow NG (same as 135), Kayanol Milling Yellow 5GW (same as 127), Kayanol Milling Yellow 6GW (same as 142), Sumitomo Fast Scarlet A (C.I. Acid Red 8), Kayaku Silk Scarlet (same as 9), Solar Rubin Extra (same as 14), Daiwa New Kokushin (same as 18), Aizen Bonsaw RH (same as 26), Daiwa Red No. 2 (same as 27), Suminol Leveling Brilliant Red S3B (same as 35), Kayasil Rubinol 3GS (same as 37), Aizen Erythrosine (same as 51), Kayaku Acid Rhodamine FB (same as 52), Suminol Leveling Rubinol 3GP (same as 57), Diacid Alizarin Rubinol F3G 200% (same as 82), Aizen Eosin GH (same as 87), Water Pink #2 (same as 92), Aizen Acid Phloxine PB (same as 92), Rose Bengal (same as 94), Kayanol Milling Scarlet FGW (same as 111), Kayanol Milling Rubin 3BW (same as 129), Sumino All Milling Brilliant Red 3BN Concentrate (same as 131), Sumino All Milling Brilliant Red BS (same as 138), Aizen Opal Pink BH (same as 186), Sumino All Milling Brilliant Red B Concentrate (same as 2 49), Kayaku Acid Brilliant Red 3BL (same 254), Kayaku Acid Brilliant 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 ( 15), Orient Soluble Blue OBC (22), Suminol Leveling Blue 4GL (23), Mitsui Nylon Fast Blue G (25), Kayasil Blue AGG (40), Kayasil Blue BR (41), Mitsui Alizarin Sapphirol SE (43), Suminol Leveling Sky Blue R Extra Concentrate (62), Mitsui Nylon Fast Sky Blue B (78), Sumitomo Brilliant Indocyanine 6Bh/c (83), Sandran Cyanine N-6B 350% (90), Water Blue Examples include #115 (C.I. 90), Orient Soluble Blue OBB (C.I. 93), Sumitomo Brilliant Blue 5G (C.I. 103), Kayanol Milling Ultra Sky SE (C.I. 112), Kayanol Milling Cyanine 5R (C.I. 113), Eisen Opal Blue 2 GLH (C.I. 158), Daiwa Guinea Green B (C.I. Acid Green 3), Acid Brilliant Milling Green B (C.I. 9), Daiwa Green #70 (C.I. 16), Kayanol Cyanine Green G (C.I. 25), and Sumitomo Milling Green G (C.I. 27).

Specific examples of basic dyes include Eisenkathiron Yellow 3GLH (C.I. Basic Yellow 11), Eisenkathiron Brilliant Yellow 5GLH (C.I. Basic Yellow 13), Sumiacrylic Yellow E-3RD (C.I. Basic Yellow 15), Maxiron Yellow 2RL (C.I. Basic Yellow 19), Astrazon Yellow 7GLL (C.I. Basic Yellow 21), Kayakryl Golden Yellow GL-ED (C.I. Basic Yellow 28), Astrazon Yellow 5GL (C.I. Basic Yellow 51), Eisenkathiron Orange GLH (C.I. Basic Orange 21), Eisenkathiron Brown 3GLH (C.I. Basic Red 30), Rhodamine 6GCP (C.I. Basic Red 1), Eisen Astraphloxine (C.I. Basic Red 12), Sumiacrylic Brilliant Red E-2B (C.I. Basic Red 15), Astrazon Yellow 5GL (C.I. Basic Orange 21), Rhodamine 6GCP (C.I. Basic Red 12 ... Examples include Trazone Red GTL (C.I. 18), Eisen Katiron 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 Katiron Blue BRLH (C.I. 54), Eisen Diamond Green GH (C.I. Basic Green 1), Eisen Malachite Green (C.I. 4), and Bismarck Brown G (C.I. Basic Brown 1). These may be used alone or in combination.

Specific examples of oil-soluble dyes that can be used include acid dyes, basic dyes, metal complex dyes, salt-forming dyes, azine dyes, anthraquinone dyes, phthalocyanine dyes, and triphenylmethane dyes. Specific examples include Nigrosine Base EE, Nigrosine Base EEL, Nigrosine Base EX, Nigrosine Base EXBP, Nigrosine Base EB, Oil Yellow 101, Nigrosine Base 107, Oil Pink 314, Oil Brown BB, Nigrosine Base GR, Oil Green BG, Oil Blue 613, Oil Scarlet 308, Nigrosine Base BOS, Oil Black HBB, Nigrosine Base 860, Nigrosine Base BS, and Varifast Yellow 1101. 1105, 1108, 1109, 3104, 3105, 3108, 4120, AUM, Balifast Orange 2210, 3209, 3210, Balifast 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, 2 606, 2610, 2620, Varifast Violet 1701, 1702, 1731, Varifast 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.), Aizenspiron Yellow 3RH, GRLH Special, C-2GH, C-GNH new, Aizenspiron Aizen Spiron Orange 2RH, Aizen Spiron GRH Concentrate Special, Aizen Spiron Red GEH, BEH, GRLH Special, C-GH, C-BH, Aizen Spiron Violet RH, C-RH, Aizen Spiron Brown BH Concentrate, RH, Aizen Spiron Mahogany RH, Aizen Spiron Blue GNH, 2BNH, C-RH, BPNH, Aizen Spiron Green C-GH, 3GNH Special, Aizen Spiron Black BNH, MH, RLH, GMH Special, BH Special, S.B.N. Orange 703, S.B.N. Violet 510, 521, S.P.T. Orange 6, S.P.T. Blue 111, SOT Pink 1, SOT Blue 4, SOT Black 1, SOT 6, SOT 10, SOT 12, SOT 13 Liquid, Eisen Rhodamine B Base, Eisen Methyl Violet Base, Eisen Victoria Blue B Base (all manufactured by Hodogaya Chemical Co., Ltd.), Oil Yellow CH, Oil Pink 330, Oil Blue 8B, Oil Black S, Eisen FS Special A, Eisen 2020, Eisen 109, Eisen 215, AL Yellow 1106D, Eisen 3101, AL Red 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.), Sanibel Yellow 2GLS, Yellow RLS, Yellow 2RLS, Sunil Orange RLS, Sunil Fire Red GLS, Sunil Red 3BLS, Sunil Pink 6BLS, Sunil Blue RN, Sunil GLS, Sunil Green 2GLS, Sunil Brown GLS (all manufactured by Sandoz, Switzerland), Magenta SP 247%, Crystal Violet 10B 250%, Malachite Green Crystal Conc, Brilliant Green Crystal H 90%, Examples include 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), and Methyl Violet 2B Base (all manufactured by National Anilne Div., USA). These may be used alone or in combination.

Specific pigments include carbon blacks such as furnace black, contact black, thermal black, and acetylene black, black iron oxide, yellow iron oxide, red iron oxide, ultramarine, Prussian blue, cobalt blue, titanium yellow, turquoise, molybdate orange, titanium oxide, gold powder, silver powder, copper powder, aluminum powder, brass powder, tin powder, mica pigments, and 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, 1 22, 123, 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 include C.I. Pigment Yellow 1, 3, 12, 13, 24, 93, 94, 95, 97, 99, 108, 109, 110, 117, 120, 139, 153, 166, 167, 173, C.I. Pigment Green 7, 10, and 36. These can be used alone or in combination of two or more.

In addition to these pigments, processed pigments can also be used. Examples include Renol Yellow GG-HW30, HR-HW30, Orange RL-HW30, Red HF2B-HW30, FGR-HW30, F5RK-HW30, Carmine FBB-HW30, Violet RL-HW30, Blue B2G-HW30, CF-HW30, Green GG-HW30, Brown HFR-HW30, and Black R-HW30 (all manufactured by Clariant Japan Co., Ltd.), UTCO-001 Yellow, 012 Yellow, and Examples include 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.).

To improve the dispersibility of the pigment, anionic, cationic, nonionic, or amphoteric surfactants or polymer resins can be used as auxiliary agents. Specific examples include anionic, nonionic, or cationic surfactants such as higher fatty acids, higher alcohol 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 may be used alone or in combination of two or more.

In some embodiments, the dispersion medium can be an organic solvent used in oil-based ballpoint pen inks. Due to safety and odor concerns, alcohol, glycol, or glycol ether is preferred as the organic solvent.

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, triethylene glycol monomethyl ether, triethylene glycol dimethyl ether, triethylene glycol monobutyl ether, polyethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, propylene glycol monophenyl glycol ethers such as dipropylene glycol monomethyl ether, dipropylene glycol dimethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butyl acetate, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, hexylene glycol, octylene glycol, glycerin, polyethylene glycol, 3-methyl-1,3-butanediol, 1,3-propanediol, 1,3-butanediol, 1 , 5-pentanediol, and other glycols; benzyl alcohol, β-phenylethyl alcohol, α-methylbenzyl alcohol, ethanol, 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, and other alcohols; methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, and 2-ethylhexyl ether, and other esters; 2-ethylhexyl acetate, isobutyl isobutyrate, ethyl lactate, butyl lactate, and other esters.
In consideration of 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.

Ink compositions according to some embodiments may contain a dispersant for dispersing particles such as the rubber elastic particles described above. Dispersant resins and surfactants can be used, and examples include polybutyral resins, polymers with acidic groups, acrylic copolymers, phosphate copolymers, phosphate polyesters, alkylol ammonium salts of copolymers containing acidic groups, carboxylic acid esters with hydroxyl groups, and nonionic surfactants.

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/ 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), W9011 (acid value 65 mg KOH/g) and more, all manufactured by BYK Japan Co., Ltd.
The amine value expressed here is expressed as the number of milligrams (mg) of potassium hydroxide (KOH) equivalent to the amount of hydrochloric acid required to neutralize the primary, secondary, and tertiary amines contained in 1 g of sample.

Dispersants can be used alone or in combination, and are preferably used in an amount of 5.00% by weight or more and 200% by weight or less relative to the rubber elastic particles.

In some embodiments, a resin may be added to the oil-based ink composition to adjust the viscosity of the ink and improve the fixation of handwriting.

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, and TEGO 3350 UV (manufactured by Evonik Japan Co., Ltd.).
These may be used alone or in combination of two or more.

In some embodiments, a resin having acidic groups may be used as the resin described above. By using a resin having acidic groups as the resin described above, the apparent bulk 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. In addition, when rewriting after writing, the silicone composite particles that acted as a sealant are quickly loosened, reducing smearing when starting to write (hereinafter referred to as "initial stroke smearing").

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

Furthermore, if the resin contains OH groups, the interaction with the acidic groups will improve the adsorption to the silicone composite particles, improving the lubricity and the writing feel.
The amount of OH groups is expressed as an OH value, which is determined by acetylating a sample 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 the sample.

Specific examples of resins having acidic groups 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. 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.).

In some embodiments, it is preferable to use a cellulose derivative, particularly hydroxypropyl cellulose, as the resin. The coexistence of silicone composite particles within the molecular network of hydroxypropyl cellulose not only provides a sealing effect in the ink flow path, but is also thought to prevent ink from spreading when the pen tip is not retracted and is pressed against a display, as the hydroxypropyl cellulose and silicone composite particles immediately orient themselves on the ink surface.

Specific examples include NISSO HPC-VH, H, M, L, SL, and SSL (all manufactured by Nippon Soda Co., Ltd.), and Klucel-H, M, G, J, L, and E (all manufactured by Ashland Japan Co., Ltd.).

The 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. , Nymeen T2-230, Nymeen T2-260, Nymeen DT-203, Nymeen DT-208 and other alkyl polyether amines (all manufactured by Nippon Oil & Fats Co., Ltd.), diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, triethylamine, dimethylaminoethanol, diethylaminoethanol, methyldiethanolamine, butyldiethanolamine, dibutylethanolamine, diethylisopropanolamine, butylisopropylamine, butylbenzylamine, and butoxypropylamine (all manufactured by Kanto Chemical Co., Ltd.).
By maintaining the pH of the ink within an appropriate range, the adsorption of acidic substances to the metal ballpoint pen tip can be increased, preventing dotted lines in handwriting and improving the writing feel. The pH range of the ink composition is preferably from 2.5 to 7.5, more preferably from 3.5 to 6.0.

The oil-based ink composition according to some embodiments may contain a rust inhibitor. Benzotriazole, etc., can be used as the rust inhibitor.

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 tracking becoming poor and the handwriting smearing when writing, i.e., the initial stroke smearing, may worsen. 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 abrasion 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 writing 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.

In some embodiments, an ink backflow preventer can be placed at the ink interface within the ink reservoir tube to prevent unintended ink movement away from the pen tip and 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 co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, etc. These non-volatile and/or low-volatile liquids may be used alone or in combination of two or more. 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. Additionally, solids such as synthetic resin pillars known as floats may be placed within the ink backflow prevention composition to narrow the apparent space in which the backflow prevention composition is placed, making it less likely to move in response to external forces and improving impact resistance.

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 HIBON 9800, HIBON 9822, HIBON 9876, HIBON 9877, HIBON 9888 (all manufactured by Resonac Co., Ltd.). These can be used alone or as a mixture of two or more kinds.

A specific method for applying and solidifying a thermoplastic resin to the ink discharge port, which is the opening at the tip of the ballpoint pen tip, and using it 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 controller, and melted at a specified temperature. The ballpoint pen tip is turned downwards, and the molten thermoplastic resin is applied 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 at least five seconds to solidify the thermoplastic resin, which acts as a packing to block the ink discharge port.

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

The viscosity in the examples was measured using an MCR302 (Anton Paar) 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)

The pH values in the examples were measured at 25°C using a Halo 2 (Hanna Instruments Japan Co., Ltd.).

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 (by weight) of each material in the oil-based ink composition.

<Materials for ballpoint pens>
Coil spring (1): SUS304 (unplated bare wire)
Coil spring (2): Ni-plated SUS304 (plated wire)

<Ink composition materials>
Phosphate ester (1): Phosphanol GF-199 (a mixture of lauryl ether phosphate monoester, diester, and triester, HLB 5.5, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 12
Phosphate ester (2): Phosphanol LS-500 (phosphate ester, a mixture of mono-, di-, and triesters of polyoxyethylene (4) tridecyl ether phosphate, HLB 9.0, manufactured by Toho Chemical Industry Co., Ltd.), number of carbon atoms in hydrocarbon group: 13
Phosphate ester (3): Phosphanol LB-400 (phosphate ester, a mixture of mono-, di-, and triesters of polyoxyethylene (4) oleyl ether phosphate, 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, a mixture of mono-, di-, and triesters of polyoxyethylene (6) phenyl ether phosphate, 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

Water: Ion-exchanged water

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.)

Organic amine (1): Triisopropanolamine (Tokyo Chemical Industry Co., Ltd.)
Organic amine (2): Nymeen L201 (polyethylene glycol-1 laurylamine, NOF Corporation)
Organic amine (3): Triethanolamine (Tokyo Chemical Industry Co., Ltd.)

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.)

Dye (1): SPILON RED C-GH (a salt-forming dye of a xanthene-based basic dye and alkyldiphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Co., Ltd.)
Dye (2): SPILON YELLOW C-GNH new (a salt-forming dye of an indolinone-based basic dye and alkyldiphenyl ether disulfonic acid, manufactured by Hodogaya Chemical Industry Co., Ltd.)
Dye (3): VALIFAST RED 1364 (a salt-forming dye of C.I. Basic Red 1:1, alkylbenzenesulfonic acid, and alkyldiphenyletherdisulfonic acid, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (4): VALIFAST YELLOW 1108 (colorant, disazo dye, manufactured by Orient Chemical Industries, Ltd.)
Dye (5): OIL BLUE 613 (colorant, mixture of C.I. Solvent Blue 5 and rosin-modified resin, manufactured by Orient Chemical Industries, Ltd.)
Dye (6): VALIFAST BLUE 1631 (a salt-forming dye of C.I. Basic Blue 7 and a colorless organic acid, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (7): VALIFAST BLUE 1605 (metal complex dye of C.I. Solvent Blue 38, manufactured by Orient Chemical Industries Co., Ltd.)
Dye (8): VALIFAST BLUE 2680 (C.I. Basic Blue 70 phthalocyanine dye, manufactured by Orient Chemical Industries, Ltd.)
Dye (9): OIL PINK 314 (a mixture of C.I. Solvent Red 49 and other dyes, manufactured by Orient Chemical Industries, Ltd.)
Dye (10): SPILON RED C-BH (a salt-forming dye made from 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 Industries Co., Ltd.)

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)

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 rosin, acid value 100 mg KOH/g, Tg 175°C, manufactured by Arakawa Chemical Industries, Ltd.)
Resin (7): Harima T-80 (maleic rosin, acid value 185 mg KOH/g, Tg 85°C, manufactured by Harima Chemicals Co., Ltd.)
Resin (8): 42% acrylic acid-acrylic methacrylic acid ester copolymer in ethylene glycol monophenyl ether (acid value 510 mg KOH/g, OH value 130 mg KOH/g, Tg 80°C, calculated as solid)
Resin (9): 42% acrylic acid-styrene-methacrylic acid ester copolymer solution in ethylene glycol monophenyl ether (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.)

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/cm, 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/cm, manufactured by Shin-Etsu Chemical Co., Ltd.)
Rubber elastic particles (4): X-52-7030 (crosslinked silicone composite particles, average particle size 0.8 μm, rubber hardness 75 durometer A, true specific gravity 1.01 g/cm, manufactured by Shin-Etsu Chemical Co., Ltd.)
Rubber elastic particles (5): Techpolymer ABX-8 (crosslinked polybutyl acrylate particles, average particle size 8 μm, manufactured by Soken Chemical & Engineering Co., Ltd.)
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 Seiyaku Co., Ltd.)

Non-rubber elastic particles (for comparison) (1): AKP-20 (alumina particles, average particle size 0.5 μm, manufactured by Sumitomo Chemical Co., Ltd.)
Non-rubber elastic particles (for comparison) (2): JR-800 (titanium oxide particles, average particle size 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.)

Dispersant (1): DISPERBYK-111 (a copolymer containing an acid group, acid value 129 mg KOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (2): DISPERBYK-102 (a copolymer having an acidic group, acid value 101 mg KOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (3): BYK-P105 (a low molecular weight unsaturated carboxylic acid polymer, acid value 365 mg KOH/g, manufactured by BYK Japan Co., Ltd.)
Dispersant (4): DISPERBYK-180 (an alkylol ammonium salt of a copolymer containing an acid group, 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.)

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

The oil-based ink composition was prepared by stirring organic solvent or ion-exchanged water, phosphate ester, surfactant, colorant, and resin at 60°C with a propeller stirrer, then adding other additives and rubber-elastic particles or non-rubber-elastic particles either directly or after being uniformly dissolved or dispersed in a solvent with a propeller stirrer, and stirring with a propeller for 2 hours to obtain the oil-based ink composition.

The ink backflow preventer 16 was prepared as follows: 50.0 wt. % Spectrasyn 100 (α-olefin oligomer, base material, Exxon)
A backflow preventer composition was obtained by mixing 45.3 wt% of Lucant HC-100 (ethylene-α-olefin oligomer, base material, manufactured by Mitsui Petrochemical Co., Ltd.), 3.50 wt% of Aerosil R972 (fine particle silica, gelling agent, manufactured by Nippon Aerosil Co., Ltd.), and 1.20 wt% of Leopearl KL (dextrin fatty acid ester, manufactured by Chiba Flour Milling Co., Ltd.) and stirring with a hot stirrer at 150°C for 2 hours. 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.

(Creating test ballpoint pens)
Based on the ballpoint pen tip 10 shown in the figure, the ballpoint pen tip used in the test was made to the dimensions shown below. The numerical value in parentheses for each dimension is the ratio of that 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.

Diameter A of ball 13 = 0.50 mm
Inner diameter B of tip opening 19 = 0.48 mm
The distance C of the ball 13 moving in the forward and backward direction = 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
Ball seat diameter H = 0.44 mm
Center hole diameter I = 0.28mm
Seat angle α of ball holding portion 21: 100 degrees Crimping angle β = 80 degrees
Chamfer angle γ=56°
Taper angle δ=30°

When the coil spring 18 was placed inside the ball holder 14, the pressing load on the ball 13 was set to 0.15 N.

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

The arithmetic mean height, which is the surface roughness of ball 13 in the examples, was calculated from the average value measured at three randomly selected locations in a 20 μm x 20 μm area using a scanning probe microscope (AFM5100N; manufactured by Hitachi High-Tech Science Corporation).

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.

The following tests and evaluations were conducted on the ink compositions of each example and comparative example. The evaluation and measurement results are shown in Tables 1 to 15.

(Writing resistance value when writing with low load)
Three test ballpoint pens with the above-mentioned ballpoint pen tips were prepared for each Example and Comparative Example, and after removing the packing, the writing resistance was measured in an environment of 25°C and 65% relative humidity. The writing resistance was measured at 25°C using a static friction tester TL201Sa (manufactured by Trinity Lab Co., Ltd.) (unit: N). The evaluation criteria are as follows:
A: The average written resistance value is 0.15 or less. B: The average written resistance value is greater than 0.15 and less than 0.20. C: The average written resistance value is greater than 0.20 and less than 0.30. D: The average written resistance value is greater than 0.30.

(Low-load written test)
Three test ballpoint pens with the above-mentioned ballpoint pen tips were prepared for each Example and Comparative Example, and after removing the packing, a writing test was conducted using spiral writing at a temperature of 25°C and a relative humidity of 65%, with 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 when writing with low pressure. B: Writing can be completed with some smearing when writing with low pressure. C: Writing can be completed with some smearing when writing with low pressure.

(Low load written test (over time))
Three test ballpoint pens with the above-mentioned ballpoint pen tips 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 and 65% relative humidity. After that, a writing test was conducted on the aged products in an environment of 25°C and 65% relative humidity using spiral writing with 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 when writing with low pressure. B: Writing can be completed with some smearing when writing with low pressure. C: Writing can be completed with some smearing when writing with low pressure.

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. This allows a stable phosphate ester lubricating film to form on the surface of the ball and coil spring, and rubber elastic particles to penetrate into this lubricating film, maintaining a highly cushioned lubricating film. It is believed that this 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 an extended period of time.

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 when writing with a low load.

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, resulting in a lower writing resistance when writing with a low load.

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

Furthermore, in the ballpoint pens of Comparative Examples 2 and 4, because the coil springs were plated, the film formed between the phosphate ester and rubber elastic particles was not stable over time, which is thought to have caused smudges when writing with low loads, made it impossible to finish the writing, and also resulted in an increase in writing resistance.

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

Furthermore, because 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 ball, resulting in smearing, making it impossible to finish writing, and also resulting in increased writing resistance when writing with a low load.

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

[1] At least one embodiment of the ballpoint pen refill (200) of the present invention comprises:
an ink reservoir (12);
an oil-based ink composition filled in the ink reservoir;
a ballpoint pen tip (10) attached to the front end of the ink reservoir tube so that the oil-based ink composition is supplied;
Equipped with
The ballpoint pen tip is
A ball (13),
a ball holder (14) for holding the ball so that the ball is located at the front end of the ballpoint pen tip and can rotate;
a coil spring (18) for biasing the ball forward;
Including,
the coil spring includes bare stainless steel wire;
The oil-based ink composition comprises
at least one phosphate ester;
Rubber elastic particles;
Contains:

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

Furthermore, in the above-mentioned configuration [1], since the coil spring is formed from bare stainless steel wire (i.e., unplated stainless steel wire), 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 portion of the coil spring from being detached as a precipitate due to reaction with the phosphate ester in the oil-based ink composition, making it easier for a lubricating film containing 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 affected by changes in the moisture content and pH of the oil-based ink composition over time. As a result, the above-mentioned elastic lubricating film can be stably formed on the surface of the coil spring over an extended period of time.

As a result, with the configuration [1] above, the lubricating film described above allows the friction between the ball and the coil spring to remain low even after the ballpoint pen has been used for an extended period of time. This makes it possible to obtain a ballpoint pen that writes well even when writing with a low load, even after extended use.

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

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. This allows the second phosphate ester to penetrate 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 this lubricating film makes it easier 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.

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

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

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

In accordance with the above-mentioned configuration [4], the oil-based ink composition contains rubber elastic particles made of silicone, which makes it easier to increase the elasticity of the lubricating film formed on the surface of the ball and coil spring. Therefore, when writing with a ballpoint pen at a low load, friction between the ball and coil spring tends to be reduced, which means that the user of the ballpoint pen feels less resistance due to friction when writing, resulting in a more pleasant writing experience.

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

According to the above-mentioned configuration [5], by using rubber elastic particles containing acrylic particles, styrene particles, or urethane particles, a highly cushioning lubricating film containing phosphate ester and rubber elastic particles can be formed on the surface of the ball and coil spring. As a result, when writing with a ballpoint pen using a low load, friction between the ball and coil spring is reduced, so the user of the ballpoint pen feels less resistance due to friction when writing, resulting in a smooth writing experience.

[6] In some embodiments, in any of the configurations [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.

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 prevents the ink composition from seeping out during writing and leaking 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 surface of the ball and coil spring to break down, and reduces friction between the ball and coil spring when writing with a low load using the ballpoint pen. Therefore, with the configuration [6] above, it is possible to maintain a good writing feel when writing with a low load for a long period of time while preventing the ink composition from seeping out or leaking.

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

In the configuration [7] above, the wire diameter of the coil spring is 0.05 mm or more, which prevents localized pressure buildup in the ball and 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 means the spring constant is not too large and the spring load does not become too large, making the lubricating film less likely to break down. Therefore, with the configuration [7] above, a lubricating film is stably formed on the surfaces of the ball and coil spring over a long period of time, making it easier to maintain a good writing feel over a long period of time when writing with a low load.

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

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 the lubricating film remains stable on the surfaces of the ball and coil spring for a long period of time, making it easier to maintain a good writing feel over a long period of time when writing with a low load.

[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],
A barrel (1) in which the ballpoint pen refill is housed;
Equipped with.

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

Furthermore, in the above-mentioned configuration [9], since the coil spring is formed from bare stainless steel wire (i.e., unplated stainless steel wire), 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 portion of the coil spring from being detached as a precipitate due to reaction with the phosphate ester in the oil-based ink composition, making it easier for a lubricating film containing 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 affected by changes in the moisture content and pH of the oil-based ink composition over time. As a result, the above-mentioned elastic lubricating film can be stably formed on the surface of the coil spring over an extended period of time.

As a result, with the configuration [9] above, the lubricating film described above allows the friction between the ball and the coil spring to remain low even after the ballpoint pen has been used for an extended period of time. This makes it possible to obtain a ballpoint pen that writes well even when writing with a low load, even after extended use.

The above describes embodiments of the present invention, but the present invention is not limited to the above-described embodiments and also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

In this specification, expressions expressing relative or absolute arrangement such as "in a certain direction,""along a certain direction,""parallel,""orthogonal,""center,""concentric," or "coaxial" not only express such an arrangement strictly, 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 such as "identical,""equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained.
Furthermore, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent rectangular shapes or cylindrical shapes in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained.
Furthermore, in this specification, the expressions "comprise,""include," or "have" a component are not exclusive expressions that exclude the presence of other components.

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 (9)

an ink reservoir;
an oil-based ink composition filled in the ink reservoir;
a ballpoint pen tip attached to the front end of the ink reservoir tube so as to supply the oil-based ink composition;
Equipped with
The ballpoint pen tip is
The ball and
a ball holder for holding the ball so that the ball is located at the front end of the ballpoint pen tip and can rotate;
a coil spring for biasing the ball forward;
Including,
the coil spring includes bare stainless steel wire;
The oil-based ink composition comprises
at least one phosphate ester;
Rubber elastic particles;
A ballpoint pen refill containing The at least one phosphate ester is
a first phosphate ester having a hydrocarbon group;
a second phosphate ester having a hydrocarbon group with a carbon number greater than that of the hydrocarbon group of the first phosphate ester;
The ballpoint pen refill according to claim 1 , comprising: the first phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having 4 to 17 carbon atoms,
3. The ballpoint pen refill according to claim 2, wherein the second phosphate ester is a polyoxyethylene hydrocarbon phosphate ester having a hydrocarbon group having 18 to 30 carbon atoms. 4. The ballpoint pen refill according to claim 1, wherein the rubber elastic particles are made of silicone. The ballpoint pen refill according to claim 1 , wherein the rubber elastic particles include acrylic particles, styrene particles, or urethane particles. 4. The ballpoint pen refill according to claim 1, 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. 4. The ballpoint pen refill according to claim 1, wherein the wire diameter of the coil spring is 0.05 mm or more and 0.2 mm or less. 4. The ballpoint pen refill according to claim 1, wherein the effective number of turns of the coil spring is 10 or more and 40 or less. A ballpoint pen refill according to any one of claims 1 to 3;
a barrel in which the ballpoint pen refill is housed;
A ballpoint pen equipped with