Ballpoint pen

Abstract

Provided is a ballpoint pen (1) including: a first caulking part (14a) in which the ink viscosity of an ink composition for an oil-based ballpoint pen is in a range of 500 mPa·s to 15,000 mPa·s at 20 °C and at a shear rate of 500 sec-1, the ball diameter of a ball (20) is 0.5 mm or less, and a chip tip part (13) has an inclination (α) of 90 degrees to 100 degrees; and a second caulking part (14b) that is provided closer to a tip side of a ballpoint pen chip (11) than the first caulking part (14a) and has an inclination angle of 110 degrees to 130 degrees, wherein an angle (γ) of a bottom wall (19) of a ball holding chamber (15) is the same as the inclination angle of the second caulking part (14b).

Description

Technical Field

[0001] The present invention relates to a ballpoint pen.

Background Art

[0002] Conventionally, a ballpoint pen equipped with a ballpoint pen tip has been known. The ballpoint pen tip has, for example, an ink flow hole formed at the center of the bottom wall of the ball holding chamber and a plurality of ink flow grooves extending radially from the ink flow hole. As a ballpoint pen tip, a ball is placed on a substantially arc-shaped ball seat provided on the bottom wall of the ball holding chamber, and a part of the ball is projected from the tip edge of the tip by caulking the tip end portion inward to rotatably hold the ball.

[0003] In addition, writing instruments are likely to be affected by the writing resistance between the ballpoint pen tip and the writing surface during writing, which affects the writing feel of ballpoint pens, marking pens, etc. In particular, a ballpoint pen has a ballpoint pen tip including a metal tip body made of stainless steel or the like at the tip and a ball made of a metal such as super steel held on the ball seat of the metal tip body. For this reason, the ballpoint pen has a problem that wear occurs on the ball seat due to the rotation of the ball during writing, resulting in skipping of lines, streaks, etc. in the handwriting and deterioration of the writing feel. In particular, when the ball diameter is made as small as 0.5 mm or less, the ball is likely to sink into the paper surface due to the writing pressure, and a paper contact phenomenon occurs in which the outer surface of the caulked portion contacts the writing surface, and the smoothness during writing tends to be inferior.

[0004] In order to improve the smoothness during writing, which is important for ballpoint pens, the wall thickness of the caulked part is reduced or the angle of the caulked part is made smaller. Specifically, the closer the angle of the tapered surface, which tapers from the large-diameter part towards the tip of the chip, is to the direction of the tip of the chip, the less likely it is to touch the paper. For example, since the angle of the tapered surface was often about 30 degrees, a technique has been disclosed in which the angle of the caulked part is set to 90 degrees or less to make it difficult to touch the paper (see, for example, Patent Document 1). However, reducing the wall thickness of the caulked part or reducing the inclination angle (caulking angle) will reduce the durability of the ballpoint pen tip, such as making it easier for the ball to fall out of the ball holding chamber.

[0005] Also, in order to improve the durability of the ballpoint pen tip, it is conceivable to increase the wall thickness of the caulked part. However, this will reduce the smoothness during writing, such as making it easier for the caulked part to come into contact with the writing surface. That is, improving the smoothness will reduce the durability, and conversely, improving the durability will reduce the smoothness.

[0006] By the way, in a ballpoint pen tip, in order to prevent ink leakage from the tip of the chip, etc., it has been disclosed to form a sealing surface in a substantially arc shape on the inner wall of the tip of the chip (see, for example, Patent Document 2). However, since the wall thickness at the caulked part becomes thinner, the chip durability tends to decrease.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] In particular, in a ballpoint pen using a small-diameter ball with a ball diameter of 0.5 mm or less, when writing the same distance, the smaller the diameter of the ball, the higher the rotation speed of the ball. Further, when using a small-diameter ball, a load is applied to the ball seat, so the wear of the ball seat is severe, which causes writing defects. Therefore, when using a small-diameter ball, new problems were likely to occur.

[0009] An object of the present invention is to provide a ballpoint pen using a small-diameter ball with a ball diameter of 0.5 mm or less, which can obtain stable rotation of the ball and stable ink outflow.

Means for Solving the Problems

[0010] In order to solve the above problems, the ballpoint pen of the present invention includes a ballpoint pen refill having an ink storage cylinder filled with an oil-based ballpoint pen ink composition therein and a ballpoint pen tip attached to the tip of the ink storage cylinder, The tip body of the ballpoint pen tip has a ball holding chamber that rotatably holds a part of the ball so that it protrudes from the tip of the tip, a ball seat provided on the bottom wall of the ball holding chamber, on which the ball is placed and which is an arc-shaped surface along the outer shape of the ball, an ink flow hole formed in the center of the bottom wall of the ball holding chamber, and a plurality of ink flow grooves extending radially from the ink flow hole. The ink viscosity of the oil-based ballpoint pen ink composition is in the range of 500 mPa·s or more and 15,000 mPa·s or less at 20°C and a shear rate of 500 sec-1. The ball diameter of the ball is 0.5 mm or less. An arc-shaped sealing surface is formed on the inner wall of the tip of the tip. The tip of the tip has a first caulking portion with an inclination angle of 90 degrees or more and less than 100 degrees, and a second caulking portion provided on the tip side of the ballpoint pen tip from the first caulking portion and having an inclination angle of 110 degrees or more and 130 degrees or less. The angle of the bottom wall of the ball holding chamber is the same as the inclination angle of the second caulking portion.

[0011] It further includes a coil spring that presses the ball toward the tip side of the tip of the chip, and the pressing load of the coil spring is 5 gf or more and 10 gf or less.

[0012] The ink composition for the oil-based ballpoint pen contains a colorant, an organic solvent, a saturated fatty acid, and a phosphate ester, and the phosphate ester is C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 or more and 30 or less).

[0013] The saturated fatty acid has 10 to 20 carbon atoms.

[0014] The carbon chain (l, m) of the terminal alkyl group of the phosphate ester is 1 to 15.

[0015] The ink composition for the oil-based ballpoint pen contains a ketone resin or a polyvinyl butyral resin.

[0016] The colorant is a pigment or a salt-forming dye. [Effect of the Invention]

[0017] In the ballpoint pen using a small-diameter ball with a ball diameter of 0.5 mm or less, the present invention has been able to obtain a ballpoint pen in which stable rotation of the ball and stable ink outflow can be obtained. [Brief Description of the Drawings]

[0018]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0019] In this specification, "parts", "%", "ratio", etc. indicating formulation are based on mass unless otherwise specified. Also, in the present invention, "front" means the side of the ballpoint pen tip for a ballpoint pen, and for a ballpoint pen tip, it means the side of the ball.

[0020] (Ballpoint pen) FIG. 1 is a cross-sectional view showing an example of the ballpoint pen 1 of the present embodiment.

[0021] The ballpoint pen 1 of the present embodiment includes a ballpoint pen refill 4. The ballpoint pen refill 4 is a replacement core of the ballpoint pen 1.

[0022] The ballpoint pen refill 4 is housed in an outer cylinder body in which the front shaft 2 and the rear shaft 3 in the ballpoint pen 1 are detachably screwed. The ballpoint pen refill 4 is urged rearward by a coil spring 5 and stored.

[0023] Note that the rear and the rear end portion mean one end side in the extending direction X of the ballpoint pen 1, and the direction on the side where the ball 20 is not provided and the end portion in the extending direction X. Also, the front, the tip side, the front end portion, and the tip portion mean one end side in the extending direction X of the ballpoint pen 1, and the direction on the side where the ball 20 is provided and the end portion in the extending direction X.

[0024] FIG. 2 is a cross-sectional view of an example of the ballpoint pen refill 4 of the present embodiment. FIG. 2 shows a main part with a part of the configuration of the ballpoint pen refill 4 omitted.

[0025] The ballpoint pen refill 4 has an ink storage cylinder 22 and a ballpoint pen tip 11.

[0026] The ink storage cylinder 22 is cylindrical and long in the extending direction X. The extending direction X of the ink storage cylinder 22 and the ballpoint pen 1 coincides. Inside the ink storage cylinder 22, an ink composition for an oil-based ballpoint pen is filled. At the rear end of the ink storage cylinder 22, a tail plug 24 is attached (see Fig. 1).

[0027] At one end (tip) in the extending direction X of the ink storage cylinder 22, a ballpoint pen tip 11 is provided. The extending direction X of the ink storage cylinder 22 and the extending direction X of the ballpoint pen 1 coincide. Hereinafter, the extending direction X may be referred to as the axial direction for explanation. The extending direction X is, that is, the direction along a straight line (central axis J) passing through the center of the cross-section of the cylindrical ink storage cylinder 22. In other words, the extending direction X is the direction along the central axis J of the cylindrical ink storage cylinder 22.

[0028] The ballpoint pen tip 11 is a member that rotatably holds the ball 20. That is, the ballpoint pen tip 11 holds the ball 20 at the tip, which is one end in the extending direction X of the ink storage cylinder 22. The ball 20 is a spherical member with a ball diameter of 0.5 mm or less. The ball diameter of the ball 20 may be more than 0.1 mm and 0.5 mm or less.

[0029] Specifically, the ballpoint pen tip 11 is attached to the tip of the ink storage cylinder 22 via a tip holder 23.

[0030] Returning to Fig. 1, the description continues.

[0031] In this embodiment, the ballpoint pen 1 is an example of a retractable ballpoint pen 1. Specifically, the ballpoint pen 1 is configured such that the front end of the ballpoint pen tip 11, which is the pen tip of the ballpoint pen refill 4, can protrude from and retract into the front end opening 2a of the front shaft 2 by pressing the knock member 7 by a retracting mechanism using a rotary cam 6. For example, a clip 8 is disposed on the rear shaft 3. Also, a grip 9 made of, for example, an olefin-based thermoplastic elastomer is attached to the gripping portion of the front shaft 2.

[0032] Specifically, the ballpoint pen 1 is provided with a rotation cam 6 and a cam mechanism (not shown) as a retractable mechanism. The rotation cam 6 is provided on the rear shaft 3 and switches the retraction and protrusion of the ballpoint pen tip 11 of the ballpoint pen refill 4. The cam mechanism has a cam groove that engages with the rotation cam 6.

[0033] When the knock member 7 is pressed while the ballpoint pen tip 11 of the ballpoint pen refill 4 is immersed in the front shaft 2, the rotation cam 6 slides along the cam groove. The pressing operation of the knock member 7 may be referred to as a knock operation. By the sliding of the rotation cam 6, the ballpoint pen tip 11 of the ballpoint pen refill 4 protrudes forward from the opening 2c of the front shaft 2. Further, by rotating the rotation cam 6 by the action of the cam mechanism, the relative movement of the ballpoint pen refill 4 in the axial rear direction is restricted. For this reason, this protruding state is maintained even after the pressing operation ends. Also, when the knock member 7 is pressed again (knock operation) in this protruding state, the relative movement of the ballpoint pen refill 4 in the axial rear direction is allowed by the action of the cam mechanism. By this relative movement, the ballpoint pen refill 4 and the knock member 7 are pushed back in the axial rear direction by the biasing force of the coil spring 5 and returned to the initial state.

[0034] FIG. 3 is an enlarged cross-sectional view of an example of the ballpoint pen tip 11 of the present embodiment. FIG. 3 shows a main part with a part of the configuration of the ballpoint pen tip 11 omitted.

[0035] The ballpoint pen tip 11 includes a tip body 12. The tip body 12 is provided with a ball holding chamber 15, an ink flow hole 16, an ink flow groove 17, a ball seat 19a, and the like.

[0036] The ball holding chamber 15 rotatably holds a part of the ball 20 protruding from the tip end portion 13 of the chip. The ball holding chamber 15 is provided at the tip end portion in the extending direction X of the ink flow hole 16. On the bottom wall 19 of the ball holding chamber 15, a ball seat 19a having a shape along the outer shape of the ball 20 is provided. As described above, the ball 20 is spherical. Therefore, the ball seat 19a is formed in a substantially arc surface shape. The ball 20 is placed on the ball seat 19a. The bottom wall 19 of the ball holding chamber 15 is continuous with the seal surface 14c provided at the chip tip end portion 13 on the inner wall of the ball holding chamber 15, and is a region on the rear side of the ball pen 1 from the seal surface 14c.

[0037] The ink flow hole 16 is a hole portion that penetrates in the extending direction X and through which ink flows. The ink is an ink composition for an oil-based ball pen. The ink flow hole 16 is formed at the center of the bottom wall 19 of the ball holding chamber 15. The ink flow groove 17 is a groove portion that communicates with the ink flow hole 16 and extends radially from the ink flow hole 16. A plurality of ink flow grooves 17 are provided in the ball pen tip 11. These plurality of ink flow grooves 17 are provided so as to communicate with the ink flow hole 16 and not communicate with the chip rear hole 18.

[0038] The tip end portion 13 of the ball pen tip 11 has a caulked portion 14 caulked inward. The ball 20 is placed on the ball seat 19a of the ball holding chamber 15, and the tip end portion 13 has the caulked portion 14, so that the ball holding chamber 15 rotatably holds a part of the ball 20 protruding from the tip end portion 13 of the chip. Further, on the inner wall of the tip end portion 13, a seal surface 14c having a substantially arc surface shape, that is, a shape along the outer shape of the ball 20, is formed.

[0039] As described above, the tip end portion 13 of the ball pen tip 11 has a caulked portion 14 caulked inward. The caulked portion 14 is composed of a first caulked portion 14a and a second caulked portion 14b.

[0040] The first caulking part 14a has an inclination angle of 90 degrees or more and less than 100 degrees. The second caulking part 14b is provided on the tip side of the ball pen tip 11 with respect to the first caulking part 14a, and has an inclination angle of 110 degrees or more and 130 degrees or less. When explaining the inclination angle of the first caulking part 14a, it may be referred to as the first inclination angle α. Also, when explaining the inclination angle of the second caulking part 14b, it may be referred to as the second inclination angle β. These inclination angles may be referred to as caulking angles.

[0041] As shown in FIG. 3, the first inclination angle α is an angle formed by a line Lα1 and a line Lα2, which are two lines along the inclined surface of the first caulking part 14a, in a cross section along the extending direction X of the ball pen tip 11. The second inclination angle β is an angle formed by a line Lβ1 and a line Lβ2, which are two lines along the inclined surface of the second caulking part 14b, in a cross section along the extending direction X of the ball pen tip 11.

[0042] Also, the angle γ of the bottom wall 19 of the ball holding chamber 15 is the same angle as the inclination angle (second inclination angle β) of the second caulking part 14b. In the present invention, the same angle means that, considering measurement errors and the like, if it is about ±3 degrees, it is defined as the same angle.

[0043] As shown in FIG. 3, the angle γ of the bottom wall 19 is an angle from one end to the other end of the bottom wall 19 along the outer peripheral direction of the ball 20 in a cross section along the extending direction X of the ball pen tip 11. Specifically, the angle γ of the bottom wall 19 is an angle formed by the line Lγ1 and the line Lγ2. Also, the angle γ is the angle on the ball 20 side (inside the ball holding chamber 15) in the angle formed by the line Lγ1 and the line Lγ2. The line Lγ1 is a straight line passing through one end of the bottom wall 19 along the outer peripheral direction of the ball 20 and the intersection of the bottom wall 19 and the central axis J in a cross section along the extending direction X of the ball pen tip 11. The line Lγ2 is a straight line passing through the other end of the bottom wall 19 along the outer peripheral direction of the ball 20 and the intersection of the bottom wall 19 and the central axis J in the cross section.

[0044] The ball 20 placed on the ball seat 19a is held in a state of being pressed toward the tip of the ball pen tip 11 by the coil spring 21.

[0045] In order to suppress ink leakage, it is preferable to adopt a configuration in which the ball 20 rotatably held at the tip of the ball pen tip 11 is pressed toward the inner wall of the tip portion 13 of the tip by the coil spring 21 directly or via a pressing body. Pressing toward the inner wall of the tip portion 13 of the tip means pressing toward the tip side of the ball pen tip 11. Further, it is preferable to adopt a configuration further provided with a valve mechanism that gives a gap between the inner wall of the tip portion 13 of the tip and the ball 20 by the pressing force during writing to allow the ink to flow out, and closes even a minute gap at the tip of the tip when not in use.

[0046] From the viewpoint of improving writing feel, it is preferable to set the pressing load of the ball 20 by the coil spring 21 to 30 gf or less. In particular, from the viewpoint of making the ball diameter of the ball 20 0.5 mm or less and maintaining higher lubricity even when a load is locally applied between the ball 20 and the ball seat 19a and easily maintaining good writing feel, it is preferable to set the pressing load of the ball 20 by the coil spring 21 to 3 gf or more and 15 gf or less. Further, from the viewpoints of suppressing ink leakage and improving ink followability, it is preferable to set the pressing load of the ball 20 by the coil spring 21 to 5 gf or more and 10 gf or less.

[0047] The arithmetic mean roughness (Ra) of the ball surface of the ball 20 is not limited. For example, the arithmetic mean roughness (Ra) of the ball surface is preferably 0.1 nm or more and 12 nm or less. If the arithmetic mean roughness (Ra) is less than 0.1 nm, it is difficult for the ink to sufficiently adhere to the ball surface, and it is difficult to obtain a thick writing trace during writing, and the writing trace is likely to have breaks and streaks. If the arithmetic mean roughness (Ra) exceeds 12 nm, the ball surface is too rough, and the rotational resistance between the ball 20 and the ball seat 19a is large. For this reason, the writing feel is likely to be inferior, and furthermore, it is likely to affect the writing performance such as streaks, breaks, and uneven lines in the writing trace. Considering more, the arithmetic mean roughness (Ra) of the ball surface is preferably 0.1 nm or more and 10 nm or less, and more preferably 0.5 nm or more and 5 nm or less. The arithmetic mean roughness (Ra) can be obtained with a model name SPI3800N manufactured by Seiko Epson Corporation.

[0048] The material used for the ball 20 is not particularly limited. Examples of the material used for the ball 20 include cemented carbide balls mainly composed of tungsten carbide, metal balls such as stainless steel, ceramic balls such as silicon carbide, silicon nitride, alumina, silica, and zirconia, and ruby balls.

[0049] Examples of the material of the ball pen tip 11 include metal materials such as stainless steel, nickel silver, brass (yellow brass), aluminum bronze, and aluminum, and resin materials such as polycarbonate, polyacetal, and ABS. Among these, considering the wear of the ball seat 19a and the stability over time, it is preferable to use stainless steel as the material of the ball pen tip 11.

[0050] The movement amount of the ball 20 of the ballpoint pen tip 11 in the extending direction X is not limited. For example, the movement amount of the ball 20 in the extending direction X is preferably 3 μm or more and 30 μm or less. If it is less than 3 μm, it is difficult to obtain a thick writing trace and good writing feel. If it exceeds 30 μm, it is likely to affect the ink dripping performance. Considering more, the movement amount of the ball 20 in the extending direction X is preferably 10 μm or more and 25 μm or less. This is because the space for storing ink can be enlarged by the first caulking portion 14a and the second caulking portion 14b. However, if the movement amount of the ball 20 in the extending direction X is less than 10 μm, it is difficult to obtain a thick writing trace and good writing feel.

[0051] In particular, when the ball diameter is relatively small, with a ball diameter of 0.5 mm or less, the ink consumption is likely to be reduced, and it is also likely to affect the writing feel. For this reason, the movement amount of the ball 20 of the ballpoint pen tip 11 in the extending direction X is preferably 12 μm or more and 25 μm or less. Considering more, it is preferably 14 μm or more and 25 μm or less. Setting the movement amount of the ball 20 in the extending direction X within this range is preferable because it is effective even when the ball diameter is 0.4 mm or less, and it is also effective and preferable even when the ball diameter is 0.3 mm or less.

[0052] The ink consumption per 100 m of the ballpoint pen 1 is preferably 20 mg or more and 70 mg or less. If the ink consumption per 100 m is less than 20 mg, it is difficult to obtain a thick writing trace and good writing feel. If the ink consumption per 100 m exceeds 70 mg, it is likely to affect the suppression of ink leakage due to the gap between the ball 20 and the tip end portion 13 of the tip, and furthermore, writing performance and bleeding are likely to occur. Considering more, the ink consumption per 100 m is preferably 20 mg or more and 60 mg or less.

[0053] In particular, when the ball diameter is relatively small, i.e., 0.5 mm or less, the ink consumption tends to be low, and it is likely to affect the writing feel such as writing quality and scratching. Therefore, the ink consumption per 100 m is preferably 20 mg or more and 50 mg or less, and more preferably 20 mg or more and 45 mg or less when considering more factors.

[0054] Also, when the ball diameter is 0.5 mm or less, in order to improve darker handwriting, writing feel, and ink leakage prevention, it is effective to consider not only setting the ink consumption but also the relationship with the ball diameter. Specifically, the ratio of the ball diameter (mm) to the ink consumption (mg) per 100 m of the ball pen 1 (ball diameter: ink consumption) is preferably in the range of 1:40 or more and 1:140 or less. By setting such a relationship different from the conventional one, it is preferable because darker handwriting, writing feel, and ink leakage prevention can be easily obtained. Further considering, the ball diameter: ink consumption is preferably 1:50 or more and 1:130 or less, and more preferably 1:60 or more and 1:120 or less.

[0055] Regarding the ink consumption, a spiral writing test is conducted using 5 test samples at a writing speed of 4 m / min under the conditions of a writing temperature of 20°C, a writing angle of 70° on JIS P3201 writing paper, and a writing load of 200 g. Then, the average value of the ink consumption per 100 m is defined as the ink consumption per 100 m.

[0056] When writing is done using the ball pen 1 of the present embodiment configured as described above, the ink, which is an oil-based ball pen ink composition flowing out from the ink storage cylinder 22, is supplied from the ink flow hole 16 to the ball 20 held in the ball holding chamber 15 via the ink flow groove 17. When ink is supplied to the ball 20, writing with the ink is made on the paper surface or the like.

[0057] As described above, the ballpoint pen 1 of the present embodiment includes a ball seat 19a and a sealing surface 14c. Further, the tip portion 13 of the ballpoint pen chip 11 has a caulked portion 14 caulked inward. The caulked portion 14 is composed of a first caulked portion 14a and a second caulked portion 14b. The first caulked portion 14a has a first inclination angle α of 90 degrees or more and less than 100 degrees. The second caulked portion 14b is provided on the tip side of the ballpoint pen chip 11 with respect to the first caulked portion 14a, and has a second inclination angle β of 110 degrees or more and 130 degrees or less. Further, the angle γ of the bottom wall 19 of the ball holding chamber 15 is the same as the second inclination angle β of the second caulked portion 14b.

[0058] The ballpoint pen 1 of the present embodiment has an effect of smoothly rotating the ball 20 by including the ball seat 19a and the sealing surface 14c. Further, it is considered that the ink flowing from the ink flow hole 16 into the ball holding chamber 15 and the ink (ink return) that does not transfer from the tip portion 13 of the chip to the paper surface but flows from the tip portion 13 of the chip into the ball holding chamber 15 can stabilize the flow of the ink in the ball holding chamber 15. For this reason, even when the ball seat 19a or the sealing surface 14c is worn, an effect of obtaining a stable ink outflow amount can also be achieved.

[0059] Further, when forming the ball seat 19a and the sealing surface 14c, the ball 20 is transferred to the wall surfaces of the same angle of the bottom wall 19 of the ball holding chamber 15 and the inner wall of the second caulked portion 14b. Therefore, even if the curvature changes due to springback after transfer, the curvatures of the obtained transfer surfaces are approximated, and the deviation of the ball 20 can be suppressed. Thus, uneven wear of the ball seat 19a and the sealing surface 14c of the tip portion 13 due to the rotation of the ball 20 can also be suppressed. That is, stable rotation of the ball 20 and stable ink outflow can be obtained.

[0060] Furthermore, in the ballpoint pen 1 of the present embodiment, the first caulking portion 14a at the tip of the tip 13 has a first inclination angle α of an obtuse angle of 90 degrees or more and 100 degrees or less. By setting the first inclination angle α as an obtuse angle, a space for accumulating ink can be increased between the ball 20 and the tip of the tip 13 as compared with the case where the inclination angle (caulking angle) is less than 90 degrees. Therefore, the ink can easily return, the creeping up of the ink can be suppressed, the ink bleeding can be suppressed, and it is easy to improve the thick handwriting, writing feeling, and wear resistance of the ball seat.

[0061] In addition, in the ballpoint pen 1 of the present embodiment, by setting the second inclination angle β of the second caulking portion 14b to 110 degrees or more and 130 degrees or less, the ball holding force can be increased, and the second inclination angle β and the bottom wall 19 of the ball holding chamber 15 can be easily made the same angle.

[0062] Therefore, the ballpoint pen 1 of the present embodiment can realize stable rotation of the ball 20 and stable ink outflow in the ballpoint pen 1 using a small-diameter ball 20 with a ball diameter of 0.5 mm or less.

[0063] In addition, as described above, it is preferable that the pressing load of the ball 20 by the coil spring 21 is 5 gf or more and 10 gf or less. By setting the pressing load of the ball 20 to 5 gf or more and 10 gf or less, it is easy to keep the writing feeling good. Further, by setting the pressing load of the ball 20 within the above range, even when the ball diameter is 0.5 mm or less and a load is locally applied between the ball 20 and the ball seat 19a, higher lubricity can be maintained and the writing feeling can be easily kept good. Considering the writing feeling, it is preferable to set the pressing load of the coil spring 21 to 10 gf or less. Further, considering that it is easy to improve ink leakage prevention and ink followability, it is more preferable that the pressing load of the coil spring 21 is 5 gf or more.

[0064] (Ink composition for oil-based ballpoint pen) Next, the ink composition for oil-based ballpoint pen used in the ballpoint pen 1 of the present embodiment will be described in detail.

[0065] The ink viscosity of the oil-based ballpoint pen ink composition used in the ballpoint pen 1 of the present embodiment is 500 mPa·s or more and 15,000 mPa·s or less at 20°C and a shear rate of 500 sec -1 (during writing).

[0066] When the ink viscosity of the oil-based ballpoint pen ink composition exceeds 15,000 mPa·s, the ball rotation resistance during writing increases, the writing feel tends to be heavy, it is likely to affect the wear suppression of the ball seat, and furthermore, it is likely to affect the writing performance and the ink follow-up performance. For this reason, for the oil-based ballpoint pen ink composition of the ballpoint pen 1, an oil-based ballpoint pen ink composition having an ink viscosity of 15,000 mPa·s or less at 20°C and a shear rate of 500 sec -1 (during writing) is used. Considering further improvement in the writing feel and wear suppression of the ball seat 19a, the ink viscosity is preferably 10,000 mPa·s or less, and considering further improvement in the writing feel and wear suppression of the ball seat, the ink viscosity is preferably 8,000 mPa·s or less. The ink viscosity of the oil-based ballpoint pen ink composition is more preferably 6,000 mPa·s or less. Also, when the ink viscosity at 20°C and a shear rate of 500 sec -1 (during writing) is less than 10 mPa·s, it is likely to affect the wear suppression of the ball seat, bleeding in the handwriting, and ink dripping. For this reason, the ink viscosity of the oil-based ballpoint pen ink composition at 20°C and a shear rate of 500 sec -1 (during writing) is preferably 10 mPa·s or more. Further considering, the ink viscosity of the oil-based ballpoint pen ink composition is preferably 100 mPa·s or more, and further considering the wear suppression of the ball seat, the ink viscosity is preferably 500 mPa·s or more, and further considering, it is preferably 1,000 mPa·s or more, and preferably 2,000 mPa·s or more.

[0067] Here, for the purpose of improving the lubricity between the ball 20 of the ballpoint pen tip 11 and the ball seat 19a, many oil-based ballpoint pen ink compositions using various lubricants have been proposed.

[0068] For example, Document A (Japanese Patent Laid-Open No. 5-331403, "Oil-based ballpoint pen ink") using alkyl β-D-glucoside, Document B (Japanese Patent Laid-Open No. 7-196971, "Ink composition for oil-based ballpoint pen") using polyethylene glycol with an average molecular weight of 200 to 4000000, Document C (Japanese Patent Laid-Open No. 2007-176995, "Oil-based ballpoint pen ink") using N-acyl amino acid, N-acyl methyl tauric acid, and N-acyl methyl alanine, and Document D (Patent No. 3500552, "Oil-based ink composition for ballpoint pen") using phosphate ester, etc. are disclosed.

[0069] However, when using various lubricants such as those in Documents A to D, while the writing feel can be improved to a certain extent and wear of the ball seat 19a can be suppressed, the lubricity is not satisfactory and there is room for improvement. Further, when using a small-diameter ball with a ball diameter of 0.5 mm or less, the smaller the ball diameter, the more the number of rotations of the ball increases when writing the same distance. Also, since a small-diameter ball applies a load to the ball seat 19a, wear of the ball seat 19a becomes severe, which causes writing defects. For this reason, in the prior art, new problems were likely to occur when using a small-diameter ball.

[0070] Also, an ink composition for an oil-based ballpoint pen that improves the writing performance when the tip end portion 13 of the tip is left in the air and the tip end portion 13 dries is desired. In particular, when using a retractable oil-based ballpoint pen such as a knock-type oil-based ballpoint pen or a rotary feed oil-based ballpoint pen, it is important because it easily affects the writing performance.

[0071] The inventor uses, as the ink composition for an oil-based ballpoint pen used in the ballpoint pen 1 of the present embodiment, an ink viscosity that satisfies the above range, and a saturated fatty acid, C l H 2l+1 O-C 2 H 4 O or C m H 2m+1By using an ink composition for an oil-based ballpoint pen containing a phosphate ester having O(l, m = 1 or more and 30 or less), it has been found that lubricity can be improved, wear of the ball seat 19a can be suppressed, writing feel can be improved, and writing performance can be further enhanced.

[0072] Saturated fatty acid, C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 By including a phosphate ester having O(l, m = 1 or more and 30 or less), the lubricating layer formed by the saturated fatty acid and the phosphate ester can improve lubricity and maintain the lubricity between the ball 20 and the tip body 12. Also, it is possible to suppress wear of the ball seat 19a, suppress blurring of the writing, and improve the writing feel. Furthermore, when the tip end portion 13 of the tip is left in the air, it is possible to improve the writing performance when the tip end portion 13 dries.

[0073] (Saturated fatty acid) The saturated fatty acid contained in the ink composition for an oil-based ballpoint pen can maintain the lubricity between the ball 20 and the tip body 12 and suppress wear of the ball seat 19a. Also, by including the saturated fatty acid in the ink composition for an oil-based ballpoint pen, it is possible to suppress blurring of the writing and improve the writing feel. Particularly, even when using a small-diameter ball with a ball diameter of 0.5 mm or less, it is possible to suppress wear of the ball seat 19a, suppress blurring of the writing, and maintain a good writing feel. This is because the saturated fatty acid can adsorb onto the metal surfaces of the ball 20 and the tip body 12 of the ballpoint pen tip 11, thereby suppressing metal contact between the ball 20 and the tip body 12. Therefore, it is possible to suppress wear of the ball seat 19a, suppress blurring of the writing, and improve the writing feel. Furthermore, it is possible to improve the writing performance.

[0074] Examples of saturated fatty acids include branched saturated fatty acids and straight-chain saturated fatty acids. Considering the wear inhibition of the ball seat 19a and the writing feel, branched saturated fatty acids are preferred. By using saturated fatty acids having a branched chain, a bulky structure can be obtained, and the area covering the metal surface increases. For this reason, it becomes easier to adsorb on the metal surfaces of the ball 20 of the ballpoint pen tip 11 and the chip body 12. Therefore, metal contact between the ball 20 and the chip body 12 can be suppressed, wear of the ball seat can be suppressed, and it becomes possible to suppress streakiness of the writing and improve the writing feel.

[0075] Regarding saturated fatty acids, considering lubricity, it is preferable that the number of carbon atoms of the saturated fatty acid is 10 or more and 20 or less. This is because when the number of carbon atoms is 10 or more, it is an alkyl group length suitable for improving the desired lubricity and is likely to adsorb on the metal surface of the ballpoint pen tip. On the other hand, when the number of carbon atoms exceeds 20, the alkyl group is too long, and molecules repel each other, inhibiting adsorption to the metal surface and making it easy to inhibit the improvement of lubricity. Furthermore, considering lubricity more, it is preferable that the number of carbon atoms of the saturated fatty acid is 16 or more and 20 or less, and considering improving wear inhibition of the ball seat 19a more, it is preferable that the number of carbon atoms of the saturated fatty acid is 18 or more and 20 or less.

[0076] Examples of saturated fatty acids include branched saturated fatty acids such as methyl-branched undecanoic acid, methyl-branched dodecanoic acid, methyl-branched tridecanoic acid, methyl-branched tetradecanoic acid, methyl-branched pentadecanoic acid, methyl-branched hexadecanoic acid, methyl-branched heptadecanoic acid, methyl-branched octadecanoic acid (methyl-branched stearic acid), methyl-branched nonadecanoic acid, methyl-branched icosanoic acid, methyl-branched docosanoic acid, and straight-chain saturated fatty acids such as undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid, pentadecanoic acid, hexadecanoic acid, octadecanoic acid (stearic acid), octadecanoic acid, nonadecanoic acid, docosanoic acid.

[0077] Among these, considering suppressing wear of the ball seat 19a, suppressing writing streaks, and improving writing feel, a methyl-branched saturated fatty acid having a chemical structure in which a methyl group is branched from the main chain of a saturated fatty acid is preferable.

[0078] In other words, since the ink composition for an oil-based ballpoint pen contains a methyl-branched saturated fatty acid, the lubricating layer formed by the methyl-branched saturated fatty acid can improve lubricity and maintain the lubricity between the ball 20 and the tip body 12. Further, it is possible to suppress wear of the ball seat 19a, suppress writing streaks, and improve writing feel. Furthermore, when the ballpoint pen tip 11 (tip end portion 13) is left in the air, the writing performance when the ballpoint pen tip 11 (tip end portion 13) is dried can be made good, which is preferable.

[0079] By using a methyl-branched saturated fatty acid, a bulky structure can be formed, and the area covering the metal surfaces of the ball 20 and the tip body 12 of the ballpoint pen tip 11 increases. That is, the methyl-branched saturated fatty acid easily adsorbs to the metal surfaces of the ball 20 and the tip body 12 of the ballpoint pen tip 11, and metal contact between the ball 20 and the tip body 12 of the ballpoint pen tip 11 can be suppressed. For this reason, a friction-reducing action works, and the writing resistance of the ballpoint pen tip 11 can be suppressed. Therefore, it is possible to suppress wear of the ball seat 19a, suppress writing streaks, and improve writing feel. Further, it is also possible to improve writing performance, which is particularly effective.

[0080] Also, as described above, the ball diameter of the ball 20 of the ballpoint pen 1 of the present embodiment is 0.5 mm or less. When using a methyl-branched saturated fatty acid, even when a small-diameter ball with a ball diameter of 0.5 mm or less is used, wear of the ball seat 19a is suppressed, streak marks in writing are suppressed, the writing feel is kept good, and even when a load is locally applied between the ball 20 and the ball seat 19a as in the case of a small-diameter ball, it is easy to maintain lubricity and is effective. Further, since the ball diameter is small, specifically, even when the ball diameter is 0.4 mm or less, and further 0.3 mm or less, the effect is maintained, so the effect is remarkable.

[0081] Regarding the methyl-branched saturated fatty acid, in consideration of lubricity, it is preferable that the number of carbon atoms of the methyl-branched saturated fatty acid is 10 or more and 20 or less. This is because when the number of carbon atoms is 10 or more, it is an alkyl group length suitable for improving the desired lubricity and is likely to adsorb on the metal surface of the ballpoint pen tip 11. On the other hand, when the number of carbon atoms exceeds 20 and the alkyl group becomes longer, the molecules repel each other, which inhibits adsorption on the metal surface and is likely to inhibit the improvement of lubricity. Further, in consideration of more lubricity, it is preferable that the number of carbon atoms of the methyl-branched saturated fatty acid is 16 or more and 20 or less. In consideration of further improving the wear suppression of the ball seat 19a, it is preferable that the number of carbon atoms of the methyl-branched saturated fatty acid is 18 or more and 20 or less.

[0082] Note that it is also possible to use a methyl-branched unsaturated fatty acid instead of, or together with, the methyl-branched saturated fatty acid. In consideration of lubricity, it is preferable to use a methyl-branched saturated fatty acid.

[0083] Specific examples of the methyl-branched saturated fatty acid include methyl-branched undecanoic acid, methyl-branched dodecanoic acid, methyl-branched tridecanoic acid, methyl-branched tetradecanoic acid, methyl-branched pentadecanoic acid, methyl-branched hexadecanoic acid, methyl-branched heptadecanoic acid, methyl-branched octadecanoic acid (methyl-branched stearic acid), methyl-branched nonadecanoic acid, methyl-branched docosanoic acid, and the like.

[0084] Among these, considering suppressing wear of the ball seat 19a, suppressing writing smears, and improving writing feel, methyl-branched hexadecanoic acid, methyl-branched octadecanoic acid (methyl-branched stearic acid), and methyl-branched eicosanoic acid are preferable. Further considering, 16-methyloctadecanoic acid (16-methylstearic acid) is preferable. In particular, when the ball diameter is 0.5 mm or less, even when a load is locally applied between the ball 20 and the ball seat 19a, it is easy to maintain lubricity, so it is effective. Also, when the ball diameter is 0.4 mm or less, it is effective, so it is preferable, and further, when the ball diameter is 0.3 mm or less, it is effective and preferable.

[0085] More specifically, preferable methyl-branched saturated fatty acids include 10-methylundecanoic acid, 10-methyldodecanoic acid, 12-methyltridecanoic acid, 12-methyltetradecanoic acid, 14-methylpentadecane, 14-methylhexadecane, 16-methylheptadecanoic acid, 16-methyloctadecanoic acid (16-methylstearic acid), 10-methylnonadecanoic acid, 10-methylheptadecanoic acid, 10-methylhexadecanoic acid, 10-methylpentadecanoic acid, and the like.

[0086] The content of the saturated fatty acid is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the ink composition for an oil-based ballpoint pen. Considering lubricity more, it is preferably 0.5% by mass or more and 10% by mass or less. Further considering ink stability over time and the like, it is preferably 1% by mass or more and 5% by mass or less. If the content of the saturated fatty acid based on the total amount of the ink composition for an oil-based ballpoint pen is less than 0.1% by mass, there is a possibility that the desired lubricating effect cannot be obtained, and if it exceeds 10% by mass, there is a possibility of affecting the ink stability over time.

[0087] (Phosphate ester) Considering improving the lubricity of the ball pen tip 11 and suppressing writing resistance, the ink composition for an oil-based ballpoint pen preferably contains a phosphate ester.

[0088] Furthermore, considering more the wear suppression of the ball seat 19a and the improvement of writing feel, it is preferable to use a phosphate ester having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (where l, m = 1 or more and 30 or less). By forming a lubricating layer with a phosphate ester having C l H 2l+1 O-C 2 H 4 O (alkoxyethyl group) or C m H 2m+1 O (alkoxyl group), it is easy to improve the lubricity of the ball pen tip 11, suppress the wear of the ball seat 19a, suppress the writing streak, and improve the writing feel. It is particularly effective when used in the oil-based ball pen 1.

[0089] By using a saturated fatty acid and a phosphate ester in combination, a high lubricity that could not be obtained conventionally can be obtained due to the lubricating effect by the interaction of the two-layer lubricating layer formed. In particular, it is preferable to use a methyl-branched saturated fatty acid and a phosphate ester having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (where l, m = 1 to 30). Furthermore, when the ball diameter is 0.5 mm or less and a load is locally applied between the ball 20 and the ball seat 19a, it is effective for maintaining higher lubricity. It is also effective and preferable when the ball diameter is 0.4 mm or less, and it is also effective and preferable when the ball diameter is 0.3 mm or less. Furthermore, it is possible to improve the writing performance.

[0090] Regarding phosphate esters, considering that they are stable in the ink and easily improve lubricity, those represented by general formulas (Chemical Formula 1) and (Chemical Formula 2) are preferred. This is because in the phosphate esters of general formulas (Chemical Formula 1) and (Chemical Formula 2), the O adjacent to P in the structure of general formulas (Chemical Formula 1) and (Chemical Formula 2) adsorbs to the metal ballpoint pen tip body or the ball, and C l H 2l+1 O-C 2 H 4 O (alkoxyethyl group) or C m H 2m+1 O (alkoxyl group) is for forming the lubricating layer. Therefore, it is easy to improve lubricity, suppress wear of the ball seat 19a, suppress writing streaks, and improve writing feel. In particular, considering suppressing wear of the ball seat 19a, it is preferable to use general formula (Chemical Formula 1) having C l H 2l+1 O-C 2 H 4 O (alkoxyethyl group).

[0091]

Chemical Formula

[0092]

Chemical Formula

[0093] Also, among the phosphate esters such as general formulas (Chemical Formula 1) and (Chemical Formula 2), it is preferable that the carbon chains (l, m) of the terminal alkyl groups of C l H 2l+1 O-C 2 H 4 O (alkoxyethyl group), C m H 2m+1 O (alkoxyl group) are specific carbon chains (l, m). This effect is presumed as follows.

[0094] C l H 2l+1 O-C 2 H 4 O, C m H 2m+1The carbon chain (l, m) of the terminal alkyl group of O is preferably 1 or more and 15 or less. C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 When the carbon chain (l, m) of the terminal alkyl group of O exceeds 15, although the writing feel and writing performance are good, the carbon chain becomes too long, and it is difficult to obtain wear suppression of the ball seat 19a. This is because the carbon chains are easily entangled with each other, the orientation of the carbon chain arrangement becomes random and does not become an aligned arrangement, so that a lubricating layer with sufficient lubricity cannot be obtained, and it is difficult to obtain wear suppression of the ball seat 19a. Furthermore, when the carbon chain (l, m) of the terminal alkyl group exceeds 15, the polarity of the terminal alkyl group tends to shift to the low-polarity side, so that the affinity for a polar organic solvent is poor, and the dissolution stability is easily affected. In particular, the glycol ether solvent is likely to be affected, and problems are likely to occur in the dissolution stability in the ink. For this reason, due to the influence of metal ions and the like in the metal tip during long-term storage, metal salt precipitates are likely to occur, the ink stability over time is likely to be poor, and it is difficult to obtain a lubricating effect like the present invention. Therefore, the carbon chain (l, m) of the terminal alkyl group is preferably 1 or more and 15 or less. Considering more, the carbon chain (l, m) of the terminal alkyl group is preferably 1 or more and 10 or less. Considering more the wear suppression of the ball seat 19a and the suppression of the writing streak, the carbon chain (l, m) of the terminal alkyl group is preferably 1 or more and 5 or less.

[0095] On the one hand, when the carbon chain (l, m) of the terminal alkyl group is 3 or less, although the wear of the ball seat 19a is well suppressed, in the ink, a lubricating layer with a sufficient thickness of the alkyl group cannot be obtained. For this reason, the lubricating layer between the ball 20 and the ball seat 19a has insufficient cushioning properties, which easily affects the writing feel, writing performance, and wear suppression of the ball seat 19a. Therefore, by using butoxyethyl acid phosphate (l = 4) having a butyl group (carbon chain of the terminal alkyl group: 4), butyl acid phosphate (m = 4), etc., the wear of the ball seat 19a can be suppressed, and the effects of improving the writing feel and writing performance can be easily obtained, which is preferable. Particularly, butyl acid phosphate having a butoxyethyl group (C 4 H 9 OCH 2 CH 2 O, carbon chain of the terminal alkyl group 4) is preferable. Particularly, when the ball diameter is 0.5 mm or less, even when a load is locally applied between the ball 20 and the ball seat 19a, it is easy to maintain lubricity, so it is effective and preferable for suppressing the wear of the ball seat 19a. Even when the ball diameter is 0.4 mm or less, it is effective and preferable, and even when it is 0.3 mm or less, it is effective and preferable.

[0096] Furthermore, for phosphate esters such as general formula (Chemical Formula 1) and (Chemical Formula 2), examples include monoester of phosphate ester (n = 1 in Chemical Formula 1 and Chemical Formula 2), diester of phosphate ester (n = 2 in Chemical Formula 1 and Chemical Formula 2), triester of phosphate ester (n = 3 in Chemical Formula 1 and Chemical Formula 2), and mixtures thereof. Among them, considering the suppression of wear of the ball seat 19a and the writing feel, it is preferable to use a mixture of monoester of phosphate ester (n = 1 in Chemical Formula 1 and Chemical Formula 2) and diester of phosphate ester (n = 2 in Chemical Formula 1 and Chemical Formula 2). This is because for the triester of phosphate ester (n = 3 in Chemical Formula 1 and Chemical Formula 2), C l H 2l+1 O-C 2 H 4 O (alkoxyethyl group), C m H 2m+1This is because if there are too many O(alkoxyl groups), it is likely to affect the stability of the ink over time.

[0097] Furthermore, considering suppressing the wear of the ball seat 19a, it is preferable to mix a monoester of a phosphoric acid ester and a diester of a phosphoric acid ester. Regarding the mixing ratio in that case, for the diester of the phosphoric acid ester (n = 2 in Chemical Formula 1 and Chemical Formula 2), C l H 2l+1 O-C 2 H 4 O(alkoxyethyl group) and C m H 2m+1 Since there are many O(alkoxyl groups), it acts favorably on lubricity. Furthermore, since the stability of the ink over time can also be maintained, it is preferable that there be more of the diester of the phosphoric acid ester. Therefore, the mixing ratio of the monoester of the phosphoric acid ester and the diester of the phosphoric acid ester is preferably in the range of 1:1 or more and 1:5 or less, and further considering, the range of 1:1 or more and 1:3 or less is preferable.

[0098] Also, as specific examples of the phosphoric acid ester such as in General Formula (Chemical Formula 1) and (Chemical Formula 2), General Formula (Chemical Formula 1) includes butoxyethyl acid phosphate (l = 4), etc. (Chemical Formula 2) includes methyl acid phosphate (m = 1), ethyl acid phosphate (m = 2), butyl acid phosphate (m = 4), 2-ethylhexyl acid phosphate (m = 8), isodecyl acid phosphate (m = 10), lauryl acid phosphate (m = 12), alkyl (m = 12, 14, 16, 18) acid phosphate, isotridecyl acid phosphate (m = 13), oleyl acid phosphate (m = 18), tetracosyl acid phosphate (m = 24), etc.

[0099] Also, the C l H 2l+1 O-C 2 H 4 O or C m H 2m+1The content of the phosphate ester having O(l, m = 1 or more and 30 or less) is more preferably 0.1% by mass or more and 10% by mass or less with respect to the total amount of the ink composition for an oil-based ballpoint pen. This is because when it is less than 0.1% by mass, it tends to be difficult to obtain the desired lubricity, and when it exceeds 10% by mass, the ink tends to become unstable over time. Considering these tendencies, 0.1% by mass or more and 5% by mass or less is preferable, and further considering, 0.3% by mass or more and 3% by mass or less is preferable.

[0100] Let X be the total content of the saturated fatty acid with respect to the total amount of the ink composition for an oil-based ballpoint pen, and Y be the content of the phosphate ester having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O(l, m = 1 or more and 30 or less) with respect to the total amount of the ink composition. In this case, considering the wear suppression of the ball seat 19a and the improvement of the writing feeling, the relationship of 0.1 ≦ X / Y ≦ 5 is preferable, and further considering, 0.3 ≦ X / Y ≦ 3 is preferable, and furthermore, the relationship of 0.5 ≦ X / Y ≦ 2 is preferable.

[0101] (organic amine) Also, the saturated fatty acid, the C l H 2l+1 O-C 2 H 4 O or C m H 2m+1When using a phosphate ester having O(l, m = 1 or more and 30 or less), it is preferable to use an organic amine. This is because the saturated fatty acid and the phosphate ester can be dissolved and stabilized in the ink by neutralizing them with an organic amine. Therefore, the effects of the saturated fatty acid and the phosphate ester can be easily obtained, and the stability over time of other ink components such as the colorant can be easily improved. Considering the stability of the organic amine, the saturated fatty acid, the phosphate ester, and the colorant, it is preferable to use a secondary amine or a tertiary amine. This is because, regarding the reactivity in the oil-based ink, the primary amine has the strongest reactivity, followed by the secondary amine and the tertiary amine with decreasing reactivity. The primary amine easily reacts with the phosphate ester, the saturated fatty acid, the colorant, and other components, and is likely to affect the ink stability over time. Therefore, it is preferable to use a secondary amine or a tertiary amine, and more preferably a tertiary amine in consideration.

[0102] Also, specifically for the organic amine, examples include amines having ethylene oxide such as oxyethylene alkylamine and polyoxyethylene alkylamine, alkylamines such as laurylamine and stearylamine, and aliphatic amines such as distearylamine, dimethyllaurylamine, dimethylstearylamine, and dimethyloctylamine. Among these, considering the stability in the ink, amines having ethylene oxide and dimethylalkylamines are preferable, and more preferably amines having ethylene oxide.

[0103] Furthermore, considering the stability with the phosphate ester, the saturated fatty acid, the colorant, and other components, the total amine value of the organic amine is preferably 100 (mgKOH / g) or more and 300 (mgKOH / g) or less. If it exceeds 300 (mgKOH / g), the reactivity is strong and it easily reacts with the above components, so the ink stability over time is likely to be poor. Also, if the total amine value is less than 100 (mgKOH / g), the saturated fatty acid in the ink, C l H 2l+1 O-C 2 H4 O or C m H 2m+1 It is likely to affect the stability of the phosphate ester having O (l, m = 1 or more and 30 or less). When applied to the ballpoint pen 1, the adsorbability of metals such as the ball 20 and the chip body 12 is likely to be poor, and it is difficult to obtain lubricating performance. Considering the stability and lubricity with the above components, a range of 150 (mgKOH / g) or more and 300 (mgKOH / g) or less is preferable. Considering more stability, 200 (mgKOH / g) or more and 300 (mgKOH / g) or less is preferable. Considering most, 230 (mgKOH / g) or more and 270 (mgKOH / g) or less is preferable.

[0104] Note that the total amine value indicates the total amount of primary, secondary, and tertiary amines, and is expressed by the number of mg of potassium hydroxide equivalent to the hydrochloric acid required to neutralize 1 g of the sample.

[0105] Examples of the organic amine include oxyethylene alkylamine and polyoxyethylene alkylamine. Specific examples of the oxyethylene alkylamine and polyoxyethylene alkylamine include Naimine L-201 (total amine value: 232 - 246, secondary amine), L-202 (total amine value: 192 - 212, tertiary amine), L-207 (total amine value: 107 - 119, tertiary amine), S-202 (total amine value: 152 - 166, tertiary amine), S-204 (total amine value: 120 - 134, tertiary amine), S-210 (total amine value: 75 - 85, tertiary amine), DT-203 (total amine value: 227 - 247, tertiary amine), DT-208 (total amine value: 146 - 180, tertiary amine) (manufactured by NOF Corporation), etc. Specific examples of the alkylamine include Farmin 80 (total amine value: 204 - 210, primary amine), Farmin D86 (total amine value: 110 - 119, secondary amine), Farmin DM2098 (total amine value: 254 - 265, tertiary amine), Farmin DM8680 (total amine value: 186 - 197, tertiary amine) (manufactured by Kao Corporation), Nissan Tertiary Amine BB (total amine value: 243 - 263, tertiary amine), FB (total amine value: 230 - 250, tertiary amine) (manufactured by NOF Corporation), etc. These may be used alone or in combination of two or more.

[0106] Considering the stability with the saturated fatty acid, the phosphate ester, the colorant and other components, the content of the organic amine is preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the oil-based ballpoint pen ink composition. Further considering the neutralization with the surfactant to be described later, it is preferably 0.5% by mass or more and 5% by mass or less.

[0107] Let A be the total content of the phosphate ester and the saturated fatty acid based on the total amount of the ink composition, and B be the content of the organic amine based on the total amount of the ink composition. In this case, considering the ink stability over time due to neutralization, the relationship of 0.01 ≦ A / B ≦ 5 is preferably satisfied. More preferably, 0.1 ≦ A / B ≦ 3, and further preferably, 0.1 < A / B < 1.

[0108] (Colorant) The colorant used in the ink composition for the oil-based ballpoint pen of this embodiment is not particularly limited, such as dyes and pigments, and can be appropriately selected and used. Dyes and pigments may be used in combination. Examples of dyes include oil-soluble dyes, acid dyes, basic dyes, metal-containing dyes, etc., and various salt-forming types of dyes thereof, such as salt-forming dyes of acid dyes and basic dyes, salt-forming dyes of basic dyes and organic acids, and salt-forming dyes of acid dyes and organic amines. These dyes may be used alone or in combination of two or more.

[0109] Regarding dyes, specifically, Valifast Black 1802, Valifast Black 1805, Valifast Black 1807, Valifast Violet 1701, Valifast Violet 1704, Valifast Violet 1705, Valifast Blue 1601, Valifast Blue 1605, Valifast Blue 1613, Valifast Blue 1621, Valifast Blue 1631, Valifast Red 1320, Valifast Red 1355, Valifast Red 1360, Valifast Yellow 1101, Valifast Yellow 1151, Nigrosine Base EXBP, Nigrosine Base EX, BASE OF BASIC DYES ROB-B, BASE OF BASIC DYES RO6G-B, BASE OF BASIC DYES VPB-B, BASE OF BASIC DYES VB-B, BASE OF BASIC DYES MVB-3 (above, manufactured by Orient Chemical Industries, Ltd.), Eisenspirone Black GMH-Special, Eisenspirone Violet C-RH, Eisenspirone Blue GNH, Eisenspirone Blue 2BNH, Eisenspirone Blue C-RH, Eisenspirone Red C-GH, Eisenspirone Red C-BH, Eisenspirone Yellow C-GNH, Eisenspirone Yellow C-2GH, S.P.T. Blue 111, S.P.T. Blue GLSH-Special, S.P.T. Red 533, S.P.T. Orange 6, S.B.N. Yellow 510, S.B.N. Yellow 530, S.R.C-BH (above, manufactured by Hodogaya Chemical Co., Ltd.), etc. can be mentioned.

[0110] Furthermore, as the colorant, considering the stability over time due to the compatibility with saturated fatty acids and phosphate esters, it is preferable to use at least salt-forming dyes. Considering that the stability over time can be maintained due to the stable salt-forming bond, it is preferable to use salt-forming dyes of basic dyes and organic acids, salt-forming dyes of basic dyes and acid dyes, and salt-forming dyes of acid dyes and organic amines.

[0111] Upon further consideration, it is preferable to use salt-forming dyes composed of basic dyes and organic acids, and salt-forming dyes composed of acidic dyes and organic amines. Moreover, upon further consideration, it is preferable to use salt-forming dyes having an azo-based skeletal dye, salt-forming dyes having a xanthene-based dye, and salt-forming dyes having an aromatic amine among them. Among these, since the influence on saturated fatty acids and phosphate esters is less likely to occur due to stable binding, it is preferable to use salt-forming dyes composed of azo-based basic dyes and organic acids, and salt-forming dyes composed of acidic dyes and aromatic amines.

[0112] Regarding the organic acid of the salt-forming dye composed of a basic dye and an organic acid, if it is an organic acid having a phenylsulfone group, it is easy to form a lubricating film that is easily adsorbed to the metal, improves lubricity, and makes the writing feel and wear suppression of the ball seat good, so it is preferable. Furthermore, considering long-term stability in the ink, it is preferable to use alkylbenzene sulfonic acid as the organic acid.

[0113] Also, regarding acidic dyes and organic amines, in order to improve lubricity and have good light resistance, acidic gold-containing dyes containing Cu, Cr, Fe, and Co are preferable, and it is preferable to use salt-forming dyes composed of acidic gold-containing dyes and organic amines. In order to stabilize the acidic gold-containing dye in the oil-based ink, among the organic amines, it is preferable to carry out a neutralization reaction with an amine having an aromatic ring to form a salt-forming dye.

[0114] Regarding the acidic gold-containing dye, considering good stability over time in the ink, it is preferable to use an acidic gold-containing dye containing Cu. Furthermore, there are phthalocyanine-based, azo-based, etc., among which it is preferable to use a copper phthalocyanine-based acidic dye. Furthermore, examples of those having a sulfo group (-SO 3 H) or a carboxyl group (-COOH) in the structure of the acidic gold-containing dye can be mentioned. Considering further improvement in lubricity, an acidic gold-containing dye having a sulfo group (-SO 3 H) is preferable. This is because the sulfo group (-SO 3When it has (H), it is considered that a strong lubricating layer is easily formed between the ball 20 and the ball seat 19a, and thus the lubricity is likely to be improved. Also, it is considered that a synergistic lubricating effect can be obtained by using it in combination with an amine having an aromatic ring.

[0115] Also, examples of the pigment include inorganic, organic, and processed pigments. Specifically, carbon black, aniline black, ultramarine, lead yellow, titanium oxide, iron oxide, phthalocyanine-based, azo-based, quinacridone-based, diketopyrrolopyrrole-based, quinophthalone-based, perylene-based, triphenylmethane-based, perinone-based, perylene-based, dioxazine-based, metallic pigments, pearl pigments, fluorescent pigments, phosphorescent pigments, and the like.

[0116] As the colorant, considering lubricity, it is preferable to use a pigment. This is because by using pigment particles, the pigment particles enter the gap between the ball 20 and the chip body 12, and the action like a bearing easily works. For this reason, metal contact can be suppressed, lubricity can be improved, writing feel can be improved, and the effect of suppressing wear of the ball seat 19a can be easily obtained. In particular, due to the synergistic effect of the bearing action between the lubricating layer formed by a phosphate ester having saturated fatty acid, C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 or more and 30 or less) and the pigment particles, it becomes easy to maintain lubricity. For this reason, it is possible to suppress wear of the ball seat 19a and improve the writing feel. Also, considering the gap relationship inside the ballpoint pen tip 11, the average particle diameter is preferably 1 nm or more and 500 nm or less. More preferably, it is 30 nm or more and 350 nm or less, and still more preferably, it is 50 nm or more and 300 nm or less. The average particle diameter can be determined by the particle diameter (D50) at 50% volume cumulative of the particle size distribution measured based on the numerical values calibrated using a standard sample and other measurement methods using a laser diffraction method, specifically, a laser diffraction type particle size distribution measuring machine (trade name "Microtrac HRA9320-X100", Nikkiso Co., Ltd.).

[0117] Furthermore, in order for the pigment to exhibit the above-described effects in the ink composition for an oil-based ballpoint pen in terms of the dispersion state of the pigment, it is preferable to determine the particle diameter in the dispersion state. Further, the pigment is preferably excellent in water resistance and light resistance and can provide good color development.

[0118] As for the type of pigment, considering the lubricity due to the compatibility with a phosphate ester having a saturated fatty acid, C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 or more and 30 or less), it is preferable to use from among carbon black, quinacridone-based, perylene-based, and diketopyrrolopyrrole-based pigments. Further, considering the ink stability over time due to the compatibility over time, it is preferable to use a diketopyrrolopyrrole-based pigment.

[0119] The content of the colorant is preferably 5% by mass or more and 30% by mass or less with respect to the total amount of the ink composition for an oil-based ballpoint pen. This is because if it is less than 5% by mass, it tends to be difficult to obtain a dark handwriting, and if it exceeds 30% by mass, it tends to affect the solubility in the ink. Considering this tendency more, it is preferably 7% by mass or more and 25% by mass or less, and further considering it, it is 10% by mass or more and 20% by mass or less.

[0120] (Organic solvent) Examples of the organic solvents used in the ink composition for an oil-based ballpoint pen of the present embodiment include glycol ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol dimethyl ether, ethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol dimethyl ether, 3-methoxybutanol, and 3-methoxy-3-methylbutanol; glycol solvents such as diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, and ethylene glycol; alcohol solvents such as benzyl alcohol, methanol, ethanol, 1-propanol, 2-propanol, isopropanol, isobutanol, t-butanol, propargyl alcohol, allyl alcohol, 3-methyl-1-butyn-3-ol, ethylene glycol monomethyl ether acetate, and other higher alcohols, and organic solvents generally used as inks for writing instruments can be exemplified.

[0121] Among these organic solvents, considering the solubility with the saturated fatty acid or the phosphate ester having C l H 2l+1 O-C 2 H 4 O or the C m H 2m+1 O (l, m = 1 or more and 30 or less), it is preferable to use a glycol ether solvent because the effect of improving lubricity can be easily obtained. This is because the affinity of the glycol ether solvent with the saturated fatty acid or the phosphate ester having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 or more and 30 or less) tends to be good, and dissolution is stable. Therefore, the ink tends to be stable over time even during long-term storage.

[0122] Furthermore, when using a glycol ether solvent, since it is prone to moisture absorption, it softens the strength of the film formed when the tip 13 of the chip dries, and it is also easy to improve the writing performance. Therefore, it is more effective when used in combination with a surfactant described later, and considering the stability in the ink, it is preferable to use an aromatic glycol ether solvent.

[0123] Regarding organic solvents other than glycol ether solvents, it is preferable to use an alcohol solvent. This is because the alcohol solvent volatilizes, making it easier to dry at the tip 13 of the chip. Therefore, it is possible to thicken the inside of the writing tip (inside the tip 13 of the chip) more quickly, suppress ink leakage from the gap of the writing tip, and improve the ink leakage suppression performance, which is preferable. Furthermore, aromatic alcohols such as benzyl alcohol also have the effect of improving lubricity, so it is preferably used at least. Therefore, it is preferable to use a glycol ether solvent and an alcohol solvent in combination.

[0124] Also, considering improving solubility, writing trace dryness, bleeding, etc., the content of the organic solvent is preferably 10% by mass or more and 70% by mass or less based on the total amount of the oil-based ballpoint pen ink composition. Also, considering the dryness at the tip 13 of the chip, the content of the alcohol solvent is preferably 30% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 90% by mass or less, based on the total organic solvent.

[0125] (Resin) In the present invention, a resin may be used as the viscosity modifier. Specific examples of the viscosity modifier include polyvinyl butyral resin, polyacetal resin, polyvinyl alcohol resin, cellulose resin, polyvinyl pyrrolidone resin, ketone resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, and the like.

[0126] Among these, ketone resins are preferred because they can suppress the wear of the ball seat 19a and facilitate the suppression of writing streaks. In particular, they have good compatibility with the saturated fatty acid and the phosphate ester, and by synergistically improving the lubricity without inhibiting the lubricity which is a feature of the present invention, it is easier to suppress the wear of the ball seat 19a, so it is preferred.

[0127] Among ketone resins, it is preferable to use a ketone resin having a cyclic structure such as an aromatic ring skeleton (such as a phenyl group, an acetophenone group, a naphthalene group having a benzene ring) or a cyclohexane skeleton (such as a cyclohexane group, a cyclohexanone group having a cyclohexane ring). This is because a cushioning effect can be obtained by the ketone resin having a cyclic structure, the lubricity is improved, the wear of the ball seat 19a is suppressed, and it is easy to suppress writing streaks. More preferably, a ketone resin having an aromatic ring has a large number of double bond structures, so it is easier to obtain a stronger cushioning effect and is effective for lubricity, so it is preferred. Furthermore, for the ketone resin, it is preferable that the hydroxyl value is 100 (mgKOH / g) or more. This is because when it is 100 (mgKOH / g) or more, it is easily soluble in organic solvents such as alcohol solvents and glycol solvents. Therefore, the effect of suppressing the wear of the ball seat 19a due to the interaction by using it in combination with the methyl-branched fatty acid and the phosphate ester can be easily obtained. Considering more the suppression of the wear of the ball seat 19a, it is preferable that the hydroxyl value is 200 (mgKOH / g) or more, and considering further, it is preferable that the hydroxyl value of the ketone resin is 300 (mgKOH / g) or more. In particular, when the ball diameter is 0.5 mm or less and a load is locally applied between the ball 20 and the ball seat 19a, it is preferable because it is easy to maintain lubricity and is effective for suppressing the wear of the ball seat 19a. Also, when the ball diameter is 0.4 mm or less, it is effective and thus preferable, and further when the ball diameter is 0.3 mm or less, it is effective and preferable.

[0128] Also, while it is possible to easily suppress the wear of the ball seat 19a, it is difficult to sufficiently improve the writing feel. Therefore, it is preferable to use a polyvinyl butyral resin in combination.

[0129] Regarding the polyvinyl butyral resin, by using it in combination with the saturated fatty acid and the phosphate ester, it is easy to form a lubricating layer that provides a higher lubricating effect. Therefore, an elastic ink layer can always be formed between the ball 20 and the ball seat 19a, making it difficult for them to come into direct contact, and it is easy to improve the writing feel. Furthermore, when the polyvinyl butyral resin is used, the formed film makes it easier to improve ink leakage, which is preferable. Also, when a pigment is used as the colorant, a pigment dispersion effect can be obtained, so it is preferable to use the polyvinyl butyral resin.

[0130] Here, the polyvinyl butyral resin is obtained by reacting polyvinyl alcohol (PVA) with butyraldehyde (BA), and has a structure having butyral groups, acetyl groups, and hydroxyl groups.

[0131] Also, the polyvinyl butyral resin preferably has a hydroxyl group content of 25 mol% or more. This is because a polyvinyl butyral resin with a hydroxyl group content of less than 25 mol% has insufficient solubility in organic solvents, and it is difficult to obtain a sufficient writing feel improvement effect and an ink leakage suppression effect. Furthermore, considering the writing performance due to hygroscopicity, it is preferable to use a polyvinyl butyral resin with a hydroxyl group content of 25 mol% or more. Also, the polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more is preferable because the writing feel is likely to be improved. This is because during writing, frictional heat is generated by the rotation of the ball 20, warming the ink at the tip of the chip 13 and increasing the temperature of the ink. Different from other resins, the polyvinyl butyral resin has the property of making it difficult to lower the ink viscosity even when the ink temperature rises. Therefore, an ink layer with elasticity can always be formed between the ball 20 and the ball seat 19a, making it difficult for them to come into direct contact, and the writing feel can be improved. Also, when using a polyvinyl butyral resin with a hydroxyl group content exceeding 40 mol%, the amount of moisture absorption tends to increase, and it is likely to affect the stability over time with the ink components. For this reason, a polyvinyl butyral resin with a hydroxyl group content of 40 mol% or less is preferable. Also, a polyvinyl butyral resin with a hydroxyl group content of 30 mol% or more and 40 mol% is preferable, and more preferably, a hydroxyl group content of 30 mol% or more and 36 mol% or less is preferable.

[0132] Note that the hydroxyl group content (mol%) of the polyvinyl butyral resin indicates the content rate of hydroxyl groups (mol%) with respect to the total mol amount of butyral groups (mol%), acetyl groups (mol%), and hydroxyl groups (mol%).

[0133] Also, regarding the average degree of polymerization of the polyvinyl butyral resin, when the average degree of polymerization is 200 or more, the ink leakage suppression performance is likely to improve. When the average degree of polymerization exceeds 2500, the ink viscosity becomes too high and tends to affect the writing feel. Therefore, the average degree of polymerization is preferably 200 or more and 2500 or less. Further, considering the writing feel and ink leakage suppression more, the average degree of polymerization is preferably 1500 or less, and more preferably 1000 or less. The average degree of polymerization refers to the number of basic units constituting one molecule of the polyvinyl butyral resin, and a value measured based on the method specified in JIS K6728 (2001 edition) can be adopted.

[0134] Also, when the ketone resin and the polyvinyl butyral resin are used in combination, let the content of the ketone resin with respect to the total amount of the ink composition be C, and the content of the polyvinyl butyral resin with respect to the total amount of the ink composition be D. In this case, considering suppressing the wear of the ball seat 19a, suppressing the streak of the handwriting, and easily improving the writing feel and ink leakage suppression in a well-balanced manner, the relationship of 0.1 ≦ C / D ≦ 10 is preferable. Considering more, 0.5 ≦ C / D ≦ 7 is preferable, and further, the relationship of 1.5 ≦ C / D ≦ 5 is preferable.

[0135] If the total content of the resin is less than 1% by mass with respect to the total amount of the oil-based ballpoint pen ink composition, the desired writing feel, wear suppression of the ball seat, and ink leakage suppression performance are likely to be inferior. If it exceeds 40% by mass, the solubility in the ink is likely to be inferior. Therefore, with respect to the total amount of the oil-based ballpoint pen ink composition, 1% by mass or more and 40% by mass or less is preferable. Further, considering more, 5% by mass or more is preferable. If it exceeds 30% by mass, the ink viscosity becomes too high and tends to affect the writing feel, so 5% by mass or more and 30% by mass or less is preferable.

[0136] Resins other than ketone resin and polyvinyl butyral resin may be appropriately used with a drawability-imparting agent. In particular, by blending polyvinyl pyrrolidone resin, the binding property of the ink can be enhanced, and the generation of excess ink at the tip of the chip can be easily suppressed. For this reason, it is preferable to contain polyvinyl pyrrolidone resin. If the content of the polyvinyl pyrrolidone resin is less than 0.01% by mass based on the total amount of the oil-based ballpoint pen ink composition, it tends to be difficult to suppress the generation of excess ink. Also, if it exceeds 3.0% by mass, the solubility in the ink tends to be poor. For this reason, 0.01% by mass or more and 3.0% by mass or less is preferable based on the total amount of the oil-based ballpoint pen ink composition. Considering the above reasons, 0.1% by mass or more and 2.0% by mass or less is preferable. Specifically, product names such as PVP K-15, PVP K-30, PVP K-90, and PVP K-120 manufactured by ISP Japan Co., Ltd. can be mentioned. These may be used alone or in combination of two or more.

[0137] (Surfactant) In the present invention, as the above lubricity, considering suppressing the wear of the ball seat 19a, suppressing the writing streak, improving the writing feeling, and the writing performance when the tip of the chip is dried in a state where the tip of the chip is left in the air, it is preferable to use a surfactant. This is because when a surfactant is used, the formed film tends to be softened, the writing performance can be improved, and the lubricity can also be improved. Examples of the surfactant include unsaturated fatty acids, silicone-based surfactants, fluorine-based surfactants, and phosphate ester-based surfactants (excluding phosphate esters having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 or more and 30 or less)).

[0138] Among these, considering the above effects, unsaturated fatty acids, silicone-based surfactants, and phosphate ester-based surfactants (C l H 2l+1 O-C 2 H 4O or C m H 2m+1 (excluding phosphate esters having O (l, m = 1 or more and 30 or less)), it is preferable to use one or more thereof, and more preferably two or more thereof.

[0139] In particular, regarding the phosphate ester used in the present invention, the phosphate ester-based surfactant (C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 (excluding phosphate esters having O (l, m = 1 or more and 30 or less)) has phosphoric acid as the same skeleton, so it has good compatibility and is likely to obtain a synergistic lubricating effect. For this reason, it is preferable to use a phosphate ester-based surfactant. By using a phosphate ester and a phosphate ester-based surfactant (C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 (excluding phosphate esters having O (l, m = 1 or more and 30 or less)) in combination, the lubricating layer of the phosphate ester and the lubricating layer of the phosphate ester-based surfactant interact with each other. Due to this interaction, a lubricating layer having higher lubricity can be formed. For this reason, it is presumed that it has the effect of maintaining lubricity, suppressing wear of the ball seat 19a, suppressing writing streaks, and easily improving writing feel.

[0140] Furthermore, the phosphate ester-based surfactant (C l H 2l+1 O-C 2 H 4 O or C m H 2m+1When using (excluding phosphate esters having O(l, m = 1 or more and 30 or less)), the acid value is preferably 160 (mgKOH / g) or less. This is to facilitate the improvement of lubricity by the phosphate ester surfactant. Further considering the stability and lubricity in the ink, the acid value is preferably 30 (mgKOH / g) or more and 160 (mgKOH / g) or less. More preferably, the acid value is 70 (mgKOH / g) or more and 120 (mgKOH / g) or less.

[0141] Note that the acid value is represented by the number of mg of potassium hydroxide required to neutralize the acidic components contained in 1 g of the sample.

[0142] Furthermore, when using the above-mentioned saturated fatty acid, ketone resin, and polyvinyl butyral resin, it is more preferable because it is easier to improve lubricity.

[0143] Regarding the surfactant, considering the improvement of both lubricity and writing performance, the HLB value is preferably 6 or more and 14 or less. This is because when the HLB value exceeds 14, the hydrophilicity tends to increase, the solubility in the oil-based ink tends to be poor, the effect of the surfactant is difficult to obtain, and the lubricating effect is difficult to obtain. Also, when the HLB value is less than 6, the lipophilicity becomes too strong, which easily affects the compatibility with the organic solvent, the ink stability over time is poor, and the writing performance is difficult to improve. Further considering lubricity, the HLB value is preferably 12 or less, preferably 6 or more and 12 or less. Considering writing performance more, the HLB value is preferably 7 or more and 12 or less.

[0144] Incidentally, the HLB value can be determined by the Griffin method, Kawakami method, etc. As an example, it can be determined from the general formula HLB = 7 + 11.7 log (Mw / Mo) (Mw: molecular weight of hydrophilic group, Mo: molecular weight of lipophilic group). In particular, in retractable writing instruments such as knock-type writing instruments and rotary retractable writing instruments, unlike cap-type writing instruments, the pen tip is always exposed to the outside, so it is likely to affect the writing performance during drying at the writing tip. Therefore, it is more preferable to use a surfactant having the above HLB value.

[0145] Specific examples of the surfactant include, as unsaturated fatty acids, oleic acid, linoleic acid, etc. Examples of silicone-based surfactants include dimethyl silicone, methylphenyl silicone, polyether-modified silicone, higher fatty acid ester-modified silicone, etc. Examples of fluorine-based surfactants include perfluoro group butyl sulfonate, perfluoro group-containing carboxylate, perfluoro group-containing phosphate ester, perfluoro group-containing phosphate ester type compound, perfluoroalkyl betaine, perfluoroalkylamine oxide compound, etc.

[0146] Phosphate ester-based surfactants (excluding phosphates having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 to 30)) include mono-phosphates of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, di-phosphates of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, tri-phosphates of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether, alkyl phosphate esters, alkyl ether phosphate esters, or their derivatives, etc.

[0147] The content of the surfactant is more preferably 0.1% by mass or more and 5.0% by mass or less based on the total amount of the ink composition for an oil-based ballpoint pen. This is because if it is less than 0.1% by mass, it tends to be difficult to obtain the desired lubricity, and if it exceeds 5.0% by mass, the ink tends to become unstable over time. Considering these tendencies, it is preferably 0.3% by mass or more and 3.0% by mass or less based on the total amount of the ink composition for an oil-based ballpoint pen. Further considering, 0.5% by mass to 3.0% by mass is most preferable.

[0148] (Fatty acid ester) In the present invention, considering improving the above lubricity and the writing performance when the tip end portion 13 of the chip dries in a state where the tip end portion 13 of the chip is left in the air, it is preferable to use a fatty acid ester. By softening the film strength formed at the time of ink drying at the tip end portion 13 with the fatty acid ester, it is easy to improve the writing performance. Furthermore, since it is easy to improve the lubricity, it is preferable because it suppresses the wear of the ball seat 19a, suppresses the streak of the handwriting, and easily improves all of the writing feel and the writing performance. Therefore, by using a phosphate ester having C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 O (l, m = 1 to 30) and a fatty acid ester in combination, it is easy to obtain high lubricity that could not be obtained conventionally due to the lubricating effect by the interaction with the formed lubricating layer. That is, it is preferable because it is easy to improve the wear suppression of the ball seat 19a, the writing feel, and the writing performance in a well-balanced manner.

[0149] A fatty acid ester is obtained by subjecting a fatty acid and an alcohol such as a monohydric alcohol or a polyhydric alcohol to an esterification reaction. Among the fatty acid esters, in consideration of further improving the writing performance, it is preferable to use a fatty acid ester having a branched alkyl group. This is because a fatty acid ester having a branched alkyl group has a bulkier structure than a linear structure. Due to the bulkiness of the branched alkyl group, when adsorbed on the surface of a metal ball or the ball seat of the chip body, a thick lubricating film is formed, and the lubricity is more likely to be improved. At the same time, due to the bulkiness of the branched alkyl group, the film strength formed during ink drying at the tip 13 of the chip is softened, improving the writing performance.

[0150] Furthermore, for the fatty acid ester, it is preferable that the acid value is 0.01 (mgKOH / g) or more and 5 (mgKOH / g) or less. This is because the compatibility of the methyl-branched fatty acid, the phosphate ester and other components in the ink composition for an oil-based ballpoint pen is good. Since it is stable in the ink for a long time, it is possible to improve the writing performance and lubricity over a long time and to easily improve the writing feel. Considering further, the acid value is preferably 0.01 (mgKOH / g) or more and 2.5 (mgKOH / g) or less, and more preferably 0.05 (mgKOH / g) or more and 1.0 (mgKOH / g) or less.

[0151] Note that the acid value is represented by the number of mg of potassium hydroxide required to neutralize the acidic component (free fatty acid) contained in 1 g of the sample.

[0152] The alcohol used in the esterification reaction of the fatty acid ester is preferably a polyhydric alcohol. Although the reason is not clear, it is presumed that the more hydroxyl groups the alcohol used in the esterification reaction of the fatty acid ester has, the easier it is for the moisturizing effect to work. Therefore, since the strength of the film formed when the tip of the chip 13 dries is softened and the rotation of the ball 20 is smoothed, it is presumed that the writing performance is improved without the occurrence of writing streaks. Considering further improvement in writing performance and lubricity, it is preferable that the polyhydric alcohol has three or more hydroxyl groups, and more preferably five or more hydroxyl groups. Also, if there are too many hydroxyl groups, the stability in the oil-based ink is likely to be affected, so it is preferable that the number of hydroxyl groups is eight or less, and more preferably six or less.

[0153] Specific examples of the alcohol used in the esterification reaction of the fatty acid ester include, as monohydric alcohols, pentanol, cyclohexanol, hexanol, heptanol, octanol, 2-ethylhexanol, nonanol, isononanol, decanol, lauryl alcohol, myristyl alcohol, stearyl alcohol, docosanol, and the like. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, polyalkylene glycol, 1,3-propanediol, diethylene glycol, glycerin, 2-methylpropanetriol, neopentyl glycol, trimethylolethane, triethylolethane, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, and the like. Among these, considering improvement in writing performance and ink stability over time, it is preferable to contain a fatty acid ester esterified with pentaerythritols such as pentaerythritol, dipentaerythritol, and tripentaerythritol. Further considering this, it is preferable to contain a fatty acid ester esterified with dipentaerythritol.

[0154] Further, the content of the fatty acid ester is more preferably 0.1% by mass or more and 10% by mass or less based on the total amount of the ink composition for an oil-based ballpoint pen. This is because if it is less than 0.1% by mass, it tends to be difficult to obtain the desired lubricity and writing performance, and if it exceeds 10% by mass, the ink tends to become unstable over time. Considering this tendency, 0.1% by mass or more and 5% by mass or less is preferable, more preferably 0.1% by mass or more and 3% by mass, and most preferably 0.3% by mass or more and 2% by mass or less.

[0155] Also, as others, as a viscosity modifier, a thixotropic agent such as fatty acid amide or hydrogenated castor oil may be used, and a colorant stabilizer, a plasticizer, a chelating agent, water, etc. may be appropriately used. These may be used alone or in combination of two or more.

[0156] As described above, the ink viscosity of the ink composition for an oil-based ballpoint pen of this embodiment is -1 in the range of 500 mPa·s or more and 15000 mPa·s or less at 20°C and a shear rate of 500 sec

[0157] When the ink viscosity exceeds 15000 mPa·s, the ball rotation resistance during writing increases, the writing feel tends to become heavy, it is likely to affect the wear suppression of the ball seat 19a, and furthermore, the writing performance and ink follow-up performance are likely to be affected. For this reason, the ink viscosity at 20°C and a shear rate of 500 sec -1 (during writing) is preferably 15000 mPa·s or less. Considering the improvement of the writing feel and wear suppression of the ball seat 19a, 10000 mPa·s or less is preferable, considering the writing feel and wear suppression of the ball seat 19a more, it is preferably 8000 mPa·s or less, and considering the writing feel further, it is preferably 6000 mPa·s or less.

[0158] Also, at 20°C and a shear rate of 500 sec -1When the ink viscosity during writing is less than 10 mPa·s, it is likely to cause wear of the ball seat 19a, bleeding in the handwriting, and ink dripping. Therefore, at 20 °C and a shear rate of 500 sec -1 It is preferable that the ink viscosity during writing is 10 mPa·s or more. More preferably, the ink viscosity is 100 mPa·s or more. Further considering the wear prevention of the ball seat 19a, it is preferable that the ink viscosity is 500 mPa·s or more. More preferably, it is 1000 mPa·s or more, and still more preferably, it is 2000 mPa·s or more.

Example

[0159] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0160] The ink composition for an oil-based ballpoint pen of Example 1 was prepared as follows. After adding a pigment and a pigment dispersant to an organic solvent and dispersing them with a disperser, a pigment dispersion, a dye, an organic solvent, a polyvinyl butyral resin, a ketone resin, a phosphate ester, an organic amine, a surfactant, a fatty acid ester, and a resin for imparting drawability were employed, and a predetermined amount of these was weighed and heated to 60 °C. After this heating, an ink composition for an oil-based ballpoint pen was prepared by completely dissolving it using a dispersing stirrer. The specific blending amounts are as follows.

[0161] Example 1 Colorant (salt-forming dye of acid dye and basic dye) 10.0% by mass Colorant (salt-forming dye of basic dye and organic acid) 5.0% by mass Pigment dispersion (pigment content 20%, diketopyrrolopyrrole-based pigment) 15.0% by mass Saturated fatty acid (methyl-branched octadecanoic acid (carbon number: 18) 2.0% by mass C l H 2l+1 O-C 2 H 4 O or C m H 2m+1 Phosphate ester having O (Chemical formula 1: As l = 4, a mixture of n = 1 and n = 2) 2.0% by mass Alcohol solvent (benzyl alcohol) 25.0% by mass Glycol ether solvent (ethylene glycol monophenyl ether) 19.5% by mass Surfactant (phosphate ester surfactant) 2.0% by mass Organic amine 2.0% by mass Fatty acid ester (acid value: 0.1 mgKOH / g, hydroxyl group 6-valent) 2.0% by mass Polyvinyl butyral resin (hydroxyl group content: 36 mol%) 5.0% by mass Ketone resin (ketone resin having an aromatic ring) 10.0% by mass Yarn-drawing property-imparting resin (polyvinyl pyrrolidone resin) 0.5% by mass

[0162] In Example 1, 0.3 g of the ink composition for an oil-based ballpoint pen prepared with the above blending amounts was directly filled into the ink storage cylinder 22 (made of polypropylene) of the ballpoint pen 1 shown in FIGS. 1 to 3, and the ballpoint pen 1 of Example 1 was obtained.

[0163] Also, the specifications of the ballpoint pen refill 4 of the ballpoint pen 1 used in Example 1 were as follows.

[0164] · Ball 20: A ball 20 made of tungsten carbide with a diameter of φ0.3 mm · Tip body 12: Produced by cutting a stainless steel wire rod with a diameter of φ2.3 mm and a hardness of 230 Hv to 280 Hv to a desired length. · Pressing load of coil spring 21: 8 gf / mm · Holding force of ball 20: 300 gf · Movement amount of ball 20 in the extending direction X: 18 μm · Arithmetic mean roughness (Ra) of the ball surface of ball 20: 2 nm · First inclination angle α: 90 degrees · Second inclination angle β: 120 degrees · Angle γ of the bottom wall 19 of the ball holding chamber 15: 120° · Ball protrusion H from the tip of the tip when the ball 20 is placed on the bottom wall 19: 30% of the ball diameter · Angle δ from the tip of the chip 13 to the rear: 30° · Clearance in the extending direction X of the ball 20: 18 μm

[0165] In Example 1, the ballpoint pen refill 4 with the above specifications was disposed in an oil-based ballpoint pen manufactured by Pilot Corporation, and the ballpoint pen 1 described with reference to FIGS. 1 to 3 was produced.

[0166] Examples 2 to 36 As shown in the table, except for changing each component, they were blended in the same procedure as in Example 1 to obtain the ink compositions for oil-based ballpoint pens of Examples 2 to 36. In Examples 2 to 36, the ballpoint pen 1 with the same specifications as in Example 1 was used except that the ink compositions for oil-based ballpoint pens were different.

[0167] Comparative Examples 1 to 2 The ink compositions for oil-based ballpoint pens having the formulations shown in the table were used. Specifically, the same ink composition for oil-based ballpoint pen as in Example 1 was used for Comparative Example 1, and the same ink composition for oil-based ballpoint pen as in Example 33 was used for Comparative Example 2. Then, using the ink composition for oil-based ballpoint pen, a ballpoint pen 1 having the same specifications as in the examples except that the second inclination angle β was 150 degrees, the angle γ of the bottom wall 19 of the ball holding chamber 15 was 120 degrees, and the second inclination angle β and the angle γ were different angles, was produced as the comparative ballpoint pens of Comparative Examples 1 and 2.

[0168] In addition, when measuring the ink viscosity of the ink compositions for oil-based ballpoint pens used in Examples 1 to 33 and Comparative Example 1 using a viscometer Brookfield viscometer RVDVII+Pro CP-52 spindle, in an environment of 20 °C and a shear rate of 500 sec -1 it was in the range of all 500 mPa·s or more and 15000 mPa·s or less.

[0169] Specifically, the ink viscosities of the ink compositions for oil-based ballpoint pens used in each example and comparative example at a shear rate of 500 sec in an environment of 20 °C -1 were as follows.

[0170] Examples 1 - 2: Ink viscosity = 4500 mPa·s Example 13: Ink viscosity = 3700 mPa·s Examples 19 - 20: Ink viscosity = 2800 mPa·s Example 21: Ink viscosity = 4300 mPa·s Example 23: Ink viscosity = 3500 mPa·s Example 29: Ink viscosity = 5900 mPa·s Example 30: Ink viscosity = 7100 mPa·s Example 31: Ink viscosity = 1500 mPa·s

[0171] Tests and evaluations For the ballpoint pens 1 produced in Examples 1 - 33 and the comparative ballpoint pen produced in Comparative Example 1, the following tests and evaluations were carried out using writing paper JIS P3201 as the writing test paper.

[0172] The measurement and evaluation results are shown in the table.

[0173] [Table 1]

[0174] [Table 2]

[0175] [Table 3]

[0176] [Table 4]

[0177] [Table 5]

[0178] In the table, (1) to (15) represent the following respectively.

[0179] (1) Manufactured by Hodogaya Chemical Co., Ltd. (2) Manufactured by Orient Chemical Industries Co., Ltd. (3) Manufactured by Nissan Chemical Industries, Ltd., 16-methylstearic acid (4) Manufactured by Nissan Chemical Industries, Ltd. (5) Manufactured by Kao Corporation, oleic acid (6) Mixture ratio of a mixture of a monoester of butoxyethyl acid phosphate and a diester of butoxyethyl acid phosphate = 4:6 (7) Manufactured by Toho Chemical Industry Co., Ltd., Phosphanol (HLB: 8.6, acid value: 85) (8) Manufactured by Toho Chemical Industry Co., Ltd., Phosphanol (HLB: 10.5, acid value 82) (9) Manufactured by NOF Corporation, Nimene L201 (total amine value: 232 - 246) (10) Manufactured by Sekisui Chemical Co., Ltd. (11) Manufactured by NOF Corporation, Unister HR170R (12) Manufactured by NOF Corporation, Unister H334R (13) Manufactured by Hitachi Chemical Co., Ltd. (14) Manufactured by ISP Japan Co., Ltd., PVP K-90 (15) Manufactured by Kao Corporation, Farmine DM2098 (total amine value: 254 - 265)

[0180] Regarding the ratio of the ball diameter (mm) to the ink consumption (mg) per initial 100 m of the oil-based ball pens in Example 1, Example 2, Example 13, and Example 19 (ball diameter: ink consumption), in Example 1 it was 1:100, in Example 2 it was 1:90, in Example 13 it was 1:83, and in Example 19 it was 1:80. When the spiral writing test was conducted with an oil-based ball pen, the ink consumptions per initial 100 m were 30 mg / 100 m, 27 mg / 100 m, 25 mg / 100 m, and 40 mg / 100 m respectively.

[0181] Regarding the ratio of the ball diameter (mm) to the ink consumption (mg) per initial 100 m of the oil-based ball pens in Example 1, Example 2, Example 13, and Example 19 (ball diameter: ink consumption), in Example 1 it was 1:100, in Example 2 it was 1:90, in Example 13 it was 1:83, and in Example 19 it was 1:80.

[0182] Regarding the ratio E:F of the ink consumption Emg at the initial 0 m to 100 m and the ink consumption Fmg in the last 100 m before the end of the ink for Examples 1, 2, 13, and 19, for Example 1, it was 30:33 = 1:1.1; for Example 2, it was 27:25 = 1:0.93; for Example 13, it was 25:27 = 1:1.08; and for Example 19, it was 40:42 = 1:1.05.

[0183] Ink flow stability test: After the writing test was conducted using a running tester with a load of 100 gf, a writing angle of 70°, and a running speed of 4 m / min, the writing trace was checked. There was no influence of uneven wear on the sealing surface 14c of the second caulking portion 14b, the ink flow was stable, there was no ink clogging, and the writing trace was dark... ○ Due to the influence of uneven wear on the sealing surface 14c of the second caulking portion 14b, the ink flow was unstable and ink clogging occurred... ×

[0184] Writing test per sheet of paper: When handwriting was done on the paper surface with a load of 100 gf and a writing angle of 70°, it was observed whether the outer surface of the second caulking portion 14b came into contact with the paper surface. The outer surface of the second caulking portion 14b did not catch on the paper surface and writing could be done well ... ○ The outer surface of the second caulking portion 14b caught on the paper surface and writing could not be done well ... ×

[0185] Wear resistance test (wear test of the ball seat 19a): After the writing test was conducted using a running tester with a load of 100 gf, a writing angle of 70°, and a running speed of 4 m / min, the wear of the ball seat 19a was measured. Those with wear of the ball seat 19a less than 5 μm... ◎ Those with wear of the ball seat 19a of 5 μm or more and less than 10 μm... ○ Those with wear of the ball seat 19a of 10 μm or more and less than 20 μm, but still capable of writing ... △ Those with severe wear of the ball seat 19a resulting in poor writing... ×

[0186] Writing feel: Evaluated by conducting a sensory test using handwriting. Very smooth... ◎ Smooth... ○ Smoothness at a level with no practical problems... △ Heavy... ×

[0187] Writing performance test: After handwriting, the tip of the chip was left out and placed in an environment of 20°C and 65% RH for 30 minutes. Then, writing was carried out under the following writing conditions in a running test, and the length of the writing smear was measured. <Writing conditions> Evaluation was carried out by performing straight-line writing on a running tester under the conditions of a writing load of 70 gf, a writing angle of 70°, and a writing speed of 4 m / min. Those with a writing smear length of less than 10 mm... ◎ Those with a writing smear length of 10 mm or more and less than 20 mm... ○ Those with a writing smear length of 20 mm or more and less than 40 mm... △ Those with a writing smear length of 40 mm or more... ×

[0188] Ink aging test: The ink inside the chip body was observed under a microscope. Those with no precipitate and in good condition... ◎ Those with slightly generated precipitate... ○ Those with precipitate generated but with no practical problems... △ Those with precipitate generated and causing smears or writing defects... ×

[0189] In Examples 1 to 31, good performance was obtained in both the wear resistance test (wear test of the ball seat 19a), writing feel, writing performance test, and ink aging test.

[0190] In addition, Examples 1 to 36 obtained better results in the ink flow stability test and the writing-on-paper test compared to Comparative Examples 1 and 2. Specifically, in Comparative Examples 1 and 2, uneven wear of the sealing surface 14c of the first caulking portion 14a progressed, the ink flow became unstable, and ink clogging occurred. Also, in Comparative Examples 1 and 2, during writing, the second caulking portion 14b caught on the paper, resulting in a scratching writing feel and making it impossible to write well. This is presumably because in Comparative Examples 1 and 2, the second inclination angle β and the angle γ are different angles, and the second inclination angle β is as large as 150 degrees.

[0191] Also, when using a retractable oil-based ballpoint pen such as a click-type oil-based ballpoint pen or a rotating feed oil-based ballpoint pen, since writing performance is one of the important performances, it is effective to use at least an oil-based ballpoint pen ink composition like the present invention.

[0192] In addition, in this example, a ballpoint pen 1 in which a ballpoint pen refill 4 containing an oil-based ballpoint pen ink composition is disposed in a shaft cylinder was exemplified. However, the ballpoint pen 1 of the present invention may be a direct filling type oil-based ballpoint pen in which the shaft cylinder itself is an ink storage cylinder and the oil-based ballpoint pen ink composition is directly stored in the shaft cylinder, or a structure in which the one (ballpoint pen refill 4) containing the oil-based ballpoint pen ink composition in the ink storage cylinder 22 is used as the ballpoint pen 1 as it is.

Industrial Applicability

[0193] The present invention can be used as a ballpoint pen, and more specifically, it can be widely used as a ballpoint pen such as a cap type or a click type.

Explanation of Reference Numerals

[0194] 1... Ballpoint pen 2... Front shaft, 2a... Opening 3... Rear shaft (shaft cylinder body) 4... Ballpoint pen refill 5... Coil spring 6... Rotating cam 7…Knocking member 8…Clip 9…Grip 11…Ball pen tip 12…Tip body 13…Tip front end portion 14…Caulking portion, 14a…First caulking portion, 14b…Second caulking portion, 14c…Sealing surface 15…Ball holding chamber 16…Ink flow hole 17…Ink flow groove 18…Rear hole of tip 19…Bottom wall, 19a…Ball seat 20…Ball 21…Coil spring 22…Ink storage cylinder 23…Tip holder 24…Tail plug

Claims

1. A ballpoint pen comprising an ink storage cylinder filled with an ink composition for an oil-based ballpoint pen and a ballpoint pen refill having a ballpoint pen tip attached to the tip of the ink storage cylinder, wherein the tip body of the ballpoint pen tip has a ball holding chamber that rotatably holds a part of the ball protruding from the tip of the tip, a ball seat provided on the bottom wall of the ball holding chamber, on which the ball is placed and which has an arcuate surface along the outer shape of the ball, an ink flow hole formed at the center of the bottom wall of the ball holding chamber, and a plurality of ink flow grooves extending radially from the ink flow hole, The ink viscosity of the oil-based ballpoint pen ink composition is in the range of 500 mPa·s or more and 15,000 mPa·s or less at 20°C and a shear rate of 500 sec －１ -1 wherein the ball diameter of the ball is 0.5 mm or less, wherein an arcuate sealing surface is formed on the inner wall of the tip of the tip, wherein the tip of the tip, has a first caulking portion with an inclination angle of 90 degrees or more and less than 100 degrees, and a second caulking portion provided on the tip side of the ballpoint pen tip from the first caulking portion with an inclination angle of 110 degrees or more and 130 degrees or less, and the angle of the bottom wall of the ball holding chamber is the same as the inclination angle of the second caulking portion. Ballpoint pen.

2. The ballpoint pen according to claim 1, further comprising a coil spring that presses the ball toward the tip side of the tip of the tip, wherein the pressing load of the coil spring is 5 gf or more and 10 gf or less.

3. The ink composition for an oil-based ballpoint pen, It comprises a colorant, an organic solvent, a saturated fatty acid, and a phosphate ester, wherein the phosphate ester has C ｌ H ２ｌ＋１ O—C ２ H ４ O or C ｍ H ２ｍ＋１ O (where l, m = 1 or more and 30 or less). The ballpoint pen according to claim 1 or claim 2, characterized by this.

4. The ballpoint pen according to claim 3, wherein the saturated fatty acid has 10 to 20 carbon atoms.

5. The ballpoint pen according to claim 3 or claim 4, wherein the carbon chain (l, m) of the terminal alkyl group of the phosphate ester is 1 to 15.

6. The ballpoint pen according to any one of claims 3 to 5, wherein the ink composition for an oil-based ballpoint pen contains a ketone resin or a polyvinyl butyral resin.

7. The ballpoint pen according to any one of claims 3 to 6, wherein the colorant is a pigment or a salt-forming dye.

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