Ballpoint pen tips, ballpoint pen refills and ballpoint pens

Abstract

To suppress dryness of ink in a ball-point pen.SOLUTION: A ball-point pen 40 has a ball 42 with a diameter of 0.5 mm or less, and a tip body 50 holding the ball, in which the tip body has a ball holding chamber 52 holding the ball, a rear hole 57 positioned at the rear part of the ball holding chamber, an ink circulation hole 62 making the ball holding chamber and the rear hole communicate with each other, and an ink circulation groove 64 that extends in a radial direction dr from the ink circulation hole, is opened to the ball holding chamber and does not reach the rear hole. A ratio (A / B) of ink consumption A per handwriting of 100 m to a diameter B of the ball is 200 mg / mm or more and 800 mg / mm or less, when a front end 64a of the ink circulation groove is defined as a starting point S1 and a position of 0.3 mm toward the rear part from the front end 62a of the ink circulation hole is defined as an end point S2, a volume of a first space part SA in the ink circulation hole and the ink circulation groove from the starting point to the end point is 0.02 mm3 or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a ballpoint pen tip, a ballpoint pen refill, and a ballpoint pen. [Background technology]

[0002] Conventionally, ballpoint pens have utilized ballpoint pen tips that include a ball and a tip body that holds the ball.

[0003] Patent Document 1 discloses a ballpoint pen tip equipped with a ball holding chamber for storing a ball, a rear hole located behind the ball holding chamber, an ink guide hole connecting the ball holding chamber and the rear hole, and an ink groove extending radially from the ink guide hole, as well as a ballpoint pen equipped with this ballpoint pen tip. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-52884 Summary of the Invention [Problem to be solved by the invention]

[0005] In conventional ballpoint pens, if the pen is left unused for a long period of time, the ink may dry out and solidify in the ball-holding chamber. In this case, ink may not be properly supplied to the ball, resulting in problems such as blurred writing or complete inability to write. Therefore, it is desirable to prevent the ink from drying out in the ball-holding chamber of a ballpoint pen tip, even if the pen is left unused for a long period of time.

[0006] The present invention has been made in consideration of these points, and has as its object to suppress the drying of ink in a ballpoint pen tip. [Means for solving the problem]

[0007] The ballpoint pen tip according to the present invention comprises: A ball having a diameter of 0.5 mm or less and a tip body that holds the ball, The chip body includes: a ball holding chamber that holds the ball; a rear hole located rearward of the ball-holding chamber; an ink flow hole that connects the ball holding chamber and the rear hole; an ink flow groove extending radially from the ink flow hole, opening into the ball holding chamber, but not reaching the rear hole; When the ink consumption per 100 m of handwriting is A (mg) and the diameter of the ball is B (mm), the ratio (A / B) of the ink consumption A to the diameter B of the ball is 200 mg / mm or more and 800 mg / mm or less, When the front end of the ink flow groove is the starting point and the position 0.3 mm rearward from the front end of the ink flow hole is the ending point, the volume of the space in the ink flow hole and the ink flow groove from the starting point to the ending point is 0.02 mm 3 That's all.

[0008] In the ballpoint pen tip according to the present invention, The volume of the space in the ink flow hole and the ink flow groove from the starting point to the ending point may be 1.5 times or more the volume of the space in the ball holding chamber from the tip of the tip body to the starting point.

[0009] In the ballpoint pen tip according to the present invention, The inner diameter of the ink flow hole may be 40% or more of the diameter of the ball.

[0010] In the ballpoint pen tip according to the present invention, The length of the ink flow hole may be 90% or less of the diameter of the ball.

[0011] In the ballpoint pen tip according to the present invention, The length of the region of the ink flow hole where the ink flow groove is not formed may be 90% or less of the diameter of the ball.

[0012] In the ballpoint pen tip according to the present invention, The device may further include a resilient member having a spring portion and a rod portion extending forward from the spring portion and abutting against the ball from behind.

[0013] In the ballpoint pen tip according to the present invention, The range of movement of the ball in the front-rear direction relative to the tip body may be 0.015 mm or more and 0.06 mm or less.

[0014] The ballpoint pen refill according to the present invention comprises: The ballpoint pen tip described above; and an ink storage cylinder for storing ink.

[0015] In the ballpoint pen refill according to the present invention, The ink may be a thermochromic ink.

[0016] The ballpoint pen according to the present invention comprises: The ballpoint pen refill is provided as described above. [Effects of the Invention]

[0017] According to the present invention, it is possible to suppress the drying of ink in the ballpoint pen tip. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram for explaining one embodiment of the present invention, and is a vertical cross-sectional view showing an example of a ballpoint pen incorporating a ballpoint pen refill having a ballpoint pen tip. [Figure 2] FIG. 2 is an enlarged longitudinal sectional view showing the ballpoint pen tip of FIG. [Figure 3] FIG. 3 is a vertical cross-sectional view showing the vicinity of the tip of the ballpoint pen tip in a further enlarged manner. [Figure 4] FIG. 4 is a cross-sectional view corresponding to the line IV-IV in FIG. [Figure 5] FIG. 5 is a graph showing the calculation results of the volume of the space in the ink flow holes and ink flow grooves of the ballpoint pen tip. DETAILED DESCRIPTION OF THE INVENTION

[0019] An embodiment of the present invention will now be described with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

[0020] Furthermore, terms used in this specification that specify shapes, geometric conditions, and their degrees, such as "parallel," "orthogonal," and "identical," as well as values ​​of lengths and angles, are not to be construed as being bound by strict meanings, but rather as including a range within which similar functions can be expected.

[0021] In this specification, the direction in which the central axis A of the ballpoint pen 10 extends (longitudinal direction, up and down direction in a longitudinal cross section) is referred to as the axial direction da, the direction perpendicular to the central axis A is referred to as the radial direction dr, and the direction along the circumference around the central axis A is referred to as the circumferential direction dc. Also, along the axial direction da, the side that comes close to the surface to be written on, such as paper, when writing is referred to as the front, and the side that moves away from the surface to be written on is referred to as the rear. In other words, the pen tip side is the front, and the side opposite the pen tip is the rear.

[0022] 1 is a diagram illustrating one embodiment of the present invention, and is a cross-sectional view showing an example of a ballpoint pen 10. In this embodiment, an example will be described in which the ballpoint pen 10 is a so-called side-knock type ballpoint pen. The ballpoint pen 10 includes a barrel 20, a ballpoint pen refill 30 incorporated in the barrel 20, a retraction mechanism 12 for causing the tip of the ballpoint pen refill 30 to protrude and retract from the barrel 20, a friction member 14 for rubbing handwriting, and a clip 16.

[0023] Barrel tube 20 includes front barrel 21, rear barrel 25 connected to front barrel 21, rear end cap 28 attached to the rear end of rear barrel 25, and grip member 29 disposed surrounding the outer surface of front barrel 21. Front barrel 21 has opening 22 at its front end through which the tip of ballpoint pen tip 40 of ballpoint pen refill 30 can be inserted and removed, first engagement portion 23 on the inner surface of the front region, and male thread portion 24 on the outer surface of the rear region. Rear barrel 25 has female thread portion 26 on the inner surface of the front region. Front barrel 21 and rear barrel 25 are coupled to each other by threading male thread portion 24 of front barrel 21 with female thread portion 26 of rear barrel 25. Rear end cap 28 is fitted onto the rear end of rear barrel 25. Grip member 29 is intended to be held with the user's fingers when writing with ballpoint pen 10. The front axle 21, the rear axle 25 and the rear end cap 28 are made of, for example, resin, and the grip member 29 is made of, for example, rubber.

[0024] In this embodiment, the clip 16 functions as an operating part that is operated by the user when knocking. The barrel 20 is provided with a slide hole 27 that extends in the axial direction da and penetrates the wall of the barrel 20. The slide hole 27 is provided across the rear region of the rear barrel 25 and the front end of the rear end cap 28. In the illustrated example, the clip 16 extends from inside the barrel 20 to outside the barrel 20 through the slide hole 27. The range of movement of the clip 16 in the axial direction da can be defined by the front and rear ends of the slide hole 27.

[0025] The ballpoint pen refill 30 is accommodated in the barrel 20 so as to be retractable. The ballpoint pen refill 30 includes an ink reservoir 32 that accommodates ink, a tip holder 34 arranged in front of the ink reservoir 32, and a ballpoint pen tip 40 arranged in front of the tip holder 34. In the example shown in FIG. 1, the rear end of the tip holder 34 is inserted into the front end of the ink reservoir 32, and the rear end of the ballpoint pen tip 40 is inserted into the front end of the tip holder 34. The ballpoint pen refill 30 has a second engagement portion 36 provided on the outer surface of the front region. In the example shown, the second engagement portion 36 is provided on the outer surface of the tip holder 34. When the ballpoint pen refill 30 is assembled, the second engagement portion 36 of the ballpoint pen refill 30 is located rearward of the first engagement portion 23 of the front barrel 21, and a coil spring 18 is arranged in a compressed state between the first engagement portion 23 and the second engagement portion 36. As a result, the coil spring 18 biases the ballpoint pen refill 30 rearward.

[0026] As the ink, any ink that can be used for a ballpoint pen can be used without any particular limitation. As an example, a thermochromic ink can be used as the ink. The thermochromic ink may be a reversible thermochromic ink. As an example of the reversible thermochromic ink, a heat-discoloring type reversible thermochromic ink that changes from a colored state to a colorless state when heated and changes from the colorless state back to a colored state when cooled can be used.

[0027] Specifically, general-purpose inks can be applied depending on the type of ballpoint pen tip, such as shear-thinning aqueous gel ink, low-viscosity aqueous ink, low-viscosity oil-based ink, high-viscosity oil-based ink, emulsion ink, etc. Among these, shear-thinning aqueous gel ink is particularly effective.

[0028] Furthermore, in the shear-thinning aqueous gel ink, the colorant is not particularly limited, and dyes, pigments, metallic luster pigments, fluorescent pigments, titanium oxide, thermochromic pigments, etc. can be used. In particular, when the ink contains 10% by weight or more of pigment solids, the ink is likely to dry and solidify in the ballpoint pen tip, and the effects of this embodiment can be more effectively exhibited. Furthermore, when titanium oxide or a thermochromic pigment, which requires a pigment solids content of 10% by weight or more for the writing density, is used as the ink, the effects of this embodiment can be even more effectively exhibited.

[0029] The viscosity of the water-based gel ink with shear thinning properties is 3.84 sec at a shear rate of 20°C. -1 When measured under the conditions of a shear rate of 384 sec-1 at a temperature of 20°C, the viscosity is preferably 1 to 2000 mPa·s, more preferably 3 to 1500 mPa·s, and even more preferably 500 to 1000 mPa·s. -1 When measured under these conditions, the viscosity is preferably 1 to 200 mPa·s, more preferably 10 to 100 mPa·s, and even more preferably 20 to 50 mPa·s, because this allows for good ink discharge from the pen tip of a ballpoint pen.

[0030] The viscosity was measured using a rheometer (TA Instruments, product name: Discovery HR-2, cone plate (diameter 40 mm, angle 1°)) at a shear rate of 3.84 sec. under a temperature of 20°C. -1 , or shear rate 384 sec -1 The values ​​were measured under the following conditions.

[0031] When the ink composition of the present invention is filled into an aqueous ballpoint pen, it is preferable that the ball diameter and ink consumption satisfy a specific relationship. Specifically, when the ink consumption per 100 m of an aqueous ballpoint pen is A (mg) and the ball diameter is B (mm), the relationship is preferably 200≦A / B≦800, and more preferably 300≦A / B≦700. This is because, by maintaining the ink consumption within an appropriate range relative to the ball diameter, the ink fluidity is improved, and handwriting smearing and the like are suppressed, making it easier to obtain good handwriting.

[0032] The friction member 14 of this embodiment is a member for rubbing the ink writing. If the ink is thermochromic, the friction member 14 can be a friction member that rubs against a writing surface, such as paper, on which handwriting has been formed, thereby heating the ink forming the handwriting by frictional heat. In this case, the friction member 14 can be formed, for example, from an elastic material. The friction member 14 can be fixed to the rear end cap 28 by press-fitting, engagement, screwing, fitting, adhesive, two-color molding, or the like. Furthermore, if the ink is not thermochromic, the friction member 14 can be, for example, a member that rubs against a writing surface, such as paper, on which handwriting has been formed, to scrape off the handwriting, such as a sand eraser.

[0033] The retraction mechanism 12 is a mechanism for alternately switching the ballpoint pen 10 between a knock state in which the tip of the ballpoint pen tip 40 protrudes from the opening 22 of the front barrel 21 and a non-knock state in which the tip of the ballpoint pen tip 40 retracts from the opening 22. FIG. 1 shows the ballpoint pen 10 in the knock state. In the non-knock state, the elastic force of the coil spring 18 urges the ballpoint pen refill 30 rearward, causing the tip of the ballpoint pen tip 40 to retract from the opening 22. When a user pushes and slides the clip 16 forward with their finger, the ballpoint pen refill 30 moves forward, causing the tip of the ballpoint pen tip 40 to protrude forward from the opening 22. Even when the user releases their finger from the clip 16, the ballpoint pen refill 30 maintains a state in which the tip of the ballpoint pen tip 40 protrudes forward from the opening 22. When the user again pushes and slides the clip 16 forward with his / her finger, the ballpoint pen refill 30 moves forward by a small distance. When the user releases his / her finger from the clip 16 or releases the forward pressure on the clip 16, the resilience of the coil spring 18 urges the ballpoint pen refill 30 rearward, and the tip of the ballpoint pen tip 40 retracts from the opening 22. The retraction mechanism 12 that realizes such a retraction operation is well known, so a detailed description will be omitted. As an example, the retraction mechanism disclosed in JP 2012-6315 A can be used as the retraction mechanism 12.

[0034] The ballpoint pen tip 40 will be further described with reference to Figures 2 to 4. Figure 2 is an enlarged longitudinal cross-sectional view of the ballpoint pen tip 40, Figure 3 is an enlarged longitudinal cross-sectional view of the vicinity of the tip of the ballpoint pen tip 40, and Figure 4 is a transverse cross-sectional view corresponding to line IV-IV in Figure 3.

[0035] The ballpoint pen tip 40 includes a ball 42 and a tip body 50 that holds the ball 42. The tip body 50 is preferably made of a metal material such as stainless steel. Considering corrosion resistance, the tip body 50 is preferably made of stainless steel. The ball 42 is also preferably made of a metal material such as a tungsten carbide-based superhard material. The diameter of the ball 42 can be greater than 0 mm and less than 0.5 mm. Preferably, the diameter of the ball 42 can be greater than 0.2 mm and less than 0.5 mm. The tip body 50 guides ink contained in the ink reservoir 32 to the ball 42. When writing, the user presses the ball 42 against a writing surface, such as paper, and moves it across the writing surface, causing the ball 42 to rotate on the writing surface. This transfers the ink adhering to the ball 42 to the writing surface. The transferred ink then forms a mark on the writing surface. If a water-based shear-thinning ink, whose viscosity decreases as the ball 42 rotates, is used as the ink, the ink adhering to the ball 42 penetrates into the surface as the ball 42 rotates on the surface, and the penetrating ink forms a mark on the surface.

[0036] The tip body 50 is fabricated, for example, by cutting. If burrs remain on the inner surface of the tip body 50 due to cutting during fabrication, the burrs may impede the flow of ink within the tip body 50. To solve this problem, cleaning the inner surface of the tip body 50 after fabricating the tip body 50 by cutting is considered. This cleaning removes burrs and reduces the surface roughness (arithmetic mean roughness Ra) of the inner surface of the tip body 50, resulting in a mirror-finished surface. However, the present inventors' studies have revealed that cleaning the inner surface of the tip body 50 does not significantly improve the flow of ink within the tip body 50. This is presumably because, when using a water-based ink such as a water-based ink or a water-based shear-thinning ink, a stainless steel surface with a larger surface roughness than a mirror-finished surface, for example, one with an arithmetic mean roughness Ra of less than 10 nm, increases the ink contact angle on the surface, suppresses ink spreading, and facilitates ink flow. Therefore, the surface roughness of at least one of the inner surfaces constituting the first space portion SA described below, the inner surface constituting the second space portion SB described below, and the inner surface constituting the third space portion SC described below in the chip body 50 is preferably 10 nm or more and 1 μm or less in terms of arithmetic mean roughness Ra specified in JIS B0601:2013, more preferably 100 nm or more and 500 nm or less, and even more preferably 100 nm or more and 150 nm or less.

[0037] The ballpoint pen tip 40 of this embodiment has a resilient member 44 for biasing the ball 42 forward. In the example shown in FIG. 2, the resilient member 44 includes a spring portion 46 and a rod portion 48 that extends forward from the spring portion 46 and abuts the ball 42 from behind. The spring portion 46 is formed, for example, by a coil spring. The rear end of the rod portion 48 is connected to the spring portion 46, and the front end of the rod portion 48 abuts the ball 42 from behind. In the example shown, the rear end of the spring portion 46 abuts the tip holder 34. In this state, the spring portion 46 is in a compressed state, generating a biasing force in the direction in which the spring portion 46 expands. The rod portion 48 transmits the biasing force of the spring portion 46 to the ball 42. As a result, a force biasing the ball 42 forward is constantly applied to the ball 42. The diameter D2 of the rod portion 48 can be, for example, 0.01 mm or more and 0.3 mm or less. Preferably, the diameter D2 can be set to be equal to or greater than 0.05 mm and equal to or less than 0.2 mm.

[0038] The tip body 50 has a ball holding chamber 52, a rear hole 57, an ink flow hole 62, and an ink flow groove 64. The ball holding chamber 52 has the function of holding the ball 42 and also the function of retaining ink within the ball holding chamber 52 and applying the ink to the ball 42. The ball holding chamber 52 is composed of a hole formed from the front end of the tip body 50 toward the rear. The ball holding chamber 52 has a rear wall 54. The rear wall 54 is a wall that defines the rear portion of the ball holding chamber 52. The central axis of the tip body 50 coincides with the central axis A of the ballpoint pen 10. Therefore, in this specification, the central axis of the tip body 50 is sometimes referred to as the central axis A. After the ball 42 is placed in the ball holding chamber 52, the tip of the tip body 50 is crimped so that it deforms inward (toward the central axis A), thereby holding the ball 42 in the ball holding chamber 52. Therefore, the tip body 50 has a crimped portion 56 at the tip end that is deformed inward (toward the central axis A).

[0039] Within the ball holding chamber 52, the ball 42 is movable in the front-to-rear direction. In FIG. 3 , the ball 42 is indicated by a solid line when it is positioned at the rearmost position within the ball holding chamber 52, and by a two-dot chain line when it is positioned at the forwardmost position within the ball holding chamber 52. When not writing, the biasing force of the resilient member 44 causes the ball 42 to be positioned at the forwardmost position within the ball holding chamber 52 and abut against the crimped portion 56 of the tip body 50. At this time, the gap between the ball 42 and the crimped portion 56 is sealed. This prevents ink from leaking out when not writing and prevents the ink in the ball holding chamber 52 from drying out. When writing with the ballpoint pen 10, a backward force due to writing pressure acts on the ball 42, causing the ball 42 to move rearward against the biasing force of the resilient member 44, creating a gap between the ball 42 and the crimped portion 56. As the ball 42 rotates on the writing surface, ink adhering to the ball 42 passes through this gap and is carried from the ball holding chamber 52 to the writing surface, adhering to the writing surface. When the ball 42 is positioned at the rearmost position within the ball holding chamber 52, the ball 42 abuts against the junction of the rear wall 54 and the ink flow hole 62 (the front end 62a of the ink flow hole 62). The range of movement (clearance) C of the ball 42 in the front-to-rear direction relative to the tip body 50 can be, for example, 0.015 mm or more and 0.06 mm or less. Preferably, the range of movement C of the ball 42 can be 0.020 mm or more and 0.05 mm or less.

[0040] The rear hole 57 is located rearward of the ball holding chamber 52 and extends along the axial direction da. The rear hole 57 is in communication with the ink reservoir 32 via the tip holder 34 and functions as a flow path for ink from the ink reservoir 32 to the ball holding chamber 52. The rear hole 57 is composed of a hole formed forward from the rear end of the tip body 50. The rear hole 57 includes a cylindrical hole. The central axis of the rear hole 57 coincides with the central axis A of the tip body 50. The rear hole 57 includes multiple cylindrical hole portions with different diameters, and the diameters of each cylindrical hole portion increase toward the rear.

[0041] The ink flow hole 62 is located between the ball holding chamber 52 and the rear hole 57 and connects the ball holding chamber 52 and the rear hole 57. The ink flow hole 62 extends linearly along the axial direction da. In the illustrated example, the ink flow hole 62 is a cylindrical through-hole. The ink flow hole 62 functions as a flow path for ink from the rear hole 57 to the ball holding chamber 52. The inner diameter (diameter) D1 of the ink flow hole 62 can be, for example, 40% to 90% of the diameter of the ball 42. Preferably, the inner diameter D1 can be 50% to 80% of the diameter of the ball 42. Furthermore, the inner diameter D1 can be, for example, 0.2 mm to 0.45 mm. Preferably, the inner diameter D1 can be 0.25 mm to 0.4 mm. The central axis of the ink flow hole 62 coincides with the central axis A of the tip body 50. Therefore, the distance R1 from the central axis A of the tip body 50 to the peripheral wall of the ink flow hole 62 is equal to the radius of the ink flow hole 62.

[0042] The length L1 of the ink flow hole 62 can be, for example, more than 0% and not more than 90% of the diameter of the ball 42. Preferably, the length L1 can be 40% or more and 80% or less of the diameter of the ball 42. The length L1 can be, for example, more than 0 mm and not more than 0.45 mm. Preferably, the length L1 can be 0.2 mm or more and not more than 0.4 mm. Here, the length L1 of the ink flow hole 62 is the length along the axial direction da from the front end 62a of the ink flow hole 62 to the rear end 62b of the ink flow hole 62. In the illustrated example, the front end 62a of the ink flow hole 62 is the forward-most portion of the portion having the inner diameter D1, and the rear end 62b of the ink flow hole 62 is the rear-most portion of the portion having the inner diameter D1. The front end 62a of the ink flow hole 62 abuts against the ball 42 when the ball 42 is positioned at the rearmost position within the ball holding chamber 52. When the ink circulation hole 62 has such dimensions D1 and / or L1, the amount of ink flowing through the ink circulation hole 62 can be appropriately ensured.

[0043] The ink flow groove 64 extends in the radial direction dr from the ink flow hole 62 and opens into the ball holding chamber 52. The ink flow groove 64 communicates with the ink flow hole 62 and the ball holding chamber 52. However, the ink flow groove 64 does not reach the rear hole 57. The front end 64a of the ink flow groove 64 is located on the rear wall 54 of the ball holding chamber 52. The rear end 64b of the ink flow groove 64 is located on the peripheral wall of the ink flow hole 62. Because the tip body 50 has this ink flow groove 64, even when the ball 42 is located at the rearmost position within the ball holding chamber 52 and abuts against the front end 62a of the ink flow hole 62 (see FIG. 3 ), a gap is formed between the ball 42 and the front end 64a of the ink flow groove 64, allowing ink to flow from the ink flow hole 62 through the ink flow groove 64 to the ball holding chamber 52.

[0044] The ink flow groove 64 has a peripheral wall 66 facing the ink flow hole 62. The peripheral wall 66 defines the outer contour of the ink flow groove 64 in the radial direction dr. The peripheral wall 66 includes a main portion 67 and an inclined portion 68 located rearward of the main portion 67. In the example shown in FIGS. 3 and 4 , the main portion 67 extends along both the axial direction da and the circumferential direction dc. The inclined portion 68 connects the main portion 67 to the ink flow hole 62. The inclined portion 68 extends in a direction inclined with respect to both the axial direction da and the radial direction dr so as to approach the ink flow hole 62 toward the rear. The distance R2 from the central axis A of the tip body 50 to the peripheral wall 66 (main portion 67) of the ink flow groove 64 can be, for example, 40% to 200% of the diameter of the ball 42. Preferably, the distance R2 can be 60% to 150% of the diameter of the ball 42. The distance R2 can be set to, for example, 0.2 mm or more and 1 mm or less, and preferably, 0.3 mm or more and 0.7 mm or less.

[0045] As described above, the ink flow groove 64 does not reach the rear hole 57. Therefore, the ink flow hole 62 has a region behind the ink flow groove 64 where the ink flow groove 64 is not formed. This region has the smallest cross-sectional area perpendicular to the central axis A in the ink flow path from the rear hole 57 to the ball holding chamber 52. According to the inventors' investigations, the length of this region along the axial direction da affects the amount of ink flowing through the ink flow path within the tip body 50. To ensure an appropriate ink flow rate within the tip body 50, the length L2 of the region of the ink flow hole 62 where the ink flow groove 64 is not formed can be set to, for example, 20% to 80% of the diameter of the ball 42. Preferably, the length L2 can be set to, for example, 40% to 60% of the diameter of the ball 42. Furthermore, the length L2 can be set to, for example, 0.1 mm to 0.4 mm. Preferably, the length L2 is set to 0.2 mm or more and 0.3 mm or less. The length L2 is defined as the length from the rear end 64b of the ink flow groove 64 to the rear end 62b of the ink flow hole 62.

[0046] The width W of the ink flow groove 64 along a direction perpendicular to both the axial direction da and the radial direction dr can be, for example, 0.01 mm or more and 0.15 mm or less. Preferably, the width W can be 0.05 mm or more and 0.1 mm or less.

[0047] The tip body 50 has one ink distribution groove 64 or multiple ink distribution grooves 64. When the tip body 50 has multiple ink distribution grooves 64, the ink distribution grooves 64 may be arranged at equal angular intervals from one another along the circumferential direction dc. In the example shown in Fig. 4, the tip body 50 has four ink distribution grooves 64 arranged at equal angular intervals from one another along the circumferential direction dc.

[0048] As described above, in conventional ballpoint pens, if the pen is left unused for an extended period of time, the ink can dry and solidify in the ball holding chamber. In this case, ink is not properly supplied to the ball, resulting in problems such as faint writing or complete inability to write. The present inventors conducted extensive research into ways to resolve this problem and discovered that drying of ink in the ball holding chamber 52 can be effectively suppressed when the volume of the space (first space) SA in the ink flow hole 62 and ink flow groove 64, measured rearward from the front end 64a of the ink flow groove 64, is equal to or greater than a predetermined value. The following describes this space SA.

[0049] The front end 64a of the ink flow groove 64 is defined as the start point S1 of the space SA. The position where the distance L3 measured rearward from the front end 62a of the ink flow hole 62 is 0.3 mm is defined as the end point S2. The volume of the space SA in the ink flow hole 62 and ink flow groove 64 from the start point S1 to the end point S2 is then defined. In Figure 3, the length along the axial direction da from the start point S1 to the end point S2 of the space SA is indicated by L4.

[0050] The space SA is defined under the following conditions: The ball 42 is positioned at the rearmost position within the ball holding chamber 52 and is in contact with the front end 62a of the ink flow hole 62. In this case, a portion of the ball 42 is positioned within the ink flow hole 62. The space within the ball holding chamber 52 is not included in the space SA. Portions of the ball 42 that are not filled with ink, even if they are positioned within the length L4, are not included in the space SA. Portions that are not filled with ink include, for example, the portion occupied by the ball 42 and the portion occupied by the resilient member 44. Specifically, the portion occupied by the ball 42 is the portion of the ball 42 that is positioned within the ink flow hole 62. Furthermore, the portion occupied by the resilient member 44 is the portion of the rod portion 48 of the resilient member 44 that is positioned between the start point S1 and the end point S2 of the space SA. More specifically, the portion occupied by the resilient member 44 is the portion between the front end of the rod portion 48 and the end point S2. The space SA is defined under the above conditions, and the volume of this space SA can be calculated.

[0051] In this embodiment, the volume of the space SA is 0.02 mm 3 Preferably, the volume of the space SA is 0.02 mm or more. 3 More than 0.08mm 3 More preferably, the volume of the space SA is 0.25 mm 3 More than 0.05mm 3 It can be as follows:

[0052] The present inventors have found that the drying of ink in the ball holding chamber 52 can be suppressed by ensuring a sufficient amount of ink in the area behind and close to the ball 42. Further investigation has revealed that the volume of the space SA of the ink flow hole 62 and the ink flow groove 64, particularly in the area between the front end 64a of the ink flow groove 64 and a position 0.3 mm rearward from the front end 62a of the ink flow hole 62, has a significant effect on the drying of ink in the ball holding chamber 52. This has made it clear that the drying of ink in the ball holding chamber 52 can be controlled based on the volume of the space SA, regardless of the shape and dimensions of the ink flow hole 62 and the ink flow groove 64. This is thought to be because, even when not writing, the ink in ball holding chamber 52 tends to dry out due to tiny gaps that occur between the tip end (crimped portion 56) and ball 42 due to dents or fibers. However, if the volume of space SA is sufficiently secured, the ink in ball holding chamber 52 is moistened by a sufficient amount of ink present in space SA located behind ball holding chamber 52, preventing the ink from drying out. The present inventors further investigated the range of the volume of space SA and identified the above range as an appropriate range. This technical concept of being able to control the drying rate of ink in ball holding chamber 52 based on the volume of space SA was not previously known, and it can be said that the present invention makes a significant technical contribution to the prior art.

[0053] In this embodiment, the space (second space SB) in the ink flow hole 62 and ink flow groove 64, extending from the starting point S1 to a position 60% of the diameter of the ball 42 from the front end 62a of the ink flow hole 62 rearward in the axial direction da, is defined under the following conditions: The ball 42 is positioned at the rearmost position within the ball holding chamber 52 and in contact with the front end 62a of the ink flow hole 62. In this case, a portion of the ball 42 is positioned within the ink flow hole 62. The space within the ball holding chamber 52 is not included in the space SB. Portions of the ball 42 that are not filled with ink, even if they are positioned within the length L4, are not included in the space SB. Portions that are not filled with ink include, for example, the portion occupied by the ball 42 and the portion occupied by the resilient member 44. Specifically, the portion occupied by the ball 42 is the portion of the ball 42 that is positioned within the ink flow hole 62. Furthermore, the portion occupied by the resilient member 44 is a portion of the rod portion 48 of the resilient member 44 that is located between the start point S1 and a position that is 60% of the diameter of the ball 42, extending rearward in the axial direction da from the front end 62a of the ink flow hole 62. More specifically, the portion occupied by the resilient member 44 is a portion that is located between the front end of the rod portion 48 and a position that is 60% of the diameter of the ball 42, extending rearward in the axial direction da from the front end 62a of the ink flow hole 62. The space SB is defined under the above conditions, and the volume of this space SB can be calculated.

[0054] The present inventors have found that, like the volume of the space SA, the volume of the space SB of the ink flow hole 62 and the ink flow groove 64 in the region extending from the front end 62a of the ink flow hole 62 rearward, starting from the front end 64a of the ink flow groove 64, to a position 60% of the diameter of the ball 42, also has a significant effect on the drying property of the ink in the ball holding chamber 52. This has revealed that the drying property of the ink in the ball holding chamber 52 can be controlled based on the volume of the space SB, regardless of the shape and dimensions of the ink flow hole 62 and the ink flow groove 64. Specifically, the inventors have found that by defining a space SC in the ball holding chamber 52 from the tip 50a of the tip body 50 to the starting point S1, the drying property of the ink in the ball holding chamber 52 can be controlled when the ratio of the volume of the space SB to the volume of the space SC is within a certain range.

[0055] The space (third space) SC in the ball holding chamber 52 from the tip 50a of the tip body 50 to the starting point S1 is defined under the following conditions: The ball 42 is positioned at the rearmost position within the ball holding chamber 52, and is in contact with the front end 62a of the ink flow hole 62. Portions of the space SC that are not filled with ink, even if they are positioned between the tip 50a and the starting point S1, are not included in the space SC. Specifically, the portions that are not filled with ink are the portions occupied by the ball 42. The space SC is defined under the above conditions, and the volume of this space SC can be calculated.

[0056] The volume of the space SB can be set to 1.6 times or more the volume of the space SC. This ensures a sufficient volume for the space SB, further suppressing drying of the ink in the space SC of the ball holding chamber 52. Preferably, the volume of the space SB can be set to 1.6 times or more and 5 times or less the volume of the space SC. Also, preferably, the volume of the space SB can be set to 1.7 times or more the volume of the space SC. More preferably, the volume of the space SB can be set to 1.7 times or more and 3 times or less the volume of the space SC.

[0057] Furthermore, the volume of the space SA can be set to 1.5 times or more the volume of the space SC. This ensures a sufficient volume for the space SA, further suppressing drying of the ink in the space SC of the ball holding chamber 52. Preferably, the volume of the space SA can be set to 1.5 times or more and 5 times or less the volume of the space SC. Also, preferably, the volume of the space SA can be set to 1.7 times or more the volume of the space SC. More preferably, the volume of the space SA can be set to 1.7 times or more and 3 times or less the volume of the space SC.

[0058] The ballpoint pen tip 40 of this embodiment includes a ball 42 having a diameter of 0.5 mm or less and a tip body 50 that holds the ball 42. The tip body 50 has a ball holding chamber 52 that holds the ball 42, a rear hole 57 located behind the ball holding chamber 52, an ink flow hole 62 that connects the ball holding chamber 52 and the rear hole 57, and an ink flow groove 64 that extends in the radial direction dr from the ink flow hole 62, opens into the ball holding chamber 52, and does not reach the rear hole 57. When the ink consumption per m is A (mg) and the diameter of the ball 42 is B (mm), the ratio (A / B) of the ink consumption A to the diameter B of the ball 42 is 200 mg / mm or more and 800 mg / mm or less, and when the front end 64a of the ink flow groove 64 is set as the starting point S1 and a position 0.3 mm rearward from the front end 62a of the ink flow hole 62 is set as the ending point S2, the volume of the space SA in the ink flow hole 62 and the ink flow groove 64 from the starting point S1 to the ending point S2 is 0.02 mm 3 That's all.

[0059] The ballpoint pen refill 30 of this embodiment includes the ballpoint pen tip 40 described above and an ink reservoir tube 32 that contains ink.

[0060] The ballpoint pen 10 of this embodiment includes the ballpoint pen refill 30 described above.

[0061] With this ballpoint pen tip 40, ballpoint pen refill 30, and ballpoint pen 10, the volume of the space SA of the ink flow hole 62 and the ink flow groove 64 is sufficiently secured in the area close to the ball 42, particularly in the area between the front end 64a of the ink flow groove 64 as the starting point S1 and the end point S2 at a position 0.3 mm rearward from the front end 62a of the ink flow hole 62. This makes it possible to increase the amount of ink present in the area close to the ball 42. This effectively prevents ink from drying out in the ball holding chamber 52. In particular, even when the ballpoint pen 10 is left unused for an extended period of time, the ink is effectively prevented from drying out in the ball holding chamber 52.

[0062] In the ballpoint pen tip 40 of this embodiment, the volume of the space SA in the ink flow hole 62 and the ink flow groove 64 from the starting point S1 to the ending point S2 is 1.5 times or more the volume of the space SC in the ball holding chamber 52 from the tip 50a of the tip body 50 to the starting point S1.

[0063] According to such a ballpoint pen tip 40, the volume of the space SA can be sufficiently ensured, so that the ink in the space SC of the ball holding chamber 52 can be further prevented from drying out.

[0064] In the ballpoint pen tip 40 of this embodiment, the inner diameter D1 of the ink flow hole 62 is 40% or more of the diameter of the ball 42.

[0065] According to such a ballpoint pen tip 40, the cross-sectional area of ​​the ink flow hole 62 can be ensured sufficiently, so that the amount of ink present in the area close to the ball 42 can be further increased.

[0066] In the ballpoint pen tip 40 of this embodiment, the length L1 of the ink flow hole 62 is 90% or less of the diameter of the ball 42.

[0067] With this ballpoint pen tip 40, it is possible to reduce the length along the axial direction da of the ink flow hole 62, which has a relatively small cross-sectional area among the ink flow paths from the rear hole 57 to the ball holding chamber 52, thereby reducing resistance to the flow of ink in the ink flow hole 62. Therefore, it is possible to increase the flow rate of ink from the rear hole 57 to the ball holding chamber 52 and ensure a sufficient amount of ink in the area close to the ball 42.

[0068] In the ballpoint pen tip 40 of this embodiment, the length L2 of the region of the ink flow hole 62 where the ink flow groove 64 is not formed is 90% or less of the diameter of the ball 42.

[0069] The region of the ink flow hole 62 where the ink flow groove 64 is not formed is the region with the smallest cross-sectional area of ​​the ink flow path from the rear hole 57 to the ball holding chamber 52. According to the ballpoint pen tip 40 of this embodiment, the length along the axial direction da of this region with the smallest cross-sectional area can be reduced, thereby reducing resistance in the ink flow path. Therefore, it is possible to further increase the flow rate of ink from the rear hole 57 to the ball holding chamber 52 and ensure a sufficient amount of ink in the region close to the ball 42.

[0070] The ballpoint pen tip 40 of this embodiment further includes a resilient member 44 having a spring portion 46 and a rod portion 48 that extends forward from the spring portion 46 and abuts against the ball 42 from behind.

[0071] With this ballpoint pen tip 40, when not writing, the biasing force of the resilient member 44 causes the ball 42 to be positioned at the frontmost position within the ball holding chamber 52 and to abut against the crimped portion 56 of the tip body 50. At this time, the gap between the ball 42 and the crimped portion 56 is sealed. This prevents ink from leaking out when not writing, and also prevents the ink in the ball holding chamber 52 from drying out.

[0072] In the ballpoint pen tip 40 of this embodiment, the movable range C of the ball 42 in the front-rear direction relative to the tip body 50 is 0.015 mm or more and 0.06 mm or less.

[0073] When the ball 42 has such a movable range C, the gap that can occur between the ball 42 and the crimped portion 56 becomes relatively large, and the ink in the ball holding chamber 52 tends to dry out. Therefore, in such a ballpoint pen tip 40, the volume of the space SA is set to 0.02 mm 3 By doing so, the effect of suppressing the drying of ink in the ball holding chamber 52 is greatly achieved. [Example]

[0074] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples.

[0075] Five ballpoint pen tip samples, designated as sample numbers 1 to 5 below, were prepared, and each sample was left for a predetermined period of time, after which a writing test was carried out and the quality of the writing was evaluated.

[0076] Sample dimensions and material The following conditions were common to all samples. Ball diameter: 0.5 (mm) Number of ink flow channels: 4 Distance from the central axis to the main part of the peripheral wall of the ink flow groove R2: 0.245 (mm) Ink flow groove width: 0.09 (mm) Length of the main part of the ink flow groove wall: 0.13 (mm) Ball material: Tungsten carbide Tip body material: Stainless steel Material of spring: Stainless steel

[0077] Ink composition An ink composition was prepared by mixing 25 parts by weight of a thermochromic microencapsulated pigment (previously cooled to −20° C. or below to develop a black color), 0.3 parts by weight of a shear thinning agent (xanthan gum), 10 parts by weight of urea, 10 parts by weight of glycerin, 0.5 parts by weight of a nonionic penetrating agent (manufactured by San Nopco Ltd., product name: Nopco SWWET-366), 0.1 parts by weight of a modified silicone antifoaming agent (manufactured by San Nopco Ltd., product name: Nopco 8034), 0.5 parts by weight of a phosphate ester surfactant (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Plysurf AL), 0.5 parts by weight of a pH adjuster (triethanolamine), 0.2 parts by weight of an antifungal agent (manufactured by Lonza Japan Ltd., product name: Proxel XL-2), and 52.9 parts by weight of water. The pH of the resulting ink composition at 20°C was 8.0, and the viscosity measured at 20°C was 3.84 sec -1 At 780 mPa·s, shear rate 384 sec -1 The value was 35.0 mPa·s.

[0078] A ballpoint pen tip of Samples 1 to 5 shown in Table 1 was attached to one end of a polypropylene ink reservoir via a tip holder, and the ink composition was filled into the ink reservoir. An ink backflow preventer was then placed in close contact with the rear end surface of the ink to obtain a ballpoint pen refill. The ink consumption per 100 m of writing with this ballpoint pen refill was 140 mg.

[0079] Evaluation method Each sample was left standing in a thermostatic chamber set at 50°C and 0% humidity for 60 days, and then the pen tip was moved to draw continuous circles with a diameter of 10 mm while in contact with the paper surface to form handwriting. In this case, some circles from the beginning of the handwriting may become smudged. In this example, the resulting handwriting was evaluated according to the following evaluation criteria using the number of circles with smudged handwriting. A: The number of circles with smudges is 6 or less. B: The number of circles with smudges is 7 or more. When the rating is A, the number of circles with smudges is relatively small, which means that the ink drying in the ball holding chamber is sufficiently suppressed. On the other hand, when the rating is B, the number of circles with smudges is relatively large, which means that the ink drying in the ball holding chamber is not sufficiently suppressed. In particular, a rating of B here is considered to be at a level that is not practically usable.

[0080] In Table 1, D1 is the inner diameter (mm) of the ink flow hole. D2 is the diameter (mm) of the rod portion of the resilient member. L1 is the length (mm) of the ink flow hole. L5 is the length (mm) from the front end (64a) of the ink flow groove to the front end (62a) of the ink flow hole along the axial direction da. L6 is the length (mm) of the inclined portion of the peripheral wall of the ink flow groove along the axial direction da, i.e., the length (mm) from the rear end (67a) of the main portion to the rear end (64b) of the inclined portion along the axial direction da. V1 is the volume (mm) of the first space portion (SA). 3 ) V2 is the volume (mm 3 ) V3 is the volume (mm 3 ) V1 / V3 is the volume V3 (mm 3 ) to volume V1 (mm 3 ) V2 / V3 is the ratio of the volume V3 (mm 3 ) to volume V2 (mm 3 ) is the ratio of V1 to V2. In samples 1 to 5, where the ball diameter is 0.5 mm, the length at 60% of the ball diameter (diameter) is 0.3 mm, and the values ​​of V1 and V2 are the same. Accordingly, in samples 1 to 5, the values ​​of V1 / V3 and V2 / V3 are the same.

[0081] [Table 1]

[0082] FIG. 5 is a graph showing the calculation results of the volume of the space (SA) in the ink flow hole and ink flow groove for each sample. In the graph of FIG. 5, the horizontal axis represents the distance (mm) from the front end (62a) of the ink flow hole, more specifically, the distance measured rearward along the axial direction da, with the front end of the ink flow hole set at 0 mm. Negative distances on the horizontal axis represent portions located forward of the front end of the ink flow hole. The vertical axis represents the cumulative volume (mm) of the space (SA) at each position along the axial direction da. 3 This cumulative volume is calculated starting from the front end (64a) of the ink flow groove. That is, the cumulative volume is 0 mm at the front end of the ink flow groove. 3 Here, the front end of the ink flow groove is located forward of the front end of the ink flow hole (see Figure 3). Therefore, if the cumulative volume is 0 mm 3 The distance on the horizontal axis at the point where the cumulative volume is 0 mm is negative. 3 It is larger than that.

[0083] As shown in Table 1 and Figure 5, in Samples 1 and 2, the cumulative volume was 0.2 mm at the point where the distance on the horizontal axis, i.e., the distance from the front end of the ink flow hole, was 0.3 mm. 3 On the other hand, in samples 3 to 5, the cumulative volume is 0.2 mm at the point where the distance on the horizontal axis is 0.3 mm. 3 The cumulative volume at a distance of 0.3 mm from the front end of the ink flow hole corresponds to the volume of the space (SA). In samples 2 and 5, where the length L1 of the ink flow hole is 0.3 mm, the volume of the rear hole is accumulated in the region where the distance on the horizontal axis exceeds 0.3 mm, so the cumulative volume increases sharply at the 0.3 mm point.

[0084] In Table 1, the volume V1 is 0.02 mm 3 The evaluation of Samples 1 and 2 is A. That is, the volume V1 of the space SA is 0.02 mm 3From the above, it can be seen that drying of the ink in the ball holding chamber 52 is effectively suppressed. This is because the volume V1 of the space SA is 0.02 mm 3 This is thought to be because a sufficient amount of ink was able to be present in the area close to the ball 42 due to the above. Furthermore, samples 1 and 2, in which the V1 / V3 value was 1.5 times or more, were evaluated as A. In other words, it can be seen that the drying of ink in the ball holding chamber 52 is effectively suppressed because the V1 / V3 value was 1.5 times or more. Furthermore, samples 1 and 2, in which the V2 / V3 value was 1.6 times or more, were evaluated as A. In other words, it can be seen that the drying of ink in the ball holding chamber 52 is effectively suppressed because the V2 / V3 value was 1.6 times or more. [Explanation of symbols]

[0085] 10 ballpoint pens 12 Appearance mechanism 14 Friction material 16 clips 18 Coil spring 20 shaft cylinder 21 Front axle 22 Opening 23 First engagement portion 24 Male thread 25 rear axle 26 Female thread 27 Slide hole 28 Rear end cap 29 Grip material 30 ballpoint pen refills 32 Ink reservoir 34 Tip holder 36 Second engagement portion 40 Ballpoint Pen Tips 42 balls 44 Elastic member 46 Spring part 48 Rod section 50 Chip body 50a tip 52 Ball Holding Room 54 Back wall 56 Crimping part 57 Rear hole 62 Ink flow hole 62a front end 62b rear end 64 Ink flow groove 64a front end 64b rear end 66 Peripheral wall 67 Main Section 67a rear end 68 Slope SA space section (first space section) SB space section (second space section) SC space part (3rd space part) S1 Starting point S2 End point

Claims

1. A ballpoint pen tip comprising a ball having a diameter of 0.5 mm or less and a tip body that holds the ball, The chip body includes: a ball holding chamber that holds the ball; a rear hole located rearward of the ball-holding chamber; an ink flow hole that connects the ball holding chamber and the rear hole; an ink flow groove extending radially from the ink flow hole, opening into the ball holding chamber, but not reaching the rear hole; When the ink consumption per 100 m of handwriting is A (mg) and the diameter of the ball is B (mm), the ratio (A / B) of the ink consumption A to the diameter B of the ball is 200 mg / mm or more and 800 mg / mm or less, When the front end of the ink flow groove is the starting point and the position 0.3 mm rearward from the front end of the ink flow hole is the ending point, the volume of the space in the ink flow hole and the ink flow groove from the starting point to the ending point is 0.02 mm ３ That's it, ballpoint pen tip.

2. 2. The ballpoint pen tip according to claim 1, wherein the volume of the space in the ink flow hole and the ink flow groove from the starting point to the ending point is 1.5 times or more the volume of the space in the ball holding chamber from the tip of the tip body to the starting point.

3. 3. The ballpoint pen tip according to claim 1, wherein the inner diameter of the ink flow hole is 40% or more of the diameter of the ball.

4. 4. The ballpoint pen tip according to claim 1, wherein the length of the ink flow hole is 90% or less of the diameter of the ball.

5. The ballpoint pen tip according to any one of claims 1 to 4, wherein the length of the region of the ink flow hole where the ink flow groove is not formed is 90% or less of the diameter of the ball.

6. The ballpoint pen tip according to any one of claims 1 to 5, further comprising a resilient member having a spring portion and a rod portion extending forward from the spring portion and abutting the ball from behind.

7. The ballpoint pen tip according to any one of claims 1 to 6, wherein the range of movement of the ball in the front-to-rear direction relative to the tip body is 0.015 mm or more and 0.06 mm or less.

8. The ballpoint pen tip according to any one of claims 1 to 7, A ballpoint pen refill having an ink storage tube for storing ink.

9. 9. The ballpoint pen refill according to claim 8, wherein the ink is a thermochromic ink.

10. A ballpoint pen equipped with the ballpoint pen refill according to claim 8 or 9.

Images