Ballpoint pen point and ink core

Abstract

A ballpoint pen head is provided with: a cylindrical holder having a ball seat therein, the tip of the holder being configured from a pressing part having a diameter reduced toward the inside; a first tapered surface formed on the outer periphery of the holder, the tip of the first tapered surface being tapered; a second tapered surface having a tapered tip, which is formed on the outer periphery of the holder at a position closer to the tip side of the holder than the first tapered surface, and has a taper angle of 60 degrees or more and greater than the taper angle of the first tapered surface; a third tapered surface which is formed on the outer periphery of the pressing part, is connected to the second tapered surface, and has a tapered angle larger than that of the second tapered surface; and a writing ball which is accommodated in the ball seat in a state in which a part of the writing ball protrudes from the front end of the holder, and the protruding amount of the writing ball protruding from the front end of the holder is 25% or more of the diameter of the ball.

Description

Technical Field

[0001] This disclosure relates to ballpoint pen tips and ink cartridges mounted on ballpoint pens. Background Technology

[0002] It is known that in a ballpoint pen tip, a second shoulder is provided behind the extrusion shoulder, and the extrusion shoulder is positioned outside the imaginary tangent between the writing ball and the second shoulder (see Japanese Patent Application Publication No. 2022-190491). Summary of the Invention

[0003] The problem the invention aims to solve

[0004] However, when the writing angle is shallow, the squeezing part of the ballpoint pen tip may come into contact with the paper and deform inward.

[0005] The purpose of this invention is to provide a technique that can suppress the inward deformation of the extrusion portion of a ballpoint pen tip during use.

[0006] Solution for solving the problem

[0007] The first technical solution disclosed herein is a ballpoint pen tip comprising: a retainer, which is cylindrical and has a ball seat inside, the front end of which is formed by a compression portion that tapers inward; a first conical surface that tapers at the front end and is formed on the outer periphery of the retainer; a second conical surface that tapers at the front end and is formed on the outer periphery of the retainer at a position closer to the front end of the retainer than the first conical surface, the conical angle being 60° or more and larger than the conical angle of the first conical surface; a third conical surface that tapers at the front end and is formed on the outer periphery of the compression portion and connected to the second conical surface, the conical angle being larger than the conical angle of the second conical surface; and a writing ball that is partially protruding from the front end of the retainer and housed in the ball seat, the protrusion amount being 25% or more of the ball diameter.

[0008] For the ballpoint pen tip of the second technical solution of this disclosure, in the ballpoint pen tip of the first technical solution, in the imaginary cross section including the axis of the retainer, the angle of the second conical surface with respect to the imaginary tangent is less than 20°, the imaginary tangent being the boundary between the second and third conical surfaces and the imaginary tangent of the writing ball.

[0009] For the ballpoint pen tip of the third technical solution of this disclosure, in the ballpoint pen tip of the first or second technical solution, in an imaginary cross section including the axis of the retainer, the wall thickness length of the retainer extending from the diameter portion of the writing ball toward the outer periphery in the state where the writing ball rests on the ball support of the retainer is 16% or more of the diameter of the writing ball.

[0010] The fourth technical solution disclosed herein is an ink core comprising: a ballpoint pen tip according to any one of the first to third technical solutions; and an ink collection tube having the rear end of the ballpoint pen tip installed at its front end and filled with ink inside.

[0011] Furthermore, the viscosity of the ink in the ink core is 1 mPa·sec to 100 mPa·sec.

[0012] Invention Effects

[0013] According to this disclosure, it is possible to suppress the inward deformation of the extrusion portion of the ballpoint pen tip during use. Attached Figure Description

[0014] Figure 1 This is a front cross-sectional view of a ballpoint pen with a ballpoint pen tip that applies an embodiment of the present disclosure.

[0015] Figure 2 It means in Figure 1 A front sectional view of a ballpoint pen with the sealing component moved from the front of the tip to the rear of the push button.

[0016] Figure 3 This is a three-dimensional view of the sealing component.

[0017] Figure 4 It is applied to Figure 1 A front cross-sectional view of the ink cartridge of a ballpoint pen.

[0018] Figure 5 It is applied to Figure 4 A front cross-sectional view of a ballpoint pen tip according to one embodiment of the ink core disclosed herein.

[0019] Figure 6 It is by Figure 5 A magnified view of the portion indicated by arrow 6X.

[0020] Figure 7 yes Figure 6 The front view of the front end of the ballpoint pen tip is shown.

[0021] Figure 8 yes Figure 6 Arrow 8X-8X sectional view.

[0022] Figure 9 yes Figure 6 The image shown is an enlarged view of the tip of a ballpoint pen before it is squeezed. Detailed Implementation

[0023] Hereinafter, the methods for implementing this disclosure will be described based on the accompanying drawings. Components indicated by the same reference numerals in the various drawings refer to the same or identical components. Furthermore, in the embodiments described below, repeated descriptions and reference numerals are sometimes omitted. In addition, the drawings used in the following description are schematic, and the dimensional relationships and ratios of the elements shown in the drawings may not be consistent with reality. Furthermore, the dimensional relationships and ratios of the elements may not be consistent between the various drawings. Furthermore, in the following description, the side where the ballpoint pen tip is located is designated as the "front end," and the opposite side, i.e., the side where the click lever (also called the click button) is located, is designated as the "rear end." Furthermore, at any position of the ballpoint pen, the direction of the front end is designated as "forward," and the direction of the rear end is designated as "backward."

[0024] exist Figure 1 and Figure 2 The image shows a front cross-sectional view of a ballpoint pen 20 that incorporates a ballpoint pen tip 40 according to an embodiment of the present disclosure. Specifically, the ballpoint pen 20 includes an ink cartridge 30 (hereinafter, appropriately referred to as "pen cartridge 30") on which the ballpoint pen tip 40 is incorporated.

[0025] like Figure 1 As shown, the ballpoint pen 20 is a push-button type ballpoint pen. The ballpoint pen 20 includes: a barrel body 22; a pen tip 30, which is housed in the barrel body 22 in a manner that allows it to move forward and backward axially; and a push-button mechanism 70, which causes the tip of the built-in pen tip 30 to protrude and sink into the barrel body 22 relative to the front end of the barrel body 22.

[0026] The main body 22 has a cylindrical pen barrel 24 that houses the pen refill 30 inside and a generally conical mouth front member 26 that is threadedly connected to the front end portion of the pen barrel 24.

[0027] A pen clip component 28 is provided at the rear end of the pen barrel 24.

[0028] The bottom surface of the front end member 26 is open, and a threaded groove is formed on its outer peripheral surface. Thus, the front end member 26 is mounted on the pen barrel 24.

[0029] [Ink Core 30]

[0030] like Figure 4 As shown, the pen refill 30 includes a ballpoint pen tip 40, an ink collection tube 32, and a connector 34.

[0031] The details of ballpoint pen tip 40 will be described later.

[0032] The ink receiving tube 32 is a tube for receiving ink 31A. In this embodiment, as an example, a tube made of polypropylene is used for the ink receiving tube 32. The interior of the ink receiving tube 32 is, for example, filled with ink 31A with a viscosity of 1 mPa·sec to 100 mPa·sec. Specifically, the viscosity of ink 31A is 383 sec at 25°C and a shear rate of 383 sec. -1 The viscosity at that time. In addition, in the ink collection tube 32, a follower 31B is housed behind the ink 31A.

[0033] The connector 34 is a component for mounting the ballpoint pen tip 40 to the front end of the ink collection tube 32. An ink flow hole with a diameter smaller than the diameter of the press-in portion between the connector 34 and the ballpoint pen tip 40 is formed in the connector 34.

[0034] [Ballpoint pen tip 40]

[0035] like Figure 5 and Figure 6 As shown, the ballpoint pen tip 40 is a component constituting the pen refill 30. The rear end of the ballpoint pen tip 40 is attached to the front end of the ink collection tube 32 via a connector 34. Furthermore, the "front end" of the ballpoint pen tip 40 referred to here is the writing tip side of the ballpoint pen tip 40. The side of the ballpoint pen tip 40 opposite to the writing tip is the "rear end".

[0036] like Figure 6 As shown, the ballpoint pen tip 40 includes a retainer 42, a first conical surface 44, a second conical surface 46, a third conical surface 48, and a writing ball 50. The writing ball 50 is seated in the ball support 58 of the retainer 42.

[0037] (Retaining component 42)

[0038] The retainer 42 constitutes the main body of the ballpoint pen tip 40. The retainer 42 is cylindrical and has a ball bearing seat 52 inside. In addition, the term "cylindrical" as used herein refers to the shape of the internal space connecting the front end (one end) 42A and the rear end (the other end) 42B of the retainer 42, and there is no particular limitation on the shape of the inner and outer circumferences.

[0039] The ball holder 52 is an internal space formed on the front end 42A side of the retainer 42 to accommodate the writing ball 50.

[0040] In addition, the retainer 42 has a rear hole 54. The rear hole 54 extends from the rear end of the retainer 42 into the interior space of the retainer 42 near the ball bearing seat 59. The rear hole 54 guides the ink 31A housed in the ink collection tube 32 to the ball bearing seat 52.

[0041] In addition, a spring (not shown) is inserted inside the rear hole 54. (Set as...) Figure 4In the case of the ink core 30 shown, the spring is used to press the writing ball 50 from the rear end of the retainer 42 toward the front end.

[0042] Furthermore, the retainer 42 has an ink hole 56 between the ball bearing seat 52 and the rear hole 54. The ink hole 56 is the internal space of the retainer 42 that connects the ball bearing seat 52 and the rear hole 54. The ink hole 56 is a circular hole with a diameter smaller than that of the rear hole 54. Around the ink hole 56 in the retainer 42, a plurality of grooves (three in this embodiment) extending axially along the retainer 42 are formed at equal intervals, namely channel grooves 60.

[0043] The ink 31A, guided to the front end of the rear hole 54, reaches the ball bearing seat 52 from the ink hole 56 via the various channel grooves 60. Alternatively, if the ink 31A used is of high viscosity and difficult to generate a direct flow, the channel groove 60 may extend to the rear hole 54 from the viewpoint of ink 31A flow. On the other hand, if the ink 31A used is of low viscosity and easily generates a direct flow, it may not extend to the rear hole 54, but rather... Figure 6 It stops midway through the ink hole 56 as shown.

[0044] Then, the ink 31A that reaches the ball bearing 52 adheres to the surface of the writing ball 50 and is transferred to the writing surface.

[0045] Furthermore, the front end of the retainer 42 is composed of a compression portion 51 that is compressed inward and narrowed in diameter. Specifically, the retainer 42 extends from... Figure 9 Starting from the state before compression shown, the front end portion of the second conical surface 46 is compressed radially inward, becoming... Figure 6 The state after compression is shown. The compression part 51 has the function of holding the writing ball 50 in the ball holder 52 and preventing it from falling.

[0046] Furthermore, the writing ball 50, inserted into the ball bearing seat 52, is pressed backward through a process known as "tapping." Additionally, a portion of the curved surface of the writing ball 50 is transferred onto the bottom surface of the ball bearing seat 52 to form a concave surface. This concave surface is the ball bearing support 58 (see reference). Figure 6 and Figure 8 ).

[0047] Furthermore, the rear end portion of the retainer 42 is configured as an insertion portion 43 with a reduced outer diameter. For example... Figure 4 As shown, the inserted part 43 is inserted into the front end side of the connector 34.

[0048] The retainer 42 is formed, for example, by machining a cylindrical material made of metal such as stainless steel. Alternatively, depending on the application, the retainer 42 can also be formed by plastic deformation and machining of the tubing. Preferably, it is formed by machining a cylindrical material made of bismuth-containing ferritic stainless steel with a Vickers hardness of 270 (based on measurements of five retainers). Although bismuth has properties similar to lead (Pb), an additive commonly used to achieve machinability, bismuth is a substance with a lower tendency to ionize than lead. Therefore, it is less likely to dissolve into the ink compared to lead. Furthermore, unlike harmful lead, bismuth is a harmless substance that has no impact on the environment. Ideally, the Vickers hardness should be 200 or higher and 450 or lower. When the Vickers hardness is below 200, the ball bearing 58 is significantly worn down as the writing ball 50 rotates during writing, making it difficult to write continuously for extended periods. Furthermore, when the Vickers hardness exceeds 450, the machining and formation of the extrusion portion 51 becomes difficult. In addition, the Vickers hardness measurement point is set at the position inside the holder 42 0.2 mm from the outer surface toward the center, and other measurement methods are in accordance with JIS Z2244.

[0049] (First cone surface 44)

[0050] The first conical surface 44 is a tapered surface formed on the outer periphery of the retainer 42. The cone angle α of the first conical surface 44 is, for example, set to be 25° or more and 35° or less.

[0051] (Second cone surface 46)

[0052] The second conical surface 46 is a conical surface formed on the outer periphery of the retainer 42, tapering towards the front end 42A of the retainer 42 compared to the first conical surface 44. The cone angle β of the second conical surface 46 is larger than the cone angle α of the first conical surface 44. Furthermore, the cone angle β of the second conical surface 46 is 60° or more. For example, the cone angle β of the second conical surface 46 is set to be 60° or more and 80° or less.

[0053] In this embodiment, such as Figure 6 and Figure 7 As shown, the second conical surface 46 is connected to the first conical surface 44, but this disclosure is not limited to this structure. For example, one or more other conical surfaces with tapered front ends may also be arranged between the second conical surface 46 and the first conical surface 44.

[0054] (3rd cone surface 48)

[0055] The third conical surface 48 is a tapered surface with a tapered front end formed on the outer periphery of the extrusion section 51. In other words, the third conical surface 48 is a tapered surface with a tapered front end formed on the outer periphery of the front end of the retainer 42. Furthermore, the third conical surface 48 is connected to the second conical surface 46. The cone angle γ of the third conical surface 48 is larger than the cone angle β of the second conical surface 44. Furthermore, the cone angle γ of the third conical surface 48 is, for example, set to be 85° or more and 110° or less.

[0056] (Writing ball 50)

[0057] The writing ball 50 is housed in the ball holder 52 with a portion protruding from the front end 42A of the retainer 42. Specifically, the writing ball 50 housed in the ball holder 52 is pressed from the rear end 42B toward the front end 42A by a spring (not shown), thus becoming a state in which a portion protrudes from the front end 42A of the retainer 42.

[0058] The writing ball 50 is, for example, a metal sphere made of ultra-hard stainless steel. Preferably, the arithmetic mean height Sa of the surface of the writing ball 50 is 0.06 μm or less. Since the arithmetic mean height Sa of the surface of the writing ball 50 is 0.06 μm or less, wear on the ball support 58 caused by the rotation of the writing ball 50 can be suppressed. The arithmetic mean height Sa is the value measured by Taylor Hobson's Talysurf CCI Lite, as specified in ISO 25178, with a measurement range of 50 μm × 50 μm on the ball surface, a measurement magnification of 100x, and a Gaussian filter of 25 μm.

[0059] Furthermore, the protrusion H of the writing ball 50 protruding from the front end of the retainer 42 is 25% or more of the ball diameter D. Additionally, the protrusion H is set to be 25% or more and 45% or less of the ball diameter D.

[0060] In addition, such as Figure 6 As shown, at the axis C containing the retainer 42 (refer to...) Figure 5 In the imaginary cross-section, the angle θ of the second conical surface 46 relative to the imaginary tangent L can be set to 20° or less. The imaginary tangent L is the imaginary tangent between the second boundary 47 between the second conical surface 46 and the third conical surface 48 and the writing ball 50. Alternatively, the angle θ can be set to greater than 0°. For example, the angle θ can also be set to 8° or more and 15° or less. Furthermore, the second boundary 47 is the part that becomes the minimum outer diameter of the second conical surface 46 and the part that becomes the maximum outer diameter of the third conical surface 48. In addition, the second boundary 47 is sometimes referred to as the extrusion shoulder.

[0061] Furthermore, the imaginary cross-section including the axis C of the retainer 42 refers to the cross-section in the ballpoint pen tip 40 of this embodiment, assuming that there exists a cross-section including the axis C of the retainer 42, for example... Figure 6The cross-section shown. Furthermore, the imaginary tangent refers to the tangent line in the imaginary cross-section, assuming a tangent exists between the writing bead 50 and the second boundary 47.

[0062] Furthermore, in the imaginary cross-section of the axis C including the retainer 42, with the writing ball 50 seated on the ball support 58 of the retainer 42, the wall thickness T of the retainer 42 on the ball centerline CL of the writing ball 50 can also be set to 16% or more of the ball diameter D of the writing ball 50. Additionally, the first boundary 45 is the portion that becomes the minimum outer diameter of the first conical surface 44, and the portion that becomes the maximum outer diameter of the second conical surface 46.

[0063] like Figure 1 As shown, the press mechanism 70 includes: a coil spring 71 clamped between the rod body 22 and the ink collection tube 32; a press part 72 disposed at the rear end of the pen barrel 24; a rotating body 74 disposed between the press part 72 and the pen refill 30; a plurality of cams 76 protruding from the outer peripheral surface of the rotating body 74; and a rear pen barrel 80 integrally formed with the pen clip member 28 and having a plurality of strips 78 protruding from the inner peripheral surface.

[0064] The press-fit part 72 and the rotating body 74 each have corresponding cam inclined surfaces, namely the press-fit cam (not shown) and the press-fit cam (not shown), configured such that by pressing forward axially, the rotating body 74 rotates in a predetermined angle in only a certain direction each time. Furthermore, when the press stops after the press-fit action, the pen refill 30 is always subjected to a rearward force by the coil spring 71, causing the rotating body 74 to rotate in the same direction as the aforementioned press-fit part 72 and rotating body 74 via the cam 76 of the rotating body 74 and the corresponding bar 78 of the rear pen barrel 80. That is, the rotating body 74 rotates at a predetermined angle, completing one revolution at a certain moment (through two presses in the above structure), repeating this action. In addition, the front end of the rotating body 74 always abuts against the pen refill 30, and the front-rear position of the cam 76 determines the position of the pen tip at the front end of the pen refill 30.

[0065] exist Figure 1 A cross-sectional view of the ballpoint pen 20 before use is shown. Furthermore, in... Figure 2 The image shows a cross-sectional view of the ballpoint pen 20 in its writing state after use. On the front end side of the ballpoint pen tip 40 before use, a [missing information - likely a component or material] is pressed into the opening at the front end of the pen barrel. Figure 3 The sealing member 90 is shown in a perspective view. This prevents ink evaporation when the pen is not in use. After use, the sealing member 90 can be installed on the push rod (operating part) at the rear of the ballpoint pen 20. The sealing member 90 is formed of a deformable thermoplastic elastomer. Furthermore, it can also be used to cushion the impact when the ballpoint pen 20 falls when installed on the push rod, or as a friction element that facilitates easy thermochromic changes when the ink 31A is thermochromic.

[0066] Next, the effects of this embodiment will be explained.

[0067] When the third conical surface 48 contacts the paper surface, stress concentration occurs at the compression shoulder (second boundary 47), and the compression part 51 is prone to deforming inward. Therefore, in the ballpoint pen tip 40 of this embodiment, the cone angle β of the second conical surface 46 is set to 60° or more. This ensures the wall thickness of the compression shoulder, that is, ensures the rigidity of the compression part 51, and suppresses deformation of the compression shoulder. Moreover, by ensuring the rigidity of the compression part 51, the ball drop load is increased, and the anti-drop effect of the writing ball 50 is improved. Furthermore, in the ballpoint pen tip 40 of this embodiment, the protrusion amount H of the writing ball 50 protruding from the front end 42A of the retainer 42 is set to 25% or more of the ball diameter D. By setting it in this way, as Figure 6 As shown, by setting the angle θ of the second conical surface 46 relative to the imaginary tangent L within a specified range, the range of the writing angle at which the third conical surface 48 contacts the paper can be narrowed. Here, when the third conical surface 48 contacts the paper, stress concentration occurs at the pressing shoulder. Therefore, by narrowing the range of the writing angle at which the third conical surface 48 contacts the paper, the inward deformation of the pressing portion 51 containing the third conical surface 48 is suppressed.

[0068] Furthermore, when the cone angle β of the second cone surface 46 is less than 60°, the rigidity of the third cone surface 48 is not sufficiently ensured, and the effect of suppressing the inward deformation of the pressing part 51 is low. On the other hand, when the cone angle β of the second cone surface 46 exceeds 80°, the difference between it and the cone angle γ of the third cone surface 48 is small. When the writer observes the front end of the ballpoint pen tip 40 while writing, the contact part between the writing ball 50 and the paper surface is obscured by the first boundary 45 and is difficult to see. This may make writing difficult or create the illusion that the writing ball 50 is larger than the actual ball diameter D, which may result in a sense of incongruity in the line width during writing. Therefore, it is preferable that the cone angle β of the second cone surface 46 is set to be 60° or more and 80° or less.

[0069] Furthermore, when the protrusion H of the writing ball 50 is less than 25%, the contact portion between the writing ball 50 and the paper surface is obscured by the first boundary 45 and is difficult to see. Additionally, the effect of suppressing the inward deformation of the pressing portion 51, including the third conical surface 48, is reduced. Moreover, when the protrusion H of the writing ball 50 is 45% or less, the writing ball 50 is prone to falling off. Therefore, it is preferable that the protrusion H of the writing ball 50 is set to be 25% or more and 45% or less.

[0070] In the ballpoint pen tip 40 of this embodiment, the angle θ of the second conical surface 46 relative to the imaginary tangent L is set to 20° or less. Therefore, as... Figure 6As shown, the writing angle at which the third conical surface 48 contacts the paper is close to the writing angle at which the second conical surface 44 contacts the paper. That is, the range of the writing angle at which the third conical surface 48 contacts the paper is narrowed. Here, since stress concentration occurs at the pressing shoulder when the third conical surface 48 (the periphery of the pressing shoulder of the third conical surface 48) contacts the paper, narrowing the range of the writing angle at which the third conical surface 48 contacts the paper suppresses the inward deformation of the pressing part 51, including the third conical surface 48.

[0071] In the ballpoint pen tip 40 of this embodiment, when the writing ball 50 is seated in the ball support seat 58 of the retainer 42, the wall thickness T of the retainer 42 on the ball center line CL of the writing ball 50 is set to 16% or more of the ball diameter D of the writing ball 50, thereby improving the effect of suppressing the deformation of the extrusion part 51 inward.

[0072] In the ink core 30 of this embodiment, the shear rate of ink 31A is 383 seconds. -1 The viscosity at 25°C is set to 1 mPa·sec to 100 mPa·sec, resulting in a smooth writing experience. Furthermore, by setting the ink surface tension to 20 mN / m to 40 mN / m, bleed-through of the ink is prevented.

[0073] Preferably, the ink specifically comprises at least a colorant, water, pigment, and a polyester resin emulsion with a solid content of 0.5% to 30% by mass relative to the total amount of the ink composition and a number-average molecular weight (Mn) of 10,000 or higher. The polyester resin emulsion can be obtained by using at least a polyol component and polycarboxylic acid components such as polycarboxylic acid, polycarboxylic anhydride, and polycarboxylic acid ester. When the number-average molecular weight (Mn) is 10,000 or higher, it exhibits excellent anti-drip properties and long-term storage stability. Furthermore, the number-average molecular weight (Mn) is a value measured using gel permeation chromatography (GPC), for example, using "RID-6A" manufactured by Shimadzu Corporation (column: "TSK-GEL" manufactured by Tosoh Corporation, solvent: tetrahydrofuran (THF), column temperature: 40°C), determined from a standard curve prepared using polystyrene standard samples. Examples of commercially available polyester resin emulsions include Elitel KA-0134, Elitel KA-3556, and Elitel KA-6137 manufactured by Unitika Co., Ltd.

[0074] Alternatively, the ink may contain at least a colorant, water, an organic solvent in an amount of 0.1% to 30% by weight relative to the total amount of the ink composition, and sugars in an amount of 0.1% to 30% by weight relative to the total amount of the ink composition. The main backbone is glycerol with a degree of polymerization of 2 to 8. It is supplemented with 80 to 150 moles of ethylene oxide and contains 0.1% to 30% by weight of an epoxyalkane addition glycerol ester with an average molecular weight of 2800 to 10000 and an HLB of 15 to 19.5, which is ester-bonded with a fatty acid or aromatic carboxylic acid having 4 to 25 carbon atoms. When the molar amount of carboxylic acid is set as X and the degree of polymerization of glycerol is set as Y, X / [Y+2] is 0.25 to 0.7.

[0075] Example

[0076] For the ballpoint pen 20 shown in the above embodiment, the diameter D of each writing ball 50 used by the ballpoint pen tip 40 is set to 0.38mm, 0.5mm, and 0.7mm, respectively. As ink 31A, the following black ink is used, set as... Figure 4 The shape of the pen refill shown was used to measure whether the extrusion part was deformed under the following conditions.

[0077] The preparation and properties of the ink used in the DC test are as follows. Total amount 100% by mass.

[0078] Colorant: Colored resin particles (black, solid content 40% by mass; average particle size 0.5μm): 40%

[0079] Resin: Polyester resin emulsion (Elitel KA-0134): 5%

[0080] Resin: Polyester resin emulsion (Elitel KA-6137): 5%

[0081] Thickener: Xanthan Gum (KELZAN S): 0.3%

[0082] pH adjustment material: Triethanolamine: 0.1%

[0083] Rust inhibitor: Benzotriazole: 0.3%

[0084] Preservative: Benzisothiazolinone (Bayden 421): 0.3%

[0085] Lubricant: Phosphate ester (RD-510Y): 0.3%

[0086] Organic solvent: Glycerin: 10%

[0087] Water: Distilled water: Balance

[0088] Ink viscosity: 16 mPa·s (using E-type rotational viscometer [VISCOMETER RE 215 (manufactured by Toki Sangyo Co., Ltd.)], at cone: 1°34' R24, measurement time 60 seconds, shear rate 383 seconds -1 (Measurement at an environment with a measurement temperature of 25℃)

[0089] Surface tension: 37.4 mN / m (Made by Kyowa Interface Science Co., Ltd., measured using a CBVP-Z surface tension measuring device at a temperature of 25°C)

[0090] In the DC test, under an environment of 23±2℃ and 65±10% relative humidity, the writing tip was removed from the ink cartridge of each embodiment or comparative example. Figure 2 With the tip of the ballpoint pen (weighing 11g) extended, the pen is dropped from a height of 1m onto a support plate at a 50° angle relative to the horizontal. Then, five circles of approximately 20-25cm are written freehand, immediately fixed downwards, and left for 60 minutes. The size of the ink droplets accumulated at the tip is then measured. The judgment criteria are shown below.

[0091] Evaluation A: No ink droplets were produced.

[0092] Rating B: The size of the ink droplets is greater than 0 mm but less than 1 mm.

[0093] Rating C: The size of the ink droplets is greater than 1 mm but less than 2 mm.

[0094] Rating D: The ink droplet size exceeds 2mm.

[0095] As shown in Table 1, the examples are used to evaluate A and B, while the comparative examples are used to evaluate C and D. Therefore, it can be confirmed that the DC test results of the examples are better than those of the comparative examples.

[0096] [Table 1]

[0097]

[0098] The result of measuring whether the extrusion part was deformed confirmed that the extrusion part was not deformed in all embodiments of the ballpoint pen.

[0099] Industrial availability

[0100] This disclosure can be used in ballpoint pens.

Claims

1. A ballpoint pen tip, wherein, This ballpoint pen tip has: The retainer is cylindrical and has a ball bearing seat inside. The front end is formed by an extrusion section that narrows inward. A first tapered surface that tapers at the front end is formed on the outer periphery of the retainer; A second tapered surface, tapering at the front end, is formed on the outer periphery of the retainer at a position closer to the front end of the retainer than the first tapered surface, and has a tapered angle of 60° or more and larger than the tapered angle of the first tapered surface; A third conical surface, tapering at the front end, is formed on the outer periphery of the extrusion section and connected to the second conical surface; its cone angle is larger than that of the second conical surface. The writing ball is housed in the ball holder with a portion protruding from the front end of the retainer, the amount of protrusion being more than 25% of the ball diameter.

2. The ballpoint pen tip according to claim 1, wherein, In an imaginary cross-section containing the axis of the retainer, the angle of the second conical surface relative to the imaginary tangent is less than 20°, which is the imaginary tangent between the boundary of the second and third conical surfaces and the writing ball.

3. The ballpoint pen tip according to claim 1, wherein, In an imaginary cross-section including the axis of the retainer, with the writing ball resting on the ball support of the retainer, the wall thickness of the retainer extending from the diameter portion of the writing ball toward the outer periphery is 16% or more of the diameter of the writing ball.

4. An ink cartridge, wherein, This ink cartridge features: The ballpoint pen tip according to any one of claims 1 to 3; and The ink collection tube has the rear end of the ballpoint pen tip attached to its front end and is filled with ink inside.

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