JP4355060B2 - Ball for ballpoint pen - Google Patents

Description

【００３７】
つぎに、上記各実施例および比較例のボールについて、図３に示すペン先にセットし、精機工業社製ライティングテスター（ＭＯＤＥＬ ＴＳ−４Ｃ−１０）を使用して下記の条件で連続筆記試験を行った。
［試験条件］
筆記角度 ：６５°
荷 重 ：１００ｇ
筆記速度 ：７ｃｍ／ｓｅｃ
筆記距離 ：５００ｍ
ペン先本体：ステンレス
［使用インク］
Ｐｉｇ．Ｒｅｄ２５８ ：５重量％
スチレンアクリル樹脂 ：１重量％
架橋型ポリアクリル酸 ：０．２４重量％
キサンタンガム ：０．２４重量％
グリセリン ：７重量％
エチレングリコール ：１５重量％
ジエチレングリコール ：６重量％
安息香酸ナトリウム ：０．２４重量％
１，２−ベンズイソチアゾリン−３−オン ：０．４重量％
ポリオキシエチレンアルキルエーテルリン酸エステル：１．５重量％
イオン交換水 ：６３．３８重量％
【００３８】
上記各実施例１〜４の筆記試験前の表面状態写真をそれぞれ図１０〜図１３に示す。また、比較例１の筆記試験前後の表面状態写真をそれぞれ図１４および図１５に、比較例２の筆記試験前の表面状態写真を図１６に示す。上記各表面状態写真は、走査型電子顕微鏡による撮影像であり、写真中央下部の白線が５μｍのスケールになっている。また、図１０，１１，１４，１５，１６において、矢印で示しているのは、粒子境界の測定位置であり（各１０箇所）、この位置の粒子間隔を測定して粒子境界の平均間隔を求めている。
【００３９】
また、上記各実施例および比較例の粒子境界の平均間隔、ならびに筆記試験後のボールの沈み込み量（ペン先本体の摩耗量）の測定結果を下記の表２に示す。
【００４０】
【表２】

【００４１】
上記図１０〜図１６および表２から明らかなように、各実施例は、比較例に比べ粒子境界の平均間隔が小さく、ボールの沈みも良好な結果が得られることがわかる。
【００４２】
【発明の効果】
以上のように、本発明のボールペン用ボールによれば、硬質粒子同士の隙間が極めて薄くなり、表面の結合金属の部分に露呈する硬質粒子の小片がそれだけ微小なものとなり、その数も極めて少なくなる。したがって、使用中に脱落して研磨剤として作用する小片の数が非常に少なくなり、ペン先本体の摩耗が防止され、ボールのペン先本体内への沈み込みが防止される。
【００４３】
また、結合金属を使用せずに硬質粒子を焼結したものであっても、粒子境界の間隔が狭いことから、境界部分のエッジがペン先本体に対する切刃として作用することが少なくなり、ペン先本体の摩耗が防止され、ボールのペン先本体内への沈み込みが防止される。
【００４４】
したがって、従来のように、インク溝が塞がれてインクが流出しにくくなったり、ボールとペン先本体との接触面積が大きくなることによる摩擦抵抗の増大が防止される。また、筆記可能角度の増大も抑えられる。このように、従来のボールのように、早期に書き味が悪くなるようなことがほとんどなく、長期間にわたって良好な書き味が維持される。しかも、ペン先本体の摩耗が抑えられることから、ボール径を小さくしても摩耗が少ないため、細字に対応することができる。
【図面の簡単な説明】
【図１】本発明の一実施の形態のボールペン用ボールを示す要部拡大断面図である。
【図２】上記ボールペン用ボールの筆記試験後の状態を示す要部拡大断面図である。
【図３】ボールペンのペン先を示す断面図である。
【図４】上記ペン先の要部拡大断面図である。
【図５】ペン先本体のＡ−Ａ断面図である。
【図６】上記ペン先の使用状態を示す断面図である。
【図７】従来のボールペン用ボールを示す要部拡大断面図である。
【図８】上記ボールペン用ボールの摩耗状態を示す要部拡大断面図である。
【図９】ペン先本体が摩耗した状態を示す要部拡大断面図である。
【図１０】実施例１の表面状態写真である。
【図１１】実施例２の表面状態写真である。
【図１２】実施例３の表面状態写真である。
【図１３】実施例４の表面状態写真である。
【図１４】比較例１の表面状態写真である。
【図１５】比較例１の筆記試験後の表面状態写真である。
【図１６】比較例２の表面状態写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a ball for a ballpoint pen used for a pen tip of a ballpoint pen.
[0002]
[Prior art]
Conventionally, the pen tip of the gel ink ballpoint pen has a structure as shown in FIG. In the figure, reference numeral 10 denotes a hollow nib body, the tip side of which is tapered, and a ballpoint ball (hereinafter referred to as “ball”) 11 is rotatably attached to the tip. The rear end side of the nib body 10 is connected to an ink cylinder (not shown), and ink supplied from the ink cylinder to the hollow portion is supplied to the ball 11 through the ink flow path 12. .
[0003]
The tip of the pen tip will be described in detail. As shown in FIG. 4, a ball receiving recess 13 communicating with the ink flow path 12 is formed at the tip, and the caulking portion is caulked at the opening of the ball receiving recess 13 when the ball 11 is received. By forming 14, the ball 11 is rotatably held. The inner surface of the ball housing recess 13 is formed in a mortar-shaped tapered surface 15, and, as shown in FIG. 5, the five ink grooves 16 are radially formed on the tapered surface 15 in order to secure an ink outflow amount. Is formed.
[0004]
When writing with the nib, the tilted nib ball 11 is pressed against the paper 22 as shown in FIG. At this time, the ball 11 is shifted obliquely upward in the ball housing recess 13 (arrow B in the figure). Then, the ink is guided from the hollow portion of the nib body 10 through the ink flow path 12 and the ink groove 16 into the ball housing recess 13, and flows out from the gap between the wall surface of the ball housing recess 13 and the ball 11 by gravity. (Arrow C shown). Next, along with the rotation of the ball 11, ink is transferred to the paper surface 22 along the surface of the ball 11, and writing is performed.
[0005]
As the ball 11, a super hard alloy is generally used, and the super hard alloy is polished into a spherical shape. As shown in FIG. 7, such a ball 11 has a surface 19 formed of a super hard alloy in which hard intermetallic compound particles 17 such as WC are sintered via a bonding metal 18 such as Co. Is formed by polishing the mirror surface.
[0006]
[Problems to be solved by the invention]
However, in the conventional ball 11, since the layer of the bonding metal 18 is formed in the gap between the hard intermetallic compound particles 17, when the surface 19 is polished to a mirror surface, the portion of the bonding metal 18 on the surface is formed. The hard intermetallic compound pieces 20 are exposed. During use, the surface of the bonded metal 18 is worn, and the small piece 20 falls off as shown in FIG. The pieces 20 thus dropped off act as an abrasive and cause the nib body 10 to wear.
[0007]
Further, when the soft bonded metal 18 portion between the hard intermetallic compound particles 17 is worn, the edge 21 of the hard intermetallic compound particle 17 which has been polished is exposed. Then, the ball 11 with the edge 21 exposed on the surface rotates while receiving the writing pressure, so that the edge 21 acts as a cutting edge with respect to the nib body 10, and as shown in FIG. As a result, the tapered surface 15 of the ten ball receiving recesses 13 is worn, and the ball 11 sinks into the nib body 10.
[0008]
As described above, when the tapered surface 15 of the nib body 10 is worn, the ink groove 16 is blocked and the ink hardly flows out. Further, the contact area between the ball 11 and the nib body 10 is increased, the frictional resistance is increased, and the ball 11 is difficult to rotate. In addition, since the ball 11 sinks into the nib body 10, the caulking portion 14 of the nib body 10 hits the paper surface and becomes hazy unless the pen is raised. That is, the angle between the paper surface 22 and the pen that can be written without fading (the writable angle) increases. As described above, when the writable angle increases, the deviation of the ball 11 during writing (the movement distance of the ball 11 in the direction of arrow B in FIG. 6) decreases, and the gap through which ink flows out (the wall surface of the ball housing recess 13). Between the ball and the ball 11 becomes narrower, and it becomes difficult for the ink to come out. As described above, the conventional ball 11 has a problem in that the nib body 10 is worn early and becomes difficult to write or fades during use, and the writing quality is deteriorated at an early stage.
[0009]
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a ballpoint pen ball that can reduce wear of the nib body and maintain good writing for a long period of time.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the ball-point pen ball of the present invention is a ball-point pen ball made of a sintered body in which hard particles are sintered, and the average interval between particle boundaries is 0.3 μm or less. And
[0011]
That is, the ball-point pen ball of the present invention has an average particle boundary interval of 0.2 μm or less. In this way, since the average interval between the particle boundaries is narrower than that of the conventional ball, the gap between the hard particles becomes extremely thin, and the small pieces of the hard particles that are exposed to the bonded metal portion on the surface become so small that the The number is also very small. Therefore, the number of small pieces that fall off during use and act as an abrasive becomes very small, wear of the nib body is prevented, and sinking of the ball into the nib body is prevented.
[0012]
In addition, even if hard particles are sintered without using a binding metal, the edge of the boundary portion is less likely to act as a cutting edge for the pen nib body due to the narrow interval between the particle boundaries. The tip body is prevented from being worn, and the ball is prevented from sinking into the pen tip body.
[0013]
Therefore, as in the prior art, it is possible to prevent an increase in frictional resistance due to the ink groove being blocked and the ink being less likely to flow out, and the contact area between the ball and the nib body being increased. In addition, an increase in the writable angle can be suppressed. Thus, unlike the conventional balls, writing quality is hardly deteriorated at an early stage, and good writing quality is maintained over a long period of time. In addition, since the wear of the nib body is suppressed, the wear can be reduced even if the ball diameter is reduced, so that fine characters can be handled.
[0014]
In the ballpoint ball of the present invention, when the hard particles are ceramic particles, the boundary between the ceramic particles is narrow, so that the edge of the boundary portion is less likely to act as a cutting blade for the pen nib body, The wear of the main body is prevented and the sinking of the ball into the nib main body is prevented.
[0015]
When the ballpoint pen for the ballpoint pen of the present invention is used for a ballpoint pen for high-viscosity ink or used for a ballpoint pen for ink containing an inorganic pigment, writing is performed by preventing wear of the nib body. The effect of maintaining the taste is more remarkable and effective. In other words, the inorganic pigment is hard, for example, titanium white, and when an ink containing such a hard pigment is used, the conventional ball is heavily worn by the bonded metal part, and the hard particle small pieces are dropped off. Abrasive action is severe and wears the nib body. In addition, in high viscosity inks, inorganic pigments having a high specific gravity can be sufficiently dispersed, so that they are frequently used recently. In the ball of the present invention, the bonding metal layer in the gap between the hard particles is extremely thin, and the hard particle pieces exposed on the surface of the bonding metal are extremely small and few. Even if the ink is used, the wear of the nib body due to the polishing action of the hard particle pieces is greatly reduced.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described in detail.
[0017]
FIG. 1 shows an embodiment of the ballpoint ball of the present invention. The ball 1 is basically the same as that shown in FIG. 7, and the same reference numerals are given to the same parts. That is, the hard particles 17 such as WC are made of a sintered body sintered through a bonding metal 18 such as Co, the sintered body is formed in a spherical shape, and the surface 19 is polished to a mirror finish.
[0018]
The material of the hard particles 17 is not limited to WC, and various materials are used. For example, carbides such as TiC, VC, Cr ₃ C ₂ , TaC, NbC, Mo ₂ C, B ₄ C, ZrC, SiC, Al ₂ O ₃ , CrO ₃ , MgO, SiO ₂ , BeO, ThO ₂ , TiO _2, CaO, TiO, various oxides such as _{ZrO 2, TiN, c-BN} , Si 3 N 4, various nitrides such as _AlN, ZrB _{2, CrB,} various borides such as TiB _2, MoSi _2, TiSi ₂ and various silicides such as CrSi ₂ . These may be used alone or in combination.
[0019]
The particle size of the hard particles 17 is preferably 0.1 μm or more and 10 μm or less in terms of average particle size. The upper limit of the particle size is more preferably 7 μm or less, and even more preferably 5 μm or less. If it is less than 0.1 μm, the particle size is too small to sufficiently obtain the effects of the present invention, and the cost is increased. If it exceeds 10 μm, the crystal grains become coarse and the strength is lowered.
[0020]
The bonding metal 18 is not limited to Co, and various types can be used. For example, various materials such as Cu, Sn, P, Be, Fe, Ni, Cr, W, Mo, Al, Ti, Zr, and Mn are used. These may be used alone or in combination.
[0021]
That is, as a sintered body used for the ball 1 of the present invention, for example, WC-Co, WC-Co-CrC, WC-TiC-Co, WC-TiC-TaC (NbC) -Co, WC -Various super hard alloys such as -TaC (NbC) -Co, and various cermets such as carbide, oxide, nitride, boride and silicide. A ceramic sintered body that does not use the bonding metal 18 such as a SiC sintered body, a ZrO ₂ sintered body, and an Al ₂ O ₃ sintered body is also used for the ball 1 of the present invention.
[0022]
Among the sintered bodies, in the case of a super-hard alloy or cermet, the content of the bonding metal 18 in the sintered body is preferably 10% or less in terms of a weight ratio with respect to an element having an atomic weight of sodium or more, and 9% or less. More preferred. Most preferably, it is 5% or less. If it exceeds 10%, the layer of the bonding metal 18 in the gap between the hard particles 17 becomes thick, the small pieces of hard particles exposed on the surface 19 become large and many, and wear of the nib body increases. In the case of a super-hard alloy or cermet, the content of the bonding metal 18 in the sintered body is preferably at least 1% in order to ensure the bonding force between the hard particles 17.
[0023]
And it is preferable that the ball | bowl 1 of this invention is a thing with an average space | interval of the particle | grain boundary of the hard particles 17 of 0.2 micrometer or less.
[0024]
That is, when the average interval between the particle boundaries of the hard particles 17 exceeds 0.2 μm, small pieces of hard particles exposed to the portion of the bonding metal 18 on the surface 19 become large, and the small pieces fall off during use of the ball 1. This is because it acts as an abrasive, wear of the nib body 10 increases, and sinking of the ball 1 into the nib body 10 also increases. Further, when the interval between the particle boundaries is increased, the edge of the boundary portion acts as a cutting edge with respect to the nib body 10, the wear of the nib body 10 is increased, and the sink of the ball 1 into the nib body 10 is also increased. Because it becomes.
[0025]
The average interval between the particle boundaries can be measured, for example, as follows. That is, the surface photograph of the ball 1 is taken with a scanning electron microscope at a magnification of about 500 to 5000 times, the width between the hard particles 17 is measured from about 10 to 30 places from a wide place, and the average value is calculated. . This average value is defined as the average interval between particle boundaries. The ball 1 is attached to a predetermined nib body and, for example, a writing test is performed under the following conditions. As shown in FIG. After the formation, the average interval may be calculated by measuring the width of the recess 2 with a scanning electron microscope.
[Writing test conditions]
Writing angle: 65 °
Load: 100g
Writing speed: 7cm / sec
Writing distance: 500m
[0026]
The ball of the present invention can be produced, for example, as follows. That is, first, predetermined hard particles 17 are sintered under predetermined sintering conditions to form a substantially spherical shape. Next, the sphere is rolled together with diamond powder between two grindstones held at regular intervals, and the diamond powder is gradually refined to polish the surface 19 to a mirror finish (see FIG. 1).
[0027]
The ball 1 is attached to a predetermined nib body and used as a part of the nib of the ballpoint pen (see FIGS. 3, 4 and 6).
[0028]
The ink used in the ballpoint pen is not particularly limited, and various inks such as oil-based inks, water-based inks, and gel inks are used. Particularly, high-viscosity ink having a viscosity of 100 mPa · s to 20000 mPa · s is preferable. {ELP viscometer 3 ° (R14) cone, measured at 0.5 rpm (20 ° C)}. The lower limit of the ink viscosity is more preferably 500 mPa · s or more. That is, in the high-viscosity ink in the above viscosity range, even a hard inorganic pigment having a high specific gravity can be sufficiently dispersed. When such an ink in which a hard inorganic pigment is dispersed is used, in the conventional ball, wear of the bonded metal 18 portion is intense, polishing action due to falling off of the hard particle pieces is increased, and the nib body is severely worn. In the ball of the present invention, since the hard particle pieces exposed on the surface of the bonding metal 18 on the surface are extremely small and few, even if the ink in which the hard inorganic pigment is dispersed as described above is used, The wear of the nib body due to the polishing action is greatly reduced.
[0029]
The inorganic pigment is not particularly limited, and various pigments are used. For example, zinc white, titanium oxide, petal, chromium oxide, iron black, titanium yellow (TiO ₂ · BaO · NiO, TiO ₂ · NiO · Sb ₂ O ₃ , TiO ₂ · Sb ₂ O ₃ · NiO, ZnO · Fe ₂ O ₃ , ZnO.Fe ₂ O ₃ .Cr ₂ O ₃ , TiO ₂ .CoO.NiO.ZnO, CoO.Al ₂ O ₃ .Cr ₂ O _3, etc.), cobalt blue, cerulean blue, cobalt Various oxides such as green, various hydroxides such as alumina white, yellow iron oxide, viridian, various sulfides such as cadmium yellow, cadmium red, vermilion, lithopone, various chromium such as chrome lead, molybdate orange, zinc chromate Acids, gypsum, various sulfates such as barium sulfate, various carbonates such as calcium carbonate and lead white, silicates such as ultramarine, manganese violet, Various phosphates such as cobalt violet, arsenates such as emerald green, ferrocyanides such as bitumen, various metal powders such as carbon black, ocher, barium yellow, aluminum powder, bronze powder, zinc dust, natural pearl essence, basicity Various pearl pigments such as lead carbonate, bismuth oxychloride, and mica titanium are listed.
[0030]
Among the inorganic pigments, in particular, titanium oxide and zinc white are frequently used recently for producing a milky white color. However, the ball 18 of the present invention has a high degree of wear on the bonded metal 18 portion in a ballpoint pen using a conventional ball. When 1 is used, the effect of preventing wear is great.
[0031]
When writing with the pen tip, when the tilted pen tip ball 1 is pressed against the paper surface 22 (see FIG. 6), the ball 1 is tilted upward in the ball receiving recess 13. Deviation in direction. Then, the ink is guided from the hollow portion of the nib body 10 through the ink flow path 12 and the ink groove 16 into the ball housing recess 13, and flows out from the gap between the wall surface of the ball housing recess 13 and the ball 1 by gravity. . Next, along with the rotation of the ball 1, the ink is transferred to the paper surface 22 along the surface of the ball 1 and writing is performed.
[0032]
At this time, in the ball 1, since the small pieces 20 of the hard particles in the gap between the hard particles 17 on the surface are minute and small, they are less likely to fall off during use and act as an abrasive. For this reason, even if the ball 1 rotates in the ball accommodating recess 13 while receiving the writing pressure, the wear of the nib body 10 is suppressed, and the sinking of the ball 1 into the nib body 10 is prevented. Therefore, the ink groove 16 is blocked and it is difficult for the ink to flow out, an increase in frictional resistance between the ball 1 and the nib body 10 and an increase in the writable angle are prevented, and a good writing quality is maintained.
[0033]
In the above embodiment, the mirror polishing of the ball 1 is performed by grinding with a grindstone. However, the present invention is not limited to this, and various methods such as polishing with a magnetic fluid, electrolytic polishing, electrolytic grinding, and chemical polishing are used. . Moreover, although the spherical thing was illustrated as the ball | bowl 1, it is not limited to this, It is the meaning which can also be applied to a cylindrical thing etc.
[0034]
Next, examples will be described together with comparative examples.
[0035]
Examples and Comparative Examples
A sintered body using WC, SiC, ZrO ₂ as hard particles and Cr, Co or the like as a bonding metal was mirror-polished into a spherical shape having a diameter of 0.5 mm to obtain a ball for a ballpoint pen. The compositions of the balls of the examples and comparative examples are shown in Table 1 below.
[0036]
[Table 1]

[0037]
Next, about the ball | bowl of each said Example and a comparative example, it sets to the pen tip shown in FIG. 3, and uses the Seiki Kogyo Co., Ltd. writing tester (MODEL TS-4C-10), and performs a continuous writing test on the following conditions. went.
[Test conditions]
Writing angle: 65 °
Load: 100g
Writing speed: 7cm / sec
Writing distance: 500m
Nib body: Stainless steel [Ink used]
Pig. Red258: 5% by weight
Styrene acrylic resin: 1% by weight
Cross-linked polyacrylic acid: 0.24% by weight
Xanthan gum: 0.24% by weight
Glycerin: 7% by weight
Ethylene glycol: 15% by weight
Diethylene glycol: 6% by weight
Sodium benzoate: 0.24% by weight
1,2-benzisothiazolin-3-one: 0.4% by weight
Polyoxyethylene alkyl ether phosphate: 1.5% by weight
Ion exchange water: 63.38% by weight
[0038]
The surface state photograph before the writing test of each of the above Examples 1 to 4 is shown in FIGS. Moreover, the surface state photograph before and after the writing test of Comparative Example 1 is shown in FIGS. 14 and 15, respectively, and the surface state photograph before the writing test of Comparative Example 2 is shown in FIG. Each surface state photograph is a photographed image taken by a scanning electron microscope, and the white line at the lower center of the photograph has a scale of 5 μm. In addition, in FIGS. 10, 11, 14, 15, and 16, the arrows indicate the measurement positions of the particle boundaries (each 10 locations), and the particle interval at this position is measured to determine the average interval between the particle boundaries. Looking for.
[0039]
In addition, Table 2 below shows the measurement results of the average interval between the particle boundaries and the amount of sinking of the ball after the writing test (wear amount of the nib body) in each of the above Examples and Comparative Examples.
[0040]
[Table 2]

[0041]
As apparent from FIGS. 10 to 16 and Table 2, it can be seen that each example has an average particle boundary interval smaller than that of the comparative example, and a good result of the ball sinking can be obtained.
[0042]
【The invention's effect】
As described above, according to the ball-point pen ball of the present invention, the gap between the hard particles becomes extremely thin, the small pieces of hard particles exposed on the surface of the bonding metal on the surface become very small, and the number thereof is extremely small. Become. Therefore, the number of small pieces that fall off during use and act as an abrasive becomes very small, wear of the nib body is prevented, and sinking of the ball into the nib body is prevented.
[0043]
In addition, even if hard particles are sintered without using a binding metal, the edge of the boundary portion is less likely to act as a cutting edge for the pen nib body due to the narrow interval between the particle boundaries. The tip body is prevented from being worn, and the ball is prevented from sinking into the pen tip body.
[0044]
Therefore, as in the prior art, it is possible to prevent an increase in frictional resistance due to the ink groove being blocked and the ink being less likely to flow out, and the contact area between the ball and the nib body being increased. In addition, an increase in the writable angle can be suppressed. Thus, unlike the conventional balls, writing quality is hardly deteriorated at an early stage, and good writing quality is maintained over a long period of time. In addition, since the wear of the nib body is suppressed, the wear can be reduced even if the ball diameter is reduced, so that fine characters can be handled.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view showing a main part of a ball-point pen ball according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view showing a main part of the ballpoint pen ball after a writing test.
FIG. 3 is a cross-sectional view showing a pen tip of a ballpoint pen.
FIG. 4 is an enlarged cross-sectional view of a main part of the nib.
FIG. 5 is an AA cross-sectional view of the nib body.
FIG. 6 is a cross-sectional view showing a usage state of the pen tip.
FIG. 7 is an enlarged cross-sectional view showing a main part of a conventional ballpoint pen ball.
FIG. 8 is an enlarged cross-sectional view of a main part showing a worn state of the ballpoint ball.
FIG. 9 is an enlarged cross-sectional view of a main part showing a state in which a nib body is worn.
10 is a surface state photograph of Example 1. FIG.
11 is a surface state photograph of Example 2. FIG.
12 is a surface state photograph of Example 3. FIG.
13 is a surface state photograph of Example 4. FIG.
14 is a surface state photograph of Comparative Example 1. FIG.
15 is a surface state photograph after the writing test of Comparative Example 1. FIG.
16 is a surface state photograph of Comparative Example 2. FIG.

Claims (4)

A ball-point pen ball comprising a sintered body obtained by sintering hard particles, wherein an average interval between particle boundaries is 0.2 μm or less. The ballpoint ball according to claim 1, wherein the hard particles are ceramic particles. The ballpoint ball according to claim 1 or 2, which is used for a ballpoint pen for high viscosity ink. The ballpoint ball according to any one of claims 1 to 3, which is used for a ballpoint pen for an inorganic pigment-containing ink.

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