Ballpoint pen

Abstract

A ballpoint pen 10 includes: a ballpoint pen tip 20 having a writing ball 30 and a holder 21 holding the writing ball 30; a shaft tube 12 to which the rear end part of the ballpoint pen tip 20 is mounted; and ink 40 accommodated in the shaft tube 12. The holder 21 has an ink guiding hole 26 formed from the rear end thereof toward the head end thereof and a ball house 22 formed with the inner circumference near the head end of the holder 21 expanded. The writing ball 30 is formed of a zirconia sintered body with the content of an aluminum element being less than 0.1 weight %, and the ink 40 contains inorganic particles 41.

Claims

1. A ballpoint pen, comprising: a ballpoint pen tip having a writing ball and a holder holding the writing ball; a shaft tube to which a rear end part of the ballpoint pen tip is mounted; and ink accommodated in the shaft tube, the holder having: an ink guiding hole formed from a rear end of the holder toward a head end of the holder; and a ball house formed with an inner circumference near a head end of the holder expanded, the writing ball being formed of a zirconia sintered body with a content of an aluminum element being less than 0.1 weight %, and the ink containing inorganic particles, wherein at least some of said inorganic particles of said ink have a Vickers hardness that is larger than the Vickers hardness of the zirconia sintered body of said writing ball, and wherein dark color regions derived from alumina are not observed when a surface or a cross section of the writing ball is observed with a scanning electron microscope.

2. The ballpoint pen according to claim 1, wherein the inorganic particles are selected, at least, from carbon black, alumina, boron nitride or titanium oxide.

3. The ballpoint pen according to claim 1, wherein convex parts derived from alumina are not observed on a surface of the writing ball when writing is finished.

4. The ballpoint pen according to claim 1, wherein the holder has a ball receiving seat provided on a bottom of the ball house and formed around the ink guiding hole, a plurality of ink grooves arranged equidistantly around the ink guiding hole so as to connect the ball receiving seat and the ink guiding hole.

5. The ballpoint pen according to claim 1, wherein said content of said aluminum element is 0.06 weight % or less.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a front cross-sectional view showing a ballpoint pen according to the embodiment of the present invention.

(2) FIG. 2 is an enlarged front cross-sectional view showing the vicinity of a pen-tip's point in the ballpoint pen according to the embodiment of the present invention.

(3) FIGS. 3A and 3B are graphs showing a relationship between a writing distance and the flow of ink in a mechanical writing test for Examples. FIGS. 3C, 3D and 3E are graphs showing a relationship between a writing distance and the flow of ink in a mechanical writing test for Comparative Examples.

(4) FIGS. 4A and 4B are cross-sectional images of a writing ball, which were taken by a scanning electron microscope for the Examples. FIGS. 4C, 4D and 4E are cross-sectional images of a writing ball, which were taken by the scanning electron microscope for the Comparative Examples.

(5) FIGS. 5A and 5B are views showing the state of a ball surface after writing is finished or after writing becomes impossible for the Examples. FIGS. 5C, 5D and 5E are views showing the state of a ball surface after writing is finished or after writing becomes impossible for the Comparative Examples.

DESCRIPTION OF EMBODIMENT

(6) An embodiment of the present invention will be described below with reference to the drawings.

(7) (1) Ballpoint Pen 10

(8) A ballpoint pen 10 according to this embodiment is like one illustrated in FIG. 1. The ballpoint pen 10 comprises: a cylindrical shaft tube 12, the head end of which is opened and the rear end of which is closed; a ballpoint pen tip 20 mounted on the head end of the shaft tube 12 via a joint 11; an ink guiding part 13 which penetrates the shaft center of a collector storing part 14 corresponding to a front half portion of the internal space of the shaft tube 12; ink 40 which is in a direct liquid state and which is accommodated in the internal space of an ink accommodating part 15 corresponding to a rear half portion of the internal space of the shaft tube 12; and a cap (not shown), which performs capping from the point of the ballpoint pen tip 20 to the vicinity of the rear end of the collector storing part 14.

(9) In a space from the inner face of the collector storing part 14 to the outer face of the ink guiding part 13 is formed a collector 17 in which ring-shaped thin plates are repeated in an axial direction. The collector 17 is intended to retain the ink 40 and to prevent the ink from leaking to the exterior when the air in the ink accommodating part 15 expands due to the change of an atmospheric pressure or temperature in a direct liquid type ballpoint pen.

(10) The ink 40 may not be supplied in a direct liquid type method, but may be supplied in a cotton pad type one. Moreover, the ink accommodating part 15 may not be provided in the shaft tube 12 itself, but a separate ballpoint pen refill may be internally mounted.

(11) FIG. 2 is an enlarged cross-sectional view showing the vicinity of the point of the ballpoint pen tip 20. The ballpoint pen tip 20 comprises a holder 21 having a cylindrical body (not shown) and a tapered part 27 so formed that the diameter of the tapered part 27 may decrease from the head end of this body toward the point of the ballpoint pen tip 20, and a spherical writing ball 30 held inside the holder 21. Moreover, the holder 21 comprises an ink guiding hole 26 which is penetrated from the rear end of the ballpoint pen tip 20, a ball house 22 which is formed by cutting and expanding the inner circumference near the head end of the holder 21, and a narrowed part 23 which is a part sandwiched between the head end of the inner circumference face of the ball house 22 and the head end of the tapered part 27 and which is narrowed through a plastic deformation of the writing ball 30 toward a central direction. Moreover, the holder 21 has a ball receiving seat 24, which is provided on the bottom of the ball house 22 and which is formed around the ink guiding hole 26, and four ink grooves 25 which are placed equidistantly around the ink guiding hole 26 so as to connect the ball receiving seat 24 and the ink guiding hole 26. The widths and the number of the ink grooves 25 may be varied according to the viscosity coefficient etc. of the ink 40.

(12) When the holder 21 is assembled, the writing ball 30 is inserted into the ball house 22 from the head end of the holder 21. Further, by pressing the upper part of the writing ball 30 in the direction of the rear end, the ball receiving seat 24 is deformed along the external form of the ball 30. After that, by applying narrowing processing to the head end of the tapered part 27 using a tapered roller in order to provide the narrowed part 23, the holder 21 is thus formed.

(13) This holder 21 is formed of stainless steel with a Vickers hardness of about 200 to 420. Although the holder 21 can be formed using a metal material such as nickel silver or brass, or a resin material, it is desirable that the Vickers hardness is in a range from 170 to 450. The measurement of Vickers hardness is based on a Japanese standard called JIS Z2244 Vickers hardness test and test method.

(14) Furthermore, although the holder 21 is formed using cutting processing from a solid wire rod in this embodiment, processing is not limited to the cutting processing from the wire rod, but the holder 21 may be formed by using the plastic processing of a hollow-shaped pipe material, for example.

(15) (2) Writing Ball 30

(16) The writing ball 30 of this embodiment is formed by mixing Y.sub.2O.sub.3 or CaO, etc. as a stabilizer into zirconia (ZrO.sub.2) powder. The powder, for the writing ball 30, composed of the above raw materials is kneaded and sintering is performed after the powder is formed into a substantially spherical shape. Further, this spherical body is rolled together with diamond powder between two grindstones held at a predetermined interval, and a ball surface 31 is finished to a mirror surface. The Vickers hardness of this ball surface 31 is 1,100.

(17) It is desirable that the Vickers hardness of the ball surface 31 is in a range from 1,000 to 1,500.

(18) Whether the writing ball 30 contains alumina or not can be determined by observing the surface or the cross section of the writing ball 30 with a scanning electron microscope. Since obtained contrast depends on an atomic number in an image observed by the scanning electron microscope, alumina contained in the writing ball 30 is displayed in a dark color while most of the writing ball 30, i.e., a zirconia sintered body, is displayed in a bright color. Accordingly, the existence of alumina can be confirmed if a dark color region is observed. A required condition for this is that the dark color region is observed regardless of the magnification of the scanning electron microscope.

(19) Moreover, when writing is finished or when writing become impossible, whether alumina is contained or not can be confirmed by conducting a measurement on the surface. When alumina is contained, convex parts caused by the exposure of alumina appear markedly.

(20) (3) Ink 40

(21) The ink 40 of this embodiment is water-based ink in which carbon black is blended as inorganic particles 41.

(22) The above inorganic particles 41 are not limited to carbon black, but other hard inorganic particles like titanium oxide, etc. and a mixture with various inorganic particles may be used. Moreover, composite particles may be used, in which the surfaces of organic particles, i.e., mother particles, are covered by and reformed by inorganic fine particles by using a surface reforming device or the like. Concrete inorganic particles include alumina, boron nitride, titanium oxide, zinc white, red iron oxide, chromium oxide, iron black, cobalt blue, yellow iron oxide, viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmium red, chrome yellow, a molybdate orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, precipitated barium sulphate, baryte powder, calcium carbonate, white lead, Prussian blue, manganese violet, aluminum powder, bronze powder, brass powder, etc.

(23) Furthermore, with respect to the classification by the solvent of ink, ink is not limited to water-based ink, but gel ink or oil-based ink may be used. However, in the case of oil-based ink, since a boundary between both the ball receiving seat 24 and the bottom face of the ball house 22 and the ball surface 31 is always lubricated, wear to the ball receiving seat 24 and the bottom face of the ball house 22 is less likely to occur than in the case of water-based ink. Therefore, applying water-based ink will exhibit a greater effect of suppressing the wear of the ball receiving seat 24.

(24) (4) Action and Effect

(25) During writing, the ink 40 of the ink accommodating part 15 is fed to the ball house 22 through the ink guiding part 13, the ink guiding hole 26 and the ink grooves 25, and is sufficiently supplied to the writing ball 30 accommodated in the ball house 22. Further, the ink 40 supplied through the rotation of the writing ball 30 is transferred to or permeates into a recording body like a sheet of paper, etc., and writing is completed.

(26) Here, when alumina is contained in the writing ball 30 and if the Vickers hardness of the inorganic particles 41 is greater than that of the writing ball 30, which is in a range from 1,000 to 1,500, the ball surface 31 will be worn down by continuing writing. Moreover, since the Vickers hardness of the alumina contained in the writing ball 30 is 2,000, when the Vickers hardness of the inorganic particles 41 is 2,000 or less, alumina particles are exposed as convex parts on the ball surface 31, and the convex parts will wear the ball receiving seat 24 and the bottom face of the ball house 22. Accordingly, when hard inorganic particles meeting the above Vickers hardness condition are blended in the ink 40, the ball receiving seat 24 and the bottom face of the ball house 22 are worn down by the zirconia ball containing alumina, and the writing ball 30 blocks the ink grooves 25 and the ink guiding hole 26. As a result, the flow of the ink 40 decreases rapidly, and writing becomes impossible.

(27) In this embodiment, when the content of the aluminum element composing alumina is less than 0.1 weight %, the convex parts caused by alumina particles are not formed; even if carbon black particles, i.e., hard inorganic particles, are blended in the ink 40, the effect of preventing wear is great.

Examples

(28) Examples of the present invention will be described below in comparison with Comparative Examples.

(29) Five kinds of writing balls 30 were prepared, which had different alumina contents with respect to each other. They were spherically shaped zirconia balls having the diameter of 0.5 mm with the ball surface 31 processed to a mirror surface. Writing tests were performed using a mechanical writing test machine which was adapted to a Japanese standard called JIS S6054 water-based ballpoint pen and refill. The writing ball 30 was mounted on a pen tip, Uni-ball eye (model number: UB-150) produced by Mitsubishi Pencil Co., Ltd., and watercolor pigment black ink containing carbon black was used for the ink 40. Writing test conditions were as follows.

(30) [Writing Test Conditions]

(31) Writing angle: 60

(32) Load: 1 N

(33) Writing speed: 4.5 m/min

(34) Writing distance: Until ink stops discharging (1500 m at most)

(35) Test conditions other than the above followed the standard, JIS S6054 water-based ballpoint pen and refill.

(36) [Test Results]

(37) The results of the above tests are shown in Table 1, and graphs presenting a relationship between a writing distance and the flow of ink are shown in FIGS. 3A to 3E. Each measured value for the flow of ink represents the quantity of ink (mg) consumed every 100-m writing.

(38) TABLE-US-00001 TABLE 1 Examples Comparative Examples 1 2 1 2 3 Maximum Amount 17 6 62 65 58 of Wear of the Ball Receiving Seat (m) Writing Status Writing Writing Writing Writing Writing Finished Finished Impossible Impossible Impossible

(39) From the results of Table 1 and FIG. 3, the maximum amount of wear of the ball receiving seat 24 was 17 m for Example 1 and was 6 m for Example 2, and the writing status was judged as Writing Finished, indicating that writing was possible until the writing distance specified in the test conditions is reached. On the other hand, in Comparative Examples 1, 2 and 3, the maximum amount of wear of the ball receiving seat 24 was in a range from 58 to 65 m, and the writing status was judged as Writing Impossible, indicating that writing was finished before the specified writing distance was reached.

(40) [Confirmation Method of Cross-Sectional Image]

(41) Next, the cross section of the writing ball 30 was observed using a scanning electron microscope, S-3400N produced by Hitachi High-Technologies Co. The cross-sectional images are shown in FIG. 4A to 4E. The confirmation conditions of a dark color region were as follows.

(42) Mode: Low-vacuum mode Internal pressure of chamber 50 Pa

(43) Probe current: 60 A

(44) Acceleration voltage: 15 kV

(45) Image: Reflection electron composition image

(46) Magnification: 2000 times

(47) Moreover, the content of the aluminum element composing alumina was measured by energy dispersive X-ray spectroscopy using an X-ray spectrometer, EMAX ENERGY EX-250 produced by HORIBA Ltd. The measured results are shown in Table 2. Measurement conditions were as follows.

(48) Acceleration voltage: 15 kV

(49) Magnification: 2000 times

(50) Dead time: 20%

(51) Analysis time: 100 seconds

(52) TABLE-US-00002 TABLE 2 Examples Comparative Examples 1 2 1 2 3 Aluminum Content Not 0.06 0.2 0.2 1.2 (weight %) Detected

(53) In the cross-sectional images of FIGS. 4A to 4E, a large number of dark color regions are observed for Comparative Examples 1, 2 and 3. When a qualitative analysis was conducted for these dark color region by energy dispersive X-ray spectroscopy, an aluminum element (Al) composing alumina was detected. Further, when the content of aluminum for each of Examples and Comparative Examples was quantitatively analyzed by energy dispersive X-ray spectroscopy, the obtained results are presented in Table 2. Aluminum was not detected for Example 1, and the content of aluminum was 0.06 weight % for Example 2. Moreover, the content of aluminum was in a range from 0.2 to 1.2 weight % for Comparative Examples. Dark color regions were observed for Example 1, but these were cavities on the ball surface 31. Moreover, aluminum was contained with the content of 0.06 weight % for Example 2, but no dark color region was observed.

(54) [Confirmation Method of Surface Roughness Measurement]

(55) Next, using an ultraprecise noncontact three-dimensional surface property measuring apparatus, Taly surf CCI Lite produced by Taylor Hobson Ltd., the surface state of the writing ball 30 was measured for Examples 1 and 2 and Comparative Examples 1, 2 and 3 when the writing ball 30 was in the status of Writing Finished or Writing Impossible in a continuous mechanical writing test. FIGS. 5A to 5E show the measured results of the roughness of the ball surface 31 when the writing ball was in the status of Writing Finished or Writing Impossible in the continuous mechanical writing test. It was shown that there was a greater height difference as color deepens. The deep color part of Example 1 and 2 showed a cavity corresponding to a concave part which slowly lowered from a contour part toward a center. On the other hand, the deep color parts of Comparative Examples 1, 2 and 3 corresponded to sharp convex parts. It can be confirmed that alumina particles were exposed at the sharp convex parts. The ball receiving seat 24 and the bottom face of the ball house 22 are worn down by these convex parts.

(56) From the above results, the content of an aluminum element for the writing ball 30 of the present invention is determined to be 0.1 weight % or less in consideration of error in a quantitative analysis. When the content of the aluminum element is equal to this value or less, since alumina particles are not exposed as convex parts on the ball surface 31, the ball receiving seat 24 is not worn down. Further, since the writing ball 30 does not block the ink grooves 25 and the ink guiding hole 26 and since the flow of the ink 40 does not decrease, there can be provided a ballpoint pen, with a zirconia ball, which can maintain a good writing condition for a long period of time.

REFERENCE SIGNS LIST

(57) 10 Ballpoint pen 12 Shaft tube 14 Collector storing part 17 Collector 20 Ballpoint pen tip 22 Ball house 24 Ball receiving seat 26 Ink guiding hole 30 Writing ball 40 Ink 11 Joint 13 Ink guiding part 15 Ink accommodating part 21 Holder 23 Narrowed part 25 Ink groove 27 Tapered part 31 Ball surface 41 Inorganic particle