JP2011126188A - Ball-point pen chip and ball-point pen using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a smooth writing sensation by forming a wide range of a lubricating ink layer on the surface of a ball and on the inner wall surface of a ball holder. <P>SOLUTION: In the ball-point pen chip, a ball transfer part substantially transferred to the curvature of a ball by pushing the inside face of the ball holder to the surface of the ball is formed in a ball receiving seat part and the inner wall surface of a distal end caulking part. The total area of the ball transfer part satisfies 22% to 29% of the surface area of the ball, the average surface roughness (Ra) of the ball transfer part is 2.0 nm to 10.0 nm, and maximum minimum level difference (Ry) is 20 nm to 100 nm. The ball-point pen chip includes radial through grooves as ink flowing paths, and uses an oily ink containing a phosphoric acid ester base lubricant. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a ball-point pen tip including at least a ball as a writing member and a ball holder that partially holds and holds the ball from a tip opening.

Conventionally, in order to make a ballpoint pen with good writing quality, the device described in Japanese Utility Model Laid-Open No. 2-22883 (Patent Document 1) discloses a ballpoint pen that defines the diameter of the ball seat and the diameter of the center hole. Yes.
Further, in the invention described in Japanese Patent Application Laid-Open No. 8-252998 (Patent Document 2), a ballpoint pen that defines the projected area of the ball seat is disclosed in order to obtain a smooth and light writing texture.

Japanese Utility Model Publication No. 2-22883 (Scope of Claim for Utility Model Registration) JP-A-8-252998 (Claims)

In the ballpoint pen tip disclosed in the above-mentioned patent document, the projected dimension when the ballpoint tip is viewed from the tip side (ball side) is defined, and the amount in the longitudinal direction (depth direction) is taken into consideration. Therefore, it cannot be said that the amount of the contact portion between the ball and the ball holder is substantially defined, and only the size of the ball seat portion that serves as the ball retraction restricting portion is considered. Usually, when a ballpoint pen is held and written at an angle of about 70 degrees with a writing surface such as a paper surface, the ball is pushed from an oblique direction, so that it can move to a biased position. In addition, when the parts other than the ball seat are in contact with each other, the smooth writing quality may be impaired.
In addition, depending on the type of ink used, particularly the blended lubricating component, a large contact area with the ball may cause a large amount of direct contact between metals, which may hinder smooth writing.

  According to a first aspect of the present invention, there is provided a ballpoint pen tip including at least a ball as a writing member and a ball holder that partially protrudes and holds the ball from a tip opening, and the inner surface of the ball holder is a surface of the ball. A ball pen tip having a total area of a ball transfer portion formed by being transferred to the curvature of the ball by being pressed to 22.0% or more and 31.0% or less of the surface area of the ball, According to a second aspect of the present invention, the ball transfer portion includes at least a ball seat portion and an inner surface of the tip caulking portion, and a ratio of the surface area of the inner surface ball transfer portion of the tip caulking portion to the surface area of the ball seat ball transfer portion is 0. The ball-point pen tip according to claim 1, wherein the third aspect of the present invention is the ball receiving ball transfer portion and the tip caulking portion. The portion between the surface ball transfer portion straddles the equator portion of the ball when the ball is positioned at the rearmost portion, and the length of the portion in between is 24.0% to 34.0% of the ball diameter. A gist of the ballpoint pen tip according to claim 1 or claim 2.

The ball transfer part formed by pressing the inner surface of the ball holder against the surface of the ball to be transferred to the curvature of the ball is written in the writing state, in particular, held obliquely with an angle of about 70 degrees to the paper surface. When the ball transfer portion is formed, a spring back phenomenon occurs and the radius of curvature of the ball is not completely the same. In addition, the spring back becomes larger at the contact boundary portion during processing, and by having substantially the same radius of curvature with respect to the radius of curvature of this ball, a slight gap intervening with ink can be formed. When the area is 22.0% or more and 31.0% or less of the surface area of the ball, a layer using ink as a lubricant can be formed, and the ink flow rate is restricted more than necessary. It is also without, and that smooth writing feel is obtained.
In particular, if a phosphate ester compound that has a strong adsorptivity to the metal surface is used as a lubricity imparting component in the ink, the entire ball transfer portion becomes a lubricity wall surface on which the phosphate ester compound is adsorbed. Furthermore, since the lubricating wall surface can form a thin ink layer by affinity with the ink component, smooth rotation of the ball is guaranteed, and a smoother writing feeling can be obtained.

  If the total area of the ball transfer portion is less than 22.0%, the ink intervening in the portion that receives the force with which the ball is pressed against the ball holder becomes insufficient, and the smoothness decreases particularly in oblique writing. When the total area of the ball transfer portion exceeds 31.0%, the ink circulation amount is insufficient, and a portion where ink is not transferred, such as scumming or missing, tends to occur in the handwriting.

  Further, since the ball transfer portion is the ball receiving portion and the inner surface of the tip crimping portion, the ball is supported on both the bottom side and the opening side during writing. Ball bearing seat The ball transfer part is formed in the inward protruding part that restricts the back movement of the ball, so it receives a force to the back side, but the ball moves back and forth for ink ejection Therefore, even if only the ball receiving portion and the ball transfer portion are widened, if the ball is displaced laterally, the ball support effect by the ball transfer portion cannot be obtained. The tip caulking part inner surface ball transfer part serves as a support part from the side of the ball, and even when the ball is displaced from the ball receiving part ball transfer part, the effect of supporting the ball transfer part can be exhibited. The wide transfer portion suppresses the ball from rotating at a position shifted from the ball transfer portion. However, since the tip caulking portion inner surface ball transfer portion is a portion close to the ink discharge opening, even if it is too wide, there is a possibility of restricting abundant ink discharge. The value obtained by dividing the surface area of the ball by the ball seat portion and the ball transfer portion surface area is 0.8 or more and 1.3 or less, and the ball transfer area ratio of the both is about the same, and the tip caulking portion inner surface ball transfer portion surface area ratio is increased. As a result, it is possible to guarantee stable rotation of the ball by receiving the ball in the lateral direction without restricting the ink flow rate more than necessary, and a clean handwriting and a smooth writing feeling can be obtained. . In particular, a smooth writing feeling can be obtained even with an oblique writing in which the angle between the paper surface and the writing instrument is small, and the force in the lateral direction against the ball is large.

  Furthermore, the portion between the ball receiving ball transfer portion and the tip caulking portion inner surface ball transfer portion straddles the equator portion of the ball when the ball is positioned at the rearmost portion, and the length of the portion between the ball diameter is the diameter of the ball 24.0% or more and 34.0% or less, the impact when the ball moves between the ball receiving ball transfer portion and the tip caulking portion inner surface ball transfer portion is alleviated, and the rotation of the ball is rampant. This eliminates the feeling of being caught during writing and the poor writing quality due to slight vibration.

The longitudinal cross-sectional view of an example of the ball-point pen of this invention. The longitudinal cross-sectional view of an example of the ball-point pen tip of this invention. The I section enlarged view of FIG. FIG. 11 is a cross-sectional view taken along line II-II ′ in FIG. 3. 10 is a graph showing the writing resistance value every 0.1 second in Example 5.

The ball serving as the writing member is formed of a cemented carbide such as tungsten carbide or a ceramic sintered body such as silicon carbide.
Such balls include, for example, tungsten carbide of 75 wt% to 95 wt%, and a binder metal such as cobalt, nickel, and chromium of 5 wt% to 25 wt%. Preferably, tungsten carbide is 87.5 wt% to 95.5 wt%, and binder metal such as cobalt, nickel, and chromium is 4.5 wt% to 12.5 wt%. Is a main compound in which fine binder metal is removed by physical and / or chemical polishing of the surface, and fine concave portions of about 0.2 μm to 2.0 μm are formed on the ball surface. .
In the case of a ballpoint pen using an ink using a phosphate ester lubricant, a cemented carbide metal is preferable due to its adsorptive power, and the viscosity is 200 to 800 mPa · s, and the shear thinning index is 0.9 to 1. 0.0 ink makes it easy for the ink to penetrate into the recesses on the surface described above, and it is easy to ensure that the ball surface is wet with the ink, so that the ink is more likely to intervene between the ball and the ball transfer portion. Ink is preferred because it tends to work as a lubricant in the rotation of the ball. The ball surface may be coated with titanium oxide or the like.

The ball holder for holding the ball has an inward protruding portion as a ball retraction restricting portion in the middle of the ink passage as a through hole, and a caulking portion processed to have a diameter smaller than the diameter of the ball at the tip opening portion. It is formed to prevent the ball from coming off.
The inward projecting portions are divided approximately evenly by the center hole and the radial through groove, and are arranged in a circumferential shape. The radial grooves serve as a path for allowing ink to flow into the outer portion of the ball. If only the ink flow rate is taken into consideration, a larger number and a wider width are preferable, but the area of the ball seat portion is reduced. Therefore, the number and the width are adjusted as appropriate. If there are three or more radial grooves, it can be said that it is preferable because it is easy to supply ink evenly around the ball. When the radial groove is formed using a metal pipe material, a plurality of inward projections are formed in a circumferential shape by denting the pipe side wall inward by pressing with a punch from the outside. Can also be obtained. When obtained by such processing, the smaller the diameter of the pipe using a small diameter ball such as 0.3 mm, the finer the processing, so increasing the number of radial grooves is the width and opening of each radial groove. Since the area will be small, it is preferable to have three or four radial grooves.

  The crimped portion of the tip of the ball holder that has been machined to a diameter smaller than the diameter of the ball is a part that is formed by pressing the rotating roll member, etc., and then falling inside after the ball is inserted. A ball transfer portion can be obtained by pressing the inner surface of the ball against the ball. In addition to the formation of the caulking portion for preventing the ball from coming off, the ball transfer portion can be formed by pressing the inner surface of the ball holder against the ball by a pressing force applied from the outside. By making these pressing ranges wide, the area of the ball transfer portion can be widened. Specifically, when pressing, including caulking, the position of the ball is relative to the tip. Wide ball transfer part by setting the pressure position of the crimping tool to a low position, making the pressing angle of the crimping tool (the angle formed by the pressing surface of the pressing tool with respect to the pen axis), or increasing the load during pressing. can do.

  After the ball is installed and the ball is prevented from being removed by caulking, the inward projecting portion is deformed by pressing the ball against the inward projecting portion to form a ball seat portion which is a ball transfer portion. By strongly pressing the ball, the amount of deformation of the inward protruding portion can be increased (deeply), and as a result, the ball transfer portion can be widened. This process increases the distance that the ball can move back and forth, and the maximum opening amount of the ink ejection port formed at the tip of the ball holder can be set by setting.

  These ball transfer portions are formed by rolling by strongly pressing the ball and the inner surface of the ball holder, or pressing a jig having the same radius of curvature as the ball against the inner surface of the ball holder. At this time, rotation may be applied to the ball or jig to smooth the recess as a ball transfer portion formed on the inner surface of the ball holder. In general, deformation processing by pressing a metal material causes a push-back phenomenon called springback, but the deformation amount is often different between the contact boundary portion and the middle of the pressing member. Although the pressing amount is designed in consideration of such a springback amount, the difference in the springback amount depending on the portion appears as a difference in the radius of curvature of the recess. The fact that the radius of curvature of the recess, which is the ball transfer section, is not exactly the same as the radius of curvature of the ball forms an interstitial space between the inks, which is advantageous for obtaining the ink lubrication effect, but has a very different curvature. Since the radius is also a factor that hinders the rotation of the ball, the radius of curvature of the ball transfer portion with respect to the radius of curvature of the ball is preferably 101% to 104%.

  It is also possible to insert a coil spring into the ink path of the ball holder and urge the ball forward at its tip directly or via a member. The rearward movement restriction of the coil spring can be a caulking of the rear end of the ball holder, or a step formed on an ink tank or a connection member with the ink tank. In addition, the coil spring has a shape in which the tip portion that comes into contact with the ball is linearly extended, so that a pressing force is reliably applied to the ball even in a portion that is a narrow hole due to the presence of an inward protruding portion or the like. be able to. By biasing the ball forward by the coil spring, the ball can come into circumferential contact with the ball holder when not in use, and leakage of unnecessary ink can be suppressed.

  The material of the ball holder can be an alloy such as stainless steel, white or white, or a wear-resistant resin material such as polyoxymethylene, but it is durable and adsorbable with ink using a phosphate ester lubricant. From the above, stainless steel, which is an iron alloy, is preferable.

Such a ball holder is connected to a member to be an ink tank directly or via a connecting member.
Ink used as a ballpoint pen can be any of pigment inks using pigments as colorants, dye inks using dyes, water-based inks using water as the main solvent, and oil-based inks using organic solvents. However, it is preferably an ink containing a surfactant as a lubricant or a phosphate ester lubricant. Moreover, since the ink viscosity affects the lightness of writing, it is preferably a relatively low-viscosity ink of about several mPa · s to 1300 mPa · s, and is assumed in the case of ink with shear thinning viscosity. It can be said that the ink preferably has a viscosity of about several mPa · s to 500 mPa · s in the vicinity of a shear rate of 3000 [1 / sec] generated by the rotation of the ball during writing. However, when the ink is an ink having a shear thinning index of 1.0 or close to it and having almost no shear thinning viscosity, the viscosity at the time of stationary and the viscosity at the time of writing are almost the same, so that several mPa · s˜ It is about 500 mPa · s.
Examples of the phosphoric acid ester lubricant include polyoxyethylene alkyl ether phosphoric acid monoester or diester and triester. The number of added moles of ethylene oxide is 0 to 20, and the carbon number of the alkyl group of the terminal alkyl ether. 9 to 18 can be exemplified.
Examples of the lubricant to be used in combination other than the phosphate ester-based lubricant include, for example, polyoxyethylene alkyl ether, glycerin fatty acid ester, polyglycerin fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbit fatty acid ester, polyoxyethylene castor oil , Polyoxyethylene hydrogenated castor oil, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkylamine, N-acylamino acid and the like.
These may be used alone or in combination, and the amount used is preferably about 0.1 to 5% by weight.

FIG. 1 shows a ballpoint pen formed by joining a ball holder 2 which is a ball 1 as a writing member and is rotatably held in a state in which the ball 1 partially protrudes from a tip opening 2 a and an ink containing portion 3. It is an example. Although it is shown as what is called a refill that is housed and used in an exterior body, illustration and description of the exterior are omitted.
A ballpoint pen tip composed of a ball 1, a ball holder 2, and a coil spring, which will be described later, is fixed by press-fitting the small-diameter portion at the rear end thereof to the tip of an ink containing portion 3 that is an extruded pipe made of polypropylene resin or the like.
An oil-based ink 4 is stored in the ink storage portion 3, and a backflow preventing body composition 5 that is a high-viscosity fluid that is incompatible with the ink is disposed in contact with the rear end interface of the oil-based ink 4. In particular, when a low-viscosity ink is used, it is effective to dispose a backflow prevention body composition in order to suppress the ink from moving backward.

  As shown in FIG. 2 which is an enlarged view of only the ballpoint pen tip, a coil spring 6 for preventing ink leakage is disposed inside the ball holder 2. The coil spring 6 is inserted into the ball holder 2, and then pushed into the rear end opening 2 b of the ball holder 2 in a state where the coil spring 6 is pushed in and compressed in its entire length, thereby performing the rear end of the ball 1. It is fixed with the end biased. The coil spring 6 includes a winding portion 6a that expands and contracts and a straight tip portion 6b. The tip straight portion 6b directly pushes the rear end of the ball through a through-hole that is an ink passage of the ball holder 2, and 1 is placed around the inner edge of the tip opening 2 a of the ball holder 2.

FIG. 3 shows an enlarged view of a portion I in FIG. 2, for convenience of explanation, illustration of the coil spring 6 is omitted, and the ball 1 is shown by a broken line.
The ball holder 2 has a ball holding chamber 7, a center hole 8, a radial groove 9, and a rear hole 10 from the front end side as a penetrating ink passage.
Between the ball holding chamber 7 and the rear hole 10, a plurality (6 in this example) of inward protruding portions 11 are formed circumferentially at equal intervals, and each of the adjacent inward protruding portions is formed. Between 11 is a radial groove 9. The radial grooves 9 are opened in the outer portion of the ball in the ball holding chamber 7, and ink can be supplied to a portion not blocked by the ball 1 even when the ball 1 moves to the rear end.
The tip of the ball holder 2 is a portion subjected to a so-called caulking process in which, after the ball 1 is installed, it is subjected to plastic deformation that causes the ball 1 to fall inward, and the diameter of the ball holder 2 is reduced to an opening having a diameter smaller than the diameter of the ball 1. Specifically, a rotating roll member or the like is pressed against the outer side of the tip portion of the ball holder 2 in an oblique direction to reduce the diameter in a circumferential shape.
During the caulking process, the inner side of the ball holder 2, that is, the inner surface of the tip side of the ball holding chamber 7 is pressed against the ball 1, and the tip end ball transfer onto which the surface of the ball 1 is transferred. The part 12 is formed in a strip shape.

  After the ball 1 is retained by the caulking process, an impact force is applied to the ball 1 with a hammer tool, and the ball 1 is pressed against the inward projecting portion 11 that is a part that restricts the backward movement of the ball 1. By this processing, the contact portion of the inward projecting portion 11 with the ball 1 is deformed into the shape of the ball 1 to form a curved ball receiving ball transfer portion 13 which is a ball transfer portion to which the surface of the ball 1 is transferred. To do.

In the ballpoint pen tip of this example, the tip end ball transfer portion 12 and the ball seat ball transfer portion 13 are ball transfer portions, and the total area of each curved surface is 22% or more of the surface area of the ball 1 31. % Or less.
That is, when a 0.7 mm ball is used, the total area of the ball transfer portion is in the range of 0.34 mm ^{2 to} 0.48 mm ² .
The tip end ball transfer portion 12 which is a part of the ball transfer portion can be formed as a band-like portion from the tip end of the opening of the ball holder 2, but the tip end can be adjusted by adjusting the position and angle of the caulking process described above. It can also be formed from a slightly rear part, for example, from behind about 3% of the ball diameter. In this case, a slight gap is formed between the ball 1 urged forward by the coil spring 6 and the tip opening 2 a of the ball holder 2. This gap helps the ink that has not been applied to the paper surface in the ink on the ball to be collected again in the ball holder 2 and suppresses the phenomenon that the ink runs on the outside of the ball holder 2 as much as possible. Is. Further, when a coating film of a component repelling ink such as a fluorine compound is formed on the outer surface of the ball holder 2, the outside can be prevented from getting wet with the ink, and the ink can be prevented from running up. Moreover, when such a component that repels ink is also applied to the inner surface of the ball holder 2, extended wetting of the ink is limited, and ink leakage from the tip opening in a stationary state can be suppressed.

  It is preferable that the rear end point of the tip end ball transfer unit 12 be positioned as far back as possible to increase the area as the ball transfer unit, but the ball transfer unit is the closest part to the ball 1. The ink passage can be a narrow portion. Therefore, the maximum total area of the ball transfer portion is limited to 31% of the ball surface area, but in order to secure a more abundant ink flow, a portion other than the ball transfer portion of the ball holding chamber 7 is secured widely. It is important that the radial grooves 9 are opened.

  Further, when the ball receiving ball transfer unit 13, which is the other ball transfer unit, presses the ball 1, forming a deeper recess increases the area as the ball transfer unit. As shown in FIG. 4 which is a sectional view taken along the line II-II ′ of FIG. 3, the area of the ball seating ball transfer portion 13 is the size in the depth direction in the projected area viewed from the direction of the arrow. Although not considered, forming the ball receiving ball transfer portion 13 deeply makes it possible to secure a large area of the portion in contact with the ball while opening the center hole 8 to a certain extent.

  Further, since the tip end ball transfer unit 12 and the ball receiving ball transfer unit 13 are processed in the order of ball installation, tip end ball transfer unit formation, and ball seat receiving unit formation, the tip end ball transfer unit 12 Is formed at the front position, and the ball receiving ball transfer portion 13 is formed at the front position, so that the two are formed closer to each other. The amount of movement in the horizontal direction is smaller than the amount of movement in the direction, the amount of displacement of the ball 1 is small at the time of writing, and there is no unpleasant vibration in writing, or it is large for a moment when the writing direction is changed. There is an effect that the maximum writing resistance value such as writing resistance is reduced. However, as described above, if the total area of the ball transfer portion becomes too large, the space for the ink passage may be reduced, so the portion between the ball seating ball transfer portion and the tip caulking portion inner surface ball transfer portion It is preferable that L straddles the equator part of the ball when the ball is positioned at the rearmost part, and the length of the part between them is 24.0% or more and 34.0% or less of the ball diameter.

  Further, the surface of these ball transfer portions preferably has an average surface roughness (Ra) of 2 nm or more and 15 nm or less and a maximum / minimum height difference (Ry) of 20 nm or more and 200 nm or less. Since the portion is formed by transferring the surface of the ball by being pressed against the ball, the surface roughness can be adjusted by the surface roughness of the ball used for formation. However, it is not necessarily the same as the writing ball. For example, after the ball transfer portion is formed, the ball can be extracted and the writing ball can be installed. At this time, in order to prevent the writing ball from coming off, the tip of the ball holder is subjected to a caulking process which is a diameter reducing process, but it is necessary to press the inner surface of the ball holder against the ball during the caulking process. In addition, it is possible to adjust the surface roughness of the tip end ball transfer portion 12 by pressing the balls with different surface roughness during the caulking process.

For the above example, various writing test samples were prepared.
(1) A ballpoint pen tip in which the total area of the ball transfer portion is different by adjusting the areas of the tip ball transfer portion and ball receiving portion.
(2) A ballpoint pen tip in which the area of the tip ball transfer portion and the ball seat portion is adjusted, and the ratio of the surface area of the tip caulking portion inner surface ball transfer portion to the surface area of the ball seat ball transfer portion is different.
(3) Ballpoint pen tips having different distances between the ball receiving ball transfer portion and the tip caulking portion inner surface ball transfer portion.
(4) A ballpoint pen tip using balls 1 having a diameter of 1.0 mm, 0.7 mm, 0.5 mm, and 0.3 mm.

The calculation of the total area of the ball transfer portion was based on the following method.
(1) Front end ball transfer area When the ball is regarded as a sphere, its surface area is equal to the side wall area of the cylinder circumscribing the sphere, so if the diameter of the sphere is D, the circumference Dπ of the circle of diameter D And the height D of the cylinder, that is, πD ² .
The surface area of the tip ball transfer portion is the area of the belt portion in a certain height range of the sphere, and this is the side wall of the width projected from the belt-like portion of the tip ball transfer portion among the side walls of the cylinder circumscribing the sphere. Since it corresponds to the area, if the projected height of the tip end ball transfer portion is T, πTD is obtained.
(2) Ball seat area (total)
The surface area (total) of the ball seat portion is an area obtained by subtracting the opening area of the width portion corresponding to the radial groove from the area of the strip portion corresponding to the width of the ball seat portion in the surface of the sphere.
Similarly, the area of the belt-shaped portion corresponding to the width serving as the ball seat portion corresponds to the side wall area of the width projected from the belt-shaped portion of the ball seat portion among the side walls of the cylinder circumscribing the sphere. If the projected height of H is H, then πHD.
Next, the opening area of one radial groove is a portion corresponding to the ball seat portion in the band-shaped portion having the width of the radial groove centered on the equator of the sphere. Assuming that the width of the radial groove is F, the band-like portion of the width of the radial groove around the equator of the sphere is πFD.
The ratio of the portion corresponding to the ball seat portion of the strip-shaped portion of the width of the radial groove centered on the equator of the sphere is the occupancy ratio to the entire circumference of the angle formed at the center of the sphere, so the ball seat portion When the angle formed by the portion is θ, it is (θ / 360 °), and the opening area of one radial groove is πFD (θ / 360 °).
When the number of radial grooves is n, the total opening area of the radial grooves is
n · πFD (θ / 360 °).
(3) Total Area of Ball Transfer Part From the above, the total area of the ball transfer part is derived by the following formula.
πTD + πHD-n · πFD (θ / 360 °)
π: Circumference ratio D: Diameter of the ball T: Projection height of the tip ball transfer portion H: Projection height of the ball seat portion n: Number of radial grooves F: Width of the radial groove θ: Ball seat portion In the actual measurement, T: the projected height of the tip ball transfer portion, and H: the ball seating portion, by taking a picture of the surface of the ball-point pen chip cut in half. F: The width of the radial groove can be obtained, and θ: The angle formed by the ball seat portion from the ball center is determined from the diameter of the ball seat portion, the diameter of the center hole, and the diameter of the ball. It can be derived from the three-square theorem.

Moreover, the ball-point pen tip created as a writing sample is provided with a coil spring having a ball biasing force of 20 g, and is fixed to an ink containing pipe of a 0.7 mm ball-point pen “Rolly” (product code: BP127) manufactured by Pentel Co., Ltd. Filled with oil-based ink, which will be described later, so that the centrifugal force works in the direction of the nib, and centrifuge with a centrifuge (manufactured by Japan Centrifuge Co., Ltd .: tabletop centrifuge H-103N). The test ballpoint pen sample was obtained by removing the gas present in the sample.
Table 1 shows the dimensions of each part in the ballpoint pen samples of Examples and Comparative Examples.

The composition of the ink used in the test is as follows.
In order to produce ink, it is obtained by mixing dispersed pigment and other components such as viscosity adjusting resin, solvent, lubricant, etc., and dissolving and mixing until uniform with a stirrer such as a homomixer. However, in some cases, the mixed ink may be further dispersed by a disperser, or the obtained ink may be filtered or centrifuged to remove coarse particles and insoluble components.
Printex 35 (carbon black, manufactured by Degussa Huls Japan)
6.0 parts SPILON VIOLET C-RH (oil-based dye, manufactured by Hodogaya Chemical Co., Ltd.)
16.3 parts VALIFAST YELLOW C-GNH (oil-based dye, Orient Chemical Industry Co., Ltd. 3.1 parts diethylene glycol monomethyl ether 50.1 parts ethylene glycol monoisopropyl ether 16.0 parts ESREC BL-1 (polyvinyl butyral, Sekisui Chemical Co., Ltd.) 1.6 parts ESREC BH-3 (polyvinyl butyral, manufactured by Sekisui Chemical Co., Ltd.) 0.4 parts phosphanol LB400 (polyoxyethylene alkyl ether phosphate, activator, Toho Chemical Co., Ltd.) )) 1.5 parts Nimene L201 (polyethylene glycol-1 laurylamine, manufactured by NOF Corporation) 1.0 parts HITanol 1501 (alkylphenol resin, manufactured by Hitachi Chemical Co., Ltd.) 0.5 part FZ-7002 ( Polyether-modified silicone oil, Toray Dow Ningu Ltd.) 0.25 parts Nikkol HCO-10 manufactured by (POE hydrogenated castor oil, Nikko Chemicals Co.)
2.0 parts Among the above components, the total amount of diethylene glycol monomethyl ether and the total amount of S-Rec BL-1 were stirred at 70 ° C, mixed and dissolved, then allowed to cool to room temperature, and then the total amount of Printex 35 was added. A dyno mill (bead mill, manufactured by Shinmaru Enterprise Co., Ltd.) was used 10 times using zirconia beads having a diameter of 0.3 mm to obtain a black paste.
Next, the entire amount of the remaining material was added to this paste, and the mixture was stirred at 70 ° C. for 3 hours to obtain a black oil-based ink for ballpoint pens.
In the above composition, “parts” simply means “parts by weight”.

The following writing test was conducted. The results are shown in Table 2.
(Writing test 1)
Lightness of writing is judged by handwriting sensory test at a writing angle of about 70 °.
○: Light writing taste △: Feel heavy writing taste occasionally ×: Heavy writing taste

(Ink ejection test 1)
A writing test was carried out using the above test sample with a PEN WRITTING TESTER MODEL TS-4C-10 manufactured by Seiki Kogyo Co., Ltd., which is an automatic writing machine, and the ink ejection amount after 100 m writing was measured.
Writing conditions with an automatic writing machine were written in accordance with JIS S 6039 at a writing angle of 70 °, a writing load of 150 g, and a writing speed of 7 cm / sec.
Three samples were written, and the average ink discharge amount was determined according to the following criteria when the average ink discharge amount of the ball area pen sample (Comparative Example 1) with the minimum total area of the ball transfer portion was 100%.
○: 90% or more Δ: 86-89%
X: 85% or less

(Writing resistance test 1)
The above test sample is placed on the exterior of a 0.7 mm ballpoint pen “Rolly” (product code: BP127) manufactured by Pentel Co., Ltd. In this case, the load in the writing direction is sensed by the load cell provided in the holding part of the exterior, and the magnitude of the force with which the ballpoint pen body is pulled in the paper movement direction by the movement of the paper is detected. Resistance value was used.
Write 15cm under the conditions of 150g for pressing the ball against the paper, 70 ° for the angle between the paper and the exterior, and 7cm / sec for the paper movement speed. Every 0.005sec between 0.005sec and 2.0sec An average of the detected 400 resistance values was defined as an average writing resistance value.

The following writing test was conducted. The results are shown in Table 3.
(Writing test 2)
Smoothness of writing feeling is judged by handwriting sensory test at a writing angle of almost 50 °.
○: Smooth writing taste △: Feeling tingling / slight vibration occasionally ×: Writing feeling feeling tingling / slight vibration

(Ink ejection test 2)
The ink ejection test 1 was carried out at the writing angle of 50 ° according to the same method and evaluation criteria.

(Writing resistance test 2)
The same method and evaluation criteria as in the writing resistance test 1 were performed at a writing angle of 50 °.
Moreover, since the difference in resistance value that occurs at intervals of less than 0.1 sec as vibration perceived by humans does not significantly disturb the writing feel, the measured values obtained were compared as average values every 0.1 sec. FIG. 5 shows an example of this (Example 5) as a graph. In particular, when the average value of the difference between the adjacent resistance values higher than the average writing resistance value is 1.5 g or more, it can be said that fine vibrations that are rigorous are easily detected during writing and are easily recognized as poor writing feeling. Therefore, an average value of the difference between adjacent resistance values every 0.1 sec higher than the average writing resistance value was calculated.

DESCRIPTION OF SYMBOLS 1 Ball | bowl 2 Ball holder 2a Front-end opening part 2b Rear-end opening part 3 Ink accommodating part 4 Oil-based ink 5 Backflow prevention body composition 6 Coil spring 6a Winding part 6b Straight end part 7 Ball holding chamber 8 Center hole 9 Radial groove 10 Rear hole 11 Inward projecting portion 12 Tip portion ball transfer portion 13 Ball seat ball transfer portion

Claims (4)

In a ball-point pen tip comprising at least a ball as a writing member and a ball holder that partially holds and holds the ball from the tip opening, the curvature of the ball is substantially reduced by pressing the inner surface of the ball holder against the surface of the ball. A ball-point pen tip having a total area of a ball transfer portion formed by being transferred to 22.0% or more and 31.0% or less of the surface area of the ball. The ball transfer portion is composed of at least a ball receiving portion and an inner surface of the tip caulking portion, and a ratio of the surface area of the ball receiving ball transfer portion to the surface area of the inner surface of the tip caulking portion is 0.8 to 1.3. The ballpoint pen tip according to claim 1, wherein: The portion between the ball receiving ball transfer portion and the tip caulking portion inner surface ball transfer portion straddles the equator portion of the ball when the ball is positioned at the rearmost portion, and the length of the portion between the ball diameter is the diameter of the ball The ballpoint pen tip according to claim 1 or 2 which is 24.0% or more and 34.0% or less. A ballpoint pen containing oil-based ink containing a phosphoric ester lubricant in an ink tank in which the ballpoint pen tip according to any one of claims 1 to 3 is connected directly or through a connecting member to a tip.

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