JP7586702B2 - Mounting structure for soft member and thermochromic writing implement - Google Patents

Description

The present invention relates to a soft member attachment structure for attaching a soft member used to cause thermochromic ink adhering to a paper surface to change color by frictional heat to a thermochromic writing instrument. The present invention also relates to a thermochromic writing instrument in which the soft member is attached to the rear end of the barrel or the top of the cap by the soft member attachment structure.

In 1975, the applicant succeeded in developing a thermochromic ink that changes color depending on the temperature, and in 2002 released the first thermochromic writing instrument incorporating thermochromic ink. In 2005, the applicant succeeded in expanding the temperature change range of the thermochromic ink to approximately 80 degrees (-20°C to 65°C), and in 2006 released a thermochromic writing instrument with the product name "FriXion Ball (registered trademark)" in Europe. Currently, the "FriXion (registered trademark)" series of thermochromic writing instruments manufactured and sold by the applicant are widely used all over the world.

Thermochromic ink changes from one color to another, from one color to colorless, or from colorless to color, by heating or cooling. Conventional thermochromic writing instruments have a friction part for thermochromic ink markings written on paper. The friction part is made of an elastic material such as rubber or elastomer, and generates frictional heat between the friction part and the paper surface. The frictional heat generated when the thermochromic ink markings are rubbed against the friction part can cause the thermochromic ink markings to thermochromic change color. Conventionally, friction parts have been attached to thermochromic writing instruments by an attachment structure such as the one shown below.

International Publication No. 2011/096357 discloses a structure for attaching a friction part to the rear end of a barrel. An attachment hole is provided at the rear end of the barrel. An inward protrusion that protrudes toward the inside of the attachment hole is formed on the inner peripheral surface of the attachment hole. Meanwhile, the friction part is composed of a large diameter part and a small diameter part. The large diameter part is used to thermally discolor the handwriting of the thermochromic ink. The small diameter part is used to attach the friction part to the rear end of the barrel. An outward protrusion that protrudes toward the outside of the small diameter part is formed on the outer peripheral surface of the small diameter part. By inserting the small diameter part into the attachment hole, the outward protrusion and the inward protrusion are engaged with each other. In this way, the friction part is attached to the rear end of the barrel.

JP 2012-232484 A discloses a mounting structure for a friction part that can change the hardness of the friction part. This mounting structure includes an operating part and a movable body. The operating part is rotatably provided at the rear end of the barrel. The movable body is housed inside the operating part, and moves back and forth along the central axis by rotation of the operating part. A cavity consisting of a large diameter part and a small diameter part is provided inside the friction part. A rod-shaped core part provided in the movable body is inserted into the cavity of the friction part. By rotating the operating part, the length of the core part inserted into the cavity of the friction part changes. This makes it possible to change the hardness of the friction part.

JP 2009-214515 A discloses a friction part mounting structure that allows the friction part to be easily mounted to the barrel or cap. This mounting structure includes a protrusion provided on the barrel or cap and a mounting hole that passes through the friction part. By inserting the protrusion into the mounting hole, the friction part can be easily mounted to the barrel or cap.

Although not a friction part mounting structure, JP 2013-139135 A discloses an erasing member mounting structure that allows an erasing member to be easily mounted on a barrel or cap. This mounting structure includes a fitting portion and a connection portion provided on the barrel or cap, and a fitting hole that penetrates the erasing member. The connection portion protrudes from the end of the barrel or cap. The fitting portion is provided on the upper end of the connection portion and has a width greater than that of the protruding portion. The fitting hole of the erasing member has a size that can receive the fitting portion and the connection portion. When the fitting portion and the connection portion are inserted into the fitting hole, frictional resistance occurs between the fitting portion and the fitting hole, but no frictional resistance occurs between the connection portion and the fitting hole. This allows the erasing member to be easily mounted on the barrel or cap.

International Publication No. 2011/096357 JP 2012-232484 A JP 2009-214515 A JP 2013-139135 A International Publication No. 2018/116767

<Development of a new thermochromic writing instrument>
As disclosed in International Publication No. 2018/116767, the present applicant is attempting to commercialize a thermochromic writing instrument incorporating a thermochromic ink containing a metallic luster pigment. The metallic luster pigment is, for example, a core particle whose surface is coated with a metal oxide, giving the ink color a metallic luster. The metallic luster pigment particles contained in the thermochromic ink each reflect light and sparkle, forming a decorative handwriting. However, by incorporating a metallic luster pigment into the thermochromic writing instrument, technical problems specific to the thermochromic writing instrument have arisen. Below, several problems that the present invention aims to solve are listed.

<Removal of metallic luster pigments>
When the thermochromic ink built into the thermochromic writing implement has a property of changing color from colored to colorless by heating, the conventional friction part cannot erase the metallic luster pigment contained in the handwriting from the paper surface. That is, the conventional friction part can chemically erase the handwriting of the thermochromic ink written on the paper surface by thermally changing the color of the thermochromic ink from colored to colorless. However, the metallic luster pigment blended in the thermochromic ink is composed of particles of metal, mineral, glass, etc., and does not have thermochromic properties. For this reason, the metallic luster pigment cannot be erased from the paper surface by the frictional heat of the friction part, and remains on the paper surface. Furthermore, the metallic luster pigment rubbed off by the friction part scatters on the paper surface, staining the paper surface after the thermochromic ink is erased.

<Softening of friction parts>
Therefore, as disclosed in WO 2018/116767, the applicant invented a method of adding a viscoelastic body to the material of the friction part and reducing the hardness of the friction part compared to conventional methods. Such a novel friction part can generate frictional heat to chemically erase thermochromic ink, and can also physically erase it by peeling off particles of metallic luster pigment from the paper surface.

However, the friction part that has been softened by adding a viscoelastic body undergoes a large amount of deformation when rubbing the handwriting of thermochromic ink. That is, when rubbing the handwriting of thermochromic ink, the top of the friction part is brought into contact with the handwriting and moved back and forth. When the friction part is softened, the top of the friction part does not move easily in response to the reciprocating motion, and the entire friction part is greatly deflected. The large deflection of the entire friction part reduces the amount and speed of movement of the top of the friction part on the paper surface, preventing the generation of frictional heat. For this reason, a friction part that is softer than before does not provide sufficient friction performance to efficiently thermochromic ink.

<Conventional friction part mounting structure>
The mounting structure of the friction part disclosed in WO 2011/096357 mounts the friction part to the rear end of the barrel by engaging the outward protrusion of the friction part with the inward protrusion of the mounting hole. The friction part is provided with an inner hole for facilitating deformation of the friction part. By providing the inner hole, the small diameter part of the friction part is easily deformed, and the outward protrusion and the inward protrusion can be easily engaged. However, if the friction part provided with the inner hole is softened, the friction part becomes even more easily deformed. As a result, it becomes impossible to maintain the engagement between the outward protrusion and the inward protrusion by resisting the reciprocating motion when rubbing the handwriting, and the friction part becomes more likely to come off the mounting hole.

The mounting structure of the friction part disclosed in JP 2012-232484 A is configured to change the hardness of the friction part by inserting a core part provided in a movable body into a cavity of the friction part. However, the cavity of the friction part is composed of a large diameter part and a small diameter part similar to the friction part, with respect to the straight rod-shaped core part. Only the tip of the core part can contact the inner peripheral surface of the large diameter part of the friction part. The part other than the tip of the core part cannot contact the inner peripheral surface of the large diameter part of the friction part. Therefore, the part other than the top part of the large diameter part of the friction part is easily deformed by the cavity, and the rigidity of the friction part required for efficiently thermally discoloring the thermochromic ink cannot be obtained. If the friction part provided with the cavity is softened, the difference in rigidity between the top part of the large diameter part of the friction part and the part other than the top part becomes large, making it difficult to efficiently thermally discolor the thermochromic ink.

The mounting structure of the friction part disclosed in JP 2009-214515 A is configured so that a protrusion on the barrel or cap is inserted into a mounting hole in the friction part. However, the large diameter part of the friction part is easily deformed by the mounting hole that passes through its center. If the friction part through which the mounting hole passes is softened, the large diameter part becomes even more easily deformed, and the rigidity of the friction part required for efficiently thermochromic ink to thermochromic change cannot be obtained. In addition, because the mounting hole opens at the top of the friction part, frictional heat cannot be generated by the top of the friction part.

The mounting structure of the eraser disclosed in JP 2013-139135 A is configured to fit a fitting hole in the eraser into a fitting portion provided on the barrel or cap. However, similar to the above-mentioned JP 2009-214515 A, the eraser is easily deformed by the mounting hole that passes through its center. If the eraser through which the fitting hole passes is softened, the large diameter portion becomes even more easily deformed, and the eraser does not have the rigidity required to efficiently thermally change the color of thermochromic ink. In addition, because the fitting hole opens at the top of the eraser, frictional heat cannot be generated by the top of the eraser.

<Wear of friction parts>
The friction part softened by adding a viscoelastic body is easily worn away by rubbing against the paper surface. The friction part disclosed in JP 2012-232484 A has a thin wall thickness at the large diameter part due to the provision of a cavity. If the friction part with a cavity is softened, the top of the friction part will wear away after a short period of use. This causes the tip of the core part that was in contact with the top of the friction part to be exposed to the outside, which may damage the paper surface.

The friction part disclosed in JP 2009-214515 A has an attachment hole that passes through its center, so the amount of material that makes up the large diameter part is reduced by the amount of the attachment hole. The erasing member disclosed in JP 2013-139135 A also has a fitting hole that passes through its center, so the amount of material that makes up the large diameter part is reduced by the amount of the fitting hole. If these friction parts and erasing members were softened, the large diameter part would wear out after a short period of use, making it impossible to erase thermochromic ink marks.

<Difficulty of installation work>
The mounting structure of the erasing member disclosed in JP 2013-139135 A is configured to fit the fitting hole of the erasing member into the fitting portion surrounded by the cylindrical support wall. The maximum diameter of the fitting portion is larger than the minimum diameter of the fitting hole. In addition, the insertion portion of the erasing member is provided with an engagement protrusion that abuts against the inner circumferential surface of the support wall. In order to mount the erasing member, the insertion portion of the erasing member is pushed into the cylindrical support wall while the fitting portion is inserted into the fitting hole of the erasing member. At this time, a force from the fitting portion toward the inner circumferential surface of the support wall and a force from the inner circumferential surface of the support wall toward the fitting portion are applied to the insertion portion of the erasing member. That is, in the process of pushing the insertion portion of the erasing member into the support wall, the fitting portion applies a force toward the inner circumferential surface of the support wall to the fitting hole by pressing the inner circumferential surface of the fitting hole. Meanwhile, the inner circumferential surface of the support wall applies a force toward the fitting portion to the insertion portion by pressing the engagement protrusion. Thus, in order to push the insertion portion of the eraser into the support wall, a force greater than the opposing forces applied inside and outside the insertion portion is required, making the installation of the eraser difficult, and particularly difficult when installed by an automated assembly machine.

Object of the Invention
The soft member mounting structure and thermochromic writing implement of the present invention have the following objectives a) to d).
a) The rigidity of the softened friction portion is improved and deformation of the friction portion is suppressed, thereby allowing the friction portion to exhibit good friction performance.
b) The inside and outside of the mounting portion of the softened friction portion can be firmly fixed by forces in opposite directions, and the mounting operation of the friction portion does not require a large force.
c) Even if the softened friction portion wears, it will not damage the paper surface.
d) It is possible to chemically and physically erase marks made from thermochromic ink containing metallic luster pigments.

(1) In order to achieve the above object, the soft member mounting structure of the present invention is a soft member mounting structure for mounting a soft member used to cause thermochromic ink adhering to a paper surface to be thermochromic by frictional heat to a thermochromic writing instrument, the soft member comprising a mounting hole that is provided to penetrate the rear end of a barrel or the top of a cap constituting the thermochromic writing instrument along a vertical central axis and has an inner circumferential surface between two openings located at the upper and lower ends, and a mounting hole that is provided below the large diameter portion of the soft member used for thermochromic ink discoloration and has an inner circumferential surface between the large diameter portion .... The soft member is configured to be attached to the mounting hole by inserting the mounting part into the mounting hole, the soft member having a straight inner hole that is provided along the vertical center axis of the soft member and opens at least at the lower end of the soft member, and a rod-shaped core having an outer diameter that can be inserted into the inner hole, a length that fits into the inner hole, and an outer peripheral surface that contacts the inner peripheral surface of the inner hole, and the soft member is configured to be attached to the mounting hole by inserting the mounting part into the mounting hole and inserting the core into the inner hole.

(2) Preferably, in the mounting structure for the soft member described in (1) above, the mounting portion is formed integrally below the large diameter portion using the same material as the soft member, the inner hole is provided in the soft member from the mounting portion to a position that reaches the large diameter portion, and when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core is held in a position corresponding to the inner peripheral surface of the mounting hole, so that the mounting portion is sandwiched between the outer peripheral surface of the core and the inner peripheral surface of the mounting hole.

(3) Preferably, in the mounting structure for the soft member described in (2) above, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length that extends from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole.

(4) Preferably, in the mounting structure for the soft member of (2) above, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole.

(5) Preferably, in the mounting structure for the soft member described in (2) above, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length that does not reach from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole.

(6) Preferably, in the mounting structure for the soft member of (4) or (5) above, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the upper end of the core is inserted into the inner hole to a position that exceeds the opening at the upper end of the mounting hole.

(7) Preferably, in any of the above (2) to (6) soft member mounting structures, the maximum outer diameter of the core is substantially the same as or larger than the inner diameter of the inner hole, and when the core is inserted into the inner hole, the outer peripheral surface of the core and the inner peripheral surface of the inner hole are pressed against each other.

(8) Preferably, in the soft member mounting structure of (7) above, a lubricant is interposed between the outer peripheral surface of the core and the inner peripheral surface of the inner hole.

(9) Preferably, in the soft member mounting structure of any of (1) to (8) above, the inner hole is a hole that opens at the lower end of the soft member and is closed at one end that does not open at the upper end of the soft member, and a ventilation portion is provided in the core to exhaust air from within the inner hole during the process of inserting the core into the inner hole.

(10) Preferably, in the mounting structure for the soft member of (9) above, the ventilation portion is a through hole that penetrates from one end of the core to the other end along the vertical central axis of the core.

(11) Preferably, in the mounting structure for the soft member of (9) above, the ventilation portion is at least one groove or protrusion that continues from one end of the core to the other end along the outer circumferential surface of the core.

(12) Preferably, in any of the above (2) to (11) mounting structures for a soft member, a flange having a diameter larger than the inner diameter of the inner hole is provided at the lower end of the core, and when the core is inserted into the inner hole, the flange abuts against the lower end of the mounting portion.

(13) Preferably, in the mounting structure for a soft member according to any one of (2) to (12) above, an inward protrusion that protrudes toward the inside of the mounting hole is formed on the inner peripheral surface of the mounting hole, and an outward protrusion that protrudes toward the outside of the mounting part is formed on the outer peripheral surface of the mounting part, and when the mounting part is inserted into the mounting hole, the outward protrusion rides over the inward protrusion, thereby engaging the outward protrusion and the inward protrusion, and the core is held in a position corresponding to the inner peripheral surface of the mounting hole, so that the mounting part is sandwiched between the outer peripheral surface of the core and the outward protrusion of the mounting hole.

(14) In order to achieve the above object, the thermochromic writing instrument of the present invention is configured such that the soft member is attached to the rear end of the barrel or the top of the cap by any of the soft member attachment structures (1) to (13) above.

Here, in the mounting structure of the soft member of the present invention, "up" of the mounting hole means the direction toward the rear end of the barrel or the direction toward the top of the cap, and "down" of the mounting hole means the opposite direction. On the other hand, "up" of the soft member means the direction toward the large diameter portion, and "down" of the soft member means the direction toward the mounting portion.

The soft member mounting structure and thermochromic writing implement of the present invention provide the following advantages a) to d).
a) The rigidity of the softened friction portion is improved and deformation of the friction portion is suppressed, thereby allowing the friction portion to exhibit good friction performance.
b) The inside and outside of the mounting portion of the softened friction portion can be firmly fixed by forces in opposite directions, and the mounting operation of the friction portion does not require a large force.
c) Even if the softened friction portion wears, it will not damage the paper surface.
d) It is possible to chemically and physically erase marks made from thermochromic ink containing metallic luster pigments.

FIG. 1 is a cross-sectional view showing a soft member that constitutes a soft member mounting structure according to an embodiment of the present invention and a mounting hole provided at the rear end of a barrel, showing the state before the mounting portion of the soft member is inserted into the mounting hole. 11 is a cross-sectional view showing a temporary insertion state during the process of inserting the mounting portion of the soft member into the mounting hole. FIG. 13 is a cross-sectional view showing a state in which the insertion of the soft member into the mounting hole is completed. FIG. FIG. 4 is a cross-sectional view showing a mounting structure for a soft member according to an embodiment of the present invention, in which the core according to the first embodiment is inserted into the inner hole of the soft member of FIG. 3 . FIG. 4 is a cross-sectional view showing a mounting structure for a soft member according to an embodiment of the present invention, showing a state in which a core according to a second embodiment is inserted into an inner hole of the soft member of FIG. 3 . 6 is a cross-sectional view showing a state in which a lubricant is interposed between the inner hole and the center core of the soft member of FIG. 5 . 6 is a cross-sectional view showing a state in which a lubricant is interposed between the inner hole and the center core of the soft member of FIG. 5 . 6 is a cross-sectional view showing a state in which the upper end of the core in FIG. 5 is inserted into the inner hole to a position that exceeds the opening at the upper end of the mounting hole. FIG. 4 is a cross-sectional view showing a mounting structure for a soft member according to an embodiment of the present invention, showing a state in which a core according to a third embodiment is inserted into an inner hole of the soft member of FIG. 3 .

The following describes the soft member mounting structure and thermochromic writing instrument according to an embodiment of the present invention with reference to the drawings.

1. Overview The soft member attachment structure of this embodiment is for attaching a soft member used to cause thermochromic ink adhering to a paper surface to change color by frictional heat to a thermochromic writing instrument. In Figures 1 to 9, the entire thermochromic writing instrument is not shown, and only the rear end of the barrel that constitutes the thermochromic writing instrument is shown.

The mounting structure of the soft member in this embodiment is mainly composed of the mounting hole 2, mounting portion 5, inner hole 31 shown in Figures 1 to 3, and the core 7 shown in Figures 4 to 9. The mounting hole 2 is provided at the rear end of the shaft tube 1. The mounting portion 5 is integrally formed below the large diameter portion 4 of the soft member 3. The inner hole 31 is provided from the mounting portion 5 in the soft member 3 to a position that reaches the center of the large diameter portion 4. The core 7 is a single component independent of the shaft tube 1 and the soft member 3. As shown in Figures 3 and 4, the core 7 is inserted into the inner hole 31 of the soft member 3 when the mounting portion 5 of the soft member 3 is completely inserted into the mounting hole 2 of the shaft tube 1. The mounting structure of the soft member 3 will be described in detail below.

2. Mounting hole As shown in FIG. 1, a mounting hole 2 is provided at the rear end of the barrel 1. The mounting hole 2 penetrates the rear end of the barrel 1 along the vertical central axis. The mounting hole 2 has an inner circumferential surface between two openings located at the upper and lower ends. An annular inward protrusion 21 is formed below the inner circumferential surface of the mounting hole 2. A guide surface 21a, which is an inverted cone-shaped tapered surface, is formed on the outer circumferential surface of the inward protrusion 21. The diameter of the guide surface 21a gradually decreases from top to bottom. The lower end of the guide surface 21a is continuous with the vertical outer circumferential surface of the minimum inner diameter portion 21b, which is the opening at the lower end of the mounting hole 2. The horizontal cross-sectional shape of such a mounting hole 2 is a circle with a different diameter.

Here, the barrel 1 is manufactured by injection molding a synthetic resin (e.g., polypropylene). The mounting hole 2 and the inward projection 21 are integrally molded into the rear end of the barrel 1 by injection molding. Note that the mounting hole 2 is not limited to the rear end of the barrel 1, and may be provided, for example, at the top of a cap that constitutes a thermochromic writing instrument.

3. Soft member As shown in Fig. 1, the soft member 3 of this embodiment is configured such that an attachment portion (small diameter portion) 5 having a smaller diameter than the large diameter portion 4 is integrally molded below the bullet-shaped large diameter portion 4. The large diameter portion 4 is a portion that functions as the friction portion 32 of the thermochromic writing instrument, and is used to thermally discolor the thermochromic ink attached to the paper surface by frictional heat. Furthermore, the large diameter portion 4 of this embodiment has a function of adsorbing and peeling off the metallic luster pigment mixed in the thermochromic ink from the paper surface. The attachment portion 5 is used to attach the soft member 3 to the attachment hole 2 of the barrel 1.

3.1 Large diameter section (friction section)
The outer peripheral surface of the large diameter portion 4 is a convex curved surface that can contact the paper surface at various inclination angles. The diameter of the lower end of the large diameter portion 4 is larger than the diameter of the opening at the upper end of the mounting hole 2, and is preferably smaller than the diameter of the rear end face of the barrel 1. An annular surface 41 that abuts on the rear end face of the barrel 1 is formed at the boundary between the large diameter portion 4 and the mounting portion 5. When the mounting portion 5 is attached to the mounting hole 2, the large diameter portion 4 protrudes upward beyond the rear end face of the barrel 1.

3.2 Mounting portion The mounting portion 5 is made of a cylindrical wall portion, and has a diameter smaller than the diameter of the lower end of the large diameter portion 4 and capable of being inserted into the mounting hole 2. An annular outward protrusion 51 is formed in the center of the outer circumferential surface of the mounting portion 5. An annular bulge 52 is formed above the outward protrusion 51 on the outer circumferential surface of the mounting portion 5. Below the outward protrusion 51 on the mounting portion 5, a cylindrical portion 53 is formed.

A guide surface 51a, which is an inverted cone-shaped tapered surface, is formed on the outer peripheral surface of the outward protrusion 51. The diameter of the guide surface 51a gradually increases from bottom to top. The upper end of the guide surface 51a is continuous with the vertical outer peripheral surface of the maximum outer diameter portion 51b of the outward protrusion 51. The upper end of the vertical outer peripheral surface of the maximum outer diameter portion 51b is continuous with a horizontal annular upper end surface.

Here, the diameter of the maximum outer diameter portion 51b of the outward projection 51 is larger than the diameter of the minimum inner diameter portion 21b of the inward projection 21 of the mounting hole 2 described above, and smaller than the diameter of the opening at the upper end of the mounting hole 2. For example, the dimensional difference between the maximum outer diameter portion 51b and the minimum inner diameter portion 21b is within the range of 0.5 mm to 2.0 mm, preferably within the range of 0.5 mm to 1.0 mm. Due to such a dimensional difference, when the mounting part 5 is inserted into the mounting hole 2, the outward projection 51 passes smoothly through the inward projection 21, making it possible to easily engage the outward projection 51 and the inward projection 21 (see Figures 2 and 3).

When the mounting portion 5 is fully inserted into the mounting hole 2, the bulge portion 52 comes into contact with the inner circumferential surface of the opening at the upper end of the mounting hole 2 (see FIG. 3). This prevents the soft member 3 from wobbling in the radial direction. The diameter of the bulge portion 52 is approximately the same as the diameter of the opening at the upper end of the mounting hole 2. The diameter of the bulge portion 52 is also smaller than the diameter of the lower end of the large diameter portion 4 and larger than the diameter of the maximum outer diameter portion 51b of the outward projection 51.

The diameter of the cylindrical portion 53 is smaller than the diameter of the minimum inner diameter portion 21b of the inward protrusion 21 of the mounting hole 2 described above. The cylindrical portion 53 is for temporarily inserting the mounting portion 5 into the mounting hole 2. This temporarily inserted state is shown in FIG. 2. Such a cylindrical portion 53 makes it easier to attach the soft member 3. That is, the soft member 3 can be dropped toward the mounting hole 2 to be in the temporarily inserted state shown in FIG. 2. Then, the soft member 3 is pushed toward the mounting hole 2 to completely insert the mounting portion 5 into the mounting hole 2, and at the same time, the outward protrusion 51 and the inward protrusion 21 are engaged (see FIG. 3). Note that the outer peripheral surface below the outward protrusion 51 of the mounting portion 5 is not limited to the circumferential surface of the cylindrical portion 53, and may be, for example, an inverted cone-shaped tapered surface.

3.3 Formation of annular space The outer diameter of the middle part of the mounting part 5 (part between the bulging part 52 and the outward protrusion 51) is smaller than the inner diameter of the vicinity of the entrance of the mounting hole 2 (part above the inward protrusion 21). As a result, in the temporary insertion state shown in FIG. 2, an annular space 6 is formed between the mounting part 5 and the mounting hole 2. Due to this annular space 6, the middle part of the mounting part 5 is not pressed against the inner circumferential surface near the entrance of the mounting hole 2. That is, after the temporary insertion state shown in FIG. 2, the outward protrusion 51 of the mounting part 5 rides over the inward protrusion 21 of the mounting hole 2. At this time, the outward protrusion 51 is strongly pressed against the inward protrusion 21, so that the middle part of the mounting part 5 is elastically deformed and bulges outward in the radial direction. If the middle part of the mounting part 5 is pressed against the inner circumferential surface near the entrance of the mounting hole 2, frictional resistance that prevents the mounting part 5 from being inserted will be generated. The annular space 6 accommodates the intermediate portion of the mounting portion 5 which bulges radially outward, thereby preventing the intermediate portion of the mounting portion 5 from being pressed against the inner circumferential surface near the entrance of the mounting hole 2 .

3.4 Axial clearance As shown in FIG. 1, the length A from the upper end of the mounting portion 5 to the upper end of the outward projection 51 is slightly larger than the length B from the upper end of the mounting hole 2 to the lower end of the inward projection 21. This ensures that the entire outward projection 51 passes through the inward projection 21. In other words, if the lengths A and B were the same, the upper end surface of the maximum outer diameter portion 51b of the outward projection 51 may not be able to pass through the inward projection 21 due to frictional resistance generated between the outward projection 51 and the inward projection 21. By making the length A of the mounting portion 5 slightly larger than the length B of the mounting hole 2, the entire outward projection 51 can pass through the inward projection 21 even after the annular surface 41 of the large diameter portion 4 abuts against the rear end of the barrel 1. This ensures that the entire outward projection 51 passes through the inward projection 21 even if frictional resistance occurs between the outward projection 51 and the inward projection 21. Here, the difference in dimensions between lengths A and B appears as a clearance C between the outward projection 51 and the inward projection 21 shown in Fig. 3. The clearance C is preferably in the range of 0.05 mm to 1.0 mm, and more preferably in the range of 0.1 mm to 0.5 mm. With such a small clearance C, the soft member 3 does not move in the direction of the central axis, and the engagement between the outward projection 51 and the inward projection 21 does not loosen.

3.5 Inner Hole An inner hole 31 is provided inside the soft member 3. The inner hole 31 is a straight hole provided along the central axis of the soft member 3, and opens at least at the lower end of the soft member 3. In this embodiment, the inner hole 31 is a hole that extends from the lower end of the mounting portion 5 to the center of the large diameter portion 4, and is closed on one side, not opening at the upper end of the soft member 3. The inner hole 31 is provided from the lower end of the mounting portion 5 to a position that reaches at least the upper end of the outward protrusion 51. Such an inner hole 31 makes it easier for the outward protrusion 51 to deform radially inward. This makes it easy to engage the outward protrusion 51 and the inward protrusion 21. Furthermore, the center core 7, which will be described later, is inserted into the inner hole 31.

3.6 Hardness and Viscosity of Soft Member The material constituting the soft member 3 is preferably a synthetic resin having elasticity (rubber, elastomer), such as silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butylene-styrene copolymer), fluorine-based resin, chloroprene resin, nitrile resin, polyester-based resin, ethylene propylene diene rubber (EPDM), etc.

Here, the soft member 3 of this embodiment has a lower hardness than the conventional friction part in order to physically erase the metallic luster pigment blended in the thermochromic ink described below from the paper surface. The soft member 3 with a low hardness is able to penetrate into the depressions of the handwriting formed on the paper surface.

The hardness of the soft member 3 is represented by the Shore A hardness value measured in accordance with the "Durometer hardness test method for plastics" specified in the Japanese Industrial Standards JIS K 7215-1986. The durometer used to measure the Shore A hardness value has a spring-loaded indenter, and the amount of indenter pressure on the object being measured is displayed as the Shore A hardness value. The softer the object being measured, the smaller the Shore A hardness value, and the harder the object being measured, the larger the Shore A hardness value.

It is preferable that the Shore A hardness value of the soft member 3 measured by a test method in accordance with JIS K 7215-1986 satisfies the following conditions i) and ii).

i) The Shore A hardness value immediately after the initiation of contact with the indenter is 60 or more and 85 or less.
ii) The value of ΔHS defined by the following formula is 0 or more and less than 5.

ΔHS=(Shore A hardness value immediately after the indenter starts contacting)−(Shore A hardness value 15 seconds after the indenter starts contacting)

In the above i) and ii), "immediately after the indenter starts to come into contact" means within one second after the indenter comes into contact with the object to be measured.

The Shore A hardness value immediately after the start of the indentation contact in i) above is preferably 60 to 80, more preferably 65 to 75. In order to satisfy the above conditions i) and ii), a viscoelastic body may be added to the material constituting the soft member 3. As the viscoelastic body, for example, a polymeric material such as a rubber component, a resin component, or an elastomer component may be added. In particular, it is preferable to use a highly viscous α-olefin copolymer composition, which is made by adding paraffin oil to an α-olefin copolymer, as the main component. Specifically, a highly viscous α-olefin copolymer composition is used as the main component, and polystyrene elastomer, olefin elastomer, and crystalline polyolefin, which are elastic bodies, are appropriately melt-mixed therewith. The mixing ratio of these materials is selected taking into consideration the efficiency of frictional heat generation, the peelability of the metallic luster pigment, and the processability of the soft member.

By satisfying the Shore A hardness value in i) above, the soft member 3 generates more frictional heat efficiently. This allows the soft member 3 to easily thermally discolor handwriting of thermochromic ink. In addition, the soft member 3 that satisfies the Shore A hardness value in i) above is softer than conventional friction parts and can penetrate into the depressions in the handwriting formed on the paper surface. Furthermore, by the soft member 3 satisfying the ΔHS value in ii) above, it becomes possible to adsorb and peel off metallic luster pigments from within the depressions in the handwriting.

The value of ΔHS in ii) above indicates the relaxation time of stress relaxation (change in stress over time) when a certain strain is applied to the soft member 3. The relaxation time of stress relaxation is a criterion for distinguishing whether a material is an elastic body, a viscoelastic body, or a viscous body. A soft member 3 that satisfies the ΔHS value in ii) above can be said to be an elastic body with appropriate viscosity that enables it to adsorb metallic luster pigments. On the other hand, a material with a ΔHS value of 5 or more can be said to be a viscoelastic body or a viscous body. If the soft member 3 is a viscoelastic body or a viscous body, the amount of deformation when the handwriting of the thermochromic ink is rubbed against it will be too large, and sufficient friction performance will not be obtained. Therefore, it is preferable that the ΔHS value of the soft member 3 is 0 or more and less than 5.

The Shore A hardness values in i) and ii) above may be values obtained by converting the Shore D hardness value of the soft member 3 measured by a test method conforming to JIS K 7215-1986 into a Shore A hardness value.

3.7 Amount of wear of the soft member In order to physically erase the metallic pigment blended in the thermochromic ink from the paper surface, the soft member 3 is preferably one that is scraped off by rubbing the paper surface and generates a small amount of wear debris (eraser debris). The soft member 3 removes the metallic pigment from the paper surface by adhering it to the wear debris and enveloping it as it wears itself.

The amount of wear of the soft member 3 is represented by the tensile strength at break Tb and the elongation at break Eb, which are calculated in accordance with, for example, "Vulcanized rubber and thermoplastic rubber - Determination of tensile properties" specified in JIS K 6251:2017 of the Japanese Industrial Standards. The tensile strength at break Tb is the tensile force recorded when the measured object is broken divided by the cross-sectional area of the measured object before the test. The elongation at break Eb is the elongation when the measured object is broken, and is expressed as a ratio (%) to the length of the measured object before the test.

The inventors have found that the wear amount of the soft member 3 is inversely proportional to the value of Tb×Eb. That is, the wear amount of the soft member 3 is affected by the mechanical strength and elongation of the material. By combining appropriate values of the tensile strength at break Tb and the elongation at break Eb, the wear amount of the soft member 3 can be controlled. The value of Tb×Eb represents the energy required to wear the soft member 3. Therefore, the more easily the measured object is worn, the smaller the value of Tb×Eb, and the more difficult the measured object is to wear, the larger the value of Tb×Eb.

It is preferable that the value of Tb × Eb of the soft member 3 calculated by a method in accordance with JIS K 6251:2017 satisfies the following condition iii).

iii) 5,000≦Tb×Eb≦18,000

In the above iii) the unit of the tensile strength at break Tb is "MPa" and the unit of the elongation at break Eb is "%", but these may be converted into other units.

In the above iii), 8,000≦Tb×Eb≦16,000 is preferable, and 10,000≦Tb×Eb≦14,000 is more preferable. The soft member 3 that satisfies the above iii) generates an appropriate amount of wear debris through normal frictional action by hand. This makes it possible for the metallic luster pigment blended in the thermochromic ink to adhere to and encase the wear debris.

In the above iii), if the value of Tb×Eb exceeds 18,000, it becomes difficult to wear down the soft member 3 by normal manual friction. For this reason, it is not possible to attach the metallic luster pigment to the wear debris and envelop it while wearing down the soft member 3.

On the other hand, in the above iii), if the value of Tb x Eb is smaller than 5,000, the soft member 3 is easily scraped off by normal manual friction. As a result, the frictional heat generated by the soft member 3 is lost along with the wear debris, making it difficult to efficiently thermo-change the thermochromic ink.

4. Core The core 7 is made of a synthetic resin or metal that is harder than the soft member 3. The material that constitutes the core 7 will be described later. By inserting the core 7 into the inner hole 31 of such a soft member 3, it is possible to improve the rigidity of the soft member 3 and suppress deformation of the soft member 3. As a result, even if the hardness of the soft member 3 is reduced, good friction performance can be exhibited.

The core 7 of the first embodiment shown in Figure 4 has a length that reaches from the opening at the lower end of the inner hole 31 to the center of the large diameter portion 4. By inserting a core 7 of such length into the inner hole 31, the rigidity of both the large diameter portion 4 and the attachment portion 5 can be improved and deformation due to frictional action can be suppressed.

The core 7 is a small cylindrical part with an outer diameter that is approximately the same as the inner diameter of the inner hole 31. The outer peripheral surface of the cylindrical core 7 contacts the inner peripheral surface of the inner hole 31 over its entire length. Preferably, the core 7 has an outer diameter larger than the inner diameter of the inner hole 31, and the outer peripheral surface of the core 7 is pressed against the inner peripheral surface of the inner hole 31 over its entire length. In this embodiment, the upper half of the core 7 is called the upper core portion 72, and the lower half of the core 7 is called the lower core portion 73.

4.1 Upper core The upper core 72 contacts or presses against the inside of the large diameter portion 4 to improve the rigidity of the large diameter portion 4. The upper core 72 prevents the large diameter portion 4 from being deformed by friction. In particular, when the Shore A hardness value of the soft member 3 is greater than 85 or the ΔHS value is 5 or greater, the upper core 72 effectively prevents the deformation of the entire large diameter portion 4. That is, the large diameter portion 4 of this embodiment has a convex curved outer periphery and can contact the paper surface at various inclination angles. No matter which part of the top, the vicinity of the top, or the side of the large diameter portion 4 rubs against the paper surface, the deformation of the large diameter portion 4 is prevented by the upper core 72, and frictional heat required for thermal discoloration can be generated. In addition, if the large diameter portion 4 has a rigidity that is not deformed by friction, the overall length of the soft member 3 may be shortened so that the upper core 72 does not contact the inside of the large diameter portion 4 (see FIG. 5).

4.2 Lower Core Portion The lower core portion 73 contacts or presses against the inside of the mounting portion 5, improving the rigidity of the mounting portion 5. The lower core portion 73 has the following two important mechanical effects in mounting the soft member 3 to the rear end portion of the barrel 1.

First, the lower core portion 73 prevents the mounting portion 5 from deforming inwardly, preventing the engagement between the outward protrusion 51 and the inward protrusion 21 from coming loose. That is, the soft member 3 of this embodiment is generally more deformable due to the provision of the inner hole 31 and the reduced hardness. In particular, the mounting portion 5 is tubular with a thin wall thickness and is therefore more likely to deform inwardly due to friction. The lower core portion 73 prevents the mounting portion 5 from deforming inwardly by contacting or pressing against the inside of the mounting portion 5. This prevents the engagement between the outward protrusion 51 and the inward protrusion 21 from coming loose due to friction.

Secondly, the lower core portion 73 presses the mounting portion 5 outward, strengthening the engagement between the outward protrusion 51 and the inward protrusion 21. That is, the lower core portion 73 presses the entire mounting portion 5 outward by contacting or pressing against the inside of the mounting portion 5. The outward protrusion 51 of the mounting portion 5 is urged outward by the pressing force of the lower core portion 73. Meanwhile, the inward protrusion 21 of the mounting hole 2 generates a reaction force in response to the pressing force of the lower core portion 73, pressing the mounting portion 5 inward. This inward and outward force strengthens the engagement between the outward protrusion 51 and the inward protrusion 21.

4.3 Ventilating Part The inner hole 31 in this embodiment is a hole that opens at the lower end of the soft member 3 and does not open at the upper end of the soft member 3, and is closed on one side. On the other hand, the core 7 is a small cylindrical part having an outer diameter equal to or larger than the inner diameter of the inner hole 31. When such a core 7 is inserted into the inner hole 31 with one side closed, the air in the inner hole 31 is compressed by the core 7, and the core 7 may not be smoothly inserted into the inner hole 31. Therefore, the core 7 is provided with a ventilating part 71. The ventilating part 71 in this embodiment is a through hole that penetrates from one end to the other end of the core 7 along the central axis in the vertical direction of the core 7. In the process of inserting the core 7 into the inner hole 31, the air in the inner hole 31 passes through the ventilating part 71 and is discharged to the outside. Such a ventilating part 71 makes it easier to insert the core 7 into the inner hole 31, and allows the core 7 to be inserted by an automatic assembly machine.

Note that the ventilation part 71 is not limited to the configuration shown in FIG. 4. For example, the cross-sectional shape of the ventilation part 71 is not limited to a circle, and may be a shape other than a circle. The ventilation part 71 may be provided shifted from the central axis of the core 7. Furthermore, the ventilation part 71 is not limited to a through hole, and may be, for example, at least one groove or protrusion provided on the outer peripheral surface of the core 7. The groove or protrusion as the ventilation part 71 may be linear or may be a shape other than a straight line. For example, the ventilation part 71 may be four grooves or four protrusions provided at positions 0°, 90°, 180°, and 270° on the outer peripheral surface of the cylindrical core 7. Also, for example, the ventilation part 71 may be a spiral groove or protrusion provided along the outer peripheral surface of the core 7. The spiral groove or protrusion has a non-slip effect that prevents the core 7 from slipping out of the inner hole 31. Furthermore, instead of providing the ventilation portion 71 to the core 7, the above-mentioned groove or protrusion may be provided on the inner surface of the inner hole 31.

4.4 Shape of the core It is preferable that the core 7 has a shape symmetrical from top to bottom with respect to the horizontal central axis as shown in Fig. 4. By making the core 7 symmetrical from top to bottom, there is no distinction between the top and bottom of the core 7, and the core 7 can be inserted into the inner hole 31 from either the top or bottom.

Conversely, the core 7 may have an asymmetric shape. For example, at least the upper edge of the core 7 may be chamfered to facilitate insertion into the inner hole 31. The upper core portion 72 may be thinned and the lower core portion 73 may be thickened. For example, the outer diameter of the upper core portion 72 may be substantially the same as the inner diameter of the inner hole 31. On the other hand, the outer diameter of the lower core portion 73 may be larger than the inner diameter of the inner hole 31, so that the outer peripheral surface of the lower core portion 73 is pressed against the inner peripheral surface of the inner hole 31. In this configuration, the thin upper core portion 72 allows the core 7 to be easily inserted into the inner hole 31. The thick lower core portion 73 also allows the outward protrusion 51 and the inward protrusion 21 to be firmly engaged.

4.5 Retention of the core In order to prevent the core 7 inserted into the inner hole 31 from easily slipping out, a non-slip surface can be provided on the outer circumferential surface of the core 7. To prevent slipping, for example, the outer circumferential surface of the core 7 may be roughened to increase the frictional resistance against the inner circumferential surface of the inner hole 31. Also, minute protrusions may be provided on the outer circumferential surface of the core 7 to prevent slipping. Furthermore, the outer diameter of the core 7 may be made significantly larger than the inner diameter of the inner hole 31 to prevent the core 7 from easily slipping out of the inner hole 31.

4.6 Material of the Core The core 7 is made of a synthetic resin or metal harder than the soft member 3. Examples of the synthetic resin that can be used include polypropylene, polyethylene, polystyrene, polycarbonate, polyethylene terephthalate, polyacetal, acrylic, nylon, acrylonitrile-styrene copolymer resin (AS resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), etc. In addition, rubber or elastomer harder than the soft member 3 may be used as the synthetic resin. Examples of the rubber or elastomer that can be used include silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butylene-styrene copolymer), fluorine-based resin, chloroprene resin, nitrile resin, polyester-based resin, and ethylene propylene diene rubber (EPDM). Examples of the metal that can be used include aluminum alloy, stainless steel, brass, etc. The synthetic resin core 7 can be manufactured by cutting or injection molding, for example. On the other hand, the metallic core 7 can be manufactured by, for example, cutting or plastic processing.

5. Method for Attaching Soft Member Next, a method for attaching the soft member 3 according to this embodiment will be described with reference to FIGS.

As shown in Figure 1, the soft member 3 is placed above the mounting hole 2 at the rear end of the barrel 1, and then dropped directly into the mounting hole 2. Then, as shown in Figure 2, the cylindrical portion 53 of the mounting part 5 enters the minimum inner diameter portion 21b of the mounting hole 2, and the mounting part 5 is temporarily inserted into the mounting hole 2. At this time, the guide surface 51a of the mounting part 5 abuts against the guide surface 21a of the mounting hole 2, so that the temporarily inserted state of the mounting part 5 is stably maintained.

Next, the soft member 3 in the provisionally inserted state is pushed into the mounting hole 2. Then, the outward protrusion 51 of the mounting portion 5 passes over the inward protrusion 21 of the mounting hole 2. At this time, the outward protrusion 51 is strongly pressed against the inward protrusion 21, so that the middle part of the mounting portion 5 elastically deforms and bulges radially outward. The middle part of the mounting portion 5 bulging radially outward is accommodated in the annular space 6 in the mounting hole 2. As a result, the middle part of the mounting portion 5 is not pressed against the inner circumferential surface near the entrance of the mounting hole 2, and does not interfere with the insertion of the mounting portion 5. Therefore, the outward protrusion 51 smoothly passes over the inward protrusion 21, and the outward protrusion 51 and the inward protrusion 21 are engaged. This completes the insertion of the mounting portion 5 into the mounting hole 2 (see FIG. 3).

Then, as shown in FIG. 4, the core 7 is inserted into the inner hole 31 of the soft member 3. In the process of inserting the core 7 into the inner hole 31, the air in the inner hole 31 passes through the ventilation section 71 and is discharged to the outside. Such ventilation section 71 allows the core 7 to be easily inserted into the inner hole 31. The core 7 inserted into the inner hole 31 presses the attachment section 5 outward, strengthening the engagement between the outward projection 51 and the inward projection 21. This completes the attachment of the soft member 3 to the rear end of the barrel 1.

According to the method for attaching the soft member 3 of this embodiment, the highly flexible attachment portion 5 can be inserted into the attachment hole 2 before the core 7 is inserted into the inner hole 31, and the outward protrusion 51 and the inward protrusion 21 can be easily engaged. Then, by inserting the core 7 into the inner hole 31, a force acts in the inward and outward directions on the attachment portion 5, and the engagement between the outward protrusion 51 and the inward protrusion 21 is firmly maintained. In addition, since the core 7 is inserted into the inner hole 31 after the attachment portion 5 is inserted into the attachment hole 2, the attachment work of the soft member 3 shown in Figures 1 to 4 does not require a large force.

6. Core according to the second embodiment Next, the core 7 according to the second embodiment will be described with reference to Fig. 5. Fig. 5 shows a state in which the mounting portion 5 is inserted into the mounting hole 2 at the rear end of the barrel 1, and the core 7 according to this embodiment is inserted into the inner hole 31. In Fig. 5, the configuration other than the core 7 is the same as in Fig. 4.

As shown in FIG. 5, the core 7 according to the second embodiment has a length from the opening at the lower end of the inner hole 31 to the opening at the upper end of the mounting hole 2. The upper end of the core 7 inserted into the inner hole 31 does not exceed the opening at the upper end of the mounting hole 2, and does not reach the inside of the large diameter portion 4. In other words, the core 7 is held in a position corresponding to the inner circumferential surface of the mounting hole 2, and does not come into contact with the inside of the large diameter portion 4 at all.

Even if the Shore A hardness value of the soft member 3 satisfies the above conditions i) and ii), the rigidity of the large diameter portion 4 can be increased by increasing the thickness of the top, the vicinity of the top, and the sides of the large diameter portion 4. If the large diameter portion 4 has a rigidity that is not deformed by frictional action, the overall length of the core 7 can be shortened.

The core 7 of the second embodiment can firmly fix the mounting portion 5 to the mounting hole 2, and furthermore, even if the soft member 3 wears, it does not damage the paper surface. That is, the soft member 3 of this embodiment satisfies the wear amount condition iii) above, and the large diameter portion 4 wears with use. Even if the large diameter portion 4 wears, the upper end of the core 7 does not protrude above the opening at the upper end of the mounting hole 2. As a result, even if the large diameter portion 4 wears, the upper end of the core 7 does not damage the paper surface.

6 and 7, a lubricant may be interposed between the outer circumferential surface of the core 7 and the inner circumferential surface of the inner hole 31. In Fig. 6 and 7, the thick line between the core 7 and the inner hole 31 indicates a lubricant-adhering portion 74. The lubricant reduces the pressing force required to insert the core 7 into the inner hole 31 of the soft member 3, making it easier to insert the core 7 into the inner hole 31.

For example, as shown in FIG. 6, the lubricant is applied to the outer circumferential surface of the core 7 before inserting the core 7 into the inner hole 31. By simply applying the lubricant only to the core 7, the lubricant can also be applied to the inner hole 31, eliminating the need for a process for attaching the soft member 3. In addition, the lubricant does not adhere to the large diameter portion 4, which is the friction portion 32, so the lubricant does not adhere to the paper surface due to frictional action.

Also, for example, as shown in FIG. 7, the lubricant is applied to the inner surface of the inner hole 31 before inserting the core 7 into the inner hole 31. Since the lubricant does not adhere to either the outer surface of the soft member 3 or the outer surface of the core 7, these parts are easy to handle and the soft member 3 can be attached smoothly.

As the lubricant, for example, liquid lubricants such as silicone-based compounds, fluorine-based compounds, and surfactants, or other powder lubricants can be used.

As the silicone-based compound, for example, silicone oil, silicone gum, etc. can be used. As the fluorine-based compound, for example, polyvinylidene fluoride, polyvinyl fluoride, etc. can be used. As the surfactant, for example, anionic, cationic, nonionic, or amphoteric surfactants can be used. Antistatic agents containing these as the main components may also be used.

Examples of powder lubricants that can be used include molybdenum disulfide, polytetrafluoroethylene (PTFE), tetrafluoroethylene (TFE), stearyl erucamide, stearic acid amide, erucic acid amide, behenic acid amide, ethylene bisstearic acid amide, n-oleyl behenic acid amide, magnesium stearate, calcium stearate, boron nitride, melamine cyanurate, and methyl silicone. These powder lubricants have the advantage that they are inactive against thermochromic inks or inks used in other writing instruments.

8. Position of the core in the inner hole Figure 8 shows a state where the upper end of the core 7 in Figure 5 described above is inserted into the inner hole 31 to a position that exceeds the opening at the upper end of the mounting hole 2. From the viewpoint of firmly fixing the mounting portion 5 of the soft member 3 to the mounting hole 2, the core 7 only needs to be in a position that corresponds to at least the entire mounting hole 2 and the outward protrusion 51 of the mounting portion 5. Therefore, even if the short core 7 shown in Figure 5 is inserted into the inner hole 31 to the position shown in Figure 8, there is no disadvantage in that the fixing of the mounting portion 5 becomes weak or the tip of the core 7 scratches the paper surface. Rather, there is an advantage in that the upper end of the core 7 comes into contact or is pressed against the inside of the base of the large diameter portion 4, thereby suppressing deformation of the large diameter portion 4 with the base as a fulcrum.

9. Positioning of the core In order to keep the position of the core 7 inserted into the inner hole 31 constant, a flange 74 shown in Fig. 9 may be provided at the rear end of the core 7. The flange 74 comes into contact with the lower end of the attachment part 5 when the core 7 is inserted into the inner hole 31. This causes the position of the lower end of the core 7 to coincide with the opening at the lower end of the inner hole 31, and the position of the core 7 inserted into the inner hole 31 is always constant. Such a flange 74 allows the core 7 to correspond to the entire attachment hole 2 and the outward protrusion 51 of the attachment part 5, and also makes it possible to keep the position of the tip of the core 7 constant.

10. Thermochromic Writing Instruments Thermochromic writing instruments include a wide range of writing instruments to which thermochromic ink can be applied, such as fountain pens, marking pens, ballpoint pens, mechanical pencils, and pencils.

10.1 Thermochromic ink Thermochromic ink is applied to a thermochromic writing instrument in either liquid or solid form. For example, when the thermochromic writing instrument is a fountain pen, a marking pen, or a ballpoint pen, a liquid thermochromic ink is used. On the other hand, when the thermochromic writing instrument is a mechanical pencil or a pencil, a solid thermochromic ink processed into a lead core is used.

Thermochromic ink has the ability to fade or change color when heated. As a colorant to be blended in the thermochromic ink, it is preferable to use a reversible thermochromic composition that contains at least three components: an electron-donating color-forming organic compound, an electron-accepting compound, and a reaction medium for determining the temperature at which the coloring reaction of these compounds occurs. In particular, a microencapsulated pigment in which the reversible thermochromic composition is encapsulated in a microcapsule is effective as a colorant.

The average particle size of the microencapsulated pigment is, for example, in the range of 0.05 μm to 5.0 μm, preferably 0.1 μm to 4.0 μm, and more preferably 0.5 μm to 3.0 μm. By setting the average particle size of the microencapsulated pigment to be in the range of 0.05 μm to 5.0 μm, good writing performance and writing density can be obtained. Furthermore, when the average particle size of the microencapsulated pigment is set to 2.0 μm or more, the soft member 3 of this embodiment can chemically erase thermochromic ink and physically erase metallic luster pigment.

The average particle size of the microcapsule pigment is the average particle size of particles equivalent to an equal volume sphere measured using Mountec's image analysis particle size distribution measurement software "MacView". If the particle size of most of the particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to an equal volume sphere using Beckman Coulter's product name "Multisizer 4e".

10.2 Metallic Luster Pigment In addition to the above-mentioned microcapsule pigment, the thermochromic ink of this embodiment contains a metallic luster pigment. The metallic luster pigment imparts a metallic luster to the color of the ink. The average particle diameter of the metallic luster pigment is preferably 10 μm or more. By making the average particle diameter of the metallic luster pigment 10 μm or more, a highly lustrous handwriting can be obtained, and physical erasure by the soft member 3 can be improved.

Preferred examples of the metallic luster pigment include transparent metallic luster pigments. Transparent metallic luster pigments appear as if they have been completely erased when the microencapsulated pigment is thermally discolored to colorless. Examples of transparent metallic luster pigments include glittering pigments in which a core material selected from natural mica, synthetic mica, flat glass pieces, flaky aluminum oxide, etc. is coated with a metal oxide, and cholesteric liquid crystal glittering pigments.

The luster pigments that have natural mica as a core material are preferably those that have a titanium oxide coating on the surface, or those that have a layer of iron oxide or a non-thermochromic dye pigment coated on top of the titanium oxide. For example, products such as "Iriodin" manufactured by Merck and "Lumina Colors" manufactured by Engelhard can be used.

The luster pigment with synthetic mica as the core material is preferably one whose surface is coated with a metal oxide such as titanium oxide. For example, metal oxides such as titanium, zirconium, chromium, vanadium, and iron can be used, and metal oxides mainly composed of titanium oxide are particularly preferred. For example, the product name "Altimica" manufactured by Nihon Kohken Kogyo Co., Ltd. can be used.

The luster pigment, which has a flat glass piece as the core material, is preferably one whose surface is coated with a metal oxide such as titanium oxide. For example, the product name "Metashine" manufactured by Nippon Sheet Glass Co., Ltd. can be used.

Luster pigments with flaky aluminum oxide as the core material can be used that have their surface coated with a metal oxide such as titanium oxide. Examples of metal oxides that can be used include titanium, zirconium, chromium, vanadium, and iron, and metal oxides that are primarily composed of titanium oxide are particularly preferred. For example, a product called "Xiralic" manufactured by Merck can be used.

The liquid crystal polymers used as cholesteric liquid crystal type luster pigments have the property of reflecting light in certain spectral regions and transmitting all light in other spectral regions due to the optical interference effect. Cholesteric liquid crystal type luster pigments have excellent metallic luster, color flop properties in which the hue changes depending on the viewpoint, and transparency. For example, the product name "Helicone HC" manufactured by Wacker Chemie can be used as a cholesteric liquid crystal type luster pigment.

After gold, silver, or other metals are vacuum-deposited onto the film, the foil is peeled off and finely pulverized to produce a lustrous material, such as "LG neo" made by Oike Kogyo Co., Ltd.

The average particle size of the metallic luster pigment is in the range of 0.1 μm to 50 μm, preferably 2 μm to 40 μm, and more preferably 10 μm to 40 μm. By setting the average particle size of the metallic luster pigment in the range of 0.1 μm to 50 μm, good writing performance and lustrous handwriting can be obtained. The average particle size of the metallic luster pigment is determined by measuring the particle size distribution using, for example, a laser diffraction/scattering particle size distribution measuring device "LA-300" manufactured by Horiba, Ltd., and calculating the average particle size (median size) on a volume basis based on the numerical value.

11. Effects The above-mentioned mounting structure of the soft member 3 improves the rigidity of the softened friction part 32 (large diameter part 4) by inserting the core 7 into the inner hole 31, and suppresses the deformation of the friction part 32, thereby allowing the friction part 32 to exhibit good friction performance. In addition, the mounting part 5 of the soft member 3 can be firmly fixed by a force in the inward and outward directions, and the mounting work of the soft member 3 does not require a large force. Furthermore, even if the softened friction part 32 wears, it does not damage the paper surface. In addition, the softened friction part 32 makes it possible to chemically and physically erase handwriting of thermochromic ink containing a metallic luster pigment.

12. Others The attachment structure of the soft member of the present invention is not limited to the above-mentioned embodiment. For example, the location where the soft member 3 is attached is not limited to the rear end of the barrel 1 constituting the thermochromic writing instrument. For example, the attachment structure of the soft member of the present invention allows the soft member 3 to be attached to the top of the cap constituting the thermochromic writing instrument.

The core 7 in this embodiment has a length that reaches from the lower opening of the inner hole 31 to the upper opening of the mounting hole. The length of the core 7 is not limited to the above-mentioned embodiment. The core 7 may have a length that does not reach from the lower opening of the inner hole 31 to the upper opening of the mounting hole. The core 7 only needs to have a length that corresponds to at least the inner circumferential surface of the mounting hole 2.

The outward projection 51 of the mounting portion 5 and the inward projection 21 of the mounting hole 2 are not essential components of the soft member mounting structure of the present invention. For example, the outer peripheral surface of the mounting portion 5 and the inner peripheral surface of the mounting hole 2 may both be circumferential surfaces having a single diameter.

The "soft member" in this invention is not limited to the friction part of a thermochromic writing implement. The "soft member" includes, for example, an eraser attached to a mechanical pencil, or an input part attached to a touch pen used for inputting data on a touch panel. In other words, the attachment structure of the soft member of this invention can firmly fix a flexible eraser and input part, and does not require a large force for the attachment work.

REFERENCE SIGNS LIST 1 barrel 2 mounting hole 21 inward projection 21a guide surface 21b minimum inner diameter portion 3 soft member 31 inner hole 32 friction portion 4 large diameter portion 41 annular surface 5 mounting portion (small diameter portion)
51 Outward projection 51a Guide surface 51b Maximum outer diameter portion 52 Bulging portion 53 Cylindrical portion 6 Annular space 7 Center core 71 Ventilation portion 72 Upper core portion 73 Lower core portion 74 Lubricant attachment portion A Length from the upper end of the mounting portion to the upper end of the outward projection B Length from the upper end of the mounting hole to the lower end of the inward projection C Clearance between the inward projection and the outward projection

Claims (14)

A structure for attaching a soft member to a thermochromic writing instrument, the soft member being used to cause thermochromic ink adhering to a paper surface to change color by frictional heat, comprising:
a mounting hole that is provided so as to penetrate the rear end of a barrel or the top of a cap constituting the thermochromic writing instrument along a central axis in a vertical direction, the mounting hole having an inner peripheral surface between two openings located at the upper and lower ends;
a mounting portion located below a large diameter portion of the soft member used for thermal color change, the mounting portion having a diameter smaller than that of the large diameter portion and capable of being inserted into the mounting hole;
a straight bore extending along a longitudinal central axis of the flexible member and opening at least at a lower end of the flexible member;
a rod-shaped core having an outer diameter that allows the core to be inserted into the inner hole, a length that allows the core to fit into the inner hole, and an outer circumferential surface that contacts the inner circumferential surface of the inner hole;
A mounting structure for a soft member configured so that the soft member is mounted to the mounting hole by inserting the mounting portion into the mounting hole and the core into the inner hole. the attachment portion is integrally formed below the large diameter portion and made of the same material as the soft member,
the inner hole is provided in the soft member from the attachment portion to a position reaching the large diameter portion,
2. The mounting structure for a soft member as described in claim 1, wherein when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core is held in a position corresponding to the inner peripheral surface of the mounting hole, so that the mounting portion is sandwiched between the outer peripheral surface of the core and the inner peripheral surface of the mounting hole. The mounting structure for a soft member according to claim 2, wherein when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length that extends from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole. The mounting structure for a soft member according to claim 2, wherein when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole. The mounting structure for a soft member according to claim 2, wherein when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core has a length that does not extend from the opening at the lower end of the inner hole to the opening at the upper end of the mounting hole. The mounting structure for a soft member according to claim 4 or 5, wherein, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the upper end of the core is inserted into the inner hole to a position that exceeds the opening at the upper end of the mounting hole. 7. A mounting structure for a soft member according to any one of claims 2 to 6, wherein a maximum outer diameter of the core is approximately the same as or larger than an inner diameter of the inner hole, and when the core is inserted into the inner hole, an outer peripheral surface of the core and an inner peripheral surface of the inner hole are pressed against each other. The soft member mounting structure according to claim 7, in which a lubricant is interposed between the outer peripheral surface of the core and the inner peripheral surface of the inner hole. A mounting structure for a soft member as described in any one of claims 1 to 8, wherein the inner hole is a hole that opens at the lower end of the soft member and is blocked on one side not opening at the upper end of the soft member, and a ventilation portion is provided in the core to exhaust air from within the inner hole during the process of inserting the core into the inner hole. The soft member mounting structure according to claim 9, wherein the ventilation portion is a through hole that penetrates the core from one end to the other end along the longitudinal central axis of the core. The mounting structure for a soft member according to claim 9, wherein the ventilation portion is at least one groove or protrusion that continues from one end of the core to the other end along the outer circumferential surface of the core. The mounting structure for a soft member according to any one of claims 2 to 11, in which a flange having a diameter larger than the inner diameter of the inner hole is provided at the lower end of the core, and when the core is inserted into the inner hole, the flange abuts against the lower end of the mounting part. An inward protrusion is formed on an inner circumferential surface of the mounting hole so as to protrude toward the inside of the mounting hole,
An outward protrusion is formed on an outer circumferential surface of the mounting portion so as to protrude outward from the mounting portion,
When the mounting portion is inserted into the mounting hole, the outward protrusion overcomes the inward protrusion, whereby the outward protrusion and the inward protrusion are engaged with each other,
A mounting structure for a soft member described in any one of claims 2 to 12, wherein the core is held at a position corresponding to the inner circumferential surface of the mounting hole, and the mounting portion is sandwiched between the outer circumferential surface of the core and the inward protrusion of the mounting hole. A thermochromic writing implement in which the soft member is attached to the rear end of the barrel or the top of the cap by the attachment structure for the soft member described in any one of claims 1 to 13.

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