JP2020179630A - Ball point pen refill - Google Patents

Abstract

To provide a ball point pen refill which does not change the color of a thermochromic ink inside a ballpoint pen tip, can reliably remove a pen tip protection member, and suppress manufacturing cost.SOLUTION: A ballpoint pen refill 1 includes a ballpoint pen tip 2, an ink storage tube 5 of which the ballpoint pen tip 2 is provided at front end part and thermochromic ink is housed inside, and a pen tip protection member 6. The pen tip protection member 6 is made of a synthetic resin pipe which has the same cross-sectional shape in the longitudinal direction and an inner hole 61 penetrating in the longitudinal direction. An inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to a straight-cylindrical outer surface 44 of the ballpoint pen tip 2, and a ball 3 of the ballpoint pen tip 2 is exposed inside the inner hole 61 of the pen tip protection member 6.SELECTED DRAWING: Figure 1

Description

The present invention relates to a ballpoint pen refill in which a thermochromic ink is contained.

Conventionally, for example, Patent Document 1 relates to a method for producing a ballpoint pen refill in which a heat-discolorable ink that changes color by heating is contained and a resin film is provided at the tip of the ballpoint pen tip. Described is a manufacturing method in which a resin film is fixed and then cooled in order to eliminate discoloration of the ink in the pen tip.

Japanese Unexamined Patent Publication No. 2011-25655

The ballpoint pen refill of Patent Document 1 increases the manufacturing process and the manufacturing cost. Further, in the ballpoint pen refill of Patent Document 1, the resin film cannot be reliably removed, and a part of the resin film may be left on the ballpoint pen tip.

The present invention solves the above-mentioned conventional problems, does not discolor the heat-discoloring ink in the ballpoint pen tip, can reliably remove the pen tip protection member, and has a manufacturing cost. It is intended to provide a ballpoint pen refill that can suppress.

In the present invention, "front" refers to the ballpoint pen tip side, and "rear" refers to the opposite side.

The first invention of the present application is a ballpoint pen tip 2 in which a ball 3 is rotatably held at the front end, and an ink storage tube 5 in which the ballpoint pen tip 2 is provided at the front end and contains heat-discoloring ink inside. A ballpoint pen refill comprising the above, comprising a pen tip protection member 6 made of a synthetic resin pipe having the same cross-sectional shape in the longitudinal direction and having an inner hole 61 penetrated in the longitudinal direction. The ballpoint pen tip 2 includes a straight-cylindrical outer surface 44, and the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the straight-cylindrical outer surface 44 of the ballpoint pen tip 2, so that the ball 3 of the ballpoint pen tip 2 is formed. It is a requirement that the pen tip protection member 6 is exposed inside the inner hole 61.

The ballpoint pen refill 1 of the first invention includes a pen tip protection member 6 made of a synthetic resin pipe having the same cross-sectional shape in the longitudinal direction and having an inner hole 61 penetrated in the longitudinal direction. The ballpoint pen tip 2 includes a straight-cylindrical outer surface 44, and the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the straight-cylindrical outer surface 44 of the ballpoint pen tip 2, so that the ball 3 of the ballpoint pen tip 2 is formed. By being exposed inside the inner hole 61 of the pen tip protection member 6 (that is, a straight pipe made of the synthetic resin was used without using a coating resin for covering the ball for pen tip protection. Therefore, the heat-discoloring ink in the ballpoint pen tip 2 is not discolored, the pen tip protection member 6 can be reliably removed, and the manufacturing cost can be suppressed. The configuration in which the ballpoint pen tip 2 is provided at the front end of the ink storage tube 5 is, for example, a configuration in which the ballpoint pen tip 2 is directly fixed to the ink storage tube 5, or the ballpoint pen tip 2 is provided via a connecting member or the like. Examples thereof include a configuration in which the ink is fixed to the ink storage tube 5.

A second invention of the present application is the straight line of the ballpoint pen tip 2 in the ballpoint pen refill of the first invention in a state where the pen tip protection member 6 is fitted to the rectangular outer surface 44 of the ballpoint pen tip 2. It is a requirement that the length A of the pen tip protection member 6 located in front of the cylindrical outer surface 44 in the longitudinal direction is 10 mm or more.

The ballpoint pen refill 1 of the second invention is in front of the straight-cylindrical outer surface 44 of the ballpoint pen tip 2 in a state where the pen tip protection member 6 is fitted to the right-cylindrical outer surface 44 of the ballpoint pen tip 2. Since the length A in the longitudinal direction of the pen tip protection member 6 located at is 10 mm or more (preferably 12 mm or more), the pen in front of the ballpoint pen tip 2 when the pen tip protection member 6 is removed from the ballpoint pen refill body. Only the tip protection member 6 can be securely pinched by fingers, and there is no risk of accidentally removing the ballpoint pen tip 2 together with the pen tip protection member 6 from the ballpoint pen refill body.

If the length of the pen tip protection member 6 located in front of the linear cylindrical outer surface 44 of the ballpoint pen tip 2 in the longitudinal direction is smaller than 10 mm, the pen tip is removed when the pen tip protection member 6 is removed from the ballpoint pen refill body. The ballpoint pen tip 2 may be pinched by a finger via the protective member 6, and the ballpoint pen tip 2 may be accidentally removed from the ballpoint pen refill body together with the pen tip protection member 6.

According to the third invention of the present application, in the ballpoint pen refill of the first or second invention, the pull-out load when the pen tip protection member 6 is pulled out from the outer surface of the ballpoint pen tip 2 is less than 0.3 kgf. Make it a requirement.

The ballpoint pen refill 1 of the third invention has a pen tip because the pull-out load when the pen tip protection member 6 is pulled out from the outer surface of the ballpoint pen tip 2 is less than 0.3 kgf (preferably less than 0.2 kgf). When removing the protective member 6 from the ballpoint pen refill main body, there is no risk of accidentally removing the ballpoint pen tip 2 together with the pen tip protective member 6 from the ballpoint pen refill main body.

A fourth invention of the present application is in the ballpoint pen refill according to any one of the first to third inventions, in the longitudinal direction of the linear cylindrical outer surface 44 of the ballpoint pen tip 2 into which the pen tip protection member 6 is fitted. The requirement is that the length be less than 7 mm.

In the ballpoint pen refill 1 of the fourth invention, the length of the rectangular outer surface 44 of the ballpoint pen tip 2 into which the pen tip protection member 6 is fitted in the longitudinal direction is smaller than 7 mm (preferably more than 6 mm). (Because it is small), when the pen tip protection member 6 is removed from the ballpoint pen refill main body, there is no possibility that the ballpoint pen tip 2 is sandwiched between the pen tip protection member 6 and the ballpoint pen tip 2 is accidentally removed from the ballpoint pen refill main body.

In the fifth aspect of the present application, in the first to fourth inventions, the ballpoint pen tip 2 is attached to the ink storage tube 5 via a connecting member 7, and the connecting member 7 is made of an opaque synthetic resin. It is a requirement that the pen tip protection member 6 is made of a transparent or translucent synthetic resin.

In the ballpoint pen refill 1 of the fifth invention, the ballpoint pen tip 2 is attached to the ink storage tube 5 via a connecting member 7, the connecting member 7 is made of an opaque synthetic resin, and the pen tip protecting member 6 Is made of a transparent or translucent synthetic resin, so that the connecting member 7 and the pen tip protecting member 6 can be easily distinguished from each other. Therefore, when the pen tip protecting member 6 is removed from the ballpoint pen refill body, it is mistakenly made. There is no possibility that the connecting member 7 is pinched by fingers and the connecting member 7 is pulled out from the ink storage tube 5.

A sixth aspect of the present application is the ballpoint pen in the first to fifth aspects, in which the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the rectangular outer surface 44 of the ballpoint pen tip 2. The refill 1 is housed in a package 9 made of a synthetic resin film, and the length C of the ballpoint pen refill 1 in the longitudinal direction is set to 80% to 95% of the length D in the longitudinal direction inside the package 9. Is a requirement.

The ballpoint pen refill 1 of the sixth invention is the length in the longitudinal direction of the ballpoint pen refill 1 in a state where the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the rectangular outer surface 44 of the ballpoint pen tip 2. By setting C to 80% to 95% of the length D in the longitudinal direction inside the package 9, it is possible to prevent the pen tip protection member 6 from coming off from the ballpoint pen tip 2 inside the package 9. ..

In the seventh invention of the present application, in the first to sixth inventions, the pen tip protection member 6 can rub the handwriting of the heat-discoloring ink, and the handwriting can be thermally discolored by the frictional heat generated at that time. It is required to be a friction member.

In the ballpoint pen refill 1 of the seventh invention, the pen tip protection member 6 rubs the handwriting of the heat-discoloring ink and becomes a friction member capable of thermally discoloring the handwriting by the frictional heat generated at that time. After the start of use, the user is prevented from discarding the pen tip protection member 6, which contributes to the reduction of waste.

The ballpoint pen refill of the present invention does not discolor the heat-discoloring ink in the ballpoint pen tip, the pen tip protection member can be reliably removed, and the manufacturing cost can be suppressed.

It is a front view of the whole of the Embodiment of this invention. It is an enlarged vertical sectional view of the main part of FIG. It is an enlarged vertical sectional view of the main part of FIG. It is an enlarged vertical sectional view of a main part in a state where the pen tip protection member of FIG. 2 is removed from a ballpoint pen refill main body. It is a front view which shows the state which the ballpoint pen refill of FIG. 1 is housed in a package. It is explanatory drawing which shows the discoloration behavior of a thermochromic ink.

The ballpoint pen refill 1 of the embodiment of the present invention is shown in FIGS. 1 to 5. The ballpoint pen refill 1 of the present embodiment includes a ballpoint pen tip 2, a connecting member 7 to which the rear portion 42 of the ballpoint pen tip 2 is fixed, an ink storage tube 5 to which the rear portion of the connecting member 7 is fixed, and the ballpoint pen tip. A pen tip protection member 6 fitted to the outer surface of 2 is provided.

-Ballpoint pen tip The ballpoint pen tip 2 includes a tip body 4 and a ball 3 rotatably held by a front end portion of the tip body 4. The ball 3 is rotatably held between the inwardly facing front end edge 45 and the ball receiving seat 46 formed behind the ball 3. Inside the chip body 4, an ink flow hole 47 for supplying heat-discoloring ink from the rear to the ball 3 at the front end is formed.

The chip body 4 includes a front portion 41, a rear portion 42, and a step portion 43 formed between the front portion 41 and the rear portion 42. The front portion 41 of the chip body 4 is integrally connected to the front detail having an outer surface in which the ball 3 is held at the front end and the diameter is reduced toward the front, and is integrally connected to the rear of the tip detail in the front-rear direction. A straight-cylindrical outer surface 44 having a constant outer diameter is provided.

The rear portion 42 of the chip body 4 has a straight cylindrical outer surface 44 having an outer diameter smaller than that of the front portion 41. The rear portion 42 of the chip body 4 is press-fitted and fixed to the mounting hole 74 of the connecting member 7, which will be described later. When the chip body 4 is fixed to the connecting member 7, the step portion 43 of the chip body 4 comes into contact with the front end surface of the connecting member 7.

The chip body 4 is formed of a metal material (eg, stainless steel). The balls 3 are obtained from a cemented carbide (for example, a sintered body of tungsten carbide).

A spring 8 that constantly urges the ball 3 forward is housed inside the spring tip body 4. The spring 8 includes a rod portion 81 whose front end abuts on the rear surface of the ball 3 and a coil portion 82 integrally connected to the rear of the rear end of the rod portion 81, and is formed of a metal wire rod. The rear end of the spring 8 is locked to the locking wall portion behind the mounting hole 74. The spring 8 presses the ball 3 against the inner surface of the front end edge 45 when not in use, suppressing evaporation of the heat-discoloring ink and intrusion of air from the outside.

-Connecting member The connecting member 7 is made of a molded body of synthetic resin (for example, polypropylene). The connecting member 7 includes a cylindrical front cylinder portion 71, a cylindrical rear cylinder portion 72, and a collar portion 73 formed between the front cylinder portion 71 and the rear cylinder portion 72. The front tubular portion 71 of the connecting member 7 includes a cylindrical outer surface. The rear cylinder portion 72 of the connecting member 7 is press-fitted and fixed to the front end opening of the ink storage tube 5. The flange portion 73 of the connecting member 7 comes into contact with the front end of the ink storage tube 5.

Inside the connecting member 7, an mounting hole 74 that opens from the front end and an ink supply hole 75 that is connected to the rear of the mounting hole 74 and opens from the rear end are formed. The rear portion 42 of the chip body 4 is press-fitted and fixed to the mounting hole 74.

The connecting member 7 is colored opaque (for example, black, blue, red, white, etc.).

-Ink storage tube The ink storage tube 5 is a cylindrical body of synthetic resin (for example, polypropylene) and is obtained by extrusion molding. The inside of the ink storage tube 5 is filled with a heat-discoloring ink and a follower (for example, a high-viscosity fluid) that is arranged at the rear end of the heat-discoloring ink and advances with the consumption of the heat-discoloring ink. Ink.

-Heat-changing ink As the heat-changing ink, a reversible heat-changing ink is preferable. The reversible thermochromic ink adopts a structure in which color memory retention is adopted, in which the color is decolorized by heating from the color development state, and the color development state or the decolorization state is alternately stored in a specific temperature range.

Further, the coloring material contained in the reversible thermochromic ink is a conventionally known (a) electron-donating color-developing organic compound, (b) electron-accepting compound, and (c) the color reaction of both. A reversible thermochromic pigment in which a reversible thermochromic composition containing at least three essential components of a reaction medium for determining the occurrence temperature of the above is encapsulated in a microcapsule is preferably used.

In the present embodiment, as shown in FIG. 6, the shape of the curve plotting the change in coloring density due to the temperature change is higher than the discoloration temperature range, contrary to the case where the temperature is raised from the lower temperature side than the discoloration temperature range. The color changes by following a different path from the case of descending from the side, and the color development state in the low temperature range below the complete color development temperature (t1) or the decolorization state in the high temperature range above the complete decolorization temperature (t4) , It is preferable to apply a color memory retention type thermochromic ink capable of memory retention in a specific temperature range [temperature range between t2 to t3 (substantial two-phase retention temperature range)]. In FIG. 6, ΔH indicates a temperature width (that is, a hysteresis width) indicating the degree of hysteresis. If the value of ΔH is small, only one of the two states before and after discoloration can exist. When the value of ΔH is large, it becomes easy to maintain each state before and after discoloration.

In the present embodiment, the discoloration temperature of the heat-discolorable ink is set to 25 ° C. to 95 ° C. (preferably 36 ° C. to 95 ° C.). That is, in the present embodiment, the high temperature side discoloration point [complete decolorization temperature (t4)] is set in the range of 25 ° C. to 95 ° C. (preferably 36 ° C. to 90 ° C.), and the low temperature side discoloration point. It is effective to set the [complete color development temperature (t1)] in the range of −30 ° C. to + 20 ° C. (preferably −30 ° C. to + 10 ° C.). As a result, it is possible to effectively maintain the color exhibited in the normal state (daily life temperature range).

-Pen tip protection member The pen tip protection member 6 has an inner hole 61 having the same cross-sectional shape in the longitudinal direction and penetrating in the longitudinal direction, and is obtained by extrusion molding of a synthetic resin (for example, polypropylene). A ridge or a groove extending in the longitudinal direction can be provided on the inner surface of the inner hole 61 of the pen tip protection member 6. A ridge or a groove extending in the longitudinal direction can be provided on the outer surface of the pen tip protection member 6. Slits that penetrate in the longitudinal direction and the radial direction can be provided on the side wall of the pen tip protection member 6. The pen tip protection member 6 is formed of a transparent or translucent synthetic resin.

In the present embodiment, the length (overall length) of the pen tip protection member 6 in the longitudinal direction is set to 14 mm or more, specifically 20 mm. The length of the pen tip protection member 6 located in front of the straight-cylindrical outer surface 44 of the ballpoint pen tip 2 in the longitudinal direction when the pen tip protection member 6 is fitted to the straight-cylindrical outer surface 44 of the ballpoint pen tip 2. A is set to 10 mm or more, specifically 14.6 mm. The length of the rectangular outer surface 44 of the ballpoint pen tip 2 into which the pen tip protection member 6 is fitted in the longitudinal direction is set to be smaller than 7 mm, specifically to 5.4 mm.

In the present embodiment, the pull-out load when the pen tip protection member 6 is pulled out from the outer surface of the ballpoint pen tip 2 is the load required to pull out the pen tip protection member 6 from the outer surface of the ballpoint pen tip 2 when the user starts using the pen tip 2. It is set to less than 0.3 kgf.

Further, the pen tip protection member 6 can be made into a friction member capable of heat-discoloring by rubbing the handwriting of the heat-discoloring ink contained in the ink storage tube 5 and the frictional heat generated at that time. At that time, the pen tip protection member 6 is preferably formed of an elastic synthetic resin (rubber, elastomer). The elastic synthetic resin is, for example, a silicone resin, an SBS resin (styrene-butadiene-styrene copolymer), a SEBS resin (styrene-ethylene-butadiene-styrene copolymer), a fluororesin, a chloroprene resin, or a nitrile resin. , Polyester resin, olefin resin, ethylene propylene diene rubber (EPDM) and the like. The elastic synthetic resin is not a highly wear-resistant elastic material (for example, an eraser or the like), but a low-wear elastic material that does not generate wear debris during friction.

Further, the length (total length) of the pen tip protection member 6 in the longitudinal direction is preferably 14 mm or more (preferably 18 mm or more). As a result, the pen tip protection member 6 has a sufficient length in the longitudinal direction, and one end of the pen tip protection member 6 removed from the ballpoint pen tip 2 can be securely gripped with a finger, and at the same time, other than the pen tip protection member 6. The end portion can be reliably exposed to form a friction portion, and the pen tip protection member 6 can be sufficiently used as a single friction member.

One or more ballpoint pen refills 1 are housed inside the package 9 and sold.
The package 9 is formed by stacking two synthetic resin films (front film and back film) and sealing the periphery thereof by adhesion or heat fusion to form a bag-shaped storage space inside. Examples of the material of the synthetic resin film include polypropylene, polyethylene, polyester and the like. A hanging hole 91 is formed in the header portion of the package 9.

The longitudinal length C of the ballpoint pen refill 1 with the pen tip protection member 6 attached to the ballpoint pen refill body is 80% to 95% (preferably) of the longitudinal length D of the accommodation space inside the package 9. Is set to 85% to 95%). As a result, it is possible to prevent the pen tip protection member 6 from coming off from the ballpoint pen refill main body inside the package 9, and the smooth storage work of the ballpoint pen refill inside the package 9 is maintained.

The ballpoint pen refill 1 of the present invention is a cap-type ballpoint pen that is housed in the main body and has a ballpoint pen tip 2 protruding from the front end of the main body, and a cap is detachably attached to the ballpoint pen tip side of the main body. It is used for a haunting ballpoint pen that is movable and has a ballpoint pen tip that can be haunted from the front end.

The ballpoint pen refill 1 of the present embodiment includes a pen tip protection member 6 made of a synthetic resin pipe having the same cross-sectional shape in the longitudinal direction and having an inner hole 61 penetrated in the longitudinal direction, and is a ballpoint pen tip. 2 has a straight-cylindrical outer surface 44, the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the straight-cylindrical outer surface 44 of the ballpoint pen tip 2, and the ball 3 of the ballpoint pen tip 2 is the pen tip protection member 6. By being exposed inside the inner hole 61 of the ballpoint pen (that is, by using the straight pipe made of the synthetic resin instead of using the ballpoint pen coating resin for protecting the pen tip), the heat inside the ballpoint pen tip 2 The discolorable ink does not discolor, the pen tip protection member 6 can be reliably removed, and the manufacturing cost can be suppressed.

The ballpoint pen refill 1 of the present embodiment is a pen located in front of the straight-cylindrical outer surface 44 of the ballpoint pen tip 2 in a state where the pen tip protection member 6 is fitted to the straight-cylindrical outer surface 44 of the ballpoint pen tip 2. Since the length A of the tip protection member 6 in the longitudinal direction is 10 mm or more (preferably 12 mm or more), the pen tip protection member 6 in front of the ballpoint pen tip 2 when the pen tip protection member 6 is removed from the ballpoint pen refill body. Only can be securely pinched with fingers, and there is no risk of accidentally removing the ballpoint pen tip 2 together with the pen tip protection member 6 from the ballpoint pen refill body.

In the ballpoint pen refill 1 of the present embodiment, when the pen tip protection member 6 is removed from the ballpoint pen refill main body because the pulling load when the pen tip protection member 6 is pulled out from the outer surface of the ballpoint pen tip 2 is less than 0.3 kgf. In addition, there is no risk of accidentally removing the ballpoint pen tip 2 together with the pen tip protection member 6 from the ballpoint pen refill body.

In the ballpoint pen refill 1 of the present embodiment, the length in the longitudinal direction of the rectangular outer surface 44 of the ballpoint pen tip 2 into which the pen tip protection member 6 is fitted is smaller than 7 mm, so that the pen tip protection member 6 is a ballpoint pen. When removing from the refill main body, there is no possibility that the ballpoint pen tip 2 is sandwiched between the pen tip protection member 6 and the ballpoint pen tip 2 is accidentally removed from the ballpoint pen refill main body.

In the ballpoint pen refill 1 of the present embodiment, the ballpoint pen tip 2 is attached to the ink storage tube 5 via the connecting member 7, the connecting member 7 is made of an opaque synthetic resin, and the pen tip protecting member 6 is transparent or translucent. Since the connecting member 7 and the pen tip protecting member 6 can be easily visually identified by being composed of the synthetic resin of the above, when the pen tip protecting member 6 is removed from the ballpoint pen refill main body, the connecting member 7 is mistakenly pointed to. There is no possibility that the connecting member 7 is pulled out from the ink storage tube 5 by sandwiching the connecting member 7.

The ballpoint pen refill 1 of the present embodiment has a length C in the longitudinal direction of the ballpoint pen refill 1 in a state where the inner surface of the inner hole 61 of the pen tip protection member 6 is fitted to the rectangular outer surface 44 of the ballpoint pen tip 2. By setting the length D in the longitudinal direction inside the package 9 to 80% to 95%, it is possible to prevent the pen tip protection member 6 from coming off from the ballpoint pen tip 2 inside the package 9.

In the ballpoint pen refill 1 of the present embodiment, the pen tip protection member 6 rubs the handwriting of the heat-discoloring ink and becomes a friction member capable of heat-discoloring the handwriting by the frictional heat generated at that time. , It suppresses the user from discarding the pen tip protection member 6, and contributes to the reduction of waste.

1 Ballpoint pen refill 2 Ballpoint pen tip 3 Ball 4 Chip body 41 Front 42 Rear 43 Step 44 Straight cylindrical outer surface 45 Front edge 46 Ball receiving seat 47 Ink flow hole 5 Ink storage tube 6 Pen tip protection member 61 Inner hole 7 Connection member 71 Front cylinder 72 Rear cylinder 73 Flange 74 Mounting hole 75 Ink supply hole 8 Spring 81 Rod 82 Coil 9 Package 91 Hanging hole A Located in front of the linear cylindrical outer surface of the ballpoint pen tip. Longitudinal length of the pen tip protection member B Longitudinal length of the rectangular outer surface of the ballpoint pen tip C Longitudinal length of the ballpoint pen refill D Longitudinal length inside the package

Claims (7)

A ballpoint pen refill comprising a ballpoint pen tip in which a ball is rotatably held at the front end and an ink storage tube in which the ballpoint pen tip is provided at the front end and contains heat-discoloring ink inside. The ballpoint pen tip is provided with a pen tip protection member made of a synthetic resin pipe having the same cross-sectional shape in the direction and having an inner hole penetrated in the longitudinal direction, and the ballpoint pen tip has a straight cylindrical outer surface. The ballpoint pen refill is characterized in that the inner surface of the inner hole of the pen tip protection member is fitted to the straight cylindrical outer surface of the ballpoint pen, and the ball of the ballpoint pen tip is exposed inside the inner hole of the pen tip protection member. .. In a state where the pen tip protection member is fitted to the straight-cylindrical outer surface of the ballpoint pen tip, the length of the pen tip protection member located in front of the straight-cylindrical outer surface of the ballpoint pen tip in the longitudinal direction is 10 mm or more. The ballpoint pen refill according to claim 1. The ballpoint pen refill according to claim 1 or 2, wherein the pull-out load when the pen tip protection member is pulled out from the outer surface of the ballpoint pen tip is less than 0.3 kgf. The ballpoint pen refill according to any one of claims 1 to 3, wherein the length in the longitudinal direction of the rectangular outer surface of the ballpoint pen tip into which the pen tip protection member is fitted is smaller than 7 mm. The ballpoint pen tip is attached to the ink storage tube via a connecting member, the connecting member is made of an opaque synthetic resin, and the pen tip protection member is made of a transparent or translucent synthetic resin. The ballpoint pen refill according to any one of 4. A ballpoint pen refill in which the inner surface of the inner hole of the pen tip protection member is fitted to the rectangular outer surface of the ballpoint pen tip is housed in a package made of a synthetic resin film, and the length of the ballpoint pen refill in the longitudinal direction. The ballpoint pen refill according to any one of claims 1 to 5, wherein the length is set to 80% to 95% of the length in the longitudinal direction inside the package. The ballpoint pen refill according to any one of claims 1 to 6, wherein the pen tip protecting member is a friction member capable of thermally discoloring the handwriting by rubbing the handwriting of the heat-discoloring ink and the frictional heat generated at that time.

Images