Thermochromic writing implements

Abstract

The present invention is a thermochromic writing implement comprising thermochromic ink and a frictional element for thermally altering, via frictional heat, the color of writing made using the thermochromic ink, wherein: a metallic glossy pigment is added to the thermochromic ink; an attachment hole 2 for attaching a frictional element 3 is provided in the thermochromic writing implement; the frictional element 3 comprises an attaching part 5 that is inserted into the attachment hole 2, and a frictional part 32 that projects from the attachment hole 2 and has an convex surface shape; the volume Ve of the frictional part 32 and the volume Vp of the metallic glossy pigment satisfy 5 ≤ Ve / Vp ≤ 35; the maximum outer diameter D of the frictional part 32 and the projecting length L thereof satisfy 0.1 ≤ L / D ≤ 1.5; the value of the Shore A hardness of the material of the frictional element 3 immediately after initiating indenter contact is in a range of 60 to 85, inclusive, as measured according to JIS K 7215 of the Japanese Industrial Standards; and the value (ΔHS) of Shore A hardness, as defined according to the following formula, is at least 0 and less than 5. ΔHS = (Shore A hardness value immediately after initiating indenter contact) – (Shore A hardness value 15 seconds after initiating indenter contact)

Description

[Technical field]

[0001] The present invention relates to a writing instrument, and more particularly to a writing instrument equipped with a friction body for thermally discoloring handwriting made of thermochromic ink. [Background technology]

[0002] In recent years, thermochromic writing instruments have become widespread. Thermochromic writing instruments contain thermochromic ink. Handwriting of thermochromic ink can be discolored or erased by heating. Thermochromic writing instruments are equipped with a friction body that generates frictional heat to erase or discolor handwriting of thermochromic ink. Note that "discoloration" of thermochromic ink means changing from one color to another color. "Erasing" is one form of discoloration, and means changing from one color to colorless.

[0003] For example, WO 2018 / 116767 discloses a writing instrument with a thermochromic ink containing a metallic luster pigment added to the thermochromic ink. This thermochromic writing instrument includes a friction body containing a viscoelastic body. This friction body is capable of chemically and physically erasing the thermochromic ink containing the metallic luster pigment. That is, the friction body containing a viscoelastic body erases the thermochromic ink by frictional heat, and adsorbs the metallic luster pigment by viscoelasticity and peels it off from the paper surface. In this way, the friction body containing a viscoelastic body disclosed in WO 2018 / 116767 has both chemical erasability that erases the thermochromic ink by frictional heat and physical erasability that peels off the metallic luster pigment by viscoelasticity. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 116767 Summary of the Invention [Problem to be solved by the invention]

[0005] However, a friction body containing a viscoelastic body has a problem in that the amount of deformation of the friction body gradually increases due to the reciprocating motion (hereinafter referred to as "frictional action") when rubbing the handwriting of thermochromic ink. That is, a viscoelastic body has a property that the amount of deformation increases over time when a certain external force is applied. For this reason, a friction body containing a viscoelastic body gradually becomes more deformed by repeated frictional action. When the amount of deformation of the friction body becomes large, it may not be possible to generate the frictional heat required to discolor or erase the handwriting of thermochromic ink.

[0006] On the other hand, if the force for frictionally moving the friction body is gradually reduced, the deformation amount of the friction body can be kept constant. However, there are cases where the force for frictionally moving the friction body is too small to generate the frictional heat required to discolor or erase the handwriting of the thermochromic ink. In particular, the elastic modulus of a friction body made of synthetic resin depends on temperature. For this reason, when the temperature of the friction body itself is increased by frictional heat, or when the friction body is used in a high-temperature environment, the friction body is more likely to deform significantly.

[0007] The present invention has been made to solve the above-mentioned problems, and has an object to provide a thermochromic writing instrument that makes it possible to chemically and physically erase handwriting of thermochromic ink containing a metallic luster pigment, and that can cause the friction body to exhibit the desired friction performance by suppressing deformation of the friction body. [Means for solving the problem]

[0008] (1) In order to achieve the above object, the thermochromic writing instrument of the present invention is a thermochromic writing instrument comprising a thermochromic ink and a friction body for thermally discoloring a mark written with the thermochromic ink by frictional heat, wherein a metallic luster pigment is added to the thermochromic ink, the thermochromic writing instrument is provided with a mounting hole for mounting the friction body, the friction body includes a mounting portion to be inserted into the mounting hole and a friction portion having a convex curved shape protruding from the mounting hole, a volume Ve of the friction portion and a volume Vp of the metallic luster pigment satisfy 5≦Ve / Vp≦35, a maximum outer diameter D and a protruding length L of the friction portion satisfy 0.1≦L / D≦1.5, and the material of the friction body satisfies JIS K The Shore A hardness measured in accordance with JIS H7215 immediately after the start of contact with the indenter is in the range of 60 to 85, and the Shore A hardness (ΔHS) defined by the following formula is 0 to 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)

[0009] The friction body provided in the thermochromic writing instrument of (1) above can chemically discolor or decolorize the handwriting of the thermochromic ink by frictional heat, and can also physically peel off the metallic luster pigment added to the thermochromic ink. On the other hand, by making the ΔHS of the material of the friction body less than 5, it is possible to give the friction part sufficient rigidity against frictional action. This suppresses deformation of the friction part when it is subjected to frictional action, and allows the friction part to exhibit the desired frictional performance.

[0010] (2) Preferably, in the thermochromic writing instrument of (1) above, the material of the friction body has a product (Tb×Eb) of the tensile strength at break Tb and the elongation at break Eb, measured in accordance with JIS K 6251 of the Japanese Industrial Standards, of 5,000 or more and 18,000 or less.

[0011] By setting the product of the tensile strength at break Tb and the elongation at break Eb (Tb x Eb) of the friction body material to between 5,000 and 18,000, the friction body generates an appropriate amount of wear debris when rubbing handwriting. This makes it possible for the metallic luster pigment added to the thermochromic ink to adhere to and be wrapped up in the wear debris.

[0012] (3) Preferably, in the thermochromic writing instrument of (1) or (2) above, the mounting hole 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 the vertical direction, and has an inner circumferential surface between two openings located at the upper end and the lower end, an inward protrusion protruding toward the inside of the mounting hole is formed on the inner circumferential surface of the mounting part, an outward protrusion protruding toward the outside of the mounting part is formed on the outer circumferential 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 with each other, and the friction body is provided with a straight inner hole along the central axis in the vertical direction, opening at least at the lower end of the mounting part, and the inner hole A rod-shaped core having a length that fits into the inner hole and an outer peripheral surface that contacts the inner peripheral surface of the inner hole is inserted into the mounting 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 inward protrusion of the mounting hole.

[0013] The mounting portion of the friction body is sandwiched between the outer peripheral surface of the core and the inward protrusion of the mounting hole, and is firmly fixed to the mounting hole. This increases the rigidity of the entire friction portion, suppresses deformation of the friction portion when frictionally operated, and enables the friction portion to exhibit the desired friction performance. In particular, even if the friction portion is made of a material with low hardness, the entire friction portion can be given the desired rigidity. This allows the handwriting of the thermochromic ink to be efficiently thermochromic. Furthermore, the core is inserted into the inner hole of the friction body after the inward protrusion of the mounting hole and the outward protrusion of the mounting portion are engaged. This allows the friction body to be easily attached to the thermochromic writing instrument without requiring a large force.

[0014] (4) Preferably, in the thermochromic writing instrument of (3) above, when the attachment portion is inserted into the attachment 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 attachment hole.

[0015] Since the core has a length from the lower opening of the inner hole to the upper opening of the mounting hole, even if the friction portion wears, the core will not be exposed from the friction portion and will not damage the paper surface.

[0016] (5) Preferably, in the thermochromic writing instrument of (3) or (4) above, when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the lower end of the core is located at the same position as the lower end of the mounting portion or higher than the lower end of the mounting portion.

[0017] By positioning the lower end of the core at the same position as the lower end of the mounting portion or higher than the lower end of the mounting portion, it becomes easy to insert the core into the friction body, improving assembly.

[0018] (6) Preferably, in any of the thermochromic writing instruments (3) to (5) above, the inner hole is a hole that opens at the lower end of the attachment portion and is blocked at one end, i.e., does not open at the upper end of the friction portion, 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.

[0019] In the process of inserting the core into the inner hole, the air in the inner hole is not compressed by the core and is discharged to the outside, which makes it easier to insert the core into the friction body and ensures that the core is securely attached to the inner hole.

[0020] (7) In the thermochromic writing instrument of (6) above, preferably, the ventilation portion is a through hole that penetrates from one end of the core to the other along the vertical central axis of the core.

[0021] In the process of inserting the core into the inner hole, the air in the inner hole is not compressed by the core and is reliably discharged to the outside through the through hole, which makes it easy to insert the core into the friction body and ensures that the core is attached to the inner hole reliably.

[0022] (8) Preferably, in the thermochromic writing instrument of (6) above, the ventilation portion is at least one groove or protrusion that continues from one end of the core to the other along the outer circumferential surface of the core.

[0023] In the process of inserting the core into the inner hole, the grooves or protrusions of the core form a gap between the outer circumferential surface of the core and the inner circumferential surface of the inner hole. This ensures that the air in the inner hole is not compressed by the core and is reliably discharged to the outside through the gaps formed by the grooves or protrusions. This makes it easy to insert the core into the friction body and ensures that the core is attached reliably to the inner hole.

[0024] (9) Preferably, in the thermochromic writing instrument of any one of the above (3) to (8), the center core has a vertically symmetrical shape.

[0025] Since the core is symmetrical in the vertical direction, there is no distinction between the top and bottom of the core. This means that the core can be inserted into the inner hole from either the top or bottom, making it easier to insert the core into the inner hole.

[0026] (10) In the thermochromic writing instrument according to any one of the above (3) to (9), preferably, the inner core is provided on an outer peripheral surface of the inner core. hole A protrusion is provided which comes into contact with the inner circumferential surface of the

[0027] The protrusions provided on the outer circumferential surface of the core hold the core more firmly within the inner hole, thereby reliably preventing the core from falling out of the inner hole.

[0028] (11) In order to achieve the above object, the thermochromic writing instrument of the present invention is a thermochromic writing instrument comprising a thermochromic ink and a friction body for thermally discoloring a mark made with the thermochromic ink by frictional heat, wherein at least one of a fluorescent pigment, a phosphorescent pigment, and titanium dioxide is added to the thermochromic ink, the thermochromic writing instrument is provided with a mounting hole for mounting the friction body, the friction body includes a mounting portion to be inserted into the mounting hole and a friction portion having a convex curved shape protruding from the mounting hole, and the material of the friction body has a product (Tb×Eb) of 5,000 or more and 18,000 or less of tensile strength at break Tb and elongation at break Eb measured in accordance with JIS K 6251 of the Japanese Industrial Standards.

[0029] By setting the product of the tensile strength at break Tb and the elongation at break Eb (Tb x Eb) of the friction body material to between 5000 and 18000, the friction body generates an appropriate amount of wear debris when rubbing handwriting. This makes it possible for at least one of the fluorescent pigment, phosphorescent pigment, and titanium dioxide added to the thermochromic ink to adhere to and encase the wear debris. Effect of the Invention

[0030] The thermochromic writing instrument of the present invention makes it possible to chemically and physically erase handwriting made with thermochromic ink containing added metallic luster pigments, and by suppressing deformation of the friction body, it is possible to cause the friction body to exhibit the desired friction performance.

[0031] Here, in this specification, "front" of a thermochromic writing instrument means the direction of the pen tip, and "rear" of a thermochromic writing instrument means the opposite direction to the pen tip. Furthermore, "up" of a mounting hole means the direction of the rear end of the barrel or the direction of the top of the cap, and "down" of a mounting hole means the opposite direction. Furthermore, "up" of a friction body means the direction of the friction part, and "down" of a friction body means the direction of the mounting part. In addition, the content of multiple components constituting the composition described in this specification means the total amount of the substance corresponding to each component, unless otherwise specified. In addition, the term "metallic luster pigment" broadly includes pigments that can impart brilliance to the writing of a thermochromic ink. For example, both transparent metallic luster pigments and metal vapor deposition resin pigments are included in the term "metallic luster pigment". [Brief description of the drawings]

[0032] [Figure 1] FIG. 1 is a cross-sectional view showing a main part of a thermochromic writing instrument according to a first embodiment of the present invention, illustrating a state before an attachment part of a friction body is inserted into an attachment hole of a barrel. [Diagram 2] 10 is a cross-sectional view showing a temporary insertion state during the process of inserting the mounting portion of the friction body into the mounting hole of the barrel. FIG. [Diagram 3] 11 is a cross-sectional view showing a state in which the mounting portion of the friction body is inserted into the mounting hole of the barrel. FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a state in which a core is inserted into an inner hole of a friction body. [Diagram 5] FIG. 4 is a cross-sectional view showing a thermochromic writing instrument according to a second embodiment of the present invention. [Figure 6] FIG. 11 is an external view showing a writing set including a thermochromic writing instrument and a friction body according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermochromic writing instrument according to an embodiment of the present invention will now be described with reference to the drawings.

[0034] 1. Overview 1 to 4 show the main parts of a thermochromic writing instrument according to a first embodiment of the present invention. In Figs. 1 to 4, the entire thermochromic writing instrument is not shown, and only the rear end of a barrel 1 constituting the thermochromic writing instrument is shown. The thermochromic writing instrument of this embodiment comprises a barrel 1, a friction body 3, and a core 7. An attachment hole 2 is provided at the rear end of the barrel 1. The friction body 3 is attached to the attachment hole 2. The friction body 3 is provided with an inner hole 31 along the vertical central axis. The core 7 is inserted into the inner hole 31.

[0035] 2. Mounting holes 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. The inner circumferential surface of the inward protrusion 21 is formed with a guide surface 21a, which is an inverted cone-shaped tapered surface. 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 inner circumferential surface of the minimum 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.

[0036] Here, the barrel 1 is manufactured by injection molding a synthetic resin (e.g., polypropylene). The attachment hole 2 and the inward projection 21 are integrally molded by injection molding at the rear end of the barrel 1. Note that the attachment 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 constituting a thermochromic writing instrument.

[0037] 3.Friction body As shown in Fig. 1, the friction body 3 of this embodiment is configured such that an attachment section 5 (small diameter section) having a smaller diameter than the friction section 32 is integrally molded below a bullet-shaped friction section 32 (large diameter section 4). The friction section 32 is used to cause the thermochromic ink attached to the paper surface to thermally discolor by frictional heat. Furthermore, the friction section 32 of this embodiment has a function of adsorbing and peeling off the metallic luster pigment added to the thermochromic ink from the paper surface. The attachment section 5 is used to attach the friction body 3 to the attachment hole 2 of the barrel 1.

[0038] 3.1 Friction part (large-diameter part) The outer peripheral surface of the friction part 32 has a convex curved surface shape that can contact the paper surface at various inclination angles. The diameter of the lower end of the friction part 32 is larger than the diameter of the upper end opening of the mounting hole 2, and preferably smaller than the diameter of the rear end surface of the shaft cylinder 1. An annular surface 41 that abuts against the rear end surface of the shaft cylinder 1 is formed at the boundary between the friction part 32 and the mounting part 5. When the mounting part 5 is mounted in the mounting hole 2, the friction part 32 protrudes above the rear end surface of the shaft cylinder 1.

[0039] As shown in FIG. 1, the maximum outer diameter D of the friction part 32 and the protruding length L of the friction part 32 satisfy 0.1 ≦ L / D ≦ 1.5, and preferably satisfy 0.5 ≦ L / D ≦ 1.1. The ratio L / D of the maximum outer diameter D to the protruding length L of the friction part 32 serves as a measure of the size of the portion of the friction part 32 exposed to the outside and the rigidity of the friction part 32. When the value of L / D is 0.1 or more, the friction part 32 has sufficient rigidity to friction the handwriting on the paper surface. On the other hand, when the value of L / D is 1.5 or less, the friction part 32 has an exposed portion of sufficient size to erase a large number of handwriting. The friction part 32 of the present embodiment has a maximum outer diameter D = 6.1, a protruding length L = 6.3, and L / D ≒ 1.0.

[0040] In addition, when the friction part 32 has a convex curved surface shape, it is preferable to make the wall thickness at the top of the friction part 32 the thickest. As a result, the rigidity of the top and the vicinity of the top used when frictioning the handwriting on the paper surface becomes high, and the friction operation can be performed smoothly.

[0041] 3.2 Mounting part The mounting part 5 is composed of a cylindrical wall part, has a diameter smaller than the diameter of the lower end of the friction part 32, and is insertable into the mounting hole 2. An annular outward protrusion 51 is formed at the center of the outer peripheral surface of the mounting part 5. An annular bulging part 52 is formed above the outward protrusion 51 on the outer peripheral surface of the mounting part 5. The lower part of the mounting part 5 below the outward protrusion 51 is a cylindrical part 53.

[0042] 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.

[0043] 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 above-mentioned mounting hole 2, 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 a range of 0.5 mm to 2.0 mm, preferably within a range of 0.5 mm to 1.0 mm. Due to such a dimensional difference, in the process of inserting the mounting part 5 into the mounting hole 2, the outward projection 51 passes smoothly through the inward projection 21, and the outward projection 51 and the inward projection 21 can be easily engaged with each other (see FIGS. 2 and 3).

[0044] When the mounting portion 5 is completely 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 suppresses radial wobble of the friction body 3. 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 smaller than the diameter of the lower end of the friction portion 32 and larger than the diameter of the maximum outer diameter portion 51b of the outward projection 51.

[0045] The diameter of the cylindrical portion 53 is smaller than the diameter of the minimum inner diameter portion 21b of the inward projection 21 of the mounting hole 2 described above. The cylindrical portion 53 is for putting the mounting portion 5 into a temporary insertion state into the mounting hole 2. This temporary insertion state is shown in FIG. 2. Such a cylindrical portion 53 makes it easy to attach the friction body 3. That is, the friction body 3 can be dropped toward the mounting hole 2 to put it into the temporary insertion state shown in FIG. 2. Thereafter, the friction body 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 projection 51 and the inward projection 21 are engaged with each other (see FIG. 3). Note that the outer peripheral surface below the outward projection 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.

[0046] 3.3 Formation of annular space The outer diameter of the middle part of the mounting part 5 (the 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 (the 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 overcomes 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 is generated. The annular space 6 accommodates the intermediate portion of the mounting portion 5 which bulges outward in the radial direction, thereby preventing the intermediate portion of the mounting portion 5 from coming into pressure contact with the inner circumferential surface near the entrance of the mounting hole 2 .

[0047] 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 longer than the length B from the upper end of the mounting hole 2 to the lower end of the inward projection 21. This allows the entire outward projection 51 to pass through the inward projection 21 reliably. 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 allows the entire outward projection 51 to pass through the inward projection 21 reliably even if frictional resistance occurs between the outward projection 51 and the inward projection 21. Here, the difference between the 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 within a range of 0.05 mm to 1.0 mm, and more preferably within a range of 0.1 mm to 0.5 mm. With such a small clearance C, the friction body 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.

[0048] 3.5 Inner hole An inner hole 31 is provided inside the friction body 3. The inner hole 31 is a straight hole provided along the central axis of the friction body 3, and opens at least at the lower end of the friction body 3. In this embodiment, the inner hole 31 is a hole that extends from the lower end of the attachment portion 5 to the center of the friction portion 32, and is closed on one side, not opening at the upper end of the friction portion 32. The inner hole 31 is provided from the lower end of the attachment 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.

[0049] Here, the inner hole 31 in this embodiment opens at the lower end of the attachment portion 5 of the friction body 3, and does not open at the upper end of the friction portion 32. If the inner hole 31 opens at the upper end of the friction portion 32, it will not be possible to friction the handwriting at the upper end of the friction portion 32, and the friction performance of the friction portion 32 will be reduced.

[0050] In addition, since the inner hole 31 does not open at the upper end of the friction portion 32, the rigidity of the friction portion 32 is increased, improving the friction performance of the friction portion 32. Furthermore, when the friction body 3 is attached to the attachment hole 5, the entire friction body 3 is prevented from bending, making the attachment work easier.

[0051] 3.6 Hardness and viscosity of friction body The material constituting the friction body 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.

[0052] Here, the friction body 3 of the present embodiment has a lower hardness than conventional friction bodies in order to physically erase the metallic luster pigment added to the thermochromic ink described later from the paper surface. The friction body 3 with a low hardness can enter into the depression of the handwriting formed on the paper surface.

[0053] The hardness of the material of the friction body 3 is represented by, for example, a Shore A hardness value measured in accordance with the "Durometer hardness test method for plastics" specified in JIS K 7215-1986 of the Japanese Industrial Standards. A durometer used to measure the Shore A hardness value has a spring-biased indenter, and the amount of indenter pressure on the object to be measured is displayed as the Shore A hardness value. The softer the object to be measured, the smaller the Shore A hardness value, and the harder the object to be measured, the larger the Shore A hardness value.

[0054] It is preferable that the Shore A hardness value of the material of the friction body 3 measured by the test method conforming to JIS K 7215-1986 satisfies the following conditions i) and ii). i) The Shore A hardness value immediately after the start of the indenter contact 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 start of the indenter contact) - (Shore A hardness value 15 seconds after the start of the indenter contact) Note that "immediately after the start of the indenter contact" in the above i) and ii) means the time within 1 second after the indenter contacts the measurement object.

[0055] The Shore A hardness value immediately after the start of the indenter contact in the above i) is preferably 60 or more and 80 or less, and more preferably 65 or more and 75 or less. The friction body 3 made of a material satisfying the condition of the above i) has a higher friction heat generation efficiency than a conventional friction body. Thereby, the friction body 3 can easily thermochromically change the handwriting of the thermochromic ink. Further, the friction body 3 made of a material satisfying the condition of the above i) is softer than a conventional friction body and can enter into the recesses of the handwriting formed on the paper surface. Furthermore, when the material of the friction body 3 satisfies the value of ΔHS in the above ii), it becomes possible to adsorb and peel off the metallic luster pigment from the recesses of the handwriting.

[0056] 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 material of the friction body 3. The stress relaxation time is a criterion for distinguishing whether a material is an elastic body, a viscoelastic body, or a viscous body. A material of the friction body 3 that satisfies the value of ΔHS in ii) above can be said to be an elastic body with a suitable viscosity that allows it to adsorb metallic luster pigments. On the other hand, a material with a value of ΔHS of 5 or more can be said to be a viscous body or a viscoelastic body. If the friction body 3 is a viscous body or a viscoelastic body, the deformation amount when the handwriting of the thermochromic ink is rubbed becomes too large, and sufficient friction performance cannot be obtained. In particular, the elastic modulus of the friction body 3 made of synthetic resin depends on temperature. For this reason, when the temperature of the friction body 3 itself rises due to frictional heat, and when the friction body 3 is used in a high-temperature environment, the friction body 3 is more likely to deform significantly. Therefore, it is preferable that the value of ΔHS of the material of the friction body 3 is 0 or more and less than 5. Here, the value of ΔHS in ii) above can be set arbitrarily depending on the type and / or composition of one or more comonomers contained in the polymer material.

[0057] The Shore A hardness values ​​in i) and ii) above may be values ​​obtained by converting the Shore D hardness value of the material of the friction body 3 measured by a test method in accordance with JIS K 7215-1986 into a Shore A hardness value.

[0058] 3.7 Wear of friction body In order to physically erase the metallic pigment added to the thermochromic ink from the paper surface, the friction body 3 is preferably one that is scraped off by rubbing the paper surface and generates a small amount of wear debris (eraser debris). The friction body 3 removes the metallic pigment from the paper surface by adhering it to the wear debris and enveloping it as it wears itself.

[0059] The wear amount of the friction body 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 a value obtained by dividing the tensile force recorded when the measured object is broken 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 represented as a ratio (%) to the length of the measured object before the test.

[0060] The inventors have found that the wear amount of the friction body 3 is inversely proportional to Tb×Eb. That is, the wear amount of the friction body 3 is affected by the mechanical strength and elongation of the material. The wear amount of the friction body 3 can be controlled by appropriately combining the tensile strength at break Tb and the elongation at break Eb. The value of Tb×Eb represents the energy required to wear the friction body 3. Therefore, the more easily the measured object wears, the smaller the value of Tb×Eb, and the more difficult the measured object wears, the larger the value of Tb×Eb.

[0061] It is preferable that the value of Tb×Eb of the material of the friction body 3 calculated by a method conforming to JIS K 6251:2017 satisfies the following condition iii). iii) 5000≦Tb×Eb≦18000 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.

[0062] In the above iii), 8000≦Tb×Eb≦16000 is preferable, and 10000≦Tb×Eb≦14000 is more preferable. When the material of the friction body 3 satisfies the above condition iii), the friction body 3 generates an appropriate amount of wear debris by normal frictional action by human hand. This makes it possible for the metallic luster pigment added to the thermochromic ink to adhere to and be wrapped in the wear debris.

[0063] In the above iii), when the value of Tb×Eb exceeds 18000, it becomes difficult to wear down the friction body 3 by normal manual frictional action. Therefore, it is not possible to make the metallic luster pigment adhere to and envelop the wear debris while wearing down the friction body 3.

[0064] On the other hand, in the above iii), if the value of Tb×Eb is smaller than 5000, the friction body 3 is easily worn down by normal manual friction. Therefore, the frictional heat generated by the friction body 3 is lost together with the wear debris, making it difficult to efficiently thermo-change the thermochromic ink.

[0065] 4. Core The core 7 is made of a synthetic resin or metal harder than the friction body 3. The material constituting the core 7 will be described later. The core 7 in this embodiment is a small cylindrical part having an outer diameter substantially the same as the inner diameter of the inner hole 31. Such a core 7 is inserted into the inner hole 31 of the friction body 3. The outer peripheral surface of the core 7 comes into contact with the inner peripheral surface of the inner hole 31, so that the friction body 3 is firmly fixed to the mounting hole 2 of the barrel 1. This increases the rigidity of the entire friction portion 32, and prevents the friction portion 32 from deforming. As a result, even if the hardness of the material of the friction body 3 is reduced, good friction performance can be exhibited.

[0066] Furthermore, the outer peripheral surface of the core 7 comes into contact with the inner peripheral surface of the inner hole 31, thereby increasing the rigidity of the outward protrusions 51 provided on the mounting portion 5 of the friction body 3, and suppressing the inward deformation of the outward protrusions 51. As a result, the outward protrusions 51 and the inward protrusions 21 are firmly engaged with each other, preventing the friction body 3 from falling off from the mounting hole 2.

[0067] Furthermore, it is preferable that the outer peripheral surface of the core 7 is pressed against the inner peripheral surface of the inner hole 31, rather than simply contacting it. In order to press the outer peripheral surface of the core 7 against the inner peripheral surface of the inner hole 31, the outer diameter of the core 7 should be set to be equal to or larger than the inner diameter of the inner hole 31. Pressing the outer peripheral surface of the core 7 against the inner peripheral surface of the inner hole 31 increases the rigidity of the friction portion 32 and the outward protrusions 51, and more reliably prevents the core 7 and friction body 3 from falling off.

[0068] Here, the "rigidity" of the friction portion 32 means the deformation resistance of the friction portion 32 against an external force, and includes tensile rigidity, compressive rigidity, bending rigidity, shear rigidity, torsional rigidity, etc. The external force is mainly a force applied to the friction portion 32 during frictional operation. It is preferable that the friction portion 32 has a rigidity that does not buckle due to the external force during frictional operation.

[0069] 4.1 Core material The core 7 is made of a synthetic resin or metal harder than the friction body 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. Also, rubber or elastomer harder than the friction body 3 may be used. 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). The synthetic resin core 7 can be manufactured by cutting or injection molding. Examples of the metal that can be used include aluminum alloy, stainless steel, brass, etc. On the other hand, the metal core 7 can be manufactured by cutting or plastic processing, for example.

[0070] 4.2 Shape of the core As shown in Fig. 4, it is preferable that the core 7 has a shape that is symmetrical from top to bottom with respect to the horizontal central axis. 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 a shape that is asymmetrical from top to bottom. For example, at least the edge portion of the upper end of the core 7 may be chamfered to make it easier to insert the core 7 into the inner hole 31.

[0071] 4.3 Ventilation In this embodiment, the inner hole 31 is a hole that opens at the lower end of the attachment portion 5 and does not open at the upper end of the friction portion 32, 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 inserted smoothly into the inner hole 31. Therefore, the core 7 is provided with a ventilation portion 71. The ventilation portion 71 in this embodiment is a through hole that penetrates from one end to the other end of the core 7 along the vertical central axis 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 ventilation portion 71 and is discharged to the outside. Such ventilation portion 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.

[0072] 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. 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 circumferential surface of the core 7. For example, the ventilation part 71 may be a spiral groove or protrusion provided along the outer circumferential surface of the core 7. The spiral groove or protrusion has an anti-slip effect that prevents the core 7 from falling off the inner hole 31. Instead of providing the ventilation part 71 on the core 7, the above-mentioned groove or protrusion may be provided on the inner circumferential surface of the inner hole 31.

[0073] 4.4 Upper and lower cores In this embodiment, the upper half of the middle core 7 is referred to as the upper core portion 72, and the lower half of the middle core 7 is referred to as the lower core portion 73. As already described, the middle core 7 has a cylindrical shape with the same outer diameter over its entire length. However, the middle core 7 may have a tapered shape in which the outer diameter of the lower core portion 73 is larger than the outer diameter of the upper core portion 72. This facilitates the insertion of the middle core 7 into the inner hole 31. Also, due to the larger outer diameter of the lower core portion 73, the rigidity of the outward protrusion 51 is increased, and the inward deformation of the outward protrusion 51 is suppressed. As a result, the outward protrusion 51 and the inward protrusion 21 are strongly locked, and the detachment of the friction body 3 is prevented.

[0074] 4.5 Holding of the middle core In order to prevent the middle core 7 inserted into the inner hole 31 from easily coming out, an anti-slip measure can be provided on the outer peripheral surface of the middle core 7. As the anti-slip measure, for example, the outer peripheral surface of the middle core 7 can be processed into a rough surface to increase the frictional resistance against the inner peripheral surface of the inner hole 31. Also, minute protrusions can be provided on the outer peripheral surface of the middle core 7 to serve as an anti-slip measure. Further, by making the outer diameter of the middle core 7 significantly larger than the inner diameter of the inner hole 31, the middle core 7 can be prevented from easily coming out of the inner hole 31.

[0075] 5. Mounting method of the friction body Next, the mounting method of the friction body 3 according to this embodiment will be described with reference to FIGS. 1 to 4.

[0076] As shown in FIG. 1, after the friction body 3 is disposed above the mounting hole 2 at the rear end portion of the shaft cylinder 1, it is dropped as it is toward the mounting hole 2. Then, as shown in FIG. 2, the cylindrical portion 53 of the mounting portion 5 enters the minimum inner diameter portion 21b of the mounting hole 2, and the mounting portion 5 is in a temporarily inserted state with respect to the mounting hole 2. At this time, by the guide surface 51a of the mounting portion 5 coming into contact with the guide surface 21a of the mounting hole 2, the temporarily inserted state of the mounting portion 5 is stably maintained.

[0077] Next, the friction body 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 portion of the mounting portion 5 is elastically deformed and bulges outward in the radial direction. The middle portion of the mounting portion 5 bulging outward in the radial direction is accommodated in the annular space 6 in the mounting hole 2. As a result, the middle portion of the mounting portion 5 is not pressed against the inner circumferential surface near the entrance of the mounting hole 2, and does not hinder 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 with each other. This completes the insertion of the mounting portion 5 into the mounting hole 2 (see FIG. 3).

[0078] Thereafter, as shown in Fig. 4, the core 7 is inserted into the inner hole 31 of the friction body 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 portion 71 and is discharged to the outside. Such ventilation portion 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 portion 5 outward, strengthening the engagement between the outward projection 51 and the inward projection 21. This completes the attachment of the friction body 3 to the rear end portion of the barrel 1.

[0079] According to the method for attaching the friction body 3 of this embodiment, at a stage before inserting the core 7 into the inner hole 31, the highly flexible attachment portion 5 can be inserted into the attachment hole 2, and the outward projections 51 and the inward projections 21 can be easily engaged with each other. Thereafter, 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 projections 51 and the inward projections 21 is firmly maintained. Moreover, since the core 7 is inserted into the inner hole 31 after inserting the attachment portion 5 into the attachment hole 2, the attachment work of the friction body 3 shown in Figs. 1 to 4 does not require a large force.

[0080] 6. Thermochromic ink The thermochromic ink contained in the thermochromic writing instrument of the present embodiment may be any of water-based ink, oil-based ink, and gel ink, as long as it can form a thermochromic mark. The form of the thermochromic ink is not limited to liquid, and may be solid, such as a pencil lead. The thermochromic ink will be described in detail below.

[0081] The thermochromic ink incorporated in the thermochromic writing implement is one that changes color or fades when heated. As the colorant added to the thermochromic ink, it is preferable to use a reversible thermochromic composition that contains an electron-donating color-forming organic compound, an electron-accepting compound, and a reaction medium for determining the temperature at which the color reaction of these compounds occurs. In particular, a microencapsulated pigment having a structure in which the reversible thermochromic composition is encapsulated in a microcapsule is more preferable.

[0082] Examples of the first reversible thermochromic composition include those described in JP-B-51-44706, JP-B-51-44707, and JP-B-1-29398. The reversible thermochromic compositions described in these publications have a color change point on both the high-temperature side and the low-temperature side. The color change point refers to a predetermined temperature that is the boundary at which color change occurs. The first reversible thermochromic composition becomes a decolorized state in a temperature range above the high-temperature side color change point, and becomes a colored state in a temperature range below the low-temperature side color change point. In the normal temperature range, either the decolorized state or the colored state is maintained. The other state is maintained only while the temperature reaches the high-temperature side color change point or the low-temperature side color change point. When the temperature is no longer the high-temperature side color change point or the low-temperature side color change point, the one state is restored. In other words, the first reversible thermochromic composition has a relatively small hysteresis characteristic width ΔH (for example, ΔH is 1°C or more and 7°C or less).

[0083] As the second reversible thermochromic composition, for example, JP-B-4-17154, JP-A-7-179777, JP-A-7-33997, JP-A-8-39936, JP-A-2006-137886, JP-A-2006-188660, JP-A-2008-45062, and JP-A-2008-280523 disclose reversible thermochromic compositions having a large hysteresis characteristic width ΔH (for example, a ΔH value of 8°C or more and 50°C or less).

[0084] Here, the magnitude of the width ΔH of the hysteresis characteristic is indicated by the shape of a curve plotting the color density of the reversible thermochromic composition against the temperature. For example, assume that the reversible thermochromic composition is in a completely decolorized state in a temperature range above the high-temperature side discoloration point, and in a completely colored state in a temperature range below the low-temperature side discoloration point. The temperature at which the completely decolorized state is reached is called the "completely decolorized temperature," and the temperature at which the completely colored state is reached is called the "completely colored temperature." In the curve plotting the color density of this reversible thermochromic composition against the temperature, if the path of the curve from the completely decolorized temperature on the low-temperature side to the completely colored temperature on the high-temperature side is significantly different from the path of the curve from the completely colored temperature on the high-temperature side to the completely decolorized temperature on the low-temperature side, the width ΔH of the hysteresis characteristic becomes large. Furthermore, such a reversible thermochromic composition has a color memory property that maintains a colored state or a decolored state in a specific temperature range, for example, in the normal temperature range (daily living temperature range).

[0085] In the reversible thermochromic composition having color memory, the complete coloring temperature is preferably set to a low temperature outside the normal temperature range, and the complete decolorization temperature is preferably set to the temperature of frictional heat that can be generated by a friction body. The complete coloring temperature is, for example, in the range of -50°C to 0°C, preferably -40°C to -5°C, more preferably -30°C to -10°C. On the other hand, the complete decolorization temperature is, for example, in the range of 50°C to 95°C, preferably 50°C to 90°C, more preferably 60°C to 80°C. Furthermore, by setting the width ΔH of the hysteresis characteristic to 40°C to 100°C, the colored state or decolorized state is well maintained in the normal temperature range.

[0086] By encapsulating the above-mentioned reversible thermochromic composition in a microcapsule, a thermally decolorable microcapsule pigment can be produced. The average particle size of the microcapsule pigment is, for example, within the range of 0.05 μm to 5.0 μm, preferably 0.1 μm to 4.0 μm, more preferably 0.5 μm to 3.0 μm. This improves the writing performance and writing density of the thermochromic writing instrument. Furthermore, when the average particle size of the microcapsule pigment is 2.0 μm or more, it is possible to not only chemically decolorize the handwriting of the thermochromic ink, but also physically erase it from the paper surface. That is, the microcapsule pigment with an average particle size of 2.0 μm or more is physically peeled off from the paper surface by being adsorbed to a friction body, and is irreversibly erased.

[0087] The average particle size of the microencapsulated pigment is measured using image analysis type particle size distribution measurement software "Mac-View" manufactured by MOUNTECH Co., Ltd. First, the particle area of ​​the microencapsulated pigment is identified, then the projected area equivalent circle diameter (Heywood diameter) is calculated from the area of ​​the particle area, and then the average particle size of particles equivalent to a sphere of equal volume is measured based on the projected area equivalent circle diameter value.

[0088] In addition, when the particle diameter of all or most of the microencapsulated pigments contained in the thermochromic ink exceeds 0.2 μm, it is possible to measure it using a particle size distribution measuring device "Multisizer (registered trademark) 4e" manufactured by Beckman Coulter, Inc. In this case, the equivalent volume sphere diameter of the microencapsulated pigment is measured by the Coulter method, and the average particle diameter is calculated based on this measurement value.

[0089] Furthermore, as a coloring component, a general dye or pigment that does not have thermochromism may be added. This makes it possible to impart a desired color that does not change color due to heat to the handwriting of the thermochromic ink. For example, acid dyes, basic dyes, direct dyes, etc. can be used as general dyes. For example, inorganic pigments such as carbon black and ultramarine, organic pigments such as copper phthalocyanine blue and benzidine yellow, and dispersed pigment products that are finely and stably dispersed in a medium in advance using a surfactant can be used as general pigments. In addition, metallic luster pigments such as metal powder and pearl pigments, fluorescent pigments, phosphorescent pigments, and special pigments such as titanium dioxide can also be used. In addition, these coloring components may be used in combination with the above-mentioned microcapsule pigments, or may be encapsulated in the microcapsule pigments.

[0090] 6.1 Metallic luster pigments By adding a metallic luster pigment to the thermochromic ink, the thermochromic ink becomes metallic and a glittering handwriting is formed. Preferably, a transparent metallic luster pigment is added to the thermochromic ink. The transparent metallic luster pigment imparts glitter to the thermochromic ink handwriting, and when the thermochromic ink handwriting is chemically erased, it appears as if it has been completely erased without any glittering.

[0091] The transparent metallic luster pigment may be a glittering pigment having a core material coated with a metal oxide, or a cholesteric liquid crystal type glittering pigment. The core material may be, for example, a material selected from natural mica, synthetic mica, flat glass flakes, flaky aluminum oxide, etc.

[0092] Effective examples of the luster pigments having natural mica as a core material include those having a surface coated with titanium oxide, and those having an upper layer of the titanium oxide coated with iron oxide or a non-thermochromic dye pigment. Examples of luster pigments having natural mica as a core material include those sold under the trade name "Iriodin" by Merck KGaA and "Lumina" by BASF SE.

[0093] The luster pigment having synthetic mica as a core material is effective when its surface is coated with a metal oxide such as titanium oxide. For example, oxides of titanium, zirconium, chromium, vanadium, iron, etc. can be used as the metal oxide, and metal oxides mainly composed of titanium oxide are preferred. For example, the product name "ULTIMICA (registered trademark)" manufactured by Nihon Koken Kogyo Co., Ltd. can be used as the luster pigment having the surface of synthetic mica coated with a metal oxide.

[0094] The bright pigment having a flat glass piece as a core material is effective when the surface is coated with a metal oxide such as titanium oxide. For example, the product name "Metashine (registered trademark)" manufactured by Nippon Sheet Glass Co., Ltd. can be used as the bright pigment having the surface of the flat glass piece coated with a metal oxide.

[0095] A bright pigment having a flaky aluminum oxide core material and having its surface coated with a metal oxide such as titanium oxide is effective. For example, oxides of titanium, zirconium, chromium, vanadium, iron, etc. can be used as the metal oxide, and metal oxides mainly composed of titanium oxide are preferred. For example, the trade name "Xirallic (registered trademark)" manufactured by Merck KGaA can be used as a bright pigment having a flaky aluminum oxide surface coated with a metal oxide.

[0096] The liquid crystal polymer used as the cholesteric liquid crystal type bright pigment has the property of reflecting light in a part of the light incident in a wide spectral range and transmitting all light in the other ranges due to the light interference effect. The cholesteric liquid crystal type bright pigment has excellent metallic luster, color flop property in which the hue changes depending on the viewpoint, and transparency. For example, the product name "HELICONE (registered trademark) HC" manufactured by Wacker Chemie AG can be used as the cholesteric liquid crystal type bright pigment.

[0097] Also, a photoluminescent material manufactured by a vacuum deposition method can be used. This photoluminescent material is manufactured by vacuum depositing a metal such as gold or silver on a film to form a foil, and then peeling the foil off the film and pulverizing it into fine pieces. As such a photoluminescent material, the product name "LG neo (registered trademark)" manufactured by Oike Kogyo Co., Ltd. can be used.

[0098] 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, more preferably 10 μm to 40 μm. This improves the writing performance and writing brightness of the thermochromic writing instrument. As a method for measuring the average particle size of the metallic luster pigment, for example, the particle size distribution is measured using a particle size distribution measuring device "LA-300" manufactured by Horiba Ltd., and the average particle size (median size) is calculated on a volume basis based on the measured value of the particle size distribution.

[0099] 6.2 Physical Removal of Metallic Pigments Metallic pigments do not easily penetrate the paper surface. Therefore, when handwriting of thermochromic ink containing metallic pigments is rubbed, the metallic pigments scatter on the paper surface, and the appearance of the handwriting becomes poor after erasing. In particular, on black paper, the shine of the metallic pigments is emphasized, and the appearance of the handwriting becomes even worse after erasing.

[0100] Therefore, the material of the friction body 3 of this embodiment satisfies the above condition i) that the Shore A hardness value immediately after the indentation of the indentation needle is 60 or more and 85 or less. This allows the friction body 3 to enter into the depression of the handwriting formed on the paper surface. In addition, the material of the friction body 3 of this embodiment satisfies the above condition ii) that the value of ΔHS is 0 or more and less than 5. This allows the friction body 3 to adsorb and peel off the metallic luster pigment from within the depression of the handwriting. That is, according to the friction body 3 of this embodiment, it is possible to physically erase the metallic luster pigment added to the thermochromic ink without scattering it on the paper surface. In addition, the handwriting of the thermochromic ink is chemically erased by frictional heat.

[0101] Furthermore, when a metallic luster pigment is added to the thermochromic ink, it is preferable that the volume Vp of the metallic luster pigment and the volume Ve of the friction portion 32 satisfy the following condition iv). iv) 5≦Ve / Vp≦35

[0102] The volume Vp of the metallic luster pigment indicates the amount of the metallic luster pigment that gives the handwriting a brilliance. The volume Ve of the friction portion 32 indicates the amount of the friction portion 32 that physically erases the metallic luster pigment by wearing. By setting the value of Ve / Vp within the range of 5 to 35, a balance is maintained between the amount of the metallic luster pigment added to the thermochromic ink and the amount of the friction portion 32 required to erase this amount of the metallic luster pigment. That is, when Ve / Vp is the upper limit value of 35, the metallic luster pigment is the minimum amount that gives visible brilliance to the handwriting. In this case, the friction portion 32 is the maximum amount that can erase the minimum amount of the metallic luster pigment 100%. On the other hand, when Ve / Vp is the lower limit value of 5, the metallic luster pigment is the maximum amount that gives high brilliance to the handwriting. In this case, the friction portion 32 is the minimum amount that can erase the maximum amount of the metallic luster pigment 30%. The value of Ve / Vp is preferably 8 to 26, more preferably 10 to 20.

[0103] 6.3 Other Additives The thermochromic ink may contain various additives that have been known in the past.When the thermochromic ink is water-based, for example, pH adjusters, rust inhibitors, preservatives, antifungal agents, wetting agents, defoamers, surfactants, lubricants, fixatives such as resins, shear thinning agents, pen tip drying inhibitors, sagging inhibitors, etc. may be added.When the thermochromic ink is oil-based, for example, viscosity adjusters, preservatives, rust inhibitors, defoamers, lubricants, dispersants, anti-scratch agents, anti-leak agents, surfactants, etc. may be added.

[0104] 7. Thermochromic writing implements The type of the thermochromic writing instrument of the present embodiment is not particularly limited, and may be, for example, any of a fountain pen, a marking pen, a ballpoint pen, a retractable solid writing instrument, and the like. The thermochromic writing instrument may be either a cap type or a retractable type. The cap type thermochromic writing instrument is provided with a cap for covering the nib (tip). The retractable thermochromic writing instrument is provided with a retractable mechanism capable of putting the nib in a protruding state from the barrel and in a retracted state in which the nib is stored in the barrel. The retractable mechanism may be, for example, a knock type, a rotating type, a sliding type, or the like. Furthermore, the retractable thermochromic writing instrument may be provided with two or more refills, and may be configured to selectively put any one of the two or more refills in a protruding state. In this case, the two or more refills may be configured to have different types of nibs and / or thermochromic inks of different colors.

[0105] The pen tip of the marking pen may be, for example, any of a fiber tip, a felt tip, a plastic tip, a metal tip, and the like. The thermochromic ink used in the marking pen may be impregnated in an ink absorbing body made of a fiber bundle. The ink absorbing body is accommodated in a barrel. The thermochromic ink impregnated in the ink absorbing body is supplied to the pen tip. The thermochromic ink used in the marking pen may also be directly accommodated in the barrel. In this case, the barrel is provided with an ink flow rate adjustment member made of a comb groove or a fiber bundle. The thermochromic ink directly accommodated in the barrel is supplied to the pen tip via the ink flow rate adjustment member. The barrel may be provided with a valve mechanism that supplies a predetermined amount of ink to the pen tip instead of the ink flow rate adjustment member.

[0106] The thermochromic ink used in the ballpoint pen is filled, for example, in an ink reservoir tube with a ballpoint tip attached to the tip. In this case, an ink backflow prevention body is disposed at the rear end of the thermochromic ink in the ink reservoir tube. The thermochromic ink used in the ballpoint pen may also be directly contained in the barrel. In this case, an ink backflow prevention body is disposed at the rear end of the thermochromic ink in the barrel. Furthermore, the thermochromic ink used in the ballpoint pen may be impregnated in an ink occlusion body made of a fiber bundle. The barrel may be provided with an ink flow rate adjustment member made of a comb groove or a fiber bundle. A predetermined amount of thermochromic ink is supplied to the pen tip via the ink flow rate adjustment member.

[0107] In the various types of thermochromic writing instruments described above, the friction body 3 of this embodiment is attached to any of the components constituting the thermochromic writing instrument, thereby becoming one with the thermochromic writing instrument (see FIG. 5). For example, the friction body 3 is attached to a cap, clip, head cap, ferrule, barrel, tail plug, grip, and an operating part for extending and retracting the pen tip, which constitute the thermochromic writing instrument. The friction part 32 may be covered with a cover to prevent dirt.

[0108] The friction body 3 of this embodiment may not be attached to any of the components constituting the thermochromic writing instrument, and may be separate from the thermochromic writing instrument (see FIG. 6). The separate friction body 3 may be configured to be made only of the above-mentioned low-hardness synthetic resin material. The separate friction body 3 may also be configured to be attached to another component made of a high-hardness material.

[0109] 8. Effects The friction body 3 of this embodiment, like conventional friction bodies, can discolor or erase handwriting of thermochromic ink by generating frictional heat. Furthermore, the frictional portion 32, which has low hardness, penetrates into the depressions of the handwriting, adsorbs the metallic luster pigment added to the thermochromic ink, and peels it off from the paper surface. The metallic luster pigment adsorbed to the frictional portion 32 is caught in the wear debris of the frictional portion 32 and is completely removed from the paper surface. In this way, the frictional body 3 of this embodiment can chemically and physically erase handwriting of thermochromic ink to which a metallic luster pigment has been added.

[0110] By using the friction body 3 of this embodiment, the handwriting of the thermochromic ink containing the metallic luster pigment can be erased without leaving any color. Therefore, the appearance of the paper surface after erasing the handwriting is good. In particular, the metallic luster pigment having an average particle size of 10 μm or more can impart high brilliance to the handwriting of the thermochromic ink and is easily adsorbed to the friction part 32.

[0111] Here, the conventional friction body cannot erase the handwriting of the pencil lead because the Shore A hardness value is too large. In order to erase the handwriting of the pencil lead, it is necessary to use an eraser with a small Shore A hardness value. In contrast, the friction body 3 of the present embodiment has a Shore A hardness value smaller than that of the conventional friction body. In addition, the friction body 3 has a property similar to that of an eraser, that is, it is scraped by rubbing the paper surface and generates a small amount of wear debris. Therefore, it is possible to erase both the handwriting of the thermochromic ink and the handwriting of the pencil lead with one friction body 3.

[0112] The friction body 3 of this embodiment may be a separate object from the thermochromic writing instrument (see friction body 201 in FIG. 6). The friction body 3 separate from the thermochromic writing instrument is preferably attached to a support for holding with fingers. The support is formed of, for example, a hard synthetic resin or metal. The friction body 3 separate from the thermochromic writing instrument is combined with the thermochromic writing instrument to form one writing set. EXAMPLES

[0113] Hereinafter, examples of the thermochromic writing implement of the present invention will be described with reference to FIG. 5 and FIG. 6. In the first and second examples described below, the numerical values ​​indicating the content of the composition indicate parts by mass. The average particle size of the thermochromic pigment was measured using a particle size distribution measuring device "Multisizer (registered trademark) 4e" manufactured by Beckman Coulter, Inc. The equivalent volume sphere diameter of the thermochromic pigment was measured by the Coulter method, and the average particle size was calculated from this measurement. The average particle size of the metallic luster pigment was measured using a particle size distribution measuring device "LA-300" manufactured by Horiba, Ltd. The particle size distribution of the metallic luster pigment was measured, and the average particle size (median diameter) was calculated on a volume basis based on this measurement. The Shore A hardness of the material of the friction body was measured by a test method conforming to JIS K 7215 of the Japanese Industrial Standards. A sample of a predetermined shape, thickness, and size was prepared using the same material as the friction body. The Shore A hardness was measured by pressing this sample with a manual durometer.

[0114] First Example In the first example, a thermochromic writing instrument 103 according to the second embodiment shown in Fig. 5 was used. A friction body 101 is attached to the rear end of a barrel 182 of the thermochromic writing instrument 103.

[0115] The friction body 101 is made of a polyester elastomer that satisfies the above conditions i) to iv). The Shore A hardness value of the polyester elastomer immediately after the indenter started to contact the indenter was 70, and the Shore A hardness value 15 seconds after the indenter started to contact the indenter was 69. Therefore, the ΔHS value of the polyester elastomer is 1.

[0116] The tensile strength at break Tb and elongation at break Eb of the polyester elastomer were measured by a test method conforming to JIS K 6251:2017. As a result of the measurement, the tensile strength at break Tb was 14 MPa, and the elongation at break Eb was 890%. Therefore, the value of Tb x Eb of the polyester elastomer is 12460.

[0117] The above-mentioned polyester elastomer was injection molded to obtain a milky white friction body 101 having the shape shown in Fig. 5. The friction body 101 includes a friction portion 111 having a convex curved surface shape and a cylindrical attachment portion 112. A stepped locking portion is formed at the lower end of the attachment portion 112. By making the friction portion 111 have a convex curved surface shape, the friction action is stabilized, making it easier to rub handwriting on paper.

[0118] The mounting portion 112 of the friction body 101 is inserted into a mounting hole 181 provided at the rear end of the shaft tube 182. Two ring beads are formed on the inner circumferential surface of the mounting hole 181. The mounting portion 112 is sandwiched between the two ring beads within the mounting hole 181. Furthermore, the locking portion of the mounting portion 112 is locked to the lower end of the mounting hole 181. The maximum outer diameter D of the friction portion 111 is 6, and the protruding length L from the mounting hole 181 is also 6. Therefore, the L / D value of the friction portion 111 is 1.

[0119] The thermochromic writing instrument 103 is a retractable ballpoint pen. The pen tip (ballpoint pen tip) 105 of the thermochromic writing instrument 103 is brought into a protruding or retracted state by sliding the operating part 184 forward. The operating part 184 protrudes to the outside from the side of the barrel 182. A retraction mechanism for retracting the pen tip 105 is housed inside the barrel 182. The retraction mechanism mainly comprises a sliding body 18. 4 a, a refill holding portion 185, a coil spring 183, and a locking member 186. The refill 104 is accommodated in front of the refill holding portion 185 inside the barrel 182.

[0120] The barrel 182 is composed of a front barrel 182b and a rear barrel 182a. An opening 182c is provided at the tip of the front barrel 182b. The opening 182c has a diameter that allows the pen tip 105 of the refill 104 to protrude or retract. The rear barrel 182a is screwed to the rear end of the front barrel 182b. The above-mentioned retraction mechanism is housed inside the rear barrel 182b. In order to house the sliding body 184a integrally molded with the operating unit 184, the rear barrel 182a is composed of first and second parts that can be separated in the front-rear direction. A slide hole extending in the front-rear direction is formed in the second part that constitutes the rear of the rear barrel 182a. When the sliding body 184a is housed inside the rear barrel 182a, the operating unit 184 protrudes to the outside from the slide hole.

[0121] The sliding body 184a is a substantially cylindrical resin molded product integrally molded with the operating portion 184. A plurality of sawtooth-shaped protrusions are formed at the tip of the sliding body 184a. The refill holding portion 185 is disposed in front of the sliding body 184a in the rear shaft 182a. The refill holding portion 185 is a substantially cylindrical resin molded product that fits into the rear end of the refill 104. A plurality of steps are formed at the rear end of the refill holding portion 185. The plurality of steps mesh with the sawtooth-shaped protrusions of the sliding body 184a. In addition, a plurality of ribs extending in the axial direction are formed at equal intervals on the outer peripheral surface of the refill holding portion 185. Meanwhile, a plurality of grooves are formed at equal intervals on the inner surface of the first part that constitutes the front of the rear shaft 182a. The plurality of grooves guide the plurality of ribs of the refill holding portion 185 in the axial direction.

[0122] The front end of the refill holding portion 185 has an outer diameter smaller than the other portions, and is inserted into the rear end of the coil spring 183. The front end of the coil spring 183 is locked to a locking member 186 fixed inside the rear shaft 182a. The coil spring 183 biases the refill holding portion 185 and the refill 104 rearward.

[0123] When the operating unit 184 is slid forward with the pen tip 105 in the immersed state, the multiple ribs of the refill holding part 185 are guided into the multiple grooves in the rear shaft 182a, and the refill holding part 185 moves forward. When the multiple ribs pass through the multiple grooves, the sawtooth convex part of the sliding body 184a engages with the step part of the refill holding part 185, rotating the refill holding part 185 by a predetermined angle. As a result, the end faces of the multiple ribs come into contact with the end faces of the multiple grooves, and the refill holding part 185 is fixed in the state where it has moved forward. As a result, the pen tip 105 of the refill 104 is maintained in a state protruding from the opening 182c of the front shaft 182b.

[0124] When the operating part 184 is slid forward with the pen tip 105 protruding, the sawtooth convex part of the sliding body 184a engages with the step part of the refill holding part 185, rotating the refill holding part 185 by a predetermined angle. This releases the contact between the end faces of the multiple ribs and the end faces of the multiple grooves, and the multiple ribs of the refill holding part 185 are guided into the multiple grooves in the rear shaft 182a. The refill holding part 185 moves rearward due to the biasing force of the coil spring 183. As a result, the pen tip 105 of the refill 104 is immersed in the opening 182c of the front shaft 182b.

[0125] The refill 104 is composed of a pen tip 105, an ink reservoir 106, and a connecting member 107. A ball is rotatably held at the front end of the pen tip 105. The ink reservoir 106 is a metal pipe with openings at the front and rear ends. The connecting member 107 is made of a transparent synthetic resin. The pen tip 105 is connected to the opening at the front end of the ink reservoir 106 via the connecting member 107. A thermochromic ink composition 161 and an ink follower composition 162 are contained in the refill 104.

[0126] The components of the thermochromic ink composition 161 are a reversible thermochromic pigment (11 parts), a transparent metallic luster pigment (3 parts), a metal vapor deposition resin pigment (2 parts), a shear thinning agent (0.3 parts), urea (10 parts), glycerin (10 parts), a nonionic penetrating agent (0.6 parts), a hydrophobic silica-based defoamer (0.1 part), a preservative (0.1 part) and water (62.9 parts).

[0127] The reversible thermochromic pigment is a microcapsule containing a reversible thermochromic composition that changes color from pink to colorless. The reversible thermochromic pigment has a color-developing temperature of -10°C, a color-fading temperature of 65°C, and an average particle size of 2.5 μm.

[0128] As the transparent metallic luster pigment, the product name "Iriodin (registered trademark) 6103 Icy White" manufactured by Merck KGaA was used. This transparent metallic luster pigment is made of silver particles in which the surface of synthetic mica is coated with metal oxide. The average particle diameter of the transparent metallic luster pigment is 25 μm. As the metal vapor deposition resin pigment, the product name "LG neo (registered trademark) Silver #325" manufactured by Oike Kogyo Co., Ltd. was used. The color of the particles of this metal vapor deposition resin pigment is silver, and the average particle diameter is 35 μm. The ratio Ve / Vp of the volume Ve of the friction part 111 to the total volume Vp of the transparent metallic luster pigment and the metal vapor deposition resin pigment is 15.

[0129] Xanthan gum was used as a shear thinning agent. SN Wet 366, a product name of San Nopco Ltd., was used as a nonionic penetrating agent. Nopco 8034, a product name of San Nopco Ltd., was used as a hydrophobic silica-based defoaming agent. Proxel (registered trademark) XL2, a product name of Lonza Japan Ltd., was used as a preservative.

[0130] The components of the ink follower composition 162 are polybutene (98.5 parts) as a base oil and fatty acid amide (1.5 parts) as a thickener. The mixture of polybutene and fatty acid amide was kneaded with a three-roll mill to obtain the ink follower composition 162.

[0131] Using the thermochromic writing implement 103, a handwriting of the thermochromic ink composition 161 was formed on the surface of "writing paper A" (100% chemical pulp, whiteness 75.0 or more) conforming to the Japanese Industrial Standard JIS P3201. The pink thermochromic pigment was the base of the handwriting, and the silver transparent metallic luster pigment and the metal vapor deposition resin pigment were dispersed in the handwriting. As a result, the handwriting of the thermochromic ink composition 161 exhibited a metallic pink color on the white paper surface. In addition, a handwriting of the thermochromic ink composition 161 was formed on the black paper surface. As a result, the hue of the handwriting formed on the black paper surface was the same as that on the white paper surface. However, the brilliance of the handwriting formed on the black paper surface was particularly higher than that on the white paper surface.

[0132] The handwritings formed on the white and black paper surfaces can be chemically and physically erased by the friction body 101 attached to the thermochromic writing implement 103. That is, the handwritings formed on the paper surface are repeatedly rubbed by the friction part 111. Then, the friction part 111 generates frictional heat, and the thermochromic pigment in the handwriting changes color from pink to colorless and transparent. In addition, the friction part 111, which has low hardness, enters the depressions of the handwriting, adsorbs the silver transparent metallic luster pigment and the metal-deposited resin pigment, and peels off from the paper surface. Furthermore, the transparent metallic luster pigment and the metal-deposited resin pigment adsorbed by the friction part 111 are wrapped up in the wear debris of the friction part 111 and are completely removed from the paper surface. In this way, the friction body 101 cleanly erases the handwriting of the thermochromic ink composition 161 without soiling the paper surface. In particular, the metallic luster pigment and the metal-deposited resin pigment remaining on the black paper have a problem of shining depending on the viewing angle and being visually recognized. This problem is solved by using the friction body 101.

[0133] Table 1 below shows the results of the evaluation test of each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4. The friction bodies of Examples 1 to 4 satisfy all of the conditions related to Shore A hardness and Ve / Vp of the present invention. The friction bodies of Comparative Examples 1 to 4 do not satisfy either of the conditions related to Shore A hardness and Ve / Vp of the present invention. Each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4 has the same shape as the friction body 101 shown in FIG. 5, and is attached to the rear end of the barrel 182 of the thermochromic writing instrument 103. The refill 104 of the thermochromic writing instrument 103 contains the thermochromic ink composition 161 and the ink follower composition 162, which are composed of the above-mentioned components. The pen tip 105 of the refill 104 is a ballpoint pen tip.

[0134] [Table 1]

[0135] The friction bodies of Examples 1 to 4 are all made of a polyester-based elastomer. The hardness of the friction bodies of Examples 1 to 4 was varied by mixing polyester-based elastomers having different hardnesses. The friction bodies of Examples 1 to 4 all satisfy the conditions of the present invention, that is, the Shore A hardness immediately after the indenter starts to contact is 60 or more and 85 or less, the ΔHS value is 0 or more and less than 5, and the Ve / Vp value is 5 or more and 35 or less.

[0136] The friction body of Comparative Example 1 is made of a polyester elastomer having the same hardness as that of Example 1. The friction body of Comparative Example 1 has a Ve / Vp value of 4. In this respect, the friction body of Comparative Example 1 does not satisfy the condition of the present invention, that is, the Ve / Vp value of 5 or more and 35 or less.

[0137] The friction body of Comparative Example 2 is composed of 40% α-polyolefin copolymer, 40% styrene-based elastomer, and 20% crystalline polypropylene. The friction body of Comparative Example 2 has a Shore A hardness of 90 immediately after the indenter starts to contact, and a ΔHS value of 18. In these respects, the friction body of Comparative Example 2 does not satisfy the conditions of the present invention, that is, a Shore A hardness of 60 to 85 immediately after the indenter starts to contact, and a ΔHS value of 0 to less than 5.

[0138] The friction body of Comparative Example 3 is made of a styrene-based elastomer (product name "AR-885C" by Aron Chemical Industries, Ltd.). The friction body of Comparative Example 3 has a Shore A hardness of 88 immediately after the indenter starts to contact the friction body of Comparative Example 3. In this respect, the friction body of Comparative Example 3 does not satisfy the condition of the present invention that the Shore A hardness immediately after the indenter starts to contact the friction body of Comparative Example 3 is 60 or more and 85 or less.

[0139] The friction body of Comparative Example 4 was made from a commercially available eraser made of polyvinyl chloride resin (product number "ER-F6" by Pilot Corporation). The friction body of Comparative Example 4 had a Shore A hardness value of 50 immediately after the indenter started to contact the indenter, and a ΔHS value of 25. In these respects, the friction body of Comparative Example 4 does not satisfy the conditions of the present invention, that is, the Shore A hardness value immediately after the indenter started to contact the indenter is 60 or more and 85 or less, and the ΔHS value is 0 or more and less than 5.

[0140] Using each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4, the handwriting of the thermochromic writing instrument 103 was erased, and the erasability, wear debris, continuous erasability, and erasable amount, which will be described below, were evaluated.

[0141] <Evaluation of erasability> Eight sheets of white paper and eight sheets of black paper were prepared. The white paper was "writing paper A" (100% chemical pulp, whiteness 75.0 or higher) conforming to the Japanese Industrial Standard JIS P3201. The black paper was black paper made of 100% chemical pulp. The thickness of the white and black paper was 0.09 mm, and the basis weight was 80 g / m 2 Using the thermochromic writing implement 103, handwriting was formed of the thermochromic ink composition 161 on the surface of each of the white paper and the black paper. The handwriting was a circular spiral pattern. Ten spiral patterns were handwritten in one line on one sheet of paper. Thereafter, the ten spiral patterns formed on the surface of each of the white paper and the black paper were erased using each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4. The state of the paper surface after erasure was visually confirmed.

[0142] The erasability evaluation in Table 1 is as follows. A: The handwriting was erased without leaving any color. B: The pink color of the thermochromic pigment or the silver color of the metallic luster pigment remained faintly. C: The pink color of the thermochromic pigment or the silver color of the metallic luster pigment was not erased.

[0143] <Evaluation of wear debris> In the evaluation of the erasability described above, ten spiral patterns formed on the surface of each of white and black paper were erased using each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4, and then the state of the wear debris generated from each of the friction bodies was visually confirmed.

[0144] The wear debris evaluation in Table 1 is as follows: A: There were no practical problems. B: Wear debris adhered to the friction body, causing practical problems. C: A large amount of wear debris was generated, which was problematic for practical use.

[0145] <Evaluation of continuous erasability> Eight sheets of white paper were prepared. The white paper was "Writing Paper A" (100% chemical pulp, whiteness 75.0 or higher) conforming to the Japanese Industrial Standard JIS P3201. The thickness of the white paper was 0.09 mm, and the basis weight was 80 g / m 2 Using the thermochromic writing implement 103, handwriting of the thermochromic ink composition 161 was formed on the surface of a blank sheet of paper. The handwriting was a circular spiral pattern. Ten spiral patterns were handwritten on each of 30 lines on one sheet of paper, totaling 300 spiral patterns. Then, using each of the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4, the 30 lines of spiral patterns formed on each of the eight blank sheets of paper were continuously erased. In the process of erasing the 30 lines of spiral patterns, it was confirmed how many lines the friction performance of the friction body was maintained immediately after the start of erasing. In such an evaluation of continuous erasability, the erasability of the metallic luster pigment and the state of the wear debris were not taken into consideration.

[0146] The continuous erasability evaluation in Table 1 is as follows. A: The friction performance immediately after the start of erasing was maintained until 30 lines of the spiral pattern were erased. B: The frictional performance immediately after the start of erasure was maintained until 20 lines of the spiral pattern were erased. C: The frictional performance immediately after the start of erasure was maintained until 10 lines of the spiral pattern were erased.

[0147] <Evaluation of Erasable Amount> In the evaluation of the continuous erasability described above, for each friction member of Examples 1 to 4 and Comparative Examples 1 to 4, 30 lines of the spiral pattern were completely erased. Thereafter, the consumption amount of the thermochromic ink composition 161 for handwriting 30 lines of the spiral pattern and the wear amount of the friction member for erasing 30 lines of the spiral pattern were measured. Based on these measured values, the weight (erasable amount) of the thermochromic ink composition 161 that could be erased until all the friction portions of each friction member of Examples 1 to 4 and Comparative Examples 1 to 4 were worn out was calculated. It was clarified what percentage of the ink weight contained in one refill 104 this erasable amount corresponded to, and the practicality of the friction member was evaluated.

[0148] The evaluation of the erasable amount in Table 1 is as follows. A: It is possible to erase 30% or more of the ink weight per refill, and there is no problem with practicality. C: It is not possible to erase 30% or more of the ink weight per refill, and there is a problem with practicality.

[0149] ·Second Embodiment In the second embodiment, the friction member 201 of the third embodiment shown in FIG. 6 and the thermochromic writing instrument 203 were used. The configuration of the thermochromic writing instrument 203 is the same as that of the thermochromic writing instrument 103 of the first embodiment described above. The friction member 201 is a separate item from the thermochromic writing instrument 203. The combination of the friction member 201 and the thermochromic writing instrument 203 constitutes one writing set 209.

[0150] The friction body 201 is fitted to the tip of the support 202 made of hard PP resin (polypropylene). The part of the friction body 201 protruding from the tip of the support 202 becomes the friction part 211. The friction part 211 is used to chemically and physically erase thermochromic ink to which a metallic luster pigment has been added. The cross sections of the friction body 201 and the support 202 are both elliptical. Seven friction bodies 201 were injection molded using the same materials as those of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1 above.

[0151] On the other hand, the components of the thermochromic ink composition 161 used in the thermochromic writing implement 203 are the same as those in the above-mentioned first embodiment. That is, the components of the thermochromic ink composition 161 are a reversible thermochromic pigment (11 parts), a transparent metallic luster pigment (3 parts), a metal-vapor-deposited resin pigment (2 parts), a shear-thinning agent (0.3 parts), urea (10 parts), glycerin (10 parts), a nonionic penetrable agent (0.6 parts), a hydrophobic silica-based defoamer (0.1 parts), a preservative (0.1 parts), and water (62.9 parts).

[0152] The reversible thermochromic pigment was a microcapsule containing a reversible thermochromic composition that changes color from blue to colorless. The transparent metallic luster pigment was made by Merck KGaA under the trade name "Iriodin (registered trademark) 6107 Icy White Lightning." This transparent metallic pigment was made of silver particles with an average particle size of 25 μm.

[0153] As in the first embodiment described above, the thermochromic ink composition 161 is contained in the refill 104 of the thermochromic writing instrument 203. The pen tip of the refill 104 is a ballpoint pen tip. By sliding the operating part 184 forward, the pen tip 105 of the refill 104 is brought into a protruding or retracted state.

[0154] Using the thermochromic writing implement 203, a handwriting of the thermochromic ink composition 161 was formed on the surface of "writing paper A" (100% chemical pulp, whiteness 75.0 or more) conforming to the Japanese Industrial Standard JIS P3201. A blue thermochromic pigment was the base of the handwriting, and a silver transparent metallic luster pigment and a metal-deposited resin pigment were dispersed in the handwriting. As a result, the handwriting of the thermochromic ink composition 161 exhibited a metallic blue color on the white paper surface. In addition, a handwriting of the thermochromic ink composition 161 was formed on the black paper surface. As a result, the hue of the handwriting formed on the black paper surface was the same as that on the white paper surface. However, the brilliance of the handwriting formed on the black paper surface was particularly higher than that on the white paper surface.

[0155] As described above, seven friction bodies 201 were injection molded using the same materials as those in Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1. Seven writing sets 209 were constructed by combining each of the seven friction bodies 201 with a thermochromic writing implement 203. Each of the seven writing sets 209 was used to evaluate erasability, wear debris, continuous erasability, and erasable amount. The evaluation results were similar to those of Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1.

[0156] All four friction bodies 201 made of the same material as Examples 1 to 4 in Table 1 showed good results in the erasability test. The handwriting of the thermochromic ink composition 161 is rubbed repeatedly by the friction part 211. Then, the friction part 211 generates frictional heat, and the thermochromic pigment in the handwriting changes color from blue to colorless and transparent. In addition, the friction part 211, which has low hardness, enters the depression of the handwriting, adsorbs the silver transparent metallic luster pigment and the metal-deposited resin pigment, and peels off from the paper surface. Furthermore, the transparent metallic luster pigment and the metal-deposited resin pigment adsorbed by the friction part 211 are wrapped up in the wear debris of the friction part 211 and are completely removed from the paper surface. In this way, the friction body 201 cleanly erases the handwriting of the thermochromic ink composition 161 without soiling the paper surface. In particular, the transparent metallic luster pigment and the metal-deposited resin pigment remaining on the black paper have a problem of shining depending on the viewing angle and being visually recognized. This problem is solved by using the friction body 201. [Explanation of symbols]

[0157] 1 shaft cylinder 2 Mounting holes 21 Introvert process 21a Guide surface 21b Minimum inner diameter 3 Friction body 31 Inner Hole 32 Friction part 4 Large diameter section 41 Annular Surface 5 Mounting part (small diameter part) 51 External process 51a Guide surface 51b Maximum outer diameter 52 Bulge 53 Lower extension 6 Annular Space 7 Core 71 Ventilation section 72 Upper core 73 Lower core A: The axial length from the top of the mounting part to the top of the outward projection B: Axial length from the top of the mounting hole to the bottom of the inward projection C Clearance between inward and outward projections

Claims

1. A thermochromic writing instrument comprising a thermochromic ink and a friction body for thermally discoloring a mark written with the thermochromic ink by frictional heat, The thermochromic ink contains a metallic luster pigment, The thermochromic writing instrument is provided with a mounting hole for mounting the friction body, the friction body includes a mounting portion that is inserted into the mounting hole, and a friction portion that has a convex curved surface shape and protrudes from the mounting hole, a volume Ve of the friction portion and a volume Vp of the metallic luster pigment satisfy 5≦Ve / Vp≦35, The maximum outer diameter D and the protruding length L of the friction portion satisfy 0.1≦L / D≦1.5, The material of the friction body is a thermochromic writing instrument whose Shore A hardness immediately after the indenter starts to contact the material, as measured in accordance with JIS K 7215 of the Japanese Industrial Standards, is in the range of 60 to 85, and whose Shore A hardness (ΔHS) value defined by the following formula is 0 to 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)

2. 2. The thermochromic writing instrument according to claim 1, wherein the material of the friction body has a product (Tb x Eb) of tensile strength at break Tb and elongation at break Eb, measured in accordance with JIS K 6251 of the Japanese Industrial Standards, of 5,000 or more and 18,000 or less.

3. the mounting hole is provided to penetrate the rear end of the barrel or the top of the cap constituting the thermochromic writing instrument along a central axis in a vertical direction, and has an inner circumferential surface between two openings located at the upper end and the lower end; 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, The friction body has a straight inner hole extending along a longitudinal central axis and opening at least at a lower end of the mounting portion; a rod-shaped core having a length that fits into the inner hole and an outer circumferential surface that contacts the inner circumferential surface of the inner hole is inserted into the inner hole; A thermochromic writing instrument as described in claim 1 or 2, 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 surface of the mounting hole, so that the mounting portion is sandwiched between the outer surface of the core and the inward protrusion of the mounting hole.

4. A thermochromic writing instrument as described in claim 3, 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.

5. A thermochromic writing instrument as described in claim 3 or 4, wherein when the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the lower end of the core is positioned at the same position as the lower end of the mounting portion or higher than the lower end of the mounting portion.

6. A thermochromic writing instrument as described in any one of claims 3 to 5, wherein the inner hole is a hole that opens at the lower end of the attachment portion and is blocked on one side, not opening at the upper end of the friction portion, 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.

7. 7. The thermochromic writing instrument according to claim 6, wherein the ventilation portion is a through hole that penetrates the core from one end to the other along a vertical central axis of the core.

8. 7. The thermochromic writing instrument according to claim 6, 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.

9. The thermochromic writing instrument according to any one of claims 3 to 8, wherein the center core has a vertically symmetrical shape.

10. 10. The thermochromic writing implement according to claim 3, wherein a protrusion is provided on an outer circumferential surface of the center core, the protrusion contacting the inner circumferential surface of the inner hole.

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