Thermochromic writing instrument

Abstract

To chemically and physically erase marks of thermochromic ink containing a metallic luster pigment.SOLUTION: The thermochromic ink contains a metallic luster pigment, the thermochromic writing instrument is provided with a mounting hole 2 for mounting a friction body 3, the friction body 3 includes a mounting portion 5 inserted into the mounting hole 2 and a friction portion 32 having a convex curved surface that protrudes from the mounting hole 2, a volume Ve of the friction portion 32 and a volume Vp of the metallic luster pigment satisfy 5≤Ve / Vp≤35, a maximum outer diameter D and protruding length L of the friction portion 32 satisfy 0.1≤L / D≤1.5, and the material of the friction body 3 has a Shore A hardness measured in accordance with JIS K 7215 of the Japanese Industrial Standards immediately after the start of indenter contact in the range of 60 to 85, and a Shore A hardness value (ΔHS) defined by the following formula is greater than or equal to 0 and less than 5: ΔHS=(Shore A hardness immediately after the start of indenter contact)-(Shore A hardness 15 seconds after the start of indenter contact).SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a writing instrument. More specifically, it relates to a writing instrument provided with a friction body for thermally changing the handwriting of thermochromic ink.

Background Art

[0002] In recent years, thermochromic writing instruments have become widely popular. A thermochromic writing instrument incorporates thermochromic ink. The handwriting of the thermochromic ink can be discolored or erased by heating. A thermochromic writing instrument is provided with a friction body that generates frictional heat for erasing or changing the color of the handwriting of the thermochromic ink. Note that "color change" of the thermochromic ink means a change from one color to another color. "Erasure" is a form of color change and means a change from a colored state to a colorless state.

[0003] For example, International Publication No. 2018 / 116767 discloses a writing instrument incorporating thermochromic ink with a metallic luster pigment added thereto. This thermochromic writing instrument is provided with a friction body containing a viscoelastic body. This friction body can chemically and physically erase the thermochromic ink with the metallic luster pigment added thereto. That is, the friction body containing the viscoelastic body erases the thermochromic ink by frictional heat and adsorbs the metallic luster pigment by viscoelasticity to peel it off from the paper surface. Thus, the friction body containing the viscoelastic body disclosed in International Publication No. 2018 / 116767 has both chemical erasability for erasing the thermochromic ink by frictional heat and physical erasability for peeling off the metallic luster pigment by viscoelasticity.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, a friction body containing a viscoelastic body has a problem that the amount of deformation of the friction body gradually increases due to the reciprocating motion (hereinafter referred to as "friction operation") when rubbing the handwriting of the thermochromic ink. That is, the viscoelastic body has a property that when a certain external force is applied, the amount of deformation increases with the passage of time. For this reason, the friction body containing the viscoelastic body gradually deforms greatly by repeating the friction operation. When the amount of deformation of the friction body increases, it may not be possible to generate the frictional heat necessary to change or erase the handwriting of the thermochromic ink.

[0006] On the other hand, if the force for causing the friction body to perform the friction operation is gradually reduced, the amount of deformation of the friction body can be kept constant. However, if the force for causing the friction body to perform the friction operation becomes too small, it may not be possible to generate the frictional heat necessary to change or erase the handwriting of the thermochromic ink. In particular, the elastic modulus of a friction body made of a synthetic resin depends on temperature. For this reason, when the temperature of the friction body itself rises due to frictional heat and when the friction body is used in a high-temperature environment, the friction body is more likely to deform greatly.

[0007] The present invention has been made to solve the above-described problems, and an object thereof is to provide a thermochromic writing instrument that can chemically and physically erase the handwriting of a thermochromic ink added with a metallic luster pigment and can cause the friction body to exhibit a desired frictional performance by suppressing the deformation of the friction body.

Means for Solving the Problems

[0008] (1) 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 the handwriting formed by the thermochromic ink by frictional heat. In the thermochromic ink, a metallic luster pigment is added. In the thermochromic writing instrument, a mounting hole for mounting the friction body is provided. The friction body includes a mounting portion inserted into the mounting hole and a convex curved surface-shaped friction portion protruding from the mounting hole. The volume Ve of the friction portion and the volume Vp of the metallic luster pigment satisfy 5 ≤ Ve / Vp ≤ 35. The maximum outer diameter D of the friction portion and the protruding length L satisfy 0.1 ≤ L / D ≤ 1.5. The material of the friction body has a value of the Shore A hardness measured in accordance with JIS K 7215 of the Japanese Industrial Standards in the range of 60 or more and 85 or less immediately after the start of the indenter contact, and a value (ΔHS) defined by the following formula of the Shore A hardness 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)

[0009] The friction body provided in the thermochromic writing instrument of the above (1) can chemically discolor or decolor the handwriting of the thermochromic ink by frictional heat, and can further physically peel off the metallic luster pigment added to the thermochromic ink. On the other hand, by setting ΔHS of the material of the friction body to less than 5, it becomes possible to give sufficient rigidity to the friction portion against the frictional operation. Thereby, the deformation of the friction portion during the frictional operation is suppressed, and the desired frictional performance can be exhibited by the friction portion.

[0010] (2) Preferably, in the thermochromic writing instrument of the above (1), the material of the friction body has a value (Tb × Eb) of the product 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 in the range of 5000 or more and 18000 or less.

[0011] By setting the value (Tb×Eb) of the tensile strength Tb and the elongation Eb at the time of cutting of the material of the friction body to be 5000 or more and 18000 or less, the friction body when the handwriting is rubbed generates an appropriate amount of wear debris. As a result, it becomes possible to attach and enclose the metallic luster pigment added to the thermochromic ink to the wear debris.

[0012] (3) Preferably, in the thermochromic writing instrument of the above (1) or (2), the mounting hole is provided so as to penetrate the rear end portion of the shaft cylinder or the top portion of the cap constituting the thermochromic writing instrument along the vertical central axis, has an inner peripheral 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 peripheral surface of the mounting hole, and an outward protrusion protruding toward the outside of the mounting portion is formed on the outer peripheral surface of the mounting portion. When the mounting portion is inserted into the mounting hole, the outward protrusion overrides the inward protrusion, so that the outward protrusion and the inward protrusion are locked to each other. The friction body is provided with a straight inner hole that opens at least at the lower end of the mounting portion along the vertical central axis. 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 inside. In a state where the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the core is held at a position corresponding to the inner peripheral surface of the mounting hole, so that the mounting portion is configured to be sandwiched between the outer peripheral surface of the core and the outward 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. As a result, the rigidity of the entire friction portion is increased, the deformation of the friction portion during the friction operation is suppressed, and it becomes possible to cause the friction portion to exhibit a desired frictional performance. In particular, even when the friction portion is formed of a material having a low hardness, a desired rigidity can be imparted to the entire friction portion. As a result, the handwriting of the thermochromic ink can be efficiently thermochromed. Further, the core is inserted into the inner hole of the friction body after locking the inward protrusion of the mounting hole and the outward protrusion of the mounting portion. As a result, the friction body can be easily attached to the thermochromic writing instrument without requiring a large force.

[0014] (4) Preferably, in the thermochromic writing instrument according to (3) above, in a state where the attachment portion is inserted into the attachment hole and the refill is inserted into the inner hole, the refill 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 refill 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, when the friction portion wears, the refill does not protrude from the friction portion and damage the paper surface.

[0016] (5) Preferably, in the thermochromic writing instrument according to (3) or (4) above, in a state where the attachment portion is inserted into the attachment hole and the refill is inserted into the inner hole, the lower end of the refill is at the same position as the lower end of the attachment portion or is located above the lower end of the attachment portion.

[0017] Since the lower end of the refill is at the same position as the lower end of the attachment portion or is located above the lower end of the attachment portion, the insertion of the refill into the friction body becomes easy and the assemblability is improved.

[0018] (6) Preferably, in the thermochromic writing instrument according to any one of (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 that does not open at the upper end of the friction portion. In the process of inserting the refill into the inner hole, a ventilation portion is provided in the refill to discharge the air in the inner hole.

[0019] In the process of inserting the refill into the inner hole, the air in the inner hole is not compressed by the refill and is discharged to the outside. Thereby, the insertion of the refill into the friction body becomes easy and the refill can be securely attached to the inner hole.

[0020] (7) Preferably, in the thermochromic writing instrument according to (6) above, the ventilation portion is a through hole that penetrates from one end to the other end of the refill along the longitudinal central axis of the refill.

[0021] In the process of inserting the refill into the inner hole, the air inside the inner hole is not compressed by the refill and is surely discharged to the outside through the through hole. As a result, the insertion of the refill into the friction body becomes easy, and the refill can be surely attached to the inner hole.

[0022] (8) Preferably, in the thermochromic writing instrument of the above (6), the vent portion is at least one groove or protrusion that extends continuously from one end to the other end of the refill along the outer peripheral surface of the refill.

[0023] In the process of inserting the refill into the inner hole, the groove or protrusion of the refill forms a gap between the outer peripheral surface of the refill and the inner peripheral surface of the inner hole. As a result, the air inside the inner hole is not compressed by the refill and is surely discharged to the outside through the gap formed by the groove or protrusion. As a result, the insertion of the refill into the friction body becomes easy, and the refill can be surely attached to the inner hole.

[0024] (9) Preferably, in the thermochromic writing instrument of any one of the above (3) to (8), the refill has a symmetric shape in the vertical direction.

[0025] Since the refill has a symmetric shape in the vertical direction, there is no distinction between the upper and lower parts of the refill. As a result, the refill can be inserted into the inner hole from either the upper or lower part of the refill, and the operation of inserting the refill into the inner hole becomes easy.

[0026] (10) Preferably, in the thermochromic writing instrument of any one of the above (3) to (9), a protrusion that contacts the inward inner peripheral surface is provided on the outer peripheral surface of the refill.

[0027] The protrusion provided on the outer peripheral surface of the refill firmly holds the refill inside the inner hole. As a result, it is possible to surely prevent the refill 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 including a thermochromic ink and a friction body for thermochromically changing the handwriting formed by the thermochromic ink by frictional heat. 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 inserted into the mounting hole and a friction portion having a convex curved surface shape protruding from the mounting hole. The material of the friction body has a value (Tb×Eb) of the product of the tensile strength Tb at break and the elongation Eb at break measured in accordance with JIS K 6251 of the Japanese Industrial Standards, which is 5000 or more and 18000 or less.

[0029] By setting the value (Tb×Eb) of the product of the tensile strength Tb at break and the elongation Eb at break of the material of the friction body to be 5000 or more and 18000 or less, the friction body when the handwriting is rubbed generates an appropriate amount of wear debris. Thereby, it becomes possible to adhere and enclose at least one of the fluorescent pigment, the phosphorescent pigment, and titanium dioxide added to the thermochromic ink to the wear debris.

Advantages of the Invention

[0030] The thermochromic writing instrument of the present invention enables chemically and physically erasing the handwriting of the thermochromic ink added with a metallic luster pigment, and by suppressing the deformation of the friction body, the friction body can exhibit a desired frictional performance.

[0031] Here, in this specification, "front" with respect to the thermochromic writing instrument means the direction of the pen tip, and "rear" with respect to the thermochromic writing instrument means the direction opposite to the pen tip. Also, "upper" with respect to the mounting hole means the direction of the rear end portion of the shaft cylinder or the direction of the top of the cap, and "lower" with respect to the mounting hole means the direction opposite to these. Further, "upper" with respect to the friction member means the direction of the friction portion, and "lower" with respect to the friction member means the direction of the mounting portion. In addition, unless otherwise specified, the content of a plurality of components constituting the composition described in this specification means the total amount of substances corresponding to each component. Also, the term "metallic luster pigment" widely includes pigments capable of imparting luster to the writing of the thermochromic ink. For example, both the transparent metallic luster pigment and the metal vapor deposition resin pigment are included in the term "metallic luster pigment".

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0033] Hereinafter, the thermochromic writing instrument according to the embodiment of the present invention will be described with reference to the drawings.

[0034] 1. Overview Figures 1 to 4 show the main part of the thermochromic writing instrument according to the first embodiment of the present invention. In Figures 1 to 4, the entire thermochromic writing instrument is not shown, and only the rear end portion of the shaft cylinder 1 constituting the thermochromic writing instrument is shown. The thermochromic writing instrument of the present embodiment includes a shaft cylinder 1, a friction member 3, and a refill 7. An attachment hole 2 is provided at the rear end portion of the shaft cylinder 1. A friction member 3 is attached to the attachment hole 2. An inner hole 31 is provided in the friction member 3 along the central axis in the longitudinal direction. The refill 7 is inserted into the inner hole 31.

[0035] 2. Attachment Hole As shown in Figure 1, an attachment hole 2 is provided at the rear end portion of the shaft cylinder 1. The attachment hole 2 penetrates the rear end portion of the shaft cylinder 1 along the central axis in the longitudinal direction. The attachment hole 2 has an inner peripheral surface between two openings located at the upper end and the lower end. An annular inward projection 21 is formed below the inner peripheral surface of the attachment hole 2. A guide surface 21a, which is an inverted conical tapered surface, is formed on the inner peripheral surface of the inward projection 21. The diameter of the guide surface 21a gradually decreases from top to bottom. The lower end of the guide surface 21a is continuous with the vertical inner peripheral surface of the minimum diameter portion 21b, which is the opening at the lower end of the attachment hole 2. The cross-sectional shape of the attachment hole 2 in the lateral direction is a circle with different diameters.

[0036] Here, the shaft cylinder 1 is manufactured by injection molding a synthetic resin (for example, polypropylene). The attachment hole 2 and the inward projection 21 are integrally formed at the rear end portion of the shaft cylinder 1 by injection molding. Note that the attachment hole 2 is not limited to the rear end portion of the shaft cylinder 1, and may be provided, for example, at the top of the cap constituting the thermochromic writing instrument.

[0037] 3. Friction Member As shown in Figure 1, the friction member 3 of the present embodiment has a configuration in which a mounting portion 5 (small diameter portion) having a smaller diameter than the friction portion 32 is integrally formed below the bullet-shaped friction portion 32 (large diameter portion 4). The friction portion 32 is used to thermally change the color of the thermochromic ink attached to the paper surface by frictional heat. Further, the friction portion 32 of the present embodiment has a function of adsorbing and peeling off the metallic luster pigment added to the thermochromic ink from the paper surface. The mounting portion 5 is used to attach the friction member 3 to the attachment hole 2 of the shaft cylinder 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 opening at the upper end 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 attached to 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 this embodiment has a maximum outer diameter D = 6.1, a protruding length L = 6.3, and L / D ≒ 1.0.

[0040] 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 can be inserted 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] On the outer peripheral surface of the outward protrusion 51, a guide surface 51a, which is an inverted conical tapered surface, is formed. 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 protrusion 51 is larger than the diameter of the minimum inner diameter portion 21b of the inward protrusion 21 of the mounting hole 2 described above, and smaller than the diameter of the opening at the upper end of the mounting hole 2. For example, the dimensional difference between the maximum outer diameter portion 51b and the minimum inner diameter portion 21b is within the range of 0.5 mm to 2.0 mm, preferably within the range of 0.5 mm to 1.0 mm. Due to such a dimensional difference, in the process of inserting the mounting portion 5 into the mounting hole 2, the outward protrusion 51 can smoothly pass through the inward protrusion 21, and the outward protrusion 51 and the inward protrusion 21 can be easily locked (see FIGS. 2 and 3).

[0044] The bulging portion 52 contacts the inner peripheral surface of the opening at the upper end of the mounting hole 2 when the mounting portion 5 is completely inserted into the mounting hole 2 (see FIG. 3). Thereby, the radial wobbling of the friction body 3 is suppressed. The diameter of the bulging portion 52 is substantially the same as the diameter of the opening at the upper end of the mounting hole 2. Also, the diameter of the bulging 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 protrusion 51.

[0045] The diameter of the cylindrical portion 53 is smaller than the diameter of the minimum inner diameter portion 21b of the inward protrusion 21 of the mounting hole 2 described above. The cylindrical portion 53 is for temporarily inserting the mounting portion 5 into the mounting hole 2. This temporarily inserted state is shown in FIG. 2. Such a cylindrical portion 53 facilitates the mounting operation of the friction body 3. That is, by dropping the friction body 3 toward the mounting hole 2, the temporarily inserted state shown in FIG. 2 can be achieved. Thereafter, by pushing the friction body 3 toward the mounting hole 2, the mounting portion 5 is completely inserted into the mounting hole 2, and at the same time, the outward protrusion 51 and the inward protrusion 21 are locked (see FIG. 3). Note that the outer peripheral surface below the outward protrusion 51 in the mounting portion 5 is not limited to the circumferential surface of the cylindrical portion 53, and may be, for example, an inverted conical tapered surface.

[0046] 3.3 Formation of an annular space The outer diameter of the intermediate portion of the mounting portion 5 (the portion between the bulging portion 52 and the outward protrusion 51) is smaller than the inner diameter of the vicinity of the entrance of the mounting hole 2 (the portion above the inward protrusion 21). Thereby, in the temporarily inserted state shown in FIG. 2, an annular space 6 is formed between the mounting portion 5 and the mounting hole 2. This annular space 6 prevents the intermediate portion of the mounting portion 5 from coming into pressure contact with the inner peripheral surface near the entrance of the mounting hole 2. That is, after the temporarily inserted state shown in FIG. 2, the outward protrusion 51 of the mounting portion 5 gets over the inward protrusion 21 of the mounting hole 2. At this time, when the outward protrusion 51 is strongly pressed against the inward protrusion 21, the intermediate portion of the mounting portion 5 is elastically deformed and bulges radially outward. If the intermediate portion of the mounting portion 5 comes into pressure contact with the inner peripheral surface near the entrance of the mounting hole 2, a frictional resistance that hinders the insertion of the mounting portion 5 will occur. The annular space 6 accommodates the intermediate portion of the mounting portion 5 that bulges radially outward, so that the intermediate portion of the mounting portion 5 does not come into pressure contact with the inner peripheral 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 protrusion 51 is slightly larger than the length B from the upper end of the mounting hole 2 to the lower end of the inward protrusion 21. As a result, the entire outward protrusion 51 can surely pass through the inward protrusion 21. That is, if the lengths A and B were the same, due to the frictional resistance generated between the outward protrusion 51 and the inward protrusion 21, it might occur that the upper end surface of the maximum outer diameter portion 51b of the outward protrusion 51 could not pass through the inward protrusion 21. By making the length A of the mounting portion 5 slightly larger than the length B of the mounting hole 2, even after the annular surface 41 of the large diameter portion 4 abuts against the rear end of the shaft cylinder 1, the entire outward protrusion 51 can pass through the inward protrusion 21. Thus, even when frictional resistance occurs between the outward protrusion 51 and the inward protrusion 21, the entire outward protrusion 51 can surely pass through the inward protrusion 21. Here, the dimensional difference between the lengths A and B appears as the clearance C between the outward protrusion 51 and the inward protrusion 21 shown in FIG. 3. The clearance C is preferably in the range of 0.05 mm to 1.0 mm, and more preferably in the range of 0.1 mm to 0.5 mm. With such a slight clearance C, the friction body 3 will not move in the direction of the central axis, nor will the locking between the outward protrusion 51 and the inward protrusion 21 become loose.

[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. The inner hole 31 of the present embodiment is a hole that reaches from the lower end of the mounting portion 5 to the center of the friction portion 32 and is blocked at one end that does not open at the upper end of the friction portion 32. The inner hole 31 is provided from the lower end of the mounting portion 5 to at least the position reaching the upper end of the outward protrusion 51. Such an inner hole 31 makes the outward protrusion 51 more likely to deform radially inward. Thereby, the outward protrusion 51 and the inward protrusion 21 can be easily locked. Further, a core 7 described later is inserted into the inner hole 31.

[0049] Here, the inner hole 31 of the present 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 were to open at the upper end of the friction portion 32, it would be impossible to friction the handwriting at the upper end of the friction portion 32, and the friction performance of the friction portion 32 would deteriorate.

[0050] Also, since the inner hole 31 does not open at the upper end of the friction portion 32, the rigidity of the friction portion 32 increases, and the friction performance of the friction portion 32 improves. Furthermore, when the friction body 3 is attached to the attachment hole 5, the deflection of the entire friction body 3 is suppressed, and the attachment work becomes easier.

[0051] 3.6 Hardness and Viscosity of the Friction Body The material constituting the friction body 3 is preferably a synthetic resin (rubber, elastomer) having elasticity. For example, silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butylene-styrene copolymer), fluororesin, chloroprene resin, nitrile resin, polyester resin, ethylene propylene diene rubber (EPDM), etc. can be mentioned.

[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 low hardness can enter into the recesses of the handwriting formed on the paper surface.

[0053] The hardness of the material of the friction body 3 is represented by, for example, the Shore A hardness value measured in accordance with the "Plastic Durometer Hardness Test Method" specified in JIS K 7215-1986 of the Japanese Industrial Standards. The durometer used for measuring the Shore A hardness value is provided with a pressing needle biased by a spring, and the amount of penetration of the pressing needle into the measurement object is displayed as the Shore A hardness value. The Shore A hardness value becomes smaller as the measurement object is softer and larger as the measurement object is harder.

[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) In addition, "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 that satisfies 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 that satisfies 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 the above ii) indicates the relaxation time of stress relaxation (time change of stress) when a certain strain is applied to the material of the friction body 3. The time of stress relaxation serves as a criterion for distinguishing whether the substance is an elastic body, a viscoelastic body, or a viscous body. It can be said that the material of the friction body 3 that satisfies the value of ΔHS in the above ii) is an elastic body with appropriate viscosity that can adsorb metallic luster pigments. On the other hand, a substance with a ΔHS value 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 amount of deformation when rubbing the handwriting of the thermochromic ink 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. Therefore, 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 greatly. Therefore, the value of ΔHS of the material of the friction body 3 is preferably 0 or more and less than 5. Here, the value of ΔHS in the above ii) can be arbitrarily set by the type and / or composition of one or more comonomers contained in the polymer material.

[0057] Note that the Shore A hardness value in the above i) and ii) may be the Shore D hardness value of the material of the friction body 3 measured by a test method conforming to JIS K 7215-1986, converted to the Shore A hardness value.

[0058] 3.7 Wear Amount of Friction Body In order to physically erase the metallic luster pigment added to the thermochromic ink from the paper surface, the friction body 3 preferably shaves by rubbing the paper surface to generate a small amount of wear debris (shavings). The friction body 3 removes the metallic luster pigment from the paper surface by adhering the metallic luster pigment to the wear debris while wearing itself and wrapping it.

[0059] The wear amount of the friction body 3 is represented by the tensile strength at break Tb and the elongation at break Eb calculated in accordance with, for example, "Vulcanized Rubber and Thermoplastic Rubber - Method for Determining 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 cut 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 cut and is expressed as a ratio (%) to the length of the measured object before the test.

[0060] The inventor has obtained the finding 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 rate of the material. By setting the tensile strength at break Tb and the elongation at break Eb to an appropriate combination of values, the wear amount of the friction body 3 can be controlled. The value of Tb×Eb represents the energy required to wear the friction body 3. Therefore, the value of Tb×Eb becomes smaller as the measured object is more likely to wear, and larger as the measured object is less likely to wear.

[0061] It is preferable that the value of Tb×Eb of the material of the friction body 3 calculated by the method compliant with JIS K 6251:2017 satisfies the following condition iii). iii) 5000≦Tb×Eb≦18000 Note that the unit of the tensile strength at break Tb in the above iii) is "MPa", and the unit of the elongation at break Eb is "%", but these may be converted to other units.

[0062] In the above iii), it is preferable that 8000≦Tb×Eb≦16000, and more preferably 10000≦Tb×Eb≦14000. When the material of the friction body 3 satisfies the condition of the above iii), the friction body 3 produces an appropriate amount of wear debris by normal frictional operation by human hands. As a result, it becomes possible to adhere and enclose the metallic luster pigment added to the thermochromic ink with the wear debris.

[0063] In the above (iii), when the value of Tb × Eb exceeds 18,000, it becomes difficult to wear the friction body 3 by a normal frictional operation by hand. For this reason, it is impossible to attach and wrap the metallic luster pigment to the wear debris while wearing the friction body 3.

[0064] On the other hand, in the above (iii), when the value of Tb × Eb is less than 5,000, the friction body 3 is easily shaved off by a normal frictional operation by hand. For this reason, the frictional heat generated by the friction body 3 is lost together with the wear debris, and it becomes difficult to efficiently thermochromically change the thermochromic ink.

[0065] 4. Core The core 7 is formed 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 of the present 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. By the outer peripheral surface of the core 7 coming into contact with the inner peripheral surface of the inner hole 31, the friction body 3 is firmly fixed to the mounting hole 2 of the shaft cylinder 1. As a result, the rigidity of the entire friction part 32 is increased, and deformation of the friction part 32 is suppressed. As a result, even when the hardness of the material of the friction body 3 is reduced, good frictional performance can be exhibited.

[0066] Further, by the outer peripheral surface of the core 7 coming into contact with the inner peripheral surface of the inner hole 31, the rigidity of the outward protrusion 51 provided on the mounting portion 5 of the friction body 3 is increased, and 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 friction body 3 is prevented from falling off from the mounting hole 2.

[0067] Furthermore, the outer peripheral surface of the core 7 preferably does not merely come into contact with the inner peripheral surface of the inner hole 31 but is press-contacted. In order to press-contact the outer peripheral surface of the core 7 with the inner peripheral surface of the inner hole 31, the outer diameter of the core 7 may be made larger than or equal to the inner diameter of the inner hole 31. By the outer peripheral surface of the core 7 being press-contacted with the inner peripheral surface of the inner hole 31, the rigidity of the friction part 32 and the outward protrusion 51 becomes higher, and the core 7 and the friction body 3 are more reliably prevented from falling off.

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

[0069] 4.1 Material of the core The core 7 is formed of a synthetic resin or metal harder than the friction body 3. As the synthetic resin, for example, polypropylene, polyethylene, polystyrene, polycarbonate, polyethylene terephthalate, polyacetal, acrylic, nylon, acrylonitrile-styrene copolymer resin (AS resin), acrylonitrile-butadiene-styrene copolymer resin (ABS resin), etc. can be used. Also, a rubber or elastomer harder than the friction body 3 may be used. As the rubber or elastomer, for example, silicone resin, SBS resin (styrene-butadiene-styrene copolymer), SEBS resin (styrene-ethylene-butylene-styrene copolymer), fluororesin, chloroprene resin, nitrile resin, polyester resin, ethylene propylene diene rubber (EPDM) can be used. The synthetic resin-made core 7 can be manufactured by cutting or injection molding. Further, as the metal, for example, aluminum alloy, stainless steel, brass, etc. can be used. On the other hand, the metal-made core 7 can be manufactured by, for example, cutting or plastic working.

[0070] 4.2 Shape of the core As shown in FIG. 4, the core 7 preferably has a shape symmetric about the horizontal central axis. By making the core 7 have a symmetric shape, the distinction between the upper and lower parts of the core 7 disappears, and it can be inserted into the inner hole 31 from either the upper or lower part of the core 7. On the contrary, the core 7 may have an asymmetric shape. For example, at least the edge part of the upper end of the core 7 may be chamfered to facilitate insertion into the inner hole 31.

[0071] 4.3 Ventilation part The inner hole 31 of this embodiment is a hole that opens at the lower end of the mounting portion 5 and is closed at one end without opening at the upper end of the friction portion 32. On the other hand, the core 7 is a small cylindrical component 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 end closed, the air in the inner hole 31 may be compressed by the core 7, and it may not be possible to smoothly insert the core 7 into the inner hole 31. Therefore, a ventilation portion 71 is provided in the core 7. The ventilation portion 71 of this embodiment is a through hole that penetrates from one end to the other end of the core 7 along the central axis in the longitudinal direction of the core 7. In the process of inserting the core 7 into the inner hole 31, the air in the inner hole 31 passes through the ventilation portion 71 and is discharged to the outside. Such a ventilation portion 71 facilitates the operation of inserting the core 7 into the inner hole 31, and it becomes possible to perform the insertion operation of the core 7 by an automatic assembly machine.

[0072] Note that the ventilation portion 71 is not limited to the configuration shown in FIG. 4. For example, the cross-sectional shape of the ventilation portion 71 is not limited to a circular shape, and may be a shape other than a circular shape. Also, the ventilation portion 71 may be provided so as to be shifted from the central axis of the core 7. Furthermore, the ventilation portion 71 is not limited to a through hole, and for example, it may be at least one groove or protrusion provided on the outer peripheral surface of the core 7. Also, for example, the ventilation portion 71 may be a spiral groove or protrusion provided along the outer peripheral surface of the core 7. The spiral groove or protrusion has an anti-slip effect of preventing the core 7 from falling off from the inner hole 31. Furthermore, instead of providing the ventilation portion 71 in the core 7, the above-described groove or protrusion may be provided on the inner peripheral surface of the inner hole 31.

[0073] 4.4 Upper core portion and lower core portion 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, preventing the friction body 3 from falling off.

[0074] 4.5 Retaining 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, the guide surface 51a of the mounting portion 5 abuts against the guide surface 21a of the mounting hole 2, thereby stably maintaining the temporarily inserted state of the mounting portion 5.

[0077] Next, the friction member 3 in the temporarily inserted state is pushed into the mounting hole 2. Then, the outward protrusion 51 of the mounting portion 5 gets over the inward protrusion 21 of the mounting hole 2. At this time, since the outward protrusion 51 is strongly pressed against the inward protrusion 21, the intermediate portion of the mounting portion 5 is elastically deformed and bulges radially outward. The intermediate portion of the mounting portion 5 that has bulged radially outward is accommodated in the annular space 6 in the mounting hole 2. Thereby, the intermediate portion of the mounting portion 5 does not press against the inner peripheral 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 through the inward protrusion 21, and the outward protrusion 51 and the inward protrusion 21 are locked. Thereby, the insertion of the mounting portion 5 into the mounting hole 2 is completed (see FIG. 3).

[0078] Thereafter, as shown in FIG. 4, the core 7 is inserted into the inner hole 31 of the friction member 3. In the process of inserting the core 7 into the inner hole 31, the air in the inner hole 31 is discharged to the outside through the ventilation portion 71. With such a ventilation portion 71, the core 7 can be easily inserted into the inner hole 31. The core 7 inserted into the inner hole 31 presses the mounting portion 5 outward, strengthening the locking between the outward protrusion 51 and the inward protrusion 21. Thereby, the attachment of the friction member 3 to the rear end portion of the shaft cylinder 1 is completed.

[0079] According to such an attachment method of the friction member 3 of the present embodiment, before the core 7 is inserted into the inner hole 31, the highly flexible mounting portion 5 can be inserted into the mounting hole 2, and the outward protrusion 51 and the inward protrusion 21 can be easily locked. Thereafter, by inserting the core 7 into the inner hole 31, a force in the inner and outer directions acts on the mounting portion 5, and the locking between the outward protrusion 51 and the inward protrusion 21 is firmly maintained. Further, since the core 7 is inserted into the inner hole 31 after the mounting portion 5 is inserted into the mounting hole 2, a large force is not required for the attachment work of the friction member 3 shown in FIGS. 1 to 4.

[0080] 6. Thermochromic Ink The thermochromic ink incorporated in the thermochromic writing instrument of the present embodiment may be any of aqueous ink, oil-based ink, or gel ink as long as it can form thermochromic handwriting. Further, the form of the thermochromic ink is not limited to a liquid, and may be a solid such as a pencil lead, for example. Hereinafter, the thermochromic ink will be described in detail.

[0081] As the thermochromic ink incorporated in the thermochromic writing instrument, those that change color or fade by heating are applied. As the colorant added to the thermochromic ink, it is preferable to use a reversible thermochromic composition containing an electron-donating color-developing organic compound, an electron-accepting compound, and a reaction medium for determining the color-developing temperature of the color reaction of these compounds. In particular, a microcapsule pigment having a structure in which the reversible thermochromic composition is encapsulated in microcapsules is more preferable.

[0082] Examples of the first reversible thermochromic composition include those described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, and Japanese Patent Publication No. 1-29398. The reversible thermochromic compositions described in these publications have a color change point on each of the high-temperature side and the low-temperature side. The color change point refers to a predetermined temperature that serves as the boundary at which color change occurs. The first reversible thermochromic composition becomes a faded state in a temperature range equal to or higher than the high-temperature side color change point and a colored state in a temperature range equal to or lower than the low-temperature side color change point. At room temperature, either the faded state or the colored state is maintained. The other state is maintained only while the temperature of the high-temperature side color change point or the low-temperature side color change point is reached. When the temperature is not the temperature of the high-temperature side color change point or the low-temperature side color change point, it returns to one state. That is, the first reversible thermochromic composition has a relatively small width ΔH of the hysteresis characteristic (for example, 1 °C or more and 7 °C or less for ΔH).

[0083] As the second reversible thermochromic composition, for example, in Japanese Patent Publication No. 4-17154, Japanese Patent Application Laid-Open No. 7-179777, Japanese Patent Application Laid-Open No. 7-33997, Japanese Patent Application Laid-Open No. 8-39936, Japanese Patent Application Laid-Open No. 2006-137886, Japanese Patent Application Laid-Open No. 2006-188660, Japanese Patent Application Laid-Open No. 2008-45062, and Japanese Patent Application Laid-Open No. 2008-280523, reversible thermochromic compositions with a large width ΔH of the hysteresis characteristic are described (for example, the ΔH value is 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 the curve obtained by plotting the color density and temperature of the reversible thermochromic composition. For example, assume that the reversible thermochromic composition becomes completely decolorized in the temperature range above the high-temperature-side color change point and becomes completely colored in the temperature range below the low-temperature-side color change point. The temperature at which it becomes completely decolorized is called the "complete decolorization temperature," and the temperature at which it becomes completely colored is called the "complete coloration temperature." In the curve obtained by plotting the color density and temperature of this reversible thermochromic composition, when the path of the curve from the complete decolorization temperature on the low-temperature side to the complete coloration temperature on the high-temperature side and the path of the curve from the complete coloration temperature on the high-temperature side to the complete decolorization temperature on the low-temperature side are significantly different, the width ΔH of the hysteresis characteristic becomes large. Furthermore, such a reversible thermochromic composition has color memory properties for maintaining the colored state or decolorized state in a specific temperature range, for example, at room temperature (the daily life temperature range).

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

[0086] By encapsulating the above-described reversible thermochromic composition in microcapsules, a heat-decoloring type microcapsule pigment can be produced. The average particle diameter of the microcapsule pigment is, for example, in the range of 0.05 μm or more and 5.0 μm or less, preferably 0.1 μm or more and 4.0 μm or less, and more preferably 0.5 μm or more and 3.0 μm or less. Thereby, the writing performance and the handwriting density of the thermochromic writing instrument become good. Further, when the average particle diameter of the microcapsule pigment is 2.0 μm or more, not only can the handwriting of the thermochromic ink be chemically decolored, but also physically erased from the paper surface. That is, the microcapsule pigment having an average particle diameter of 2.0 μm or more is physically peeled off from the paper surface and irreversibly erased by being adsorbed to a friction body.

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

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

[0089] Furthermore, as a coloring component, general dyes and pigments that do not have thermochromic properties may be added. By doing so, it is possible to give a desired color that does not thermochromically change to the handwriting of the thermochromic ink. As general dyes, for example, acid dyes, basic dyes, direct dyes, etc. can be used. As general pigments, for example, inorganic pigments such as carbon black and ultramarine blue, organic pigments such as copper phthalocyanine blue and benzidine yellow, and in addition, a dispersed pigment product that has been finely and stably dispersed in a medium using a surfactant in advance can be used. In addition, metallic luster pigments such as metal powders and pearl pigments, fluorescent pigments, phosphorescent pigments, and special pigments such as titanium dioxide can also be used. Note that these coloring components may be used in combination with the above-described 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 handwriting with brilliance is formed. Preferably, a transparent metallic luster pigment may be added to the thermochromic ink. The transparent metallic luster pigment gives brilliance to the handwriting of the thermochromic ink and, when the handwriting of the thermochromic ink is chemically erased, is visually perceived as being completely erased without brilliance.

[0091] As the transparent metallic luster pigment, a brilliant pigment in which a core substance is coated with a metal oxide or a cholesteric liquid crystal type brilliant pigment may be used. As the core substance, for example, a material selected from natural mica, synthetic mica, flat glass pieces, flaky aluminum oxide, etc. can be used.

[0092] As a brilliant pigment having natural mica as a core substance, those having titanium oxide coated on its surface and those having iron oxide or a non-thermochromic dye or pigment coated on the upper layer of the titanium oxide are effective. As a brilliant pigment having natural mica as a core substance, for example, products with the trade names "Iriodin (registered trademark)" manufactured by Merck KGaA and "Lumina (registered trademark)" manufactured by BASF SE can be used.

[0093] For a brilliant pigment with synthetic mica as the core material, it is effective to coat its surface with a metal oxide such as titanium oxide. As the metal oxide, for example, oxides of titanium, zirconium, chromium, vanadium, iron, etc. can be used, and a metal oxide mainly composed of titanium oxide is preferred. As a brilliant pigment with the surface of synthetic mica coated with a metal oxide, for example, the product named "ULTIMICA (registered trademark)" manufactured by Nippon Kogaku Kogyo Co., Ltd. can be used.

[0094] For a brilliant pigment with flat glass flakes as the core material, it is effective to coat its surface with a metal oxide such as titanium oxide. As a brilliant pigment with the surface of flat glass flakes coated with a metal oxide, for example, the product named "Metashine (registered trademark)" manufactured by Nippon Sheet Glass Co., Ltd. can be used.

[0095] For a brilliant pigment with flaky aluminum oxide as the core material, it is effective to coat its surface with a metal oxide such as titanium oxide. As the metal oxide, for example, oxides of titanium, zirconium, chromium, vanadium, iron, etc. can be used, and a metal oxide mainly composed of titanium oxide is preferred. As a brilliant pigment with the surface of flaky aluminum oxide coated with a metal oxide, for example, the product named "Xirallic (registered trademark)" manufactured by Merck KGaA can be used.

[0096] The liquid crystal polymer used as a cholesteric liquid crystal type brilliant pigment has the property of reflecting light in a part of the region of the light incident in a wide spectral region and transmitting all the light in other regions due to the light interference effect. The cholesteric liquid crystal type brilliant pigment has excellent metallic luster, color floppiness in which the hue changes depending on the viewing angle, and transparency. As the cholesteric liquid crystal type brilliant pigment, for example, the product named "HELICONE (registered trademark) HC" manufactured by Wacker Chemie AG can be used.

[0097] Also, a luminescent material manufactured by a vacuum deposition method can be used. This luminescent 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 from the film and finely pulverizing it. As such a luminescent material, the product name "LG neo (registered trademark)" manufactured by Oike Kogyo Co., Ltd. can be used.

[0098] The average particle diameter of the above-described metallic luster pigment is in the range of 0.1 μm or more and 50 μm or less, preferably 2 μm or more and 40 μm or less, and more preferably 10 μm or more and 40 μm or less. Thereby, the writing performance and the handwriting luminance of the thermochromic writing instrument become good. As a method for measuring the average particle diameter 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 based on the measured value of this particle size distribution, the average particle diameter (median diameter) is calculated on a volume basis.

[0099] 6.2 Physical Erasure of Metallic Luster Pigment The metallic luster pigment is difficult to penetrate into the paper surface. Therefore, by rubbing the handwriting of the thermochromic ink added with the metallic luster pigment, the metallic luster pigment scatters on the paper surface, and the appearance after erasing the handwriting deteriorates. In particular, on black paper, since the luster of the metallic luster pigment is emphasized, the appearance after erasing the handwriting becomes even worse.

[0100] Therefore, the material of the friction body 3 of the present embodiment satisfies the condition that the Shore A hardness value immediately after the start of the needle contact in the above i) is 60 or more and 85 or less. Thereby, the friction body 3 can enter into the recesses of the handwriting formed on the paper surface. Further, the material of the friction body 3 of the present embodiment satisfies the condition that the value of ΔHS in the above ii) is 0 or more and less than 5. Thereby, the friction body 3 can adsorb and peel off the metallic luster pigment from the recesses of the handwriting. That is, according to the friction body 3 of the present embodiment, it is possible to physically erase the metallic luster pigment added to the thermochromic ink without scattering it on the paper surface. Further, 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 condition of the following 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 luster. Also, the volume Ve of the friction portion 32 indicates the amount of the friction portion 32 that physically erases the metallic luster pigment by abrasion. By setting the value of Ve / Vp within the range of 5 or more and 35 or less, the balance 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 is maintained. That is, when Ve / Vp is 35, which is the upper limit value, the metallic luster pigment is the minimum amount that gives the handwriting a visible luster. In this case, the friction portion 32 is the maximum amount that can completely erase the minimum amount of the metallic luster pigment. On the other hand, when Ve / Vp is 5, which is the lower limit value, the metallic luster pigment is the maximum amount that gives the handwriting a higher luster. In this case, the friction portion 32 is the minimum amount that can erase 30% of the maximum amount of the metallic luster pigment. The value of Ve / Vp is preferably 8 or more and 26 or less, and more preferably 10 or more and 20 or less.

[0103] 6.3 Other Additives Various conventionally known additives may be added to the thermochromic ink. When the thermochromic ink is aqueous, for example, a pH adjuster, a rust inhibitor, a preservative, a fungicide, a wetting agent, an antifoaming agent, a surfactant, a lubricant, a fixing agent such as a resin, a shear thinning viscosity imparting agent, a pen tip drying inhibitor, a sagging inhibitor, etc. may be added. Also, when the thermochromic ink is oily, for example, a viscosity regulator, a preservative, a rust inhibitor, an antifoaming agent, a lubricant, a dispersant, a scuffing inhibitor, a leakage inhibitor, a surfactant, etc. may be added.

[0104] 7. Thermochromic Writing Instrument 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, etc. Further, the thermochromic writing instrument may have either a cap type or a retractable type configuration. The cap type thermochromic writing instrument is provided with a cap for covering the pen tip (tip). Further, the retractable type thermochromic writing instrument is provided with a retractable mechanism configured to be able to bring the pen tip into a protruding state from the shaft cylinder and a retracted state in which the pen tip is housed in the shaft cylinder. The retractable mechanism may be, for example, any of a knock type, a rotary type, a slide type, etc. Further, the retractable type thermochromic writing instrument may be configured to include two or more refills and be able to selectively bring any one of the two or more refills into a protruding state. In this case, the two or more refills may be configured to have different types of pen tips and / or thermochromic inks of different colors from each other.

[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, etc. The thermochromic ink used in the marking pen may be impregnated in an ink absorber made of a fiber bundle. The ink absorber is housed in the shaft cylinder. The thermochromic ink impregnated in the ink absorber is supplied to the pen tip. Further, the thermochromic ink used in the marking pen may be directly housed in the shaft cylinder. In this case, the shaft cylinder is provided with a comb groove or an ink flow rate adjusting member made of a fiber bundle. The thermochromic ink directly housed in the shaft cylinder is supplied to the pen tip via the ink flow rate adjusting member. Instead of the ink flow rate adjusting member, the shaft cylinder may be provided with a valve mechanism for supplying a predetermined amount of ink to the pen tip.

[0106] The thermochromic ink used in a ballpoint pen is filled, for example, in an ink storage tube with a ballpoint pen tip attached to its tip. In this case, an ink backflow preventer is disposed at the rear end of the thermochromic ink in the ink storage tube. Further, the thermochromic ink used in a ballpoint pen may be directly stored in a barrel. In this case, an ink backflow preventer is disposed at the rear end of the thermochromic ink in the barrel. Furthermore, the thermochromic ink used in a ballpoint pen may be impregnated in an ink storage body made of a fiber bundle. The barrel may be provided with an ink flow rate regulating member made of a comb groove or a fiber bundle. A predetermined amount of thermochromic ink is supplied to the pen tip through the ink flow rate regulating member.

[0107] In the various types of thermochromic writing instruments described above, the friction member 3 of the present embodiment is attached to any of the components constituting the thermochromic writing instrument, thereby being integrated with the thermochromic writing instrument (see FIG. 5). For example, the friction member 3 is attached to a cap, a clip, a crown, a mouthpiece, a barrel, a tail plug, a grip, and an operation portion for protruding and retracting the pen tip, which constitute the thermochromic writing instrument. The friction portion 32 may be covered with a cover for preventing dirt.

[0108] Note that the friction member 3 of the present embodiment may not be attached to any of the components constituting the thermochromic writing instrument and may be a separate item from the thermochromic writing instrument (see FIG. 6). The separate friction member 3 may be formed of only the above-described low-hardness synthetic resin material. Further, the separate friction member 3 may be configured to be attached to another component formed of a high-hardness material.

[0109] 8. Operational 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 instrument of the present invention will be described with reference to FIGS. 5 and 6. In the first and second embodiments described below, the numerical values indicating the content of the composition represent parts by mass. The average particle diameter of the thermochromic pigment was measured using a particle size distribution measuring device "Multisizer (registered trademark) 4e" manufactured by Beckman Coulter, Inc. By the Coulter method, the equivalent volume sphere diameter of the thermochromic pigment was measured, and the average particle diameter was calculated from this measured value. The average particle diameter 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 based on this measured value, the average particle diameter (median diameter) was calculated on a volume basis. The Shore A hardness of the material of the friction body was measured by a test method conforming to JIS K 7215 of Japanese Industrial Standards. A sample having a predetermined shape, thickness, and size was prepared from the same material as the friction body. The Shore A hardness was measured by pressing this sample with a manual durometer.

[0114] ·First Embodiment In the first embodiment, the thermochromic writing instrument 103 of the second embodiment shown in FIG. 5 was used. A friction body 101 is attached to the rear end of the shaft cylinder 182 of the thermochromic writing instrument 103.

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

[0116] The tensile strength at break Tb and the elongation at break Eb of the polyester-based 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 × Eb of the polyester-based elastomer is 12460.

[0117] By injection molding the above-mentioned polyester-based elastomer, a milky white friction body 101 having the shape shown in FIG. 5 was obtained. The friction body 101 includes a convex curved surface-shaped friction portion 111 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 frictional operation becomes stable and it becomes easier to friction the handwriting on the paper surface.

[0118] The attachment portion 112 of the friction body 101 is inserted into an attachment hole 181 provided at the rear end of the shaft cylinder 182. Two ring beads are formed on the inner peripheral surface of the attachment hole 181. The attachment portion 112 is sandwiched between the two ring beads within the attachment hole 181. Further, the locking portion of the attachment portion 112 is locked to the lower end of the attachment hole 181. The maximum outer diameter D of the friction portion 111 is 6, and the protruding length L from the attachment hole 181 is also 6. Therefore, the value of L / D 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 becomes a protruding state or a retracted state by sliding the operation portion 184 forward. The operation portion 184 protrudes outward from the side surface of the shaft cylinder 182. Inside the shaft cylinder 182, a retracting mechanism for retracting and protruding the pen tip 105 is accommodated. The retracting mechanism mainly includes a sliding body 182a, 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 shaft cylinder 182.

[0120] The shaft cylinder 182 is composed of a front shaft 182b and a rear shaft 182a. An opening 182c is provided at the tip of the front shaft 182b. The opening 182c has a diameter that allows the pen tip 105 of the refill 104 to protrude or retract. The rear shaft 182a is screwed to the rear end of the front shaft 182b. The above-described protruding and retracting mechanism is housed inside the rear shaft 182b. To accommodate the sliding body 184a integrally formed with the operation part 184, the rear shaft 182a is composed of first and second parts that can be divided 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 shaft 182a. When the sliding body 184a is housed inside the rear shaft 182a, the operation part 184 protrudes outside from the slide hole.

[0121] The sliding body 184a is a substantially cylindrical resin molded product integrally formed with the operation part 184. A plurality of serrated convex parts are formed at the tip of the sliding body 184a. A refill holding part 185 is arranged in front of the sliding body 184a inside the rear shaft 182a. The refill holding part 185 is a substantially cylindrical resin molded product that fits onto the rear end of the refill 104. A plurality of stepped parts are formed at the rear end of the refill holding part 185. The plurality of stepped parts engage with the serrated convex parts of the sliding body 184a. Further, a plurality of ribs extending in the axial direction are formed at equal intervals on the outer peripheral surface of the refill holding part 185. On the other hand, a plurality of groove parts 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 groove parts guide the plurality of ribs of the refill holding part 185 in the axial direction.

[0122] The front end part of the refill holding part 185 has a smaller outer diameter than the other parts and is inserted into the rear end part of the coil spring 183. The front end part 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 part 185 and the refill 104 rearward.

[0123] When the operation unit 184 is slid forward in the immersed state of the pen tip 105, a plurality of ribs of the refill holding part 185 are guided by a plurality of grooves in the rear shaft 182a, and the refill holding part 185 moves forward. When the plurality of ribs pass through the plurality of grooves, the serrated convex part of the sliding body 184a meshes with the stepped part of the refill holding part 185, and the refill holding part 185 is rotated by a predetermined angle. As a result, the end surfaces of the plurality of ribs contact the end surfaces of the plurality of grooves, and the refill holding part 185 is fixed in the state of moving forward. As a result, the pen tip 105 of the refill 104 is maintained in a state of protruding from the opening 182c of the front shaft 182b.

[0124] When the operation unit 184 is slid forward in the protruding state of the pen tip 105, the serrated convex part of the sliding body 184a meshes with the stepped part of the refill holding part 185, and the refill holding part 185 is rotated by a predetermined angle. As a result, the contact between the end surfaces of the plurality of ribs and the end surfaces of the plurality of grooves is released, and the plurality of ribs of the refill holding part 185 are guided by the plurality of grooves in the rear shaft 182a. The refill holding part 185 moves backward by the biasing force of the coil spring 183. As a result, the pen tip 105 of the refill 104 is in a state of being immersed in the opening 182c of the front shaft 182b.

[0125] The refill 104 is composed of a pen tip 105, an ink storage cylinder 106, and a connecting member 107. A ball is rotatably held at the front end of the pen tip 105. The ink storage cylinder 106 is a metal pipe with openings at the front end and the rear end. The connecting member 107 is formed of a transparent synthetic resin. The pen tip 105 is connected to the opening at the front end of the ink storage cylinder 106 via the connecting member 107. A thermochromic ink composition 161 and an ink follower composition 162 are accommodated 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 viscosity imparting agent (0.3 parts), urea (10 parts), glycerin (10 parts), a nonionic penetrability imparting agent (0.6 parts), a hydrophobic silica-based defoaming agent (0.1 part), a preservative (0.1 part), and water (62.9 parts).

[0127] The reversible thermochromic pigment has a structure in which a reversible thermochromic composition that changes color from pink to colorless is encapsulated in microcapsules. The color development temperature of the reversible thermochromic pigment is -10°C, the color fading temperature is 65°C, and the average particle diameter is 2.5 μm.

[0128] As the transparent metallic luster pigment, the product named "Iriodin® 6103 Icy White" manufactured by Merck KGaA was used. This transparent metallic luster pigment consists of silver-colored particles with the surface of synthetic mica coated with metal oxides. The average particle diameter of the transparent metallic luster pigment is 25 μm. As the metal vapor-deposited resin pigment, the product named "LG neo® Silver #325" manufactured by Oike Kogyo Co., Ltd. was used. The color of the particles of this metal vapor-deposited resin pigment is silver, and the average particle diameter is 35 μm. The value of 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-deposited resin pigment is 15.

[0129] Xanthan gum was used as the shear-thinning viscosity-imparting agent. As the nonionic penetrant, the product named "SN Wet 366" manufactured by Sannopco Ltd. was used. As the hydrophobic silica-based antifoaming agent, the product named "Nopco 8034" manufactured by Sannopco Ltd. was used. As the preservative, the product named "Proxel® XL2" manufactured by Lonza Japan Ltd. was used.

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

[0131] Using the thermochromic writing instrument 103, a handwriting of the thermochromic ink composition 161 was formed on the paper surface of "Writing Paper A" (100% chemical pulp, whiteness 75.0 or more) conforming to JIS P3201 of Japanese Industrial Standards. A pink thermochromic pigment serves as the base of the handwriting, and a silver transparent metallic luster pigment and a metal vapor-deposited resin pigment are dispersed in this handwriting. As a result, the handwriting of the thermochromic ink composition 161 exhibits a metallic pink color on the white paper surface. Also, 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 in the case of the white paper surface. However, the glossiness of the handwriting formed on the black paper surface was particularly higher than that in the case of the white paper surface.

[0132] Each of 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 instrument 103. That is, the friction part 111 repeatedly frictions the handwriting formed on the paper surface. Then, the friction part 111 generates frictional heat, and the thermochromic pigment in the handwriting changes from pink to colorless and transparent. Also, the friction part 111 with low hardness enters into the recesses of the handwriting, adsorbs the silver transparent metallic luster pigment and the metal vapor-deposited resin pigment, and peels off from the paper surface. Furthermore, the transparent metallic luster pigment and the metal vapor-deposited resin pigment adsorbed by the friction part 111 are wrapped by the wear debris of the friction part 111 and completely removed from the paper surface. In this way, the friction body 101 erases the handwriting of the thermochromic ink composition 161 cleanly without soiling the paper surface. In particular, there is a problem that the metallic luster pigment and the metal vapor-deposited resin pigment remaining on the black paper shine depending on the viewing angle and are recognized visually. This problem is solved by using the friction body 101.

[0133] Table 1 below shows the results of the evaluation tests of the friction members of Examples 1 to 4 and Comparative Examples 1 to 4. The friction members of Examples 1 to 4 all satisfy the conditions regarding the Shore A hardness and Ve / Vp of the present invention. The friction members of Comparative Examples 1 to 4 do not satisfy any one of the conditions regarding the Shore A hardness and Ve / Vp of the present invention. Each of the friction members of Examples 1 to 4 and Comparative Examples 1 to 4 has the same shape as the friction member 101 shown in FIG. 5 and is attached to the rear end of the shaft cylinder 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 composed of the above-described components. The pen tip 105 of the refill 104 is a ball pen tip.

[0134]

Table 1

[0135] The friction members of Examples 1 to 4 are all made of a polyester-based elastomer. By mixing polyester-based elastomers with different hardnesses, the hardnesses of the friction members of Examples 1 to 4 were made different from each other. The friction members of Examples 1 to 4 all satisfy the conditions of the present invention that the value of the needle penetration contact start of the Shore A hardness is 60 or more and 85 or less, the value of ΔHS is 0 or more and less than 5, and the value of Ve / Vp is 5 or more and 35 or less.

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

[0137] The friction member of Comparative Example 2 is composed of 40% of an α-olefin copolymer, 40% of a styrene-based elastomer, and 20% of crystalline polypropylene. The friction member of Comparative Example 2 has a value of 90 for the needle penetration contact start of the Shore A hardness and a value of 18 for ΔHS. In these respects, the friction member of Comparative Example 2 does not satisfy the conditions of the present invention that the value of the needle penetration contact start of the Shore A hardness is 60 or more and 85 or less and the value of ΔHS is 0 or more and less than 5.

[0138] The friction member of Comparative Example 3 is made of a styrene-based elastomer (trade name "AR-885C" of Aron Kasei Co., Ltd.). The friction member of Comparative Example 3 has a value of 88 for the Shore A hardness immediately after the start of indenter contact. In this regard, the friction member of Comparative Example 3 does not satisfy the condition of the present invention that the value of the Shore A hardness immediately after the start of indenter contact is 60 or more and 85 or less.

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

[0140] Using each of the friction members of Examples 1 to 4 and Comparative Examples 1 to 4, the erasability, wear debris, continuous erasability, and erasable amount described below were evaluated by erasing the writing of the thermochromic writing instrument 103.

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

[0142] The evaluation of erasability in Table 1 is as follows. A: The writing was erased without any remaining 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 above-mentioned erasability evaluation, after erasing 10 spiral patterns formed on the paper surfaces of white paper and black paper respectively using the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4, the state of wear debris generated from each friction body was visually confirmed.

[0144] The evaluation of wear debris in Table 1 is as follows. A: There was no problem in practical use. B: Wear debris adhered to the friction body, and there was a problem in practical use. C: A large amount of wear debris was generated, and there was a problem in 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 more) conforming to JIS P3201 of Japanese Industrial Standards. The thickness of the white paper was 0.09 mm and the basis weight was 80 g / m 2 . Using the thermochromic writing instrument 103, the handwriting of the thermochromic ink composition 161 was formed on the paper surface of the white paper. The handwriting was in the form of a circular spiral pattern. A total of 300 spiral patterns, 10 for each of 30 lines on one paper surface, were handwritten. Then, using the friction bodies of Examples 1 to 4 and Comparative Examples 1 to 4 respectively, the spiral patterns for 30 lines formed on the paper surfaces of each of the eight sheets of white paper were continuously erased. In the process of erasing the spiral patterns for 30 lines, it was confirmed how many lines the friction performance immediately after the start of erasing of the friction body was maintained. In such an evaluation of continuous erasability, the erasability of the metallic luster pigment and the state of wear debris were not considered.

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

[0147] <Evaluation of erasable amount> In the evaluation of the continuous erasability described above, for each of the friction members of Examples 1 to 4 and Comparative Examples 1 to 4, all 30 lines of the spiral pattern were 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 can be erased until all the friction portions of the friction members of Examples 1 to 4 and Comparative Examples 1 to 4 are 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 of one refill, and there is no problem with practicality. C: It is not possible to erase 30% or more of the ink weight of one refill, and there is a problem with practicality.

[0149] ·Second Example In the second example, 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 a support body 202 made of a hard PP resin (polypropylene). The portion of the friction body 201 protruding from the tip of the support body 202 serves as the friction portion 211. The friction portion 211 is used to chemically and physically erase a thermochromic ink to which a metallic luster pigment has been added. The cross-sections of both the friction body 201 and the support body 202 are elliptical. Seven friction bodies 201 were injection-molded using the same materials as in 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 instrument 203 are the same as those in the first embodiment described above. 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-deposited resin pigment (2 parts), a shear-thinning viscosity-imparting agent (0.3 parts), urea (10 parts), glycerin (10 parts), a nonionic penetrability-imparting agent (0.6 parts), a hydrophobic silica-based antifoaming agent (0.1 parts), a preservative (0.1 parts), and water (62.9 parts).

[0152] However, the reversible thermochromic pigment has a structure in which a reversible thermochromic composition that changes color from blue to colorless is encapsulated in microcapsules. Also, as the transparent metallic luster pigment, the product name "Iriodin (registered trademark) 6107 Icy White Lightning" manufactured by Merck KGaA was used. This transparent metallic pigment is composed of silver-colored particles with an average particle diameter of 25 μm.

[0153] Similar to the first embodiment described above, the thermochromic ink composition 161 is housed in the refill 104 of the thermochromic writing instrument 203. The pen tip of the refill 104 is a ball pen tip. By sliding the operation portion 184 forward, the pen tip 105 of the refill 104 becomes either a protruding state or a retracted state.

[0154] Using the thermochromic writing instrument 203, the handwriting of the thermochromic ink composition 161 was formed on the paper surface of "Writing Paper A" (100% chemical pulp, whiteness of 75.0 or more) conforming to JIS P3201 of the Japanese Industrial Standards. A blue thermochromic pigment serves as the base of the handwriting, and a silver transparent metallic luster pigment and a metal vapor-deposited resin pigment are dispersed in this handwriting. As a result, the handwriting of the thermochromic ink composition 161 exhibits a metallic blue color on the white paper surface. Also, the 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 in the case of the white paper surface. However, the glossiness of the handwriting formed on the black paper surface was particularly higher than in the case of the white paper surface.

[0155] As described above, seven friction members 201 were injection-molded using the same materials as in Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1. By combining each of the seven friction members 201 with the thermochromic writing instrument 203, seven writing sets 209 were configured. Using each of the seven writing sets 209, erasability, wear debris, continuous erasability, and erasable amount were evaluated. The results of the evaluation were the same as in Examples 1 to 4 and Comparative Examples 1 to 3 in Table 1.

[0156] All four friction members 201 made of the same materials as in Examples 1 to 4 in Table 1 had good results in the erasability test. The friction part 211 repeatedly rubs the handwriting of the thermochromic ink composition 161. Then, the friction part 211 generates frictional heat, and the thermochromic pigment in the handwriting changes from blue to colorless and transparent. Also, the friction part 211 with low hardness enters into the indentation of the handwriting, adsorbs the silver transparent metallic luster pigment and the metal vapor-deposited resin pigment, and peels off from the paper surface. Furthermore, the transparent metallic luster pigment and the metal vapor-deposited resin pigment adsorbed by the friction part 211 are wrapped in the wear debris of the friction part 211 and completely removed from the paper surface. In this way, the friction member 201 can cleanly erase the handwriting of the thermochromic ink composition 161 without soiling the paper surface. In particular, there is a problem that the transparent metallic luster pigment and the metal vapor-deposited resin pigment remaining on the black paper shine depending on the viewing angle and are visually recognized. This problem is solved by using the friction member 201.

Explanation of Signs

[0157] 1 shaft cylinder 2 mounting holes 21 inward protrusion 21a guide portion 21b minimum inner diameter portion 3 friction body 31 inner hole 32 friction portion 4 large diameter portion 41 annular surface 5 mounting portion (small diameter portion) 51 outward protrusion 51a guide portion 51b maximum outer diameter portion 52 bulging portion 53 downward extension portion 6 annular space 7 core 71 ventilation portion 72 upper core portion 73 lower core portion A Axial length from the upper end of the mounting portion to the upper end of the outward protrusion B Axial length from the upper end of the mounting hole to the lower end of the inward protrusion C Clearance between the inward protrusion and the outward protrusion

Claims

1. A thermochromic writing instrument comprising a thermochromic ink and a friction body for thermochromically changing the handwriting formed by 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 inserted into the mounting hole and a friction portion having a convex curved surface shape protruding from the mounting hole, the volume Ve of the friction portion and the volume Vp of the metallic luster pigment satisfy 5 ≤ Ve / Vp ≤ 35, the maximum outer diameter D of the friction portion and the protruding length L satisfy 0.1 ≤ L / D ≤ 1.5, the material of the friction body is such that the value of the Shore A hardness immediately after the start of the indenter contact measured in accordance with JIS K 7215 of the Japanese Industrial Standards is in the range of 60 or more and 85 or less, and the value (ΔHS) defined by the following formula of the Shore A hardness is 0 or more and less than 5. A thermochromic writing instrument. 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)

2. The thermochromic writing instrument according to claim 1, wherein the material of the friction body has a value (Tb × Eb) of the product 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 in the range of 5000 or more and 18000 or less.

3. The mounting hole is provided so as to penetrate the rear end portion of the shaft cylinder constituting the thermochromic writing instrument or the top of the cap along the vertical central axis, and has an inner peripheral 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 peripheral surface of the mounting hole, an outward protrusion protruding toward the outside of the mounting portion is formed on the outer peripheral surface of the mounting portion, when the mounting portion is inserted into the mounting hole, the outward protrusion rides over the inward protrusion, whereby the outward protrusion and the inward protrusion are locked to each other, the friction body is provided with a straight inner hole that opens at least at the lower end of the mounting portion along the vertical central axis, 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 inside, In a state where the mounting portion is inserted into the mounting hole and the core is inserted into the inner hole, the mounting portion is held at 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 outward protrusion of the mounting hole. The thermochromic writing instrument according to claim 1 or 2.

4. The thermochromic writing instrument according to claim 3, wherein in a state where 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. The thermochromic writing instrument according to claim 3 or 4, wherein in a state where 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 at the same position as the lower end of the mounting portion or is located above the lower end of the mounting portion.

6. The inner hole is a hole that opens at the lower end of the mounting portion and is blocked at one side that does not open at the upper end of the friction portion. In the process of inserting the core into the inner hole, a ventilation portion is provided in the core to discharge the air in the inner hole. The thermochromic writing instrument according to any one of claims 3 to 5.

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

8. The thermochromic writing instrument according to claim 6, wherein the ventilation portion is at least one groove or protrusion that is continuous from one end to the other end of the core along the outer peripheral surface of the core.

9. The thermochromic writing instrument according to any one of claims 3 to 8, wherein the core has a symmetric shape in the vertical direction.

10. The thermochromic writing instrument according to any one of claims 3 to 9, wherein a protrusion that contacts the inner peripheral surface of the inner hole is provided on the outer peripheral surface of the core.

11. A thermochromic writing instrument comprising a thermochromic ink and a friction body for thermochromically changing the handwriting by the thermochromic ink with frictional heat, 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 inserted into the mounting hole and a friction portion having a convex curved surface shape protruding from the mounting hole, the material of the friction body is a thermochromic writing instrument in which the value (Tb × Eb) of the product 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 is 5000 or more and 18000 or less.

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