Thermochromic writing instrument

Abstract

To provide a thermochromic writing implement capable of easily and reliably switching between a writing state and a non-writing state for one writing style selected from a plurality of writing styles. [Solution] The thermochromic writing instrument 1 comprises a barrel 2, a plurality of writing bodies 6 movably arranged within the barrel 2, a plurality of pressing members 10 provided on the side of the barrel 2, friction portions 90 formed on the outer surfaces of the plurality of pressing members, a plurality of engagement portions 35 that engage with each of the writing bodies 6 in the axial direction to regulate the movement of the corresponding writing body 6, and a first elastic member 70 arranged near the central axis of the barrel 2 corresponding to the pressing member 10; when the pressing member 10 is pressed radially, the engagement portions 35 are disengaged, allowing the corresponding writing body 6 to move due to gravity and the first elastic member 70 is compressed radially; and when the pressure is released, the restoring force of the first elastic member 70 causes the engagement portions 35 to engage with the writing body 6.

Description

Technical Field

[0001] The present invention relates to a thermochromic writing instrument capable of changing the color of handwriting by frictional heat.

Background Art

[0002] Conventionally, various writing instruments using thermochromic ink capable of changing the color of written handwriting have been proposed. In particular, a reversible thermochromic microcapsule pigment containing a reversible thermochromic composition composed of an electron-donating color-developing organic compound, an electron-accepting compound as a color developer, and a reaction medium serving as a discoloration temperature adjuster for determining the occurrence temperature of the color reaction between the two, a thermochromic ink containing at least water, and a writing instrument containing the thermochromic ink have been disclosed with a technique having a friction part capable of changing the color of the handwriting by frictional heat (Patent Document 1).

[0003] In the thermochromic writing instrument according to Patent Document 1, a writing body containing thermochromic ink as the thermochromic ink is built into a shaft cylinder, and the writing part of the writing body is projected forward from the front end of the shaft cylinder or retracted into the shaft cylinder by an operation part provided on the rear side of the shaft cylinder. Further, a friction part capable of changing the color of the thermochromic ink by friction is provided at a position different from the operation part.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the writing instrument according to Patent Document 1, since the operation part and the friction part are arranged at different positions, the feeding operation and the discoloration operation of the writing body are different, so the location of the friction part is difficult to understand. Further, since the operation part is located at the rear part of the shaft cylinder, there is a large movement when changing the gripping position of the shaft cylinder during the switching operation between the writing state and the non-writing state, and there are difficulties in performing a quick switching operation.

[0006] Therefore, an object of the present invention is to provide a writing instrument that can easily grasp the position of the friction part and can simply and surely switch between the writing state and the non-writing state.

Means for Solving the Problems

[0007] According to one aspect of the present invention, there is provided a thermochromic writing instrument capable of changing the color of the handwriting, comprising a shaft cylinder, a writing body movably disposed within the shaft cylinder and containing at least one thermochromic ink, a pressing member which is an operation part provided on the side surface of the shaft cylinder, and a friction part capable of changing the color of the handwriting of the thermochromic ink, wherein the friction part is formed on the outer surface of the pressing member, and the pressing member is provided at a part in the middle of the entire axial length of the shaft cylinder. Here, the middle part mentioned herein is in the range of 35% to 65% with respect to the entire axial length of the writing instrument, and corresponds to the vicinity of the center of gravity position of the writing instrument.

[0008] Further, according to another aspect, there is provided a thermochromic writing instrument comprising a shaft cylinder, a plurality of writing bodies movably disposed within the shaft cylinder, a plurality of pressing members provided on the side surface of the shaft cylinder, a plurality of engaging parts that engage with each of the writing bodies in the axial direction to restrict the movement of the corresponding writing body, and a first elastic member disposed near the central axis of the shaft cylinder corresponding to the pressing member. When the pressing member is pressed in the radial direction, the engagement of the engaging part is released, and the corresponding writing body becomes movable by gravity, and the first elastic member is compressed in the radial direction. When the pressing is released, the engaging part engages with the writing body by the restoring force of the first elastic member, and further comprises a plurality of engaging members formed in a cylindrical shape, wherein the engaging part is provided on the inner surface of the engaging member, the first elastic member is spherical, and further comprises a second elastic member that assists the return of the pressing member when the pressing is released, and is a dome-shaped spring made of a thin plate.

Effects of the Invention

[0009] According to an aspect of the present invention, by forming the friction portion on the outer surface of the operation portion, since the operation portion and the friction portion are provided at the same location and in the intermediate portion in the axial direction of the shaft cylinder, that is, near the so-called center of gravity position, it is easy to recognize the location of the friction portion, and for one writing body selected from a plurality of writing bodies, there is a common effect that the writing state and the non-writing state can be switched easily and surely.

Brief Description of the Drawings

[0010]

Figure 1

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Figure 18

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, common reference numerals are assigned to corresponding components.

[0012] FIG. 1 is a side view of the writing state of the thermochromic writing instrument according to an embodiment of the present invention, FIG. 2 is a perspective view of the thermochromic writing instrument of FIG. 1 with the rear shaft omitted, FIG. 3 is a longitudinal sectional view of the writing state of the thermochromic writing instrument of FIG. 1, and FIG. 4 is a longitudinal sectional view of the non-writing state of the thermochromic writing instrument of FIG. 1.

[0013] The thermochromic writing instrument 1 has a shaft cylinder 2 and a clip member 3. The shaft cylinder 2 has a cylindrical front shaft 4 and a cylindrical rear shaft 5 whose front end portion is press-fitted into the rear end portion of the front shaft 4. Inside the shaft cylinder 2, a plurality of writing bodies 6 are accommodated so as to be movable back and forth, that is, reciprocally. In this embodiment, three writing bodies 6 are accommodated. A hole is formed at the tip of the front shaft 4, and the writing portion 6a at the tip of the selected writing body 6 can protrude and retract. That is, the thermochromic writing instrument 1 can be switched between a writing state (FIG. 3) in which any one of the writing portions 6a protrudes from the tip of the shaft cylinder 2 and a non-writing state (FIG. 4) in which all of the writing portions 6a are immersed in the shaft cylinder 2. In this specification, in the axial direction of the thermochromic writing instrument 1, the side of the writing portion 6a is defined as the "front" side, and the side opposite to the writing portion 6a is defined as the "rear" side.

[0014] The notepad 6 is filled with thermochromic ink inside, and a ballpoint pen tip holding a writing ball or a marking pen core made of a porous material is attached to the writing part 6a. In this embodiment, three notepads 6 are accommodated. If it is a ballpoint pen tip, it is preferable that each writing part 6a is formed with a different ball diameter, and if it is a marking pen, it is preferable that they are formed with different thicknesses. Thermochromic ink refers to ink that maintains a predetermined color (first color) at room temperature (for example, 25°C), changes to another color (second color) when heated to a predetermined temperature (for example, 65°C), and then returns to the original color (first color) when cooled to a predetermined temperature (for example, -10°C). Generally, the second color may be colorless, and a configuration may be adopted in which a drawing line written in the first color (for example, red) is heated to become colorless. Therefore, the drawing line is rubbed against the paper surface or the like on which the line is written by the friction body 9 to generate frictional heat, thereby changing the drawing line to colorless. Of course, the second color may be a color other than colorless. More specifically, examples of the thermochromic microcapsule pigment that serves as the coloring material of the thermochromic ink include those obtained by microencapsulating a thermochromic composition containing at least a leuco dye, a developer, and a discoloration temperature adjuster. The average value of the particle diameter of the reversible thermochromic microcapsule pigment is preferably in the range of 0.1 to 5.0 μm, more preferably 0.5 to 2 μm. The reversible thermochromic microcapsule pigment is preferably blended in an amount of preferably 4 to 30% by weight based on the total amount of the ink composition. The average particle diameter was measured using a particle size measuring instrument N4Plus (manufactured by COULTER). During the measurement, the sample was diluted with water until it reached the recommended concentration of N4Plus and measured under temperature conditions of 25°C.

[0015] The leuco dye that can be used is not particularly limited as long as it is an electron-donating dye and functions as a developer. Specifically, from the viewpoint of obtaining ink with excellent coloring characteristics, conventionally known ones such as triphenylmethane-based, spiropyran-based, fluoran-based, diphenylmethane-based, rhodamine lactam-based, indolyl phthalide-based, and leuco auramine-based can be used alone (one kind) or in combination of two or more (hereinafter, simply referred to as "at least one kind").

[0016] Specifically, 6-(dimethylamino)-3,3-bis[4-(dimethylamino)phenyl]-1(3H)-isobenzofuranone, 3,3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3-(4-diethylaminophenyl)-3-(1-ethyl-2-methylindol-3-yl)phthalide, 3-(4-diethylamino-2-ethoxyphenyl)-3-(1-ethyl-2-methylindol-3-yl)-4-azaphthalide, 1,3-dimethyl-6-diethylaminofluoran, 2-chloro-3-methyl-6-dimethylaminofluoran, 3-dibutylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-anilinofluoran, 3-diethylamino-6-methyl-7-xylylidino-fluoran, 2-(2-chloroanilino)-6-dibutylaminofluoran, 3,6-dimethoxyfluoran, 3,6-di-n-butoxyfluoran, 1,2-benz-6-diethylaminofluoran, 1,2-benz-6-dibutylaminofluoran, 1,2-benz-6-ethylisoamylaminofluoran, 2-methyl-6-(N-p-tolyl-N-ethylamino)fluoran, 2-(N-phenyl-N-methylamino)-6-(N-p-tolyl-N-ethylamino)fluoran, 2-(3'-trifluoromethylanilino)-6-diethylaminofluoran, 3-chloro-6-cyclohexylaminofluoran, 2-methyl-6-cyclohexylaminofluoran, 3-di(n-butyl)amino-6-methoxy-7-anilinofluoran, 3,6-bis(diphenylamino)fluoran, methyl-3',6'-bisdiphenylaminofluoran, chloro-3',6'-bisdiphenylaminofluoran, 3-methoxy-4-dodecoxystilinoquinoline, etc. can be mentioned, and at least one of these can be used.

[0017] These leuco dyes have a lactone skeleton, a pyridine skeleton, a quinazoline skeleton, a bisquinazoline skeleton, etc., and develop color by the ring opening of these skeletons (rings). Preferably, it is desirable to use a leuco dye that changes from colored to colorless by heat.

[0018] The color developer that can be used is a component having the ability to develop the above leuco dye, and examples thereof include phenolic resin compounds, salicylic acid metal chlorides, salicylic acid resin metal salt compounds, solid acid compounds, etc. Specifically, o-cresol, tertiary butyl catechol, nonylphenol, n-octylphenol, n-dodecylphenol, n-stearylphenol, p-chlorophenol, p-bromophenol, o-phenylphenol, hexafluorobisphenol, n-butyl p-hydroxybenzoate, n-octyl p-hydroxybenzoate, resorcinol, dodecyl gallate, 2,2-bis(4'-hydroxyphenyl)propane, 4,4-dihydroxydiphenyl sulfone, 1,1-bis(4'-hydroxyphenyl)ethane, 2,2-bis(4'-hydroxy-3-methylphenyl)propane, bis(4-hydroxyphenyl) sulfide, 1-phenyl-1,1-bis(4'-hydroxyphenyl)ethane, 1,1-bis(4'-hydroxyphenyl)-3-methylbutane, 1,1-bis(4'-hydroxyphenyl)-2-methylpropane, 1,1-bis(4'-hydroxyphenyl)n-hexane, 1,1-bis(4'-hydroxyphenyl)n-heptane, 1,1-bis(4'-hydroxyphenyl)n-octane, 1,1-bis(4'-hydroxyphenyl)n-nonane, 1,1-bis(4'-hydroxyphenyl)n-decane, 1,1-bis(4'-hydroxyphenyl)n-dodecane, 2,2-bis(4'-hydroxyphenyl)butane, 2,2-bis(4'-hydroxyphenyl)ethyl propionate, 2,2-bis(4'-hydroxyphenyl)-4-methylpentane, 2,2-bis(4'-hydroxyphenyl)hexafluoropropane, 2,2-bis(4'-hydroxyphenyl)n-heptane, 2,2-bis(4'-hydroxyphenyl)n-nonane, etc. at least one kind can be mentioned.

[0019] The amount of the color developer used may be arbitrarily selected according to the desired color density and is not particularly limited, but usually, it is preferably selected within the range of about 0.1 to 100 parts by mass with respect to 1 part by mass of the above-mentioned leuco dye.

[0020] The discoloration temperature regulator is a substance that controls the discoloration temperature in the color development of the leuco dye and the developer, and conventionally known ones can be used. For example, alcohols, esters, ketones, ethers, acid amides, azomethines, fatty acids, hydrocarbons, etc. can be mentioned. Specifically, at least one of bis(4-hydroxyphenyl)phenylmethane dicaprylate (C7H15), bis(4-hydroxyphenyl)phenylmethane dilaurate (C11H23), bis(4-hydroxyphenyl)phenylmethane dimyristate (C13H27), bis(4-hydroxyphenyl)phenyl ethane dimyristate (C13H27), bis(4-hydroxyphenyl)phenylmethane dipalmitate (C15H30), bis(4-hydroxyphenyl)phenylmethane dibehenate (C21H43), bis(4-hydroxyphenyl)phenyl ethyl hexylidene dimyristate (C13H27), etc. can be mentioned.

[0021] FIG. 5 is an enlarged longitudinal sectional view of the thermochromic writing instrument 1 of FIG. 1, and FIG. 6 is a sectional view taken along line X-X of FIG. 5. The thermochromic writing instrument 1 includes a switch 10 which is a pressing member at an intermediate portion in the axial direction of the thermochromic writing instrument 1, a positioning member 20, an engaging member 30, a spring holding member 40, a weight member 50, an engaging rod 60, a first elastic member 70, a second elastic member 80, and a friction portion 90 capable of discoloring the thermochromic ink on the outer peripheral surface of the switch 10. Hereinafter, each component will be described in detail with reference to FIGS. 5 and 6 and the corresponding drawings.

[0022] FIG. 7 is a longitudinal sectional view of the rear shaft 5. In FIG. 7, the left side is the front side of the thermochromic writing instrument 1, and the right side is the rear side of the thermochromic writing instrument 1. On the side surface of the rear shaft 5, three substantially elliptical mounting holes 5a for receiving the three switches 10 are formed corresponding to the number of the writing bodies 6. On the inner surface of the rear shaft 5 behind the mounting holes 5a, a partition wall 5b is provided annularly along the circumferential direction. A through hole 5c is defined by the partition wall 5b. On the front end surface of the partition wall 5b, two protruding rotation stoppers 5d are formed to face each other. Inside the rear shaft 5 behind the partition wall 5b, three weight members 50 are arranged. On the inner surface of the rear shaft 5 behind the partition wall 5b, three guide walls 5e extending in the axial direction are formed to space the weight members 50 from each other in the circumferential direction and guide them along the axial direction.

[0023] FIG. 8 is a perspective view of the switch 10, and FIG. 9 is a longitudinal sectional view of the switch 10. The thermochromic writing instrument 1 has the same number of switches 10 as the number of writing bodies 6. In the present embodiment, three switches 10 are evenly arranged in the radial direction. The switch 10 includes a switch body 11 formed in a substantially elliptical column shape, a pressing surface 12 located on the upper surface of the switch body 11 and pressed by the user, and a first protrusion 13 and a second protrusion 14 formed in a column shape and located on the lower surface of the switch body 11. At the time of assembly, the first protrusion 13 is arranged on the front side of the thermochromic writing instrument 1, and the second protrusion 14 is arranged on the rear side of the thermochromic writing instrument 1. A recess 15 is formed on the lower surface of the switch body 11 between the first protrusion 13 and the second protrusion 14. The switch body 11 is integrally formed from a relatively hard resin material such as polycarbonate resin. On the outer surface of the pressing surface 12 of the switch body 11, there is provided a friction part 90 capable of changing color by frictional heat generated by a frictional operation of the thermochromic ink. The friction part 90 is composed of a rubber elastic material such as a thermoplastic elastomer such as silicone rubber, nitrile rubber, ethylene propylene rubber, ethylene propylene diene rubber, styrene-based elastomer, olefin-based elastomer, polyester-based elastomer, a mixture of two or more rubber elastic materials, and a rubber elastic material composed of a mixture of a rubber elastic material and a synthetic resin. In particular, by containing a basic magnesium carbonate porous body, not only can the handwriting of the thermochromic writing instrument be discolored, but also the handwriting of an erasable writing instrument other than the thermochromic ink provided with a mechanical pencil or the like can be erased by a frictional operation, which is preferable. The low wear property mentioned here means that the taper wear amount in the JIS K7204 test method H22 is less than 15 mg, so that there is little wear even by a frictional operation, and deformation of the friction part 90 accompanying the frictional operation can be prevented. The switch body 11 and the friction part 90 are integrally fixed by adhesion, welding, fitting, two-color molding, etc., but they may be formed as a single part from the same material. The friction part 90 includes a contact surface 91 that contacts the pressing surface 12 and a contact part 92 that is touched by a finger or the like when the switch 10 is pressed. The contact part 92 preferably has a different shape depending on the ink color of the writing body 6, the ink discoloration temperature, the type of the writing body 6, etc., so that the writing body 6 can be easily identified by the feeling of contact with the contact part 92 even without visual recognition.

[0024] FIG. 10 is a perspective view of the positioning member 20, and FIG. 11 is a rear view of the positioning member 20. The positioning member 20 is a cylindrical member having both end faces parallel to each other. The outer diameter of the positioning member 20 is set to be slightly smaller than the outer diameter of the rear shaft 5. In the positioning member 20, three notches 21 are formed, which are rectangularly notched forward from the rear end face, corresponding to the number of the writing bodies 6. The remaining portions that are not notched form three corner portions (horn portions) 22 protruding rearward. In other words, the notches 21 are defined by the three corner portions 22. The end faces 21a of the notches 21 facing each other in the circumferential direction are parallel to each other.

[0025] FIG. 12 is a perspective view of the engaging member 30, and FIG. 13 is a longitudinal sectional view of the engaging member 30. The thermochromic writing instrument 1 has three engaging members 30 corresponding to the number of the writing bodies 6. The engaging member 30 is arranged in the shaft cylinder 2 such that the left side is the front side of the thermochromic writing instrument 1 and the right side is the rear side of the thermochromic writing instrument 1 in FIG. 13. Specifically, the three engaging members 30 are respectively arranged in the three notches 21 of the positioning member 20. Therefore, the overall length of the engaging member 30 is set to be slightly shorter than the depth of the notch 21 of the positioning member 20, that is, the length in the axial direction. Note that since the engaging member 30 has a symmetric shape, the front and rear arrangements may be reversed.

[0026] The engaging member 30 is formed in a cylindrical shape having both end faces parallel to each other and an inner surface shape of a cylinder. At the time of assembly, the outer peripheral surface portion of the engaging member 30 facing the inner surface of the shaft cylinder 2 forms a cylindrical outer surface 31 with a relatively large curvature. The outer surface 31 has substantially the same curvature as the outer peripheral surface of the positioning member 20. The outer peripheral surface portions on both sides adjacent to the outer surface 31 form flat side surfaces 32 that are parallel to each other. The distance between the two side surfaces 32 is set to be slightly smaller than the distance between the two end faces 21a that define one notch 21 of the positioning member 20. Therefore, the engaging member 30 can be disposed within the notch 21 such that the end face 21a of the positioning member 20 and the side surface 32 of the engaging member 30 face each other with a slight gap therebetween. At this time, the outer surface 31 of the engaging member 30 is flush with the outer peripheral surface of the positioning member 20.

[0027] A circular through-hole 33 is formed in the central portion of the outer surface 31. The first protrusion 13 of the switch 10 is inserted into the through-hole 33. A spherical recess 34 is formed in the outer surface portion that is axisymmetric with the through-hole 33 of the outer surface 31. The curvature of the spherical portion of the recess 34 is set such that the spherical first elastic member 70 described later can be fitted therein. On the inner surface of the portion where the recess 34 is formed, a protruding engaging portion 35 with a flat upper surface is formed. The engaging member 30 is integrally formed from a relatively hard resin material such as polycarbonate resin or the like.

[0028] FIG. 14 is a perspective view of the spring holding member 40, and FIG. 15 is a longitudinal sectional view of the spring holding member 40. The spring holding member 40 is disposed within the shaft cylinder 2 such that in FIG. 15, the left side is the front side of the thermochromic writing instrument 1 and the right side is the rear side of the thermochromic writing instrument 1. The spring holding member 40 is a cylindrical member having both end faces parallel to each other. The outer diameter of the spring holding member 40 is set to be slightly smaller than the outer diameter of the rear shaft 5 and is the same as the outer diameter of the positioning member 20.

[0029] The spring holding member 40 is formed with two receiving portions 41 that are notched in a minute rectangular shape from the rear end face toward the front. The spring holding member 40 is arranged in the shaft cylinder 2 such that its front end face abuts against the rear end face of the positioning member 20, and each of the receiving portions 41 is arranged to fit with the rotation stopper 5d of the rear shaft 5. By fitting the receiving portion 41 of the spring holding member 40 with the rotation stopper 5d of the rear shaft 5, rotation of the spring holding member 40 around the central axis in the shaft cylinder 2 is prevented.

[0030] On the outer peripheral surface of the spring holding member 40, three circular and shallow recesses 42 are formed corresponding to the number of the writing bodies 6. A flat plane 43 is formed on the inner surface of the portion where the recess 42 is formed. The spring holding member 40 is integrally formed from a relatively hard resin material such as polycarbonate resin or the like.

[0031] FIG. 16 is a longitudinal sectional view of the weight member 50. The weight member 50 is arranged in the shaft cylinder 2 in FIG. 16 such that the left side is the front side of the thermochromic writing instrument 1 and the right side is the rear side of the thermochromic writing instrument 1. The thermochromic writing instrument 1 has three weight members 50 corresponding to the number of the writing bodies 6. The weight member 50 is a columnar solid member having a fan-shaped cross-sectional shape divided corresponding to the number of the writing bodies 6 (FIG. 2). Each of the weight members 50 is arranged between three guide walls 5e in the rear space separated by the partition wall 5b of the rear shaft 5. The weight member 50 serves as a weight that moves back and forth in accordance with the posture of the thermochromic writing instrument 1, that is, in the direction in which gravity acts. A circular insertion hole 51 is formed in the front end face of the weight member 50. The weight member 50 is formed from a metal material such as aluminum or brass.

[0032] FIG. 17 is a side view of the engagement rod 60. In FIG. 17, the engagement rod 60 is disposed in the shaft cylinder 2 such that the left side is the front side of the thermochromic writing instrument 1 and the right side is the rear side of the thermochromic writing instrument 1. The thermochromic writing instrument 1 has three engagement rods 60 corresponding to the number of the writing bodies 6. The engagement rod 60 is a rod-shaped member as a whole and has an engagement rod body 61. The front end portion and the rear end portion of the engagement rod 60 are formed to have a small diameter in the engagement rod body 61. That is, a writing body fitting portion 62 that is inserted into and fitted to the rear end portion of the tubular writing body 6 is formed at the front end portion of the engagement rod 60. An insertion portion 63 that is inserted into and fitted to the insertion hole 51 of the weight member 50 is formed at the rear end portion of the engagement rod 60. The writing body 6 and the weight member 50 are integrally connected by the engagement rod 60.

[0033] Two annular recesses arranged in parallel along the axial direction are formed in the engagement rod body 61. As will be described later, the recess disposed on the front side is a non-writing maintenance recess 64 that engages with the engagement portion 35 of the engagement member 30 so as to maintain the non-writing state, and the recess disposed on the rear side is a writing maintenance recess 65 that engages with the engagement portion 35 of the engagement member 30 so as to maintain the writing state. The engagement rod 60 is integrally formed from a relatively hard resin material such as polycarbonate resin or the like, but may be formed from a metal material such as aluminum or brass.

[0034] The first elastic member 70 is a spherical member made of an elastic material such as a rubber material such as silicone rubber or a thermoplastic elastomer such as a polyester-based elastomer. Since the first elastic member 70 is formed in a spherical shape, the same restoring force can be obtained regardless of the direction in which the first elastic member 70 is compressed and elastically deformed. The thermochromic writing instrument 1 has only one first elastic member 70 regardless of the number of the writing bodies 6.

[0035] The thermochromic writing instrument 1 has three second elastic members 80 corresponding to the number of writing bodies 6. Each of the second elastic members 80 is arranged in a recess 42 of a spring holding member 40 as shown in FIG. 5. In the present embodiment, the second elastic member 80 is a dome spring. The dome spring is an elastic member formed by processing a thin plate flat material such as a single sheet of metal into a dome shape. When the apex of the dome is pressed and elastically deformed, a corresponding restoring force is obtained. This dome spring is, for example, a dome spring made of metal and formed in a thin wall. The second elastic member 80 may be arranged with other elastic members, such as coil springs, rubber elastic materials such as silicone rubber, or elastic materials such as thermoplastic elastomers such as polyester-based elastomers.

[0036] With reference to FIGS. 3 to 6, particularly FIGS. 5 and 6, the relationship between the members of the thermochromic writing instrument 1 will be described. As shown in FIG. 5, the positioning member 20 and the spring holding member 40 are fixed by being sandwiched between the rear end face of the front shaft 4 and the front end face of the partition wall 5b of the rear shaft 5 within the shaft cylinder 2. As described above, the engaging members 30 are respectively arranged in the three notches 21 of the positioning member 20. Thereby, the three engaging members 30 are arranged at equal intervals along the circumferential direction. Since the total length of the engaging member 30 is slightly shorter than the axial length of the notch 21 of the positioning member 20, the axial movement of the engaging member 30 is restricted by the notch 21 and the rear end face of the spring holding member 40, while the engaging member 30 is movable in the radial direction.

[0037] Referring to FIG. 6, the three engaging members 30 are arranged around the central axis of the thermochromic writing instrument 1, and a first elastic member 70 is arranged at the central position of the three engaging members 30. That is, the first elastic member 70 is arranged near the central axis of the shaft cylinder 2 corresponding to the portion of the switch 10. More specifically, the first elastic member 70 fits into each recess 34 of the three engaging members 30 and is arranged to be supported from three directions.

[0038] As shown in Fig. 5, the three switches 10 are respectively arranged in the three mounting holes 5a of the rear shaft 5. At this time, the first protrusion 13 of the switch 10 is inserted into the through hole 33 of the engaging member 30, and the second protrusion 14 of the switch 10 is arranged to abut against the second elastic member 80 disposed in the recess 42 of the spring holding member 40. That is, the second protrusion 14 of the switch 10 is arranged at the dome-shaped apex of the dome spring. The integrally connected writing body 6, engaging rod 60 and weight member 50 are arranged in the shaft cylinder 2 through the through hole 5c of the rear shaft 5, the spring holding member 40, and the positioning member 20, that is, the corresponding engaging member 30.

[0039] When the switch 10 is pressed, the engaging member 30 moves radially inward through the first protrusion 13, causing the first elastic member 70 to elastically deform, and the second elastic member 80 to elastically deform by the second protrusion 14. When the pressing of the switch 10 is released, the engaging member 30 and the switch 10 return to their original positions by the restoring forces of the first elastic member 70 and the second elastic member 80. Since the switch 10 has the recess 15, the switch 10 can be pressed without interfering with the spring holding member 40.

[0040] When the switch 10 is not pressed, the first elastic member 70 is not elastically deformed or is slightly elastically deformed to bias the switch 10. That is, the engaging member 30 is located closer to the radially outer side in the shaft cylinder 2 of the thermochromic writing instrument 1. At this time, the engaging portion 35 of the engaging member 30 is arranged in one of the two recesses formed in the engaging rod 60, that is, either in the non-writing maintaining recess 64 or the writing maintaining recess 65. Therefore, the engaging portion 35 of the engaging member 30 and the recess which is the engaged portion of the engaging rod 60 are engaged in the axial direction, restricting the forward and backward movement of the writing body 6, and maintaining the non-writing state or the writing state.

[0041] When the other party presses the switch 10, as described above, the engaging member 30 moves radially inward, causing the first protrusion 13 to press the first elastic member 70, and the first elastic member 70 elastically deforms radially. As a result, when the engaging portion 35 of the engaging member 30 moves radially inward, the path inhibited by the engaging portion 35 is opened, and the writing body 6 can be moved back and forth.

[0042] FIG. 18 is an enlarged longitudinal sectional view for explaining the switching between the non-writing state and the writing state of the thermochromic writing instrument 1 of FIG. 1. FIG. 18(A) shows the non-writing state of the thermochromic writing instrument 1 and shows the same state as the thermochromic writing instrument 1 shown in FIG. 5. That is, in FIG. 18(A), the engaging portion 35 of the engaging member 30 is disposed within the non-writing maintenance recess 64.

[0043] FIG. 18(B) shows a state in which the switch 10 is pressed. That is, due to the radial movement of the engaging member 30, the engaging portion 35 moves radially inward until the engagement between the engaging rod 60 and the non-writing maintenance recess 64 is released. As a result, the engaging rod 60 can move freely in the axial cylinder 2 in the front-rear direction. That is, when the posture of the thermochromic writing instrument 1 is changed while pressing the switch 10, the engaging rod 60 moves forward or backward in the axial cylinder 2 due to the gravity acting on the writing body 6, the engaging rod 60, and the weight member 50 that are integrally connected, that is, the self-weight.

[0044] When the user holds the thermochromic writing instrument 1 so that the front end faces downward while pressing the switch 10, the engaging rod 60 moves forward due to gravity. The forward movement of the engaging rod 60 is restricted by the contact between the weight member 50 and the partition wall 5b of the rear shaft 5. When the pressing of the switch 10 is released at this time, the engaging member 30 moves radially by the restoring force of the first elastic member 70, and as shown in FIG. 18(C), the engaging portion 35 is disposed within the writing maintenance recess 65 of the engaging rod 60. As a result, the engaging member 30 and the engaging rod 60 are engaged, and the writing state is maintained.

[0045] When the user grips the thermochromic writing instrument 1 with the front end facing upward while releasing the engagement between the engaging portion 35 and the writing maintenance recess 65 of the engaging rod 60 by pressing the switch 10, the engaging rod 60 moves rearward by gravity. The rearward movement of the engaging rod 60 is restricted by the contact between the weight member 50 and the portion of the clip member 3 inserted into the rear end portion of the rear shaft 5. When the pressing of the switch 10 is released at this time, the engaging member 30 moves radially inward by the restoring force of the first elastic member 70, and as shown in FIG. 18(A), the engaging portion 35 is disposed within the non-writing maintenance recess 64 of the engaging rod 60. As a result, the engaging member 30 and the engaging rod 60 engage with each other, and the non-writing state is maintained.

[0046] According to the present invention, since the engagement between the engaging portion 35 of the engaging member 30 and the non-writing maintenance recess 64 or the writing maintenance recess 65 of the engaging rod 60 is released by the radially inward movement of the engaging member 30 caused by the pressing of the switch 10, the writing state and the non-writing state can be switched easily and surely. Further, since the engaging portion 35 of the engaging member 30 has an appropriate clearance in the front-rear direction in a state where it is disposed within the non-writing maintenance recess 64 or the writing maintenance recess 65 of the engaging rod 60, the pressing operation of the switch 10 is not hindered. Also, since the writing body 6, the engaging rod 60, and the weight member 50 are integrally connected and the weight member 50 serves as a weight, it operates smoothly and stably, and the writing state and the non-writing state can be surely switched.

[0047] When the switch 10 corresponding to the selected writing body 6 to be written on is pressed, the first elastic member 70 is pressed via the engaging member 30. The movement of the first elastic member 70 is restricted by the engaging members 30 corresponding to the other two writing bodies 6 that were not selected. That is, since the other two engaging members 30 and switches 10 cannot move further radially outward, as a result, as described above, the first elastic member 70 elastically deforms. In other words, while any one of the switches 10 to be selected is being pressed, the other switches 10 receive a force in the opposite direction, so the other switches 10 cannot be moved radially inward. Therefore, in the thermochromic writing instrument 1, only the selected switch 10 can be surely pressed, and for one writing body 6 selected from among the plurality of writing bodies 6, the writing state and the non-writing state can be easily and surely switched.

[0048] According to the present invention, since it is only necessary to secure the radial stroke of the switch 10 corresponding to the distance required for the engagement and disengagement between the engaging member 30 and the engaging rod 60, it is possible to realize a thermochromic writing instrument with an outer diameter thinner than that of conventional products.

[0049] In this embodiment, the thermochromic writing instrument 1 had three writing bodies 6, but it may have two or four or more. The first elastic member 70 may have a shape other than spherical, for example, a cylinder or a prism arranged along the axial direction, as long as it generates an equal restoring force with respect to the engaging members 30 arranged around it.

[0050] As described above, since the pressing of the switch 10 elastically deforms the second elastic member 80, that is, the dome spring in this embodiment, the user can feel a sure click feeling with a short pressing stroke and obtain a comfortable operating feeling. The second elastic member 80 is used to obtain such a comfortable operating feeling and to assist the sure return of the switch 10, but it may be omitted.

[0051] Examples based on this embodiment include the following forms. As Example 1, the writing part 6a of the writing body 6 is a ballpoint pen tip, and a composite thermochromic ballpoint pen capable of obtaining handwriting of different thicknesses with ball diameters of 0.38 mm, 0.5 mm, 0.7 mm, or 0.5 mm, 0.7 mm, and 1.0 mm for each ballpoint pen tip can be provided. Also, it is preferable that the contact surface 92 of the friction part 90 also has different shapes. Further, in order to make each writing distance substantially the same, it is preferable to make the inner diameter of the writing body 6 different while varying the ink amount of the writing body 6 according to the ball diameter to obtain substantially the same ink length.

[0052] As Example 2, when the thermochromic ink accommodated in the writing body 6 is heated to 60 - 70 °C, it changes to another color (second color), and then when it is cooled to - 15 - - 5 °C, it returns to the original color (first color). For other writing bodies 6, when heated to 75 - 85 °C, it changes to another color (second color), and then when cooled to 0 - 10 °C, it returns to the original color (first color). Also, when heated to 40 - 50 °C, it changes to another color (second color), and then when cooled to - 35 - - 25 °C, it returns to the original color (first color). By making the discoloration temperatures of each different, a thermochromic writing instrument that can withstand use in various temperature environments around the world can be provided.

Explanation of Reference Numerals

[0053] 1 Thermochromic writing instrument 2 Shaft cylinder 4 Front shaft 5 Rear shaft 6 Writing body 10 Switch 20 Positioning member 30 Engaging member 35 Engaging part 40 Spring holding member 50 Weight member 60 Engaging rod 70 First elastic member 80 Second elastic member 90 Friction part

Claims

**Claim 1** A writing instrument having a plurality of writing bodies, wherein at least two of the plurality of writing bodies are provided with a thermochromic ink that changes from a first color to colorless upon heating and returns from the colorless to the first color upon cooling, and the temperatures at which the at least two thermochromic inks change from the first color to colorless are different from each other, the temperature difference between the at least two thermochromic inks when changing from the first color to colorless is 5°C or more, and the writing instrument is characterized by comprising a friction part capable of changing the color of the handwriting by the writing body due to frictional heat. **Claim 2** The writing instrument according to claim 1, comprising the same number as the plurality of writing bodies and at least three of the friction parts.

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