Friction body, writing instrument and writing instrument set

Abstract

There is provided a friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, a thermal conductivity of a friction portion of the friction body is set to be within 0.05 W/(m.Math.K) to 50 W/(m.Math.K).

Claims

1. A friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, wherein thermal conductivity of a friction portion of the friction body is ranging from 0.05 W/(m.Math.K) to 50 W/(m.Math.K).

2. The friction body according to claim 1, wherein the thermal conductivity of the friction portion of the friction body is ranging from 0.05 W/(m.Math.K) to 20 W/(m.Math.K).

3. The friction body according to claim 2, wherein the thermal conductivity of the friction portion of the friction body is ranging from 0.05 W/(m.Math.K) to 10 W/(m.Math.K).

4. The friction body according to claim 1, wherein a friction coefficient between the friction portion of the friction body and the paper surface is ranging from 0.2 to 1.0.

5. The friction body according to claim 1, wherein when a friction coefficient between the friction body and the paper surface is defined as ; a vertical load imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as W (N); a velocity at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as V (m/s); and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of (WV)/A4.

6. The friction body according to claim 5, wherein the friction body satisfies a relation of (WV)/A15.

7. The friction body according to claim 5, wherein the friction body satisfies a relation of (WV)/A2000.

8. The friction body according to claim 5, wherein the load W is selected from a range from 0.9 N to 10 N, and the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

9. The friction body according to claim 5, wherein, when frictional motion is manually performed, the velocity V is selected from a range from 0.1 m/s to 1.0 m/s.

10. The friction body according to claim 1 wherein, when a vertical load W imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 4.9 N; and a velocity V at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 0.5 m/s, and a friction coefficient between the friction body and the paper surface is defined as ; and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of /A1.5.

11. The friction body according to claim 10, wherein the friction body satisfies a relation of /A6.

12. The friction body according to claim 10, wherein the friction body satisfies a relation of /A200.

13. The friction body according to claim 10, wherein the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

14. A writing instrument comprising: the friction body defined in claim 1; and a thermochromic ink which is adapted to be flowed out.

15. The writing instrument according to claim 14, comprising: a writing instrument main body; the thermochromic ink incorporated in the writing instrument main body; and a pen tip made up of a ball-point-pen tip and capable of supplying the thermochromic ink, the pen tip being provided at a front end of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body.

16. The writing instrument according to claim 14, comprising: a writing instrument main body; the thermochromic ink incorporated in the writing instrument main body; a pen tip made up of a ball-point-pen tip and capable of supplying the thermochromic ink, the pen tip being provided at a front end of the writing instrument main body; and a removable cap provided at a pen tip side of the writing instrument main body, wherein the friction body is provided at a top of the cap.

17. The writing instrument according to claim 14, comprising: a pen tip made of a processed fibrous element or a porous element which is capable of supplying the thermochromic ink; a writing instrument main body comprising: an ink tank which stores thermochromic ink and to which the pen tip is attached so as to be movable back and forward; and a valve mechanism which opens when the pen tip is pressed rearward; and a removable cap provided at the pen tip side of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body or a top of the cap.

18. The writing instrument according to claim 14, comprising: a writing instrument main body comprising: an ink absorbing element which is made of an element having continuous pores and impregnated with the thermochromic ink and a pen tip which is made of a processed fibrous element or a porous element, which is connected to the ink absorbing element and which supplies the thermochromic ink; and a removable cap provided at a pen tip side of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body or the top of the cap.

19. The writing instrument according claim 14, comprising: a writing instrument main body comprising: a pen tip made up of a ball-point-pen tip which supplies the thermochromic ink; an ink tank storing the thermochromic ink; and an ink reservoir which is interposed between the pen tip and the ink tank and which temporarily holds overflowing ink when an internal pressure of the ink tank increases; and a removable cap provided at a pen tip side of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body or a top of the cap.

20. A writing instrument set comprising: the friction body defined in claim 1; and a writing instrument which incorporates and supplies the thermochromic ink.

21. A friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, wherein when a friction coefficient between the friction body and the paper surface is defined as ; a vertical load imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as W (N); a velocity at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as V (m/s); and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of (WV)/A4.

22. The friction body according to claim 21, wherein the friction body satisfies a relation of (WV)/A2000.

23. The friction body according to claim 21, wherein the friction coefficient 4 between the friction portion of the friction body and the paper surface is ranging from 0.2 to 1.0.

24. The friction body according to claim 21, wherein the load W is selected from a range from 0.9 N to 10 N and the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

25. The friction body according to claim 21, wherein when frictional motion is manually performed, the velocity V is selected from a range from 0.1 m/s to 1.0 m/s.

26. A writing instrument comprising, the friction body defined in claim 21; and a thermochromic ink which is adapted to be flowed out.

27. The writing instrument according to claim 26, comprising: a writing instrument main body; the thermochromic ink incorporated in the writing instrument main body; and a pen tip made up of a ball-point-pen tip and capable of supplying the thermochromic ink, the pen tip being provided at a front end of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body.

28. The writing instrument according to claim 26, comprising: a writing instrument main body; the thermochromic ink incorporated in the writing instrument main body; a pen tip made up of a ball-point-pen tip and capable of supplying the thermochromic ink, the pen tip being provided at a front end of the writing instrument main body; and a removable cap provided at a pen tip side of the writing instrument main body, wherein the friction body is provided at a top of the cap.

29. The writing instrument according to claim 26, comprising: a pen tip made of a processed fibrous element or a porous element which is capable of supplying the thermochromic ink; a writing instrument main body comprising: an ink tank which stores the thermochromic ink and to which the pen tip is attached so as to be movable back and forward; and a valve mechanism which opens when the pen tip is pressed rearward; and a removable cap provided at the pen tip side of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body or a top of the cap.

30. The writing instrument according to claim 26, comprising: a writing instrument main body comprising: an ink absorbing element which is made of an element having continuous pores and impregnated with the thermochromic ink and a pen tip which is made of a processed fibrous element or a porous element, which is connected to the ink absorbing element and which supplies the thermochromic ink; and a removable cap provided at a pen tip side of the writing instrument main body; wherein the friction body is provided at a rear end of the writing instrument main body or the top of the cap.

31. The writing instrument according claim 26, comprising: a writing instrument main body comprising: a pen tip made up of a ball-point-pen tip which supplies the thermochromic ink; an ink tank storing the thermochromic ink; and an ink reservoir which is interposed between the pen tip and the ink tank and which temporarily holds overflowing ink when an internal pressure of the ink tank increases; and a removable cap provided at a pen tip side of the writing instrument main body, wherein the friction body is provided at a rear end of the writing instrument main body or a top of the cap.

32. A writing instrument set comprising: the friction body defined in claim 21; and a writing instrument which incorporates and supplies the thermochromic ink.

33. A friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, wherein when a vertical load W imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 4.9 N; and a velocity V at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 0.5 m/s, and a friction coefficient between the friction body and the paper surface is defined as ; and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of /A1.5.

34. The friction body according to claim 33, wherein the friction body satisfies a relation of /A200.

35. The friction body according to claim 33, wherein the friction coefficient between the friction portion of the friction body and the paper surface is ranging from 0.2 to 1.0.

36. The friction body according to claim 33, wherein the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

37. A friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, wherein when a friction coefficient between the friction body and the paper surface is defined as ; a vertical load imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as W (N), a velocity at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as V (m/s); and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of (WV)/A15.

38. The friction body according to claim 37, wherein the friction body satisfies a relation of (WV)/A2000.

39. The friction body according to claim 37, wherein the friction coefficient between the friction portion of the friction body and the paper surface is ranging from 0.2 to 1.0.

40. The friction body according to claim 37, wherein the load W is selected from a range from 0.9 N to 10 N and the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

41. The friction body according to claim 37, wherein, when frictional motion is manually performed, the velocity V is selected from a range from 0.1 m/s to 1.0 m/s.

42. A friction body which is adapted to rub a thermochromic image or handwriting formed on a paper surface by use of thermochromic ink to thermally discolor the thermochromic image or handwriting by frictional heat resultant from rubbing, wherein when a vertical load W imparted to the paper surface by the friction body when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 4.9 N; and a velocity V at which the friction body travels over the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is set to be 0.5 m/s, and a friction coefficient between the friction body and the paper surface is defined as ; and a contact area where the friction body contacts the paper surface when the thermochromic image or handwriting on the paper surface is rubbed with the friction body is defined as A (cm.sup.2), the friction body satisfies a relation of /A6.

43. The friction body according to claim 42, wherein the friction body satisfies a relation of /A200.

44. The friction body according to claim 42, wherein the friction coefficient between the friction portion of the friction body and the paper surface is ranging from 0.2 to 1.0.

45. The friction body according to claim 42, wherein the contact area A is selected from a range from 0.005 cm.sup.2 to 0.3 cm.sup.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a longitudinal cross-sectional view of a writing instrument of a first embodiment of the present invention;

(2) FIG. 2 is a longitudinal cross-sectional view of a writing instrument of a second embodiment of the present invention;

(3) FIG. 3 is a longitudinal cross-sectional view of a writing instrument of a third embodiment of the present invention;

(4) FIG. 4 is a longitudinal cross-sectional view of a writing instrument of a fourth embodiment of the present invention;

(5) FIG. 5 is a longitudinal cross-sectional view of a writing instrument of a fifth embodiment of the present invention;

(6) FIG. 6 is a longitudinal cross-sectional view of a writing instrument of a sixth embodiment of the present invention;

(7) FIG. 7 is a longitudinal cross-sectional view of a friction body of the sixth embodiment of the present invention; and

(8) FIG. 8 is a descriptive view showing discoloration behavior of thermally color fadable reversible thermochromic ink.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

(9) A first embodiment of the present invention will be described (see FIG. 1).

(10) The present embodiment is directed toward a writing instrument 1 including: a writing instrument main body 2;

(11) a cap 6 removably attached to a pen tip of the writing instrument main body 2; and a friction body 7 attached to a rear end of the writing instrument main body 2. Thermochromic ink 4 is stored in the writing instrument main body 2 and the thermochromic ink 4 is supplied onto a paper surface from a pen tip 3.

(12) A thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument main body 2 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(13) The writing instrument main body 2 includes: the pen tip 3 made up of a ball-point-pen tip; a pen tip holder 22 to which the pen tip 3 is fixed at a front end thereof, an ink storage cylinder 23 to which the pen tip holder 22 is fixed at a front end thereof, a tail plug 24 which is attached to an opening formed in a rear end of the ink storage cylinder 23 and has a ventilation opening; and a barrel 21 accommodating the ink storage cylinder 23. The thermochromic ink 4 and a following element 5 are housed in the ink storage cylinder 23. The following element 5 is disposed at a rear end of the thermochromic ink 4 and forwardly advances in association with consumption of the thermochromic ink 4

(14) A ball is held at the front end of the pen tip 3 in a rotatable manner. An elastic element (a coil spring) 31 is housed in the pen tip 3. The ball is urged forwardly by the elastic element 31, whereby the ball is brought into compressed contact with an inwardly-facing interior surface of the front end of the pen tip 3.

(15) A pen tip seal member 61 made from a soft material is housed in the cap 6. When the cap 6 is attached to the pen tip side of the writing instrument, the pen tip 3 comes into close contact with the pen tip seal member 61, whereupon the pen tip 3 is sealed.

(16) The barrel 21 is made up of a front barrel 21a and a rear barrel 21b that are screw-engaged with each other. The pen tip 3 projects outwardly from a front-end hole of the barrel 21 (the front barrel 21a). The friction body 7 formed from soft synthetic resin is attached to a rear-end hole of the barrel 21 (the rear barrel 21b). An outward protrusion 71 is formed on an exterior surface of the friction body 7. An inward protrusion 21c is formed on an interior surface of the rear-end hole of the barrel 21. The outward protrusion 71 and the inward protrusion 21c are engaged with each other in a climbing manner, so that removal of the friction body 7 from the rear end hole can be avoided.

(17) In the present embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

Second Embodiment

(18) A second embodiment of the present invention will now be described (see FIG. 2).

(19) The present embodiment is directed toward the writing instrument 1 including a writing instrument main body 2, a cap 6 removably attached to a pen tip of the writing instrument and the friction body 7 attached to the top of the cap 6. A thermochromic ink 4 is stored in the writing instrument main body 2 and supplied from the pen tip 3. The thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument main body 2 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(20) The writing instrument main body 2 includes: a pen tip 3 made up of a ball-point-pen tip; a pen tip holder 22 to which the pen tip 3 is fixed at a front end thereof; an ink storage cylinder 23 to which the pen tip holder 22 is fixed at to a front end of the ink storage cylinder; a tail plug 24 that is attached to an opening formed in a rear end of the ink storage cylinder 23 and that has a ventilation opening; and a barrel 21 accommodating the ink storage cylinder 23. The thermochromic ink 4 and the following element 5, which is disposed at the rear end of the thermochromic ink 4 and forwardly advances in association with consumption of the thermochromic ink 4, are housed in the ink storage cylinder 23. The barrel 21 is made up of the front barrel 21a and the rear barrel 21b that are screw-engaged with each other. The pen tip 3 protrudes outside from the front-end hole of the barrel 21 (the front barrel 21a).

(21) A ball is held at the front end of the pen tip 3 in a rotatable manner. The elastic element (a coil spring) 31 is housed in the pen tip 3. The ball is urged forwardly by the elastic element 31, whereby the ball is brought into compressed contact with an inwardly-facing interior surface of the front end of the pen tip 3.

(22) The pen tip seal member 61 made from a soft material is housed in the cap 6. When the cap 6 is attached to the pen tip side of the writing instrument, the pen tip 3 comes into close contact with the pen tip seal member 61, whereupon the pen tip 3 is sealed. The friction body 7 formed from soft synthetic resin is attached to a mount hole opened in the top of the cap 6.

(23) In the present embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

Third Embodiment

(24) A third embodiment of the present invention will now be described (see FIG. 3).

(25) The present embodiment is directed toward the writing instrument 1 including a writing instrument main body 2, a cap 6 removably attached to a pen tip of the writing instrument main body 2 and a friction body 7 attached to a rear end of the writing instrument main body 2. A thermochromic ink 4 is stored in the writing instrument main body 2 and is supplied from the pen tip 3. A thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument main body 2 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(26) The writing instrument main body 2 includes: a pen tip 3 made up of a processed fibrous element or a porous element; an ink tank 25 attached to the front end of the pen tip 3 so as to be movable front and back; a valve 26 that opens as a result of the pen tip 3 being pressed backwardly; a barrel 21 holding a rear portion of the ink tank 25; and a friction body 7 made up of soft synthetic resin attached to the rear end of the barrel 21. An agitation member 41 is housed in the ink tank 25.

(27) In the embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

Fourth Embodiment

(28) A fourth embodiment of the present invention will now be described (see FIG. 4).

(29) The present embodiment is directed toward the writing instrument 1 including a writing instrument main body 2, a cap 6 removably attached to a pen tip of the writing instrument main body 2 and a friction body 7 attached to the rear end of the writing instrument main body 2. The thermochromic ink is stored in the writing instrument main body 2 and the thermochromic ink is emitted from the pen tip 3. A thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument main body 2 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(30) The writing instrument main body 2 includes: the pen tip 3 formed from a processed fibrous element or a porous element; a pen tip holder 22 that holds the pen tip 3; a barrel 21 which has the pen tip holder 22 at a front end thereof and accommodates an ink absorbing element 27 therein; and a friction body 7 that is attached to the rear end of the barrel 21 and that is formed from soft synthetic resin. The ink absorbing element 27 is formed from a member having continuous pores (e.g., a processed fibrous element and a porous material such as a porous foam) and the ink absorbing element 27 is impregnated with thermochromic ink. A rear end of the pen tip 3 is connected to a front end of the ink absorbing element 27. The friction body 7 is attached to an exterior surface of a rear end of the barrel 21 by fitting or the friction body and the rear end of the barrel are formed integrally by coinjection molding.

(31) In the present embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

Fifth Embodiment

(32) A fifth embodiment of the present invention will now be described (see FIG. 5).

(33) The present embodiment is directed toward the writing instrument 1 including a pen tip 3 attached to the front end of the writing instrument main body 2 and a friction body 7 attached to the rear end of the writing instrument main body 2. The thermochromic ink 4 is stored in the writing instrument main body 2 and supplied from the pen tip 3. A thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument main body 2 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(34) The writing instrument main body 2 includes: a pen tip 3 formed from a ball-point-pen tip; a pen tip holder 22 holding the pen tip 3; an ink reservoir 28 having the pen tip holder 22 at a front end thereof; and an ink tank 25 that has the ink reservoir 28 at a front end thereof and that directly stores the thermochromic ink 4. The ink reservoir 28 is a member that is interposed between the pen tip 3 and the ink tank 25 and that temporarily retains overflowing ink resultant from an increase in the internal pressure of the ink tank 25. A comb-shaped member is adopted for the ink reservoir. The friction body 7 is formed from a soft synthetic resin and attached to the rear-end hole of the ink tank 25.

(35) In the present embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

Sixth Embodiment

(36) A sixth embodiment of the present invention will now be described (see FIGS. 6 and 7).

(37) The present embodiment is directed toward a writing instrument set having the writing instrument 1 and the friction body 7. The thermochromic ink 4 is stored in the writing instrument 1 and supplied from the pen tip 3. A thermochromic image or handwriting is formed on the paper surface as a result of the pen tip 3 of the writing instrument 1 contacting the paper surface. The thermochromic image or handwriting can be thermally discolored by rubbing the image or handwriting formed on the paper surface with the friction body 7.

(38) The writing instrument 1 is made up of the writing instrument main body 2 which has the pen tip 3 at the front end thereof and stores the thermochromic ink 4 and the cap 6 removably attached to the pen tip side of the writing instrument main body 2.

(39) The writing instrument main body 2 includes: a pen tip 3 made up of a ball-point-pen tip, a pen tip holder 22 to which the pen tip 3 is fixed at the front end thereof, an ink storage cylinder 23 to which the pen tip holder 22 is fixed at the front end thereof, the tail plug 24 that is attached to an opening formed in a rear end of the ink storage cylinder 23 and has a ventilation opening; and a barrel 21 accommodating the ink storage cylinder 23. The thermochromic ink 4 and the following element 5, which is disposed at the rear end of the thermochromic ink 4 and forwardly advances in association with consumption of the thermochromic ink 4, are housed in the ink storage cylinder 23. The barrel 21 is made up of the front barrel 21a and the rear barrel 21b that are screw-engaged with each other. The pen tip 3 protrudes outside from the front-end hole of the barrel 21 (the front barrel 21a).

(40) A ball is held at the front end of the pen tip 3 in a rotatable manner. The elastic element (a coil spring) 31 is housed in the pen tip 3. The ball is urged forwardly by the elastic element 31, whereby the ball is brought into compressed contact with an inwardly-facing interior surface of the front end of the pen tip 3.

(41) The pen tip seal member 61 made from a soft material is housed in the cap 6. When the cap 6 is attached to the pen tip side of the writing instrument, the pen tip 3 comes into close contact with the pen tip seal member 61, whereupon the pen tip 3 is sealed.

(42) The outward protrusion 71 is provided on the exterior surface of the friction body 7 formed from a soft synthetic resin. The friction body 7 is attached to the front end of the friction body holder 8. The friction body holder 8 is cylindrical and the inward protrusion 81 is formed on the interior surface of the front end of the friction body holder. The inward outward protrusions 81, 71 are engaged with each other in a climbing manner, thereby preventing removal of the friction body 7.

(43) In the present embodiment, the thermal conductivity of a friction portion of the friction body 7 is ranging from 0.05 W/(m.Math.K) to 1.0 W/(m.Math.K) and a friction coefficient of the friction portion of the friction body 7 to the paper surface is ranging from 0.2 to 1.0.

EXAMPLES

(44) Table 1 shows results of tests for thermochromism property when thermochromic handwriting formed in thermochromic ink was rubbed under the certain values of (WV)/A, which is given by arbitrary selecting values of a friction coefficient between the friction body and the paper surface; vertical load W (N) imparted to the paper surface by the friction body during frictional motion; velocity V(m/s) at which the friction body travels over the paper surface during frictional motion; and a contact area A (cm.sup.2) at which the friction body contacts the paper surface during frictional motion.

(45) In the tests, a total of four types of friction bodies consisting of (two types of) styrene-based resin, silicone resin and polypropylene resin were used. In the tests, thermochromic handwriting formed in thermochromic ink having a discoloration temperature (a high-temperature point of discoloration) of 45 C. was rubbed at an ambient temperature of 25 C. with a plurality of types of friction bodies.

(46) Evaluations of thermochromism in the table are as follows:

(47) I: Handwriting was totally discolored

(48) II: Handwriting was essentially discolored

(49) III: Handwriting was slightly discolored

(50) IV: Handwriting remained completely undiscolored

(51) TABLE-US-00001 TABLE 1 test No. W V A ( w v)/A thermochromism 1 0.283 0.98 0.1 0.025 1.1 IV 2 0.780 1.96 0.1 0.071 2.2 IV 3 0.780 2.94 0.1 0.071 3.2 IV 4 0.476 1.96 0.1 0.022 4.2 II 5 0.780 4.90 0.1 0.071 5.4 II 6 0.476 2.96 0.1 0.024 5.9 I 7 0.497 3.92 0.1 0.027 7.2 II 8 0.497 4.90 0.1 0.031 7.9 I 9 0.283 3.92 0.2 0.025 8.9 II 10 0.283 2.94 0.3 0.025 10.0 II 11 0.283 4.90 0.2 0.025 11.1 I 12 0.476 0.98 0.5 0.019 12.3 I 13 0.780 2.94 0.4 0.071 12.9 I 14 0.497 3.92 0.2 0.027 14.4 I 15 0.476 4.90 0.2 0.031 15.0 I 16 0.497 4.90 0.2 0.031 15.7 I 17 0.476 2.94 0.3 0.025 16.8 I 18 0.497 2.94 0.3 0.025 17.5 I 19 0.780 5.88 0.3 0.071 19.4 I 20 0.283 5.88 0.3 0.025 20.0 I 21 0.497 3.92 0.3 0.027 21.6 I 22 0.283 3.92 0.5 0.025 22.2 I 23 0.476 4.90 0.3 0.031 22.6 I 24 0.497 4.90 0.3 0.031 23.6 I 25 0.476 5.88 0.3 0.034 24.7 I 26 0.497 5.88 0.3 0.034 25.8 I 27 0.780 4.90 0.5 0.071 26.9 I 28 0.497 3.92 0.4 0.027 28.9 I 29 0.476 2.94 0.5 0.024 29.2 I 30 0.497 2.94 0.5 0.025 29.2 I

(52) Table 2 shows results of tests for thermochromism property when thermochromic handwriting formed in thermochromic ink was rubbed under the certain values of /A, which is given by arbitrary selecting values of a friction coefficient between the friction body and the paper surface; and a contact area A (cm.sup.2) at which the friction body contacts the paper surface during frictional motion, and also setting the vertical load W (N) imparted to the paper surface by the friction body during frictional motion as 4.9 N; and the velocity V(m/s) at which the friction body travels over the paper surface during frictional motion as 0.5 m/s.

(53) In the tests, a total of four types of friction bodies consisting of (two types of) styrene-based resin, silicone resin and polypropylene resin were used. In the tests, thermochromic handwriting formed in thermochromic ink having a discoloration temperature (a high-temperature point of discoloration) of 45 C. was rubbed at an ambient temperature of 25 C. with a plurality of types of friction bodies.

(54) Evaluations of thermochromism in the table are as follows:

(55) I: Handwriting was totally discolored

(56) II: Handwriting was essentially discolored

(57) III: Handwriting was slightly discolored

(58) IV: Handwriting remained completely undiscolored

(59) TABLE-US-00002 TABLE 2 test No. A /A thermochromism 1 0.283 0.283 1.0 IV 2 0.476 0.317 1.5 II 3 0.476 0.238 2.0 II 4 0.476 0.190 2.5 I 5 0.780 0.260 3.0 I 6 0.476 0.136 3.5 I 7 0.283 0.071 4.0 II 8 0.476 0.106 4.5 I 9 0.283 0.057 5.0 I 10 0.283 0.051 5.5 I 11 0.283 0.047 6.0 I 12 0.476 0.073 6.5 I 13 0.780 0.111 7.0 I 14 0.497 0.066 7.5 I 15 0.476 0.060 7.9 I 16 0.497 0.058 8.6 I 17 0.476 0.053 9.0 I 18 0.497 0.052 9.6 I 19 0.780 0.078 10.0 I 20 0.283 0.027 10.5 I 21 0.497 0.045 11.0 I 22 0.283 0.025 11.3 I 23 0.476 0.040 11.9 I 24 0.497 0.040 12.4 I 25 0.476 0.037 12.9 I 26 0.497 0.037 13.4 I 27 0.780 0.056 13.9 I 28 0.497 0.034 14.6 I 29 0.476 0.032 14.9 I 30 0.497 0.032 15.5 I

(60) Table 3 shows results of tests for thermochromism property when thermochromic handwriting formed in thermochromic ink was rubbed under the certain values of (WV)/A, which is given by arbitrary selecting values of a friction coefficient between the friction body and the paper surface; vertical load W (N) imparted to the paper surface by the friction body during frictional motion; velocity V(m/s) at which the friction body travels over the paper surface during frictional motion; and a contact area A (cm.sup.2) at which the friction body contacts the paper surface during frictional motion.

(61) In the tests, a total of five types of friction bodies consisting of (two types of) styrene-based resin, silicone resin, polypropylene resin and iron were used. In the tests, thermochromic handwriting formed in thermochromic ink having a discoloration temperature (a high-temperature point of discoloration) of 60 C. was rubbed at an ambient temperature of 25 C. with a plurality of types of friction bodies.

(62) Evaluations of thermochromism in the table are as follows:

(63) I: Handwriting was totally discolored

(64) II: Handwriting was essentially discolored

(65) III: Handwriting was slightly discolored

(66) IV: Handwriting remained completely undiscolored

(67) TABLE-US-00003 TABLE 3 test No. W V A ( w v)/A thermochromism 1 0.121 2.94 0.1 0.031 1.1 IV 2 0.780 1.96 0.1 0.074 2.1 IV 3 0.283 2.94 0.1 0.025 3.3 IV 4 0.780 3.92 0.1 0.074 4.1 IV 5 0.780 0.98 0.5 0.075 5.1 IV 6 0.497 2.94 0.1 0.025 5.8 IV 7 0.497 3.92 0.1 0.027 7.2 IV 8 0.497 4.90 0.1 0.031 7.9 IV 9 0.283 1.96 0.4 0.025 8.9 IV 10 0.283 2.94 0.3 0.025 10.0 IV 11 0.283 1.96 0.5 0.025 11.1 IV 12 0.476 0.98 0.5 0.019 12.3 III 13 0.780 2.94 0.4 0.071 12.9 III 14 0.497 3.92 0.2 0.027 14.4 III 15 0.476 4.90 0.2 0.031 15.0 II 16 0.497 4.90 0.2 0.031 15.7 II 17 0.476 2.94 0.3 0.025 16.8 II 18 0.497 2.94 0.3 0.025 17.5 II 19 0.780 5.85 0.3 0.072 19.0 I 20 0.283 5.88 0.3 0.025 20.0 II 21 0.497 3.92 0.3 0.028 20.9 II 22 0.283 4.90 0.4 0.025 22.2 II 23 0.476 4.92 0.3 0.031 22.7 I 24 0.497 4.90 0.3 0.031 23.6 I 25 0.476 5.88 0.3 0.034 24.7 I 26 0.497 5.88 0.3 0.034 25.8 I 27 0.780 4.90 0.5 0.071 26.9 I 28 0.497 3.92 0.4 0.028 27.8 I 29 0.476 2.94 0.5 0.024 29.2 I 30 0.497 2.94 0.5 0.024 30.4 I

(68) Table 4 shows results of tests for thermochromism property when thermochromic handwriting formed in thermochromic ink was rubbed under the certain values of /A, which is given by arbitrary selecting values of a friction coefficient between the friction body and the paper surface; and a contact area A (cm.sup.2) at which the friction body contacts the paper surface during frictional motion, and also setting the vertical load W (N) imparted to the paper surface by the friction body during frictional motion as 4.9 N; and the velocity V(m/s) at which the friction body travels over the paper surface during frictional motion as 0.5 m/s.

(69) In the tests, a total of four types of friction bodies consisting of (two types of) styrene-based resin, silicone resin and polypropylene resin were used. In the tests, thermochromic handwriting formed in thermochromic ink having a discoloration temperature of (a high-temperature point of discoloration) 60 C. was rubbed at an ambient temperature of 25 C. with a plurality of types of friction bodies.

(70) Evaluations of thermochromism in the table are as follows:

(71) I: Handwriting was totally discolored

(72) II: Handwriting was essentially discolored

(73) III: Handwriting was slightly discolored

(74) IV: Handwriting remained completely undiscolored

(75) TABLE-US-00004 TABLE 4 test No. A /A thermochromism 1 0.283 0.283 1.0 IV 2 0.476 0.317 1.5 IV 3 0.476 0.238 2.0 IV 4 0.476 0.190 2.5 IV 5 0.780 0.260 3.0 IV 6 0.476 0.136 3.5 IV 7 0.283 0.071 4.0 IV 8 0.476 0.106 4.5 IV 9 0.283 0.057 5.0 IV 10 0.497 0.090 5.5 III 11 0.476 0.079 6.0 II 12 0.476 0.073 6.5 I 13 0.780 0.111 7.0 I 14 0.497 0.066 7.5 II 15 0.476 0.060 7.9 I 16 0.497 0.058 8.6 I 17 0.476 0.053 9.0 I 18 0.497 0.052 9.6 I 19 0.780 0.078 10.0 I 20 0.283 0.027 10.5 I 21 0.497 0.045 11.0 I 22 0.283 0.025 11.3 I 23 0.476 0.040 11.9 I 24 0.497 0.040 12.4 I 25 0.476 0.037 12.9 I 26 0.497 0.037 13.4 I 27 0.780 0.056 13.9 I 28 0.497 0.034 14.6 I 29 0.476 0.032 14.9 I 30 0.497 0.032 15.5 I

(76) While the invention has been described in connection with the exemplary embodiments, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.