Notebook

Abstract

To provide a writing instrument that allows visual recognition of the shape of a pen tip, the color tone, and the remaining amount of ink in the writing instrument, without impairing the appearance due to discoloration or browning of the handwriting formed by the writing instrument from the beginning, while the writing instrument uses a member formed of a transparent material.SOLUTION: The writing instrument comprises an ink, an ink occlusion body 7 containing the ink, a barrel 8 containing the ink occlusion body 7, a pen tip 3 capable of discharging ink, a holder 4 holding the pen tip 3, and a cap 2 detachably attached to the pen tip side of barrel 8 and formed of a transparent material. The cap 2 contains an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the cap 2.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a writing instrument. More specifically, it relates to a writing instrument with improved light resistance of the ink contained therein.

Background Art

[0002] Conventionally, many colorants contained in the ink accommodated in writing instruments are such that their color tones fade or change due to light. Therefore, it has been disclosed to add ultraviolet absorbers such as benzophenone-based, salicylic acid-based, benzotriazole-based, cyanoacrylate-based, etc. to the ink (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

[0006] This invention has been made in view of the above findings, and its objective is to provide a writing instrument that uses a component made of a transparent material, in which the handwriting produced by the writing instrument does not fade or brown from the beginning, thus impairing its appearance, and in which the shape of the pen tip and the color tone and remaining amount of ink inside the writing instrument can be seen. In this invention, "front" refers to the pen tip side, and "back" refers to the opposite side. [Means for solving the problem]

[0007] The present invention relates to a writing instrument comprising: an ink containing a reversible thermochromic material, a photochromic organic material, a dye, and a fluorescent pigment, comprising (a) an electron-donating organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the color reaction of the components of (a) and (b) occurs; an ink storage body containing the ink; a barrel containing the ink storage body; a pen tip from which the ink can be dispensed; a holder for holding the pen tip; and a cap detachably attached to the pen tip side of the barrel and made of a transparent material, wherein the cap contains an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light-stable layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the cap.

[0008] According to the present invention, by including an ultraviolet absorber or a transparent ultraviolet shielding agent in the cap, or by providing a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent on the surface of the cap, the writing instrument, while using a component made of a transparent material, does not suffer from fading or browning from the beginning, thus maintaining its appearance, and the shape of the pen tip and the color and remaining amount of ink in the writing instrument can be visually confirmed. [Effects of the Invention]

[0009] The present invention provides a writing instrument that uses a component made of a transparent material, yet the writing produced by the writing instrument does not fade or brown from the beginning, thus not detracting from its appearance. Furthermore, because the shape of the pen tip and the color and remaining amount of ink inside the writing instrument can be visually confirmed, it can provide a writing instrument with high commercial value. [Brief explanation of the drawing]

[0010] [Figure 1] This is a longitudinal cross-sectional view showing an embodiment of the present invention. [Figure 2] This is an enlarged view of the main part of Figure 1. [Figure 3] Figure 3(a) is a longitudinal cross-sectional view of the holder according to an embodiment of the present invention. Figure 3(b) is a cross-sectional view taken along line AA in Figure 3(a). Figure 3(c) is a cross-sectional view taken along line BB in Figure 3(a). [Figure 4] Figure 4(a) is a front view of the pen tip of an embodiment of the present invention. Figure 4(b) is a perspective view of the pen tip. [Figure 5] Figure 2 is an enlarged longitudinal cross-sectional view of the main part. [Figure 6] Figure 5 shows an exploded view of the front and rear axles. (Other parts are omitted.) [Figure 7] This is an explanatory diagram showing the color change behavior of heat-decolorizing microcapsule pigments. [Figure 8] This is an explanatory diagram showing the color change behavior of color-memory-retaining microcapsule pigments. [Figure 9] This is an explanatory diagram showing the color change behavior of heat-activated microcapsule pigments. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below with reference to the drawings. The writing instrument 1 mainly consists of a cap 2, a pen tip 3, a holder 4 that holds the pen tip 3, an ink-absorbing element 7, and a front barrel 5 and a rear barrel 6 that house the ink-absorbing element 7. The holder 4 is press-fitted into the holder fitting portion 58 of the front barrel 5. The writing instrument 1 is also designed so that the front barrel 5 can be detachably attached to the opening of the rear barrel 6 which houses the ink-absorbing element 7, and the ink-absorbing element 7 can be replaced or refilled by removing the front barrel 5 from the opening of the rear barrel 6. The structure of the writing instrument 1 is not particularly limited, and examples include a marking pen in which the pen tip is attached to the writing tip, ink is impregnated into an ink-absorbing body made of fiber bundles housed inside the barrel, and ink is supplied to the writing tip; a structure in which ink is directly housed inside the barrel and an ink flow rate adjustment member in the shape of a comb or made of fiber bundles is interposed; and a structure in which ink is directly housed inside the barrel and a predetermined amount of ink is supplied to the writing tip by a valve mechanism.

[0012] Pen nib The pen tip 3 has one end that protrudes forward from the front edge 44 of the front opening of the holder 4 as the writing portion 31, and the other end (rear portion 35) is connected in a piercing manner to one end of the ink-absorbing body 7. The writing portion 31 is processed into a chisel shape. The writing portion 31 is not limited to a chisel shape, but may also be processed into a shape that suits the purpose, such as a bullet shape, a rectangular prism shape, or a plate shape. The form of the writing instrument 1 of the present invention is not limited to the illustrated example, and may be a double-ended writing instrument in which pen tips of different shapes are attached to both ends of the ink-absorbing body 7.

[0013] As shown in FIGS. 2 and 4, the pen tip 3 includes a front portion 33 having a writing portion 31 at its tip, a cylindrical central portion 34 whose outer surface is sandwiched in the front-rear direction by a holder 4 and a front shaft 5, and a cylindrical rear portion 35 that is connected in a piercing manner to one end of an ink storage body 7. The front portion 33 of the pen tip 3 has a substantially rectangular cross-section, and during writing, the front portion 33 of the pen tip 3 has flexibility to bend and deform on the long side of the substantially rectangular cross-section. The pen tip 3 has a flat portion on the long side of the rectangular cross-section. Conventionally, this would easily cause the fading or browning of the colorant in the ink, and thus the handwriting obtained by writing would also show fading or browning, easily impairing the commercial value. However, according to the present invention, as will be described later, by containing an ultraviolet absorber or a transparent ultraviolet shielding agent in the holder or the cap, or by providing a light-stable layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent on the surface of the holder, even though the writing instrument 1 uses a member formed of a transparent material, the handwriting formed by the writing instrument 1 does not fade or brown from the beginning and does not impair the appearance, and the pen tip shape, the color tone and the remaining amount of the ink in the writing instrument 1 can be visually recognized.

[0014] The pen tip 3 is preferably made of a porous body of a synthetic resin having continuous bubbles. This increases the degree of freedom in the pen tip shape and enables a sharp design that appeals to the user's vision. By using a member (cap) formed of a transparent material, the pen tip shape inside the cap can be visually recognized from the outside of the cap, enabling the user to claim a visual feature (a sharp design), and the handwriting formed by the writing instrument does not fade or brown from the beginning and does not impair the appearance, and the pen tip shape, the color tone and the remaining amount of the ink in the writing instrument can be visually recognized. In addition, the pen tip 3 may be any other thing through which ink can flow, and specifically, examples include a fiber pen tip, a felt pen tip, a brush pen tip, a plastic pen tip having an axial capillary passage, and the like.

[0015] Also, the pen tip is not particularly limited to the illustrated structure and shape. For example, the pen tip may include an ink guiding portion and a writing portion that derives ink from the ink guiding portion, and may have a visible portion where the writing direction can be visually recognized directly above the axial direction of the writing portion.

[0016] Further, it may include a pen tip serving as a writing portion and a holding body that holds the pen tip and has at least one ink guiding portion for supplying ink to the writing portion, and has a relay core for supplying the ink contained in the writing implement body to the ink guiding portion provided in the holding body, and the holding body may be configured to be a visible portion where the writing direction can be visually recognized.

[0017] · Ink reservoir The ink reservoir 7 may be made of a member having continuous pores capable of impregnating ink. For example, a thermally fused body of fiber bundles, a resin processed body of fiber bundles, a resin processed body of felt, a needle punched body of felt, a porous body (e.g., a continuous foam of synthetic resin such as sponge), etc. may be mentioned. Further, the ink reservoir 7 may have a skin made of a synthetic resin film or the like on its outer peripheral surface.

[0018] The ink reservoir preferably has a skin formed of a transparent material on its outer peripheral surface, and contains an ultraviolet absorber or a transparent ultraviolet shielding agent described later in the skin, or provides a light stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent on the surface of the skin. Thereby, while being a writing implement 1 using a member (ink reservoir) formed of a transparent material, the handwriting formed by the writing implement 1 does not fade or brown from the beginning and deteriorate in appearance, and the color tone and remaining amount of the ink in the writing implement 1 can be visually recognized..

[0019] When the front shaft 5 is removed from the opening of the rear shaft 6, the ink reservoir 7 is removed from the rear shaft 6 and held by a holding rib 59 that extends axially rearward from the rear end of the longitudinal rib 57, and is housed and held inside the front shaft 5. This improves the workability when replacing the ink reservoir 7 or replenishing ink to the ink reservoir 7. Note that the holding rib 59 may extend to the inner surface of the fitting portion 51.

[0020] ·cap The cap 2, which covers the front barrel 5 when not writing, is a cylindrical bottomed body consisting of a bottom wall and a peripheral wall, with an open rear end and a closed front end, and is obtained by injection molding of a transparent synthetic resin (e.g., polypropylene). The cap 2 contains an ultraviolet absorber or a transparent ultraviolet shielding agent, as described later, or a light-stable layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the cap 2. As a result, even though the writing instrument 1 uses a component (cap 2) made of a transparent material, the writing marks formed by the writing instrument 1 do not fade or brown from the beginning, impairing their appearance, and the shape of the pen tip and the color and remaining amount of ink inside the writing instrument 1 can be visually confirmed.

[0021] In particular, the pen tip, in which the holder is configured to be a visible part that allows the writing direction to be seen, has a cutting-edge design that appeals to the user's visual sense. By using a component (cap) made of a transparent material, the pen tip inside the cap can be seen from the outside of the cap, allowing the user to assert its visual characteristics (cutting-edge design), and the writing marks formed by the writing instrument do not fade or brown from the beginning, thus detracting from its appearance, and the shape of the pen tip and the color and remaining amount of ink inside the writing instrument can be seen.

[0022] The cap 2 is detachably connected to the rear barrel 6. Specifically, the rear barrel fitting portion 22 provided on the inner surface of the opening of the cap 2 is fitted into the cap fitting portion 65 provided on the outer surface of the opening of the rear barrel 6. At the same time, the annular seal portion 21 provided in front of the rear barrel fitting portion 22 is airtightly fitted into the airtight portion 64 provided in front of the cap fitting portion 65. In other words, when not writing, the cap 2 covers the front barrel 5, the inner surface of the cap 2 is fitted into the outer surface of the rear barrel 6, and the inner surface of the cap 2 (annular seal portion 21) is in close contact with the outer surface of the rear barrel 6 (airtight portion 64) around its entire circumference.

[0023] Furthermore, the cap 2 is not particularly limited to the structure and shape shown in the illustration. For example, it may be configured in which an inner cap that seals the pen tip is fitted and fixed to the inner surface of the cap 2 body. In this case, it is assembled using a front barrel and a rear barrel made of polypropylene resin that are airtightly fitted together, an inner cap made of transparent polypropylene resin, and a cap 2 made of transparent polycarbonate resin. The inner cap contains an ultraviolet absorber or a transparent ultraviolet shielding agent, which will be described later, or a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the inner cap. As a result, even though the writing instrument 1 uses components (cap 2 and inner cap) made of transparent materials, the writing marks formed by the writing instrument 1 do not fade or brown from the beginning, impairing their appearance, and the shape of the pen tip and the color tone and remaining amount of ink in the writing instrument 1 can be seen.

[0024] ·Shaft cylinder The barrel 8 consists of at least one of either the front shaft 5 or the rear shaft 6. The front shaft 5 is a cylindrical body obtained by injection molding of synthetic resin, with both ends open. As shown in Figure 2, a holder fitting portion 58 is formed on the inner surface of the front end of the front shaft 5, into which the outer surface of the rear end of the holder 4 (the second rib 43b) is press-fitted. In addition, multiple (eight in this case) longitudinal ribs 57 extending in the axial direction are integrally formed on the rear inner circumferential surface of the holder fitting portion 58 of the front shaft 5 at equal intervals in the circumferential direction. The central portion 34 of the pen tip 3 is clamped in the front-rear direction by the first contact wall portion 42 of the holder 4 and the second contact wall portion 56a at the front end of the longitudinal ribs 57. This prevents the pen tip 3 from falling out of the holder 4 or becoming embedded in the holder 4 (front shaft 5), and also allows for precise control of the amount the pen tip 3 protrudes from the holder 4. Furthermore, the third contact wall portion 56b at the rear end of the vertical rib 57 clamps the front end of the ink-absorbing body 7 in the front-rear direction.

[0025] The front axle 5 is provided with a fitting portion 51 on its rear outer surface, and the fitting portion 51 is detachably locked into a fitted portion 61 formed on the inner surface of the opening of the rear axle 6. The fitting portion 51 comprises a cylindrical small-diameter base portion 52, an outward-facing locking portion 53 provided on the outer surface of the small-diameter base portion 52, and at least one axially extending slit 54 that penetrates radially across at least the outward-facing locking portion 53. This makes it easy to set and maintain an appropriate fitting force for detachably connecting the front axle 5 and the rear axle 6.

[0026] The fitting portion 51 preferably comprises a first outward-facing locking portion 53a, which is an outward-facing locking portion 53, and a second outward-facing locking portion 53b provided behind the first outward-facing locking portion 53a. More preferably, the front shaft 5 has a stepped portion 55 that the opening of the rear shaft 6 abuts against, and the first outward-facing locking portion 53a and the second outward-facing locking portion 53b are annular projections 531.

[0027] Furthermore, the front barrel 5 may be provided with a direction-identifying part on its outer surface, which consists of an axially extending projection that identifies the orientation of the pen tip 3. This eliminates the need to visually check the orientation of the pen tip 3 immediately before writing, allowing for immediate use after exposing the pen tip 3.

[0028] The rear axle 6, which is connected to the rear end of the front axle 5, is a cylindrical bottomed body consisting of a bottom wall and a circumferential wall, with an open front end and a closed rear end, and is obtained by injection molding of a synthetic resin (for example, polypropylene). The front axle 5 is detachably connected to the rear axle 6.

[0029] The fitting portion 61 comprises a cylindrical large-diameter base portion 62 into which the small-diameter base portion 52 is inserted, and an inward-facing locking portion 63 provided on the inner surface of the large-diameter base portion 62. When the front shaft 5 and the rear shaft 6 are connected, the front shaft and the rear shaft are pressed together radially.

[0030] The fitted portion 61 preferably comprises an inward-facing locking portion 63, which includes a first inward-facing locking portion 63a that locks with the first outward-facing locking portion 53a, and a second inward-facing locking portion 63b provided behind the first inward-facing locking portion 63a that locks with the second outward-facing locking portion 53b. This stabilizes the connection between the front shaft 5 and the rear shaft 6, ensuring that the barrel and the stopper are connected without axial and radial rattle during writing, resulting in a smoother writing experience and stable writing.

[0031] Furthermore, preferably, when the front shaft 5 and the rear shaft 6 are connected, the outer surface of the fitting portion 51 and the inner surface of the tip of the rear shaft 6 are not in contact in the radial direction. For example, if the outer surface of the fitting portion 51 and the inner surface of the tip of the rear shaft 6 are in contact in the radial direction when the front shaft 5 and the rear shaft 6 are connected, the outer diameter of the rear shaft 6 after connection (i.e., the outer diameter of the airtight portion 64) may become too large. As a result, when the cap 2 is fitted to the outer surface of the rear shaft 6, the fitting force between the cap 2 and the rear shaft 6 may become too high.

[0032] In contrast, when the front shaft 5 and the rear shaft 6 are connected, if the outer surface of the fitting portion 51 and the inner surface of the tip of the rear shaft 6 are not in contact radially, the fitting portion 51 does not affect the outer diameter dimension of the airtight portion 64. As a result, high dimensional accuracy is not required for the small diameter base portion 52, an appropriate fitting force can be set and maintained to detachably connect the front shaft 5 and the rear shaft 6, and the productivity of the parts (front shaft 5 and rear shaft 6) is improved. Furthermore, because the outer surface shape and outer diameter of the rear shaft 6 are stable, reliable airtightness and fitting force can be obtained when fitting the cap 2 and the rear shaft 6.

[0033] The first inward locking portion 63a is an annular groove 631 that can lock with the first outward locking portion 53a, and the second inward locking portion 63b is a smooth contact surface 632 that can contact the second outward locking portion 53b. When the front shaft 5 and the rear shaft 6 are connected, the opening of the rear shaft 6 and the stepped portion 55 come into contact, the first outward locking portion 53a and the annular groove 631 engage in the axial direction, and the second outward locking portion 53b and the contact surface 632 are pressed together radially. As a result, the front shaft 5 and the rear shaft 6 are fitted into the appropriate locking position, making it possible to more reliably obtain the appropriate fitting force for detachably connecting the front shaft 5 and the rear shaft 6. In addition, the user can be made aware that the front shaft 5 and the rear shaft 6 have been properly connected. When the front shaft 5 and rear shaft 6 (i.e., barrel 8) are formed from a transparent material, it is preferable that they contain an ultraviolet absorber or a transparent ultraviolet shielding agent, as described later, or that a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the front shaft 5 and rear shaft 6 (i.e., barrel 8). As a result, even though the writing instrument 1 uses a component (barrel 8) made of a transparent material, the writing produced by the writing instrument 1 does not fade or brown from the beginning, impairing its appearance, and the color tone and remaining amount of ink inside the writing instrument 1 can be visually confirmed.

[0034] Furthermore, the writing instrument 1 may be provided with a friction element 9. Preferably, the friction element 9 is provided as part of the writing instrument, containing a thermochromic ink and capable of dispensing the thermochromic ink from the pen tip 3. Examples of providing the friction element 9 as part of the writing instrument 1 include providing the friction element 9 on the side of the writing instrument body opposite the pen tip, or providing the friction element 9 on the top of a detachable cap 2 attached to the pen tip side of the writing instrument body. The friction element can also be combined with a writing instrument that contains a thermochromic ink and capable of dispensing the thermochromic ink from the pen tip 3 to form a writing instrument set. Furthermore, the friction element 9 may be configured to directly grip its outer surface during friction, or it may be configured to be gripped via a friction element holder.

[0035] When attaching the friction element to the writing instrument 1, it can be attached by fitting a separate component onto the writing instrument, or by integrally molding it with the writing instrument body or writing instrument components through two-color molding. When fitting it as a separate component, the friction element can be shaped like a writing instrument component such as a cap, barrel, crown, or end cap, and the number of parts can be reduced by directly forming the writing instrument. Furthermore, the friction element can be easily provided by two-color molding together with the writing instrument body or writing instrument components.

[0036] In this embodiment, the elastic material constituting the friction body 9 is preferably an elastic synthetic resin (rubber, elastomer), such as 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), a mixture of two or more rubber elastic materials, and a mixture of a rubber elastic material and a synthetic resin. The elastic synthetic resin constituting the friction body 9 is not a highly abrasive elastic material (e.g., an eraser), but a low-abrasion elastic material that produces almost no wear residue (eraser residue) during friction. The friction body can also be used to create a writing instrument set by combining the writing instrument with a friction device that is a separate component of any shape, but providing the friction body to the writing instrument makes it more portable.

[0037] The friction body 9 may be formed from a mixture of polypropylene resin and styrene-based thermoplastic elastomer, or a mixture of polypropylene resin and polypropylene-based thermoplastic elastomer. The mixing ratio of the mixtures is 1:1 to 1:4 by weight, and it does not contain abrasives, plasticizers, or fillers. It is made of a material with a durometer hardness A of 70° to 100° as specified in JIS K6251, and is formed from a low-wear elastic material that does not contain plasticizers and has an erasing ability (erasing rate) of 70% or less of pencil lines as specified in JIS S 6050-2002. As a result, the friction body is effective because it does not generate eraser residue when rubbed and has excellent thermal discoloration properties.

[0038] ·Holding body The holder 4 is preferably a cylindrical body with open ends, and the holding portion 41 has a flat portion, formed by injection molding of a transparent synthetic resin. In this case, it is preferable that the holder contains an ultraviolet absorber or a transparent ultraviolet shielding agent, or that a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the holder. As a result, even though the writing instrument 1 uses a component (holder) made of a transparent material, the writing marks formed by the writing instrument 1 do not fade or brown from the beginning, impairing their appearance, and the shape of the pen tip and the color tone and remaining amount of ink in the writing instrument 1 can be visually confirmed.

[0039] On the circular inner surface of the rear end of the holder 4, there are several (four in this case) first ribs 43a extending in the axial direction into which the central portion 34 of the pen tip 3 is press-fitted. On the circular outer surface of the rear end of the holder 4, there are several (six in this case) second ribs 43b extending in the axial direction into which the holder fitting portion 58 of the front shaft 5 is press-fitted, and these are formed at equal intervals. The communication holes formed by the second ribs 43b and the holder fitting portion 58 of the front shaft 5 function as air vents, enabling smooth ink discharge from the pen tip 3.

[0040] As shown in Figure 2 or Figure 3, the holder 4 has a substantially rectangular cross-section holder portion 41 at its tip that surrounds the front part 33 of the pen tip 3, and the writing portion 31 protrudes forward from the front end edge 44 of the holder 4. The holder portion 41 has a flat portion on the long side of the rectangular cross-section. Conventionally, this would make it easy for the coloring agent in the ink to fade or brown, and therefore the handwriting produced would also show fading or browning, thus easily impairing the commercial value. However, with the present invention, by containing an ultraviolet absorber or a transparent ultraviolet shielding agent in the holder 4 or cap 2, or by providing a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent on the surface of the holder, the writing instrument 1, which uses a component made of a transparent material, does not show fading or browning from the beginning, thus impairing its appearance, and the shape of the pen tip and the color tone and remaining amount of ink in the writing instrument 1 can be visually confirmed.

[0041] Furthermore, as shown in Figure 2, the top portion 32 of the pen tip 3 protrudes forward from the front edge portion 44 of the holder 4, and the amount of protrusion is preferably greater than 0.2 mm and less than 6.0 mm, more preferably greater than 1.0 mm and less than 5.0 mm. Within the preferred range, a smaller amount of protrusion results in a firmer, more rigid writing feel, while a larger amount of protrusion within the preferred range results in a softer writing feel.

[0042] The front edge 44 of the holder 4 is provided with a chamfer or radius. It is particularly preferable that the edge on the pen tip 3 side, which may come into contact with the pen tip 3, be chamfered or has a radius. This ensures that even if the pen tip 3 bends excessively, it may come into contact with the front edge 44 of the holder 4, but the load on the front part 33 of the pen tip 3 can be minimized, thereby more reliably preventing breakage or damage to the pen tip 3.

[0043] As shown in Figure 2 or 3, the front edge 44 of the holder 4 is formed in a substantially straight line, the top 32 of the writing section 31 is formed in a substantially straight line, and the angle of the front edge 44 of the holder 4 with respect to the axis is substantially the same as the angle of the top 32 of the writing section 31 with respect to the axis. As a result, the load on the pen tip 3 from the front edge 44 of the holder 4 caused by excessive bending of the pen tip 3 is evenly distributed to the front part 33 of the pen tip 3, reliably preventing breakage or damage to the pen tip 3.

[0044] The angle of the front edge 44 of the holder 4 with respect to the axis refers to the portion of the angle between the front edge 44 of the holder 4 and the axis that is 90 degrees or less, and the angle of the top 32 of the writing portion 31 with respect to the axis refers to the portion of the angle between the top 32 and the axis that is 90 degrees or less. Furthermore, the fact that these two angles are approximately the same means, in other words, that the front edge 44 of the holder 4 and the top 32 are approximately parallel. These angles are set to be between 30 degrees and 90 degrees, and preferably between 45 degrees and 90 degrees.

[0045] As shown in Figure 2, when viewing the entire writing instrument from a direction along the extension of the short side of the writing section 31 that contacts the paper surface, the shape of the pen tip 3 exposed from the holder 4 is approximately a parallelogram or rectangle. As a result, the shape and direction of the writing section 31 can be determined by the shape of the front edge 44, eliminating the need to check the direction solely by the orientation of the pen tip 3 immediately before writing. After exposing the pen tip 3, it can be used for writing immediately.

[0046] Furthermore, the color of the holder 4 may differ from the color of the pen tip 3 (i.e., the ink color). This makes the orientation of the front edge 44 more prominent, making it easier to confirm the shape and direction of the writing section 31. If the pen tip 3 itself is colored with a dark color such as black, and the holder 4 is colored with a lighter color different from the pen tip 3, the orientation of the front edge 44 will stand out even more, making it easier to confirm the shape and direction of the writing section 31.

[0047] Furthermore, the structure of the present invention for detachably fitting the front shaft 5 and the rear shaft 6 may also be applied to the fitting structure between the holder 4 and the front shaft 5. This allows the holder 4 and the front shaft 5 to be detachably fitted together, making it easy to connect the holder 4 and the front shaft 5 with appropriate fitting force, providing a comfortable feeling to the user, allowing the user to recognize that the holder 4 and the shaft 5 are properly connected, and making it easy to replace the pen tip.

[0048] Furthermore, the holder is not particularly limited to the structure and shape shown in the illustration. For example, the holder may hold the ink guide section and the writing section, with at least a part of the holder being a visible section that allows the writing direction to be seen. Alternatively, the holder may hold the pen tip that forms the writing section, have at least one ink guide section for supplying ink to the writing section, and be a visible section that allows the writing direction to be seen. To describe the holder in more detail, the holder is a transparent resin or glass material that allows the writing direction to be seen, specifically a transparent resin or glass material with a parallel light transmittance of 30% or more, preferably 50% or more, and more preferably 70% or more, with a wide, smooth visible section at the front and a shaft section at the rear. If the resin or glass material has a parallel light transmittance of less than 30%, the writing direction cannot be clearly seen, which is undesirable. Examples of resins that satisfy these physical properties include styrene-isoprene resin, ionomer resin, SBR-PP blend resin, acrylic resin, nylon resin, and polymethylpentene.

[0049] Furthermore, the ink described later may be used in practical applications by filling it into a writing instrument such as a ballpoint pen with a tip (pen nib) attached to the writing end.

[0050] When filling a ballpoint pen with the ink described later, the structure and shape of the ballpoint pen itself are not particularly limited. For example, examples include a structure in which ink is impregnated into an ink-absorbing body made of fiber bundles housed inside the barrel and supplied to the writing tip; a structure in which ink is directly housed inside the barrel and an ink flow rate adjustment member in the shape of a comb or made of fiber bundles is interposed; and a ballpoint pen having an ink-filled tube inside the barrel, the ink-filled tube communicating with a tip to which a ball is attached, and further having a liquid stopper to prevent backflow tightly attached to the end face of the ink.

[0051] To explain the ballpoint pen tip in more detail, the following types of tips can be used: a tip in which a ball is held in a ball-holding portion formed by pressing the tip of a metal pipe inward from the outer surface; a tip in which a ball is held in a ball-holding portion formed by cutting a metal material with a drill or the like; a tip in which a resin ball seat is provided inside a metal or plastic tip; or a tip in which the ball held in the tip is biased forward by a spring. Furthermore, the balls can be made of materials such as cemented carbide, stainless steel, ruby, ceramic, resin, or rubber, with a diameter of approximately 0.2 to 3 mm. Furthermore, the ink-filled writing instrument of the present invention includes one equipped with a rolling mechanism, such as a roller, at the tip of the writing instrument, which forms a line of writing through a rolling motion similar to that of a ball.

[0052] The ink container tube, which holds the ink, is made of a transparent molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon. The transparency of the aforementioned ink storage tube includes colored transparent, translucent, and colored translucent, and the ink color and ink You can check the remaining amount, etc. The ink reservoir tube is fitted with a refill to which the tip is connected either directly or via a connecting member, and the refill is housed in a transparent barrel to constitute a writing instrument. Alternatively, a writing instrument can be constructed by directly filling the transparent barrel itself, to which a tip is attached, with ink. The transparency of the barrel includes colored transparent, translucent, and colored translucent, allowing for confirmation of ink color, ink level, etc.

[0053] An ink backflow prevention element can also be filled into the rear end of the ink contained in the ink storage tube or barrel. The aforementioned ink backflow prevention composition consists of a non-volatile liquid or a low-volatility liquid. Specifically, examples include petrolatum, spindle oil, castor oil, olive oil, refined mineral oil, liquid paraffin, polybutene, α-olefin, α-olefin oligomer or co-oligomer, dimethyl silicone oil, methylphenyl silicone oil, amino-modified silicone oil, polyether-modified silicone oil, fatty acid-modified silicone oil, etc., and one or more of these can be used in combination.

[0054] It is preferable to add a gelling agent to the non-volatile and / or non-volatile liquid to increase its viscosity to a suitable level. Examples of such gelling agents include silica with a hydrophobic surface treatment, fine particle silica with a methylated surface treatment, aluminum silicate, swollen mica, clay-based thickeners such as hydrophobic bentonite and montmorillonite, fatty acid metal soaps such as magnesium stearate, calcium stearate, aluminum stearate, and zinc stearate, dextrin compounds such as triphenzylidene sorbitol, fatty acid amides, amide-modified polyethylene wax, hydrogenated castor oil, and fatty acid dextrins, as well as cellulose compounds. Furthermore, the liquid ink backflow prevention composition and a solid ink backflow prevention body can be used in combination. The form of the ballpoint pen is not limited to those described above; it may also be a twin-type writing instrument equipped with pen tips of different shapes or pen tips that dispense ink of different colors.

[0055] The reversible thermochromic material used as the coloring agent is effective in which a reversible thermochromic composition containing at least three essential components of a conventionally known coloring agent—(a) an electron-donating coloring organic compound, (b) an electron-accepting compound, and (c) a reaction medium that determines the temperature at which the coloring reaction of both occurs—is encapsulated in a microcapsule. As a heat-decolorizing type microcapsule pigment that decolorizes upon heating from the colored state, those described in Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 51-44707, Japanese Patent Publication No. 1-29398, etc., can be used. The aforementioned material changes color before and after a predetermined temperature (color change point), exhibiting a decolorized state in the temperature range above the complete decolorization temperature and a colored state in the temperature range below the complete color development temperature. Of these two states, only one specific state exists in the room temperature range. That is, the other state is maintained as long as the heat or cold required to bring about that state is applied, but returns to the state exhibited in the room temperature range once the application of such heat or cold is stopped, exhibiting a relatively small hysteresis width (ΔH A It has a temperature range of 1-7°C (see Figure 7).

[0056] Furthermore, the large hysteresis characteristics (ΔH) described in Japanese Patent Publication No. 4-17154, Japanese Patent Publication No. 7-179777, Japanese Patent Publication No. 7-33997, Japanese Patent Publication No. 8-39936, etc. B The curve plotting the change in color intensity due to temperature changes exhibits the following significantly different paths for color change depending on whether the temperature is raised from a temperature below the color change temperature range or decreased from a temperature above the color change temperature range. This allows for the application of heat-decolorizing microcapsule pigments that can retain color in a specific temperature range [the temperature range between t2 and t3 (effectively the two-phase retention temperature range)], either in the colored state at low temperatures below the complete color development temperature (t1) or in the decolorized state at high temperatures above the complete decolorization temperature (t4) (see Figure 8). Furthermore, as a heat-decolorizing microcapsule pigment capable of retaining color memory, one using an ester compound represented by the following general formula (1) as component (c) is preferable because it exhibits a wide hysteresis range (40-70°C) in relation to the color density-temperature curve and changes color. In order to have only one of the two states before and after discoloration exist in the room temperature range, the hysteresis width is 40 to 70°C, preferably 50 to 70°C, more preferably 60 to 70°C, the complete decolorization temperature (t4) is 45°C or higher, preferably 50°C or higher, and the color development start temperature (t2) is 0°C or lower, preferably -5°C or lower. [ka] The aforementioned ester compound is an ester compound composed of an alcohol compound having two aromatic rings in its molecule and a saturated or unsaturated fatty acid having four or more carbon atoms. In the formula, R represents an alkyl or alkenyl group having 4 or more carbon atoms, preferably a group with 6 carbon atoms. A alkyl group with approximately 20 carbon atoms, more preferably an alkyl group with 8 to 18 carbon atoms. Specifically, the aforementioned compounds include 4-benzyloxyphenylethyl butanoate, 4-benzyloxyphenylethyl pentanoate, 4-benzyloxyphenylethyl hexanoate, 4-benzyloxyphenylethyl heptanoate, 4-benzyloxyphenylethyl octanoate, 4-benzyloxyphenylethyl nonanoate, 4-benzyloxyphenylethyl decanoate, 4-benzyloxyphenylethyl undecanoate, 4-benzyloxyphenylethyl dodecanoate, 4-benzyloxyphenylethyl tridecanoate, 4-benzyloxyphenylethyl tetradecanoate, 4-benzyloxyphenylethyl pentadecanoate, 4-benzyloxyphenylethyl hexadecanoate, and heptadecanoate. Examples include 4-benzyloxyphenylethyl acid, 4-benzyloxyphenylethyl octadecanoate, 4-benzyloxyphenylethyl nonadecanoate, 4-benzyloxyphenylethyl eicosanoate, 4-benzyloxyphenylethyl tricosanoate, 4-benzyloxyphenylethyl tetracosanoate, 4-benzyloxyphenylethyl pentacosanoate, 4-benzyloxyphenylethyl hexacosanoate, 4-benzyloxyphenylethyl heptacosanoate, 4-benzyloxyphenylethyl octacosanoate, 4-benzyloxyphenylethyl nonacosanoate, 4-benzyloxyphenylethyl triacontanoate, and 4-benzyloxyphenylethyl hentriacontanoate.

[0057] Furthermore, as heat-activated microcapsule pigments, systems using specific alkoxyphenol compounds having linear or side-chain alkyl groups with 3 to 18 carbon atoms as electron-accepting compounds (Japanese Patent Publication No. 11-129623, Japanese Patent Publication No. 11-5973), systems using specific hydroxybenzoic acid esters (Japanese Patent Publication No. 2001-105732), systems using gallic acid esters, etc. (Japanese Patent Publication No. 51-44706, Japanese Patent Publication No. 2003-253149) can also be used (see Figure 9). Here, a non-thermochromic dye, pigment, or other coloring agent can be incorporated into the reversible thermochromic microcapsule pigment or ink to create a configuration that exhibits an alternating color change from colored (1) to colored (2).

[0058] The microcapsule pigment may have a circular cross-sectional shape or a non-circular cross-sectional shape. The average particle size of the microcapsule pigment is 0.5 to 5.0 μm, preferably 1 to 4 μm, and more preferably 1 to 3 μm. When the average particle size exceeds 5.0 μm, ink flowability tends to decrease, and adhesion to the writing surface tends to decline. On the other hand, when the average particle size is less than 0.5 μm, it becomes difficult to achieve high-density color development. Furthermore, if the ratio of the reversible thermochromic composition to the wall film becomes too large, the wall film becomes too thin, leading to a decrease in resistance to pressure and heat. Conversely, if the ratio of the wall film to the reversible thermochromic composition becomes too large, a decrease in color density and vividness during color development is unavoidable. Therefore, a ratio of reversible thermochromic composition / wall film of 6 / 1 to 1 / 1 (by weight) is preferable.

[0059] Here, the average particle size of the microcapsule pigment is the arithmetic mean of the maximum particle size of each particle measured by image analysis of observation images using a digital microscope, in accordance with JIS Z 8827-1:2008. For image analysis, for example, the image analysis-based particle size distribution measurement software "Mac-View" manufactured by Mountec can be used.

[0060] The average particle size is measured using MAGVIEW, an image analysis-based particle size distribution software manufactured by Mountec, to determine the particle area, calculate the projected area circle equivalent diameter (Heywood diameter) from the area of ​​the particle area, and then measure the average particle size of particles equivalent to an equivolute sphere based on that value. In addition, if the particle size of all or most of the particles exceeds 0.2 μm, it is also possible to measure the average particle size of particles equivalent to an equivolute sphere using the Coulter method with a particle size distribution analyzer (Beckman Coulter, Ltd., product name: Multisizer 4e).

[0061] The reversible thermochromic microcapsule pigment can be blended in an amount of 2 to 50% by weight, preferably 3 to 40% by weight, and more preferably 4 to 30% by weight, relative to the total amount of ink. Below 2% by weight, the color density is insufficient, and above 50% by weight, the ink flowability decreases, impairing writing performance.

[0062] While known methods such as interfacial polymerization, interfacial polycondensation, in situ polymerization, and coacervate can be applied to microencapsulate the aforementioned reversible thermochromic composition, in order to obtain microencapsulated pigments with a non-circular cross-sectional shape and particle size range that satisfy the requirements of the present invention, it is effective to apply an interfacial polymerization method or an interfacial polycondensation method that is less prone to aggregation and coalescence.

[0063] The aforementioned photochromic organic materials include benzopyran compounds such as 6-methoxy-2,2-diphenyl-2H-1-benzopyran, naphthopyran compounds such as 3,3-diphenyl-3H-naphtho[2,1-b]pyran, spiropyran compounds such as 1,3,3-trimethyl-indolino-6′-nitrobenzospiropyran, and 1,3-dihydro-1,3,3-trimethyl-6′-(1-piperidinyl)-spiro[2H-indole-2,3′-[3H Examples of spirooxazine compounds and diarylethene compounds include [naphtho[2,1-b][1,4]oxazine], 1,3-dihydro-1,3,3,4,5-pentamethyl-spiro[2H-indole-2,3′-[3H]naphtho[2,1-b][1,4]oxazine], and 1-(2,4-dichlorobenzyl)-3,3-dimethyl-5,6-dichlorospiro[indoline-2,3′-[3H]naphtho[2,1-b][1,4]oxazine]. The aforementioned photochromic organic material can also be used encapsulated in the aforementioned microcapsules.

[0064] Examples of dyes used in oil-based inks include organic solvent-soluble dyes classified as solvent dyes in the color index. The dyes used in water-based inks can include all types of dyes that are soluble in water-based media: acidic dyes, basic dyes, and direct dyes. As pigments, fluorescent pigments in the form of fine synthetic resin particles, in which various fluorescent dyes are solid-solved in a resin matrix, can be used. Furthermore, non-fluorescent pigments, pearl pigments, metal powder pigments, phosphorescent pigments, white pigments such as titanium dioxide, silica, and calcium carbonate, fragrances, and fragrance-encapsulated pigments can also be used in combination, if desired. The aforementioned dye, fluorescent pigment, or photochromic organic material is used in an amount of 1 to 25% by weight, preferably 2 to 15% by weight, relative to the total amount of ink.

[0065] The ink used in this invention is effective in which a colorant is dissolved or dispersed in a solvent. Examples of the aforementioned inks include shear viscosity-reducing inks containing shear viscosity-reducing agents, coagulating inks in which pigments or transparent metallic luster pigments are suspended in a loosely aggregated state using water-soluble polymer flocculants, and low viscosity inks with a viscosity of several mPa·s.

[0066] For oil-based inks, organic solvents are used as solvents, while for water-based inks, water and, if necessary, water-soluble organic solvents are used. For organic solvents used in oil-based inks, conventionally available solvents can be used, and they are used in an amount ranging from 40 to 80% by weight in the ink. Examples of the aforementioned organic solvents include benzyl alcohol, ethylene glycol, diethylene glycol, propylene glycol, benzyl glycol, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monoethyl ether, diethylene glycol monophenyl ether, propylene glycol monoethyl ether, propylene glycol monophenyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monophenyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monophenyl ether, methyl lactate, ethyl lactate, and γ-butyrolactone.

[0067] Furthermore, using a solvent with a vapor pressure of 5.0 to 50 mmHg at 20°C, which is easily volatile as an organic solvent, as the main solvent results in excellent drying properties for the ink. Organic solvents with a vapor pressure of 5.0-50 mmHg (20°C) include alcohol-based organic solvents such as ethyl alcohol (45), n-propyl alcohol (14.5), isopropyl alcohol (32.4), n-butyl alcohol (5.5), isobutyl alcohol (8.9), sec-butyl alcohol (12.7), tert-butyl alcohol (30.6), and tert-amyl alcohol (13.0). Glycol ether-based organic solvents such as ethylene glycol monomethyl ether (8.5), ethylene glycol diethyl ether (9.7), ethylene glycol monoisopropyl ether (6.0), and propylene glycol monomethyl ether (7.6), Hydrocarbon organic solvents such as n-heptane (35.0), n-octane (11.0), isooctane (41.0), methylcyclohexane (37.0), ethylcyclohexane (10.0), toluene (24.0), xylene (5.0-6.0), and ethylbenzene (7.1). Ketone-based organic solvents such as methyl isobutyl ketone (16.0), methyl n-propyl ketone (12.0), methyl n-butyl ketone (12.0), and di-n-propyl ketone (5.2). Examples of ester-based organic solvents include n-butyl formate (22.0), isobutyl formate (33.0), n-propyl acetate (25.0), isopropyl acetate (48.0), n-butyl acetate (8.4), isobutyl acetate (13.0), ethyl propionate (28.0), n-butyl propionate (45.0), methyl butyrate (25.0), and ethyl butyrate (11.0). The numbers in parentheses indicate the vapor pressure of each organic solvent at 20°C.

[0068] In the case of water-based inks that use water as a solvent, a water-soluble organic solvent that is compatible with water can also be added. Examples of the aforementioned water-soluble organic solvents include ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, sulforane, 2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0069] As resins, ketone resins, ketone-formaldehyde resins, amide resins, alkyd resins, rosin-modified resins, rosin-modified phenolic resins, phenolic resins, xylene resins, polyvinylpyrrolidone, α- and β-pinene-phenol polycondensate resins, polyvinyl butyral resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, dextrin, etc., can also be used, and can be used to impart adhesion and viscosity to the paper surface.

[0070] Furthermore, a shear-reducing viscosity-imparting agent can be added as needed. By adding the aforementioned shear-reducing viscosity-imparting agent, aggregation and sedimentation of the coloring agent can be suppressed, as well as bleeding of the handwriting. Furthermore, if the writing instrument that fills the ink is in the form of a ballpoint pen, it is possible to prevent ink leakage from the gap between the ball and the tip when not in use, and to prevent ink backflow when the writing tip is left upright. Furthermore, the viscosity of the ink to which the shear-reducing viscosity-imparting agent has been added is 3.84 S at 20°C using an E-type viscometer in the case of an oil-based ink. -1Preferably, the ink viscosity at the shear rate is 100 mPa·s or higher, and the shear viscosity reduction index is 0.3 to 0.9. In the case of water-based inks, the shear viscosity measured by an E-type rotational viscometer at 20°C is 3.84S. -1 Preferably, the ink viscosity at the shear rate is 20 to 300 mPa·s, and the shear viscosity reduction index is 0.1 to 0.9. By specifying the viscosity range and shear viscosity index mentioned above, it is possible to further prevent ink leakage and ink backflow. The shear viscosity index (n) is obtained from fluid dynamics measurements using a viscometer, such as shear stress (T) and shear rate (j), using the empirical formula T = Kj. n This value is calculated by applying the formula (where K is the non-Newtonian viscosity coefficient).

[0071] Examples of organic solvents used in oil-based inks include cross-linked acrylic resins, emulsions of cross-linked acrylic resins, non-cross-linked acrylic resins, cross-linked N-vinyl carboxylic acid amide polymers or copolymers, non-cross-linked N-vinyl carboxylic acid amide polymers or copolymers, hydrogenated castor oil, fatty acid amide waxes, waxes such as oxidized polyethylene wax, fatty acid metal salts such as stearic acid, palmitic acid, octyl acid, and aluminum salts of lauric acid, dibenzylidene sorbitol, N-acyl amino acid compounds, smectite inorganic compounds, montmorillonite inorganic compounds, bentonite inorganic compounds, hectorite inorganic compounds, silica, and the like. In the case of water-based inks using water as a solvent, xanthan gum, gellan gum, succinoglycans (average molecular weight approximately 1 to 8 million), which are heteropolysaccharides with organic acid modifications of glucose and galactose, alkasi gum, guar gum, locust bean gum and its derivatives, hydroxyethylcellulose, alkyl alginates, polymers with a molecular weight of 100,000 to 150,000 mainly composed of alkyl esters of methacrylic acid, glucomannan, gelling polysaccharides extracted from seaweed such as agar and carrageenan, benzylidene sorbitol and benzylidene Nonionic surfactants with an HLB value of 8 to 12, such as denxylitol or its derivatives, crosslinkable acrylic acid polymers, inorganic fine particles, polyglycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyethylene glycol fatty acid esters, polyoxyethylene castor oil, polyoxyethylene lanolin / lanolin alcohol / beeswax derivatives, polyoxyethylene alkyl ethers / polyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers, and fatty acid amides, as well as salts of dialkyl or dialkenyl sulfosuccinate. Examples include mixtures of N-alkyl-2-pyrrolidone and anionic surfactants, and mixtures of polyvinyl alcohol and acrylic resins. Furthermore, the shear viscosity reducing agent can be used in combination, and the polymer can also be used as a resin.

[0072] When using the ink of the present invention by filling it into a ballpoint pen, it is preferable to add a lubricant such as a higher fatty acid such as oleic acid, a nonionic surfactant having a long-chain alkyl group, a polyether-modified silicone oil, thiophosphite triesters such as thiophosphite tri(alkoxycarbonylmethyl ester) or thiophosphite tri(alkoxycarbonylethyl ester), phosphate monoester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, phosphate diester of polyoxyethylene alkyl ether or polyoxyethylene alkylaryl ether, or metal salts, ammonium salts, amine salts, or alkanolamine salts thereof to provide an anti-wear effect on the ball bearing seat.

[0073] In addition, for water-based inks, pH adjusters such as inorganic salts like sodium carbonate, sodium phosphate, and sodium acetate, and organic basic compounds such as water-soluble amine compounds may be used as needed; rust inhibitors such as benzotriazole, tolyltriazole, dicyclohexylammonium nitride, diisopropylammonium nitride, and saponins; preservatives or fungicides such as carbolic acid, sodium salt of 1,2-benzthiazolin 3-one, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, and 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine may be used; urea, nonionic surfactants, reduced or non-reduced starch hydrolysates, oligosaccharides such as trehalose, sucrose, cyclodextrin, glucose, dextrin, sorbitol, mannitol, and sodium pyrophosphate may be used; wetting agents, defoamers, dispersants, and fluorinated surfactants or nonionic surfactants to improve ink penetration may also be used.

[0074] In the present invention, the ink storage tube and / or barrel contain an ultraviolet absorber or a transparent ultraviolet shielding agent, or are provided with a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent. Specifically, the configuration involves housing a refill containing ink in a transparent ink storage tube within a transparent barrel, with the barrel containing an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent. Alternatively, the configuration involves housing a refill containing ink in a transparent ink storage tube within a transparent barrel, with the ink storage tube containing an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent provided on the surface of the barrel containing the ink. Furthermore, when using both a transparent ink reservoir tube and a transparent barrel, both the ink reservoir tube and the barrel may contain an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent may be provided. In the writing instrument configuration described above, if a transparent cap is provided to cover the tip of the writing instrument, it is preferable that the cap contains an ultraviolet absorber or a transparent ultraviolet shielding agent, or that a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the cap.

[0075] The UV absorber mentioned above is: 2,4-hydroxybenzophenone, 2-Hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-Hydroxy-4-methoxybenzophenone-5-sulfonic acid, 2-Hydroxy-4-octoxybenzophenone, Bis-(2-methoxy-4-hydroxy-5-benzoylphenyl)-methane 2-[2'-hydroxy-3'-5'-di-t-amylphenyl]-benzophenone, 2-Hydroxy-4-dodecyloxy-benzophenone [Trade name: Seesorb 103, manufactured by Cipro Chemical Co., Ltd.] 2-Hydroxy-4-octadecyloxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-Hydroxy-4-benzyloxybenzophenone, Benzophenone-based UV absorbers such as 2-[2'-hydroxy-3'-5'-di-t-amylphenyl]-benzophenone.

[0076] Phenyl salicylate, para-t-butylphenyl salicylate, Paraoctylphenyl salicylate, 2-4-di-t-butylphenyl-4-hydroxybenzoate, 1-hydroxybenzoate, 1-hydroxy-3-t-butyl-benzoate, 1-hydroxy-3-t-octylbenzoate, Salicylic acid-based UV absorbers such as resorcinol monobenzoate.

[0077] Ethyl-2-cyano-3,3'-diphenylacrylate, 2-Ethylhexyl-2-cyano-3,3'-diphenylacrylate, Cyanoacrylate-based UV absorbers such as 2-ethylhexyl-2-cyano-3-phenylsinnate.

[0078] 2-[5-t-butyl-2-hydroxyphenyl]-benzotriazole [trade name: Tinuvin-PS, manufactured by Ciba-Geigy] 2-[5-methyl-2-hydroxyphenyl]-benzotriazole, 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-[3,5-di-t-butyl-2-hydroxyphenyl]-benzotriazole, 2-[3-t-butyl-5-methyl-2-hydroxyphenyl]-5-chlorobenzotriazole, 2-[3,5-di-t-butyl-2-hydroxyphenyl]-5-chlorobenzotriazole, 2-[3,5-di-t-amyl-2-hydroxyphenyl]-benzotriazole [trade name: Tinuvin 328, manufactured by Ciba-Geigy], Methyl-3-[3-t-butyl-5-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]propionate-polyethylene glycol, molecular weight 300 [product name: Tinuvin 1130, manufactured by Ciba-Geigy] 2-[3-dodecyl-5-methyl-2-hydroxyphenyl]benzotriazole, Methyl-3-[3-(2H-benzotriazol-2-yl)-5-t-butyl-4-hydroxyphenyl]propionate-polyethylene glycol, molecular weight 300. 2-[3-t-butyl-5-propyloctylate-2-hydroxyphenyl]-5-chlorobenzotriazole, 2-[2-hydroxyphenyl-3,5-di-(1,1'-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-[2-hydroxy-5-t-octylphenyl]-2H-benzotriazole, 2-[3-t-butyl-5-octyloxycarbonylethyl-2-hydroxyphenyl]-benzotriazole [Trade name: Tinuvin 384, manufactured by Ciba-Geigy] 2-[2-hydroxy-5-tetraoctylphenyl]-benzotriazole, 2-[2-hydroxy-4-octooxyphenyl]-benzotriazole, 2-[2'-hydroxy-3'-(3"4"5"6"-tetrahydrophthalimidomethyl)-5'-methylphenyl]-benzotriazole, Benzotriazole-based UV absorbers such as 2-(2-hydroxy-5-t-butylphenyl)-benzotriazole.

[0079] Ethanediamide-N-(2-ethoxyphenyl)-N'-(4-isododecylphenyl), Examples of oxalate anilide-based UV absorbers include 2,2,4,4-tetramethyl-20-(β-lauryl-oxycarbonyl)-ethyl-7-oxa-3,20-diazodispiro(5,1,11,2)heneicoate-21-one.

[0080] Examples of the transparent light-shielding agent include a transparent metallic luster pigment in which the surface of a core material selected from natural mica, synthetic mica, glass, and alumina is coated with a metal oxide. The aforementioned transparent metallic luster pigment possesses both light absorption (or light reflection) and light transmission properties, absorbing or reflecting ultraviolet light, and also transmitting an appropriate amount of visible light without obstructing vision, allowing the color tone and remaining amount of the ink contained within to be visually confirmed.

[0081] Furthermore, a light stabilizer can be used in combination with the aforementioned UV absorber or transparent light shielding agent. Examples of the aforementioned light stabilizers include antioxidants, anti-aging agents, singlet oxygen quenchers, superoxide anion quenchers, ozone quenchers, visible light absorbers, infrared absorbers, and the like. Among these, hindered amine-based photosafeties are preferably used, for example, poly[[6-(N-morpholino)-1,3,5-triazine-2,4-diyl][(2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene[(2,2,6,6-tetramethyl-4-piperidyl)imino] [product name: Sumisolve 500, manufactured by Sumitomo Chemical Co., Ltd.], 1,2,3,4-butanetetracarboxylic acid tetra(2,2,6,6-tetramethyl-4-piperidyl) (manufactured by Adeka Argus), poly[[6-1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl] (2,2,6,6-tetramethyl-4-piperidyl)imino]hexamethylene [(2,2,6,6-tetramethyl-4-piperidyl)imino] (product name: Tinuvin 944-LD, manufactured by Ciba-Geigy), dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate succinate (product name: Tinuvin 622LD, manufactured by Ciba-Geigy), 2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonate bis(1,2,2,6,6-pentatyl-4-piperidyl) (product name: Tinuvin 144, manufactured by Ciba-Geigy), N, N, -Bis(3-aminopropyl)ethylenediamine-2,4-bis[N-butyl-N-(1,2,2,6,6-pentamethyl-4-piperidyl)amino]-6-chloro-1,3,5-triazine condensate, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate [product name: Sanol LS770, manufactured by Sankyo Co., Ltd.], bis(N-methyl-2,2,6,6-tetramethyl-4-piperidyl)sebacate [product name: Sanol LS292, manufactured by Sankyo Co., Ltd.], 4-benzoyloxy-2,2,6,6-tetramethyl-4-piperidine [product name: Sanol LS-744, manufactured by Sankyo Co., Ltd.], 8-acetyl-3-dodecyl-7,7,9,9-tetramethyl-1,3,8-triazaspiro [4.5) Decane-2,4-dione [Product name: Sanol LS-440, manufactured by Sankyo Co., Ltd.], 1-[2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl]-4-[3-3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine [manufactured by Sankyo Co., Ltd.], 2,2,4,4-tetramethyl-20-(β-lauryl-oxycarbonyl)-ethyl-7-oxa-3,20-diazadispio(5,1,11,2)heneicosan-21 Examples include -one (trade name: Sanduvor 305, manufactured by Sandoz), [N-(2,2,6,6-tetramethyl-4-piperidyl)-β-alanine] dodecyl ester, myristyl ester mixture (trade name: Sanduvor 3052, manufactured by Sandoz), 5-norbornene-2,3-dicarboxic acidobis(2,2,6,6-tetramethyl-4-piperidyl) ester, and 5-norbornene-2,3-dicarboxic acidobis(N-methyl-2,2,6,6-tetramethyl-4-piperidyl) ester. [Examples]

[0082] Examples are described below. In the examples, "parts" refers to parts by mass. Example 1 Preparation of water-based ink composition for ballpoint pens A water-based ink composition for ballpoint pens was obtained by mixing and stirring 4.0 parts of red acid dye [manufactured by Hodogaya Chemical Co., Ltd., trade name: Eosin], 10.0 parts of glycerin, 20.0 parts of ethylene glycol, 0.3 parts of xanthan gum (manufactured by Sansho Co., Ltd., trade name: Kelzan ST, shear viscosity reducing agent), 0.3 parts of phenol, and 65.4 parts of water.

[0083] Manufacturing of writing instruments A ballpoint pen refill was obtained by filling a polypropylene pipe with an inner diameter of 4.4 mm with a mixture of 0.25 parts of 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (manufactured by BASF Japan Ltd., trade name: Chinuvin 328, UV absorber) and 0.25 parts of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (manufactured by BASF Japan Ltd., trade name: Chinuvin 770, light stabilizer), and connecting it to a ballpoint pen tip via a resin holder. The ballpoint pen tip is formed by pressing the tip of a metal pipe inward from its outer surface, and then holding a stainless steel ball with a diameter of 0.5 mm in the tip of the tip. Next, an ink backflow prevention body (liquid stopper) having polybutene as its main component is filled into the rear of the polypropylene pipe, and then the barrel, tip, end plug, and cap with a rubber seal inside are assembled to obtain a ballpoint pen.

[0084] Example 2 Preparation of aqueous ink compositions for marking pens A water-based ink composition for marking pens was obtained by mixing and stirring 40.0 parts of a pink fluorescent pigment dispersion [manufactured by Nippon Fluorescent Chemicals Co., Ltd., product name: Lumicol NKW-3907.E40, pigment content 33.5%], 10.0 parts of glycerin, 0.5 parts of triethanolamine, 0.3 parts of phenol, 0.5 parts of a preservative [manufactured by Hokko Chemical Co., Ltd., product name: Hokuside R-150], and 48.7 parts of water.

[0085] Manufacturing of writing instruments The ink is impregnated into an ink-absorbing body made of polyester sliver coated with a synthetic resin film, and the ink-absorbing body is housed in a barrel made of opaque polypropylene resin. The pen body attached to the front end of the barrel comprises a pen tip that serves as the writing section, and a holder that holds the pen tip and has at least one ink guide section for supplying ink to the writing section. It also has a relay core for supplying ink contained in the writing instrument body to the ink guide section provided on the holder, and the holder serves as a viewing section that allows the writing direction to be visually confirmed. A marking pen was obtained by assembling a cap made of polypropylene resin containing a mixture of 0.25 parts of 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (manufactured by BASF Japan Ltd., trade name: Tinuvin 328, UV absorber) and 0.25 parts of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (manufactured by BASF Japan Ltd., trade name: Tinuvin 770, light stabilizer).

[0086] Example 3 Preparation of aqueous ink compositions for marking pens A water-based ink composition for marking pens was obtained by mixing and stirring 40.0 parts of a yellow fluorescent pigment dispersion [manufactured by Nippon Fluorescent Chemicals Co., Ltd., product name: Lumicol NKW-3905.E, pigment content 33.5%], 10.0 parts of glycerin, 0.5 parts of triethanolamine, 0.3 parts of phenol, 0.5 parts of a preservative [manufactured by Hokko Chemical Co., Ltd., product name: Hokuside R-150], and 48.7 parts of water.

[0087] Manufacturing of writing instruments The marking pen is assembled using a barrel and inner cap made of polypropylene resin mixed with 0.25 parts of 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (manufactured by BASF Japan Ltd., trade name: Chinuvin 328, UV absorber) and 0.25 parts of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (manufactured by BASF Japan Ltd., trade name: Chinuvin 770, light stabilizer), and a cap made of polycarbonate resin. The ink is contained in liquid form inside the barrel, a resin-processed pen tip made of polyester fiber is provided at the tip of the barrel, and the cap with the inner cap placed inside is assembled to the writing instrument body to obtain a marking pen. Furthermore, a comb-shaped ink flow adjustment member is provided at the rear of the pen tip inside the barrel.

[0088] Example 4 Preparation of reversible thermochromic microcapsule pigments A reversible thermochromic composition consisting of (a) 4.5 parts of 2-(2-chloroanilino)-6-di-n-butylaminofluorane as component, (b) 3.0 parts of 1,1-bis(4′-hydroxyphenyl)n-decane and 5.0 parts of 2,2-bis(4′-hydroxyphenyl)hexafluoropropane as component, and (c) 40.0 parts of n-butyl stearate and 10.0 parts of n-butyl palmitate as component was uniformly heated and dissolved. A solution was mixed with 30.0 parts of aromatic polyvalent isocyanate prepolymer as a wall material and 40.0 parts of a co-solvent, and the solution was emulsified and dispersed in an 8% aqueous polyvinyl alcohol solution to form fine droplets. After stirring at 65°C for about 1 hour, 2.5 parts of water-soluble aliphatic modified amine were added, and stirring was continued at 90°C for 5 hours to obtain a reversible thermochromic microcapsule pigment suspension. Reversible thermochromic microcapsule pigments were isolated from the suspension by centrifugation. The aforementioned microcapsule pigment changed color from black to colorless at temperatures above approximately 23°C, and then changed back to black when cooled to below 15°C.

[0089] Preparation of reversible thermochromic ink composition A reversible thermochromic ink was prepared by mixing and stirring 25.0 parts of the microcapsule pigment, 0.2 parts of succinoglycan (shear viscosity reducing agent), 0.5 parts of triethanolamine, 5.5 parts of urea, 7.5 parts of glycerin, 0.5 parts of phosphate ester surfactant (lubricant), 0.2 parts of defoamer, 0.1 parts of 1,2-benzthiazolin-3-one [manufactured by Abyssia Co., Ltd., trade name: Proxel XL-2, preservative] and 60.5 parts of water.

[0090] Manufacturing of writing instruments 0.95 g of the aforementioned ink was filled into a polypropylene pipe with an inner diameter of 4.4 mm, which contained a mixture of 0.25 parts of 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (manufactured by BASF Japan Ltd., trade name: Chinuvin 328, UV absorber) and 0.25 parts of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (manufactured by BASF Japan Ltd., trade name: Chinuvin 770, light stabilizer), and connected to a ballpoint pen tip via a resin holder. The ballpoint pen tip is constructed by pressing the tip of a metal pipe inward from the outer surface, and a stainless steel ball with a diameter of 0.7 mm is held in the tip of the tip, and the ball is biased forward by a spring. Next, an ink backflow prevention body (liquid stopper) having polybutene as its main component is filled into the rear of the polypropylene pipe, a tail plug is fitted onto the rear of the pipe, a front barrel and a rear barrel made of polycarbonate resin are assembled, degassing is performed by centrifugal treatment, and then a cap is fitted to obtain a ballpoint pen.

[0091] Example 5 Manufacturing of writing instruments In Example 4, 0.95 g of the reversible thermochromic ink composition was filled into a polypropylene pipe with an inner diameter of 4.4 mm and connected to a ballpoint pen tip via a resin holder. The ballpoint pen tip is constructed by pressing the tip of a metal pipe inward from the outer surface, and a stainless steel ball with a diameter of 0.7 mm is held in the tip of the tip, and the ball is biased forward by a spring. Next, a viscoelastic ink backflow prevention body (liquid stopper) mainly composed of polybutene is filled into the rear of the polypropylene pipe, and a tail plug is fitted onto the rear of the pipe. The pen is then assembled using a front barrel and rear barrel made of polycarbonate resin mixed with 0.5 parts of 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole (manufactured by BASF Japan Ltd., trade name: Chinuvin 234, UV absorber). After assembling the front barrel and rear barrel and performing degassing by centrifugation, a cap is fitted to obtain a ballpoint pen.

[0092] Example 6 Manufacturing of writing instruments 0.95 g of the reversible thermochromic ink composition obtained in Example 4 was filled into a 4.4 mm inner diameter polypropylene pipe mixed with 0.25 parts of 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol [BASF Japan Ltd., trade name: Chinuvin 328, UV absorber] and 0.25 parts of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate [BASF Japan Ltd., trade name: Chinuvin 770, light stabilizer], and connected to a ballpoint pen tip via a resin holder. The ballpoint pen tip is constructed by pressing the tip of a metal pipe inward from the outer surface, and a stainless steel ball with a diameter of 0.7 mm is held in the tip of the tip, and the ball is biased forward by a spring. Next, an ink backflow prevention body (liquid stopper) having polybutene as its main component and having viscoelastic properties was filled into the rear of the polypropylene pipe, and then a tail plug was fitted to the rear of the pipe. Furthermore, the front and rear barrels, made of polycarbonate resin, were spray-coated with an ink consisting of 50 parts acrylic polyol resin (50% solids), 1.0 part 2-(2H-benzotriazol-2-yl)-4,6-bis(1,1-dimethylpropyl)phenol (Tinuvin 328, manufactured by BASF Japan, UV absorber), 60 parts xylene, and 10 parts hexamethylene diisocyanate-based curing agent. After heat treatment at 70°C for 30 minutes, the parts were assembled with the aforementioned pipe, degassed by centrifugation, and then a cap was attached to obtain a ballpoint pen.

[0093] Example 7 Preparation of photochromic microcapsule pigments A photochromic material consisting of 2.0 parts of an organic photochromic compound [spironaphthoxazine compound (manufactured by the Recording Materials Research Institute, trade name: Sunny Color Pink)] and 45.0 parts of a styrene-α-methylstyrene copolymer (manufactured by Rika Hercules Co., Ltd., trade name: Picoralustic A5, weight-average molecular weight 317)] was uniformly heated and dissolved. The mixture was then emulsified and dispersed in a 6% aqueous polyvinyl alcohol solution to form fine droplets by adding 20.0 parts of an aromatic polyvalent isocyanate prepolymer as a film material and 20.0 parts of a co-solvent. The reaction was carried out at 70°C for 1 hour. Subsequently, the liquid temperature was maintained at 90°C and stirring was continued for 3 hours to obtain a photochromic microcapsule pigment suspension. Photochromic microcapsule pigments were isolated from the suspension by centrifugation. The aforementioned microcapsule pigment was white before exposure to sunlight, but changed to pink when exposed to sunlight. After being left indoors for a while, the pink color disappeared, and it returned to its original white color. This color change could be repeated.

[0094] Preparation of light-color-changing ink compositions A photochromic ink composition was prepared by mixing and stirring 25.0 parts of the microcapsule pigment, 0.2 parts of λ-calazinan, 0.5 parts of triethanolamine, 15.0 parts of diethylene glycol, 0.5 parts of phosphate ester surfactant (lubricant), 0.2 parts of defoamer, 0.1 parts of 1,2-benzthiazolin-3-one [manufactured by Abyssia Co., Ltd., trade name: Proxel XL-2, preservative] and 58.5 parts of water.

[0095] Manufacturing of writing instruments 0.95 g of the light-color-changing ink was filled into a polypropylene pipe with an inner diameter of 4.4 mm and connected to a ballpoint pen tip via a resin holder. The ballpoint pen tip was constructed by pressing the tip of a metal pipe inward from the outer surface, and a stainless steel ball with a diameter of 1.0 mm was held at the tip of the tip, and the ball was biased forward by a spring. Next, a viscoelastic ink backflow prevention body (liquid stopper) mainly composed of polybutene was filled into the rear of the polypropylene pipe, and a tail plug was fitted onto the rear of the pipe. Then, a front barrel and rear barrel made of polycarbonate resin mixed with 0.5 parts of 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole (manufactured by BASF Japan Ltd., trade name: Chinuvin 234, ultraviolet absorber) were assembled, and after degassing by centrifugation, a cap was fitted to obtain a ballpoint pen.

[0096] Comparative Example 1 In the preparation of the writing instrument in Example 1, a ballpoint pen was obtained in the same manner as in Example 1, except that a UV absorber was not mixed into the polypropylene pipe.

[0097] Comparative Example 2 In the preparation of the writing instrument in Example 2, a marking pen was obtained in the same manner as in Example 2, except that a UV absorber was not mixed into the cap made of polypropylene resin.

[0098] Comparative Example 3 In the preparation of the writing instrument of Example 3, a marking pen was obtained in the same manner as in Example 3, except that a UV absorber was not mixed into the barrel and inner cap made of polypropylene resin.

[0099] Comparative Example 4 In the preparation of the writing instrument in Example 4, a ballpoint pen was obtained in the same manner as in Example 4, except that a UV absorber and a light stabilizer were not mixed into the polypropylene pipe.

[0100] Comparative Example 5 In the preparation of the writing instrument in Example 7, a ballpoint pen was obtained using the same method as in Example 7, except that a UV absorber was not mixed into the front and rear barrels made of polycarbonate resin.

[0101] Lightfastness test The following lightfastness tests were conducted using the ballpoint pens and marking pens of Examples 1 to 7 and Comparative Examples 1 to 5. Each ballpoint pen and marking pen was irradiated with light for 100 hours using a fade meter (Suga Test Instruments, Long Life Carbon Arc applied). After that, the caps were removed, and writing was done on paper and compared to the initial handwriting. Handwriting samples using thermochromic and photochromic inks were comprehensively evaluated in both their pre- and post-discoloration states. The following table shows the results of the lightfastness test.

[0102] [Table 1]

[0103] The following is an evaluation of the symbols in the test results shown in the table. ◎: The handwriting showed no change compared to the initial sample. ○: Although slight fading is observed compared to the initial state, the handwriting obtained is perfectly usable. △: Browning is observed compared to the initial state, and even in the case of color-changing inks, browning of the writing is visible. ×: Significant discoloration and browning are observed compared to the initial state, and even in the case of discoloration-prone inks, browning of the writing is still visible. [Explanation of symbols]

[0104] 1 writing implements 2 caps 21 Annular seal section 22 Rear shaft fitting part 3. Pen nib 31 Writing section 32 Top 33 Front 34 Central part 35 Rear 4 Holding body 41 Holding part 42 First contact wall section 43a First rib 43b Second rib 44 Front edge 5 Front axle 51 Fitting part 52 Small diameter base 53 Outward locking part 53a First outward locking part 53b Second outward locking part 531 Annular projection 532 Pressure contact surface 54 slits 55 Step part 56a Second contact wall 56b Third contact wall 57 Vertical ribs 58 Retaining body fitting part 59 Retaining Ribs 6 rear axle 61 Fitting part 62 Large diameter base 63 Inward locking part 63a First inward locking part 63b Second inward locking part 631 Ring groove 632 Pressure contact surface 633 Annular projection 64 Airtight parts 65 Cap fitting section 7. Ink absorber 8 shaft cylinder 9 Friction body t1 Complete color development temperature of heat-decolorizing microcapsule pigments and color-memory-retaining microcapsule pigments t2: Color development start temperature of heat-decolorizing microcapsule pigments and color-memory-retaining microcapsule pigments t3 Decolorization start temperature of heat-decolorizing microcapsule pigments and color-memory-retaining microcapsule pigments Complete decolorization temperature of t4 heat-decolorizing microcapsule pigments and color-memory-retaining microcapsule pigments Complete decolorization temperature of T1 heat-activated microcapsule pigments Decolorization onset temperature of T2 heat-activated microcapsule pigments T3 Heat-Developing Microcapsule Pigment: Color Development Initiation Temperature Complete color development temperature of T4 heat-activated microcapsule pigments

Claims

1. A writing instrument comprising: an ink containing an electron-donating organic compound, an electron-accepting compound, and a reversible thermochromic material, a photochromic organic material, a dye, and a fluorescent pigment, comprising a reaction medium that determines the temperature at which the color reaction of the components of (a) and (b) occurs; an ink-absorbing body containing the ink; a barrel containing the ink-absorbing body; a pen tip from which the ink can be dispensed; and a holder for holding the pen tip, The holder is made of a transparent material and has a rectangular cross-section with a flat surface on the longer side, and the writing portion is formed by one end of the pen tip protruding forward from the front edge of the holder. The transparent material forming the holder contains an ultraviolet absorber or a transparent ultraviolet shielding agent, or a light-stabilizing layer containing an ultraviolet absorber or a transparent ultraviolet shielding agent is provided on the surface of the holder. The shaft cylinder is composed of a front shaft and a rear shaft, and the retaining body is fitted onto the front shaft. The pen tip has a cylindrical central portion, and the outer surface of the central portion is held between the holder and the front shaft of the writing instrument.

2. The writing instrument according to claim 1, wherein the pen tip is made of a porous synthetic resin having open cells, has a flat portion on the long side of the rectangular cross-section, and the writing portion is flexible and can be deformed by bending on the long side of the rectangular cross-section.

3. The writing instrument according to claim 1 or 2, wherein the writing part is processed into a chisel shape.

4. The writing instrument according to any one of claims 1 to 3, wherein the writing part has a rectangular prism shape or a plate shape.

5. The writing instrument according to any one of claims 1 to 4, wherein the holder is detachably fitted to the front shaft, and the pen tip can be replaced together with the holder.

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