Fiber bundles for writing instruments, pen nibs using the same, writing instruments

Abstract

The present invention provides a fiber bundle for writing instruments that is excellent in strength and durability, and can be suitably used for the pen tips, ink supply cores, and intermediate cores of writing instruments such as marking pens and felt-tip pens, as well as pen tips and writing instruments using the same. [Solution] The fiber bundle for writing instruments of this disclosure is a fiber bundle for writing instruments used as an ink guide core for a pen tip or a writing pen core, characterized in that the fiber bundle for writing instruments is composed of a multifilament of long fibers having fibers with different melting points, and the multifilament contains at least crimped fibers.

Description

Technical Field

[0001] This specification relates to a fiber bundle body for writing implements that can be suitably used for pen tips of writing implements such as marking pens and signature pens, ink supply cores, relay cores, etc., a pen tip using the same, and a writing implement.

Background Art

[0002] Conventionally, writing implements using a fiber bundle body made of fibers such as synthetic resin fibers or natural fibers for pen tips, relay cores, etc., and applicators used for coating bodies such as cosmetics have various structures and are known. The fiber bundle bodies used in these writing implements and cosmetics are used as ink supply cores such as pen cores and relay cores, and liquid supply cores such as coating bodies.

[0003] Among these fiber bundle bodies, binderless (without using a thermosetting resin for adhesion) fiber bundle bodies are known as those that can meet a wide range of required qualities where it is easy to adjust hardness and porosity. As this binderless fiber bundle body, for example, a fibrous liquid supply core formed by mixing a large number of two or more types of fibers including main fibers and heat-fusing fibers having a low melting point part with a lower melting point than the main fibers on at least a part or all of the outer surface, aligning them in the longitudinal direction, bundling them, and compressing them, characterized in that when the fibers are heat-melted in a state where continuous pores are present between the fibers, they are bound by the low melting point part and are formed into a solid rod shape with the fiber direction oriented in the longitudinal direction (for example, see Patent Document 1) and the like are known.

[0004] The technique described in Patent Document 1 above uses two or more types of fibers, one of which is a low melting point fiber. However, due to problems with dimensional stability due to heat shrinkage of the low melting point fiber, it is difficult to produce only with composite long fibers such as core-sheath type multifilaments. In order to stably fix the low melting point fiber, it was necessary to mix two or more types of short fibers with a melting point difference (not substantially the same as the length of the pen core to be formed, but a fiber length formed short for heat welding). However, in fiber bundles using short fibers, when the pen core, intermediate core, liquid supply core, etc., have a slender cross-section, for example, cores with a rectangular or irregular cross-section, especially when forming fiber bundle cores with a small diameter, it is necessary to reduce the amount of bundled short fibers. In this case, when the yarn bundle is pulled out, tension is applied to the front and back in the longitudinal direction, which may cause misalignment in the entanglement of the short fibers. This can lead to variations in the yarn density in the longitudinal direction of the core, or in the worst case, weakening of the entanglement of the short fibers, causing the yarn bundle to separate at the front and back. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2011-20443 (Claims, Examples, etc.) [Overview of the project] [Problems that the invention aims to solve]

[0006] This disclosure aims to address the problems of the prior art described above, and provides a fiber bundle for writing instruments used in pen nibs, intermediate nibs, liquid supply nibs, etc., which, even when used in cores with rectangular or irregular cross-sections, or especially in fiber bundles with small diameters, does not impair the liquid supply performance such as ink as a fiber bundle, has no variation in thread density in the longitudinal direction of the core, and exhibits excellent strength and durability, as well as a pen tip and writing instrument using the same. [Means for solving the problem]

[0007] In view of the above-mentioned conventional problems, the present inventors have sought to resolve them and have found that a fiber bundle for writing instruments, used as an ink guide core for a pen tip or a writing pen core, wherein the fiber bundle for writing instruments is composed of multifilaments of long fibers having different melting points, and the multifilaments contain at least fibers with specific physical properties, thereby obtaining the above-mentioned fiber bundle for writing instruments, a pen tip using the same, and a writing instrument, and have completed this disclosure.

[0008] In other words, the writing instrument fiber bundle of the present disclosure is a writing instrument fiber bundle used as an ink guide core for a pen tip or a writing pen core, and the writing instrument fiber bundle is composed of a multifilament of long fibers having fibers with different melting points, and the multifilament contains at least crimped fibers. The crimped fiber is preferably of a crimp ratio of 1 to 50%, which can be determined by the following formula (I). Crimp ratio = (crimp width ÷ crimp length) × 100 ……(I) [In equation (I) above, the distance from one peak to the next on the corrugated surface of the fiber is defined as the "crimp length," and the distance between the peak (mountain) and trough (lower point) of the wave in a direction perpendicular to the crimp length is defined as the "crimp width."] However, the crimp shape is not limited to a wave shape; it may also include loop shapes, as shown in Figure 1(d). The content of the crimped fibers is preferably 10 to 100% by mass relative to the total amount of the fiber bundle for writing instruments. These fiber bundles for writing instruments preferably have a rectangular cross-sectional shape. The pen tip of this disclosure is a pen tip having a writing pen core, characterized in that the writing pen core is made of a fiber bundle for a writing instrument having the above configuration, and is also a pen tip having an ink guiding core for guiding ink to the writing part, characterized in that the ink guiding core is made of a fiber bundle for a writing instrument having the above configuration. The writing instrument of this disclosure is characterized by comprising a pen tip having a writing nib having the above-described configuration, and / or a pen tip having an ink-guiding nib that guides ink to the writing portion having the above-described configuration. In this disclosure, "crimped fiber" refers to a fiber that has been given bulkiness and elasticity by imparting two-dimensional or three-dimensional crimping and strain to the fiber, fixing this strain in an appropriate manner, and disrupting the parallelism between the fibers. In this disclosure, as described above, a preferred crimped fiber is one in which the crimp ratio determined by formula (I) above is within the above range. [Effects of the Invention]

[0009] According to this disclosure, even when the core has a rectangular or irregular cross-section, or is a fiber bundle core with a particularly small diameter, the fiber bundle does not impair the liquid supply performance such as ink as a fiber bundle, and there is no variation in the fiber density in the longitudinal direction of the core, resulting in excellent strength and durability. The invention also provides a fiber bundle for writing instruments, a pen tip using the same, and a writing instrument. The purposes and effects of this disclosure are recognized and obtained by using the components and combinations indicated in the claims in particular. Both the general description above and the detailed description below are illustrative and explanatory and do not limit the disclosure as described in the claims. [Brief explanation of the drawing]

[0010] [Figure 1] (a) is a schematic perspective view showing an example of an embodiment of the writing instrument fiber bundle of the present disclosure; (b) is an explanatory diagram illustrating the crimp rate of the crimped fibers in the writing instrument fiber bundle of the present disclosure; (c) is an electron microscope (SEM) image showing an example of having crimped fibers in the writing instrument fiber bundle; and (d) is an electron microscope (SEM) image showing an example of the case in which the crimp shape of the crimped fibers in the writing instrument fiber bundle of the present disclosure is not limited to a wave shape but includes a loop shape. [Figure 2](a) and (b) are schematic views shown in a cross-sectional aspect for explaining the form of multifilaments having different melting points used in the fiber bundle body for writing instruments of the present disclosure. (a) shows the side-by-side type, and (b) shows the core-sheath type. [Figure 3] It is a schematic perspective view showing another example of an embodiment of the fiber bundle body for writing instruments of the present disclosure. [Figure 4] It is a schematic view showing an example of an embodiment of a manufacturing process for manufacturing the fiber bundle body for writing instruments of the present disclosure in a cross-sectional aspect. [Figure 5] (a) is an end face view of an example (example) of the fiber bundle body for writing instruments of the present disclosure and an electron microscope (SEM) photograph of an enlarged view thereof, and (b) is an end face view of an example of a fiber bundle body for writing instruments showing a comparative example outside the scope of the present disclosure and an electron microscope (SEM) photograph of an enlarged view thereof. [Figure 6] It is an example of a writing instrument of the present disclosure, showing an embodiment of a twin-type writing instrument having pen tips at both ends. (a) is a front view, and (b) is a longitudinal cross-sectional view in a front view. [Figure 7] Each drawing shows a state in which the caps at both ends of the writing instrument in FIG. 6 are removed. (a) is a plan view, (b) is a front view, and (c) is a longitudinal cross-sectional view in a front view. [Figure 8] In the twin-type writing instrument of FIG. 8, it is an enlarged perspective view showing an enlarged half of the writing instrument including a pen tip having one writing pen core. [Figure 9] Each drawing shows an example of an embodiment of a holding body that holds the writing pen core of the pen tip in FIG. 8. (a) is a perspective view seen from the front side, (b) is a plan view, (c) is a perspective view seen from the rear side, (d) is a right side view, (e) is a front view, (f) is a left side view, (g) is a longitudinal cross-sectional view in a front view, and (h) is a bottom view. [Figure 10] In the twin-type writing instrument of FIG. 6, it is an enlarged perspective view showing an enlarged half of the writing instrument including a pen tip having the other ink supply core. [Figure 11]These are drawings showing an example of an embodiment of an ink supply core at the tip of a pen and a holder for holding a writing part in FIG. 10. (a) is a perspective view seen from the front side, (b) is a plan view, (c) is a perspective view seen from the rear side, (d) is a right side view, (e) is a front view, (f) is a left side view, (g) is a longitudinal sectional view in a front view, and (h) is a bottom view.

Mode for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, note that the technical scope of the present disclosure is not limited to each of the embodiments described in detail below, and extends to the invention described in the claims and its equivalents.

[0012] The fiber bundle for writing instruments of the present disclosure is composed of multifilaments of long fibers having fibers with different melting points (in the present disclosure, even when there is no melting point but a softening point, it is included as the melting point), and the multifilaments include at least crimped fibers. FIG. 1(a) is a schematic perspective view showing an example of an embodiment of a fiber bundle for writing instruments having a rectangular cross-sectional shape.

[0013] Fibers generally include filaments (monofilaments, multifilaments) and slivers. To obtain a fiber bundle with a uniform density in the longitudinal direction, monofilaments or multifilaments are used. However, in the present disclosure, the fiber bundle for writing instruments is formed of multifilaments of long fibers having fibers with different melting points, and a part of the multifilaments of the long fibers includes crimped fibers.

[0014] In this disclosure, multifilaments with different melting points include those composed of a combination of two or more polymers with different chemical structures. Examples include combinations of polymers with different melting points selected from polyester, acrylic, polypropylene, fully aromatic polyester, fully aromatic polyesteramide, polyamide, semi-aromatic polyamide, fully aromatic polyamide, fully aromatic polyether, fully aromatic polycarbonate, polyimide, polyamide-imide (PAI), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), poly-p-phenylenebenzobisoxazole (PBO), polybenzimidazole (PBI), polytetrafluoroethylene (PTFE), ethylene-vinyl alcohol copolymer, etc. Furthermore, even if at least a part of them has a common chemical structure, the melting points can be different by introducing other structural units to form a copolymer. For example, a combination of polyethylene terephthalate and a copolymer polyethylene terephthalate copolymer with a lower melting point is preferred.

[0015] For example, as shown in Figures 2(a) and (b), both core-sheath type and side-by-side type multifilaments having low-melting-point fibers and high-melting-point fibers can be used. In the core-sheath type, the single filament is a multifilament composed of a core component and a sheath component, while in the side-by-side type, the single filament is a multifilament in which two or more polymers are compounded side-by-side. Among these, the core-sheath type multifilament is preferred, and it is even more preferred that the sheath component of the core-sheath type has a lower melting point than the core component. In this disclosure, the melting point difference (high melting point temperature - low melting point temperature) should be at least 30°C, preferably 50°C or more. A melting point difference of 30°C or more facilitates the thermal melting of only the sheath portion of the core-sheath type multifilament, and the point bonding of the intertwined points between fibers whose parallelism has been disrupted by crimping, thereby forming a three-dimensional network structure and solidifying them together. There is no upper limit to the melting point difference as long as it is a heat-fusible composite fiber that can be crimped and is available on the market, but 100°C is realistic. In this disclosure, the melting point is a value measured in accordance with JIS K 7121:2012.

[0016] In this disclosure, the multifilament of long fibers having fibers with different melting points includes at least crimped fibers. The crimped fibers used are fibers that have been given bulkiness and elasticity by applying two-dimensional or three-dimensional crimping and strain to the multifilament of long fibers having fibers with different melting points, fixing this strain in an appropriate manner, and disrupting the parallelism between the fibers. The crimped fibers used in this disclosure preferably have a crimp ratio of 1 to 50%, and more preferably 1 to 20%, as shown in the following formula (I) and Figure 1(b), from the standpoint of adhesion and solidification, which allows for point bonding of interlocking points between fibers to form a three-dimensional network structure, and from the standpoint of forming a fiber bundle core with a high porosity due to the entanglement of fibers with high bulkiness. Crimp ratio = (crimp width ÷ crimp length) × 100 ……(I) [In equation (I) above, the distance from one peak to the next on the corrugated surface of the fiber is defined as the "crimp length," and the distance between the peak (mountain) and trough (lower point) of the wave in a direction perpendicular to the crimp length is defined as the "crimp width."] In the crimped fibers of the writing instrument fiber bundle described herein, the crimp shape is not limited to a wave shape, but includes a loop shape as shown in Figure 1(d). In this case, the crimp ratio can be calculated as the "crimp width," which is the distance from the apex of the loop to the bottom point (valley) of the fiber, similar to the crimp of a wave-shaped fiber.

[0017] By setting the crimp ratio to 1% or more, the interlocking points between fibers are bonded together to form a three-dimensional network structure, creating a fiber bundle core with high porosity due to the intertwining of fibers with high bulkiness. On the other hand, by setting it to 50% or less, the parallelism between fibers is not lost, and an optimal flow path for ink outflow can be formed. From the above standpoint, the content of the crimped fibers is preferably 10 to 100% by mass relative to the total amount of fiber bundles for writing instruments.

[0018] The fineness of the long multifilaments having fibers with different melting points, as well as the fineness of the crimped fibers, is preferably 1 to 20 denier or less, from the viewpoint of ink retention and writing feel when used as a pen tip.

[0019] The fiber bundle for writing instruments of this disclosure is formed by aligning and bundling long multifilaments having fibers with different melting points and crimped fibers having the above-described structure in a predetermined ratio, heating this fiber bundle, and solidifying the fibers together by heating and pressurizing without using short fibers or solvents that act as a binder resin, that is, forming a fiber bundle in which the fibers are solidified and bound together. For example, as shown in Figure 4, long multifilaments having fibers with different melting points and crimped fibers having the above-described structure are arranged in a predetermined ratio in a thermoforming machine 10, aligned longitudinally while being pulled by tension rollers 11 positioned towards the front, and then bundled together and solidified by heating and pressurizing without using binder resin or solvents to form a fiber bundle of a predetermined shape such as a sheet-like body with a rectangular cross-section, a cylindrical body, a polygonal prism, or a star-shaped polygonal prism. In this process, it is important to ensure that the heating method does not cause complete fusion of the fibers. The heating temperature and time should be within a range that allows the purpose of thermoforming to solidify and bind the fibers together by heat and pressure, forming a fiber bundle with a binding force that exceeds the die pull resistance. These will vary depending on the type of fiber and the size of the fiber bundle being manufactured, but the goal is to form a fiber bundle in which the fibers are solidified and bound together by heat by heating at a temperature above the melting point of the lower of two types of fibers with different melting points, and above the temperature at which the thermal shrinkage of the crimp is completed. For example, if crimped fibers made of thermoplastic resin are PET fibers and the thermal shrinkage is completed at 150°C, the fibers can be solidified and bound together by heating at a temperature of 150°C or higher, above the melting point of the fiber with the lower melting point, and below the melting point of the fiber with the higher melting point. Furthermore, the strength of the fiber bundle can be controlled by adjusting the amount of fiber added (basis weight), the heating temperature, and the heating time to control the degree of fusion of low-melting-point fibers.

[0020] The shape, size, and thickness of the fiber bundle for writing instruments obtained by the above method can be any shape (rectangular cross-section, sheet-like, cylindrical, polygonal prism-like, star-shaped polygonal prism-like), depending on the application, such as cotton wick, pen tip, ink guide core, or intermediate core. The fiber bundle obtained by the above method can be cut to any length according to its intended use, such as a pen core, ink guide core, or intermediate core, and then processed as needed for each application to obtain the desired fiber bundle for writing instruments. Figure 1(a) shows an example of an embodiment of the sheet-like fiber bundle A for writing instruments, which has a rectangular cross-sectional shape, and Figure 3 is a schematic perspective view of the cylindrical fiber bundle B for writing instruments.

[0021] In the resulting fiber bundle for writing instruments, it is preferable that the fiber bundle has a substantially uniform density. To obtain a fiber bundle with substantially uniform density, a density of 2,000 to 7,000 d / mm² is preferred. 2 This can be achieved by forming a fiber bundle that has a certain thread density. Furthermore, in this manufacturing method, for rectangular cross-sections, the thickness is 0.1 to 10 mm, and for circular cross-sections, the outer diameter is 0.1 mm or more, with a fiber density of 2,000 d / mm². 2 The above-mentioned fiber bundles can be manufactured successfully. Furthermore, the porosity and hardness of the fiber bundle for writing instruments vary depending on the type of ink, the type of writing instrument, etc., and by adjusting the fiber bundle density, molding temperature, heating time, etc. during the above manufacturing process, the porosity can be set to, for example, 30-80%. In this disclosure, "porosity" is calculated as follows. First, a fiber bundle for writing instruments having a known mass and apparent volume is immersed in water, and after it has been thoroughly soaked in water, the mass is measured after it is removed from the water. From the measured mass, the volume of water soaked into the writing lead is derived. Assuming that this volume of water is the same as the pore volume of the fiber bundle for writing instruments, the porosity is calculated from the following formula. Porosity (unit: %) = (volume of water) / (apparent volume of writing instrument fiber bundle) × 100

[0022] In the writing instrument fiber bundle described herein, even when the core has a rectangular or irregular cross-section, or is a fiber bundle core with a particularly small diameter, it is possible to obtain a fiber bundle suitable for application tools such as writing instruments and cosmetic tools that does not impair the liquid supply performance such as ink as a fiber bundle, has no variation in thread density in the longitudinal direction of the core, has excellent strength and durability, and can be manufactured easily, efficiently, and at low cost.

[0023] Next, the pen nib and writing instrument of this disclosure will be described. The pen tip of this disclosure is characterized by: 1) having a writing pen core, wherein the writing pen core is made of a fiber bundle for writing instruments having the above configuration; and 2) having an ink guiding core for guiding ink to the writing portion of the pen tip, wherein the ink guiding core is made of a fiber bundle for writing instruments having the above configuration. The writing instrument of this disclosure is characterized by having a pen tip having a writing nib having the above-described configuration, and / or a pen tip having an ink-guiding nib that guides ink to the writing section having the above-described configuration.

[0024] Figures 6 to 11 are drawings showing the fiber bundle for writing instruments obtained above as a pen tip, and examples of various embodiments in which this pen tip is used in a writing instrument. Figures 6 and 7 show the state before and after attaching the cap to a twin-type writing instrument having a pen tip with a writing tip at both ends and a pen tip with an ink-guiding tip. Figures 8 and 9 are magnified views of the pen tip with a writing tip and drawings of the holder for attaching the writing tip. Figures 10 and 11 are magnified views of the pen tip with an ink-guiding tip and drawings of the holder for attaching the ink-guiding tip. As shown in Figures 6 and 7, the writing instrument X of this embodiment comprises a shaft member 10 which forms the body of the writing instrument, ink holders 20 and 21 which store ink contained within the shaft member 10, pen tips 30 and 50 which are fixed to both ends of the shaft member 10 via front shafts 15 and 16 respectively, and detachable caps 70 and 71 which surround the pen tips 30 and 50, respectively.

[0025] The shaft member 10, which forms the body of the writing instrument, is formed in a cylindrical shape and is made of thermoplastic resins such as polyacetal resin, polyethylene resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, polyolefin resin, polyvinyl resin, polycarbonate resin, polyether resin, and polyphenylene resin, as well as thermosetting resins (hereinafter, each of the above resins will simply be referred to as "each resin"). Front shafts 15 and 16, which hold the pen tips 30 and 50, are attached to the openings at both ends. Inside this shaft member 10 are ink holders 20 and 21 that store ink, and these ink holders 20 and 21 are separated by a partition member 23 in the center, and the ink impregnated in the ink holders 20 and 21 is supplied to each pen tip 30 and 50.

[0026] The ink holders 20 and 21 are impregnated with ink compositions for writing instruments, such as water-based ink, oil-based ink, and thermochromic ink. For example, they may include fiber bundles made from one or more combinations of natural fibers, animal hair fibers, polyacetal resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, and polyphenylene resins, processed fiber bundles such as felt, and porous bodies such as sponges, resin particles, and sintered bodies.

[0027] The composition of the writing instrument ink composition to be impregnated into the ink holders 20 and 21 is not particularly limited, and a suitable formulation such as water-based ink, oil-based ink, or thermochromic ink can be used depending on the application of the writing instrument (sign pen, marking pen, felt-tip pen, etc.). For example, in an underline pen, a fluorescent dye, such as Basic Violet 11 or Basic Yellow 40, can be used in the ink, and thermochromic microcapsule pigments can also be included. In this embodiment, the ink holders 20 and 21 are impregnated with the same ink composition. However, the ink holders 20 and 21 may be impregnated with inks having different compositions.

[0028] As shown in Figures 6 to 9, the pen tip 30 has a writing nib 31 and a holder 40 for mounting the writing nib 31, and the writing nib 31 is made of the fiber bundle for writing instruments with the above configuration. The writing nib 31 of this embodiment has dimensions of 1.0 mm in thickness, 2.0 mm in width, and 16 mm in length. The tip of this writing nib 31 becomes the writing section 32, and the rear end is mounted inside the tip side of the ink holder 20, so that the ink impregnated in the ink holder 20 is supplied to the writing section 32 by the tip of the writing nib 31.

[0029] As shown in Figures 6 to 9, the holder 40 is fixed to the tip opening of the front shaft 15 of the shaft body 10 by attaching and securing the writing pen nib 31, which serves as the writing lead. The holder 40 has a bulging mounting body portion 41, a flange portion 42 on the front side of the body portion 41, and a window frame portion 43 with a clear, trapezoidal cross-section. Mounting holes 44 and 45 for attaching the writing pen nib 31 are formed inside the mounting body portion 41 and on the tip side of the window frame portion 43, respectively, and the holder has a structure for attaching and holding the writing pen nib 31. The mounting body portion 41 of the retainer 40, which is composed of these components, has a concave fitting portion 46a formed on its outer circumferential surface in the width direction, and linear air circulation grooves 46b and 46c formed on the double-sided air circulation grooves that form the outer circumferential surface in the longitudinal direction. The entire retainer 40, as constructed in this manner, is made of, for example, synthetic resin, metal, glass, etc.

[0030] As shown in Figures 6, 7, 10, and 11, the pen tip 50 has an ink supply core 51, and the tip side of the ink supply core 51 has a writing section 52 made of a porous material, and a holder 60 for mounting the ink supply core 51 and the writing section 52, and the ink supply core 51 is made of a fiber bundle for writing instruments with the above configuration. The ink supply core 51 of this embodiment efficiently guides (supplies) the ink impregnated in the ink holder 21 to the writing section 52, and has dimensions of 0.8 mm in thickness, 1.6 mm in width, and 16 mm in length.

[0031] As shown in Figures 6, 7, 10, and 11, the retainer 60 is composed of a plate-shaped retaining portion 61, a flange portion 62 integrally formed at the rear end of the plate-shaped retaining portion 61 and projecting radially outward, and a bulging mounting body portion 63 integrally formed behind the flange portion 62. The plate-shaped holding portion 61 is composed of two plate surface portions 61a and 61b, and a plate thickness surface portion 61c that surrounds the front and one side of the plate surface portions 61a and 61b and is formed in the thickness direction. The writing portion 52, which consists of a writing lead, is held by the plate thickness surface portion 61c of the plate-shaped holding portion 61. The plate surface portions 61a and 61b are provided on both sides so as to sandwich the plate thickness surface portion 61c. Each plate surface portion 61a and 61b is formed by a surface that is substantially perpendicular to the plate thickness surface portion 61c (i.e., a surface substantially perpendicular to the thickness direction). In addition, triangular continuous recesses and protrusions 64, 64 are formed on both outer surfaces of the plate surface portions 61a and 61b, providing the plate-shaped holding portion 61 with appropriate flexibility in the thickness direction. A retaining groove 65 is formed in the thick surface portion 61c, which holds the writing portion 42. In addition, retaining grooves 66 are formed at the upper ends of the surface portions 61a and 61b, and the ink guide core 51 is attached to the retaining grooves 66. A recessed fitting portion 63a is formed on the outer peripheral surface in the width direction of the mounting body portion 63 of the retainer 60, which is composed of these members, and linear air circulation grooves 63b and 63c are formed on both sides that form the outer peripheral surface in the longitudinal direction, respectively.

[0032] The entire holder 60 constructed in this manner can be made of relatively hard synthetic resins such as polypropylene, polyethylene, polystyrene, polycarbonate, polyethylene terephthalate, polyacetal, acrylic, nylon, acrylonitrile-styrene copolymer resin (AS resin), and acrylonitrile-butadiene-styrene copolymer resin (ABS resin). The material constituting the holder 43 can be an elastic synthetic resin, such as soft polyethylene, soft polypropylene, nylon, or rubber elastic materials (e.g., thermoplastic elastomers such as styrene-based elastomers, olefin-based elastomers, and polyester-based elastomers). Furthermore, the synthetic resin constituting the holder 60 may be a transparent resin, which allows the contact state between the writing part 52, which consists of the writing lead, and the paper surface during writing to be visually observed.

[0033] In the pen tip 30 of the above embodiment, the writing pen core 31 is made of the above-described fiber bundle for writing instruments, and although the cross-section is rectangular and the dimensions are 1.0 mm thick x 2.0 mm wide x 16 mm long, even if the thickness is reduced, the ink supply performance as a fiber bundle is not impaired, there is no variation in the fiber density in the longitudinal direction of the core, and as a writing pen core, it has excellent strength against writing load and excellent durability. The pen tip 50 of this embodiment has an ink-guiding core 51 that guides ink to the writing section, and the ink-guiding core 51 is made of the above-described fiber bundle for writing instruments, and without impairing the ink supply performance of the fiber bundle, there is no variation in the fiber density in the longitudinal direction of the core, and it is also excellent in strength and durability as a sheet-like ink-guiding core. Furthermore, in this embodiment, the pen tip 50 has a plate-shaped holding portion 61 that includes uneven bodies 64, 64 having depth in the thickness direction, thereby enabling the plate-shaped holding portion 61 to have appropriate flexibility in the thickness direction. In addition, by making the plate-shaped holding portion 61 out of an elastic synthetic resin, the plate-shaped holding portion 61 can reliably achieve flexibility in the thickness direction.

[0034] As described above, the writing instrument of this disclosure, which has a pen tip 30 and a pen tip 50 at both ends, does not impair the ink supply performance or writing performance as a fiber bundle, and the core has no variation in thread density in the longitudinal direction, resulting in a writing pen core or ink supply core that is strong and durable.

[0035] The writing instruments of this disclosure may be further modified in various ways without altering the technical concept of this disclosure, and are not limited to the embodiments described above. In the above embodiment, a twin-type writing instrument was described in detail, which has a pen tip 30 with a writing nib 31 at both ends of the shaft 10 and a pen tip 50 with an ink-guiding core 51 that guides ink to the writing section 52. However, a single-type writing instrument may also be provided, which has a pen tip 30 with a writing nib 31 and a pen tip 50 with an ink-guiding core 51 that guides ink to the writing section 52. Furthermore, although the above embodiments were described using inks for writing instruments (water-based inks, oil-based inks, and thermochromic inks), liquid substances such as liquid cosmetics, liquid pharmaceuticals, coating solutions, and correction fluids may also be used. [Examples]

[0036] Next, the present disclosure will be further described by examples and comparative examples, but the present disclosure is not limited to the following examples.

[0037] (Example 1) Using fibers made of the following thermoplastic resin, a fiber bundle for writing instruments was obtained by the method shown below. (Multifilament of long fibers with different melting points: core-sheath composite fibers) Core-sheath composite fiber: A composite fiber (5 denier thickness) in which the sheath portion is made of polyethylene terephthalate copolymer with a low melting point (melting point: 160°C) and the core portion is made of polyethylene terephthalate with a high melting point (melting point: 250°C). (Crimped fiber) The above-mentioned core-sheath type composite fiber was crimped by a false twisting process. The crimp percentages of the crimped fibers were calculated to be 5% and 15%. Furthermore, the crimped fiber content was assumed to be 100% by mass relative to the total amount of fiber bundles for both types.

[0038] (Method for manufacturing fiber bundles) As shown in Figure 4, a thermoforming machine 10 was used to align the fibers in the longitudinal direction, and a fiber bundle was formed by solidifying and binding the thermoplastic resin fibers together. The solidification and binding temperature was 160°C, and the time for passing through the die was 30 seconds. Specifically, the resulting fiber bundle was a sheet-like fiber bundle with a thickness of 1.0 mm and a width of 2.0 mm. In this case, the fibers with a crimp rate of 5% had a fiber density of 5000 d / mm². 2 The material was adjusted to achieve a porosity of 50%. The other fiber, with a crimp rate of 15%, had a fiber density of 3000 d / mm². 2 The material was adjusted to achieve a porosity of 65%. When this fiber bundle was examined using an electron microscope (SEM), it was confirmed that a uniform cross-sectional structure was formed in which there was almost no difference in density distribution between the core and the outer layer, as shown in Figure 5(a). This fiber bundle was cut to a length of 16 mm to form the writing pen tip 30 and writing lead 31 shown in Figure 1.

[0039] (Example 2) Using fibers made of the following thermoplastic resin, a fiber bundle for writing instruments was obtained by the method shown below. (Multifilament of long fibers with different melting points: core-sheath composite fibers) Core-sheath composite fiber: A composite fiber (5 denier thickness) in which the sheath portion is made of polyethylene terephthalate copolymer with a low melting point (melting point: 160°C) and the core portion is made of polyethylene terephthalate with a high melting point (melting point: 250°C). (Crimped fiber) The above-mentioned core-sheath type composite fiber was crimped by a false twisting process. The crimp rate of the crimped fibers was calculated to be 5%. Furthermore, the content of these crimped fibers was assumed to be 100% by mass relative to the total amount of fiber bundles.

[0040] (Method for manufacturing fiber bundles) As shown in Figure 4, a thermoforming machine 10 was used to align the fibers in the longitudinal direction, and a fiber bundle was formed by solidifying and binding the thermoplastic resin fibers together. The solidification and binding temperature was 160°C, and the time for passing through the die was 30 seconds. Specifically, the resulting fiber bundle had a thickness of 0.8 mm, a width of 1.6 mm, and a fiber density of 4,000 d / mm². 2 A sheet-like fiber bundle was obtained. The porosity was 60%. When this fiber bundle was examined using an electron microscope (SEM), it was confirmed that, similar to the one shown in Figure 5(a), a uniform cross-sectional structure was formed in which there was almost no difference in density distribution between the core and the outer layer. This fiber bundle was cut to a length of 16 mm to form the ink supply core 51 of the pen tip 50 shown in Figure 1.

[0041] (Example 3) Using fibers made of the following thermoplastic resin, a fiber bundle for writing instruments was obtained by the method shown below. (Multifilament of long fibers with different melting points: side-by-side composite fibers) Side-by-side composite fiber: A composite fiber (5 denier thickness) with one side made of 66 nylon (melting point: 265°C) and the other side made of 6 nylon (melting point: 225°C) in a mass ratio of 1:1. (Crimped fiber) The above side-by-side composite fibers were crimped using a push-in (gear-type) crimping process. The crimp rate of the crimped fibers was calculated to be 8%. Furthermore, the content of these crimped fibers was assumed to be 100% by mass relative to the total amount of fiber bundles.

[0042] (Method for manufacturing fiber bundles) As shown in Figure 4, a thermoforming machine 10 was used to align the fibers in the longitudinal direction, and a fiber bundle was formed by solidifying and binding the thermoplastic resin fibers together. The solidification and binding temperature was 225°C, and the time for passing through the die was 30 seconds. Specifically, the resulting fiber bundle had a thickness of 1.0 mm, a width of 2.0 mm, and a fiber density of 5,000 d / mm². 2 A sheet-like fiber bundle was obtained. The porosity was 50%. When this fiber bundle was examined using an electron microscope (SEM), it was confirmed that a uniform cross-sectional structure was formed in which there was almost no difference in density distribution between the core and the outer layer, as shown in Figure 5(a). This fiber bundle was cut to a length of 16 mm to form the writing pen tip 30 and writing lead 31 shown in Figure 1.

[0043] (Comparative Example 1) In Example 1 described above, instead of using crimped fibers of core-sheath type multifilaments with different melting points, the conventional method of molding crimped fibers of single-component polyester multifilaments, impregnating them with polyurethane binder resin, and solidifying the binder in a heating furnace was replaced with the same manufacturing method as in Example 1. The resulting fiber bundle had a thickness of 1.0 mm, a width of 2.0 mm, and a fiber density of 5,000 d / mm². 2 A sheet-like fiber bundle was obtained. The crimp rate of the crimped fibers was 13%, and the content of these crimped fibers was 100% by mass of the total fiber bundle. The porosity was 50%. When this fiber bundle was examined using an electron microscope (SEM), as shown in Figure 5(b), it was found that the polyurethane binder resin was concentrated in the outer layer of the core due to the effects of solvent evaporation, resulting in a non-uniform cross-sectional structure with a large difference in density distribution between the center of the core and the outer layer. This fiber bundle was cut to a length of 16 mm to form the writing pen tip 30 and writing lead 31 shown in Figure 1.

[0044] Using the fiber bundles obtained in Examples 1-3 and Comparative Example 1, a pen body as shown in Figure 6 was assembled, and its writing performance was evaluated. The results showed that it was superior to the fiber bundle of Comparative Example 1, which used a conventional binder, in the following respects. (1) By adjusting the amount of fiber used (basis weight), heating temperature, and heating time, sufficient strength and durability for writing were obtained without using a binder. (2) Because the binder is not unevenly distributed and the pen tip has no variation in hardness, the feeling of discomfort when writing due to direction has been eliminated. (3) Ink retention improved by more than 10%. (4) The ink's fluidity and diffusivity became uniform.

[0045] (Examples of pen nibs and writing instruments) The fiber bundles obtained in Examples 1 and 2 above were used as the pen nib 31 and the ink supply core 51 to create a writing instrument conforming to Figures 6 to 11. The dimensions of the writing instrument, each pen nib 31, and the ink supply core 51 were as shown above. In addition, a writing instrument ink with the following composition was used.

[0046] (Composition of writing instruments) Shaft tube 10: Made of polypropylene, length 100mm, inner diameter of central part 8mm; outer diameter 10mm Ink holders 20 and 21: Made of PET fiber, 85% porosity, size: φ6 x 45 mm Holder 40: Made of acrylic resin, clear window frame: 5 x 4 x 11.5 mm Writing section 52: Polyethylene sintered core, 50% porosity, size: 4 x 3 x 6 mm Holder 60: Made of acrylic resin, clear window frame: 5 x 2.5 x 12 mm

[0047] (Writing instrument ink composition, ink color: black) The following ink composition (total 100% by mass) was used as the ink for the writing instrument. Surfactant: Megafac F410 (fluorinated anionic surfactant, perfluoroalkyl group-containing carboxylate, manufactured by DIC Corporation) 1% by mass Antifungal agent: Benzoisothiazolin-3-one 0.2% by mass Glyceryl glucoside aqueous solution: αGG (high-concentration α-glyceryl glucoside aqueous solution, 60% α-glyceryl glucoside aqueous solution, manufactured by JTS Corporation) 3% by mass Pigment aqueous dispersion: FUJI SP BLACK 8041 (black pigment aqueous dispersion, solids content 20%, manufactured by Fuji Pigment Co., Ltd.) 20% by mass Water-soluble organic solvent: Glycerin 5% by mass Water-soluble organic solvent: Ethylene glycol 5% by mass Water (solvent): Deionized water 65.8% by mass Viscosity (25°C): 3.6 mPa·s (Complete viscometer, TOKIMEC TV-20) Surface tension (25°C): 40 mN / m (Automatic surface tension meter, Kyowa Interface Science Co., Ltd., DY-300)

[0048] The writing instrument X, equipped with a writing pen core 31 and an ink supply core 51 made from the fiber bundles obtained in Examples 1 and 2 above, was confirmed to provide a writing instrument with excellent strength and durability, without impairing the ink supply performance for the writing instrument, and without variations in thread density in the longitudinal direction of the core. [Industrial applicability]

[0049] An ink-guiding core used in the nibs of writing instruments, a fiber bundle suitable for writing instrument nibs, a nib using the same, and a writing instrument can be obtained. [Explanation of Symbols]

[0050] X writing instrument A Fiber bundle for writing instruments B. Fiber bundle for writing instruments 30 nibs 31 Writing pen nib 50 nibs 51 Ink guide core

Claims

1. A fiber bundle for a writing instrument, used as an ink guide core for a pen tip or for a writing pen core, wherein the fiber bundle for a writing instrument is composed of multifilaments of long fibers having different melting points, and the multifilaments include crimped fibers obtained by false-twisting at least core-sheath type composite fibers, and the crimped fiber content is 10 to 100% by mass of the total amount of the fiber bundle for a writing instrument.

2. A fiber bundle for a writing instrument, used as an ink guide core for a pen tip or as a writing pen core, wherein the fiber bundle for a writing instrument is composed of multifilaments of long fibers having different melting points, and the multifilaments include crimped fibers obtained by crimping at least side-by-side composite fibers, and the crimped fiber content is 10 to 100% by mass of the total amount of the fiber bundle for a writing instrument.

3. The writing instrument fiber bundle according to claim 1 or 2, characterized in that the crimped fiber has a crimp ratio of 1 to 50% determined by the following formula (I). Crimp ratio = (crimp width ÷ crimp length) × 100 ……(I) [In the above equation (I), the distance from one peak to the other of the corrugated fiber is defined as the "crimp length," and the distance between the peak (mountain) and trough (lower point) of the wave in a direction perpendicular to the crimp length is defined as the "crimp width."]

4. A fiber bundle for writing instruments according to any one of claims 1 to 3, characterized in that its cross-sectional shape is rectangular.

5. A pen tip having a writing nib, characterized in that the writing nib is composed of a fiber bundle for a writing instrument as described in any one of claims 1 to 4.

6. A pen tip having an ink-guiding core for guiding ink to the writing part, characterized in that the ink-guiding core is composed of a fiber bundle for writing instruments described in any one of claims 1 to 4.

7. A writing instrument characterized by having the pen tip described in claim 5 or 6.

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