WO2024075805A1

WO2024075805A1 - Writing implement

Info

Publication number: WO2024075805A1
Application number: PCT/JP2023/036319
Authority: WO
Inventors: 俊史神谷
Original assignee: 三菱鉛筆株式会社
Priority date: 2022-10-06
Filing date: 2023-10-05
Publication date: 2024-04-11

Abstract

Provided is a writing implement that can reliably supply ink to the tip of a pen and can improve ink diffusion properties.　A writing implement A according to the present disclosure is characterized by comprising a cotton wadding 17 having two or more fine pore size distributions. The cotton wadding 17 is preferably such that a frequency of occurrence of less than 90 µm is high in a region having a radius of 0.5 mm from the center as determined through cross-sectional image analysis.

Description

Writing implements

This specification relates to a writing instrument that can reliably supply ink to the pen tip and improve ink diffusion.

2. Description of the Related Art Conventionally, there have been known writing implement batting having enhanced ink diffusibility for the purpose of reliably supplying ink to a pen tip, and writing implements using the same.
For example, a reservoir having a rod having a core component having fibers and a surrounding component having fibers, the core component having a first property and the surrounding component having a second property different from the first property, the first property and the second property being independently selected from the group consisting of fiber bulk density, fiber diameter, fiber material, fiber morphology, fiber surface tension, capillary force, fluid absorption capacity, color, and combinations thereof, and a reservoir for a non-uniform fiber fluid used in a writing instrument such as an oil-based marker or a highlighter, the fiber bulk density being in the range of about 0.01 g/cm ³ to about 0.4 g/cm ³ and the fiber diameter being in the range of about 0.5 μm to about 50 μm (see, for example, Patent Document 1).

This reservoir is equivalent to the so-called batting used in writing instruments, and by making the fiber bulk density of the batting "coarse/dense batting," the ink supplied into the batting can spread, allowing ink to be reliably supplied to both pen tips at both ends of the barrel for writing. This coarse/dense batting is characterized by having a dense fiber section in the radial center of the batting and a sparse fiber section around the circumference, and when ink is filled into the coarse/dense batting, the dense section preferentially absorbs the ink, and ink is quickly supplied to both ends of the batting, enhancing the ink diffusibility of the batting.

Furthermore, in other documents, for example, a marking pen (see Patent Document 2 by the present applicant) is known that is characterized by having a barrel, a batting housed inside the barrel and located toward the axis in a cross section perpendicular to the longitudinal direction, the batting being made up of a dense portion with a relatively low porosity and a sparse portion located around the dense portion and having a relatively high porosity, an aqueous ink impregnated into the batting and having a static surface tension value of 35 mN/m or less, and a writing tip that is connected to the dense portion and guides the aqueous ink to the tip by capillary force.

However, although the above-mentioned

Patent Documents

1 and 2 describe a new writing instrument padding and a writing instrument using the same, there are still cases where Patent Document 1 does not allow ink to be efficiently supplied to the pen tip, and there is currently a demand for

Patent Documents

1 and 2 to have even better ink diffusibility.

JP 2022-501226 A (claims, FIG. 1, etc.) JP 2021-66043 A (Claims, FIG. 7, etc.)

The present disclosure seeks to address the issues and current state of the prior art described above, and aims to provide a writing instrument that can more efficiently supply ink to the pen tip and further improve ink diffusibility.

As a result of extensive research into solving the above-mentioned problems, the present inventor discovered that a writing instrument that satisfies the above-mentioned objectives can be obtained by giving the filling made of fiber bundles a specific configuration, which led to the completion of this disclosure.

That is, the writing instrument of the present disclosure is characterized by having a filling having two or more types of pore size distribution.
It is preferable that the frequency of particles smaller than 90 μm is high in a region having a radius of 0.5 mm from the center of the padding, as determined by cross-sectional image analysis.
The ink composition stored in the filling material is preferably an ink composition containing a resin fine particle pigment including a dye.

According to the present disclosure, a writing instrument is provided that can more efficiently supply ink to the pen tip and further improve ink diffusibility.
The objects and advantages of the disclosure will be realized and obtained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the disclosure as claimed.

1A and 1B are drawings of a writing instrument showing an example of an embodiment of the present disclosure, in which (a) is a front view, (b) is a plan view, (c) is a vertical cross-sectional view as seen from the front, and (d) is a vertical cross-sectional view of (b). 2A to 2E are drawings showing the writing instrument of FIG. 1 with the cap removed, where (a) is a plan view, (b) is a front view, (c) is a bottom view, (d) is a vertical cross-sectional view of (b), and (e) is a vertical cross-sectional view of (c). 2A and 2B are enlarged views showing the pen tip side of the writing instrument of FIG. 1, in which FIG. 2A is a front view and FIG. 2B is a longitudinal sectional view thereof. 4A is a perspective view of the pen tip of the writing implement of FIG. 3 as seen from the front side, and FIG. 4B is a perspective view of the pen tip as seen from the rear side. FIG. 1A is a front view showing an example of a filling for a writing instrument according to the present disclosure, and FIG. 1B is an X-X line cross-sectional view of the filling in (a), showing a schematic diagram of a state in which the pore size distribution has two or more types. 1A and 1B are drawings showing an example of a holder having a visible portion of a pen tip used in a writing instrument, in which (a) is an oblique view seen from the front side, (b) is a plan view, (c) is an oblique view seen from the rear side, (d) is a left side view, (e) is a front view, (f) is a right side view, (g) is an oblique view seen from above the front side, (h) is a vertical cross-sectional view, (i) is an oblique view seen from above the rear side, and (j) is a bottom view. 7A to 7D are diagrams showing an example of a writing part attached to the pen tip of Figure 6, where (a) is a plan view, (b) is a perspective view, (c) is a front view, and (d) is a right side view. 1A and 1B are drawings of an optical microscope cross-sectional observation of an image analysis pattern of Production Example 1 (Sample A) and a binarized image (image resolution is about 1.27 μm/pixel), respectively. 1A and 1B are drawings of an optical microscope cross-sectional observation of an image analysis pattern of Production Example 2 (sample B) and a binarized image (image resolution is about 1.28 μm/pixel), respectively. 1 is a pore distribution diagram (the largest circle inscribed in the pore portion) of Production Example 1 (Sample A). In the pore distribution diagram, the numerous circular gray (yellow) circles represent pores with diameters of 90 μm or more, the white dots represent pores, and the black dots represent fibers. The dark gray (green) region that is the entire area other than the circular gray, white dots, and black dots represents pores with diameters of less than 90 μm, and the dark gray (green) and circular gray (yellow) circles represent an almost uniform pore distribution diagram overall. FIG. 13 is a pore distribution diagram (the largest circle inscribed in the pore portion) of Production Example 2 (Sample B). In the pore distribution diagram, the numerous gray (yellow) circles represent pores with diameters of 90 μm or more, the white dots represent pores, and the black dots represent fibers. The entire area other than the circular gray, white dots, and black dots is dark gray (green), with more dark gray (green) in the central portion and fewer circular gray (yellow) in the central portion. 13(c) is a graph showing the pore size distribution (the distribution of the largest circle inscribed in the pore portion) of Production Examples 1 and 2 (Samples A and B) [horizontal axis: pore diameter (μm), vertical axis: areal frequency (moving average value: %)], where the areal frequency is calculated using the moving average value for each data point, and the measurement area is the semicircular portion shown in FIG. 13(c). Graphs showing the relationship between the spatial distribution of pores (distance from the center of a circle and pore area frequency) in Production Examples 1 and 2 (Samples A and B) and drawings explaining the measurement method, in which (a) is a graph for pore diameters of less than 90 μm (horizontal axis: radius from the center (μm), vertical axis: area frequency (moving average value)), (b) is a graph for pore diameters of 90 μm or more (horizontal axis: radius from the center (μm), vertical axis: area frequency (moving average value)), and (c) is an explanatory diagram explaining the measurement method of the radius from the center and the area frequency, in which measurements are taken at an arbitrary radius from the center (measurements are taken on the yellow solid line for the radius of the yellow arrow), and the area frequency is calculated using the moving average value for each data point. 1 is a graph showing the pore diameter and area frequency plotted with threshold values of 50 μm, 90 μm, and 100 μm in the pore distribution (the maximum circular distribution inscribed in the pore portion) of Production Examples 1 and 2 (Samples A and B). FIG. 1 is a diagram of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 100 μm for Production Example 1 (Sample A). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 100 μm, circular gray (yellow) represents pores with a diameter of 100 μm or more, white dots represent pores, and black dots (red) represent fibers. The dark gray (green) and circular gray (yellow) represent an almost uniform pore distribution diagram overall. FIG. 1 is a diagram of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 90 μm for Production Example 1 (Sample A). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 90 μm, circular gray (yellow) represents pores with a diameter of 90 μm or more, white dots represent pores, and black dots (red) represent fibers. The dark gray (green) and circular gray (yellow) represent an almost uniform pore distribution diagram overall. FIG. 1 is a diagram of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 50 μm for Production Example 1 (Sample A). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 50 μm, circular gray (yellow) represents pores with a diameter of 50 μm or more, white dots represent pores, and black dots (red) represent fibers. The dark gray (green) and circular gray (yellow) represent an almost uniform pore distribution diagram overall. FIG. 1 is a drawing of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 100 μm for Production Example 2 (Sample B). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 100 μm, circular gray (yellow) represents pores with a diameter of 100 μm or more, white dots represent pores, and black dots (red) represent fibers. This is a pore distribution diagram with more dark gray (green) in the center and fewer circular gray (yellow) in the center. FIG. 1 is a drawing of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 90 μm for Production Example 2 (Sample B). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 90 μm, circular gray (yellow) represents pores with a diameter of 90 μm or more, white dots represent pores, and black dots (red) represent fibers. This is a pore distribution diagram with more dark gray (green) in the center and fewer circular gray (yellow) in the center. FIG. 1 is a drawing of the pore distribution (the largest circle inscribed in the pore portion) at a threshold value of 50 μm for Production Example 2 (Sample B). In the pore distribution diagram, dark gray (green) represents pores with a diameter of 0 to less than 50 μm, circular gray (yellow) represents pores with a diameter of 50 μm or more, white dots represent pores, and black dots (red) represent fibers. This is a pore distribution diagram with more dark gray (green) in the center and fewer circular gray (yellow) in the center. 1A to 1C are drawings showing the relationship between the distance from the circle center (pore diameter 0 to less than 100 μm, pore diameter 100 μm or more) and the pore diameter frequency for Production Examples 1 and 2 (samples A and B), and drawings showing the measurement method, in which (a) is a graph for pore diameters of 0 to less than 100 μm (horizontal axis: radius from the center (μm), vertical axis: frequency), (b) is a graph for pore diameters of 100 μm or more (horizontal axis: radius from the center (μm), vertical axis: frequency), and (c) is an explanatory diagram explaining the measurement method for the radius from the center and the number frequency. 1A to 1C are drawings showing the relationship between the distance from the circle center (pore diameter 0 to less than 90 μm, pore diameter 90 μm or more) and the pore diameter frequency for Production Examples 1 and 2 (samples A and B), and drawings showing the measurement method, in which (a) is a graph for pore diameters of 0 to less than 90 μm (horizontal axis: radius from the center (μm), vertical axis: frequency), (b) is a graph for pore diameters of 90 μm or more (horizontal axis: radius from the center (μm), vertical axis: frequency), and (c) is an explanatory diagram explaining the measurement method for the radius from the center and the number frequency. 1A to 1C are drawings showing the relationship between the distance from the circle center (pore diameter 0 to less than 50 μm, pore diameter 50 μm or more) and the pore diameter frequency for Production Examples 1 and 2 (samples A and B), and drawings showing the measurement method, in which (a) is a graph for pore diameters of 0 to less than 50 μm [horizontal axis: radius from the center (μm), vertical axis: frequency], (b) is a graph for pore diameters of 50 μm or more [horizontal axis: radius from the center (μm), vertical axis: frequency], and (c) is an explanatory diagram explaining the measurement method for the radius from the center and the number frequency. Graphs (a) to (d) show the relationship between the distance from the circle center and the pore diameter frequency for Production Examples 1 and 2 (samples A and B). Graph (a) shows the pore diameters (50 μm, 90 μm, 100 μm) of Production Example 1 (sample A) below the threshold [horizontal axis: radius from the center (μm), vertical axis: frequency]. Graph (b) shows the pore diameters (50 μm, 90 μm, 100 μm) of Production Example 1 (sample A) above the threshold [horizontal axis: radius from the center (μm), vertical axis: frequency]. Graph (c) shows the pore diameters (50 μm, 90 μm, 100 μm) of Production Example 2 (sample B) below the threshold [horizontal axis: radius from the center (μm), vertical axis: frequency]. Graph (d) shows the pore diameters (50 μm, 90 μm, 100 μm) of Production Example 2 (sample B) above the threshold [horizontal axis: radius from the center (μm), vertical axis: frequency].

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, it should be noted that the technical scope of the present disclosure is not limited to the embodiments described in detail below, but covers the inventions described in the claims and their equivalents.
In each drawing, the "front" of the writing instrument A and its components indicates the direction of the tip of the writing instrument A, the "rear" indicates the opposite direction, the "axial direction" indicates the direction of the axis that passes through the writing instrument body (barrel) from the front to the rear, and the "transverse direction" indicates the direction perpendicular to the axial direction. Also, the reference numerals commonly used in each drawing represent the same configuration or members even if not specifically mentioned in the description of each drawing.

(First embodiment: overall configuration)
1 to 7 are drawings illustrating a marking pen-type writing instrument A according to a first embodiment of the present disclosure, a filling 17 having two or more types of pore size distribution that is a component used in the writing instrument, a pen tip 20, and an example of a writing part 25.
1(a) to 1(d), the writing instrument A of this embodiment is a twin-type writing instrument that includes a pen tip 20 having a visible portion that guides ink supplied from a writing instrument body (barrel) 10 and allows the writing direction to be visually confirmed, and also includes a rod-shaped polyacetal pen tip 40 on the opposite side of the pen tip 20. In addition, a cap 50 that protects the pen tip 20 and that is detachable, and a cap 60 that protects the pen tip 40 are attached to both sides of the writing instrument body 10. The cap 50 has a clip portion 51, a friction body 53, and an air hole 54.

(Writing instrument body 10, rear barrel 11)
As shown in Figures 1 to 4, the writing instrument body 10 of this embodiment is composed of a rear barrel 11 and a front barrel 16. The rear barrel 11 is composed of a cylindrical body and contains a padding 17 impregnated with writing instrument ink, and one end side, which is the right side in the drawings, is a reduced-diameter holding portion 13 having a fitting portion 12 for fixing a holder 45 that holds a rod-shaped fine-point pen tip 40 by fitting, and a cap 60 is removably attached to the large-diameter outer periphery 13a of this holding portion 13.
A front barrel 16 for fixing a pen tip 20 having a visible portion that allows the writing direction to be visually confirmed is fixed by fitting or the like to an opening at the other end, which is the left side of the rear barrel 11. Furthermore,

flat portions

14, 14 are formed on the upper and lower surfaces of the outer periphery on the axial front side of the rear barrel 11, and as described below, when these

flat portions

14, 14 are held with the fingers, writing (marking) can be performed immediately without changing the grip, that is, they serve as a gripping indication surface that makes it easy to understand the direction of the flat-shaped pen tip 20.

(Front shaft 16)
1 to 4, front barrel 16 is configured as a generally circular tubular body and is provided with at least flange 16a near the rear of the center, rear portion 16b having a fitting step on the rear side of flange 16a, front portion 16c having a fitting step on the front side, and an inclined opening 16d on the tip side of front portion 16c, and within inclined opening 16d, a protrusion (not shown) for reliably directing ink guide portion 26 to the center of padding 17 which serves as an occlusion body, and an annular abutment portion (not shown) for abutting the rear end portion of holder 30. Note that reference numeral 16a1 in the figure denotes an inclined surface portion that corresponds slightly to flat surface 14 of rear barrel 11 on the rear end surface of flange 16a for the purpose of alignment with rear barrel 11.
The writing instrument body 10, which is composed of the front barrel 16 and the rear barrel 11, is formed from a thermoplastic resin, a thermosetting resin, or the like, and is molded into the above-mentioned configuration using a resin such as polypropylene, and functions as the writing instrument body (shaft body). The writing instrument body 10 is molded to be opaque or transparent (and translucent), but either may be adopted from the viewpoint of appearance and practicality.

(Padding 17)
The padding 17 serves as an ink storage body and is impregnated with an ink composition for a writing instrument, such as a water-based ink, an oil-based ink, or a thermochromic ink. In the present disclosure, the padding is composed of padding having two or more types of pore size distribution.
FIG. 5(a) is a front view showing an example of the filling 17, and (b) is a longitudinal cross-sectional view of the filling 17 in (a), which is a schematic diagram showing a state in which the pore size distribution has two or more types.
This filling 17 is a filling having two or more types of pore size distribution, and has an outer skin 17a made of a resin film on the outer circumferential side, 17b being a first pore size portion, and the outer circumferential side of the first pore size portion 17b being a second pore size portion 17c.
Whether or not the filling 17 has two or more types of pore size distribution can be verified, for example, by (1) different pore distributions measured by a mercury porosimeter, (2) different distributions of inscribed circle diameters measured by cross-sectional image analysis, or (3) different distributions of equivalent pore diameters measured by cross-sectional image analysis.

The measurement using a mercury porosimeter can be confirmed by measuring the pores in the filling with a mercury porosimeter and determining the difference in their distribution.
Normal batting with no pore size distribution has a pore distribution with approximately one peak, whereas batting with two or more pore size distributions has two peaks, i.e., the pore distribution can be considered to have two peaks. This pore distribution with two peaks means that the pores in the batting have fine and coarse parts. It only represents the distribution of the pore state, and is different from conventional batting that has sparse and dense states. The conventional sparse and dense states represent the difference in the volume ratio of pores to fibers (the same applies to the cross-sectional area ratio).
On the other hand, the capillary force generated between the filling and the ink is determined by the fineness and coarseness of the pores. In order to increase the ink diffusion, it is necessary to create areas with low and high capillary forces within the filling, which is achieved (not by density, but essentially) by the coarseness and fineness of the pores.

In the measurement using a mercury porosimeter, the presence or absence of a pore size distribution in the filling can be measured by calculating the number of peaks in the pore distribution described below.
In the mercury porosimeter, the number of peaks in the pore distribution is determined by pressing mercury into the padding to impregnate it, and the distribution of the equivalent diameter of the pores is calculated from the pressure and the impregnated volume. The resulting graph of the equivalent diameter of the pores and their frequency is then peak-separated. Peak separation is a common method, but in this study, the peak separation method proposed by the Japan Society of Energy was used.
The above analysis separates the peaks of the pore size distribution of the filling. The separated peak positions are displayed logarithmically, so they are returned to the original values. From this result, the distance between the peaks is calculated, half the half-width of the component peaks is calculated, and the sum of these is calculated. If the distance between the peaks is smaller than the sum of half the peak widths, and the two peaks cannot be observed separately, there is no pore distribution.
In contrast, for fillings having two or more types of pore size distributions, the number of peaks in the pore distribution can be calculated in the same manner as described above, i.e., using the results of peak separation, it can be confirmed from the relationship between the distance between the component peaks and each line width that the filling has two peaks, i.e., that it has two pore size distributions.

In addition, by measuring the distribution of inscribed circle diameters through cross-sectional image analysis, it is possible to determine whether or not the filling has a pore size distribution.
The presence or absence of pore size distribution can be determined by image analysis of the cross section of the filling, specifically, by observing a cut surface of the filling and analyzing the image to determine the pore sizes (inscribed circle diameter distribution).
The measurement method was to inject a curable resin (en-thiol resin-based photocurable adhesive: manufactured by Nichika Co., Ltd.) into the obtained batting and harden it. Next, it was cut in the direction perpendicular to the axis, the cross section was polished, and the cut surface was observed and photographed using an optical microscope (VHX-8000 manufactured by Keyence Co., Ltd.). This was decomposed into the fiber part and the pore part (impregnated resin part) using image analysis (material development comprehensive package software GeoDict manufactured by Math2Market). When the maximum circular distribution inscribed in the pore part was obtained, it was thought that the characteristics were expressed at the boundary of the pore diameter of 90 μm.
The batting with a pore size distribution has a high frequency of pores smaller than 90 μm. When the frequency distribution is analyzed by dividing the inscribed circle into less than 90 μm and 90 μm or more, the frequency of pores smaller than 90 μm is higher in the sample (dense part) in the region with a radius of 0.5 mm from the center, and the frequency of pores larger than 90 μm is lower in the region with a radius of 0.5 mm from the center. From the above analysis, it was found that the batting with a pore size distribution has a distribution of pore sizes when the frequency of pores smaller than 90 μm is high. It is preferable that the frequency of pores smaller than 90 μm is high in the region with a radius of 0.5 mm from the center, and in the batting with a pore size distribution, the frequency of pores (fine parts) smaller than 90 μm is high in the radial center, but the location of these fine parts may be the circumferential part. As described above, it was found that the batting has a pore size distribution when there is a difference in the diameter distribution of the inscribed circle of the pores in the batting in a certain region.

Furthermore, by measuring the distribution of equivalent pore diameters by cross-sectional image analysis, batting with two or more pore size distributions can be verified.
The cut surface of the filling is observed, and the distribution of the equivalent diameter of the pores is obtained by image analysis. The resolution of the cross-sectional image of the above measurement method is increased, and the fiber circumference (l) and the area of the space (s) within a certain space (for example, a square area of 1 x 1 mm) are obtained. Although the pores are not circular but have irregular shapes, the diameter (2r: equivalent diameter) can be calculated from the circumference and area using the following formula when considered as a circle.
Circumference/area of circle = 2πr/ ^πr2 = 2/r = l/s = fiber circumference/area of space When calculating the equivalent diameter of the pores in the above-mentioned micro-region, the equivalent diameter is small in "fine" (dense) regions and large in "coarse" (sparse) regions. In the first place, capillary force is expressed as l/s x γ (surface tension) x cos θ (contact angle) and is determined by the circumference of the pores and their area. It was found that "fine" (dense) regions in the batting have small equivalent diameters and "coarse" (sparse) regions have large equivalent diameters, and when the diameter distribution of the inscribed circles of the pores in this micro-region differs in a certain region, the batting has a pore size distribution. This analysis is essential in terms of the capillary force distribution in the batting.
Any of the above (1) to (3) can be used to verify a filling having two or more types of pore size distribution.
It is preferable to measure the presence or absence of a pore size distribution in the filling by measuring the distribution of the inscribed circle diameter by image analysis of the cross section of the above (2) in view of operability, measurement accuracy, and measurement man-hours (the above (2) requires fewer observation images than the above (3). Visibility does not decrease even if the resolution is low).

To obtain a filling having two or more types of pore size distributions, the filling can be produced, for example, by using fibers having different fiber bulk densities, fiber diameters, fiber materials, fiber morphologies, fiber surface tensions, and capillary forces, or by suitably combining two or more of these.
Examples of fibers that can be used include 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, either alone or in combination.

Specifically, as an example, it can be produced as follows.
After each of them was converged, the yarn bundle having the second pore size distribution was inserted into the center of the yarn bundle having the first pore size distribution, and a polypropylene cylinder having a length of 80 mm and an inner diameter of 6 mm was used as a shaft tube, which was filled with the batting of each of the following Examples and Comparative Examples, and subjected to the following experiments. The yarn bundle was made by compressing and bundling polyester fibers, and the weight was measured so as to obtain a predetermined dense part ratio. By filling the polypropylene cylinder, it is possible to obtain a batting for a writing instrument having the above pore size distribution characteristics with two or more pore size distributions.

(Ink for writing instruments)
The composition of the ink for the writing instrument used is not particularly limited, and a suitable formulation such as water-based ink, oil-based ink, thermochromic ink, etc. can be used depending on the application of the writing instrument, etc. For example, in the case of an underline pen, the ink can contain a fluorescent dye such as Basic Violet 11, Basic Yellow 40, or a thermochromic microcapsule pigment.
A pigment ink composition containing resin fine particles containing a dye is preferable.
Examples of resin microparticle pigment inks containing dyes include those containing a dispersion of colored resin microparticles in water, the colored resin microparticles being composed of at least a cyclohexyl (meth)acrylate monomer and a basic dye or an oil-soluble dye, wherein the content of the cyclohexyl (meth)acrylate monomer is 30 mass% or more relative to the total polymer components constituting the colored resin microparticles and the content of the basic dye or oil-soluble dye is 15 mass% or more relative to the total polymer components, a water-soluble organic solvent, and water.
Furthermore, by adjusting the types of ink formulation components and the amounts of each component, it is possible to set the ink viscosity (25°C: Complate type viscometer) of these ink compositions to 1 to 5 mPa·s and the surface tension to 30 to 60 mN/m. Furthermore, in combination with the properties of the writing instrument batting disclosed herein, it is possible to easily set the amount of ink flowing out from the marking pen-type writing instrument nib 20 and nib 40 to a preferred range, in this embodiment, 5 to 20 mg/m.

In addition, when a thermochromic microcapsule pigment-containing ink composition is used, for example, as shown in Figures 1(c) and (d), a cylindrical friction body 53 made of a thermoplastic elastomer with an erasability (erasability rate) of pencil lines as specified in JIS S 6050-2002 of less than 70% can be fixed to the recess 52 of the cap 50. The rubbing action of this friction body 53 makes it easy to generate frictional heat and has low wear, which reduces the generation of eraser dust during friction and prevents stains on the surrounding area. The ventilation hole 54 is a ventilation hole for making it easier to attach and remove the friction body 53.

(Pen tip 20)
As shown in Figures 1 to 7, the pen tip 20 has at least a writing portion 25, an ink guide portion 26 that guides ink in the writing instrument body 10 to the writing portion 25, and a holder 30 having a visible portion, and the writing portion 25 and the ink guide portion 26 are attached to the holder 30 by adhesive bonding, welding, fitting, etc.
The writing part 25 has an inclined (knife-cut) shape so that the upper side of the rectangular parallelepiped base is inclined to make writing easier. The inclination of the writing part 25 is appropriately set according to the ease of use of writing, etc. As shown in Figs. 7(a) to 7(d), the writing part 25 has a writing part 25a with a large line width W1 and a writing part 25b with a small line width W2 so that the line width can be adjusted, and the line widths W1 and W2 can be adjusted (selected) by inclining the shaft. In this embodiment, the ratio of W1:W2 is 2 or more:1. The line width W1 is 2.0 to 5.0 mm, and the line width W2 is 1.0 to 2.5 mm.

The writing part 25 may be made of a porous material having air holes, such as a sponge, a sintered body, a fiber bundle, a foam, a spongy body, a felt body, or a porous body. Materials for forming these porous bodies include, for example, natural fibers, animal hair fibers, polyacetal resins, polyethylene resins, acrylic resins, polyester resins, polyamide resins, polyurethane resins, polyolefin resins, polyvinyl resins, polycarbonate resins, polyether resins, and polyphenylene resins. The writing part 25 of this embodiment is made of a sintered core made of sintered plastic powder (e.g., PE) to improve the writing feel.

The ink guide portion 26 is thin plate-like and has an inclined portion 26a on the rear side, and the cross section thereof is preferably rectangular or elliptical in order to maximize (widen) the area of the visible portion. In this embodiment, the cross section is rectangular.
The ink guide portion 26 is not particularly limited as long as it efficiently guides (supplies) the ink in the padding 17 absorbed in the writing instrument body 10 to the writing portion 25 via the ink guide portion 26, and examples of the ink guide portion 26 include those made of fabrics such as nonwoven fabrics, woven fabrics or knitted fabrics, fiber bundle cores, or liquid-permeable materials such as liquid-permeable foams and sintered bodies. Note that the writing portion 25 and the ink guide portion 26 can be integrally formed from one type of material, but it is preferable to form the ink guide portion 26 by connecting or bonding separate members to each other, or by connecting or bonding via a holder as described later, in order to further exert the effects of the present disclosure, efficiently supply ink, and further improve the writing feel at the writing portion.
In this embodiment, the term "nonwoven fabric" refers to a cloth-like structure formed by not weaving a mass of one or more layers of fibers. As the fiber material, synthetic fibers, natural fibers, animal hair fibers, inorganic fibers, etc. are used. As the synthetic fiber material used, for example, one or a combination of two or more of polyacetal resin, polyethylene resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, polyolefin resin, polyvinyl resin, polycarbonate resin, polyether resin, polyphenylene resin, etc. can be mentioned.

The fibers constituting the fabric can be obtained by known methods such as melt spinning, dry spinning, wet spinning, direct spinning (melt blowing, spunbonding, electrostatic spinning, etc.), a method of extracting fibers having a small fiber diameter by adsorbing one or more resin components from composite fibers, and a method of beating fibers to obtain split fibers.
The fibers constituting the fabric may be composed of one or more types of resin components, and composite fibers generally called composite fibers, such as core-sheath type, sea-island type, side-by-side type, orange type, etc., can be used.

The fineness of the fibers constituting the fabric is not particularly limited, but the fineness is preferably 0.1 to 500 dtex, and more preferably 2 to 5 dtex. The length of the fibers is also not particularly limited, but short fibers, long fibers, or continuous fibers can be used.
When the fabric is a woven or knitted fabric, it can be prepared by weaving or knitting the fibers prepared as described above.

When the fabric is a nonwoven fabric, a method for preparing a fiber web capable of producing a nonwoven fabric can be, for example, a dry method or a wet method. As a method for entangling and/or integrating the fibers constituting the fiber web to form a nonwoven fabric, for example, a method for entangling with a needle or a water flow, a method for integrating the fibers with a binder, or, when the fiber web contains a thermoplastic resin, a method for melting the thermoplastic resin by heat-treating the fiber web to integrate the fibers can be mentioned. In addition, as a method for heat-treating the fiber web, for example, a method for heating and pressurizing with a calendar roll, a method for heating with a hot air dryer, a method for melting the thermoplastic resin fibers by irradiating infrared rays under no pressure, etc. can be used. In addition, a nonwoven fabric can be prepared by collecting fibers spun using a direct spinning method.
Examples of fiber bundle cores include parallel fiber bundles made of the above-mentioned fiber materials (synthetic fibers, natural fibers, animal hair fibers, inorganic fibers, polyphenylene resins, etc., one or a combination of two or more of them) that have been processed or resin-processed.
In the case of a liquid-permeable foam, it can be prepared by a known method, for example, by pouring a molten resin into a mold, forming, and foaming, etc. In addition, the sintered body can be composed of a porous body (sintered core) obtained by sintering a plastic powder such as a polyacetal resin, a polyethylene resin, an acrylic resin, a polyester resin, a polyamide resin, a polyurethane resin, a polyolefin resin, a polyvinyl resin, a polycarbonate resin, a polyether resin, or a polyphenylene resin.

The shape, thickness, etc. of the ink guide portion 26 are set based on the manner of attachment to the holder 30, the shape of the writing portion 25, maximizing the visible area of the visible portion, efficiently flowing (supplying) ink to the writing portion 25, etc., and preferably the widthwise length and the lengthwise length are approximately the widthwise length and approximately the lengthwise length of the attachment surface of the holder 30 described later to which the thin plate-like ink guide portion 26 is fixed, respectively, and suitable lengths are set to efficiently flow ink to the writing portion 25. Furthermore, the thickness t of the thin plate-like ink guide portion 26 (the width as viewed from the perpendicular direction to the visible portion surface) is preferably less than 1.5 mm, more preferably 1.2 mm or less, and particularly preferably 0.8 mm or less, as shown in Fig. 4(b), from the viewpoint of maximizing the visible area of the visible portion, etc., and the lower limit is preferably 0.5 mm or more from the viewpoints of suitable supply of ink amount, productivity, etc.
In this embodiment, the ink guide section 26 is made of a fiber bundle core made of PET and has a rectangular cross-section, which allows ink to flow efficiently with a small cross-sectional area, and has a longitudinal length of 20 mm, a width length of 2 mm, and a thickness t of 0.8 mm.
The rear end 26a of the ink guide 26 is inserted inside the tip end of the inner fiber 17, and the tip end 26b is in contact with the writing part 25 via the holder 30. With this configuration, a suitable amount of ink in the inner fiber 17 is efficiently supplied to the writing part 25 via the ink guide 26 by capillary force.

(Holding body 30)
As shown in Figures 2 to 7, the holding body 30 fixes the writing portion 25 and ink guide portion 26, and has its rear end fixed within the inclined opening 16d of the tip shaft 16 of the writing instrument body 10. The holding body 30 has a bulging main body portion 31, a flange portion 32 on the front side of the main body portion 31 that abuts against the end face of the writing instrument body 10, and a visible portion 33 that allows the writing direction to be visually confirmed. The holding body 30 also has

front holding portions

34a, 34b that hold the tip side (end face) of the writing portion 25 on the tip side of the visible portion 33, and

anti-slip portions

34c, 34d that receive the end face of the writing portion 25 provided at one end of each holding portion.
Further, a rear holding portion 35 is provided on the bottom surface side of the rear side of the main body portion 31, and is connected to the main body portion 31. A structure is formed on the entire bottom surface side in the longitudinal direction of the holder 30 composed of these members, in order to maximize the visible area of the visible portion 33, and is attached (disposed) to the bottom surface of the holder 30. Specifically, a concave holding groove 36 is formed on the entire longitudinal bottom surface of the holder 30, into which the thin plate-like (rectangular cross-sectional shape) ink guide portion 26 is fitted and held. Furthermore, a concave fitting portion 31a is formed on the outer circumferential surface in the width direction of the main body portion 31.

Furthermore, on both sides of the concave holding groove 36 to which the writing part 25 is fixed and the concave holding groove 36 to which the ink guide part 26 is fixed,

ribs

37, 37..., 38, 38... are formed at predetermined intervals in a direction perpendicular to the axis on the surfaces where the writing part 25 and the ink guide part 26 come into contact, so that the fragile legs and the like of the writing part 25 and the ink guide part 26, which may cause dimensional variations due to molding, can be stably assembled to the holder 30. In this embodiment, the width direction length of the mounting surface 36a of the holding groove 36 is set to be slightly shorter than the width direction length of the tip side 26b of the ink guide part 26, so that the tip side 26b of the ink guide part 26 is pressed against the holding groove 36a to be fitted and held therein, thereby increasing the fixing force and reliably holding the connection with the writing part 25.
The thin plate-like ink guide portion 26 is fixed to the mounting surfaces 36 a , 36 b of the holding groove 36 of the holding body 30 by bonding with an adhesive, welding, or the like, and is thus fixed to the writing portion 25 .
In this writing instrument A, the writing part 25 is fixed (attached) to the holding body 30 by fitting the writing part 25 between the

front holding parts

34a, 34b, and further, in order to ensure the fixing (prevention of falling off) of the writing part 25, adhesive bonding, welding, etc. may be used.
In addition,

air circulation grooves

39, 39 are formed on the outer longitudinal surface of the main body 31, so that even if the air pressure inside the writing instrument expands, the

air circulation grooves

39, 39 can adjust the expansion and prevent ink leakage, etc.

The ink guide portion 26 is made of a fiber bundle core having a rectangular or elliptical cross section, and in this embodiment has a rectangular cross section, and the writing portion 25 is made of a sintered resin body, and the writing portion 25 and the ink guide portion 26 are fixed to the holding groove 36 and mounting

surfaces

36a and 36b of the holding body 30, and the ink guide portion 26 and the writing portion 25 are pressed against each other and fixed, so that ink from the padding 17 is supplied well to the writing portion 25 via the ink guide portion 26.

The entire holder 30 thus constructed is made of a hard material, and is made of, for example, a hard material having visibility, such as glass or a resin having no rubber elasticity. Examples of resins having no rubber elasticity that are visible include PP, PE, PET, PEN, nylon (including amorphous nylon in addition to general nylons such as nylon 6 and nylon 12), acrylic, polymethylpentene, polystyrene, ABS, and other materials having a visible light transmittance of 50% or more, so that characters written in the writing direction can be effectively viewed in the visible portion 33. Note that only the visible portion 33 may be made of a material having visibility. Note that the visible light transmittance can be obtained by measuring the reflectance with a multi-light source spectrophotometer (manufactured by Suga Test Instruments Co., Ltd., (MSC-5N)).
In addition, the holder 30 may be constructed using one of the above materials, or two or more of the materials in terms of further improving durability and visibility, and can be molded by various molding methods such as injection molding and blow molding.

In this embodiment, as shown in Fig. 3(b), the visible portion 33 of the holder 30 has a minimum width S in the width direction of 3.7 mm or more, and the length Y of the visible portion 33 is set to 7.4 mm or more. In this embodiment, the width S of the visible portion 33 of the holder 30 is configured to increase from the front end side to the rear side, and the minimum width S is the length in the width direction of the front end side of the visible portion 33 of the holder 30, and the width (parallel to the pen tip) is 3.7 mm or more. In this embodiment, the maximum width of the visible portion 33 in the width direction is 4.5 mm.
By setting the minimum width S to 3.7 mm or more, 10.5 point (No. 5 type) printed on the document can be clearly seen in the visible portion 33. Generally, in Japan, No. 5 type is often used as the standard for general official documents.
The length Y of the visible portion 33 is twice the minimum width S, i.e., 7.4 mm or more. For example, when the writing angle is 60°, the 3.7 mm wide character fits within the visible portion 33 even when viewed from above (3.7 mm/cos 60°=7.4 mm).
In order to set the minimum width S of the visible portion 33 to 3.7 mm or more and its length Y to 7.4 mm or more, the structure, shape, etc. of each part of the pen tip 20 (writing portion 25, ink guide portion 26, holder 30) can be configured (specified) as described above and appropriately combined, thereby setting these.

Furthermore, in this embodiment, in order to ensure that a necessary and sufficient ink flow rate is guided to the writing portion 25 and to increase the area of the visible portion 33 that can be further viewed, the width t of the ink guide portion 26 (the length as viewed from the perpendicular direction to the surface of the visible portion 33) is less than 1.5 mm, more preferably 1.2 mm or less, and particularly preferably 0.8 mm or less.
In addition, the ink guide portion 26 is fixed by being fitted and held in the concave retaining groove 36 and the mounting

surfaces

36a, 36b, and furthermore, from the standpoint of efficient assembly and productivity, the side surface is not structured to cover the entire ink guide portion 26 but is open to the outside air, so that the overall width length including the width t of the ink guide portion 26 is kept to the minimum necessary, with the width S of the visible portion 33 being maximized.

Furthermore, by having one ink guide portion 26 on one side of the visible portion 33 as shown in FIG. 3(b), that is, by arranging the ink guide portion 26 on the front side when writing (the side where the pen tip 20 forms an obtuse angle with respect to the ink guide portion 26), the visible portion 33 can be seen clearly regardless of the character in the direction of writing, even when a natural writing angle is used. If the ink guide portion 26 were arranged on the rear side (upper side) rather than on the front side when writing, the mechanism of action of the visible portion 33 would be different in that it would cross the character in the direction of writing (marking) and hide part of it.

Next, the pen tip 40 for fine writing is a rod-shaped pen tip for fine writing, as shown in Figures 1 (c) and (d), with a circular cross section. The rear end (the middle cotton side) of the pen tip 40 is inserted into the middle cotton 17, and the ink in the middle cotton 17 is supplied to the pen tip 40 by capillary force.
The pen tip 40 is constructed from a porous material, such as parallel fiber bundles made of one or a combination of two or more types of natural fibers, animal hair fibers, polyacetal resin, polyethylene resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, polyolefin resin, polyvinyl resin, polycarbonate resin, polyether resin, polyphenylene resin, etc.; a fiber core obtained by processing fiber bundles such as felt or resin-processing such fiber bundles; or a porous body (sintered core) obtained by sintering plastic powder of thermoplastic resins such as polyolefin resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, etc.
Preferred pen tips 40 are fiber bundle cores, fiber cores, sintered cores, felt cores, sponge cores, and inorganic porous cores, and fiber cores are particularly preferred from the viewpoints of deformation moldability and productivity. The porosity, size, hardness, etc. of the pen tip 40 used vary depending on the type of ink, the type of writing implement, etc., and for example, the porosity is preferably 30 to 60%. In addition, in this disclosure, the "porosity" of the writing core is calculated as follows. First, a writing core having a known mass and apparent volume is immersed in water, and after the writing core is sufficiently saturated with water, the mass is measured in a state where it is taken out of the water. The volume of water soaked into the writing core is derived from the measured mass. The porosity is calculated from the following formula, assuming that the volume of this water is the same as the pore volume of the writing core.
Porosity (unit: %)=(volume of water)/(apparent volume of pen tip 40)×100

In the writing instrument A configured in this manner, the writing instrument batting of the present disclosure that absorbs the writing instrument ink is inserted into the writing instrument body 10, that is, the batting 17 having two or more types of pore diameter distribution, the first pore diameter being 50 to 300 μm, and the second pore diameter being 50 to 90% of the first pore diameter, is inserted and held in place, and the pen tip 20 (writing portion 25, ink guide portion 26, holder 30) configured as described above is fixed to the tip side by sequentially fitting the tip 20 (writing portion 25, ink guide portion 26, holder 30) via the tip barrel 16. The other end of the pen can be fitted with a holder 45 to which the pen tip 40 is attached, allowing the twin-type writing instrument A to be easily produced. The ink absorbed in the writing instrument batting 17 of the present disclosure can be efficiently supplied to the writing part 25 and the pen tip 40 through the thin ink guide part 26 in the pen tip 20 by capillary force, resulting in a writing instrument batting that can further enhance ink diffusibility, and a writing instrument using the same.

In this writing instrument A, the pen tip 40 is the same as a conventional general-purpose pen tip, so the function of the pen tip 20 will be explained below.
The pen tip 20 of this writing instrument A has a visible portion (window portion) 33 that allows the writing direction to be visually confirmed, as shown in Figures 1 to 4, and the ink in the writing instrument inner batting 17 of the present disclosure reaches the writing portion 25 and the pen tip 40 by the capillary force of the inner batting 17, and is used for writing. When writing, by looking at the visible side through the visible portion (window portion) 33, it becomes easier to align the starting position of the stroke, and it is possible to stop the stroke exactly where you want it to end, preventing overstroking or overflowing.

The pen tip in the above embodiment has at least a writing section 25 with two selectable line widths, a holder 30 with a visible section 33, and an ink guide section 26 that guides the ink in the writing instrument body 10 to the writing section. By configuring the visible section 33 to have a minimum width (S) of 3.7 mm or more and a length (Y) of 7.4 mm or more (hereinafter, this configuration will be referred to as "Configuration 1"), or by configuring the ink guide section 26 to be provided on the near side during writing, that is, by configuring the ink guide section 26 to be positioned on the near side during writing (the side where the pen tip 20 forms an obtuse angle with respect to the ink guide section 26) when fixed to the holder 30 (hereinafter, this configuration will be referred to as "Configuration 2"), it is possible to achieve a high degree of both maximization of the effective area of the visible section 33 that allows the writing direction to be visually confirmed, ease of visibility, and ease of writing.

In the above configuration 2, even when a natural writing angle is used, the ink guide portion 26 provides a better view of the visible portion 33 regardless of the character in the direction of travel. If the ink guide portion 26 is placed at the back (upper side) rather than the front side when writing, or if it is U-shaped or C-shaped with two ink guide portions placed on either side of the writing portion, the mechanism of action of the visible portion 33 is different in that it crosses the character in the direction of travel and hides part of it when writing (marking). Even in this form, it is possible to maximize the effective area of the visible portion 33, while also achieving a high level of visibility and ease of writing, and the wider visible portion 33 makes the writing direction even clearer, further improving ease of writing.

By configuring the width t of the ink guide portion 26 to be 1.2 mm or less when viewed from the perpendicular plane of the visible portion 33 (hereinafter, this configuration will be referred to as "configuration 3"), the area of the visible portion can be further maximized, thereby enabling the effects of the present disclosure to be achieved to an even greater extent.
Furthermore, in the ink guide portion 26, the cross section is formed from a fiber bundle core having a rectangular or elliptical shape, the writing portion 25 is formed from a sintered resin body, and the ink guide portion 26 and the writing portion 25 are fixed to the holding body 30 and the ink guide portion 26 and the end portion of the writing portion 25 abut each other (hereinafter, this configuration will be referred to as "configuration 4"), whereby the ink guide portion 26 can efficiently flow (supply) ink to the writing portion 25 with a small cross-sectional area, resulting in a good writing feel and enabling the effects of the present disclosure to be achieved to an even higher degree.
Furthermore, this writing instrument A has a distribution of two or more pore sizes, with the first pore size being 50 to 300 μm and the second pore size being 50 to 90% of the first pore size, and due to the writing instrument inner batting 17 of the present disclosure, ink outflow is favorable, so that even when writing is performed with the pen tip 20 (or pen tip 40) moving at a high speed, the ink supply follows favorably, and a writing instrument is obtained that does not cause smearing of handwriting, etc.

The writing instrument of the present embodiment is not limited to the above-mentioned configurations, and can be further modified in various ways.
For example, the writing implement may be provided with a fiber bundle core having no window, or may be loaded with oil-based ink. Also, a ballpoint pen tip may be provided instead of a marking pen tip.

In the writing instruments of the above embodiments, each writing instrument is configured with the above configuration 1 or configuration 2, but each writing instrument may also be configured with a configuration that combines

configurations

1 and 2, and a configuration that combines

configuration

1 or 2 with the above configuration 3 and/or configuration 4.
Furthermore, in the above embodiment, in the writing instrument of configuration 1, as a preferred embodiment, the ink guide portion 26 is provided on one side of the visible portion 33; however, the effects of the present disclosure can also be achieved in the configuration of configuration 1 having two ink guide portions on the top and bottom surfaces of the visible portion 33 (even if the

ink guide portions

26, 26 are U-shaped or C-shaped and have two

ink guide portions

26, 26, which are either integral with or separate from the writing portion 25, on both sides of the writing portion 25, they may cross the characters in the direction of travel during writing (marking), but the visible portion 33 may have an unprecedentedly wide configuration, i.e., a configuration in which the minimum width (S) of the visible portion 33 is 3.7 mm or more and the length (Y) is 7.4 mm or more).
In addition, the methods of bonding the holding body 30 to the writing part 25 and the ink guiding part 26 include bonding by fitting them to the holding body 30, bonding by a hot melt adhesive, bonding by solvent penetration, bonding by ultrasonic welding, bonding by a reactive adhesive (moisture curing, UV curing, oxygen curing, two-component curing), bonding by a solvent-based adhesive (soluble synthetic resin, emulsion, rubber), bonding by tape, and bonding by double-sided tape.
It is preferable that the porosity of the writing portion 25 be within the following range.
The porosity is preferably 30 to 80%, and more preferably 40 to 70%.

Furthermore, although the writing instrument A of the present disclosure is a twin-type writing instrument, the pen tip 40 may be omitted (the shaft body being a cylindrical shaft body with a bottom) to make it a single-type writing instrument equipped with the pen tip 20, and it may also be a writing instrument in which the pen tip 20 appears and retracts by a knock mechanism.
In the writing implement A of each of the above embodiments, the cross section of the shaft of the writing implement body is formed into a circular shaft, but it may be triangular, rectangular, or other irregular shape, such as an elliptical shape. Also, although the case has been shown in which the entire pen tip 20 is made of a transparent material, the pen tip 20 may be made of at least a transparent material, and the main body part 31 side to be attached inside the writing implement body may be a two-color molded product made of a resin material other than a transparent material.
Furthermore, in each of the above embodiments, the ink (water-based ink, oil-based ink, thermochromic ink) for writing instruments is described, but the ink may also be any liquid such as liquid cosmetics, liquid medicines, coating fluids, and correction fluids.

Next, the present disclosure will be described in further detail with reference to manufacturing examples, examples, and comparative examples, but is not limited to the manufacturing examples below.

[Production Example 1: Production of Filling (Sample) A]
The filling A was made by using 5d (denier, hereinafter the same) 650 threads and 3d 460 threads manufactured by Toray Industries, Inc., and after converging, the yarn bundle having the second pore size distribution was inserted into the center of the yarn bundle having the first pore size distribution, and a polypropylene cylinder with a length of 80 mm and an inner diameter of 6 mm was used as a shaft tube, which was filled with the filling of each of the following Examples and Comparative Examples, and subjected to the following experiments. The yarn bundle was compressed and bundled with polyester fibers, and the weight was measured so that the ratio of the dense parts was set. The filling A was filled into a polypropylene cylinder to produce two types of pore size distributions, which were the first porosity, the second porosity, and the porosity ratio.
The filling B was made by bundling 15,300 3 denier fibers manufactured by Toray Industries, Inc., and then subjecting the bundle to the following experiment using a polypropylene cylinder with a length of 80 mm and an inner diameter of 6 mm as a shaft tube. The polyester fibers were compressed and bundled to obtain a bundle, and the weight was measured so as to obtain a predetermined dense portion ratio. The bundle was filled into a polypropylene cylinder to produce filling B having one pore size distribution with a first porosity.

The presence or absence of pore size distribution for the padding (samples) A and B obtained in Production Examples 1 and 2 above was verified using the following measurement method.

[Measurement method: Measurement of the distribution of inscribed circle diameters by image analysis of cross sections]
The pore distribution was measured based on the results of optical microscope observation of the test specimens, fillings (samples) A and B. The apparatus and measurement conditions used are as follows.
Equipment name: Material development comprehensive package software Math2Market GeoDict Nissan Arc development program (applied to Fig. 13)
Measurement item: diameter of maximum inscribed circle for pores Measurement conditions: Optical microscope photographs were input to an image analyzer and binarized to separate fibers and pores. Then, the diameter of maximum inscribed circle for pores was measured. For the pore size distribution, a moving average value was used due to the number of data points.

The presence or absence of pore size distribution was determined by image analysis of the cross section of the filling A, specifically, the cut surface of the filling A was observed, and the pore sizes (inscribed circle diameter distribution) were determined by image analysis.
The measurement method was to inject a curable resin (en-thiol resin-based optical evaluation adhesive: manufactured by Nichika Co., Ltd.) into the obtained padding A and B, and harden them. Next, they were cut perpendicular to the axis, the cross section was polished, and observed and photographed with an optical microscope (VHX-8000 manufactured by Keyence Co., Ltd.). The fiber part and the pore part (impregnated resin part) were separated by image analysis (material development comprehensive package software GeoDic manufactured by Math2Market Co., Ltd.). The maximum circle distribution inscribed in the pore part was obtained for both samples A and B, and the results shown in Figures 8 to 24 were obtained.

8 and 9 are drawings of optical microscope cross-section observations and binarized images of the filling of Production Examples 1 and 2 (samples A and B), and Figs. 10 and 11 are pore distribution diagrams (maximum circle inscribed in the pore portion) of Production Examples 1 and 2 (samples A and B). The optical microscope cross-section observation diagram in Fig. 10 is displayed in black and white, but the original optical microscope cross-section is displayed in four colors: green, yellow, white, and red, and in Figs. 10, 11, and 15 to 20, "yellow" represents a circular gray, "white" represents a white dot, "red" represents a black dot, and "green" represents the entire area other than the above "yellow, white, and red". The following Examples 12 to 20 are also displayed in black and white as above, and the original optical microscope cross-section is displayed in four colors: green, yellow, white, and red.
Next, FIG. 12 is a graph of the pore size distribution (the largest circle inscribed in the pore portion) of Production Examples 1 and 2 (samples A and B), FIG. 13 is a graph showing the relationship between the spatial distribution of pores (the distance from the circle center and the pore area frequency) of Production Examples 1 and 2 (samples A and B) and a drawing explaining the measurement method, FIG. 14 is a graph showing the pore diameter and area frequency plotted with thresholds of 50 μm, 90 μm, and 100 μm in the pore distribution (the largest circle inscribed in the pore portion) of Production Examples 1 and 2 (samples A and B), FIGS. 15 to 20 are drawings of the pore distribution (the largest circle inscribed in the pore portion) of Production Examples 1 and 2 (samples A and B) with thresholds of 100 μm, 90 μm, and 50 μm, and FIG. 21 is a graph showing the relationship between the spatial distribution of pores (the distance from the circle center and the pore area frequency) of Production Examples 1 and 2 (samples A and B) and a drawing explaining the measurement method, FIG. 22 is each drawing showing the relationship between the distance from the circle center (pore diameter 0 to less than 90 μm, pore diameter 90 μm or more) and the pore diameter frequency for Production Examples 1 and 2 (samples A and B) and a drawing showing the measurement method; FIG. 23 is each drawing showing the relationship between the distance from the circle center (pore diameter 0 to less than 50 μm, pore diameter 50 μm or more) and the pore diameter frequency for Production Examples 1 and 2 (samples A and B) and a drawing showing the measurement method; and FIG. 24 is each graph showing the relationship between the distance from the circle center and the pore diameter frequency for Production Examples 1 and 2 (samples A and B).

　When the results of Figures 8 to 24 are evaluated comprehensively, the characteristics of the padding (samples A and B) of Production Examples 1 and 2 are evident at the pore diameter of 90 μm. In other words, when the results of Figures 12 to 14 and Figures 21 to 24 are compared, the padding (sample B) of Production Example 2 has a high frequency of pores smaller than 90 μm. When the frequency distribution is analyzed by dividing the inscribed circle into less than 90 μm and 90 μm or more, the frequency of pores smaller than 90 μm is higher (dense part) in the padding of Production Example 1 in the region with a radius of 0.5 mm from the center, and the frequency of pores larger than 90 μm is lower in Sample A of Production Example 1 in the region with a radius of 0.5 mm from the center. From the above analysis, it was found that the padding (sample A) of Production Example 1 has a distribution of pore diameters, while the padding (sample B) of Production Example 2 has no distribution of pore diameters. In the padding of Production Example 1 (Sample A), there are many pores (fine parts) smaller than 90 μm in the radial center, but the location of these fine parts can also be on the circumference. As described above, it was confirmed that there is a pore size distribution when there is a difference in the diameter distribution of the inscribed circle of the pores in the padding in a certain region.

[Example 1 and Comparative Example 1]
The padding (samples) A and B obtained in Production Examples 1 and 2, a writing instrument having the following configuration and a pen tip conforming to Figures 1 to 7, and a writing instrument ink having the following composition were used. The pen tip dimensions, etc., were as shown below.

[Configuration of the pen tip 20 (writing part 25, ink guide part 26, holder 30)]
Writing part 25: Sintered polyethylene core, porosity: 50%, 4 x 3 x 6 mm, T = 3 mm, W1 = 4 mm, W2 = 1.5 mm
Ink guide portion 26: PET fiber core, width direction length: 2 mm, length direction length: 20 mm, thickness t: 0.8 mm

Holder 30: Made of acrylic resin, visible light transmittance 85% (reflectance was measured with a multi-light source spectrophotometer (MSC-5N) manufactured by Suga Test Instruments Co., Ltd., and the visible light transmittance was determined.)
Size of visible portion (window portion) 33 (rectangle): S = 3.8 mm (maximum 4.5 mm) x Y = 8 mm x width (thickness) 2.5 mm

Writing implement padding: The padding A to B (φ6×80 mm) obtained in Production Examples 1 and 2 above were used.
Outer cover: PET film Writing instrument body 10, caps 50, 60: Made of polypropylene (PP) Pen tip 40: Polyester fiber bundle core, porosity 60%, φ2×40 mm
Friction body 52: a styrene-based elastomer selected from the group consisting of styrene-ethylene-propylene-styrene (SEPS), styrene-ethylene-ethylene-propylene-styrene (SEEPS), and styrene-ethylene-butadiene-styrene (SEBS).

(Writing ink composition: Ink color: fluorescent pink)
As the ink for the writing instrument, an ink having the following composition (total 100% by mass) was used.
Dispersion: 50% by weight
Triethanolamine: 2% by mass
Ethylene glycol: 5% by mass
Surfactant: 0.5% by mass
Distilled water: 42.5% by mass
pH: 4.0
Viscosity (25°C): 3.5 mPa·s (Complate type viscometer, TOKIMEC, TV-20)
Surface tension (25°C): 35 mN/m (automatic surface tensiometer, Kyowa Interface Science Co., Ltd., DY-300)

In the writing implement using the pen tip 20 of Example 1 based on Figures 1 to 7, the inner batting A has a distribution of two or more types of pore diameters, so that ink can be reliably supplied to the

pen tip

20, 40 and ink diffusibility can be improved. In addition, the ink from the inner batting A is guided to the writing part 25 by an open type ink guide part 26 in a thin plate shape with flowability, the writing part 25 is composed of a resin sintered core, and the ink guide part 26 is composed of a fiber bundle core, so that the capillary force is strong relative to the porosity, and the thickness can be made extremely thin, so that the ink flowability is good, and there is no need to design the ink guide part to be thick, and the minimum width S of the visible part 33 is 3.7 mm or more, and the length Y is 7.4 mm or more, so that the effective area of the visible part 33 where the writing direction can be visually recognized, the ease of visibility, and the ease of writing can be highly simultaneously achieved.
In addition, since the ink guide portion 26 is positioned on the front side when writing, even when a natural writing angle is used, the visibility of the visible portion 33 is improved regardless of the direction of the ink guide portion 26, and when a right-handed person writes from left to right, the user can draw a line with the writing portion 25 while visually checking the writing direction with the visible portion 33, and the ink outflow is also good, and it was confirmed that a writing instrument that can achieve significantly easier visibility and writing of the visible portion 33 without impairing the outflow of ink is obtained. It was also confirmed that writing can be done without smearing even after being dropped from a height of 1m onto a cedar board.

Furthermore, this writing instrument was set in an automatic writing device, and a straight line was written on high-quality paper at a writing angle of 65°, a writing load of 1N, and a speed of 7cm/s according to the test method compliant with JIS S6037.The condition of the written line was then visually checked, and it was found that, because the above-mentioned preferred ink composition was used, the ink flow rate (10mg/m) of the pen tip 20 was good, and while the drying of the pen tip was suppressed, the ink had excellent drying properties and low-temperature stability, and the lines were free of bleeding or bleed-through.

In contrast, in the writing instrument of Comparative Example 1, which is equipped with padding B that does not have a pore size distribution, it took more than an hour to supply ink to

nibs

20 and 40, and in five of the 100 nibs, the nib was not saturated with ink even after one day, and in some cases ink could not be supplied.

The writing implement batting of this embodiment can be suitably used as batting for marking-type writing implements such as Underline (registered trademark) pens, oil-based markers, and water-based markers.

10 Writing instrument body 11 Rear barrel 16 Front barrel 17 Filling (ink occluding body)
20 Pen tip 25 Writing part 26 Ink guide part 30 Holder 33 Visible part

Claims

A writing instrument characterized by having a filling with two or more types of pore size distribution.
The writing implement of claim 1, characterized in that the frequency of particles smaller than 90 μm in the filling is high in an area with a radius of 0.5 mm from the center, as determined by cross-sectional image analysis.
The writing instrument according to claim 1 or 2, characterized in that the ink composition absorbed in the padding is an ink composition containing a resin fine particle pigment containing a dye.