JP7488654B2 - Writing implements - Google Patents

Description

The present invention relates to a writing instrument having a pen tip made of a fiber processed material or a synthetic resin porous material.

Conventionally, writing implements or pen cores used in writing implements have a nib that forms a writing part and is arranged so as to protrude from the tip of a barrel, and this nib is made of a fiber processed body obtained by bundling fibers and bonding and curing them with a binder resin, and the tip shape is tapered, and the nib is easily flexible (see, for example, Patent Document 1).

In addition, a writing instrument pen tip made of a fiber bundle obtained by bundling fibers and bonding and curing them with a binder resin is known, in which at least the writing surface of the fiber bundle is coated with a sintered body made of thermoplastic resin powder, and the outer layer and inner layer are different (see, for example, Patent Document 2).

In addition, a writing instrument pen tip made of a fiber-processed body or a synthetic resin porous body is known in which the outer periphery of the pen tip is hard and the inside is soft, and the tip shape is polished into a curved shape to expose the soft part inside and serve as an application part (see, for example, Patent Document 3).

Patent document 1 has a pen tip made of processed fiber bundles and is flexible with consideration given to crush resistance, while patent documents 2 and 3 are pen tips with different inner and outer layers that allow the drawn line to be thickened by changing the writing pressure.

However, no pen core capable of drawing as wide a line as possible with a limited outer diameter has been disclosed.

JP 2015-199353 A JP 2004-98518 A JP 2019-14117 A

In view of this situation, the present invention aims to provide a writing instrument that can draw as wide a line as possible with a limited outer diameter.

The present invention is a writing instrument in which a pen tip having a writing part formed in a pen core is disposed so as to protrude from a tip end of a barrel,
the pen core is configured to include a fiber processed body or a synthetic resin porous body,
The pen tip has a curved tip shape,
The writing implement has a pen core configured so that the elastic load _y1 (N) during the displacement _x1 of 0 (mm) to 1 (mm) when the pen tip is pressed downward in the vertical direction at an angle of 65° to the writing surface by ₀ (mm) to ₁ (mm) is between _y1 = _20x1 and _y1 = 45x1, more preferably between _y1 = _20x1 and _y1 = _30x1 .

According to the writing implement of the present invention, the pen core is a nib containing a processed fiber body or a porous synthetic resin body, the tip shape is formed into a curved surface, and the pen core is configured so that when the nib is pressed downward vertically by 0 (mm) to 1 (mm) at an angle of 65° to the writing surface by ₀ (mm) to 1 (mm), the displacement (mm) is _x1 , and the elastic load _y1 (N) during the displacement x1 of 0 (mm) to ₁ (mm) falls between _y1 = _20x1 and _y1 = 45x1. This makes it possible to achieve the excellent effect of being able to draw the thickest possible lines on the writing surface with limited external dimensions.

1A is an explanation of a writing instrument according to a first embodiment of the present invention, in which (a) is a front view, (b) is a side view rotated 90° circumferentially from (a), and (c) is a longitudinal cross-sectional view along line CC of (a). 2 is an explanatory diagram of the writing part of FIG. 1 with the cap removed, (a) is a front view, (b) is a longitudinal sectional view along line B-B of (a), and (c) is an enlarged sectional view of the tip portion indicated by the two-dot chain line C of (b). 10 is an explanation of a writing instrument according to a second embodiment of the present invention, in which (a) is a front view, (b) is a side view rotated 90° circumferentially from (a), and (c) is a longitudinal cross-sectional view along line CC of (a). 2 is an explanatory diagram of the writing part of FIG. 1 with the cap removed, (a) is a front view, (b) is a longitudinal sectional view along line B-B of (a), and (c) is an enlarged sectional view of the tip portion indicated by the two-dot chain line C of (b). FIG. 11 is a component diagram of the pen core, holding pipe, and nozzle plug, in which (a) is an explanatory diagram of the components used in the writing instrument of the second embodiment before assembly, (b) is a partial assembly diagram of the components in (a) assembled, (c) is an explanatory diagram of the components in (a) rotated 90 degrees before assembly, and (d) is a partial assembly diagram of the components in (b) rotated 90 degrees. 1 is an explanatory diagram of a state in which the writing instrument of the embodiment is at an angle of 65° to the writing surface. FIG. This is a comparative explanation of the pen cores of Examples 1 to 3 and the pipes used therewith. FIG. 1 is an explanatory diagram of the tip shape and line width of the pen core of Examples 1 to 3 used in the writing instrument of the embodiment, in which (a) and (b) are longitudinal and transverse cross-sectional images of the tip of the pen core of Examples 1 and 2, (c) and (d) are longitudinal and transverse cross-sectional images of the tip of the pen core of Example 3, and (e) is a comparative explanatory diagram of the line widths of Examples 1 to 3. FIG. 1 is an explanatory diagram of the pen core of Examples 1 to 3, where (a) is an explanatory diagram of the state in which the pen core is compressed in the radial direction, (b) is an enlarged cross-sectional image of the pen core of Example 1, (c) is an enlarged cross-sectional image of the tip of the pen core of Example 2, and (d) is an enlarged cross-sectional image of the tip of the pen core of Example 3. FIG. 4 is an explanatory diagram of the characteristics of the pen cores of Examples 1 to 3, where (a) is a diagram comparing the elasticity of each of Examples 1 to 3, and (b) is a diagram comparing the drawn line width of each of Examples 1 to 3. 4A and 4B are diagrams illustrating the characteristics of the pen core of Example 1, in which (a) shows the elastic characteristics when compressed and released in the radial direction, and (b) shows the elastic characteristics when compressed in the radial direction. 10A and 10B are diagrams illustrating the characteristics of the pen core of Example 2, in which (a) shows the elastic characteristics when compressed and released in the radial direction, and (b) shows the elastic characteristics when compressed in the radial direction. 10A and 10B are diagrams illustrating the characteristics of the pen core of Example 3, in which (a) shows the elastic characteristics when compressed and released in the radial direction, and (b) shows the elastic characteristics when compressed in the radial direction. FIG. 11 is an explanatory diagram of a pen tip elasticity property test at a writing angle of 65° for the pen cores of Examples 1 to 3, in which (a) is an explanatory diagram of the state in which the pen core is compressed at a writing angle of 65°, (b) is an enlarged image of the tip of the pen core of Example 1, (c) is an enlarged surface image of the tip of the pen core of Example 2, and (d) is an enlarged image of the tip of the pen core of Example 3. 4A and 4B are diagrams illustrating the elastic properties of the pen core of Example 1 at a writing angle of 65°, where FIG. 4A shows the elastic properties when compressed and released, and FIG. 4B shows the elastic properties when compressed. 1A and 1B are diagrams illustrating the elastic properties of the pen core of Example 2 at a writing angle of 65°, where (a) shows the elastic properties when compressed and released, and (b) shows the elastic properties when compressed. 11A and 11B are diagrams illustrating the elastic properties of the pen core of Example 3 at a writing angle of 65°, in which (a) shows the elastic properties when compressed and released, and (b) shows the elastic properties when compressed.

The following describes an embodiment of the present invention with reference to the attached drawings.

Figures 1 and 2 are explanatory diagrams of a writing instrument according to a first embodiment. Figures 3 and 4 are explanatory diagrams of a writing instrument according to a second embodiment, and Figure 5 is an explanatory diagram of a pen core of the writing instrument according to embodiments 1 and 2.

The writing instrument according to the first embodiment is a writing instrument in which the pen tip 12, on which the writing portion 12a is formed, is arranged so as to protrude from the tip of the barrel 14, as shown in Figs. 1 and 2. The state in which the cap 16 is removed is shown in Fig. 2.

The barrel 14 is a cylindrical body with the tip 14a tapered in stages from the center. The rear end of the barrel 14 is closed by a tail plug 18, forming a storage section 14b in the center. A batting 20 that is impregnated with ink is contained in the storage section 14b. The pen core 10, with a holding pipe 24 attached to the inside of a roughly cylindrical mouthpiece (support) 22, is inserted and supported by the tip 14a.

The pen core 10 is made of a fiber-processed material or a synthetic resin porous material, and the tip of the pen tip 12 is curved.

The pen core 10 is configured such that the elastic load y _{1 (N) during the displacement x 1 of} 0 (mm) to 1 (mm) when the pen tip ₁₂ is pressed downward in the vertical direction at an angle of 65° to the writing surface 26 is between y ₁ = 20x ₁ and y ₁ = 45x ₁ .

It is preferable that the pen tip 12 be made of a fiber processed body obtained by bundling fibers and bonding and solidifying them with a binder resin.

In addition, the pen tip 12 has different displacement curves for the pressing load and the returning load.

As shown in FIG. 2(c), the tip plastic 22 supports the pen core 10 with the holding pipe 24 inserted from the tip to partway to the rear end.

As shown in Fig. 5(a) and (b), the pen core 10 is inserted into the holding pipe 24 and is inserted and held in the mouth plastic 22. As shown in the figure, the outer circumference of the mouth plastic 22 is tapered to a tip like an umbrella, and the rear part is cylindrical and chamfered. As shown in the figure, the pen core 10 has a hemispherical or bullet-shaped tip and is tapered to a narrower rear part to make it easier to insert into the padding. As shown in Fig. 5(a), the holding pipe 24 is roughly cylindrical before attachment (before assembly), and as shown in Fig. 5(b), in the attached state (assembled state), the tip part 24a is crimped (reduced in diameter) so that it is thinner than before processing.

As shown in FIG. 2(c), the pen core 10 of the first embodiment is configured such that the outer periphery 10o is harder and the interior 10i is softer, and the pen tip 12 is formed into a hemispherical or bullet-shaped curved surface, with the softer part of the interior exposed forward from the outer periphery.

As shown in FIG. 2(c), the tip of the cap 22 has a retaining pipe 24 attached from the tip to the rear end, and the rear end of the retaining pipe 24 abuts against a stepped portion of the inside of the rear end that is tapered in diameter, thereby positioning the retaining pipe 24 and preventing it from coming loose. The tip 24a of the retaining pipe 24 is tapered to secure the pen core 10 in place.

The outer periphery of the mouthpiece 22 is uneven, which allows it to fit tightly into the tip 14a of the barrel 14 and prevents it from slipping out.

Fig. 6 shows the writing state. In the writing instrument of the embodiment, as shown in Fig . 8 , the softer part of the interior 10i is exposed forward of the outer periphery 10o, and the soft layer at the tip of the pen core 10 can be elastically deformed by the writing pressure during writing. As shown in Fig. 6, the pen core 10 is brought into contact with the writing surface 26, such as the flat surface of the writing object, the paper surface, or the sheet surface, at an angle θ of 65°, so that the soft layer at the tip of the pen tip 12 and the tip of the harder outer periphery are simultaneously in contact.

Figures 3 and 4 are explanatory diagrams of a writing implement according to the second embodiment. Figures 5(c) and (d) show the pen core 10, holding pipe 24, and tip plug 22 according to the second embodiment. In Figures 3 and 4, the same parts as in the first embodiment are given the same reference numerals.

In the second embodiment, as shown in FIG. 4(c), the pen core 10 has a substantially uniform hardness both inside and outside, and is configured such that the displacement (mm) when the pen core 10 is pressed 0 (mm) to 0.2 (mm) in the radial direction perpendicular to a plane is _x2 , and the elastic load _y2 (N) when the displacement _x2 is pressed 0 (mm) to 0.2 (mm) is less than _y2 = _60x2 .

As shown in Figure 4, the pen core 10 has a generally uniform hardness both inside and outside. As shown in Figures 5(c) and 5(d), the mouthpiece 22 has a rib 22a formed on the outer periphery of the rear part, and the outer surface of the rib 22a is in contact with and fixed inside the tip 14a of the barrel 14. The outer surface of the rib 22a is uneven to prevent it from slipping out of the tip 14a. As shown in Figure 6, the pen core 10 is in contact with the writing surface 26, such as the flat surface of the writing object, paper or sheet surface, at an angle θ of 65°, and is formed so that the tip of the pen tip 12 is pushed out by the writing pressure.

The various parts used in the first and second embodiments are explained below.

[Pen core 10]
In an embodiment, examples of the fiber processed body that constitutes the pen core 10 include a fiber bundle core in which fibers are bundled and then bonded and hardened by welding or a binder resin, etc., and felt or nonwoven fabric in which fibers are bonded together by mixing them with heat, pressure, or a binder.

Examples of fibers that can be used include natural fibers, animal hair fibers, polyacetal fibers, acrylic fibers, acrylonitrile fibers, polyester fibers, polyamide fibers, polyolefin fibers, polyvinyl fibers, polycarbonate fibers, polyether fibers, polyphenylene fibers, and the like, and fibers consisting of one or a combination of two or more of these fibers can be used. Examples of the fiber yarn form that can be used include filaments and slivers. Examples of binder resins include those used for adhesive curing, such as unsaturated polyester resins, melamine resins, phenolic resins, urea resins, epoxy resins, polyurethane resins, and furan resins.

The synthetic resin porous body constituting the pen core 10 may be, for example, a porous body (sintered core) or a foam made by sintering synthetic resin powder such as polyacetal resin, polyethylene resin, acrylic resin, polyester resin, polyamide resin, polyurethane resin, polyolefin resin, polyvinyl resin, polycarbonate resin, polyether resin, polyphenylene resin, fluorine resin, or styrene resin.

In the above-mentioned fiber processed body or synthetic resin porous body that constitutes the pen core 10, methods for making the outer periphery 10o of the pen core 10 harder and the inner part 10i softer can be, for example, in the case of a fiber processed body, by reducing the degree of welding or the amount of binder resin on the inner side and increasing the degree of welding or the amount of binder resin on the outer periphery side, or when bundling and heat welding the fibers, by firmly welding the outer side and then allowing the binder resin to penetrate, or by making the amount of fiber on the inner side less than that on the outer side to adjust the capillary force balance through which the binder penetrates (the more fiber there is, the denser the material becomes and the higher the capillary force), or in the case of a synthetic resin porous body, by making the particle diameter on the outer side smaller than the particle diameter on the inner side (making the specific adhesive surface area larger on the outer side), or by making the temperature on the outer side higher than the temperature on the inner side under melting temperature conditions.

The writing ink contained in the storage section 14b of the barrel 14 of the applicator is preferably a writing ink whose viscosity, measured at 100 rpm at 25°C using a cone-plate type rotational viscometer, is 1 to 100 mPa·s. From the standpoint of ink outflow and ink spillage, it is preferable that the viscosity of the writing ink is 10 to 100 mPa·s measured at 10 rpm using a rotational viscometer at 25°C, and 20 to 400 mPa·s measured at 1 rpm.

Ink viscosities of this type with a measured value at 100 rpm of less than 1.0 mPa·s are extremely difficult to formulate, and even if they can be formulated, they are undesirable because they require a high ink flow rate and result in poor line drying. On the other hand, ink viscosities exceeding 100 mPa·s are undesirable because they require a low ink flow rate and cannot ensure sufficient hiding power.

The writing ink is preferably an alkaline ink composition with a pH value of 7.5 to 9.5, more preferably 8 to 9. If the pH value of the ink composition is within the above range, the binder resin contained in the pen core can be softened, providing a soft feel when writing. The pH value can be measured at 20°C, for example, using an IM-40S pH meter (manufactured by DKK-TOA Corporation).

The surface tension of the writing ink is preferably 4 to 45 mN/m (measurement temperature: 25°C, measuring device: surface tension measuring device manufactured by Kyowa Interface Science Co., Ltd.), and more preferably in the range of 10 to 40 mN/m. By using a writing ink with the above characteristics, a stable application width (writing width) can be ensured even if the pen tip is deformed. If the surface tension is less than 4 mN/m, the direct current phenomenon is likely to occur, and the pigment is likely to settle or aggregate. On the other hand, if it exceeds 45 mN/m, the amount of ink flow becomes unstable depending on the storage environment and writing conditions, and the density and width of the drawn lines are likely to vary, which is not preferable.

Furthermore, it is preferable that the ink flow rate of the writing implement is 100 to 400 mg/2.5 m at a writing angle of 65° and a writing speed of 4 m/min with a load of 100 g.

The writing ink can be composed of at least water, a colorant, a dispersant, a resin, and a penetrant.

The ink composition of the writing ink mentioned here is described in detail. The colorant is a pigment, and can be selected from inorganic pigments, organic pigments, and glossy glitter pigments. Specifically, inorganic pigments include metal oxides such as carbon black, titanium oxide, zinc oxide, iron oxide, yellow iron oxide, red iron oxide, and composite oxide pigments, and ultramarine. Organic pigments include azo pigments, indigo pigments, phthalocyanine pigments, quinacridone pigments, thioindigo pigments, threne pigments, perinone pigments, perylene pigments, phthalone pigments, dioxane pigments, isoindolinone pigments, metal complex pigments, methine azomethine pigments, and diketopyrrolopyrrole pigments. Glossy glitter pigments include aluminum pigments and glass flake pigments. In addition, the pigment is preferably surface-treated with a coating material, and the coating material is preferably an inorganic oxide such as silica, alumina, zirconia, or zinc oxide, a metal such as molybdenum, or a phosphate. This is because surface-treating the pigment with the coating material suppresses aggregation of the pigments in the ink, stabilizing the dispersion of the pigment, and suppressing the reaction between the pigment and water, thereby suppressing the generation of bubbles. Furthermore, when a pigment containing metal is subjected to shear force from a mixer or the like during ink production, the pigment is prevented from being deformed or damaged, and the elution of metal ions is suppressed, so that the ink stability over time can be improved. In consideration of the dispersion stability in the ink, the coating material for the pigment is more preferably an inorganic oxide containing silica or alumina. With respect to the pigment, the coating amount of the pigment surface-treated with the coating material is preferably 0.01% to 20% by mass, and more preferably 0.1% to 8.0% by mass, based on 100 parts by mass of the pigment after surface treatment with the coating material. If the coating amount is within the above numerical range, the dispersion of the ink and the suppression of elution of metals can be easily achieved. In addition, when a pigment surface-treated with an inorganic oxide is used, the pigment surface-treated with an inorganic oxide preferably has a positive or negative surface charge in consideration of the dispersion stability in the ink. In particular, when a pigment treated with an inorganic oxide containing silica is used, the pigment preferably has a negative surface charge, and when a pigment treated with an inorganic oxide containing alumina is used, the pigment preferably has a positive surface charge. Such a pigment exhibits good dispersibility in the composition, but the dispersibility and redispersibility can be further improved by combining it with a dispersant described later. When the surface-treated pigment has the above-mentioned surface charge, the surface-treated pigment is preferably titanium oxide in consideration of the dispersion stability in the ink. The average particle size of the pigment is preferably 0.01 μm to 30 μm, more preferably 0.05 μm to 15 μm, and even more preferably 0.1 μm to 5 μm. If the average particle size of the pigment is within the above numerical range, even when the pigment is written on a writing material having large gaps between fibers such as paper and cloth, the pigment is unlikely to enter the gaps between the fibers, and vivid color development is likely to be obtained. In addition, when an ink composition containing a pigment having an average particle size within the above numerical range is used in a writing instrument such as a marker, the ink ejection properties can be improved. The average particle size of the pigment can be measured, for example, by the particle size (D50) at 50% cumulative volume of the particle size distribution measured by a laser diffraction method using a laser diffraction particle size distribution measuring instrument (product name "MicrotracHRA9320-X100", Nikkiso Co., Ltd.). In this specification, the "average particle size" of the pigment refers to the average particle size on a volume basis, unless otherwise specified. The content of the pigment in the ink composition is preferably 1% by mass to 40% by mass, more preferably 2% by mass to 30% by mass, based on the total amount of the ink composition. If the content of the pigment is within the above numerical range, it is possible to prevent a decrease in ink ejection properties, and to maintain the clarity and hiding power of the ink composition and the handwriting formed using it.

The dispersant, when combined with the pigment, can suppress the aggregation of the pigments and enhance the stability of the ink. The dispersant is not particularly limited as long as it has the effect of enhancing the dispersibility of the pigment. However, when a pigment surface-treated with an inorganic oxide is used, it is preferable to use a dispersant having an anionic adsorption group or a cationic adsorption group in consideration of the dispersion stability of the pigment. When a pigment surface-treated with an inorganic oxide containing silica is used in the ink composition, it is preferable for the dispersant to have a cationic adsorption group. When considering the stability of the ink composition, it is preferable for the acid-base property of the ink composition to be close to neutral, but in this liquid property, the above-mentioned pigment in the ink composition has a negative surface charge, so that the cationic adsorption group is easily adsorbed to the pigment by electrical attraction, and dispersion can be facilitated. The dispersant having a cationic adsorption group used in the ink composition of the present invention is not limited to these. One or more types of dispersant can be used. Furthermore, when a pigment surface-treated with an inorganic oxide containing alumina is used in the ink composition, it is preferable for the dispersant to have an anionic adsorption group. In the acid-base solution, the pigment has a positive surface charge, so that the anionic adsorption group is easily adsorbed to the pigment by electrical attraction, and dispersion can be facilitated. The dispersant having an anionic adsorption group is not limited to the above. One or more dispersants can be used. The content of the dispersant in the ink composition is preferably 0.01% by mass to 5% by mass, and more preferably 0.05% by mass to 3% by mass, based on the total amount of the ink composition, in terms of the solid content of the active ingredients. In addition, when the total content of the pigment surface-treated with the inorganic oxide is S and the total content of the dispersant is T, T/S is preferably 0.005≦T/S≦0.5, and more preferably 0.01≦T/S≦0.2. When the content of the dispersant and the ratio of the content of the dispersant to the content of the pigment surface-treated with the inorganic oxide are within the above numerical ranges, the pigment has good dispersibility, and the viscosity of the ink composition can be prevented from becoming excessively high.

The ink composition may contain a guar gum derivative. The guar gum derivative adsorbs to pigment particles and polyolefin particles described later in the ink composition to form bulky pigment aggregates, which prevents the pigment from penetrating through the gaps between the fibers into the writing object when written on a writing object having large gaps between fibers, such as paper or cloth, and makes it easier for the pigment to adhere to the fibers on the surface of the writing object, improving the color development of the writing. In addition, the guar gum derivative imparts shear thinning properties to the ink composition, suppressing bleeding of the writing when written, suppressing the pigment in the ink composition from forming a hard cake, and suppressing ink leakage from the ink ejection section of the writing object when the writing object using the ink composition, particularly a ballpoint pen, is left stationary. Guar gum is a polysaccharide in which galactose (α-D-galactopyranose) is bonded by α-(1-6)-bonds to a linear main chain of mannose (β-(1-4)-D-mannopyranose), with the mannose and galactose being in a ratio of 2:1. The main chain has a linear structure resulting from the β-bonds of mannose, and the hydroxyl groups in the guar gum molecule are present on the cis side. Therefore, when guar gum comes into contact with a substance having hydroxyl groups such as cellulose, the hydroxyl groups of both molecules tend to bond with each other, forming a strong bond. The guar gum derivatives are cationic guar gum obtained by modifying guar gum with a quaternary ammonium salt, carboxymethylated guar gum obtained by adding a carboxymethyl group, hydroxypropyl guar gum obtained by adding a hydroxypropyl group, and amphoteric guar gum obtained by mixing a cationic guar gum modified product and an anionic guar gum modified product, and can be preferably used because they have affinity with cellulose that guar gum has, and can be stably dispersed in an ink composition to form bulky pigment aggregates, thereby improving the color development of handwriting. Among these guar gum derivatives, cationic guar gum, carboxymethylated guar gum, and hydroxypropyl guar gum are preferred, considering that the ink composition can be used in combination with a poorly water-soluble resin described below to easily improve the color development of handwriting. In particular, hydroxypropyl guar gum forms a crosslinked structure in the ink composition, which makes it easier to form bulkier pigment aggregates, and is therefore effective in improving the color development of handwriting, and can be preferably used. When the above-mentioned cationized guar gum is used in the ink composition, the pigment preferably has a negative surface charge in the ink composition. Since the cationized guar gum is ionized to become a cation in the ink composition, such a combination makes it easy for the pigment and the cationized guar gum to be adsorbed by electrical attraction to form a bulky aggregate, and the color development and fixability of the handwriting can be improved. Furthermore, when the above-mentioned carboxymethylated guar gum is used in the ink composition of the present invention, the pigment preferably has a positive surface charge in the ink composition. Since the carboxymethylated guar gum is ionized to become an anion in the ink composition, such a combination makes it easy for the pigment and the carboxymethylated guar gum to be adsorbed by electrical attraction to form a bulky aggregate, and the color development and fixability of the handwriting can be improved. In addition, since the cationized guar gum and hydroxypropyl guar gum are neutralized in the ink composition, the effect of improving the color development and fixability of the handwriting can be easily expressed, it is preferable to use a neutralizing agent when using the cationized guar gum or hydroxypropyl guar gum. Specific examples of the neutralizing agent include organic acids such as citric acid, lactic acid, malic acid, and acetic acid, and inorganic acids such as hydrochloric acid, sulfuric acid, and nitric acid, which are preferably used. In consideration of the good dispersion stability of the aggregates of cationized guar gum or hydroxypropyl guar gum and pigment in the ink composition, the neutralizing agent is more preferably an organic acid. The content of the guar gum derivative is preferably 0.005% by mass to 1% by mass based on the total amount of the ink composition. When the content of the guar gum derivative is within the above range, the ink viscosity is prevented from becoming too high and the ink dischargeability during writing is prevented from decreasing, and the guar gum derivative is adsorbed to the pigment to form a bulky aggregate, thereby improving the color development of the handwriting. In addition, in consideration of the fixability, color development, and writing properties of the handwriting, it is preferable that V/U is 0.0005≦V/U≦0.05, where U is the total content of the pigment relative to the total amount of the ink composition, and V is the total content of the guar gum derivative relative to the total amount of the ink composition. This is because within the above numerical range, the pigment is more easily fixed to the surface of the writing surface, improving color development, and the viscosity of the ink composition is not too high, improving ink ejection properties and making it easy to achieve excellent writing properties.

The ink composition contains a poorly water-soluble resin as a resin. The poorly water-soluble resin is a resin whose solubility in water (amount of solute per 100 g of water) is less than 1.0 g, and in the ink composition, it is bound to the bulky aggregates, pigments, and polyolefin particles described later, and adheres to the surface to be written on during writing, thereby improving the fixability and abrasion resistance of the handwriting and improving the color development of the handwriting. Therefore, in the aqueous ink composition, it is important to use both a guar gum derivative and a poorly water-soluble resin in combination, as this improves the fixability and color development of the handwriting. The poorly water-soluble resin is preferably used as an emulsion or dispersion, which allows the poorly water-soluble resin to be in a stable dispersed state. Specific examples of the poorly water-soluble resin used in the ink composition include acrylic resins, urethane resins, styrene-butadiene resins, alkyd resins, ketone resins, sulfamide resins, maleic acid resins, polyvinyl acetate resins, ethylene vinyl acetate resins, vinyl chloride-vinyl acetate resins, copolymers of styrene and maleic acid ester, styrene-acrylonitrile resins, cyanate-modified polyalkylene glycols, ester gums, xylene resins, urea resins, urea aldehyde resins, phenolic resins, alkylphenolic resins, terpene phenolic resins, rosin-based resins and hydrogenated compounds thereof, rosin phenolic resins, polyvinyl butyrals, polyvinyl acetals, polyvinyl alkyl ethers, polyamide resins, polyolefin resins, nylon resins, polyester resins, and cyclohexanone-based resins, and can be preferably used. These can be used alone or in combination. In consideration of the improvement of the color development, fixation, and abrasion resistance of handwriting, it is more preferable that the composition of the present invention contains one or more selected from polyolefin resins, acrylic resins, nylon resins, and polyester resins. Considering the above-mentioned writing performance, the composition more preferably contains a polyolefin resin or an acrylic resin, and particularly preferably contains a polyolefin resin. By containing a polyolefin resin or an acrylic resin, the ink composition can achieve both good color development and high writing fixation and abrasion resistance, and such effects are effectively expressed by using a guar gum derivative in combination with the above-mentioned poorly water-soluble resin. Examples of the polyolefin resin used include polymers with olefins such as ethylene, propylene, or butene as monomers, as well as polymers and modified products of olefins and monomers other than olefins. Specifically, polyethylene, polypropylene, polybutene, ethylene-propylene copolymers, ethylene-butene copolymers, propylene-butene copolymers, ethylene-propylene-butene copolymers, copolymers of ethylene and acrylic acid, copolymers of ethylene and methacrylic acid, copolymers of ethylene and maleic anhydride, copolymers of ethylene and vinyl acetate, etc. can be preferably used. Considering the color development and fixability of the aqueous ink composition, the polyolefin resin used in the ink composition is more preferably a copolymer of ethylene and acrylic acid, and more preferably a self-emulsifying copolymer of ethylene and acrylic acid modified. The acrylic resin used is a polymer containing acrylic acid or methacrylic acid in the repeating unit, and it is possible to use a single acrylic resin or multiple acrylic resins. Specifically, acrylic ester resin, acrylic styrene resin, acrylic silicone resin, acrylic urethane resin, acrylic nitrile resin, acrylic styrene nitrile resin, acrylic vinyl acetate resin, methacrylic ester resin, etc. can be preferably used. Among these acrylic resins, acrylic styrene resin is preferable, and self-crosslinking acrylic styrene copolymer resin is more preferable, considering further improvement of fixability and abrasion resistance of handwriting. The molecular weight of the acrylic resin is 1,000 to 1,000,000 in mass average molecular weight. The content of the poorly water-soluble resin is preferably 0.1% by mass to 10% by mass with respect to the total amount of the ink composition. In addition, when the total content of the guar gum derivative relative to the total amount of the ink composition is V, and the total content of the poorly water-soluble resin relative to the total amount of the ink composition is X, it is preferable that X/V is 5≦X/V≦75. If the content of the poorly water-soluble resin and the ratio of the content of the poorly water-soluble resin to the content of the guar gum derivative are within the above numerical ranges, the fixation of the pigment to the writing surface is improved and excellent writing properties are easily achieved.

Examples of solvents that can be used include water and mixed solvents of water and organic solvents. Conventional water such as ion-exchanged water, distilled water, and tap water can be used as water, and when a mixed solvent of water and an organic solvent is used, ethanol, normal propanol, isopropanol, and the like can be used as the organic solvent. Diols or triols with relatively high boiling points such as glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and polyethylene glycol can be used, but it is preferable that the amount of the organic solvent is small. The content of the organic solvent is preferably 1% to 30% by mass, and more preferably 1% to 20% by mass, based on the total mass of the solvent. In particular, the content of the diols or triols is preferably 1% to 10% by mass. If the content of the organic solvent is within the above numerical range based on the total mass of the solvent, good dry-up performance and handwriting drying properties can be achieved at the same time. The content of the solvent in the ink composition is preferably 20% to 90% by mass, and more preferably 30% to 80% by mass, based on the total amount of the ink composition. As long as the solvent content is within the above numerical range, each component can be stably dissolved or dispersed, and bulky aggregates that are easily redispersible in the aqueous ink composition can be produced.

By including a penetrant, the ink composition can lower the surface tension of the ink composition, improving wettability, and improving the writing ability on non-permeable surfaces such as glass, plastic, and enamel that are prone to repel ink. As the penetrant used in the present invention, it is preferable to select and use one or more from among phosphate ester surfactants, surfactants having an acetylene bond, fluorine-based surfactants, silicone-based surfactants, and succinic acid-based surfactants. By including the above-mentioned surfactants in the ink composition, the surface tension can be lowered, the wettability of the ink composition on non-permeable recording media such as films can be improved, and writing ability can be improved by improving handwriting blur and hollowing on the non-permeable recording media. Among the above penetrants, the penetrants preferred according to the present invention are phosphate ester surfactants and surfactants having an acetylene bond. The phosphate ester surfactant is a surfactant having a phosphate group in its structure, and as described above, has the effect of lowering the surface tension of the ink composition and improving writing ability on non-permeable surfaces. Considering the effect of improving wettability and the stability of dissolution in the ink composition, the phosphate surfactant preferably has an HLB value of 4 to 18, calculated from the general formula HLB value = 7 + 11.7 log (Mw/Mo), (Mw: molecular weight of the hydrophilic group, Mo: molecular weight of the lipophilic group). Surfactants having an acetylene bond are very stable and can continuously improve wettability and improve writing properties. Examples of surfactants having an acetylene bond include acetylene alcohol surfactants and acetylene glycol surfactants. In particular, acetylene glycol surfactants are preferable because they are excellent in suppressing the generation of bubbles, suppress foaming of handwriting during writing, and easily exhibit the effect of smoothing the handwriting surface. Considering the effect of improving wettability and the dissolution stability in the ink composition, the surfactant having an acetylene glycol bond has an HLB value calculated from the general formula HLB value = 20 x (mass % of hydrophilic group) = 20 x (total formula weight of hydrophilic group / molecular weight of surfactant) of preferably 4 to 18, more preferably 6 to 15, and particularly preferably 7 to 11. The ink composition preferably uses the phosphate ester surfactant and a surfactant having an acetylene glycol bond in combination, and by using both in combination, the writing property on a non-permeable surface is further improved. The content of the penetrant in the present invention is preferably 0.001% by mass to 1.5% by mass, more preferably 0.01% by mass to 0.7% by mass, based on the total amount of the ink composition. When the content is within the above numerical range, it is possible to achieve both the suppression of foaming of handwriting and the improvement of wettability. When using a penetrant in combination, particularly when using a phosphate ester surfactant in combination with a surfactant having an acetylene glycol bond, if the total content of the phosphate ester surfactant in the total amount of the ink composition is Y and the total content of the surfactant having an acetylene glycol bond in the ink composition is Z, then Y/Z is preferably 0.5≦Y/Z≦15, and more preferably 1≦Y/Z≦5. When Y/Z is within the above numerical range, it is possible to achieve both good writing performance on non-penetrating surfaces, lubricity, suppression of foaming in handwriting, and dissolution stability of the penetrant.

In addition, the ink composition can impart high fixability and abrasion resistance to handwriting by using polyolefin resin particles. The polyolefin resin particles are fine particles having surface lubricity, consisting of polyolefins such as polyethylene and polypropylene, and mixtures thereof, and suppress the application of excessive force to handwriting when the handwriting is subjected to external forces such as rubbing, and are a type of polyolefin resin different from the above-mentioned poorly water-soluble resin. The polyolefin may be a linear polyolefin, a branched polyolefin, or a modified polyolefin into which a functional group has been introduced. For example, when polyethylene is used as the polyolefin, low-density polyethylene, linear low-molecular polyethylene, high-density polyethylene, modified polyethylene, modified high-density polyethylene, etc. can be used. The molecular weight of these polyolefins is not particularly limited, but for example, polyolefins having a mass average molecular weight of 500 to 100,000 are preferable, and a weight average molecular weight of 800 to 5,000 is even more preferable. If the mass average molecular weight of the polyolefin resin particles is within the above numerical range, when writing is performed with this ink composition, higher lubricity and high abrasion resistance can be imparted to the written lines formed, and good handwriting can be obtained. The polyolefin resin particles may contain materials other than polyolefins as necessary. Therefore, it is preferable to use the poorly water-soluble resin in combination with a polyolefin resin, since it is easier to improve the color development, fixation, and abrasion resistance of handwriting, and it is particularly easy to write well even when writing on a non-permeable recording medium. The shape of the polyolefin resin particles is not particularly limited, and can be any shape such as amorphous, spherical, needle-like, plate-like, and rectangular. The average particle diameter of the polyolefin resin particles is preferably 0.1 μm to 35 μm. If the average particle diameter of the polyolefin resin particles is within the above numerical range, when writing is performed with this writing ink, it is possible to impart higher lubricity and associated high abrasion resistance to the written line formed, and a good handwriting can be obtained. The average particle diameter of the polyolefin resin particles can be measured by the Coulter counter method. The content of the polyolefin resin particles in the ink composition is preferably 0.01% by mass to 10% by mass with respect to the total amount of the ink composition. If the content of polyolefin resin particles is within the above numerical range, the ink ejection performance can be maintained and the writing line can be given higher lubricity.

The writing implement is characterized in that the outer periphery of the pen core, which is made of a fiber processed body or a synthetic resin porous body, is made hard and the inside is made soft, and the tip shape is polished into a curved shape, for example, a bullet shape, exposing the soft part inside to form an application part, and when applying, the application pressure elastically deforms the soft layer at the tip of the pen tip, and the tip and the tip of the hard outer layer are simultaneously brought into contact with the writing surface. Therefore, for example, the curved shape can be a sphere or a dome shape in addition to a bullet shape, and in the above embodiment, a cylindrical fiber processed body is used to form the applicator pen tip, but a sheet-shaped fiber processed body (felt) or a synthetic resin porous body (sintered core) can also be used to form the applicator pen tip.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

The performance required for the pen core used in the writing instruments of the first and second embodiments was examined.
(1) The line width (average value) can be kept comparable to conventional products.
(2) It can provide stable pen tip retention.

Figure 7 shows electron microscope photographs (SEM images) of examples 1 to 3 of writing implement pen cores made from the obtained fiber processed body. The photographs show a cross section of the tip and a cross section in the radial direction.

As is clear from the photographs, in Examples 1 and 2, the inside is loose and the outer layer is dense, and it can be seen that the outer periphery of the pen core is formed to be hard and the inside to be soft. In Example 3, the outer periphery and the inside of the pen core are made to be of approximately uniform hardness. Examples 1 and 2 can be used in the writing instrument of embodiment 1. Also, Example 3 can be used in the writing instrument of embodiment 2.

As shown in Figure 7, Example 1 had an outer diameter of φ1.3 (mm), fiber type of PET (polyethylene terephthalate), thread thickness of 5 denier, and tip shape of hemispherical (SR). The pipe (holding pipe 24 in the first and second embodiments) was a regular pipe with an outer diameter of φ1.65 (mm) and an inner diameter of φ1.40 (mm).

In Example 2, the outer diameter was φ1.4 (mm), the fiber type was PET (polyethylene terephthalate), the thread thickness was 5 denier, and the tip shape was bullet-shaped (tapered). The pipe specifications were thin-walled pipes, with an outer diameter of φ1.65 (mm) and an inner diameter of φ1.45 (mm).

Example 3 had an outer diameter of φ1.4 (mm), fiber type of PET (polyethylene terephthalate), thread thickness of 3 denier, and tip shape of hemisphere (SR). The pipe was a thin-walled pipe with an outer diameter of φ1.65 (mm) and an inner diameter of φ1.45 (mm).

As shown in the cross-sectional image of the tip of the pen core in Fig. 8(a) and the cross-sectional image in Fig. 8(b), the pen core 10 in Examples 1 and 2 has a harder outer periphery 10o and a softer interior 10i. The softer part of the interior is exposed further forward than the outer periphery.

In this case, the outer periphery of the pen core 10 is hardened (dense, to maintain the strength of the pen core), while the inside is softened (roughly finished), and the tip is polished into a hemispherical, bullet-like shape.

As shown in the cross-sectional image of the tip of the pen core in Figure 8 (c) and the cross-sectional image in Figure 8 (d), the outer periphery and the inside are made to have a substantially uniform hardness, and since Example 3 uses thinner fibers than Examples 1 and 2, it is softer overall.

Figure 8 (e) is an image diagram of the writing state for each of Examples 1 to 3. As shown in the figure, in Examples 1 and 2, deformation is suppressed by the hard outer periphery 10o, so deformation is difficult to cause by writing pressure. In Example 1, the tip shape is hemispherical, so the drawn line width R1 is narrow. In Example 2, the tip shape is bullet-shaped, so the drawn line width R2 is thicker than in Example 1.

In Example 3, there is no hard outer periphery, so the amount of deformation is very large, and the drawn line width R3 is thicker than in Examples 1 and 2.

Elastic properties and line widths of Examples 1 to 3
Fig. 9 is an explanatory diagram of the pen cores of Examples 1 to 3. As shown in Fig. 9(a), the pen core 10 was placed horizontally on a stand 28 and compressed in the radial direction (F direction) by a press member 30 for testing. Fig. 9(b) is an enlarged cross-sectional view of the pen core of Example 1, (c) is an enlarged cross-sectional view of the pen core of Example 2, and (d) is an enlarged cross-sectional view of the pen core of Example 3.

Figures 10 and 11 to 13 show the experimental results comparing elastic properties and line width.

The elasticity of the pen cores of Examples 1 to 3 was compared. Figure 10(a) shows the radial displacement x (mm) when the radial load (N) of Examples 1, 2, and 3 (indicated by the symbols "J1," "J2," and "J3") was changed from 0 to 10 (N). As can be seen, the outer periphery 10o of Examples 1 and 2 was hard, resulting in large displacement, while Example 3 was very soft compared to the other examples, resulting in gentle displacement.

Tests were conducted on the line width. Writing conditions were a writing angle of 65° (see Figure 6), a line load of 0.5 (N), and circular writing (with rotation). As shown in Figure 10 (b), the test results showed that the line width changed almost in proportion to the vicinity of 0.5 (mm) to 0.8 (mm). In the figure, Examples 1 to 3 are indicated with the symbols J1 to J3. Comparative Examples 1 and 2 (indicated with the symbols K1 and K2) have a structure in which the line width is set by changing the outer diameter of the pen core.

From Figure 10(b), it can be seen that the line width can also be changed in Examples 1 to 3 in response to the changes in line width in Comparative Examples 1 and 2.

Looking at the relationship between Comparative Examples 1-2 and Examples 1-3 shown in Figure 10(b), it can be seen that the line widths (average values) of Examples 1-3 are proportional to the Comparative Examples.

Figures 11 to 13 show the elastic properties of the pen core when compressed in the radial direction for Examples 1 to 3.

Figure 11 relates to the pen core of Example 1. Figure 11(a) shows the radial displacement of approximately 0.00 to 0.14 (mm) in response to a load of approximately 0 to 20 (N) when the pen core is compressed in the radial direction. It shows the change Ff during compression with a load applied, and the return change Fb when the load is released. Also, in each example, the pen tip elasticity characteristics show a hysteresis curve with different displacement curves for the pressing load and the return load.

Figure 11 (b) shows the elastic properties when a load is applied to each of three pen cores. When the asymptote is drawn, the first one is y=182.2x-2.0, the second one is y=161.6x-1.6, and the third one is y=143.3x-0.7.

Figure 12 relates to the pen core of Example 2. Figure 12(a) shows the radial displacement of 0.00 to 0.10 (mm) in response to a load of 0 to 20 (N) when the pen core is compressed in the radial direction. The graph shows the change Ff during compression with a load, and the change Fb during return when the load is released. In addition, in each example, the pen tip elasticity characteristics show a hysteresis curve with different displacement curves for the pressing load and the return load.

Figure 12 (b) shows the elastic properties when a load is applied to each of three pen cores. When the asymptote is drawn, the first one is y=208.3x-2.5, the second one is y=207.5x-2.2, and the third one is y=195.9x-2.1.

Figure 13 relates to the pen core of Example 3. Figure 13(a) shows the radial displacement of approximately 0.00 to 0.20 (mm) relative to a load of approximately 0 to 10 (N) when the pen core is compressed in the radial direction. The graph shows the change Ff during compression with a load applied, and the return change Fb when the load is released. In addition, in each example, the pen tip elasticity characteristics show a hysteresis curve with different displacement curves for the pressing load and the return load.

Figure 13(b) shows the elastic properties of three pen cores as they are compressed under load. The asymptote is drawn as follows: the first one is y=54.4x-0.7, the second one is y=52.3x-0.5, and the third one is y=43.2x-0.5.

The pen core of Example 3 has a substantially uniform hardness on the outer periphery and inside, and in order to make it easier to obtain thicker lines even with the same outer diameter as Example 2, the pen core is configured so that the displacement (mm) when the pen core is pressed 0 (mm) to 0.2 (mm) perpendicular to a plane in the radial direction is _x2 , and the elastic load _y2 (N) while the displacement _x2 is 0 (mm) to 0.2 (mm) is less than _y2 = _60x2 , which is significantly lower than those of Examples 1 and 2.

As shown in Fig. 14(a) for Examples 1 to 3, the deformation characteristics of the pen tip when the pen tip is compressed with a writing angle of 65° are shown. Fig. 14(b) is an enlarged image of the tip of the pen tip of Example 1, (c) is an enlarged surface image of the tip of the pen tip of Example 2, and (d) is an enlarged image of the tip of the pen tip of Example 3.

Figure 15 relates to the pen core of Example 1. Figure 15 (a) shows the deformation characteristics when the pen core is compressed with a writing angle of 65°. The deformation characteristics of Example 1 were a displacement of the pen tip of approximately 0.00 to 0.15 (mm) for a load of approximately 0 to 5 (N). The graph shows the change Ff during compression with the application of a load, and the return change Fb when the load is released.

Figure 15 (b) shows the elastic properties when a load is applied to each of the pen cores when the number of pen cores, n, is set to 3. The approximate curves are y=36.5x-0.1 for the first pen core, y=41.9x-0.4 for the second pen core, and y=33.6x-0.6 for the third pen core.

Figure 16 relates to the pen core of Example 2. Figure 16(a) shows the deformation characteristics when the pen core is compressed with a writing angle of 65°. The deformation characteristics of Example 2 were a pen tip displacement of approximately 0.00 to 0.25 (mm) for a load of approximately 0 to 5 (N). The graph shows the change Ff during compression with a load applied, and the return change Fb when the load is released. Also, in each Example, the pen tip elasticity characteristics show a hysteresis curve with different displacement curves for the pressing load and the return load.

Figure 16 (b) shows the elastic properties when a load is applied to each of three pen cores. When the asymptote is drawn, the first one is y=23.6x-0.2, the second one is y=23.3x-0.6, and the third one is y=23.0x-0.5.

Figure 17 relates to the pen core of Example 3. Figure 17(a) shows the deformation characteristics when the pen core is compressed with a writing angle of 65°. The deformation characteristics are a displacement of the pen tip of approximately 0.00 to 0.20 (mm) for a load of approximately 0 to 5 (N). The graph shows the change Ff during compression with a load applied, and the return change Fb when the load is released. In addition, in each example, the pen tip elasticity characteristics show a hysteresis curve with different displacement curves for the pressing load and the return load.

Figure 17(b) shows the elastic properties when a load is applied to each of three pen cores. When the asymptote is drawn, the first one is y=25.2x-0.3, the second one is y=24.7x-0.2, and the third one is y=22.8x-0.4.

The writing inks used in the above tests are as follows:
(1) pH = 8.5 (20°C): IM-40S pH meter (manufactured by DKK-TOA Corporation)
(2) Viscosity = 180 mPa·s: E-type rotational viscometer (DV-II+Pro, cone-type rotor CPE-42, manufactured by Brookfield), shear rate 3.8 sec-1 (rotation speed 1 rpm)
(3) Surface tension = 36.5 mN/m: surface tension meter (20°C environment, vertical plate method, manufactured by Kyowa Interface Science Co., Ltd.)
(4) Pigment content: 30% by mass: silica, titanium oxide surface-treated with alumina, average particle size 0.26 μm, manufactured by Sakai Chemical Industry Co., Ltd., product name: GTR-100
Dispersant = 1.5% by mass: pigment dispersant having a cationic adsorptive group, solid content 52%, manufactured by BYK-Chemie Corporation, product name: DISPERBYK-184
Guar gum derivative = 0.1% by mass: cationized guar gum, manufactured by Sansho Co., Ltd., product name: JAGUAR C-500STD
Poorly water-soluble resin = 10% by mass: self-emulsifying polyolefin dispersion, solid content 25%, manufactured by Sumitomo Seika Chemicals Co., Ltd., product name: ZAIKXEN L
Citric acid = 0.1% by mass
Diethylene glycol = 2% by mass
Defoamer = 0.3% by mass: Silicone-based defoamer, manufactured by BYK-Chemie Co., Ltd., product name BYK-024
Preservative = 0.2% by mass: Benzisothiazolin-3-one, manufactured by Lonza Japan Co., Ltd., product name: Proxel XL-2
Ion-exchanged water = balance (5) Procedure 1. Dissolve the guar gum derivative in ion-exchanged water in half the amount of the formulation below, and then add citric acid to obtain an aqueous solution of the guar gum derivative.
2. Mix the remaining amount of ion-exchanged water with the raw materials other than the guar gum derivative and citric acid at room temperature for 1 hour to obtain a dispersion of the pigment, etc.
3. The above guar gum derivative aqueous solution and a dispersion of pigment, etc. are mixed at room temperature for 1 hour.

As described above, it _{is understood that the pen core is configured such that the elastic load y 1 (N) during the displacement x 1 is} between 0 (mm) and 1 (mm) when the pen tip is pressed downward vertically at an angle of 65° to the writing surface, and falls between y ₁ =20x ₁ and y ₁ =45x ₁ in Example 1, and between y ₁ =20x ₁ and y ₁ =30x ₁ in Examples 2 and 3. The pen cores of Examples 1 to 3 can be used in writing implements to make a writing implement set in which the line widths are proportional to _each other at the same writing load and writing angle. For example, a set of writing implements using the pen cores of Comparative Examples 1 to 2 and Examples 1 to 3 can be conveniently used as a writing implement set for various drawing, such as designs, illustrations, blueprints, and the like, for each line width.

The present invention is not limited to the embodiments and examples, and can be freely modified within the technical scope of the present invention. The pen cores in Examples 1 to 3 were used, but this is only an example, and can be modified within the scope of the present invention.

The writing instrument of the present invention can be used as a writing instrument equipped with a pen core.

10 Pen core 10i Inside of pen core 10o Outer periphery of pen core 12 Pen tip 12a Writing portion 14 Body tube 14a Tip portion 14b Storage portion 16 Cap 18 End cap 20 Filling 22 Mouthpiece 22a Rib 24 Holding pipe 24a Tip portion 26 Writing surface 28 Base 30 Press member

Claims (5)

A writing instrument in which a pen tip on which a writing part is formed is disposed so as to protrude from a tip end of a barrel,
the pen core is configured to include a PET fiber processed body having an outer diameter of Φ1.3 to Φ1.4 mm and a thread thickness of 5 denier ;
The pen tip has a curved tip shape,
When the pen tip is pressed against a writing surface at an angle of 65° with a load of 0 to 5 (N) in the vertical direction and displaced 0 (mm) to 0.25 (mm), the elastic properties of the pen core are such that each displacement ( mm) x ₁ and load (N) y ₁ are between y ₁ = 20x ₁ and y ₁ = 45x ₁ over the entire range of loads 0 to 5 (N) ,
Furthermore, the pen core is configured so that the outer periphery is hard and the inside is soft, and the softer part of the inside of the pen tip is exposed further forward than the harder outer periphery, and the softer part of the tip of the pen tip is formed so as to be elastically deformable by the writing pressure when writing,
This writing implement has a pen core configured such that, when writing, the pen tip is brought into contact with the writing surface at an angle of 65°, and the exposed softer part is elastically deformed by writing pressure, so that the softer part at the tip of the pen tip and the tip of the harder outer periphery come into contact at the same time. A writing instrument in which a pen tip on which a writing part is formed is disposed so as to protrude from a tip end of a barrel,
The pen core is configured to include a PET fiber processed body having an outer diameter of Φ1.4 mm and a thread thickness of 3 denier,
The pen tip has a curved tip shape,
When the pen tip is pressed against the writing surface at an angle of 65° in the vertical direction with a load of 0 to 5 (N) and displaced 0 (mm) to 0.20 (mm), the elastic properties of the pen core are such that each displacement (mm) x ₁ and load (N) y ₁ are between y ₁ = 20x ₁ and y ₁ = 45x ₁ over the entire range of loads from 0 to 5 (N) ;
Furthermore, the pen core has a substantially uniform hardness at its outer periphery and inside,
During writing, the pen tip is brought into contact with the writing surface at an angle of 65°, and the tip of the pen tip is pushed out by the writing pressure,
A writing implement having a pen core configured such that when the pen core is displaced radially by 0 (mm) to 0.2 (mm) when compressed radially with a load of 0 to 10 (N) applied perpendicular to a plane, the elastic properties of the pen core during compression are such that displacement (mm) x ₂ and load (N) y ₂ fall within the range of y ₂ = 43.2x ₂ to y ₂ = 54.4x ₂ over the entire range of the compression load of 0 to 10 (N) . 3. The writing instrument according to claim 1 , wherein the writing ink used in said writing instrument has a pH of 7.5 to 9.5. 3. The writing implement according to claim 1, wherein the displacement curves of the pressing load and the returning load are different. A writing instrument set comprising the writing instrument according to claim 1 and claim 2 .

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