Refills and writing instruments

Abstract

To provide a refill capable of suppressing DC phenomena at a high level, and a writing instrument equipped with said refill. [Solution] A filter having an average pore size within a specific range is placed in the refill, and an ink composition having a viscosity within a specific range is filled in. Specifically, the refill, which is attached to a writing instrument, comprises at least a tip and a cylindrical ink container connected to the tip, wherein the tip and the ink container are filled with an ink composition, the ink container includes a filter made of a porous material that flows through the ink composition and is positioned perpendicular to the direction in which the ink composition follows, the filter has an average pore size of 0.01 μm to 9 μm as measured by the half-dry method, and the ink composition has a shear rate of 380 sec. -1 The refill has a viscosity of 5 to 90 mPa·s.

Description

[Technical Field]

[0001] This invention relates to a refill and a writing instrument in which the refill is installed. [Background technology]

[0002] Traditionally, water-based ballpoint pens have been prone to a phenomenon known as "DC leakage," where ink drips or leaks due to gravity from the gap between the holder and the ball. This DC leakage phenomenon is particularly common when the tip is accidentally damaged.

[0003] To suppress such DC phenomena, solutions involving the composition of the ink have been proposed. For example, Patent Document 1 discloses an ink composition containing a colorant, a solvent, water, a thickener, and a specific amount of crystalline cellulose. Patent Document 2 also discloses a ballpoint pen ink composition containing at least crystalline cellulose and resin particles.

[0004] Furthermore, Patent Document 3 discloses an aqueous ballpoint pen ink composition comprising at least water, a colorant, and fermented cellulose, and Patent Document 4 describes an aqueous ballpoint pen ink composition comprising water, a colorant, organic resin particles, and polysaccharide fibers. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-001381 [Patent Document 2] Japanese Patent Publication No. 2013-103986 [Patent Document 3] Japanese Patent Publication No. 2013-091730 [Patent Document 4] Japanese Patent Publication No. 2017-222113 [Overview of the project] [Problems that the invention aims to solve]

[0006] The ink compositions described in Patent Documents 1 to 4 attempt to prevent ink dripping and leakage and suppress the occurrence of DC phenomena by adding specific components to the ink. However, a higher level of suppression of DC phenomena is required, and these methods have not yet been satisfactory.

[0007] The present invention has been made in view of the above, and aims to provide a refill that can suppress the DC phenomenon at a high level, and a writing instrument in which the refill is installed. [Means for solving the problem]

[0008] The inventors diligently conducted research to achieve the above objective. They discovered that by placing a filter having an average pore size within a specific range in the refill and filling it with an ink composition having a viscosity within a specific range, the DC phenomenon can be suppressed to a high degree, thus completing the present invention.

[0009] In other words, the present invention includes the following embodiments.

[0010] A refill for a writing instrument, comprising at least a tip and a cylindrical ink reservoir connected to the tip, The chip and the ink container are filled with an ink composition. The ink container comprises a filter made of a porous material that flows through the ink composition and is positioned perpendicular to the direction in which the ink composition follows, The filter has an average pore size of 0.01 μm or more and 9 μm or less, as measured by the half-dry method. The aforementioned ink composition is subjected to a shear rate of 380 sec. -1 The viscosity is between 5 mPa·s and 90 mPa·s. Refill.

[0011] The ink composition preferably has a static surface tension of 45 mN / m or less.

[0012] The ink composition preferably contains a pigment.

[0013] The pigment preferably has an average particle diameter of 0.05 μm or more and 4 μm or less.

[0014] The porous body is preferably at least one selected from the group consisting of a non-woven fabric, a fiber laminate, and a porous film.

[0015] The porous body preferably consists of at least one kind of fiber selected from the group consisting of cellulose, glass, hydrophilic PTFE, polyethylene, and polypropylene.

[0016] Another invention of the present invention is a writing instrument provided with the refill of the present invention described above.

Effects of the Invention

[0017] The refill of the present invention has a filter with an average pore diameter within a specific range and is filled with an ink composition having a viscosity within a specific range. When attached to a writing instrument, it can suppress the DC phenomenon at a high level.

[0018] Furthermore, if an ink composition with a static surface tension of a specific value or less is filled, the occurrence of scratching can be suppressed during writing at high speed.

[0019] Furthermore, if the average particle diameter of the pigment blended in the ink composition is within a specific range, the writing performance after storing the writing instrument upright can be ensured.

[0020] Furthermore, if the filter is made of a specific material, the occurrence of scratching can be suppressed during writing at high speed.

Brief Description of the Drawings

[0021] [Figure 1] It is a cross-sectional view showing the whole refill of the present invention according to one embodiment. [Figure 2]This is an enlarged cross-sectional view showing a magnified view of the tip of the refill shown in Figure 1. [Modes for carrying out the invention]

[0022] Refill The refill of this disclosure is provided for a writing instrument and comprises at least a tip and a cylindrical ink reservoir connected to the tip. The tip and the ink reservoir are filled with an ink composition.

[0023] Here, as used herein, a refill is sufficient if it includes at least a tip and a cylindrical ink reservoir connected to the tip, as described above. In addition, in the present invention, the refill itself may be used as a writing instrument, that is, the refill may be the writing instrument itself.

[0024] The refill of this disclosure is equipped with a filter having an average pore size within a specific range and is filled with an ink composition having a viscosity within a specific range, thereby enabling a high level of suppression of the DC phenomenon.

[0025] <Refill composition> Embodiments of this disclosure will be described below with reference to the drawings. In the following description, "tip" refers to the side of the refill where the writing tip (e.g., writing ball) is provided, and "rear end" refers to the opposite side. Reference numerals common to each drawing indicate the same component or part unless otherwise specified in the following description of the drawings. In each drawing, the left side is the tip side and the right side is the rear end side.

[0026] Figure 1 is a cross-sectional view showing the entire refill 100 of the first embodiment of this disclosure. Figure 2 is an enlarged cross-sectional view showing the tip of the refill 100 shown in Figure 1. The refill 100 of this embodiment includes a cylindrical ink container 10 containing an ink composition, a connector 11 attached to the tip of the ink container 10, a tip 12 attached to the tip of the connector 11, and a filter 13 that flows the ink composition and is arranged perpendicular to the direction in which the ink composition follows.

[0027] More specifically, the connector 11 in the refill 100 of the first embodiment has a cylindrical rear end portion that connects to the ink container 10, and a cylindrical front end portion with a smaller outer diameter than the rear end portion. The tip 12 is inserted and attached from the rear end portion of the connector 11 such that the tip of the tip 12 protrudes from the front end portion of the connector 11. The ink container 10 is connected to the rear end portion of the connector 11 by the rear end portion of the connector 11 being press-fitted into the front end of the ink container 10. In this way, the ink container 10 and the tip 12 are connected via the connector 11 so that the ink composition can flow through them.

[0028] Furthermore, adhesive may be applied in advance to the rear end portion of the joint 11 to provide a certain level of bonding strength at the joint with the ink container 10. In this state, the rear end portion of the joint 11 may be pressed into the front end of the ink container 10 to improve the bonding strength between the joint 11 and the ink container 10.

[0029] <Ink container 10> The ink container 10 is not particularly limited as long as it has a cylindrical shape. Its cross-section may be circular, polygonal, or any other shape.

[0030] The material of the ink reservoir 10 is not particularly limited, but may be, for example, a synthetic resin whose interior is visible. Examples of synthetic resins include polypropylene resin. Alternatively, for the purpose of reducing environmental impact, it may be a composite material with a multilayer structure using a paper base material.

[0031] The ink container 10 may be a direct-liquid type container with a hollow interior into which the ink composition is directly filled, or it may be a cotton-filled type container with an absorbent material such as cotton filling inside, into which the ink composition is impregnated.

[0032] [Filter 13] The ink container 10 includes a porous filter 13. Specifically, the filter 13 allows the ink composition to flow through it and is positioned perpendicular to the direction in which the ink composition follows within the ink container 10. The ink composition contained in the refill 100 is divided by the filter 13 so that it can flow between the leading and trailing ends of the refill.

[0033] In the refill 100 of the first embodiment of the present disclosure shown in Figure 1, the filter 13 is positioned at the interface between the ink container 10 and the tip 12, in a direction perpendicular to the long axis of the ink container 10, and the ink composition contained in the refill is divided into a leading end and a trailing end of the refill by the filter 13.

[0034] The filter 13 can be any porous material having connecting holes through which the ink composition can flow. Furthermore, the filter 13 may be a single-layer structure or a laminate of two or more layers, as long as it allows the ink composition to flow through it.

[0035] (Average pore size of filter 13) In this disclosure, the filter 13 has an average pore size of 0.01 μm or more and 9 μm or less, as measured by the half-dry method. If the average pore size is within this range, DC phenomena can be suppressed to a high degree.

[0036] The average pore size of filter 13 may be 0.05 μm or larger, 0.10 μm or larger, 0.15 μm or larger, 0.2 μm or larger, 0.25 μm or larger, 0.3 μm or larger, 0.35 μm or larger, 0.4 μm or larger, or 0.45 μm or larger. On the other hand, the average pore size of filter 13 may be 0.85 μm or smaller, 0.8 μm or smaller, 0.75 μm or smaller, 0.7 μm or smaller, 0.65 μm or smaller, 0.6 μm or smaller, or 0.55 μm or smaller.

[0037] Here, "average pore diameter measured by the half-dry method" refers to the pore diameter determined using a PMI palm porometer (model: CFP-1200-AEXL) and PMI Gullwick (surface tension 15.9 dyn / cm) as the immersion solution, according to the half-dry method specified in ASTM E1294-89. The measurement temperature is 25°C, and the measurement pressure is varied within the range of 0 kPa to 600 kPa.

[0038] (Filter 13 configuration) The filter 13 is not particularly limited as long as it is a porous material having the above-mentioned average pore size, but examples include nonwoven fabrics, fibril-like materials in a three-dimensional network structure, semipermeable membranes, hollow fiber membranes, membrane filters, liquid chromatography columns (ion exchange resins), or breathable waterproof materials (e.g., Gore-Tex®). Among these, it is preferable that it be at least one selected from the group consisting of nonwoven fabrics, fiber laminates, and porous films, as these are readily available.

[0039] (Materials for filter 13) The porous body that forms the filter 13 is preferably formed from at least one fiber selected from the group consisting of cellulose, glass, hydrophilic PTFE, polyethylene, and polypropylene. If the filter material is hydrophobic or if the surface tension of the ink composition is high, the wetting of the ink composition to the filter will be poor, causing air bubbles to remain and resulting in streaking during rapid writing. If the filter material is selected from the above group, excellent line quality can be maintained during rapid writing.

[0040] Furthermore, the filter 13 may be treated with surfactants, silane coupling agents, plasma treatment, or the like, for the purpose of improving the wettability of the ink composition.

[0041] (Thickness of filter 13) The thickness of the filter 13 is not particularly limited, but is preferably 1 μm or more and 3000 μm or less, more preferably 5 μm or more and 1000 μm or less, and even more preferably 8 μm or more and 500 μm or less. If the thickness of the filter 13 is less than 1 μm, it becomes difficult to suppress the backflow phenomenon, while if the thickness of the filter 13 exceeds 3000 μm, the flow of the ink composition becomes difficult, which may cause streaking during rapid writing.

[0042] Here, the "thickness" of filter 13 refers to the average value obtained by measuring the film thickness of the filter at 10 locations using a micrometer (manufactured by Mitutoyo).

[0043] It should be noted that commercially available filters can also be used as the filter 13 mentioned above. Examples of commercially available filters include polyethylene filters (GELLEC, SU04, SU05, SU07, SU07X, SU09, SU09LD, SG12S, SG12HD), polypropylene filters (3M Japan, average pore size: 1 μm, 2.5 μm, 5 μm), and cellulose mixed ester MCE filters (GVS Japan Co., Ltd., average pore size: 0.22 μm, 0.45 μm, 0.8 μm).

[0044] (Placement of filter 13) As described above, the filter 13 is positioned perpendicular to the direction in which the ink composition follows within the ink container 10, and the ink composition contained in the refill 100 is divided by the filter 13 so that it can flow between the leading and trailing ends of the refill. In the refill 100 shown in Figure 1, the filter 13 is positioned at the interface between the ink container 10 and the tip 12.

[0045] In the refill of this disclosure, it is preferable that the ratio of the ink volume contained on the front end side of the refill (the volume of the ink composition contained on the writing end side of the filter) to the ink volume contained on the rear end side of the refill (the volume of ink contained in the ink container at the rear end of the filter) is 0.1 or more and 10 or less. By having the above ratio of the volume of the ink composition between the front and rear ends of the refill, which are separated by the filter, it becomes possible to further suppress the DC phenomenon.

[0046] <Ink composition> The materials constituting the ink composition filled into the refill of this disclosure are not particularly limited and may be known materials applicable to writing instruments.

[0047] The ink composition to be filled into the refill of this disclosure is preferably an aqueous ink composition containing at least water and a colorant. Writing instruments using an aqueous ink composition are writing instruments in which the DC phenomenon, which is the issue of this invention, is prone to problems, and therefore the effects of this invention can be enjoyed to the fullest extent.

[0048] Furthermore, the ink composition filled into the refill of this disclosure may contain glycol-based solvents or surfactants for the purpose of improving wettability of the filter. The surfactants are not particularly limited, but examples include acetylene-based, silicone-based, and phosphate esters.

[0049] [viscosity] The ink composition to be filled into the refill of this disclosure is subject to a shear rate of 380 sec. -1 The viscosity is between 5 mPa·s and 90 mPa·s. Shear rate: 380 sec. -1 When the viscosity of the ink composition is less than 5, it becomes difficult to suppress the DC phenomenon. On the other hand, at a shear rate of 380 sec -1 If the viscosity of the ink composition exceeds 90 mPa·s, the followability of the ink composition flowing through the filter decreases.

[0050] Shear rate 380 sec -1 The viscosity may be 8 mPa·s or higher, 10 mPa·s or higher, 12 mPa·s or higher, 14 mPa·s or higher, 16 mPa·s or higher, 18 mPa·s or higher, or 20 mPa·s or higher. On the other hand, the shear rate is 380 sec. -1 The viscosity may be 85 mPa·s or less, 80 mPa·s or less, 75 mPa·s or less, 70 mPa·s or less, 65 mPa·s or less, 60 mPa·s or less, or 55 mPa·s or less.

[0051] Here, "shear rate 380 sec -1 Viscosity was measured using a rheometer MCR-302 (Anton Paar) with a cone plate (diameter: 25 mm, angle: 2°) at 25°C, based on steady flow.

[0052] Shear rate 380 sec -1 The viscosity is not particularly limited, but can be adjusted by, for example, the amount of solids in the ink composition, the concentration of pigments and dyes contained in the ink composition, and the type and amount of thickeners contained in the ink composition.

[0053] [Static surface tension] The ink composition preferably has a static surface tension of 45 mN / m or less. If the static surface tension of the ink composition exceeds 45 mN / m, the wetting of the ink composition to the filter will be poor, resulting in residual air bubbles and causing streaking during rapid writing.

[0054] The static surface tension of the ink composition is more preferably 42 mN / m or less, 40 mN / m or less, 38 mN / m or less, 36 mN / m or less, 34 mN / m or less, or 32 mN / m or less. On the other hand, the lower limit of the static surface tension of the ink composition is not particularly limited and is acceptable as long as it is a static surface tension that allows for the preparation of the ink composition.

[0055] Here, "static surface tension of the ink composition" refers to the value measured using an automatic surface tension meter DY-300 (Kyowa Interface Science Co., Ltd.) under conditions of 25°C.

[0056] [Colorants] The ink composition to be filled into the refill of this disclosure preferably contains a colorant. By including a colorant in the ink composition, the ink composition can be colored to any desired color.

[0057] The colorants incorporated into the ink composition are not particularly limited, and known colorants used in writing instruments can be applied. Examples of colorants incorporated into the ink composition include dyes, pigments, and colored resin particles. Here, the dyes and pigments may be organic or inorganic. Furthermore, multiple types of colorants may be used in the ink composition, and two or more types of dyes, pigments, and colored resin particles may be used in combination.

[0058] (Pigment) The colorant incorporated into the ink composition of this disclosure is preferably a pigment, as its particles are hard and less likely to clog the filter.

[0059] The pigments applicable to the ink compositions of this disclosure are not particularly limited, and pigments known in the field of writing instruments can be used. Furthermore, the pigments may be organic pigments or inorganic pigments.

[0060] Examples of inorganic pigments include carbon black, lead sulfate, lead yellow, zinc yellow, red iron oxide, cadmium red, Prussian blue, ultramarine blue, Prussian blue, chromium oxide green, cobalt green, amber, titanium black, and synthetic iron black.

[0061] Examples of organic pigments include azo, phthalocyanine, quinacridone, isoindolinone, imidazolon, diketopyrrolopyrrole, dioxazine, and perinone.

[0062] (Average particle size of pigment in the ink composition) If the ink composition of this disclosure contains a pigment, the average particle size of the pigment in the ink composition is preferably 0.05 μm or more and 4 μm or less. If the average particle size of the pigment in the ink composition exceeds 4 μm, the pigment will clog the filter if the writing instrument with the refill installed is stored with the tip facing upwards, reducing the followability of the ink composition and causing streaking during fast writing.

[0063] It is more preferable that the average particle size of the pigment in the ink composition is 3.5 μm or less, 3 μm or less, or 2.5 μm or less. On the other hand, it is more preferable that the average particle size of the pigment in the ink composition is 0.1 μm or more, 0.15 μm or more, or 0.2 μm or more.

[0064] Here, "average particle diameter" refers to the D-50 value measured with a laser diffraction / scattering particle diameter analyzer (model: LA-960, Horiba, Ltd.). The shape of the colorant incorporated into the ink composition of this disclosure may be spherical or non-spherical.

[0065] <Tip 12> Tip 12 is not particularly limited, and any known tip that forms the end of a writing instrument can be used. For example, if the writing instrument is a fountain pen, it may be a nib; if the writing instrument is a ballpoint pen, it may be a ballpoint pen tip; if the writing instrument is a felt-tip pen, it may be a writing tip made of felt; if the writing instrument is a felt-tip pen (marker pen), it may be a writing tip made of a fiber bundle; and if the writing instrument is a needle pen, it may be a thin, tubular writing tip.

[0066] <Joint 11> The connector 11 is not particularly limited, and in a writing instrument, it is sufficient to connect the tip 12 and the ink reservoir 10, allowing the ink composition contained in the ink reservoir 10 to flow in the direction of the tip 12, which is the following direction. It may have various shapes depending on the shapes of the tip 12 and the ink reservoir 10. [Examples]

[0067] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. The term "parts" below refers to parts by mass.

[0068] <Materials for ink composition> The materials of the ink compositions used in the examples and comparative examples are shown below.

[0069] [Colorants] • Black inorganic pigment: Carbon black MCF88 (Mitsubishi Chemical Corporation) • Pink colored resin particles: NKW-3207E (Nippon Fluorescent Co., Ltd.) • Black colored resin particles: Microsphere A (created using Reference Example 1) • Heat-changed particles: Heat-changed microcapsule pigment B (created using Reference Example 2) • Black colored resin particles: Art Pearl C800 (Negami Chemical Industry Co., Ltd.)

[0070] [pH adjuster] Triethanolamine

[0071] [Thickener] • Xanthan gum (KELZNS, manufactured by Sankyo Co., Ltd.)

[0072] [Preservatives] • Benzoisothiazoline (Bioden 421, Yamato Scientific Co., Ltd.)

[0073] [Lubricant] • Phosphate ester (Phosphanol RB-410, Toho Chemical Co., Ltd.)

[0074] [Wetting agent] • Acetylene-based surfactant (Orphine EXP4123, Nisshin Chemical Industrial Co., Ltd.)

[0075] [solvent] Glycerin ·water

[0076] <filter> • Cellulose mixed ester MCE filter (GVS Japan Co., Ltd., average pore size: 0.45 μm) • Polyethylene filter (GELLEC, SU09, average pore size: 0.3 μm) • Polypropylene filter (3M Japan, average pore size: 1 μm) • Polypropylene filter (3M Japan, average pore size: 10 μm) • Glass fiber filter (Advantech Toyo Co., Ltd., average pore size: 0.3 μm) • Hydrophobic PTFE filter (Advantech Toyo Co., Ltd., average pore size: 0.3 μm)

[0077] <Reference Example 1> Synthesis of Microsphere A 12.5 parts by mass of ethyl acetate was heated to 60°C, and 3.5 parts by mass of oil-soluble black dye (OilBlack860, Orient Chemical Industries, Ltd.) and 0.5 parts by mass of terpene phenol resin (YS Polystar N125, Yasuhara Chemical Co., Ltd.) were added and stirred. Then, 8 parts by mass of isocyanurate-modified hexamethylene diisocyanate (TLA-100, Asahi Kasei Chemicals Corporation) was added as a prepolymer to prepare an oil phase solution.

[0078] 200 parts by mass of distilled water was heated to 60°C, and 15 parts by mass of polyvinyl alcohol (PVA-205, Kuraray Co., Ltd.) was added as a dispersant to prepare an aqueous solution.

[0079] The oil phase solution prepared above was added to the aqueous phase solution maintained at 60°C, and emulsion polymerization was carried out for 6 hours using a homogenizer. The resulting mixture was centrifuged to recover the solid content, and black microspheres A were obtained.

[0080] <Reference Example 2> Synthesis of Thermochromic Microcapsule Pigment B 1 part by mass of methyl-3’,6’-bis(diphenylamino)fluoran as a leuco dye, 2 parts by mass of 2,2-bis(2-hydroxy-5-biphenylyl)propane as a developer, and 24 parts by mass of bis(4-hydroxyphenyl)phenylmethane dicaprylate as a discoloration temperature adjuster were mixed, heated and melted at 100 °C, and 27 parts by mass of a homogeneous composition was obtained.

[0081] While heating and stirring the obtained hot solution composition, 40 parts by mass of a methyl vinyl ether / maleic anhydride copolymer resin (Gantrez AN-179, ISP Co., Ltd.) as a protective colloid agent was dissolved in 100 parts by mass of an aqueous solution at 90 °C and pH 4, and gradually added thereto to disperse it in an oil droplet form with a diameter of about 0.5 to 1.0 μm.

[0082] Next, 20 parts by mass of methylol melamine (Sumitex Resin M-3, an aqueous solution containing 80% of an active ingredient, Sumitomo Chemical Co., Ltd.) as a raw material for a capsule film agent was gradually added, and heated at 90 °C for 30 minutes to perform microencapsulation, and a microcapsule dispersion of a thermochromic composition in which the film agent is made of a melamine resin was obtained. After cooling the dispersion to room temperature, acid addition, filtration, and washing with water were performed, and drying was performed using a spray dryer to obtain a powdery thermochromic microcapsule pigment B.

[0083] <Examples 1 to 11, Comparative Examples 1 to 3> [Preparation of Ink Composition] A colorant, a pH adjuster, a thickener, a preservative, a lubricant, and a wetting agent were blended in an aqueous solvent composed of a mixed solution of ion-exchanged water and glycerin at the combinations and mass ratios shown in Table 1 (100% by mass in total, and emulsions etc. are based on the mass of the solid content). The blend was thoroughly mixed with a homomixer to prepare an aqueous ink composition.

[0084] [Evaluation of Ink Composition] The physical properties of the prepared ink composition were evaluated by the following methods. The results are shown in Table 1.

[0085] (Viscosity at a shear rate of 380 sec -1 ) Using a rheometer MCR-302 (Anton Paar), steady-state flow measurements were performed at 25°C with a cone plate (diameter: 25 mm, angle: 2°).

[0086] (static surface tension) The measurement was performed using an automatic surface tension meter DY-300 (Kyowa Interface Science Co., Ltd.) under conditions of 25°C.

[0087] (Average particle size of colorant particles) Using the LA-960 series laser diffraction / scattering particle size distribution analyzer (Horiba, Ltd.), the 50th percentile particle size (D50 value) of the cumulative particle size distribution calculated based on volume measured by the laser diffraction method was determined.

[0088] [Manufacturing of writing instruments] Water-based ballpoint pens were manufactured by combining each of the prepared ink compositions with the filters shown in Table 1. Specifically, a barrel from a ballpoint pen (Mitsubishi Pencil Co., Ltd., product name: Signo UM-100) was used, and a fitting was prepared having a polypropylene ink reservoir tube with an inner diameter of 4.0 mm and a length of 113 mm, a stainless steel tip (carbide ball, ball diameter 0.7 mm), and a filter positioned perpendicular to the direction in which the ink composition follows, at the rear. An empty refill was made by connecting the ink reservoir tube and the tip with the fitting. Subsequently, each of the prepared ink compositions was filled into the empty refill, and an ink-following body was loaded at the rear end of the ink to manufacture a water-based ballpoint pen. Comparative Example 1 is an example using a fitting without a filter (an example of a refill without a filter).

[0089] [Evaluation of writing instruments] The following evaluations were conducted on the manufactured writing instruments. The results are shown in Table 1.

[0090] (Damage resistance to DC current) Using the water-based ballpoint pens prepared as described above, in an environment of 23±2℃ and 65±10% relative humidity, the pens were dropped from a height of 1m onto a receiving plate inclined at 50° to the horizontal plane, with the writing tip extended from the end of the barrel, and the pens were dropped with the writing tip facing downwards. Afterward, five circles of approximately 20-25cm in diameter were written freehand, and the pens were immediately fixed in a downward position and left for 60 minutes. After 60 minutes, the size of the ink droplets accumulated at the tip of each ballpoint pen (maximum vertical length) was measured. The evaluation criteria are shown below. A: 0mm (no ink droplets) B: Over 0mm, less than 2mm C: More than 2mm

[0091] (Speed ​​handwriting) Using the water-based ballpoint pens prepared as described above, the speed writing performance was evaluated by writing five spiral circles of approximately 20-25 cm in diameter freehand on writing paper conforming to ISO standards at normal writing speed (approximately 3 m / min), double speed (approximately 6 m / min), and triple speed (approximately 9 m / min). The evaluation criteria are shown below. A: No smudging occurred when writing at 3x speed. B: No skipping occurred when writing at 2x speed, but skipping occurred when writing at 3x speed. C: Clear smudging occurred when writing at double speed.

[0092] (Writability after storage upright) Using the water-based ballpoint pens prepared as described above, the pens were left standing upright for 6 months in an environment of 23±2℃ and 65±10% relative humidity. Then, on writing paper conforming to ISO standards, five spiral circles of approximately 20-25cm in diameter were written freehand at a normal speed (approximately 3m / min) to evaluate the writing performance after upright storage. The evaluation criteria are shown below. A: No smudging occurred. B: Slight smudging occurred. C: Obvious smudging occurred.

[0093] [Table 1] [Industrial applicability]

[0094] The refill of the present invention has a filter having an average pore size within a specific range and is filled with an ink composition having a viscosity within a specific range, thereby enabling a high level of suppression of the DC phenomenon when installed in a writing instrument.

[0095] Furthermore, by filling the pen with an ink composition having a static surface tension below a specific value, setting the average particle size of the pigments blended into the ink composition to a specific range, or using a filter made of a specific material, it is possible to suppress the DC phenomenon to a high degree, suppress the occurrence of skipping during fast writing, and ensure writing performance even after storage upside down.

[0096] Therefore, the refill of the present invention provides a writing instrument that excels in suppressing DC current at the pen tip, maintains excellent line quality even when writing quickly, and does not cause any problems with writing performance after being stored upright. [Explanation of symbols]

[0097] 100 refills 10 ink reservoirs 11 Fittings 12 chips 13 filters

Claims

1. A refill for a writing instrument, comprising at least a tip and a cylindrical ink reservoir connected to the tip, The chip and the ink container are filled with an ink composition. The ink container comprises a filter made of a porous material that flows through the ink composition and is positioned perpendicular to the direction in which the ink composition follows, The filter has an average pore size of 0.01 μm or more and 9 μm or less, as measured by the half-dry method. The ink composition has a shear rate of 380 sec. －１ The viscosity is between 5 mPa·s and 90 mPa·s. Refill.

2. The refill according to claim 1, wherein the ink composition has a static surface tension of 45 mN / m or less.

3. The refill according to claim 1 or 2, wherein the ink composition comprises a pigment.

4. The refill according to claim 3, wherein the pigment has an average particle size of 0.05 μm or more and 4 μm or less.

5. The refill according to claim 1 or 2, wherein the porous material is at least one selected from the group consisting of nonwoven fabric, fiber laminate, and porous film.

6. The refill according to claim 1 or 2, wherein the porous body is made of at least one fiber selected from the group consisting of cellulose, glass, hydrophilic PTFE, polyethylene, and polypropylene.

7. A writing instrument comprising a refill as described in any one of claims 1 to 6.

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