Water-based ink composition for writing instruments and writing instruments containing the same

Abstract

This invention provides a more practical water-based ink composition for writing instruments and a writing instrument containing it, which can be added to water-based inks in the acidic range, maintain sufficient preservative effect without causing changes in ink properties even after long periods of time, and uses materials that are safe, thereby enabling stable handwriting formation over a long period of time. [Solution] An aqueous ink composition for writing instruments containing at least one benzoamine compound represented by general formula (1) or (2) described in the specification, comprising 0.05% by mass or more of the total amount of the ink composition, and having a pH in the range of 2 to 6.8, and a writing instrument incorporating the same.

Description

Technical Field

[0001] The present invention relates to an aqueous ink composition for writing instruments. More particularly, it relates to an aqueous ink composition for writing instruments that can form stable handwriting even after long-term storage, and a writing instrument using the same.

Background Art

[0002] Conventionally, in aqueous ink compositions, mold may occur in the ink or in fiber members such as the pen tip due to long-term storage under high temperature and high humidity conditions, resulting in poor writing. Therefore, preservatives are added. Particularly in recent years, there has been an increasing awareness of safety, and techniques have been disclosed in which those used as food preservatives such as potassium sorbate are applied, or diols are used in combination to reduce the amount of isothiazolines used as preservatives (for example, see Patent Document ***).

[0003] Since potassium sorbate is defined as a preservative for food additives, it is highly safe as a preservative, but a large amount of addition is required for use as an additive for writing instrument ink, and it has been difficult to obtain a sufficient effect. Also, isothiazolines such as benzisothiazoline (1,2-benzisothiazolin-3-one) have different effects depending on the pH of the ink. When the ink is in the acidic range, the effect is not exhibited.

[0004] Regarding the pH of the above-mentioned ink, when using a basic dye, it is necessary to adjust the ink to the acidic range in consideration of the solubility of the dye. Under such conditions, a technique of using 2-chloroacetamide in combination as a preservative that does not cause precipitation of the dye or discoloration of the ink over a long period of time has been disclosed (for example, see Patent Document ***). However, 2-chloroacetamide has been pointed out in recent years for its toxicity as a substance that causes skin irritation and allergic reactions, and its application to writing instruments has been postponed. Therefore, a preservative suitable for aqueous ink in the acidic range is eagerly desired.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-63363 [Patent Document 2] Japanese Patent Application Publication No. 6-336565 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention provides a more practical aqueous ink composition for writing instruments and a writing instrument containing it, which can be added to aqueous inks in the acidic range, exhibits a sufficient preservative effect continuously without causing changes in ink properties even after long periods of time, and uses materials that take safety into consideration, thereby enabling stable handwriting formation over a long period of time. [Means for solving the problem]

[0007] The present invention requires an aqueous ink composition for writing instruments that contains at least one benzoamine compound shown in the following general formula (1) or (2) in an amount of 0.05% by mass or more of the total amount of the ink composition, and has a pH in the range of 2 to 6.8. [ka] Furthermore, the surface tension at 20°C must be within the range of 38 to 55 mN / m. Furthermore, the requirements include a writing instrument containing the aqueous ink composition for writing instruments described in any of the above, a direct-liquid type writing instrument equipped with an ink flow rate adjustment member that arranges a large number of thin plates in parallel to form comb-like spacing and allows for gas-liquid exchange between ink and outside air, and a pen tip having a slit extending rearward from the pen point at the front end. [Effects of the Invention]

[0008] The aqueous ink composition for writing instruments of the present invention, by using a specific amount or more of the benzoamine compound shown in general formulas (1) and (2), can suppress the long-term growth of mold and other bacteria without causing changes in ink properties even after long periods of time, even when adjusted to an acidic range. Furthermore, since the benzoamine compound itself functions as a blue coloring agent, it is possible to form an ink that is extremely safe compared to conventional inks that required the separate addition of preservatives. Therefore, it is possible to form a more practical aqueous ink composition for writing instruments and a writing instrument containing it, which can continuously produce good handwriting without causing writing defects even after long periods of time, not only in ink form but also in writing instrument form. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described in detail below. In this specification, unless otherwise specified, "parts," "%," "ratio," etc., used to indicate the composition are based on mass.

[0010] The aqueous ink composition for writing instruments according to the present invention (hereinafter, it may be referred to as "aqueous ink composition," "ink composition," or "ink" as it may be referred to) comprises at least water and a specific benzoamine compound. The components constituting the aqueous ink composition according to the present invention will be described below.

[0011] The benzoamine compounds shown in general formulas (1) and (2) above can maintain a stable solubility even in acidic aqueous media and function as blue colorants. In water-based inks, benzoamine compounds that take on a salt structure exhibit a high preservative effect because the aniline skeleton and multiple nitrogen atoms constituting the thiazole or triazole rings in their molecular structure act against mold and bacteria.

[0012] A benzoamine compound can provide a preservative effect if it is present in an amount of 0.05% by mass or more relative to the total amount of the ink composition. There is no particular upper limit, but when combining it with the function of a coloring agent without using other dyes or pigments, it is preferable to use an amount of about 1 to 5% by mass. When considering the preservative effect, it is used in an amount of 0.05 to 10% by mass, preferably 0.1 to 5% by mass, relative to the total amount of the ink composition. In this case, one type may be used alone, or two types may be used in combination.

[0013] The aforementioned benzoamine compound exhibits excellent water solubility in acidic regions and high coloring performance, allowing for the formation of water-based inks with a simple composition. Therefore, there is no risk of particle formation such as precipitates over time. Even when incorporated into a writing instrument that uses an ink flow rate adjustment member that arranges numerous thin plates in parallel to create comb-like spacing and allows for gas-liquid exchange between ink and outside air, high flow rate adjustment performance can be maintained without clogging by precipitate particles when ink flows into the comb grooves or is collected into the ink reservoir due to pressure changes within the writing instrument. Furthermore, fountain pens, along with their ink flow rate adjustment components, require capillary force to guide the ink from the ink reservoir to the nib that forms the stroke. As a result, if precipitated particles are generated, the ink discharge becomes unstable, making them writing instruments prone to poor writing. Therefore, the aqueous ink composition of the present invention is particularly useful because it enables stable ink guidance during writing over a long period, even with fountain pens.

[0014] In the aqueous ink of the present invention, a basic dye can be used in combination with a benzoamine compound. Basic dyes include di and triarylmethane dyes, azine dyes (including nigrosine), quinone imine dyes such as oxazine and thiazine dyes, xanthene dyes, triazole azo dyes, thiazole azo dyes, benzothiazole azo dyes, azo dyes, methine dyes such as polymethine, azomethine, and azamethine, anthraquinone dyes, and phthalocyanine dyes.

[0015] Specifically, examples include each dye described in the COLOR INDEX such as C.I. Basic Yellow (-1, -2, -9, -80, etc.), C.I. Basic Orange (-1, -2, -7, -34, etc.), C.I. Basic Red (-1, -2, -3, -53, etc.), C.I. Basic Violet (-1, -2, -3, -39, etc.), C.I. Basic Blue (-1, -2, -5, -88, etc.), C.I. Basic Green (-1, -4, -6, -10, etc.), C.I. Basic Brown (-1, -2, -4, -15, etc.), C.I. Basic Black (-1, -2, -7, -8, etc.). Examples of commercially available products include AIZEN CATHILON YELLOW GLH, AIZEN CATHILON RED BLH, AIZEN CATHILON RED RH, AIZEN CATHILON TURQUOISE BLUE LH, AIZEN CATHILON BROWN GH manufactured by Hodogaya Chemical Co., Ltd., Diacryl Supra Brilliant Red 2G, Diacryl Supra Brilliant Green 2GL manufactured by Mitsubishi Chemical Corporation, Sumiacryl Red B manufactured by Sumitomo Chemical Co., Ltd., Janus Brown R manufactured by Nippon Chemical Co., Ltd., and the like. In addition, according to the application, acidic dyes or direct dyes that can be dissolved in an aqueous medium can also be used in combination.

[0016] The above dyes can be used by appropriately mixing one or more of them, and are used in the range of 1 to 25% by mass, preferably 1 to 20% by mass in the ink composition.

[0017] Furthermore, according to the application, a small amount of a pigment that can be dispersed in an aqueous medium can also be used in combination for color adjustment. Examples of the pigment include inorganic pigments such as carbon black and ultramarine blue, organic pigments such as copper phthalocyanine blue and benzidine yellow, and aqueous dispersion pigment products that are finely and stably dispersed in an aqueous medium in advance using a surfactant or the like. In addition, examples include fluorescent pigments, pearl pigments, metallic pigments such as gold and silver, phosphorescent pigments, white pigments such as titanium dioxide, metal powders such as aluminum, and further, capsule pigments obtained by directly encapsulating or microencapsulating thermochromic compositions, photochromic compositions, fragrances, and the like.

[0018] The ink composition according to the present invention contains water. The water is not particularly limited, and examples thereof include tap water, ion-exchanged water, ultrafiltration water, distilled water, and the like. The content rate of water with respect to the total mass of the ink composition is not particularly limited, but is preferably in the range of 45 to 99.5% by mass, more preferably 50 to 99% by mass.

[0019] In the ink composition according to the present invention, in addition to the above components, optional components can be blended within a range that does not impair the effects of the present invention.

[0020] For example, conventionally widely used water-soluble organic solvents compatible with water can also be used. Specifically, ethanol, propanol, butanol, glycerin, sorbitol, triethanolamine, diethanolamine, monoethanolamine, ethylene glycol, diethylene glycol, thiodiethylene glycol, hexylene glycol, 1,3-butanediol, neoprene glycol, polyethylene glycol, propylene glycol, butylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, propylene glycol monoethyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, and the like can be mentioned. In addition, the water-soluble organic solvent can be used alone or in combination of two or more, and is used in the range of 1 to 50% by mass, preferably 5 to 35% by mass in the ink composition.

[0021] Furthermore, a water-soluble resin can be added to impart adhesion and viscosity to the paper surface. Examples of water-soluble resins include alkyd resins, acrylic resins, styrene-maleic acid copolymers, cellulose derivatives, polyvinylpyrrolidone, polyvinyl alcohol, and dextrin. One or more water-soluble resins can be used in combination, and they are used in an amount ranging from 1% to 30% by mass in the ink composition.

[0022] Other rust inhibitors include benzotriazole, toltriazole, 2,5-dimercapto-1,3,4-thiadiazole, and saponins. Urea, nonionic surfactants, sorbitol, mannitol, sucrose, glucose, reduced starch hydrolysate, sodium pyrophosphate and other humectants, In addition, defoaming agents, dispersants, specific gravity adjusters, etc., may be used. Furthermore, bubbles can be chemically removed by adding ascorbic acid, erythorbic acid, α-tocopherol, catechins, synthetic polyphenols, kojic acid, alkylhydroxylamines, oxime derivatives, α-glucosylrutin, α-lipoic acid, phosphonates, phosphinates, sulfites, sulfoxylates, dithionites, thiosulfates, thiourea dioxide, etc. Furthermore, the function in the retractable form can be enhanced by adding thickening inhibitors such as N-vinyl-2-pyrrolidone oligomer, N-vinyl-2-piperidone oligomer, N-vinyl-2-pyrrolidone, N-cyclohexyl-2-pyrrolidone, ε-caprolactam, and N-vinyl-ε-caprolactam oligomer. Furthermore, lubricants can be added, such as metal soaps, polyalkylene glycol fatty acid esters, ethylene oxide-additive cationic surfactants, phosphate ester surfactants, β-alanine-type surfactants, N-acyl amino acids, N-acylmethyl taurine, 2,5-dimercapto-1,3,4-thiadiazole or its salts or oligomers, 3-amino-5-mercapto-1,2,4-triazole, thiocarbamate, dimethyldithiocarbamate, α-lipoic acid, condensates of N-acyl-L-glutamic acid and L-lysine or their salts. Furthermore, depending on the purpose, small amounts of common preservatives or fungicides such as carbolic acid, 1,2-benzisothiazolin-3-one or its sodium salt, sodium benzoate, sodium dehydroacetate, potassium sorbate, propyl parahydroxybenzoate, methylisothiazolinone, and N-butylcarbamate 3-iodo-2-propynyl may be used in combination.

[0023] Furthermore, shear-thickening agents can be added to the ink composition. Examples include water-soluble polysaccharides, polymers with a molecular weight of 100,000 to 150,000 mainly composed of alkyl esters of methacrylic acid, poly-N-vinyl carboxylic acid amide crosslinks, benzylidene sorbitol and its derivatives, benzylidene xylitol and its derivatives, alkali-thickening acrylic resins, crosslinkable acrylic acid polymers, inorganic fine particles, nonionic surfactants with an HLB value of 8 to 12, and metal salts or amine salts of dialkyl sulfosuccinate. Examples of water-soluble polysaccharides include xanthan gum, gellan gum, zeta-C gum, dieutan gum, macrophopsis gum, succinoglycans (average molecular weight of approximately 1 million to 8 million), which are heteropolysaccharides with organic acid modifications of glucose and galactose, guar gum, locust bean gum and its derivatives, hydroxyethylcellulose, alkyl alginates, glucomannan, and gelling carbohydrates extracted from seaweed such as agar and carrageenan. Shear viscosity reducing agents can be used individually or in combination of two or more types. Furthermore, the shear viscosity reduction of ink refers to the rheological property where, in a static state or under low stress, it has high viscosity and is difficult to flow, but as stress increases, its viscosity decreases and it exhibits good fluidity. This property is also known as thixotropy or pseudoplasticity.

[0024] The surface tension of the ink composition according to the present invention is not particularly limited, but is preferably 38 to 55 mN / m at a temperature of 20°C. Having a surface tension within this range makes it easier to suppress ink bleed-through and smudging. Furthermore, when incorporated into a writing instrument using an ink flow rate adjustment member, good ink followability can be ensured without dripping. The aforementioned surface tension was measured using a surface tension measuring instrument [Kyowa Interface Science Co., Ltd., product name: DY-300], with the ink composition placed in an environment of 20°C, and measured using the vertical plate method with a platinum plate.

[0025] Furthermore, the viscosity of the ink composition according to the present invention is not particularly limited, but is preferably 1 to 5 mPa·s and more preferably 1 to 3 mPa·s at a temperature of 20°C. Having a viscosity within the above range makes it easier to achieve good ink discharge stability, in conjunction with the aforementioned ink drying properties, even in writing instruments such as fountain pens, which have narrow ink flow passages leading to the pen tip. The viscosity was measured using an EL-type rotational viscometer [manufactured by Toki Sangyo Co., Ltd., product name: RE-80L, cone-type rotor: standard type (1°34′×R24)] with the ink composition placed in an environment of 20°C.

[0026] The aqueous ink composition for writing instruments of the present invention is used to fill writing instruments with caps or retractable tip designs, such as marking pens, ballpoint pens, and fountain pens, which are equipped with fiber tips, felt tips, plastic tips, or ballpoint pen tips at the tip of the writing instrument.

[0027] When filling a marking pen, the structure and shape of the marking pen itself are not particularly limited. For example, a marking pen may have a tip (bullet-shaped, chisel-shaped, brush-pen-shaped, etc.) such as a fiber tip, felt tip, or plastic tip attached to the writing tip, and ink may be impregnated into an ink-absorbing material made of fiber bundles housed inside the barrel to supply ink to the writing tip. Another example is a marking pen that houses ink directly inside the barrel and supplies a predetermined amount of ink to the writing tip via a comb-shaped ink flow control member or an ink flow control member made of fiber bundles. Yet another example is a marking pen that houses ink directly inside the barrel and supplies a predetermined amount of ink to the writing tip via a valve mechanism. Furthermore, the ink storage part can also be a cartridge. In addition to having a single pen tip, a double-ended design may also be available, with pen tips of different thicknesses and shapes at both ends of the barrel. Furthermore, in the aforementioned double-ended design, one end may be a ballpoint pen.

[0028] When filling a ballpoint pen, the structure and shape of the ballpoint pen itself are not particularly limited. Examples include a structure in which ink is impregnated into an ink-absorbing body made of fiber bundles housed inside the barrel and supplied to the writing tip; a structure in which ink is directly housed inside the barrel and an ink flow rate regulating member with comb-like grooves or an ink flow rate regulating member made of fiber bundles is interposed; and a ballpoint pen having an ink-retaining tube filled with an ink composition inside the barrel, the ink-retaining tube communicating with a tip to which a ball is attached, and further having an ink backflow prevention body in close contact with the end face of the ink.

[0029] The ink backflow prevention body can be either liquid or solid. Examples of liquid ink backflow prevention bodies include non-volatile media such as polybutene and silicone oil, and silica, aluminum silicate, etc., can be added to the media if desired. Furthermore, a resin molded product can be used as a solid ink backflow prevention body. It should be noted that the liquid and solid ink backflow prevention bodies can also be used in combination.

[0030] When filling a fountain pen, the structure and shape of the fountain pen itself are not particularly limited. An example is one that has a nib with a slit extending from the front end of the pen point to the rear, and has an ink flow rate adjustment member interposed between it and the ink filling mechanism.

[0031] Examples of pen nibs (tips) include the so-called fountain pen type, which has a pen point, which is the front end that contacts the paper when writing, a slit that extends a predetermined length backward from the pen point, and a hole located approximately in the center of the pen point. Pen nibs can be made from metal plates such as cemented carbide, stainless steel, gold-plated stainless steel, gold alloy, pure gold, or iridium, which are cut into a tapered shape and then bent or curved, or from resin molded into a pen nib shape.

[0032] The ink filling mechanism (ink storage section) is not particularly limited, and examples include an ink storage body capable of being filled with ink, which may be a molded body made of a thermoplastic resin such as polyethylene, polypropylene, polyethylene terephthalate, or nylon, or a tubular metal body. The ink filling mechanism can be detachably replaced on the writing instrument body and may be a cartridge type using pre-filled ink cartridges. In this case, after the ink in the ink cartridge of the writing instrument is used up, the writing instrument can be used again by replacing it with a new ink cartridge. Alternatively, it may be an ink-filling type equipped with an ink-filling mechanism that allows ink to be refilled from an ink bottle or the like. The ink-filling mechanism may be directly attached to the body of the writing instrument, or it may be detachably attached to the body of the writing instrument, like a converter.

[0033] The ink flow rate adjustment member interposed between the pen tip and the ink filling mechanism is also applicable to the aforementioned marking pens and ballpoint pens. For example, it can be used in a configuration in which a number of discs are arranged in parallel with comb-like spacing, and slit-shaped ink guide grooves and ventilation grooves are provided that penetrate the discs axially, with an ink guide core positioned at the axis as needed to guide ink from the ink filling mechanism to the pen tip, or in a configuration in which a number of thin plates are arranged in parallel with comb-like spacing and allow for gas-liquid exchange between ink and outside air. The comb grooves are structured to temporarily store ink, and when the internal pressure of the ink filling mechanism changes, excess ink flows into the comb grooves and is retained, thereby suppressing ink leakage and overflow from the pen tip, and further adjusting the ink discharge performance, resulting in a good writing finish. In the ink storage, if precipitates are generated in the ink, the flow into the comb grooves is obstructed, causing ink leakage. Therefore, the aqueous ink composition of the present invention, which has high dissolution stability, is particularly useful.

[0034] Particularly preferred as a writing instrument to which the aqueous ink composition of the present invention is applied is a fountain pen having a metal nib in the shape of a fountain pen, an ink filling mechanism, and an ink flow rate adjusting member, with a slit extending rearward from the pen point at the front end. Since fountain pens have a structure that guides and supplies ink from the ink filling mechanism to the nib using capillary force via an ink flow rate adjustment member, the present invention, which allows for the formation of water-based ink with a simple composition, eliminates the risk of precipitates (particles) forming over time. This results in excellent ink discharge stability during writing without hindering ink guidance to the nib or ink discharge from the nib. Furthermore, high flow rate adjustment performance can be maintained without clogging by particles when ink flows into the comb grooves or when it is collected in the ink storage section. [Examples]

[0035] Examples are described below, but the present invention is not limited to these examples. Table 1 shows the composition of the aqueous inks in the examples and comparative examples. The composition values ​​in the table represent parts by mass.

[0036] [Table 1]

[0037] The contents of the raw materials are shown below, according to the note numbers in the table. (1) Benzoamine compounds shown in general formula (1) (2) Benzoamine compounds shown in general formula (2) (3) Manufactured by Hodogaya Chemical Industry Co., Ltd., product name: Aizen Cathilon Orange RH (4) Manufactured by Hodogaya Chemical Co., Ltd., Product name: SWT Red-4 (5) Manufactured by Hodogaya Chemical Co., Ltd., Product name: Diamond Green GH (6) Benzoisothiazoline (1,2-benzoisothiazoline-3-one) (7) Potassium sorbate

[0038] Preparation of ink composition A water-based ink composition for writing instruments was obtained by stirring and mixing each raw material in the specified proportions at room temperature for one hour.

[0039] Making a fountain pen 0.9 g of the ink compositions of the above examples and comparative examples were placed in a polyethylene ink cartridge [Pilot Corporation, IRF-12S] to form an ink filling mechanism. Furthermore, a fountain pen was manufactured by connecting and housing the previously formed ink filling mechanism (ink cartridge) into a cap-type fountain pen [Pilot Corporation, FKKN-12SR] which has a fountain pen-shaped nib (nib width: F) having a slit extending from the front end of the pen point to the rear, and an ink flow rate adjustment member (pen nib) having a comb groove for temporarily storing ink, an ink flow passage and an air passage as an ink supply mechanism, with the ink filling mechanism being a separate component and connected to the nib via the ink supply mechanism. The resulting fountain pen was positioned with the nib facing downwards, allowing the filled ink to flow up to the nib, making it ready for writing.

[0040] Making a marking pen A marking pen [Pilot Corporation, SW-VSP] was manufactured by directly placing 1.5 g of the ink composition of the above example and comparative example inside the barrel, interposing a comb-shaped ink flow adjustment member (including a guide core), assembling a polyester fiber tip, and then attaching a cap. The following evaluations were performed using the obtained ink compositions and writing instruments. Note that Comparative Example 6 did not contain any coloring components and therefore the writing was not visible; therefore, only a preservative efficacy test was performed.

[0041] <Preservative efficacy test> In accordance with the preservation efficacy tests described in the reference information of the "18th Revised Japanese Pharmacopoeia," test samples were obtained by inoculating each ink composition with various test bacterial solutions and mixing them uniformly. Each test sample was stored in a light-shielded environment at 20°C for 7 days, and the number of viable bacteria in the test sample was measured. The preservative efficacy was evaluated based on the increase or decrease in the number of viable bacteria. The test organisms used were two types of bacteria, Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa), and two types of fungi, Candida albicans (C. albicans) and Aspergillus brasiliensis (A. braziliensis). (Evaluation Criteria) ○: A decrease in the number of viable bacteria was observed after 7 days. △: No change was observed in the number of viable bacteria after 7 days. ×: An increase in the number of viable bacteria was observed after 7 days.

[0042] <Written Exam> After confirming that each writing instrument was capable of writing, it was left undisturbed for 60 days in a 20°C environment. Then, a 15cm straight line was handwritten parallel to the shorter side of an A4-sized test sheet (portrait orientation) made of JIS P3201 writing paper A. The resulting handwriting was visually inspected. (Evaluation Criteria) ○: The handwriting was good, without smudging or skipping lines, and possessed consistent density and line width. △: There are slight smudges or skipped lines in the handwriting, or the handwriting is too faint. ×: Numerous smudges and skipped lines were observed in the handwriting. Alternatively, the paper was unusable due to precipitates. The evaluation results are shown below.

[0043] [Table 2]

Claims

1. An aqueous ink composition for writing instruments containing at least one benzoamine compound shown in the following general formula (1) or (2) in an amount of 0.05% by mass or more of the total amount of the ink composition, and having a pH in the range of 2 to 6.

8. 【Chemistry 1】

2. The aqueous ink composition for writing instruments according to claim 1, comprising a basic dye.

3. The aqueous ink composition for writing instruments according to claim 1, wherein the surface tension at 20°C is in the range of 38 to 55 mN / m.

4. A writing instrument containing the aqueous ink composition for writing instruments described in any one of claims 1 to 3.

5. The writing instrument according to claim 4, which is a direct-liquid type writing instrument equipped with an ink flow rate adjustment member that allows for the exchange of liquid and gas between ink and outside air, and which has a number of thin plates arranged in parallel to form comb-like spacing.

6. The writing instrument according to claim 4, comprising a pen tip having a slit extending backward from the pen point at the front end.

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