Oily ink composition for ballpoint pen

Abstract

Provided are: an ink flow rate design which has an excellent mottle phenomenon suppression effect, a smooth writing feeling, excellent initial writing properties (not being erased at the beginning), quick-drying properties, no ink stretching during wiping due to mottle, and improved wire jumping, thereby ensuring a stable ink flow rate without relying on a tip; an oil-based ink composition for a ballpoint pen, which is capable of suppressing mottle and quick-drying properties, and which is also capable of improving print-through properties; and an oily ballpoint pen. The oil-based ink composition for ballpoint pens is characterized by containing at least a colorant, a resin component, a solvent and water, the content of the solvent and water being 40% by mass or more with respect to the total amount of the ink composition, and the content of the solvent and water being 40% by mass or more when a resin having a mass-average molecular weight of 40,000 or more is contained as the resin component. The content of the resin component is 0.5 mass% or less relative to the total amount of the ink composition, and the weight loss ratio A when the ink composition is left to stand for 2 hours in an open state at 50 DEG C and a relative humidity of 35 + / -5% RH is 25% or more. And the ratio A / B of the weight loss ratio A to the weight loss ratio B when the ink composition is left to stand for 2 hours in an open state in an environment of 50 DEG C and a relative humidity of 85 + / -5% RH is 0.8-1.2. The oil-based ballpoint pen is characterized in that the oil-based ink composition for the ballpoint pen is loaded.

Description

Technical Field

[0001] The present specification relates to an oil-based ink composition for a ballpoint pen and an oil-based ballpoint pen. Background Art

[0002] Generally, the writing feel of oil-based ballpoint pens tends to be relatively heavy. To improve this, conventional techniques have been used to design low-viscosity inks, such as setting the viscosity at about 1000 mPa·s at 5 rpm, but this has not resulted in sufficient quality, such as reduction of ink spots.

[0003] Therefore, conventionally, in oil-based ballpoint pens, there have been known oil-based ink compositions for ballpoint pens that suppress the above-mentioned ink spot phenomenon or make the writing feel smooth.

[0004] For example, there are known: (a) an oil-based ink comprising at least a colorant, one or more solvents selected from propylene glycol monomethyl ether, dipropylene glycol monomethyl ether, and aliphatic alcohols having 4 or less carbon atoms, and a resin having a hydrophilic group and a resin having a hydrophobic group that are soluble in the aforementioned solvents and are immiscible with each other (see, for example, Patent Document 1);

[0005] (b) A low-viscosity oil-based ballpoint pen, comprising a ballpoint pen refill in which an ink storage tube is connected to a tip end of a ball-fitting sleeve via a joint, the ink storage tube being filled with low-viscosity oil-based ballpoint pen ink and a follower located on the rear end surface of the ink, the tip end having a spring that constantly presses the tip end ball in a manner such that the tip end ball is in close contact with the inner edge of the ball-fitting portion at the tip end when not writing and is released from the close contact state when writing, the low-viscosity oil-based ballpoint pen ink being formed of a solvent containing 60% by weight or more of an organic solvent having a vapor pressure of 0.2 mmHg (25° C.) or less, a colorant, and an additive, and having an ink viscosity of 300 mPa·S (20 rpm, 25° C.) or less and a TI value (5 rpm / 20 rpm, 25° C.) or more of 1.1 (for example, refer to Patent Document 2 previously filed by the applicant of the present invention);

[0006] (c) A low-viscosity oil-based ballpoint pen having a refill, wherein the refill is filled in an ink container with: (1) a solvent containing 60% by weight or more of an organic solvent having a vapor pressure of 0.1 mmHg (20° C.) or less, a colorant, and an additive, wherein the viscosity of the ink is 400 s at a shear rate of 100 s. -1 The pressure is below 200 mPa·S and the shear rate is 5 s -1 The invention relates to a method for producing a low-viscosity oily ballpoint pen ink having a viscosity of 300 mPa·s or more; and (2) a follower including at least one solvent selected from the group consisting of a low-volatile organic solvent and a non-volatile organic solvent, a gelling agent formed by particulate silica, and a silane-based surface modifier on the rear end face of the ink (for example, refer to Patent Document 3 previously applied by the applicant of the present invention).

[0007] (d) An oil-based ink for a ballpoint pen, which is composed of at least an oil-soluble resin, an oil-soluble dye, a glycol ether-based solvent having a boiling point in the range of 160° C. to 200° C., and ethylene glycol monopropyl ether (see Patent Document 4).

[0008] The mechanism for improving ink spots in existing oil-based ballpoint pens equipped with the aforementioned various existing oil-based ink compositions is to improve the ink's stringiness according to the type of resin contained in the ink, the combination with other components, etc., and to recover the excess ink around the tip into the tip, thereby suppressing ink spots.

[0009] However, in this method, the remaining ink that is not recovered into the tip accumulates near the tip plug as writing proceeds, forming a large ink spot that falls on the line, so there is a problem that the line quality deteriorates and the effect of reducing ink spots is not sufficient. In particular, in order to make the writing feel smooth, when the ink viscosity is designed to be low, the ink spot improvement effect is also small. In addition to the further ink spot improvement effect, it is expected to further improve the smooth writing feel, the initial writing property (no rubbing at the beginning), and further improve the so-called jump line when writing, where part of the solid line falls off and becomes a dotted line, and part of the line falls off significantly and becomes blurred.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 4-139273 (claims, examples, etc.)

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 8-192594 (claims, examples, etc.)

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 8-134392 (claims, examples, etc.)

[0015] Patent Document 4: Japanese Patent Application Publication No. 2009-197205 (claims, examples, etc.) Summary of the invention

[0016] Problem that the invention aims to solve

[0017] The present disclosure is made in view of the problems and current status of the aforementioned prior art and aims to eliminate them, and its purpose is to provide: an oily ink composition for ballpoint pens that minimizes the ink spot phenomenon, has a smooth writing feel, good initial writing properties (no rubbing at the beginning), and has improved line skipping, thereby ensuring a stable ink flow rate without relying on the ink flow design of the tip; and an oily ballpoint pen equipped with the oily ink composition.

[0018] Solutions for solving problems

[0019] The present inventors have conducted intensive research in view of the above-mentioned existing problems, and as a result, have found that: an oil-based ink composition for a ballpoint pen comprising at least a colorant, a resin component, a solvent and water, wherein the content of the above-mentioned resin component and the content of the above-mentioned solvent and water are optimized respectively, and the ratio of the weight loss rate under two measurement conditions that become the ink properties is within a specified range, etc., thereby obtaining the above-mentioned target oil-based ink composition for a ballpoint pen and an oil-based ballpoint pen, and the present disclosure has been completed.

[0020] That is, the oil-based ink composition for a ballpoint pen disclosed in the present invention is characterized in that it contains at least: a colorant, a resin component, a solvent and water, the content of the aforementioned solvent and water is 40% by mass or more relative to the total amount of the aforementioned ink composition, when a resin with a mass average molecular weight of 40,000 or more is contained as the aforementioned resin component, the content of the resin component is 0.5% by mass or less relative to the total amount of the aforementioned ink composition, the weight loss rate A when the aforementioned ink composition is left to stand for 2 hours in an open state at 50°C and a relative humidity of 35±5%RH is 25% or more, and the ratio A / B of the aforementioned weight loss rate A to the weight loss rate B when the aforementioned ink composition is left to stand for 2 hours in an open state at 50°C and a relative humidity of 85±5%RH is 0.8 to 1.2.

[0021] It is preferred that the resin component contain a resin having a mass average molecular weight of less than 40,000.

[0022] It is preferred that the viscosity of the oil-based ink composition for ballpoint pens at 25°C measured by a cone-plate rheometer is within a range of a shear rate of 200 to 2000 s. -1 The range is 1 to 200 mPa·s, using a rheometer at 25°C with a shear rate of 20 s -1 Viscosity / shear rate 200s -1 The viscosity ratio is 0.90 to 1.10.

[0023] The oil-based ballpoint pen disclosed in the present invention is characterized by being equipped with the oil-based ink composition for a ballpoint pen having the above-mentioned composition.

[0024] Effects of the Invention

[0025] According to the present disclosure, there are provided: an oily ink composition for ballpoint pens that minimizes the ink spot phenomenon, has good initial writing properties (no rubbing at the beginning), quick-drying properties, and no ink stretching during rubbing due to ink spots, and improved line jumps, thereby ensuring a stable ink flow rate without relying on the ink flow rate design of the tip, and that can also improve the print-through properties due to the aforementioned suppression of ink spots and quick-drying properties; and an oily ballpoint pen.

[0026] The objects and effects of the present disclosure can be realized and achieved particularly by using the constituent elements and combinations pointed out in the claims.Both the above general description and the following detailed description are exemplary and illustrative and do not limit the present disclosure described in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a longitudinal sectional view showing an example of the main part of the tip of the oil-based ballpoint pen on which the oil-based ink composition for a ballpoint pen of the present disclosure is mounted. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present disclosure in detail. However, the protection scope of the present disclosure is not limited to the embodiments described in detail below, and attention should be paid to the contents described in the claims and aspects related to their equivalents.

[0029] The oil-based ink composition for a ballpoint pen disclosed in the present invention is characterized in that it contains at least: a colorant, a resin component, a solvent and water.

[0030] The content of the solvent and water is 40% by mass or more relative to the total amount of the ink composition.

[0031] When a resin having a mass average molecular weight of 40,000 or more is contained as the resin component, the content of the resin component is 0.5% by mass or less relative to the total amount of the ink composition.

[0032] The weight loss rate A of the ink composition when left in an open state at 50°C and a relative humidity of 35±5%RH for 2 hours is greater than 25%, and the ratio A / B of the weight loss rate A to the weight loss rate B of the ink composition when left in an open state at 50°C and a relative humidity of 85±5%RH for 2 hours is 0.8 to 1.2.

[0033] 〈Colorants〉

[0034] Examples of usable colorants include inorganic pigments and organic pigments, and these can be used alone or in combination of two or more.

[0035] Examples of the inorganic pigment include carbon black, titanium oxide, zinc oxide, iron oxide, chromium oxide, iron black, cobalt blue, alumina white, iron oxide yellow, chrome green, zinc sulfide, cadmium yellow, vermilion, cadmium red, chrome yellow, molybdenum orange, zinc chromate, strontium chromate, white carbon, clay, talc, ultramarine, barite mineral powder, white lead, Prussian blue, manganese violet, aluminum powder, and brass powder.

[0036] As the organic pigment, for example, at least one of azo lakes, insoluble azo pigments, chelated azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dye lakes, nitro pigments, nitroso pigments, etc. (each alone or as a mixture of two or more, the same applies hereinafter) can be cited.

[0037] In addition, at least one colorant selected from the group consisting of acid dyes, reactive dyes, basic dyes, disperse dyes, direct dyes, fluorescent dyes, CI Basic Yellow 35, CI Basic Yellow 40, CI Acid Orange 28, CI Acid Blue 92, Eosin, Fluorescent Pink, Water Yellow #6-C, Acid Red, Water Blue #105, Brilliant Blue FCF, Aniline Black NB, Direct Black 154, Direct Lake Blue 5B, Purple BB Rhodamine, and Methyl Violet may also be used.

[0038] Furthermore, at least one of the following may be used: processed pigments whose surfaces have been modified with resins, surfactants, etc.; colorants dispersed with pigments or dyes; colorants obtained by micronizing acrylic resins, benzoguanamine resins, etc.; thermochromic microcapsule pigments; and photochromic microcapsule pigments.

[0039] The content of these colorants varies depending on the type of oil-based ballpoint pen, ink storage form (cotton type, straight liquid type), dispersibility, storage stability, etc., but is about 0.5 to 40% by mass based on the total amount of the ink composition.

[0040] 〈Resin ingredients〉

[0041] As the resin component used in the present disclosure, for example, polyvinyl butyral, ketone resin, polyvinyl pyrrolidone, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, maleic acid resin, styrene maleic acid resin, alkylphenol resin, rosin-modified resin, terpene phenol resin, styrene acrylic resin, etc. can be mentioned, and they can be used alone or in combination of two or more (hereinafter referred to as "at least one").

[0042] In the present disclosure, from the perspective of suppressing ink spots and line skipping, when a resin having a mass average molecular weight of 40,000 or more is used as a resin component, the content of the resin component is 0.5% by mass or less, preferably 0.4% by mass or less, and more preferably 0 (zero) to 0.3% by mass, relative to the total amount of the ink composition, in terms of solid content. In the present disclosure, when the resin having a mass average molecular weight of 40,000 or more exceeds the above content range, it becomes difficult to exert the effect of the present disclosure, and line skipping may occur, which is not preferred.

[0043] As a preferred resin component, it is desirable to use a resin having a mass average molecular weight of less than 40,000. From the perspective of further suppressing ink spots and further preventing line skipping, at least one of polyvinyl butyral, ketone resin, polyvinyl pyrrolidone, polyacetal resin, polyvinyl alcohol resin, cellulose resin, terpene resin, alkyd resin, phenoxy resin, polyvinyl acetate resin, maleic acid resin, styrene maleic acid resin, alkylphenol resin, rosin-modified resin, terpene phenol resin, styrene acrylic resin, etc. having a mass average molecular weight of less than 40,000 can be cited.

[0044] Among these, polyvinyl butyral, ketone resin, and polyvinyl pyrrolidone having a mass average molecular weight of less than 40000 are preferably used, and polyvinyl butyral and ketone resin having a mass average molecular weight of 20000 or less are more preferably used. In the present disclosure, the mass average molecular weight used is a value measured in terms of styrene by the GPC method.

[0045] Here, the polyvinyl butyral resin is obtained by reacting polyvinyl alcohol (PVA) and butyraldehyde (BA), and has a structure having a butyraldehyde group, an acetyl group, and a hydroxyl group.

[0046] Specific examples of the resin that can be used include polyvinyl butyrals such as BL-1, BL-10, BM-1, BM-5, and BH-3 manufactured by Sekisui Chemical Co., Ltd., and Mowital B14S and B30T manufactured by KURARAY CO., LTD.

[0047] Examples of ketone resins include Ketone resin K-90 (trade name) manufactured by Arakawa Chemical Industries, Ltd. and Resin SK (trade name) manufactured by Degussa Corporation.

[0048] Examples of polyvinyl pyrrolidone include Pitzcol K-17 (trade name) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. and PVP K90 (trade name) manufactured by Ashland Co., Ltd.

[0049] More preferably, from the perspective of suppressing ink spots and line skipping, a 3-methyl-3-methoxy-1-butanol solution containing 10% by mass of the resin is prepared at 25° C. and a rheometer shear rate of 100 s. -1 The viscosity below is 1000 mPa·s or less, more preferably 500 mPa·s or less.

[0050] Regarding the content of these resin components (solid content), when using the aforementioned resin having a mass average molecular weight of 40,000 or more, the content of the resin component is 0.5% by mass or less as a solid content relative to the aforementioned ink composition, and the content of other resin components (solid content) varies depending on the type of oil-based ballpoint pen, ink storage form (medium-cotton type, straight liquid type), dispersibility, storage stability, etc., but it is expected that the content is preferably 25% by mass or less, more preferably 15% by mass or less, and particularly preferably 1 to 5% by mass as a solid content relative to the total amount of the ink composition.

[0051] By reducing the content of resins other than the resins having a mass average molecular weight of 40,000 or more in the total amount of ink to 25% by mass or less, ink spots can be suppressed. On the other hand, if the content exceeds 25% by mass, ink spots and skipped lines tend to occur, and initial writing properties may also deteriorate.

[0052] 〈Solvent〉

[0053] As the solvent in the present disclosure, for example, aromatic solvents, alcohols, polyols, glycol ethers, hydrocarbons, esters, etc. can be used. These solvents can be used alone or in combination of two or more.

[0054] As the aromatics, for example, benzyl alcohol, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monophenyl ether, alkyl sulfonate phenyl ester, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, etc. can be used.

[0055] As alcohols, for example, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butanol, 1-pentanol, isopentanol, sec-pentanol, 3-pentanol, tert-pentanol, n-hexanol, methylpentanol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n-decanol, undecanol, n-decanol, trimethylnonanol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclohexanol, etc. can be used.

[0056] As the polyol, for example, ethylene glycol, diethylene glycol, 3-methyl-1,3-butanediol, triethylene glycol, dipropylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1,5-pentanediol, hexanediol, octanediol, etc. can be used.

[0057] As the glycol ethers, for example, methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1-butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tert-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monobutyl ether and the like can be used.

[0058] As the hydrocarbons, for example, linear hydrocarbons such as hexane, isohexane, heptane, octane, nonane, and decane, and cyclic hydrocarbons such as cyclohexane, methylcyclohexane, and ethylcyclohexane can be used.

[0059] As the esters, for example, propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, propyl acetate, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, propyl isobutyrate , methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl pivalate, ethyl pivalate, propyl pivalate, methyl caproate, ethyl caproate, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic triglyceride, tributyl citrate, octyl hydroxystearate, propylene glycol monoricinoleate, methyl 2-hydroxyisobutyrate, 3-methoxybutyl acetate, etc.

[0060] Among these solvents, from the perspective of suppressing ink spots and line drying properties, it is desirable to preferably use a solvent having a vapor pressure of 100 Pa or more at 25° C. It is more desirable to use a solvent having a vapor pressure of 1000 Pa or more at 25° C., and it is even more desirable to use a solvent having a vapor pressure of 5000 Pa or more at 25° C.

[0061] Particularly preferred solvents include 3-methoxy-3-methyl-1-butanol (25°C, vapor pressure: 125 Pa), propylene glycol monomethyl ether (25°C, vapor pressure: 1667 Pa), ethanol (25°C, vapor pressure: 7906 Pa), isopropanol (25°C, vapor pressure: 5870 Pa), and xylene (25°C, vapor pressure: 1121 Pa).

[0062] The content of these solvents is desirably 30 to 80% by mass, and preferably 40 to 70% by mass, based on the total amount of the ink composition.

[0063] In the present disclosure, it is desirable to contain water, and purified water, ion exchange water, pure water, ultrapure water, etc. can be used, and it is desirable to specifically be 0.5 to 10% by mass relative to the total amount of the ink composition. If the ballpoint pen refill equipped with the oily ink composition for ballpoint pens disclosed in the present disclosure is left for a long time, it slowly absorbs moisture in the air, and therefore, by adding water in advance, the physical property changes caused by moisture absorption can be suppressed. For this reason, it is desirable to contain water.

[0064] In the present disclosure, the total content of the solvent and water must be 40% by mass or more, and is desirably preferably 40 to 80% by mass, based on the total amount of the ink composition.

[0065] If the total content of the solvent and water is less than 40% by mass, the volatility of the ink decreases, and thus ink spots around the plug are easily accumulated, which is not preferable.

[0066] 〈Other ingredients〉

[0067] The ballpoint pen oil-based ink composition of the present disclosure may contain other components in appropriate amounts within the range that does not impair the effects of the present disclosure. Examples of other components include leveling agents, rust inhibitors, antiseptics, lubricants, and the like.

[0068] As the leveling agent, for example, a fluorine-based surfactant, a silicone-based surfactant, a phosphate-based surfactant, etc. can be used. As the lubricant, for example, a phosphate ester can be mentioned.

[0069] The oil-based ink composition for a ballpoint pen disclosed in the present invention is characterized in that it contains at least: a colorant, a resin component, a solvent and water, the content of the aforementioned solvent and water is 40% by mass or more relative to the total amount of the aforementioned ink composition, when a resin with a mass average molecular weight of 40,000 or more is contained as the aforementioned resin component, the content of the resin component is 0.5% by mass or less relative to the aforementioned ink composition, the weight loss rate A when the aforementioned ink composition is left to stand for 2 hours in an open state at 50°C and a relative humidity of 35±5%RH is 25% or more, and the ratio A / B of the aforementioned weight loss rate A to the weight loss rate B when the aforementioned ink composition is left to stand for 2 hours in an open state at 50°C and a relative humidity of 85±5%RH is 0.8 to 1.2.

[0070] By setting the weight loss rate A to 25% or more and the weight loss rate ratio A / B to 0.8 to 1.2, the effects of the present disclosure can be effectively exerted. Specifically, ink drying properties for suppressing ink spots can be obtained while maintaining good initial writing properties.

[0071] In the present disclosure, the weight loss rates A and B are measured at different humidities in order to ensure that a certain volatility is maintained regardless of whether it is in a dry environment or a high humidity environment.

[0072] If the weight loss rate A is less than 25%, quick-drying properties will be poor.

[0073] If the weight loss ratio A / B is less than 0.8, the line drying property will be poor. On the other hand, if the weight loss ratio A / B exceeds 1.2, the temporal stability of the ink will be poor.

[0074] The weight loss ratio A / B can be adjusted to fall within the above-specified range by adjusting the amount of the solvent having a vapor pressure of 100 Pa or more at 25° C. and the amount of the solid content.

[0075] Furthermore, in order to further exert the effects of the present disclosure, that is, to minimize the ink spot phenomenon and to achieve a high degree of smooth writing feel, the oil-based ink composition for a ballpoint pen preferably satisfies the following conditions 1) to 2).

[0076] 1) 25℃, shear rate 200~2000s -1 The ink viscosity is between 1 and 200 mPa·s.

[0077] 2) Ink viscosity when using a cone and plate (CP25-1, manufactured by Anton Paar) was measured using a rheometer (MCR302, manufactured by Anton Paar) at 25°C at a shear rate of 20 s. -1 Viscosity / shear rate 200s -1 The viscosity ratio is 0.90 to 1.10.

[0078] The above-mentioned condition 1) that the ink viscosity is 200 mPa·s or less is related to the occurrence of the ink spot phenomenon. By satisfying this condition, further ink spot phenomenon can be suppressed, and good initial writing properties can be achieved.

[0079] More preferably, the temperature is 25°C and the shear rate is 200 to 2000 s. -1 The ink viscosity is preferably between 1 and 110 mPa·s.

[0080] The above-mentioned condition 2) that the ratio is 0.90 to 1.10 is related to the amount of dye pigment, resin, and the ratio of volatile solvent. By satisfying this condition, the suppression of the ink spot phenomenon can be further improved.

[0081] In order to adjust the oil-based ink composition for ballpoint pens that satisfies the above conditions 1) and 2), it can be adjusted by preferably selecting the type of colorant, resin, and solvent suitable for combination, optimizing the content of each component, and the kneading method described below.

[0082] The oil-based ink composition for a ballpoint pen disclosed in the present invention can be produced according to the production method of other oil-based ink compositions.

[0083] That is, the oil-based ink composition for a ballpoint pen disclosed in the present invention contains at least the aforementioned colorant, a resin component, a solvent and water, and the oil-based ink composition for a ballpoint pen can be manufactured as follows: the content of the aforementioned resin component is 6% by mass or less relative to the total amount of the ink composition, the content of the aforementioned solvent and water is 40% by mass or more relative to the total amount of the ink composition, the other components are appropriately combined according to the use of the ballpoint pen ink, a mixer, etc., and further, for example, a bead mill, a homomixer, a homogenizer, etc. that can apply strong shearing are used, and the stirring conditions are set to appropriate conditions and mixed and stirred, and then coarse particles in the ink composition are removed by filtration or centrifugal separation as needed, thereby, the oil-based ink composition for a ballpoint pen can be manufactured.

[0084] The oil-based ink composition for a ballpoint pen disclosed in the present invention is mounted on a ballpoint pen having a pen tip such as a ballpoint pen tip, for example.

[0085] As the ballpoint pen in the present disclosure, there can be mentioned: one in which the oily ink composition for ballpoint pens of the above-mentioned composition is stored in a ballpoint pen ink storage body (pen core), for example, it can be produced by filling the oily ink composition for ballpoint pens in an oily ballpoint pen body having a ball tip with a ball having a diameter of 0.18 to 2.0 mm, preferably a diameter of 0.28 to 1.0 mm.

[0086] In the oil-based ballpoint pen equipped with the oil-based ink composition for ballpoint pens of the above-mentioned properties disclosed in the present invention, in order to further exert the effect of suppressing the ink spot phenomenon from the perspective of the structure of the ballpoint pen, the structure of the ballpoint pen tip X fixed to the front end of the ink storage body (pen core) is, for example, Figure 1 As shown, there are a ball 10 and a bracket 20 for holding the ball 10, a ball cover 25 for storing the ball 10 is provided near the front end of the bracket 20, and a plugging portion 26 is provided at the front end of the bracket 20 for preventing the ball 10 stored in the ball cover 25 from flying out of the ball cover 25. The length of the sealing surface Y between the inner circumference of the plugging portion 26 and the ball 10 is preferably 20 to 170 μm, and the diameter of the ball 10 is also expected to be 0.28 to 1.0 mm.

[0087] Therefore, in coordination with the characteristics of the aforementioned oil-based ink composition for ballpoint pens, due to the structure of the ballpoint pen, as writing proceeds, the residual oil-based ink will not accumulate near the plug at the tip, and therefore will not become ink spots and fall on the line, and the line quality will also be improved, and the effect of reducing ink spots can be further enhanced. By optimizing the above-mentioned solvent type and the content of the solvent, water, etc. in the ink composition and also satisfying the aforementioned conditions 1) to 2), the residual ink that affects the ink spots that are not completely transferred to the paper surface can be further controlled, and the ink accumulation near the plug will not increase.

[0088] It should be noted that the structure of the ballpoint pen is not particularly limited. For example, it can be a straight-liquid oil-based ballpoint pen having a collector structure (ink retaining mechanism) in which the barrel itself serves as an ink container and the barrel is filled with the oil-based ink composition for ballpoint pens of the above-mentioned structure.

[0089] The oil-based ink composition for a ballpoint pen of the present disclosure thus constituted is characterized in that it contains at least: a colorant, a resin component, a solvent and water, the content of the above-mentioned solvent and water is 40% by mass or more relative to the total amount of the above-mentioned ink composition, when a resin having a mass average molecular weight of 40,000 or more is contained as the above-mentioned resin component, the content of the resin component is 0.5% by mass or less relative to the total amount of the above-mentioned ink composition, and the weight loss rate A when the above-mentioned ink composition is left to stand for 2 hours at 50°C and a relative humidity of 35±5%RH in an open state is 25% or more, and the above-mentioned weight loss rate A is greater than that when the above-mentioned ink composition is left to stand for 2 hours at 50°C and a relative humidity of 35±5%RH in an open state. The weight loss rate B ratio A / B when left to stand for 2 hours in an environment with a relative humidity of 85±5%RH is 0.8 to 1.2, thereby ensuring that a certain fixed volatility is maintained regardless of whether it is in a dry environment or in an environment with high humidity, thereby obtaining an oily ink composition for ballpoint pens that minimizes the ink spot phenomenon, has a smooth writing feel, good initial writing properties (no rubbing at the beginning), quick-drying properties, and is free of ink spots. The ink stretching and jump lines during wiping are improved, thereby ensuring a stable ink flow rate without relying on the ink flow rate design of the tip, and also improving the print-through properties due to the aforementioned suppression of ink spots and quick-drying properties; and an oily ballpoint pen.

[0090] Furthermore, in the oil-based ink composition for ballpoint pens, the viscosity of the rheometer at 25° C. using a cone and plate is within a range of a shear rate of 200 to 2000 s. -1 The range is 1 to 200 mPa·s, using a rheometer at 25°C with a shear rate of 20 s -1 Viscosity / shear rate 200s -1The viscosity ratio is 0.90 to 1.10, so that the remaining ink from the tip is not recovered, and even if the ink accumulates around the plug, it will evaporate, so that writing can be done without forming ink spots. Therefore, the ink spot phenomenon is suppressed as much as possible, and a smooth writing feel is highly taken into account, thereby further exerting the effect of the present invention.

[0091] The oil-based ink composition for a ballpoint pen and the oil-based ballpoint pen equipped with the same of the present disclosure have an extremely excellent sustained effect of exerting the above-mentioned effects of the present disclosure, and the duration of the effects is long, and the stability over time is also excellent.

[0092] Example

[0093] Next, the present disclosure will be described in further detail based on Examples 1 to 14 and Comparative Examples 1 to 6 of the oil-based ink composition for a ballpoint pen and the oil-based ballpoint pen equipped with the same, but the present disclosure is not limited to the following Examples and the like.

[0094] [Examples 1 to 14 and Comparative Examples 1 to 6]

[0095] According to the mixing formula of colorant, resin component, solvent, water, etc. shown in Table 1 below, the materials were added and heated and stirred at 60°C to prepare each oil-based ink composition for ballpoint pens. It should be noted that the resin component is expressed as a solid content. In addition, for the resin used, the columns (*8 to *13) in Table 1 record the 25°C, rheometer (manufactured by Anton Paar) 100s of 3-methyl-3-methoxy-1-butanol solution in which 10% by mass of the resin was dissolved. -1 The viscosity below.

[0096] For each of the obtained ballpoint pen oil ink compositions (total amount 100 mass%), the weight loss rate A and weight loss rate B of each ballpoint pen oil ink composition were determined by the following measurement methods, and the ratio A / B was calculated.

[0097] In addition, the rheometer (MCR302, manufactured by Anton Paar) at a shear rate of 200 to 2000 s at 25° C. using a cone and plate (CP25-1, manufactured by Anton Paar) was calculated according to the following measurement methods. -1 The viscosity of the ink between the two was measured by a rheometer (MCR302, manufactured by Anton Paar) at a shear rate of 20 s using a cone and plate (CP25-1, manufactured by Anton Paar) at 25°C. -1 Viscosity / shear rate 200s -1 The viscosity is expressed as a ratio.

[0098] Furthermore, an oil-based ballpoint pen of the following structure was prepared and evaluated for suppression of the ink spot phenomenon, initial writing property (no rubbing at the beginning), quick-drying property, line skipping, and improvement effect of print-through according to the following evaluation methods.

[0099] These results are shown in Table 1 below.

[0100] [Method for determining weight loss rate A and weight loss rate B]

[0101] 1 g of each of the obtained oil-based ink compositions for ballpoint pens was placed in a metal container having a diameter of 4.5 cm, and the weight loss rate A when the ink composition was left standing in an open state at 50° C. and a relative humidity of 35±5% RH for 2 hours was determined. The weight loss rate B when the ink composition was left standing in an open state at 50° C. and a relative humidity of 85±5% RH for 2 hours using the metal container was similarly determined. The ratio A / B of the weight loss rate A to the weight loss rate B was calculated.

[0102] 〔25℃, shear rate 200~2000s -1 Ink viscosity value between: measured at 25°C using a cone and plate (CP25-1, manufactured by Anton Paar) at a shear rate of 20 s using a rheometer (MCR302, manufactured by Anton Paar) -1 Viscosity / shear rate 200s -1 Method for determining the ratio of viscosity expressed as

[0103] The obtained ballpoint pen oil-based ink compositions were measured at 25° C. and a shear rate of 200 to 2000 s using a rheometer (MCR302, manufactured by Anton Paar) using a cone and plate (CP25-1, manufactured by Anton Paar). -1 The viscosity values ​​of each ink between the two are calculated to express their ratio (shear rate 20s -1 / Shearing speed 200s -1 ) ratio.

[0104] (Production of Oil-Based Ballpoint Pens)

[0105] Using the shaft of an oil-based ballpoint pen (manufactured by Mitsubishi Pencil Co., Ltd., trade name: SA-R), each pen core formed by a polypropylene ink container with an inner diameter of 1.7 mm and a length of 115 mm and a ballpoint pen tip (holder: stainless steel, ball: superhard alloy ball, ball diameter 0.7 mm), a clearance of 13 μm between the ball and the plug, a sealing surface of 70 μm, and a joint connecting the container tube and the tip, was filled with each of the oil-based ink compositions obtained above to produce oil-based ballpoint pens (5 each).

[0106] (Evaluation method of the effect of suppressing the black spot phenomenon)

[0107] A writing test was conducted using the aforementioned oil-based ballpoint pen and a writing test machine (MiniTec writing test machine, Mitsubishi Pencil) in accordance with JIS standard: S6039-2001, at a writing speed of 4.5 m / min, an angle of 60°, a writing load of 40 g, no rotation, and intermittent writing of 1 week of writing and 1 week of rest. The effect of suppressing the ink spot phenomenon when writing for 5 m was evaluated using the following criteria.

[0108] Evaluation criteria:

[0109] ◎: No line spots or attached spots, the lines are in good condition

[0110] ○: Almost no line spots or adhesion spots occur, and the line condition is good.

[0111] △: Clearly visible ink spots occurred in either line spots or adhesion spots.

[0112] ×: Clearly visible ink spots occurred in both line spots and adhesion spots, and the lines were dirty.

[0113] (Evaluation method for initial writing (whether the beginning is erased))

[0114] The above-mentioned oil-based ballpoint pen was used to write on PPC paper in spiral writing, and the initial writing property was evaluated according to the following evaluation criteria.

[0115] Evaluation criteria:

[0116] ○: Writing can be performed without any problem from the beginning.

[0117] △: Blurring exceeding 0 mm and less than 5 mm was observed from the start of writing.

[0118] ×: Blurring of 5 mm or more was observed from the beginning of writing.

[0119] (Evaluation method for quick-drying properties)

[0120] "Mitsubishi Pencil" was written on PPC paper using the aforementioned oil-based ballpoint pen, and the line was wiped off by hand immediately after writing, and quick-drying properties were evaluated based on the following evaluation criteria.

[0121] Evaluation criteria:

[0122] ○: The ink of the line does not extend at all and the line condition is good.

[0123] △: The ink of the line is slightly extended.

[0124] ×: The ink of the line extends significantly.

[0125] (Jumper wire evaluation method)

[0126] The aforementioned oil-based ballpoint pen was used to evaluate line skipping when writing continuously for 100 m at a writing speed of 6.0 m / min, an angle of 60°, a writing load of 100 g, with rotation, using a writing tester (MiniTec writing tester, Mitsubishi Pencil) in accordance with JIS standard: S6039-2001, according to the following evaluation criteria.

[0127] Evaluation criteria:

[0128] ○: There are no line jumps in the written lines.

[0129] △: There is some line skipping on the writing line.

[0130] ×: The writing line as a whole has skipped lines.

[0131] (Transparency improvement effect)

[0132] The writing test was conducted by using the aforementioned oil-based ballpoint pen and a writing tester (MiniTec writing tester, Mitsubishi Pencil) in accordance with JIS standard: S6039-2001, writing at a writing speed of 2.25 m / min, an angle of 60°, a writing load of 200 g, with self-rotation, and continuous writing, and spiral writing was performed on writing test paper in accordance with JIS standard P3201. The following evaluation criteria were used to evaluate the printability of the paper surface that became the writing surface after writing for 100 m. The printability was judged by whether the line was deeply visible.

[0133] Evaluation criteria:

[0134] ◎: No ink showing through.

[0135] ○: A darkened portion is seen in part of the line.

[0136] △: A darkened portion is visible halfway along the line.

[0137] ×: The color becomes darker overall.

[0138] [Table 1]

[0139]

[0140] *1 to *17 in the above Table 1 are as follows.

[0141] *1: Printex#35, manufactured by Degussa

[0142] *2: Cromophtal Blue A-3R, manufactured by Ciba-Geigy

[0143] *3: Made by DPP BP and Ciba-Geigy

[0144] *4: Spiron Purple CR-H, manufactured by Hodogaya Chemical Industry Co., Ltd.

[0145] *5: Spiron Yellow C-GNH, manufactured by Hodogaya Chemical Industry Co., Ltd.

[0146] *6: Spiron Blue CR-H, manufactured by Hodogaya Chemical Industry Co., Ltd.

[0147] *7: Spiron Red C-GH, manufactured by Hodogaya Chemical Industry Co., Ltd.

[0148] *8: Ketone resin K-90, manufactured by Arakawa Chemical Industries, Ltd., mass average molecular weight: 450, 25°C / rheometer (100s -1 ) in viscosity: 48mPa·s

[0149] *9: Polyvinyl pyrrolidone Pitzcol K-17, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., mass average molecular weight: 9000, 25°C / rheometer (100s -1 ) in viscosity: 59mPa·s

[0150] *10: Polyvinyl butyral BL-1, manufactured by Sekisui Chemical Co., Ltd., mass average molecular weight: 19000, 25°C / rheometer (100s -1 ) in viscosity: 219mPa·s

[0151] *11: Polyvinyl pyrrolidone, PVP K-90, manufactured by Ashland, mass average molecular weight: 1,200,000, 25°C / rheometer (100 s -1 ) in viscosity: 3393mPa·s

[0152] *12: Polyvinyl butyral BH-3, manufactured by Sekisui Chemical Co., Ltd., mass average molecular weight: 110,000, 25°C / rheometer (100s -1 ) in viscosity: 9685mPa·s

[0153] *13: Polyvinyl butyral BM-5, manufactured by Sekisui Chemical Co., Ltd., mass average molecular weight: 56,000, 25°C / rheometer (100 s -1 ) in viscosity: 1513mPa·s

[0154] *14: 25℃, vapor pressure: 125Pa

[0155] *15: 25℃, vapor pressure: 1667Pa

[0156] *16: 25℃, vapor pressure: 7906Pa

[0157] *17: 25℃, vapor pressure: 12.5Pa

[0158] The results in the aforementioned Table 1 clearly confirm that the oil-based ballpoint pen equipped with the oil-based ink composition for ballpoint pens of Examples 1 to 14 that fall within the scope of the present disclosure has an excellent effect in suppressing the ink spot phenomenon, a smooth writing feel, good initial writing properties (no rubbing at the beginning), quick-drying properties, and improved ink stretching and line skipping during wiping due to no ink spots, thereby ensuring a stable ink flow rate without relying on the ink flow rate design of the tip, and also improving the print-through properties due to the aforementioned suppression of ink spots and quick-drying properties.

[0159] Industrial Applicability

[0160] An oil-based ink composition for a ballpoint pen suitable for an oil-based ballpoint pen and an oil-based ballpoint pen equipped with the composition are obtained.

Claims

1. An oil-based ink composition for a ballpoint pen, characterized in that: Contains at least: colorant, resin component, solvent and water, The content of the solvent and water is 40% by mass or more relative to the total amount of the ink composition. When the resin component contains a resin having a mass average molecular weight of 40,000 or more, the content of the resin component is 0.5% by mass or less relative to the total amount of the ink composition. The weight loss rate A of the ink composition when left in an open state at 50° C. and a relative humidity of 35±5% RH for 2 hours is 25% or more, and The ratio A / B of the weight loss rate A to the weight loss rate B when the ink composition is left to stand in an open state at 50° C. and a relative humidity of 85±5% RH for 2 hours is 0.8 to 1.

2.

2. The oil-based ink composition for a ballpoint pen according to claim 1, characterized in that: A resin having a mass average molecular weight of less than 40,000 is contained as the resin component.

3. The oil-based ink composition for a ballpoint pen according to claim 1 or 2, characterized in that: The viscosity of the oil-based ink composition for ballpoint pens at 25° C. using a cone-plate rheometer is 200 to 2000 s at a shear rate of -1 The range is 1 to 200 mPa·s, using a rheometer at 25°C with a shear rate of 20 s -1 Viscosity / shear rate 200s -1 The viscosity ratio is 0.90 to 1.

10.

4. An oil-based ballpoint pen, characterized in that: The oil-based ink composition for a ballpoint pen according to claim 1 or 2 is loaded therein.

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